Clarke, SM, Cain, T, Leslie, A, Kelly, M and Krabbendam, M (2016) Evidence for pre-Caledonian discontinuities in the Achnashellach Culmination, Moine Thrust Zone: the importance of a pre-thrust template in influencing fold and thrust belt development. Scottish Journal of Geology, 52 (2). pp. 103-109.

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Abstract

South of the Loch Maree Fault in the Northwest Highlands of Scotland, an unexplained step-wise thickening of Torridon Group strata, from c. 200–1000 m, occurs towards the Loch Maree Fault, within the trailing edges of the stacked thrust sheets of the Achnashellach Culmination in the Caledonian Moine Thrust Zone. This thickening cannot be explained readily by Caledonian thrust tectonics alone, and suggests that thrusting was superimposed upon a pre-Caledonian non-layer-cake template giving rise to a thrust-parallel thickness change of Torridon Group strata in the thrust belt. Cross-section constructions within the culmination constrain discrete abrupt thickness changes of the Torridon Group succession preserved within the Coire nan Clach and Toll Ban thrust sheets. We infer the existence of a pre-existing discontinuity in the form of either a set of pre-Caledonian faults striking parallel or sub-parallel to the long-lived Loch Maree Fault in its southwestern wall, or palaeovalleys creating locally greater thicknesses of Torridon Group sediments in the pre-thrust template. Such palaeovalleys may have been eroded along pre-existing discontinuities. In either case, these discontinuities will have contributed to generating step-wise thickness changes in preserved Torridon Group strata prior to Cambro-Ordovician overstep and then contributed to controls on the observed (lateral) variations in thrust architecture and the northwards step-wise thinning of the Achnashellach Culmination towards the Loch Maree Fault. This northern termination of the Achnashellach Culmination demonstrates the importance of the pre-thrust template in constraining the three-dimensional architecture of lateral changes within fold-and-thrust belts.

Item Type: Article
Additional Information: This is the author accepted manuscript (AAM); published by the Geological Society and available from http://dx.doi.org/10.1144/sjg2015-002 - please refer to the publisher's conditions of use.
Uncontrolled Keywords: basement Caledonian Orogeny Cambrian clastic rocks Europe faults fold and thrust belts gneisses Great Britain Laxfordian Lewisian Complex Mesoproterozoic metamorphic rocks Moine thrust zone Ordovician paleorelief Paleozoic Precambrian Proterozoic quartzites sandstone Scotland Scottish Highlands sedimentary rocks stratigraphy three-dimensional models United Kingdom upper Precambrian Western Europe Torridon Group Durness Group Loch Maree Fault Eriboll Formation Achnashellach Culmination Beinn Eighe Massif
Subjects: Q Science > QE Geology
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Depositing User: Symplectic
Date Deposited: 12 Dec 2016 13:19
Last Modified: 08 Apr 2019 10:34
URI: http://eprints.keele.ac.uk/id/eprint/2608

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