Ichnofossils of the Permian-Triassic Sediments in the Southern Verkhoyansk Region (Tiryakh-Kobyume Section, Republic of Sakha (Yakutia), Russia)

The paper presents the first detailed evidence for the Permian and Early Triassic ichnofossils of the Southern Verkhoyansk Region. The possibility of using ichnofossils for reconstruction of terrigenous sedimentation at high latitudes, including environments related to the events of the great Permian mass extinction, was discussed. The results obtained are based on ichnofacial and ichnotextural analyses of about 600 samples collected in 2019 from the Tiryakh-Kobyuma section. We found that the Permian and Triassic sediments of the studied section contain numerous icnofossils attributed to 11 ichnogenera. Four ichnoassemblages were identified. They were referred to two ichnofacies - Zoophycos and Skolithos. The Zoophycos ichnofacies includes two ichnoassemblages: Helmintopsis - Phycosiphon - Zoophycos and the depleted Helmintopsis - Phycosiphon ichnoassemblages. This ichnofacies is confined to well-sorted substrates formed in calm temperately deep-water shelf environments, below the level of storm waves, with reduced oxygen content. The Skolithos ichnofacies includes two ichnoassemblages: Arenicolites - Skolithos and Diplocraterion - Arenicolites. It is characteristic of coastal environments with active hydrody-namics and large inputs of clastic and organic matter. The ichnofacies alternate across the section, reflecting sedimentological changing during the accumulation. The sediments of the lower part of the Nekuchan For-mation, corresponding to the Permian mass extinction event, accumulated in calm conditions of a relatively deep shelf. This interval is characterized by the Zoophycos ichnofacies with a depleted Helmintopsis - Phy-cosiphon ichnoassemblage. The depletion of ichnoassemblage and absence of benthic fossils in this part of the section may be caused by anoxic conditions at the basin bottom. The reconstruction of the Permian and Early Triassic environments agrees well with the results of previous studies based on sedimentological and biofacies data

First Record of the Genus Unionites Wissmann (Bivalvia) in the Boreal Permian of Northeast Russia

Abstract: Representatives of the bivalve genus Unionites Wissmann are found in the Upper Permian deposits of Northeast Russia, together with the typical high-Boreal Inoceramus-like bivalves Intomodesma sp. Previously, Unionites had been considered exclusively Triassic–Early Jurassic and were only recently found in the Upper Permian of Italy. The finding of representatives of the genus Unionites in the Boreal Upper Permian indicate increased connections of high-Boreal basins and Tethys Superrealm towards the end of the Permian, which began as early as the Middle and Late Wuchiapingian. A new species U. kobyumensis Biakov is described

Asselian–Sakmarian brachiopod zonation of the left bank of the lower reaches of the Lena River, Northeast Russia

This article summarizes the results of our study of the Early Permian brachiopods collected 5.9–6.3 km northwest of the village of Chekurovka that were used to develop the first biostratigraphic zonation of the Asselian–Sakmarian deposits on the left bank of the lower reaches of the Lena River. At the base of the Permian section, the Jakutoproductus lenensis Beds were identified. They are overlain by the Jakutoproductus insignis Zone with numerous shells of the index species. The Jakutoproductus terechovi and Jakutoproductus rugosus Zones, which are characterized by index species, occur even higher in the section. The boundary between the Khorokytian and Echian Regional Stages is defined by the first occurrence of J. insignis at the base of the Insignis Zone. The identified zonal sequence is identical to the previously studied Kubalakh section on the right bank of the lower reaches of the Lena River. However, the thickness of the biostratigraphic zones on the left bank is reduced by half, and a significant lower part of the Khorokytian Regional Stage (below the Lenensis Beds) is missing because it falls on the stratigraphic break between the Cambrian and Permian deposits. The zonation performed shows that there is a direct correlation between the Chekurovka section and the Asselian–Sakmarian deposits of Western Verkhoyanie and the Omolon Massif due to common index species of the biostratigraphic units

Brachiopods of the Imtachan Formation in the Upper Permian of the Southern Verkhoyanie, Northeast Russia

