Model for Transgressive Stratigraphic Play Types: Holocene Martha Brae Delta-Reef Complex, Falmouth, Jamaica
Stephen M. Roberts, John D. Pigott
Modern analogs of ancient mixed clastic-carbonate depositional systems have received little attention and are poorly understood. Lithologic dominance in mixed clastic-carbonate depositional systems is dependent on a complex interplay among a number of contemporaneous physical and biological processes. A modern example of lithofacies migration through time on a transgressed ramp is portrayed by the post-Wisconsin Martha Brae delta-reef environment of Falmouth, Jamaica. Analyses of borehole cuttings from 18 shallow (< 15 m) wells reveal avulsed clastic depositional pulses punctuated by carbonate sedimentation with an additional contributing factor--tectonic and eustatic sea level changes occurring through time and space. Owing to fringing-reef development accompanying re ative sea level rise, the overall onlapping retrogradational delta changes from a wave-dominated regime with associated peripheral ooid shoals and reworked clastic and carbonate sands to a fluvial-dominated regime with consequent drowning of patch reefs by paralic beach and storm-washover sands and muds. Subsequently, spit formation and continued lagoonal infilling with mangrove-stabilized shoreline progradation occur. At least three major stratigraphic play types on this condensed (10 km2) high-resolution example can be extrapolated to much larger scale ancient environmental analogs: (1) drowned reefs, (2) retrograde deltas, and (3) carbonate sand encapsulation.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.