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Late Quaternary Climate Changes in Central Africa as Inferred from Terrigenous Input to the Niger Fan

Published online by Cambridge University Press:  20 January 2017

Matthias Zabel
Affiliation:
Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, D-28334, Bremen, Germany, E-mail: mzabel@uni-bremen.de
Ralph R. Schneider
Affiliation:
Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, D-28334, Bremen, Germany, E-mail: mzabel@uni-bremen.de
Thomas Wagner
Affiliation:
Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, D-28334, Bremen, Germany, E-mail: mzabel@uni-bremen.de
Adesina T. Adegbie
Affiliation:
Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, D-28334, Bremen, Germany, E-mail: mzabel@uni-bremen.de
Uwe de Vries
Affiliation:
Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, D-28334, Bremen, Germany, E-mail: mzabel@uni-bremen.de
Sadat Kolonic
Affiliation:
Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, D-28334, Bremen, Germany, E-mail: mzabel@uni-bremen.de

Abstract

Time series of terrigenous source elements (Al, K, Ti, Zr) from core GeoB4901-8 recovered from the deep-sea fan of the Niger River record variations in riverine sediment discharge over the past 245,000 yr. Although the flux rates of all the elements depend on physical erosion, which is mainly controlled by the extent of vegetation coverage in central Africa, element/Al ratios reflect conditions for chemical weathering in the river basin. Maximum sediment input to the ocean occurs during cold and arid periods, when precipitation intensity and associated freshwater runoff are reduced. High carbonate contents during the same periods indicate that the sediment supply has a positive effect on river-induced marine productivity. In general, variations in the terrestrial signals contain a strong precessional component in tune with changes in low-latitude solar radiation. However, the terrestrial signal lags the insolation signal by several thousand years. K/Al, Ti/Al, and Zr/Al records reveal that African monsoonal precipitation depends on high-latitude forcing. We attribute the shift between insolation cycle and river discharge to the frequently reported nonlinear response of African climate to primary orbital configurations, which may be caused by a complex interaction of the secondary control parameters, such as surface albedo and/or thermohaline circulation.

Information

Type
Research Article
Copyright
University of Washington

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