Understanding the Terroir of Burgundy: Part 3.4 The Grand Crus

 By Dean Alexander

While working my first wine shop job twenty years ago, I asked the store manager – who was a Burgundy guy of significant reputation: “Why is Rousseau’s Ruchottes-Chambertin not as good as as his Clos de Bèze and Chambertin?”  The answer I got was honest: “I don’t know. I’ll have to ask next time I’m there.”

It years later that realized that I had asked the wrong question. The question I should have asked was: What causes these neighboring vineyards to produce wines of such different character? 

Today, twenty years later, I can answer that question. If you have read my previous 12 articles in this series on Understanding the Terroir of Burgundy, it is likely you can answer it too. More importantly, some of the lessons here can be used to understand other appellations where less concrete information is known.

Clos des Ruchottes to the right, and Ruchottes du bas, on the left. photo: googlemaps

Clos des Ruchottes to the right, and Ruchottes du bas, on the left. photo: googlemaps

The short answer

Chambertin, Chambertin-Clos de Bèze, and Ruchottes-Chambertin

These three grand cru vineyards sit in a row, shoulder to shoulder on the same hillside. All have their upper-most vines smack up against the forested hillside, and all have virtually the same exposition. The legendary domaine of Armand Rousseau farms and makes wine from all three of these vineyards; yet one, the cru of Ruchottes-Chambertin, does not seem to be cut from the same cloth. The wine made from Ruchottes is not as rich or opulent. It tends to be lighter, more fine-boned, and more angular in its structure. The primary reason for this difference in wine character is that right at the border of Clos de Bèze and Ruchottes, the limestone beneath changes significantly. Unlike the other two vineyards, Ruchottes-Chambertin sits over very hard and pure limestone that is composed of almost completely of calcium carbonates and very little in the way of impurities, such as mud or clay.

The impurities within the stone, (bonded by the calcite) is what determines how much clay and other materials will be left behind as bedding materials when the stone has weathered. The more impurities in the limestone, the more nutrients will be available for the vines when the stone weathers chemically.  Further, it will reflect not just how fractured the stone has become due to extensional stress, but it will have often been the determining factor of whether the bedding has become friable as well. The wines of Chambertin and Clos de Bèze have this sort of impure limestone as a bedding under three-quarters of its surface area. It is a significant factor in giving the wines of Chambertin and Clos de Bèze a heavier weight and richer character than the wines from Ruchottes.

Another major factor in this differential in wine weight is that Ruchottes is a much smaller appellation, which confines it solely to the upper-slope. Its location makes it subject to all of the factors that challenge upper slope vineyards, details that are examined in Part 3.3.  Conversely, both Chambertin or Clos de Beze extend almost three times farther down the hill, all the way to the curb of the slope. Additionally, while the degree of slope may kick up in the upper final meters of the Clos de Bèze and Chambertin, the area under vine upon upper slope (that will produce a lighter wine) is relatively small compared to the entire surface area of those vineyards.  

Unlike Ruchottes, the long slopes of Chambertin and Clos de Bèze will reach down to almost to where the slope completely leveled off. There at the base of the slope, rock and soil colluvium will have been transported by gravitational erosion, adding generously to the depth the soil. This depth allows more water to be absorbed and retained for use by the vines. It is rich in limestone rubble, gravel, and catches and holds more fine earth fractions including transported clay that has flocculated there. Above ground scree litters the vineyards

The fact that most ownership parcels run in vertical rows, from the top of the vineyard, to the bottom, assures that any lighter, more finessed wines will contribute, but not dominate the overall blend. In other words, blending of heavier wines lower on the slope masks the lighter wines from the top of the slope. 

It is abundantly clear that the vines benefit from the higher levels of nutrients in these deeper soils. They develop grapes that carry more color (anthocyanins) and brings many times more dry extract to the wine. This translates as the wines of these vineyards having a richer, more velvety texture, increased depth, all of which covers the structure. On the opposite end of the spectrum, the upper-slope position of Ruchottes-Chambertin dictates that the soils there are very shallow, and while there is a high percentage of colluvium, it is not as rich in sand, silt or clay sized particles.  In fact, there are places the topsoil has completely eroded away, leaving fractured stone and primary clay and marly-limestone between the voids and breaks in the rock.

New research allows new understanding

Today we can examine this variation of limestone within a vineyard with a precision that was not possible a decade ago. This is due to the groundbreaking work of geologist Françoise VannierPetit and her mapping of the dominant limestone beddings of Gevrey. Through her work, we know that Ruchottes is a very homogeneous terroir, one with a very pure and hard limestone bedding dominating the vineyard. While the stone does not provide much in the way of nutrients to nurture the vines, we know it is well-fractured by two large faults that run through the vineyard.  Because of the vigorous faulting and fracturing throughout the vineyard, Ruchottes does produce a grand cru class wine, but it is a grand cru of a different character.

The geological factors in Ruchottes do not typically produce a wine with the substantial fruit or thickness of a Chambertin, and this ‘reduced’ level fruit often does not completely ‘blanket’ of structure in the wines from Ruchottes. This obvious structure is often mentioned in wine reviews, noting heightened acids and tannins, lending the wines a more angular construction than in other grand crus. By the same token, the wine from Ruchottes is often quite aromatic, with finer bones, for this wine, it means exhibiting more finesse, as well as giving the taster a heightened awareness of the wine’s precise rendering of detail. In another vineyard, this might be attributed to the grapes achieving less phenolic maturity, but the wines of Ruchottes are ripe, they just aren’t typically as large scaled or heavy. Moreover, they can be remarkably beautiful wines that can age effortlessly, for decades; often gaining poise, polish, and balance while doing so.

The gentle slopes of Chambertin. Photo: googlemaps

The gentle slopes of Chambertin. Photo: googlemaps

The substrata of Chambertin and Clos de Bèze is much more varied. With Vannier-Petit’s mapping information, we know that 35 million years ago the vineyards of Chambertin and Clos de Bèze were opened up by a large fault. This exposing the older (2 million years +/-) of softer bedding planes below.  They are both divided by four bedding planes, three of them being of soft, friable, impure materials, giving excellent nutrients.  This softer, highly fractured bedding allows the vines to thrive, and produce wines with much higher levels of fruit. This is the heart of Chambertin and Clos de Bèze.

Additionally, the twin vineyards are perfectly situated, mostly upon a gentle gradient which will resist erosion, or better yet, at the curb of the slope, where the soil is deeper,  The vineyards are well protected from wind, being squarely behind the hillside of Montagne de Combe Grisard. These two vineyards sit in the sweet spot of the heat trap formed by the hyperbolic concave of the slope. This positioning allows ripening occur even in most cold, wet years. Ruchottes, while fairly well protected, it is nearer the Combe de Lavaux through which cooling winds flow down the vast gorge.

