late cretaceous volcanic rocks and associated granites in gyeongsang basin se korea their chronological ages and tectonic implications for cratonic destruction of the north china craton abstract the gyeongsang basin is the largest exclusively non marine sedimentary basin in korean peninsula located in southeastern part of the peninsula its sedimentary setting magma source tectonic nature and formation age are important to understand the mesozoic tectonic evolution of not only the sino korea craton but also the entire northeast asia the gyeongsang supergroup the basin fill is divided into the sindong hayang and yucheon groups in ascending order the sindong and hayang groups are composed of sandstone shale minor amounts of conglomerate and marl deposited in a non marine environment whereas the yucheon group is characterized by the dominance of volcanic rocks precise isotopic ages and geochemical analyses are scarce for the volcanic elements of this basin restricting our understanding of its geodynamic setting and evolution in this study we present new u pb zircon ages from the volcanic rocks of the yucheon group and associated granites in the gyeongsang basin thirteen volcanic samples yielded ages ranging from 94 4 to 78 4 ma and four granite samples give ages 72 ma these data confirm that a major magmatic event occurred during late cretaceous and the gyeongsang volcano sedimentary complex represents a rock association representing a late cretaceous island arc in comparison with the sambagawa metamorphic belt the jurassic chichibu accretionary complex ac with cretaceous strike slip basin sediments and the cretaceous shimanto melange zone in southwest japan it is likely that above motioned complexes constitute the trace of a continuous subduction related island arc system in se korea extending from sw japan although the peak ages of the magmatic rocks in the eastern part of the north china craton ncc are 130 10 ma indicating an important time of continental lithospheric thinning under the ncc the ages of the gyeongsang magmatic rocks are markedly younger late cretaceous magmatism was very weak in the eastern ncc therefore it is probable that early middle mesozoic lithospheric thinning beneath the eastern ncc is triggered by multiple tectonic factors not only by the subduction of the pacific plate suggested by some previous studies in addition 20 inherited xenocrystic zircons from these volcanic rocks give archean ages ranging from 2 5 to 2 6 ga suggesting the existence of late archean rocks in the yeongnam massif the yeongnam massif is predominated by the latest archean crustal growth at 2 50 ga consistent with the characteristics of the north china craton

phytodetritus entering the benthic boundary layer and aggregated on the sea floor in the abyssal ne pacific macro and microscopic composition abstract phytodetritus which can originate in surface waters following seasonal phytoplankton blooms is considered to be an important food resource for abyssal fauna we analyzed the composition of phytodetritus sampled discretely in situ at an abyssal station in the ne pacific the phytodetritus was collected during two time periods straddling a seasonal maximum in the flux of particulate matter into a sediment trap moored within the benthic boundary layer using the sediment trap record and concurrent time lapse photographs of the sea floor in addition to the results for the composition of sea floor phytodetritus we created a scenario for the origin accumulation and degradation of phytodetritus at the study site it appeared that the sediment trap record did not entirely account for the accumulation and composition of phytodetritus on the sea floor likely due to the undersampling of large sinking aggregates by the sediment trap within each sea floor sampling period two types of aggregated phytodetritus were identified based on macroscopic appearance loosely or strongly cohesive the loosely cohesive phyto detritus collected just before the maximum sinking flux was flocculent and contained large numbers of chain forming diatoms the bulk of the loosely cohesive phytodetritus collected one month later consisted of phaeodarians that appeared to have entrained both older and new diatom floc material the strongly cohesive discrete aggregates collected during both sampling periods appeared to be derived from zooplankton mucous webs although samples within each time period were heterogeneous microscopic composition of phytodetritus in terms of several phytoplankton and protozooplankton components differed significantly between sampling periods these results suggest that phytodetritus can change dramatically over a short time period this may have implications for the potential food resource and feeding behavior of abyssal fauna

constraints on the permeability structure of alluvial aquifers from the poro elastic inversion of multifrequency p wave sonic velocity logs we have explored the possibility of obtaining first order permeability estimates for saturated alluvial sediments based on the poro elastic interpretation of the p wave velocity dispersion inferred from sonic logs modern sonic logging tools designed for environmental and engineering applications allow one for p wave velocity measurements at multiple emitter frequencies over a bandwidth covering 5 to 10 octaves methodological considerations indicate that for saturated unconsolidated sediments in the silt to sand range and typical emitter frequencies ranging from approximately 1 to 30 khz the observable velocity dispersion should be sufficiently pronounced to allow one for reliable first order estimations of the permeability structure the corresponding predictions have been tested on and verified for a borehole penetrating a typical surficial alluvial aquifer in addition to multifrequency sonic logs a comprehensive suite of nuclear and electrical logs an s wave log a litholog and a limited number laboratory measurements of the permeability from retrieved core material were also available this complementary information was found to be essential for parameterizing the poro elastic inversion procedure and for assessing the uncertainty and internal consistency of corresponding permeability estimates our results indicate that the thus obtained permeability estimates are largely consistent with those expected based on the corresponding granulometric characteristics as well as with the available evidence form laboratory measurements these findings are also consistent with evidence from ocean acoustics which indicate that over a frequency range of several orders of magnitude the classical theory of poro elasticity is generally capable of explaining the observed p wave velocity dispersion in medium to fine grained seabed sediments

u pb ages of detrital zircons in lower cretaceous non marine successions of the gyeongsang basin northeast asia implications for sediment provenance abstract the cretaceous gyeongsang basin is the largest non marine mesozoic sedimentary basin of the korean peninsula the lower cretaceous successions of the gyeongsang basin are coevally correlated to those of the cretaceous gunsan basin in the yellow sea which is located far to the west of the gyeongsang basin this study presents u pb ages of detrital zircons to evaluate the sediment provenances of the gyeongsang basin the detrital zircon ages clearly show the different distributions between the northern uiseong area and southern jinju area areas of the gyeongsang basin the detrital zircons of the northern area have an age cluster in the jurassic or triassic whereas the detrital zircons of the southern area show a wide range of ages from early cretaceous to neoarchean in the gunsan basin detrital zircons from a core also yield ages ranging from early cretaceous to neoarchean the age distribution from the gunsan basin is similar to those of the southern gyeongsang basin except for the absence of jurassic detrital zircons the petrographic modal analysis of sandstones in the gyeongsang basin suggests a mixed provenance this study indicates that possible sediment provenances of the gyeongsang basin were shared with those of the gunsan basin we suggest that the sediment provenance of the northern gyeongsang basin was adjacent basement highs whereas sediments to the southern gyeongsang basin were probably derived from relatively distant source areas that possibly were located in the vicinity of the gunsan basin during the early cretaceous ca 113 ma

the radiocarbon age of organic carbon in marine surface sediments abstract long term carbon cycling and climate change are strongly dependent on organic carbon oc burial in marine sediments radiocarbon 14 c has been widely used to constrain the sources sinks and processing of sedimentary oc to elucidate the dominant controls on the radiocarbon content of total organic carbon 14 c toc accumulating in surface sediments we construct a box model that predicts 14 c toc in the sediment mixed layer measured as fraction modern fm our model defines three distinct oc pools degradable semi labile and refractory and assumes that 14 c toc flux to sediments is exclusively derived from surface ocean primary productivity and hence follows a generic surface ocean dissolved inorganic carbon dic bomb curve model predictions are compared to a set of 75 surface sediment samples which span a wide geographic range and reflect diverse water column and depositional conditions and for which sedimentation rate and mixed layer depth are well characterized our model overestimates the fm value for a majority 65 of these sites especially at shallow water depths and for sites characterized by depleted 13 c toc values the model is most sensitive to sedimentation rate and mixed layer depth therefore slight changes to these parameters can lead to a match between modeled and measured fm values at many sites yet in some cases we find that measured fm values cannot be simulated without large and unrealistic changes to sedimentation rate and mixed layer depth these results point to sources of pre aged oc to surface sediments and implicate soil derived terrestrial oc reworked marine oc and or anthropogenic carbon as important components of the organic matter present in surface sediments this approach provides a valuable framework within which to explore controls on sedimentary organic matter composition and carbon burial over a range of spatial and temporal scales

surface nuclear magnetic resonance tomography groundwater is the principal source of freshwater in many regions worldwide expensive drilling borehole logging and hydrological testing are the standard techniques employed in groundwater exploration and management it would be logistically beneficial and cost effective to have surface based nonintrusive methods to locate and quantify groundwater occurrences and to estimate other key hydrological parameters surface nuclear magnetic resonance snmr techniques which are based on the spin magnetic moment precession of protons in the hydrogen atoms of water offer the possibility of achieving these goals current snmr practices are based on 1d inversion strategies these simple strategies impede applications of snmr techniques in hydrologically complex areas to address this issue we introduce a very fast 2d snmr tomographic inversion scheme and apply it to four series of measurements simulated for a perched water lens model whereas the new 2d scheme correctly reconstructs all important characteristics of the original model 1d strategies produce highly inaccurate misleading results

deposition of bomb 14c in continental slope sediments of the mid atlantic bight assessing organic matter sources and burial rates abstract as part of the ocean margins program omp organic carbon 14c measurements have been made on benthic fauna and kasten core sediments from the north carolina continental slope these analyses are used to evaluate the nature and burial flux of organic matter in the omp study area off cape hatteras despite the fact that surface sediment 14c contents ranged from 41 to 215 per mil the benthic fauna primarily polychaetes all contained significant amounts of bomb 14c body tissue 14c contents ranging from 20 to 82 per mil bomb 14c clearly is reaching the seabed on the north carolina slope and the labile planktonic material carrying this signal is a primary source of nutrition to the benthic ecosystem the enrichment of 14c in benthic faunal tissue relative to the 14c content of bulk surface sediment organic matter a difference of 150 per mil is attributed to a combination of particle selection and selective digestive processes organic carbon burial rates from 12 stations on the north carolina slope varied from 0 02 to 1 7 mol of c m 2 yr 1 with a mean value of 0 7 mol of c m 2 yr 1 the accumulation of organic matter on the upper slope accounts for

