Detrital muscovite Ar-40/Ar-39 ages from Carboniferous sandstones of the British Isles: Provenance and implications for the uplift history of orogenic belts
Fm. Stuart et al., Detrital muscovite Ar-40/Ar-39 ages from Carboniferous sandstones of the British Isles: Provenance and implications for the uplift history of orogenic belts, TECTONICS, 20(2), 2001, pp. 255-267
Major progradations of elastic sediments are recorded in the sedimentary re
cord of the Famennian and the Visean-Namurian of the United Kingdom acid su
rrounding waters. We have determined Ar-40/(39)A, ages of 162 detrital musc
ovites from 11 coarse sandstones which were deposited between 370 and 465 M
a, spanning both progradations. Detrital mica ages are dominated by a peak
at 415 Ma, with minor peaks at 440 Ma and 390 Ma. The 415 Ma muscovites are
derived from the unroofing of the Scandian nappes during the compressional
phase of the Caledonian orogeny in Scandinavia. The 440 Ma muscovites reco
rd pre-Scandian orogenic activity, which is rarely preserved in the orogeni
c record. Thermochronological evidence suggests that episodic postorogenic
uplift, and exhumation events kept the Scandian orogen a major topographic
feature and likely a sediment source for over 100 million years after nappe
emplacement and implicates tectonic rather than climatic control on the el
astic sediment progradations. The near total absence of detrital muscovites
with ages <415 Ma suggests that the Scandian nappes had not been entirely
eroded despite repeated uplift during the postorogenic extension. The river
(s) which supplied the sediments probably ran parallel to the strike of the
major Scandian thrusts, along the length of the Caledonian orogen, in a ma
nner analogous to the major river systems of contemporary orogenic highland
s.