reactive transport modelling of reflux dolomitization in the arab d reservoir ghawar field saudi arabia it has long been recognized that the arab d reservoir in ghawar field has been significantly dolomitized and that the distribution of dolomites is highly heterogeneous across this reservoir previous studies indicated that dolomite occurs with either a stratigraphic or non stratigraphic distribution when mapped dolomite tends to form several parallel linear trends across the field although stratigraphic dolomite was suggested to be formed early from highly evaporated pore fluids sourced from overlying evaporite deposits non stratigraphic dolomite was thought to be generated primarily from hydrothermal fluids sourced from below this study focuses primarily on these non stratigraphic dolomites and proposes that i these dolomites initially formed via seepage reflux but were reinforced by late stage hydrothermal dolomitization and ii reflux is also responsible for the formation of parallel linear trends of dolomite the reflux model hypothesizes that an evaporative lagoon which is the source of dolomitizing fluids formed during the falling stage systems tract of a depositional sequence and that with continuing sea level fall this lagoon migrated progressively towards deeper parts of an intrashelf basin adjacent to the ghawar field leaving behind lines of dolomite bodies along a series of temporary coastlines two dimensional reactive transport models have been built to test this hypothesis and have resulted in a predicted pattern of dolomite bodies that agrees with both the observed vertical distribution of non stratigraphic dolomite as well as the mapped lateral distribution of the dolomite trends in addition the major ion compositions of late jurassic seawater are calculated based on fluid inclusion data in the literature using jurassic seawater in current models leads to the absence of anhydrite cements and less potential of over dolomitization than using modern seawater

cretaceous pco2 estimation from stomatal frequency analysis of gymnosperm leaves of patagonia argentina abstract stomatal frequency of fossil conifers and ginkgoals cuticles were considered as potential indicators of the p co 2 values in the patagonian palaeoatmosphere during the cretaceous samples are from continental deposits of early upper aptian age anfiteatro de tico and punta del barco formations and upper albian lower cenomanian age kachaike formation both outcropping in andean and extra andean portions of santa cruz province argentina it can be inferred that the co 2 atmospheric content was similar during both stages or was slightly higher toward the late albian early cenomanian the co 2 content estimated from the conifers is between 700 and 1400 ppmv or lower from the mid aptian ginkgoals this co 2 range is consistent with those predicted worldwide by previous studies stomatal indices biogeochemical models and carbon isotopes and implies a co 2 content 2 3 4 0 times higher than present the high atmospheric co 2 content during the middle aptian and late albian early cenomanian was probably linked to a warming process at high latitudes during these times this is consistent with the floristic development recorded during both stages in patagonia

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

new constraints on atmospheric co2 concentration for the phanerozoic earth s atmospheric co2 concentration ca for the phanerozoic eon is estimated from proxies and geochemical carbon cycle models most estimates come with large sometimes unbounded uncertainty here we calculate tightly constrained estimates of ca using a universal equation for leaf gas exchange with key variables obtained directly from the carbon isotope composition and stomatal anatomy of fossil leaves our new estimates validated against ice cores and direct measurements of ca are less than 1000 ppm for most of the phanerozoic from the devonian to the present coincident with the appearance and global proliferation of forests uncertainties obtained from monte carlo simulations are typically less than for ca estimates from other approaches these results provide critical new empirical support for the emerging view that large 2000 3000 ppm long term swings in ca do not characterize the post devonian and that earth s long term climate sensitivity to ca is greater than originally thought key points a novel co2 proxy calculates past atmospheric co2 with improved certainty co2 is unlikely to have exceeded 1000 ppm for extended periods post devonian earth s long term climate sensitivity to co2 is greater than originally thought

changes in occurrence of cold surges over east asia in association with arctic oscillation 1 it has been newly found that the occurrence of cold surges in east asia is significantly influenced by the arctic oscillation ao in the present study the events of cold surge are objectively determined based on several synoptic criteria and the phase dependency of its occurrences in association with the ao has been revealed during the negative ao phase the frequency of cold surge occurrence is relatively increased than that of neutral and positive ao phases the variation of upper level trough and jet stream over east asia and the siberian high in association of ao are suggested to explain the change of cold surge occurrences

motion of the pacific plate relative to eurasia and its potential relation to cenozoic extension along the eastern margin of eurasia extension along the eastern margin of eurasia has been regarded commonly as a far field effect of the india eurasia collision however some aspects of the timing and location of this extension make a link between the collision and extension difficult we suggest that some extensional features commonly interpreted as effects of the collision may be related more simply to changes in plate convergence rates along the eastern plate boundary of eurasia an analysis of the motion of the pacific plate relative to eurasia suggests that the rate of pacific eurasia convergence varied significantly during the tertiary period from a late cretaceous convergence rate of 120 140 mm yr the rate declined substantially during early tertiary time and reached a minimum in eocene time of 30 40 mm yr in oligocene to earliest miocene time the average convergence rate increased moderately to 70 95 mm yr then decreased again to 65 70 mm yr during early to middle miocene time from late miocene to the present the rate of convergence increased to an average of 100 110 mm yr the paleocene through middle miocene episode of relatively slow convergence correlates with a period of widespread extension along the eastern margin of eurasia decreased convergence may have been related to a net reduction in horizontal compressional stress transmitted between the pacific and eurasian plates which resulted in widespread extension adjacent to the margin of eurasia

ordovician cyanobacterial calcification a marine fossil proxy for atmospheric co2 abstract ordovician atmospheric co2 level was an important influence on climate and life however modelled estimates of ordovician co2 differ widely and in contrast to much of the subsequent phanerozoic they lack fossil proxy constraints in vivo cyanobacterial sheath calcification promoted by carbon dioxide concentrating mechanisms ccms creates distinctive microfossils these provide a direct ecophysiological link to ambient concentrations of co2 and to a lesser extent o2 cyanobacteria do not calcify at high co2 concentrations experiments show that ccms can be induced in present day cyanobacteria at co2 levels below 10 times present atmospheric level pal and that this promotes sheath calcification we compiled a global database of cyanobacterial calcification in marine environments throughout the ordovician 485 443 myr ago and compared it with modelled estimates of atmospheric co2 and o2 these data show that many genera of marine calcified cyanobacteria reappeared from cambrian series 2 or first appeared globally during the late middle to late upper ordovician late darriwilian to late katian in carbonate platform facies resulting in a previously unrecognized ten fold increase in global diversity such a large increase in calcification suggests widespread induction of ccm expression in cyanobacteria consistent with sustained decline in external co2 concentrations below 10 pal together with increase in dissolved o2 level during the late darriwilian sandbian and katian stages 460 445 myr ago these cyanobacterial calcification fossil proxy data provide a first order constraint on modelled estimates of atmospheric co2 for the ordovician estimated co2 outputs from copse and recent geocarb based models are broadly consistent with this cyanobacterial calcification proxy for the ordovician in view of the long history of cyanobacteria the calcified cyanobacterial proxy offers potential to assist interpretation of co2 deeper into geological time

a north pacific short wave train during the extreme phases of enso abstract sea surface temperatures ssts exhibit an interannual seesaw between the eastern and western tropical pacific in concert with the el nino southern oscillation enso cycle evidence accumulated from previous studies suggests that a teleconnection link may exist between enhanced rainfall convection in the western pacific and precipitation severe weather over north america the aforementioned link could possibly be established by a teleconnection wave pattern induced by the anomalously warm cold sst anomalies in the western tropical pacific to demonstrate this possibility a fourier scale separation was introduced to divide the enso anomalous circulation into two wave regimes long wave waves 1 3 and short wave waves 4 15 the classic pacific north american teleconnection pattern is formed by the long wave regime in contrast emerging in the short wave regime is a well organized wave train that propagates from the western subtropical pacific along the north pacific rim into north america in

north and south china collision along the eastern and southern north china margins abstract lithofacies distribution and petrography and intracontinental deformation in the north china block ncb and the south china block scb show an active continental margin flanked by the eastern ncb and a passive continental margin was present along the west side of the scb both margins initially trending n ne the tanlu fault possibly initiated as part of the subduction zone during paleozoic time along the eastern margin on the ncb the ncb and the scb were divided along the eastern southern north china margin by the qinling dabie tanlu sulu imjingang yanji zone from southwest to northeast these two continental blocks made contact first in the northeast during late early permian time finally in the southeast at late triassic time and the clockwise collision probably lasted to middle jurassic time the eastern suture the yanji imjingang sulu tanlu zone was dominated by contractional deformation the southern suture the qinling dabie zone was a transpression belt dominated by right lateral strike slip

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

collision between the north and south china blocks a crustal detachment model for suturing in the region east of the tanlu fault a crustal detachment model based on the interpretation of linear aeromagnetic anomalies surface geological observations and deep seismic profiles is proposed for the continent continent collision between the north and south china blocks east of the tanlu fault the model suggests that during the mid mesozoic collision between the two continental blocks the upper crust of the south china block in the subei yellow sea region was detached from the lower crust and thrust over the north china block for 400 km whereas the lower part of the lithosphere was subducted under the north china block along a subsurface suture running east from nanjing the sinistral offset of the qinling suture by the tanlu fault is only 110 120 km in the deep crust much less than previously suggested

error analysis of co2 and o2 estimates from the long term geochemical model geocarbsulf long term carbon and sulfur cycle models have helped shape our understanding of the phanerozoic history of atmospheric co 2 and o2 but error analyses have been largely limited to testing only a subset of input parameters singly as a result the full ranges of probable co2 and o 2 are not quantitatively known here we investigate how variation in all 68 input parameters of the geocarbsulf model both singly and in combination affect estimated co 2 and o 2 we improve formula tions for land area runoff and continental temperature the latter of which now excludes land area not experiencing chemical weathering we find our resampled model co 2 and o2 estimates are well bounded and provide high confidence for a double hump in co2 during the phanerozoic with high values during the early paleozoic and mesozoic and low values during the late paleozoic and late mesozoic to cenozoic our analyses also support a distinct atmospheric o2 peak during the late paleozoic 30 followed by low values near the triassic jurassic boundary 10 most of the spread in co2 is contributed by three factors climate sensitivity to co 2 doubling and the plant assisted chemical weathering factors life and gym c o2 estimates during the paleozoic to early mesozoic are highly concordant with indepen dent records from proxies but are offset to lower values during the globally warm late mesozoic to early cenozoic the model proxy mismatch for the late mesozoic can be eliminated with a change in gym within its plausible range but no change within plausible ranges can resolve the early cenozoic mismatch either the true value for one or more input parameters during this interval is outside our sampled range or the model is missing one or more key processes

