Mary E. Pettit

Last Interglacial and Devensian deposits of the River Great Ouse at Woolpack Farm, Fenstanton, Cambridgeshire, UK

Abstract This paper describes Pleistocene fluvial deposits of the River Great Ouse at Woolpack Farm, Fenstanton, Cambridgeshire, UK. These sediments consist of a basal gravel, fossiliferous fluviatile muds, sands and gravels later disturbed and formed into a diamicton, and overlying gravels. The regional climate inferred from palaeobotany, Mollusca, Coleoptera and vertebrates from the diamicton indicates temperate conditions. Coleopteran evidence suggests a mean July temperature of ca . 21°C, 4°C warmer than today in eastern England, and winter temperatures a little colder than at present. Molluscan assemblages indicate a slight brackish influence during deposition of the muds which form the diamicton. The gravel succession is represented by three members which have a broad distribution in the Great Ouse Valley, and which were laid down in a braided river under periglacial conditions. The occurrence of permafrost is indicated by the presence of ice wedge casts in the gravels. The pollen and macrofossil evidence from the diamicton suggests correlation with Ipswichian substage IpII ( Pinus – Quercetum mixtum – Corylus phase). The basal gravel is of pre-Ipswichian age. A Devensian age is proposed for the overlying gravels and their attendant periglacial phenomena.

The margin of a middle Pleistocene ice advance at Tottenhill, Norfolk, England

Exposures at Tottenhill quarry, west Norfolk, are described. Detailed sediment logs, lateral sediment distribution and facies relationships are presented, together with palaeocurrent measurements and pebble counts. It is concluded that the sequence represents a delta-like subaquatic fan accumulation that was deposited by glacier meltwater at the eastern margin of the present Fenland. The ice must have entered the area from the west to northwest. An arctic leaf flora is associated with still water pool sediments within the fan sequence. Pollen assemblages appear to be largely derived by reworking from underlying in situ temperate stage sediments which are correlated with the Hoxnian Stage. The age of the deposits is discussed and it is concluded that the glaciation concerned must date from the early part of the Wolstonian Stage on the basis of the previously established stratigraphical sequence in the area.

Late and Middle Pleistocene deposits at Somersham, Cambridgeshire, U.K.: a model for reconstructing fluvial/estuarine depositional environments

Gravel quarries at Somersham, Cambridgeshire, have yielded evidence for a Pleistocene channel of the R. Great Ouse, containing temperate stage sediments between cold stage sediments. In the earlier cold stage, fluviatile gravels and floodplain loessic sediment accumulated. In the later cold stage a further series of gravel units and floodplain sediments were deposited, together with lake sediments. The lake sediments are associated with Lake Sparks, dammed by Late Devensian ice in the Wash at ca. 18.5 ka BP. The lake sediments overlie gravels with a radiocarbon date from an organic horizon indicating a Middle Devensian age. Clast lithological analyses from the earlier and later gravels suggest that reworking of gravels has occurred within a relatively stable catchment. The petrography of the earlier cold stage loessic sediment and temperate stage fine sediment indicates an Anglian affinity, which conflicts with the biostratigraphic interpretation. Pollen and macroscopic plant remains from sediments of both cold stages and from the temperate stage indicate, respectively, assemblages with a typical full-glacial aspect with a rich flora of shrubs and open ground herbs(including an assemblage at ca. 18 ka), and temperate freshwater and marine-influenced organic sediments. On the basis of pollen analysis these are ascribed to substages Ip II and III of the Ipswichian Stage(O.I.S. 5e), with a Pinus-Quercus-Corylus biozone in the former and a biozone with Carpinus in the latter. Marine-influenced sediments, at −3.7 to −0.3 m OD, indicate transgression in Ip II and regression in Ip III. Molluscan assemblages from the temperate stage and the later cold stage are described; two are from the Late Devensian, at a time near the maximum extension of ice into the Wash. Foraminifer and ostracod faunas are described from post-Ipswichian sediments and may be reworked. Radiocarbon dates confirm the age of the later gravel suite as Devensian and a calibration of the measurements is given. Amino acid ratios from Corbicula fluminalis valves from temperate stage sediments are reported, with measurements from different parts of the valve; the results tend to support an Ipswichian age. TL measurements of the earlier cold stage loessic sediment and associated sand indicate a pre-Ipswichian age for the sediments. The earlier cold stage is correlated with the pre-Ipswichian cold stage, the Wolstonian of Mitchell et al.(1973); problems with this correlation are discussed. Various periglacial phenomena, including thermal contraction networks and cracks, diapirs, involutions and coversand are associated with the Devensian sequence. The complex environmental history, based on stratigraphy and palaeontology, is described, and related to other nearby sites in southern Fenland.

