millennial scale changes in sea surface temperature and ocean circulation in the northeast pacific 10 60 kyr bp 1 a new centennial scale mg ca temperature record from the california margin odp site 1017e reveals large millennial scale oscillations between 10 to 60 kyr this record indicates that sea surface temperature on the california margin warmed rapidly on the deglacial by 7 4 0 8 c and was preceded by a pre bolling temperature oscillation of 2 6 1 2 c millennial scale events of the last glacial episode were marked by sea surface temperature oscillations of between 3 and 7 c on the california margin and interstadials were associated with an increase in surface water salinity the data are consistent with evidence for a glacial southward shift in the polar jet stream and concomitant strengthening of the relatively cold fresh california current during stadial events the data also support previous hypotheses suggesting a tight coupling between the north atlantic and northeast pacific response to climate instability of the last glacial episode

changing atmospheric δ14c and the record of deep water paleoventilation ages we propose a new calculation method to better estimate the deep water ventilation age from benthic planktonic foraminifera 14 c ages our study is motivated by the fact that changes in atmospheric 14 c through time can cause contemporary benthic and planktonic foraminifera to have different initial 14 c values this effect can cause spurious ventilation age changes to be interpreted from the geologic data using a new calculation method 14 c projection ages we recalculate the data from the pacific ocean contrary to previous results we find that the pacific intermediate and deep waters were about 600 years older than today at the last glacial maximum in addition there are possible signals of ventilation age change prior to ice sheet melting and at the younger dryas however the data are still too sparse to constrain these ventilation transients

a model data comparison of δ13c in the glacial atlantic ocean 1 we compare a compilation of 220 sediment core 13c data from the glacial atlantic ocean with three dimensional ocean circulation simulations including a marine carbon cycle model the carbon cycle model employs circulation fields which were derived from previous climate simulations all sediment data have been thoroughly quality controlled focusing on epibenthic foraminiferal species such as cibicidoides wuellerstorfi or planulina ariminensis to improve the comparability of model and sediment core carbon isotopes the model captures the general 13c pattern indicated by present day water column data and late holocene sediment cores but underestimates intermediate and deep water values in the south atlantic the best agreement with glacial reconstructions is obtained for a model scenario with an altered freshwater balance in the southern ocean that mimics enhanced northward sea ice export and melting away from the zone of sea ice production this results in a shoaled and weakened north atlantic deep water flow and intensified antarctic bottom water export hence confirming previous reconstructions from paleoproxy records moreover the modeled abyssal ocean is very cold and very saline which is in line with other proxy data evidence

formation and evolution of the tancheng lujiang wrench fault system a major shear system to the northwest of the pacific ocean abstract in the northwestern peri pacific tectonic belt on the continental margin of east asia there is a series of major faults trending ne nne i e the tancheng lujiang wrench fault system this fault system extends more than 5000 km with a width of 800 1000 km in the continent and a general strike of n30 e on the basis of the results of special research on the major faults and a lot of new information about the fault system the authors discuss early mesozoic triassic jurassic period sinistral transcurrent faulting in the different regions it is suggested that in the eastern continent of east asia the e w trending tectonic pattern of the paleozoic and beginning of the mesozoic appear in the nuclei of the sino korean continent massif and the yangtze continent massif these ancient continent massifs accreted both southwards and northwards which finally led to their collision and suturing to the angura continent massif later this tectonic framework was changed greatly by the tancheng lujiang wrench fault system along which left lateral horizontal displacement of 1000 1500 km took place since the mesozoic the dislocation and deformation of horizontal displacement of the tancheng lujiang fault system produced a series of structures trending ne nne in the continental margin which have greatly transformed the ancient structures of the preceding mesozoic this is an important diktyogenese in the continent of east asia during the horizontal displacement motion of these faults the folds nappes and decollement structures pull apart basins and subductions within the continent occurred in the continent at the same time some large sinistral ductile shear zones of horizontal displacement appeared the depth of the deformed horizon of ductile shear which belongs to simple shear was controlled by the tectonic element and distance away from the continental margin whilst the ductile shear deformation occurred the fault dynamo thermal metamorphism and the fault remelting took place and magma activity appeared within the continent in the mesozoic the fault zones used to be high energy zones and recently became the seismic belts within the continent formation of the tan lu fault system was due to the collision between the southern and northern blocks its large sinistral horizontal displacement in the mesozoic was closely related to the kula plate moving northwards therefore the continent disintegrated by shearing which produced some new terranes the shear edge belt was formed between the continent and ocean the change of relative motion between the continent and pacific ocean plate transformed the tan lu fault system into first extension and then compression clarifying the characteristics of the tan lu fault system is an important key in understanding the evolution of the east asia continent since the mesozoic

deep structures underneath the sihong segment of the tan lu fault zone eastern china interpretations of gravity anomaly and seismic profiles abstract the sihong segment of the tan lu fault zone sstlfz is located in the sihong county of the jiangsu province and composed of 5 branches which are mainly buried faults the tan lu fault zone is characterized by segmentation and its regional distribution deep structures and geodynamic evolution in the sihong area remains controversial we provided evidence of gravity anomaly and seismic reflection profiles suggesting that the xinyi xindian fault f2 and qiaobeizhen suqian fault f5 of the sstlfz are segmented which appear as thrust faults in the north and normal faults in the south the f2 f5 and mohe lingcheng fault f3 are inferred as quaternary faults based on the inversion of gravity anomaly the tectonic structure of the bedrock consists of two grabens and one horst and the moho discontinuity depth in the sihong area shows an obvious uplift we conclude that a fault depression superimposed basin developed inner the sstlfz the northern segments of the f2 and f5 were inverted due to the continuous compression since quaternary

high resolution 3 d crustal shear wave velocity model reveals structural and seismicity segmentation of the central southern tanlu fault zone eastern china abstract the early mesozoic collision between the north and south china cratons resulted in different tectonic and geologic structures including the tanlu fault zone one way to understand the geodynamic processes beneath these structures is by studying the velocity structures and spatial distribution of earthquakes in the region we performed ambient noise tomography for the region around the central southern tanlu fault zone using the vertical component of continuous ambient noise data obtained in central east china empirical green s functions were retrieved from ambient noise cross correlation functions from which we extracted the rayleigh wave phase velocity dispersion curves and performed quality control on the dispersion data the direct surface wave tomography method was used to invert all phase velocity dispersion data for the 3 d shear wave velocity model in the crust and uppermost mantle our results show velocity segmentations with high velocity structures existing beneath orogenic belts and uplifts within the first 10 km depths which correspond to the high pressure ultra high pressure metamorphic rocks in the area the existence of high velocity structures beneath orogenic belts at shallow depths implies that the exhumation of eclogites is confined to the uppermost crust generally fault zones in this area are characterized by a low velocity from 0 to 5 km and relatively high velocity in the lower part of the upper crust and the middle crust the spatial distribution of earthquakes along tanlu fault reveals two seismicity zones the southern segment and the suqian tancheng segment with a low velocity transitional zone at suqian which suggests that the two segments respond differently to stresses regions of dense earthquake distribution correspond to the transition zones of high to low shear wave velocities which could be as a result of instability in the upper mantle and variation in compositions of crustal materials

