an 15 000 year record of el nino driven alluviation in southwestern ecuador debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the pacific ocean in ecuador these storm induced events were dated by radiocarbon and the age of laminae that are less than 200 years old matches the historic record of el nino events from about 15 000 to about 7000 calendar years before the present the periodicity of clastic deposition is greater than or equal to 15 years thereafter there is a progressive increase in frequency to periodicities of 2 to 8 5 years this is the modern el nino periodicity which was established about 5000 calendar years before the present this may reflect the onset of a steeper zonal sea surface temperature gradient which was driven by enhanced trade winds

relationship between magnetic fabrics and shear directions in melange within the miyama formation shimanto accretionary complex japan article i nfo the magnetic fabrics of tectonic melange in the miyama formation shimanto accretionary complex of kii peninsula japan are examined using anisotropy of magnetic susceptibility ams data and they are com pared with shear directions estimated by traditional measurements of p y intersections in the melange in most cases ams data are consistent with the estimated shear directions and they can be divided into two types one with kmax the maximum magnetic susceptibility axes oriented parallel to the shear direction on the shear planes and another with kmax axes oriented parallel to the p y intersections in both types the kmin the minimum magnetic susceptibility axes are oriented perpendicular to the melange foliation however some sites exhibit unexpected kmax axes orientations trending perpendicular to the melange foli ation analyses of texture and magnetic properties indicate that such unexpected orientations are caused by a predominance of single magnetic domains of magnetite and or the existence of ankerite and siderite veins in which the long axes of crystals are oriented perpendicular to the foliation in the melange as a consequence the restored shear direction deduced from ams data improved the credibility of the kinematics of ancient plate motions although ams data provide useful information on shear directions in melanges it is essential to examine the magnetic carriers and their magnetic domain structures for accuracy of the analyses

strain decoupling across the decollement in the region of large slip during the 2011 tohoku oki earthquake from anisotropy of magnetic susceptibility abstract the integrated ocean drilling program iodp expedition 343 japan trench fast drilling project jfast drilled and cored across the plate boundary decollement at site c0019 near the japan trench where large slip occurred during the 2011 tohoku oki earthquake m w 9 0 anisotropy of magnetic susceptibility ams data obtained from core samples show a striking change in magnetic fabric across the decollement in the frontal prism above the decollement the maximum ams axes display a strong preferred orientation in the northeast southwest direction with the intermediate and minimum ams axes distributed in the vertical plane in the underthrust sediments below the decollement the maximum and intermediate ams axes are subhorizontal but variable in direction and the minimum ams axes display an approximately vertical preferred orientation the ams ellipsoids for all samples have an oblate component but the ams ellipsoids of the underthrust sediments are generally less oblate than those of the frontal prism the magnetic fabric of the sediments in the prism are consistent with horizontal tectonic shortening nearly parallel to the plate convergence direction in the japan trench while that in the underthrust sediments represents a vertical uniaxial strain the magnetic fabrics of the frontal prism and underthrust sediments indicate an abrupt change in strain across the decollement at shallow depths and imply that large co seismic slip occurred along a weak plate boundary decollement that is mainly decoupled over the long term

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

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

bed load and suspended load contributions to migrating sand dunes in equilibrium dunes dominate the bed of sand rivers and are of central importance in predicting flow roughness and water levels the present study has focused on the details of flow and sediment dynamics along migrating sand dunes in equilibrium using a recently developed acoustic system acoustic concentration and velocity profiler new insights are obtained in the behavior of the bed and the suspended load transport along mobile dunes our data have illustrated that due to the presence of a dense sediment layer close to the bed and migrating secondary bedforms over the stoss side of the dune toward the dune crest the near bed flow and sediment processes are significantly different from the near bed flow and sediment dynamics measured over fixed dunes it was observed that the shape of the total sediment transport distribution along dunes is mainly dominated by the bed load transport although the bed load and the suspended load transport are of the same order of magnitude this means that it was especially the bed load transport that is responsible for the continuous erosion and deposition of sediment along the migrating dunes whereas the bed load is entirely captured in the dune with zero transport at the flow reattachment point a significant part of the suspended load is advected to the downstream dune depending on the flow conditions for the two flow conditions measured the bypass fraction was about 10 for flow with a froude number fr of 0 41 and 27 for flow with froude number of 0 51 this means that respectively 90 for the fr 0 41 flow and 73 for the fr 0 51 flow of the total sediment load that arrived at the dune crests contributed to the migration of the dunes

