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1.
The determination of uranium series disequilibria in fluvial environments is proposed as a method of calculating catchment mass balances. The technique is based on two main principles. Firstly, 234U is more mobile than 238U, especially during the early stages of weathering. Secondly, uranium is far more mobile than either thorium or protactinium. Consequently, teaching during weathering results in the loss of the uranium found in the fresh rock, leaving the two immobile daughters behind. The ratio of uranium carried by sediment to that dissolved, US/UW can, therefore, be determined from river water and sediment isotopic activity ratios. Fluxes of uranium can then be calculated from average concentrations in the water and the associated sediment, from which a sediment yield can be inferred. The Witham catchment in Lincolnshire has been used to test the proposed method. A US/UW ratio of between 5 and 7 is determined and a sediment yield of 2.51 ± 2.12 tonnes yr?1 km?2 is proposed. Although some problems concerning environmental chemistry have arisen, the validity of the approach is confirmed by the close correspondence between the results obtained and those inferred by earlier workers using more conventional methods. 相似文献
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D.O. Olago F.A. Street-Perrott R.A. Perrott M. Ivanovich D.D. Harkness 《Journal of African Earth Sciences》2000,30(4):1113
In this paper, a sequence of five Late Quaternary tephras occurring as discrete, well-preserved horizons in lake sediments on the northeastern flank of Mount Kenya are characterised and their ages determined by a combination of high-resolution indirect radiocarbon dating and direct
dating. The grain size characteristics suggest that the tephras are of fairly local origin. These Na---K-rich alkali pyroclasts with a trachytic chemical composition have a highly correlated chemistry and mineralogy, suggesting that they were probably derived from the same genetic series and possibly erupted from a single source vent. Morphological differences are attributed to the peculiar characteristics of each eruption episode. The magma source was probably a small, highly differentiated magma chamber following the olivine basalt-trachyandesite-trachyte-phonolite series, which broadly reflects the Quaternary rock suite of Mount Kenya. 相似文献
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J. R. L. Allen J. E. Rae G. Longworth S. E. Hasler M. Ivanovich 《Estuaries and Coasts》1993,16(3):670-677
The210Pb dates from a salt-marsh sediment sequence at Tites Point, Severn Estuary, southwest England, were compared with the results of three other independent dating techniques. These methods are inspection of dated topographic maps for the presence of absence of the salt marsh, dating of artifacts in a well-defined horizon within the sequence, and counting annual bands. All four sets of dates showed good agreement to about 30 cm depth from the present marsh surface; thereafter, dates from the210Pb method are earlier than those from the other methods, which are themselves in agreement. It is concluded that a wide range of methods can be successfully used for dating salt-marsh sediments (e.g., radiometric techniques, topographic maps, archaeological evidence, annual banding). Where possible, it is important to confirm dates using at least two independent techniques. 相似文献
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Animal bones, associated with Palaeolithic artefacts and skeletal remains of early hominids from the cave of La Chaise-de-Vouthon, have been dated using a new approach to uranium series dating of bone. Speleothem (cave calcite) interstratified with bone-bearing sediments in the two chambers of Grotte Bourgeois-Delaunay and Grotte Suard have previously been dated by the 230Th/234 U method. This provides a chronological control for the bone ages, for which the method is still at an experimental stage. A good agreement is shown in most cases between the calcite and the bone ages, showing the cave to have been a stable environment for the deposition of bone and the acquisition of uranium. 相似文献
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Ivan Borisovich Gratchev Kyoji Sassa Viktor Ivanovich Osipov Hiroshi Fukuoka Gonghui Wang 《Geotechnical and Geological Engineering》2007,25(3):349-367
In this work, the cyclic behavior of bentonite–sand mixtures and factors affecting it were studied by means of a ring-shear
apparatus and a scanning electron microscope. It was found that bentonite content had a significant influence on the liquefaction
potential of the studied soils. A small amount of bentonite in the mixtures would cause the formation of “loose” microstructures,
resulting in the occurrence of rapid liquefaction under cyclic loading, while a high bentonite content would cause the formation
of clay matrixes, thus raising the soil resistance to liquefaction. In addition, the effect of pore water chemistry on the
cyclic behavior of a high plasticity bentonite–sand mixture was carefully examined. It was also found that the presence of
ions in pore water would change the clay microfabric, making it more open and thus more vulnerable to liquefaction. Finally,
the effects of loading frequency on the cyclic behavior of mixtures with different amounts of bentonite were investigated.
