SUBSURFACE GEOLOGY OF ARSENIC-BEARING PERMIAN SEDIMENTARY ROCKS IN THE GARBER-WELLINGTON INTERVAL OF THE CENTRAL OKLAHOMA AQUIFER, CLEVELAND COUNTY, OKLAHOMA By BEN NICHOLAS ABBOTT Bachelor of Science Oklahoma State University Stillwater, Oklahoma 2002 Submitted to the Faculty of the Graduate College of Oklahoma State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December, 2005 SUBSURFACE GEOLOGY OF ARSENIC-BEARING PERMIAN SEDIMENTARY ROCKS IN THE GARBER-WELLINGTON INTERVAL OF THE CENTRAL OKLAHOMA AQUIFER, CLEVELAND COUNTY, OKLAHOMA Thesis Approved: Stanley T. Paxton Thesis Advisor James Puckette Surinder Sahai Gordon Emslie Dean of the Graduate College ii COPYRIGHT By Ben Nicholas Abbott December, 2005 iii ACKNOWLEDGEMENTS I wish to express my sincerest gratitude to my advisor, Dr. Stan Paxton, whose help was invaluable and instrumental to the completion of this thesis. I also would like to thank my committee, Dr. Jim Puckette and Dr. Surinder Sahai for their assistance. Jim Roberts’ help and expertise were priceless. And this thesis would certainly not have been possible without support from the EPA. Finally, thanks to my lovely wife, Erin Abbott, for putting up with me during the course of this work. iv TABLE OF CONTENTS Chapter Page I. INTRODUCTION………………………………….……………………..…………1 II. PURPOSE AND OBJECTIVES…………………….……………..………………..6 III. BACKGROUND AND PREVIOUS WORK………………………….….………...8 General Geology…………………………………………………………………8 Hydrogeology…………………………………………………………………...16 IV. METHODOLOGY……….……………………………………….………………..28 Data Acquisition and Interpretation…….………………….…….………....…...28 Construction of Maps and Cross Sections………………….….….……………..35 V. RESULTS AND DISCUSSION……………………………….….………………...38 Well Log Data Summary………………………………………………………...38 Maps…………………………………………………………………..……........39 Large Scale Cross Sections.……….……………………………………….…….50 Small Scale Cross Sections and Well Log Response Patterns…………………..50 VI. CONCLUSIONS AND SUGGESTIONS FOR FUTURE WORK…………….…..59 REFERENCES CITED………………………………………………………………….62 APPENDICES…………………………………………………………………………...64 APPENDIX A – WELL HEADER DATA……………………………………...65 APPENDIX B – FORMATION TOP DATA ………………………….……….74 APPENDIX C – NORMAN WATER WELL DATA…………………………..85 APPENDIX D – UNIVERSITY OF OKLAHOMA WATER WELL DATA….93 APPENDIX E – GARBER-WELLINGTON CONTACT STUDY……………102 v LIST OF TABLES Table Page 1. Summary Statistics for OU and Norman Wells……………………………………….46 vi LIST OF FIGURES Figure Page 1. Location Map, Central Oklahoma Aquifer……………………………………...…….2 2. Stratigraphic Column, Central Oklahoma Aquifer………………………....…...…….5 3. Garber Sandstone Map and Cross Section (1928)...………………………….....…...21 4. Oklahoma City Anticline and Associated Structures (1968)….…...………………...22 5. Positions of Gamma Ray Cutoff Lines……………………………………....………31 6. Type Log, Garber-Wellington Aquifer……………………………………..…..........34 7. Type Log, Garber Sandstone……………………………………………..………….34 8. Comparison of OU and Norman Water Wells……………………………………….46 9. Histograms, Units A, B, and C, Net Clean Sandstone Content……………..….……47 10. Histograms, Units A, B, and C, Percent Clean Sandstone Content……………….…48 11. Histograms, Units A, B, and C, Percent Shaly Sandstone Content…………...…..…49 12. Location of Large Scale Cross Sections……………………………………………..51 13. Location of Small Scale Cross Sections……………………………………………..52 14. Detail of Cross Section H-H’………………………………………………………...54 15. Detail of Cross Section D-D’………………………………………………………...54 16. Potential Arsenic Zones Map…………………………………………………….…..61 vii LIST OF PLATES Plate 1. Base Map..……………………………………………………………………..In Pocket 2. Structure Map, Top of Garber Sandstone and Garber Isopach…………….….In Pocket 3A. Garber Lithofacies Maps……….......…………………………….…….……In Pocket 3B. Percent Shaly Sandstone Map with Arsenic Overlay………….………….…In Pocket 4. Residual Trend Structure Maps…......................................................................In Pocket 5. Unit A: Isopach Map, Net Clean Sandstone Map, Percent Clean Sandstone Map, Percent Shaly Sandstone Map………………...………………………….In Pocket 6. Unit B: Isopach Map, Net Clean Sandstone Map, Percent Clean Sandstone Map, Percent Shaly Sandstone Map…...……………………………………….In Pocket 7. Unit C: Isopach Map, Net Clean Sandstone Map, Percent Clean Sandstone Map, Percent Shaly Sandstone Map……………...…………………………….In Pocket 8. Cross Section Line Map..……………………………………………………...In Pocket 9. Cross Sections X-X’ and Y-Y’………………………………………………...In Pocket 10. Cross Sections A-A’ and B-B’…………….………………………...……….In Pocket 11. Cross Sections C-C’ and D-D’…………..…………………………………...In Pocket 12. Cross Sections E-E’ and F-F’………………………………………………...In Pocket 13. Cross Sections G-G’ and H-H’………..