triassic polyphase deformation in the feidong zhangbaling massif eastern china and its place in the collision between the north china and south china blocks the feidong zhangbaling massif is located between the dabieshan and sulu areas along the tan lu fault in eastern china five tectonic metamorphic events are distinguished there the earliest deformation d1 corresponds to a southward compression that occurred during subduction of the south china block below the north china block top to the south shearing is coeval with late permian early triassic blueschist facies metamorphism and possibly with the development of south verging recumbent folds in the neoproterozoic paleozoic sedimentary cover of the south china foreland the main ductile deformation d2 is an extensional one characterized by top to the north shearing coeval with the early stage of exhumation of the high pressure rocks a top to the nw ductile shearing and microfolds overturned to the northwest belong to a second deformational phase of exhumation d3 which is distinct from the main event d2 previous 40ar 39ar mica dates ranging between 245 and 212 ma suggest late permian early triassic ages for the d1 to d3 events the d4 event produced ne sw trending folds in the sedimentary cover interpreted as gravity collapse structures a late cretaceous brittle extensional event d5 controls the opening and infill of continental half grabens in the study area the tan lu fault is a cretaceous brittle normal fault the lack of ductile deformation presented along the tan lu fault suggests that it did not play a significant role in the exhumation of high pressure metamorphic rocks

fluid inclusion and h o isotope evidence for immiscibility during mineralization of the yinan au cu fe deposit shandong china abstract the fluid inclusion and h o isotope studies have provided the evidences for the source of ore forming fluids and helped to recognize two types of immiscibility and their relationships with mineralization hydrogen and oxygen isotopic geochemistry shows that the earlier ore forming fluids during the anhydrous skarn stage i and the hydrous skarn magnetite stage ii were mainly derived from magmatic water while the later fluids during the quartz sulfide stage iii and the carbonate stage iv were mainly from magmatic water mixed with small amounts of meteoric water various types of fluid inclusions including abundant vapor or liquid rich two phase aqueous inclusions daughter minerals bearing multiphase inclusions co2 h2o inclusions and less abundant liquid inclusions vapor inclusions and melt inclusions are present in hydrothermal minerals of different stages the liquid vapor fluid inclusions are mainly composed of h2o with significant amounts of co2 and a small amount of ch4 in the opaque bearing fluid inclusions the hematite and fahlore tetrahedrite were identified the homogenization temperature of the aqueous fluid inclusions decreases from stage i 520 410 c through stage ii 430 340 c and iii 250 190 c to stage iv 190 130 c the coexistence of melt inclusions with simultaneously trapped vapor or liquid rich two phase aqueous inclusions and daughter minerals bearing multiphase inclusions in garnet diopside and epidote of stages i and ii suggests an immiscibility between silicate melt and hydrothermal fluid it is an effective mechanism on scavenging and transporting ore forming components from magmas the aqueous fluid inclusions with various vapor liquid ratios from 65 commonly coexist with simultaneously trapped liquid inclusions vapor inclusions daughter minerals bearing multiphase inclusions and co2 h2o inclusions in the quartz of stage iii and the different kinds of the fluid inclusions have similar homogenization temperatures this indicates that the boiling another kind of immiscibility widely took place during stage iii it resulted in the precipitation and enrichment of gold copper and iron

consistent relationship between global climate and surface nitrate utilization in the western subarctic pacific throughout the last 500 ka 1 the open subarctic pacific is at present a high nitrate low chlorophyll hnlc region where nitrate is perennially abundant at the surface theoretically the hnlc status of this region is subject to modification by ocean circulation and or micronutrient supply with implications for the effectiveness of the biological pump and hence carbon sequestration in the ocean interior records of biogenic detritus in sediments from throughout the subarctic pacific indicate that export production was generally lower during glacial maxima while nitrogen isotope measurements from the bering sea have shown that nitrate consumption there was more complete during the last glacial period than it is today here nitrogen isotopic analyses of bulk sediments 15nbulk from three deep water sites in the open subarctic pacific are evaluated in terms of regional nitrate isotopic composition and local relative nitrate utilization the eastern subarctic pacific 15nbulk record bears great similarity to 15nbulk records from the western margin of north america over the last glacial cycle suggesting that variability in the isotopic composition of subeuphotic zone nitrate the growth substrate is reasonably coherent throughout the northeast pacific and dominates at these sites however the two western subarctic pacific records which lie at the heart of the hnlc region display a different pattern implying that significant changes in local relative nitrate utilization overlie the regional background variability after a novel correction intended to remove the background signal associated with denitrification in the eastern tropical north pacific these nitrate utilization records are correlated with a benthic oxygen isotope stack reflecting global deep ocean temperature and ice volume r2 0 65 the correlation implies a strong link between global climate and subarctic pacific nitrate utilization with nearly complete nitrate consumption during glacial periods when export production was low

patterns of deglacial warming in the pacific ocean a review with emphasis on the time interval of heinrich event 1 abstract based on a compilation of currently available records of past sea surface temperature sst variability estimated from a variety of different proxies the regional scale deglacial sst development in the pacific ocean is tentatively classified into four endmember types the subtropical and tropical pacific is characterized by a continuous deglacial warming without marked interruption during the time interval of heinrich event 1 h1 whereas the subarctic north pacific exhibits centennial scale warm cold oscillations during this time interval sst records from marginal seas of the pacific show a deglacial warming interrupted by a cooling event coeval with h1 followed by a marked bolling sst increase a single sst record from the southwestern subantarctic pacific displays a continuous deglacial warming across h1 followed by an antarctic cold reversal type cooling during the allerod thus in contrast to the deglacial sst development in the atlantic which has been inferred to be overwhelmingly driven by the redistribution of heat through changes in the meridional overturning circulation moc none of the open oceanic pacific sst records reviewed here displays any obvious and or dominant response to the reduction of the moc and or the reorganization of atmospheric circulation during h1 within the limits of absolute chronologies all tropical and subtropical pacific sst records show an onset of deglacial warming at 19 1 ka coeval with the onset of the deglacial rise in sea level

a 15 000 year paleoenvironmental record from meiji seamount far northwestern pacific late glacial and holocene hemipelagic sediments from meiji seamount in the far northwest pacific contain common to abundant planktonic and benthic foraminifera for ams 14c dating for stable isotope analysis and for interpreting paleoclimate change we present here chronostratigraphic faunal and geochemical results from a piston core which indicate that during glacial times as young as 14 000 yrs bp the northwest pacific sea surface salinity was at least as low as today effectively inhibiting convective overturn between 12 000 and 13 000 yrs ago after a major flux of ice rafting there is faunal and 18o evidence of an abrupt decrease in surface ocean salinity coincident with this event was an increase in biological productivity shown by higher fluxes of calcium carbonate organic carbon opal and greater abundances and lower 13o of the benthic foraminifera uvigerina oxygen isotope ratios in uvigerina and cibicidoides show step like decreases at about 13 000 14 000 11 000 10 000 and 6000 8000 yrs bp these events may be analogous to steps in the north atlantic 18o record during meltwater events if this interpretation is correct then the temperature and salinity history of the deep pacific lags that of the north atlantic by about 1000 yrs consistent with the transport time of deep water from the north atlantic to the north pacific

