Showing papers in "Marine Geology & Quaternary Geology in 2013"

Tectonic transition and plate reconstructions of the east asian continental magin

Abstract: It is a hot debate on the Meso-Cenozoic dynamics of the East Asian continental margins,since the nature,type and evolution of its continental margins are not well-knownThis paper systematically summarizes the results of plate reconstructions on the East Asian continental margin since Permian over the past 40 years with emphasis on the new research results in the past 10 yearsThe paper mainly focuses on the variation in types of the East Asian continental margin since Late Triassic,the transitions among different tectonic domainsOur data suggests that the East Asian continental margins as a whole experienced a pre-Triassic passive continental margin,a Late Triassic-Early Cretaceous continental magmatic arc of the Andean-type active continental margin,a Late Cretaceous-Eocene strike-slipping Andean-type active continental margin with of pull-apart basins,and a post-Oligocene Japanese-type active continental margin successivelyTectonic trasition is important for understanding of the formation of the Bohaisx Bay,the Yellow Sea,the East China Sea and the South China Sea basins in East ChinaThe changes of the continent-ocean distribution,plate configuration and dynamics at the various stages are also discussed

Basin dynamics and basin groups of the south china sea

Abstract: The South China Sea was formed in Cenozoic.Basins in the South China Sea could be divided into different types,such as continental shelf basins,continental slope basins and deep sea basins,which are closely related with the rifting and transition of the continental margins,and thus could be grouped into strike-slip-related pull-apart and extensional basins,extrusion-escape-related rifting basins,extension-and subduction-related buckling basins.They developed further into some ridge-spreading-related oceanic sub-basins in different stages.These basins were formed not under a single dynamics but under a very complex and changeable dynamics.These basins have suffered from a series of Cenozoic tectonic movements,such as the Shenhu,the South China Sea,the Dongsha,resulting in the formation and spatial-temperal migration of complex angular unconformities in these basins.Accompanying with the tectonic migrations and evolutions in these basins,faulting,magmatism,shifting of sedimentary subsidence centers and depocenters,oil accumulation and geohazards show a significant feature of jumping.The complex dynamic settings of the South China Sea have caused many controversies on their origin.The plate dynamic factors include the Pacific Plate subduction and the indentation of the Philippine Sea Plate along the Taiwan Orogen to the east side of the South China Sea,and the Indian Plate oblique subduction and mid-ocean ridge subduction to the west side.They may also be responsible for the uplifting of the Tibetan Plateau and the related extrusions of continental blocks to the north side.At the same time,the mantle dynamics of deep-seated magma underplating,delamination,mantle plume and mantle-hydrated process should not be ignored.At last,this paper proposes one strike-slipping pull-apart model to explain the onset of the South China Sea Basin which is closely related to the tectonic evolution of the Pacific Tectonic Domain.

Basic strcutural pattern and tectonic models of the south china sea:problems,advances and controversies

Abstract: The South China Sea is located at a juncture among the Eurasian,the Indian-Australian and the Pacific plates,being the largest continental marginal sea along the East Asian continental margin.It has experienced a complex transition of continental marginal types.The northern margin was an Andean-type continental margin before 80 Ma,then gradually transferred into a rifted continental margin in the Eocene and a typical passive continental margin since the middle Miocene.The eastern margin was an open water before 17 Ma and gradually became a subduction zone of the trench-arc-basin system by one-way subduction to double-way subduction,when the South China Sea became semi-closed basin since 6 Ma.The western boundary gradually transformed into a continental margin with strike-slipping faulting or transform faulting since 34 Ma.The southern margin was an asymmetric rift-type continental margin corresponding to the northern margin before 34 Ma,and became a passive continental margin during 34~16 Ma and gradually a thrusting-type continental margin after 16 Ma.Complex dynamic settings of the South China Sea have caused many controversies on their origin.The plate dynamic factors include either the Pacific Plate subduction and the indentation of the Philippine Sea Plate along the Taiwan Orogen to the east side the South China Sea,or the Indian Plate oblique subduction and mid-ocean ridge subduction to the west side.They may also be responsible for the uplifting of the Tibetan Plateau and the related extrusions of continental blocks to the north side.At the same time,the mantle dynamics of deep-seated magma underplating,delamination,mantle plume and mantle-hydrated process should not be ignored.

