Kinematical distances to open star clusters     

Ram Sagar  Harish C. Bhatt 《Journal of Astrophysics and Astronomy》1988,9(2):117-124

Kinematical distances are estimated for six open star clusters. They agree fairly well with the photometric distances. The kinematical distances cannot, at present, be estimated better than the photometric distances. When more accurate proper motion measurements become available the kinematical distances will improve considerably and may then be used to calibrate the cosmic distance scale.  相似文献   

Rapeseed-mustard acreage estimation using IRS LISS-II data     

S. A. Sharma  H. P. Bhatt  Ajai  Sandeep Nanavaty 《Journal of the Indian Society of Remote Sensing》1991,19(1):59-65

The present paper describes the remote sensing-based acreage estimation of rapeseed-mustard crop in Mehsana and Banaskantha districts of Gujarat, using four-band data and Maximum Likelihood classification. IRS LISS-II data of November 25, 1989 has been used to estimate the acreage of rapeseed-mustard. It is found that the data of November 25 is useful in discriminating rapeseedmustard from other rabi crops. Talukawise acreage estimation has also been done for three talukas of Mehsana and two talukas of Banaskantha district.  相似文献   

The Neogene/Quaternary boundary in India: A review     

D P Agrawal  D K Bhatt  Sheela Kusumgar  R K Pant 《Journal of Earth System Science》1981,90(2):111-123

The Neogene/Quaternary boundary has been variously defined in different continents. A global review of the problem shows that only the Olduvai event on the palaeomagnetic timescale may provide an universally acceptable isochronous datum for delineating this boundary. The N/Q boundary in the Siwaliks, Kashmir and the Andamans in India is defined in the light of recent research.  相似文献   

CaMg ratio classification of main limestones (Mississippian) in South Wales,U.K.     

J.J. Bhatt 《Sedimentary Geology》1973,10(3):225-231

The highly dolomitized Main Limestones of approximately Mississippian age, which crop out in South Wales, are classified according to their $\text{Ca}\text{Mg}$ ratio values. The results based upon the $\text{Ca}\text{Mg}$ ratio determination of these rocks permitted their classification into six major categories, namely: (1) limestone; (2) slightly dolomitized limestone; (3) dolomitic limestone; (4) calcitic dolostone; (5) dolostone proper; and (6) magnesian dolostone.It is concluded that dolostone proper and calcitic dolostone tend to dominate in the Main Limestone rocks of South Wales.  相似文献   

Application of GPR in the study of shallow subsurface sedimentary architecture of Modwa spit,Gulf of Kachchh     

S. B. Shukla  A. K. Patidar  Nilesh Bhatt 《Journal of Earth System Science》2008,117(1):33-40

The coastline constitutes a very sensitive geomorphic domain constantly subjected to dynamic coastal processes. The study of its ever-changing physiography and stratigraphy provides a wealth of information on its history and evolution, in many cases at decadal and annual scales. The present study was carried out on the Modwa beach complex between Rawal Pir and Modwa, about 10 km east of Mandvi on the northern coast of the Gulf of Kachchh. The Modwa spit is a 7-km long WNW-ESE trending prograding amalgamated beach ridge complex that is about 0.5 km wide at its western end and 1.5 km wide at its eastern end. This Ground-Penetrating Radar (GPR) survey delineated a variety of the radar surfaces and radar facies which reflects not only large scale sedimentary architecture, but depositional facies of the beach ridge complex. These are bounding surfaces separating the radar facies outline beach ridge (br), washover (wo), coastal dune (cd) and swale (sw) depositional environments. The internal sedimentary structures like tangential, parallel, concave and convex upward stratifications could also be visualized from the GPR profiles. The architecture suggests the formation of this complex due to a combined process of eastward littoral drift of locally derived sediments and its onshore deposition by storms and eolian activities.  相似文献   

Archaeological Evidence for Modern Coastal Uplift at Diu,Saurashtra Peninsula,India     

Mikls Kzmr  Nilesh Bhatt  Vishal Ukey  Siddharth Prizomwala  Danko Taboro&#x;i  Balzs Szkely 《Geoarchaeology》2016,31(5):376-387

