The Loess Plateau-Northeastern Tibetan Plateau in China is famous for its deep andcontmuous distributed loess, in which soils (developed from loess) vary gradually with differentbiological climates changing from subhu...The Loess Plateau-Northeastern Tibetan Plateau in China is famous for its deep andcontmuous distributed loess, in which soils (developed from loess) vary gradually with differentbiological climates changing from subhumid to arid, which provide a natural proving ground forstUd}' the coupling of loess-paleosol and climatic changes quantitatively. Thirty-two sections weresampled (collected) for measuring chemical element contents, clay content (and other items) and 60sections were collected for carbonate analysis to establish transfer functions between pedogenesisand climate. Finally, we estimated the paleoclAnate (P/T) in the region with transfer functions,It isrevealed that the variation of paleocldriate reflected by transfer functions accorded closely with theclimatic pattern resulted from recent work. Specifically, it was about 140 ha BP that summermonsoon reached Lanzhou or further, paleosol S1 (equaling to MIS 5 in deep sea records) developedstrongly in a large scale, even touching upon northeanstern Tibetan Plateau. And, the estimated P/Tinformation also indicated the cold and humid period during 50-30 ka BP, mean annual Precipitationwas about 400-500 nun in Angutan recorded by mega-interstadial paleosol Sm.展开更多
Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits （SWDs） was found interbedded in the Holocene Ioe...Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits （SWDs） was found interbedded in the Holocene Ioess-paleosol sequence at the Guchuanzhen site （GCZ）. These palaeoflood SWDs were studied by field observations and laboratory analyses including concentrations of chemical elements and optically stimulated luminescence （OSL） dating. The results showed that the palaeoflood SWDs were the result of the secondary separations of the surface soil and weathered soil layers during the process of water transport and deposition, and without obvious weathering during soil development. These extraordinary flood events were dated back to 3,200-3,000 a B.P. with the OSL method and checked by archaeological dating of the human remains retrieved from the profile. These extraordinary flood events were therefore considered as regional expression of known climatic events and demonstrated the climatic instability in the Holocene. This result is important for understanding the effects of global climate change on the dynamics of river systems.展开更多
This paper aims to compare the geochemical characteristics of loess-paleosol sequences in the upper reaches of the Hanjiang and Weihe river valleyswhich are located in the semi-humid temperate zone and humid subtropic...This paper aims to compare the geochemical characteristics of loess-paleosol sequences in the upper reaches of the Hanjiang and Weihe river valleyswhich are located in the semi-humid temperate zone and humid subtropical zonerespectively. The Mituosi（MTS） profile in the upper reaches of the Hanjiang River valley and the Yaohecun（YHC） profile in the Weihe River valley were selected for this comparative research. The stratigraphic characteristicscompositionchemical weathering intensityleaching rates of Ca and Namobility of major elementsand transport features of Na and Fe were analyzed with respect to depth and compared between the two profiles. This study reached the following conclusions.（1） The composition of the loess-paleosol sequences in two regions are quite similar to the average composition of the upper continental crust（UCC）indicating that the loess in the two regions came from multiple sources and was mixed well. Thereforethe loess in the two regions is considered aeolian loess.（2） Compared with the loess-paleosol sequence in the Weihe River valleythe loess-paleosol sequence in the upper reaches of the Hanjiang River valley features a darker color; a higher chemical index of alteration（CIA） value; higher leaching rates of Na and Ca; higher migration ratio（relative to K） of AlSiMgand Na; and lower migration ratio of Fe and Ca. This evidence indicates that the loess-paleosol sequence in the humid subtropical environment experienced stronger chemical weathering intensity than the loess-paleosol sequence in the semi-humid temperate zone.（3） Both the YHC profile and MTS profile record a period of climate deterioration at 6000–5000 a BP. The period punctuated the mid-Holocene Climatic Optimum（8500–3100 a BP） in the study area.展开更多
