Silurian-Devonian and Jurassic Thermal Events in the Ordos Basin, China: Indications from K-Ar Dating on Illites   总被引：1，自引：0，他引：1  

Hans Ahrendt  Klaus Wemmer  Hans-J rgen Behr 《《地质学报》英文版》1996,70(4):435-447

In the Ordos basin, two distinct thermal events of different ages have been identified for the first time by means of K-Ar dating combined with illite crystallinity analysis. For the Late Triassic and Late Permian samples, the K-Ar ages of the < 0.2μm fractions (159-173 Ma) reflect an illitization age related to the Yanshanian movement and indicate a short thermal event in the Middle Jurassic; the K-Ar ages of the <2 μm fractions (210-308 Ma) are interpreted as mixed ages of detrital material and authigenic illites. The K-Ar ages of both < 0.2μm and < 2μm fractions of a Middle Cambrian sample (368 Ma and 419 Ma) correspond to the ages of the metamorphism and earliest granite intrusion in the northern Caledonian Qinling fold zone (380-420 Ma) and show a thermal event during Silurian-Devonian time.  相似文献   

Urbanization and agricultural intensification in the Lower Fraser River valley,: Impacts on water use and quality   总被引：2，自引：0，他引：2  

Ken J. Hall  Hans Schreier 《GeoJournal》1996,40(1-2):135-146

The Fraser River drains a quarter of the province of British Columbia and is renown as one of the greatest salmon rivers in the world. The Fraser watershed is under threat from rapid urbanization in its lower reaches as pollutants generated from domestic and industrial wastes, and stormwater runoff threaten the health of the aquatic ecosystem. Plans for secondary sewage treatment in the metropolitan area will reduce waste loadings of some contaminants, but rapid growth will soon offset these benefits. Intensive urbanization, spreading up the Lower Fraser valley, with a network of impervious roads and increased traffic volumes contribute pollutants in surface runoff that are difficult to control. Rapid growth in agrobusiness to provide fresh produce to the nearby markets has resulted in very high densities of farm animals and excessive use of fertilizers and pesticides on the land. These pollutants threaten the groundwater and many of the remaining salmonid streams in the lower valley. The Fraser Basin Management Program, the Fraser River Estuary Management Program, and a variety of government agencies are coordinating studies and analyzing issues and conflicts to develop a strategy for sustainable development in the region.  相似文献   

鄂尔多斯盆地志留—泥盆纪和侏罗纪热事件—伊利石K—Ar年龄证据   总被引：12，自引：2，他引：12  

赵孟为 Ahren.  H 《地质学报》1996,70(2):186-194

利用伊利石K-Ar测年法,结合伊利石结晶度分析,首次在鄂尔多斯盆地确定出两期不同时代热事件。晚三叠世和晚二叠世<0.2μm粒级的岩石样品的K-Ar年龄(159-173Ma)反映了与燕山运动有关的伊利石化年龄,指示有一期中侏罗世的热事件;其<2μm粒级的K-Ar年龄(210-308Ma)则被解释为碎屑物和自生伊利石的混合年龄。中寒武世<0.2μm和<2μm粒级的岩石样品K-Ar年龄(368Ma与419Ma)对应于北秦岭加里东褶皱带变质作用与最早期花岗岩侵入的时代(380-420Ma),表明在志留-泥盆纪发生了一期热事件。  相似文献   

V_pIV_s ratio structure of the Lofoten continental margin, northern Norway, and its geological implications     

Shuichi Kodaira  Martin Bellenberg    Takaya Iwasaki    Toshihiko Kanazawa    Hans B. Hirschleber  Hideki Shimamura 《Geophysical Journal International》1996,124(3):724-740

  相似文献   

Theoretical and numerical analyses of pore-fluid flow focused heat transfer around geological faults and large cracks     

Chongbin Zhao  Bruce E. Hobbs  Alison Ord  Peter Hornby  Hans Mühlhaus  Shenglin Peng 《Computers and Geotechnics》2008,35(3):357-371

In this paper, theoretical and numerical methods are used to investigate pore-fluid flow focused temperature distribution patterns around geological faults and cracks of any length-scales in hydrothermal systems. If the far field inflow is uniform and the long axis of an elliptical fault of any length-scale is parallel to the far field inflow direction, a complete set of analytical solutions has been presented for the pore-fluid velocity, stream function and excess pore-fluid pressure around the elliptical fault embedded in fluid-saturated porous media. Because the analytical solutions are explicitly expressed in the conventional Cartesian coordinate system, not only can they be used to gain a theoretical insight into the pore-fluid flow patterns around geological faults and large cracks, but also they can be used as valuable benchmark solutions for validating any numerical methods. After a finite element computational model is validated by comparing the numerical solutions with the present analytical solutions, it is used to investigate pore-fluid flow focused heat transfer around geological faults in hydrothermal systems. Some interesting conclusions in relation to the effects of geological faults on pore-fluid flow focused heat transfer have been made through both the theoretical and the numerical analyses.  相似文献   

100 years Jura décollement hypothesis: how it affects Steinmann’s (1892) “Schwarzwaldlinie”     

