Fluvial response to subsidence determined from remote sensing

Conference · Tue May 01 00:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6935558

Kraus, M J ^[1]

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1. Univ. of Colorado, Boulder (USA)

Well-exposed rocks of the fluvial Willwood Formation covering approximately 5,000 km{sup 2} of the central part of the Big Horn basin, Wyoming, were analyzed with Thematic Mapper (TM) data. False-color images and field analysis were used to characterize and map large-scale lithologic packages in this lower Eocene unit. Field criteria used to distinguish among the packages include mudstone coloration and type and abundance of nodules, both of which reflect the type of alluvial paleosol that developed; abundance, geometry, and paleotransport direction of sand bodies; and abundance and geometry of carbonaceous shales. The lithologic packages reflect both spatial and temporal variability; biostratigraphic data were used to establish which packages are time correlative. Differences among time-correlative fluvial packages (facies) reflect variability in local moisture regimes and sediment accumulation rates, factors that influenced the location of major stream channels and the types of palesols that formed on overbank deposits. Facies distribution demonstrates that east-west-trending lineaments, which segment the Bighorn Mountains, extend into the basin and were active faults during the early Eocene. The lithologic heterogeneity is attributed to differential crustal subsidence on either side of the lineament. Vertical changes in lithology record temporal variability in basin subsidence rates. Subsidence rates slowed over time producing brighter mudstones (more mature paleosols) higher in the section and changes in carbonaceous shale type and abundance. The location of major channel sand bodies also appears to have shifted westward over time. Fluvial Willwood rocks arc capped by the lacustrine Tatman Formation in certain parts of the basin. TM images suggest that the north-south extent of the lake deposits was determined by the location of several of the lineaments.

• OSTI ID: 6935558
• Report Number(s): CONF-900605-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC FORMATIONS
MAPPING
REMOTE SENSING
ALLUVIAL DEPOSITS
LITHOLOGY
SEDIMENTARY BASINS
SHALES
STRATIGRAPHY
TERTIARY PERIOD
WYOMING
CENOZOIC ERA
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
NORTH AMERICA
ROCKS
SEDIMENTARY ROCKS
USA
580000* - Geosciences