a synthesis of cretaceous palaeomagnetic data from south korea tectonic implications in east asia summary tectonic provinces in south korea include the precambrian gyeonggi massif palaeozoic okcheon belt precambrian yeongnam massif and cretaceous gyeongsang basin from northwest to southeast the cretaceous strata mainly occur in the gyeongsang basin as well as in several small basins along the boundaries of the okcheon belt and on the gyeonggi massif this paper reviews and analyses previously published palaeomagnetic data from the cretaceous successions in south korea a total of 23 cretaceous palaeomagnetic poles from 18 studies satisfy more than four standard reliability criteria the palaeomagnetic pole positions from the gyeongsang basin and from small basins in the gyeonggi massif and the okcheon belt are consistent with one another indicating that the korean peninsula has been a single terrane since the cretaceous however based on the comparison of the palaeomagnetic pole positions and the palaeolatitudes of blocks in the gyeongsang basin it was observed that the gyeongsang basin had experienced tectonic adjustments during the cretaceous period within the gyeongsang basin the geographically northern area yeongyang block was rotated counterclockwise by 16 3 4 6 with respect to the southern area milyang and uiseong blocks based on the comparison of palaeomagnetic pole positions between the two areas this palaeomagnetic result and some geological features in the gyeongsang basin collectively indicate that the yeongyang block underwent counterclockwise rotations accompanied by northwestward protrusion into the yeongnam massif during the late cretaceous these relative tectonic movements within the gyeongsang basin were probably due to the northwestward subduction of the proto pacific oceanic plate during the late cretaceous the gradual eastward displacement of the korea s cretaceous palaeopoles from the eurasian pole increases with stratigraphic age indicating that the korean peninsula underwent progressive clockwise rotations with respect to eurasia during the cretaceous period the clockwise rotation of southwest japan with respect to eurasia is ascribed to the miocene opening of the east sea and has no connection with the cretaceous clockwise rotations of the korean peninsula indicating that the korean peninsula and southwest japan may have been independent terranes during the cretaceous period

tectonic evolution of the cretaceous gyeongsang back arc basin se korea transition from sinistral transtension to strike slip kinematics abstract the gyeongsang basin the largest cretaceous nonmarine sedimentary basin in korea formed as a continental back arc basin related to nnw directed subduction of the proto pacific plate underneath the eurasia plate the basin can be divided into an earlier formed western back arc depression and a later formed eastern volcanic arc platform we investigated the basin evolution and the associated tectonic settings largely based on an analysis of structures individuated in the field in the back arc region from 127 ma the basin initiated as a nne trending narrow depression bordered by nne striking sinistral faults and then progressively expanded under a transtensional kinematics induced by progressive trench roll back sinistral shearing of inherited nne striking structures played an important role in basin subsidence and secondary wnw to nw striking transverse faults acted as normal faults the nne striking principal displacement zone in the west of the basin runs along the western marginal area of the jinju and daegu domains and passes through the uiseong domain from south to north but most of this zone is now preserved as deep structures volcanic activity starting at ca 115 ma was characterized mainly by episodic basaltic eruptions occurring contemporaneously with back arc deposition of a sedimentary sequence after ca 90 ma a transtensional kinematics changed to a strike slip one and the basin expansion and sedimentation in the back arc region terminated during the strike slip event rhyolitic dacitic volcanism increased in intensity as a large ne trending volcanic arc developed close to subduction zone and its loading caused the stratal flexure in the back arc region and the orientations of the shortening and stretching axes remained nw se and ne sw respectively additionally continuing sinistral shear generated local depressions along the faults located in the west of the back arc region and within the volcanic arc

origin of the cenozoic mesozoic magnetite series and ilmenite series granitoids in east asia abstract among the phanerozoic granitoids of east asia the most prevailing cenozoic mesozoic rocks are reviewed with respect to gabbro granite ratio bulk composition of granitoids redox state and o and sr isotopic ratios quaternary volcanic rocks ranging from basalt to rhyolite but typically felsic andesite in terms of bulk composition in island arcs are oxidized type possibly due to oxidants from subducting oceanic crust into the source regions miocene plutonic rocks in the back arc of japan could be a root zone for such volcanism but are more felsic in composition cenozoic mesozoic plutonic zones are classified by 1 the redox state magnetite ilmenite series and 2 average bulk composition granodiorite granite the granodioritic magnetite series occur with fairly abundant gabbro and diorite in the back arc of island arcs greentuff belt and intercontinental rapture zones yangtze block these rocks are mostly juvenile in terms of the 87sr 86sri and 18o values the granitic magnetite series with some gabbroids occur in rapture zones along the continental coast gyeongsang basin fujian coast and the back arc of island arc sanin belt they were generated mostly in felsic continental crust with the help of heat and magmas from upper mantle the generated granitic magmas had little interaction with c and s bearing reducing materials due probably to extensional tectonic settings the 18o value gives narrow ranges but the 87sr 86sri ratio varies greatly depending upon the age and composition of the continental crust granitic ilmenite series are characterized by high 18o values implying much contribution of sediments the 87sr 86sri ratios are low in island arcs but very high in continental interior settings amount of mafic magmas from the upper mantle seems a key to control the composition of granitoid series in island arc settings while original composition of the protolith may be the key to control granitoid composition in continental interiors

tectonic and sedimentary evolution of a cretaceous continental arc backarc system in the korean peninsula new view abstract this paper focuses on the tectonic and sedimentary evolution of the cretaceous volcanic rocks and nonmarine successions in the southeastern part of the korean peninsula which constitute an ancient continental arc system the arc system gyeongsang arc system comprising an arc platform gyeongsang volcanic arc and a backarc basin gyeongsang backarc basin was a southwestward extension of the japanese arc formed by oblique northward subduction of the proto pacific izanagi plate under the asian continent the backarc basin was initiated in the southeastern part of the korean peninsula in the early cretaceous as a narrow ns trending trough the basin was bounded by a major fault in the northern part of the basin from which sediments largely emanated sediments were deposited in streamflow dominated alluvial fans adjacent to the fault bounded basin margin in the north and low gradient fluvial systems of braided channels that extended southward and southeastward for tens of kilometers sediments were also derived from the western highland margin draining precambrian to jurassic basement rocks the initially narrow trough progressively expanded toward the east resulting in eastward migration of depocenters that eventually generated a broad fluvio lacustrine plain fringing the volcanic arc platform the arc platform played an important role for the derivation of volcanogenic materials and accreted sediments into the backarc basin via extensive fluvial network pyroclastic density currents and landslides which originated from the arc platform also entered the basin in addition extrusion of basaltic volcanic rocks was continual within the basin during basin expansion the resultant succession of mixed sedimentary and volcanogenic rocks is generally indicative of a temporal increase in volcanic activity in the arc platform and in subsidence rate of the basin in the late cretaceous andesitic to rhyolitic volcanism became climactic in the arc platform producing a number of calderas or volcanotectonic depressions volcaniclastic aprons fringing the arc platform encroached upon the basin fill intraarc basins produced by sinistral shearing of the arc platform received sediments from active volcanoes and footwalls of contemporaneous faults forming small scale streamflow dominated alluvial fans and floodplains with later development of a deep lake overall the gyeongsang arc system formed under an extensional or transtensional sinistral strike slip stress regime suggesting that the subducting and the overriding plates were not strongly coupled both the volcanic arc and the backarc basin ceased to develop as volcanic activities shifted progressively eastward in the paleogene accompanied with rollback of the subduction of the izanagi plate

the first record of redfieldiiform fish actinopterygii from the upper triassic of korea implications for paleobiology and paleobiogeography of redfieldiiformes abstract a new genus and species of redfieldiiform fish hiascoactinus boryeongensis gen et sp nov is described based on a nearly complete specimen from the upper triassic amisan formation of south korea hiascoactinus is distinguished from other redfieldiiforms by having a barely ornamented dermal skull surface except for the snout region two heteromorphic suborbitals arranged vertically behind the postorbital a pistol shaped suprascapular and dorsal and anal fins with divided fin membranes between rays the morphological features of the snout region and dorsal and anal fins of hiascoactinus provide important clues to understand its feeding and swimming behavior all previously proposed asian redfieldiiform fossils are inaccurately classified and consequently hiascoactinus is regarded as the only valid redfieldiiform taxon in asia hiascoactinus is assigned to the basal group of redfieldiiforms primarily based on the presence of an antopercle the basal phylogenetic position of hiascoactinus indicates that basal redfieldiiforms dispersed from the southern gondwanaland to the easternmost laurasia through the terrestrial water system and these two landmasses were connected during the late triassic

palaeomagnetic study of eastern tibet deformation of the three rivers region summary a palaeomagnetic study was undertaken for cretaceous red beds and granitic rocks of three geological provinces the lhasa the qiangtang and the sichuan along a road between chengdu and lhasa in eastern tibet in an attempt to determine aspects of deformation of se asia high temperature characteristic directions were isolated from 20 sites the tilt corrected data from the qiangtang terrane at markam 29 7 n 98 6 e exhibit largely clockwise deflected declinations with steep inclinations d 48 2 i 49 0 a95 8 8 whereas the lhasa terrane at basu 3o l0n 96 9 e and the sichuan province at ya an 3o l0n 103 0 e have northerly directions with shallow inclinations d 3 9 i 23 4 a95 19 2 and d 2 lo z 30 7 ag5 11 3 respectively the palaeomagnetic data indicate that the qiangtang terrane was subjected to clockwise rotation through 50 with respect to the neighbouring provinces of the lhasa and sichuan since the cretaceous tectonic deformation occurred later than the cretaceous in the eastern part of the qiangtang terrane and formed the arcuate shape of the orogenic belt in the three rivers region

sedimentation and evolution of the cretaceous gyeongsang basin southeastern korea the sedimentation and evolutionary history of the gyeongsang basin and their implications for plate tectonics are reviewed based mainly on sedimentological work on the gyeongsang strata and the regional geology of the japanese islands during the cretaceous e asia was characterized by an andean type continental margin formed by subduction of the kula plate and kula pacific ridge the marginal zone was subjected to precursory extensional tectonism of the magmatic arc so that fault bounded continental depressions developed including the proto gyeongsang basin the gyeongsang strata about 9 000 m thick consist in ascending order of the sindong the hayang with volcanic9 stics and volcanic yuchon groups during the sindong period extensional tectonism prevailed a the proto gyeongsang basin was a graben occupied by alluvial fan fluvial plain and lake environments from the margins to the centre of the basin streams flowed from the upthrown lip areas to the centre alluvial fans expanded periodically with rejuvenation of fault activity while the fluvial plaid lake boundary shifted in response to climatic changes during the hayang period the faults were no longer active and consequently the basin extended beyond them probably by back faulting the water level of the lake s at the basin centre fluctuated with changes of the evaporation precipitation ratio during parts of the period the marginal fluvial plain was drained by ephemeral streams which disappeared before reaching the lake s depositing fluvial sequences lacking channel sandstones localized volcanism formed volcanic terrains and supplied pyroclastics this volcanism was climactic during the yuchon period and terminated the sedimentation granitic plutons intruded all the gyeongsang strata at about the end of the cretaceous

