Abstract

A nearly complete Paleozoic section of exceptionally simple structure containing 16,450 feet of Lower Cambrian to Mississippian(?) beds is well exposed in the southern Ruby Mountains. In addition several thousand feet of undifferentiated Carboniferous rocks, partly Pennsylvanian, appear only in thrust sheets and fault blocks. The thickness and details of this section fit well with previously developed concepts of paleogeography in the northeastern Great Basin.

The internal structure of the range is a simple eastward-dipping homocline complicated to the north by granitic intrusions and to the south by a mosaic o high-angle normal faults. Along the west-central flank is a low-angle westward-dipping thrust with a probable minimum eastward displacement of 7 to 10 miles. The thrusting can be dated with certainty only as post-Pennsylvanian and pre-Miocene but by analogy with other areas is probably early Tertiary.

The boundary structure passes from a westward-tilted horst, typical of the northern two-thirds of the range, to a simple westward-tilted fault block in the southernmost part. Movements along the boundary faults have occurred at intervals from Miocene to Pleistocene.

Early Wisconsin (Iowan) and later Wisconsin glaciers occupied the higher parts of the range and indicate a Wisconsin orographic snow line at approximately 10,000 feet. This snow line rose southward with a gradient of 200 to 300 feet per 100 miles.

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