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U-Bar Cave

NM: Hidalgo Co.: SE 1/4 SE 1/4 Sec. 35, T32S, R16W, ca. 1540 m

Age. Mid Wisconsin, Late Wisconsin, and Holocene. ¹⁴C dates range from 13,130 ± 180 to 21,210 ± 320 for the deposits considered by Harris (1989) and are treated here as Late Wisconsin. In the series considered by Harris in 1987, dates ranged from 26,150 ± 1,450 to 35,890 ± 2,640 BP among finite dates; these are considered here to be Mid Wisconsin in age. Emslie (1987) gave a date on a condor coracoid from miner's spoil as 13,030 ± 180 (AA-1492). A number of elements were recovered from material processed by guano miners; some may be placed to their source by color or remnants of matrix; others are unassignable; two taxa otherwise unrepresented are listed under Mid Wisconsin with the additional statement that they might be Late Wisconsin.

General Description. A large chamber in U-Bar Limestone in an outlier of the Alamo Hueco Mountains.

Discussion. Originally, specimens stored at UTEP were considered to be on long-term loan from the Museum of New Mexico, since U-Bar Cave is state land (except for surface rights, which are BLM). However, apparently as of May 1990, the BLM has taken over both archaeological and paleontological control and the U-Bar material is now considered as having the same status as other BLM material for which UTEP serves as repository.

The historic opening to the cave was small (greatest dimensions according to Lambert and Ambler 1965 were 8 ft wide by 4.5 ft tall). With commencement of mining activities, the entrance was greatly enlarged (Fig. 3).

Fig. 1. U-Bar Cave. The entrance to the cave can be seen in the center near the crest of the mountain. The light area beneath it is spoil and disturbance from mining. Mining equipment and a small building connected with the guano mining is barely visible at the base of the slope. Photograph by A. H. Harris, March 1984.

Fig. 2. The setting of U-Bar Cave (white circle). Image from Google Earth.

The site originally was an archaeological site designated as LA 5689 (Lambert and Ambler 1961). During the archaeological excavations, Pleistocene fossils were recovered and sent to the U.S. National Museum for identification (Johnson 1961). At a later date, a guano mining permit was granted by the state, mining equipment was installed, and mining commenced. When the state realized that a mining permit had been issued for a known archaeological and paleontological site, a compromise was considered to allow mining to continue while establishing a degree of monitoring to prevent serious loss of scientific information.

Fig. 3. View of the enlarged entrance from within, with mining equipment in place.

The compromise included the presence of a monitor on-site during mining operations (this usually was Harris) with the ability to salvage scientifically important specimens and the authority to limit mining to areas of the cave deemed of minimal scientific value. A number of trips were made during non-mining times to clear areas for later exploitation.

Many fossils were recovered from spoil resulting from miners processing guano by screening at the base of the mountain. This was especially the case at the beginning of the monitoring activities where there was considerable material remaining from earlier mining, but some material was recovered from spoil throughout the period.

For the most part, it's clear which fossils are mid Wisconsin and which are late Wisconsin. Generally, mid-Wisconsin matrix is distinctly red in color whereas most later deposits are tan to whitish. It is believed that a large portion of the mid-Wisconsin matrix is decomposed bat guano (a maternity colony of Brazilian Free-tailed Bats was active for several years during the mining activity before apparently abandoning the site).

The mid Wisconsin and late Wisconsin faunas are listed separately.

The late Wisconsin deposits are more finely dated than the earlier, mid-Wisconsin sediments. Table 1 (adapted from Harris 1989) gives the dates for Area B, which consisted of several 1-m² grids (H-230-1 to -3, H-231-1 to -3, and H-232-1 to -3) near the eastern wall close to the present entrance. Since this area is well dated, the report of faunal remains are arranged by approximate age, as seen in Table 2. (A few records are from outside Area B but dated as shown.) In the 1989 publication of Harris, Dry Cave faunal remains occurring in the same time spans also were noted, allowing comparison of contemporaneous faunas separated by nearly the entire width of New Mexico. In the present presentation of faunas, some earlier identifications that now seem overly optimistic have been withdrawn, while others have been withdrawn as not clearly present in the time span indicated.

Fauna.

Mid Wisconsin

Late Wisconsin

Table 2. Temporal occurrences of taxa in Area B, U-bar Cave, Hidalgo County, New Mexico (adapted in part from Harris (1989); nomenclature up-dated).

* Probably intrusive

Literature. Carraway 2010; Emslie 1987; Goodwin 1995; Harris 1985a, 1985b, 1987, 1988, 1989, 1990b, 1993c; Harris and Carraway 1993; Johnson 1961; Lambert and Ambler 1961; Russell and Harris 1986.

Last Update: 6 Feb 2013