Geomorphic development of the Canadian River Valley, Texas Panhandle: An example of regional salt dissolution and subsidence
THOMAS C. GUSTAVSON Bureau of Economic Geology, The University of Texas, Austin, Texas 78713
ABSTRACT dian River Valley is primarily the result of regional salt dissolution and subsidence that have been active throughout the late Tertiary and Quater- Development of the Canadian River Valley in the Texas Pan- nary. The Deaf Smith County nuclear waste repository site, one of three handle resulted mostly from regional subsidence following dissolution recently identified sites, is located in the southern part of the study area of Permian bedded salts. Salts of the Clear Fork, Glorieta, San (Fig. 1). Andres, and Seven Rivers Formations have undergone dissolution along the margins of the Palo Duro, Dalhart, and Anadarko Basins. GEOLOGIC SETTING The Canadian River Valley follows a zone of subsidence for >208 km (130 mi) across the High Plains. High solute loads (3,000 ppm Late Paleozoic tectonic movements resulted in the Amarillo Uplift, chloride) in the Canadian River and historical development of sink- the Cimarron Arch and the Bravo Dome, and the adjacent Palo Duro, holes indicate that dissolution and subsidence processes are still active. Dalhart, and Anadarko Basins (Fig. 2) (Birsa, 1977). By middle Permian Evidence that these processes have been active in the region since the time, these basins were essentially filled, and the area evolved into an middle Tertiary includes Pliocene lake sediments and Quaternary extensive marine shelf, covering the northern portion of the Permian basin, terrace alluvium that have been deformed by dissolution-induced sub- where salt and other evaporites accumulated (Dutton and others, 1979; sidence as well as former sinkholes filled with lacustrine sediments of Handford and Dutton, 1980). The area was differentially uplifted during the lower Ogallala Formation (Miocene). the Triassic to form the fluviolacustrine basin of the Dockum Group and was uplifted again during the Late Cretaceous-early Tertiary, which re- INTRODUCTION sulted in the middle Tertiary erosional surface and later deposition of the Ogallala Formation (McGowen and others, 1979; Seni, 1980). The Canadian River, with headwaters in northeastern New Mexico, The Canadian River region is underlain by Permian, Triassic, Ter- flows south along the western margin of the Central High Plains (Fig. 1). tiary, and Quaternary strata (Fig. 3). Permian sediments consist of dolo- At its intersection with the Conchas River, the Canadian River turns mite, red beds, and thick evaporite sequences of salt, anhydrite, and gypsum east-northeast across the High Plains of New Mexico and the Texas Pan- (Presley, 1979a, 1979b, 1980a, 1980b; McGillis and Presley, 1981; Ho- handle at a high angle to the regional southeasterly slope. In Texas, the vorka, 1983; Boyd and Murphy, 1984). Triassic Dockum Group strata Canadian has incised through the Tertiary Ogallala Formation and into consist of nonmarine sandstones and mudstones (McGowen and others, Triassic and Permian strata to form a valley which is as much as 64 km 1979). Triassic and locally Permian strata are overlain unconformably by (40 mi) wide and 300 m (1,000 ft) deep. This valley has developed since Tertiary fluvial and eolian clastics of the Ogallala Formation (Seni, 1980). the end of deposition of the Ogallala Formation 3 to 5 m.y. ago (Schultz, The Ogallala Formation is overlain locally by late Pliocene lacustrine 1977). The High Plains north of the valley of the Canadian lie -75 m (250 sediments of the Rita Blanca Formation and is mantled by Quaternary ft) lower than do the High Plains south of the valley. These conditions eolian sands and silts of the Blackwater Draw Formation (Anderson and suggest that the position and, possibly, the development of as much as 208 Kirkland, 1969; Reeves, 1976; Holliday, 1984). km (130 mi) of the length of the Canadian River Valley may be struc- Gustavson (1982), Gustavson and Finley (1982,1985), and Dolliver turally controlled where it crosses the High Plains. (1984) have stated that the path of the Canadian River in the Texas In order to understand the geomorphic development of this part of Panhandle and eastern New Mexico was strongly influenced by dissolu- eastern New Mexico and the Texas Panhandle, several questions must be tion of Permian bedded salt and collapse of overlying strata. The position answered, including the following. (1) Why did the Canadian River Valley of several segments of the Canadian River Valley outside of the Texas develop at a high angle to the regional southeasterly slope of the Southern Panhandle has been attributed to adjustment to bedrock structure. In High Plains? (2) Why are the High Plains on the northern side of the eastern New Mexico, Spiegel (1972) attributed the morphology of the Canadian River Valley 75 m (250 ft) lower than are the High Plains on the Canadian River Valley to the river's adjustment to mid-Pleistocene normal southern side of the valley? (3) How was a stream as small as the Canadian faults. Fay (1959) suggested that the present-day course of the Canadian River able to incise such a large valley? River in western Oklahoma is a result of the river's adjustment to the strike This study, which is part of an ongoing research program designed to of Permian rocks exposed across the regional surface slope and of stream determine the feasibility of disposing of high-level nuclear waste in bedded piracy. Brown (1967) offered an alternative explanation, suggesting that Permian salt in the Texas Panhandle, tests the hypothesis that the Cana- the river has adjusted to deeply buried structures in western Oklahoma
Geological Society of America Bulletin, v. 97, p. 459-472,10 figs., April 1986.
Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 460 T. C. GUSTAVSON
100° 103° 37° DO'
Contour intervals: Texas 200 ft EXPLANATION N.M. OK. New Mexico 500 ft
Caprock Escarpment TX.
Deaf Smith Waste Isolation 30 60 mi Site —Il — -h 50 100 km
Figure 1. Physiography of eastern New Mexico and the Texas and Oklahoma Panhandles. Dashed lines tie topographic contours across the Canadian River Valley (Breaks). If the strike of contour lines on the Southern High Plains is projected across the Canadian River Valley, it is apparent that the northern side of the valley is -75 m (250 ft) lower in elevation than is the south rim of the valley. U.S. Department of Energy stratigraphic test wells include Stone and Webster Engineering Corporation No. 1 Mansfield (A), No. 1 J. Friemel (B), No. 1G. Friemel (C), and No. 1 Detten (D) wells, and the DOE/Gruy Federal No. 1 Rex White well (E). Qtl = Quaternary terrace containing Lava Creek B Ash.
following dissolution and collapse of Permian anhydrites. Walker (1978) GEOMORPHIC PROCESSES stated that the Canadian River Valley formed during the Pleistocene by headward erosion into the High Plains. Dissolution Tierra Blanca ("reek, which lies south of the Canadian River, is also thought to be structurally controlled (Gustavson and Budnik, 1985) Downstream from the Ute reservoir in eastern New Mexico (Fig. 1), (Fig. 1). Like the Canadian River, Tierra Blanca Creek flows northeast the solute load of the Canadian River reaches 3,000 ppm chloride (U.S. across the regional southeast slope of the High Plains. It overlies a Geological Survey, 1969-1982). The U.S. Bureau of Reclamation (1S>79) northeast-trending zone of subsidence induced by dissolution of salts of the estimated that >55,000 metric tons of sodium chloride are carried annu- Seven Rivers Formation. ally by the Canadian River to Lake Meredith, Texas. Gustavson and others
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l&ïS'ff Basement structural high
Figure 2. Regional structural elements, Texas Panhandle and eastern New Mexico. The peripheral salt dissolution zone in the Palo Duro and Anadarko Basins, along the margins of the Glorieta through Seven Rivers salt limit lines, follows the upturned edges of Permian strata along the basin margins, which illustrates that dissolution of salt tends to occur in structurally high areas where salts are nearest to the surface. The study area occurs along the Amarillo Uplift and Bravo Dome.
