geochronology of early to middle paleozoic tectonic development in the southwest newfoundland gander zone southwest newfoundland s gander zone was once considered part of the collided eastern margin of an early paleozoic iapetus ocean distinguished from the rest of the gander zone by the extensive exposure of a polydeformed amphibolite to greenschist facies sequence considered devonian in age overlying presumed precambrian basement it was later found that truly devonian strata were confined to the cape ray fault system the local northwestern boundary of the zone u pb zircon isotopic ages of 452 13 51 ma and 458 22 29 ma on metavolcanic rocks in the upper part of the sequence southeast of the fault system indicate that ordovician and possibly older rocks underlie the gander zone itself a temporal framework for the three main stages of regional deformation corresponding to pre metamorphic recumbent folding d 1 and transpression d 2 and d 3 is presented using u pb and 40 ar 39 ar dates of granitoid and metamorphic rocks d 1 is bracketed as late o

the seismic cycle in the area of the 2011 mw9 0 tohoku oki earthquake we model seismic and aseismic slip on the japan megathrust in the area of the m w9 0 2011 tohoku oki earthquake based on daily time series from 400 gps stations of the geonet network and campaign measurements of six sea floor displacements the coseismic and postseismic slip distributions are inverted simultaneously using principal component analysis based inversion method pcaim exploring a wide range of boundary conditions and regularization constraints we found the coseismic slip distribution to be quite compact with a peak slip between 30 and 50 m near the trench our model shows deep afterslip fringing the downdip edge of the coseismic rupture but also a dominant zone of shallow afterslip afterslip over the first 279 days following the main shock represents about 40 of the coseismic moment we compare the coseismic and postseismic models with an interseismic coupling model derived from inland and sea bottom measurements determined in a self consistent manner assuming that seismic and aseismic slip had to match the long term slip rate along the megathrust the recurrence time of m w9 0 earthquakes is estimated to 100 300 years while historical and paleotsunami records suggest a return period more of the order of 1000 years the discrepancy is smaller if the shallower portion of the megathrust is assumed to produce both aseismic slip as the afterslip model suggests and seismic slip during occasional large tsunamigenic earthquakes

sediment redistribution versus paleoproductivity change weddell sea margin sediment stratigraphy and biogenic particle flux of the last 250 000 years deduced from 230thex 10be and biogenic barium profiles high resolution 230thex and 10be and biogenic barium profiles were measured at three sediment gravity cores length 605 850 cm from the weddell sea continental margin applying the 230thex dating method average sedimentation rates of 3 cm kyr for the two cores from the south orkney slope and of 2 4 cm kyr for the core from the eastern weddell sea were determined and compared to 18o and lithostratigraphic results strong variations in the radionuclide concentrations in the sediments resembling the glacial interglacial pattern of the 18o stratigraphy and the 10be stratigraphy of high northern latitudes were used for establishing a chronostratigraphy biogenic ba shows a pattern similar to the radionuclide profiles suggesting that both records were influenced by increased paleoproductivity at the beginning of the interglacials however 230thex0 fluxes 0 stands for initial exceeding production by up to a factor of 4 suggest that sediment redistribution processes linked to variations in bottom water current velocity played the major role in controlling the radionuclide and biogenic barium deposition during isotope stages 5e and 1 the correction for sediment focusing makes the true vertical paleoproductivity rates deduced from the fluxes of proxy tracers like biogenic barium much lower than previously estimated very low 230thex0 concentrations and fluxes during isotope stage 6 were probably caused by rapid deposition of older resedimented material delivered to the weddell sea continental slopes by the grounded ice shelves and contemporaneous erosion of particles originating from the water column

late quaternary and coseismic crustal deformation across the focal area of the 2008 iwate miyagi nairiku earthquake abstract we investigated late quaternary and coseismic crustal deformation rates in the 2008 iwate miyagi nairiku earthquake 2008 imeq focal area we identified five fluvial terraces and used tephrochronology and 14c dating to correlate them with marine isotope stages miss 6 5 slightly younger than 5 3 5 2 4 5 2 1 and 1 the late quaternary uplift rates calculated from the relative heights of the mis 6 5 120 140 ka and 2 1 10 ka terrace surfaces were 0 18 0 21 0 13 m ky and 0 62 0 74 0 13 m ky on the downthrown and upthrown sides of the 2008 imeq fault respectively we developed a fault model that reflected the coseismic vertical displacements and surface ruptures this model had a fault plane dipping to the west at 40 with slip of 4 4 m on the deep 10 3 km depth part of the fault plane and of 0 3 m on the shallow 3 0 km depth part the late quaternary and coseismic deformation pattern of the ground surface roughly agree furthermore the recurrence interval 2 9 4 2 ky calculated from the late quaternary vertical offset and coseismic vertical deformation roughly agrees with the findings of a previous trenching study thus the slip on the fault of the 2008 imeq was a characteristic earthquake event

rapid crustal uplift in patagonia due to enhanced ice loss abstract a vertical crustal uplift rate of 39 mm yr 1 is measured between 2003 and 2006 using global positioning system gps measurements at the northeastern edge of the southern patagonia icefield spi this is the largest present day glacial isostatic rate ever recorded the combination of spi s rapid melting and the unique regional slab window tectonics that promotes a relatively low viscosity is central to our interpretation of the observations the two effects lead to a strong interaction of short relaxation times with ice loads that change on a comparable time scale the profile of gps observations link ice loss to the soft viscoelastic isostatic flow response over the time scale of the little ice age lia including ice loss in the period of observation the agreement of the results with our model predictions strongly suggests the large crustal uplift in patagonia is due an accelerated glacier wasting since the termination of the lia and that the effective regional mantle viscosity is near 4 0 8 0 10 18 pa s a century long diminution of the icefields at rates that are about 1 4 1 2 the contemporary loss rates is consistent with multidecadal scale temperature trends estimated for the past 50 100 years and is in fact a key feature in any model capable of explaining the uplift data

late quaternary sediment flux on sedimentary drifts in the northeast atlantic abstract comparison between the last glacial and holocene periods of the terrigenous and carbonate sediment flux distributions in the whole northeastern atlantic basin points out the role of deep circulation relative to other processes during the holocene the global terrigenous flux is similar to that during the glacial period 4 compared with 4 7 g cm 2 ky 1 despite a general decrease of terrigenous supplies the flux distribution however is different high values are located in areas of bottom current sedimentation contourite drifts instead of along continental margins where downslope processes are dominant and areas with major ice rafting the global carbonate flux is higher during the holocene 3 compared with 1 5 g cm 2 ky 1 but the carbonate flux distribution matches that of the terrigenous flux both flux patterns are strongly controlled by reworking and redeposition of sediments by bottom currents flux variation in three cores collected on the feni gardar and faro drifts compared to areas of little or no bottom current activity highlights the deep water circulation fluctuations since the last glacial maximum in areas dominated by downslope processes bay of biscay or by ice rafted sediment deposition mid atlantic ridge around 45 n the sediment fluxes are maximum during the deglacial warming and minimum during the holocene period areas dominated by bottom current sedimentation are all characterized by highest sedimentation during the holocene but the flux variations reveal that the norwegian sea water overflow nswo and the mediterranean outflow mo fluctuated differently according to the regional climatic context and the latitudinal transgression of climatic warming on the feni and gardar drifts higher holocene fluxes coincide with the re initiation of nswo at about 10 000 yrs bp the highest flux on the gardar drift results from a stronger outflow across the iceland faeroe ridge than across the faeroe scotland ridge this flow is responsible for high sediment fluxes all along the eastern side of the mid atlantic ridge as far south as 45 n on the faro drift the reactivation of the mediterranean outflow mo took place earlier as three episodes of greater bottom current activity occurred since about 15 000 yrs bp fluxes are maximum during the deglacial warming and remain high during the holocene

millennial scale crustal movements inferred from holocene sedimentary succession of the omoto plain northern sanriku coast northeast japan relevance for modeling megathrust earthquake cycles abstract crustal movements on a millennial timescale 103 104 years are important data for assessing the deformation of subduction zones during megathrust earthquake cycles such data did not exist until recently for the sanriku coast near the source region of the 2011 tohoku oki earthquake since the 2011 earthquake studies of holocene sedimentary successions have documented subsidence on the central to southern segment of the sanriku coast on a millennial timescale but comparable data are lacking for the northern sanriku coast this study derived millennial scale crustal movements from a well dated holocene sedimentary succession in the omoto plain on the northern sanriku coast sedimentary and fossil evidence record the following sequence of environmental changes influenced by sea level changes upward growth and landward progradation of a barrier and flood tidal delta from 10 000 9000 cal bp an estuarine environment from 9000 to 8000 cal bp after growth and progradation of the barrier and flood tidal delta ceased and a regressive delta and subsequent fluvial environment after 8000 cal bp thick deposit of delta to floodplain sediment since mid holocene is not apparent in the omoto plain whereas this feature typical of subsidence area is documented along the central sanriku coast although the absolute direction of the vertical deformation trend could not be well constrained in the study area because of compaction effects the evidence indicates that subsidence during the mid and late holocene was either absent or not noticeable on the omoto plain this difference in deformation histories corresponds to a contrast in coseismic subsidence during the 2011 earthquake between the northern sanriku coast small subsidence and the central to southern sanriku coast large subsidence the results of this study suggest that the northern and central to southern parts of the sanriku coast should be considered separately when assessing regional crustal deformation related to subduction

geodetic slip model of the 2011 m9 0 tohoku earthquake 1 the three dimensional crustal displacement field as sampled by gps is used to determine the coseismic slip of the 2011 m9 0 tohoku earthquake we employ a spherically layered earth structure and use a combination of onland gps out to 4000 km from the rupture and offshore gps which samples the high slip region on the interplate boundary along the japan trench inversion of the displacement field for dip slip assuming an interplate boundary of variable dip and striking 195 yields a compact slip maximum of about 33 m located 200 km east of sendai the geodetic moment is 4 06 1022 n m corresponding to mw 9 0 the area of maximum slip is concentrated at a depth of about 10 km is updip of the rupture areas of the m 7 miyagi oki earthquakes of 1933 1936 1937 and 1978 and roughly coincides with the rupture area of the m7 1 1981 miyagi oki earthquake the overlap of the 2011 slip area with several preceding ruptures suggests that the same asperities may rupture repeatedly with m 7 events within several decades of one another