All of these factors make the wines made from Chambertin and Clos de Bèze much easier wines to understand because they have so much to give. They can be very seductive and complex, and can be drunk either young or old.  Are they typically better wines than can be made in Ruchottes?  The knee-jerk reaction is yes, as Ruchottes can be equated to the man fighting with one hand tied behind his back. But when a well-made wine from Ruchottes is opened at the right time, and served with the right meal, it can be perfection.

Armand Roussaux parcel map

Chambertin clos de Beze

 

Digging deeper 

Gevrey-Chambertin topography

Generally speaking, when compared to vineyards in some of other villages, the grand vineyards of Gevrey are fairly mild in their gradient. The uppermost vineyard sites of the Chambertin-named vineyards butt up against the Montagne de Combe Grisard’s “chaumes”, (or ‘scruff ‘ in English). But unlike the steep upper hillsides of Vosne or Volnay that were able to be planted to vine, there is an unarable, rocky, forested landscape. Here in the chaumes, where no vines are planted, the hillside above Gevrey becomes steep.

The premier cru of Bel-Air is the one real exception. Carved out of a void in the rocky forest, and perched directly above Chambertin Clos de Bèze, Bel Air is a steep vineyard. It is a superb example of the struggles upper-slope vineyards face. See Part 3.3.1 for more on this. According to Vannier-Petit, a white Oolite formation underlies the uppermost section of Bel Air, and Premeaux Limestone underlies the lower part. Several writers have describe Clos de Bèze as having Oolite formations below the soils, but Vannier-Petit does not note this. Instead, it is likely that Oolite has slid, as scree, or even in large chunks as a rock slide, into Clos de Bèze, from Bel Air above.

A prominent feature of the area, as outlined by the late James E. Wilson, a geologist, and author of Terroir (1998), is a rocky outcropping he referred to as a “Comblanchien cap“. While this was not part of the vineyard landscape, he described it as a major feature of the “Nuits Strata Package.” This term,“Nuits Strata Package,” as coined by Wilson, is an overarching reference to the bands of limestone bedding that stretch from Marsannay to Nuits-St-George, a layering of limestones unique to the Côte de Nuits. An upper-band of Comblanchien stone, he wrote, formed a structural bulwark or ‘cap’ which has allowed the upper-hillside to resist erosion, while the softer center eroded more quickly. This has caused the Côte de Nuits to develop its hyperbolic concave slope-shape. This concave slope relief, as I wrote earlier, allows the heat of the sun is trapped, allowing fruit to ripen fully. This is particuularly true for vineyards such as this that sit in a wind shadow which is created by the trees and hillside above.

Interestingly, a much more recent map of Gevrey by Vannier-Petit, does not deem it necessary to include hillside construction above the vineyards.  So while she shows no Comblanchien cap rock at the edge of the Gevrey’s vineyards, as it seems Wilson described them, she does shows that the Premeaux stone extends one hundred or so meters up-slope. This extends well beyond the farthest, uppermost edges of the vineyard land.  While she may have felt the composition was outside the scope of the project, certainly anything that will wash, slide, or roll into a vineyard, is of great importance to our understanding of the physical vineyard makeup.

Ruchottes-Chambertin: a largely homogeneous appellation 

Here, a photo by Armand Rousseau illustrating the lack of topsoil, and the width of the fractures in the Premeaux limestone. No doubt this is a more extreme section, but it gives us the understanding of the relationship between the hard stone, fracturing and the difficulty of dealing with erosion in these vineyards.

Here, a photo from Armand Rousseau illustrates the lack of topsoil, and the width of the fractures in the Premeaux limestone. No doubt this is a more extreme section, but it gives us the understanding of the relationship between the hard stone, fracturing and the difficulty of dealing with erosion in these vineyards.

Ruchottes-Chambertin, and it’s ying-yang partner. Mazy-Chambertin (also spelled Mazis-Chambertin), sit at the tail end of the string of grand cru vineyards. The primary limestone beneath both vineyards is the significantly calcium-pure, Premeaux. Premeaux limestone, which is marketed as marble, is highly desirable for construction and prized for its pink color. It is very similar to Comblanchien (which is a creamy white), but slightly less pure, (hence the color), and slightly less resistant to geological strain. See Part 1.1 for detailed compressional strengths of various commercial limestones.

Technically, the Ruchottes appellation is made up of three small, roughly equally-sized vineyards:  Ruchottes Bas, (meaning the below) Ruchottes Hauts, (meaning above), and next to that, against the forested outcroppings at the top of the hill, Clos des Ruchottes. The Clos, is a monopole owned by the firm of Armand Rousseau.

While the lower half of the Clos des Ruchottes shares the rest of Ruchottes’ Premeaux limestone, the uppermost section, is covered in a layer of white Oolitic stone. Oolitic stone is made up of millions of small, oval, carbonate Oolite (egg stone) pellets that are fused by mineral cement. This composite construction makes the stone more susceptible to fracture, and the vines find it far easier to penetrate the many weak spots in this more porous stone. If anything, this is a benefit that the Clos des Ruchottes has over the rest of the Ruchottes appellation, especially since it is so high upon the hill. However we don’t know if the Oolite is of significant depth, and it is likely that Premeaux lies directly beneath it anyway. In either case, as vineyards go, the entire appellation of Ruchottes-Chambertin, is remarkably homogeneous in character.

The excellent Armand Rousseau website discusses Ruchottes Oolitic limestone, as well as shows the firm’s holdings in the vineyard, and is fairly detailed, and seemingly competent in their geological explanations, a surprising rarity in Burgundian marketing. Below is an excerpt.

The soil is composed of a shallow layer of red marl up to the top of the area. It is very pebbly, shallow and not fertile. The vines are based on oolithic limestone dating from Bathonien which disintegrates if frozen producing scree. This soil type forces the roots to go deeper into the rock. This results in a more fragrant, mineral style of wine that is lighter in colour but with a fine and elegant body. domaine-rousseau.com/en

Examining Ruchottes faulting and fracturing

We know through of the study of fracturing along the Arugot fault in the Dead Sea Basin, that as the distance from the fault increases, fracturing diminishes in frequency. This means that fracturing still occurs in its clusters, but the spacing between clusters is farther apart, leaving stretches of relatively undisturbed stone between areas of fracturing. As Ruchottes is located at the farthest possible distance in Gevrey from the main Saône fault, we rightly might expect this hard stone to be only intermittently fractured. Certainly there have been numerous accounts over the past century of vignerons having to dynamite sections of these vineyards to break up the stone enough to plant their vines.

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

Unknown before Vannier-Petit’s work were the locations of sub-faulting that occurred at the same time that the Saône Fault developed.(1) Two sub-faults bi-sect Ruchottes and Mazy, right at the border with Clos de Bèze. The vertical fault-line follows the boundary between the Premeaux stone and the various beddings that make up Clos de Bèze.

