Late Quaternary high‐resolution biomarker and other sedimentary climate proxies in a Northeast Atlantic Core

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; 48°23′N, 25°05′W, 3193 m water depth, 790 cm core length) with a well‐resolved δ 18 O stratigraphy. The abundances of three land‐derived, long‐chain compound classes, the n ‐alkanes (C 27 , C 29 , and C 31 ), the n ‐alkanoic acids (C 24 , C 26 , and C 28 ), and the n ‐alkanols (C 24 , C 26 , and C 28 ) 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 (U K′ 37 ) give an average SST during interglacial periods of 13°C, which is about 3–4°C higher than the average glacial SST estimate. The U K′ 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.