THE BEAUTY IN THE OVERBURDEN—SCIENTIFIC INSIGHTS GAINED FROM DETAILED MAPPING OF LATE CENOZOIC ALLUVIAL AND LACUSTRINE DEPOSITS IN NEVADA

The Nevada Bureau of Mines and Geology has recently undertaken a series of detailed geologic mapping efforts focused on the late Cenozoic geologic history of rivers, lakes, and alluvial fans in various parts of Nevada. Mapping along the Lower Colorado River near the southern tip of Nevada has found previously unknown stratigraphic relations that contradict conventional models of the river's evolution and provide new impetus for understanding its history in detail. Mapping along the Lower Truckee River and its delta at Pyramid Lake in western Nevada, have helped to augment existing knowledge and further understand the complex history of the interaction between the Truckee and pluvial Lake Lahontan. It is also documenting the response of the river-lake system to Holocene climate variability, historical flow diversions, and recent floods. Detailed geologic mapping of the Middle Humboldt River floodplain in central Nevada has revealed a wealth of geologic data documenting the occasionally dynamic response of the river to Late Quaternary climate variability and tectonism. Mapping of alluvial deposits in Ivanpah Valley, between Las Vegas and California, also documents the influence of climate on landscape evolution and is being used to assist floodplain management in this soon-to-be developed area. A variety of remote-sensing data are being used to supplement this effort and to evaluate their applicability to recon-level mapping in similar areas for similar reasons. In addition to detailed delineation of Quaternary alluvial deposits, mapping in Ivanpah Valley has identified landforms dating from the Pliocene and late Miocene and has revealed a suite of Miocene fluvial gravels that have intriguing paleohydrologic implications. In each of these instances, detailed geologic mapping has led to important new insights into regional geology and general geologic processes that would not have been gained otherwise. The value of geologic mapping for understanding regional geology and for stimulating important scientific insights cannot be understated, even when it is not bedrock being mapped. Geologic mapping is the foundation of geologic understanding at any point along the continuum of Earth history.