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1.
Jonathan S. Price 《水文研究》1994,8(2):167-177
Over an oceanic peatland, the concentration of Na in fog averaged 38.1 mgl?1 compared with 1.8 mgl?1 in rain, resulting in a significant flux of mineral elements to the surface. Between 16 May and 20 June 1990 the average mass flux of Na to the bog surface by fog, rain, and dry deposition was 21.9, 10.4 and 7.0 mg m?2 d?1. There was little long-term storage of Na within the peatland system, where Na losses measured in stream runoff averaged 34.8 mg m2 d?1, and deep groundwater losses 4 mg m?2 d?1. Calcium and Mg were preferentially retained in the organic soil, whereas K was relatively mobile. Potassium tended to become concentrated in the unsaturated zone. Stream runoff had a consistently higher pH than groundwater, corresponding to higher Ca and Mg concentrations, which may have been from mineral sources in the headwater ponds. Otherwise, the stream water chemistry was closely related to groundwater in the upper layers of the peat deposit. 相似文献
2.
沉积物粒度分析在厦门市第四纪环境研究和地层划分对比中的应用 总被引:6,自引:0,他引:6
采用MS2000型激光粒度分析仪进行测试,利用计算机粒度分析软件对数据进行整理和计算,绘制出样品的频率曲线、概率累积曲线以及粒度众数位值曲线等图件并进行沉积环境分析。厦门地区第四纪环境演化经历了中更新世同安组(含泥中粗砂、含泥细中砂、砂为主)海积一冲积一更新统上部龙海组(含泥粗中砂、含泥细中砂、含泥粗砂、粗砂、细中砂、含细砾中粗砂、中细砂等)冲积一洪冲积一更新世上部东山组(砂、砂砾、含泥中粗砂、粗砂、泥质中细砂、细砂、中粗砂等)冲洪积及部分海积(粉砂、细粉砂、含碳质泥、粘土、淤泥质粘土、粉砂质粘土等)一全新世长乐组(粉砂,淤泥质粘土、粉砂质粘土、碳质粘土、含砂淤泥质粘土,粉砂质亚粘土、粉细砂亚粘土等)海湾沉积。在解释环境变化的同时,说明粒度变化曲线在一定程度上可以作为地层划分的依据之一,并以此对研究区地层进行了详细划分。 相似文献
3.
In the Bavarian Alps (Germany), west of the Isar River, the abyssal deposits of the Lower Barremian to Upper Campanian Rhenodanubian Group consist of siliciclastic and calcareous turbidites alternating with hemipelagic non-calcareous mudstones. The up to 1500-m-thick succession, deposited in the Penninic Basin to the south of the European Plate, is characterized by a low mean sedimentation rate (c. 25 mm kyr−1) over 60 million years. Palaeocurrents and turbidite facies distribution patterns suggest that sedimentation occurred on a weakly inclined abyssal plain. The highest sedimentation rates (up to 240 mm kyr−1) were associated with the calcareous mud turbidites of the newly defined Röthenbach Subgroup, which includes the Piesenkopf, Kalkgraben and Hällritz formations (Middle Coniacian to Middle Campanian). These calcareous turbidites prograded from the west, and interfinger towards the east with red hemipelagic claystone. A high sea level presumably favoured pelagic carbonate production and accumulation on the shelves and on internal platforms in the western part of the basin, whereas siliciclastic shelves with steep slope angles have bordered the eastern part of the basin, where a dearth of turbidite sedimentation and increased Cretaceous oceanic red beds deposition occurred. In contrast to the eustatically-induced Middle Coniacian to Lower Campanian Cretaceous oceanic red beds (calcareous nannoplankton zones CC14 to CC18), red hemipelagites of Early Cenomanian age (upper part of calcareous nannoplankton zone CC9) and early Late Campanian age (upper part of zone CC21 and zone CC22) are interpreted as the result of regional tectonic activity. 相似文献
4.
