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David PETERS 《地球学报》2010,31(Z1):55-56
Currently there is no ready reference source of pterosaur pedes available to match ichnotaxa to potential trackmakers. While presently recognized pterosaur ichnites all indicate a plantigrade pes and a quadrupedal mode of locomotion, those configurations were not basal or universal. 相似文献
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Very low ozone episodes due to polar vortex displacement 总被引：1，自引：0，他引：1
P. M. JAMES D. PETERS D. W. WAUGH 《Tellus. Series B, Chemical and physical meteorology》2000,52(4):1123-1137
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Thorium-230 concentrations have been determined in 11 CCRMP (Canadian Certified Reference Materials Project) reference rock and ore samples using alpha spectroscopy following a chemical separation of the thorium. Literature data are available for only one of these 11 reference samples. 相似文献
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Petrographic and petrologic investigations of upper amphibolitefacies metacarbonates from the East Humboldt Range core complex,Nevada, provide important constraints on P-T-XCO2 conditionsand fluid flow during metamorphism. Three marble assemblagesare observed [(1)dol+cc+bt+cpx+q+ruscapkspamph; (2) cc+bt+cpx+plag+q+sphscapksp;(3) cc+cpx+plag+q+sphscapksp], all of which equilibrated withrelatively CO2-rich fluid compositions, at P-T conditions of6 kbar and 600–750C. The most recent equilibration eventis recorded in some calcsilicate gneisses where retrograde amphiboleand epidotegarnet replace clinopyroxene and plagioclase, respectively.This is attributed to infiltration of H2O-rich fluids at and/orafter peak metamorphic temperatures, which continued as therocks were cooled and rapidly uplifted after a Tertiary extension-relatedheating event. Likely sources for the retrograde fluids are the abundant pegmatiticleucogranites in the area. Volumetric fluid-rock ratios of 0.02–0.4are required to generate the retrograde assemblage, and observedleucogranite proportions are more than adequate to provide therequired volume of fluid. Estimates of retrograde fluid fluxesrange from 0.25 to 5102 cm3/cm2 for a transient temperaturegradient of 5C/m, to 3103 to 7104 cm3/cm2 for a temperaturegradient of 35C/km. These gradients are characteristic of askarn-type contact metamorphic environment and a regional crustalgeotherm, respectively. They imply different time-scales andlength-scales for the retrograde fluid flow system, with theformer more akin to a contact metamorphic setting with local,meter-scale retrograde fluid flow, and the latter to a regionalmetamorphic setting with regionally high mid- and lower-crustaltemperatures and fluid flow throughout a significant thicknessof the middle crust. Higher gradients are considered more likelygiven the proximity of leucogranites to retrogressed calc-silicategneisses, and the resultant relatively small fluxes are consistentwith a magmatic source. The length-scale of reaction within the retrograde fluid flowsystem was of the order of meters to hundreds of meters andinvolved both pervasive and (later) fracture-controlled down-temperatureflow. Retrograde fluid flow in this terrance, as well as othersdominated by magmatic volatiles, is in the form of multiplediscrete bursts of fluid released in a discontinuous mannerpotentially over long periods of time (1–10 Ma) with locallyvariable thermal gradients along the flow path. 相似文献
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The frequency response of different types of sonic anemometers due to spatialaveraging of turbulent fluctuations along the sonic path is investigated byapplying modeling procedures and by sonic measurements. The data wereobtained simultaneously at up to 4 heights over extreme smooth andhomogeneous terrain during stationary situations, varying fromslightly stable to unstable. It is shown thatcorrections for the variance of the vertical wind component areneeded for measurements close to the ground. A correction procedure, based ona response function for the vertical wind and on parameters derived frompower spectra, is applied to the measurements. At a height of about onemetre, the variance of the vertical wind component is typicallyunderestimated by about 10%. The error decreases with increasing height. It isalso shown that in the height range down to one metre other turbulencequantities, as for example the variances of the horizontal wind components andthe turbulent fluxes of momentum and sensible heat, are not markedly affectedby the sonic spatial response. Experimental data support these findings. 相似文献
