Understanding the Terroir of Burgundy: Part 4.2 Erosion: fundamentally changing terroir

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Erosion is constantly changing the terroir of Burgundy, and in turn, it is altering the weight and character of the wines from virtually every vineyard on the Côte. How significant is erosion in Burgundy today? As mentioned in Part 4.1, a study during the late 1990’s measured the soil loss in unspecified vineyards of Vosne-Romanée to be 1 mm per year, and the same erosional levels were measured off of the vineyards of Aloxe-Corton.  Ath that alarming rate, losses over the next century would have averaged 10 centimeters or almost 4 inches of topsoil if corrections were not taken. On the even steeper slopes of Monthelie, a study measured almost twice the erosion at 1.7 mm (± 0.5 mm year), with sections of the vineyard which measured a shocking eroded up to 8.2 mm (± 0.5 mm) erosional rate. Luckily, many growers have improved their farming practices, particularly since 2010, and these figures should be lower today. Only future studies can tell us what improvement has been made.

The grape harvest Annonymous 16th century, Southern Holland

“The grape harvest” Anonymous 16th century, Southern Holland

For centuries the solution for this problem was to bring in soil from outside areas to replace what was lost on the slopes of the Côte d’Or. However, in the name of terroir, this is no longer allowed. Current law allows growers to redistribute only the alluvium that comes to rest within appellation boundaries. One can imagine that the laborious process of shoveling out the alluvium from the toe of the plot and redistributing higher in the vineyard is a yearly chore. What earth escapes the appellation lines however, is gone to that appellation forever.

The intention of preserving the purity Burgundy’s unique terroir by forbidding introduction of exogenous soils is somewhat paradoxical, since it is only attempting to preserve the terroir à la minute. While in reality it is ultimately is failing at that – due to erosion. 

A positive, unintended consequence of this inability to replace soil is that growers have finally realized that soil conservation is now more critical than any time in Burgundies’ 1500+ year-old viticultural history. They now know that they must fully understand the factors of soil structure and erosion, while at a municipal level, their villages must invest in effective storm water management; both of which are in various states of development or improvement. 

The long uninterrupted run of vertically oriented rows presents unrelenting erosional pressures on this section of Les Folatieres.

The long uninterrupted run of vertically oriented rows presents unrelenting erosional pressures on this section of Les Folatières. photo googlemaps

While the best modern practices are stemming the tide of erosion, vineyards still can be threatened. Even great vineyards on the mid-slope, like Les Folatières in Puligny-Montrachet, which have long, open stretches of vines without significant breaks in planting, are prone to extensive erosion. While soils are depleted not only in terms of depth, they are changing in terms of particle size and makeup. Erosion most easily targets fine earth fractions, detaching them from their aggregate groupings, and sending them into vineyards farther down slope. Light to medium runoff acts like a sieve, carrying away only the smallest particles, leaving behind material with of larger particles sizes. This in a very real way changes the vineyard’s terroir, and in turn, the wines that are grown there. Wines from vineyards that retain only course soils of large particle size (1) tend to produce wines with less fruit the and less weight, and by consequence revealing a more structured, minerally character.

Even more critical is that soil loss can threaten the vitality and health of the vines, as the soil is literally carried away from beneath them. A vine’s main framework roots is said to require a minimum 11-13 inches to anchor itself to the earth and survive. The problem arises when a section of vineyard does not have extensive fracturing, and the soil level begins to drop below that one foot level. To address this, various growers have responded by “reconditioning” their land. By using a back hoe to break up the limestone below, this can give new vines planted there the living space so the vineyard can continue. Does this change the terroir and the future wine more than inputs of exogenous soil? I should think the answer is yes, significantly. 

 

Rainfall and rain strike: the first stage of erosion

rainstrike. photo: agronomy.lsu.edu/

rainstrike. photo: agronomy.lsu.edu/

Rainfall is measured by its size and velocity. A raindrop from a drizzle is typically .5 mm in size, and has a terminal velocity (the maximum speed the drop can reach) of 2 meters per second, or 4.5 miles per hour, in still air. The speed it falls, with no assistance from the wind is determined by its ratio of mass to drag. Large raindrops of 5 mm, have more mass in relationship to its drag and accelerate to 9 meters per second, or 20 mph.

Rainfall, meaning the actual physical strike of each drop, can break down soil aggregates (fine sand,  silt clay, and organic materials) and disperse them. Splash erosion has been recorded to drive particles of earth up to 60 cm into the air, and 1.5 m from its point of origin.

Once their limited bonds are broken, the ensuing runoff can carry these materials downslope. Runoff, the most obvious form of erosion, occurs when rainwater cannot infiltrate the soil quickly enough, and exacerbated by the lack of cover crop, lack of organic material, lack of soil structure and negative effects of soil compaction. Of course, this process is most noticeable during high-intensity rainstorms, the amount of soil lost during longer but low-intensity rainfall can be significant. This slower erosion can go largely unnoticed until most of the productive topsoil has been removed by what is referred to as sheet erosion.

Seasonal protection from rainstrike

Compared to most growing regions, the Côte d’Or has a very wet growing season. Storms during this period can bring irregular and unpredictable rain events that can be heavy and long in duration. The winds during harvest tend to be westerly, with warm humid winds bringing rain first over the Hautes Côtes, then to the Côte d’Or, then out across the Saône Valley. The wet warm humid conditions often encourage powdery mildew in the wake of the storms, so there is a tendency to want to prune to open up the canopy for ventilation to prevent mildew. However, the vine canopy can provide significant protection against rainfall strike, depending of course, on the orientation the rows and the of the wind direction. So good canopy coverage for the period that half of the precipitation occurs (April – September)(2) is beneficial in terms of protection from erosion.

As winter arrives, the vines will have lost their foliage, exposing the soil directly for the entire winter and spring to whatever nature has in store.

Rain Rate

storm.1

Summer storms. Bottom right Photograph: Louise Flanagan theGuardian.com, Bottom left photo Caroline Parent-Gros of A.F. Gros, Top photo Decanter.com

Rainfall is typically measured in millimeters per hour, with a light rainfall slightly tipping the scales at up to 2.5 mm per hour or less than a tenth of an inch per hour. Moderate rainfall is considered to be from 2.5 mm per hour to 10 mm per hour. A heavy rainfall falls between the range of 10 to 50 mm, and a violent rainfall is above 50 mm per hour.

 

Light rain – drizzle 2.5 mm per hour with a terminal velocity of 2 meters per second

Moderate rain 2.5 mm per hour to 10 mm per hour

Heavy Rain  10 mm per hour to 50 mm per hour

Violent rain, above 50 mm per hour

 

Good soil structure resists damage from rainstrike and runoff

Good soil structure is the result of the binding of soil into clumps of both small and larger aggregates, meaning sections of soil will bind more strongly together, than those next to them. This allows the soil to maintain the necessary small and large pore spacing, which allows water, air and nutrient infiltration and movement through the soil. Larger amounts of older, more stable organic matter tend to strengthen soil aggregates so any farming practice that increases organic matter, and the subsequent microbiological activity will result in healthier soils.  Stable soil aggregates allow the soil to resist disintegration due rain strike and thusly helps deter erosion.  It also encourages root penetration by creating weak spots between aggregate masses.

Conversely, unstable soil aggregates are more easily dispersed by rainstrike, and the ensuing erosion clogs larger pore spaces of the surface soil. This clogging forming hard crusts on the surface which both restricts both air and water absorption and increases runoff.

The fix apparently is simple. According to soilquality.org, soil forms aggregates readily with the addition of organic manure, as well as allowing cover crops to grow, which has the additional benefit of protecting the soil from rain strike and the ensuing erosion.

Infiltration rate

Erosion Runoff Ardeche

Rill Runoff running fast in Ardeche. Photo http://www.geo.uu.nl/

The speed at which rain can be absorbed into the soil is referred to as infiltration rate. An infiltration rate of 50 mm per hour is considered ideal for farming, because even in heavy rainfall, a well-structured loam will not allow puddling. While the farmers of Burgundy do have some loam in their soils, the geological and topographical factors they face are far more and varied and thus more complex than that of the typical farming situation. I could find no studies done specific to infiltration rates of Burgundian soils, but below are the general rain infiltration rates of general soil types, starting with clay.

The infiltration rate of clay soils, with good to average soil structure, unsurprisingly, do not drain all particularly well, due to their very small-sized particles. Clays typically have an IR of 10mm-20mm per hour. And as we know, transported clay, with its aligned particles, and plasticy quality greatly restricts water flow, and while it will absorb water, it will not allow water to pass through until the entire structure is saturated, greatly slowing drainage. Worse, due to poor farming practices, clay soils can have a decayed structure, which can slow absorption to less than 10 mm per hour. Water tends to puddle on clays with poor structure, causing them deteriorate to the point of deflocculation.

The study of water and how it drains is researched acutely in areas where water is scare, whereas little study of drainage is done in France where rain and water are plentiful. Hence, my investigation of water infiltration in calcium-rich soils lead me to agricultural water policy studies conducted in Palestine and Spain. One such study found that Clayey Marl, with a plasticy character, had an infiltration rate of only 4-8 mm per hour. This low rate of infiltration suggests the soil structure had already been degraded through poor farming practices. Often the villain of low infiltration rates is a combination of frequent deep tillage, herbicide and pesticide use and compaction by walking on or working wet soils, which collapses weaken soil aggregates.  In deeper soils, like at the base of the slope, collapsed soil aggregates can result in hardpan development below ground, while on sloped vineyards, disrupted soil aggregates are very susceptible to erosion.

Clay-loam and clayey-marls, like those found on many lower-slope vineyards, that retain good soil structure, have IR rates beginning at 20 mm per hour. As the percentage of loam increases (equal parts sand, silt, and clay) the IR rate increases up to 50 mm per hour as long as it retains good aggregate stability and there is no compaction.

Loam to sandy soils, which some Bourgogne-level and Village-level vineyards possess, can have very good infiltration rates, again as long as soil structures are good.  Ideally, they can absorb 50 mm of rain per hour, which is the amount that a heavy rainstorm will produce. These vineyards, however, receive all the runoff from the slopes above, and their “well-drained” soils can be overwhelmed.

Sandy soils and Calcareous (limestone) soils can have infiltration rates well in excess 150mm per hour to 200+mm per hour. The problem is these soils drain excessively well, and tend to not retain water well, and are prone to high evaporation rates.  Off point, but quite interesting, are two studies in south-eastern Australia Bennetts et al. (2006) and Edwards & Webb (2006) found that rainwater remained relatively unchanged as it moved though these porous soils that lacked significant amounts of fine earth fractions and organic material. However, water changed its chemical signature quite significantly as it passed much more slowly through clay-rich soils. This finding certainly challenges the long-held assumption that it is the limestone lends many Burgundies their mineral character.

Infiltration Rate, Slope, and Runoff.

Vogue's parcel of Musigny. Source Googlemaps

Vogue’s parcel of Musigny. Grass growth does not seem to be encouraged here. Given Cerdà’s study regarding the erosion of bare soils, one can only wonder how much greater this vineyard could be? The mitigating factor is the vineyard runs horizontally along the top of the hill, and is not deep or highly sloped. Runoff has little opportunity to gain significant suspension velocity. Photo Source googlemaps.com

A study in Spain by A. Cerdà (Univ. de València) examined infiltration rates, runoff, and erosion, on clay, marl, limestone and sandstone. Additionally, he ran these trials with three levels of vegetation covering the soil material: bare, intermediate and vegetated.  The amount of water delivered was 55 mm per hour (which some soils easily absorbed). The study showed slower rates of infiltration on the bare soils, while more highly vegetated soils reduced and almost eliminated runoff and erosion.  Interestingly, marl soils fare the worst for both runoff and erosion rates on bare soils. Yet on vegetated soils, runoff and erosion of the marl were minimal.

They observed, of bare soils, an infiltration rate of  3 to 55 mm per hour, the runoff from 0 to 83%, and the erosion rates from 0 to 3720 grams per hour.

The easily erodible marl soils had up to 83% runoff and a maximum erosion of 3720 grams per hour. So it turns out that marl soils are particularly vulnerable to erosion which sets up an interesting dichotomy: Burgundian’s penchant for discouraging ground cover between the vines, actually encourages erosion – something they seek to, and direly need to avoid.

Clay (soil) and limestone (soil) both had what Cerdà considered to be intermediate levels of runoff and erosion; with a maximum of 46% runoff, and a maximum of 131 grams of soil material eroded per hour.

When we talk about erosion, we are implying there is a slope.

Nearly level: Level, 0% Nearly level <3%
Gently sloping: Very gently sloping >1%, Gently sloping <8%
Strongly sloping: Sloping >4%, Moderately sloping <8%, Strongly Sloping <16%

Source: nrcs.usda.gov

On the rockier terrain of upper slopes, the uneven the soil surface can slow the momentum of water coming down the hillside, despite the steeper grade. However, as the runoff moves downslope, and the soil becomes smoother, the water grows in volume as in joins other rainfall which has not yet infiltrated the topsoil. This increase in volume causes the runoff to increase in its speed and its velocity. Speed and velocity increases are exponential, as its mass allows it overcomes the friction of moving over the soil below. 

Despite the fact that these moderate slopes can attain fairly significant soil depth with normal, moderate rainfall, they are also prone to erosion when exposed to heavier storm-induced runoff. Any long, uninterrupted stretch across these moderate slopes encourages a fast, and often damaging, runoff. As the speed of the water increases, it achieves a volume sufficient to carry larger and larger particles. Cerdà’s study suggests that the marl that has developed on these slopes are particularly vulnerable to heavy runoff if no vegetative cover is allowed to grow among the rows. 

Suspension velocity

water suspension velocity

water suspension velocity source: water.me.vccs.edu/

The ratio of surface area to weight determines a soil particle or rock’s suspension velocity. This is the amount of water velocity needed to carry the object in its flow. As the flow decreases, rocks with higher suspension velocity, meaning they require fast-moving water to carry them, settle out quickly, and are said to have a low settling velocity. As the water slows, it is these, the densest objects, that fall out of suspension first.

Silt and Clay particles have a very low suspension velocity due to their extremely small size, regardless of their density. These particles are easily picked up and washed away by water movement. Unless the clay particles in suspension are adsorbed as it slowly passes a homogeneous clay body (ie. a kaolinite clay body attracts kaolinite clay particles and illite particles will flocculate with an illite body), clay particles will not settle out of solution until the water becomes still and ponds. The same is true with silt, with its slightly larger particle size.

Sand and gravel are larger, with enough density to resist slow-moving water. They are considered to have a higher suspension velocity than silt or clay. But neither sand, gravel, nor even rocks the size of the palm of your hand, are immune from alluvial transport.

Up next: Erosion 4.3 In the water’s path: Studies of Erosion in Vosne

 


(1) It could be argued that because of Burgundy’s monoculture and high erosion rates will only allow calcisol, and because of that soil development (pedogenesis) is not possible due to the filtering out of fine particles, both mineral, and organic, by erosional processes. Conservation tilling or zero till could greatly change that dynamic, and it is possible with these and other techniques, that growers could expose the truer terroir of Burgundy.

(2) The Wines of Champagne, Burgundy, Eastern and Southern France,  by John J. Baxevanis Rowman & Littlefield Publishers (October 28, 1987)

(3) Could this chemical signature change the flavor of wine? This certainly raises a whole host of questions regarding the impact of fast draining limestone on the flavor or minerality of in wine. This study would suggest the long-held belief by many that limestone gives wines a minerally characteristic is false.

 

 
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Understanding the Terroir of Burgundy: Part 4 the history of erosion and man

 

 

 

Erosion and man

by Dean Alexander

Erosion has had a monumental impact on the character of the wines of Burgundy. It took several decades once the INAO began preventing exogenous soil additions (early 20th century), before growers slowly began to realize that they must change the way they work their fields. They could no longer hit reset, by bringing in new soil to fix what they had damaged through poor farming practices.  The vineyards have since responded positively; with increasingly healthier soils, and far better soil retention. The region is now producing the finest wines in its long history. But without a doubt, the erosional damage of the past has been so immense and irreparable, that we will never really know what the terroir of Burgundy might have been. 

 

How long ago this happened, will certainly surprise you.

 

The First Farmers

Plow were first widely used as agricultural neolithic man move into central France around 4,000 BC .

The plow: 4500 BC

With the recession of the Ice Age, the Neolithic hunter-gatherers of the region were now free to venture northward, allowing the arrival of agricultural Neolithic man in central France, 6,500 years ago. Around that time, the first plows were developed, and with the economy of effort it provided, more food could be produced. This in turn allowed the population to grow, greatly increasing the need for arable land.

As agriculture began to be adopted by Neolithic man, particularly after the development of the plow, erosion became a significant issue across Europe.To meet that demand, they burned to clear forests for pasture and fields. This was an expedient means of what would otherwise take years of work. The unintended consequences of burns to facilitate clearing, were often massive, fast-moving wildfires that swept though forested and grassland areas.

Without the protection of trees and grasses upon the hillsides, the erosion that ensued was monumental. There may have been more erosion in the 700 years Neolithic man farmed the land of central Europe, than in the preceding 35 million years since the Côte d’Or was formed, and perhaps more than all of the time since. Although through intervening centuries have seen the reforestation of the hillsides, the damage done by Neolithic man permanently changed the landscape of France.

What did Neolithic man look like? Click here.

