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Evolution du réseau hydrographique dans le Sud-Ouest du Bassin de Paris pendant le Pliocène et le Quaternaire.

1983; Volume: 20; Issue: 4 Linguagem: Inglês

10.3406/quate.1983.1464

2804-1836

Jean Jacques Macaire,

Geological formations and processes

Mineralogical composition, paleopedological types and spatially distribution studies of Loire, Cher, Indre, Vienne and Creuse'alluvial deposits, in Touraine and bordering area, let to trace the way of primitive flows and reveal seven formations dated from Pliocene to Holocene. The present Vienne'outline was already settled during the Pliocene, while the "pré-Cher" and "pré-Indre - pré-Creuse" wandered on the surface of plateaux : these rivers were bound to the "redonian" sea. The Loire river flowed then away to the central Paris basin. Diversion of the Loire from Orleans to western country, individualization of Creuse and Indre and increasing incision in bed-rock arose during "redonian" regression (Tiglian ?). These events, and further acceleration of valleys incision appeared later (old Quaternary) in middle Touraine than in more southern or estern locations (Pliocene or Plio-Quaternary), result from epirogenic movements. Alluvial and erosion phases are compared, and influence of the Loire on morphogenic evolution of his affluents valleys is discussed.