Mesoproterozoic rift-related alkaline magmatism at Elchuru, Prakasam Alkaline Province, SE India   总被引：6，自引：0，他引：6  

D. Upadhyay  M.M. Raith  K. Mezger  K. Hammerschmidt 《Lithos》2006,89(3-4):447-477

The Elchuru alkaline complex in the Prakasam igneous province represents one occurrence of several alkaline bodies within the craton–Eastern Ghats Belt contact zone in Peninsular India. Nepheline syenites and associated mafic rocks intruded the cratonic crust at ≈1321 Ma and were deformed–metamorphosed to amphibolite facies condition during Pan-African times. Trace element compositions and Sr, Nd and Pb isotopic systematics indicate that the alkaline magma was derived from an enriched mantle source in the sub-continental lithosphere. The adjacent crusts of the Eastern Dharwar craton and the Eastern Ghats Belt were not involved either as source or as contaminants. The enriched mantle source was at least 1.9–2.1 Ga old as seen from the depleted mantle model ages of the rocks. The primary parent magma was a basanitic liquid that fractionated ferrokaersutite and clinopyroxene in the mantle, lowering the density sufficiently for the residual melt to intrude the crust. Magmatic differentiation in the suite can be explained by a two stage fractional crystallization model involving the removal of amphibole, clinopyroxene, allanite, titanite, apatite and zircon. The rift-related intra-continental setting of the complex indicates that alkaline magmatism represents the manifestation of a Mesoproterozoic continental breakup. Rifting along the cratonic margin may have led to the formation of several cratogenic basins (e.g., Chattisgarh basin, Indravati basin etc.) where stable shelf-type sediments could have been deposited on the passive margin during the Proterozoic. It could also have opened an ocean where some of the sediments of the Eastern Ghats Province may have been deposited.  相似文献   

New record of Bathonian–Callovian calcareous nannofossils in the eastern Karakoram block: a possible clue to understanding the dextral offset along the Karakoram Fault     

Rajeev Upadhyay  Jyotsana Rai  Anshu K Sinha 《地学学报》2005,17(2):149-157

We report the first record of Bathonian–Callovian calcareous nannofossils from a marine sedimentary sequence of the eastern Karakoram block, in northern India. The calcareous mudstones and packstones, occasionally bearing red chert nodules, yielded calcareous nanofossils and Middle Jurassic Choffatia furcula ammonoids. Middle to Upper Jurassic nannofossil assemblage is dominated by representatives of the genus Watznaueria. The occurrence of Ansulasphaera helvetica whose range is Upper Bathonian–Upper Callovian, indicates a correlation with nannofossil zones NJ12–13. The occurrence of Cyclagelosphaera wiedmannii further infer an Upper Bathonian–Callovian age. These specimens show affinities with those found in a similar sedimentary formation exposed in north Karakoram. This suggests the existence of a narrow and elongated sedimentary basin, oriented in a NW–SE direction, at a latitude of c. 25°–30°N. At that time, the Karakoram block was situated near the already welded Qiangtang block of Asia. The northern and eastern Karakoram blocks were connected during Middle Jurassic. The activity and dextral offset of the Karakoram fault separated the Jurassic sedimentary formations of the northern and eastern Karakoram blocks by c. 150 km.  相似文献   

The VLT-UVES survey for molecular hydrogen in high-redshift damped Lyman α systems: physical conditions in the neutral gas     

Raghunathan Srianand  Patrick Petitjean  Cédric Ledoux  Gary Ferland  Gargi Shaw 《Monthly notices of the Royal Astronomical Society》2005,362(2):549-568

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The effect of Coriolis force on acceleration covariance in MHD turbulent dusty flow with rotational symmetry     

