TRACING THE ORIGINS OF THE STRATA THAT HOST THE OGALLALA AQUIFER

The Neogene Ogallala Formation lies east of the Rocky Mountains in the Great Plains and is a crucial unit because it: (1) hosts the largest aquifer in the United States, (2) preserves critical records of climatic change across the Great Plains, and (3) likely reflects a major phase of drainage reorganization. Although important work has been completed on the modern aquifer and climatic records, critical questions remain regarding the drivers of continental-scale drainage reorganization. Localized detrital zircon studies suggest that seven igneous provinces served as major contributors to the Ogallala Formation: Archean and Paleoproterozoic shield provinces (>1825 Ma), Yavapai-Mazatzal orogenic belt (1800-1535 Ma), Granite and rhyolite intrusions in southwestern and central U.S. (1500-1332 Ma), Grenville orogeny (1300-920 Ma), Appalachian-Ouachita orogenic terranes (750-300 Ma), Cordilleran orogeny (250-44 Ma), and Mid-Cenozoic ignimbrite flare-up (40-24 Ma). Detrital geochronology of sedimentary rocks in the Rocky Mountain basins yields similar results, suggesting fluvial linkages. We present a regional dataset of detrital zircon U-Pb geochronology and heavy mineral analysis on a sample set from Wyoming, Colorado, Nebraska, Kansas, and Oklahoma. We compare our data with published data from upper Paleogene strata within basins in the central Rocky Mountains adjacent to the Great Plains and several new samples from the age equivalent Rio Grande Rift to establish a record of sediment transport, which will provide crucial context for late Cenozoic epeirogeny of the Rocky Mountains.