The geological evolution of the Gangpur Schist Belt,eastern India: Constraints on the formation of the Greater Indian Landmass in the Proterozoic     

Tuhin Chakraborty  Dewashish Upadhyay  Sameer Ranjan  Kamal L. Pruseth  Jayanta K. Nanda 《Journal of Metamorphic Geology》2019,37(1):113-151

The Central Indian Tectonic Zone (CITZ) is a Proterozoic suture along which the Northern and Southern Indian Blocks are inferred to have amalgamated forming the Greater Indian Landmass. In this study, we use the metamorphic and geochronological evolution of the Gangpur Schist Belt (GSB) and neighbouring crustal units to constrain crustal accretion processes associated with the amalgamation of the Northern and Southern Indian Blocks. The GSB sandwiched between the Bonai Granite pluton of the Singhbhum craton and granite gneisses of the Chhotanagpur Gneiss Complex (CGC) links the CITZ and the North Singhbhum Mobile Belt. New zircon age data constrain the emplacement of the Bonai Granite at 3,370 ± 10 Ma, while the magmatic protoliths of the Chhotanagpur gneisses were emplaced at c. 1.65 Ga. The sediments in the southern part of the Gangpur basin were derived from the Singhbhum craton, whereas those in the northern part were derived dominantly from the CGC. Sedimentation is estimated to have taken place between c. 1.65 and c. 1.45 Ga. The Upper Bonai/Darjing Group rocks of the basin underwent major metamorphic episodes at c. 1.56 and c. 1.45 Ga, while the Gangpur Group of rocks were metamorphosed at c. 1.45 and c. 0.97 Ga. Based on thermobarometric studies and zircon–monazite geochronology, we infer that the geological history of the GSB is similar to that of the North Singhbhum Mobile Belt with the Upper Bonai/Darjing and the Gangpur Groups being the westward extensions of the southern and northern domains of the North Singhbhum Mobile Belt respectively. We propose a three‐stage model of crustal accretion across the Singhbhum craton—GSB/North Singhbhum Mobile Belt—CGC contact. The magmatic protoliths of the Chhotanagpur Gneisses were emplaced at c. 1.65 Ga in an arc setting. The earliest accretion event at c. 1.56 Ga involved northward subduction and amalgamation of the Upper Bonai Group with the Singhbhum craton followed by accretion of the Gangpur Group with the Singhbhum craton–Upper Bonai Group composite at c. 1.45 Ga. Finally, continent–continent collision at c. 0.96 Ga led to the accretion of the CGC with the Singhbhum craton–Upper Bonai Group–Gangpur Group crustal units, synchronous with emplacement of pegmatitic granites. The geological events recorded in the GSB and other units of the CITZ only partially overlap with those in the Trans North China Orogen and the Capricorn Orogen of Western Australia, indicating that these suture zones are not correlatable.  相似文献   

N2O emissions of India: an assessment of temporal, regional and sector trends     

Amit Garg  P. R. Shukla  Jigeesha Upadhyay 《Climatic change》2012,110(3-4):755-782

This paper estimates the national level trend of India’s N₂O emissions from 1985–2005 and detailed sub-regional (594 districts) level and sector emissions for the year 2005. N₂O emissions are estimated using the latest methodologies (IPCC 2006), disaggregated activity data and indigenized emission factors. The estimates show that India’s N₂O emissions have grown from 144?Gg in 1985 to 267?Gg in 2005 exhibiting a compounded annual growth rate of 3.1%, which has been gradually declining from 4.7% over 1985–1990 to 2.4% over 2000–2005. N-fertilizer application contributed most to N₂O emissions, a 49% share in 2005 compared to 40% in 1985. Sub-regional (district-level) distribution of N₂O emissions showed rising mean and spread over the years, with average emissions per districts increasing from 305?ton N₂O per year in 1990 to 450?tons in 2005. The main reason being increased use of N-fertilizer. However crop selection plays an important role in N₂O emissions and there are crops providing high economic returns but low N-fertilizer requirements. Agriculture sector could contribute considerably to GDP even with very low N₂O emissions. Indian agriculture practices vary widely in input applications and crop yields across states. The gradual transition from traditional to modern agriculture over past two decades has enhanced the intensity of inputs like N-fertilizer. A simple correlation based on 1985–2005 trends shows that, ceteris paribus, a 10% increase in total crop production is accompanied with a 12.4% increase in N-fertilizer application and a 9.7% increase in total N₂O emissions from India.  相似文献   

