regional warming pliocene 3 ma paleoclimate of europe and the mediterranean the paleoclimate of the middle pliocene ca 3 ma was generally warmer than present particularly at middle to high latitudes it has been suggested that this period may represent an analogue for future climate change mechanisms that have been proposed to account for this warming are enhanced thermohaline circulation and or greater concentrations of co 2 in the atmosphere we present new climate model simulations supported by geological data that suggest that in the european and mediterranean region the climate was warmer by 5 c wetter by 400 1000 mm yr and less seasonal than present modeling results suggest that an intensification of the icelandic low pressure system and the azores high pressure system occurred during the middle pliocene as a direct result of higher annual sea surface temperatures and reduced ice cover in the northern hemisphere this change increased the surface pressure gradient over the region and strengthened annual westerly wind velocity by 4 m s 1 associated increases in wind stress by 20 n m 2 over the north atlantic ocean may have enhanced the flow of surface currents such as the gulf stream and north atlantic current which in turn would have sustained the higher sea surface temperatures these changes to the regional climate system would have driven greater atmospheric and oceanic transport of heat from equatorial regions to the north atlantic ocean particularly during winter such conditions are proposed as a likely cause of the warming indicated for europe and the mediterranean ca 3 ma

potbellies wasp waists and superparamagnetism in magnetic hysteresis because the response of a magnetic substance to an applied field depends strongly on the physical properties of the material much can be learned by monitoring that response through what is known as a magnetic hysteresis loop the measurements are rapid and quickly becoming part of the standard set of tools supporting paleomagnetic research yet the interpretation of hysteresis loops is not simple it has become apparent that although classic single domain pseudo single domain and multidomain loops described in textbooks occur in natural samples loops are frequently distorted having constricted middles wasp waisted loops or spreading middles and slouching shoulders potbellies such complicated loops are often interpreted in oversimplified ways leading to erroneous conclusions the physics of the problem have been understood for nearly half a century yet numerical simulations appropriate to geological materials are almost unavailable in this paper we discuss results of numerical simulations using the simplest of systems the single domain superparamagnetic sd sp system examination of the synthetic hysteresis loops leads to the following observations 1 wasp waisting and potbellies can easily be generated from populations of sd and sp grains 2 wasp waisting requires an sp contribution that saturates quickly resulting in a steep initial slope and potbellies require low initial slopes the sp contribution approaching saturation at higher fields the approach to saturation is dependent on volume hence the cube of grain diameter therefore there is a very strong dependence of hysteresis loop shape on the assumed threshold size 3 we were unable to generate potbellies using an sp sd threshold size as large as 30 nm and wasp waists cannot be generated using a threshold size as small as 8 nm the occurrence of both potbellies and wasp waists in natural samples is consistent with a room temperature threshold size of some 15 nm 5 4 simulations using a threshold size of 15 20 nm with populations dominated by sp grain sizes that is with a small number of sd grains produce synthetic hysteresis loops consistent with measured hysteresis loops and transmission electron microscopic observations from submarine basaltic glass 5 simulations and measurements using two populations with distinct coercivity spectra can also generate wasp waisted loops a relatively straightforward analysis of the resulting loops can distinguish the latter case from wasp waisting resulting from sp sd behavior

characterization of hematite α fe2o3 goethite α feooh greigite fe3s4 and pyrrhotite fe7s8 using first order reversal curve diagrams 1 first order reversal curve forc diagrams have become a standard tool in rock magnetism yet magnetite is the only magnetic mineral that is well characterized using forc diagrams we present forc diagrams for predominantly single domain sd synthetic aluminous hematite a fe2 xalxo3 and goethite a feal ooh and natural greigite fe3s4 and pyrrhotite fe7s8 to constrain interpretation of forc diagrams from natural samples hematite and goethite have low spontaneous magnetizations and negligible magnetic interactions while greigite and pyrrhotite have higher spontaneous magnetizations and can have strong magnetic interactions the coercivity of hematite systematically increases with al content only for samples produced using the same synthesis method but it is variable for samples produced with different methods even for similar al content this precludes use of magnetic coercivity alone to quantify the al content of natural hematites goethite has much higher coercivity than hematite for all measured samples sd and superparamagnetic sp behavior is common in natural greigite samples with peak coercivities ranging from

reassessment of continental growth during the accretionary history of the central asian orogenic belt we argue that the production of mantle derived or juvenile continental crust during the accretionary history of the central asian orogenic belt caob has been grossly overestimated this is because previous assessments only considered the palaeozoic evolution of the belt whereas its accretionary history already began in the latest mesoproterozoic furthermore much of the juvenile growth in central asia occurred in late permian and mesozoic times after completion of caob evolution and perhaps related to major plume activity we demonstrate from zircon ages and nd hf isotopic systematics from selected terranes within the caob that many neoproterozoic to palaeozoic granitoids in the accreted terranes of the belt are derived from melting of heterogeneous precambrian crust or through mixing of old continental crust with juvenile or short lived material most likely in continental arc settings at the same time juvenile growth in the caob occurred during the latest neoproterozoic to palaeozoic in oceanic island arc settings and during accretion of oceanic island arc and precambrian terranes however taking together our data do not support unusually high crust production rates during evolution of the caob significant variations in zircon ehf values at a given magmatic age suggest that granitoid magmas were assembled from small batches of melt that seem to mirror the isotopic characteristics of compositionally and chronologically heterogeneous crustal sources we reiterate that the chemical characteristics of crustally derived granitoids are inherited from their source s and cannot be used to reconstruct tectonic settings and thus many tectonic models solely based on chemical data may need re evaluation crustal evolution in the caob involved both juvenile material and abundant reworking of older crust with varying proportions throughout its accretionary history and we see many similarities with the evolution of the sw pacific and the tasmanides of eastern australia

separation of local signals from the regional paleomonsoon record of the chinese loess plateau a rock magnetic approach we propose a method based on thermal unblocking of low temperature saturation remanent magnetization for a quantitative estimation of the superparamagnetic cullity 1972 fraction size d 30 nm of magnetite produced by pedogenesis in the chinese loess plateau liu 1988 we applied this method to the proxy climatic records of the last 130 ka from two sites 250 km apart but separated by the mountain range liupan shan xifeng to the east 35 7 n 107 6 e and baicaoyuan to the west 36 2 n 105 0 e currently have humid and arid microclimates respectively as expected the superparamagnetic fraction increases during known warm temperature intervals at each site furthermore the more humid site clearly has higher overall superparamagnetic fractions during most of the last 130 ka however during the period 5 to 10 ka ago the relative humidity at both sites was the same within experimental errors bulk grain size evidence confirms the magnetic data and we suggest that the present easterly summer monsoon in china came from a more southerly direction during this time to flow parallel to liupan shan resulting in very similar summer humidity at xifeng and baicaoyuan

quantification of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation abstract a new method of analysing isothermal remanent magnetisation irm acquisition curves based on cumulative log gaussian analysis robertson and france phys earth planet inter 82 1994 223 234 is proposed it is based on the curve fitting of the irm acquisition curve versus the logarithm of the applied field with i the acquisition curve on a linear scale ii the acquisition curve expressed as a gradient and iii the acquisition curve on a probability scale even when a sample is not saturated its magnetic properties can be defined although with less certainty the number of magnetic components required for an optimal fit to a measured irm acquisition curve is evaluated statistically the method discriminates on the basis of different mineral coercivity therefore additional rock magnetic tests are still required to separate minerals with similar coercivities