Temporal and spatial distribution of the igneous rocks in the east china sea shelf basin and its adjacent regions

Abstract: Two-dimensional seismic and gravity-magnetic data were processed and interpreted by the authors in order to study the temporal and spatial distribution of igneous rocks in the East China Sea Shelf Basin and its adjacent regions.Data from the land,mainly from Zhejiang and Fujian provinces were collected for the purpose of correlation.Igneous rocks are widely distributed in Zhejiang and Fujian.They occur in a NE trending to the north and NNE trending to the south of 28 N.They are shallowly buried and controlled mainly by major faults.The igneous rocks offshore are mainly distributed upon uplifts or along the fault boundaries of depressions.Temporally,the igneous rocks in the study area can be subdivided into four stages,i.e the Yanshan stage,Sichuan stage,Huabei stage and Himalayan stage and spatially occur in four zones,say the Zhe-Min uplifted zone,Central uplifted zone,Diaoyu Island folded uplifting zone and Ryukyu arc zone.

Cenozoic Tectonics and Dynamics of Basin Groups of the Northern South China Sea

Abstract: There are a lot of Cenozoic basins from west to east in the northern margin of the South China Sea,including the Beibu Gulf,the Qiongdongnan,the Pearl River Mouth and the Taixinan basins.Previous studies suggested that these basins are derived gradually during the rifting of the southeast continental margin of the South China Block and the formation of the northern passive margin of the South China Sea.However,a large number of seismic profiles revealed that some major basin-controlling faults in the northern margin of the South China Sea are landward-dipping,which are clearly inconsistent with the major seaward dipping faults of a typical passive continental margin basin.Thus,the Mckenzie's extension model of passive continental margin remains controversial for the formation mechanism of the northern marginal basins of the South China Sea.This article,based on the comparison between a large number of field observation and marine seismic data,reveals that the northern continental margin of the South China Sea is not a passive continental margin before 34Ma.The early faults were well developed in NE—NNE-striking,corresponding to the strike-slipping faults in the southeast South China.These dextral,right-step strike-slipping faults are NE—NNE striking,controlling the secondary faults with near-EW or NEE strikes and the distribution of tectonic units in the pull-apart basins.Therefore,a series of Cenozoic basins in the northern margin of the South China Sea is dextral,right-step pull-apart basin group,having close relation in dynamics.This pull-apart model is consistent with the migration of sedimentary-subsidence centers and depocenters,tectonic jumping and magmatic migration within Cenozoic basins.The northern continental margin of the South China Sea actually became a typical passive continental margin since 15 Ma,when the South China Sea oceanic crust terminated spreading.At last,all structures in the northern continental margin of the South China Sea are offset by the late,diffusive NWW-striking faults resulting from the gradual indentation of the Philippines Plate to the Eurasian Plate along the Luzon Arc and the Taiwan Orogenic Belt between 10 Ma and about 5 Ma.Basin dynamics in northern continental margin of the South China Sea is mainly related to the dynamics of the Pacific Plate.