Two-three paleosol layers were formed in the western part of the Northeast Plain. China during Holocene. These paleosol layers interlaid with eolian fine sand layers. Dated by 14C dating. archeology and TL and analyze...Two-three paleosol layers were formed in the western part of the Northeast Plain. China during Holocene. These paleosol layers interlaid with eolian fine sand layers. Dated by 14C dating. archeology and TL and analyzed by statistics.the formation periods of paleosols are divided from the results. The periods are 11, 000- 7000 5500-4500. 3500- 2800 and 1400- 1000 a B. P. respectively.According to the spore-pollen compositions in more than ten sand dune paleosol profiles, it is discovered th.t there is little spore-pollen in the sand layers and a little spore-pollen in the paleosol layers. The spore-pollen compositions in the paleosols are simple. mainly Artemisia (50% - 70%) and Chenopodiaceae. In the paleosols of 11,000 - 7000 a B. P.. the spore-pollen composition is Artemisia-Rubiaceaechenopodiaceae. The contents of Ephedra pollen in the lower and upper parts of the layer are less than that in the middle part. In the paleosols of 5500- 4500 a B. P.,the spore-pollen composition is Artem isal - Chenopod iaceae - Melilotus. There is some Salix sp. and Betula sp. pollen in the lower part of the layer and some Ephedra pollen in the upper part. In the paleosols of 3500- 2800 a B. P.. the spore-pollen composition is Artemisia Chenopodiaceae - Rubiaceae. There are som e Kochia and Baryaceae. In the paleosols of 1400-1000 a B. P., the spore-pollen composition is also Artemisia-Chjenopod tao eae - Rubiaceae. There is a little pine pollen. The grain size of paleosol is relatively coarse, but still finer than that of eolian sand and becomes coarser from the bottom to the top of the profile. This fact reflects that the weathering environments during the paleosol formation periods were wetter than that during the eolian periods and became dryer from middle to late Holocene.展开更多
Based on field investigations,laboratory analyses and 14C dating,this paper discusses the laws of the formation and development of the paleosols in the northeast region of the Qinghai-Xizang Plateau since Late Pleisto...Based on field investigations,laboratory analyses and 14C dating,this paper discusses the laws of the formation and development of the paleosols in the northeast region of the Qinghai-Xizang Plateau since Late Pleistocene.The authors reconstruct basic conditions of climate,vegetation,soil and natural zones during the three periods in which the paleosols were formed,i.e.the last interglacial of the Late Pleistocene,warm stage of Late Glacial and the Optimum of Holocene.Finally,this paper discusses the relationship between the paleosols and the uplift of the Qinghai-Xizang Plateau.展开更多
This paper presents a set of bulk geochemical and mineralogical data from a paleoweathering profile located in Zunyi District, Northern Guizhou, China. It was formed at the top of the Hanjiadian Formation of the Lower...This paper presents a set of bulk geochemical and mineralogical data from a paleoweathering profile located in Zunyi District, Northern Guizhou, China. It was formed at the top of the Hanjiadian Formation of the Lower Silurian. A truncated, argillic, gleyed, kryptic paleospodosol is recognized in the paleoweathering profile. Ratios of immobile elements（Ti/Zr, Ti/Al） and their binary（e.g., Nb vs. Zr/TiO_2 and Th/Sc vs. Zr/Sc）, triangular diagrams（La-Th-Sc, Th-ScZr/10, Zr-Cr-Ga） reflect that the Gaojiayan paleosol is the product of in-situ weathering of gray-green silty mudstone of the underlying Hanjiadian Formation. Mass balance calculations indicate K enrichment and Na enrichment in the upper and lower portions of paleosol, respectively. These findings both are the results of transgression, which brings substantial concentrations of such elements as K, Na, and Sr. In particular, K enrichment is achieved by the illitization of kaolinite. The biological processes of terrestrial vascular plants also enhance K concentration, especially at the top of the paleosol. Na enrichment is a consequence of albitization and/or adsorption by clay minerals through cation exchange. The mass distributions and relative mass changes of rare earth elements（REEs） in the studied profile display characteristics of vertical zonation. Three peaks in total REEs content are observed, indicating two paleoclimatic or paleoenvironmental changes. Mineralogical characteristics indicate that the paleoclimate changed first from warm and humid to cold and dry and later, to dry and lightly warmer. The corresponding soil environment varies from weakly acidic to strongly alkaline and later, to weakly acidic. Mass translocation characteristics of REEs and several transition metals suggest that the Gaojiayan paleosol may have undergone top erosion.展开更多
A paleosol horizon is described from the contact of the Sausar Group（w2400 Ma） and its basement（Tirodi Gneiss; 〉2500 Ma） in Central India. Physical evidence of pedogenesis is marked by the development of stress c...A paleosol horizon is described from the contact of the Sausar Group（w2400 Ma） and its basement（Tirodi Gneiss; 〉2500 Ma） in Central India. Physical evidence of pedogenesis is marked by the development of stress corrosion cracks, soil peds, corestone weathering and nodular rocks. XRD and SEM-EDX data indicate the presence of siderite, ankerite, uraninite, chlorite, alumino-silicate minerals, ilmenite,rutile and magnetite, in addition to quartz, feldspar and mica. The chemical index of alteration, the plagioclase index of alteration, and the chemical index of weathering show an increasing trend from parent rock to the paleosol and indicate a moderate trend of weathering. The A-CN-K plot indicates loss of feldspars, enrichment in Al2O3 and formation of illite. Different major element ratios indicate baseloss through hydrolysis, clay formation, leaching of some elements, and more precipitation with good surface drainage. The paleosol is depleted in HREE in comparison to the parent rock indicating high fluid-rock interaction during weathering. The paleosol samples show flat Ce and Eu anomalies, low SREE, and high（La/Yb）N, indicative of a reducing environment of formation. Reducing condition can also be inferred from the concentration of elements such as V, Co, Cu, Pb, and Zn in the paleosol profile. Although enriched in Fe and Mg, the overall geochemical patterns of the paleosol indicate oxygen deficient conditions in the atmosphere and development by weathering and leaching processes associated with high precipitation and good surface drainage at the time of development of this paleosol during the Archeane Paleoproterozoic transition.展开更多
