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Amba Datt Kharkwal 《Contributions to Mineralogy and Petrology》1959,7(1):45-62
Zusammenfassung Das Rhät-Lias-Profil am westlichen Stadtrand von Göttingen wurde optisch, röntgenographisch, chemisch und mit der Differentialthermoanalyse untersucht. Es handelt sich um ein einheitliches Profil aus teils mergeligen, aber stets karbonatführenden Tonen mit zwischengeschalteten, teils kalkigen Sandsteinen. Der Tonmineralbestand setzt sich aus Illit als Hauptbestandteil, Kaolinit, Chlorit und Wechsellagerungen Illit/ Montmorillonit und Illit/Chlorit zusammen. Die Zusammensetzung des Karbonatbestandteils ändert sich im Profil vom Liegenden zum Hangenden von einem Karbonat mit 60 Mol-% Ca und 40 Mol-% Mg (unten) zu reinem Kalzit (oben). In der obersten untersuchten Schicht, dem Angulaten Sandstein, wurden einige Basaltgeröllchen und Schwerminerale basaltischer Herkunft gefunden.
A petrographical study of the Rhät-Lias succession of rocks exposed in the quarries of some brickworks at Göttingen has been carried out by optical and chemical methods and by means of X-ray diffraction and differential thermal analysis (DTA). These sediments consist of dark grey shales with interbedded marl and fine- to mediumgrained sandstones. With the exception of one rocktype viz., the Hagenowi Sandstone, all the other rocks contain carbonate in smaller or larger amounts.In the present section, the mineralogical composition of the elastic constituents is almost uniform from top to bottom. The coarse fractions (> 6,3 ) are composed of quartz, mica (muscovite and biotite), feldspars (Na and K), quartz-mica aggregates, chlorite, haematite and heavy minerals (tourmaline and zirkon). The clay fractions are characterised by a predominance of dioctahedral illite. Other components of the clay fractions are kaolinite, chlorite and irregular illite-montmorillonite mixed layers. Regular illite-chlorite mixed layers have also been found in the fine fraction of the Hagenowi Sandstone. Quantitative determination of the clay minerals was made partly with DTA and partly from the X-ray diffraction patterns.The carbonates show, on the other hand, a striking qualitative variation. The lower part of the section is characterised by the occurrence of a mixed carbonate approaching dolomite in composition (35–40 Mol-% Mg), which is replaced more and more towards the top by pure calcite. The latter is the dominant carbonate in the upper beds.Authigenic pyrite, gypsum, barite and lepidocrocite have been found.Pebbles of basalt and heavy minerals of basaltic origin such as augite and hornblende found in the uppermost bed i. e., the Angulaten Sandstone, have geological significance, because until now evidence of volcanic activity in Mesozoic has not been known from the northern part of Middle Europe.相似文献
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The peculiar rainfall pattern in Indiarenders the country highly vulnerable to floods. Forty million hectares of land, roughlyone-eighth of the country's geographical area, is prone to floods. Each year, floods cause extensive damage to life and property, losses being exacerbated by rapid population growth, unplanned development and unchecked environmental degradation. The country has been tackling the problem through structural and non-structural measures. While non-structural measures like flood forecasting aim at improving the preparedness to floods by seeking to keep people away from floodwaters, structural measures involve the construction of physical structures like embankments, dams, drainage channels, and reservoirs that prevent floodwaters from reaching potential damage centres. Almost 48% of the vulnerable area has been provided with reasonable protection, though floods continue to cause widespread losses year after year. This paper examines the incidence of floods and the trends in consequent losses in the eastern region of the country – one of the most vulnerable – with the objective of studying the efficacy of flood protection measures in the region. Based on a simple regression exercise for three highly vulnerable states in the region, the paper argues that flood protection measures have been inadequate in controlling losses and reducing vulnerability. Regressions for the three states over the period 1971 to 1996 indicate that the level of protection is an insignificant explanatory variable in explaining the number of people (adjusted for increases in density) affected by floods; while area affected, as an indicator of the intensity of floods remains the main loss-determining factor. 相似文献
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The N-th root process applied to seismic array data 总被引：2，自引：0，他引：2
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Pankaj Chauhan Nilendu Singh Devi Datt Chauniyal Rajeev S Ahluwalia Mohit Singhal 《Journal of Earth System Science》2017,126(2):22