1 8 ga svecofennian post collisional shoshonitic magmatism in the fennoscandian shield abstract at least 14 small 1 11 km across 1 8 ga svecofennian post collisional bimodal intrusions occur in southern finland and russian karelia in a 600 km long belt from the aland islands to the nw lake ladoga region the rocks range from ultramafic calc alkaline apatite rich potassium lamprophyres to peraluminous hibasr granites and form a shoshonitic series with k 2 o na 2 o 5 k 2 o na 2 o 0 5 al 2 o 3 9 over a wide spectrum of sio 2 32 78 although strongly enriched in all rocks the lile ba and sr and the lree generally define a decreasing trend with increasing sio 2 depletion is noted for hfse ti nb and ta available isotopic data show overlapping values for lamprophyres and granites within separate intrusions and a cogenetic origin is thus not precluded initial magmas mg 65 in this shoshonitic association are considered to be generated in an enriched lithospheric mantle during post collisional uplift some 30 ma after the regional svecofennian metamorphic peak however prior to the melting episode the lithospheric mantle was affected by carbonatite metasomatism more extensively in the east than in the west the melts generated in the more carbonate rich mantle are extremely enriched in p 2 o 5 4 f 12 000 ppm lile ba 9000 ppm sr 7000 ppm lree la 600 ppm and ce 1000 ppm the parental magma underwent 55 60 fractionation of biotite clinopyroxene apatite magnetite sphene whereupon intermediate varieties were produced after further fractionation 60 80 of k feldspar amphibole plagioclase minor magnetite sphene and apatite leucosyenites and quartz monzonites were formed in the west where the source was less affected by carbonatite metasomatism calc alkaline lamprophyres vogesites minettes and spessartites and equivalent plutonic rocks monzonites were formed removal of about 50 of biotite amphibole plagioclase magnetite apatite and sphene produced peraluminous hibasr granites the impact of crustal assimilation is considered to be low at about 1 8 ga the post collisional shoshonitic magmatism brought juvenile material particularly enriched in alkalis lile lree and f into the crust although areally restricted the regional distribution of the post collisional intrusions may indicate that larger volumes of 1 8 ga juvenile material resides in unexposed parts of the crust

a 6 ma chemical weathering history the grain size dependence of chemical weathering intensity and its implications for provenance change of the chinese loess red clay deposit abstract major element chemical analyses of the baishui loess red clay sequence 35 24 10 n 106 54 43 e gansu province china reveal that the chemical weathering intensities inferred from cia chemical index of alteration values have progressively weakened and increased in amplitude with decreasing age the general trend of the cia can be correlated well with the oxygen isotope variations of the deep sea sediments analyses of multiple size fractions

mantle dynamics uplift of the tibetan plateau and the indian monsoon convective removal of lower lithosphere beneath the tibetan plateau can account for a rapid increase in the mean elevation of the tibetan plateau of 1000 m or more in a few million years such uplift seems to be required by abrupt tectonic and environmental changes in asia and the indian ocean in late cenozoic time the composition of basaltic volcanism in northern tibet which apparently began at about 13 ma implies melting of lithosphere not asthenosphere the most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere the initiation of normal faulting in tibet at about 8 3 ma suggests that the plateau underwent an appreciable increase in elevation at that time an increase due solely to the isostatic response to crustal thickening caused by india s penetration into eurasia should have been slow and could not have triggered normal faulting another process such as removal of relatively cold dense lower lithosphere must have caused a supplemental uplift of the surface folding and faulting of the indo australian plate south of india the most prominent oceanic intraplate deformation on earth began between about 7 5 and 8 ma and indicates an increased north south compressional stress within the indo australian plate a tibetan uplift of only 1000 m if the result of removal of lower lithosphere should have increased the compressional stress that the plateau applies to india and that resists india s northward movement from an amount too small to fold oceanic lithosphere to one sufficient to do so the climate of the equatorial indian ocean and southern asia changed at about 6 9 ma monsoonal winds apparently strengthened northern pakistan became more arid but weathering of rock in the eastern himalaya apparently increased because of its high altitude and lateral extent the tibetan plateau provides a heat source at midlatitudes that should oppose classical symmetric hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons for the simple case of axisymmetric heating no dependence on longitude of an atmosphere without dissipation theoretical analyses by hou lindzen and plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal monsoonlike circulation than such a source centered on the equator but only if heating exceeds a threshold whose level increases with the latitude of the heat source because heating of the atmosphere over tibet should increase monotonically with elevation of the plateau a modest uplift 1000 2500 m of tibet already of substantial extent and height might have been sufficient to exceed a threshold necessary for a strong monsoon the virtual simultaneity of these phenomena suggests that uplift was rapid approximately 1000 m to 2500 m in a few million years moreover nearly simultaneously with the late miocene strengthening of the monsoon the calcite compensation depth in the oceans dropped plants using the relatively efficient c4 pathway for photosynthesis evolved rapidly and atmospheric co2 seems to have decreased suggesting causal relationships and positive feedbacks among these phenomena both a supplemental uplift of the himalaya the southern edge of tibet and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the himalaya that in turn enhanced extraction of co2 from the atmosphere thus these correlations offer some support for links between plateau uplift a downdrawing of co2 from the atmosphere and global climate change as proposed by raymo ruddiman and froehlich mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts but might also play an important role in altering regional and global climates

lead isotope variations across terrane boundaries of the tien shan and chinese altay the altaid orogen was formed by aggregation of paleozoic subduction accretion complexes and precambrian basement blocks between the late proterozoic and the early mesozoic because the altaids are the site of abundant granitic plutonism and host some of the largest gold deposits in the world understanding their formation has important implications on the comprehension of phanerozoic crustal growth and metallogeny in this study we present the first extensive lead isotope data on magmatic and metasedimentary rocks as well as ore deposits of the southern part of the altaids including the tien shan tianshan and southern altay altai orogenic belts our results show that each terrane investigated within the tien shan and southern altay is characterized by a distinct pb isotope signature and that there is a sw ne pb isotope gradient suggesting a progressive transition from a continental crust environment in the west the kyzylkum and kokshaal segments of the southern tien shan to an almost 100 juvenile morb type mantle derived crust environment in the east altay the pb isotope signatures of the studied ore deposits follow closely those of magmatic and metasedimentary rocks of the host terranes thus supporting the validity of lead isotopes to discriminate terranes whereas this apparently suggests that no unique reservoir has been responsible for the huge gold concentration in this region masking of a preferential pb poor au bearing reservoir by mixing with pb rich crustal reservoirs during the mineralizing events cannot be excluded

man s influence on the erosion and transport of sediment by asian rivers the yellow river huanghe example during the holocene sediment input from the yellow river to the yellow sea and adjacent areas has amounted to about 3000 km 3 detailed records from river gauging stations over the past 70 yrs together with estimates based on earlier historic records suggest that the river has contributed 2300 km 3 of sediment during the last 2300 yrs an average discharge of 1 km 3 yr 1 x 10 9 t yr prior to extensive agricultural use of the loess plateau in northern china beginning about 200 bc therefore the river s load must have been about 0 1 km 3 yr an order of magnitude lower than that at present a broad delta 20 m below sea level suggests that early holocene rates were higher than the pre agricultural average and therefore that middle holocene loads were low

age and petrogenesis of the neoproterozoic chon ashu alkaline complex and a new discovery of chalcopyrite mineralization in the eastern kyrgyz tien shan abstract neoproterozoic volcanics and granitoids formed at rodinia margins within a time span of 880 ma 700 ma are well documented in many terranes of the southern central asian orogenic belt caob ages younger than 550 ma corresponding to the opening of the terskey ocean are also common however so far there were very few published ages in the range 700 ma 550 ma from the kyrgyz tien shan in this paper we present new data for the alkaline chon ashu complex emplaced at the end of the cryogenian period of the neoproterozoic 850 635 ma gradstein et al 2012 the alkaline complex intrudes the precambrian metamorphic rocks north of the nikolaev line which separates the northern and middle tien shan terranes in the eastern kyrgyzstan the undeformed shallow level alkaline rocks range from olivine gabbro to nepheline and cancrinite syenites and leucosyenites the differentiated rock assemblage can be explained by fractional crystallization of high silica mineral phases which drives nepheline normative melts away from the silica saturation boundary the alkaline rocks of chon ashu are enriched in lile and hfse indicative of their origin from lithospheric mantle an age of 678 9 ma u pb shrimp was obtained for a protolith of country gneiss and an age of 656 4 ma was obtained for the crosscutting alkaline rocks of the chon ashu complex seven zircon grains recovered from gneiss and alkaline rocks had bright overgrown rims which yielded a cumulative age of 400 8 ma a metamorphic event followed by uplift and emplacement of shallow level alkaline complex constrains the geodynamic setting alkaline rocks usually form in an extensional setting and originate from lithospheric mantle the 690 ma xenoliths of mafic granulite from the nw tarim have been interpreted to originate by mafic underplating this mafic underplating may have been responsible for metamorphism in the middle crust prior to emplacement of the chon ashu complex the 670 ma 630 ma period of extension and emplacement of enriched alkaline rocks can be also traced on a regional scale through southern kazakhstan and the northern tarim we tentatively interpret these events as a result of mafic underplating and subsequent rifting related to the break up of rodinia during field work at chon ashu rich chalcopyrite mineralization has been discovered in carbonate veinlets in leucosyenite alkaline dikes and has also been found in the adjacent cambrian gabbro and granites shown on the map as undivided devonian silurian stockwork mineralization predominates though disseminated mineralization is also present the cu content reaches 16 184 ppm and is associated with elevated concentrations of pb zn and ag the polyphase structural evolution of the area suggests that mineralization could have formed in several genetically unrelated stages based on structural and mineralogical evidence we tentatively relate the earliest stage of chalcopyrite mineralization to the late magmatic co2 rich fluids emanating from the cryogenian alkaline complex the early devonian thermal event registered by growth of new zircon at 400 ma has important metallogenic implications on a regional scale however the origin of two zones of alteration in the undivided silurian devonian granites is ambiguous because their age was not determined geochronologically the 522 4 ma cambrian gabbro of the tashtambektor formation is strongly foliated along the splays of the nikolaev line indicating a hercynian origin of the fabric superimposed mineralized stockwork postdates the foliation and suggests a late hercynian age of mineralization in gabbro the new data enable a reassessment of the metallogenic potential of the eastern kyrgyz tien shan presence of not eroded high level mineralized neoproterozoic alkaline intrusions points to a previously underestimated metallogenic potential of pre hercynian granitoids which may host preserved porphyry systems skarns and shear related mineralization finally the devonian magmato metamorphic event which caused formation of a number of ore deposits in central kyrgyzstan and kazakhstan could also create potential exploration targets in eastern kyrgyzstan

