The wood anatomy of corystosperms is fundamentally consistent with that of gymnosperms,yet their growth ring boundaries share anatomical features with extant angiosperms.This transitional morphology strongly supports ...The wood anatomy of corystosperms is fundamentally consistent with that of gymnosperms,yet their growth ring boundaries share anatomical features with extant angiosperms.This transitional morphology strongly supports the interpretation of corystosperms as an evolutionary intermediate between gymnosperms and angiosperms.The first application of X-Ray fluorescence(XRF)chemical analysis to fossil wood taxa of Fengweioxylon yielded the above conclusion.By using growth ring analysis and ecological reconstructions,we suggest that corystosperms were large evergreen trees with leaf retention periods of three to five years.They likely thrived in warm summer environments where prolonged foliage retention provided adaptive benefits.展开更多
Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions...Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.展开更多
Aliphatic and aromatic biomarkers derived from higher land plants,conventional biomarkers,as well as the carbon stable isotope ratios of kerogens in late Eocene source rocks from the western margin of the Xihu Sag are...Aliphatic and aromatic biomarkers derived from higher land plants,conventional biomarkers,as well as the carbon stable isotope ratios of kerogens in late Eocene source rocks from the western margin of the Xihu Sag are presented here.Using these geochemical data,the organic matter source and depositional environment of the source rocks,and the correspondence between aliphatic and aromatic palaeovegetation indicators is evaluated.This allows for a reconstruction of the palaeovegetation and palaeoclimate,and reveals the influence of the organic matter source on thermal maturity proxies.Abnormally abundant aliphatic and aromatic diterpenoids from gymnosperms and trace amounts of oleanane-,ursane-and lupane-type triterpenoids from angiosperms were detected.Various source-related proxies,abundant diterpenoids,and non-hopanoid triterpenoids,indicate that the predominant organic matter source was higher land plants.Detection of microbe-derived biomarkers suggest that abundant microbial activity resulted in an additional source of organic matter input.Palaeovegetation proxies,based on aromatic terpenoids from higher plants,are in agreement with those based on aliphatic terpenoid biomarkers.Collectively,they indicate that gymnosperms,rather than angiosperms,contributed the majority of the organic matter.Palaeovegetation composition indicates that during late Eocene,the region surrounding the Xihu Sag was characterized by a relatively cool climate.Elevated Pr/Ph ratios,along with other biomarker indices,further indicate that the source rocks were deposited in a relatively oxic and sulphate-poor,fluvio-deltaic environment.A comprehensive evaluation of maturity indices demonstrates that samples are relatively immature and remain in the early-oil generation window.Despite this,some alkylnaphthalene-and alkylphenanthrene-based thermal maturity parameters were affected by the generation of 1,2,5-trimethylnaphthalene,1,2,5,6-tetramethylnaphthalene and 1-methylphenanthrene,and organic facies that are related to resins.Additionally,the methyldibenzothiophene ratio could be not applied to assess maturity for low mature samples.These indicate that caution must be exercised when viewing alkylnaphthalene-,alkylphenanthrene-and alkyldibenzothiophene-based thermal maturity parameters.Biomarker distributions suggest the Pinghu Formation could be the source of light oils discovered in the Xihu Sag.展开更多
Since continental sediments （in addition to the marine geological record） offer important means of deciphering environmental changes, the sediments hosted by the successive flows of the continental flood basalt prov...Since continental sediments （in addition to the marine geological record） offer important means of deciphering environmental changes, the sediments hosted by the successive flows of the continental flood basalt provinces of the world should be treasure houses in gathering the palaeoclimatic data. Palaeosols developed on top of basalt flows are potentially ideal for palaeoenvironmental reconstructions because it is easy to determine their protolith geochemistry and also they define a definite time interval. The present paper summarizes the nature of the basalt-hosted palaeosols formed on the flood basalts provinces from different parts of the ~lobe havin~ different ages.展开更多
The Qinghai-Tibet plateau is one of major saline lake regions in China, where saline lakes are widespread and constitute an important object of researches on the palaeoclimatic change in the region. On the basis of co...The Qinghai-Tibet plateau is one of major saline lake regions in China, where saline lakes are widespread and constitute an important object of researches on the palaeoclimatic change in the region. On the basis of comprehensive investigations of the evolution of the lake's surface and sediments on the plateau, the authors have further demonstrated the existence of a pan-lake stage (river and lake flooding stage) on the Qinghai-Tibet plateau during the period of about 40+-28 ka B.P. and analyzed the palaeoclimatic characteristics of the pan-lake period and relationships between the ancient monsoons and the uplift of the plateau since the beginning of the Quaternary.展开更多
Yunnan in southwestern China is renowned for its high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate the past biodiversity throughout the geological time.In this ...Yunnan in southwestern China is renowned for its high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate the past biodiversity throughout the geological time.In this review,we present a summary on plant diversity,floristics and climates in the Cenozoic of Yunnan and document their changes,by compiling published palaeobotanical sources.Our review demonstrates that thus far a total of 386 fossil species of ferns,gymnosperms and angiosperms belonging to 170 genera within 66 families have been reported from the Cenozoic,particularly the Neogene,of Yunnan.Angiosperms display the highest richness represented by 353 species grouped into 155 genera within 60 families,with Fagaceae,Fabaceae,Lauraceae and Juglandaceae being the most diversified.Most of the families and genera recorded as fossils still occur in Yunnan,but seven genera have disappeared,including Berryophyllum,Cedrelospermum,Cedrus,Palaeocarya,Podocarpium,Sequoia and Wataria.The regional extinction of these genera is commonly referred to an aridification of the dry season associated with Asian monsoon development.Floristic analyses indicate that in the late Miocene,Yunnan had three floristic regions:a northern subtropical floristic region in the northeast,a subtropical floristic region in the east,and a tropical floristic region in the southwest.In the late Pliocene,Yunnan saw two kinds of floristic regions:a subalpine floristic region in the northwest,and two subtropical floristic regions separately in the southwest and the eastern center.These floristic concepts are verified by results from our areal type analyses which suggest that in the Miocene southwestern Yunnan supported the most Pantropic elements,while in the Pliocene southwestern Yunnan had abundant Tropical Asia(Indo e Malaysia)type and East Asia and North America disjunct type that were absent from northwestern Yunnan.From the late Miocene to late Pliocene through to the present,floristic composition and vegetation types changed markedly,presumably in response to altitude changes and coeval global cooling.An integration of palaeoclimate data suggests that during the Neogene Yunnan was warmer and wetter than today.Moreover,northern Yunnan witnessed a pronounced temperature decline,while southern Yunnan experienced only moderate temperature changes.Summer precipitation was consistently higher than winter precipitation,suggesting a rainfall seasonality.This summary on palaeoclimates helps us to understand under what conditions plant diversity occurred and evolved in Yunnan throughout the Cenozoic.展开更多
