The program described herein （LEADAT） serves to calculate sediment date and sedimentation rate using the ^210pb method for the studies of environmental processes and pollution history on a time scale of 100 - 150 a....The program described herein （LEADAT） serves to calculate sediment date and sedimentation rate using the ^210pb method for the studies of environmental processes and pollution history on a time scale of 100 - 150 a. The program written in MATLAB （ Version7.0） permits the user to select the principal models of ^210pb method, i. e. , the constant fluxes of sediment and lead-210 （ CF- SL） model, the constant flux of lead-210 （CFL） model, the constant initial concentration of lead-210 （CICL） model and the twolayer mixing （TLM） model. Although appropriate model selection is essentially based on understanding of the sedimentary processes, the pattern of the excess ^210pb profile is also helpful for model selection. The excess ^210pb profiles for two sediment cores collected from a brackish lake and an embayment respectively are used to demonstrate the application of the program. With a graphical user interface, the program can be easily executed. Not only ASCII but also graphical output can be generated by means of the program. Meanwhile, the code can be modified easily for extension.展开更多
The 'Old Red Sand' is a type of semicemented medium-fine sandy sediment that is red(10R_4/8) or brown red(2.5YR_4/8) in colour and is found in late Quaternary deposits. The sediments have distinctive character...The 'Old Red Sand' is a type of semicemented medium-fine sandy sediment that is red(10R_4/8) or brown red(2.5YR_4/8) in colour and is found in late Quaternary deposits. The sediments have distinctive characteristics and are a critical archive for understanding climatic changes in the coastal areas of East Asia. The ages of the late Quaternary aeolian sand dunes from Haitan Island in the coastal area of South China are still in debate. In this study, three sets of marine terraces were identified in the northern region of Haitan Island. Aeolian dune sands are well preserved on the top of these terraces. Quartz Optically Stimulated Luminescence dating and the distribution of the formation ages demonstrated that the palaeo-dunes are deposits from the middle-late period of the Late Pleistocene(Q_3^(2-3)). The period may be divided into three stages, 100-90 ka, 70-60 ka, and 40-20 ka, in which the palaeo-dunes of the first two stages are more widespread and were formed separately during a low-sea level period of the Marine Isotope Stages 5 b and 4. Several depositional palaeo-flood event records were preserved during the last stage due to the increasing gradient of mountain gullies formed during the Last Glacial Maximum.展开更多
Zircons are abundant in the beach sediments.In this study,surface microtexture,mineralogy,bulk sediment geochemistry,trace element composition and U−Pb isotopic geochronology of detrital zircons collected from the Ria...Zircons are abundant in the beach sediments.In this study,surface microtexture,mineralogy,bulk sediment geochemistry,trace element composition and U−Pb isotopic geochronology of detrital zircons collected from the Riachuelos and Palma Sola beach areas,southwestern Gulf of Mexico were performed to infer the sediment provenance and palaeoenvironment.The zircon microtexture was categorized as mechanically-and/or chemically-induced features.The weathering index values for the Riachuelos(~72−77)and Palma Sola(~71−74)beach sediments indicated moderate weathering of both of the two source areas.The major and trace element data of bulk sediments suggested passive margin settings for the two areas.The trace elemental ratios and chondrite-normalized rare earth element(REE)patterns of bulk sediments revealed that the sediments were likely sourced by felsic and intermediate igneous rocks.And the zircon Th/U ratios(mostly more than 0.2)and zircon REE patterns(with negative Eu and positive Ce anomalies)suggested a magmatic origin for both of the beach sediments from these two areas.Two distinct zircon age peaks respectively belonging to the Paleozoic and the Cenozoic were identified both in the Riachuelos and Palma Sola beach sediments.Zircon geochronology comparison research between the Riachuelos−Palma Sola beach sediments and potential source areas in SW Gulf of Mexico revealed that the source terrane supplied the Paleozoic zircons of this study was identified as the Mesa Central Province(MCP),and the Cenozoic zircons were transported from the nearby Eastern Alkaline Province(EAP).Moreover,although the Precambrian zircons were very few in the studied sediments,their geochronology and geochemistry results still could infer that they were contributed by the source terranes of Grenvillian igneous suites in the Oaxaca and the Chiapas Massif Complexes.展开更多
