


Том 24, № 2 (2016)
- Год: 2016
- Статей: 7
- URL: https://ogarev-online.ru/0869-5938/issue/view/10987
Article
Age range of formation of sedimentary-volcanogenic complex of the Vetreny Belt (the southeast of the Baltic Shield)
Аннотация
As a result of studying the Vetreny Belt greenstone structure (the southeast of the Baltic Shield), zircons from terrigenous deposits of the Toksha Formation, underlying the section of the sedimentary-volcanogenic complex, and zircons of the Vetreny Belt Formation, deposits of which crown the section, were dated. The results of analysis of age data of detrital zircons from quartzites of the Toksha Formation indicate that Mesoarchean greenstone complexes and paleo-Archean granitogneisses of the Vodlozero Block (Karelia) were the provenance area from which these zircons were derived. The occurrence of the youngest zircons with age of 2654.3 ± 38.5 Ma is evidence that the formation of the Vetreny Belt, including the Toksha Formation, began no earlier than this time. Zircons from volcanic rocks of the Vetreny Belt yielded the age of 2405 ± 5 Ma. Thus, the age interval of the formation of the sedimentary-volcanogenic complex of the Vetreny Belt ranges from 2654.3 ± 38.5 to 2405 ± 5 Ma.



Middle Triassic pteridosperms (Pinophyta) of the Timan–Pechora basin
Аннотация
The collection of fossil plants sampled by geologists from VNIGRI at the end of the 20th century from Triassic continental sections drilled by many wells and cropping out in several natural localities and stored at the Museum of Petroleum Geology and Paleontology of the same institute was critically revised. The use of the epidermal method for the study of plant remains with consideration of recent publications dedicated to continental sections of Central Europe made it possible to substantially broaden the taxonomic composition of the Triassic flora and first specify the composition of its pteridosperm representatives. Unlike the Triassic floras of Western Europe, the pteridosperms the Pechora region appeared to be relatively diverse. They number 37 species of 11 genera, which are confined to the upper part of the Triassic sequence: Anguran and Naryan-Mar formations and their analogs. The Middle Triassic, mainly, Ladinian, age of these formations is reliably substantiated both by paleontological (vertebrate and palynological) data and by results of the comparative analysis of the Anguran–Naryan-Mar taphofloras and coeval European type floras dated back to the Anisian–Ladinian by marine faunal remains. The stratigraphic significance of pteridospermous plant remains becomes undoubted for continental sections of the Timan–Pechora basin, while the genera Scytophyllum, Kalantarium, and Kirjamkenia may be considered with respect to their diversity and abundance as representing orthostratigraphic taxa.



Radiolarian-Based zonal scheme of the cretaceous (Albian–Santonain) of the Tethyan regions of Eurasia
Аннотация
A scheme of radiolarian zonal subdivision is proposed for the upper Albian–Santonian of the Tethyan regions of Eurasia. The upper Albian contains one zone: Crolanium triangulare; the Cenomanian contains three zones: Patellula spica (lower Cenomanian), Pseudoaulophacus lenticulatus (middle Cenomanian), and Triactoma parva (upper Cenomanian); the Turonian contains four zones: Acanthocircus tympanum (lower Turonian (with no upper part)), Patellula selbukhraensis (upper part of the lower Turonian), Phaseliforma turovi (middle Turonian (with no upper part)), and Actinomma (?) belbekense (upper part of the middle Turonian–upper Turonian); the Coniacian contains two zones: Alievium praegallowayi (lower part of the Coniacian) and Cyprodictyomitra longa (upper part of the Coniacian); the Santonian contains three zones: Theocampe urna (lower Santonian), Crucella robusta (middle Santonian–lower part of the upper(?) Santonian), and Afens perapediensis (upper part of the upper Santonian). The biostratigraphic subdivisions are correlated with biostrata in the schemes proposed previously for the Tethys and Pacific. A new species Patellula selbukhraensis Bragina sp. nov. is described.



