Analysis of the Rock Accretions in the Lower Pecos Region of Southwest Texas
Physics and Astronomy
Calcium oxalate (whewellite) was found to be the primary component of crusts on limestone in the dry rock shelters throughout the Lower Pecos region of Texas. This material forms a translucent patina that covers the pictographs in this area. Evidence from analyses using SEM/EDS, FTIR, XRD, Raman spectroscopy, and AMS is presented that suggests the oxalate-rich crusts were produced by metabolic activity of lichen or fungi on or near the surface of the limestone substrate. The paucity of hyphae and microbes in samples studied using SEM may indicate that the organisms responsible for the production of the oxalate are no longer present on the shelter walls. Radiocarbon ages of three oxalate samples range from 2100 to 5570 years B. P., indicating that the crust may be used for obtaining chronological information on the rock art.
J. Russ, R.L. Palma, D.H. Loyd, D.W. Farwell and H.G.M. Edwards, 1995. Analysis of the Rock Accretions in the Lower Pecos Region of Southwest Texas. Geoarchaeology 10, No. 1, 43-63.
Publisher's Copyright and Source
Copyright © 1995 John Wiley and Sons. Article published by John Wiley and Sons in Geoarchaeology, volume 10, issue number 1, January 1995, pages 43-63. Available online on January 9, 2007: http://dx.doi.org/10.1002/gea.3340100104