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Boreham, Steve
(2002).
DOI: https://doi.org/10.21954/ou.ro.0000fc14
Abstract
This study attempts to record and interpret Pleistocene geological data from the Cambridge District in a comprehensive format. The author has established a central study area comprising twenty 5km squares, embracing part of the lower Ouse valley and much of the Cam valley. This area has yielded some 5000 individual existing borehole and trial pit records. In addition, about a hundred boreholes and trial pits have carried out during this project. These have yielded detailed stratigraphic data, and more than three hundred sediment samples to which a variety of laboratory analyses have been applied. The author has used a novel rigorous lithostratigraphic approach as the primary line of evidence for correlation in this study, in place of the traditional morphostratigraphic paradigm. Existing stratotype localities in the study area have been reviewed and modified where appropriate, and several new stratotypes for lithostratigraphic members have been proposed.
Many classic Cambridge sites including Traveller's Rest Pit, Histon Road, Barnwell Abbey, Barnwell Station, Grantchester and Barrington have been re-evaluated and new exposures investigated wherever possible, allowing the construction of databases of stratigraphic, physical and palaeontological information from a myriad of sources. Geochronological techniques including OSL, radiocarbon dating and aminostratigraphy have also been used for the correlation of deposits, together with biostratigraphic evidence. The presence of deposits from more than one temperate stage has been confirmed or strongly inferred for many of the major sites investigated. The relative antiquity of deposits at the Traveller's Rest Pit has been confirmed, and the dating of the most recent phase of temperate deposition at Barrington and Histon Road established as Ipswichian (MIS 5e). In contrast, the majority of deposits at sites such as Grantchester and Swan's Pit are strongly correlated with MIS 7. This study has enabled confident correlation of Anglian glacial, and post-Anglian fluvial deposits of the Great Ouse and Cam systems within the Cambridge District. It has also allowed the correlation of these deposits with others elsewhere in southern England. However, the reworking of faunal and floral remains between interglacials has been highlighted, and has major implications for biostratigraphy.
This study has unravelled a complex Pleistocene geological history including the advance of the Anglian ice sheets, the genesis of the Ouse and Cam river systems, major landscape change and the development of the drainage patterns observed today. The Ouse and Cam river systems initially developed along lines of Anglian sub-glacial drainage. In cold stages these rivers occupied high-energy braidplains characterised by episodic erosion, and the aggradation of gravels and sands. In temperate stages, they occupied relatively stable low-energy channels, resulting in the accretion of fines and organics. The study has also allowed the interpretation and understanding of many different Pleistocene palaeoenvironments within the Cambridge District including, subglacial, proglacial, tundra, scrub-tundra, steppic grassland, boreal forest and temperate woodland.
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