Neodymium isotope constraints on provenance, dispersal, and climate‐driven supply of Zambezi sediments along the Mozambique Margin during the past ∼45,000 years

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 17; no. 1; pp. 181 - 198
• Main Authors: van der Lubbe, H. J. L., Frank, Martin, Tjallingii, Rik, Schneider, Ralph R.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.01.2016
• Subjects: Atmospheric precipitations; Circulation; Clay; clay provenances; Climate; Climate change; Climate variability; continental margin; Environmental conditions; Holocene; Insolation; Isotope composition; Isotopes; Latitude; Marine; Marine sediments; Monsoons; Mozambique Channel; Neodymium; neodymium isotopes; Ocean circulation; Offshore; Provenance; Records; Rivers; Sea level; Sea level rise; Sediment; Sediment distribution; Sediment load; Sediments; southeast African monsoon; Time series; Variability; Water depth; Weathering; Younger Dryas; Zambezi River; ISW, Mozambique; Mozambique; Africa, Zambezi R; Africa
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1002/2015GC006080

Marine sediments deposited off the Zambezi River that drains a considerable part of the southeast African continent provide continuous records of the continental climatic and environmental conditions. Here we present time series of neodymium (Nd) isotope signatures of the detrital sediment fraction during the past ∼45,000 years, to reconstruct climate‐driven changes in the provenance of clays deposited along the Mozambique Margin. Coherent with the surface current regime, the Nd isotope distribution in surface sediments reveals mixing of the alongshore flowing Zambezi suspension load with sediments supplied by smaller rivers located further north. To reconstruct past changes in sediment provenances, Nd isotope signatures of clays that are not significantly fractionated during weathering processes have been obtained from core 64PE304‐80, which was recovered just north of the Zambezi mouth at 1329 m water depth. Distinctly unradiogenic clay signatures (ɛNd values <−14.2) are found during the Last Glacial Maximum, Heinrich Stadial 1, and Younger Dryas. In contrast, the Nd isotope record shows higher, more radiogenic isotope signatures during Marine Isotope Stage 3 and between ∼15 and ∼5 ka BP, the latter coinciding with the timing of the northern hemisphere African Humid Period. The clay‐sized sediment fraction with the least radiogenic Nd isotope signatures was deposited during the Holocene, when the adjacent Mozambique Shelf became completely flooded. In general, the contribution of the distinctly unradiogenic Zambezi suspension load has followed the intensity of precession‐forced monsoonal precipitation and enhanced during periods of increased southern hemisphere insolation and high‐latitude northern hemispheric climate variability. Key Points: Nd isotope composition of clays deposited along the Mozambique Margin Offshore deposition of Zambezi clays reflects southeast African monsoon variability Zambezi sediment distribution on the slope is also strongly affected by oceanic circulation and postglacial sea level rise