deep water formation in the north pacific and deglacial co2 rise deep water formation in the north atlantic and southern ocean is widely thought to influence deglacial co 2 rise and climate change here we suggest that deep water formation in the north pacific may also play an important role we present paired radiocarbon and boron isotope data from foraminifera from sediment core md02 2489 at 3640 m in the north east pacific these show a pronounced excursion during heinrich stadial 1 with benthic planktic radiocarbon offsets dropping to 350 years accompanied by a decrease in benthic 11 b we suggest that this is driven by the onset of deep convection in the north pacific which mixes young shallow waters to depth old deep waters to the surface and low ph water from intermediate depths into the deep ocean this deep water formation event was likely driven by an increase in surface salinity due to subdued atmospheric monsoonal freshwater flux during heinrich stadial 1 the ability of north pacific deep water npdw formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity earth system model these experiments also show that breakdown of stratification in the north pacific leads to a rapid 30 ppm increase in atmospheric co 2 along with decreases in atmospheric 13 c and 14 c consistent with observations of the early deglaciation our inference of deep water formation is based mainly on results from a single sediment core and our boron isotope data are unavoidably sparse in the key hs1 interval so this hypothesis merits further testing however we note that there is independent support for breakdown of stratification in shallower waters during this period including a minimum in 15 n younging in intermediate water 14 c and regional warming we also re evaluate deglacial changes in north pacific productivity and carbonate preservation in light of our new data and suggest that the regional pulse of export production observed during the bolling allerod is promoted by relatively stratified conditions with increased light availability and a shallow potent nutricline overall our work highlights the potential of npdw formation to play a significant and hitherto unrealized role in deglacial climate change and co 2 rise

links between iron supply marine productivity sea surface temperature and co2 over the last 1 1 ma received 3 july 2008 revised 9 october 2008 accepted 27 october 2008 published 14 february 2009 1 paleoclimatic reconstructions have provided a unique data set to test the sensitivity of climate system to changes in atmospheric co2 concentrations however the mechanisms behind glacial interglacial g ig variations in atmospheric co2 concentrations observed in the antarctic ice cores are still not fully understood here we present a new multiproxy data set of sea surface temperatures sst dust and iron supply and marine export productivity from the marine sediment core ps2489 2 odp site 1090 located in the subantarctic atlantic that allow us to evaluate various hypotheses on the role of the southern ocean so in modulating atmospheric co2 concentrations back to 1 1 ma we show that antarctic atmospheric temperatures are closely linked to changes in so surface temperatures over the last 800 ka and use this to synchronize the timescales of our marine and the european project for ice coring in antarctica epica dome c edc records the close correlation observed between iron inputs and marine export production over the entire interval implies that the process of iron fertilization of marine biota has been a recurrent process operating in the subantarctic region over the g ig cycles of the last 1 1 ma however our data suggest that marine productivity can only explain a fraction of atmospheric co2 changes up to around 40 50 ppmv occurring at glacial maxima in each glacial stage in this sense the good correlation of our sst record to the edc temperature reconstruction suggests that the initial glacial co2 decrease as well as the change in the amplitude of the co2 cycles observed around 400 ka was most likely driven by physical processes possibly related to changes in antarctic sea ice extent surface water stratification and westerly winds position

constraint of the co2 rise by new atmospheric carbon isotopic measurements during the last deglaciation 1 the causes of the 80 ppmv increase of atmospheric carbon dioxide co2 during the last glacial interglacial climatic transition remain debated we analyzed the parallel evolution of co2 and its stable carbon isotopic ratio 13co2 in the european project for ice coring in antarctica epica dome c ice core to bring additional constraints agreeing well but largely improving the taylor dome ice core record of lower resolution our 13co2 record is characterized by a w shape with two negative 13co2 excursions of 0 5 during heinrich 1 and younger dryas events bracketing a positive 13co2 peak during the bolling allerod warm period the comparison with marine records and the outputs of two c cycle box models suggest that changes in southern ocean ventilation drove most of the co2 increase with additional contributions from marine productivity changes on the initial co2 rise and 13co2 decline and from rapid vegetation buildup during the co2 plateau of the bolling allerod

rain driven by receding ice sheets as a cause of past climate change 1 the younger dryas cold period which interrupted the transition from the last ice age to modern conditions in greenland is one of the most dramatic incidents of abrupt climate change reconstructed from paleoclimate proxy records changes in the atlantic ocean overturning circulation in response to freshwater fluxes from melting ice are frequently invoked to explain this and other past climate changes here we propose an alternative mechanism in which the receding glacial ice sheets cause the atmospheric circulation to enter a regime with greater net precipitation in the north atlantic region this leads to a significant reduction in ocean overturning circulation causing an increase in sea ice extent and hence colder temperatures positive feedbacks associated with sea ice amplify the cooling we support the proposed mechanism with the results of a state of the art global climate model our results suggest that the atmospheric precipitation response to receding glacial ice sheets could have contributed to the younger dryas cooling as well as to other past climate changes involving the ocean overturning circulation

boron and magnesium isotopic composition of seawater the isotopic systems of boron and magnesium are increasingly being used as proxies for a number of environmental variables and processes the isotopic composition of seawater for both systems plays a central role in these studies and is an important interlaboratory standard given the long residence times of both elements 10 7 years it is commonly assumed that seawater is isotopically homogenous for these systems yet no systematic studies currently exist here we present the b and mg isotopic composition of 26 28 seawater samples from a number of ocean basins that encompass a significant range in salinity 32 to 38 psu temperature 0 3 to 25 9c and water depth 0 to 1240 m we find no significant or systematic variation for either system in accordance with their long residence times we recommend that the mean values we report 11 b 39 61 0 04 2 s e n 28 25 mg 0 43 0 01 2 s e n 26 26 mg 0 82 0 01 2 s e n 26 be used in future studies involving mg and b isotopes copyright 2010 by the american geophysical union

millennial climate oscillations in ne pacific surface waters over the last 82 kyr new evidence from alkenones 1 a climate instability in the last glacial corresponding to dansgaard oeschger d o events has been already recognized in the california margin in northeast pacific detailed sea surface temperature sst changes in this region however have not been so far well elucidated here we report estimates of alkenone derived ssts with the do time scale from odp hole 1017e off point conception over the last 80 kyr our results show that alkenone ssts clearly record d o and heinrich events we also found that alkenone ssts during 82 58 ka and 18 15 ka were considerably higher and those in 15 12 ka were lower than those derived from 18o of planktonic foraminifera these results appear to reflect fluctuations of water masses

cenozoic structural deformation and dynamic processes of the bohai bay basin province china abstract cenozoic structures in the bohai bay basin province can be subdivided into eleven extensional systems and three strike slip systems the extensional systems consist of normal faults and transfer faults the normal faults predominantly trend nne and ne and their attitudes vary in different tectonic settings paleogene rifting sub basins were developed in the hanging walls of the normal faults that were most likely growth faults neogene quaternary sequences were deposited in both the rifting sub basins and horsts to form a unified basin province the extensional systems were overprinted by three nne trending right lateral strike slip systems fault zones although the principal displacement zones pdz of the strike slip fault zones are developed only in the basement and lower basin sequences in some cross sections the structural deformation characteristics of the upper basin sequences also indicate that they are basement involved right lateral strike slip fault zones according to the relationships between faults and sedimentary sequences the extensional systems were mainly developed from the middle paleocene to the late oligocene whereas the strike slip systems were mainly developed from the oligocene to the miocene strike slip deformation was intensified as extensional deformation was weakened extensional deformation was derived from horizontal tension induced by upwelling of hot mantle material whereas strike slip deformation was probably related to a regional stress field induced by plate movement

