The Badain Jaran Desert,located in the Alxa Plateau,Northwest China,features mega-dunes and a unique dune-lake alternation landscape.This paper presented the aeolian sediment structures of three representative dunes i...The Badain Jaran Desert,located in the Alxa Plateau,Northwest China,features mega-dunes and a unique dune-lake alternation landscape.This paper presented the aeolian sediment structures of three representative dunes in the Badain Jaran Desert using ground-penetrating radar (GPR).We processed and analyzed the GPR data and investigated the feasibility of using integrated GPR and sedimentological data to reconstruct dunes structure,sedimentary environment and geomorphological evolution.The results show that the internal structures of star dune and transverse dune represent various stages of mega-dune evolution: the main deposition processes of mega-dune are similar to those of transverse dunes but have a more complicated mechanism of sand transport and deposition because of the superimposition of dunes;the upper section of the mega-dune has a structure similar to that of star dune,with vertical aggradations on top.Diffraction hyperbolae in the GPR profile indicates that the presence of ancient dunes characterized by calcareous cementation layers is involved in the maintenance of mega-dunes,and water levels,shown by continuous,sub-horizontal GPR reflections,are supposed to be closely related to mega-dunes and the interdune lakes.Outcrop of wet sand and horizontal stratifications on the GPR image indicate moisture potentials with different levels inside mega-dunes.The multiplex geomorphology in the Badain Jaran Desert is the result of global climatic undulation,the unique geographical location,the geological structural features,etc.展开更多
Based on geomorphologic and digital elevation model(DEM) data, the topographic characteristics of the northwestern edge of the Qinghai-Tibet Plateau are analyzed. Five representative peaks are first determined accordi...Based on geomorphologic and digital elevation model(DEM) data, the topographic characteristics of the northwestern edge of the Qinghai-Tibet Plateau are analyzed. Five representative peaks are first determined according to the topographic profile maps for the ridge and piedmont lines, and then the topographic gradient characteristics are analyzed according to the representative topographic profile acquisition method.Based on the geomorphologic database data, the regions between the ridge and the piedmont lines are divided into four geomorphologic zones; and the topographic characteristics are finally analyzed for the different geomorphologic zones regions using the DEM data. The research results show that from the piedmont to the ridge, there exist four geomorphologic zones: arid, fluvial, periglacial and glacial. The arid has the lowest elevation, topographic gradient, relief and slope characteristics. The fluvial has lower elevation and the highest topographic gradient, but with lower relief and slope characteristics. With higher elevation, the periglcial has lower topographic gradient, but the highest relief and slope characteristics. The glacial has the highest elevation with higher topographic gradient, relief and slope characteristics.展开更多
Spatial variation of dissolved organic carbon(DOC) in soils of riparian wetlands and responses to hydro-geomorphologic changes in the Sanjiang Plain were analyzed through in situ collecting soil samples in the Naoli R...Spatial variation of dissolved organic carbon(DOC) in soils of riparian wetlands and responses to hydro-geomorphologic changes in the Sanjiang Plain were analyzed through in situ collecting soil samples in the Naoli River and the Bielahong River. The results showed that the average contents of DOC for soil layer of 0–100 cm were 730.6 mg/kg, 250.9 mg/kg, 423.0 mg/kg and 333.1 mg/kg respectively from riverbed to river terrace along the transverse directions of the Naoli watershed. The content of the soil DOC was the highest in the riverbed, lower in the high floodplain and much lower in the river terrace, and it was the lowest in the low floodplain. The difference in the content and vertical distribution of DOC between the riverbed and the three riparian wetlands was significant, while it was not significant among the low floodplain, the high floodplain and the river terrace. The variability of soil DOC was related to the hydrological connectivity