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The study of amorphous biogenic silica content in marine sediments makes it possible to evaluate changes in the silicon cycle in the world ocean, while periods of intense silicon deposition record changes in the water chemistry and the atmosphere. The technique of sequential leaching of silica with subsequent calculation of the contribution of clay minerals is actively used by researchers for Quaternary deposits. This study used sediments that differ in age (Neogene, Cambrian), composition (clay minerals content from 0 to 27%, quartz content from 9 to 88%), and paleoenvironment (oxic and anoxic conditions, marine and coastal environments). Three rock types were taken for comparison: Miocene siltstones (N1s2, Sarmatian regional stage, Taman, Russia), bituminous limestone, flint, and rocks of the mixed siliceous–clay–carbonate composition of the Inikan Formation of the Lower-Middle Cambrian (Є1-2in), and Middle-Upper Cambrian siltstones of the Evenki Formation (Є2-3ev) (Eastern Siberia, Russia). The alkaline leaching method has been improved to prevent possible changes in the reaction kinetics and to account for the heterogeneity of the sample at low estimated amorphous silica content. As a result of these studies, it has been found that the Si/time and Si/Al are the most optimal among the considered methods for calculating the content of amorphous silica in Neogene and Cambrian rocks with low amorphous silica content. When there is little discrepancy between the average values of conditionally biogenic silica, the Si/Al method is preferable for terrigenous rocks. The amount of amorphous silica available for extraction in the rocks of the Inikan (Є1-2) and Evenki (Є2-3) formations was estimated at 0–2.0 wt% and 1.6–3.0 wt%, respectively. Research Highlights: Sedimentary rocks of different ages (Neogene, Cambrian), composition (clay minerals content from 0 to 27%, quartz content from 9% to 88%), and paleoenvironment (oxic and anoxic conditions, marine and coastal environments) were studied. The alkaline leaching method has been improved to prevent possible changes in the reaction kinetics and to account for the heterogeneity of the sample at low estimated amorphous silica content. As a result of these studies, it has been found that the Si/time and Si/Al are the most optimal among the considered methods for calculating the content of amorphous silica in Neogene and Cambrian rocks with low amorphous silica content. Methodological issues related to the calculation of the contribution of clay minerals were discussed, as well as the role of catagenetic transformation for Paleozoic rocks. [ABSTRACT FROM AUTHOR]

The Cenozoic marine deposits (two formations) developed in the eastern part of the Opukha–Pekulney Depression of the Koryak Upland are described. Until recently, there was scarce information about them. The lower (Retyrveem) formation is composed of dark conglomerates and sandstones with a large number of carbonate nodules and representative assemblages of bivalve and gastropod mollusks (more than 400 tests and imprints were studied) and Early Eocene benthic foraminifers. Two subformations and six units were distinguished in the formation. The upper (Morzhovaya) formation is composed of light loose gravestones and sandstones, including fragments of Early Miocene mollusks and foraminifers. The study of faunal assemblages makes it possible to correlate these formations with stratigraphic units of adjacent areas and to reveal hiatuses in the section covering most of the Paleocene sequence, on one hand, and the Upper Eocene and Oligocene, on the other hand. The Retyrveem Formation encloses warm-water molluscan assemblages, the appearance of which in the northern boreal latitudes is supposed to be related to the Early Eocene global warming. Images of the characteristic molluscan remains are given for the first time. [ABSTRACT FROM AUTHOR]

The amphisbaenian and anguimorph fossil lizards from the late Miocene (MN 13) Solnechnodolsk locality (southern European Russia) are described. Amphisbaenians are represented only by isolated vertebrae of which more precise allocation is difficult. The anguine material shows the presence of at least two taxa which are described from this area for the first time: Anguis cf. rarus and Ophisaurus cf. spinari. The A. rarus was previously known only from the early Miocene of Germany. Ophisaurus spinari has a broad stratigraphic range – from the early and middle Miocene of Central Europe, with the last occurrence documented from the late Pliocene of Italy. However, no record was known from the late Miocene, which would show an important part of the story. The parietal of A. cf. rarus forms the first evidence of its survival to the end of the Miocene by its shifting to south areas of Eastern Europe, together with O. spinari. The Solnechnodolsk material is evidence of a broad spatial and/or temporal distribution of both these anguine taxa and the parietal of Anguis unambiguously documents the presence of this taxon in Russia already in the late Miocene. The thermophilic forms in Solnechnodolsk are represented by monitor lizards (Varanus). [ABSTRACT FROM AUTHOR]

The almost complete skeleton of a fossil dreamer, identified as Oneirodes sp., is described from the middle–upper Miocene Kurasi Formation of southern Sakhalin Island, Russia. This is the second fossil skeletal record of oneirodid anglerfishes following those described from the Puente Formation of California, USA. The new specimen possesses morphological features very similar to those of the recent and fossil members of its genus, and cannot be separated from them at the species level. This finding confirms the idea of the high level of speciation of this fish family prior to the middle–late Miocene and demonstrates the wide geographic distribution of the genus Oneirodes already at this time. [ABSTRACT FROM AUTHOR]

