The origin of anomalous carbonate units outcropping at the salt sediment interface of the southern end of Gypsum Valley Salt Wall, Paradox Basin, southwest Colorado

Allison Marie Mast, University of Texas at El Paso

Abstract

Understanding structural, stratigraphic, and petrographic complexities at the salt-sediment interface of diapirs has important implications in accurately assessing hydrocarbon reservoir quality and near-diapir trap geometries, and may aid in more accurate predictions for locating the true margin of salt in diapiric layered evaporites. The southwest margin of the exhumed Gypsum Valley Salt Wall, Paradox Basin, southwest Colorado, provides a rare view of this interface where onlapping and overlapping wedges of Late Permian and Jurassic halokinetic sequences overlie an angular unconformity truncating near-vertical, highly deformed carbonate beds formerly mapped as Pennsylvanian Honaker Trail Formation. This study investigates three possible alternative origins of these anomalous carbonates including: 1) lateral carbonate caprock; 2) large intrasalt clast of non-evaporite bearing Paradox Formation; and 3) lateral continuation of the Gypsum Valley megaflap. Detailed stratigraphic, petrographic, structural, and carbon and oxygen isotope datasets were collected in order to determine the origin of the carbonate units. Characteristics of the carbonate beds include: 1) location directly northwestward along strike of the Gypsum Valley megaflap: 2) composed of cycles of interbedded dolomitic shale and dolostone that resemble that of diagenetically altered upper Paradox Formation strata; 3) complicated intrastratal folding sub-parallel to the axis of the diapir; 4) division into three deformation zones (concordant, semiconcordant, and completely discordant) based on the degree of intrastratal deformation within the carbonate beds along strike of the Gypsum Valley megaflap. Based on these attributes the anomalous carbonate units are interpreted to be uppermost Paradox Formation cycles present in the northwestward extension of the Gypsum Valley megaflap. This end of the megaflap deformed prior to angular onlap of the Permian upper Cutler Formation and is thought to be associated with the process of halokinetic drape-folding that produced the Gypsum Valley megaflap.^

Subject Area

Geology|Sedimentary geology

Recommended Citation

Mast, Allison Marie, "The origin of anomalous carbonate units outcropping at the salt sediment interface of the southern end of Gypsum Valley Salt Wall, Paradox Basin, southwest Colorado" (2016). ETD Collection for University of Texas, El Paso. AAI10252431.
http://digitalcommons.utep.edu/dissertations/AAI10252431

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