In addition to its well-known fossils,the Upper Miocene Baogeda Ula Formation is coupled with multiple basaltic lava flows,creating an ideal setting for studying its depositional history,geochronology,and associated v...In addition to its well-known fossils,the Upper Miocene Baogeda Ula Formation is coupled with multiple basaltic lava flows,creating an ideal setting for studying its depositional history,geochronology,and associated vertebrate fossils.This paper,in honor of Prof.Qiu Zhanxiang for his widely admired emphasis on the geological contexts of vertebrate fossils,attempts to synthesize known contact relationships,existing K-Ar dates,and capping basalt elevations to reframe our concept of the lithostratigraphy,magnetostratigraphy,and lateral distribution of the Baogeda Ula Formation.Within this new framework,the Baogeda Ula Formation is defined by unconformable contact with the underlying Tunggur Formation at the lower boundary and a capping basalt at the upper boundary.In many sections,two or three layers of basalts are interbedded within sedimentary strata,with the capping basalts typically belonging to the top two basalts.The newly defined Baogeda Ula Formation includes a lower member as exemplified by Halajin Hushu section and Ulan Hushuyin Nur section,and an upper member at Baogeda Ula section.This expanded concept of the Baogeda Ula Formation includes two major faunas,i.e.,the Bahean Halajin Hushu Fauna and Baodean Baogeda Ula Fauna,both falling within the Upper Miocene.We also describe rare fossil skunks(Promephitis)found in recent years that support the age assessments presented herein.展开更多
Our purpose in this paper is to describe the hamster-like rodents(Cricetidae)from a Late Miocene age site in Linxia Basin,Gansu Province,and discuss their significance for the changing ecology of central Asia.The micr...Our purpose in this paper is to describe the hamster-like rodents(Cricetidae)from a Late Miocene age site in Linxia Basin,Gansu Province,and discuss their significance for the changing ecology of central Asia.The micromammal site known as Yihachi was introduced previously(Qiu et al.,2023;Qiu and Li,2023),when its squirrels were discussed in some detail.We take this opportunity to describe the more abundant cricetids.There are four genera,common Nannocricetus and Sinocricetus plus the less abundant living Mesocricetus.A few specimens represent the high-crowned and lophodont Rhinocerodon.The cricetids and other faunal elements indicate an early Late Miocene age,and the pattern of occurrence of the hamster species is consistent with a picture of a changing paleoenvironment due to increasing effects of the East Asia monsoon system.After the disappearance of older and archaic genera,Yihachi represents growing endemism in the Late Miocene of northern China due to increasing seasonal rain and the declining average temperature.展开更多
Dikes are widely distributed in volcanic outcrops and volcanic basins around the world.The pores and fractures in these dikes control the fluid-rock interactions and fluid flow.The quantitative reservoir characteristi...Dikes are widely distributed in volcanic outcrops and volcanic basins around the world.The pores and fractures in these dikes control the fluid-rock interactions and fluid flow.The quantitative reservoir characteristics of dikes with primary vesicles remain unclear.In this manuscript,the Miocene hypabyssal dikes in Lyttelton Volcano,Christchurch,New Zealand,are taken as an example.The porosity content,porosity,permeability,and reservoir controlling factors are analyzed through field outcrop surveys,porosity-permeability testing,nuclear magnetic resonance(NMR)testing,X-ray-computed tomography(X-CT)scanning,and permeability calculations.The results show that the types of reservoir spaces in the hypabyssal dikes in Lyttelton Volcano are mainly vesicles,followed by cooling and shrinkage fractures(especially columnar joints).They are a pore-fracture type reservoir.There were two types of vesicles,namely,pipe-like-elliptical directionally oriented vesicles with large diameters and discrete circular vesicles with small diameters.The surface porosity of the former was 58.4%–96.0%,with a geometric mean of 78.9%.The columnar joints can be classified into regular and irregular joints.The irregular joints have a higher fracture intensity.The geometric means of the porosity and permeability of the joints are 22.34%and 0.09×10^(-15)m^(2),respectively.The shapes of the NMR T_(2)spectra are bimodal,trimodal,and unimodal in descending order of abundance.This means that the pore diameter is large.The X-CT results indicate that there are four types of pore-throat connectivity modes:macro-pores and macro-throats,macro-pores and micro-throats,micro-pores and micro-throats,and micro-pores and macrothroats.The columnar joints are the main cause of the high permeability of the dikes,and the side amount and side length of the columnar joints control the dikes'permeability.The pores can be connected by the columnar joints,and their connectivity is controlled by the side amount,side length,and side azimuth of the columnar joint.The initial connectivity ratio of the vesicles in the dikes in Lyttelton Volcano was up to 47.6%based on the surface porosity.In conclusion,the shallow dikes with primary pores and fractures have a good reservoir quality and fluid migration capacity,and fluid flow studies of volcanic strata should pay attention to the important influence of the primary porosity and permeability of dikes.展开更多
The Series Barbini(subfamily Cyprininae sensu lato)is the most species-rich group within the family Cyprinidae,primarily confined to warm regions of southern Eurasia and Africa.The distribution patterns and evolutiona...The Series Barbini(subfamily Cyprininae sensu lato)is the most species-rich group within the family Cyprinidae,primarily confined to warm regions of southern Eurasia and Africa.The distribution patterns and evolutionary history of Chinese cyprinins have been effectively shaped by the Cenozoic uplift of the Qinghai-Tibet Plateau and the evolution of the Asian monsoon.Here,we describe two new fossil fishes from the early and middle Miocene of the Lunpola Basin in central Qinghai-Tibet Plateau,China,preserving the ethmoid and the rear of the occipital regions of the neurocranium,infraorbitals,hyopalatine arch,abdominal vertebrae,and some dorsal-fin pterygiophores and unbranched fin rays.Through detailed morphological comparisons,these fossils show definite affinities to Cyprinidae according to the morphology of the neurocranium,vertebral column,and dorsal fin rays;and one of which is classified into the Series Barbini,while the other can only be assigned to the Cyprinidae family level.These findings reveal that the hinterland of the plateau of the early Neogene should have hosted cyprinin fishes of greater diversity than today.This also indicates a warm-temperate paleoclimate suitable for their survival during that period,consistent with the paleoenvironmental and paleoclimatical conditions reconstructed from the contemporaneous mammalian fossil and palynological evidences.展开更多