Organo-clay complexes in source rocks——a natural material for hydrocarbon generation

Abstract: Traditionally,it is believed that kerogen,a organic matter insoluble in organic solvents separated chemically from source rock,is a material for hydrocarbon generation[1].The procedure to treat samples as such,however,may destroy the original occurrence and relationship between organic matter and clay in source rocks.We extracted an organo-clay complex(2μm) from the crushed source rocks in the depth of 280~3 500 m,in the Jiyang sag,East China.The complex is mainly composed of layered illite-smectite(I-S) and illite with a value of TOC up to 2.62%~9.78%.After treatment with H2 O2,TOC remains as high as 1.23%~4.63%,suggesting that it is the components in which organic matters are enriched.The diffraction peak(d001) of the complex is 1.3~1.4nm at 250℃,and moves to 1.0 nm at 550 ℃ in XRD curves,and the exothermic peaks of the complex is extraordinary stable at 350 ℃ in DTA curves.;The result is consistent in both the XRD and DTA observations.It indicates that organic matter can enter the interlayer space of clay minerals.With PY-GC analysis,the organic matter of C5 and C25 is released from the complex in a temperature range of 250~650 ℃,and reaches a peak at about 450 ℃.Our findings reveal that organic matter can enter interlayer of clay minerals forming a kind of natural and highly stable organo-clay complex,and the composition of the organic matter in the complex is similar to the crude oil.As a kind of natural material,the organo-clay complex plays an important role in hydrocarbon generation in source rocks.

Research of Landslides and Debris Flows in Bailong River BASIN:PROGRSS and Prospect

Abstract: The Bailong River catchment is located in the intersection of Tibetan Plateau,Loess Plateau and Sichuan Basin.It is also the cross point of the east-west and north-south seismic zones.Due to complex geological structures,the region is characterized by steep slopes,high relative reliefs and deep incised valleys.Weak rocks,which are widely distributed,and heavy rainfalls made the region one of the four areas in China most severely affected by landslide and debris flow disasters.Based on the data from field investigation and on-going research projects,this paper deals with the characteristics of landslides and debris flows,and their genetic mechanisms.The management of monitoring and early-warning systems and hazard prevention in this region are also discussed,with the purpose to encourage further researches on geohazards and mitigation measures in the region.

Cenozoic Basin-Controlling Faults and Their Bearing on Basin Groups Formaion in the Southern South China Sea

Abstract: There are many small and medium-sized Cenozoic sedimentary basins in the southern South China Sea,such as the Nanweixi Basin,the Beikang Basin,the Liyue Basin,the Zengmu Basin,the Nansha Trough,the Brunei-Sabah Basin,the Northwest Palawan Basin and other basins from north to south.In general,NE-trending faults control the formation of the half grabens with faulting in the north and overlapping in the south.However,single grabens are mainly developed in the northern continental slope,while two-layered basins developed in the south of the region,of which the lower layer is the graben and the upper layer the imbricated nappes.According to the nature of main controlling faults and the transition of the basins at different evolutionary stages,these basins can be divided into three groups: the rift basin group(the Nanweixi,Beikang and Liyue basins),the rift-pull-apart-foreland superimposed basin group(the Zengmu basin) and the rift-foreland basin group(the Nansha Trough,Brunei-Sabah,the Northwest Palawan basins).The formation of these basin groups is closely related to major marginal faults of the basins and secondary faults in the sub-basins.Based on the nature of the faults,the basin-controlling fault belts can be subdivided into three types: tensile,shear and compressional,including the extensional fault belt in the northern edge of the Nansha Trough,the strike-slip fault belts at the west edge of the Wanan Basin and the Lupar and the Tingjia-Lee Jun Fault belts,and the thrust fault belt in the southern edge of the Nansha Trough.Tectonic events which happened in southern South China Sea,such as the South China Sea Movement in Oligocene and the Nansha Movement in the Middle Miocene,affected the basins to various degrees.As the result,there was the inversion from a rift basin/pull-apart basin to a marine foreland basin,as well as the inversion of fault belts from normal faults to reverse faults or strike-slip faults.The kinetic mechanism of the basin groups varies in different stages.In the early stage,it may be related to the continental rifting of the southeast edge of the Eurasia continent,and the subduction and dragging of the Paleo-South China Sea slab resulted in the splitting of southern South China Sea from the South China continent,and then,half garbens formed with faulting in the north and overlapping in the south.In the later period(about 16 Ma),the north-directed imbricated thrust nappes propagated forward in the southern South China Sea due to the collision of the southern Australian Plate to the northern Eurasian Plate,which resulted in the transition of basin types and the counterclockwise rotation of the Borneo Block.

