Thermal Maturity Patterns CAI and Ro in the Ordovician and Devonian Rocks of the Appalachian Basin in New York State

The classic study by Epstein and others (1977), using conodont alteration index (CAI) isograds, is the established standard for evaluating thermal maturity patterns of lower and middle Paleozoic rocks and associated oil and gas accumulation in the Appalachian basin. Maps from the Epstein and others (1977) and Harris and others (1978) studies show basin wide thermal maturity patterns for the Ordovician, Silurian through Middle Devonian, and Upper Devonian through Mississippian. Despite the value of these maps, they have a strong bias toward outcrop samples and, in many parts of the basin, CAI isograds have been extrapolated several hundreds of miles without being constrained by subsurface control points. Wandrey and others (1997) converted the CAI isograds of Harris and others (1978) to vitrinite reflectance equivalents (VTE) for the Ordovician of the central Appalachian basin; however, few new data points were added. Also, several vitrinite reflectance (%Ro) maps are available for evaluating thermal maturity patterns in the Appalachian basin but they are limited to smaller areas than the CAI-based maps. Among the best examples of these vitrinite reflectance maps are those of Upper Devonian black shale units by Streib (1981) and Boswell (1996) and of Pennsylvanian coal beds by Chyi and others (1987) and Zhang and Davis (1993).