--> Abstract: Macrobenthic Bioerosional Processes And Morphological Succession On Continental Shelf Carbonate Hardbottoms, by S. R. Riggs and S. W. Snyder; #90928 (1999).

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RIGGS, STANLEY R., and SCOTT W. SNYDER
Department of Geology, East Carolina University, Greenville, NC 27858

Abstract: Macrobenthic Bioerosional Processes and Morphological Succession on Continental Shelf Carbonate Hardbottoms

Bioeroders degrade carbonate hardbottoms, sculpting morphological features that range from millimeters to tens of meters in scale. These features evolve from flat freshly broken hardbottom surfaces (young) to more irregular surfaces with increased relief and surface area that support a greater diversity and abundance of benthic bioeroders (mature). Composition of this benthic community is determined by lithology and latitude. Lithology determines rates, scales, and mechanisms of morphological evolution. Well indurated lithologies on sloped surfaces support a diverse endolithic infauna and epilithic fauna and flora. Because of high rates of bioerosion, weakly to moderately indurated lithologies on sloped surfaces support a less diverse endolithic infauna and only minor epilithic fauna and flora. Mobil epibenthos and nekton accentuate the rate of degradation. Well indurated flat hardbottoms, often covered with thin (<5 cm) ephemeral sands, are colonized largely by epifloral macroalgae which chemically degrade and pluck carbonate to initiate development of 3-D morphology that increases surface area and species diversity. Increased relief exposes more sloped surfaces above the sand and provides habitat for infaunal borers. In temperate conditions, bioeroders produce 'new' sediment to the modern regime at minimum rates ranging from 0.03 kg/m2/yr on highly lithified flat hardbottoms to 0.4 kg/m2/yr on moderately lithified sloped surfaces to 5.5 kg/m2/yr on soft mudstone sloped surfaces with scarp recession rates of 2-4 cm/yr. Comparison of carbonate hardbottoms in the mid-latitude North Atlantic with high latitude Kattegat Sea reveals differing benthic community compositions but similar morphological successions.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas