A late Middle Pleistocene temperate–periglacial–temperate sequence (Oxygen Isotope Stages 7–5e) near Marsworth, Buckinghamshire, UK

121

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract: Late Cenozoic (and especially Quaternary) fluvial deposits and related landforms provide valuable information about landscape evolution, not just in terms of changing drainage patterns but also documenting changes in topography and relief. Recently compiled records from river systems worldwide have shed much light on this subject, particularly records of terrace sequences, although other types of fluvial archive can be equally informative. Terraces are especially valuable if they can be dated with reference to biostratigraphy, geochronology or by other means. The various data accumulated support the hypothesis that the incision observed from river terraces has been a response to progressive uplift during the Late Cenozoic. This has not occurred everywhere, however. Stacked fluvial sequences have formed in subsiding depocentres and have greater potential for surviving to become part of the longer-term geological record. More enigmatic are regions in the ancient cores of continents (cratons), which show little indication of sustained uplift or subsidence, with fluvial deposits of various ages occurring within a restricted range of elevation with respect to the valley floor. In areas of dynamic crust that were glaciated during the Last Glacial Maximum post-glacial river valleys are typically incised and often terraced in a similar way to valleys on post-Precambrian crust elsewhere, although the terraces and gorges in these systems are very much younger (~15 ka) and therefore the processes have been considerably more rapid. This paper is illustrated with various case-study examples of these different types of archives and discusses the implications of each for regional landscape evolution.

Section: Dating Fluvial Sedimentsmentioning

confidence: 99%

Quaternary fluvial archives and landscape evolution: a global synthesis

Bridgland

Westaway

2014

121

“…2b and 3;Murton et al, 2001). (2) The Upper Channel deposits were examined in three small, adjacent areas c. 100-150 m northwest of the northwestern limit of the Lower Channel deposits.…”

Section: Stratigraphy and Sedimentologymentioning

confidence: 99%

“…Evans and Oakley's (1952) section in the No. 1 Quarry; NE and SE = Evans ' (1966) sections beside Pitstone Hill; EV = Evans and Valentine's (1974) section; Upper and Lower Channels and site B of Green et al (1984) and Murton et al (2001). Scale: National Grid at 1 km intervals.…”

Section: Pleistocene Geologymentioning

confidence: 99%

“…The deposits at Marsworth contain a particularly wellpreserved sedimentary sequence that spans at least two temperate and one intervening periglacial episode during the late Middle and Late Pleistocene (Green et al, 1984). The infills of two river channels have been assigned to MIS 7 and 5e, and the intervening sheet of periglacial slope deposits to MIS 6 (Murton et al, 2001). High-precision uranium-series dating of tufa fragments from the older river channel suggests that tufa formed during both substages 7e and 7c, and that the main part of the channel fill accumulated during either sub-stages 7b or 7a (Candy and Schreve, 2007).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Middle and Late Pleistocene environmental history of the Marsworth area, south-central England

