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Geology and Geohydrology of the Palo Duro Basin, Texas Panhandle A Report on the Progress of Nuclear Waste Isolation Feasibilily Studies (l9/9]
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by T C. Gustavson M. W Presley C R Handford. R. J. Finley. S. P. Dutton, R W Baumgardner, Jr., K. A. McGilliS, and W W. Simpkins
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~ DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER
Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Geological Circular 80-7
GEOLOGY AND GEOHYDROLOGY OF THE
PALO DURO BASIN, TEXAS PANHANDLE·
A Report on the Progress of Nuclear Waste
Isolation Feasibility Studies 0979)
------DISCLAIMER------, This boo~> was prepared as an aceount of work sponsored by an agency of the U~ited States Go:;:.::~'· 1 Neither the United Stat7s ~vernment nor anva:e~cva:n~i~~:i· 1~ u~rail;~~';~,i~;p;:~~~ ac~;ra:. warranty, express or •mplied, ,oranassui::rma~on~ apparatus, product, or process disclosed,. ~r completen~, o_r us::u:,e;d ~ot i:fringe privately owned rights. Reference herein to anv_ spec•hc represent~ t at ItS u or service by trade name, trademark, manufacturer, or otherwJSO, ~ocs I commerc•al ~~rod:~~~~:e~r imply Its endorsement, recommendation. or favoring by th_e United t/ by ~~;,~:~~~ent or any agency thereof. The views and opinions of authors expressed here1n do not necessarily state or reflect those of the United States Government or a~y agency thereof.
T. C. Gustavson, M. W. Presley, C. R. Handford, R. J. Finley,
S. P. Dutton, R. W. Baumgardner, Jr., K. A. MCGillis, and W. W. Simpkins·
Burea1,1 of Economic Geology The University of Texas at Austin Austin, Texas 78712 W." L. Fisher, Director a: IU g0 IU (I) 0 Funded by U.S. Department of Energy, ~ > ) jjj"' Contract No. DE-AC97-79ET44614 0 ;::)" IU .Jv~ Q. a: 1980 OF THIS UNLIM\(':3 "to•"'"U gl•li-'WI •••to" i1 QllCyi~EtW1S· ..·.c_ ' ''!'
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'- . TABLE OF CONTENTS
Purpose and scope -. 1
Palo Duro and Dalhart Basin studies-- A summary of second-year research activities 3
Lithofacies and depositional environments of evaporite-bearing strata based on Randall and Swisher County cores • 5
Mapping of facies by well log interpretation • 8
Upper Permian salt-bearing stratigraphic units 12
Salt depositional systems--an example from the Tubb Formation 24
Salt depth a!"ld thickness studies 33
Petroleum source rock quality and thermal maturity • 41
Preliminary aspects of deep-basin hydrology • 47
Climatic analysis 52
Slope erosion mechanisms • 58
Suspended sediment concentration and stream discharge relationships for the Prairie Dog Town Fork of the Red River: an approach to determine erosion rates 63
Shallow ground-water hydrology--a preliminary review 67
Rates of salt dissolution 71
Preliminary rates of slope retreat and salt dissolution along the eastern Caprock Escarpment of the Southern High Plains and in the Canadian River Valley 7 6
Faulting and salt dissolution 83
Collapse chimneys, collapse surfaces, and breccia zones 88
Landsat analysis of surface linear elements • 92
References ...
iii •• '"· • •• I· • ....·. :: . ·:. . : . .
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·· .. :..'' ·~\ ·-':. :T.filS''''PAGE--:>·._· I .. WAS 'INTENTlON:ALLY LEFT BLANK ILLUSTRATIONS
Figures 1. Structure of Texas Panhandle Program .- 2 2. Log facies cross section, upper Clear Fork Formation • 10
3. Log facies cross section, Glorieta Formation • 11
4. Regional structural setting of the Palo Duro and Dalhart Basins • .. 15
t 5. North-south cross section, Upper Permian salt-bearing strata, Texas Panhandle 16
6. East-west cross section, Upper Permian salt-bearing strata, Texas Pan handle .. 17
7. Upper Clear Fork- Glorieta.Formations, north_.south cross section C-C', Texas Panhandle • 18
· 8. Thickness of upper Clear Fork- Glorieta Formations, Texas Panhandle 19
9. San Andres Formation, north-south cross section D-D', Texas Panhandle 20
10. Thickness of San Andres Formation, Texas Panhandle 21
11. Post-San Andres Formations, north-south cross section E-E', Texas Panhandle 22
12. Thickness of post-San Andres Formations, Texas Panhandle • 23
13. Facies and environments recorded in Tubb strata of the Palo Duro and Dalhart Basins • - 26
14. Diagrammatic north-south cross section of Tubb strata
15. Diagrammatic representation of the interrelationship between Tubb red-bed (siliciclastic) units and evaporite-carbonate units 28
16. Northwest-southeast cross section, Tubb Formation·,- Palo Duro Basin 29
17. Net mudstone of a siliciclastic-dominant bed in the Tubb Formation (Tubb unit G) • 30
18. Facies maps of evaporite-carbonate units 1, 2, and 3 (oldest to· youngest) of the Tubb Formation 31
19. North-south cross section of Tubb evaporite-carbonate unit 2, il -e lustrating southward shift of carbonate and evaporite facies 32
v 20. · Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), lower Clear Fork Formation, Texas Panhandle 34
21. Salt deposits with more than 50 ft (15 m) net ·salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), upper Clear Fork Formation, Texas Panhandle 35
22. Salt deposits with more than 50 ft (15 m). net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), Glorieta Formation, Texas Panhandle 36
23. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), lower part of San Andres Formation, Texas Panhandle 37
24. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), upper part of San Andres Formation, Texas Panhandle 38
25. Salt deposits .with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), Seven Rivers Formation, Texas Panhandle • 39
26. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000. ft (305 and 915 m), Salado Formation, Texas Panhandle 40
27. Wells in the Palo Duro Basin, Texas, with good to very good Penn sylvanian and Wolfcampian source rock potential on the basis of total organic carbon content 44
28. Geographic distribution of organic carbon in Pennsylvanian and Wolf- campian strata of the Palo Duro Basin, Texas. 45
. 29. Kerogen color (thermal alteration index) and vitrinite reflectance values of Pt;-nnc;ylvr~nirt.n source rocks in the Palo Duro Basin, Texas, related to hydrocarbon facies (from Schwab, 1977) • 46
30. Potentiometric surface ·of Pennsylvanian strata (excluding granite wash) in the Palo Duro and Dalhart Basins, Texas • 49
31. Potentiometric surface. of Lower Permian (Wolfcampian) str·ata in the Palo Duro and Dalhart Basins, Texas 50
32. Pressure versus depth curves for drill stem tests in Bailey and Donley Counties, Texas 51
33. Rainfall intensity-duration profiles for two storms, recorded at erosion monitoring localities 55 ··... 34. Hourly rainfall intensity expressed as a percent of the total time p'eriod of rainfall with intensity > 0.25 inch (6.4 mm) per hour; also, hourly rainfall intensities for a single storm at Amarillo, Texas • 56
vi 35. Four-inch (102 mm) isohyets compiled from daily 24-hour .rainfall distribution maps for the period 1947-1976 57
36. Net erosion and deposition for 39 erosion pins measured ·on December 12, 1978, and August 8, 1979 61
37. Net erosion and deposition for erosion pins at four monitoring localit ies for the periods (1) December 12, 1978, to August 8, 1979, at Caprock Canyons State Park, (2) June 26, 1978, to ·August 24, 19?9, at Palo Duro Canyon State Park, (3) June 6, 1978, to· May 1, 1979, at Muleshoe National Wildlife Refuge, and (4) February 3, 1978, to Dec~mber ll, 1978, at Buffalo Lake National Wildlife Refuge . • 62
38. Suspended sediment concentration and stream discharge relationships f~r two regions--one semiarid and one humid • 65
39. Suspended sediment load and stream discharge relationships for two streams in semiarid regions • . • 66
. 40. ConceptuaJ grou.nd-water flow model for the High Plains and Rolling Plains regions, showing ground-water flow paths in relation to regional recharge and discharge areas and to th~ pattern of salt dissolution · (from Gustavson and others, in press) 70
41. Drainage sub-basins and water-quality monitoring stations,_ Canadian River Valley and Rolling Plains (see table 6 for solute loads) 74
42. Salt dissolution zones, Texas Panhandle. • 75
43. Longitudinal profile .of Holmes Creek, Briscoe County, Texas, from the Caprock Escarpment to below Lake Thea, illustrating 0.69 mi (1.1 km) of escarpment retreat resulting from 40 ft (12.2 m) of downcutting in the Lake Thea area 80
44. Topographic and geological profiles across the Texas Panhandle and adjacent parts of New Mexico and Oklahoma • 81
45. Combined interpretations of the easternmost extent of the Ogallala Formation 82
46. Stratigraphic and structural cross section showing thinning of Artesia Group strata • 85
47. Cross section between the Bonita Fault and the Alamosa Creek Fault, showing no evidence of displacement 86
48. Stratigraphic and structural cross section showing thinning of Artesia Group strata • 87
49. An oblique section of a collapse chimney • 90
50. A collapse chimney composed of carbonate-cemented gravels and ·e breccia • 90
vii 51. Gypsum filling fractures along bedding planes and across ·bedding planes in Permian red mudstones exposed in Caprock Canyons State Park, north of Quitaque, Texas • 91
52. Three anticlines and two synclines occurring in Permian ·strata along Texas Highway 136. 91
53. Distribution of lineament length by 10° azimuth category for the Southern High Plains and parts of adjacent physiographic provinces • 94
54. Lineament density over the central Texas Panhandle and adjacent eastern New Mexico 95
Tables
1. Carbonate-evaporite facies of upper Clea·r Fork - Glorieta rocks, based on core descriptions and well log patterns 9
2. Stratigraphic chart 14
3. Wells sampled for geochemical source rock analyses 43
4. Depth-frequency relationships for 24-hour rainfall for stations in the Texas Panhandle • · 54
5. Soil characteristics of the two most common soils of the Rolling Hills physiographic province in Briscoe County, Texas 60 ·
6. Salt dissolution expressed as rates of vertical and horizontal dissolu- tion • 73
7. Rates of slope retreat for areas along the eastern Caprock Escarpment and for portions of the Canadian River Valley 79
Well Log
Randall County core test well in pocket
viii PURPOSE AND SCOPE
Research Staff
Integrated study of the physical stratigraphy, tectonic history, hydrogeology, geo morphology, resource potential, and rock physics of the Palo Duro and Dalhart Basins in the Texas Panhandle is part of a national evaluation of ancient salt basins as potential sites for isolation and management of nuclear wastes. ·
Since early 1977, the Bureau of Economic Geology has been evaluating several salt-bearing basins within the State of Texas as part of the national nuclear repository· program. The Bureau, a research unit of The University of Texas at Austin and the State of Texas, is carrying out a long-term program to gather and interpret all . geologic and hydrologic information necessary for description, delineation, and evalua tion of salt-bearing strata in the Palo Duro and Dalhart Basins of the Texas Panhandle. The program in FY 79 has been subdivided into four broad research tasks, which are addressed by a basin analysis group, a surface studies group, a geohydrology group, and a host-rock analysis group (fig. 1). The ·basin analysis group has delineated the structural and stratigraphic framework of the basins, initiated natural resource assessment, and integrated data from 8,000 ft (2,400 m) of core material into salt stratigraphy models. Salt depth and thickness have been delineated for seven salt bearing stratigraphic units. Concurrently, the surface studies group has collected ground and remotely sensed data to describe surficial processes, including salt solution, slope retreat/erosion mechanisms, geomorphic evolution, and fracture system development. The basin geohydrology group has begun evaluating both shallow and deep fluid circulation within the basins •. The newly formed· host-rock analysis group has initiated study of cores from two drilling sites for analysis of salt and the various lithologies overlying and interbedded with salt units. This paper, a summary report of progress in FY 79, presents principal conclusions and reviews methods used and types of data and maps generated. Topical reports, discussing various geological aspects of the Palo Duro and Dalhart Basins in detail, will be forthcoming as phases of the study are completed. This research was supported by the Department of Energy under contract· number DE-AC97 -79ET44614.
1 COORDINATOR
..----.... RESEARCH cnouro 11
CYEAR 3, 4, 5, 6) PRINCIPAL INVESTIGATOR
RESEARCH TASK 2
L • M N
Figure 1. Structure of Texas Panhandle Program.
2 PALO DURO AND DALHART BASIN STUDIES--A SUMMARY OF SECOND-YEAR RESEARCH ACTIVITIES
Research Staff
The second year of analysis was highlighted by acquisition· and characterization of salt-bearing cores, continuation of genetic stratigraphic facies mapping, initiation of petroleum source rock analyses and hydrogeologic mapping, continued climatic geomorphic monitoring of the Texas Panhandle, and continued investigations of the processes, timing, and rates of salt dissolution. Each study provides a basis for detailed data interpretation and future inte~ration of research elements.
During the second year of Palo Duro and Dalhart Basin studies, significant sources of data were acquired for direct analysis by each research task group (remote sensing/surficial studies, hydrogeology, host-rock, and basin analysis). Among these new sources of data were (1) 8,000 ft (2,438 m) of salt-bearing core, which is the single most important geologic sample for present and future basin analysis and host-rock studies, (2) petroleum source rock quality and thermal maturity data for resource assessment studies, (3) drill stem test data for regional hydrogeologic studies, and (4) quantitative climatic, erosional, and shallow subsurface salt dissolution data needed to predict the long-term geomorphic integrity of the Texas Panhandle. Acquisition of two salt-bearing cores from the Palo Duro Basin provided the first opportunity to determine salt character and quality, and to conceptualize salt depositional models based upon sedimentological features of the cores and modern salt depositional settings. Banded to massive salt (> 85% halite) and chaotic mudstone-salt (< 85% halite) are the dominant salt facies. Each facies is stratigraphically and geographically associated with dolomite, anhydrite, and red-bed strata to form numerous large-scale and _small-scale genetic stratigraphic units, all of which suggest deposition in environments ranging from continental and coastal sabkha to shallow marine shelf. Carbonate-evaporite and siliciclastic or mud-rich sabkha deposits are recognized, exhibiting cyclicity and basinward migration through time. Cores drilled during the year permitted improved calibration of geophysical well logs with lithic composition of the salt-bearing sequences. Consequently, salt quality can now be predicted with greater accuracy using well logs. Furthermore, core data enabled research-staff geologists to refine further the depositional models developed during FY 78 that were based principally upon geophysical well- logs. Hence, by the end of FY 79, interpretation of the various cyclic salt sequences reached a high level of
3 sophistication and accuracy. Generalized salt depth/thickness maps were prepared for each of seven salt-bearing sequences, illustrating regions where further evaluation should be undertaken. Drill cuttings from numerous wells across the Palo Duro Basin were submitted for organic geochemical analyses. These analyses indicated that petroleum source rocks are present and that they reached the early stages of oil generation. Since the basin also contains potential hydrocarbon reservoirs and traps, it will probably be the focus of increasing oil and gas exploration activity. Preliminary hydrogeologic mapping of deep-basin aquifers is based entirely upon pressure data derived frorn drill stem tests of oil and gas exploratory ventur~s. Results show that deep-basin ground water flows from west to cast, recharging in the northwestern Panhandle and discharging both in the southeastern Palo Duro Basin a_nd near the Amarillo Uplift. Facies control over ground-water flow is also recognized. An understanding of processes and rates of sediment removal, stream propaga tion, slope retreat, and salt dissolution is required to ensure the long-term integrity of any potential nuclear waste management site. An integrated program of geomorphic, hydrologic, and shallow stratigraphic studies has provided preliminary results on rates of surface erosion, stream incision and development, and rates and direction of movement of salt dissolution fronts. Estimates of slope retreat rates along the eastern Caprock Escarpment of the Southern High Plains were developed from three different data sets, yet the rates differ by less than a factor of 1.8. Preliminary slope retreat rates are approximately 0.6 mi (1 km) per 9,000 years. Minimum horizontal salt dissolution rates for the same area may exceed 0.21 mi (0.34 km) in 10,000 years.·
4 LITHOFACIES AND· DEPOSITIONAL ENVIRONMENTS OF EVAPORITf...,BEARING STRATA BASED ON RANDALL AND SWISHER COUNTY CORES
C. Robertson Handford
$iliciclastics, salt, anhydrite, and dolomite are present in the Randall and Swisher County cores. Each facies is composed of numerous subfacies that record deposition in inner shelf and sabkha environments.
