Partitioning of convergence in Northwest Sub-Himalaya: estimation of late Quaternary uplift and convergence rates across the Kangra reentrant,North India     

V. C. Thakur  M. Joshi  D. Sahoo  N. Suresh  R. Jayangondapermal  A. Singh 《International Journal of Earth Sciences》2014,103(4):1037-1056

The Kangra reentrant constitutes a ~ 80-km-wide zone of fold-thrust belt made of Cenozoic strata of the foreland basin in NW Sub-Himalaya. Earlier workers estimated the total long-term shortening rate of 14 ± 2 mm/year by balanced cross-section between the Main Boundary Thrust and the Himalayan Frontal Thrust. Geologically estimated rate is nearly consistent with the GPS-derived slip rate of 14 ± 1 mm/year. There are active faults developed within 4–8 km depth of the Sub-Himalayan fold-thrust belt of the reentrant. Dating the strath surfaces of the abandoned fluvial terraces and fans above the thrust faults, the uplift (bedrock incision) rates are computed. The dips of thrust faults are measured in field and from available seismic (depth) profiles. From the acquired data, late Quaternary shortening rates on the Jawalamukhi Thrust (JT), the Soan Thrust (ST) and the Himalayan Frontal Thrust (HFT) are estimated. The shortening rates on the JT are 3.5–4.2 mm/year over a period 32–30 ka. The ST yields a shortening rate of 3.0 mm/year for 29 ka. The corresponding shortening and slip rates estimated on the HFT are 6.0 and 6.9 mm/year during a period 42 ka. On the back thrust of Janauri Anticline, the shortening and slip rates are 2.0 and 2.2 mm/year, respectively, for the same period. The results constrained the shortening to be distributed largely across a 50-km-wide zone between the JT and the HFT. The emergence of surface rupture of a great and mega earthquakes recorded on the reactivated HFT implies ≥100 km width of the rupture. The ruptures of large earthquakes, like the 1905 Kangra and 2005 Kashmir, remained restricted to the hinterland. The present study indicates that the high magnitude earthquakes can occur between the locking line and the active thrusts.  相似文献   

Soil loss estimation by field measurements in the badlands along Pravara river (Western India)     

Veena U. Joshi 《Journal of the Geological Society of India》2014,83(6):613-624

Nearly 4 million hectares of land in India is affected by rill and gully erosion. It is a severe form of soil erosion rendering vast tracts of lands into wastelands giving rise to the formation of badlands. Rate of land degradation through gullying is triggered recently due to the ill-advised landuse practices all over the country. The study area represents one such badland locality along the banks of Pravara river and two of its tributaries in the Deccan trap region, Maharashtra. The area is extensively reclaimed in the last two decades for agricultural practices. The rates in the cross profile changes as well as land lowering were measured with the help of a self fabricated micro-profilometer and erosion pin method. Five first order gullies were monitored using the micro-profilometer. Results of the micro-profilometer technique reveal considerable changes in the cross-sectional areas of individual gullies in this area, which shows the dynamic soil removal mechanism operating in this region. In addition to this, two well developed gully catchments were surveyed using a theodolite and erosion pins were installed in these basins in May 2007. After one year, the exposed pinheads were measured and net gain and net loss in the volume of the sediments were calculated for both the basins. The same practice continued in May 2009. After two years of monitoring the sediment yields were calculated. Average of these two years indicates an annual sediment yield of 1.79 kg/m² for sample basin 1 and 0.76 kg/m² for sample basin 2. The calculated yield was compared with the threshold values of soil tolerance limits and it was found that the area has crossed the threshold limit of soil tolerance.  相似文献   

Post-peak,fluid-mediated modification of granulite facies zircon and monazite in the Trivandrum Block,southern India     

Richard J. M. Taylor  Chris Clark  Ian C. W. Fitzsimons  M. Santosh  M. Hand  Noreen Evans  Brad McDonald 《Contributions to Mineralogy and Petrology》2014,168(2):1-17

