Loess from the Pleistocene of the Wirral Peninsula, Merseyside

Abstract

A pale coloured silt from the cliffs at Dawpool has many of the distinctive characteristics of loess. It occurs as a thin, irregular bed in a complex sequence between two thick Pleistocene tills. A sample underwent rapid collapse when flooded under load and was clearly metastable. Grain size analysis revealed a poorly sorted silt with a clay tail. However, scanning electron microscopy showed silt-sized aggregates of clay grade quartz particles. X-ray diffraction indicated the presence of quartz, feldspar, mica, dolomite, calcite and chlorite but no other clay minerals. Parallels are drawn with other loess deposits and with other sediments. The identification of the loess deposit implies a definite order of events and conflicts with the view that there was a single ice advance or that the overlying till was a lacustrine clay. It is suggested that there are two types of loess deposit in Britain: distinct, unweathered, localised beds and thin, weathered, superficial sheets. The former have been recognised only occasionally while the latter occur mainly in the east and south of England and mainly on limestone bedrock. In view of the porous, friable, metastable, homogeneous nature of the sediment at Dawpool it is considered to be a true eolian loess of the first type, hitherto unrecorded from this area.