Chapter 102 - Quartzite and quartz sandstone caves of South America

Abstract

South America is well endowed with quartzite outcrops and caves, especially in southern Venezuela and along eastern Brazil. Quartzite caves may display branchwork, anastomotic and network patterns similar to carbonate caves, showing strong geological control associated with layers less resistant to erosion. Vertical caves close to scarps develop along unloading joints and may be at least in part tectonic features. Cave initiation involves loosening of quartz grain by intergranular dissolution or chemical removal of silica-rich matrix, kaolinite, or mica. Mechanical removal of quartz residue may enlarge cave passages once there is an opened evacuation route. Microbial mediation may play a role, especially in generating unique stromatolitic speleothems. Slow rates of dissolution, low content of silica in the groundwater and the old age of the bedrock favor a long term evolution for quartzite speleogenesis, perhaps orders of magnitude slower than in carbonate settings.