Four major lithofacies are recognized in Permian evaporite-bearing strata cored in the Randall County, DOE/Gruy Federal, Inc., Rex White no. 1 well (in pocket) and the Swisher County, DOE/Gruy Federal, Inc., D. M. Grabbe no. 1 well. They are (1) siliciclastic facies, (2) salt, (3) anhydrite, and (4) dolomite. Each· lithofacies is composed of numerous subfacies that generally reflect deposition in restricted, inner marine shelf and coastal sabkha environments. Lithofacies descriptions and inter pretations of depositional environments follow. Siliciclastic facies. Red, brown, and red- to green-banded sandstone, siltstone, mudstone, and claystone primarily occur in the Permian Red Cave, Tubb, and Glorieta Formations., and post-San Andres strata. Sandstones and siltstones are loosely cemented ·with halite and minor silica; mudstones and claystones are soft and easily broken. Structures include rare crossbedding· and wispy, irregular laminae. Some wispy laminae are similar to adhesion-rippled laminae described by Glennie 0972) and may be diagnostic of eolian deposition on moist surfaces. Siliciclastic facies generally interfinger southward with marine evaporites and dolomite. Although specific depositional settings varied, facies characteristics and distri bution suggest that siliciclastic strata were deposited in mud-rich sabkhas bordering a shallow marine basin. Sedimentary sources lie northwest and northeast of the Palo Duro Basin. Sediment was principally transported into the basin by fluvial processes. Eolian and marine processes were probably important sediment-reworking agents. Salt. Bedded salt is present in every Permian stratigraphic unit cored except the Red Cave Formation and subjacent Wichita Group. Two basic types of salt are recognized: banded to massive salt and chaotic mudstone-salt. Banded to massive salt is generally clear, or milky colored to gray, and consists of anhedral to subhedral halite crystals ranging from several millimeters to 5 em (2 inches) in diameter. Crystals are equant or elongate normal to bedding. Beds range from less than 3 ft to 10 ft (1 m to 3 m) thick and are commonly disrupted by distinctive, black, organic-rich bands (0.8 percent total organic carbon by weight measured in a lower Clear For-k salt
5 sample) that are 1 to 6 inches (2.5 to 15 em) thick. Chaotic mudstone-salt consists of clear, subhedral to euhedral halite crystals up to lYz inches (4 em) in diameter set in a matrix of red mudstone and claystone. Halite and matrix content are extremely variable, ranging from predominantly mudstone with isolated halite crystals to predominantly salt with minor intercrystalline mudstone or claystone. As exemplified by lower San Andres and upper Clear Fork strata, banded to massive salt is relatively purer (&5 to >95 percent halite vs. <85 percent halite) and generally forms thicker units than chaotic mudstone-salt. Although log response (gamma ray, sonic, density) is more variable and erratic in· chaotic mudstone-salt than in banded massive salt, the following characterizes their well log patterns:
Banded to Massive Salt Chaotic Mudstone-Salt
Gamma ray log 5 to 15 API units 15 to 45 API units (radioactivity increases as mudstone increases)
Sonic log 67 to 70 microseconds 60 to 90 microseconds (travel time increases as mudstone increases)
Facies characteristics and distribution suggest salt deposition in upper sabkha environments. Chaotic mudstone-salt was deposited in saline mudflats adjacent to distal edges of desert wadi, or alluvial/eolian plains. Just seaward of the saline mudflats, broad, frequently flooded salt pans or brine pans were the sites of banded to massive salt deposition. Anhvdrite. In complete evaporite cycles, anhydrite normally underlies salt and overlies dolomite. Elsewhere it is intercalated with salt, doiomite, and siHclclastic facies. Anhydrite is the dominant sulfate mineral phase at depths greater than approximately 600 to 900 ft (1&0 to 275 m), but at shallower depths, anhydrite is replaced by gypsum. Most anhydrite is blue to gray and may be nodular, massive, or laminated. In several prograding evaporite cycles, laminated anhydrite overlies nodular and massive anhydrite, perhaps suggesting, according to Walther's Law, that laminated anhydrite was deposited in a more landward position than nodular anhydrite. Laminated anhydrite commonly consists of carbonate-anhydrite laminae with vertically oriented anhydrite pseudomorphs after swallowtail gypsum. Laminae are planar to wavy and contorted. Nodular anhydrite consists of single nodules set in a matrix of carbonate or siliciclastics. Where nodules have coalesced and are tightly packed, nodular, mosaic or even massive structures may result.
6 Comparison of Permian and Recent anhydrite occurrences indicates that Per mian anhydrite was deposited in lower to upper (or outer to inner) sabkha environ ments. Nodular anhydrite formed in the lower sabkha vadose zone by displacive precipitation and growth of Caso penecontemporaneous with deposition of sur 4 rounding sediment. Laminated anhydrite may have formed subaqueously and in association with algal mats in and around hypersaline salt pans or brine pans on the upper sabkha. Dolomite. The basal lithologic member of most complete evaporite cycles is dolomite, and it is a major facies component of the Wichita Group, Red Cave, and San Andres Formations. These rocks include nearly all textural varieties of Dunham's (19G2) classification scheme. Allochems include ooids, pellets, intraclasts, and a few skeletal components. Cementing agents are dolomite, anhydrite, and halite. Parallel laminae, crenulated algal laminae, and minor, large-scale crossbedding· are the dominant primary sedimentary structures. Secondary structures include burrows and salt-filled fenestrae. Depositional environments ranged from shallow subtidal (burrowed facies), to intertidal (grain-supported facies), and supratidal (laminated mudstone). A modern analog of Permian carbonate facies and environments is the Trucial Coast of the Persian Gulf.
7 MAPPING OF FACIES BY WELL LOG INTERPRETATION
Kathy A. McGillis
Calibration of geophysical well logs with core permits identification of log facies that can be mapped throughout the basin. Regional variations in salt quality can be predicted.
Cores through the entire Upper Permian salt-bearing interval of the Palo Duro Basin were interpreted from two test wells drilled by the Department of Energy in Randall and Swisher Counties. A complete geophysical log suite for both wells provided an excellent opportunity Ior calibration of logs with lithology provided by cores. Figures 2 and 3 illustrate well log interpretations for the upper Clear Fork and Glorieta Formations. Detailed interpretations of logs without core can now be made on the basis of this work (fig. 3), thus allowing recognition of various salt facies. Two salt facies have been identified: massive-banded salt and chaotic salt-mudstone mixtures (table 1). In addition, dolomite and anhydrite facies were recognized. Massive-banded salt consists of clear halite containing minor mudstone or organic impurities. It is characterized by low radioactivity (5 to 15 API units) on gamma ray logs and an interval transit time of 67 to 70 microseconds. Density porosity logs register anomalously high readings, but neutron porosity values average approximately 0. Chaotic mudstone-salt facies vary in make-up, ranging from 15 to 20 percent mudGtone to prl;'dnminantly mudstone with some scattered salt crystals. Gamma ray values, interval tran~it times, and neutron porosity values are greater with increasing mudstone content. Density porosity values decrease with increasing mudstone. Regional variations in salt quality in terms of mudstone content can be predicted within each evaporite sequence. Massive salt is present with anhydrite and dolomite in the southern part o-f the basin (fig. 2). In an updip (north) direction, anhydrite and dolomite decrease in each sequence and the mudstone content of the salt facies increases. Salt quality also varies upsection, as shown in the upper Clear Fork cycles in figure 2. Six cycles are identified (lA, lB, 2A, 2B, 2C, and 2D), and mudstone content increases upsection within each cycle and through the whole formation. Analyses .of log and core data are continuing in an attempt. to further quantify interpretive parameters and. to permit precise discrimination of facies.
8 Table. 1. Carbonate-evaporite facies of upper Clear Fork- Glorieta rocks, based on core descriptions and well log patterns.
~SHELF SABKHA------+ Intertidal- - ~ ------· · · · · · · · ---- Lower Sabkha------Upper Sabkha Laminated or nodular Laminated dolomite Massive-banded salt Chaotic mudstone-salt mosaic anhydrite Core descriptions Tan to dark gray-green Bluish gray, laminated Clear halite, commonly Gear halite and dolomite-mudstone. or nodular mosaic appears red-brown with red-brown mudstone. Commonly with gray anhydrite. red mudstone impurities. Mixtures vary from Lithology anhydrite laminae and crystalline salt with and cofor nodules. Halite is com intercrystalline mudstone mon, filling fractures to predominantly mud and porosity. stone with a few sea tte red salt crystals.
Dolomite occurs in beds Occurs in beds up to Massive salt beds up to Chaotic mudstone-salt up to 10ft (3 m) thick. 10ft (3m) thick. 10ft (3m) thick are beds are commonly on Individual dolomite Laminae are up to commonly banded into the order of 1 to 20ft laminae are up to 0.2 inch (0.5 em) layers 1 to 6 inches (0.3 to 6 m) thick. 0.5 inch (1.3 em) thick; thick, and are com (2.5 to 15 em) thick anhydrite stringers are monly separated by by variation in Bed-laminae up to 0.25 inch (0.6 em) thin carbonate/ percentage of red dimensions thick; beds of nodules organic films. mudstone and other are 0.5 to 1.0 inch impurities. Intervals (1.3 to 2.5 em) thick. of relatively pure salt are up to 3 ft (1 m) thick. Some anhydrite is present as thin (0.1 inch, 0.25 em) stringers. Anhydrite nodules Upper surfaces of lami Salt crystal size com Salt crystals are up to commonly distorted, nated anyhydrite may monly 0.5 to 1.0 inch 1.5 inch (3.8 em) in elongate parallel to exhibit dovetail anhy (1.3 to 2.5 em) in diameter but are most bedding. Individual drite crystals as pseudu diameter with crystals commonly 0.25 to nodules are less than morphs after gypsum, up to 2 inches (5 em) 0.5 inch (0.6 to 1.3 em). 0.5 inch (1.3 em) in extending upward, in diameter. Crystals Salt and mudstone average diameter. commonly into salt. generally equant, appear randomly inter Some laminae exhibit anhedraL mixed. Salt crystals are wavy bedding or en generally equant, and Textural terol ithic deformation. anhedral. Subhedral to relationships Anhydrite nodules euhedral crystal bound average 0.5 to 1 inch aries are common where (1.3 to 2.5 em) in salt contacts mud. diameter. Nodules may be equidimensional or elongate parallel to bedding, and are sepa rated by carbonate/ organic films.
Dolomite facies register Uniform, low radio Low radioactivity Radioactivity is directly moderate radioactivity activity (average less (5 to 15 API units) proportional to mud (20 to 60 API units) as than 15 API units) on gamma ray logs. stone content. Gamma recorded on gamma ray on gamma ray logs. Interval transit time ray values 15 to 45 API logs. Values on sonic Interval transit time 67 to 70 micro units. Sonic travel times Well log logs average 60 to 70 50 to 60 microseconds seconds. average 60 to 90 micro patterns microseconds. Higher on sonic logs; "clean seconds. Travel time percentages of anhy est" anhydrite values greater with drite result in lower approaches 50 micro increasing mudstone. radioactivity and lower seconds. values of transit time.
9 SOUTH NORTH SWISHER COUNTY RANDALL COUNTY D.O. E.- Gruy Federal, I Grabbe D.O. E. -Gruy Federal, I Rex White
Inch 6 16
A.P.I. Units 0 150 I Microseconds \ 140 67 50 40 Colipe Inch 6 !6 r--...4 .-" '------'-----' 0 150 Gomm 0 A.P.I. Units • ~ < Roy ""< . < . . , ..I .... <\ W// ------;;::'!>
3400
I I jE
lA 3800-
3000
EXPLANATION
~ Massive Salt 53 Dolomite 0!0 ft m [~<"~'I Chaotic salt /mudctone ~ Mudstl)nP. 50 15 r22J Anhydrite ~)i/ifo/J Sandstone
Figure 2. Log facies cross section, upper Clear Fork Formation. Core was used for calibration of both wells.
10 WEST EAST CASTRO COUNTY SWISHER COUNTY Phillips , I Morris ... J .. D.O. E.- Gruy Federal, I Grabbe
Inch 6,______,._....:,16 Inch 6 16
A.P.I. Units A.P.I. Units 150 Microseconds 67 50 40
3800-
Sonic
3900-
4000-
4100-
4200-
oio ft m
50 15
EXPLANATION
m Massive salt B Dolomite I Anhydrite
Q Chaotic salt /mudstone t====3 Mudstone
~Anhydrite t-:-:...:._j Siltstone I mudstone
Figure 3. Log facies cross section, Glorieta Formation. Core was used for calibration of Swisher County well.
11 UPPER PERMIAN SALT ..;BEARING STRATIGRAPHIC UNITS
Mark W. Presley
Upper Permian strata ·in the Texas Panhandle comprise numerous cyclic units composed of evaporites, carbonates, and red beds. Understanding the origin of this cyclicity permits subdivision of the stratigraphy and prediction of regional composi tional and facies variations.
This section des~ribes facies-related genetic units of Late P~rmian age in the Palo Duro and Dalhart Basins. Upper Permian strata in the Texas Panhandle are composed of salt, anhydrite and/or gypsum, rare limestone, and red beds. These rocks occur in cyclic units and were deposited in a range of shelf, supratidal, and terrestrial environments. Cyclicity is identified at a number of scales. Upper Permian rocks may be subdivided (upward) into at least four major cyclic genetic units that record regional changes in facies patterns: (1) the lower Clear Fork and Tubb Formations, (2) the upper Clear Fork and Glorieta Formations, (3) the· San Andres Formation, and (1+) post-San Andres Guadalupian and Ochoan strata (table 2, figs. 4, 5, and 6). Each genetic sequence can be subdivided into second-order cycles, which record more localized variations of shifting facies patterns. In general, within each cyclic unit, regardless of the scale, the strata record a gradual, basinward (southerly) facies shift through time.
Lower Clear Fork - Tubb genetic unit. The Tubb Formation (described in detail in the following section on salt depositional systems) is the upper part of a major genetic unit comprising strata of the lower Clear' Fork C::LIIu Tubb Formations (table 2, figs. 5 and 6). Lower Clear Fork strata lack thick red-bed tongues. exhibited by the Tubb Formation, and record early-stage dominance of coastal evapor·ite and carbonate environments in the study area. Tubb strata record late-stage dominance of siliciclastic (mud-flat) environments, which migrated basinward.· through time from updip areas. Individual evaporite-carbonate units of the Tubb Formation are second order cycles within th~s. larger lower Clear Fork - Tubb sequence.
Upper Clear Fork - Glorieta genetic unit. Upper Clear Fork - Glorieta Formations comprise another major genetic unit and exhibit a facies succession similar to that of lower. Clear Fork - Tubb rocks (fig. 7). Upper Clear Fork and Glorieta strata contain a high proportion of siliciclastics intercalated with evaporites (fig. 8). Upper Clear Fork rocks record early-stage dominance of coastal evaporite .and carbonate environments in the study area. Glorieta rocks record late-stage. dominance of
12 siliciclastic (mud-flat) environments. Continental sabkha (terrestrial salt flat) envi ronments also developed extensively during Glorieta time in landward areas of the northern Panhandle. Numerous second-order cycles displayed by upper Clear Fork - Glorieta strata are delineated in cross section (fig. 7).
