Oxygen isotope evidence for subduction and rift-related mantle metasomatism beneath the Colorado Plateau–Rio Grande rift transition     

George B. Perkins  Zachary D. Sharp  Jane Selverstone 《Contributions to Mineralogy and Petrology》2006,151(6):633-650

Spinel lherzolite and pyroxenite xenoliths from the Rio Puerco Volcanic Field, New Mexico, were analyzed for oxygen isotope ratios by laser fluorination. In lherzolites, olivine δ¹⁸O values are high (+5.5‰), whereas δ¹⁸O values for pyroxenes are low (cpx=+5.1‰; opx=+5.4‰) compared to average mantle values. Pyroxenite δ¹⁸O values (cpx=+5.0‰; opx=+5.3‰) are similar to those of the lherzolites and are also lower than typical mantle oxygen isotope compositions. Texturally and chemically primary calcite in pyroxenite xenoliths is far from isotopic equilibrium with other phases, with δ¹⁸O values of +21‰. The isotopic characteristics of the pyroxenite xenoliths are consistent with a petrogenetic origin from mixing of lherzolitic mantle with slab-derived silicate and carbonatite melts. The anomalously low δ¹⁸O in the pyroxenes reflects metasomatism by a silicate melt from subducted altered oceanic crust, and high δ¹⁸O calcite is interpreted to have crystallized from a high δ¹⁸O carbonatitic melt derived from subducted ophicarbonate. Similar isotopic signatures of metasomatism are seen throughout the Rio Puerco xenolith suite and at Kilbourne Hole in the southern Rio Grande rift. The discrete metasomatic components likely originated from the subducted Farallon slab but were not mobilized until heating associated with Rio Grande rifting occurred. Oxygen diffusion modeling requires that metasomatism leading to the isotopic disequilibrium between calcite and pyroxene in the pyroxenites occurred immediately prior to entrainment. Melt infiltration into spinel-facies mantle (xenoliths) prior to eruption was thus likely connected to garnet-facies melting that resulted in eruption of the host alkali basalt.  相似文献   

Evolution of the Caledonian Collisional Orogen: Insight into Processes at the Base of the Tibetan Plateau     

William C McCLELLAND  Jane A GILOTTI 《《地质学报》英文版》2013,87(Z1):171-172

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The scramble for the Waste Lands: Tracking colonial legacies,counterinsurgency and international investment through the lens of land laws in Burma/Myanmar     

Jane M. Ferguson 《Singapore journal of tropical geography》2014,35(3):295-311

This article traces the revenue category and legal concept of the Waste Land in Burma/Myanmar from its original application by the British colonial apparatus in the nineteenth century, to its later use in tandem with Burma Army counterinsurgent tactics starting in the 1960s, and finally to the 2012 land laws and current issues in international investment. This adaptation of colonial ideas about territorialization in the context of an ongoing civil war offers a new angle for understanding the relationship between military tactics and the political economy of conflict and counterinsurgent strategies which crucially depended on giving local militias—both government and nongovernment—high degrees of autonomy. The recent government changes, including the more civilian representation in parliament and its shift to engage with Western economies, raise questions regarding the future of the military, as well as local autonomy and the rural peasantry's access to land. As increasing numbers of international investors are poised to enter the Myanmar market, this article will revisit notions of land use and appropriation, and finally the role of the army and its changing relationship with Waste Lands.  相似文献   

The role of horizontal resolution in simulating drivers of the global hydrological cycle   总被引：1，自引：1，他引：0  

Marie-Estelle Demory  Pier Luigi Vidale  Malcolm J. Roberts  Paul Berrisford  Jane Strachan  Reinhard Schiemann  Matthew S. Mizielinski 《Climate Dynamics》2014,42(7-8):2201-2225

