Analysis of the rock accretions in the lower pecos region of southwest texas

Abstract

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 SEMIEDS, 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. 0 1995 John Wiley & Sons, Inc.

Raman microscopy in archaeological science

“…The presence of whewellite (CaC 2 O 4 ÁH 2 O) was confirmed and its occurrence was attributed to biological activity of lichens [115,116] as indicated previously for deteriorating wall paintings and ecclesiastical architecture [51]. The red and black pigments used in the pictographs were identified as red ochre (Fe 2 O 3 C clays) and an unspecified MnO 2 mineral, respectively [53].…”

“…Transparent accretions found above and below prehistoric pictographs at numerous cave sites in the southwestern United States were investigated by FTRaman microscopy to identify the nature of the layers [53,116]. The presence of whewellite (CaC 2 O 4 ÁH 2 O) was confirmed and its occurrence was attributed to biological activity of lichens [115,116] as indicated previously for deteriorating wall paintings and ecclesiastical architecture [51].…”

Raman spectroscopic study of 3000-year-old human skeletal remains from a sambaqui, Santa Catarina, Brazil

“…Several important scenarios have been investigated along these lines, including pigment-binder identifications in manuscripts and wall paintings 5,6 and the identification of the onset of a biogeological degradation in mediaeval frescoes and prehistoric rock art caused by lichen or fungal attack on plaster or rock substrata. 7 -9 In this paper, we report for the first time a Raman spectroscopic study of pigmented human skeletal remains from the excavation of a 3000-year-old skeleton.…”

Calcified microbial mats date prehistoric canals—Radiocarbon assay of organic extracts from travertine

“…(1992) used a laser to oxidize the organic carbon compounds in oxalate-rich crusts associated with petroglyphs, for radiocarbon dating. Russ et al (1995), also using AMS to radiocarbon date oxalate-rich crusts, suggest that the crusts were produced by the metabolic activity of lichens or fungi. While these applications are not directly analogous to the present discussion (the material analyzed consists of metallic oxalates rather than carbonates), they provide other examples of the utility of specialized analyses of organic carbon residues for solving specific problems.…”