Late Quaternary upwelling offshore northwest Africa: new micropalaeontological evidence.

Haslett, S.K and Smart, C.W (2006) 'Late Quaternary upwelling offshore northwest Africa: new micropalaeontological evidence.' Journal of Quaternary Science, 21. pp. 259-269. ISSN 0267-8179

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Planktonic foraminifera and radiolaria have been analysed in a Late Quaternary (40–0 ka) sediment sequence from Ocean Drilling Program (ODP) Hole 658C located under a coastal upwelling system near Cap Blanc, offshore northwest Africa, in order to document the palaeoceanographic history of the area. Temporal variations in species abundance and faunal assemblage analysis reveal a tripartite phased sequence of palaeoceanographic change through the Late Quaternary. Phase 1 spans 40–14.5 ka and is characterised by moderate upwelling, but Heinrich event 2 is distinguished as a brief episode of strengthened upwelling. Phase 2 begins with a change in a number of variables at ca. 14.5 ka and extends to ca. 5.5 ka. This phase is characterised by a general strengthening of upwelling, but may be subdivided into three minor phases including (a) the recognition of the Younger Dryas, marked by a temporary reduction in upwelling strength, followed by (b) an intensification of upwelling, and (c) upwelling and high productivity between 8 and 5.5 ka. This phase of upwelling corresponds with maximum Holocene cooling, possibly triggered by the collapse of the Laurentide ice sheet. Phase 3 extends from 5.5 to 0 ka and is characterised by weak upwelling and significant calcite dissolution. These phases are related to climatic events, particularly the African Humid Period (AHP), which is coincident with Phase 2. The AHP is characterised by increased precipitation, linked to an intensification of the African monsoon that enhances North East Trade Wind-driven coastal upwelling and is associated with the expansion of continental vegetation across North Africa.

Item Type: Article
Keywords: northwest Africa, Late Quaternary, planktonic foraminifera, radiolaria, upwelling
Divisions: School of Sciences
Chancelry and Research Management
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Date Deposited: 18 Nov 2012 04:45
Last Modified: 28 Nov 2023 17:57
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