pacific ocean heat content during the past 10 000 years observed increases in ocean heat content ohc and temperature are robust indicators of global warming during the past several decades we used high resolution proxy records from sediment cores to extend these observations in the pacific 10 000 years beyond the instrumental record we show that water masses linked to north pacific and antarctic intermediate waters were warmer by 2 1 0 4 c and 1 5 0 4 c respectively during the middle holocene thermal maximum than over the past century both water masses were 0 9 c warmer during the medieval warm period than during the little ice age and 0 65 warmer than in recent decades although documented changes in global surface temperatures during the holocene and common era are relatively small the concomitant changes in ohc are large

a simple evaluation of cleaning procedures on fossil benthic foraminiferal mg ca 1 recent studies suggest that benthic foraminiferal mg ca may be useful in reconstructing deep water temperature changes during the quaternary and on longer timescales rosenthal et al 1997 lear et al 2000 martin et al 2002 because changes in deep water temperature may be small sample preparation could play an important role in reconstructing accurate temperatures from shell mg ca a simple examination of changes in measured shell chemistry of benthic foraminifera from two intervals subjected to increasingly rigorous cleaning reveals that fossil benthic foraminiferal samples cleaned by oxidation yield lower mg ca values than samples only rinsed and weak acid leached reductive cleaning further lowered the shell mg ca of one of the two benthic species examined lower mg ca values following oxidation and reduction appear to reflect removal of contaminant mg associated with remnant organic matter and adsorbed phases

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

thermocline dynamics in the northwestern tropical pacific over the past 700 kyr abstract variations in thermoclinal conditions play an important role in the evolution of the western pacific warm pool wpwp and in connecting the tropical and extratropical regions of the pacific ocean however secular thermoclinal changes in the northwestern part of the wpwp and their forcing mechanisms are not yet well understood particularly on orbital timescales in this study we report thermoclinal variation at site md06 3047 b in the western philippine sea over the last 700 kyr our data show that variations in thermocline temperature and salinity in the study area were correlated with changes in earth s obliquity with warmer and saltier colder and fresher thermocline waters corresponding to high low earth axial obliquity at high obliquity increases in thermocline temperature and salinity may have been linked to advection of warm north pacific tropical water in the study area a lower higher vertical temperature gradient in the upper water column suggests a deeper shallower thermocline during glacials interglacials the main factor leading to thermoclinal deepening during glacials was strengthening of the east asian winter monsoon eawm and more la nina like conditions may have contributed to concurrent subsurface warming and thus thermoclinal deepening in phase thermoclinal deepening in the northern and peri equatorial southern wpwp during glacial stages may have been triggered by changes in glacial boundary conditions such as increased ice sheet thickness through intensification of the eawm and strengthening of the tropical trade winds

difference in acoustic properties at seismogenic fault along a subduction interface application to estimation of effective pressure and fluid pressure ratio abstract fluid pressure along subduction plate boundaries plays a role in seismogenesis and tsunami genesis because it is strongly related to the physical properties of faults in this study we conducted p wave velocity vp and s wave velocity vs measurements for the hanging wall and footwall of a fossil subduction interface with pseudotachylyte located at the northern edge of the mugi melange in the cretaceous shimanto belt shikoku southwest japan this area corresponds to the depth of the shallow seismogenic zone in the transition zone between the inner and outer wedges by combining the acoustic properties with parameters obtained from amplitude variation with offset avo analysis on the nankai seismic profile we estimated the fluid pressure at the seismogenic fault the mugi melanges are composed of shale matrices and are juxtaposed with the coherent unit of the hiwasa formation in the north which is composed mainly of sandstone we collected 5 sandstone samples from the hanging wall hiwasa formation and 4 mudstone samples from the footwall mugi melange we conducted velocity measurements while controlling both the fluid pressure and confining pressure by using two pumps the effective pressure in each measurement ranged from 5 to 65 mpa with intervals of 5 mpa the vp and vs of sandstone increase exponentially with effective pressure from 4500 to 5000 m s and 2500 to 3000 m s respectively the vp and vs of the mudstone also increased exponentially from 4100 to 4500 m s and 1900 to 2200 m s respectively we used avo parameters along the decollement based upon a seismic profile of the nankai trough which is off muroto 40 45 km landward from the trench axis corresponding to approximately 66 mpa of effective pressure under a hydrostatic condition by combining the velocities obtained from this study and the avo parameters derived from the muroto seismic data we estimate the mean effective pressures for the hanging wall and the footwall as approximately 10 20 mpa and 8 10 mpa respectively the normalized fluid pressure ratios for the hanging wall and the footwall correspond to approximately 0 82 0 91 and 0 91 0 93 respectively this high fluid pressure indicates a very low effective friction coefficient along the decollement in the transition zone possibly causing a rupture to propagate to the shallower outer wedge and thus generating a large tsunami