Stratigraphic Features of the Mesozoic ``GREAT East China SEA''—A New Exploration Field

Abstract: Based on the latest re-processed and newly acquired seismic data and using the integrated approaches including seismic,well drilling,inverse gravity and magnetic processing and land sea correlation,we studied the distribution of the Mesozoic in the southern East China Sea Shelf Basin,and got some new understandings about the three uplifts,namely the Yandang,Taibei and Guanyin uplifts,defined by previous studies.It is found that the Yandang Uplift is in fact not a continuously uplift from north to south,but an old Proterozoic uplift made up of three en echelon uplifts,which disappear southward.Mesozoic strata occur steadily on both the Guanyin and Taibei uplifts.Our results show that the Mesozoic strata in the Southern East China Sea Shelf Basin are quite thick and widely distributed.According to our data,it is thicker in the south and east,and thinner in the north and west.In this regard,the concept of Mesozoic Great East China Sea is proposed in this paper to conclude the new discoveries.

The environmental change recorded in jiangxigou loess sections in qinghai lake region

Abstract: The Qinghai Lake area is a hot spot in global change studies,due to its sensitivity to global warming.During the last deglaciation,aeolian deposits were widely distributed in the region,with drastic environmental and climatic changes.In this paper,we studied two loess sections(JXG1and JXG2) near the Jiangxigou town to the south of Qinghai Lake,upon which we reconstructed the regional environmental changes since the last deglaciation.The results show that :(1) During 13～11.5kaBP,the paleolclimate was cold and dry there.Aeolian deposition prevailed and sandy loess formed.In general,the region was changing from a cold and dry to a cool and humid environment;(2) During 11.5～5kaBP,pedogenesis was relatively strong.Maximum moisture levels occurred during the period of 9～5kaBP,and in general,the paleoclimate was warm and wet;(3) After 5kaBP,climate often alternated,dust storm occurred frequently,vegetation coverage decreased,and the climate entered a relatively unstable stage.The environmental changes of the Jiangxigou Loess section are comparable with those revealed by the boreholes in the Qinghai Lake and the Heimahe loess section.The redness of the Jiangxigou loess section is a sensitive index to environmental change.The loess deposition since the last deglaciation in Qinghai Lake area was mainly controlled by the ice volume of the northern hemisphere,which was driven by the summer solar irradiation at the high latitude.The Westerlies played the role as a cold-air conveyer between the North Atlantic and the northeastern Tibetan Plateau.

Holocene foraminifera from the mud area of the inner shelf,east china sea and their paleoenvironmental significance

Abstract: The mud area on the inner shelf of the East China Sea is one of the depocenters since the high sea-level of the HoloceneSedimentary records since the post-glacial saved in this area provide excellent materials for studying paleoceanographic and paleoenvironmental changes during the HoloceneThe Core of MZ02 was recovered from the middle of the mud area(12189°E,2817°N,water depth 32 m,core length 353 m),and radiocarbon dating,grain-size and foraminiferal analyses were performed for paleoceanographic and paleoenvironmental reconstructionResults show that the environmental evolution in the Holocene can be divided into 4 stages: the stage I was the coastal inner shelf during 108~105 calkaBP;the stage II was the period of the rapid sea-level rise from coastal shelf to the middle shelf during 105~83 calkaBP;the stage III was the inner-middle shelf with the Taiwan Warm Current close to the studied area during 83~52 calkaBP;and the stage IV was the inner shelf under the action of the enhanced coastal currentThe abundance of warm-water species increased markedly at 84 calkaBP,suggesting the invasion of the Taiwan Warm Current since thenThe lower δ18O in benthic foraminifera and higher abundance of epifaunal species are thought to be closely related to the enhancement of the coastal current since ~40 calkaBP