geochemical discrimination of metabasalt rocks of the fan karategin transitional blueschist greenschist belt south tianshan tajikistan seamount volcanism and accretionary tectonics the fan karategin metamorphic belt south tianshan tajikistan is regarded to be an ancient subduction accretionary complex and is composed of three tectonostratigraphic units which display lithologies consistent with different tectonic settings the mafic schists which make up the major part of the older unit of the belt contain both alkali and tholeiitic metabasalts on the basis of rare earth and other immobile element characteristics the alkali metabasalts are akin to within plate ocean island basalts whereas the tholeiitic metabasalts resemble e type morb the association is interpreted to have been formed on seamount like structures under a within plate plume bedded cherts and marbles in the unit are regarded as ancient pelagic sediments and carbonate caps developed upon basaltic seamounts respectively dismemberment of the seamount related basalts and pelagic sediments and the high p low t prograde metamorphism of the unit rocks up to transitional blueschist greenschist facies was the result of paleoseamount submergence into a subduction zone this unit is tectonically overlain by arc derived metavolcanic unit and a disrupted mainly clastic unit of upper ordovician lower silurian age metavolcanic and metasedimentary rocks of the two upper units have geochemical characteristics compatible with subduction related origin the lithological assemblages of the individual units and their juxtaposition suggest an origin involving collision accretionary processes the fan karategin belt is a subduction accretionary complex which formed during subduction of oceanic crust under a volcanic arc and was subjected to tectonic juxtaposition and imbrication of seamount deep sea trench and volcanic arc sequences

magnetostratigraphy of a long quaternary sediment core in the south yellow sea abstract continental shelves serve as a bridge between the continent and ocean and sediments in this region are sensitive to land sea interaction sea level variation and local subsidence in this study we present a comprehensive magnetic study of the longest sediment core csdp 1 300 1 m recovered from the south yellow sea the major magnetic minerals in the studied sediments are magnetite hematite and greigite greigite records a chemical remanent magnetization which can be removed effectively by thermal demagnetization the magnetostratigraphy defined in this study contains the matuyama brunhes boundary m b 781 ka at 73 68 m which is consistent with results from adjacent cores the base of the quaternary 2 6 ma in the yellow sea is recovered for the first time at a depth of 227 16 m the basal age of the core is estimated to be 3 50 ma it indicates that the first transgression of the yellow sea occurred no later than 1 7 ma succeeding large amplitude regressions occurred in some cold periods such as during mis 20 mis 18 and mis 10 our results provide the first chronology that brackets the entire quaternary and we reconstruct the sedimentary evolution of the yellow sea with robust age constraints which provides an important framework for further paleoenvironmental and tectonic studies

a review on the provenance discrimination of sediments in the yellow sea the yellow sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including china and korea although sedimentological mineralogical and geochemical approaches have been tried to solve the problems especially including the identification of sediment sources in and around the yellow sea the published results are not enough for understanding them suggestions on sediment origins budgets sediment accumulation rates mineralogical and geochemical compositions are not coincident to each other and sometimes even controversial for example conflicts on the distribution patterns of smectite and calcium carbonate the provenance of the southeastern yellow sea mud and sedimentation rates in there the ratios of v al and mn al in korea and china river sediments the origin of ba and pb in sandy sediments of the northeastern yellow sea and so on various geochemical indicators from the literature for the provenance discrimination in the yellow sea are reviewed here in depth and corresponding discussions are described separately research topics for the future study also are suggested for the proper access to the understanding of the origin and dispersal patterns of the yellow sea sediments especially focusing on the geochemical approaches d 2003 elsevier science b v all rights reserved

geomagnetic excursions knowns and unknowns geomagnetic excursions are short lived episodes when earth s magnetic field deviates into an intermediate polarity state understanding the origin frequency amplitude duration and field behavior associated with excursions is a forefront research area within solid earth geophysics recent advances in excursion research are summarized here and key further research is suggested to resolve major unanswered questions improving the global distribution of excursion records particularly from the southern hemisphere obtaining high resolution sedimentary excursion records with good age control from sites with sedimentation rates 10 cm kyr obtaining volcanic excursion records coupled with high precision geochronology and estimating excursion duration with high chronological precision will all facilitate hypothesis testing concerning the deep earth dynamics that generate geomagnetic excursions

the eurasia north pacific oscillation in atmospheric mass variations independent of both iho and ao and its possible impacts on winter climate using ncep ncar reanalysis we have investigated the features of migrations of atmospheric mass am between land and ocean in eurasia north pacific domain in boreal winter after having both signals of inter hemispheric oscillation and arctic oscillation removed from the physical quantities it is found that there is a eurasia north pacific oscillation enpo in surface air pressure anomalies this enpo pattern characterizes with two oppositely signed anomalous surface pressure centers over eurasia and north pacific respectively indicating strong connections between siberian high and aleutian low during period 1979 2012 the maintenance of this enpo teleconnection is significantly associated with three factors including the anomalous am flows and zonal circulation cell over eurasia north pacific domain the rossby wave energy propagations and the thermal forcing contrasts near the surface between eurasia and north pacific during boreal winter the variations of both wintertime rainfall and temperature over eurasia may be strongly affected by enpo when the enpo index is positive negative there occurs the am accumulation depletion over eurasia with simultaneous depletion accumulation over mid latitude north pacific correspondingly this anomalous surface pressure pattern along with the related circulation anomalies at different isobaric levels possibly results in winter precipitation decreases increases over siberian plain and east china whereas increases decreases over southeastern europe xinjiang of china and the west coast of sea of okhotsk on the other hand surface air temperature decreases increases over large areas of eurasia these results are helpful for our better understanding the mechanisms behind circulation and winter climate variations over eurasia north pacific region

response of western pacific marginal seas to glacial cycles paleoceanographic and sedimentological features abstract this paper reviews the recent progress in late quaternary studies in five northwestern pacific marginal seas especially the south china sea as an example a series of marginal seas separate asia from the pacific ocean and significantly modify the material and energy flux linkage between land and sea during glacial cycles the sea level induced environmental signal was amplified in the marginal seas giving rise to drastic changes in areas and configurations of these seas and to reorganization of sea water circulation in basins since most of the western pacific marginal seas are influenced by monsoon circulation and some of these are located within the western pacific warm pool the glacial geographic changes have produced a profound impact on regional and global climate for example the decrease of sea area and sea surface temperature sst in the marginal seas was one of the factors responsible for the enhanced aridity of inland china during the glaciation glacial intensification of the winter monsoon and increased seasonality of sst in marginal seas might explain at least partly the apparent discrepancy between the tropical paleotemperature estimations based on terrestrial and open ocean records in this region as the western pacific marginal seas trap terrigenous material supplied by east asia the deep water sedimentation rates there can be one to two orders of magnitude higher than in the open ocean down slope sediment transport is more active when the sea level changes particularly during the deglaciation at least four types of carbonate cycles have been recognized in the western pacific marginal seas and each of those contains environmental signals from the surface and deep sea water as well as from the drainage basin

