Six geologic maps and an explanation sheet showing the surficial geology of the North Fork Gunnison River Valley, Delta and Gunnison Counties. Includes 1) Gray Reservoir Quadrangle, 2) Bowie Quadrangle, 3) Somerset Quadrangle, 4) Paonia Reservoir Quadrangle, 5) Hotchkiss Quadrangle, 6) Paonia Quadrangle, and 7) Explanation sheet. 7 plates (1:24,000). Digital PDF download. OF-78-04D
From the General Description on Plate 7:
The geologic setting of the study area is relatively simple: flat lying Cretaceous and Tertiary sedimentary rocks are locally intruded by younger igneous rocks. These were sculpted during the late tertiary and Quaternary by erosional processes that formed the present mesa and mountain landscape. Various thin surficial deposits, possibly related to glacial stages, suggest that fluvial and mass-wasting activities were the dominant geomorphic processes in the formation of the present landscape.