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Exhumation of the Central Alps: evidence from 40 Ar/ 39 Ar laserprobe dating of detrital white micas from the Swiss Molasse Basin
Author(s) -
Von Eynatten H.,
Schlunegger F.,
Gaupp R.,
Wijbrans J.R.
Publication year - 1999
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1046/j.1365-3121.1999.00260.x
Subject(s) - geology , molasse , orogeny , metamorphic rock , sedimentary rock , paleontology , alpine orogeny , denudation , structural basin , paleozoic , foreland basin , clastic rock , metamorphism , geomorphology , geochemistry , mesozoic , tectonics
40 Ar/ 39 Ar single‐grain laserprobe dating of detrital white micas from early Oligocene to middle Miocene (31–14 Ma) sedimentary rocks of the central Swiss Molasse basin reveals three distinct clusters of cooling ages for the hinterland. Two Palaeozoic age clusters reflect cooling after the Variscan orogeny with only limited reheating during the Alpine orogeny. The third Tertiary age cluster reflecting late Alpine cooling is restricted to sediments younger than 20 Myr old. Micas with cooling ages < 30 Myr are interpreted to originate from the footwall of the Simplon detachment fault, thus representing formerly exposed upper levels of the present‐day Lepontine metamorphic dome. Erosion of these levels is reflected by an increase of low‐grade metamorphic lithic grains in the sandstones. This interpretation puts constraints on the timing of exhumation as well as on the evolution of the drainage pattern of the Central Alps.