reconstruction of northeast asian deformation integrated with western pacific plate subduction since 200 ma abstract the configuration and kinematics of continental deformation and its marginal plate tectonics on the earth s surface are intrinsic manifestations of plate mantle coupling the complex interactions of plate boundary forces result in plate motions that are dominated by slab pull and ridge push forces and the effects of mantle drag these interactions also result in continental deformation with a complex basin mountain architecture and evolution the kinematics and evolution of the western pacific subduction and northeast asian continental margin deformation represent a first order tectonic process whose nature and chronology remains controversial this paper implements a deep time reconstruction of the western pacific subduction continental accretion or collision and basin mountain deformation in northeast asia since 200 ma based on a newly revised global plate model we use gplates software to examine strain recovery geological and seismic tomography constraints for the western pacific plate subduction and sequentially backward rotations of deforming features the results indicate a nw se oriented shortening from 200 to 137 ma a nww see oriented extension from 136 to 101 ma a nearly n s oriented extension and uplift with a short term nww see oriented compressional inversion in northeast china from 100 to 67 ma and a nw se and nearly n s oriented extension from 66 ma to the present day the western pacific oceanic plate subducted forward under east asia along mudanjiang honshu island during the jurassic and the trenches retreated to the sikhote alin north shimanto and south shimanto zones from ca 137 128 ma ca 130 90 ma and in ca 60 ma respectively our time dependent analysis of plate motion and continental deformation coupling suggests that the multi plate convergent motion and ocean continent convergent orogeny were induced by advance subduction during the jurassic and earliest cretaceous our analysis also indicates that intra continent rifting and back arc extension were triggered by trench retreat during the cretaceous and that the subduction of the oceanic ridge and arc were triggered by trench retreat during the cenozoic therefore reconstructing the history of plate motion and subduction and tracing the geological and deformation records in continents play a significant role in revealing the effects of complex plate motions and the interactions of plate boundary forces on plate mantle coupling and plate motion intracontinental deformation coupling

lower cretaceous stratigraphic characteristics and tectonic control of the eastern depression north yellow sea basin north china the lower cretaceous of the eastern depression in the north yellow sea basin is a set of residual strata that can be divided into k1sq1 and k1sq2 sequences there are four lithology lithofacies arc

mesozoic sequence stratigraphy and its response to tectonic evolution of the eastern depression north yellow sea basin north china abstract the north yellow sea basin is a meso cenozoic continental sedimentary basin located between the tan lu fault and the imjingang orogenic belt the mesozoic strata of the eastern depression in the north yellow sea basin consist of lower lower part of the upper jurassic lower cretaceous middle upper part of the upper jurassic lower cretaceous and upper lower cretaceous supersequences comprising six third order sequences as inferred from seismic core and well log data there are five lithology lithofacies architectures summarized in the third order sequences of wells a f d e j g and h and they are the interbedded coarse and fine asymmetric coarse fine fine coarse fine coarse fine coarse and asymmetric fine coarse the basin controlling faults and their assembly configurations during each tectonic stage were inherited and differential in the depression the basin controlling faults were dominated by extension and strike slip movement increased gradually during the early stage of the late jurassic early cretaceous the strike slip faults were dominant at the late stage of the late jurassic early cretaceous right lateral trans extensional faulting created the uplift depression structural framework of the eastern depression there was another trans extension in the depression during the early cretaceous wells a f and d record subsidence at three different structural locations in a trans extensional tectonic setting from the late jurassic to the early cretaceous the fault movement changed from transtension to transpression and the eastern uplift extended from the basin edge into the depression center now the center turned into a structural high the present day central structural belt is a potential area for hydrocarbon accumulation and its extended or down dip area may become prospective areas for oil hydrocarbon traps analogous to the buried hill or igneous type oil reservoirs may be present in the up dip area of the eastern uplift

