Fall,classification and cosmogenic records of the Sabrum (LL6) chondrite     

S. Ghosh  S. V. S. Murty  P. N. Shukla  A. D. Shukla  R. R. Mahajan  N. Bhandari  N. C. Pant  J. B. Ghosh  S. Shome 《Meteoritics & planetary science》2002,37(3):439-448

Abstract— The petrographic and chemical characteristics of a fresh Indian meteorite fall at Sabrum are described. Its mean mineral composition is defined by olivine (Fa_31.4), orthopyroxene (Fs_25.1,Wo_2.0), clinopyroxene (Wo₄₅En_45.6Fs_9.4) and plagioclase (An_10.6Ab_83.6Or_5.8). The meteorite shows moderate shock features, which indicate that it belongs to the S4 category. Based on mineralogical and chemical criteria the meteorite is classified as an LL6 brecciated veined chondrite. Several cosmogenic radioisotopes (⁴⁶Sc, ⁷Be, ⁵⁴Mn, ²²Na and ²⁶Al), noble gas (He, Ne, Ar, Kr and Xe), nitrogen isotopes, and particle tracks density have been measured. Concentrations of cosmogenic ²¹Ne and ³⁸Ar indicate that its cosmic‐ray exposure age is 24.8 Ma. Small amounts of trapped Kr and Xe, consistent with petrologic class 5/6, are present. The track density in olivines is found to be (1.3 ± 0.3) × 10⁶/cm². Activities of most of the short‐lived isotopes are lower than those expected from solar cycle variation. ²²Na/²⁶Al (1.12 ± 0.02) is found to be significantly anomalous, being ?25% lower than expected from the Climax neutron monitor data. These results indicate that the cosmic‐ray flux during the terminal segment of the meteoroid orbit was low. The activities of ²⁶Al and ⁶⁰Co and the track density indicate small meteoroid size with a radius ?15 cm.  相似文献   

Solar and galactic cosmic‐ray records of the Fermo (H) chondrite regolith breccia     

G. Bonino  N. Bhandari  S. V. S. Murty  R. R. Mahajan  K. M. Suthar  A. D. Shukla  P. N. Shukla  G. Cini Castagnoli  C. Taricco 《Meteoritics & planetary science》2001,36(6):831-839

Abstract— ‐We demonstrate the presence of solar flare as well as neutron capture effects in the isotopic composition of rare gases in the Fermo regolith breccia acquired on its parent body based on the measurements of tracks, rare gases and radionuclides. The track density along a 3.2 cm long core decreases by a factor of about 6 and by more than a factor of 13 within the meteorite, indicating small (2–9 cm) and asymmetrical ablation. Rare gases show a large trapped component; the isotopic ratios, particularly ²⁰Ne/²²Ne ? 11 and ²⁰Ne/³⁶Ar = 10 are indicative of a solar component. The galactic cosmic‐ray exposure age is determined to be 8.8 Ma. Activities of a dozen radionuclides ranging in half‐life from 16 day ⁴⁸V to 0.73 Ma ²⁶Al are consistent with their expected production rates. Track, rare gas and radionuclide data show that the meteoroid was a small body (≤ 120 kg) and had a simple, one‐stage exposure history to cosmic rays in the interplanetary space. However, ⁸²Kr and ¹²⁸Xe show an excess due to neutron irradiation on the parent body of the meteorite. The presence of solar gases and the neutron capture effects indicate several stages of irradiation on the parent asteroid. The chemical composition of Fermo confirms that it belongs to the H group of ordinary chondrites with lithic clasts having varying compositions. δ¹⁵N is found to be 8.3 ± 1.2%0, close to the typical values observed in H chondrites.  相似文献   

Book review     

Narendra Saxena 《Marine Geodesy》2013,36(1):117-118

Sea Surveying, edited by Alan Ingham (London: John Wiley & Sons, 1975), 2 volumes, 306 and 233 pp., hardcover, $49.50.  相似文献   

Sub‐meter acoustic surveying     

Lester Q. Spielvogel  Narendra K. Saxena  Stevens P. Tucker 《Marine Geodesy》2013,36(2-3):137-151