between different landscape position of the riparian wetlands and the adjacent stream. Extremely significant correlations were observed between DOC and total organic carbon(TOC), total iron(TFe), ferrous iron(Fe(II)) whose correlation coefficients were 0.819, –0.544 and –0.709 in riparian wetlands of the Naoli River. With the increase of wetland destruction, soil p H increased and soil DOC content changed. The correlation coefficients between soil DOC and TOC, TFe, Fe(II) also changed into 0.759, –0.686 and –0.575 respectively in the Bielahong River. Under the impact of drainage ditches, the correlations between soil DOC and TFe, Fe(II) were not obvious, while the soil p H was weakly alkaline and was negatively correlated with soil DOC in the previous high floodplain. It indicates that riparian hydro-geomorphology is the main factor that could well explain this spatial variability of soil DOC, and the agricultural environmental hydraulic works like ditching also must be considered.展开更多
In this paper a geomorphic-centered system was proposed for classifying the wetlands on the Qinghai-Tibet Plateau in western China, where the flora comprises primarily grasses. Although the geomorphic properties (e.g....In this paper a geomorphic-centered system was proposed for classifying the wetlands on the Qinghai-Tibet Plateau in western China, where the flora comprises primarily grasses. Although the geomorphic properties (e.g., elevation and morphology) of wetlands form the primary criteria of classification, this system also takes hydrological processes into implicit consideration. It represents an improvement over the hydrogeomorphic perspective as the relative importance of the two components (wetness and landform) of wetlands is clearly differentiated. This geomorphic-centered perspective yields insights into the hydrogeomorphic dynamics of plateau wetlands while indicates their vulnerability to change and degradation indirectly. According to this geomorphic-centered perspective, all plateau wetlands fall into one of the seven types of alpine, piedmont, valley, terrace, floodplain, lacustrine, and riverine in three elevational categories of upland, midland, and lowland. Upland (alpine and piedmont) wetlands with the steepest topography are the most sensitive to change whereas midland (floodplain, terrace and valley) wetlands are less vulnerable to degradation owing to a high water reserve except terrace wetlands. They have a dry surface caused by infrequent hydrological replenishment owing to their higher elevation than the channel. Low lying (lacustrine and riverine) wetlands are the most resilient. The geomorphic-centered perspective developed in this paper provides a framework for improving recognition and management of wetlands on the Plateau. Resilient wetlands can be grazed more intensively without the risk of degradation. Fragile and vulnerable wetlands require careful managementto avoid degradation.展开更多
A planation hypothesis is proposed to explain landform evolution of the Tibet Plateau. A denudation threshold (T), the maximum potential denudation rate for a certain type of rock, is introduced to explain the combi...A planation hypothesis is proposed to explain landform evolution of the Tibet Plateau. A denudation threshold (T), the maximum potential denudation rate for a certain type of rock, is introduced to explain the combined effects of lithology and tectonics on landform evolution. If the tectonic uplifting rate (U) is equal to or less than the threshold rate (U ≤ T), the tectonic uplifting and terrain denudation are in dynamic equilibrium, and landforms are in a steady state. The end product should be planation surfaces whether the original landforms are flat plains or deeply dissected mountains. If U 〉 T, uplift and denudation are not able to reach a dynamic equilibrium state. The plateau surface is mostly underlain by soft rocks, such as the Mesozoic epimetamorphic argillites and Tertiary sedimentary rocks, while the mountain ranges comprise hard rocks, such as granite, gneiss and limestone. In soft rock regions, hills are low with a relative relief of mostly less than 100 m and the slopes are gentle at a gradient of 〈200. In contrast, hills can maintain steep slopes in hard rock regions. The Tibet Plateau has been under an equilibrium condition between tectonic uplifting and denudation except for the mountain ranges. The plateau might have reached the present altitudes before the Quaternary.展开更多
