Distribution and fluxes of metals in the St. Lawrence River from the outflow of Lake Ontario to Québec City     

Ken R. Lum  K. L. E. Kaiser  C. Jaskot 《Aquatic Sciences - Research Across Boundaries》1991,53(1):1-19

Six anchor stations in the St. Lawrence River from the outflow of Lake Ontario to Quebec City, were occupied for ca. 24 hours in June 1987 during low flow conditions. Samples of water and suspended particulate matter were separated by continuous-flow centrifugation, and were collected every two hours.During this sampling period, fluxes of dissolved forms of zinc, copper and nickel increased in Lac St. François and downstream relative to the sum of the fluxes for the two upstream stations at the outflow of Lake Ontario. Increases in the flux of dissolved zinc and copper were pronounced below Montreal and above Lac St. Pierre. For particulate forms of metals, all five metals show that there are significant inputs in the section of the St. Lawrence River between Lac St. François and the station just above the entrance to Lac St. Pierre.The average concentrations of dissolved cadmium, lead, zinc, copper and nickel ranged from 7–23 ng/l; 9–35 ng/l; 0.434–0.939 g/l; 0.15–0.89 g/l and 0.58–1.12 g/l respectively.Regression analysis of the dissolved and particulate metal concentrations suggests that the concentration of dissolved cadmium, lead, zinc and nickel can be predicted from the regression equation and the determination of particulate metal concentration. This prediction appears to be independent of the suspended particulate matter concentration which varies from ca. 1 to 10 mg/l from the outflow of Lake Ontario to Québec City.  相似文献   

    

Guocheng Pan  D. P. Harris 《Mathematical Geology》1991,23(6):861-886

A new multidimensional scaling (MS) technique, referred to as the Pijk model, is formulated on the basis of associations among triple objects (samples or variables), instead of pairs of objects as used in the usual MS methods, such as factor analysis. The computational scheme provided for this method is the reduction of an original problem to a standard eigenvalue-eigenvector problem. The major goal of the technique is simplification and reduction of data structures and the rescaling of original objects into a new and reduced space, so that patterns and relations of the original objects can be conventiently examined in two-dimensional factor plots. The Pïjk method is illustrated and tested by using a set of geochemical data related to the epithermal gold and silver vein deposits in the Walker Lake quadrangle of Nevada and California. The characteristics of element associations suggested in the Pijk analysis are consistent with field observations. A preliminary comparison between the new method and the ordinary factor analysis also is made on the basis of the same data set. Results are encouraging in that analysis by the Pijk model captures triple-object associations that might be missed by the ordinary factor analysis which considers only pair-variable correlations  相似文献   

岩体三维节点偶对分析及其应用          下载免费PDF全文

王思敬  张菊明 《地质科学》1991,(3):277-287

本文讨论了节点偶对分析的三维扩展。节点偶对分析是针对摩擦滑动节理单元的约束边界进行的序列矢量判定。在三维节理单元的分析中,几何约束和相应的力学判据极为复杂,采用节点偶对等效结合力方法才能迎刃而解。文中对三维转向节理模型的分析得到合理的结果,它表明本文所提出的方法可成功地应用于节理岩体的有限元分析。  相似文献   

Quaternary fault segmentation and interaction in the epicentral area of the 1561 earthquake (Mw = 6.4), Vallo di Diano, southern Apennines, Italy     

V. Spina  E. Tondi  P. Galli  S. Mazzoli  G. Cello 《Tectonophysics》2008,453(1-4):233

The main structural characteristics of the Caggiano and Polla faults, exposed in the epicentral area of the 1561 earthquake (Mw = 6.4), southern Italy, have been investigated in detail to assess their spatial and temporal properties, and to evaluate their seismogenic potential. These right stepping normal faults show an overlap of about 7 km and an across strike separation of about 4 km. The geometric relationships between the Caggiano and Polla faults, but also the displacement distribution along each fault, demonstrate that they have been strongly interacting throughout the Pleistocene. Nevertheless, geological evidence of Holocene tectonic activity was mainly recognized along the Caggiano Fault (faulted late glacial deposits) and in the southernmost part of the Polla Fault (faulted deposits of probably Late Pleistocene age). This suggests that the Caggiano Fault can be considered as the most tectonically active fault in the Vallo di Diano Fault System. By calculating Coulomb stress changes, we have constrained modes of mechanical interactions between the two faults in a scenario compatible with the 1561 earthquake. This approach allows us to argue that both the Caggiano and the Polla Faults are probably linked at depth, and part of the same seismogenic structure which may be potentially responsible for composite ruptures with magnitude ≥ 6.5.  相似文献   

Statistical analysis of sand grain/bed collision process recorded by high-speed digital camera   总被引：1，自引：0，他引：1  

