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Title: Records of late Quaternary climatic change from Tswaing crater lake, South Africa, and the Central Kenyan Rift
Author: Thorpe, Joanna Lucy
ISNI:       0000 0001 3533 0518
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2006
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The relative influence of precessionally-driven changes in direct insolation and changes in boundary conditions associated with glacial-interglacial cycles on climatic conditions at low latitudes remains uncertain. This thesis presents records of late Quaternary climatic change from Tswaing crater lake in South Africa and from the Naivasha and Nakuru-Elmenteita basins in the Central Kenya Rift, with the aim of increasing our understanding of the nature and causes of climatic change at low latitudes in Africa. The sedimentary sequence from Tswaing crater lake provides some of the longest terrestrial records of palaeoclimatic change in southern Africa, but the confidence associated with these records is limited by chronological uncertainty. This thesis presents five new 230Th/234U dates from the lower, previously undated section of the sequence, which are used to construct a new age-depth model for the sediments. When viewed in light of this chronology, new sedimentological, geochemical, and diatom assemblage records from the sequence indicate that boundary conditions associated with glacial-interglacial cycles determined climatic conditions at the site over the last -150 kyr, and that the obliquity of the earth's axis may have affected conditions between -150 and -350 kyr B.P. Diatomite beds deposited in the Naivasha and Nakuru-Elmenteita basins at the time of the last interglacial document a period in which deep, dilute lakes existed in the Central Kenya Rift. 518Odiatom records from these 40Ar/39Ar-dated beds are used to reconstruct palaeohydrological conditions during this lake-level highstand. The records indicate that lake levels in both basins responded to increases in precipitation driven by peaks in March and September insolation on the equator, and by increased tropical sea-surface temperatures. It is therefore concluded that precipitation in the Central Kenya Rift was influenced by both precessionally-driven changes in insolation and global boundary conditions during this period.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available