Negi P.S.,Wadia Institute of Himalayan Geology
Tropical Ecology | Year: 2012
The study of alpine treeline as a climate marker may be used as an important indicator in mountain ecosystem dynamics. However, the terms, yardsticks and methods usually applied worldwide are not comparable among various studies. An appraisal of the relevant literature with special reference to the work by Panigrahy et al. (2010) in northwestern Indian Himalaya to promote and advocate adopting uniform pattern and interdisciplinary observations is attempted. It is observed that the terminological variability and the resultant confusion, variable definition of tree and treeline and their relative validation at the ground, remain major impediment in developing standardized and quantitative assessment protocols of treeline dynamics as a precise climate change response. This situation has resulted in generating differential reliability in treeline study from local to the global level. In order to address this issue ecologically compatible terminology and UNESCO standard sampling methodology has been proposed. It is also concluded that treeline dynamics is more related to the deflected snow precipitation system rather than global warming in the Himalaya. © International Society for Tropical Ecology.
Tewari V.C.,Wadia Institute of Himalayan Geology
Geological Society Special Publication | Year: 2012
The breakup of Rodinia resulted in the formation of rift basins and passive margins c. 650 Ma. Major palaeoclimaticevents such as Neoproterozoic global glaciation (known as 'snowball Earth'; Hoffman et al. 1998) followed by global warming have been recorded on different continents, including the Indian Lesser Himalaya (Blaini-Krol Cryogenian-Ediacaran Period). The reconstruction of the Rodinia supercontinent (Powell et al. 1993; Li et al. 2003) and the palaeoposition of India (including Lesser Himalaya-Southern China shelf facies, Tewari 2010) strongly suggest that a connection of the Lesser Himalayan Neoproterozoic sedimentary basins with Rodinia must have existed. Early Earth possibly witnessed its most extreme climatic fluctuations during the mid late Neoproterozoic between 750 and 550 Ma. Palaeoglaciers even reached theequator c. 635 Ma, covering the whole Earth. Evidence from Australia, Africa, Antarctica, South America, South China andthe Indian Lesser Himalaya suggest that there may have been three or more palaeoglacial events during this 200 million year interval. The global decline of Meso-Neoproterozoic stromatolites, biotic evolution, diversification, extinctions and the discovery of Ediacaran life following the cold climate are of great significance. Carbon isotopic excursions from all pink cap carbonates from the Lesser Himalaya capping the Blaini glacial diamictites have shown strong negative excursions, whereas the overlying Ediacaran Krol carbonates are characterized by a positive shift in carbon isotope ratios (Tewari 2010). In the Lesser Himalayan Krol belt, extending from the Solan in Himachal to Nainital in Uttarakhand Lesser Himalaya, the Upper Krol Formation (Krol D Member, Auden, 1934, 1937) is a typical Ediacaran (terminal Neoproterozoic) microbial carbonate sedimentation facies. Krol D contains Ediacaran metazoan fossils and abundant microbial structures in the form of columnar, domal and stratified stromatolites. Peloids, oncoids and microphytolites are also microbially formed structures. Carbonate grainstones and packstones are common in Krol D, and the allochemical constituents are intraclasts, ooids, coated grains, peloids, microbial grains and catagraphs. A diagenesis and cathodoluminescence study of the Krol ooids has been done in detail for the first time. The sedimentary structures present in the non-stromatolitic Krol carbonates include bird's eye, cross beddings, symmetrical ripples and shallow channel structures. An intertidal to supratidal carbonate ramp depositional environment with some moderate currents and intermittent periods of exposure has been suggested for the Upper Krol carbonates of the Lesser Himalaya. A moderate to high content of organic matter (kerogen) in the Neoproterozoic microbial fossils indicates the presence of probable hydrocarbon source rocks. © The Geological Society of London 2012.
