changes in itcz location and cross equatorial heat transport at the last glacial maximum heinrich stadial 1 and the mid holocene article history tropical paleoclimate records provide important insights into the response of precipitation patterns and the hadley circulation to past climate changes paleo records are commonly interpreted as indicating north south shifts of the intertropical convergence zone itcz with the itcz s mean position moving toward the warmer hemisphere in response to changes in cross equatorial temperature gradients though a number of records in tropical central and south america north africa asia and the indo australian region are consistent with this interpretation the magnitudes and regional variability of past itcz shifts are poorly constrained combining estimates of past tropical sea surface temperature sst gradients with the strong linear relationship observed between zonally averaged itcz position and tropical sst gradients in the modern seasonal cycle and in models of past climates we quantify past shifts in zonally averaged itcz position we find that mean itcz shifts are likely less than 1 latitude during the last glacial maximum lgm heinrich stadial 1 hs1 and mid holocene 6 ka climates with the largest shift during hs1 the itcz s position is closely tied to heat transport between the hemispheres by the atmosphere and ocean accordingly these small mean itcz shifts are associated with relatively large 0 1 0 4 pw changes in cross equatorial atmospheric heat transport ahteq these ahteq changes point to changes in cross equatorial ocean heat transport or net radiative fluxes of the opposite sign during hs1 the increase in northward ahteq is large enough to compensate for a partial or total shutdown in northward heat transport by the atlantic ocean s meridional overturning circulation the large ahteq response for small changes in mean itcz position places limits on the magnitude of past shifts in the globally averaged itcz large 5 meridional displacements of the itcz inferred from regional compilations of proxy records must be limited in their zonal extent and itcz shifts at other longitudes must be near zero for the global mean shift to remain 1 as suggested by our results our examination of model results and modern observations supports variable regional and seasonal changes in itcz precipitation this work thus highlights the importance of a dense network of tropical precipitation reconstructions to document the regional and seasonal heterogeneity of itcz responses to past climate changes

role of seasonal transitions and the westerlies in the interannual variability of the east asian summer monsoon precipitation a recent hypothesis holds that changes to the east asian summer rainfall are characterized by changes in the timing and duration of its intraseasonal stages controlled by the meridional position of the westerlies relative to the tibetan plateau this hypothesis is examined in the context of the leading mode of east asian summer july aug rainfall one phase of this tripole mode characterized by less rainfall over central eastern china and increased rainfall over northeastern and southeastern china is tied to an earlier termination of meiyu that results in a significantly shorter meiyu and longer midsummer stage this phase also exhibits an earlier northward transition of the westerlies to the north of the plateau essentially mirroring the changes to precipitation seasonality the reverse does not hold true for the opposite phase our results show direct observational evidence for the meridional position of the westerlies to control east asian summer monsoon seasonality

nd and sr isotopic variations in chinese eolian deposits during the past 8 ma implications for provenance change a record of changes in nd and sr isotopic composition of the eolian deposits from the central loess plateau has been determined for the past 8 ma the isotopic records of the silicate fraction of the quaternary and tertiary eolian deposits allow interpreting the interplay between the sr isotopic variations in the eolian deposits and the late cenozoic tectonic and climatic changes the results indicate that the temporal variations of nd and sr isotopes show remarkable changes around the beginning of the quaternary the lower values of the 143 nd 144 nd and the decreasing trend of the 87 sr 86 sr ratios after 2 58 ma ago are attributed to the additions of relatively younger crust materials in response to the climatic cooling and the late cenozoic uplift induced glacial grinding in the high orogenic belts in central asia in this context the substantial changes in climate and tectonics have modified dust sources significantly and the quaternary loess forming processes are preferentially sampling relatively younger and high relief crust materials than that of the tertiary red clay d 2005 elsevier b v all rights reserved

role of orbital forcing in east asian monsoon climates during the last 350 kyr evidence from terrestrial and marine climate proxies from core rc14 99 proxy records of northeast asian precipitation marine pollen and northwest pacific sea surface temperatures marine fauna contain concentrations of variance frequency peaks coincident with those of orbital variations eccentricity obliquity and precession time series of these monitors of various components of the east asian monsoon system are coherent with changing solar insolation and climate boundary conditions ice volume snow cover albedo at 41 and 23 kyr frequencies winter sea surface temperature wsst maxima are in phase with global ice volume minima at all three milankovitch frequencies 100 41 and 23 kyr periods wsst maxima are also linearly related to summer insolation at 30 n lagging radiation maxima by 55 3 5 kyr across the precessional frequency band 23 kyr period our east asian monsoon rainfall indicator cryptomeria reaches highest values immediately following summer insolation maxima during periods of low ice volume interglacials across the eccentricity frequency band 100 kyr period cryptomeria maxima are in phase with ice volume minima at the higher frequency of orbital precession monsoon rainfall lags both summer radiation maxima 125 8 kyr and ice volume minima 60 3 8 kyr whereas much of the variation in northwest pacific wsst can be attributed to summer radiation forcing and changes in global climate mechanisms driving east asian monsoon precipitation are more complex involving other possibly internal factors

itcz and enso pacing on east asian winter monsoon variation during the holocene sedimentological evidence from the okinawa trough deep sea fan sediments provide an excellent geological archive for paleoenvironment reconstruction grain size clay mineral and elemental ti fe ca compositions were measured for a core retrieved from a submarine fan in the okinawa trough varimax rotated principal component analysis v pca on time evolution of grain size spectrum reveals that since the holocene sediment was transported mainly by the benthic nepheloid layer 33 and upper layers 33 which is driven by the east asian winter monsoon eawm the intensification of the kuroshio current during the holocene masks the fluvial signal of the summer monsoon and obstructs clay minerals derived from the yellow river a major contributor prior to 12 ka bp a new grain size index gsi which represents the eawm well exhibits a negative correlation with the delta o 18 record in dongge cave china during the holocene when sea level was relatively steady this anti correlation suggests the southward migration of the intertropical convergence zone itcz the consistency among our records and rainfall records in peru ti counts in the cariaco basin monsoon records in oman and the averaged summer insolation pattern at 30 degrees n further support the itcz s impact on monsoon systems globally cross correlation analyses for gsi and log ti ca against delta o 18 record in dongge cave reveal a decoupling between the east asian winter and summer monsoon during 5500 2500 cal yr bp with greater complexity in the last 2500 years this can be attributed to exacerbated enso mode fluctuations and possibly anthropogenic interference superimposed on insolation and itcz forcing

a 550 000 year record of east asian monsoon rainfall from 10be in loess cosmogenic 10 be flux from the atmosphere is a proxy for rainfall using this proxy we derived a 550 000 year long record of east asian summer monsoon easm rainfall from chinese loess this record is forced at orbital precession frequencies with higher rainfall observed during northern hemisphere summer insolation maxima although this response is damped during cold interstadials the 10 be monsoon rainfall proxy is also highly correlated with global ice volume variations which differs from chinese cave 18 o which is only weakly correlated we argue that both easm intensity and chinese cave 18 o are not governed by high northern latitude insolation as suggested by others but rather by low latitude interhemispheric insolation gradients which may also strongly influence global ice volume via monsoon dynamics

provenance and climate change inferred from sr nd pb isotopes of late quaternary sediments in the huanghe yellow river delta china we present a provenance study of core zk2 from the huanghe yellow river delta in order to assess the impacts of climate change on the sediment supplies during the last glacial interglacial cycle facies analysis and sequence stratigraphy methods are used to construct the age model sr isotopic compositions of zk2 range from 0 716389 to 0 723884 with 87sr 86sr increased with decreasing grain size nd and pb isotopic compositions display two large major excursions during marine oxygen isotope stages mis 2 and 4 with less radiogenic end and lower 208pb 204pb 207pb 204pb and 206pb 204pb values during these periods these excursions have been explained in terms of changes in the mixing proportion of sediments from the loess plateau and ordos plateau resulting from east asian monsoon intensity variations the weak summer monsoon precipitation resulted in decreased erosion of loess plateau during mis 2 4 and the middle of mis 3 meanwhile both the intensified east asian winter monsoon and the southward expansions of mu us desert significantly enhanced the eolian sand entering the huanghe therefore our results highlight the impact of monsoon variability on erosion patterns in the huanghe basin

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

angles of repose that exceed modern angles angles of repose for naturally occurring materials are known to be a function of among other geologic parameters the acceleration of gravity and cohesion between particles thus steeper angles may have been recorded in ancient sediments because earth9s acceleration of gravity was less than now published data suggest that eolian and aqueous sediments have documented these changes previously angles of repose steeper than modern angles were attributed to structural steepening and soft sediment deformation more detailed study is required to separate the contribution that each of many factors may have had in specific cases of ancient angles of deposition

rare earth element geochemistry and nd isotope composition of stream sediments south han river drainage basin korea abstract chemical analyses of parent rock soil and stream sediments were done to determine to what extent the river sediments retain the geochemical signature of the parent rocks the study area consists mainly of mesozoic biotite granite and precambrian biotite gneiss located in the central korean peninsula the drainage system consists of tributaries of the south han river such as bokhacheon shinduncheon and yanghwacheon stream sediments were collected every march during 2004 2006 the sediments collected were divided into coarse gravel to sand size and fine silt to clay size more than 90 is coarse sediment the major element composition of the coarse and fine sediments are not identical to the weathering trend of granite however molar proportions of al2o3 cao na2o and k2o in the sediments show that they were derived from granitoids rather than from biotite gneiss the total fe2o3 cao mgo na2o and mno contents and ree concentrations of the fine sediments are higher than those of the coarse sediments in a weathering profile from the granite and gneiss area there was no change of ree distribution pattern from the fresh rock to soil compared to biotite granite normalized ree pattern for the sediment both coarse and fine sediments have relatively flattened ree patterns and all the coarse sediment have positive eu anomalies whereas in the fine sediments negative eu anomalies prevail nd isotopic composition of the sediments is similar to that of the biotite granite rather than the biotite gneiss stream sediments in the icheon area were derived from the granite nd isotope geochemistry as well as ree geochemistry is useful tool for tracing the provenance of the river sediments

