Understanding The Terroir of Burgundy part 4.4: Erosion: a challenge to the authenticity of terroir

Erosion Vosne wider implications

Our best understanding of soils of the Côte de Nuits:

In trying to grasp the relationship of the wines made soil from particular crus, many writers, myself included, have come to many fundamentally incorrect conclusions regarding terroir. My version could be summarized into this:

I believed that chemical and mechanical weathering of the limestone bedding naturally created soil types that were dictated by their position on the slope. Highest on the slope, the compact limestone soils were produced by the simultaneous production of clay and the erosion of clay. Lower on the slope, where transported clay enriched the otherwise arid, colluvial soils, I believed that if farmed carefully, clay production could remain in a relative of a state equilibrium with clay erosion. While, it most of these vineyards may not absolutely been in their natural state as when the Romans arrived, of many mid-slope Burgundy vineyards, I felt were relatively authentic in their terroir.  

A challenge to the authenticity of terroir:

Vosne-Romanée Les Damaudes, sitting upon the upper-most slope, with a 12% grade had equal parts clay and gravel in 2004. This is despite already having lost 54mm depth of clay sized particle since 1952. In the foreground, Vosne Malconsorts is allowed to grow it's grass in June of 2012. photo: googlemaps
Vosne-Romanée Les Damaudes, sitting upon the upper-most slope, with a 12% grade had equal parts clay and gravel in 2004. This is despite already having lost 54mm depth of clay-sized particle since 1952. In the foreground, Vosne Malconsorts is allowed to grow its grass in June of 2012. photo: googlemaps

The 2008 study on the changes to soil composition following a heavy rain event by Quiquerez, Brenot, Garcia, Petit, and Catena, presents, in my view, far greater implications than the study’s more simple intent of establishing hard erosional data following heavy rain events.

The study’s plot site, high up on the hillside, with a long, 12% grade, would challenge the perception that upper-slope, Burgundian soils naturally carry low percentages of clay or silt. This vineyard, with its 40% clay content, at the onset of the study, is doubly surprising, given that the data showed these materials exhibited a high erosional rate out of the plot area. What the soil recording reveal natural soil composition of this hillside originally contained far more clay than we could have ever expected based on the compact gravel “soil” condition of even the best of the upper slope vineyards today.

This study not only gives us a prophetic view of this vineyard’s future soil but also clearly illuminated a much more fertile soil in the past. Just as this vineyard once had an exceptionally high clay content, there is every reason to believe this was also true across the breadth of Burgundy vineyards, indicating a very different erosional story played out regarding the ‘arid’ soils of elite mid-slope vineyards. This information directly challenges our perception of the authenticity of the terroir within many of today’s Burgundy vineyards. 

What the study of this vineyard tells us is that, at least on this site, there has been a relatively tight erosional timeline, with much of the damage occurring over the past half-century. Additionally, the erosion is projected to finish its ‘third act’ in Les Damaudes over the next 25 years, at which point it will have a classic Burgundian compact limestone soil.  While it would appear that mechanized farming as the most erosive in this vineyard’s largely unreported history, we know that there was massive erosion in other vineyards over the centuries. The remaining question is: What about the historical farming of this vineyard allowed its clay to remain in this parcel of Les Damaudes?

*This article is based on the findings a pair of studies chronicled in Part 4.3, and centers upon the upper hillside plot of Vosne-Romanée’s village cru of Les Damaudes.

Why is this study so important to our understanding of Burgundy?

It has slowly become apparent that the problem in talking about the terroir of Burgundy is this: We really don’t know what the wines of Burgundy might have naturally been, had men had both the knowledge and forethought to do what it would take to preserve these vineyards centuries ago. However, a study like this (click here) gives us the ability to hypothetically see both where this vineyard is going, and what it might have been like before man caused so much erosion upon the hillsides. We were lucky that the researchers chose this particular vineyard at the top of VosneRomanée for their study. Les Damaudes is a steep hillside vineyard (in the most revered of villages) that is only midway through its journey of erosional destruction.  A study of a vineyard from any of the other lesser appellations could easily be dismissed as not being applicable to les grands villages de Bourgogne. But with a vineyard within VosneRomanée, there is no doubt as to the applicability of the information, as this vineyard is in the immediate vicinity of some of the greatest vineyards in the world, including La Tache and Romanée-Conti.

soil projection
The projected future soil composition of Les Damaudes over the next 5 storms (roughly 25 years) Click to enlarge.

It has become increasingly clear through the research in preparing this series of articles, that vineyards like Ruchottes-Chambertin have been so seriously degraded by the techniques of the farming employed there, that the terroir we talk about today is one that wears immense repercussions of the farming practices of the past centuries. However, it seemed plausible, that the upper slopes could naturally have developed a compact limestone soil, (one that is 85 to 90% crushed limestone and only 10 to 15 % clay). But these studies re-orient our thinking, forcing us to realize that this is not a soil type that is natural to Burgundy. Because of that, it is not a terroir that is natural to Burgundy.

