Search

We present significant findings of the Kausani Granite Gneiss within the Inner Lesser Himalayan Sedimentary Zone (iLHSZ) just north of the North Almora Thrust (NAT). The Kausani Granite Gneiss body lies within the quartzite of the Someshwar Formation and has a tectonized contact and a discordant relationship on the north side. Detailed seismic profiling across the body also confirms a similar result. Cathodoluminescence images of zircon from the Kausani body show no inheritance of older cores. The U–Pb ages from the zircon populations separated from the Kausani body give a crystallization age of 1866 ± 3 Ma. Along with the Upalda granite gneiss and Toneta granite gneiss near the Alakhnanda Thrust in the Garhwal Himalaya and the Dungeshwari granite gneiss near the Dailekh Thrust in Nepal, the Kausani Granite Gneiss north of NAT Kumaun Himalaya forms a major terrain boundary. These gneissic bodies mark the southernmost extent of felsic magmatism at NAT, rather than the Main Central Thrust. An about 1.8 billion years‐old magmatic event in the LHSZ suggests that it is a currently active continental margin inside the 'Greater India' region, now situated in the Himalayan domain. However, the Pb‐loss modelling of the U–Pb zircon data reveals thermal events during the Himalayan Orogeny (~45 Ma). [ABSTRACT FROM AUTHOR]

Sediment grains are progressively rounded during their transport down a river. For more than a century, Earth scientists have used the roundness of pebbles within modern sediment, and of clasts within conglomerates, as a key metric to constrain the sediment's transport history and source area(s). However, the current practices of assessment of pebble roundness are mainly qualitative and based on time-consuming manual measurement methods. This qualitative judgement provides the transport history only in a broad sense, such as classifying distance as "near" or "far". In this study, we propose a new model that quantifies the relationship between roundness and the transport distance. We demonstrate that this model can be applied to the clasts of multiple lithologies including modern sediment, as well as conglomerates, deposited by ancient river systems. We present field data from two Himalayan catchments in Nepal. We use the normalized isoperimetric ratio (IRn), which relates a pebble's area (A) to its perimeter (P), to quantify roundness. The maximum analytical value for IRn is 1, and IRn is expected to increase with transport distance. We propose a non-linear roundness model based on our field data, whereby the difference between a grain's IRn and the maximum value of 1 decays exponentially with transport distance, mirroring Sternberg's model of mass loss or size reduction by abrasion. This roundness model predicts an asymptotic behaviour for IRn , and the distance over which IRn approaches the asymptote is controlled by a rounding coefficient. Our field data suggest that the roundness coefficient for granite pebbles is 9 times that of quartzite pebbles. Using this model, we reconstruct the transport history of a Pliocene paleo-river deposit preserved at the base of the Kathmandu intermontane basin. These results, along with other sedimentary evidence, imply that the paleo-river was much longer than the length of the Kathmandu Basin and that it must have lost its headwaters through drainage capture. We further explore the extreme rounding of clasts from Miocene conglomerate of the Siwalik zone and find evidence of sediment recycling. [ABSTRACT FROM AUTHOR]

Sediment grains are progressively rounded during their transport down a river. For more than a century, Earth scientists have used the roundness of pebbles within modern sediment, and of clasts within conglomerates, as a key metric to constrain the sediment's transport history and source area(s). However, the current practices of assessment of pebble roundness are mainly qualitative and based on time consuming manual measurement methods. This qualitative judgement provides the transport history only in a broad sense, such as classifying distance as 'near' or 'far'. In this study, we propose a new model that quantifies the relationship between roundness and the transport distance. We demonstrate that this model can be applied to the clasts of multiple lithologies including modern sediment as well as conglomerates deposited by ancient river systems. We present field data from two Himalayan catchments in Nepal. We use the Normalized Isoperimetric Ratio (IRn) which relates a pebble's area (A) to its perimeter (P), to quantify roundness. The maximum analytical value for IRn is 1, and IRn is expected to increase with transport distance. We propose a non-linear roundness model based on our field data, whereby the difference between a grain's IRn and the maximum value of 1 decays exponentially with transport distance, mirroring Sternberg's model of mass loss or size reduction by abrasion. This roundness model predicts an asymptotic behaviour for IRn , and the distance over which IRn approaches the asymptote is controlled by a rounding coefficient. Our field data suggest that the roundness coefficient for granite pebbles is eight times that of quartzite pebbles. Using this model, we reconstruct the transport history of a Pliocene paleo-river deposit preserved at the base of the Kathmandu intermontane Basin. These results, along with other sedimentary evidence, imply that the paleo-river was much longer than the length of the Kathmandu Basin, and that it must have lost its headwaters through drainage capture. We further explore the extreme rounding of clasts from Miocene conglomerate of the Siwaliks Zone and find evidence of sediment recycling. [ABSTRACT FROM AUTHOR]