environmental control on granular clinoforms of ancient carbonate shelves the purpose of this paper is to document the influence of depositional environments on shallow water low relief clinoforms from the description of five ancient carbonate platforms the neoproterozoic namibia middle jurassic france lower cretaceous france upper cretaceous oman and miocene turkey these examples have been investigated on the basis of field observations the clinoforms are described with reference to geometric and compositional attributes declivity shape height sedimentary structures sediment fabric and components the results show great variability in stratal geometry declivity and facies distribution 1 depositional profiles vary from exponential to sigmoidal to oblique 2 maximal slope angles range from 3 to 25 most of them being grouped between 10 and 18 3 facies differentiation identified from lateral facies successions along beds and vertical facies successions through beds is pronounced to subtle this study documents linkages between depositional environments and clinoform attributes proximal shallow clinoforms display round edged exponential profiles sediment deposition has resulted from unidirectional currents in the upper convex section and storm generated oscillatory currents in the lower concave part the sediment fabric changes gradually along this type of clinoform there is little vertical facies differentiation through these clinobeds which have formed from a continuous amalgamation of deposits by contrast distal clinoforms shelf break distally steepened ramp settings yield a much broader spectrum of profiles and are generally shorter and steeper sedimentary structures in gravel sized deposits of the upper slope indicate pure traction by unidirectional currents conversely marks of oscillatory flows undular wavy top bounding surfaces of clinobeds are common in the lower slope intercalation of massive fine grained deposits suggests offshore transport of carbonate mud by suspension each distal clinobed represents a single flow event accordingly facies differentiation is weak laterally but may be pronounced through the clinobeds our study suggests that low relief forms of proximal shallow environments which contain coarse grained and photo independently produced debris record hydrodynamic equilibrium profiles whereas the higher relief forms of this setting rather reflect a high differential production rate of carbonate sediment with water depth the carbonate sediment of the distal clinobeds mainly derives from skeletal production by oligophotic and photo independent biota of the middle shelf ramp and upper portion of the clinoforms the contribution by in situ skeletal biota only becomes significant on the lower slope indicating that the distal submerged slopes of carbonate platforms are not organically but hydrodynamically generated our compilation shows that the slope angles of shallow marine low relief clinoforms do not simply correlate to the sediment grain size and fabric in contrast to what has been documented for the high linear slope profiles this difference stems from the depositional settings namely the involved transport mechanisms low relief clinoform accretion seems to be dominantly influenced by wave induced sediment transport in contrast to linear flanks of high relief clinoforms that build to the angle of repose and for which gravity is the primary transport process

an optimized scheme of lettered marine isotope substages for the last 1 0 million years and the climatostratigraphic nature of isotope stages and substages a complete and optimized scheme of lettered marine isotope substages spanning the last 1 0 million years is proposed lettered substages for marine isotope stage mis 5 were explicitly defined by shackleton 1969 but analogous substages before or after mis 5 have not been coherently defined short term discrete events in the isotopic record were defined in the 1980s and given decimal style numbers rather than letters but unlike substages they were neither intended nor suited to identify contiguous intervals of time substages for time outside mis 5 have been lettered or in some cases numbered piecemeal and with conflicting designations we therefore propose a system of lettered substages that is complete without missing substages and optimized to match previous published usage to the maximum extent possible our goal is to provide order and unity to a taxonomy and nomenclature that has developed ad hoc and somewhat chaotically over the decades our system is defined relative to the lr04 stack of marine benthic oxygen isotope records and thus it is grounded in a continuous record responsive largely to changes in ice volume that are inherently global this system is intended specifically for marine oxygen isotope stages but it has relevance also for oxygen isotope stages recognized in time series of non marine oxygen isotope data and more generally for climatic stages which are recognized in time series of non isotopic as well as isotopic data the terms stage and substage in this context are best considered to represent climatostratigraphic units and thus climatic stages and climatic substages because they are recognized from geochemical and sedimentary responses to climate change that may not have been synchronous at global scale

quantitative compositional analysis of a triassic carbonate platform southern alps italy abstract we have estimated abundance and distribution of automicrite marine cements and skeletal grains in the triassic sella massif an isolated platform flanked by steep 25 35 clinoforms 108 samples were taken at constant intervals from measured sections of the major zones of the platform edifice the platform top margin upper slope and lower slope in a first step carried out in the field and on hand specimen purely detrital deposits were separated from automicrite facies i e beds with automicrite cement filled primary vugs and admixtures of skeletal carbonate and lithoclasts in the second step samples with automicrite facies were thin sectioned and point counted the categories used for point counting were a automicrite b vugs and cement c microspar or neomorphic spar d skeletal grains and e internal sediments at the platform top 46 of samples are pure detrital deposits 27 consist of automicrite facies and 27 are too strongly altered by dolomitization to allow classification at the margin upper slope 68 of samples consist of automicrite facies 22 are pure detrital sediments and 10 are strongly altered at the lower slope 63 are detrital deposits 10 automicrite facies and 27 are extensively dolomitized the most important contributors to the automicrite facies are automicrite 41 on the platform top 29 on the margin upper slope 28 on the lower slope and early marine cement 35 on the platform top 48 on the margin upper slope 27 on the lower slope the amount of skeletal grains is less than 10 the automicrite facies stabilized the platform margin and upper slope automicrite abundant early marine cements and micro organisms such as tubiphytes formed a rigid framework thus substituting for the lack of a metazoan reef on the upper slopes the framework of automicrite facies stabilized the slope but intermittently the automicrite layers are frequently dissected by sediment filled fractures or are broken into clasts we assume that they slid on the layers of loose detritus bigger slides turned into rubbly debris flows that formed metre thick breccias at the lower slope and the proximal basin floor the planar shape and steep angle of the clinoforms indicate that the large scale geometry of the slope was not controlled by the automicrite but rather by non cohesive layers of sand and rubble piled up to the angle of repose the production mode of the sella is comparable of that of a mud mound factory this factory was highly productive in 1 ma the platform aggraded over 300 m and prograded over 2000 m in all directions

carbonate slopes and gravity deposits in this special volume a series of papers are presented that concentrate on sedimentation patterns observed on the slopes and within the basins surrounding shallow water carbonate depositional systems four papers discuss depositional patterns on the slope to basin transect of the cainozoic sedimentary system of the bahamas four other papers examine gravity deposits of jurassic and cretaceous carbonate depositional systems

geochemistry of the pliocene red clay formation in the chinese loess plateau and implications for its origin source provenance and paleoclimate change abstract recent field observations and sedimentological studies suggest the eolian origin of the late tertiary red clay formation underlying the pleistocene loess soil sequence in the loess plateau thereby extending the wind blown record from 2 6 ma down to 7 0 ma in north central china to address the source provenance of the red clay major and trace element concentrations were analyzed on the samples from a north south loess transect of the loess plateau and a red clay section at jiaxian results show that there is a good agreement of both major and trace element compositions between the last glacial interglacial loess soil units and the jiaxian red clay record the ree distribution patterns of the loess soil and red clay samples are remarkably similar in shape with enriched lree and fairly flat hree profiles and clear negative eu anomaly the geochemical features of the red clay are also identical to those of upper continental crust these chemical characteristics provide further evidence for eolian sedimentation of the red clay from the relations both between na2o al2o3 and k2o al2o3 ratios and between u pb and th pb ratios the eolian loess and red clay materials must have been subject to thorough sedimentary differentiation and moderate chemical weathering in the source area the chemical similarity between soil unit s1 and the red clay implies that such an environment as occurred in the last interglacial period may have already formed in northwestern china during the late tertiary comparison of down section variations in elemental ratios with field observations of pedogenic development of the red clay suggests that cao al2o3 sr rb and sr ba are more sensitive to climate changes than magnetic susceptibility and can be used to reconstruct the climate history of the late cenozoic

detrital sediment supply in the southern okinawa trough and its relation to sea level and kuroshio dynamics during the late quaternary abstract during leg 195 of the ocean drilling program site 1202 was drilled in the subtropical northwestern pacific ocean beneath the kuroshio black current between northern taiwan and the ryukyu island arc on the northern flank of the i lan ridge at 1274 m water depth the upper 110 m of the site 1202 section composed of dark grey calcareous silty clay provide an expanded record of environmental changes during the last 28 kyr the sediments were deposited at high sedimentation rates between 3 0 and 5 0 m kyr and peak values of 9 0 m kyr between 15 1 and 11 2 ka bp variations in the modes and sources of detrital sediment input as inferred from sediment granulometry mineralogy and elemental xrf scanner data reflect changes in environmental boundary conditions related to sea level changes kuroshio variability and the climate driven modes of fluvial runoff the provenance data point to increased sediment supply from northwestern taiwan between 28 and 19 5 ka bp and from east china sources between 19 5 and 11 2 ka bp the change in provenance at 19 5 ka bp reflects increased fluvial runoff from the yangtze river and strong sediment reworking from the east china sea shelf in the course of increased humidity and postglacial sea level rise particularly after 15 1 ka bp the holocene was dominated by sediments that originated from rivers in northeastern taiwan for the pre holocene period prior to 11 2 ka bp low portions of sortable silt 63 10 m show that the kuroshio did not enter the okinawa trough because of low sea level in turn high proportions of sortable silt and sediment provenance from northeastern taiwan point to strong ocean circulation under the direct and persistent influence of the kuroshio during the holocene the reentrance of the kuroshio to the okinawa trough was heralded by two pulses in relative current strengthening at 11 2 and 9 5 ka bp as documented by stepwise increases in sortable silt in the lower holocene section from a global perspective environmental changes in the southern okinawa trough show affinities to climate change in the western pacific warm pool with little influence of climate teleconnections from the north atlantic realm otherwise seen in many other marine and terrestrial palaeoclimate records from southeastern asia

dynamics of tethyan carbonate platforms tethyan carbonate platforms are relatively short lived depositional systems which were born developed died and sometime resurrected in a tectonically active area in contrast with pericratonic platforms which are generally huge in size hundreds of kilometers across and show wide facies belts very gentle slopes ramps and transitional boundaries tethyan carbonate platforms are smaller tens of kilometers and have steep slopes generally faulted boundaries and abrupt facies changes it appears clear that the overall control on these two contrasting systems is the geodynamic milieu relatively stable in the first case where eustatic oscillations and long term subsidence are probably the main dictators quite dynamic and aggressive in the second one where carbonate platforms developed through the entire geodynamic spectrum rifting transtension transpression and collision of the wilson cycle primary controls on tethyan carbonate platforms appear to be tectonics most important and eustatic sea level oscillations which determine their emplacement growth and decay their overall shape and architecture are a function of these factors secondary factors affecting tethyan carbonate platform evolution are physiography oceanographic conditions and biology as a function of geologic time especially across the mesozoic tertiary boundary facies and facies distribution and to a lesser extent their shape are controlled by thesemore variables less

