Deposition and Porosity Evolution of a Lower Cretaceous Rudist Buildup, Shuaiba Formation of Eastern Arabian Peninsula
S. H. Frost, D. M. Bliefnick, P. M. Harris, 1983. "Deposition and Porosity Evolution of a Lower Cretaceous Rudist Buildup, Shuaiba Formation of Eastern Arabian Peninsula", Carbonate Buildups-A Core Workshop, Paul M. Harris
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A carbonate buildup was cored in the Lower Cretaceous Shuaiba Formation of the eastern Arabian Peninsula. The sequence is 58 m (190 ft) thick and consists of a basal algal bank overlain by a bioherm composed of caprinid rudists with point-to-point contact in a muddy matrix. Upward growth of the bioherm into the surf zone led to development of extensive sheets of skeletal sand and gravel. Subsequent subaerial exposure and fresh water leaching led to creation of secondary moldic and microvugular porosity.
Proximity to open basins, a pre-existing topographic high, and either rapid subsidence or eustatic rise to channel the accumulation of successive rudist generations vertically are necessary to construct buildups of sufficient size and thickness to be hydrocarbon exploration targets. Early and Middle Cretaceous rudists lacked framework constructing potential, as a result their communities are typically developed in sheltered habitats or below wavebase and the resultant buildup is mud-dominated. Creation of reservoir-quality porosity and permeability in such buildups usually requires fresh-water leaching, dolomitization or fracturing.
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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