Biostratigraphy of the Çeşmeler and Elmalι Dere formations: First records of upper Cretaceous planktonic foraminifera and radiolarians from the Eastern Pontides (Maçka, Trabzon, Turkey)
Аннотация
Upper Cretaceous pelagic deposits outcropping in the Maçka (Trabzon) region include radiolarians and pelagic foraminifera. The Çatak Group represented by the volcano-sedimentary successions consists of three formations having different properties. Two sections, ÇTK1 and ÇTK2, are selected from the Çe meler and Elmalι Dere formations, respectively, establishing the biostratigraphy of outcropping sedimentary units. A total of 17 species of Whiteinella, Helvetoglobotruncana, Marginotruncana, Dicarinella, Praeglobotruncana, Archaeoglobigerina and Hedbergella demonstrating the early Turonian–Coniacian are established in the ÇTK1 stratigraphic section. The early Turonian radiolarian fauna consisting of Halesium sexangulum Pessagno, 1971, Crucella cachensis Pessagno, 1971, Stichomitra communis Squinabol, 1903 is also defined in the same section. A total of 30 species of Crucella, Halesium, Pessagnobrachia, Patulibracchium, Alievium, Archaeospongoprunum, Dicyomitra, Stichomitra, Diacanthocapsa, Dactiyliodiscus, Amphipydax, Pseudoaulophocus, Acaeniotyle, Archaeodictyomitra, Actinomma, Xitus, Neosciadocapsidae characterizing the early and late Turonian, as well as the Coniacian–early Santonian are recognized from red-coloured pelagic limestones of the ÇTK2 section. Also, planktonic foraminifera species of Marginotruncana, Hedbergella, Heterohelix, Globotruncana, Globotruncanita, Archaeoglobigerina, Dicarinella characterizing the Coniacian–Santonian are described in the thin sections of the same samples. The age of red-coloured limestones is identified as the Coniacian–Santonian benefit from radiolarians and pelagic foraminifera. Consequently, radiolarians and pelagic foraminifera within sedimentary successions of the investigation area are distributed in two intervals that coincide with the early Turonian–Coniacian and Coniacian–Santonian intervals.



New data on age of the Pleistocene fauna from the Trlica locality (Montenegro, Central Balkans) and its correlation with other faunas of Europe
Аннотация
New data specifying the age of the fauna from the Trlica locality near Pljevlja (Montenegro, Central Balkans) derived from material of excavations in 2010–2014 are discussed with the biostratigraphic analysis of two defined faunal levels TRL11–10 and TRL6–5 and its correlation with other faunas of Europe. It is shown that the fauna from the lower faunal level (TRL11–10) is correlative with the second half of the Early Pleistocene (Late Villafranchian, Zone MNQ 18, while the fauna from the upper faunal level existed in the post-Villafranchian time and its age is estimated to be the early Middle Pleistocene (MIS 19), not older.



Subrecent spore–pollen spectra from the Lower Kolyma River basin and their importance for the reconstruction of the Quaternary paleogeography of the region
Аннотация
Spore–pollen spectra of surface samples characterizing different plant associations in the Lower Kolyma River basin are studied. The formation features of the studied spore–pollen spectra are determined, as well as their potential for past vegetation reconstruction, paleogeographic constructions, and stratigraphic correlation of Quaternary deposits in Northeastern Russia.



Short Communications
Early Vendian stage of folding in the Patom folded zone: Syn-folded clastic dikes in the Dalnetaiginsky Group, Central Siberia
Аннотация
This work describes clastic dikes which intruded along cleavage planes into Lower Vendian clay shales of the Barakun Formation (the eastern part of the Patom folded zone). Dikes are composed of sandstones, which are common in other parts of the Barakun Formation, or more often by thin intercalations of finely oolitic limestones in surrounding shales. It is evident that dikes were formed as a result of elision processes synchronous to the folding, the major system of cleavage planes, and dehydration of clayey rocks of the Dalnetaiginsky Group at the end of Early Vendian. This stage of folding can be considered as one of the first phases of the Baikal folding by N.S. Shatsky.


