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

doi:10.1016/S0016-7878(88)80056-7

Proceedings of the Geologists' Association

Volume 99, Issue 4, 1988, Pages 315-333

https://doi.org/10.1016/S0016-7878(88)80056-7 Get rights and content

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.

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The complex Geological Conservation Review (GCR) site at Clacton-on-Sea, Essex, was notified in 1986 as a Site of Special Scientific Interest. It is an internationally important geosite and Britain's only Lower Palaeolithic type locality, giving its name to the Clactonian stone-tool industry. Fossil- and artefact-bearing channel-fill deposits laid down by the River Thames ~ 420,000 years ago, during the Hoxnian Interglacial (Marine Isotope Stage 11c), have been observed in foreshore and cliff exposures, and beneath developed and open ground in an inland arcuate footprint. These sediments provide a record of the lower reaches and estuary of the Thames during this lengthy and warm interglacial, an important partial analogue for the Holocene. Palaeoclimatic and palaeoecological evidence has been obtained from assemblages of fossil molluscs, ostracods and vertebrates, together with pollen and plant macrofossils; Clacton is also the type locality for several of the represented animal taxa, including the biostratigraphically significant ostracod Scottia browniana and a large subspecies of fallow deer, Dama dama clactoniana. This paper provides an overview of the continuing importance of the Clacton GCR site and Site of Special Scientific Interest (SSSI), summarizing recently acquired data that have enhanced understanding of the Hoxnian and the palaeoenvironments that prevailed at the time of deposition. The wider geosite has benefitted from sustained Palaeolithic archaeological interest, with the local planning authority mandating investigation of the sediments as a condition for development projects. SSSI status ensures that the significant collections of palaeontological and archaeological material amassed from the Clacton deposits over almost two centuries can be related to their context, and studies of both these archived collections and new material from the protected in situ sediments continue to provide new data and contribute to the development of cutting-edge techniques.
Differentiation of MIS 9 and MIS 11 in the continental record: vegetational, faunal, aminostratigraphic and sea-level evidence from coastal sites in Essex, UK
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Citation Excerpt :
The floor of the channel is lined with sands and gravels that form the basal member of the Pleistocene sequence and directly overlie London Clay. These reach a maximum recorded thickness (3.10 m) in borehole CG1 (Fig. 4), then thin progressively south-westwards towards the channel margin, where they taper into a 1–2 cm pebble lag (Figs. 4 and 5), the ‘Cudmore Grove Channel lag’ (Bridgland et al., 1988). The persistence of Unit 1 to the northeast of borehole CG1 is unknown.
Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 °C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed.
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Citation Excerpt :
Located ∼1 km NE of East Mersea at TM067144, the Cudmore Grove site provides cliff and foreshore exposures of a temperate-stage channel-fill and overlying fluvial gravels. The assignment of this site to the Hoxnian (Bridgland et al., 1988) was called into question by Roe (1995) on biostratigraphic grounds. Schreve (2001a) placed it within MIS 9 (her Purfleet MAZ) from the mammalian biostratigraphy.
The concentration ratio of the amino acids alanine and serine in calcite opercula of freshwater gastropods of genus Bithynia has been assessed as an age proxy for British Middle and Late Pleistocene sites. Due to decomposition of peptide-bound serine within intra-crystalline protein molecules, alanine/serine ratios increase with sample age, enabling resolution of the marine oxygen-isotope stage of almost all sites and substage resolution for some sites. However, slight overlaps are evident in alanine/serine ratios between some sites from late in one temperate stage and early in the next; this effect results from the low decomposition rates during cold stages, combined with an evident slight dependence of decomposition rates on site conditions. The technique, which can be extended to the Early Pleistocene without technical refinements, is amenable to quantitative calibration using a first-order rate equation, making it feasible in future to present results as numerical ages, subject to an assumed temperature history. Most Pleistocene sites investigated are shown using this technique to have the same ages as previously deduced using biostratigraphy. However, the serine–alanine ages obtained preclude glaciation of southeast England during MIS 16 or of central England during MIS 10.
Context: A perspective on D.R. Bridgland's paper 'The Middle and Upper Pleistocene sequence in the Lower Thames: A record of Milankovitch climatic fluctuation and early human occupation of southern Britain'
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The sequence of Pleistocene river terraces in the Lower Thames, long recognized as an important repository of evidence for Palaeolithic human activity, can now be interpreted in the context of the last five Milankovitch (100 ka) climate cycles, beginning with cold marine oxygen isotope stage (MIS) 12, when ice sheets blocked an earlier Thames course in Hertfordshire and Essex. This interpretation stems from empirical evidence from the Lower Thames deposits, in which the preservation of faunal and archaeological remains is unusually common. These deposits were laid down as climatically generated river terraces, formed in synchrony with the climatic cycles, although the progressive incision to ever-lower valley-floor levels is a response to background uplift. Interpretation of this evidence is revised here for the Dartford-Purfleet area in recognition of a phase of minor downcutting at the ends of interglacials. Previously regarded as insignificant, it is now realized that this erosion phase has resulted in interglacial sediments forming the higher of two facets within each terrace in the Lower Thames. Guided by this revision, the Lower Thames (Thames-Medway) terrace sequence further downstream, in eastern Essex, is reappraised in the light of the better preserved and better understood record from the Dartford-Purfleet area. It is concluded that Thames-Medway drainage northwards to the Clacton area (NE Essex) persisted until after the Hoxnian (MIS 11), so that the Clactonian (Palaeolithic) type locality lay in the main Thames valley at the time when the Clactonian knappers were operating. Despite its relegation in recent years from the earliest British Palaeolithic culture to little more than a curious anomaly, with doubts expressed about its separate existence, recent interpretations of the Clactonian hold that it appeared within the Thames sequence on two separate occasions, both coincident with a glacial to interglacial transition. These separate Clactonian occupations, at the MIS 12-11 and 10-9 transitions, together with the first appearance of the Levallois technique at around the MIS 9-8 boundary, can be linked to the chronology and to the cyclic climatic record that together underpin the Lower Thames sequence.
The evolution of the river Medway, SE England, in the context of Quaternary palaeoclimate and the palaeolithic occupation of NW Europe
2003, Proceedings of the Geologists' Association
The Medway is a river of considerable antiquity that has had an important role within the evolution of drainage in southeast England. Its upper catchment has expanded during the latter part of the Quaternary as a result of river capture. However, it has a much shorter course as an independent river than it did half a million years ago, since its lower course was truncated when the Anglian glaciation caused the Thames to be diverted into the lower Medway valley, across what is now eastern Essex.
Correlation of gravel terraces in the present Lower Medway with those of the Lower Thames is readily achieved by long-profile projection to and from the Southend area, where terraces of the now-drowned post-diversion Thames-Medway valley are preserved. Correlation between the Lower and Upper Medway is more problematical, but a revised scheme can be suggested, one that requires most of the surviving deposits in the upper valley to be of relatively recent age. The suggested correlations take account of faunal and archaeological components of the deposits, as well as projected downstream gradients and the height above the river of terrace remnants, the latter newly established as an important measure of fluvial incision in response to progressive uplift and, therefore, as a potential means of age estimation.

