Summary: [The Journal of Geology, 1999, volume 107, p. 353­374] 1999 by The University of Chicago. All rights reserved. 0022-1376/99/10703-0007$01.00
353
Early Carboniferous Unroofing in Western Norway: A Tale of Alkali
Feldspar Thermochronology
E. A. Eide, T. H. Torsvik,1
T. B. Andersen,2
and N. O. Arnaud3
Geological Survey of Norway, N-7491 Trondheim, Norway
(e-mail: Elizabeth.Eide@ngu.no)
A B S T R A C T
40
Ar/39
Ar thermochronologic data from an extensional detachment zone in western Norway document punctuated
late Paleozoic through Mesozoic tectonothermal activity. Diffusion and thermal modeling of alkali feldspars sampled
in a profile through the detachment replicate laboratory argon release patterns when feldspars comprise three or four
diffusion domains with differing activation energies that represent high-, intermediate-, and low-closure temperatures.
These domains correspond to distinct changes in late Paleozoic cooling rates: (1) slow cooling at 0.4 ­2.2 C/m.yr.
from ca. 380­360 Ma; (2) rapid cooling at 15 C/m.yr. in Late Devonian­Early Carboniferous time (360­340 Ma); (3)
slow cooling at 0.4 ­1.7 C/m.yr. after ca. 340 Ma, with partial argon loss in Permian and Late Jurassic­Early Cretaceous
times. The Early Carboniferous rapid cooling event recorded by the feldspars links the western Norway margin to

Source: Andersen, Torgeir Bjørge - Centre for Physics of Geological Processes & Department of Geosciences, Universitetet i Oslo

Collections: Geosciences