Considerable controversy exists over whether or not extensive glaciation occurred during the global Last Glacial Maximum（LGM） in the Larsemann Hills.In this study we use the in situ produced cosmogenic nuclide ^（10...Considerable controversy exists over whether or not extensive glaciation occurred during the global Last Glacial Maximum（LGM） in the Larsemann Hills.In this study we use the in situ produced cosmogenic nuclide ^（10）Be（half life 1.51 Ma） to provide minimum exposure ages for six bedrock samples and one erratic boulder in order to determine the last period of deglaciation in the Larsemann Hills and on the neighboring Bolingen Islands.Three bedrock samples taken from Friendship Mountain（the highest peak on the Mirror Peninsula,Larsemann Hills;～2 km from the ice sheet） have minimum exposure ages ranging from 40.0 to 44.7 ka.The erratic boulder from Peak 106（just at the edge of the ice sheet） has a younger minimum exposure age of only 8.8 ka.The minimum exposure ages for two bedrock samples from Blundell Peak（the highest peak on Stornes Peninsula,Larsemann Hills;～2 km from the ice sheet） are about 17 and 18 ka.On the Bolingen Islands（southwest to the Larsemann Hills;～10 km from the ice sheet）,the minimum exposure age for one bedrock sample is similar to that at Friendship Mountain（i.e.,44 ka）.Our results indicate that the bedrock exposure in the Larsemann Hills and on the neighboring Bolingen Islands commenced obviously before the global LGM（i.e.,20-22 ka）,and the bedrock erosion rates at the Antarctic coast areas may be obviously higher than in the interior land.展开更多
Does Cenozoic exhumation occur in the Larsemann Hills, East Antarctica？ In the present paper, we conducted an apatite fission-track thermochronologic study across the Larsemann Hills of East Antarctica. Our work reve...Does Cenozoic exhumation occur in the Larsemann Hills, East Antarctica？ In the present paper, we conducted an apatite fission-track thermochronologic study across the Larsemann Hills of East Antarctica. Our work reveals a Cenozoic exhumation event at 49.8 ± 12 Ma, which we interpret to be a result of exhumation caused by crustal extension. Within the uncertainty of our age determination, the timing of extension in East Antarctica determined by our study is coeval with the onset time of rifting in West Antarctica at c.55 Ma. The apatite fission-track cooling ages vary systematically in space, indicating a coherent block rotation of the Larsemann Hills region from c.50 Ma to c.10 Ma. This pattern of block tilting was locally disrupted by normal faulting along the Larsemann Hills detachment fault at c.5.4 Ma. The regional extension in the Larsemann Hills, East Antarctica was the result of tectonic evolution in this area, and may be related to the global extension. Through the discussion of Pan-Gondwanaland movement, and Mesozoic and Cenozoic extensions in West and East Antarctica and adjacent areas, we suggest that the protracted Cenozoic cooling over the Larsemann Hills area was caused by extensional tectonics related to separation and formation of the India Ocean at the time of Gondwanaland breakup.展开更多
Schirmacher Oasis and Larsemann Hills areas represent two different periglacial environments of East Antarctica. Schirmacher Oasis is characterized by a vast stretch of ice-shelf in the north and East Antarctic Ice Sh...Schirmacher Oasis and Larsemann Hills areas represent two different periglacial environments of East Antarctica. Schirmacher Oasis is characterized by a vast stretch of ice-shelf in the north and East Antarctic Ice Sheet(EAIS) to its south. Whereas, in Larsemann Hills area the northern and north-western boundary is coastal area and EAIS in the southern part,exhibiting polar lowland between the marine and continental glacial ecosystems. Physico-chemical parameters of water samples from different lakes of both of these two distinct locations are quite contrasting and have indicated influence of lithology, weathering, evaporation and precipitation. The lake water chemistry in Larsemann Hills area is mainly governed by the lithology of the area while Schirmacher lakes exhibit influence of precipitation and rock composition. All major ions of lake waters indicate balanced ionic concentrations. The atmospheric precipitation has significantly modified the ionic distributions in the lakes and channels. Carbonation is the main proton supplying geochemical reactions involved in the rock weathering and this is an important mechanism which controls the hydrochemistry. The lake water hydrochemistry differs widely not only between two distant periglacial zones but also within a short distance of a single periglacial entity, indicating influence of territorial climate over hydrochemistry.展开更多