San Andres genetic unit. The San Andres Formation in the region was deposited largely in coastal evaporite and carbonate environments (figs. 9 and 10). These strata lack significant quantities of intercalated siliciclastics characteristic of the older Clear Fork strata (table 2);, consequently, massive red-bed tongues deposited on siliciclastic mud flats are largely absent. Thick, laterally persi~tent, shallow-marine carbonate beds in the lower part of the San Andres record marine transgression ~hat was extensive· over large portions of the study region in early San Andres time. Each transgression initiated a second-order San Andres cycle and was followed by progra dation (regression) of evaporite environments. Regression was the dominant trend in shifting facies patterns, as exhibited in the area's upper San Andres strata, which contain only minor carbonate facies and record a late-stage dominance of evaporite environments.
Post-San Andres genetic unit. Post-San Andres formations are composed dominantly of siliciclastics and salt deposited in evaporite, mud-flat, and terrestrial eolian/continental sabkha environments. Two major post-San. Andres salt-bearing units are the Seven Rivers and Salado Formations (figs. 11 and '12). Within ·these formations, mudstone-dominant beds interfinger basinward with more massive salt. Salt facies relationships are similar to those observed in updip Clear Fork evaporite facies. Salt environments extended south and west of the Panhandle area Jnto the Midland and Delaware Basins. In the Panhandle area, red beds intertongue downdip with salt. In conclusion, Upper Permian strata in the Texas Panhandle comprise an orderly succession of cyclic genetic units. Cyclicity can be identified at a n~:~mber of scales. Overall genetic character of the stratigraphy indicates a general southerly migration of facies through time. Lateral and· vertical facies changes follow systematic patterns, providing a means to predict both regional and local salt quality variations.
13 Table 2. Stratigraphic chart.
System Serie! Palo Duro Basin Dalhart Basin
-;;; Dewey Lake Dewey Lake "'0 Formation "0"' Formation ..c 1:: ., u !l co c Alibates Formation Alibates Formation 0 - "0., 1:"' 0! f--- "0 Salado Formation ., c c ·;;; <( Yates Formation c co .!. Vl"' Seven Rivers Formation 0 Q.. Cl) Undifferentiated 0.. -0 Q.. Queen/Gray burg ::::l Formation ~ " "'::::l <..:) San z Andres Blaine <( Formation Formation - ~ Glorieta Sandstone ~ Glorieta Formation w 0. :::> upper Clear Fork Clear Fork !'"ormation 0... ~ Formation l:) "2 .>f. :;:; Tubb Formation ~ .u. 0 - ~ lower Clear Fork Cl) Undifferentiated ...J .,"' Formation u Tubb- Wichita Red Cave Formation Red Beds
Wichita Group
,.:.c.. -Eo., :S:u
14 Figure 4. Regional structural setting of the Palo Duro and Dalhart Basins.
15 A A SOUTH I, I NORTH LAMB CASTRO DEAF 'SMITH'. OLDHAM I HARTLEY DALLAM
EXPLANATION
.Salt
600 500 150 400 tt 30o lOOm 200 50 100 10 20 30 Mi 0 0 10 20 30 40 50 Km
Figure 5. North-south cross section, Upper Permian salt-bearing strata, Texas Pan handle. Generalized Ealt units are correlated. Location of section in figure 4. B 81 WEST EAST
CURRY PARMER CASTRO SWISHER ARMSTRONG DONLEY COLLINGSWORTH
3 20 39 31 26
EXPLANATION
.SALT 0f:o ~m; 100 10 20km 20050 It m 300 1()0 400
Figure 6. East-west cross section, Upper Permian salt-bearing strata, Texas Pan handle. Generalized salt units are correlated. Location of section in figure 4. c C' SOUTH NORTH
LUBBOCK HALE I.. SWISHER !ARMSTRONd RANDALL POTTER MOORE SHERMAN DALLAM 12 I I I I I I 13
,_ 00
DALHART BASIN
EXPLANATION 0 Salt/mudstone (Upper ~Dolomite/sandstone/mudstone PALO DURO BASIN ~0IO:~km Sab Figure 7. Upper Clec.r Fork - Glorieta Formations, north-south cross section C-C', Texas Panhandle. 0 40ml 0 40 km Contour interval =50 feet ( 15 m) Figure 8. Thickness of upper Clear Fork - Glorieta Formations, Texas Panhandle. Cross section C-C' shown in figure 7. 19 , D AMARILLO UPLIFT PALO DURO BASIN MATADOR ARCH D NORTH ' ' SOUTH CARSON RANDALL SWISHER LAMB N 0 a Soli solution R Salt /mudstone (upper Sabkha) - Anhydrite /mudstone/dolomite ( lower Sabkha) oro5 10 mi 10 20km ~ Dolomite /anhydrite (inner shelf) It 100 25m ~ Dolomite (carbonate shelf) 50 E't't:t~=~ Mudstone/siltstone (red beds) 200 . Figure 9. San Andres fjrmation, north-south cross section D-D', Texas Panhandle. • ,~oO ~. z5o • / --r~~~;~ I : PARME~ Ic"A~TRO --- [ • I h~0 •• I,....,, 1 BAILEY • LAMB ~ I I I I Figure 10. Thickness of San Andres Formation, Texas Panhandle. Cross section D-D' shown in figure 9. 21 E e' NORTH SOUTH CARSON ARMSTRONG SWISHER HALE LUBBOCK 20 14 0 5 10 mi 0 20km 100f'o 25m ft 50 200 N N • Soll/mudslone (Upper Sobkha) • Anhydrite/mudstone/dolomite (Lower Sabkha) ~ Dolomite/anhydrite ~~~~~~~~ Mudstone (Red beds) I;·:::.··;J Sandstone/mudstone (Red beds) ~, 6 ::Ex Zt- D Salt solution -+-s Figure 11. Post-San Andres Formations, north.;..south cross section E-E', Texas Panhandle. 0 40 mi r----.--~-r----~ 0 40 km Contour interval = 50ft(l5m) I L I I ' I I ' . I ---~KING------~ ' ' I ' I ' ______I Figure 12. Thickness of post-San Andres Formations, Texas Panhandle. Cross-section E-E' shown in figure 11. 23 SALT DEPOSITIONAL SYSTEMS--AN EXAMPLE FROM THE TUBB FORMATION Mark W. Presley Facies of a salt-bearing formation-the Tubb Formation-are described as one example of evaporite facies in the Palo Duro and Dalhart Basins. The Tubb Formation comprises two facies associations: ( 1) red beds (siliciclastics), and (2) evaporites and carbonates, which intertongue updip with red beds. Evaporite-carbonate and silici clastic sedimentation alternated. Both facies associations grade basinward (to the south) from supratidal to subtidal. This section presents facies interrelationships within a single, Leonardian salt bearing formation--the Tubb Formation (table 2). Facies in other salt-bearing units in the Palo Duro and Dalhart Basins record variations of Tubb facies relationships. The Tubb Formation in the Palo Duro and Dalhart Basins is composed dominantly of red beds (mudstone, siltstone, and fine sandstone), salt, anhydrite, and dolomite. Within the Tubb Formation are a number of red-bed units, which . are laterally persistent over much of the study region. These red beds exhibit a distinctive facies association, with facies grading basinward (to the south), ranging from (1) mudstone siltstone, deposited in supratidal mud flats, to (2) sandstone and dolomite sequences, deposited in subtidal to intertidal sand flats (figs. 13 through 16). Tubb red-bed units are separated by laterally persistent evaporite-carbonate units. The evaporites and carbonates pinch out into landward facies in the north-· western and eastern parts of the Palo Duro Basin study area. This intertonguing of red beds and evaporites-carbonates records per iud~ of dominant siliciclastic (red bed) sedimentation alternating with periods of dominant chemical (evaporite-carbonate) sedimentation. Evaporite-carbonate facies grade basinward -(to the south) from (1) chaotic salt-mudstone, deposited in supratidal salt-mud flats to (2) massive-banded . salt, formed in flooded brine pans to (3) laminated anhydrite, deposited in algal gypsum flats, and to (4) carbonates, formed ih intertidal to subtidal environments (figs. 13 through 16). Siliciclastic unit G from the middle part of the Tubb Formation demonstrates red bed facies variations (figs. 16 and 17). Mud flats were dominant to the north during G time. A thick net mudstone trend in unit G ranging from Roosevelt County, New Mexico, northeast to Swisher County, Texas, is a wedge of mud-flat sediments that prograded over shelf carbonates of the underlying unit (unit 1, figs. 17 and 18). 24 Facies variations for Tubb evaporite-carbonate unit 2, which overlies red-bed unit G, are shown in cross section (fig. 19). Maps of unit 2, as well as two additional evaporite-carbonate units (the older unit 1 and younger unit 3) show regional distribution of salt, anhydrite, and carbonate facies, as well as a basinward shift through time of facies boundaries (fig. 18). Following time G, flooding (transgression) of the G mud flat permitted resumption of evaporite-carbonate ·sedimentation to form unit 2. Carbonates, which were formed in a range of subtidal to supratidal environments, occur basinward and in updip areas in the lower part of the uhit 2 cycle (figs. 17 and 18). Carbonates are overlain by laminated anhydrite, and finally by salt. The quantity of mudstone associated with salt increases updip (to the north) and also upsection. This upsection increase in mudstone reflects the basinward shifting of salt mud environments late in unit 2 time. Comparison of evaporite-carbonate units 1, 2, and 3 shows an overall basinward shift through time in the occurrence of evaporite facies. In summary, two general Tubb facies associations--(!) red beds and (2) evap orites-carbonates--exhibit cyclic patterns. During Tubb time, periods of predominant evaporite deposition alternated with periods of predominant red-bed deposition (fig. 14). During sedimentation of each facies association, environrnents shifted pro gressively basinward (fig. 15). Evaporite-carbonate environments shifted basinward through time; consequently, facies prograded seaward (to the south) from updip areas. Evaporite-carbonate sedimentation was terminated when mud-flat sediments pro graded over evaporite and shelf carbonate environments. This example represents one style of evaporite-carbonate sedimentation re corded in salt-bearing rocks of the Palo Duro and Dalhart Basins. General relation ships, however, are fundamental to other clastic/evaporite sequences. Understanding detailed evaporite facies variations is important in developing predictive models for variations in lithology of salt and associated strata. 25 +sEAWARD Intertidal-Supratidal EVAPORITE CARBONATE FACIES . Brine Pond =- Laminated Laminated Massive/banded Chaotic dolomite anhydrite salt mudstone-salt wind Eolian facies CLASTIC SHELF · mudflats Sl LICICLASTIC FACIES Sandstone mudstone mudstone · dolomite Figure 13. Facies and environments recorded in Tubb strata of the Palo Duro and Dalhart Basins. Evaporite-carbonate facies record a gradual basinward shift in environments. Siliciclastic (red-bed) facies· dominate the Tubb sequence, and were deposited in tidal mud flats, which graded basinward into tidal sand flats. 26 Red beds (mud flats) Sandstone -dolomite (clastic shelf) Anhydrite (algol-gypsum flats) Carbonates (carbonate shelf) ' Massive-bonded salt (brine pan) Chaotic sandstone salt (salt flats) Figure 14. Diagrammatic north-south cross section of Tubb strata. Facies vary north to south (basinward) from supratidal to subtidal. Periods of siliciclastic sedimentation, in which mud flats prograded seaward, alternated with periods of net accumulation of evaporites and carbonates. The overall genetic aspect of the stratigraphy is a gradual regressive facies shift through time. 27 ·Evaporites develop on older mud-flat platform Figure 15. Diagrammatic representation of the interrelationship between Tubb red bed (siliciclastic) units and evaporite-carbonate units. 28 B s' SE NW DICKENS FLOYD SWISHER RANDALL !DEAF SMIT~ OLDHAM ft m EXPLANATION 100 30 • Salt-mudstone ~ Anhydrite-dolomite ~~~=j Mud~tone-siltstone ~ Dolomite-anhydrite(± sandstone) FEBJ Sandstone-dolomite-mudstone Figure 16. Northwest-southeast cross section, Tubb Formation, .Palo Duro Basin. Relationships are shown diagrammatically in figure 14. 29 i, I i i ~.-., i i i t i N I 0 I() 0 10 20 30km Contour Interval =5ft (1.524m} EXPLANATION E22J 20-30 j/ii@fi~\l > 30 ® Core location Figure 17. Net mudstone of a siliciclastic-dominant bed in the Tubb Formation (Tubb unit G). This bed lies between units 1 and 2 shown in figure 16. Net mudstone is calculated from gamma-ray data. Thick mudstone in the central Palo Duro Basin resulted from southerly progradation of mud flats into shelf environments, allowing a seaward migration of supratidal facies. 30 Figure 18. Facies ·maps of evaporite-carbonate units 1, 2, and 3 (oldest to youngest) of the Tubb Formation. Unit 2 is shown in cross section in figure 19. Salt is dominant in updip regions to· the north; carbonate is dominant. to the south. These units show progressive southerly migration of evaporite-carbonate facies. 31 c c' SOUTH NORTH I i SWISHER CO BRISCOE CO RANDALL CO 1,.,.) N SALT FLATS {Upper sabkha) ALGAL GYPSUM FLATS SUBTIDAL TO INTERTIDAL REGRESSIVE TO SALT FLATS CARBONATE SHELF {Lower to upper sabkha) Ft M 100 30 E~PLANATION L05-LITHOL.DGY ~Anhydrite (• dolomite) ~~lomite{* anhydrite/sonolstone) 50 15 liilJllll Massive/bonded soli Q :hootlc mud~:one/solt BMudstone 0 0 Figure 19. North-south cross section of Tubb evaporite-carbonate unit 2, illustrating southward shift of carbonate and evaporite facies. Cycle defined by unit comprises dolomite, overlain by anhydrite, capped by massive-banded salt and then chaotic mudstone-salt. Gamma ray (GR), caliper (CAL), sonic (SON), laterolog (LL), and neutron porosity (SNP) curves illustrate log-facies interpretation criteria. SAT..T DEPTH AND TI-IICKNESS STUDIES Mark W. Presley Regions have been delineated where more than 50 ft ( 15 m) of net salt occurs at a depth between 1,000 and 3,000 ft (305 and 915 m). Maps are provided for each of seven salt-bearing units. Maps that show selected salt depth and net-salt values for each salt-bearing unit in the Texas Panhandle (figs. 20 through 26) outline areas where continued compre hensive study is necessary to determine salt quality, resource potential, thickness of individual beds, hydrologic integrity, and rates of surface erosion. Salt-bearing units that were evaluated and mapped are defined in cross sections in this report (figs. 5, 6, 7, 9, and 11). The seven stratigraphic units, from oldest to youngest, are (1) lower Clear Fork Formation, (2) upper Clear Fork Formation, (3) Glorieta Formation, (4) lower part of the San Andres Formation, (5) upper part of the San Andres Formation, (6) Seven Rivers Formation, and (7) Salado Formation. Contour lines that define depths of 1,000 and 3,000 ft (305 and 915 m) from the . - surface to the top and base of each salt-bearing sequence and net salt thicknesses of 50 and 100 ft (15 and 30 m) are plotted for each salt-bearing unit. Salt dissolution zones and lateral pinch-out of salt beds further define sal~ distribution. The southern boundary of each map outlines the limit of the study area. Considered . collectively, the maps show that in most areas of the Texas Panhandle there are significant subsurface accumulations of salt at depths between 1,000 and 3,000 ft (305 and 915. m). Accumulations of salt within the ranges of depth and thickness studied occur farther south in each progressively younger salt-bearing unit. 33 .------.------1 UNION -.' ------.-·-·------··-, ._._ . c.IMARRON 1 :ExAs • Well control 1 r-1 Sail >50ft ~et lhtckoess at depths I I S.:.J of 1000 to 3000 ft -...... Salt scluftOn.' arrows pomt I I. '- toward sotut10n zone \ ~ Contours of depth 8 net th1ckness, respectively. I · '\.. \ Holchures indtcule lh1cker areas. : OKLAHOMA I, , r;;:·------.---~------·------0 OALLAM ·TPAS:. .• •I S~E~MAN • • 'i H~NSfORO : ••• _; • ·1 OCHILTRE~ • • • i'I:SC~MB : • •. " • : 0 I ~·;____~.. f '· .·. ; .. !:''··., >... J ·.· .·.· ..·.. I 0 '\J .. /.~: __ _:_ ___ ·.;....~-"·-'· --~----.:~.J~ ·--::.~·::i.;.·_~ ) : HAR.TLEY • . • • • • I~~C}RE • • IH"uTCHINSOI'l • :·: • •• I .. . . ;, , , ·.! •· ·. , . i. . .. ·. . . /. ' ,__ j i QUAY r·-·_j / ....-'L. _ _j /: i I I ! r·-·_J-' ~--,-.·--,' I I" I I· ' I ,.' I. I ' I I .... .1 ,...... · L__l ·.. L __._ I I·. j .· Figure 20. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3~000 ft (305 and 915 m), lower Clear Fork Formation, Texas Panhandle. 34 .... ------.---- 1 UNION -~-.------~-F·~------.-~~n~~o-1--·-·------·-- !7701 Soli >50ft. net thick~e5s at depths W....6J of 1000 lo 3000 ft. 1 ~ Salt solution' arrows po>nt I. "'--- lcword solution zone 0 0 I .--l' '----- :.__ ,.-_J_J --,-.·-,• I I. I I ' I· I '--,' 0 I IL_r C__ ._ ·. I I I Figure 21. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), upper Clear Fork Formation, Texas Panhandle. 35 ~r -l :·- - , - I . 1_ _J r------·--- . I --.- :PARMER • • I~AS~RO • ISWI~H ~--.. --,... '! ..., I . . : i I I I· . . . · ·· j. L: ___· -----~-----~---1· __:_ -l .. . j ._ ROOSEVELT • I BAILEY • iLAMB ---.-~-HALE ------,;L-;.;--- L. . . i· = .: . i .l'· I / .-!. .· .<>.-=·:.'j. . . j I :_ _ ···!"'·-~(:. ·..!__ .. ·-~- 1· 1· . L__,l ~~;A~-~: ·j~:~K:E; .:-~~:0\>,:-Tu~·.~-~i:cROSB~ ~- L __._I [. • ·j - j.··.. · 'i. i .·. Figure 22. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), Glorieta Formation, Texas Panhandle. 36 Figure 23. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), lower part of San Andres Formation, Texas Panhandle. 37 . "'· : ·I l __._ . - . I I.. "i. . I : .: . I Figure 24. Su.lt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), upper part of San Andres Formation, Texas Panhandle. 38 .. L . . . -··--~:__~·-·:-~--~:.~-~:i 0 . LuBBOCK· ·DICK~NS IKING • i [ .... ·.1 I ... I ·. · .·. · I : Figure 25. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), Seven Rivers Formation, Texas Panhandle. 39 Figure 26. Salt deposits with more than 50 ft (15 m) net salt that occur at depths between 1,000 and 3,000 ft (305 and 915 m), Salado Formation, Texas Panhandle. 40 PETROLEUM SOURCE ROCK QUALITY AND THERMAL MATURITY Shirley P. Dutton The quality of hydrocarbon source rock in the Palo Duro Basin is fair to good on the basis of total organic carbon content. Kerogen color and vitrinite reflectance indicate source rocks reached the early stages of hydrocarbon generation. · Source rock quality is measured by total organic carbon content (TOC). To determine whether sediments in the Palo Duro Basin contained sufficient organic matter to generate hydrocarbons, 341 samples collected from 20 geographically scattered wells were analyzed for TOC (table 3). Samples were taken from a range of depths and stratigraphic intervals, with sampling concentrated in ·Pennsylvanian and lower Permian shales from basin and prodelta facies. Recognition of the petroleum potential is important in future evaluation of nuclear waste isolation in the basin. Total organic carbon content ranges between 0.008 and 6.866 percent. One hundred thirty-four samples contain greater than 0.5 percent TOC, which is the cutoff between poor and fair source rocks (Dow, 1978). Highest values of TOC occur in Upper Permian San Andres dolomite in the southern portion of the basin. Pennsylvanian and· Wolfcampian basinal shales contain up to 2.4 percent TOC p.nd are fair to very good source rocks (fig. 27). Organic carbon in Pennsylvanian and Wolfcampian strata is most abundant in the basin-center deposits (fig. 28). Source beds in the Palo Duro Basin had to reach sufficiently high temperatures to generate hydrocarbons from disseminated organic matter. Physical characteristics of the remaining organic m·aterial, especially color and reflectance, indicate maximum paleotemperatures. Kerogen color and vitrinite reflectance were studied for all samples containing greater than 0.5 percent TOC. Kerogen darkens progressively with increasing temperature, and the color indicates thermal metamorphism (Staplin, 1969). Pennsylvanian and Wolfcampian samples were yellow-orange to orange, which corresponds to slight thermal alteration, or a thermal alteration index of 3.0 in the Geo-Strat (Schwab, 1977) system (fig. 29). This indicates that temperatures were probably high enough to begin to generate hydrocarbons from lipid-rich amorphous organic material (Tissot and Welte, 1978). The amount of light reflected by vitrinite particles is another paleothermometer for source rocks. Palo Duro Basin samples have a broad range of vitrinite reflectance values (Ro), but populations with ~he lowest reflectance probably indicate the true temperatures that were reached in the basin. Vitrinite with higher reflectance was 41 probably reworked from older sediments (Tissot and Welte, 1978). The average reflectance in representative Pennsylvanian vitrinite was 0.52 percent (fig. 29); in Wolfcampian samples the average reflectance was 0.48 percent. These values are consistent with the kerogen color and suggest that basinal source rocks in the Palo Duro Basin may have begun to generate hydrocarbons. 42 Table 3. Wells sampled for geochemical source rock analyses. BEG BEG County Operator Well name County Operator Well name number number Armstrong 1 Standard of Texas #1A Palm Hale 10 Amerada #1 Kurfees Bailey 20 Shell #1 Nichols Hall 1 Amarillo #1 Cochran Briscoe 13 Weaver #1 Adair Hartley 25 Phillips #1A Cattle Castro 11 Sun #1 Herring Lamb 26 Stanolind #1 Hopping Childress 48 Griggs #1 Smith Motley 1 Central #1 Ross Cottle 41 Baria & Werner #1 Mayes Oldham 52 Stanolind #1 Herring Dallam 22 Harrington #1 Brown & Tovra Parmer 4 Stanolind #1 Jarrell Deaf Smith 12 Honolulu #1 Ponder Randall 18 Slessman #1 Nunce Donley 20 Doswell #1 McMurty · Swisher 6 Standard #1 Johnson Floyd 10 Sinclair #1 Massie Swisher 13 Sinclair #1 Savage 43 3000 4000 3000 bOOO oOOO / p t' t; SWISHER CO. )M"ro'Weaver II Adairoo M 0 0 3 0 3 %TOC % TUC % TOC 2000 a..DHAM CO. Slonotind tl Herring ( 3000 8000 M HALL 00. M CHILDRESS CO. Amarillo tt Cochrc:ln Griggs t I Smith 0 2 3 0 3 0 2 3 %TOG %TOC % TOC POOR FAIR l>WU vt:rwr;(Y'In 0-0.5% 0.5-1.0% 1.0-2.0% 2.0-4.0% Figure 27. Wells in the Palo Duro Basin, Texas, with good to very good Pennsylvanian and Wolfcampian source rock potential on the basis of total organic carbon content. 44 / EXPLANATION • Well control Contour Interval= 0.2% TOC 0 40mi 0 40km I i i -~ r_j . ' I ' Figure 28. Geographic distribution of organic carbon in Pennsylvanian and Wolf campian strata of the Palo Duro Basin, Texas. 45 - ----··------~ % Ro II I TAl II HYDROCARBON FACIES ~vrlrnrnrhnn (~PnAr'ntitUI ,.. .2 1.0 .3 w uz ~ u ~ I- .6 lJ._ w ~ ~ .8' _J ~ <( g: .9 ~ 14.5 5 5.0 > 1.0 I 5.5 I- 1.5 2.0 2.5 .,.(! 4.0 *! Kerogen Rich In LiQids lp- Primary imporlonceoAmorphous sapropel and olgGe ls- Secondary importance' Spores, pollen, and cuticle Kerogen Very Leon In LiQids V- Vitrinite- Woody debris 1- lnerts- Coaly debris Figure 29. Kerogen color (thermal alteration index) and vitrinite reflectance values of Pennsylvunian sourc::e rocks in the Palo Duro Basin, Texas, related to hydrocarbon facies (from Schwab, 1977). 46 PRELIMINARY ASPECTS OF DEEP-BASIN HYDROLOGY C. Robertson Handford Potentiometric surfaces of Pennsylvanian and Lower Permian hydrogeologic units in the Palo Duro and Dalhart Basins generally indicate (l) west to east flow of deep-basin fluids, (2) facies control of head distribution, and (3) significant vertical flow. · Sedimentary basins are dynamic and subject to physical and chemical processes throughout their history. Just as they evolve depositionally and tectonically, they also undergo hydrologic evolution. In young, geologically active basins, fluids are forced out of the sedirnents and toward the periphery of basins as a result of loading and compaction. As sedimentary basins mature and their sediments are consolidated, compaction processes slowly cease and circulation of basin fluids is partly reversed. Fresh meteoric water recharges aquifers at their outcrops in topographically high areas and, under the effects of gravity and pressure, or head, water flows toward central, deep areas of basins, flushes out original formation water, and discharges as brines in topographically low; peripheral areas. Circulation in compacted basins may occur in local, shallow systems and regional, large-scale, deep systems. The Palo Duro and Dalhart Basins are old, compacted basins that are marked by both shallow and deep-basin hydrologic systems. To determine deep-basin hydro dynamics, potentiometric-surface maps were constructed for two Pennsylvanian and Lower Permian d.eep-basin aquifers, or hydrogeologic units (Toth, 1978) (figs. 30 and 31). These maps are based upon formation pressures measured during drill stem tests of porous strata carried out during oil exploration and pressure-depth curves (fig. 32). The maps show the height to which water will rise in a well that penetrates the aquifer. Pressure-depth curves and head maps do not truly reflect either the variable density of ground water nor hydrostatic conditions at the point of measurement, but show instead that deep-basin fluids are dynamic. Potentiometric-surface maps of Pennsylvanian and Lower Permian shelf and shelf-margin carbonate units reflect the primary directions of deep-basin ground water flow (figs. 30 and 31). For both of these hydrogeologic units in the Dalhart Basin, recharge apparently occurs at the western side of the basin, and discharge, at the eastern side near the northwestern end of the Amarillo Uplift. In the Palo Duro Basin, ground water in the Lower Permian aquifer tends to flow from west to east and e. northeast, discharging along the southeastern and northeastern edge~ of the basin. 47 Regional flow in the Pennsylvanian aquifer, however, is not marked by simple patterns, which may reflect a relative lack of data control. In both aquifers there is firm evidence for facies control. of head distribution and, thus, regional ground-water flow (figs. 30 and 31). Head contours fairly closely match carbonate-shale facies trends and the positions of relict shelf-margins. Several closed contours that represent areas of both high and low head suggest significant vertical flow through aquifers. Directions of vertical flow and flux are not currently known, but should be addressed ·in forthcoming studies. 48 - ~N----! HANSFORD--.- -1 OCHILTREE-, L~PSCOMB I PA , ______I BAILEY I I · i 1'-j.__ ,-----I EXPLANATION !:::::;:: I> 2500 fl. above sea level ltmr::::::\i\\li500- 2500 ft. above sea level [illl < 1500 ft. above sea level 0 40mi ~--r--L-~--~ ~ >400ft. net carbonate 0 40 km • Drill stem tests in Pennsylvanian (excluding granite wash) X Basement uplift and arches e. Figure 30. Potentiometric surface of Pennsylvanian strata (excluding granite wash) in the Palo Duro and Dalhart Basins, Texas. 49 I DALLAM I HANSFORD I I ROBERTS - -rE_M_P_H-IL_L_- ~ __ L __ CARSON I GRAY 01 w !. ··:·.· .... ·.:.: j > 2500 ft above sea level l'/~\ii/11500- 2500 ft. above sea level [IIIml < 1500 ft. above sea level 0 40mi 1------,----L~------~ ~ > 70% carbonate 0 40km • Drill stem tests in Wolfcampian X Basement uplif1 and arches Figure 31. Potentiometric surface of Lower Permian (Wolfcampian) strata in the Palo Duro and Dalhart Basins, Texas. · · 50 Bailey County fl. Donley County fl. 0· 0 0 0 1000 1000 500 500 2000 2000 .. N • 19 3000 N• 10 3000 Gradient • 0.44 W Gradient • 0.659 ~ 1000 .. .. Correlation Coefficient .::. 0.431 .. Correlation Coefficient:: 0.938 4000 .. 4000 :I: :I: 1- 1- a. 5000 1500 a. 5000 w w Cl Cl 6000 6000 2000 7000 7000 8000 8000 2500 9000 9000 3000 10,000 .L.:.::C:.:---,----.-----.-----.------,-----,----< '0·000'-'o--,--.-,50-o--',o,-oo--',50r-o--2-or-oo--2-5r-oo--30--.-oo---l3500 0 500 1000 1500 2000 2500 3000 3500 PRESSURE PRESSURE (PSI) (PSI) Figure 32. Pressure versus depth curves for drill stem tests in Bailey and Donley Counties, Texas. Correlation coefficients for these two examples are extremely variable and may reflect the dependability of the drill stem tests, or they may indicate the presence or absence of hydrologic continuity between aquifers. 51 CLIMATIC ANALYSIS Robert J. Finley Under the continental climatic regime of the Texas Panhandle, processes of slope erosion are related to episodes of intense rainfall, and there is a potential for high erosion rates. Present climatic norms must be understood as a basis for ongoing field monitoring and assessment of field data. Climate is among the dominant independent variables that control land denuda tion, along with time, initial relief, and geology (lithology and structure) (Schumm and Lichty, 1965). The preciRitation pattern in the Texas Panhandle is characterized by intense, localized thunderstorm rainfall during the spring and summer months (/\pril through September), when 72 percent of the annual precipitation falls (Haragan, 1976). Intense rainfall ~ 2 inches/h (50 mm/h) induces erosion by impact, because of the larger drop sizes characteristic of intense rainfall and the action of slopewash and rillwash when rainfall volumes exceed infiltration capacity plus surface detention. These processes lower the land surface and, in the study area, result in the retreat of the Caprock Escarpment, which bounds the High Plains •. Over a period of .10 4 to 1-0 5 years, erosion will reduce the volume of rock surrounding any waste repository in the Palo Duro Basin. Within a 22-county study area of the Texas Panhandle, data from 25 stations were analyzed for rainfall patterns and rainfall intensity. At most localities, rainfall . . is reported in observational day increments, and an annual series of maximum daily rainfalls must be relied upon to calculate return period~ of intense storms. Appro priate corrections (Hershfield, 1961) are applied to. derive 24-hour values for the equivalent partial-duration series (table 4). The underlined values in table 4 are 10 to 20 percent greater than rainfall amounts interpolated from published national maps (Hershfield, 1961), whereas other values are generally 5 to 10 percent smaller. Published data have been smoothed to fit a national pattern; therefore, the data of table 4 probably better represent local variations. A temporal trend in depth-frequency relationships, however, cannot be entirely ruled out. It should be recognized that thunderstorm rainfall is normally concentrated in a period of several hours, and is most intense for periods of 20 to 60 minutes. Rainfall amounts as listed in table 4, therefore, would rarely be spread out over 24-hour periods. 52 Hourly rainfall data from Amarillo, Texas, and short periods of record for other stations show that hourly intensities which exceed 1 inch/h (25 mm/h), while the most significant geologically, occur during less than 10 percent of the rainfall in the period of record studied (fig. 33). Even the hourly reporting interval does not reveal the rainfall intensity patterns seen on continuous rain gauge records available from erosion process monitoring sites. Data plotted in 1/10-hour increments normally show 12- to 18-minute rainfall intensity peaks (fig. 34), during which erosion potential is high. Field observations confirm these peaks as the most important in slope denudation processes. The June 1.979 storm (fig. 33) at Caprock Canyons State Park is one of several storms that resulted in an average of 0.6 inch (1.4 em)· of erosion (for 19 erosion pins) in the period April-August 1979. Areal rainfall patterns show that the area east of the Caprock Escarpment, in the direction of greater mean annual rainfall, has experienced a greater frequency of intense storm events (fig. 35). These storms affect erosion in the Rolling Hills physiographic province and ultimately affect the rate of ·retreat of the Caprock Escarpment as fluvial downcutting continues under the present climatic regime. It is highly probable, on the basis of studies in Arizona (Fogel and Duckstein, 1969), that each observer location failed to record at least on·e convective storm that affected the local drainage basin; hence the rainfall pattern of figure 35 is only a minimum distribution. Thorough study of the present climate will serve as a baseline for the evaluation of paleoclimatic data and, in turn, consideration of the impact climatic change may have on present erosion mechanisms. Long-term climatic norms must be established for comparison with the weather patterns observed during the several years of erosion measurements in the field. It can then be said whether or not the observed. erosion rates have been affected by typical or atypical precipitation distribution • . 