The stalagmite δ18O record is known to be associated with the climate, but the specifics of the relationship remain unclear. It may not represent variation in air temperature or precipitation, but instead reflect int...The stalagmite δ18O record is known to be associated with the climate, but the specifics of the relationship remain unclear. It may not represent variation in air temperature or precipitation, but instead reflect integral changes of monsoon circulation, especially water vapor sources(the so-called "circulation effect"). Since large-scale atmospheric-oceanic modes such as the Atlantic Multidecadal Oscillation(AMO), Pacific Decadal Oscillation(PDO), and North Atlantic Oscillation(NAO) exert significant effects on Asian monsoon, in this paper the authors investigate the relationships of the East Asian stalagmite δ18O record with these modes. The last three centuries form the focus of our study, for which the authors use reconstructed as well as instrumental data. Considering the impacts of human activity, our analysis is conducted with respect to two periods—the pre- and post-industrial periods. The results show significant lead-lag connections: a positive correlation peaks when the PDO leads East Asian stalagmite δ18O by 3 years, which is persistent over the past 300 years; while the relationships of the AMO and NAO with the East Asian stalagmite δ18O record show significant differences in the post-industrial relative to the pre-industrial period. This implies that the East Asian stalagmite δ18O record may primarily reflect the PDO signal.展开更多
NATURAL materials, which possess annual lamination and record annually climatic or environmental changes, can be termed 'natural clocks'. They include tree rings, coral layers, varves, ice layers, and laminate...NATURAL materials, which possess annual lamination and record annually climatic or environmental changes, can be termed 'natural clocks'. They include tree rings, coral layers, varves, ice layers, and laminated speleothems which were reported only in the last few years. The growth layer rhythm in stalagmites is related to high-frequency and short-term climatic oscillations. The luminescent density of annual layers of stalagmites is the signal of environmental changes. The organic matter contained in drip展开更多
A high-resolution climate record from 163.00 kaBP to 113.80 kaBP has been obtained through TIMS-U series dating and carbon and oxygen isotope analysis of the three large stalagmites from two caves in the south of Guiz...A high-resolution climate record from 163.00 kaBP to 113.80 kaBP has been obtained through TIMS-U series dating and carbon and oxygen isotope analysis of the three large stalagmites from two caves in the south of Guizhou Province, China. The record of the oxygen isotopes from the stalagmites reveals that the undulation characteristics between the cooling event of the glacial period and the warming event of the interglacial period in the research area can compare well to those of ice cores, lake sediments, loess and deep sea sediments on the scale of ten-thousand years or millennium time scale. The climate undulation provided by the record of the stalagmites has a coherence with the global changes and a tele-connection to the paleoclimate changes in the north polar region. Our results suggest that the direct dynamics of paleo-monsoon circulation changes reflected in the record of the stalagmites might be caused by changes of the global ice volume, and in turn related to various factors, including the solar radiation strength at the mid-latitudes in the Northern Hemisphere, the southern extension of the ice-rafted event in the North Atlantic, and changes of the equatorial Pacific sea surface temperature at the low-latitudes. Using °18O values, we have calculated the temperatures and the results show that the temperature difference between the penultimate glacial period (with an average temperature of 8.1°C, and a minimum temperature range from 0.65°C to-1.43°C at stage 6) and the last interglacial period (with an average temperature of 18.24°C at sub-stage 5e) was about 10°C. This temperature difference from the record of the stalagmites corresponds in general to the record temperature variation (about 10°C) of measured ice cores. The climate records from the three stalagmites in the two caves have shown that the circulation strength of the Asian summer monsoon and the winter monsoon in the penultimate glacial period and the last inter-glacial period had a clear change.With the TIMS-U series method, termination II of the penultimate glacial period has been precisely dated at an age of (129.28± 1.10) kaBP for the three stalagmites in the south of Guizhou Province, China. This borderline age represents the beginning of the last interglacial period or the boundary between the Middle Pleistocene and the Late Pleistocene, and corresponds to the beginning age of the last interglacial period shown by the ice cores and in the SPECMAP curve of the marine oxygen isotopes. The chronology determination of termination II is not only of stratigraphic and chronological significance, but also lays an important foundation for discussing the short time scales of climate oscillation and rapidly changing events of paleoclimate in the circulation region of the East Asian monsoon.展开更多
Lipids in stalagmites have been shown the potential for the paleoclimate reconstruction. However, the low lipid content leads to the difficulty in gaining high resolution lipid record in stalagmites because large mass...Lipids in stalagmites have been shown the potential for the paleoclimate reconstruction. However, the low lipid content leads to the difficulty in gaining high resolution lipid record in stalagmites because large mass of samples are required. Previous studies have validated that the acid digestion can improve the yield of lipids, especially fatty acids （FAs） and 3-hydroxy fatty acids （3- OH-FAs）. In order to obtain more content of FAs and 3- OH-FAs with limited stalagmite sample weight, we investigate here how the acid digestion conditions （HC1 concentration, heating temperature and time duration） could affect the yields of FAs and 3-OH-FAs. Under different concentration of HC1, from 2.0 to 6.0 mol/L, the FAs keep the same step in content variation with 3-OH- FAs, and the highest yields of both two appeared under the 3 mol/L HCl. The content of 3-OH-FAs increases posi- tively with the heating temperature from 80℃ to 150℃, while FAs showed the highest content at 130℃. Both of FAs and 3-OH-FAs firstly increased to a high content and then decreased as the heating time duration varies from 1.0 to 4.0 h, with the highest yields of both two being at 3.0 h. Consequently, we suggest the optimized acid digestion condition is under 3 mol/L HC1, heating at 130℃ for 3 h and 5 g of each stalagmite sample are sufficient for the lipid analysis.展开更多
The environmental magnetic proxies of stalagmites hold significant potential for reconstructing regional hydroclimate changes by revealing the content and grain size of magnetic particles within stalagmites.In this st...The environmental magnetic proxies of stalagmites hold significant potential for reconstructing regional hydroclimate changes by revealing the content and grain size of magnetic particles within stalagmites.In this study,we present the contents and grain sizes of magnetic particles within a stalagmite SZ-1,from Shizhu Cave in southwestern China from 70.4 to 22.3 thousand years ago(ka)during the last glacial period.Specifically,the parameters IRM_(soft),soil-derived magnetic minerals,and ARM/SIRM(anhysteretic remanent magnetization/saturation isothermal remanent magnetization),the ratio of fine magnetic particles to total ferrimagnetic particles preserved in stalagmite SZ-1,indicate the fluctuation of regional precipitation.Obvious half-precessional cycles are evident in these two proxies,indicating that hydroclimatic variations in southwestern China may predominantly arise from the heat and moisture transported from tropical oceans.These variations are likely influenced by shifts in the Intertropical Convergence Zone and fluctuations in the Asian Summer Monsoon.展开更多
