Elephant Butte Lake is literally an oasis in the Lower Sonoran desert of south New Mex- ico. It provides, for nine months of the year, facilities for water skiers, boaters, and bathers in an area of the state where the averageyearly rainfall is only inches, and fishermen may en- joy catching bass, catfish, pike, and crappie the year round. Elephant Butte Lake (formally Hall Lake) is situated only 5 mi from Truth or Conse- El.phonl Porh quences in Sierra County and owes its exis- + Bull. Loka Slol. tenceto a 306-ft . after 5 yrs of construction at a cost of about $5 operations during negotiations with the History and scenery million and became the world's largest dam Apache Indians and was apparently aban- and created the second largest man-made doned when the Apache were settled on reser- Extensive irrigation in southern Colorado water impoundment. The dam is over 300 ft vations. The fort was named after Captain and northern , beginning in about high and I,100 ft long with a V+-miroad along McRae, a member of the Union Army who 1860, caused increased hardship for the its length. In 1940, a hydroelectric generating was killed at the , which farmers in the Mesilla Valley of southern New plant with a capacity of 24,300 kilowatts was took placeduring the Civil War about 35 mi to Mexico and the El Paso-JuarezValley of west installed. The presentElephant Butte the north near . and Mexico. The initial notion, sug- still has over 8090 of its initial capacity of To the north at Hot Spring Landing is an gestedin 1888,was for an international dam 2,634,000acre ft and sedimentation rates have extensivemarina with docks and landings for to be built 3 mi upstream from El Paso to pro- beenmuch lower than predicted. boats, a center for fishing, sailing, and water vide irrigation water for west Texas and Mex- Elephant Butte Lake became a New Mexico skiing where boats may be rented. North of ico. New Mexico farmers objected for not StatePark on July l,1964, after a 50-yr agree- the State Parks Information Office is an ex- only would they not benefit from the dam, but ment with the Bureau of Reclamation and is tensive picnicking and camping area offering moreover they would lose much of the fertile now open the year around. The Park itself is shaded picnic tables, grills, and washrooms Mesilla Valley to flood water. Before this split into two locations-one at Elephant along a north-south-trending ridge that leads project came to fruition the Dam Butte dam and the other 3 mi upstream at to Lions Beach. West of Lions Beach is a large and Irrigation Company obtained a charter Lions Beach,where the park headquartersand camping and picnicking area with electrical from the Department of the Interior to build a information office are located. hookups,washrooms, and shelteredtables. private dam across the Rio Grande at Ele- At Elephant Butte are cabins, a restaurant, From the highestand most southerlypicnic phant Butte. The company was unable to con- the Anchor Room Lounge, a store, and a post table on the hilltop overlooking Hot Springs struct the dam for financial and legal reasons. office all set amid the restful shade of cot- Landing, a spectacular view across the lake However, following the drought of 1902-03, tonwood trees.West of the Anchor Room is a with Horse Island and Long Ridge to the east farmers in both countries renewed their call walk along the top of the steep bank where splitting Hot Springs Landing bay from the for a dam and in 1904the Reclamation service wisteria vines drape over a natural stone- main body of the lake can be seen.Across the of the Department of the Interior decided the columned arbor. The cabins are on a bay of lake is a flat-topped lava-covered mesa, atop only logical place for a dam was at Elephant the lake southeastof ElephantButte itself. which are the sub-conical remnants of once Butte. Following an international water North from the patio of the Anchor Room violent volcanoes. allocation treaty in 1906, work on the dam the dark and lonely mass of Elephant Butte On the northwest skyline are the ridges of began.The dam was finally completedin 1916 thrusts itself through the quiet waters of the the San Andres Mountains that lie 40 mi to the lake, rising over 400 ft from the lake floor; east across the barren , from this area of the park one can see the named by the early Spanish for the hostility of elephantineshape of this striking island. At this arid plain. timesof low water, a neckof land connectsthe To the northeastin the middle of the lake is Butte to the east shore. but even when