Molecular composition and paleobotanical origin of Eocene resin from northeast India     

Arka Rudra  Suryendu Dutta  Srinivasan V Raju 《Journal of Earth System Science》2014,123(5):935-941

The molecular composition of fossil resins from early to middle Eocene coal from northeast India, has been analyzed for the first time to infer their paleobotanical source. The soluble component of fossil resin was analyzed using gas chromatography–mass spectrometry (GC–MS). The resin extracts are composed of cadalene-based C₁₅ sesquiterpenoids and diagenetically altered triterpenoids. The macromolecular composition was investigated using pyrolysis gas chromatography-mass spectrometry (Py-GC–MS) and Fourier transform infrared (FTIR) spectroscopy. The major pyrolysis products are C₁₅ bicyclic sesquiterpenoids, alkylated naphthalenes, benzenes and a series of C₁₇–C₃₄ n-alkene-n-alkane pairs. Spectroscopic analysis revealed the dominance of aliphatic components. The presence of cadalene-based sequiterpenoids confirms the resin to be Class II or dammar resin, derived from angiosperms of Dipterocarpaceae family. These sesquiterpenoids are often detected in many SE Asian fluvio-deltaic oils. Dipterocarpaceae are characteristic of warm tropical climate suggesting the prevalence of such climate during early Eocene in northeast India.  相似文献   

Impact of the 2004 Indian Ocean tsunami along the Tamil Nadu coastline: field survey review and numerical simulations     

G. Gopinath  F. Løvholt  G. Kaiser  C. B. Harbitz  K. Srinivasa Raju  M. Ramalingam  Bhoop Singh 《Natural Hazards》2014,72(2):743-769

The 2004 Indian Ocean tsunami had a significant impact on the Tamil Nadu coast in India. In this paper, a range of field survey data collected by different survey teams available in literature have been analyzed and compiled to serve as a basis for validation of numerical tsunami simulations. The individual field surveys reveal a significant scatter in the run-up data between the different teams, which point out that the uncertainty in these data must be taken into account when using them for validation. The inundation of the 2004 Indian Ocean tsunami is simulated for the coastlines of Chennai and Nagapattinam based on high-resolution topography. Different spatially uniform Manning friction as well as heterogeneous friction maps is used. Overall, the simulation results showed a good agreement with the field observations, but there are also some observed spatial variability in the goodness of the fit between the data and simulations. In some areas, clear discrepancies are found. The results obtained using detailed land use maps including spatially variable friction are not significantly more accurate than those employing spatially constant values. For most areas, parameters indicating relatively low friction provided best match with the observations. This may also suggest that the inundation is often strongly governed by local variations in topography.  相似文献   

Distribution and sources of carbon,nitrogen, phosphorus and biogenic silica in the sediments of Chilika lagoon     

Sadaf Nazneen  N Janardhana Raju 《Journal of Earth System Science》2017,126(1):13

The present study investigated the spatial and vertical distribution of organic carbon (OC), total nitrogen (TN), total phosphorus (TP) and biogenic silica (BSi) in the sedimentary environments of Asia’s largest brackish water lagoon. Surface and core sediments were collected from various locations of the Chilika lagoon and were analysed for grain-size distribution and major elements in order to understand their distribution and sources. Sand is the dominant fraction followed by silt + clay. Primary production within the lagoon, terrestrial input from river discharge and anthropogenic activities in the vicinity of the lagoon control the distribution of OC, TN, TP and BSi in the surface as well as in the core sediments. Low C/N ratios in the surface sediments (3.49–3.41) and cores (4–11.86) suggest that phytoplankton and macroalgae may be major contributors of organic matter (OM) in the lagoon. BSi is mainly associated with the mud fraction. Core C5 from Balugaon region shows the highest concentration of OC ranging from 0.58–2.34%, especially in the upper 30 cm, due to direct discharge of large amounts of untreated sewage into the lagoon. The study highlights that Chilika is a dynamic ecosystem with a large contribution of OM by autochthonous sources with some input from anthropogenic sources as well.  相似文献   

SAR polarimetric decomposition with ALOS PALSAR-1 for agricultural land and other land use/cover classification: case study in Rajasthan,India     

Iyyappan Muthukumarasamy  Ramakrishnan S. Shanmugam  Srinivasa Raju Kolanuvada 《Environmental Earth Sciences》2017,76(13):455

