Peter Allen

Middle Pleistocene stratigraphy in south-east Suffolk

A conspicuous horizon of rubification, clay and iron enrichment, involutions and ice-wedge casts is attributed to two stages of soil formation. It comprises a rubified sol lessivé formed in warm temperate conditions, which was altered to an arctic structure soil by periglacial processes. These palaeosols indicate that the sand and gravel deposits beneath the Lowestoft Till comprise two units, and provide the basis of a revised Middle Pleistocene stratigraphy. The Kesgrave Sands and Gravels were formed during the Beestonian in a periglacial environment by a major river which drained towards the north-east. Subsequently the Valley Farm Rubified Sol Lessivé was formed during the Cromerian Interglacial, and the Barham Arctic Structure Soil and the associated Barham Loess were formed during the early Anglian Glacial. Both soils and the wind-blown sediments were formed on low relief terrace topography and are the remnants of a formerly extensive land surface. This feature was subsequently trimmed by meltwater rivers, then overlain by the Barham (outwash) Sands and Gravels and the Lowestoft Till which were deposited during the Anglian Glaciation.

Sedimentology, palaeontology and archaeology of late Middle Pleistocene River Thames terrace deposits at Purfleet, Essex, UK

Middle Pleistocene fluvial deposits of the Corbets Tey Formation at Purfleet, Essex, provide evidence of an un-named and previously poorly recognized interglacial, thought to corrrelate with Oxygen Isotope Stage (OIS) 9. Previous attributions of the sediments to the Ipswichian (Last Interglacial) Stage are refuted. New investigations have yielded rich molluscan, mammalian and ostracod assemblages that indicate fully temperate conditions and the distal influence of marine transgression. Pollen analyses suggest a previously unrecorded phase of interglacial vegetational development. Clast composition, geomorphological evidence and the occurrence of molluscs that favour large rivers all point to deposition by the Thames, rather than in a minor tributary, as suggested previously. Three separate Palaeolithic industries in stratigraphical superposition are recognized at Purfleet, these being Clactonian, Acheulean and Levallois. Purfleet is therefore a key locality in the understanding of the early human occupation and exploitation of southern Britain, as well as for the interpretation and correlation of the terrace sequence in the Thames Valley.

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.

Report of Geologists' Association Field Meeting in north-east Essex, May 22nd–24th, 1987

During this two day field meeting based at Colchester, participants were shown a number of important sites illustrating the Pleistocene history and evolution of the Thames-Medway drainage system. Pre-Anglian interglacial deposits were seen at Ardleigh and Little Oakley, the former site also boasting cold-climate biogenic sediments and a complex stratigraphy. A further pre-Anglian interglacial site at Wivenhoe, discovered since the excursion, is also described. At St Osyth and Holland-on-Sea complementary stratigraphic sites were examined which provide evidence for the glacial blockage of the Thames during the Anglian. The resultant diversion of the river was then demonstrated at Clacton, where recent excavation of the West Cliff had revealed the edge of the Clacton Channel deposits. The entire second day was spent at East Mersea, where a complex of Thames-Medway sediments is exposed in close juxtaposition to later Blackwater deposits, interglacial material (of different ages) forming part of both.

Key Middle Pleistocene localities of the Lower Thames: site conservation issues, recent research and report of a Geologists' Association excursion, 8 July, 2000

A review of published data spanning two centuries, combined with new investigations at a number of critical sites, has confirmed the Lower Thames terrace staircase to be one of the most complete and best dated archives of late Middle Pleistocene environmental change in Europe. This recognition comes at a time when access to exposures of the key sediments has diminished to just a handful of conservation sites, mainly Sites of Special Scientific Interest (SSSIs), under increasing pressure from development. Four such sites, central to the recognition of the oxygen isotope stage (OIS) 9 and OIS 7 interglacials within the Lower Thames sequence, were visited by a GA excursion in July 2000. This paper combines a report of the excursion with discussion of the importance of the sites as well as conservation management issues.