Time filter

Source Type

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.

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.

Discover hidden collaborations