Remote sensing analysis of southern Walker Lane

Abstract

A comprehensive analysis of Landsat 4 and 5 Thematic Mapper (TM) imagery, and topographic, geologic, and aeromagnetic maps demonstrates that the Walker Lane is a continuous feature through the southwestern Nevada volcanic field. A strong northwest pattern of lineaments is apparent in rock units older than 9.5 m.y. These lineaments correspond to sites of aligned preferential erosion, and at intersections with lineaments of different trends, may be northwest-trending vertical fractures and faults. The lineaments in volcanic rocks are thought to owe their origin to movement on northwest-trending structures in the underlying Paleozoic basement. A conspicuous lack of northwest-trending lineaments occurs in rock units younger than 9.5 m.y. The lack of the lineaments in young volcanic units may suggest that movement on the underlying structures ceased by the time of, or soon after, their deposition. Relative ages of the gradual cessation of movement are provided by tuff units of the Black Mountain and Stonewall Mountain calderas. The 8.5 to 6.3 m.y. ages of the calderas agree with other evidence which supports a clockwise rotation of the stress regime at about the same time. The lineament distribution therefore suggests the cessation of movement along northwest-trending structures is directly related to a change in the orientation of the stress regime. The lineament analysis also demonstrates the advantages of the multiband format of Landsat TM imagery. Linear features not apparent in bands 1-4 were noted in the longer wavelength bands. This is due to spectral reflectance and resolution differences between bands. Bands 5, 6, and 7 were found to be most useful for structural analysis of the southwestern Nevada region.