Depositional facies and the sequence stratigraphic control of a mixed-process influenced clastic wedge in the Cretaceous Western Interior Seaway: The Gallup System,New Mexico,USA

Depositional facies have been hypothesized to be linked to sequence stratigraphic positions. Also, shoreline systems are built by mixed processes, including rivers, storms, fair-weather waves and tides. Resolving the complexity of shoreline deposition requires detailed quantitative facies analysis with particular attention to heterolithic successions. In this study, 71 sections in a 130 km long outcrop belt of the Cretaceous Gallup Formation in the north-west of the San Juan Basin were measured. Five major facies associations were identified using sedimentological and iconological interpretations, including offshore shelf, non-deltaic shoreline sandstones, deltas, coastal bayline and fluvial. Each facies association also comprises subordinate facies. Depositional facies interpretations are placed in a high-resolution sequence stratigraphic framework that allows for reconstructions of the palaeogeography of individual parasequence sets that demonstrate temporal and spatial evolution of facies associations and depositional processes. The results show that the Gallup is a mixed-process-controlled depositional system with fair-weather and storm-wave dominance, river influence and tide-effect, contrasting with previous interpretations of a solely fair-weather wave-dominated environment. Depositional processes and the resultant facies change with sequence stratigraphic positions in response to relative sea-level changes – particular facies are only deposited in certain systems tracts. Distinction and transition between non-deltaic shorefaces and wave-dominated deltas have also been documented in this study. Non-deltaic shorefaces are characterized by homogeneous sandstones with a wide-range bioturbation index and the absence of mudstones. Wave-dominated deltas are subject to river influence and contain prodelta facies. This study shows the importance of detailed facies analysis with high-resolution sequence stratigraphic control using outcrops for documenting sedimentary processes of shallow marine shoreline systems.     

Study of X-ray transients with Scanning Sky Monitor (SSM) onboard AstroSat

Scanning Sky Monitor (SSM) onboard AstroSat is an X-ray sky monitor in the energy range 2.5–10 keV. SSM scans the sky for X-ray transient sources in this energy range of interest. If an X-ray transient source is detected in outburst by SSM, the information will be provided to the astronomical community for follow-up observations to do a detailed study of the source in various other bands. SSM instrument, since its power-ON in orbit, has observed a number of X-ray sources. This paper discusses observations of few X-ray transients by SSM. The flux reported by SSM for few sources during its Performance Verification phase (PV phase) is studied and the results are discussed.     

Peculiarities of Rayleigh wave displacement in a transversely isotropic half space

We consider a transversely isotropic medium with vertical axis of symmetry (VTI). Rayleigh wave displacement components in a homogeneous VTI medium contain exp(±kr_jz), where z is the vertical coordinate, k is the wave number, and j?=?1, 2; r_j may be considered as depth-decay factor. In a VTI medium, r_j can be a real or imaginary as in an isotropic medium, or it can be a complex depending on the elastic parameters of the VTI medium; if complex, r₁ and r₂ are complex conjugates. In a homogeneous VTI half space, Rayleigh wave displacement is significantly modified with a phase shift when r_j changes from real to complex with variation of VTI parameters; at the transition, the displacement becomes zero when r₁?=?r₂. In a liquid layer over a VTI half space, Rayleigh waves are dispersive. Here, also Rayleigh wave displacement significantly modified with a phase shift when r_j changes from real to complex with a decrease of period. At very low period, phase velocity of Rayleigh waves becomes less than P-wave velocity in the liquid layer giving rise to Scholte waves (interface waves). The amplitudes of Scholte waves with a VTI half space are found to be significantly larger than those with an isotropic half space.     

