16. EARLY EOCENE PALYNOFLORAS FROM HOLES 915A, 916A, 917A, AND 918D, EAST GREENLAND1David W. Jolley2 |
ABSTRACTThe dinoflagellate cysts, algae, pollen, and spores from the sediments immediately overlying the basalt seaward-dipping reflector sequences (SDRS) in Holes 915A, 916A, 917A, and 918D of Ocean Drilling Program Leg 152 were quantitatively recorded. Only the samples from Holes 916A and 918D yielded rich palynofloras, which in part proved to be correlative with each other. From the quantitative palynological data, a series of associations that represented sedimentation during at least three depositional sequences (parasequences?) was recognized and an age was attributed to the palynofloras using published dinoflagellate zonations. These results demonstrated that the normal polarity sediments recovered from the base of Hole 918D are attributable to Chron 23n, with the oldest sediments that rest on the SDRS being no older than 52 Ma. Analysis of archive material also suggested that sediments of this age are probably present on shore in East Greenland, as the Bopladsdalen Formation. Comparison with previously published accounts of the post-SDRS palynofloras in the Norwegian Sea suggests a similar age for the initiation of sedimentation in other areas of the region. The rich terrestrial component of the pollen and spore flora is in accordance with the 51–52 Ma period of the Eocene temperature maximum; it contains several megatherm taxa and a high proportion of "paleotropical" forms. The dominant vegetation in the neighboring onshore areas during deposition of the immediately post-SDRS sediments appears to have been a notophylous evergreen forest. However, one period of short-term land-surface temperature fall is evident within the interval, with mean annual temperatures possibly cooling by up to 2°C for a period of less than 0.25 m.y. During this period vegetation appears to have changed to a mixed mesophytic angiosperm swamp forest. |
|