The Middle Ages

William Shepard, Historical Atlas 1923

Tenant Farming example. William Shepard, Historical Atlas 1923

Since the Neolithic, two subsequent periods of deforestation occurred, each time followed by large-scale erosion. The least destructive of the two was the periods between the 12th and 15th century, which despite the black plague in the middle 1300s, saw a large population growth in France.

The king, or the Duke in Burgundy’s case (1), would grant large parcels of land from the royal demesne (domaine) to his nobility, who were considered the servants of the Duke. Known as seigneurs, the nobility, would then use the land to raise money to fund the Duchey. The seigneur granted strips of land to tenants (serfs) to farm in open fields. These fields where then were farmed communally by the inhabitants of the manor. Intermixed with the tenant parcels were the demesne of the seigneur, and the demesne of the church – all of the land which was worked by the surf communally as partial payment for their tenant rights.

The rights the tenants had to the land were very strong and generational. They could not be evicted from the land by the seigneur. Additionally, the tenants were able to accumulate rights to more than one strip of land, meant parcels could be scattered across the manor. A transfer of land rights typically happened when a tenant died and had no heirs. At that time another tenant would assume the right to work that parcel. This occurred on a massive scale in the wake of the black plague, which arrived in Lyon in 1348. Lyon, which was only 155 km, or 96 miles along the main highway, the Via Agrippa, from wine villages of the Cote d’Or. There is little doubt that the plague struck the Cote d’Or very hard.

Newcomers to the manor who had no land rights worked for tenants that had more land than they could work themselves. It is estimated that half the of the agricultural community consisted of landless serfs.

Farming with plow

From an early 15th century manuscript. The Granger Collection, New York

The manor model, with its communal farming, required everyone to adhere to the norms of the region, and this discouraged innovation and adoptions of new techniques, causing production per hectare to lag behind farms in England, Holland and elsewhere in the world. The farmer’s dependence on the communal sharing of prohibitively expensive horses and plows needed to farm the heavy clay soils of central Europe only reinforced the status quo.

The inefficiencies of farming under this system meant that as the population grew, it required that the economy remained primarily both rural and agrarian. The existing estates could not supply enough food if population grew mainly in urban centers, so population tended to grow in rural areas. More mouths to feed, and more able hands to employ, meant economic opportunity for the Duchy if new arable land could be developed from the forests.

Even though the open field system inherently discouraged innovation and suppressed productivity, the system proved to be so economically successful its existence eclipsed the time of feudalism. Right up to the revolution, the open field system to continue to fund well-heeled landowners in this very capitalist endeavor. But even then, to say the open field system was gone, might be an incomplete truth. The people may have then owned the land, but their situation had not greatly changed. In fact, until only recently, the wide-spread division of small parcels ensured the impoverishment of paysans across Bourgogne-Franche-Comté, with an obvious, strong parallel to the medieval tenant arrangement. Indeed, the old lord-tenant arrangement of métayage (sharecropping) would reemerge. post-1789 revolution, between those who owned the land, and laborers who would work it. In 1929 there were 200,000 Métayers in France, farming the same 11 percent of agricultural land. This was truly not so differently as had been the arrangement in 1729, or in 1529 for that matter.

As with a population that doubled in the 3 centuries after 1000 AD, the needs for timber and hardwood also increased. Wood was needed for construction, woodworking, iron smelting and metal working, not to mention fuel for heating.  All of these needs multiplied the pressures on deforestation. Although forest management had to various degrees been practiced, it tended to be exercised on forests on properties owned by the aristocracy and the church. Elsewhere, woods fell to the ax and saw.

18th century: The last major assault on terroir

A devastatingly cold 17th century followed, slowing the population growth and economies. The end of that century saw the failed harvest of 1693, when the death toll, according to David Huddart, and Tim Stott of Europeans is thought to have numbered in the millions. This period of economic lull set the stage for a final epoch of deforestation and erosion of France.

By the mid 18th century, the average temperature had risen enough to achieve food security. Once again, with food in their bellies, populations rebounded, and focus on innovation brought healthy economies. Industrial development ensued, bringing expansion and colonialism.  Massive fleets were built, from forests felled for the needed timber. As the population grew again, farming and pastureland expanded once again to support the needed food supplies. The open field system prevailed through this period, and given their inefficiencies, yet more land was needed to feed the population. To these pressure, the forests fell away, leading to erosion.

The protected hunting forests of the Aristocracy, and those belonging to the Church, alone stood untouched. While these forests were often noted as early forestry, it is somewhat disingenuous call this entitlement “forest husbandry”. Indeed, by the time of the French Revolution the royal forests had become a hated symbol of privilege.(2)

Unlike the medieval period that saw erosion primarily because of deforestation, this dawn of industrialization created many new erosional sources.  Iron works and foundries required mines and open pits to be dug to excavate ore, while limestone, prized for its hardness, was quarried across the country, including within the vineyard land of the Cote d’Or.

quarriesandbeyond.org

 

It was the wealth of the times that created a demand for Burgundy’s limestone. Thousands of large building projects: for the Church, wealthy private citizens, the aristocracy, for government buildings and public works, all of which required vast amounts of building materials. The high demand created such soar value for the “marble”. I had originally concluded when first writing this article, that the value of the limestone below, outsized the value of the grape production of that location, but I have since come to what I believe to be a more valid conclusion. I submit that the quarries dug in locations in which the limestone remained unfractured, examples of which can be seen in the climates of Meursault Perrières, Clos de Beze, Bonnes-Mares, and some submit, even Romanee-Conti, made those particular locations unsuitable for quality vine cultivation, unlike the superb plots which surrounded them.

It was used in its solid slab form for wall paneling and floors, but the rubble was also burned in special kilns to produce Quick lime (calcium oxide) which is the primary ingredient of both mortar and plaster. Softer limestones were often sought for the production of quicklime, as it was far easier to excavate the softer stone than the harder, unfractured stone which was required for floors and wall paneling.

The excavation of the limestone not only changed the substratum and topography of these vineyards, but greatly affected vineyard lands to either side of these projects, and with substantial impact to the vineyards below. This is where the overburden (the topsoil and useless rubble) was cast, in the most expeditious manner, downhill.

Meursault Perrieres quarry site175 years later, the disruption of such a quarry site to the terroir of the region is easily seen in the two vineyards of Les Perrières in Meursault, and Les Charmes, which lies just below. A large quarry was cut out of the hillside of MeursaultPerrières Dessous. The location of bulk of the excavation appears to now have been declassified from Les Perrières, as well as a wide strip above the exposed limestone wall.  The sub-plot of Clos des Perrières which is owned by Albert Grivault vineyard is just below the main area of excavation, but it was certainly was part of the quarry itself. The area directly behind the removal site would certainly have been utilized for temporary buildings, for staging or even storage of limestone before transport, a loading area for horse carts, and space for any other logistical needs a quarry would require.  The slope of this entire area was more or less leveled from it previous gradient. Clos des Perrières begins that the overburden would have been spread, although. The dirt roads of the regions were also impacted, by the transit of thousands of heavily loaded wagons, itself causing extensive erosion. And then it would rain.

The likely disposition of overburden and erosion from the quarry in Les Perrières, with finer sediment with higher suspension

The likely disposition of overburden and erosion from the quarry in Les Perrières, with finer sediment with higher turbidity / suspension velocity travels farther down-slope. The original map this diagram was taken from, and more information on Les Perrières can be found at clivecotes.com.  Click to enlarge

The sections of Les Charmes-Dessus, lying just below this quarry received the discharge of overburden, deepening the soil along this half mile of roadway. That this discharge and erosion onto Les Charmes Dessus, and no doubt Les Charmes Dessous, lying just below that, is without question. The soil depth was increased by the alluvial soils eroded from the quarry site, in addition to any normal erosional deposits that would have occurred, giving the vines more depth than they require, mimicking vineyards that are actually lower on the slope.  The wines from Meursault Charmes, are fairly commonly described as fat, without the vibrancy and minerality of Les Perrières, and often given the faint praise of being rather hedonistic.

Excavations by Thierry Matrot in 1990 in his parcel of MeursaultPerrières (parcel 15 in the map to the right) found roughly one foot of topsoil before striking the limestone base. Whereas, digging into his plot of Meursault-Charmes however proved to be far more work. Here a pit of 6 feet was dug before hitting the limestone substrata.(3) This indicates, a significant amount of limestone colluvium had developed in Charmes, that has mixed with transported clay to attain this six-foot depth of marl dominated soil.. I have not been able to determine the location of the Matrot’s plot (or plots) in Les Charmes. It is a large vineyard and without the dig location, this information doesn’t have nearly as much meaning as it would otherwise. It does illustrate the dramatic effect erosion has had on the vineyards of Burgundy and the character of the wines from each location.

 ~

Much more on the effect slope position and soil depth on the character of wine can be here for vineyards on the lower slopes, and here for vineyards on the upper slopes.

 

This diagram illustrates the changes in temperature in Northern Europe, as well as major historical in intellectual periods.

This diagram illustrates the changes in temperature in Northern Europe, as well as major historical in intellectual periods.

(1) The Burgundians were an Eastern Germanic tribe which likely crossed the Rhine in 406 AD, in a combined force with the Vandals, Alans and Suebi tribes. The Roman forces there had largely departed four years earlier to deal with Visigoth king, and sometimes Roman ally, Alaric, who would ultimately be an actor in the fall of Rome. But the crossing signaled the end of Roman rule Central Europe.

The Kingdom of the Burgundies, ruled the lands east of Paris, down to the Mediterranean with various boundaries. A series of smaller Duchy, including the Duchy of Burgundy, succeeded the Kingdom of Burgundies in 1032. The Duchy was relatively sovereign, but owed its allegiance to the French crown. The influence and power of the Duchy expanded greatly in 1384 with a union with the Hapsburgs. The house of Valois – Burgundy, the ruling family of the Duchy of Burgundy at the time, ultimately expanded its control of fiefs in Holland and the Netherlands, parts of northern France and Luxembourg.  In a bid to gain independence from France, 1477 Charles the Bold was killed in battle by a combined force of the Duke of Lorraine and a Swiss Confederacy. With no heir to Charles, and a weak hold on their power, the Valois were unable to prevent the Duchy from eventually being absorbed into France.

(2) Empire Forestry and the Origins of Environmentalism, Gregory Allen Barton (p.11) Cambridge University Press


Earth Environments: Past, Present, and Future, David Huddart, Tim Stott, John Wiley & Sons,, 2013

Class and State in Ancien Regime France: The Road to Modernity?

By David Parker

Understanding the Terroir of Burgundy: Part 3.3.1 Fracturing variations within upper vineyards

Vineyard and plot variation confuses our understanding of Burgundy

High on the upper slopes, the farthest away from the Saône Valley Fault, the magnitude of fracturing within the same vineyard can vary significantly, even within the span of a few meters. Not only that, but there is evidence that the farther one moves from the main fault, the occurrence of fracturing patterns widens in its spacing, being further and further apart, and more irregular in its distribution. This means that if the fracturing is unequal within a vineyard, so can it to be unequal within a parcel. Following this uneven fracturing distribution, it becomes quite clear that a wine produced from different vineyard sections may produce wines of differents weights, and possibly character. We can only assume that this kind of intermittent fracturing, hidden beneath the topsoil, has unequally affected not only the wine made by these plots but the reputation of the vignerons who farm these plots as well.

Fractured limestone of Les Perrieres

The patterns of fracture propagation

Looking back at Part 1.2 about the deformation and fracturing of limestone, the stress that causes the main fault, and many of the parallel faults also weakens the entire stone structure through deformation. Micro-fractures appear throughout the stone, independently of one another, usually in clusters. As the cracks propagate, they do so often in a tree-like pattern, forking and spreading upward from the origin fracture, deeper within the stone. Depending on the brittleness of the limestone and the direction of the strain, these microcracks will form tensile fractures (extensional strain) or shear planes (compressional strain). Additional strain will be concentrated on the most fractured, weakest part of the stone, and this becomes the path of the fracture. Because these areas have been forced to bend and ultimately fail, this movement causes the strain to localize, increased by the stone’s own failure, causing even greater fracturing.  Alternately in the areas between the crack arrays, the stone will be only lightly fractured, and in some places, maybe not at all. It is this that makes plots within the same vineyard unequal, as much as the skill and style vignerons are unequal.

 

I have laid a vertical tree in a horizontal fashion to more dramatically illustrate fracturing within parcels. Fracturing actually happens from deeper in the stone and moves upwards to the surface, often widening and splintering as it goes. Fracturing does not always reach the surface, and this shows the disparity in fracturing one area vs. another. Mechanical weathering will accentuate fracturing where it does extend to the surface, breaking up the stone, while chemical weathering will reduce the stone to Co3 and primary clay, creating marly limestone.

I have laid a vertical tree in a horizontal fashion to more dramatically illustrate fracturing within parcels. Fracturing actually happens from deeper in the stone and moves upwards to the surface, often widening and splintering as it goes. Fracturing does not always reach the surface, and this shows the disparity in fracturing one area vs. another. Mechanical weathering will accentuate fracturing where it does extend to the surface, breaking up the stone, while chemical weathering will reduce the stone to Co3 and primary clay, creating marly limestone.

 

Clues to the Côte by examining another fault/escarpment

 

The Arugot Fault near Jerusalem is unique because the fractures to its dolomite slabs (limestone containing magnesium) lie above ground, not covered by sand or soil. Geologists are reasonably certain that the Arugot fault was an extensional occurrence (like the Saône Fault), not caused by slip-shear or other earthquake-related stresses. The Arugot fault, like the Saône Fault, was created an escarpment as the Dead Sea Basin pulled away, in a horst/graben relationship.  The area is prone to flash flooding, particularly through the deep canyons that bisect the escarpment (not unlike the combes of the Cote), and it was the erosion that rapid water movement causes have left the vertically fractured dolomite uncovered and available to be studied. The general geographical similarities of the Saône and Arugot are marred by the fact that the Dead Sea escarpment is twice as tall (600 meters), and many times more steep, with very steep angles of 75% to 80% that drop into the Dead Sea depression.

The fault itself is believed to extend several hundred meters into the earth. Parallel to the fault, a series many extensional fractures were formed, marching up the escarpment away from the main fault.  There is ample evidence that these fractures propagated from below, as the fractures are tree-like, branching vertically, splitting the rock into smaller and smaller divisions as they move toward the surface. They often, but not always, fracture through the top of the stone. Nearest to the Arugot fault itself, the fractures are very close together, and the farther away from the fault the wider the spacing between fractures until they discontinue hundreds of meters away from the main fault. The relevance of this increased space between fractures is that explains the variation between well-fractured sections of limestone, and poorly fractured sections, all within the space of a few meters. This variation extends to, and explains not only to the difference between two vineyards, but the difference between plots, or even within sections of the same plot.

fracture propagation from the Arugot fault near Jerusalem. The fractures are tree-like, and as you move away from the fault, the fractures are spaced wider and wider apart. source: earthquakes.ou.edu

Fracture propagation from the Arugot fault near Jerusalem. The fractures are tree-like, and as you move away from the fault, the fractures are spaced wider and wider apart. source: earthquakes.ou.edu

Understanding the Terroir of Burgundy: Part 3.3 The Upper Slopes

Shallow topsoil over hard limestone: a site of struggle

As I touched on in the introduction of slope position in Part 3.2, there are significant variables effecting which vineyards can produce weightier wines further up the slope. However, as a general rule, the steep upper-slopes are far less capable of producing dense, weighty and fruit filled Burgundies that are routinely produced on the mid and lower slopes.

The lack of water, nutrients and root space

The scree filled Les Narvaux in Meursault. photo: googlemaps

The scree filled Les Narvaux in Meursault. photo: googlemaps

In many of these upper vineyards, the crushed, sandy, and in some places powdery, or typically firmer and more compact, the marly limestone topsoil overlies a very pure limestone, such as Comblanchien, Premeaux and Pierre de Chassagne. Here, the extent of that the stone is fractured determines the vines ability to put down a healthy volume of roots to support both growth and fruit bearing activity. Any gardener can tell you that insufficient root space, whether grown above a shallow hardpan or in a pot, will cause a plant to be root bound and less healthy.

Because these steeper vineyards can neither develop, nor hold much topsoil to its slopes. The topsoil, which can be measured in inches rather than feet, tends to be very homogeneous in its makeup; a single horizon of compact, marly limestone, with a scant clay content of roughly 10-15%. The infiltration of rainwater and the drainage are one and the same. Retention of the water is performed almost solely by this clay content, and evaporation in this confined root zone can be a significant hazard to the vine. Fortunately rain in Burgundy during the growing season is common, although rainfall from April to October, and particularly in July, the loss of water in the soil is swifter than it’s replacement from the sky (Wilson, “Terroir” p120).

Infiltration Rates of Calcareous Soils

A study by A. Ruellan, of the Ecole National Supérieure Agronomique, examined the calcareous (limestone) soils of Mediterranean and desert regions, where available water and farming can be at critical odds.  He studied two major limestone soil types. The first was a light to medium textured, loamy, calcareous soil (60 – 80% CaCO3), and the second was a powdery and dry limestone soil with no cohesion. This second soil had a calcium carbonate content that exceeded 70%, and had 5% organic matter and a low clay content. The water holding capacity of this soil was a mere 14%. The depth of this soil was over 2 meters deep, which likely does not allow weathered clay accumulate near the surface, as it does in Burgundy.

