HYPOGENE KARST AND SUFLATE DIAGENESIS OF THE DELAWARE BASIN: SOUTHEASTERN NEW MEXICO AND FAR WEST TEXAS By Kevin Wayne Stafford A dissertation submitted to the faculty of New Mexico Institute of Mining and Technology in partial fulfillment of the requirements for the Degree of Doctorate of Philosophy in Geology in the Department of Earth and Environmental Science Socorro, New Mexico May 2008 ABSTRACT Hypogene speleogenesis is widespread throughout the Delaware Basin region as evidenced by intrastratal dissolution, hypogenic caves and suites of diagenetic minerals. The world famous carbonate caves of the Capitan reef facies of the Guadalupe Mountains have long been associated with sulfuric acid processes and recently have been associated with semi-confined, hypogene dissolution. However, evaporite karst within Permian backreef and basin-filling facies has been traditionally associated with surficial, epigene processes. On the eastern edge of the Delaware Basin cavernous porosity associated with oil reservoirs in Permian carbonates have been attributed to eogenetic karst processes. Interbedded (evaporite / carbonate), backreef facies within the Seven Rivers Formation exhibit characteristics of hypogene dissolution associated with semi-confined dissolution controlled by the eastward migration and entrenchment of the Pecos River. Coffee Caves is a classic example of hypogene dissolution, forming a multi-storey, rectilinear maze with abundant morphologic features suites (i.e. risers, channels and cupolas) indicative of hypogene speleogenesis. Other caves within the Seven Rivers and Rustler Formations show similar patterns, yet often less developed. Within the Delaware Basin, Castile Formation evaporites have been extensively modified by hypogene processes. Field mapping coupled with GIS analyses clearly shows karst development and evaporite calcitization are highly clustered throughout the iii outcrop area. Individual caves commonly exhibit complex morphologies, including complete suites of morphologic features indicative of intrastratal dissolution. Clusters of hypogene caves are commonly associated with clusters of evaporite calcitization and often occurrences of secondary selenite bodies, suggesting all three are genetically related. Brecciated cores and associated native sulfur deposits indicate that calcitized occurrences are the result of semi-confined sulfate reduction in the presence of ascending hydrocarbons. Hypogene caves are currently being overprinted by epigene processes as surface denudation results in breaching of previously confined solutional conduits. However, castile buttes stand as resistant masses attesting to the widespread importance of hypogene processes within the Castile Formation. On the Central Basin Platforms southern end, the spatial distribution of cavernous porosity, secondary mineralization and abundant karst fabrics within the carbonate strata of the Yates Field all provide convincing evidence that karst porosity, at least locally, within the San Andres and overlying Permian strata is the result of hypogene speleogenesis. Porosity development appears to have been enhanced by high geothermal gradients and the addition of sulfuric acid-rich fluids, reminiscent of the same processes that have been recently proposed for the extensive carbonate caves of the Guadalupe Mountains. Recognition of the widespread occurrence of hypogene speleogenesis throughout the Delaware Basin region indicates that the regional diagenetic evolution has been significantly affected by confined fluid migration, including not only the development of porosity but also the emplacement of many secondary mineral deposits. This indicates that future natural resource management plans must consider the nature of hypogene karst iv in site evaluations throughout the region in order to better predict geohazards, potential groundwater contamination and characterize mineral resources. v ACKNOWLEDGEMENTS This author expresses his gratitude to the many people who have provided support and assistance through the course of this project. This project would not have been possible without the support of funding agencies. This includes grants from the American Association of Petroleum Geologist (Mimi Atwater Memorial Grant), Geological Society of America, New Mexico Geological Society and New Mexico Tech Graduate Student Association. Special thanks to the National Cave and Karst Research Institute for scholarship support for my graduate studies. Thanks to all of the private land owners and ranchers in Texas that provided gracious access to their land throughout this study, including: Jack Blake, Draper Brantley, Stanley Jobe, Lane Sumner, and Clay Taylor. Thanks to all of the individuals that assisted with fieldwork and the mapping of