DAWEI WANG  YUAN WANG  BIN YANG  WEI ZHANG† 《Sedimentology》2008,55(2):461-470

A high‐speed digital camera was employed to record the sand grain/bed collision process. With image processing and a statistical method, a series of parameters of the collision process were obtained. The results show that the collision process of a grain with rebounding can be represented by two parameters: the kinetic energy restitution coefficient and the collision angle. Both parameters satisfy a normal distribution, and they are dependent on one another. With an increase of the collision angle, the distribution of the kinetic energy restitution gradually reduces from a broad to a narrow range with low values. The percentage of vertical velocity restitution coefficients greater than 1 can reach 70% or more, which ensures that the settling time of the sand grains in the air increases and that they receive more energy from the air to progress the saltation movement.  相似文献   

Techniques to measure grain-size distributions of loamy sediments: a comparative study of ten instruments for wet analysis   总被引：2，自引：0，他引：2  

DIRK GOOSSENS 《Sedimentology》2008,55(1):65-96

Ten instruments for measuring the grain‐size distribution of loamy sediments in water were tested in a comparative study. Instruments tested were: the Malvern Mastersizer S, the Coulter LS 200, the Fritsch Analysette 22 (version C), the Horiba Partica LA‐950, the Sedigraph 5100, the Atterberg cylinder, the Coulter Multisizer 3, the CIS‐100, the EyeTech and the image analysis software Histolab. The first four instruments use laser diffraction. The Sedigraph and Atterberg cylinder are based on sedimentation. The Coulter Multisizer 3 uses impedance measurements and the last three instruments use optical techniques. Grain‐size analyses were carried out on four sediments with median grain diameters of approximately 35, 30, 12 and 9 μm, respectively, and with no particles >90 μm. The laser diffraction instruments produced the best results for the various criteria considered in this study, followed by the Coulter Multisizer 3 (electrical sensing zone technique), the sedimentation techniques and the optical methods. However, the study also showed that there is no such thing as an ‘ideal’ method because techniques may score differently according to the criterion tested. An appropriate evaluation thus requires that various criteria be considered. Issues to be taken into account are: type of sediment, quantity of sediment available, speed of measurement, complexity of the measurement protocol, processing of the data, reproducibility of the results and the specific aims of the study undertaken.  相似文献   

Distinct climate change synchronous with Heinrich event one, recorded by stable oxygen and carbon isotopic compositions in stalagmites from China   总被引：2，自引：0，他引：2  

Houyun Zhou  Jianxin Zhao  Michael K. Gagan  Jun Yan 《Quaternary Research》2008,69(2):306-315

Uranium-series dating of oxygen and carbon isotope records for stalagmite SJ3 collected in Songjia Cave, central China, shows significant variation in past climate and environment during the period 20-10 ka. Stalagmite SJ3 is located more than 1000 km inland of the coastal Hulu Cave in East China and more than 700 km north of the Dongge Cave in Southwest China and, despite minor differences, displays a clear first-order similarity with the Hulu and Dongge records. The coldest climatic phase since the Last Glacial Maximum, which is associated with the Heinrich Event 1 in the North Atlantic region, was clearly recorded in SJ3 between 17.6 and 14.5 ka, in good agreement in timing, duration and extent with the records from Hulu and Dongge caves and the Greenland ice core. The results indicate that there have been synchronous and significant climatic changes across monsoonal China and strong teleconnections between the North Atlantic and East Asia regions during the period 20-10 ka. This is much different from the Holocene Optimum which shows a time shift of more than several thousands years from southeast coastal to inland China. It is likely that temperature change at northern high latitudes during glacial periods exerts stronger influence on the Asian summer monsoon relative to insolation and appears to be capable of perturbing large-scale atmospheric/oceanic circulation patterns in the Northern Hemisphere and thus monsoonal rainfall and paleovegetation in East Asia. Climatic signals in the North Atlantic region propagate rapidly to East Asia during glacial periods by influencing the winter land-sea temperature contrast in the East Asian monsoon region.  相似文献   

Development of the mixed conifer forest in northern New Mexico and its relationship to Holocene environmental change     

R. Scott Anderson  Renata B. Jass  Jaime L. Toney  Craig D. Allen  Marcey Hess  Julianna Fessenden 《Quaternary Research》2008,69(2):263-275

Chihuahueños Bog (2925 m) in the Jemez Mountains of northern New Mexico contains one of the few records of late-glacial and postglacial development of the mixed conifer forest in southwestern North America. The Chihuahueños Bog record extends to over 15,000 cal yr BP. An Artemisia steppe, then an open Picea woodland grew around a small pond until ca. 11,700 cal yr BP when Pinus ponderosa became established. C/N ratios, δ¹³C and δ¹⁵N values indicate both terrestrial and aquatic organic matter was incorporated into the sediment. Higher percentages of aquatic algae and elevated C/N ratios indicate higher lake levels at the opening of the Holocene, but a wetland developed subsequently as climate warmed. From ca. 8500 to 6400 cal yr BP the pond desiccated in what must have been the driest period of the Holocene there. C/N ratios declined to their lowest Holocene levels, indicating intense decomposition in the sediment. Wetter conditions returned after 6400 cal yr BP, with conversion of the site to a sedge bog as groundwater levels rose. Higher charcoal influx rates after 6400 cal yr BP probably result from greater biomass production rates. Only minor shifts in the overstory species occurred during the Holocene, suggesting that mixed conifer forest dominated throughout the record.  相似文献   