sequence stratigraphy and environmental background of the late pleistocene and holocene occupation in the southeast primor ye the russian far east abstract the paper presents the results of quaternary palaeoecology and geoarchaeology studies in the zerkal naya basin with new insights about sequenced natural shifts during the prehistoric occupation of this marginally explored ne asian maritime territory the basin is part of the continental drainage system and the main physiographic and biotic corridor for peopling of the transitive coastal interior se primor ye region the final pleistocene and holocene environmental biotic and abiotic proxy records from the upper final palaeolithic to early historical sites document a dynamic climate change with vegetation cover transformations within riverine and mountain valley ecosystems of the russian far east most of the archaeological sites located on the low terraces and bedrock promontories along the main river channel and its tributary streams suggest traditional hunter gathered lifestyles based on seasonal salmon fishing supplemented by pastoral economy tundra forests with larch trees dwarf birch thickets and polypod ferns from the basal stratigraphic units of the late last glacial occupation sites associated with the upper palaeolithic micro blade and bifacial stone tool traditions 14c dated to 19 000 12 000 cal yrs bp indicate rather pronounced conditions and much lower mat comparing today following a final pleistocene cooling event a major climate warming marked the onset of holocene accompanied by a regional humidity increase promoting the formation of a mixed broadleaved coniferous oak dominant taiga and culminating in the mid holocene climatic optimum the appearance of mosaic parklands ca 5 000 4 000 cal yrs bp may be partly attributed to the expansion of the far eastern neolithic cultures practicing forest clearance for pastures and dwellings a progressing landscape opening indicated by the spread of light demanding thickets and birch dominated riverine biotopes with artemisia suggests a further vegetation cover transformation during the late neolithic and the early palaeo metal bronze age periods this trend corroborates the documented climate deterioration between 3 400 and 2 600 cal yrs bp causing a regional aridification with a parkland steppe broadening in the main se primor ye river valleys the late holocene climate development persisted until the little ice age which led to formation of the present settlement ecosystems with mixed oak cedar fir dominated temperate maritime woodlands

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

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

tectonic and sedimentary evolution of the korean peninsula a review and new view abstract this review focuses on the tectonics and sedimentation of major sedimentary basins and orogenic belts late proterozoic neogene in the korean peninsula the korean peninsula is part of the amuria plate and represents an important link between continental blocks of north and south china and the island arcs of japan the basement rocks exposed in the kyonggi and yongnam massifs consist of 2 7 to 1 1 ga high grade gneiss and schist these massifs are separated by the okchon fold belt which comprises metasedimentary rocks and bimodal meta volcanic rocks the stratigraphy of the okchon group is unclear at present the okchon basin was probably initiated as an intraplate rift prior to the late proterozoic the hwanggangri formation clast bearing phyllite most likely represents deposition by subaqueous debris flows in slope environments of an enclosed basin the stratigraphic relationship between the okchon group and the choson supergroup cambro ordovician of the taebaeksan basin is poorly constrained the choson supergroup unconformably overlies the yongnam massif and consists mainly of carbonate sequence that formed mostly in shallow marine and tidal environments reflecting numerous sea level fluctuations the sequence is disconformably overlain by siliciclastic sequence of pyongan supergroup carboniferous triassic which formed most likely in shallow marine deltaic and fluvial environments the imjingang belt is an east trending fold and thrust zone and consists of metasedimentary rocks and volcaniclastics devonian carboniferous underlain unconformably by proterozoic basement rocks late proterozoic amphibolites of oceanic affinity were metamorphosed at about 8 13 kbar and 630 740 c during the late permian to the early triassic the south vergent contraction and top down to the north normal faulting are suggestive of a suture belt between the north china block sino korea craton and the south china block yangtze craton an extension of sulu belt across the yellow sea entire peninsula experienced strong deformation and metamorphism during the suturing event namely songrim orogeny during this orogenic event the kyonggi massif and the okchon basin accreted to the yongnam massif and taebaeksan basin along the south korean tectonic line running northeast southwest a series of northward trending thrust formed along the boundary zone to the east kaktong and kongsuwon thrusts and others piggyback basins locally developed along the thrust faults forming the taedong group the crustal deformation resumed in the early to late jurassic daebo event under contractional setting dextral ductile shearing associated with thrusting and folding continued in the mid southern part of the peninsula it was due to orthogonal northwestward subduction of the izanagi plate under the asian continent the yongnam massif experienced continuous dextral offset along the honam shear zone in the early cretaceous the izanagi plate began to subduct northward and caused formation of strike slip basins in retroarc setting i e kyongsang basin in the southeastern part and a number of small scale basins in the mid southwestern part of the peninsula small scale alluvial fans and fluvial channel networks formed in the basin margin and were transitional to ephemeral lacustrine systems under semiarid to arid conditions extensive intrusion of granitoids occurred from triassic to early tertiary with a gap between 160 and 100 ma representing continental magmatic arc in the tertiary the southeastern margin of the korean peninsula experienced back arc opening pull apart basins formed in the miocene bounded by the yangsan and hupo faults the yonil group sedimentary fill of the pohang basin comprises more than 1 km thick siliciclastic sequence which represents deposition in fan delta systems on the hanging wall of the yangsan fault thick more than 10 km thick sediments in the ulleung basin margin were deformed in the late miocene due to the northward movement of kyushu block quarternary volcanic events in cheju island represent intraplate hot spots