hydrocarbon accumulation in strike slip fault restraining bends new insights into the tectonic controls on the penglai 19 3 and penglai 25 6 oil fields tan lu fault zone east china as the largest active strike slip fault zone of east asia the tan lu fault zone is the most significant tectonic feature controlling the hydrocarbon accumulation in bohai bay the penglai 19 3 and penglai 25 6 fields are the most typical examples among the fields found in the tan lu fault zone the structures related to the two fields are fault restraining bends produced by dextral strike slip movement on faults within the tan lu fault zone the structures initiated at the late depositional stage of the third member of the eocene shahejie formation ca 40 ma after the deposition of the main source rocks of the basin they then experienced a main development stage during deposition of the second and first members of the eocene shahejie formation and the oligocene dongying formation 40 25 ma during the neogene the structures continued to be enhanced slightly because of continued strike slip until the early to middle pleistocene these structures were characterized by the absence of the preponderance of the reverse separations on faults and might represent the restraining bends in a divergent wrench deformation zone this study shows that restraining bend structures along intrabasinal strike slip systems formed after the deposition of the source rocks are very favorable for hydrocarbon accumulation

geologic constraints on the glacial amplification of phanerozoic climate sensitivity the long term carbon cycle depends on many feedbacks silicate weathering consumes atmospheric co2 but is also enhanced by the increased temperatures brought about by this important greenhouse gas the long term sensitivity t2x of climate to co2 doubling modulates the strength of this negative feedback we update the model experiment of royer and others 2007 by estimating an empirical probability density function pdf of t2x for the phanerozoic by using an improved geocarbsulf carbon cycle model to predict a larger recalibrated set of proxy co2 measurements from the present day to 420 ma the new geocarbsulf parameterizes the rapid weathering of volcanic rocks relative to plutonic rocks updates to the carbon cycle model and the proxy co2 data set induce opposing model responses as a result our experiment maintains an agreement with t2x estimates based on numerical climate models and late cenozoic paleoclimate for a climate sensitivity t2x that is uniform throughout the phanerozoic the most probable value is 3 to 4 c geocarbsulf fits the proxy co2 data equally well and with far more parameter choices if t2x is amplified by at least a factor of two during the glacial intervals of the paleozoic 260 340 ma and cenozoic 0 40 ma relative to non glacial intervals of earth history for glacial amplification of two the empirical pdfs for glacial climate sensitivity predict t2x g 2 0 c with 99 percent probability t2x g 3 4 c with 95 percent probability and t2x g 4 4 c with 90 percent probability the most probable values are t2x g 6 to 8 c this result supports the notion that the response of earth9s present day surface temperature will be amplified by the millennial and longer term waxing and waning of ice sheets

geographical dependence of upper level blocking formation associated with intraseasonal amplification of the siberian high abstract intraseasonal amplification events of the surface siberian high in winter are generally associated with blocking ridge formation in the upper troposphere composite analysis applied to the 20 strongest intraseasonal events of upper level anticyclonic anomalies at every grid point over siberia reveals that the blocking formation differs fundamentally between the east and west of the climatological upper level trough over the far east to the west what can be called wave train atlantic origin type is common where a blocking ridge develops from anomalies as a component of a quasi stationary rossby wave train propagating across the eurasian continent under modest feedback forcing from transient eddies to the east of the trough what can be called pacific origin type dominates where a blocking ridge forms in association with westward development of anticyclonic anomalies from the north pacific under stronger feedback forcing from the pacific storm track regardless of a particular type of bl

quaternary activity along the tan lu fault zone in the bohai bay east china evidence from seismic profiles abstract the middle segment of the nne ssw striking tan lu fault zone tlfz crosses the bohai bay in east china this fault zone is a large seismically active belt that was responsible for the 1969 m magnitude 7 4 bohai earthquake however the geometry kinematics and detailed characteristics of the most recent quaternary seismic activity along the tlfz in the bohai bay area are debated primarily as the fault crops out below sea level in this area here we present the results of a series of seismic profiles that enable the identification of quaternary activity along the tlfz within the bohai bay area these data indicate that the quaternary tlfz crops out over a wide area of the bohai bay and is dominated by two main faults both of which dip steeply to the west each of these two main faults consists of several left stepping en echelon faults quaternary activity along the tlfz was generally focused along pre existing paleogene neogene faults the seismic profiles combined with the distribution of earthquakes in this area demonstrate that the tlfz in the southern and central areas of the bohai bay was last active during the holocene whereas the last movements along the faults in the northern bohai bay area range from late pleistocene in the south to early middle pleistocene and the end of the neogene in the north the seismic profiles show both normal and reverse offset of the base of the quaternary sediments by the tan lu faults although the normal offset predominates anticlines developed in quaternary sediments occur close to the quaternary tan lu faults and the tlfz is also associated with an angular unconformity between holocene and pleistocene sediments it is likely that the tlfz was dominated by reverse dextral slip during the holocene whereas all of the quaternary faulting before this involved alternating reverse and normal dextral slip oblique extension is most likely responsible for the normal dextral slip along the tlfz whereas focal mechanisms gps global positioning system data and in situ stress measurements all suggest that ene wsw compression led to the reverse dextral faulting associated with numerous recent earthquakes in the bohai bay area

the role of the siberian high in northern hemisphere climate variability the dominant mode of sea level pressure slp variability during the winter months in the northern hemisphere nh is characterized by a dipole with one anomaly center covering the arctic with the opposite sign anomaly stretched across the mid latitudes associated with the slp anomaly is a surface temperature anomaly induced by the anomalous circulation we will show that this anomaly pattern originates in the early fall on a much more regional scale in siberia as the season progresses this anomaly pattern propagates and amplifies to dominate much of the extratropical nh making the siberian high a dominant force in nh climate variability in winter also since the slp and surface temperature anomalies originate in a region of maximum fall snow cover variability we argue that snow cover partially forces the phase of winter variability and can potentially be used for the skillful prediction of winter climate

late early cretaceous climate and pco2 estimates in the liupanshan basin northwest china abstract the extinct conifer family cheirolepidiaceae especially pseudofrenelopsis is commonly used to reconstruct the atmospheric palaeo co2 concentration pco2 during the cretaceous period in recent years many pseudofrenelopsis specimens have been collected from the uppermost stratum of the naijiahe formation in the liupanshan basin ningxia hui autonomous region northwest china the stomatal parameters such as stomatal density stomatal index stomatal pore length and stomatal pore depth and the stable carbon isotope composition of the present pseudofrenelopsis were analyzed the palaeo co2 levels of the liupanshan basin during the late early cretaceous late albian were reconstructed using stomatal ratio sr and mechanistic model approaches the sr method yielded a semi quantitative pco2 estimate of 620 ppmv on the basis of the recent standardization and 1030 ppmv on the basis of the carboniferous standardization which show similarities with other sr based and geochemical based reconstructions for the late early cretaceous the pco2 was about 670 ppmv on the basis of mechanistic model method similar to the estimated pco2 values recovered by the sr method corrected with the recent standardization based on comparative studies of previously published pco2 results of the early cretaceous pco2 levels varied during the early cretaceous and pco2 was relatively stable during the late early cretaceous furthermore environmental conditions of the liupanshan basin during the late early cretaceous were studied the stable carbon isotope composition of pseudofrenelopsis leaves ranged from 21 5 to 24 3 with an average of 22 8 indicating an arid semi arid and high evaporation climate during the late early cretaceous in the liupanshan basin these environmental conditions were also supported by palynological lithological and geochemical evidence

evolutionary characteristics of the sags to the east of tan lu fault zone bohai bay basin china implications for hydrocarbon exploration and regional tectonic evolution abstract some cenozoic half grabens sags have been found to the east of the tan lu fault zone in the bohai bay basin east china the evolutionary history of these sags is consistent with the entire bohai bay basin besides some remarkable characteristics which had not been mentioned in previous studies of the bohai bay basin are presented and they are the keys to understand the regional tectonic evolution among them two characteristics are emphasized 1 the structural and evolutionary features of the sags were markedly changed at about 38 ma 2 the paleogene basin underwent several times of uplifts and denudations during paleogene the first characteristic shows that the normal faulting was the dominant structural deformation before 38 ma and after then the strike slip movement might initiate to influence the basin the second characteristic indicates remarkable reducing of the present day residual basin relative to the original basin and implies the episodic uplifting of the jiaoliao massif besides our estimation on the hydrocarbon exploration potential of these sags shows that part of them can sustain the formation of medium large oilfield independently while part can contribute to the formation of large oilfield

causes and consequences of low atmospheric pco2 in the late mesoproterozoic abstract based upon various proxy theoretical and model constraints paleoproterozoic atmospheric p co 2 was much higher than phanerozoic levels however relatively little is known about the transition between the two climate states here geochemical mass balance from 1 1 ga old midcontinent rift system usa paleosols is used to reconstruct atmospheric p co 2 during the mesoproterozoic the calculations robustly indicate low atmospheric p co 2 p co 2 minimum is best explained as the culmination of a long term c burial event by the biosphere that is also indicated by marine carbonate 13 c changes during the mesoproterozoic and which is consistent with changes in the biosphere including increased stromatolite abundance and diversity evolution of sulfur utilizing bacteria and the spread of microbial mats into continental environments

fault fracture mesh petroleum plays in the zhanhua depression bohai bay basin part 1 source rock characterization and quantitative assessment abstract in the prolific zhanhua depression of the bohai bay basin eastern china over 76 of the proven petroleum reserves occur in the neogene guantao and minhuazhen formations detailed geological and geochemical mapping of the phanerozoic strata in this area reveals that oil shales and dark mudstones in the es4 es3 and es1 members of the eocene oligocene shahejie formation have excellent potential as petroleum source rocks regional distributions of total organic carbon content kerogen type and thermal maturation indicate that abundant mature source rocks are present in several discrete sag areas bounded by extensive basement related fault networks in contrast source rocks along the paleo topographic highs are currently immature with respect to the generation of conventional oils this study examined the key molecular characteristics for the common isoprenoid hopanoid and steroid biomarkers in relation to source facies variations in lacustrine sediments the hydrocarbon source potential and expulsion efficiency for each of the source rock units were evaluated which integrated the source rock characteristics with regional thermal subsidence and sediment burial an important observation made during this study is the striking contrast between the source potential and proven oil reserves within each stratigraphic section illustrating how significant the migration of hydrocarbon fluids derived from deep mature source kitchens through over 2000 m of fine grained formations must have been to form several giant oil accumulations in the shallow strata these results support the concept of the neogene fault fracture mesh petroleum plays proposed by zhang et al 2004 marine petroleum geology 21 651 668 and the vital role that the faults and fracture systems have in controlling hydrocarbon migration conduits and accumulation habitat in this rift basin