地处我国东亚季风边缘区的毛乌素沙地,因其对气候变化响应敏感而成为研究古气候环境变迁的理想场所。利用毛乌素沙地东南缘厚273 cm的沉积地层,通过分析沉积物粒度端元特征和环境指示意义,并结合光释光(OSL)测年结果和磁化率指标,重建...地处我国东亚季风边缘区的毛乌素沙地,因其对气候变化响应敏感而成为研究古气候环境变迁的理想场所。利用毛乌素沙地东南缘厚273 cm的沉积地层,通过分析沉积物粒度端元特征和环境指示意义,并结合光释光(OSL)测年结果和磁化率指标,重建了研究区2.6 ka B.P.以来的环境变化过程。结果表明:①剖面沉积物的粒度组成以粗粉砂、极细砂和细砂为主,其中细砂最多,平均体积分数为57.29%;粉砂层细砂体积分数明显低于砂层,粗粉砂和极细砂显著增多;沉积物粒度频率分布曲线多呈现典型的风成沉积物特点,峰高且窄,分选性较好。②剖面沉积物粒度可分离为3个端元组分,端元EM1是最细的粒度端元组分,指示了短时间的强尘暴活动,端元EM2和EM3是在不同风动力条件下跃移搬运的亚组分,端元EM3指示了当地风沙活动的强弱。③研究区晚全新世环境变化过程可分为3个阶段。2.6 ka B.P.之前,冬季风较强,气候冷干;2.6 ka B.P.之后到近百年,冬季风减弱,气候趋于暖湿;近百年以来,风沙活动增强,人类活动影响较大。展开更多
The Litang fault(LTF),located in the southeast of the Qinghai-Tibetan Plateau,is known for its high level of present-day seismicity,whereas its Pleistocene activity has been scarcely documented.This study focused on a...The Litang fault(LTF),located in the southeast of the Qinghai-Tibetan Plateau,is known for its high level of present-day seismicity,whereas its Pleistocene activity has been scarcely documented.This study focused on a tract of banded travertine deposits precipitated from thermal waters along the NW–SE-trending LTF trace.The role of travertine deposits in recording neotectonic activity has been studied by identifying their internal structure.Typical soft-sediment deformation structures observed within the banded travertines include micro folds,liquefied breccia,and liquefied diapirs.These deformed structures,which are restricted to a single unit separated unconformably by undeformed layers,can be traced for tens of meters,indicating that they were formed by seismic shaking triggered by LTF activity.The deformation of the banded travertine layers is attributed to the combined effects of seismic shaking,liquefaction,and fluidization,and it can be related to a paleo earthquake event with a magnitude of MS>5.The U-series ages obtained from the banded travertine deposits perturbed by the earthquakes are in the range of 130.59–112.94 ka,indicating an important fault-assisted neotectonic activity that occurred during the Middle–Late Pleistocene.Analysis of such structures,in combination with the use of U-series dating methods,can yield a reliable timing of neotectonic activity and provide new evidence for under-standing the seismotectonic setting of the Litang area.展开更多
In this paper, several sediment cores from three lakes (Gucheng Lake, Dianchi Lake and Dabusopao Lake) in the different regions of China were dated radiometrically by 210 Pb, 137 Cs and in Dianchi a...In this paper, several sediment cores from three lakes (Gucheng Lake, Dianchi Lake and Dabusopao Lake) in the different regions of China were dated radiometrically by 210 Pb, 137 Cs and in Dianchi also by 241 Am. The study shows that the profiles of 137 Cs in lake sediment of China generally have 2—4 distinct chronological markers, i.e. the onset of fallout in 1954 and peak fallout in 1963, 1974 and 1986. As many places of the northern hemisphere, the peak fallout in 1963 was the result of the atmospheric atomic weapons test. But in some areas of China, there may be have one or two other peaks of 137 Cs fallout, one can derive from Chernobyl fallout in 1986 and the other is caused by the nuclear testing fallout in early 1970s. So in these areas, the profiles of 137 Cs can have 2 or 3 peaks as the time markers. 241 Am, which is another fallout product from nuclear weapons testing, also provides a useful dating marker in Dianchi. These time markers are of considerable value to confirm 210 Pb dates in the three lakes. Despite there are some questions remain concerning the interpretation of these radionuclide records in lake sediments, coupling with 210 Pb and 137 Cs (and/or 241 Am) is suggested to be a valuable limnological tool for establishing sediment chronologies for the lake sediments in China.展开更多
Using the Ge centers of quartz sediments, the buried ages of fluvial sediments were determined by ESR technique. The ESR ages obtained from Ge centers are consistent with the TL ages, correspond with their horizons, a...Using the Ge centers of quartz sediments, the buried ages of fluvial sediments were determined by ESR technique. The ESR ages obtained from Ge centers are consistent with the TL ages, correspond with their horizons, accord with the geological background, and every ESR age is available. In this paper, determination of total dose of natural radiation (TD) and the reliability of ESR age using Ge center are also discussed.展开更多