The paper makes some analyses on 11 trace elements in the Milanggouwan stratigraphical section in the Salawusu River valley, which is regarded as a prototype geology-palaeoclimate record since 150 ka BP. The results s...The paper makes some analyses on 11 trace elements in the Milanggouwan stratigraphical section in the Salawusu River valley, which is regarded as a prototype geology-palaeoclimate record since 150 ka BP. The results show that the content and variation of trace elements has experienced remarkably regular changes in the pace with coarse and fine sedimentary cycles of palaeo-aeolian sands to its overlying fluvio-lacustrine facies or/and palaeosols. The trace elements with chemical properties of relatively active (V, Sr, Cu, Ni, As) and relatively stable (P, Pb, Rb, Mn, Nb, Zr) are a manifestation of the corresponding 27 changeable cycles between peak and valley values, appearing a multi-fiuctuational process line of relative gathering and migration since then. The low numerical value distribution of these two types of trace elements in the aeolian sand facies represents erosion and accumulation under wind force during the cold-dry climate. Whereas their enrichments in both fluvio-lacustrine facies and palaeosols are related to the valley’s special low-lying physiognomic position between the Ordos Plateau and the Loess Plateau under the warm and humid climate conditions. The above relatively migrated and gathered change of the trace elements is the result of 27 climatic cycles of cold-dry and warm-humid, which is probably caused by repeated alternations of winter monsoon and summer monsoon in the Mu Us Sandy Land influenced by the climate vicissitudes in northern hemisphere during glacial and interglacial periods since 150 ka BP.展开更多
This paper gives the stable carbon isotopic data in coals from the Late Namurian to Kazanian stages in the Serteng Mt., Xishan and Huainan coalfields of the North China Platform. Its stratigraphic pattern shows that s...This paper gives the stable carbon isotopic data in coals from the Late Namurian to Kazanian stages in the Serteng Mt., Xishan and Huainan coalfields of the North China Platform. Its stratigraphic pattern shows that several isotopic shifts are apparent, and the large δ13C negative shifts (approximately 2.5 to 3.0 %%) occurred during the Stephanian, Artinskian and Kazanian are observed in three Permo-Carboniferous coalfields. Those negative shifts are neither related to the coal rank and coal macerals, nor caused by the variety of peat-forming plants. The general decrease in the δ13C values of the Stephanian, Artinskian and Kazanian coals is consistent with an overall decrease in the δ13C values of ambient atmospheric CO2 and/or a relative increase in atmospheric Pco2 during the coal-forming periods. Therefore the authors postulate that the oxidation of peat, and the δ13C-depleted CO2 flux into the atmosphere during the above stages may have contributed to coeval palaeoclimatic warming by way of the greenhouse effect.展开更多
Since the middle Early Pleistocene (1.20 Ma B.P.), the desert steppe climate and environment have predominated in the Lop Nur area, Xinjiang, characterized by warm humid epochs interrupted by dry cold intervals. The g...Since the middle Early Pleistocene (1.20 Ma B.P.), the desert steppe climate and environment have predominated in the Lop Nur area, Xinjiang, characterized by warm humid epochs interrupted by dry cold intervals. The grain-size and magnetic susceptibility curves record 30 climatic oscillations, each with a ca. 40 ka cycle, in the area since 1.2 Ma B.P., which reflects the controlling effects exerted by the astronomic factor on the environment. The Quaternary sedimentary environment in the Lop Nur gradually changed from a fresh lake through a brackish lake to a saline lake, showing a spiral evolution, and finally it evolved into a playa.展开更多
Based on the sedimentary characteristics study of Holocene borax\|bearing mirabilite beds of Dong Co(lake) two sections, DZ01 and DZ02, in the center of North\|Tibetan Plateau,combined with dating of 14 C, applied the...Based on the sedimentary characteristics study of Holocene borax\|bearing mirabilite beds of Dong Co(lake) two sections, DZ01 and DZ02, in the center of North\|Tibetan Plateau,combined with dating of 14 C, applied theory and method of comparative salinology, it is determined that the palaeoclimate framework of Dong Co during early\|middle Holocene, and reckoned the range of the temperature variation. Furthermore, after completing regional analogue, discovered that the palaeoclimate environment is fully comparative and consistent with the synchronous lake\|water retreating trace of Zhaduixiong spits in Zabuye Lake basin, with palaeoclimate changes recorded by pollen in adjacent Zabuye Lake, with Holocene plaeoclimate environment indicated by drilling\|hole in Bangong Co,with palaeoclimate significance traced by δ 18 O value in Qinghai Lake and Siling Co and with the palaeoclimate framework during the 5th Level Arid (Salinization) Extension Period of Quaternary arid center of Western China.展开更多
The investigation of the fossil floras from the Turgai plateau (central Kazakhstan) contributes to a better understanding of the origin of the temperate Turgai type flora which spread to Kazakhstan and adjacent areas ...The investigation of the fossil floras from the Turgai plateau (central Kazakhstan) contributes to a better understanding of the origin of the temperate Turgai type flora which spread to Kazakhstan and adjacent areas during the Oligocene-Miocene transition. In this paper, we present the results of a carpological and palynological study of the Kumyrtas flora collected from a flora-bearing horizon of the regional coalbearing Zhilanchik suite, dated to the Aquitanian period. Pollen analysis identified 33 taxa, with are dominated by angiosperms (about 73%) and reflect zonal vegetation. The high percentages of Betula (27%) and Pterocarya (7.5%) that were found in this flora allows comparisons with other Aquitanian floras of Kazakhstan. Based on descriptions of fossil fruits and seeds, we determined that 19 taxa were dominant;these taxa had meosphytic herbaceous components, suggesting mostly edaphic local conditions. The incongruence between the carpological and the pollen records suggests a significant taphonomical effect. Quantitative reconstruction of the palaeoclimate based on pollen records supports—and slightly extends—previous findings based on fossil leaf data, but contradicts findings deduced from the carpological record. Plant Functional Type (PFT) classification was used to characterize the vegetation patterns. Pollen records show that about 45% of diversity relates to the arboreal broadleaved deciduous components and ca. 35% to conifers. Fossil fruit and seed data indicate riverine vegetation with a high diversity of aquatic components and shrub stratum.展开更多
