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A sequence-stratigraphic framework for the Upper Devonian Woodford Shale, Permian Basin, west Texas

Hemmesch, N.T.; Harris, N.B.; Mnich, C.A.; Selby, D.

A sequence-stratigraphic framework for the Upper Devonian Woodford Shale, Permian Basin, west Texas Thumbnail


Authors

N.T. Hemmesch

N.B. Harris

C.A. Mnich



Abstract

Criteria for recognizing stratigraphic sequences are well established on continental margins but more challenging to apply in basinal settings. We report an investigation of the Upper Devonian Woodford Shale, Permian Basin, west Texas based on a set of four long cores, identifying sea level cycles and stratigraphic sequences in an organic-rich shale. The Woodford Shale is dominated by organic-rich mudstone, sharply overlain by a bioturbated organic-poor mudstone that is consistent with a second-order eustatic sea level fall. Interbedded with the organic-rich mudstone are carbonate beds, chert beds, and radiolarian laminae, all interpreted as sediment gravity-flow deposits. Bundles of interbedded mudstone and carbonate beds alternate with intervals of organic-rich mudstone and thin radiolaria-rich laminae, defining a 5–10 m (16–33 ft)-thick third-order cyclicity. The former are interpreted to represent highstand systems tracts, whereas the latter are interpreted as representing falling stage, lowstand, and transgressive systems tracts. Carbonate beds predominate in the lower Woodford section, associated with highstand shedding at a second-order scale; chert beds predominate in the upper Woodford section, responding to the second-order lowstand. Additional variability is introduced by geographic position. Wells nearest the western margin of the basin have the greatest concentration of carbonate beds caused by proximity to a carbonate platform. A well near the southern margin has the greatest concentration of chert beds, resulting from shedding of biogenic silica from a southern source. A well in the basin center has little chert and carbonate; here, third-order sea level cycles were primarily reflected in the stratigraphic distribution of radiolarian-rich laminae.

Citation

Hemmesch, N., Harris, N., Mnich, C., & Selby, D. (2014). A sequence-stratigraphic framework for the Upper Devonian Woodford Shale, Permian Basin, west Texas. AAPG Bulletin, 98(1), 23-47. https://doi.org/10.1306/05221312077

Journal Article Type Article
Acceptance Date May 22, 2013
Publication Date Jan 1, 2014
Deposit Date Apr 23, 2014
Publicly Available Date Jan 19, 2015
Journal AAPG Bulletin
Print ISSN 0149-1423
Electronic ISSN 1558-9153
Publisher American Association of Petroleum Geologists
Peer Reviewed Peer Reviewed
Volume 98
Issue 1
Pages 23-47
DOI https://doi.org/10.1306/05221312077