Raman spectroscopic study of lichen-assisted weathering of sandstone outcrops in the High Atlas Mountains, Morocco

Abstract

The lichen Aspicilia caesiocinerea agg. colonizing Triassic sandstone rock outcrops between 1600 and 2800 m elevation in the High Atlas Mountains of Morocco has been observed to have some unusual growth strategies, including a probably unique undercutting of escarpments, which produce severe bioweathering of the substrata. Fourier transform Raman spectroscopy was applied to studies of lichen-substratal surface transects in order to identify key wavenumber spectral markers of the biogeological changes. The Raman data were combined with previously determined energy-dispersive x-ray spectral information on similar specimens to build up a picture of the survival strategy of the lichen in this seasonally and environment, where temperature extremes on rock surfaces range between -20 and +60 °C and precipitation varies from rain and surface snow cover in winter to long periods of drought in summer. Copyright © 2002 John Wiley & Sons, Ltd.