The last erosional stage of the Molasse Basin and the Alps |
| |
Authors: | Fritz Schlunegger Jon Mosar |
| |
Institution: | 1.Institute of Geological Sciences, University of Bern,Bern,Switzerland;2.Department of Geosciences—Earth Sciences,University of Friboug,Fribourg,Switzerland |
| |
Abstract: | We present a synoptic overview of the Miocene-present development of the northern Alpine foreland basin (Molasse Basin), with
special attention to the pattern of surface erosion and sediment discharge in the Alps. Erosion of the Molasse Basin started
at the same time that the rivers originating in the Central Alps were deflected toward the Bresse Graben, which formed part
of the European Cenozoic rift system. This change in the drainage direction decreased the distance to the marine base level
by approximately 1,000 km, which in turn decreased the average topographic elevation in the Molasse Basin by at least 200 m.
Isostatic adjustment to erosional unloading required ca. 1,000 m of erosion to account for this inferred topographic lowering.
A further inference is that the resulting increase in the sediment discharge at the Miocene–Pliocene boundary reflects the
recycling of Molasse units. We consider that erosion of the Molasse Basin occurred in response to a shift in the drainage
direction rather than because of a change in paleoclimate. Climate left an imprint on the Alpine landscape, but presumably
not before the beginning of glaciation at the Pliocene–Pleistocene boundary. Similar to the northern Alpine foreland, we do
not see a strong climatic fingerprint on the pattern or rates of exhumation of the External Massifs. In particular, the initiation
and acceleration of imbrication and antiformal stacking of the foreland crust can be considered solely as a response to the
convergence of Adria and Europe, irrespective of erosion rates. However, the recycling of the Molasse deposits since 5 Ma
and the associated reduction of the loads in the foreland could have activated basement thrusts beneath the Molasse Basin
in order to restore a critical wedge. In conclusion, we see the need for a more careful consideration of both tectonic and
climatic forcing on the development of the Alps and the adjacent Molasse Basin. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|