Age of the Marwar Supergroup,NW India:A note on the U–Pb geochronology of Jodhpur Group felsic volcanics

The Marwar Supergroup(NW Peninsular India)is thought to be of Ediacaran-Cambrian age,based on previous paleontological and geochronological studies.However,direct constraints on the onset of sedimentation within the Marwar basin are still scarce.In this study,we report U–Pb zircon,LA-ICP-MS,and SIMS ages from the Chhoti Khatu felsic volcanic rocks,interlayered with the Jodhpur Group sandstones(Lower Marwar Supergroup).The cathodoluminescence images of the zircons indicate complex morphologies,and core-rim textures coupled with the wide range of ages indicate that they are likely inherited or in the case of thin poorly indurated ash-beds,detrital in origin.The age spectra of 68 zircon analyses from our sampling display a dominant 800–900 Ma age peak corresponding to the age of basement"Erinpura granite"rocks in the region.The youngest inherited zircon from a felsic ash layer yielded a U–Pb age of651 Ma±18 Ma that,together with previous studies and paleontological evidence,indicates a postCryogenian age for the initiation of Marwar sedimentation following a~125 Ma hiatus between the end of Malani magmatism and Marwar deposition.     

Twelve years of tracking 52-Hz whale calls from a unique source in the North Pacific

A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones.     

The Structure of A Turbulent Jet in A Crossflow-Effect of Jet-Crossflow Velocity

A comprehensive numerical study on the three-dimensional structure of a turbulent jet in crossflow is performed. The jet-to-crossflow velocity ratio (R) varies in the range of 2 - 16; both vertical jets and inclined jets without excess streamwise momentum are considered. The numerical results of the Standard two-equation k-ε model show that the turbulent structure can be broadly categorised according to the jet-to-crossflow velocity ratio. For strong to moderate jet discharges, i.e. R> 4, the jet is characterized by a longitudinal transition through a bent-over phase during which the jet becomes almost parallel with the main freestream, to a sectional vortex-pair flow with double concentration maxima; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless distance of around 20-60. The similarity coefficients are only weakly dependent on R. The cross-section scalar field is kidney-shaped and bifurcated, vvith distinct double concentr     

The utility of the terms "bioavailability" and "bioavailable fraction" for metals

Because concentrations of total or dissolved metal usually are not good predictors of the acute toxicity of metals to aquatic biota (i.e. not all of the metal appears to be bioavailable), it has been tempting for researchers and regulators to attempt to identify a form or combination of forms of a metal that is the bioavailable fraction. But from geochemical, biological, and analytical perspectives, the term 'bioavailable fraction" is context-specific (i.e. not generalizable) and quantitatively elusive. Although the term "bioavailability" conveys a useful, general concept and should be retained in the aquatic-toxicology lexicon, the term "bioavailable fraction" should be avoided.     

Economic benefit of the protection program for the Steller sea lion

This paper examines willingness to pay (WTP) for an endangered species across geographically nested samples using the Contingent Valuation Method (CVM). The three samples range from (1) the boroughs that contain critical habitat for the Steller sea lion to (2) the state that contains these boroughs to and (3) the entire United States. Depending on the assumptions of the model, WTP varies tremendously from sample to sample. WTP for the United States is the highest and it is the lowest for the boroughs. The null hypotheses that mean WTP estimates are greater then zero were rejected for the boroughs and the state but were not rejected for the United States based on the 95% confidence intervals.     

A critical review of three methods used for the measurement of mercury (Hg)-dissolved organic matter stability constants

Three experimental techniques – ion exchange, liquid–liquid extraction with competitive ligand exchange, and solid-phase extraction with competitive ligand exchange (CLE–SPE) – were evaluated as methods for determining conditional stability constants (K) for the binding of mercury (Hg²⁺) to dissolved organic matter (DOM). To determine the utility of a given method to measure stability constants at environmentally relevant experimental conditions, experimental results should meet three criteria: (1) the data must be experimentally valid, in that they were acquired under conditions that meet all the requirements of the experimental method, (2) the Hg:DOM ratio should be determined and it should fall within levels that are consistent with environmental conditions, and (3) the stability constants must fall within the detection window of the method. The ion exchange method was found to be limited by its detection window, which constrains the method to stability constants with log K values less than about 14. The liquid–liquid extraction method was found to be complicated by the ability of Hg–DOM complexes to partition into the organic phase. The CLE–SPE method was found to be the most suitable of these methods for the measurement of Hg–DOM stability constants. Stability constants for DOM isolates measured using the CLE–SPE method at environmentally relevant Hg:DOM ratios were log K = 25–30 (M⁻¹). These values are consistent with the strong Hg²⁺ binding expected for reduced S-containing binding sites.     

