Chaos Structure and Turtleback Dome, Mineral Ridge, Esmeralda County, Nevada

Abstract

Blocks of late Precambrian and Lower Cambrian sedimentary rocks are in fault contact with the underlying complexly deformed Pre-cambrian units of Mineral Ridge in Nevada. A structure contour map of the contact between the metamorphic and sedimentary rocks was constructed using the topography of low-relief areas on the metamorphic rocks. This map shows the structure to be a dome, with smaller-scale elevations and depressions superimposed on the dome shape. The disordered and yet unfolded aspect of the fault blocks and the age relationships of the rocks involved are strikingly similar to the characteristics of the Amargosa Chaos of the Death Valley area; moreover, the form of the fault contact resembles the turtleback domes associated with the chaos at Death Valley. Similarities to areas of gravity sliding, including a possible erosion surface overriden by the thrust blocks, indicate the chaotic structures of Mineral Ridge may be the results of near-surface gravity movements rather than the secondary features of strike-slip faults.