A method for determining Mg/Ca of stalagmite by LA-MC-ICPMS is studied. 24Mg/44Ca (Mass 22, intensity of 44Ca2+ , collected by ion counting and mass 24, intensity of 24Mg+, collected by Faraday cup) ratios were measur...A method for determining Mg/Ca of stalagmite by LA-MC-ICPMS is studied. 24Mg/44Ca (Mass 22, intensity of 44Ca2+ , collected by ion counting and mass 24, intensity of 24Mg+, collected by Faraday cup) ratios were measured in replace of Mg/Ca ratios. Both diameter of laser sampling spot and laser moving increment were 20 μm. The curve of Mg/Ca vs. distance directly was obtained. The result indicates that relative Mg/Ca ratios changed from 0.5 to 2.0 in this stalagmite and it is enough to reflect environmental factors act.展开更多
Geotechnical properties of sedimentary rocks exposed along upper Egypt-Red Sea road were investigated to evaluate their geotechnical behavior. One of the most important aims of this work was to determine the engineeri...Geotechnical properties of sedimentary rocks exposed along upper Egypt-Red Sea road were investigated to evaluate their geotechnical behavior. One of the most important aims of this work was to determine the engineering problems affected on the road due to the geotechnical behavior of the studied sedimentary rocks and to suggest the suitable solution. Specific weight, unconfined compressive strength, slaking durability and free swelling were measured. The results showed that the studied crystalline limestone, marly limestone and Issawia limestone had higher unconfined compressive strength values ranging from 34,184.00 kN/m2 to 42,602.00 kN/m2 and the studied shale, siltstone and coral reef had lower values ranging from 3,689.00 kN/m2 to 6,933.00 kN/m2. The results showed also that the studied shale, siltstone and mudstone had fast to very fast slaking rate and their slaking amount described as low to medium after Gamble＇s slake durability classification. Replacement and/or chemical stabilization （using lime and/or cement kiln dust） of the expansive sedimentary rocks （shale and mudstone） were recommended to reduce the swelling. Geophysical investigations including shallow seismic, microgravity and GPR （ground penetrating radar） were recommended to scan the sub-grade of the road at El Maaza plateau to determine possible other caves and large voids under the road to avoid its collapse.展开更多
: Comprehensive studies on a stalagmite from the Panlong cave, Guilin, have shown that the isotopic records and sedimentary characteristics can reflect the changes of both palaeotemperatures and palaeorainfall, that i...: Comprehensive studies on a stalagmite from the Panlong cave, Guilin, have shown that the isotopic records and sedimentary characteristics can reflect the changes of both palaeotemperatures and palaeorainfall, that is to say, it is possible to get some information about the changes in climate of the area from the speleothem. The results suggest that: (1) the Younger Dryas event might have persisted in the area from 11 300 to 10 800 a B.P.; (2) from 9000 to 7000 a B.P., the climate got warmer and wetter, and the summer monsoon was gradually enhanced; (3) from 7000 to 4500 a B.P., the climate was warm and wet, and the summer monsoon prevailed; and (4) from 4500 a B.P. on, the summer monsoon was weakened and the modern climate pattern appeared, but there were several cold and dry periods, namely, from 4000 to 2500 a B.P., ca. 2400 a B.P. and < 1000 a B.P.展开更多
Holoceneδ^18O records from various archives(ice cores,cave stalagmites,and peat sediments)from the Xinjiang region of northwestern China,in arid central Asia(ACA),are all derived ultimately from local precipitationδ...Holoceneδ^18O records from various archives(ice cores,cave stalagmites,and peat sediments)from the Xinjiang region of northwestern China,in arid central Asia(ACA),are all derived ultimately from local precipitationδ^18O(δ^18Op).Nevertheless,they have been proposed as indicators of different climatic parameters,such as wetness and temperature changes.This article summarizes previously reported records of moisture sources for the Xinjiang region and the results of modern observations conducted at an ice core site and a peat site in the Altai Mountains.The findings are used to propose that the overall positive trends in Holoceneδ^18O records from the various archives from the Xinjiang region primarily reflect the Holocene's long-term warming trend.It is concluded that more site-specific modern observations are needed to further elucidate the environmental significance of Holoceneδ^18O records from this region,especially for the separation of different seasonal temperature signals present withinδ^18O records.展开更多
In this paper the authors report a preliminary study on a Holocene stalagmite from Shihua Cave in Southwest Beijing.The result shows that the thickness of annual growth layers which is defined by annual deposit hiatus...In this paper the authors report a preliminary study on a Holocene stalagmite from Shihua Cave in Southwest Beijing.The result shows that the thickness of annual growth layers which is defined by annual deposit hiatuses preserve changes with precipitation. In light with the thickness of annual layers the authors reconstruct the climatic variation history of the last 2300 years in Beijing area.The climatic patterns seems to reappear irregularly on millennium to decade scales in the last 1000 years. The stable isotopic sequence interprets that the climate and environment in Beijing could be separated into two stages in the late Holocene: the monsoon was strong and the environment was wet in the former stage and in the latter stage the monsoon was weak and the environment was dry. The annual layers and oxygen isotope could be taken as natural signals and carbon isotope as a comprehensive signal containing the natural information and the information of anthropogenic activity.展开更多
Beijing Shihua Cave is located at the northeastern part of the granite fringed Paleozoic to Mesozoic synclinal belt in Fangshan,which is face to face with the Peking Man(Homo erectus pekinensis) Relic Site.The stratig...Beijing Shihua Cave is located at the northeastern part of the granite fringed Paleozoic to Mesozoic synclinal belt in Fangshan,which is face to face with the Peking Man(Homo erectus pekinensis) Relic Site.The stratigraphy sequence is composed of Majiagou Formation limestone formed before 460 Ma in Middle Ordovician.The large forms of cave began to展开更多
