Holocene Systems Tracts on Carbonate Platforms

Wolfgang Schlager and Paul Enos

We have taken an actualistic approach to characterize the facies of carbonate systems tracts. On many Holocene carbonate platforms the three basic systems tracts currently are forming side by side. The Bahamas may serve as an example for the combined effects of eustasy, sediment supply and topography on systems tracts. Parts of the windward margins of the Bahama platforms still rise above sea level. These islands restrict modern sedimentation to a narrow shelf that abuts with a sea cliff on the old highstand deposits. These shelves are analogues of lowstand tracts. They are covered by reefs and skeletal sands. Most of the flooded parts of the Bahama platforms represent transgressive systems tracts: the sediment body is thin and low in mud; the succession deepens upward; hardgrounds an patch reefs are common, barrier reefs are discontinuous. Oolite shoals have wide channels and extend far into the lagoons. In some areas, sedimentation has outpaced sea-level rise and produced a sediment body with the characteristics of a highstand systems tract: it progrades seaward, the facies succession shoals upward, often terminating with tidal or terrestrial deposits; oolite shoals have broad crests and narrow channels.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California