Vendian basin evolution in East Greenland and NE Svalbard

Abstract

In order to help focus new biostratigraphic and chemostratigraphic work, the sedimentology and stratigraphy of Vendian successions in central East Greenland and NE Svalbard (NE Spitsbergen and Nordaustlandet) are reviewed. These areas originally formed part of a contiguous sedimentary basin as illustrated by comparison of two measured sections, 750 m thick, in which a number of matching divisions occur. At the base, a carbonate platform succession (“bed-group 20” in Greenland, Elborbreen Formation member E1 in Spitsbergen) is followed by two discrete glacial facies associations separated by non-glacial sediments (Ulvesø, Arena and Storeelv Formations of Greenland and members E2, E3–E4 and the Wilsonbreen Formation of Spitsbergen), and a transgressive shale succession (Canyon Formation and Dracoisen Formation, respectively) with basal dolostone. Whereas NE Spitsbergen displays a further 300 m of section within the Dracoisen Formation, mostly of probable playa lake facies, in Greenland a 50-m-scale regressive dolostone unit (upper Canyon Formation) is capped by only 20 m of lacustrine facies (Spiral Creek Formation). In each case, lower Cambrian sandstones rest on the Vendian sections. Later Vendian times (Ediacaran interval) seem to be virtually unrepresented by marine strata. Reconstruction of the stratigraphic architecture along the 180 km N S outcrop belt in NE Svalbard and the 300 km N S belt in East Greenland reveals few lateral changes because of an orientation nearly parallel to the depositional strike. Syn-depositional faulting apparently controlled accelerated subsidence in the East Greenland area, leading to the development of carbonate slope facies (“bed-group 19”), either overlain locally by “bed-group 20”, or conformably overlain by glacimarine deposits. A section towards the southeastern limit of the basin in East Greenland, in Canning Land, shows the glacigenic Storeelv Formation resting on a major erosion surface on platform carbonates. In the far southwest, it rests directly on basement; this represents the main source area of sediments in the basin. The upper Canyon Formation shows evidence of progradation from the south. Chronostratigraphic interpretation of the succession leads us to the belief that the base of each glacial unit represents a sequence boundary, although only limited erosion occurred within the main outcrop belt. A sequence boundary may also be present at the base of the Elbobreen Formation. Submarine erosion must have led to a slight hiatus at the close of the second glaciation, temporally following but spatially coincident with a sequence boundary. The upper Canyon Formation is probably a highstand systems tract and the overlying base of the Spiral Creek Formation is a sequence boundary. The transgressive base of the Cambrian sandstones overprints another sequence boundary, at least in Greenland.