dynamic cause of marginal lithospheric thinning and implications for craton destruction a comparison of the north china superior and yilgarn cratons we present a comparative tectonic analysis of the north china craton ncc which has lost parts of its root with the yilgarn and superior cratons which preserve their roots we compare the geophysical structure and tectonic histories of these cratons to search for reasons why some cratons lose their roots while others retain them based on the comparison and analysis of geological geophysical and geochemical data it is clear that the lithospheric thinning beneath craton margins is a common phenomenon which may be caused by convergence between plates however craton destruction is not always accompanied by lithospheric thinning except for cratons that suffered subduction and collision from multiple sides the western block also known as the ordos block of the ncc yilgarn and superior cratons have not experienced craton destruction the common ground among them is that they are surrounded by weak zones e g mobile belts or orogens that sheltered the cratons from deformation which contribute

a tectonic escape model for the formation of sedimentary basins in the yangzhou block of the lower yangtze region eastern china abstract this paper presents a tectonic escape model for the formation of sedimentary basins in the yangzhou block of the lower yangtze region eastern china nine sedimentary basins are identified in which the pukou formation of the upper cretaceous has been deposited from south to north the nine sedimentary basins are named wangjing qianshan wuwei nanxuan changzhou jurong nanjing quanjiao and subei basins they form a wedge shape fragment the yangzhou block occupying an area of 100 000 km2 in the lower yangtze region the two side boundaries of the yangzhou block are the strike slip tanlu fault and the strike slip quangjiao xiangshui fault on the northwest and the strike slip qingyang nantong fault on the southeast the wide end of the wedge faces the southern yellow sea in the northeast and the narrow end contacts the dabie block in the southwest during the early mesozoic collision between the yangtze block and the north china block resulted in the formation of the qinling dabie orogenic belt and caused the lower yangtze region to become a foreland basin with many strike slip faults during the late mesozoic wide spread extension in eastern china and shortening in qinling dabie shan and in the huaying shan region resulted following establishment of an andean type arc margin to the east of the southern yellow sea area when greater japan collided with asia consequently the wedge shaped yangzhou block escaped tectonically toward the northeast and formed distinctive geological features in nine sedimentary basins during pukou time in the late cretaceous these geological features are reflected in basin spatial distributions basin geometries sedimentary facies sediment thicknesses sedimentary environments and the petrology of fanglomerates and sandstones these basins are part of a large population of arc crestal rifts formed on top of that andean arc the proposed tectonic escape model could be useful in petroleum exploration and mining in the region

prospecting for jurassic slabs seismic tomography a technique for imaging earth s deep interior is becoming ever more refined the latest work tracks the subduction of a lithospheric slab below siberia down to 2 800 km beneath the earth s surface and back to jurassic times

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

arctic ice ocean simulation with optimized model parameters approach and assessment 1 we present an optimized 1992 2008 coupled ice ocean simulation of the arctic ocean a green s function approach adjusts a set of parameters for best model data agreement overall model data differences are reduced by 45 the optimized simulation reproduces the negative trends in ice extent in the satellite records volume and thickness distributions are comparable to those from the ice cloud and land elevation satellite 2003 2008 the upper cold halocline is consistent with observations in the western arctic the freshwater budget of the arctic ocean and volume heat transports of pacific and atlantic waters across major passages are comparable with observation based estimates we note that the optimized parameters depend on the selected atmospheric forcing the use of the 25 year japanese reanalysis results in sea ice albedos that are consistent with field observations simulated pacific water enters the bering strait and flows off the chukchi shelf along four distinct channels this water takes 5 10 years to exit the arctic ocean at the canadian arctic archipelago nares or fram straits atlantic water entering the fram strait flows eastward merges with the st ana trough inflow and splits into two branches at the southwest corner of the makarov basin one branch flows along lomonosov ridge back to fram strait the other enters the western arctic circulates cyclonically below the halocline and exits mainly through the nares and fram straits this work utilizes the record of available observations to obtain an arctic ocean simulation that is in agreement with observations both within and beyond the optimization period and that can be used for tracer and process studies

