Waiting for the snow to melt…
This study suggests that the Permian rocks in northwestern Colorado and northeastern Utah were deposited in shallow-marine shelf, transitional, and terrestrial environments. The Wolfcampanian and early Leonardian upper layers of the Weber formation are predominantly eolian quartz sandstones deposited in a broad coastal area of low relief. This coastal area was at the northwestern end of the ancestral Uncompahgre uplift, and was intermittently covered by seawater as indicated by the few thin marine carbonate rocks. The upper Weber intertongues with the Grandeur Member of the Park City Formation in the study area. The carbonates and cherts of the Grandeur were deposited in shallow-marine waters during a transgressive cycle which was probably caused by a crustal downwarping f the shelf. The Meade Peak Member of the Phosphoria Formation was deposited on top of the Grandeur by cold, phosphorous-rich, upwelling water as a result of continued Early Permian transgression. Landward from the phosphorites, carbonates were contemporaneously deposited, and further landward, siltstones. Regression near the end of Leonardian shifted the depositional environment belts westward and resulted in deposition of the Franson Member carbonates and cherts on top of the phosphorites. Maximum regression during the Guadalupian produced very shallow and highly saline waters in the area and subaerial exposure for long periods, combined with a significant increase of terrestrial, fine-grained sediment supply. These conditions led to the deposition of interstratified gypsum, silt, and shale of the Mackentire Tongue redbeds. The eastern half of the study area is characterized by greenish-gray and tawny beds which are partly time-equivalent of the Meade Peak, Franson, and Mackentire. The environments of deposition are interpreted to be those of a reducing, restricted marine embayment. These beds are more closely related to the Goose Egg Formation in central Wyoming than to any other formation in the area and are so designated. Extensive regression beginning in late Guadalupian continued into the Triassic and caused the deposition of the Moenkopi red beds. End_of_Article - Last_Page 728------------
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