(1982) found that sinkholes had occurred historically along the Canadian several lower, undated terraces indicate that incision has been active River Valley in the study area wherever the valley is underlain by Permian throughout the late Quaternary. bedded salts. These data confirm that salt dissolution is locally an active process beneath the Canadian River Valley and suggest that subsidence is PROCEDURES accompanying dissolution. To test the hypothesis that dissolution of Permian salt and subsidence Erosion and Deposition have controlled the development of the Canadian River Valley in the study area, the likelihood that salt was present in areas where it is now absent Until recently, the Canadian River, which lies at the floor of a broad, must be established. Also, structures attributed to dissolution-induced sub- V-shaped valley flanked by bedrock exposures, was probably incising its sidence must be separated from tectonically induced structures. valley. Unpaired terraces, which contain 610,000-yr-old Lava Creek B The Tubb interval of the Clear Fork Group underlies all salt-bearing Ash (Izett and Wilcox, 1982), lie -60 m (200 ft) above the river on the units suspected of having been affected by dissolution. A structure-contour south side of the valley near Lake Meredith (Fig. 1). These terraces and map on the Tubb interval, therefore, will show deformation of Permian
Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 PALO DURO DALHART ANADARKO AGE BASIN BASIN BASIN WEST a CENTRA -i—i—i—i—i—I- ~i 1 I I—i I i i 1 i i—'— QUATERNARY Blockwoter Draw Fm. Blockwoter Draw Fm! Blockwoter Draw Fm. Rito f BloncaFm—»..».f.. - TERTIARY Xtttt E ££t Ogollala Formation Ogollala Formation Ogollala Formation
TRIASSIC Dockum Group Dockum Group
Quartermaster Quartermaster Ixl Dewey Lake Formotion Formation OC Formotion Lü CO Alibates Formation Alibotes Dolomite Alibates Dolomite < Salado Formation O X Tensili Formation o Yates Formotion Q. Cloud Chief a: 3 Formotion LÜ Ow 0_ ¿¡Seven Rivers¡ii:;: o co o Artesia Group DC UJ Sii:Formotion :::•:•:::•:: '55 LU oc a> UJ Rush Springs Q_ co £L Queen and Sandstone Z5 -I < O Dog Creek < VY.Çj.tQn.: Shale «:;:;:¡:¡:;:;:;:;:; Blaine Formation Blaine Formation Fjowerpot SaltSiv ¿¿Flowerpot Saltïix Glorieta Glorieto Sandstone Glorieta Sandstone I Sandstone JZ Hennessey (S) Shale UJ oc UJ í:-:*:*:*:* U p p e ríííííííííí: OL íííííííUpperíííííí:; Q. Up P.Ç f...... cr (/> 3 •xiClear Fork SoltíS: 3 •:Clear Fork Salt: Cimarrón S à 11 O O UJ w w Û- o O Cimarron Anhydrite Cimarron Anhydrite Cimarron Anhydrite a jí. JÉ CC cr < £ Tubb interval £ Tubb interval Tubb interval IxJ h. z o o £ o a> — O lílííSS: LowerWxjxlííxj UJ t_> o *íí Lower -Sii::::::::: SICleor Fork Salt::*::-: l:::x::::Cimorron Salt :::::: Red Cove Formotion Hennessey Shale WOLFCAMPIAN SERIES Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 GEOMORPHIC DEVELOPMENT OF CANADIAN RIVER VALLEY, TEXAS 463 Figure 3. Stratigraphie nomenclature of Permian and younger strata above the remaining San Andres salt beds decreases significantly, strata, Texas Panhandle. Principal salt units are stippled. Modified which suggests dissolution of salt and subsidence of overlying strata. Sim- from Johnson (1976). ilarly, changes in thicknesses of San Andres/Blaine Formation salts are accompanied by radical changes in apparent dips of overlying units be- tween well 8 and well 6, which suggests dissolution of San Andres Forma- tion salts and subsidence of overlying strata. strata which cannot be attributed to dissolution-induced subsidence. The A 25-m- (75-ft-) thick remnant of San Andres/Blaine Formation salt Alibates Formation overlies all salt-bearing units, and the differences in in well 3 on the southern flank of the Dalhart Basin and the marked changes structural patterns between the Tubb interval and the Alibates Formation in apparent dips of San Andres and younger strata on the flanks of the reflect the effects of dissolution-induced subsidence as well as subsidence Dalhart and Palo Duro Basins are additional evidence that San Andres resulting from compaction or tectonic movement during the middle and and younger salts formerly extended across the Bravo Dome and into the Late Permian. Dalhart Basin. Several lines of evidence suggest that thick salts formerly existed A facies change from salt to sandstone occurs in the upper Glorieta beneath the Canadian River Valley and that dissolution has occurred along Sandstone without significant change in stratal thickness between well 6 the northern margin of the Palo Duro Basin, along the western margin of and well 4. A facies change from salt to