The source rock from which the sillimanite gneisses derive mainly was the biotite plagioclase gneiss in the Larsemann Hills. It is the deformation-metamorphism process under special pressure and temperature condition,...The source rock from which the sillimanite gneisses derive mainly was the biotite plagioclase gneiss in the Larsemann Hills. It is the deformation-metamorphism process under special pressure and temperature condition, not the original rock compositions, that controls the presence of sillimanite. To a great degree, the sillimanite gneiss was the mixture of the detaining materials of the migrating felsic melt from the bt-plagioclase gneiss that underwent partial melting and the relics when the melt was removed. In sillimanitization the original rock had been changed substantially in chemical composition. The related metamorphism process severely deviated from the isochemical series, the process was of, therefore, an open system. In addition, the Al2O3 contents of the original rock was an important, but not critical factor for the formation of sillimanite, i. e. , the sillimanite-bearing rock need not be of aluminum rich in composition, and vise contrarily, the aluminum rock may not produce sillimanite. The authors of the present paper postulate that the source rock from which the aluminum rich rock derives need not be of aluminum rich, but sillimanitization is generally the Al2O3 increasing process. The aluminum rich sediments such as clay or shale need not correspond directly to sillimanite-rich gneisses. No argillaceous rock present equals to sillimanite-rieh gneiss in chemical composition. The protoliths to the sillimanite gneisses from the Larsemann Hills, east Antarctica, and their adjacent area may be pelite, shale greywacke, sub-greywaeke, quartz sandstone and quartz-tourmalinite. If correct, the conclusion will be of significant implication for the determination of the sillimanite gneiss formation process and the reconstruction of the protolith setting.展开更多
Information on the organic compounds in water of Mochou Lake and Heart Lake, Antarctica is given in this paper. 93 organic compounds were identified from 121 chemical constituents in lake water, including n alkanes,...Information on the organic compounds in water of Mochou Lake and Heart Lake, Antarctica is given in this paper. 93 organic compounds were identified from 121 chemical constituents in lake water, including n alkanes, lipidal isopentadienes, aromatic hydrocarbons, polycyclic aromatics, alcohols, aldehydes, ketones, esters, monocarboxylic acids and phthalic esters in the range of 0.0274.79 μg/L. Organic compounds of global occurrence like BHC, DDT and PCBs were detected in the water, at the concentration of 0.0120.356 μg/L.展开更多
Based on the setting up of the function relation between the radiant brightness of ice surface and the elevation control point in Antarctica, the experiments for the extraction of elevation information by using therm...Based on the setting up of the function relation between the radiant brightness of ice surface and the elevation control point in Antarctica, the experiments for the extraction of elevation information by using thermal infrared image of Landsat TM band 6, and the ice surface topographical maps in area nearby Larsemann Hills have been performed.展开更多
1 Geological setting THE Larsemann Hills, East Antarctica consist mainly of Mirror, Broknes and Stornes Peninsulas and many islands(fig. 1), with an area of 60 km^2, and form part of extensive Neoproterozoic (1000 Ma)...1 Geological setting THE Larsemann Hills, East Antarctica consist mainly of Mirror, Broknes and Stornes Peninsulas and many islands(fig. 1), with an area of 60 km^2, and form part of extensive Neoproterozoic (1000 Ma) high-grade metamorphic terranes of East Antarctica. The major outcrops in the region are composed of amphibolite to granulite facies metapelites, metapsammites, quartzites, migmatitie paragneisses, felsic orthogneisses and mafic granulites.展开更多
基金supported by the National Science Fund of China(No.40506003 and 40631004)the Chinese Polar Science Strategy Research Fund(No.20070219).
文摘Considerable controversy exists over whether or not extensive glaciation occurred during the global Last Glacial Maximum（LGM） in the Larsemann Hills.In this study we use the in situ produced cosmogenic nuclide ^（10）Be（half life 1.51 Ma） to provide minimum exposure ages for six bedrock samples and one erratic boulder in order to determine the last period of deglaciation in the Larsemann Hills and on the neighboring Bolingen Islands.Three bedrock samples taken from Friendship Mountain（the highest peak on the Mirror Peninsula,Larsemann Hills;～2 km from the ice sheet） have minimum exposure ages ranging from 40.0 to 44.7 ka.The erratic boulder from Peak 106（just at the edge of the ice sheet） has a younger minimum exposure age of only 8.8 ka.The minimum exposure ages for two bedrock samples from Blundell Peak（the highest peak on Stornes Peninsula,Larsemann Hills;～2 km from the ice sheet） are about 17 and 18 ka.On the Bolingen Islands（southwest to the Larsemann Hills;～10 km from the ice sheet）,the minimum exposure age for one bedrock sample is similar to that at Friendship Mountain（i.e.,44 ka）.Our results indicate that the bedrock exposure in the Larsemann Hills and on the neighboring Bolingen Islands commenced obviously before the global LGM（i.e.,20-22 ka）,and the bedrock erosion rates at the Antarctic coast areas may be obviously higher than in the interior land.
