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Depositional history of Lower Permian (Wolfcampian-Leonardian) carbonate buildups, Midland Basin, Upton County, Texas
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A north-south oriented trend of Wolfcampian-Leonardian carbonate buildups is located in the southwestern Midland Basin, Upton County, Texas. The buildup trend is located west of the eastern faulted margin of the Central Basin Platform and north of the Ozona Arch. This trend was deposited during late Paleozoic time, just after major uplift of the Central Basin Platform and as the Midland Basin subsided. Chevron U.S.A. Production Company has actively explored for petroleum in the buildup trend since the early 1980s and loaned their data set to Texas A&M University for this study. The carbonate buildups lie stratigraphically within the Eddleman and Amacker formations. The Eddleman (middle Wolfcampian (PW-2)-late Wolfcampian (PW-3)) and smacker (early Leonardian (PL-1)-early middle Leonardian (PL-2-A)) formations are composed of varying amounts of shallow-water skeletal limestones, matrix-supported limestones, lithoclastic facies, and minor boundstone facies. Dominant grain types include dasycladacean green algae, Tubiphytes, phylloid algae, crinoids, fusulinids, foraminifera, and coated grains. Carbonate deposition begins during lowstand times within or just below wave base in a low energy environment. Separating the two carbonate units is a basibal dark-colored calcareous shale known informally as the Twenty-one formation (late Wolfcampian) that was deposited during a rapid relative sea-level rise. The Tippett shale overlies the Amacker formation and consists of transgressive, basibal, dark-colored calcareous shale that terminated carbonate deposition in the southwestern Midland Basin during early middle Leonardian time. Two basic types of carbonate buildups, skeletal-sand and carbonate-debris, have been identified in this interval. The buildups formed on a ramp-like depositional profile with subtle paleobathymetric highs and lows that were created by mostly post-strewn (middle Pennsylvanian) deformation. The importance of the paleohighs and lows is that the cleaner skeletal-sand buildups initiated growth within the paleolows, and the carbonate-debris buildups (largely sediment gravity-flow deposits) were deposited on paleohighs. The skeletal-sand buildups created synoptic relief during Leonardian time that forced sediment gravity-flows to move between the buildups. This resulted in the abrupt lateral facies transitions within the Eddleman-Amacker interval. Understanding the depositional history of this carbonate buildup trend is important for establishing models for carbonate deposition in the southwestern Midland Basin, where active deformation, rapid subsidence, and major sea-level fluctuations influenced sedimentation.
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Includes bibliographical references (leaves 109-116).
Issued also on microfiche from Lange Micrographics.
Merriam, Catherine O'Hara (1999). Depositional history of Lower Permian (Wolfcampian-Leonardian) carbonate buildups, Midland Basin, Upton County, Texas. Master's thesis, Texas A&M University. Available electronically from
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