Topographic shielding(TS) is an important factor in cosmogenic nuclide surface exposure dating. The development of geographic information systems(GIS) and the availability of digital elevation models(DEMs) make it pos...Topographic shielding(TS) is an important factor in cosmogenic nuclide surface exposure dating. The development of geographic information systems(GIS) and the availability of digital elevation models(DEMs) make it possible to derive this factor directly from a DEM. Most available GIS models derive the TS factors for an area(all cells in a DEM) without the consideration of surface conditions of individual sites, such as the strike, dip,and height above ground, into the calculation. This paper presents a new GIS model to derive the TS factors for discrete sample sites. This model uses the Skyline and Skyline Graph functions in ArcGIS to extract the set of azimuth and elevation angles of topographic obstructions around each site from a DEM(considering the sample height above ground)and then incorporates the strike and dip information of the sample surface to derive the TS factor. All processing tools and steps are streamlined in ArcGIS modelbuilder and this model can be run like a standard ArcGIS geoprocessing tool. It provides an easy and user-friendly means to derive the TS factors for discrete samples based on a DEM and the measured strike, dip and sample height for each site.展开更多
The glacial landforms of the Qinghai-Tibetan Plateau (QTP) provide a unique opportunity to research hemispheric and global environmental changes. In this study, we focus on the glacial history of the palaeo-Daocheng...The glacial landforms of the Qinghai-Tibetan Plateau (QTP) provide a unique opportunity to research hemispheric and global environmental changes. In this study, we focus on the glacial history of the palaeo-Daocheng Ice Cap (p-DIC) in the southeastern QTP during the last glacial cycle. Based on field investigations, morphostratigraphy, and surface exposure dating of roche moutonnée, polished surface and moraine debris through the terrestrial cosmogenic nuclides (TCN) ^10Be and ^26Al. We identify glacial deposits of the last deglaciation, with minimum ages of 14.9±1.3-18.7±1.7 ka, the Last Glacial Maximum (LGM) of 24.7±2.2 ka, and the early part of the last glacial period (marine oxygen isotope stage (MIS) 3) of 37.1±3.4-45.2±3.9 ka. Our results show that in this region, the extent of the glacial advance during MIS 3 was larger than that during the traditional LGM (MIS 2). These ages are consistent with prior chronologies, and the ^10Be age is consistent with the ^26Al age for the same sample. Thus, these data provide reliable constraints on climate change in the QTP, during the last glaciation.展开更多
Intrinsic radiation of materials is one of the major backgrounds for many rare-event search experiments.Thus,the production of pure materials in an underground laboratory is a promising approach for eliminating cosmog...Intrinsic radiation of materials is one of the major backgrounds for many rare-event search experiments.Thus,the production of pure materials in an underground laboratory is a promising approach for eliminating cosmogenic radionuclides.In this paper,we demonstrate a procedure to evaluate the yields of cosmogenic radionuclides in copper and germanium in the second phase of the China Jinping Underground Laboratory.Our results show that for copper and germanium materials,the largest cosmogenic background comes from 3 H and57,58,60Co,and 3 H and 68Ge,respectively,which all have yields on the order of 10-7 kg-1 day-1.The corresponding radioactivities after 90 days pf exposure underground are estimated to be lower than 10-6μBq kg-1.展开更多
Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates.Traditionally,this parameter is measured in the field and uncertainty ...Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates.Traditionally,this parameter is measured in the field and uncertainty and/or inconsistency may exist among different investigators.This paper provides an ArcGIS python code to determine topographic shielding factors using digital elevation models(DEMs).This code can be imported into ArcGIS as a geoprocessing tool with a user-friendly graphical interface.The DEM-derived parameters using this method were validated with field measurements in central Tian Shan.Results indicate that DEM-derived shielding factors are consistent with field-measured values.It provides a valuable tool to save fieldwork efforts and has the potential to provide consistent results for different regions in the world to facilitate the comparison of cosmogenic nuclide results.展开更多
