FM Radiotelemetry Coupled with Sonic Transducers for Remote Monitoring of Water Levels in Deep Aquifers     

Joseph W. Alderman 《Ground Water Monitoring & Remediation》1986,6(2):114-116

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Assessment of trace element geochemistry of Hampton Roads harbor and lower Chesapeake Bay area sediments   总被引：5，自引：1，他引：5  

Rule  Joseph H. 《Environmental Geology》1986,8(4):209-219

Acid extractable Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb. and Zn were determined in sediments from the Inner Virginia Shelf, and from shipping channels in the lower Chesapeake Bay and Hampton Roads, Virginia, harbor system. Data were evaluated by a variety of techniques Levels of Cd, Cu, Pb, and Zn exceeded average crustal abundances for most of the study sites. Cumulative frequency curves suggested that there were two major populations for all metals and perhaps a third and smaller, one for Cd, Cr, and Mn Plots of metal vs Fe indicated no anthropogenic inputs of metals for shelf and Chesapeake Bay channel sites, but suggested anthropogenic influences for all metals in several of the inshore sites. Enrichment factor calculations showed enrichment of Cd, Pb, and Zn with respect to average crustal abundances for all sites and of Cu for the industrial harbor system. A recommendation of this study for evaluation of environmental geochemical metals data is to utilize mean concentrations, cumulative frequency plots, and metal vs Fe and/or enrichment factor calculations when evaluating the pollution status of sediments.  相似文献   

Widespread distribution of some estuarine crustaceans (Cyathura polita,Chiridotea almyra,Almyracuma proximoculi) in the limnetic zone of the lower Hudson River,New York     

Karl W. Simpson  Joseph P. Fagnani  Dean M. DeNicola  Robert W. Bode 《Estuaries and Coasts》1985,8(4):373-380

From June through September 1983, a survey was conducted to document the occurrence, abundance and distribution of benthic macroinvertebrates in the main channel, Hudson River Estuary. The survey was restricted to a 118-km reach of the limnetic zone from just below Albany to New Hamburg, New York. Results indicated that two crustacean species,Cyathura polita (Stimpson) andChiridotea almyra Bowman, are widely distributed and common throughout the limnetic zone, including areas more than 100 km upstream from the northernmost(=most upstream) intrusion of ocean-derived brackish water.Almyracuma proximoculi Jones and Burbanck was much less common, but also was found in areas well removed from any brackish-water influences. All three species previously have been thought to occur primarily in estuarine waters with at least some salinity. We could find no evidence to suggest that non-ocean derived sources were supplementing the levels of dissolved ions in the river water or sediments. Therefore, it appears that all three species have established permant populations in a truly freshwater habitat.  相似文献   

Biological marker distribution and significance in oils and rocks of the Monterey Formation,California     

Joseph A. Curiale  Douglas Cameron  Dean V. Davis 《Geochimica et cosmochimica acta》1985,49(1):271-288

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Tectonics of the Easter plate     

Joseph F. Engeln  Seth Stein 《Earth and Planetary Science Letters》1984,68(2):259-270

We present a new model for the Easter plate in which rift propagation has resulted in the formation of a rigid plate between the propagating and dying ridges. We use the distribution of earthquakes, eleven new focal mechanisms, and existing bathymetric and magnetic data to describe the tectonics of this area. Both the Easter-Nazca and Easter-Pacific Euler poles are sufficiently close to the Easter plate to cause rapid changes in rates and directions of motion along the boundaries. The east and west boundaries are propagating and dying ridges; the southwest boundary is a slow-spreading ridge and the northern boundary is a complex zone of convergent and transform motion.The Easter plate may reflect the tectonics of rift propagation on a large scale, where rigid plate tectonics requires boundary reorientation. We use simple schematic models to illustrate the general features and processes which occur at plates resulting from large-scale rift propagation.  相似文献   

Tunica Hills revisited: A reply     

John J. Alford  Joseph C. Holmes 《Quaternary Research》1984,22(1):138-139

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New constraints on the tectonic evolution of the eastern Indian Ocean     

Char-Shine Liu  Joseph R. Curray  J.M. McDonald 《Earth and Planetary Science Letters》1983,65(2):331-342

From marine magnetic anomaly studies, a fossil spreading ridge is identified beneath the Nicobar Fan in the northwestern Wharton Basin. Several north-south-trending transform faults offset this ridge left-laterally east of the 86°E transform fault. Our findings show that this ridge, which was part of the plate boundary between the Indian and Australian plates, ceased its spreading shortly after formation of magnetic anomaly 20 (～ 45.6m.y. B.P.). Since the breakup of Australia and Antarctica probably occurred sometime between 110 and 90 m.y. B.P., we suggest that the Indian, Australian, and Antarctic plates were moving relative to one another from about 90 to 45 m.y. B.P. A triple junction would have existed in the southeastern Indian Ocean during that period of time. At anomaly 19 time (～ 45m.y. B.P.), the junction became inactive, and Australia and India became a single plate. The northwest-southeast-trending Southeast Indian Ridge was formed by connecting the India-Antarctica spreading center with the Australia-Antarctica spreading center. Its activity has continued to the present time.  相似文献   

