Cryoconite samples were collected from two different climatic domains i.e.,the Sutri Dhaka glacier,western Himalaya India and Svalbard glaciers,the Spitsbergen,Arctic,to understand the elemental source and elemental d...Cryoconite samples were collected from two different climatic domains i.e.,the Sutri Dhaka glacier,western Himalaya India and Svalbard glaciers,the Spitsbergen,Arctic,to understand the elemental source and elemental deposition patterns.The data of geochemical analysis suggest that the Himalayan cryoconite samples accumulate higher concentrations as compared to the cryoconite samples of the Arctic glaciers.The concentration of lithophile elements(Cs,Li,Rb and U)was recorded higher in the cryoconite holes of the Himalayas,especially,in the lower to the higher parts of the glacier,whereas,lower concentrations were recorded in the Arctic samples.Chalcophile elements in the Himalayan cryoconites are enriched in As and Bi while the Arctic cryoconite samples show a higher concentration of Bi,Pb and As.The higher concentrations are responsible for influencing the ecosystem and in human health related issues.Siderophile elements(Co,Fe,Mn and Ni)show high concentrations in the Himalayan samples,whereas,the Arctic samples show minor variations and low elemental concentration in these elements,respectively.In addition,a few elements,such as Ag,Mg,and Ca show higher concentration in the Himalayan glacier samples.Ca also occurs in high concentrations in Arctic glacier samples.R-mode factor analysis of the Himalayas(Arctic)samples indicate that the elements are distributed in four(three)factors,explaining 89%(90%)of the variance in their elemental distribution.The Factor 1 suggests statistically significant positive loadings for most of the lithophile,chalcophile and siderophile elements of the "Himalayan" and the Arctic cryoconite samples.The sample-wise factor score distribution shows a considerable variation in the sampling locations along the glaciers of both the regions.Factors 2 and 3,demonstrate insignificant loading for most of the elements,except statistically significant positive loading in some of the elements of the both,Himalayan and Arctic "cryoconites".The higher elemental concentration in the cryoconites of the Himalayan region may be an indicator of the natural processes and/or attributed to the rapid industrialization in the Asian countries.展开更多
The western continental margin of India is one of the highly productive regions in the global ocean.Primary productivity is induced by upwelling and convective mixing during the southwest and northeast monsoons respec...The western continental margin of India is one of the highly productive regions in the global ocean.Primary productivity is induced by upwelling and convective mixing during the southwest and northeast monsoons respectively.Realizing the importance of high primary productivity,a sediment core was collected below the current oxygen minimum zone（OMZ） from the southwestern continental margin of India.This was dated by AMS radiocarbon and as many as 60 paleoclimate/paceoceanographic proxies,such as particle size,biogenic components,major,trace and rare earth elements（REEs） which were measured for the first time to determine sources of sediment,biogeochemical processes operating in the water column and their variations since the last glacial cycle.R-mode factor analysis of comprehensive data indicates that the dominant regulator of paleoproductivity is the southwest monsoon wind induced upwelling.Other paleoproductivity related factors identified are the marine biogenic component and biogenic detritus（as an exported component from the water column added to the bottom sediment）.All paleoproductivity components increased significantly during the marine isotope stage-1（MIS-1）compared to those accumulated from MIS-4 to MIS-2.The second group of factors identified are the terrigenous sediments with heavy minerals like zircon and ilmenite.The terrigenous sediment,in particular,increased during MIS-2 when the sea-level was lower;however,the heavy mineral component fluctuated over time implying pulsed inputs of sediment.The diagenetic fraction and reducing component are the third group of factors identified which varied with time with increased accumulation during the MIS transitions.The primary productivity along the southwestern continental margin of India seems to have been controlled principally by the upwelling during the southwest monsoon season that was weaker from MIS-4 to MIS-2,as relative to that during the MIS-1.In contrast,increased glacial productivity noticed in sediments deposited below the current oxygen minimum zone（OMZ） along the north of the study area that can be linked to entrainment of nutrients through the intensified convective mixing of surface water during the northeast monsoon.The sequestration of greenhouse gases by the western continental margin of India was higher during glacial than interglacial cycles.展开更多
