The name Hamnbukt Sandstone Formation is proposed for the sequence of shallow-water sandstones, shales, and conglomerates found on the peninsula Oldereidhalvöya at the head of Porsangerfjord. This formation is thrust over a thin layer of autochthonous 'Hyolithes Zone' rocks which, in turn, lie unconformably upon the crystalline basement. The Hamnbukt Sandstone Formation is cut by olivine-dolerite intrusives which post-date the folding, but pre-date the thrusting, of the formation. The absence of fossils in the Hamnbukt Sandstone Formation indicates a Precambrian age. Comparisons with other Precambrian sedimentary sequences of Finnmark show that no lithostratigraphical correlaticn is yet possible. Further investigations east of Porsangerfjord may yield successions similar to that found in Oldereidhalvöya.