tectonic evolution of the tancheng lujiang tan lu fault via middle triassic to early cenozoic paleomagnetic data the north striking tancheng lujiang tan lu fault is a conspicuous and controversial feature of the eastern asian landscape near the southeast extremity of the fault in anhui province we collected paleomagnetic samples at 17 middle triassic t2 and 10 upper cretaceous k2 to lower cenozoic e1 sites t2 remanent magnetizations are interpreted as primary in two of three areas the three areas are rotated 37 to 137 counterclockwise with respect to the south china block scb reference direction k2 e1 remanent magnetization directions pass regional fold and reversals tests and are not rotated with respect to surrounding areas counterclockwise rotation of t2 strata therefore ended before k2 and is attributed to left lateral shear acting along tan lu during the north china block ncb scb collision in shandong province 700 km north of the anhui sites four areas containing 33 upper jurassic j3 and cretaceous sites have negligible declination differences except for one which has dispersed directions the fold test is inconclusive for this latter area and positive for the other three regional concordance of the j3 e1 paleomagnetic data including paleolatitudes together with observed deformation patterns suggest that an extensional regime prevailed in the late cretaceous and cenozoic euler pole positions that constrain the north south china collision and account for tan lu motion suggest at least 500 km of sinistral shear took place along the fault and either 1 subduction and related ultrahigh pressure uhp metamorphism occurred near the present location of the qinling dabieshan and sulu uhp belts while tan lu acted as a transform fault that connected the two subduction zones or 2 tan lu and sulu were parts of the same transform fault system and no uhp rocks formed in situ at sulu in either case uhp rocks originally exhumed near dabieshan could have been transported by plate capture toward sulu along tan lu after north and south china impacted near dabieshan the tan lu fault grew within the scb as the dabieshan corner indented the scb causing folds in scb cover rocks to conform to the ncb margin late cretaceous to cenozoic reactivation of tan lu with both right lateral strike slip and normal fault motion occurred as the scb extruded east relative to the ncb under the influence of the india asia collision

eastern tropical pacific hydrologic changes during the past 27 000 years from d h ratios in alkenones 1 the tropical pacific plays a central role in the climate system by providing large diabatic heating that drives the global atmospheric circulation quantifying the role of the tropics in late pleistocene climate change has been hampered by the paucity of paleoclimate records from this region and the lack of realistic transient climate model simulations covering this period here we present records of hydrogen isotope ratios dd of alkenones from the panama basin off the colombian coast that document hydrologic changes in equatorial south america and the eastern tropical pacific over the past 27 000 years a and the past 3 centuries in detail comparison of alkenone dd values with instrumental records of precipitation over the past 100 a suggests that dd can be used as a hydrologic proxy on long timescales our records indicate reduced rainfall during the last glacial period that can be explained by a southward shift of the mean position of the intertropical convergence zone and an associated reduction of pacific moisture transport into colombia precipitation increases at 17 ka in concert with sea surface temperature sst cooling in the north atlantic and the eastern tropical pacific a regional coupled model forced by negative sst anomalies in the caribbean simulates an intensification of northeasterly trade winds across central america increased evaporative cooling and a band of increased rainfall in the northeastern tropical pacific these results are consistent with the alkenone sst and dd reconstructions that suggest increasing precipitation and sst cooling at the time of heinrich event 1

the universal ratio of boron to chlorinity for the north pacific and north atlantic oceans abstract we report seawater boron concentration mg kg 1 and chlorinity values measured in seawater samples n 139 collected at various depths in the north pacific and north atlantic oceans and the east japan sea located in the western temperate north pacific our results indicate that variations in seawater boron concentration are strongly coupled to variations in chlorinity and salinity yielding a mean boron to chlorinity ratio of 0 2414 0 0009 mg kg 1 1 boron to salinity ratio 0 1336 0 0005 mg kg 1 1 this ratio was surprisingly universal throughout the water column in the three marine basins and across widely different ocean surface regimes but differs from the generally accepted ratio of 0 232 0 005 mg kg 1 1 determined by uppstrom 1974 which was based on only 20 measurements at four sites in the tropical pacific ocean in converting total alkalinity to carbonate alkalinity and vice versa for thermodynamic calculations the difference between these two ratios leads to a difference of 5 mol kg 1 in estimates for ocean surface waters where the contribution of borate to total alkalinity is typically greatest we suggest the use of the new boron to chlorinity ratio for predicting seawater boron concentrations using chlorinity or salinity data

palaeoceanography polar twins ice ages in the north pacific ocean and the southern ocean were marked by low productivity accumulating evidence indicates that strong stratification restricted the supply of nutrients from the deep ocean to the algae of the sunlit surface in these regions

cretaceous deformation history of the middle tan lu fault zone in shandong province eastern china abstract based on field analysis of fault slip data from different rock units of the cretaceous basins along the middle part of the tan lu fault zone shandong province eastern china we document polyphase tectonic stress fields and address the changes in sense of motion of the tan lu fault zone during the cretaceous the cretaceous deformation history of the tan lu fault zone can be divided into four main stages the first stage during the earliest cretaceous was dominated by n s extension responsible for the formation of the jiaolai basin we interpret this extension to be related to dextral strike slip pull apart opening guided by the tan lu fault zone the second stage during the middle early cretaceous was overwhelmingly rift dominated and characterized by widespread silicic to intermediate volcanism normal faulting and basin subsidence it was at this stage that the tan lu parallel yi shu rift was initiated by e w to wnw ese extension the tectonic regime then changed during the late early cretaceous to nw se oriented transpression causing inversion of the early cretaceous rift basin and sinistral slip along the tan lu fault zone during the late cretaceous dextral activation of the tan lu fault zone resulted in pull apart opening of the zhucheng basin which was subsequently deformed by ne sw compression this deformation chronology of the tan lu fault zone and the associated cretaceous basins allow us to constrain the regional kinematic models as related to subduction along the eastern margin of asia or related to collision in the tibet region

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

origin of cenozoic reverse faults in northeastern china an example from the rongxintun fault in the liaohe basin china abstract in northeastern china cenozoic reverse faults can be found in most basins it was proposed that these faults were the products of inversion tectonics during a cenozoic regional compressional event this explanation is inconsistent with regional structures that are dominated by normal faults on seismic profile as a typical example the rongxintun fault in northeastern liaohe basin is systemically analyzed on the basis of deformation style sedimentary character and systemic mapping using seismic data we conclude that the rongxintun fault was related to right lateral strike slipping of the yannan main fault during the late paleogene when the dongying deposition occurred and it was a secondary right lateral reverse fault p plane fault of the yannan strike slip fault system the fold was a fault related fold formed as a result of movement along the rongxintun fault according to this analysis of the rongxintun fault we conclude that the cenozoic reverse fault in northeastern china was a secondary right lateral reverse fault of a strike slip fault system and did not represent a compressional event this kind of mechanism of reverse faulting is consistent with the fact that there was large scale strike slip faulting in northeastern china during the cenozoic