The loess deposits comprise several paleosol layers reflecting alternation of drier and wetter climate during Quaternary. Such a situation occurs in north of Barlad, on The Sohodau＇s Hill. Morphological study of the ...The loess deposits comprise several paleosol layers reflecting alternation of drier and wetter climate during Quaternary. Such a situation occurs in north of Barlad, on The Sohodau＇s Hill. Morphological study of the quarry paleosols from north of Barlad was accomplished based on field observations and macroscopic physic-chemical results. Three levels of paleosols with variable thickness were determined. These three fossils layers are interbedded by four loess deposits. The physical-chimical data provide important information for the paleosol genesis and depositional/climatic environments. The carbon content and C/N ratio indicate the strength of pedogenesis in the Pleistocene and trends of biomass accumulation.展开更多
The AD 79 eruption of Somma-Vesuvius completely buried the ancient landscape around Pompeii (Italy) to some extent conserving the pre-AD 79 Roman paleosols of the Sarno River plain. To estimate potential post-burial s...The AD 79 eruption of Somma-Vesuvius completely buried the ancient landscape around Pompeii (Italy) to some extent conserving the pre-AD 79 Roman paleosols of the Sarno River plain. To estimate potential post-burial soil developments of these paleosols detailed soil liquid and solid phase analysis were carried out. Firstly, an in-situ soil hydrological monitoring was conducted within a pre-AD 79 paleosol in natural undisturbed stratification. The results show that soil water flow and nutrient transport from the overlying volcanic deposits into the pre-AD 79 paleosol take place. Secondly, to estimate their influence on the paleosol’s mineral soil properties, the solid phase of four pre-AD 79 paleosols and associated modern unburied soils were analysed and compared. By combining the data from the soil liquid and solid phase analysis, potential post-burial changes in the paleosols were estimated. Finally, a rise of the mean groundwater table was determined since AD 79. This distinguishes the Sarno River plain into two different zones of post-burial soil developments: 1) lower altitudes where formerly terrestrial paleosols are now influenced by groundwater dynamics and 2) higher altitudes where the paleosols are still part of the vadose zone and rather influenced by infiltration water or interflow. Thus, the mechanism of potential post-burial soil development being active in the pre-AD 79 paleosols is not uniform for the entire Sarno River plain but strongly depends on the paleotopographic situation.展开更多
A number of Precambrian sedimentary basins of the Indian subcontinent offer scope for tracking early oxygenation history of atmosphere and hydrosphere.Available studies,though certainly not exhaustive,record signature...A number of Precambrian sedimentary basins of the Indian subcontinent offer scope for tracking early oxygenation history of atmosphere and hydrosphere.Available studies,though certainly not exhaustive,record signatures of pre-great oxygenation event(GOE)whiffs of atmospheric oxygenation between 3.29 and 3.02 Ga.展开更多
34 samples of loess-paleosol from the Luochuan and kifeng sections in the Loess Plateau, north-ern China were separated into sand, silt and clay fractions and analyzed for their mineral composi -tions. The results ind...34 samples of loess-paleosol from the Luochuan and kifeng sections in the Loess Plateau, north-ern China were separated into sand, silt and clay fractions and analyzed for their mineral composi -tions. The results indicate that there is almost no difference between loess and paleosol in mineralcomposition. Major mineral species are quartz, mica, feIdspar and chlorite, accounhng for about88-92% of the total, other minerals are kandite, smectite, vermiculite and a few heavy minerals. Thecalcite, magnetite and hematite were not taken into consideration because of their removal in the pro-cess of sample preparation. The main difference with respect to the mineral composition of samplescollected from different sections and different stratigraphic leveIs lies in the amount and grain sise ofminerals hosted. Comparisons between the Luochuan section and the kifeng section, between paleosoland loess and between the upper part and the lower part of some paleosol layers show that the for-mers contain less feldspar but more mica and vermiculite and are finer in grain sise, indicahng theco-occurrence of both biochemical weathering process responsible for mineral change and physicalweathering process leading to grain-stie change during the soiI-forming processes. This result favourssuch an explanation of the soi1-forming mechanism that loess deposition and paleosol developmentoccurred synchronously, though the rate of soil formation was greater than that of loess deposition,thus leading to soil development.展开更多