53 140 5.0 120 40 ~ 4.0 ~ 100 Caprock Canyons 0 100 Palo Duro Canyon .t:: State Park .t:: State Park ::0 'E '"' July I, 1978 0 June 8,1979 .t:: 5 .t:: .s 00 "' 0 80 >- Total rainfall 62.8 mm 3.0 .s .t:: Total rainfall 29.2 mm 3.0-;;; Q) ·;;; 'E .t:: c: >- E u ~ 60 ·;;; 60 .5 c: c: >- 2.0 ?: = 2.0 -~ ·;;; .E "'c: c: !'! 40 Q) ·5 40 .5 :ec: -~ ll: ·c; 1.0 ll: 1.0 .E :ec: 20 ·c; 20 ·c;c: ll: ll: O~--£LLUU4~~LUUU~~LLLU~~~LL~~~DL 0 0 -L--~-U-U-UL-~------~_u_u_u~~-0 1700 1800 1900 2000 2100 2000 2100 2200 2300 Time (hours) Time (hours) Figure 33. Rainfall intensity-duration profiles for two storms, recorded at erosion monitoring localities. 55 3.5-r90 June 20,1958 80 3.0- 70 "'cu Total rainfall g 2.5 ~0 3.69inches c (93.7mm) 2.0150 0~ e.§. 70 ~. 1.5 40 0 0:: 30 ~ 60 ::::> --Amarillo 1.0- 0 .r:. --- Brice 20 ~ II> "''g ~50 .r:. u -.-·- Hereford 0.5- ... - c .. 0 ·- (510 ·········Kress ....- aN 40 -··-Matador o II\ J I I I I --cc; 2100 2200 2300 2400 100 200 cu .... ' ::::> Hours of doy t' .!: 30 0 cu 0 .r:. a.. ~ 4 ~.II> £ "''::::JCU o.r:. "i 20 .r:.u c 3 ~~£N .... d 2 10 o II\ c~ ~~-·~-.· cu .... ::::····-············ cue~-= ··- o,. - I J) I I a..~ ol I I I I en .s::. en <;t ··l·' <;t en en <:1: ft en ~ ~ /C ! 1'-: C1'! N <:1: tt, gj ~ 0 d d ....: ....: ~ I I N N r<) I I 1 I I I l(i I I I I lO 0 lO 0 lO lO 0 lO lO N lO 0 lO 0 0 N lO 1'- q "! 1'-: I"' ....: 0 N ~ C\i ~ 0 d d C\i C\i N ,.., Rainfall intensity Rainfall intensity inches /hour inches/hour Figure 34. Hourly rainfall intensity expressed as a percent of the total time period of rainfall with intensity > 0.25 inch (6.4 mm) per hour; also, hourly rainfall intensities for a single storm at Amarillo, Texas. · 56 I - _l______jI I ---- ~--·----- I : I I I I : I L _____ .vega _ _L_ : I -----~=-~~ I I : I I I r----~ 1 I I .... I ~_j:::::::::k::::::: 1 Mule.sil.oe:::::: :::: 1 ·r : I • I I /. : I ~- ___ +____ Littlef~ld ----+---__j- I {1947-76) Number of rainfalls 34 inches per 24 hours 0 25 50mi r::;::] ~2 ~3 r------r---~--~------~ 12d~~· 0 10 20 30km •Figure 35. Four-inch (102 mrn) isohyets compiled from daily 24-:-hour rainfall distribution maps for the period 1947-1976. 57 SLOPE. EROSION MECHANISMS Robert J. Finley and Thomas C. Gustavson Rainsplash, sheetwash, and rillwash are the dominant erosional processes on slopes in the Texas Panhandle under the present climatic regime. Greatest erosion occurs on slopes of 20° or more with lO percent or, less vegetative cover, which characterizes much of the actively eroding Caprock Escarpment bounding the Southern High Plains. The influence of climate on erosion in the Texas Panhandle is determined by the semiarid regional climate and its effect on vegetation, and by the erosional me . chanisms characteristic of that climate. In the Texas Panhandle, surface processes are associated with short-duration, high-intensity rainfall. Surface processes are most active where the full energy of the raindrop can be expended on soil and on weathered rock rather than on vegetation, and where plants do not retard shallow overland flow. The thin soils on moderate to steep slopes in the Rolling Hills physiographic province below the Caprock Escarpment, as exemplified by those in Briscoe County, Texas, have a low capacity to hold moisture and are poorly suited to the growth of vegetation (table 5) (Geiger and Mitchell, 1977). Vegetation on these slopes has also been affected by grazing. Rainsplash erosion (involving particle displacement due to raindrop impact), sheetwash (consisting of thin films of water flowing down slopes), and rillwash (occurring when sheetwash becomes concentrated in small channels a few centimeters deep and wide) are primary mechanisms of surface denudation in the Texas Panhandle. Raindrop lrnpact loosens soil particles, breaks up soil structure, and seals the soil surface by dispersing clay particles, which decreases infiltration. Pat·ticles are al~o transported downslope as a result of the angle of impact of the raindrop (Young, 1972). Raindrop impact is ·an important cause of soil particle detachment, as· is evident from soil· accumulations 3.9 to 5.9 inches (10 to 15 em) above the ground surface on outer surfaces of rain gauges used for field monitoring of erosion processes. Surface flow includes both sheetwash and rillwash, and begins when rainfall intensity exceeds infiltration rate plus surface detention capacity. Excess water then moves downslope, in a sheet which is slightly variable in depth. The water moves around the larger soil aggregates. Subparallel channels, or rills, 0.8 to 1.2 inches (2 to 3 em) wide and deep, may form where surface flow becomes concentrated. 58 Extensive Nosion pin fields have been established at five erosion monitoring locations to record the combined effects of rainsplash erosion and surface flow on slopes. A total of 399 pins have been placed in different slope classes and across different lithologies. Measurements of the ground surface height relative to these pins have shown continuous surface denudation for most pins, and net deposition for few pins, generally in lower slope classes. These data indicate greater erosion on steeper slopes where vegetation is less dense and where erosion reduces the ability of the vegetation to become establish~d. An erosion pin field in Caprock Canyons State Park, set in the soils listed in table 5,. has an average vegetative cover of 7.8 percent (varying from 0 to 32 percent for 47 measurements), indicating that vegetation is sparse on slopes varying from 3° to 44° (average 21 °). Data from the south side of John Haynes Ridge in Caprock Canyons State Park (fig. 36) suggest that vegetative cover decreases with increasing slope angle. This same relationship applies to the combined data distributions from four. monitoring localities (fig. 37). Erosion pins showing greatest net erosion are generally on slopes of 20° or greater with 10 percent or' less vegetative cover. Individual pins may deviate from this general trend depending on their location relative to preferred paths of sheetwash and rillwash. In Caprock Canyons State Park, two pins on slopes of 29° and 33° showed net deposition of 0.69 inch (1.7 em), comparable to erosion of 0.71 inch (1.8 em) on a 35° slope for the period December 12, 1978, through April 11, 1979. Future work will include analysis of erosion pin data from additional locations and the relationship of these data to substrate variation, shape of slope profiles, and correlation with styles of slope retreat. / 59 Table 5. Soil characteristics o.f the two most common soils of the Rolling Hills physiographic 1=rovince in Briscoe County, Texas Jrom Geiger and Mitchell, 1977). Water Erosion Soil Series Depth Drc.inage Runoff Hazard· Burson· 3.2-11.8 inches weJ drained medium to severe dominantly 20 (8-30 em) to excessively very rapid to 45 percent in drained; Burson and steep moderate Quinlan soils unit permeability; very low water cc.pacity I Quinlan 9.8-20 inches well drained; medium to severe 10 to 30 percent (25-50 em) rr.oderately rapid · in Quinlan and hilly rapid Burson soils unit · permeability; l•)W water capacity Suitability for Vegetation Herbaceous Soil Series Upland Plants Grasses Shrubs Burson poor very poor fair Quinlan fair fair fair 50 Net deposition (em) E9 = 0-0.5 40 "" Net erosion (em) ~ 0 =0-0.5 0 0 0 • =0.5-1.0 E9~ 0=1.0-3.0 -30 6 = 3.0-5.0 (/) 6 Q) 0 =5.0-7.5 Q)... 0"1 Q) 0 0 "U 0 I 0 ~ • "" 0"1 c 0 0 0 Q) 20 a. 0 0 0 "" ~ (/) 0 0 0 0 10 0 "" 0~ 0 • 0 0 • "" 0 0 10 20 30 " 40 Percent vegetation Figure 36. Net erosion and deposition for 39 erosion pins measured on December 12, 1978, and August 8, 1979. Dashed line indicates a generalized upper limit for the amount of vegetation relative to land surface slope. 61 50 Net deposition E9 =0- 0.5 ~ Net erosion () =0- 0.5 ~ • =0.5-1.0 " a =1.0-30 a a " =3.0-5.0 a 0 () a """'" = 5.0-10.0 E9 () " " E9 E9 E9 ~- () -;;;- 30 a Q) ~e () Figure 37. Net erosion and deposition for erosion. pins at four monitoring localities for the periods (l) December 12, 1978, to August 8, 1979, at Caprock Canyons State Park, (2) June 26, 1978, to August 24, 1979, at Palo Duro Canyon State Park, (3) June 6, 1978, to May 1, 1979, at Muleshoe National Wildlife Refuge, and (4) February 3, 1978, to December 11, 1978, at Buffalo Lake National Wildlife Refuge. 62 SUSPENDED SEDIMENT CONCENTRATION AND STREAM DISCHARGE RELATION SHIPS FOR THE PRAIRIE DOG TOWN FORK OF THE RED RIVER: AN APPROACH TO DETERMINE EROSION RATES Robert W. Baumgardner, Jr. A positive correlation exists between suspended sediment concentration and stream discharge in the Prairie Dog Town Fork of the Red River near Btice, Texas. Estimates of suspended sediment load based on this relationship can be used to compute rates of denudation for the Prairie Dog Town Fork drainage basin. Rivers are the primary agents by which sediment is removed from drainage basins in the Texas Panhandle. Consequently, records of suspended sediment load of these rivers could be used to compute rates of sediment removal and denudation. However, records of sediment load for rivers draining the study area are very limited, and the longest available record (Lakeview gauge on Prairie Dog Town Fqrk of the Red River) is only 9 water-years. Mean annual denudation rate based on these data is 0~0 15 inch/yr (0.39 mm/yr) but is subject to considerable error because of the small sample size. Streamflow data, however, have been recorded for as long as 40 years at some stations. Using both these data to infer sediment load provides a better means of estimating the amount of sediment being removed from the basins, as well as current rates of denudation. Because there is a correlation between suspended sediment concentration (C) or suspended sediment load (Q ) and stream discharge (Q), it is possible, using data from s years when both types of data were recorded, to project figures for those periods when stream discharge only was recorded. These estimates of suspended sediment con centration or load can then be used to compute rates of denudation. It is necessary first to determine the sediment concentration/streamflow rela tionship for a given stream by constructing. a sediment rating curve for the period of available record. Sediment rating curves (figs. 38 and 39) describe the manner in which suspended sediment concentration and suspended sediment load vary with changes in discharge of a stream. These relationships are expressed by the following equations: (1) C = aQb where C= suspended sediment concentration (ppm) Q= discharge (cfs) (2) Q = aQd suspended sediment load (tons/day) s Q s = a = a constant b and d are exponents giving slope values of the sediment rating curve. 63 The value for exponent b (equation 1) from the Prairie Dog Town Fork of the Red . River is lower than that reported for more' humid climates (Gregory and Walling, 1973). For example, for streams in east Devon, England, b = 1.43, compared with b = 0.51 for the stream in this study (fig. 38). Sediment concentration is less dependent upon discharge in. the semiarid region stream. In addition, the suspended sediment concentration is at least 2.5 times greater at any given discharge in the Prairie Dog Town Fork than in streams in humid east Devon (fig. 38). On the other hand, the value of d (equation 2) from this study (d = 1.48) approaches that (d = 1.84) of the Powder River near Arvada, Wyoming (fig. 39) (Leopold and Maddock, 1953). The rate at which suspended sediment load increases with increasing discharge is approximately the same for both streams. )ntense thunderstorms and the ephemeral stream f:lydrologic cycle affect the slope of the sediment rating curve for the Prairie Dog Town For.k. Difference between suspended sediment concentration of high and low discharges is less for this stream than for the humid region streams (fig. 38). Because flow of the Prairie Dog Town Fork is more dependent on intermittent pulses of storm runoff, suspended sediment concentration is high even at low discharges. Low flows in humid-region streams are sustained by baseflow having low suspended sediment concentration, whereas high flows from storm runoff have much .greater values of suspended sediment concentra tion (fig. 38). Sediment rating curves are used to estimate the sediment loads of streams for periods when no sampling data are available, or for time periods longer than available records. Although there are serious difficulties associated with this approach to computing erosion rates, at least minimum values should be obtained (Campbell, 1977). Sediment load and streamtlow dald arc currf:'ntly being collected on the Prairie Dog Town Fork of the Red River to be used in future calculations of this type. A regional perspective on the amount of suspended sediment being removed from the study area will then be possible, and consequently, another means of predicting the rate of r~moval of exposed strata overlying the salt beds will be attained. 64 50,000 ...... # ...... u II .:: 0 ...... ~... 'E ...... Q) ... 0 ... c: 0 ... 0 ...... c: 0 51 ...... -Q) C=340Q · ... -~ ...... "'0 Q) "' "'0 ... Q) "'0 c: ... Q) a. ::> ...... en"' IO~~------L------~----~~------~5~0------~------~50=0~--~IOOO Discharge = Q (cfs) figure 38. Suspended sediment concentration and stream discharge relationships for two regions--one semiarid and one humid. Data points are from the Prairie Dog Town Fork of the Red River near Brice, Texas (U.S. Geological Survey, 1954, 1955). The (solid) regression line for the Prairie Dog Town Fork data has a more gradual slope and higher values of suspended sediment concentration for any given discharge than the (dashed) regression line representing data from east Devon, England· (Gregory and Walling, 1973, fig. 4.9A). 65 5000 • •• • • • • •• f • • • 7. • ..:4 • /. I • I . en 0 I ·• II -o I •• 0 .2 • c: I. -Q) .§ I• -o Q) (/) I • -o • Q) -o I c: Q) 0. (/) en::1 • I 1 50 500 1000 doily discharge= Q (cfs) Figure 39. Suspended sediment load and stream discharge relationships for two streams in semiarid regions. Data points are from the Prairie Dog Town Fork of the Red River near Brice, Texas (U.S. Geological Survey, 1954, 1955). The slope of the (solid) regression line for the Prairie Dog Town Fork data is similar to that of the (dashed) regression line representing data from the Powder River at Arvada, Wyoming (Leopold and Maddock, 1953, fig. 13). 