The lithostratigraphy, biostratigraphy and chronostratigraphy of coastal pleistocene deposits in Gower, South Wales

Abstract

The thesis is concerned with three coastal caves and two open coastal sites in south Gower. The Pleistocene succession at each locality is described and classified using a multidisciplinary approach, which involves sedimentological. faunal and pollen analyses. An informal lithostratigraphic, biostratigraphic and chronostratigraphic classification is proposed. Two interglacial high sea level events are recognised. The earlier is represented by the Inner Sand Beach of Minchin Hole and is correlated with oxygen isotope sub-stage 7a (210 ka BP) using amino acid dating. The younger is represented by the Outer Gravel Beach of Minchin Hole and is correlated by amino acid dating with oxygen isotope stage 5e (125 ka BP). Evidence is presented of three cold events in Gower. The earliest antedates the Minchin Hole Inner Sand Beach, the second is related to oxygen isotope stage 6 on the basis of lithostratigraphy and amino acid dating, and the youngest represents the last (Devensian) Glaciation. Detailed evidence of climatic and environmental change from the Last Interglacial (oxygen isotope stage 5e) to the Last Glaciation is described. The Last Interglacial in Gower is marked by a high sea level event, interglacial weathering of sediments, a temperate fauna with some southern species and an inferred regional vegetation of mixed temperate forest. This is followed by a continuous fall in sea level to the low stand of the Last Glaciation, which accompanied by a gradual change from a temperate to a boreal fauna, an inferred deterioration of climate and reduction in the vegetation cover., and the commencement of colluviation and sheetwashing of weathered sediments on the plateau surfaces of Gower. The Last Glaciation in Gower is represented by a boreal fauna and periglacial sedimentation, with head deposits and loess.