Cosmogenic Ne isotopes are stable and are routinely used for constraining the timing of events and the rate of surface change beyond the limit that can be studied with radionuclides ^(10)Be,^(26)Al, and ^(36)Cl. Cosmo...Cosmogenic Ne isotopes are stable and are routinely used for constraining the timing of events and the rate of surface change beyond the limit that can be studied with radionuclides ^(10)Be,^(26)Al, and ^(36)Cl. Cosmogenic Ne analysis can be used in quartz and in a range of other minerals. Analysis typically requires significantly less material than do cosmogenic ^(10)Be and^(26)Al, opening up the technique for small samples—individual pebbles in river sediments, for example. Analysis is easier and faster than for radionuclides, not least because Ne measurements do not require significant chemical procedures. However, the presence of other sources of Ne in minerals tends to restrict the use of cosmogenic ^(21)Ne to old landscapes and long exposure durations. In this review we briefly outline the background of cosmogenic Ne production in rocks and minerals at the Earth's surface, then document the key uses of the technique by highlighting some earlier studies, and finish with a short perspective on the future of the technique.展开更多
Objective Structural lows and major rift systems provide the basis for the creation of large rivers.The uplift of the Qinling and Daba Mountains structural belts and Tibetan Plateau would have provided the basis for t...Objective Structural lows and major rift systems provide the basis for the creation of large rivers.The uplift of the Qinling and Daba Mountains structural belts and Tibetan Plateau would have provided the basis for the origin and northwest–southeast flow of the ancient Hanjiang River(Lu et al.,2018).After a long-term evolution,the present pattern of Hanjiang River has been formed.Five to six river terraces in the Hanzhong and Yunxian basins along the flanks of Hanjiang River valleys had been identified and some terraces had been dated by using optically stimulated luminescence(OSL),paleomagnetic,and electron spin resonance(ESR)dating methods,and correlating the pedostratigraphy and magnetic susceptibility with the Luochuan loess section by our team(Sun et al.,2016,2017).These terraces are composed of fluvial deposits overlaid with eolian deposits,and record the evolution history of the Hanjiang River.(Fig.1).This study is aimed to deduce the birth time of the present Hanjiang River by using 26Al/10Be burial dating method to date the highest fluvial terraces of the Hanjiang River.展开更多
Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault(LSPF),one of the most active faults in the Hetao fault zone in Inner Mongolia,N...Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault(LSPF),one of the most active faults in the Hetao fault zone in Inner Mongolia,North China.The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history.Using cosmogenic (10)~Be exposure dating,we measured the exposure ages of the western Langshankou scarp,located in the middle segment of the LSPF.Our data revealed at least two earthquakes that occurred at 22.2±3.3 ka and 7.2±2.4 ka,respectively.These events are consistent with previous paleoseismic trench studies.The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 +0.05/-0.06 mm/yr,which issignificantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr,as estimated from the offset of the T_2 terraces by previous studies.This indicates that the slip of the LSPF may have been accommodated by other fault branches.展开更多