Ruchottes origin during of the Côte’s creation 

The once level Premeaux limestone bedding of Ruchottes came under great strain as the land that now forms the Saône Valley Basin pulled away and began its slide down. As the limestone slab was pulled extensionally, the once solid piece of limestone bedding first began to microfracture, then to fracture throughout the body of the stone. As understood by the study of fluid mechanics, stress intensifies exponentially upon weakest areas of the stone, from which fracturing propagates, until the main horizontal break, or fault occurs.

As this faulting occurred, the neighboring blocks of limestone were pulled downward by the void made by the dropping/falling off the fledgling Saône Valley. As this happened, bedding of Ruchottes began to tilt and slide downwards, both pulled and sliding with the adjacent formations. It is not clear if this was a rapid, cataclysmic event, or that it happened over the span of hundreds of thousands, or even millions of years. Either way, the stress upon the Premeaux bedding of Ruchottes was extraordinary, and what fracturing that was not caused the faulting, certainly occurred as it tilted and moved its position downward.

Often times, faulting can cause one plate to sit significantly higher than the next, forming a drop off which may or may not fill with soil.  In some locations, such as the fault between Chevalier-Montrachet and Le Montrachet, this has occurred What soil was lost by Chevalier to erosion, found a fine resting place in Le Montrachet, allowing the soils of Le Montrachet to become much deeper (and richer).  In other instances, erosion may once again level any difference in bedding height created by faulting. Alternately, the bedding may remain at the same height following the fault creation.  To the best of my knowledge, any height differential between Ruchottes du bas and Mazy Hauts is not documented.

Looking at the satellite image, there are certainly several visual clues that this faulting exists. Most obvious are the signs of significant stress are the limestone ridges, where the bedding has folded upon itself, that pushed above the topsoil. These are dominate features directly above the southern end of Mazy Haut, and just like the walls of Clos, these limestone ridges greatly reduce erosion in these areas, which results in deeper richer soils and thus weightier wines, not only in Mazy, but in that area of Ruchottes du Dessus.

Clos de Beze & Chambertin: four distinct bedding planes

Here the soft friable makeup explains the ease that the vines have in extracting nutrients and water from the base rock

Here the soft friable makeup explains the ease that the vines have in extracting nutrients and water from the base rock

While Chambertin and Chambertin Clos de Bèze are very similar to each other, they are unique to all other vineyards in Gevrey. Both vineyards share the same four bands of bedding planes, in roughly the same proportions. The one largest difference between them is that there is a higher percentage of Crinoidal stone in Clos de Bèze than exists in the northern end of Chambertin.  However, what is farmed depends completely on the parcels owned, not what exists in the vineyard itself.  It is increasingly clear is that a parcel is a vineyard in itself, and sections within parcels can hold wide variation in the character of wine it will produce.

Upper-slope Bathonian beddings:

Premeaux limestone and Argillaceous limestone/Shaley limestone

The uppermost sections of both Clos de Bèze and Chambertin sit over the very pure, and hard, Premeaux limestone, formed during the Bathonian which is a 2 million year period of the upper middle Jurassic. As in Ruchottes, we can expect this Premeaux limestone to be fairly well-fragmented. If this were the only stone found below the surface of these vineyards, the wines would taste much more like Ruchottes, but that is not the case.

The middle-upper section of these sibling vineyards is argillaceous limestone. This is a calcium-rich clay matrix may be indurated into stone, or it also may be soft and more marly. The clay, or argile as it is called in French, normally composes up to 50% the matrix, with roughly the balance being calcium carbonate and impurities. To this Vannier-Petit adds the word hydraulique, (in parenthesis), which refers to the fact that this particular limestone contains silica and alumina, that will yield a lime that will harden under water.  The assumption is that this Calcaire Argilleux formed underwater in the Jurassic lagoon or seashore, by secreting quicklime which bound with the clay, 168 million years ago.

Decanter Magazine alternately, and perhaps inaccurately, translates from the French Calcaire Argilleux, into Shaley Limestone, (as seen in the map box). That said, Françoise VannierPetit describes in an interview, that the relationship of clay and shale, is almost as one material that continually is in a transition from clay to shale – and back again, depending on how hardened (indurated) it becomes, or degraded. That stated, shale is generally regarded as lithified clay mixed with silt, the blend of which causes the notable horizontal striations, while a body of transported clay (of a single type, ie. Kaolin) that has been indurated (hardened) is termed claystone. Geologist are notorious for their loose use of terms, which makes it challenging for the rest of us to catch up, and I suspect Vannier-Petit is often guilty of this. AC Shelly is credited with writing in 1988 that “The term shale, however, could perhaps be usefully abandoned by geologists, except when communicating to engineers or management‟

Nothing is as simple as a name. Shale can be found in many forms. The relationship between clay and shale is very tight, just like water and ice.

Nothing is as simple as a name. Shale can be found in many forms. The relationship between clay and shale is very tight, just like water and ice.

Middle to lower slope Bajonien beddings: 

Marnes à Ostrea acuminata & Crinoidal Limestone

The oyster, and other fossils that sedimentologists are constantly mentioning as being present the bedding is really only relevant because it allows the scientist to easily reference age of the material. The fact certain creatures lived only during distinct periods of time, and only in certain environments. So not only does it give scientists the age of the strata, but it tells them a lot about the particular conditions that existed in that location, quickly allows the scientist to assign the formation of the bedding material to a particular period of time. As the fossils display different signs of evolution, (in the case some oysters, their valve position changed over long periods of time) the sedimentologist can establish the age bedding, and allow them to recognize a change of bedding (at on the surface) simply by the fossils in each location.

Using this methodology, the scientist gleans information about how the bedding has shifted position, or even its location. These shifts have been very significant in the Côte. By categorizing strata by type, and fossil type. and date, they can match one strata in one location with its mate in another.  This methodology allows sedimentologists to correlate strata worldwide.

Oyster bedIn the vineyard of Chambertin, the marl (Marnes à Ostrea acuminata) lies in a layer just beneath the argillaceous material that once was an ancient oyster bed. It is loaded with fossilized oyster shells (Ostrea)  from the upperBajocien period. This soil, into which the fossils are bedded, contains a large amount of the clay, montmorillonite, which has a very high cation exchange rate, and such soils, with their negative charge, attract and hold positively charged ions called cations (minerals like calcium (Ca++), magnesium (Mg++), potassium (K+), ammonium (NH4+), hydrogen (H+) and sodium (Na+) that are crucial for plant growth. This makes this particular marl which lies in the heart of Chambertin, a particularly sweet spot for vines. And because this is a bedding plane that underlies the Argillaceous material above it, those vines whose roots can reach that deeply, may benefit from the Marnes à Ostrea acuminata too. That said, the deeper roots, it is reported, do not typically supply vines significantly with nutrients, that vines rely on their shallower root systems for this function.

gevrey pre slideThe age of the Marnes à Ostrea acuminata dates back to the very late Bajocian, parkinsoni zone 168.3 +/-, well before the Premeaux which lies above it was formed on top of it. This important because this decisively shows that the Comblanchien bedding, which lies at the base of the hillside (and was formed later in the Bathonian), slid down slope, and was pulled eastward with the falling valley. This slide of the Comblanchien, which at one time overlaid the argillaceous and oyster marl material and lay next to the Premeaux, moved downward almost 100 meters and eastward by roughly 200 meters. exposing this older marl and crinoidal bedding to the air, after having been buried underground for the previous 133 million years. The next bedding plane is the also Bajocien in origin, again being older than the Premeaux higher on the hill, and older than the Comblanchien which sits below both Chambertin and Clos de Beze.

