Thrust sequences and the significance of low-angle, out-of-sequence faults in the northernmost Moine Nappe and Moine Thrust Zone, NW Scotland

R. Holdsworth, Rob Strachan, G. Alsop, C. Grant, R. Wilson

    Research output: Contribution to journalArticlepeer-review

    Abstract

    In common with most thrust belts, the Moine Thrust Zone, Scotland, preserves a foreland-propagating sequence of thrusting. However, significant examples of local to regional overstep sequences are also recognized and their interpretation remains controversial. Remapping of the northernmost Moine Thrust Zone has defined a thick belt of mylonites in the centre of which lies the ductile WNW-directed Moine Thrust. The base of the mylonite belt, however, is marked by a regionally significant, low-angle, west-directed brittle fault, here termed the Lochan Riabhach Thrust, that truncates thrust-related structures in its footwall. Comparison of the tectonic stratigraphy of the mylonite belt with that preserved in a downfaulted outlier to the west at Durness indicates that the Lochan Riabhach Thrust cuts down-section in its footwall and therefore appears to be extensional. Locally, it is unequivocally breached by underlying imbricate thrusts. We prefer to interpret the Lochan Riabhach ‘Thrust’ as an extensional fault that formed during a hiatus in thrust stacking. We relate this faulting episode to the changes in the stability of the evolving orogenic wedge and reiterate that such extensional faults may be common, although possibly unrecognized, features in many other thrust belts.
    Original languageEnglish
    Pages (from-to)801-814
    Number of pages14
    JournalJournal of the Geological Society
    Volume163
    Issue number5
    DOIs
    Publication statusPublished - Sep 2006

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