role of seasonal transitions and westerly jets in east asian paleoclimate abstract the summer rainfall climate of east asia underwent large and abrupt changes during past climates in response to precessional forcing glacial interglacial cycles as well as abrupt changes to the north atlantic during the last glacial however current interpretations of said changes are typically formulated in terms of modulation of summer monsoon intensity and do not account for the known complexity in the seasonal evolution of east asian rainfall which exhibits sharp transition from the spring regime to the meiyu and then again from the meiyu to the summer regime we explore the interpretation that east asian rainfall climate undergoes a modulation of its seasonality during said paleoclimate changes following previous suggestions we focus on role of the westerly jet over asia namely that its latitude relative to tibet is critical in determining the stepwise transitions in east asian rainfall seasons in support of this linkage we show from observational data that the interannual co variation of june july august rainfall and upper tropospheric zonal winds show properties consistent with an altered timing of the transition to the meiyu summer and with more northward shifted westerlies for earlier transitions we similarly suggest that east asian paleoclimate changes resulted from an altered timing in the northward evolution of the jet and hence the seasonal transitions in particular the transition of the jet from south of the plateau to the north that determines the seasonal transition from spring rains to the meiyu in an extreme scenario which we speculate the climate system tended towards during stadial cold phases of d o stadials and periods of low northern hemisphere summer insolation the jet does not jump north of the plateau essentially keeping east asia in prolonged spring conditions we argue that this hypothesis provides a viable explanation for a key paleoproxy signature of d o stadials over east asia namely the heavier mean 18o of precipitation as recorded in speleothem records the southward jet position prevents the low level monsoonal flow which is isotopically light from penetrating into the interior of east asia as such precipitation there will be heavier consistent with speleothem records this hypothesis can also explain other key evidences of east asian paleoclimate changes in particular the occurrence of dusty conditions during north atlantic stadials and the southward migration of the holocene optimal rainfall

seasonal transitions and the westerly jet in the holocene east asian summer monsoon abstractthe holocene east asian summer monsoon easm was previously characterized as a trend toward weaker monsoon intensity paced by orbital insolation it is demonstrated here that this evolution is more accurately characterized as changes in the transition timing and duration of the easm seasonal stages spring pre mei yu mei yu midsummer and tied to the north south displacement of the westerlies relative to tibet to this end time slice simulations across the holocene are employed using an atmospheric general circulation model self organizing maps are used to objectively identify the transition timing and duration of the easm seasonal stages compared to the late holocene an earlier onset of mei yu and an earlier transition from mei yu to midsummer in the early to mid holocene are found resulting in a shortened mei yu and prolonged midsummer stage these changes are accompanied by an earlier northward positioning of the westerlies relative to tibet invoking changes to seasonal transitions al

eoalpine and mesoalpine tectonics in the southern alps according to structural and stratigraphic data eoalpine and mesoalpine tectonics can be clearly recognized in the southern alps and distinguished from the better known neoalpine deformation

sr nd isotopic and ree geochemical constraints on the provenance of fine grained sands in the ordos deserts north central china surface sands and sandstones in the ordos region alluvial sands from the surrounding mountains and fluvial sands in the yellow river are systemically collected for granulometric mineralogical geochemical and isotopic analyses fine grained fractions are small for the ordos desert sands as well as alluvial sands of the surrounding mountains whereas they are abundant for fluvial sands of the yellow river quartz feldspar and muscovite are common minerals but their relative proportions are variable for various sediments ree geochemical compositions are roughly identical but isotopic compositions particularly end 0 values of fine grained sands vary significantly in the ordos deserts based on the integrated sr nd isotopic data the possible source areas are isotopically divided into four regions for fine grained sands in the ordos deserts region a the helan yin mountain ranges region b the ordos sandstone areas region d the tarim basin the alxa plateau the hexi corridor the northern qinghai xizang plateau and the yellow river drainage and region e the jungger basin and the southern mongolia through geochemical and particularly isotopic comparisons in combination with expert meteorological and geographical knowledge fine grained sands in the ordos deserts originated both from weathering of local sandstones and from blowing of fine sediments in region d the input from region d is subordinate to the local source for fine grained sands in the ordos deserts contributions from weathering of local sandstones might be roughly homogeneous from the west to the east of the ordos region as well as the input of fine grained sediments from remote areas such as the tarim basin the qinghai xizang plateau and the alxa plateau geographical nd isotopic variations of fine grained sands in the ordos deserts might be caused by the input from adjacent places such as the yellow river drainage due to the near surface winds

provenance sea level and monsoon climate controls on silicate weathering of yellow river sediment in the northern okinawa trough during late last glaciation abstract high resolution multi proxy records including geochemical and grain size data from detrital sediments of iodp site u1429 in the northern okinawa trough provide reliable evidence for constraining sediment source and transport processes they also allow silicate weathering and erosion controlled by sea level change and east asian summer monsoon evolution since 34 ka to be reconstructed provenance proxies indicated that sediments in the northern okinawa trough were mainly supplied by the yellow river middle reach at 34 8 ka the low sea level and proximity of paleo yellow river mouth to the northern okinawa trough were the causes of the dominant yellow river input after 8 ka a retreated yellow river mouth coupled with the blocking effect of the kuroshio current and its branches together with strong east asian summer monsoon precipitation resulted in relatively strong sediment input from kyushu to the northern okinawa trough meanwhile yellow river upper reach supplied more sediments to the study site than that during the 34 8 ka on glacial interglacial scale silicate weathering proxies indicate that the core sediment was more weathered during the last glacial and deglacial than that in the modern yellow river we attribute this to the increased upper reach sediment input which supplied more weak weathered sediment to the study site during the holocene besides composite effect of weathering during glacial and deglacial sediment production and additional weathering upon subaerial exposure of shelf deposits during low sea level stage as well as older weathered sediments reworking during sea level rise could also account for this weathering regime on multi millennial scale from 34 to 18 5 ka silicate weathering was mainly controlled by the east asian summer monsoon with a cooling and drying climate associated with weakened summer monsoon activity this is consistent with the reduced alteration of sediments eroded from the yellow river basin from 18 5 to 8 ka strong reworking of older weathered sediments overwhelmed the east asian summer monsoon in controlling silicate weathering which induced a continuous increase in chemical alteration of the sediments during this period

orbital forcing of climate over south africa a 200 000 year rainfall record from the pretoria saltpan late pleistocene variations in rainfall in subtropical southern african are estimated from sediments preserved in the pretoria saltpan a 200000 year old closed basin crater lake on the interior plateau of south africa we show that south african summer rainfall covaried with changes in southern hemisphere summer insolation resulting from orbital precession as predicted by orbital precession geometry berger 1978 this south african record is out of phase with north african palaeomonsoon indices street and grove 1979 rossignol strick 1983 mcintyre et al 1989 the amplitude of the rainfall response to insolation forcing agrees with climate model estimates prell and kutzbach 1987 these results document the importance of direct orbital insolation forcing on both subtropical north and south african climate as well as the predicted antiphase sensitivity to precessional insolation forcing

interglacials of the last 800 000 years interglacials including the present holocene period are warm low land ice extent high sea level end members of glacial cycles based on a sea level definition we identify eleven interglacials in the last 800 000 years a result that is robust to alternative definitions data compilations suggest that despite spatial heterogeneity marine isotope stages mis 5e last interglacial and 11c 400 ka ago were globally strong warm while mis 13a 500 ka ago was cool at many locations a step change in strength of interglacials at 450 ka is apparent only in atmospheric co2 and in antarctic and deep ocean temperature the onset of an interglacial glacial termination seems to require a reducing precession parameter increasing northern hemisphere summer insolation but this condition alone is insufficient terminations involve rapid nonlinear reactions of ice volume co2 and temperature to external astronomical forcing the precise timing of events may be modulated by millennial scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere a variety of temporal trends is observed such that maxima in the main records are observed either early or late in different interglacials the end of an interglacial glacial inception is a slower process involving a global sequence of changes interglacials have been typically 10 30 ka long the combination of minimal reduction in northern summer insolation over the next few orbital cycles owing to low eccentricity and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future

the growth potential of a bypass margin great bahama bank abstract observations and sampling to 350 m from a two person submersible off chub cay berry islands bahamas suggest that accretion is occurring to varying degrees in all subdivisions of the platform margin profile at the chub cay dive site a nearly vertical wall extends to 140 m subsea below and extending to the limit of the dives is a low relief fore reef slope ca 50 of limestone veneered with sediment this study supports the idea that the upper portion of the wall from 30 to 85 m the brow or deep reef is a principal source of talus now cemented that foots the windward margins of great bahama bank we infer that the brow grows outward so rapidly that it calves periodically the resulting debris largely bypasses the deeper wall but some is perched on the steep fore reef slope below where it is soon incorporated into the slope by submarine cementation this model further explains the observation that carbonate platform margins tend to steepen through time and shows how those steepened slopes can be maintained during their continued growth

a comparison of shear strength in calcareous and siliciclastic marine sediments abstract more than 2000 measurements of shear strength versus depth in fine grained marine sediments were collected from the literature and our own experiments in order to study the relationship between carbonate content and strength behavior of marine sediments depositional environments include slope rise and abyssal plain with most data originating from the slopes the depth range is restricted to 6 m subbottom depth in order to minimize diagenetic effects contour plots of shear strength versus depth for calcareous and siliciclastic sediments clearly reveal different trends whereas shear strength in siliciclastic sediments shows low variability and increases only gradually with depth the shear strength in the calcareous population is highly variable and increases rapidly with depth the difference in strength behavior of the two sediment groups has implications for the stability of submarine slopes previous research has shown that carbonate sediments build up steeper and more variable slopes than siliciclastic sediments this difference in slope angle can be explained at least in part by the higher internal strength of the carbonate sediments

distinct control mechanism of fine grained sediments from yellow river and kyushu supply in the northern okinawa trough since the last glacial high resolution multi proxy records including clay minerals and sr nd pb isotopes of the clay sized silicate fraction of sediments from iodp site u1429 in the northern okinawa trough provide reliable evidence for distinct control mechanism on fine grained sediments input from the yellow river and the southern japanese islands to the northern okinawa trough since 34 ka bp provenance analysis indicates that the sediments were mainly derived from the yellow river and the island of kyushu since the last glacial clay sized sediments transported from the yellow river to the study site were strongly influenced by sea level fluctuation during low sea level stage 34 14 ka bp the paleo yellow river mouth was positioned closer to the northern okinawa trough favoring large fluvial discharge or even direct input of detrital sediments which resulted about four times more flux of clay sized sediments supply to the study area as during the relatively high sea level stage 14 0 ka bp the input of kyushu derived clay sized sediments to the study site was mainly controlled by the kuroshio current and tsushima warm current intensity with increased input in phase with weakened kuroshio current tsushima warm current our study suggests that the kuroshio current was very likely flowed into the okinawa trough and thus influenced the fine grained sediment transport in the area throughout the last glacial and deglacial during 34 11 ka bp the kyushu clay sized sediment input was mainly controlled by the kuroshio current since 11 ka bp the occurrence of tsushima warm current became important in influencing the kyushu fine grained sediment input to the northern okinawa trough

