Lichenometric dating of rock surfaces in the northern cascade range, usa

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.

Fechamiento de flujos de lava del Holoceno tardío en el volcán Citlaltépetl (Pico de Orizaba) mediante el isótopo cosmogénico 36Cl y liquenometría e implicaciones para la cronología eruptiva

“…Los talos seleccionados fueron aquéllos con una forma circular mejor definida, situados en superficies lisas para evitar la unión de varios individuos y no sobreestimar su edad. Este procedimiento ha sido ampliamente utilizado en ambientes volcánicos y su validez se ha verificado al comparar los resultados con los obtenidos en la colonización de superficies artificiales de edad conocida (Burbank, 1981;Porter, 1981;O'Neal, y Schoenenberger, 2003;O'Neal et al, 2013).…”

Dating late Holocene lava flows in Pico de Orizaba (Mexico) by means of in situ-produced cosmogenic 36Cl, lichenometry and dendrochronology

“…Because the dated features are lava flows, there is no possibility of inheritance of thalli as may occur on sedi-mentary deposits. This criterion has usually been applied in volcanic environments and has been validated by the analysis of artificial sur-faces with a known age (Burbank, 1981;Porter, 1981;O'Neal, and Schoenenberger, 2003;O'Neal et al, 2013).…”