T. Dixit  B. N. Upadhyay 《Astrophysics and Space Science》1989,153(2):257-268

In this paper we have considered MHD turbulent dusty flow of an incompressible, viscous fluid which is nearly isotropic with rotational and spatially homogeneous. The expression for acceleration covariance in the presence of Coriolis force has been derived and solution has been obtained in terms of defining scalars.  相似文献   

Focal mechanism solutions and dynamic parameters of earthquakes in the eastern Himalayas and northern Burma     

S. K. Upadhyay  V. K. Ahuja  V. Sri Ram 《Tectonophysics》1983,93(3-4)

Focal-mechanism solutions of four earthquakes in the eastern Himalayas and northern Burma are determined using the first motion of compressional waves. Two possible solutions thus obtained for each event reveal steeply dipping fault with predominantly strike-slip motion. The stress directions inferred from the focal mechanism solutions are interpreted in the light of predictions of the plate tectonics theory, viz., the underthrusting of the Indian plate in the Burma region in an easterly direction.Dynamic parameters (seismic moment, apparent stress and average dislocations) are obtained using the corrected spectra of Love waves. The earthquakes are found to possess low seismic moment and apparent stress values. A comparison of these estimates with values for intraplate earthquakes is given. It is suggested that these earthquake might be a consequence of a nonhomogeneous rupture process.  相似文献   

Non-linear laminar flow into well partially penetrating a porous aquifer of finite thickness     

K. K. Upadhyay 《Pure and Applied Geophysics》1977,115(3):631-638

In steady state condition, non-linear laminar flow of fluid into a well partially penetrating a porous aquifer of finite thickness is considered. The influence of such a flow on discharge and its dependence on related physical quantities are investigated. It is observed that the discharge into the well decreases as the depth of the well is decreased and the region of non-linear laminar flow is widened, which is quite obvious from physical considerations. As a particular case, result for a fully penetrating well has been deduced.  相似文献   

Temporal MODIS data for identification of wheat crop using noise clustering soft classification approach   总被引：1，自引：0，他引：1  

Priyadarshi Upadhyay  S.K. Ghosh  Anil Kumar 《国际地球制图》2016,31(3):278-295

In this study, temporal MODIS-Terra MOD13Q1 data have been used for identification of wheat crop uniquely, using the noise clustering (NC) soft classification approach. This research also optimises the selection of date combination and vegetation index for classification of wheat crop. First, a separability analysis is used to optimise the date combination for each case of number of dates and vegetation index. Then, these scenes have undergone for NC soft classification. The resolution parameter (δ) was optimised for the NC classifier and found to be a value of 1.6 × 10⁴ for wheat crop identification. Classified outputs were analysed by receiver operating characteristics (ROC) analysis for sub-pixel detection. Highest area under the ROC curve was found for soil-adjusted vegetation index corresponding to the three different phenological stages data sets. From this study, the data sets corresponding to the Sowing, Flowering and Maturity phenological stages of wheat crop were found more suitable to identify it uniquely.  相似文献   

Pioneer Venus Orbiter Measurements of Solar EUV Flux During Solar Cycles 21 and 22     

K. K. Mahajan  Hari Om Upadhyay  N. K. Sethi  W. R. Hoegy  W. D. Pesnell  L. H. Brace 《Solar physics》1998,177(1-2):203-216

The Pioneer Venus Orbiter (PVO) had on board the electron temperature probe experiment which measured temperature and concentration of electrons in the ionosphere of Venus. When the probe was outside the Venus ionosphere and was in the solar wind, the probe current was entirely due to solar photons striking the probe surface. This probe thus measured integrated solar EUV flux (Ipe) over a 13-year period from January 1979 to December 1991, thereby covering the declining phase of solar cycle 21 and the rising phase of solar cycle 22. In this paper, we examine the behavior of Ipe translated to the solar longitude of Earth (to be called EIpe) during the two solar cycles. We find that total EUV flux changed by about 60% during solar cycle 21 and by about 100% in solar cycle 22. We also compare this flux with other solar activity indicators such as F_10.7 , Lα, and the solar magnetic field. We find that while the daily values of EIpe are highly correlated with F_10.7 (correlation coefficient 0.87), there is a large scatter in EIpe for any value of this Earth-based index. A comparison of EIpe with SME and UARS SOLSTICE Lα measurements taken during the same period shows that EIpe tracks Lα quite faithfully with a correlation coefficient of 0.94. Similar comparison with the solar magnetic field (Bs) shows that EIpe correlates better with Bs than with F_10.7 . We also compare EIpe with total solar irradiance measured during the same period.  相似文献   