el nino variability off peru during the last 20 000 years here we present a high resolution marine sediment record from the el nino region off the coast of peru spanning the last 20 000 years sea surface temperature photosynthetic pigments and a lithic proxy for el nino flood events on the continent are used as paleo el nino southern oscillation proxy data the onset of stronger el nino activity in peru started around 17 000 calibrated years before the present which is later than modeling experiments show but contemporaneous with the heinrich event 1 maximum el nino activity occurred during the early and late holocene especially during the second and third millennium b p the recurrence period of very strong el nino events is 60 80 years el nino events were weak before and during the beginning of the younger dryas during the middle of the holocene and during medieval times the strength of el nino flood events during the last millennium has positive and negative relationships to global and northern hemisphere temperature reconstructions

deformation and fluid flow of a major out of sequence thrust located at seismogenic depth in an accretionary complex nobeoka thrust in the shimanto belt kyushu japan 1 nobeoka thrust in kyushu southwest japan was investigated to understand the relationship between the seismogenic out of sequence thrust ost and fluid flow in accretionary prisms the nobeoka thrust is a fossilized ost being active at seismogenic depth the hanging wall exhibits a penetrative plastic deformation while a brittle cataclastic melange like occurrence characterizes the footwall although both of them have same shale and sandstone dominant protolith vitrinite reflectance analyses indicate that the maximum temperatures of the hanging wall and footwall are approximately 320 and 250 c respectively this thermal gap across the thrust corresponds to 8 6 14 4 km of displacement assuming a 28 47 c km geothermal gradient the brittle damage zone of the thrust is asymmetric only 2 m for hanging wall side and 100 m for footwall three types of mineral veins quartz and carbonate are well developed especially in the damaged footwall the tension crack filling vein the fault filling vein and postmelange one the first is harmonious with fabric perpendicular to the p surface fluid inclusion geothermobarometry indicates the p t of fluid in the intensively damaged zone of the footwall is 300 c 230 250 mpa higher than that from vitrinite reflectance which suggests that hydrothermal fluid flow is associated with deformation the same type vein in the lowest portion of the footwall damaged zone includes a much lower p t fluid this difference suggests that continuous underplating caused the damaged zone to propagate downward with cooling and shallowing which differs from faults characterized by shear localization and might be unique to aquiferous ost in accretionary complexes