east asian monsoon variation during the last 130 000 years evidence from the loess plateau of central china and lake biwa of japan abstract the loess paleosol sequence on the loess plateau of central china constitutes an excellent proxy record of variations in asian monsoon climate over the past 2 5 ma magnetic susceptibility of loess and paleosols has been used as a proxy indicator for summer monsoon intensity while the median diameter of quartz isolated from the loess and paleosols has been regarded as a proxy index of the strength of winter monsoon winds that were responsible for most of the dust transport the eolian quartz flux to lake biwa of central japan during the last 130 000 yr provides direct information on variations of the east asian winter monsoon whereas the fluvial quartz flux reflects significant changes in paleoprecipitation over the lake area the intervals of high eolian quartz flux values during marine oxygen isotope substages 5d and 5b and stages 4 and 2 correspond to the periods of large quartz median diameter values of the chinese loess and paleosols indicating strengthened winter monsoon winds whereas the intervals of high fluvial quartz flux values during isotope substages 5e 5c and 5a and stages 3 and 1 correlate to the periods of high magnetic susceptibility values of the chinese loess and paleosols suggesting increased summer monsoon intensity variations in winter monsoon strength indicated by the eolian quartz flux and quartz median diameter proxies bear a general inverse relation to those in summer monsoon intensity inferred from the fluvial quartz flux and magnetic susceptibility proxies

mid latitude interhemispheric hydrologic seesaw over the past 550 000 years an interhemispheric hydrologic seesaw in which latitudinal migrations of the intertropical convergence zone itcz produce simultaneous wetting increased precipitation in one hemisphere and drying in the other has been discovered in some tropical and subtropical regions for instance chinese and brazilian subtropical speleothem cave formations such as stalactites and stalagmites records show opposite trends in time series of oxygen isotopes a proxy for precipitation variability at millennial to orbital timescales suggesting that hydrologic cycles were antiphased in the northerly versus southerly subtropics this tropical to subtropical hydrologic phenomenon is likely to be an initial and important climatic response to orbital forcing the impacts of such an interhemispheric hydrologic seesaw on higher latitude regions and the global climate system however are unknown here we show that the antiphasing seen in the tropical records is also present in both hemispheres of the mid latitude western pacific ocean our results are based on a new 550 000 year record of the growth frequency of speleothems from the korean peninsula which we compare to southern hemisphere equivalents the korean data are discontinuous and derived from 24 separate speleothems but still allow the identification of periods of peak speleothem growth and thus precipitation the clear hemispheric antiphasing indicates that the sphere of influence of the interhemispheric hydrologic seesaw over the past 550 000 years extended at least to the mid latitudes such as northeast asia and that orbital timescale itcz shifts can have serious effects on temperate climate systems furthermore our result implies that insolation driven itcz dynamics may provoke water vapour and vegetation feedbacks in northern mid latitude regions and could have regulated global climate conditions throughout the late quaternary ice age cycles

response of heterogeneous rainfall variability in east asia to hadley circulation reorganization during the late quaternary abstract the quaternary east asian summer rainfall evolution reconstructed with the chinese speleothem 18o records shows the consistency throughout the region of east asia and has long been considered equivalent to the monsoon intensity its variation and teleconnection with global climate were usually interpreted by the meridional shift of the intertropical convergence zone itcz however many other proxy records climate simulations and meteorological observations suggest the inconsistent rainfall patterns in the different regions of east asia on multi timescales such spatial heterogeneity in quaternary east asian summer rainfall indicates that the hydroclimate in this region is not fully paced by the migration of the itcz here we report a sediment record of rainfall evolution during the last 400 ka in the northern east china sea and this record in combination with a transient climate model simulation indicates an out of phase relationship between rainfall over middle southeastern east asia and northern and southwestern east asia on the precession band with high boreal summer insolation corresponding to the increased rainfall intensity in the northern and southwestern east asia however decreased rainfall intensity in the middle east asia we attribute this regional heterogeneity in east asian rainfall to the reorganization of the hadley circulation including shifts in the ascending branch itcz and descending branch subtropical westerly jet in response to changes in the hemispheric meridional temperature gradient our results highlight the crucial role of the hadley circulation in the east asian hydroclimate and have important implications for future climate projections

quantifying the geometry and sediment fabric of linear slopes examples from the tertiary of italy southern alps and gargano promontory the geometries and sediment characteristics of two well exposed submarine slope successions of ancient carbonate platforms were studied to analyse the relationship between inclinations of linear slopes and sediment fabric the two examples are an oligocene platform to slope succession exposed on the brione mountain in the southern alps and an eocene slope tobasin succession exposed on the saraceno mountain in the gargano promontory the planar slope of the brione mountain outcrop is inclined up to 20 25j and consists of fine to coarse sand sized skeletal packstones and grainstones and that of the saraceno mountain outcrop has a modal angle of 15 22 5j and comprises very fine to coarse sand sized poorly washed skeletal packstones grainstones and rudstones the good agreement between the inclinations of the linear slope profiles and angles of repose published in the literature implies that these slopes are at or very close to the angle of repose the general rule that in systems built to the angle of repose slope angle is directly correlated to sediment fabric can be applied to linear slopes d 2002 elsevier science b v all rights reserved

the asian monsoon over the past 640 000 years and ice age terminations oxygen isotope records from chinese caves characterize changes in both the asian monsoon and global climate here using our new speleothem data we extend the chinese record to cover the full uranium thorium dating range that is the past 640 000 years the record s length and temporal precision allow us to test the idea that insolation changes caused by the earth s precession drove the terminations of each of the last seven ice ages as well as the millennia long intervals of reduced monsoon rainfall associated with each of the terminations on the basis of our record s timing the terminations are separated by four or five precession cycles supporting the idea that the 100 000 year ice age cycle is an average of discrete numbers of precession cycles furthermore the suborbital component of monsoon rainfall variability exhibits power in both the precession and obliquity bands and is nearly in anti phase with summer boreal insolation these observations indicate that insolation in part sets the pace of the occurrence of millennial scale events including those associated with terminations and unfinished terminations records of the asian monsoon have been extended to 640 000 years ago and confirm both that the 100 000 year ice age cycle results from integral numbers of precessional cycles and that insolation influences the pacing of major millennial scale climate events prior records of the asian monsoon have revealed cyclic variations over hundreds of thousands of years probably driven by variations in insolation caused by the precession of earth s orbit hai cheng and colleagues now provide a speleothem record from chinese cave samples that extends earlier records to 640 000 years ago close to the maximum age possible with uranium thorium dating this spectacular record confirms that the characteristic 100 000 year ice age cycle corresponds to an integral number four or five of precession cycles and that insolation influences millennial scale variations in monsoon strength

carbonate platform flanks slope angle and sediment fabric more than 20 examples of fossil carbonate platform systems were compared for slope angle and sediment fabric plots of slope angle versus sediment fabric show that grainy non cohesive mud free sediments build steeper slopes than muddy cohesive sediments examples near the end members of grainy and muddy carbonate platform flanks are found in the triassic of the dolomites in northern italy and in the bahamas respectively they document the flank geometry and the processes readjusting the slope profile once the limiting slope angle is exceeded the grainy flank sediments in the dolomites modified by shearing and avalanching produce straight slope profiles with declivities up to 35 whereas the muddy bahamian flank sediments modified by large scale creep and rotational to translational sliding and slumping produce a concave upwards slope profile inclined at less than 4 the comparison between slope angle and sediment fabric indicates that the physical behaviour of sediments in the gravity field angle of shearing and mode of readjustment processes is linked to the composition of the slope sediment among the variables such as sea level subsidence climate plate motion and oceanographic setting windward leeward sediment fabric is suggested to be a major if not the major control on slope angle and slope curvature of carbonate platform flanks besides the recently documented tendency of carbonate sediments to build steeper slopes than siliciclastics this proposed relation sheds new light on the analysis and quantification of the variables influencing the geometry and depositional evolution of carbonate systems furthermore it provides an opportunity to deduce sediment composition from seismic lines and predict lithology prior to drilling

ocean circulation and iceberg discharge in the glacial north atlantic inferences from unmixing of sediment size distributions variability in iceberg discharge and deep ocean circulation in the north atlantic during the last glacial period is inferred from the grain size distribution and trace elemental composition of terrigenous sediments in a deep sea core taken on reykjanes ridge south of iceland end member modeling of the grain size distributions is used to unmix the signals of varying bottom current speed and iceberg discharge the size distribution within the silt fraction appears to be influenced by both factors based on th sc la relationship we established that during the ice rafted detritus events continental material of likely greenlandic origin increased to 87 and that bottom current derived material contains to 40 mid oceanic ridge fines probably of icelandic origin our results have important implications for the use of silt grain size as an indicator for paleocurrent speed in the glacial north atlantic we show that reconstructions of variations in bottom current speed based on the raw grain size data are opposite to inferences from the unmixed record the latter indicates that deep water convection decreased during periods of enhanced iceberg discharge which is in general agreement with paleoceanographic reconstructions of the north atlantic

timing duration and transitions of the last interglacial asian monsoon thorium 230 ages and oxygen isotope ratios of stalagmites from dongge cave china characterize the asian monsoon and low latitude precipitation over the past 160 000 years numerous abrupt changes in 18o 16o values result from changes in tropical and subtropical precipitation driven by insolation and millennial scale circulation shifts the last interglacial monsoon lasted 9 7 1 1 thousand years beginning with an abrupt less than 200 years drop in 18o 16o values 129 3 0 9 thousand years ago and ending with an abrupt less than 300 years rise in 18o 16o values 119 6 0 6 thousand years ago the start coincides with insolation rise and measures of full interglacial conditions indicating that insolation triggered the final rise to full interglacial conditions