interplate coupling beneath ne japan inferred from three dimensional displacement field 1 the northeastern japan arc is located in a typical subduction zone and is a seismically active region where large interplate earthquakes have occurred repeatedly the nationwide gps network has made it possible to investigate the crustal deformation in unprecedented detail however vertical displacements are less accurate than the horizontal ones and have not been used to constrain interplate coupling models in this study gps carrier phase data are analyzed in order to estimate three components of site displacements the result indicates uplift along the japan sea coast and subsidence along the pacific ocean coast using the vertical site velocities together with the horizontal ones as the data for a geodetic inversion method a new model of interplate coupling is constructed to explain both the horizontal and vertical velocities for the interseismic period from 1997 to 2001 the model demonstrates strong coupling in the area off miyagi and in the area off aomori through the area off tokachi including the areas of asperities the downdip limit of the locked fault zone on the plate boundary has been estimated seismologically to be at a depth of 50 60 km in northeastern japan and the distribution of slip deficits derived in this study indicates that the transition zone extends down to a depth of about 100 km

itrf2000 a new release of the international terrestrial reference frame for earth science applications 1 for the first time in the history of the international terrestrial reference frame the itrf2000 combines unconstrained space geodesy solutions that are free from any tectonic plate motion model minimum constraints are applied to these solutions solely in order to define the underlying terrestrial reference frame trf the itrf2000 origin is defined by the earth center of mass sensed by satellite laser ranging slr and its scale by slr and very long baseline interferometry its orientation is aligned to the itrf97 at epoch 1997 0 and its orientation time evolution follows conventionally that of the no net rotation nnr nuvel 1a model the itrf2000 orientation and its rate are implemented using a consistent geodetic method anchored over a selection of itrf sites of high geodetic quality ensuring a datum definition at the 1 mm level this new frame is the most extensive and accurate one ever developed containing about 800 stations located at about 500 sites with better distribution over the globe compared to past itrf versions but still with more site concentration in western europe and north america about 50 of station positions are determined to better than 1 cm and about 100 sites have their velocity estimated to at or better than 1 mm yr level the itrf2000 velocity field was used to estimate relative rotation poles for six major tectonic plates that are independent of the trf orientation rate a comparison to relative rotation poles of the nuvel 1a plate motion model shows vector differences ranging between 0 03 and 0 08 m y equivalent to approximately 1 7 mm yr over the earth s surface itrf2000 angular velocities for four plates relative to the pacific plate appear to be faster than those predicted by the nuvel 1a model the two most populated plates in terms of space geodetic sites north america and eurasia exhibit a relative euler rotation pole of about 0 056 0 005 m y faster than the pole predicted by nuvel 1a and located about 10 n 7 e more to the northwest compared to that model

boundary scavenging in the pacific ocean a comparison of 10be and 231pa concentrations of u th 231pa and 10be were measured in holocene sediments from two cores collected off the west coast of south america two cores from the east pacific rise two from the equatorial pacific and one from the south pacific central gyre our results together with data from 5 cores reported in the literature show that boundary scavenging plays a major role in the removal of 10be from the pacific ocean deposition rates of 10be at three margin sites are more than an order of magnitude greater than at sites of red clay accumulation in the deep central pacific deposition of 231pa is 4 to 5 fold greater at the margin sites the residence time of 10be with respect to chemical scavenging defined as its inventory in the water column divided by its rate of removal to the sediments varies regionally from 1000 years at the red clay sites in the deep central pacific to 100 years at the margin sites different factors control boundary scavenging of pa and be for example scavenging of 231pa is enhanced by metal oxide coatings of particles whereas this seems to have little influence on the scavenging of 10be 1990

on the importance of opal carbonate and lithogenic clays in scavenging and fractionating 230th 231pa and 10be in the ocean abstract the influence of particle composition on the scavenging of 230 th 231 pa and 10 be in the ocean is critically re examined based on the particle solution distribution coefficient k d data reported by chase et al earth planet sci lett 204 2002 215 229 our re examination shows that the k d s for these radionuclides are strongly influenced by the amount of lithogenic material lithogenics in particulates as reported previously by us and that a strong correlation between the lithogenic and carbonate contents in open ocean particulates results in an apparent non linear correlation between caco 3 and k d for each of the three radionuclides using a three end member model we estimate that the respective k d s g g of 230 th 231 pa and 10 be in the open ocean are 2 3 10 8 1 2 10 7 and 3 8 10 6 for lithogenics 1 0 10 6 1 0 10 5 and 3 0 10 4 for carbonate and 2 5 10 5 1 2 10 6 and 7 5 10 5 for opal suggesting that lithogenics have a much stronger affinity for any of the three nuclides than does carbonate or opal lithogenics and carbonate preferentially scavenge 230 th over 231 pa and 10 be whereas opal slightly favors 231 pa and 10 be over 230 th relative to lithogenics carbonate plays a very limited role in fractionating 230 th 231 pa and 10 be due to its orders of magnitude smaller k d values for the three nuclides our results indicate that fractionations between pa and th and between be and th through particle scavenging are mainly determined by the opal to lithogenic ratio in particulates rather than the opal to carbonate ratio suggested by chase et al

fault slip and seismic moment of the 1700 cascadia earthquake inferred from japanese tsunami descriptions 1 the 1700 cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in japan computed coseismic seafloor deformation for hypothetical ruptures in cascadia and tsunami modeling in the pacific ocean reports of damage and flooding show that the 1700 cascadia tsunami reached 1 5 m heights at seven shoreline sites in japan three sets of estimated heights express uncertainty about location and depth of reported flooding landward decline in tsunami heights from shorelines and post 1700 land level changes we compare each set with tsunami heights computed from six cascadia sources each source is vertical seafloor displacement calculated with a three dimensional elastic dislocation model for three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip for the other sources ruptures of ordinary width extend 360 670 km to compute tsunami waveforms we use a linear long wave approximation with a finite difference method and we employ modern bathymetry with nearshore grid spacing as small as 0 4 km the various combinations of japanese tsunami heights and cascadia sources give seismic moment of 1 9 1022 n m equivalent to moment magnitude 8 7 9 2 this range excludes several unquantified uncertainties the most likely earthquake of moment magnitude 9 0 has 19 m of coseismic slip on an offshore full slip zone 1100 km long with linearly decreasing slip on a downdip partial slip zone the shorter rupture models require up to 40 m offshore slip and predict land level changes inconsistent with coastal paleoseismological evidence

three dimensional structure of vp vs and vp vs beneath northeastern japan implications for arc magmatism and fluids we estimated both p v p and s wave velocity v s structures beneath northeastern japan by applying a tomographic method to 169 712 p and 103 993 s wave arrival time data from 4338 local events the average value of v p v s ratio is 1 69 in the upper crust 1 75 in the lower crust and 1 77 in the uppermost mantle these differences in v p v s ratio may mainly reflect the lithological variations with depth low v p low v s and high v p v s zones are extensively distributed along the volcanic front in the uppermost mantle and are downward to the back arc side in the mantle wedge here the low v p low v s and high v p v s values are interpreted because of partial melting materials which imply the presence of a vast amount of melt in the uppermost mantle in the lower crust low v p low v s and high v p v s zones are not continuously visible along the volcanic front but are confined to individual volcanic areas which suggests that melting of lower crustal materials occurs just beneath each active volcano in contrast the upper crust beneath active volcanoes exhibits low v p low v s and low v p v s these results suggest that the partial melting zones under northeastern japan spread out from the uppermost mantle along the volcanic front up to the midcrust right beneath active volcanoes the low v p low v s and low v p v s features in the upper crust suggest the existence of h 2 o rather than melt right beneath active volcanoes

productivity control of fine particle transport to equatorial pacific sediment accumulation rates of 3he from cosmic dust 230th produced in the water column barite produced in the water column during decay of organic matter and fe and ti arriving with wind borne dust all are positively correlated in an equatorial pacific core tt013 pc72 01 1 n 139 4 w water depth 4298 m these accumulation rates are also positively correlated with the accumulation rates of noncarbonate material they are not significantly correlated to the mass accumulation rate of carbonate which makes up the bulk of the sediment the fluctuations in accumulation rates of these various components from different sources thus must result from variations in some process within the oceans and not from variations in their original sources sediment focusing by oceanic bottom currents has been proposed as this process marcantonio et al 1996 we argue that the variations in the accumulation rates of all these components are dominantly linked to changes in productivity and particle scavenging 3he 230th fe ti by fresh phytoplankton detritus which delivers ba upon its decay in the equatorial pacific upwelling region we speculate that as equatorial pacific productivity is a major component of global oceanic productivity its variations over time might be reflected in variations in atmospheric levels of methanesulfonic acid an atmospheric reaction product of dimethyl sulfide which is produced by oceanic phytoplankton and recorded in antarctic ice cores

glacial to interglacial changes in carbonate and clay sedimentation in the atlantic ocean estimated from 230th measurements abstract the cause of the climatically controlled fluctuations in the carbonate content of deep sea sediments remains the subject of uncertainty and debate three variables are involved supply of biogenic carbonate loss by dissolution and dilution by non carbonate phases it is suggested that 230 th which is produced in the ocean at a constant rate provides a reliable reference for measuring variations in rate of sedimentation on a regional scale results of a preliminary analysis based on published data indicate that for depths at and above the lysocline the carbonate fluctuations observed in cores from the north atlantic ocean are due primarily to variations in the terrigenous clay input which was 2 5 times higher during glacials than during interglacials carbonate deposition appears to have been somewhat reduced during glacials but probably not by more than a factor of 2 from published 230 th 232 th profiles it appears that the south atlantic ocean also received increased inputs of terrigenous clay during glacial periods

rise of the central andean coast by earthquakes straddling the moho coastlines above subduction zones often uplift over geological timescales analysis of landscape evolution and seismicity at the central andean margin suggests that earthquakes on the deep plate interface help build up coastal topography

directly measured mid depth circulation in the northeastern north atlantic ocean the circulation of water masses in the northeastern north atlantic ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes but the ocean circulation at depths below the reach of satellite observations is difficult to measure and only recently have comprehensive direct observations of whole ocean basins been possible here we present quantitative maps of the absolute velocities at two levels in the northeastern north atlantic as obtained from acoustically tracked floats we find that most of the mean flow transported northward by the gulf stream system at the thermocline level about 600 m depth remains within the subpolar region and only relatively little enters the rockall trough or the nordic seas contrary to previous work our data indicate that warm saline water from the mediterranean sea reaches the high latitudes through a combination of narrow slope currents and mixing processes at both depths under investigation currents cross the mid atlantic ridge preferentially over deep gaps in the ridge demonstrating that sea floor topography can constrain even upper ocean circulation patterns

