Petrologic characterization and differentiation of Neogene and Pleistocene sediments in the Verdi-Reno Truckee River corridor

Sedimentary strata ranging in age from Miocene to Pleistocene are exposed in the modern Truckee River Valley west of Reno, Nevada. Although the sediment sources for these strata are local, they are highly varied and their availability and modes of transport are thought to reflect the evolution of the pre-Truckee River and ancestral Truckee landscapes and drainages.;The primary hypothesis of this work is that systematic compositional differences should exist between the Tertiary and Quaternary strata in the area due to climatically and tectonically-driven geomorphic changes in local watersheds that exposed different bedrock units to erosion. Additionally, physical differences may exist between these units with regard to the presence (or absence) and nature of the cement binding the grains. A secondary hypothesis is that the different Quaternary units among themselves may have compositional differences for the same reasons, and that these can be isolated and used as petrographic signatures for these units.;Analyses of the results obtained in this study reveal that significant compositional differences do exist between the Quaternary units and the Tertiary section. Quartz percentages in Quaternary samples are consistently and significantly higher than percentages observed in Tertiary samples. This result indicates the Gravels of Reno are genetically linked to the Quaternary outwash in the Verdi and Reno area rather than the underlying Tertiary section. However, these analyses show no significant compositional difference between the various Quaternary units.