Ghuttu tectonic window is a structural window and is exposed around Ghuttu village in Bhilangana Valley, tectonically surrounded with overlying ductile deformed and sheared granite gneiss of Bhilangana Formation. The dominant lithology in the window comprises geochronologically undifferentiated quartzite, dolomitic limestone, carbonaceous slate and argillite/calc-argillite belonging to Lesser Himalayan sequence. The granite gneisses of Bhilangana Formation are metamorphosed up to lower amphibolite facies and tectonically lie above the low-grade greenschist facies rocks of Ghuttu tectonic window along Main Central Thrust (MCT-III). Both the hanging and footwall units are co-folded into doubly plunging antiformal structure of the window. The signatures of multiple ductile deformations as the folding of various generations, development/effect of ductile shear zone, and related modifications in the pre-existing and Himalayan shear-related folds are unequivocal. The various deformation events, viz., D1–D4 (type of folds) are identified and their kinematic history is studied. We propose a tectonic model of the structural evolution of both mechanically anisotropic and layered litho-tectonic units in Ghuttu Window and overlying mylonitised Bhilangana Formation. Research highlights: The structural and lithological mapping of Bhilangana Formation and Ghuttu window reveals the development of sequential deformation. One Pre-Himalayan and three Himalayan deformations (two orogen-transverse and one orogen-parallel) are identified under various stages of southward movement of Bhilangana Formation with minimum transportation distance of ~20 km along Bhilangana Thrust during Tertiary Tectonics. [ABSTRACT FROM AUTHOR]

The rocks of the Himalayan terrain are highly deformed and distorted due to complex geological and tectonics setup. Failures of slopes are always reported along National Highway (NH)-7, in the Uttarakhand Himalayan region, which causes loss of lives, traffic blockage, and destruction of property and also deterioration of the environment gradually. The road cut slope stability analysis of five locations were carried out along NH-7, between Shivpuri to Kaudiyala in Uttarakhand, India. For that a rigorous field investigation was done to collect the geotechnical parameters of slopes and also the potential instability condition of cut slopes were monitored with real time. To know the characteristic of rock mass, the geotechnical data's were studied based on rock mass rating (RMR) and geological strength index (GSI). The kinematics of the blocky (good and fair) rock-mass shows in general wedge, toppling and planar type of failures for different rock slopes. The petrography of representative rock samples was also carried out to see the mineralogical variation in quartzite and phyllitic quartzite. The comparative analysis of different empirical methods for slope stability as slope mass rating (SMR), continuous slope mass rating (Co-SMR), and Chinese slope mass rating (CSMR) shows a decent correlation and revealed that slopes are mostly partially stable. Qslope stability has also been applied to reveal the stability problems and to find out stable slope angle for different slopes. Further to clarify the stability of these slopes, numerical models (LEM and FEM) were applied. The numerical result, (FoS) of different slopes revealed that slopes are stable, critically stable and unstable, with a good agreement between LEM and FEM models. The collective effort of slope stability analysis through analytical and numerical methods will give the better perception to find out the potential remedial measures and optimum slope design. [ABSTRACT FROM AUTHOR]

In the present work, dynamic stress-strain response of Himalayan quartzite is tested under high loading rates using split Hopkinson pressure bar (SHPB) device for the first time in the literature. The physical and static mechanical properties of quartzite e.g. dry and saturated density, specific gravity, static compressive strength and elastic modulus values are also determined. Petrological studies of quartzite are carried out through X-ray diffraction (XRD) test and scanning electron microscope (SEM) test. In the SHPB tests, it is observed from the stress-strain response that the dynamic peak stress increases with increasing strain rate whereas the elastic modulus does not show any clear trend with increase in strain rate. Dynamic force equilibrium at the incident and transmission bar ends of the rock samples is attained in all tests till the failure of the rock samples. Dynamic increase factor ( DIF ) for the rock is determined at a particular strain rate by comparing the dynamic to static peak compressive stress. Correlation equation for dynamic strength increase factor with respect to strain rate has been proposed herein. [ABSTRACT FROM AUTHOR]

