A contribution to Pleistocene chronology in southeast Essex,England

Parallel to the Essex coast north of the mouth of the Thames, a series of gravel spreads ranging in altitude from near sea level westward to more than 200 ft O.D. (mean sea level) proved to be the remnants of an abandoned Thames/Medway terrace system, rather than a series of “raised” beaches, as their location had suggested. The seaward side of the ancient river valley has subsequently been “captured” by subsidence.Evidence is given for five terraces, with surface levels between 5 and 75 ft O.D. Because of subsidence of the Essex coast, the terrace levels are not easily correlatable with either the Thames or Medway terrace levels. Temporal placement is attempted on the basis of one site in the 25 ft Barling terrace, which yielded a Middle Acheulian archaeological assemblage associated with a cool temperate fauna including an early form of mammoth. An ice wedge cast in the Barling terrace was filled with floodloam which weathered to a parabraunerde soil during an interglacial climate warmer than now. For these reasons man is thought to have lived on the floodplain of the Barling terrace either at the onset of the Wolstonian (Riss) glacial or during an interstadial of that stage. The question of possible linkages between Swanscombe and Clacton terraces is discussed.     

U-series dating of Hoxnian interglacial deposits at Marks Tey,Essex, England

A U–Th dating study was carried out on the authigenic carbonate component of interglacial lake sediments at Marks Tey, Essex, England. Isochron methods were necessary because of the presence of non-carbonate detritus. Calculated dates around the limit of the U–Th method were obtained for two horizons. Error limits were determined by Monte Carlo sampling from the normal distributions of errors in the isotope ratios. Comparison of the resulting empirical distribution functions with the marine oxygen isotope time-scale indicates with 87% confidence that the Marks Tey sediments correlate with OIS 11 or some older stage. As the Marks Tey deposits rest without stratigraphical break on Anglian till, and can be firmly correlated with the Hoxnian interglacial type site at Hoxne, Suffolk, England, this result implies that the Anglian glaciation took place in OIS 12 and the Hoxnian Stage of the British chronostratigraphy commenced in OIS 11. Copyright © 1999 John Wiley & Sons, Ltd.     

Middle pleistocene interglacial sediments at Tye green,Stansted Airport,Essex, England

Interglacial lake deposits at Tye Green, Stansted, resting on unweathered till and overlain by a weathered diamicton are correlated with the temperate Hoxnian Stage. The sediments represent the infilling of an isolated kettle-hole type of lake basin formed at the end of the cold Anglian Stage. Through the temperate period this basin was infilled by inorganic and organic sediments that record the development and decline of deciduous forest. Later periglacial conditions are indicated by the final infilling of the basin by reworked till. The sedimentary sequence and vegetational development recorded in the sediments at Tye Green are compared with other Hoxnian sites in eastern England. Changes in deposition rates are interpreted as representing water-table fluctuations resulting from changes in precipitation. The deposits at Tye Green provide a useful stratigraphical marker in the glacial sequence of the district. Copyright © 1999 John Wiley & Sons, Ltd.     

Middle Pleistocene lacustrine deposits in eastern Essex,England and their palaeogeographical implications

Investigations in quarry exposures in the Asheldham Gravel and related deposits of southeast Essex are described. Section logging, mapping and borehole investigations are supported by clast lithological, heavy and clay mineralogical determinations. The sediments are derived from reworking of local Thames basin materials, fine sediment being predominantly from the London Clay. The sequence is shown to represent an aggradation that began as the fluvial infilling of the River Medway valley. The River Thames, diverted into this valley by glaciation further west, overwhelmed the Medway, reworking the deposits. The valley was subsequently drowned and fine laminated lake sediment was initially deposited. This was during a period when the valley was drowned by the glacial lake ponded in the southern North Sea basin by the Anglian/Elsterian ice sheet. Progradation by a braid-delta complex advanced along the valley and subsequently fluvial deposition returned. Valley widening and straightening accompanied the delta progradation. The deposits were dissected by deep fluvial valleys infilled by Hoxnian interglacial sediments. The Asheldham Gravel is therefore placed in the Anglian/Elsterian Stage.     

