TAFONI ON COASTAL SLOPES, SOUTH DEVON, UK

Cavernous weathering (tafoni development) occurs on coastal slopes in greenschist bedrock at elevations up to 40 m above sea level. The fres hly weathered surfaces of the cavern interiors are irregular in morpho logy, discordant to major rock structure, formed by substantially weak ened rock and associated with granular weathering debris. The weatheri ng debris contains soluble elements in proportions similar to those pr esent in seawater, and the penetration of elements associated with sea salts into the weathering surface to estimated depths of at least 0.1 -0.2 m is indicated by the presence of chlorine. Scanning electron mic roscopy and microprobe analyses suggest that rock breakdown occurs pri ncipally through limited chemical weathering at grain boundaries. The mechanism for the emplacement of marine salts within sheltered rock su rfaces in the tafoni is postulated to be a combination of dry depositi on under turbulent atmospheric conditions and wetting by coastal fog.