Abstract

Patterns of linear trends as traced from ERTS - 1 imagery in Utah and Nevada suggest that there is a network of interrelated regional structural trends across the two state area. Where trends of one orientation intersect trends of another orientation, there appears to be mutual offsetting. Intersections of a number of trends may be at intrusive centers or show other evidence of crustal disturbance. Mutual offsetting of two intersecting faults having the same relative direction of movement might cause dilation, resulting in downwarping or step-faulting, and create conduits for possible basic intrusion. Mutual offsetting of faults having the opposite relative direction of movement might cause compression, crushing, thrusting and upwarping, and possibly melting of deeper crustal material to create centers of silicic igneous activity.

Some alignments of structural trends show a regular change of orientation, forming circular segments. They may range in diameter from a few hundred meters to more than 1000 kilometers, may be traced as concentric sets, and have the mutually offset trends as their geometric centers. This suggests that the centers are axes of rotation for moving blocks of crust, and that the stress release follows latitudes of rotation. Non-vertical controlling structures would cause tilting of the rotated block.

Arcuate trends around a number of adjacent centers overlap in time and space and offset each other, creating complex structural and geologic patterns. Compression followed by tension at many centers could explain present Basin-range structures.