anhydrite occurs in the upper the Anadarko Basin, and over part of the Amarillo Uplift. (1) Interpreta- Seven Rivers salt between well 8 and well 9. Most of the thinning of the tion of geophysical logs (for example, from wells 6 and 7, Fig. 4) indicates upper Seven Rivers salt, however, is probably due to dissolution. Strati- that where there is structural collapse of overlying beds, abrupt loss of graphic units immediately above and below the upper Seven Rivers For- subjacent salt sequences between oil and gas wells is probably in response mation salt do not change in thickness between well 8 and well 9, but a to salt dissolution rather than facies change (Gustavson and others, 1980; diminished regional dip between the two wells indicates that -50 m (150 Gustavson, 1982; McGookey and others, 1985; Gustavson and Finley, ft) of salt may have been lost from well 8. Thick insoluble residues and 1985). (2) Brecciated zones, fractures with slickensides, extension fractures collapse breccias that occur above remaining salt are evidence of dissolu- filled with gypsum, and insoluble residues composed of soft mudstone, tion in core of the upper Seven Rivers Formation from the No. 1 Mans- anhydrite, or dolomite overlie the uppermost salts in cores from wells A field well -40 km (25 mi) northeast of well 9 (Fig. 5). through E (Fig. 1). (3) Permian outcrops along parts of the Canadian Upper Clear Fork and lower Glorieta Formation salts and mudstones River Valley contain folds, systems of gypsum-filled extension fractures, pinch out or thin over the Bravo Dome. This may represent a facies change and breccia-filled chimneys that are interpreted to have resulted from related to a minor uplift of the Bravo Dome during Permian time, or salts dissolution of salt and collapse of overlying beds (Eck and Redfield, 1963; may have been deposited but later dissolved during the Permian. Gustavson and others, 1980; Collins, 1984) (see Goldstein and Collins, 1984, and Machel, 1985, for discussions of gypsum-filled extension frac- STRUCTURE ON THE TUBB INTERVAL tures). (4) Hydrologic testing of the strata immediately above uppermost salts in the No. 1 Mansfield well produced sodium chloride brines (Dutton A structure-contour map on the Tubb interval of the Clear Fork and others, 1985), which suggests that dissolution of salts of the Seven Group illustrates parts of the Anadarko, Dalhart, and Palo Duro Basins as Rivers Formation may be active. Finally, (5) high chloride contents in well as parts of the Bravo, Bush, and John Ray Domes; the Cimarron Canadian River waters indicate that salt dissolution is active, at least Arch; and the Amarillo Uplift (Fig. 5). The Tubb interval, an informal locally, along the valley. Recognition of effects of salt dissolution in out- subsurface stratigraphic unit recognized on geophysical logs, underlies all crop, in cores, in stratigraphic sections, and in the chemistry of Canadian of the salt-bearing formations that have been affected by dissolution, and, River waters is strong evidence that Permian salts formerly extended thus, structure on top of the Tubb interval has not been influenced by farther to the north, northeast, and northwest beneath the valley of the dissolution and subsidence. Canadian River. Major tectonic features include the Bush Dome and the John Ray Dome in Potter County which have dome crests separated by 240 m (800 STRATIGRAPHY BENEATH THE ft) of elevation. The trough between these two features has -60 m (200 ft) CANADIAN RIVER VALLEY of relief. In Carson County, the subtly defined Whittenburg trough occurs along the southern flank of the Amarillo Uplift. Relief on Whittenburg Regional stratigraphic relations between the Palo Duro Basin to the trough is -60 m (200 ft). In southwestern Carson County, the Tubb south, the Bravo Dome, and the Dalhart Basin to the north are shown in surface dips uniformly to the southwest. A 360-m- (1,200-ft-) deep struc- cross section H-H' (Fig. 4). The abrupt thinning of salt along the flank of tural trough connects the Dalhart and Palo Duro Basins in eastern Oldham the Palo Duro Basin and over the crest of the Bravo Dome is due primarily County. to salt dissolution and, to a lesser extent, to facies change or dissolution shortly after deposition. SALT THICKNESS Nonsalt units, such as the Alibates Dolomite, dolomites within the San Andres/Blaine Formation, and anhydrites within the upper Clear Salts of the upper Clear Fork, Glorieta, San Andres/Blaine, and Fork Formation, do not thin significantly over the Bravo Dome. Strata Seven Rivers Formations thin rapidly along the margins of the Anadarko between