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Reconstructing the climatic history of the western coast of Africa over the past 1.5 million years. A comparison of proxy records from the Congo Basin and the Walvis Ridge

Durham, Emma Louise; (2000) Reconstructing the climatic history of the western coast of Africa over the past 1.5 million years. A comparison of proxy records from the Congo Basin and the Walvis Ridge. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

A multi-proxy approach, including the use of stable isotopes, magnetic characterisation analyses and organic geochemistry, has been adopted to consider factors such as productivity, and terrigenous inputs in two areas off the western coast of Africa over the past 1.5 million years. These factors can in turn be used to consider variability in ocean circulation and upwelling, in addition to changes in chmate on the African continent. In particular, studies have focussed on the influence of glacial-interglacial cycles and evidence for the Mid-Pleistocene Revolution (MPR), a complex change in climate which occurred approximately 1 million years ago (Ma). A comparison of the records from the two areas, drilled by Ocean Drilling Program Leg 175, the Congo Basin at a latitude of 5°S (Holes 1076A and 1077A); and the Walvis Ridge (Hole 1081 A) at 17°S demonstrates that these sites are affected by different localised factors. The sites within the Congo Basin are strongly influenced by freshwater and sediment from the Congo River, whereas the site at the Walvis Ridge is located within the centre of oceanic upwelling and contains a more marine signal. Evidence also suggests that the two sites have responded quite differently both to long- and short-term climatic variations. In particular, the response at the Walvis Ridge to the MPR occurs over an extended period, from 1.1 until 0.8 Ma, and is associated with a change in the dominant source of terrigenous input to the site, in conjunction with a change in the productivity signal. Within the Congo Basin, the response to the MPR is more rapid, occurring between 0.9 and 0.8 Ma. During this period, the influence of the Congo River begins to become significant. However, productivity records only begin to respond towards the end of this interval, at 0.8 Ma.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Reconstructing the climatic history of the western coast of Africa over the past 1.5 million years. A comparison of proxy records from the Congo Basin and the Walvis Ridge
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10123333
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