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1.
V. Kumaravel S. J. Sangode N. Siva Siddaiah Rohtash Kumar 《Journal of the Geological Society of India》2009,73(6):759-772
Elemental mobility based on major element geochemistry from 58 horizons related to six paleosols profiles in a typical Miocene
— Pliocene Siwalik fluvial sequence in the NW Himalaya has been reported here. The paleosols developed over felsic parent
material of fine to medium grained sandstone indicate notable enrichment of sesquioxides (Al2O3 = 29 % and Fe2O3 = 54 %) depicting significant leaching and dissolution. The depletion of base cations (mean wt% of Na2O = 0.24; CaO = 0.51) and SiO2 (mean wt% = 63.6) in the pedogenic layers and its enrichment in the parental material (mean wt% of Na2O = 0.44; CaO = 1.3; SiO2 = 70.1) shows a good gradient of elemental mobility due to pedogenesis. Bivariate plots of the base ratios (Na2O/K2O, CaO/K2O, and MgO/K2O) vs. Al2O3 reveal independent distribution for parent material, pedogenic horizons and the incipient zone indicating the gradual addition/removal
of immobile/mobile elements with varying pedogenesis. Discontinuous and segmented pattern of the geochemical parameters enables
discrimination of multiple pedogenic episodes and recognition of soil welding processes in the multistorey composite paleosols.
We also test the applicability of the geochemical climofunctions: the Mean Annual Precipitation (MAP) and Mean Annual Temperature
(MAT); that demands more data for calibration in the Siwalik paleosols. 相似文献
2.
Petrochemical studies of granitoid rocks from the eastern part of Kumaun region suggest that the leading edge of India represents an active arc during Late Paleoproterozoic times. It has been observed that melt generation for granodiorite rocks from the eastern Almora Nappe and Chhiplakot klippe along with the Askot klippe was caused through a subduction‐related process involving hydrous partial melting of a Paleoproterozoic amphibole‐ and/or garnet‐bearing mafic source with the involvement of sediments from the subduction zone. The medium‐ to high‐K basic rocks, common in subduction‐related magmatic arcs, can also explain the generation of the high‐K granodiorites of the Chhiplakot klippe. The augen gneisses from the eastern Almora nappe and Chhiplakot klippe along with the Askot klippe further show geochemical similarity with the associated granodiorites, suggesting there is a genetic linkage with one another. 相似文献
3.
Radon in Himalayan springs: a geohydrological control 总被引：3，自引：0，他引：3
This paper presents the results of radon measurements in springs of the Himalayan region by using radon emanometry technique.
The radon was measured in different springs, draining from different geohydrological setups, and from stream water in order
to find the geohydrological control over radon concentration in groundwater emanating in the form of spring. The radon values
were found to vary from 0.4 Bq/l to 887 Bq/l, being observed lowest for a turbulent stream and highest for the spring. The
radon values were recorded highest in the springs draining through gneiss, granite, mylonite, etc. Radon concentrations have
been related with four spring types viz. fracture-joint related spring, fault-lineament related spring, fluvial related spring
and colluvial related spring, showing geohydrological characteristics of the rocks through which they are emanating. The high
radon concentration in fracture-joint and fault-lineament spring is related to increased ratio of rock surface area to water
volume and uranium mineralisation in the shear zones present in the close vicinity of fault and thrust. The low concentration
of radon in fluvial and colluvial springs is possibly because of high transmissivity and turbulent flow within such deposits
leading to natural de-emanation of gases.
Received: 6 January 1998 · Accepted 11 May 1999 相似文献
4.
Carbon stocks and carbon accumulation in the earth's drylands have gained increasing attention. The winter-cold deserts of Middle Asia, i.e. in Kazakhstan, Uzbekistan, and Turkmenistan, cover an area of 2.5 million km2. Within these deserts, the two Saxaul species White Saxaul (Haloxylon persicum Bunge ex Boiss. & Buhse) and Black Saxaul (Haloxylon aphyllum (Minkw.) Iljin) are dominant woody species with a potential distribution area of about 500,000 km2. From the 1950s until today, the Saxaul vegetation has been degraded through logging and over-grazing. In this paper, we estimate the current and potential living above ground and below ground biomass of the Saxaul vegetation and its carbon stock. The living above ground biomass ranges between 1.5 t/ha and 3 t/ha. The potential carbon stocks above ground and below ground amount to 29.4–52.1 million t and 22–81.4 million t, respectively. Today, only 11%–28% of the potential biomass and carbon stock have remained. The carbon stock of the Saxaul vegetation is low compared to other ecosystems of the earth, but restoration and conservation of Saxaul vegetation is one way to sequester carbon through vegetation for Uzbekistan and Turkmenistan, which do not have much other woody vegetation. 相似文献
5.
