Ашық рұқсат
Рұқсат берілді
Тек жазылушылар үшін
Том 33, № 6 (2025)
Revision of the Zonal Brachiopod Species Jakutoproductus protoverkhoyanicus Kashirtsev from the Carboniferous-Permian Boundary Deposits of Verkhoyanie, North-Eastern Russia
Аннотация
A revision of the brachiopod genus Jakutoproductus of the Upper Kysyltasian Regional Substage (Gzhelian) of the Verkhoyanie was carried out. Previously, these Jakutoproductus belonged to the species Jakutoproductus protoverkhoyanicus Kashirtsev, 1959, whose presence distinguished the same-named biostratigraphic zone. The holotype of Jakutoproductus protoverkhoyanicus Kashirtsev, 1959 founds from the Lower Kysyltas Subformation, it has been established based on the materials of geological records. The holotype does not come from the Solonchan Formation, as indicated by the author of the species, and not from the Upper Kysyltas Subformation, as was later assumed. A monographic study of collections of Jakutoproductus from the Upper Kysyltas Regional Stage has shown that all Late Kysyltasian representatives of the genus Jakutoproductus morphologically differ from the holotype of J. protoverkhoyanicus and cannot belong to this species. Due to the lack of reliable finds of J. protoverkhoyanicus in the same-named zone, the use of this biostratigraphic unit is impractical. Since the holotype of J. protoverkhoyanicus was lost, new collections of brachiopods at the type locality of the species, located in the upper reaches of the Arkachan River in the Western Verkhoyanie, and subsequent selection of a neotype are necessary for species validation. Two brachiopod complexes have been established in the Upper Kysyltasian Regional Substage, separated by powerful flora-bearing sandstones of the Upper Kysyltas Formation. The main element of the first (Upper Kysyltasian) complex are small Jakutoproductus with a strongly elongated shell and a well-defined deep sinus of the ventral valve. These forms are assigned to a new species J. rimmae sp. nov. In the second (Kysyltasian–Khorokytian) complex, brachiopods of the genus Jakutoproductus are distinguished by significantly larger shell sizes and a less developed sinus of the ventral valve. Their important common feature is the presence in the anterior part of the ventral valve of several rows of straight spines with ringshaped ridges at the base. Kysyltasian–Khorokytian Jakutoproductus have been distinguished into two new species: J. budnikovi sp. nov. and J. allaraensis sp. nov. Instead of the Jakutoproductus protoverkhoyanicus Zone, the Jakutoproductus rimmae Zone with a stratotype on the Settandya River of the Upper Reaches of the Barajy River of the Western Verkhoyansk region is proposed. In the upper part of the Jakutoproductus rimmae Zone, Jakutoproductus budnikovi Beds are highlighted.
Stratigraphy and Geological Correlation. 2025;33(6):3-33
3-33
Early Cretaceous Belemnites of the Anabar Region (Northern East Siberia): Taxonomic Composition, Paleoecology and Biodiversity
Аннотация
Based on the study of a representative collection of Cylindroteuthididae rostra from the Ryazanian–lower Hauterivian deposits of the Anabar region (Nordvik Peninsula, Anabar River, eastern shore of the Gulf of Anabar), the ideas about the taxonomic composition and stratigraphic distribution of belemnites in the Lower Cretaceous of northern East Siberia have been significantly refined. Analysis of taxonomic and paleoecological rearrangements with an assessment of the impact of environmental factors has shown a noticeable influence of changes in the depth of the paleobasin, both on the dynamics of the taxonomic diversity of belemnites and on the ecological structure of their communities. The influence of the climatic factor in the study of biodiversity curves constructed for separate sections is not obvious for all time intervals. At the end of the Berriasian–beginning of the Valanginian, intensive migrations-influences of nektobenthic forms of belemnites of low-boreal European origin are recorded, which leads to a significant change in the taxonomic and ecological structure of the Anabar belemnic communities. In this regard, the Berriasian and Valanginian stages of their development are clearly distinguished, but at the same time, a transitional stage is recognized, which falls on the second half of the late Berriasian.
