Geologic and Hydrogeologic Framework of Regional Aquifers in the Twin Mountains, Paluxy, and Woodbine Formations near the SSC Site, North-Central Texas Topical Report by Alan R. Dutton, Robert E. Mace, H. Seay Nance, and Martina Bli.im Prepared for Texas N ational Research Laboratory Commission under Contracts No. IAC(92-93)-0301 and No. IAC 94-0108 Bu reau of Economic Geology Noel Tyler, Director The University of Texas at Austin University Station, Box X Austin, Texas 78713-7508 April 1996 QAe7128 Geologic and Hydrogeologic Framework of Regional Aquifers in the Twin Mountains, Paluxy, and Woodbine Formations near the SSC Site, North-Central Texas .I I, Topical Report I I I I by i i Alan R Dutton, Robert E. Mace, H. Seay Nance, and Martina Blum : ! __ J ' ' I ' Prepared for Texas National Research Laboratory Commission under Contracts No. IAC(92-93)-0301 and No. IAC 94-0108 Bureau of Economic Geology Noel Tyler, Director The University of Texas at Austin University Station, Box X Austin, Texas 78713-7508 April 1996 '' ' : I I - } r1 CONTENTS ABSTRACT ....................................................................................................................... 1 INTRODUCTION ............................................................................................................ 2 REGIONAL HYDROGEOLOGIC SETTING ................................................................ 7 Hydrologic Units .................................................................................................. 7 North-Central Texas Regional Aquifer System ............................................ 7 Regional Confining System............................................................................... 9 Surficial Aquifers ............................................................................................... 10 Regional Structure............................................................................................. 11 · Physiography, Climate, and Land Use ........................................................... 16 PREVIOUS GEOLOGIC STUDIES ............................................................................... 17 Trinity Group...................................................................................................... 19 Paluxy Formation .............................................................................................. 20 Woodbine Formation ....................................................................................... 22 PREVIOUS HYDROGEOLOGIC STUDIES ................................................................ 23 METHODS AND DATA ............................................................................................... 24 Stratigraphic Data............................................................................................... 24 Hydrologic Data ............ :..................................................................................... 26 Numerical Modeling of Ground-Water Flow ............................................. 29 Cross-Sectional Model .......................................................................... 32 Three-Dimensional Model .................................................................. 39 • l_ Model Size and Finite-Difference Grid ............... :···· .. ···········39 Boundary Conditions ................................................................ 39 Hydraulic Properties and Calibration ....................................44 Estimates of Pumping Rates:·························· .. ······ ................. 49 ,---. iii \ ,i I STRATIGRAPHY .......................................................................................................... .58 Stratigraphic Occurrences of Sandstone........................................................ 58 Description of Aquifer Units and Depositional Systems .......................... 59 Twin Mountains Formation ............................................................... 62 Paluxy Formation .................................................................................. 65 Woodbine Formation ........................................................................... 67 Summary of Aquifer Stratigraphic Framework.......................................... 69 HYDROGEOLOGY ......................................................................................................... 70 Ground-Water Production ......................................, ....................................... 70 Hydraulic Head................................................................................................... 71 Hydrologic Properties........................................................................................ 78 Recharge ............................................................................................................... 88 Discharge..................................................................................... ......................... 88 Flow Velocity ....................................................................................................... 89 Summary of Aquifer Hydrologic Framework ................ '. ............................ 90 SIMULATION OF GROUND-WATER FLOW ....................................................... 91 Cross-Sectional Model ...................................................................................... 91 Calibration ............................................................................................... 92 Results ...................................................................................................... 93 Regional Three-Dimensional Model .......................................................... 100 Steady-State Flow System................................................................... 100 11 I I Historical Flow System ........................... ;........................................... 109 Comparison of hydrographs .................................................. 110 Comparison of potentiometric surfaces.............................. 114 Prediction of Future Ground-Water Levels................................... 117 iv Regional Water Budget ...................................................................... 118 SUMMARY ................................................................................................................... 127 ACKNOWLEDGMENTS ............................................................................................ 128 REFERENCES ............................................................................................................... 129 FIGURES 1. Location of study area in North-Central Texas ............................................. 3 2. Schematic relationship between stratigraphic units .. :................................. 8 3. Major structural•· features and paleogeographic elements......................... 12 4. Elevation of the top of the Twin Mountains Formation.......................... 13 5. Elevation of the top of the Paluxy Formation .......................... :.................. 14 6. Elevation of the top of the Woodbine Formation...................................... 15 7. Histogram of water-level measurements from 1901 through 1992 ....................................................................................................... 27 8. Relation between specific capacity and transmissivity .............................. 31 9. Geologic cross section showing hydrostratigraphic units used for numerical profile model .................................................................. 34 10. Finite-difference grid used for numerical cross-sectional model.................................................................................................................... 35 11. Active blocks used to represent the Twin Mountains Formation ............................................................................................................ 40 ., 12. Active blocks used to represent the Paluxy Formation ............................. 41 13. Active blocks used to represent the Woodbine Formation...................... 42 V ! I 14. Location of selected water wells for comparison between recorded and simulated water levels ............................................................. 48 15. Model of high-destructive delta system........................................................ 60 16. Early Cretaceous (Coahuilan) paleogeology and paleogeography................................................................................................... 61 17. Net sandstone map of the Twin Mountains sandstones .......................... 63 18. Net sandstone map of the Paluxy Formation .............................................. 66 19. Net sandstone map of the Woodbine Formation ...................................... 68 20. Estimated historical and projected future ground-water.. production ........................................................................................................... 72 21. Water-level declines in Twin Mountains, Paluxy, and Woodbine Formations ..................................................................................... 74 22. Estimated potentiometric surfaces for the Twin Mountains Formation in 1900 and 1990 ....................................................... 75 23. Estimated potentiometric surfaces for the Paluxy Formation in 1900 and 1990............................................................................. 76 24. Estimated potentiometric surfaces for the Woodbine Formation in 1900 and 1990