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

modeling the early paleozoic long term climatic trend the early paleozoic climate has been described as warm and equable however recent data based on conodont oxygen isotopic composition reveal a large long cooling trend through the ordovician followed by an abrupt cooling during the late ordovician glaciation this long term climate change is associated with a major radiation in the earth life history nonetheless the driving mechanisms for this cooling trend remain unknown carbon dioxide consumption by the weathering of fresh rocks from volcanic arcs has recently been suggested as a possible driver for this climate change however the impact of the plate motion context has not been explored yet although it might have a major impact on atmospheric co 2 levels simulations with a climate model coupled to a biogeochemical model geoclim show that the atmospheric co 2 decreased from more than 20 pal 5600 ppmv in the furongian down to approximately 10 pal 2800 ppmv in the llandovery before rising again in the early devonian we suggest that changes in geography and exposure of fresh volcanic rocks on continents are required to explain the large co 2 drawdown that led to the onset of cooler to glacial conditions from the middle ordovician to the llandovery the weathering of fresh volcanic rocks is itself responsible for 33 of the late ordovician atmospheric co 2 decrease the rest being related to the continent motion through the intertropical convergence zone itcz mean annual continental temperature falls by 3 c in the early ordovician reaching 13 5 c during the glacial interval and rises to 16 c in the early devonian

seismic reflection imaging of a major strike slip fault zone in a rift system paleogene structure and evolution of the tan lu fault system liaodong bay bohai offshore china the tan lu fault system in the liaodong bay bohai offshore china affords an exceptional opportunity to document the structural features of a major strike slip fault using two and three dimensional seismic reflection data as well as evolution of a strike slip fault developed coeval with a rift system the fault zone displays a relatively straight throughgoing trace longitudinally bisecting the rift valley it consists of positive and negative flower structures and en echelon folds in the south bay and three parallel flower structure systems northward the middle fault bifurcates northward into two semiparallel vertical fault strands to the north the west strand bends clockwise and merges with the east strand the stepping pattern and orientation of en echelon structures indicate right lateral sense and about n10 35e azimuth of slip the fault apparently accrued about 30 40 km 20 25 mi of post early eocene slip based on the current distribution of deformation zones and depocenters tan lu fault segments with clockwise and counterclockwise orientation relative to the regional slip direction are characterized by divergent and convergent structures i e restraining and releasing bends respectively waning of rifting eliminated the cause of a major restraining bend putting an end to development of associated convergent structures in the south bay area near the central north bay deformation occurred along major normal faults related to the basin rifting although a prominent feature reflecting regional strain partitioning the tan lu fault apparently was not a major factor in the paleogene opening of the liaodong bay basin and the larger north china rift basin

the cenozoic evolution of the north china basin the cenozoic evolution of the north china basin consists of early tertiary rifting and differential subsidence late tertiary regional subsidence and quaternary rifting and differential subsidence present cenozoic sediment fill shows that tertiary subsidence was greatest where the present thickness of pre cenozoic crust is least in contrast quaternary subsidence has been greatest where the present thickness of pre cenozoic crust is greatest the present crustal structure geologic history and cenozoic sediment fill of the basin suggest a nearly constant crustal thickness of 40 km at the onset of rifting middle eocene if the present thickness of pre cenozoic crust is due solely to crustal thinning from early tertiary mechanical extension then the central north china basin has been extended at least 30 of its initial width this is greater than estimates of total mesozoic plus cenozoic extension derived from basement faulting 20 at the present time any possible discrepancies cannot be resolved due to uncertainties in the data tertiary subsidence of the basin derived from backs tripping the present sedimentary sequence is not satisfactorily explained by either a simple uniform or two layer extensional model no single extension parameter uniform or pair of extension parameters two layer can account for the variable sediment thicknesses or the alternating horst and graben configuration of the basin we can however use the parameters derived from simple one or two layer extensional modeling to infer lower bounds for both the average regional extension of the bohai and the local extension of the depressions within the basin for example we find that the neogene subsidence of a major part of the basin the central bozhong depression has been nearly as rapid as that of young oceanic crust furthermore the present heat flow in this area is consistent with that for oceanic crust of 16 24 million years of age post rift time this indicates that the subsidence may be due to decay of a lithospheric thermal anomaly that is nearly as large as that in young oceanic crust this is difficult to understand with a simple extensional framework because reported estimates of early tertiary extension from basement faulting are only 10 30 possible sources of this excess heat are mesozoic tectonics effects of plate subduction at the pacific margin or energy input from regional tectonics during the early tertiary our conclusions cast doubt upon the adequacy of simple extensional models to explain the cenozoic evolution of the north china basin however these conclusions can only be tentative due to inadequacies in the basic data set

detrital zircon u pb geochronology and stratigraphy of the cretaceous sanjiang basin in ne china provenance record of an abrupt tectonic switch in the mode and nature of the ne asian continental margin evolution abstract the age spectra obtained from 505 spots of detrital zircon u pb ages of five representative sandstone samples from the sanjiang basin in ne china point to a significant change in its provenance during the coniacian santonian the predominant detrital source for the sanjiang basin during the early cretaceous was the zhangguangcai range magmatic belt and jiamusi block along its western and southern periphery whereas it changed in the late cretaceous to its eastern periphery the timing of these inferred changes in the detrital source regions and drainage patterns nearly coincide with the age of a regional unconformity in and across the basin the time interval of non deposition and unconformity development was coeval with a transitional period between an extensional tectonic regime in the early cretaceous and a contractional deformation episode in the late cretaceous the sanjiang basin evolved during this time window from a backarc to a foreland basin the migration of the coastal orogenic belt and the fold and thrust belt development farther inland during the late cretaceous marked the onset of regional scale shortening and surface uplift in the upper plate of a flat or very shallow dipping subduction zone the stratigraphic record the detrital source and geochronology of the basinal strata and the internal structure of the sanjiang basin present therefore an important record of a tectonic switch in the nature of continental margin evolution of northeast asia during the late mesozoic

50 ma initiation of hawaiian emperor bend records major change in pacific plate motion the hawaiian emperor bend has played a prominent yet controversial role in deciphering past pacific plate motions and the tempo of plate motion change new ages for volcanoes of the central and southern emperor chain define large changes in volcanic migration rate with little associated change in the chain s trend which suggests that the bend did not form by slowing of the hawaiian hot spot initiation of the bend near kimmei seamount about 50 million years ago ma was coincident with realignment of pacific spreading centers and early magmatism in western pacific arcs consistent with formation of the bend by changed pacific plate motion

the morphology of northern hemisphere blocking abstract the morphology of regional blocking in the northern hemisphere is discussed using the 40 yr ecmwf re analysis era 40 dataset and a measure of blocking based on the reversal at storm track latitudes of meridional contrasts on a potential vorticity pv surface representative of the tropopause the focus is on cyclonic and anticyclonic rossby wave breaking that is inherent to the blocking development and the extent to which this is determined by the climatological jet position and the ambient shears more generally the importance of the climatological planetary scale is discussed the approach is mainly through composite behavior but informed by consideration of many individual events a diversity of behavior is found with longitude in both winter and summer and there is a striking reversal of the sense of the wave breaking between the two seasons that is generally consistent with the difference in the jet locations preferred behaviors are found in various regions and seasons and retrogre

geometry styles and quantification of inversion structures in the jiyang depression bohai bay basin eastern china abstract inversion structures of jiyang depression evolved during mesozoic and cenozoic are classified into positive and negative inversion geometry styles the geometry styles of the reactivated faults in the study area are attributed to their multi phase history which includes at least four phases of compressive deformation and subsequent subsidence caused by extensional reactivation of faults since mesozoic in the case of negative inversion style the negative inversion ratios cannot be calculated by the same method of calculating the degree of positive inversion thus a new method of quantifying the negative inversion ratio is presented in this paper negative inversion ratio is defined as the ratio of extensional displacement to contractional displacement measured along the fault this method provides a useful complement to conventional estimation of the degree of inversion and adapts to any negative inversion faults based on this method we obtained the negative inversion ratios of some faults in the jiyang depression which indicates a decrease in deformational degree from east to west in the whole region

evaluation of atmospheric carbon dioxide concentrations during the cretaceous studying the role of atmospheric carbon dioxide concentration pco2 regulating temperature during the cretaceous is important to understand the evolution of the cretaceous climate however the pco2 variation during the cretaceous remains uncertain here we present a new paleo pco2 variation record spanning the barremian to maastrichtian time the new paleo pco2 calculations are based on analyses of pedogenic carbonate from the gyeongsang basin korea and data from the literature on pedogenic carbonates our results show that the mid cretaceous pco2 levels were higher than those observed during the early and the late cretaceous and that the highest pco2 was achieved between the cenomanian and the turonian this pco2 trend is in agreement with the paleotemperature records our results also show that three intervals of low pco2 400 ppmv in the early and the late cretaceous seem to be associated with climatic changes suggestive of glacial episodes these results suggest that the cretaceous climatic change was associated with pco2 variations variations in the rate of outgassing caused by variations of oceanic crust production rate have been known as a major cause of the mid cretaceous warmth however our results show the discrepancy in the timing between the highest rate of oceanic crust production and the highest pco2 levels during the mid cretaceous we interpret that large subaerial volcanisms in the caribbean and madagascar large igneous provinces were instrumental for providing additional co2 to the atmosphere resulting in the warmest mid cretaceous

exploring the usability of isotopically anomalous oxygen in bones and teeth as paleo co2 barometer fluctuations in atmospheric pco2pco2 may have played the key role in global climate throughout earth s history for the quantification of past variations in atmospheric pco2pco2 several geological proxy approaches and geochemical models have been developed here we evaluate a new co2 proxy approach that is based on the triple oxygen isotope composition 16o 17o 18o of skeletal apatite of terrestrial mammals our approach utilizes the relation between an anomaly in 17o of tropospheric air o2 and atmospheric pco2pco2 the anomaly is transferred from inhaled air o2 to skeletal apatite of mammals hence triple oxygen isotope data of mammalian bioapatite provide information regarding pco2pco2 during the animal s lifetime the approach was calibrated with a detailed mass balance model that was verified by analyses on a set of recent mammals we evaluate the potential of this new independent terrestrial paleo co2 proxy in a case study including eocene to miocene samples the present investigation provides promising results that are in good agreement with existing proxy and model data the uncertainty intrinsic to the proxy is mainly due to uncertainties in physiological parameters

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

a new dynamical index for classification of cold surge types over east asia the cold surges over east asia can be classified into wave train type and blocking type according to their dynamic origins in the present study two dynamic indices are proposed to objectively identify cold surge types using potential temperature on the dynamic tropopause at 2 potential vorticity units 2 pvu surface the two indices are designed to represent primary characteristics of the two types of cold surge the wave train index wi is defined as a difference of anomalous on the 2 pvu surface between the western north pacific and northeast china which captures a southward northward intrusion of cold warm air mass related to the trough ridge pattern the blocking index bi is defined as a difference of anomalous between the subarctic region and northeast china which indicates air mass overturning related to a reversal of the usual meridional gradient commonly observed in the occurrence of blocking type cold surge composite analyses based on the distribution of the wi and bi clearly demonstrate the dynamic evolutions of corresponding cold surge types the wave train cold surge is associated with a southeastward expansion of the siberian high and northerly wind near surface which is caused by growing baroclinic waves during the blocking cold surge a geopotential height dipole indicating the subarctic blocking and deepening of east asian coastal trough induces a southward expansion of the siberian high and northeasterly wind compared to the wave train type the blocking cold surge exhibits a longer duration and stronger intensity in the new framework of these dynamic indices we can detect a third type of cold surge when both the wave train and the blocking occur together in addition we can exclude the events that do not have the essential features of the upper tropospheric disturbances or the subarctic anticyclonic circulation which are responsible for cold surge occurrence using the new indices

phanerozoic atmospheric oxygen new results using the geocarbsulf model modifications of the geocarbsulf model for phanerozoic atmospheric oxygen have been made to account for new carbon isotopic data reconsideration of the fractionation of carbon isotopes between carbonate and organic matter deposited in sediments and different rates of weathering of volcanic rocks versus granitic rocks results indicate distinctly higher o2 values than geocarbsulf for the mesozoic and cenozoic lack of an appreciable drop in o2 below 15 percent at any time and a small late cenozoic decline of o2 to the present