Since the mid-Pliocene, East Asian climates have experienced significant changes. One view suggests that significant uplift of the Tibetan Plateau during this period could have been responsible for these dramatic changes in the strength of the East Asian monsoon and for Asian interior aridification, while some other authors attribute these changes to the ongoing global cooling and rapid growth of the Arctic ice-sheet. Up to the present, which factor dominates the major changes of East Asian climate in the mid-Pliocene is still a contentious issue. This study presents an analysis of several climate proxies including grain-size, (CaO* + Na2O + MgO)/TiO2 ratio, Na/Ka ratio and dust accumulation rates of the Xifeng Red Clay sequence in the eastern Chinese Loess Plateau and the Xihe Pliocene loess-soil sequence in West Qinling. They reveal that aridity in the continental interior and winter monsoon circulation both intensified, whereas the East Asian summer monsoon showed a weakening rather than intensifying trend since the mid-Pliocene. These changes are also supported by the other multi-proxy records from various regions in East Asia. Previous numerical modeling studies have demonstrated that uplift of the Tibetan Plateau would have simultaneously enhanced continental-scale summer and winter monsoon strength as well as central Asian aridity. The mid-Pliocene climate changes in East Asia are therefore unlikely to be a response to Plateau uplift. On the contrary, our recent modeling results give support to the view that ongoing cooling could have intensified both the aridity of the interior and the strength of the winter monsoon, but weakened the summer monsoon in East Asia. 相似文献
6.
Geochemical studies of granitoids from Shyok tectonic zone of Khardung-Panamik section,Ladakh, India
The Shyok tectonic zone lies to the north of Ladakh magmatic arc or the Ladakh batholith in the Trans-Himalaya of Ladakh district,
J & K. Investigations were carried out on the granitoids exposed along Leh-Siachan highway between Khardung and Panamik villages.
The granitoid bodies under study are: Khardung granite (KG), Tirit granite (TG) and Panamik granite (PG) belonging to Ladakh
batholith, Shyok ophiolitic mélange and Karakoram batholith respectively. Though the granitoids belong to different litho-tectonic
units, yet they have subduction related geochemical characters typical of Andean-type granitoids. Re-melting of crustal rocks
of volcanic arc affinity has played an important role for the origin of KG rocks which are more evolved, while the TG and
PG rocks represent transitional tectonic environment from primitive to mature arc. 相似文献
7.
Vikram Gupta S. C. Vaideswaran D. P. Dobhal 《Journal of the Geological Society of India》2014,84(3):335-340
Lichenometric application used mainly for the dating of moraines, involves the calibration of growth rate curve with the inclusion of colonization delay of a specific type of lichen. In the present study, the colonization delay of Rhizocarpon geographicum species of lichen found on the boulders of granite and gneisses in the Gangotri glacier environment has been interpreted. It has been concluded that the colonization delay for the said species is different for both the rock-types. It is about 78 years for granite and between 50 and 78 years for the gneisses. The study will help to establish the absolute ages of the various terminal moraines of the Gangotri glacier, which in turn will help to ascertain the recession history of the glacier. 相似文献
8.
While constraining Cenozoic evolution of the Himalaya through enlightening fossils we find that Dharmsala Group (intervening Subathu Group and Siwalik Group) in Kangra Valley and adjoining coevals yield sporadic fossils. Hence, this first record of fossil rodents from Dharmsala Group is an important addition to an earlier report of dinothere from these horizons. The rodent material from grey facies of the Dharmsala Group comprises of an isolated premolar and fragments of a tooth and an incisor. Available crown details in conjunction with distinctive dimensions of the premolar lead to its assignment to Hodsahibia, a baluchimyine taxon; this taxon of Eocene lineage of south Asian-African distribution is already on record from early Oligocene horizons in Bugti area, Pakistan. 相似文献
9.
10.
A.K. Mundepi J.J. Galiana-Merino Kamal Conrad Lindholm 《Soil Dynamics and Earthquake Engineering》2010
Local site conditions substantially affect the characteristics of seismic waves and its potential to cause earthquake damage. To accurately identify the variation of seismic hazard at different locations within the cities, measurements from a three-component station may be used for estimating the resonance frequencies and evaluate the expected level of damage at each site. This information can also be complemented with array measurements of ambient noise in order to estimate the Vs profiles and characterize the corresponding sediment layers at each site. 相似文献