automicrite in a nummulite bank from the monte saraceno southern italy evidence for synsedimentary cementation following introduction of the term nummulite bank there has been debate regarding interpretation of these types of deposits as autochthonous automicrite or allochthonous detrital micrite these banks are made up of large foraminifera and ill defined fine grained components the fine grained components consist mainly of micrites the recognition of automicrite has deep implications for the synsedimentary cementation and stabilization of the bank in order to distinguish between automicrite and detrital micrite the nanomorphology geochemistry and organic matter remains in the microfacies of a nummulite bank in the middle eocene of monte saraceno gargano southern italy were analysed optical and scanning electron microscope investigations showed that the micrites have been recrystallized to aggrading microsparite epifluorescence observations on selected micrite microsparite areas with peloidal texture revealed the presence of organic matter scanning electron microscope analyses on epifluorescent micrites showed that the microbial peloids have smaller crystal sizes than those in organic matter depleted areas the geochemical characterization of extracted organic matter performed through the functional group analyses by fourier transform infrared spectroscopy shows strong prevalence of the aromatic fraction over the aliphatic and carboxylic ones these characteristics of organic compounds indicate both their thermal maturation and their likely derivation from degradation of bacterial communities the local presence of peloidal anti gravity textures bright epifluorescence and organic molecules in clotted peloidal areas suggest that the metabolic activity of microbial communities could have induced precipitation of these micrites and consequently the syndepositional cementation of the nummulite bank this type of cementation can rapidly stabilize sediments and promote the depositional bank geometry

variation of east asian monsoon precipitation during the past 21 k y and potential co2 forcing paleoclimatic research can provide critical insight on causes of change in the east asian monsoon which influences the lives of 1 6 billion people today in this study we use paleoclimatic indexes from chinese loess deposits which have clear climatic implications and are independently dated to reconstruct the monsoon precipitation since 21 ka our results show that monsoon precipitation persistently decreased from 21 ka to ca 8 ka and increased after ca 8 ka with a precipitation peak at 8 3 ka these changes in east asian summer monsoon precipitation are synchronous with changes in high northern latitude ice volume ice cover and atmospheric co2 these new data suggest that variation of the monsoon precipitation was probably driven by co2 forced high northern latitude temperature changes shifting the location of the intertropical convergence zone that dominates monsoon precipitation our trace 21000 modeling experiment supports this interpretation

fluctuations in the east asian monsoon over the last 144ka in the northwest pacific based on a high resolution pollen analysis of images core md01 2421 abstract a high resolution pollen analysis of images core md01 2421 45 83 m from the northwest pacific off central japan was used to clarify the vegetation history of central japan over the past 144 ka an age model was constructed using the oxygen isotope stratigraphy of benthic foraminifera 12 accelerator mass spectrometry ams 14c datings and two tephra layers with known eruption ages the pollen temperature index t p 1 0 0 t w t c t w where tw is the sum of temperate taxa and tc the sum of subalpine taxa values were high during 129 119 115 100 82 76 53 49 and 15 0 ka cool temperate broad leaved forests developed during the high tp periods and subalpine conifer forests grew during the low tp periods the tp fluctuated synchronously with summer insolation at 36 n where the core was collected during periods with abundant cryptomeria or sciadopitys 120 118 115 89 78 70 and 4 0 3 ka the east asian summer monsoon was stronger and the annual precipitation was greater in central japan than at present 2000 vs 1500 mm fluctuations in the sea surface temperature sst calculated from the oxygen isotopes of foraminifera in core md01 2421 and changes in the strength of the summer monsoon were synchronous the sst was determined by the currents passing over the core site rather than by the strength of summer insolation northward movement high sst of the kuroshio current which is under the influence of the summer okhotsk high pressure was strong near the summer insolation minima when precipitation was high particularly around 116 94 and 71 ka thus the strengths of both summer insolation and the east asian summer monsoon have determined the vegetation history of central japan for the last 144 ka

temperature and leaf wax δ2h records demonstrate seasonal and regional controls on asian monsoon proxies orbital scale precipitation isotope records can elucidate climate forcing mechanisms and provide benchmarks for climate model validation the ability to differentiate the influence of temperature seasonality and vapor transport history on precipitation isotope proxies is critical to both objectives we present a 300 k y leaf wax hydrogen isotope record from the south china sea with the effects of local condensation temperature removed 2 h wax t 2 h wax t reflects annually integrated precipitation 2 h in the pearl river catchment of southeast china depleted 2 h wax t lags minimum precession p min by 1 0 0 7 k y reflecting the influence of maximum summer insolation and minimum winter insolation with a minor influence of global ice volume which lags p min by 3 3 0 4 k y in contrast annually integrated cave 18 o minima in central china 1000 km north of our site lag p min by 2 7 0 3 k y in phase with ice volume minima this phase indicates that precipitation 18 o in central china is more strongly influenced by ice volume forcing at the precession band with a lesser influence of northern hemisphere insolation our new 2 h wax t data demonstrate that precipitation isotopes in asia have strong regional variability interpreting water isotope records within the context of regionally varying temperature seasonality and sensitivity to changing glacial boundary conditions is imperative to understanding asian hydroclimatic change

an environmental investigation of the mineralogical geotechnical hydrogeologic and botanical properties of subsurface flow constructed wetlands in akumal mexico akumal is one of the few locations where subsurface flow constructed wetland systems can be compared directly without major differences in environmental setting these systems in akumal have highly variable geotechnical properties and performance and most systems are not well functioning a basic water quality survey indicates sfcw effluent in no case meets unep or usepa guidelines for ammonia or phosphate for sensitive waters systems are undersized and many are planted with less than optimal vegetation aggregate is generally too coarse and pores are commonly occluded with organic matter the mineralogy of the locally sourced aggregate used in the systems is dominated by calcite aragonite quartz boehmite and chlorite and is generally beneficial for improving the water quality of the systems however dissolution is observed and is of some concern major systematic retrofit efforts to improve these systems are warranted and should focus on better vegetation choices use of locally sourced smaller and less soluble aggregate exclusive use of the local limestone source containing boehmite more frequent exchange of the aggregate and an increase of overall cell size the systems in akumal are a classic example of a technological solution to an environmental problem caused by human development that has outpaced the designed capacity for wastewater treatment this investigation serves as a baseline for numerous future interdisciplinary investigations and outlines challenges facing coastal communities attempting to use subsurface flow constructed wetlands

quantification of topography using a laser transit system a laser transit is a surveying instrument that projects a pulsing laser beam at a point of interest and calculates the three dimensional coordinates of the point from the reflection we tested the laser transit on a rock slope and compared the results with a photogrammetric survey the case study showed that laser technology is a fast and accurate technique to quantify topography with a range of 350 m and an accuracy of 10 cm the three dimensional model of the topography can be printed in real time and can serve as basis for geological mapping and determination of bed thicknesses dips and other structural elements of the rock we foresee applications in seismic modeling of outcrops and studies of sediment anatomy and structural geology

formation and tectonic evolution of southeastern china and taiwan isotopic and geochemical constraints abstract the southern part of china consists of the proterozoic yangtze craton and the phanerozoic south china foldbelts including the himalayan foldbelt of taiwan models for continental growth have been many and controversial isotopic and geochemical data from mesozoic and younger granitoids and sediments are used here to place constraints on the tectonic evolution of southeastern china and to evaluate whether the young phanerozoic foldbelts are representative of old rejuvenated landmass whether they characterize crustal accretion through successive subduction processes hence suggesting a net growth of continental mass or whether they represent some intermediate situation available sm nd isotopic data for phanerozoic granitoids and metasediments from the south china foldbelts and taiwan invariably show proterozoic model ages t dm ranging from 1 to 2 5 ga with a mean of 1 54 0 30 1 ga all rocks have negative nd t values 2 to 15 suggesting variable but important contributions of old continental materials to the sources of the phanerozoic rocks obviously they do not represent wholesale growth of continental mass the granitoids of the south china foldbelts have multiple origins as viewed from their chemical and isotopic characteristics secular geochemical variation has been established for inland granitoids of proterozoic to mesozoic age their high i sr values 0 710 0 737 suggest that most granitoids are essentially anatectic products of ancient continental crust this is compatible with remelting via microcontinental collision or terrane accretion repeated intracrustal reprocessing by partial fusion and differentiation has undoutedly contributed to important mineralization mesozoic granitoids excluding a type alkaline granites in the coastal region and taiwan show relatively low i sr 0 705 0 710 and high nd values implying that greater amounts of mantle components have been added to ancient continental material in the generation of these rocks this means that mesozoic magmatism in the coastal region resulted from subduction of a paleo pacific plate kula beneath the asian continent the overall geochemical evidence seems to be consistent with a model of serial collisions between microcontinental blocks for the bulk of the south china foldbelts the latest arc continent collision began about 4 ma ago in eastern taiwan

synchronicity of kuroshio current and climate system variability since the last glacial maximum the kuroshio current kc is the northward branch of the north pacific subtropical gyre npg and exerts influence on the exchange of physical chemical and biological properties of downstream regions in the pacific ocean resolving long term changes in the flow of the kc water masses is therefore crucial for advancing our understanding of the pacific s role in global ocean and climate variability here we reconstruct changes in kc dynamics over the past 20 ka based on grain size spectra clay mineral and sr nd isotope constraints of sediments from the northern okinawa trough combined with published sediment records surrounding the npg we suggest that the kc remained in the okinawa trough throughout the last glacial maximum together with earth system model simulations our results additionally indicate that kc intensified considerably during the early holocene eh the synchronous establishment of the kc water barrier and the modern circulation pattern during the eh highstand shaped the sediment transport patterns this is ascribed to the precession induced increase in the occurrence of la nina like state and the strength of the east asian summer monsoon the synchronicity of the shifts in the intensity of the kc kuroshio extension and el nino la nina southern oscillation enso variability may further indicate that the western branch of the npg has been subject to basin scale changes in wind stress curl over the north pacific in response to low latitude insolation superimposed on this long term trend are high amplitude large century and millennial scale variations during last 5 ka which are ascribed to the advent of modern enso when the equatorial oceans experienced stronger insolation during the boreal winter

carbonate buildup flank deposits an example from the permian barents sea northern norway challenges classical facies models mounds seen on seismic in the barents sea offshore northern norway occur in the upper palaeozoic of the finnmark platform a 160 m long cored section from such a mound dated as unspecified asselian artinskian lower permian documents a carbonate buildup of microbial origin and rich in stromatactis fabric the cored section of a buildup where depositional dip angles vary from a few degrees to about 45 approximately 2 3 of the flank consists of in situ microbial boundstone with abundant stromatactis and in the upper part bryozoan cement framestone the remainder is gravity flow sediment deposited on the flank and at the toe of the buildup consisting of argillaceous sediment alternating with crinoid grainstones modal thin section analysis indicates that biogenic particles make up 38 of the buildup flank diagenetic products such as early fibrous cement microcrystalline cement and late blocky calcite 46 and lime mud including that interpreted as microbially induced 16 the studied core interval shows that steeply inclined buildup flanks can be largely in situ deposits rather than allochthonous as predicted in classical facies models