……………………………………...In Pocket viii I. INTRODUCTION As an important source of drinking water in central Oklahoma, the Central Oklahoma Aquifer (COA) has been the focus of much attention in recent years because of elevated levels of naturally occurring arsenic. The City of Norman, located in Cleveland County, Oklahoma (Figure 1), obtains its groundwater from the Garber- Wellington portion of the Central Oklahoma Aquifer; Norman has the second highest levels of naturally occurring arsenic in drinking water in the United States, exceeded only by Albuquerque, NM. In 2006, the Environmental Protection Agency (EPA) will lower the maximum allowable limit of arsenic in drinking water from the current level of 50 ppb to 10 ppb; numerous wells currently producing from the Central Oklahoma Aquifer will not meet the new standard. The City of Norman would like to remediate the arsenic- in-drinking-water-problem so that city wells will not have to be taken off line. The city is also trying to avoid the expense of surface treatment techniques. OSU, in conjunction with the EPA and the United States Geological Survey (USGS), is evaluating remediation techniques and preparing preventative guidelines to the City of Norman and other municipalities that obtain their drinking water from the Central Oklahoma Aquifer. Previous work by the USGS has indicated that arsenic concentration may be proportional to the volume of shale in a wellbore (Schlottmann et al., 1998). Therefore, some approaches to achieving the goal of lowered arsenic levels are: 1) selective production 1 Central Oklahoma Aquifer Norman I Ouachita I Uplift I I 0 50 100 MILES 0 50 100 KILOMETERS ~ Figure 1. Location map of the Central Oklahoma Aquifer and surrounding geologic features (modified after George N. Breit, The Diagenetic History of Permian Rocks in the Central Oklahoma Aquifer, in USGS Water-Supply Paper 2357-A) 2 of water from low arsenic stratigraphic intervals; 2) squeezing off high-arsenic intervals in existing wells; and 3) drilling new wells in areas with low arsenic potential. In order to implement these approaches, the need arises for subsurface mapping of the Garber- Wellington Aquifer, in terms of lithofacies (sandstone, shale, shaly sandstone) and sediment packages. This work should provide a better understanding of the Garber Sandstone and Wellington Formation not only with respect to arsenic, but also with respect to the depositional system from which the rocks originated. To fulfill the need for better definition of the geology of the Garber-Wellington Aquifer, this study, along with two other OSU graduate theses, begins to establish a geologic-stratigraphic framework for this part of the COA. With the exception of Quaternary fluvial terrace deposits, all rocks in the Central Oklahoma Aquifer are Permian (Artinskian, formerly Leonardian) aged. The Garber Sandstone and the Wellington Formation are the most significant water-bearing units in the Central Oklahoma Aquifer; other formations in the COA are the underlying Council Grove, Chase, and Admire Groups. The aquifer is overlain and in some places confined by the Hennessey Shale and underlain by the Pennsylvanian Vanoss Formation (Figure 2). The Garber Sandstone and the underlying Wellington Formation consist of amalgamated lenticular fluvial sandstones interbedded with mudstones, siltstones, and some conglomerates (Breit et al., 1990). Previous work by the U.S. Geological Survey has shown that arsenic content in the Garber-Wellington Aquifer is a function of grain- size, i.e., arsenic concentration is higher where the rocks are finer-grained (Schlottmann et al., 1998). It has also been suggested by the USGS that arsenic is elevated in sandstones isolated by finer-grained rocks, due to a lack of flushing-out of these rocks. 3 In this study, the Garber-Wellington Aquifer was analyzed in terms of the geometry, continuity, and spatial distribution of different lithofacies. The two other OSU theses focus on the physical properties of the rocks, especially outcrop gamma-ray measurements, grain size analyses, and whole-rock geochemistry (Gregory Gromadzki), and outcrop description and mapping (Kathy Kenney). These three studies are intended to complement each other and enhance understanding of arsenic distribution in the Garber-Wellington Aquifer through integration of both surface and subsurface work. 4 Hennessey Shale i---:...----==--------=== - - l L..._. ---~- •• Garber Sandstone and Wellington Formation i---:...----==-- ·o o b. = (\ PERMIAN Central Oklahoma Aquifer Council Grove, Chase, and Admire Groups ,Ir PENNSYLVANIAN Vanoss Formation .:....,.· . ... - Figure 2. Stratigraphic column of the Central Oklahoma Aquifer (modified after George N. Breit, The Diagenetic History of Permian Rocks in the Central Oklahoma Aquifer, in USGS Water-Supply Paper 2357-A) 5 II. PURPOSE