Growth, Depositional Facies, and Diagenesis of a Modern Bioherm, Galeta Point, Panama
Details of the growth history of a coral reef are available from thirteen closely-spaced cores retrieved from Galeta Reef, Panama. The core holes were drilled along two transects extending from inshore mangroves to the outer reef slope of this small fringing reef, which is located 6 km (3.7 mi) east of the Panama Canal off the Caribbean coast. This reef is at least 14 m (50 ft) thick, has six distinct reef facies, and is established on the erosional surface of the middle Miocene Gatun Formation, which consists of a calcareous argillaceous siltstone (Macintyre and Glynn, 1976).
Core analysis has revealed that throughout most of its development Galeta Reef was a typical Caribbean fringing reef dominated by the branching coral Acropora palmata, but having a mixed coral-head community on its seaward slope. A marked reduction in the rates of seA-1evel rise during the latter stages of the Holocene transgression restricted the further development of Galeta Reef, so that it became an emergent reef with a well-cemented, shallow fore-reef pavement and an extensive coral-rubble reef flat (Macintyre and Glynn 1976).
Despite its small size in comparison with oil-reservoir reefs, Galeta Reef provides insight into the contemporaneous distribution of submarine cements and porosity in reef facies. Both are related primarily to (I) the rate of skeletal frame accumulation and (2) the degree of water agitation in the various environments of reef deposition. Rapid framework construction has produced an open network and has limited the time for development of submarine cement, a near-surface phenomenon at Galeta. Agitation affects porosity by controlling deposition of fine sediments and precipitation of submarine cements; the latter is enhanced in areas of increased water agitation.
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Carbonate buildups have long been a focus of intense geological study. An underlying reason is the importance of carbonate buildups as significant hydrocarbon reservoirs. This core workshop is intended to provide a “hands on” look at the subsurface geologic record created by carbonate buildups with emphasis on lithofacies, stratigraphy of buildups and their surrounding deposits, geometry, “reef”-building and sediment-producing organisms, and diagenesis and porosity evolution