--> Abstract: Integrated Microfossil Characterization of the Neogene Sand Members of Offshore Norway; #90063 (2007)

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Integrated Microfossil Characterization of the Neogene Sand Members of Offshore Norway

 

Anthonissen, Erik D.1 (1) NHM, University of Oslo, Oslo, Norway

 

The Norwegian offshore consists of a number of sub-basins from the shallower epeiric North Sea to the deeper Norwegian Sea, and farther northwards to the Barents Sea. While the pre-Neogene stratigraphy of the Norwegian continental margin is relatively well understood due to petroleum exploration coring activities, the Nordic Neogene biostratigraphy has until now remained poorly constrained.

 

Traditionally, local foraminiferal zonations relied heavily on a poorly-calibrated benthic component in shallow-water datasets, lacking standard low-latitude marker species. This study employs an age model based upon a new calibration of this local biostratigraphy to the global time scale of Gradstein et al. (2004). An example is the Pliocene/Pleistocene boundary, globally defined as occurring just above the Olduvai magnetochron, and previously defined locally based on diachronous benthic foraminifera. Via paleomagnetics of local Ocean Drilling Sites new boundary criteria are recognized: the highest occurrence of Neogloboquadrina atlantica (dextral) together with the lowest common occurrence of N. pachyderma (sinistral) foraminifers, and/or the highest occurrence of the dinocyst Filisphaera filifera.

 

Here we present an improved biofacies characterization of the Neogene sands in the North and Norwegian seas. The study involved combining calcareous microfossil (foraminifera, Bolboforma calcareous algae) and organic-walled microfossil (dinoflagellate cysts) datasets from previous exploration well studies, together with new results from cored sections. The biostratigraphy was integrated with wireline-logs, in a seismic and sequence stratigraphic framework. Three main sand units were identified: the Skade, Utsira and Molo Members/Formations. Analysis of the type well for the Utsira Formation confirms its recent chronostratigraphic re-assignement (Middle Miocene-Lower Pliocene).

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California