Mesozoic Tectonic Evolution and Prototype Basin Characters in the Southern East China Sea Shelf Basin

Abstract: The Southern East China Sea Shelf Basin is a Mesozoic-Cenozoic superimposed basin developed on the pre-Mesozoic basement at the junction of the Eurasian,Pacific and Indian plates.It has experienced the superimposed deformations of the Jilong,Yushan and Yandang movements and the tectonic evolution is obviously influenced by both the subduction of the Paleo-Pacific plate and the Thethys-Himalayas Tectonic Domain.Studies of Mesozoic igneous events,basin tectonic deformation,sedimentology and comparative study between land and sea have been carried out in this region.Results suggest that the Southern East China Sea Shelf Basin might be a passive continental margin basin facing the Paleo-Pacific in Early-Middle Triassic;a fore-arc basin along the active ocean margin while the Paleo-Pacific Plate intensely subducted under the East Asia continent in Late-Triassic and Jurassic;a strike-slip pull apart basin controlled by the offshore Fault in the Cretaceous and a backarc rift basin in Palaeocene-Eocene when volcanic arc migrated eastwards.

Basin-controlling faults and formation mechanism of the cenozoic basin groups in the western south china sea

Abstract: A series of medium and small-scale Cenozoic sedimentary basins are developed in the western South China Sea.They are,from north to south,the Yinggehai,the Zhongjiannan,the Wan'an and the Zengmu basins,respectively.These basins are developed along the Red River Fault Belt,the Western-edge Fault Belt of South China Sea and the Eastern-edge Fault of the Wanan Basin,which occurred as sinistral,left-step faults at the earlier stage,and dextral,right-step faults at the later stage.The fault belt shows a tulip-flower structure.From north to south,the main fault planes shows a ribbon pattern with the Red River Fault dipping southwestward,and the Western-edge Fault Belt and the Eastern-edge Fault The Wanan Basin dipping eastward.The South China Sea is characterized by the east-dipping fault and the Eastern-edge Fault of the Wanan Basin acts as the east-dipping fault,too.These basins developed along the fault belt are a set of pull-apart basin groups and closely related with each other in origin.The NE-trending faults within the basins are secondary faults controlling over depressions.The displacements of these fauts are limited,and thus the basin group should not be the results of the combined effects of the 700 km extrusion tectonics of the Indochina Block or some deep mantle plumes,but Cenozoic pull-apart basins.In addition,the basin group is also related to the sustainable indentation and collision of the Indian-Australian Plate to the Eurasian Plate based on the comparison of tectonic events.Therefore,the main dynamics of the basin group is derived from the dynamic system in the west of the South China Sea.The dextral,right-step fault belt is offset by the late NWW-trending left-step,sinistral faults which are continuous and consistent in strike with the NWW-trending faults in the Luzon Arc.Therefore,the dynamic system of the indentation of the Philippine Sea Plate to the Eurasian Plate along the island arcs may extend to the study area at the later stage.

Distribution Pattern of Heavy Metals in the Surface Sediments of the Area of Circum-Bohai Bay and Ecological Environment Assessment

Abstract: The distribution pattern of heavy metals in the surface sediments around the Circum-Bohai Bay and its influencing factors were studied in the paper.The Nemerow comprehensive index method is adopted for ecological assessment.Results show that the Liaodong Bay is the most seriously polluted area from among the three studied areas.Cd and Hg are highly beyond the standard.Spatially,high values occur in the west of the northern Liaodong Bay and the Xiaoling River estuary off the Huludao.Cu,Pb and Zn show similar distribution pattern due to similar provenance and granularity.The assessment of ecological risk indicates that the area near Huludao is the most vulnerable area in heavy metal pollution.