The role of atmospheric general circulation model (AGCM) horizontal resolution in representing the global energy budget and hydrological cycle is assessed, with the aim of improving the understanding of model uncertainties in simulating the hydrological cycle. We use two AGCMs from the UK Met Office Hadley Centre: HadGEM1-A at resolutions ranging from 270 to 60 km, and HadGEM3-A ranging from 135 to 25 km. The models exhibit a stable hydrological cycle, although too intense compared to reanalyses and observations. This over-intensity is explained by excess surface shortwave radiation, a common error in general circulation models (GCMs). This result is insensitive to resolution. However, as resolution is increased, precipitation decreases over the ocean and increases over the land. This is associated with an increase in atmospheric moisture transport from ocean to land, which changes the partitioning of moisture fluxes that contribute to precipitation over land from less local to more non-local moisture sources. The results start to converge at 60-km resolution, which underlines the excessive reliance of the mean hydrological cycle on physical parametrization (local unresolved processes) versus model dynamics (large-scale resolved processes) in coarser HadGEM1 and HadGEM3 GCMs. This finding may be valid for other GCMs, showing the necessity to analyze other chains of GCMs that may become available in the future with such a range of horizontal resolutions. Our finding supports the hypothesis that heterogeneity in model parametrization is one of the underlying causes of model disagreement in the Coupled Model Intercomparison Project (CMIP) exercises.  相似文献   

Assessment of Offshore New Jersey Sources of Beach Replenishment Sand by Diversified Application of Geologic and Geophysical Methods     

J. S. Waldner  D. W. Hall  Jane Uptegrove  R. E. Sheridan  G. M. Ashley  Dominic Esker 《Marine Georesources & Geotechnology》2013,31(2-3):139-140

Beach replenishment serves the dual purpose of maintaining a source of tourism and recreation while protecting life and property. For New Jersey, sources for beach sand supply are increasingly found offshore. To meet present and future needs, geologic and geophysical techniques can be used to improve the identification, volume estimation, and determination of suitability, thereby making the mining and manag ing of this resource more effective. Current research has improved both data collection and interpretation of seismic surveys and vibracore analysis for projects investigating sand ridges offshore of New Jersey. The New Jersey Geological Survey in cooperation with Rutgers University is evaluating the capabilities of digital seismic data (in addition to analog data) to analyze sand ridges. The printing density of analog systems limits the dynamic range to about 24 dB. Digital acquisition systems with dynamic ranges above 100 dB can permit enhanced seismic profiles by trace static correction, deconvolution, automatic gain scaling, horizontal stacking and digital filtering. Problems common to analog data, such as wave-motion effects of surface sources, water-bottom reverberation, and bubble-pulse-width can be addressed by processing. More than 160 line miles of digital high-resolution continuous profiling seismic data have been collected at sand ridges off Avalon, Beach Haven, and Barnegat Inlet. Digital multichannel data collection has recently been employed to map sand resources within the Port of New York New Jersey expanded dredge-spoil site located 3 mi offshore of Sandy Hook, New Jersey. Multichannel data processing can reduce multiples, improve signal-to-noise calculations, enable source deconvolution, and generate sediment acoustic velocities and acoustic impedance analysis. Synthetic seismograms based on empirical relationships among grain size distribution, density, and velocity from vibracores are used to calculate proxy values for density and velocity. The seismograms are then correlated to the digital seismic profile to confirm reflected events. They are particularly useful where individual reflection events cannot be detected but a waveform generated by several thin lithologic units can be recognized. Progress in application of geologic and geophysical methods provides advan tages in detailed sediment analysis and volumetric estimation of offshore sand ridges. New techniques for current and ongoing beach replenishment projects not only expand our knowledge of the geologic processes involved in sand ridge origin and development, but also improve our assessment of these valuable resources. These reconnaissance studies provide extensive data to the engineer regarding the suitability and quantity of sand and can optimize placement and analysis of vibracore samples.  相似文献   

Composition and flight periodicity of adult caddisflies in New Zealand hill‐country catchments of contrasting land use     

Brian J. Smith  Kevin J. Collier  N. Jane Halliday 《新西兰海洋与淡水研究杂志》2013,47(4):863-878

A total of 6085 adult Trichoptera (excluding Hydroptilidae) representing 12 families, 31 genera, and 56 species were collected by a combination of Malaise net and light trapping from July 1998 to July 1999 at three hill‐country sites of contrasting catchment land use (100% native forest, a pasture site with native forest headwaters, and 100% pasture) in the Waikato, northern New Zealand. Forty‐eight species of Trichoptera were collected from Malaise nets and 45 species from light traps. Eleven species of Trichoptera were only ever collected from the Malaise nets and seven species from only the light traps. At the native forest site, Malaise nets collected more species and taxa of conservation interest than did light traps, possibly reflecting diurnal activity or non‐attraction to light by some species. Several species of Trichoptera showed site specificity and most of these were found at the native forest site. Twenty‐eight species were active for at least 6 months of the year with at least four species active all year. A minimum overnight air temperature of at least 9°C was required to induce Trichoptera flight activity, but large‐scale flight activity may require temperatures greater than 14°C. Trichoptera with free‐living and net spinning larvae exhibited extended flight periods, and for three species examined there were bi‐modal activity peaks. Adult caddisflies with cased larvae which grazed on epilithic food resources generally had reduced flight periods and one species had a well‐defined, synchronous periodicity. These findings suggest flight periodicity may partly be a functional response to larval food availability.  相似文献   

