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Benthic Foraminiferal Carbonate Preservation from the Late Miocene - Pliocene, Northwest Svalbard Continental Shelf (ODP Hole 910C)

Soma Baranwal1, Katrine Husum2, Jochen Knies1, and Kari Grøsfjeld1
1Quaternary Geology and Climate, Norges Geologiske Undersøkelse (NGU), Trondheim, Norway.
2Geology, Universitetet i Tromsø, Tromsø, Norway.

The present study on Hole 910C from the Yermak Plateau northwest Svalbard continental shelf, elucidate the paleoceanographic changes in the Atlantic-Arctic gateway during the late Cenozoic. New biostratigraphic data indicate an early late Miocene age (~11 Ma) for the base of Hole 910C and the remaining upper part of the investigated interval is of Pliocene age. The foraminiferal analysis shows very few Arctic planktic foraminifera, and an Arctic benthic foraminiferal fauna characteristic of an outer shelf-upper slope environment. During the Pliocene the benthic foraminiferal fauna show relative changes of the inflow of warm surface-water masses into the generally cold waters of the Fram Strait. A relatively continuous stable δ18O and δ13C isotope record has been derived from benthic foraminifera Cassidulina teretis. The stable isotope record show heavier peaks at 2.32 and 2.45 Ma indicating interglacials. Lighter stable isotopic values indicate higher freshwater inputs and weaker ventilation in the Arctic during glacial periods. The carbonate preservation was studied under scanning electron microscope (SEM) on benthic foraminiferal tests of Cassidulina reniforme and Melonis barleeanus. Four progressive stages of dissolution were distinguished ranging from tests unaffected by dissolution to strongly dissolved tests. A semi quantitative scale describing the preservation was established with 0 as the best preservation and 3 as the poorest preservation. Maximum carbonate dissolution were found at 2.32, 2.48, 2.6, 2.63, 2.72 and 2.77-2.8 Ma and correlated well with peaks of ice-rafted debris (IRD) and heavy δ18O values. This may represent episodes of severe glaciations (periods of production of carbonate-corrosive dense brines due to sea-ice formation). These events occurred immediately before distinct CaCO3 maxima. This indicates that the CaCO3 maxima occur close to major deglaciations when deepwater reorganizations occur. The reorganizations are also indicated by carbon isotope excursions.


AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.