AAPG Foundation 2019 Grants-in-Aid Projects

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Revise the Paleozoic North American regional time scales by volcanic ashes in the Midland Basin


As the second largest oil field in the world, the Permian Basin in West Texas makes remarkable contributions to the Texas economy. Yet the chronostratigraphic framework of the basin fill remains unclear. A better chronostratigraphic framework of the basin fill will help improve the depositional model of lower Permian strata in the basin, better understand the subsidence curve and thermal heating history of the sediments and guide future hydrocarbon and mineral exploration. The Permian Period in the International Permian Scale is divided into the Cisuralian (early Permian), Guadalupian (middle Permian), and Lopingian (late Permian) Epochs. Previous biostratigraphic studies support that the Wolfcampian and Leonardian North American Stages in the Permian Basin in West Texas are of early Permian (Cisuralian) age. Without high-resolution absolute age constrains, correlation between the Wolfcampian and Leonardian Stages in the Permian Basin and the International Permian Scale would be very difficult. Despite the fact that major efforts have been made in the past two decades to understand the relationship between the International and North American scales, the absolute ages of the North American Stages have not been well constrained due to the low-precision radiometric dating techniques and the lack of appropriate materials to date. Recent discovery of multiple volcanic ash beds in subsurface strata of the Midland Basin presents an opportunity to obtain absolute depositional ages of the basin fill. This project aims to use high-resolution zircon U-Pb to refine the Early Permian chronostratigraphy of the Midland Basin and provide clear evidence to correlate the North American Stages with the International Permian Scale.