Deformation mechanisms in the frontal Lesser Himalayan Duplex in Sikkim Himalaya,India

Understanding deformation mechanisms in Himalayan rocks is a challenging proposition due to the complex nature of the deformed rocks and their genesis. Crustal deformation in the Himalayan thrust belt typically occurs in elastico-frictional (EF) or quasi-plastic (QP) regimes at depths controlled mainly by regional strain-rate and geothermal gradient. However, material property, grain-size and their progressive changes during deformation are also important controlling factors. We present evidence of EF deformation from Gondwana rocks developed during the emplacement of one of the frontal horses (Jorthang horse) in the Lesser Himalayan Duplex (LHD) structure associated with Lesser Himalayan rocks in the footwall of the Ramgarh thrust in the Rangit window near Jorthang in the Sikkim Himalaya. The rocks in the horse exhibit systematic changes in microand meso-structures from an undeformed protolith to cataclasite suggesting that it was emplaced under elastico-frictional conditions. Meso- to micro-scale shear fractures are seen developed in Gondwana sandstone and slate while intercalated fine-grained shale-coal-carbonates are deformed by cataclastic flow suggesting that material property and grain-size have played an important role in the deformation of the Jorthang horse. In contrast, the hanging wall schists and quartzites of the Ramgarh thrust exhibit quasi-plastic deformation structures. This suggests that the Jorthang horse was emplaced under shallower crustal conditions than the antiformally folded Ramgarh thrust sheet even though the Ramgarh sheet presently overlies the Jorthang horse.     

Agricultural land use in the coastal area of the Alexander von Humboldt National Park, Cuba and its implication for conservation and sustainability

In the Alexander von Humboldt National Park in eastern Cuba many endemic animals and plants are found in various different natural habitats, which are considered to be the most important ones for in-situ conservation in the entire Insular Caribbean. In some areas of the National Park agriculture is practised. Thus, the objective of this study was to document and analyse the different land use activities and their consequences for local resource management and conservation of biodiversity in two village areas. A particular question was: what has changed since the foundation of the National Park in 1996? As time series data for land use and aerial photographs were not available for this part of Cuba, a qualitative evaluation was carried out. For this, six different land use units were mapped in 2001 and additional information gathered for areas with special interest related to sustainable land use and resource conservation. Although most parts of the study area are influenced to various degrees by human impact, the different types of land use seem presently not to have a crucial or detrimental impact on the land resources of the Alexander von Humboldt National Park. However, exploitation of the natural resources in certain areas could be improved with different management options to reach sustainability as well as to meet the conservation objectives of the National Park. This includes reduced or abandoned agricultural use of steep slopes to reduce erosion risk as well as a facilitated regeneration of natural vegetation in many parts of the study area to be able to conserve the high valuable biodiversity of the Park. Environmental education seems to have played an important and successful role since the foundation of the Park in 1996. Since then, cropping on steep slopes as well as illegal logging and poaching could be reduced.     

Environmental protection in the Apuseni Mountains: The role of Environmental Non-Governmental Organisations (ENGOs)

The Apuseni Mountains constitute one of the most interesting parts of the Carpathians in terms of landscape, biodiversity and culture. Yet dislocations are now severe and there are development threats which also require a significant response. On the one hand there are some severe pollution problems associated with mining areas developed in the communist period which require remedial action and the cases of Roşia Montana and Zlatna are discussed. On the other hand, there are forest and pasture zones – especially the Padiş Plateau – which are coming under heavy pressure from farmers seeking to enhance their incomes following the decline of mining and manufacturing which has left many households without salaries. At the same time, tourist pressure is growing. Actions are already being taken to limit pollution damage and develop sustainable landuse practices. There is a national park project linked with nature reserves comprising picturesque landscapes, a rare flora and fauna and distinct geological and palaeotological formations (including fossil ice). There are major tourist attractions and with proper management they could become part of a development programme of the countryside. However it is essential that all stakeholders adopt sustainable practices and this means that official programmes – including the future national park authority administration's work in environment protection and tourism management – are backed up by Environmental Non-Governmental Organisations (ENGOs). The paper reviews their diverse activities and concludes that they are making a very substantial contribution in ensuring that the potentials of isolated regions can be utilised in a manner consistent with nature conservation. This revised version was published online in July 2006 with corrections to the Cover Date.     

