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The Enigmatic Rattlesnake Knoll, Spring Valley, East-Central Nevada—A Geophysical Perspective

Open-File Report 2023-1002
By: , , and 
https://doi.org/10.3133/ofr20231002

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Abstract

Rattlesnake Knoll is a small, 30-meter-high mound of igneous breccia in the center of Spring Valley, east-central Nevada. In the past, researchers have disagreed as to whether the unusual-looking outcrop is intrusive or volcanic. The breccia possesses a normal magnetic polarity, but this is not apparent in aeromagnetic survey data. These data instead show that the knoll lies within a small aeromagnetic low that partially overlaps the extent of a small gravity high. The small gravity anomaly associated with the knoll, combined with an initial, limited ground magnetic survey taken at the knoll, indicates that the knoll rocks extend northward in the subsurface. A second, more extensive ground magnetic traverse was also done north of the knoll. Taking into consideration these new survey data and preexisting data, a two and one-half dimensional modeling program based on Webring (1985) was used to produce a geophysical model that accounts for gravity and magnetic properties, satisfies available geologic information, and conforms to current estimates of basin thickness. This model and the field observations support the interpretation that the knoll consists of gently west-dipping beds of Tertiary volcanic flow breccia, mudflow breccia, and conglomerate.

Suggested Citation

Mankinen, E.A., Rowley, P.D., and McKee, E.H., 2023, The enigmatic Rattlesnake Knoll, Spring Valley, east-central Nevada—A geophysical perspective: U.S. Geological Survey Open-File Report 2023–1002, 13 p., https://doi.org/10.3133/ofr20231002.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments 
  • Abstract 
  • Geologic Setting 
  • Geophysical Expression 
  • Potential Field Modeling 
  • Conclusions 
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title The enigmatic Rattlesnake Knoll, Spring Valley, east-central Nevada—A geophysical perspective
Series title Open-File Report
Series number 2023-1002
DOI 10.3133/ofr20231002
Year Published 2023
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description vi, 13 p.
Country United States
State Nevada
Other Geospatial Spring Valley
Online Only (Y/N) Y
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