the influence of particle composition and particle flux on scavenging of th pa and be in the ocean we have examined the relative affinity of th pa and be for sorption from seawater onto particles of variable composition opal carbonate lithogenic particles and organic carbon nuclide concentrations in particles collected from time series sediment traps were normalized by the dissolved nuclide concentration in the overlying water column in order to compute partition coefficients under conditions spanning a wide range of particle flux and particle composition our results suggest that the affinity of particles for pa and be increases with their increasing opal content and decreasing carbonate content while the affinity of particles for th increases with increasing carbonate content and decreases with increasing opal content we find no correlation between the aluminosilicate content of particles and their affinity for scavenging of any of these elements extrapolating to a pure caco3 end member the partition coefficient for th 9 0 106 g g 1 is 40 times greater than for pa and roughly 100 times greater than for be whereas for a pure opal end member the partition coefficient for th 3 9 105 g g 1 is slightly less than that for pa and be partition coefficients decrease with increasing particle flux in open ocean settings but not in an ocean margin region this kinetic effect reflects the increasing contribution of unaltered surface material reaching the sediment traps as particle flux increases the degree of fractionation between pa and th and between be and th depends on the opal carbonate rain ratio these results challenge the use of sedimentary 231pa 230th and 10be 230th ratios as simple proxies of particle flux however the strong dependence of nuclide scavenging on the opal carbonate rain ratio may provide a needed tool for reconstructing past changes in planktonic community composition

interplate coupling in the tohoku district japan deduced from geodetic data inversion the spatial distribution and the temporal change of the strength of interplate coupling between the subducting pacific plate and overlying continental plate in the tohoku district northeast japan have been investigated through the inversion analysis of geodetic data the geodetic data used for this analysis are the rates of vertical 1966 1995 and horizontal 1979 1991 displacements which presumably represent average crustal movements during the interseismic period we incorporate smoothing constraints on back slip distribution into the observed data the degree of the constraints is controlled by hyperparameters whose optimal values are determined by minimizing akaike s bayesian information criterion abic under the assumption of abic we can obtain a unique solution the result of the inversion analysis shows that there are two regions of high coupling the first extending from 20 to 45 km in the north 40 5 n and the second extending from 25 to 55 km in the south 38 5 n the average back slip rate in the northern region reaches 55 11 mm yr 1 and in the southern region 41 14 mm yr 1 also the inversion analysis shows that the direction of the plate convergence at the japan trench is n71 3 w in the northern region and n48 5 w in the southern region the interplate coupling becomes weaker toward the shallower and deeper portions and exhibits significant temporal variation

late quaternary cryptotephra detection and correlation in loess in northeastern japan using cummingtonite geochemistry abstract we detected late pleistocene cummingtonite bearing cryptotephras in loess deposits in ne japan and correlated them with known tephras elsewhere by using major element compositions of the cummingtonite this is the first time cryptotephras have been identified by analysis of a crystal phase rather than glass shards in central ne japan four cummingtonite bearing tephras the ichihasama pumice the dokusawa tephra the naruko nisaka tephra and the adachi medeshima tephra are present in late pleistocene loess deposits because the cummingtonite chemistry of each tephra is different and characteristic it is potentially a powerful tool for detecting and identifying cryptotephras an unidentified cummingtonite bearing cryptotephra previously reported to be present in the late pleistocene loess deposits at kesennuma pacific coast did not correlate with any of the known cummingtonite bearing tephras in central ne japan but instead with the numazawa kanayama tephra erupted from the numazawa caldera southern ne japan although kesennuma is well beyond the previously reported area of the distribution of the numazawa kanayama tephra three new cummingtonite bearing cryptotephras in the mid and late pleistocene loess deposits estimated to be less than 82 ka 100 200 ka and ca 250 ka on the isawa upland were also detected

a comparative study of accumulation rates derived by he and th isotope analysis of marine sediments abstract we present a detailed down core analysis of helium isotope ratios and concentrations for bulk sediments from the central equatorial pacific that span the last two glacial interglacial cycles measured 3 he 4 he ratios range from 1 0 10 5 to 2 1 10 4 or 7 4 to 149 times the atmospheric ratio the 3he from interplanetary dust particles idps constitutes virtually all of the 3he measured within the sediment because carbonate accumulation rates are high in the equatorial pacific the measured 3he concentrations are lower than have been measured elsewhere and range from 4 7 10 13 to 3 0 10 12 cm3stp g 1 if the cosmic dust 3he flux is constant with time sediment mass accumulation rates can be determined from the 3he concentration in sediments the excess 230th technique is an entirely independent method for calculating sediment mass accumulation rates because its source is in situ decay of 234u in seawater to first order initial excess 230th activities correlate with 3he concentrations within this core based on the 230th results we estimate the 3he flux to the earth s surface as 9 6 2 0 10 16 cm3stp cm 2 a 1 if this flux has remained constant over extended periods of time it can be used to determine sediment accumulation rates beyond the 230th range 300 000 yr

interseismic deformation at the nankai trough japan subduction zone uplift along the coast of southwestern japan following the 1944 tonankai ms 8 0 and 1946 nankaido ms 8 2 earthquakes has been inferred from the 1950 1985 tide gage records although uplift rates vary with geographic position the temporal dependence at each site can be described as the superposition of an exponentially decaying time constant 5 years transient significant only in the first decade postseismic and a steady interseismic rate the steady interseismic uplift rate is defined only over the 1956 1985 interval but the linearity in time ofthat uplift record is such that uplift over the remainder of the interseismic cycle 80 years might reasonably be expected to occur at the same rate moreover the spatial pattern and magnitude of the steady uplift rate are reasonably close to those predicted by a simple dislocation model of subduction however the currently observed steady uplift rate is not consistent with the uplift rate inferred from geodetic leveling for the final half of the previous earthquake cycle thus either the hypothesis of a steady interseismic uplift rate after the first decade postseismic is wrong or the strain accumulation pattern for one earthquake need not be the same as for the preceding earthquake on the same segment

vertical deformation of the japanese islands 1996 1999 1 the interseismic vertical deformation field of the japanese islands is derived from the global positioning system gps data between 1996 and 1999 although vertical components of the gps velocities have rarely been used as important information because of their higher noise level information on the vertical deformation field will enable us to separate rigid plate motions from deformation due to interplate coupling because horizontal displacements contain both effects whereas vertical displacements contain only the interplate coupling effect the results show that 1 the precision of the vertical velocity is generally better than 2 mm yr 2 the existence of clear uplift peaks of about 8 mm yr in the shikoku and tokai regions is consistent with strong coupling with a gradual brittleplastic transition zone at the nankai and the suruga trough respectively 3 clear uplift peaks do not seem to exist in the tohoku region because the japan trench plate boundary is too far oceanward from the gps sites 4 significant uplift is obtained in the western part of hokkaido which may be associated with the long term postseismic deformation due to the 1983 japan sea and the 1993 hokkaido nansei oki m 7 6 earthquakes and 5 uplift in northeastern japan along the japan sea coast is apparently associated with distributed compression due to incipient subduction

direct dating of the oxygen isotope record of the last deglaciation by 14c accelerator mass spectrometry major trends of quaternary global climate are reflected in the continental ice volume changes which have been reconstructed by oxygen isotope analysis1 2 18o records from deep sea sediments show that the net glacial build up occurs relatively slowly3 but that the end of an ice age occurs quickly in less than 10 000 yr implying a nonlinear response4 5 to simple milankovitch theory6 the latter observation suggests that the cause of the most recent deglaciation was the maximum in summer calorific radiation at the upper latitudes of the northern hemisphere centred around 11 000 yr ago a view supported by early studies7 later work has produced conflicting dates the main source of confusion being problems with obtaining accurate and reliable dates here by using accelerator mass spectrometry we have measured 14c for various species of foraminifera to produce a reliable timescale for the oxygen isotope record our results show that at the end of the last ice age continental ice sheets began to melt more than 4 000 yr before the northern hemisphere maximum of summer calorific radiation

high resolution climate records from the north atlantic during the last interglacial the two deep ice cores recovered by the grip1 and gisp22 projects at summit greenland agree in detail over the past 100 000 years3 and demonstrate dramatic climate variability in the north atlantic region during the last glacial before the current period of holocene stability this glacial climate instability has subsequently been documented in the marine sedimentary record of surface ocean conditions in the north atlantic4 before 100 kyr ago the two ice core records are discrepant however casting doubt on whether the oxygen isotope fluctuations during the last interglacial eemian seen in the grip core1 5 represent a true climate signal here we present high resolution records of foraminiferal assemblages and ice rafted detritus from two north atlantic cores for the interval 65 kyr to 135 kyr ago extending the surface ocean record back to the eemian the correlation between our records and the greenland ice core records is good throughout the period in which the two ice cores agree suggesting a regionally coherent climate response during the eemian our marine records show a more stable climate than that implied by the grip ice core suggesting that localized phenomena may be responsible for the variability in the latter record during the eemian