Kumahara Y.,Gunma University |
Jayangondaperumal R.,Wadia Institute of Himalayan Geology
Geomorphology | Year: 2013
New paleoseismic evidence is presented from the Bhatpur (N 31°18'16.28", E 76°9'50.00") Trench site along the Himalayan Frontal Thrust (HFT) on western margin of the Janauri Anticline in NW Himachal Himalaya, India. The latest surface rupture at this site demonstrates coseismic displacement of at least 9.3. m.Radiocarbon dating of trench samples indicates that the surface ruptures occurred at A.D. 1400-1460. After comparison with other trench results along the Himalayan Front, two scenarios are presented of the latest surface rupturing earthquake event in the northwestern Indian Himalaya: (1) a single-event surface rupturing for a minimum fault length of 450. km, or (2) two-events of different lateral extent. According to the former scenario, the latest surface rupture occurred between A.D. 1404 and 1422. The latter scenario suggests the latest surface rupture occurred between A.D. 1404 and A.D. 1460 in the northwestern extent from Kala Amb to Hajipur with ~ 9.0. m of coseismic displacement over a minimum fault length of 200 km Yet another surface rupture event in the southeastern extent from Kala Amb to Ramnagar has occurred between A.D. 1282 and A.D. 1422, with displacement ranging from 16.0. m to 26.0. m, and a minimum surface rupture length of 230. km. On the basis of these observations and historical earthquakes, it is suggested that the potential for earthquakes larger than those in the historical records are capable of producing surface-rupture lengths greater than the ~ 200 to ~ 230 km or ~ 450. km in the northwestern Indian Himalayan Front. © 2012 Elsevier B.V.
Kohn M.J.,Boise State University |
Paul S.K.,Wadia Institute of Himalayan Geology |
Corrie S.L.,Boise State University
Bulletin of the Geological Society of America | Year: 2010
The lower Lesser Himalayan sequence marks the northern extremity of the exposed Indian plate, and is generally interpreted as a passive margin. Five lines of evidence, however, collectively suggest a continental arc setting: (1) igneous intrusions and volcanic rocks occur at this stratigraphic level across the length of the Himalaya, (2) ages of intrusive and metavolcanic (?) rocks cluster at 1780-1880 Ma but also indicate a long-lived igneous process, (3) detrital zircon ages in clastic rocks cluster at 1800-1900 Ma, with a unimodal age distribution in some rocks, (4) the mineralogy and chemistry of metasedi mentary rocks differ from typical shales and suggest a volcanogenic source, (5) traceelement chemistries of orthogneisses and meta basalts are more consistent with either an arc or a collisional setting. Intercalation of volcanic rocks with clastic sediments and a general absence of Proterozoic metamorphic ages do not support a collisional origin. An arc model further underscores the profound unconformity separating lower-upper Lesser Himalayan rocks, indicating that a Paleoproterozoic arc may have formed the stratigraphic base of the northern Indian margin. This, in turn, may indicate disposition of the Indian plate adjacent to North America in the ca. 1800 Ma supercontinent Columbia. Felsic orthogneisses ("Ulleri") likely represent shallow intrusions, not Indian basement. © 2010 Geological Society of America.
Negi P.S.,Wadia Institute of Himalayan Geology
Ecological Indicators | Year: 2013
A field based technique has been developed to identify and delineate the areas of potential hill slope instability with the help of ecological indicator. Habitat characteristics and spatial-temporal occurrence of indicator taxon were investigated with respect to its natural environment. The study includes extensive field surveys, laboratory studies and comparison of historical maps at local scale coupled with literature appraisal at local, regional and global scales. Instability generated due to slope disturbances by natural and anthropogenic activities along the roads, ravines, stream banks, terraces, cultivated land, old landslide sites and human settlements was investigated during the years 2000-2005. It was followed by regional and global scale study during the years 2009-2011. It is established that the instability is manifested by occurrence of indicator species and its spatial dominance delineates the areas of potential instability. The investigated inherent characteristic features of the indicator species viz.; rapid growth (145 cm/year), primary succession, nitrogen fixation and obtrapezoid-winged seed structure, roots and suckers morphology and associated microclimatic scenario have been found extremely decisive to the process of manifestation of slope instability. Study at three experimental sites and vicinity also confirmed that wide-spread occurrence of indicator taxon is not related to specific soil and rock type, gradient or aspect but is exclusively attributable to its unstable environment. The indicator taxon has been identified as Alnus nepalensis D. Don and its invasion delay to the unstable slopes was reported by one to two years. Indicator's habitat affinity to instability and its phyto-geographical range was explored between 1000-2590 m asl at local scale in Garhwal Himalaya and 900-2700 m at regional scale in Indian Himalayan and other mountain states viz.; Himachal Pradesh, Uttarakhand, Sikkim, Assam and Meghalaya, while it is reported between 200 m and 2800 m at global scale in Asian countries like Nepal, Tibet, Bhutan, China, Myanmar and Bangladesh. The proposed ecological approach to identify and delineate the areas of potential hill slope instability seems to be promising and may be termed innovative, as it involves only local resource as a scientific tool and traditional wisdom as technical excellence. Unlike geotechnical methods of slope instability assessment, this being simple, eco-friendly, self sustainable and cost effective, it is socially acceptable and can also be used by non-scientists for planning and management in Himalayan region and similar other regions of the world. © 2012 Elsevier Ltd.
