12. PLANKTONIC FORAMINIFER BIOSTRATIGRAPHY AND PALEOENVIRONMENTAL IMPLICATIONS OF LEG 152 SITES (EAST GREENLAND MARGIN)1Silvia Spezzaferri2 |
ABSTRACTFive sites and eight holes drilled on the East Greenland Margin during Ocean Drilling Program Leg 152 recovered Quaternary to middle Eocene sediments. Planktonic foraminiferal assemblages display generally low diversity; abundance and preservation varies from layer to layer. Several intervals devoid of planktonic foraminifers were identified in middle Miocene through Pliocene, lower upper Oligocene, and Eocene sediments. The more complete sedimentary sequence recovered at Site 918 spans the interval from the Quaternary to the middle Eocene. However, a major hiatus is recorded in the interval that spans the upper Eocene and the lower Oligocene. Two minor hiatuses occur in the lowermost Miocene and probably in the upper part of the middle Miocene, respectively. Paleoclimatic interpretations based on species diversity, changes in assemblages, and comparison with the stable isotope record indicate that several alternating glacial-interglacial episodes occurred during the Pliocene and the Quaternary. These two intervals are, however, separated by a warmer episode in the early Pliocene. Cool conditions and glacial episodes also prevailed in the late Miocene, whereas a slight warming probably occurred in the middle Miocene. This period was, however, cooler than the late Oligocene, the early Miocene, and the middle Eocene. These latter intervals were characterized by a warmer climate as indicated by the presence of several warmer water taxa. The first occurrence of Neogloboquadrina pachyderma and the changes in coiling direction of Neogloboquadrina atlantica are also climatically controlled. Comparison with previously drilled sites in the same area indicates that the short early Miocene hiatus and part of the hiatus spanning the late middle Eocene and the early Oligocene identified in Hole 918D may have interregional extensions in the North Atlantic Ocean. |
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