Integrated chronological control on an archaeologically significant Pleistocene river terrace sequence: the Thames-Medway,eastern Essex,England

Late Middle Pleistocene Thames-Medway deposits in eastern Essex comprise both large expanses of Palaeolithic artefact-bearing river sands/gravels and deep channels infilled with thick sequences of fossiliferous fine-grained estuarine sediments that yield valuable palaeoenvironmental information. Until recently, chronological control on these deposits was limited to terrace stratigraphy and limited amino-acid racemisation (AAR) determinations. Recent developments in both this and optically stimulated luminescence (OSL) dating make them potentially powerful tools for improving the chronological control on such sequences. This paper reports new AAR analyses and initial OSL dating from the deposits in this region. These results will help with ongoing investigation of patterns of early human settlement.Using AAR, the attribution by previous workers of the interglacial channel deposits to both MIS 11 (Tillingham Clay) and MIS 9 (Rochford and Shoeburyness Clays) is reinforced. Where there are direct stratigraphic relationships between AAR and OSL as with the Cudmore Grove and Rochford Clays and associated gravels, they agree well. Where OSL dating is the only technique available, it seems to replicate well, but must be treated with caution since there are relatively few aliquots. It is suggested on the basis of this initial OSL dating that the gravel deposits date from MIS 8 (Rochford and Cudmore Grove Gravels) and potentially also MIS 6 (Dammer Wick and Barling Gravels). However, the archaeological evidence from the Barling Gravel and the suggested correlations between this sequence and upstream Thames terraces conflict with this latter age estimate and suggest that it may need more investigation.     

Middle Pleistocene interglacial deposits at Barling,Essex, England: evidence for a longer chronology for the Thames terrace sequence

Results are presented from a multidisciplinary study of fossiliferous interglacial deposits on the northern side of the Thames estuary. These fill a channel cut into London Clay bedrock and overlain by the Barling Gravel, a Thames–Medway deposit equivalent to the Lynch Hill and Corbets Tey Gravels of the Middle and Lower Thames, respectively. The channel sediments yielded diverse molluscan and ostracod assemblages, both implying fully interglacial conditions and a slight brackish influence. Pollen analysis has shown that the deposits accumulated during the early part of an interglacial. Plant macrofossils, particularly the abundance of Trapa natans, reinforce the interglacial character of the palaeontological evidence. A beetle fauna, which includes four taxa unknown in Britain at present, has allowed quantification of palaeotemperature using the mutual climatic range method (T_max 17 to 26 °C; T_min ?11 to 13 °C). A few vertebrate remains have been recovered from the interglacial deposits, but a much larger fauna, as well as Palaeolithic artefacts, is known from the overlying Barling Gravel. The age of the interglacial deposits is inferential. The geological context suggests a late Middle Pleistocene interglacial, part of the post‐diversion Thames system and therefore clearly post‐Anglian. This conclusion is supported by amino acid ratios from the shells of freshwater molluscs. The correlation of the overlying Barling Gravel with the Lynch Hill/Corbets Tey aggradation of the Thames valley constrains the age of the Barling interglacial to marine oxygen isotope stages 11 or 9. The presence of Corbicula fluminalis and Pisidium clessini confirms a pre‐Ipswichian (marine oxygen isotope substage 5e) age and their occurrence in the early part of the interglacial cycle at Barling precludes correlation with marine oxygen isotope stage 11, as these taxa occur only later in that interglacial at sites such as Swanscombe and Clacton. Thus by process of elimination a marine oxygen isotope stage 9 age would appear probable. Copyright © 2001 John Wiley & Sons, Ltd.     

A conceptual model for loess in England: Principles and applications

PTD, an acronym for Provenance - Transport - Deposition, is a multilayer geomorphotechnical system, the combination of geomorphology, Quaternary Sciences, and geotechnical consequences of its implementation in groundworks and other crosscutting disciplines. Embedded in its three layers are geographical, geochemical, geophysical, mineralogy, dating, lithological and geotechnical inputs. In this state-of-the-art review contribution and for Loess in England, Syngenetic and Epigenetic mechanisms are drawn out and used to generate the three constitutive layers for three conceptual PTD models and the interrelationships among them. The developed models are then deployed to inform earthworks design for three HS2 embankments in Chiltern Hills.     