The micromammal fossils collected from the Shangzhuang Formation of the Linxia Basin,Gansu,are described here.The assemblage consists of 16 species of 13 genera belonging to 7 families,including one new species and on...The micromammal fossils collected from the Shangzhuang Formation of the Linxia Basin,Gansu,are described here.The assemblage consists of 16 species of 13 genera belonging to 7 families,including one new species and one taxon previously unknown from China.Among them 5 genera are Oligocene holdovers and 11 genera/species are known to make their first appearances in Early Miocene,indicating an Early Miocene age for the Gucheng Fauna.The absence of Oligocene survivors such as Tataromys,Yindirtemys,Eucricetodon and Tachyoryctoides,which usually occur in the Xiejian age of Early Miocene,and the presence of newcomers Protalactaga,Megacricetodon and Gobicricetodon,that made their first appearance only in the Shanwangian age of late Early Miocene,suggest that the Gucheng Fauna is of a later age of Early Miocene.The new species,Sinolagomys guchengensis,showing more derived morphology than in S.ulunguensis,seems to support an assessment of the fauna in Shanwangian age.Thus,the Gucheng Fauna may belong to late Early Miocene Shanwangian,partially equivalent to MN 3/4 of the European land mammal zonation.Ecological analysis of the fauna indicates that the palaeoecological condition of the Gucheng area might still be a predominantly arid shrub-steppe in late Early Miocene.展开更多
The Govanda Formation was deposited during the Miocene in the intermontane areas between the Zagros suture and imbricate zones.The Govanda Formation was studied in the Sherwan Mazin area within Mergasor district,Erbil...The Govanda Formation was deposited during the Miocene in the intermontane areas between the Zagros suture and imbricate zones.The Govanda Formation was studied in the Sherwan Mazin area within Mergasor district,Erbil Governorate to identify the lithostratigraphy and microfacies analysis in order to determine the depositional environment of the formation.The formation in the studied section is 116 m thick and mainly consists of reddish-brown,hard,thickbedded,chert-bearing conglomerate,pinkish shale and yellowish-grey,thick-bedded,detrital,fossiliferous limestone.The formation is unconformably underlain by the Upper Cretaceous Tanjero Formation and conformably overlain by the Merga Red Beds series.Four different lithostratigraphic units were identified,based on field observation and petrographic analysis,including a basal conglomerate unit(A),a shale unit(B),a well-bedded limestone unit(C)and a thick and massively-bedded limestone unit(D).The presence of a thick conglomerate bed at the base of the formation indicates a large unconformity that lasted nearly 40 million years.Based on detailed microfacies analysis of carbonate rocks,five main microfacies and 15 submicrofacies are recognized.The main microfacies types include mudstone,wackestone,packstone,grainstone and boundstone microfacies.Based on the microfacies types the depositional environment are defined as open lagoon,reef,fore-reef and back-reef environments of normal to saline,nutrient rich water.展开更多
The Zhujiang River Mouth Basin,a primary depocenter for terrigenous sediments in the western Pacific,presents a semienclosed tectonic setting with limited exchange with the open ocean.This unique feature enables syste...The Zhujiang River Mouth Basin,a primary depocenter for terrigenous sediments in the western Pacific,presents a semienclosed tectonic setting with limited exchange with the open ocean.This unique feature enables systematic linkages among sedimentary processes,climate change,regional sea-level fluctuations,and tectonic events.To explore these linkages,this study focuses on Well PY35 in the Baiyun Sag of the Zhujiang River Mouth Basin.By integrating microfossil analysis with Milankovitch cycle analysis of well log data,an astronomical time scale(ATS)(17.54-7.80 Ma)and a high-resolution stratigraphic framework were established,allowing for the calculation of sedimentation rates across different hierarchical sequences and time intervals.The results indicate that between 17.54 Ma and 7.80 Ma,the sedimentation rate initially increased and then decreased,ranging from 6.1 cm/ka to 45.7 cm/ka,with an average rate of 22.2 cm/ka.During the Middle Miocene Climatic Optimum(MMCO),sedimentation rates were moderate and exhibited an increasing trend,largely driven by increased sediment input due to enhanced weathering from rising temperatures and by expanded accommodation space resulting from tectonic subsidence.Meanwhile,the Middle Miocene Climate Transition(MMCT)was marked by a notable rise in sedimentation rates,consistent with a major sea-level fall due to global cooling,which promoted the direct seaward progradation of marginal sediments.The Late Middle Miocene to Late Miocene had the lowest sedimentation rates,which can be attributed to reduced weathering under cold and arid conditions,along with a sea-level rise induced by regional tectonics.The short-term increase in the sedimentation rate observed at 10.4 Ma may have been driven by sea-level fluctuations.This study provides both theoretical and empirical support for understanding the influence of abrupt climate changes on sedimentary processes.展开更多
The temporal and spatial evolution of the Ailao Shan-Red River(ASRR)fault zone,which serves as an important accommodation zone for the extrusion and escape of the Southeastern Tibetan Plateau,is crucial for analyzing ...The temporal and spatial evolution of the Ailao Shan-Red River(ASRR)fault zone,which serves as an important accommodation zone for the extrusion and escape of the Southeastern Tibetan Plateau,is crucial for analyzing the uplift and growth of the plateau.Based on the petrology and apatite fission track analysis,the tectonic history and active pattern of the ASRR fault zone since the middle Miocene are determined in this study.The ASRR fault zone exhibits 12-8Ma and 8-4 Ma rapid cooling phases since the middle Miocene.The 12-8 Ma and 8-4 Ma cooling may imply that the dextral movement of the ASRR fault zone presents a migration trend from northwest to southeast,accompanied by the weakening of the activity intensity,which is directly related to deformation processes,including extrusion boundary migration and active tectonic movements of the southeastern Tibetan Plateau,since the middle-late Miocene.展开更多
Late Miocene woods were investigated from the Luhe Basin in Chuxiong Borough, central Yunnan, China. The calcified woods preserved in the Shigucun member of the Shihuiba Formation, are represented by fallen logs and s...Late Miocene woods were investigated from the Luhe Basin in Chuxiong Borough, central Yunnan, China. The calcified woods preserved in the Shigucun member of the Shihuiba Formation, are represented by fallen logs and stumps. Two species of fossil wood, Taxodioxylon cryptomeripsoides Schonfeld 1953 and T. cunninghamioides Watari 1948, are described. Their anatomical structure shows striking similarities to the woods of Cryptomeria and Cunninghamia respectively. That the two fossil woods are classed in the Taxodiaceae suggest a subtropical, humid, and warm environment in Lithe during Late Miocene. They compare favorably to other fossil specimens and species reported from localities ranging from Cretaceous to Pliocene. This is the first record of the presence of the species T. cryptomeripsoides and T. cunninghamioides in late Miocene of Yunnan.展开更多
