Earth and Atmospheric Sciences, Department of


Date of this Version



Published in Proceedings of the Ocean Drilling Program, Scientific Results 101: 473-480. Paper number 30. Copyright 1988, Ocean Drilling Program. Used by permission.


Leg 101 of the Ocean Drilling Program recovered Albian through Holocene sediments from a variety of carbonate depositional environments. Data from four microplanktonic groups (calcareous nannofossils, planktonic foraminifers, radiolarians, and dinoflagellates) and four benthic groups (larger foraminifers, smaller benthic foraminifers, ostracodes, and sponge spicules) yield a biostratigraphic and paleoecologic framework for these varied sediments. Winnowed, skeletal-planktonic foraminiferal packstones and grainstones from the central Straits of Florida (Site 626) reflect a late Oligocene to Holocene history of sporadic sedimentation greatly influenced by strong bottom-current activity. Neogene to Quaternary sediments from two carbonate-slope transects (Sites 627 to 633) indicate significant slope accretion and progradation during the latest Miocene through early Pliocene, erosion and/or nondeposition during part of the late Pliocene, and slower accretion and slope progradation during the Quaternary. The Turonian through late Oligocene of the Little Bahama Bank area (Sites 627 and 628) was characterized by sporadic pelagic carbonate sedimentation punctuated by lengthy hiatuses in sediment accumulation, indicating sediment starvation and low surface-water productivity. Brief periods of siliceous biogenic sedimentation in the northwestern Bahamas during the late Oligocene, early Miocene, middle Eocene, and late Campanian are expressions of temporarily higher surface water fertility and productivity. Uppermost Albian through middle Cenomanian hemipelagic marly limestones at Site 627 (Little Bahama Bank) record an upward-deepening sequence developed over a drowned upper Albian shallow-water carbonate platform. Bathyal middle to upper Albian organic-rich marly chalks in Northeast Providence Channel (Site 635) indicate that a deep-water channel existed there at approximately the same time that shallow-water carbonate-platform conditions prevailed north of Little Bahama Bank (Site 627).