The 8.2 and 4.2 ka BP abrupt climate events had significant impacts on Earth's climate system.However,the spatiotemporal pattern of these events remains ambiguous in the East Asian summer monsoon(EASM)region.In th...The 8.2 and 4.2 ka BP abrupt climate events had significant impacts on Earth's climate system.However,the spatiotemporal pattern of these events remains ambiguous in the East Asian summer monsoon(EASM)region.In this study,we collected thirteen previously published stalagmite δ^(18)O sequences from the EASM region to assess spatial and temporal patterns of the 8.2 and 4.2 ka BP events during the~8.7-7.7 ka BP and~4.7-3.7 ka BP periods,respectively.Our results reveal that highresolution stalagmite δ^(18)O sequences from nearby locations exhibit strong consistency during the Holocene,thus capturing regional patterns of climate variability.Sensitivity experiments indicate that the temporal resolution and geographical location significantly affect the ability of the stalagmite δ^(18)O sequences to record the 8.2 and 4.2 ka BP events.High-resolution stalagmite δ^(18)O records from both northern and southern China show a distinct positive δ^(18)O excursion corresponding with the 8.2 ka BP event,beginning at 8.23 ka BP and ending at 8.08 ka BP,thus lasting~150 yr,with an explained variance reaching~55% on centennial timescales.In contrast,there are significant north-south differences in the δ^(18)O signal during the period~4.26-3.97 ka BP,with a shift from negative to positive δ^(18)O values in northern China and a contrasting pattern in southern China.The application of the Monte Carlo empirical orthogonal function(MCEOF)method effectively reproduces the pronounced positive δ^(18)O excursion during the period~8.7-7.7 ka BP and exhibits fluctuations based on the long-term increase in δ^(18)O during the period~4.7-3.7 ka BP.The positive δ^(18)O excursion during the 4.2 ka BP event is primarily contributed by stalagmites from southern China,in particular the Dongge and Heshang Caves.Our study highlights the importance of using multiple high-resolution climate records to assess abrupt events both in space and time.展开更多
On orbital timescales,stable oxygen isotope(δ^(18)O)records from stalagmites in Central China and East Asian summer monsoon(EASM)intensity/precipitation amount records reconstructed from loess-paleosol sequences in N...On orbital timescales,stable oxygen isotope(δ^(18)O)records from stalagmites in Central China and East Asian summer monsoon(EASM)intensity/precipitation amount records reconstructed from loess-paleosol sequences in North China,have been suggested to show different change patterns.Here,high-resolution trace element/Ca ratios(Mg/Ca,Sr/Ca,Ba/Ca,Al/Ca,P/Ca)of stalagmite PS1 from Zhenzhu(ZZ)cave in North China over the past 130 kyr have been reconstructed.Based on two years of monitoring results from ZZ cave and the relationships among trace element/Ca ratios,it is demonstrated that the PS1 Mg/Ca could be a robust indicator of local effective precipitation.The Mg/Ca andδ^(13)C records of stalagmite PS1 exhibit highly in-phase co-variations on multi-millennial to orbital timescales and consistent long-term trends over the past 130 kyr,which is supported by the loess-based EASM precipitation amount records from the western Chinese Loess Plateau.These similarities indicate that effective precipitation of the ZZ cave area is mainly controlled by EASM precipitation amount in North China,and also support the long-term variation trend of the EASM precipitation amount,that is,decreasing from marine isotope stage(MIS)5e–MIS5c–MIS5a–MIS3,followed by an increase to MIS1.This long-term variation trend of EASM precipitation amount in North China over the past 130 kyr is primarily driven by solar insolation and global ice volume.These results confirm that proxies with the same indicative significance from both stalagmites and loess-paleosol profiles within the same region(such as North China)can corroborate each other.展开更多
Stalagmite is one kind of secondary carbonates formed in limestone caves(speleothem). After cave water droplets containing Ca2+and HCO3 drip onto floor, carbonate in the water might become supersaturated due to CO2 de...Stalagmite is one kind of secondary carbonates formed in limestone caves(speleothem). After cave water droplets containing Ca2+and HCO3 drip onto floor, carbonate in the water might become supersaturated due to CO2 degassing under certain conditions, resulting in the formation of stalagmite in a process year after year. Stalagmite is one of important geological archives for paleoclimate research. The advantages include wide spatial distribution, suitable for U-Th and U-Pb dating, enriched in climate proxies, continuity, long time span, comparability and lower sampling cost etc. These factors have propelled stalagmite paleoclimate research to the forefront of global paleoclimatology with an irreplaceable role. The stalagmite paleoclimate study started in the western countries, mainly in Europe and America in 1960 s–1970 s, while the relevant research in China was progressively developed in the 1980 s–1990 s after the Reform and Opening up. Although there was a huge gap between the overall research level in China and western countries, a solid research foundation, as well as a number of talent teams were established during the period. In the 21 st century, starting from the publication of stalagmite records from Hulu Cave in Nanjing in 2001, the stalagmite paleoclimate research in China has ushered in a flourishing development and a real leap on the basis of international cooperation, resulting in significant international impacts. The landmark achievements, including establishment of the world’s longest(640000 years) East Asian monsoon stalagmite record, as well as the longest Indian monsoon(280000 years),South American monsoon(250000 years), North American westerly climate(330000 years), Central Asian westerly climate(135000 years), and northwestern China westerly climate(500000 years), have laid a milestone in the paleoclimate study in these climate domains. Importantly, these stalagmite records have revealed the relationship of Asian monsoon variations with solar insolation climate change in polar regions, and the South American monsoon changes on orbital-suborbital timescales, which have provided new geological observations for the development of orbital-suborbital climate theory;elaborated coupling and differentiation relationships between the Asian monsoon and the westerly climate;reconstructed the history of Asian monsoon changes in the Holocene in detail, and thus the hydrological and climate variances behind Chinese and Indian civilizationcultural evolutions. Furthermore, a large number of high-resolution stalagmite records over the past 2000 years have been reconstructed, which are important for understanding short-term climate variability and magnitude, events, cycles, and thus the future climate projection. The achievements have also involved the improvements of a number of important techniques, such as U-Th dating method, the establishments of various hydroclimatic proxies, as well as the contributions to the reconstruction of the atmosphere14C variation history over the past ~54000 years. On the perspective of the future, the Chinese stalagmite community should continue to develop key techniques, further clarify the hydroclimatic significance of stalagmite proxies, impel the integration of related disciplines, and concentrate on key scientific issues in global climate change and major social demands.展开更多
Knowledge of the evolution of pedogenic processes in the carbonate area is important to understand the dynamics of rock desertification.A precisely-dated stalagmite δ13C record between 61.3 and 50.5 ka BP from southw...Knowledge of the evolution of pedogenic processes in the carbonate area is important to understand the dynamics of rock desertification.A precisely-dated stalagmite δ13C record between 61.3 and 50.5 ka BP from southwestern China,potentially related to soil biogenic CO2 production,shifts within a narrow range between -9‰ and -7‰,and exhibits a prominent cycle of 350-470 a,independent of the Asian monsoon changes.This indicates that a threshold effect might control the amplitude of calcite δ13C variability,likely associated with the vertical soil loss in the carbonate area.The periodic δ13C changes reflect that the loss/recovery of soil cover can operate on centennial scale.Thus,the rock desertification in southwestern China might at least initiate 60 ka ago and should be of natural origin.展开更多