modeling of middle pliocene climate with the ncar genesis general circulation model abstract a climate modeling study was carried out which used boundary conditions created by the usgs prism group the model used for this study is the national center for atmospheric research ncar genesis climate model genesis is an atmospheric general circulation model gcm that is coupled to a land surface model and contains submodels for snow and soil boundary conditions incorporated into the model which were specific to the middle pliocene 3 ma are 1 present day continent configuration modified by a 35 m rise in sea level 2 modified present day elevations 3 reduced continental ice cover on both greenland and antarctica 4 pliocene vegetation and 5 pliocene sea surface temperatures ssts and sea ice distribution atmospheric pco 2 and orbital parameters were set at current values the greatest influence of the specified warm ssts upon the resulting climate was occurrence of warmer and more humid high latitudes than observed in the current climate especially in the winter season the global mean surface temperature was 3 6 c warmer than in a present day control case and global mean precipitation increased by 5 relative to the control case with most excess precipitation occurring over the african continent and the oceans zonal winds weakened slightly in the pliocene case but hadley cell extent and jet stream locations were unchanged relative to the control case model results predict specific areas in which middle pliocene climate should have differed substantially from the present climate which can be tested with paleoclimate data

early cenozoic two phase extension and late cenozoic thermal subsidence and inversion of the bohai basin northern china abstract the bohai basin is one of a family of early cenozoic extensional basins that lie along the eastern margin of asia from russia to vietnam initial extension was probably triggered by subduction roll back of the oceanic pacific plate from the asian continent there were two phases in the bohai basin s rift history the earlier paleocene early eocene phase resulted in the deposition of the kongdian formation and the fourth lowest member of the shahejie formation in a series of elongate half grabens these half grabens have master faults with a nne ssw orientation secondary normal faults are typically clockwise oblique to the master faults indicating a component of dextral transtension deposition was focused in the west and south of the present basin these rocks are mainly alluvial fan and fluvial red beds the architecture of the basin underwent an important change at ca 43 45 ma middle eocene beginning with the deposition of the third member of the shahejie formation in part these sediments were deposited in the same half grabens as the kongdian formation but the bozhong depression in the central part of the basin originated at this time and became the major depocentre the bozhong depression superficially resembles a pull apart basin it formed when continued transtension of the earlier tertiary fault systems to the east and west created an extensional overlap between them during this phase the basin as a whole had a geometry with elements typical of both pull apart and transtensional basins regional extension in many east asian basins ended at the end of the oligocene probably because of the onset of transpression within eastern asia caused by the collision of australia with the philippine sea plate dextral transpression caused minor inversion of some of the earlier normal faults in bohai but as a whole the basin began to subside in a post rift phase of thermal subsidence that has lasted until the present day

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

thermal tectonic evolution of the yellow sea and east china sea implication for transformation of continental to oceanic crust and marginal basin formation abstract the yellow sea was developed in a craton environment into basins of deposition by rifting followed by intrusions of heated materials in a phase of basification of the continental crust the east china sea was developed by the same processes on a mobile zone with extensive subsidence into a basin bordered by a parageosynclinal zone in which back arc spreading was in operation the evolution of these two seas is recognized to be the result of transformation of continental to oceanic crust in which tensional activities in the form of rifting in the initial stage created open space to be filled with heated materials in the form of hot spot volcanism these two phases of operation create density instabilities and anomalous mantle structure that induce extensive subsidence accompanied by formation of oceanic type crust in the basins the transformation of continental to oceanic crust in the case of the yellow sea and the east china sea can be visualised as progressing though three stages 1 1 the yellow sea is in a state of greater tensional activities but less volcanism 2 2 the east china sea is in a more advanced stage of greater volcanism and subsidence 3 3 the okiniwa trough is created by back arc spreading as a typical marginal basin these three basins separated by their submarine ridges manifest a stress pattern characteristic of a basin range structure in a time scenario for the tertiary evolution of asian continental margin

tropical convection and precipitation regimes in the western united states abstract the authors have documented the relationship between tropical convection and precipitation regimes in the western united states circulation patterns associated with precipitation regimes are described and physical mechanisms are proposed contributions from intraseasonal and interannual bands are examined when enhanced convection is located in the western pacific dry conditions in the southwest sw and wet conditions in the pacific northwest pnw are observed fluctuations in both intraseasonal and interannual bands contribute to the rainfall variability enhanced convection in the western pacific is accompanied by suppressed convection in the central pacific the associated rossby wave vorticity source s anomalies keep the pacific jet west of 150 w a westward shift of the storm track to the north pacific also contributes to dry conditions in the sw and wetness in the pnw when enhanced tropical convection is located near 150 e substantial contributions to outgoing longwave radiation ano

chronology of the terrestrial upper cretaceous in the songliao basin northeast asia the cretaceous was a period of great environmental biological and geodynamical change but a paucity of an accurate time frame for continental strata has prevented our understanding of the terrestrial processes and the integration of marine and terrestrial records here we present an integrated chronology for the terrestrial upper cretaceous in east asia based on new high resolution magnetostratigraphic results and previously published sims u pb zircon analyses of the cretaceous continental scientific drilling borehole sequence from the songliao basin in northeast china hereafter termed ccsd sk i which consists of a sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and sims u pb zircon geochronologic data and lithostratigraphy our correlation suggests that the ccsd sk i sedimentary sequence spans from the upper chron c34n to chron c29r the age of the sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m in the songliao basin can thus be constrained to an interval from the turonian to the maastrichtian ages in addition our correlation puts the cretaceous paleogene boundary in the upper part of member 2 of the mingshui formation k2m2 the constructed comprehensive chronology allows the precise correlation of the terrestrial upper cretaceous of the songliao basin to marine strata as well as other continental sequences

cenozoic extensional tectonics in china abstract this paper gives a brief review of the cenozoic extensional structures of china during the cenozoic eastern china was in a rifted setting where divergent plate motion and extensional structures were dominant subsidence has occurred initially in response to attenuation of the crust and was enhanced later by subsidence due to thermal contraction in western china particularly in the qinghai tibetan plateau where rifting occurs in an orogenic setting in which convergent plate movements are dominant the rifting is associated with continental collision and lateral escape and large intra continental transform boundaries extensional structures in china may be grouped into eleven graben systems in eastern china and four in western china they occur in different styles linear rift valley basin and range structures and pull apart basins associated with strike slip faults the geometric characteristics kinematics of extension and the mechanism of continental extension in china are discussed the cenozoic extrusion structural model proposed by tapponnier et al 1982 elegantly accounts for the gross tectonics and the formation of the graben systems of western china however in considering the overall strain pattern during the extension of the early tertiary basin and range region in eastern china a large scale simple shear kinematic model may be preferable to the pure shear rift model

sedimentary history of the coastal plain of the south yellow sea since 5 1 ma constrained by high resolution magnetostratigraphy of onshore borehole core gzk01 abstract the thick sedimentary sequences of the east asian continental shelves are archives of information on tectonics sea level fluctuations flood plain evolution and changes in the east asian monsoon climate however long sedimentary sequences with a reliable chronological framework from this setting are scarce here we present an integration of lithostratigraphic rock magnetic and magnetostratigraphic results for the sedimentary sequence of a 285 0 m core gzk01 recovered from the northern jiangsu coastal plain of the onshore south yellow sea eastern china alluvial fluvial lacustrine and marine deposits were identified according to lithofacies analysis and detrital magnetite and hematite are the main magnetic carriers the magnetostratigraphic results show that core gzk01 records the brunhes matuyama gauss and gilbert chrons and has an extrapolated basal age of 5 1 ma this record is the oldest sedimentary sequence yet reported from the continental shelf of the south yellow sea integrating the geochronological framework with changes in lithofacies a conceptual model of the environmental evolution of the northern jiangsu coastal plain is proposed for a long interval during the pliocene the drilling area was a lacustrine environment from the late pliocene to the early pleistocene the disappearance of the paleolake and a transition to a fluvial and marine environment suggests the peneplanation of the northern jiangsu coastal plain cumulative land sea interactions since 0 8 ma subsequently shaped the modern geomorphology the observed process of sedimentary evolution was possibly controlled by regional tectonics and long term climate changes