The Isle of Portland,Dorset, England

The Isle of Portland is one of the jewels in the crown of the ‘Jurassic Coast’ of Dorset, southern England. Thomas Hardy aptly described this limestone peninsula as the ‘Gibraltar of Wessex’, and used its stone quarries as the backdrop for one of his novels (The Well‐Beloved). Quarries then, as now, work the world‐famous Portland Stone—a Jurassic oolitic limestone—from which St Paul's Cathedral and many other well‐known buildings are constructed. Rocks exposed in the numerous disused quarries scattered across the isle, together with exposures in spectacular sea‐cliffs, paint a vivid picture of life and environments, ～150 million years ago. In addition to Jurassic patch‐reefs, coastal sabhkas, fossil forests and dinosaur footprints found in the bedrock, more recent geological phenomena include two Quaternary raised beaches, solution caves filled with vertebrates, and massive coastal landslips. The aim of this article is to provide a field guide for those wishing to explore the geology of this little‐known region for themselves.     

Pleistocene sediments,soils and landscape evolution at Stebbing,Essex

Pleistocene sediments and soils exposed at Stebbing in central Essex, England are described, analysed and interpreted. The sand and gravel units above Eocene London Clay and Upper Pliocene Red Crag are shown to be a high level member of the Kesgrave Formation, with a surface immediately beneath that of the Westland Green Gravels, which are tentatively assigned to the Pre-Pastonian ‘a’ Stage of the British Quaternary succession. The rubified, argillic soil developed in the surface of these fluvial deposits is a composite of the Valley Farm and Barham Soils and displays micromorphological evidence of several phases of clay illuviation, gleying and clay coating disruption. Originally truncated and buried beneath Anglian gelifluction deposits, cover sand and till, the soil has been exhumed in most places by subsequent erosion. The full succession, however, is preserved within large gulls that formed by periglacial cambering prior to this erosion. More recent loess incorporation and pedogenesis have modified the exhumed soil and the materials within the gulls.     

The loess of West Europe

During the last thirthy years, many studies about loess and periglacial deposits have allowed to present a correlation table from the Netherlands and Belgium to north-west France. For the Quaternary, 11 main interglacial soils were recognized, separated during Early Pleistocene by combe-rock and solifluction deposits, and during Middle and Late Pleistocene by loess cycles. Two main loess basins exist in France. The most important is the Northern basin, continuing the sandy area of Belgium (cover sand) and the desert pavement of the Netherlands. The second is developed in Normandy and results from the Channel landscape open during pleniglacial periods. We have now stratigraphic tables at different time-scales. The main research axes must be now to attain a better knowledge about sources of loess materials, to estimate the volume of loess and its climatic significance and landscape variation during the pleniglacial events. Absolute datings of Middle Pleistocene stratigraphic details are needed to evaluate the differences between the different climatic cycles.     

The Widdington Sands: High-level Kesgrave Sands and Gravels near the Cam-Stort interfluve,Northwest Essex,UK

A small but stratigraphically significant exposure of Quaternary sandy sediments (Widdington Sands) was observed and recorded in the early 1970s in northwest Essex. These data are here re-examined and re-evaluated, yielding new insights into early proto-Thames aggradation following the marine recession of the Norwich Crag Formation (MIS 74–71, about 2 Ma). As the proto-Thames trajectory shifted south eastwards, a period of landscape stability ensued in the early Middle Pleistocene (MIS 19–13) during which the Valley Farm Soil was formed. This and the succeeding Barham Soil can be recognised in the stratigraphy, the second palaeosol heralding the arrival of glaciation in the Anglian Stage (MIS 12, 480–420 ka). These pedogenic signatures are enclosed within palaeokarstic features in the form of infilled sinkhole pipes. A large doline has functioned as a sediment trap preserving pre-truncation structures including reverse ring faults. These confirm basal support removal leading to upward migration of a dissolution cavity and roof collapse within the sinkhole pipe. The process and timing of subsidence can thus be defined more clearly than for similar features found in comparable Kesgrave aggradations of the Middle Thames. The likely glacitectonic origin of the planar sub-till surface is examined and discussed. Dating of Early Pleistocene fluvial activity is constrained by estimating the height of a former terrace surface whose elevation points to a correlation with the higher Stoke Row Member (MIS 64, 1.8 Ma), suggesting the oldest known proto-Thames activity within southern East Anglia.