Faulting of Eocene rocks in the central Bighorn Basin of Northwest Wyoming : possible implications /
Analysis and interpretation of geological and geophysical
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736824551&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Analysis and interpretation of geological and geophysical data available for the central Bighorn Basin suggest the presence of an E-W-trending wrench fault zone in the vicinity of Tatman Mountain, referred to as the Fenton Pass Fault Zone (FPFZ). A NW-trending seismic profile, oriented at a high angle to the wrench fault, displays a positive flower structure with a series upward and outward branching faults connected to a zone of subvertical faults which appear to offset Precambrian basement along a zone approximately 6.4 to 8 km (4-5 miles) wide. The zone of basement wrench fault offset appears to be located beneath and parallel to the four E-W-trending Pleistocene terraces of Tatman Mountain. These observations correlate with the E-W-trending anomalies interpreted from residual aeromagnetic data acquired for the central basin area. A series of NE-trending faults initially field mapped in this area appears to be genetically related to the existence of the E-W-trending wrench fault zone. Additional mapping over a wider area, using Landsat Thematic Mapper imagery, indicates a pattern of interconnected surface faults which resemble the geometry of R, R' and P shears as mapped in other wrench fault zones. The various orientation of the shears (faults), which are largely confined within the E-Wtrending FPFZ, suggests left-lateral displacement has occurred regionally across large segment of the central Bighorn Basin. Analysis of a series of parallel, NE-oriented seismic profiles that extend across the E-W-trending wrench fault zone has identified local leftlateral offset of specific basement thrust locations within the central basin. The apparent offset along the Worland Trend is on the order of 0. 8 to 1. dc lines provide enough data to construct a relatively detailed map of basement faults across the Tatman Mountain- central basin area. Interpretation of the basement fault map suggests that the locations of E-W-trending wrench fault offsets of NW-trending thrusts, such as at the Worland Trend, could represent a series of "quasipiercing points", indicating the direction and magnitude of lateral displacement. The magnitude of left-lateral offset of the NW-trending Worland Trend appears to be significantly greater than the amount of local crustal shortening, suggesting that the timing of the lateral offset (along the FPFZ) and basement thrusting are not strictly coeval. Nevertheless, thrusting and left-lateral wrench fault movement appear to be somehow genetically related to Laramide deformation of the central Bighorn Basin, possibly with wrench fault offset of the thrust fault front occurring during latest-Laramide. |
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| Item Description: | Vita. "Major Subject: Geology". Maps in pocket. |
| Physical Description: | viii, 89 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 81-87. |