DATING ROCKFALL-AVALANCHE DEPOSITS FROM DEGREE OF ROCK-SURFACE WEATHERING BY SCHMIDT-HAMMER TESTS - A STUDY FROM NORANGSDALEN, SUNNMORE, NORWAY

In order to obtain age estimates for the formation of two rockfall-ava lanche deposits in Norangsdalen, degree of rock-surface weathering was measured using a type 'N' Schmidt hammer at six sites in Norangsdalen /Nibbedalen, Sunnmore, Norway. By assuming a linear weathering rate, t he mean Schmidt hammer rebound (R-) values obtained on the rockfall-av alanche deposits compared to mean R-values obtained on sites of 'known ' age indicate that the rockfall at skylstad may have occurred 6000 +/ - 700 BP, while the rockfall avalanche at Uraseter may have been depos ited 4200 +/- 800 BP. The indication that these rockfall events occurr ed in the mid-Holocene may suggest that they were initiated in connect ion with the deteriorating and changing climate conditions characteriz ing the period after the Holocene climatic optimum. This study demonst rates the potential for using the Schmidt hammer to obtain age estimat es for rockfall-avalanche deposits in Norway.