Both limestone soils had very high permeability, with an infiltrate at a rate at a lightning fast 10 to 20 meters per day (or between 416 mm per hour and 832 mm per hour).  Even if rainwater infiltrated at half that rate through Burgundy’s compact limestone soils, it would virtually disappear from the topsoil. This is the area where the majority of the vines root system exists, and part of the root system responsible for nutrient uptake is within this topsoil region.  In this case of these soils, the vines must send down roots to gain water in the aquifer. Wittendal, who I wrote of in Part 3, suggests in that the vines literally wrap their roots around the stone, and suck the water from them.  I have seen little evidence that limestone actually absorbs water due to many limestone’s high calcium content and lack of porosity. This would be particularly true on the upper slopes under consideration now. It would be up to the roots to attempt to penetrate the stone in search of the needed water.

The root zone

Root development through soil

This slide represents the root development in shallow topsoil over a lightly fractured limestone base vs a deeper soil situation with four or five separate bedding horizons, such as exists lower on the slopes of burgundy.The effect infiltration rates have depends significantly on the distribution of vine roots. In most planting situations, 60 percent of vine roots are within the first two feet of topsoil, and have been known to attain a horizontal spread of 30 feet, although the majority of the root mass remains near the trunk.

By design, vines rely on the roots established within the surface soil – which is where nutrients (ie nitrogen, phosphorus, potassium) are found – to gain the majority of their sustenance. They send down deeper roots to gain water when it is not available nearer the surface. However in Burgundy, many of the steeper slopes present planting situations where not only is the soil very shallow, but the nutrients are poor. The limestone in these vineyards often is hard and clear of impurities, and within the same vineyard may vary significantly in how fractured the stone is. Because of this, in some locations vines have difficulty establishing vigorous root penetration of the limestone base, and this can dramatically limit the vine’s root zone.

Additionally, because of the soil’s shallow depth, , and because of the soils high porosity and low levels of clay and other fine earth fractions, only a limited volume of water can be retained

Water is critical for both clay’s formation and its chemical structure, and the clay will not give up the last of what it needs for it own composition. The evaporation rate of what little water there might remain, can be critically swift.

Rainwater’s infiltration of the limestone base, and its retention of water can also be limited where significant fracturing has not occurred. Any water that cannot easily infiltrate either the soil or the limestone base, will start downward movement across the topsoil as runoff. That means any vine that has been established in shallow topsoil, or the topsoil has suffered significant losses due to erosion, will be forced to send roots down to attempt to supply water and nutrients.

Vine roots and a restricted root zone

In non-cultivated, non-clonal vines, powerful tap roots are sent down for the purpose of retrieving water when it is not available in from the surface soils. However our clonal varieties are more “highly divided” according to the “Biology of the Grapevine” by Michael G. Mullins, Alain Bouquet, Larry E. Williams, Cambridge University Press, 1992. The largest, thickest, roots develop fully in their number of separate roots, by the vine’s third year, and are called the main framework roots. Old established vines in good health may have main framework roots as thick as 100cm (40 inches) thick. This main framework root system, in normal soils, typically sinks between 30 cm (11 inches) and 35 cm (13 inches) below the surface.  In shallow soils, they may hit hard limestone before full growth, and may have to turn away, or stop growing. Anne-Marie Morey, of Domaine Pierre Morey, echoes this in talking with Master of Wine, Benjamin Lewin, of their plot in Meursault Tessons. “This is a mineral terroir: the rock is about 30 cms down and the roots tend to run along the surface.”

From the main framework, grows the permanent root system. These roots are much smaller, between 2 and 6 cm, and may either grow horizontally (called spreaders) or they may grow downward (known as sinkers).  From these permanent roots grow the fibrous or absorbing roots. These absorbing roots are continually growing and dividing, and unlike the permanent roots, are short-lived. When older sections absorbing roots die, new lateral absorbing roots to replace them.

This cutaway of the topsoil of Gevrey Bel Air shows just how limited the root zone is in this premier cru vineyard. The Comblanchien below is being 'reconditioned' in this plot. More on this in a near future article. click to enlarge.

This cutaway of the topsoil of Gevrey Bel Air shows just how limited the root zone is in this premier cru vineyard. The limestone below is being ‘reconditioned’ in this plot. click to enlarge.

Although the permanent sinker roots may dive down significant depths, the absorbing roots (which account for major portion of a vine’s root system account for the highest percentage of root mass, typically only inhabit the first 20cm to 50cm, or between 8 inch and 19 inches of a soils depth (Champagnol,  Elements de Physiologie de la Vigne et de Viticulture Générale 1984). Clearly this is an issue if the topsoil is only 30 cm (12 inches) to begin with.  If the absorbing roots are not growing sufficiently on the sinkers, the vine must rely on the exceptionally poor topsoil of the marly limestone.

South African soil scientist Dr. Philip Myburgh found (1996) that restricted root growth correlated with diminished yields. He also found that the “critical limit’ of penetration by vine root was 2 MPa through a “growing medium”. Weakness in the bedrock, and the spacing of these weaknesses, contributed to a vines viability.

The vines on these slopes, on which there is limited fracturing of the harder, non-friable limestone, have difficulty surviving. These locations often shorten the lifespan of the vines planted there, compared to other, more fertile locations in Burgundy, where vines can grow in excess of 100 years. It is these vines, with barely sufficient nutrients that make wines that don’t have the fruit weight that I wrote of before, simply because they cannot gain the water and nutrients necessary to develop those characteristics. The amount of struggle the vine endures directly determines the wine’s weight, or lack of it.

It is ironic, that when we research the issues the catchphrases of wine describe, ie, the “vines must struggle”, or that a vineyard is “well-drained”, or the vineyards are “too wet to produce quality wine”, we see the simplicities, inaccuracies, or the shortcuts that those words cover up. Yet these catchphrases are so ingrained in wine writing, that we don’t even know to question them, or realize that they require significantly more nuance, or at minimum, point of reference. Yes, the vines on the upper-slopes are particularly well-drained. They do indeed struggle, sometimes to the point of producing vines are not healthy, and cannot the quality or the weight of wine that the producer (dictated by their customers) feels worthy of the price.

Extreme vineyard management

Blagny sous la dos d'Ane's shallow red soils produce a Pinot that is too light for the market to bear at the price it must be sold. photo: googlemaps

Blagny sous la dos d’Ane’s shallow red soils produce a Pinot that is too light for the market to accept – at the price it must be sold. photo: googlemaps

In Blagny, the Sous le dos d’Ane vineyard, which lies directly above the small cru of  Aux Perrières, has seen at least one frustrated producer graft their vines from Pinot Noir to Chardonnay. The Pinot, from the red, shallow, marly limestone soils, was felt to be unsatisfactorily light in weight. Not only would a lighter-styled, and minerally Chardonnay be well received, the producer will be able to sell it much more easily – and for more money because he could then label it as MeursaultSous le dos d’Ane, a much more marketable name.

Bel Air. More photos on this excellent website, and a terrific discussion in the comment section, albeit in French. Worth running through a translator. source: http://www.verre2terre.fr/

Bel Air. More photos on this excellent website, and a terrific discussion in the comment section. source: http://www.verre2terre.fr/

Producers in the Côte de Nuits rarely have the option to switch varietals. They typically must produce Pinot Noir to label as their recognized appellation. In the premier cru of Gevrey-Chambertin “Bel Air”, and Nuits St-Georges “Aux Torey”, growers have gone to the extreme lengths and expense of ‘reconditioning’ their plots. To do this, they must rip out their vines, strip back the topsoil and breaking up the limestone below. In the adjacent photo, a field of broken Premeaux limestone and White Oolite has been tenderized, if you will. The soil is replaced and the vineyard replanted. The entire process requires a decade before useful grapes can be harvested once again from the site, costing an untold number of Euros spent, not to mention the money not realize had the old vines been allowed to limp on. The same has been done in Puligny Folatières in 2007 by Vincent Girardin, and there again in 2011 by another unknown producer. Ditto with Clos de Vergers, a 1er cru in Pommard in 2009.

 

http://www.wineterroirs.com/2009/11/landscaping.html

click here: for the previous article, Understanding the Terroir of Burgundy: Part 3.2 The lower slopes

Understanding the Terroir of Burgundy: Part 3.2 The lower slopes

by Dean Alexander

° of Slope =  Soil Type + Soil Depth  → Wine Weight

In Part 3.1, I covered how the position and degree of slope determined the type of topsoil that lies there. In the next two sections, I will talk about how the position on the slope not only greatly influences topsoil composition but independent of winemaking decisions, is a significant determiner of the weight of the wine. In this section I will discuss this concept, focusing primarily on the vineyards below the slope, the flatlands vineyards most burgundy aficionados have traditionally ignored. This disdain for these lower-lying vineyards is changing because massive improvements in wine quality have made them relevant, and equally massive increases in wine prices have left them as the only wines tenable to those without the deepest of pockets. Additionally, sommeliers looking for high-quality wines of relative value, have begun to much more closely examine the wide-reaching Bourgogne appellations and the village level wines of the Côte d’Or. These are wines that fit price points and quality standards premier cru vineyards used to fill and often fill that void admirably.  


 The relationship of slope to wine weight

Soil depth and type can greatly determine wine weight and character

Soil depth and type can greatly determine wine weight and character

It has become increasingly apparent over the past decade, that there is a direct connection between the depth and richness of soil, to the weight of the wines produced from those vines. Vineyards that have a modicum of depth, and at least a fair amount of clay or other fine earth elements, coupled with a fractured limestone base, produce weightier wines. These vineyards typically exist from quite low on the slope to roughly mid-slope. The higher up the slope one goes, the more crucial it is that the stone below is well-fractured to be easily penetrated by vine roots. Softer limestone bases, like the friable, the fossil-infused crinoidal limestone, which is weakened by the ancient sea lilies trapped within it, or like clay-ladened argillaceous limestone, makes it possible to produce great wine from the steeper, upper-slopes. Examples of these vineyards include the uppermost section of Romanee-Conti and all of La Romanee, which sits above it. These appear to be rare exceptions, however.

Most wines produced from the steeper, upper slope vineyards, with shallower, marly-limestone (powdery, crushed-stone with low clay content) soils, lie over harder, purer limestone types like Comblanchien, Premeaux, and Pierre de Chassagne. These limestone types must have at least moderate fracturing and a high enough degree of ductile strain to plant above them. Wines from these types of vineyards are, without question, finer in focus and have greater delineation of flavor. It is not unusual for these wines to be described as spicier, more mineral laden, and have greater tannic structure. The short explanation is the upper-slope wines have less fruit to cover up their structure, while the wines from more gently sloped vineyards have more weighty fruit.  This fruit provides the gras, or fat, that obscures the structure of these weightier, more rounded wines. The upper slope vineyards will be covered in greater depth in the upcoming Part 3.3.

Because of the weathering of limestone on the upper slopes, and subsequent erosion, the soils, and colluvium collect on lower on the slope, making the topsoil there both deep and heavy. They are full of a wider array of fine earth fractions, and more readily retain water and nutrients necessary for the vines health and propagation of full, flavorful, berries.  On the curb of the slope they do this splendidly, with an excellent mix of clay and colluvium, giving the proper drainage for the typical amount of rainfall, yet retaining the right amount of water most times of year when rain does not fall.

The last vineyard before the pastures begin. The village of Puligny Montrachet is in the distance

The last vineyard before the pastures begin. The village of Puligny-Montrachet is in the distance. source: googlemaps.com

The “highway” and the low-lying vineyards below

For decades we have been told that the low-lying vineyards of Burgundy, were too wet to grow high-quality grapes, and we could expect neither concentration nor quality, from these village and Bourgogne level vineyards. The reason, we were told, was grapes grown from these flat, low-lying vineyards became bloated with water, and the result was acidic, thin, and “diluted” village and Bourgogne level wines. Alternately we were told the wines from lower vineyards were too “flabby”, as James E. Wilson ascribes on in his groundbreaking book Terroir published in 1988 (p.128). Thusly, an entire swath of vineyards, from below the villages of Gevrey and Vosne, all along the Côte, all the way to down to Chassagne, were dismissed as thin and shrill, lacking both character and concentration. These wines were generally considered by connoisseurs to be unworthy of drinking, much less purchasing.  At that time, given the poor quality being produced, that seemed perfectly reasonable.

This set in motion a series of generalizations and biases, many of which remain to this day. “The highway”, as Route Nationale 74 is often referred, became the demarcation between the possibility of good wine and bad. The notion that this roadway, something that is built for the sole purpose of moving from one village to the next, had become an indicator of wine quality, is so pervasive, that the grand crus with N74 at their feet, such as MazoyèresChambertin and Clos Vougeot, have been cast in a bad light simply due to their proximity to it. It has colored perceptions so much, that many people, to this day, equate being higher on the slope with being “better situated”. The fact that there are grand crus and premier crus on the upper slope, but none on the lower slopes only buttressed this idea.  However…

We now know this is not true.

Puligny Folatieres after a rain

The road below Paul Pernot’s Clos des Folatières, filled with water. However, this water is not allowed to enter the 1er Cru of Clavoillon below. This is an example of containing and redirecting excess water coming down the hillside, into noncrucial areas. click to enlarge photo source: googlemaps.com

There are many Bourgogne level vineyards that are more than capable of producing wines with good concentration, so long as the vigneron sought to produce quality over quantity, and the plot is not in an excessively poor location. So why were these myths that Bourgogne level vineyards could only produce light, thin, acidic wines, propagated by winemakers, wine writers, and importers?

The optimist would point to a lack of technical knowledge in the field and cellar made this true. The optimist would also say that the long tradition of creating simple, inexpensive, quaffing wine made it acceptable.

But there were other factors. Cold weather patterns from the mini ice-age, which ended in the 1850s, certainly set up long-standing expectations of wine the wine quality that was capable from various vineyards. These expectations were absolutely cemented in after the widely influential book by Jules Lavalle, Histoire et Statistique de la Vigne de Grands Vins de la Côte-d’Or was published in 1855. In this revered reference, Lavalle classified the vineyards of Burgundy the same year the French Government classified the chateaux of Bordeaux. No doubt the timing of this gave Lavalle’s unsanctioned work credence. After the first half degree average temperature increase which occurred around 1860, the climate in central Europe only gradually grew warmer over the next 135 years until 1990 when global warming really began in earnest. Before that, the weather would not allow the consistent ripening patterns that routinely we see today.

Another major factor was that there was not a complete understanding of how to control and divert runoff. Nor, prior to 1990, was it likely the villages along the Côte wealthy enough to make the large-scale improvements that were necessary to control rainwater runoff. Until the prices of Burgundy began to rise, overall the region was experiencing some economic depressed. This economic struggle, coupled with the inevitable political obstacles required to spend sparse civic funds, could delay improvements a decade.

On the other hand, the skeptic would point to the problems of greed, and it’s accomplice, over cropping. Vignerons could achieve 3 to 5 times higher production levels from the same vines, which was profitable, and required far less knowledge, less diligence in the field, and other than taking up more labor in bottling and space in the cellars, far less work in the cellars. It was not only the Bourgognes that fell into this net of profit over quality, but the village level wines were often fairly low in concentration, with under-ripe fruit, and low in quality. Even now, a producer that has reduced yields by a division of 3 in order to make a quality village or Bourgogne, is making less money per hectare than they would if they still over-cropped – and working harder in the field to do it.

Overcoming wet soil issues

Water features below Puligny Les Pucelles. Controlling and redirecting water away from lower vineyards is a major key to improving quality there. photo: googlemaps

Water features below Puligny Les Pucelles. Controlling and redirecting water away from lower vineyards is a major key to improving quality there.  click to enlarge  photo: googlemaps.com

Excess water in lower vineyards is a serious issue, and each vineyard is not equal in its ability to contend with heavy rainfall. Although flat is the quickest descriptor, the topography of each vineyard varies, as does the bedding (layers of soil) of each vineyard. These variances can dramatically determine the challenges presented to each grower in each day, season, and year, be it rain storm or drought.

In farming, an infiltration rate of roughly 50mm of rainfall per hour is considered ideal. That is precisely what a well-structured loam can typically absorb at normal rainfall rates, without significant puddling and runoff. Clays, however, drain much more slowly, with an infiltration 10-20mm per hour.  These optimal figures can all be thrown out the window, however, if the soil structure has been degraded through compaction or farming practices that commonly degrade the soil. Poorly structured clay soils can drain as slowly as 5-8-10mm per hour.

Alluvial soils, with their graded bedding, created by heavier gravel and sand falling out of water suspension before silt and clays, typically have good infiltration rates. Loam soils that have moved in from the Saône Valley pasture lands, and have weaved themselves into the fabric of the lower vineyards, have ideal infiltration rates. Sandy sections are likely to exist in some vineyards, will have very rapid infiltration and drainage, 150mm to 200+ mm per hour. Where solid layers of transported clay, in thick slabs have formed, drainage can be severely affected.  These plastic-y clays may repel water as much as they slowly absorb it. I wrote a much more complete examination of soils in Part 2.2.

What is important to consider, is that in all but the upper-most vineyards, soils are layered in horizons of soil types. It is normal, around the world, that there are typically 5 horizons of soil and subsoil layers in any given place, although there may be more, or as on slopes, fewer. Each horizon will affect the drainage of the plot, depending on its soil makeup. Geologist Francois Vannier-Petit presided over an excavation of Alex Gamble’s village-level Les Grands Champs vineyard in Puligny-Montrachet. In this vineyard, she records two horizons within the 80 cms that they dug, and she noted most of the vines roots existed in this zone. At the time of the excavation, she noted the soil was damp, but not wet, with good drainage.

