--> --> Abstract: Porosity Distribution Throughout Modern Caribbean Fringing Reef, Galeta Point, Panama, by Ian G. MacIntyre; #90968 (1977).

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Abstract: Porosity Distribution Throughout Modern Caribbean Fringing Reef, Galeta Point, Panama

Ian G. MacIntyre

A series of closely spaced core holes across a modern fringing reef off Galeta Point, Panama, reveals that porosity distribution is related primarily to (1) rate of skeletal frame accumulation, and (2) degree of water agitation in 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.

The highest porosity in Galeta reef is preserved in the main and central structural unit, which is composed of Acropora palmata, a rapidly growing coral that requires relatively high wave energy in order to thrive. Therefore, fine sediment generally is lacking and accumulation rates are high enough to prevent extensive cementation. Good porosity also is exhibited in the overlying and extensively bored reef-flat rubble facies. In this environment of slow deposition, intermittent high agitation is sufficient to remove fine sediments but generally not adequate to promote widespread cementation. The shallow fore-reef pavement and deeper fore-reef coral-head facies are lithified extensively, in association with conditions of high agitation and/or slow accumulation of the substrate. The bac -reef sediments and fore-reef talus have high accumulation rates, but little porosity develops in these areas of low agitation that lack rigid framework and are characterized by extensive deposition of fine sediments.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC