OF-WTWI-1984-20

JOINTING HISTORY OF THE PALO OUR BASH'

by

E. W. Co 11 ins

Prepared for the U. S. Department of Energy Office of Nuclear Waste Isola ion under contract no. DE-AC-97-83W 46615

Bureau of Economic Geology W. L. Fisher, Director The University of Texas at Aus in University Station, P. O. Box X Austin, Texas 78712

1984 Jointing History of the Palo Duro Basin

E. W. Colli ns

Joints are fractures or partings in a rock hat exhibit no displacement

(Bates and Jackson, 1980, p. 334). Two styles 0 joints are systematic joints and nonsystematic joints (Hodgson, 1961). atic jOints occur in sets. Joints composing each set are subparallel and are commonly orthogonal to the upper and lower surfaces of the rock units in wh'ch they are present. Non- I systematic joints display no preferred orientati~n and truncate against systematic joints. I

Origin of Joints

Previous work on the origin of joints has de ermined different mechanisms to explain fracturing. Some researchers have ex lained joints in terms of their relationship to tectonic deformation and m jor structural elements (Harris and others, 1960; Price, 1966; Stearns a d Friedman, 1972). Others have shown that joints may develop independently rom tectonic ... qef,"Qrmation and .;ff';- \',,(;,':. that joints may form in sedimentary rocks early in the~t~~,6.r~~,t"ker, 1942; (~~, "::',,< \ "'~ ..... Hodgson, 1961; Price, 1966; Cook and Johnson,~2 \,;J~,,,, ~ ";'::'e ~ investigated

~":"t ~\~~~.. ~ ~~~.1l~ the development of joints and stress syst~rtr~\ . :~~" ':.::\ :~:~:. ~~t; accumulation of a sedimentary series,~;4;~§.~.ommw and subsequent uplift, and accompanying dewatering of the sed~nts. ints can also result from unloading due to erosion (Chapman, 1958). sedimentary rocks is dependent on three factors (Hobbs, 1967): (1) physical properties of both the fractured rock bed and th surrounding rock beds; 2

(2) thickness of the rock bed; and (3) degree of tectonic deformation of the beds. Joints in Pennsylvanian and Permian strata f the Palo Duro Basin area were probably formed by stress systems associate with the development of the basin and the surrounding areas of uplift. Join orientations in Triassic and Permian rocks are similar in some areas, suggesting the same stress systems affected these sediments (see section on Fractur Orientations in Swisher and Deaf Smith Counties, page 5). Joints in Tertiary rocks are not common. Some joints and fractures are related to folds and fa lts that occur along the margins of the Palo Duro Basin (see section on Fults, Folds and Joints, page 3). Fractures have also developed from processes associated with collapse or downwarping of strata related to evaporite disso ution (see section on Frac­ tures and Veins in Core, page 6).

Regional Fracture Tre

Ongoing studies to determine the regional f trends of the Texas Panhandle consist of measuring joint strikes in utcrop and fracture orienta­ tions from fracture identification logs. Most d ta have been collected along the High Plains Escarpment and the Canadian Rive Valley (fig. 1). Outcrops are sparse in the Texas Panhandle; thus, there is a wide range (10 to >100) in the number of measurements that were made at the various study locations. Stations with the greater number of measurements are given more emphasis for interpretations. Dominant fracture trends were etermined using the X2 test of significance at a 95 percent confidence interval. Methods for using this statistical test have been described in detail b Dix and Jackson (1981). Figure 2 shows the dominant fracture orient ions in the Texas Panhandle and Eastern New Mexico. A group of east-west oriented fractures with an 3 azimuth range of 0700-1200 occur throughout the tudy area. Several sets occur within this fracture group. One set striking 10 0-1200 (2800-3000) is important, because it trends across Swisher Coun y and possibly through Deaf Smith County (fig. 3). Two sets of northwest-or ented fractures strike at 3000-3200 and 3300-3500 (figs. 4 and 5). These factures appear to be most common northeast of Swisher and Deaf Smith Count es; however, data are sparse southwestward. A group of fractures striking no theast at 0300-0600 probably occur in two sets (fig. 6). This group of fract res prevails in the north­ western part of the study area and are not commo southeast of Deaf Smith I County. A fracture set oriented at 0000-0200 is less common than the other fracture trends (fi g. 7).

Faults, Folds, and Jo nts

Fracture orientations at various locations i the Texas Panhandle and Eastern New Mexico coincide with trends of fault and folds. At the western margin of the Palo Duro Basin, joint trends are imilar to the strikes of faults mapped from surface exposures (fig. 8). he Bonita Fault and the Alamosa Creek Fault strike at 0400-0500• The Bo County, 1972b), Stearns (1972), Berkstresser and Mourant others (1946), and Wi nchester (1933). trends 0450, dips 600 westward, and It is associated with an antithetic fault zone, so nita Fault System consists of a tilted graben block up to 1.5 aceous age strata are faulted against Triassic Dockum rocks. Shear and extens on fractures are associated with the Bonita Fault Zone (Stearns, 1972). In northern Roosevelt County the Alamosa Cre k Fault has been mapped by Lovelace (1972b). The fault strikes at 055 0; the dip and throw have not been 4 determined. The total faulted system comprises graben block with Cretaceous age strata faulted against Triassic Dockum strat , similar to the Bonita Fault System. Undisturbed Tertiary Ogallala sediments are mapped over both faults, suggesting pre-Ogallala fault movement. Ongoing field studies are investigat­ ing possible post-Ogallala fault movement at the lamosa Creek Fault, because a post-Ogallala stream valley diverts the surface rainage and follows the fault. The Bonita and Alamosa Creek structures are also Irecognized in the subsurface in figure 9. The structure exhibited at the base of the Permian San Andres Formation is below any salt dissolution that mig t have occurred in this area. Boreholes drilled to basement are too sparse to if basement structure exists. These faults strike similar to the regional racture group shown in figure 6. Also aligned with these northeast tren ing structures is an unnamed

0 1 0 1 fault located in Potter County, Texas, near lati ude 35 30 , longitude 101 45 (fig. 10). This small, normal fault strikes at 0 50 and dips 800-900 to the southeast. The Permian Alibates Formation is offset 30 feet and faulted Permian Quartermaster strata are overlain by undi turbed Tertiary Ogallala sediments. Data also indicate fractures are associated ith broad, drape folds related to the Amarillo Uplift. East and west of the U.S Highway 287 bridge crossing the Canadian River in Potter County, Texas, Permi n and Triassic strata dip gently off the John Ray and Bush Domes (fig. 10). About 5 km east of the high­ way, Permian, Triassic, and Tertiary strata dip 0 15 0 south-southwestward off of John Ray Dome. Also flanking John Ray Dom is a surface fault that displaces Permian and Triassic rocks (Barnes, 19 9). The strike of this fault is 310°-295°. Joints in the folded Permian and T iassic strata strike 310°, similar to the fault trend in this area (fig. 11) The joints are almost S perpendicular to the sandstone beds; thus, joint in dipping strata dip only 80 0-900 northeastward. The close spacing of fra tures is apparent in the thick Triassic sandstone beds; 10-16 fractures per 2 m occur in beds 1 to 2 m thick. The trends of joint sets and small-scale fau ts in basal, Tertiary Ogallala sandstones and conglomerates suggest st ess directions changed after fracturing of the Triassic rocks. Joint sets in the Tertiary Ogallala rocks strike at 02S o and 29S o (fig. 11). Normal faults with displacements less than 0.5 m also occur in the Ogallala strata (fig. 12. Two categories are based on the dip of the faults. Faults dip (1) nearly ve tical and (2) SOo-600 north­ northeast and south-southwest. Most faults stri e between 270 0 to 3000 • Beds thicken on the downthrown blocks of several faul s that dip 500-60 0• This indicates some syndepositional fault movement. aults and fractures are usually not common in Tertiary Ogallala rocks in the Tex s Panhandle. The fractures are believed to be caused by e tension related to the folding of the strata. The John Ray Dome is one of seve al regional anticlines asso­ ciated with the Amarillo Uplift (Rogatz, 1939). Early studies by Powers (1922) identified only a few faults with small displace ents associated with these domes. He explained these domes by differential compaction of strata over basement highs rather than by recurrent motion 0 fault-bound basement blocks. However, basement fault motion should not be dis issed as a possible cause of the doming (Budnik, 1984) (Budnik, see SCR secti ns 3.3.2.2 Faulting History and 3.3.2.3 Folding History). Extensive drilling throughout the region has identified more faults in the subsurface.

Fracture Orientations in Swisher and D af Smith Counties

Fracture orientations in Pennsylvanian, Permian, Triassic and Tertiary strata were measured from Schlumberger fracture identification logs in Swisher 6 and Deaf Smith Counties (figs. 13 and 14). A fr cture set striking at 2BOo- 3000 occurs within the Pennsylvanian, Permian, a d Triassic strata in Swisher County (fig. 13). Within the Permian salt zone nits fracture sets also strike

0 0 0 at 000 -020 and OBOo-090 ; fractures striking a 030 0-040 0 and 3200-330 0 are not as abundant. In the Tule Canyon area joints in Triassic rocks predomi­ nantly strike 2BOo-290 0 and 3000-3200• Less com on joint sets strike 3300-

3500 , 000 0-020 0 , and 030 0-040 0• In northeast Deaf Smith County, fractures or ented eastward and northeast­ ward prevail (fig. 14). Pennsylvanian strata ha e dominant fracture sets striking 290 0-3000 and 020 0-0300 • Other fractur s trend at OBO o-0900 and 3400-

0 O 350 • A strong east-west (OBO -1000 ) fracture s t occurs in the Wolfcamp strata. Fracture sets striking at 0700-1000 and 030 0-050 0 occur in Permian salt zone units, as well as Triassic and Tertiar rocks.

Fractures and Veins in Core

The abundance of fractures and veins in Perm an strata has been analyzed in core from boreholes drilled in Oldham, Deaf S ith, and Swisher Counties (fig. 15). The cored strata range from Wolfcamp Group to the Alibates Forma­ tion. Units are grouped into three categories b sed on lithology and strati­ graphic sequence (Hovorka, personal communicatio , 19B3). The categories are (1) strata below salt units (Wolfcamp Group), (2 salt zones units, and (3) dissolution zone units. The boundary between th dissolution zone units and the salt zone units is not the same at each bore ole. The number of one-foot intervals that contai fractures are recorded for all of the cored intervals. The percentage of f actured core for each unit is determined by dividing the number of one-foot co e intervals containing frac­ tures by the total core footage, and then multi lying by one hundred (fig. 16). 7

Figure 16 compares the boreholes and the per entage of fractures in the core for the units (1) below the salt zone, (2) ithin the salt zone, and (3) within the dissolution zone. The dissolutio zone units are more fractured than salt zone units. The salt zone unit catego y contains the lowest percent­ ages of fractured core, probably because the fra tures almost always occur in thin mudstone, siltstone, and anhydrite interbed. Vein-filled fractures within the thicker salt sequences are rare. The Stone and Webster-Mansfield #1 borehole in Oldham County has the greatest perce tage of fractured core for the three categories. This might be expected, becau e this borehole is located within the Bravo Dome-Amarillo Uplift area. The uplift area borders the Palo Duro Basin on the north and is believed to have een more tectonically active than the basin during and after Permian time. T e frequency of fractures in Wolfcamp core decreases away from the Bravo Dome Amarillo Uplift. The fracture percentages in core within the salt zone units a e similar for all boreholes in the three counties. The fractures are commonly filled with gyps m, halite, anhydrite, or calcite veins. Vein fillings within the salt di solution zone strata are predominantly fibrous gypsum (fig. 17). Gypsum

Randall and Briscoe Counties have been describe ~U_'IIII·,n (1982) and Goldstein and Collins (1984). scar and are believed to be an antitaxi -seal" vein (Ramsey, 1980; Ramsey and Kligfield, 1983, veins as wide as 5 cm are common. Fractures within the salt zone units are ch racterized by fibrous, halite veins, commonly 0.5-1.0 cm wide. The veins usually occur within mudstone, siltstone, and anhydrite beds. Halite fills ove 80 percent of the fractures in the salt zone strata (fig. 18). 8

In the strata beneath the salt zone units, he fractures are commonly filled with anhydrite and calcite or have no ve n fillings (fig. 19). Halite and gypsum veins occur within upper Red Cave and Wichita strata, respectively, in the Oldham County, Stone and Webster-Mansfield #1 borehole. The fibrous veins in the units beneath the salt-bearing stra a are usually less than 1.0 cm wide.

Veins and Fractures in 0 tcrop

Detailed field studies of joints and gypsum veins have been done at Caprock Canyons State Park in Briscoe County (Go dstein and Collins, 1984; Goldstein, 1982). This area was studied because few outcrops occur in the interior of the High Plains. Caprock Canyons St te Park straddles the eastern high-plains escarpment, which has relief up to 20m in the park area (fig. 20). There are excellent exposures of Upp r Permian strata along the escarpment and in incised streams that drain eas ward into the Rolling Plains. Other exposures are rare. Exposed in the park ( ig. 21) are the Upper Permian Whitehorse Sandstone and Cloud Chief Gypsum of t e Whitehorse Group. These units are composed of interbedded shale, siltsto e, sandstone, and gypsum beds. In this area, gypsum beds near the top of the Whitehorse Group are up to 4 m thick. Massive, thickly bedded sandstones and s ales of the Permian Quarter­ master Formation overlie the Whitehorse Group. andstones, shales, and con­ glomerates of the Triassic Dockum group overlie ermian strata. The Triassic rocks are capped by Tertiary Ogallala sediments nd caliche. The park is located above a zone of regional salt dissolutio (Gustavson and others, 1982). Deformation of the Permian strata at Caproc Canyons State Park has been described in detail by Goldstein and Collins (19 4). Two zones defined on the basis of deformation structures occur within the park (fig. 21). The 9 upper, relatively undeformed strata zone occurs n the massive, thickly bedded sandstones in the upper portion of the Permian Q artermaster Formation and is characterized primarily by joints. The lower, d formed zone of strata en­ compasses the Whitehorse Group and lower Quarte master Formation (fig. 21). In this zone thinly bedded siltstones and sandstone are interlayered with bedded gypsum. Within the more deformed rocks of this ower zone are normal faults, reverse faults, and gypsum veins along fault con acts, bedded planes, and joint surfaces. Folds and funnel-shaped depressions a so occur. Systematic and nonsystematic joints are cha acteristic of the undeformed zone (fig. 21). Systematic joints are vertical, evenly-spaced, regularly oriented fractures. The predominant systematic strike north, north- east, and east. A less significant set strikes n rthwest. One or more of these four sets of joints are predominant within ifferent domains in the park area. Hackle fringes and plume structures on joint faces are evidence of horizontal propagation under the influence of ho izontal extension. Non­ systematic joints are curved, irregularly spaced, show no preferred orientation and truncate against systematic joints. Many non ystematic joints have surface markings that indicate vertical propagation dire tions (Goldstein, 1982). Zones of closely-spaced systematic joints ex·st throughout the park (Collins, 1983). Joint zones as wide as 40 m ext nd vertically through Permian and Triassic beds and horizontally up to at least 1 km (fig. 22). Within joint zones, the density of joints averages 5 joints/m or sandstone beds 3 m thick. Away from joint zones, densities average 0 to 1.5 joints/m for 3 m thick sandstone beds. Bed thickness affects the spacin of the joints within and beyond zones of closely spaced joints. In genera, joint densities in sand­ stone and siltstone beds less than 1 m thick incr ase as the bed thickness 10 decreases (fig. 23). Joint densities are almost constant for beds greater than 1 m thick. Three types of gypsum veins are present in he deformed zone of strata.

They are either vertical, parallel to bedding, 0 cut the bedding at 30 to 60 degrees (fig. 24). The veins are composed of fi rous gypsum bisected by a medial scar. They are believed to be of the ant taxial type of crack-seal veins (Ramsay, 1980; Ramsay and Kligfield, 1983, section 3.14), in which the medial scar probably marks the site of earliest ineralization with new material added at the vein-wall rock contact. T e mineral fibers denote the direction of maximum principal extension at the ime they were added to the vein. The gypsum fibers in the vertical veins are horizontal, indicating that these veins formed by horizontal extension. The e veins probably formed under high fluid pressure in the preexisting jOints. the inclined and horizontal veins are vertical, indicating mineralization occurred during vertical extension. Small-scale normal and reverse faults zone of Quartermaster and Whitehorse strata and r~ ;' displacements are typically less than 0.5 ~~o

but ~~ and west. No relative age data are The orientations reveal either a north-south horizon . m principa extension followed by an east-west extension or vice versa. Reverse faul s (fig. 25b) display similar orientations to the normal faults. Most of the everse faults exhibit north- ward, eastward, and southward dips. Reverse faults are less common than normal faults. Inclined veins (fig. 25c) have orientati ns similar to faults, sug­ gesting that they are filled faults. Nearly all veins along fault planes 11 display undeformed crystals adjacent to the vein wall rock contact, indicating that fault movement predated mineralization. The geometry of vein intersections also rev als that faulting predated mineralization (Goldstein, 1982). The mineral f bers of adjacent horizontal and inclined veins merge without a break. Some eins are composed of sigmoidal fibers, documenting that simple shear occurred d ring vein growth. For the most part, however, vein fibers are straight and do not deviate from vertical by more than about 10 degrees in the horizontal inclined veins, evidence that these veins were formed by vertical extensi n. Where the veins intersect, vertical veins are everywhere and nearly everywhere cut by the horizontal veins. Chaotic folds in the upper zone of deformed strata cause the Quartermaster and Whitehorse beds to dip commonly 10 to 20 deg ees. Detailed structural mapping has defined synclines that vary from el ngate to circular (fig. 26). These synclinal depressions are up to 1.5 km lon and are composed of conical synclines and anticlines that plunge gently up t 10 degrees toward the center of the depression (fig. 27). The amplitude of t ese folds is normally less than 10-15 m. Rim anticlines or domes may also occur along the periphery of the principal synclinal depressions, commonly se arating them. Smaller-scale folds with amplitudes less than 2 m also exist. Although they may be asso­ ciated with the formation of the larger synclina depressions, some of the smaller folds were probably formed by expansion ssociated with the conversion of anhydrite to gypsum (Fandrich, 1966). A close association exists between the syst matic joints, veins, and principal synclinal depressions. The major tren s of the depression axes are

005 0 , 025 0 , 055 0 , 0800 , and 275 0 , similar to the vertical veins and systematic joint sets (fig. 28). These structural elements also exhibit a weak northwest 12

(3100 ) trend. Within a specific depression the ost significant trend of the vertical veins parallels the axis of the depress·on. Even though the inclined veins strike in many directions, the dominant st ike parallels the orientation of the depression (fig. 29). Strikes of the sma l-scale faults exhibit a similar relationship, although the faults are le s common than the other structures. Dissolution of salt and collapse or gentle ubsidence under the influence of gravity is believed to be the process that ca sed the folds, faults, and veins observed in this area. A simplified model for the development of the deformation structures is shown in figure 30 (Go dstein, 1982). Stage 1 is a normal burial process and is recorded in nearly very sedimentary rock. Stage 2 is a result of horizontal extension and ccurred when dissolution was initiated. This extension. could have produced t e normal faults. Rarer re- verse and thrust faults indicate local horizonta compression. Stage 3 is a different stress regime characterized by vertica extension. As collapse proceeded, maximum extension changed from near h rizontal to near vertical. Gentle folding and nonsystematic fracturing cont nued due to the removal of support from below; veins are mineralized with v rtical extension of fibers. Dissolution in the Caprock Canyons occurred in a mosaic of localized areas rates of enhanced dissolution. The similarity between t~~~ f joints that predate dissolution and the synclinal de~~~~ s that enhanced fluid flow and dissolut1on was, and P~~~1~ least partially controlled by pre- dissolution joints. ~ The position of the boundary between the de ormed zone and overlying undeformed zone is a function of bed thickness a d vertical distance from dissolution (fig. 21) (Goldstein and Collins, in Beds in the zone of deformed strata are almost everywhere 1 m to 0.1 thick. Overlying undeformed 13 beds are rarely less than 2 m thick and more com only are as thick as 10 m. Thicker beds have a higher flexural rigidity and ould not flex to allow local development of extension parallel to the layers.

Clastic Dikes

Clastic dikes are among the deformational outcrop in Randall, Potter, Moore, Oldham, Briscoe, Hartley, and Hall Counties of the Texas Panhandle, as well as at localities in the klahoma Panhandle and eastern and northeastern New Mexico. These clastic dikes usually range in thickness from about 15 cm to 3 mm, although dikes in north astern New Mexico and western Oklahoma are as thick as 1.5 m. andle, poor exposures prevent tracing the vertical and lateral extent of most the dikes. Almost all of the dikes cut upper Triassic or Permian strata, a though clastic dikes have also been observed in the Pliocene Rita Blanca Fo mation in Hartley County and in Pleistocene deposits in Hall County. The mechanics of dike emplacement are diffi ult to determine unless the dikes can be traced in outcrop to source beds. T e composition of a dike usually cannot indicate a definite source bed, and Quaternary sediments have similar lithologies. of

sediments. Where a dike termination can be observed this location (fig. 31). Dikes in Hartley, Randa 1, and Oldham Counties, Texas, and dikes in southeastern Quay County, New Mexico, also appear to be due to fracture filling (fig. 31). Subsidence is the likely mechanism by which 14 horizontal strain and extension have opened the ractures or fissures. In the Texas Panhandle geomorphic features such as rece t fissures, sinkholes, .col­ lapse basins, and breccia-filled chimneys have b en attributed to subsidence processes caused by evaporite dissolution (Gust a son and others, 1980; Gustavson and others, 1982). Subsidence created by differential compaction is another mechanism that can develop fissures ( achens and Holzer, 1982), although in the Texas Panhandle evaporite dissol tion is the most likely cause for subsidence. Although most of the clastic dikes in Panhandle appear to be emplaced during the Cenozoic, dikes cutting Tria sic sediments at one locality in Palo Duro Canyon State Park appear to have or ginated from a sand unit within the Triassic. The predominant dike trend at this locality is the same as one of the joint trends, although dikes trike in other directions (fig. 31). 15

References

Barnes, V. E., 1969, Amarillo sheet: The Univer ity of Texas at Austin, Bureau of Economic Geology Geologic Atlas of Texas scale 1:250,000. Bates, R. L., and Jackson, J. A., 1980, Glossary f geology, second edition: American Geological Institute, Falls Church Virginia, p. 334. Berkstresser, C. F., Jr., and Mourant, W. A., , Ground water resources and geology of Quay County, New Mexico: Ne Mexico Bureau of Mines and Mineral Resources, Groundwater Report 9, 11 p. Budnik, R. T., 1984, Basin and range-age reactiv tion of the Ancestral Rocky Mountains in the Texas Panhandle: evidence from the Ogallala Formation (abstract): American Association of Petrol urn Geologists Bulletin, v. 68, no. 4, p. 459. Chapman, C. A., 1958, Control of Journal of Geology, v. 66, no. 5, p. 552-558. Collins, E. W., 1983, Joint density of Permian s rata at Caprock Canyons State Park, Briscoe County, Texas Panhandle, in G stavson, T. C., and others, Geology and geohydrology of the Palo Duro B sin, Texas Panhandle, a report on the progress of nuclear waste isolation easibility studies (1982):

The University of Texas at Austin, Bureau 0 Economic Geology Geological Circular. Cook, A. C., and Johnson, K. R., 1970, Early join formation in sediments: Geology Magazine, v. 107, no. 4, p. 361-368 Dix, o. R., Jackson, M. P. A., 1981, Statistical nalysis of lineaments and their relation to fracturing, faulting, halokinesis in the East Texas Basin: The University of Texas, Bureau of conomic Geology Report of Investigations No. 110, 30 p. 16

Dobrovolny, E., Summerson, C. H., and Bates, R•• , 1946, Geology of northwestern Quay County, New Mexico: U. S Geological Survey, Oil and Gas Investigations, Preliminary Map No. 62.

Fandrich, J. W., 1966, The Velloso Dome, ~ Geol gy of Palo Duro Canyon State Park and the panhandle of Texas: Guidebook for 1966 SASGS Fieldtrip, West Texas State University Geological Society, • 25-30. Finley, R. J., and Gustavson, T. C., 1981, Lineam nt analysis based on Landsat

imagery, Texas Panhandle: The University 0 Texas at Austin, Bureau of Economic Geology Geological Circular 81-5, • 25. Goldstein, A. G., 1982, Brittle deformation asso iated with salt dissolution,

Palo Duro Basin, ~ Gustavson, T. C., and others, Geology and geohydrology of the Palo Duro Basin, Texas Panhandle, a eport on the progress of nuclear waste isolation feasibility studies (1981): The University of Texas at Austin, Bureau of Economic Geology Geological Circular 81-3, p. 5-9. Goldstein, A. G., and Collins, E. W., 1984, Defo ation of Permian strata overlying a zone of salt dissolution and collapse in the Texas Panhandle: Geology, v. 12, no. 5, p. 314-317. Gustavson, T. C., Finley, R. J., and McGillis, K. A., 1980, Regional dissolu­ tion of Permian Salt in the Anadarko, Dalha t, and Palo Duro Basins of the Texas Panhandle: The University of T xas at Austin, Bureau of Economic Geology Report of Investigations No. 106, 40 p. Gustavson, T. C., Simpkins, W. W., Alhades, A., a d Hoadley, A., 1982, Evaporite dissolution and development of ka st features on the rolling plains of the Texas Panhandle: Earth Surfac Processes and Landforms, I v. 7, p. 545-563. 17

Harris, J. F., Taylor, G. L., and Wa1per, J. L., 960, Relation of deformational fractures in sedimentary roc s to regional and local structure: American Association of Petrole m Geologists Bulletin, v. 44, no. 12, p. 1853-1873. Hobbs, D. W., 1967, The formation of tension joi ts in sedimentary rocks: an explanation: Geology Magazine, v. 104, 6, p. 550-556. Hodgson, R. A., 1961, Regional study of jointing Comb Ridge-Navajo Mountain area, Arizona and Utah: American Associati n of Petroleum Geologists Bulletin, v. 45, no. 1, p. 1-38. Jachens, R. C., and Holzer, T. L., 1982, Differen ial compaction mechanism for earth fissure near Casa Grande, Arizona: G ological Society of American Bulletin, v. 93, no. 10, p. 998-1012. Lovelace, A. D., 1972a, Grady Quadrangle, in Geology and aggregate resources of District II: New Mexico State Highway Depa tment, scale 1:190,080, p. 60. Lovelace, A. D., 1972b, Ragland Quadrangle, in G ology and aggregate resources of Di stri ct II: New Mexico State Highway D partment, scale 1:190,080, I p. 59. Parker, J. M., 1942, Regional systematic jointin sedimentary rocks:

Pri ce, N. J., brittle and semi-brittle rock: Price, N. J., 1974, The development of stress sy terns and fracture patterns in undeformed sediments, in Advances in Rock M chanics: Washington, D.C., National Academy of Sciences, v. 1, Part 1, p. 487-496. Powers, S., 1922, Reflected buried hills and thei importance in petroleum geology: Economic Geology, v. 17, no. 4, p 233-259. 18

