Southern Nevada is geologically and structurally complex. Detailed geologic mapping is critical to the understanding of the geologic history and groundwater flow within the region. The Las Vegas Valley shear zone (LVVSZ) is a strike-slips fault along which approximately 50 km of right-lateral movement took place between about 15-10 Ma. The shear zone extends northwestward about 100 km from Las Vegas to Mercury, Nevada. Folded Miocene strata record contraction west of Mercury where the LVVSZ is inferred to bend westward beneath the southern Specter Range creating a positive flower structure in response to transpression. Geologic mapping southwest of Mercury shows that Neoproterozoic and Early Paleozoic carbonate and clastic strata comprise a thick section of rocks deformed by multiple gently dipping faults along which units are detached. The footwalls and hanging walls adjacent to the fault surfaces are generally marked by pebbly cataclastic breccia or less commonly by foliation in fine-grained rocks. The detachments, which commonly crop out in the northernmost Spring Mountains, dip gently north toward the Specter Range. Rare kinematic indicators record south-directed transport.
A principal hanging wall of the fault zone is composed of brecciated Late Cambrian Nopah Formation. Detachment breccias show significant secondary porosity and permeability, which may control groundwater flow between the Spotted Range and Specter Range. Adjacent to the detachment about 1.4 to 3 kilometers of strata are missing between Nopah beds and fault slices of much lower Early Cambrian Wood Canyon Formation. The footwall of the Nopah detachment comprises two parts: 1) Neoproterozoic and Cambrian strata folded about north-trending hinges and 2) an adjacent basin. Brecciated Nopah Formation and underlying fault rocks rest upon the folded strata of the footwall, and breccia also crops out in an adjacent former lake where they are recorded by crudely tabular masses of breccia intercalated with bodies of carbonate-clast conglomerate. The detachment fault zone is a contractional feature that is compatible with transpression expected along the left-step restraining bend in the LVVSZ.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-08072007-104828 |
| Date | 19 September 2007 |
| Creators | Piaschyk, Damian |
| Contributors | Dr. Thomas H. Anderson, Dr. Charles E Jones, Dr. William Harbert |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-08072007-104828/ |
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