U-Pb ages of detrital zircons and composition of clastic sedimentary rocks from the southern periphery of the Siberian craton: Implications for the earliest Cambrian evolution of southern Siberia

Abstract

Data on petrography, chemistry, and U-Pb ages of detrital zircons have been obtained for clastic sedimentary rocks within the Sayan regional stratigraphic stage from different parts of the southern Siberia craton, namely for the Ust’-Tagul (Biryusa zone, Sayan area), Shamanka (Irkut zone, Sayan area), Ushakovka and Kurtun (Baikal area) formations. The sedimentary strata share much similarity in lithofacial patterns, with gradual transition from continental to shallow-marine facies. The analyzed lithic sandstones have poorly to moderately sorted clastic grains, with large percentages of lithic fragments (16–37 %). The lithic sandstones from different formations were deposited in continental and deltaic settings as a result of clastic transport from different provenance lithologies. The clastic material for the Ust’-Tagul Fm. deposition came from the Precambrian rocks of the Siberian craton and the Neoproterozoic (870–940 Ma) units: either the Yenisei Ridge of the craton or the Arzybey terrane of the Central Asian Orogenic Belt (CAOB). For the Shamanka Fm., it was Ediacaran and Early Cambrian material from blocks and terranes of the northern CAOB. The clastic inputs for the Ushakovka and Kurtun Fms. deposition were from the Precambrian basement of the Siberian craton and the Neoproterozoic (550–920 Ma) North Transbaikalian group of CAOB terranes. The youngest detrital zircons have the earliest Cambrian ages (530–540 Ma). The clastic sedimentary rocks of the Sayan regional stratigraphic stage dispersed over the southern Siberian craton were deposited in the earliest Cambrian in separate disconnected sedimentary basins which resulted from Ediacaran accretionary-collisional events in southern Siberia.