Geological Survey Professional Paper 446 Geology of the Guadalupe Mountains, New Mexico

Most of the mapped area lies in the Sacramento section of the Basin and Range physiographic province as defined by Fenneman (1931, p. 393-395), but the relatively low area southeast of the Reef Escarpment is a part of the Pecos section of the Great Plains province (Fenneman, 1931, p. 47-50). Throughout the area the youthful to mature topography is directly related to the structure and character of the underlying rocks, but in places the topography may be partly controlled by an old superimposed drainage system. An extensive limestone cavern system that was developed during an earlier erosion cycle has been partly exhumed by the modern drainage system.

MAJOR LANDFORMS

The Guadalupe Mountains are a moderately dissected plateau which is gently inclined to the northeast. The inclination results from the regional dip of the rocks. The west margin of the mountains is formed by the Big Dog Canyon and Shattuck Valley fault scarps, whereas the northeast margin is formed by the dip slope on the Huapache flexure. The southeast edge of the mountains is marked by the Reef Escarpment, held up by the resistant Capitan Limestone.

The topography of the Dog Canyon-Brokeoff Mountains area is controlled primarily by faults and folds. Big Dog Canyon is a graben. Upper Dog Canyon and Shattuck Valley are, in effect, synclinal grabens, whereas the Brokeoff Mountains are basically an anticlinal horst.

Seven Rivers Embayment (fig. 1) is a topographic depression controlled by structure and differential erosion. On the west is the Huapache monocline defining the margin of the Guadalupe Mountains. On the southeast and east are the Hess Hills, Azotea Mesa, and Seven Rivers Hills (fig. 1), all capped by dolomite tongues in the evaporite facies of the Seven Rivers Formation. North and west of those hills, where dolomite tongues were thin and scarce, the Seven Rivers Formation and much of the relatively nonresistant Queen Formation have been removed by erosion, leaving a topographic embayment.

The relatively low terrain of the Pecos section southeast of the mountains is carved from the easily eroded evaporites of the Ochoa Series. The Reef Escarpment rises above the plains primarily because of its greater resistance to erosion.

DRAINAGE

The drainage pattern in the mapped area is inherited in part from an ancestral drainage system, and like the topography, is closely controlled by the structure and the resistance to erosion of the surface bedrock. The ancestral drainage system was probably established early in Tertiary time after regional uplift, slight tilting to the northeast, and Laramide folding of the rocks adjacent to the Capitan Limestone.

Most of the major northeastward-flowing streams such as Black River, and those in Last Chance and Dark Canyons, and Rocky Arroyo, probably originated early in Tertiary time. Another consequent Tertiary stream, here called Walnut Creek, probably flowed northeastward along the axis of Walnut Canyon syncline between Dark Canyon and Black River.

Following uplift of the Guadalupe-Delaware Mountains block probably in late Pliocene or early Pleistocene time, soft and soluble rocks southeast of the Capitan Limestone were quickly eroded and the Reef Escarpment was exhumed. Headward erosion of consequent streams flowing off the Reef Escarpment then cut into the old Walnut Creek, which trended northeastward parallel to the reef, and diverted the stream flow southeastward at many points. West Slaughter and South Rattlesnake Canyons and the upper ends of Walnut and Wood Canyons were established by old Walnut Creek. Meanders that had developed in the mature older streams were incised during the uplift of the mountains to produce such features as the Serpentine Bends of Dark Canyon (fig. 26). Thus, the dendritic drainage pattern and meanders in the mountains from Dark Canyon northwestward probably are inherited also from the early Tertiary drainage system. To the southeast the Tertiary drainage has been largely destroyed by headward erosion of drainage off the Reef Escarpment. The sharp westward bends near the heads of many of the smaller drainage courses flowing off the Reef Escarpment, such as at Calamity Cove and Lefthook and Nuevo Canyons, are apparently controlled by the joint system parallel to the escarpment.

FIGURE 26.—Incised meanders of Dark canyon at Serpentine Bends. Undercut bank at top left is 600 feet high. The lower two-thirds of the cliff is held up by dolomite of the Seven Rivers Formation; the Yates Formation is in slope at top.