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

tectonic control on coarse grained foreland basin sequences an example from the cordilleran foreland basin utah newly released reflection seismic and borehole data combined with sedimentological provenance and biostratigraphic data from upper cretaceous paleocene strata in the proximal part of the cordilleran foreland basin system in utah establish the nature of tectonic controls on stratigraphic sequences in the proximal to distal foreland basin during campanian time coarse grained sand and gravel were derived from the internally shortening charleston nebo salient of the sevier thrust belt a rapid regional campanian progradational event in the distal foreland basin 200 km from the thrust belt in 8 m y can be tied directly to active thrust generated growth structures and an influx of quartzose detritus derived from the charleston nebo salient eustatic sea level variation exerted a minimal role in sequence progradation

possible eastward extension of chinese collision belt in south korea the imjingang belt structural petrological and geochronological data from the middle korean peninsula indicate that the qinling dabie sulu collisional belt of east central china crosses the yellow sea and extends into the imjingang belt the yeoncheon complex first identified as the western imjingang belt comprises primarily north dipping metamorphic sequences 1 the northern jingok unit consisting of barrovian type metapelites and 2 the southern samgot unit consisting of calc silicate and amphibolitic rocks south vergent structures with reverse sense shearing are dominant in the jingok unit whereas late normal sense shearing is pervasive in the samgot unit and the deformed granitoid to the south these structural patterns are interpreted to correspond to extensional deformation associated with uplift following compression in a collisional belt pressure temperature p t estimates from the amphibolites suggest a high p amphibolite facies metamorphism 8 13 kbar and 630 790 c possibly evolving from eclogite facies conditions along a clockwise p t path sm nd and rb sr geochronological data suggest that the amphibolites emplaced in late proterozoic time were metamorphosed during permian triassic time

characteristics of the early cretaceous igneous activity in the korean peninsula and tectonic implications abstractthis study presents sensitive high resolution ion microprobe shrimp u pb zircon ages k ar ages and whole rock chemical and isotopic sr nd compositions of the early cretaceous igneous activity in western south korea the volcanics and plutons yield zircon u pb ages of ca 110 ma in the albian of the late early cretaceous k ar biotite and plagioclase ages are slightly younger ca 103 ma the geochemical signatures of the rocks are characterized by negative nb ta and ti anomalies relatively low nd t values between 15 91 and 9 36 and enrichment in light rare earth elements suggesting the effects of subduction related magmatism together with the sr and nd isotopic compositions of the intermediate to acid volcanics geochemical characteristics reflect a lower crustal magma source this albian event over the korean peninsula is related to early jurassic subduction and subsequent lithospheric delamination and or slab rollback after the early cretaceous amalgamation between the north c

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

arctic ice ocean prediction system evaluating sea ice forecasts during xuelong s first trans arctic passage in summer 2017 in an effort to improve the reliability of arctic sea ice predictions an ensemble based arctic ice ocean prediction system arciops has been developed to meet operational demands the system is based on a regional arctic configuration of the massachusetts institute of technology general circulation model a localized error subspace transform ensemble kalman filter is used to assimilate the weekly merged cryosat 2 and soil moisture and ocean salinity sea ice thickness data together with the daily advanced microwave scanning radiometer 2 amsr2 sea ice concentration data the weather forecasts from the global forecast system of the national centers for environmental prediction drive the sea ice ocean coupled model the ensemble mean sea ice forecasts were used to facilitate the chinese national arctic research expedition in summer 2017 the forecasted sea ice concentration is evaluated against amsr2 and special sensor microwave imager sounder sea ice concentration data the forecasted sea ice thickness is compared to the in situ observations and the pan arctic ice ocean modeling and assimilation system these comparisons show the promising potential of arciops for operational arctic sea ice forecasts nevertheless the forecast bias in the beaufort sea calls for a delicate parameter calibration and a better design of the assimilation system