Objective The Qinling Mountains (QM) in Central China is a natural harrier that corresponds to the boundary between the southern and northern climate and environment (Gong Hujun et al., 2017). Northern QM is rela...Objective The Qinling Mountains (QM) in Central China is a natural harrier that corresponds to the boundary between the southern and northern climate and environment (Gong Hujun et al., 2017). Northern QM is relatively steep, and southern QM is in contrast relatively low and gentle. Investigations have shown that the average uplift rate of northern QM since 17.8 Ma is approximately 0.19 mm/a (Yin Gongming et al., 2001), whereas that of central QM since 0.36 Ma is approximately 0.32 mm/a (Wang Fei et al., 2004). To date, however, few investigations have yet been conducted on the uplift rate of southern QM. Accordingly, we aim to obtain the uplift rate of southern QM by using the cosmogenic ^26A1/^10 Be burial dating method to determine the age of the highest river terrace on the southern slope of QM.展开更多
Tibet is the largest and highest plateau on the Earth (having 82% of the world’s land surface area falling >4km above sea level) attributed to the India and Asian convergence tectonics. Recently, high\|resolution ...Tibet is the largest and highest plateau on the Earth (having 82% of the world’s land surface area falling >4km above sea level) attributed to the India and Asian convergence tectonics. Recently, high\|resolution digital topography data (Fielding et al., 1994) confirmed the earlier observations about flat erosional surfaces in the central part of the plateau (Jujin, et al., 1995) and suggested extraordinary flatness at a wide range of scales. Much of the Tibetan plateau across different accreted terranes has shallow slopes between 5°~10° and variation in relief of about 1 km, except in its marginal parts (Himalayan ranges; Kunlun mountains) where rough and high topography with intense fluvial dissections (variations in relief up to 7km) is quite frequent. However, in the southern and south\|central part of the plateau along the Pliocene\|Quaternary grabens, slopes generally steepen.展开更多
Quantitative glacial chronologies of past glaciations are sparse in the Himalaya, and mostly absent in the Kashmir Himalaya. We used cosmogenicBe exposure dating, and geomorphological mapping to reconstruct glacial ad...Quantitative glacial chronologies of past glaciations are sparse in the Himalaya, and mostly absent in the Kashmir Himalaya. We used cosmogenicBe exposure dating, and geomorphological mapping to reconstruct glacial advances of the Thajwas Glacier(TG) in the Great Himalayan Range of the Kashmir Himalaya. FromBe exposure dating of ten moraine boulders, four glacial stages with ages ~20.77 ±2.28 ka, ~11.46 ± 1.69 ka, ~9.12 ± 1.39 ka and ~4.19 ± 0.78 ka, were identified. The reconstructed cosmogenic radionuclide ages confirmed the global Last Glacial Maximum(g LGM), Younger Dryas, Early Holocene, and Neoglaciation episodes. As per area and volume change analyses, the TG has lost 51.1 km~2 of its area and a volume of 2.64 km~3 during the last 20.77 ± 2.28 ka. Overall, the results suggested that the TG has lost 64% of area and 73% of volume from the Last glacial maximum to Neoglaciation and about 85.74% and 87.67% of area and volume, respectively, from Neoglaciation to the present day. The equilibrium line altitude of the TG fluctuated from 4238 m a.s.l present to3365 m a.s.l during the g LGM(20.77 ± 2.28 ka). The significant cooling induced by a drop in mean ambient temperature resulted in a positive mass balance of the TG during the g LGM. Subsequently the melting accelerated due to the continuing rise of the global ambient temperature. Paleo-glacial history reconstruction of the Kashmir Himalaya, with its specific geomorphic and climatic setting, would help close the information gap about the chronology of past regional glacial episodes.展开更多
The Hengduan Mountains is in the transitional zone between the Qinghai-Tibet Plateau(QTP)and the YunnanGuizhou Plateau in China,and a key area for elucidating the Quaternary environmental changes in Asia.The paleo-Dao...The Hengduan Mountains is in the transitional zone between the Qinghai-Tibet Plateau(QTP)and the YunnanGuizhou Plateau in China,and a key area for elucidating the Quaternary environmental changes in Asia.The paleo-Daocheng ice cap was located on the Shaluli Hilly Plateau in the northeastern Hengduan Mountains,the oldest moraines in the Hengduan Mountains region were found in the ice cap area.Such glacial landforms provide key evidence to study the timing when this area entered the cryosphere with the uplift of the QTP.However,it is difficult to collect suitable glacial boulders from these moraines for traditional