An assessment of the potential impact of climate change on flood risk in Mumbai

Managing risks from extreme events will be a crucial component of climate change adaptation. In this study, we demonstrate an approach to assess future risks and quantify the benefits of adaptation options at a city-scale, with application to flood risk in Mumbai. In 2005, Mumbai experienced unprecedented flooding, causing direct economic damages estimated at almost two billion USD and 500 fatalities. Our findings suggest that by the 2080s, in a SRES A2 scenario, an ??upper bound?? climate scenario could see the likelihood of a 2005-like event more than double. We estimate that total losses (direct plus indirect) associated with a 1-in-100 year event could triple compared with current situation (to $690?C$1,890 million USD), due to climate change alone. Continued rapid urbanisation could further increase the risk level. The analysis also demonstrates that adaptation could significantly reduce future losses; for example, estimates suggest that by improving the drainage system in Mumbai, losses associated with a 1-in-100 year flood event today could be reduced by as much as 70%.,We show that assessing the indirect costs of extreme events is an important component of an adaptation assessment, both in ensuring the analysis captures the full economic benefits of adaptation and also identifying options that can help to manage indirect risks of disasters. For example, we show that by extending insurance to 100% penetration, the indirect effects of flooding could be almost halved. We conclude that, while this study explores only the upper-bound climate scenario, the risk-assessment core demonstrated in this study could form an important quantitative tool in developing city-scale adaptation strategies. We provide a discussion of sources of uncertainty and risk-based tools could be linked with decision-making approaches to inform adaptation plans that are robust to climate change.     

On Improving the Solution by Using Lower Bound Finite Elements Limit Analysis and Linear Programming

This study presents an improved technique for obtaining the collapse loads for any geotechnical stability problem with the application of the lower bound finite elements limit analysis in combination with linear programming. In the proposed method, a lower order polygon is initially used throughout the problem domain to model the Mohr–Coulomb yield function; the order of the polygon refers to its total number of sides. After obtaining the initial solution, the problem domain is then discretized into a number of zones in which a different order polygon is used to model the yield surface. It is noted that a higher order polygon needs to be chosen only in a region, not everywhere, where the stress state approaches towards the yield. The total memory usage as well as the computational time needed to solve the problem with the proposed technique becomes significantly smaller. In order to check the validity of the method, the bearing capacity factor N_γ was computed for smooth as well as rough strip footing and the obtained computational results were found to be quite encouraging.     

Ecological consideration of trace element contamination in sediment cores from Sundarban wetland,India

This article reports on the concentration of selected trace elements (Mn, Zn, Cr, Cu, Ba, As, B, V, and Hg) and major elements (Fe and Al) from the intertidal sediment cores from Sundarban wetland, India. This is a typical meso-macrotidal estuarine area affected by domestic and industrial activities located upstream. The overall concentrations range is low to moderate, indicating the environmental conditions in the outfall zone (grain size, hydrodynamic regime, and confinement), which favors the in situ accumulation of pollutants. The extent of contamination from trace elements in Sundarban core sediments is evaluated through a two-pronged approach: (i) by determining the metal enrichment in the sediments through the calculation of Pollution Load Index (PLI), Enrichment Factor (EF) and Index of Geoaccumulation (I _geo), and (ii) by defining a potential level of biological risk by the use of quality criteria such as Threshold Effect Level (TEL) and Effects Range-Low (ERL) benchmarks. On the basis of the calculated indices, sediments are particularly enriched with Cr, Cu, B, V, and As. Those enrichments seem to be due to the fine granulometry of the regions with Fe and Mn oxi-hydroxides being the main metal carriers. Trace Elements input to the Sundarban wetland need to be kept under strict control in future specially with reference to As since, according to TEL and ERL benchmarks, it already appears to be associated with a potential biological risk.     

An investigation on the relationship between solar irradiance signal from ERBS and 8B solar neutrino flux signals from SNO

In the present work an attempt has been made to investigate statistical association between solar neutrino flux data (both D₂O and Salt data) collected from Sudbury Neutrino Observatory and solar irradiance data detected by Earth Radiation Budget Satellite. To serve the present purpose we have used the Multifractal Detrended Cross Correlation Analysis (MF-DCCA) based on Detrended Fluctuation Analysis (MF-X-DFA) method and the Detrending Moving Average Analysis (MF-X-DMA) which explores the long term power-law cross correlations between above two pairs of data sets. Investigation also has been made to find the frequency and time dependent local phase relationship in each pair of data sets using continuous wavelet transform (CWT) based Semblance Analysis. The Semblance Analysis reveals that there exists positive phase correlation as well as negative phase correlation between solar irradiance and D₂O data at different time sub-intervals. This type of mixed phase correlation is also experienced between solar irradiance and Salt data at different time sub-intervals. The causal relationship between the D₂O and the solar irradiance time series and that between Salt and solar irradiance time series have been revealed using Singular Spectral Analysis (SSA). Calculations indicate that possibly the present solar neutrino flux data (both D₂O and Salt data) is supportive to predict the solar irradiance data but may not the vice versa which in turn suggests that the variability of nuclear energy generation process inside the Sun may influence the solar activity.     