Peat in boreholes is the most important ^(14)C dating material used for constructing age framework. 20 bulk peat samples were collected from five boreholes, the ^(14)C ages of two fractions(organic sediment fraction a...Peat in boreholes is the most important ^(14)C dating material used for constructing age framework. 20 bulk peat samples were collected from five boreholes, the ^(14)C ages of two fractions(organic sediment fraction and peat fraction) of the bulk peat samples were investigated by AMS-dating and which fraction is better to help construct an age framework for the boreholes were compared and discussed. The results indicated that the peat fraction give a good dating results sequence in the boreholes, compared with the corresponding organic sediment fraction. And the dating results of organic sediment fraction show 161-6 702 years older than corresponding peat fraction, which was caused by marine influence. Then, we suggest an experience formula as y =0.99 x-466.5 by the correlation analysis for correcting the marine influenced organic sediment ages within the conventional ages between 4 000 to 9 000 yrs BP, and more study should be carried out for the AMS ^(14)C dating of the bulk organic sediments.展开更多
Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic s...Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic section and full time formation since 400 kaBP were based on the results of the analyses using the dating methods with various instruments such as the ancient geomagnetism, electronics spin resonance （ESR）, 36C1 and lumines- cence dating, etc. Corresponding to these data, it identified the paleomagnetic polarity events including Biwa- III event （320 kaBP）, Biwa- 1I event （260 kaBP）, Biwa- I event （180 kaBP, scarcity due to the disturbance of the iron dish）, Blake event （100 kaBP） and Laschamp event （20 kaBP, didn＇t grow due to the activities of the surface）, etc. Combined with the sequence stratigraphy, layer type characteristics and its sediment environment, the strati- graphic can be divided into 4 stages of development respectively ： Stage [ is the climate period of glacial epoch （200-400 kaBP）; stage 11 is the climate period of interglacial epoch （100-200 kaBP）; stage llI is the climate peri- od of periglacial epoch （10-100 kaBP）; stage IV is the climate period ofpostglacial epoch （0-10 kaBP）.展开更多
文摘The program described herein （LEADAT） serves to calculate sediment date and sedimentation rate using the ^210pb method for the studies of environmental processes and pollution history on a time scale of 100 - 150 a. The program written in MATLAB （ Version7.0） permits the user to select the principal models of ^210pb method, i. e. , the constant fluxes of sediment and lead-210 （ CF- SL） model, the constant flux of lead-210 （CFL） model, the constant initial concentration of lead-210 （CICL） model and the twolayer mixing （TLM） model. Although appropriate model selection is essentially based on understanding of the sedimentary processes, the pattern of the excess ^210pb profile is also helpful for model selection. The excess ^210pb profiles for two sediment cores collected from a brackish lake and an embayment respectively are used to demonstrate the application of the program. With a graphical user interface, the program can be easily executed. Not only ASCII but also graphical output can be generated by means of the program. Meanwhile, the code can be modified easily for extension.
基金funded by the National Natural Science Foundation of China (Grants Nos. 41301012, 41771020 and U1405231)Natural Science Foundation of Fujian (Grant No. 2018R1034-5)Innovation Research Team Fund of Fujian Normal University (Grant No. IRTL1705)
文摘The 'Old Red Sand' is a type of semicemented medium-fine sandy sediment that is red(10R_4/8) or brown red(2.5YR_4/8) in colour and is found in late Quaternary deposits. The sediments have distinctive characteristics and are a critical archive for understanding climatic changes in the coastal areas of East Asia. The ages of the late Quaternary aeolian sand dunes from Haitan Island in the coastal area of South China are still in debate. In this study, three sets of marine terraces were identified in the northern region of Haitan Island. Aeolian dune sands are well preserved on the top of these terraces. Quartz Optically Stimulated Luminescence dating and the distribution of the formation ages demonstrated that the palaeo-dunes are deposits from the middle-late period of the Late Pleistocene(Q_3^(2-3)). The period may be divided into three stages, 100-90 ka, 70-60 ka, and 40-20 ka, in which the palaeo-dunes of the first two stages are more widespread and were formed separately during a low-sea level period of the Marine Isotope Stages 5 b and 4. Several depositional palaeo-flood event records were preserved during the last stage due to the increasing gradient of mountain gullies formed during the Last Glacial Maximum.
