Late Quaternary sediment dating and quantification of lateral sediment redistribution applying230Thex: a study from the eastern Atlantic sector of the Southern Ocean     

M. Frank  A. Mangini  R. Gersonde  M. Rutgers van der Loeff  G. Kuhn 《International Journal of Earth Sciences》1996,85(3):554-566

High-resolution records of the natural radionuclide²³⁰Th were measured in sediments from the eastern Atlantic sector of the Antarctic circumpolar current to obtain a detailed reconstruction of the sedimentation history of this key area for global climate change during the late Quaternary. High-resolution dating rests on the assumption that the²³⁰Th_ex flux to the sediments is constant. Short periods of drastically increased sediment accumulation rates (up to a factor of 8) were determined in the sediments of the Antarctic zone during the climate optima at the beginning of the Holocene and the isotope stage 5e. By comparing expected and measured accumulation rate of²³⁰Th_ex, lateral sediment redistribution was quantified and vertical particle rain rates originating from the surface water above were calculated. We show that lateral contributions locally were up to 6.5 times higher than the vertical particle rain rates. At other locations only 15% of the expected vertical particle rain rate were deposited.  相似文献   

Stress orientations found in north-east Germany differ from the West European trend   总被引：1，自引：0，他引：1  

F. Roth  & P. Fleckenstein 《地学学报》2001,13(4):289-296

Knowledge about the acting stresses is of crucial importance for understanding the tectonics of a region. Data about the stress field in north-eastern Germany used to be very rare. In general, it was assumed that the orientation of the larger horizontal principal stress (S_H) is similar to that found for western Germany and central West-Europe, i.e. NW–SE. To check this, several borehole logs of the late 1980s were analysed for information on the principal horizontal stress orientations: they include Four-Arm-Dipmeter and borehole televiewer data from 15 boreholes. The depth range of our stress results reaches from 1500 to 6700 m. They were compared to a few other data, especially from hydraulic fracturing, and to recent findings on the stresses in the Northwest German basin. In contrast to expectation, S_H derived from breakout orientations below the salt layers displayed N to NE orientation. The latter was found at 10 locations spread over the NE-German basin from Berlin to the Baltic sea, from the Polish border to the former border between East and West Germany. Moreover, this stress rotation in the subsaline formations seems to be the continuation of a trend found in the NW German basin.  相似文献   

A structural phase-transition in K(Mg1−xCux)F3 perovskite     

Peter C. Burns  Frank C. Hawthorne  Anne M. Hofmeister  Stephanie L. Moret 《Physics and Chemistry of Minerals》1996,23(3):141-150

A complete solid-solution series between cubic (Pm 3 m) KMgF₃ and tetragonal (I4/mcm) KCuF₃ was synthesized at 730–735 °C in an inert atmosphere. X-ray powder-diffraction at room temperature shows that the transition between the cubic and tetragonal perovskite structures in the series K (Mg_1?xCu_x) F₃ occurs at x ～ 0.6. Rietveld structure-refinements were done for selected compositions. In the cubic phase, all parameters are linear with composition up to the transition point. At the transition point, there is a strong discontinuity in the cell volume; this is strongly anisotropic with expansion along the a axes and contraction along the c axis due to a pronounced axial elongation of the (Mg, Cu) F₆ octahedron that increases with increasing Cu content. The phase transition is first-order, with a discontinuity of ≈2% in the symmetry-breaking strain at x_C. It is proposed that the phase transition in K (Mg, Cu) F₃ is due to the onset of the cooperative Jahn-Teller effect. Compositional relationships for lattice vibrations in this solid solution were established using thin-film infrared spectroscopy. A phase transition occurring above 60 mole % KCuF₃ is indicated by the appearance of one of the two modes expected for the tetragonal phase; the weaker mode is not resolved below 80 mole % KCuF₃. Modes common to both structures vary smoothly and continuously across the binary; however, frequencies do not depend linearly on composition, nor is mode-softening discernable. Two-mode behaviour is observed only for the bending motion of the cubic phase, because this peak alone has non-overlapping end-member components.  相似文献   

On wind shear at fronts and inversions     

Ch. Jacobi  A. H. Siemer  R. Roth 《Meteorology and Atmospheric Physics》1996,59(3-4):235-243

Summary In the past, experimental investigations as well as theoretical considerations have shown that within fronts and inversions wind shear and vertical temperature gradient adjust in such a way that the Richardson number is at its critical value. Results from aircraft measurements now suggest that the shear within moving cold fronts, warm fronts and inversions shows different behaviour because of the different mechanisms controlling the Richardson numbers. This leads to higher Richardson numbers, and therefore to lower amounts of wind shear within moving cold fronts when compared to warm fronts and inversions.With 9 Figures  相似文献   

中国南京与美国德克萨斯稻田甲烷排放的比较(英文)   总被引：2，自引：0，他引：2  

黄耀  蒋静艳  宗良纲  Ronald L.Sass  Frank M.Fisher 《大气科学进展》2001,(6)

