Late Pleistocene stratigraphy, glaciation chronology and Middle Weichselian environmental history from Klintholm, Møn, Denmark

A new and fundamental outline of the Late Pleistocene geological history in SE Denmark is obtained from examination of exposed cliff sections along the Baltic coast of M0n. Multi­diciplinary studies including lithostratigraphic classification, analyses of glaciotectonic struc- tures, biostratigraphic studies, amino acid chronology and radiocarbon and luminescence dating indicate the following: A shallow boreo-lusitanian sea that characterized the Eemian interglaciation (130-115 ka BP) was followed by periglacial conditions during the Early Weichselian (l 15-75 ka BP). In the early part of the Middle Weichselian (75--c. 40 ka BP) Baltic glaciers invaded the region twice, intenupted by an ice free and periglacial interval around 50 ka BP. The first ice stream left a reddish coloured till dominated by exotic rock-types of eastern Baltic provenance. From about 40-35 ka BP to slightly before 20 ka BP ameliorated conditions with periglacial terrestrial and lacustrine environments are recorded. A lake basin in the western part of the Baltic was surrounded by a low releif mammoth-steppe with an almost treeless vegetation of grasses, sedges, heather and dwarf shrubs. Increasing amounts of diamicton dominated by Palaeozoic shale and limestone towards the top of the muddy and slightly organic lake sediments suggest ice-rafting in the basin by the end of the late Middle Weichselian. Deposits suffered strong glaciotectonic deformation during the Late Weichselian glacial maximum (25-15 ka BP).

Stratigraphy and palaeoenvironments of the Red Crag and Norwich Crag formations between Aldeburgh and Sizewell, Suffolk, England

This study uses a variety of criteria to examine short-range correlation within the Crag deposits in order to assess the validity of longer-range correlations within the British Pleistocene stage system. To this end, six rotary cored boreholes spaced at 0.5-1.0 km intervals were drilled along a north-south-aligned traverse between Aldeburgh and Sizewell, Suffolk. These show that the thick Red/Norwich Crag sequence is confined to a deep, sharply bounded basin, which is of probable erosional rather than tectonic origin. The undisturbed borehole core material enabled an assessment of the limits of stratigraphic resolution within these dominantly high-energy, shallow marine sediments to be made. Subdivision of the sequence was done on the basis of lithostratigraphical and biostratigraphical (foraminifera, pollen and spores, dinoflagellate cysts, and molluscs) criteria; chronostratigraphical methods (palaeomagnetism and amino acid chronology) were also applied. The various subdivisions indicated by each of these disciplines were in large part consistent, demonstrating that valid stratigraphic units had been identified. Only amino acid chronology did not indicate any obvious subdivision of the sequence. Three lithostratigraphical units were recognized within the thick Crag sequence. The lowest unit (AS-Lith 1) consists of coarse shelly sands interbedded with thinly laminated muds and fine sands. The middle unit (AS-Lith 2) consists of fine- to coarse-grained shelly sands arranged in two coarsening-upwards cycles. Units AS-Lith 1 and AS-Lith 2 are correlated on a lithostratigraphical basis with the Red Crag Formation of the adjacent Aldeburgh-Orford area to the south and are named the Sizewell Member and the Thorpeness Member respectively. The uppermost unit (AS-Lith 3) comprises fine- to medium-grained, well-sorted sands; it correlates with the Chillesford Sand Member of the Norwich Crag Formation of the adjacent Aldeburgh-Orford area. The Sizewell Member of the Red Crag Formation is normally magnetized and palaeontologically distinctive. The pollen, foraminifera and dinoflagellate assemblages firmly establish it as Pre-Ludhamian in age, and probably equivalent to an interval within the Reuverian C to Praetiglian Stages of the Netherlands. The Thorpeness Member of the Red Crag Formation is less easy to place within the British Pleistocene stage system. It is reverse magnetized, at least in part, and foraminifera assemblages suggest possible correlation with the Ludhamian Stage. No identifiable pollen or dinoflagellate assemblages were obtained. The Chillesford Sand Member of the Norwich Crag Formation is largely unfossiliferous but the borehole material has yielded a single pollen spectrum that suggests correlation with the Bramertonian Stage.