基金This study was supported by the Consejo Nacional de Ciencia y Tecnologfa(CONACyT)(Project No.Al-S-21287)Direcci6n General de Asuntos del Personal Academico(DGAPA)—Programa de Apoyoa Proyectos de Investigacione Innovacion Tecnologia(PAPIIT)(Project No.IN 107020)Instituto de Ciencias del Mary Limnologia Institutional Fund(Project No.616).
文摘Zircons are abundant in the beach sediments.In this study,surface microtexture,mineralogy,bulk sediment geochemistry,trace element composition and U−Pb isotopic geochronology of detrital zircons collected from the Riachuelos and Palma Sola beach areas,southwestern Gulf of Mexico were performed to infer the sediment provenance and palaeoenvironment.The zircon microtexture was categorized as mechanically-and/or chemically-induced features.The weathering index values for the Riachuelos(~72−77)and Palma Sola(~71−74)beach sediments indicated moderate weathering of both of the two source areas.The major and trace element data of bulk sediments suggested passive margin settings for the two areas.The trace elemental ratios and chondrite-normalized rare earth element(REE)patterns of bulk sediments revealed that the sediments were likely sourced by felsic and intermediate igneous rocks.And the zircon Th/U ratios(mostly more than 0.2)and zircon REE patterns(with negative Eu and positive Ce anomalies)suggested a magmatic origin for both of the beach sediments from these two areas.Two distinct zircon age peaks respectively belonging to the Paleozoic and the Cenozoic were identified both in the Riachuelos and Palma Sola beach sediments.Zircon geochronology comparison research between the Riachuelos−Palma Sola beach sediments and potential source areas in SW Gulf of Mexico revealed that the source terrane supplied the Paleozoic zircons of this study was identified as the Mesa Central Province(MCP),and the Cenozoic zircons were transported from the nearby Eastern Alkaline Province(EAP).Moreover,although the Precambrian zircons were very few in the studied sediments,their geochronology and geochemistry results still could infer that they were contributed by the source terranes of Grenvillian igneous suites in the Oaxaca and the Chiapas Massif Complexes.
文摘地处我国东亚季风边缘区的毛乌素沙地,因其对气候变化响应敏感而成为研究古气候环境变迁的理想场所。利用毛乌素沙地东南缘厚273 cm的沉积地层,通过分析沉积物粒度端元特征和环境指示意义,并结合光释光(OSL)测年结果和磁化率指标,重建了研究区2.6 ka B.P.以来的环境变化过程。结果表明:①剖面沉积物的粒度组成以粗粉砂、极细砂和细砂为主,其中细砂最多,平均体积分数为57.29%;粉砂层细砂体积分数明显低于砂层,粗粉砂和极细砂显著增多;沉积物粒度频率分布曲线多呈现典型的风成沉积物特点,峰高且窄,分选性较好。②剖面沉积物粒度可分离为3个端元组分,端元EM1是最细的粒度端元组分,指示了短时间的强尘暴活动,端元EM2和EM3是在不同风动力条件下跃移搬运的亚组分,端元EM3指示了当地风沙活动的强弱。③研究区晚全新世环境变化过程可分为3个阶段。2.6 ka B.P.之前,冬季风较强,气候冷干;2.6 ka B.P.之后到近百年,冬季风减弱,气候趋于暖湿;近百年以来,风沙活动增强,人类活动影响较大。
基金This work is supported financially by Spark Program of Earthquake Sciences,China Earthquake Administration(XH202301Y and XH23048C)State Key Laboratory of Earthquake Dynamics,Institute of Geology,CEA(LED2020B02)+1 种基金Lhasa National Geophysical Observation and Research Station(NORSLS21-04)Earthquake Science and Technology Special Project of Sichuan Earthquake Agency(LY2205 and LY2206).