The lowest section of Chambertin, and the largest percentage of Clos de Beze’s acreage consists of the well-fractured Crinoidal Limestone. This is the most common base rock upon which, the classified crus of Gevrey are planted.

Crinoids were extremely prevalent the lagoons and Jurassic seas worldwide, until the Permo-Triassic extinction when they were virtually wiped off of the geologic record. Their fossilized remains create weakness in the stone that encases them. This weakness in the stone, coupled with the geological fracturing of the area, has made it relatively easy for the vine’s roots to penetrate deep into this rock strata. Impurities in the stone’s construction, allows for chemical weathering, brought about by rainwater infiltration, to create rich primary clay bedding for the vines, within the breaks and gaps in the rock. These factors have proved that Crinoidal limestone provides a very effective and fertile bedding for Pinot Noir to grow.

Wilson described the Crinoidal limestone as being “cracked by numerous small faults which ‘shuffle the cards’ of strata, but generally are not large enough to ‘cut the deck’ to introduce markedly new strata.” Terroir (1998) p.131.  This is typical of his breezy style, and while it is visual (in terms of cards), it really doesn’t have much concrete meaning, other than being a colorful way to say the crinoidal stone is well-fractured. He does go on to say that this extensive fracturing allows the stone to be a good aquifer for the vines.

crinoids

Colluvium: atop the bedding planes

Almost every grand cru vineyard in the Côte de Nuits has significant amounts of colluvium mixed in their soils. While Ruchottes-Chambertin does have colluvium is one of the most glaring exceptions it is not significant in quantity.  Typically, this colluvium is accompanied by a fair amount of transported clay, which when together often forms marl.(2)  Rarely does one exist without the other in vineyards that have been classified as grand cru.

In the Côte de Nuits, there tends to be more colluvium in the colluvium to clay matrix, while in the Côte de Beaune, there tends to be more clay.  This tends to the case because there are many more marl bedding planes in the Côte de Beaune than there are in the Côte de Nuits, where marl bedding is rarer. There may be more shale in the Côte de Beaune as well.

 

The tête de cru, –  the very finest of the grand cru vineyards, have relatively equal proportions of marl and colluvium and sit only upon the slightest of slopes. This applies to the vast majority of Chambertin and Clos de Bèze vineyard area. These crus possess a perfect planting bed for vines: they have colluvium/marl based topsoil that is at least 50 cm (19 inches) deep where the absorbing roots are active.(3)  Because of this construction, the soil has good porosity for root and water infiltration but is not so porous a material that the water does not drain right through it, or cause it evaporates quickly from it. Additionally, because of its rocky nature, the grand cru soils tend to resists compaction.

While there is a band of harder, less fertile Premeaux stone on the uppermost slopes of Chambertin and Clos de Bèze, this represents a minority proportion of these vineyards. Parcels that have vines on these upper slopes, often lend a measure of finesse to the finished wine, without impacting the palate impression of the finished blend. For these reasons, Chambertin and Chambertin Clos de Bèze are among the finest vineyards in the Côte de Nuits.

Clos des Ruchottes, (and Ruchottes in general) is a far different vineyard than its two neighbors. With the near-pure calcium stone beneath its shallow soils, the low levels of impurities mean that when it weathers,  very little clay is produced. Because of the scant soil, the vineyard their neither contains nor can it attract, as much in the way of nutrients for the vines as can Clos de Bèze with which it shares a border. The resulting wines typically have less fruit, less color, seem more structured or tannic, and have a finer, though thinner texture. On the upside, the vineyard produces a very classy wine that can have excellent aromatics, remarkable finesse, and has excellent age ability.

Agree? Disagree? Comments are welcome and encouraged! Please feel free to like or share this, or any other article in this series!


Note: Many authors note that Clos de Bèze has Oolitic limestone. Vannier-Petit does not note this on her map. Instead, she places the Oolitic stone in the premier cru of Bel Air, which sits directly above it. A likely explanation of Oolite being cited as existing in Chambertin is scree/colluvium from Bel Air has slid down, to litter Clos de Bèze from above.

(1) The problem with always talking about the Saône Fault, is it ignores the fact that the fault is really the most minor part of the geological event that happened. It was a continent being pulled apart, that caused a void into which the land adjacent to the Cote d’Or fell into a trough which would become the Saône Valley. The Saône Fault is nothing more than as scar marking that event. And in fact, the Saône Fault lies buried quite deeply underground – its general location is only estimated.

(2) Marl would require a smaller particle size than just rock and gravel sized limestone pieces to produce the non-clayey consistency that marl displays.

(3) Despite the conventional wisdom to the contrary, it is this shallow absorbing root system that gathers the majority of nutrients that vines require.

 

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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 1.3: The Question of Amoureuses and Comblanchien

 by Dean Alexander

And then there is the issue of Amoureuses.  Early last year, Decanter magazine published an article profiling Francoise Vannier-Petit, in which the geologist noted that the soils of Amoureuses have “only 10cm–15cm of soil above the subsoil”. It was in the context of another subject, so nothing was mentioned about the stone below, but given this lack of topsoil over Amoureuses, I would not expect a hard stone like Comblanchien to lie below just below the surface. This is a stone prized by architects and designers for is grains so fine that it is virtually impervious to water, for its immense strength, and its high levels of elasticity, all which are due to its nearly pure 99% calcium carbonate content. In other words it is very resistant to fracturing. But that is just what two of the premier experts on Burgundy, Clive Coates and Remington Norman, have written: Comblanchien lies below Amoureuses.

amoureuses topography

Amoureuses hangs off of Le Musigny like a broken appendage, with topography unlike any other vineyard in Burgundy.

I first became aware of this reported bedding of Amoureuses, when Neal Martin, in his introduction to reviewing the wines of the vineyard, mentioned that the vines were planted to a bedrock of Comblanchien. It seemed that this information could not to possibly be true. This stone’s ability to resist fracturing was proved again and again in quarries across the Côte. I emailed The Wine Advocate, suggesting this information may not be correct, and if they had a geological source for that information. I was beyond curious. Neal Martin kindly responded, citing Clive Coates’ book, “My Favorite Burgundies”.  This would come up again once I finished Part 1.2 of this series. In the comments section, a very knowledgeable reader, Victor discusses that both Coates and Remington Norman claims Comblanchien lies beneath Amoureuses.