rapid growth rates of syndepositional marine aragonite cements in steep marginal slope deposits bahamas and belize abstract growth rates of marine botryoidal aragonite cements from steep 35 45 marginal slope deposits in the bahamas and belize have been determined by accelerator mass spectrometer radiocarbon dating of samples taken at the base and top of individual botryoids the pore filling cements which range from approximately 11 000 13 000 years old grew at average rates of 8 10 mm 100 yr with maximum rates 25 mm 100 yr radiocarbon dating of coexisting skeletal components indicates that cementation was syndepositional microsampling transects across individual botryoids for stable isotope analyses show little variation in 13c and 18o supporting the conclusion that cementation was extremely rapid although the cements show a progressive depletion in isotopic composition of approximately 1 13c and 2 18o from 13 ka to 11 ka the average variation 1 within individual por filling cements ranging in size from 2 mm to 32 mm bottom to top was 0 11 13c and 0 14 18o results of this study provide the first quantitative data on growth rates of marine carbonate cements in a marginal slope environment the data indicate that marginal slope deposits may lithify within several tens of years and suggest that geologically instantaneous cementation may be critical in stabilizing steep carbonate slope deposits at or above angles of repose

subsidence and sedimentation on jurassic passive continental margin southern alps italy the southern alps of italy preserve a tectonically intact array of jurassic facies that record the evolution of a part of the margin of the apulian plate from its ancestral beginnings in a complex of permian and triassic rifted continental basins through the initial stages of breakup and stepwise foundering of a carbonate platform breakup was accompanied first by the rapid accumulation of thick prisms of carbonate turbidites in newly formed fault troughs then as the new ligurian oceanic basin began to open farther west and as subsidence gradually slowed accumulation of a succession of slowly deposited biogenous pelagic sediments recorded not only the increasing depths of the seafloor but also fluctuations in oceanographic conditions of fertility carbonate dissolutio levels and the strength of bottom currents estimates of the history of seafloor depths based on a simple subsidence law of the form subsidence k age 12 provide a basis for the construction of a set of curves showing the changing depths of significant carbonate dissolution surfaces during the jurassic in this region the rapid 1 km deepening of the compensation depth for calcite during the late jurassic may be due to a change in regional oceanic vertical circulation patterns from upwelling fertile silica rich carbonate dissolving to downwelling less fertile silica poor carbonate preserving

development of volcanic insular shelves insights from observations and modelling of faial island in the azores archipelago a variety of geological processes contribute to the development of volcanic island shelves although their relative importance remains unclear we have mapped the morphology of faial island s shelf in the azores from geophysical multibeam sonar chirp and boomer seismic reflection and geological data sediment sampling a wave erosional model and a eustatic record of glacially induced oscillations of sea level which modulated the elevation at which the waves operated through time was used to determine the contribution of mechanical wave erosion to shelf development wave regimes varied according to the orientation of the coast the model was run for 10 to 800 ka depending on the age of the various coastal sectors based on published radiometric data the modelling replicated the shape of the island s shelf reasonably well supporting the contention that it developed primarily through mechanical wave erosion operating in an intertidal zone that migrated landwards and seawards with changes in the level of the sea disparities between modelled and actual shelf morphologies may reflect varied geological resistance to erosion errors in the radiometric dates more recent unrecognised volcanic deposits sediment deposition and tectonic vertical movements there were some variation in rates of shelf development over different time scales but over the long term the relationship between shelf age and width was essentially linear the depth of the shelf break in some areas suggests that there have been differential vertical movements of the land around the island probably related to local faults the poor development or absence of terraces on the shelf may be attributed either to recent volcanic progradation or to sediment infilling of the space created by earlier erosion however poorly developed terraces on the southern shelf of faial are similar to those predicted by the model given appropriate adjustments for vertical movements of the land

the apulia carbonate platform gargano promontory italy upper jurassic eocene the upper jurassic to eocene carbonate rocks of the gargano promontory belong to the apulia carbonate platform acp and provide a spectacular and complete succession of slope and base of slope resedimented gravity flow carbonates with preserved reservoir properties and with its coeval carbonate platform displaying various tectonostratigraphic architectures the acp margin is characterized by an overall aggrading architecture and different geometric and depositional features facies types and sedimentary dynamics of the carbonate slope and gravity deposits can be analyzed with respect to the stratigraphic architecture of the platform to basin transition these outcrops are the only analogs of some important oil reservoirs and plays present in the equivalent slope to basin succession in the adriatic offshore and elsewhere

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

seasonality and interannual variability of the westerly jet in the tibetan plateau region abstract in this study 40 yr ecmwf re analysis era 40 data are used for the description of the seasonal cycle and the interannual variability of the westerly jet in the tibetan plateau region to complement results based on the analysis of monthly mean horizontal wind speeds an occurrence based jet climatology is constructed by identifying the locations of the jet axes at 6 hourly intervals throughout 1958 2001 thus a dataset describing the highly transient and localized features of jet variability is obtained during winter and summer the westerly jet is located respectively to the south and north of the tibetan plateau during the spring and autumn seasons there are jet transitions from south to north and vice versa the median dates for these transitions are 28 april and 12 october the spring transition is associated with large interannual variations while the fall transition occurs more reliably within a 3 week period the strength of the jet exhibits a peculiar seasonal cycle during northw

east asian hydroclimate modulated by the position of the westerlies during termination i speleothem oxygen isotope records have revolutionized our understanding of the paleo east asian monsoon yet there is fundamental disagreement on what they represent in terms of the hydroclimate changes we report a multiproxy speleothem record of monsoon evolution during the last deglaciation from the middle yangtze region which indicates a wetter central eastern china during north atlantic cooling episodes despite the oxygen isotopic record suggesting a weaker monsoon we show that this apparent contradiction can be resolved if the changes are interpreted as a lengthening of the meiyu rains and shortened post meiyu stage in accordance with a recent hypothesis model simulations support this interpretation and further reveal the role of the westerlies in communicating the north atlantic influence to the east asian climate

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

sedimentation on a lower jurassic carbonate platform flank geometry sediment fabric and related depositional structures djebel bou dahar high atlas morocco abstract along the southern margin of the high atlas morocco carbonate platforms of lower jurassic age developed in a transtensional basin the south atlas trough complete exposure and preservation of the platform margin flank and basin of the djebel bou dahar allowed the subdivision of the slope into an upper mid and lower slope based on geometry sediment fabric and depositional structures at ca 50 m below the platform margin coral algal patch reefs and ooid sand shoals grade into the depositional slope the straight upper slope showing discontinuous bedding at angles up to 29 extends down to ca 250 m and consists mainly of poorly sorted mixtures of sand and gravel almost devoid of mud avalanching rockfall and shearing of the coarse gravelly sediment are the dominant processes readjusting the upper slope the middle and lower part of the slope profile extending down to ca 500 m below the margin is separated from the upper slope by a distinct slope break slope angles range from 19 near the slope break down to 4 8 where the slope merges with the basin plain the irregularly bedded mid slope is characterized by scouring and deposition of muddy sands and non cohesive gravelly debris flows sedimentation on the dominantly muddy concave upwards lower slope can be separated into evenly bedded shales muddy sands and mud free gravel sand mixtures deposited as debris sheets the results of this study emphasize the relationship between sediment fabric and the slope geometry of a carbonate platform flank the overall geometry internal heterogeneity and depositional structures are suggested to be strongly related to the original character of the sediment supplied to the djebel bou dahar platform flank

nd and sr isotopic characteristics of chinese deserts implications for the provenances of asian dust silicate nd sr isotopes of the fine grained fractions of the 10 major deserts and sandy lands in north china and the loess in chinese loess plateau were systematically investigated wide ranges in nd sr isotopic compositions have been observed the results of the 7 0 b the deserts on the northern margin of tibetan plateau with end 0 ranging from 11 9 to 7 4 and c the deserts on the ordos plateau with the lowest end 0 11 5 the distribution of the threes isotopic regions is controlled by the tectonic setting in north china which implies that the materials of the deserts are derived from the locally eroded rocks from the surrounding mountains and the nd sr isotopic signatures of these deserts could be quit stable over the past million years on the sub tectonic time scales if there is any desert at those times the nd sr isotopic compositions of the loess are mostly close to those of the deserts in isotopic region b suggesting that the main source regions of the last glacial loess in the chinese loess plateau are badain jaran desert tengger desert and qaidam desert also the comparison between the nd sr isotopes of the 5 lm silicate fractions of the deserts and the ancient dust falls in the north pacific and greenland show that the asian end members of these dust falls are derived most from the deserts in the isotopic region b and less from those in the isotopic region c

hydrogeology of the south eastern yucatan peninsula new insights from water level measurements geochemistry geophysics and remote sensing summary the yucatan peninsula is one of the world s largest karstic aquifer systems it is the sole freshwater source for human users and ecosystems the region hosts internationally important groundwater dependent ecosystems gdes in the 5280 km2 sian ka an biosphere reserve the gdes are threatened by increasing groundwater abstractions and risks of pollution hydrogeological exploration work is needed as basis for sound groundwater management a multidisciplinary approach was used to study this data scarce region geochemical data and phreatic surface measurements showed distinct hydrogeological units in the groundwater catchment of sian ka an the hilly southwestern areas had a low hydraulic permeability likely caused by a geology containing gypsum whereas the transition zone and flat areas in the east and north had a high permeability in the latter areas the fresh groundwater could be described by a dupuit ghyben herzberg lens geophysical borehole logging and time domain electromagnetic soundings identified a shallow low resistive and high gamma radiation layer present throughout the hilly area and transition zone its thickness was 3 8 m apparent conductivity was 200 800 ms m and natural gamma radiation about 80 counts pr second the layer is proposed to be ejecta from the chicxulub impact cretaceous paleogene boundary spatial estimates of recharge were calculated from modis imagery using the triangle method average recharge constituted 17 of mean annual precipitation in the study area recharge was greatest in the hilly area and towards valladolid near the coast average actual evapotranspiration exceeded annual precipitation the multidisciplinary approach used in this study is applicable to other catchment scale studies

a new locality of palygorskite rich clay from the southeastern yucatan a potential material source for environmental applications a palygorskite unit was discovered in a road cut of undifferentiated tertiary limestone between the villages of el pariso and san roman 18 49 309n 88 37 861w in the southeastern yucatan peninsula mexico this is the southern most locality of a clay rich sedimentary unit reported in the literature for the tertiary carbonates of the yucatan peninsula this occurrence indicates a much wider range of palygorskite rich clay deposition than previously recognized the lithology is 99 clay and 1 sand to silt size diagenetic quartz grains the clay consists of approximately 85 palygorskite 15 montmorillonite and trace amounts of titanium oxides eds analyses on palygorskite are largely consistent with sedimentary palygorskites from other coastal marine settings however palygorskite has a low total fe content average 0 40 wt expressed as fe2o3 compared to many other sedimentary palygorskites montmorillonite chemical compositions are typical and compared to the palygorskite have substantially higher fe2o3 concentrations average 3 90 wt the low percentage of coarse grains in the lithology combined with a high proportion of palygorskite and lack of detrimental trace minerals suggest the deposit is of industrial grade however it has limited reserves 6 000 m3 the unit could be potentially used in a wide array of environmental applications which are needed in the region including liners for landfills and constructed wetlands the unit is in a geographic location which would serve the expanding economy of the region this resource has the potential to have great impact on the quality of the local environment and the economy of a region under great environmental threat