文摘The Litang fault(LTF),located in the southeast of the Qinghai-Tibetan Plateau,is known for its high level of present-day seismicity,whereas its Pleistocene activity has been scarcely documented.This study focused on a tract of banded travertine deposits precipitated from thermal waters along the NW–SE-trending LTF trace.The role of travertine deposits in recording neotectonic activity has been studied by identifying their internal structure.Typical soft-sediment deformation structures observed within the banded travertines include micro folds,liquefied breccia,and liquefied diapirs.These deformed structures,which are restricted to a single unit separated unconformably by undeformed layers,can be traced for tens of meters,indicating that they were formed by seismic shaking triggered by LTF activity.The deformation of the banded travertine layers is attributed to the combined effects of seismic shaking,liquefaction,and fluidization,and it can be related to a paleo earthquake event with a magnitude of MS>5.The U-series ages obtained from the banded travertine deposits perturbed by the earthquakes are in the range of 130.59–112.94 ka,indicating an important fault-assisted neotectonic activity that occurred during the Middle–Late Pleistocene.Analysis of such structures,in combination with the use of U-series dating methods,can yield a reliable timing of neotectonic activity and provide new evidence for under-standing the seismotectonic setting of the Litang area.
文摘In this paper, several sediment cores from three lakes (Gucheng Lake, Dianchi Lake and Dabusopao Lake) in the different regions of China were dated radiometrically by 210 Pb, 137 Cs and in Dianchi also by 241 Am. The study shows that the profiles of 137 Cs in lake sediment of China generally have 2—4 distinct chronological markers, i.e. the onset of fallout in 1954 and peak fallout in 1963, 1974 and 1986. As many places of the northern hemisphere, the peak fallout in 1963 was the result of the atmospheric atomic weapons test. But in some areas of China, there may be have one or two other peaks of 137 Cs fallout, one can derive from Chernobyl fallout in 1986 and the other is caused by the nuclear testing fallout in early 1970s. So in these areas, the profiles of 137 Cs can have 2 or 3 peaks as the time markers. 241 Am, which is another fallout product from nuclear weapons testing, also provides a useful dating marker in Dianchi. These time markers are of considerable value to confirm 210 Pb dates in the three lakes. Despite there are some questions remain concerning the interpretation of these radionuclide records in lake sediments, coupling with 210 Pb and 137 Cs (and/or 241 Am) is suggested to be a valuable limnological tool for establishing sediment chronologies for the lake sediments in China.
文摘Using the Ge centers of quartz sediments, the buried ages of fluvial sediments were determined by ESR technique. The ESR ages obtained from Ge centers are consistent with the TL ages, correspond with their horizons, accord with the geological background, and every ESR age is available. In this paper, determination of total dose of natural radiation (TD) and the reliability of ESR age using Ge center are also discussed.
基金Supported by the China Geological Survey(No.121201006000182401)the National Natural Science Foundation of China(Nos.41476074,41372173)
文摘Peat in boreholes is the most important ^(14)C dating material used for constructing age framework. 20 bulk peat samples were collected from five boreholes, the ^(14)C ages of two fractions(organic sediment fraction and peat fraction) of the bulk peat samples were investigated by AMS-dating and which fraction is better to help construct an age framework for the boreholes were compared and discussed. The results indicated that the peat fraction give a good dating results sequence in the boreholes, compared with the corresponding organic sediment fraction. And the dating results of organic sediment fraction show 161-6 702 years older than corresponding peat fraction, which was caused by marine influence. Then, we suggest an experience formula as y =0.99 x-466.5 by the correlation analysis for correcting the marine influenced organic sediment ages within the conventional ages between 4 000 to 9 000 yrs BP, and more study should be carried out for the AMS ^(14)C dating of the bulk organic sediments.
基金Open Foundation for State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences(No.SKLLQG0701)Hunan Province Key Subject Construction Item(No.ZRDL0701)Open Foundation for State Key Laboratory of Continental Dynamics,Northwest University(No.DL2006001)
文摘Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic section and full time formation since 400 kaBP were based on the results of the analyses using the dating methods with various instruments such as the ancient geomagnetism, electronics spin resonance （ESR）, 36C1 and lumines- cence dating, etc. Corresponding to these data, it identified the paleomagnetic polarity events including Biwa- III event （320 kaBP）, Biwa- 1I event （260 kaBP）, Biwa- I event （180 kaBP, scarcity due to the disturbance of the iron dish）, Blake event （100 kaBP） and Laschamp event （20 kaBP, didn＇t grow due to the activities of the surface）, etc. Combined with the sequence stratigraphy, layer type characteristics and its sediment environment, the strati- graphic can be divided into 4 stages of development respectively ： Stage [ is the climate period of glacial epoch （200-400 kaBP）; stage 11 is the climate period of interglacial epoch （100-200 kaBP）; stage llI is the climate peri- od of periglacial epoch （10-100 kaBP）; stage IV is the climate period ofpostglacial epoch （0-10 kaBP）.