radiocarbon and stable isotope constraints on last glacial maximum and younger dryas ventilation in the western north atlantic 1 foraminiferal abundance 14c ventilation ages and stable isotope ratios in cores from high deposition rate locations in the western subtropical north atlantic are used to infer changes in ocean and climate during the younger dryas yd and last glacial maximum lgm the 18o of the surface dwelling planktonic foram globigerinoides ruber records the present day decrease in surface temperature sst of 4 c from gulf stream waters to the northeastern bermuda rise if during the lgm the modern 18o salinity relationship was maintained this sst contrast was reduced to 2 c with lgm to interglacial 18o changes of at least 2 2 ssts in the western subtropical gyre may have been as much as 5 c colder above 2 3 km glacial 13c was higher than today consistent with nutrient depleted younger bottom waters as identified previously below that 13c decreased continually to 0 5 about equal to the lowest lgm 13c in the north pacific ocean seven pairs of benthic and planktonic foraminiferal 14c dates from cores 2 5 km deep differ by 1100 340 years with a maximum apparent ventilation age of 1500 years at 4250 m and at 4700 m apparent ventilation ages are presently unavailable for the lgm 2 5 km because of problems with reworking on the continental slope when sea level was low because lgm 13c is about the same in the deep north atlantic and the deep north pacific and because the oldest apparent ventilation ages in the lgm north atlantic are the same as the north pacific today it is possible that the same water mass probably of southern origin flowed deep within each basin during the lgm very early in the yd dated here at 11 25 0 25 n 10 conventional 14c kyr bp equal to 12 9 calendar kyr bp apparent ventilation ages 2 3 km water depth were about the same as north atlantic deep water today below 2 3 km four yd pairs average 1030 400 years the oldest apparent ventilation age for the yd is 1600 years at 4250 m this strong contrast in ventilation which indicates a front between water masses of very different origin is similar to glacial profiles of nutrient like proxies this suggests that the lgm and yd modes of ocean circulation were the same

the mesozoic cenozoic east china rift system abstract the mesozoic cenozoic rift system of eastern china extends in a n s direction over a distance of some 4000 km and has a width of 600 1000 km to the east it reaches into the coastal areas of the east and south china sea and extends onto the continental shelf this very large rift system evolved on a heterogenous basement consisting of a number of terranes which were amalgamated during the indosinian orogeny a first rifting phase spanned late jurassic early cretaceous times it was followed by a period of relative tectonic quiescence and thermal relaxation a latest cretaceous phase of compressional tectonics giving rise to partial basin inversion was followed by a renewed rifting cycle spanning eocene early neogene times development of the east china rift system involving vertical as well as lateral crustal movements was probably induced by physico chemical changes within the earth s mantle that can be related to activity along the pacific subduction zones the mesozoic cenozoic east china rifts contain some important hydrocarbon provinces which rely to a large extent on syn rift sediments for source and reservoir rocks

glacial water mass geometry and the distribution of δ13c of σco2 in the western atlantic ocean 1 oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa cibicidoides and planulina from 25 new piston cores gravity cores and multicores from the brazil margin the cores span water depths from about 400 to 3000 m and intersect the major water masses in this region these new data fill a critical gap in the south atlantic ocean and provide the motivation for updating the classic glacial western atlantic 13c transect of duplessy et al 1988 the distribution of 13c of co2 requires the presence of three distinct water masses in the glacial atlantic ocean a shallow 1000 m southern source water mass with an end member 13c value of about 0 3 0 5 vpdb a middepth 1500 m northern source water mass with an end member value of about 1 5 and a deep 2000 m southern source water with an end member value of less than 0 2 and perhaps as low as the 0 9 values observed in the south atlantic sector of the southern ocean ninnemann and charles 2002 the origins of the water masses are supported by the meridional gradients in benthic foraminiferal 18o a revised glacial section of deep water 13c documents the positions and gradients among these end member intermediate and deep water masses the large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

petrology and zircon u pb geochronology of metamorphic massifs around the middle segment of the tan lu fault to define the boundary between the north and south china blocks abstract the tan lu fault tlf is a significant linear structure of eastern china the middle segment of the tlf in the northern anhui province separates the north china block ncb and south china block scb lack of geological work makes the plate boundary here ambiguous detailed field survey and laboratory analyses have been conducted to constrain the formation and evolution of the tlf to the west of the tlf the wuhe massif underwent a granulite facies metamorphism with t 778 836 c p 1 0 1 2 gpa during 2 41 2 43 ga according to la icp ms u pb zircon dating on the contrary to the east of the tlf the zhangbaling massif suffered a greenschist to lower amphibolite facies metamorphism with the average metamorphic temperature at around 340 440 c with the protolith igneous ages of ca 750 ma these differences indicate that the two massifs belong to the different blocks furthermore the granitic gneiss in the central part of tlf gives three populations of zircon u pb age at 667 504 ma 228 2 ma and 211 2 ma respectively the later two groups of spectra correspond to the periods of subduction and exhumation of the dabie massif 245 200 ma combined with previous study the precise plate boundary between ncb and scb has been delineated as the zhuding shimenshan fault and the initial time of the motion for the tlf is also discussed

cenozoic tectonic model of the bohai bay basin in china modelling results and seismic interpretation illustrate that the cenozoic evolution of the bohai bay basin bbb can be divided into different stages a transtensional phase during paleocene early oligocene time created ne trending strike slip faults and e w trending normal faults which were driven roughly by n s extension making an angle of 25 with the strike slip faults seismic data interpretation yields evidence that inversion phases occurred within the ne xialiaohe depression of the greater bohai bay basin this inversion phase is attributed to rotation and partial inversion that occurred during late oligocene time leading to formation of inversion structures along the ne part of tanlu fault this episode is attributed to an anticlockwise rotation of the eastern part of the bbb driven by the convergence between the pacific and eurasian plates the tectonic scenario described was simulated in scaled analogue models which were extended by pulling two basement plates away from each other partial inversion was simulated by rotation of one of the plates relative to the other model results show many of the features observed in the bbb our model results are used to argue that unlike the two episode extension and whole basin inversion models previously proposed for the bbb a single n s aligned extension followed by anticlockwise rotation accounts for the cenozoic evolution of the bbb and produces some of the structural complexities observed in the basin

lacustrine cave carbonates novel archives of paleohydrologic change in the bonneville basin utah usa records of past changes in lake levels and lake water isotopic composition in closed basins provide key insights into past variations in the hydrological cycle however these records are often limited by dating precision and temporal resolution here we present data from lacustrine cave carbonates a previously unexplored class of carbonates that comprise a promising new archive of past hydrologic changes in the bonneville basin of the northeastern great basin usa these dense carbonates precipitated within caves crevices and other protected spaces flooded by lake bonneville during its highstand in the last glacial period we report on deposits in cathedral and craners caves located 50 km apart at similar elevations approximately 100 m above the modern great salt lake and almost 200 m below lake bonneville s highstand shoreline carbonates from the two caves show similar chronologies mineralogical transitions isotopic compositions and uranium concentrations these findings suggest that lacustrine cave carbonates record changes in lake level and in the isotopic composition and chemistry of lake water importantly the deposits can be precisely dated by u th methods providing the first records of lake bonneville s water balance changes tied to precise u th ages close agreement between paired u th and calibrated 14 c ages in the deposits suggests a minimal o200 a carbon reservoir effect in the lake and allows 14 c dating to be used for age control in portions of the deposits less suitable for u th dating we use ages for the onset and cessation of lacustrine cave carbonate deposition to offer new constraints on past changes in lake level and the carbonate saturation state of lake water we also present precisely dated high resolution oxygen and uranium isotope records from the deposits within a first phase of deposition reflecting the lake s transgression between 26 and 18 ka our isotopic data suggest a large influx of freshwater during heinrich stadial 2 a hiatus in deposition beginning at 18 270 3 ka may be the result of freshening related to the lake s overflow calcite deposition resumes at cathedral cave at 16 470 2 ka suggesting that basin overflow had ceased by this time and that the lake s calcite saturation state had increased andd 18 o values increase markedly after 15 9 ka consistent with drying at this time these data imply that the lake s deglacial regression began well before the bolling warming cessation of this second phase of deposition at 14 770 2 ka coincident with the bolling warming may reflect the lake s drop below cathedral cave s elevation a final stage of aragonite deposition between 13 8 and 13 6 ka differs from the underlying facies and may not reflect deposition from lake waters filling the cave