marginal basin evolution the southern south china sea abstract the southern south china sea is divided into contrasting morphology by the west baram line to the west is the sundaland extinct passive margin in which rifting began in the eocene 46 ma and ceased at 19 21 ma anomaly 6 where sea floor spreading began much later than along the shelf of china the break up hiatus lasted 3 5 ma marked by the mid miocene unconformity also preserved on land sarawak the post rift strata date from 16 ma and drape over the rifted topography to the east is a convergent margin that became a collision zone in the middle miocene the sunda shelf is of uniform 30 km thickness except in localised deep basins and extends to a water depth of 200 m the continental slope is narrow the continental rise dangerous grounds is covered by water ranging from 500 m to 3 5 km depth at the continent ocean transition its width ranges from 170 to 330 km the rajang delta extends over the shelf and continental slope its post rift sediments drape over the rifted proximal topography of the dangerous grounds to the east the drape is thinner and has not completely buried the rifted topography the cuestas appear to have supported the carbonate build up infrastructures of the spratly islands whose slopes rise abruptly from a sea floor of 2 3 km depth the sabah and brunei margin is a collision zone that was formerly convergent the on land geology indicates a mesozoic ophiolitic basement the main collision feature is the western cordillera constructed mainly of sandy eocene to lower miocene turbidites predominantly oligocene to lower miocene in the west crocker 32 18 ma uplifted episodically throughout the upper miocene and pliocene 14 8 ma the 2 km deep northwest borneo trough may be a relict of the convergence phase but could also be a collisional foredeep the oil prolific baram delta resulting from uplift and erosion of the western cordillera has built out as far as the northwest borneo trough it is suggested that the passive margin continental rise dangerous grounds has been underthrust beneath sabah to cause uplift of the western cordillera the west baram line accordingly abruptly separates the collision zone from the western extinct passive margin and is a now extinct major right lateral transform fault

boreal winter links between the madden julian oscillation and the arctic oscillation abstract there is increasing evidence that the madden julian oscillation mjo modifies the mid to high latitude circulation and in particular appears to have a relationship to the leading mode of extratropical variability the arctic oscillation ao in this study new insights into the observed similarities between the mjo and the ao are explored it is shown that the eastward progression of the convectively active phase of the mjo is associated with a corresponding shift in the tendency and sign of the ao index moreover the ao and the mjo share several analogous features not only in the global circulation but also in surface temperature fields also the ao is linked to a pattern of eastward propagating mjo like variability in the tropics that is partially reproduced in free runs of the ncep climate forecast system cfs model finally it is shown that the structure of the ao as defined by the leading mode in the 1000 hpa geopotential height field is significantly altered based on the phase o

hercynian post collisional magmatism in the context of paleozoic magmatic evolution of the tien shan orogenic belt abstract the hercynian tien shan tianshan orogen formed during late palaeozoic collision between the karakum tarim and the kazakhstan paleo continents in order to constrain timing of hercynian post collisional magmatism 27 intrusions were sampled for u pb zircon dating along a ca 2000 km long profile in uzbekistan and kyrgyzstan the samples were dated utilizing sensitive high resolution ion microprobe shrimp ii the obtained ages together with previously published age data allowed the timing of hercynian post collisional magmatism to be constrained and interpreted in the context of the paleozoic magmatic evolution of the region apart from hercynian post collisional magmatism two older magmatic episodes have been recognized and the following sequence of events has been established 1 approximately 10 ma after cessation of continuous caledonian magmatism a number of late silurian early devonian intrusions were emplaced in the middle and northern tien shan terranes between 420 and 390 ma the intrusions probably formed in an extensional back arc setting during coeval subduction under the margins of caledonian paleo kazakhstan continent 2 the next relatively short late carboniferous episode of subduction under paleo kazakhstan was registered in the kurama range of the middle tien shan calc alkaline volcanics and granitoids with ages 315 300 ma have distinct metallogenic affinities typical for subduction related rocks and are not found anywhere outside the middle tien shan terrane west of the talas farghona fault 3 the early permian hercynian post collisional magmatism culminated after the closure of the paleo turkestan ocean and affected the whole region across terrane boundaries the post collisional intrusions formed within a relatively short time span between 295 and 280 ma the model for hercynian post collisional evolution suggests that after collision the tien shan was affected by trans crustal strike slip motions which provided suitable conduits for ascending asthenospheric material and heat influx in the crust this produced both granitoid magmas and hydrothermal fluid flow as a result post collisional intrusions and orogenic au deposits known in the region formed coevally and were tectonically controlled 4 between 240 and 220 ma a triassic thermal event affected the region resulting in resetting and growth of new zircon grains which is detected on a regional scale probably the influx of heat into the crust during the triassic was tectonically focused and varied significantly in different terranes in the region under investigation the triassic thermal event was not accompanied by any significant magmatic activity thus after cessation of hercynian post collisional magmatism ca 280 ma ago there was a long magmatically quiet period in the tien shan

mjo modulation on 2009 10 winter snowstorms in the united states abstractduring the winter of 2009 10 a number of record breaking snowfall events registered in the eastern united states are shown to have been modulated by the pulsation of tropical mjo through an atmospheric teleconnection pattern the intraseasonal variability over the eastern subtropical pacific near mexico the equatorial central pacific had reached the maximum second largest strength since 1979 80 from late december to mid february the convection over these two regions experienced a remarkable wet dry wet cycle correspondingly the daily snowfall over the eastern united states also exhibited a wet dry wet cycle as the mjo convection reached the central pacific a teleconnection pattern extended to north america resulting in a westward tilted deep anomalous trough anchored over the eastern united states producing a low level pressure dipole anomaly with an anticyclone cyclone centered at the u s west east coast the convection over the indian ocean varied in phase with the central paci

unraveling the teleconnection mechanisms that induce wintertime temperature anomalies over the northern hemisphere continents in response to the mjo abstractsignificant extratropical surface air temperature variations arise as a result of teleconnections induced by the madden julian oscillation mjo the authors elucidate the detailed physical processes responsible for the development of temperature anomalies over northern hemisphere continents in response to mjo induced heating using an intraseasonal perturbation thermodynamic equation and a wave activity tracing technique a quantitative assessment demonstrates that surface air temperature variations are due to dynamical processes associated with a meridionally propagating rossby wave train over east asia a local hadley circulation causes adiabatic subsidence following mjo phase 3 to be a main driver for the warming meanwhile for north america and eastern europe horizontal temperature advection by northerlies or southerlies is the key process for warming or cooling a ray tracing analysis illustrates that rossby waves with zonal wavenumbers 2 and 3 influence the surface warming over north amer

tectonic uplift in the northern tibetan plateau since 13 7 ma ago inferred from molasse deposits along the altyn tagh fault abstract in response to the collision of india with asia thick molasse deposits were shed off the high evolving edge of the northern tibetan plateau providing great potential for understanding the relationships between mountain building rock denudation and sediment deposition a precise knowledge of the initial accumulation of the molasse deposits is important for understanding uplift history along the northern margin of tibet field investigations indicate that thick neogene sediments in the piedmont depression zones of the altun mountains are strongly deformed in a fold and thrust system indicating crustal shortening and thickening in the late cenozoic detailed magnetostratigraphic studies of the molasse deposits along the altyn tagh fault show that the accumulation of coarse conglomerate began ca 13 7 ma ago the source material of the deposits changing at the same time together with the remarkable increase in the sedimentation rate after 13 7 ma we attribute the accumulation of the conglomerates to the tectonic uplift along the northern edge of the tibetan plateau a process that continued until at least 9 ma ago

a geotraverse across two paleo subduction zones in tien shan tajikistan abstract we present first la icp ms u pb zircon ages as well as geochemical and sr nd pb isotope data for 14 magmatic rocks collected along ca 400 km profile across the chatkal kurama terrane in the mogol tau and kurama ranges and the gissar segment of the tien shan orogen in tajikistan these new data from supra subduction and post collisional magmatic rocks of two late paleozoic active margins constrain a tectonic model for terrane motions across two paleo subduction zones 1 the 425 ma old muzbulak granite of the mogol tau range formed in a supra subduction setting at the northern margin of the turkestan ocean the north dipping plate was subducted from the early silurian to the earliest middle devonian thereafter the northern side of the turkestan ocean remained a passive margin until the early carboniferous 2 in the early carboniferous subduction under the northern margin of the turkestan ocean resumed and the 315 to 305 ma old kara kiya muzbek and karamazar intrusions formed in a supra subduction setting in the mogol tau and kurama ranges 3 at the same time in the early carboniferous rifting of the southern passive margin of the turkestan ocean formed the short lived gissar basin separated from the turkestan ocean by the gissar micro continent north dipping subduction in the gissar basin is documented by the 315 ma kharangon plagiogranite and the voluminous ca 321 312 ma andean type supra subduction gissar batholith the kharangon and khanaka gabbro plagiogranite intrusions of the southern gissar range have geochemical and sr nd isotopic compositions 87sr 86sr t 0 7047 0 7056 end of 1 5 to 2 3 compatible with mantle derived origin typical for plagiogranites associated with ophiolites the supra subduction rocks from the gissar batholith and from the mogol tau kurama ranges have variably mixed sr nd pb isotopic signatures 87sr 86sr t 0 7057 0 7064 end of 2 1 to 5 0 typical for continental arcs where mantle derived magmas interact with continental crust 4 in the latest carboniferous the turkestan ocean and the gissar basin were closed the early permian chinorsay 288 ma and dara i pioz 267 ma post collisional intrusions emplaced in the northern part of the gissar micro continent after a long period of amagmatic evolution have intraplate geochemical affinities and isotopic sr nd pb isotopic compositions 87sr 86sr t 0 7074 0 7086 end of 5 5 to 7 4 indicating derivation from precambrian continental crust which is supported by old nd model ages 1 5 and 1 7 ga and by the presence of inherited zircon grains with ages 850 500 ma in the chinorsay granodiorite the post collisional intrusions in the southern gissar and in the mogol tau and kurama ranges 297 286 ma emplaced directly after supra subduction magmatic series have geochemical and isotopic signatures of arc related magmas the distinct shoshonitic affinities of post collisional intrusions in the mogol tau and kurama ranges are explained by the interaction of hot asthenospheric material with subduction enriched wedge of lithospheric mantle due to slab break off at post collisional stage despite origination from different tectonic environments all magmatic rocks have relatively old nd model ages 1 7 1 0 ga indicating a significant proportion of paleoproterozoic or older crustal material in their sources and their model ages are similar to those of post collisional intrusions from the alai and kokshaal segments of the south tien shan