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

do geochemical estimates of sediment focusing pass the sediment test in the equatorial pacific 1 the paleoceanographic recording fidelity of pelagic sediments is limited by chemical diagenesis and physical mixing bioturbation and horizontal sediment transport diagenesis and bioturbation are relatively well studied but the effects of physical sedimentation have been largely ignored modeling u series isotopes e g 230th can potentially quantify horizontal sediment movement but model horizontal sediment focusing often equals or exceeds the vertical particle rain we find no evidence of this level of sediment focusing in the equatorial pacific from geophysical data or sediment core comparisons the overestimate of sediment focusing by 230th is probably caused by poor model assumptions that sediment does not fractionate does not sort according to size during transport and that 230th cannot leak from slowly accumulating sediments both assumptions are weak u series methods do hold promise to quantify sediment focusing if properly calibrated with calibration the trade offs between seeking high sedimentation rates for better time resolution and the blurring by horizontal sediment focusing can be better assessed

japan s sediment flux to the pacific ocean revisited abstract quantifying volumes and rates of delivery of terrestrial sediment from island arcs to subduction zones is indispensable for refining estimates of the thickness of trench fills that may eventually control the location and timing of submarine landslides and tsunami generating mega earthquakes despite these motivating insights knowledge about the rates of erosion and sediment export from the japanese islands to their pacific subduction zones remains patchy regardless of the increasing availability of highly resolved data on surface deformation climate geology and topography traditionally natural erosion rates across the island arc have been estimated from regression of topographic catchment metrics and reservoir sedimentation rates that were recorded over several years to decades we review current research in this context correct for a systematic bias in one of the most widely used predictions and present new estimates of decadal to millennial scale erosion rates of japan s terrestrial inner forearc we draw on several independent and unprecedented inventories of mass wasting reservoir sedimentation and concentrations of cosmogenic 10be in river sands we find that natural 10be derived denudation rates of several mm yr 1 in the japanese alps have been sustained over several centuries to millennia and are within error roughly consistent with sediment yields inferred from artificial reservoir sedimentation local exceptions may likely result from release of sediment storage or regional landsliding episodes that trigger transient sediment pulses our synopsis further reveals that catchments draining japan s eastern seaboard differ distinctly in their tectonic lithological topographic and climatic characteristics between the tohoku japanese alps and nankai inner forearc segments which is underscored by a marked asymmetric pattern of erosion rates along the island arc erosion rates are highest up to at least 3 mm yr 1 in the japanese alps that mark the collision of two subduction zones where high topographic relief hillslope and bedrock channel steepness foster rapid denudation by mass wasting comparable if slightly lower erosion rates characterise the nankai inner forearc in southwest japan most likely due to higher typhoon driven rainfall totals and variability rather than its high topographic relief in contrast our estimated erosion and flux rates are lowest in the tohoku inner forearc catchments that feed sediment into the japan trench we conclude that collisional mountain building of the japanese alps drives some of the highest erosion rates in the island arc despite similar uplift and precipitation controls in southwest japan we infer that prior to extensive river damming reservoir construction and coastal works the gross of japan s total sediment export to the pacific ocean entered the accretionary margin of the nankai trough as opposed to the comparatively sediment starved japan trench compared to documented contemporary rates of sediment flux from mountainous catchments elsewhere in the pacific the rivers draining japan s inner forearc take an intermediate position despite high relief steep slopes very high seismicity and frequent rainstorms however the average rates of millennial scale denudation in the japanese alps particularly are amongst the highest reported worldwide local mismatches between these late holocene and modern rates emphasise the anthropogenic fingerprint on sediment retention that may have significantly reduced the island arc s mass flux to its subduction zones as is the case elsewhere in east and southeast asia

redox sensitive element uptake in north east atlantic ocean sediments benthic boundary layer experiment sites regularly increasing radiocarbon age depth profiles and near constant sediment composition with depth have demonstrated that sediment accumulation has been relatively constant during the late holocene at two north east atlantic sites on rockall bank and feni drift uk benthic boundary layer experiment sites in such a quasi steady state situation the geochemical responses to early diagenesis of the redox sensitive elements cd mn mo re se and u are readily discerned through changes in element concentrations with depth collectively a colour change in the sediments surficial mnox enriched layers and 210pbexcess profiles allow an estimate of the mean position of the oxic post oxic boundary in the sediments at both sites this boundary is situated deeper than the 210pbexcess surface mixed layer but shallower than the 14c surface mixed layer which represent mixing on 102 and 103 year time scales respectively this implies that the well defined surface mnox enrichment and its associated 226ra and mo fractions must have been efficiently recycled first by downwards mixing into anoxic conditions and then by subsequent reduction and diffusive migration back up into oxic conditions this occurs in 40 years at the feni drift site and in 103 years at the rockall bank site authigenic enrichments of se cd and u are evident immediately below the oxic post oxic boundary although re enrichment does not occur until a few centimetres deeper the long term fluxes of authigenic se cd u and re uptake are evaluated with steady state assumptions while diffusion from bottom waters can supply sufficient se u and re an additional source likely corg is required for cd

subsidence along the central to southern sanriku coast northeast japan near the source region of the 2011 tohoku oki earthquake estimated from the holocene sedimentary succession along a ria coast abstract along the sanriku coast northeast japan discrepancies in crustal movement have been reported between uplift on a scale of 105 years versus subsidence on a scale of 101 102 years well dated holocene incised valley fill sediments provide records of millennial scale vertical crustal movement which is key to understanding the tectonic history in this area previous studies of the age and distribution of early holocene intertidal deposits in incised valleys reported that the southern sanriku coast has subsided during the holocene at an average rate of about 1 mm yr here we studied three sediment cores tgi1 tgi2 and tgi3 collected from the tsugaruishi plain on the central sanriku coast and recognized a holocene deltaic sediment succession in all three cores in core tgi3 from the farthest inland site the intertidal sediment facies deposited from 7500 to 7000 cal bp and the overlying 6 m thick floodplain facies deposited from 7000 to 5000 cal bp are both below the present sea level because a sea level highstand due to hydroisostatic uplift around japan occurred in the mid holocene we inferred that the tsugaruishi plain subsided during the holocene and the estimated subsidence rate 1 1 1 9 mm yr at maximum is consistent with the recently reported subsidence rate along the southern sanriku coast the results of this study confirm that the central to southern sanriku coast is subsiding in contrast to an interpretation based on the study of marine terraces that this part of the coast is uplifting the empirical data presented here will be useful for constructing an earthquake cycle model related to plate subduction

coccolith sr ca as a new indicator of coccolithophorid calcification and growth rate 1 polyspecific coccolith separates from core top sediments in the eastern equatorial pacific show variations of 15 in sr ca ratios across the equatorial upwelling zone with sr ca highest at the equator and decreasing off axis these variations cannot be due to changes in the sr ca of seawater which varies by less than 2 in the surface ocean variations in sr ca of coccolith sediments are similar to variations in primary productivity and alkenone estimated coccolithophorid growth rates in overlying surface waters and to caco3 rain rates measured in sediment traps because of these relationships and because calcification rate exerts a strong control on sr ca in abiogenic calcites we suggest that the observed sr ca variations in coccoliths may be strongly controlled by coccolithophorid growth and calcification rates although temperature may also influence coccolith sr ca to a lesser degree changes in dissolution intensity and coccolith assemblages appear to exert a minor influence if any on coccolith sr ca in these sediment core tops if further work confirms relationships between coccolith sr ca and coccolithophorid productivity sr ca records of past changes in coccolithophorid productivity may be useful in reconstructing past variations in the rain ratio of organic to carbonate carbon an important control on deep ocean ph and partitioning of co2 between the atmosphere and ocean in addition coccolith sr ca might provide an independent record of past changes in coccolithophorid growth rates which in combination with data on the carbon isotopic fractionation in coccolithophorid organic matter may permit more reliable calculations of past dissolved co2 in the surface ocean

spatial variations in present day deformation kenai peninsula alaska and their implications from four years of global positioning system gps measurements we find significant spatial variations in present day deformation between the eastern and western kenai peninsula alaska sites in the eastern kenai peninsula and prince william sound move to the nnw relative to north america in the direction of pacific north america relative plate motion velocities decrease in magnitude from nearly the full plate rate in southern prince william sound to about 30 mm yr at seward and to about 5 mm yr near anchorage in contrast sites in the western kenai peninsula move to the sw in a nearly trenchward direction with a velocity of about 20 mm yr the data are consistent with the shallow plate interface offshore and beneath the eastern kenai and prince william sound being completely locked or nearly so with elastic strain accumulation resulting in rapid motion in the direction of relative plate motion of sites in the overriding plate the velocities of sites in the western kenai along strike to the southwest are opposite in sign with those predicted from elastic strain accumulation these data are incompatible with a significant locked region in this segment of the plate boundary trenchward velocities are found also for some sites in the anchorage area we interpret the trenchward velocities as being caused by a continuing postseismic transient from the 1964 great alaska earthquake there may be significant along strike differences in the long term behavior of the plate interface between the western and eastern kenai based on roughly coincident boundaries in the coseismic slip distribution cumulative postseismic uplift present day plate coupling and stress field the present postseismic response appears to generate purely trenchward motion suggesting a creep process that is purely dip slip our observations suggest that postseismic processes after the largest earthquakes can influence patterns of deformation for decades after the event

magnetic susceptibility patterns and provenance of ice rafted material at feni drift rockall trough implications for the history of the british irish ice sheet abstract piston core enam 97 09 from feni drift atlantic margin west of ireland provides a record of ird input variability and provenance during the last 250 000 yrs the ird patterns can be related to late devensian detrital carbonate and meta sedimentary rock fragments represent two major ird types which were dominantly derived from irish inland ice and the irish sea ice stream respectively additional evidence for the latter source is based on heavy mineral data input from other circum north atlantic ice sheets notably the laurentide ice sheet is minor compared to british irish ird at least during periods of maximum expansion of the biis this is consistent with the marginal location of the core site with reference to the main north atlantic ird belt on the other hand laurentide ird presumably accounts for minor ird peaks at times of reduced ice volume in the british isles the main magnetic susceptibility peak during late isotope stage 2 termination i can be related to ird input from the laurentide ice sheet following early decay of the biis a similar pattern is observed during oxygen isotope stage 6 these observations are consistent with recent provenance studies indicating that only laurentide ird carries a strong magnetic susceptibility signal

late quaternary uplift rate inferred from marine terraces shimokita peninsula northeastern japan a preliminary investigation of the buried shoreline angle after estimating tectonic uplift rates along the northern part of the northeast japan forearc the overriding plate in the northeast japan subduction zone by mapping the elevation of the inner edges of marine terrace surfaces we refined this estimate through elevation measurements of the buried shoreline angle beneath well dated marine terrace surfaces from which we could derive more accurate paleo sea levels the uplift rate initially inferred from the inner edge of marine terrace t4 correlated with marine isotope stage mis 5e by tephrochronology increases eastward from 0 11 0 22 m ky 1 around the backarc volcanic front to 0 17 0 32 m ky 1 in the forearc on the peninsula of shiriyazaki we refined the uplift rates for t4 on the basis of the shoreline angle elevation from the reconstructed profile of the paleo sea cliff and wave cut platform on a rocky coast and the reconstructed profile of the swash zone sediments and terrace deposits on a sandy coast the refined uplift rates were 0 14 0 25 m ky 1 on the rocky coast and 0 14 0 23 m ky 1 on the sandy coast slightly slower than the rates we inferred from the height of t4 and about one half to three fourths of previously reported rates by extrapolation from the example of the sandy coast the refined uplift rate around the volcanic front was 0 09 0 18 m ky 1 the vertical deformation across the forearc of the shimokita peninsula since mis 5e is possibly associated with regional isostatic uplift of 0 09 0 18 m ky 1 and anticlinal deformation by an offshore fault interpreted from acoustic profiles of 0 05 0 07 m ky 1