cenozoic faulting of the bohai bay basin and its bearing on the destruction of the eastern north china craton abstract the cenozoic bohai bay basin is located at the center of the eastern block of the north china craton the structural architecture of this basin provides important clues on the deep seated lithosphere thinning of the north china craton the cenozoic regional stress field is characterized by nw oriented extension however the various cenozoic structural patterns of normal faulting and related transverse folding in the bohai bay basin are controlled not only by cenozoic stress field but also by strain field and mesozoic basement fault assemblages in this area regionally the cenozoic tectonic features and the dynamic evolution of the eastern north china craton are dominated by two lithosphere penetrating fault systems including the sinistral tan lu fault system and the dextral lan liao fault system to the west of the lan liao fault system cenozoic extensional tectonics includes nne trending listric normal faults that controlled half grabens however between these two fault systems are wnw trending half grabens which show basement involved faulting in the north and overlapping relations between sedimentary cover and basement in the south to the east of the tan lu fault the north yellow sea basin is a wnw trending fault depression with faulting in the south and overlapping relations in the north these structural features are inherited from the mesozoic tectonic framework of this area whose tectonic characteristics were completely controlled by two opposite strike slipping faults the trans extensional or oblique rifting in the paleogene followed by extensional faulting and subsequent subsidence furthermore the culmination of the decratonization of the north china craton was also related to an eastward jump of cenozoic subduction of the pacific plate and the far field effect of eastward extrusion of cenozoic subduction of the indian plate and was not essentially restricted to the early mesozoic processes therefore the cenozoic especially 25 ma marks the time of cessation of the processes that led to lithosphere thinning and destruction of the eastern block of the north china craton

permo triassic collision subduction zone metamorphism and tectonic exhumation along the east asian continental margin abstractconvergent plate motion at 320 210 ma generated the tongbai dabie sulu east central china imjingang gyeonggi central korea renge suo southwestern japan sikhote alin orogen along the paleo pacific edge of cratonal asia this amalgamated belt reflects collision between the sino korean and yangtze cratons on the sw portion and accretion of outboard oceanic arcs sialic fragments against the ne margin subducted proterozoic paleozoic continental and oceanic crustal complexes underwent high and ultrahigh pressure metamorphism at low to moderate temperatures tectonic slices of sialic crust episodically disengaged from the downgoing plate and driven by buoyancy ascended rapidly to midcrustal levels from depths exceeding 90 200 km after continental collision in east central china plus or minus korea and from 30 50 km after arrival of far traveled oceanic terranes in sw japan and the russian far east on achieving neutral buoyancy and stalling out at 10 20 km depth later doming gravitation

carbon dioxide effects of antarctic stratification north atlantic intermediate water formation and subantarctic nutrient drawdown during the last ice age diagnosis and synthesis in a geochemical box model in a box model synthesis of southern ocean and north atlantic mechanisms for lowering co2 during ice ages the co2 changes are parsed into their component geochemical causes including the soft tissue pump the carbonate pump and whole ocean alkalinity when the mechanisms are applied together their interactions greatly modify the net co2 change combining the antarctic mechanisms stratification nutrient drawdown and sea ice cover within bounds set by observations decreases co2 by no more than 36 ppm a drawdown that could be caused by any one of these mechanisms in isolation however these antarctic changes reverse the co2 effect of the observed ice age shoaling of north atlantic overturning in isolation the shoaling raises co2 by 16 ppm but alongside the antarctic changes it lowers co2 by an additional 13 ppm a 29 ppm synergy the total co2 decrease does not reach 80 ppm partly because antarctic stratification antarctic sea ice cover and the shoaling of north atlantic overturning all strengthen the sequestration of alkalinity in the deepest ocean which increases co2 both by itself and by decreasing whole ocean alkalinity increased nutrient consumption in the sub antarctic causes as much as an additional 35 ppm co2 decrease interacting minimally with the other changes with its inclusion the lowest ice age co2 levels are within reach these findings may bear on the two stepped co2 decrease of the last ice age

structural and sedimentary characteristics of the liangjia wangchang strike slip region yitong basin china abstract the yitong basin a typical strike slip basin is part of the northern segment of the world famous tanlu strike slip fault area in china research is needed to understand how the strike slip tectonic environment affects the development of structures and depositional systems within the basin the aim of this paper is to analyze how the right lateral strike slip movement of the northwestern boundary faults in this region controls extensional faulting and to analyze differences in two main sedimentary sequences termed sysq1 and sysq2 that result from strike slip movement the study is based on geological and geophysical data the following conclusions are drawn 1 the two periods of strike slip movement of the boundary fault generated two episodes of extensional fault inside the basin the extensional faults have a characteristically episodic activity related to the episodic strike slip movement the extensional faults have small fault throw and their activity lags behind the strike slip movement of the northwestern boundary faults 2 the strike slip movement of the boundary faults generated the extensional faults inside the basin and changed the locus of depocenters with complimentary changes in the paleogeomorphology and in the distribution of depositional facies it is this strike slip movement that caused the differences in sedimentary and structural characteristics between sequences sysq1 and sysq2

destruction mechanism of the north china craton insight from p and s wave mantle tomography abstract the eastern part of the north china craton ncc was reactivated and its lithosphere was destructed during the mesozoic to cenozoic several destruction models have been proposed by geochemical and geologic studies in this work we determined detailed p and s wave velocity and poisson s ratio structures under the ncc which show different structural patterns in different blocks of the ncc the present results provide important new constrains on the ncc evolution mechanism integrating geochemical and geologic observations and our tomographic results we consider that deep subduction of the pacific slab under east asia caused local or regional scale lithospheric delamination that first took place along some special locations such as the trans north china orogen dabie sulu and yanshan orogenic belts in early mesozoic or paleoproterozoic as a result asthenospheric upwelling in the big mantle wedge above the stagnant pacific slab led to widespread magmatism in and around the eastern part of the ncc hence the thermal erosion and or chemical metasomatism might be a main dynamic mechanism for the lithospheric evolution of eastern ncc during the mesozoic to cenozoic we suggest that the tanlu fault zone and trans north china orogen may have acted as two main conduits for the asthenospheric upwelling which have played an important role in the mesozoic cenozoic destruction of the pre existing archean lithospheric mantle

