Biomarker Compositions as Source Indicators of Heinrich Layers in the Northern North Atlantic (IODP Exp. 303/306, Site 1305)

Jens.Hefter [ at ]


AB: During IODP Expeditions 303/306, multiple cores from different locations in the North Atlantic were recovered. One of the major objectives of these expeditions was to capture Miocene-Quaternary millenial-scale climate variability in sensitive regions at the mouth of the Labrador Sea and in the North Atlantic ice-rafted debris (IRD) belt. Site 1305 is located in the Labrador Sea close to the southwest extremity of the Eirik Drift and in proximity to the former major iceberg discharge pathway derived via the Hudson Strait from the Laurentide-Ice- Shield (LIS). The upper Pleistocene part of Site 1305 afforded discrete IRD-containing detrital carbonate sections known as Heinrich layers (HL). About 30 samples from within and in between these layers were investigated in terms of quantitative and qualitative biomarker distribution using gas chromatography-mass spectrometry to (a) extend previous knowledge of biomarker inventories from identified Heinrich layers and (b) to investigate the potential of specific compounds to trace the occurrence and first appearance of Heinrich event-like episodes. Samples from HL1, HL2 and HL4 at Site 1305 are clearly distinguishable from samples between those layers due to the abundance of characteristic biomarker groups such as benzohopanes, D-ring monoaromatic 8,14- secohopanes, mono- and triaromatic steranes, aryl isoprenoids including isorenieratene-derivatives and increased pristane/n-C17 and phytane/n-C18 ratios. Such biomarker compositions are typically observed as diagenetic products within different types of mature (including Palaeozoic) source rocks and oils found in different North American/Canadian Basins, but cannot derive from sources contemporary to the time when Heinrich events occurred. More likely, these compounds originate from LIS basal erosion of Palaeozoic sedimentary outcrops, subsequently transported as IRD through the Hudson Strait and released at Site 1305 during Heinrich events. Thus, the study of specific biomarkers has a great potential not only to trace the origin and delivery pathways of IRD in the Northern North Atlantic, but also for the detection of such events within longer stratigraphic records like those newly drilled during IODP Expeditions 303/306.

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Conference (Poster)
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Event Details
Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract PP23D-1791..
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Hefter, J. and Stein, R. (2006): Biomarker Compositions as Source Indicators of Heinrich Layers in the Northern North Atlantic (IODP Exp. 303/306, Site 1305) , Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract PP23D-1791. .

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