Middle Pennsylvanian (Desmoinesian) strata of the Lower Desert Creek (LDC) sequence within the sub-surface Greater Aneth Field (GAF) reflect a hierarchy of 4th and 5th order carbonate-dominated cycles. The Lower Desert Creek sequence, along the studied transect are composed of eight carbonate facies deposited on an east-facing shelf. There is a lateral transition from open marine algal buildup from the southeast (cores R-19, Q-16, O-16, and J-15) to a more restricted lagoonal environment to the northwest (core K-430 and E-313). The Lower Desert Creek sequence within the GAF contains three main parasequence sets: a basal, relatively deep-water unit (LDC 1), a middle skeletal to algal unit (LDC 2-4), and a shallow, open-marine/restricted lagoon unit (LDC 5-7). The southeast cores (R-19, Q-16, O-16, and J-15) contain the dolomitized basal unit in parasequence LDC 1. The northwest cores (K-430 and E-313) also contain the dolomitized basal unit in LDC 1, but show a deeper facies succession through LDC 2-4. Parasequences LDC 2-4 are the heart of the algal buildup in the GAF particularly in the southern part of the transect. The upper few parasequences (LDC 5-7) are dominated by an open marine environment represented by robust fauna. The upper parasequences (LDC 5-7) show the same shallowing upward trends with algal facies in K-430 and restricted lagoon facies in E-313. Shoaling upward trends that characterize the Lower Desert Creek sequence terminate with an exposure surface at the 4th order (Lower Desert Creek-Upper Desert Creek) sequence boundary. Porosity and permeability is weakly correlated to facies. Diagenesis within the algal reservoir is the most important factor in porosity and permeability. Marine diagenesis is observed in the form of micritization of Ivanovia, a phylloid algae. Thin fibrous isopachous rims of cloudy cement also indicate early marine diagenesis. Ghost botryoidal cements are leached during meteoric diagenesis. Meteoric drusy dog tooth cements as well as sparry calcite fill most depositional porosity. Neomorphism of micrite and the isopachous rim cements reflect meteoric diagenesis. Burial diagenesis is represented by baroque dolomite cement, compaction, and mold-filling anhydrite cement.



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Physical and Mathematical Sciences; Geological Sciences



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Lower Desert Creek, Paradox Formation, Paradox Basin, Reservoir Characterization, Petroleum Geology



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Geology Commons