|
This poster presents a glaciotectonic model for raft emplacement based upon a study of large and small-scale deformation structures associated with the accretion of chalk rafts at three Middle Pleistocene sites on the north Norfolk coast, eastern England. Detailed structural measurements taken from the three localities indicate an overall sense of ice movement and raft emplacement towards the south-east, suggesting a source area for the rafts located to the north of the present Norfolk coast in the offshore area of the North Sea.
Analysis of foraminifera from samples obtained from the rafts and in-situ chalk bedrock at Overstrand also indicates a northerly directed near-shore provenance for the chalk. Mechanisms for the detachment, transport and accretion of the rafts are explored, and it is concluded that pressurised pore water played an important role in all three phases. An imbricate thrust-stack model of glaciotectonic raft generation is presented, with the structural history of raft emplacement explained by the geometric relationships between the large-scale basal shear planes and associated deformation structures within adjacent preglacial and glacial sediments.
|