Some Miocene ratite eggshell fragments from Gashunyinadege (about 17.5 Ma) and Baogedawula (7.11 ± 0.48 Ma), Inner Mongolia, China, are described. The outer surfaces of eggshell fragments from Gashunyinadege are ...Some Miocene ratite eggshell fragments from Gashunyinadege (about 17.5 Ma) and Baogedawula (7.11 ± 0.48 Ma), Inner Mongolia, China, are described. The outer surfaces of eggshell fragments from Gashunyinadege are smooth with a sting pore pattern, while their entire thickness is around 2.12 mm. In a cross-sectional view, the surface crystal layer is very thin and the ratio of cone layer to the those from Gashunyinadege, but seem much thinner and have a lower pore density. Both characteristics fit aepyornithid-type eggshells, implying that the distribution of aepyornithid-type eggshells can be extended to East Asia. The sediments at Gashunyinadege date to approximately 17.5 Ma, implying that the specimens from this locality are relatively early examples of aepyornithid-type eggshells. Aepyornithidtype eggshells seem to have appeared in Eurasia much earlier than struthionid-type eggshells. The faunal compositions in the two localities reflect gradual drying of the Mongolian plateau during the Miocene. A reduction in the number of pores 10 Ma ago, probably occurred in response to this drying process.展开更多
Numerous leaf compressions of Glyptostrobus europaeus (Brongn.) Ung. (Taxodiaceae) are found in Aquitanian (Lower Miocene) lignified clay localities Bolattam and Akzhar in the Southern Turgay, on the right bank of the...Numerous leaf compressions of Glyptostrobus europaeus (Brongn.) Ung. (Taxodiaceae) are found in Aquitanian (Lower Miocene) lignified clay localities Bolattam and Akzhar in the Southern Turgay, on the right bank of the Dulygaly-Zhilanshik river (Central Kazakhstan). The finely preserved lignified compression remains of leafy shoots make micro-morphological investigation feasible. Comparative studies of the epidermal features both living G. pensilis C. Koch and a new finding of G. europaeus from Early Miocene of Kazakhstan and illustrate their certain difference. The cuticular organization and epidermal features of fossil leaves, which have been compared with these of 'the nearest living relative', G. pensilis, were studied by scanning electron microscopy (SEM) and light microscopy (LM). The fossil leaves of G. europaeus from Kazakhstan are distinguished by stronger, than in living species, G. pensilis, developed 'micro-papillae' ('Kristallucken'), visible in SEM as ring-like structures left on the outer surface of cuticle in both nonstomatal and stomatal zones.展开更多
The Tunggurian Age was nominated in 1984, and the Second National Commission on Stratigraphy of China formally suggested establishing the corresponding chronostratigraphic unit, the Tunggurian Stage, based on the Tung...The Tunggurian Age was nominated in 1984, and the Second National Commission on Stratigraphy of China formally suggested establishing the corresponding chronostratigraphic unit, the Tunggurian Stage, based on the Tunggurian Age in 1999. The name of this stage comes from a lithostratigraphic unit, the Tunggur Formation, and the stratotype section is located at the Tunggur tableland, 15 km southeast of Saihan Gobi Township, Sonid Left Banner, Inner Mongolia. The Tunggurian Age is correlated to the Astaracian of the European land mammal ages, and they share the same definition of the lower boundary at the base of the paleomagnetic Chron C5Bn.1r with an age of 15.0 Ma. In the Tairum Nor section on the southeastern edge of the Tunggur tableland, this boundary is situated within the successive deposits of reddish-brown massive mudstone of the lower part of the Tunggur Formation, with a distance of 7.6 m from the base of the grayish-white sandstones in the middle part of the section. The Tunggurian is approximately correlated to the upper part of the marine Langhian and the marine Serravallian in the International Stratigraphical Chart. The Tunggurian Stage includes two Neogene mammal faunal units, i.e. NMU 6 （MN 6） and NMU 7 （MN 7/8）. The Tairnm Nor fauna from the Talrnm Nor section corresponds to NMU 6, and the Tunggur fauna （senso stricto） from the localities on the northwestern edge of the Tunggur tableland, such as Platybelodon Quarry, Wolf Camp and Moergen, corresponds to NMU 7. Among the Middle Miocene mammalian faunas in China, the Laogou fauna from the Linxia Basin, Gansu, the Quantougou fauna from the Lanzhou Basin, Gansu, the Halamagai fauna from the northern Junggar Basin, Xinjiang, and the Dingjiaergou fauna from Tongxin, Ningxia correspond to NMU 6.展开更多
The gravity flow deposit were mainly developed in the lowstand systems tract（LST） of the first member of Upper Miocene Huangliu Formation（Ehl1） in Dongfang area, Yinggehai Basin, has become a valuable target for g...The gravity flow deposit were mainly developed in the lowstand systems tract（LST） of the first member of Upper Miocene Huangliu Formation（Ehl1） in Dongfang area, Yinggehai Basin, has become a valuable target for gas exploration and production. The gravity flow sedimentary characteristics of lithofacies associations, sedimentary texture, seismic facies and logging facies were described in detail on the basis of integrated analysis of cores, logging and seismic data. The sedimentary microfacies types composed of neritic sandbar, continental shelf mud, main channel, bifurcated or cross-cutting distributary channel, overspill, and natural levee are revealed under the constraint of high resolution sequence stratigraphic framework in the Ehl1. The gravity flow deposit system in the LST is divided into three evolution stages corresponding to periods of three parasequence sets. The gravity flow deposit was induced in the early LST, expanded rapidly in the middle LST and decreased slightly in the late LST. But its developing scale decreased sharply in the transgression systems tract（TST） and finally vanished in the highstand systems tract（HST）. This spatial evolution rule is constrained by the integrated function of sediments supply of the Vietnam Blue River in the LST, the development of local gradient change in sea floor（micro-topography, i.e., flexure slope break）, and the fall in relative sea level. On the basics of the deep study of the coupling relationship among the three main control factors, the sedimentary model is established as an optimal component of ＂source-channel-sink＂ for shallow marine turbidite submarine fan.展开更多
A significant geologic event occurred on the Oligocene/Miocene boundary at 23.8 Ma in the northern South China Sea, which is named the Baiyun （白云） movement in this article. This event strongly affected not only th...A significant geologic event occurred on the Oligocene/Miocene boundary at 23.8 Ma in the northern South China Sea, which is named the Baiyun （白云） movement in this article. This event strongly affected not only the South China Sea, but also East Asia. After the Baiyun event, the ridge of seafloor spreading of the South China Sea jumped southward and rotated counterclockwise, and a strong subsidence occurred in the Baiyun sag of the Pearl River Mouth basin. The shelf break shifted suddenly from the south to the north of the Baiyun sag, and the deposition environment in this sag changed from continental shelf with neritic deposition to continental slope with deep-water deposition. Sediment geochemistry study indicated that the Baiyun event played a key role in the rapid change of sediment provenance for the Pearl River Mouth basin. Between 32 and 23.8 Ma, the source of sediments was mainly from the granites in South China, while after 23.8 Ma some sediments might have come from the eastern Himalaya, as the Pearl River drainage extended westward after the uplift of Tibet since that time. The Baiyun event led to a great change in the drainage framework of the paleo- Pearl River, sediment types and the depositional environments in the Pearl River Mouth basin, and relative sea level of the northern South China Sea, as well as sedimentation and hydrocarbon accumulation in the area.展开更多