The geomorphic evolution of northwestern China during the Cenozoic has been a subject of much geological interest because of its link with the uplift of the Himalayan-Tibetan complex.Much information about these chang...The geomorphic evolution of northwestern China during the Cenozoic has been a subject of much geological interest because of its link with the uplift of the Himalayan-Tibetan complex.Much information about these changes is recoverable from the sedimentary sequences of the region.We report here on the thick eolian deposits mantling the Huajialing Mountains,a relatively flat mountain range in the western Loess Plateau.Correlation of magnetic susceptibility stratigraphy with the QA-I Miocene eolian sequence dates a 134.7 m section(NL-VII) for the interval from 18.7 to 11.8 Ma,as confirmed by micro-mammalian fossils.These eolian deposits demonstrate a much wider distribution of the Miocene eolian deposits,and also indicate that the topography contrasts in the western Loess Plateau,including the uplifts of the Huajialing Mountains and the bedrock highlands in the Qinan region,were formed by the early Miocene.The near-continuous Miocene eolian sequence from 18.7 to 11.8 Ma indicates that the substratum of Huajialing had not experienced any intense tectonic changes during this time interval,which suggests further,the relative tectonic stability of the nearby Tibetan Plateau.展开更多
The Tibetan Plateau is a large-scale tectonic geomorphologic unit formed by the interactions of plates.It has been commonly believed that convective removal of the thickened Tibetan lithosphere,or lateral flow of the ...The Tibetan Plateau is a large-scale tectonic geomorphologic unit formed by the interactions of plates.It has been commonly believed that convective removal of the thickened Tibetan lithosphere,or lateral flow of the lower crust beneath the Tibetan plateau plays a crucial role in the formation of the large-scale tectonic geomorphologic features.Recent geological and geo-physical observations have provided important evidence in support of the lower crustal channel flow model.However,it re-mains unclear as how the geometry of lower crustal channel and the lateral variation of crustal rheology within the lower crust channel may have affected spatio-temporal evolution of the tectonic geomorphologic unit of the Tibetan Plateau.Here,we use numerical methods to explore the mechanical relations between the lower crustal channel flow and the tectonic geomorpho-logic formation around the eastern Tibetan plateau,by deriving a series of governing equations from fluid mechanics theory.From numerous tests,our results show that the viscosity of the channeled lower crust is about(1-5)×1018 to(1-4)×1020 Pa s(Pa.s) beneath the margin of the eastern Tibetan Plateau,and increases to about 1022 Pa s beneath the Sichuan Basin and the southern region of Yunnan Province.Numerical tests also indicate that if channel flows of the lower crust exist,the horizontal propagation and the vertical uplifting rate of the eastern Tibetan Plateau margin could be accelerated with the time.Thus,the present results could be useful to constrain the rheological structure of the crust beneath the eastern Tibetan plateau,and to understand the possible mechanics of rapid uplift of the eastern Tibetan Plateau margin,especially since its occurrence at 8Ma as revealed by numerous geological observations.展开更多
The influence of pre-quaternary underlying terrain on the formation of loess landforms, i.e., the geomorphological inheritance issue, is a focus in studies of loess landforms. On the basis of multi-source information,...The influence of pre-quaternary underlying terrain on the formation of loess landforms, i.e., the geomorphological inheritance issue, is a focus in studies of loess landforms. On the basis of multi-source information, we used GIS spatial analysis methods to construct a simulated digital elevation model of a pre-quaternary paleotopographic surface in a severe soil erosion area of the Loess Plateau. To reveal the spatial relationship between underlying paleotopography and modern terrain, an XY scatter diagram, hypsometric curve, gradient and concavity of terrain profiles are used in the experiments. The experiments show that the altitude, gradient and concavity results have significant linear positive correlation between both terrains, which shows a relatively strong landform inheritance relationship, particularly in the intact and complete loess deposit areas. Despite the current surface appearing somewhat changed from the original shape of the underlying terrain under different erosion forces, we reveal that the modern terrain generally smoothes the topographic relief of underlying terrain in the loess deposition process. Our results deepen understanding of the characteristics of geomorphological inheritance in the formation and evolution of loess landforms.展开更多