66 / SHALLOW GROUND-WATER HYDROLOGY --A PRELIMINARY REVIEW William W. Simpkins Studies of the shallow ground-water hydrology in the Permian through Holocene strata of the High Plains, Rollir:tgs Plains, and Pecos Plains regions are intended to determine the occurrence, direction, and rate of ground-water movement in order to deter·mine the mechanism of salt dissolution in the region. Existing data ·and literature have been collected and reviewed. Aquifer Characteristics -- Availability. of hydrologic data for water-bearing units in the region varies directly with the amount of pumpage from the units. The best available data are for the major aquifer of the High Plains, the Tertiary Ogallala Formation (Myers, 1969; Wyatt and others, 1976, 1977). Limited data are available for the Cretaceous, Triassic, and Permian units below the Ogallala Formation, because the water is generally saline and is rarely used for domestic and agricultural purposes (Cronin, 1961; Fink, 1963). Small amounts of water are pumped from Permian aquifers off the High Plains (Cronin, 1972; Mourant and Shomaker, 1970). Ground-water Movement -- Ground water is generally under water-table or unconfined conditions in -the High Plains and Rolling Plains regions in Texas and the Pecos Plains in New Mexico (Cronin, 1961, 1969; Mourant and Shomaker, 1970; Popkin, 1973; Smith, 1973; NFS/National Soil Services, 1979). The water table slopes about 10 ft/mi (2 m/km) to the southeast beneath the High Plains surface within Triassic, Tertiary, and Quaternary units (Cronin, 1961). The gradient steepens at the Caprock Escarpment becau.se of the break in slope and changes in the hydraulic conductivities of the units (Smith, 1973). The slope of the water table (hydraulic gradient) decreases in the Permian ~trata of the Rolling Plains region, in places varying from 10 to 200 ft/mi (2 to 38 m/km), and the direction of flow becomes more easterly (Smith, 1973). In the Pecos Plains region, the water table slopes towards the Pecos River from 30 to 100 ft/mi (6 to 19 m/km) (Mourant and Shomaker, 1970). Ground water discharges locally into streams through springs and seeps. Spring~ commonly occur at the base of sand units in outcrops of the Ogallala Formation and Dockum Group, and in Permian dolomite. Gr~und water under artesian or confined conditions occurs locally in the Tertiary Ogallala Formation and in Permian rocks off the Caprock Escarpment. Extent of confined conditions in the Permian rocks beneath the High Plains is not well known. 67 Mourant and Shomaker (1970) note water under artesian pressure in the San Andres Formation in New Mexico where those beds dip eastward under the High Plains. It is assumed that some water may continue under confining pressure to the east, as a part of a deeper, regional ground-water flow system. Alternation of Permian dolomite, mudstone, and evaporite units would be an ideal situation for the development of artesian aquifer systems. Recharge to the hydrologic system occu~s mainly through precipitation on the High Plains, Rolling Plains, and Pecos Plains regions. Annual recharge to the Ogallala Formation is about 0.8 inch (2.0 em) in Lea County, New Mexico (Havens, 1966) and 0.5 inch (1.3 em) on the Southern High Plains of ~exas (Theis, 1937). Recharge to units below the Ogallala Formation. is not documented. Regional ground-water discharge from the Permian strata occurs on the Rolling Plains surface and is inarked by springs and seeps with high total dissolved solids (TDS), chloride, and sulfate concentrations. These springs and seeps may discharge directly into streams, which often display increases in chloride and sulfate concentra tions below such discharges (U.S. Army Corps of Engineers, 1976; Ward, 1961). Some storage of ground-water brine may occur in floodplain alluvium, only to be flushed out at ·higher river discharges (Engineering Enterprises, 1975). Estelline Spring, located approximately .J-'2 mi (0.8 km) east of Estelline, Texas, is· a major brine spring that discharges into the Prairie Dog Town Fork of the Red River. Ground water discharges through a sinkhole cut 125 ft (38 m) into alluvium and bedrock of the Permian Pease River Group (Galegar and DeGeer, 1969). Before it was capped by the U.S. Army Corps of Engineers in 1963, flow from the spring was estimated at 4 ft3/s and chloride concentration wa3 28,000 ppm. Jonah Creek, a tributary of the Prairie Dog Town Fork of the Red Rlver 6 rni (9.6 km) east of Estelline, is another major source of saline water and contributes 420 tons/day (381 metric tons/day) of chlorides to the river (U.S. Army Corps of Engineers, 1976). Temperature measurements in observation wells indicate that wh_ile the near surface ground-water temperature ranges from 50° to 54°F (10° to 12°C) in winter, temperatures in deeper wells completed in Permian bedrock approach 64°F (18°C) (Engineering Enterprises, 1974). Such large temperature changes within only 100 ft (30 m) of vertical section do not follow the geothermal gradient, and they suggest a deeper and more regional source for this ground water. However, previous tritium dating of ground water. in similar areas by Ward (1961) indicates that most of the water is f)O more than 20 years old, and that it is not part of a large, regional ground-water flow system. Possible contamination of deep ground water by local flow systems was 68 not discussed in that analysis. Future studies will attempt to retrieve more representative, uncontaminated samples from deeper wells, and utilize other ground water dating techniques, including carbon-14. Ground-Water Flow Model -- A conceptual grourid-water flow model for Permian through Holocene strata has been presented by Gustavson and others (in press) (fig. 40). The conc"ept requires an initial input of fresh water at higher elevations on the High Plains and Rolling Plains, which drives the flow of water through the Permian salt uni,ts, diss~lves the salts, and discharges in salt springs and seeps on the Rolling Plains. Smaller, local ground-water flow systems also occur on the Rolling Plains. Although simplified, the rriodel explains patterns of salt dissolution identified in Dutton and others (1979), and also predicts areas of major ground-water discharge east of the High Plains. Collapse features, faults, breccias, and fractures associated with salt dissolution may also provide avenues for ground-water movement, thus making ground-water flow at times interformational rather than strictly intraformational. However, attempts to retrieve fluids from u·nits encountered in the Randall (DOE/Gruy Federal, Inc., Rex White Jr., No. 1) and Swisher (DOE/Gruy Federal, Inc., D.M. Grabbe, No. 1) County test wells were largely unsuccessful, suggesting that the Permian formations have low hydraulic conductivities at those sites. 69 ...; .., ::;: c:: .Q X w• !li ...J ci ~ "S \j T BRISCOE CO. HALl CO. CHILDRESS CO. 3000 900 800 2500 700 p 2000 600 500 EXPLANATION ~Sandstone/ IRsalt 0 10 20 km ~Mudstone ~Dolomite 0 5 10 mi ~Anhydrite Salt dissolution !ltj~{;ii:l\~~~ Alluvium l22,2&l (locally converted to gypsum) Q Figure 40. Conceptual gr::>und-water flow model for the High Plains and Rolling Plains regions, showing ground-water flow paths in relation to regional recharge and discharge areas and to the pattern of salt dissolution (from Gustavson and others, in press). RATES OF SALT DISSOLUTION Thomas C. Gustavson Maximum rates of horizontal salt dissolution locally exceed 0.16 ft/yr (4.8 cm/yr). Mean rates of salt dissolution range from 0.0019 ft/yr (0.057 cm/yr) to 0.1138 ft/yr (3.468 cm/yr) • Westward and southward expansion of the active dissolutiqn zone can be projected if current rates of dissolution are known. The average annual solute discharge for the Southern High Plains of Texas from 6 1969 to 1974 was 2.7572 x 106 tons of dissolved solids per year, including 1.1343 x 10 tons of chloride and 0.513 x 106 tons of sulfate (U.S. Geological Survey, 1969-1974). Nearly half of this load was supplied by the Prairie Dog Town Fork of the Red River, 5 the average load of which, for the same period, was equivalent to 119.54 x 10 ft3 of halite. Methodology of sampling suggests that these are minimum values for solute loads, as discharge through alluvium is not included. To develop a rate for horizontal salt dissolution, two figures must be compared: an estimate of the cross-sectional area of the salt body undergoing dissolution and an estimate of the volume of salt removed from the dissolution surface during a known period of time. The volume of salt exported from the active dissolution zone on the eastern and northern sides of the Palo Duro Basin can be determined from the annual solute load of streams draining the area. Annual solute load--in terms of tons of total dissolved solids, chloride, sulfate, sodium, and calcium--is known for all major· and - . several minor drainage basins along the northern and eastern margins of the Southern High Plains (table 6, fig. 41). The divides of the surface drainage basins are approximate boundaries of ground-water systems· providing base flow to surface streams. The dissolved load of surface streams then represents a minimum value for the dissolved load removed by the ground water beneath each drainage basin. It is also assumed that only a relatively small amount of ground water leaves each basin by subsurface flow, and that surface discharge accounts for all but a small part of the total discharge from a basin. The distribution of salt-bearing units is known, as are the areas where these strata are undergoing dissolution (fig. 42). Examination of geophysical logs indicates that the bed undergoing solution thins abruptly. The thickness of the salt beds exposed • along the solution front is also known. By multiplying the length of the solution front 71 for each salt unit by the thickness of the salt unit, a figure approximating the cross sectional ar:ea of the salt unit is obtained for each drainage basin (fig. 42). By dividing the export volume by the cross-sectional area of all the salt units within a drainage basin, a figure for the mean annual horizontal dissolution rate is obtained (table 6). This analysis of salt dissolution rates indicates that, at present, salt dissolution is more rapid along the eastern escarpment than along the Canadian River Breaks. Maximum mean annual r~tes of horizontal salt dissolution range from 0.0019 ft/yr (0.057 cm/yr)to0.1138ft/yr (3.468cm/yr). The maximum rate of vertical dissolution ranges . from 0.767 x 10-5 ft/yr (2.34 x 10-3 cm/yr) to 30.886 x 10-5 ft/yr (94.141 x 10-3 cm/yr). In 1980, similar analyses will be completed for the western margin of the Palo Duro Basin--between the western Caprock Escarpment and the Pecos River in eastern New Mexico. 72 Table 6. Salt dissolution expressed as rates of vertical and horizontal dissolution. Mean Annual Annual Rates of Solute Load Vertical Dissolution Horizontal Dissoluti·)n BASIN xl0 5 ft 3 of Mean Max. Mean Max. Min. halite x10- 5 ft/y~0- 3 cm/yr x10-5ft/yr ft/yr cm/yr f.t/yr ft/yr lA (5 years) Canadian River 4.460 1.0499 3.2001 1.367 0.735. 0.00189 0.0576 0.00246 0.00132 (Tascosa) 1B Canadian River 1.0312 3-.1431 1.306 0.452 0.00188 0.0575 0.00239 0.00081 (Amarillo) 1C (3 years) Canadian River 7.9221 ·0.7665 2.3362 1.072 0.484 0.00186 0.0568 0.00261 0.00118 (Canadian) 3 9 years) Salt Fork of the 2.1199 0.7405 2.2571 1.509 0.183 0.00621 0.1893 0.01265 0.00154 Red River (Wellington) 4A (9 years) Prairie Dog Town Fork 2.3232 3.1804 9.6939 7.716 1.243 0.00564 0.1719 0.01368 0.00220 of the Red River (Wayside) 4B (9 years) Prairie Dog Town Fork 24.1188 5.6674 17.2742 11.926 2.637 0.01297 0.3952 0.02728 0.00603 of the Red River (Lakeview) 4C (9 years) Little Red River 12.851 27.1130 82.6404 51.172 14.157 0.07712 2.3506 0.14555 0.04027 (Turke ) 4D (9 years) Prairie Dog Town Fork 119.5366 17.7560 54.1203 29.142. 11.816 0.05643 1.7200 0.09261 0.03755 of the Red River (Childress) 5A 5 years) North Pease River 4.3677 1.7911 5.4593 2.672 1.261 0.00626 0.1908 0.00934 0.00441 (Childress) 5B (5 years) Middle Pease River 0.5515 0.2027 0.6177 0.500 0.037 0.00061 0.0857 0.00150 0.00011 (Paducah) 5C (3 years) Pease River 32.5842 5.8465 17.8200 8.056 4.216 0.02033 . 0.6196 0.02801 0.01466 (Childress) 6-10 (5-9 years) Area includes basins 115.5136 30.8860 94.1405 42.910 20.92p O.ll378 3.4680 0.15807 0.07709 6-10 EXPLANATION Watershed of sampling V station · I ______j_' ______ Figure 41. Drainage sub-basins and water-quality monitoring stations, Canadian River Valley and Rolling Plains (see table 6 for solute loads). 74 '·""';:;:~c,;::;;::-;;:rl'::-:rr-' -- -~ I EXPLANATION ~ Salado Formation '% Glorieta Formation • Seven Rivers Formation # Upper Cleor Fork For motion ~ Upper Son Andres Formation (i:~ :.·t::: ::·.~ H1gh Plains surface ~ Lower Son Andres Formation • Figure 42. Salt dissolution zones, Texas Panhandle • 75 PRELIMINARY RATES OF SLOPE RETREAT AND SALT DISSOLUTION ALONG THE EASTERN CAPROCK ESCARPMENT OF THE SOUTHERN HIGH PLAINS AND IN THE CANADIAN RIVER VALLEY Thomas C. Gustavson, Robert J. Finley, and Robert w. Baumgardner, Jr. Preliminary analyses indicate possible slope retreat rates of 0.63 mi ( 1 km) per 5,500 to 9,000 years for the eastern Caprock Escarpment, and 0.63 mi ( 1 km) per 24,000 to 32,000 years for the Canadian River Valley. Preliminary analyses indicate minimum salt dissolution rates of 820 to 1,150 ft (250 to 350 m) per 10,000 years along the ·eastern Caprock Escarpment. The zone of active dissolution in Permian bedded salts closely parallels the escarpment of the southern High Plains (Dutton and others, 1979). If this relationship is not fortuitous, then retreat of the escarpment and southward and westward expansion of the dissolution zone may occur at similar rates. To ensure safe storage of nuclear waste, the integrity of the storage site must be protected from exposure by erosion or salt dissolution. Therefore, it is necessary to develop the capability to predict rates of scarp retreat and salt dissolution. Three :time periods :vere used for analyses of retreat of the eastern Caprock Escarpment: (1) since the end of deposition of the Ogallala Formation about 3,000,000 years ago, (2) since the end of deposition of the Seymour Gravel about 600,000 years ago, and (3) since the deposition of a Holocene . terrace about 8,000 years ago. Although rates of slope retreat probably varied with climatic cycles, determining slope retreats over long time intervals averages out variations resulting from climatic cycles. Initial results of these :,ludic:; are DPing reviewed. The significance of a single slope retreat rate determined by whatever method is always questionable, partlculdi'ly if it is to be used to predict future slope retreat rates. However, since slope retreat rates calculated by three different methods and the maximum salt dissolution rates (table 7) established for areas east of the High Plains differ by less than a factor of 4, some creditability should be given to these rates•. Determination of slope retreat rates is described in detail below. Erosional retreat of the eastern Caprock Escarpment at the head of Holmes Creek, Briscoe County, Texas, has been estimated at 0.69 mi ( 1.1 km) over the past 7,900 to 9,500 years, based on dated archeological evidence. A stratified archeological site along the Holmes Creek tributary of the Little . Red River near Quitaque, Texas, contains radiocarbon-dated bison bones in a sequence 76 of ·alluvial deposits. The location, known as the Lake Theo Site, includes a Paleo Indian butchering station and campsite -at the base of the excavated sequence (Harrison and Killen, 1978), within which bones were found in a deposit of caliche gravel. The Quaternary stratigraphic sequence in the immediate vicinity of the site includes fluvial gravels, some with crossbedding, and at least one buried soil, all of which have been exposed by the downcutting of Holmes Creek. The bed of Holmes Creek adjacent to the archeological site is covered by Lake Theo, a man-made lake, but the vertical distance between the gravel bed which contains the dated bones and the channel.bottom can be estimated using projected slope profiles. A preliminary site survey indicate~ that 41 ft (12.5 m) of downcutting has taken place since the bone-laden gravel was deposited, suggesting an average 0.057 inches/yr (1.45 mm/yr) minimum rate of downcutting over the past 7,900 to 9,500 years. If the present bed of Holmes Creek is lowered by an additional 41 ft (12.5 m) at the site and is accompanied by parallel slope retreat at the head of the creek, the Caprock Escarpment will be cut back a distance of 0.69 mi (1.1 km) in the next 7,900 to 9,500 years (fig. 43). This assumes that climatic conditions will remain similar to those of the last 9,500 years. Archeological materials are present in other localities along the Caprock Escarp ment, and further studies relating dated materials to Quaternary stratigraphy will be undertaken. This may prove t~ be a valuable method for evaluating erosion rates over the past 10,000-year period. Examination of topographic profiles from the Pecos River on the west to central Oklahoma on the east suggests that the eastern Caprock Escarpment may have retreated 200 mi (322 km) since the end of Ogallala Formation deposition (late Pliocene). A series of regularly spaced east-west topographic profiles were constructed across eastern New Mexico, the Texas. Panhandle, and western Oklahoma (fig .. 