terrestrial in-situ cosmogenic nuclide(TCN)exposure dating because of long-term severe moraine degradation.Here,we collected clast samples from the moraine surface and depth profile to constrain the age of the oldest moraine in Kuzhaori(moraine E)using TCN^(10)Be dating technique.The minimum^(10)Be ages of five clast samples from the moraine surface range from 187.4±1.5 to 576.8±4.3 ka,implying that the moraine has been seriously degraded since deposition.Based on the TCN^(10)Be concentrations of the samples from a depth profile and simulations,the exposure-erosion-inheritance history of the profile was obtained.By fitting to the profile^(10)Be concentrations using the chi-square test,the simulations yielded a reliable age of 626.0±52.5 ka for the moraine.Therefore,the oldest moraine(moraine E)in Kuzhaori was most likely formed at about 0.63Ma ago,corresponding to the marine isotope stage(MIS)16.This glaciation represents the maximum Quaternary glaciation after the QTP was elevated into the cryosphere by the Kunlun-Yellow River Tectonic Movement.展开更多
An expeditionary study of the area of the alleged impact event that occurred on 3.08.1993 in the area of the Lower Konkuli River(southeast of the Aldan Highlands,Lurikan Range,Russia)was carried out.According to the m...An expeditionary study of the area of the alleged impact event that occurred on 3.08.1993 in the area of the Lower Konkuli River(southeast of the Aldan Highlands,Lurikan Range,Russia)was carried out.According to the materials of remote sensing,the places of collision with the earth of a cosmic body are determined.In the area of the impact of the shock wave on the Earth’s surface,peat samples were selected,the micro probe analysis of which showed the presence of a cosmogenic substance in concentrations 6-8 times higher than the background.Silicate and magnetite micro spheres,native iron,moissanite,and carbon micro tubes coated with a film consisting of pure nickel were found.Of particular interest were the findings of specific Ni film micro structures that allow us to make an assumption about the cometary nature of the Uchur cosmic body.Most researchers associate the observed flights of fireballs with the subsequent fall of meteorites.Researchers are trying to find the massive body of the fallen space body.However,often,even after many years of searching,a massive cosmic body cannot be found.This happened when studying the site of the fall of the Tunguska cosmic body.In this case,it remains to be assumed that the cosmic body contained microscopic dust particles.The structure and composition of such particles can only be studied using microscopic research methods.When studying the Uchur cosmic body,the authors concluded that it could be of a cometary nature due to the findings of specific particles-thin films of pure nickel on the surface of plant remains of terrestrial origin.This hypothesis arose from the recent discovery of atomic nickel vapors in comets.展开更多
基金support by the National Science Foundation of the United States(Grant No.BCS-1227018)the National Nature Science Foundation of China(Grant No.41328001)
文摘Topographic shielding(TS) is an important factor in cosmogenic nuclide surface exposure dating. The development of geographic information systems(GIS) and the availability of digital elevation models(DEMs) make it possible to derive this factor directly from a DEM. Most available GIS models derive the TS factors for an area(all cells in a DEM) without the consideration of surface conditions of individual sites, such as the strike, dip,and height above ground, into the calculation. This paper presents a new GIS model to derive the TS factors for discrete sample sites. This model uses the Skyline and Skyline Graph functions in ArcGIS to extract the set of azimuth and elevation angles of topographic obstructions around each site from a DEM(considering the sample height above ground)and then incorporates the strike and dip information of the sample surface to derive the TS factor. All processing tools and steps are streamlined in ArcGIS modelbuilder and this model can be run like a standard ArcGIS geoprocessing tool. It provides an easy and user-friendly means to derive the TS factors for discrete samples based on a DEM and the measured strike, dip and sample height for each site.