the top of the Tubb interval and the top of the lower San Andres and Palo Duro Basins (Fig. 6). Most of the abrupt thinning of salt is Formation do not thin substantially between well 9 and well 8. These interpreted to have resulted from dissolution; however, as previously dis- relations indicate that the Permian strata were not substantially affected by cussed, facies changes and differential subsidence rates during the middle differential subsidence between the Bravo Dome and the Palo Duro or Permian probably account for some local salt thinning. Dalhart Basins during Permian time. Differential subsidence, therefore, Comparison of the salt thickness map to the structure map on top of probably did not significantly affect original salt thickness in this area the Tubb interval shows that (1) thick San Andres salts are missing over during the Permian. the structurally high areas of the axis of the Amarillo Uplift and the John Salts of the upper San Andres Formation thin substantially between Ray and Bravo Domes, (2) Glorieta salts are missing over the John Ray well 9 and well 8; nonsalt units do not thin noticeably, and the south dip of Dome and the Amarillo Uplift, (3) Clear Fork salts thin over the Amarillo Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 H Nort h I! HARTLEY CO I OLDHAM CO DALHART BASIN- BRAVO DOME- EX PLAN ATION WELLS LITHOLOGY ® SINCLAIR OIL © SHELL OIL p^rcs Tertiary and Quaternary IS Salt #/ Reynolds Cattle # 2-68 Strot Test undifferentiated SINCLAIR OIL SUPERIOR OIL Unconformity Figure 4. Stratigraphic cross section H-H' illustrates the loss of >200 m (600 ft) of salt along the northern margin of the Palo Duro Baiiin. Structural collapse of overlying units and the continuation of nonsalt evaporite units in the upper part of the section across the structurally high Bravo Dome withou t significant change suggests that salts have thinned because of dissolution and not because of facies change. A facies change from salt to sandstone occurs in the upper Glorieta Formation. See Figure 5 for the location of cross section H-H'. Cross section modified from McGookey and others (1985). Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 H' South DEAF SMITH CO 1-200 _ sea level All logs are gamma-ray logs -200 Vertical exaggeration =53x Datum: sea level -400 L-600 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 466 T. C. GUSTAVSON Uplift and the John Kay Dome, (4) upper San Andres and Seven Rivers em Carson County. The crests of the John Ray and Bush Domes are at the salts thin over the Bush Dome, and (5) San Andres salts extend farthest same elevations, and the structural relief of the trough between the two north in the area of the Whittenburg trough between the Dalhart and Palo domes has increased from 60 m (200 ft) on the top of the Tubb interval Duro Basins in eastern Oldham County (Figs. 5 and 6). These relations (Fig. 5) to -90 to 120 m (300 to 400 ft). A shallow structural trough suggest that dissolution has occurred preferentially in structurally high extends northeastward, normal to the southeast trend of the AmariLlo areas. Similar relationships are seen along the eastern and western margins Uplift, from central Potter County to Hutchinson County. of the Palo Duro Bisin (Fig. 2) (Gustavson and Finley, 1982, 1985; The change in structural configuration between the Tubb interval and McGookey and others, 1985). the overlying Alibates Formation is apparently mostly the result of post- Permian dissolution of salt from strata between the two structural horizons STRUCTURE ON THE ALIBATES FORMATION (compare Figs. 5,6, and 7). For example, dissolution of -180 m (600 ft) of salt (San Andres Formation) from over the John Ray Dome but :iot Structure on the top of the Alibates Formation (Fig. 7), which over- from over the Bush Dome accounts for most of the change in relief and lies the salt-bearing interval, is markedly different from structure on the elevation between the two features. Dissolution of -180 to 240 m (60(1 to Tubb interval (Fig. 5). At the level of the Alibates Formation, large, closed 800 ft) of San Andres and Seven Rivers Formation salts in the Dalhart structural basins occur in Oldham and Hartley Counties and in southeast- Basin and over the Bravo Dome has resulted in subsidence of the Alibates EXPLANATION Contour interval = 200 ft • V/ell location O 30 mi o COE stratigraphic test well -i—.—-T- i ,-L —I 48 km —-Fault Figure 5. Stracture-contour map on top of the middle Permian Tubb interval shows the major structural elements of the study area unaffected by salt dissolution (after Budnik, 1984). H-H' locates Figure 4. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 GEOMORPHIC DEVELOPMENT OF CANADIAN RIVER VALLEY, TEXAS 467 Formation but has permitted the Alibates to retain the shape of the Dal- Comparison of Figures S, 6, and 7 suggests that salt dissolution can hart Basin as expressed on top of the Tubb interval in the northern part of account for most of the changes in structural configuration between the top the area. Salt remains along the southern margin of the Dalhart Basin, and, of the Tubb and the top of the Alibates; however, from 30 to 60 m (100 to because less dissolution-induced subsidence has occurred here, the basin 200 ft) of the change cannot be explained by this process. These differences has structural closure of ~ 120 m (400 ft). Salt remaining in southwestern may be related to local, tectonically induced subsidence of the Dalhart Carson County accounts for the structurally high southwestern rim of a Basin or of the Whittenburg trough during the Permian (McGookey, deep, closed structural basin. Dissolution of parts of the Blaine, Glorieta, 1981; Budnik, 1984). and upper Clear Fork salts over parts of the Amarillo Uplift and along the southwestern margin of the Anadarko Basin accounts, in part, for the MIDDLE TERTIARY EROSIONAL SURFACE structural trough which extends from Potter County to Hutchinson County. Comparison of Figures 6 and 7 shows that the areas of change in An extensive unconformity separates Triassic and Permian strata structural pattern between the top of the Tubb interval and the top of the from the overlying Miocene-Pliocene Ogallala Formation. Figure 8 is a Alibates closely correspond to the area of rapid salt thinning. structure-contour map on the base of the Ogallala Formation or of the Figure 6. Net salt thickness map of slices of the upper Clear Fork Group, Glorieta (Sandstone) Formation, lower San Andres Formation (includes Blaine Formation salts in the Dalhart Basin and Flowerpot Formation salts in the Anadarko Basin), upper San Andres Formation, and Seven Rivers Formation. For each formation, only the salt-bearing interval which is not overlain by salt in younger strata is included. Salt thickness data for Hutchinson County are from McGookey (1981). H-H' locates Figure 4. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 468 T. C. GUSTAVSON middle Tertiary erosional surface. Much of this surface has been deformed dissolution-induced subsidence, developed during or following Ogallala as a result of dissolution and subsidence (Gustavson and others, 1980; deposition and are Miocene or younger. Gustavson and Budnik, 1985). Structural lows on the erosion surface overlie similar basirs on the top of the Alibates Formation in Hartley and TOPOGRAPHY Oldham, Potter and Hutchinson, and Carson Counties (Figs. 7 and 8). The middle Tertiary erosional surface is 100 to 200 m (300 to 600 ft) lower Regional topography in eastern New Mexico and the Texas Pariian- beneath the Canadian River than beneath the southern margin of the dle is dominated by the flat, east-southeast-sloping High Plains surface. Canadian River Valley. In these areas, basal Ogallala strata dip to the The Canadian River flows east-northeast across the High Plains at a high north and northwest, whereas mapped distributary directions and paleo- angle to the regional slope (Figs. 1 and 9). The Canadian River Valley also current directions measured in outcrop clearly indicate that the Ogallala crosses depositional trends of the Ogallala Formation at a high angle, originally dipped to the south and southeast (Fig. 8). There is almost 225 which indicates that the origin of the Canadian River is not related to m (700 ft) of closure in each of these basins. Similar structural troughs also former drainages of the Ogallala alluvial system (Figs. 8 and 9). Where it occur both on the base of the Ogallala and on top of the Alibates forma- crosses the High Plains, the valley follows the structural trough eviden t on tion beneath the present Canadian River Valley. The similarity in structu- the Alibates and the base of the Ogallala structural surfaces as well a;; the ral patterns indicates that structural changes to both the middle Tertiary zone of salt thinning (compare Figs. 6 through 9). This relationship indi- unconformity and the Alibates Formation, attributed primarily to cates that the position of the valley of the Canadian River is controlled by EXPLANATION Contour interval = 100 ft • Well location 0 30 mi o DOE stratigraphie test well 1 "-i 1—i—1 H 1 O 48 km ° Outcrop elevation (Barnes, 1969-1984) Waste Isolation/^p^Lo Site basin Figure 7. Structure-contour map on the Upper Permian Alibates Formation. H-H' locates Figure 4. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 GEOMORPHIC DEVELOPMENT OF CANADIAN RIVER VALLEY, TEXAS 469 structures that resulted primarily from dissolution of Permian bedded salts. River Valley. Differences in elevation between the plains north and south Furthermore, it suggests that part of the depth of the Canadian River of the Canadian River and subsidence of the middle Tertiary unconformity Valley is due to dissolution-induced subsidence. Structural control of the beneath the Canadian River suggest that 100 to 200 m (300 to 600 ft) of Canadian River Valley as a result of dissolution-induced subsidence prob- subsidence has occurred regionally. Radial drainage has developed in an ably extends into eastern New Mexico and western Oklahoma across area overlying the John Ray Dome (Figs. 5 and 9). Radial drainage much of the Permian basin (Brown, 1967; Gustavson, 1982; Gustavson commonly follows the dip of the Ogallala and Dockum Formations and and Finley, 1985). suggests that the Ogallala and Dockum Formations have been let down The High Plains surface north of the Canadian River Valley lies over the John Ray Dome, at least in part, as underlying salts were -75 m (250 ft) lower than does the High Plains surface south of the dissolved. Canadian River Valley (Fig. 1). Differences in elevation between the To the west, Rita Blanca and Punta de Agua Creek Valleys have Central and Southern High Plains to either side of the Canadian River developed above and subparallel to the structural axes of the Dalhart Basin Valley apparently resulted from subsidence in response to dissolution of (compare Figs. 5, 7, 8, and 9). Post-Ogallala strata consisting of late the same units that were responsible for the development of the Canadian Pliocene Rita Blanca lacustrine sediments occur over the deepest parts of Figure 8. Structure-contour map on the base of the High Plains aquifer (Ogallala Formation) (modified from Knowles and others, 1982). The Ogallala Formation was deposited on the middle Tertiary erosional surface, and, therefore, this map is also a structure-contour map of the unconformity between the base of the Ogallala Formation and the underlying Permian and Triassic systems. Ogallala depositional trends are from Seni (1980). Ogallala outcrop pattern from Barnes (1969,1984). Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 470 T. C. GUSTAVSON EXPLANATION Contour interval = 100 ft on High Plains surface 500ft in Canadian River Valley Stream Caprock Escarpment 0 30 mi h- —I ^ Rita Blanca Formation 48 km ! Waste Isolation Site Figure 9. Topography of the study area. Topography from U.S. Geological Survey 1:250,000 topographic map series. the basin and dip southwestward into the axis of Punta de Agua Creek. TIMING OF DISSOLUTION AND These features developed as San Andres/Blaine salts, which were formerly SUBSIDENCE, CANADIAN RIVER VALLEY present in this basin, underwent dissolution. A simple model of the development of a subsidence basin shows how East of the study area, a Clarendonian (Miocene) vertebrate fauna dissolution of middle and Upper Permian salt along the northern margin of occurs in basal Ogallala lacustrine strata filling sinkholes attributed to the Palo Duro Basin has led to a wedge-shaped salt margin where strati- dissolution of Permian salts (Schultz, 1977). This indicates that dissolution graphically and structurally higher salts have been preferentially dissolved may have occurred in the study area as early as Miocene time. The middle (Fig. 10). As dissolution occurred during a period of time, a lens-shaped Tertiary erosional surface is deformed over the zone of salt dissolution and cross section of salt was removed, and a corresponding lens-shaped cross the Ogallala thickens into subsidence basins on the erosion surface, which section of strata above the area of dissolution underwent subsidence. Sur- indicates that dissolution and subsidence continued during Ogallala depo- face subsidence over the zone of dissolution was instrumental in defining sition. Pliocene lacustrine sediments of the Rita Blanca Formation overlie the present position, of the Canadian River. Continued dissolution and -75 m (250 ft) of Ogallala sediments along the east side of Punta de Agua subsidence helped to deepen the valley. and Rita Blanca Creeks. The lake sediments overlie the structurally lowest Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 GEOMORPHIC DEVELOPMENT OF CANADIAN RIVER VALLEY, TEXAS 471 LATE PLIOCENE Canadian River Valley Surface subsidence 2^Allai a I surface ~T I FORMATION I Subsidence of AM bates