The Brunhes-Matuyama boundary in Western Beringia: a review

Early-Middle Pleistocene deposits have been studied in Central and Northern Yakutia, the Magadan region, and Chukotka. The Brunhes-Matuyama boundary occurs in the Ozheleznenye Galechniki (=Ferruginated pebblestones) beds of Central Yakutia that belong to the Talagay horizon of the Early-Middle Pleistocene. These layers include classic Aldan mammal fauna. In Eastern Yakutia sediments of Early-Middle Pleistocene belong to the Akan horizon, and the Early Pleistocene sediments are from the Chukochya horizon. These sediments which belong to the Olyor Formation and its age-equivalents yielded numerous mammal remains, termed the Olyor faunal complex. The Brunhes-Matuyama boundary is located in Akan horizon. In the upper reaches of the Kolyma River, the Brunhes-Matuyama boundary occurs in sediments of the Middle Pleistocene Belichan horizon. The boundary of the Brunhes-Matuyama is characteristic within the Elhkakvun and Enmakay formations of Chukotka. In Kamchatka, the boundary of Matuyama and Brunhes is evident in volcanic sequences. In the eastern part of the peninsula, this boundary is located in the Tumrok or Iult volcanic complex and in Central Kamchatka in the Kreruk volcanic complex.     

Platinum‐group elements and rhenium in mantle xenoliths from the East Sayan volcanic field (Siberia,Russia): evaluation of melt extraction and refertilization processes in lithospheric mantle of the Tuva‐Mongolian massif

We determined the concentrations of platinum‐group elements (PGE) and rhenium in granular spinel lherzolites entrained as xenoliths in the Late Cenozoic volcanic rocks of the East Sayan within the Sarkhoi palaeo‐arc block of the Tuva‐Mongolian massif. Major element, PGE and rhenium variations in the East Sayan xenoliths can be explained by impregnation of up to 15% of arc‐type melt into initially depleted mantle harzburgite. Such a refertilization process probably took place in the Middle Neoproterozoic, when the Tuva‐Mongolian massif was in a subduction environment. East Sayan xenoliths show close similarities to Vitim xenoliths, whose host basalts erupted within an off‐cratonic crustal block. Both East Sayan and Vitim xenoliths are different from cratonic and circum‐cratonic peridotite xenoliths of worldwide localities.     

Tectonics of the Northern Urals and Western Siberia: General History of Development

Geotectonics - A review of the materials obtained over the past decade on the geology and tectonics of the North Urals and its continuation in the basement of the West-Siberian Plate allows us to...     

Seismic evidence for gas accumulation related to the area of mud volcanism in the deep Black Sea

 Bright spots were observed on seismic time sections acquired in 1991 and 1993 during cruises carried out within the UNESCO-ESF Training-through-Research (TTR) program in the deep Black Sea mud volcanic area. We demonstrate the results of detailed study of the anomalous reflections, which indicate that gas is responsible for the bright spots in the study area. Most of the bright spots are characterized by inverted polarity and enlarged elastic energy attenuation.     

Distribution, stocks, and age structure of the invader Mya arenaria before and after mass mortalities in the Black Sea

The distribution, stocks, and age structure of the invader soft-shell clam Mya arenaria populations before and after the mass mortalities in the northwestern Black Sea have been studied from 1967 to 1987. At the prolonged influence of mortalities from 1973 to 1985, the number of age classes decreased from six in the period before the mortalities to three in 1985. The restoration of the stocks of Mya arenaria and the possibility of fishing these mollusks after the improvement of the ecological state in this part of the sea are predicted.     

A Comprehensive Study of the Perseid Stream Bolide Using the Data of the SkyLine Baseline Video Monitoring System

Astronomy Reports - We carried out a detailed study of a bright meteor detected over the Khamar-Daban mountain range on August 12, 2020 at 14:37:35 UT by two automatic video monitoring stations...     

The Time of Rock Formation in the Talakhtakh Diatreme (Arctic Siberia) according to Laser 40Ar/39Ar Dates

Doklady Earth Sciences - As a result of comprehensive study and laser 40Ar/39Ar dating of sanidines from the rocks of the Talakhtakh diatreme (TD) (Arctic Siberia), it has been found that the...     

Segmental closure of the Mongol-Okhotsk Ocean: Insight from detrital geochronology in the East Transbaikalia Basin

The Late Paleozoic–Early Mesozoic Mongol-Okhotsk Ocean extended between the Siberian and Amur–North China continents.The timing and modalities of the oceanic closure are widely discussed.It is largely accepted that the ocean closed in a scissor-like manner from southwest to northeast(in modern coordinates),though the timing of this process remains uncertain.Recent studies have shown that both western(West Transbaikalia)and eastern(Dzhagda)parts of the ocean closed almost simultaneously at the Early–Middle Jurassic boundary.However,little information on the key central part of the oceanic suture zone is available.We performed U-Pb(LA-ICP-MS)dating of detrital zircon from wellcharacterized stratigraphic sections of the central part of the Mongol-Okhotsk suture zone.These include the initial marine and final continental sequences of the East Transbaikalia Basin,deposited on the northern Argun-Idemeg terrane basement.We provide new stratigraphic ages for the marine and continental deposits.This revised chronostratigraphy allows assigning an age of~165–155 Ma,to the collisionrelated flexure of the northern Argun-Idemeg terrane and the development of a peripheral foreland basin.This collisional process took place 5 to10 million years later than in the western and eastern parts of the ocean.We demonstrate that the northern Argun-Idemeg terrane was the last block to collide with the Siberian continent,challenging the widely supported scissor-like model of closure of the MongolOkhotsk Ocean.Different segments of the ocean closed independently,depending on the initial shape of the paleo continental margins.     

A Comparison Between Machine Learning and Functional Geostatistics Approaches for Data-Driven Analyses of Sediment Transport in a Pre-Alpine Stream

Mathematical Geosciences - The problem of providing data-driven models for sediment transport in a pre-Alpine stream in Italy is addressed. This study is based on a large set of measurements...