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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 63 (1979)

Issue: 3. (March)

First Page: 429

Last Page: 429

Title: Depositional-Diagenetic History of Macae Carbonate Reservoirs (Albian-Cenomanian), Campos Basin, Offshore Rio de Janeiro, Brazil: ABSTRACT

Author(s): Albert V. Carozzi, Frank U. H. Falkenhein, Celso F. Lucchesi, Milton R. Franke

Article Type: Meeting abstract

Abstract:

The Macae platform sedimentary sequence consists of juxtaposed oncolitic calcarenite bars and intervening calcilutite bands extending parallel with depositional strike. The stacked oncolitic bars display a vertical evolution from infratidal to high intertidal. The depositional-diagenetic sequence of reservoir generation begins with development of geopetal internal sediment in a high-intertidal environment. This first stage of reorganization is followed by cavity-filling sparite cementation of beachrock, leaving some interparticle primary porosity. Subsequent vadose solution destroys large portions of the sparite, encroaches on the internal sediment and the framework, and generates secondary vuggy porosity. Preservation of the latter requires rapid burial, whereas any furt er emergence leads to complete obliteration of porosity by vadose blocky sparite.

The interbar calcilutites become increasingly restricted upward and are abnormally thick in comparison with contemporaneous oncolitic bars, a situation attributed to overproduction of micrite by calcareous green algae.

The juxtaposition of relatively heavier and thicker calcilutites with relatively lighter and thinner oncolitic calcarenites generated gravitational disequilibrium. After the sequence reached a critical thickness, halokinesis and related growth faulting occurred in underlying evaporites, thus accounting for the depositional evolution of the carbonate rocks.

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