The stratigraphy of the lower part of the Neoproterozoic Murchisonfjorden Supergroup in Nordaustlandet, Svalbard

Abstract

This paper concerns the lowermost formations of the Neoproterozoic succession (Murchisonfjorden Supergroup) on easternmost Svalbard, particularly their development in central Nordaustlandet. New sections are described, including a basal unit, the Galtedalen Group (new name), composed of conglomerates, sandstones (quartzites), carbonates and shales, in all c. 230 m thick, that rests with major unconformity on an underlying Grenville-age complex of phyllites (mainly turbidites) and volcanites, intruded by c. 950 Ma granites. Previously described basal units of the Murchisonfjorden Supergroup, the Djevleflotta Formation of central Nordaustlandet and the Meyerbukta Formation of northwestern areas, are partly correlatives of the Galtedalen Group. The Galtedalen Group underlies the Persberget Formation (c. 300 m) quartzites and subordinate shales of the Franklinsundet Group; overlying Westmanbukta Formation (c. 650 m) multicoloured shales and subordinate sandstones, and Kapp Lord Formation (c. 300 m) quartzites, shales and subordinate limestones and dolomites are also included in the Franklinsundet Group. Most units of the Galtedalen and Franklinsundet groups of central Nordaustlandet increase in thickness westwards to western Nordaustlandet and, apparently, also to eastern Ny Friesland. Greywackes replace some shale units in this direction. Correlatives of the Murchisonfjorden Supergroup occur in the central East Greenland Caledonides in the Eleonore Bay Supergroup, apparently composing the southwestern part of a shallow basin, that extended along the northeastern margin of Laurentia during the Neoproterozoic.