a statistical analysis of relationships between western north pacific tropical cyclones and extratropical circulation patterns accompanying the madden julian oscillation abstractrelationships between the madden julian oscillation mjo and the extratropical circulation have been studied extensively and applied in operational settings to improve subseasonal predicti

organic carbon paleo pco2 and marine ice core correlations and chronology here we present evidence that marine organic matter 13 c measurements can closely reproduce the vostok ice core co 2 record and in addition can be used to evaluate the absolute vostok chronology and the transfer of that chronology between the marine and terrestrial realm our data supports recent speculations that the base of the vostok ice core 2755 m is still within oxygen isotope stage 7 in agreement with recent orbitallytuned ice core chronologies

middle pliocene vegetation reconstructions paleoclimatic inferences and boundary conditions for climate modeling abstract the general characteristics of global vegetation during the middle pliocene warm period can be reconstructed from fossil pollen and plant megafossil data the largest differences between pliocene vegetation and that of today occurred at high latitudes in both hemispheres where warming was pronounced relative to today in the northern hemisphere coniferous forests lived in the modern tundra and polar desert regions whereas in the southern hemisphere southern beech apparently grew in coastal areas of antarctica pliocene middle latitude vegetation differed less although moister than modern conditions supported forest and woodland growth in some regions now covered by steppe or grassland pliocene tropical vegetation reflects essentially modem conditions in some regions and slightly cooler than or warmer than modern climates in other areas changes in topography induced by tectonics may be responsible for many of the climatic changes since the pliocene in both middle and lower latitudes however the overall latitudinal progression of climatic conditions on land parallels that seen in the reconstruction of middle pliocene sea surface temperatures pliocene paleovegetational data was employed to construct a 2 2 global grid of estimated mid pliocene vegetational cover for use as boundary conditions for numerical general circulation model simulations of middle pliocene climates continental outlines and topography were first modified to represent the pliocene landscape on the 2 2 grid a modern 1 1 vegetation grid was simplified and mapped on this pliocene grid and then modified following general geographic trends evident in the pliocene paleovegetation data set

persistent north pacific circulation anomalies and the tropical intraseasonal oscillation abstract a composite analysis of multiyear 1985 93 global reanalyses produced by the ncep ncar and the nasa dao is used to show that the development of persistent north pacific pnp circulation anomalies during nh winter is linked to tropical intraseasonal oscillations the development is initiated over the tropical west pacific by anomalous convection characterized by an east west dipole structure one to two weeks prior to the extratropical onset time in both reanalyses as tropical heating moves eastward toward the central pacific anomalous divergent outflow associated with the local hadley circulation generates an anomalous rossby wave sink source in the subtropics consistent with the retraction extension of the pacific jet prior to onset the signature of the forced anomalies is a pair of cyclonic anticyclonic circulation anomalies centered near the node of the tropical heating dipole wave trains extending from the region of anomalous convection into the extratropics set the stage for th

cenozoic motion of the philippine sea plate palaeomagnetic evidence from eastern indonesia the history of motion of the philippine sea plate is poorly known because it is isolated from the oceanic ridge system interpretation of palaeomagnetic results from the plate has been controversial because declination data have been obtained only from the eastern margin where subduction related tectonic processes may have caused local rather than plate wide rotations new palaeomagnetic data relevant to the problem have been obtained from 34 sites north of the sorong fault and 29 sites within the sorong fault system these sites record south ward movement during the eocene and northward movement during the neogene sites within the sorong fault system record both counterclockwise and clockwise rotations interpreted as the result of neogene block movements at the southern boundary of the philippine sea plate north of the sorong fault all sites record clockwise declinations neogene rocks have small deflections consistent with rotation about the present day eurasia philippine sea plate pole oligocene middle eocene rocks show consistent clockwise declination deflections of 40 o declinations of lower eocene rocks indicate 90 o of clockwise rotation we propose that the entire area north of the sorong fault in east indonesia has always been part of the philippine sea plate and that the whole plate has rotated clockwise in a discontinuous manner by approximately 90 o since the early eocene the new data from north of the sorong fault provide a basis for determining rotation poles which satisfy all the palaeomagnetic data from the philippine sea plate and permit its reconstruction

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

oligo miocene magnetostratigraphy and rock magnetism of the xishuigou section subei gansu province western china and implications for shallow inclinations in central asia magnetostratigraphy of 222 remanent directions together with late oligocene to early miocene mammal and charophyte paleontology suggest that 2179 m of the xishuigou section subei gansu province china were deposited from 26 to 19 ma stratigraphic patterns of bulk susceptibility anisotropy of magnetic susceptibility parameters and natural and anhysteretic remanent magnetization intensities demonstrate that 1 faulting does not significantly affect the record 2 sediment deposition was relatively continuous 3 sediment source changed around 23 ma and 4 rapid uplift near subei occurred at 21 ma subei rotated 27 5 counterclockwise with respect to the 20 ma pole from the eurasian synthetic apparent polar wander path folding and rotation of the section took place after 19 ma the paleolatitude of subei is 14 less than at present and 19 3 less than predicted from the reference pole both rock magnetic and paleomagnetic data sets suggest that the unusually low paleolatitude is the result of synsedimentary inclination shallowing a phenomenon which has likely affected other paleomagnetic data from central asia

an observed connection between the north atlantic oscillation and the madden julian oscillation abstract based on the bivariate madden julian oscillation mjo index defined by wheeler and hendon and 25 yr 1979 2004 of pentad data the association between the north atlantic oscillation nao and the mjo on the intraseasonal time scale during the northern hemisphere winter season is analyzed time lagged composites and probability analysis of the nao index for different phases of the mjo reveal a statistically significant two way connection between the nao and the tropical convection of the mjo a significant increase of the nao amplitude happens about 5 15 days after the mjo related convection anomaly reaches the tropical indian ocean and western pacific region the development of the nao is associated with a rossby wave train in the upstream pacific and north american region in the atlantic and african sector there is an extratropical influence on the tropical intraseasonal variability certain phases of the mjo are preceded by the occurrence of strong naos a significant change of upper zonal

a unique yellow river derived distal subaqueous delta in the yellow sea abstract newly acquired high resolution chirp sonar profiles reveal a unique yellow river derived alongshore distributed bidirectional landward and seaward across shelf transported omega shaped distal subaqueous deltaic lobe deposited around the eastern tip of the shandong peninsula in the yellow sea this clinoform deposit directly overlies the postglacial transgressive surface featured by convex up seafloor morphology up to 40 m thick locally radiocarbon 14 dates from the underlain pre holocene and transgressive sediments indicate this distal lobe has formed since the middle holocene highstand under a relatively stable sea level this along shelf distributed distal clinoform has been deposited mainly by the resuspended yellow river sediments carried down by the coastal current interacting with the local waves tides and upwelling collectively over the past 7000 years nearly 30 of the yellow river derived sediment has been re suspended and transported out of the bohai sea into the yellow sea overall the yellow river derived sediment could reach the 80 m water depth in the central south yellow sea about 700 km from the river mouth in contrast a very small fraction of the modern riverine sediment could escape the outer shelf or reach the okinawa trough