tropical pacific ocean thermocline depth reconstructions for the last glacial maximum we evaluate the relationship between ten surface ocean 0 300 m hydrographic parameters and the spatial distribution of factor analyzed core top planktonic foraminiferal abundances in the tropical pacific ocean 24 n 24 s for core tops 3800 m the spatial distribution of the first three faunal factor loadings 88 of the variance are most highly correlated to subsurface variability mixed layer depth thermocline depth and resistant species percent rsp however rsp is not related to dissolution but is related to thermocline depth factor i mixed layer species g glutinata g ruber and factor iii g ruber can be distinguished from each other by low abundances of g glutinata in factor iii both assemblages spatially comprise the deep mixed layer region of the western tropical and equatorial pacific ocean but are associated with distinct water mass properties a combination of factor i and iii loadings shows a higher correlation to thermocline depth r 0 70 factor ii loadings dominated by thermocline dwelling species n dutertrei are most significantly correlated with the thermocline depth r 0 73 most factors show only marginally significant correlation to sea surface temperatures ssts indicating that sst is not the primary forcing factor on the planktonic foraminiferal species distributions in the tropical pacific a new transfer function was calculated to predict tropical pacific thermocline depth from planktonic foraminifera abundances using the imbrie kipp method ikm standard deviation of residuals 22 m 1 an additional 5 m error is attributed to low species counts in the core top database the modern analog technique mat was also used to predict thermocline depth standard deviation of residuals 21 m while last glacial maximum lgm thermocline depth changes by ikm and mat were generally within error estimated changes were geographically uniform suggesting an oceanographic response to climate forcing we estimate that the thermocline depth of the lgm was shallower than present by 20 m south of 8 s possibly due to a shift in the south pacific anticyclone to the northeast both the ikm and mat estimate a steeper east west thermocline slope along the equator suggesting that zonal wind stress walker circulation was intensified during the lgm collectively the thermocline estimates for the lgm suggest an equatorward compression of the climate zones in both hemispheres

decoupled holocene variability in surface and thermocline water temperatures of the indo pacific warm pool 1 the holocene variability in sea surface and thermocline water temperatures sst and twt in the indo pacific warm pool ipwp has been reconstructed by planktonic foraminiferal mg ca from sediments of the western tropical philippine sea afterward the younger dryas interval yd sst warmed gradually till 10 ka and remained approximately constant afterwards but twt rose more rapidly to a peak between 12 and 10 ka and then declined by 1 5 c through the holocene the trend of twt closely followed the boreal summer insolation and could be correlated to tropical climate changes represented by southward movement of the inter tropical convergence zone itcz and related changes in east asian monsoons

millennial scale dynamics of the winter cold tongue in the southern south china sea over the past 26 ka and the east asian winter monsoon millennial scale variations of the east asian winter monsoon eawm remain elusive due to sparse and controversial reconstructions by compiling a variety of alkenone based sea surface temperature sst estimates we find that the west east sst gradient in the southern south china sea scs well documents the temporal dynamics of the winter cold tongue off the southern vietnam and by inference variations in the eawm intensity over the past 26 ka our results reveal that the winter cold tongue ssts were significantly colder during heinrich event 1 and the younger dryas event resulting in an increased west east sst gradient in the southern scs due to a strengthened eawm within dating uncertainties an intensified eawm during cold stadials was coeval with the shutdown or a reduction in strength of the atlantic meridional overturning circulation amoc exhibiting a strong linkage between the amoc and the eawm system the west east sst gradient also indicates an enhanced eawm during the early holocene which may be induced by postglacial ice sheet dynamics and a strong seasonal contrast in solar insolation our findings suggest that the eawm was probably modulated by a complex interplay between the amoc solar insolation and ice sheet dynamics on sub orbital time scales

changes in the thermocline structure of the indonesian outflow during terminations i and ii we present centennial records of sea surface and upper thermocline temperatures in core md01 2378 from the timor sea which provide new insights into the variability of the indonesian outflow across the last two glacial terminations mg ca in globigerinoides ruber white s s indicates an overall increase of 3 2 degrees c in sea surface temperature sst over termination i following an early holocene plateau at 11 3 6 4 ka ssts cooled by 0 6 degrees c during the middle to late holocene 6 4 0 7 ka the early holocene warming occurred in phase with increasing northern hemisphere summer insolation coinciding with northward displacement of the intertropical convergence zone enhanced boreal summer monsoon and expansion of the indo pacific warm pool thermocline temperatures pulleniatina obliquiloculata mg ca gradually decreased from 24 5 to 21 5 degrees c since 10 3 ka reflecting intensification of a cool thermocline throughflow the vertical structure of the upper ocean in the timor sea evolved in similar fashion during the holocene and mis5e although the duration of sst plateaux differed 11 3 to 6 4 ka in termination i and from 129 to 119 ka in termination 11 which was probably due to the more intense northern hemisphere summer insolation during mis 5e during both terminations sst increased simultaneously in the southern high latitudes and the tropical eastern indian ocean suggesting virtually instantaneous atmospheric climate feedbacks between the high and low latitudes c 2008 elsevier b v all rights reserved

