Styles of Reef Development from a Shelf Margin Mixed System: Miocene-Pliocene of the Cibao Basin, Northern Dominican Republic

Donald F. McNeill¹, James S. Klaus², and Gregor P. Eberli^1
1Marine Geology & Geophysics, RSMAS University of Miami, Miami, FL
²Geological Sciences, University of Miami, Coral Gables, FL

The Cibao Basin, part of the northern shelf of Hispaniola, records an ~4 my period of carbonate-siliciclastic mixing during the late Miocene and Pliocene. The “in situ” type of mixing, as defined by Mount (1984), consists of mainly skeletal carbonates in a predominantly muddy siliciclastic matrix derived from weathering in the nearby metamorphic Cordillera Central. The carbonates are largely derived from coral reefs developed within the siliciclastic-dominated shelf. Recent refinement of ages (strontium isotope, magnetostratigraphy) in several key sections has provided a reliable and precise intra-basin correlation and temporal control on carbonate admixing. We find that deposition at two key sections (12 km apart) is generally congruent with respect to the major lithologic units. Carbonate deposition is grouped into three main styles: 1) late Miocene isolated patch reefs-these reefs occur as isolated patches approximately 15-20 m thick and 300-400 m wide as part of a shallow dipping clinoformal shelf; 2) late Miocene-early Pliocene cyclic coral-mud beds-approximately 40 m of cyclic coral thicket (2-4 m thick) or coral debris beds (1-3 m thick) interbedded with mud beds that formed during progressive deepening from shallow shelf to middle shelf during the Miocene-Pliocene transgression (Zanclean Flood); and 3) early Pliocene-late Pliocene reefal clinoforms-carbonate clinoforms with well-defined foresets and topsets associated with the middle Pliocene transgression and highstand. Lateral stacking of these clinoforms reflect progradation during rising sea level to highstand conditions. Our findings suggest that if conditions are favorable for corals, the resulting carbonate geometries can be distinct (and predictable). These geometries are closely tied to the prevailing sea level motif (initial transgressive, progressive deepening, and highstand) in the mixed system.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas