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Title: Reconstructing North-West African palaeoclimate from speleothem geochemistry : past climate variability and implications for human history
Author: Barrott, Julia Jayne
ISNI:       0000 0004 5365 6935
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2014
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Climate north of the Atlas Mountain belt in NW Africa is dominated by extratropical disturbances. However, climatic controls to the south, where climate transitions from extratropical to tropical regimes, are poorly understood due to a paucity of both instrumental and palaeoclimate data. In this thesis past climate change between the High Atlas Mountains and Sahara Desert is reconstructed using the stable isotopic composition and radiometric dating of speleothems. A high-resolution record from the mid-Holocene and a discontinuous record covering the past 400,000 years are developed. Supplemented by U-Th dating of a further four samples, these records indicate increased humidity in this area concomitant with the wider African Humid Period, and indicate a link between the West African Monsoon and humidity north of 30°N. Reconstructed glacial-interglacial scale increases in humidity overlap with "green Sahara" conditions and evidence a recurrent humid corridor connecting NW Africa and the central Sahara that is highly relevant to discussions of prehistoric human migrations. Evidence for a strong influence of high-latitude and solar forcing on decadal to millennial time- scales in this area is also presented. Further to this work, the potential of cadmium-to-calcite ratios as a novel proxy for palaeo-hydrology is confirmed using an annually-resolved trace element, stable isotope and calcite fabric dataset from a North Moroccan stalagmite. The first measurements of cadmium-to-calcite ratios in natural speleothem are here presented, and the palaeoclimatic significance and potential of this proxy for aiding the quantitative reconstruction of changes in calcite precipitation behaviour are demonstrated.
Supervisor: Henderson, Gideon M.; Barton, R. Nick E. Sponsor: Boise Fund
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geochemistry ; Environmental change ; Africa ; Archeology ; palaeoclimate ; climate change ; speleothem ; stalagmite ; Morocco ; North Africa ; Sahara ; cadmium ; proxy development