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

fault fracture mesh petroleum plays in the zhanhua depression bohai bay basin part 2 oil source correlation and secondary migration mechanisms abstract the chemical compositions of crude oils from over 20 oilfields in the zhanhua depression bohai bay basin were studied in order to understand their genetic relationships thermal maturity and biodegradation ranking molecular geochemical parameters indicate the presence of three possible oil families in reservoirs ranging from paleozoic basement to neogene a number of biomarker features support deposition of the source rocks for these oils under a wide range of depositional environments the majority of the oils discovered in the depression belong to the fl family and display characteristics consistent with a dominantly freshwater to slightly brackish water lacustrine source rock in the es 3 member of the shahejie formation the somewhat geographically restricted sl family oils are apparently linked to saline lacustrine carbonate evaporite source rocks distributed mostly in the upper es 4 member of the shahejie formation from the bonan gubei sag areas the thermally less mature bl family oils occur mostly within the es 1 es 2 or dongying formation reservoirs near the central sag areas and show close affinities to the interbedded or intercalating es 1 calcareous mudstones and oil shales deposited in a slightly saline to dominantly brackish water lacustrine setting the sl and fl family oils are generally mature whereas most of the bl family oils usually show low maturity oil source correlation demonstrates strong genetic relationships between the mature es 4 and es 3 source rocks of the eocene oligocene shahejie formation in the sag areas and the oils accumulated in the shallow neogene petroleum plays the geochemical data provide strong support for two sharply contrasting hydrocarbon migration scenarios 1 short distance lateral migration is dominant in the central sag areas and 2 the fault fracture mesh facilitated vertical migration and coupled with the regional porous guantao formation sand sheets makes the structural stratigraphic and lithological features over basement high blocks the focal points for petroleum accumulation therefore further exploration in this highly mature petroleum province should focus on heavy oils in the shallow neogene strata and light oils in the tight sandstones of the deep sag areas

co2 forced climate thresholds during the phanerozoic abstract the correspondence between atmospheric co2 concentrations and globally averaged surface temperatures in the recent past suggests that this coupling may be of great antiquity here i compare 490 published proxy records of co2 spanning the ordovician to neogene with records of global cool events to evaluate the strength of co2 temperature coupling over the phanerozoic last 542 my for periods with sufficient co2 coverage all cool events are associated with co2 levels below 1000 ppm a co2 threshold of below 500 ppm is suggested for the initiation of widespread continental glaciations although this threshold was likely higher during the paleozoic due to a lower solar luminosity at that time also based on data from the jurassic and cretaceous a co2 threshold of below 1000 ppm is proposed for the initiation of cool non glacial conditions a pervasive tight correlation between co2 and temperature is found both at coarse 10 my timescales and fine resolutions up to the temporal limits of the data set million year timescales indicating that co2 operating in combination with many other factors such as solar luminosity and paleogeography has imparted strong control over global temperatures for much of the phanerozoic

erosion of deccan traps determined by river geochemistry impact on the global climate and the 87sr 86sr ratio of seawater abstract the impact of the deccan traps on chemical weathering and atmospheric co2 consumption on earth is evaluated based on the study of major elements strontium and 87sr 86sr isotopic ratios of the main rivers flowing through the traps using a numerical model which describes the coupled evolution of the chemical cycles of carbon alkalinity and strontium and allows one to compute the variations in atmospheric pco2 mean global temperature and the 87sr 86sr isotopic ratio of seawater in response to deccan trap emplacement the results suggest that the rate of chemical weathering of deccan traps 21 63 t km2 yr and associated atmospheric co2 consumption 0 58 2 54 106 mol c km2 yr are relatively high compared to those linked to other basaltic regions our results on the deccan and available data from other basaltic regions show that runoff and temperature are the two main parameters which control the rate of co2 consumption during weathering of basalts according to the relationship f r f c 0 exp ea r 1 t 1 298 where f is the specific co2 consumption rate mol km2 yr rf is runoff mm yr c0 is a constant 1764 mol l ea represents an apparent activation energy for basalt weathering with a value of 42 3 kj mol determined in the present study r is the gas constant and t is the absolute temperature k modelling results show that emplacement and weathering of deccan traps basalts played an important role in the geochemical cycles of carbon and strontium in particular the traps led to a change in weathering rate of both carbonates and silicates in carbonate deposition on seafloor in sr isotopic composition of the riverine flux and hence a change in marine sr isotopic composition as a result deccan traps emplacement was responsible for a strong increase of atmospheric pco2 by 1050 ppmv followed by a new steady state pco2 lower than that in pre deccan times by 57 ppmv implying that pre industrial atmospheric pco2 would have been 20 higher in the absence of deccan basalts pco2 evolution was accompanied by a rapid warming of 4 c followed after 1 myr by a global cooling of 0 55 c during the warming phase continental silicate weathering is increased globally since weathering of continental silicate rocks provides radiogenic sr to the ocean the model predicts a peak in the 87sr 86sr ratio of seawater following the deccan traps emplacement the amplitude and duration of this spike in the sr isotopic signal are comparable to those observed at the cretaceous tertiary boundary the results of this study demonstrate the important control exerted by the emplacement and weathering of large basaltic provinces on the geochemical and climatic changes on earth

late jurassic paleoclimate of central africa abstract paleopedology and geochemical analysis of upper jurassic deposits in the stanleyville group of central africa indicate harsh late jurassic paleoclimates in the interior of gondwana subsurface samples collected from the samba borehole near the center of the congo basin show only weak morphological evidence of pedogenesis but are characterized by an abundance of shrink swell vertic features and rare calcium carbonate nodules indicating seasonal variations in moisture availability and net soil moisture deficiency respectively x ray diffraction analysis of paleosol matrix material reveals the presence of analcime and the clay mineral palygorskite strong indicators of hot arid climatic conditions the 18 o and d values of clay minerals from paleosol profiles range from 22 3 to 25 4 and 44 4 to 39 6 smow respectively and correspond to crystallization temperatures between 25 c and 40 c these crystallization temperatures compare favorably with austral summer surface temperature estimates for central africa that result from late jurassic global circulation models calculations of soil co 2 production using the 13 c values of pedogenic carbonates and plant derived organic matter produce lower co 2 production estimates for the stanleyville group relative to the roughly contemporary morrison formation of the western u s these low soil co 2 production estimates provide further support for arid late jurassic climate conditions in the congo basin the paleoclimatic conditions inferred here from the stanleyville group are similar to those reconstructed from other upper jurassic african continental localities between 5 s and 20 s paleolatitude however penecontemporaneous terrestrial coastal sites within this latitudinal belt of gondwana retain evidence of generally wetter conditions suggesting that those regions may have received more rainfall than the continental interior the paleoclimatic setting reconstructed here from geologic indicators and geochemical proxies suggests that general circulation models accurately predict unique paleoenvironmental conditions that lack modern analogs

seismic reflection imaging of a pull apart sag within tan lu strike slip fault zone cenozoic structure and evolution of the weibei sag southeastern bohai bay basin china abstractthe weibei sag is a cenozoic sag located within the tan lu strike slip fault zone southeast of the bohai bay basin china the sag is controlled by two branches of the tan lu right lateral strike slip fault zone strike n30 e and the gucheng weihekou normal fault strike e w this sag was thought to be a promising exploration area after several oil fields were found there however the most highly productive oil and gas wells are located on traps far from the source rocks a situation thought to be related to the tectonic evolution of this sag thus a regional study of the weibei sag involving three dimensional seismic data sets and drilling cores has been undertaken to document the sag s evolution five groups of secondary faults are distinguished within the weibei sag wnw e w and ene striking normal faults and nnw and nne striking strike slip faults except for the preexisting wnw striking faults the other four groups of faults developed under cenozoic tectonic movement the combined

synoptic behavior of baroclinic eddies during the blocking onset abstract synoptic behavior of individual baroclinic eddies in the course of their interactions with amplifying blocking anticyclones is examined based upon a 30 year record of the tropospheric circulation in the northern hemisphere winter high pass filtered as well as unfiltered fields of geopotential height and potential vorticity were composited relative to the onset of the five different types of blocking patterns before the compositing the entire sequence of the fields was slightly shifted in time and space in such a way that the strongest baroclinic eddy during the onset of each blocking event occupies a prescribed position in the upstream storm track when it reaches its maximum intensity since this shifting considerably reduces the cancellation between the individual high frequency migratory eddies this type of compositing can present a more synoptically oriented view of those interactions than conventional compositing in our composite results one or two pairs of cyclonic and anticyclonic

tectonic characteristics of the central segment of the tancheng lujiang fault zone shandong peninsula eastern china abstract the tancheng lujiang fault zone tlfz in the central segment in the shandong peninsula eastern china is composed of four major faults called f1 f4 from east to west forming a 50 km wide zone detailed field study demonstrates that neogene volcanic and sedimentary strata quaternary deposits and topographic surfaces cover the fractured zones of faults f3 and f4 and are not deformed or displaced the same rocks and surfaces on faults f1 and f2 however are clearly displaced the geological and seismological data show that the f1 and f2 are presently active as a major seismic zone in eastern china whereas the f3 and f4 have been inactive since the neogene fabrics of foliated cataclastic rocks generated in the fracture zones show left lateral strike slip on the f3 and f4 between cretaceous and neogene time and high angle reverse or normal faulting with a dextral component on faults f1 and f2 in late quaternary time field evidence and analysis of the fabrics of fault related rocks reveal the changes of shear sense and activity of faults f1 f4 of the central segment of the tlfz from cretaceous to quaternary time in the shandong peninsula