Ramsay, J. G., 1980, The "crack-seal" mechanism f rock deformation: Nature, v. 284, p. 135-139. Ramsay, J. G., and Kligfield, R., 1983, Strain m asurement: techniques and tectonic implications: short course notes: Geological Society of America Division of Structural Geology and Tectonic Short Course, November 3-5 Rogatz, H., 1939, Geology of Texas Panhandle oil and gas field: American Association of Petroleum Geologists Bulleti , v. 23, no. 7, p. 983-1053. Stearns, D. W., 1972, Structural interpretation f the fractures associated with the Bonita Fault, in Guidebook of East Central New Mexico: New Mexico Geological Society, Twenty-third fie d conference, p. 161-164. Stearns, D. W., and Freidman, M., 1972, Reservoi s in fractured rock, in Stratigraphic oil and gas fields--classific tion, exploration methods, and case histories: American Association of Pe roleum Geologists Memoir 16, p. 82-106. Winchester, D. E., 1933, The oil and gas resource of New Mexico: New Mexico School of Mines, State Bureau of Mines and ineral Resources, Bulletin No.9, p. 133-134. Wise, D. U., and McCrory, T. A., 1982, A new meth d of fracture analysis: azimuth versus traverse distance plots: Ge logical Society of American Bulletin, v. 93, no. 9, p. 889-897. 19

Figure Captions

Figure 1. Station locations for fracture measur ments in the Palo Duro Basin Area, Texas Panhandle. Figure 2. Strikes of predominant fracture sets n the Palo Duro Basin area, Texas Panhandle.

Figure 3. Locations where a predominant fractur set strikes at 2800-3000 •

Figure 4. Locations where a predominant fractur set strikes at 3000-3200 •

Figure 5. Locations where a predominant fracturj set strikes at 3300-3500 •

Figure 6. Locations where a predominant fractur group strikes at 0300-

0600 • I

Figure 7. Locations where a predominant fractur set strikes at 0000-0200 • Figure 8. Strikes of faults and joints of the Palo Duro Basin in eastern New Mexico. Figure 9. Structure contour map on base of the ermian San Andres Formation in Quay, Curry, and Roosevelt Counties, eastern New Mexico. Figure 10. Locations of the John Ray and Bush D Texas. Figure 11. Joint strikes in overlying Permian, T and.. ~i.\~tiary rocks exposed at a northwest trending drape fold on th ~ ~~, of John Ray ,,~.~;, Dome, Potter County, Texas (fig. 10). ' ...... Figure 12. Poles to normal faults cutt~~~ northwest trending drape fold on ~~~~ John Ray Dome, Potter County, Texas (fig. 10). Fault di~ents ar less than 0.5 m. Figure 13. Strikes of fractures in Pennsylvanian Permian, and Triassic strata in Swisher County, Texas. Fracture orientations On Pennsylvanian and Permian strata were determined with fracture identification logs from the Stone and Webster-Harman #1 and Stone and Webster-Zeeck #1 boreholes. Joints in Triassic strata were measured from outcrop. 20

Figure 14. Strikes of fractures in Pennsylvania, Permian, Triassic, and Tertiary strata in Deaf Smith County, Texas. Fr cture orientations were determined with fracture identification logs fro the Stone and Webster- G. Friemel #1, Stone and Webster-Detten #1, and tone and Webster-J. Friemel #1 boreholes. Figure 15. Locations of boreholes used for frac ure studies in the Palo Duro Basin area. Figure 16. Percentage of fractured Permian core from boreholes in Oldham, Deaf Smith, and Randall Counties, Texas. Abbreviatio s of Permian formations are as follows: A - Alibates; SIT - Salado-Tansill; Y Yates; SR - Seven Rivers; QG - Queen Grayburg; SA -San Andres; G - Gloriet uCF - upper Clear Fork; T - Tubb; lCF - lower Clear Fork. Figure 17. Composition of veins in core of the ed Cave Formation and Wichita and Wolfcamp Groups. These units are stratigraphically below the Permian salt­ bearing units. Figure 18. Composition of veins in core of Perm an salt-bearing strata. Figure 19. Composition of veins in core of Perm an strata that has been affected by salt dissolution. Figure 20. Structural setting of the Palo Duro (A) and location of Caprock Canyons State Park (B). Figure 21. Stratigraphy and deformational eleme ts at Caprock Canyons State Park. Figure 22. Cross-section view of a joint zone ex ending through Permian and Triassic rocks at Caprock Canyons State Park in riscoe County. Overlying Tertiary Ogallala sediments are also fractured, lthough it is uncertain if the Ogallala fractures are actually systematic joint that are part of the joint zone. 21

Figure 23. Graph showing weighted joint densit vs. log of bed thickness for data from Caprock Canyons State Park, Palo Duro anyon State Park, and joint zones at both parks. Joint densities were weigh ed using the following expression (Jackson, personal communication, 198 ):

n N. ~ 1 double weighted +~ 1 = 1 N mean joint density m n = 5 in 5 point weighting n = 3 in 3 pOint weighting subscript m refers to value for midpoint Figure 24. Gypsum veins in Permian strata at Ca rock Canyons State Park. Figure 25. Lower hemisphere, equal-area net p10 s of faults and veins mapped at Caprock Canyons State Park (from Goldstein an Collins, in press): (A) poles to normal faults, (B) poles to reverse faults; (C) poles to inclined veins; and (D) azimuths of vertical veins as a rose diagram. Figure 26. Map of structural elements of an are within Caprock Canyons State Park (from Collins, 1983). Figure 27. Detailed map of structural elements f individual synclinal depressions located 2 km (1.25 mi) north of Lake heo. The major axes of the two depressions trend NE-SE (0450-2250). Figure 28. Histograms of (A) systematic joints nd (B) axes to synclinal depressions in Caprock Canyons State Park (from oldstein and Collins, in press). The data have been smoothed by a 10-deg ee running average every 2 degrees of azimuth. Vertical axis is a concentr tion factor (Wise and McCrory, 1982) • 22

Figure 29. Orientations of veins in synclinal d mapped in figure 27, Caprock Canyons State Park. A. Rose diagra of orientations of vertical veins. B. Lower hemisphere equal-area net plot for poles to inclined veins. Figure 30. Conceptual model of brittle deformat on above dissolution zones. Stage 1 represents normal burial; Stage 2 repres nts horizontal extension as a precursor to dissolution collapse; and Stage 3 r presents collapse (from Goldstein, 1982). Figure 31. Comparison of clastic dikes and join orientations in the Texas Panhandle and eastern New Mexico. Data were coll cted from the following localities: (a) near Buffalo Lake dam, western andall County, Texas; (b) U.S. Highway 385 at the southern edge of the anadian River Valley, eastern Oldham County, Texas; (c) New Mexico State Highw y 93 at the western caprock escarpment, Quay County, eastern New Mexico; and (d) 1.8 km north of Lighthouse Peak at Palo Duro Canyon State Park, eastern Ran all County, Texas. The clastic dikes cut Triassic Dockum sediments and t e joints were measured in Triassic Dockum (Trd) and Tertiary Ogallala (To) ocks. The joint data from the Buffalo Lake locality (a) are from Finley an Gustavson (1981, p. 25). i) I 103 00 I

I 0 k.\c.. .