paleomagnetic constraints on the geodynamic history of the major blocks of china from the permian to the present paleomagnetic study of china and its environs has been the center of a major international effort for the last 10 years in this paper we critically review all available paleomagnetic poles of upper permian to tertiary age from the main blocks of china with the goal of placing constraints on models of the formation and the subsequent deformation of the region after selecting reliable poles by applying objective criteria we divide our analysis into first order motions of blocks and second order deformation within blocks for first order analysis apparent polar wander paths are constructed for the major blocks we discuss the compatibilities and contradictions between the geological and paleomagnetic records a sequence of paleogeographic configurations taking into account geological constraints but remaining within paleomagnetic uncertainties is presented in general the major blocks were probably in contact throughout the permian and triassic but the jurassic was the key age during which most of the movement toward china s present configuration took place our reconstructions include certain details which are suggested by the paleomagnetic record but whose geological signatures seem to have been hidden by subsequent events during the cretaceous chinese poles agree with poles from other continents transferred onto eurasia at the second order we observe that for almost each period with sufficient data the paleomagnetic poles are streaked along a small circle centered on the sampling region indicating that much of china has been affected by small 20 differential rotations this we interpret as deformation caused in part by the extrusion of the chinese blocks away from the indian collision the complete annotated list of poles is given as an appendix

contrasting behavior between dispersive seismic velocity and attenuation advantages in subsoil characterization a careful look into the pertinent models of poroelasticity reveals that in water saturated sediments or soils the seismic p and s wave velocity dispersion and attenuation in the low field seismic frequency band 20 200 hz have a contrasting behavior in the porosity permeability domain taking advantage of this nearly orthogonal behavior a new approach has been proposed which leads to unique estimates of both porosity and permeability simultaneously through realistic numerical tests the effect of maximum frequency content in data and the integration of p and s waves on the accuracy and robustness of the estimates are demonstrated

source age dynamics of estuarine particulate organic matter using fatty acid δ13c and δ14c composition this study used a multiproxy approach to elucidate the source and age composition of estuarine particulate organic matter pom using bulk stable isotopes 13cpoc fatty acid fa biomarkers and compound specific isotopic analyses in surface waters along the delaware river and bay delaware estuary hereafter 13c values of fa 13cfa ranged more widely 30 9 to 21 8 than 13cpoc 27 5 to 23 5 providing greater insight about pom sources along the estuary 13c values of c16 0 phospholipid fa primarily aquatic sources increased along the salinity gradient 29 8 to 23 4 while 13cfa values of long chain neutral fatty acid terrestrial sources decreased 28 6 to 30 9 13cfa values for c18 s fa indicated the importance of marsh derived organic matter within delaware estuary compound specific radiocarbon analysis showed the heterogeneous age structure of fa associated with pom fapom 14c ages of fa ranged from modern postbomb to 1790 bp aged fa 120 bp to 1700 bp derived primarily from the watershed whereas modern fa were produced within delaware estuary 14c ages of short chain fa aquatic sources reflected differences in the age of dissolved inorganic carbon along the estuary and had older 14c ages at the river end member 14c ages of fa from terrigenous sources were older than water and sediment residence times indicating this source derived from the watershed this study is the first to document the complex age distribution of fapom along the estuarine salinity gradient and shows that inorganic carbon sources watershed inputs and autochthonous production contribute to variation in the ages of pom

a laboratory study of the dependence of elastic wave velocities on pore scale fluid distribution laboratory data have been collected during a continuous imbibition drainage experiment that show a clear dependence of elastic wave velocities on the details of the pore scale distribution of water and air in a sandstone compressional wave velocity vp was measured at a frequency of 1 mhz shear wave velocity vs was measured at a frequency of 600 khz during the experiment vp showed little variation with the level of water saturation sw during increasing sw through imbibition until sw 0 80 at which point vp increased dramatically when sw was decreased pronounced saturation induced hysteresis was observed in the region 03 0 4 as a simple model we consider the imbibition process as producing a partially saturated state in all pores i e all pores contain both air and water the drainage process in contrast favors the existence of either air filled or water filled pores as elastic wave velocities are very sensitive to the saturation state in the smaller crack like pores these variations in fluid distribution cause related variations in velocities

coupling of near bottom pelagic and benthic processes at abyssal depths in the eastern north pacific ocean a time series site was established in the eastern north pacific ocean to study the coupling between near bottom pelagic and benthic processes at abyssal depths in an area with well documented seasonality in surface water productivity particulate total mass ptm particulate organic c poc particulate total n ptn and particulate calcium carbonate p caco fluxes were measured from sediment trap collections at 600 and 50 m above bottom from february 1990 to october 199 1 606 d the sea floor at 4 100 m was concurrently monitored with a time lapse camera over a 386 d period from july 1990 to july 199 1 during this study in situ measurements of sediment community oxygen consumption scoc were made and surface sediment samples collected seasonally with a free vehicle grab respirometer ptm poc ptn and p cac0 fluxes exhibited a strong seasonal signal with episodic peaks from spring through fall and lows in winter scoc increased sharply between winter and summer coinciding with spring peaks in particulate fluxes detrital aggregates appeared on the sea floor in pulses over a 6 month period from july to december 1990 coinciding with periods when particulate fluxes were elevated but delayed 1 5 months after the initial peaks in particulate flux mobile epibenthic megafauna monitored with time lapse photography consisted primarily of holothuroids and echinoids and were twice as active when detrital aggregates were observed on the sea floor as during the rest of the year our results show a temporal relationship between the flux of particulate matter entering the benthic boundary layer the arrival and residence of detritus on the sea floor and the activity of the sediment community and mobile epibenthic megafauna

polyphase tectono magmatic episodes as revealed by shrimp u pb geochronology and microanalysis of zircon and titanite from the central okcheon belt korea abstract the south central okcheon belt of the southern korean peninsula experienced polyphase granitic magmatism and deformation during the mesozoic this study presents integrated results of ion microprobe u pb geochronology and microtextural and microchemical analyses of zircon and titanite from pre tectonic baegnok and cheongsan and post tectonic boeun and sokrisan plutons with respect to the cheongsan shear zone the baegnok granodiorite sample yielded coherent zircon and titanite 206pb 238u ages of 225 6 1 8 and 223 9 4 4 ma indicating a rapid early cooling of the pluton the cheongsan k feldspar megacryst bearing biotite granite sample yielded a coeval zircon 206pb 238u age of 224 7 1 8 ma on the other hand the titanite grains from this rock are categorized into two age populations corresponding to the late triassic 214 3 7 9 ma and the late cretaceous 96 2 8 2 ma growth the older population is clearly of igneous origin considering partly preserved oscillatory zoning in back scattered electron images therefore the age indicates contrasting early cooling paths of the two pre tectonic plutons the younger population is interpreted to be the product of superimposed metasomatic reactions involving plagioclase ilmenite rutile epidote and calcite the two populations show different patterns in their atomic al fe ratios zircons from the boeun and sokrisan plutons yielded 206pb 238u ages of 172 2 2 1 and 94 2 2 1 ma respectively with the latter being indistinguishable from the younger titanite age of the cheongsan pluton the shrimp u pb age of syn deformational fine grained titanite grains lying on sigmoidal foliations in a mylonite from the cheongsan shear zone has a large error 165 47 ma due to their low u pb ratios possibly affected by post tectonic magmatic activities this study highlights the importance of detailed microanalysis prior to the isotopic dating of samples that have experienced complex tectono magmatic episodes

the lower cretaceous reference pole for north china and its tectonic implications summary a palaeomagnetic study of lower cretaceous continental sediments from the south southwestern part of the ordos basin north china block ncb has been carried out stepwise thermal demagnetization was used to isolate magnetic components the low temperature component is generally removed between 200 c and 350 c and corresponds to the earth s present field direction a hightemperature component of magnetization with two polarities was defined from 10 sites with d 16 4 i 50 5 k 50 8 ugs 6 8 the corresponding pole position is located at 75 8 n 208 7 e d 6 lo d 9 1 this lower cretaceous pole compares well with the hairpin loop of the eurasian synthetic apw path besse courtillot 1991 that is inferred from the north american eurasian african and indian plates the available late mesozoic palaeomagnetic data from the ncb and adjacent south china block scb are reviewed comparison of these data suggests important intraplate deformation the area to the east of the tancheng lujiang fault may have undergone local clockwise post cretaceous rotations of 10 29 relative to the stable western craton of the ncb the data also indicate that no palaeomagnetically significant eastward movement of the scb with respect to the ncb and eurasia occurred after the cretaceous

sedimentary rocks as sources of ancient organic carbon to the ocean an investigation through δ14c and δ13c signatures of organic compound classes chemical and isotopic variability of particulate organic carbon poc was examined in samples from the santa clara river watershed and adjacent shelf to investigate the processing of fossil poc derived from bedrock the santa clara is a small coastal river that drains mountainous terrain in southern california united states organic carbon in shale river suspended sediment and coastal marine sediment was separated into three operationally defined organic compound classes total extractable lipids acid hydrolyzable material and the nonhydrolyzable residue in all samples the nonhydrolyzable fraction was dominant 50 of poc while lipids and acid hydrolyzable moieties were relatively minor 22 and 13 respectively the 14c and 13c signatures of the isolated fractions varied dramatically not only across different sample types but also for a given sample at the shale exposure low 14c values 30 the nonhydrolyzable fraction displayed intermediate 14c values 190 that increased steadily downstream with decreasing 13c values 22 2 to 25 0 possibly from mixing of shale and surface soil poc our results indicate that most of the fossil poc discharged by the santa clara is composed of non acid hydrolyzable material but its elusive molecular structure and marine like 13c signature may render its detection in the ocean difficult in contrast fossil lipids may be more amenable to detection if their resistant components e g asphaltic material are unique to crustal sources

fast inversion of formation permeability from stoneley wave logs using a simplified biot rosenbaum model this paper describes a fast algorithm for estimating formation permeability from stoneley wave logs the procedure uses a simplified biot rosenbaum model formulation the input to the inversion is the stoneley wave spectral amplitudes at each receiver position the bore hole fluid properties velocity and density the borehole caliper log the formation density and porosity from log data and the compressional and shear velocities for the interval of interest the model uses the borehole caliper and elastic properties to compute the stoneley wave excitation that is predicted amplitude without permeability effects as a function of frequency and the porosity and permeability to compute the fluid flow amplitude reduction this method also uses a reference depth of known permeability and compares amplitude variations at other depths relative to the reference depth the permeability value obtained from the inversion represents the best fit over all receivers and all relevant frequencies a processing example is shown to demonstrate the ability of this technique to extract formation permeability from stoneley wave logs

