Colin A. Whiteman

Thames River sediments of the British Early and Middle Pleistocene

Abstract The Thames drainage system contains the most complete record of fluvial sediments in the British Quaternary. The Kesgrave Sands and Gravels form the main body of this sediment having been deposited over an interval that spans the later part of the Early Pleistocene and most of the Middle Pleistocene (conventional stages: Pre-Pastonian a through to early Anglian, ca. 1.2 ma). This deposit provides a stratigraphic context for related bio-, morpho-, and pedostratigraphic evidence and for the recognition of pre-Anglian (pre-OI Stage 12) upland glaciation in the Welsh mountains and intense periglaciation in lowland England. It also facilitates correlation with the stratigraphy of northern Europe and the global pattern of orbitally forced climatic change. This paper describes the first catchment-wide correlation of Thames river sediments, and proposes a formal redefinition of the lithostratigraphic units concerned. The scheme outlined here is based on two lithologically distinctive formations defined at type areas, reflecting significant changes in catchment dimensions. The earlier Sudbury Formation was formed when the Thames catchment extended into Wales and drained northwards across East Anglia; the later Colchester Formation was formed after the upper catchment had been reduced in extent to that of the present river, but continued to flow across East Anglia. The whole sediment body is now named the Kesgrave Group.

The Kesgrave Sands and Gravels: ‘pre-glacial’ Quaternary deposits of the River Thames in East Anglia and the Thames valley

This paper reviews the Kesgrave Sands and Gravels as evidence for the pre-glacial history of the River Thames and its main tributaries. Attention is given to the definitions of the deposit, the lithological and sedimentological properties, and the geographical and stratigraphical variations of these properties. Also described are the terrace landforms formed by the Kesgrave Sands and Gravels and the Iithostratigraphical and geomorphological basis by which individual terraces are correlated across the region. The relationship of the Kesgrave Sands and Gravels to the palaeosols developed on their surfaces, to contemporaneous coastal sedimentation and to neotectonic uplift in the headwater regions and subsidence around the North Sea margins is outlined, along with possible evidence for glaciation in the headwater regions. The paper concludes with a review of the palaeoclimatic and stratigraphical evidence which indicates that most of the unit was deposited by periglacial river activity during the late Early Pleistocene and the early Middle Pleistocene between about 1.81 and 0.46 Ma bp A possible scenario explaining the factors forcing river activity in this part of the Quaternary is proposed. The paper also outlines the role of Richard Hey in the identification and interpretation of this sediment body.

Stratigraphy and glaciotectonic structures of permafrost deformed beneath the northwest margin of the Laurentide ice sheet, Tuktoyaktuk Coastlands, Canada

The upper 5-20 m of ice-rich permafrost at three sites overridden by the northwest margin of the Laurentide ice sheet in the Tuktoyaktuk Coastlands, western Arctic Canada, comprise massive ice beneath ice-rich diamicton or sandy silt. The diamicton and silt contain (1) truncated ice blocks up to 15 m long, (2) sand lenses and layers, (3) ice veins dipping at 20-30°, (4) ice lenses adjacent and parallel to sedimentary contacts, and (5) ice wedges. The massive ice is interpreted as intrasedimental or buried basal glacier ice, and the diamicton and silt as glacitectonite that has never thawed. Deformation of frozen ground was mainly ductile in character. Deformation was accompanied by sub-marginal erosion of permafrost, which formed an angular unconformity along the top of the massive ice and supplied ice clasts and sand bodies to the overlying glacitectonite. After deformation and erosion ceased, postglacial segregated ice and ice-wedge ice developed within the deformed permafrost.