Hans Laubscher 《International Journal of Earth Sciences》2008,97(6):1231-1245

Steinmann, then professor of geology at Freiburg (Germany), more than a 100 years ago wondered about the southern end of the extensional Rhinegraben and proposed that elements of the graben penetrated the contractional Jura. In particular, he recognized the "Schwarzwaldlinie” in the southern prolongation of the eastern border of the southern Rhinegraben, a line-up of topographic as well as structural irregularities. He conjectured that it was caused by normal faults of the Rhinegraben system. Subsequently—100 years ago—Buxtorf (1907) proposed the hypothesis, that the Jura was a thin-skinned nappe sheared off on Triassic evaporites. In the autochthonous basement underneath the wrinkled skin, the ``Schwarzwald line” is difficult to define. It probably consists of a gentle flexure punctuated by faults that approximately coincides with Steinmann’s original projection, although he sought to identify its constituent faults in the badly deformed allochthonous skin. Current data place the thin-skin elements of the Schwarzwald line in a more westerly, allochthonous position where most of them were reactivated into sinistrally transpressional structures.  相似文献   

A new ophiuroid (Geocoma schoentalensis sp. nov.) from the Middle Jurassic of northwestern Switzerland and remarks on the family Aplocomidae Hess 1965     

Hans Hess  Christian A. Meyer 《Swiss Journal of Geoscience》2008,101(1):29-40

A new ophiuroid species from the Hauptrogenstein Formation (Middle Jurassic, Bajocian) of the Rehhag ridge near Schöntal, northwestern Switzerland, is described based on 34 specimens. The impression of an indeterminate astropectinid sea star has also been found. The fully articulated specimens have been smothered by mobile oolitic dunes or sandwaves. The site can be genetically classified as an obrution deposit and belongs to the widely recognized “Hauptrogenstein type”. The remains are assigned to the genus Geocoma d’Orbigny 1850, best known from the type species, G. carinata (Münster), from the Tithonian Plattenkalk of Zandt. As suggested by Kutscher (1997) this species also includes Ophiocten kelheimense Boehm 1889, now documented by numerous well-preserved specimens from the Plattenkalk of Hienheim. Kutscher assigned the Hienheim specimens to the genus Sinosura Hess 1964 and used both names though G. carinata has priority. Despite rather small differences Sinosura is retained as a valid genus besides Geocoma, and both are placed in the family Aplocomidae Hess 1965. Geocoma and Sinosura share small adpressed arm spines with Aplocoma d’Orbigny 1852. Aplocoma is represented by a number of Triassic and Jurassic species, and the subfamily Aplocominae is proposed herein for the three genera. A second subfamily, Ophiopetrinae, is proposed for the genera Ophiopetra Enay &; Hess 1962 and Ophiohybris Hess 1964, and is characterized by larger, erect arm spines.  相似文献   

Ammonoids of the middle/late Anisian boundary (Middle Triassic) and the transgression of the Prezzo Limestone in eastern Lombardy-Giudicarie (Italy)     

Claude Monnet  Peter Brack  Hugo Bucher  Hans Rieber 《Swiss Journal of Geoscience》2008,101(1):61-84

  相似文献   

Binary statistics and star formation     

Hans Zinnecker 《Astrophysics and Space Science》1984,99(1-2):41-70

Binary statistics, in particular the distributions of mass ratios and orbital periods, are reviewed in an attempt to obtain clues to possible star formation and cloud fragmentation processes. Various observational selection effects which hamper the establishment of the true distributions are discussed. Four different theories of binary formation are compared (fission, fragmentation, capture, and the disintegration of small star clusters), none of which can be ruled out. We conclude that there may be many ways to form binary systems. The dominant mode of binary formation could be ring fragmentation or disc fragmentation depending upon whether the distribution of mass ratios is found to decrease or to increase towards small mass ratios. Future speckle interferometric measurements of a sufficiently large sample of close visual binaries are suggested to settle this important observational question. The present paper is special in that it brings together a wealth of useful information, both observational and theoretical, in one place.Atoms form molecules, stars form binaries.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.We quote Su-Shu Huang in IAU-Colloquium No. 33=Revista Mexicana, Vol. 3 (1977). Many papers related to the present problem can be found there.  相似文献   

Lidar measurements of plume statistics     

Hans E. Jørgensen  Torben Mikkelsen 《Boundary-Layer Meteorology》1993,62(1-4):361-378

Surface-layer aerosol diffusion experiments have been conducted using artificial smoke plume releases at ground level over flat and homogeneously vegetated terrain at the Meppen proving grounds in the Federal Republic of Germany (1989). At fixed downwind locations in the range out to 800 m from the source, instantaneous crosswind plume profiles were detected repetitively at high spatial (1.5 m) and temporal (3 sec) intervals by use of a mini LIDAR system. The experiments were accompanied by measurement of the surface-layer mean wind and turbulence quantities by sonic anemometers. On the basis of measured crosswind concentration profiles, the following statistics were obtained: 1) Mean profile, 2) Root mean square profile, 3) Fluctuation intensities, and 4) Intermittency factors. Furthermore, some experimentally determined probability density functions (pdf's) of the fluctuations are presented. All the measured statistics are referred to a fixed and a moving frame of reference, the latter being defined as a frame of reference from which the (low frequency) plume meander is removed. Finally, the measured statistics are compared with statistics on concentration fluctuations obtained with a simple puff diffusion model (RIMPUFF) developed at Risø.  相似文献