seasonal change in foraminiferal production in the western equatorial pacific warm pool evidence from sediment trap experiments seasonal changes in the flux of individual planktonic foraminifera in the deep ocean have been studied in the western equatorial pacific warm pool using material collected by sediment traps over a period of 1 yr 1991 1992 mean total foraminiferal fluxes tffs were 171 and 97 shells m 2 day 1 at sites n1 2 59 8 n 135 01 5 e and n2 4 07 5 n 136 16 6 e respectively the seasonal change in tffs was much higher than for organic matter om and carbonate fluxes the major species of planktonic foraminifera were pulleniatina obliquiloculata neogloboquadrina dutertrei globigerinoides sacculifer globigerinella aequilateralis and globigerinoides ruber symbiont bearing species and n dutertrei were predominant in the western equatorial pacific warm pool comparison between the warm pool and upwelling deep sea research ii 43 1996 1257 mar micropaleontology 33 1998 157 indicates that the foraminiferal assemblage trapped at the western equatorial pacific warm pool was comparable with the south equatorial and subtropical assemblages during a plankton tow study conducted at 140 w in 1992 it suggests that fairly oligotrophic conditions prevailed in the western equatorial pacific warm pool in association with terrestrial nutrient inputs or temporary mixing by wind bursts the om flux was more positively correlated with the 63 m carbonate fraction mainly composed of coccoliths r 0 87 and biogenic opal which suggests that om fluxes were more affected by phytoplankton productivity although food availability is generally important for foraminiferal production tffs were poorly correlated with om fluxes at sites n1 and n2 which is partly attributed to the significant influence of symbiont photosynthesis the 18o values of p obliquiloculata and n dutertrei showed maxima in association with high om fluxes during period 2 from august to october and period 4 from late december to april at site n1 reflecting thickening of the mixed layer following wind bursts g sacculifer showed a lunar reproduction cycle when between july and october carbonate production was more predominant than biogenic opal production a similar profile was evident for g ruber orbulina universa and g aequilateralis these four species are generally predominant at low latitudes therefore the lunar reproduction cycle may significantly affect the fluctuation in carbonate production in the equatorial ocean

variations in the western pacific warm pool across the mid pleistocene evidence from oxygen isotopes and coccoliths in the west philippine sea abstract we present planktonic foraminifera oxygen isotope and florisphaera profunda abundance data from the international marine global change study program images core md06 3050 which was collected in the west philippine sea on the margin of the western pacific warm pool wpwp our records reveal marked changes in the upper water structure in the kuroshio source region as early as 1 5 ma continuing through the mid pleistocene climate transition mpt these changes are evidenced by reconstructions of the thermocline based on planktonic foraminiferal oxygen isotope differences and the nutricline based on the relative abundance of the coccolithophore species florisphaera profunda in the kuroshio source region the evolution of the thermocline nutricline featured three prominent phases 1 phase i 1 5 1 1 ma which was characterized by low amplitude variations in a shallow thermocline 2 phase ii 1 1 0 8 ma which was characterized by high amplitude variations in a relatively shallow thermocline nutricline and 3 phase iii 0 8 0 5 ma which was characterized by low amplitude variations in a deep thermocline nutricline combined with the zonal sea surface temperature gradient in the tropical pacific the evolution of the upper water structure can be linked to tropical climatic changes across the mpt including the intensification of atmospheric circulation and a gradual cessation of the long term el nino like state the upper water structure of the wpwp was asymmetric before 0 8 ma with a shallow thermocline nutricline along the northern margin and a deep thermocline nutricline in the center of the wpwp and south china sea scs the modern wpwp was established by approximately 0 8 ma and the upper water structure has changed synchronously as a whole since that time a comparison of the 18 o values derived from globigerinoides ruber tests from the md06 3050 core with those from other cores in the western pacific suggests that the lower glacial interglacial g ruber 18 o values in md06 3050 before 0 8 ma could be related to the enhancement of the wpwp and to changes in atmospheric circulation patterns

