Conditions of sedimentation of deposits of the redkolesnaya formation of the Irkineevo-Chadobets rift zone

DOI: 10.24412/2076-6785-2023-1-14-20

Abstract
The aim of this work was to establish the conditions of sedimentation of the vendian redkolesnaya formation within the Irkineevo-Chadobets rift zone in the southwest of the Siberian platform. The work is based on 184 thin section samples and 240 meters of core material from deep drilling wells of the Irkineevo-Chadobets rift zone, as well as stock material and the results of geophysical, lithological, petrophysical studies. According to the results of lithological and cyclostratigraphic studies, three sedimentary cyclites are distinguished in the volume of the redkolesnaya formation, having a transgressive structure, which is expressed in the change of sandy and siltstone rocks to sulfate-carbonate deposits in the roofing parts of the cyclites. The mineral composition contains fragments of quartz, feldspars, quartzites, and clay shales, the source of which was the metamorphic rocks of the Yenisei ridge, as well as igneous rocks of the Baikal anteclise arch. The latter were the main source for the deposits of the redkolesnaya formation. Based on the results of lithofacial analysis, it was revealed that the formation of deposits of the redkolesnaya formation occurred under the conditions of fluvial relief forms (a time-migrating cone) and salt marches in the zones of the supratidal, intertidal and subtidal, during the development of the Vendian transgression of the marine basin in the southwest of the Siberian Platform.

Materials and methods
The work is based on 240 meters of core material from deep drilling wells of the Irkineevo-Chadobets rift zone e, as well as stock material and the results of geophysical, lithological, petrophysical studies. The results of the study of rocks in 184 thin sections, on an electron microscope and an X-ray diffractometer were used. Experimental studies were carried out using a polarizing microscope Axio Imager A2m Carl Zeiss and a stereomicroscope Carl Zeiss Micro Imaging GmbH; studies of the mineral composition of lithotypes, as well as the elemental composition of rocks, were performed using an energydispersive spectrometer on a scanning electron microscope (SEM) JEOL JSM-6610LV
with an attachment for microanalysis OXFORD INSTRUMENTS IE350-IW500-HKL; The study of the mineral composition of the rocks was carried out using a RIGAKU (XRD) SmartLab X-ray diffractometer.

Keywords
redkolesnaya formation, vendian, Irkineevo-Chadobets rift zone, Siberian platform, sedimentation conditions