44). The cross sections illustrate the flat, eastward-sloping surface of the Ogallala Formation. This flat surface can be projected eastward until it intersects the present day surface. The point of intersection is a gross approximation of the original eastward limit of the Ogallala Formation. This technique is conservative because it uses a straight-line projection and not a line segment of a hyperbolic curve, a curve that is more truly representative of a depositional surface. A straight-line projection places the eastern limit of the Ogallala somewhat west of the actual eastern limit. On the other hand, • ·the technique does not consider. vertical lowering of the surface at the point of intersection, which would extend the point of intersection too far eastward. It is 77 ------ probable that the two effects cancel each other so that these projections remain useful as very approximate estimates of the eastern limit of the Ogallala Formation. Preliminary results of these projections suggest that the Ogallala Formation originally extended between 128 mi (206 km) and 261 mi (420 km) east of the modern eastern Caprock Escarpment (fig. 45). These projections are coupled with those of Byrd (1971), Harris (1970), Thomas (1972), and Menzer and Slaughter (1971). Taken collectively, it appears that the Ogallala may have retreated as 'much as 200 mi (322 km) since the end of deposition late in the Pliocene Epoch. Further evidence of the rapid retreat of the Caprock Escarpment can be found in the Seymour Gravels. The. gravels are thought to be derived from Ogallala sediments and to have been deposited "during Kansan time (600,000 B.P .) (Menzer and Slaughter, 1971). If the eastern limit of the Ogallala during Kansan time was immediately west of the Seymour Gravels, then the escarpment in that region has retreated 68 mi (110 km) since the end of Seymour deposition (fig. 45). Mapping of Kansan terrace deposits along the Canadian River Valley indicates that the Canadian River has deepened its Willey approximately 200 ft (62 m) in the past 600,000 years. Assuming parallel slope retreat, 200 ft (62 m) of valley deepening was probably accompanied by 11.6 to 15.2 mi (18.7 to 24.5 km) of valley widening. Several levels of terraces have been mapped on both sides of the Canadian River Valley. In the Lake Meredith National Recreational Area, terrace deposits in three localities overlie volcanic ash beds. Volcanic ash from two localities has been tentatively identified as being in the Pearlette Type 0 family (Jzett, personal commulliLation, 1979)) which would indicate a late Kansan age (600,000 years B.P.). Terrace gravels that overlie the ashes, then, may be of Kansan age m ~llghtly youngPr. At both localities, terraces are approximately 200 ft (62 m) above the present Canadian River. Thus~ the Canadian River has deepened its valley approximately 200 ft (62 m) in the last 600,000 years. Assuming that slope retreat is parallel (Bryan, 1940), it is possible to calculate the slope retreat that accompanied 200 ft (62 m) of valley incision. For cross sections that include the dated ash beds, 3.3 to 6 mi (5.3 to 9.7 km) of valley widening has occurred on the northern flank of the valley and 8.3 to 9.2 mi (13.6 to 14.8 km) of valley widening has occurred on the southern flank of the valley. Valley widening is measured relative to the position of th~ modern Canadian River. 78 Table 7. Rates of slope retreat for areas along the eastern Caprock Escarpment and for portions of the Canadian River Valley. Area Rate Little Red River Basin 0.63 mi (1 km) per 7,200-8,600 yrs Caprock Escarpment retreat since deposition of the Seymour Gravel 0.63 mi (1 km) per 5,500 yrs Caprock Escarpment retreat since deposition of the Ogallala Formation 0.63 mi (1 km) per 9,000 yrs Slope retreat of the Canadian River Valley near Fritch, TX 0.63 mi (1 km) per 24,000 to 32,000 yrs • 79 w E 0.69ml(l.llkm) r-'---, 3200 \ -Profile enlarged 950 ' , at left 3000 900 I .. I 1::>.c 3100 I C) .... I 800 ·~ .~ I ·~ Q:; 2800 ~Ogallala Formation 2700 800 1>:>:>1 Do~kum Group m Quorterm r 2500 Figure 43. Longitudinal profile of Holmes Creek, Briscoe County, Texas, from the Caprock Escarpment to below Lake Theo, illustrating 0.69 mi (1.1 km) of escarpment retreat resulting from 40 ft (12.2 m) of downcutting in the Lake Theo area. Gener alized geology and longitudinal profile of Holmes Creek and the Little Red River are shown on inset. · 80 ~Rock unit contact based an well dolo ··----···- Rack unit contact based an surficial geology HORIZONTAL SCALE o tn(lmi IOOkm 6 4 5 Wo!.hitoRiver . ---!..--' '""- Wa~hiloRr-er· T :_ Ogallala K: Cretaceous (undifferentiated) li: Dockum P: Permian (undifferentiated) Figure 44. Topographic and geological profiles across the Texas Panhandle and • adjacent parts of New Mexico and Oklahoma . 81 / \!):.~:~)~~=~ Present day Ogallala sediments ~ Present day Seymour gravel deposits ------Projections of Ogallala sediments :~ Menzer and Slaughter (1971), furthest extent of ,:;:;:;:;:;:;:::::::;:;: Ogallala deposition ::::::.:-:-:::·:·:· Menzer and Slaughter(l971),extent .of Ogallala ::::::::::::::::::: sediments in Kansan time ·I :,;._,-,:;.·.:·.'.::,;: Byrd ( 197l), furthest Oga II a Ia extent 1:~=:~ ~:·: .'.'.'.'t. ~ Har·ris· (!970) furthest. Ogallala extent \\\\\\\\W mnn 1homas (1972), furthest Ogallala extent a 50 laO a 50 100 150 200 km Austin• Figure 45. Combined interpretations of the easternmost extent of the Ogallala Formation (Harris, 1970; Menzer and Slaughter, 1971; Byrd, 1971; Thomas, 1972). Position of topographic profiles (9-19) in figure 44 are shown. Black dots show points of intersection of projected Southern High Plains surface, with the surface of the ·Osage Plains in .Oklahoma. 82 FAULTING AND SALT DISSOLUTION Thomas \.. Gustav5on Quaternary faulting along the western Caprock Escarpment in eastern New Mexico and · modern faulting east of the eastern Caprock Escarpment in Texas may have resulted from salt dissolution. Quaternary Faults Two northeast-trending fault systems occur along the western Caprock Escarp ment in eastern New Mexico. The Bonita Fault extends more than 10 mi (16 km), from T8N R32E to T9N R33E S35. Another fault (referred to here as Alamosa Fault) lies along Alamosa Creek and extends more than 7 mi (11 km), from T3N R29E Sl2 to T4N R30E S24. Both fault systems are grabens, consisting of normal faults dipping to the northwest and one or more antithetic faults dipping to the southeast. As mapped by Barnes (1977) the Alamosa fault system extends along Alamosa Creek about 7 mi (11 km). However, differences in elevation of stratigraphic units on either side of Alamosa Creek Valley and alignment of the creek along the fault suggest that the fault may extend southwestward for several kilometers beneath Quaternary alluvium. A stratigraphic cross section constructed across the lower reach of Alamosa Creek and across the extension of the Alamosa Fault (fig. 46) shows that the San Andres Formation is stratigraphically continuous beneath the fault projection. The ovedying Artesia Group (equivalent to the San Andres Formation in Texas) thins approximately 180 ft (55 m) near the fault between the Franklin Ill Gephart well and the Shell Ill Swink et al. well. Thinning of the Artesia Group is due to the dissolution of salt beds. Thinning of the Artesia Group in the Shell Ill Swink well has allowed collapse of the overlying strata, including the Alibates Dolomite Lentil. The Alamosa fault system cuts strata of both the Triassic Dockum Group and Tertiary Ogallala Formation, indicating that the fault is at most late Tertiary and possibly Pleistocene in age. Stearns (1972) considered the Alamosa Fault as a southeasterly extension of the Bonita Fault. The Bonita Fault displaces Permian, Triassic, and Cretaceous rocks, but Pliocene Ogallala sediments overlying the fault are not displaced (Barnes, 1977). Therefore, it appears that the Bonita Fault is significantly older than and not directly related to the Alamosa fault system. A stratigraphic section of the area between the two faults shows no evidence of abrupt structural displacement, although salt ' dissolution has occurred and increases northwestwardly (fig. 47). Stearns relates the • Bonita fault system to Laramide deformation. Analysis of a stratigraphic section \ 83 across the fault, based on geophysical and lithological well logs, suggests an alter native interpretation (fig. 48). Between the Gibson Oil Company Ill Parks well on the southeast side of the fault and the Lee Ill Dennis well on the northwest side, approximately 250 ft (75 m) of thinning occurs within the Artesia Group. The thinning can be explained by dissolution of salts and the subsequent collapse of overlying strata, including the Alibates. The subsurface collapse is manifested at the surface by the Bonita fault ~ystem, where surface displacement is also approximately 250 ft (75 m) along the line of the cross section. Modern Faulting Small-scale fault~ng has occurred in Hall County, south of the Prairie Dog Town Fork of the Red River and approximately 12 mi (19 km) west of Estelline, Texas. Six fractures were recognized by freshly repaired cracks in a paved secondary .road. Faults crossing the road were continuous with open fractures in adjacent cultivated . . fields and were up to 4 inches (10 em) in width. Vertical displacementacross faults on the. road surface ranged from 0.4 to 1.6 inches (1 to 4 em). All the faults were aligned between N 25°E and N 60°E. These faults are associated with two large, undrained depressions. This area of Hall County lies within the zone of active salt dissolution, and Estelline Spring, the largest saline spring in this region, is only 13 mi (20 km) east of the fault area. Undrained· depressions, a saline spring, and faults suggest that salt dissolution and collapse is occurring beneath the fault area. 84 M FT NW SE SHoLL OIL 00 FRANKLIN PET. CORP. St"l Test 124-69 • E~tplonotion Gephar (Dickerson) 4t 1 ~~ SHELL OIL 00. Strot Test tt43-69 -Sol! ,...... rPARMER o,_~---"-.--~_:;2 mi l§gAnhydrite I 0 I 2 3 km -Sol! ~~flr=d~~d Sample ~ Sandstone CAPROCK V£o 15.0 ~il! ** Sail dissolution Log ~ Dolomite ESCARPMENT ~ • 'RoostVELT jsA.tLEY /#' Inferred fault ~Shale L1 j ~mi ~Limestone ~ 'Ll LjCOCHRAN ..' Figure 46. Stratigraphic and structural cross section showing thinning of Artesia Group strata. Thinning and resultant ·fault are probably due to salt dissolution. in the Artesia Group strata northwest of the fault. M FT NW SE 5000 Q U .l!.Y co 1500 4000 ~' • ~ f ; 1000 3000 2000 500 TENNECO OIL CO. Holl Mosely II 1000" -Salt SOUTHERN PET EXPL. INC. RL Keelers II - lnlerbedded soli and mud VE' 27 X L·:::::::J Soli solulian Figure 47. Cross section between the Bonita Fault and the Alamosa Creek Fault shows no evidence of displacement. This indicates that the Bonita and Alamosa Creek Faults are not continuous. -\ Quay Co. Curry Co. It 1400 4600 4400 4000 1200 3600 Alibotes 1000 3200 Artesia 2800 800 2400 Son Andres Son Andres 600 2000 co 'J 1600 400 Glorieta 1200 Glorieta Gibson oil E. M. Parks ""I (S.L.; cable tool l 800 200 400 Upper Clear Fork -- Lower 0 MSL Explanation Clear Fork ~Sandstone Lower Cleor t::------3 Shale James Lee ~Anhydrite 0 2 4 5 M; Dennis"! l!iiii!!i!i!il! Salt 012345678Km -zoo- Shell oil ~Dolomite VE~26.5 Exxon co. ·9oo North Pueblo* 2 c=:.::::J No Sample Evelyn Brown*! .----- Faull ( Dotted where i1ferred) Slick Moorman Co. W. A. Dorgherty *I Figure 48. Stratigraphic and structural cross section showing thinning of Artesia Group strata. Thinning and resultant fault are probably due to salt dissolution in Artesia Group strata northwest of the fault. COLLAPSE CHIMNEYS, COLLAPSE SURF ACES, AND BRECCIA ZONES Thomas C. Gustavson Numerous collapse chimneys occurring throughout Permian exposures in the Texas Panhandle give evidence of salt dissolution. Collapse chimneys filled with breccia are common in parts of the Panhandle region. They are a result of natural stoping or roof fall into voids created by salt . dissolution. Collapse in most cases was probably not a single event but rather a series of roof falls. Barnes (1970) has mapped 36 breccia-filled collapsed chimneys along the boundary of Texas County and Beaver County in. Oklahoma, 2 to.10 mi (3 to 15 km) north of the Texas-Oklahoma border. The chimneys occur in the Permian Cloud Chief Formation and are filled with sandstone and conglomerate of the Cretaceous Dakota Group. Ten miles west-northwest of Guymon, Oklahoma, sandstones and conglo merates of the Cretaceous Dakota Group and Kiowa Formation occur as collapse breccia infillings in 15 chimneys within the sandstone and shell of the Triassic Trujillo Formation (Barnes, 1970). A total of 27 filled ,collapse chimneys were discovered in the Permian Whitehorse Formation during construction of the Sanford Dam on the Canadian River, 64 km (40 mi) northeast of Amarillo (Eck and Redfield, 1963). Chimneys range from circular to elliptical in cross section and are filled with slumped r~nd brecciated sediments from the overlying Triassic Dockum Group, Pliocene Ogallala Formation, or from Quaternary Canadian River terraces. The largest chimney exposed at the dam site is approximately 1,000 ft (305 m) in diameter. Characteristically, chimneys consist of (l) slumped or downwarped Permian sediments, (2) a collapse breccia of Permian material followed by a core of Triassic, or (3) Tertiary or Quaternary sediments (figs. 49 and 50). The boundary between competent Permian beds and a collapse chimney core is normally a zone of strong shearing exhibiting nearly vertical beddings. Slickensides rarely occur. In some cases, the cores of chimneys consist of near-vertical beds of younger sediments. Some chimneys contain collapse breccias strongly cemented with Caco ; other breccias may not be 3 cemented (figs. 49 and 50). Collapse over salt dissolution zones produces breccia· zones and complexly folded terrain. 