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Isolated Archosaur teeth from the green sandstone capping the Coralline Limestone (Bagh Group) of the Narmada valley: Evidence for the presence of pre‐Late to Late Maastrichtian abelisaurids in India 下载免费PDF全文
Guntupalli V.R. Prasad Vishal Verma Pooja Grover Rajkumari Priyadarshini Ashok Sahni Ranjit S. Lourembam 《Island Arc》2016,25(6):410-420
Recent field prospecting in the Cretaceous sequences of the lower Narmada valley has led to the discovery of three isolated archosaur teeth from the upper part of marine Cretaceous rocks of the Bagh Group. The specimens were recovered by surface prospecting from an oyster‐bearing green sandstone bed occurring at the top of the Coralline Limestone (Coniacian) from a site near Phutibawri village, Dhar District, Madhya Pradesh, India. Of the three teeth recovered from this horizon, two are identified with abelisaurid dinosaurs and the third one with an indeterminate crocodile. The abelisaurid teeth conform to the premaxillary and maxillary tooth morphology of Majungasaurus and Indosuchus. Earlier reports of abelisaurid dinosaurs from India are from the Upper Cretaceous (Maastrichtian) Lameta Group of Jabalpur, Pisdura (Central India) and Balasinor (Western India) and Upper Cretaceous (Late Maastrichtian) Kallamedu Formation (South India). As no associated age diagnostic fossils are found, the specimens described here are considered to represent pre‐Late to Late Maastrichtian age based on the known ages of the underlying and overlying formations. The new finds, therefore, document stratigraphically the oldest occurrence of abelisaurid dinosaurs known from the Indian subcontinent. 相似文献
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Comparison of two methods for ground level vapour sampling and influence of meteorological parameters on its stable isotopic composition at Roorkee,India 下载免费PDF全文
Ground level vapour (GLV) samples were collected at Roorkee, Uttarakhand, India using two methods: liquid condensation (LC) at 0 °C and cryogenic trap (CT) at ?78 °C for the period 2009–2011. The study reveals that there is a considerable fluctuation in stable isotopic composition of GLV throughout the year. The study area receives complex moisture source during different seasons, which is evident from the moisture flux received during different seasons. The isotopic composition of the GLV in both methods shows depleted nature during rainout process. CT method shows exact isotopic signature of GLV because of maximum trapping of air moisture and its condensation, whereas LC method shows depleted or enriched character because of the prevalence of kinetic and diffusive fractionation. The d value shows that LC method acts as magnifier of the CT method and clearly shows seasonal effect than the clustered CT method. Hence, to decipher the original isotopic signature of GLV, isotopic composition of GLVLC can be converted to GLVCT by deriving an empirical relationship with changing season and locations. Meteorological parameters show varied behaviour with GLVCT and LC because of moisture sources in all seasons. The GLVCT and LC method shows significant correlation with meteorological parameters when the region is dominated by single moisture source. The GLVLC method magnifies the correlation with meteorological parameters when the region is influenced by more than one source. The study shows that the GLVLC methods can be used in place of GLVCT when the objective is to understand the influence of different moisture sources on GLV. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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This work includes a study of some properties such as speed, apparent width, acceleration and latitudes, etc. of all types of Prominence Eruptions (PEs) and the associated Coronal Mass Ejections (CMEs) observed during the period of 1997–2006 by Nobeyama Radioheliograph (NORH) and SOHO/LASCO covering the solar cycle 23. The average speed of prominences and associated CMEs are 51 km/sec and 559 km/sec, respectively. The average angular width is 32° and 74°, respectively. As expected the associated CMEs are relatively faster and wider than the prominences. 相似文献
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Operational activities in the ocean like planning for structural repairs or fishing expeditions require real time prediction of waves over typical time duration of say a few hours. Such predictions can be made by using a numerical model or a time series model employing continuously recorded waves. This paper presents another option to do so and it is based on a different time series approach in which the input is in the form of preceding wind speed and wind direction observations. This would be useful for those stations where the costly wave buoys are not deployed and instead only meteorological buoys measuring wind are moored. The technique employs alternative artificial intelligence approaches of an artificial neural network (ANN), genetic programming (GP) and model tree (MT) to carry out the time series modeling of wind to obtain waves. Wind observations at four offshore sites along the east coast of India were used. For calibration purpose the wave data was generated using a numerical model. The predicted waves obtained using the proposed time series models when compared with the numerically generated waves showed good resemblance in terms of the selected error criteria. Large differences across the chosen techniques of ANN, GP, MT were not noticed. Wave hindcasting at the same time step and the predictions over shorter lead times were better than the predictions over longer lead times. The proposed method is a cost effective and convenient option when a site-specific information is desired. 相似文献
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Mafic alkalic magmatism in central Kachchh,India: a monogenetic volcanic field in the northwestern Deccan Traps 总被引:1,自引:0,他引:1
Magmatism in Kachchh, in the northwestern Deccan continental flood basalt province, is represented not only by typical tholeiitic
