Nd isotope composition of the Ediacaran and earliest Cambrian phosphorite nodules and Fe sulphide from the East European Platform

An enhanced concentration of phosphorus has been found at the stratigraphic level of the disappearance of Ediacaran taxa in two areas, the Cis-Dniester region and the Moscow syneclise, on the East European Platform (EEP). The isotope composition of neodymium was determined in Fe sulphide and phosphorite in the same beds. Measured εNd(t) values in diagenetic phosphate nodules are similar to those in iron sulphide from the same layer. During the Ediacaran − Early Cambrian, accumulation of radiogenic Nd in the epeiric basins on the EEP increased progressively from −17.9 and −19.4 in pyrite from the sequence bottom to −7.9 and −8.5 in the Early Cambrian pyrite of the central part of the EEP. The Ediacaran phosphate nodules show εNd(t) ranging from −12.9 to −15.0, while that in the Early Cambrian nodules is typically c. −9.0. These data indicate the secular change in Nd isotope composition of the water reservoir on the EEP from Ediacaran to Cambrian.

Radioisotopic and biostratigraphic constraints on the classical Middle–Upper Permian succession and tetrapod fauna of the Moscow syneclise, Russia

The East European Platform and the PreUrals are the regions where the Permian System was first established, but the provincialism of fossils and lack of radioisotopic age control have prevented the use there of the regional Permian subdivisions used outside of the region. We report the first U-Pb zircon chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) age of 253.95 ± 0.06 Ma for a volcanic tuff from the terrestrial upper part of the lower Vyatkian Regional Stage in the Moscow syneclise (Russia). This age greatly improves the correlation of the East European Platform and the PreUrals with the international geologic time scale, and contributes to our understanding of sedimentation within the Permian-Triassic transition in the studied region. The new radioisotopic age integrated within the regional chronostratigraphic framework reveals the synchrony in extinction of faunas of the Dinocephalian superassemblage in the studied region with that in South Africa.

Supplemental Material: Radioisotopic and biostratigraphic constraints on the classical Middle–Upper Permian succession and tetrapod fauna of the Moscow syneclise, Russia

Figures S1–S4 (photos, stratigraphic logs, stratigraphy, and results of single grain chemical abrasion ID-TIMS analysis) and Tables S1 and S2 (fossils, and U-Pb isotopic data).<br>

Supplemental Material: Radioisotopic and biostratigraphic constraints on the classical Middle–Upper Permian succession and tetrapod fauna of the Moscow syneclise, Russia

Figures S1–S4 (photos, stratigraphic logs, stratigraphy, and results of single grain chemical abrasion ID-TIMS analysis) and Tables S1 and S2 (fossils, and U-Pb isotopic data).<br>

Supplemental Material: Radioisotopic and biostratigraphic constraints on the classical Middle–Upper Permian succession and tetrapod fauna of the Moscow syneclise, Russia

Figures S1–S4 (photos, stratigraphic logs, stratigraphy, and results of single grain chemical abrasion ID-TIMS analysis) and Tables S1 and S2 (fossils, and U-Pb isotopic data).<br>

Biostratigraphic significance of the tetrapod assem¬blages of the Timan- North Urals region and adjacent areas

New and specified data on the composition of the Triassic tetrapod assemblages of the Timan-North Urals region, the Mezen syneclise and the eastern part of the Moscow syneclise have been given. The succession of the Triassic tetrapod communities known in this area includes eight assemblages, seven of which correspond to the contemporary communities of the terrestial vertebrates known from other regions of the East European platform and the Cisurals. The first assemblage, known from the basal Triassic of the Mezen and Moscow syneclises, is Early Induan in age. The second, third and fourth assemblages are dated by Early Olenekian age and typical for the middle part of the Early Tri-assic section of the Timan-North Urals region, the Mezen and Moscow syneclises. The Late Olenekian fifth and sixth assemblages characterize the upper part of the Lower Triassic of the Northern Cisurals, the Moscow and Mezen syneclises. The seventh assemblage characterizes the base of the Middle Triassic (Lower Anisian) of the Northern Cisurals and has no analogues in other regions of the platform and of the Cisurals. The eighth assemblage is known from the upper part of the Middle Triassic of the Northern Cisurals and is Late Ladinian in age.

Potencial of rock-magnetic methods in paleoecological reconstructions: case study of Mikhailovtsement reference section (Ryazan region)

On the basis of detailed, combined rock-magnetic, lithological, and micropaleontological study of the Mikhailovtsement section of the Moscow syneclise (Ryazan region), the fluctuations in Central Russian Sea level in Callovian–Early Oxfordian were reconstructed. According to the variations of rock-magnetic parameters over the section, seven rock-magnetic intervals were established which correspond to different stages of basin evolution. These stages are compared with sea level fluctuations established on the basis of changes in the lithology of rocks and the ostracod complexes. In general, the nature of sea level change in Callovian–Oxfordian, revealed by combination of the methods during the study of Mikhailovtsement section coincides with global trend.