The spatial distribution patterns of surficial sediment samples from different sedimentary domains （shallow to deep-sea regions） of the eastern Arabian Sea were studied using sediment proxies viz. environmental magn...The spatial distribution patterns of surficial sediment samples from different sedimentary domains （shallow to deep-sea regions） of the eastern Arabian Sea were studied using sediment proxies viz. environmental magnetism, geochemistry, particle size and clay mineralogy. Higher concentrations of magnetic minerals （high Xlf） were recorded in the deep-water sediments when compared with the shallow water sediments. The magnetic mineralogy of one of the shallow water samples is influenced by the presence of bacterial magnetite as evidenced from the XARM/Xlf VS. XARM/Xfd biplot. However, the other samples are catchment-derived. The high correlation documented for Xlf, anhysteretic remanent mag- netisation （XARM） and isothermal remanent magnetisation （IRM） with Al indicates that the deep-sea surflcial sediments are influenced by terrigenous fluxes which have been probably derived from the southern Indian rivers, the Sindhu （the Indus） and the Narmada-Tapti rivers. A lower Mn concentration is recorded in the upper slope sediments from the oxygen minimum zone （OMZ） but a higher Mn/AI ratio is documented in the lower slope and deep-sea sediments. Clay minerals such as illite （24-48.5%）, chlorite （14.1-34.9%）, smectite （10.6-28.7%） and kaolinite （11.9-27.5%） dominate the sediments of shallow and deep-sea regions and may have been derived from different sources and transported by fluvial and aeolian agents. Organic carbon （OC） data indicate a low concentration in the shallow/shelf region （well oxygenated water conditions） and deeper basins （increased bottom-water oxygen concentration and low sedimentation rate）. High OC concentrations were documented in the OMZ （very low bottom-water oxygen concentration with high sedimentation rate）. The calcium carbonate concentration of the surface sediments from the continental shelf and slope regions （〈 1800 m） up to the Chagos-Laccadive Ridge show higher concentrations （average - 58%） when compared to deep basin sediments （average - 44%）. Our study demonstrates that particle size as well as magnetic grain size, magnetic minerals and elemental variations are good indicators to distinguish terrigenous from biogenic sediments and to identify sediment provenance.展开更多
Influence of structural and lithological controls of various drainage patterns and their stream orientations（for 2nd, 3rd and 4th order steams） were identified to evaluate the direction and controlling factors of dr...Influence of structural and lithological controls of various drainage patterns and their stream orientations（for 2nd, 3rd and 4th order steams） were identified to evaluate the direction and controlling factors of drainage network. To investigate the prospect of groundwater, hydrogeomorphological features of river basin viz. Mulki-Pavanje were identified and mapped. To evaluate the characteristics of the basin, different morphometric parameters（linear, areal and relief） were computed in sub-basin wise（SB-I to-VII）. The linear parameters suggest drainage network is controlled by geomorphology. The form factor（Ff）, elongation ratio（Re） and circularity ratio（Rc） suggest that the basin is in an elongated shape. The drainage density（Dd） indicates resistant/permeable strata under medium-dense vegetation with moderate relief. The areal parameters of the sub-basins（except SBI and Ⅲ） indicates moderate ground-slopes associated with moderately permeable rocks, which promote moderate run-off and infiltration. Drainage texture（T） of the whole basin indicates coarse texture while the SB-I, and Ⅲ showing an intermediate texture. The relief parameters namely ruggedness number（Rn） infers low basin relief and poor drainage density. To identify the most deficit/surplus zones of groundwater suitable weightages were assigned to the hydrogeomorphological units and morphometric parameters. The study reveal that the basin manifest that SB-Ⅲ shall be most deficit zone of groundwater, whereas SB-VII, VI and V are found to show increase in groundwater potentiality. Groundwater prospect area in this basin is estimated to be 7% area under poor, 44% area under moderate and 49% area under good to excellent. This paper demonstrated the potential application of geographical information system（GIS） techniques to evaluate the groundwater prospect in absence of traditional groundwater monitoring data.展开更多
