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   

News and notes     

N. Purnachandra Rao  Sukanta Roy  Kusumita Arora  B. K. Rastogi  Suman Sarkar  M. Venkataswamy  Raymond A. Duraiswami 《Journal of the Geological Society of India》2013,81(5):722-730

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Geothermal investigations in the Upper Vindhyan sedimentary rocks of Shivpuri area,central India     

P. Nagaraju  Labani Ray  G. Ravi  Vyasulu V. Akkiraju  Sukanta Roy 《Journal of the Geological Society of India》2012,80(1):39-47

Heat flow has been determined by combining temperature measurements in 7 boreholes with thermal conductivity measurements in the Upper Vindhyan sedimentary rocks of Shivpuri area, central India. The boreholes are distributed at 5 sites within an area of 15 × 10 km²; their depths range from 174 to 268 m. Geothermal gradients estimated from borehole temperature profiles vary from 8.0–12.7 mK m⁻¹ in the sandstone-rich formations to 25.5–27.5 mK m⁻¹ in the shale-rich formations, consistent with the contrast in thermal conductivities of the two rock types. Heat flow in the area ranges between 45 and 61 mW m⁻², with a mean of 52±6 mW m⁻². The heat flow values are similar to the >50 mW m⁻² heat flow observed in other parts of the northern Indian shield. The heat flow determinations represent the steady-state heat flow because, the thermal transients associated with the initial rifting, convergence and sedimentation in the basin as well as the more recent Deccan volcanism that affected the region to the south of the basin would have decayed, and therefore, the heat flow is in equilibrium with the radiogenic heat production of the crust and the heat flow from the mantle. The present study reports the heat flow measurements from the western part of the Vindhyan basin and provides heat flow information for the Bundhelkhand craton for the first time. Radioelement (Th, U and K) abundances have been measured both in the sedimentary rocks exposed in the area as well as in the underlying basement granite-gneiss of Bundelkhand massif exposed in the adjacent area. Radioactive heat production, estimated from those abundances, indicate mean values of 0.3 μW m⁻³ for sandstone with inter-bands of shale and siltstone, 0.25 μW m⁻³ for sandstone with inter-bands siltstone, 0.6 μW m⁻³ for quartzose sandstone, and 2.7 μW m⁻³ for the basement granitoids. With a total sedimentary thickness not exceeding a few hundred metres in the area, the heat production of the sedimentary cover would be insignificant. The radioactive heat contribution from the basement granitoids in the upper crust is expected to be large, and together with the heat flow component from the mantle, would control the crustal thermal structure in the region.  相似文献   

Revisiting the Koyna-Warna seismic zone: strain budget,present-day potential and associated hazard     

Sutar  Anup K.  Roy  Sukanta  Tiwari  V. M. 《Journal of Seismology》2021,25(5):1265-1279

Journal of Seismology - The Koyna-Warna region in western India is well known around the globe for recurrent reservoir-triggered seismicity soon after the impoundment of the Koyna and Warna...  相似文献   

Thermal conductivity of Higher Himalayan Crystallines from Garhwal Himalaya, India     

Labani Ray  Anurup Bhattacharya  Sukanta Roy   《Tectonophysics》2007,434(1-4):71-79

We report the measurements of thermal conductivity for some Higher Himalayan Crystalline rocks from Joshimath and Uttarkashi areas of the Garhwal Himalaya. Seventy-three rock samples including gneiss, metabasic rock and quartzite were measured. Gneissic rocks, which include augen gneiss, banded gneiss, felsic gneiss and fine-grained gneiss, exhibit a wide range in conductivity, from 1.5 to 3.6 Wm^− 1K^− 1 for individual samples, and 2.1 to 2.7 Wm^− 1K^− 1 for the means. Among these, augen gneisses and banded gneisses show the largest variability. Of all the rock types, quartzites (mean 5.4 Wm^− 1K^− 1) and metabasic rocks (mean 2.1 Wm^− 1K^− 1) represent the highest and lowest mean values respectively. The range in conductivity observed for gneissic rocks is significantly higher than that generally found in similar rock types in cratonic areas. The rock samples have very low porosity and exhibit feeble anisotropy, indicating that they do not contribute to the variability in thermal conductivity. Besides variations in mineralogical composition, the heterogeneous banding as well as intercalations with metabasic rocks and quartz veins, a common occurrence in structurally complex areas, appears to cause the variability in conductivity. The study therefore brings out the need for systematic characterization of thermophysical properties of major rock types comprising the Himalayan region for lithospheric thermal modeling, assessment of geothermal energy and geo-engineering applications in an area. The dataset constitutes the first systematic measurements on the Higher Himalayan Crystalline rocks.  相似文献   

