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1.
Eocene paleomagnetism of the Caucasus (southwest Georgia): oroclinal bending in the Arabian syntaxis
The Caucasus is very important for our understanding of tectonic evolution of the Alpine belt, but only a few reliable paleomagnetic results were reported from this region so far. We studied a collection of more than 300 samples of middle Eocene volcanics and volcano-sedimentary rocks from 10 localities in the Adjaro–Trialet tectonic zone (ATZ) in the western part of the Caucasus. Stepwise thermal demagnetization isolates a characteristic remanent magnetization (ChRM) in 19 sites out of 31 studied. ChRM reversed directions prevail, and a few vectors of normal polarity are antipodal to the reversed ones after tilt correction. The fold test is positive too, and we consider the ChRM primary. Analysis of Tertiary declinations and strikes of Alpine folds in the Adjaro–Trialet zone and the Pontides in Northern Turkey shows a large data scatter; Late Cretaceous data from the same region, however, reveal good correlation between paleomagnetic and structural data. Combining Late Cretaceous and Tertiary data indicates oroclinal bending of the Alpine structures which are locally complicated with different deformation. The overall mean Tertiary inclination is slightly shallower than the reference Eurasian inclination recalculated from one apparent polar wander path (APWP), but agrees with other. This finding is in accord with geological evidence on moderate post-Eocene shortening across the Caucasus. We did not find any indication of long-lived paleomagnetic anomalies, such as to Cenozoic anomalously shallow inclinations further to the east in Central Asia. 相似文献
2.
The Pamir-Punjab syntaxis consists of two structural arcs with the crests facing northward—the Pamir and Hindu-Kush-Karakorum arcs. These arcs are mutually disharmonious, and the exterior (Pamir) arc is more tight, as compared to the inner one. Paleomagnetic study of the Pamir arc has shown that the structures of the future Pamirs had a northeastern strike in the Paleogene and Cretaceous, and they occurred on the eastern limb of the Darvaz-Kopetdag structural arc, whose crest faces south. The Pamir arc originated after the Paleogene during the process of the formation of the Pamir-Punjab syntaxis. Knowledge of the kinematics of the Pamir arc, combined with data on the geometry of the syntaxis and the character of its boundaries, enable us to choose a model of the development of the syntaxis. The process of “plastic flow” of crustal masses around the underthrusting segment of the Indian plate was likely of paramount importance. 相似文献
3.
V. S. Burtman 《Geotectonics》2012,46(3):185-211
The tectonic and geodynamic consequences of the collision between Hindustan and Eurasia are considered in the paper. The tectonic evolution and deformation of Tibet and the Tien Shan in the Late Cenozoic is described on the basis of geological, geophysical, and geodetic data. The factual data and their interpretation, which shed light on the kinematics of the tectonic processes in the lithosphere and the geodynamics of the interaction between the Tien Shan, Tarim, and Tibet are discussed. A geodynamic model of their interaction is proposed. 相似文献
4.
The geodynamics of the Pamir-Punjab syntaxis 总被引：1，自引：0，他引：1
V. S. Burtman 《Geotectonics》2013,47(1):31-51
The collision of Hindustan with Eurasia in the Oligocene-early Miocene resulted in the rearrangement of the convective system in the upper mantle of the Pamir-Karakoram margin of the Eurasian Plate with subduction of the Hindustan continental lithosphere beneath this margin. The Pamir-Punjab syntaxis was formed in the Miocene as a giant horizontal extrusion (protrusion). Extensive nappes developed in the southern and central Pamirs along with deformation of its outer zone. The Pamir-Punjab syntaxis continued to form in the Pliocene-Quaternary when the deformed Pamirs, which propagated northward, were being transformed into a giant allochthon. A fold-nappe system was formed in the outer zone of the Pamirs at the front of this allochthon. A geodynamic model of syntaxis formation is proposed here. 相似文献
5.
A. M. Korjenkov S. V. Abdieva V. S. Burtman L. A. Orlova D. Rust A. Tibaldi 《Geotectonics》2013,47(6):485-494
A paleoseismological study in the Talas-Fergana Fault Zone of the Tien Shan was accompanied by age determination of ancient seismic events. The calibrated radiocarbon datings of recent and buried soils allowed us to recognize the fault segments reactivated during strong earthquakes that occurred in the 14th- 16th centuries A.D. The magnitude of the paleoseismological event in the 16th century was no lower than 7.0 and no lower than IX in seismic intensity. 相似文献
6.