The type, grain size and origin of ferrimagnetic minerals separated from red paleosols of Pleistocene Epoch (Q\-2) in eastern China, were studied by using mineral magnetic measurement, X\|ray powder diffraction and el...The type, grain size and origin of ferrimagnetic minerals separated from red paleosols of Pleistocene Epoch (Q\-2) in eastern China, were studied by using mineral magnetic measurement, X\|ray powder diffraction and electron microscopy. Results showed that the iron oxides in red paleosols were composed of hematite (α\|Fe\-2O\-3), maghemite (γ\|Fe\-2O\-3) and goethite(α\|FeOOH). Mineral magnetic parameters and X\|ray diffraction patterns indicated that maghemite was the dominant remanence carrier in red paleosols, which is characterized by superparamagnetic (SP) and stable single domain (SSD) grains. The variations of magnetic susceptibility (χ), anhysteretic magnetic susceptibility (χ\-\{ARM\}) and saturation isothermal remanent magnetization (SIRM) for red paleosols following heating to various temperatures showed two peak values at 700℃ and 900℃. The spherulitic magnetic particles measuring \{250-1000\}μm in diameter in red paleosols were separated by the magnetic separation method, indicating that these magnetic particles were an assemblage of superparamagnetic and stable single domain ferrimagnetic grains. It is suggested that the ferrimagnetic minerals of red paleosols be a pedogenic ferrimagnetic component under high temperature and high humid conditions in the Pleistocene Epoch (Q\-2). It is concluded that the magnetism characteristics of red paleosols can be used to evaluate the environmental changes of Quaternary in eastern China.展开更多
Changes in global climate have a positive effect on the changes in hydrologic cycle, and leave their traces in the cycles of hydrogenic sediments and geomorphic evolutions. It is possible to explain the law of the cli...Changes in global climate have a positive effect on the changes in hydrologic cycle, and leave their traces in the cycles of hydrogenic sediments and geomorphic evolutions. It is possible to explain the law of the climate change and tectonic movement in the course of the environmental evolutions during the Quaternary by way of identifying the different cycles and ages of hydrogenic sediments in each geomorphic period. This study is very much展开更多
人类起源及演化与地球系统环境演化相互关联的科学研究不仅是传统第四纪研究的关键内容之一,也是当今宜居地球研究的首要问题。文章回顾了黄土高原及邻近地区第四纪地层中发现的重要古人类遗存(包括古人类化石和旧石器)的主要成就,阐述...人类起源及演化与地球系统环境演化相互关联的科学研究不仅是传统第四纪研究的关键内容之一,也是当今宜居地球研究的首要问题。文章回顾了黄土高原及邻近地区第四纪地层中发现的重要古人类遗存(包括古人类化石和旧石器)的主要成就,阐述了前人提出的“黄土石器工业”和“黄土地质考古带”研究思路的萌生和发展历程,介绍了学者们运用黄土-古土壤序列对第四纪不同类型沉积物中埋藏的古人类遗存研究的概况。在此基础上,根据前人的大量资料以及笔者自身数十年积累的第一手调查研究数据,提出了一种新的科学思路:针对“全球变化”研究中的薄弱环节,运用独一无二的中国黄土连续序列的“地圈”优势,去寻找“生物圈”古人类活动的连续“序列性”踪迹,研究古气候古环境演化对古人类生存环境的制约及其反馈等重大科学问题。以新的思路和科学问题为宗旨,运用黄土-古土壤序列标准年代框架标尺,以蓝田地区上陈、公王岭、陈家窝、吉家湾-甘峪-刁寨剖面的含石器或古人类化石的26个黄土-古土壤组合旋回(其中包括21个古土壤层和15个黄土层)为基础数据,初步构建了一个年代大约2.12~0.01 Ma B. P.的较高分辨率的古人类古文化演化序列——“黄土-古土壤-古人类遗存序列”框架,期望为人类演化和黄土环境研究拓展新路。展开更多
The advantages of thermal methods for mineral-magnetic research of loess/paleosolsequences are illustrated in an introductory overview. When applying thermal methods, magnetiteand maghemite can be distinguished, somet...The advantages of thermal methods for mineral-magnetic research of loess/paleosolsequences are illustrated in an introductory overview. When applying thermal methods, magnetiteand maghemite can be distinguished, something which is difficult with field-dependentmeasurements at room temperature. Also, variable low-temperature oxidation that is related toclimate may be quantified. Thirdly, grain-size estimates pertaining to the whole superparamagneticrange can be inferred from LT warming experiments and to a lesser extent from variable chemicalalteration during heating. Application of mineral-magnetic techniques may lead to thedevelopment of quantifiable proxy parameters for paleoclimate.展开更多
The relationship between the carbon isotopic composition of paleosols and paleovegetation on the Loess Plateau is still unclear. One of the main reasons is that we are short of knowledge about the characteristics of t...The relationship between the carbon isotopic composition of paleosols and paleovegetation on the Loess Plateau is still unclear. One of the main reasons is that we are short of knowledge about the characteristics of the carbon isotopic composition of modern soil in this area. A preliminary investigation of the carbon isotopic compositions of the modern soil and the loess/paleosol sequence on the Loess Plateau shows that the carbon isotopic composition of modern soil is consistent with the distribution of modern plants on the Loess Plateau, where the ecosystem is dominated by a mixture of C4 and C3 plants. Comparing theδ13C values of modern soil and loess-paleosol sequences from the Xunyi profile, we conclude that C3 plants dominated the landscape during loess sediment stages, while C4 plants expanded during paleosol stages.展开更多