paleonutrient and productivity records from the subarctic north pacific for pleistocene glacial terminations i to v our study addresses fundamental questions of the mode and timing of orbital and millennial scale changes in the meridional overturning circulation moc of the subarctic north pacific particular concerns are the vertical mixing the present and past abundance of nutrients in surface waters despite strong stratification and the north pacific north atlantic seesaw of oscillations in sea surface temperature sst we do this by generating and interpreting multiple records for glacial terminations i v down two long piston cores one each from the western and eastern subarctic pacific chlorins and biogenic opal are proxies for surface water productivity delta 13 c of epibenthic foraminifera is a record of deepwater ventilation and the delta 13 c of n pachyderma sin is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing the degree of mixing is traced by pairing sst and delta 18 o records of planktic surface and subsurface pycnocline dwellers tight age control is deduced from a suite of age calibrated 14 c plateau boundaries for termination i and benthic delta 18 o and geomagnetic events for the last 800 ka carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short term changes in moc over termination i we have defined a standard sequence of short term productivity events for termination i also evident during terminations ii to v and subsequent interglacials over the last 450 ka the peak glacial regime of stable stratification and low productivity terminated together with the end of ice rafting and melting near 17 ka similar to 2000 years after the onset of termination i pulses of vertical mixing and incursion of warm surface waters from the subtropics followed convected young water masses finally penetrated down to 3600 m water depth at 17 0 to less than 14 5 ka significantly improving bottom water ventilation through the late deglacial and earliest interglacial mixing with upwelled nutrients from the pycnocline induced short term maxima in algal production of chlorins and biogenic opal near 17 15 and 15 12 ka respectively deglacial meltwater incursions in the aleutian current and silica input from north american rivers also promoted east pacific productivity after 15 5 ka productivity decreased during the late deglacial and early interglacial coeval with an exceptional peak in caco 3 preservation caused by both low organic flux and well ventilated deepwater subsequently low salinity and cool surface waters and in turn stratification were gradually restored a second opal dominated productivity maximum marked the ends of interglacials the deglacial pulses of vertical mixing around 17 11 ka imply an important contribution of the north pacific to the coeval release of oceanic co 2 into the atmosphere and support the east west seesaw model of climate change

shortcomings of the isolated abyssal reservoir model for deglacial radiocarbon changes in the mid depth indo pacific ocean severely negative 14c anomalies from the mid depth pacific and the arabian sea have been taken as support for the hypothesized deglacial release of a previously isolated extremely 14c deplete deep ocean carbon reservoir we report box model simulations that cast doubt on both the existence of the hypothesized deep reservoir and its ability to explain the mid depth 14c anomalies first the degree of ice age isolation needed to substantially reduce the deep 14c of the deep reservoir causes anoxia and the trapping of alkalinity from caco3 dissolution the latter increasing atmospheric co2 second even with a completely 14c free deep reservoir achieving the mid depth 14c anomalies of observed duration requires ad hoc stifling of aspects of deep circulation to prevent rapid dissipation of the anomalous 14c free carbon to the rest of the ocean and the atmosphere we suggest that the mid depth anomalies do not record basin scale 14c changes but are instead local phenomena

mechanisms for millennial scale global synchronization during the last glacial period global climate during the last glacial period was punctuated by abrupt warmings and occasional pulses of freshwater into the north atlantic that disrupted deepwater production these massive freshwater pulses known as heinrich events arose in part from instabilities within the laurentide ice sheet paleoevidence from the north atlantic suggests that these events altered the production of deep water and changed downstream climate throughout the northern hemisphere in the tropical western pacific sea surface temperatures and salinity varied together with ocean and climate changes at high latitudes here we present results from coupled modeling experiments that shed light on a possible dynamical link between the north atlantic ocean and the western tropical pacific this link involves a global oceanic standing wave pattern brought about by millennial scale glacial density variations in the north atlantic atmospheric teleconnections triggered by meridional sea surface temperature gradients and local air sea interactions furthermore our modeling results are compared with hydrological records from the cariaco basin the indian ocean the sulu sea and northern australia

cretaceous cenozoic history of the southern tan lu fault zone apatite fission track and structural constraints from the dabie shan eastern china apatite fission track aft and structural data outline the late cretaceouscenozoic history of the southern tan lu fault zone tlfz one of asia s major faults the triassic jurassic dabie orogen earth s largest track of ultrahigh pressure rock exposure and its foreland the yangtze foreland fold thrust belt the fission track analyses utilized the independent z and n methods for age determination which yielded within error identical ages ages from triassic jurassic syn orogenic foreland sediments are younger than their depositional age and thus were reset a group of ages records rapid cooling following shallow emplacement of granitoids of the widespread latest jurassicearly cretaceous yanshanian magmatism most ages are 90 to 55 ma and document cooling following reheating at 110 90 ma the time when the basement units of the dabie shan were last at 200 jc this cooling coincides with rifting marked by the late cretaceouseocene red bed deposition in eastern china during this period the dabie basements units exhumed in the footwall of the tan lu fault with the qianshan basin in the hanging wall the associated stress field is transtensional nw trending principal extension direction the youngest fission track ages and temperature time path modeling point to enhanced cooling in the footwall of the tan lu and associated faults at 45f10 ma the related stress field is transtensional with the principal extension direction changing trend from nw to w it may be the far field expression of the india asia collision superposed on the back arc extension setting in eastern china a regional unconformity at f25 ma marks an upper bound for the inversion of the late cretaceouseocene rift structures during the neogene further subsidence in the eastern china basins was accommodated by sub horizontal ne sw extension and followed by the presently active nw se extension the tan lu fault along the eastern edge of the dabie shan had normal

subarctic pacific evidence for a glacial deepening of the oceanic respired carbon pool abstract measurements of benthic foraminiferal cadmium calcium cd ca have indicated that the glacial interglacial change in deep north pacific phosphate po4 concentration was minimal which has been taken by some workers as a sign that the biological pump did not store more carbon in the deep glacial ocean here we present sedimentary redox sensitive trace metal records from ocean drilling program odp site 882 nw subarctic pacific water depth 3244 m to make inferences about changes in deep north pacific oxygenation and thus respired carbon storage over the past 150 000 yr these observations are complemented with biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment our results suggest that the deep subarctic pacific water mass was depleted in oxygen during glacial maxima though it was not anoxic we reconcile our results with the existing benthic foraminiferal cd ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed rather than remineralized this change would have corresponded to an increase in the deep pacific storage of respired carbon which would have lowered atmospheric carbon dioxide co2 by sequestering co2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea the magnitude of change in preformed nutrients suggested by the north pacific data would have accounted for a majority of the observed decrease in glacial atmospheric pco2

u th he thermochronology of metallic ore deposits in the liaodong peninsula implications for orefield evolution in northeast china abstract the liaodong peninsula is an important region where polymetallic ores are mined in northeast china but precise thermochronological data needed to effectively constrain the evolution of this orefield are presently lacking for this study fifteen samples of granitoid rocks were collected from the qingchengzi and wulong orefields located in the liaodong peninsula to undertake u th he study of zircon and apatite single grain zhe and ahe ages from the qingchengzi orefield range from 73 to 166 ma and from 22 to 48 ma respectively whereas single grain zhe and ahe ages from the wulong orefield range from 42 to 88 ma and from 21 to 56 ma respectively some samples yield dispersed ages comprehensive analyses indicate that the main causes of the dispersion in the zhe ages are heterogeneous distribution of u and th within the crystals radiation damage and cooling rates whereas the dispersion in the ahe ages is primarily due to the first two factors based on the helium ages we calculate the average exhumation and cooling rates of the two orefields during different periods and the associated denudation which are 4 3 km for the qingchengzi orefield and 4 7 km for the wulong orefield the mineralization depths are estimated using homogenization temperature and the salinity of fluid inclusions and are calculated to be 1 5 3 2 km and 1 0 2 2 km for the qingchengzi pb zn and au ag deposits respectively and 2 1 3 1 km for the wulong au deposit these results are much less than the total denudation suggesting that the orebodies have been heavily eroded in conjunction with the distribution of the helium ages the modeled low t thermal histories of the two orefields reveal that the liaodong peninsula experienced three stages of relatively rapid cooling during the early cretaceous ca 135 115 ma from the end of the late cretaceous to the early eocene ca 70 50 ma and from the late eocene to the oligocene ca 38 26 ma the last stage of cooling affected both orefields and represents a period of relatively intense tectonic activity finally these results are compared with those of previous studies from the adjacent jiaodong peninsula this discussion shows that the cooling experienced by the orefields in the liaodong peninsula is largely consistent with that experienced by the jiaodong peninsula these data provide valuable information for further studies of the evolution of orefields in northeast china

