Palaeogene basin development: New evidence from the Southern Petrockstow Basin, Devon

The Petrockstow Basin is bounded by faults belonging to the Sticklepath-Lustleigh fault zone (SLFZ). New exposures in the Woolladon and Stockleigh ball clay pits at the southern end of the basin show the faulted contacts on both the east and west sides of the basin. On both sides the Palaeogene basinal sediments are overlain by the Upper Carboniferous Bude Formation. The faulted contacts dip away from the basin margin at angles between sub-horizontal and 25°. Field evidence suggests active vertical fault movement coeval with sedimentation. Basin development was clearly related to reactivation of major Variscan strike-slip faults, although the sense of fault motion is uncertain.