Quartzitic pelites forms a part of Higher Himalayan Crystalline of higher geotectonic zone in Garhwal Himalaya. Quartzitic pelites (locally known as Pandukeshwar Quartzite) in Garhwal Himalaya is sandwiched between high grade metamorphic rocks of Central Crystallines and Badrinath Formation. Fluid inclusion studies are carried out on the detrital, and recrystallized quartz grains of quartzitic pelites to know about the fluid phases present during recrystallization processes at the time of maximum depth of burial. The quartzitic pelite (Pandukeshwar Quartzite) essentially consists of recrystallised quartz with accessory minerals like mica and feldspar. Fluid microthermometry study reveals the presence of three types of fluids: (i) high-salinity brine, (ii) CO 2-H 2O and (iii) H 2O-NaCl. These fluids were trapped during the development of grain and recrystallization processes. The high saline brine inclusions and CO 2-H 2O fluid with the density of 0.90 to 0.97 gm/cm 3 are remnants of provenance area. CO 2 density in detrital quartz grains characterise the protolith of the sandstone as granite or metamorphic rock. The H 2O-NaCl fluids involved in the recrystallization processes at temperature-pressure of 430-350°C; 4.8 to 0.5 Kbars as constrained by fluid isochores of CO 2-H 2O and H 2O-NaCl inclusions and bulging and subgrain development during recrystallization processes. The re-equilibration of the primary fluid due to elevated internal and confining pressure is evident from features like ‘C’ shaped cavities, stretching of the inclusions, their migration and decrepitation clusters. The observed inclusion morphology revealed that the rocks were exhumed along an isothermal decompression path. [ABSTRACT FROM AUTHOR]

A detailed geological, geomorphological and landuse/landcover study has been carried in a small watershed of Himalaya by visual interpretation of FCC prepared from band 123 of ASTER satellite imagery. On the basis of interpretation and field check, major litounits identified in the study area include Lesser Himalaya conglomerate consisting of quartzite, granite, phyllite boulder and pebble, Middle Siwalik sandstone and Upper Siwalik boulder beds and valley fill with Doon gravel of Holocene age. Geomorphologically the study area is characterized by typical Himalayan topography with rugged terrain. Various landforms identified and recognized include, Doon Fan Gravel Terrace, Doon Fan Gravel Dissected hill, Sub Recent Fan Terrace, Moderately Dissected Structural Hill, Piedmont Dissected Slope, River Terrace, Channel Bar and River channel. Supervised classification of ASTER False Colour Composite (FCC) (123) shows that the major landuse category in the study area is agriculture while major landcover class is forest covered land. The study shows the effect of geology and geomorphology on the type of landuse and landcover in an active tectonic zone of the study area. [ABSTRACT FROM AUTHOR]

Carbonate and calcareous-quartzite of Miri-Buxa Group in the Siang Window of Eastern Himalaya intruded by mafic rocks of gabbroic affinity. These intrusive rocks are low-Ti tholeiites (Ti/Y = 379−478; Nb/La = 0.99−1.88) and characterized by enriched LILE-LREE, depleted in HFSE with minor REE fractionation [(La/Yb) = 2.72−3.35)]. Geochemical behaviour of the incompatible trace elements with the rare earth elements abundances indicates their cogenetic nature and their emplacement in a continental rift tectonic environment. The liquidus olivine temperature of these mafic rocks ranges from 1262°C to 1380°C showing a gentle decrease of [Mg] with a steep increase of [Fe]. These charters thus imply that the rocks are either related to the extent of common source or fractionational crystallization of plagioclase and clinopyroxene from a single batch parental magma. Petrogenetic modeling of [Mg]-[Fe] and REE indicates that these mafic intrusives probably derived from a mantle source similar to komatiitic composition at moderate to high degree (8%-20%) of partial melting. [ABSTRACT FROM AUTHOR]

Abstract: The quantification of various textural parameters and petrophysical & mechanical properties of quartzites located in the Lesser and Higher Himalayas has been carried out. A dimensionless quantity ‘Texture Coefficient’ representing rock texture incorporates various textural parameters like grain shape, orientation, degree of grain interlocking and relative proportion of grain and matrix (packing density) has been measured, besides shape preferred orientation and grain suturing (fractal dimension). These have been correlated with the seismic properties like P- and S- wave velocities and attenuation characteristics and unconfined compressive strength. It has been noted that seismic velocity in rocks is a function of various textural parameters, like with the increase of aspect ratio, grain size and shape preferred orientation, velocity increases and with the increase of suturing (fractal dimension) the velocity decreases. The Texture Coefficient is noted to be inversely proportion to the velocity and there exits strong positive relationships (R=0.71) between Texture Coefficient and the unconfined compressive strength. However the relation between the velocity and the unconfined compressive strength is meaningless. [Copyright &y& Elsevier]

Abstract  Satluj valley, located in the Higher Himalaya, is undergoing rapid development, mainly because of its high hydropower potential. The paper reports a study to determine whether the engineering properties of the granites, gneisses, quartzites and marbles encountered in the higher Himalayan terrain in the Satluj valley can realistically be determined using the Schmidt hammer and ultrasonic velocity. The results indicate a positive correlation for the granites, quartzites and marbles, but not for the folded, anisotropic gneisses. [ABSTRACT FROM AUTHOR]