A new species, Tsuga nanfengensis sp.nov.（Pinaceae）, is described on the basis of lignified fossil wood from the late Miocene of the Xianfeng Basin, central Yunnan, southwestern China.Detailed observation of the fos...A new species, Tsuga nanfengensis sp.nov.（Pinaceae）, is described on the basis of lignified fossil wood from the late Miocene of the Xianfeng Basin, central Yunnan, southwestern China.Detailed observation of the fossil wood specimens show the following characteristics： distinct growth rings, absence of resin canals, uniseriate bordered pits in the radial wall of tracheids, ray tracheids and piceoid and cupressoid cross-field pits.These features indicate similarities to the wood of extant Tsuga canadensis, T.chinensis, and T.dumosa.According to the fossil record, Tsuga was present in Xundian County during the Miocene.Today Tsuga is drought intolerant, preferring wet conditions with no extant species growing naturally in Xundian County.The presence of Tsuga in the Miocene of Xundian County indicates a humid climate consistent with previous palaeoclimatic reconstructions showing a wetter and probably shorter dry season in the Miocene, relative to the present day.Therefore, the change in the local climate such as increasing aridity through the Miocene might explain the local extinction of Tsuga from central Yunnan.展开更多
Paleoclimate record was revealed in Core MZ01 covering the mid-Holocene in age,located in the mud area of the inner continental shelf of the East China Sea. The ancient environment featured low-energy shallow sea shel...Paleoclimate record was revealed in Core MZ01 covering the mid-Holocene in age,located in the mud area of the inner continental shelf of the East China Sea. The ancient environment featured low-energy shallow sea shelf deposition formed mainly by coastal currents. The results show that temporal variation in geochemistry corresponds with the climate changes inferred from historical record. Relatively low MgO/Al 2 O 3,CaO/K 2 O and high Al 2 O 3 /Na 2 O,K 2 O/Na 2 O,MnO/CaO values reflected a warm and humid climate in general,and vice versa. Therefore,these chemical indices could be applied to identify the variation of palaeoclimate in eastern China. The authors reconstructed the history of mid-Holocene climatic variation of the inner continental shelf of the East China Sea. From 8 300 a BP to 4 200 a BP,the climate was moderately warm and humid. From 4 200 a BP to 2 000 a BP,the climate turned cool and dry,and the regional climate frequently fluctuated in alternation of cool-dry periods(3 700 a BP,2 850 a BP and 2 400 a BP) and warm-wet periods(3 250 a BP and 2 650 a BP) . After 2 000 a BP,the climate of the study area gradually turned warm again,while the Little Ice Age,a cold event centered at around 250 a BP was indicated by those geochemical indices as mentioned above.展开更多
The sedimentary system of Kalimantan has undergone significant development since the Oligocene.Previous research have largely ignored the capacity of the Cretaceous–Eocene sediments to produce hydrocarbons,focusing i...The sedimentary system of Kalimantan has undergone significant development since the Oligocene.Previous research have largely ignored the capacity of the Cretaceous–Eocene sediments to produce hydrocarbons,focusing instead primarily on the Oligocene–Miocene coal as the principal source rocks.Shales and coals from the outcrops in the northern margin of Kalimantan were analyzed with palynological and geochemical methods to characterize the palaeoenvironmental and palaeoecological differences between the Cretaceous–Eocene and the Oligocene–Miocene samples.The high proportion of Cheirolepidoaceae,Schizaeoisporites and Ephedripites in the pollen assemblage from the Cretaceous–Eocene outcrops reflects an arid tropical/subtropical climate.The relatively low abundances of gymnosperm-derived biomarkers including isopimarane,β-phyllocladane,β-kaurane,suggest the gymnosperm features in flora.High C_(27)/C_(29)ααα20R sterane ratios,(C_(19)–C_(29))tricyclic terpanes/C_(30)αβhopane and extremely low oleanane/C_(30)αβhopane,bicadinane T/C_(30)αβhopane,and diterpenoid abundance indicate that there was a dominance of algae relative to higher plants in the organic matter.The gymnosperm-derived biomarkers,including isopimarane,β-phyllocladane,β-kaurane,suggest that palaeovegetation during this period was dominated by gymnosperms.The saline and reducing conditions in the bathyal and abysmal sea,evidenced by rather low Pr/Ph and high Gammarerane index,are beneficial for the preservation of hydrogen-rich organic matter.It is presumed that the Cretaceous–Eocene shales had great hydrocarbon generation potential in the southern South China Sea.During the period of Oligocene to Miocene in the Zengmu Basin and the Baram-Sabah Basin,the climate changed to a dominant humid and warm condition,which is corroborated by abundant pollen of Florschuetzia and Magnastriatites hawardi.Low C_(27)/C_(29)ααα20R sterane ratios,(C_(19)–C_(29))tricyclic terpanes/C_(30)αβhopane,and high oleanane/C_(30)αβhopane,bicadinane T/C_(30)αβhopane suggest that the palaeovegetation was dominated by angiosperms including the mangrove plants.The extremely abundant higher plants provide ample terrigenous organic matter for the formation of coal-measures in delta facies.The low gammacerane index and high Pr/Ph indicate the fresh and sub-oxic water in delta-neriticabysmal faces,which is not beneficial for the accumulation of hydrogen-rich organic matter.Thus,the Oligocene–Miocene marine argillaceous rocks can be potential sources of natural gas.展开更多
The palaeo-mobile dune sands and fluvio-lacustrine facies with palaeosols in Milanggouwan stratigraphic section of the Salawusu River valley situated at the southeast of the Mu Us Desert experienced abundant remarkabl...The palaeo-mobile dune sands and fluvio-lacustrine facies with palaeosols in Milanggouwan stratigraphic section of the Salawusu River valley situated at the southeast of the Mu Us Desert experienced abundant remarkable alternative changes of coarse and fine rhythms in grain-size since 150 ka BP, and the grain-size parameters Mz,σ, Sk, Kg and SC/D also respond to the situation of multi-fluctuational alternations between peak and valley values. Simultaneity the grain-size eigenvalues F5, F16, F25, F50, F75, F84 and F95 are respondingly manifested as greatly cadent jumpiness. Hereby, the Milanggouwan section can be divided into 27 grain-size coarse and fine sedimentary cycles, which can be regarded as a real and integreted record of climate-geological process of desert vicissitude resulted from the alternative evolvement of the ancient winter and summer monsoons of East Asia since 150 ka BP.展开更多