the Rattlesnake Island, connected to Lions Beach Butte is isolated goats may be seen on its by a narrow gravel bar. Sudden spring flood- towering cliffs. ings of the lake concentratesnakes here. Distant views from this portion of the park To the north loom the rugged Fra Cristobal are blockedby ElephantButte, but on the west Mountains with the more distant Magdalena edge of the lake can be seenthe north-south Mountains lying west of due north. Barely trending Long Ridge. To the eastof the Butte, visible to the west is the Black Range lying on on the skyline, are the Fra Cristobal Moun- the east edge of the rugged Mogollon-Datil tains and closer are several flat lava-topped volcanic plateau. Much nearer to the south- mesas. west are the Mud Springs Mountains with Northwest of Elephant Butte is an area dolomites, sandstones,and limestonesform- called "The Jungles" becauseit is alternately ing a sinuous pattern on the range's northern flooded and exposed and is often covered by slopes. low vegetation.It is near the mouth of McRae To the south are the Canyon which stretchesoff to the east drain- where one can seethe pattern of the strata that ing flood waters from the Jornada del Muerto dip to the east under the Jornada del Muerto (Spanish: journey of death)around Engle, l 5 but rise again further to the east in the San An- mi to the east.Along this canyon are the some- dres Mountains. timesflooded ruins of Fort McRae. To the north-northwest is the flat-topped The fort was built in 1869 and abandoned Kettle Top Butte, an erosional remnant of the by the Army in 1876.It was usedas a baseof lava mesa to the east. In contrast to the

FebruaryI 982 New Mexico Geology horizontal lava flows, to the east beyond bles resulting from abrasion as they ascended Pliocene-Pleistocene because they followed Horse Island at the mouth of McRae Canyon an intrusive ionduit. This area has beenpostu- deposition of the McRae Formation and fail is a vertical dike of igneous rock. lated as a source for the conglomeratic mate- to cut into the Pliocene-Pleistocene basalt Long Point, on the west side of the lake rial of the JoseCreek Member. flows. directly to the north, reaches its low, mostly The upper unit of the McRae Formation is Below the stillnessof the lake the rocks tell a vegetation-coveredpeninsula eastward toward the Hall Lake Member comprising purple story of violence, of volcanoes such as that Kettle Top Butte to make the middle nartows shales and sandstones.This member is much which once rose above Elephant Butte, of a of Elephant Butte Lake. more widespreadthan the Jose Creek and con- huge thickness of volcanic ash that buried stitutes most (2,900 ft) of the thickness of the some of the mighty dinosaurs, and of huge Geology formation. This unit crops out around the lava flows which still lie, scorning erosion, on Butte and along the eastern the easternside of the lake. The quiet serenity of the placid waters belie base of Elephant the reservoir. Ceratopsian (horned Gold, silver, copper, lead, zinc, barite, the often violent geological history of this shore of were found at the base of fluorspar, iron ore, pumice, perlite, and ben- area. The rocks in the immediate vicinity are dinosaur) remains indicating a tonitic clay all occur in the nearby ranges, but young geologically, ranging only from Late this member early in this century, Plant remains are fairly at present the preeminent value of this region Cretaceous to Pleistocene, but they record at Late Cretaceousage. fossils are must be Elephant Butte Lake, truly an oasis in least two periods of violent volcanism and ma- common, but no time-diagnostic part the member; the desert. jor fracturing of the earth. known from the upper of has been postulated ACKNOwLEDGMENTS-Severalsources were The oldest rocks are of the Mesaverde nevertheless.the member perhaps into the Paleocene or heavily relied upon in this article including Group, outcrops of which can be seenon both to range Hawley and Seager(1978) and Mueller (1978), sidesof NM-52 and in the vicinity of the dam. Eocene. plugs in the area, the both included in the excellentguidebook to the Long Ridge, northwest of the cafe and lying Severalvolcanic are prominent which is Elephant Butte Rio Grande rift in New Mexico and Colorado along the west edgeof the lake and the dam, is most of plug intruded through the compiled by Hawley (1978), as well as Bush- also composed of this unit, as are the rock itself. This is representsthe remains nell (1953),Nicholson (1971),and Kottlowski walls of the cafe. McRae Formation and material (1e63). The Mesaverde is approximately 3,300 ft of a vent for a cone which extruded onto an erosion surface several hundred feet thick and consistsof alternating beds of sand- References above the present surface. The Butte is con- stone, shale, siltstone, and mudstone. Bachman. C. O , and Mehnert, H. H ' 1978' New K-Ar sidered Pliocene-Pleistocene in age and is Thin beds of coal are present in the lower dates and the Iate Pliocene to Holocene geomorphic sequencecapping the one-third of the section. In the immediate area related to the extrusive history of the central Rio Grande region, New Mexico: reservoir. These lava flows Geological Society of America, Bull., v 89' no. 2' of the Park, coal beds are very thin; however, mesas east of the rest on a broad erosional surface cut into Late p.283-292 Lee (1905)reported one bed of clean coal in H P 1953,Geology of the McRae Canyon area, Cretaceousrocks. Bushnell, , Mescal Canyon that was I ft in thickness and Sierra County, New Mexico: M.S. thesis, University of (Pliocene-Pleistocene) which, he wrote, was comparable in quality Upper Santa Fe beds New Mexico, 106 P. in the area represent ancestral Rio Grande Hawley, J. W (compiler), 1978, Guidebook to Rio Grande to those found in the Mesaverde in the north- deposits, and a basalt tongue in the upper part rift in New Mexico and Colorado: New Mexico Bureau ern part of the state (now being mined near and Mineral Resources,Circ. 163'241 p. has been dated with a K-Ar age of 2.9+0.3 ofMines Gallup). Coal has been mined in the past in the Hawley, J W., and Seager, W. R., 1978' New Mexico- (Bachman Mehnert, 1978).The San- Engle field to the east of the reservoir. m.y. and Texas state line to , in Guide- against Hall Lake book to Rio Grande rift in New Mexico and Colorado' J The sandstones are usually discontinuous ta Fe beds are downfaulted beds by the Hot Springs fault, which is the W Hawley, compiler: New Mexico Bureau of Mines and and sometimes contain beautifully preserved Resources,Circ 163,p.7l-89 largest and most dramatic of many faults in Mineral leaves.Petrified wood is fairly common and is Kottlowski, F. E., 1963, Paleozoic and Mesozoic strata of 6 mi progressively more abundant up through the the area. This fault runs from at least southwestern and south-central New Mexico: New Mex- (west of the main dam) ico Bureau of Mines and Mineral Resources, Bull 79, formation. The rocks are generally olive south of the wing dam north-northeast across the reservoir. The 100P brown to brown with the shales sometimes Lee, W T., 1905, The Engle coal field, New Mexico: U.S other main fault zone in the area is the gray or green. Quarry Geological SurveY,Bull 285, P 240 mouth of Jose The uppermost part of the Mesaverdeis the fault that runs through the Mueller, J., 1978, and reservoir, ln past McRae and has been Guidebook to Rio Crande rift in New Mexico and Colo- Ash Canyon Member, good exposures of Creek up Fort mapped for at least 9 mi. rado, J W Hawley, compiler: New Mexico Bureau of which can be seenin Ash Canyon although the and Mineral Resources,Circ 163, p. 90-91 The many other faults follow two major Mines type locality is immediately southeastof Kettle Nicholson, A., 1971, Elephant Butte Lake: New Mexico virtually normal Top Butte. These beds are conglomeratesthat trends north-northeasterly, Bureau of Mines and Mineral Resourcesand New Mexico faults are normal State Park and Recreation Commission, pamphler, 6 p. have a fairly local distribution and are be- to the Quarry fault. Most The ages are Iieved to have originated as a result of local with dips from 60-80'. post-Cretaceous pre- -Adrian Hunt, 1981 Late Cretaceous uplift in the Caballo Moun- predominantly and tains. Overlying the Mesaverderocks is the McRae Formation whose basal portions are also con- glomeratic but which can be separatedon the large degreeof andesitic material. This forma- tion was named for Fort McRae and consists of a thickness of about 3,200 ft of non-marine clastic beds. The McRae has been split into two members. the lower of which is the Jose Creek unconformably overlying the Mesa- verde and consisting of brown conglomerates, sandstones. and shales. The Jose Creek con- tains petrified wood and leaf florales similar to those of the Raton Formation of northeast New Mexico. Dinosaur bones, virtually always fragmentary, are occasionally found. On NM-52 near the mouth of Ash Canyon is a unit interpreted as a local igneous breccia intrusion with the roundness of the large cob- ELrpunNrBurrr Rrsenvotn

New Mexico Geology February1982 ll