Middle Devensian deposits of the Ivel Valley at Sandy, Bedfordshire, England

Fluvial gravels exposed beneath the surface of the low terrace of the River Ivel have been investigated in a quarry south of Sandy, Bedfordshire. Sedimentological investigations suggest that deposition occurred as bars and sheets in a braided river regime. Fossiliferous silt lenses occur within the gravel and their contents indicate deposition under slow moving or still water conditions in abandoned small channels. The palaeontological data from plant macrofossil remains, Mollusca and Coleoptera present a consistent picture of a harsh climate similar to that of the tundra areas of arctic Russia at the present day. Mutual Climatic Range (MCR) estimates based on Coleoptera indicate a mean temperature of the warmest month between +8°C and +11°C, and a mean temperature of the coldest month between -10°C and -28°C. Radiocarbon ages of 34 055+330-310 (Q-2936) and 29 250+460-420 (Q-2935) yrs BP suggest dates for the lower part of the gravelly sequence, in the Middle Devensian, at the end of the Upton Warren Interstadial Complex.

Late Pleistocene interglacial deposits at Pennington Marshes, Lymington, Hampshire, southern England

Fossiliferous organic sediments interstratified within fluvial gravels at Pennington Marshes, Lymington, have been recovered in boreholes and investigated. The organic deposit, here defined as the Pennington Organic Bed, occurs between −3.9 to −5.3 m OD and has been traced 200 m across the immediate area. Pollen analyses indicate a temperate flora of interglacial character. Molluscan and ostracod assemblages contain no brackish elements and are typical of a shallow, freshwater stream or abandoned channel. A change from an aquatic to a terrestrial molluscan fauna indicates progressive drying out of the water body. The Pennington Organic Bed cannot be confidently attributed to any particular stage, but since it occurs within a lower terrace than that at Stone Point, 15 km to the NE, it is probably younger and an early Ipswichian age (Ip Ha?) is suggested. The Pennington Lower Gravel, below the organic deposit, is therefore probably Wolstonian and the Pennington Upper Gravel, above them, Devensian in age. The estuarine interglacial deposits at Stone Point, previously believed to have been Ipswichian, are likely to belong to an earlier stage. It is possible, although less likely, that they accumulated during a later part of the Ipswichian as the transgression aggraded to the level of the higher terrace surface. Similarly, if the gravels at Stone Point resulted from a tributary river, rather than the Solent River itself, this could also explain the altimetric differences and allow the organic deposits to be attributed to different parts of the same stage. However, there is no evidence to support either of these alternative possibilities.

The sedimentology and palaeoecology of the Westleton Member of the Norwich Crag Formation (early Pleistocene) at Thorington, Suffolk, England

Extensive sections in the Thorington gravel quarry complex in eastern Suffolk include the most complete record to date of sedimentary environments of the Westleton Beds Member of the Norwich Crag Formation. New palaeoecological and palaeomagnetic evidence is presented, which confirms that the Member was deposited at or near a gravelly shoreline of the Crag Sea as sea level fluctuated during a climatic ameloriation within or at the end of the Baventian/ pre-Pastonian ‘a’ Stage (Tiglian C4c Substage).

Late Pleistocene deposits at Chatteris, March and Wimblington, Cambridgeshire, UK

Sites at Chatteris, March Town End and Wimblington Common have yielded evidence for Late Pleistocene vegetational history, sea-level change and gravel aggradation. Analysis of pollen, macroscopic plant remains and Foraminifera indicate that temperate freshwater and marine sediments were deposited in the Ipswichian Stage, substages II and HI. The freshwater sediments formed above 3.5 m OD, and the marine sediments from −3 m to 1.4 m OD. Gravel aggradations that followed contain reworked marine faunas, and include the so-called March Gravels. These are considered to be Devensian, and show a series of aggradations with heights declining during this cold stage. It is suggested that the term March Gravels be restricted to Devensian gravels, while the Ipswichian marine-influenced sediments are placed in a separate unit, the Wimblington Beds.

Plant macroscopic remains from recent sediments of Banks Island, Northwest Territories, and Bathurst Island, Nunavut, Canada, and the interpretation of Quaternary cold stage plant macroscopic assemblages

Macroscopic plant remains were extracted from recent sediments of streams on Banks Island and Bathurst Island. Analyses of the samples are given and their general relation to the vegetation is described. Problems of interpretation of the contemporary and Quaternary cold stage macroscopic assemblages include the variation of the representation of taxa, the significance of taphonomy, especially under fluvial conditions, and the origin of the assemblages in a mosaic of vegetation. The contribution of analyses of macroscopic remains to interpretations of vegetation and environment based on pollen analysis is emphasised. Copyright