Contrasting styles of fault control on position of pre-Dakota unconformity and on depositional environments of Dakota sandstone, northern San Juan basin, Colorado
- Geological Survey, Denver, CO (USA)
Detailed subsurface analyses of depositional environments and sandstone geometry of rocks from the upper part of the Upper Jurassic Morrison Formation through the Upper Cretaceous Dakota Sandstone indicate that faulting was a major control on distribution and preservation of lithofacies in the northern San Juan basin. The faults have a predominant northwest trend and were episodically active from Late Jurassic through early Late Cretaceous time. The main effect of faulting on the Morrison Formation and Lower Cretaceous Burro Canyon Formation was in the preservation and/or erosion of rock. These formations were uniformly deposited across the study area and then locally removed across horsts. Although depositional thinning of the Morrison occurs from west to east across the northern part of the basin, thickness differences (as much as 200 ft) between the Bridge Creek Limestone Member of the Mancos Shale and the Todilto Limestone of the Wanakah Formation cannot be solely attributed to regional thinning. Among closely spaced drill holes (1-3 mi apart) erosion is evidenced by thinning or local absence of the Burro Canyon and/or loss of section at the top of the underlying Morrison. The unconformity below the Dakota is not a simple regionally inclined surface from north to south across the San Juan basin. Rather, its development in the northern part of the basin is more intense on uplifted areas among a series of parallel northwest-trending vertical faults.
- OSTI ID:
- 5498539
- Report Number(s):
- CONF-8910195-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 73:9; Conference: AAPG Rocky Mountain Section meeting, Albuquerque, NM (USA), 1-4 Oct 1989; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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COLORADO
SANDSTONES
DEPOSITION
CRETACEOUS PERIOD
GEOLOGIC FORMATIONS
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SEDIMENTARY BASINS
SHALES
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CARBONATE ROCKS
DRILLING
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC STRUCTURES
MESOZOIC ERA
NORTH AMERICA
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SEDIMENTARY ROCKS
USA
020200* - Petroleum- Reserves
Geology
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