Based on 33 U/Th dates and 1020 oxygen isotopic data from stalagmite Y1 from Yamen Cave, Guizhou Province, China, a record of the Asian Summer Monsoon (ASM) was established. The record covers the last deglaciation and...Based on 33 U/Th dates and 1020 oxygen isotopic data from stalagmite Y1 from Yamen Cave, Guizhou Province, China, a record of the Asian Summer Monsoon (ASM) was established. The record covers the last deglaciation and the early Holocene (from 16.2 to 7.3 ka BP) with an average oxygen isotope resolution of 9 years. The main millennial-scale deglacial events first identified in Greenland (Greenland Interstadial Events: GIS 1e through GIS 1a) and later in China are clearly present in the Y1 record. By analogy to earlier work, we refer to these as Chinese Interstadials (CIS): CIS A.1e to CIS A.1a. The onset of these events in Y1 δ18O records are nominally dated at: 14750±50, 14100±60, 13870±80, 13370±80, and 12990±80 a BP. The end of CIS A.1a or the beginning of the Younger Dryas (YD) event is nominally at 12850±50 a BP and the end of the YD dates to 11500±40 a BP. The δ18O values shift by close to 3‰ during the transition into the Bφlling-Allerφd (BA, the onset of CIS A.1e) and at the end of the YD. Comparisons of Y1 to previously published early Holocene records show no significant phase differences. Thus, the East Asia Monsoon and the Indian Monsoon do not appear to have been out of phase during this interval. The Y1 record confirms earlier work that suggested that solar insolation and North Atlantic climate both affect the Asian Monsoon.展开更多
The isotope records which range from 3.9 kaBP to 15.7 kaBP with an average resolution of 90 a have been obtained from 45 cm to 193.6 cm of the upper part of D4 stalagmite from Dongguo Cave in Libo, Guizhou, by using s...The isotope records which range from 3.9 kaBP to 15.7 kaBP with an average resolution of 90 a have been obtained from 45 cm to 193.6 cm of the upper part of D4 stalagmite from Dongguo Cave in Libo, Guizhou, by using system TIMS U-series dating and carbon and oxygen stable isotope analyses.The study indicates that the last cold event, the YD (Younger Dryas) event, of the last glacial period was apparently shown in D4 record, which started from 12.80 kaBP and ended in 11.58 kaBP, with a great range of drop in temperature. The end of the last glacial period was consistent with the termination I in oceanic isotope records and was with time limit of 11.3 kaBP. The three most distinct cold events in the early and middle Holocene occurred respectively in 10.91 kaBP, 8.27 kaBP and 4.75 kaBP, with a range of drop in tem- perature reaching 2—5℃. The climate abrupt events in thousand and hundred years scale re- corded in stalagmite δ O can be compared to those in GISP2 ice cores from Greenland in their 18 happening time and the range of their lasting time. The cold events in 8.27 kaBP and 4.75 kaBP can also be compared to CC3 stalagmite records in Ireland, which indicate that climate changes of short range in China monsoon areas, western Europe and polar regions, have the same driv- ing factor. This has a global significance. In addition, the trend of record curves in some time- stages is apparently different, which reflects probably the difference between environment in monsoon climate areas and in polar regions.展开更多
Interfaces of microlayers, in most stalagmites from China, consist of opaque and organic materials. Observed with microscope, the interfaces seem dark under transmitted light and luminiferous under reflected fluoresce...Interfaces of microlayers, in most stalagmites from China, consist of opaque and organic materials. Observed with microscope, the interfaces seem dark under transmitted light and luminiferous under reflected fluorescent light. Stalagmites in which the two optical characters are unified spatially would be most suitable for cross-dating use, and can play an important role in the study on speleochronology and speleoclimatology.展开更多
Two national stalagmite standard （GBW04412, GBW04413） and one international coral standard （RKM4） have been determined by using thermal ionization mass spectrometry （TIMS） method. The values of （ 234 U/ 238 U）...Two national stalagmite standard （GBW04412, GBW04413） and one international coral standard （RKM4） have been determined by using thermal ionization mass spectrometry （TIMS） method. The values of （ 234 U/ 238 U） act , （ 230 Th/ 234 U） act and age are all consistent in error range with the standard values obtained by using α spectrometry.展开更多
A stalagmite from Qixing Cave, Guizhou Province was dated with the TIMS U-series method and its oxygen isotope composition was analyzed. On the basis of the ages and the variations of the δ18O of the stalagmite, the ...A stalagmite from Qixing Cave, Guizhou Province was dated with the TIMS U-series method and its oxygen isotope composition was analyzed. On the basis of the ages and the variations of the δ18O of the stalagmite, the climate change of the last 7.7 ka has been reconstructed in this area: 7.7-5.8 ka, summer monsoon maximum period; 5.8-3.8 ka summer monsoon weakening period; 3.8-0.15 ka, weakened summer monsoon and high amplitude climate fluctuations period. We put forward that the increasing trend of δ18O of the stalagmite reflected not only the weakening of the summer monsoon, which was caused by the decreasing of solar radiation in the Northern Hemisphere, but also the possibly decreasing contribution of the southwest monsoon to the rainfall of this area. These results are consistent with the output of the numerical climate-model modeling. The high amplitude fluctuation of the δ18O may imply the quick shift of the contributions of different moisture sources to the precipitation in this area.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA11010401)the National Natural Science Foundation of China (Grant No. NSFC41375085)
文摘The stalagmite δ18O record is known to be associated with the climate, but the specifics of the relationship remain unclear. It may not represent variation in air temperature or precipitation, but instead reflect integral changes of monsoon circulation, especially water vapor sources(the so-called "circulation effect"). Since large-scale atmospheric-oceanic modes such as the Atlantic Multidecadal Oscillation(AMO), Pacific Decadal Oscillation(PDO), and North Atlantic Oscillation(NAO) exert significant effects on Asian monsoon, in this paper the authors investigate the relationships of the East Asian stalagmite δ18O record with these modes. The last three centuries form the focus of our study, for which the authors use reconstructed as well as instrumental data. Considering the impacts of human activity, our analysis is conducted with respect to two periods—the pre- and post-industrial periods. The results show significant lead-lag connections: a positive correlation peaks when the PDO leads East Asian stalagmite δ18O by 3 years, which is persistent over the past 300 years; while the relationships of the AMO and NAO with the East Asian stalagmite δ18O record show significant differences in the post-industrial relative to the pre-industrial period. This implies that the East Asian stalagmite δ18O record may primarily reflect the PDO signal.
