Integrated
Microfossil Characterization of the Neogene Sand
Members of Offshore
Anthonissen, Erik D.1
(1) NHM,
The Norwegian offshore consists of a
number of sub-basins from the shallower epeiric
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