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

cenozoic evolution of the yilan yitong graben in ne china an example of graben formation controlled by pre existing structures abstract the ne trending yilan yitong graben yyg occurs along the yilan yitong fault zone in the northern segment of the tan lu fault zone northeastern china it shows an unusually narrow straight shape in map view with a length of ca 600 km and width of

the structural and tectonic relationships of the major fault systems of the tan lu fault zone with a focus on the segments within the north china region abstract the jiashan lujiang yishu and bohai segments have been the most tectonically active parts of the tan lu fault system since the mesozoic any analysis of faulting processes in the tan lu system is highly dependent on the relationships among the three segments here we divide the tan lu system into three styles of faulting strike slip faulting regional extensional faulting and listric normal faulting on the basis of emap data seismic profiles and geological evidence we suggest that 1 the strike slip faults which formed in the late jurassic include mainly the jiashan lujiang fault the deep parts of the chihe taihu fault and the guhe sanbing fault these three faults have had the most dramatic effect on the jiashan lujiang segment the strike slip style of faulting produced a huge positive flower structure that extends between the deep section of the chihe taihu fault and the guhe sanbing fault and overlaps with the position of the zhangbaling ductile shear zone 2 the regional extensional style of faulting whose characteristics are reflected best in the yishu fault zone is composed of the changyi dadian anqiu quxian yishui yangtou and tangwu gegou faults all of which were active during the early cretaceous these extension dominated faults extend southwards to the jiashan and hefei basins and die out in front of the dabie mountains to the north the faults penetrate the deeper parts of the weibei depression where they controlled cretaceous deposition in graben horst graben structures 3 the listric normal faults which were initiated in the paleogene generally occur around the bohai bay basin and include a series of ne trending faults in the weibei depression such as the tandong and tanxi faults these listric faults differ from the regional extensional faults in their localized occurrence and association with basin formation our study indicates that these three styles of faulting varied not only in timing and mechanical properties but developed at different levels at different locations resulting in different tectonic relationships and the formation of different geologic features in the different segments of the tan lu master system

deep root of a continent continent collision belt evidence from the chinese continental scientific drilling ccsd deep borehole in the sulu ultrahigh pressure hp uhp metamorphic terrane china abstract the chinese continental scientific drilling ccsd deep borehole which reached a depth of 5158 m in the sulu ultrahigh pressure uhp metamorphic terrane provides a new window into the deep root of a continent continent collision belt and the tectonic processes by which supracrustal material is recycled into the mantle by subduction and then uplifted to the surface major research themes of the ccsd project were to 1 determine the three dimensional composition structure and geophysical character of the deep root of this orogenic belt 2 investigate the nature and timing of the uhp metamorphism 3 investigate the processes of crust mantle interaction involved in the formation and exhumation of the uhp rocks 4 study the process of fluid circulation and mineralization during subduction and exhumation 5 study the rheological properties of the various rocks during subduction and exhumation 6 develop and refine dynamic models for deep subduction and exhumation of crustal rocks and 7 establish a long term natural laboratory for the study of present day crustal dynamics e g stress strain fluid activity the ccsd has developed precise oriented profiles of the main borehole in terms of lithology geochemistry oxygen isotopes zircon shrimp u pb ages 40ar 39ar ages deformation rheology mineralization physical properties of the rocks petrophysical logs seismic reflections and underground fluids the present paper summarizes the integrated research results of this project especially the new findings concerning the deep root of a continent continent collision

response in atmospheric circulation and sources of greenland precipitation to glacial boundary conditions the response in northern hemisphere atmospheric circulation and the resulting changes in moisture sources for greenland precipitation to glacial boundary conditions are studied in ncar s ccm3 atmospheric general circulation model fitted with a moisture tracking functionality we employ both the climap sst reconstruction and a modification thereto with reconstructions of glacial ice sheets and land masks the individual components of the boundary conditions are added first one at a time and finally together these steps show the atmospheric circulation to respond approximately linearly to the boundary condition changes and the full glacial change may thus be decomposed into contributions from sst and topography changes respectively we find that using the climap sst reconstruction leads to a shift from atlantic toward pacific source regions not found with the modified reconstruction having cooler tropics and less sea ice the occurrence of such a shift depends chiefly on the sst reconstruction and not on the existence of the large northern hemisphere glacial ice sheets the influence of these circulation changes on important factors for ice core interpretation such as precipitation seasonality condensation temperatures and source temperatures are assessed

is pore water oxygen content decoupled from productivity on the california margin trace element results from ocean drilling program hole 1017e san lucia slope california 1 trace element evidence from the california margin ocean drilling program hole 1017e shows significant changes in sediment redox chemistry at intermediate water depths over the last 60 kyr the influence of export production on intermediate water oxygen content can be distinguished from lateral ventilation through comparisons among proxies representing export production flux percent corg and sediment surface i br and pore water mo ag cd re and u oxygenation proxies sulfate reduction within the uppermost sediment column occurred during late quaternary interstadials and the holocene indicating reduced intermediate water ventilation however sulfate reduction was most intense during major interstadials when productivity was enhanced decoupling between export production and pore water oxygen content is demonstrated during deglaciation when the sediment pore water oxygen content increases without a corresponding reduction in export productivity thus both export production and intermediate water ventilation play a role in oxygen minimum zone processes on the california margin

direct ventilation of the north pacific did not reach the deep ocean during the last deglaciation 1 despite its tremendous size the deep north pacific has received relatively little attention by paleoceanographers it was recently suggested that the deep north pacific was directly ventilated by dense waters formed in the subarctic pacific during heinrich stadial 1 hs1 of the early deglaciation here we present new redox sensitive trace metal data from a sediment core at 2393 m in the subarctic pacific in comparison with previously published data from elsewhere in the region the combined picture shows no sign of ventilation during the early deglaciation in any available core from water depths of 2393 m and deeper while the deepest core to display clear signs of enhanced ventilation during hs1 was raised from 1366 m water depth thus it appears likely that although the north pacific was well ventilated to intermediate depths during hs1 the deep ocean did not receive a significant input of dense waters from a local source but remained isolated from the surface waters above

abyssal atlantic circulation during the last glacial maximum constraining the ratio between transport and vertical mixing transport to vertical diffusivity in the deep atlantic our calculations suggest that the ratio was at least twice as large at the lgm we speculate that the primary cause was reduced mixing between northern and southern component waters associated with movement of this water mass boundary away from the zone of intense mixing near the seafloor the shallower water mass boundary yields an order of magnitude increase in the volume of southern component water suggesting its residence time may have increased substantially our analysis supports the idea that an expanded volume of antarctic bottom water and limited vertical mixing enhanced the abyssal ocean s ability to trap carbon during glacial times