Carbonate rocks are important reservoirs for global petroleum exploration.The largest oilfield in the South China Sea,Liuhua 11-1,is distributed in the massive carbonate reef area of the Zhujiang(Pearl)River Mouth Bas...Carbonate rocks are important reservoirs for global petroleum exploration.The largest oilfield in the South China Sea,Liuhua 11-1,is distributed in the massive carbonate reef area of the Zhujiang(Pearl)River Mouth Basin.Previous studies showed that one 802.17-m-long core from well Xichen-1 in the South China Sea mainly consisted of white and light gray-white organic reefs.Recently,a Miocene whole core(161.9 m long)of well Xiyong-2,near well Xichen-1,was found to contain six layers of yellowish brown,light yellowish gray,iron black,or light yellowish gray-white organic reefs.Scanning electron microscope images of these layers reveal a typical ferroan dolomite rich in Fe(up to 29%),with the high concentrations of Mn,Cu,W,Zn,Cr,Ni,and Co.Systematic X-ray powder diffraction analysis yields a 1.9–6.1 match in phase ratio with ankerite,5.4–26.9 with dolomite,and zero with calcite,which indicate that the samples can be classified as ferroan dolomite.The iron and heavy metals are inferred to be originated from multiple volcanic eruptions of Gaojianshi Island in the Dongdao Atoll during the middle-late Miocene.These elements were dissolved in seawater,likely as a sol,and carried to Yongxing Island in the Xuande Atoll by sea currents and tides enhanced by prevailing winds,and deposited as a part of the sedimentation process in the study area.The ferroan dolomite has Sr content of (125–285)×10^(-6),which is lower than the accepted Sr boundary value of dolomite.This finding suggests that dolomitization occurred during large-scale global glacial regression in the late Miocene.The isolated Xisha carbonate platform,exposed to air,underwent freshwater leaching and dolomitization induced by mixed water,and caused the extensive Fe-Mg exchange along the organic reef profile to form ankerite and ferroan dolomite.These results may help to understand paleoceanographic environmental changes in the South China Sea during the Miocene.展开更多
Dextral-slip in the Nyainqentanglha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The ...Dextral-slip in the Nyainqentanglha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The east-west dextral-slip Gangdise fault system merges eastward into the northeast-trending, southeast-dipping Nyainqentanglha thrust system that swings eastward farther north into the dextral-slip North Damxung shear zone and Jiali faults. These faults were took shape by the Early Miocene, and the large Nyainqentanglha granitic batholith formed along the thrust system in 18.3-11.0 Ma as the western block drove under the eastern one. The dextral-slip movement ended at -11 Ma and the batholith rose, as marked by gravitational shearing at 8.6-8.3 Ma, and a new fault system developed. Northwest-trending dextral-slip faults formed to the northwest of the raisen batholith, whereas the northeast-trending South Damxung thrust faults with some sinistral-slip formed to the southeast. The latter are replaced farther to the east by the west-northwest-trending Lhtinzhub thrust faults with dextral-slip. This relatively local uplift that left adjacent Eocene and Miocene deposits preserved was followed by a regional uplift and the initiation of a system of generally north-south grabens in the Late Miocene at -6.5 Ma. The regional uplift of the southern Tibetan Plateau thus appears to have occurred between 8.3 Ma and 6.5 Ma. The Gulu, DamxungYangbajain and Angan graben systems that pass east of the Nyainqentanglha Mountains are locally controlled by the earlier northeast-trending faults. These grabens dominate the subsequent tectonic movement and are still very active as northwest-trending dextral-slip faults northwest of the mountains. The Miocene is a time of great tectonic change that ushered in the modern tectonic regime.展开更多
Clay mineral assemblages, crystallinity, chemistry, and micromorphology of clay particles in sediments from ODP Site 1146 in the northern South China Sea （SCS） were analyzed, and used to trace sediment sources and o...Clay mineral assemblages, crystallinity, chemistry, and micromorphology of clay particles in sediments from ODP Site 1146 in the northern South China Sea （SCS） were analyzed, and used to trace sediment sources and obtain proxy records of the past changes in the East Asian monsoon climate since the Miocene, based on a multi-approach, including X-ray diffraction （XRD） and scanning electron microscopy combined with energy dispersive X-ray spectrometry （SEM-EDS）. Clay minerals consist mainly of illite and smectite, with associated chlorite and kaolinite. The illite at ODP Site 1146 has very well-to-well crystallinity, and smectite has moderate-to-poor crystallinity. In SEM the smectite particles at ODP Site 1146 often appear cauliflower-like, a typical micromorphology of volcanic smecites. The smectite at ODP Site 1146 is relatively rich in Si element, but poor in Fe, very similar to the smectite from the West Philippine Sea. In contrast, the chemical composition of illite at ODP Site 1146 has no obvious differences from those of the Loess plateau, Yellow River, Yangtze River, and Pearl River. A further study on sediment source indicates that smectite originates mainly from Luzon, kaolinite from the Pearl River, and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River. The clay mineral assemblages at ODP Site 1146 were not only controlled by continental eathering regimes surrounding the SCS, but also by the changing strength of the transport processes. The ratios of （illite＋chlorite）/smectite at ODP Site 1146 were adopted as proxies for the East Asian monsoon evolution. Relatively higher ratios reflect strongly intensified winter monsoon relative to summer monsoon, in contrast, lower ratios indicate a strengthened summer monsoon relative to winter monsoon. The consistent variation of this clay proxy from those of Loess plateau, eolian deposition in the North Pacific, planktonic, benthic foraminifera, and black carbon in the SCS since 20 Ma shows that three profound shifts of the East Asian winter monsoon intensity, and aridity in the Asian inland and the intensity of winter monsoon relative to summer monsoon, occurred at about 15 Ma, 8 Ma, and the younger at about 3 Ma. The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at 15 Ma, 8 Ma, and 3 Ma.展开更多
文摘In addition to its well-known fossils,the Upper Miocene Baogeda Ula Formation is coupled with multiple basaltic lava flows,creating an ideal setting for studying its depositional history,geochronology,and associated vertebrate fossils.This paper,in honor of Prof.Qiu Zhanxiang for his widely admired emphasis on the geological contexts of vertebrate fossils,attempts to synthesize known contact relationships,existing K-Ar dates,and capping basalt elevations to reframe our concept of the lithostratigraphy,magnetostratigraphy,and lateral distribution of the Baogeda Ula Formation.Within this new framework,the Baogeda Ula Formation is defined by unconformable contact with the underlying Tunggur Formation at the lower boundary and a capping basalt at the upper boundary.In many sections,two or three layers of basalts are interbedded within sedimentary strata,with the capping basalts typically belonging to the top two basalts.The newly defined Baogeda Ula Formation includes a lower member as exemplified by Halajin Hushu section and Ulan Hushuyin Nur section,and an upper member at Baogeda Ula section.This expanded concept of the Baogeda Ula Formation includes two major faunas,i.e.,the Bahean Halajin Hushu Fauna and Baodean Baogeda Ula Fauna,both falling within the Upper Miocene.We also describe rare fossil skunks(Promephitis)found in recent years that support the age assessments presented herein.
