青岛地区边界层结构的数值模拟

本文建立了一个非静力的三维细网格边界层模式，对青岛地区复杂下垫面条件下的边界层结构和湍流特征作了数值模拟，模式采用能量闭合方案，舍弃了静力近似，以提高空间分辨率和模式精度。模拟以实测资料为初始输入，对该地区风场和湍流场作了较细致的模拟分析，与观测资料相比，结果合理地一致。结果表明了陡峭地形和不规则海岸线对局地风场和湍流场影响很大。     

Geometrical textures of faults，evolution of physical field and instability characteristics

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Present situation of the research and application of engineering multiwave seismic prospecting in China

ＰｒｅｓｅｎｔｓｉｔｕａｔｉｏｎｏｆｔｈｅｒｅｓｅａｒｃｈａｎｄａｐｐｌｉｃａｔｉｏｎｏｆｅｎｇｉｎｅｅｒｉｎｇｍｕｌｔｉｗａｖｅｓｅｉｓｍｉｃｐｒｏｓｐｅｃｔｉｎｇｉｎＣｈｉｎａＸＩＡＯ－ＰＩＮＧＷＵ（吴小平），ＨＯＮＧ－ＲＵＺＨＡＯ（赵鸿儒）（Ｄ...     

New data on the geology and age of the Koreyskaya River area (south Sikhote-Alin)

Abstract The geological structure of the Koreyskaya River area exhibits a complex combination of turbidite—olistostrome deposits making up a matrix and synsedimentary tectonic enclosures represented by allochthons of formations different in age and genesis. Three tectono-stratigraphic units can be distinguished, that have been combined into a single section by accretion. New data on radiolarians have been used to date the tectonic enclosures and matrix. Abundant Mesozoic radiolarians (from Triassic to Late Jurassic) and also Late Permian radiolarians were found in cherty and siliceous mudstone olistoliths and cherty allochthons.     

Mesozoic radiolarians and radiolarian-bearing sequences in the circum-Pacific regions: A report of the symposium-'Radiolarians and Orogenic Belts'

Abstract This paper contains extended abstracts of the seven papers presented at the symposium 'Radiolarians and Orogenic Belts' held at the seventh meeting of the International Association of Radiolarian Paleontologists (INTERRAD). Important results of the symposium include the following: (1) Upper Paleozoic and Mesozoic cherts are widely distributed within accretionary complexes in the circum-Pacific orogenic belt. Radiolarian dating reveals that long durations of chert sedimentation in a pelagic environment are recorded on both sides of Pacific-rim accretionary complexes (e.g. New Zealand, Japan, Russian Far East, Canadian Cordillera). (2) Triassic radiolarian faunas from New Zealand and the Omolon Massif, northeast Siberia are similar in composition and are characterized by the absence of typical Tethyan elements. This suggests that radiolarian faunal provincialism may have been established as early as the Triassic. High-latitude radiolarian taxa exhibit a bi-polar distribution pattern. (3) The Lower Triassic interval in chert dominant pelagic sequences is mechanically weaker than other levels and acted as a décollement in accretionary events. This lithologic. contrast in physical property is considered to reflect radiolarian evolution, such as the end-Permian mass extinction.     

Episodic accretion and metamorphism of Jurassic accretionary complex based on biostratigraphy and K-Ar geochronology in the western part of the Mino-Tanba Belt, Southwest Japan

Abstract The low grade metamorphic Jurassic accretionary complex in the western part of the Mino-Tanba Belt, Southwest Japan, is a chaotic sedimentary complex which consists of argillaceous matrices with allochthonous blocks of chert, greenstone, siliceous mudstone, terrigenous sandstone and mudstone. The complex is divided into three distinct geologic units, Units I, II and III, with a tectonic boundary (thrust) between them, forming a pile-nappe structure. They have different features for lithologies, fossil age, metamorphic condition and K-Ar age. Microfossil researches revealed that their timings of accretion were in the early Early Jurassic ( ca 195 Ma) for Unit III, in the early Middle Jurassic ( ca 175 Ma) for Unit II and in the latest Late Jurassic (ca 147 Ma) for Unit I. On the other hand, K-Ar age determinations of white mica separated from pelitic rocks of the three units clarified that the subsequent subduction-related metamorphism was 23 million years after the accretion of each unit. These results strongly suggest that the accretionary and metamorphic process had taken place episodically with an interval of 20 to 28 million years during Mesozoic time in the western part of the Mino-Tanba Belt, Southwest Japan.     