Kongur Mountain is the largest center of modern glaciation on the Pamir Plateau.During the glacial-interglacial cycles of the Quaternary,Kongur Mountain was extensively and repeatedly glaciated,and the glacial landfor...Kongur Mountain is the largest center of modern glaciation on the Pamir Plateau.During the glacial-interglacial cycles of the Quaternary,Kongur Mountain was extensively and repeatedly glaciated,and the glacial landforms from multiple glaciations are well-preserved in valleys,in basins,and on the piedmonts.Dating samples have been collected according to the distribution and weathering of the glacial tills,the relationship among the glacial deposits,and the loess or soil developed on the moraines. Electron spin resonance(ESR) dating of the samples was done using the germanium(Ge) centers in the glacial quartz grains,which are sensitive to both sunlight and grinding.The ages of the glacial deposits can be divided into four clusters,i.e.,13.1±0.8-27.0±2.2,36.4±3.3-48.7±5.7,65.6±6.8-86.6±8.9,and 105.6±9.4-178.3±17.8 ka.Six glacial advances in this region have been confirmed,which are equivalent in age to the Little Ice Age(LIA) ,Neoglaciation,marine oxygen isotope stages(MIS) 2,mid-MIS3,MIS4,and MIS6.The largest local last glacial maximum(LGML) occurred during MIS4 rather than the global Last Glacial Maximum(LGMG) of MIS2,and a glacial advance that occurred during mid-MIS3 was also larger than the LGMG.Furthermore,deeply weathered tills below 3500 m a.s.l.on the western slope of Kongur Mountain,when compared with the ages of the oldest glaciation of the Muztag Ata region,likely occurred prior to the penultimate glacial cycle.The glacial landforms prior to the penultimate glacial cycle on the northern slope are not well-preserved due to erosion after deposition. Several glacial deposits are only speculated to be distributed at higher elevations on the southwest side of the Gaizi Checkpoint. The extensive hummocky moraines on the western slope were formed by multiple glacial advances,and the latest glacial advance corresponded to mid-MIS3.展开更多
基金Under the auspices of National Natural Science Foundation of China (No.50879033,41001116)Specialized Research Fund for the Doctoral Program of Higher Education (No.20090211110025)Fundamental Research Funds for the Central Universities (No.lzujbky-2010-221)
文摘The Badain Jaran Desert,located in the Alxa Plateau,Northwest China,features mega-dunes and a unique dune-lake alternation landscape.This paper presented the aeolian sediment structures of three representative dunes in the Badain Jaran Desert using ground-penetrating radar (GPR).We processed and analyzed the GPR data and investigated the feasibility of using integrated GPR and sedimentological data to reconstruct dunes structure,sedimentary environment and geomorphological evolution.The results show that the internal structures of star dune and transverse dune represent various stages of mega-dune evolution: the main deposition processes of mega-dune are similar to those of transverse dunes but have a more complicated mechanism of sand transport and deposition because of the superimposition of dunes;the upper section of the mega-dune has a structure similar to that of star dune,with vertical aggradations on top.Diffraction hyperbolae in the GPR profile indicates that the presence of ancient dunes characterized by calcareous cementation layers is involved in the maintenance of mega-dunes,and water levels,shown by continuous,sub-horizontal GPR reflections,are supposed to be closely related to mega-dunes and the interdune lakes.Outcrop of wet sand and horizontal stratifications on the GPR image indicate moisture potentials with different levels inside mega-dunes.The multiplex geomorphology in the Badain Jaran Desert is the result of global climatic undulation,the unique geographical location,the geological structural features,etc.