Except for Black River, which may follow the approximate course of an early Tertiary stream, most of the other drainage courses in the area are directly or indirectly controlled by the late Pliocene and early Pleistocene structure of the region. This is particularly evident in the Dog Canyon-Brokeoff Mountain area where most major drainage courses follow synclinal axes, grabens, faults, and joints, and the tributaries are resequent drainage courses normal to fault scarps. A major exception is an obsequent tributary of Upper Dog Canyon which has cut through El Paso Ridge at El Paso Gap to capture the Shattuck Valley drainage.

In the Castile Formation in the southeastern part of the area, east-northeastward-draining stream courses, such as Hay Hollow and Cottonwood Draw, are apparently consequent streams following the regional dip.

The drainage courses between the Guadalupe Mountains and Black River, those draining into the Salt Flat, and some of those in the Seven Rivers Embayment are typical arid-climate bajada- and pediment-forming washes.

Nearly all the stream courses are dry except after heavy rains, and the only perennial streams are in stretches of certain drainage courses below large springs.

Except for about an 8-mile stretch beginning about 2 miles below the discharge of Rattlesnake Spring, Black River flows perennially from near Bottomless Lakes to its confluence with the Pecos River outside the mapped area. A 3-mile stretch of nearly constant spring-fed streamflow is present in Dark Canyon above X-Bar Ranch headquarters. Very short stretches of perennial flow are found below springs in Juniper, Last Chance, and Sitting Bull Canyons.

CAVES

Cave openings, some of which are now blocked by talus, are numerous in the report area. Most of the caves are in the Capitan Limestone and carbonate rock of the Artesia Group between Dark Canyon and the Reef Escarpment, but a few small caves are in the San Andres Limestone in Last Chance Canyon and in the Rocky Arroyo drainage. At least one is in the large calcareous tufa deposit at Sitting Bull Falls. Seventeen cave openings are shown on the geologic map. These are probably most of the larger caves, but several other small caves are known (table 1).

TABLE 1.—Descriptive data on some caves in the Guadalupe Mountains

By far the largest known cave in the area is the Carlsbad Cavern which underlies an area nearly 1 mile long by more than one-half mile wide (figs. 27, 28; table 1). Except for New Cave and Cottonwood Cave, which has a corridor one-fourth of a mile long (Bretz, 1949, p. 456), most of the other caves in the area are no more than a few hundred feet in maximum dimension, and some are apparently no more than chimneys. However, so far as is known, the interiors of only 9 of the caves have been described, and only 4 have been mapped.

FIGURE 27.—Section C—C' through the Capitan Limestone and associated rocks showing position of Carlsbad cavern (solid black area). (See pl. 1 for line of section.) Most of the cave is in the massive member of the Capitan Limestone (Pcm), but the south end of the Big Room is in the breccia member of the Capitan (Pcb); a basal sandstone tongue of the Yates Formation (Pya) is present in the New Mexico Room; higher beds of the Yates are present in the Main corridor: and the cavern entrance and other chambers (not shown) are in the Tansill Formation (Pt). Other units in the cross section are the Seven Rivers Formation (Psr), Goat Seep Dolomite (Pgs), Cherry Canyon Formation (Pcc), Bell Canyon Formation (Pbc), Castile Formation (Pcs), and gravel (Qg) of Quaternary age.

FIGURE 28.—Outline maps of three caves of the Guadalupe Mountains showing relative sizes and shapes of the joint-controlled passages. The map of Lechuguilla cave is by George W. Moore, of the U.S. Geological Survey; the map of Carlsbad Cavern is based on the original map of Willis T. Lee with modifications and additions made by or for the U.S. National Park Service.

Carlsbad Cavern was first mapped and described by Lee (1925) and has since been discussed in many papers, such as those by Davis (1930, p. 572-578), Bretz (1942, 1949), T. M. Black (1954), Gale (in Hayes, 1957), Good (1957), and Moore (1960). New Cave, formerly Slaughter Canyon Cave, was also mentioned in several of those papers, but was described more fully by Burnet (1938). It was mapped (fig. 28) during fieldwork for the present project. Bretz (1949) has briefly described significant features of Black, Hidden, Cottonwood, and Mudgetts caves (table 1). George Moore mapped and described a small cave in Lechuguilla Canyon (fig. 28) known as Lechuguilla Cave, and Howard (1935, p. 63-65) described Burnet Cave (not shown on pl. 1) in Last Chance Canyon. Most of the other caves have been briefly described by Crisman (1960), and Goat Cave was briefly examined during the present investigation. Table 1 shows comparative data on 11 of the caves in the area.