moho depth variation in the central part of northeastern japan estimated from reflected and converted waves abstract we detected reflected p and s waves at the moho in seismograms of shallow crustal earthquakes in the central part of northeastern ne japan p to s and s to p mode converted waves at the moho are also detected in seismograms of intermediate depth earthquakes in the subducted pacific slab the depth distribution of the moho in the central part of ne japan is estimated by using travel time differences between these later phases and the first p and s arrivals we collected travel time data of 496 reflected waves from 67 shallow earthquakes and 200 converted waves from 65 intermediate depth earthquakes the depth to the moho estimated is deep beneath the land and becomes shallower toward the eastern and western coastlines the moho depth is about 34 km in the middle of the land area about 30 km under the coastline of the japan sea and 27 29 km under the coastline of the pacific ocean

the indian bay formation fossiliferous early ordovician volcanogenic rocks in the northern gander terrane newfoundland and their regional significance the first reported fossiliferous rocks in the northern gander terrane of the newfoundland appalachians occur at indian bay big pond in an area previously mapped as unfossiliferous quartzose sedimentary rocks of the gander group brachiopods trilobites and bryozoans in argillaceous tuff indicate a late arenigian late early ordovician age the rocks associated with the fossils are similar to coeval rocks of the dunnage terrane in newfoundland but are atypical of the gander terrane the sequence that includes the fossiliferous rocks at indian bay big pond is here named the indian bay formation the indian bay formation may overlie the gander group stratigraphically but structural geophysical and geochemical data suggest that the rocks of the indian bay formation are contained in a klippe thrust onto the gander terrane

space geodetic observation of deep basal subduction erosion in northeastern japan abstract observation of tectonic erosion von huene and scholl rev geophys 29 1991 279 316 in a subduction zone has been difficult as it leaves little geological and geophysical evidence three dimensional velocity profiles of crustal movement obtained by global positioning system across ne and sw japan agree well with those predicted by the elastic loading of the subducting slabs however vertical velocities in the ne japan forearc show significant negative deviation relative subsidence this may indicate loss of material at the plate interface that can be attributed to the erosion of the upper plate by the underthrusting slab basal subduction erosion the estimated rate 15 mm yr down to a slab depth of 90 km is somewhat faster than the geological average the erosion speed may be variable being controlled by the surface roughness of subducting slabs

late quaternary crustal shortening rates across thrust systems beneath the ou ranges in the ne japan arc inferred from fluvial terrace deformation abstract we documented the existence of a blind thrust along the volcanic front in northeast japan and calculated the crustal shortening rate across the ou ranges we detected broad anticlinal deformation of the longitudinal profiles of fluvial terraces dated by using tephro and cryptotephrostratigraphy we inferred that the daizaki flexure located along the southern extension of the 2008 iwate miyagi nairiku earthquake imeq fault indicated the presence of an underlying thrust daizaki fault newly named there therefore we inferred the existence of a west dipping thrust system along the volcanic front at the eastern edge of the ou ranges consisting from north to south of the kitakami teichi seien fault zone the 2008 imeq fault and the daizaki fault to estimate rates of crustal deformation due to this thrust we determined the uplift rate distribution from a pair of accumulation terrace surfaces one formed during the marine isotope stage mis 6 5 glacial to interglacial transition and the other during the mis 2 1 transition because the overall uplift rate distribution includes crustal deformation at both regional and local scales we calculated the fault related deformation area by subtracting the regional uplift rate 0 15 0 18 m ky 1 obtained from a pair of fluvial terraces on the stable footwall from the total uplift rate distribution across the fault a mass balance calculation of the fault related deformation area showed the crustal shortening rate across the 2008 imeq fault to be 0 50 0 19 0 59 0 22 m ky 1 an east dipping thrust system along the western edge of the ou ranges eastern part of the shinjo basin fault zone has also contributed to crustal shortening during the late quaternary at a previously estimated rate of 0 65 1 42 m ky 1 therefore the shortening rates of the eastern and western thrust systems individually account for about 0 6 0 7 and 0 7 1 6 respectively total 1 3 2 3 of the convergence between the pacific and eurasian plates this westward increase in the shortening rate across the ou ranges is in accordance with the crustal structure which reflects the tectonic history since the miocene backarc spreading of the japan sea

pitfalls of normalization of marine geochemical data using a common divisor abstract normalization of trace element contents of sediment through division by the content of an immobile element usually aluminum is common practice in marine geochemical studies this might appear to be a simple way of correcting for dilution by sedimentary phases barren of a particular trace element for instance carbonates or silica and for comparison with its content in a standard clay or shale the purpose of this paper is to revive the awareness of the pitfalls of this practice by giving numerical examples of the often unexpected results of normalization taking a statistical perspective it is first shown that uncorrelated variables acquire spurious correlations when normalized but normalization can also increase decrease change sign of or even blur the correlations between unmodified variables next a number of realistic scenarios are worked out to show that the correlations between normalized element contents still suffer from the closure effect only in a few simple cases it is possible to extract from the normalized data realistic estimates of trace element contents in distinct sedimentary phases such as organic matter this is ascertained from data on copper contents in sediment from the black sea and arabian sea when the coefficient of variation i e standard deviation divided by the mean of the aluminum data is relatively low and much lower than for the original values of the trace elements comparisons of correlations can equally well or even better be made on the basis of the unmodified values then the comparison of trace element data with their values for standard shales is discussed the inherent problem is that the composition of the commonly used standard shale and consequently the reference values of normalized elements are not necessarily representative of the local or regional sediments in the study area also this method falls short of identifying the processes responsible for enrichment or diminution in trace element contents finally consideration is given to some aspects of a proper use of al normalization

holocene sediment fluxes in the northeast atlantic from 230thexcess and radiocarbon measurements radiocarbon and 230thexcess data from six ne atlantic box cores are considered the cores form a transect from the porcupine abyssal plain over the east thulean rise to the southern end of feni drift the chronology for the cores is established from bulk sediment carbonate radiocarbon data and reveals that sections exhibiting constant accumulation rates can be identified in all the cores with rates of 3 0 3 5 cm kyr 1 on the plain through the holocene and late holocene rates of 4 3 6 6 cm kyr 1 elsewhere five out of the six cores show accumulations of more 230thexcess than is produced in the overlying water column with the greatest inventories up to 225 of production in the cores from the rise and drift a size fraction comparison between two cores from the plain and rise reveals that the higher overall accumulation rates and 230thexcess inventories in the off plain cores are due to an increased fine 5 m component fraction whereas the flux of coarser material is similar to that received on the plain this suggests that the higher fluxes of materials observed are physically rather than biogeochemically driven and also that drift formation has been continuously active in the late holocene sections of all the cores where regular accumulation is defined by the radiocarbon data are modeled first by a linear radiocarbon age depth model and second by a constant rain 230thexcess 0 model prorated for the observed core inventories these modeling approaches yield historical mass accumulation rate estimates which are generally in reasonable agreement 30 but the differences observed appear to be well organized in time rather than random

geophysical interpretation of the geology of the northeast gander terrane newfoundland new gravity data from the northeastern portion of the gander terrane of newfoundland are analysed in association with existing gravity data these are combined with the digitized and filtered aeromagnetic and geochemical data to produce an interpretation of the subsurface geology interpretation of these data suggests that there are two extensive areas underlain at depth by rocks similar to the dunnage terrane mafic and ultramafic rocks that outcrop at the gander river ultrabasic belt these regions of ultramafic and mafic rocks extend in two north south belts throughout the study area and both may have tongues continuing seaward beneath the deadman s bay pluton the western belt the ocean pond belt probably consists of a series of granitic plutons underlain by mafic and ultramafic rocks geophysical modelling corroborates an earlier geological interpretation that the eastern belt the indian bay big pond thrust belt is a thrust sheet the lateral extent of the thrust belt is accurately determined by n

the northwest portion of the gander zone a geophysical interpretation geophysical data from the northwestern portion of the gander zone of newfoundland are used to test existing geological models and to propose amended ones for the upper crustal structure of the regi

stress driven relaxation of heterogeneous upper mantle and time dependent afterslip following the 2011 tohoku earthquake stress driven relaxation of heterogeneous upper mantle and time dependent afterslip following the 2011 tohoku earthquake yan hu 1 roland burgmann 1 naoki uchida 2 paramesh banerjee 3 and jeffrey t freymueller 4 university of california berkeley berkeley ca united states graduate school of science tohoku university japan earth observatory of singapore nanyang technological university singapore singapore university of alaska fairbanks fairbanks ak united states corresponding author yan hu earth and planetary science university of california berkeley 307 mccone hall berkeley ca 94720 usa yhu seismo berkeley edu this article has been accepted for publication and undergone full peer review but has not been through the copyediting typesetting pagination and proofreading process which may lead to differences between this version and the version of record please cite this article as doi 10 1002 2015jb012508 2015 american geophysical union all rights reserved

long term and short term vertical velocity profiles across the forearc in the ne japan subduction zone abstract we estimated the long term vertical velocity profile across the northeastern japan forearc by using the height distribution of late quaternary marine and fluvial terraces and we correlated the ages of the two marine terraces with marine isotope stages mis 5 5 and 5 3 or 5 1 by cryptotephra stratigraphy the uplift rate estimated as 0 11 0 19 m ka 1 from the relative heights between the terrace surfaces and eustatic sea levels was nearly equal to or slightly slower than the uplift rate farther inland 0 15 0 19 m ka 1 as determined from the relative heights of fill terrace surfaces in contrast the short term vertical velocity profile obtained from gps observations showed that the forearc is currently subsiding at a maximum rate of 5 4 0 4 mm yr 1 thus the current short term geodetic subsidence does not reflect long term geological tectonic movement short term vertical deformation is probably driven by subduction erosion or elastic deformation caused by interplate coupling or both however long term uplift is probably due not to moment release on the mega thrust but to crustal thickening

