The Sticklepath-Lustleigh fault zone: Tertiary sinistral reactivation of a Variscan dextral strike-slip fault

Abstract

Dextral strike-slip movement on the Sticklepath-Lustleigh fault zone (SLFZ) is indicated by displacements of ?Permian and older rocks. Previous authors have inferred that the main dextral movement which caused these displacements was post- Permian and, noting the presence of small Tertiary pull-apart basins along the fault zone, probably of Tertiary age. However, the geometry of these early Tertiary pull-apart basins indicates sinistral rather than dextral strike-slip movement. We present an alternative model for the history of the Sticklepath-Lustleigh fault zone, summarized below: 1 Late Variscan strike-slip movement, with a total displacement of up to 10 km, produced the SLFZ and offset dextrally an earlier Variscan thrust. 2. Extensional reactivation of this thrust led to rapid Permo-Triassic subsidence in the Crediton Trough and a dextrally offset neighbour, the Hatherleigh outlier. 3. Approximately 6 km of early Tertiary sinistral movement on the SLFZ produced small pull-apart sedimentary basins, and reduced the net dextral offset across the fault. 4. In mid-Tertiary times, minor dextral movements on the SLFZ may have produced reverse faulting on the margins of the Tertiary basins.