Abstract: Facies Variability and Three Dimensional Reef Structure of the Enriquillo Fringing Reef, Dominican Republic

etailed understanding of three dimensional facies distributions within coral reefs can provide valuable predictive information on lateral and vertical porosity and permeability trends in the subsurface. The well preserved Holocene Enriquillo reef (Dominican Republic) provides a unique opportunity to examine three dimensional aspects of normal reef formation, as well as vertical facies variations associated with a siliciclastic/carbonate depositional cycle. The aim of this project is to document facies changes associated with; (1) reef initiation in a siliciclastic-dominated system, (2) the evolution and maturation of a fringing reef, and (3) reef demise in a restricted marine setting. This study should provide data that will help refine models for stratigraphic traps in ancient, reef-dominated, mixed depositional systems.

During the Holocene, rising seas flooded the Enriquillo Valley, creating a marine environment with circulation sufficient for coral growth. Colonization by reef corals ensued approx. 9000 years bp. at an estimated paleo-depth of approx. 34 meters. By the mid-Holocene, a fringing reef had fully developed. As the rate of transgression slowed during the late Holocene, the valley became choked with sediment and was cut off from the sea resulting in a gradual change from marine to brackish water conditions approx. 5000 years bp. Once closed, Lake Enriquillo evaporated to its current position below sea-level, exposing an extensive three-dimensional reef structure. We hope that extensive field mapping and stable isotope analysis, in conjunction with precise U/Th dating, will reveal the accurate timing and causation of key facies changes within the reef anatomy.
 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid