сеноман

The Albian-Cenomanian rocks compose a single complex of terrigenous deposits over the Volga Region. Delineation of the boundaries of the Cretaceous system units generally tends to cause difficulties, accounted for by rare finds of the fossils. In the northern part of the DonMedveditsa dislocations, natural outcrops of the Albian and the Cenomanian beds in the Burluk river valley have been examined since the 1950s. The authors have earlier made some case studies on the Gordienki, Krasny Yar, Melovatka and Moiseyevo sections.

The distinctions of the late cretaceous lithofacies are considered. The genetic groups are marked. These groups conform to the different zones of the sea basin starting from littoral zones with an active hydrodynamics up to the abyssal zones and the areas of the depressions. The inharting of monotyped facial zones of different time levels is established. Three facial regions which are following each other in space are established

The authors consider the compound of the late cretaceous deposits opened up in the bore hole number 13, 62 at the Gremyachinsk field of the potassium soils in the Volgograd region. According to the sediment basins evolution from the epicontinental basins (cenoman, turon-cognacian) to the subpelagic basins (cenonian) the lithotipe which form in the late cretaceous level the regular repeated layers of the terrigenous, carbonate, argillaceous-siliceous deposits are characterized

The earliest assemblage of Cretaceous sponges has been found in the Cenomanian terrigenous rocks (the Melovatka suite) from the south of the Volga right bank region. A noticeable element of the assemblage is composed of small-sized Camerospongia, newly recognized in the region and peculiar for forming monotype colonies as well.

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 paper presents biostratinomical characteristics of the Cenomanian and the Turonian fossil complexes found in the Middle Turonian phosphorite horizon from the Senomanskaya Stenka section (Volgograd region, Zhirnovsk district) constituting the basis of the benthic colonies and nekton communities. Probable interpretations for the settings contributory to generation of the phosphorite inclusion clusters are provided.

The paper analyzes the taxonomic composition and the habitat of the representatives of the Middle – Late Cenomanian and the Middle Turonian marine biota. The examined fossils have been isolated from the bulk sample obtained from the phosphorite horizon lying in the bottom of the Middle Turonian carbonate rocks in the Senomanskaya Stenka section (Volgograd Region, Zhirnovsk district).