nd sr systematics of the setouchi volcanic rocks southwest japan a clue to the origin of orogenic andesite abstract twenty three volcanic rocks from the setouchi volcanic belt southwest japan were analyzed for nd and sr isotopic compositions for the purpose of examining the genetic relationships among the basalt high magnesium andesite hma and evolved porphyritic andesite the andesites have higher 87 sr 86 sr 0 70487 0 70537 and lower 143 nd 144 nd 0 512509 0 512731 than the basalts i e 0 70408 0 70468 and 0 512691 0 512830 respectively this result confirms earlier conclusions obtained from petrologic study that the andesites cannot be fractionation products of basaltic magma but that the andesitic and basaltic magmas were generated independently on the basis of melting experiments for hma and basalt it is inferred that there is an isotopically stratified mantle beneath southwest japan evolved porphyritic andesites have essentially identical sr and nd isotopic ratios to hma and can be derived by fractionation of primary andesitic magma a model to produce orogenic andesite is proposed on petrologic experimental and isotopic bases

long term event stratigraphy of the apulia platform margin upper jurassic to eocene gargano southern italy abstract the upper jurassic to eocene apulia platform margin and the eastward transition to the adjacent basinal deposits are well exposed in the gargano promontory southern italy a carbonate block that is part of the slightly deformed foreland of the southern apennine thrust belt the long term stratigraphy of this margin and slope transect is punctuated by five major dynamic phenomena that subdivide the succession into six second order sequences these events include 1 a valanginian drowning unconformity 2 an early aptian albian drowning and demise of the platform 3 late albian cenomanian platform margin failures 4 a santonian campanian retreat of the platform margin and 5 eocene uplift and platform margin collapse the first event is documented worldwide and is probably eustatic in origin the second is concomitant with some oceanic anoxic events oae the last three processes are probably related to foreland reaction to subduction and collision in the dinarides and hellenides thrust belts the ultimate cause of the albian cenomanian failures is more problematic a worldwide eustatic regression is documented at this time but regional geology seems to favor tectonic uplift

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

sedimentary responses to the pleistocene climatic variations recorded in the south china sea grain size analyses coupled with end member modelling have been performed on the terrigenous fraction of two leg 184 ocean drilling program sites 1144 and 1146 from the south china sea the grain size distributions over the last 1 8 ma enable a new interpretation of their connections to sea level variations and east asian monsoon strength previous investigations in this area have associated grain size variability with enhanced eolian input during glacial stages end member modelling downgrades the importance of this eolian contribution and indicates that the sediments can be described as a mixture of three end members fluvial mud inputs shelf reworking and river mouth migration grain size variations in the pleistocene section of the cores indicate a multiple stage evolution i from 1 8 to 1 25 ma the downcore grain size variations are low but show a correspondence between monsoon rainfall intensity and the fine grain sized fluvial inputs no link with sea level variations is noticeable ii from 1 25 to 0 9 ma there is an increase decrease in the intermediate fine end member 100 kyr cycle that is associated with the onset of a stronger summer monsoon and modest shelf reworking iii from 0 9 to 0 ma the grain size record is dominated by global sea level variations each glacial stage is associated with extensive shelf reworking and conveyance of coarse particles to the basin 2007 university of washington all rights reserved

concordant monsoon driven postglacial hydrological changes in peat and stalagmite records and their impacts on prehistoric cultures in central china asian monsoon records are widely documented but specific proxies of monsoonal rainfall are limited we present here two new independent proxy records from peatland and stalagmite archives that indicate a high degree of concordance between monsoon driven hydrological changes occurring since the last deglaciation in a broad region of central china the wet periods elevated the water table in the dajiuhu peatland as recorded by reduced mass accumulation rates of hopanoids biomarkers for aerobic microbes confirmed by molecular phylogenic analyses the hopanoid based reconstruction is supported by the first report of the environmental magnetism parameter arm sirm anhysteretic remanent magnetization saturation isothermal remanent magnetization ratio of fine magnetic particles to total ferrimagnetic particles in a stalagmite from heshang cave in central china heavy rainfall resulted in the enhanced transport of coarse particles to the cave and thus low arm sirm values in the stalagmite the hydrological conditions inferred from the two records reveal three relatively long wet periods in central china 13 11 5 k y ago 9 5 7 0 k y ago and 3 0 1 5 k y ago archaeological evidence for the hydrological impacts on regional populations comes from the observation that temporal shifts among six distinctive cultures of the neolithic period to the iron age in central china occurred during wet periods or flood episodes spatiotemporal distributions of 1600 prehistoric settlement sites correlate with the proxy inferred fluctuating hydrological conditions with enhanced flooding risk forcing major relocations of human settlements away from riparian zones

compositional changes in sigmoidal carbonate clinoforms late tithonian eastern sardinia italy insights from quantitative microfacies analyses quantitative analysis of sediment composition was performed on a kilometre wide section of upper tithonian low relief up to 70 m gently inclined 3 to 15 sigmoidal carbonate clinoforms eastern sardinia to identify changes in sediment composition along the slope and across the studied succession these changes may reflect modifications of the carbonate factory and of processes responsible for sediment transport point count analysis of carbonate microfacies q mode r mode cluster analysis and spearman s rank provided a composition based classification of microfacies and highlighted relationships among sediment components the studied clinoforms are mainly composed of non skeletal grains 70 such as peloids and lithoclasts together with micrite and cements and only a limited contribution from coated grains 2 among skeletal grains 28 the greatest contribution derives from a coral stromatoporoid encruster reef that provided 15 of the components crinoids brachiopods and other along slope thriving biota provided nearly 5 of the allochems whilst fragments of molluscs gastropods bivalves and diceratids from the backreef sourced another 2 the contribution of platform interior biota is negligible 1 the association of composition based facies varies along the slope the upper slope beds consist of coral stromatoporoid grainstone to rudstone the middle slope deposits are dominated by encruster lithoclast grainstone and packstone at the lower slope peloidal lithoclastic packstone as well as brachiopod crinoidal wackestone prevail also the association of skeletal grains changes along the slope the encruster frame builder association typifies the upper slope whilst encrusters characterize the middle slope sediments in the lower slope encrusters are equally represented as the brachiopod crinoid association along slope compositional changes evidence a scarce downslope transport of frame builders and a progressive enrichment in along slope thriving biota quantitative analysis of microfacies allowed the sigmoidal clinoforms to be grouped into six sets each set gathers sigmoids with a similar sediment composition coated grains are dominant in the first set whilst they are lacking in the overlying sets reflecting a change in the carbonate factory other major compositional changes among the sets concern the relative amounts of peloids micrite frame builders corals and stromatoporoids and encrusters the contribution of peloids varies inversely to that of cements and micrite as evidenced in the third and fifth sets which respectively record the highest occurrence of peloids or cement and micrite variations in the amount of frame builders and encrusters are instead non linear high percentages of both frame builders and encrusters as recorded in the second and fifth sets are related to low amounts of peloids and lithoclasts that probably reflect episodes of reduced background sedimentation this study demonstrates that quantitative analysis of carbonate microfacies represents a powerful tool that can improve the reconstruction of the stacking pattern in carbonate slope successions both in outcrop and in subsurface settings

delayed build up of arctic ice sheets during 400 000 year minima in insolation variability an east asian winter monsoon proxy record using grain size variations in chinese loess over the past 900 000 years shows that for up to 20 000 years after the interglacials at 400 000 year intervals the weak monsoon winds maintain a mild non glacial climate at high northern latitudes qingzhen hao and colleagues present a record of grain size variations in the chinese loess plateau a proxy of variations in the strength of the east asian winter monsoon and show that relatively high insolation at 400 000 year intervals held off the inception of the subsequent ice age for about 20 000 years relative to other glacial inceptions mechanistically the extension of warm conditions was probably linked to a weak siberian high pressure system associated with a delayed build up of northern ice and snow the authors speculate that these observations imply that arctic climate may remain in non glacial mode for more than 40 000 years even in the absence of anthropogenic greenhouse gases knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial1 may help to inform our understanding of future climate change unfortunately long term continuous records of ice sheet variability in the northern hemisphere only are scarce because records of benthic 18o content represent an integrated signal of changes in ice volume in both polar regions2 however variations in northern hemisphere ice sheets influence the siberian high3 an atmospheric pressure system so variations in the east asian winter monsoon eawm as recorded in the aeolian dust deposits on the chinese loess plateau can serve as a useful proxy of arctic climate variability before the ice core record begins here we present an eawm proxy record using grain size variations in two parallel loess sections representative of sequences across the whole of the chinese loess plateau over the past 900 000 years the results show that during periods of low eccentricity and precessional variability at approximately 400 000 year intervals the grain size inferred intensity of the eawm remains weak for up to 20 000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis in contrast there is a rapid increase in the eawm after the end of most other interglacials we conclude that for both the 400 000 year interglacials the weak eawm winds maintain a mild non glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records during these times the less severe summer insolation minima at 65 n ref 4 would have suppressed ice and snow accumulation leading to a weak siberian high and consequently weak eawm winds

nd isotopic study of precambrian basement of south korea evidence for early archean crust we carried out a sm nd isotopic reconnaissance study of south korea eight river sediments gave crustal residence ages t dm between 1 7 and 2 7 ga implying that on average the crust of south korea was formed in early to middle proterozoic time twenty six precambrian basement rocks yielded t dm between 1 4 and 3 8 ga more than half of them exceed 2 5 ga indicating that south korea has a long history of crustal evolution four of the samples have t dm from 3 2 to 3 8 ga suggesting the possibility that there may be ancient continental crust in korea having ages comparable to those of the oldest cratons in the world however these samples also have preferentially higher sm nd so their old ages could be artifacts thus requiring confirmation the large variation in t dm of south korea is reminiscent of that for the south china block however the existence of early archean ages better matches that of the north china block because the basement of south china was thought to be mostly proterozoic in age the recent discovery of rare archean basement rocks in the south china block may favor models that attempt to correlate south korea with south china