The accurately determining the lake ^14C reservoir age has a crucial significance for climatic reconstruction. In this study, the optically stimulated luminescence （OSL） dating method is employed to date samples fro...The accurately determining the lake ^14C reservoir age has a crucial significance for climatic reconstruction. In this study, the optically stimulated luminescence （OSL） dating method is employed to date samples from highstand lacustrine sediments, palaeoshoreline, fluvial terrace, and the alluvial fan of the Heihai Lake catchment. Accelerator mass spectrometry （AMS） 14C dating was also used to date fossil plants from highstand lacustrine sediments. Based on the calculations of linear regression with OSL against radiocarbon ages for same layers of two sections, the quantitative ^14C reservoir ages were estimated to lie between 3 353 and 3 464 yr during the 1.8 to 2.4 ka, which showed temporal variation. The sources of old carbon are the dissolution of carbonate bedrocks distributed along the Kunlun Mountain. The OSL ages of the different members of the hydatogen sedimentary system at Heihai Lake catchment indicate that a stronger hydrologic condition occurred from 3.0±0.2 to 1.8±0.2 ka, with a maximum lake level of 9 m higher than present. This humid stage was widely recorded in different sediments on the QTP and Chinese Loess Plateau （CLP）, indicating its broad synchronicity across the Asian Summer Monsoon region. The enhanced East Asian Summer Monsoon （EASM） and the Indian Summer Monsoon （ISM） resulted in the increase of moisture availability for the Heihai Lake area during this stage.展开更多
The TMS5e sequence from the Tumen section, at the southern edge of Tengger Desert in the northwestern China, is synchronous with Marine Isotope Stage 5e （MIS5e）. It consists of 16 layers of aeolian dune sands, 11 la...The TMS5e sequence from the Tumen section, at the southern edge of Tengger Desert in the northwestern China, is synchronous with Marine Isotope Stage 5e （MIS5e）. It consists of 16 layers of aeolian dune sands, 11 layers of lacustrine loess-like facies, and 5 layers of lacustrine facies. The results of grain-size analysis shows that the pa- laeo-mobile dune sands, palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands, ranging from 70% to 96%; their silt contents ranged from 4% to 20%, and their clay contents ranged from 1% to 5%; the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form, which is caused by the dominance of the cold, dry East Asian winter monsoon. In contrast, the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands, but have higher silt and clay contents, most of their sand content ranged from 30% to 60%, their silt contents ranged from 35% to 55%, and their clay contents ranged from 6% to 20%. The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm, humid East Asian summer monsoon based on their similarity with modern sediments. The grain-size indicator Mz （mean grain diameter） and the SC/D value in the TMS5e sequence indicate climatic insta- bility at the southern edge of the Tengger Desert during MIS5e, with at least 14 fluctuations between a warm, humid climate and a cold, dry climate, divided into five stages： TMS5e5 （139 kyr to 129.3 kyr B.P.）, TMS5e4 （129.3 kyr to 124 kyr B.P.）, TMS5e3 （124 kyr to 119.5 kyr B.P.）, TMS5e2 （119.5 kyr to 116.5 kyr B.P.）, and TMS5el （116.5 kyr to 113.7 kyr B.P.）. These correspond roughly to MIS5e5, MIS5e4, MIS5e3, MIS5e2, and MIS5el, respectively, in the GRIP ice core data.展开更多
Employing the regression equations relating mean annual runoff to mean annual temperature and mean annual precipitation derived with modern data, palaeorunoff values were calculated from palaeoclimatic information for...Employing the regression equations relating mean annual runoff to mean annual temperature and mean annual precipitation derived with modern data, palaeorunoff values were calculated from palaeoclimatic information for three localities in the eastern part of the North China Plain (37-41°N, 115-120°E) during the last 12 000 years. These results present a general pattern of temporal and spatial variations of the Holocene palaeorunoff occurring in this region. The annual runoff was the highest during 8000-3000 a B.P., the second high during 12 000-8000 a B.P., and the lowest during 3000-0 a B.P. Spatially the annual runoff was the highest at the downstream area of the Luanhe River in the north, the second highest at the area around Beijing in the middle, and the lowest at the area around Xingtai in the southwest. These results were further compared to other palaeohydrological reconstruction achieved by other researchers or with other methods, which usually indicates the similar trend of hydrological changes for this region.展开更多
Information on the palaeoenvironm ent from Late Pleistocene to Holocen e in northwestern Yannan Plateau has been deduced from a study of a 28.81m-long core taken from Napahai Lake.The results from Relative Brightness ...Information on the palaeoenvironm ent from Late Pleistocene to Holocen e in northwestern Yannan Plateau has been deduced from a study of a 28.81m-long core taken from Napahai Lake.The results from Relative Brightness In-dex(RBI )as well as those from the lithological analyses of bulk sediments,total organic carbon and granulometric analy-ses have been used to reconstruct the environmental and climatic evoluti on of the area.The ages were provided by three 14 C datings.The record suggested a climate fluctuation between warm-dry a nd cool-wet from ca.57to 32ka B.P.,which led a shallowing and swamping of the l ake.The water level again increased quickly at ca.32ka B.P.,reached it’ s peak during LGM(Last Glacial Maximum,ca.18-20ka B.P.)and remained relative high until ca.15ka B.P.The high wa-ter level at LGM is attributed to cold-wet conditions.The area experienced an abrupt and unstable climatic ch anges dur-ing the transition period from15to 10ka B.P.with a dominated littoral en vironment.Awarm-dry climate led to the contrac-tion of the lake during the Holocene a nd reed-swamps became dominant.After a minor wet-cool pulse during the L ate Holocene,the modern climate became to be established.展开更多
Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human history periods, this paper reviews the researches and progresses on the development of the sandy deserts in Xinjiang. It p...Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human history periods, this paper reviews the researches and progresses on the development of the sandy deserts in Xinjiang. It pointed out that the features of tectonic structure in Xinjiang had made both the Tarim Basin and the Junggar Basin being influenced greatly by the foehn effects originated from the planetary wind system of westerly, the East Asian ocean-continental monsoon and the topographical mountain-valley winds. The regional patterns of climate and environment since the Quaternary were characterized by the overall persistent drought accompanied by fluctuations in the secondary scale. Formations of aeolian sediments in the basins and at the margins are a potential response to global climate change, particularly the aridification of the Asian hinterland deduced by the uprising of the Tibetan Plateau and its surrounding highlands. For the question about the formation time of the Tak- lamakan Desert, because the research methods, objects and information carriers used in previous studies are different, there are many disputes in the academic circles at present. Evidences from aeolian deposits/rocks at the edge and in the hinterland of these sandy de- serts and their chronological data indicate that an arid climate and land surface aeolian processes have occurred at the edge of the Tarim Basin and its hinterland areas since the Tertiary period. However, the duration time of these processes at mass scale should have begun after the middle Pleistocene and lasted to the Holocene. Occurrence of dune fields in recent 2000 years in the oasis areas should be greatly influenced by human factors.展开更多
基金supported by the National Natural Science Foundation of China(U2544204,42172034,42330208,42288201)the China Geological Survey Project(Grant Nos.DD20243469,DD20221829).
