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Phanerozoic Global tectonic cycles (rifting of supercontinents, drifting and disassembly, closure and assembly) have a major impact of the development of the carbonate system. Volcanism during rifting affects global climate, leading to icehouse and greenhouse global climate conditions which affects marine abiotic carbonate mineralogy (aragonite seas during icehouse times, calcite seas during greenhouse times). During rifting and drifting stages, well-developed shelf margins and deep oceanic basins prevail, while during the assembly stage, shallow cratonic basins are characteristic. Ice house and greenhouse conditions impact the development of carbonate shelves. During icehouse conditions, high amplitude sea-level cycles favor development of rimmed shelves, thick fourth-order cycles, and deep karsting at sequence boundaries. Greenhouse conditions favor accretionary shelves with many thin parasequences and mild exposure surfaces. Biologic evolution also has a major impact on the carbonate system. The development of framework reefs is cyclical through the Phanerozoic as reef-building organisms evolve, leading to reef-free periods. The majority of carbonate sediments owe their mineralogy to the preferred mineralogy of the biota responsible for the sediments. As these groups evolve and become extinct, the sediment mineralogy mirrors these changes. A major carbonate database developed by Exxon/Mobil (termed the CATT hypothesis) has enormous potential as a tool to assist the exploration geoscientist in developing well-constrained conceptual geologic models and the development team to develop viable analogs for their reservoirs. |
