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Mid to late holocene changes in the environment, Sedgemoor Valley, Somerset Levels, UK

Eales, C (2005) Mid to late holocene changes in the environment, Sedgemoor Valley, Somerset Levels, UK. PhD thesis, Bath Spa University.

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Abstract

The mid to Late Holocene environmental development of the Sedgemoor Valley, Somerset Levels is examined using a multidisciplinary approach involving lithostratigraphy, biostratigraphy and radiocarbon dating. Three sites along a transect of the valley and one in the Bristol Channel are studied producing a temporal and spatial model of its palaeoenvironmental development. A common red clay is seen in all three sites which has been interpreted as a palaeosol and its surface varies between -1 .33 m 00 and 6.2 m 00 mantling the bedrock topography. Lithostratigraphic evidence indicates the red palaeosol was inundated by mid Holocene sea level rise as it is overlain by a blue clay that contains marine foraminifera. The surface of this blue marine clay varies in altitude between -1 . 1 4 m 00 and 5.51 m 00, above which a peat deposit occurs demonstrating a marine regression and a change to freshwater conditions. Radiocarbon analysis has been carried out on five peat samples immediately above the clay-peat contact to date the marine regression. They vary from between 6920 and 6450 cal. yrs BP at a altitude of -0.87 m 00 and 4795 and 4 1 70 cal . yrs.BP at 4.71 m 00. This study supports previous research suggesting that the peat began to form at a low altitude and subsequently extended vertically and laterally to cover the exhumed clay surface. The peat deposit initially contains Phragmities and then becomes either detrital or turfa in nature up core. The detrital peat contains freshwater molluscs indicating that large lake-like fringing waterbodies persisted in the valley for much of the late Holocene. Later the influence of humans is seen in the lithostratigraphy as drainage works become evident, marked by a change from organic to more minerogenic deposition. A saltmarsh at Stert is studied to examine the current intertidal area, and to calibrate and partially fill the gap in the stratigraphical record between the end of the peat samples in the valley and today.

Item Type: Thesis (PhD)
Additional Information:

A thesis submitted in partial fulfilment of the requirements of the University of the West of England, Bristol for the degree of Doctor of Philosophy at Bath Spa University College

Divisions: College of Liberal Arts
Date Deposited: 02 Jul 2013 12:50
Last Modified: 29 Apr 2016 14:12
URI: http://researchspace.bathspa.ac.uk/id/eprint/1456
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