SR-87 86, PHYTOPLANKTON, AND THE NATURE OF THE LATE CRETACEOUS AND EARLY CENOZOIC ARCTIC-OCEAN/

The Arctic Ocean's link to the lower latitude World Ocean during the L ate Cretaceous and early Cenozoic is puzzling. The tectonic developmen t of the Arctic Ocean evidently included termination of the Pacific-Ar ctic connection late in the Cretaceous, and the Atlantic link was not significant until at least the Eocene. Yet, during the Late Cretaceous Arctic Ocean mollusks indicate that there was no more than partial re striction, and Late Cretaceous and middle Eocene phytoplankton species are the same in both the Arctic and World Ocean. Sr isotope ratios of fish associated with the phytoplankton are higher than that accepted as the World Ocean's ratios for any time during this interval, yet the se high ratios do not indicate an isolated Arctic Basin. The Arctic wa s linked with the World Ocean and the best evidence for this is the ph ytoplankton similarity, but the location of the marine connection rema ins enigmatic.