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Spatial and temporal variations in exhumation of the central Swiss Alps and implications for exhumation mechanisms

1999; Geological Society of London; Volume: 154; Issue: 1 Linguagem: Inglês

10.1144/gsl.sp.1999.154.01.07

2041-4927

Fritz Schlunegger, Sean D. Willett,

Pleistocene-Era Hominins and Archaeology

Abstract Information about the structural and thermal evolution of the Alps, interpreted through thermal and mechanical models, provides an improved understanding of the processes that led to the exhumation of the Alps. We synthesize published thermochronometric data, analyse these data in terms of cooling rates and interpret the spatial and temporal patterns of cooling. Cooling rates are interpreted in terms of exhumation rates, aided by the use of a one-dimensional thermal model. Our study reveals that rapid exhumation of the Lepontine core occurred during the interval of 35-20 Ma. Existing data cannot determine whether this was by rapid erosion at rates exceeding 1 km Ma −1 or by a relatively brief period of tectonic exhumation, although the correlation between extensional fault motion and high cooling rates supports the tectonic exhaumation hypothesis. Peripheral regions of the Alps cooled at rates consistent with low to moderate exhumation rates of 400–500 m Ma −1 , initiating later than cooling of the Lepontine core, consistent with outward growth of the orogen. Outward growth of the orogen is potentially the result of either lower exhumation rates or higher rates of crustal accretion as demonstrated by a two-dimensional, coupled erosion-deformation model. In particular, the growth of the Southern Alps after c. 20 Ma is evidence for a decrease in the exhumation rate relative to the crustal accretion rate. This could represent a decrease in exhumation rate after cessation of normal faulting, or it could reflect initiation of accretion of a larger fraction of the European crust.