Woodford Shale (Upper Devonian-Lower Mississippian) and associated phosphate nodules
- Bridge Oil (U.S.A.) Inc., Dallas, TX (USA)
A deep-water marine environment is inferred for the Woodford Shale formation (Upper Devonian-Lower Mississippian) in the Arbuckle and Ouachita mountains of southern Oklahoma. Black shales and associated phosphate nodules were deposited peripherally to the carbonate shelf adjacent to the North American craton. Analysis indicates that shales and interbedded cherts lack siliciclastic detritus and shallow-water fauna, and that they have an abundance of siliceous organisms. Depletion of Ce in the Woodford Shale relative to average shale compositions suggests the influence of deep oceanic water. Carbon isotope compositions of shales, cherts, and phosphates for {delta}{sup 13}C range from {minus}27.5 to {minus}30.2 {per thousand}. These values are comparable to Devonian-Mississippian values reported for distal marine sediments that get successively lighter farther from shore. In-situ phosphate nodules occurring in the top of the formation are early diagenetic features that formed in the upper few centimeters of organic-rich sediment in a poorly oxygenated subaqueous environment. A hierarchy of apatite morphologies in nodules indicates stages of diagenesis. Structureless collophane probably is representative of primary marine apatite. Higher order apatite phases successively include globular collophane, botryoidal apatite, and apatite crystallites. The latter commonly is associated with silicified nodules. Silicification of phosphate nodules represents the most advanced stage of diagenesis prior to sediment lithification, and it implies that silica diagenesis within the Woodford occurred after nodules formed. Preserved radiolarians and sponge spicules observed in nodules also indicate that apatite precipitated before biogenic silica dissolved.
- OSTI ID:
- 6891768
- Report Number(s):
- CONF-9003145-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:2; Conference: American Association of Petroleum Geologists (AAPG) southwest section meeting, Wichita Falls, TX (USA), 11-13 Mar 1990; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Potential for producing oil and gas from the Woodford Shale (Devonian-Mississippian) in the southern mid-continent, USA
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Related Subjects
OKLAHOMA
PETROLEUM DEPOSITS
SOURCE ROCKS
DEPOSITION
BLACK SHALES
CARBON 13
CARBONIFEROUS PERIOD
DEVONIAN PERIOD
DIAGENESIS
GEOLOGIC FORMATIONS
ISOTOPE RATIO
PHOSPHATE ROCKS
BITUMINOUS MATERIALS
CARBON ISOTOPES
CARBONACEOUS MATERIALS
CHATTANOOGA FORMATION
ENERGY SOURCES
EVEN-ODD NUCLEI
FEDERAL REGION VI
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
ISOTOPES
LIGHT NUCLEI
MATERIALS
MINERAL RESOURCES
NORTH AMERICA
NUCLEI
OIL SHALES
PALEOZOIC ERA
RESOURCES
ROCKS
SEDIMENTARY ROCKS
STABLE ISOTOPES
USA
020200* - Petroleum- Reserves
Geology
& Exploration