基金supported by the National Natural Science Foundation of China (Grant No.40572097)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) (Grant No.164320H116)by the Yulong Mountain tourism development and management committee special project
文摘The glacial landforms of the Qinghai-Tibetan Plateau (QTP) provide a unique opportunity to research hemispheric and global environmental changes. In this study, we focus on the glacial history of the palaeo-Daocheng Ice Cap (p-DIC) in the southeastern QTP during the last glacial cycle. Based on field investigations, morphostratigraphy, and surface exposure dating of roche moutonnée, polished surface and moraine debris through the terrestrial cosmogenic nuclides (TCN) ^10Be and ^26Al. We identify glacial deposits of the last deglaciation, with minimum ages of 14.9±1.3-18.7±1.7 ka, the Last Glacial Maximum (LGM) of 24.7±2.2 ka, and the early part of the last glacial period (marine oxygen isotope stage (MIS) 3) of 37.1±3.4-45.2±3.9 ka. Our results show that in this region, the extent of the glacial advance during MIS 3 was larger than that during the traditional LGM (MIS 2). These ages are consistent with prior chronologies, and the ^10Be age is consistent with the ^26Al age for the same sample. Thus, these data provide reliable constraints on climate change in the QTP, during the last glaciation.
基金supported by the National Natural Science Foundation of China(No.U1865205).
文摘Intrinsic radiation of materials is one of the major backgrounds for many rare-event search experiments.Thus,the production of pure materials in an underground laboratory is a promising approach for eliminating cosmogenic radionuclides.In this paper,we demonstrate a procedure to evaluate the yields of cosmogenic radionuclides in copper and germanium in the second phase of the China Jinping Underground Laboratory.Our results show that for copper and germanium materials,the largest cosmogenic background comes from 3 H and57,58,60Co,and 3 H and 68Ge,respectively,which all have yields on the order of 10-7 kg-1 day-1.The corresponding radioactivities after 90 days pf exposure underground are estimated to be lower than 10-6μBq kg-1.
基金supported by the Professional Development Award of the University of Tennessee
文摘Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates.Traditionally,this parameter is measured in the field and uncertainty and/or inconsistency may exist among different investigators.This paper provides an ArcGIS python code to determine topographic shielding factors using digital elevation models(DEMs).This code can be imported into ArcGIS as a geoprocessing tool with a user-friendly graphical interface.The DEM-derived parameters using this method were validated with field measurements in central Tian Shan.Results indicate that DEM-derived shielding factors are consistent with field-measured values.It provides a valuable tool to save fieldwork efforts and has the potential to provide consistent results for different regions in the world to facilitate the comparison of cosmogenic nuclide results.
基金supported by the basic scientific research fund, Institute of Geology, China Earthquake Administration (Grant Nos. IGCEA1504 and IGCEA1417)
文摘Cosmogenic Ne isotopes are stable and are routinely used for constraining the timing of events and the rate of surface change beyond the limit that can be studied with radionuclides ^(10)Be,^(26)Al, and ^(36)Cl. Cosmogenic Ne analysis can be used in quartz and in a range of other minerals. Analysis typically requires significantly less material than do cosmogenic ^(10)Be and^(26)Al, opening up the technique for small samples—individual pebbles in river sediments, for example. Analysis is easier and faster than for radionuclides, not least because Ne measurements do not require significant chemical procedures. However, the presence of other sources of Ne in minerals tends to restrict the use of cosmogenic ^(21)Ne to old landscapes and long exposure durations. In this review we briefly outline the background of cosmogenic Ne production in rocks and minerals at the Earth's surface, then document the key uses of the technique by highlighting some earlier studies, and finish with a short perspective on the future of the technique.
基金supported by the National Natural Science Foundation of China(Grant Nos.41572155,41690111).
文摘Objective Structural lows and major rift systems provide the basis for the creation of large rivers.The uplift of the Qinling and Daba Mountains structural belts and Tibetan Plateau would have provided the basis for the origin and northwest–southeast flow of the ancient Hanjiang River(Lu et al.,2018).After a long-term evolution,the present pattern of Hanjiang River has been formed.Five to six river terraces in the Hanzhong and Yunxian basins along the flanks of Hanjiang River valleys had been identified and some terraces had been dated by using optically stimulated luminescence(OSL),paleomagnetic,and electron spin resonance(ESR)dating methods,and correlating the pedostratigraphy and magnetic susceptibility with the Luochuan loess section by our team(Sun et al.,2016,2017).These terraces are composed of fluvial deposits overlaid with eolian deposits,and record the evolution history of the Hanjiang River.(Fig.1).This study is aimed to deduce the birth time of the present Hanjiang River by using 26Al/10Be burial dating method to date the highest fluvial terraces of the Hanjiang River.