the relationship between the madden julian oscillation mjo and southeastern new england snowfall abstractthe winter of 2014 15 brought record snow totals to portions of southeastern new england additionally over 90 of boston logan airport snowfall during the winter fell during phases 7 and 8 of the madden julian oscillation mjo index this motivated the authors to investigate potential connections between intense southeastern new england snowstorms and the mjo in the historical record it was found that southeastern new england snowfall measured since the 1930s at several stations in the region recorded higher than average winter snowfalls when enhanced mjo convection was located over the western pacific and the western hemisphere phases 7 8 similarly snowfall was suppressed when enhanced mjo convection was located over the maritime continent phases 4 5 the mjo also modulates the frequency of nor easters which contribute the majority of new england s snowfall as measured by reanalysis derived cyclone tracks these tracks were more numerous during the same mjo phases that lead to enhan

tectonic and climatic controls on long term silicate weathering in asia since 5 ma determining the interplay between tectonic deformation climate atmospheric co2 concentrations and continental weathering and erosion is key to understanding the mechanisms that forced cenozoic global cooling in contrast with studies of paleo climate and pco 2 the history of long term silicate weathering in the himalaya and tibetan plateau htp during the late cenozoic remains unclear we reconstruct 5 m y of silicate sedimentary records at ocean drilling program odp site 1143 in the south china sea to explore the weathering history of the mekong river basin that supplied the sediment coherent variation of weathering proxies from the south china sea bay of bengal loess plateau as well as the yangtze and yellow rivers indicates weakening chemical weathering intensity since the late pliocene as the climate cooled this cooling coupled with tectonic activity shifted the dominant weathering regime from more transport limited to more weathering limited causing less chemical depletion of silicate minerals while silicate weathering rates became strongly correlated to erosion rates they were decoupled from chemical weathering intensity physical denudation and associated silicate weathering rates in the htp area increased in the pliocene driven by both rock uplift and stronger monsoon precipitation decreasing atmospheric co2 concentrations and so contributing to northern hemisphere glaciation nhg citation wan s p d clift a li z yu t li and d hu 2012 tectonic and climatic controls on long term silicate weathering in asia since 5 ma geophys res lett 39 l15611 doi 10 1029 2012gl052377

tertiary volcanism of the galatia province north west central anatolia turkey abstract large volumes of trachyandesitic dacitic lava flows and pyroclastics of miocene age are associated with small volumes of alkali basalt lava flows in the galatia volcanic province northwest central anatolia turkey the volcanism postdates continental collision occurring in a transtensional tectonic setting associated with movement along the north anatolian fault zone major and trace element including ree and sr nd isotope data and k ar ages for representative samples of mafic intermediate volcanic rocks have been obtained from a series of localities within the province the k ar age data indicate that alkali basalts were erupted during two distinct time periods in the early miocene 17 19 ma and late miocene

magnetostratigraphy of a greigite bearing core from the south yellow sea implications for remagnetization and sedimentation sediments from the continental shelf are sensitive to sea level climatic changes and local tectonic history in this study we carried out a high resolution magnetostratigraphic investigation on the longest core nhh01 125 64 m recovered from the south yellow sea sys an abnormal interval dominated by negative inclinations was discovered by applying alternating field demagnetization afd on samples from a greigite bearing layer 44 90 51 80 m in contrast the inclinations of most greigite bearing samples changed from negative to positive when heated to 360 c this strongly indicates that this inclination anomaly revealed by the afd alone is not a true negative subchron after neglecting the effects of greigite bearing layers the straightforward correlation of the interpreted magnetostratigraphy defines the matuyama brunhes boundary 781 ka and the jaramillo top 990 ka at 68 64 m and 101 54 m respectively the linearly extrapolated basal age of the core is 1 10 ma in addition several short lived inclination anomalies can be tentatively assigned to magnetic excursions which indicates that the sedimentation could be continuous even at the millennial time scale at depth intervals bracketing these fast geomagnetic events moreover the excellent correspondence between clay content variations of the core and the marine oxygen isotope record indicates the potential of clay content as a paleoclimatic proxy in the studied region in the past 1 ma in brief our study provides not only a robust age model in the sys but also a methodological guide for paleomagnetic studies in continental shelf region

evolution of the yellow sea warm current and the yellow sea cold water mass since the middle pleistocene abstract the yellow sea warm current yswc and the yellow sea cold water mass yscwm are the most significant hydrological characteristics of the yellow sea as they strongly influence the matter transportation sedimentation and the benthic and pelagic environments of the region previous studies focused mostly on formation and evolution of the yswc and the yscwm on shorter time scales e g since the holocene and studies on longer time scales are rather sparse this study conducted a high resolution magnetostratigraphic investigation on core dlc70 3 with a water depth of 71 2 m in the northern part of the south yellow sea results show that the brunhes matuyama polarity reversal boundary is located at a depth of 59 08 m constrained by both magnetostratigraphy and 14c dating three sedimentation episodes revealed by the benthic foraminifera content correspond to high sea level periods of marine isotope stage mis 5 mis9 mis11 mis17 and mis19 mis21 respectively cold water benthic foraminifera species total organic carbon total sulfur molybdenum element and long chain unsaturated alkenones index of the studied sediments show that both the yswc and the yscwm have evolved since the middle pleistocene mainly due to combined effects of fluctuations of sea level and local tectonic subsidence more specifically both the yswc and the yscwm were intensified during high sea level periods of mis5e mis9 mis19 and mis21 in addition occurrence of the yswc and the yscwm are not always coeval as in the mis5a 5d period which is characterized by relatively stronger yscwm but absence of the yswc these studies significantly improve our understanding of the evolution mechanism of both the yswc and the yscwm in this region

genesis of collision volcanism in eastern anatolia turkey late cenozoic volcanism in eastern anatolia extends in a broad sw ne trending belt across the arabia eurasia collision zone from the arabian foreland basin in the southwest and to the kars plateau and lesser caucasus in the northeast foreland volcanism is dominated by basaltic shield and fissure eruptions of transitional tholeiitic alkaline composition volcanism on the thickened crust north of the bitlis thrust zone varies from the mildly alkaline volcano nemrut and older mus volcanics in the south through the transitional calc alkaline alkaline volcanoes bingol and suphan and the alkaline volcano tendurek to the calc alkaline volcano ararat and older kars plateau volcanics in the north isotope sr nd and trace element systematics indicate that the lavas from the foreland were derived from the mantle lithosphere of the arabian continent which had been enriched by small volumes of asthenospheric melts over a period of time and that lavas from the alkaline volcanic area around mus and the volcanoes nemrut and tendurek north of the bitlis thrust zone were derived from a lithospheric source of similar composition either from the same underthrust arabian continent or from the bitlis massif microcontinent by contrast the transitional lavas from bingol and suphan and the calc alkaline lavas from ararat and kars were derived from lithosphere carrying a distinct subduction signature inherited from pre collision subduction events positive correlations between 87sr 86sr and sio2 and rb nb and sio2 in the alkaline and transitional lavas suggest that combined assimilation and fractional crystallization was an important process within at least part of the thickened crust of the collision zone trace element covariation diagrams such as y rb indicate the importance of hornblende crystallization at depth and orthopyroxene at shallow levels within the calc alkaline provinces in contrast to the consistently anhydrous crystallization sequences of the alkaline lavas trace element diagrams based on the covariation of compatible and incompatible elements point to moderate low degrees of partial melting with residual clinopyroxene throughout and residual garnet in the foreland province consideration of mineral stabilities mantle solidi and geothermal gradients before and after collision suggest that lithospheric thickening should both increase the thickness of metasomatized lithosphere and depress the metasomatized zone to greater depths probably beneath the amphibole and dolomite breakdown curves perturbation of the thickened lithosphere by delamination of the thermal boundary layer perhaps coupled with local stretching associated with pull apart basins on strike slip fault systems is then sufficient to generate melt the composition of that melt being largely dependent on the enrichment history of the lithosphere in question in eastern anatolia volcanism appears to have started between about 8 and 6 ma ago some 5 ma after the start of rapid uplift of the east anatolian plateau