An extensive collection of fossil brachiopods, all assigned to the Wuchiapingian Stage, was recovered from the lower part of the Imtachan Formation along the Ustupnyi Creek (right tributary of the Setorym River) in the Southern Verkhoyanie. It comprises strophalosiids (Strophalosia? aff. vollossovitschi (Fredericks), Strophalosia? sp., Subtaeniothaerus lungersgauzeni Solomina, Marginalosia? magna Abramov et Grigorjeva), spiriferids (Crassispirifer monumentalis Abramov et Grigorjeva, Crassispirifer cf. monumentalis Abramov et Grigorjeva, Crassispirifer sp.), athyridids (Cleiothyridina nikolaevi Grunt, Cleiothyridina sp. 1, Bajtugania sp.), and terebratulids (Marinurnula? aff. mantuanensis (Campbell), Marinurnula? sp.). The identified assemblage is associated with brachiopods from the lower part of the Khalpirki Formation of the Western Verkhoyanie, the appearance of which marks the boundary between the Dulgalakhian and Khalpirkian Regional Stages and also substantiates the lower boundary of the Crassispirifer monumentalis Zone. Single finds of Crassispirifer cf. monumentalis in the lower part of the Middle Imtachan Subformation indicate that the entire lower subformation and the lower part of the middle subformation belong to the C. monumentalis Zone. There are no reliable finds of brachiopods at higher levels of the Imtachan Formation

New Find of Inoceramus-Like Bivalves of the Genus Atomodesma in the Southern Verkhoyansk Region, and Invasions of Extra-Boreal Mollusks into Northeastern Asia during the Permian

© 2020, Pleiades Publishing, Ltd. Abstract: Inoceramus-like bivalves of the bipolar species Atomodesma variabile Wanner were first found and precisely associated with the Upper Permian (Wuchiapingian) section in the Southern Verkhoyansk Region. The appearance of this exotic taxon in Boreal basins is associated with the short-term invasion of several Tethyan taxa into high-Boreal basins due to transgression. It is concluded that the similarity of the Permian marine biota from the Boreal and Notal (Gondwanan) paleobiogeographic superrealms is largely due to periodic invasions of notal elements into Boreal basins. The species A. variabile is described and illustrated

Biostratigraphy of the terminal Carboniferous of the lower reaches of the Lena River (Kubalakh section, Russia)

The main objective of the study is to solve the question of the age and paleontological characteristics of the Kubalakh Formation of the Upper Paleozoic of the lower reaches of the Lena River. The Kubalakh Formation has been attributed by various researchers either to the Upper Carboniferous or to the base of the Permian according to biostratigraphic data. However, the data on the paleontological characteristics of this straton have been often contradictory. In the course of studying the stratotype of the Kubalakh Formation, which is located near the mouth of the Kubalakh Creek in the lower reaches of the Lena River, the lithological structure of the section was clarified and the representative paleontological material of brachiopods was collected. The following species were identified in the lower part of the Kubalakh Formation: Jakutoproductus protoverkhoyanicus Kaschirzew, Verchojania abramovi Makoshin, Verchojania cf. monstrosus (Ganelin), Cancrinella? alazeica Zavodowsky, and Tornquistia kolymensis Afanasjeva. They all indicate that this part of the formation belongs to the Jakutoproductus protoverkhoyanicus Zone. Brachiopods from the upper part of the Kubalakh Formation were previously assigned to the Jakutoproductus verkhoyanicus Zone of the Khorokytian Regional Stage of the Permian. The results obtained indicate that the lower part of the Kubalakh Formation belongs to the Jakutoproductus protoverkhoyanicus Zone of the Kygyltasian Regional Stage (Gzhelian) of the Verkhoyansk Region. The finding of Verchojania cf. monstrosus (Ganelin) allowed comparing the lower part of the Kubalakh Formation with the Verchojania monstrosus Zone of the Upper Parenian Regional Super Stage of the Upper Carboniferous of the Kolyma-Omolon Region, which revealed that the border between the Kygyltasian and Khorokytian Regional Stages of the Verkhoyansk Region is sub-synchronous with the border between the Parenian and Munugudzhakian Regional Super Stages of the Omolon Massif. The new data expand the understanding of the historical development of biota under the specific (subarctic) conditions of the Eastern Boreal waters at the turn of the Carboniferous and Permian and can be helpful for geological mapping in the region

Ichnofossils of the Permian-Triassic sediments in the Southern Verkhoyansk Region (Tiryakh-Kobyume section, Republic of Sakha (Yakutia), Russia)

