Brittle structures of the Somerset Coast

The Somerset coast displays fantastic exposures of faults, folds, veins and joints (Hancock, 1985) in Permo-Triassic marls and sandstones and in Liassic shales and limestones (Whittaker and Green, 1983). The ~E-W striking normal faults formed during Mesozoic extension (Dart et al., 1995). They have throws of up to several hundred metres. The faults exhibit various stages of growth and linkage, which in many cases can be observed on both the wave-cut platform and in the adjacent cliffs. Folds accommodate displacement variations along the normal faults, veins occur in damage zones, and gouge and veining occurs along the faults. Sandstone dykes and deformation bands occur in Permo-Triassic sandstones west of Watchet. Some normal faults east of Lilstock show evidence of reactivation as strike-slip faults, including steepened and breached relay ramps. Cenozoic contraction, probably related to the Alpine Orogeny, inverted many of the normal faults and created thrusts, strike-slip faults, veins, pressure solution cleavage and folds. The strike-slip faults typically cross-cut the inverted normal faults and the folds and typically show veins and pressure solution in damage zones (McGrath and Davison, 1995). The youngest structures are joints (Passchier et al., 2021), which abut or cross the strike-slip faults.