Upper Llandoverian Grogal Sandstones and Aberystwyth Grits in the New Quay area, Central Wales: A possible upwards transition from contourites to turbidites

Abstract

AbstractThe lower boundaries of the Aberystwyth Grits Formation and the underlying Grogal Sandstones Formation (new name) in the New Quay area are defined. The Grogal Sandstones Formation is described, and interpreted as a contourite deposit on a continental rise; we believe these are the first rocks in the British Isles to be identified as contourites. The transition within a few tens of metres from Grogal Sandstones Formation contourite facies, displaying bimodal current directions, to Aberystwyth Grits Formation turbidite facies, with unimodal current directions, can be seen well in two places on the coast southwest of New Quay. Regionally, an upward transition from finegrained contourites to turbidites of varying facies can be recognised. Our results are compatible with Ziegler's interpretation of early Upper Llandoverian palaeogeography.