Thursday, February 27, 2020

Alsace Part 2: The Geology - The Vosges Mountain Paleozoic Evolution

Who knew that learning about the geology of the Alsace would be so complicated. I've already written three blogposts about it!
My first blogpost, Alsace Part 2: The Geology - The Layout of the Land was to give a general overview of the geology of the Alsace. Then I began getting into the weeds with Alsace Part 2: The Geology - The Location of the Upper Rhine Graben, in order to give a context to the next blogpost, Alsace Part 2: The Geology - The Vosges and the Black Forest Mountain.
My focus today will be on the Vosges Mountains. I am interested in learning about the geology of the Vosges Mountains because it is in this location, the sub-Vosgian Hills that the Alsatian vineyards have found a home.
To understand how the different soil types were formed, we have to go way back to the Paleozoic times, some 380 million years ago in the Middle Devonian Period to the late Lower Carboniferous Period (330–320 Ma).
Traditionally, the Vosges Mountains were divided into two parts, the northern Vosges of Saxothuringian affinity and the southern Vosges correlated with the Moldanubian domain.
Skrzypek divided the Vosges Mountains into three parts, based on the underlying rock strata (lithostratigraphy).1
I found the reference by Etienne Skrzypek to be the most helpful in understanding the Paleozoic origins of the Vosges Mountains. Looking at the illustrations contained in the reference summarized the extensive and detailed information contained in the 36 page book chapter.
In the illustration below, I've labeled the major features.1
The above illustration and the cross section below, which begins from the Northern Vosges Bruche unit and ends at the southern end of the Vosges Mountains, tells the story of the various rock types contained therein.1
The authors used lithological, structural, petrological and geochronological data to recreate the sedimentation, magmatism, metamorphism, and deformation forces that comprised the geodynamic history of the Vosges Mountains.
I think a picture is worth a thousand words so with those two illustrations above, I will end the blogpost, but hope to synthesize this information with a final blogpost on the geology of the Alsace and it's relevance to the Grand Cru vineyards of today.
References:
1. Etienne Skrzypek, Karel Schulmann, Anne-Sophie Tabaud and Jean-Bernard Edel, (Palaeozoic evolution of the Variscan Vosges Mountains) in K., Martınez Catalan, J. R., Lardeaux, J. M., Janousek,V.&Oggiano, G. (eds) The Variscan Orogeny: Extent, Timescale and the Formation of the European Crust, Geological Society, London, Special Publications, 405, http://dx.doi.org/10.1144/SP405.8, The Geological Society of London 2014.

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