D.Q. Bowen

The stratigraphic and sedimentological significance of Late Devensian Ice Sheet surging in Holderness, Yorkshire, U.K.

Amino acid analyses of marine mollusc valves show that the Basement Till of Holderness, Yorkshire, is of Late Devensian age (ca. 20,000 BP) and not pre-Ipswichian (>125,000 BP) as is traditionally supposed. Together with the overlying Skipsea and Withernsea Tills the Basement Till is argued to be a ‘deformation till’ resulting from the repeated onshore surging of Late Devensian ice over a muddy sea floor, and the subglacial transport, attenuation and mixing of marine sediment. Silts on the surface of the Basement Till, yielding 14C dates of 18,500 and 18,240 BP, have been regarded as minimum ages for Late Devensian glaciation in eastern England (e.g. the Dimlington Stadial of Rose, 1985, 1989). The amino acid data presented here indicates that the maximum of the Late Devensian glaciation in eastern England occurred earlier. Sedimentological interpretation of the Late Devensian tills of Holderness as glacially-reworked marine sediments supports previous glaciological models of the British Ice Sheet involving surging of ice lobes along the coast of eastern England. The Basement, Skipsea and Withernsea tills are separated by shallow marine sediments and may be representative of ‘deformable bed’ till facies deposited below Pleistocene ice sheets moving over soft, fine-grained sediments.

Pleistocene geology of the lower Severn valley, U.K.

Abstract The lower Severn valley contains a sequence of fluvial, glaciofluvial and glaciogenic deposits of Pleistocene age which is divided into two formations. Glaciogenic sediments are correlated with members of the Wolston Formation (Anglian). A new formation, the Severn Valley Formation, which consists of fluvial deposits, is defined. It is sub-divided into six members, the four oldest of which are considered in this paper. The oldest deposits in the lower Severn basin are the till and glaciofluvial outwash gravels of the Woolridge Member. The till is correlated with the Thrussington Member of the Wolston Formation which is correlated with the Lowestoft Formation of the Anglian Stage (Oxygen Isotope Stage 12). The oldest member of the Severn Valley Formation, the Spring Hill Member, is provisionally correlated with OI Stage 10. The Bushley Green Member represents deposition during OI Stages 9 and 8, the basal fossiliferous sediments (Bushley Green Fossil Bed) are correlated with OI Stage 9 by amino acid geochronology. The Kidderminster Station Member records a significant input of lithologies not seen in quantity in the higher members, and evidence is presented which suggests that this is a response to renewed glaciation in the upper basin. This glaciation was responsible for the deposition of the Ridgacre Formation of the Birmingham area. Amino acid geochronology and Chlorine-36 ages from erratic boulders show that the Kidderminster Station Member and Ridgacre Formation are of OI Stage 6 (Warthe) age. The basal deposits of the Holt Heath Member include the Stourbridge Fossil Bed, with a temperate fauna believed to be Ipswichian (‘last interglacial’, OI Substage 5e), and the Upton Warren Fossil Bed (OI Substage 5a). Most of the Holt Heath Member consists of outwash from an Irish Sea ice sheet which entered the Severn basin during the Late Devensian (OI Stage 2).

Last Interglacial deposits at Folkestone, Kent

Pleistocene temperate-climate deposits at Folkestone Battery, Kent are described and attributed to a small stream draining from the nearby Chalk escarpment. Their contained molluscan fauna is indicative of conditions similar to those at the present in southeast England. The occurrence of a mammal fauna with Hippopotamus amphibius (Linne) and of D : L amino-acid ratios from molluscan shell with a mean of 0.124 combine to suggest an age in the Last Interglacial (Oxygen Isotope Substage 5e).

An arietitid ammonite from Gower: its palaeogeographical and geomorphological significance

The discovery of an arietitid ammonite (Bucklandi Zone), with evidence for the timing of its emplacement into Pleistocene deposits soon after oxygen isotope sub-stage 5e (5.5), is used to infer that the coastal plateau immediately north of Horton, Port Eynon Bay, is approximately coincident with an exhumed sub-Mesozoic surface. A resistivity survey of the overlying glacial Llanddewi Formation has revealed that this erosion surface is widespread in southwest Gower, thus confirming the hypothesis of A. E. Trueman that the ‘200 foot platform’ of Gower is an exhumed sub-Mesozoic surface.