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South African Journal of Science

On-line version ISSN 1996-7489

S. Afr. j. sci. vol.103 n.3-4 Pretoria Mar./Apr. 2007

 

RESEARCH IN ACTION

 

Documenting lichen-induced mechanical weathering of quartzitic sandstone at Kaapsehoop, Mpumalanga

 

 

Candice McKechnieI; Stefan GrabI; Gillian DrennanII

ISchool of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa
IISchoolof Geosciences, University of the Witwatersrand

 

 


ABSTRACT

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.


 

 

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* Author for correspondence. E-mail: candice@crg.bpb.wits.ac.za

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