88 The writers have identified numerous collapse chimneys in Permian rocks exposed along the Canadian River, from 3 mi (4.8 km) east of Highway 87 northeast ward to the town of Phillips, Texas, a distance of approximately 30 mi (48 km). Collapse chimneys are uncommon east of the Caprock Escarpment. A collapse chimney in the Permian Whitehorse Sandstone, approximately 10 mi (16 km) east of the Caprock Escarpment and adjacent to Texas Highway 256, is filled with a breccia composed of sandstone and shale of the Triassic Dockum Group. A possible collapse chimney, filled with sediments of the Dockum Group, was found in the Permian Quartermaster Formation, 9 mi (14.5 km) south of Quitaque, Texas, and 2 mi (3.2 km) east of Ranch to Market Road 1065. Collapse breccias and the structure of the collapsed Permian surface are exposed locally along the northern and eastern margins of the Southern High Plains. At several localities in Palo Duro Canyon and near Caprock Canyons State Park, red Permian mudstones have been complexly fractured, and the fractures have been filled with white satin spar gypsum (fig. 51). The complex fracturing probably occurred as a result of collapse of strata over areas of salt dissolution. As salts were removed, roof collapse propagated upward, and fractures that developed in the collapsing overburden were filled with gypsum. Close examination of the fracture fillings indicates that several episodes of fracturing occurred. Fracture fillings are broken and displaced and locally sheared or torn. Furthermore, collapse of overlying beds as a result of salt dissolution has resulted in the structurally complex folded erosion surface exposed near Borger, Texas. The folded erosion surface is exposed where Triassic and younger sediments have been stripped from the Alibates Dolomite Lentil (fig. 52). The Alibates Dolomite is a resistant bed and protects the underlying mudstones from erosion. At the same time, the Alibates reflects the complex nature of the fold surface, consisting of anticlines, synclines, domes, and basins randomly pierced by collapse chimneys. 89 Figure 49. Person is standing in an oblique section of a collapse chimney. The upper portion of the chimney is truncated by undisturbed Quaternary terrace. Note that Permian strata are broadly folded and dip toward the chimney. Photograph was taken from Texas Highway 136, 3 mi (5 km) north of Borger, Texas. Figure 50. The erosional remnant behind the figure is a collapse chimney cornposed of carbonate-cemented gravels and breccia. The contact with the surrounding Permian strata is shown by the dashed line. Photograph was taken in the Lake Meredith Recreation Area. 90 Figure 51. Gypsum fills fractures along bedding planes and across bedding planes in Permian red mudstones exposed in Caprock Canyons State Park, north of Quitaque, Texas. Holocene alluvium fills the channel, cut into Permian strata. Figure 52. Three anticlines and two synclines occur in Permian strata along Texas Highway 136, approximately 5 mi (8 km) north of Borger, Texas. This structure results from collapse of Permian strata over zones of salt dissolution. 91 ------~ LANDSAT ANALYSIS OF SURFACE LINEAR ELEMENTS Robert J. Finley A pronounced northwest-southeast trend of surface lineaments across the Palo Duro Basin shows a relationship to Ogallala water chemistry which should be investigated further as an indication of vertical fluid migration. To establish lineament density, lineaments in each 7 .5-minute U.S. Geological Survey quadrangle were measured, and the length of the more than 4,700 lineaments totaled 12,294 mi (19,785 km). The orientations of lineaments on the High Plains (fig. 53) show northwest and subordinate northeast trends. A strong north to north northeast trend, with subordinate northeast and northwest trends, is apparent in the Rolling Plains, Canadian Breaks, Pecos Plains, and a small section of the Edwards Plateau physiographic provinces. Lineament density is high along the Caprock Escarpment where topographic scarps are most evident, and east of the escarpment where linear drainage features have developed in the Rolling Plains. A northwest-southeast trending lineament belt over the Palo Duro Basin has a peak density of 53 mi (86 km) per quadrangle in the Dodd SE quadrangle in southern Castro County, Texas (fig. 54). This lineament belt, first noted by Finch and Wright (1970) and termed the Running Water Draw - White River Ltn~:~wnent, is lfi to 18 mi (26 to 29 km) wide and extends 150 mi (242 km) from Crosby County, Texas, to Curry County, New Mexiu.). Aligm~d playas, some with incipient drainage developed between playas, and linear draws (Woodruff and others, 1979) form individual lineaments within the trend. The belt of high lineament density overlies an area of greater net sand, which has increased hydraulic conductivity, within the Ogallala Formation. Greater recharge through these sands may have enhanced playa development. Correlation between lineament orientation and jointing measured around the margins of the High Plains, and the apparent structural control of stream courses in the Rolling Plains, suggests that a regional joint pattern may control the orientation of lineaments on the High Plains surface. Such joints could act as preferred pathways for ground-water migration and thereby influence the water chemistry of the Ogallala Formation. However, data available from the Texas Department of Water Resources 92 for a regional base of more than 1,100 Ogallala wells did not show a clear relationship to the lineament trend. No correlation between chloride or sulfate concentration and the lineament trend was .noted. Somewhat lower fluoride and silica values do correlate with the lineament trend, but they may be influenced by Ogallala sedimentary facies variations (Seni, personal communication, 1979). Since the lineament trend overlies a generalized net sand thick which probably possesses greater hydraulic conductivity, lower fluoride and silica values may therefore reflect lower residence time of water in the Ogallala Formation rather than dilution by meteoric water preferentially recharged along the lineament trend. Data from the Ogallala Formation in the Oklahoma Panhandle show increasing chloride and su~fate from west to east, considered to be the result of upwelling water from Permian deposits (Krothe and Oliver, 1979). Very little water chemistry data are available for formations underlying the Ogallala beneath the High Plains. Comparison of water chemistry in the Ogallala Formation with the underlying Dockum Group, within the area of highest lineament density (southwest Castro County), would be informative with respect to vertical fluid migration • • 93 Rolling Plains Canadian Breaks N High Plains N Pecos Plains Edwards Plateau I 8,942 km I 10,843km 15 10 5 0 5 10 10 5 0 5 10 Percent Percent Figure 53. Distribution of lineament length by 10° azimuth category for the Southern High Plains and parts of adjacent physiographic provinces. 94 33° ~l4-.~~~L__j _____Ll_ __ ~~~----_j~~~I0~2~.~--_J~88~----~~~~~~------~IOO•w Lineament Density km/7.5 minute quadrangle 10 0 10 20 30 40 mi •> 75 U}~~·'i1 45 10 0 10 20 30 40 50km Rj60 f;;:.;ifl 30 Figure 54. Lineament density over the central Texas Panhandle and adjacent eastern New Mexico. 95 ------I REFERENCES Barnes, V. E., 1970, Geologicai Atlas of Texas, Perryton Sheet: The University of Texas at Austin, Bureau of Economic Geology. ----:----,..,------, 1977, Geologic Atlas of Texas, Clovis Sheet: The University of Texas at Austin, Bureau of Economic Geology. Bryan, Kirk, 1940, The retreat of slopes: Annals of the Association of American Geographers, v. 30, p. 2254-2268. Byrd, c. L., 1971, Origin and history of the Uvalde gravel of Central Texas: Waco, Texas, Baylor University, Baylor Geological Studies Bulletin No. 20, 43 p. Campbell, I. A., 1977, Stream discharge, suspended sediments and erosion rates in the Red Deer River basin, Alberta, Canada, in Erosion and solid matter transporta tion in inland waters: Symposium, International Association of Hydrological Sciences, IAHS Publication 122, p. 244-259. Cronin, J. G.t 1961, A summary of the occurrence and development of ground water in the Southern High Plains of Texas: Texas Board of Water Engineers Bulletin No. 6107' 104 p. ----=,----,--- 1969, Ground water in the Ogallala Formation in the Southern High Plains of Texas and New Mexico: U.S. Geological Survey Hydrologic Investiga tions Atlas HA-330, 5 sheets. 1972, Ground water in Dickens and Kent Counties, Texas: Texas Water ---=---:-- Development Board Report No. 158, 79 p. Dow, W. G., 1978, Petroleum source beds on continental slopes and rises: American Association of Petroleum Geologists Bulletin, v. 62, p. 1584-1606. Dunham, R. J., 1962, Classifirn.tion of carbonate rocks according to depositional texture, in Classifications of carbonate rocks: Arnericiln As"ociation of Petro leum Geologists Memoir 1, p. 108-121. Dutton, S. P., and others, 1979, Geology and geohydrology of the Palo Duro Basin, Texas Panhandle: The University of Texas at Austin, Bureau of Economic Geology Geological Circular 79-1, p. 87-95. Eck, William and Redfield, R. C., 1963, Geology of Sanford Dam, Borger, Texas: Panhandle Geological Society Fieldtrip Guidebook, p. 54-61. Engineering Enterprises, Inc., 1974, Ground-water flow evaluation, Areas IX, XIII, and. XIV, Red River Chloride Control Project, Oklahoma and Texas: report for the Department of the Army, Tulsa District Corps of Engineers, Contract No. DACW 56-74-C-0088, 83 p. 1975, Evaluation of alluvial brine replacement, Red River Chloride Control Project, Texas and Oklahoma: report for the U.S. Army Corps of Engineers, Tulsa District, Contract No. DAWC 56-74-C-0213, 165 p. 96 _j Finch, W. I. and Wright, J. C., 1970, Linear features and ground-water distribution in the Ogallala Formation of the Southern High Plains: Texas Tech University, Lubbock, International Center for Arid and Semiarid Land Studies, Ogallala Aquifer Symposium, p. 49-57. Fink, B. E., 1963, Ground-water geology of Triassic deposits, northern part of the Southern High Plains of Te~as: High Plains Underground Water Conservation District No. 1, Report No. 163, 76 p. Fogel, M. M., and Duckstein, L., 1969, Point rainfall frequencies in convective storms: Water Resources Research, v. 5, no. 6, p. 1229-1237. Galegar, W. C.~ and DeGeer, M. W., 1969, Measuring subsurface spring flow with radiotracers: Journal of the Sanitary Engineering Division, Proceedings of the American Society of Civil Engineers, p. 1097-ll03. Geiger, L. C. and Mitchell, W. D., 1977, Soil survey of Briscoe County, Texas: U.S. Department of Agriculture, Soil Conservation Service, 63 p. Glennie, K. W., i 972, Permian Rotliegendes of Northwest Europe interpreted in light of modern desert sedimentation studies:· American Association of Petroleum Geologists Bulletin, v. 56, no. 6, p. 1048-1071. Gregory, K. J., and Walling, D. E., 1973, Drainage basin form and process: New York, John Wiley, 456 p. Gustavson, T. C., Finley, R. J., and McGillis, K. A., in press, Regional salt dissolution in . the Texas Panhandle: The University of Texas at Austin, Bureau of · Economic Geology Report of Investigations. Haragan, D. R., 1976, Spatial variation of precipitation on the Texas High Plains: Water Resources Bulletin, v. 12, no. 6, p. 1191-1204. Harris, S. A., 1970, Bends of the South Canadian: Shale Shaker, v. 20, p. 80-84. Harrison, B. R. and Killen, K. L., 1978, Lake Theo: a stratified, early-maJi, bison butchering and camp site, Briscoe County, Texas, Archeological investigations Phase II: Canyon, Texas, Panhandle-Plains Historical Museum, Special Archeo- logical Report 1, 108 p. · Havens, J. S., 1966, Recharge studies on the High Plains in northern Lea County, New Mexico: New Mexico State Engineer Office Technical Report 1, 35 p. Hershfield, D. M., 1961, Rainfall frequency atlas of the United States for durations from 30 minutes to 24 hours and return periods from 1 to 100 years: Washington, D.C., U.S. Department of Commerce, Weather Bureau, Technical Paper 40, 115 p. Krothe, N. C., and Oliver, J., 1979, The hydrogeochemistry of the Oklahoma section of the High Plain (abs.): Geological.Society of America, Abstracts with Programs, . v. 11, p. 461. Leopold, L. B., and Maddock, Thomas, 1953, The hydraulic geometry of stream channels and some physiographic implications: U.S. Geological Survey Pro fessional Paper 252, 57 p. 97 L______~ ·Menzer, F. J. and Slaughter, B. H., 1971, Upland gravels in Dallas County, Texas, and their bearing on the former extent of the High Plains Physiographic Province: the Texas Journal of Science, v. 22, p. 217-222. Mourant, W. A., and Shomaker, J. W., 1970, Reconnaissance of water resources of De Baca, New Mexico: New Mexico State Bureau of Mines and Mineral Resources Ground-Water Report 10, 87 p. Myers, B. N., 1969, Compilation of results of aquifer tests in Texas: Texas Water Development Board Report No. 98, 532 p. NFS/National Soil Services, Inc., 1979, Salt Area IX, Basin Chloride Control, Arkansas Red River, Site Investigation and Evaluation, Pump Test: report to the Tulsa District Army Corps of Engineers, Contract No. DACW 56-78-C-0257, 25 p. Popkin, B. P ., 1973, Ground .. water resources of HaH and eastern Briscoe Counties, Texas: Texas Water Development Board Report No. 167, 85 p. Schumm, S. A. and Lichty, R. W., 1965, Time, space, and causality in geomorphology: American Journal of Science, v. 263, p. 110-119. Schwab, K. W., 1977, Source rock evalu<;1tion (visual kerogen): Commercial brochure, Houston, Texas. Smith, J. T ., 1973, Ground-water resources of Motley and northeastern Floyd Counties, Texas: Texas Water Development Board Report No. 165, 66 p. Staplin, F. L., 1969, Sedimentary organic matter, organic metamorphism, and oil a.nd gas occurrence: Canadian Petroleum Geologists Bulletin, v.l7, p. 47-66. Stearns, D. W., 1972, Structural interpretation of the fractures associated with the Bonita Fault, in Kelley, V. C. and Trauger, F. D., eds., Guidebook of 23rd Conference of the New Mexico Geological Society: East Central New Mexico Geological Survey, p. 161-164. Theis, C. V ., 1937, Amount of ground-water recharge in the Southern High Plains: American Geophysical Union Transactions, 18th Annual Meeting, v. 18, p • . 564-568. Thomas, R. G., 1972, The geomorphic evolution of the Pecos River system: Waco, Texas, Baylor University, Baylor Geological Studies Bulletin 22, 31 p. Tissot, B. P. and Welte, D. H., 1978, Petroleum formation and occurrence: New York, Springer-Verlag, 538 p. Toth, J., 1978, Gravity-induced cross-formational flow of formation fluids, Red Earth region, Alberta, Canada: analysis, patterns, and evolution: Water Resources Research, v. 14, p. 805-843. U.S. Army Corps of Engineers, 1976, Arkansas-Red River Basin Chloride Control: Design Memorandum No. 25, General Design Phase 1--Plan Formulation, v. I and II, 7 appendices. U.S. Geological Survey, 1954, Quality of surface waters of the United States, 1950: U.S. Geological Survey Water-Supply Paper 1188, pt. 7-8, 446 p. 98 ---.,--- 19.55, Quality of surface waters of the United States, 1951: U.S. Geological Survey Water-Supply Paper 1199, pt. 7-8:~490 p. _____ Water resources data for Texas, 1969-1974, Part II: Water-quality records: U.S. Geological Survey Basic-Data Report. Ward, P. E., 1961, Geology and ground-water features of salt springs, seeps, and plains in the Arkansas and Red River basins of western Oklahoma and adjacent parts of Kansas and Texas: U.S. Geological Survey Open-File Report, 94 p. · Woodruff, C. M., Jr., Gustavson, T. C., and Finley, R. J., 1979, Playas and draws on the Llano Estacado--tentative findings based on geomorphic mapping of a test area in Texas: Texas Journal of Science, v. 31, p. 213-223. Wyatt, A. W-., Bell, A. E., and- Morrison, S., 1976, Analytical study of the Ogallala aquifer in Floyd County, Texas: Texas Water Development Board Report No. 2ll, 63 p. ---=--- 1977, Analytical study of the Ogallala aquifer in Briscoe County, Texas: Texas Water Development Board Report No. 212, 63 p. Young, A., 1972, Slopes: New York, Longman Group Limited, 288 p. 99