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Chemostratigraphy of Early Cretaceous Terrestrial Strata in Gansu Province, China

Marina Suarez
The University of Kansas Lawrence, Kansas; [email protected]

The purpose of this project is to generate total organic carbon and sedimentary organic d13C chemostratigraphic records to constrain the ages of continental Early Cretaceous strata of the Hekou and Xinminpu Groups in Gansu Province, China. The Hekou Group occurs in the Xining-Minhe-Lanzhou sub-basins between the Ordos Basin to the east and the Qaidam Basin to the west. The group consists of fluvio-lacustrine conglomerates to mudstones whose deposition resulted from fault controlled subsidence with sediments sourced from the south and east. Subsidence was part of overall extension and strike-slip deformation from the late Jurassic to Cretaceous. The Xinminpu Group strata outcrop along the Altyn Tagh fault system that separates the Qaidam Basin to the east-southeast and Tarim Basin to the west-northwest. Strata consist of fluvio-lacustrine conglomerates to mudstones and organic-rich shales. The Cretaceous deposition in the Tarim Basin was likely the result of compressional tectonics linked to accretionary events. Biostratigraphy and magnetostratigraphy have been previously used to generally assign an Early Cretaceous age. Our preliminary data reveal total organic carbon as high as 6% in lacustrine units and suggest an early Aptian age. In addition to improving our understanding of the sedimentary and tectonic history of Mesozoic strata in northwestern China, total organic carbon data can assist in identification of potential petroleum source rocks, and help constrain the ages of important paleontological discoveries in the region (dinosaurs and early birds).

AAPG Search and Discovery Article #90083 © 2008 AAPG Foundation Grants in Aid