基金supported by the strategic plan project of science and technology of Institute of Geographic Sciences and Natural Resources Research (Grant No. 2012ZD009)the National Science Technology Support Plan Project (Grant No. 2012BAH28B01-03)+1 种基金the National Natural Science Foundation of China (Grant No. 41171332)the National Science Technology Basic Special Project (Grant No.2011FY110400-2)
文摘Based on geomorphologic and digital elevation model(DEM) data, the topographic characteristics of the northwestern edge of the Qinghai-Tibet Plateau are analyzed. Five representative peaks are first determined according to the topographic profile maps for the ridge and piedmont lines, and then the topographic gradient characteristics are analyzed according to the representative topographic profile acquisition method.Based on the geomorphologic database data, the regions between the ridge and the piedmont lines are divided into four geomorphologic zones; and the topographic characteristics are finally analyzed for the different geomorphologic zones regions using the DEM data. The research results show that from the piedmont to the ridge, there exist four geomorphologic zones: arid, fluvial, periglacial and glacial. The arid has the lowest elevation, topographic gradient, relief and slope characteristics. The fluvial has lower elevation and the highest topographic gradient, but with lower relief and slope characteristics. With higher elevation, the periglcial has lower topographic gradient, but the highest relief and slope characteristics. The glacial has the highest elevation with higher topographic gradient, relief and slope characteristics.
基金Under the auspices of National Natural Science Foundation of China(No.41101080,41171047)Natural Science Foundation of Shandong Province(No.ZR2014DQ028)
文摘Spatial variation of dissolved organic carbon(DOC) in soils of riparian wetlands and responses to hydro-geomorphologic changes in the Sanjiang Plain were analyzed through in situ collecting soil samples in the Naoli River and the Bielahong River. The results showed that the average contents of DOC for soil layer of 0–100 cm were 730.6 mg/kg, 250.9 mg/kg, 423.0 mg/kg and 333.1 mg/kg respectively from riverbed to river terrace along the transverse directions of the Naoli watershed. The content of the soil DOC was the highest in the riverbed, lower in the high floodplain and much lower in the river terrace, and it was the lowest in the low floodplain. The difference in the content and vertical distribution of DOC between the riverbed and the three riparian wetlands was significant, while it was not significant among the low floodplain, the high floodplain and the river terrace. The variability of soil DOC was related to the hydrological connectivity between different landscape position of the riparian wetlands and the adjacent stream. Extremely significant correlations were observed between DOC and total organic carbon(TOC), total iron(TFe), ferrous iron(Fe(II)) whose correlation coefficients were 0.819, –0.544 and –0.709 in riparian wetlands of the Naoli River. With the increase of wetland destruction, soil p H increased and soil DOC content changed. The correlation coefficients between soil DOC and TOC, TFe, Fe(II) also changed into 0.759, –0.686 and –0.575 respectively in the Bielahong River. Under the impact of drainage ditches, the correlations between soil DOC and TFe, Fe(II) were not obvious, while the soil p H was weakly alkaline and was negatively correlated with soil DOC in the previous high floodplain. It indicates that riparian hydro-geomorphology is the main factor that could well explain this spatial variability of soil DOC, and the agricultural environmental hydraulic works like ditching also must be considered.
基金supported by Program of International S&T Cooperation,the Ministry of Science and Technology of the People's Republic of China(Grant No.2011DFA20820)International Science&Technology Cooperation Program of China,MOST(Grant No.2011DFG93160)+1 种基金the Qinghai Science and Technology Department(Grant No.2009-J-806)Department of International Exchange&Cooperation of the Ministry of Education(Grant Nos.2009-1599,2010-1595)
文摘In this paper a geomorphic-centered system was proposed for classifying the wetlands on the Qinghai-Tibet Plateau in western China, where the flora comprises primarily grasses. Although the geomorphic properties (e.g., elevation and morphology) of wetlands form the primary criteria of classification, this system also takes hydrological processes into implicit consideration. It represents an improvement over the hydrogeomorphic perspective as the relative importance of the two components (wetness and landform) of wetlands is clearly differentiated. This geomorphic-centered perspective yields insights into the hydrogeomorphic dynamics of plateau wetlands while indicates their vulnerability to change and degradation indirectly. According to this geomorphic-centered perspective, all plateau wetlands fall into one of the seven types of alpine, piedmont, valley, terrace, floodplain, lacustrine, and riverine in three elevational categories of upland, midland, and lowland. Upland (alpine and piedmont) wetlands with the steepest topography are the most sensitive to change whereas midland (floodplain, terrace and valley) wetlands are less vulnerable to degradation owing to a high water reserve except terrace wetlands. They have a dry surface caused by infrequent hydrological replenishment owing to their higher elevation than the channel. Low lying (lacustrine and riverine) wetlands are the most resilient. The geomorphic-centered perspective developed in this paper provides a framework for improving recognition and management of wetlands on the Plateau. Resilient wetlands can be grazed more intensively without the risk of degradation. Fragile and vulnerable wetlands require careful managementto avoid degradation.
