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Showing 1 to 13 of 13 for “"Cryogenian"”.
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Space-Time Analysis of Magmatism: Evidence for a Early Cryogenian Plume Track in Eastern Laurentia
… of Virginia and North Carolina, nearly thirty Cryogenian volcanic/plutonic complexes have been recognized. A-type granites and rhyolites dominate the igneous complexes within the Cryogenian Magmatic Province (CMP), but compositional variations range from gabbro through syenites. The mineralogy, …
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The Neoproterozoic São Francisco Basin, central Brazil: tectonic evolution, paleoclimate, and mineral systems
… margin stage. The overlying Bambuí Group is a Cryogenian-Ediacaran mixed biochemical-siliciclastic succession (ca. 650-550 Ma) composed of six stratigraphic sequences. Sequence 1 contains Marinoan glacial diamictites and cap carbonate (ca. 635 Ma) with distinctive barite and aragonite crystal …
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Stable isotope and organic biomarker analysis of the late Proterozoic Coppercap formation in the MacKenzie Mountains
… environment existing directly before the Cryogenian glacial episodes. Based on aryl isoprenoids, n-propyl cholestane, isopropyl cholestane, total organic carbon, carbonate mineral analysis, [delta]34S from pyrite, [delta]13Corganic and [delta]13Ccarbonate values, environmental conditions …
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Triple oxygen isotope measurements in chert: insights into the Snowball Earth glaciations
… a carbonate sequence immediately underlying a Cryogenian diamictite to better understand this relationship, particularly the chemistry of subglacial meltwater. Using triple oxygen isotope measurements, clumped isotope palaeothermometry, uranium-lead geochronology, and SEM/EDS and XRD analyses, …
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Re-Os geochronology and geochemistry of Proterozoic sedimentary successions
… with Sturtian glaciations rather than middle Cryogenian events. Laboratory-based hydrous pyrolysis experiments were employed to evaluate the complexation of Re and Os in ORS and their transfer behaviour into petroleum. The findings from these experiments demonstrate that the Re-Os …
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Geochemical and Paleontological investigations of the Neoproterozoic-Cambrian Transition: Case Studies on geochemical clast provenance, emerging paleo redox proxies, and ambiguous dubiofossils
… a glacial diamictite deposited at the end of the Cryogenian Period in South China. By determining the source locality of those carbonate clasts using stable carbon and oxygen isotope compositions, we can better understand the extent of the Marinoan Glaciation and the intensity of its impact on the …
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Integrated High-resolution Stratigraphy of the Doushantuo Formation, South China
… events, such as the termination of the Cryogenian glaciations, the Neoproterozoic Acraman impact event, and oxygenation of the deep oceans may have played an integral role in the evolution of Ediacara organisms and early animals. However, the extent to which these events shaped …
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Studying Redox Conditions of Devonian and Neoproterozoic Oceans Using I/ca Proxy From Bulk Carbonate Rocks
… cap carbonates formed following the Cryogenian glaciations, from basal Doushantuo Formation, one of the most extensively studied Ediacaran units in South China. Among the four sections from a shallow-to-deep water transect, the slope section has the lowest I/(Ca+Mg) values, suggesting …
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The tectonic evolution of the Southern Granulite Terrane of India and its role in the amalgamation of Gondwana.
… part of Madurai Block yielded Neoarchaean and Cryogenian (ca.2.7 - 2.5 Ga and 795 ± 17 Ma) crystallization ages with metamorphic overprinting at ca. 535 Ma. Their Nd and Sr isotopic ratios (εNd₍τ₎ = -16.9 and +4.55, ⁸⁷Sr/⁸⁶Sr = 0.7017 - 0.7567) suggest they were generated by variable mixing of …
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Supercontinents and glaciation: a perspective from western Gondwana.
… results from western Gondwana. The Cryogenian-aged Toekems Sub-basin in the Damara Belt, Namibia comprises a wedge dominantly clastic, glacially influenced sediments. Our field observations and results imply a significant disconformity beneath the Naauwpoort Volcanics and suggest …
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The palaeoredox condition and morphological variation of microbialites from the Nama Group, South Africa
… redox conditions occurred throughout the Cryogenian and Ediacaran Periods and the early Palaeozoic Era before this stability was reached. While oxic surface waters were present throughout the Proterozoic, there are open questions as to the maximum dissolved oxygen levels, and where oxic …
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Geochemical investigation of the co-evolution of life and environment in the Neoproterozoic Era
… contains isotopically superheavy pyrite from the Cryogenian Tiesi'ao and Datangpo formations. The second set of samples contains pyritic rims from the Ediacaran Doushantuo Formation; these pyrite rims are associated with fossiliferous chert nodules and do not have superheavy sulfur isotopes. For …
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Next generation sequencing technology and phylogenomics enhance the resolution of deep node phylogenies: A study of the Protostomia
… (2011) and dos Reis et al. (2015) findings of a Cryogenian origination for the Metazoa and a Lower Cambrian radiation of animal lineages. The arachnids were the last of the terrestrial arthropods to colonize land in the Upper Ordovician (450 MYA), with the hexapods colonizing land in the Lower …