文摘NATURAL materials, which possess annual lamination and record annually climatic or environmental changes, can be termed 'natural clocks'. They include tree rings, coral layers, varves, ice layers, and laminated speleothems which were reported only in the last few years. The growth layer rhythm in stalagmites is related to high-frequency and short-term climatic oscillations. The luminescent density of annual layers of stalagmites is the signal of environmental changes. The organic matter contained in drip
基金IGCP-448 'World Correlation of Karst Geology and Its Relevant Ecosystem', a key project of the Science and Technology Ministry (Grant No. 2000-026) the National Natural Science Foundation of China (Grant No. 40152002).
文摘A high-resolution climate record from 163.00 kaBP to 113.80 kaBP has been obtained through TIMS-U series dating and carbon and oxygen isotope analysis of the three large stalagmites from two caves in the south of Guizhou Province, China. The record of the oxygen isotopes from the stalagmites reveals that the undulation characteristics between the cooling event of the glacial period and the warming event of the interglacial period in the research area can compare well to those of ice cores, lake sediments, loess and deep sea sediments on the scale of ten-thousand years or millennium time scale. The climate undulation provided by the record of the stalagmites has a coherence with the global changes and a tele-connection to the paleoclimate changes in the north polar region. Our results suggest that the direct dynamics of paleo-monsoon circulation changes reflected in the record of the stalagmites might be caused by changes of the global ice volume, and in turn related to various factors, including the solar radiation strength at the mid-latitudes in the Northern Hemisphere, the southern extension of the ice-rafted event in the North Atlantic, and changes of the equatorial Pacific sea surface temperature at the low-latitudes. Using °18O values, we have calculated the temperatures and the results show that the temperature difference between the penultimate glacial period (with an average temperature of 8.1°C, and a minimum temperature range from 0.65°C to-1.43°C at stage 6) and the last interglacial period (with an average temperature of 18.24°C at sub-stage 5e) was about 10°C. This temperature difference from the record of the stalagmites corresponds in general to the record temperature variation (about 10°C) of measured ice cores. The climate records from the three stalagmites in the two caves have shown that the circulation strength of the Asian summer monsoon and the winter monsoon in the penultimate glacial period and the last inter-glacial period had a clear change.With the TIMS-U series method, termination II of the penultimate glacial period has been precisely dated at an age of (129.28± 1.10) kaBP for the three stalagmites in the south of Guizhou Province, China. This borderline age represents the beginning of the last interglacial period or the boundary between the Middle Pleistocene and the Late Pleistocene, and corresponds to the beginning age of the last interglacial period shown by the ice cores and in the SPECMAP curve of the marine oxygen isotopes. The chronology determination of termination II is not only of stratigraphic and chronological significance, but also lays an important foundation for discussing the short time scales of climate oscillation and rapidly changing events of paleoclimate in the circulation region of the East Asian monsoon.
基金Acknowledgements This work was supported by the National Basic Research Program of China （No. 2011CB808800）, the National Natural Science Foundation of China （Grant Nos. 40930210 and 41130207）, and the 111 Project of Education of Ministry of China （No. B08030）, and the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources （MSFGPMR200804, MSFGPMR200904）. We thank Dr. Yang Pu and Miss Jun Cao for their help during samples preparation and experiments and two anonymous reviewers for comments on the manuscript.
文摘Lipids in stalagmites have been shown the potential for the paleoclimate reconstruction. However, the low lipid content leads to the difficulty in gaining high resolution lipid record in stalagmites because large mass of samples are required. Previous studies have validated that the acid digestion can improve the yield of lipids, especially fatty acids （FAs） and 3-hydroxy fatty acids （3- OH-FAs）. In order to obtain more content of FAs and 3- OH-FAs with limited stalagmite sample weight, we investigate here how the acid digestion conditions （HC1 concentration, heating temperature and time duration） could affect the yields of FAs and 3-OH-FAs. Under different concentration of HC1, from 2.0 to 6.0 mol/L, the FAs keep the same step in content variation with 3-OH- FAs, and the highest yields of both two appeared under the 3 mol/L HCl. The content of 3-OH-FAs increases posi- tively with the heating temperature from 80℃ to 150℃, while FAs showed the highest content at 130℃. Both of FAs and 3-OH-FAs firstly increased to a high content and then decreased as the heating time duration varies from 1.0 to 4.0 h, with the highest yields of both two being at 3.0 h. Consequently, we suggest the optimized acid digestion condition is under 3 mol/L HC1, heating at 130℃ for 3 h and 5 g of each stalagmite sample are sufficient for the lipid analysis.