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

a revised dislocation model of interseismic deformation of the cascadia subduction zone 1 cas3d 2 a new three dimensional 3 d dislocation model is developed to model interseismic deformation rates at the cascadia subduction zone the model is considered a snapshot description of the deformation field that changes with time the effect of northward secular motion of the central and southern cascadia forearc sliver is subtracted to obtain the effective convergence between the subducting plate and the forearc horizontal deformation data including strain rates and surface velocities from global positioning system gps measurements provide primary geodetic constraints but uplift rate data from tide gauges and leveling also provide important validations for the model a locked zone based on the results of previous thermal models constrained by heat flow observations is located entirely offshore beneath the continental slope similar to previous dislocation models an effective zone of downdip transition from locking to full slip is used but the slip deficit rate is assumed to decrease exponentially with downdip distance the exponential function resolves the problem of overpredicting coastal gps velocities and underpredicting inland velocities by previous models that used a linear downdip transition a wide effective transition zone etz partially accounts for stress relaxation in the mantle wedge that cannot be simulated by the elastic model the pattern of coseismic deformation is expected to be different from that of interseismic deformation at present 300 years after the last great subduction earthquake the downdip transition from full rupture to no slip should take place over a much narrower zone

preceding coseismic and postseismic slips of the 2011 tohoku earthquake japan 1 we estimated the spatial and temporal evolution of the preceding aseismic slip from january 2003 to january 2011 the coseismic slip of the tohoku earthquake and the postseismic slip after the earthquake based on global positioning system gps data time dependent analysis indicates aseismic slip offshore of miyagi and fukushima prefectures from 2004 associated with a series of subduction earthquakes that overlap the aseismic slip area these preceding aseismic and coseismic slip areas are centered between the centers of the coseismic and afterslip areas of the tohoku earthquake offshore of miyagi prefecture while they overlap the coseismic and afterslip areas of the tohoku earthquake off fukushima prefecture the timing of moment magnitude nine mw9 class earthquakes appears to be controlled by multiple preceding slip events smaller earthquakes and their afterslip the preceding aseismic and coseismic slip decreased the coupling rate off the tohoku coast suggesting the possibility that the preceding slip represented a precursive stage of the tohoku earthquake the afterslip of the tohoku earthquake occurred in an area where the coseismic slip was not large complementing the large coseismic slip zone the afterslip along iwate miyagi extends up to 80 km in depth and is currently the sole mechanism of strain release in this depth range the source region of the anticipated miyagi oki earthquake shows small postseismic slip after the tohoku earthquake reflecting the energy release at the time of the earthquake aftershock activity is roughly governed by an afterslip process

removal of 230th and 231pa at ocean margins abstract uranium thorium and protactinium isotopes were measured in particulate matter collected by sediment traps deployed in the panama basin and by in situ filtration of large volumes of seawater in the panama and guatemala basins concentrations of dissolved th and pa isotopes were determined by extraction onto mno 2 adsorbers placed in line behind the filters in the in situ pumping systems concentrations of dissolved 230 th and 231 pa in the panama and guatemala basins are lower than in the open ocean whereas dissolved 230 th 231 pa ratios are equal to or slightly greater than ratios in the open ocean particulate 230 th 231 pa ratios in the sediment trap samples ranged from 4 to 8 in contrast to ratios of 30 or more at the open ocean sites previously studied particles collected by filtration in the panama basin and nearest to the continental margin in the guatemala basin contained 230 th 231 pa ratios similar to the ratios in the sediment trap samples the ratios increased with distance away from the continent suspended particles near the margin show no preference for adsorption of th or pa and therefore must be chemically different from particles in the open ocean which show a strong preference for adsorption of th ocean margins as typified by the panama and guatemala basins are preferential sinks for 231 pa relative to 230 th furthermore the margins are sinks for 230 th and to a greater extent 231 pa transported by horizontal mixing from the open ocean

gravity and magnetic interpretation of the deer lake basin newfoundland detailed reconnaissance gravity surveys in the deer lake carboniferous basin have been conducted using a station spacing of 2 5 km the digitized aeromagnetic data for the basin were reduced to a 1 253 440 scale composite map these two data bases were used to determine the configuration of major features and the total sediment thickness at various locations in the basin preliminary seismic results from reflection and refraction seismic surveys planned on the basis of these results are discussed modelling of gravity and magnetic data indicates that the humber syncline contains approximately 1 2 km of sediments underlain on the west by rocks similar to the long range complex the eastern limb of the syncline is underlain by rocks similar to the gull pond igneous suite the howley formation is deduced to be approximately 1 5 km thick and floored by rocks similar to the topsails igneous suite

radiometrically determined sedimentary fluxes in the sub polar north atlantic during the last 140 000 years abstract we have examined the record of sediment input during the last 140 000 years in a deep sea core from 49 27 n 22 16 w in the eastern north atlantic using uranium series disequilibria to constrain time we have calculated mass fluxes of total sediment as well as mass and particle fluxes of major sedimentary components sediment accumulation rates were generally lower and relatively constant during broadly defined interglacial intervals driven primarily by the burial of biogenic material accumulation rates were higher and more variable during glacial intervals and were influenced primarily by terrigenous material peaks in bulk mass fluxes were associated with particular episodes heinrich events within the last glacial and during each of the last two deglaciations the flux of ice rafted debris as uniquely identified by coarse detrital fragments was higher during layers representing each of the glacial heinrich events with modest increases during events h3 and h6 and dramatic increases during the others confirming the widespread interpretation of these layers as episodes of enhanced iceberg delivery the burial flux of foraminifera was markedly lower during each of the glacial heinrich events also confirming the original identification of these layers as barren intervals ice rafting events within marine isotope stage 5 left neither a large detrital nor biogenic flux imprint at our study site variations in the burial rates of non carbonate sediments were largely responsible for overall changes in sediment accumulation throughout the last climate cycle ice rafting was apparently an important delivery mechanism for this terrigenous material the instantaneous chronometer established here for the last 140 000 years in the subpolar north atlantic allows the transformation of existing and subsequent data from relative values to absolute burial fluxes

reply to comment on on the importance of opal carbonate and lithogenic clays in scavenging and fractionating 230th 231pa and 10be in the ocean we extend our analysis of the chase et al data earth and planetary science letters 204 2002 215 229 to those other than from the equatorial pacific and the southern ocean the analysis offers support to our previous conclusion that kd th for carbonate is on the order of 1 0 106 g g or about two orders of magnitude smaller than that for open ocean lithogenics there is a lowering of kd th of lithogenics at high lithogenic sites attributable to factors including the sediment remobilization from ocean margin deposits but the lowered kd th of lithogenics is still about one order of magnitude greater than that of carbonate at those high lithogenic sites using an independent method we estimate that kd l th is 2 2 0 9 108 g g at stations adjacent to our eqpac sites reinforcing our conclusion that the major scavenger for 230th is lithogenic not carbonate particles even in the low lithogenic open ocean

three dimensional dislocation model for great earthquakes of the cascadia subduction zone there have been no historical cascadia great subduction thrust earthquakes but there is good recent evidence that very large earthquakes have occurred in the past and that strain is building up toward a future great event geodetic measurements in the coastal region from northern california to southern british columbia show vertical and horizontal deformation as expected for the strain accumulation of a locked thrust fault the segment of the subduction thrust that is locked and may rupture in future great events has previously been estimated through two dimensional 2 d elastic dislocation modeling of interseismic deformation geodetic data in this study a general 3 d dislocation model for thrust faults has been developed that accommodates curved fault geometry and nonuniform interseismic locking or coseismic rupture the model is based on die surface deformation due to shear faulting in an elastic half space the 3 d model of the cascadia subduction zone calculates the surface deformation for a locked zone or a rupture zone of variable width along the margin the bend in the margin trend and subducting slab end effects are included there is a downdip transition zone between interseismic completely locked and free slip portions of the fault or between coseismic full rupture and no displacement an initial 3 d model based upon 2 d dislocation models and upon thermal constraints was adjusted to optimize the fit of the predicted interseismic surface deformation to current deformation geodetic data the best fit model has the thrust locked along the whole margin with an average locked zone width of 60 km and a transition zone width of 60 km the two zones lie mainly offshore beneath the continental shelf and slope the locked and transition zone widths vary smoothly along the margin being greater off northern washington where the thrust dip is shallow and narrower off central oregon assuming that the locked plus transition zones approximate the maximum coseismic rupture area these widths permit amw 9 earthquake

holocene sediment deposition on a ne atlantic transect including feni drift quantified by radiocarbon and 230thexcess methods radiocarbon and 230thexcess measurements were undertaken on the sediments from fifteen box cores recovered between 48 58 n and 12 22 w at water depths of 1100 4500 m in the northeast atlantic eight of the cores were from feni drift in the rockall trough at depths of 1700 2500 m and the remaining seven formed an approximate north south transect at various water depths from the abyssal plain north on to rockall plateau mean holocene sediment accumulation fluxes for all cores were established from profiles of bulk sediment radiocarbon age against depth to be in the range 3 7 cm ky 1 off the drift and 4 23 cm ky 1 on the drift when compared with these radiocarbon based sediment accumulation rates precision measurements of 230th reveal that the 230thexcess levels present in the sediments match or slightly exceed the potential supply from the vertically overlying water column in a majority of the cores one core from the open abyssal plain that had the lowest radiocarbon based accumulation rate in the entire set also had a close balance between predicted and measured 230thexcess values with the assumption that only 230thexcess produced in the overlying water column is supplied to the sediments the 230thexcess values in this core and the other six containing carbonate ooze sediments all imply a rather constant regionally averaged sedimentation flux of 2 0 0 2 1 n 7 min 1 8 max 2 3 g cm 2 ky 1 rather than matching the 230thexcess fluxes implied by the radiocarbon data this singular value is similar to the mean holocene flux reported for the northeast atlantic by previous work that utilized the 230thexcess method although it is somewhat lower than estimates for the holocene based on oxygen isotope stratigraphy or radiocarbon methods the current transport processes that result in the high sediment accumulation rates on feni drift have also resulted in a compositional fractionation of the sediments all sediments from feni drift have lower caco3 contents than the remainder of the sediments studied and these are accompanied by lower 230thexcess specific activities than are found at comparable water column depths elsewhere on the transect consistently higher and more variable regional sediment accumulation fluxes are therefore calculated from the feni drift 230thexcess data with the constant flux assumption average 2 8 0 4 g cm 2 ky 1 n 8 min 2 3 max 3 3 some 40 higher than the constant value measured in the other cores it seems likely that the mean sediment accumulation flux at feni drift inside rockall trough is consistently higher than on the open ocean margin of the basin so that the regionally averaged sedimentation fluxes indicated for the drift by the measured 230thexcess data are also consistently higher than the singular value measured elsewhere in the northeast atlantic