Surface Energy Balance Measurements Above an Exurban Residential Neighbourhood of Kansas City,Missouri

Previous measurements of urban energy balances generally have been limited to densely built, central city sites and older suburban locations with mature tree canopies that are higher than the height of the buildings. In contrast, few data are available for the extensive, open vegetated types typical of low-density residential areas that have been newly converted from rural land use. We made direct measurements of surface energy fluxes using the eddy-covariance technique at Greenwood, a recently developed exurban neighbourhood near Kansas City, Missouri, USA, during an intensive field campaign in August 2004. Energy partitioning was dominated by the latent heat flux under both cloudy and near clear-sky conditions. The mean daytime Bowen ratio (β) values were 0.46, 0.48, and 0.47 respectively for the cloudy, near clear-sky and all-sky conditions. Net radiation (R _n ) increased rapidly from dawn (−34 and −58W m⁻²) during the night to reach a maximum (423 and 630W m⁻²) after midday for cloudy and near clear-sky conditions respectively. Mean daytime values were 253 and 370W m⁻², respectively for the cloudy and near clear-sky conditions, while mean daily values were 114 for cloudy and 171W m⁻² for near clear-sky conditions, respectively. Midday surface albedo values were 0.25 and 0.24 for the cloudy and near clear-sky conditions, respectively. The site exhibited an angular dependence on the solar elevation angle, in contrast to previous observations over urban and suburban areas, but similar to vegetated surfaces. The latent heat flux (Q _E ), sensible heat flux (Q _H ), and the residual heat storage ΔQ _s terms accounted for between 46–58%, 21–23%, and 18–31% of R _n , respectively, for all-sky conditions and time averages. The observed albedo, R _n , and Q _E values are higher than the values that have been reported for suburban areas with high summer evapotranspiration rates in North America. These results suggest that the rapidly growing residential areas at the exurban fringe of large metropolitan areas have a surface energy balance that is more similar to the rural areas from which they were developed than it is to the older suburbs and city centres that make up the urban fabric to which they are being joined.     

Numerical simulations of the tropical air-sea planetary boundary layer

A one-dimensional numerical model of the planetary boundary layer was used to investigate thermal and kinetic energy budgets. The simulation experiments were based on two sets of data. The first set was based on a ‘typical’ June with climatological data extracted for the oceanic region slightly northeast of Barbados. The second set used data from the third phase of project BOMEX, for approximately the same area and time of year as the first set. Comparison with observations of three simulated elements (viz., sea surface temperature and wind and humidity at 6 m) which are important in determining the near-interface energy transports shows that:

1. the model is capable of realistic simulations of both ‘typical’ conditions, and conditions for a specific four-day period;
2. the model is capable of realistically simulating the differences between prevailing values of these parameters in the two cases (‘typical’ and specific four-day period).

The simulated interface fluxes are those of incoming and outgoing short- and long-wave radiation; transmitted radiation at -0.5 m in the ocean, sensible heat transfer into the ocean and air, and latent heat flux of evaporation. Comparison with observational analyses shows that the diurnal variations in net radiation and heat storage in the mixed layer are realistically simulated. The simulated values of evaporation are consistent with other estimates for both ‘typical’ conditions and specific conditions during this four-day period. The rate of heat storage varies between +51 and -37 percent of the diurnal maximum incoming radiation, and the evaporation varies between +16% and -13% of this term. The non-dimensional transfer coefficients (C _D, C_T, C_q) computed from the model show general agreement with the coefficients calculated from observations in the simulated region (Pondet al., 1971). The simulated vertical profiles of temperature are in general agreement with observed profiles, except in the uppermost portions of the atmospheric boundary layer where deviations of approximately 1.5C occur. Simulated vertical profiles of wind speed are generally consistent with observed profiles, with the largest deviations appearing to be of the order of 0.5 m s^-1. Simulated vertical profiles of the eddy fluxes of sensible heat, water vapor, and momentum are generally consistent with Bunker's (1970) aircraft-based measurements of these quantities. The time averages of these simulated profiles show regular decreases with height, while simulated profiles for specific hours of the day show intermediate maxima and minima, which are also seen in the measured profiles. The vertically integrated kinetic energy budgets of the modelled atmospheric layer are presented through the four terms of the kinetic energy budget, viz., the upper and the lower boundary drags, dissipation, and potential-to-kinetic conversion. The dominant terms in the atmospheric energy budgets are the production and dissipation terms, with kinetic energy being exported both to the overlying atmospheric layer and to the underlying oceanic layer at rates of about 2 to 6% of the production, respectively. Comparisons between the climatological and BOMEX simulations are presented. The vertically integrated humidity budgets are presented for the two simulation experiments. Under ‘typical’ conditions, the humidity budget reveals an upper boundary flux of about +29% of the lower boundary flux with the vertically integrated advective flux being -59% of the lower flux. For the specific four-day simulation, the upper boundary flux and advection are about +28 and -70%, respectively, of the lower boundary flux.