It was found that as the bentonite content increased, the influence became more pronounced. 相似文献
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Antony J. Sutcliffe Thomas C. Lord Russell S. Harmon Miro Ivanovich Angela Rae John W. Hess 《Quaternary Research》1985,24(1):73-86
Cave sediments from Stump Cross Cave in northern England contain Pleistocene mammal remains. Uranium-series dating of calcium carbonate deposits closely associated with the fossiliferous horizons has established an absolute age of 83,000 ± 6000 yr B.P. for a faunal assemblage largely comprised of wolverines (Gulo gulo). This date lies firmly within the younger portion of oxygen-isotope stage 5. The occurrence of wolverines in the vicinity of Stump Cross Cave at ca. 83,000 yr B.P. indicates a significant climatic deterioration from ca. 120,000 yr B.P., when an Ipswichian interglacial fauna with hippopotamus was present in this part of northern England. 相似文献
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Manuela Lodemann Peter Fritz Manfred Wolf Miro Ivanovich Bent T. Hansen Eckehart Nolte 《Applied Geochemistry》1997,12(6):831-849
Highly saline fluids were encountered during the German Continental Deep Drilling Project (KTB) from depths ranging between 2 and 3 km to about 9 km. The most reliable data were obtained from samples extracted during a long-term pumping test in the 4000-m deep KTB pilot hole. Some 460 m3 CaNaCl brines with about 68 g l−1 total dissolved solids (TDS) and some 270 m3 associated gases, mainly N2 and CH4 were pumped to the surface from the main fracture system situated near the bottom of the pilot hole. Geochemical and isotopic data support the hydraulic tests which suggest the presence of an open and large fluid reservoir at depth. The pumped fluids from this main fracture system were released from a deep reservoir situated at more than 5500 m depth which is hydraulically connected with the 9101 m deep KTB main hole, drilled some 250 m to the northeast of the pilot hole.While Ca and Sr contents of the extracted brines may be the result of water-rock interaction, Cl is most likely of external origin. The Cl is hypothesized to derive from geotectonic processes rather than to descending infiltration of paleo-seawater (evaporitic brines). The sampled fluids have probably migrated from a deeper reservoir to their present position since the Cretaceous-Tertiary period due to tectonic activity. However, several isotopic studies have identified an admixture of descending paleowaters down to more than 4000 m depth. The high 36ClCl ratio of the fluids sampled during the long-term pumping test point to a host rock highly enriched in UTh, unlike the sampled KTB country rocks. The fluid reservoir is believed to be in contact with the Falkenberg granite massif situated about 2 km to the E of the KTB holes capable of supplying sufficient neutron flux for considerable subsurface production of 36C1. The NaCl(K, SO4) precursor fluids of the CaNaCI brines were produced in the course of extensive tectonic processes since the Late Caledonian within the Bohemian Massif. 相似文献
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Dušan Jovanović Miro Govedarica Filip Sabo Dubravka Sladić Aleksandar Ristić 《国际地球制图》2015,30(5):483-505
Main objective of this study was to establish a relationship between land cover and land surface temperature (LST) in urban and rural areas. The research was conducted using Landsat, WorldView-2 (WV-2) and Digital Mapping Camera. Normalised difference vegetation index and normalised difference built-up index were used for establishing the relation between built-up area, vegetation cover and LST for spatial resolution of 30 m. Impervious surface and vegetation area generated from Digital Mapping Camera from Intergraph and WV-2 were used to establish the relation between built-up area, vegetation cover and LST for spatial resolutions of 0.1, 0.5 and 30 m. Linear regression models were used to determine the relationship between LST and indicators. Main contribution of this research is to establish the use of combining remote sensing sensors with different spectral and spatial resolution for two typical settlements in Vojvodina. Correlation coefficients between LST and LST indicators ranged from 0.602 to 0.768. 相似文献