基金supported by the National Natural Sciences Foundation of China(Grant Nos.40599421 and 90502002)
文摘A planation hypothesis is proposed to explain landform evolution of the Tibet Plateau. A denudation threshold (T), the maximum potential denudation rate for a certain type of rock, is introduced to explain the combined effects of lithology and tectonics on landform evolution. If the tectonic uplifting rate (U) is equal to or less than the threshold rate (U ≤ T), the tectonic uplifting and terrain denudation are in dynamic equilibrium, and landforms are in a steady state. The end product should be planation surfaces whether the original landforms are flat plains or deeply dissected mountains. If U 〉 T, uplift and denudation are not able to reach a dynamic equilibrium state. The plateau surface is mostly underlain by soft rocks, such as the Mesozoic epimetamorphic argillites and Tertiary sedimentary rocks, while the mountain ranges comprise hard rocks, such as granite, gneiss and limestone. In soft rock regions, hills are low with a relative relief of mostly less than 100 m and the slopes are gentle at a gradient of 〈200. In contrast, hills can maintain steep slopes in hard rock regions. The Tibet Plateau has been under an equilibrium condition between tectonic uplifting and denudation except for the mountain ranges. The plateau might have reached the present altitudes before the Quaternary.
基金supported by National Natural Science Foundation of China (Grant No. 40730104)Chinese Academy of Sciences (Grant Nos. KZCX2-YW-Q1-15 and KZCX2-YW-117)
文摘The geomorphic evolution of northwestern China during the Cenozoic has been a subject of much geological interest because of its link with the uplift of the Himalayan-Tibetan complex.Much information about these changes is recoverable from the sedimentary sequences of the region.We report here on the thick eolian deposits mantling the Huajialing Mountains,a relatively flat mountain range in the western Loess Plateau.Correlation of magnetic susceptibility stratigraphy with the QA-I Miocene eolian sequence dates a 134.7 m section(NL-VII) for the interval from 18.7 to 11.8 Ma,as confirmed by micro-mammalian fossils.These eolian deposits demonstrate a much wider distribution of the Miocene eolian deposits,and also indicate that the topography contrasts in the western Loess Plateau,including the uplifts of the Huajialing Mountains and the bedrock highlands in the Qinan region,were formed by the early Miocene.The near-continuous Miocene eolian sequence from 18.7 to 11.8 Ma indicates that the substratum of Huajialing had not experienced any intense tectonic changes during this time interval,which suggests further,the relative tectonic stability of the nearby Tibetan Plateau.