Major and trace element analyses of the Luochuan loess-paleosol sequence in China were performed in order to understand the cheniical weathering processes occurring on the I.oess Plateau during the last 600 ka. Result...Major and trace element analyses of the Luochuan loess-paleosol sequence in China were performed in order to understand the cheniical weathering processes occurring on the I.oess Plateau during the last 600 ka. Results reveal that most elements in the loess remain immobile durlng chemical weathering. The typical stable elements are Al, K, Ti, Rb and REE, while the main mobile elements are Ca, Sr, P, Mg and Na. 120ess and paleosol experience the incipient stage of chemical weathering characterized by acid leaching and carbonate dissolution. Alteration of silicates in the sequence seems to be limited. Features of less chemical weathering of the loess and paleosol could he indicators for the dry-cold clinlate dominated on the Loess Plateau during the Quaternary.展开更多
文摘The Loess Plateau-Northeastern Tibetan Plateau in China is famous for its deep andcontmuous distributed loess, in which soils (developed from loess) vary gradually with differentbiological climates changing from subhumid to arid, which provide a natural proving ground forstUd}' the coupling of loess-paleosol and climatic changes quantitatively. Thirty-two sections weresampled (collected) for measuring chemical element contents, clay content (and other items) and 60sections were collected for carbonate analysis to establish transfer functions between pedogenesisand climate. Finally, we estimated the paleoclAnate (P/T) in the region with transfer functions,It isrevealed that the variation of paleocldriate reflected by transfer functions accorded closely with theclimatic pattern resulted from recent work. Specifically, it was about 140 ha BP that summermonsoon reached Lanzhou or further, paleosol S1 (equaling to MIS 5 in deep sea records) developedstrongly in a large scale, even touching upon northeanstern Tibetan Plateau. And, the estimated P/Tinformation also indicated the cold and humid period during 50-30 ka BP, mean annual Precipitationwas about 400-500 nun in Angutan recorded by mega-interstadial paleosol Sm.
基金funded by the National Natural Science Foundation of China(41030637)the Science and Technology Project of Baoji City(14SFGG-2)+1 种基金the Fundamental Research Funds for Key Subject Physical Geography of Baoji University of Arts and ScienceShaanxi Province and the Key Library Program of Education Department of Shaanxi Province(15JS008)
文摘Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits （SWDs） was found interbedded in the Holocene Ioess-paleosol sequence at the Guchuanzhen site （GCZ）. These palaeoflood SWDs were studied by field observations and laboratory analyses including concentrations of chemical elements and optically stimulated luminescence （OSL） dating. The results showed that the palaeoflood SWDs were the result of the secondary separations of the surface soil and weathered soil layers during the process of water transport and deposition, and without obvious weathering during soil development. These extraordinary flood events were dated back to 3,200-3,000 a B.P. with the OSL method and checked by archaeological dating of the human remains retrieved from the profile. These extraordinary flood events were therefore considered as regional expression of known climatic events and demonstrated the climatic instability in the Holocene. This result is important for understanding the effects of global climate change on the dynamics of river systems.
基金National Natural Science Foundation of China,No.41271108,No.41471071,No.41371029The Fundamental Research Funds for the Central Universities,No.XDJK2016C091,No.SWU114067
文摘This paper aims to compare the geochemical characteristics of loess-paleosol sequences in the upper reaches of the Hanjiang and Weihe river valleyswhich are located in the semi-humid temperate zone and humid subtropical zonerespectively. The Mituosi（MTS） profile in the upper reaches of the Hanjiang River valley and the Yaohecun（YHC） profile in the Weihe River valley were selected for this comparative research. The stratigraphic characteristicscompositionchemical weathering intensityleaching rates of Ca and Namobility of major elementsand transport features of Na and Fe were analyzed with respect to depth and compared between the two profiles. This study reached the following conclusions.（1） The composition of the loess-paleosol sequences in two regions are quite similar to the average composition of the upper continental crust（UCC）indicating that the loess in the two regions came from multiple sources and was mixed well. Thereforethe loess in the two regions is considered aeolian loess.（2） Compared with the loess-paleosol sequence in the Weihe River valleythe loess-paleosol sequence in the upper reaches of the Hanjiang River valley features a darker color; a higher chemical index of alteration（CIA） value; higher leaching rates of Na and Ca; higher migration ratio（relative to K） of AlSiMgand Na; and lower migration ratio of Fe and Ca. This evidence indicates that the loess-paleosol sequence in the humid subtropical environment experienced stronger chemical weathering intensity than the loess-paleosol sequence in the semi-humid temperate zone.（3） Both the YHC profile and MTS profile record a period of climate deterioration at 6000–5000 a BP. The period punctuated the mid-Holocene Climatic Optimum（8500–3100 a BP） in the study area.