There is a tank hewn into coastal Pleistocene limestone near Diu city on the Saurashtra Peninsula of western India. Site survey and a review of similar structures worldwide provide evidence that this tank could have been used for holding fish or Murex snails. The approximately 5 × 5 m tank is connected to the sea by a 1‐m‐deep canal; today it would be impossible to use the tank, given that not even the high spring tides can fill it. It is suggested that the Diu coast was uplifted by ∼0.5 m after the tank was hewn in the coastal platform. Since that time, the carved surfaces have been modified by coastal karst dissolution and have developed deep gouge marks. Uplift of the Diu coast raises the possibility of a major seismic event in Diu during the latter part of the last millennium.  相似文献   

Crystallochemical studies on davidite from Bichun,Jaipur District,Rajasthan, India     

Yamuna Singh  Anubhooti Saxena  A K Bhatt  R Viswanathan  T S Shaji  L K Nanda 《Journal of Earth System Science》2018,127(1):4

Crystallochemical data on metamict davidite from albitites and albitised rocks from the Bichun area (Jaipur district, Rajasthan, India) of Banded Gneissic Complex (BGC) are provided. Davidite occurs as euhedral, subhedral to anhedral crystals in the form of disseminated grains and also as fracture filled veins. The crystals of davidite are up to 8 cm in length and 6 cm in width. The powder X-ray diffraction (XRD) pattern of the heat-treated davidite (at \(900{^{\circ }}\hbox {C}\)) reveals well-defined reflections of crystallographic planes. The calculated unit-cell parameters of the heat treated davidite are: \(\hbox {a}_{0} = \hbox {b}_{0} = 10.3556 \, \text {\AA }\) and \(\hbox {c}_{0} = 20.9067 \, \text {\AA }\), with unit-cell volume \(\hbox {(V)} = 1941.6385 \, \text {\AA }^{3}\); and \({\upalpha }={\upbeta }= 90^{\circ }\) and \({\upgamma }= 120^{\circ }\), which are in agreement with the values of davidite standard. Geochemical data reveals that the investigated davidite contains 51.5–52.6% \(\hbox {TiO}_{2}\), 14.8–15.1% \(\hbox {Fe}_{2} \hbox {O}_{3}\), 9.8–10.2% FeO, 6.97–7.12% \(\hbox {U}_{3} \hbox {O}_{8}\), 6.72–6.92% \(\hbox {RE}_{2} \hbox {O}_{3}\), 3.85–3.61% \(\hbox {K}_{2}\hbox {O}\), 0.9–1.4% \(\hbox {Al}_{2} \hbox {O}_{3}\), and 0.8–1.2% \(\hbox {SiO}_{2}\). The calculated structural formulae of the two davidite crystals are: D-1: \(\hbox {K}_{0.0044/0.004} \hbox {Ba}_{0.0044/0.005} \hbox {Ca}_{0.20/0.20} \hbox {Na}_{0.012/0.012} \hbox {Mn}_{0.053/0.053} \hbox {Mg}_{0.14/0.14} \hbox {Pb}_{0.0076/0.008} \hbox {Fe}_{2.675/2.675} \hbox {Fe}_{1.59/1.59} \hbox {Y}_{0.1175/0.118} \hbox {P}_{0.053/0.053} \hbox {Nb}_{0.008/0.008} \hbox {Sn}_{0.001/0.001} \hbox {Zr}_{0.033/0.033} \hbox {U}_{0.468/0.468} \hbox {Th}_{0.009/0.009} \,\,\hbox {REE}_{0.6829/0.683})_{6.05/6.05} (\hbox {Ti}_{12.15/12.15}\,\, \hbox {Fe}_{1.9022/1.903} \hbox {Si}_{0.372/0.372}\,\, \hbox {Al}_{0.517/0.517}\,\, \hbox {Cr}_{0.018/0.018} \hbox {Co}_{0.009/0.009} \hbox {Ni}_{0.027/0.027})_{15/15} \hbox {O}_{36/36} (\hbox {OH}_{0.319/0.319[]1.681/1.681})_{2/2}\) and D-2: \((\hbox {K}_{0.004/0.004} \hbox {Ba}_{0.005/0.005} \hbox {Ca}_{0.20/0.20} \hbox {Na}_{0.012/0.012} \hbox {Mn}_{0.05/0.05} \hbox {Mg}_{0.094/0.094} \hbox {Pb}_{0.007/0.007} \hbox {Fe}_{2.58/2.58} \hbox {Fe}_{1.71/1.71} \hbox {Y}_{0.112/0.112} \hbox {P}_{0.106/0.106} \hbox {Nb}_{0.006/0.006} \hbox {Sn}_{0.001/0.001} \hbox {Zr}_{0.03/0.03} \hbox {U}_{0.48/0.48} \hbox {Th}_{0.009/0.009} \hbox {REE}_{0.665/0.665})_{6.088/6.088} (\hbox {Ti}_{12.48/12.48} \hbox {Fe}_{1.87/1.87} \hbox {Si}_{0.249/0.249} \hbox {Al}_{0.334/0.334} \hbox {Cr}_{0.019/0.019} \hbox {Co}_{0.008/0.008} \hbox {Ni}_{0.04/0.04})_{15/15} \hbox {O}_{36/36} (\hbox {OH}_{0.098/0.098[]1.90/1.90})_{2/2}\). The calculated structural formulae are not fully stoichiometric, which could be due to metamict nature of davidite. The characteristic feature of distribution pattern of REE in davidite is unusually high concentration of LREE and HREE and substantially low content of MREE. It may be due to the occupation of REEs in two distinct crystallographic sites in davidite structure, i.e., M(1) and M(O) sites. Chondrite-normalised plot of davidite reveals a pronounced negative Eu-anomaly (\(\hbox {Eu}/\hbox {Eu}^{*} = 0.30{-}0.39\)), which suggests extremely fractionated nature of the metasomatising fluids from which davidite had crystallized. Metamict davidite-bearing U ores not only from Rajasthan, but also from other parts of India are likely to yield very high U leachability, thereby making them attractive sources of U, which otherwise are ignored by mineral engineers as uneconomic U ores.  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   