melange and its seismogenic roof decollement a plate boundary fault rock in the subduction zone an example from the shimanto belt japan 1 the mugi melange located in western shikoku of the shimanto belt shows systematic y p deformation fabrics formed by microshear and pressure solution that penetrate throughout the melange pile magnetic susceptibility ellipsoids obtained from the anisotropy of magnetic susceptibility ams are highly oblate maximum and minimum axes of the ellipsoids are consistent with the shear orientation of the melange and the mean pole of p surfaces respectively this agreement suggests that the mugi melange was formed as a result of underthrusting of trench filling sediment vitrinite reflectance ranges from 2 52 to 3 08 which corresponds to a maximum paleotemperature of 180 200 c pseudotachylyte evidence of a seismogenic slip was found in the upper boundary roof fault of the mugi melange however there is not a thermal gap between the melange and the overlying coherent piles and the temperature from vitrinite reflectance gradually rises downward from the coherent piles to the melange beyond the boundary fault which suggests that paleoisotherms parallel the boundary fault orientation the isotherms in the seismogenic zone are estimated as subparallel to the plate boundary decollement therefore the setting of the cataclastic boundary fault which includes pseudotachylyte appears to be a major plate boundary thrust or a subhorizontal splay fault a probable geologic setting that accounts for the mugi melange and the seismogenic roof fault is partitioning of the slip along the plate boundary fault in space and time interseismic slip in the melange and seismic slip along the roof fault

underplated units in an accretionary complex melange of the shimanto belt of eastern shikoku southwest japan imbricated thrust stacks composed of melange and oceanic slabs occur in the shimanto belt eastern shikoku sw japan the melanges are divided into two types melange i consists of lenticular sandstone blocks surrounded by scaly shale matrix and melange ii is composed of blocks of oceanic material such as basalts cherts and red shale in a scaly matrix of shale melange ii is observed only near the boundaries between melange i and oceanic slabs the fabric of melange i indicates progressive deformation during underthrusting of originally coherent trench fill turbidites layer parallel extension characterizes early deformation and is divided into two stages an early stage formed during normal faulting and a subseguent stage formed perpendicular to the early extension the early extension is interpreted in terms of riedel shear associated with layer parallel shearing and tectonically induced loading normal to the layering the second extension is due to sticking thrust movement late deformation of melange i is represented by folding in association with layer parallel shearing this appears to be related to compression just before or during underplating of melange i beneath the accretionary prism layer parallel shear extends downward due to strain hardening of sheared sediments and then reaches to the base of the sediments subsequently the shear zone penetrates pelagic sediments and finally oceanic basement at this time melange ii is formed by the shearing an imbricated stack of melanges i ii and oceanic slabs forms duplexes during the underplating process the weak metamorphism of the melange complex in the study area suggests that underplating occurs at shallow depths where trench fill is thin

a new source of water in seismogenic subduction zones 1 seismogenic plate boundary faults at accretionary margins e g the nankai margin southwest japan may occur where the uppermost part of subducting oceanic crust composed of basaltic rocks is in contact with the overriding plate of a lithified accretionary prism the plate boundary faults in ancient accretionary complexes typically record high velocity slip under fluid rich conditions although previous studies have emphasized the mechanical significance of fluids in terms of dynamic slip weakening the source of fluid in seismogenic subduction zones remains poorly constrained in this work we focus on the hydrous smectite in the uppermost oceanic crust an alteration product of intact basalt before arrival at the trench axis a comparison between 1 new mineralogical data on basalt drillcore recovered by integrated ocean drilling program iodp expedition 322 at site c0012 a reference site for subduction input to the nankai trough and 2 mineralogical data on basalt within ancient oceanic crust embedded in a fossil accretionary complex of the shimanto belt southwest japan suggests that progressive smectite chlorite conversion would liberate bound fluids at a rate of 0 34 to 0 65 10 14 s 1 along the plate interface this rate of fluid production appears to be more than an order of magnitude greater than that from other possible sources including from overlying sediments via smectite illite conversion and the expulsion of pore fluids and may facilitate seismic slip along plate boundary faults