paleomagnetic and astronomical dating of sediment core bh08 from the bohai sea china implications for glacial interglacial sedimentation abstract sediments from the continental shelf coastal region bear significant signals of sea level climate change as well as local tectonic information this study presents a high resolution magnetostratigraphic and rock magnetic study of a 212 4 m core bh08 with a basal age of 1 06 ma recovered from the shallow 18 o records at 40 and 100 kyr cycles indicating that the sediments in the study area are continuous at least at orbital timescales regardless of significant base level variations this is likely due to continued subsidence in the basin and creation of accommodation space the significant lower sedimentary accumulation rates since 750 ka might be due to the deviation of the depositional locus from core site because of extreme low sea level stands during the glacials since the mid pleistocene transition mpt especially the glacial sea level lowstands might have resulted in bypassing or erosion of sediments on the bh08 core site during peak glacials mis 6 mis 10 and mis 16 limiting the sediment preservation potential this study documents the longest quaternary sedimentary succession in the bohai sea and provides for the first time a clear link between sedimentation in the area and glacial interglacial climate driven sea level changes this study also highlights the feasibility of astronomical tuning to obtain high resolution chronology for shallow shelf deposits which is otherwise very difficult to be achieved on the basis of magnetostratigraphic data alone

geochemical compositions of core sediments in eastern china implication for late cenozoic palaeoenvironmental changes three deep drill holes with depth exceeding 300 m were collected from eastern china for geochemical study in order to reconstruct late cenozoic palaeoenvironmental changes the late cenozoic strata in eastern china are predominantly composed of lacustrine fluvial and littoral sediments degrees of chemical weathering during the late cenozoic were estimated by using geochemical proxies including caco3 contents chemical index of alteration and al2o3 cao na2o k2o diagrams the results show that chemical weathering was intense in eastern china in the late neogene and progressively weakened during the quaternary albeit with amplified fluctuations although the palaeoclimatic conditions reconstructed from the drill holes in eastern china are generally comparable with those records from the loess palaeosol sequences red clay and deep sea sediments in east asia they changed asynchronously in north central and southeast china during the neogene the late neogene palaeoclimate was overall warmer in southeast china than on the north china plain except for some extreme cooling periods in the late pleistocene in contrast the north china plain experienced moderate to weak chemical weathering with the intensification of east asian winter monsoon activities during the late quaternary regional differentiation of palaeoclimatic variability since the pliocene in eastern china is comparable with today s climate regimes in the changjiang and huanghe drainage basins but with different intensities suggesting different impacts of the east asian palaeomonsoon during the late cenozoic d 2005 elsevier b v all rights reserved

plio quaternary stepwise drying of asia evidence from a 3 ma pollen record from the chinese loess plateau abstract a 3 ma pollen record was obtained from a continuous red clay loess paleosol sequence at chaona in the central chinese loess plateau clp the record shows a permanent change of a domination of typical cupressaceae forest vegetation representative of an ecological environment with a relative warm and humid climate during 3 0 2 6 ma to largely steppe vegetation under dry climate conditions after 2 6 ma the later is further manifested itself as steppe to forest or forest steppe spruce forest mostly mesophilous herbs between 2 6 ma and 1 5 ma forest steppe pine grass between 1 5 ma and 0 95 ma open forest steppe mesophilous and xeromorphic herbs pine between 0 95 ma and 0 5 ma and steppe xeromorphic herbs after 0 5 ma suggesting a process of stepwise aridification in central asia at the late pliocene and the quaternary

magnetostratigraphy and luminescence dating on a sedimentary sequence from northern east china sea constraints on evolutionary history of eastern marginal seas of china since the early pleistocene owing to the large and increasing population density in low lying coastal regions even small changes in sea level can have substantial societal and economic impacts alternations of terrestrial and marine sediments deposited in coastal areas or continental shelves are important and effective indicators of sea level changes and thus have been widely studied in the marginal seas of china over the past 30 years however sea level change results from not only eustatic factors but also tectonic activity the zhe min or zhejiang fujian uplift zmu was such an important factor in geomorphology and formed a barrier preventing entry of sea water into the northern marginal seas of china but its quaternary history is poorly known

enso regulation of mjo teleconnection the extratropical teleconnections associated with madden julian oscillation mjo are shown to have an action center in the north pacific where the pressure anomalies have opposite polarities between the phase 3 convective indian ocean and phase 7 convective western pacific of the mjo the teleconnection in the same phase of mjo may induce opposite anomalies over east asia and north america between el nino and la nina years during mjo phase 3 a gigantic north pacific anticyclonic anomaly occurs during la nina making coastal northeast asia warmer wetter than normal but the west us colder drier whereas during el nino the anticyclonic anomaly is confined to the central north pacific hence the northwest us experiences warmer than normal weather under influence of a downstream cyclonic anomaly during phase 7 an extratropical cyclonic anomaly forms over the northwest pacific during la nina due to convective enhancement over the philippine sea causing bitter winter monsoon over japan whereas during el nino the corresponding cyclonic anomaly shifts to the northeast pacific due to enhanced convection over the equatorial central pacific which causes warm and wet conditions along the west coast of us and canada further the presence of enso induced seasonal anomalies can significantly modify mjo teleconnection but the aforementioned mjo teleconnection can still be well identified during phase 3 the mjo teleconnection pattern over north pacific will be counterbalanced enhanced by el nino la nina induced seasonal mean anomalies during phase 7 on the other hand the mjo teleconnection anomalies in the northeastern pacific will be enhanced during el nino but reduced during la nina thereby the impacts of mjo teleconnection on the north america is expected to be stronger during el nino than during la nina

wasp waisted hysteresis loops mineral magnetic characteristics and discrimination of components in mixed magnetic systems rock magnetic studies of complex systems that contain mixtures of magnetic minerals or mixed grain size distributions have demonstrated the need for a better method of distinguishing between different magnetic components in geological materials hysteresis loops that are constricted in the middle section but are wider above and below the middle section are commonly observed in mixed magnetic assemblages such wasp waisted hysteresis loops have been widely documented particularly with respect to rare earth permanent magnets basaltic lava flows remagnetized paleozoic carbonate rocks and an increasingly wide range of other rocks our modelling combined with a review of previous work indicates that there are several conditions that give rise to as well as magnetic properties that are characteristic of wasp waisted hysteresis loops first at least two magnetic components with strongly contrasting coercivities must coexist this condition can arise from either mixtures of grain sizes of a single magnetic mineral or a combination of magnetic minerals with contrasting cocrcivities or a combination of these two situations second materials that give rise to wasp waisted hysteresis loops will have relatively high ratios of the coercivity of remanence to coercive force b cr b c because b0 is controlled by the soft low coercivity component whereas bcris controlled by the hard high coercivity component third values of b cr b c 10 usually only occur for strongly wasp waisted loops when the low coercivity component comprises an overwhelmingly large fraction of the total volume of magnetic grains fourth a given mixture of superparamagnetic and single domain sd grains is more likely to give rise to wasp waisted hysteresis loops than an equivalent mixture of sd and multidomain grains fifth our results provide empirical confirmation that the total magnetization of a material is the sum of the weighted contributions of each component in the absence of significant magnetic interaction between particles thus to contribute significantly to wasp waisted behavior a mineral magnetic component must give rise to a significant portion of the total magnetization of the rock as a result minerals with weak magnetic moments such as hematite need to occur in large concentrations to cause wasp waistedness in materials that also contain ferrimagnetic minerals we outline a method for determining the magnetic components that can give rise to wasp waisted hysteresis loops this method is based on high and low temperature magnetic measurements that are used to identify the dominant remanence bearing mineral s and on mineral magnetic techniques that are used to discriminate between different magnetic domain states the method is illustrated with several examples from archaeological geological and synthetic materials

sedimentary architecture of the bohai sea china over the last 1 ma and implications for sea level changes abstract sedimentary architecture dominated by transgression regression cycles in the shallow bohai shelf region contains information about global sea level climate and local tectonics however previous studies of transgression regression cycles in this region at orbital timescales that extend back to the early pleistocene are sparse mainly because of the shortage of well dated long cores although transgression regression sedimentary cycles in the region have been interpreted in terms of local tectonics sea level and climate change the detailed structure of marine transgressions and their significance for quaternary global sea level variations remains to be examined in this study we present an integrated sedimentological geochemical and paleontological study of a 212 4 m 1 ma core bh08 recovered from the bohai sea china for which an astronomically based age model is available correspondence between marine terrestrial sedimentary cycles and global sea level fluctuations suggests that stacking of marine and terrestrial sediments was driven mainly by glacio eustatic sea level fluctuations in a context in which tectonic subsidence was largely balanced by sediment supply over the last 1 ma we report a dominant 100 kyr cycle beginning at 650 ka which reflects the worldwide influence of the mid pleistocene transition mpt in sea level records we find that neritic deposits after the mpt were relatively thicker than before the mpt which indicates an important control of the mpt on sedimentary architecture through lengthening of the duration of sea level highstands