基金Ministry of Earth Science,New Delhi and Indian Council of Agriculture Research for their financial support
文摘Cryoconite samples were collected from two different climatic domains i.e.,the Sutri Dhaka glacier,western Himalaya India and Svalbard glaciers,the Spitsbergen,Arctic,to understand the elemental source and elemental deposition patterns.The data of geochemical analysis suggest that the Himalayan cryoconite samples accumulate higher concentrations as compared to the cryoconite samples of the Arctic glaciers.The concentration of lithophile elements(Cs,Li,Rb and U)was recorded higher in the cryoconite holes of the Himalayas,especially,in the lower to the higher parts of the glacier,whereas,lower concentrations were recorded in the Arctic samples.Chalcophile elements in the Himalayan cryoconites are enriched in As and Bi while the Arctic cryoconite samples show a higher concentration of Bi,Pb and As.The higher concentrations are responsible for influencing the ecosystem and in human health related issues.Siderophile elements(Co,Fe,Mn and Ni)show high concentrations in the Himalayan samples,whereas,the Arctic samples show minor variations and low elemental concentration in these elements,respectively.In addition,a few elements,such as Ag,Mg,and Ca show higher concentration in the Himalayan glacier samples.Ca also occurs in high concentrations in Arctic glacier samples.R-mode factor analysis of the Himalayas(Arctic)samples indicate that the elements are distributed in four(three)factors,explaining 89%(90%)of the variance in their elemental distribution.The Factor 1 suggests statistically significant positive loadings for most of the lithophile,chalcophile and siderophile elements of the "Himalayan" and the Arctic cryoconite samples.The sample-wise factor score distribution shows a considerable variation in the sampling locations along the glaciers of both the regions.Factors 2 and 3,demonstrate insignificant loading for most of the elements,except statistically significant positive loading in some of the elements of the both,Himalayan and Arctic "cryoconites".The higher elemental concentration in the cryoconites of the Himalayan region may be an indicator of the natural processes and/or attributed to the rapid industrialization in the Asian countries.
基金National Centre for Antarctic and Ocean Research(NCAOR) for continuous support and encouragementthe MoES(MoES/36/OOIS/Siber/07) for funding a GEOTRACES project
文摘The western continental margin of India is one of the highly productive regions in the global ocean.Primary productivity is induced by upwelling and convective mixing during the southwest and northeast monsoons respectively.Realizing the importance of high primary productivity,a sediment core was collected below the current oxygen minimum zone（OMZ） from the southwestern continental margin of India.This was dated by AMS radiocarbon and as many as 60 paleoclimate/paceoceanographic proxies,such as particle size,biogenic components,major,trace and rare earth elements（REEs） which were measured for the first time to determine sources of sediment,biogeochemical processes operating in the water column and their variations since the last glacial cycle.R-mode factor analysis of comprehensive data indicates that the dominant regulator of paleoproductivity is the southwest monsoon wind induced upwelling.Other paleoproductivity related factors identified are the marine biogenic component and biogenic detritus（as an exported component from the water column added to the bottom sediment）.All paleoproductivity components increased significantly during the marine isotope stage-1（MIS-1）compared to those accumulated from MIS-4 to MIS-2.The second group of factors identified are the terrigenous sediments with heavy minerals like zircon and ilmenite.The terrigenous sediment,in particular,increased during MIS-2 when the sea-level was lower;however,the heavy mineral component fluctuated over time implying pulsed inputs of sediment.The diagenetic fraction and reducing component are the third group of factors identified which varied with time with increased accumulation during the MIS transitions.The primary productivity along the southwestern continental margin of India seems to have been controlled principally by the upwelling during the southwest monsoon season that was weaker from MIS-4 to MIS-2,as relative to that during the MIS-1.In contrast,increased glacial productivity noticed in sediments deposited below the current oxygen minimum zone（OMZ） along the north of the study area that can be linked to entrainment of nutrients through the intensified convective mixing of surface water during the northeast monsoon.The sequestration of greenhouse gases by the western continental margin of India was higher during glacial than interglacial cycles.
