PALEOCLIMATIC SIGNIFICANCE OF THE STRATIGRAPHIC OCCURRENCE OF PHOTOSYNTHETIC BIOMARKER PIGMENTS IN THE NORDIC SEAS

Sedimentary chlorins and porphyrins are diagenetic products of chlorop hyll molecules and are considered to be chemical fossils or biomarkers of phototrophic organisms. The stratigraphic occurrence of such compo nents was investigated in four cores from the Nordic seas that span th e last deglacial period, The presence of chlorins in all the samples d eposited during the Younger Dryas and at the end of the last glacial p eriod indicated that photosynthetic activity occurred during these col d episodes and hence that ice-free conditions existed, at least season ally, in the Nordic seas, Vanadyl porphyrins were found in sediments d eposited 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 Bare nts ice sheet, Thus, we suggest that the sedimentary occurrence of van adyl porphyrins in Nordic sea cores can be used as a marker of ice-raf ted debris from the Barents ice sheet. The absence of such components during Termination Ib indicates that the complete destruction of the B arents ice sheet took place during the first stage of the deglaciation .