An evaluation of the inverted metamorphic gradient at Langtang National Park, Central Nepal Himalaya

Abstract The crystalline core of the Himalayan orogen in the Langtang area of Nepal, located between the Annapurna-Manaslu region and the Everest region, contains middle to upper amphibolite grade pelitic gneisses and schists. These rocks are intimately associated with the Main Central Thrust (MCT), one of the major compressional structures in the northern Indian plate, which forms a 3.7-km-wide zone containing rocks of both footwall and hangingwall affinity. An inverted metamorphic gradient is noticeable from upper footwall through hangingwall rocks, where metamorphic conditions increase from garnet grade near the MCT zone to sillimanite + K-feldspar grade in the upper hangingwall. Petrographic data distinguish two metamorphic episodes that have affected the area: a high-pressure, moderate-temperature episode (M1) and a moderate-pressure, high-temperature episode (M2). Comparison with appropriate reaction boundaries suggests that conditions for M1 in the hangingwall were approximately 900–1200 MPa and 425–525°C. Thermobarometric results for 24 samples from the footwall, MCT zone and hangingwall reflect P-T conditions during the M2 phase of 400–1200 MPa and 490–660° C. The decrease in estimated palaeopressures from footwall to hangingwall approximate a lithostatic gradient of 27 MPa km^-1, with slight fluctuations in the MCT zone reflecting structural discontinuities. In contrast to the palaeopressures, palaeotemperatures are indistinguishable across the entire area sampled. Although field evidence suggests the presence of the inverted palaeothermal gradient well known in the Himalaya, quantitative thermobarometry indicates that temperatures of final equilibration were all within error of each other across 17 km of section. At Langtang, change in pressure is responsible for the presence of the sequence of index minerals through the section. I interpret these data to reflect diachronous attainment of equilibrium temperature conditions in a lithostatic palaeopressure profile after ductile faulting of the sequence.     

Applying deep learning and benchmark machine learning algorithms for landslide susceptibility modelling in Rorachu river basin of Sikkim Himalaya,India

Landslide is considered as one of the most severe threats to human life and property in the hilly areas of the world. The number of landslides and the level of damage across the globe has been increasing over time. Therefore, landslide management is essential to maintain the natural and socio-economic dynamics of the hilly region. Rorachu river basin is one of the most landslide-prone areas of the Sikkim selected for the present study. The prime goal of the study is to prepare landslide susceptibility maps(LSMs) using computer-based advanced machine learning techniques and compare the performance of the models.To properly understand the existing spatial relation with the landslide, twenty factors, including triggering and causative factors, were selected. A deep learning algorithm viz. convolutional neural network model(CNN) and three popular machine learning techniques, i.e., random forest model(RF), artificial neural network model(ANN), and bagging model, were employed to prepare the LSMs. Two separate datasets including training and validation were designed by randomly taken landslide and nonlandslide points. A ratio of 70:30 was considered for the selection of both training and validation points.Multicollinearity was assessed by tolerance and variance inflation factor, and the role of individual conditioning factors was estimated using information gain ratio. The result reveals that there is no severe multicollinearity among the landslide conditioning factors, and the triggering factor rainfall appeared as the leading cause of the landslide. Based on the final prediction values of each model, LSM was constructed and successfully portioned into five distinct classes, like very low, low, moderate, high, and very high susceptibility. The susceptibility class-wise distribution of landslides shows that more than 90% of the landslide area falls under higher landslide susceptibility grades. The precision of models was examined using the area under the curve(AUC) of the receiver operating characteristics(ROC) curve and statistical methods like root mean square error(RMSE) and mean absolute error(MAE). In both datasets(training and validation), the CNN model achieved the maximum AUC value of 0.903 and 0.939, respectively. The lowest value of RMSE and MAE also reveals the better performance of the CNN model. So, it can be concluded that all the models have performed well, but the CNN model has outperformed the other models in terms of precision.     