So it was time to search out Coates’ now oft-mentioned passage. It follows.

The soil here is similar but shallower than the lower sections of Musigny above. There is more rock and more limestone on the section closest to the overhang, and there is some sand. But overall it is very gravelly, mixed with limestone debris, the limestone being less active than elsewhere in the commune, directly over the mother rock, Comblanchien in origin.  Clive Coates, My Favorite Burgundies

In considering what he wrote, these are my takeaways: The limestone debris he writes of, typically would have slid downslope from above, onto Amoureuses. However, if the stone was significantly fractured, and with 10 to 15cm of soil, at some of this colluvium could have been developed in situ. It is very likely that centuries of farming would have churned up stone below to combine with debris accumulated from other locations.

When he talks of  the limestone being less active, he is referring to the fact that the gravel and stone of the vineyard is tightly pored, causing it to resist chemical weathering. This would be consistent with a very tightly grained, limestone with a very high calcium carbonate content. This is certainly a clue pointing toward Premeaux or Comblanchien limestone as the base for the colluvium. It means the calcium carbonate is not as active in becoming solvent due to carbonization, and very little clay is being formed at the site. It may also mean that the soil has a lower pH than other vineyards in Burgundy. This is all covered in-depth in part 2.1.

The primary limestones of the Cote de Nuits.

Four of the several limestones of Marsannay and the Côte de Nuits. photo: Organisme de Défense et de Gestion de l’AOC Marsannay

With all that description, however, he never mentions any fracturing to the “mother rock,” and at least to me, this is the key the issue at hand. If the stone was indeed Comblanchien, then it would have to be significantly fractured for vines to grow there. Given that in all of Gevrey, where there is significant Comblanchien, the stone is never present where the soil was shallow.

Further bolstering my doubt, was that stone had been quarried only a matter of feet from the vines Amoureuses, where the premier cru vineyard of Vougeot “Les Petit Vougeot” is located today. The stone cut from Les Petit Vougeot site was used for the construction of  Abbaye de Cîteaux, which after the revolution in 1790, was seized from the church and renamed the Chateau de Clos Vougeot. Certainly, the Abbey wasn’t built out of fractured and crumbling stone.  If the limestone in Amoureuses is, in fact, a hard stone, much less the hardest stone, the base rock could not just have a few fractures. It would have to be shattered. I was virtually sure the stone had been misidentified.

however…

However, a very visible fault cuts through the vineyard that seems to end abruptly at the quarry site. The lower section of the vineyard having been torn away, and down from the upper portion. This required extensional stress, the kind which is most damaging to stone, literally pulling it end from end. From that extensional stress, we can expect deformation and fracturing throughout the stone structure, on either side of the fault.
We also know that the longer the elastic range of stone (and Comblanchien is very elastic due to its 99% calcium carbonate content), the shorter the ductile deformation range. In other words, like a rubber band, it will stretch significantly before it snaps; but when it does, it will snap suddenly.

Topographically speaking, there are no other vineyard locations in the Côte de Nuits-like this stair-stepped vineyard, save Haut Doix which is joined at its hip. They are remarkably unique vineyards for the area. Certainly, something geologically special had happened here.

So with no more information, the question of Amoureuses remained open. But perhaps I would be able to answer the question whether it is possible to plant vines in shallow soil above Comblanchien, or in other words, remove my doubt. I would begin a look for examples of Comblanchien at shallow depth in other vineyards…and I really wanted to know what shattered Comblanchien might look like. I would find answers to both.

Enter parallel evidence.

Marsannay En la Montagne

Marsannay cru of La Montagne: Against the base of the hill sits a steep face of 12% slope. Here the soil is very shallow, with compact soils, and notably geologist Vannier-Petit has identified the stone below as Comblanchien. Interestingly, Vannier-Petit doesn't show any faulting at its base, which I would have expected. I makes me wonder what the reason for this for transition of stone type, and what caused the dramatic change in elevation? Folding would explain the elevation gain, but not the change in limestone. As always, there are more questions with no answers.

After an initial flat section of vineyard, a hillside of Comblanchien stone rises in the middle of the La Montagne vineyard. The slick PR brochure claims the hill to be a 12% grade, but it appears to be much less. The soil on the base is claimed in the brochure to be shallow and compact, two characteristics I would expect on a steeper slope. Vannier-Petit’s map shows a major fault just to its north-east. I wonder what the reason for this for transition bedding, without faulting, and what caused the change in elevation? Folding would explain the elevation gain, but not the change in limestone. As always, there are more questions with no answers. map source: Organisme de Défense et de Gestion de l’AOC Marsannay

Combe du La Montagne sits near the mouth of the Combe du Pré, a large ravine or valley, just north, above this photo. Interestingly, but not unusual, the map shows vineyard plots that don't exist. According to the map, there should be a small sliver of a vineyard between the two vineyards on the upper right of the photo, but there is not one that I can detect from satellite images. It is solid forest in that location.

The vineyard En la Montagne sits near the mouth of the Combe du Pré, a large ravine or valley, just north, above this photo. Interestingly, but not unusual, the map shows vineyard plots that don’t seem to exist. According to the map, there should be a small sliver of a vineyard between the two vineyards on the upper right of the photo, but I can detect none from satellite images of the region. There is nothing but continuous forest in that location.

Geologist, Francoise Vannier-Petit’s work in Marsannay was commissioned by the regional trade organization, the Organisme de Défense et de Gestion de l’AOC Marsannay, and the results were released to the public in March of 2012. This information was assembled for a public relations brochure, developed to support the organization’s application for gaining premier cru status for various top vineyards within Marsannay.

I had discovered the publication (which is entirely in French) in June of 2014 but had really only inspected the sections germane to our producer of Marsannay wines, Domaine Joseph Roty. In truth I had completely forgotten I had this information in my possession, until I started to wonder if Comblanchien could be found in Marsannay, an area Vannier-Petit had surveyed. Apparently, there is an English version available but have not been able to find it.

Regarding Marsannay in general, she brings up some really interesting observations I had never seen in regards to Burgundy. This is relevant because many authors have mentioned that Marsannay and Gevrey are very similar in terms of soil types.

“The horizontal layers of limestone and marl are fractured; they form broad stairs of several hundred meters, collapsing from West to East. The intense fracturing of the clay-limestone alternations composed a geological mosaic on which is superimposed on the plot lace localities of the appellation. The expression of the multifaceted local proves through this great geological diversity.”

Clearly, the google translation is not perfect, despite this, it is of considerable interest that she mentions that the “clay-limestone alterations” are “intensely fractured”.  Within this paragraph are several illuminating concepts that I have never read before regarding Burgundy, and are very likely a significant factor understanding soil production for the Côte. 

