Earth and Planetary Sciences ETDs

Publication Date



Along the western border of the San Juan Basin a prominent cliff-forming, orange sandstone has been incorrectly mapped as a part of the Recapture Shale Member of the Morrison Formation. This stratigraphic unit is here given the informal name, Beautiful Mountain member, and has stratigraphic continuity with the Salt Wash Sandstone Member in Red Rock Valley and the Cow Springs Sandstone in Todilto Park, New Mexico. The Recapture Shale Member is restricted to the pink and pale-green, slope-forming sandstone above these orange sandstone beds and below the Westwater Canyon Sandstone Member.

The Beautiful Mountain member is predominantly a lenticularly bedded, fine-grained sandstone. It has poor bedding continuity and contains reddish􀀥brown mudstone flakes randomly scattered throughout. Two granule-bearing sandstone beds are useful as marker beds in much of the area of this report. Bone fragments, possible worm burrows, and fossil wood fragments are the only fossils found in the Beautiful Mountain member and are uncommon. The Recapture Shale Member is a slope-forming, fairly well sorted, fine-grained sandstone containing beds and lenses of reddish­brown mudstone.

Sedimentologic and stratigraphic relationships suggest that the Beautiful Mountain member was deposited by streams in an area between the Salt Wash Sandstone to the north and northwest and the Cow Springs Sandstone to the west and south. Stratigraphic evidence suggests that the Defiance uplift was a low positive area during early Morrison depositional time.

Degree Name

Earth and Planetary Sciences

Level of Degree


Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Vicent C. Kelley

Second Committee Member

Stuart A. Northrop

Third Committee Member

Charles B Read



Document Type


Included in

Geology Commons