文摘The wood anatomy of corystosperms is fundamentally consistent with that of gymnosperms,yet their growth ring boundaries share anatomical features with extant angiosperms.This transitional morphology strongly supports the interpretation of corystosperms as an evolutionary intermediate between gymnosperms and angiosperms.The first application of X-Ray fluorescence(XRF)chemical analysis to fossil wood taxa of Fengweioxylon yielded the above conclusion.By using growth ring analysis and ecological reconstructions,we suggest that corystosperms were large evergreen trees with leaf retention periods of three to five years.They likely thrived in warm summer environments where prolonged foliage retention provided adaptive benefits.
基金Supported by the Research Project of China National Offshore Oil Corporation(SCKY-2023-HN-3)。
文摘Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.
基金The National Natural Science Foundation of China under contract No.42302189the National Natural Science Foundationof China Joint Fund for Enterprise Innovation and Devel-opment under contract No.U24B6002.
文摘Aliphatic and aromatic biomarkers derived from higher land plants,conventional biomarkers,as well as the carbon stable isotope ratios of kerogens in late Eocene source rocks from the western margin of the Xihu Sag are presented here.Using these geochemical data,the organic matter source and depositional environment of the source rocks,and the correspondence between aliphatic and aromatic palaeovegetation indicators is evaluated.This allows for a reconstruction of the palaeovegetation and palaeoclimate,and reveals the influence of the organic matter source on thermal maturity proxies.Abnormally abundant aliphatic and aromatic diterpenoids from gymnosperms and trace amounts of oleanane-,ursane-and lupane-type triterpenoids from angiosperms were detected.Various source-related proxies,abundant diterpenoids,and non-hopanoid triterpenoids,indicate that the predominant organic matter source was higher land plants.Detection of microbe-derived biomarkers suggest that abundant microbial activity resulted in an additional source of organic matter input.Palaeovegetation proxies,based on aromatic terpenoids from higher plants,are in agreement with those based on aliphatic terpenoid biomarkers.Collectively,they indicate that gymnosperms,rather than angiosperms,contributed the majority of the organic matter.Palaeovegetation composition indicates that during late Eocene,the region surrounding the Xihu Sag was characterized by a relatively cool climate.Elevated Pr/Ph ratios,along with other biomarker indices,further indicate that the source rocks were deposited in a relatively oxic and sulphate-poor,fluvio-deltaic environment.A comprehensive evaluation of maturity indices demonstrates that samples are relatively immature and remain in the early-oil generation window.Despite this,some alkylnaphthalene-and alkylphenanthrene-based thermal maturity parameters were affected by the generation of 1,2,5-trimethylnaphthalene,1,2,5,6-tetramethylnaphthalene and 1-methylphenanthrene,and organic facies that are related to resins.Additionally,the methyldibenzothiophene ratio could be not applied to assess maturity for low mature samples.These indicate that caution must be exercised when viewing alkylnaphthalene-,alkylphenanthrene-and alkyldibenzothiophene-based thermal maturity parameters.Biomarker distributions suggest the Pinghu Formation could be the source of light oils discovered in the Xihu Sag.
文摘Since continental sediments （in addition to the marine geological record） offer important means of deciphering environmental changes, the sediments hosted by the successive flows of the continental flood basalt provinces of the world should be treasure houses in gathering the palaeoclimatic data. Palaeosols developed on top of basalt flows are potentially ideal for palaeoenvironmental reconstructions because it is easy to determine their protolith geochemistry and also they define a definite time interval. The present paper summarizes the nature of the basalt-hosted palaeosols formed on the flood basalts provinces from different parts of the ~lobe havin~ different ages.
文摘The Qinghai-Tibet plateau is one of major saline lake regions in China, where saline lakes are widespread and constitute an important object of researches on the palaeoclimatic change in the region. On the basis of comprehensive investigations of the evolution of the lake's surface and sediments on the plateau, the authors have further demonstrated the existence of a pan-lake stage (river and lake flooding stage) on the Qinghai-Tibet plateau during the period of about 40+-28 ka B.P. and analyzed the palaeoclimatic characteristics of the pan-lake period and relationships between the ancient monsoons and the uplift of the plateau since the beginning of the Quaternary.
基金supported by the National Natural Science Foundation of China (No. U1502231)the Foundation of the State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (No. 163108)the foundation of the Yunnan Key Laboratory for Palaeobiology, Yunnan University (No. 2015DG007-KF01)
文摘Yunnan in southwestern China is renowned for its high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate the past biodiversity throughout the geological time.In this review,we present a summary on plant diversity,floristics and climates in the Cenozoic of Yunnan and document their changes,by compiling published palaeobotanical sources.Our review demonstrates that thus far a total of 386 fossil species of ferns,gymnosperms and angiosperms belonging to 170 genera within 66 families have been reported from the Cenozoic,particularly the Neogene,of Yunnan.Angiosperms display the highest richness represented by 353 species grouped into 155 genera within 60 families,with Fagaceae,Fabaceae,Lauraceae and Juglandaceae being the most diversified.Most of the families and genera recorded as fossils still occur in Yunnan,but seven genera have disappeared,including Berryophyllum,Cedrelospermum,Cedrus,Palaeocarya,Podocarpium,Sequoia and Wataria.The regional extinction of these genera is commonly referred to an aridification of the dry season associated with Asian monsoon development.Floristic analyses indicate that in the late Miocene,Yunnan had three floristic regions:a northern subtropical floristic region in the northeast,a subtropical floristic region in the east,and a tropical floristic region in the southwest.In the late Pliocene,Yunnan saw two kinds of floristic regions:a subalpine floristic region in the northwest,and two subtropical floristic regions separately in the southwest and the eastern center.These floristic concepts are verified by results from our areal type analyses which suggest that in the Miocene southwestern Yunnan supported the most Pantropic elements,while in the Pliocene southwestern Yunnan had abundant Tropical Asia(Indo e Malaysia)type and East Asia and North America disjunct type that were absent from northwestern Yunnan.From the late Miocene to late Pliocene through to the present,floristic composition and vegetation types changed markedly,presumably in response to altitude changes and coeval global cooling.An integration of palaeoclimate data suggests that during the Neogene Yunnan was warmer and wetter than today.Moreover,northern Yunnan witnessed a pronounced temperature decline,while southern Yunnan experienced only moderate temperature changes.Summer precipitation was consistently higher than winter precipitation,suggesting a rainfall seasonality.This summary on palaeoclimates helps us to understand under what conditions plant diversity occurred and evolved in Yunnan throughout the Cenozoic.