glacial interglacial changes in sediment rain rate in the sw indian sector of subantarctic waters as recorded by 230th 231pa u and δ15n high resolution records of opal carbonate and terrigenous fluxes have been obtained from a high sedimentation rate core md84 527 43 50 s 51 19 e 3269 m by normalization to 230th this method estimates paleofluxes to the seafloor on a point by point basis and distinguishes changes in sediment accumulation due to variations in vertical rain rates from those due to changes in syndepositional sediment redistribution by bottom currents we also measured sediment 15n to evaluate the changes in nitrate utilization in the overlying surface waters associated with paleoflux variations our results show that opal accumulation rates on the seafloor during the holocene and stage 3 based on 14c dating were respectively tenfold and fivefold higher than the vertical rain rates at this particular location changes in opal accumulation on the seafloor appear to be mainly controlled by sediment redistribution by bottom currents rather than variations in opal fluxes from the overlying water column correction for syndepositional sediment redistribution and the improved time resolution that can be achieved by normalization to 230th disclose important variations in opal rain rates we found relatively high but variable opal paleoflux during stage 3 with two maxima centered at 36 and 30 kyr b p low opal paleoflux during stage 2 and deglaciation and a pronounced maximum during the early holocene we interpret this record as reflecting variations in opal production rates associated with climate induced latitudinal migration of the southern ocean frontal system sediments deposited during periods of high opal paleoflux also have high authigenic u concentrations suggesting more reducing conditions in the sediment and high pa 231 th 230 ratios suggesting increased scavenging from the water column sediment 15n is circa 1 5 per mil higher during isotopic stage 2 and deglaciation the low opal rain rates recorded during that period appear to have been associated with increased nitrate depletion this suggests that opal paleofluxes do not simply reflect latitudinal migration of the frontal system but also changes in the structure of the upper water column increased stratification during isotopic stage 2 and deglaciation could have been produced by a meltwater lid leading to lower nitrate supply rates to surface waters

asynchronous alkenone and foraminifera records from the benguela upwelling system abstract radiocarbon stratigraphy is an essential tool for high resolution paleoceanographic studies age models based on radiocarbon ages of foraminifera are commonly applied to a wide range of geochemical studies including the investigation of temporal leads and lags the critical assumption is that temporal coupling between foraminifera and other sediment constituents including specific molecular organic compounds biomarkers of marine phytoplankton e g alkenones is maintained in the sediments to test this critical assumption in the benguela upwelling area we have determined radiocarbon ages of total c37 c39 alkenones in 20 samples from two gravity cores and three multicorer cores the cores were retrieved from the continental shelf and slope off namibia and samples were taken from holocene deglacial and last glacial maximum core sections the alkenone radiocarbon ages were compared to those of planktic foraminifera total organic carbon fatty acids and fine grained carbonates from the same samples interestingly the ages of alkenones were 1000 to 4500 yr older than those of foraminifera in all samples such age differences may be the result of different processes bioturbation associated with grain size effects lateral advection of recycled material and redeposition of sediment on upper continental slopes due to currents or tidal movement are examples for such processes based on the results of this study the age offsets between foraminifera and alkenones in sediments from the upper continental slope off namibia most probably do not result from particle selective bioturbation processes resuspension of organic particles in response to tidal movement of bottom waters with velocities up to 25 cm s recorded near the core sites is the more likely explanation our results imply that age control established using radiocarbon measurements of foraminifera may be inadequate for the interpretation of alkenone based proxy data observed temporal leads and lags between foraminifera based data and data derived from alkenone measurements may therefore be secondary signals i e the result of processes associated with particle settling and biological activity

variations in terrigenous input into the deep equatorial atlantic during the past 24 000 years estimates of terrigenous fluxes at three different water depths at two sites in the equatorial atlantic by normalization against excess 230 th flux indicate that the flux of terrigenous material to the seafloor was significantly higher during the last glacial period than it is today fluxes started to decrease during deglaciation and reached minimal values in the middle of the holocene from 15 000 to 5 000 years ago there was a substantial increase in flux with increasing water depth below 2 800 meters this increase may reflect resuspension and lateral transport of slope and rise sediment possibly because of intensification of deepwater circulation during that period

accurate determination of the pleistocene uplift rate of the ne japan forearc from the buried mis 5e marine terrace shoreline angle abstract we used tephra and phytolith stratigraphy to refine pleistocene marine terrace chronology with reference to reported eustatic sea levels associated with the dated marine terraces and estimated uplift rates along the northern part of the northeast ne japan forearc the overriding plate in the northeast japan subduction zone by using elevation measurements of the buried shoreline angle beneath well dated marine terrace surfaces to derive more accurate paleo sea levels on the kamikita plain northernmost honshu island the t4 and t3 marine terraces were correlated to marine isotope stage mis 5e and mis 7c or 7e respectively by the stratigraphic positions of the tephras toya mis 5d and wp mis 7b the t2 terrace surface which had previously been assigned to mis 7 is buried by loess correlated to mis 8 by its phytolith assemblage therefore this terrace can be reasonably re correlated to mis 9 the reported optically stimulated luminescence ages for middle pleistocene terrace deposits tend to be younger than these refined terrace ages we used the buried shoreline angle elevation determined from the reconstructed profile of the marine terrace deposits and paleo sea cliff to refine the uplift rate of t4 since mis 5e the accurate rate thus determined 0 18 0 26 m ky is slower than the rates initially inferred from the inner edge of t4 but faster than the reported rate 0 14 0 19 m ky as recalculated here inferred from the assumed mis 5e shoreline elevation in addition it is roughly compatible with the rate inferred by using the top of t2 lagoon deposits to determine the shoreline elevation during mis 9 therefore during the last 300 ka the uplift rate of the kamikita plain has been constant at about 0 2 m ky this pleistocene uplift is probably attributable to a combination of moment release on the megathrust isostatic uplift driven by crustal thickening and reverse faulting of the upper crust

distribution of 230th in the labrador sea and its relation to ventilation abstract measurements of dissolved and particulate230th and232th by thermal ionization mass spectrometry were made on samples collected from the labrador sea and the denmark strait and iceland scotland overflow waters the large scale feature of low and invariant230th evident in deep waters of the labrador sea and previously observed in the deep northern atlantic can be reproduced using a reversible scavenging model that includes the effect of ventilation advective transport also must be important in the redistribution of230th in other regions of the atlantic and for other long lived tracers such as231pa 26al and10be

an assessment of coastal tectonics along the sanriku coast northeast japan from a holocene sedimentary succession in the kuji plain abstract holocene sedimentary successions in tectonically active regions are key to understanding coastal tectonics because they provide information on millennial scale crustal movements recent analyses of holocene sedimentary successions along the sanriku coast near the source region of the 2011 tohoku oki earthquake have reported millennial scale subsidence in central to southern parts of the coast but only one comparable dataset is available for the northern part of the coast to obtain a comprehensive understanding of millennial scale crustal movements along the sanriku coast we obtained well dated holocene sediment cores from the kuji plain in the northern part of the coast these cores record a transgressive barrier lagoon system from ca 9500 to 8000 cal bp a regressive prodelta to delta front from ca 8000 to 6500 cal bp and a subsequent wave influenced shallow marine and fluvial environment the early to mid holocene relative sea level in the study area estimated from the sedimentary environment at that time is higher than that in the tsugaruishi plain central sanriku coast where millennial scale subsidence was previously inferred this discrepancy indicates that the kuji plain has been uplifted relative to the tsugaruishi plain on a millennial scale the contrast in the millennial scale crustal movements between relative uplift on the northern sanriku coast and recently inferred subsidence on the central to southern sanriku coast confirms that the sanriku coast contains multiple areas of crustal deformation furthermore this spatial distribution of millennial scale crustal movements is in good agreement with the recently reported mis 5 marine terrace distribution suggesting a continuous southward tilting trend along the sanriku coast since ca 100 ka

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

sediment flux patterns in the northeastern atlantic variability since the last interglacial abstract the distribution of terrigenous and carbonate absolute accumulation rates in the northeastern atlantic during the last climatic cycle shows that climate and sediment accumulation are closely coupled either directly or through oceanic circulation and eustatic variation the strong contrast between the glacial and holocene flux distribution is related to oceanic circulation changes either surface circulation which governs both the ice rafting supply and the planktonic biogenic production or more particularly deep circulations via the reinitiation of the iceland scotland overflow glacial erosion and the low sea level stand enhance the terrigenous supply but the holocene deep circulation reinforcement leads to important material reworking as a consequence an almost constant average sediment flux is obtained 4g 2 ky 1 during the holocene compared to 4 7 g cm 2 ky 1 during the glacial period during the holocene period the notable increase in mean carbonate flux from 1 5 to 3 g cm 2 ky 1 is associated with carbonate biogenic production but the carbonate flux distribution shows the influence of redistributive agents on margins fluxes do not simply decrease from continental sources to the oceanic basin eustatic drops leads to a shift in the areas of preferential accumulation from the upper to the lower slope during the deglacial warming period the fluxes are respectively an average of two and three times higher than during the holocene and the glacial periods their importance highlights the major impact of rapid climatic changes finally local conditions the location of terrigenous sources and the presence of contour currents are among the many factors which will modify the trends observed on a global scale

spatial and temporal offsets between proxy records in a sediment drift chronologies for late quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information a key premise is that microfossils and other indicators within a given sediment horizon are of equal age we show here that haptophyte derived alkenones isolated from bermuda rise drift sediments are up to 7000 years older than coexisting planktonic foraminifera this temporal offset which is apparently due to lateral transport of alkenones on fine grained particles from the nova scotian margin markedly influences molecular estimates of sea surface temperatures more broadly the observation raises questions about both the temporal and the geographic fidelity of paleoenvironmental records encoded by readily transported components of sediments

microfossil evidence for land movements associated with the ad 1964 alaska earthquake microfossil diatom and pollen data from a number of cores at coastal marshes at girdwood flats and kenai flats in cook inlet alaska suggest that there was a phase of gradual land subsidence prior to the main shock of the ad 1964 earthquake this phase followed a long period of gradual land uplift since the last large earthquake which occurred about 730 900 years ago caesium 137cs records indicate that subsidence started approximately 15 years before the 1964 earthquake this pre seismic subsidence is evident in the coastal marsh sediment sequences in changes in diatom and pollen assemblages that indicate changes in tidal marsh environments or a change from raised bog to marsh conditions the microfossil evidence indicates 0 15 m pre seismic land subsidence at both girdwood flats and kenai flats and co seismic subsidence of 1 8 m and 0 2 m respectively