基金supported by the National Natural Science Foundation of China (Grant No.41171001)the 1:50000 Active Fault Mapping of Langshan Piedmont Fault (Grant No.201408023)the Basic Research Business Foundation of the China Earthquake Administration (Grant No.ZDJ2012-02)
文摘Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault(LSPF),one of the most active faults in the Hetao fault zone in Inner Mongolia,North China.The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history.Using cosmogenic (10)~Be exposure dating,we measured the exposure ages of the western Langshankou scarp,located in the middle segment of the LSPF.Our data revealed at least two earthquakes that occurred at 22.2±3.3 ka and 7.2±2.4 ka,respectively.These events are consistent with previous paleoseismic trench studies.The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 +0.05/-0.06 mm/yr,which issignificantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr,as estimated from the offset of the T_2 terraces by previous studies.This indicates that the slip of the LSPF may have been accommodated by other fault branches.
基金supported by the National Natural Science Foundation of China(grants No.41572155 and 41690111)the Global Change Program of the Ministry of Science and Technology of China(grant No.2016YFA0600503)
文摘Objective The Qinling Mountains (QM) in Central China is a natural harrier that corresponds to the boundary between the southern and northern climate and environment (Gong Hujun et al., 2017). Northern QM is relatively steep, and southern QM is in contrast relatively low and gentle. Investigations have shown that the average uplift rate of northern QM since 17.8 Ma is approximately 0.19 mm/a (Yin Gongming et al., 2001), whereas that of central QM since 0.36 Ma is approximately 0.32 mm/a (Wang Fei et al., 2004). To date, however, few investigations have yet been conducted on the uplift rate of southern QM. Accordingly, we aim to obtain the uplift rate of southern QM by using the cosmogenic ^26A1/^10 Be burial dating method to determine the age of the highest river terrace on the southern slope of QM.
文摘Tibet is the largest and highest plateau on the Earth (having 82% of the world’s land surface area falling >4km above sea level) attributed to the India and Asian convergence tectonics. Recently, high\|resolution digital topography data (Fielding et al., 1994) confirmed the earlier observations about flat erosional surfaces in the central part of the plateau (Jujin, et al., 1995) and suggested extraordinary flatness at a wide range of scales. Much of the Tibetan plateau across different accreted terranes has shallow slopes between 5°~10° and variation in relief of about 1 km, except in its marginal parts (Himalayan ranges; Kunlun mountains) where rough and high topography with intense fluvial dissections (variations in relief up to 7km) is quite frequent. However, in the southern and south\|central part of the plateau along the Pliocene\|Quaternary grabens, slopes generally steepen.
基金conducted with the help of grants from the Department of Science and Technology (DST), Government of India under the sponsored research project titled “Centre of Excellence for Glacial Studies in Western Himalaya”granting fellowship to Omar Jaan Paul under the project No. UFR-59313。
文摘Quantitative glacial chronologies of past glaciations are sparse in the Himalaya, and mostly absent in the Kashmir Himalaya. We used cosmogenicBe exposure dating, and geomorphological mapping to reconstruct glacial advances of the Thajwas Glacier(TG) in the Great Himalayan Range of the Kashmir Himalaya. FromBe exposure dating of ten moraine boulders, four glacial stages with ages ~20.77 ±2.28 ka, ~11.46 ± 1.69 ka, ~9.12 ± 1.39 ka and ~4.19 ± 0.78 ka, were identified. The reconstructed cosmogenic radionuclide ages confirmed the global Last Glacial Maximum(g LGM), Younger Dryas, Early Holocene, and Neoglaciation episodes. As per area and volume change analyses, the TG has lost 51.1 km~2 of its area and a volume of 2.64 km~3 during the last 20.77 ± 2.28 ka. Overall, the results suggested that the TG has lost 64% of area and 73% of volume from the Last glacial maximum to Neoglaciation and about 85.74% and 87.67% of area and volume, respectively, from Neoglaciation to the present day. The equilibrium line altitude of the TG fluctuated from 4238 m a.s.l present to3365 m a.s.l during the g LGM(20.77 ± 2.28 ka). The significant cooling induced by a drop in mean ambient temperature resulted in a positive mass balance of the TG during the g LGM. Subsequently the melting accelerated due to the continuing rise of the global ambient temperature. Paleo-glacial history reconstruction of the Kashmir Himalaya, with its specific geomorphic and climatic setting, would help close the information gap about the chronology of past regional glacial episodes.
