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S. V. Rud’ko 《Lithology and Mineral Resources》2018,53(4):307-323
The paper presents results of the lithological study of Upper Jurassic limestones, flyschoids and limestone breccias on the southern side of the Baidar Valley in the Crimean Mountains. Study of the microfacies revealed that the limestones are represented by deposits on lagoons, platform edge shoals, reefs, and forereef aprons on the carbonate platform slope. Flyschoids include deposits in the distributive turbidite channels and hemipelagic sediments in the deep-water part of the basin. Limestone breccias were formed by gravitation flows on the carbonate platform toe-of-slope and slope. The presence of gravitation deposits in the Upper Jurassic carbonate complexes of the Crimean Mountains can testify to the primary clinoform structure of this sedimentary sequence. Comparison of the obtained sedimentological data made it possible to reconstruct the facies model of the Crimean carbonate platform and main episodes of its formation. Development of the carbonate shelf was related to two transgressive-regressive cycles. A dome-shaped reef was formed away from the coast at the initial (Oxfordian) stage. The carbonate platform was formed at the early Kimmeridgian lowstand stage when sediments were deposited in the internal part of the platform adjacent to land. In the late Kimmeridgian and early Tithonian, configuration of the carbonate platform profile resembled a distally steepened ramp, and its active progradation and shelf expansion took place in the course of transgression. Regression in the late Tithonian–early Berriasian led to regressive transformation of the ramp into platform with a flattened shallow-water shelf. Tectonic deformations at the Jurassic/Cretaceous transition promoted the formation of megabreccias on the carbonate platform foreslope. The tectonically reworked rock sequence of the “extinct” carbonate platform was overlapped transgressively by the upper Berriasian or lower Valanginian, relatively deep-water deposits of the Cretaceous platform cover. 相似文献
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Christian Kronborg Henry Bender Regnar Bjerre Rud Friborg Hans O. Jacobsen Lars Kristiansen Poul Rasmussen Poul R. Sørensen Gunnar Larsen 《Boreas: An International Journal of Quaternary Research》1990,19(3):273-287
Glaciostratigraphic investigations at one key locality (Haldum), 9 major and about 160 minor localities in East and Central Jutland, Denmark, together with laboratory work, have led to the establishment of a stratigraphy consisting of 10 till units, usually separated by meltwater deposits. The stratigraphy is in some degree supported by thermoluminescence datings. The complete sequence includes one till unit with associated meltwater deposits of Menapian age, three till units with intercalated meltwater deposits of Elsterian age, marine sediments deposited during the Holsteininan, and three till units with intercalated of Elsterian age, marine sediments deposited during the Holsteinian, and three till units with intercalated glaciofluvial sedimants of Saalian age. Eemian deposits are present above this level, and the whole sequence is capped by till and meltwater deposits related to three glacial advances during the Weichselian. 相似文献
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We analyze radio observations, magnetograms and extrapolated field line maps, Hα filtergrams, and X-ray observations of two
flare events (6 February 1992 in AR 7042 and 25 October 1994 in AR 7792) and study properties, evolution and energy release
signatures of sigmoidal loop systems. During both events, the loop configuration seen in soft X-ray (SXR) images changes from
a preflare sigmoidal shape to a relaxed post-flare loop system. The underlying magnetic field system consists of a quadrupolar
configuration formed by a sheared arcade core and a remote field concentration. We demonstrate two possibilities: a sigmoidal
SXR pattern can be due to a single continuous flux tube (the 1992 event). Alternatively, it can be due to a set of independent
loops appearing like a sigmoid (the 1994 event). In both cases, the preflare and post-flare loops can be well reproduced by
a linear force-free field and potential field, respectively, computed using preflare magnetograms. We find that thermal and
non-thermal flare energy release indicators of both events become remarkably similar after applying spatial and temporal scale
transformations. Using the spatial scaling between both events we estimated that the non-thermal energy release in the second
event liberated about 1.7 times more energy per unit volume. A two-and-a-half times faster evolution indicates that the rate
of the energy release per unit volume is more than four times higher in this event. A coronal type II burst reveals ignition
and propagation of a coronal shock wave. In contrast, the first event, which was larger and released about a 10 times more
energy during the non-thermal phase, was associated with a CME, but no type II burst was recorded. During both events, in
addition to the two-ribbon flare process an interaction was observed between the flaring arcade and an emerging magnetic flux
region of opposite polarity next to the dominant leading sunspot. The arcade flare seems to stimulate the reconnection process
in an `emerging flux-type' configuration, which significantly contributes to the energy release. This regime is characterized
by the quasiperiodic injection of electron beams into the surrounding extended field line systems. The repeated beam injections
excite pulsating broadband radio emission in the decimetric-metric wavelength range. Each radio pulse is due to a new electron
beam injection. The pulsation period (seconds) reflects the spatial scale of the emerging flux-type field configuration. Since
broadband decimetric-metric radio pulsations are a frequent radio flare phenomenon, we speculate that opposite-polarity small-scale
flux intrusions located in the vicinity of strong field regions may be an essential component of the energy release process
in dynamic flares. 相似文献
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Razumovskiy A. A. Novikov I. A. Ryazantsev A. V. Rud’ko S. V. Kuznetsov N. B. Yashunskiy Yu. V. 《Doklady Earth Sciences》2020,495(2):867-871
Doklady Earth Sciences - U–Th–Pb (SHRIMP II) isotopic dating of accessory zircons from Vendian (Ediacaran) ash tuffs of the Basa formation section (Asha Group, Southern Ural) was... 相似文献
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S. V. Rud’ko P. Yu. Petrov A. B. Kuznetsov A. V. Shatsillo O. L. Petrov 《Doklady Earth Sciences》2017,477(2):1449-1453
New data were obtained on δ13Сcarb and δ18O variations in the sequence of deposits of the Dal’nyaya Taiga series at the western and eastern flanks of the Ura anticline. The summary δ13С curve was plotted in view of the correlation of sequence–stratigraphic data of the basin analysis. A series of positive anomalies was found within the succession. Alternatives for global chemostratigraphic correlation of the Dal’nyaya Taiga series of the Ura uplift were considered. 相似文献
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The first finding of prints of the Vendian Beltanelloides sorichevae Sokolov 1965 in the lower part of the Barakun Formation confirms the Vendian age of the Far Taiga Group, Patom Complex. This finding also raises a problem concerning the lower propagation limit of Beltanelloides sorichevae. 相似文献
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N. B. Kuznetsov N. S. Priyatkina S. V. Rud’ko A. V. Shatsillo W. J. Collins T. V. Romanyuk 《Doklady Earth Sciences》2018,479(1):286-289
The main results are presented on U/Pb-isotope dating of 100 detrital zircons and, selectively, on the Lu/Hf-isotope system of 43 grains from sandstones of the Lopatinskii formation (the lower stratigraphic level of the Chingasan group). Ages from 896 ± 51 to 2925 ± 38 Ma were obtained with a pronounced maximum of ~1890 Ma in the curve of probability density, along with εHf estimates from +8.4 to–15.1, which allow one to throw doubt upon the molasse nature of the Lopatinskii formation. 相似文献
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