caves within the study area, including: Goshia Allison, Stan Allison, Paul Burger, Megan Curry, Jon Jasper, Jim Kennedy, Lucas Middleton, Laura Rosales-Lagarde, Charley Savvas, Pat Seiser, Bev Shade and Vickie Siegel. Thanks to the Carlsbad Bureau of Land Management for their assistance with research within New Mexico, specifically the assistance of Dave Belski, Jim Goodbar, and Jon Jasper. ii Thanks to Tim Hunt for his assistance and land access to University of Texas Lands within the study area. Thanks to fellow graduate students Megan Curry and Laura Rosales-Lagarde for the many productive discussions we had over the course of our graduate studies. Thanks to Gary Axen, Bruce Harrison, Lewis Land and Dana Ulmer-Scholle for their useful guidance and support throughout this project as committee members. Thanks specifically to my advisor Penny Boston for her continued support of my research even though it falls outside of her primary fields of study. She has helped expand my realm of interests beyond purely terrestrial pursuits, opening up new avenues of research. Special thanks to Ray Nance and Alexander Klimchouk. Ray Nance provided invaluable support throughout this research as we discussed ideas on countless trips to the field. Alexander Klimchouk of the Ukrainian Institute of Speleology provided invaluable mentoring throughout this project, fueling my interest in hypogene processes. iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS LIST OF TABLES LIST OF FIGURES PREFACE CHAPTER I. INTRODUCTION Delaware Basin Speleogenesis Calcium Sulfate Diagenesis Overview II. EVAPORITE SPELEOGENESIS OF THE GYPSUM PLAIN: NEW MEXICO AND FAR WEST TEXAS Abstract Introduction Geologic Setting Northern Gypsum Plain: San Andres Formation Central Gypsum Plain: Seven Rivers Formation East Central Gypsum Plain: Rustler Formation Southern Gypsum Plain: Castile Formation Minor Regions Within New Mexico Other Evaporite Karst Manifestations Evaporite Karst Speleothems Summary III. HYPOGENIC SPELEOGENESIS WITHIN SEVEN RIVERS EVAPORITES: COFFEE CAVE, EDDY COUNTY, NEW MEXICO Abstract iv Page Introduction Geologic Setting Hydrologic Setting Hypogenic Speleogenesis Coffee Cave Discussion Conclusions Acknowledgements IV. CASTILE EVAPORITE KARST POTENTIAL MAP OF THE GYPSUM PLAIN, EDDY COUNTY, NEW MEXICO AND CULBERSON COUNTY, TEXAS: A GIS METHODOLOGICAL COMPARISON Abstract Introduction Geologic Setting Field Studies GIS Analyses Discussion Conclusions Acknowledgements V. EPIGENE AND HYPOGENE GYPSUM KARST MANIFESTATIONS OF THE CASTILE FORMATION: EDDY COUNTY, NEW MEXICO AND CULBESON COUNTY, TEXAS, USA Abstract Introduction Study Area Castile Karst Surficial Karst Epigene Caves Hypogene Caves Intrastratal Breccia Discussion and Conclusions Acknowledgements VI. HYPOGENE SPELEOGENETIC CALCITIZATION: LIMESTONE BUTTES OF THE CASTILE FORMATION, DELAWARE BASIN Abstract Introduction Geologic Setting v Page Evaporite Calcitization Calcitization Occurrences in the Castile Formation Speleogenesis in the Delaware Basin Discussion and Conclusions Acknowledgements VII. NEW INSIGHTS INTO YATES FIELD RESERVOIR CHARACTERIZATION: HYPOGENIC ORIGIN FOR CAVERNOUS POROSITY Abstract Introduction Speleogenesis: Three Basic Models Syngenetic Karst: Eogenesis Hypogenic Karst: Mesogenesis and Early Telogenesis Epigenic Karst: Late Telogenesis Geologic Setting Karst Development: Regional and Local Karst Manifestations Surficial Manifestations within the Permian Basin Region Yates Field: Caves and Secondary Porosity Yates Field: Secondary Mineralization Speleogenetic Models for the Yates Field Island Karst Model: 20th Century Theory of Yates Field Speleogenesis Hypogenic Karst Model: 21st Century Theory of Yates Field Speleogenesis Conclusions: Evolution of Speleogenetic Concepts Acknowledgements VIII. CONCLUSIONS AND IMPLICATIONS Delaware Basin Hypogene Speleogenesis Implications for Natural Resource Management Implications for Future Research REFERENCES CITED APPENDIX vi LIST OF FIGURES FIGURE Page I.1 Map showing location of the Delaware Basin and extent of the Capitan Reef (blue) that defines the boundary of the basin (adapted from Hill, 1996) I.2 Map showing the configuration of the Delaware Basin, Midland Basin and Central Basin Platform during Guadalupian time (~270-259 mya) (from Scholle et al., 2004) I.3 Speleogenesis in relation to burial diagenesis (adapted from Klimchouk, 1996) I.4 Calcium sulfate mineral conversion associated with diagenesis (modified from Murray, 1964) II.1 Map showing outcrop regions of gypsum formations in New Mexico and Far West Texas II.2 Diagramatic representation of Permian formations (Leonardian through Ochoan) associated with the Guadalupe Mountains II.3 Scaled comparison of the 16 caves discussed in detail in the manuscript and a typical