A new kinematic evolutionary model for the growth of a duplex — an example from the Rangit duplex, Sikkim Himalaya, India

The Lesser Himalayan duplex (LHD) is a prominent structure through much of the Lesser Himalayan fold–thrust belt. In the Darjeeling - Sikkim Himalaya a component of the LHD is exposed in the Rangit window as the Rangit duplex (RD). The RD consists of ten horses of the upper Lesser Himalayan Sequence (Gondwana, Buxa, Upper Daling). The duplex varies from hinterland-dipping in the north, through an antiformal stack in the middle to foreland-dipping in the south. The Ramgarh thrust (RT) is the roof thrust and, based on a balanced cross-section, the Main Himalayan Sole thrust is the floor thrust at a depth of ~ 10 km and with a dip of ~ 3.5° N.Retrodeformation suggests that the RD initiated as a foreland-dipping duplex with the Early Ramgarh thrust as the roof thrust and the RT as the floor thrust. The RT became the roof thrust during continued duplexing by a combination of footwall imbrication and concurrent RT reactivation. This kinematic history best explains the large translation of the overlying MCT sheets. The restoration suggests that RD shortening is ~ 125 km, and the original Gondwana basin extended ~ 142 km northward of its present northernmost exposures within the window.     

Chemistry of springwater in Almora, Central Himalaya, India

 A field study was conducted to assess variations in physico-chemical characteristics of water of the springs located within the boundary of a Central Himalayan town where the springwater is used for drinking purposes. Monitoring of 12 springs was carried out for three seasons (winter, summer and monsoon). The results indicate direct influence of unplanned sewage disposal on the springwater quality as reflected by significant regional variations in the concentration of nitrates, chlorides, sulfates, sulfides and electrical conductivity. Population density varies within the town from 3110 to 14 137 persons/km^–2 and has direct relationship with water quality. Springs located in the densely populated area had higher concentrations of all these compounds. Concentrations of nitrates up to 60 ppm were observed in some springs, making water unsuitable for human consumption. No significant changes were observed in springwater quality during different seasons. Received: 3 February 1995 · Accepted: 27 February 1996     

Attenuation of coda waves in the Nubra-Siachen region,Himalaya, India

The attenuation properties have been estimated in the Nubra-Siachen region situated in the highly mountainous region of Himalayan belt. Coda wave quality factor (Q_c) has been determined for this virgin region by using the single backscattering method. A total of thirty earthquakes recorded in this region, which fall in the epicentral distance range of 3 to 115km have been used for the present work. A 30 sec window length of coda waves at different central frequencies 1.5, 3.0, 6.0, 9.0, 12.0, 18.0 and 24.0 Hz have been studied to determine Q_c at different recording stations. The frequency dependent coda wave quality factor relationships of the form Q_c(f) = Q_ofⁿ, have been computed at each recording stations separately: BASE: Q_c(f) = (137 ± 4.2) f^{(0.99 ± 0.12)}, CHALUNKA: Q_c(f) = (116±3.8)f^(1.0±0.05), PARTA: Q_c(f) = (122±3.0)f^(1.0±0.02), and SASOMA: Q_c(f) = (111±4.1)f^(1.0±0.03). A regional Q_c relation has been developed for the Nubra-Siachen region by using the average value of Q_c at different frequencies obtained at each recording station of the form Q_c(f) = (121±7.2)f^(1.0±0.04). The average Q_c values vary from 183 at 1.5 Hz to 3684 at 24 Hz central frequencies. The present regional relation developed for Nubra-Siachen region indicates heterogeneous and tectonically active region.     

Siwalik sedimentation in a part of the Kumaun Himalaya,India

The Siwalik Group in a part of the Kumaun Himalaya has been studied with respect to its sedimentologic properties. Size-based environmental data indicate a fluviatile environment for the Middle and Upper Siwalik sediments. The Lower Siwalik samples indicate a border-line environment, possibly a fluvial-deltaic complex. Petrologically, the Siwalik samples are essentially sublitharenites and litharenites. Variation in petrological character in successive Siwalik units is not very marked, although the heavy-mineral assemblages serve the purpose of stratigraphic identification.Sedimentary structures, though not profuse, show a well-developed cyclic development corresponding to the idealised fining-upward sequence of alluvial sediments. They indicate deposition by laterally shifting braided streams. A major portion of the Siwalik detritus may be considered to have its provenance in the Himalayan metamorphic areas.     