Synthetic aperture radar (SAR) has operational applications in crop mapping and monitoring in many countries due to the distinct backscatter signature at various stages of crop growth. Polarimetric analysis of SAR data from different satellites was used for information extraction from different types of scatters in imaged terrain. The scattering processes were analyzed through the received scatter matrix derived from the target decomposition of SAR data. Three decomposition techniques, namely Freeman–Durden, Cloude–Pottier and Touzi decomposition of the ALOS PALSAR-1 data, were used in this study to extract land use/cover information with a specific emphasis on agriculture. The decomposed output parameters from these techniques were classified with supervised classifier of support vector machine (SVM) using region of interest (ROI) selected land use/cover classes. An accuracy assessment for the classified output was carried out using the ROI. The Ramgarh village in Jaisalmer district of Rajasthan with the predominance of agricultural land, sand dunes and settlements was chosen as the study area. Freeman–Durden decomposition resulted in the highest overall accuracy of about 85% in the land use/cover classification among the three decomposition techniques adopted in the study. It was also observed that the accuracy of land use/cover mapping derived from Cloude–Pottier and Touzi decompositions improved with the use of eigenvalues in the SVM classification. Higher accuracies in the classification of agriculture land were noted with all the three decomposition techniques. The four parameters of Cloude–Pottier (H, A, α, β) and Touzi (α _s, Φ _s, ψ, τ) decompositions improved the classification accuracy for all the classes due to eigenvalues. The overall classification accuracy was above 88% for both the decomposition techniques with four parameters. The soil moisture values for agriculture land and sand dunes were validated through soil moisture maps generated using Oh 1992 and 2004 models.  相似文献   

Delineation of potential fluoride contamination zones in Birbhum,West Bengal,India, using remote sensing and GIS techniques     

Raju Thapa  Srimanta Gupta  Harjeet Kaur 《Arabian Journal of Geosciences》2017,10(23):527

Birbhum district in West Bengal, India, is one of the most severely affected districts by fluoride-contaminated groundwater. Fluoride content as high as 20.4 mg/L has been reported. Several cases of fluoride-related disorder such as dental fluorosis and skeletal fluorosis have been reported to be endemic in the district. Proper management of groundwater is very crucial. This contribution has been carried out for delineating potential fluoride-contaminated zones (PFCZ) in Birbhum district with the implementation of weighted overlay analysis in GIS environment. Twelve different potentially influential environmental parameters are integrated and evaluated. The final output map was categorised into two subclasses, i.e. ‘low’ and ‘high’, where the low region represents fluoride concentration of 1.5 mg/L and below and the high region represents fluoride concentration above 1.5 mg/L. The outcome reveals that approximately 24.35% of the study area falls under PFCZ, whereas about 75.65% of the study area falls under the safe zone with respect to potential fluoride contamination. On validation of the PFCZ, the reported fluoride contamination data in groundwater shows an overall 87.50% accuracy in prediction via superimposition method and 89.06 and 85.85% success and prediction rates, respectively, when validated with success and prediction rates.  相似文献   

Sensitivity Studies of Convective Schemes and Model Resolutions in Simulations of Wintertime Circulation and Precipitation over the Western Himalayas     

P. Sinha  P. R. Tiwari  S. C. Kar  U. C. Mohanty  P. V. S. Raju  S. Dey  M. S. Shekhar 《Pure and Applied Geophysics》2015,172(2):503-530

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A Kaapvaal craton debate: Nucleus of an early small supercontinent or affected by an enhanced accretion event?   总被引：1，自引：1，他引：0  

Patrick G. Eriksson  Santanu Banerjee  David R. Nelson  Martin J. Rigby  Octavian Catuneanu  Subir Sarkar  R. James Roberts  Dmitry Ruban  Mtimkulu N. Mtimkulu  P.V. Sunder Raju 《Gondwana Research》2009,15(3-4):354-372