transport and depositional process of soil organic matter during wet and dry storms on the tet inner shelf nw mediterranean article i nfo river floods and storm waves are major processes for the dispersal and deposition of terrestrial organic matter om in river dominated coastal areas a wet storm is connected to a flood with a high river discharge while a dry storm is not associated with a flood to better understand the sedimentation dynamics of terrestrial om especially soil om at the land ocean interface during wet and dry storms we studied sediment trap and core material collected on the tet inner shelf nw mediterranean using multiple organic proxies in combination with hydrodynamic parameters the proportion of soil om to the total om in the trap material calculated based on the bit branched and isoprenoid tetraether index was higher during both wet 40 and dry 30 storms than during non storm periods 10 however only surface sediments 1 cm thick layers recovered after december wet and moderate storms in 2003 showed enhanced soil om percentages compared to the deeper sediments deposited during the last century given that the wet storm eroded 4 cm of seabed at the study site flood induced fresh soil om was not deposited on the tet inner shelf during the wet storm however the following moderate storm caused resuspension of flood associated soil om which was previously trapped nearshore accordingly soil om was transported to the tet inner shelf and stored there until the dry storm occurred

clockwise rotations recorded in early cretaceous rocks of south korea implications for tectonic affinity between the korean peninsula and north china recent interest has focused on whether south korea may have undergone variable tectonic rotations since the cretaceous in an effort to contribute to the answer to this question we have completed a palaeomagnetic reconnaissance study of early cretaceous sedimentary and igneous rocks from the kyongsang basin in southeast korea stepwise thermal demagnetization isolated well defined characteristic magnetization in all samples the palaeomagnetic directions reveal patterns of increasing amounts of clockwise cw rotation with increasing age for aptian rock units palaeomagnetic declinations indicate clockwise vertical axis rotations of r 34 3 6 9 for the early aptian rock unit r 24 9 10 6 for the middle aptian and r 0 9 11 8 for the late aptian relative to eastern asia the new cretaceous palaeomagnetic data from this study are consistent with the hypothesis that korea and other major parts of eastern asia occupied the same relative positions in terms of palaeolatitudes in the cretaceous an analysis of and comparison with previously reported palaeomagnetic data corroborates this hypothesis and suggests that much of korea may have been connected to the north china block since the early palaeozoic a plausible cause of the rotation is the westward subduction of the kula plate underneath the asian continent which is inferred to have occurred during the cretaceous according to several geological and tectonic analyses

timing of the north south china collision from new middle to late mesozoic paleomagnetic data from the north china block we collected paleomagnetic samples from 43 sites of middle and upper jurassic and cretaceous rocks along a 250 km wide east west trending belt located north of the suture between the north and south china blocks in each case laboratory treatment isolates dual polarity antipodal magnetizations that are demonstrably pre folding the paleomagnetic poles show very good coherence with coeval poles from other localities from the north china block ncb suggesting the apparent polar wander path apwp from the ncb is not distorted by post middle jurassic local vertical axis block rotations a comparison of the ncb apwp with that from the south china block suggests that collision continued after the early jurassic and ended no later than the late jurassic a cusp in the ncb apwp coincides with a marked angular unconformity that separates middle jurassic from upper jurassic and younger sediments together these observations indicate that the scissor like collision and associated deformation ceased at the middle to late jurassic boundary 159 ma the time of rapid 1 ma relative angular velocity between the two plates 225 to 190 ma coincides with a peak in u pb and ar ar dates obtained from metamorphic rocks in the suture the combined late jurassic and cretaceous paleomagnetic data from both blocks suggest that the united china plate traveled 2000 km north relative to eurasia during the late jurassic before docking in the cretaceous this younger collision event is also marked by a cusp on the cretaceous part of the eurasian apwp

earth s surface responses during geodynamic evolution numerical insight from the southern east china sea continental shelf basin west pacific abstract the interaction between the earth s surface and deep geodynamic processes has a great influence on sedimentary patterns and characteristics of sedimentary systems especially in the continental margin such as the southern part of the east china sea continental shelf basin ecscsb however the exact processes and dynamics are poorly understood the numerical tool badlands was adopted to simulate the geological evolution of the southern ecscsb during the mesozoic transitional regime of the west pacific continental margin between 200 and 100 ma the numerical model involving four dimensional 4d sequence stratigraphy was validated by comparing with the tectono morphology sedimentary environments and sediment distribution according to our findings the transition was mainly controlled by three structural stages the first transitional stage of the southern ecscsb was mainly controlled by lithospheric scale tectonic evolution in the second stage the dynamic topography contributed to slow regional uplift while the last stage showed mantle induced dynamic subsidence the model results on 4d geomorphic characteristics sediment distribution of basin evolution and deep dynamic topography provided a quantitative image for geological evolution of the west pacific continental margin in the mesozoic

paleomagnetotectonics of east asia in the proto tethys ocean abstract seven paleomagnetic poles are obtained from early ordovician late carboniferous permo triassic jurassic early cretaceous miocene and quaternary rocks in korea these poles define the apparent polar wander path for the southern part of korean peninsula the comparisons of apwps from the north china block yangtze block and korea reveals that the east asia is comprised of two blocks the north sino korean and south sino korean which were parts of gondwana during the paleozoic time the north sino korean block was migrated northwards in late permian and accreted with laurasia in triassic time during middle late triassic time the north sino korean block collided with the south sino korean and subsequently divided into two the western part of the north sino korean block suffered counter clockwise rotation while the eastern part rotated clockwise until jurassic time complicated shear senses of the early mesozoic fault systems in east asia are well matched by this scenario

evidence for significant clockwise rotations of the korean peninsula during cretaceous abstract in an effort to evaluate the cretaceous magnetostratigraphy for the korean peninsula and to establish the tectonic coherence of its various elements we collected paleomagnetic data from 121 samples from 20 sites within the chilgok formation 108 3 109 9 ma in the gyeongsang basin together with previously published data we evaluate the results from a total of 163 sites in the basin we combine our age model with results from recent stratigraphic paleomagnetic and radiometric geochemical studies in this study we found that two distinct declination shifts decrease with younging direction indicating two clockwise rotational events of the korean peninsula with respect to the eurasia continent the earlier event took place during 130 100 ma phase i newly termed goguryeo disturbance and a later one during 80 50 ma phase iii belonging to bulguksa orogeny the mean rotation rate in the interval from 115 2 to 103 8 ma phase i is about 0 74 ma while the rate from 90 9 to 79 8 ma phase ii is 0 19 ma based on paleolatitude change during phase i we infer that the korean peninsula eastern part of the sino korea block migrated southward about 300 km after the complete amalgamation of the sino korea block into the eurasian continent resulting in n s compression within the korean peninsula and manchuria large scale strike slip faults e g tan lu fault okcheon boundary fault were probably rejuvenated in the sino korea block during phase i

compound specific radiocarbon dating of the varved holocene sedimentary record of saanich inlet canada 1 the radiocarbon contents of various biomarkers extracted from the varve counted sediments of saanich inlet canada were determined to assess their applicability for dating purposes calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve count ages the same conclusion could be drawn for a more general archaeal biomarker gdgt 0 although this biomarker proved to be less reliable due to its less specific origin the results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon dic as their carbon source the average reservoir age offset r of 430 years determined using the crenarchaeol radiocarbon ages varied by 110 years this may be caused by natural variations in ocean atmosphere mixing or upwelling at the ne pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages

origin of remineralized organic matter in sediments from the rhone river prodelta nw mediterranean traced by δ14c and δ13c signatures of pore water dic rivers are important links between continents and oceans by transporting terrestrial particulate organic matter pom to continental shelf regions through estuaries or deltas and the mediterranean basin is a good example of this strong linkage in the vicinity of river mouths an important fraction of the terrestrial pom settles on the seafloor sometimes mixed with marine pom where both can be recycled or buried in the rhone river prodelta previous studies have investigated the origin of the pom in the sediments they pointed at the large fraction of terrestrial pom in the sediments and the transition to older pom fractions in offshore direction these studies suggested that terrestrial pom could be an important food source for benthic heterotrophic organisms in this area in this study the 13c and 14c signatures of dissolved inorganic carbon dic and dic nh4 ratio in sediment pore water have been measured along a nearshore offshore transect the data were compared with available datasets concerning isotopic signature and c n of the pom in bottom waters and suspended particles from the rhone river and sediments from its delta in order to determine which fraction of the pom is actually mineralized our results show that a fraction of terrestrial pom corresponding to riverine plankton is preferentially mineralized indeed 13c depleted riverine pom 13c 25 to 27 which is enriched with 14c 14c 400 to 500 and shows a c n 8 gets mostly mineralized this isotopic signature differs from that of sediment pom which highlights the selective mineralization already observed in other river deltas in the mediterranean context with large human influence in river watersheds such as dam building our results highlight the importance of riverine primary production versus eroded organic matter in coastal carbon budgets

bacterial incorporation of relict carbon in the hydrothermal environment of guaymas basin abstract radiocarbon analyses of bulk carbon and individual organic compounds are presented for the hydrothermal environment of the rebecca s roost vent in the southern trough of the guaymas basin hydrothermal field the 14 c values of co 2 and ch 4 in the hottest hydrothermal fluids 317 c are nearly radiocarbon dead 944 and 923 respectively in contrast the 14 c values of sediments and individual fatty acids 418 to 227 obtained from a bacterial mat located south of the vent site are similar to values previously reported for hydrothermal petroleum in this environment and are more depleted in 14 c than overlying waters hydrothermal fluids moving through the sediments appear to supply 14 c of intermediate age to the bacteria this carbon may take the form of or may be supplied by processes similar to the generation of hydrothermal petroleum although the bacterial mat visibly was dominated by beggiatoa spp such mats are known to include numerous other species individual compound data show that preaged carbon is being consumed by the integrated bacterial assemblage values of 13 c and 14 c indicate that petroleum derived carbon is incorporated directly into fresh bacterial biomass subsequently some of this newly synthesized material also is consumed by heterotrophs as eukaryotic sterols from the same sample also have 14 c depleted values 14 c 136 to 110 therefore the entire system may operate as a complex consortium to transform relict carbon back into biomass bacterial consumption of relict carbon occurs despite the ample supply of fresh carbon delivered from the productive overlying water column