Stochastic analysis of structures and piping systems subjected to stationary multiple support excitations     

Meng-Chi Lee  Joseph Penzien 《地震工程与结构动力学》1983,11(1):91-110

A stochastic method has been developed for seismic analysis of structures and piping systems subjected to multiple support excitations. In either the time or the frequency domain, mean and extreme values of structural and piping system response can be found, including the effects of cross-correlations of modal response and cross-correlations of multiple support excitations. Stationary white noise and stationary filtered white noise ground excitations are used. A computer program has been developed to carry out the stochastic seismic analysis. Results for a realistic nuclear power plant structure and piping system with and without modal cross-correlations and support excitation cross-correlations are compared. From these results, it is concluded that neglecting cross-correlations can lead to large errors. The stochastic method reported is shown to be more accurate than the response spectrum method and more economical than the time-history method; therefore, it is recommended for seismic analysis of nuclear power plants.  相似文献   

Estimating the Impact of Global Change on Flood and Drought Risks in Europe: A Continental, Integrated Analysis   总被引：11，自引：0，他引：11  

Bernhard Lehner  Petra Döll  Joseph Alcamo  Thomas Henrichs  Frank Kaspar 《Climatic change》2006,75(3):273-299

Most studies on the impact of climate change on regional water resources focus on long-term average flows or mean water availability, and they rarely take the effects of altered human water use into account. When analyzing extreme events such as floods and droughts, the assessments are typically confined to smaller areas and case studies. At the same time it is acknowledged that climate change may severely alter the risk of hydrological extremes over large regional scales, and that human water use will put additional pressure on future water resources. In an attempt to bridge these various aspects, this paper presents a first-time continental, integrated analysis of possible impacts of global change (here defined as climate and water use change) on future flood and drought frequencies for the selected study area of Europe. The global integrated water model WaterGAP is evaluated regarding its capability to simulate high and low-flow regimes and is then applied to calculate relative changes in flood and drought frequencies. The results indicate large ‘critical regions’ for which significant changes in flood or drought risks are expected under the proposed global change scenarios. The regions most prone to a rise in flood frequencies are northern to northeastern Europe, while southern and southeastern Europe show significant increases in drought frequencies. In the critical regions, events with an intensity of today's 100-year floods and droughts may recur every 10–50 years by the 2070s. Though interim and preliminary, and despite the inherent uncertainties in the presented approach, the results underpin the importance of developing mitigation and adaptation strategies for global change impacts on a continental scale.  相似文献   

Spatial, temporal and geochemical characteristics of Silurian collision-zone magmatism, Newfoundland Appalachians: An example of a rapidly evolving magmatic system related to slab break-off   总被引：3，自引：0，他引：3  

Joseph B. Whalen  Vicki J. McNicoll  Cees R. van Staal  C. Johan Lissenberg  Frederick J. Longstaffe  George A. Jenner  Otto van Breeman 《Lithos》2006,89(3-4):377-404

Silurian plutonic suites in the Newfoundland Appalachians include abundant gabbro, monzogabbro and granite to granodiorite and lesser quartz diorite and tonalite. Most are medium- to high-K, but included are some low-K and shoshonitic mafic compositions. Felsic rocks are of both alkaline (A-type or within-plate granite (WPG)) and calc-alkaline volcanic arc granite (VAG) affinity. Mafic rocks include both arc-like (Nb/Th < 3) calc-alkaline and non-arc-like (Nb/Th > 3) transitional calc-alkaline basalt to continental tholeiitic affinity compositions. ε_Nd(T) values range from − 9.6 to + 5.4 and δ¹⁸O (VSMOW) values range from + 3.1 to + 13.2‰.

A rapid progression from exclusively arc-type to non-arc-like mafic and then contemporaneous WPG plus VAG magmatism has been documented using precise U–Pb zircon dating. Earlier arc-like plutonism indicates subduction, while asthenosphere-derived mafic magmas support slab break-off, due to subduction of a young, warm back-arc basin. Contemporaneous mafic magmas with arc and non-arc geochemical signatures may reflect tapping of asthenospheric and subcontinental lithospheric mantle (SCLM) sources and/or contamination of asthenosphere-derived magmas by SCLM or crust.

The brevity (< 5 Ma) of the mafic magmatic pulse agrees with the transient nature of magmatism associated with slab break-off. The subsequent ca. 1 to 2 m.y. period of voluminous WPG and VAG plutonism likely reflects mafic magma-driven partial melting of both SCLM and crustal sources, respectively. Continuation of VAG-like magmatism for an additional 2 to 5 m.y. may reflect lower solidus temperatures of crustal materials, enabling anatexis to continue after mantle melting ceased. East to west spatial variation of ε_Nd and (La/Yb)_CN in Silurian plutons suggests a transition from shallow melting of juvenile sources proximal to the collision zone to deeper melting of old source materials in the garnet-stability field further inboard.

Previous work has demonstrated that geochemical discriminaton of post-collisional granitoid magmatism (PCGM) is difficult in the absence of other constraints. Our example should contribute to the understanding and identification of PCGM if it can be employed as a ‘fingerprint’ for slab break-off-related PCGM within the Paleozoic geological record.  相似文献