Thayyen R.J.,Wadia Institute of Himalayan Geology |
Thayyen R.J.,National Institute of Hydrology |
Gergan J.T.,Wadia Institute of Himalayan Geology
Cryosphere | Year: 2010
A large number of Himalayan glacier catchments are under the influence of humid climate with snowfall in winter (November-April) and south-west monsoon in summer (June-September) dominating the regional hydrology. Such catchments are defined as "Himalayan catchment", where the glacier meltwater contributes to the river flow during the period of annual high flows produced by the monsoon. The winter snow dominated Alpine catchments of the Kashmir and Karakoram region and cold-arid regions of the Ladakh mountain range are the other major glaciohydrological regimes identified in the region. Factors in- fluencing the river flow variations in a "Himalayan catchment" were studied in a micro-scale glacier catchment in the Garhwal Himalaya, covering an area of 77.8 km2. Three hydrometric stations were established at different altitudes along the Din Gad stream and discharge was monitored during the summer ablation period from 1998 to 2004, with an exception in 2002. These data have been analysed along with winter/summer precipitation, temperature and mass balance data of the Dokriani glacier to study the role of glacier and precipitation in determining runoff variations along the stream continuum from the glacier snout to 2360ma.s.l. The study shows that the inter-annual runoff variation in a "Himalayan catchment" is linked with precipitation rather than mass balance changes of the glacier. This study also indicates that the warming induced an initial increase of glacier runoff and subsequent decline as suggested by the IPCC (2007) is restricted to the glacier degradation-derived component in a precipitation dominant Himalayan catchment and cannot be translated as river flow response. The preliminary assessment suggests that the "Himalayan catchment" could experience higher river flows and positive glacier mass balance regime together in association with strong monsoon. The important role of glaciers in this precipitation dominant system is to augment stream runoff during the years of low summer discharge. This paper intends to highlight the importance of creating credible knowledge on the Himalayan cryospheric processes to develop a more representative global view on river flow response to cryospheric changes and locally sustainable water resources management strategies.
Ray Y.,Wadia Institute of Himalayan Geology |
Srivastava P.,Wadia Institute of Himalayan Geology
Quaternary Science Reviews | Year: 2010
Cut-and-fill type fluvial terraces are ubiquitous in the Lesser Himalayan zone of the Alaknanda-Ganga (Ganges) rivers system, which flows perpendicular to Himalayan lithotectonic units and traverses a steep climatic gradient. Lithofacies analysis of the sedimentary sequences of cut-and-fill terraces indicated that the valley aggradation took place via (1) channel bar development and excess sediment supply, (2) debris flows composed of mixed rounded to sub-rounded lithoclasts, resulting from episodic high intensity rainfalls in the upper catchment or (3) debris flows or rockfalls generated by local landslides. The luminescence chronology indicates that valley aggradation took place in two phases: ∼49. -25. ka and 18. -11. ka. The incision of the fill started soon after 11. ka. Paleoclimatic records from marine sediments indicate that the aggradation and incision in the Alaknanda-Ganga River has oscillated in-phase with global climatic variations. Glaciation. -deglaciation processes in the upper catchment produced huge amounts of sediment between 63 and 11. ka, which was fluvially transferred to the lower valley via several cycles of erosion and deposition, leading to extensive aggradation. The climatic amelioration at ∼11. ka and the completion of deglaciation processes led to increased fluvial discharge and decreased sediment supply, conditions conducive for incision of the alluvial fills. Records from the Indo-Gangetic plain and the Ganga Delta demonstrate that the phase of aggradation was regional but that incision in the foreland started at least 2. -3. ka later, after 7. ka.Bedrock incision rates, as calculated from dated alluvial covers of terraces that are separated by bedrock steps, are spatially variable and fall within the range of rates reported from across the Himalaya. These estimated rates, however, are higher than the basin average erosion rates calculated using isotopic mass balance in riverbed sediments. This study suggests that during the last 50. ka river dynamics in the Himalayas were dominated by monsoon variability and the role of tectonic activity was limited to bedrock incision in few reaches only. © 2010 Elsevier Ltd.
