Distribution of reworked planktic foraminifera in Neogene sediments of core CLINO from the Great Bahama Bank (Table 1)
A rich, uniquely distributed assemblage (>80 species) of reworked Paleogene to early Neogene (~66-15 Ma) planktic foraminifera is documented within >470 m of late Neogene (~5.7-1.6 Ma) borehole limestone from the Great Bahama Bank west margin. Tests vary in size from 0.13 to 1.0 mm and are unusually well preserved. Where obtainable from the rock, the relict species constitute an estimated 20% to 50% of all taxa. Paleocene faunas occur in upper Miocene host rocks, Eocene species occur in upper Miocene and basal upper Pliocene rocks, and mixed Oligocene and early Miocene taxa occur throughout the section, including the uppermost Pliocene (i.e., the oldest groups disappear successively uphole). Each host-rock interval is separated by major disconformities. This record provides a substantial proxy for: (1) a probable source feature (an epipelagic marine tectonic wall, escarpment, or outcrop composed of pelagic and hemipelagic sediments); (2) a probable tectonically active source area (northern Cuba or southern Bahamas) ; and (3) a variety of events that span >60 Myr and have wide-ranging implications, from local (progressive isolation of the oldest faunas), to regional (changes in water depth indicated by the faunas), to global (hiatuses that correlate with one or more major sequence boundaries in the Atlantic, Bahamas, and Gulf of Mexico, as well as proposed eustatic lowstands). Seven unidentified foraminiferal biozones correspond to a proposed early Eocene composite condensed section on the eustatic curve and may have regional implications. The relict faunas also have significant implications for the timing and types of Paleogene and early Neogene sedimentation or nondeposition, sea-level fluctuations, slumping or changing depth of effective marine erosion, and regional late Neogene events that occurred over 4 Myr (age of host rocks). The direction of the source area from the secondary-emplacement site and the estimated percentages of relict faunas indicate that not all the microfossils in the late Neogene borehole sediments and, by extrapolation therefore, along the entire west margin of the platform, were locally derived. The amount of a possible attendant sedimentary component is not known.