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Laminated black shale-chert cyclicity in Woodford Formation (Upper Devonian of southern Mid-Continent)

Conference · · AAPG Bull.; (United States)
OSTI ID:5797243

The Woodford formation, a known hydrocarbon source rock, is contemporaneous with other mid-Paleozoic (Frasnian to Tournasian) black shales occurring throughout North America and Europe. Much of the Woodford formation in outcrop along the southern flank of the Arbuckle uplift (Carter County, Oklahoma) consists of rhythmic alternating beds of laminated black shale and chert. A time series analysis of the chert-black shale couplets displays an approximately 20-ka periodicity, suggesting that deposition was controlled by external orbital forcing of the earth (Milankovitch cyclicity). Total organic carbon ranges from 3 to 9% in the chert and from 10 to 28% in the black shale; carbonate carbon content is essentially zero. Carbon isotope (/delta//sup 13/C = /minus/ 29 per mil), pyrolysis-gas chromatography, and Rock-Eval Analyses indicate that the kerogen is of marine origin and is oil-prone type II. Except for the difference in organic carbon contents, the kerogens of the chert-black shale couplets are analytically similar.

Research Organization:
Univ. of Texas at Dallas, Richardson (USA)
OSTI ID:
5797243
Report Number(s):
CONF-880301-
Journal Information:
AAPG Bull.; (United States), Journal Name: AAPG Bull.; (United States) Vol. 72:2; ISSN AABUD
Country of Publication:
United States
Language:
English