MoradO( A.(CIt ~ o 50 100 ... !"-'---+:"' -----II o eo' l60km N 1

o 30n,. 11------1,', o So\::_

• Station Location T-50 Number of Measurements n Tertiary Strata K-50 Number of Measurements n Cretaceous Strata Jr-50 Number of Measurements n Jurassic Strata Tr-50 Number of measurements n Triassic Strata P-50 Number of measurements n Permian Strata

Figure 1. Station Locations for fracture me surements in the Palo Duro Basin area, Texas Panhandle. o I I I IQ30c OKLA. N. MEX. I -----rEi--~-: ! lOki • .~------N Te;<

o ~ 100"'; 1 I o ao 160 .....

N 1 ! i

't- o I ~ -T '\ -lsoo -;f-~ ~4 -I- De"f s",,;t-c. c..,. ~ ""'} \ x. ~ -- +~ ~ ! s ..... ;,.he. c •. ~ --~ -- \ , -r:- Yt(

{) 30,....; ~ i I I 0 50K...- \

Figure 2. Strikes of predominant frac ure sets in the Palo Duro Basin area, Texas Panhandle. Q I 10,30 0 IOk\", Te."". N

• • " Mala40f ArCrt a 50 100 ... } I I , a aa 160'"- t.J

• • • • -- 1 - ...... - • -- o I -"3500 ~---- ...... • • -- b ~{' S":.tt. Co. -- , '-...... • -- s... ~s".t.,. Ca. • . -- • --- • •

• •

Figure 3. Locations where a predomina t fracture set strikes at 280 0 -3000 , o , I /D,oO I I N.MEX.~- __ I 101<1",. Ne.w N "'ex. ITex I I I " MQrador A ft 0 50 100.... \ ~ I I , 0 ao l&Ok ...· I I ",I !

I. '. • i \ 1I \ I [ i \ ""\ • \ . . \ - 3 Sooa I ~e .. t s... ·.k.. Co. '" • " '" .~ ,

S.... :s"e~ '" , c., "'" . "" • "'"'" \

o 30 !'>I" 1--__...L 1 \ I o 50~"",

• Station Location \ Fracture Set Striking at

Figure 4. Locations where a predominant frac ure set strikes at 300°-320°. .) Q 103 00 , I OKlA.. N.MEX. ~ I --ro:-7-, otIc... . N'? .• , I I f,,\ ~'I. • i

• • 1.1 todor AreA o 50 100"" !"-I------tl o ao '10_ N 1 • \ \ . \ \ .

•

o , .. -3500 • . . \ \ • DeQ f S •. ;.~ C~, \ \ . \ • • • $_:,"«r t. •. \ \

o, o 50 K"" \ • Station Location \ Fracture Set

Figure 5. Locations where a predominant racture set strikes at 330°-350°. fD?J 00 I I ~. MEX. ~ OKI.A. I -re:i~- -: I Okr~ !

N

f i \ , MQraGor Arcn 0L1- _---='0:-°I _..:;,00I!.. I N o ao l&Ok", \ I / Y .. / ,/' 1i • j I ~ / I /

• • ~o , . . • - l j co

/ •

/

• • /

o '30"",', If----~I I o :0 K. "'" • • Station Location / Fracture Group Striking

Figure 6. Locations where a predominant racture group strikes at 0300-060°. o i IO? 00 I

o kl" I

N

I QladOt ArCft ~ o 50 100mi- !-'---+:' ---:" I o ao 160km- N i i I. 1 I 1 /

·1 o , I -')5 00

1 I r

o \ o

Figure 7. Locations where a predomin nt fracture set strikes at 000°-020°. N

N N I 1 210' I .... o CI"~+a.C.'."'lo r.c.ks I h::39 o /0 IC._

TrIASS ,·(. rtc.k\ n:: 38

030·

a•• \'.

";; I' __~ 3500'

~ .... , C,,J,, ~ NeW 1'1;;(. Tex. /01 AI ..... • ..... Ic.""c.1:: 'F_\~ I

~ 3. (J ~ . ., """, ." Alo.MO\.. Creel<. F,,~I~

Figure 8. Strikes of faults and joint at the western margin of the Palo Duro Basin in easte New Mexico. 0" ,8o ," ',I I

I / , ! ;!WI i ) '. NEW TEX . .~ ME:<.

/

\) ,...() ~I

\ \ } ------r---

.s +r ... c+~·e. 017 b<> ~ e. o{ So.- A.dre, F", , /0"" I I Q ------: •

Figure 9. Structure contour map on base 0 the Permian San Andres Formation in Quay, Curry, and Roosevelt Counties, eastern New Mexico. .r--- / '" / "" "'- f{ I NEW t'\E'i..·1 TE~. ( :Sohn R'4 \)Q~e ~,/ I. S .'"- \ +--"'1 \\:t: \ c:t a:re..... d~' Poth.r Co. I- ~ 5·00' \ \ \'" ( J '~ ' .... , / "'-' ,f.. -- -\JO . ~ - I vel"

o 5 rr.,:,. ~ I / o 10 1<.""

\\ ~ . Strike and Dip of Bedding ( B L' ~ h \) cn'\e } 10 ~ Fault \ Figure 10. Locations of the John Ray and Bush "'- ;/' Domes, Potter County, Texas. "" '--- ~ 3"o;",t$ Te.rh::",.1 C)~o.llc..le. F "'" un: tf~ 0'10

3" 0',,,, t !> Tr\·o. ... , I'e.. Doc;."'I.1...... , Gop n= 87

tr: 100

Figure 11. Joint strikes in overlying Pe an, Triassic, and Tertiary Rocks exposed at a northwest ding drape fold on the southwest flank of John Ray Dome, r County, Texas. (fig. 10) ----_ •... --- -_._. ---.------.-_. __ .- -.------..--

------.-.------f--

N ----,..rr-:-::!---r:-a -no t" "" ~~f~ .... m--··--

-----'~'_f'--';=o.._'_r~ 0. \ 'Co.. 'Co. F"'"'

1 n~/7

~.. .~

\j- .-----.------I ! / ------_._-_. / I I

I I ______~c~o~~~~_~u~~;n~t~~~i~~~~I~s~---- ______

Figure 12. Poles to normal faults cutting T rtiary Ogallala strata at a northwest trending drape fold on the so thwest flank of John Ray Dome, Potter County, Texas (fig. 10). F ult displacements are less than 0.5m. () "t.:. -fr ". : I. tl,,\rn,p

Tr p

Dt,4 t. -fr.~", I. s¢r,.J- ?ee,tk1/1

z.., <; f W - liar ""'" -II I

n = 'f'!

Dt'.tG. -~rD'''' ~ I, S(w-c.

p 1P

Figure 13. Strikes of fractures in Pennsylvanian Permian, S,,');S.t-,(1 te. and Triassic strata in Swisher County, Texas. 'F cture ori en- tations in Pennsylvanian and Permian strata were rmined with fracture identification logs from the Stone nd Webster-Harman #1 and Stone and Webster-Zeeck #1 boreholes. Joints in riassic strata were mea- sured from outcrop. Do.t .. { •• _'. s l", - G- ....·, .... 1111 . s ~ OJ) • De ~I ~ t, tl I . :, h.J - 3. r t.;~ .\1/ ,

n't'' {, 0_ '. ,. S ~ ,~ - (" ",. ;, .. ,' H' ? shJ - t>.\1

-G-, ~'e:M~1 ill -D~1Ie~d, ." F,e;.,.1 -til

[): +~ -C ..... ', 5 1.1 t l.) - :!. J:: r.' ' .... e I :ttl !

