Provenance of the Middle Permian, Delaware Mountain Group: Delaware basin, southeast New Mexico and west Texas

Abstract

The siliciclastic strata of the Middle Permian (Guadalupian), Delaware Mountain Group of the Delaware basin, located in southeast New Mexico and west Texas have long been interpreted to record deep marine deposition that were pre-sorted by eolian processes; however, the provenance of the Delaware Mountain Group is still debated. The majority of previous researchers have suggested the crystalline basement uplifts of the Ancestral Rocky Mountains as the primary source for the Delaware Mountain Group due to the observed arkosic-subarkosic mineralogy. This study combines point-count data of 54 thin sections from the three formations that comprise the Delaware Mountain Group (Bell Canyon, Cherry Canyon, and Brushy Canyon) and U-Pb detrital zircon geochronology analyses from four subsurface whole core samples of the Delaware Mountain Group to shed further light on the potential source terranes delivering siliciclastics to the Delaware basin during the Middle Permian. Samples exhibit the commonly observed arkosic-subarkosic mineralogy which has been associated with an Ancestral Rocky Mountain source; however, ages obtained via detrital zircon geochronology disagree with previous interpretations. Instead of an abundance of ages indicative of an Ancestral Rocky Mountain source (late Paleoproterozoic, 1600-1800 Ma), predominant age populations include, Mid-Paleozoic (275-490 Ma), Neoproterozoic/Early Paleozoic (510-790 Ma), and Mesoproterozoic (950-1200Ma) age grains. New data from this study further suggest that the Ancestral Rocky Mountains were not a major contributor of siliciclastic sediment to the Delaware basin during the Middle Permian. The predominately subarkosic mineralogy and detrital zircon ages reported in this study can best be reconciled with a Ouachita orogen source, including key "peri-Gondwanan" source terranes such as the Yucatan-Maya and Oaxaquia terrane.

Additionally, this study provides missing Cherry Canyon Formation detrital zircon age dates. Comparison of reported ages in this study with ages previously reported in the Delaware Mountain Group reveal that there was a provenance evolution after deposition of the Brushy Canyon and the onset of deposition of the Cherry Canyon Formation. Furthermore, this timing coincides with the disappearance of inland seas, the filling of the Midland basin, and continued accretion of terranes along the Ouachita-Marathon suture zone.