The palaeogeography and correlation of pre-Anglian-Glaciation terraces of the River Thames in Essex and the London Basin

Evidence from boreholes and exposures in Essex and adjacent counties indicates at least eight Thames terrace aggradations. They can be divided lithologically and altitudinally into two groups of four members, the higher older Sudbury Formation and the younger lower Colchester Formation, together comprising the Kesgrave Group, formerly the Kesgrave Formation. Palaeogeographical reconstruction of the terraces shows a series of surfaces declining from south-west to north-east during the time of the Sudbury Formation, and from west to east or south-east during the time of the Colchester Formation. Their longitudinal gradients are less than those assumed in most previous correlation schemes and are attributed to a greater postulated maximum size of the Thames catchment when it extended north-westwards beyond the Cotswolds escarpment. These revised longitudinal terrace gradients combined with lithological and other properties, are used to revise substantially existing correlations of pre-Anglian-Glaciation Thames terraces in the London Basin.

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.

Palaeoenvironmental and stratigraphic significance of the Valley Farm and Barham Soils in Eastern England

Abstract The Valley Farm and Barham Soils are important stratigraphic units representing an Early and/or Middle Pleistocene depositional hiatus within parts of Eastern England. The Barham Soil, buried beneath Anglian sediments, is recognised by a variety of large- and small-scale cryogenic features which developed in Cromerian sediments or were superimposed upon the Valley Farm Soil during the early Anglian. The Valley Farm Soil is rubified, mottled and contains substantial quantities of translocated clay. Originally attributed solely to temperate (Cromerian stage) pedogenesis, its stratigraphic status has changed over recent years as the age range of its Kesgrave Sands and Gravels parent material has been extended. Currently, the Valley Farm Soil is regarded as a complex stratigraphic unit with component soils developed on a series of different age surfaces, perhaps spanning cold and temperate intervals over more than a million years. Detailed micromorphological studies of the Valley Farm Soil on some of these surfaces have confirmed its variable pedological complexity. A number of theoretical and practical problems, however, need to be confronted and solved before its pedological record can be used routinely to provide an independent means of dating and reconstructing detailed palaeoenvironments.

Snow and Ice-Related Hazards, Risks, and Disasters: A General Framework

Abstract Snow and ice constitute the cryosphere on Earth and influence human activities at various scales of time and space. Through their proximity to phase-change thresholds, they are strongly linked to climatic conditions and presently subject to rapid changes induced by ongoing trends of global warming. Hazards, risks, and disasters related to snow and ice not only result from direct impacts on humans and their infrastructure by, for instance, snow avalanches, floods from glacial lakes, or accelerated erosion of permafrost coasts, they are also a consequence of the expansion of human activities into previously avoided dangerous regions, such as new shipping routes in the polar ocean, and tourist installations in cold mountains that are becoming ice free. The loss of goods and benefits from reducing or even vanishing cryosphere components constitutes serious threats to human well-being through, for example, diminishing meltwater supply in high-mountain rivers during dry seasons or rising global sea level. Further protection, mitigation, and adaptation procedures, combined with modern observational technologies will be required to anticipate, monitor, and deal with the challenges created by complex and highly interconnected geo- and ecosystems under conditions of growing disequilibrium.

Processes of terrestrial glacial deposition

Publisher Summary This chapter addresses the process of terrestrial glacial deposition. It discusses the factors that influence glacial deposition, mechanisms of glaciogenic deposition, and examples of problems in determining depositional processes based upon sedimentary characteristics. Glaciogenic diamictons are deposited when certain conditions are fulfilled. The fundamental mechanisms involved in glacial deposition are flow, melt and frictional resistances, acting separately or in concert. Deposition may result from ambient or internal changes, such as a reduction in bed gradient, a decrease in flow mass thickness, a loss of interstitial fluids by drainage through permeable substrates, a blockage of the flow path, or an addition of dry sediment that increases bulk density and reduces the relative water content of the debris.

Field meeting: landscape evolution in the eastern South Downs, with particular reference to sarsens and Quaternary deposits, Saturday 17 October, 1998

The development of chalkland landscapes has long been a subject of debate in the UK. This excursion provided an opportunity to review some of these ideas in the context of the eastern South Downs. The morning was devoted principally to discussion of established theories, in particular the nature of Sussex sarsens and their origins: in the afternoon attention switched to Quaternary landscapes and the sensitive question of geological conservation.