Author: Russell V. Di Fiori and Sean P. Long

Year: 2022

Series: Open-File Report 2022-04

Format: sheet: 58.5 x 38.5 inches, color, cross sections; text: 10 pages, color

Scale: 1:24,000

The Diamond Mountains are located in east-central Nevada, east and northeast of the town of Eureka (fig. 1). Early geologic mapping in the surrounding region by Nolan et al. (1962, 1971) revealed exposures of several thrust faults and folds, which have since been interpreted as part of the central Nevada thrust belt (CNTB), a system of N-striking contractional structures that branch northward off of the Sevier fold-thrust belt in southern Nevada (e.g., Taylor et al., 2000; Long, 2012, 2015; Long et al., 2014; Di Fiori et al., 2021). The southern part of the Diamond Mountains have been important for this interpretation, as they contain exposures of the Cretaceous Newark Canyon Formation (NCF), which has long been hypothesized to have been deposited during regional contractional deformation (e.g., Nolan et al., 1956; Vandervoort and Schmitt, 1990; Long et al., 2014; Long, 2015). However, there have been significant variations in interpretations of the style, timing, and magnitude of contractional deformation in the southern Diamond Mountains across multiple generations of studies (e.g., Nolan, 1962; Nolan et al., 1971; Druschke et al., 2011; Long et al., 2014). In addition, several generations of Late Cretaceous to Cenozoic normal faults have extensionally dismembered the region (Long et al., 2015), which further complicates the regional structural architecture.

In this study, our goal is to present an updated view of the structural geometry and deformational and depositional history of this complex region of central Nevada, by presenting a new 1:24,000-scale geologic map of the southern Diamond Mountains that covers an area of ~235 km², including the exposed extent of the NCF (fig. 1). Our field work consisted of new geologic mapping focused on two main exposures of the Newark Canyon Formation, accompanied by compilation and field-checking of key localities on the 1:31,680-scale geologic map of the Eureka 15′ quadrangle (Nolan et al., 1971) and the 1:12,000-scale map of the Eureka mining district (Nolan, 1962). We also present three retro-deformable cross sections, which illustrate the deformation geometry both above and below the modern erosion surface. This map and technical report are meant to accompany Di Fiori et al. (2020), which presents details on the stratigraphy, deposition timing, and deformational history of the NCF in the southern Diamond Mountains. This report presents detailed descriptions of members of the NCF that we defined in our mapping, as well as descriptions of Paleozoic sedimentary rock units, and explains revisions to the older structural interpretations that we have performed in our new work.

This map covers portions of the following 1:24,000-scale USGS quadrangles: North of Eureka, Rattlesnake Mountain, Eureka, Diamond Peak, Pinto Summit, and Silverado Mountain.

Di Fiori, R.V., and Long, S.P., 2022, Geologic map of the southern Diamond Mountains, Eureka and White Pine counties, Nevada: Nevada Bureau of Mines and Geology Open-File Report 2022-04, scale 1:24,000, 10 p.

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