C- and Sr-isotope chemostratigraphy and Pb–Pb age of carbonaceous sediments of the vorogovka group (neoproterozoic), northwestern Yenisei ridge

Abstract

C- and Sr-isotope record is received and Pb–Pb age is determined from carbonaceous sedimentary rocks of Vorogovka Group in the type section at Vorogovka River, northwestern Yenisei Ridge. The sequence of the group consists of the Severnaya Rechka, Mutnina and Sukhaya Rechka Formations that fill a large trough, and lithological and textural features indicate the rapid sedimentation. Most carbonaceous rocks are presented by limestones with low Fe/Sr and Mn/Sr relations and average δ 18 O value –6.0 ± 1.6‰ V-PDB indicating the well-preserved isotope systems of the rocks. 87 Sr/ 86 Sr relations and δ 13 С values vary within narrow limits as 0.70816–0.70826 and –1.4…+0.8‰ for upper Severnaya Rechka limestones and as 0.70818 – 0.70829 and +1.0…+2.0‰ for Sukhaya Rechka limestones, respectively. Pb–Pb isochronous age of carbonaceous rocks of the Severnaya Rechka Formation is 580 ± 40 Ma (MSWD = 1.4), and of Sukhaya Rechka Formation is 565 ± 90 Ma (MSWD = 1.1). Judging from chemostratigraphical and isotope-geochronological data, the forming of limestone sediments of Vorogovka Group could occur at 580–550 Ma ago, that corresponds to the Late Vendian or the Late Ediacaran. The endurance of accumulation of Vorogovka Group likely not exceeded 10–15 Myr. Vorogovka Trough differed in the type of sedimentation from other Late Vendian marginal troughs at the southwestern Siberian Platform, and formed independently from them.