For the reconstruction of past climate variations,investigations on the history of glaciers are necessary.In the Himalaya,investigations like these have a rather short tradition in comparison with other mountains on e...For the reconstruction of past climate variations,investigations on the history of glaciers are necessary.In the Himalaya,investigations like these have a rather short tradition in comparison with other mountains on earth.At the same time,this area on the southern margin of Tibet is of special interest because of the question as to the monsoon-influence that is connected with the climate-development.Anyhow,the climate of High Asia is of global importance.Here for the further and regionally intensifying answer to this question,a glacial glacier reconstruction is submitted from the CentralHimalaya,more exactly from the Manaslu-massif.Going on down-valley from the glacial-historical investigations of 1977 in the upper Marsyandi Khola(Nadi) and the partly already published results of field campaigns in the middle Marsyandi Khola and the Damodar- and Manaslu Himal in the years 1995,2000,2004 and 2007,new geomorphological and geological field- and laboratory data are introduced here from the Ngadi(Nadi) Khola and the lower Marsyandi Nadi from the inflow of the Ngadi(Nadi) Khola down to the southern mountain foreland.There has existed a connected ice-stream-network drained down to the south by a 2,100-2,200 m thick and 120 km long Marsyandi Nadi main valley glacier.At a height of the valley bottom of c.1,000 m a.s.l.the Ngadi Khola glacier joined the still c.1,300 m thick Marsyandi parent glacier from the Himalchuli-massif(Nadi(Ngadi) Chuli) – the south spur of the Manaslu Himal.From here the united glacier tongue flowed down about a further 44 km to the south up to c.400 m a.s.l.(27°57'38 "N/84°24'56" E) into the Himalaya fore-chains and thus reached one of or the lowest past ice margin position of the Himalayas.The glacial(LGP(Last glacial period),LGM(Last glacial maximum) Würm,Stage 0,MIS 3-2) climatic snowline(ELA = equilibrium line altitude) has run at 3,900 to 4,000 m a.s.l.and thus c.1,500 altitude meters below the current ELA(Stage XII) at 5,400-5,500 m a.s.l.The reconstructed,maximum lowering of the climatic snowline(ΔELA = depression of the equilibrium line altitude) about 1,500 m corresponds at a gradient of 0.6°C per 100 altitude meters to a High Glacial decrease in temperature of 9°C(0.6 × 15 = 9).At that time the Tibetan inland ice has caused a stable cold high,so that no summer monsoon can have existed there.Accordingly,during the LGP the precipitation was reduced,so that the cooling must have come to more than only 9°C.展开更多
Rishi Khola,a sub-watershed of Teesta river,traverses along the Main Central Thrust(MCT)with a multitude of litho units and structural entities.This study examines the impact of tectonic and lithologic controls in con...Rishi Khola,a sub-watershed of Teesta river,traverses along the Main Central Thrust(MCT)with a multitude of litho units and structural entities.This study examines the impact of tectonic and lithologic controls in configuring the catchment characteristics of Rishi Khola,Sikkim,India.Corrected SRTM 30m DEM and Landsat 8 satellite image have been used for extracting the river network,preparing the sub-catchments,the longitudinal profile and thereby calculating the morphotectonic indices.An aggregated tectonic index(ATI)has been prepared to map the intensity of tectonic perturbations in the fluvial environment using the entropy weightage method(EWM)and Weighted Linear Combination(WLC).The undulating nature of the longitudinal profile with prominent knick points confirms the presence of tectonic disturbances and lithological variations.From all the computed morphotectonic indices and the ATI,it has been evident that the region has experienced surface deformations.When viewed at the entire catchment,the morphotectonic indices suggest ample responses to the tectonic perturbations due to the dominance of lithology-controlled hill slope processes and fluvial erosion.The spatiality of the tectonic sensitiveness is rather concentrated into certain pockets of differential stress field formed due to fault thrusting of the Himalayas.The study chiefly focuses on the peculiarity of the watershed which displays a complex response of tectonic and rock structure;wherein the proposed methodology has been successful in excavating such complex responses around the Himalayan thrusts.展开更多
