Recurrent faulting and petroleum accumulation, Cat Creek Anticline, central Montana
- Illinois State Geological Survey, Champaign (United States)
The Cat Creek anticline, scene of central Montana's first significant oil discovery, is underlain by a south-dipping high-angle fault (Cat Creek fault) that has undergone several episodes of movement with opposite sense of displacement. Borehole data suggest that the Cat Creek fault originated as a normal fault during Proterozoic rifting concurrent with deposition of the Belt Supergroup. Reverse faulting took place in Late Cambrian time, and again near the end of the Devonian Period. The Devonian episode, coeval with the Antler orogeny, raised the southern block several hundred feet. The southern block remained high through Meramecian time, then began to subside. Post-Atokan, pre-Middle Jurassic normal faulting lowered the southern block as much as 1,500 ft. During the Laramide orogeny (latest Cretaceous-Eocene) the Cat Creek fault underwent as much as 4,000 ft of reverse displacement and a comparable amount of left-lateral displacement. The Cat Creek anticline is a fault-propagation fold; en echelon domes and listric normal faults developed along its crest in response to wrenching. Oil was generated mainly in organic-rich shales of the Heath Formation (upper Chesterian Series) and migrated upward along tectonic fractures into Pennsylvanian, Jurassic, and Cretaceous reservoir rocks in structural traps in en echelon domes. Production has been achieved only from those domes where structural closure was retained from Jurassic through Holocene time.
- OSTI ID:
- 6006377
- Report Number(s):
- CONF-9107109-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:6; Conference: American Association of Petroleum Geologists (AAPG) Rocky Mountain Section meeting, Billings, MT (United States), 28-31 Jul 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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58 GEOSCIENCES
MONTANA
PETROLEUM DEPOSITS
GEOLOGIC TRAPS
ANTICLINES
CARBONIFEROUS PERIOD
CRETACEOUS PERIOD
GEOLOGIC FAULTS
GEOLOGIC HISTORY
JURASSIC PERIOD
RESERVOIR ROCK
TECTONICS
DEVELOPED COUNTRIES
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FRACTURES
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MESOZOIC ERA
MINERAL RESOURCES
NORTH AMERICA
PALEOZOIC ERA
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USA
020200* - Petroleum- Reserves
Geology
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580000 - Geosciences