Cambro-Ordovician strata in Ny Friesland, Spitsbergen and their palaeotectonic significance

Abstract

SummaryField and petrologic investigations of Cambro-Ordovician strata in Ny Friesland, Spitsbergen reveal a stratigraphic, sedimentologic, and diagenetic history for those rocks that bear striking similarities to coeval strata in central East Greenland, northwest Scotland and western Newfoundland. Parallels between these presently widely separated areas include: stratigraphic sequence (including enigmatic gaps), sedimentary structures, faunal assemblages, trace fossils, geochemical anomalies, and diagenetic sequences. It seems inescapable that the Cambro-Ordovician successions in Ny Friesland, central East Greenland, northwest Scotland, and western Newfoundland were developed on a once contiguous shelf on the margin of the lapetus Ocean. A tentative sequential tectono-sedimentological facies model of the ‘North Atlantic Geosyncline’ extending in time from late Proterozoic to the opening of the Atlantic Ocean is proposed to explain the empirical data. Slow closure of the lapetus basin, simultaneously involving transgression of the ‘North American’ plate and subduction of lapetus oceanic crust beneath a Euro-Balto-Scandinavian plate, followed by collision of the two continental plates, in turn followed by reopening along the approximate collision boundary appears to explain the observed relationships. This palaeotectonic/sedimentologic model is subject to further testing. The lithostratigraphic scheme is further refined.

Late Silurian and Early Devonian stratigraphy and probable strike-slip tectonics in northwestern Spitsbergen

“…Close similarities between the late Proterozoic and early Palaeozoic strata of Ny Friesland (eastern Svalbard) and East Greenland were first noted by Kulling (1934), and then made more forcibly by Harland (1959Harland ( , 1965Harland ( , 1969Harland ( , 1971, Swett (1981), Hambrey (1983), Fairchild & Hambrey (1995), hence the arguments for strike-slip displacement of at least 1000 km. Because it is generally accepted that Eastern Svalbard occupied a position with the rest of Spitsbergen north of North Greenland from Carboniferous through Cretaceous time, the earlier affinity with East Greenland led to a terrane subdivision of Svalbard as developed by Harland & Wright (1979), Harland (1985), Gee (1986Gee ( , 1994, Harland et al (1992) and Harland, Hambrey & Waddams (1993).…”

Salterella and Volborthella from the Early Cambrian of Spitsbergen: the evolution of agglutinating organisms during the Neoproterozoic-Cambrian transition

“…The Salterella Bed of Gobbett and Wilson (1960) occurs approximately 60m into the unit, consisting of abundant Salterella tests randomly orientated within a sparry dolomite matrix. A similar thin bed containing abundant Salterella is reported to occur 120m above the base of the Ditlovtoppen Dolomite (Swett 1981).…”

“…Inarticulate brachiopod and trilobite fragments were observed in the field by the author and phosphatized hyoliths are reported from this unit (Knoll and Swett 1987). The Topiggane Shale is interpreted as the onset of a moderately deepening, transgressive sequence (Swett 1981).…”

“…The trace fossils Planolites, Diplocraterion, Monocraterion, Skolithos and Cruziana are present within this member, together with patchily developed planar cross-bedding. Swett (1981) proposed a marine littoral paleoenvironment for this member and assigned it an Early Cambrian age on the basis of trace fossil diversity.…”

Thermodynamic and kinetic description of dolomitization of calcite and calcitization of dolomite (dedolomitization)

“…Thanks are given to Keene Swett for providing a graduate research environment in which radically new ideas could be pursued and for the thin section which ultimately kindled the above theory (see Swett, 1981, Plate 3, Fig. D).…”