Stratigraphy and Geological Correlation. 2025;33(6):34-62
34-62
New Data on Diatoms and Silicoflagellates of the Late Cretaceous of the Ust'-Manya Section, Severnaya Sos'va River, Subpolar Trans-Urals
Аннотация
During the re-examination of the outcrop of marine Upper Cretaceous deposits on the Severnaya Sosva River in the area of the settlement of Ust-Manya, the complexes of the Costopyxis antiqua Zone for diatoms and the Cornua trifurcata Zone for silicoflagellates, presumably dated to the middle Campanian, were established for the first time in the diatomic layer. The associations, numbering at least 40 species of diatoms and 10 species of silicoflagellates, are typical of an epicontinental basin with seasonal contrast. Analogues are known from sections of the eastern slope of the Urals, Northern territories of Canada and the southeastern part of the East European Platform, which indicates stable interbasin connections of the Panboreal realm in the Campanian.
Stratigraphy and Geological Correlation. 2025;33(6):63-74
63-74
Biostratigraphy of the Campanian–Maastrichtian Boundary Deposits of the Eastern Part of the European Palaeobiogeographic Province (Section Lesnaya Respublika) by Microfauna
Аннотация
New data on the taxonomic composition and stratigraphic distribution of planktonic and benthic foraminifera and ostracods in the Campanian and Maastrichtian of the Middle Volga region (Lesnaya Respublika section, Saratov) are presented. The understanding of the compositions of microfauna assemblages has been considerably expanded. Based on the results of biostratigraphic analysis, biostratons were identified in the rank of beds and zones: for benthic foraminifera, the Assemblage Zone Neoflabellina praereticulata/N. reticulata (LC19) of the eastern part of the European Palaeobiogeographic Province, for planktonic foraminifera – Beds with Laeviheterohelix glabrans, for ostracods – Beds with Eopajienborhella marssoni–Cytherelloidea levigata–Cythereis zygopleura varia. All the identified units cover boundary deposits; it was not possible to establish criteria for the Campanian and Maastrichtian subdivision in this section. Different sedimentation conditions were reconstructed for the upper part of the Ardym Formation, the Nalitovo Formation, and the basal part of the Lokh Formation: two associated with a cooling period and one with a warmer period. The dependence of the preservation of microfauna with skeletons of different chemical composition on pH variations in sediment was revealed.
Stratigraphy and Geological Correlation. 2025;33(6):75-102
75-102
Influence of Climate Change on Sedimentation Processes of the Spitsbergen Archipelago in the Late Holocene (on the Example of the Little Ice Age and Modern Warming)
Аннотация
The results of long-term studies of the geochronology of sedimentation processes on the Spitsbergen archipelago are summarized and presented. The response of the sedimentary basin to climate change is demonstrated using climatic fluctuations of the last centuries as an example. The study covers various sedimentation basins of the Spitsbergen archipelago, including lake systems, fjords, bays, straits and the shelf zone of the Spitsbergen archipelago. It was found that variations in the granulometric composition of bottom sediments and sedimentation rates in the study area represent a direct response of sedimentogenesis to climatic fluctuations. The change in the sedimentation regime, which began after the Little Ice Age with lake and fjord basins, spread to the shelf zone of the archipelago by the first half of the 20th century, covering an area with a radius of at least 100 km from the sources of demolition. The studies revealed that in the estuarine zones and fjords up to 90% of the late Holocene bottom sediments were formed during periods of climatic optimums of the Subatlantic time, while for the shelf zone of the Spitsbergen archipelago this figure is about 75%.
Stratigraphy and Geological Correlation. 2025;33(6):103-120
103-120
Discussions
Some Aspects of the Study of the Geology of Wrangel Island (Commentary to the Article by M.I. Tuchkova and Co-Authors "New Data on the Late Paleozoic Conglomerates of Wrangel Island and Their Geological Interpretation")
Аннотация
Critical remarks are given to the article by M.I. Tuchkova and co-authors "New data on the Late Paleozoic conglomerates of Wrangel Island and their geological interpretation", published in the journal Stratigraphy and Geological Correlation", 2025, vol. 33, no. 2. pp. 59–80. Doubts are expressed about the of using term "tectonostratigraphic units" instead of formations and strata in the geological mapping of the island. It is concluded that, in paleogeographic terms, the Late Paleozoic DeLong basin had closer links with the Verkhoyansk-Kolyma basins than with those of the Canadian Arctic.
Stratigraphy and Geological Correlation. 2025;33(6):121-128
121-128