基金the officers and expeditioners of CNARE(Chinese National Antarctic Research Expedition) for their assistance during the 2002/2003 field seasonLogistical support by the Arctic and Antarctic Administration of China and financial supports by the National Tenth Five-Year Project for Antarctic Sciences (No.2001DIA50040)the Basic Research Foundation of the Institute of Geomechanics,CAGS (DZLXJK200703)
文摘Does Cenozoic exhumation occur in the Larsemann Hills, East Antarctica？ In the present paper, we conducted an apatite fission-track thermochronologic study across the Larsemann Hills of East Antarctica. Our work reveals a Cenozoic exhumation event at 49.8 ± 12 Ma, which we interpret to be a result of exhumation caused by crustal extension. Within the uncertainty of our age determination, the timing of extension in East Antarctica determined by our study is coeval with the onset time of rifting in West Antarctica at c.55 Ma. The apatite fission-track cooling ages vary systematically in space, indicating a coherent block rotation of the Larsemann Hills region from c.50 Ma to c.10 Ma. This pattern of block tilting was locally disrupted by normal faulting along the Larsemann Hills detachment fault at c.5.4 Ma. The regional extension in the Larsemann Hills, East Antarctica was the result of tectonic evolution in this area, and may be related to the global extension. Through the discussion of Pan-Gondwanaland movement, and Mesozoic and Cenozoic extensions in West and East Antarctica and adjacent areas, we suggest that the protracted Cenozoic cooling over the Larsemann Hills area was caused by extensional tectonics related to separation and formation of the India Ocean at the time of Gondwanaland breakup.
文摘Schirmacher Oasis and Larsemann Hills areas represent two different periglacial environments of East Antarctica. Schirmacher Oasis is characterized by a vast stretch of ice-shelf in the north and East Antarctic Ice Sheet(EAIS) to its south. Whereas, in Larsemann Hills area the northern and north-western boundary is coastal area and EAIS in the southern part,exhibiting polar lowland between the marine and continental glacial ecosystems. Physico-chemical parameters of water samples from different lakes of both of these two distinct locations are quite contrasting and have indicated influence of lithology, weathering, evaporation and precipitation. The lake water chemistry in Larsemann Hills area is mainly governed by the lithology of the area while Schirmacher lakes exhibit influence of precipitation and rock composition. All major ions of lake waters indicate balanced ionic concentrations. The atmospheric precipitation has significantly modified the ionic distributions in the lakes and channels. Carbonation is the main proton supplying geochemical reactions involved in the rock weathering and this is an important mechanism which controls the hydrochemistry. The lake water hydrochemistry differs widely not only between two distant periglacial zones but also within a short distance of a single periglacial entity, indicating influence of territorial climate over hydrochemistry.
基金supported by the National Natural Science Foundation of China(No.40572041)the Chinese Geological Survey(No.1212010711509)Basic Outlay of the Ministry(J0704)
文摘The source rock from which the sillimanite gneisses derive mainly was the biotite plagioclase gneiss in the Larsemann Hills. It is the deformation-metamorphism process under special pressure and temperature condition, not the original rock compositions, that controls the presence of sillimanite. To a great degree, the sillimanite gneiss was the mixture of the detaining materials of the migrating felsic melt from the bt-plagioclase gneiss that underwent partial melting and the relics when the melt was removed. In sillimanitization the original rock had been changed substantially in chemical composition. The related metamorphism process severely deviated from the isochemical series, the process was of, therefore, an open system. In addition, the Al2O3 contents of the original rock was an important, but not critical factor for the formation of sillimanite, i. e. , the sillimanite-bearing rock need not be of aluminum rich in composition, and vise contrarily, the aluminum rock may not produce sillimanite. The authors of the present paper postulate that the source rock from which the aluminum rich rock derives need not be of aluminum rich, but sillimanitization is generally the Al2O3 increasing process. The aluminum rich sediments such as clay or shale need not correspond directly to sillimanite-rich gneisses. No argillaceous rock present equals to sillimanite-rieh gneiss in chemical composition. The protoliths to the sillimanite gneisses from the Larsemann Hills, east Antarctica, and their adjacent area may be pelite, shale greywacke, sub-greywaeke, quartz sandstone and quartz-tourmalinite. If correct, the conclusion will be of significant implication for the determination of the sillimanite gneiss formation process and the reconstruction of the protolith setting.
文摘Information on the organic compounds in water of Mochou Lake and Heart Lake, Antarctica is given in this paper. 93 organic compounds were identified from 121 chemical constituents in lake water, including n alkanes, lipidal isopentadienes, aromatic hydrocarbons, polycyclic aromatics, alcohols, aldehydes, ketones, esters, monocarboxylic acids and phthalic esters in the range of 0.0274.79 μg/L. Organic compounds of global occurrence like BHC, DDT and PCBs were detected in the water, at the concentration of 0.0120.356 μg/L.
文摘Based on the setting up of the function relation between the radiant brightness of ice surface and the elevation control point in Antarctica, the experiments for the extraction of elevation information by using thermal infrared image of Landsat TM band 6, and the ice surface topographical maps in area nearby Larsemann Hills have been performed.
文摘1 Geological setting THE Larsemann Hills, East Antarctica consist mainly of Mirror, Broknes and Stornes Peninsulas and many islands(fig. 1), with an area of 60 km^2, and form part of extensive Neoproterozoic (1000 Ma) high-grade metamorphic terranes of East Antarctica. The major outcrops in the region are composed of amphibolite to granulite facies metapelites, metapsammites, quartzites, migmatitie paragneisses, felsic orthogneisses and mafic granulites.
