Shoal deposits of ooids mark the rim of the peri tidal Late Cambrian carbonate platform that formerly extended along the eastern United States. These oolites are evidence of tidal activity on the Iapetus (Proto-Atlantic) shelf edge. Buildup of shoals not only controlled circulation to interior shelf environments, but were themselves diagenetically altered by former zones of hypersalinity.
Reports of oolites (Steele, 1825) from the Upper Cambrian Hoyt Formation of New York State announced the first discovery of those particles in North America. This study reveals that they are strati graphically equivalent to subsurface oolite lenses within the Conasauga Formation of central Alabama. Alabama ooid textures indicate former proximity to shelf interior hypersalinity, including radial-fibrous fabrics, euhedral authigenie quartz and intraparticle secondary dolomitization. New York ooids received far more detrital quartz, indicating shoaling took place closer to a cratonic source. Both oolites underwent early cementation by marine pore waters and extensive burial pressure solution creating stylolitic seams and secondary dolomitization.
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Carbonate Sands-A Core Workshop
Carbonate sands, both skeletal and non-skeletal, have been studied by geologists as intensely as carbonate buildups. The underlying reason for the studies is the importance of those sands as significant hydrocarbon reservoirs. This core workshop is intended to provide a “hands on” look at the subsurface geologic record of carbonate sands with emphasis on lithofacies, stratigraphy of the sands and surrounding deposits, geometry of the sand deposits, diagenesis and porosity evolution, and wireline log data.