The paper presents the first detailed evidence for the Permian and Early Triassic ichnofossils of the Southern Verkhoyansk Region. The possibility of using ichnofossils for reconstruction of terrigenous sedimentation at high latitudes, including environments related to the events of the great Permian mass extinction, was discussed. The results obtained are based on ichnofacial and ichnotextural analyses of about 600 samples collected in 2019 from the Tiryakh-Kobyuma section. We found that the Permian and Triassic sediments of the studied section contain numerous icnofossils attributed to 11 ichnogenera. Four ichnoassemblages were identified. They were referred to two ichnofacies – Zoophycos and Skolithos. The Zoophycos ichnofacies includes two ichnoassemblages: Helmintopsis – Phycosiphon – Zoophycos and the depleted Helmintopsis – Phycosiphon ichnoassemblages. This ichnofacies is confined to well-sorted substrates formed in calm temperately deep-water shelf environments, below the level of storm waves, with reduced oxygen content. The Skolithos ichnofacies includes two ichnoassemblages: Arenicolites – Skolithos and Diplocraterion – Arenicolites. It is characteristic of coastal environments with active hydrodynamics and large inputs of clastic and organic matter. The ichnofacies alternate across the section, reflecting sedimentological changing during the accumulation. The sediments of the lower part of the Nekuchan Formation, corresponding to the Permian mass extinction event, accumulated in calm conditions of a relatively deep shelf. This interval is characterized by the Zoophycos ichnofacies with a depleted Helmintopsis – Phycosiphon ichnoassemblage. The depletion of ichnoassemblage and absence of benthic fossils in this part of the section may be caused by anoxic conditions at the basin bottom. The reconstruction of the Permian and Early Triassic environments agrees well with the results of previous studies based on sedimentological and biofacies data

About the age of fossil flora of the Kygyltasian Regional Stage of the Upper Paleozoic in the Verkhoyansk Region, Northeastern Russia

The Kygyltasian Regional Stage is widespread throughout the Verkhoyansk Region, where it reflects a large transgressive-regressive cycle of the Verkhoyanian terrigenous sedimentation. Over the years, a huge amount of material has been accumulated on biostratigraphic division, facies features, and paleontological characteristics of this large stratigraphic unit, but its age is still debatable. The main fossils in the upper part of the Kygyltasian Regional Stage are higher plants, the remains of which were studied in the last century using outdated taxonomy. This study is devoted to revision of the collection of fossil plants from the type locality of the Kygyltasian Regional Stage (Western Verkhoyanie) in order to clarify the taxonomic composition and the age of the Upper Kygyltasian floristic association. The dominant cordaite leaves in the association were studied using the morphological and microstructural methods. This made it possible to clarify the previous paleontological definitions of the genus Noeggerathiopsis and bring them in line with modern taxonomy. The species Noeggerathiopsis heteroclitus Tolstych and N. khorokytica Tolstych were validated for type specimens. The following species were identified from the Upper Kygyltas Subformation of the Levyi Khorokyt section: Cordaites heteroclitus (Tolstych), C. cf. neuburgae Gluchova, C. cf. zalesskyi Durante, C. krychtofovichii (Radczenko), Cordaites? khorokytica (Tolstych), Cordaites sp. 1, Cordaites sp. 2, Cordaites sp. 3, Cordaites sp. 4, Rufloria (Praerufloria) ex gr. theodorii (Tschirkova et Zalessky) S. Meyen, Samaropsis skokii Neuburg, S. cf. pauxilla Zalessky, S. aff. pumila Suchov, S. aff. auriculata Neuburg, Cordaicarpus baranovii Suchov, Crassinervia sp., Astrogaussia sp., Sphenophyllum cf. thonii Mahr, Sphenophyllum? sp., Sphenopteris sp., Paracalamites sp. Based on the results of the study, the Upper Kygyltasian floristic association of the Western Verkhoyansk Region was compared with floristic associations of the Alykaeva Formation (Kuzbass) and the Upper Kata Subformation (Tunguska basin). From the above, the Late Carboniferous age of the upper part of the Kygyltasian Regional Stage follows. The results obtained are in good agreement with the correlation of the Verkhoyanian Carboniferous-Permian deposits for marine invertebrates

EARLY TRIASSIC CONCHOSTRACANS from the TIRYAKHKOBYUME SECTION (SOUTHERN VERKHOYANSK REGION, REPUBLIC of SAKHA (YAKUTIA))

© 2020 Kazan Federal University. All rights reserved. Conchostracans (Crustacea) from the Induan deposits of the Tiryakh-Kobyume section (southern Verkhoyansk region) were studied. We identified the following seven conchostracan species belonging to five genera: Pseudestheria Raymond, 1946; Euestheria Deperet et Mezeran, 1912; Sphaerestheria Novojilov, 1954; Lioestheria Deperet et Mezeran, 1912; Wetlugites Novojilov, 1958. Most of the previously identified species in the Tiryakh-Kobyume region (“Pseudestheria sibirica”, “Ps. tumaryana”, “Ps. kashirtzevi”, and “Sphaerestheria aldanensis”) were described in the middle of the 20th century from the basal Triassic in the western Verkhoyansk region (Balbuk section). Revision of these species with the use of modern methods of conchostracan classification is needed