More than just limestone

Marlstone 

sedimentary stone flowchart

sedimentary stone flowchart. Click to enlarge

The first mention is of fractured marl (small limestone particles mixed with clay), indicating this was marl which over long periods had been indurated (hardened) by geologic pressures. Marlstone was a favorite building material of the Romans, who prized it for its workability, but it is more prone to fracturing and chemical weathering than limestone. This is likely due to its relative porosity, as well as its weaker chemical bonding of the mixed materials that make it up.

Claystone

very low on the slope This limestone is found at a turn in the road, very low on the slope, just before the road tilts upward. sits this stone which is heavily colored by the rust from the soil. This certainly looks like a fault line, and the hillside above is steep, suggesting the bedding plane is tilted. The stone is holding together, but just barely, with heavy horizontal fracturing evident by the long striations. Certainly the root systems of the trees and bushes are adding its destruction.

This stone is found before D108s first hairpin, very low on the slope. The stone is holding together, but just barely, with heavy horizontal fracturing evident by the long striations. Certainly, the root systems of the trees and bushes are aiding its destruction. photo: Googlemaps. click to enlarge

Also mentioned in the next sentence is layers of clay which also had been indurated into claystone. Claystone, which is harder than steel, can fracture due to hydraulic expansion as it gains moisture. Further frost wedging and can shatter into many small, hard fragments which can be dispersing throughout the soil. If it is chemically weathered, it can regain its plasticity, and return to its clay form. Much more about the formation clay and its close relationship to limestone in Part 2.1.

Mudstone and Shale

Now depending on the amount of silt (particles of feldspar and quartz that are larger than the particles of clay) mixed into the clay, this hybrid material can be termed as mudstone. Mudstone which is made up of many fine layers is considered to be laminated, and if it can be split into many layers, it is considered to have fissile. And just like that, we are now talking about shale. The relationship between these materials is so close, that through mechanical and chemical weathering, the shift forms from one to anther, and back.

The brochure and the search for fractured Comblanchien

While a couple of other vineyards had notable amounts of Comblanchien low on the slopes where there would be deeper soils, these were not of interest. Only the only the upper slopes where the soil would be shallow like Amoureuses were relevant. One vineyard, in particular, fits the criteria, En la Montagne.

Marsannay en la Montagne. Map Vannier Petit & Emmanuel Chevigny

Marsannay en la Montagne. Map Vannier Petit & Emmanuel Chevigny

En la Montagne is in the northern most section of Marsannay la Côte, the largest of the three villages that are entitled to use the name Marsannay.  The vineyard sits just below the mouth of an enormous ravine, the Combe du Pré. Several of these ravines cut through the significant hills above Marsannay, and are have a significant impact on the wines of the region, having spilled wide areas of alluvial soils across swaths of vineyard land, and allowing air to travel easily east-west through their openings, cooling the region. The hillside has a pair of significant faults which water likely exploited, cutting through the hillside, creating the Combe du Pré via thousands, if not hundreds of thousands of years of constant erosion.

Regarding En La Montagne {from the brochure}:

Located at the top of the hillside vineyard between Chenôve and Marsannay-la-Côte, the place called “In this Mountain” (En la Montagne) a large topographic variation, from 292 to 354 meters above sea level, with an average altitude of 315 meters. The slope is small foot hill ( 3%) and high hillside high (12%) , with an average value of 5%for the locality. The climate is south facing. 

La Montagne is based exclusively on limestone bedrock. The limestone Prémeaux, white Oolite and especially the Comblanchien provide abundant clear stones and a very thin soil.

Clear stones, I can only assume means thant they are free from impurities, and are nearly pure in calcium carbonate.

 

Upper slopes of La Montagne. The slope is more gentle than the name or brochure suggests. You can see D108 winding up the hill in the background.

Upper slopes of La Montagne. The slope is more gentle than the name suggests. You can see D108 winding up the hill in the background.

The vineyard itself is quite small, with a flat section at the bottom, and a relatively short rise before the tree line. I would not expect exceptionally shallow soils due to its relatively gentle rise of 3%. This rise is where the Comblanchien lies. The slope rises more steeply once in the trees. The small plots above, which also have Comblanchien as bedrock are not significantly steep either, however. The vineyard section in the photo below looks to be around 4% to 5% near the top, but the bottom it looks to be a bit steeper.

An upper plot of la Montagne which is over Comblanchien

An upper plot of la Montagne which is over Comblanchien. This looks to be 7 to 8% grade near the bottom, and more like 4 to 5% toward the top. Ironically, this road leads to a small public drop off point for garbage.

While it there are no direct correlation that made from en la Montagne to les Amoureuses, as their circumstances, soil and locations are very different, the existence of Comblanchien below this vineyard and the highly fractured Comblanchien in the hills above, certainly gives evidence that Comblanchien is no more immune from severe fracturing than any other limestone, given the right circumstances.

Yes. Amoureuses could very well be fractured Comblanchien. Additionally, the photos below show that while significant fracturing can occur in one location, the stone, just a few yards away, may remain intact.

Comblanchien?

What does fractured limestone look like below the vineyards Burgundy? Here is the answer. This taken via googlemaps, on the lower slopes of D108.  Photo: googlemaps  click to enlarge

 

This map is difficult to determine where the road is as the line indicating it stops before it reaches the section of D108 where these photos are taken. The road clearly does cross at least one fault line (the red lines on the map) Map Vannier-Petit and Françoise Dumas

 

La Montagne to the right and the road up the combe to the left.

La Montagne to the right and the road up the combe to the left.

 

lower on the slope

This is also shot on lower on the slope, just after the first curve going up the hill. Although the Terre rouge or soil containing iron-oxide which stains the stone, it appears these may be two separate beddings. The white stone on the bottom center appears to be Comblanchien, while the yellow stone to its right may be Premeaux or other another limestone. This would match the change in Vannier-Petit’s map, but determining the location impossible.  photo: googlemaps  click to enlarge

Higher on the slope

Higher on the slope, this white limestone is likely fractured Comblanchien. While on the incomplete section of the map, Comblanchien is indicated this far up on the hillside. Photo: googlemaps  click to enlarge

limestone  photos: googlemaps  click to enlarge

unfractured limestone

Unfractured limestone low on the slope of the first turn. Why didn’t this stone on the left side of the photo fracture, when all else did? The right side of the photo shows some fracturing.  photo:googlemaps  click to enlarge

 


Author’s Note: Vannier-Petit is credited at the end of the publication as being responsible for the conception and information in the brochure, so I have accepted the words within it as if she were the author, which is likely not the case.

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 Part 1.1 Limestone: formation

by Dean Alexander

Limestone Formation and Types

The Cote d'Or is the hanging wall of a faultline formed by

The Cote d’Or is the “footwall” of a fault line formed by the Saone Valley dropping away from the escarpment.

