Abstract
Magnetostratigraphic dating of a transect of cores across Little Bahama Bank (LBB) provides refined insight into timing and anatomy of platform deposition since late Miocene. Age-dating of four cores, with biostratigraphic tie-points, shows a gently northward dipping platform from late Miocene to about mid-Pleistocene (0.73 Ma) as a result of higher growth/accumulation of the southwestern platform margin. Magnetostratigraphic dating coupled with Sr-isotope ages from LBB dolomites significantly improves the late Cenozoic depositional/diagenetic framework. Dolomitization episodes at about 2.2-3.4 and 1.6 Ma correspond with a prolonged period of subaerial exposure and formation of large aquifer systems and perhaps providing a mechanism to pump dolomitizing fluids (seawater) through the platform. A distinct northward slope of the dolomite may be explained by either: (1) a northward-dipping platform top, which supported different aquifer levels during fluctuating sea level lowstand events, or (2) the thickness of the freshwater lens which in turn is controlled by differences in permeability and platform slope between the northern and southern margins.
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