文摘Our purpose in this paper is to describe the hamster-like rodents(Cricetidae)from a Late Miocene age site in Linxia Basin,Gansu Province,and discuss their significance for the changing ecology of central Asia.The micromammal site known as Yihachi was introduced previously(Qiu et al.,2023;Qiu and Li,2023),when its squirrels were discussed in some detail.We take this opportunity to describe the more abundant cricetids.There are four genera,common Nannocricetus and Sinocricetus plus the less abundant living Mesocricetus.A few specimens represent the high-crowned and lophodont Rhinocerodon.The cricetids and other faunal elements indicate an early Late Miocene age,and the pattern of occurrence of the hamster species is consistent with a picture of a changing paleoenvironment due to increasing effects of the East Asia monsoon system.After the disappearance of older and archaic genera,Yihachi represents growing endemism in the Late Miocene of northern China due to increasing seasonal rain and the declining average temperature.
基金supported by the National Key R&D Program of China(No.2019YFC0605402)the National Natural Science Foundation of China(No.41790453)。
文摘Dikes are widely distributed in volcanic outcrops and volcanic basins around the world.The pores and fractures in these dikes control the fluid-rock interactions and fluid flow.The quantitative reservoir characteristics of dikes with primary vesicles remain unclear.In this manuscript,the Miocene hypabyssal dikes in Lyttelton Volcano,Christchurch,New Zealand,are taken as an example.The porosity content,porosity,permeability,and reservoir controlling factors are analyzed through field outcrop surveys,porosity-permeability testing,nuclear magnetic resonance(NMR)testing,X-ray-computed tomography(X-CT)scanning,and permeability calculations.The results show that the types of reservoir spaces in the hypabyssal dikes in Lyttelton Volcano are mainly vesicles,followed by cooling and shrinkage fractures(especially columnar joints).They are a pore-fracture type reservoir.There were two types of vesicles,namely,pipe-like-elliptical directionally oriented vesicles with large diameters and discrete circular vesicles with small diameters.The surface porosity of the former was 58.4%–96.0%,with a geometric mean of 78.9%.The columnar joints can be classified into regular and irregular joints.The irregular joints have a higher fracture intensity.The geometric means of the porosity and permeability of the joints are 22.34%and 0.09×10^(-15)m^(2),respectively.The shapes of the NMR T_(2)spectra are bimodal,trimodal,and unimodal in descending order of abundance.This means that the pore diameter is large.The X-CT results indicate that there are four types of pore-throat connectivity modes:macro-pores and macro-throats,macro-pores and micro-throats,micro-pores and micro-throats,and micro-pores and macrothroats.The columnar joints are the main cause of the high permeability of the dikes,and the side amount and side length of the columnar joints control the dikes'permeability.The pores can be connected by the columnar joints,and their connectivity is controlled by the side amount,side length,and side azimuth of the columnar joint.The initial connectivity ratio of the vesicles in the dikes in Lyttelton Volcano was up to 47.6%based on the surface porosity.In conclusion,the shallow dikes with primary pores and fractures have a good reservoir quality and fluid migration capacity,and fluid flow studies of volcanic strata should pay attention to the important influence of the primary porosity and permeability of dikes.
基金supported by the National Natural Science Foundation of China(No.42272013)the National Key Research and Development Project of China(2024YFF0807603,2023YFF0804501)+1 种基金the National Natural Science Foundation of China(Nos.42302017,41872006)the NSFC BSCTPES project(No.41988101).
文摘The Series Barbini(subfamily Cyprininae sensu lato)is the most species-rich group within the family Cyprinidae,primarily confined to warm regions of southern Eurasia and Africa.The distribution patterns and evolutionary history of Chinese cyprinins have been effectively shaped by the Cenozoic uplift of the Qinghai-Tibet Plateau and the evolution of the Asian monsoon.Here,we describe two new fossil fishes from the early and middle Miocene of the Lunpola Basin in central Qinghai-Tibet Plateau,China,preserving the ethmoid and the rear of the occipital regions of the neurocranium,infraorbitals,hyopalatine arch,abdominal vertebrae,and some dorsal-fin pterygiophores and unbranched fin rays.Through detailed morphological comparisons,these fossils show definite affinities to Cyprinidae according to the morphology of the neurocranium,vertebral column,and dorsal fin rays;and one of which is classified into the Series Barbini,while the other can only be assigned to the Cyprinidae family level.These findings reveal that the hinterland of the plateau of the early Neogene should have hosted cyprinin fishes of greater diversity than today.This also indicates a warm-temperate paleoclimate suitable for their survival during that period,consistent with the paleoenvironmental and paleoclimatical conditions reconstructed from the contemporaneous mammalian fossil and palynological evidences.