Murton

Bowen

Candy

et al. 2015

A B S T R A C TTo elucidate the Middle and Late Pleistocene environmental history of south-central England, we report the stratigraphy, sedimentology, palaeoecology and geochronology of some deposits near the foot of the Chiltern Hills scarp at Marsworth, Buckinghamshire. The Marsworth site is important because its sedimentary sequences contain a rich record of warm stages and cold stages, and it lies close to the Anglian glacial limit. Critical to its history are the origin and age of a brown pebbly silty clay (diamicton) previously interpreted as weathered till.The deposits described infill a river channel incised into chalk bedrock. They comprise clayey, silty and gravelly sediments, many containing locally derived chalk and some with molluscan, ostracod and vertebrate remains. Most of the deposits are readily attributed to periglacial and fluvial processes, and some are dated by optically stimulated luminescence to Marine Isotope Stage (MIS) 6. Although our sedimentological data do not discriminate between a glacial or periglacial interpretation of the diamicton, amino-acid dating of three molluscan taxa from beneath it indicates that it is younger than MIS 9 and older than MIS 5e. This makes a glacial interpretation unlikely, and we interpret the diamicton as a periglacial slope deposit.The Pleistocene history reconstructed for Marsworth identifies four key elements: (1) Anglian glaciation during MIS 12 closely approached Marsworth, introducing far-travelled pebbles such as Rhaxella chert and possibly some fine sand minerals into the area. (2) Interglacial environments inferred from fluvial sediments during MIS 7 varied from fully interglacial conditions during sub-stages 7e and 7c, cool temperate conditions during sub-stage 7b or 7a, temperate conditions similar to those today in central England towards the end of the interglacial, and cool temperate conditions during sub-stage 7a. (3) Periglacial activity during MIS 6 involved thermal contraction cracking, permafrost development, fracturing of chalk bedrock, fluvial activity, slopewash, mass movement and deposition of loess and coversand. (4) Fully interglacial conditions during sub-stage 5e led to renewed fluvial activity, soil formation and acidic weathering.

“…Murton et al, 2001;Schreve, 2001Schreve, , 2004Bridgland et al, 2003;Desprat et al, 2006;Schreve et al, 2006;Roucoux et al, 2008) and MIS 11 (Droxler et al, 2003;Rousseau, 2003;Antoine and Limondin-Lozouet, 2004;Preece et al, 2007). Thus the Lower Thames terrace sequence at Purfleet (Fig.…”

Section: Introductionmentioning

confidence: 99%

An enhanced record of MIS 9 environments, geochronology and geoarchaeology: data from construction of the High Speed 1 (London–Channel Tunnel) rail-link and other recent investigations at Purfleet, Essex, UK

Bridgland

Harding²,

Allen

et al. 2013

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract: New data from the complex Lower Thames locality at Purfleet, Essex, reinforce the correlation of interglacial deposits there with Marine Isotope Stage (MIS) 9, the second of four postAnglian (MIS 12) interglacials recorded in the river terrace sequence east of London. Arising from various developer-funded archaeologically-driven projects, and primarily the construction of 'High Speed 1' (HS1: formerly the Channel Tunnel Rail Link), the new evidence includes additions to palaeontological knowledge of this interglacial, notably from ostracods and vertebrates, results from isotopic analyses of shell and concretionary carbonates, and the first application of numerical geochronological techniques at Purfleet. These analyses, combined with mutual climatic modelling of the ostracods, confirm that deposition of the fossilferous deposits coincided with interglacial conditions, with similar-to-or warmer-than-present summer temperatures and colder winters, providing a suggestion of greater continentality. OSL and amino-acid racemisation support correlation of the interglacial with MIS 9, whereas the climatic and sedimentological evidence points to correlation with the earliest and warmest substage (MIS 9e). There is also evidence that a greater part of the Purfleet sequence might date from the interglacial, although whether these also represent MIS 9e or later parts of the complex stage cannot be determined. The additional archaeological material is consistent with previous interpretations of a tripartite stratigraphical sequence of lithic traditions: basal Clactonian, above which is Acheulian (handaxe manufacture), followed by one of the earliest British appearances of Levallois technique. ABSTRACTNew data from the complex Lower Thames locality at Purfleet, Essex, reinforce the correlation of interglacial deposits there with Marine Isotope Stage (MIS) 9, the second of four post-Anglian (MIS 12) interglacials recorded in the river terrace sequence east of London. Arising from various developer-funded archaeologically-driven projects, and primarily the construction of 'High Speed 1' (HS1: formerly the Channel Tunnel Rail Link), the new evidence includes additions to palaeontological knowledge of this interglacial, notably from ostracods and vertebrates, results from isotopic analyses of shell and concretionary carbonates, and the first application of geochronological techniques at Purfleet. These analyses, combined with palaeotemperature estimates from the Mutual Ostracod Temperate Range...