The quarry at Kottavattom in the Trivandrum Block of southern India contains spectacular examples of fluid-assisted alteration of high-grade metamorphic rocks. Garnet-biotite gneiss has undergone a change in mineral assemblage to form submetre scale orthopyroxene-bearing patches, later retrogressed to form an amphibole-bearing lithology. These patches, often referred to as arrested or incipient charnockite, crosscut the original metamorphic foliation and are typically attributed to passage of a low aH₂O fluid through the rock. Whilst this conversion is recognised as a late stage process, little detailed chronological work exists to link it temporally to metamorphism in the region. Zircon and monazite analysed from Kottavattom not only record metamorphism in the Trivandrum Block but also show internal, lobate textures crosscutting the original zoning, consistent with fluid-aided coupled dissolution-reprecipitation during formation of the orthopyroxene-bearing patches. High-grade metamorphism at the quarry occurred between the formation of metamorphic monazite at ~585 Ma and the growth of metamorphic zircon at ~523 Ma. The fluid-assisted alteration of the garnet-biotite gneiss is poorly recorded by altered zircon with only minimal resetting of the U–Pb system, whereas monazite has in some cases undergone complete U–Pb resetting and records an age for fluid infiltration at ~495 Ma. The fluid event therefore places the formation of the altered patches at least 25 Myr after the zircon crystallisation in the garnet-biotite gneiss. The most likely fluid composition causing the modification and U–Pb resetting of zircon and monazite is locally derived hypersaline brine.  相似文献   

Geochemistry,and zircon U–Pb and molybdenite Re–Os geochronology of Jilongshan Cu–Au deposit,southeastern Hubei Province,China     

A‐Juan Pang  Sheng‐Rong Li  M. Santosh  Qing‐Yu Yang  Bao‐Jian Jia  Cheng‐Dong Yang 《Geological Journal》2014,49(1):52-68

The Jilongshan skarn Cu–Au deposit is located at the Jiurui ore cluster region in the southwestern part of the Middle–Lower Yangtze River valley metallogenic belt. The region is characterized by NW‐, NNW‐ and EW‐trending faults and the mineralization occurs at the contact of lower Triassic carbonate rocks and Jurassic granodiorite porphyry intrusions. The intrusives are characterized by SiO₂, K₂O, and Na₂O concentrations ranging from 61.66 to 67.8 wt.%, 3.29 to 5.65 wt.%, and 2.83 to 3.9 wt.%, respectively. Their A/CNK (A/CNK = n(Al₂O₃)/[n(CaO) + n(Na₂O) + n(K₂O)]) ratio, δEu, and δCe vary from 0.77 to 1.17, 0.86 to 1, and 0.88 to 0.96, respectively. The rocks show enrichment in light rare earth elements ((La/Yb)_N = 7.61–12.94) and large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE), such as Zr, Ti. They also display a peraluminous, high‐K calc‐alkaline signature typical of intrusives associated with skarn and porphyry Cu–Au–Mo polymetallic deposits. Laser ablation inductively coupled plasma spectrometry (LA‐ICP‐MS) zircon U–Pb age indicates that the granodiorite porphyry formed at 151.75 ± 0.70 Ma. A few inherited zircons with older ages (677 ± 10 Ma, 848 ± 11 Ma, 2645 ± 38 Ma, and 3411 ± 36 Ma) suggest the existence of an Archaean basement beneath the Middle–Lower Yangtze River region. The temperature of crystallization of the porphyry estimated from zircon thermometer ranges from 744.3 °C to 751.5 °C, and 634.04 °C to 823.8 °C. Molybdenite Re–Os dating shows that the Jilongshan deposit formed at 150.79 ± 0.82 Ma. The metallogeny and magmatism are correlated to mantle–crust interaction, associated with the subduction of the Pacific Plate from the east. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Environmental justice discourses in Indian climate politics     

Shangrila Joshi 《GeoJournal》2014,79(6):677-691

This paper examines India’s participation in ongoing climate politics with a lens of environmental justice (EJ). Using key-informant interviews conducted in Delhi and Copenhagen, I sought to understand how Indian officials conceptualized EJ in the context of climate change. I found my respondents to largely privilege ideas of historical responsibility and per capita equity in a North–South context. The North was seen to have an ecological debt towards the South and the South was seen to have a right to development and ecological space. I highlight two questions that inevitably arise from this framing of international environmental justice. What are the implications of this line of argument for the issue of domestic inequities within states? A related question is that if justice is seen as right to development, what exactly is meant by development? My findings indicate for the most part an uncritical acceptance of a neo-liberal vision of development based on an economic growth paradigm. Consequently, a direct link is observed between emissions and development, despite the impetus to delink them. There was also a marked reluctance among officials to discuss the topic of domestic inequities in India, and an inclination to dismiss them as a sovereignty issue. I suggest that an approach to EJ that combines the imperative of historical responsibility and ecological debt in an international context, with a ‘capabilities’ approach to EJ and development within the domestic context has potential to be more forceful and convincing than one that emphasizes the former but ignores the latter.  相似文献   