Formation Dissolution and subsidence of Upper San Andres Formation. Dissolution and subsidence of Lower San Andres Formation. Dalhart Basin Palo Duro Basin • 60 mi 100 Km N MIDDLE PLIOCENE POST-OGALLALA SURFACE Condition following Ogallala deposition in the vicinity of Oldham County. I Palo Duro 1 Basin Figure 10. Dissolution of salt in the late Tertiary and early Pleistocene in structurally high areas resulted in subsidence of overlying strata. Areas undergoing dissolution and subsidence were roughly lens-shaped in cross section. Surface subsidence resulted in the development of the Canadian River Valley and accounts, in part, for the depth of the valley. parts of the Dalhart Basin and dip southwest into the axis of the creek Quaternary terraces containing Lava Creek B Ash (Izett and Wilcox, valley. Deformation of these beds suggests that dissolution-induced subsi- 1982) are present in several areas along the south side of the Canadian dence continued into the late Pliocene. River Valley in Potter and Moore Counties (Fig. 1). Locally, these terraces The Canadian River, which flows across the regional southeast slope are folded and faulted and overlie complexly folded and fractured Permian and at a high angle to Ogallala depositional trends, is clearly a post- strata that contain breccia-filled collapse chimneys. Deformation of Ogallala feature. The Canadian River Valley follows the dissolution- Permian strata has been attributed to dissolution-induced subsidence by induced structural trough both on the Alibates Formation and on the base Eck and Redfield (1963); Gustavson and others (1980), and Collins of the middle Tertiary erosional surface. These relations also indicate that (1984). This indicates that dissolution and subsidence have occurred at dissolution and the development of the Canadian River were occurring least locally along the Canadian River Valley during the Quaternary and during the late Pliocene (see Gustavson and Finley, 198S, for a discussion account, in part, for the depth of the valley. High solute loads in waters of of the physiographic evolution of the Pecos and Canadian River Valleys). the Canadian River and historical collapse events to form sinkholes indi- Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021 472 T. C. GUSTAVSON Dutton, S. P., Finley, R. J., Galloway, W. E„ Gustavson, T. C., Handford, C. R., and Presley, M. W., 1979, Geology and cate that dissolution which began as early as the middle Miocene continues geohydrology of the Palo Duro Basin, Texas Panhandle: A report on the progress of nuclear waste isolation to be active along the Canadian River Valley. feasibility studies (1978): The University of Texas at Austin, Bureau of Economic Geology Geological Circular 79-1,99 p. Dutton, A. R., Fisher, R. S., Richter, B. C., and Smith, D. A., 1985, Hydrologic testing in the salt-dissolution zone of the Palo Duro Basin, Texas Panhandle: Preliminary report on field data at Sawyer #2 and Mansfield #2 w ills: The CONCLUSIONS University of Texas at Austin, Bureau of Economic Geology Open-File Report OF-WTWI-1985-3,15 p. Eck, W., and Redfield, R. C., 1963, Geology of Sandford Dam, Borger, Texas: Panhandle Geological Society F eld Trip Guidebook, p. 54-61. 1. Salts thin rapidly at the structural margins of the Dalhart, Palo Duro, Fay, R. O., 1959, Geology and mineral resources of Woods County, Oklahoma: Oklahoma Geological Survej Bulletin 106,189 p. and Anadarko Basins, which indicates that dissolution occurs preferen- Goldstein, A. G., and Collins, E W., 1984, Deformation of Permian strata overlying a zone of salt dissolution anc, collapse tially in structurally high areas. Apparently, structurally high strata are in the Texas Panhandle: Geology, v. 12, p. 314-317. Gustavson, T. C., 1982, Structural control of major drainage segments surrounding the Southern High Plains, iit Gustav- more accessible to ground waters undersaturated with respect to sodium son, T. C., and others, Geology and geohydrology of the Palo Duro Basin: A report on the progress if nuclear waste isolation feasibility studies (1981): The University of Texas at Austin, Bureau of Economic Geology chloride. Geological Circular 82-7, p. 176-181. Gustavson, T. C., and Budnik, R. T., 1985, Structural influences on geomorphic processes and physiographic features, 2. The base of the Ogallala has subsided 100 to 200 m (300 to 600 Texas Panhandle: Technical issues in siting a nuclear-waste repository: Geology, v. 13. ft) along the Cana Printed in U.S.A. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/4/459/3445145/i0016-7606-97-4-459.pdf by guest on 02 October 2021