Variation of sediment load at the major tributaries in the middle reaches of yellow river and its impacts on the sediment flux to the sea

Abstract: The loess plateau plays a critical role in the sediment budget of Huanghe River and its flux to the seaHere in this paper,we studied the variations in annual water discharge and sediment load in seven main tributaries in the middle reach of the Huanghe RiverAnnual water and sediment data have been acquired from seven major hydrographic stations for 7 tributaries(Huangfuchuan River,Kuyehe River,Wudinghe River,Yanhe River,Beiluohe River,Jinghe River and Weihe River) and the Tonguan Station in the middle reach of the Huanghe River in 1950-2009Besides,we studied the annual sediment load of the seven major tributaries and several hydrological stations in the mainstream(Tongguan and Lijin)The results indicate that the annual water discharge and sediment load decreased sharply over the past 60 years,the total sediment loads have dropped from 135 108t/a in 1950s-1960s to only 34 108t/a in 2000-2009,with a reduction of about 75%Time series data of sediment loads from the major tributaries and Lijin station indicate that tributaries in the loess plateau played a dominant role in the decrease in Huanghe sediment flux to the sea,while the rapid increases in water consumption and redistribution in the low reaches sinc the 1980s accelerated the reduction of sediment flux to the sea

Beach Erosion Along the Coast of Shandong Province and Protection Countermeasures

Abstract: The coastal beach,as a precious natural heritage,is the most beautiful natural landscape and the engine for tourism development along the coast.It has raised great attention both at home and abroad.The working group of Ocean University of China has established the Shandong coastal beach information archives after three years of systematic investigation and research.There are 123 coastal beaches in Shandong,with a total length of 365 kilometers of coastline.They,in terms of spatial distribution,look like a bunch of beautiful pearls inlaid around the Shandong peninsula.This study,however,has found that 98 of the coastal beaches have been under erosion,accounting for about 80% of the total number of beaches,caused by human activities.In view of the important value of coastal beaches in social civilization and development,we suggested that Shandong province and all levels of governments under it should raise the awareness of coastal beach protection and focus more on the countermeasures against coastal erosion,with rationale planning as the first priority.

Estimation of gas hydrate saturation with modified biot gassmann theory: a case from northern south china sea: estimation of gas hydrate saturation with modified biot gassmann theory: a case from northern south china sea

Abstract: The modified Biot-Gassmann theory(BGTL) proposed by Lee(2002) is applied in this study to estimation of the saturation of gas hydroate in the deep-water unconsolidated clayey sediments from the Well A,Shenhu area,northern South China Sea.The BGTL theory assumes that the ratio of the shear to compressional velocities of an unconsolidated sediment is related to the ratio of the shear to compressional velocities of the solid matrix in the sediment and its porosity.Parameters involved in the model are related to the occurrence of gas hydrate,mineral components,pressure differentiation,porosity,and pore structure of the sediments.The cross plot of velocity from sonic logging vs.concentration of gas hydrate from core measurements suggest that the occurrence of gas hydrate in the sediments of Well A is more or less close to the matrix model.Statistics from core smear slide data suggest that the sediment matrix in well A can be simplified as three major mineral components,i.e clay,carbonate,and terrigenous clastic minerals.The elastic modulus and density values of the matrix are calculated by the elastic modulus and density values of the individual mineral components and their volume percentage.As estimated,the gas hydrate in Well A is mainly distributed in the depth interval of 195 to 220 meters below sea floor with a highest concentration of gas hydrate up to 47%,which matches well with the results from core measurements.

