New insights on petrography and geochemistry of impactites from the Lonar crater,India

The Lonar impact crater, India, is one of the few known terrestrial impact craters excavated in continental basaltic target rocks (Deccan Traps, ~65 Ma). The impactites reported from the crater to date mainly include centimeter‐ to decimeter‐sized impact‐melt bombs, and aerodynamically shaped millimeter‐ and submillimeter‐sized impact spherules. They occur in situ within the ejecta around the crater rim and show schlieren structure. In contrast, non–in situ glassy objects, loosely strewn around the crater lake and in the ejecta around the crater rim do not show any schlieren structure. These non–in situ fragments appear to be similar to ancient bricks from the Daityasudan temple in the Lonar village. Synthesis of existing and new major and trace element data on the Lonar impact spherules show that (1) the target Lonar basalts incorporated into the spherules had undergone minimal preimpact alteration. Also, the paleosol layer as preserved between the top‐most target basalt flow and the ejecta blanket, even after the impact, was not a source component for the Lonar impactites, (2) the Archean basement below the Deccan traps were unlikely to have contributed material to the impactite parental melts, and (3) the impactor asteroid components (Cr, Co, Ni) were concentrated only within the submillimeter‐sized spherules. Two component mixing calculations using major oxides and Cr, Co, and Ni suggest that the Lonar impactor was a EH‐type chondrite with the submillimeter‐sized spherules containing ~6 wt% impactor components.     

Palaeoclimatic inferences from the behaviour of radiocarbon dates of carbonates from Sand Dunes of Rajasthan

Radiocarbon dates on pedogenic CaCO₃, accumulated at various depths in a stabilised dune at Budha Pushkar, Rajasthan, show inversion with respect to ‘stratigraphy’. Occurrence of younger carbonates overlain by older ones at various levels, is interpreted in terms of a shift in climatic conditions causing pedogenic carbonates to be leached to greater depths. Based on this model, several wetter regions during the last 6000 years have been identified. The most significant shift from a dry to a wet phase seems to have taken place between 5000 and 4500 years ago. Conclusions drawn from this study is in agreement with that based on pollen data and extends this method as a potential palaeoclimatic indicator.     

Aqueous heavy metals removal by adsorption on β-diketone-functionalized styrene–divinylbenzene copolymeric resin

An investigation was undertaken regarding the adsorption of different heavy metal ions from aqueous solutions using ??-diketone-functionalized styrene divinylbenzene resin under different experimental conditions such as initial concentration of metal ions, contact time, pH, and chelating capacity. The functionalization of resin was carried out by the condensation reaction of sodium salt of ??-diketones (pentane-1,3-dione) and chloromethylated styrene?Cdivinylbenzene resin in dichloromethane. Functionalized resin beads were characterized by Fourier transform infrared spectroscopy. The batch method was employed using different metal ions solution from 5 to 15?mg/L at different contact times. The adsorption kinetics was tested for the pseudo-first order, pseudo-second order reaction at different experimental conditions. The rate constant of adsorption kinetic models were also calculated and good correlation coefficient (R ²?>?0.9941) was obtained for pseudo-second order kinetic model. The maximum adsorption value obtain for lead (0.725728?mg/g), chromium (0.9199?mg/g), nickel (0.4974?mg/g), cobalt (0.6196?mg/g) and cadmium (0.6519?mg/g) at equilibrium condition, which shows that ??-diketone-functionalized styrene divinylbenzene resin is an effective adsorbent for toxic metal ions.     

Hydrous pyrolysis of a Type III source: fractionation effects during primary migration in natural and artificially matured samples

A core from the Cambay Shale Formation of the Cambay Basin, containing immature Type III organic matter, was pyrolysed at 300°C for different durations of time to different maturation levels. Fractionation effects were studied employing a three-step extraction technique after removal of the expelled pyrolysate. The extractable organic matter (EOM) obtained on extraction of the whole core is assumed to be that present in open pores, while that obtained on finely crushing the sample is assumed to be that present in closed pores. The EOM obtained from 1 cm chips is termed EOM from semi-open pores. The gross composition of the pyrolysates expelled during pyrolysis is not similar to the oils reservoired in the area, and there is no significant fractionation observed between expelled pyrolysates and unexpelled EOM. Our study indicates movement of fluids between closed, semi-open and open pores. In both systems, there is a higher concentration of EOM in open pores than in semi-open and closed pores, and the fraction of EOM in open pores is much greater in the artificial system than in the natural system. Fractionation effects on n-alkane and isoprenoid hydrocarbon-based parameters were also studied. n-Alkenes are present in semi-open and closed pores of the immature core and in the core after it was pyrolysed to 300°C for 6 and 48 h, but are absent in the open pores. n-Alkenes are present in closed pores in the naturally matured core. Presence of n-alkenes in the pyrolysates expelled during the 6 and 48 h experiments, but their absence in the open pores of the core, indicates that expulsion also occurs through temporary microfractures during laboratory pyrolysis, whereas in the natural system expulsion from closed pores seems to be only via semi-open and open pores.     

