Geochronologic connections between the Chinle Formation and Dockum Group

Abstract

The Late Triassic Chinle Formation and the correlative Dockum Group span most of the southwestern United States, exposed in outcrop from Texas to Nevada. Although the Chinle Formation west of the Rocky Mountains is extensively studied and dated and shown to be lithostratigraphically and broadly time equivalent to the more eastern Dockum Group, a more refined geochronologic correlation is needed to confirm western Chinle strata is equivalent to Dockum strata east of the Rockies in basins such as the Palo Duro and Tucumcari Basins. This study provides clarity to initial assessments for provenance of the Dockum Group and paleogeographical ties to the Chinle Formation through various sedimentological and geochronological methods, painting a clearer picture of the Late Triassic during a megamonsoonal climate and initial rifting of the Gulf of Mexico.