Climatic extremes including precipitation are bound to intensify in the global warming environment. The present study intends to understand the response of the Tons sub-watershed in Lesser Himalaya, in 3 years with entirely different hydrological conditions (July 2008–June 2011) in terms of discharge, sediment flux and denudation rates. Within an uncertainty limit of ±20%, the mean interannual discharge (5.74 ± 1.44 m 3 s ?1) (±SE), was found highly variable (CV: 151%; 0.8–38 m 3 s ?1). In a normal rainfall year (2008–2009; ～1550 mm), the discharge was 5.12 ± 1.75 m 3 s ?1, whereas in a drought year (2009–2010), it reduced by 30% with the reduction in ～23% rainfall (CV: 85%). In an excessive rainfall year (once-in-a-century event) (2010–2011; ～3050 mm), discharge as well as total solid load was ～200% higher. Monsoon months (July–September) accounted for more than 90% of the annual solid load transport. The ratio of dissolved to suspended solid (C/P ratio) was consistently low (<1) during monsoon months and higher (1–7) during the rest of the dry period. C/P ratio was inversely (R 2=0.49), but significantly (P <0.001) related to the rainfall. The average mechanical erosion rate in the three different rainfall years was 0.24, 0.19 and 1.03 mmyr ?1, whereas the chemical erosion was estimated at 0.12, 0.11 and 0.46 mmyr ?1, respectively. Thus, the average denudation rate of the Tons sub-watershed has been estimated at 0.33 mmyr ?1 (excluding extreme rainfall year: 1.5 mmyr ?1). Our results have implications to understand the hydrological behaviour of the Lesser Himalayan watersheds and will be valuable for the proposed and several upcoming small hydropower plants in the region in the context of regional ecology and natural resource management. 相似文献
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Slowness measurements on first and later arrivals from earthquakes in the Philippine and Taiwan regions recorded at the Warramunga array in Australia indicate abrupt decreases in slowness of the first arrival as well as triplications in the travel time curve at epicentral distances of about 38 and 43°. These results imply the presence of regions of rapid or discontinuous velocity increase at depths of about 900 and 1050 km, respectively. Between these regions of sharp velocity increases the dT/dΔ measurements indicate that the velocity gradients are lower than those determined by previous investigators. The observed extensions of the 650- and 770-km branches out to 50° can be explained in terms of the triplications if small negative velocity gradients of the order of 0.1 km/s per 100 km exist between 650–770 and 770–900 km depths. An alternative explanation of these observed extensions may be provided in terms of underside reflections from the bottom of the velocity discontinuities. Either of the two explanations require sharp velocity gradients at the depth of the velocity discontinuities. These observations are at variance with earth models where the P-wave velocity increases continuously with depth below a depth of 650 km. 相似文献
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Surface energy balance of seasonal snow cover for snow-melt estimation in N-W Himalaya 总被引：2，自引：0，他引：2
Prem Datt P. K. Srivastava P. S. Negi P. K. Satyawali 《Journal of Earth System Science》2008,117(5):567-573
This study describes time series analysis of snow-melt, radiation data and energy balance for a seasonal snow cover at Dhundi
field station of SASE, which lies in Pir Panjal range of the N-W Himalaya, for a winter season from 13 January to 12 April
2005. The analysis shows that mean snow surface temperature remains very close to the melting temperature of snow. It was
found close to −1°C for the complete observational period which makes the snow pack at Dhundi moist from its beginning. The
average air temperature over this period was found to be 3.5°C with hourly average variation from −5.5°C to 13°C. The snow
surface at this station received a mean short wave radiation of 430W m−2, out of which 298W m−2 was reflected back by the snow surface with mean albedo value of 0.70. The high average temperature and more absorption of
solar radiation resulted in higher thermal state of the snowpack which was further responsible for faster and higher densification
of the snowpack. Net radiation energy was the major component of surface energy budget with a mean value of 83W m−2. Bulk transfer model was used to calculate turbulent fluxes. The net energy was utilized for satisfying cold content and
snow-melt by using measured snow surface temperature and density of snow pack. The mean square error between calculated and
measured daily snow-melt was found to be approximately 6.6mm of water equivalent. 相似文献
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Slowness data from earthquakes in the Mindanao and Philippine regions recorded at the Warramunga array indicate a small, but abrupt, decrease in dT/dΔ at a distance of 29.5°. There is evidence also of a triplication in the P travel-time curve at about this distance. These data strongly suggest the presence of a rapid or discontinuous velocity increase of about 2% in P-wave velocity at a depth of about 770 km. Such a velocity increase is consistent with the occurrence of more than one phase change between 600 and 900 km, as predicted by the pyrolite model of Ringwood.Previous observations of increasing dT/dΔ with distance may have resulted from the predominance of the 650-km branch as it approaches its cusp. If so, then it is not necessary to invoke a decrease in velocity with depth near 800 km to explain the increase in mdT/dΔ observed between 32–34°. 相似文献
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Ram Datt 《Physics of the Earth and Planetary Interiors》1981,24(1):33-52
The fine structure of regional travel-time curves is investigated. About 200 events from the region north of Australia, recorded at the Warramunga array, are analysed to give the P-wave velocity structure for that region. The events were confined to a very narrow azimuth range. Results show that the 20° discontinuity is more complicated than a single velocity increase near 400 km depth, and that there are regions of rapid or discontinuous velocity increase at depths below 650 km. 相似文献
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