The spalling of overgrowths during experimental freeze-thaw of a quartz sandstone as a mechanism of quartz silt production
The experimental frost weathering of a quartz sandstone is being carried out as part of a series of laboratory simulations to investigate geomorphic mechanisms capable of producing loess-sized quartz silt. The preliminary results are reported in this paper. Frost weathering simulations involved two different temperature regimes: (a) -5 degrees C-+15 degrees C, and (b) -12 degrees C-+15 degrees C. Debris production was observed for both temperature regimes with the blocks subjected to the more intense freezing regime experiencing the most disintegration. Scanning electron microscopic (SEM) examination and particle size analysis revealed that the debris produced by both these experiments included a significant silt sized fraction. Further SEM examinations of this debris demonstrated the presence of silt sized fragments of quartz overgrowths among the debris. It is suggested that overgrowth detachment occurs during frost weathering by either the penetration into and subsequent freezing of water in the gaps between overgrowths and host grains, or pressures applied to the outer surfaces of overgrowths during frost cycles causes them to collapse onto the underlying grain.
Wright
JS
Geography Division, Staffordshire University, Staffordshire ST4 2DF, Stoke-on-Trent, UK.