paleomagnetism of tertiary rocks on the korean peninsula tectonic implications for the opening of the east sea sea of japan abstract two different distributions of declinations with dual polarities are found in the tertiary rocks of the yeonil basin and yangnam basin along the yangsan fault in the southeastern part of the korean peninsula these are northward declinations in the middle miocene yeonil group and strong eastward declinations in the early miocene yangbuk group and in the eocene volcanic rocks this is interpreted by invoking 1 the yangsan fault as a dextral wrench fault system by spreading in the uleung basin of the east sea sea of japan and 2 a clockwise vertical rotation caused by the movement of the fault at around 17 3 ma just prior to the sedimentation of the yeonil group the timing of the deflection found in korea is distinguished from that in southeastern and northwestern japan at around 15 ma two stages of spreading are thus constrained in the east sea area parallel at 23 15 ma and pivotal at around 15 ma crustal thinning also occurred a reliable pole position 84 9 n 292 6 e d p d m 3 3 4 8 for the miocene about 15 ma in korea is obtained from the yeonil group

radiocarbon studies of organic compound classes in plankton and sediment of the northeastern pacific ocean radiocarbon 14c and stable carbon isotopes 13c were measured in total hydrolyzable amino acid thaa total carbohydrate tcho total lipid and acid insoluble organic fractions that had been separated from phytoplankton zooplankton sediment floc and sediment samples from an abyssal site in the northeastern pacific ocean thaa tcho and lipid fractions accounted for 91 99 of the total organic carbon toc in phytoplankton and zooplankton 57 of toc in sediment floc and 18 38 of toc in sediment based on concentration profiles in sediment first order degradation rate constants below the bioturbation zone were calculated using a multi g model considering both labile and refractory organic fractions the calculated rate constants were in the order thaa tcho toc tn lipid indicating the relative reactivities of these compound classes in the sediment during early diagensis bioturbation affected the distribution of these compound classes in the top few centimeters of the sediment the 14c values of all organic fractions decreased in the order plantkon in surface water to sediment floc to sediments at 4100 m depth distinct differences of 14c exist among thaa tcho and lipid fractions in sediment floc and sediments the lipid fraction exhibited lower 14c signatures than thaa and tcho fractions differential decomposition of organic matter and sorption and or biological incorporation of old doc into sediment appear to be the major processes that likely control the observed 14c signatures and abundances 13c values of the organic compound classes in sediment are similar to their values in plankton indicating that organic matter input to sediment in the northeastern pacific is mainly from marine sources also distinct 13c signatures were found in each of the four organic fractions

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

a borehole model derived algorithm for estimating qp logs from full waveform sonic logs we develop a processing algorithm to estimate the intrinsic seismic attenuation qp 1 from p head waves of full waveform sonic logs the algorithm based on an extended version of the amplitude spectral ratio asr method corrects the apparent attenuation for the effects of multiple raypaths within the borehole geometric spreading of head waves and formation inhomogeneity the algorithm is derived from two ray models the first model simulates the interaction among rays reflected within the borehole and rays reflected from layer interfaces this model removes these reflections and extracts the leading borehole wavelet the second model uses a single ray model for the borehole head wave in layered formations this model provides the transmission coefficients across the layer interfaces between the source depth and the receiver depth with sectional geometric spreading within these layers we use these two models to simultaneously separate correct for and normalize the effects of the borehole geometric

seismic signatures of permeability in heterogeneous porous media in homogeneous poroelastic systems the permeability tensor practically does not influence propagating seismic waves in the low frequency range 0 1000 hz see e g schmitt 1989 gelinsky and shapiro 1996 in this paper we show that this situation changes in heterogeneous systems such as layered or fractured sediments due to the heterogeneities of poroelastic structures the attenuation of p waves is influenced by the permeability in an enhanced way we show however that such a seismic permeability can differ very strongly from the hydraulic permeability

new paleomagnetic results from northern china collision and suturing with siberia and kazakhstan abstract we report new results from our paleomagnetic studies of the inner mongolia autonomous region in northeastern china and the xinjiang autonomous region in northwestern china primary magnetizations are isolated in tertiary cretaceous late jurassic and late permian rocks and secondary components of magnetization of late jurassic and recent ages are seen in strata of inner mongolia western junggar basin and part of the tarim block suffered widespread complete tectono thermal remagnetization at about 280 ma permian the paleomagnetic evidence suggests that the sampled areas in inner mongolia have been part of the north china block at least since late permian time and the junggar block collided with the tarim block by late permian time our own paleomagnetic results together with available data from other parts of eastern eurasia suggest a tectonic model in which kazakhstan europe and siberia collided with each other and formed the europe siberia kazakhstan plate eur sib kaz in late permian time to the east mongolia outer mongolia inner mongolia and the north china block were also wedged together forming the mongolia north china plate mon nc by this time these two composite continental plates were not a stable unit in the late permian the geometrical relationship of the paleomagnetic poles for these two plates suggests that collision initially occurred in the late permian near the western end 50 n 75 e of the southern siberian fold belt and progressed eastward as the mon nc plate rotated and clockwise about 117 relative to the eur sib kaz plate during the early mesozoic suturing and rotation were probably complete by the late jurassic significant relative motion between the tarim and siberia blocks continued from early triassic to late jurassic as tarim moved northeastward 1400 km relative to siberia

geochronological and geochemical constraints on the petrogenesis of mesozoic high k granitoids in the central korean peninsula abstract mesozoic granitoids are prevalent throughout the korean peninsula but precise geochronological and petrogenetic information of these granitoids is not available for this study 14 granitoid samples from the gyeonggi massif and okcheon belt in central korea were chosen for zircon and titanite u pb age determination these granitoids can be divided into two age groups 230 225 and 184 167 ma triassic granitoids are metaluminous shoshonitic diorite while jurassic granitoids range from metaluminous to peraluminous high k calc alkaline biotite granite nd isotopic data for both groups suggest that the granitoids were derived from younger lower crustal rocks instead of precambrian basement rocks in close proximity high alkali content within the triassic diorite implies a post collisional signature and cessation of indosinian songrim orogeny on the korean peninsula the geochemical transition in granitoids from triassic shoshonitic to a jurassic high k calc alkaline series suggests a change in tectonic environments from continent continent collision to active continental margin the temporal difference in triassic high k magmatism indicates that the extension after indosinian orogeny most likely began earlier in the korean peninsula than in the north china block which might be related to differences in geodynamics rather than a diachronous continental collision

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

a generalized effective anisotropic poroelastic model for periodically layered media accounting for both biot s global and interlayer flows we present a generalized effective poroelastic model for periodically layered media in the mesoscopic scale range which accounts for both biot s global and interlayer wave induced fluid flow as well as for the anisotropy associated with the layering correspondingly it correctly predicts the existence of the fast and slow p waves as well as quasi and pure s waves the proposed analytical model is validated through comparisons of the p wave and s wave phase velocity dispersion and attenuation characteristics with those inferred from a one dimensional numerical solution of biot s poroelastic equations of motion we also compare our model with the classical mesoscopic model of white for a range of scenarios the results demonstrate that accounting for both wave induced fluid flow mechanisms is essential when biot s global flow prevails at frequencies that are comparable or smallerwith respect to those governing interlayer flow this is likely to be the case in media of high permeability such as for example unconsolidated sediments clean sandstones karstic carbonates or fractured rocks conversely when interlayer flow occurs at smaller frequencies with respect to biot s global flow the predictions of this model are in agreement with white s model which is based on quasi static poroelasticity

revised and synthetic apparent polar wander paths of the african eurasian north american and indian plates and true polar wander since 200 ma we have reviewed paleomagnetic data available for the eurasian african north american and indian plates over the last 200 ma selection criteria are those generally accepted with an emphasis on evidence for lack of remagnetization accurate dating and proper structural analysis this results in 23 35 51 and 2 poles for eurasia africa north america and india respectively we believe that this limited set of higher quality data is more likely to reveal key features of apparent polar wander apw paths than averaging of larger data sets involving less stringent selection criteria we propose and describe revised apw paths but more importantly we next use relative motion models to transfer all data in a common reference frame we find good agreement between transferred data when they are averaged separately for each plate in independent 20 ma windows this is a check on consistency of paleomagnetic data kinematic models and of the geocentric dipole hypothesis transferred data from all plates are averaged in 20 ma windows to generate synthetic apw paths for all plates studied these synthetic paths are in agreement with the original revised apw paths that use only data from a single plate moreover both geographic and time resolution are improved spatial confidence intervals are of the order of 5 the synthetic paths display interesting features such as a previously ill recognized apw loop for eurasia paleomagnetic and hotspot apw are next compared and a determination of true polar wander tpw is derived we find significant tpw amounting to over 20 in the last 200 ma tpw appears to be episodic with a standstill between 180 and 110 ma there is general agreement with a previous study of livermore et al 1984 the tpw standstill appears to correlate with a time of decreasing reversal frequency ending with the cretaceous long normal superchron other periods of fast tpw would seem to correspond to increasing reversal frequency however it is suggested that the major tpw hairpin at 50 ma might correspond to the collision of india with eurasia tentative correlations with core or mantle indicators can be understood as a result of couplings between the core mantle and lithosphere we believe primarily related to episodic evolution of the d layer

high elevation of jiaolai basin during the late cretaceous implication for the coastal mountains along the east asian margin abstract a large body of evidence suggests that there were extensive coastal mountains along the east asian margin during the late cretaceous however current knowledge of the paleo mountains the period range and elevation is limited therefore direct paleoaltimetry is needed to validate and evaluate the paleo mountains in east asia our study area is jiaolai basin which is located at the east asian continental margin we estimate the paleoelevation of jiaolai basin during the late cretaceous using carbonate clumped isotope paleothermometry after correcting for seasonal preference latitudinal difference and secular climate change we conclude that the paleoelevation of jiaolai basin was almost certainly 2 0 km at 80 ma combined with the evidence from stratigraphy paleogeography and paleoclimatology our results suggest that the existence of coastal mountains along east asia during the late cretaceous is likely and the model of okhotomorsk east asia collision is preferred