基金National Natural Science Foundation of China, No. 49971009State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment, CAS, No. SKLLQG0008+1 种基金National Key Project for Basic Research No. G2000048701
文摘The paper makes some analyses on 11 trace elements in the Milanggouwan stratigraphical section in the Salawusu River valley, which is regarded as a prototype geology-palaeoclimate record since 150 ka BP. The results show that the content and variation of trace elements has experienced remarkably regular changes in the pace with coarse and fine sedimentary cycles of palaeo-aeolian sands to its overlying fluvio-lacustrine facies or/and palaeosols. The trace elements with chemical properties of relatively active (V, Sr, Cu, Ni, As) and relatively stable (P, Pb, Rb, Mn, Nb, Zr) are a manifestation of the corresponding 27 changeable cycles between peak and valley values, appearing a multi-fiuctuational process line of relative gathering and migration since then. The low numerical value distribution of these two types of trace elements in the aeolian sand facies represents erosion and accumulation under wind force during the cold-dry climate. Whereas their enrichments in both fluvio-lacustrine facies and palaeosols are related to the valley’s special low-lying physiognomic position between the Ordos Plateau and the Loess Plateau under the warm and humid climate conditions. The above relatively migrated and gathered change of the trace elements is the result of 27 climatic cycles of cold-dry and warm-humid, which is probably caused by repeated alternations of winter monsoon and summer monsoon in the Mu Us Sandy Land influenced by the climate vicissitudes in northern hemisphere during glacial and interglacial periods since 150 ka BP.
文摘This paper gives the stable carbon isotopic data in coals from the Late Namurian to Kazanian stages in the Serteng Mt., Xishan and Huainan coalfields of the North China Platform. Its stratigraphic pattern shows that several isotopic shifts are apparent, and the large δ13C negative shifts (approximately 2.5 to 3.0 %%) occurred during the Stephanian, Artinskian and Kazanian are observed in three Permo-Carboniferous coalfields. Those negative shifts are neither related to the coal rank and coal macerals, nor caused by the variety of peat-forming plants. The general decrease in the δ13C values of the Stephanian, Artinskian and Kazanian coals is consistent with an overall decrease in the δ13C values of ambient atmospheric CO2 and/or a relative increase in atmospheric Pco2 during the coal-forming periods. Therefore the authors postulate that the oxidation of peat, and the δ13C-depleted CO2 flux into the atmosphere during the above stages may have contributed to coeval palaeoclimatic warming by way of the greenhouse effect.
基金This research was supported by Xinjiang Project 305 “Development and Utilization of Potash Resources of the Lop Nur,Xinjiang”(95-915-08-05).
文摘Since the middle Early Pleistocene (1.20 Ma B.P.), the desert steppe climate and environment have predominated in the Lop Nur area, Xinjiang, characterized by warm humid epochs interrupted by dry cold intervals. The grain-size and magnetic susceptibility curves record 30 climatic oscillations, each with a ca. 40 ka cycle, in the area since 1.2 Ma B.P., which reflects the controlling effects exerted by the astronomic factor on the environment. The Quaternary sedimentary environment in the Lop Nur gradually changed from a fresh lake through a brackish lake to a saline lake, showing a spiral evolution, and finally it evolved into a playa.
文摘Based on the sedimentary characteristics study of Holocene borax\|bearing mirabilite beds of Dong Co(lake) two sections, DZ01 and DZ02, in the center of North\|Tibetan Plateau,combined with dating of 14 C, applied theory and method of comparative salinology, it is determined that the palaeoclimate framework of Dong Co during early\|middle Holocene, and reckoned the range of the temperature variation. Furthermore, after completing regional analogue, discovered that the palaeoclimate environment is fully comparative and consistent with the synchronous lake\|water retreating trace of Zhaduixiong spits in Zabuye Lake basin, with palaeoclimate changes recorded by pollen in adjacent Zabuye Lake, with Holocene plaeoclimate environment indicated by drilling\|hole in Bangong Co,with palaeoclimate significance traced by δ 18 O value in Qinghai Lake and Siling Co and with the palaeoclimate framework during the 5th Level Arid (Salinization) Extension Period of Quaternary arid center of Western China.
基金project of the Botanical Institute of the Russian Academy of Sciences (Saint Petersburg, Russia) NAAAA-A19-119021190031-8Our study was funded by RFBR and NSFC according to the research project No 19-55-53010+1 种基金Pioneer Hundred Talents Program of the Chinese Academy of Sciences No. 419 115 30 105 to Y.W. Xingthe Chinese Academy of Sciences 135 program (No. 2017XTBG- F01)
文摘The investigation of the fossil floras from the Turgai plateau (central Kazakhstan) contributes to a better understanding of the origin of the temperate Turgai type flora which spread to Kazakhstan and adjacent areas during the Oligocene-Miocene transition. In this paper, we present the results of a carpological and palynological study of the Kumyrtas flora collected from a flora-bearing horizon of the regional coalbearing Zhilanchik suite, dated to the Aquitanian period. Pollen analysis identified 33 taxa, with are dominated by angiosperms (about 73%) and reflect zonal vegetation. The high percentages of Betula (27%) and Pterocarya (7.5%) that were found in this flora allows comparisons with other Aquitanian floras of Kazakhstan. Based on descriptions of fossil fruits and seeds, we determined that 19 taxa were dominant;these taxa had meosphytic herbaceous components, suggesting mostly edaphic local conditions. The incongruence between the carpological and the pollen records suggests a significant taphonomical effect. Quantitative reconstruction of the palaeoclimate based on pollen records supports—and slightly extends—previous findings based on fossil leaf data, but contradicts findings deduced from the carpological record. Plant Functional Type (PFT) classification was used to characterize the vegetation patterns. Pollen records show that about 45% of diversity relates to the arboreal broadleaved deciduous components and ca. 35% to conifers. Fossil fruit and seed data indicate riverine vegetation with a high diversity of aquatic components and shrub stratum.