Hyperspectral Remote Sensing of Forests: Technological advancements,Opportunities and Challenges     

Vipin Upadhyay  Amit Kumar 《Earth Science Informatics》2018,11(4):487-524

In real world what we are able to see is just because of light or energy reflected or emitted from the viewing object is falling upon retina of human eye. The variations in intensity of light reflected back from any object in different wavelengths are sensed and provide ability of discriminating different objects having similar size and shape. In the same way, in spectroscopy we sense the reflected light through artificial sensors and record as image (in airborne and satellite spectroscopy) or as spectrum (in field spectroscopy). In remote sensing discrimination of different object mainly depends on difference in reflection of energy in different wavelength region of light. Considering this behaviour of light, in hyperspectral remote sensing the reflected light coming from object is split into multiple continuous and small-small wavelength bands and are sensed in each wave band separately. Therefore we are having reflection response of object in multiple and narrow wavelength regions, which can be used in discrimination of different objects that are not separable in multispectral remote sensing due to less number of broad range wave bands. Collection of data is one aspect of the technology but as soon as these data are collected, a question arises how to and where to use this data? To answer where to use, a list of applications like discrimination, mapping and monitoring of different features and process of landforms in ecosystem have been reported, and forestry is one of them. And question of how to use these data in each applications involve converting the raw data into useful information using a multistep process of atmospheric, radiometric and geometric correction, removal of bad data and data redundancy, transformation and extraction of most useful data, data segmentation and extraction of useful information. For this purpose variety of data processing techniques, algorithms, concepts and schemes have been reported from time to time. In this review article we have summarized the available technical developments in hyperspectral remote sensing during the last three decades and tried to discuss the opportunities and challenges in hyperspectral remote sensing applications in the forestry sector.  相似文献   

An approach of understanding acid volcanics and tuffaceous volcaniclastics from field studies: A case from Tadpatri Formation,Proterozoic Cuddapah basin,Andhra Pradesh,India     

Sukanta Goswami  P K Upadhyay  Sangeeta Bhagat  Syed Zakaulla  A K Bhatt  V Natarajan  Sukanta Dey 《Journal of Earth System Science》2018,127(2):20

The lower stratigraphic part of the Cuddapah basin is marked by mafic and felsic volcanism. Tadpatri Formation consists of a greater variety of rock types due to bimodal volcanism in the upper part. Presence of bimodal volcanism is an indication of continental rift setting. Various genetic processes involved in the formation of such volcanic sequence result in original textures which are classified into volcaniclastic and coherent categories. Detailed and systematic field works in Tadpatri–Tonduru transect of SW Cuddapah basin have provided information on the physical processes producing this diversity of rock types. Felsic volcanism is manifested here with features as finger print of past rhyolite-dacite eruptions. Acid volcanics, tuffs and associated shale of Tadpatri Formation are studied and mapped in the field. With supporting subordinate studies on geochemistry, mineralogy and petrogenesis of the volcanics to validate field features accurately, it is understood that volcanism was associated with rifting and shallow marine environmental condition. Four facies (i.e., surge, flow, fall and resedimented volcaniclastic) are demarcated to describe stratigraphic units and volcanic history of the mapped area. The present contribution focuses on the fundamental characterization and categorization of field-based features diagnostic of silica-rich volcanic activities in the Tadpatri Formation.  相似文献