Incorporation of the Kaapvaal craton within a speculative Neoarchaean–Palaeoproterozoic supercontinent has long been debated, and this idea provides a potential solution to solving the apparently enigmatic provenance of the huge quantities of gold within the famous Witwatersrand auriferous deposits of Kaapvaal. Within a framework of a postulated Neoarchaean “Kenorland” (“northern”; present-day reference) supercontinent, we examine possible “southern” cratons that may have been contiguous with Kaapvaal: Pilbara, Zimbabwe, Dharwar, São Francisco, Amazon, Congo. Brief reviews of their basic geology and inferred evolution in syn-Witwatersrand basin times (c. 3.1–2.8 Ga) show no obvious support for any such supercontinental amalgamations. An alternative idea to explain a measure of gross similarity amongst several Neoarchaean cratons is through global events, such as a c. 3125–3000 Ma cratonic-scale erosive event interpreted for both Pilbara and Kaapvaal, and a much more widespread magmatic event at c. 2760–2680 Ma. We postulate that a global superplume event at c. 3.0 Ga included a plume beneath the Kaapvaal cratonic nucleus, thus halting any subduction around that terrane due to the thermal anomaly. Such a speculative global magmatic event is assumed to have enhanced production of juvenile oceanic crust at mid-ocean ridges, including those “offshore” of the thermally elevated Kaapvaal nucleus. Intra-oceanic obduction complexes may have built up fairly rapidly under such conditions, globally, and once the plume event had abated, “normal” plate tectonics would have resulted in composite (greenstone-tonalite, possibly also including granite) terranes accreting with nuclei such as Kaapvaal. This enhanced plume-related cratonic growth can be seen as a rapid accretion event. Formation of the envisaged ophiolite complexes possibly encompassed deformation-related first-order concentration of gold, and once accretion occurred around Kaapvaal's nucleus, from north and west (present-day frame of reference), a second-order (deformation-related) gold concentration may have resulted. The third order of gold concentration would logically have occurred once placer systems reworked detritus derived from the orogens along the N and W margins of Kaapvaal. Such conditions and placer gold deposits are known from many Neoarchaean cratons. The initial source of gold was presumably from the much hotter Mesoarchaean mantle and may have been related to major changes in Earth's tectonic regime at c. 3.0 Ga. The unique nature of Kaapvaal is probably its early stabilization, enabling formation of a complex flexural foreland basin system, in which vast quantities of placer sediments and heavy minerals could be deposited, and preserved from younger denudation through a unique post-Witwatersrand history.  相似文献   

Phodong (Sikkim) earthquake of 14 February 2006 and its aftershocks—Coulomb stress analysis     

P. Solomon Raju  V.K. Gahalaut  M. Ravi Kumar 《Journal of Geodynamics》2008,46(1-2):63-67

The 14 February 2006 Phodong (Sikkim) earthquake of moderate magnitude (Mw 5.3) triggered several aftershocks that were recorded by a local seismic network. The thrust earthquake is part of the continuing earthquake activity in the Himalayan seismic belt region that occurs on the detachment or ramp under the Higher Himalaya. The aftershocks of the earthquake occurred in increased stress regions caused by the earthquake rupture. Triggering of aftershocks by such a moderate magnitude earthquake implies that the faults in the Himalaya are critically stressed and even a small change of stress, about 0.001–0.002 MPa, can trigger earthquakes on such faults.  相似文献   

Variation in the Width of Transition Region Network Boundaries     

K. P. Raju 《Solar physics》2016,291(12):3519-3526

The transition region network seen in solar extreme ultraviolet (EUV) lines is the extension of the chromospheric network. The network appears as an irregular web-like pattern over the solar surface outside active regions. The average width of transition region network boundaries is obtained from the two-dimensional autocorrelation function of SOlar and Heliospheric Observatory (SOHO)/Coronal Diagnostic Spectrometer (CDS) synoptic images of the Sun in two emission lines, He i 586 Å and O v 630 Å during 1996?–?2012. The width of the network boundaries is found to be roughly correlated with the solar cycle variation with a lag of about ten months. A comparison of the widths in the two emission lines shows that they are larger for the He i line. The SOHO/CDS data also show large asymmetry in boundary widths in the horizontal (x) and vertical (y) image directions, which is shown to be caused by image distortions that are due to instrumental effects. Since the network boundary widths are related to the magnetic flux concentration along the boundaries, the results are expected to have implications on the flux transport on the solar surface, solar cycle, and the mass and energy budget of network loops and jets.  相似文献   

Representation of monsoon intraseasonal oscillations in regional climate model: sensitivity to convective physics     

U. Umakanth  Amit P. Kesarkar  Attada Raju  S. Vijaya Bhaskar Rao 《Climate Dynamics》2016,47(3-4):895-917

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