Reconstructing the glacial history of Upgang, North Yorkshire: a North Sea ice lobe readvance during the termination of the last glacial maximum?

Abstract

Around Great Britain at the end of the Last Glacial Maximum (LGM) there is evidence for a number of glacial readvances, specifically in the Irish Sea Basin and Eastern Scotland. These readvances have been correlated with Heinrich Event 1 (HI) (16.1 - 17.6 cal. years BP; Bond et al. 1992). However, the presence of a synchronous HI readvance on the Yorkshire coast has not been investigated, although it is known from previous work that a number of readvances occurred during the end of the LGM. Therefore, this study aims to establish, firstly, if a readvance signal exists in Yorkshire and, secondly, if this signal can be correlated with HI. In order to achieve this, the coastal section of Upgang in North Yorkshire is examined using a multi-proxy approach. This involves the study of the sediments, clast form, clast fabric and clast lithological analysis along with geochemistry and geomorphological mapping. The sequence at Upgang shows a distinct advance - retreat - readvance signal. Two lower subglacial tills, Dl and D2 represent an initial ice advance and are a glaciotectonite or overrun proglacial thrust feature and a subglacial traction till respectively. Deposited above these is an extensive sand and gravels lithofacies association, indicative of an infilled lake after the ice had retreated. This lithofacies also represents the increasingly ice proximal nature of the site with the Upper facies representing proglaeial subaerial sandur sedimentation. The section is capped by the readvance till, D3, another subglatial traction till. Using local vegetation and varve records from Kildale and the Tees Estuary a proxy climate record is produced. This along with Ше correlation of the Upgang tills with those at Dimlmgton allows the production of a chronostratigraphic framework. This shows that the initial ice advance occurred shortly after 21 000 cal. years BP. The readvance then occurred around 16 ООО cal. years BP in conjunction with a deterioration in climate. Therefore, this readvance is tentatively correlated with Heinrich Event 1， which is also seen as the mechanism for other Last Glacial Maximum readvances around Great Britain, although without absolute dating control no great certainty can be placed upon this.