National Science Foundation

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University of Nevada, Las Vegas

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Las Vegas, Nevada

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Cryptotephra (small volcanic shards ranging 20-80 microns in size) were discovered within Unit X of the Las Vegas Formation at Whitney Mesa Nature Preserve, Henderson, Nevada. Cryptotephra are deposited soon after a volcanic eruption and can be used as a dating tool to create narrow time constraints for surrounding sediments. Cryptotephra have many applications but are mainly useful as a dating tool. Their study has important implications for the understanding of the timing of palaeoclimatological and paleoenvironmental events as well as for archaeological studies to date important events in human history.

The Whitney Mesa cryptotephra were correlated with the Bishop Tuff, dated at 766 ka. The Las Vegas Formation underlies much of the Las Vegas Valley but, due to expansive urbanization, it is now best exposed at Tule Springs Fossil Beds National Monument, Whitney Mesa Nature Preserve, and Charlie Frias Park. The Las Vegas Formation is divided into five main units with an E member on top and an X member as the base. The age of Unit X (the subject of this study) is poorly known, with previous dates ranging from 232 to 573 ka. The discovery of cryptotephra and correlation with Bishop Tuff provide the first precise date for Las Vegas Formation Unit X. This work was accomplished using sediment sample collection, wet-lab techniques at UNLV’s Cryptotephra Laboratory for Archaeological and Geologic Research (CLAGR), petrographic microscope analysis, and electron microprobe geochemical analysis at UNLV’s Electron Microanalysis and Imaging Laboratory (EMiL).


Cryptotephra; Whitney Mesa; Las Vegas; Nevada; Las Vegas Formation; Unit X; Pleistocene; Bishop Tuff; Long Valley Caldera; Tephrochronology


Earth Sciences | Geochemistry | Geology | Stratigraphy | Volcanology

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This paper uses GSA citation guidelines

Committee Members:

Eugene Smith

Racheal Johnsen

Simon Jowitt

Lisa Menegatos


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