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71.
Petrological, chronological and geotectonic geological analysis of Precambrian metamorphic rock in Korean Peninsula shows that the remnants ( 〉3.4 Ga) of continental nuclei crust were formed in the Paleoarchean in the Rangrim Massif. In the massif, the main formation ages of continental crust range from 3.2 Ga to 2.5 Ga, its important growing period was 2.8 - 2. 5 Ga. The subsequent expansion period of the Rangrim Massif was 2. 4 - 2. 2 Ga. The division events occurred in 1.85 Ga and in the Late Paleoproterozoic-Early Mesoproterozoic, respectively. Since then the massif was relatively stable. However, the last division of the Rangrim Massif occurred at 793 Ma. 相似文献
72.
Since Late Proterozoic era, the Korean Peninsula has been evolved into a state with relatively stable regions and orogenic beltswhich were developed differently each other. The Late Paleozoic (Late Carboniferous-Early Triassic) sediments are well developed in the Korean Peninsula, and called the Pyongan System. The Pyongan System from Late Carboniferous to Lower Triassic is distributed in the Pyongnan and Hyesan-Riwon Basins, and Rangrim Massif, and divided into Hongjom (C2 ) , Ripsok (C2 ) , Sadong (C2-P1 ) , Kobangsan and Rokam ( Taezhawon) ( P2-T1 ) sequences. The sediments of the Tumangang Orogenic Belt are called Tuman System which is composed of the Amgi Series, consisting of clastic formation with mafic effusive material, overlaid by the Kyeryongsan Series, consisting mainly of mafic volcano sediments. The Songsang Series which rests on the Kyeryongsan Series mainly consists of clastic formation with minor felsic effusive material. In the Tuman- gang Orogenic Belt the tectonic movement, called Tumangang Tectonic Movement, occurred in the Lower Permian-Lower Triassic. 相似文献
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75.
KIM AARIS-SBRENSEN 《Boreas: An International Journal of Quaternary Research》1995,24(4):355-365
Investigations at a Late Weichselian freshwater basin in northwestern Jutland, Denmark, yielded a fairly rich assemblage of vertebrate remains, mostly bones and teeth of small mammals. The remains are primarily allochthonous and the bones have been subjected to different taphonomic pathways and agents. AMS 14 C-dates on terrestrial organic remains provided ages of Middle to Late Allerød time. Identifications revealed the first fossil record in Scandinavia of Rana arvalis, Sorex minutus, Ochotona cf. pusilla, Microtus gregalis, Microtus oeconomus , and Sicista cf. betulinu. Spermophilus cf. major and Desmana moschata , previously found only once and twice respectively, were retrieved, and Sorex araneus and Arvicola terrestris were recovered for the first time beyond the Atlantic chronozone. Ecologically, the Nørre Lyngby small mammal fauna can be characterized by its very high and almost equal proportions of boreal forest and steppe elements followed by a relatively high proportion of tundra elements. The fossil species share a modern area of sympatry north of the Caspian Sea from the river Volga in the west to the southern and western slopes of the Urals. If, however, the large Allerød mammals are added, the fauna is without modern analogues. The Nørre Lyngby fauna can be seen as a last expansion of the North European glacial fauna. Provided that an absolute chronology and a differentiated sea-level curve for the area can be established, the Nsrre Lyngby fauna could become important for studies in mammalian dispersal and migration rates. 相似文献
76.
Based on the maximum-entropy(ME)principle,a new power spectral estimator for random waves is derived in the form of S~(ω)=a/8H~2(2π)~(d 1)ω~-~((d 2))exp[-b(2π/ω)~n],by solving a variational problem subject to some quite general constraints.This robust method is comprehensive enough to describe the wave spectra even in extreme wave conditions and is superior to periodogram method that is not suitable to process comparatively short or intensively unsteady signals for its tremendous boundary effect and some inherent defects of FFT.Fortunately,the newly derived method for spectral estimation works fairly well,even though the sample data sets are very short and unsteady,and the reliability and efficiency of this spectral estimator have been preliminarily proved. 相似文献
77.