biogeochemical evidence of holocene east asian summer and winter monsoon variability from a tropical maar lake in southern china abstract lake huguangyan 21 9 n 110 17 e a maar lake located near the south china sea can provide valuable sedimentary data regarding past changes of the east asian monsoonal system here we used the proxies of toc 13corg 15n and leaf wax n alkane 13c values 13cwax to reconstruct the lake conditions which in turn revealed patterns in monsoonal changes during the holocene two distinct patterns of proxy changes were identified in the sedimentary profile a marked shift in the 13cwax value at 9 2 ka thousand years ago suggests the abrupt disappearance of c4 plants signaling the enhancement of east asian summer monsoon easm between 9 2 and 1 8 ka a nearly pure c3 terrestrial ecosystem was present with the climax at ca 7 6 ka after ca 3 ka fewer tropical species and a reappearance of c4 plants at 1 8 ka indicate a weakened easm in the late holocene the toc concentration and 15n value proxies appear to be associated with lake aquatic production and upwelled nutrient supply and utilization which are modulated by and thus indicative of the strength of the east asian winter monsoon eawm the two eawm records suggest a weakening trend from the early to late holocene with the most significant transition at 6 ka thus the eawm trend was broadly in phase with that of the easm however the marked easm intensification at 9 2 ka occurred within the period of a strong eawm between 10 5 and 6 ka and lagged the monsoonal enhancement as inferred from the dongge cave 18o values our easm records displays an overall arid wet arid pattern which is in phase with the hydrological variability in tropical australia and anti phase with that in the outer tropical andes these phase relationships might be linked to changes in the thermal state of the tropical pacific during the holocene

investigations of subsurface flow constructed wetlands and associated geomaterial resources in the akumal and reforma regions quintana roo mexico subsurface flow constructed wetlands in the village of akumal quintana roo mexico were surveyed to determine the general status of the wetland systems and provide baseline information for long term monitoring and further study twenty subsurface flow wetlands were surveyed and common problems observed in the systems were overloading poor plant cover odor and no secondary containment bulk mineral composition of aggregate from two subsurface flow constructed wetlands was determined to consist solely of calcite using bulk powder x ray diffraction some soil structure is developed in the aggregate and aggregate levels in wetlands drop at an estimated rate between 3 and 10 cm year for overloaded wetlands owing to dissolution mineral composition from fresh aggregate samples commonly is a mixture of calcite and aragonite trace amounts of pb zn co and cr were observed in fresh aggregate coefficients of permeability k varied from 0 006 to 0 027 cm s with an average values being 0 016 cm s grain size analysis of fresh aggregate samples indicates there are unimodal and multimodal size distributions in the samples with modes in the coarse and fine sand being common investigations of other geologic media from the reforma region indicate that a dolomite with minor amounts of fe oxide and palygorskite is abundant and may be a better aggregate source that the current materials used a ca montmorillonite bed was identified in the reforma region as well and this unit is suitable to serve as a clay liner to prevent leaks for new and existing wetland systems these newly discovered geologic resources should aid in the improvement of subsurface flow constructed wetlands in the region although problems do exist in these wetlands with respect to design these systems represent a successful implementation of constructed wetlands at a community level in developing regions

orbital scale timing and mechanisms driving late pleistocene indo asian summer monsoons reinterpreting cave speleothem δ18o 1 southeast china cave 18o often interpreted as a pure east asian summer monsoon proxy lags maximum northern hemisphere summer insolation by 2 9 0 3 kyrs at the precession cycle the arabian sea summer monsoon stack lags by 8 1 kyr consistent with 13 other indian and east asian summer monsoon proxies from marine lake and terrestrial archives this 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology it requires reconciliation in the context of proxy interpretation both of these lags are incompatible with a direct response to northern hemisphere summer insolation implicating additional forcing mechanisms analysis of heterodynes in the cave 18o spectrum demonstrates that variance contained in the arabian sea summer monsoon proxies also resides in the cave 18o record this variance is subtracted from the cave 18o record yielding a residual that is highly coherent and in phase with precession minima reflecting the impact of winter temperature change on cave 18o meteorological precipitation under cold conditions thus we argue that the timing of light cave 18o peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone the 2 9 kyr precession band phase lag of cave 18o reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima this interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast china

the rare earth element compositions of the changjiang yangtze and huanghe yellow river sediments thirty four samples from the changjiang and huanghe were analyzed to characterize their rare earth element ree compositions although ree concentrations in the changjiang sediments are higher than those of the huanghe sediments the former are less variable bulk samples and acid leachable fractions have convex ree patterns and middle ree enrichments relative to upper continental crust whereas flat patterns are present in the residual fractions source rock composition is the primary control on ree composition and weathering processes play a minor role grain size exerts some influence on ree composition as demonstrated by the higher ree contents of clay minerals in sediments from both rivers heavy minerals contribute about 10 20 of the total ree in the sediments apatite is rare in the river sediments and contributes less than 2 of the ree content but other heavy minerals such as sphene allanite and zircon are important reservoirs of residual ree fractions the fe mn oxides phase accounts for about 14 of bulk ree content in the changjiang sediments which could be one of the more important factors controlling ree fractionation in the leachable fraction 6 2002 elsevier science b v all rights reserved

geochemical provenance of sediments from the northern east china sea document a gradual migration of the asian monsoon belt over the past 400 000 years abstract the reconstruction of the long term evolution of the east asian monsoon remains controversial in this study we aim to give a new outlook on this evolution by studying a 400 kyr long sediment record u1429 from the northern east china sea recovered during iodp expedition 346 neodymium isotopic ratios and rare earth element concentrations of different grain size fractions reveal significant provenance changes of the sediments in the east china sea between east asian continental sources mainly yellow river and sediment contributions from the japanese archipelago these provenance changes are interpreted as the direct impact of sea level changes due to the reorganization of east asian river mouth locations and ocean circulation on the east china sea shelf and latitudinal shifts of the intertropical convergence zone itcz from the interior of asia to the western north pacific ocean our data reveal the dominance of winter and summer monsoons during glacial and interglacial periods respectively except for glacial mis 6d 150 180 ka during which unexpected summer monsoon dominated conditions prevailed finally our data suggests a possible strengthening of the interglacial summer monsoon rainfalls over the east asian continent and japan throughout the past 400 kyr and between mis 11 and mis 5 in particular this could result from a gradual northward migration of the itcz

evaluating drivers of pleistocene eastern tropical pacific sea surface temperature sea surface temperature sst of the eastern equatorial pacific is a key component of tropical oceanic and atmospheric circulation with global teleconnections forcing factors such as local and high latitude insolation changes ice sheet size and albedo feedbacks and greenhouse gas radiation have been proposed as controls of long term eastern tropical pacific sst though the precise role each mechanism plays is not fully known on glacial interglacial or longer timescales here proposed mechanisms are evaluated by comparing orbital scale records of eastern pacific sst with forcing variability over the past 1 5 ma the primary sst records are a compilation of new and existing data from ocean drilling program site 1239 at the northeastern margin of the modern eastern pacific cold tongue and site 846 sst within the cold tongue using time series analysis we test previously proposed mechanisms for control of long term tropical sst change and sst gradients in the eastern pacific we find that within statistical uncertainties in the precession band eastern pacific sst is consistent with direct forcing by equatorial radiation changes in the tropical cold season summer fall rather than inversely correlated as previously suggested in the obliquity band high latitude solar forcing leads or is in phase with eastern equatorial pacific sst while in the eccentricity band atmospheric greenhouse gas concentrations are closely associated with cold tongue sst pleistocene eastern pacific sst gradients indicate that the gradient on the northern margin of the cold tongue strengthened through the mid pleistocene transition a result compatible with the cold tongue becoming more focused at 900 650 ka

smnd isotopic geochemistry of sediments from taiwan and implications for the tectonic evolution of southeast china abstract an isotopic and geochemical study on the miocene to late paleozoic sediments and metasediments of taiwan has been conducted in order to decipher the crustal evolution of se china with the exception of a few late paleozoic sediments most samples from taiwan have a narrow range in sr and nd isotopic ratios and sm nd crustal residence ages t dm assuming derivation from a depleted mantle source the isotopic characteristics are similar to those of suspended material from major rivers around the world in particular they closely resemble those reported for the yangtze river sediment and the pre cretaceous granitoids of se china no obvious trend in t dm or isotopic ratios has been found with respect to the depositional ages indicating no pronounced secular variation however a few late paleozoic samples might have been influenced by fresh mantle inputs to their provenance proterozoic t dm of the sediments combined with proterozoic pb components in zircons from taiwan s granitoids suggest that important crustal growth in se china took place in the middle proterozoic the isotopic and geochemical characteristics of the sediments suggest that their sources were primarily recycled pre existing continental crust ree contents of taiwan sediments measured in this study are similar to the suspended load in major rivers paas post archean average australia shale nasc north american shale composite and the continental shelf slope sediments from the east china sea off the mouth of the yangtze they seem to represent products derived from typical continental crust lower hree abundances in taiwan sediments suspended load in major rivers and surface sediments from the e china sea than those of paas suggest that the source of hree in paas is likely to be slightly different from that for these recent terrigenous sediments an alternative for the explanation of this hree discrepancy is that a certain proportion of hree in these recent sediments were left in the residue partially dissolution of heavy mineral in analysis procedures particularly zircon even in a teflon bomb might cause this hree discrepancy late yanshanian granitoids now widely exposed on the se china coast have higher nd and lower sr isotopic ratios than those for taiwan s sediments so these granitic intrusions were not a major source for the sediments indicating that they were not exposed to erosion until the miocene or later

analysis of the field dependence of remanent magnetization curves 1 a new method to calculate and analyze coercivity distributions of measured acquisition demagnetization curves of remanent magnetization is presented the acquisition demagnetization curves are linearized by rescaling both the field and the magnetization axes an appropriate filtering of the linearized curves efficiently removes measurement errors prior to evaluating the coercivity distributions the filtered coercivity distributions are modeled using a set of generalized probability density functions in order to estimate the contributions of different magnetic components an error estimation is calculated for these functions with analytical and numerical methods in order to evaluate whether the model is significantly different from the measured data three sediment samples from baldeggersee switzerland and three samples of urban atmospheric particulate matter pm have been analyzed using this method it is found that the coercivity distributions of some of the magnetic components show significant and consistent deviations from a logarithmic gaussian function large deviations are found also in the coercivity distributions of theoretical af demagnetization curves of single domain and multidomain particles constraints in the shape of model functions affect the identification and quantification of magnetic components from remanent magnetization curves and should be avoided as far as possible the generalized probability density function presented in this paper is suitable for appropriate modeling of gaussian and a large number of non gaussian coercivity distributions