文摘The micromammal fossils collected from the Shangzhuang Formation of the Linxia Basin,Gansu,are described here.The assemblage consists of 16 species of 13 genera belonging to 7 families,including one new species and one taxon previously unknown from China.Among them 5 genera are Oligocene holdovers and 11 genera/species are known to make their first appearances in Early Miocene,indicating an Early Miocene age for the Gucheng Fauna.The absence of Oligocene survivors such as Tataromys,Yindirtemys,Eucricetodon and Tachyoryctoides,which usually occur in the Xiejian age of Early Miocene,and the presence of newcomers Protalactaga,Megacricetodon and Gobicricetodon,that made their first appearance only in the Shanwangian age of late Early Miocene,suggest that the Gucheng Fauna is of a later age of Early Miocene.The new species,Sinolagomys guchengensis,showing more derived morphology than in S.ulunguensis,seems to support an assessment of the fauna in Shanwangian age.Thus,the Gucheng Fauna may belong to late Early Miocene Shanwangian,partially equivalent to MN 3/4 of the European land mammal zonation.Ecological analysis of the fauna indicates that the palaeoecological condition of the Gucheng area might still be a predominantly arid shrub-steppe in late Early Miocene.
文摘The Govanda Formation was deposited during the Miocene in the intermontane areas between the Zagros suture and imbricate zones.The Govanda Formation was studied in the Sherwan Mazin area within Mergasor district,Erbil Governorate to identify the lithostratigraphy and microfacies analysis in order to determine the depositional environment of the formation.The formation in the studied section is 116 m thick and mainly consists of reddish-brown,hard,thickbedded,chert-bearing conglomerate,pinkish shale and yellowish-grey,thick-bedded,detrital,fossiliferous limestone.The formation is unconformably underlain by the Upper Cretaceous Tanjero Formation and conformably overlain by the Merga Red Beds series.Four different lithostratigraphic units were identified,based on field observation and petrographic analysis,including a basal conglomerate unit(A),a shale unit(B),a well-bedded limestone unit(C)and a thick and massively-bedded limestone unit(D).The presence of a thick conglomerate bed at the base of the formation indicates a large unconformity that lasted nearly 40 million years.Based on detailed microfacies analysis of carbonate rocks,five main microfacies and 15 submicrofacies are recognized.The main microfacies types include mudstone,wackestone,packstone,grainstone and boundstone microfacies.Based on the microfacies types the depositional environment are defined as open lagoon,reef,fore-reef and back-reef environments of normal to saline,nutrient rich water.
基金The National Natural Science Foundation of China under contract Nos 42372170,42472055,42272177,and 42077410the Safety Discipline“double first-class”to found Project of China under contract No.AQ20240305.
文摘The Zhujiang River Mouth Basin,a primary depocenter for terrigenous sediments in the western Pacific,presents a semienclosed tectonic setting with limited exchange with the open ocean.This unique feature enables systematic linkages among sedimentary processes,climate change,regional sea-level fluctuations,and tectonic events.To explore these linkages,this study focuses on Well PY35 in the Baiyun Sag of the Zhujiang River Mouth Basin.By integrating microfossil analysis with Milankovitch cycle analysis of well log data,an astronomical time scale(ATS)(17.54-7.80 Ma)and a high-resolution stratigraphic framework were established,allowing for the calculation of sedimentation rates across different hierarchical sequences and time intervals.The results indicate that between 17.54 Ma and 7.80 Ma,the sedimentation rate initially increased and then decreased,ranging from 6.1 cm/ka to 45.7 cm/ka,with an average rate of 22.2 cm/ka.During the Middle Miocene Climatic Optimum(MMCO),sedimentation rates were moderate and exhibited an increasing trend,largely driven by increased sediment input due to enhanced weathering from rising temperatures and by expanded accommodation space resulting from tectonic subsidence.Meanwhile,the Middle Miocene Climate Transition(MMCT)was marked by a notable rise in sedimentation rates,consistent with a major sea-level fall due to global cooling,which promoted the direct seaward progradation of marginal sediments.The Late Middle Miocene to Late Miocene had the lowest sedimentation rates,which can be attributed to reduced weathering under cold and arid conditions,along with a sea-level rise induced by regional tectonics.The short-term increase in the sedimentation rate observed at 10.4 Ma may have been driven by sea-level fluctuations.This study provides both theoretical and empirical support for understanding the influence of abrupt climate changes on sedimentary processes.
基金supported by the National Natural Science Foundation of China(Grant Nos.41530963,42406077)the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2022QD087)the National Natural Science Foundation of China(Grant Nos.42376060,41176038)。
文摘The temporal and spatial evolution of the Ailao Shan-Red River(ASRR)fault zone,which serves as an important accommodation zone for the extrusion and escape of the Southeastern Tibetan Plateau,is crucial for analyzing the uplift and growth of the plateau.Based on the petrology and apatite fission track analysis,the tectonic history and active pattern of the ASRR fault zone since the middle Miocene are determined in this study.The ASRR fault zone exhibits 12-8Ma and 8-4 Ma rapid cooling phases since the middle Miocene.The 12-8 Ma and 8-4 Ma cooling may imply that the dextral movement of the ASRR fault zone presents a migration trend from northwest to southeast,accompanied by the weakening of the activity intensity,which is directly related to deformation processes,including extrusion boundary migration and active tectonic movements of the southeastern Tibetan Plateau,since the middle-late Miocene.
文摘Late Miocene woods were investigated from the Luhe Basin in Chuxiong Borough, central Yunnan, China. The calcified woods preserved in the Shigucun member of the Shihuiba Formation, are represented by fallen logs and stumps. Two species of fossil wood, Taxodioxylon cryptomeripsoides Schonfeld 1953 and T. cunninghamioides Watari 1948, are described. Their anatomical structure shows striking similarities to the woods of Cryptomeria and Cunninghamia respectively. That the two fossil woods are classed in the Taxodiaceae suggest a subtropical, humid, and warm environment in Lithe during Late Miocene. They compare favorably to other fossil specimens and species reported from localities ranging from Cretaceous to Pliocene. This is the first record of the presence of the species T. cryptomeripsoides and T. cunninghamioides in late Miocene of Yunnan.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-120)the Key Laboratory of Evolutionary Systematics of Vertebrates,Chinese Academy of Sciences(2010LESV007)
文摘Some Miocene ratite eggshell fragments from Gashunyinadege (about 17.5 Ma) and Baogedawula (7.11 ± 0.48 Ma), Inner Mongolia, China, are described. The outer surfaces of eggshell fragments from Gashunyinadege are smooth with a sting pore pattern, while their entire thickness is around 2.12 mm. In a cross-sectional view, the surface crystal layer is very thin and the ratio of cone layer to the those from Gashunyinadege, but seem much thinner and have a lower pore density. Both characteristics fit aepyornithid-type eggshells, implying that the distribution of aepyornithid-type eggshells can be extended to East Asia. The sediments at Gashunyinadege date to approximately 17.5 Ma, implying that the specimens from this locality are relatively early examples of aepyornithid-type eggshells. Aepyornithidtype eggshells seem to have appeared in Eurasia much earlier than struthionid-type eggshells. The faunal compositions in the two localities reflect gradual drying of the Mongolian plateau during the Miocene. A reduction in the number of pores 10 Ma ago, probably occurred in response to this drying process.