 

As the Burgundy legend has it, it is the limestone that sets Burgundy apart, and makes the wine that comes from there so special. But what does all of this limestone really do? Does it impart flavor, as some people say, imparting a minerality, or does it create a perfect growing condition for the vines? How does it interplay with what is possibly the most important component of farming, the clay, and what is its relationship with the limestone? Then there is the scree, or gravel, intermixing with what geologists sometimes refer to as colluvium. Together this makes soil, but how it got there, and how it is changing perhaps most important. The forces of erosion that constantly tear down the geological structures with its wind and rain and freezing temperatures. This is where the rubber meets the road of terroir, and I will look at all of these factors quite carefully over the next few writings. But first, for Part 1.1, it’s all about the formation and types of limestone that makes up the escarpment.

From the beginning

We typically think of hillsides as being pushed up, and indeed the hills of the Hautes-Cotes de Nuits were formed by folds in the sedimentary bedding. But the Cote itself was formed when the Sôane Valley was pulled down and away from the Côte d’Or  Burgundy 35 million years ago by a large fault that runs near the highway RN74, as the Saône Valley dropped away as a graben. The Côtes d’Or is actually the broken facewall of the horst. But before that, the story of Burgundy started with a sea, teeming with unbridled marine life.

ammonite

ammonite: courtesy of the Natural History Museum http://www.nhm.ac.uk

Just how much marine life has impacted this planet is represented by the vast majority of limestone formations that have grown here, constituting 10% of the total volume sedimentary rock, which represents 75% of all geological formations. Most limestone is credited to biologically produced calcium carbonate that is naturally extracted from eroding shells sea animals. Shell production, for defense against predators, began in the Cambrian period (500 million years ago.) This occurred with a change in the ocean chemistry which allowed the calcium compounds to become stable enough for allow for shell production. While at the same time (give or take a few million years), the animals adapted through mutation, to produce the needed proteins and polysaccharides, and the ability to produce shells for protection against predators. The success of this new animal life led to an explosion of species, and the warm shallow seas that covered central France were densely populated. The seas of the Jurassic period were filled with calcium producing crinoids, ammonites, oysters, and as corals. As the exoskeletons of generations dead sea creatures accumulated on the seabed, eroding, the waters filled with high concentrations of calcite and (or) metastable aragonite, (depending on the water chemistry of the period), where it precipitated into a thick, jelly-like solution at the bottom of calm lagoons and shallow seas. Eventually, this layer would solidify and compression would indurate (or harden) the (CaCO3) into limestone. Non-marine limestone is less common, with calcium being deposited in a location by the water, or calcium carbonate can accumulate at the bottom of lake beds, forming limestone.

Modern Crinoids are animals, organisms with a nervous system, and the larvae are capable of swimming freely before metamorphosing to the sessile form seen in this photo.

“…crinoids are animals, organisms with a nervous system, and the larvae are capable of swimming freely before metamorphosing to the sessile form seen in this photo.” http://www.mnh.si.edu/LivingFossils/crinoid1/htm

 

Calcium carbonate is soluble in groundwater containing relatively low acid levels and is responsible for the chemical weathering that forms limestone caverns and sinkholes. Interestingly, the calcium carbonate in limestone is more soluble in low-temperature environments than in warmer tropical climates that it began in. In a cycle that will likely continue during earth’s lifespan, limestone is formed, and then eroded (and been transported) by groundwater, to reform in another location. Limestones are sedimentary rock formations that contain at least 50% calcium carbonate in the form of calcite and or aragonite. The higher the percentage of calcium, the harder, the less porous, and more water-resistant the limestone becomes. Even the hardest limestone of Burgundy contain at least some silica, which after the chemical weathering of limestone becomes phyllosilicate minerals, the primary element in clay.  However, the higher the percentage of silica and other impurities renders a stone that is more porous and more easily friable (the ability to fracture or crumble) It is my belief that it was these impurities that have allowed Burgundy to become the great growing region it is today. Had all the limestone been the pure hard Comblanchien that the region is so famed for, I suspect there would not have been enough viable, arable land to have any significant grape growing area. But that is supposition on my part. Back to more fact-based information.

Comblanchien Limestone Quarry in the Cote de Nuits

Comblanchien Limestone Quarry in the Cote de Nuits

There are a number of common limestones in Burgundy, each which contain varying percentages of calcium and differing levels of impurities. The harder limestones are typically named after the towns that they were quarried for building materials, while softer, non-commercial limestones can be named for their fossilized sea life contained in them, or by the shape of their construction. Don’t be confused by names like Bajocian limestone and Bathonian limestone: these are not types of limestone, rather they are periods of time within the Jurassic when the limestone was formed. It is easy to be confused. I recently read this snippet from a knowledgeable, professional wine critic trying to explain the geological differences between the Côte de Beaune and Côte de Nuits. They wrote “…the Comblanchien limestone to the north and the Jurassic rock formation to the south…”  apparently unaware that Comblanchien is a limestone formed during the Jurassic period. I mention this only because it highlights the confusion even highest-level of wine professionals have about terroir and the geology of Burgundy.

Limestone Types (that you may read about)

Calcaire: The fact that English speaking wine writers use the word calcaire, is simply confusing to almost everyone trying to actually learn something. Calcaire is nothing more than the French word for Limestone.  We say limestone, they say calcaire.

comblanchien-limestone-

Comblanchien-limestone-

Comblanchien is a name bandied often by wine writers as if it is an attribute in a wine’s character. But the facts point to this stone having a negligible if any effect on the vines grown directly above it. Comblanchien is 99% pure calcium carbonate, often giving the stone a white color. As a building material that is commonly referred to as Comblanchien Marble. It is so dense and fine-grained that it can be polished. It can be white (clair), beige, or slightly pink.

Comblanchien formed from still water lagoons that were hyper-rich in calcium, and relatively void of sea creatures that would cause impurities. Presumably, the calcium solution was so concentrated that sea life did not live there, and generally did not disturb the (CaCO3) sludge in the areas where Comblanchien was forming. The spots in Comblanchien are not fossils or impurities, but the trails of worms that wiggled through the thickening lime ooze. The hole made by the passing worm was then filled by pure, clear calcium carbonate, and like a glue, it cemented the whole into a solid, amazingly dense block of stone.

Comblanchien Clair Limestone

Comblanchien Clair Limestone

Most defining in its role in terroir picture is Comblanchien’s exceptionally low-level of porosity. The stone virtually does not absorb water so it will not crack when frozen. Vine roots cannot penetrate Comblanchien if it has not already been fractured, which tends not to happen since it is so water-resistant. Where a vineyard grows over Comblanchien, (1) there is a need for a deep layer of topsoil for the vine roots to inhabit. Where Comblanchien reaches the surface at the top of the vineyards in the Gevrey-Chambertin, no vines are grown (or can grow?) A strata of Comblanchien sit at the top of the Côte de Nuits‘ vineyard as a cap rock, and it’s hardness and resistance to decomposition keeps the hill above from eroding. The result kept the depth of vineyards there, (this is particularly evident above the grand crus of Gevrey) in a very narrow band  An opposite example would be the Côte de Beaune. In Beaune the cap rock (if in fact there is one) is much softer. Because of that, the hillside is eroding at a much faster rate, a creating lower hill lines and much deeper (east to west) growing areas. Off topic, but not have to rehash this later, writers often contribute Beaune’s faster erosion rate to its younger limestone makeup (mid-Jurassic compared to upper-Jurassic which younger), but I believe it is the impurities or the porosity of the limestone, not the age (curing) of the limestone, are the factors of its faster erosion.