It is not to say that these vineyards, with their degraded soils, do not produce beautiful or interesting wines, but we must realize that this is a vineyard condition that has been inflicted by man. In the truest sense, Burgundy now has a terroir that has been drastically altered, metamorphosed by the actions of man.

Note: at the bottom of this article I discuss data gaps and the certain information the study might have provided which would have been key to a more complete understanding of the soil of Vosne Les Damaudes. 

2004: Establishing a soil base-line

Although the changes to the soil makeup after the 2004 storm were covered in-depth the latter half of Part 4.3, it is the basis for projecting what the soil make up was in 1952, so it bears a brief retelling now.

Click to enlarge. Adapted from the paper "Soil degradation caused by a high-intensity rainfall event : implications for medium-term soil sustainability in Burgundian vineyards" Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008
Click to enlarge. Adapted from the paper “Soil degradation caused by a high-intensity rainfall event: implications for medium-term soil sustainability in Burgundian vineyards” Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008

In June of 2004, a storm, which was unusually large for Burgundy, dropped 40 mm of water on Vosne Romanee over a 24 hour period. The effects of that storm were studied, and the researchers determined that the vineyard plot had irrevocably lost between 1.8 mm and 4 mm soil due to erosion, a vast majority of which were very fine particles under 63 μm in size.  The material lost was clay and silt since erosion most efficiently targets these tiny particles. (1)

To the right is a graphic I adapted from the study to show the grain size distribution of the soil after the 2004 storm. Each rectangle represents a range of particle size. I also included the before level of clay and silt sized particles to illustrate the loss of those materials, which was shown as 25% in a graph in the study.

 

1952: the soil content of the past

Given the study’s data, we can extrapolate, at least conceptually, what the clay content on these slopes the vineyard was planted in 1952.(2)  Starting with the fact 2004 the hillside contained roughly equal parts clay and gravel at 40+% each; the balance being sand, that we can add 54 mm more super-fine material (smaller than 63 μm) that it did in 2004.  If we assume that past soil loss rates were similar to that of the 2004 storm, we can postulate how much clay would have been present in 1952.  This figure would be much easier to arrive at if the researchers had given us the soil depth, which would allow us to estimate the volume of gravel (colluvium) and allow us a much more accurate estimate, but that information was not within the scope of the study.

Click to enlarge. Adapted from the paper "Soil degradation caused by a high-intensity rainfall event : implications for medium-term soil sustainability in Burgundian vineyards" Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008
Click to enlarge. Adapted from the paper “Soil degradation caused by a high-intensity rainfall event: implications for medium-term soil sustainability in Burgundian vineyards” Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008

The soil loss projections of the next five large storms, predicts that erosion will remove up to 20 mm in-depth in places. The lost material, it is expected would continue to consist of primarily be smaller than 63 μm in size. 

However, would it not be logical assume soil losses of previous storms were similar to that of the 2004 storm? If so, it would not be unreasonable to apply the projected soil loss, in order to estimate the vineyards clay percentage in the past.  If these big storms (of 40+mm rainfall per event) happen every 5 or so years, we can estimate that thirty years ago this same hillside may have had as much as a 70% clay content. How much clay existed before the plot was planted in 1952 can not readily be determined without establishing a rough estimate of the volume of gravel in the vineyard, but it is likely that the vineyard, may have had clay content 85%.  Such a high percentage suggests that either this plot was either not farmed before it was planted in 1952, or was farmed quite differently in the past than it is now. 

In Retrospect

We should not have been surprised that the soils of Burgundy are not as nature created them. We should have suspected something was amiss long ago because the soil type in Burgundy today is one of an arid climate. France, and the surrounding Burgundian countryside, however, do not have an arid climate at all. Rather the climate is classified as semi-continental, where rain is frequent and happens virtually year around. These soils would naturally have at least some petrogenetic development, which it is doubtful that any vineyard in the Côte d’Or does. We were told and simply wanted to believe that the wines of Burgundy are naturally and uniquely sparse of nutrients and clay. Additionally, we have not wanted to believe that, in the course of making these great wines, man has precipitously hastened the decline of the greatest vineyards of the world, though poor farming decisions that have been made throughout the centuries. This has never been truer since the organization of vineyards for the mechanization of farming.


 

Gaps in the data: deficiencies in quantification

As transformative as this study is to our understanding of the wines of Burgundy, the paper, unfortunately, omits some fairly important information. First and foremost, it is unclear how the samples for the data were collected, and secondly how well the data actually represents the soil of the slope in the root zone. The report does say that the soil of the vineyard was homogeneous in its makeup, and no petrogenetic development was observed; meaning the entire vineyard was the same, with no observable generation of new soil. This indicates that what little organic deterioration may develop was washed away by erosion, and no soil horizons (layering) could develop  Lack of soil development and soil horizons would be caused the dual soil disruptions created by regular tilling and erosion.