Image quality characterization of fine resolution RISAT-1 data using impulse response function     

Gautam Dadhich  Shweta Sharma  Mihir Rambhia  Aloke K. Mathur  P. R. Patel  Alpana Shukla 《国际地球制图》2019,34(6):586-596

This study presents the results obtained from image quality assessment of Radar Imaging SATellite (RISAT-1). Image quality parameters such as spatial resolution, peak to sidelobe ratio (PSLR) and integrated sidelobe ratio (ISLR) are calculated by the analysis of impulse response function (IRF) of the point target. The study is carried out to assess temporal stability and consistency of image quality parameters obtained from analysis of IRF of 44 point targets. The results obtained from this study show that the mean values of the range and azimuth resolution are 2.048 ± 0.081 m and 3.383 ± 0.097 m for RH and 1.981 ± 0.081 m and 3.348 ± 0.076 m for RV, respectively. PSLR/ISLR values for RH channel are obtained as ?26.492 dB/?26.823 dB for azimuth and ?19.209 dB/?19.921 dB for the range. For RV channel, PSLR/ISLR values are ?26.300 dB/?27.572 dB for azimuth and ?19.146 dB/?19.827 dB for range.  相似文献   

Magnetic fields in cometary globules – II. CG 30–31 complex     

H. C. Bhatt 《Monthly notices of the Royal Astronomical Society》1999,308(1):40-44

Optical linear polarization measurements of stars in the region of the cometary globules CG 30–31 in Vela–Puppis are presented. A polarization map representing the geometry of the magnetic field in the cometary globule complex is produced. The magnetic field is found to be nearly perpendicular to the cometary tails. This is unlike the case of the cometary globule CG 22 in which the field had earlier been found to be aligned with the tail. The observed field direction is more or less parallel to the bipolar molecular outflow from the young stellar object IRS 4 embedded in the head of CG 30.  相似文献