Lithostratigraphy and correlation of the Archean and Early Proterozoic rocks of Finnmarksvidda and Sørvaranger district.

Abstract

Archean and Early Proterozoic rocks of Finnmarksvidda and the SørvarangerDistrict are grouped into lithostratigraphic and lithodemic units aresystematically described. Some correlations are proposed and the foundationsfor these correlations are discussed. The lithostratigraphic successionsof the Kautokeino and Karasjok greenstone belts are correlated with eachother and with the older Precambrian rocks exposed in the tectonic windows.From this emerges an outline of geological events which occurred in theEarly Precambrian in these terranes. Contacts between the Archean rock unitsof the Sørvaranger District are often faulted and therefore stratigraphicrelationships between the various gneiss complexes and groups are uncertain.There are, however, indications that the Bjørnevann Group and part of theJarfjord Gneiss are correlative, the same is true for parts of the Varangerand Kirkenes Gneiss Complexes. There seem to be two, stratigraphicallyunrelated banded-iron formations, both formerly assigned to the Bjørnevannformation and now described separately as the Bjørnevann and Garsjø Groups.The Early Proterozoic Petsamo Group is subdivided into four formations andstratigraphic relations within the group are discussed. The complex Archeanstratigraphy of the Sørvaranger district does not have equivalents on Finn-marksvidda. The volcano-sedimentary sequences of the Kautokeino and Karasjokgreenstone belts may at the present stage of work onlu roughly be comparedwith the Petsamo Group.