Evidence for a glacial origin of Neoproterozoic III striations at Oaibaččannjar'ga, Finnmark, northern Norway

Abstract

The origin of the famous late Precambrian striated pavement at Oaibaččannjar'ga (Bigganjargga), northern Norway, remains controversial. Most investigators have accepted a glacial formation, but some prefer a soft-sediment mechanism. However, a newly discovered c. 2.5 mm thick zone of brecciation under rare polished striations indicates a hard substrate during formation and thus a glacial origin for the striations. Other points indicating that the striations formed in a hard substrate are: (1) the striated platform (in the Veidnesbotn Formation) is c. 150 Ma older than the overlying diamictite (Smalfjord Formation); having been buried to c. 2.5 km depth, cementation should have started before Smalfjord times; (2) the marked irregularity of the sub-Smalfjord Formation palaeotopography on Skjåholmen; (3) the presence of rounded Veidnesbotn Formation boulders in the diamictite above the striations. Imprints of clasts appearing to lie across the striations are re-interpreted as relicts of mud-flakes within the Veidnesbotn Formation which were cut across and quarried-out during pavement formation. The origin of the overlying diamictite (tillite vs. debris-flow) is not constrained by the presence of glacial striations and most probably was deposited some time after striation formation.