文摘Two-three paleosol layers were formed in the western part of the Northeast Plain. China during Holocene. These paleosol layers interlaid with eolian fine sand layers. Dated by 14C dating. archeology and TL and analyzed by statistics.the formation periods of paleosols are divided from the results. The periods are 11, 000- 7000 5500-4500. 3500- 2800 and 1400- 1000 a B. P. respectively.According to the spore-pollen compositions in more than ten sand dune paleosol profiles, it is discovered th.t there is little spore-pollen in the sand layers and a little spore-pollen in the paleosol layers. The spore-pollen compositions in the paleosols are simple. mainly Artemisia (50% - 70%) and Chenopodiaceae. In the paleosols of 11,000 - 7000 a B. P.. the spore-pollen composition is Artemisia-Rubiaceaechenopodiaceae. The contents of Ephedra pollen in the lower and upper parts of the layer are less than that in the middle part. In the paleosols of 5500- 4500 a B. P.,the spore-pollen composition is Artem isal - Chenopod iaceae - Melilotus. There is some Salix sp. and Betula sp. pollen in the lower part of the layer and some Ephedra pollen in the upper part. In the paleosols of 3500- 2800 a B. P.. the spore-pollen composition is Artemisia Chenopodiaceae - Rubiaceae. There are som e Kochia and Baryaceae. In the paleosols of 1400-1000 a B. P., the spore-pollen composition is also Artemisia-Chjenopod tao eae - Rubiaceae. There is a little pine pollen. The grain size of paleosol is relatively coarse, but still finer than that of eolian sand and becomes coarser from the bottom to the top of the profile. This fact reflects that the weathering environments during the paleosol formation periods were wetter than that during the eolian periods and became dryer from middle to late Holocene.
文摘Based on field investigations,laboratory analyses and 14C dating,this paper discusses the laws of the formation and development of the paleosols in the northeast region of the Qinghai-Xizang Plateau since Late Pleistocene.The authors reconstruct basic conditions of climate,vegetation,soil and natural zones during the three periods in which the paleosols were formed,i.e.the last interglacial of the Late Pleistocene,warm stage of Late Glacial and the Optimum of Holocene.Finally,this paper discusses the relationship between the paleosols and the uplift of the Qinghai-Xizang Plateau.
基金supported by 12th Five-Year Plan Project of State Key Laboratory Of Ore Deposit Geochemistry Chinese Academy of Sciences(SKLODGZY125-08)funds from State Key Laboratory of Palaeobiology and Stratigraphy Chinese Academy of SciencesChinese National Program on Key Basic Research and Development(2007CB411408)
文摘This paper presents a set of bulk geochemical and mineralogical data from a paleoweathering profile located in Zunyi District, Northern Guizhou, China. It was formed at the top of the Hanjiadian Formation of the Lower Silurian. A truncated, argillic, gleyed, kryptic paleospodosol is recognized in the paleoweathering profile. Ratios of immobile elements（Ti/Zr, Ti/Al） and their binary（e.g., Nb vs. Zr/TiO_2 and Th/Sc vs. Zr/Sc）, triangular diagrams（La-Th-Sc, Th-ScZr/10, Zr-Cr-Ga） reflect that the Gaojiayan paleosol is the product of in-situ weathering of gray-green silty mudstone of the underlying Hanjiadian Formation. Mass balance calculations indicate K enrichment and Na enrichment in the upper and lower portions of paleosol, respectively. These findings both are the results of transgression, which brings substantial concentrations of such elements as K, Na, and Sr. In particular, K enrichment is achieved by the illitization of kaolinite. The biological processes of terrestrial vascular plants also enhance K concentration, especially at the top of the paleosol. Na enrichment is a consequence of albitization and/or adsorption by clay minerals through cation exchange. The mass distributions and relative mass changes of rare earth elements（REEs） in the studied profile display characteristics of vertical zonation. Three peaks in total REEs content are observed, indicating two paleoclimatic or paleoenvironmental changes. Mineralogical characteristics indicate that the paleoclimate changed first from warm and humid to cold and dry and later, to dry and lightly warmer. The corresponding soil environment varies from weakly acidic to strongly alkaline and later, to weakly acidic. Mass translocation characteristics of REEs and several transition metals suggest that the Gaojiayan paleosol may have undergone top erosion.
文摘A paleosol horizon is described from the contact of the Sausar Group（w2400 Ma） and its basement（Tirodi Gneiss; 〉2500 Ma） in Central India. Physical evidence of pedogenesis is marked by the development of stress corrosion cracks, soil peds, corestone weathering and nodular rocks. XRD and SEM-EDX data indicate the presence of siderite, ankerite, uraninite, chlorite, alumino-silicate minerals, ilmenite,rutile and magnetite, in addition to quartz, feldspar and mica. The chemical index of alteration, the plagioclase index of alteration, and the chemical index of weathering show an increasing trend from parent rock to the paleosol and indicate a moderate trend of weathering. The A-CN-K plot indicates loss of feldspars, enrichment in Al2O3 and formation of illite. Different major element ratios indicate baseloss through hydrolysis, clay formation, leaching of some elements, and more precipitation with good surface drainage. The paleosol is depleted in HREE in comparison to the parent rock indicating high fluid-rock interaction during weathering. The paleosol samples show flat Ce and Eu anomalies, low SREE, and high（La/Yb）N, indicative of a reducing environment of formation. Reducing condition can also be inferred from the concentration of elements such as V, Co, Cu, Pb, and Zn in the paleosol profile. Although enriched in Fe and Mg, the overall geochemical patterns of the paleosol indicate oxygen deficient conditions in the atmosphere and development by weathering and leaching processes associated with high precipitation and good surface drainage at the time of development of this paleosol during the Archeane Paleoproterozoic transition.