基金supported by the National Natural Science Foundation of China(Nos.42074071,42274094,42261144739)the Shenzhen Science and Technology Program(No.KQTD20170810111725321)+2 种基金supported by the Taiwan University Core Consortiums Project(No.112L894202)the Higher Education Sprout Project of the Ministry of Education(No.112L901001)the National Science and Technology Council(No.111-2116-M-002-022-MY3)。
文摘The environmental magnetic proxies of stalagmites hold significant potential for reconstructing regional hydroclimate changes by revealing the content and grain size of magnetic particles within stalagmites.In this study,we present the contents and grain sizes of magnetic particles within a stalagmite SZ-1,from Shizhu Cave in southwestern China from 70.4 to 22.3 thousand years ago(ka)during the last glacial period.Specifically,the parameters IRM_(soft),soil-derived magnetic minerals,and ARM/SIRM(anhysteretic remanent magnetization/saturation isothermal remanent magnetization),the ratio of fine magnetic particles to total ferrimagnetic particles preserved in stalagmite SZ-1,indicate the fluctuation of regional precipitation.Obvious half-precessional cycles are evident in these two proxies,indicating that hydroclimatic variations in southwestern China may predominantly arise from the heat and moisture transported from tropical oceans.These variations are likely influenced by shifts in the Intertropical Convergence Zone and fluctuations in the Asian Summer Monsoon.
文摘A method for determining Mg/Ca of stalagmite by LA-MC-ICPMS is studied. 24Mg/44Ca (Mass 22, intensity of 44Ca2+ , collected by ion counting and mass 24, intensity of 24Mg+, collected by Faraday cup) ratios were measured in replace of Mg/Ca ratios. Both diameter of laser sampling spot and laser moving increment were 20 μm. The curve of Mg/Ca vs. distance directly was obtained. The result indicates that relative Mg/Ca ratios changed from 0.5 to 2.0 in this stalagmite and it is enough to reflect environmental factors act.
文摘Geotechnical properties of sedimentary rocks exposed along upper Egypt-Red Sea road were investigated to evaluate their geotechnical behavior. One of the most important aims of this work was to determine the engineering problems affected on the road due to the geotechnical behavior of the studied sedimentary rocks and to suggest the suitable solution. Specific weight, unconfined compressive strength, slaking durability and free swelling were measured. The results showed that the studied crystalline limestone, marly limestone and Issawia limestone had higher unconfined compressive strength values ranging from 34,184.00 kN/m2 to 42,602.00 kN/m2 and the studied shale, siltstone and coral reef had lower values ranging from 3,689.00 kN/m2 to 6,933.00 kN/m2. The results showed also that the studied shale, siltstone and mudstone had fast to very fast slaking rate and their slaking amount described as low to medium after Gamble＇s slake durability classification. Replacement and/or chemical stabilization （using lime and/or cement kiln dust） of the expansive sedimentary rocks （shale and mudstone） were recommended to reduce the swelling. Geophysical investigations including shallow seismic, microgravity and GPR （ground penetrating radar） were recommended to scan the sub-grade of the road at El Maaza plateau to determine possible other caves and large voids under the road to avoid its collapse.
文摘: Comprehensive studies on a stalagmite from the Panlong cave, Guilin, have shown that the isotopic records and sedimentary characteristics can reflect the changes of both palaeotemperatures and palaeorainfall, that is to say, it is possible to get some information about the changes in climate of the area from the speleothem. The results suggest that: (1) the Younger Dryas event might have persisted in the area from 11 300 to 10 800 a B.P.; (2) from 9000 to 7000 a B.P., the climate got warmer and wetter, and the summer monsoon was gradually enhanced; (3) from 7000 to 4500 a B.P., the climate was warm and wet, and the summer monsoon prevailed; and (4) from 4500 a B.P. on, the summer monsoon was weakened and the modern climate pattern appeared, but there were several cold and dry periods, namely, from 4000 to 2500 a B.P., ca. 2400 a B.P. and < 1000 a B.P.
基金We dedicate this paper to the memory of Prof.ZiChu Xie,who passed away in early 2020.Prof.ZiChu Xie was an inspirational mentor and friend.This work was supported by the National Science Foundation of China(41772373,41372181)the Hunan Provincial Natural Science foundation of China(2018JJ1017)+1 种基金the National Key R&D Program of China(2018YFA0606404)and the Construction Program for First-Class Disciplines(Geography)of Hunan Province,China(5010002).We thank Dr.Jan Bloemendal for improving the English language.
文摘Holoceneδ^18O records from various archives(ice cores,cave stalagmites,and peat sediments)from the Xinjiang region of northwestern China,in arid central Asia(ACA),are all derived ultimately from local precipitationδ^18O(δ^18Op).Nevertheless,they have been proposed as indicators of different climatic parameters,such as wetness and temperature changes.This article summarizes previously reported records of moisture sources for the Xinjiang region and the results of modern observations conducted at an ice core site and a peat site in the Altai Mountains.The findings are used to propose that the overall positive trends in Holoceneδ^18O records from the various archives from the Xinjiang region primarily reflect the Holocene's long-term warming trend.It is concluded that more site-specific modern observations are needed to further elucidate the environmental significance of Holoceneδ^18O records from this region,especially for the separation of different seasonal temperature signals present withinδ^18O records.
文摘In this paper the authors report a preliminary study on a Holocene stalagmite from Shihua Cave in Southwest Beijing.The result shows that the thickness of annual growth layers which is defined by annual deposit hiatuses preserve changes with precipitation. In light with the thickness of annual layers the authors reconstruct the climatic variation history of the last 2300 years in Beijing area.The climatic patterns seems to reappear irregularly on millennium to decade scales in the last 1000 years. The stable isotopic sequence interprets that the climate and environment in Beijing could be separated into two stages in the late Holocene: the monsoon was strong and the environment was wet in the former stage and in the latter stage the monsoon was weak and the environment was dry. The annual layers and oxygen isotope could be taken as natural signals and carbon isotope as a comprehensive signal containing the natural information and the information of anthropogenic activity.
