The upper Bajocian of the Crimean Mountains: Paleogeography and sedimentation conditions from palynological data

Based on the spore-pollen data, the mineral composition of clay rocks, analyzed structures and facies, and a general paleogeographic analysis, the sedimentation conditions and landscapes of islands located during the Late Bajocian in the region of the present-day the Crimean Mountains have been reconstructed. It is shown that the sublatitudinally elongated insular land zone had a width of 30 km, the heights of the islands were no more than 1 km, with steep mudflow-affected northern slopes and with an extensive river system on the southern slopes.     

Textural-structural,mineralogical, isotopic,and age characteristics of Jurassic terrigenous rocks of the northwestern Caucasus (the Belaya River section)

Results of the comprehensive study of structural, lithological, mineralogical, and isotopic characteristics of Lower Jurassic rocks exposed in the Belaya River valley (Adygeya) in meganticlinorium of the Greater Caucasus are presented. Deformation microstructures were studied. Lithological and textural-structural changes in sequences related to intense secondary transformations should affect the state of isotopic systems of rocks. To reveal basic trends in the evolution of isotopic systems, investigation using the K-Ar method was carried out. Clay fraction (less than 1 μm) separated from rocks and bulk samples were analyzed. Cleavage development, approximate value of rock contraction, and isotopic characteristics are compared with the available data on alteration of clay mineral assemblages. Relationship between the degree of rock deformation at the microlevel and calculated K-Ar ages has been established. K-Ar systems of clayey rocks indicate the age of cleavage formation and correspond to the Bajocian-Bathonian contraction period.     

Palaeopascichnids from the Upper Vendian Chernyi Kamen Formation of the Middle Urals (Perm Region)

Doklady Earth Sciences - In 2020–2021 the palaeopascichnid fossils were found in the Krasnaya Gorka Site (Shirokovsky Reservoir, Kosva River area, Perm Region), a type Vendian fossil locality...     

The Chenka sandstone Sequence (Lower Jurassic) of the Crimean Mountains: Stratigraphy and depositional environments

The position of the Chenka Sequence in the section, original data on its clay minerals, facies and structural parageneses with consideration of volcanic and climatic events, as well as the available published information provide grounds for accepting it as Pliensbachian-Toarcian in age. It is shown that the Chenka sandstones are a facies or group of facies deposited in deltaic-plain or delta-front environments and that it cannot be ranked as an autonomous formation or other stratigraphic unit.     

Fossil Coals (Gagates) from Pleistocene Sediments in Black Sea Terraces,Southeastern Crimea

Lithology and Mineral Resources - The marine Quaternary (Chaudian) terrace V in the outskirts of Sudak accommodates layers saturated with lenses and fragments of fossil coal scrutinized by the...     

Estimation of the Deformation Value in Terrigenous Rocks by the Random Cross-Section Method (Belaya River,Northern Slope of the Greater Caucasus)

The deformation value in the Lower and Middle Jurassic terrigenous rocks from the valley of the Belaya River (the northern slope of the Greater Caucasus) is quantified by the morpholology of the cleavage zones. The numeral determination of the axis ratios of the deformation ellipses by the Fry method is performed as well. It is shown that for a statistical sample of the random cross-sections of the thin sections in the terrigenous rocks with cleavage structure the deformation value can be estimated correctly. The method of random cross-sections described in this work can be used for the quantitative estimation of deformation in nonoriented samples of terrigenous rocks.     

Circulation conditions of the abnormally cold winter of 2005/06 over Siberia

Circulation conditions of the abnormally cold winter of 2005/06 in Eurasia, where the intensification of meridional flow was accompanied by frequent intrusions of cold air masses into midlatitudes and their subsidence in the lower troposphere, are studied. The development of deep upper-level cyclones over Siberia and the Urals was preceded by stratospheric warming and long-term blocking processes in the troposphere over Europe and Yakutia. Strong cyclonic wind shears and intensified jet streams were observed in the high-level convergence zone over Siberia. Generally the weakened westerly flow in the substantial atmosphere thickness, a reduced number of deep cyclones in the western Arctic sector, and stratospheric warming provide high predictability of short-term climate changes in Eurasia in the wintertime.     

The mineralogical,isotope (K–Ar), structural,and textural features of the Jurassic siliciclastic complex in various tectonic environments (Greater Caucasus,Chechnya, and Georgia)

The variations in the structural, textural, mineralogical, and geochemical (isotope) features of Lower to Middle Jurassic siliciclastic sediments along the Chanty-Argun River in Mountainous Chechnya and Georgia are discussed. This profile transects areas with various types of deformed sediments, from the northern comparatively weakly deformed and altered zone, to the southern zone of intense deformation and cleavage. Southward along the profile, these alterations are accompanied by the evolution of clay mineral assemblages, as well as polytypic modifications of micas and their crystallinity index. Increasing intensity of rock alteration and cleavage leads to a change of the K–Ar system, which results in a substantially rejuvenated isotope age of the sediments with a simultaneous increase of their stratigraphic age.     

Paleomagnetic,Sedimentological, and Isotopic Data on Neoproterozoic Periglacial Sediments of Siberia: A New Perspective on the Low-Latitude Glaciations Problem

Izvestiya, Physics of the Solid Earth - Abstract—Paleo- and rock magnetic, sedimentological, and isotope geochemical study is carried out for the carbonate member of Late Neoproterozoic...