基金This work was supported by Knowledge Innovation Program of the Chi-nese Academy of Sciences (Grant No.KZCX2-YW-134)National Nat-ural Science Foundation of China (Grant No.41030320)
文摘The Tibetan Plateau is a large-scale tectonic geomorphologic unit formed by the interactions of plates.It has been commonly believed that convective removal of the thickened Tibetan lithosphere,or lateral flow of the lower crust beneath the Tibetan plateau plays a crucial role in the formation of the large-scale tectonic geomorphologic features.Recent geological and geo-physical observations have provided important evidence in support of the lower crustal channel flow model.However,it re-mains unclear as how the geometry of lower crustal channel and the lateral variation of crustal rheology within the lower crust channel may have affected spatio-temporal evolution of the tectonic geomorphologic unit of the Tibetan Plateau.Here,we use numerical methods to explore the mechanical relations between the lower crustal channel flow and the tectonic geomorpho-logic formation around the eastern Tibetan plateau,by deriving a series of governing equations from fluid mechanics theory.From numerous tests,our results show that the viscosity of the channeled lower crust is about(1-5)×1018 to(1-4)×1020 Pa s(Pa.s) beneath the margin of the eastern Tibetan Plateau,and increases to about 1022 Pa s beneath the Sichuan Basin and the southern region of Yunnan Province.Numerical tests also indicate that if channel flows of the lower crust exist,the horizontal propagation and the vertical uplifting rate of the eastern Tibetan Plateau margin could be accelerated with the time.Thus,the present results could be useful to constrain the rheological structure of the crust beneath the eastern Tibetan plateau,and to understand the possible mechanics of rapid uplift of the eastern Tibetan Plateau margin,especially since its occurrence at 8Ma as revealed by numerous geological observations.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40930531, 41171320)the National High Technology Research and Development Program of China (Grant No. 2011AA120303)Open Foundation of State Key Laboratory of Resources and Environmental Information System (Grant No. 2010KF0002SA)
文摘The influence of pre-quaternary underlying terrain on the formation of loess landforms, i.e., the geomorphological inheritance issue, is a focus in studies of loess landforms. On the basis of multi-source information, we used GIS spatial analysis methods to construct a simulated digital elevation model of a pre-quaternary paleotopographic surface in a severe soil erosion area of the Loess Plateau. To reveal the spatial relationship between underlying paleotopography and modern terrain, an XY scatter diagram, hypsometric curve, gradient and concavity of terrain profiles are used in the experiments. The experiments show that the altitude, gradient and concavity results have significant linear positive correlation between both terrains, which shows a relatively strong landform inheritance relationship, particularly in the intact and complete loess deposit areas. Despite the current surface appearing somewhat changed from the original shape of the underlying terrain under different erosion forces, we reveal that the modern terrain generally smoothes the topographic relief of underlying terrain in the loess deposition process. Our results deepen understanding of the characteristics of geomorphological inheritance in the formation and evolution of loess landforms.
基金supported by National Natural Science Foundation of China(Grant No.40771049)Knowledge Innovation Project of Chinese Academy of Sciences(Grant No.KZCX2-YW-GJ04)the Program of Ministry of Science and Technology of China(Grant No. 2006FY110200)
文摘Kongur Mountain is the largest center of modern glaciation on the Pamir Plateau.During the glacial-interglacial cycles of the Quaternary,Kongur Mountain was extensively and repeatedly glaciated,and the glacial landforms from multiple glaciations are well-preserved in valleys,in basins,and on the piedmonts.Dating samples have been collected according to the distribution and weathering of the glacial tills,the relationship among the glacial deposits,and the loess or soil developed on the moraines. Electron spin resonance(ESR) dating of the samples was done using the germanium(Ge) centers in the glacial quartz grains,which are sensitive to both sunlight and grinding.The ages of the glacial deposits can be divided into four clusters,i.e.,13.1±0.8-27.0±2.2,36.4±3.3-48.7±5.7,65.6±6.8-86.6±8.9,and 105.6±9.4-178.3±17.8 ka.Six glacial advances in this region have been confirmed,which are equivalent in age to the Little Ice Age(LIA) ,Neoglaciation,marine oxygen isotope stages(MIS) 2,mid-MIS3,MIS4,and MIS6.The largest local last glacial maximum(LGML) occurred during MIS4 rather than the global Last Glacial Maximum(LGMG) of MIS2,and a glacial advance that occurred during mid-MIS3 was also larger than the LGMG.Furthermore,deeply weathered tills below 3500 m a.s.l.on the western slope of Kongur Mountain,when compared with the ages of the oldest glaciation of the Muztag Ata region,likely occurred prior to the penultimate glacial cycle.The glacial landforms prior to the penultimate glacial cycle on the northern slope are not well-preserved due to erosion after deposition. Several glacial deposits are only speculated to be distributed at higher elevations on the southwest side of the Gaizi Checkpoint. The extensive hummocky moraines on the western slope were formed by multiple glacial advances,and the latest glacial advance corresponded to mid-MIS3.