Title: Re-Os geochronology of the Neoproterozoic – Cambrian Dalradian Supergroup of Scotland and Ireland: Implications for Neoproterozoic stratigraphy, glaciations and Re-Os systematics
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Sr/Sr chemostratigraphy of Neoproterozoic Dalradian limestones of Scotland and Ireland: constraints on depositional ages and time scales
New calcite Sr/Sr data for 47 limestones from the metamorphosed and deformed Neoproterozoic–Cambrian Dalradian Supergroup of Scotland and Ireland are used to identify secular trends in seawater Sr/Sr through the Dalradian succession and to constrain its depositional age. Dalradian limestones commonly have Sr .1000 ppm, indicating primary aragonite and marine diagenesis. Low Mn, Mn/Sr ,0.6, O an...
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Late Neoproterozoic-Early Cambrian schists have been occurred in southwest of Zanjan city from the Soltanieh belt. The Soltanieh belt in northwest of Iran is uplifted basement of Precambrian-Paleozoic in main central Iran zone and includes outcrops of Precambrian, Paleozoic and Mesozoic Formations. Late Neoproterozoic-Early Cambrian schists, the oldest stratigraphy unit in the region, consist o...
متن کاملTesting for the presence of a terrane boundary within Neoproterozoic (Dalradian) to Cambrian siliceous turbidites at Callander, Perthshire, Scotland
The Southern Highland Group (Dalradian) and Keltie Water Grit Formation, which includes the Lower Cambrian Leny Limestone, form an inverted, 1.4 km thick, largely arenaceous, sequence at Callander. The grits have the same detrital mineralogy throughout, mainly quartz, plagioclase (An1–3), muscovite, and biotite. Chlorite formed from detrital biotite during low-grade regional metamorphism (T<270...
متن کاملA Cryogenian chronology: Two long-lasting synchronous Neoproterozoic glaciations
The snowball Earth hypothesis predicts globally synchronous glaciations that persisted on a multimillion year time scale. Geochronological tests of this hypothesis have been limited by a dearth of reliable age constraints bracketing these events on multiple cratons. Here we present four new Re-Os geochronology age constraints on Sturtian (717–660 Ma) and Marinoan (635 Ma termination) glacial de...
متن کامل740 Ma vase-shaped microfossils from Yukon, Canada: Implications for Neoproterozoic chronology and biostratigraphy
Biostratigraphy underpins the Phanerozoic time scale, but its application to pre-Ediacaran strata has remained limited because Proterozoic taxa commonly have long or unknown stratigraphic ranges, poorly understood taphonomic constraints, and/or inadequate geochronological context. Here we report the discovery of abundant vase-shaped microfossils from the Callison Lake dolostone of the Coal Cree...
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