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Near‐surface sediments (0–45 mm depth interval) from the Iceland Basin (59°N, 21°W, 3070‐m water depth) and Biscay Abyssal Plain (48°N, 17°W, 4105‐m water depth) were sectioned at millimeter‐scale resolution to assess alterations in key lipid biomarkers during early diagenesis. Inventories (µg cm−2 in the topmost 45 mm) of biomarkers from presumed terrestrial sources (>C20 linear n‐alkanes, n‐alkanoic acids, n‐alkanols) and from phytoplankton sources (phytosterols, long‐chain alkenones and alkenoates) were 1.5–4 times more abundant in the Iceland Basin core than in the Biscay Abyssal Plain core, indicating greater sedimentary inputs and/or preservation at the Iceland Basin site. Biomarker concentrations varied significantly over millimeter‐scale depth intervals. Pronounced subsurface concentration maxima were present at both sites. At the Biscay Abyssal Plain site, steep concentration gradients in the uppermost few mm of the sediment column indicate extensive diagenetic losses at or near the sediment/water interface. Strong covariance was seen in the concentrations of various compounds within each class (e.g., long‐chain n‐alkanes, n‐alkanols, n‐alkanoic acids and long‐chain alkenones and alkyl alkenoates), indicating that individual compounds within each class are associated with the same organic matrix and have similar degradation and mixing rates. Thus biomarker indices for assessment of land‐derived inputs (CPI, C29/C31, ACL) and sea surface temperature (IPT) remain largely unaltered by early diagenetic processes in oxic, abyssal sediments in spite of extensive bioturbation and degradative losses within the uppermost few centimeters of the sediment column.

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Abstract. We studied variations in terrigenous input and sea surface temperature over the last 208 ka using a multiproxy approach, involving direct comparison of terrigenous and marine molecular biomarker, foraminiferal abundance, and other sedimentological data for the same horizons in a single northeast Atlantic core (core T88-9P; 48o23 ' N, 25o05 ' W, 3193 m water depth, 790 cm core length) with a well-resolved •5180 stratigraphy. The abundances of three landderived, long-chain compound classes, the n-alkanes (C27, C29, and C 3 l), the n-alkanoic acids (C24, C26, and C28), and the n-alkanols (C24, C26, and C28) show glacial/interglacial related changes in the past 208 ka which generally parallel the weight percent noncarbonate. The abundances of these three compound classes are higher in glacial than in interglacial sediments. Such changes are consistent with the expected higher dust inputs during glaciations as well as enhanced advection of particulate matter in current systems. Ice-rafted debris (Heinrich events) may also contribute to the terrigenous biomarker record. The sea surface temperature (SST) signals derived from the alkenone unsaturation index (uK'37) give an average SST during interglacial periods of 13øC, which is about 3-4øC higher than the average glacial SST estimate. The uK'37 -derived SST values dropped markedly in some Heinrich layers, while sometimes leading the onset of the layer; the percent Neogloboquadrina pachyderma(s), which is another frequently used qualitative temperature proxy, generally shows maxima coinciding with the layers. Our results show that most Heinrich layers were produced during times of intensely cold waters in the eastern North Atlantic. They demonstrate that sufficient alkenones are present in the sediments for alkenone stratigraphy to be used as a tool for the assessment of short-term variations in sea surface temperatures even in these oligotrophic North Atlantic waters.