Paleogene paleoceanography of the Arctic Ocean is constrained by the middle or late Eocene age of USGS Core Fl-422: Evidence from silicoflagellates

Arctic Ocean Core Fl-422 has been of central importance in Arctic tectonics and paleoceanography because it provides the sole evidence for early Cenozoic marine conditions in the Arctic. The presence of several Eocene and Eocene or Oligocene guide species of silicoflagellates in samples from this core shows that it is no older than middle Eocene, and is not Paleocene as previously reported. There is no evidence of any Paleocene (54 to 65 Ma) siliceous microfossils from Core Fl-422. Paleoceanographic inferences conerning the Cretaceous-Tertiary boundary and the timing of silica deposition in the Arctic have been erroneous because of unsupported biostratigraphic correlations.