Characterisation of the recreational fishery for southern rock lobster,Jasus edwardsii,in Tasmania,Australia: Implications for management     

Jeremy M. Lyle  Alastair J. Morton  Jane Forward 《新西兰海洋与淡水研究杂志》2013,47(3):703-713

Southern rock lobster (Jasus edwardsii) support significant commercial and recreational fisheries in Tasmania, Australia. Since the mid 1990s the number of persons holding recreational lobster licences increased by over 80%, with c. 15 500 persons licensed in 2002/03. Assessment of the recreational fishery has been undertaken periodically since 1996 using a telephone‐diary survey method. The fishery was concentrated off the south‐east and east coasts of Tasmania and characterised by strong seasonality in catch and effort, which peaked markedly early in the fishing year (November‐January). Although pots were the most popular fishing method, daily catch rates by divers were more than double those for pots. Divers selectively harvested larger lobsters than those taken by pots and more frequently attained the daily bag limit of 5 lobsters. The estimated recreational harvest increased significantly since 1996/97 and in 2002/03 effectively reached a management trigger level of 10% of the total allowable commercial catch, flagging a review of recreational management arrangements.  相似文献   

Overview of GIS Applications in Estuarine Monitoring and Assessment Research     

John F. Paul  Jane L. Copeland  Michael Charpentier  Peter V. August  Jeffrey W. Hollister 《Marine Geodesy》2013,36(1-2):63-72

Geographic information systems (GIS) tools are now considered integral in estuarine monitoring and assessment research. A synopsis is presented of our estuarine applications of GIS in the Northeast region of the U.S. The applications discussed cover sample site selection, support for field sampling activities, quality assurance of data, spatial display of geographic referenced information, quantitative spatial analysis of data, and communication of results.  相似文献   

Groundwater resources and quality in northeastern Jordan: safe yield and sustainability     

Jane Dottridge  Nizar Abu Jaber 《Applied geography (Sevenoaks, England)》1999,19(4):450

Over-abstraction of groundwater is one concern of the Badia Research and Development Programme. The upper aquifer of the Azraq basin forms the largest resource of good-quality water, but current abstraction exceeds both average recharge and the safe yield of the aquifer, which is over-exploited. Although there has been no deterioration in water quality and only minor drawdown, the springs at Azraq have dried up, with severe, undesirable environmental impacts. Total abstraction of 20 × 10⁶ m³ yr⁻¹ appears to be sustainable and would allow some springflow, but this leaves a shortfall of 40 × 10⁶ m³ yr⁻¹ for domestic supply and agriculture.  相似文献   

Spatial variations of DMS, DMSP and phytoplankton in the Bay of Bengal during the summer monsoon 2001     

Shenoy DM  Paul JT  Gauns M  Ramaiah N  Kumar MD 《Marine environmental research》2006,62(2):83-97

Data on the distribution of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) in relation to phytoplankton abundance in different oceanic environments is important to understand the biogeochemistry of DMS, which plays an important role in the radiation balance of the earth. During the summer monsoon of 2001 measurements were made for DMS and DMSPt (total DMSP) together with related biological parameters in the Bay of Bengal. Both DMS and DMSPt were restricted to the upper 40 m of the water column. Diatoms accounted for more than 95% of the phytoplankton and were the major contributors to the DMS and DMSPt pool. The mean concentration of DMS in the upper 40 m was observed to be around 1.8+/-1.9 nM in the study area, while DMSPt concentrations varied between 0.7 nM and 40.2 nM with a mean of 10.4+/-8.2 nM. The observed lower DMSPt in the northern Bay in spite of higher mean primary productivity, chlorophyll a and phytoplankton cell counts seemed to result from grazing. Though salinity divides the Bay into different biogeochemical provinces there is no relation between salinity and DMS or DMSPt. On the other hand DMS was linearly related to chlorophyll a:phaeopigments ratio. The results suggest the need for deeper insight into the role of diatoms in the biogeochemical cycling of DMS.  相似文献