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Kinematics And Timing Of Deformation Of Nellis Dunes Recreational Area, Nellis, Nevada


Kinematics and origin of transfer, accommodation and strike-slip zones is of paramount significance in understanding the kinematic models of continental extension. The Las Vegas Valley Shear Zone (LVVSZ) is a NW-striking right-lateral fault system in the central Basin and Range province. Despite its prominence among the structures of the region and its role in the regional tectonic development, little is understood about its eastern portion. Nellis Dunes Recreational Area (NDRA), north of Frenchman Mountain, lies along the eastern part of LVVSZ. The area exposes structures, the Muddy Creek Formation and Quaternary deposits. Previous mapping suggested that the area under the NDRA formed as a pull-apart basin between the LVVSZ in the northern part of the area and the Munition fault that lies to south and bounds the northern end of the Frenchman Mountain block. However, some structural geometries are inconsistent with the regional pull-apart basin model of Nellis basin. The purpose of this study is to collect and analyze more detailed data and suggest a deformation model consistent with the entire fold and fault geometries. Larger scale mapping (1:8,000) provided complex structural geometries and kinematics. Secondary NE-oriented folds are interpreted to be related to right-lateral strike-slip faults that dominate the northwestern and northeastern parts of NDRA, while the central part is dominated by NW-oriented folds with NE-striking normal faults. Structural analysis showed that area exhibits three different strains. The right-lateral faults are part of the LVVSZ and cut Muddy Creek Formation suggesting that the LVVSZ was active after 4.7 Ma. Later, during the Quaternary, the LVVSZ was cut by NE-oriented left-lateral strike-slip faults with associated folds consistent with the recent NE strain direction. The northern end of Frenchman Mountain fault curves to the NE forming a left-lateral fault splay in the southern part of NDRA. Consequently NE-striking faults and NW-oriented folds dominated the southern part of NDRA as secondary structures associated with that left-lateral deformation.