Big boulders of tillite rock in Porsanger, Northern Norway.

Abstract

In 1959 numerous erratic boulders of tillite rock were discovered at the head of Austerbotn, the eastern arm of the Porsangerfjord. Some of the boulders are very big, having volumes of up to 20m3. In 1965 another two boulders were found about 7 km to the south-east of the head of the fjord. The presence of the tillite boulders shows that Eocambrian tillite occurs - or at least has existed - in the Porsanger region. No deposits of tillite occurring in siu have, however, been reported from this district. The writer suggests that the source of the boulders is most probably in Rocidalen, a depression in the Precambrian surface of the broad Lakselv valley, about 10 km south of the head of the Porsangerfjord. As there are no rock exposures in the bottom of Rocidalen on account of the thick cover of Quaternary deposits, this theory can hardly be proved. Possible future finds of tillite boulders may bring other parts of the Lakselv valley into focus.