Modeling of strong motion generation areas of the 2011 Tohoku,Japan earthquake using modified semi-empirical technique     

A. Joshi  Sandeep  Kamal 《Natural Hazards》2014,71(1):587-609

Modification in the semi-empirical technique for the simulation of strong ground motion has been introduced to incorporate the strong motion generation areas (SMGA) in the modeled rupture plane. Strong motion generation areas identified within the rupture plane of the Tohoku earthquake of March 11, 2011 (M _w = 9.0), have been modeled using this modified technique. Two different source models having four and five SMGAs, respectively, are considered for modeling purpose. Strong motion records using modified semi-empirical technique have been simulated at two near-field stations located at epicentral distance of 137 and 140 km, respectively, using two different source models. Comparison of the observed and simulated acceleration waveforms is made in terms of root mean square error (RMSE) at both stations. Minimum root mean square error of the waveform comparison has been obtained at both the stations for source model having five SMGAs. Simulations from same rupture model have been made at other four stations lying at epicentral distance between 154 and 249 km. Comparison of observed and simulated records has been made in terms of RMSE in acceleration records, velocity records and response spectra at each six station. Simulations have been made at six other stations to obtain distribution of peak ground acceleration and peak ground velocity with hypocentral distance. Peak ground acceleration and velocity from simulated and observed records are compared at twelve stations surrounding the source of Tohoku earthquake. Comparison of waveforms and parameters extracted from observed and simulated strong motion records confirms the efficacy of the developed modified technique to model earthquake characterized by SMGAs.  相似文献   

Rainfall variability and indices of extreme rainfall-analysis and perception study for two stations over Central Himalaya,India   总被引：1，自引：1，他引：0  

Sneh Joshi  Kireet Kumar  Varun Joshi  Bimal Pande 《Natural Hazards》2014,72(2):361-374

The analysis of rainfall pattern and indices of extreme rainfall events is performed for two meteorological stations located in the Central Himalayan Region which is highly vulnerable to rain-induced hazards. The records of these rain-induced disasters suggest that such events are generally observed in later part of monsoon season, when soil is saturated after monsoon rains. An attempt is made here to test trends of 19 different extreme rainfall indices that have been widely used in the literature, using daily rainfall data for two urban centres (Nainital and Almora) over the period 1992–2005. We have used statistical tools such as Sen’s method and Mann–Kendall test for detection of trend in annual rainfall, monsoon rainfall, number of rainy days and 1-day extreme rainfall. Principal component analysis gives the correlation between different extreme rainfall indices. Time series of principal components are representing the trends of extreme indices, their variation and interrelation between different indices. The perception study conducted in the same sites indicates that extreme rainfall events and change in rainfall amount and timing are well perceived by the local people.  相似文献   

On the infrared opacity of sunspots     

G. C. Joshi  L. M. Punetha  M. C. Pande 《Solar physics》1979,64(2):255-259

In the umbral atmosphere the depth dependence of the opacity due to the vibration rotation bands of various abundant molecules in the wavelength region 1 m to 10 m has been calculated. In the higher layers of the umbral atmosphere, the molecular opacity seems to dominate the opacity due to the negative hydrogen ion.  相似文献   

Doppler width of CH lines     

L. M. Punetha  G. C. Joshi 《Astrophysics and Space Science》1991,181(2):327-329

Twenty-one CH line profiles at the centre of the solar disk were Fourier-transformed to derive the Doppler widths. The Doppler width increases linearly with the equivalent width.  相似文献   

Development of a three channel photometer for UPSO, Naini Tal     

B. N. Ashoka  Kumar  V. C. Babu  S. Seetha  V. Girish  S. K. Gupta  Ram Sagar  S. Joshi  P. Narang 《Journal of Astrophysics and Astronomy》2001,22(1):131-144

The design and performance of a portable three channel photometer installed at the Uttar Pradesh State Observatory (UPSO), Naini Tal is described. The photometer is modular and the whole unit can be disassembled as individual channels such that the system can also be used as a single channel or two channel photometer. The system also has provision to monitor a guide star. The instrument was put into operation since November 1999 on the 1m Sampurnanand telescope at UPSO, Naini Tal. Since then, it is used extensively for the ‘Survey of rapidly oscillating Ap (roAp) stars in the northern sky’ from UPSO. Observational results using this new photometer in its initial phase of operation are discussed. The advantage of having continuous sky measurement is demonstrated.  相似文献