André W. Droxler1
(1) Rice University, Houston, TX
Abstract: Rapid response of neritic carbonates to sea level fluctuations at Milankovitch frequencies and longer time scale: Oligocene to late Quaternary case studies
Benthic oxygen isotope records at Milankovitch frequencies and longer timescale have been recognized to be the most reliable proxy for sea level fluctuations during the Quaternary/Pliocene and with some caution the Miocene/Oligocene. The late Quaternary transgressions are recorded by coralgal buildups established on top of lowstand siliciclastic coastal deposits and by the rapid flooding of flat carbonate bank-tops that triggered with no observable delay the neritic carbonate export towards the slope and the sea floor of adjacent. The first transgression of 120 + meters in the past 6 My at about 420 ky ago explain the establishment of modern barrier reefs and the sharp increase of offbank transport in the surroundings explained by the flooding of previously exposed carbonate platform tops. The carbonate platform margins in the Maldives Inner Sea back retreated and partially drowned during a 5 My-long late Oligocene transgression. Following the highstand shedding concept defined in the late Quaternary interglacial stages, the early Pliocene 2 My–long sea level highstand is linked to thick periplatform deposits on the slope and basins in the western margin of Great Bahama Bank and in the Maldive Inner Sea. The middle Miocene stepwise sea level fall corresponds to well-developed progradations of carbonate bank margins in the Maldives. As during the series of late Quaternary sea level lowstands, the accumulation rates of sediments on slopes and basin floors adjacent to exposed carbonate platforms become typically pelagic during the late Pliocene-early Pleistocene 2.5 My-long overall sea level lowstand.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana