Significance of thick deposits of colluvium on hillslopes: a case study involving the use of pollen analysis in the coastal mountains of northern California.

Distinct bedrock hollows with a colluvial fill are sites of recurrent emptying by landsliding and subsequent slower refilling with colluvium. On a hillslope in northern California we have quantified the time since emptying and the three-dimensional configurations of the underlying bedrock surface. The oldest colluvium was deposited 11 000 to 13 500 years ago in the bedrock hollow. Since then deposition of colluvium in the hollow has been equivalent to 1.5 m of landscape lowering in the surrounding source area and to a local lowering rate of about 0.1 mm/yr. -from Authors