Abstract

During May 1985, a comprehensive GPS and acoustic navigation data set was collected off the Monterey, California coast. Three types of GPS units, a LORAN‐C, and a Miniranger operated concurrently with an OCEANO acoustic system to resolve state‐of‐the‐art accuracies for at‐sea geodetic positioning. This report details the acoustic system which displayed baseline errors of only ±0.25 m over distances to 2600 m. Unfiltered point‐to‐point acoustic navigation errors had a standard deviation of ± 1.25 m, which included ship motion errors in addition to surveying errors. Ninety percent of the stations had navigation standard deviations below ±0.75 m The experiment showed that sub‐meter acoustic surveying is the state‐of‐the‐art.  相似文献   

Letter from the editor     

Narendra K. Saxena Editor‐in‐Chief 《Marine Geodesy》2013,36(4)

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1971-2009 年珠穆朗玛峰地区尼泊尔境内气候变化   总被引：3，自引：0，他引：3  

祁威  张镱锂  高俊刚  杨续超  刘林山  Narendra Raj KHANAL 《地理学报》2013,68(1):82-94

利用珠穆朗玛峰南坡尼泊尔境内(科西河流域) 的10 个气象站1971-2009 年月平均气温、月平均最高、最低气温和逐月降水资料, 采用线性趋势、Sen 斜率估计、Mann-Kendall 等方法分析区域气候变化状况及其时空特征, 并与珠穆朗玛峰北坡地区气候进行比较, 分析了珠穆朗玛峰地区气候变化的特征与趋势。结果表明:(1) 1971-2009 年间, 珠穆朗玛峰南坡年平均气温为20.0℃, 线性升温率为0.25℃/10a, 与北坡主要受年平均最低气温影响相反, 增幅主要受年平均最高气温升高的影响, 并且在1974 年及1992 年间出现两次显著增温, 增温特别明显的月份为2 月和9 月;(2) 该地区降水变化的局地性较强, 近40 年间年平均降水量为1729.01 mm, 年平均降水量以每年约4.27 mm的线性增幅有所增加, 但并不显著, 且降水月变化和季变化特征均不明显;(3) 由于珠穆朗玛峰南坡受到季风带来暖湿气流和喜马拉雅山阻挡的双重影响, 珠峰南坡的年平均降水量远高于北坡;(4) 珠穆朗玛峰南坡气温变暖的海拔依赖性并不明显, 且南坡地区的变暖趋势并没有北坡变暖趋势明显。  相似文献   

Decadal glacial lake changes in the Koshi basin,central Himalaya,from 1977 to 2010, derived from Landsat satellite images     

Finu Shrestha  Xiao Gao  Narendra Raj Khanal  Sudan Bikash Maharjan  Rajendra Bahadur Shrestha  Li-zong Wu  Pradeep Kumar Mool  Samjwal Ratna Bajracharya 《山地科学学报》2017,14(10):1969-1984

Changes in glacial lakes and the consequences of these changes, particularly on the development of water resources and management of glacial lake outburst flood(GLOF) risk, has become one of the challenges in the sustainable development of high mountain areas in the context of global warming. This paper presents the findings of a study on the distribution of, and area changes in, glacial lakes in the Koshi basin in the central Himalayas.Data on the number of glacial lakes and their area was generated for the years 1977, 1990, 2000, and 2010 using Landsat satellite images. According to the glacial lake inventory in 2010, there were a total of 2168 glacial lakes with a total area of 127.61 km~2 and average size of 0.06 km~2 in the Koshi basin. Of these,47% were moraine dammed lakes, 34.8% bedrock dammed lakes and 17.7% ice dammed lakes. The number of glacial lakes increased consistently over the study period from 1160 in 1977 to 2168 in 2010, an overall growth rate of 86.9%. The area of glacial lakes also increased from 94.44 km~2 in 1977 to 127.61 km~2 in 2010, a growth rate of 35.1%. A large number of glacial lakes in the inventory are small in size(≤ 0.1km~2). End moraine dammed lakes with area greater than 0.1 km~2 were selected to analyze the change characteristics of glacial lakes in the basin. The results show that, in 2010, there were 129 lakes greater than 0.1 km~2 in area; these lakes had a total area of 42.92km~2 in 1997, increasing to 63.28 km~2 in 2010. The distribution of lakes on the north side of the Himalayas(in China) was three times higher than on the south side of the Himalayas(in Nepal).Comparing the mean growth rate in area for the 33 year study period(1977-2010), the growth rate on the north side was found to be a little slower than that on the south side. A total of 42 glacial lakes with an area greater than 0.2 km~2 are rapidly growing between 1977 and 2010 in the Koshi basin, which need to be paid more attention to monitoring in the future and to identify how critical they are in terms of GLOF.  相似文献   

