Abstract

Sedimentary chlorins and porphyrins are diagenetic products of chlorophyll molecules and are considered to be chemical fossils or biomarkers of phototrophic organisms. The stratigraphic occurrence of such components was investigated in four cores from the Nordic seas that span the last deglacial period. The presence of chlorins in all the samples deposited during the Younger Dryas and at the end of the last glacial period indicated that photosynthetic activity occurred during these cold episodes and hence that ice-free conditions existed, at least seasonally, in the Nordic seas. Vanadyl porphyrins were found in sediments deposited during Termination Ia in only two of the cores, close to the Barents Shelf. We argue that they derive from erosion and advection of organic-rich deposits as ice-rafted debris during melting of the Barents ice sheet. Thus, we suggest that the sedimentary occurrence of vanadyl porphyrins in Nordic sea cores can be used as a marker of ice-rafted debris from the Barents ice sheet. The absence of such components during Termination Ib indicates that the complete destruction of the Barents ice sheet took place during the first stage of the deglaciation.

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