Ichthyofauna of the border sediments of the Severodvinsky and Vyatsky stages in the Late Permian localities in the west of the Orenburg region (Samara river basin)

A detailed study of the section of the severodvinsky and vyatsky stages of the Upper Permian with layer-by-layer sampling of ichthyofauna in the western part of the Orenburg region (basin of the lower reaches of the Samara River) was carried out. Based on the fish complexes, a paleontological justification of the stratigraphic boundary between the severodvinsky and vyatsky stages was obtained in the region for the first time.

A gap in sedimentation in the Silurian section of the Subpolar Urals at the Ludlow-Pridoli boundary

Research subject. The article discusses the results of a new detailed study of a reference section of the Upper Silurian in the Subpolar Urals. This study was undertaken to clarify the existing contradictions concerning the age of the Ludlow-Pridoli boundary deposits and the definition of the Ludlow-Pridoli boundary, which is based on the study of different fauna groups.Materials and methods. The newly collected collections contained more than 100 samples of sedimentary rocks with fossil macro fauna, 22 tests on microfauna, 198 tests on chemical analysis for determining the content of Ba, Sr and δ13C and δ18O isotopes in carbonates. The results of experiments were confirmed by the authors’ bio-sedimentological, paleo-ecological and chemostratigraphic data.Results. The conducted research confirmed the existence of a gap in sedimentation at the end of Ludlow; clarified the thickness of the Sizim stage in the reference section; elucidated its sedimentological and chemostratigraphic characteristics; allowed changes in biodiversity due to a change in the sedimentation regime, paleoecological impact on biota in the late Ludlow and restoration of biota in the early Pridoli to be traced. The study also demonstrated that the time boundaries of the transgressive and regressive stages in the development of the Northern Ural sea basin and the event-stratigraphic boundary of the Ludlow-Pridoli were directly related to the main global events in the Late Silurian (Lau Event, Lower Pridolian Event), the traces of which are preserved in the studied section.Conclusions. The intensification of regressive tendencies across the largest part of the Northern Ural paleobasin in the Late Ludlow, widespread development of microbial biota, cessation of the Silurian reef formation, as well as the extinction of Pentamerida brachiopods – exclusively, indicate a significant ecosystematic restructuring in the late Ludlow. It can be assumed that the absence of a significant positive deviation of the δ13C global Lau Event in this section is associated with the identified gap, the amplitude of which correlates with the Ozarkodina snajdri and Ozarkodina crispa zones located above the Polygnathoides siluricus zone in the conodont sequence of the Upper Ludlow.

Where the Meghalayan meets the Anthropocene: Stratigraphic signals of human-environmental interactions on the periphery of Indian civilisation

The aims of this study were to review human-environment interactions during the Meghalayan and to search for the stratigraphic boundary of a new epoch, informally termed the Anthropocene, as well as to determine whether the stratigraphic signals of human activity on the Meghalaya Plateau in Northeast India can be correlated globally. This plateau is the base of the Meghalayan Age that was determined from a speleothem in a cave located on it. Review indicates that study region developed on the periphery of ancient Indian civilisation, with stratigraphic signals of human activity being apparent in only the last few thousand years; that is, substantially later than the neighbouring ancient Indian civilisation. The stratigraphic signals are heterogeneous and diachronous, not only as a result of various human activities, but also in the effect of the diverse sensitivities of the environment to anthropogenic disturbances. A discrete and visible cultural layer that relates to the development of settlements and the production of new materials is still being formed and reworked. The only synchronous stratigraphic signal with a global range seems to be associated with the artificial radionuclide fallout from nuclear weapons testing, which covers a topsoil layer of up to tens of centimetres thick

The chronostratigraphic method is unsuitable for determining the start of the Anthropocene

This paper responds to and supports the earlier ‘Three Flaws’ paper by William Ruddiman (this journal, 2018). It builds upon his critique of the method used by the Anthropocene Working Group in determining the start date of the Anthropocene. While chronostratigraphy is acknowledged as the best means of establishing a framework for the division of deep time – on geological timescales of millions of years – it is argued that the method is unsuitable for use on archaeological and historical timescales. Close proximity in time between the chronostratigraphic observer and the stratigraphic boundary in question renders the placement of a precisely defined, globally synchronous timeline onto highly time-transgressive evidence inappropriate on these scales of analysis. Application of the method hinders rather than helps understanding of the role of human impact on Earth System change; it leads to a loss of the bigger picture and to relative neglect of the crucial evidence provided by humanly modified ground – the missing strata in most chronostratigraphic accounts of the Anthropocene start. A more ground-up approach is called for. Recognition of humans as geological agents needs to be accompanied by recognition of the distinctive traces of human agency in the ground, which are unprecedented in the stratigraphic records of earlier geological time periods.

The petrographic characteristics and the upper stratigraphic boundary of limestone late permian in the geological section in South – Eastern region, Vietnam

In the South – Eastern region, Vietnam, the stratigraphic boundary of Late Permian - Early Triassic has long been considered as an unconformity boundary between Ta Vat formation (Late Permian) and Song Saigon formation (Early Triassic). Recent studies on the petrographic and geological structure of this section suggested that it may be a conformable stratigraphic boundary, where there is the transition from limestone series such as grainstone, packstone, wackstone of Ta Vat formation to the sedimentary rocks such as claystone, and marl. This characteristic was closey related to the geological structure of Song Saigon.

Low diversity cockroach assemblage from Chernovskie Kopi in Russia confirms wing deformities in insects at the Jurassic/Cretaceous boundary

The Jurassic/Cretaceous (J/K) boundary is of great importance for the evolution of cockroaches as 6 (of the total of 27) families and orders of termites and mantodeans evolved from them during this interval. The Jurassic affinities of most taxa and a complete lack of any characteristic Cretaceous cockroach taxa combined with the presence of two termites indicate a position close to the J/K stratigraphic boundary for the locality Chernovskie Kopi in Transbaikalian Siberia. Among 41 specimens the dominant species was Blattula discors sp. n. (n = 14 (15?)) closely related to Blattula vidlickai Vršanský, 2004 from the roughly coeval locality Shar-Teg in Mongolia. Rhipidoblattina lacunata sp. n. (Caloblattinidae; n = 10) and Archimesoblatta kopi sp. n. were common, while Mongolblatta sanguinea sp. n. (Mesoblattinidae; n = 6, 1) and Rhipidoblatta grandis sp. n. (Caloblattinidae; n = 2) were rare. Six specimens, all possibly representing an unknown genus of the family Liberiblattinidae remain indetermined. Such composition of an assemblage with a low diversity, resulting from a destabilized ecosystem resembles Early Jurassic assemblages from Mintaja, Australia and diverse Toarcian localities in Germany and England rather than Middle or Late Jurassic assemblages. The present samples also contain plant remains. The almost complete lack of bodies, pronota and hind wings suggest a significant transport prior to deposition. Twenty deformities distributed on nine wings amounting to 22.5% of wings support the occurrence of mass mutations near the J/K boundary.