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M.Phil. dissertation abstracts 2000 - 2001

Copies of these dissertations are held in the University of Cambridge, Department of Geography Library.

Jenny Bennett

Dissertation "Pleistocene deposits in the Portsmouth area: an investigation into their chronology and correlation with neighbouring areas.", supervised by Dr. Phil Gibbard (Cambridge).

Pleistocene deposits in the Portsmouth area: an investigation into their chronology and correlation with neighbouring areas

Climatic changes during the Quaternary are reflected in the landforms and sediments deposited and this can be seen in the areas around the streams draining the Sussex Weald and South Downs. These were investigated in the first half of the last century, but using geomorphological rather than geological evidence, and their chronology is unclear.

The rivers have thick valley infillings of alluvial-estuarine sediments in their lower reaches in response to marine transgression and there is also evidence of offshore drowned valleys. Terrace aggradations potentially span the later Middle to Late Pleistocene in these valleys, but these have not yet been very precisely dated. The relationship of these raised beach deposits on the Sussex plain to the alluvial-estuarine deposits is also unclear. The area has been subject to complex relative changes in sea levels since the Pleistocene, due not only to eustatic and isostatic adjustments, but also to continuing tectonic influences. The tectonic influences appear to be much more significant than has previously been thought, and cause additional complications in the field relations.

The primary goal of this project is to investigate the dating of these sediments, concentrating on one of the river systems. The dating of the sediments is problematic as many are lacking in organic material, which means that radio-carbon dating is not feasible, so techniques such as Optically Stimulated Luminescence will be used. Then an attempt will be made to link the dates obtained by OSL to radio-carbon dates from the work currently being undertaken by Rebecca Briant.

Geological field techniques, such as mapping and analysis of the provenance of the pebbles, will be used to establish age relationships , and it is also hoped to investigate the off-shore borehole data and available seismic evidence held by the British Geological Survey, and to consult with colleagues at the Geological Survey.There may also be archaeological content in the sediments, which will also aid, or at least put limits on, dating. Data gathered will then be used to start to develop a chronology for the evolution of these rivers.

George Speller

Dissertation "Palaeoenvironmental analysis of a colluvial sequence from a Roman villa at Rock, Brighstone, Isle of Wight" ,supervised by Dr. Richard Preece (Cambridge).

Palaeoenvironmental analysis of a colluvial sequence from a Roman villa at Rock, Brighstone, Isle of Wight

The unique discovery of an artefact dated Roman villa built on and buried underneath approximately 2 metres of hillwash has provided an exciting opportunity for palaeoenvironmental analyses of sediments contemporary with pre-Roman, Roman and post-Roman occupation phases.

The calcareous nature of the colluvium has favoured the preservation of land snail shells. The presence of Helix aspersa throughout the pre-villa and post-villa sequences indicates a Roman and later age for the colluvium. Initiation of colluviation is attributed to Roman activity, specifically agricultural practices in the surrounding area.

Above the basal chalky gravel washes and underlying the Roman colluvium is a buried horizon that yielded a snail fauna of an open-marsh environment. The species within this assemblage are mainly indicative of a Late-glacial age.

Mollusca from the overlying Roman hillwashes suggest a predominantly open environment with some restricted areas of shade, for both the pre-villa and post-villa sequences. Both arable and pastoral habitats are suggested to have existed contemporaneously at the site. Following a period of more shaded environment linked to the abandonment of the villa, more intensive arable and then pastoral activity is suggested during later occupation phases.

Small vertebrate bones extracted from a ditch-fill deposit reflect mollusc data although at a larger spatial scale. The amplification of spatial resolution allows a wider area to be studied. Taphonomic alteration of the bones indicates accumulation by a bird of prey, possibly tawny owl (Strix aluco). The presence of house mouse ( Mus musculus) and harvest mouse (Micromys minutus) are especially noteworthy, adding to the sparse early records of these species in Britain. The presence of harvest mouse represents one of the earliest secure records in Britain.