seasonal variations in the southern hemisphere storm tracks and associated wave propagation abstract seasonal variations in the southern hemisphere sh storm track characteristics and associated wave propagation are studied using 19 years of ncep ncar gridded data it is found that the sh storm track is strongest in the austral autumn season and weakest in spring the characteristics of wave packets are studied by computing 1 point lag correlation maps with unfiltered meridional wind at 300 hpa it is found that the eastward group velocities of waves are much higher than the phase velocities in the transition seasons this shows that the downstream development occurs throughout the year and is a basic feature of upper tropospheric waves in the midlatitudes of the sh this extends previous studies made for winter and summer seasons based on the indices that show wave coherence and correlation maps it is found that the pathways in the transition seasons split into two branches east of australia in a way similar to what happens in the zonal wind distribution

variations in sea surface hydrology in the southern makassar strait over the past 26 kyr we present centennial scale records of sea surface temperature and oxygen isotopes in a sediment core from mandar bay offshore sulawesi in the southern makassar strait which provide new insights into the variability of indonesian climate over the past 26 kyr the age model for the core is constrained by 17 ams radiocarbon ages with a surface ocean reservoir age correction based on paired wood and foraminiferal samples small holocene reservoir ages of 105 180 years point to intense surface ocean atmosphere interchange linked to increased monsoonal precipitation whereas last glacial maximum and deglacial reservoir ages are significantly higher mg ca derived sea surface temperature reconstructions based on globigerinoides ruber s s white exhibit an extended plateau during the antarctic cold reversal suggesting an atmospheric connection to high latitude southern hemisphere climate and a seasonal bias on g ruber this is in agreement with southern hemisphere sites along the track of the indonesian throughflow and in contrast to northern hemisphere records from the south china sea sulu sea and western pacific off mindanao which exhibit warming during the bolling allerod ice volume corrected delta o 18 seawater delta o 18 sw increased during heinrich stadial 1 and the younger dryas whereas the bolling allerod is characterized by low delta o 18 sw we attribute delta o 18 sw variability in the southern makassar strait during the last glacial maximum and glacial termination to changes in provenance and seasonality of precipitation rather than to variability in the amount of local precipitation and runoff c 2016 elsevier ltd all rights reserved

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

splay fault branching along the nankai subduction zone seismic reflection profiles reveal steeply landward dipping splay faults in the rupture area of the magnitude m 8 1 tonankai earthquake in the nankai subduction zone these splay faults branch upward from the plate boundary interface that is the subduction zone at a depth of approximately 10 kilometers approximately 50 to 55 kilometers landward of the trough axis breaking through the upper crustal plate slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion

early interglacial carbonate dilution events in the south china sea implications for strengthened typhoon activities over subtropical east asia abstract a compilation of many late quaternary marine sediment records from the northern south china sea scs continental slope confirms 15 50 reductions in sedimentary calcium carbonate concentrations between 11 0 and 8 5 ka bp in the early holocene this low carbonate event occurred at a time when the regional sea level rose from 50 m to 10 m which drowned large areas of continental shelves especially those near and within the taiwan strait this event is associated with a significant increase in bulk sedimentation rates on the upper continental slope and the relative abundance of fine grained detritus sediment provenance analyses suggest a dominant terrigenous input from taiwan and a minor contribution from luzon during the low carbonate event similar to the background terrigenous deposition in other periods of the holocene two comparable low carbonate events respectively from the beginning of marine isotope stages 5 5 and 7 3 have also been recognized pointing to similar causal factors while carbonate dissolution and carbonate accumulation rate should not have been responsible increased terrigenous input and dilution is considered as the main cause for the recurrent low carbonate events in early interglacials we further hypothesize that during early interglacials fluvial sediment discharge from taiwan and luzon intensified due to stronger typhoon activities and massive fine grained sediments from these two end members may have been transported to the northern scs continental slope via surface and deep ocean currents the conjecture of strengthened typhoon activities over east asia during the early holocene is supported by high ocean heat contents in the west pacific warm pool area with the prevailing la nina like conditions

