### The Las Vegas Formation

By: Kathleen B. Springer**Jeffrey S. Pigati**Craig R. MankerShannon A. Mahan**

                            https://doi.org/10.3133/pp1839

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- Related Work:  **Fact Sheet 2018-3038—**  The Geology and Paleontology of Tule Springs Fossil Beds National Monument, Nevada
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#### Abstract

First posted December 20, 2018

**For additional information, contact:**
Director, Geosciences and Environmental Change Science CenterU.S. Geological SurveyBox 25046, MS-980Denver, CO 80225-0046

The Las Vegas Formation was established in 1965 to designate the distinctive light-colored, fine-grained, fossil-bearing sedimentary deposits exposed in and around the Las Vegas Valley, Nevada. In a coeval designation, the sediments were subdivided into informal units with stratigraphic and chronologic frameworks that have persisted in the literature. Use of the Las Vegas Formation name over the past half century has been hampered because of the lack of a robust definition and characterization of the entire lithostratigraphic sequence, its geographic distribution, and chronology. This study evaluates and describes deposits attributed to the Las Vegas Formation with detailed stratigraphy, sedimentology, and field relations. A large suite of radiocarbon and luminescence ages facilitates revision and temporal expansion of the geochronology. In all, we characterize 17 informal geologic units within the formation, each dating to a unique period of geologic time, with stratigraphically ascending members X, A, B, D, and E and attendant beds in members B, D, and E. The age of the Las Vegas Formation spans at least the middle Pleistocene to early Holocene (from approximately 573 to 8.53 kilo-annum [thousands of years before present]) and is related to past episodes of groundwater discharge in the Las Vegas Valley. The contextual information derived from this new framework is dually noteworthy because the sediments entomb one of the most significant Pleistocene vertebrate faunas in the American Southwest, the Tule Springs local fauna, and represent a paleohydrologic system that responded dynamically to abrupt changes in climate throughout the late Quaternary. Characterizing the nature of these important deposits stabilizes the nomenclature, promotes the continued use of the informal units within the formation, and facilitates studies of similar deposits associated with desert wetland ecosystems elsewhere in the southwestern United States.

#### Suggested Citation

Springer, K.B., Pigati, J.S., Manker, C.R., and Mahan, S.A., 2018, The Las Vegas Formation: U.S. Geological Survey Professional Paper 1839, 62 p., https://doi.org/10.3133/pp1839.

ISSN: 2330-7102 (online)

ISSN: 1044-9612 (print)

#### Study Area

#### Table of Contents

- Acknowledgments
- Abstract
- Introduction
- Methods
- Results and Discussion
- Conclusions
- References
- Appendix 1. Summary of Radiocarbon Ages Obtained Previously for the Las Vegas Formation
- Appendix 2. Summary of Thermoluminescence Ages Obtained Previously for the Las Vegas Formation
- Appendix 3. Summary of Sample Information and Optically Stimulated Luminescence Ages From This Study

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