Comprehensive Characteristics of the Mechetlino Section (Southern Urals, Russia)

The Mechetlino section is located on the right bank of the Yuryuzan River near the village of Mechetlino (Southern Urals, Russia). The section exposes terrigenous-carbonate deposits of the Artinskian and Kungurian Stages, containing a rich fossil assemblage. Following years of comprehensive research, the Mechetlino section has been proposed as a GSSP for the Kungurian Stage of the International Stratigraphic Scale. However, this section, which possesses enormous stratigraphic potential, is currently not considered in this capacity. Conodonts have been studied in detail in the Artinskian-Kungurian boundary, where several phyletic lineages have been traced. The first one is associated with the transition of the Artinskian species Sweetognathus somniculosus Chernykh into Kungurian species Sw. barskovi Chernykh. The next two phyletic lineages are associated with the genus Neostreptognathodus: the species N. pequopensis Behnken evolved into N. pneviKozur et Movschovitsch, and the species N. ruzhencevi Kozur evolved into N. lectulus Chernykh. Both species are also known from coeval deposits in the USA and Canada; they can equally serve as markers of the lower boundary of the Kungurian Stage. The Mechetlino section exhibits a wide variety of ammonoids. The Uraloceras fedorowi beds have been identified in the Artinskian, while the Clausiuraloceras mechetlense beds have been identified at the base of the Kungurian (Neostreptognathodus pnevi Zone). The appearance of Clasiuraloceras mechetlense Kutygin at the base of the Kungurian stage reflects an important stage in the morphogenetic development of the family Paragastrioceratidae, allowing this species to be considered an additional marker of the Artinskian-Kungurian boundary. Numerous small foraminifera are found throughout the section. In the lower part, there are species Protonodosaria proceraformis (Gerke), Nodosinelloides cf. cubanicus elongatus Filimonova, etc., characteristic of the Artinskian Stage of the Urals, northern Russia, the Pamirs and Turkey. In the deposits of the Kungurian Stage, Howchinella impolita (Crespin), H. breggeri (Sossipatrova), etc. appear, typical of the Kungurian Stage of Australia and Spitsbergen. In the Artinskian deposits the fusulinids Pseudofusulina urasbajevi urasbajevi Rauser, Ps. seleukensis Rauser and Ps. postsolida Tschuvashov occur. Small foraminifera and zonal species of fusulinids provide a direct correlation with the Tethys, Spitsbergen, and Australia. At the base of the Kungurian Stage, a rich association of radiolarians was discovered: Alexialeks distinctusAfanasieva, Apophysiacus sakmaraensis (Kozur et Mostler), Astroentactinia mirifica Afanasieva, and others. Here within the scope of the Neostreptognathodus pnevi Zone, the Astroentactinia mirifica ecozone is distinguished. Brachiopods, fish, and trilobites were also studied. The detailed lithological, geochemical, and paleomagnetic investigations were conducted, and stable carbon and oxygen isotopes were analyzed. The strontium isotope ratio 87Sr/86Sr in conodonts from the lower Kungurian stage is 0.707394±10. With the inclusion of the Mechetlino section in the Yangan-Tau UNESCO Global Geopark, it has become a geotourism centre in the Russia. In the near future, a geological museum complex is planned for the Mechetlino section. All of the above made it possible to propose the Mechetlino section as a stratotype for the lower boundary of the Kungurian stage of the General Stratigraphic Scale of Russia.