p wave seismic attenuation by slow wave diffusion effects of inhomogeneous rock properties recent research has established that the dominant p wave attenuation mechanism in reservoir rocks at seismic frequencies is because of wave induced fluid flow mesoscopic loss the p wave induces a fluid pressure difference at mesoscopic scale inhomogeneities larger than the pore size but smaller than the wavelength typically tens of centimeters and generates fluid flow and slow diffusion biot waves continuity of pore pressure is achieved by energy conversion to slow p waves which diffuse away from the interfaces in this context we consider a periodically stratified medium and investigate the amount of attenuation and velocity dispersion caused by different types of heterogeneities in the rock properties namely porosity grain and frame moduli permeability and fluid properties the most effective loss mechanisms result from porosity variations and partial saturation where one of the fluids is very stiff and the other is very compliant such as a highly permeable sandstone at shallow depths saturated with small amounts of gas around 10 saturation and water grain and frame moduli variations are the next cause of attenuation the relaxation peak moves towards low frequencies as the background permeability decreases and the viscosity and thickness of the layers increase the analysis indicates in which cases the seismic band is in the relaxed regime and therefore when the gassmann equation can yield a good approximation to the wave velocity

geochronological constraints on multiple deformations of the honam shear zone south korea and its tectonic implication abstract the ne trending honam shear zone south korea is a tectonic scale shear zone consisting of several parallel mylonite zones jeonju sunchang and yecheon shear zones here we report the sensitive high resolution ion microprobe shrimp u pb zircon ages from the mylonitic precambrian orthogneiss and hornblende biotite granitoid near the myeongho area within the yecheon shear zone a representative segment of the honam shear zone the core and overgrowth parts of the zircons from the foliated hornblende biotite granitoid yielded ca 187 ma and ca 178 ma respectively the former is interpreted as a timing of emplacement whereas the latter as a timing of subsequent mylonitization which is similar to zircon overgrowth age of ca 179 ma obtained from mylonitized quartz feldspar orthogneiss muscovite and biotite k ar ages of mylonitized precambrian rocks and foliated granitoids range from 162 168 ma 148 155 ma and 136 ma our geochronological results combined with those of previous geochronological and structural studies suggest that the honam shear zone is a tectonic element created during middle jurassic daebo or early yanshanian orogeny and lasted possibly as late as at early cretaceous in relation to the subduction of the izanagi plate under the asian continent

remobilization of metasomatized mantle lithosphere a new model for the jiaodong gold province eastern china the 120 ma jiaodong province in the north china craton composed of abundant mesozoic granites that intrude precambrian metamorphic basement is bordered by the sulu orogenic belt which formed through the collision between the north china and yangtze cratons in the triassic insights on the geodynamic setting and source of gold and fluids in the jiaodong gold province are based on a detailed study of the sanshandao deposit the 13cpdb and 18o values of hydrothermal calcite from this deposit range from 4 3 to 6 5 and 11 4 to 15 1 respectively which are compatible with a mantle source pre ore mafic dykes in the deposit show typical arc like geochemical features suggesting that the mantle source was metasomatized prior to the basic magmatism the 34s values of gold related pyrite from sanshandao and other large deposits in the province range from 10 9 to 11 5 and are higher than those of the country rocks but consistent with the signature of orogenic gold deposits sourced from a neoproterozoic sedimentary reservoir these high positive 34s values are interpreted to be inherited from auriferous neoproterozoic sedimentary rocks of the northern yangtze craton which were subducted into the mantle lithosphere beneath the north china craton during the formation of eclogite in the adjacent sulu orogenic belt in the triassic the syn ore lower cretaceous mafic dykes display oceanic island basalt like geochemical features suggesting that asthenosphere upwelling triggered the release of gold and sulfur from an enriched and fertilized mantle lithosphere contributing to the auriferous fluid which formed the widespread gold mineralization in the jiaodong province at ca 120 ma

high time resolution ams 14c data sets for lake baikal and lake hovsgol sediment cores changes in radiocarbon age and sedimentation rates during the transition from the last glacial to the holocene abstract high time resolution 14 c dating of lake baikal sediment cores indicates negative and positive anomalies of calculated linear sedimentation rate lsr 1 1 and 35 6 cm ka respectively during the period of climate transition from the last glacial to holocene the timing of the lake baikal apparent lsr anomalies is consistent with that of the changes in the atmospheric radiocarbon concentration 14 c during younger dryas rapid cooling event 14 c dating of lipids in the lake baikal surface sediments revealed that the sources of sedimentary lipids were different in each basin in the northern basin of lake baikal the 14 c age of total lipids from the surface sediment 4 0 14 c ka was found to be older than that of toc 1 6 14 c ka by contrast the 14 c age of total lipids in the southern basin was younger than that of the toc by ca 0 7 3 0 ka in the lake hovsgol sediment cores ages of the main lithologic boundaries during the last glacial interglacial transition were estimated based on new 14 c data sets toc concentration in the cores started to rapidly increase at 13 8 0 3 14 c ka at the base of the basinwide finely laminated layer deposited during bolling allerod the base of the layer diatomaceous mud corresponds to the end of younger dryas event 10 6 0 1 14 c ka

is the ogcheon metamorphic belt of korea the eastward continuation of the nanhua basin of china abstract the ogcheon metamorphic belt in central korea has been interpreted to be the eastward extension of the nanhua basin aulacogen of southeast china in this paper comparisons are made between the two regions based on stratigraphic thermal tectonic and other considerations from this comparison correlation of geological events between the nanhua basin and ogcheon metamorphic belt are at best equivocal the closest similarity is the presence in both regions of two major diamictite units of glacial origin and neoproterozoic age 750 690 ma range in china but of controversial origin and uncertain age in korea volcanic rocks in both regions appear to have similar petrological and geochemical traits and are interpreted to be rift related however their ages are different mostly 795 780 ma in the nanhua basin and c 750 ma in central korea so correlation remains uncertain more isotopic data from both regions may shed light on this comparison correlation between other pre carboniferous stratigraphic units in the two regions is hampered by the uncertainty about the stratigraphic age and succession in the ogcheon metamorphic belt stemming mainly from the absence of fossils and the strong tectonic metamorphic overprint both regions appear to have undergone deformation and metamorphism during the middle triassic indosinian songrim in some uncertain way related to the collision between the north and south china plates in the ogcheon metamorphic belt there has been no confirmation of a mid palaeozoic event but in the nanhua basin that event is recorded by stratigraphic and palaeogeographic evidence in the nanhua basin there is no evidence for an early permian metamorphic event that appears on isotopic grounds to have affected the ogcheon metamorphic belt this apparent difference has been interpreted as a result of diachronous deformation during late palaeozoic early mesozoic plate collisions that took place earlier in the east in korea than in the west in china

continental response to mid cretaceous global plate reorganization evidence from the tan lu fault zone eastern china abstract investigation of the 2400 km long tan lu fault zone tlfz in eastern china is the key to understanding how the izanagi plate in the western pacific basin and the east asian continental margin responded to global plate reorganization during the mid cretaceous we present new structural and geochronological data to show that the central segment of the nne ssw striking tlfz underwent a phase of sinistral transpression after the early cretaceous rifting the resultant strike slip structures are ductile shear belts in the south of the segment and brittle faults in the north quartz c axis fabrics and other microstructures indicate deformation temperatures of 350 500 c in different parts of the shear belts the brittle faults were associated with the formation of ne sw trending folds and an angular unconformity between lower and upper cretaceous volcanic or sedimentary rocks fault slip data indicate that sinistral faulting was the result of n s compression u pb dating constrains the timing of sinistral faulting between 97 and 82 ma early late cretaceous integration of these and existing data demonstrates that the entire tlfz underwent sinistral displacement at the beginning of the late cretaceous consistent with continental scale n s compression in eastern china such compression in the overriding plate was caused by rapid oblique subduction of the izanagi plate and reflected global plate reorganization at this time both the changes in the kinematics of the izanagi plate and the resultant variation of stress states in the continental margin around the mid cretaceous are ascribed to this plate reorganization

combined use of δ14c and δ13c values to trace transportation and deposition processes of terrestrial particulate organic matter in coastal marine environments accelerator mass spectrometry was used to measure radiocarbons of riverine suspended particles and sediments from the estuary continental shelf and slope off the coast of tokachi river in japan the spatial distribution of 14c and 13c values of sedimentary organic matter was divided into those of 1 estuary 2 continental shelf and 3 continental slope for shelf sediments respective maxima can be seen for 14c value c n ratio and organic carbon content at a station near the river mouth the mean grain size of surface sediments also exhibits a similar trend the 13c values show a minimum near the river mouth the shelf composition does not appear to be a simple mixture of terrestrial and marine origin from the above data it is considered that the spatial distribution of 14c and 13c values may reflect variations in dispersion and deposition processes together with the size fractionation of riverine suspended particles the resuspension of sediments and differences in the contribution of marine organic matter

preliminary phanerozoic polar wander paths for the north and south china blocks polar wander paths for the north and south china blocks suggest that 1 both were parts of gondwana in the palaeozoic 2 the north china block accreted to siberia in the late permian and 3 the south china block accreted to the north china block in the middle triassic to the early jurassic comparison of the polar wander path for the south china block with that for northern eurasia suggests that relative motion of over 4 000 km has occurred between them

late cretaceous genesis of the kula plate abstract we propose that the pacific kula ridge began spreading approximately 85 m y b p during late cretaceous time extrapolation of the great magnetic bight backwards in time results in an implausible ridge configuration this implies that plate velocity vectors for the pacific kula and farallon plates were not constant during this interval evidence for splitting of the kula plate from the pacific plate along the chinook trough is the relationship between the north striking amlia and adak fracture zones the chinook and emperor troughs and the magnetic lineations south of the aleutian trench if this hypothesis is correct it will require that mesozoic reconstructions of the pacific basin and their relation to cenozoic reconstructions be re examined a previously unrecognized mesozoic plate may be required we propose calling this the izanagi plate

microelectrode studies of organic carbon degradation and calcite dissolution at a california continental rise site fine scale porewater profiles of resistivity o2 ph and pco2 were measured in situ with microelectrodes at a site on the california continental rise they are reported here with more traditional measurements of shipboard porewater no3 alkalinity and tco2 and sediment organic c and caco3 profiles a numerical model encompassing diffusion advection and multiple reaction terms is applied to these data to characterize organic carbon degradation and caco3 dissolution processes near the sediment water interface a benthic o2 flux of 58 mol cm 2 yr 1 over the top 1 mm sediment is estimated based on one measured sub mm depth scale o2 profile the numerical model indicates that this high o2 consumption rate is related to a very labile fraction of organic c which has a degradation rate constant of approximately 4 5 10 8 s 1 1 4 yr 1 and which is not mixed downward by biological mixing seasonality in the benthic o2 consumption rate of this site may be attributed to variations in the input rate of this highly labile organic c degradation rate constants of the bulk organic c by oxygen reduction and by nitrate reduction are estimated to be about the same 1 10 9 s 1 the organic c rain rate responsible for the bulk organic c is estimated to be 53 mol cm 2 yr 1 this estimate exceeds the average rain rate determined by sediment trap collections at this site saturation state profiles calculated from the in situ ph and pco2 data and from modelling the in situ o2 and ph data both indicate that the porewater is undersaturated with respect to calcite to a depth of at least 8 cm the dissolution rate constant of calcite in this caco3 poor station is determined to be 5 10 day 1 assuming the reaction order is 4 5 which is close to the minimum estimates for environments richer in calcite a uniform calcite dissolution rate constant therefore may be adequate for representing carbonate dissolution in global scale models of ocean chemistry