The calcium, which is freed from the limestone rubble with weathering on the upper slopes, is not as prevalent and effective in the farther-flung Bourgogne vineyards. The calcium which helps disrupt the alignment the clay platelets, and aiding is drainage, may not be carried far enough by runoff to sufficiently strengthen the soils of these more distant vineyards.  Certainly, most of these vineyards are located beyond the Saône Valley fault, and the continuation of limestone that virtually sits on the surface of the Côte lays buried by at least a hundred feet of tertiary valley fill and has no effect on wine quality there, other than by its remoteness.

flooding

Turbid flood waters carry away gravel, sand, and fine earth fractions. These will be redeposited as alluvial soils, created graded bedding and clay minerals will flocculate onto, or into, other transported clay bodies. photo: decanter.com

The most severe problems revolve around the maximum amount of water the soil or clay can hold and fail to drain quickly enough through to the unsaturated/vadose zone, through capillary action to the water table below. With clay, this is called the plastic limit, or the point just before the clay loses its structure and becomes liquid. Flooding would ensue, and large volumes of soil would become suspended in turbid flowing waters, causing massive erosion, particularly from vineyards up-slope. This would truly be the worst case event, and I won’t say it doesn’t happen.

Another, significant problem, at least for vintners, although less apparent to the wine drinking public, is less wet soil is that it causes the vines to have difficulty acclimating to colder weather, and affects their hardiness if severe weather sets in.

However, in many vineyards, the wet soil has now been addressed by investments in drainage. Large yields are eliminated and concentration is gained by pruning for quality, coupled with bud thinning or green harvest. Vigilance against rot is key in these lower vineyards, as well as odium, and other mildews, which thrive in humid wet vineyards. This is a key element in quality since rainfall during the growing season is very common in Burgundy. With all of these precautions, there are now many producers who now make excellent Bourgogne level wines. And despite the tripling and quadrupling of the prices of Bourgogne, they are now well-worth drinking – often equalling  the premier cru wines of yesteryear in terms of quality.

It is often cited that Puligny-Montrachet has no underground cellars because of the high water table there. Yet Puligny is arguably the finest region for growing Chardonnay in the world. I submit that much of the success Puligny has enjoyed, is in part because the water table is high, coupled with the fact that the village and its vignerons have invested heavily in water control features to channel and redirect excess runoff.

Reshuffling the wine weight matrix

The revelation that well-concentrated wines can be produced from these “wet” vineyards, has thrown slope position into a far clearer focus. No longer did we have lighter-to-medium weight wines on the upper slopes, the heaviest wine on the curb of the slope, and the very lightest wines coming from the lowest and flattest areas of Burgundy. Now it was clear: the areas with deeper, richer soils, particularly those with clay to marl soils, can universally produce richer fuller-bodied wines. This increasing quality of Bourgogne and the lower-situated village wines has dramatically raised the bar of expectations of wines across the Côte d’Or. With Bourgogne’s challenging the more highly regarded village-level vineyard in terms of quality, and village wines posing a challenge in regards to quality to many of the premier crus, lackluster producers were now put on notice to raise their game in terms of coaxing harmony and complexity out of their wines. Now that wine weight can be achieved in vineyards all across the Côte, despite a low slope position below the highway, expectation that Bourgognes are the simple, light and often shrill wines of yesteryear has been largely shattered.

Additionally, there is adequate evidence that deeper soils, particularly those with moderate-to-high levels of clay (or other fine earth fractions), can be a positive factor, for their ability to retain water and nutrients for the vines. This allows them to develop anthocyanins and other flavor components within the grapes. The challenge in these low-lying vineyards is controlling, and dealing with excess water.  In wet years, vignerons have demonstrated that adequate investment to direct and control runoff, even most lower vineyards will not be too wet to grow good to high-quality fruit. Examples abound of village crus, from top vignerons, costing more than many grand crus; and these producers Bourgognes are not far behind in price. It’s not magic; it’s investment and hard work, in a decent vineyard, that makes this kind of quality possible.

Author’s Note: To avoid misunderstanding, this is a discussion of wine weight and concentration, not wine quality or wine complexity. Too often these things are confused, along with the notion that increased enjoyment equals increased complexity or quality. The goal is to understand and appreciate the differences and nuances that each vineyard provides by its unique situation, not to make it easier to find the most hedonistic wine possible.

Understanding the Terroir of Burgundy, Part 3.1: The confluence of stone, slope and soil

Analysis: Combining what we know about limestone and soil, and applying that to a slope allows us to be predictive of topsoil makeup.

by Dean Alexander

slope comparison

Rise ÷ Run = Slope

It has always been my contention that the slope determines a vineyard’s soil type, and it is the soil type that is a major factor in wine character. Because many vineyards carry through the various degree of slope through the profile a hillside, the soils vary greatly from top to bottom. Water and slope work together to cause this. Rainwater both causes the development of clay on the hillside, and is the reason clay and other fine earth fractions will not readily remain on a slope. But lets start with a hillside typical of one found Burgundy, and the fractured stone and scree and colluvium that resides there.

Slope diagram

The 315 meter elevation represents a grand cru vineyard profile. The 350 meter profile represents a steeper rise which would be typical of a premier cru, which sits above a grand cru located on the curb of the slope. This added elevation and degree of slope, greatly changes the soil type at the top of the hill and decreases the soil depth, and at the same time increases richens and thickens the soil type, and deepens the soil in the lower grand cru section.

The typical Cote de Nuits hillside vineyard rises about 100 meters (328 feet). The base of many appellations sit at roughly 200 to 250 meters elevation, and here the vineyards are quite flat. As you move toward the hillside (facing uphill) it is common for there to be roughly a half a degree rise on the lower slopes. After 300 to 400 meters, the slope gently increases over the next 150 to 200 meters to roughly a 2 to 3 percent slope, where the grand crus generally reside. The upper slopes can rise dramatically in places, depending on the how wide the sections of bedding plates between faults, and pulled out and down with the falling Sôane Valley, and how much the edges of those bedding plates have fractured and eroded, also sliding down the hill. Areas like Chambertin, this slope remains moderate and the vineyard land remains grand cru to the top of the slope. However, above Romanee-Conti, the slope becomes much more aggressive, and the classification switches to premier cru at the border of Les Petits Monts. This uptick in slope, and the change in classification is common, but not universal in its application. As most things in Burgundy, there are a lot of exceptions to classification boundaries, notably for historical /ownership reasons.  

fractured limestone base exposed

If we were to strip away the fine earth fractions what we would expose is a fractured limestone base. Here the exceptionally shallow soil of Meursault Perrieres is peeled away and the limestone below is laid bare. The very shallow depth of soil, despite the relatively shallow slope suggests significant erosional problems.

Limestone derived topsoil types

If you could magically strip away all the dirt from the fractured limestone base of the Côte d’Or, leaving only a coarse, gravelly, sandy, limestone topsoil, and watch the soil development, this is what would happen: Over time, with rainfall, carbonization (the act of making the calcium carbonate solvent by carbonic acid in rainwater) would produce clay within the fractures of the stone. This new clay, is called primary clay (see Part 2.1) and gravity would have it settle to the lowest point in the crevices between the stones, below actual ground level. This primary clay will be rendered from weathering limestone everywhere on the Côte, from the top of the slope to the bottom of the slope, and tends to develop into a 9:1 to a 8:2 ratio of limestone to clay. This is the origin of limestone soils, and it is called… marly limestone.

Limestone to Clay diagram

 

limestone-clay diagram 2

I developed this diagram to express the different combinations and geological names of limestone mixed with clay and their agree upon percentages by the geological community. Marl dominates a full third of this diagram from 65 percent limestone/35 % clay to 65% clay / 35% limestone.

 

Marly Limestone – upper slopes: 90% to 80% limestone to clay

There are two common (and well-defined) terms that describe essentially the same soil type, applying different names and using differing parameters. This represents the purest, least mixed soil type on the Côte, and it is found on steeper (typically upper) slopes.

Clayey Limestone: the proportion of limestone in the mix is between 80% to 90% – source Frank Wittendal, Phd. Great Burgundy Wines A Principal Components Analysis of “La Côte” vineyards 2004) 

Marly Limestonecontaining 5-15% clay and 85-95% carbonate. source: The Glossary of Geology, fifth edition. (julia a. jackson, james p. mehl, klaus k. e. neuendorf 2011).

This is new, primary clay is not sorted by size, causing it to be rough in texture. Also of note, it is not plasticky like potters clay (kaolin clay) because of the irregularity of the particle size, which doesn’t allow its phyllosilicate sheets to stack, like it will once it is transported by water and reforms lower on the slope.

 

_______________

The Limestone to Clay diagram can virtually be tilted on upward and applied to the Côte to represent its topsoil makeup. The only part of it is missing is pure limestone because wherever there is limestone, clay has weathered from it.

It is no accident that you can turn this progression of limestone to clay into a general slope-soil diagram. The reason, as always, is water.

It is no accident that you can turn this progression of limestone to clay into a general slope-soil diagram. The reason, as always, is water.

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The fact that limestone and clay continues to exist in this 9:1 to 8:2 ratio (the stone does not continue to accumulate clay although it continues to develop it) allows us to deduce two things: First, the clay gains sufficient mass (depending on how close to the surface it is developing) where it can be eroded down the hill by rainwater runoff when it reaches roughly a 5% to 20% proportion of the limestone soil matrix. This static ratio also suggests that it exists only where erosion is a constant condition, meaning marly limestone can exist only on limestone slopes. It is erosion that maintains this general ratio of clay to limestone; limestone which will always produce primary clay as long as there is rainwater present. Of course, there may be other materials as well present in this mix, perhaps fossils, quartz sand, or feldspar.

I asked Pierre-Yves Morey, a noted winemaker in Chassagne, what was the texture, or the feel, of this marly limestone soil, is, and he described it simply as compact. “You would have to come to Burgundy and come see it.” I was looking for a little more richness to his description, but that is what I got. So… the definition of compact. The Glossary of Geology, 5th ed., defines compact (among other meanings) as “any rock or soil that has a firm, solid, or dense texture, with particles closely packed.” So there you have it. Clayey Limestone/Marly Limestone.

Argillaceous Limestone – mid-slope: 80% to 65% limestone to clay

The next incremental level of limestone to clay (75% to 25%) is not commonly cited, but sometimes referred to as Argillaceous Limestone or Hard Argillaceous Limestone. As a pure descriptor, this name isn’t especially helpful, since Argillaceous means clay. I also found another reference that called this ratio of limestone to “Mergelkalk” which is the German  for “marl chalk”, and this name indicates at least a progressive amount of clay over clayey limestone. This ratio of limestone to clay is not widely used, because, I suspect, it exists in the fairly narrow area of transition areas between marly limestone and Marl.

We might presume this ratio of limestone to clay appears not on the steeper slopes (generally above), but rather as the slopes grow more gentle, where to transported clay (from the steeper grades) may begin to flocculate as the rainwater runoff slows, adding to the primary clay growing in situ.

Because primary clay is more prone to erosion because of its mixed sized particles make its construction less cohesive, it is likely some of the primary clay developed in this lower location will be eroding further downslope, even as finer clay particles traveling in the rainwater runoff are starting to flocculate into transported clay in the same location.

With this high ratio of limestone to clay, it would be likely the be a compact soil, but because of the increased amounts of clay, not to mention some of it being transported clay, it will both have more richness and better retain water and prevent rapid evaporation.  Incidentally, his ratio of 75% limestone and 25% clay incidentally, is the recipe for industrially made Portland Cement.

Grand crus on compact marly limestone or argillaceous limestone: None

 

Marl – mid to lower slope: 65% to 35% limestone to clay

The beauty of, and the problem with, the word marl is its breadth of meaning. Marl as a term covers a wide variation of soils that contain at least some clay and some limestone, with many other possible components that may have been introduced from impurities on the limestone or from other sources within or outside the Côte.(1) But since we have magically stripped away the hillside, let’s imagine marl of its most simple combination: limestone and clay. Once the proportion of clay has risen to 1/3 of the construction with limestone, it is considered marl. It will continue to be considered Marl until clay exceeds 2/3 of the matrix. This is the definition established by the American geologist Francis Pettijohn 1957 in his book, Sedimentary rocks (p410).

Marl is an old, colloquial term that geologists may not have completely adopted until fairly recently. Perhaps it is because of this, that the definition of marl has an uncharacteristically wide variance in meaning, can be applied to a fairly hard, compact limestone soil, to a loose, earthy construction to a generally fine, friable, clay soil.  I imagine that on the clay end of the marl spectrum, the soil begins to become increasingly plasticky, due to the increasing alignment of the clay platelets by the decreased lime in the soil. This is purely subjective on my part.

Marl is most often noted in the same positions on a slope as colluvium, at a resting place of not much more than a 4 or 5% grade.  To attain a concentration of clay of at least 1/3 (the minimum amount of clay to be marl) rainwater runoff must slow enough for the clay’s adsorptive characteristics to grab hold of passing by like-type phyllosilicate minerals and pull them out of the water passing over it. As you can imagine, in a heavy deluge, with high levels of water flow, this will only happen lower on the slope, but in light rain, with a much less vigorous runoff, this will occur higher on the slope. How far these clay mineral travel down the slope before flocculation all depends on the volume of water moving downhill, and its velocity, which tends to be greatest mid-slope.

We can safely deduce that the first marl construction on our magically stripped slope consists of 15% primary clay (maximum) because that is what we started with, 20% transported clay which has been adsorbed to the site, and 65% limestone rubble (rock, gravel, sand and silt). Here, the ratio of stone in the topsoil is lower than in the slope above, because the topsoil is deeper, and the stone represents a small proportion of the ratio. Additionally, it is very possible that some of the primary clay, which is more readily eroded, may have been washed further downslope, in which case the percentage of transported clay would actually be higher.

It also stands to reason that the soil level is significantly deeper where marl resides by a minimum of 15%, due, if only because of it’s increased volume of clay to those soil types above if the limestone concentration in the soil remains constant from top to bottom.  Of course, we know that fracturing of the limestone, erosion and gravity have moved limestone scree downslope.  If you could know that volume of additional limestone that had accrued on the slope, and then factor in the percentage of clay, you could effectively estimate the soil depth. Farther down the slope, marl with 65% clay to 35% limestone, we can assume to have a minimum of 30% deeper soil levels, but again, that depends on the limestone scree that has moved downslope as well. Notes of excavations by Thierry Matrot in 1990 in his parcels of MeursaultPerrières show one foot or less topsoil before hitting the fractured limestone base, whereas his plot of Meursault-Charmes just below it, was excavated to 6 feet before hitting limestone.(3) This indicates, a significant amount of limestone colluvium had developed in Charmes (some of which may have been the overburden removed from the quarry at Clos des Perrières?) that has mixed with transported clay to attain this six-foot depth of marl dominated soil.

Wittendal’s work analyzing the vineyards of Burgundy (2004) revolved around statistical methods tracking values of slope and soil type, among other 25 other factors. From that, he plotted the vineyards as data points to try to develop trends and correlations. I was not surprised by his results, as it confirmed many of my assumptions about slope causing the types of soils that develop there. Of note, though, to some degree, his work dispels some of the assertion that marl/clayey soils reside more in Beaune and limestone/colluvium soils reside primarily in the Nuits.

Wittendal plots a perfect 50-50 marl to colluvium, as point zero in the center of a four quadrant graph (Figure 8 – The Grands Crus picture components 1 & 2). On the left side of the graph would be the purest expression of marl. This represented as negative four points of standard deviation ( σ ) from zero (the mean). On the right, the purest representation of colluvium is four points positive of standard deviation ( σ)  from zero (the mean).

Grand Crus on marl soils: more than one standard deviation (neg)Corton Charlemagne (one section with a standard deviation of -3.5, and another section at -1.5 )  Chevalier-Montrachet -1.75.

Grand Crus Primarily on marl soils with some colluvium: near one standard deviation (neg). Only one lower section of the Pinot producing Corton has a surprising amount of marl – the vineyard is not named (-1.25 ) and Le Montrachet with a surprising amount of colluvium (-.8 )

Grand Crus on slightly more marl than colluvium: Romanee-Conti sits on slightly more marl than the mean  (-.3), La Tache sits right near zero.

Grand Crus on slightly more colluvium than marl: less than one-half the standard deviation. Musigny, Bonnes Mares and Ruchottes-Chambertin. (.333)

 

Ruchottes inclusion here is at first surprising. But since there appears to be little chance of colluvium to develop on this upper slope, coupled with its shallow soils, it is this soil construct makes sense. In fact, this highlights that Wittendal’s work represents the ratio of marl to colluvium, rather than the depth of marl and colluvium present.  It is my contention that the most highly touted vineyards have significant soil depth and typically have richer soils. Ruchottes, which many have suggested should not be grand cru, has little soil depth (which is a rock strewn, quite compact marl), and the vines there can struggle in the little yielding Premeaux limestone below. A vine that struggles, despite all of the marketing-speak of the last two decades, does not produce the best grapes.

 

Clay Marl – lower slope: (a subset of marl)

Clay marl seems to be within the defined boundaries of Marl. One would suspect this to be in the 35-45 limestone with the remainder being clay. It is described by the Glossary as “a white, smooth, chalky clay; a marl in which clay predominates.” No specific ratios are given.

