Abstract

The area extending southeastward from the south end of Teton Basin, Idaho, to the northern part of Green River Basin, Wyoming, exhibits two types of Laramide structure modified by Tertiary high-angle faults. Included within the area are parts of the Teton, Gros Ventre, Hoback, and Snake River ranges.

Structure in the Teton and Gros Ventre ranges consists of broad, asymmetrical anticlines, a major northeast-dipping thrust fault, and three large fault blocks. Structures in the Hoback and Snake River ranges include close folds of Appalachian type and low-angle, southwest-dipping thrust faults. Initial Teton-Gros Ventre structures probably were formed during an early phase of Laramide orogeny and, as buttresses, controlled the trend and character of the later Hoback-Snake River structures. Laramide movements appear to have begun in the Late Cretaceous and continued at least into late Eocene time. Tertiary faults of Basin-Range type and with north-south trends transect older structures and are responsible for the east scarp of the Teton Range, small fault blocks in Jackson Hole, and the western boundary structure of the northern Hoback Range.

Regional stratigraphic relations had an important effect on both the trend and type of Laramide deformation, but this influence cannot be recognized in the Basin-Range faulting.

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