Niagaran (middle Silurian) shelf and pinnacle reefs were subaerially exposed and subjected to fresh water diagenesis soon after deposition. Leaching and calichification occurred during the exposure. This was followed by deposition of Cayugan A-1 salt that encased the pinnacles, and during a subsequent rise in sea level A-1 carbonates were deposited over their tops and down the flanks. Another period of exposure occurred as the result of a major lowering of sea level following deposition of the A-1 carbonate; a second stage of leaching took place during this low stand of sea level. Subsequently sea level began to rise again and the A-2 salt was deposited around the periphery of the pinnacles, resulting in partial infill of porosity created during previous stages of leaching. Finally, the A-2 carbonate was deposited and completely encased and buried the pinnacles.
Figures & Tables
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