文摘For the reconstruction of past climate variations,investigations on the history of glaciers are necessary.In the Himalaya,investigations like these have a rather short tradition in comparison with other mountains on earth.At the same time,this area on the southern margin of Tibet is of special interest because of the question as to the monsoon-influence that is connected with the climate-development.Anyhow,the climate of High Asia is of global importance.Here for the further and regionally intensifying answer to this question,a glacial glacier reconstruction is submitted from the CentralHimalaya,more exactly from the Manaslu-massif.Going on down-valley from the glacial-historical investigations of 1977 in the upper Marsyandi Khola(Nadi) and the partly already published results of field campaigns in the middle Marsyandi Khola and the Damodar- and Manaslu Himal in the years 1995,2000,2004 and 2007,new geomorphological and geological field- and laboratory data are introduced here from the Ngadi(Nadi) Khola and the lower Marsyandi Nadi from the inflow of the Ngadi(Nadi) Khola down to the southern mountain foreland.There has existed a connected ice-stream-network drained down to the south by a 2,100-2,200 m thick and 120 km long Marsyandi Nadi main valley glacier.At a height of the valley bottom of c.1,000 m a.s.l.the Ngadi Khola glacier joined the still c.1,300 m thick Marsyandi parent glacier from the Himalchuli-massif(Nadi(Ngadi) Chuli) – the south spur of the Manaslu Himal.From here the united glacier tongue flowed down about a further 44 km to the south up to c.400 m a.s.l.(27°57'38 "N/84°24'56" E) into the Himalaya fore-chains and thus reached one of or the lowest past ice margin position of the Himalayas.The glacial(LGP(Last glacial period),LGM(Last glacial maximum) Würm,Stage 0,MIS 3-2) climatic snowline(ELA = equilibrium line altitude) has run at 3,900 to 4,000 m a.s.l.and thus c.1,500 altitude meters below the current ELA(Stage XII) at 5,400-5,500 m a.s.l.The reconstructed,maximum lowering of the climatic snowline(ΔELA = depression of the equilibrium line altitude) about 1,500 m corresponds at a gradient of 0.6°C per 100 altitude meters to a High Glacial decrease in temperature of 9°C(0.6 × 15 = 9).At that time the Tibetan inland ice has caused a stable cold high,so that no summer monsoon can have existed there.Accordingly,during the LGP the precipitation was reduced,so that the cooling must have come to more than only 9°C.
文摘Rishi Khola,a sub-watershed of Teesta river,traverses along the Main Central Thrust(MCT)with a multitude of litho units and structural entities.This study examines the impact of tectonic and lithologic controls in configuring the catchment characteristics of Rishi Khola,Sikkim,India.Corrected SRTM 30m DEM and Landsat 8 satellite image have been used for extracting the river network,preparing the sub-catchments,the longitudinal profile and thereby calculating the morphotectonic indices.An aggregated tectonic index(ATI)has been prepared to map the intensity of tectonic perturbations in the fluvial environment using the entropy weightage method(EWM)and Weighted Linear Combination(WLC).The undulating nature of the longitudinal profile with prominent knick points confirms the presence of tectonic disturbances and lithological variations.From all the computed morphotectonic indices and the ATI,it has been evident that the region has experienced surface deformations.When viewed at the entire catchment,the morphotectonic indices suggest ample responses to the tectonic perturbations due to the dominance of lithology-controlled hill slope processes and fluvial erosion.The spatiality of the tectonic sensitiveness is rather concentrated into certain pockets of differential stress field formed due to fault thrusting of the Himalayas.The study chiefly focuses on the peculiarity of the watershed which displays a complex response of tectonic and rock structure;wherein the proposed methodology has been successful in excavating such complex responses around the Himalayan thrusts.