Jurassic foraminifera from Jajiya Member,Jaisalmer Formation,Western Rajasthan   总被引：1，自引：0，他引：1  

Abu Talib  Gagnesh Upadhyay  M. Haseen 《Journal of the Geological Society of India》2014,83(1):38-46

The Jajiya Member of Jaisalmer Formation yielded a foraminiferal assemblage comprising twenty-three species dominated by the family Vaginulinidae. An Oxfordian age is assigned to the foraminiferal assemblage based on the record of some characteristic Oxfordian species reported from different parts of the world. The foraminiferal assemblage suggests an open marine shelf environment of deposition.  相似文献   

Study of microflares through soxs mission     

Rajmal Jain  Vishal Joshi  Yoichiro Hanaoka  T. Sakurai  Nipa Upadhyay 《Journal of Astrophysics and Astronomy》2006,27(2-3):339-346

We present a study of 10 microflares observed in 4–30 keV by SOXS mission simultaneously with Hα observations made at NAOJ, Japan during the interval between February and August 2004. The X-ray and Hα light curves showed that the lifetime of microflares varies between 4 and 25 min. We found that the X-ray emission in all microflares under study in the dynamic energy range of 4–30 keV can be fitted by thermal plus non-thermal components. The thermal spectrum appeared to start from almost 4 keV, low level discriminator (LLD) of both Si and CZT detectors, however it ends below 8 keV. We also observed the Fe line complex features at 6.7 keV in some microflares and attempted to fit this line by isothermal temperature assumption. The temperature of isothermal plasma of microflares varies in the range between 8.6 and 10.1 MK while emission measure between 0.5 and 2x10⁴9 cm^-3. Non-thermal (NT) emission appeared in the energy range 7–15 keV with exponent -6.8 ≤γ≤-4.8. Our study of microflares that had occurred on 25 February 2004 showed that sometimes a given active region produces recurrent microflare activity of a similar nature. We concluded from X-ray and simultaneous Hα observations that the microflares are perhaps the result of the interaction of low lying loops. It appears that the electrons that accelerated during reconnection heat the ambient coronal plasma as well as interact with material while moving down along the loops and thereby produce Hα bright kernels.  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   

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   

Cosmic ray ionization of lower Venus atmosphere     

Hari Om Upadhyay  R. P. Singh  R. N. Singh 《Earth, Moon, and Planets》1994,65(1):89-94

Cosmic ray particles passing through dense lower atmosphere of Venus decay giving rise to various charged and neutral particles. The flux and degradation of dominant cascade particles namely neutrinos and pions are computed and ionization contributions at lower altitudes are estimated. Using the height profile of pion flux, the muon flux is computed and used to estimate ionization at lower altitudes. It is shown that cosmic ray produced ionization descends to much lower altitudes intercepting the thickness of Venus cloud deck. The dynamical features of Venus cloud deck are used to allow the likely charging and charge separation processes resulting into cloud-to-cloud lightning discharges.  相似文献   

Response of Venus ions to solar wind dynamic pressure     

Hari Om Upadhyay  K. K. Mahajan 《Earth, Moon, and Planets》1996,74(3):215-222

Orbiter ion mass spectrometer measurements, as available in the UADS data files are used to study the response of dayside Venus ions at various altitudes to solar wind dynamic pressure, P _sw. Ion densities below about 200 km are not affected by changes in P _sw. At altitudes above 200 km the ions get abruptly depleted with increase in P _sw, and this abrupt depletion occurs at lower altitudes when P _sw is high. At lower P _sw, the depletion occurs at higher altitudes. The effect is similar for all ions. These results are also compared with the empirical relationship observed by Brace et al. (1980) between the ionopause altitude and P _sw from electron density measurements on orbiter electron temperature probe.  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 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