assimilating summer sea ice concentration into a coupled ice ocean model using a lseik filter the decrease in summer sea ice extent in the arctic ocean opens shipping routes and creates potential for many marine operations for these activities accurate predictions of sea ice conditions are required to maintain marine safety in an attempt at arctic sea ice prediction the summer of 2010 is selected to implement an arctic sea ice data assimilation da study the da system is based on a regional arctic configuration of the massachusetts institute of technology general circulation model mitgcm and a local singular evolutive interpolated kalman lseik filter to assimilate special sensor microwave imager sounder ssmis sea ice concentration operational products from the us national snow and ice data center nsidc based on comparisons with both the assimilated nsidc ssmis concentration and concentration data from the ocean and sea ice satellite application facility the forecasted sea ice edge and concentration improve upon simulations without data assimilation by the nature of the assimilation algorithm with multivariate covariance between ice concentration and thickness sea ice thickness fields are also updated and the evaluation with in situ observation shows some improvement compared to the forecast without data assimilation

structural and stratigraphical constraints on the kinematics history of the southern tan lu fault zone during the mesozoic anhui province china abstract the tan lu fault zone tlfz extends in a nne ssw direction for more than 2000 km in eastern china it has been considered either as a major sinistral strike slip fault as a suture zone or as a normal fault we have conducted a structural analysis of the southern segment of this fault zone stlfz in the anhui province the ages triassic to palaeocene of the formations affected by the faults have been re appraised taking into account recent stratigraphical studies to better constraint the ages of the successive stages of the kinematics of the stlfz subsequently the kinematics of the faults is presented in terms of strain stress fields by inversion of the striated fault set data finally the data are discussed in the light of the results obtained by previous workers we propose the following history of the stlfz kinematics during the mesozoic at the time of collision a nne orientated tan lu margin probably connected two margins located north of the dabie and sulu collision belts during the middle late triassic the scb has been obliquely subducted below the ncb along this margin which has acted as a compressional transfer zone between the dabie and sulu continental subduction zones the stlfz has been initiated during the early jurassic and has acted as a sinistral transform fault during the jurassic following which the ncb scb collision stopped a nw trending extension related to metamorphic domes was active during the basal early cretaceous 135 130 ma it has been followed by a nw se compression and a ne sw tension during the middle late early cretaceous 127 to 105 ma possibly 95 ma at that time the tlfz was a sinistral transcurrent fault within the eastern part of the asian continent during the late cretaceous palaeocene the stlfz was a normal fault zone under a wnw ese tension

fabric analysis in rocks of the gadag region southern india implications for time relationship between regional deformation and gold mineralization abstract in this paper the fabric in archaean age massive metabasalts and granite from the gadag region western dharwar craton southern india are identified using the anisotropy of magnetic susceptibility ams the magnetic foliation in the rocks is dominantly nw se striking this is inferred to have developed during regional d1 d2 deformation known to have affected the region which was on account of ne sw shortening the plunge of the magnetic lineation varies from nw to se this doubly plunging orientation is inferred to be a consequence of superimposition of nw se shortening d3 deformation over the earlier structure that is known to have resulted in dome basin geometry in the surrounding metapelitic rocks of the region thus it is concluded that the massive rocks preserve evidence of superposed deformation that affected the region which can be deciphered from the orientation of magnetic fabric data the gadag region comprises lode gold deposit 2500 ma in age and field investigations show that the quartz veins are dilational with dominantly nw se strike orientation the veins are inferred to have formed by dilation under nw se shortening during d3 it is envisaged that the nw se oriented fabric that formed in the metabasalt during d1 d2 channelized fluid flow thus leading to vein emplacement during d3 it is concluded that gold deposition in the veins took place during d3 which is related to the final stages of cratonization of the dharwar craton at 2500 ma