seismic scattering in the upper crystalline crust based on evidence from sonic logs summary evidence from sonic logs indicates that velocity fluctuations in the upper crystalline crust are remarkably uniform this motivates a generic approach to classifying uppercrustal seismic heterogeneity and to studying implications for seismic wave propagation the resulting canonical model of upper crustal seismic structure is characterized by a spatially isotropic von karman autocovariance function with a z 100 m 0 15 and cj 300 m s small angle scattering theory is used to predict the transition from weak to strong scattering as well as phase fluctuations and scattering attenuation compared with exponential random media v 0 50 the high fractal dimension i e small values of v of upper crustal heterogeneity causes smaller phase fluctuations and transition from weak to strong scattering at lower frequencies and shorter path lengths acoustic finite difference modelling shows that seismic reflections from deterministic features surrounded by heterogeneities are severely degraded when they fall into the strong scattering regime conversely traveltime fluctuations of transmitted waves are found to be relatively insensitive to the transition from weak to strong scattering upper crustal scattering q is predicted to lie between 600 and 1500 which is one to two orders of magnitude higher than q values inferred from seismic data this suggests that seismic attenuation in the upper crystalline crust is dominated by anelastic effects rather than by scattering

paleomagnetism of upper cretaceous rocks from south china paleomagnetic study of upper cretaceous redbeds from two areas in south china was undertaken in an effort to constrain better the history of tectonic movements in southeastern asia from the nanjing area 32 n l19 e high temperature characteristic directions which pass a fold test were obtained from ten sites 43 samples in the upper cretaceous puko and yanzijing formations the paleomagnetic pole position 76 3 n 172 6 e a95 10 3 agrees well with a late cretaceous reference pole for eurasia and thus confirms that this part of south china was fully sutured to eurasia by the end of the cretaceous with no paleomagnetically resolvable subsequent relative rotation in western sichuan 26 5 n 102 3 e high temperature characteristic directions of normal and reverse polarity were obtained from twelve samples 48 specimens in the upper cretaceous to lower paleocene xiaoba and leidashu formations a provisional paleomagnetic pole position 80 9 n 296 8 e a95 7 7 differs significantly from a late cretaceous eurasia reference pole in terms of apparent tectonic movement the difference in paleopole positions would indicate a 13 10 3 northward translation and 22 11 2 counterclockwise rotation of western sichuan relative to eurasia confirmation of this reconnaisance result which would suggest that western sichuan was pushed ahead of an impinging india is needed

one dimensional random patchy saturation model for velocity and attenuation in porous rocks porous rocks encountered in hydrocarbon reservoirs are often saturated with a mixture of two or more fluids generation of synthetic seismograms as well as interpretation of in situ attenuation measurements require a theoretical understanding of the relation between the heterogeneous distribution of fluid patches and the acoustic properties of rocks thus the problem of calculating acoustic properties of rocks saturated with a mixture of two fluids has attracted considerable interest white 1975 murphy 1982 gist 1994 mavko and mukerji 1998 pride et al 2004 at the same time this problem is also interesting from the theoretical point of view because partially saturated rocks represent a particularly interesting situation when the effects of dynamic poroelasticity may be significant at seismic or sonic frequencies indeed it is a radical departure from the situation with a porous material fully saturated with a single fluid such a fully saturated material exhibits frequency dependent effects only at frequencies comparable with biot9s characteristic frequency bourbie et al 1987 c f where f is the fluid density is fluid viscosity is permeability and is porosity for frequencies much lower than c the dynamic effects can be ignored and gassmann theory applies

the distribution of bomb radiocarbon in the ocean water column inventories are calculated for bomb radiocarbon at all the stations occupied during the geosecs and norpax expeditions and for the available tto stations the pattern of global inventories obtained in this way suggests that a sizable portion of the bomb radiocarbon that entered the antarctic the northern pacific and the tropical ocean has been transported to the adjacent temperate zones a strategy for utilizing these inventory anomalies as constraints on global ocean circulation models is presented essential to this strategy are the improvement of our knowledge of the pattern of wind speed over the ocean the establishment of the wind speed dependence of the rate of gas exchange between the atmosphere and sea and the continued mapping of the distribution of bomb produced radiocarbon in the sea

laboratory monitoring of p waves in partially saturated sand energy dissipation is observed on seismic data when a wave propagates through a porous medium involving different frequency regimes depending on the nature of rock and fluid types we focus here on the role of partial fluid saturation in unconsolidated porous media looking in particular at p wave phase velocity and attenuation the study consists in running an experiment in a sand filled tank partially saturated with water seismic propagation in the tank is generated in the khz range by hitting a steel ball on a granite plate seismic data are recorded by buried accelerometers and injecting or extracting water controls the partial saturation several imbibition drainage cycles were performed between the water and gas residual saturations a continuous wavelet transform applied on seismic records allowed us to extract the direct p wave at each receiver we observe an hysteresis in phase velocities and inverse quality factors between imbibition and drainage phase velocities and inverse quality factors are then jointly inverted to get a final poro visco elastic model of the partially saturated sand that satisfactorily reproduces the data the model formulation consists in generalizing the biot theory to effective properties of the fluid and medium permeability and bulk modulus in order to properly explain the phase velocity variation as a function of the saturation the strong level of attenuation measured experimentally is further explained by an anelastic effect due to grain to grain sliding adding to biot s losses this study shows that fluid distribution at microscopic scale has strong influence on the attenuation of direct p waves at macroscopic scale and confirms that seismic prospection may be a powerful tool for the characterization of transport phenomena in porous media

radiocarbon signatures and size age composition relationships of major organic matter pools within a unique california upwelling system abstract coastal upwelling zones are among the most productive regions in the world and play a major role in the global carbon cycle radiocarbon as 14 c is a powerful tool for tracing the source and fate of suspended particulate and dissolved organic matter pom dom and has the potential to reconcile key carbon budgets within upwelling systems however the extent to which upwelling processes influence the 14 c signature of surface dic or that of pom or dom remains almost completely unknown here we present a time series of stable carbon 13 c and 14 c isotopic data of major water column carbon pools including dissolved inorganic carbon dic large 0 7 500 m and small 0 1 100 m pom and high molecular weight hmw 1 nm 0 1 m dom from an upwelling center along the big sur coast we show that dic 14 c values ranging between 29 and 14 are strongly correlated to coastal upwelling processes and that this 14 c signal readily propagates into both the pom and hmw dom pool however the presence of negative pom and hmw dom 14 c values ranging between 46 and 56 6 and 123 and 1 and 150 respectively suggests contributions of pre aged om complicating the direct use of bulk 14 c for tracing upwelling derived carbon production export using a triple isotope mixing model 13 c 15 n 14 c we estimate that 50 90 and 45 51 of large and small pom is newly produced om while between 6 22 and 12 44 of large and small pom are derived from pre aged re suspended sediments finally we observe quantitative relationships between om size composition c n ratio and 14 c within this upwelling system possibly representing a new tool for modeling ocean c and n biogeochemical cycles

squirt flow in fully saturated rocks we estimate velocity frequency dispersion and attenuation in fully saturated rocks by employing the squirt flow mechanism of solid fluid interaction in this model pore fluid is squeezed from thin soft cracks into the surrounding large pores information about the compliance of these soft cracks at low confining pressures is extracted from high pressure velocity data the frequency dependence of squirt induced pressure in the soft cracks is linked with the porosity and permeability of the soft pore space and the characteristic squirt flow length these unknown parameters are combined into one expression that is assumed to be a fundamental rock property that does not depend on frequency the appropriate value of this expression for a given rock can be found by matching our theoretical predictions with the experimental measurements of attenuation or velocity the low frequency velocity limits as given by our model are identical to those predicted by gassmann s formula the high frequency limits may sign

the fate of river organic carbon in coastal areas a study in the rhone river delta using multiple isotopic delta c 13 delta c 14 and organic tracers a significant fraction of the global carbon flux to the ocean occurs in river dominated ocean margins riomar although large uncertainties remain in the cycle of organic matter om in these syste

eastern asia in the cretaceous new paleomagnetic data from south korea and a new look at chinese and japanese data lower cretaceous continental sediments and volcanic rocks have been sampled in the gyeongsang basin south korea a detailed analysis of 160 specimens reveals two stable components of magnetization a postfolding low temperature lt component with normal polarity and a stable high temperature ht component with both normal and reversed polarities the blocking temperature of the ht component ranges from 540 c up to the neel temperature of hematite this component predates the folding of the series and yields a pole at 68 n 205 e a95 6 the prefolding magnetization indicates that south korea stood at a latitude nearly identical to its present day latitude in the lower cretaceous comparison of korean data with revised paleomagnetic data from north and south china and japan shows that all these blocks of eastern asia occupied the same positions in term of latitude and were probably parts of a single craton since at least the lower cretaceous the paleomagnetic directions of the sino korean block show large discrepancies with respect to the expected directions of the stable eurasian siberian block an interpretation involving significant n s motion 1000 km between either north and south china or between north china and siberia appears to contradict geological data a preferred interpretation is that the siberian data are in serious error and that the combined china korea lower cretaceous pole provides a valid estimate for the eurasian plate as a whole

