Coniacian

In the right-bank part of the Saratov Region, a section of terrigenous and carbonate rocks has been determined to underlie the ?sponge? horizon conventionally dated back to the Santonian. The maximum thickness of the marls, constituting a substantial portion of the section, occurs in the western part of the region.

In the ?Ozerki? sections, in the terrigenous and carbonate rocks, a faunal complex has been determined – unusually diversified and relatively abundant for the right-bank part of the Saratov Region. Examination of the specified groups of fossil invertebrates has allowed to propose variants for biostratigraphic division and correlation of the sections under consideration. The carbonate rocks are supposed to belong to the Turonian-Coniacian and the underlying terrigenouscarbonate rocks are regarded as the Lower Turonian ones. Formation of the ?sponge?

The features of areal distribution and stratigraphic confinement of calcareous spicular sponge forms in the southeast of East European Platform are considered. The skeletons of calcareous sponges essentially representatives of the genus Porosphaera are found in the carbonates of Turonian, Coniacian, Campanian and Maastrichtian, as well as at the base of siliceous formations of the Paleocene. The Maastrichtian calcareous sponges are characterized by the highest species diversity and a wide lateral extension.

The horizon enriched in glauconite and phosphorite was revealed at the carbonatic outcrops near Volsk in the Coniacian and Campanian stage deposits. The short descriptions of studying sections are presented. The spread of synchronous deposits within Khvalynsky district was traced. The Lower and Upper Santonian and the Campanian age deposits are proved by the presence of the inoceramids, belemnites and echinoides. Its vertical distribution was traced.

The fossil assemblage taxonomical composition analysis of upper Coniacianlower Santonian, upper Santonian and lower Campanian deposits is demonstrated. The upper Coniacian and lower Santonian deposits planoconformity has been recorded, the thin upper Santonian deposits presence has been proved and the lower Campanian subface position has been defined. Fractional biostratigraphy subdivision of the Coniacian – lower Campanian interval was carried out. The distinguished strata were traced within Volsk-Khvalynsky district.

The Gubkino Horizon (Turonian-Coniacian) in the Bolshoy Kamenny ovrag section (Zhirnovsk town, Volgograd Region) has not been purposefully studied so far. As a result of biostratigraphic and magnetostratigraphic researches the carbonate rocks of the Gubkino Horizon were first divided into zones based on benthic foraminifera complexes and characterized by geomagnetic polarity and rock-magnetism data. The most part of the Bolshoy Kamenny ovrag section is covered by the reverse polarity zone.

The paper presents the results of petro- and paleomagnetic studies of two sections of Turonian – Santonian on the Samara Right Bank – near Novodevichye, Podval’e villages and detailed geological description of the Novodevichye section. The magnetostratigraphic subdivision and detailed correlation of the sections were carried out. Unknown unconformity in the Podval’e section was recognized.