Cross-bedding in the Permian Yellow Sands of County Durham

Abstract

SUMMARY Cross-bedding analyses have been carried out on the Yellow Sands mound at Sherburn Hill, County Durham, with additional analyses being made on the nearby developments at Quarrington and Ferryhill. Measurements indicate that sediment-free winds came from the north-east (on present geography) with weaker, depositional and more persistent winds from points between north-west and east. Bimodal foreset directions are shown not to be the direct product of seif dunes but to result from the complex interaction of at least two separate transverse dune bedforms, one of which was migrational. Evidence is scant for static seif structure, but exposures on the windward sides of mounds do indicate very rare south-easterly winds depositing marginal large-scale north-facing foresets. Internally, therefore, the mounds are predominantly stationary transverse southward-facing bedforms. Comparisons with other British Permo-Triassic deposits of known aeolian origin suggest that the Yellow Sands mounds are more complex than other described draa-scale aeolian bedforms. Nevertheless, despite the absence of documented modern analogues, the mounds are considered likely to be of aeolian origin, with their delicate lamination and absence of bioturbation and fossils precluding a marine origin.