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Late Miocene - Pliocene Foraminifera From ODP Hole 910C and ODP Hole 911A, Yermak Plateau: New Evidence

Katrine Husum1, Soma Baranwal2, Chiara Consolaro1, Jochen Knies2, Kari Grøsfjeld2, Karl Previous HitFabianTop2, and Morten Hald1
1Geology, University of Tromso, Tromso, Norway.
2The Geological Survey of Norway, Trondheim, Norway.

The aim of this study is to provide a detailed Late Miocene - Pliocene biostratigraphic and paleoceanographic record of the Yermak Plateau, Arctic Ocean Margin. The study is based on sediment cores from ODP Hole 910C and ODP Hole 911A. These sites are situated under modern day inflow of Atlantic Water to the Arctic Ocean. New high resolution sampling was carried out, and the samples were analyzed with regard to the planktic and benthic foraminifers using the larger than 100 µm size fractions. Hole 910C is situated at the top of the Yermak Plateau at ca. 560 m water depth, and Hole 911A is situated north - northeast of Hole 910C at 900 m water depth.

The fauna of Hole 910C contain both planktic and benthic foraminifera. The occurrence of the planktic foraminifera Neogloboquadrina atlantica (sin) sets the base of the borehole in a time frame from late Miocene to the end of Pliocene. The Pliocene benthic foraminifera Cibicides grossa was also found at the base. However, this is a benthic foraminiferal species meaning its distribution is much influenced by bathymetric changes, and biostratigraphic events may be regionally diachronous. New dinoflagellate analyses suggest that the base of ODP Hole 910 C is indeed of an early Late Miocene age. Due to the poor preservation of the planktic specimens, quantitative analysis was only performed on benthic foraminifera. The benthic assemblage consists of arctic species. The lower part of the record is dominated by Cassidulina teretis together with Islandiella helenae/norcrossi. During the Pliocene the species Cassidulina reniforme and Elphidium excavatum increase. In addition, Islandiella helenae/norcrossi and Melonis barleanus also increases. These fauna changes indicate periods of relative changes of the inflow of Atlantic water though the Pliocene and colder conditions.

Both benthic and planktic foraminifera are present in the foraminiferal assemblages of Hole 911A. The results suggest that the benthic foraminiferal assemblages are not reworked and belong to an Arctic Upper Slope - Shelf environment. However, the preservation is too poor to perform a quantitative analysis, and only the planktic fauna was quantitatively analyzed showing an Arctic assemblage. The fauna is dominated by Neogloboquadrina atlantica (sin) however fluctuations of Globigerina bulloides imply intervals of higher sea surface temperatures during the Pliocene. The occurrence of Neogloboquadrina atlantica (dex), Neogloboquadrina atlantica (sin) and Globigerina praebulloides restricts the time frame of the base of Hole 911A to Late Miocene, whereas the upper part of Hole 911A is Pliocene.

 

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

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