Predicting the Impact of Climate Change on Vulnerable Species in Gandaki River Basin,Central Himalayas     

Raju RAI  ZHANG Yili  LIU Linshan  Paras Bikram SINGH  Basanta PAUDEL  Bipin Kumar ACHARYA  Narendra Raj KHANAL 《资源与生态学报(英文版)》2022,13(2):173-185

Gandaki River Basin (GRB) is an important part of the central Himalayan region, which provides habitat for numerous wild species. However, climatic changes are making the habitat in this basin more vulnerable. This paper aims to assess the potential impacts of climate change on the spatial distributions of habitat changes for two vulnerable species, Himalayan black bear (Ursus thibetanus laniger) and common leopard (Panthera pardus fusca), using the maximum entropy (MaxEnt) species distribution model. Species occurrence locations were used along with several bioclimatic and topographic variables (elevation, slope and aspect) to fit the model and predict the potential distributions (current and future) of the species. The results show that the highly suitable area of Himalayan black bear within the GRB currently encompasses around 1642 km² (5.01% area of the basin), which is predicted to increase by 51 km² in the future (2050). Similarly, the habitat of common leopard is estimated as 3999 km² (12.19% of the GRB area), which is likely to increase to 4806 km² in 2050. Spatially, the habitat of Himalayan black bear is predicted to increase in the eastern part (Baseri, Tatopani and north from Bhainse) and to decrease in the eastern (Somdang, Chhekampar), western (Burtibang and Bobang) and northern (Sangboche, Manang, Chhekampar) parts of the study area. Similarly, the habitat of common leopard is projected to decrease particularly in the eastern, western and southern parts of the basin, although it is estimated to be extended in the southeastern (Bhainse), western (Harichaur and northern Sandhikhark) and north-western (Sangboche) parts of the basin. To determine the habitat impact, the environmental variables such as elevation, Bio 15 (precipitation seasonality) and Bio 16 (precipitation of wettest quarter) highly contribute to habitat change of Himalayan black bear; while Bio 13 (precipitation of wettest month) and Bio 15 are the main contributors for common leopard. Overall, this study predicted that the suitable habitat areas of both species are likely to be impacted by climate change at different altitudes in the future, and these are the areas that need more attention in order to protect these species.  相似文献   

Quality of spring water used for irrigation in the Almora District of Uttarakhand, India     

Bhandari N. S.  Hemant K. Joshi 《中国地球化学学报》2013,32(2):130-136

This paper aims to propose a quality profile of springs of the study area for irrigation. In the present study, fifty-four springs in Almora have been identified from rural as well as urban localities for calculation of irriga- tional water quality parameters during pre-monsoon, monsoon and post-monsoon, 2008. Spring water samples are collected and analyzed for pH, electrical conductivity (EC), total dissolved solids (TDS), Na+ , K+ , Ca2+ , Mg2+ , HCO3- , Cl- , and SO42- . Different irrigation quality parameters viz. salinity, sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium hazards (MH) and permeability index (PI) are calculated for the evaluation of spring water quality for irrigation purposes. All springs are found excellent to good based on irrigation quality parameters. Based on Wilcox diagram, about 98% of the water resources are grouped as C1S1 (low-low) and C2S1 (medium-low) classes, so springs are suitable for normal irrigation.  相似文献   

High-resolution profile of stable isotopes and iridium across a K/T boundary section from Koshak Hill, Mangyshlak, Kazakhstan     

A. Sarkar  S.K. Bhattacharya  P.N. Shukla  N. Bhandari  D.P. Naidin 《地学学报》1992,4(5):585-590

Oxygen and carbon isotopes were measured to a high depth resolution in a nannoplankton carbonate sequence spanning the Cretaceous-Tertiary boundary at Koshak Hill, Mangyshlak Peninsula, Kazakhstan. The boundary is characterized by the presence of a ∼ 1 cm thick clay layer having a sharp peak in iridium concentration with a maximum value of 3.7 ng g^-1. The δ¹⁸O data reveal rapid (∼10³ years) excursion of sea-surface temperature at the boundary where an initial cold pulse is followed by a persistent warm period. The δ¹³C data, in contrast, indicate only a gradual change in productivity across the boundary. The observations suggest a biogeochemical scenario for the boundary event pertaining to shallow epicontinental seas.  相似文献