Dating methods for chronological study of yardang landforms:a review and perspective in application

Abstract: The age of the Yardang landform is the important parameter for determination of erosion rate and erosion quantityIt is also the premise for deeper understanding of the formation and evolution of the Yardang landform,and the relationship between the Yardang and environmentAs a type of erosional landforms,the age of the Yardang landform always remains as a puzzle to researchers,and become a bottleneck in the studyIn this article,the authors made a review of the methods for dating Yardang landformThen,we made a testing of the methods by applying some of them to date the Yardang landform in the Dunhuang Yardang National Geo-parkOur results suggested that the Yardang landform was formed in a period not later than 10kaBP and not earlier than 39 kaBPAt last,we prospect the direction of the yardang formation chronology research

Preliminary Study on Spatiotemporal Pattern of Climate Change Over Tibet Plateau during Past Millennium

Abstract: Researching the climate change during past millennium over Tibet Plateau(TP) plays a vital role in the prediction of cryosphere change in such region and its far-reaching influence under future warming climate.By 15 high resolution paleoclimate series reflecting the climate evolution during past millennium over TP,this paper aims to further study the spatiotemporal pattern of climate change during past millennium over TP.The comprehensive reconstruction of temperature by these 15 series indicates that,generally,over the past millennium,TP has been characterized by a prominent Medieval Warm Period(MWP,the period before ~1450s),a moderate Little Ice Age(LIA,from ~1450s to 1870s),and the increase of temperature since then(the abrupt drop of temperature around 1920s and 1970s were evidently).By comparison,the warmth of MWP over TP shows a good agreement with that during the first half of 20th century,and that in other reconstructions of temperature over the Northern Hemisphere;the LIA over TP is relatively warmer than that over eastern China.Moreover,Empirical Orthogonal Function(EOF) analysis of these 15 series is carried out to explore the spatiotemporal pattern of climate change during past millennium over TP.It suggests that the three major "climate anomalies" during past millennium(MWP,LIA and post-industrial warming) have showed marked regional differences over sub-region of TP.The MWP lasts until ~1450s in Northeast TP and Northern TP and Western TP(the period during 1250—1300s was a cold epoch),~13th century in Karakoram region and Eastern TP;lots of materials in Southern TP revealed that the MWP would occur during 11—15th century(while the PC3 of EOF analysis,reflecting the climate information in Southern TP,indicated that the warmth of MWP was not evidently in this region).During LIA,there were three cold epochs(i.e.,1450—1520s,1650—1750s and 1780—1850s) in Northeast TP and Western TP,three cold epochs(i.e.,1450—1650s,1740—1780s and 1820—1850s) in Karakoram region,two cold epochs(i.e.,1580—1650s and 1740—1780s) in Southern TP and Eastern TP and Northern TP(the period during 1670—1730s would be a warm epoch which was also evidently in Karakoram region).Last but not least,few tree ring records in southern TP and Eastern TP have showed a decrease of summer temperature against the notable increasing of global temperature,possibly attributing to the inconsistency of temperature change in different seasons(i.e.,summer and winter) during global warming.

Distribution and source of heavy minerals in the surface sediment of the tidal sand ridges area in south yellow sea

Abstract: A total of 301 surface samples collected in 2008 from the tidal sand ridges area located to the south of the abandoned yellow river subaqueous delta in the south yellow Sea were analyzed for heavy minerals.Some distinct characteristics of heavy minerals are observed in the study area:(1)the high weight content of heavy minerals;(2)abraded mineral grains and iron-stained grain surface;and(3)sharp content variation in dominant minerals from area to area.These characteristics were dependent upon the depositional environment which was featured by strong hydrodynamics,high content of sand fraction,strong oxidation,and quick variation in water depth in the sand ridges area.Common hornblende and epidote dominate.Mica,hematite,limonite,ilmenite and magnetite are recognized as diagnostic minerals.The mineral assemblages suggest that the source would be the dominant factor controlling the distribution pattern of heavy minerals.The sediments of the tidal sand ridges area are mainly from the Yellow River and the Yangtze River.The contribution of other material sources is not obvious.The materials from the Yellow River are widely distributed in the whole tidal sand ridges area.However,its impact gradually becomes weak form north to south.By contrast,the materials of Yangtze River are mainly distributed in the middle and southern parts of the tidal sand ridges area.The distribution of stable minerals,especially zircon could be used to denote the distribution area of the materials from the Yangtze River.The content of heavy minerals and their spatial distribution demonstrate that high oxidation and severe erosion mainly occur in the outer part of tidal sand ridges area.There is no obvious differentiation of mineral composition between the sand ridges and the adjacent areas,showing that sand ridges are in the process of shrinking.The distribution of schistose minerals and weathering index indicate that there might be a path for sediment dispersion from the abandoned Yellow River subaqueous delta to the northeastern of Yangtze River mouth passing through the middle part of the tidal sand ridges area.