EXPERIMENTAL STUDY ON INCIPIENT MOTION OF SEDIMENT PARTICLES ON GENERALIZED SLOPING FLUVIAL BEDS   总被引：3，自引：0，他引：3  

Subhasish DEY Asst. Prof.  Dept. of Civil Engrg.  Indian Inst. of Tech.  Kharagpur  West Bengal  India. Fax: +   《国际泥沙研究》2001,16(3)

1 INTRODUCTIONWhen water flows over a fluvial bed, hydro-dynandc force induced by the flow is acting on thesediment particles lying on the bed. A further increase in flow velocity results in an increase in themagnitude of this fOrce; and sediment particles begin to move if a situation is eventu8lly reached whenthe hydro-dynandc force exceeds a certain critical value. This initial movement of sediment pallicles istermed inciPient motion. The erosion and sedimentation of nuvial beds can be…  相似文献   

NONUNIFORMOPEN CHANNEL FLOW WITH UPWARD SEEPAGE THROUGH LOOSE BEDS     

Subhasish DEY 《国际泥沙研究》2003,18(3)

The Reynolds stress and bed shear stress are important parameters in fluvial hydraulics. Steady-nonuniform flow in open channels with streamwise sloping beds having upward seepage through loose beds is theoretically analyzed to estimate the Reynolds stress and bed shear stress. Equations of the Reynolds stress and bed shear stress are developed, assuming a modified logarithmic velocity distribution law due to upward seepage, and using the Reynolds and continuity equations of two-dimensional flow in open channels.  相似文献   

A Cautionary Note on the Use of Monin–Obukhov Similarity Theory in Very High-Resolution Large-Eddy Simulations     

Sukanta Basu  Avraham Lacser 《Boundary-Layer Meteorology》2017,163(2):351-355

In several recent large-eddy simulation studies, the lowest grid level was located well within the roughness sublayer. Monin–Obukhov similarity-based boundary conditions cannot be used under this scenario, and in this note we elaborate on this fundamental problem and suggest potential solutions.  相似文献   

Mineral chemistry of tourmaline from Mashak Pahar,South Purulia Shear Zone (SPSZ), eastern Indian Shield     

SANTANU ACHARJEE  JYOTISANKAR RAY  PAYEL DEY  DEBAPRIYA BHATTACHARYYA  MOUSUMI BANERJEE  BASAB CHATTOPADHYAY  SHYAMAL SENGUPTA  A K BHATT  D CHOWDHURY  A K DWIVEDI  SANJOY MAHATO  ARKA RANJAN JANA  P B MAITHANI  P V RAMESH BABU 《Journal of Earth System Science》2016,125(8):1681-1696

The area of investigation at and around Mashak Pahar, Bankura district, West Bengal, India comprises a number of rock types namely: granite gneiss, migmatized quartz tourmaline gneiss, quartz pebble conglomerate, ferruginous quartzite, quartz tourmaline veins (as veins) and graphite schists. Interestingly, the study area lies in the region extending South Purulia Shear Zone (～Tamar–Porapahar Shear Zone) which marks the boundary between two contrasting tectonic blocks of eastern India, namely, the Chhotanagpur Gneissic Terrane (CGC) to the north and Singhbhum Group of rocks to the south. The rocks of the study area are poly-phasedly deformed by three phases of folding, namely, F₁, F₂ and F₃. All the tourmalines are classified to be of ‘Alkali Group’. Chemistry of tourmalines from migmatized quartz tourmaline gneiss and those from quartz tourmaline veins are in conformity with their relation to (earthquake induced) shear system evolution in this terrain. In general, the compositional evolution of tourmaline during prograde metamorphism (～400°–730°C) has been supported by both petrographic and chemical evidences. Assessment of mineral–chemical data of constituent tourmaline grains clearly suggests compositional variations across zonal boundaries within tourmaline that was controlled by changing metamorphic milieu in this terrane. Field and petrographic evidences clearly indicate activation of earlier and later shears in this region accompanied by infiltration of boron and formation of zoned tourmaline crystals.  相似文献   

Sensitivity of Initial Conditions on Diurnal Variability of Indian Summer Monsoon     

Sukanta Kumar Das  Sanjib Kumar Deb  C. M. Kishtawal  Pradip Kumar Pal 《Pure and Applied Geophysics》2015,172(10):2777-2790

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