Wyoming Geological Association: 1982 Luncheon Meetings Casper, Wyoming: Abstracts of Papers

The transition from the central to the northern block of the Bighorn Mountains is accomplished by vertical displacements of numerous, small blocks of the Precambrian basement. Structures produced in the Paleozoic cover are a series of asymmetric folds of incompatible vergence and some faults that break through the Paleozoic section. Structural relief in the block-faulted region is measured in hundreds of feet without considering the transition to the basin.

The configuration of the blocks constrains models for the northeast flank of the Bighorns to ones showing steeply dipping faults with dominantly vertical movements. Similar asymmetric structures of lower amplitude can be mapped basinward of the mountain front. The transition to the basin is probably accomplished by just such structures. The change in position of the mountain front at the Tongue River is the result of these numerous blocks; thrusting and strike slip, although not ruled as minor phenomena, were not important in controlling the structural development of the northeast flank of the Bighorns.