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

Vineyard and plot variation confuses our understanding of Burgundy

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

Fractured limestone of Les Perrieres

The patterns of fracture propagation

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

 

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

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

 

Clues to the Côte by examining another fault/escarpment

 

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

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

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

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

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2 thoughts on “Understanding the Terroir of Burgundy: Part 3.3.1 Fracturing variations within upper vineyards

  1. Hi, Dean,
    This is Victor. Just wanted to let you know that I am still following your articles on terroir and enjoy them immensely. I have recommended your blog to some fellow burgundy fanatics, too. Looking forward to more of your articles.
    From you studies, would you say that the plots within a climat such as Les Amoureuses that are close to a fault are probably be better because the underlying bedrock is more likely to be well fractured? I read in another blog that Vannier-Petit mentioned vines planted on the “upper reaches” (away from the edge of the slope, which may be caused by a fault?) of Groffier’s plot in Les Amoureuses have a hard time surviving. She seems to have attributed this to the fact that the top soil gets thinner as you go up the slope; but I wonder if it is also because the Comblanchien is less fractured as you move away from the slope (fault)?

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    • Hi Victor, thanks for the comments!
      I still think that Comblanchien is unlikely in any large quantity in Amoureuses. The wines from this super cru are uniformly to deep and rich to suggest that. A vineyard of Comblanchien would be more structured like Ruchottes, not Musigny.
      However, there is ample suggestion that there is more than one bedding in Amoureuses. Because faulting typically occurs at the junction of two limestone beddings, we might not be too far off in assuming there are two or three bedding types in this vineyard. Certainly the entire lower section was caused by faulting. Perhaps it is like Chambertin, where faulting has opened up the vineyard, exposing older softer beddings between younger harder Bathonian stone. We just won’t know unless a geologist is commissioned to do the work (and it is made public).

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