Usefulness of adaptive filtering for improved Digital Elevation Model generation

The Digital Elevation Models (DEMs), which represent the variation of elevation in a terrain at spatial level, are an important source of input to a variety of applications for deriving a number of terrain parameters such as relative relief, slope, aspect direction etc. In recent years, Synthetic Aperture Radar Interferometry has been viewed as a powerful approach to derive quality DEMs from a pair of SAR images. Despite the interferometric technique is often limited by several de-correlations several researchers demonstrate its effectiveness in topographic mapping. The DEM accuracy is strongly influenced by the effectiveness of the phase unwrapping technique. In this study an effective adaptive filtering approach has been used to reduce the phase noise due to de-correlation and in improving the accuracy of phase unwrapping. Two well known phase unwrapping approaches such as branch cut and minimum cost flow network have been used. Interferometric data from ASAR sensor onboard ENVISAT satellite have been used. A highly undulated terrain condition near Dehradun city situated in Uttarakhand state of India was selected to investigate the performance of this adaptive filtering approach. The RMS error between the InSAR derived elevations and the map derived elevations was obtained as 7.2 m using adaptive filter. However, elevation map of the study area could not be generated due to high de-correlation effect without the use of adaptive filter. This result clearly demonstrates the effectiveness of adaptive filtering approach for generation of DEM at meter level accuracy, which is sufficient for many engineering applications.     

Distribution of polycyclic aromatic hydrocarbons in recent sediments of Sundarban mangrove wetland of India and Bangladesh: a comparative approach

The present work is the first attempt to compare the data of a comprehensive study of the origin and distribution of 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) in surface sediments (<63 μm) from 18 sampling stations, 9 from Sundarban of Bangladesh and 9 from Indian counterpart. Σ19PAHs concentration in sediments showed wide variations from 208.3 to 12,993.1 ng g^?1 dry weight in Indian Sundarban, whereas 208.4 to 4,687.9 ng g^?1 in the case of Bangladesh. Fluoranthene, pyrene, benzo(b)fluoranthene, benzo(a)pyrene and dibenzo(a,h)anthracene were predominant species for both the countries. The PAH diagnostic ratios indicated that the PAHs in sediments from both the countries were of mixed source of hydrocarbons of both petrogenic and pyrolytic origin. According to the numerical effect-based sediment quality guidelines, the levels of PAHs in the Sundarban wetland of Bangladesh and India should not exert adverse biological effects. The TEQ values calculated for samples from the Bangladesh and Indian Sundarban varied from 13.68 to 1,014.75 and 1.31 to 2,451 ng g^?1 d.w. with an average of 221.02 and 358.63 ng g^?1, respectively. The overall contamination status of PAH was higher in India than Bangladesh.     

Generation of emissivity and land surface temperature maps using MODIS TIR data for lithological mapping over the Singhbhum-Orissa Craton

The present study was undertaken with four fold objectives, namely, (i) to estimate land surface temperature using MODIS TIR data; (ii) to calculate relative emissivities from MODIS TIR data; (iii) to identify various lithologies based on relative emissivity and land surface temperature estimation; and finally, (iv) to carry out comparative assessment analysis between the prepared lithological map and the published lithological map. The land surface temperatures for different pixels were estimated using two methods, viz., Reference Channel and Emissivity Normalization; whereas, relative emissivities were calculated by applying three methods, viz., Reference Channel, Emissivity Normalization and Alpha Residual. Lithological maps were subsequently prepared based on the estimated land surface temperatures and relative emissivity values. The present study shows that the Emissivity Normalization method gives the best results for land surface temperature estimation and also for lithological discrimination based on emissivity estimation. Twenty-four lithounits demarcated by the present study match with those of the published map, while four lithounits of the published map could not be identified in the present study. On the other hand, six additional unclassified lithounits could be demarcated in the present study, which need to be crosschecked by field study.