基金supported by the National Natural Science Foundation of China(Grant Nos.41971009&41503054)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA2000300)。
文摘The Hengduan Mountains is in the transitional zone between the Qinghai-Tibet Plateau(QTP)and the YunnanGuizhou Plateau in China,and a key area for elucidating the Quaternary environmental changes in Asia.The paleo-Daocheng ice cap was located on the Shaluli Hilly Plateau in the northeastern Hengduan Mountains,the oldest moraines in the Hengduan Mountains region were found in the ice cap area.Such glacial landforms provide key evidence to study the timing when this area entered the cryosphere with the uplift of the QTP.However,it is difficult to collect suitable glacial boulders from these moraines for traditional terrestrial in-situ cosmogenic nuclide(TCN)exposure dating because of long-term severe moraine degradation.Here,we collected clast samples from the moraine surface and depth profile to constrain the age of the oldest moraine in Kuzhaori(moraine E)using TCN^(10)Be dating technique.The minimum^(10)Be ages of five clast samples from the moraine surface range from 187.4±1.5 to 576.8±4.3 ka,implying that the moraine has been seriously degraded since deposition.Based on the TCN^(10)Be concentrations of the samples from a depth profile and simulations,the exposure-erosion-inheritance history of the profile was obtained.By fitting to the profile^(10)Be concentrations using the chi-square test,the simulations yielded a reliable age of 626.0±52.5 ka for the moraine.Therefore,the oldest moraine(moraine E)in Kuzhaori was most likely formed at about 0.63Ma ago,corresponding to the marine isotope stage(MIS)16.This glaciation represents the maximum Quaternary glaciation after the QTP was elevated into the cryosphere by the Kunlun-Yellow River Tectonic Movement.
基金The work was carried out within the framework of the state tasks of the IPE RAS(project no.FMWU-2022-0026,project no.FMWU-2022-0027)IVMiMG SO RAN(project no.0251-2021-0004).
文摘An expeditionary study of the area of the alleged impact event that occurred on 3.08.1993 in the area of the Lower Konkuli River(southeast of the Aldan Highlands,Lurikan Range,Russia)was carried out.According to the materials of remote sensing,the places of collision with the earth of a cosmic body are determined.In the area of the impact of the shock wave on the Earth’s surface,peat samples were selected,the micro probe analysis of which showed the presence of a cosmogenic substance in concentrations 6-8 times higher than the background.Silicate and magnetite micro spheres,native iron,moissanite,and carbon micro tubes coated with a film consisting of pure nickel were found.Of particular interest were the findings of specific Ni film micro structures that allow us to make an assumption about the cometary nature of the Uchur cosmic body.Most researchers associate the observed flights of fireballs with the subsequent fall of meteorites.Researchers are trying to find the massive body of the fallen space body.However,often,even after many years of searching,a massive cosmic body cannot be found.This happened when studying the site of the fall of the Tunguska cosmic body.In this case,it remains to be assumed that the cosmic body contained microscopic dust particles.The structure and composition of such particles can only be studied using microscopic research methods.When studying the Uchur cosmic body,the authors concluded that it could be of a cometary nature due to the findings of specific particles-thin films of pure nickel on the surface of plant remains of terrestrial origin.This hypothesis arose from the recent discovery of atomic nickel vapors in comets.