First seismic record for intra-arc strike-slip tectonics along the Liquiñe-Ofqui fault zone at the obliquely convergent plate margin of the southern Andes     

D. Lange  J. Cembrano  A. Rietbrock  C. Haberland  T. Dahm  K. Bataille 《Tectonophysics》2008,455(1-4):14-24

A temporal seismic network recorded local seismicity along a 130 km long segment of the transpressional dextral strike-slip Liquiñe-Ofqui fault zone (LOFZ) in southern Chile. Seventy five shallow crustal events with magnitudes up to M_w 3.8 and depths shallower than 25 km were observed in an 11-month period mainly occurring in different clusters. Those clusters are spatially related to the LOFZ, to the volcanoes Chaitén, Michinmahuida and Corcovado, and to active faulting on secondary faults. Further activity along the LOFZ is indicated by individual events located in direct vicinity of the surface expression of the LOFZ. Focal mechanisms were calculated using deviatoric moment tensor inversion of body wave amplitude spectra which mostly yield strike-slip mechanisms indicating a NE–SW direction of the P-axis for the LOFZ at this latitude. The seismic activity reveals the present-day activity of the fault zone. The recent M_w 6.2 event near Puerto Aysén, Southern Chile at 45.4°S on April 21, 2007 shows that the LOFZ is also capable of producing large magnitude earthquakes and therefore imposing significant seismic hazard to this region.  相似文献   

Extensional Late Paleozoic deformation on the western margin of Pangea, Patlanoaya area, Acatlán Complex, southern Mexico     

M.A. Ramos-Arias  J.D. Keppie  A. Ortega-Rivera  J.W.K. Lee 《Tectonophysics》2008,448(1-4):60-76

New mapping in the northern part of the Paleozoic Acatlán Complex (Patlanoaya area) records several ductile shear zones and brittle faults with normal kinematics (previously thought to be thrusts). These movement zones separate a variety of units that pass structurally upwards from: (i) blueschist-eclogitic metamorphic rocks (Piaxtla Suite) and mylonitic megacrystic granites (Columpio del Diablo granite ≡ Ordovician granites elsewhere in the complex); (ii) a gently E-dipping, listric, normal shear zone with top to the east kinematic indicators that formed under upper greenschist to lower amphibolite conditions; (iii) the Middle–Late Ordovician Las Minas quartzite (upper greenschist facies psammites with minor interbedded pelites intruded by mafic dikes and a leucogranite dike from the Columpio del Diablo granite) unconformably overlain by the Otate meta-arenite (lower greenschist facies psammites and pelites): roughly temporal equivalents are the Middle–Late Ordovician Mal Paso and Ojo de Agua units (interbedded metasandstone and slate, and metapelite and mafic minor intrusions, respectively) — some of these units are intruded by the massive, 461 ± 2 Ma, Palo Liso megacrystic granite: decussate, contact metamorphic muscovite yielded a ⁴⁰Ar/³⁹Ar plateau age of 440 ± 4 Ma; (iv) a steeply-moderately, E-dipping normal fault; (v) latest Devonian–Middle Permian sedimentary rocks (Patlanoaya Group: here elevated from formation status). The upward decrease in metamorphic grade is paralleled by a decrease in the number of penetrative fabrics, which varies from (i) three in the Piaxtla Suite, through (ii) two in the Las Minas unit (E-trending sheath folds deformed by NE-trending, subhorizontal folds with top to the southeast asymmetry, both associated with a solution cleavage), (iii) one in the Otate, Mal Paso, and Ojo de Agua units (steeply SE-dipping, NE–SW plunging, open-close folds), to (iv) none in the Patlanoaya Group. ⁴⁰Ar/³⁹Ar analyses of muscovite from the earliest cleavage in the Las Minas unit yielded a plateau age of 347 ± 3 Ma and show low temperature ages of  260 Ma. Post-dating all of these structures and the Patlanoaya Group are NE-plunging, subvertical folds and kink bands. An E–W, vertical normal fault juxtaposes the low-grade rocks against the Anacahuite amphibolite that is cut by megacrystic granite sheets, both of which were deformed by two penetrative fabrics. Amphibole from this unit has yielded a ⁴⁰Ar/³⁹Ar plateau age of 299 ± 6 Ma, which records cooling through  490 °C and is probably related to a Permo-Carboniferous reheating event during exhumation. The extensional deformation is inferred to have started in the latest Devonian ( 360 Ma) during deposition of the basal Patlanoaya Group, lasting through the rapid exhumation of the Piaxtla Suite at  350–340 Ma synchronous with cleavage development in the Las Minas unit, deposition of the Patlanoaya Group with active fault-related exhumation suggested by Mississippian and Early Permian conglomerates ( 340 and 300 Ma, respectively), and continuing at least into the Middle Permian (≡ 260 Ma muscovite ages). The continuity of Mid-Continent Mississippian fauna from the USA to southern Mexico suggests that this extensional deformation occurred on the western margin of Pangea after closure of the Rheic Ocean.  相似文献