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

the holocene pulleniatina minimum event revisited geochemical and faunal evidence from the okinawa trough and upper reaches of the kuroshio current abstract the holocene pulleniatina minimum event pme is characterized by a very low abundance of the planktonic foraminifer pulleniatina obliquiloculata between 4 5 and 3 ka the pme occurs widely in the okinawa trough and the south china sea and can be correlated throughout this area it has been related to variability in the kuroshio current to further explore the nature of the pme we studied cores obtained from the southern okinawa trough and the upper reaches of the kuroshio current faunal census data indicate that all cores record the pme between 4 5 and 3 ka the relative abundance of neogloboquadrina dutertrei is negatively correlated to that of p obliquiloculata in the southern okinawa trough but not in the sites at the upper reaches mg ca and 18 o measurements on globigerinoides ruber shells from the southern okinawa trough indicate that there was no change in sea surface temperature or sea surface salinity during the pme the vertical structure of the water column as reconstructed by multispecies 18 o and 13 c profiles shows no consistent anomalies in the southern okinawa trough and western philippine sea during the pme these observations suggest that 1 the pme was not restricted to marginal seas but widespread in the western north pacific 2 the high abundance of n dutertrei during the pme in the okinawa trough may be a result of higher food availability in the absence of p obliquiloculata 3 no distinctive consistent anomalies in the paleoceanographic proxies are associated with the pme implying there were no changes in hydrography and productivity the absence of a linkage between faunal variation and paleoceanographic proxies indicates that we do not yet understand what causes changes in planktonic foraminiferal assemblages this lack of understanding implies that we cannot always trust fauna based paleothermometry at millennial timescales

underplating process from melange formation to duplexing example from the cretaceous shimanto belt kii peninsula southwest japan accretionary complexes are considered to form through off scraping and underplating which results in the lateral and vertical growth of an accretionary prism accretion of the upper part of the oceanic crust and the formation of melange are important components of the accretionary process although the origin of melange is considered controversial in order to better understand the origin of melange and its role in accretion in particular during underplating we have studied the relationship between the formation of melange and duplexing in the miyama assemblage here the melange is composed dominantly of shale basalt chert and sandstone this study stresses the following features 1 the structure of the miyama assemblage appears to be a composite suite of landward and seaward dipping duplexes 2 the melange fabric displays a systematic asymmetry which may have resulted through shearing along the decollement and 3 facing of horses within duplexes changes from north to south coinciding with a change in the sense of shear inferred from the melange fabric which suggests that it formed prior to duplexing

interlaboratory comparison study of mg ca and sr ca measurements in planktonic foraminifera for paleoceanographic research thirteen laboratories from the usa and europe participated in an intercomparison study of mg ca and sr ca measurements in foraminifera the study included five planktonic species from surface sediments from different geographical regions and water depths each of the laboratories followed their own cleaning and analytical procedures and had no specific information about the samples analysis of solutions of known mg ca and sr ca ratios showed that the intralaboratory instrumental precision is better than 0 5 for both mg ca and sr ca measurements regardless whether icp oes or icp ms is used the interlaboratory precision on the analysis of standard solutions was about 1 5 and 0 9 for mg ca and sr ca measurements respectively these are equivalent to mg ca based temperature repeatability and reproducibility on the analysis of solutions of 0 2 c and 0 5 c respectively the analysis of foraminifera suggests an interlaboratory variance of about 8 rsd for mg ca measurements which translates to reproducibility of about 2 3 c the relatively large range in the reproducibility of foraminiferal analysis is primarily due to relatively poor intralaboratory repeatability about 1 2 c and a bias about 1 c due to the application of different cleaning methods by different laboratories improving the consistency of cleaning methods among laboratories will therefore likely lead to better reproducibility even more importantly the results of this study highlight the need for standards calibration among laboratories as a first step toward improving interlaboratory compatibility

