Bedded cherts in the Early Ordovician Arbuckle Group of southwestern Oklahoma
- Texas Christian Univ., Forth Worth (United States)
Bedded cherts are a rarely occurring but environmentally significant facies in the Early Ordovician Arbuckle Group. Two such units have been identified: one in the Cool Creek Formation and one in the Kindblade Formation. In each, microcrystalline calcite and dolomite alternate in thin laminae with microcrystalline silica in units up to 25 cm in thickness. The areal extent of the bedded cherts encompasses more than 130 km{sup 2}. It is hypothesized that the interlaminated cherts and micrites were deposited in very shallow marine conditions. A relatively small part of the Oklahoma Aulacogen was cut off from open ocean circulation, resulting in an isolated lagoon. The chert/micrite couplets may represent seasonal deposits in the lagoon. During seasonal flooding, slightly deeper water resulted in algal growth with accompanying precipitation of carbonates and solution of detrital quartz sand. During the dry season, the dissolved silica precipitated, resulting in thin layers of microcrystalline chart. Some carbonate layers contain small pseudomorphs after what may have been gypsum and anhydrite crystals and nodules, indicating that salinities increased enough to permit formation of evaporites. At least ten couplets occur in the thickest units, suggesting that the lagoon existed for ten wet-dry seasons.
- OSTI ID:
- 7158901
- Report Number(s):
- CONF-910403--
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 75:3; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
CALCITE
CARBONATE MINERALS
CHERT
DEPOSITION
DEVELOPED COUNTRIES
DOLOMITE
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGY
MINERALOGY
MINERALS
NORTH AMERICA
OKLAHOMA
ORDOVICIAN PERIOD
PALEOZOIC ERA
PETROLOGY
ROCKS
SEASONAL VARIATIONS
SEDIMENTARY ROCKS
USA
VARIATIONS