Paul A.,Wadia Institute of Himalayan Geology
Journal of the Geological Society of India | Year: 2010
The Garhwal-Kumaun region continues to accumulate the built-up of strain energy like the other regions of the Himalaya. But this sector unlike the other sectors is yet to release this accumulated strain energy which can be in the form of great earthquake. The region has sufficient strain energy to generate earthquake of M>8. The analysis of seven hundred ten local events recorded by ten station broad band network between August'07 to February'10 shows that most of the seismic events recorded in this region continue to occur from shallow depths (< 25 km). The evaluation of source parameters from p-wave spectral analysis indicates that the events have low stress drop values. The region continues to release energy in the form of smaller magnitude earthquakes. The epicentral location map indicates that Munsiari Thrust, which is located south of the Main Central Thrust is more active. © 2010 Geological Society of India.
Bikramaditya Singh R.K.,Wadia Institute of Himalayan Geology
Journal of the Geological Society of India | Year: 2010
Low to medium grade crystalline rocks locally known as Bomdila Group extensively covers the Lesser Himalayan region in Western Arunachal Himalaya. This Group consists dominantly of mylonitic gneisses of granitic composition of Palaeoproterozoic age, named as Bomdila mylonitic gneiss (BMG) and a small body of hornblende bearing granite of Mesoproterozoic age known as Salari granite (SG). The BMG is affinity to peraluminous (A/CNK > 1.1) with high content of SiO2, K2O/N2O ratio, normative corundum, high ratio of FeO'/MgO in biotite (3.21-5.11) that shows characteristics of S-type granite whereas SG has granodiorite composition with high Na2O, low K2O, presence of hornblende, normative diopside, low A/CNK ratio (<1.1) and low FeO1/MgO ratio in biotite (1.58-1.60) indicates metaluminous I-type granite affinity. The SG has more fractionated nature of REE [(Ce/Yb)N = 9.06-18.53] and minor negative Eu anomalies [EU N/Eu* = 0.69-0.94] as compared to BMG which has less fractionation of REE [(Ce/Yb)N = 5.95-9.16] and strong negative Eu anomalies [EuN/Eu* = 0.37-0.43]. Geochemical and petrological studies suggest that the SG and BMG are not genetically related; SG appears to have derived from igneous source whereas the BMG have been derived from sedimentary source, however these granitoids might have produced during the same thermal event. © GEOL. SOC. INDIA.
Thakur V.C.,Wadia Institute of Himalayan Geology
International Journal of Earth Sciences | Year: 2013
In the Sub-Himalayan zone, the frontal Siwalik range abuts against the alluvial plain with an abrupt physiographic break along the Himalayan Frontal Thrust (HFT), defining the present-day tectonic boundary between the Indian plate and the Himalayan orogenic prism. The frontal Siwalik range is characterized by large active anticline structures, which were developed as fault propagation and fault-bend folds in the hanging wall of the HFT. Fault scarps showing surface ruptures and offsets observed in excavated trenches indicate that the HFT is active. South of the HFT, the piedmont zone shows incipient growth of structures, drainage modification, and 2-3 geomorphic depositional surfaces. In the hinterland between the HFT and the MBT, reactivation and out-of-sequence faulting displace Late Quaternary-Holocene sediments. Geodetic measurements across the Himalaya indicate a ~100-km-wide zone, underlain by the Main Himalayan Thrust (MHT), between the HFT and the main microseismicity belt to north is locked. The bulk of shortening, 15-20 mm/year, is consumed aseismically at mid-crustal depth through ductile by creep. Assuming the wedge model, reactivation of the hinterland faults may represent deformation prior to wedge attaining critical taper. The earthquake surface ruptures, ≥240 km in length, interpreted on the Himalayan mountain front through paleoseismology imply reactivation of the HFT and may suggest foreland propagation of the thrust belt. © 2013 Springer-Verlag Berlin Heidelberg.