This study investigates the effects that lichens have on rock surfaces in which
ancient rock art (petroglyphs and pictographs) may be found. The study area includes
four sites in the United States: one quartzite site in southwest Minnesota, two sandstone
sites in Wyoming, and one volcanic site in Central New Mexico. One additional granitic
site studied is located northeast Queensland, Australia. The questions driving the pursuit
of this dissertation research are:
1. How does the chemistry of the rock change with weathering and how deep is
the profile?
2. Do lichens cause differential chemical changes?
3. How does the chemistry of the unaltered rock influence these changes?
4. Do lichens strip the patina or âÂÂdesert varnishâ from the rock surfaces?
The results of this research confirm from elemental chemical analyses that
geochemical changes do take place in the presence of lichens. The combined
mechanical and chemical processes contribute to the degradation and greater erodability
of all the rock surfaces studied. Chemically, we have demonstrated that cements that
hold grains of rocks together can be dissoluble by lichen byproducts in the presence of an aqueous environment whether the rocks are sandstone or granite. This information
regarding the mechanical and geochemical processes at work in natural environments
has significant practical benefit for the management, conservation, and preservation of
rock art sites everywhere.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4695 |
| Date | 25 April 2007 |
| Creators | Dandridge, Debra Elaine |
| Contributors | Smith, C. Wayne |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 2373236 bytes, electronic, application/pdf, born digital |
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