Segmentation of subduction system in the eastern south china sea and dynamics of related basin groups

Abstract: The east part of the South China Sea is located at the convergence zone between the Eurasian Plate and the Pacific Plate(the Philippine Sea Plate).To the east of the South China Sea,there are the Manila Subduction Zone,the Luzon Arc and the East Luzon Philippine Subduction Zone,consisting of a opposite-dipping trench-arc-basin system which is called subduction system in this paper.The system can be subdivided into three segments from north to south by the Babuyan Strike-slipping Fault and the Sibuyan Strike-slipping Fault respectively,based on the differences in geomorphology,earthquakes,volcanism,faulting,basins and geophysical characteristics.The north segment is affected by the collision of the Taiwan Orogen,and the NWW-directed indentation of the Philippine Sea Plate and the stopping of the Beikang Uplift to the west of the Taiwan Orogen,resulted in the extrusion of the continental blocks of northeastern South China Sea,and the formation of the Taixinan Basin and the Taixi Basin,which are a series of collision-wedge-extrusion related basins.The middle segment is controlled by "Slab Window" during the subduction of fossil mid-oceanic ridge of the South China Sea,the earthquakes,magmatism,geomorphology and stress fields are different from north to south,and the formation of the basin group is controlled by arc strike-slip faults.The south segment is dominated by west-dipping subduction of the Philippine Sea Plate.The intensive earthquakes and volcanism are near the Philippine Trench.However,the stopping of the Sunda Block and the Palawan Block to the west of the Manila trench and the adjustment of the Great Philippine Fault in the central Philippine islands result in curvature of the Manila Trench in plane and decrease in earthquakes and volcanism in the west of the segment.The basin group is located in the segment developed on the basement resulting from collisions of different block fragments.The adjustment and pull-apart faulting of strike-slip faults caused the present-day basin pattern and distribution.The subduction system in the east of the South China Sea is affected by the NNW-directed indentation in the north segment and west-directed subduction in the south segment of the Philippine Plate,while the tectonic evolution of the middle segment of the subduction system is dominated by the east-directed subduction of the Manila Trench.

U-Pb Ages and hf Isotopic Composition of Crystalline Zircons from Igneous Rocks of the Changjiang Drainage Basin and Their Implications for Provenance

Abstract: High-resolution provenance study has been an important target for application of single-grain microanalysis technique.It is vital to carry out high-resoulation provenance study in the Changjiang drainage to set up detail crystalline-zircon microanalysis database including U-Pb age because of its vast catchment area,complex composition and distribution of parent rocks.The data of crystalline-zircon U-Pb age and Hf isotope in the catchment were therefore systematically collected from the recent decadal publications,and analyzed together with the update geologic investigation results of parent rock lithology,age and outcropped areas.It was indicated that only a few zircon grains can be traced to their separate sources directly by their typical ages,including those of50Ma,250~270Ma and3 000Ma,which are discriminated to the sources of the Changdu Block or the Jinshajiang Suture zone in the upper reach of the catchment,the Emeishan Basalt province in the Western Yangtze Block,and the Kongling Complex in the Three Gorges region,respectively.The effectiveness of provenance discrimination can be much highly improved through combined ananlyses of zircon U-Pb age andeHf(t)value.It is worthy noting that input of recycled detrital zircons will make the source discrimation more complicated.