Abstract

In the Valley of Fire State Park of southern Nevada, the Jurassic Aztec Sandstone is deformed by two predominately strike-slip fault sets with opposite slip sense. One fault set is north-northeast oriented and shows maximum left-lateral separations that range between centimeters and kilometers. The other fault set is northwest oriented and shows maximum right-lateral separations that range between centimeters and hundreds of meters. At a regional scale, most of the right-lateral faults terminate against the larger-offset left-lateral faults and are found localized between en echelon and parallel left-lateral faults, and at the ends of the larger left-lateral faults. At a local scale, right- and left-lateral faults of smaller size show mutually abutting relationships. Furthermore, Mode I splay fractures related to fault slip are observed sharing the same orientation and abutting relationships as members of the left- and right-lateral fault sets. A conceptual model for the evolution of the strike-slip fault network in the Valley-of-Fire is presented whereby the fault network formed via progressive Mode I splay fracturing and subsequent shearing along the fractures. At the outcrop scale, at least five hierarchical generations of structures are identified. It is proposed that shearing of Mode I splay fractures is facilitated by material rotation near and between slipping faults and/or local stress rotation due to fault interaction.

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