Because the origin and development of the caves have been discussed comprehensively in other papers, only a summary of the conclusions reached in those papers is presented here. For more complete descriptions of the caves and for more detailed analyses of their development, the reader is referred to the several reports cited herein.

Davis (1930, p. 578) suggested that Carlsbad Cavern formed in two cycles, including an early period of solution in the zone of ground-water saturation (phreatic zone) which caused the excavation of the cave, followed by a period during which the cave was partly filled with dripstone and flowstone in the vadose zone. This history of development was accepted in principle by Bretz (1949). Swinnerton (1932, p. 667) and Gardner (1935), however, maintained that most solution took place at the water table, and that as the water table was lowered as a result of regional uplift, lower levels were excavated while the higher levels began to be filled by dripstone and flowstone due to precipitation of calcium carbonate from vadose waters. T. H. Black (1954, p. 137), Gale (in Hayes, 1957), and Good (1957, p. 20) adopted the two-cycle theory of phreatic solution followed by vadose precipitation, but agreed with Swinnerton that the most active solution took place at, or just below, the water table. They thus attributed the several well-defined levels of Carlsbad Cavern to long periods of stability in the level of the water table.

Both Bretz (1949) and Gale (in Hayes, 1957) presented evidence to show that most of the solution of Carlsbad Cavern and probably of all the solution caves in the area took place before the development of the present erosion surface and that the solution began along joints. Most of the solution probably took place from early in the Tertiary Period until near the end of the Tertiary or later. Motts (1959) believes that some solution is still taking place in the lower levels of Carlsbad Cavern. The late Pliocene or early Pleistocene uplift of the Guadalupe Mountains caused a lowering of the water table, and the vadose cycle of carbonate precipitation began. Carlsbad Cavern and New Cave apparently were partly refilled by water several times after the initial formation of dripstone. This is indicated by solution of some of the dripstone formations in New Cave (Bretz, 1949, p. 456; Gale, in Hayes, 1957), by the same phenomenon in Carlsbad Cavern, and by the presence of—"a clinker-like deposit of calcium carbonate deposited [on preexisting dripstone formations to a uniform level] during an episode of re-flooding" (Black, T. H., 1954, p. 140). A thick deposit of gypsum on the floor of the Big Room of Carlsbad Cavern indicates that waters heavily charged with calcium sulfate partly filled the cave after the end of the first phreatic cycle (Black, T. H., 1954, p. 140; Good, 1957, p. 19). This gypsum could have been derived from the Castile Formation before it was eroded to its present level or from somewhat more distant sulfate beds in the evaporite facies of the Artesia Group.

Although all the caves in the area are now relatively dry, in Carlsbad Cavern there is evidence that two or three vadose streams have occupied the cave (Bretz, 1949, p. 451-453; Black; T. H., 1954, p. 140-141; Gale, in Hayes, 1957). The bones of a Pleistocene ground sloth, Nothrotherium, have been found in stream-deposited silt in the lower levels of Carlsbad Cavern, thus dating the stream as no later than Pleistocene (Gale, in Hayes, 1957). These stream deposits are now covered by flowstone and large dripstone deposits.

Probably most dripstone and flowstone in the caves were deposited during wet-climate periods concurrent with the advance of the Pleistocene ice sheets farther north. That the climate in the region was much colder and probably much wetter during the latest glacial advance is shown by the occurrence of fossils of late Pleistocene arctic-alpine birds and mammals in Burnet Cave (Schultz and Howard, 1935).

Description of the varied and, in places, bizarre dripstone, flowstone, and rimstone formations of the caves, and of the unusual mineral occurrences in the caves is beyond the scope of this paper. The literature on cave deposits in general is extensive. T. H. Black (1954) and Gale (in Hayes, 1957) have described the secondary deposits of Carlsbad Cavern, and D. M. Black (1956) has described an unusual type of rimstone in New Cave which he called a "furled retaining wall." Good (1957) has described and discussed the relatively minor, but very interesting, noncarbonate deposits of Carlsbad Cavern, and Davies and Moore (1957) have described the occurrence there of the minerals endellite and hydromagnesite.