The Alluvial to Eolian Transition of the Chinle and Nugget Formations in the Southern Uinta Mountains, Northeastern Utah
Research output: Chapter in Book/Report/Conference proceeding › Book chapter › Research › peer-review
Standard
The Alluvial to Eolian Transition of the Chinle and Nugget Formations in the Southern Uinta Mountains, Northeastern Utah. / Irmis, Randall B.; Chure, Daniel J.; Engelmann, George F.; Wiersma, Jelle P.; Lindström, Sofie.
Geology of Utah’s Uinta Basin and Uinta Mountains. Utah Geological Association, 2015. p. 13-48 (Utah Geological Association Publication; No. 02, Vol. 44).Research output: Chapter in Book/Report/Conference proceeding › Book chapter › Research › peer-review
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - CHAP
T1 - The Alluvial to Eolian Transition of the Chinle and Nugget Formations in the Southern Uinta Mountains, Northeastern Utah
AU - Irmis, Randall B.
AU - Chure, Daniel J.
AU - Engelmann, George F.
AU - Wiersma, Jelle P.
AU - Lindström, Sofie
PY - 2015
Y1 - 2015
N2 - The Uinta Mountains of northeastern Utah preserve the northernmost outcrops of classic early Mesozoic stratigraphic units on the Colorado Plateau, and document the transition to equivalent strata further north in Wyoming. In this region, the predominantly fluvial Upper Triassic Chinle Formation is overlain by the predominantly eolian Upper Triassic-Lower Jurassic Nugget Sandstone, which may be partially or wholly equivalent to the Glen Canyon Group further south. Previous work on these units has reached little consensus on where the boundary between the Chinle and Nugget should be placed, whether this boundary is conformable, and what lithostratigraphic nomenclature should be used. Our stratigraphic and sedimentologic investigation of outcrops in and around the western portion of Dinosaur National Monument and north of Vernal, Utah, indicate that the orange sandstone interval and overlying purple interval are assignable to the upper member of the Chinle Formation. This purple interval is interpreted as ephemeral sheet-flow deposits dominated by mud flats. The Chinle-Nugget contact appears conformable in many areas, with no evidence of the J-0 unconformity. The lowermost 10-20 meters of the Nugget Sandstone show extensive evidence of subaqueous deposition and/or modification, with only occasional thin cross-bedded eolian units, and these transitional layers commonly contain vertebrate tracks, some of which suggest a Triassic age. Taken together, these data indicate the gradual drying of the Chinle river and floodplain system at the same time as the encroachment of the Nugget/Wingate erg. Trace and body fossils indicate this erg margin was populated by a wide variety of invertebrate and vertebrate organisms, including early dinosaurs
AB - The Uinta Mountains of northeastern Utah preserve the northernmost outcrops of classic early Mesozoic stratigraphic units on the Colorado Plateau, and document the transition to equivalent strata further north in Wyoming. In this region, the predominantly fluvial Upper Triassic Chinle Formation is overlain by the predominantly eolian Upper Triassic-Lower Jurassic Nugget Sandstone, which may be partially or wholly equivalent to the Glen Canyon Group further south. Previous work on these units has reached little consensus on where the boundary between the Chinle and Nugget should be placed, whether this boundary is conformable, and what lithostratigraphic nomenclature should be used. Our stratigraphic and sedimentologic investigation of outcrops in and around the western portion of Dinosaur National Monument and north of Vernal, Utah, indicate that the orange sandstone interval and overlying purple interval are assignable to the upper member of the Chinle Formation. This purple interval is interpreted as ephemeral sheet-flow deposits dominated by mud flats. The Chinle-Nugget contact appears conformable in many areas, with no evidence of the J-0 unconformity. The lowermost 10-20 meters of the Nugget Sandstone show extensive evidence of subaqueous deposition and/or modification, with only occasional thin cross-bedded eolian units, and these transitional layers commonly contain vertebrate tracks, some of which suggest a Triassic age. Taken together, these data indicate the gradual drying of the Chinle river and floodplain system at the same time as the encroachment of the Nugget/Wingate erg. Trace and body fossils indicate this erg margin was populated by a wide variety of invertebrate and vertebrate organisms, including early dinosaurs
M3 - Book chapter
SN - 9780980048988
T3 - Utah Geological Association Publication
SP - 13
EP - 48
BT - Geology of Utah’s Uinta Basin and Uinta Mountains
PB - Utah Geological Association
ER -
ID: 357733443