The hardest of the old rocks survived the weathering and became ridges while others became excellent soils. Granites and old volcanic rocks also metamorphosed.Limestones became compacted or marbelized.The original thick shale deposits metamorphosed into schists and slates.In addition to the indignity of erosion to a plain in the south, the old rocks of the Massif Armoricain underwent a number of physical changes (Wilson): These materials had, in turn, been deposited on remnants of the eroded Caledonian mountain range which had itself been formed in the Proterozoic Period.The Massif Armoricain was subjected to erosion and weathering during the Mesozoic such that its southern portion became a plain into which the seas of the Paris Basin advanced during the Upper Cretaceous. The material of this mountain range included schists, graywackes, limestone, lavas, tuff, granite, and puddingstones, among others, formed during the Paleozoic. The old rocks of the Massif Armoricain are the surviving elements of a once-mighty mountain range called the Hercynian whose origins extend back into the Cambrian Age of the Paleozoic Period. Southeast of Angiers, we see a clear soil delineation which the locals refer to as "Black Anjou" and "White Anjou." White Anjou refers to the white, chalky limestone of the Paris Basin while Black Anjou refers to the dark slate and stones of the Massif Armoricain - the "old rocks." The composition of the slopes are shown in the figure below and are expanded upon in the table following. The Loire transits the Paris Basin through the soft rocks of the Cretaceous and the surroundings present as rounded hills - with varying degrees of steepness - topped by cap rocks formed from cemented Tertiary gravel. (ii) During the Eocene period (Early Tertiary), rivers deposited sandy gravel which cemented into "flights of steps." These deposits have proven to be less-than-perfect as vineyard soils but they help in the aeration of the underlying chalk soils. (i)The receding seas of the Late Cretaceous left deposits of sand and flinty clays in their wake (Wilson). Soil formation in this zone has benefited from a number of contributory events. The overarching geology of the Lower Loire is as follows: Cretaceous of Paris Basin overlaying Jurassic strata for Touraine Cretaceous of Paris Basin over Jurassic for Anjou-Saumur until southeast of Angier and "old rocks" of the Massif Armoricain over Jurassic thereafter and, old rocks of Massif Armoricain over Jurassic for Pays Nantais. I have previously discussed the formation of the Kimmeridgian chain and identified Pouilly, Sancerre, and Menetou-Salon of the Central Vineyards sub-region of the Loire Valley as components of that chain. The broader Loire Valley wine region is further divided into five sub-regions which are, from east to west: Central Vineyards Touraine Saumur Anjou and Pays Nantais. While not as famous as other French wine regions (Bordeaux, Burgundy, Rhone), the Loire is understood to produce the definitive expressions of Sauvignon Blanc, Chenin Blanc, and Cabernet Franc. The Loire Valley wine region is an agglomeration of appellations located on the slopes and plateaus that line the river's 620-mile course and associated areas of its many tributaries. In the course of its passage, the Loire River transits varied climates and soil types and, as a result, the region is characterized by a diversity of wine styles. In this, my final post in the series, I discuss the origin and identity of the soils of the Loire Valley. I have set the record straight by, first, identifying the locations where Kimmeridgian soils can actually be found and, second, clarifying what soil types are to be found in Champagne, Burgundy, and the Loire. Winegeeks has identified Kimmeridgian as the top vineyard soil in the world but has erroneously attributed that soil type to the totality of vineyards in Burgundy, Champagne, and the Loire Valley.
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