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Neoproterozoic chemostratigraphy and correlation of the Port Askaig glaciation, Dalradian Supergroup of Scotland

2000; Geological Society of London; Volume: 157; Issue: 5 Linguagem: Inglês

10.1144/jgs.157.5.909

2041-479X

Martin D. Brasier, Graham Shields,

Geological and Geochemical Analysis

The δ 13 C of preglacial carbonates beneath the glaciogenic Port Askaig Formation falls from +5‰ to negative values, while least-altered 87 Sr/ 86 Sr values are close to 0.7067. Postglacial ‘cap carbonates’ of the Bonahaven Formation begin with negative δ 13 C carb values, jumping sharply to +11.7‰ near the top, which we correlate with excursions above the Elbobreen–Wilsonbreen glaciations of Svalbard and putative Sturtian (not Varanger) glaciations elsewhere, dated at c. 720 Ma. Much of the succeeding Terminal Neoproterozoic is missing in NE Svalbard and East Greenland, raising doubts about their use for global Sr and C isotope curves in the Neoproterozoic.