Preliminary Basin Analysis of Late Pennsylvanian-Permian Wood River Basin, South-Central Idaho

Brian J. Mahoney, Paul Karl Link

Stratigraphic correlation of partly coeval tectonostratigraphic units in the Smoky and Boulder Mountains, west and north (respectively) of Ketchum, Idaho, allows for reconstruction of the Late Pennsylvanian-Early Permian Wood River basin. These tectonostratigraphic units contain calcareous sandstones, silty limestones, and carbonaceous siltites and shales of the Wood River Formation (units 6 & 7--Virgilian-Wolfcampian), Grand Prize Formation (Wolfcampian(?)), and Dollarhide Formation (Wolfcampian). Interpretation of sedimentary facies, petrologic characteristics, and structural relations suggests contiguous deposition of these units in a westward deepening basin in shallow shelf, outer shelf to upper slope, and lower slope to basin environments, respectively.

In the Wood River basin, vertical facies changes within each formation are similar to lateral facies changes progressively westward between formations, as suggested by palinspastic reconstructions. Upsection and to the west, thick sequences of calcareous sands give way to fine-grained carbonaceous sediments, suggesting a deepening of depositional environments through time.

Regional sea level rise, basin subsidence, or both, during Virgilian to early Wolfcampian time, is suggested by deepening-upward facies transitions in rocks of both the Wood River basin of central Utah and Oquirrh basin of northern Utah. Both basins evolved from shallow to moderate depth shelf-and-slope environments to more restricted, deeper water environments. Paleogeography and basin development are relatively well constrained in the Oquirrh basin, but is more tentative in the Wood River basin where a lack of biostratigraphic control and structural complexities permit only tentative paleogeographic reconstruction.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.