Petrology, sedimentology and stratigraphic implications of Black Dragon Member of the Triassic Moenkopi Formation, San Rafael Swell, Utah
- Univ. of Utah, Salt Lake City (USA)
Deposition was partly controlled by paleotopographic relief of underlying Permian strata. Triassic Black Dragon sediments filled lowlands on an erosion surface (unconformity) cut into the Permian White Rim Sandstone and Kaibab Limestone. The Black Dragon Member consists of four distinct facies containing a wide variety of sedimentary structures that characterize both fluvial and tidal environments. The facies are: (1) a Chert Pebble Conglomerate (CPC) facies, characterized by calcite-cemented channel-fills of nodular and banded chert pebbles; (2) an Interbedded Sandstone, Siltstone, and Shale (SSS) facies, containing oscillation ripples and flaser bedding; (3) a large-scale Trough Cross-Stratified Sandstone (TXS) facies, consisting of 6.6-13.1 ft (2-4 m) thick sets of fine- to medium-grained sandstone; and (4) an Oolitic and Algal Limestone (OAL) facies, with cross-stratified oolitic beds, fenestral fabric, and laminated algal rip-up clasts. The CPC facies and the TXS facies were deposited by braided streams when the shoreline lay west of the San Rafael Swell. Rivers drained off and eroded localized Permian highlands, located most likely within a 62 mi (100 km) distance to the south and southeast of the study area. The SSS facies which constitutes the bulk of the Black Dragon Member, and the OAL facies are inter- and supratidal deposits formed during relative sea level highstands, when the shoreline lay within or east of the San Rafael Swell. A decrease in continent-derived sand supply and a corresponding increase in carbonate production within the OAL facies characterizes the end of Black Dragon deposition and the gradation into the overlying Sinbad Limestone Member.
- OSTI ID:
- 6286470
- Journal Information:
- Mountain Geologist; (USA), Journal Name: Mountain Geologist; (USA) Vol. 27:1; ISSN MOGEA; ISSN 0027-254X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHEMISTRY
CHERT
CONGLOMERATES
DEPOSITION
DIAGENESIS
EROSION
FEDERAL REGION VIII
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGY
LEVELS
LIMESTONE
MESOZOIC ERA
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PETROLOGY
RIVERS
ROCKS
SANDSTONES
SEA LEVEL
SEDIMENTARY ROCKS
SEDIMENTATION
SEDIMENTS
SHALES
SILTSTONES
STRATIGRAPHY
STREAMS
SURFACE WATERS
TOPOGRAPHY
TRIASSIC PERIOD
USA
UTAH