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Moving source profiling is a modification of walk-away vertical seismic profiling in which the source is moved along a line across a well while the signal is recorded in the well at a certain depth. The method was designed to better predict the target horizon below the drill bit and away from the well location. The method has several advantages in areas of complicated overburden. In overthrust regions, the receiver is placed below much of the complicated structure to minimize distortion of the reflected signal. The final seismic image is a depth presentation of the subsurface structure and stratigraphy based on wavefront calculations. This depth estimation is obtained without extensive processing of the recorded data. The final result is available within a few days and can help interpreters to decide if and where to sidetrack the well. The method is demonstrated using an example from the overthrust zone of the Lower Saxonian Basin and the Pompeckj's well in Northern Germany. 相似文献
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Simultaneous monitoring of conservative and non-conservative tracers in streamflow offers a valuable means of obtaining information on the age and flow paths of water reaching the basin outlet. Previous studies of stormflow generation in a small forested basin on the Canadian Shield used isotopic (IHS) and geochemical hydrograph separations (GHS) to infer that some event water during snowmelt reaches the stream via subsurface pathways, and that surface water runoff is generated by direct precipitation on to saturated areas (DPSA) in the stream valley. These hypotheses were tested for rainfall inputs using simultaneous IHS (18O) and GHS (dissolved silica) of basin stormflow, supplemented by hydrochemical and hydrometric data from throughflow troughs installed on basin slopes. Comparison of pre-event and subsurface water hydrographs did not provide conclusive evidence for subsurface movement of event water to the stream, owing to the appreciable uncertainty associated with the hydrograph separations. However, IHSs of runoff at the soil–bedrock interface on basin slopes indicated that event water comprised 25–50% of total runoff from areas with deep soil cover, and that these contributions supplied event water flux from the basin in excess of that attributable to DPSA. The surface water component of stormflow estimated from the GHS was also largely the result of DPSA. GHS assumes that dissolved silica is rapidly and uniformly taken up by water infiltrating the soil and that water moving via surface pathways retains the low dissolved silica level of rainfall; however, neither assumption was supported by the hillslope results. Instead, results suggest that the observed depression of silica levels in basin stormflow previously attributed to dilution by DPSA was partly a function of transport of dilute event water to the channel via preferential pathways. Implications of these results for the general use of simultaneous IHS and GHS to infer hydrological processes are discussed. © 1997 by John Wiley & Sons, Ltd. 相似文献
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氮同位素研究城市湖泊沉积物有机质来源和迁移过程——以北京为例 总被引：1，自引：0，他引：1
城市湖泊是陆地水圈的重要组成部分,与人类活动关系极为密切。然而城市发展导致城市湖泊富营养化愈发严重,湖泊生态环境问题引起了广泛关注。本文研究了2012年至2013年间北京城区12个公园湖泊表层沉积物的有机氮同位素组成、碳氮比值、总有机氮和总有机碳含量的分布情况,探讨表层沉积物生产力状态、沉积物的有机质来源定性与定量分析、湖泊营养输入程度和过程等。研究表明,后海及群明湖等的有机碳、氮含量较其他公园湖泊的高,土壤和污水有机质等对湖泊沉积物的贡献突出,表明这些湖泊初级生产力及营养程度高,具有一定的富营养化风险;各个湖泊的分布位置、周围环境以及管理方式导致了其生产力、营养状况及有机质来源的差异,应该分别从控制水土流失、减少污水输入、及时清洁水面上的浮游植物与枯枝落叶等多方面着手进行,减少湖泊环境污染风险,保持湖泊环境生态平衡。本研究为了解城市湖泊环境有机质来源和过程、湖泊现代环境的管理和防治,提供可靠的研究方法和评价体系。 相似文献
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Ernest S. GLADNEY Wanita EBERHARDT Richard J. PETERS 《Geostandards and Geoanalytical Research》1982,6(1):5-6
Radium-226 concentrations have been determined in 11 CCRMP reference rock and ore samples using instrumental gamma-ray spectrometry and radiochemical radon emanation procedures. Results are compared to the best available data. 相似文献
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