•

"\"'0.

b... t Pro .... '.

/, $ i.J -1', Fr~:,.,tl# I

Figure 14. o I /0 l. 00 I Ie KLA. NEv.; T~". ME"'-.

o I -j500

I I

\ I I

, i I 1. •

• I

3 __----h-_ _._4 ------L---.-._ .. __l,

s·

z. 5'. 51(,)· 2eec./(# ( b.5/w-tlC.r...... or.#1

o

Figure 15. Locations of boreholes used for frac ure studies in the Palo Duro Basin area. EXPLANATION

b,'sso\~+,'ot'\ Sell! e.. ,.,e. well UI':',+s ~ .. t\ ... u.. :J ~

Ll $~W - r'(\"s{,~\J:Ii \ A,S/T,Y)5R QG-,SA (., , u CF, T, I C. F

5 3. r t ,.... Co \ I A5/rY<;,R, iii a\...) - r- ¥ I , I ~R.)5A

o S hJ' \)~rr~n #I AI sIT, Y SA

f, R 0 G 0, ' s,t w . CT ,I-r"-;",,,I *' I , SA Q saw- t'te.cJ, til IT SA

o Saw - HC\l·"'D .... 1:l1 A,sIT,Y QG, S

Figure 16. Percentage of fractured Permian core from boreholes in Oldham, Deaf Smith, and Randall Counties, T xas. Abbreviations of Permian formations are as follows: A - Alib tes; SIT - Salado-Transill; Y - Yates; SR - Seven Rivers; QG - Queen Gr yburg; SA - San Andres; G - Glorieta; uCF - upper Clear Fork; T - Tubb; lCF - lower Clear Frok. 1~!F--

. t---I ----. ------.- --- I I ~o- i

~---r--

. - 0--- - : __ --_. -1.61'-., "L .wO-\.f~!'\ ~. ~+ W-l~: _L_ .Ic.rotr.:t - ''-_ .- .. Red c...~c.. ."'!l .....~+ ... . __ . _. Ie ... ~ ,~ ..... ~. _____.... :1 Gp·· Gf>- ___~~~_-Gp· -t"'"¥------.-:---._- _n -Gt>:---- -Gp -.. , ------,.,~:: --Iv- - . n ::31 . n= 16 . n~·~- . :_~7T -:--~- :,;~n-'---- .~-n.:'rza- .... ,-- .-- . Tc.~ '110 Tc::--:::~~9 Ti;-:':Zol Tc-:J'IO Tc.-=1 0'f -Te::.s zv- __ .~ T-:.w>u T -:+~ T =70S" T =

. ------_.-: j

·f!£L °/" "'ll-rJ~,h+.7luJ !r-tl~i.."e~-'--'-'-·-­ 11 ·~,...j,e" -6 l·~J-~~~;m:;~e,;J-s'-- .";",",,~~,*,,,.-.e;- -..-.. .' .... . WI': % 5'1Ps .... ", .f-.'II~cI .. -Pr-.. ,,1...'H Tc:' .foto..f---t4-kk,,, e-ss- 6',i' . ·;-cJin.--;(~e'

Figure 17. Composition of vei~s in core of Wi chita and Wolfcam Grou s. These units a the Permi an salt-bearing units. ------+------% Ver~. Cornl' 0 &', ;" In Salf -60:" Un;!.5

100.

'iu - i I l.o - .. !

'20 -

0- Q\l~e.n Son G~(>.\,,, ... rJ Ancl rt \ n=/o n= 7S Tc. .: /D75' rr.'-= /'1~ Tt..= 107'1 T= r",s- T.2.foO T=? . . S t I"J ·("1"iidi~'d '# I ' . 1 5/ J. "". #1 10 0 -

i : '

s~.,t." Q"el!.n St\n F"" R;.t,t ~ : GrG., \'~r'l. Andre "> ,,;: I ~ ,,: B n -:: 5" <{ Tc. "/10 Te:3l. Tt..= 9't'-l 1··T=311 T=-1..o 0 T=, 1.'10

S ( W - '3. F r t.·, ...... 1 -# I

tJ· ------f-----.- "-"' ....------1, ha', ·f. f:lf,,}.1:~ I / ill I, , ,', "r:!7A ~ ( n= n... er-.-{ i-t-lt>.,+ cot'e, ;",cr-e..,t,,+s w"t .f1"1l.c:.-\"''''e~ ~ 0% E1 r. T-: fh 'cbe .. $ of Urj', I :1------( ee.+) Ii T::.? b r-·dM~ r.o-f dr-,'Iled 'I ...... _._.-,-_ .. _.__ .. - .------.. _.. _----_._- ".- -fo ba H. of vn: f Il !l -.. -rr- ".-- .. ,~. -.. -"- .. 1 " Fi gure 18. Composition of veins in core of Permian salt-bearing strata. ~; i - - % . Vt.;n' ,CO pa~;fi~~: Ith! : ~ ! .. . • SaN !J/s:,ofd-,d" t /~~. Un',fs

100

lo o S<\I~

.....~------"-.'-,, -'" ""------_ .. ,',.--" .. ,-"_.. - --_._,.

er () r :I. I.e-of Core. ;"cre.me.,.,fs '0',; ~~r.;. ... "",-~·~ ... <:~,.t"" wiH -t;...ct .. re s

~ '1. a..,,~,6.;,h.· ~:\l .. d ~.t. i....e_ .,.,. .. , rl,;:cJ:It'e~5 of -;'~CDtJe.~ecJ -;;;;~-1.:r;;+r

m., 0/., ~".t,;'"~.:.:..l;\h,LJ.t~.::.r.,.h<.!:..u_. ______, , . at u,,;1 (Ieel) Cry trc.t.~~ .. , w,~ no ...... ~ .... +:11':"5 ·,d~sc."b~tI o d,.:tled "fp'--

,.-" ..---~-,- , •...,.,-,-,------._--_.. ---,. __ .,----

Flgure 19: -'Cornpo'sition of veins in core Permian strata that has been affected by salt dissolution. --~. MEx.------

__ ~L_~ ___ _ TEX. I A. 4nOd a Or/(o oSln

Tucumcari Polo Duro Basin Basin I I

LM.2.Iador Arch ... --, 0

I Midland Basin o 100 200mi I ~I--~~--~I~----~I ----_ ... -----_: o 100 260 300km

I I N. MEX. ~ ____ ~L_A..:. __ _ : TEX.

B.

N

Polo Duro Basin

Malodor Arch QAI398

Figure 20. Structural setting of the uro Basin (A) and location of Caprock Canyons State Park (B). Deformational Elements Folds Collallse Joints Faulls Veins Hales

Tertiary Or:

200fJ6om Triassic Dockum Gil. ..c ..Q ..,.. Ea ..,.. c "

Quartermaster Fm.

