Lichenometric Dating of Rock Surfaces in the Northern Cascade Range,USA |
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| Authors: | Michael A O'Neal Nicholas T Legg Brian Hanson Daniel J Morgan Allison Rothgeb |
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| Institution: | 1. Department of Geological Sciences, University of Delaware, , Newark, DE, 19716 USA;2. Department of Geography, University of Delaware, , Newark, DE, 19716 USA;3. College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, , Corvallis, OR, 97331 USA;4. Department of Earth and Environmental Sciences, Vanderbilt University, , Nashville, TN, USA |
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| Abstract: | This study presents a growth curve developed from direct and indirect growth rates of Rhizocarpon geographicum lichens from study sites on Mounts Baker, Rainier, Adams, and Hood in the northern Cascade Range of the western USA. Our observations of direct growth rates are based on 31 measurements of 11 lichens growing on different surfaces. This direct growth rate dataset is complemented by indirect growth rates based on measurements of the largest lichen observed on 20 different surfaces over 24–33‐yr periods. The direct and indirect datasets produce statistically indistinguishable mean radial growth rates of 0.48 and 0.50 mm yr?1, respectively. Statistical analysis of zero and first order fits of our growth rate data suggests that lichen growth is best characterized by the average of our mean growth rate (zero order) models at 0.49 mm yr?1. Our revised growth curve for the study area extends the applicable range for dating rock surface in the study area to the seventeenth century, approximately 175 years longer than previous calibrated curves. |
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| Keywords: | lichenometry lichenometric dating Cascade Range |
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