paleoproductivity and carbon burial across the california current the multitracers transect 42 n the multitracers experiment studied a transect of water column sediment trap and sediment data taken across the california current to develop quantitative methods for hindcasting paleoproductivity the experiment used three sediment trap moorings located 120 km 270 km and 630 km from shore at the oregon california border in north america we report here about the sedimentation and burial of particulate organic carbon corg and caco3 in order to observe how the integrated caco3 and corg burial across the transect has changed since the last glacial maximum we have correlated core from the three sites using time scales constrained by both radiocarbon and oxygen isotopes by comparing surface sediments to a two and a half year sediment trap record we have also defined the modern preservation rates for many of the labile sedimentary materials our analysis of the corg data indicates that significant amounts 20 40 of the total corg being buried today in surface sediments is terrestrial at the last glacial maximum the terrestrial corg fraction within 300 km of the coast was about twice as large such large fluxes of terrestrial corg obscure the marine corg record which can be interpreted as productivity when we corrected for the terrestrial organic matter we found that the mass accumulation rate of marine corg roughly doubled from the glacial maximum to the present because preservation rates of organic carbon are high in the high sedimentation rate cores corrections for degradation are straightforward and we can be confident that organic carbon rain rate new productivity also doubled as confirmation the highest burial fluxes of other biogenic components opal and ba also occur in the holocene productivity off oregon has thus increased dramatically since the last glacial maximum caco3 fluxes also changed radically through the deglaciation however they are linked not to caco3 production but rather to changes in deepwater carbonate chemistry between 18 ka and now

a new concept on tectonic correlation between korea china and japan histories from the late proterozoic to cretaceous abstract the dabie sulu collision belt in china extends to the hongseong odesan belt in korea while the okcheon metamorphic belt in korea is considered as an extension of the nanhua rift within the south china block the hongseong odesan belt divides korea s gyeonggi massif into northern and southern portions the southern gyeonggi massif and the yeongnam massif are correlated with china s yangtze and cathaysia blocks respectively while the northern gyeonggi massif is part of the southern margin of the north china block the southern and northern gyeonggi massifs rifted from the rodinia supercontinent during the neoproterozoic to form the borders of the south china and north china blocks respectively subduction commenced along the southern and eastern borders of the north china block in the ordovician and continued until a triassic collision between the north china and south china blocks while subduction was occurring on the margin of the north china block high p t metamorphic belts and accretionary complexes developed along the inner zone of southwest japan from the ordovician to the permian during the subduction the hida belt in japan grew as a continental margin or continental arc collision between the north and south china blocks began in korea during the permian 290 260 ma and propagated westwards until the late triassic 230 210 ma creating the sinistral tanlu fault in china and the dextral fault in the hida and hida marginal belt in japan phanerozoic subduction and collision along the southern and western borders of the north china block led to formation of the qinling dabie sulu hongseong hida yanji belt

sedimentation of particulate organic carbon on the amundsen shelf antarctica abstract we examined the recent history of sedimentary organic carbon soc accumulation on the western amundsen shelf to help characterize the biological carbon pump in the amundsen sea antarctica vertical sedimentary profiles in the upper 21 cm of soc content radio and stable carbon isotopes were obtained at four locations in the western amundsen sea near the shelf break inside the polynya near the dotson ice shelf and at both the periphery and the center of the amundsen sea polynya profiles were representative not only of various distances from the coast but also of various summertime sea ice conditions and bottom depths the soc content up to 1 1 and the radiocarbon content were distinctly higher at the periphery and at the center of the polynya than at the other sites the soc and 14c contents were generally consistent with the spatial distribution of primary productivity in the surface water a linear soc accumulation rate of about 1 0 g c m 2 yr 1 was determined from the conventional 14c ages of bulk soc below the surface mixed layer at the periphery and at the center of the polynya for the time period of 3 1 4 7 kyr before present bp this linear soc accumulation rate was about 20 times greater than the rates determined at the two other sites for the period of 4 6 15 7 kyr bp note that all values are for uncorrected 14c ages at the center of the polynya a sudden change in soc accumulation rate was observed at about 16 cm depth corresponding to 4 7 kyr bp implying that changes during this time period in physical environments greatly affected primary production soc burial and or supply of allochthonous particles to this site the vertical distribution of 14c content in the sediments implies that aged organic matter likely associated with resuspended sediments was also being deposited inside the polynya in addition to autochthonous biogenic particles if our estimation of soc accumulation is extrapolated to the western amundsen shelf between 110 w and 120 w approximately 3 1010 g c yr 1 is buried on the shelf with 90 of soc accumulation occurring in the amundsen sea polynya

shrimp u pb dating and geochemistry of the cretaceous plutonic rocks in the korean peninsula a new tectonic model of the cretaceous korean peninsula abstract the cretaceous tectonomagmatism of the korean peninsula was examined based on geochemical and geochronological data of the cretaceous plutonic rocks along with distribution of volcano sedimentary nonmarine n to ne trending fault bounded sedimentary basins we conducted sensitive high resolution ion microprobe shrimp zircon u pb ages and whole rock geochemical compositions of 21 cretaceous plutonic rocks together with previously published data from the central to southern korean peninsula four age groups of plutonic rocks were identified group i ca 119 106 ma in the northern to central area group ii ca 99 87 ma in the central southern area group iii ca 85 82 ma in the central to southern area and group iv ca 76 67 ma in the southernmost area these results indicate a sporadic trenchward younging trend of the cretaceous magmatism in the korean peninsula the group i ii and iii rocks are dominated by high k calc alkaline i type rocks with rift related a type granitoids in contrast the group iv rocks are high k calc alkaline i type plutonic rocks with no a type rocks the geochemical signatures of the entire groups indicated lrees light rare earth elements enrichments and negative nb ta and ti anomalies indicating normal arc magmatism a new tectonic model of the cretaceous korean peninsula was proposed based on temporal and spatial distribution of the cretaceous plutons represented by four age groups 1 magmatic quiescence throughout the korean peninsula from ca 160 to 120 ma 2 intrusions of the i and a type granitoids in the northern and central korean peninsula group i plutonic rocks from ca 120 to 100 ma resulted from the partial melting of the lower continental crust due to the rollback of the izanagi plate expressed as the conversion from flat lying subduction to normal subduction the gyeongsang nonmarine sedimentary rift basin in the korean peninsula and adakite magmatism preserved in the present day japanese islands supported the slab rollback followed by steepening of the izanagi plate with an injection of upwelling of the hot asthenosphere into the mantle wedge 3 alternating shallow from 100 to 85 ma to steep from 85 to 65 ma subduction resulted in the migration of the normal arc magmatism in the southern korean peninsula expressed as the intruded i and a type group iii and i type granitoids group iv respectively the tectonomagmatism of the korean peninsula showed the unique style of evolution different from those of south china and japanese islands

widespread influence of resuspended sediments on oceanic particulate organic carbon insights from radiocarbon and aluminum contents in sinking particles globally widespread also a strong correlation is found to exist between d 14 c values of organic carbon and aluminum content in sinking particles that is consistent over a range of oceanic settings together these findings imply that aged organic carbon associated with lithogenic material from sediment resuspension is responsible for the observed low d 14 c values as opposed to other processes such as incorporation of dissolved inorganic carbon or dissolvedorganiccarbonintopocatdepth anestimatebasedonpocflux weightedd 14 c values shows that about 35 of sinking poc at the locations studied is derived from resuspended sediment our results suggest that resuspension of sediment and its subsequent lateral transport is an important component of the oceanic carbon cycle and should be considered in models of oceanic carbon export and burial

an organic tracer for surface ocean radiocarbon the 14c of surface water dissolved inorganic carbon dic in the southern california bight was compared to 14c as recorded by the sterols in santa monica and santa barbara basin sediments all of the c26 c27 c28 and c29 sterols as well as dinosterol had 14c concentrations equal to surface water dic indicating that all of the major sterols were derived from phytoplanktonic production there is no detectable terrestrial component their tracer capability was confirmed by comparing the bomb 14c derived change in surface water 14cdic with the change in 14csterol the prebomb 14cdic was 82 and prebomb sterols averaged 75 19 the 14c value in 1996 was 71 eighteen measurements representing eight different sterols from the sediment water interface of both santa monica and santa barbara basins averaged 62 23 when three of these values were eliminated because of suspected contamination the remaining data averaged 71 12 the entire compound class could serve as an excellent proxy for the 14c concentration of ocean surface waters

geochemical characteristics and variations of the ryoke granitoids southwest japan petrogenetic implications for the plutonic rocks of a magmatic arc abstract geochemical characteristics and variations of the ryoke granitoids southwest japan have been elucidated based on more than 70 analyses from the mikawa and kinki districts for major and trace elements including ree the ryoke granitoids are the products of a continental margin arc magmatism of pacific asia during late cretaceous period and represent its magmatic front they are classified into the older and younger groups according to their intrusive ages and textural and petrographic characteristics the older ryoke granitoids were emplaced at ca 20 km depth during 100 85 ma and deformed and recrystallized together with the host ryoke metamorphic rocks the younger ryoke granitoids are post tectonic plutons emplaced at ca 15 km depth 85 75 ma and accompanied by the formation of contact aureoles the majority belongs to i type and ilmenite series granitoids the granitoids of both groups are geochemically quite similar calcic alkali lime index 65 very low in fe 3 fe 2 ratio and both metaluminous and peraluminous they have low rb

amplitude versus offset variations in gas sands seismic reflections from gas sands exhibit a wide range of amplitude versus offset avo characteristics the two factors that most strongly determine the avo behavior of a gas sand reflection are the normal incidence reflection coefficient r0 and the contrast in poisson s ratio at the reflector of these two factors r0 is the least constrained based on their avo characteristics gas sand reflectors can be grouped into three classes defined in terms of r0 at the top of the gas sand class 1 gas sands have higher impedance than the encasing shale with relatively large positive values for r0 class 2 gas sands have nearly the same impedance as the encasing shale and are characterized by values of r0 near zero class 3 sands have lower impedance than the encasing shale with negative large magnitude values for r0 each of these sand classes has a distinct avo characteristic an example of a gas sand from each of the three classes is presented in the paper the class 1 example involves a hartshorn channel s

seismic and ultrasonic velocities in permafrost we calculate the compressional and shear wave velocities of permafrost as a function of unfrozen water content and temperature unlike previous theories based on simple slowness and or moduli averaging or two phase models we use a biot type three phase theory that considers the existence of two solids solid and ice matrices and a liquid unfrozen water the compressional velocity for unconsolidated sediments obtained with this theory is close to the velocity computed with wood s model since biot s theory involves a wood averaging of the moduli of the single constituents moreover the model gives lower velocities than the well known slowness averaging theory wyllie s equation for consolidated berea sandstone the theory underestimates the value of the compressional velocity below 0 c computing the average bulk moduli by slowness averaging the ice and solid phases and wood averaging the intermediate moduli with the liquid phase yields a fairly good fit of the experimental data the proportion of unfrozen water and temperature are closely related fitting the wave velocity at a given temperature allows the prediction of the velocity at the whole range of temperatures provided that the average pore radius and its standard deviation are known