BURRO CREEK

Sections 4,8,9,10,15,16 R11W, T14N Kaiser Spring 7.5' Quad, southeast Mohave and west central Yavapai Counties, Arizona (see Moyer 1990). Burro Creek is the farthest northwest of all the sources in the study region. The actual source (a vitrophyre near Kaiser Spring) was investigated by Tom Moyer for master's and Ph.D. research in geology at Arizona State University (1982). Moyer was sensitive to the importance of the source for archaeology and his research at the locality was quite useful. Much of the information here derives from his work. A K-Ar date on the obsidian was 12.0 ± 0.6 Ma (Moyer 1990).

The origin of the obsidian is within a vitrophyre similar to Los Vidrios as part of a series of rhyolite domes called the Burro Complex (Moyer 1984). The nodule density at the source is not available, but the downstream density in Burro Creek Wash (up to 5 per 5m²) suggests that the nodule density in and around the vitrophyres is equal to Los Vidrios or Superior. The largest nodule recovered was 7 cm in diameter, but like Vulture and Superior, Burro Creek is a known "Apache Tear" collection area, so the density and nodule sizes observed are probably skewed. The knapping quality is excellent, equal to Vulture, Superior and Sauceda.

The aphyric Burro specimens do not have a strongly developed cortex. Some have perlite coatings, but most exhibit weathered black glass cortical material. The aphyric interior glass ranges from a translucent cloudy brown to nearly opaque brown-gray. The opaque varieties seem to predominate.

Reduced nodules and flakes occur along Burro Creek, but in very low densities (<5 per 5m²). No other cultural material was recorded. References other than Moyer (1984. 1990) include Wilson and Moore (1959).

Elemental concentrations for Burro Creek source standards. All measurements in parts per million (ppm).

`SAMPLE`	`Ti`	`Mn`	`Fe`	`Rb`	`Sr`	`Y`	`Zr`	`Nb`	`Ba`
`A`	`447.856`	`523.118`	`9574.586`	`397.376`	`7.443`	`82.471`	`106.38`	`48.459`	`42.534`
`B`	`467.263`	`472.8`	`9543.378`	`363.282`	`6.638`	`74.969`	`101.7`	`44.064`	`42.337`
`C`	`443.27`	`450.164`	`9322.295`	`359.243`	`5.398`	`75.256`	`100.365`	`50.158`	`42.626`
`D`	`510.451`	`503.48`	`9539.789`	`374.829`	`7.281`	`74.066`	`104.798`	`50.257`	`42.283`
`E`	`409.251`	`473.198`	`9055.937`	`372.791`	`5.808`	`80.875`	`102.66`	`54.106`	`41.903`
`F`	`481.486`	`508.869`	`9420.71`	`390.422`	`7.701`	`80.261`	`101.711`	`51.352`	`45.112`
`G`	`483.524`	`491.493`	`9335.461`	`386.442`	`7.296`	`80.669`	`106.894`	`46.714`	`43.189`
`H`	`458.911`	`442.12`	`8779.389`	`333.585`	`7.618`	`75.373`	`92.686`	`50.834`	`39.377`
`I`	`391.715`	`480.344`	`9640.976`	`383.091`	`6.793`	`79.091`	`103.219`	`48.695`	`42.708`
`J`	`428.097`	`438.867`	`9071.836`	`346.761`	`0`	`74.737`	`92.991`	`46.176`	`39.825`
`K`	`292.183`	`538.633`	`8636.567`	`343.839`	`4.582`	`68.367`	`103.211`	`40.266`	`42.838`
`L`	`223.775`	`555.114`	`8299.724`	`364.804`	`0`	`72.194`	`99.134`	`47.952`	`39.433`
`M`	`300.772`	`540.454`	`8689.754`	`366.699`	`6.508`	`68.476`	`100.05`	`45.742`	`41.305`

REFERENCES

Moyer, T.C., 1984, The Pliocene Kaiser Spring (AZ) Bimodal Volcanic Field: Geology, Geochemistry, and Petrogenesis. Ph.D. dissertation, Department of Geology, Arizona State University, Tempe.

Moyer, T.C., 1990, Generalized geologic map of the Kaiser Spring volcanic field, Mohave County, Arizona. Contributed Map CM-90-C, Arizona Geological Survey, University of Arizona, Tucson.

Wilson, E.D., and R.T. Moore, 1959, Geologic map of Mohave County, Arizona. Bureau of Mines, Tucson, Arizona.