基金supported by a 973 program of the Ministry of Science and Technology (Mo ST) of China (20120CB821900)the National Natural Science Foundation of China (grants 41272007, 41030212, 31350110504)+2 种基金the Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botanythe Chinese Academy of Sciences (KLBB 201201 and 2013Y1SA002)part of the NECLIME (Neogene Climate of Eurasia) network
文摘A new species, Tsuga nanfengensis sp.nov.（Pinaceae）, is described on the basis of lignified fossil wood from the late Miocene of the Xianfeng Basin, central Yunnan, southwestern China.Detailed observation of the fossil wood specimens show the following characteristics： distinct growth rings, absence of resin canals, uniseriate bordered pits in the radial wall of tracheids, ray tracheids and piceoid and cupressoid cross-field pits.These features indicate similarities to the wood of extant Tsuga canadensis, T.chinensis, and T.dumosa.According to the fossil record, Tsuga was present in Xundian County during the Miocene.Today Tsuga is drought intolerant, preferring wet conditions with no extant species growing naturally in Xundian County.The presence of Tsuga in the Miocene of Xundian County indicates a humid climate consistent with previous palaeoclimatic reconstructions showing a wetter and probably shorter dry season in the Miocene, relative to the present day.Therefore, the change in the local climate such as increasing aridity through the Miocene might explain the local extinction of Tsuga from central Yunnan.
基金Coastal Investigation and Research Project of China under contract Nos 908-01-CJ12 and 908-ZC-I-05Marine Public Welfare Research Project under contract No. 200805063China Postdoctoral Science Foundation under contract No. 20100481304
文摘Paleoclimate record was revealed in Core MZ01 covering the mid-Holocene in age,located in the mud area of the inner continental shelf of the East China Sea. The ancient environment featured low-energy shallow sea shelf deposition formed mainly by coastal currents. The results show that temporal variation in geochemistry corresponds with the climate changes inferred from historical record. Relatively low MgO/Al 2 O 3,CaO/K 2 O and high Al 2 O 3 /Na 2 O,K 2 O/Na 2 O,MnO/CaO values reflected a warm and humid climate in general,and vice versa. Therefore,these chemical indices could be applied to identify the variation of palaeoclimate in eastern China. The authors reconstructed the history of mid-Holocene climatic variation of the inner continental shelf of the East China Sea. From 8 300 a BP to 4 200 a BP,the climate was moderately warm and humid. From 4 200 a BP to 2 000 a BP,the climate turned cool and dry,and the regional climate frequently fluctuated in alternation of cool-dry periods(3 700 a BP,2 850 a BP and 2 400 a BP) and warm-wet periods(3 250 a BP and 2 650 a BP) . After 2 000 a BP,the climate of the study area gradually turned warm again,while the Little Ice Age,a cold event centered at around 250 a BP was indicated by those geochemical indices as mentioned above.
基金The National Science and Technology Major Project under contract No.2016ZX05026-004。
文摘The sedimentary system of Kalimantan has undergone significant development since the Oligocene.Previous research have largely ignored the capacity of the Cretaceous–Eocene sediments to produce hydrocarbons,focusing instead primarily on the Oligocene–Miocene coal as the principal source rocks.Shales and coals from the outcrops in the northern margin of Kalimantan were analyzed with palynological and geochemical methods to characterize the palaeoenvironmental and palaeoecological differences between the Cretaceous–Eocene and the Oligocene–Miocene samples.The high proportion of Cheirolepidoaceae,Schizaeoisporites and Ephedripites in the pollen assemblage from the Cretaceous–Eocene outcrops reflects an arid tropical/subtropical climate.The relatively low abundances of gymnosperm-derived biomarkers including isopimarane,β-phyllocladane,β-kaurane,suggest the gymnosperm features in flora.High C_(27)/C_(29)ααα20R sterane ratios,(C_(19)–C_(29))tricyclic terpanes/C_(30)αβhopane and extremely low oleanane/C_(30)αβhopane,bicadinane T/C_(30)αβhopane,and diterpenoid abundance indicate that there was a dominance of algae relative to higher plants in the organic matter.The gymnosperm-derived biomarkers,including isopimarane,β-phyllocladane,β-kaurane,suggest that palaeovegetation during this period was dominated by gymnosperms.The saline and reducing conditions in the bathyal and abysmal sea,evidenced by rather low Pr/Ph and high Gammarerane index,are beneficial for the preservation of hydrogen-rich organic matter.It is presumed that the Cretaceous–Eocene shales had great hydrocarbon generation potential in the southern South China Sea.During the period of Oligocene to Miocene in the Zengmu Basin and the Baram-Sabah Basin,the climate changed to a dominant humid and warm condition,which is corroborated by abundant pollen of Florschuetzia and Magnastriatites hawardi.Low C_(27)/C_(29)ααα20R sterane ratios,(C_(19)–C_(29))tricyclic terpanes/C_(30)αβhopane,and high oleanane/C_(30)αβhopane,bicadinane T/C_(30)αβhopane suggest that the palaeovegetation was dominated by angiosperms including the mangrove plants.The extremely abundant higher plants provide ample terrigenous organic matter for the formation of coal-measures in delta facies.The low gammacerane index and high Pr/Ph indicate the fresh and sub-oxic water in delta-neriticabysmal faces,which is not beneficial for the accumulation of hydrogen-rich organic matter.Thus,the Oligocene–Miocene marine argillaceous rocks can be potential sources of natural gas.
基金National Natural Science Foundation of China No. 49971009+5 种基金 State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment CAS No. SKLLQG0008 The Key National Project for Basic Research No. G2000048701
文摘The palaeo-mobile dune sands and fluvio-lacustrine facies with palaeosols in Milanggouwan stratigraphic section of the Salawusu River valley situated at the southeast of the Mu Us Desert experienced abundant remarkable alternative changes of coarse and fine rhythms in grain-size since 150 ka BP, and the grain-size parameters Mz,σ, Sk, Kg and SC/D also respond to the situation of multi-fluctuational alternations between peak and valley values. Simultaneity the grain-size eigenvalues F5, F16, F25, F50, F75, F84 and F95 are respondingly manifested as greatly cadent jumpiness. Hereby, the Milanggouwan section can be divided into 27 grain-size coarse and fine sedimentary cycles, which can be regarded as a real and integreted record of climate-geological process of desert vicissitude resulted from the alternative evolvement of the ancient winter and summer monsoons of East Asia since 150 ka BP.
