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Les versants du Pays nantais - étude géomorphologique

Abstract : The relief of the Pays Nantais, between the Lower Loire, the Brière and the Ancenis Basin, is composed of plateaus bordered by slopes and depressions. The problems it poses are characteristic of ancient massifs: definition of the forms of levelling, determination of the role of differential erosion and tectonics in the elaboration of landscapes, interpretation of paleogeographical legacies. Their approach is handicapped by the low local altitudes and the scarcity of surface formations. Hence the use of slopes, classified into three basic types, as the preferred means of analysis. The slopes with flats make it possible to dissociate a fundamental surface, marked by deep alteration horizons, and a peripheral erosion level, punctuated by post-pliocene stony outwash, indicative of an important rhexistatic phase. The singular slopes, simple shapes and without symmetry, testify to an intense fracturing of the basement, a dislocation of the aforementioned erosion level and a preponderant influence of the neotectonics. The valley slopes reveal a recent dissection of the relief, a prolonged Pleistocene alteration, a less efficient periglacial morphogenesis than in the north of Brittany, and the marks of neveo-eolian processes. Each of these types of slopes contributes to highlight the intervention of a major morphogenic and tectogenic episode at the end of the Pliocene and in the early Pleistocene, the determining influence of Quaternary erosion systems in the development of the landscapes, and the relative youth of the local relief.
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https://hal.archives-ouvertes.fr/tel-03344022
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Submitted on : Wednesday, September 15, 2021 - 5:20:47 PM
Last modification on : Wednesday, April 27, 2022 - 4:34:25 AM
Long-term archiving on: : Thursday, December 16, 2021 - 7:19:56 PM

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  • HAL Id : tel-03344022, version 1

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Dominique Sellier. Les versants du Pays nantais - étude géomorphologique. Géographie. Université de Nantes, 1985. Français. ⟨NNT : ⟩. ⟨tel-03344022⟩

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