Foreland structure - Beartooth Mountains, Montana and Wyoming
- Exodus - Exploration, Inc., Billings, MT (United States)
Analysis of public drilling records from the AMOCO Beartooth Number 1 and 1 A sidetrack boreholes (SW1/4, SE1/4, Section 19, T.8 S., R.20 E., Carbon County, Montana) continues. Several additional inferences are made about this large foreland structure, and subsequent interpretation of the structural model of the northeast corner of the Beartooth Mountain Block and structural relationship with the Big Horn Basin. The structure is described as a large recumbent to sub-horizontal, synclinal fold with the overturned upper limb out diagonally by the Beartooth Thrust or Thrust Zone and a complex thrust fault zone below the Beartooth Thrust. The single recorded dip angle and direction of the Beartooth Thrust at depth was 19 degrees to the northwest(?). The dipmeter dip angle on the Beartooth Thrust, 19 degrees, validates foreland structural theory of decreasing dip angles at a vertical depth of 8,232 feet (2,509 m), in the Precambrian crystalline basement. The northwest dip direction may be attributable to secondary structural folding. The record of northwest, southeast, and southwest dip of bedding surfaces and faults in sections of the overturned upper limb, in both boreholes, suggests possible, less intense secondary folding, after thrust fault deformation. Given the overall geometry of this large foreland structure, there is little doubt that the average direction of maximum principal stress (sigma 1) was oriented in a northeast - southwest direction.
- OSTI ID:
- 272610
- Report Number(s):
- CONF-9607116-; ISSN 0149-1423; TRN: 96:003409-0019
- Journal Information:
- AAPG Bulletin, Vol. 80, Issue 6; Conference: American Association of Petroleum Geologogists (AAPG) Rocky Mountain section meeting, Billings, MT (United States), 28-31 Jul 1996; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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