what drove late mesozoic extension of the northern china mongolia tract the northern china mongolia tract exhibited a tectonic transition from contractional to extensional deformation in late mesozoic time late middle to early late jurassic crustal shortening is widely thought to have resulted from collision of an amalgamated north china mongolia block and the siberian plate but widespread late late jurassic early cretaceous extension has not been satisfactorily explained by existing models some prominent features of the extensional tectonics of the northern china mongolia tract are 1 late jurassic voluminous volcanism prior to early cretaceous large magnitude rapid extension 2 overlapping in time of contractional deformation in the yinshan yanshan belt with development of extensionrelated basins in the interior of the northern china mongolia tract and 3 widespread occurrence of alkali granitic plutonism extensional basins and metamorphic core complexes in the early cretaceous a new explanation is advanced in this study for this sequence of events the collision of amalgamated north china mongolia with siberia led to crustal overthickening of the northern china mongolia tract and formation of a high standing plateau subsequent breakoff at depth of the north dipping mongol okhotsk oceanic slab is suggested as the main trigger for late mesozoic lithospheric extension of that tract slab breakoff resulted in mantle lithospheric stretching of the adjacent northern china mongolia tract with subsequent ascent of hot asthenosphere and magmatic underplating at the base of the crust collectively these phenomena triggered gravitational collapse of the previously thickened crust leading to late late jurassic early cretaceous crustal extension and importantly coeval contraction along the southern margin of the plateau in the yinshan yanshan belt the proposed model provides a framework for interpreting the spatial and temporal relationships of distinct processes and reconciling some seemingly contradictory phenomena such as the synchronous extension of northerly terranes during major contraction in the neighboring yanshan yinshan belt d 2003 elsevier b v all rights reserved

spatial temporal relationships of mesozoic volcanic rocks in ne china constraints on tectonic overprinting and transformations between multiple tectonic regimes abstract la icp ms zircon u pb ages and geochemical data are presented for the mesozoic volcanic rocks in northeast china with the aim of determining the tectonic settings of the volcanism and constraining the timing of the overprinting and transformations between the paleo asian ocean mongol okhotsk and circum pacific tectonic regimes the new ages together with other available age data from the literature indicate that mesozoic volcanism in ne china can be subdivided into six episodes late triassic 228 201 ma early middle jurassic 190 173 ma middle late jurassic 166 155 ma early early cretaceous 145 138 ma late early cretaceous 133 106 ma and late cretaceous 97 88 ma the late triassic volcanic rocks occur in the lesser xing an zhangguangcai ranges where the volcanic rocks are bimodal and in the eastern heilongjiang jilin provinces where the volcanics are a type rhyolites implying that they formed in an extensional environment after the final closure of the paleo asian ocean the early middle jurassic 190 173 ma volcanic rocks both in the erguna massif and the eastern heilongjiang jilin provinces belong chemically to the calc alkaline series implying an active continental margin setting the volcanics in the erguna massif are related to the subduction of the mongol okhotsk oceanic plate beneath the massif and those in the eastern jilin heilongjiang provinces are related to the subduction of the paleo pacific plate beneath the eurasian continent the coeval bimodal volcanic rocks in the lesser xing an zhangguangcai ranges were probably formed under an extensional environment similar to a backarc setting of double direction subduction volcanic rocks of middle late jurassic 155 166 ma and early early cretaceous 145 138 ma age only occur in the great xing an range and the northern hebei and western liaoning provinces limited to the west of the songliao basin and they belong chemically to high k calc alkaline series and a type rhyolites respectively combined with the regional unconformity and thrust structures in the northern hebei and western liaoning provinces we conclude that these volcanics formed during a collapse or delamination of a thickened continental crust related to the evolution of the mongol okhotsk suture belt the late early cretaceous volcanic rocks widely distributed in ne china belong chemically to a low to medium k calc alkaline series in the eastern heilongjiang jilin provinces i e the eurasian continental margin and to a bimodal volcanic rock association within both the songliao basin and the great xing an range the volcanics in the eastern heilongjiang jilin provinces formed in an active continental margin setting related to the subduction of the paleo pacific plate beneath the eurasian continent and the bimodal volcanics formed under an extensional environment related either to a backarc setting or to delamination of a thickened crust or both late cretaceous volcanics limited to the eastern heilongjiang jilin provinces and the eastern north china craton ncc consist of calc alkaline rocks in the eastern heilongjiang jilin provinces and alkaline basalts in the eastern ncc suggesting that the former originated during subduction of the paleo pacific plate beneath the eurasian continent whereas the latter formed in an extensional environment similar to a backarc setting taking all this into account we conclude that 1 the transformation from the paleo asian ocean regime to the circum pacific tectonic regime happened during the late triassic to early jurassic 2 the effect of the mongol okhotsk suture belt on ne china was mainly in the early jurassic middle late jurassic and early early cretaceous and 3 the late early cretaceous and late cretaceous volcanics can be attributed to the subduction of the paleo pacific plate beneath the eurasian continent