文摘Beijing Shihua Cave is located at the northeastern part of the granite fringed Paleozoic to Mesozoic synclinal belt in Fangshan,which is face to face with the Peking Man(Homo erectus pekinensis) Relic Site.The stratigraphy sequence is composed of Majiagou Formation limestone formed before 460 Ma in Middle Ordovician.The large forms of cave began to
基金was supported by the National Program on Key Basic Research Project of China(Grant No.2022YFF0801102)the National Natural Science Foundation of China(Grant No.42130511)+2 种基金the Swedish Research Council(Vetenskapsr?det,Grant No.2023-00605)the Marianne and Marcus Wallenberg Foundation(Grant No.MMW 2022-0114)the Centre for Advanced Study(CAS)at the Norwegian Academy of Science and Letters(2024/2025yr)。
文摘The 8.2 and 4.2 ka BP abrupt climate events had significant impacts on Earth's climate system.However,the spatiotemporal pattern of these events remains ambiguous in the East Asian summer monsoon(EASM)region.In this study,we collected thirteen previously published stalagmite δ^(18)O sequences from the EASM region to assess spatial and temporal patterns of the 8.2 and 4.2 ka BP events during the~8.7-7.7 ka BP and~4.7-3.7 ka BP periods,respectively.Our results reveal that highresolution stalagmite δ^(18)O sequences from nearby locations exhibit strong consistency during the Holocene,thus capturing regional patterns of climate variability.Sensitivity experiments indicate that the temporal resolution and geographical location significantly affect the ability of the stalagmite δ^(18)O sequences to record the 8.2 and 4.2 ka BP events.High-resolution stalagmite δ^(18)O records from both northern and southern China show a distinct positive δ^(18)O excursion corresponding with the 8.2 ka BP event,beginning at 8.23 ka BP and ending at 8.08 ka BP,thus lasting~150 yr,with an explained variance reaching~55% on centennial timescales.In contrast,there are significant north-south differences in the δ^(18)O signal during the period~4.26-3.97 ka BP,with a shift from negative to positive δ^(18)O values in northern China and a contrasting pattern in southern China.The application of the Monte Carlo empirical orthogonal function(MCEOF)method effectively reproduces the pronounced positive δ^(18)O excursion during the period~8.7-7.7 ka BP and exhibits fluctuations based on the long-term increase in δ^(18)O during the period~4.7-3.7 ka BP.The positive δ^(18)O excursion during the 4.2 ka BP event is primarily contributed by stalagmites from southern China,in particular the Dongge and Heshang Caves.Our study highlights the importance of using multiple high-resolution climate records to assess abrupt events both in space and time.
基金supported by the National Natural Science Foundation of China(Grant Nos.42371164,42001080&42171156)the Science and Technology Innovation Program of Hunan Province(Grant No.2023RC3130)the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province。
文摘On orbital timescales,stable oxygen isotope(δ^(18)O)records from stalagmites in Central China and East Asian summer monsoon(EASM)intensity/precipitation amount records reconstructed from loess-paleosol sequences in North China,have been suggested to show different change patterns.Here,high-resolution trace element/Ca ratios(Mg/Ca,Sr/Ca,Ba/Ca,Al/Ca,P/Ca)of stalagmite PS1 from Zhenzhu(ZZ)cave in North China over the past 130 kyr have been reconstructed.Based on two years of monitoring results from ZZ cave and the relationships among trace element/Ca ratios,it is demonstrated that the PS1 Mg/Ca could be a robust indicator of local effective precipitation.The Mg/Ca andδ^(13)C records of stalagmite PS1 exhibit highly in-phase co-variations on multi-millennial to orbital timescales and consistent long-term trends over the past 130 kyr,which is supported by the loess-based EASM precipitation amount records from the western Chinese Loess Plateau.These similarities indicate that effective precipitation of the ZZ cave area is mainly controlled by EASM precipitation amount in North China,and also support the long-term variation trend of the EASM precipitation amount,that is,decreasing from marine isotope stage(MIS)5e–MIS5c–MIS5a–MIS3,followed by an increase to MIS1.This long-term variation trend of EASM precipitation amount in North China over the past 130 kyr is primarily driven by solar insolation and global ice volume.These results confirm that proxies with the same indicative significance from both stalagmites and loess-paleosol profiles within the same region(such as North China)can corroborate each other.
基金supported by the National Natural Science Foundation of China(Grant Nos.41888101&41731174)
文摘Stalagmite is one kind of secondary carbonates formed in limestone caves(speleothem). After cave water droplets containing Ca2+and HCO3 drip onto floor, carbonate in the water might become supersaturated due to CO2 degassing under certain conditions, resulting in the formation of stalagmite in a process year after year. Stalagmite is one of important geological archives for paleoclimate research. The advantages include wide spatial distribution, suitable for U-Th and U-Pb dating, enriched in climate proxies, continuity, long time span, comparability and lower sampling cost etc. These factors have propelled stalagmite paleoclimate research to the forefront of global paleoclimatology with an irreplaceable role. The stalagmite paleoclimate study started in the western countries, mainly in Europe and America in 1960 s–1970 s, while the relevant research in China was progressively developed in the 1980 s–1990 s after the Reform and Opening up. Although there was a huge gap between the overall research level in China and western countries, a solid research foundation, as well as a number of talent teams were established during the period. In the 21 st century, starting from the publication of stalagmite records from Hulu Cave in Nanjing in 2001, the stalagmite paleoclimate research in China has ushered in a flourishing development and a real leap on the basis of international cooperation, resulting in significant international impacts. The landmark achievements, including establishment of the world’s longest(640000 years) East Asian monsoon stalagmite record, as well as the longest Indian monsoon(280000 years),South American monsoon(250000 years), North American westerly climate(330000 years), Central Asian westerly climate(135000 years), and northwestern China westerly climate(500000 years), have laid a milestone in the paleoclimate study in these climate domains. Importantly, these stalagmite records have revealed the relationship of Asian monsoon variations with solar insolation climate change in polar regions, and the South American monsoon changes on orbital-suborbital timescales, which have provided new geological observations for the development of orbital-suborbital climate theory;elaborated coupling and differentiation relationships between the Asian monsoon and the westerly climate;reconstructed the history of Asian monsoon changes in the Holocene in detail, and thus the hydrological and climate variances behind Chinese and Indian civilizationcultural evolutions. Furthermore, a large number of high-resolution stalagmite records over the past 2000 years have been reconstructed, which are important for understanding short-term climate variability and magnitude, events, cycles, and thus the future climate projection. The achievements have also involved the improvements of a number of important techniques, such as U-Th dating method, the establishments of various hydroclimatic proxies, as well as the contributions to the reconstruction of the atmosphere14C variation history over the past ~54000 years. On the perspective of the future, the Chinese stalagmite community should continue to develop key techniques, further clarify the hydroclimatic significance of stalagmite proxies, impel the integration of related disciplines, and concentrate on key scientific issues in global climate change and major social demands.