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

mesozoic to cenozoic tectonic transition process in zhanhua sag bohai bay basin east china abstract the zhanhua sag is part of the bohai bay intracontinental basin system that has developed since the mesozoic in east china the timing of this basin system coincides with the final assembly of east asia and the development of western pacific type plate margin here we use 3 d seismic and core log data to investigate the evolution of this basin and discuss its broad tectonic settings our new structural study of zhanhua sag suggests that there are four major tectonic transitions occurred in the bohai bay basin during mesozoic and cenozoic 1 the first tectonic transition was from stable craton to thrusting during the triassic mainly caused by the south china block s subduction northward beneath the north china block which induced the formation of the nw striking thrust faults 2 the second tectonic transition was mainly characterized by a change from compression to extension which can be further divided into two stages at the first stage two episodes of nw se shortening occurred in east asia during early middle jurassic and late jurassic earliest cretaceous respectively at the second stage the extension and left lateral shearing took place during early cretaceous while compression occurred during late cretaceous the nw striking thrust faults changed to normal faults and the nne striking left lateral strike slip faults started to influence the eastern part of the basin 3 the third transition occurred when the nw se extension and nne striking right lateral shearing started to form during paleogene and the peak deformation happen around 40 ma due to the change of the subduction direction of pacific plate relative to eurasia plate the ne striking normal faults are the main structure and the pre existing nne striking strike slip faults changed from left lateral to right lateral 4 the fourth transition saw the regional subsidence during neogene which was probably caused by the india asia hard collision between 25 and 20 ma

neogene quaternary postrift tectonic reactivation of the bohai bay basin eastern china bohai bay basin located in eastern china is considered a cenozoic rifted basin the basin is atypical in terms of its neogene quaternary postrift subsidence history in that it experienced intensive tectonic reactivation rather than the relative tectonic quiescence experienced during this stage by most rift basins this neogene quaternary tectonic reactivation arose principally in response to two tectonic events 1 activity on a dense array of shallow faults and 2 accelerated tectonic subsidence that occurred during the postrift stage these two events were neither strictly temporally nor spatially equivalent the dense array of shallow faults form a northwest southeast trending belt in the central part of the basin with displacement induced by the reactivation of older northeast and northwest trending basement faults and an associated substantial component of strike slip displacement occurring after 5 3 ma the intensive reactivation of these faults contributed to the atypically accelerated rate of postrift tectonic subsidence of the basin that commenced ca however this was not the sole cause of this accelerated tectonic subsidence a combination of geological activity deep within the crust led to the buildup of intraplate stresses and this combined with ongoing thermal subsidence acted as an additional contributory factor that drove unusually high rates of subsidence for this basin this episode of accelerated postrift tectonic reactivation resulted in conditions favorable for hydrocarbon accumulation

on the role of successive downstream development in east asian polar air outbreaks abstract a composite of 16 strong east asian polar outbreak occurrences widely separated in time reveals a clear sequence of events beginning over the western north atlantic six or seven days in advance of the key day as defined by the cold frontal passage over korea troughs and ridges are seen to form develop and decay successively downstream of one another across the eurasian continent until the polar outbreak occurs these troughs and ridges reach their maximum amplitude in much the same location and at the same time relative to the key day in the majority of the 16 cases the center of the wave packet moves along a curved trajectory approximating the mean 300 mb flow at a nearly constant rate of 30 longitude per day the perturbation moves as an essentially barotropic dispersive wave across most of eurasia but its evolution becomes highly baroclinic as it approaches the east asian coast the wavetrain nature of this perturbation breaks down as it propagates out over the pacific ocean this bre

inclusion of the weathering of volcanic rocks in the geocarbsulf model the carbon cycle model geocarbsulf is extended by dividing the weathering of silicates into volcanic and non volcanic rocks the proportion of volcanic weathering is calculated as a function of time from the oceanic record of 87sr 86sr the volcanic proportion is then used to modify the equations for calculating atmospheric co2 by the addition of a new non dimensional volcanic weathering factor the effect of uplift and physical erosion on weathering is also modified by using only the distribution over time of the abundance of sandstones and shales and not sr isotopic data that had been used previously results indicate moderate change from geocarbsulf in the distribution of atmospheric co2 over phanerozoic time this includes an increased minimum in co2 during the late ordovician in agreement with the presence of a continental glaciation at that time and a shift of maximum mesozoic values from the jurassic to the early cretaceous

structural architecture and tectonic evolution of the cenozoic zhanhua sag along the tan lu fault zone in the eastern north china reconciliation of tectonic models on the origin of the bohai bay basin abstract the zhanhua sag a major depocenter within the larger bohai bay basin bbb along the tan lu fault zone tlfz in the eastern north china developed through two successive phases with different stress regimes during the paleogene the kinematics and the slip history of the nw se and n s striking normal fault systems strongly controlled the internal structure and stratigraphy of the paleocene lower eocene strata in the zhanhua sag during phase 1 isopach maps of the paleocene lower eocene stratigraphy show 4000 m thick clastic rock sequences in these structurally controlled depocenters the average dip slip rates of the nw se and n s striking faults were 78 96 and 50 82 m m y respectively in the paleocene early eocene but decreased to 45 87 and 35 81 m m y in the middle late oligocene the ne sw striking fault systems and their slip history controlled the development of the middle eocene oligocene depocenters and their strata during phase 2 the average dip slip rate of the ne sw striking faults was 10 47 m m y in the paleocene early eocene but increased to 93 49 m m y in the middle late oligocene the ne sw oriented faults cut across and displace the nw se striking faults indicating their relatively younger ages these fault patterns and kinematics recorded in the zhanhua sag reflect an abrupt change in extension directions from ene wsw to nw se before and after the middle eocene that was related to a reversal in the slip direction from sinistral to dextral along the tlfz this slip reversal was in turn a result of a major change in the subduction direction of the pacific plate beneath eastern asia and in the mode of strain partitioning across the tlfz in the continental upper plate

late cretaceous tectonic switch from a western pacific to an andean type continental margin evolution in east asia and a foreland basin development in ne china the early cretaceous structure of ne china was a result of slab rollback driven extensional tectonics characteristic of western pacific type continental margins oblique docking of a microcontinent along the asian active margin in the early late cretaceous induced a compressional stress regime that brought about an andean type continental margin development partitioning of contractional transpressional strain across ne china produced a retroarc foreland basin system comprising from east to west an orogenic wedge a foredeep songliao basin a forebulge great xing an range and a back bulge depozone hailar and erlian basins a sub circular lacustrine depozone in the pre existing songliao basin evolved into a nne trending depocentre near the forebulge and acquired a westward flowing fluvial deltaic drainage system during the campanian development of this retroarc foreland basin system signals a significant tectonic switch from a western pacific type to an andean type continental margin evolution in the geological history of east asia this article is protected by copyright all rights reserved

plate tectonic history basin development and petroleum source rock deposition onshore china abstract china comprises a mosaic of distinct continental fragments separated by fold belts these fold belts are suture zones resulting from the accretion of various fragments formerly separated by intervening areas of oceanic crust the major sedimentary basins onshore china can be classified into four groups those in western china are flexural developing as a result of north south compression in contrast those in the east are extensional and related to development of the pacific oceanic margin in central china basins have a more problematic origin those of north central china ordos sichuan are flexural basins controlled by eastward directed thrusting along their western margin in contrast basins further south chuxiong shiwandashan are predominantly extensional and related to major strike slip movements by synthesizing basin stratigraphies across china in tectonostratigraphic terms and in particular comparing the nature and timing of unconformities it is possible to formulate a coherent model for the palaeoreconstruction of china we identify five major tectonostratigraphic breaks which equate with the collision of the following continental fragments tarim north china carboniferous permian south china block permian triassic qiantang late triassic early jurassic lhasa block late jurassic early cretaceous and india early tertiary prior to permian times the southern margin of eurasia ran approximately along the northern border of modern china the late carboniferous collision of tarim north china with eurasia resulted in the development of a flexural basin junggar and deposition of non marine clastics to the south of the suture shallow marine deposition continued in the late permian early triassic the progressive collision from east to west of the south china block with the north china block resulted in a change to fluvial lacutrine sedimentation across the entire north china tarim block open marine carbonate deposition in the north of the south china block passed southward into a deeper marine clastic sequence deposited in a backarc basin further south a subduction zone existed along the southeastern margin of the south china block in western china northward subduction throughout the triassic resulted in the development of the songban ganzi accretionary prism with retroarc thrusting resulting in flexure and the first development of the tarim basin oblique collision of the qiantang block in the late triassic along the east of the south china block resulted in east west directed thrusting which initiated the suchuan and ordos basins continued strike slip deformation along the south western margin of the south china block resulted in the development of basins with a significant extensional component such as chuxiong the collision of the qiantang block with the southern edge of the tarim basin early jurassic resulted in a renewed clastic influx in both the tarim and junggar basins along the eastern pacific margin a compressional arc and retroarc basin in the south passed northwards into an extensional arc system subduction rollback of the extensional arc initiated rifting in the late jurassic in the eren and songliao basins the late jurassic early cretaceous collision of the lhasa block in the west rejuvenated the thrust systems bordering the western basin and resulted in a renewed clastic influx in the southeast the compressional arc phase culminated in widespread thrusting and folding of early cretaceous age in the northeast extension continued with the progressive migration of the rift system southward with time the arrival of the indian block in the early tertiary rejuvenated the bounding thrust belts of all the western basins in the east the change in convergence of the pacific plate to a more westerly direction is marked by extension and widespread rifting along the entire length of eastern china throughout most of china mesozoic and cenozoic deposition occurred in predominantly non marine environments source rocks in such settings comprise principally mudstones deposited in lakes organic rich mudstones these can accumulate in both deep and shallow lakes in order to accumulate substantial volumes the lake must be significant in space and time in china lacustrine orms occur in both rift and flexural basins lacustrine orms deposited under humid climatic conditions are restricted to the period of maximum tectonic subsidence in the flexural basins of western china source rock deposition follows basin initiation by 20 30 ma in the extensional basins of eastern china source rock deposition takes place 5 15 ma after basin initiation by contrast semi arid and arid climate lacustrine orms whilst being best developed during the period of maximum tectonic subsidence occur at all stages in the basin history

an east asian cold surge case study abstract since a cold surge is a hazardous weather phenomenon in east asia the rapid population increase and economic growth over the past two decades require improvement in forecasting cold surges and their related weather events over this region however without a better understanding of these events this task cannot be accomplished a cold surge with a well defined cold front passing through taiwan was selected to illustrate its impact on the east asian weather system this case is typical of a large portion of surges occurring in the region major findings of this study are as follows coupling with the upper ridge trough structures of the wave train straddling the eastern seaboard of northeast asia cold surges occur sequentially a cold front with a prefront high pressure zone is formed by the new surge outflow interacting with the anticyclone of the aging surge the warm moist air advected northeastward along the cold front assists the development of the new surge s low center while the prefron

structural deformation and evolution of right lateral strike slip tectonics of the liaohe western depression during the early cenozoic abstract the tan lu fault zone tlfz traverses the liaohe western depression lhwd affords an exceptional opportunity to reveal the structural deformation and evolution of a major strike slip fault of the lhwd using three dimensional seismic data and well data in this paper based on structural interpretations of the 3 d seismic data of the lhwd combined with depth slice and seismic coherency a variety of structural features in relation to right lateral strike slip fault the western branch of the tan lu fault have been revealed presence in the depression such as thrust faults xinlongtai taian dawa and chenjia faults structural wedges positive flower structures and en echelon normal faults fault cutoffs growth strata and the neogene unconformity developed in the lhwd verify that the activity of right lateral strike slip from the late eocene to neogene ca 43 23 ma the study indicates that the right lateral strike slip played an important role in controlling the structural deformation and evolution of the lhwd in the early cenozoic moreover the front structural wedge generated the gross morphology of the xinlongtai anticline and developed the lengdong faulted anticline during the late eocene and the back structural wedge refolded the lengdong faulted anticline zone in the late eocene to the early oligocene wrench related structures the chenjia thrust fault and the en echelon normal faults were developed during the late oligocene uniform subsidence in the neogene to quaternary furthermore the driving force of the right lateral strike slip deformation was originated from n s extension stress related to the opening of the japan sea and ne sw compression as the far field effect of india eurasia convergence