文摘Numerous leaf compressions of Glyptostrobus europaeus (Brongn.) Ung. (Taxodiaceae) are found in Aquitanian (Lower Miocene) lignified clay localities Bolattam and Akzhar in the Southern Turgay, on the right bank of the Dulygaly-Zhilanshik river (Central Kazakhstan). The finely preserved lignified compression remains of leafy shoots make micro-morphological investigation feasible. Comparative studies of the epidermal features both living G. pensilis C. Koch and a new finding of G. europaeus from Early Miocene of Kazakhstan and illustrate their certain difference. The cuticular organization and epidermal features of fossil leaves, which have been compared with these of 'the nearest living relative', G. pensilis, were studied by scanning electron microscopy (SEM) and light microscopy (LM). The fossil leaves of G. europaeus from Kazakhstan are distinguished by stronger, than in living species, G. pensilis, developed 'micro-papillae' ('Kristallucken'), visible in SEM as ring-like structures left on the outer surface of cuticle in both nonstomatal and stomatal zones.
基金This work is supported by the Knowledge Innovation Program of the Chinese Academy of Sciences （KZCX2- YW-120）the National Commission on Stratigraphy of China+1 种基金the Ministry of Science and Technology of China （2006FY120300, 2006CB806400）the National Natural Science Foundation of China （40232023）.
文摘The Tunggurian Age was nominated in 1984, and the Second National Commission on Stratigraphy of China formally suggested establishing the corresponding chronostratigraphic unit, the Tunggurian Stage, based on the Tunggurian Age in 1999. The name of this stage comes from a lithostratigraphic unit, the Tunggur Formation, and the stratotype section is located at the Tunggur tableland, 15 km southeast of Saihan Gobi Township, Sonid Left Banner, Inner Mongolia. The Tunggurian Age is correlated to the Astaracian of the European land mammal ages, and they share the same definition of the lower boundary at the base of the paleomagnetic Chron C5Bn.1r with an age of 15.0 Ma. In the Tairum Nor section on the southeastern edge of the Tunggur tableland, this boundary is situated within the successive deposits of reddish-brown massive mudstone of the lower part of the Tunggur Formation, with a distance of 7.6 m from the base of the grayish-white sandstones in the middle part of the section. The Tunggurian is approximately correlated to the upper part of the marine Langhian and the marine Serravallian in the International Stratigraphical Chart. The Tunggurian Stage includes two Neogene mammal faunal units, i.e. NMU 6 （MN 6） and NMU 7 （MN 7/8）. The Tairnm Nor fauna from the Talrnm Nor section corresponds to NMU 6, and the Tunggur fauna （senso stricto） from the localities on the northwestern edge of the Tunggur tableland, such as Platybelodon Quarry, Wolf Camp and Moergen, corresponds to NMU 7. Among the Middle Miocene mammalian faunas in China, the Laogou fauna from the Linxia Basin, Gansu, the Quantougou fauna from the Lanzhou Basin, Gansu, the Halamagai fauna from the northern Junggar Basin, Xinjiang, and the Dingjiaergou fauna from Tongxin, Ningxia correspond to NMU 6.
基金supported by the National Natural Science Foundation of China (NSFC) (Nos. 41272122, 41202074, 41172123 and 40702023)the National Twelfth Five-Year Major Projects of Oil and Gas (No. 2011ZX05025-002-02-02)+1 种基金the Key Laboratory of Tectonics and Petroleum Resources (CUG)of Ministry of Education open issue (No. TPR-2013-08)the China University of Geosciences (Wuhan) Teaching Labor atory open funded projects
文摘The gravity flow deposit were mainly developed in the lowstand systems tract（LST） of the first member of Upper Miocene Huangliu Formation（Ehl1） in Dongfang area, Yinggehai Basin, has become a valuable target for gas exploration and production. The gravity flow sedimentary characteristics of lithofacies associations, sedimentary texture, seismic facies and logging facies were described in detail on the basis of integrated analysis of cores, logging and seismic data. The sedimentary microfacies types composed of neritic sandbar, continental shelf mud, main channel, bifurcated or cross-cutting distributary channel, overspill, and natural levee are revealed under the constraint of high resolution sequence stratigraphic framework in the Ehl1. The gravity flow deposit system in the LST is divided into three evolution stages corresponding to periods of three parasequence sets. The gravity flow deposit was induced in the early LST, expanded rapidly in the middle LST and decreased slightly in the late LST. But its developing scale decreased sharply in the transgression systems tract（TST） and finally vanished in the highstand systems tract（HST）. This spatial evolution rule is constrained by the integrated function of sediments supply of the Vietnam Blue River in the LST, the development of local gradient change in sea floor（micro-topography, i.e., flexure slope break）, and the fall in relative sea level. On the basics of the deep study of the coupling relationship among the three main control factors, the sedimentary model is established as an optimal component of ＂source-channel-sink＂ for shallow marine turbidite submarine fan.
