STRATIGRAPHY AND SEDIMENTOLOGY OF DEVENSIAN (DIMLINGTON-STADIAL) GLACIAL DEPOSITS, EAST YORKSHIRE, ENGLAND

The stratigraphy and sedimentology of the glacial deposits exposed alo ng the coast of east Yorkshire are reviewed. Critical sections at File y Brigg, Barmston and Skipsea are examined to reassess the stratigraph y of Devensian Dimlington Stadial glacial deposits in the light of rec ent developments in glacial sedimentology. Sedimentary and glaciotecto nic structures studied in the field and by using scanning electron mic roscopy are emphasised. Two hypotheses are considered for the genesis of the interbedded diamictons and stratified sediments. The first invo lves the deposition of lodgement till and/or deformation till followed by meltout till, which was overridden to produce more deformation til l, reflecting periods of ice stagnation punctuated by glacier thickeni ng. The second hypothesis, which is favoured on the basis of field evi dence and micromorphology, involves the vertical accretion of a deform ing till layer associated with cavity/channel or tunnel valley fills, beneath active ice. At Barmston the upper part of the diamicton contai ns elongate pendant structures containing gravels, indicating that the diamicton was saturated and able to flow. The diamictons, therefore, represent a complex sequence of tills deposited and deformed by active ice during the Dimlington Stadial. Previously published stratigraphic al schemes involving classifications of multiple tills in east simplif ied and it is more appropriate to assign these to a single formation, the Skipsea Till Formation. Rhythmic glaciolacustrine and proglacial g laciofluvial sediments overlie the tills at Barmston and Skipsea. Thes e were deposited in sag basins during deglaciation as the tills settle d and deformed under thickening sediment and as buried ice melted out. Extensive sands and gravels cap the succession and were deposited on a sandur during the later stages of deglaciation.