Petrology, sedimentology and stratigraphic implications of Black Dragon Member of the Triassic Moenkopi Formation, San Rafael Swell, Utah

Journal Article · Mon Jan 01 00:00:00 EST 1990 · Mountain Geologist; (USA)

OSTI ID:6286470

Chan, M A ^[1]; Ochs, S

---

1. 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), Vol. 27:1; ISSN 0027-254X
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC FORMATIONS
PETROLOGY
SEDIMENTATION
STRATIGRAPHY
UTAH
CALCITE
CARBONATE ROCKS
CHERT
CONGLOMERATES
DEPOSITION
DIAGENESIS
EROSION
GEOCHEMISTRY
GEOLOGIC HISTORY
LIMESTONE
RIVERS
SANDSTONES
SEA LEVEL
SEDIMENTS
SHALES
SILTSTONES
TOPOGRAPHY
TRIASSIC PERIOD
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHEMISTRY
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGY
LEVELS
MESOZOIC ERA
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
STREAMS
SURFACE WATERS
USA
580000* - Geosciences