稻田甲烷排放试验分别在南京与德克萨斯水稻生长季实施，观测期内测定甲烷排放通量、上壤温度和水稻生物量。结果表明：南京稻田土镶温度的季节性变幅为１５．３℃，甲烷排放通量与土壤温度成非线性正相关而与水稻生物量无关；德克萨斯稻田土壤温度的季节性变幅为的２．９℃，甲烷排放通量与土壤温度无关而与水稻生物量成线性正相关。由此得出结论：在持续淹水和无外源有机碳施加的条件下，土壤温度变幅大的地区驱动稻田甲烷排放季节性变化的关键因子为土壤温度，土壤温度变幅小的地区其关键驱动因子则为水稻的生长量。  相似文献   

陆相盆地中的海侵层序特征:中欧盆地三叠系与松辽盆地白垩系对比研究   总被引：5，自引：0，他引：5  

王璞珺  边伟华  MATTERN Frank 《矿物岩石》2002,22(2):47-53

中欧盆地三叠系是典型的海陆过渡相沉积，松辽盆地白垩系是含有海侵事件记录的陆相河湖盆地。两盆地的共同特点是：①大陆克拉通上长期发育的大型坳陷盆地；②靠近古大洋和（或）有向海通道；③主要由互层状泥岩、粉砂岩、碳酸盐岩和膏盐层组成；④无典型海相化石，可能发育有半咸水和（或）高盐度生物；⑤海侵层中自生矿物的δ^34S,δ^13C,δ^18O同位素比值及介质盐度指数（Sr/Ba）、碱度指数（Ca Mg)／（Si Al）、还原性指标（Zn Ni)/Ga、硫沉积通量指数（归一化硫含量）等显著高于相邻层位背景值。  相似文献   

Evolving planning systems in Madrid,Rome, and Athens     

Frank J. Costa Dr.  Allen G. Noble Dr.  Glenna Pendeleton 《GeoJournal》1991,24(3):293-303

Although possessing ancient and distinguished histories, the recent urbanization and planning approaches of Madrid, Rome and Athens are relatively unknown to English-speaking planners and urban geographers. This paper reviews the development of each city from the mid-19th century to the present. Special attention is given to the planning instruments developed in each city to guide growth. Each city experienced rapid growth over the past century because of its capital city functions. As a result of strong growth pressures, city planning policies were frequently subverted by private sector interests. Only in the latter part of the 20th century have planning measures become effective in controlling and directing urban growth.  相似文献   

Waste Injection into a Two-Phase Flow Field: Sand-Box and Hele-Shaw Models Study     

Frank L. Peterson  John A. Williams  Stephen W. Wheatcraft 《Ground water》1978,16(6):410-416

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Dielectric anisotropy as a petrofabric indicator     

Gary J. Tuck  Frank D. Stacey 《Tectonophysics》1978,50(1):1-11

A sensitive instrument for measurement of the angular dependence of dielectric constant in a rotating rock specimen is described and the precautions necessary to obtain meaningful results are summarized. An important problem is the choice of length/diameter ratio for cylindrical specimens, so that complete three-dimensional information can be obtained from a single specimen; this ratio averages 0.86, but is found to be a function of dielectric constant and of electrode geometry. The measurements reported here have been concerned with weakly anisotropic rocks which lack visible fabrics, especially sandstones and basalts. A sandstone was used in a study of the statistical “noise” or scatter in anisotropy axes of a set of 52 similar specimens. The anisotropy was found to be much greater than expected from the finite numbers of grains in a sample. It is concluded that, in spite of careful drying of specimens, the anisotropy is dominated by thin grain coatings which have very high dielectric constants or may even be conducting. A basalt has been found in which the dielectric and magnetic anisotropies have different axes, apparently reflecting different grain alignment events in the history of the rock. However, this is the only example that has been found in which all of the information obtainable from dielectric anisotropy could not have been obtained more easily from magnetic anisotropy.  相似文献   

The use of the specific interaction model to estimate the partial molal volumes of electrolytes in seawater     

Frank J Millero 《Geochimica et cosmochimica acta》1977,41(2):215-223

The specific interaction model has been used to determine the partial molal volume of electrolytes in 0.725 m NaCl and 35‰ salinity seawater solutions at 25°C. The partial molal volumes of electrolytes (MX) were estimated at a given ionic strength (I) from , where S_V is the Debye-Hückel limiting law slope, v_i is the number of ions i formed when MX dissociated, [i] is the total molality of ion i and B_MX is a specific interaction parameter that varies slowly with ionic strength. The values of $\text{V}\text{(}\text{MX}\text{)}$ estimated by using this equation were found to agree very well with experimental values in NaCl and seawater providing there are not strong interactions between M and X. For electrolytes that form ion pairs (i.e. MX°) corrections must be made. Methods are discussed for making these corrections.  相似文献