Marly Clay – lower slope 15% carbonate 

Marly Clay, and also referred to as marly soils are 15% carbonate and no more than 75% clay. At this point, it seems the use of the word limestone has been discontinued. Perhaps at this level we are dealing with limestone sand sized particles and smaller, perhaps with pebbles. There must be silt and clay sized limestone particles before complete solvency, but I have never seen mention of this. It is likely the carbonate is solvent, influencing, and strengthening the soil structure, and affecting to some degree, clay’s platelet organization? As much as I have researched these things, I have never seen this written. The soil just is the soil at this point.

Deceptive here is the need to discern limestone sand from quartz or other sands. Limestone sand will be “active” meaning it would be releasing significant calcium carbonate into the soil (disrupting the clay’s platelet alignment) and would be actually be considered marl. I imagine the degree of plasticity to the soil would be the shorthand method to determine this, although I understand if you pour a strong acid on a limestone soil, it will visually start carbonization (fizzing).

Could it be, that in marketing of limestone as the key factor in developing the legend of Burgundy, the Burgundians may have swept the subjects of claystone and shale under the rug?

 

Clayey soils – Sôane Valley fill 

Worldwide, most clayey soils develop from shale deposits. Geologist Francoise Vannier-Petit uses the word shale to explain clay to importer Ted Vance in his writing about his day with her. In fact, she virtually used the term clay and shale interchangeably. However, other than that writing, I have never seen the word shale used in Burgundy literature. This might lead one think that shale is not existent on the Côte. Clayey soils are a large component of the great white villages of the Côte de Beaune however, and ignoring shale as a major source of this clay may be a mistake. Vannier does mention alternating layers of limestone and claystone in Marsannay in the marketing material the Marsannay producer’s syndicate produced which I discussed at length in Part 1.3.  Could it be, that in marketing of limestone as the key factor in developing the legend of Burgundy, the Burgundians may have swept the subjects of claystone and shale under the rug?

 

Clayey sand and loam (no carbonate)

We've seen this before, under the guise of the USDA soil diagram. Here is the original by Francis P. Shepard

We’ve seen this before, under the guise of the USDA soil diagram. Here is the original by Francis P. Shepard

Wittendal uses “Clay with silicate sand” as one defining soil type in his statistical analysis of Burgundy vineyards. He does not give a percentage breakdown he is using for this soil type. However, reaching again to the Glossary of Geology, the most straightforward of definition is attributed to Geologist Francis Shepard: An unconsolidated sand containing 40-75% sand 12.5-50% clay and 0-20% silt.’ (Shepard 1954)“. Unconsolidated means that it is not hardened or cemented into rock. Of note: the definition attributed to Shepard is slightly at odds with the diagram to the right which Shepard is most known for, which has clayey-sand contains no more than 50% clay. The definitions of clayey-sand and loam clearly overlap. At one extreme, Clayey-sand can also be defined as a loam.

Clay-loam – clay sand

Clay-loam is a soil that contains clay (27-40%),  sand (20-45%), with the balance being silt, all of which have very different particle sizes. If you apply the lowest percentage of clay 27%, and a high percentage of sand 45%, and the remainder, silt at 28%; this combination doesn’t somehow doesn’t seem to fit the description well. Clay-sand is overlapping with clay-loam but generally consists of 60% sand, 20% silt and 20% clay.

Clayey-silt

Clayey-silt In 1922 geologist Chester Wentworth defined grain size. Clayey-silt thusly is 80% silt-sized particles, no more than 10% clay (which particles are substantially smaller), and no more than 10% coarser particles of any size, though this would be primarily of sand-sized and above.  Conversely, Francis Shepard’s definition of clayey silt in his 1954 book, is 40-75% silt, 12.5-50% clay and 0-20% sand. 

*Grand Crus on clayey soils: None

Colluvium, Breccia – mid to lower slope (and Scree – everywhere)

The scree filled Les Narvaux in Meursault. photo: googlemaps

The scree filled Les Narvaux in Meursault. photo: googlemaps

Colluvium and breccia are very similar. They are both rubble that has amassed on a resting place on a slope.

Breccia has a more specific definition, being at least 80% rubble and 10% clay, and can be loose or like any soil type, become cemented into rock. Incidentally, that 10% clay ratio has come up again, because just as the marly limestone I spoke of before, the stone will weather primary clay, but rainwater erosion consequently will remove it as the clay gains mass. The stones that form these piles are what geologists refer to as angular because they are fractured from larger rock, they have angular or sharp edges. This remains true until the stone has become significantly weathered by the carbonic acid in rainwater.

Colluvium, on the hand, is a construction of all matter of loose, heterogeneous stone and alluvial material that has collected at a resting place on a slope, or the base of a slope.  These materials tend to fall, roll, slide or be carried to the curb of the slope as scree (those loose stone that lies upon the surface) or washed there by runoff. In Burgundy, the rocks of colluvium and breccia are likely mostly limestone.

Rocky soils, such as colluvium and particularly breccia, are less prone to compaction because of the airspace is inherently formed between the rocks as they lay upon one another. This protection against compaction should not be overlooked as a major indicator of vine health and grape quality these colluvium sites provide. Drainage through a rocky colluvium surface material can be, let’s say, efficient, and this too is a natural defense against soil compaction, because a farmer must be cautious about trodding on wet soils because they compact so easily. Chemical weathering will develop primary clay deposits amongst the stone, and the stones themselves will slow water as it erodes down the hill, likely giving this primary clay significant protection from erosion.

Grand Crus on colluvium soils more than one standard deviation. With the most colluvium are the vineyards of Clos Vougeot with a range of σ ( 2 to 2.7) and Romanee St Vivant (1.8). followed by Most of the red vineyards of Corton sit largely on colluvium (1.25 to 1.75) Echezeaux (1.1).

Grand Crus on colluvium but with more marl: within 1 standard deviation. Charmes, Latricieres, and Richebourg form a cluster of vineyards with a σ of  (.5 to .75) with just a little more colluvium than the Musigny, Bonnes Mares and Ruchottes all at roughly a σ of .4.   source Wittendal 2004 (figure 8)

Here we find some interesting groupings. First, the grand crus with the most colluvium are generally considered in the second qualitative tier. The outlier there would be Romanee St-Vivant, which while great, is not considered to be in the same league as Vosne-Romanee’s other great wines, Romanee-Conti, La Tache, and depending on the producer, Richebourg. Are high levels of colluvium cause the vines more difficulty than those planted to vineyards with a heavier marl component?

Colluvium Creep and landslide, in this case at Les Rugiens in Pommard. The steep slope being Rugiens Haut, and in the foreground, its benefactor, Rugiens Bas. Here is an example of two vineyards that should be separated in the appellation, but both are labeled as Rugiens.

But this question rolls back to ratios of how much colluvium there is in relation to how much marl is in that location, what is the ratio to clay to limestone in the marl at each site (which would change the placement of zero (which would change the mean), and lastly, at what point is it no longer colluvium but marl or vice-versa?

Colluvium Creep

Colluvium is known to creep, meaning it continues to move very slowly downslope since it is not anchored to the hillside bedrock, rather it rests there. It is not uncommon to see the effects of this creep in tilted telephone poles and other structures on hillsides. Creep is essentially a imperceivably slow landslide. The most obvious creep/slide in Burgundy is the slope of Rugiens-Haut onto Rugiens-Bas, in Pommard.  Gravity, being what it is, nothing on a slope is static, and colluvium will, so very slowly, creep.

 

 


 

Authors note:

What I write here, is a distillation of the information laid out in the previous articles, and my weaving together all the information to build a picture of the various soil types and the slopes that generate them. Much of this is my own analysis, cogitation, and at perhaps at times conjecture, based on best information. 

As I mentioned my preface, I had come to some of these conclusions when researching vineyards for marketing information and noticed a correlation between slope and soil type.  The research that formed the basis of the previous series of articles, was done to see if the science of geology supported my theory that a vineyards position dictates the soil type there. I think it does.  Ultimately the goal of these articles is to lay down a basis for explaining and predicting wine weight and character, independent of producer input, based on a vineyards slope and position.

Where science generally begins and ends are with the single aspect of  their research.  That is the extent of their job. Scientists rarely will connect the dots of multiple facts for various reasons. It can move them outside their area of examination, or it may not have a direct evidence to support the correlation, or the connection of facts may have exceptions. The study of the cote is clearly would b a multi-discipline enterprise. There is no cancer to be cured, no wrong to be righted, and no money to be made off of understanding it’s terroir. So it has been largely left to the wine professional to ponder.  These are my conclusions. I encourage you to share yours.


 

(1 & 2) Vannier-Petit discusses alternating layers of Claystone and Limestone in Marsannay. While I have never read this of the rest of the Côte d’Or, the Côte has never been examined as closely as Vannier-Petit is beginning to examine it now. Layers of claystone may well exist, and given the amount of clay in the great white regions, this may well be the case.

(3) Per-Henrik Nansson “Exploring the Secrets of Great Wine” The Wine Spectator, Oct. 25, 1990

 

Understanding the Terroir of Burgundy, Part 2.2: Soil formation

We all know what soil is, or at least we think we do. If I were to ask you what was in soil, what would you say?

by Dean Alexander

In healthy soils, minerals typically only represent slightly less than half of the volume of soil, while air and water incredibly represent much of the rest. Here is the soil of La Tache in Vosne Romanee.  photo: leonfemfert.wordpress.com

Soil: 45, 25, and 25%

Despite all the talk about limestone, to really understand the terroir of Burgundy, we really have to understand what soil is and the material from which it is eroded. The mineral component, or the part we think routinely of as soil, are typically only 45% of the soil matrix. The balance is actually 25% air, and a further 25% of water, with the last 5% being split between humus (4%), roots (.05% ), and organisms (.05). It would make sense that this percentage changes seasonally, depending on how much water is in the soil from rainfall (or the lack of it) which changes the ratio of minerals, water, and air. Further, these ratios can change based on soil compaction, which decreases the air in the soil, which in turn increases the percentage of the mineral and organic component.  Why is this important? Because this is the environment that the vines live and they require a certain ratio of each of these components to produce high-quality grapes.

Cote soil influencers

I developed this graphic to illustrate the assorted soil formation processes that affect the Côte, and are described in depth in Limestone Fracturing in Part 1.2, and from Limestone to Clay in part 2.1, in earlier articles in this series. This article, Part 2.2 Soil Formation, builds upon those earlier concepts.

 The 45%: Burgundy’s mineral makeup

The French refer to the loamy Saône Valley fill as Marne des Bresse. The earth there is very deep, and typically is too wet for high-quality grape production. Historically this been used for pasture land for sheep and cattle. With every storm, this rich loam from the valley intermixes a little bit more with the soils of the boundary vineyards, and even encroaches on the loose, stony soils of the Côtes lower slopes.  ‘Interfingering’, was how geologist James E. Wilson described this mixing of soils in his 1990 book, Terroir: The Role of Geology, Climate, and Culture in the Making of French Wines.

Bore samples, according to Wilson, had indicated that this interfingering has reached westward, up the hill, to influence the soil construction of the lower sections of the grand cru Batard-Montrachet. With this information, he inferred that the Saône fault must be near.  It is notable that in 1990 precise location Saône fault was not known, and around Puligny, it still may not be. I suppose the wealthy Puligny vintners have no need to explain why Puligny-Montrachet is great. Vannier-Petit however, does tacitly show the Saône fault in her map of Gevrey, which is represented by the abrupt end of the limestone bedding east of RN74.

The ravine Combe de Lavaux defines character of most of the premier crus of Gevrey-Chambertin, but more importantly, its alluvial wash greatly expanded the growing area of vineyards below the village. Click to enlarge

The ravine Combe de Lavaux defines the character of most of the premier crus of Gevrey-Chambertin, but more importantly, its alluvial wash greatly expanded the growing area of vineyards below the village. Click to enlarge

Because the Côte is an exposure of previously buried, older limestone, younger soils line the divide on either side of the escarpment. The Saône Valley’s Marnes de Bresse brackets the Côte on the eastern, lower side of the slope, while younger rock and soil material that cover the tops of the hills, to the west, and beyond.

From the hilltops above, those younger soils have eroded down, bringing feldspar and quartz sand, silt, as well as phyllosilicate clay minerals, to help fill in and strengthen the rocky limestone soils of the Côte. In many places, geological faulting, coupled with runoff or streams, have created combes or ravines which have allowed substantial alluvial washes to extend the planting area of the Côte. A prime example of this is the Combe de Lavaux which is a dominate feature of the appellation of Gevrey-Chambertin.  It has sent a large amount of alluvial material around and below the village of Gevrey, creating good planting beds for village-level vineyards. Alluvial soils are nothing more than a loose assortment of uncemented of soil materials that have been transported by rain or river water. These materials are typically sand, silt, and clay, and depending on the water flow, various sizes of gravel particles. It is this sand and gravel that has traveled with the water flow from the Combe, that provides these vineyards that protrude past the limestone of the escarpment the drainage the vines require.  These are not, however, the soils that will produce the great premier cru, or grand cru, wines for which Burgundy is famed.

a graded sediment bedSoil suspension and graded bedding

Soil moves downslope by water erosion, the force of gravity, and even is transported by the force of significant wind. With movement, the particles within the topsoil are in a state of suspension. Geologists refer to this movement and suspension as turbidity. Because of their weight, gravel travels downward in the moving soil, creating a progressively sorted soil, with coarser pieces on the bottom, while the finer particles find their way to the top.  The result of this is called a graded sediment bed. (1)

While it is easier to see how a graded bed might be created in a stream bed below a ravine like the Combe de Lavaux, I was somewhat perplexed how this might occur in Alex Gamble’s Les Grands Champs vineyard in Puligny-Montrachet, see Clay part 2.1.  Here gravel bedding lay at 80cm, a little more than two and a half feet below the surface. Above the gravel, sat a foot and a half of heavy, yellow, clay-dominated soil. This was, in turn, topped by nearly a foot of loamy-clay soils. Vannier-Petit estimated these soil horizons, as geologists refer to them, were created between two and five million years ago by water runoff. What kind of run off?  I realized that the kind of runoff that creates graded bedding happens often, like in this photo (below), taken in Pommard during the winter/spring of 2014, by winemaker Caroline Gros Parent.

This is how graded bedding develops.

This is how graded bedding develops. Here the road to Pommard has flooded in the winter storms of 2014. Photo: Caroline Parent via twitter

Parent material

Geologists talk about a soil’s parent material because every element of soil came from a different material, which was then weathered, both mechanically and chemically, into various sizes. These minerals will then accumulate, either poorly sorted into an aggregate material, or they can be well sorted by the wind, water, or gravity into size categories. Sand and silt are generally said to have been created by mechanical weathering, although chemical weathering is always a present force, as long as there will be rain. Sand can be made of any parent rock material, but in Burgundy, there are sands made of granite, in addition to plentiful limestone sand. (2) We know this because there is loam present (as well as graded bedding), in the Grands Champs vineyard from the Saône valley fill below. The water that carried this non-limestone, Côte-foreign material, would have carried quartz sand with it as well when it created the graded bedding there. This gives us a very important insight into the construction of the soils of Burgundy.

Fine earth fractions

Fine Earth Fractions are the trinity of sand, silt, and clay. Gravel and sand can be made of limestone or other rock that has been weathered into smaller and smaller pieces, but silt is typically feldspar or quartz. Clay is much, much smaller in size, and is created by chemical weathering of rock. Its parental material can be limestone, granite or other stone.

Geologists grade soil minerals by size; the basis of which are particles that are 2 mm and smaller. These are called fine earth fractions and consist of sand, silt, and clay. In equal thirds of each of the three soil fractions is considered perfect for farming crops, and is termed loam. The various sizes of minerals in the soil makeup gives the soil its texture.

Clay, we have talked about in length in part 2.1, and differs from silt and sand because it is a construction from stone that has been chemically weathered, whereas silt and sand are derived from mechanically weathered rock. Additionally, clay is a construction of clay minerals that are bound with aluminum and oxygen by water and carries minerals within its phyllosilicate sheets. It is also important to mention that clay’s particles are considerably smaller in diameter, being less than 2 microns in size.  Soils with more clay hold more water,  so they require less frequent application. An overabundance of water in clay soils causes oxygen depletion in the root zone.  This can limit root development.  The abundant solvent calcium in the limestone soils Burgundy misaligned the clay platelets, loosening the soil, and allowing better drainage.

Diatoms (top) and Radiolarians bottom, fill the ocean floors with sediment.

Diatoms (top) and bottom, fill the ocean floors with sediment.

Silt is specifically formed from quartz and feldspar, and is larger than clay, being 0.05 mm-0.002 mm. We know that any feldspar in the soil, could not have come from weathered stone; neither limestone or granite, which was the dominant stone in the area when the limestone beds were forming, because it would have metamorphosed into a phyllosilicate clay mineral if it had. This means the feldspar has traveled onto the Côte, either from above or below the limestone strata.

While it might seem logical to assume the quartz in silt originated in the earth’s crust, and perhaps degraded from granite that was prevalent in the area, this may not be the case. The first problem is quartz is resistant to chemical weathering. And physical weathering like frost wedging of sand particles may continue to yield results beyond a certain size.