flows and dikes, but also plug-like bodies, in Mesozoic sandstone, of alkali basalt, basanite, melanephelinite and nephelinite,
containing mantle nodules. They form the base of the local Deccan stratigraphy and their volcanological context was poorly
understood. Based on new and published field, petrographic and geochemical data, we identify this suite as an eroded monogenetic
volcanic field. The plugs are shallow-level intrusions (necks, sills, dikes, sheets, laccoliths); one of them is known to
have fed a lava flow. We have found local peperites reflecting mingling between magmas and soft sediment, and the remains
of a pyroclastic vent composed of non-bedded lapilli tuff breccia, injected by mafic alkalic dikes. The lapilli tuff matrix
contains basaltic fragments, glass shards, and detrital quartz and microcline, with secondary zeolites, and there are abundant
lithic blocks of mafic alkalic rocks. We interpret this deposit as a maar-diatreme, formed due to phreatomagmatic explosions
and associated wall rock fragmentation and collapse. This is one of few known hydrovolcanic vents in the Deccan Traps. The
central Kachchh monogenetic volcanic field has >30 individual structures exposed over an area of ∼1,800 km2 and possibly many more if compositionally identical igneous intrusions in northern Kachchh are proven by future dating work
to be contemporaneous. The central Kachchh monogenetic volcanic field implies low-degree mantle melting and limited, periodic
magma supply. Regional directed extension was absent or at best insignificant during its formation, in contrast to the contemporaneous
significant directed extension and vigorous mantle melting under the main area of the Deccan flood basalts. The central Kachchh
field demonstrates regional-scale volcanological, compositional, and tectonic variability within flood basalt provinces, and
adds the Deccan Traps to the list of such provinces containing monogenetic- and/or hydrovolcanism, namely the Karoo-Ferrar
and Emeishan flood basalts, and plateau basalts in Saudi Arabia, Libya, and Patagonia. 相似文献
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Pooja?V.?Kshirsagar Hetu?C.?ShethEmail author Sheila?J.?Seaman Badrealam?Shaikh Poonam?Mohite Trupti?Gurav D.?Chandrasekharam 《Bulletin of Volcanology》2012,74(2):559-577
Spherulites and thundereggs are rounded, typically spherical, polycrystalline objects found in glassy silicic rocks. Spherulites
are dominantly made up of radiating microscopic fibers of alkali feldspar and a silica mineral (commonly quartz). They form
due to heterogeneous nucleation in highly supercooled rhyolitic melts or by devitrification of glass. Associated features
are lithophysae (“stone bubbles”), which have an exterior (sometimes concentric shells) of fine quartz and feldspar, and internal
cavities left by escaping gas; when filled by secondary silica, these are termed thundereggs. Here, we describe four distinct
occurrences of spherulites and thundereggs, in pitchstones (mostly rhyolitic, some trachytic) of the Deccan Traps, India.
The thundereggs at one locality were previously misidentified as rhyolitic lava bombs and products of pyroclastic extrusive
activity. We have characterized the thundereggs petrographically and geochemically and have determined low contents of magmatic
water (0.21–0.38 wt.%) in them using Fourier transform infrared spectroscopy. We consider that the spherulite-bearing outcrops
at one of the localities are of lava flows, but the other three represent subvolcanic intrusions. Based on the structural
disposition of the Deccan sheet intrusions studied here and considerations of regional geology, we suggest that they are cone
sheets emplaced from a plutonic center now submerged beneath the Arabian Sea. 相似文献
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An algorithm is developed to find Weak Stability Boundary transfer trajectories to Moon in high fidelity force model using forward propagation. The trajectory starts from an Earth Parking Orbit (circular or elliptical). The algorithm varies the control parameters at Earth Parking Orbit and on the way to Moon to arrive at a ballistic capture trajectory at Moon. Forward propagation helps to satisfy launch vehicle’s maximum payload constraints. Using this algorithm, a number of test cases are evaluated and detailed analysis of capture orbits is presented. 相似文献
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Ichthyofauna (Chondrichthyes,Osteichthyes) from the Upper Cretaceous intertrappean beds of Piplanarayanwar,Chhindwara District,Madhya Pradesh,India 下载免费PDF全文
A new fossiliferous intertrappean section is found 92 km southwest of the extensively studied intertrappean beds of Mohgaonkalan and Jhilmili in Chhindwara District, Central India. Application of the bulk screen‐washing method led to the recovery of a rich microvertebrate fauna represented by fish, amphibians, crocodiles, snakes and dinosaurs. In this paper, the ichthyofauna recovered from the new intertrappean section consisting of Igdabatis indicus Prasad and Cappetta, 1993, Lepisosteus indicus Woodward, 1908, Osteoglossidae gen. et sp. indet., Pycnodontidae gen. et sp. indet. and Siluriformes indet. is described. The ichthyofauna dominantly represented by the teeth of Igdabatis indicus is suggestive of a nearshore, deltaic or estuarine palaeoenvironment and Late Cretaceous (Maastrichtian) age for the intertrappean beds. The remarkable similarity of the new intertrappean fauna to that of Asifabad and the infratrappean beds of Marepalli also is suggestive of coastal‐plain conditions all along the Godavari lineament in the Late Cretaceous. Although the presence of planktonic foraminifera in the intertrappean beds of Jhilmili in the Mandla Lobe of Deccan volcanic province has been inferred in terms of a short term marine incursion from the west coast along the Narmada lineament in the Early Palaeocene, currently there is no definitive evidence for the prevalence of marine or coastal‐plain conditions along the Narmada lineament at least in the latest Cretaceous. 相似文献