基金supported by the National Natural Science Foundation of China (No. 40238060)
文摘A significant geologic event occurred on the Oligocene/Miocene boundary at 23.8 Ma in the northern South China Sea, which is named the Baiyun （白云） movement in this article. This event strongly affected not only the South China Sea, but also East Asia. After the Baiyun event, the ridge of seafloor spreading of the South China Sea jumped southward and rotated counterclockwise, and a strong subsidence occurred in the Baiyun sag of the Pearl River Mouth basin. The shelf break shifted suddenly from the south to the north of the Baiyun sag, and the deposition environment in this sag changed from continental shelf with neritic deposition to continental slope with deep-water deposition. Sediment geochemistry study indicated that the Baiyun event played a key role in the rapid change of sediment provenance for the Pearl River Mouth basin. Between 32 and 23.8 Ma, the source of sediments was mainly from the granites in South China, while after 23.8 Ma some sediments might have come from the eastern Himalaya, as the Pearl River drainage extended westward after the uplift of Tibet since that time. The Baiyun event led to a great change in the drainage framework of the paleo- Pearl River, sediment types and the depositional environments in the Pearl River Mouth basin, and relative sea level of the northern South China Sea, as well as sedimentation and hydrocarbon accumulation in the area.
基金Supported by the National Basic Research Program of China(973 Program)(No.2012CB956004)the Science and Technology Basic Resources Investigation Program of China(No.2017FY201407)+1 种基金the National Oil and Gas Major Projects of China(No.2011ZX05025-002)the National Natural Science Foundation of China(NSFC)(No.41106064)
文摘Carbonate rocks are important reservoirs for global petroleum exploration.The largest oilfield in the South China Sea,Liuhua 11-1,is distributed in the massive carbonate reef area of the Zhujiang(Pearl)River Mouth Basin.Previous studies showed that one 802.17-m-long core from well Xichen-1 in the South China Sea mainly consisted of white and light gray-white organic reefs.Recently,a Miocene whole core(161.9 m long)of well Xiyong-2,near well Xichen-1,was found to contain six layers of yellowish brown,light yellowish gray,iron black,or light yellowish gray-white organic reefs.Scanning electron microscope images of these layers reveal a typical ferroan dolomite rich in Fe(up to 29%),with the high concentrations of Mn,Cu,W,Zn,Cr,Ni,and Co.Systematic X-ray powder diffraction analysis yields a 1.9–6.1 match in phase ratio with ankerite,5.4–26.9 with dolomite,and zero with calcite,which indicate that the samples can be classified as ferroan dolomite.The iron and heavy metals are inferred to be originated from multiple volcanic eruptions of Gaojianshi Island in the Dongdao Atoll during the middle-late Miocene.These elements were dissolved in seawater,likely as a sol,and carried to Yongxing Island in the Xuande Atoll by sea currents and tides enhanced by prevailing winds,and deposited as a part of the sedimentation process in the study area.The ferroan dolomite has Sr content of (125–285)×10^(-6),which is lower than the accepted Sr boundary value of dolomite.This finding suggests that dolomitization occurred during large-scale global glacial regression in the late Miocene.The isolated Xisha carbonate platform,exposed to air,underwent freshwater leaching and dolomitization induced by mixed water,and caused the extensive Fe-Mg exchange along the organic reef profile to form ankerite and ferroan dolomite.These results may help to understand paleoceanographic environmental changes in the South China Sea during the Miocene.
文摘Dextral-slip in the Nyainqentanglha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The east-west dextral-slip Gangdise fault system merges eastward into the northeast-trending, southeast-dipping Nyainqentanglha thrust system that swings eastward farther north into the dextral-slip North Damxung shear zone and Jiali faults. These faults were took shape by the Early Miocene, and the large Nyainqentanglha granitic batholith formed along the thrust system in 18.3-11.0 Ma as the western block drove under the eastern one. The dextral-slip movement ended at -11 Ma and the batholith rose, as marked by gravitational shearing at 8.6-8.3 Ma, and a new fault system developed. Northwest-trending dextral-slip faults formed to the northwest of the raisen batholith, whereas the northeast-trending South Damxung thrust faults with some sinistral-slip formed to the southeast. The latter are replaced farther to the east by the west-northwest-trending Lhtinzhub thrust faults with dextral-slip. This relatively local uplift that left adjacent Eocene and Miocene deposits preserved was followed by a regional uplift and the initiation of a system of generally north-south grabens in the Late Miocene at -6.5 Ma. The regional uplift of the southern Tibetan Plateau thus appears to have occurred between 8.3 Ma and 6.5 Ma. The Gulu, DamxungYangbajain and Angan graben systems that pass east of the Nyainqentanglha Mountains are locally controlled by the earlier northeast-trending faults. These grabens dominate the subsequent tectonic movement and are still very active as northwest-trending dextral-slip faults northwest of the mountains. The Miocene is a time of great tectonic change that ushered in the modern tectonic regime.
基金the National Fundamental Research and Development Planning Project (No. 2007CB411703)the National Natural Science Foundation of China (No. 40706025)
文摘Clay mineral assemblages, crystallinity, chemistry, and micromorphology of clay particles in sediments from ODP Site 1146 in the northern South China Sea （SCS） were analyzed, and used to trace sediment sources and obtain proxy records of the past changes in the East Asian monsoon climate since the Miocene, based on a multi-approach, including X-ray diffraction （XRD） and scanning electron microscopy combined with energy dispersive X-ray spectrometry （SEM-EDS）. Clay minerals consist mainly of illite and smectite, with associated chlorite and kaolinite. The illite at ODP Site 1146 has very well-to-well crystallinity, and smectite has moderate-to-poor crystallinity. In SEM the smectite particles at ODP Site 1146 often appear cauliflower-like, a typical micromorphology of volcanic smecites. The smectite at ODP Site 1146 is relatively rich in Si element, but poor in Fe, very similar to the smectite from the West Philippine Sea. In contrast, the chemical composition of illite at ODP Site 1146 has no obvious differences from those of the Loess plateau, Yellow River, Yangtze River, and Pearl River. A further study on sediment source indicates that smectite originates mainly from Luzon, kaolinite from the Pearl River, and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River. The clay mineral assemblages at ODP Site 1146 were not only controlled by continental eathering regimes surrounding the SCS, but also by the changing strength of the transport processes. The ratios of （illite＋chlorite）/smectite at ODP Site 1146 were adopted as proxies for the East Asian monsoon evolution. Relatively higher ratios reflect strongly intensified winter monsoon relative to summer monsoon, in contrast, lower ratios indicate a strengthened summer monsoon relative to winter monsoon. The consistent variation of this clay proxy from those of Loess plateau, eolian deposition in the North Pacific, planktonic, benthic foraminifera, and black carbon in the SCS since 20 Ma shows that three profound shifts of the East Asian winter monsoon intensity, and aridity in the Asian inland and the intensity of winter monsoon relative to summer monsoon, occurred at about 15 Ma, 8 Ma, and the younger at about 3 Ma. The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at 15 Ma, 8 Ma, and 3 Ma.
