Abstract

The Dent Fault System forms part of the Pennine Boundary Fault System in northern England and consists of a series of vertical to steeply west-dipping, anastomosing fault strands generally striking 010°–020°. Maximum throw on the faults occurs in the south, where an easterly downthrow juxtaposes Carboniferous and Lower Palaeozoic rocks. The amount of easterly downthrow decreases northward, and westerly downthrow occurs along its northernmost extension. An east-facing and slightly overturned monocline is dissected by the fault strands along the length of the fault system, irrespective of the amount or sense of displacement across the zone.

A number of features suggest that the observed structural relationships are not simply the results of E-W directed, post-Carboniferous compression as previously thought. The most significant are: (1) the variable amount and sense of displacement along the length of the sub-vertical fault system, (2) east-directed reverse faults exhibiting oblique- and strike-slip slickenside striations, that locally may form a partial- or half-flower structure, (3) folds developed both sub-parallel and en echelon to the main fault zone, (4) the existence of conjugate sets of shear fractures, (5) the occurrence of structures analogous to strike-slip duplexes, and (6) regional considerations.

Instead, it is suggested that the fault system represents an Early Palaeozoic lineament, reactivated during Carboniferous and into early Permian time. It accommodated both the formation and N–S directed shortening (inversion) of early Carboniferous basins and later NE–SW directed extension during the formation of the Vale of Eden half-graben, by oblique-slip movement along its length. Younger movements may also have occurred but are difficult to document and are not thought to be large.

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