基金supported by the National Natural Science Foundation of China(41172148and41130210)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Knowledge of the evolution of pedogenic processes in the carbonate area is important to understand the dynamics of rock desertification.A precisely-dated stalagmite δ13C record between 61.3 and 50.5 ka BP from southwestern China,potentially related to soil biogenic CO2 production,shifts within a narrow range between -9‰ and -7‰,and exhibits a prominent cycle of 350-470 a,independent of the Asian monsoon changes.This indicates that a threshold effect might control the amplitude of calcite δ13C variability,likely associated with the vertical soil loss in the carbonate area.The periodic δ13C changes reflect that the loss/recovery of soil cover can operate on centennial scale.Thus,the rock desertification in southwestern China might at least initiate 60 ka ago and should be of natural origin.
基金supported by National Natural Science Foundation of China (Grant Nos. 40231008, 40902053, 90511004, 40672165, 40772216)US National Science Foundation (Grant No. 052535)+4 种基金Science Foundation of Southwest University (Grant No. SWUB-2008047)Foundation of Karst Dynamics Laboratory, MLR (Grant No. 2006-05)National Key Program of Science and Technology (Grant No. 2006BAC01A16)Natural Science Foundation Project of Chongqing (Grant No. CSTC, 2009BA0002)Geological Survey Project of MLR (Grant No. 1212010634805)
文摘Based on 33 U/Th dates and 1020 oxygen isotopic data from stalagmite Y1 from Yamen Cave, Guizhou Province, China, a record of the Asian Summer Monsoon (ASM) was established. The record covers the last deglaciation and the early Holocene (from 16.2 to 7.3 ka BP) with an average oxygen isotope resolution of 9 years. The main millennial-scale deglacial events first identified in Greenland (Greenland Interstadial Events: GIS 1e through GIS 1a) and later in China are clearly present in the Y1 record. By analogy to earlier work, we refer to these as Chinese Interstadials (CIS): CIS A.1e to CIS A.1a. The onset of these events in Y1 δ18O records are nominally dated at: 14750±50, 14100±60, 13870±80, 13370±80, and 12990±80 a BP. The end of CIS A.1a or the beginning of the Younger Dryas (YD) event is nominally at 12850±50 a BP and the end of the YD dates to 11500±40 a BP. The δ18O values shift by close to 3‰ during the transition into the Bφlling-Allerφd (BA, the onset of CIS A.1e) and at the end of the YD. Comparisons of Y1 to previously published early Holocene records show no significant phase differences. Thus, the East Asia Monsoon and the Indian Monsoon do not appear to have been out of phase during this interval. The Y1 record confirms earlier work that suggested that solar insolation and North Atlantic climate both affect the Asian Monsoon.
基金supported by the National Naural Science F oundation of China(Gant Nos.40231008 and 40152002)a project of the Mimistry of Science amnd Techm logy ofChina(Grant No.2003DEB6J069).
文摘The isotope records which range from 3.9 kaBP to 15.7 kaBP with an average resolution of 90 a have been obtained from 45 cm to 193.6 cm of the upper part of D4 stalagmite from Dongguo Cave in Libo, Guizhou, by using system TIMS U-series dating and carbon and oxygen stable isotope analyses.The study indicates that the last cold event, the YD (Younger Dryas) event, of the last glacial period was apparently shown in D4 record, which started from 12.80 kaBP and ended in 11.58 kaBP, with a great range of drop in temperature. The end of the last glacial period was consistent with the termination I in oceanic isotope records and was with time limit of 11.3 kaBP. The three most distinct cold events in the early and middle Holocene occurred respectively in 10.91 kaBP, 8.27 kaBP and 4.75 kaBP, with a range of drop in tem- perature reaching 2—5℃. The climate abrupt events in thousand and hundred years scale re- corded in stalagmite δ O can be compared to those in GISP2 ice cores from Greenland in their 18 happening time and the range of their lasting time. The cold events in 8.27 kaBP and 4.75 kaBP can also be compared to CC3 stalagmite records in Ireland, which indicate that climate changes of short range in China monsoon areas, western Europe and polar regions, have the same driv- ing factor. This has a global significance. In addition, the trend of record curves in some time- stages is apparently different, which reflects probably the difference between environment in monsoon climate areas and in polar regions.
文摘Interfaces of microlayers, in most stalagmites from China, consist of opaque and organic materials. Observed with microscope, the interfaces seem dark under transmitted light and luminiferous under reflected fluorescent light. Stalagmites in which the two optical characters are unified spatially would be most suitable for cross-dating use, and can play an important role in the study on speleochronology and speleoclimatology.
文摘Two national stalagmite standard （GBW04412, GBW04413） and one international coral standard （RKM4） have been determined by using thermal ionization mass spectrometry （TIMS） method. The values of （ 234 U/ 238 U） act , （ 230 Th/ 234 U） act and age are all consistent in error range with the standard values obtained by using α spectrometry.
基金This work was supported by the Chinese Academy of Sciences (Grant Nos. KZCX1-10-02 and KZCX1-Y-05) Chinese Ministry of Science and Technology (Grant No. Gl 999043401) the State Key Laboratory Foundation (Grant No. SKLLQG0014).
文摘A stalagmite from Qixing Cave, Guizhou Province was dated with the TIMS U-series method and its oxygen isotope composition was analyzed. On the basis of the ages and the variations of the δ18O of the stalagmite, the climate change of the last 7.7 ka has been reconstructed in this area: 7.7-5.8 ka, summer monsoon maximum period; 5.8-3.8 ka summer monsoon weakening period; 3.8-0.15 ka, weakened summer monsoon and high amplitude climate fluctuations period. We put forward that the increasing trend of δ18O of the stalagmite reflected not only the weakening of the summer monsoon, which was caused by the decreasing of solar radiation in the Northern Hemisphere, but also the possibly decreasing contribution of the southwest monsoon to the rainfall of this area. These results are consistent with the output of the numerical climate-model modeling. The high amplitude fluctuation of the δ18O may imply the quick shift of the contributions of different moisture sources to the precipitation in this area.
