South African Journal of Science
On-line version ISSN 1996-7489
MCKECHNIE, Candice; GRAB, Stefan and DRENNAN, Gillian. Documenting lichen-induced mechanical weathering of quartzitic sandstone at Kaapsehoop, Mpumalanga. S. Afr. j. sci. [online]. 2007, vol.103, n.3-4, pp. 117-120. ISSN 1996-7489.
The role of lichens in rock weathering is difficult to quantify and its study is still in its infancy. Here we highlight some biologically induced weathering processes observed on sandstone samples taken in a field of boulders located at Kaapsehoop in Mpumalanga province, South Africa. Light microscopy and scanning electron microscopy were used to investigate the interaction between lichen colonies and sandstone surfaces. The biological structures of lichens were observed for their effect on the rock surface, and variations in pore size, angularity and sorting of sandstone micro-granules were assessed. We demonstrate that the interlacing of lichen hyphae between sandstone grains contributes to the dislodgement and movement of these granules. We also found that lichen-induced weathering at Kaapsehoop produces smaller and more angular micro-granular sandstone surface structures than on the adjacent lichen-free surfaces.