Matthew Simpson Sethu Raman R. Suresh U. C. Mohanty 《Journal of Earth System Science》2008,117(6):897-909
Doppler radar derived wind speed and direction profiles showed a well developed sea breeze circulation over the Chennai, India
region on 28 June, 2003. Rainfall totals in excess of 100 mm resulted from convection along the sea breeze front. Inland propagation
of the sea breeze front was observed in radar reflectivity imagery. High-resolution MM5 simulations were used to investigate
the influence of Chennai urban land use on sea breeze initiated convection and precipitation. A comparison of observed and
simulated 10m wind speed and direction over Chennai showed that the model was able to simulate the timing and strength of
the sea breeze. Urban effects are shown to increase the near surface air temperature over Chennai by 3.0K during the early
morning hours. The larger surface temperature gradient along the coast due to urban effects increased onshore flow by 4.0m
s−1. Model sensitivity study revealed that precipitation totals were enhanced by 25mm over a large region 150 km west of Chennai
due to urban effects. Deficiency in model physics related to night-time forecasts are addressed. 相似文献
5.
Kyu Han Kim Keisuke Nagao Hirochika Sumino Tsuyoshi Tanaka Takamasa Hayashi Toshio Nakamura Jong Ik Lee 《Chemical Geology》2008,253(3-4):180-195
We report analyses of noble gases and Nd–Sr isotopes in mineral separates and whole rocks of late Pleistocene (< 0.2 Ma) monzonites from Ulleungdo, South Korea, a volcanic island within the back arc basin of the Japan island arc. A Rb–Sr mineral isochron age for the monzonites is 0.12 ± 0.01 Ma. K–Ar biotite ages from the same samples gave relatively concordant ages of 0.19 ± 0.01and 0.22 ± 0.01 Ma. 40Ar/39Ar yields a similar age of 0.29 ± 0.09 Ma. Geochemical characteristics of the felsic plutonic rocks, which are silica oversaturated alkali felsic rocks (av., 12.5 wt% in K2O + Na2O), are similar to those of 30 alkali volcanics from Ulleungdo in terms of concentrations of major, trace and REE elements. The initial Nd–Sr isotopic ratios of the monzonites (87Sr/86Sr = 0.70454–0.71264, 143Nd/144Nd = 0.512528–0.512577) are comparable with those of the alkali volcanics (87Sr/86Sr = 0.70466–0.70892, 143Nd/144Nd = 0.512521–0.512615) erupted in Stage 3 of Ulleungdo volcanism (0.24–0.47 Ma). The high initial 87Sr/86Sr values of the monzonites imply that seawater and crustally contaminated pre-existing trachytes may have been melted or assimilated during differentiation of the alkali basaltic magma.A mantle helium component (3He/4He ratio of up to 6.5 RA) associated with excess argon was found in the monzonites. Feldspar and biotite have preferentially lost helium during slow cooling at depth and/or during their transportation to the surface in a hot host magma. The source magma noble gas isotopic features are well preserved in fluid inclusions in hornblende, and indicate that the magma may be directly derived from subcontinental lithospheric mantle metasomatized by an ancient subduction process, or may have formed as a mixture of MORB-like mantle and crustal components. The radiometric ages, geochemical and Nd–Sr isotopic signatures of the Ulleungdo monzonites as well as the presence of mantle-derived helium and argon, suggests that these felsic plutonic rocks evolved from alkali basaltic magma that formed by partial melting of subcontinental lithospheric mantle beneath the back arc basin located along the active continental margin of the southeastern part of the Eurasian plate. 相似文献
6.