文摘The loess deposits comprise several paleosol layers reflecting alternation of drier and wetter climate during Quaternary. Such a situation occurs in north of Barlad, on The Sohodau＇s Hill. Morphological study of the quarry paleosols from north of Barlad was accomplished based on field observations and macroscopic physic-chemical results. Three levels of paleosols with variable thickness were determined. These three fossils layers are interbedded by four loess deposits. The physical-chimical data provide important information for the paleosol genesis and depositional/climatic environments. The carbon content and C/N ratio indicate the strength of pedogenesis in the Pleistocene and trends of biomass accumulation.
基金part of the interdisciplinary SALVE-research project undertaken by the German Archaeological Institute(DAI)in cooperation with the Heidelberg Academy of Sciences and Humanities(HAW)and the University of Tübingen(www.salve-research.org)Project directors are Florian Seiler(DAI)and Michael Märker(HAW)and it was funded by the Deutsche Forschungsgemeinschaft(German Research Foundation).
文摘The AD 79 eruption of Somma-Vesuvius completely buried the ancient landscape around Pompeii (Italy) to some extent conserving the pre-AD 79 Roman paleosols of the Sarno River plain. To estimate potential post-burial soil developments of these paleosols detailed soil liquid and solid phase analysis were carried out. Firstly, an in-situ soil hydrological monitoring was conducted within a pre-AD 79 paleosol in natural undisturbed stratification. The results show that soil water flow and nutrient transport from the overlying volcanic deposits into the pre-AD 79 paleosol take place. Secondly, to estimate their influence on the paleosol’s mineral soil properties, the solid phase of four pre-AD 79 paleosols and associated modern unburied soils were analysed and compared. By combining the data from the soil liquid and solid phase analysis, potential post-burial changes in the paleosols were estimated. Finally, a rise of the mean groundwater table was determined since AD 79. This distinguishes the Sarno River plain into two different zones of post-burial soil developments: 1) lower altitudes where formerly terrestrial paleosols are now influenced by groundwater dynamics and 2) higher altitudes where the paleosols are still part of the vadose zone and rather influenced by infiltration water or interflow. Thus, the mechanism of potential post-burial soil development being active in the pre-AD 79 paleosols is not uniform for the entire Sarno River plain but strongly depends on the paleotopographic situation.
基金JM acknowledges FRPDF grant for his research from Presidency University,KolkataPPC and PP acknowledges UGC major project grant for carrying out work at the Gwalior basin.
文摘A number of Precambrian sedimentary basins of the Indian subcontinent offer scope for tracking early oxygenation history of atmosphere and hydrosphere.Available studies,though certainly not exhaustive,record signatures of pre-great oxygenation event(GOE)whiffs of atmospheric oxygenation between 3.29 and 3.02 Ga.
文摘34 samples of loess-paleosol from the Luochuan and kifeng sections in the Loess Plateau, north-ern China were separated into sand, silt and clay fractions and analyzed for their mineral composi -tions. The results indicate that there is almost no difference between loess and paleosol in mineralcomposition. Major mineral species are quartz, mica, feIdspar and chlorite, accounhng for about88-92% of the total, other minerals are kandite, smectite, vermiculite and a few heavy minerals. Thecalcite, magnetite and hematite were not taken into consideration because of their removal in the pro-cess of sample preparation. The main difference with respect to the mineral composition of samplescollected from different sections and different stratigraphic leveIs lies in the amount and grain sise ofminerals hosted. Comparisons between the Luochuan section and the kifeng section, between paleosoland loess and between the upper part and the lower part of some paleosol layers show that the for-mers contain less feldspar but more mica and vermiculite and are finer in grain sise, indicahng theco-occurrence of both biochemical weathering process responsible for mineral change and physicalweathering process leading to grain-stie change during the soiI-forming processes. This result favourssuch an explanation of the soi1-forming mechanism that loess deposition and paleosol developmentoccurred synchronously, though the rate of soil formation was greater than that of loess deposition,thus leading to soil development.
