--> Abstract: Progradation and Retrogradation of Carbonate Platforms, by J. J. G. Reijmer and A. J. W. Everts; #90990 (1993).

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REIJMER, JOHN J. G., GEOMAR, Kiel, Germany; and ARNOUT J. W. EVERTS, Vrije Universiteit, Amsterdam, Netherlands

ABSTRACT: Progradation and Retrogradation of Carbonate Platforms

We have analyzed two data sets in order to establish the relationship between the production of sediments on the carbonate platform top, and the progradation/retrogradation of the platform as registered at the toe-of-slope. The first data set consists of four Triassic sections (Pico di Vallandro/Durrenstein, Dolomites, Italy). During both progradation and retreat of the toe-of-slope, the platform sheds silt- to boulder-size debris. Sand to granule material is more common during progradation; mud and rubble are most common during retrogradation. The retreating units show more oncoids and ooids, as well as an increased input of filaments, radiolarians, and carbonate mud. The second data set concerns three successions of the Vercors carbonate platform (Cretaceous, southeast France). This platform sheds silt- to pebble-sized material during both progradation and retreat. Compared to the prograding units, the retreating units contain more peloids, grapestones, and micritic ooids, and less margin-derived skeletal grains.

In both case studies, geometric relationships show that the carbonate platform was at least intermittently flooded during both progradation and retrogradation at the toe-of-slope. However, the observed differences in sediment composition may suggest that during retreating phases the platforms were slightly deeper and had less-developed marginal reefs or sand shoals. Toe-of-slope geometries may be indicative of the environmental conditions and sea level stand on carbonate platforms.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.