pacific absolute plate motion since 145 ma an assessment of the fixed hot spot hypothesis 1 using the geometry and ages from 12 pacific seamount chains we have determined two new absolute plate motion models that now extend our self consistent and high resolution models with covariance estimates back to 145 ma the wk08 a model maps the full uncertainty in the age progressions into uncertainties in rotation opening angles yielding a relatively smooth plate motion model the wk08 g model relaxes the mapping of age uncertainties in order to better isolate secondary geometry changes seen along many coregistered chains both models have been used to assess the viability of the fixed hot spot hypothesis in the pacific in determining the models we found that only a small group of age samples had to be discarded on the grounds that they were discordant with the dominant trends we were able to connect plate motions for pre and post emperor age intervals by including the ratak gilbert ellice and musicians trails in our analysis however as no active hot spot locations exist for the older chains their inclusion adds additional model parameters both age and geometry misfits increase with age reflecting the observed increase in age uncertainties and the general widening of trails secondary and short lived changes in absolute plate motion mapped in wk08 g appear to correlate with the timing and sense of motion of known pacific rim tectonic events analysis of interchain distances between coeval samples from the hawaii and louisville chains suggests possible discrepancies during the older emperor stage that are compatible with predictions of hot spot drift we computed a new apparent polar wander path for the pacific and found a high degree of correspondence with paleomagnetically derived paths as long as solutions allowing for anomalous skewness were included in the latter our polar wander path suggests that there might have been some true polar wander during the emperor stage complemented by a smaller amount of hot spot drift than otherwise required we show that chain geometries and ages combined with future paleolatitude determinations from additional sites and chains could enable an observation based description of both hot spot and plate motions without relying on predictions of hot spot drift derived from mantle flow calculations

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

coesite bearing eclogite from the dabie mountains in central china coesite and coesite pseudomorphs are recognized in eclogite from the dabie mountains a collision zone between the sino korean and yangtze cratons in central china this third known occurrence of coesite in deep crustal rocks is within an archean gneiss terrane and is the first locality where coesite has been identified as an inclusion in both omphacite and garnet crystals at the same location coesite bearing eclogite is estimated to form at pressures of 28 kbar and temperatures from 600 to 710 c the dabie mountains eclogite underwent retrograde metamorphism to amphibolite facies after its formation the preservation of coesite in eclogite is found to be strongly controlled by the pressure temperature time path that coesite bearing eclogite followed during its uplift and retrograde metamorphism

right lateral shear along the northwest pacific margin and the india eurasia collision right lateral shear along the eastern margin of asia from the eocene to the present has led to the opening of pull apart basins intracontinental such as the bohai basin or oceanic such as the japan sea we suggest in this paper that this right lateral shear is a consequence of indentation of asia by india as in small scale analog experiments we conclude that antithetic wrench faults accommodate the counterclockwise rotation of large domino blocks between two major left lateral shear zones tien shan baikal stanovoy for the northern one and qin ling for the southern one we discuss the compatibility of this mechanism which involves a rather small amount of extrusion with the fast eastward expulsion described for southeast asia we re emphasize the role played in the opening of marginal basins by the pacific subduction as a free boundary to the east

relationship between the arctic oscillation and cold surges over east asia abstract the present study reveals the changes in the characteristics of cold surges over east asia associated with the arctic oscillation ao based on circulation features cold surges are grouped into two general types wave train and blocking types the blocking type of cold surge tends to occur during negative ao periods that is the ao related polarity of the blocking type however the wave train type is observed during both positive and negative ao periods although the wave train features associated with negative ao are relatively weaker the cold surges during negative ao are stronger than those during positive ao in terms of both amplitude and duration the cold surges during positive ao in which the extent of effect is confined to inland china passes through east asia quickly because of weaker siberian high and aleutian low leading to short duration of these cold surges in contrast the cold surge during negative ao characterized by a well organized anticyclone cyclone couplet with high p

stratospheric origin of cold surge occurrence in east asia 1 in the present study we have found a precursory signal in the stratospheric circulation prior to the cold surge occurrence in east asia over northern eurasia about one week before the cold surge occurrence strong stratospheric negative potential vorticity anomalies and rising of geopotential height are observed the dynamic linkage between the stratospheric perturbations and the tropospheric adjustment along with initial disturbances for a cold surge occurrence are discussed

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

late cretaceous cenozoic intraplate extension and tectonic transitions in eastern china implications for intraplate geodynamic origin abstract the geodynamic origin of intraplate extension remains poorly understood for the case of the late cretaceous cenozoic intraplate extension in eastern china its driving mechanism remains highly controversial due to the absence of a comprehensive understanding of significant tectonic transitions this study uses the well documented cretaceous tectonic evolution as a background and integrates extensive multidisciplinary data in the jianghan basin bohai bay basin and zhejiang area to develop an integrated view of the late cretaceous cenozoic geodynamic origin for the first time during the late cretaceous rifting and depocentres were distributed in the jianghan basin and were located in the central bohai bay basin during the cenozoic rifting and depocentres were initially focused in the western basins and then progressively migrated eastward rather than continuing migrating eastward the rifting and volcanism during the middle cenozoic 50 23 ma significantly increased and all rift basins in eastern china were abandoned at the end of the middle cenozoic 26 23 ma the volcanism in the zhejiang area was markedly enhanced during the late cenozoic 23 0 ma the asthenospheric mantle sources beneath the two rift basins were isotopically more depleted with an increased extent of melting from the late cretaceous 100 65 ma to early cenozoic 65 50 ma however they became isotopically more enriched and heterogenous with a decreased melting extent significantly reduced volatile content from the early cenozoic to middle cenozoic the mantle source beneath the zhejiang area during the late cenozoic was isotopically more depleted and heterogeneous than during the middle cenozoic with an increased extent of melting these three phase tectonic transitions together with tectonic correlations directly constrain the causal relationships between the intraplate extension in eastern china and the motions of the adjacent plates consequently we propose that the late cretaceous cenozoic intraplate extension and tectonic transitions in eastern china were successively driven by the paleo pacific slab rollback during the late cretaceous the india asia collision during the early middle cenozoic and by the combination of the subduction of the pacific plate and india asia collision during the late cenozoic our study provides an integrated perspective for unraveling the geodynamic origin of intraplate extension

syn collisional transform faulting of the tan lu fault zone east china origin of the continental scale tan lu fault zone tlfz east china remains controversial about 550 km sinistral offset of the dabie orogenic belt dob and sulu orogenic belt sob is shown along the ne nne striking tlfz syn collisional sinistral ductile shear belts in the tlfz have been identified thirteen phengite bulk separates from the mylonites were dated by the 40ar 39ar method they gave cooling ages of the 198 181 ma for the shear belts along the eastern margin of the dob and 221 210 ma from the western margin of the sob distribution of the foreland basin deposits suggests that sinistral offset of the dob and sob by the tlfz took place prior to deposition of the upper triassic strata the marginal structures around the dob and sob support syn collisional faulting and indicate anticlockwise rotation of the dob during the displacement the folding and thrust faulting related to crustal subduction coeval with the tan lu faulting is older than the foreland basin deposition related to the orogenic exhumation several lines of evidence demonstrate that the tlfz was developed as a syn collisional transform fault during latest middle to earliest late triassic time when the dob and sob experienced crustal subduction of the south china block scb eastward increase of the crustal subduction rates is believed to be responsible for the sinistral transform faulting

interannual variation of the east asian cold surge activity abstract the occurrence frequency of the east asian cold surge exhibits an interannual variation in concert with the el nino southern oscillation enso cycle that is the cold surge occurs more less frequently during warm cold enso winters because the cold surge high low dipoles are coupled with the upper level synoptic short waves any mechanism modulating the activity of these waves would affect the cold surge activity the streamfunction budget analysis in the short wave regime indicates that the development of the cold surge short wave train over east asia and the northwest pacific is modulated by the north pacific enso short wave train due to the coupling between the upper level cold surge short wave train and the surface cold surge dipole it is inferred from this streamfunction budget analysis that the interannual variation of the cold surge occurrence frequency is a result of this modulation

seismogenic strike slip faulting and the development of the north china basin the actively subsiding north china sedimentary basin is associated with an unusually high level of seismic activity this oil and gas producing basin has been the site of nine large m 7 destructive earthquakes since 1600 a d an analysis of faulting during the tangshan earthquake sequence which includes some of the largest shocks that have occurred in this basin during the past 400 years showed that the dominant pattern of deformation during this sequence was associated with displacement on right stepping right lateral strike slip faults a large amount of subsidence 1 0 1 5 m occurred in pull apart regions between steps of the north northeast nne trending strike slip faults the directivity of the p wave radiation pattern and the distribution of aftershocks of the bohai gulf earthquake of july 18 1969 also indicate strike slip faulting on planes of similar nne trend together with the four largest shocks of the hsingtai sequence in 1966 earthquakes with right lateral slip on nne trending faults account for about two thirds of the seismic moment released in this region for the past 100 years the average regional strain due to seismic slip has a dominant component of dextral simple shear on nne striking planes that is approximately twice as large as north south extension or east west shortening based on a combination of published field and borehole data the dominance of horizontal dextral simple shear over subsidence seems to have begun no later than the mid pliocene and the total amount of extension over the entire basin is only about 20 30 this pattern of deformation the spatially variable heat flow values the scattered locations of rapid deposition of quaternary sediments and the fluctuating rate of sedimentation in space and time during the neogene in this basin are difficult to explain by pure extension and thermal subsidence we propose that these observations and the shape of the whole north china basin that of a lazy z are a consequence of pulling apart associated with right lateral movement on the nne trending strike slip fault systems and that the basin as a whole has formed and evolved as a composite pull apart basin due to right lateral slip on numerous right stepping faults since the eocene

diachronous onset and polyphase cooling of the taili yiwulushan metamorphic core complex corridor ne china and its relationships to the formation of adjacent extensional basins abstract the aim of the study to investigate the cooling and exhumation history of deep crustal rocks along the taili yiwulushan metamorphic core complex mcc corridor and correlate these with volcanic clastic deposition in the late jurassic to early cretaceous supra detachment fuxin yixian basin in the west and the mostly eocene liaohe basin in the east this corridor exposes low to medium grade metamorphic neoarchean rocks and late triassic late jurassic and early cretaceous granitic rocks which exhumed from the middle to shallow crustal levels new 40ar 39ar ages of muscovite biotite k feldspar and apatite u th sm he ages in combination with compiled published geochronological data from the granitic rocks constrain three major stages of cooling exhumation and deformation from late jurassic through early cretaceous to eocene interrupted by late cretaceous tectonic quiescence the onset of activity and exhumation and cooling is diachronous along the mcc corridor at taili in the south the main activity of the sinistral shear zone is constrained between 160 and 140 ma with major cooling from crystallization temperatures of granitoids from 700 750 c to 160 c first stage along the waziyu ductile detachment at the western border of the yiwulushan mcc major cooling and exhumation is bracketed between 130 ma and 100 ma second stage and thus indicates a northward progradation of deformation and exhumation activity however cooling ages as old as 159 ma along the eastern margin of the yiwulushan mcc indicate an earlier initiation of cooling and westward rolling hinge type propagation first stage late cretaceous and paleogene times are characterized by a tectonically quiet period with only minor cooling and exhumation stage three the fourth and final stage of exhumation and cooling to very low temperatures occurred during late paleocene to earliest eocene times and is associated with the transtensional or extensional opening of the liaohe basin