M. A. Levitan N. A. Belyaev M. V. Burtman J.-C. Duplessy T. A. Khusid 《Lithology and Mineral Resources》2003,38(6):564-575
It is shown that sediments accumulated in the Southern Novaya Zemlya Trench at both deglaciation and marine stages. Permanent sea ice sheet existed during the deglaciation, and glacier meltwater was intensely delivered to the bottom layer. Along with the dominant sediment supply from the Southern Island of Novaya Zemlya, southern continental sources also played a noticeable role at that stage. Seasonal sea ice freezing led to the formation of cold brines at the marine stage. Like paleoproductivity, these processes were irregular. Dissolution of calcareous benthic foraminiferal tests considerably intensified after about 7 ka BP owing to a stronger Atlantic water advection into the Western Arctic and consequent increase in paleoproductivity, whereas the relative role of southern sedimentary provenances decreased. Sedimentation rates were constant (45 cm/ka) during the entire marine stage. 相似文献
7.
The main differences and similarities between the tectonic features of the Urals and the Tien Shan are considered. In the Neoproterozoic and Early and Middle Paleozoic, the Ural and Turkestan oceanic basins were parts of one oceanic domain, with several distinct regions in which tectonic events took different courses. The Baltic continental margin of the Ural paleoocean was active, whereas the Tarim-Alay margin of the Turkestan ocean, similar in position, was passive. The opposite continental margin in the Urals is known beginning from the Devonian as the Kazakh-Kyrgyz paleocontinent. In the Tien Shan, a similar margin developed until the Late Ordovician as the Syr Darya block with the ancient continental crust. In the Silurian, this block became a part of the Kazakh-Kyrgyz paleocontinent. The internal structures of the Ural and Turkestan paleooceans were different. The East Ural microcontinent occurred in the Ural paleoocean during the Early and Middle Paleozoic. No microcontinents are established in the Turkestan oceanic basin. Volcanic arcs in the Ural paleoocean were formed in the Vendian (Ediacarian), at the Ordovician-Silurian boundary, and in the Devonian largely along the Baltic margin at different distances from its edge. In the Turkestan paleoocean, a volcanic arc probably existed in the Ordovician at its Syr Darya margin, i.e., on the other side of the ocean in comparison with the Urals. The subduction of the Turkestan oceanic crust developed with interruptions always in the same direction. The evolution of subduction in the Urals was more complicated. The island arc-continent collision occurred here in the Late Devonian-Early Carboniferous; the continent-continent collision took place in the Moscovian simultaneously with the same process in the Tien Shan. The deepwater flysch basins induced by collision appeared at the Baltic margin in the Famennian and Visean, whereas in the Bashkirian and Moscovian they appeared at the Alay-Tarim margin. In the Devonian and Early Carboniferous, the Ural and Turkestan paleooceans had a common active margin along the Kazakh-Kyrgyz paleocontinent. The sudduction of the oceanic crust beneath this paleocontinent in both the Urals and the Tien Shan started, recommenced after interruptions, and finally ceased synchronously. In the South Ural segment, the Early Carboniferous subduction developed beneath both Baltica and the Kazakh-Kyrgyz paleocontinent, whereas in the Tien Shan, it occurred only beneath the latter paleocontinent. A divergent nappe-fold orogen was formed in the Urals as a result of collision of the Kazakh-Kyrgyz paleocontinent with the Baltic and Alay-Tarim paleocontinents, whereas a unilateral nappe-fold orogen arose in the Tien Shan. The growth of the high divergent orogen brought about the appearance of the Ural Foredeep filled with molasse beginning from the Kungurian. In the Tien Shan, a similar foredeep was not developed; a granitic axis similar to the main granitic axis in the Urals was not formed in the Tien Shan either. 相似文献
8.
Provenances for the lithogenic part of the sandy fraction of sediments on the Yermak Plateau are located in northern Eurasia. Based on the study of heavy minerals, new indicators are proposed for the ice-rafted material and main systems of surficial water circulation (gyres of the Beaufort Sea and Polar and Siberian currents of the Transpolar drift). Interpretation of the grain size distribution of sediments of warm and cold stages is based on difference in mechanisms of sedimentary material introduction into sea ice. Episodes of the influx of Atlantic warm and saline waters via the Fram Strait into the Arctic Ocean are reconstructed based on CaCO3 content. The relationship between sedimentary materials transported by icebergs and sea ice during the last 190 ka is given. Hypotheses of the history of surficial circulation in the Arctic Ocean and discharges of Siberian rivers during this period are presented. 相似文献
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10.
Doklady Earth Sciences - This paper analyzes the rose diagrams of the directions of 439 faults of the Variscian province, 476 faults of the Caledonian province, and 603 presently active faults of... 相似文献