SEDIMENTARY PROVENANCE OF A REGIONAL MIOCENE-PLIOCENE AEOLIAN AND FLUVIAL DEPOSIT ON THE HIGH PLAINS: EVIDENCE FOR UNROOFING OF THE SANGRE DE CRISTO MOUNTAINS?

A regional deposit of Miocene-Pliocene aeolian and fluvial sediments, the Ogallala Formation, stretches from southern South Dakota to western Texas supplying the majority of the water necessary for agriculture and drinking water for the United States. Previous clast provenance analyses from the lower fluvial strata of the Ogallala Formation from the Southern High Plains indicates sourcing from an array of lithologies including, basalt, granite, dacite, gneiss, and limestone. The variety of lithologies implicates the Sangre de Cristo Mountains in northern New Mexico and south-central Colorado as the predominant source area. We present a new detrital zircon and paleocurrent dataset from southeast Colorado, Oklahoma panhandle, and west Texas to pair with the clast analyses from the Southern High Plains. Paleocurrent datasets from southeastern Colorado indicate flow toward the southeast. Clasts from southeastern Colorado contain similar lithologies to that found south of the Oklahoma panhandle including granite, sandstone, basalt, quartzite, and schist. Paleocurrent and clast data from southeast Colorado pair well with previous clast provenance analysis from West Texas and New Mexico. We speculate that the majority of sediment in the southern portion of the Ogallala Formation was shed from the Sangre de Cristo Mountains, implying a large-scale drainage network during Miocene-Pliocene time. Unroofing in the Sangre de Cristo Mountains may have been driven by extension of the Rio Grande Rift and associated lithospheric heating, ultimately leading to deposition of the Ogallala Formation.