Comblanchien technical statistics: Water Absorption:% 0.49  Compressive Strength: 160.0 – 203.4 MPa (Comblanchien Clair: compressive strength 203MPa)  Density:2660 kg/m3

 

Rose de Premeaux

Rose de Premeaux Limestone

Premeaux is another hard limestone used in construction, but it is not quite as hard as Comblanchien. I have not found any reference as to how much calcium carbonate is in Premeaux Limestone, but as evidenced in this photo, it does crack and fracture. This is due to the fact that it will absorb 12 to 18 times more water than Comblanchien, which when permeated, then frozen, will crack stone. Premeaux, unlike Comblanchien limestone, is found at very shallow depth under vineyard land, most notably the Grand Crus of Ruchottes and Mazy-Chambertin, where in places the vineyard was dynamited in order to allow the plants to gain a foothold.

Premeaux technical statisticsWater Absorption: 6-9 By Vol.%  Compressive Strength: 120-180 MPa  Density:2400 – 2500 kg/m3

 

Crinoidal Limestone

Crinoidal Limestone

Crinoidal Limestone is closely associated with the Bajocian period and is named for the Crinoids that team its construction. Crinoids are multi-armed sea creatures that are filter feeders. Anemones, starfish, and urchins are among the 600 species of Crinoids found in today’s seas, but during the middle Jurassic there were many times more species, and they densely populated the shallow lagoons of Burgundy. Crinoidal limestone is friable, meaning it can be broken or crumble, because of its heavy fossilization. The hillside of premier crus, including Lavaux, Estournelles and Clos St Jacques in Gevrey-Chambertin is entirely made of crinoidal limestone. This formation continues above the Route de Grand Crus, underneath Chapelle, Griotte, Latricieres,  Charmes-Chambertin, as well as the lower half of Chambertin itself and Clos de Beze. To my mind, this is ample evidence that Crinoidal limestone is one of, if not the finest limestone for growing vines.

 

A close-up of Oolitic Limestone, which composed of tiny spherical ooids bonded by a calcium secretion.

A close-up of Oolitic Limestone, which composed of tiny spherical ooids bonded by a calcium secretion.

Oolitic Limestone formations are unique and fascinating composition. Oolites are formed of oval calcium pellets called ooids that gained their shape as they were rolled around by the wave actions the ancient Burgundian seas of the Jurassic that are super-saturated with calcium carbonate. The ooid spheres begin with as a seed, such as a very small shell fragment, and as this seed rolls around the ocean floor, it chemically attracts layers of calcium to it from the water. The size of the individual oodid corresponds to the amount of time they had to form before they were covered by dirt. While the word ooid typically refers to forms made from calcium carbonate and aragonite, the name means egg so the name ooids can be used to refer to other materials in the same small oval shape. These ooids bonded under a secretion of a calcium cement forming the stone. The grand cru Ruchottes-Chambertin is famous for the ooids found it its topsoil, and presumably oolitic limestone formations are there also along with the more prevalent Premeaux limestone.

Nantoux is an oolitic limestone is named by the late geologist James E. Wilson as being the stone that was once quarried in and above Meursault- Les Perrieres. Named after a village nestled in a valley above Pommard, it appears on Vannier Petit’s Pommard map, just north of the village, very low on the slope. She labels it as an oolitic stone, Wilson gave no details of the stone other than its former quarry location. I have seen no other reference to Nantoux other than these two brief references.

Argillaceous Limestone

Argillaceous Limestone is at least 50 percent co3, with the balance being clay. A very soft stone. Perhaps the perfect limestone for vineyards?

Other limestone types that rarely, if ever, appear in writings. Of the more common: Chassagne and Ladoix both appear on Francoise Vannier-Petit’s Pommard map, but there is little reference to them elsewhere. Both stones are available commercially as building materials, and both stones have pages dedicated to them on the Contactstone.com website, listing these stones density, strength, and water absorption similar to that of Comblanchien. However, they list Ladoix being an alternate name for Comblanchien limestone (as well as an alternate name for Corton Limestone), so it is not clear what the differences actually are at the geological level.

Argillaceous Limestone consists of larger amounts of clay, often making them quite soft and friable. In many ways, it is like a hardened version of marl. The stone may appear silvery due to the substantial amount of clay component. The vineyards of Chambertin and Clos des Beze both have sections in the heart of those vineyards that is made up of argillaceous material, as well as the lower third of Lavaux St-Jacques and Clos St-Jacques. Vannier-Petit labels these sections as Calcaires Argilleux (Hydraulique) on her Gevrey map which can be found at  www.joyaux-cotedenuits.fr/

Bioturbated Limestone

Bioturbated Limestone

Bioturbated Limestone is not actually a limestone but a disturbance to the forming stone that before it completely set. Whether calcium deposit was disturbed by an animal, a wave, or geologic action, churns the curing material. This agitation, or  Bioturbation, creates weakness in the limestone and can cause it to be quite friable depending on the impurities and the amount of disruption to its structure.

Travertine is not a maritime derived stone. It is a terrestrial calcium carbonate formation that is created by geothermally heated springs. Travertine is a very porous stone (that is filled and sealed by the stone industry for use in construction), and that porosity is caused either by calcium dioxide evasion or by organisms that have grown on the stone’s surface. As far as I am aware there are no Travertines in Burgundy.

Tufa is a calcium carbonate formation similar to Travertine, but Tufa is even more porous due to its large macro biological component. Tufa has no relation to the volcanic rock Tuff, which is often referred to as “tufa”. As far as I am aware there are no Tufas of either sort in Burgundy.

Marble is a limestone that has undergone a major geological event involving high pressure and or heat. In this process, limestone carbonate materials are recrystallized, very commonly calcite or dolomite. The colors in marbles are from the metamorphosed impurities in the stone that have become new minerals.

This hopefully gives a fairly detailed overview how limestone was created, and how susceptible it is to damage. In Part 2.2 I’ll look at how this limestone has been fractured and eroded, creating the basis for what would, over millions of years, become great vineyard land.

Up Next: Understanding the Terroir of Burgundy, Part 1.2  Limestone deformation and fracturing. (click here)

Previous: Understanding the Terroir of Burgundy, Introduction (click here)

Understanding the Terroir of Burgundy, Preface (click here)

 

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(1) This is suggested by examining the geological vineyard mapping, recently published by the geologist Francoise Vannier-Petit.

* Calcium bicarbonate is what forms stalactites and stalagmites in caves and caverns.