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Part 3 Historical Synthesis |
The Vendian Period, the latest Precambrian division, and the earliest division in which several Phanerozoic methods of correlation can be applied, is a convenient time division for Svalbard. It is separated from the earlier history in which correlation has uncertainties of tens of millions of years if not more. The period is divided here into an early (Varanger) epoch and a late (Ediacara) epoch (Harland et al. 1990).
The Varanger Epoch is documented by remarkably rich sequences, correlated throughout (but limited in Prins Karls Forland and Bjornoya) by the two distinctive major glacial episodes: the earlier Smalfjord Stage and the Mortensnes Stage, with a substantial interglacial record between the diamictite horizons. The Vendian age of these glacigenic sediments is confirmed biostrati-graphically.
The Ediacara Epoch is only confirmed from the Scotia Group in Prins Karls Forland, identified by a microbiota. A number of conformable post-glacial successions are plausibly of Ediacara age: the Dracoisen and Klackbergbukta formations in the northeast; the Annabreen Formation in Oscar II Land; the Peachflya and Geikie as well as the Scotia Group in Prins Karls Forland; and the Bogstranda and Gashamna Formations in Hornsund. Nevertheless the second part of Vendian time is as yet poorly demonstrated in Svalbard.
According to the correlation followed here from Harland, Hambrey & Waddams (1993) based largely on the two glacial episodes, the outcrop area of Vendian strata is not small as shown in Fig. 13.1.
Vendian, as used here, is the latest Precambrian time-interval preceding the Cambrian Period. Whereas Cambrian and
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