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

Proc. Geol. Ass.

Proc. Geol. Ass.

Proc. Geol. Ass.

Proc. Geol. Ass.

Middle Pleistocene stratigraphy and landform development in south-east Suffolk

Field guide to the Gipping and Waveney valleys

The mammal fauna of the Early Middle Pleistocene cavern infill site of Westbury-sub-Mendip, Somerset

Spec. Pap. Palaeontol.

A reappraisal of Pleistocene stratigraphy in north Kent and eastern Essex, and new evidence concerning former courses of the Thames and Medway

Quat. Newsl.

The Quaternary fluvial deposits of north Kent and eastern Essex

Eastern essex

The rudaceous components of the East Essex Gravel; their characteristics and provenance

Quat. Studies

Soils for the archaeologist

Man and Quaternary interglacial faunas in Britain

Post-glacial beds in Mersea, Essex

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Ipswichian fauna of Victoria Cave and the marine palaeoclimatic record

Nature

Pleistocene history of the Vale of St Albans

Phil. Trans. R. Soc.

Pleistocene history of the Middle Thames Valley

The British fossil shrews

Geol. Mag.

Mid-Pleistocene microfauna of Continental Europe

Pleistocene vertebrate faunas of Hungary

Climatic variability during the past three million years, as indicated by vegetational evolution in north-west Europe and with emphasis on data from the Netherlands

Phil. Trans. R. Soc.

The macrofaunas of Continental Europe during the Middle Pleistocene: stratigraphic sequence and problems of intercorrelation

The Valley Farm Soil in southern East Anglia