Formation of Small Ventifacts

Sharp edges of small, late Pleistocene, wind-eroded pebbles (or ventifacts) embedded in bedrock at Ocean Cove, California, have an average trend oblique to inferred Pleistocene wind direction. This and other features suggest that abrasion was produced chiefly by a stream of suspended or partly suspended particles following local deflections of the wind stream. That such material would be capable of producing ventifact shapes is suggested by previous studies on wind flow over obstacles. Consideration of wind-flow deflection suggests that currently accepted concepts of ventifact abrasion by saltating sand grains must be modified, and it further suggests that source and size distribution of wind-transported abrasive material, more than size of ventifacts, may determine whether abrasion will result largely from scour by suspended material or from impact by saltating grains. Occurrence of three- and four-edged ventifacts strengthens the view that orientation of faces may be partly controlled by original pebble...