Etude stratigraphique, sédimentologique et structurale d'un bassin d'avant arc : exemple du bassin de l'Indus, Ladakh, Himalaya

Abstract : Stratigraphie analysis , together with discovery of faunas and of microfaunas , and study of depositional and environmental patterns in the Indus formations, Ladakh , allow characterization of several lithostratigraphic units. Despite fa- cies variations they have been identified along more than 100 km from West to East, and mapped on a 1/ 125. 000 scale . The overall structure consists of a dissymetric synclinorium, faulted by northward-trending reverse faults . It results from two major deformations. Microstructural analysis indicates shortening along a direction close to N 10 . Both deformation and metamorphism increase from N to S . This has been related to a Northward-trending retrothrusting phase. The geodynamic history of the Indus basin is the one of an active margin involved in an intercontinental collision. By the end of late Albian imes , a sedimentary basin makes its appearance in front of the magmatic arc linked to the South Tibetan active margin. This basin brings to mind the inner fore-arc of the present days Andean margin. From upper Cretaceous until Lower Eocene time , open sea conditions prevail in the southern part of the basin , whereas thick torrential and fluviatile formations originating from the erosion of the Ladakh magmatic arc , are deposited in its Northern part. After the Middle Eocene, a general regression follows the collision between South Tibet and India ; sedimentation becomes c ontinental throughout the whole basin; its corresponds to the superposition of several imbricated detrital forms. The continuing Northward drifting of India causes a strong tightening resulting in deformations and metamorphism in the Indus inner fore arc series , which finally undergo overthrusting by the outer fore - arc ' s formations, the Indus suture zone is now completely closed.
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Theses
Tectonics. Université Scientifique et Médicale de Grenoble, 1984. French


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Thierry Van Haver. Etude stratigraphique, sédimentologique et structurale d'un bassin d'avant arc : exemple du bassin de l'Indus, Ladakh, Himalaya. Tectonics. Université Scientifique et Médicale de Grenoble, 1984. French. <tel-00641418v2>

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