structural anatomy and dynamics of evolution of the qikou sag bohai bay basin implications for the destruction of north china craton abstract the qikou sag is a complex cenozoic faulted basin at the center of the bohai bay basin the paleogene sediments in the basin show a maximum thickness of 11 000 m in paleogene representing intense crustal extension the sag has a typical dish like structure in the upper part with the central domain represented by a deep half graben and surrounded by different types of gentle slopes and sub sags linked with the basin margin uplifts the inner structure of the sag is jointly controlled by the basin margin extensional faults intrabasinal extensional tectonics and transfer tectonics the sag is divided into four different extensional tectonic domains by the basement fault along the coastline the haihe xingang fault and the qidong fault these sub sags are in turn controlled by different detachment systems the listric cangdong and hangu faults mark the major boundary faults controlling the extensional structure of the basin the structure and tectonics of the qikou sag provide a direct record of the late stages of rifting and destruction of the north china craton the mesozoic basement structures of the sag determine the tectonic styles in different sub sags the complete inversion of the structures in mesozoic profoundly influenced the development and evolution of the basin during paleogene we identify three main stages in the tectonic evolution of the qikou the oligocene faulting stage the miocene pliocene thermal subsidence stage and the pleistocene quaternary depression stage in the oligocene fault activities and the basin architecture were mainly controlled by the listric boundary fault system of the basin and the secondary fault system in the hanging wall under the detachment and extension in the upper crust since miocene the boundary fault of the basin underwent weak extension the upwelling of the upper mantle and the formation of corresponding shallow depressions contributed to the evolution and tectonic architecture of the qikou sag

seismic profiles across the middle tan lu fault zone in laizhou bay bohai sea eastern china the stratigraphic architecture structure and cenozoic tectonic evolution of the tan lu fault zone in laizhou bay eastern china are analyzed based on interpretations of 31 new 2d seismic lines across laizhou bay cenozoic strata in the study area are divided into two layers separated by a prominent and widespread unconformity the upper sedimentary layer is made up of neogene and quaternary fluvial and marine sediments while the lower layer consists of paleogene lacustrine and fluvial facies in terms of tectonics the sediments beneath the unconformity can be divided into four main structural units the west depression central uplift east depression and ludong uplift the two branches of the middle tan lu fault zone differ in their geometry and offset the east branch fault is a steeply dipping s shaped strike slip fault that cuts acoustic basement at depths greater than 8 km whereas the west branch fault is a relatively shallow normal fault the tan lu fault zone is the key fault in the study area having controlled its cenozoic evolution based on balanced cross sections constructed along transverse seismic line 99 8 and longitudinal seismic line 699 0 the cenozoic evolution of the middle tan lu fault zone is divided into three stages paleocene eocene transtension oligocene early miocene transpression and middle miocene to present day stable subsidence the reasons for the contrasting tectonic features of the two branch faults and the timing of the change from transtension to transpression are discussed crown copyright c 2008 published by elsevier ltd all rights reserved

deep shallow coupling response of the cenozoic bohai bay basin to plate interactions around the eurasian plate abstract the bohai bay basin bbb is a meso cenozoic intracontinental petroliferous basin where four pre existing continental scale fault zones intersect in east china the bbb has experienced complex deformational and evolutionary history that records significant information about how the lithosphere there has responded to the coeval plate interactions around the eurasian plate and or their resulting deep crust mantle processes in the cenozoic now both deep and shallow deformational and evolutionary processes of the bbb have been well studied but many geodynamic mechanisms previously proposed for those processes are too general to explain them well based on various data and principles we first summarized both deep and shallow responses and processes of the bbb in the cenozoic and then matched reasonable geodynamic mechanisms for each of them the results show as follows the cenozoic differential reactivation of pre existing continental scale weak zones controlled the coeval deep shallow differential coupling evolution of the bbb the paleogene extension in the bbb was mainly caused by crust mantle processes triggered by the stagnant izanagi slab the cenozoic strike slip faulting was influenced by various plate interactions in which the oblique subduction and anticlockwise rotation of young pacific plate resulted in the complex pre oligocene strike slip history of the tan lu fault zone to the south of the zhang peng fault zone while the india eurasia collision has caused the intense and synchronous strike slip faulting of various faults there since 35 ma which was then weakened by the oblique subduction and clockwise rotation of young philippine sea plate in the neogene the compression resulting from both the india eurasia collision and the philippine sea plate s subduction contributed to the latest paleogene tectonic inversion in the bbb the arrival of mantle flow triggered by both the india eurasia collision and the stagnant slab of the pacific plate resulted in the tectonic reactivation there in the late neogene

pacific plate motion change at the time of the hawaiian emperor bend constrains the viscosity of earth s asthenosphere important constraints on asthenospheric viscosity come primarily from modeling the glacial rebound of the past 20 kyr but remain somewhat loose because of the intrinsic resolving power of these models we obtain narrower bounds by building on the notion that the asthenosphere also controls the ability to change plate motions over myr we focus on the pacific kinematic change at the time of the hawaiian emperor bend event which is linked to the coeval inception of subduction in the western pacific we sample plausible asthenospheric viscosity and thickness values by requiring the rate at which torque varied to generate the observed kinematics consistent with the nature of subduction initiation uncertainties on the bend event duration and the occurrence of pacific hot spots drift do not hamper our results that suggest that the asthenosphere viscous response to vertical shear over kyr is consistent with that to horizontal shear over myr

geologic history of seawater a magic approach to carbon chemistry and ocean ventilation abstract we explore the relationship between atmospheric o 2 and co 2 evolution and seawater chemistry with particular focus on the co 2 carbonic acid system and ocean ventilation over the phanerozoic eon using a coupled biogeochemical earth system model magic this model describes the biogeochemical cycles involving the major components of seawater ca mg na k cl so 4 co 2 hco 3 co 3 as well as components o 2 fe p organic c reduced s central to long term ecosystem productivity the magic calculations show that the first order input fluxes from weathering of continental rocks of ca mg and dissolved inorganic carbon dic to the ocean varied in a cyclical manner over the phanerozoic the cyclicity is mainly the result of the impact of changing atmospheric co 2 levels and hence temperature and runoff on these fluxes reflecting the nature of hothouse greenhouse high co 2 and warm versus icehouse low co 2 cool and continental glaciation conditions during the phanerozoic uptake of dic by seafloor basalt seawater reactions also varied in a corresponding fashion to the weathering fluxes the fluxes of ca mg dic and other seawater constituents removed in oceanic sinks were also calculated and hence with calculated inputs and outputs of seawater constituents the changes in seawater chemistry through phanerozoic time could be obtained seawater ph increased irregularly during the phanerozoic from just above 7 in the cambrian period approaching modern average values in the most recent several millions of years calcite saturation state also increased with decreasing age both ph and calcite saturation state trends exhibited a cyclic overprint of hothouse and icehouse environmental conditions dissolved sulfate changed in a cyclical manner reflecting mainly variations in weathering and accretion rates and redox conditions whereas dissolved potassium exhibited little variation in concentration using our standard model results for the chemistry of seawater and changes in atmospheric co 2 and o 2 as the basis for a series of sensitivity experiments we vary the ventilation rate of the global ocean and quantify the resulting changes in terms of processes such as net primary production organic carbon burial and oxidation pyrite weathering and sulfate reduction we use these preliminary results to discuss how changes in ocean ventilation affect atmospheric co 2 and o 2 and in turn exert changes in the sulfur organic carbon and inorganic carbon systems we postulate that periods of slow plate accretion rates associated with lower atmospheric co 2 vigorous deep water formation cooler drier climatic conditions and greater poleward temperature gradients are more likely to be associated with a strong thermohaline circulation and thus enhanced global ocean mixing conversely periods of higher accretion rates higher co 2 higher average global temperatures with more equable poleward gradients and higher sea levels resulting in extensive continental inundation would be more likely to be coincident with times of reduced mixing of the global ocean it is important to recognize that the scale of these changes depends on how major tectonic cycles controlling chemical weathering co 2 and temperature in turn affect nutrient supply global ocean productivity and global ocean thermohaline circulation the key to elucidating these changes lies in an understanding of the relationship between long term tectonic evolution which leads to changes in climate sea level and the global distribution of continental landmasses and the sedimentary environments they host and the circulation of the global ocean

transient fluctuation in paleoclimate at the end of permian new constraints from paleosol carbonates in the erlongkou section chongqing southwestern china abstract paleosol carbonates were found in the erlongkou section at the top of the changhsing formation in chongqing southwestern china detailed petrology study suggested that these paleosol carbonates have typical pedogenic structures and fabrics conodont biostratigraphy volcanic ash zircon dating and stratigraphic carbon isotopes indicated that the paleosol carbonates formed at the end of permian 252 3 1 0 ma geochemical results indicate two different provenances for the paleosol i e the micrite of the changhsing formation and volcanic ash the calcretes and carbonates in the paleosol are pedogenic calcites that precipitated under well drained conditions and they are free of carbonate debris from the bedrocks atmospheric co2 concentrations pco2 estimated based on the model of cerling 1999 suggested that there was greenhouse paleoclimates with a transient fluctuation in pco2 at the end of the permian