基金supported by the National Natural Science Foundation of China(No.41401008)West Light Foundation of the Chinese Academy of Sciences(No.Y412021005)+1 种基金Natural Science Foundation of Qinghai Province(No.2016-ZJ-926Q)the instrument function development program of the Chinese Academy of Sciences(No.Y410041013)
文摘The accurately determining the lake ^14C reservoir age has a crucial significance for climatic reconstruction. In this study, the optically stimulated luminescence （OSL） dating method is employed to date samples from highstand lacustrine sediments, palaeoshoreline, fluvial terrace, and the alluvial fan of the Heihai Lake catchment. Accelerator mass spectrometry （AMS） 14C dating was also used to date fossil plants from highstand lacustrine sediments. Based on the calculations of linear regression with OSL against radiocarbon ages for same layers of two sections, the quantitative ^14C reservoir ages were estimated to lie between 3 353 and 3 464 yr during the 1.8 to 2.4 ka, which showed temporal variation. The sources of old carbon are the dissolution of carbonate bedrocks distributed along the Kunlun Mountain. The OSL ages of the different members of the hydatogen sedimentary system at Heihai Lake catchment indicate that a stronger hydrologic condition occurred from 3.0±0.2 to 1.8±0.2 ka, with a maximum lake level of 9 m higher than present. This humid stage was widely recorded in different sediments on the QTP and Chinese Loess Plateau （CLP）, indicating its broad synchronicity across the Asian Summer Monsoon region. The enhanced East Asian Summer Monsoon （EASM） and the Indian Summer Monsoon （ISM） resulted in the increase of moisture availability for the Heihai Lake area during this stage.
基金Foundation item:Under the auspices of State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences (No.SKLLQG0901,SKLLQG1013)Research Fund for the Doctoral Program of Higher Education of China (No.20094407120004)
文摘The TMS5e sequence from the Tumen section, at the southern edge of Tengger Desert in the northwestern China, is synchronous with Marine Isotope Stage 5e （MIS5e）. It consists of 16 layers of aeolian dune sands, 11 layers of lacustrine loess-like facies, and 5 layers of lacustrine facies. The results of grain-size analysis shows that the pa- laeo-mobile dune sands, palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands, ranging from 70% to 96%; their silt contents ranged from 4% to 20%, and their clay contents ranged from 1% to 5%; the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form, which is caused by the dominance of the cold, dry East Asian winter monsoon. In contrast, the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands, but have higher silt and clay contents, most of their sand content ranged from 30% to 60%, their silt contents ranged from 35% to 55%, and their clay contents ranged from 6% to 20%. The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm, humid East Asian summer monsoon based on their similarity with modern sediments. The grain-size indicator Mz （mean grain diameter） and the SC/D value in the TMS5e sequence indicate climatic insta- bility at the southern edge of the Tengger Desert during MIS5e, with at least 14 fluctuations between a warm, humid climate and a cold, dry climate, divided into five stages： TMS5e5 （139 kyr to 129.3 kyr B.P.）, TMS5e4 （129.3 kyr to 124 kyr B.P.）, TMS5e3 （124 kyr to 119.5 kyr B.P.）, TMS5e2 （119.5 kyr to 116.5 kyr B.P.）, and TMS5el （116.5 kyr to 113.7 kyr B.P.）. These correspond roughly to MIS5e5, MIS5e4, MIS5e3, MIS5e2, and MIS5el, respectively, in the GRIP ice core data.
文摘Employing the regression equations relating mean annual runoff to mean annual temperature and mean annual precipitation derived with modern data, palaeorunoff values were calculated from palaeoclimatic information for three localities in the eastern part of the North China Plain (37-41°N, 115-120°E) during the last 12 000 years. These results present a general pattern of temporal and spatial variations of the Holocene palaeorunoff occurring in this region. The annual runoff was the highest during 8000-3000 a B.P., the second high during 12 000-8000 a B.P., and the lowest during 3000-0 a B.P. Spatially the annual runoff was the highest at the downstream area of the Luanhe River in the north, the second highest at the area around Beijing in the middle, and the lowest at the area around Xingtai in the southwest. These results were further compared to other palaeohydrological reconstruction achieved by other researchers or with other methods, which usually indicates the similar trend of hydrological changes for this region.
文摘Information on the palaeoenvironm ent from Late Pleistocene to Holocen e in northwestern Yannan Plateau has been deduced from a study of a 28.81m-long core taken from Napahai Lake.The results from Relative Brightness In-dex(RBI )as well as those from the lithological analyses of bulk sediments,total organic carbon and granulometric analy-ses have been used to reconstruct the environmental and climatic evoluti on of the area.The ages were provided by three 14 C datings.The record suggested a climate fluctuation between warm-dry a nd cool-wet from ca.57to 32ka B.P.,which led a shallowing and swamping of the l ake.The water level again increased quickly at ca.32ka B.P.,reached it’ s peak during LGM(Last Glacial Maximum,ca.18-20ka B.P.)and remained relative high until ca.15ka B.P.The high wa-ter level at LGM is attributed to cold-wet conditions.The area experienced an abrupt and unstable climatic ch anges dur-ing the transition period from15to 10ka B.P.with a dominated littoral en vironment.Awarm-dry climate led to the contrac-tion of the lake during the Holocene a nd reed-swamps became dominant.After a minor wet-cool pulse during the L ate Holocene,the modern climate became to be established.
基金National Basic Research Program of China(973 Program),No.2009CB421305National Natural Science Foundation of China,No.41371060,No.41271049
文摘Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human history periods, this paper reviews the researches and progresses on the development of the sandy deserts in Xinjiang. It pointed out that the features of tectonic structure in Xinjiang had made both the Tarim Basin and the Junggar Basin being influenced greatly by the foehn effects originated from the planetary wind system of westerly, the East Asian ocean-continental monsoon and the topographical mountain-valley winds. The regional patterns of climate and environment since the Quaternary were characterized by the overall persistent drought accompanied by fluctuations in the secondary scale. Formations of aeolian sediments in the basins and at the margins are a potential response to global climate change, particularly the aridification of the Asian hinterland deduced by the uprising of the Tibetan Plateau and its surrounding highlands. For the question about the formation time of the Tak- lamakan Desert, because the research methods, objects and information carriers used in previous studies are different, there are many disputes in the academic circles at present. Evidences from aeolian deposits/rocks at the edge and in the hinterland of these sandy de- serts and their chronological data indicate that an arid climate and land surface aeolian processes have occurred at the edge of the Tarim Basin and its hinterland areas since the Tertiary period. However, the duration time of these processes at mass scale should have begun after the middle Pleistocene and lasted to the Holocene. Occurrence of dune fields in recent 2000 years in the oasis areas should be greatly influenced by human factors.