Holocene lake-level fluctuations and beach-ridge development along the northern shore of Lake Michigan, USA

Geomorphology of a beach-ridge complex and adjacent lake basins along the northern shore of Lake Michigan records fluctuations in the level of Lake Michigan for the last 8000 to 10 000 ¹⁴C yr B.P. (radiocarbon years Before Present). A storm berm at 204.7–206 m (671.6–675.9 ft) exposed in a sandpit provides evidence of a pre-Chippewa Low lake level that is correlated with dropping water levels of Glacial Lake Algonquin (c. 10 300–10 100 ¹⁴C yr B.P.). Radiocarbon dates from organic material exposed in a river cutbank and basal sediments from Elbow Lake, Mackinac Co., Michigan, indicate a maximum age of a highstand of Lake Michigan at 6900 ¹⁴C yr B.P., which reached as high as 196.7 m (645 ft), during the early-Nipissing transgression of Lake Michigan. Basal radiocarbon dates from beach swales and a second lake site (Beaverhouse Lake, Mackinac Co.) provide geomorphic evidence for a subsequent highstand which reached 192.6 m (632 ft) at 5390±70 ¹⁴C yr B.P.Basal radiocarbon dates from a transect of sediment cores, along with tree-ring data, and General Land Office Surveyor notes of a shipwreck, c. A.D. 1846, reveal a late-Holocene rate for isostatic rebound of 22.6 cm/100 radiocarbon years (0.74 ft/100 radiocarbon years) for the northern shore of Lake Michigan, relative to the Lake Michigan-Lake Huron outlet at Port Huron, Michigan. Changes in sediment stratigraphy, inter-ridge distance, and sediment accumulation rates document a mid- to late-Holocene retreat of the shoreline due to isostatic rebound. This regression sequence was punctuated by brief, periodic highstands, resulting in progressive development over the past 5400 ¹⁴C yr of 75 pairs of dune ridges and swales each formed over an interval of approximately 72 years. Times of lake-level fluctuation were identified at 3900, 3200, and 1000 ¹⁴C yr B.P. based on changes in inter-ridge spacing, shifts in the course of Millecoquins River, and reorientation of beach-ridge lineation. Soil type, dune development, and selected pollen data provide supporting evidence for this chronology. Late-Holocene beach-ridge development and lake-level fluctuations are related to a retreat of the dominant Pacific airmass and the convergence of the Arctic and Tropical airmasses resulting in predominantly meridional rather than zonal air flow across the Great Lakes region.This is the 13th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.     

Contamination of a well in a uniform background flow

In this paper we describe the transport of pollution in groundwater in the neighbourhood of a well in a uniform background flow. We compute the rate at which contaminated particles reach the well as a function of the place of the source of pollution. The motion of a particle in a dispersive flow is seen as a random walk process. The Fokker-Planck equation for the random motion of a particle is transformed using the complex potential for the advective flow field. The resulting equation is solved asymptotically after a stretching transformation. Finally, the analytical solution is compared with results from Monte Carlo simulations with the random walk model. The method can be extended to arbitrary flow fields. Then by a numerical coordinate transformation the analytical results can still be employed.     

刘家坪杂岩体的岩石特征及时代

刘家坪杂岩体出露于扬子准地台西北边缘。该区扬子期岩浆活动,早期为刘家坪组海底喷发的中～酸性火山岩系,晚期先后侵入有角闪辉长岩—石英闪长岩—斜长花岗岩—辉绿岩脉。岩浆岩具有幔源岩浆及造山带地区火山岩的特征。据震旦系覆于刘家坪杂岩体之上,其底部砂砾岩的砾石中有杂岩体成分,以及杂岩体侵入于同位素年龄值为6.43亿年的刘家坪组之中,认为刘家坪杂岩体时代为前震旦纪。