Biomarker stratigraphic records over the last 150 kyears off the NW African coast at 25 degrees N

摘要

Terrigenous and marine biomarkers were investigated in a core off Northwest Africa in the Northeast Atlantic (25 degrees N, 16 degrees W, 1445 m depth) to assess changes in the sedimentation pattern of organic carbon (OC) over the last 150 kyears. Alkenone derived temperatures recorded a warming of 4.5 degrees C during the last deglaciation. n-Alkanol Mass Accumulation Rates (MAR) fluctuated in parallel with Northeast Trade Winds (NETW) intensity. OC and sterol MAR both increased during glacial times indicating enhanced fertility of the ocean in response to intensified NETW. Alkenone/OC ratios were higher by a factor of two over stages 4-6 than stages 1-3 thus reflecting distinct coccolirhophorid inputs. This transition coincides with a major change of alkenone producers inferred from coccolith counts. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 69]