40ar 39ar dating of strike slip motion on the tan lu fault zone east china abstract ne trending sinistral ductile shear belts in the southern part of the tan lu fault zone east china are exposed along the eastern edge of the northern dabie belt and southern zhangbaling belt three hornblende three phengite and 12 biotite separates from greenschist facies mylonites in the shear belts were dated by the 40ar 39ar method in this study a hornblende plateau age of 143 3 ma is interpreted as representing the time of sinistral motion on the zhangbaling part of the tan lu fault zone seven biotite samples from the same part yield 40ar 39ar cooling ages from 137 to 125 ma a phengite plateau age of 138 8 ma from the eastern edge of the dabie belt is considered as being close to the time of deformation in the tan lu strike slip zone five biotite 40ar 39ar ages from 120 to 110 ma and one phengite age of 121 ma from the same area represent cooling ages after the sinistral faulting it is concluded on the basis of these 40ar 39ar ages that the sinistral ductile shear belts in the southern part of the tan lu fault zone were produced in earliest early cretaceous this sinistral motion on the tan lu fault zone is considered to be related to high speed highly oblique subduction of the pacific plate at this time

addendum to inclusion of the weathering of volcanic rocks in the geocarbsulf model r a berner 2006 v 306 p 295 302 in the paper by berner 2006a 1 the compiled data presented by dessert and others 2001 2 for different values of the relative weathering rates of basalts versus granites was missed the term granite is used here to refer to all granitoid rocks including gneisses it is the primary

cenozoic evolution of the tan lu fault zone east china constraints from seismic data abstract the tan lu fault zone tlfz is a continental scale strike slip fault zone in the east china that contains rich and significant information about the mesozoic cenozoic evolution of eastern asia it experienced a long term and complex superimposed deformation characterized by mesozoic sinistral and cenozoic dextral motions the fault has a well documented mesozoic sinistral displacement history but its cenozoic history is poorly known in this study based on the observations of the interrelationships of fault kinematics fault geometry and concomitant sedimentation the cenozoic evolution of the tlfz is constrained by abundant seismic data from oil fields numerous bends along the cenozoic master fault sensitively record changes in the stress field during strike slip motion taking into account the cenozoic evolution of the bohai bay basin east china the evolutionary history of these strike slip bends is investigated and the results indicate that dextral motion along the tlfz began at about 40 ma furthermore the cenozoic evolutionary history of the tlfz is suggested to include an extensional deformation with a possible weak sinistral shear from 65 to 40 ma from 40 to 0 ma dextral motion occurred due to a change in the subduction direction of the pacific plate relative to the eurasian plate causing the fault to experience dextral shear with a component of extensional deformation dextral motion was most intense from 40 to 25 ma and then the dextral direction may have suddenly changed from a nearly ne sw trend to a nearly n s trend at around 25 ma dextral motion was relatively enhanced again after 12 ma and was particularly strong after 5 ma episodic and ephemeral thrusting deformation might have occurred during the quaternary the cumulative cenozoic dextral displacement of the tlfz is far smaller than its mesozoic sinistral strike slip displacement may be no more than 21 km

effects of different organic matter sources on estimates of atmospheric and soil pco2 using pedogenic carbonate abstract carbon isotope analysis of paleosol carbonates is one of the most widely used methods for producing quantitative estimates of co2 levels in the ancient atmosphere and is increasingly used to estimate soil pco2 as a proxy for primary productivity recent efforts to improve the carbonate co2 paleobarometer by refining input parameters e g soil temperature soil co2 production function have yielded more accurate estimates of ancient atmospheric pco2 the carbonate co2 paleobarometer is especially sensitive to input values for the carbon isotope composition of soil organic matter om which should ideally reflect the 13c value of om present when pedogenic carbonates were forming published soil pco2 estimates derived from pedogenic carbonate in upper jurassic paleosols are re evaluated here using om occluded within pedogenic carbonates rather than average values of fossilized plant material collected throughout the sampled stratigraphic sections the new soil pco2 estimates calculated using occluded om range from 4 600 to 20 000 ppmv and are much lower than the previously published estimates which were often in excess of 60 000 ppmv in order to determine which om source provides more accurate results estimates of atmospheric pco2 obtained using plant material and occluded om from a carbonate bearing modern soil are compared with measured pre industrial atmospheric co2 levels in the modern soil profile plant om 13c is highly variable and slightly more negative than the 13c of occluded om the observed 1 offset between the average 13c values of plant material and occluded om is much less than the overall range of 6 in plant om estimates of atmospheric pco2 from the modern soil that are calculated using occluded om differ by less than 100 ppmv on average from estimates based on plant om these results suggest that occluded om produces reasonably accurate pco2 estimates when used with the carbonate co2 paleobarometer applying a 1 correction to the 13c of occluded om also produces accurate pco2 estimates but the extreme variability in 13c of plant matter leads to inaccurate pco2 estimates even when samples are averaged

fractures of lacustrine shale reservoirs the zhanhua depression in the bohai bay basin eastern china abstract fractures play a vital role in the exploration and development of shale oil and gas by providing effective space for shale reservoirs and significantly improving the fluid flow capability core observations microscopic analyses of thin sections scanning electron microscopy and formation microscanner imaging fmi were used to determine the types causes of formation and development characteristics of the fractures in lacustrine shale reservoirs in the lower part of the paleogene shahejie formation es 3 in the zhanhua depression bohai bay basin eastern china x ray diffraction xrd analysis total organic carbon toc measurements and porosity and permeability measurements were used to study the controlling factors of the fractures in the shale reservoirs and to analyze the impact of the fractures on the shale reservoirs properties and subsequent exploration and development the studied shale reservoir mainly displays tectonic fractures as well as various types of non tectonic fractures the non tectonic fractures mainly include over pressure fractures diagenetic fractures inter layer bedding fractures and fractures of mixed origins in the study area the tectonic fractures which were formed under the combined action of tensile and shear stress display the following characteristics the dip angle of the tectonic fractures varies significantly unfilled or half filled effective fractures have a high proportion these fractures are mainly oriented in the ne sw nne ssw and wnw ese directions with fractures in the ne sw direction accounting for the highest proportion the tectonic and non tectonic fracture development is affected by multiple types of factors such as the presence of faults mineral composition lithology abnormal pressure and organic matter content abnormally high pore pressure is a very important factor in the development of non tectonic fracture it is inferred that the over pressure is mainly related to hydrocarbon generation during thermal evolution fractures effectively improve the porosity and permeability of the shale reservoirs and the enhancement of permeability is particularly significant the current stress field affects the fluid flow capability of the fracture reservoirs and the present maximum principal stress in zhanhua depression is oriented in the nee sww direction which has a small angle with fractures in ne sw direction we propose that the fractures in this direction have the greatest connectivity and thus are a high priority target for petroleum exploration and development

quantifying and understanding the uncertainty of atmospheric co2 concentrations determined from calcic paleosols 1 a computer program pbuq that uses monte carlo simulations to propagate uncertainty through regression equations and the equation for the paleosol carbonate co2 paleobarometer is presented pbuq includes options for all of the common approaches to determining values for input variables and incorporates several recent advancements relevant to determining values for soil respired co2 concentrations 13c values of respired co2 13c values of atmospheric co2 and temperatures of soil carbonate formation pbuq is intended to improve confidence in paleoatmospheric co2 research by helping researchers draw statistically significant conclusions pbuq can also be used to attribute and partition error among various sources and thereby advance this technique sensitivity analysis indicates that s z is the largest source of uncertainty for most paleosols and that uncertainty is minimized for soils in which co2 is an evenly balanced mixture between soil derived and atmospheric components evenly balanced mixtures are most likely for paleosols formed in deserts and for weakly developed paleosols development of proxies for soil respired co2 concentrations and 13c values of soil respired co2 specifically for such soils is perhaps the most crucial next step for improving this technique currently calcic paleosols are best used to test the significance of trends and or differences among time slices in paleoatmospheric co2 concentration application to quantifying earth system sensitivity will require large scale averaging of determinations from individual paleosols and or reduced uncertainty associated with input variables

a synoptic and dynamical characterization of wave train and blocking cold surge over east asia through an agglomerative hierarchical clustering method cold surges over east asia are classified into two distinct types based on the spatial pattern of the geopotential height anomalies at 300 hpa one is the wave train type that is associated with developing large scale waves across the eurasian continent the other is the blocking type whose occurrence accompanies subarctic blocking during the wave train cold surge growing baroclinic waves induce a southeastward expansion of the siberian high and strong northerly winds over east asia blocking cold surge on the other hand is associated with a southward expansion of the siberian high and northeasterly winds inherent to a height dipole consisting of the subarctic blocking and the east asian coastal trough the blocking cold surge tends to be more intense and last longer compared to the wave train type the wave train cold surge is associated with the formation of a negative upper tropospheric height anomaly southeast of greenland approximately 12 days before the surge occurrence further analysis of isentropic potential vorticity reveals that this height anomaly could originate from the lower stratosphere over the north atlantic cold surge of the blocking type occurs with an amplifying positive geopotential and a negative potential vorticity anomaly over the arctic and the northern eurasia in stratosphere these anomalies resemble the stratospheric signature of a negative phase of the arctic oscillation this stratospheric feature is further demonstrated by the observation that the blocking type cold surge occurs more often when the arctic oscillation is in its negative phase

mechanisms of intraseasonal amplification of the cold siberian high mechanisms of intraseasonal amplification of the siberian high are investigated on the basis of composite anomaly evolution for its strongest events at each of the grid points over siberia at each location the amplification of the surface high is associated with formation of a blocking ridge in the upper troposphere over central and western siberia what may be called wave train atlantic origin type is common where a blocking ridge forms as a component of a quasi stationary rossby wave train propagating across the eurasian continent a cold air outbreak follows once anomalous surface cold air reaches the northeastern slope of the tibetan plateau it is found through the potential vorticity pv inversion technique that interaction between the upperlevel stationary rossby wave train and preexisting surface cold anomalies is essential for the strong amplification of the surface high upper level pv anomalies associated with the wave train reinforce the cold anticyclonic anomalies at the surface by inducing anomalous cold advection that counteracts the tendency of the thermal anomalies themselves to migrate eastward as surface thermal rossby waves the surface cold anomalies thus intensified in turn act to induce anomalous vorticity advection aloft that reinforces the blocking ridge and cyclonic anomalies downstream of it that constitute the propagating wave train the baroclinic development of the anomalies through this vertical coupling is manifested as a significant upward flux of wave activity emanating from the surface cold anomalies which may be interpreted as dissipative destabilization of the incoming external rossby waves

widespread fog over the indo gangetic plains and possible links to boreal winter teleconnections boreal wintertime planetary scale atmospheric circulations and their possible consequences to widespread fog occurrences over the indo gangetic plains igp region of the himalayan valley are investigated in this study among the different fog types radiation fog type seen at night or early morning hours favored by large scale subsidence aloft and strong near surface inversion is focused in this study a composite analysis reveals that upper air circulation associated with 105 fog days over the igp region show a trail linked to circulation anomalies over the eurasian continents and the arctic circle the findings suggest that there is a footprint of the arctic oscillation ao and conventional eurasian eu circulation patterns linked to anticyclonic circulation aloft over the igp region although widespread igp fog occurrences under the large scale subsidence environment are seen to occur during both phases of ao the negative ao phase high pressure environment over the arctic circle portends a greater likelihood for fog occurrences in the igp region a coupling of positive mid tropospheric height anomalies over western eurasia and the anticyclonic circulation anomalies over the igp region is evident during the igp fog periods concomitant with eu positive height excess over siberia phase further anomalous circulation over the igp region during the fog periods appears to rely more on the strength of the ao negative phase than the circulation strengths over eurasia on the contrary the eurasian circulation largely appears to influence the subsidence aloft over the igp region irrespective of the strength of the ao positive phase it is also noted that upper air circulation during non foggy periods over the igp region has conformity with positive ao phase and rapidly progressing eu pattern these planetary scale teleconnection pathways offer new dynamical insights into comprehending widespread igp fog scenario which have been hitherto perceived mostly from a regional context