The study present the results of the integrated study on the Belgorod and Pavlovka formations (upper Campanian), Sukhodol Formation (Campanian-Maastrichtian), and Efremovo-Stepanovka Formation (Maastrichtian). Variations in lithological indicators and associated changes in the biotic assemblages were used to distinguish three stages in the basin evolution separated by hiatuses (Belgorod-Pavlovka, Sukhodol, and Efremovo-Stepanovka). This basin occupied the upland area in the north of the Paleozoic Donets Basin during late Campanian-early Maastrichtian times. Each stage was characterized by a specific depositional environment accompanied either by a decrease or by an increase in the terrigenous sediment supply from the Donets Basin and, possibly, Ukrainian Shield and sea-level and temperature fluctuations, as well as specific paleobiogeographic relations. During the Belgorod-Pavlovka stage, the basin was characterized by relatively deep-water environments, with warm waters and normal salinity, and predominantly carbonate sedimentation. The Sukhodol stage was marked by terrigenous sedimentation, a predominance of the agglutinated foraminiferal forms, and abundant radiolarians, which occurred during a marine regression and overall cooling. This stage corresponds to the global "Campanian-Maastrichtian boundary event." The first half of the Efremovo-Stepanovka stage was marked by resumed carbonate sedimentation, warming, transgression, and deepening of the basin, which were replaced by a renewed regression at the end of this time interval.

Palaeotemperatures during the late Barremian-early Aptian (Early Cretaceous) on the Russian Platform have been determined on the basis of oxygen isotope analysis of aragonitic bivalve molluscan and ammonoid shells and belemnite rostra with well-preserved microstructure from the Ulyanovsk area. Those obtained from the planispiral and heteromorph ammonoid shells from the lower Aptian Volgensis Schilovkensis, Deshayesi-Tuberculatum, and Deshayesi-Renauxianum zones range from 26.7 to 33.2 degrees C, from 292 to 33.1 degrees C, and from 27.0 to 29.5 degrees C, respectively. A heteromorph Helicancylus? cf. philadelphius shell from the uppermost lower Aptian Bowerbanki Zone was secreted in highest temperature conditions (32.8-35.2 degrees C). In contrast, upper Barremian molluscs (bivalve Cyprina sp. and belemnite Oxyteuthis sp.) of the Ulyanovsk area show significantly lower palaeotemperatures: 16.9-18.5 degrees C and 7.9-17.8 degrees C, respectively, which is in accordance with known palaeogeographic and palaeobotanical evidences, showing that a distinct climatic optimum seems to have occurred during the late early Aptian, when warm Tethyan water penetrated into the basin. Marked changes in calculated growth temperatures for investigated molluscs from the Russian Platform were most likely connected with both the general warming trend during the late Barremian early Aptian and local palaeonvironmental conditions. New data from the Bowerbanki Zone of the Russian Platform provide evidence on existence of the positive carbon isotope anomaly (2.4-6 parts per thousand,) at the end of the lower Aptian. There were apparently the three positive C-isotope anomalies during the late Barremian early Aptian. The onset of mid early Aptian Oceanic Anoxic Event (OAE) 1 a seems to coincide with both the beginning of significant warm conditions (followed by short-term cooling) and the abrupt decline in heavy carbon isotope concentrations in marine carbonates, which partly were the likely consequences of the intensive release of CO2 (biased by volcanic activity) and/or dissociation of methane gas hydrate. (C) 2013 Published by Elsevier Ltd.

Burrows of Thalassinoides, which are attributed to the group of dwelling structures, occur in all the marine and coastal facies. The Lower Cretaceous sections of southwestern and central Crimea yielded the representative collection of Thalassinoides burrows belonging to the ichnospecies Th. suevicus (Rieth, 1932), which served as an object for this investigation. The burrows are confined to coarse-grained terrigenous, carbonate, and mixed sediments and contain assemblages of ichnofossils indicating coastal and shallow-water marine Skolithos and Cruziana ichnofacies. In the Mesozoic-Cenozoic, the producers of the Thalassinoides burrows were decapods, confirmed by finds of crayfish Hoploparia in them.

This work discusses the complex characteristic of the Upper Cretaceous (Turonian-Lower Maastrichtian) section recovered by two boreholes in the southern part of the Volgograd region (right side of the Volga River) in the Gremyach'e potash deposit. Lithological and paleontological data (benthic foraminifers, radiolarians, and dinocysts) suggest several lithological-facies and biotic reorganizations. The analysis of the distribution of these microfossils through the section allowed the ages of the Zakharovo Group, Mozhzhevelovyi Ovrag, Mezino-Lapshinovka, Pudovkino, Zarya, Nalitovo, and Bereslavka Formations to be specified. Benthic foraminifers characterize zones of the Upper Cretaceous high-resolution scale available for the East European Platform and local (facies) units, while radiolarians and dinocysts reveal stratigraphic units in a bed rank. Using complex paleontological characteristics (benthic foraminifers, radiolarians, dinocysts), the defined biostratigraphic units are correlated between each other and with their counterparts in neighboring and remote regions of different paleobiogeographic regions and provinces. The Upper Cretaceous biostratigraphic scale is supplemented by the first defined dinocyst and radiolarian biostratigraphic units of the East European Platform. The new data provides evidence in favor of a three-substage division of the Campanian Stage instead the two-substage system presently accepted in Russia. It is shown that the traditional position of the lower boundary of the Maastrichtian Stage in the East European Platform is close to that of this boundary in the Standard Stratigraphic Scale. Some aspects of environmental and biotic evolution in the Volgograd region through the Late Cretaceous Epoch are considered.

Four upper Campanian-lower Maastrichtian reference sections are described in the Glubokaya and Kalitva river basins and in the Znamenka 1-A Borehole located in the northwestern Rostov region. The sections are composed of the upper Campanian Kagal'nik, Belgorod, Pavlovka, Sukhodol and lower Maastrichtian Efremovo-Stepanovka formations. They are characterized by successive stratigraphically significant macro- and microfossil assemblages: belemnites, calcareous nannoplankton, benthic foraminifers, and radiolarians. The Pavlovka and, particularly, Sukhodol formations contain a specific assemblage of coarsely-agglutinated benthic foraminifers. The first data obtained on radiolarians in upper Campanian-lower Maastrichtian sections of the northwestern Rostov region revealed four assemblages, two of which were previously unknown from Upper Cretaceous sediments of the East European Platform. Most sections enclose a hiatus at the base of the Sukhodol Formation, which comprises two upper Campanian benthic foraminiferal zones. The problem of recognition of the lower Maastrichtian boundary on the East European Platform is considered in accordance with international GSSP requirements.

The first compiled composite section comprises continuous succession of upper Tithonian-lower Berriasian strata (Jacobi Zone) from different isolated outcrops of the Feodosiya area. Based on new magnetostratigraphic and sedimentological data, the paleomagnetic section is correlated with succession of M20r, M19n, M19r, M18b chrons and M18n.1r Subchron ("Brodno"). The thorough complex bio- and magnetostratigraphic correlation of the upper Tithonian-lower Berriasian interval (Jacobi Zone) carried out through the Western Tethys and Eastern Paratethys provided grounds for first defining age analogs of the Durangites Zone in the Crimean Mountains and specifying location of the boundary between the Jurassic and Cretaceous systems, as well as for determining late Tithonian age of strata in the Dvuyakornaya Bay section barren of fossils.