Researchers from the University of Texas at Arlington used (and I cut and pasted this) a “backscattered electron and cathodoluminescence imaging and measure oxygen isotopes with an ion probe.” They found that the 100% of silt quartz found in 370 million-year-old shales of Kentucky were made from the “opaline skeletons” of plankton, radiolarians,  and diatoms. This, they reasoned, might explain the lack of these kinds of fossils during the same period. These tiny animals had all been incorporated into the then forming shale. This may also be the case for the silt quartz of Burgundy, itself too having once been a Jurassic, seaside resort. This, in fact, this information also suggests this quartz silt may come from weathered shale that is much older than the limestone of the Côte.

A sandy soil horizon

A sandy soil horizon

Sand is larger than silt. being less than 2 mm, and typically is constructed of quartz or limestone particles. The limestone sand will weather to solvent calcium carbonate, but the quartz will not weather and will remain as sand. It is likely that significant quartz sand has been washed down from the hillsides, and certainly is a major contributor to alluvial soils below the combes. Sand drains so quickly that vines grown in sandy soil have more frequent water requirements, but require a lesser amount of water.  Adequate water maintains plant growth while minimizing the loss in the root zone.

 Plant and animal soil contributors

Grasses, with their dense root systems, are positively impactful to the topsoil. In their decomposition, darker soils are created to deeper depths, and the resulting soils also tend to be more stable.  In a monoculture of grapevines, many growers are finding this to be a significant advantage. In Australia, some grape growers are using grasses to help lower soil temperature in efforts to slow down ripening in an ever-warming climate.

Much is made by those practicing sustainable and organic cover crop encourage populations beneficial predator insects and birds, but grasses and cover crops also encourage subsoil organisms and microorganisms growth as well. Most common are bacteria and actinomycetes (rod-shaped microorganisms), which by weight have been found to be four times more present by weight than earthworms in healthy soils. While these are important to the quality of the wine, they are only an intricate part of terroir if it is practiced by the farmer.

The 25%: Air (and soil compaction)

Soil compaction relates to poor water infiltration and low oxygen levels. drawing: landscaperesource.com

Soil compaction relates to poor water infiltration and low oxygen levels. drawing: landscaperesource.com

The proper amount of airspace between mineral fragments is very important for vine growth and allow for water to penetrate and be retained by the soil. Soils with diminished airspace are said to have soil compaction, and compaction is difficult to correct once it has occurred. The Overly tight spacing between the mineral component of a soil restricts oxygen levels and contributes to a poor water holding capability.  Rainfall itself can cause some soil compaction, but most commonly walking or operating farming equipment on moist soils does the most damage. In drought years, soil compaction can lead to stunted vine growth and decreased root development. In wet years, soil compaction decreases aeration of the soil and can cause both a nitrogen and potassium deficiency. Additionally, without adequate porosity to the soil, water cannot easily penetrate the soil during a rainstorm. Water that cannot infiltrate soils of flat terrain can stagnate, which further compacts the soil,  or on sloped terrain will runoff, which can create erosion problems.

Positive effects of moderate compaction

As moisture of the soil increases, so does the depth of compaction.

As moisture of the soil increases, so does the depth of compaction.

Moderate compaction can have some desirable effects. Moderate compaction forces the plant to increase root branching and encourages secondary root formation. This additional root growth is the plant’s response to not finding enough nutrients with its existing root system. Plants with more extensive root systems are more likely to find nutrients that are not carried by water, like phosphorus.  Obviously, more compaction is not better, because it impedes root growth, lessens the oxygen in the soil, and repels water from penetrating the soil.

While deep tillage 10-16 inches can shatter the hard packed soil, studies have shown that crop yields will not return to normal following the effort. While there are factors that might cause the soil to return to compaction, like a farmer, unintentionally re-compacting their soils, more than likely tilling does not return the airspace that was lost in the soil itself. Further continuous plowing and tilling at the same depth can cause serious compaction problems on the soil below the tilling depth.

The 25%: Water (the key to everything that Burgundy is)

It should be impossible to talk about soil without talking about water, given it is optimally 25% of soil’s makeup. It is certainly tempting to pass over the subject of groundwater and lump it into erosion, but that would really shortchange our understanding of the Cote. Part of Burgundy’s success can surely be attributed to relatively steady rainfall year round, coupled with the fractured limestone’s ability to hold water until its reserves of water which is held within the stone can be recharged by future storms.

Good drainage, well-drained? Let’s reset the dialogue.

The infiltration of rainfall by the soil is the first and perhaps most important factor in recharging groundwater levels. Like I wrote of compaction, the soil has to be porous enough to penetrate the topsoil and subsoils successfully. The buzz word in the wine world is drainage, with terms like well-drained, and good drainage appearing often. I suppose we picture the roots drowning in mud if there isn’t good drainage. But the idea of good drainage really simplifies the issue. Drainage can have to do as much to do with compaction as soil materials or slope. Soil drainage is important in fighting erosion as well not causing additional soil compaction. Good drainage, which is what happens with a well-aerated soil, allows the vines roots sufficient oxygen and nitrogen and allows the roots to take in nutrients like phosphorous and potassium. But none of this can happen if the soil releases rainwater too quickly, and the vine can perform none of these vital tasks. The reality is, it is not the fact that a soil well-drained, but rather it drains at the adequate rate for a given rainfall. Obviously, this will not always be a perfect equation since rainfall varies greatly depending on the year and the time of year.

The speed of drainage

water movement through various soil types. source: usda-nrcs

Water movement through various soil types. source: USDA-nrcs

The kinds of materials that make up the soils contribute greatly to the rate of water ability percolate through the material. The speed of the mater’s movement depends on the path the water is channeled in. The most direct path that is in line with gravitational pull will give the fastest drainage.

Water movement comparison through sand and clay. Soure Coloradostate-edu.

Water movement comparison through sand and clay. Source Coloradostate-edu.

Sandy soils, as one might expect, drains quickly because it consists of only slightly absorptive, small pieces of stone, that allow the water to essentially slide right past.

Clay, on the other hand, is very dense and plasticity. These characteristics, as you might expect, would be resistant to allowing water to pass through, and large bodies of transported clay can redirect horizontally, the flow of water percolating through from above due to it’s slower absorption rate. But what isn’t obvious is that clay’s construction encourages capillary action. The clay body will distribute water throughout its mass, counter to gravitational pull, becoming completely saturated, before releasing excess water through to the material below.

Argillaceous Limestone

Argillaceous Limestone with its horizontal fracturing slows water percolation. click to enlarge

Highly fractured limestone that is still in place, is often is fragmented in a prismatic pattern. However some limestones, like this soft argillaceous limestone to the right, with its high clay content, may fracture horizontally. The type of fragmentation would depend on the stresses upon the stone, the freeze-thaw effects of water and temperature, as well as the material of the stone’s construction. Clay based stones will tend to fragment horizontally and when they do, they are considered platy, and water will percolate more slowly than stones that fracture in a prismatic fashion.

Water movement through soil

The hillside of the Côte is a recharge area for water collection, while the valley below is a discharge area, where excess water is expelled. The water table is at the capillary fringe. Water uses faults and fissures to move quickly into and out of the saturated zone. It is likely there are aquifers, meaning caves which have been cut out of the limestone by carbonization below the Côte, where the water is stored.

 

a small karst aquifer Photo:planhillsborough.org/

A small karst aquifer in Florida. Photo:planhillsborough.org/

Groundwater, the water table, and karst aquifers

In writings regarding Burgundy, very little is said about ground water, other than there are no cellars built underground in Puligny because the water table is too high there. A plentiful water supply may be one of the features that propel the vineyards of Puligny into the ranks of the worlds best. As my diagram above shows, water percolates through the soil and stone. This upper section is called the vadose zone, or unsaturated zone. Slabs of limestone, fissures, faults, and clay bodies all can change the course of the water flow. Each horizon of soil and each layer of stone have their own rate of percolation. With this much limestone, it is very likely there are karst aquifers or large caves caused by the carbonization of calcium carbonate beneath the Côte, but I could find no specific mention of aquifers in close proximity to the Côte. There is a mention in a European Academies Science Advisory Council‘s country report for France, that in Burgundy there are “karsified Jurassic limestone layers” somewhere in the region, but nothing more is elaborated upon.

There is a very famous and massive karst aquifer with seven very deep layers that spans from north of Burgundy across the Paris basin to the English channel. The deepest level of water is brackish. The uppermost section is called the Albian sands sits at than 600 meters, and was first was drilled into in 1840 taking well more than 3 years to achieve. The water there is 20,000 years old, and there has been discussion whether the water should be considered fossil, meaning there is a question whether there recharge from the water above, or not.

 

Next up: Understanding the Terroir of Burgundy, Part 3: Confluence of stone, soil, and slope

 


 

(1) Interestingly, larger stones, especially the flatter, rounded shaped stones that the French refer to as galets, tend move to the surface, probably because of their larger displacement values.

(2) Sand from other parent rock material is likely to be available as well.

Understanding the Terroir of Burgundy: Part 2.1 From Limestone to Clay

© BiVB Latricieres

Latricieres under brewing storm clouds.  photo © BiVB

by Dean Alexander

The weathering of limestone: let it rain

flooding

Rain and Flooding

For the past 35 million years, rainwater has endlessly and relentlessly washed across the limestone escarpment. To varying degrees, the limestone will absorb water through its pores, but stone that has been damaged by ductile deformation is much more easily infiltrated. Faster still, water fills the cracks and fissures created by geologic strain, finding freshly broken calcium carbonate to wetten, and begin the process of chemical weathering called carbonation.

Rain rainwater, it seems is more than just H2o.  From the storm clouds above, H2o binds to with carbon dioxide (CO2) to form carbonic acid (H2CO3). And although carbonic acid is typically a mild acid when carried by the rainwater, it does slowly act as a solvent to the calcium carbonate (CaCO3) that holds the limestone together. This carbonation frees the carbonate from the calcium, and will metamorphose the calcium into calcium hydrogen bicarbonate Ca(HCO3)2, which technically only exists in solution. (1)  The material that remains behind once it is no longer bound by bonds of the stone, is whatever impurities that were in the stone when it formed. This could include clay, fossils, feldspar which is the most common mineral on earth), among many other possibilities.

Nature’s Highly Engineered, Deconstruction of Limestone

Calcium Bicarbonate photo credit: Frank Baron/Guardian

The calcium carbonate in limestone is made solvent by the carbonic acid in rainwater.  The calcium carbonate is metamorphosed into calcium hydrogen bicarbonate  or Ca(HCO3)2. Technically calcium bicarbonate exists only as a water solution. As long as enough CO2 remains in the water, calcium bicarbonate is stable. But once excess Co2 is released, calcium carbonate is dropped out of solution resulting in the scale like on the facet above. photo credit: Frank Baron/Guardian

Calcium carbonate is more soluble in colder temperatures.  If you aren’t paying attention, this, along with so many other pieces of information might seem fairly unrelated. But like everything else, it is an important piece of the puzzle. It is all part of nature’s finely detailed engineering, where every element directly is related to, and influences the next.

This fact that calcium is more soluble in colder temperatures folds beautifully together with the freeze-thaw fracturing of the limestone that I detailed in Limestone: Part 1.2. The acidic water enters the more porous limestone, where it then freezes. This exerts immense internal pressure on the rock, which causes it to split along the pores, can cause various types of fractures within the stone.  Then when the acidic ice within the rock begins to melt, it erodes the stone along the fissures, being aided by the cold temperatures. The more acidic the rainwater, the more minerals the groundwater can dissolve and be held in solution. Interestingly, because lime is alkaline (a base as opposed to acid) it naturally balances the ph of the water, and thus the soil, which is good for the health the vines.

Clay Development = great vineyards

Puligny excavation at Alex Gamble

An excavation of the village cru, Les Grands Champs by Alex Gamble and Francoise Vannier-Petit. According to Vannier-Petit’s analysis, below the first 30 centimeters of dark clay-loam soil, lies a fine-grained, yellow clay. In its most pure form it is typical of transported clay being less than 2 microns, before mixing with heavier soils of increasing size down to an 80 cm depth. Here it transitions to more loosened substratum of “angular gravel” of 2 mm in size, which she also terms “heterometric stones”, providing good drainage for the site. See more at alexgamble.com

Les Grands Champs

Visual observation: Les Grands Champs is located on the eastern edge of the village of Puligny. The land here is be quite flat, with less than a one percent grade.  It sits at the foot of the 1er cru Clavillions (where the road turns to head up hill). Folatieres lies just above that, the bottom of which is denoted by the by the plot being replanted.

Every Burgundy vineyard that is considered to be great has at least some clay and some limestone in their makeup. But that is not surprising since  clay, is the byproduct of the chemical weathering of stone. The silicate materials (essentially the building blocks almost all minerals) in the stone are metamorphosed into phyllosilicate minerals. Putting that more simply: after stone is eroded by acid, some of the weathered material (depending on what the stone was made of) is transformed into a material that will become clay – once it attracts the needed aluminum, oxygen, and water.

Clays first forms at the site (in situ) of the stone that is being weathered, and this typically is a form of surface weathering. This new material is a primary clay, and sometimes referred to as a residual clay. These primary clays tend to be grainy, lack smoothness, and do not typically have qualities that are described as plasticity. As primary clays are eroded, (typically by water) and are moved to reform in another location, they are called transported clays.

This transportation changes the clay’s properties; this is likely because the water carries the lighter, smaller gains together, away from the larger, coarser material that remains in the in situ location. When transported clay reforms, the reformation is called flocculation. This natural attraction that clays have toward homogeneous groupings, are due not only to their similar size but because they carry a net negative electrical charge, which the particles gain by adsorption. Adsorption is not to be confused with absorption, is like static-cling. Items are added, or adhered by an electrical charge, to the grains, not absorbed by the grains.

In flocculation, particles are attracted to one another, by their uniform size (typically very small, under 2 micrometers), and shape (tetrahedral and octahedral sheets). These phyllosilicate sheets organize themselves, layering one upon another, like loose pages of sheet music. Between these silicate sheets, aluminum ions and oxygen are sandwiched. These elements bind together to form a clay aggregate, even in the confluence of water. Clay formations can carry with them, varying mineral components such as calcium, titanium, potassium, sodium and iron and other minerals, making them available to the vines. To say that the chemistry of clay gets very complicated, very quickly, is an understatement.

Transported clay has plasticity, which primary clays do not. When a clay is very wet, beyond its liquid limit, (meaning the most water a clay structure can hold before it de-flocculates), the sheets slide apart, giving clay its slippery feeling. Any thick area of clay found at a location is likely to a be transported clay, as the adsorption characteristic of clay allows it to achieve significant mass.

Sand 0.02 – 2.00 mm in diameter
Silt 0.002 – 0.02 mm in diameter
Clay < 0.002 mm in diameterClay types

Francoise Vannier Petit at AlexGamble

Francoise Vannier Petit, inspects the yellow ocher-colored clay in Puligny-Montrachet, Les Grands Champs.  Clays get their pigmentation from various impurities. Brown clays get their color from partially hydrated iron-oxide called Goethite. This yellow ocher clay gets its color from hydrated iron-hydroxide, also known as limonite. Clay type, however, is not determined by its color, but instead by its chemical and material organization.

Different clay types can be found next to each other or layered on top of one another. This layering is called a stacking sequence. photo source: alexgamble.com

The type of clay that is produced from the weathering of rock depends on the what minerals make up the stone.  In the case of granite (the stone which existed in the Burgundy region, before the creation of limestone), is constructed of up to 65% feldspar, and a minimum of 20% quartz, along with some mica. While quartz will not chemically degrade in contact with the carbonic acid carried in rainwater, feldspar and mica will. Even though they originate from the same stone, these two minerals will metamorphose into two different of types clay, that belongs to two different clay family groupings. Feldspar weathers into Kaolinite clay minerals and mica weathers to an Illite clay mineral. These tend to be non-swelling clays. (3)

I probably spent twenty hours trying to figure out what kind of clay eroded from limestone, before I realized that it would depend on what impurities were mixed into the calcium carbonate when it was brewed up during the Jurassic period.  Limestone can produce any of the four families of clay.

Kandites (of which Kaolin(ite) is a subgroup), are the most common clay type, because feldspar, which is the world’s most common mineral, metamorphoses into it.

The other three clay groupings are smectite, illite, and chlorite.(4) Within these clay family groupings, there are 30 subtypes. As might be suggested by the example of the weathering of granite above, it is very common for different kinds clays reside adjacent to, or in layers with other clays. This layering of clay types is called a stacking sequence, and it can occur in either ordered or random sequences. Each are attracted to formations of its own type, by size weight, and electrical charge.

The Effect of  Weathered Limestone on Soil Quality

effect of lime on Clay

effect of lime on Clay

There are a number of significant benefits to the high levels of limestone in the soils of Burgundy. The world over, farmers make soil additions of agricultural lime (which is made from grinding limestone or chalk), in order to balance and strengthen their soils. These are additions that are unnecessary in Burgundy.  Soil salinity is increased by the calcium bicarbonate that is released by chemical weathering of limestone. This increase in soil salinity (which raises the pH) of the soil, is cited as a condition for the flocculation of the clay, allowing the phyllosilicates (clay minerals) to bind together into aggregates. But of course, citing a high ph is required for flocculation (as I have seen written by several authors) this is the chicken or the egg debate. The flocculation requires a low pH environment to occur because it creates that environment in process of its development.