文摘The type, grain size and origin of ferrimagnetic minerals separated from red paleosols of Pleistocene Epoch (Q\-2) in eastern China, were studied by using mineral magnetic measurement, X\|ray powder diffraction and electron microscopy. Results showed that the iron oxides in red paleosols were composed of hematite (α\|Fe\-2O\-3), maghemite (γ\|Fe\-2O\-3) and goethite(α\|FeOOH). Mineral magnetic parameters and X\|ray diffraction patterns indicated that maghemite was the dominant remanence carrier in red paleosols, which is characterized by superparamagnetic (SP) and stable single domain (SSD) grains. The variations of magnetic susceptibility (χ), anhysteretic magnetic susceptibility (χ\-\{ARM\}) and saturation isothermal remanent magnetization (SIRM) for red paleosols following heating to various temperatures showed two peak values at 700℃ and 900℃. The spherulitic magnetic particles measuring \{250-1000\}μm in diameter in red paleosols were separated by the magnetic separation method, indicating that these magnetic particles were an assemblage of superparamagnetic and stable single domain ferrimagnetic grains. It is suggested that the ferrimagnetic minerals of red paleosols be a pedogenic ferrimagnetic component under high temperature and high humid conditions in the Pleistocene Epoch (Q\-2). It is concluded that the magnetism characteristics of red paleosols can be used to evaluate the environmental changes of Quaternary in eastern China.
文摘Changes in global climate have a positive effect on the changes in hydrologic cycle, and leave their traces in the cycles of hydrogenic sediments and geomorphic evolutions. It is possible to explain the law of the climate change and tectonic movement in the course of the environmental evolutions during the Quaternary by way of identifying the different cycles and ages of hydrogenic sediments in each geomorphic period. This study is very much
文摘人类起源及演化与地球系统环境演化相互关联的科学研究不仅是传统第四纪研究的关键内容之一,也是当今宜居地球研究的首要问题。文章回顾了黄土高原及邻近地区第四纪地层中发现的重要古人类遗存(包括古人类化石和旧石器)的主要成就,阐述了前人提出的“黄土石器工业”和“黄土地质考古带”研究思路的萌生和发展历程,介绍了学者们运用黄土-古土壤序列对第四纪不同类型沉积物中埋藏的古人类遗存研究的概况。在此基础上,根据前人的大量资料以及笔者自身数十年积累的第一手调查研究数据,提出了一种新的科学思路:针对“全球变化”研究中的薄弱环节,运用独一无二的中国黄土连续序列的“地圈”优势,去寻找“生物圈”古人类活动的连续“序列性”踪迹,研究古气候古环境演化对古人类生存环境的制约及其反馈等重大科学问题。以新的思路和科学问题为宗旨,运用黄土-古土壤序列标准年代框架标尺,以蓝田地区上陈、公王岭、陈家窝、吉家湾-甘峪-刁寨剖面的含石器或古人类化石的26个黄土-古土壤组合旋回(其中包括21个古土壤层和15个黄土层)为基础数据,初步构建了一个年代大约2.12~0.01 Ma B. P.的较高分辨率的古人类古文化演化序列——“黄土-古土壤-古人类遗存序列”框架,期望为人类演化和黄土环境研究拓展新路。
文摘The advantages of thermal methods for mineral-magnetic research of loess/paleosolsequences are illustrated in an introductory overview. When applying thermal methods, magnetiteand maghemite can be distinguished, something which is difficult with field-dependentmeasurements at room temperature. Also, variable low-temperature oxidation that is related toclimate may be quantified. Thirdly, grain-size estimates pertaining to the whole superparamagneticrange can be inferred from LT warming experiments and to a lesser extent from variable chemicalalteration during heating. Application of mineral-magnetic techniques may lead to thedevelopment of quantifiable proxy parameters for paleoclimate.
基金This research was supported by the Chi-nese Academy of Sciences(Grant Nos.KZCX2-SW-118)the National Natural Science Foundation of China(Grant Nos.40373008 and 40121303)the foundation for the Author of National Excellent Doctonl Dissertation of China
文摘The relationship between the carbon isotopic composition of paleosols and paleovegetation on the Loess Plateau is still unclear. One of the main reasons is that we are short of knowledge about the characteristics of the carbon isotopic composition of modern soil in this area. A preliminary investigation of the carbon isotopic compositions of the modern soil and the loess/paleosol sequence on the Loess Plateau shows that the carbon isotopic composition of modern soil is consistent with the distribution of modern plants on the Loess Plateau, where the ecosystem is dominated by a mixture of C4 and C3 plants. Comparing theδ13C values of modern soil and loess-paleosol sequences from the Xunyi profile, we conclude that C3 plants dominated the landscape during loess sediment stages, while C4 plants expanded during paleosol stages.
文摘Major and trace element analyses of the Luochuan loess-paleosol sequence in China were performed in order to understand the cheniical weathering processes occurring on the I.oess Plateau during the last 600 ka. Results reveal that most elements in the loess remain immobile durlng chemical weathering. The typical stable elements are Al, K, Ti, Rb and REE, while the main mobile elements are Ca, Sr, P, Mg and Na. 120ess and paleosol experience the incipient stage of chemical weathering characterized by acid leaching and carbonate dissolution. Alteration of silicates in the sequence seems to be limited. Features of less chemical weathering of the loess and paleosol could he indicators for the dry-cold clinlate dominated on the Loess Plateau during the Quaternary.