late quaternary crustal shortening rate across the shinjo basin northeast japan 1 the active fault and fold belt in the eastern shinjo basin has contributed to late quaternary crustal shortening of the northeastern japan arc the geometries of several deformed strata and geomorphic surfaces recorded different rates of cumulative shortening fluvial terraces as old as 290 ka were dated by 14c and fission track dating and tephrochronology we used published seismic profiles to constrain the deep structure of the belt vertical offsets of different terrace surfaces show that the slip rate of the chojahara fault in the innermost basin has increased through time on the basis of its seismic profile this fault was interpreted to dip at a high angle the funagata anticline between the chojahara fault and the ou ranges was probably caused by a low angle blind thrust at about a 2 km depth the different geometries between the basin sediments and fluvial terraces caused by the blind thrust indicate downward propagation of the thrust through time synchronous development of the chojahara fault increased slip rate and the blind thrust beneath the funagata anticline downward propagation suggests that these faults form a piggyback fault system connecting to the deep part of the basin bounding kyodanbara fault estimated crustal shortening rates are averaged to be 0 65 1 05 and 0 79 1 42 m kyr over the last 200 260 and 12 28 ka respectively accounting for about 0 7 1 6 of the convergence between the pacific and eurasian plates estimated strain rates are 0 07 0 11 and 0 08 0 14 ppm yr for the last 200 260 and 12 28 ka respectively

a geophysical interpretation of the geology of conception bay newfoundland geophysical data from conception bay and the adjacent peninsulas of the avalon peninsula newfoundland are presented and quantitatively interpreted using two dimensional models to interpret the geology beneath the bay the portion of the bay underlain by mafic volcanic rocks is determined and the maximum extent of the cambro ordovician rocks containing the wabana hematite deposit is delineated all gravity and magnetic anomalies in the area are explained in terms of density and magnetic susceptibility variations confined to the upper 12 km of the crust the geophysical models indicate that mafic volcanics underlie a significant portion of the study area and are more extensive than indicated by the surface outcrop on land the models also indicate significant vertical movement on the topsail fault and on the extension of a fault passing out into the bay near holyrood the cambro ordovician sediments are confined to the southern portion of the block bounded by these faults the geophysical data are unable t

a fluvial record of long term steady state uplift and erosion across the cascadia forearc high western washington state six late quaternary river terraces preserved along the clearwater river in northwestern washington state provide a 140 ka record of long term incision and uplift across the western side of the cascadia forearc high terrace ages are constrained by weathering rind and radiocarbon dating and by correlation to dated coastal glacio fluvial deposits and the global eustatic curve the terraces overlie flat bedrock surfaces called straths which represent uplifted segments of the river channel bedrock incision is measured by the height of a strath relative to the adjacent modern river channel the straths along the clearwater show an upstream increase in bedrock incision ranging from 0 at the coast to a maximum of 110 m in the headwaters the incision at any point along the profile increases systematically with strath age the calculated incision rates range from 10 ky the clearwater river valley has maintained a steady state profile defined by a long term balance in the rates of incision and rock uplift upstream divergence of terraces is best explained by an increase in the rate of rock uplift from the coast toward the central part of the range these results are consistent with other evidence indicating a long term steady state balance between the accretionary influx and the erosional outflux for this part of the cascadia subduction wedge since 14 ma these results help show how terrace deposits form in tectonically active landscapes the dominantly fluvial clearwater drainage was forming straths while alpine glaciers were advancing in adjacent drainages in turn the straths were buried during the transition to interglacial times because of increased sediment supply due to local deglaciation and because of eustatic highstands that forced aggradation in the lower reach of the drainage and across the continental shelf as well the fluvial system shows strong forcing by the glacial climate cycle even so the river appears to have returned to the same valley profile during each cycle of strath cutting thus bedrock incision is clearly unsteady at time scales shorter than the glacial climate cycle 100 ky but appears to be relatively steady when averaged over longer time scales a simple kinematic model is used to examine how uplift of the cl our analysis indicates that the accretionary flux into the wedge occurs mainly by frontal accretion and not by underplating if accretion occurred entirely at the front of the wedge the present west coast should be moving to the northeast at 3 m ky relative to a fixed puget sound this prediction is in good agreement with offset of a 122 ka sea cliff preserved at the southwest side of the clearwater valley profile in this case the long term margin perpendicular shortening would account for 20 to 35 percent of the geodetically measured northeast southwest shortening across the olympic mountains

comment on on the importance of opal carbonate and lithogenic clays in scavenging and fractionating 230th 231pa and 10be in the ocean by s luo and t l ku luo and ku have reanalyzed part of the data set we published in 2002 to address the question of the differential scavenging of thorium protactinium and beryllium by different particulate phases organic carbon lithogenic material opal and calcium carbonate they conclude upon reanalysis that the data are consistent with their earlier proposal based on sediment separation experiments that lithogenic material possesses an affinity for th some 500 times greater than do biogenic phases while we welcome new analyses and fresh interpretations of our data set we have to disagree with their conclusion that the partition coefficient kd for adsorption of th onto lithogenic particles kd th l is on the order of 2 3 108 and far greater than the kd for adsorption of th onto calcium carbonate kd th c here we show that such a high value for kd th l is inconsistent with a large body of observations these observations suggest kd th l is closer to 1 107 consistent with our previous study

a geochemical criterion for the recognition of heinrich events and estimation of their depositional fluxes by the 230thexcess 0 profiling method abstract a core from the armorican seamount 46 23 8 n 12 32 8 w 3849 m in the deep ne atlantic southwest of the british isles exhibits unusual mg al ratios in the sediments deposited during the last glacial period high mg al ratio values are restricted within layers of 14 cm thick and mark the presence of ice rafted detrital material deposited by heinrich events h1 h2 and h4 these peaks in the ratio are caused by local increases in the dolomite quartz and feldspar content and concomitant dilutions in the phyllosilicate content which overall increase mg and decrease al the known times of the heinrich events provide a chronology for the core and indicate a considerably slower mean sediment accumulation rate during and after the glacial interglacial transition 2 2 cm ky 1 than in earlier glacial times mean 5 6 cm ky 1 within the glacial however 230 th excess 0 profiling demonstrates that accumulation fluxes were at least 7 higher than normal during the deposition of heinrich events up to 25 g cm 2 ky 1 versus a background glacial level of 3 7 g cm 2 ky 1 because of post depositional bioturbation peak fluxes are likely to have been even higher the 230 th excess 0 method also reveals the presence of event h3 which bears minor dolomite and is the least well developed of the last four heinrich events despite the marked compositional and flux variations the total mass deposited at this site is estimated at only 2 4 4 9 and 7 9 g cm 2 for events h1 h2 and h4 respectively these inventories were deposited over maximum periods of 2 0 1 1 and 0 7 ky respectively but delivery could have been much more rapid of the order of a few hundred years

the influence of caco3 dissolution on core top radiocarbon ages for deep sea sediments radiocarbon ages on caco3 from deep sea cores offer constraints on the nature of the caco3 dissolution process the idea is that the toll taken by dissolution on grains within the core top bioturbation zone should be in proportion to their time of residence in this zone if so dissolution would shift the mass distribution in favor of younger grains thereby reducing the mean radiocarbon age for the grain ensemble we have searched in vain for evidence supporting the existence of such an age reduction instead we find that for water depths of more than 4 km in the tropical pacific the radiocarbon age increases with the extent of dissolution we can find no satisfactory steady state explanation and are forced to conclude that this increase must be the result of chemical erosion the idea is that during the holocene the rate of dissolution of caco3 has exceeded the rain rate of caco3 in this circumstance bioturbation exhumes caco3 from the underlying glacial sediment and mixes it with caco3 raining from the sea surface

late quaternary uplift rate inferred from marine terraces muroto peninsula southwest japan forearc deformation in an oblique subduction zone abstract tectonic uplift rates across the muroto peninsula in the southwest japan forearc the overriding plate in the southwest japan oblique subduction zone were estimated by mapping the elevations of the inner edges of marine terrace surfaces the uplift rates inferred from marine terraces m1 and m2 which were correlated by tephrochronology with marine isotope stages mis 5e and 5c respectively include some vertical offset by local faults but generally decrease northwestward from 1 2 1 6 m ky 1 on cape muroto to 0 3 0 7 m ky 1 in the kochi plain the vertical deformation of the muroto peninsula since mis 5e and 5c was interpreted as a combination of regional uplift and folding related to the arc normal offshore muroto misaki fault a regional uplift rate of 0 46 m ky 1 was estimated from terraces on the muroto peninsula and the residual deformation of these terraces was attributed to fault related folding a mass balance calculation yielded a shortening rate of 0 71 0 77 m ky 1 for the muroto peninsula with the muroto misaki fault accounting for 0 60 0 71 m ky 1 but these rates may be overestimated by as much as 10 given variations of several meters in the elevation difference between the buried shoreline angles and terrace inner edges in the study area a thrust fault model with flat 5 10 dip and ramp 60 dip components is proposed to explain the shortening rate and uplift rate of the muroto misaki fault since mis 5e bedrock deformation also indicates that the northern extension of this fault corresponds to the older muroto flexure

palaeo oceanography deepwater variability in the holocene epoch the conversion of surface water to deep water in the north atlantic results in the release of heat from the ocean to the atmosphere which may have amplified millennial scale climate variability during glacial times1 and could even have contributed to the past 11 700 years of relatively mild climate known as the holocene epoch 2 3 4 here we investigate changes in the carbon isotope composition of benthic foraminifera throughout the holocene and find that deep water production varied on a centennial millennial timescale these variations may be linked to surface and atmospheric events that hint at a contribution to climate change over this period

late quaternary uplift rate of the northeastern japan arc inferred from fluvial terraces abstract crustal uplift rates of the isawa upland in the central part of the northeastern japan forearc are estimated using the height distribution of late quaternary fluvial terraces the ages of fluvial terraces are correlated to marine isotope stages miss by tephrochronology and 14c dating the latest and older fill terrace surfaces were correlated to mis 2 1 and mis 6 5 respectively the incision rate estimated as 0 15 0 19 0 07 m ky 1 from the relative heights of the fill terrace surfaces agrees roughly with the uplift rate along the pacific coast 0 14 0 23 m ky 1 determined from an mis 5 5 marine terrace surface in contrast geodetic surveys leveling surveys and gps observations show that the forearc is currently subsiding at a maximum rate of 5 6 mm y 1 thus the current geodetic subsidence does not reflect long term geological tectonic movement vertical deformation of the northeastern japan forearc is unique in terms of its direction and rate as a deformation process of an overriding plate in an erosion dominant subduction zone