NEW DATA ON THE BIOSTRATIGRAPHY OF MESOZOIC DEPOSITS IN WESTERN KAZAKHSTAN

The aim of our study was to carry out a detailed stratigraphic dissection of sections of the western territories of Kazakhstan using the remains of ichthyosaurs. Upper Jurassic and Lower Cretaceous ichthyosaurs were studied. Their collecting was carried out in the period of 2016-2023 from sections in the western Kazakhstan (the villages of Pogodayevo and Shchuchkino in the West Kazakhstan region, the village of Tushybek, Mangystau region (Central Mangyshlak Peninsula)) and the Middle Volga region (the village of Gorodishchi, Ulyanovsk region). The article characterizes the reference sections of the Western region of the Republic of Kazakhstan with a description of the found remains of ichthyosaurs of the genera Kazakhstanosaurus, Nannopterygius, and Platypterygius. It has been established that fragments of their skeletons are found in the Upper Jurassic sediments of the sections near the villages of Pogodayevo and Shchuchkino in the West Kazakhstan territory, and in the village of Gorodishchi in the Ulyanovsk region, as well as in the sediments of the Lower Cretaceous of the Mangystau region. The species diversity of the genus Nannopterygius is noted. Our study of the Upper Jurassic sections nearv. Pogodayevo, Shchuchkino and Gorodishchi, and the Lower Cretaceous section of nearv. Tushybek showed that the comparison of the identified Ichthyosaur genera with the Mesozoic scale complexes allowed accurate determination of the age of local stratons and the position of their boundaries.