Rainfall thresholds for the initiation of landslide at Lanta Khola in north Sikkim,India

In the Indian Himalaya, a 15 km stretch of the North Sikkim Highway that is exceptionally susceptible to landsliding is characterized by fine-grained, low permeability debris material. Lanta Khola is one of the major debris slides in this stretch and is active every year during the monsoons. Although the relationship between rainfall and landsliding in the area is obvious, there is no previous study of precipitation thresholds for landslide initiation. Review of available rainfall and landslide activity data for the area between 1998 and 2006 suggests that sliding cannot be modeled by typical exponential relationships between cumulative rainfall (E) and rainfall duration (D). An alternative rainfall threshold has been proposed that predicts sliding if normalized cumulative rainfall for more than 15 days exceeds 250 mm. It is suggested that when this cumulative rainfall threshold is exceeded, the debris zone in the affected stretch becomes saturated and fails, causing landsliding.     

Hydropower development and the meaning of place. Multi-ethnic hydropower struggles in Sikkim,India

Academic research and media tend to emphasize the strong opposition to hydropower development in Sikkim, India, and position this as resistance to an environmentally-destructive, trans-local development, particularly by the culturally-rooted, ethnic minority Bhutia and Lepcha communities. There are several accounts of contestations of hydropower development projects in India’s Eastern Himalayan States – signifying robust and predictable indigenous people-place connections. Why then, was the implementation of the largest, Teesta Stage III Hydro Electric Project, located in Chungthang Gram Panchayat Unit in North Sikkim, in the heartland of the Bhutia-Lepcha region, not contested? In unraveling this anomaly, our focus is to understand how people-place connections are shaped and differentially experienced. Our findings are that hydropower development has elicited diverse responses locally, ranging from fierce contestation to indifference, to enthusiastic acceptance. The complexity and malleability of “place” and people’s “sense of place” provide evidence that indigeneity does not always indicate resistance to large-scale project interventions. In ethnically and socio-politically fractured communities like Chungthang, trans-local developments can reinforce ethno-social divides and disparities, and re-align traditional place-based ethno-centric solidarities along new politically-motivated lines. We argue that linear, one-dimensional views of local social coalescence around place belie more complex relations, which evolve dynamically in diverse socio-cultural and politico-economic contexts.     

Normal faults in Panjal Thrust Zone in Lesser Himalaya and between the Higher Himalaya Crystallines and Chamba sequence in Kashmir Himalaya,India

Normal faults on mesoscopic scale are observed in the Panjal Thrust Zone in the Dalhousie area of western Htmachal. The boundary between the southern margin of the Higher Himalaya Crystalline (HHC) of Zanskar and the Chamba syncline sequence is also described as a normal fault, referred to as Bhadarwah Normal Fault in the Bhadarwah area of Doda district on the basis of field mapping and shear sense criteria using S-C fabric and porphyroblast rotation. The occurrence of these normal faults suggests that the extensional tectonic regime was not restricted only to the Zanskar shear zone area but that it also occurs south of the Higher Himalayan range. This suggests NE-directed subhorizontal extension and exhumation of deeper level rocks of Higher Himalaya Crystallines.     

Geomorphological evidences of post-LGM glacial advancements in the Himalaya: A study from Chorabari Glacier,Garhwal Himalaya,India

Field geomorphology and remote sensing data, supported by Optical Stimulated Luminescence (OSL) dating from the Mandakini river valley of the Garhwal Himalaya enabled identification of four major glacial events; Rambara Glacial Stage (RGS) (13 ± 2 ka), Ghindurpani Glacial Stage (GhGS) (9 ± 1 ka), Garuriya Glacial Stage (GGS) (7 ± 1 ka) and Kedarnath Glacial Stage (KGS) (5 ± 1 ka). RGS was the most extensive glaciation extending for ~6 km down the valley from the present day snout and lowered to an altitude of 2800 m asl at Rambara covering around ~31 km² area of the Mandakini river valley. Compared to this, the other three glaciations (viz., GhGS, GGS and KGS) were of lower magnitudes terminating around ~3000, ~3300 and ~3500 m asl, respectively. It was also observed that the mean equilibrium line altitude (ELA) during RGS was lowered to 4747 m asl compared to the present level of 5120 m asl. This implies an ELA depression of ~373 m during the RGS which would correspond to a lowering of ~2°C summer temperature during the RGS. The results are comparable to that of the adjacent western and central Himalaya implying a common forcing factor that we attribute to the insolation-driven monsoon precipitation in the western and central Himalaya.     