A reference section of the Paleogene and Neogene located in the Kvachina Bay, West Kamchatka, is characterized in detail with description of ancient sequences and their lithological and paleontological features. Debatable problems of division and correlation of the section are reported. Its importance for deciphering of the geological events of the region is examined, as well as for the development of the stratigraphic scheme of the Cenozoic of West Kamchatka. [ABSTRACT FROM AUTHOR]

This work presents a clarified stratigraphic scheme of the Miocene sediments of the Fore-Urals and the territory of Bashkortostan. As a result of the work carried out, the regional stratigraphic divisions of the Miocene of the Fore-Urals were described and stratotypes and reference sections were established for the first time. The stratigraphic scheme of the Miocene sediments includes the sequences of the Lower (the upper part of the Tyulganskian Formation, Kuyurgazinskian and Voroshilovskian formations), the Middle-Upper (Ushkatlinskian Formation) and the Upper (the lower sub-formation of the Tchebenkovskian Formation) Miocene. In addition, the stratigraphic scheme developed was correlated with those of the Urals, the Russian Plain and the Lower Volga Region. The scheme is based on the data obtained from study of sediments, analysis of paleontological and lithological data, and summary of literary and library materials, which allowed us to elucidate in detail the Miocene events in the Fore-Urals. [ABSTRACT FROM AUTHOR]

Palynological analysis of Sarmatian deposits found in the reference section Zelenskii Mountain-Cape Panagiya has produced new data on dinocysts and contributed to the palynological characteristics of the Sarmatian deposits of the Taman Peninsula. Six palynological assemblages have been found, reflecting the gradual replacement of forest associations with forest-steppe ones, and thus confirming the trend, revealed earlier, of climate aridization in the areas of the Eastern and Central Paratethys in the Late Sarmatian time. The distinctive cysts of the dinoflagellates Geonettia cf. clinea de Verteuil et Norris and Polykrikos schwarzii Bütschli are identified in Sarmatian deposits of the Taman Peninsula for the first time. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents magnetostratigraphic data on Paleogene–Neogene continental sediments stripped by borehole 8 at the southern periphery of the Om’ basin, in the Ishim–Irtysh interfluve, on the border with northern Kazakhstan. Pollen assemblages and zones have been distinguished, and a paleomagnetic section of borehole 8 has been compiled. The section consists of 11 magnetozones, which are associated with pollen zones and paleocarpological data. The absence of some paleomagnetic and pollen zones from the section suggests that the geological record is incomplete, because the formations in the studied sediments are partly eroded. A dinoflagellate community was first recorded in Upper Oligocene–Lower Miocene sediments at the periphery of the Om’ basin. The composition and ecologic characteristics of this community cannot give an unambiguous answer to the question whether seawater could penetrate southwestern Siberia through the Turgai Sea. The composition of pollen and spores from the Lower Oligocene sediments (Novomikhailovka Formation) and from the Chilikty Formation (northern Kazakhstan) is similar and reflects the development of Turgai flora in a huge territory. Later, in the second half of the Miocene, broad-leaved/coniferous forests were replaced by small-leaved ones. In the late Miocene, the latter were replaced by forest steppes with some arid flora. [Copyright &y& Elsevier]

The early middle Miocene (MN 5) lizards from the East Siberian Tagay locality (Baikal Lake, Russia) in Asia are described here. The lizard fauna consists of two clades, Lacertidae and Scincidae. The skink material is allocated to Chalcides. While this taxon was previously reported from Europe, it has rarely been observed in the Neogene record with only jaw fragments and frontal bones described. Its taxonomy was therefore enigmatic. The Tagay material is almost identical to the European fossils of Chalcides from Austria and Hungary, but it also contains the parietal bone. While the material is also similar to the extant Ch. ocellatus, it exhibits several morphological differences. A new species is therefore erected-Chalcides augei sp. nov. These findings further support the connection of the Baikal Lake area with central Europe during the first half of the Miocene. The comparative anatomy of the frontals, parietals and lower jaws was evaluated by micro-CT in selected skink taxa. This comparison highlights several important differences, for example, paired frontals are present in Broadleysaurus (an outgroup taxon), in Acontias and all studied members of Scincidae herein. The character optimization in Mesquite supports fused frontals as being the condition at the basal node of the Ateuchosauridae + Sphenomorphidae + Eugongylidae + Lygosomidae + Egerniidae + Mabuyidae clade. While the parapineal foramen is restricted to the parietal in most taxa studied herein, it is absent (or vestigial) in Acontias and Feylinia. In contrast to all other skinks, this foramen is located on the frontal in Ateuchosaurus chinensis. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:1901-1934, 2020. © 2019 American Association for Anatomy., (© 2019 American Association for Anatomy.)