Lime additions to agricultural lands are also beneficial in that it increases soil aeration, which in turn improves water penetration. The calcium loosened soils allow for better root penetration, and because of that root growth is improved. Additionally, agricultural lime strengthens vegetation’s cell walls, increases water and nitrogen intake, and aids in developing enzyme activity. Too much lime (and its accompanying salinity) in the soil, however, can be lethal to the vines, and various rootstock has been identified as being more resistant to the effects of high levels of limestone in the soil than others.

This loosening of soil by addition of lime/calcium carbonate is caused by the disruption of the alignment of the clay particles. Rather than doing a poor job paraphrasing an already excellent article from soilminerals.com, called “Cation Exchange Capacity,” which will I quote below.  To put the article in a frame of reference, it explains to farmers interested in organic and biodynamic farming, the proper mineral balance for healthy soils. These are conditions often exist naturally in the best sections of the slope in the Cote d’Or.

“Because Calcium tends to loosen soil and Magnesium tightens it, in a heavy clay soil you may want 70% or even 80% Calcium and 10% Magnesium; in a loose sandy soil 60% Ca and 20% Mg might be better because it will tighten up the soil and improve water retention. If together they add to 80%, with about 4% Potassium and 1-3% Sodium, that leaves 12-15% of the exchange capacity free for other elements, and an interesting thing happens. 4% or 5% of that CEC will be filled with other bases such as Copper and Zinc, Iron and Manganese, and the remainder will be occupied by exchangeable Hydrogen , H+. The pH of the soil will automatically stabilize at around 6.4 , which is the “perfect soil pH” not only for organic/biological agriculture, but is also the ideal pH of sap in a healthy plant, and the pH of saliva and urine in a healthy human.” soilminerals.com

Mud is the problem, lime is the solution

On construction sites, mud is a problem, and lime is the solution.

The industrial of use of limestone to control wet and unstable soil

The soil strengthening properties of lime is well known by the construction industry. It is used as a soil stabilizer in the construction of buildings and roadways, as well as being used to stabilize wet ground to improve the mobility of trucks and tractors. In the vineyard, soils with high levels of limestone provide the good porosity, soil structure, and drainage to clay soils, and as this construction advertisement depicts, the same for mud/dirt soils as well.

Lime is also the binding agent in cement. The first known use of lime in construction was 4000 BC when it was used for plastering the pyramids, and later the Romans extensively used lime in the preparation of mortar for various constructions. They found that mortars prepared from lime, sand, and water, would harden to a man-made limestone, with exposure to the carbon dioxide provided by the air. This, of course, sounds very familiar, knowing the formation and chemical weathering of stone.


 Next Up Soil Formation: Part 2.2, Soil, Slope and Erosion

NOTES

(1) I should note, that within the span of this short paragraph, carbon has seen several forms: in the air (in carbon dioxide CO2), as an acid (in carbonic acid CO3) carried by water, in stone as calcium carbonate CaCO3, as a mineral bi-product (as calcium bicarbonate Ca(HCO3)2 which exists in liquid solutions. This is all part of the carbon cycle, where carbon is regenerated in the air we breath, the water we drink, the earth we grow our food in.

(2) The fact that CO3 is now carried by water, is important in terms of vineyard development.

(3) Kaolinite clays are the type used in pottery.

(4) As Granite was the primary stone formation in the region prior to the development of limestone, it is likely that Kaolinite and Illites are the most common clay families in Burgundy today.

Understanding the Terroir of Burgundy: Part 1.2 Limestone: stress, deformation and fracturing

by Dean Alexander

The first steps toward vineyard formation

The world was a very different place 160 million years ago when the limestone was formed. Dinosaurs roamed the earth and Pangea was breaking apart.

The world was a very different place 160 million years ago when the limestone of the Cote d’Or was formed. Dinosaurs roamed the earth and Pangea were breaking apart.

Burgundy’s story really is one of stone into the earth, and pivots on a cast of geological stress, sub-freezing temperatures, and the simple, transformative power of water. Just how the forces of nature may have acted upon the limestone and transformed it into the great wine region it is today, is the subject of this article. Meanwhile, the ultimate goal of this series explains the intimate relationship limestone has with the wines of Burgundy.

I suspect that we all have this image of the Côte, post-Fault Event (however long that took), to be this raw 400-meter face of sheared limestone. But even then, the Côte was not a solid piece of stone. The incredible extensional forces the broke the Côte d’Or free from the Saône would have caused significant tension fracturing throughout the Côte before this much more massive fault gave way.

Just Add Water

just add water

just add water

This tensile fracturing, which surely was extensive, would allow rainwater to deeply infiltrate these fine crevices of the stone. And then, upon each surface that the water contacted, depending on the specific porosity and permeability of the limestone, rain water would penetrate the surface of the stone. This contact with water would set the stage for two very different yet significant developments in the stone.

With winter temperatures below freezing, the water in the stone will expand between 8 and 11 percent. This will yield 2000 pounds per square inch, or 150 tons per square foot of internal pressure which is more than enough  to cleave the stone. Geologists call this frost wedging, a form of mechanical weathering which breaks apart the stone due to thermal expansion and further with the eventual contraction. Thermal expansion has a culprit in shattering the stone: the cold. Most materials are inherently brittle in colder temperatures, and the limestone which has more elastic than brittle tendencies is more vulnerable to fracturing in freezing temperatures. Frost wedging is so successful in nature that the stone industry mimics it as a non-explosive technique to separate pieces of stone.

The effect of successive freeze thaw cycles, even upon undamaged exposed stone can cause the development of micro-fissures that influence the stone’s fatigue strength, and can produce vertical cracking called exfoliation joints, as well as flaking, and spalling. All along the Côte, there are numerous scars on hillsides where limestone has in the past loosened, to slide off of even moderate slopes, sending scree down the hillside to rest at the curb of the slope. Geologists refer to this rubble pile as colluvium, and it has proved a near perfect vineyard soil solution. The sliding and falling of rock further degrades the stone, abrading it as it slides, and breaking as it falls, allowing fresh broken surfaces for water to act on. Frost wedging which in part created this colluvium rubble pile, is considered mechanical weathering, and is the first development that I mentioned water would bring. Equally important to vineyard formation, is the second significant development that rainwater brings, is chemical weathering. The acid carried by the rainwater, will metamorphose these freshly broken limestone surfaces. And like magic, it will slowly dissolve the calcium carbonate which binds the stone, leaving behind clay minerals and other material.  (This process will be covered in Part 1.3 Clay and Soil Development)

Exfoliation and Other Theories on Geologic Structures with Unobservable Change

Gilbert's 1904 exfoliation weathering and unloading theory explained. Girraween National Park, Queensland

Gilbert’s 1904 exfoliation weathering and unloading theory explained. Girraween National Park, Queensland

Consider for a moment: most significant geologic changes occurs over a time frame that is far longer than the entire the evolution of mankind. This fact alone might best explain the difficulties of studying events that happen so slowly that change is not observable. These are geologic forces that can not be seen, felt, or measured. If we didn’t have evidence that these changes had occurred, we would

Like this granite, softer, more impure limestone can be prone to spalling, in part because of its porous nature. Stones, like granite, and softer limestones that have a significant amount of feldspar in their makeup, are more brittle because feldspar, and its bonds, are more brittle. Conversely, the calcium carbonate in limestone makes the material more elastic, because the chemical bonds of CO3 will tend to move or realign if the stress upon them is long and gradual. So the makeup of each limestone is critical to how prone it is to fracturing.

Like this granite, softer, more impure limestone can be prone to spalling, in part because of its porous nature. Stones, like granite, and softer limestones that have a significant amount of feldspar in their makeup. Feldspar, the most common mineral on earth, and its bonds, are brittle than calcium carbonate. Conversely, the calcium carbonate in limestone makes the material more elastic, because the chemical bonds of CaCO3 will tend to move or realign if the stress upon them is long and gradual. So the makeup of each limestone is critical to how prone it is to fracturing.

never know they were still continuing to occur around us. The scale of time and shear size and immobility of the objects makes many traditional scientific methods impossible.

Exfoliation Theory: G.K. Gilbert 1904

We know that exfoliation joints exist, but scientists are at odds about how they occur. It is agreed that mechanical strain results in large horizontal sheets of stone separating itself from the mother rock. Half Dome in Yosemite has achieved its shape in this manner. The first, and once long-held theory, was put forth by the ground breaking U.S. geologist Grove Karl Gilbert.  Gilbert’s theory of Mechanical Exfoliation concerned stone formations that had previously been buried in the earth’s crust, which were later were forced to the surface by geological up-shifts. The theory explained that the removal of the overburden (the weight of the rock or earth above) had caused unloading of stress in one direction. The resulting release of stress once on the surface and not confined upwardly, caused expansion and tensile cracking along unloading joints, eventually creating loose sheets of stone on the upper surface of these rock structures. These outer layer of stone were thusly being exfoliated. This website for Girraween National Park in Queensland, Australia, has an excellent explanation of exfoliation weathering.

Challenges to Exfoliation Theory

However, this theory has had it challenges by the mid 20th century, and is to some extent (depending on the point of view), muted or discredited.  Situations were sited that didn’t fit all of the theory’s criteria, like rocks that with exfoliation joints which have never been deeply buried, and evidence that many exfoliation joints exist in compressive stress environments, rather than being produces by extensional stress as the theory suggests. Alternative theories are thermal expansion, (and even wide diurnal expansion), and hydraulic expansion, , (which I discussed above with frost wedging), compressional stress, and in the case of Half Dome, the weight of gravity, or a combination of all of the above, including exfoliation weathering.

Along the same lines, theories revolve around minerals that are created in an anaerobic environment. These stipulate some minerals molecular structure are changed (metamorphized) when exposure to oxygen, creating new minerals. While oxygen is the most common element in the earth’s crust, most of it is bonded with silicates and oxide materials and is not free to act as a weathering agent. But when minerals are exposed to free O2 above ground, they undergo chemical weathering, that produces new minerals that are stable on the surface.  The most obvious example is when iron ions lose an electron with exposure to oxygen, rust is formed.

Bedding planes

bedding fold types: Caused by compressional stress. Although extensional stress is the major shaper of the Cote, there are some folds in the North-South direction, due to compressional stress.

bedding fold types: Caused by compressional stress. Although extensional stress is the major shaper of the Cote, there are some folds in the North-South direction, due to a compressional stress of bedding plates pushing against one another.

In many ways, I’ve put the cart before the horse by talking about the escarpment, before covering even more fundamental ideas. But that is how storytelling goes: sometimes you have to fill in the back story.

The world was a very different place 160 million years ago. This was five million years before the Allosaurus and Apatosaurus (formerly known as the Brontosaurus) roamed the earth. The limestone of the Côte, being a sedimentary material, was laid down in big, flat, shallow beds between the reef barrier that protected the lagoon, and the shore. Each layer was put down, one at a time, chronologically by age, marking millions of years. As the seas receded, and this is the main point, this would become a wide, flat valley of young, sedimentary limestone. It is likely that this bedding would eventually, be completely covered by wind-blown soils. We don’t know what happened to this young Burgundian stone in the intervening 130 million years between formation and the Fault Event, 35 million years ago, but it is unlikely it remained there unchanged. As geological stress acted upon the bedding, it would be pulled, pushed, deformed, and in all likelihood, in some way, fractured.

Author’s Note: For the remainder of this article, I will describe the stress and deformation, and potential fracturing of the stone in the body of the text, and in the photos I will show some of the results (that I am aware of), of that stress. Hopefully the two together will paint a complete picture.

It takes more than just ‘X’ to fracture

Bedding dips Bedding planes. All bedding started out horizontal, but through various stresses, the bedding planes often shift and compress one another causing folds or change their orientation.


Tilted Bedding Planes: While all sedimentary bedding was laid out horizontally, various stresses can shift the bedding planes into other orientations. Geologist measures the tilt by dip, the up/down angle, and strike the percentage off of an east-west axis.

I would love to be able to write that a particular limestone will fracture under the “X” conditions, but just doesn’t seem to be that simple. First, there are too many variables. How stone reacts to geological stress is directly related to its composition and construction as well as: its temperature, the amount of stress, multiplied by the duration of  stress. Most materials tend to be more elastic under higher temperatures and more brittle in low temperatures. It would be reasonable to assume that there was significantly more geological fracturing during ice ages because stone is more brittle in cold temperatures. At least in warmer temperatures, calcium carbonate stones tend to have good elasticity, depending on how pure their construction, as the chemical bonds in CO3 will move if pressure is applied very slowly. However, that elasticity is finite before the stone is structurally damaged as it passes its elastic limit; but more on that later.

Secondly, like I mentioned before, science cannot measure the stress, but rather the deformation due to the stress. For this geologists use a strainmeter, which they measure changes in the distance between two points. For greater distances technology has brought the laser interferometer. These tools allow the scientist to measure frequencies that represent deformation.  Over short periods of time, they record tides (I had never before considered the stress created by a 1.5 quintillion tons of water moving position above earth) and the seismic waves of earthquakes, while over longer periods of time, it can record the gradual accumulation of stress of rock formations.

The mission of this article? What I am looking for here, are some kind of answers these two questions: What conditions would make it possible for vine roots to bed into limestone bedrock? and What limestone types will fracture enough to allow this to happen? Anything learned along the way will be a bonus.

Stresses and the resulting strain

The ductile bending of this folded limestone was made under compressional stresses for a considerably long period of time. Ductile folds are not elasticity as, if released, this rock would not return to its original shape. Note the fractures that have developed almost vertically through the layers of stone.

The bending of this folded limestone was made under compressional stresses over a very long period of time. This stone. well beyond its elastic limit, has experienced a high degree of ductile strain, and is now brittle and structurally degraded. Note the fractures that have developed almost vertically through the layers of stone.

Stress causes strain of various types. Like I mentioned before, we are not able to measure the stress itself, rather only its effect by measuring the stone’s deformation. Below are the basic stresses upon objects and the resultant strains and deformations associated with them. Any deformation is considered flow (as science calls this) and it is domaine of an interdisciplinary study called Rheology. Here it is again, more simply, because its getting more complicated: Stress first.  It, in turn, causes strain. The result can be deformation, and this deformation is studied as if it were a liquid: as flow by Rheologists (a group of engineers, mathematicians, geologists, chemists, and physicists), who work together in an attempt to answer questions that transcend all of these disciplines.

6 Most Common Geologic Stresses (the first two are the most relevant to Burgundy)

  • Tensile, Tension, or extensional stress which stretch the rock or lengthen an object, will cause longitudinal or linear strain, and its effect is to lengthen an object, and can pull rocks apart. Like a rubber band pulled longitudinally, this is known as extensional rheology. As the rubber band breaks, that is called shearing flow. Rocks are significantly weaker in tension than in compression, so tensile fractures are very common. Tension stress formed the Côte d’Or.
  • Compressional stress that squeezes the rock and the resulting strain shortens an object. This too can be a linear or longitudinal strain. Stone under compressional stress can either fold (as in the photo to the right) or fault.
  • Normal Stress (can be either compressional or extensional) Normal stress that acts perpendicular to the stone.
  • Directed stress is typically a compressional stress, that comes from one direction with no perpendicular forces to counteract it. The higher the directed pressure the more deformation that occurs.
  • Lithostatic> and hydrostatic stresses are the compressional pressure of being underground or underwater. The force of the stress is uniform, causing compression from all sides.
This limestone jutting out of the vines in the Puligny vineyard, Les Combettes. Wine writers typically cite this common rock features as evidence of shallow soils, but these rock features are more likely a fold (plunging anticline) caused by compressional stress.

Wine writers typically cite these limestone outcroppings as evidence of shallow soil. But these rock features are more likely a fold (plunging anticline) caused by compressional stress. Location: Puligny, Les Combettes.

Interestingly, the effects of hydrostatic stresses upon an object are mitigated by oppositional forces. For example, the stress from below counteracts much of the force from above, and the forces from the right side counteracted by those from the left as they push against each other. So unlike directed stress, (the kind of stress that a 2 ton object exerts on top of a man), hydrostatic stress is like a scuba diver in the ocean. The stress of water upon the diver can be the same as the heavy weight upon the man, but because of counteracting stresses, strain is not expressed in the same way.

  • Shear stress is that which is parallel to an object. Shear strain (caused by shear stress) changes the angle of an object. It can cause slippage between two objects when the frictional resistance is exceeded, or even failure within an object. Faulting is an example of slippage under shear stress. I would be remiss to note that faults in Burgundy, at least to my anecdotal eye, often occur between limestone types.

 

Coaxial strain

Coaxial strain

 

The Magnitude of  Strain

Elastic strain and ductile deformation

stressesThere are two levels of strain. Elastic strain, in the effects of the strain, are reversible. The stone will change shape or deform under stress, with minimal damage to its structure, and then return to its original shape and position.

Ductile strain, is the area of strain once past the elastic level. The stone is now developing microscopic fissuring, and the stone can not return completely to its original size, shape, or position. Although the stone may not appear to be visibly damaged, any deformation into the ductile range, will harm the stone’ structural integrity. Additionally, in comparison to the deformation of the stone in the elastic range, the speed and ease of ductile deformation increases quickly (in structural geologic terms).  The deformation is now the result of micro-fissures that have emerged throughout the stone, and are now both propagating and enlarging. It is during this phase of rapid deformation that the stone can achieve dramatic folding from what had previously been flat, sedimentary stone.

