Miocene deep-water agglutinated foraminifera from ODP Hole 909c: Implications for the paleoceanography of the Fram Strait Area, Greenland Sea

摘要

Deep-water agglutinated Foraminifera (DWAF) are investigated from Miocene sediments recovered from ODP Hole 909C in the Fram Strait, Norwegian-Greenland Sea. We studied 125 samples from Cores 909C-50R to -103R, and recovered over 60 species of DWAF. The faunal succession in Hole 909C is subdivided into three assemblages based on the stratigraphic ranges of characteristic cosmopolitan taxa. These are: (1) a diverse Reticulophragmium amplectens - Reophanus berggreni Assemblage in Cores 909C-100R-2 to -91R-1 (1040.71-952.78mbsf); (2) a Reticulophragmium amplectens Assemblage in Cores 909C-87R-2, to -71R-3 (915.7-762.68mbsf); and (3) a low-diversity Reticulophragmium rotundidorsatum Assemblage in Cores 909C-71R-1 to -55R-1 (759.68-605.52mbsf). The DWAF assemblages are correlated to the standard chronostratigraphy using dinoflagellate cysts and magnetostratigraphy. The stratigraphic ranges of some well-known Paleogene DWAF species extend far into the Miocene at this locality, confirming the hypothesis that the Arctic and northern Norwegian Sea basins served as a refuge for these species long after they disappeared from the North Atlantic stratigraphic record. The taxonomic affinities of the Miocene assemblages from Hole 909C supports the idea that an estuarine circulation pattern has been in place between the Arctic Ocean and Greenland Sea basins since at least the early Miocene. Changes in the benthic foraminiferal morphogroups within the R. rotundidorsatum Assemblage correlate with an increase in total organic carbon, indicating an increase in oceanic productivity in the Fram Strait region during the late Miocene.