Meteoric diagenesis and fluid-rock interaction in the Middle Permian Capitan backreef: Yates Formation, Slaughter Canyon, New Mexico

This study examines the geochemical record of diagenesis in the Middle Permian Yates shelf, exposed in Slaughter Canyon, New Mexico. This diagenetic history significantly modified lithologies, depositional fabrics, and pore systems. Early diagenesis was dominated during sea level highstands by marine cementation and reflux dolomitization, and during sea level lowstands by meteoric cementation and stabilization—the focus of this study. This early diagenesis variably overprinted primary marine isotopic signatures, potentially leading to erroneous chemostratigraphic correlations or paleoclimate reconstructions. Four correlative sections through one m-scale cycle were analyzed for their δ13C and δ18O values. They show significant (2–4‰) δ13C and δ18O variability in coeval, texturally wellpreserved calcites. The δ13C and δ18O values of marine cements, brachiopods, bulk carbonate, micritic matrix, and the first generation of meteoric spar (from high to low values) delineate an “inverted J curve,” indicating the variable alteration of components by diagenetic fluids. Numerical models indicate that the observed stable isotope trend is most consistent with diagenetic alteration in a partially closed system by meteoric fluids mixed with a progressively diminishing contribution of recycled marine waters. In the Yates shelf, marine cements provide a more robust primary isotopic record than micritic matrix; however, neither preserves primary seawater isotopic values. Furthermore, common criteria used to diagenetically screen samples proved inadequate (e.g., textural preservation, staining, luminescence, depletion near Copyright ©2014. The American Association of Petroleum Geologists. All rights reserved. Manuscript received October 25, 2011; provisional acceptance August 28, 2012; revised manuscript received November 30, 2012; final acceptance May 20, 2013. DOI: 10.1306/05201311158 AUTHORS James W. Bishop ∼ Carbonate Stratigraphy R&D, Chevron Energy Technology Company, 1500 Louisiana Street, Houston, Texas; [email protected] James W. Bishop is in the carbonate research group at Chevron Energy Technology Company. He joined Chevron in 2008 and has also worked in new ventures and exploration, in the Middle East and in the deep-water Gulf of Mexico. He earned a Ph.D. and an M.S. degree from the University of California Davis in sedimentology and stratigraphy. David A. Osleger ∼ Department of Geology, University of California Davis, Davis, California; [email protected] David A. Osleger is a tenured lecturer in the Geology Department at the University of California Davis. His research interests include orbital stratigraphy, sea level history, carbonate platform architecture, and lacustrine sedimentation. Recent projects include the paleoclimate history of the High Sierra as deduced from Lake Tahoe sediment cores. Isabel P. Montañez ∼ Department of Geology, University of California Davis, Davis, California; [email protected] Isabel P. Montañez is a professor of geology at the University of California Davis. Her research focuses on the deep-time geologic archives of major climate transitions. She received her Ph.D. from Virginia Tech, was awarded the James Lee Wilson Young Scientist Award and Outstanding Paper awards from SEPM and AAPG (Cam Sproule Award), was an AAPG Distinguished Lecturer, and is a recent Guggenheim Fellow. Dawn Y. Sumner ∼ Department of Geology, University of California Davis, Davis, California; [email protected] Dawn Y. Sumner is a professor of geology who uses carbonate stratigraphy, petrography, and three-dimensional visualization techniques to understand the evolution of microbial life. Her research interests span Archean carbonates, AAPG Bulletin, v. 98, no. 8 (August 2014), pp. 1495–1519 1495 sequence boundaries). Instead, diagenetic resetting is resolved by analyzing multiple, closely spaced, independently correlated sections, and by delineating trends between primary and later diagenetic components in populations of isotopic data.