By The Numbers: limestone limits

Elasticity in stone

Elasticity in stone

Author’s note: The measuring of deformation and the related stress involved becomes a bit more technical, and requires a number of lingo words to be used in the same sentence. I resist this as much as possible, because it requires the reader to be very familiar with the terms. Skip ahead if this doesn’t interest you, but it gives a numerical frame of reference for limestone fracturing.

The deformation under applied pressure is called flow, and the material’s resistance to deformation is measured (in newtons). The measurement of a stone’s elasticity is called it’s Elastic Modulus  (a.k.a. Young’s Modulus).

Elasticity of rock groups. Click to enlarge

The elasticity of rock groups. Click to enlarge

The Elastic Modulus measures the tensile elasticity, meaning when a material is pulled apart by extensional stress.  This resistance to deformation is expressed in gigapascals (GPa) which are one billion newtons per square meter. 

Additionally, there is Bulk Modulus, the measurement of a stone’s lithostatic (compressed from all sides) elasticity. This is expressed in Gigapascals, (GPa) or one million newton units.

And Shear Modulus, also known as the Modulus of Rigidity, in which the elasticity of a stone under shear forces is measured.  It is defined as “the ratio of shear stress to the displacement per unit sample length (shear strain)”.

Scarp Cutaway. Click to enlarge

Scarp Cutaway. Click to enlarge

I gave the MPa compressional strength (loads that tend to shorten) of various limestone types in part 1.1. Note here MPa is used, or one million newtons per square meter. The elastic modulus of most limestone can be as low as 3 GPa for very impure limestone (we don’t know what was sampled), and up to 55 GPa depending on purity of the calcium carbonate. As a comparison of elastic modulus: Dolomite (limestone with a magnesium component) typically ranges between 7 to 15 GPa, while Sandstone typically runs 10 to 20 GPa.

  • click to enlarge

    click to enlarge

    General Limestone Modulus Ranges (the range of deformation before fracture)

  • Elastic modulus range: 3 GPa – 80 GPa  
  • Bulk modulus range: 5 GPa – 66.67 GPa
  • Shear modulus range: 3.5 GPa to 33 GPa

 

The strain rate is important: which is expressed as elongation over time (e/t). The longer the period of time, the more the material can “adapt” to the strain. The faster the stress is applied exceeding the plastic elastic limit, the shorter the plastic region. The plastic region fracture where the material breaks and is considered brittle behavior.

  • Brittle materials can have either a small (or a large) region of elastic behavior, but only a small region of ductile behavior before they fracture.
  • Ductile materials have a small region of elastic behavior and a large region of ductile behavior before they fracture.

 

From Strain to Total Failure of Stone

The description of how stone reacts to crushing pressures reminds me of those submarine movies, where the hull is slowly being strained with a chorus of creepy groaning sounds, rivets popping and water spraying from leaks in the hull. In the laboratory, geologists study stones they crush, in order to understand what has occurred to rock materials over hundreds of thousands, to several million of years.

Infinitesimal strains refer to those that are small, a few percent or less, and is part of a mathematical approach material that is “assumed to be unchanged by the deformation” (Wikipedia).  As deformation increases, micro-cracks and pores in the stone are closed and depending on the orientation of the pores in relation to the direction of the stress, this can cause the stone to begin to deform in a coaxial manner. This non-linear deformation is obvious in weaker or more porous stone.

The goal is to explain how this happens in limestone with high calcium carbonate

The goal is to explain how this happens in limestone with high calcium carbonate content. photo alexgambal.com

While in the elastic region, stone adjusts to the pressure applied to it. Micro-cracks don’t appear in the stone until it reaches the 35%-40% way-point in elastic region. At this point structural strain is largely recoverable with little damage. At 80% of the elastic limit, micro cracks are developing independently of one another, and are evenly dispersed throughout the stone’s structure, despite the fact that the stone is at maximum compaction with no volume change. As the stone nears its elastic limit, micro-cracks are now appearing in clusters as the their growth accelerates in both speed and volume. The stones appearance and size remains intact as it passes its peak strength, although the structure is highly disrupted. The crack arrays fork and coalesce, as they begin to form tensile fractures or shear planes, depending on the strength” of the limestone.(1) The rock is now structurally failing, and considered to have undergone “strain softening”.  Additional strain will be concentrated on the most fractured, weakest segments of the stone, creating strain and shear planes in these specific zones, which as it nears the fracture point will essentially become two or more separate stones, ironically bound together only by frictional resistance and the stress that divided them. information source: Properties of Rock Materials, Chapter 4 p.4-5, (LMR) at the Swiss Federal Institute of Technology, Lausanne

The Bottom Line on the Fracturing of Limestone

Roche de Solutre and Vergisson, are large, tilted bedding planes. What little information that I have found of their formation (non-scientific) claims these are plateaus which raised when the Saone Valley was formed, and have later tilted to the East. Plateaus are often formed by magma pressure causing the ground swell upwards, or by glacial erosion. The theory that 400 meters of stone were reabsorbed back into the earth by tilting, sounds like sketchy science to me. I would consider a second option more likely: only one end of this structure was pushed above ground by geologic forces.

Roche de Solutre and Vergisson, are large, tilted bedding planes. What little information that I have found of their formation (non-scientific) claims these are plateaus which raised when the Saone Valley was formed, and then later “tilted” to the East.  The theory that 400 meters of stone were reabsorbed back into the earth by “tilting”, sounds like sketchy science to me. I would consider a second option more likely: only one end of this structure was pushed above ground by geologic forces.

The truth is that we don’t have any records detailing the condition of the limestone base that lies below the topsoil. Certainly the limestone base has been exposed often enough over the past century, that had some academic organization wanted to catalog this kind of information, there would now be a large database to refer to by now. Moreover this would be a substantial advance in the knowledge of how to farm these vineyards. Today, the most progressive vignerons are now making these inquiries themselves, digging trenches to find out what lies below in order to make the best replanting and farming decisions possible. But it is unlikely that even these recent efforts are being catalogued, as they investigated.

Vineyard Development: Limestone

Tilted bedding plane, whether a plateau as one source describes or not As a tilted bedding plane, The Roche (Roc) de Solutre and Vergisson, despite their distance South of the Cote de Nuits, and their slightly more youthful age, gives an unique glimpse into the layers of limestone in Burgundy. It reminds us, that whatever the top layer is, there lies different strata just below it. Click to enlarge

Tilted bedding plane, whether a plateau as one source describes or not
As a tilted bedding plane, The Roche (Roc) de Solutre and Vergisson, despite their distance South of the Cote de Nuits, and their slightly more youthful age, gives an unique glimpse into the layers of limestone in Burgundy. It reminds us, that whatever the top layer is, there lies different strata just below it. Click to enlarge

Limestone fracturing and shallow soiled vineyards

Since deeper soils do not require the vine to penetrate the bedrock in order to have a successful vineyard, fracturing there is not required for vineyard vitality.

However any vineyard where there is shallow soil, the limestone below must be compromised structurally, to some degree, for the vines to penetrate the stone. In this way, the vines themselves are a contributor to mechanical weathering of stone in the vineyards. Limestone varieties with a high percentage of impurities, are typically more easily fractured; although they may actually be soft enough, or porous enough stone for the vines to penetrate on their own.  It is documented that composite formations with heavy fossilization (like crinoidal), or clay content (like argillaceous limestone)  are less elastic than purer limestones with high levels of CaCO3, and are much more friable. You can read about limestone construction in Limestone: part 1.1.

With a harder stone, would significant ductile deformation with fissuring make the stone weak enough for the vine roots to penetrate?  Or does a limestone based vineyard need to be significantly fractured before vines can sufficiently take root? That answer to this question is not apparent with the information available at this time, but the answer is probably yes.

Mazy and Ruchottes Chambertin with dip and strike oriented faults. Significant outcropping has emerged from this hard Premeaux stone at the convergence of these faults. Interestingly its both parallel and perpendicular to the extensional, horizontal faulting

Mazy and Ruchottes Chambertin with dip and strike oriented faults. Significant outcropping has emerged from this hard Premeaux stone at the convergence of these faults. Interestingly its both parallel and perpendicular to the extensional, horizontal faulting

Vineyards like Mazy-Chambertin and Ruchottes-Chambertin give evidence that the more brittle Premeaux limestone (with its lower compressive strength, and higher porosity), if fractured enough, can support vineyards, despite there being very shallow topsoil. There are a number of linear, east-west oriented, limestone outcroppings in these two vineyards, indicating this area has seen significant compressional stress to the bedrock there over the last 35 million years, in addition to the tensile faulting caused by extensional stress that created the region. These two stresses would have created vertical dip joints, and horizontal, strike joints, and very possibly diagonal oblique joints, and fissuring in the bedrock. Enough for the vines to survive well enough for these two vineyards to be awarded grand cru status in the late 1930s.There has been a question in my mind whether Comblanchien, which is so dense that water cannot penetrate enough to effect freeze thawing, and is also very elastic due to its 98% calcium carbonate content, would fracture enough in a vineyard location to support a vineyard in shallow soils. In fact that has been a driving question throughout this piece, and which I was inclined to believe the answer was no, until evidence proved otherwise.  Apparently that has happened. 

The Rise of Colluvium

In terms of vineyard soil development itself, geologic pressures have worked extensively to prepare the limestone bedrock. Primarily with extensional stress, but also exerting compressional stress, the strain significantly weakened and fractured the limestone bedding. This deformation and the ensuing fracturing allowed water to infiltrate its cracks and crevices. During periods of cold weather it would freeze within the fissuring, causing frost wedging. Exfoliation would ensue, ultimately causing significant limestone debris to be pulled away by gravity, itself a powerful force of mechanical weathering, to slide (and tumble) down the hillside.  As the stones fell, they would further break and abrade into yet smaller pieces. Abrasion is another agent of weathering. There they would stop at the curb of the slope, where eventually they form deep, limestone-based “colluvium” soils. This is what Coates is speaking of when he wrote “rock and more limestone on the section closest to the over-hang, and there is some sand” in AmoureusesThese are the colluvium soils that would with enough time would generate the vineyards upon the the red grand cru vines of the Cote de Nuits would grow.

But first, the story of chemical weathering would have to play out, creating clay and soil needed to feed the vines. The slopes of the Cote d’Or would slowly evolve geologically for millions of years, awaiting the arrival Roman agriculturalists who would recognize and exploit the vinous wealth of this thin strip of the hillside.

Next up: Part 1.3 Amoureuses and Parallel Evidence of Shallow Soils over Comblanchien

 

Please feel free to comment, like, follow, share, or re-blog this or any of this terroir series!

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(1) Because it is often difficult to distinguish between the different types of fractures and  faulting once the fracture has occurred, I will leave it at this. There are 3 kinds of fractures born from the three major stresses: Shear, tensile, and extensional.

(2) I have not been able to determine if  crystallization is a definition of Comblanchien limestone, or if the Comblanchien limestone in the villages Corgoloin and Comblanchien just happen to have been metamorphosed into marble, and that is why it is quarried there.

Previous articles on Terroir

Limestone Construction: part 1.1 (click here)

Introduction to Terroir (click here)

Preface to my article on Terroir (click here)

Marl: The Most Misused and Misunderstood Word in Burgundy Literature? (click here)

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Understanding the Terroir of Burgundy (introduction)

The History, the Threats, and Why Terroir is Important

 

Roman Wine FriezeTerroir as a notion: 

The notion of climate and terroir palpably began with the establishment of Clos de Bèze in 630 A.D.  And despite the countless changes of governments, laws, and ownership, the shape and size of Clos de Bèze have remained unchanged in the intervening 1384 years.  However, there were notions of terroir that appeared long before. In the first century, Columella (the only Roman agronomist whose records still exist) wrote of a varietal that had physical leaf characteristics that leave little doubt that the Romans grew Pinot Noir in Burgundy.  The quality of this wine would eventually eclipse Falernian wine in the eyes of the patrician class. That this vine was so perfectly suited to the Burgundy region, Columella wrote: “…it alone gives a good name to even the poorest of soil by reason of its own fertility.”

Monks at Clos VougeotWhile terroir is, at its heart, the physicality of a place, it is also the acceptance of terroir as a notion, that allows its expression in the glass. The concept of terroir asks that winemaker should produce the best wine they can, that still truthfully represent the site, while simultaneously requiring the wine drinker to appreciate what each site uniquely brings to the wine made from it.Interestingly it has been the historical difficulty of ripening grapes in the Côte d’Or that has made terroir apparent in Burgundy. This marginal ripening, coupled with the transparent nature of the Pinot Noir and the Chardonnay that is grown there, lay bare the influence of the vineyard position: the soils below and the weather above. In many ways, it is a quest of purity, and that is something that can easily and quickly be muddied by over extraction, over-ripeness, and blending. Jacques Lardiere, the now-retired manager of Louis Jadot used to say (in the late 1990s) that the terroir would speak, “even if you planted Syrah” in Burgundy. I mentioned Lardiere’s statement to the then winemaker of Mommessin (I don’t recall who that was) and his response was: “That’s funny coming from him.” (1)

The Historical Battle for Ripeness: The Importance of  Vineyard Protection and Exposition

Clos la Roche in winterComplete phenolic ripening in Burgundy has been the holy grail of every winemaker in the Côte d’Or since the middle ages. Given that the last so-called “Little Ice Age” only ended in the 1850s, it is not a complete surprise that only the warmest vineyard sites (the grand crus) could semi-consistently achieve ripeness.   The key to ripeness was a vineyard had to sit on a slope – facing east to southeast, angled to receive the longest rays of the harvest sun. Here, the hillside, and the flat village land at its foot created a heat trap for the ripening crop, sheltering it from the wind which might otherwise disperse the heat. In the long history of Burgundy, it has been only these protected vineyards, on the mid-slope, that could achieve the temperatures necessary to fully ripen the grapes right before harvest.

Climatic and Economic Threats

However, the climate is warming. In absolute numbers, from 1990 to 2006, the average temperature has gone up 1.2 degrees F., and it had already gone up 1.2 degrees F. in the previous thirty years. Today, the crop is consistently ripe enough to make good wine across all climates, in virtually every vintage. At this point in time, we are witnessing the greatest period of in all of Burgundy’s almost 2000 year history under vine. The confluence of winemaking and wine growing knowledge as well as perfect ripening temperatures is granting us truly remarkable wines. I think there is room for some additional warming without major concessions to wine style and terroir. Although, I suppose if it does, we’ll have bigger problems than lamenting the passing of the golden age of Burgundy.

With the increasing ripeness, the winemaker is both pushed toward, and drawn to, making wines with deeper color (anthocyanins), fuller fruit, and more structure. With the clamor for riper, richer, grand cru-styled Burgundies, regardless of how expensive they are, there is a significant economic reason for winemakers to follow this path. But as Burgundies fatten up, terroir is increasingly obscured. It is very possible there will be fewer noticeable variances between the wines from many vineyards unless winemakers and the wine buying public truly embrace terroir. The relevance (and indeed the future) of terroir in Burgundy hinges on the wine appreciation that goes far beyond what is good or bad, in a search for “the best.” The concept“the best” is often at odds, and in many ways contradictory the notion of terroir, and if we don’t actively embrace and extol the differences between vineyards, from grand cru to village lieu-dits, we will lose what is so unique about the region.

Classification

Chevaliers du Tastevin with clergy circa 1950

Chevaliers du Tastevin with clergy circa 1950

The terroir of Burgundy was codified unofficially in 1855, by Jules Lavalle, and again in 1920 by Camille Rodier, both of whom graded the vineyards in five qualitative levels, the best being the Tete de Cuvees. Governmental classification would not come until the late 1930s. Interestingly, it wasn’t until the depth of the depression, and against a backdrop of the tensions of a brewing second war in Europe, that the French Government finally moved forward with establishing the Appellation d’Origine Controlee (AOC) system. The Ministry of Agriculture established the Institut National des Appellations d’Origine (INAO) in 1935, and over the next few years this body defined the official regional appellations for wine and foods across France. It was a uniquely French thing to do, and in a marketing sense quite brilliant, but the idea was to protect these agricultural regions and heritages from change.  In doing so they both branded and secured these places and products as unique in an emerging global economy. When dividing the appellations, the INAO heeded historical ownership and village boundaries, as well as physical and observable geological observation, in as much as it was understood at the time, without intensive study and the benefits of modern technology. And it was done: nearly etched in stone.

But to look past the classifications: to the maps, the geology, and the topography of the region is the goal of this article, in order to understand why certain sites create certain types of wine. What’s more, this knowledge allows us to be predictive of what style of wine we might expect a vineyard to produce based on available geographical and geological information.The subject gains remarkable complexity if you dig too deeply, requiring significant chemistry and geological explanation, of which I’m not qualified. So I will attempt to keep this a more general overview of the important aspects of terroir in Burgundy: ripening and exposition, (meaning how a vineyard faces the sun, slope,) the amount of soil and it’s makeup (topsoil, limestone, and clay) and , and a vineyard’s protection from the wind and weather.

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Note

(1) I too disagree with Lardiere. While Syrah can be quite transparent when just ripe, like in Cote Rotie, the moment it gains weight it becomes significantly dense and can carry a remarkable level of dry extract. Pinot Noir cannot achieve the size, weight, and tannin of Syrah. The short distance between Cote Rotie and Hermitage generally produces a vastly different wine: of terroir is obscured by Hermitage’s additional size and weight.

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See the other articles in this series

Marl: The Most Misused and Misunderstood Word in Burgundy Literature?

Preface to my upcoming article: “Understanding the Terroir of Burgundy”

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