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

foraminiferal isotopic evidence for monsoonal activity in the south china sea a present lgm comparison abstract the relationship between planktonic and benthic foraminiferal stable isotope values and oceanographic conditions and factors controlling isotopic variations are discussed on the basis of oxygen and carbon isotopic analyses of 192 modern surface and last glacial maximum lgm samples from the south china sea scs the harmonic variation of benthic 18o in surface sediments with water depth and temperature implies that the temperature is the main factor influencing benthic 18o variations planktonic 18o fluctuates with sea surface temperature sst and salinity sss the n s temperature gradient results in planktonic 18o decreasing from the northeast to the south cool saline waters driven by the winter monsoon are interpreted to have been responsible for the high 18o values in the northeast scs the east asian monsoons not only bring nutrients into the south china sea and maintain high nutrient concentration levels at the southwestern and northeastern ends which cause depleted 13c both in planktonic surface and benthic bottom samples but also reduce planktonic benthic 18o differences the distribution of 18o and 13c in the surface and lgm samples are strikingly similar indicating that the impact of sst and sss has been maintained and nutrient inputs mainly from the northeastern and southwestern ends have been controlled by monsoons since the lgm comparisons of the modern and lgm 18o indicate a difference of about 3 6 c in bottom water temperature and a large surface to bottom temperature gradient during the lgm as compared to today

deformation style of slickenlines on melange foliations and change in deformation mechanisms along subduction interface example from the cretaceous shimanto belt shikoku japan abstract accretionary complexes record the histories of changes in physical properties of sediments from unlithified sediments to lithified rocks through the deformation processes along subduction interface the trench sediment suffered various deformation of particulate flow pressure solution deformation and cataclastic faultings from ductile to brittle regime during accretion in subduction zone tectonic melange is a characteristic rock in on land accretionary complexes the dominant deformation mechanism of tectonic melange formation is pressure solution on the basis of microscopic observation however brittle slickenlines are also commonly observed on melange foliations at the outcrop scale although the slickenlines as a brittle failure is common on the surface of the pressure solution foliation the relationship of their kinetic are still uncertain detailed observations of slickenlines suggest that they are formed by reactivation of the melange foliations which indicates that the slickenlines are developed after formation of block in matrix texture characterized in melange in addition melange foliations are cut by faults related to underplating of oceanic materials therefore formation of slickenlines occur before underplating in a relatively deep portion along subduction interface on the basis of p t conditions reported from other parts of the cretaceous shimanto belt the melange formation and underplating is inferred to have occurred around the seismic front or within the seismogenic zone the change in deformation mechanisms from pressure solution to brittle failure may be the first change in physical properties from plastic to brittle around seismic front

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

tsunami earthquakes as transient phenomena 1 recent modeling of tsunami waveforms caused by tsunami earthquakes indicates that fault slip occurred along the subduction boundary close to the trench axis on the other hand it is well known that seismicity is generally very low within ca 50 km from the trench axis and this has been attributed to the stable frictional sliding properties of the subducted unconsolidated sediments this makes tsunamigenic slip near the trench difficult to explain in order to solve this dilemma i propose that transition from stable sliding to nearly zero friction with a velocity weakening property occurs as a result of areal increase of zones of elevated fluid pressure which may make fairly rapid seismic slip possible following the breakage of asperities at normal seismogenic depths this transition can be identified as seismic reflections with negative polarities which may help to rate hazards for a coming large tsunami earthquake