基金The magnetic instruments used for this investigation were procured through grants(DOD Sanction No.DOD/11-MRDF/1/48/P/94ODII/12-10-96)under a research project(to RS)sponsored by the erstwhile Department of Ocean Development(now Ministry of Earth Sciences),Government of India
文摘The spatial distribution patterns of surficial sediment samples from different sedimentary domains （shallow to deep-sea regions） of the eastern Arabian Sea were studied using sediment proxies viz. environmental magnetism, geochemistry, particle size and clay mineralogy. Higher concentrations of magnetic minerals （high Xlf） were recorded in the deep-water sediments when compared with the shallow water sediments. The magnetic mineralogy of one of the shallow water samples is influenced by the presence of bacterial magnetite as evidenced from the XARM/Xlf VS. XARM/Xfd biplot. However, the other samples are catchment-derived. The high correlation documented for Xlf, anhysteretic remanent mag- netisation （XARM） and isothermal remanent magnetisation （IRM） with Al indicates that the deep-sea surflcial sediments are influenced by terrigenous fluxes which have been probably derived from the southern Indian rivers, the Sindhu （the Indus） and the Narmada-Tapti rivers. A lower Mn concentration is recorded in the upper slope sediments from the oxygen minimum zone （OMZ） but a higher Mn/AI ratio is documented in the lower slope and deep-sea sediments. Clay minerals such as illite （24-48.5%）, chlorite （14.1-34.9%）, smectite （10.6-28.7%） and kaolinite （11.9-27.5%） dominate the sediments of shallow and deep-sea regions and may have been derived from different sources and transported by fluvial and aeolian agents. Organic carbon （OC） data indicate a low concentration in the shallow/shelf region （well oxygenated water conditions） and deeper basins （increased bottom-water oxygen concentration and low sedimentation rate）. High OC concentrations were documented in the OMZ （very low bottom-water oxygen concentration with high sedimentation rate）. The calcium carbonate concentration of the surface sediments from the continental shelf and slope regions （〈 1800 m） up to the Chagos-Laccadive Ridge show higher concentrations （average - 58%） when compared to deep basin sediments （average - 44%）. Our study demonstrates that particle size as well as magnetic grain size, magnetic minerals and elemental variations are good indicators to distinguish terrigenous from biogenic sediments and to identify sediment provenance.
文摘Influence of structural and lithological controls of various drainage patterns and their stream orientations（for 2nd, 3rd and 4th order steams） were identified to evaluate the direction and controlling factors of drainage network. To investigate the prospect of groundwater, hydrogeomorphological features of river basin viz. Mulki-Pavanje were identified and mapped. To evaluate the characteristics of the basin, different morphometric parameters（linear, areal and relief） were computed in sub-basin wise（SB-I to-VII）. The linear parameters suggest drainage network is controlled by geomorphology. The form factor（Ff）, elongation ratio（Re） and circularity ratio（Rc） suggest that the basin is in an elongated shape. The drainage density（Dd） indicates resistant/permeable strata under medium-dense vegetation with moderate relief. The areal parameters of the sub-basins（except SBI and Ⅲ） indicates moderate ground-slopes associated with moderately permeable rocks, which promote moderate run-off and infiltration. Drainage texture（T） of the whole basin indicates coarse texture while the SB-I, and Ⅲ showing an intermediate texture. The relief parameters namely ruggedness number（Rn） infers low basin relief and poor drainage density. To identify the most deficit/surplus zones of groundwater suitable weightages were assigned to the hydrogeomorphological units and morphometric parameters. The study reveal that the basin manifest that SB-Ⅲ shall be most deficit zone of groundwater, whereas SB-VII, VI and V are found to show increase in groundwater potentiality. Groundwater prospect area in this basin is estimated to be 7% area under poor, 44% area under moderate and 49% area under good to excellent. This paper demonstrated the potential application of geographical information system（GIS） techniques to evaluate the groundwater prospect in absence of traditional groundwater monitoring data.
