Palaeontology and biostratigraphy of Middle Pleistocene river sediment in the Mathon Member, at Mathon, Herefordshire, England

Abstract

Organic silts and sands filling a channel underlying glacial deposits have beendiscovered in a gravel pit near Mathon, Herefordshire. These organic deposits, termed the Brays Bed, occur at the base of the Mathon Valley Formation and have yielded abundant fossils of plants (pollen and macroscopic remains) and insects (Coleoptera and Trichoptera). Palaeoecological analyses of these remains show that the deposit was largely made up of flood debris washed into an abandoned channel on the floodplain of an ancient river, thus sampling the biota from the surrounding landscape. The vegetation was chiefly made up of coniferous forest including Pinus, Picea and Larix with rarer broad-leaved trees. The insects comprise a community dependent on these trees, as well as a rich variety of species that inhabited the main river. Quantified estimates of the thermal climate using the Mutual Climatic Range method and based on the coleopteran assemblage, show that, at the time of deposition, conditions were not much different from those of the present day. A few species suggest that it might have been slightly more continental, than today. Precipitation must have been adequate to support a vigorous flow in the main river throughout the year. Correlation has been made on palaeontological grounds with four pre-Anglian deposits, two in Warwickshire, English Midlands, one in Lincolnshire and a fourth in Essex. Tentative links are also established with early Middle Pleistocene temperate deposits at Happisburgh, Norfolk, and the Boxgrove complex, which are included within the Cromerian Complex Stage (‘Cromerian Interglacial IV’), the latter assigned to Marine Isotope Stage 13.