Reliability analysis of drilled shaft behavior using finite difference method and <Emphasis Type="Italic">Monte Carlo</Emphasis> simulation

Load displacement analysis of drilled shafts can be accomplished by utilizing the “t-z” method, which models soil resistance along the length and tip of the drilled shaft as a series of springs. For non-linear soil springs, the governing differential equation that describes the soil-structure interaction may be discretized into a set of algebraic equations based upon finite difference methods. This system of algebraic equations may be solved to determine the load–displacement behavior of the drilled shaft when subjected to compression or pullout. By combining the finite difference method with Monte Carlo simulation techniques, a probabilistic load–displacement analysis can be conducted. The probabilistic analysis is advantageous compared to standard factor of safety design because uncertainties with the shaft–soil interface and tip properties can be independently quantified. This paper presents a reliability analysis of drilled shaft behavior by combining the finite difference technique for analyzing non-linear load–displacement behavior with Monte Carlo simulation method. As a result we develop probabilistic relationships for drilled shaft design for both total stress (undrained) and effective stress (drained) parameters. The results are presented in the form of factor of safety or resistance factors suitable for serviceability design of drilled shafts.     

A high-resolution ocean-atmosphere coupled downscaling of the present climate over California

A fully coupled regional ocean-atmosphere model system that consists of the regional spectral model and the regional ocean modeling system for atmosphere and ocean components, respectively, is applied to downscale the present climate (1985–1994) over California from a global simulation of the Community Climate System Model 3.0 (CCSM3). The horizontal resolution of the regional coupled modeling system is 10 km, while that of the CCSM3 is at a spectral truncation of T85 (approximately 1.4°). The effects of the coupling along the California coast in the boreal summer and winter are highlighted. Evaluation of the sea surface temperature (SST) and 2-m air temperature climatology shows that alleviation of the warm bias along the California coast in the global model output is clear in the regional coupled model run. The 10-m wind is also improved by reducing the northwesterly winds along the coast. The higher resolution coupling effect on the temperature and specific humidity is the largest near the surface, while the significant impact on the wind magnitude appears at a height of approximately 850-hPa heights. The frequency of the Catalina Eddy and its duration are increased by more than 60 % in the coupled downscaling, which is attributed to enhanced offshore sea-breeze. Our study indicates that coupling is vital to regional climate downscaling of mesoscale phenomena over coastal areas.     

Projected climate change scenario over California by a regional ocean–atmosphere coupled model system

This study examines a future climate change scenario over California in a 10-km coupled regional downscaling system of the Regional Spectral Model for the atmosphere and the Regional Ocean Modeling System for the ocean forced by the global Community Climate System Model version 3.0 (CCSM3). In summer, the coupled and uncoupled downscaled experiments capture the warming trend of surface air temperature, consistent with the driving CCSM3 forcing. However, the surface warming change along the California coast is weaker in the coupled downscaled experiment than it is in the uncoupled downscaling. Atmospheric cooling due to upwelling along the coast commonly appears in both the present and future climates, but the effect of upwelling is not fully compensated for by the projected large-scale warming in the coupled downscaling experiment. The projected change of extreme warm events is quite different between the coupled and uncoupled downscaling experiments, with the former projecting a more moderate change. The projected future change in precipitation is not significantly different between coupled and uncoupled downscaling. Both the coupled and uncoupled downscaling integrations predict increased onshore sea breeze change in summer daytime and reduced offshore land breeze change in summer nighttime along the coast from the Bay area to Point Conception. Compared to the simulation of present climate, the coupled and uncoupled downscaling experiments predict 17.5 % and 27.5 % fewer Catalina eddy hours in future climate respectively.