However, the problem lies in the word “homogeneous”. Even if at some point the soil was homogeneous from topsoil to bedrock, erosional changes to the soils would primarily affect only the material nearest to the surface, and then most acutely in the rill affected inter-rows. Now, even after one storm, the soil is no longer homogeneous in its makeup, because the soil at a certain (unknown) depth would contain more clay and silt sized particles than the topsoil. Now there would be two soil types.

Because of this, we must assume that the researchers collected a shallow soil collection for the sample in order to determine particle size.(3)  Quantifying the depth of this sample is critical, was this a  sample from the first 25mm (1 inch) or 50mm  (2 inches) or from deeper, say 200 mm (8 inches) of depth which is the deepest that most tilling reaches? Further, when the samples were collected: ie before or after anthropogenic resupply of the sediment was returned to the slope, and before or after the soil was tilled, are both important factors in understanding the distribution of soil.  Additionally, knowledge samples at various depths of the sample would be instructive as the effective depth of the erosional change. This is ever truer after workers had returned the sediment to the hillside, and tilled back into the soil.

Root development through soil
The root zone on a hillside vineyard is often restricted to no more than 300mm (12in) to 460mm (18in) represented by the brown strip in the graphic above.  Original graphic of unknown origin.

It would appear that the study only represents changes to the surface soil: those that would most be affected by erosion, and anthropogenic resupply of the sediment to the hillside. it is possible but less likely, that the soil sample may have been taken down to a 200mm depth (8in), which is the standard reach of a plow shear. But even if samples were taken from the 200mm depth, that is only 2/3s of the minimum depth required by a vine for its root zone.

Despite questions and any doubts these numerical omissions might create regarding the validity of the numbers and projections from the study, the value of this information far exceeds reaches far into the black hole of understanding that existed before. For this reason, I accept these numbers and build in a fairly wide mental fudge-factor when considering the above.

 

 

Puligny Folatieres after a rain
A tractor moves on the road between Paul Pernot’s “Clos des Folatières” and Les Clavillons in Puligny-Montrachet photo source: googlemaps

 

Musigny anthopogenic resupply
“Anthropogenic resupply” of redepositing the sediment back upslope is now done with heavy machinery at Comte de Vogüé. photo: Steen Öhman
Musigny anthopogenic resupply 2
Heavy machinery at Comte de Vogüé. Given a major cause of erosion is compression, it’s hard to imagine this is really helping the situation much. photo: Steen Öhman

*Special thanks to Steen Ohman, sleuth, and vineyard historian who writes the excellent winehog.org, for providing me with the 1827 cadastre Map show above.

 


(1) The variance between the 1.8mm figure and the 4mm figure was not explained, but it is likely that lower sections of the vineyard, which were subject to a higher volume of rainwater runoff, and had developed rill erosion, were subject to greater levels of erosional loss.

(2) While the study lumps both clay and silt into a grouping of material by size under 63 μm, according to Wikipedia, as well as other sources, say that silt is primarily made up of the parent materials feldspar or quartz. Feldspar is prone to chemical erosion, just as is limestone, both of which metamorphose into clay (phyllosilicate minerals + water and air), while quartz will not erode due the same contact with the carbonic acid in rainwater.  Although granite (the major source of quartz-silt) is common in the areas surrounding the Cote, like in Beaujolais, it is not found near the surface in the immediate area. Although silt has been washed onto the Cotes by alluvial action and transported to the soils of the Cote by wind erosion, I have to assume that silt-sized quartz fragments are a very small minority in the area’s soil makeup. For that reason, I often refer to the study’s grouping of material under 63 μm, simply as clay. Clay, of course, is actually smaller than silt. Although the size definition varies between disciplines 1–5 μm, the metamorphological change that occurs upon clay is the ultimately defines clay, not its size.  * an underlying reason that I identify this material may also be that — no wine writer has ever attributed any of Burgundy’s success to silt. Am I cowering in conformity?

 

(3) How else could one explain a 15% change in a clay content?  The planting bed must be at least 30cm  (12 inches) for vines to be viable. Most vineyards have this with a much lower clay content, often to 30% less. If we were to use 30cm depth as a baseline, it stands to reason that the depth is likely 30% more than 30cm, being at a minimum 40cm of soil over the base rock though there is likely more. So, if the soil is 400mm deep, and 240mm of that are clay minerals, a 4mm decrease in the clay represents only a 1.7% decrease in clay content in the soil.

 

 

Advertisements

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!

_________________________________________

(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)

_________________________________________

 

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)

 

Please feel free to like, share or reblog, any part, or all of these Terroir articles.

___________________________________________________________________

(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.