On the basis of the dinocyst assemblages, the Paleogene section in Hole 985A extends from Core 62X through Section 50X-5 and is predominantly Rupelian. The Rupelian/Chattian boundary is tentatively placed between Sections 162-985A-51X-2 and 50X-5, as determined from the highest or last occurrence of Areoligera semicirculata. Thus, the Rupelian is ~105 m thick; the Chattian, if present, is represented only by Section 162-985A-50X-5. The Chattian/Miocene boundary is interpreted as occurring between Sections 162-985A-50X-5 and 48X-6. This shows close agreement with the lithologic boundary between lithologic Units IV and V in Section 50X-2 (Shipboard Scientific Party, 1996, p. 265).
There is a remarkable correlation between dinocyst events at Sites 985 and 643, the latter drilled during Leg 104. This suggests that the major hiatus occurs at both sites within the Chattian. Also, there appears to be a more complete Miocene section at Site 643. Our preliminary findings indicate that of all the microfossil groups, the dinocysts offer the most potential for detailed correlation of the Oligocene-Miocene sediments in the Norwegian-Greenland Sea. More studies are needed to confirm this, but the results are encouraging.