Shu-Qing YANG In-Soo KIM Daniel S. KOH Young-Chae SONG 《中国海洋工程》2005,19(4):557-570
The aim of this paper is to present an analytical expression for the streamwise velocity distribution in a non-uniform flow in the presence of waves; the correlation between the horizontal and vertical velocity components has been compreheusively examined. Different from previous researches which attributed the deviation of velocity from the classical log-law to the wave Reynolds stress, i.e. - ρ uv^- only, this study demonstrates that the momentum flux caused by mean velocities, i.e., u^- and v^-, is also responsible for the velocity deviation, and it is found that the streamwise velocity for a flow in the presence of non-zero wall-normal velocity does not follow the classical log-law, but the modified log-law proposed in this study based on simplified mixing-length theorem. The validity of the modified log-law has been verified by use of available experimental data from published sources for combined wave-current flows, and good agreement between the predicted and observed velocity profiles has been achieved. 相似文献
78.
Jang-Woon WANG Jae-Jin KIM Wonsik CHOI Da-Som MUN Jung-Eun KANG Hataek KWON Jin-Soo KIM Kyung-Soo HAN 《大气科学进展》2017,34(12):1404-1414
This study investigated the flow characteristics altered by Jang Bogo Antarctic Research Station using computational fluid dynamics(CFD) modeling. The topography and buildings around Jang Bogo Station were constructed with computeraided-design data in the CFD model domain. We simulated 16 cases with different inflow directions, and compared the flow characteristics with and without Jang Bogo Station for each inflow direction. The wind data recorded by the site's automatic weather station(AWS) were used for comparison. Wind rose analysis showed that the wind speed and direction after the construction of Jang Bogo Station were quite different from those before construction. We also investigated how virtual wind fences would modify the flow patterns, changing the distance of the fence from the station as well as the porosity of the fence. For westerly inflows, when the AWS was downwind of Jang Bogo Station, the decrease in wind speed was maximized(-81% for west-northwesterly). The wind speed reduction was also greater as the distance of the fence was closer to Jang Bogo Station. With the same distance, the fence with medium porosity(25%–33%) maximized the wind speed reduction.These results suggest that the location and material of the wind fence should be selected carefully, or AWS data should be interpreted cautiously, for particular prevailing wind directions. 相似文献
79.
In this study, the correlation between simulated and measured radar velocity spectrum width(σv) is investigated. The results show that the dendrites growth zones(DGZs) and needles growth zones(NGZs) mostly contain dendrites(DN) and needles(NE), respectively.Clear σv zones(1.1 < σv(m s–1) < 1.3 and 0.3 < σv(m s–1) < 0.7 for the DGZ and NGZ, respectively) could be identified in the case studies(27 and 28 February 2016) n... 相似文献
80.
LEE Jeong-Hyun KIM Byeong-Jun LIANG Kun PARK Tae-Yoon S. CHOH Suk-Joo LEE Dong-Jin WOO Jusun 《《地质学报》英文版》2016,90(6):1946-1954
Mid to late Cambrian thrombolites and maze-like maceriate reefs from the western North China Platform, Wuhai, Inner Mongolia, northwestern China, occur in the middle of a succession dominated by thin-bedded lime mudstone-shale/marlstone alternations, and are laterally surrounded by limestone conglomerate and/or grainstone. Thrombolite, characterized by meter-scale lenticular mounds composed of millimeter- to centimeter-scale mesoclots and wackestone matrix, occurs in the lower middle part of the sequence. Thrombolite mesoclots are composed of microstromatolites with alternating dark gray and light gray micritic laminae. The maze-like maceriate reefs occur in the middle to the upper part of the sequence, commonly forming lenticular mounds up to 1 m thick. They are characterized by centimeter- to decimeter-scale branched maze-like structures, whose biogenic portions (maceria) are selectively dolomitized. The maceriae are composed of poorly preserved microstromatolites and siliceous sponges. Inter-macerial sediments consist of lime mud and scattered bioclasts. These Wuhai reefs are generally similar to but older than various other Cambrian reefs previously reported from the Shandong region, northeastern China. 相似文献