Geology

Among the Late Cretaceous Ventriculitidae, with the most simply constructed pariform skeleton, representatives characterized by unusual neoplasms were identified. On the paragastric surface after the lapel of these sponges (Contubernium), cone-shaped submodules are regularly based, the appearance of which is associated with incomplete blastogenesis. Paragastra of submodules are not associated with the atrium, therefore, Contubernium is considered as a perifrontal organism, occupying an intermediate position between single and modular forms of spongia.

To date, the significance of geological processes induced by fluid activity in the crust and in the Earth’s lithosphere in general has been fully revealed. The role of fluid systems in the energy and matter flow transfer, as well as in the formation of the lithospheric deep modes, its lamination and decompression structures, becomes apparent in the light of current data.

The Lower Taiga area is a part of the East-Sikhote-Alin volcanicplutonic belt (ЕSAVPB), located in the transition zone of the continentocean which has a very folded geological structure. The study of the geological and geochemical composition, structure and patterns of the placement of volcanogenic-sedimentary rocks of the Lower Taiga area (LTA) will significantly complement the data on the geological and geochemical features of the Mesozoic-Cenozoic stage of the formation of the ЕSAVPB.

Terminal layers of carbonate rocks of Maastrichtian and lower intervals of Paleocene aleurite-pelitic formations are accessible for investigation in Krasny Oktyabr and Bolshevik quarries (Volsk Depression). In the bottom of the Paleocene accumulation of skeletons of calcareous and siliceous sponges has been confirmed, mollusk and elasmobranch assemblage has been determined. Biozonal stratification of the location section and oryctocomplex analysis have contributed to specification of the processes in succession of benthic forms at the Upper Cretaceous – Paleogene boundary.