ABSTRACT: The Wind River Range: An Overview

BLACKSTONE, D. L., University of Wyoming (retired), Laramie, WY

The Wind River range, the largest discrete foreland element, is a doubly plunging anticline bounded on the southwest by a low-angle thrust fault. The range is approximately 140 mi long and 35 mi wide. The thrust fault reflects two principal foreland trends N40 degrees W and N70 degrees W. Tectonic transport is 16 mi laterally; vertical separation 9.3 mi. The range core consists of Precambrian greenstones, migmatites, gneisses, and granitic plutons ranging in age from 3.4 to 2.3 billion years. Persistent shear zones trend N20 degrees W at an angle of 20 degrees to the range orientation.

Deformation began in the Late Cretaceous (Lancian), climaxed in the Eocene (Wasatchian), and terminated in the Eocene (Bridger) prior to extensive ash falls in the Oligocene. Extensional tectonism (post-Miocene) resulted in the Continental Fault system, restricted to the hanging wall of the major thrust fault. Normal faults are down to the north (mountainward), listric faults are concave up in form, and offsets range up to 1500 ft.

At least two "high-level" erosion surfaces exist. The higher, Fremont, is the exhumed Precambrian-Cambrian interface. An extensive, severely glaciated surface flanks the range on the west and carries up to the Continental Divide. This surface is reported to be as old as Eocene, or as young as Miocene-Pliocene. The latter age best fits the pattern of maximum basin fill prior to superposition of major drainages in Wyoming. The existence of an Oligocene compressional tectonic event that elevated the core of the range is questionable.

AAPG Search and Discovery Article #91017©1992 AAPG Rocky Mountain Section Meeting, Casper, Wyoming, September 13-16, 1992 (2009)