Isotopic geochronology and biostratigraphy of Riphean deposits of the Anabar Massif, North Siberia

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• 作者：T. S. Zaitseva ; M. A. Semikhatov ; I. M. Gorokhov…
• 关键词：Upper Proterozoic ; Riphean ; Vendian ; globular phyllosilicates ; isotopic age ; General Stratigraphic Scale of Russia
• 刊名：Stratigraphy and Geological Correlation
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：24
• 期：6
• 页码：549-574
• 全文大小：
• 刊物主题：Historical Geology; Structural Geology; Geophysics/Geodesy; Sedimentology; Archaeology;
• 出版者：Pleiades Publishing
• ISSN：1555-6263
• 卷排序：24

文摘

The structure of Riphean deposits developed on the western slope of the Anabar Massif is described with analysis of their depositional environments, distribution of stromatolite assemblages and organic-walled and silicified microfossils through sections, and evolution of views on stratigraphic significance of some of these assemblages. The investigation included complex mineralogical, geochemical, structural, and isotopic‒geochronological study of globular phyllosilicates (GPS) of the glauconite‒illite series from paleontologically well substantiated Riphean sequences (Ust’-Il’ya and Yusmastakh formations of the Billyakh Group) of the Anabar Massif in the Kotuikan River basin. Isotopic dating of monomineral size and density fractions of GPS from the Billyakh Group was performed in combination with simulation of the distribution of octahedral cations and comparison of the results obtained with Mössbauer spectrometry data. The applied approach is based on an assumption that the formation and transformation of Rb‒Sr and K‒Ar systems in GPS are synchronous with stages in their structural evolution, which are determined by the geological and geochemical processes during depositional history. Such an approach combined with the mineralogical and structural analysis contributes to correct interpretation of stratigraphic significance of isotopic data. The results obtained provide grounds for the conclusion that isotopic dates of GPS from the Ust’-Il’ya (Rb‒Sr, 1485 ± 13 Ma; K‒Ar, 1459 ± 20 Ma) and Yusmastakh (Rb‒Sr, 1401 ± 10 Ma; K‒Ar, 1417 ± 44 Ma) formations mark the stage of early diagenesis of sediments and are suitable for estimating the age of formations in question.