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Analysis of the rock accretions in the lower pecos region of southwest texas
Author(s) -
Russ Jon,
Palma Russell L.,
Loyd David H.,
Farwell Dennis W.,
Edwards Howell G. M.
Publication year - 1995
Publication title -
geoarchaeology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 44
eISSN - 1520-6548
pISSN - 0883-6353
DOI - 10.1002/gea.3340100104
Subject(s) - lichen , geology , oxalate , mineralogy , substrate (aquarium) , calcium oxalate , mineral , radiocarbon dating , geochemistry , chemistry , botany , materials science , metallurgy , paleontology , oceanography , biology , organic chemistry
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.