Permian

.., ..E_ ..c

Wh",M'u Gp. I : '

State Park. Figure :>.1. Stratigraphy and deformational at Canyons elemen~sI :~prock i COl/crod

·~:}·?··~·/}~~~~/\).\ . .: :.~~ .:. ::.,: ,.~::;

.~.". ,/(:,j~';!);~~tji;~'(it ___' •.. ,." .. ··.I:~·.·,.-~-:-~. .,r.·.,-rr· .. . : :"i'l .... G7}i \ .l 1.'::.; .. :.... ··.~~~$F~~~~~< .... ".,

:t ;}'~"~~~:~~~ '~-l~'" ~:~~:~,,:., :,'\~~''':'!-: :-...~~,~:,,~,,\; .. :;-:-,~,~-;;*.:-~~,.~, 'j.:.r,V' .," " ··F~ i,;m~~.~1\i(1~)£'f;Y . .. ;';::

EXPl...ANATION TOIllory OQollolo Sand,allt.grovel, I' I'M pormlao Wnllohor .. { [:'.-'.:r;"! ~}~~ formalloo .~ ,. ood (ul":I\/I. SOl\d~IOI\' Scola Group ~~~~ SlIhlooo sand I ".'~ " Olle 3011 Tdonie Dockum r.,:··.: 35111,lon/l. aood:;1008, ol\d mudslono Group .• " ood eOl\olomorol1l I 11 0- I tOm Jalo! ,00(1 o JOlnl ~ ...ct-

Figure 22. Cross-section veiw of a joint zone extending through Permian and Triassic rocks at Caprock Canyons State Park in Briscoe County. Bed thickness 0.1 0..5 1.0 4.0 ZO I I I I I I I I

18 -E C\J on

-~

2 .6 .8 l.0 I.Z 1.4 1.6 1.8 Z.O Z.Z 2.4 2.6 Log of bed thckness tm)

o Caprock Canyons State Park data n =209 A Polo Duro Canyon State Park data =243 o joint zone data n =71

Q A.-lao:

Figure 23. Graph showing weighted joint den ity vs. log of bed thickness for data from Caprock Canyons State Park, Pa 0 Duro Canyon State Park, and joint zones at both parks. :i

II

:1 q it

..... ~~\ \,~. '.', ! , , ...... ' ..'. \", \ .. ~..... '~.:." ~ ~ :. ...; '." ~.>\

:\ Figure~4. Gypsum veins in Permian strata at Capr ck Canyons State Park.

.,:1 :1

.,\ .:, Wholt domOln No, mol loulls Whole domain Reverse luulls N n' 66 N n , 38

A. B. Contour intervol

~ 1-4% ~ 4-6% II >6% ~ 25-5% 11>6%

Whole domain Ve, 'icol veins N n '166 Whole domOln Inclined veins N n , 457

090·

c. D. t50· Contour intervol 180·

~ t-2-1. ~ 2-3% • >3%

Figure 25. Lower Hemisphere, equal-area n plots of faults and veins mapped at Caprock Canyons State Park from Goldstein and Collins, in press): (A) poles to normal fa ts; (B) poles to reverse faults; (C) poles to inclined veins; and ( ) azimuths of vertical veins plotted as a rose diagram. ark road

EXPLANATION

-t--La((~e-~Cale anticline 20 ..J- Strike and dip -t-La(l;je-~cale syncline

__ Small-~cale anticline e Horizontal beds (dipS 5") 2km

.-Small- ~cale syncline ~ Synclinal depressIons o Imi

Figure ~b. Map of structural elements of an area within aprock Canyons State Park (from Collins, in press). o o.~ Ikm I I I I I --<.0 o 0.2~ O.~ml Ii --<..! l' ~ / -',' .. ~ i Ii Ii / /'" \ 3 Ii Ii N / Ii /X I} 14 Ii 1'1 3 , :-<.. Ie I .Y ~ 2

/

I /

12'>--.

EXPLANATION ~ I~ SI".e and dip 6~ SynCline willi plunQ. Ii HorizOntal Dedi (!.!I' dip I ...... Small - 1cale anllcllne a +-t- Anllcllne Wlin plunQe ___ Small-1cale 1yncllne

QAIOI.

Figure ~7. Detailed map of structural elements of indiv' (1.25 mi) north of Lake Theo. 12

10 Systematic Joints n= 396

0 .,> 8 .E 0 Q 6 OJ Q. 0 0 "0 4 0~

2

0 270 300 330 0 030 060 090 AZimuth

20

"0 > 15 OJ Axes of Synclinal Depressions .s n= 42 0 Q 10 OJ Q. 0 '0 "0 5

0~

0 270 300 330 0 030 060 090 Azimuth 04932

Figure 28. Histograms of (A) systematic joints and (8) axes to synclinal depressions in Caprock Canyons St te Park (from Gold­ stein and Collins, in press). N Inclined veins n a 69

270 090

8 180

OAIOl2

27 Figure aq. Orientations of veins in syndinal depressions ma ,ped in figure.2f1, cap~,lk, Canyons State Park., A. Rose diagram of orientations of vertical v °ns. B. Lower h .; °o~h~re equal- area net plots for poles to indined veins. .. ~\~ .:;~\\ .. 0,,"," ~.A' \'~ .. ' stylolites, vertical jOinting; m neralization of some joints indicates 1 .rizontal extension

i Iting - predominantly normal, 0"'3 or 0"'2 i dicating horizontal extension and (locally 0"'.) v rtica I compression; occasional 2 r erse and thrust faults indicate ~I cal horizontal compression

ineralization of preexisting faults nd bedding planes - some motion ccompanies mineralization - vertical Ibers in veins indicate vertical 3 xtension

fo+---l--~--I-

• + + + + + + + + + + + + + + + + + • + + + + + • + + + + + + + + + Salt + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

* : salt dissolution !

Figure3/). Conceptual model of britt1e above dissolution zones. Stage 1 represents normal burial; Stage 2 epresents horizontal extension as a precursor to dissolution lapse; and Stage 3 repre- sents collapse (from Goldstein, 1982). Dikes cutlinQ Triassic sediments Joints N N 330° I 030° 330° I 030° a \ / \ / -20% -20% 060° 300 "" "- 060°...

-090° 270'L -os n: II To n: 35

N N 030°' I 0300 330° I 030° b \ / \ / -10% -10% 0600 060° "" ""

-090° 270L ~~. -05 n: 22 Trd n:83

N N 3300 I 030° 3300 I 0300 c \ I \ / -20% -20% 300° 300 . 060° '! ...

0 0 270 - 270 - ~ -09 n" 7 Trd n" 55

0300 N N I 0 I 330 I 0300 d \ I -20% 3000 0600 .... ""

270~ ~ -0900 -091 QAI013 n" 19 n" 25

Figure 31. Comparison of clastic dikes a joint orientations in the Texas Panhandle and eastern New Mexico