Stratigraphy of the Cambrian–Lower Ordovician Volcanogenic-Sedimentary Complexes of the Sarysu-Teniz Watershed (Central Kazakhstan): Geochronological and Paleontological Substantiation of the Ages

The results of the geological, geochronological, and micropaleontological studies of the Cambrian–Ordovician volcanic and sedimentary formations of the Sarysu-Teniz watershed in the west of Central Kazakhstan are presented, which allowed for a detailed stratigraphic division. It is shown that they formed in the interval from the end of the Early Cambrian (~515 Ma) to the end of the Middle Ordovician. The first findings of conodonts made it possible to expand the age range of accumulation of siliceous-terrigenous strata (Kusheke Formation), covering the interval from the top of the Floian Stage to the Darriwilian Stage of the Lower and Middle Ordovician. The results of U–Th–Pb isotope-geochronological (LA-ICP-MS) study of detrital zircon from sandstones indicate the predominance of Precambrian provenance areas in the accumulation of Lower–Middle Ordovician strata (Kokdombak and Kushekinskaya formations). It has been shown that the studied complexes of the Sarysu-Teniz watershed are stratigraphic and facies analogs of the volcanic and sedimentary complexes of the Jalair–Naiman zone, the formation of which was associated with the evolution of the Cambrian–Early Ordovician island arc system.