Environmental pollution impact on water and sediments of Kumaun lakes, Lesser Himalaya, India: a comparative study

A study of the water and sediment chemistry of the Nainital, Bhimtal, Naukuchiyatal and Sattal Lakes of Kumaun, has shown that the water of these lakes are alkaline and that electrical conductivity, total dissolved solid and bicarbonate HCO ₃ ⁻ are much higher in Nainital than in the other three lakes. The weathering of limestone lithology and anthropogenic pollution, the latter due to the very high density of population in the Nainital valley, are the primary sources of enhanced parameters. The low pH of Nainital Lake water is due to low photosynthesis and enhanced respiration, increasing CO₂ in the water and the consequent enhancement of Ca²⁺ and HCO ₃ ⁻ . The dissolved oxygen in Nainital Lake is less compared to other lakes, indicating anoxic conditions developing at the mud–water interface at depth. The PO ₄ ³⁻ content in Nainital is higher (124 μg/l), showing an increasing trend over time leading to eutrophic conditions. The trace metals (Cu, Co, Zn, Ni, Mn, and Sr) are present in greater amounts in the water of Nainital Lake than in the other three lakes, though Fe and Cr are high in Bhimtal and Fe in Naukuchiyatal. The higher abundance is derived from the leaching of Fe–Mg from metavolcanic and metabasic rocks. Most of the heavy metals (Cr, Ni, Cu, Mn, Fe, Sr, and Zn) significantly enrich the suspended sediments of the lakes compared to the bed sediments which due to their adsorption on finer particles and owing to multiple hydroxide coating and organic content, except for Fe, which is enriched in the bed sediments. The high rate of sedimentation, 11.5 mm/year in Nainital, compared to Bhimtal with 4.70 mm/year, Naukuchiyatal with 3.72 mm/year, and Sattal with 2.99 mm/year, has resulted in shorter residence time, poor sorting of grains, and lesser adsorption of heavy metals, leading consequently, their depletion in the bed sediments of Nainital Lake.     

The quaternary glacial history of the Lahul Himalaya,northern India

This paper presents the first glacial chronology for the Lahul Himalaya, Northern India. The oldest glaciation, the Chandra Glacial Stage, is represented by glacially eroded benches at altitudes greater than 4300 m above sea-level. This glaciation was probably of a broad valley type. The second glaciation, the Batal Glacial Stage, is represented by highly weathered and dissected lateral moraines, which are present along the Chandra valley and some of its tributaries. This was an extensive valley glaciation. The third major glaciation, the Kulti Glacial Stage, is represented by well-preserved moraines in the main tributary valleys of the Chandra valley. This represents a less extensive valley glaciation. Two minor glacial advances, the Sonapani I and II, are represented by small sharp-crested moraines, which are within a few hundred metres or few kilometres of the present-day glaciers. The change in style and extent of glaciation is attributed to an increase in aridity throughout the Quaternary, due either to global climatic change or uplift of the Pir Panjal mountains to the south of Lahul, which restricted the northward penetration of the south Asian summer monsoon. © 1996 John Wiley & Sons, Ltd.     

An engineering geological appraisal of the Lakhwar Dam, Garhwal Himalaya, India

A 204 m high solid concrete gravity dam is proposed across the River Yamuna in Garhwal Himalaya, India. It will be located on dolerite rocks which have been intruded into the slates of Chandpur Formation. The present study includes the evaluation of the dam foundation by means of drifts, drill holes, water pressure tests and abutment slope stability studies. The water pressure test indicate the necessity of providing a grout curtain below the dam foundation. The analysis of the dam abutments for stability using the Limit equilibrium method indicates that the right abutment slope is kinematically unstable for plane failure mode. The plane failure analysis of the right abutment slope was carried out by modifying the Hoek and Bray (1981, Rock Slope Engineering, 3rd ed., Institute of Mining and Metallurgy, London) technique of plane failure analysis. The analysis reveals that right abutment slope may become unstable during the stripping operation. Based upon the analysis a safe cut slope design for the abutments have been suggested. Subsurface exploration by means of cross drift and drill holes has indicated a sheared contact of slate and dolerite in the foundation area. To avoid the settlement of the dam along this shear zone precautionary measures are suggested.     