This paper presents an example of application of the double solid reactant method (DSRM) of Accornero and Marini (Environmental
Geology, 2007a), an effective way for modeling the fate of several dissolved trace elements during water–rock interaction. The EQ3/6 software
package was used for simulating the irreversible water–rock mass transfer accompanying the generation of the groundwaters
of the Porto Plain shallow aquifer, starting from a degassed diluted crateric steam condensate. Reaction path modeling was
performed in reaction progress mode and under closed-system conditions. The simulations assumed: (1) bulk dissolution (i.e.,
without any constraint on the kinetics of dissolution/precipitation reactions) of a single solid phase, a leucite-latitic
glass, and (2) precipitation of amorphous silica, barite, alunite, jarosite, anhydrite, kaolinite, a solid mixture of smectites,
fluorite, a solid mixture of hydroxides, illite-K, a solid mixture of saponites, a solid mixture of trigonal carbonates and
a solid mixture of orthorhombic carbonates. Analytical concentrations of major chemical elements and several trace elements
(Cr, Mn, Fe, Ni, Cu, Zn, As, Sr and Ba) in groundwaters were satisfactorily reproduced. In addition to these simulations,
similar runs for a rhyolite, a latite and a trachyte permitted to calculate major oxide contents for the authigenic paragenesis
which are comparable, to a first approximation, with the corresponding data measured for local altered rocks belonging to
the silicic, advanced argillic and intermediate argillic alteration facies. The important role played by both the solid mixture
of trigonal carbonates as sequestrator of Mn, Zn, Cu and Ni and the solid mixture of orthorhombic carbonates as scavenger
of Sr and Ba is emphasized.
相似文献
Luigi Marini (Corresponding author)Email: |
7.
8.
9.
Radiocarbon and total carbonate data were obtained near the 1973 GEOSECS stations in the North Pacific along 30°N and along 175°E between 1993 and 1994. In these stations, we estimated radiocarbon originating from atomic bomb tests using tritium, trichlorofluoromethane and silicate contents. The average penetration depth of bomb radiocarbon during the two decades has deepened from 900 m to 1300 m. Bomb radiocarbon inventories above the average value for the whole North Pacific were found widely in the western subtropical region around 30°N both in the 1970s and 1990s, and its area in the 1990s was broader than that in the 1970s. In most of the North Pacific, while the bomb radiocarbon has decreased above 25.4, the bomb radiocarbon flux below 25.4 was over 1 × 1012 atom m-2yr-1 in the subtropical region around 30°N. In the tropical area south of 20°N, the bomb radiocarbon inventory below 25.4 increased from zero to over 10 × 1012 atom m-2 during the last three decades. These distributions suggest that the bomb radiocarbon removed from the surface is currently accumulated with bomb 14C flux of over 1 × 1012 atom m-2yr-1 below 25.4 in the subtropical region, mainly by advection from the higher latitude, and that part of the accumulated bomb 14C gradually spread southward with about 30 years. 相似文献
10.
Claudio Campagna Alberto R. Piola Maria Rosa Marin Mirtha Lewis Teresita Fernndez 《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(12):1907-1924
This study describes the association between transient, mesoscale hydrographic features along the axis of the Brazil–Malvinas Confluence, in the SW Atlantic, and the foraging behavior of 2–3-year-old (focal) juvenile southern elephant seals, Mirounga leonina, from Península Valdés, Argentina. Departing from the dominant pattern of foraging on predictable bathymetric fronts on the Patagonian shelf and slope, three females out of 12 satellite-tracked juveniles remained at the edge of young warm-core eddies and near the outer core of cold-core eddies, coinciding with the most productive areas of these temperature fronts. Seal trajectories along high-temperature gradients were always consistent with the speed and direction of surface currents inferred from the temperature distribution and confirmed by surface drifters. Movements of foraging seals were compared with those of surface drifters, coinciding in time and space and yielding independent and consistent data on regional water circulation parameters. The diving pattern recorded for one focal seal yielded shallower dives and a loose diel pattern in the eddy, and a marked diurnal cycle compatible with foraging on vertically migrating prey in the cold waters of the Malvinas Current. Pre-reproductive females that use the mesoscale fronts of the Argentine Basin as an alternative foraging area would benefit from lower competition with more experienced seals and with other top predators that reproduce along the coast of Patagonia. 相似文献