Dendrochronological reconstruction of snow avalanche activity in the Lahul Himalaya,Northern India

Mass wasting and avalanche events substantially impact the landscape morphology and consequently human habitation throughout the Himalaya. There is, however, a paucity of snow avalanche documentation for the region. The application of dendrochronologic research methods introduces a sensitive approach to document the recurrence of snow avalanche events in a region where historical records are either non-existent or difficult to access. An exploratory dendrochronologic study was undertaken in the Lahul Himalaya of Northern India during the summer of 2006. Included within the fieldwork was an assessment of avalanche track morphology to enable identification of the slope characteristics that might be associated with an increase in avalanche activity. Thirty-six trees growing on the Ratoli avalanche track were sampled. The oldest tree was a Cedrus deodara with a pith date of 1950. A tree-ring-derived avalanche response curve highlights four avalanche events that occurred from 1972 to 2006. The successful scientific results based on the application of the method used provide the basis for local planners to quantify slope failure hazards in forested areas throughout the western Himalaya.     

Regional representation of glaciers in Chandra Basin region,western Himalaya,India

Hamtah and Chhota Shigri are two nearby, well monitored glaciers of western Himalaya, lying in the same climatic zone and driven by the same climatic conditions. In this study, topographical characteristics of both the glacier have been explored to understand the role of topography in controlling the glacier response. Further, their topographical characteristics and possible response towards climatic variations have been compared with each other and also with that of the other glaciers in the basin to find out the suitability of these two glaciers to be considered as representative of the region. Multi sensor and multi temporal remote sensing data have been used to carry out to fulfill the objectives. It is found that being in the same climatic zone, the mean accumulation area ratio of Chhota Shigri is 54% and Hamtah is 11% between 1980 and 2014. In comparison to Hamtah, Chhota Shigri glacier has a small upslope area, low compactness ratio indicating the ability of the glacier to receive direct precipitation and solar radiation. The analysis revealed that the Chhota Shigri glacier has a closer resemblance with the other glaciers in the region than Hamtah glacier. Also, the topographical settings of Chhota Shigri glacier are suitable for recording and reflecting year-to-year climatic variations.     

Temperature trend analysis in the glacier region of Naradu Valley,Himachal Himalaya,India

Two and a half decade (1985–2009) surface air temperature from Giovanni database available for the Naradu valley at High Himalaya Mountain range of Himachal Pradesh has been analysed to determine the changes in the maximum, minimum and mean air temperatures. The analysis was subjected for seasonal, annual and monthly basis and revealed a tendency towards warmer years all around, with significantly warmer winter and more significant increase in minimum temperatures. The annual maximum, minimum and mean temperatures have increase by 1,41 °C, 1,63 °C and 1,49 °C, respectively. The seasonal analysis indicates that the tendency is more pronounced in winter followed by post-monsoon, pre-monsoon and monsoon season. The trends were also examined on a maximum temperatures, and it showed a significant warning in all the months in annual mean, minimum and maximum temperatures, except February during the period of 1985–2009 in the valley. Different trend detection statistical tools have been exercised by using variety of non-parametric tests and all are in agreement.     

Seismotectonics of the 20 October 1991 Uttarkashi earthquake in Garhwal, Himalaya, North India

The 20 October 1991 Uttarkashi earthquake killed over a thousand people and caused extensive damage to property in the Garhwal Himalaya region. The body wave magnitude of the earthquake was 6.6, and the fault plane solution indicates reverse faulting. The hypocenrre was located at a focal depth of about 12 km between the Chail and Jutogh Thrusts, but movement propagated southward along the Jamak–Gangori Fault (JGF) and Dunda fault (DF) which are developed as blind faults related to the growing Uttarkashi antiform.