glacial to interglacial primary production and el nino southern oscillation dynamics inferred from coccolithophores of the santa barbara basin 1 we investigate the long term stability of el nino southern oscillation and pacific decadal oscillation based on the examination of coccolithophore assemblages in a largely laminated 35 ka sedimentary record retrieved in the santa barbara basin core md02 2503 at a centennial scale coccolith assemblages indicate low primary production in the basin from 35 to 11 5 ka b p whereas the holocene is characterized by high productivity conditions this pattern demonstrates the influence of the glacial interglacial cycles on productivity and by inference on the nutrient supply by the upwelling cell off point of conception on a shorter scale laminations associated with dansgaard oeschger events appear to be due to an injection of poorly oxygenated waters in the deepest part of the basin rather than anoxia due to high primary production a seasonal sampling in seven laminated sections spanning from 20 to 220 years extracted from holocene bolling allerod and dansgaard oeschger event 3 indicates el nino probably existed continuously during the last 28 ka the frequency of el nino varied through time between 1 2 5 and 1 5 event a 1 and appearing to follow the precession cycle el nino exhibits higher lower frequencies when the precession values are lower higher finally the holocene is characterized by a decrease in el nino s frequencies due to the reinforcement of el nino through this period

modeling river dune development and dune transition to upper stage plane bed large asymmetric bedforms known as dunes commonly dominate the bed of sand rivers due to the turbulence generation over their stoss and lee sides dunes are of central importance in predicting hydraulic roughness and water levels during floods in steep alluvial rivers dunes are observed to grow rapidly as flow strength increases undergoing an unstable transition regime after which they are washed out in what is called upper stage plane bed this transition of dunes to upper stage plane bed is associated with high transport of bed sediment in suspension and large decrease in bedform roughness in the present study we aim to improve the prediction of dune development and dune transition to upper stage plane bed by introducing the transport of suspended sediment in an existing dune evolution model in addition flume experiments are carried out to investigate dune development under bed load and suspended load dominated transport regimes and to get insight in the time scales related to the transition of dunes to upper stage plane bed simulations with the extended model including the transport of suspended sediment show significant improvement in the prediction of equilibrium dune parameters e g dune height dune length dune steepness dune migration rate dune lee side slope both under bed load dominant and suspended load dominant transport regimes the chosen modeling approach also allows us to model the transition of dunes to upper stage plane bed which was not possible with the original dune evolution model the extended model predicts change in the dune shapes as was observed in the flume experiments with decreasing dune heights and dune lee slopes furthermore the time scale of dune transition to upper stage plane bed was quite well predicted by the extended model

systematic variation of shear induced physical properties and fabrics in the miura boso accretionary prism the earliest processes during off scraping abstract the interrelations between deformation and variations in the physical properties and fabrics of a shallow level accretionary prism have been clarified using measurements of porosity pore size distribution and the anisotropy of magnetic susceptibility ams within the miura boso accretionary prism central japan based on the mode of deformation this onland example of an off scraped body can be divided into three parts from bottom to top imbricate thrusts corresponding to a decollement zone a thrust unit in the lower part of the off scraped body and an upper coherent unit in the top part of the off scraped body physical properties and fabrics are quite variable in each of the three parts even within a particular lithology these observations reflect each structural unit s individual strain history during shallow off scraping and accretion prior to the accretion the sediments underwent vertical compaction when horizontal compressional stresses subsequently began to deform the sediments precursory shear disturbed the previous compaction fabric accompanied by a pervasive porosity decrease over a zone several tens to hundreds of meters in thickness the porosity decrease occurred by large pore collapse which led to the development of an impermeable over consolidated horizon and inevitable high pore fluid pressures below that controlled the position of the subsequent decollement zone displacement along imbricate thrusts within the decollement zone took place just below the over consolidated horizon where high fluid pressure had been generated here a flattening fabric parallel to the imbricate thrust and associated further porosity and pore size reductions occurred in association with the fault movement these findings imply unrecoverable pre fractured strain information of sediments before being included in the decollement zone and suggest that the precursory formation of an over consolidated zone via grain rearrangement and pore size reduction is an essential control on subsequent large deformation i e within a decollement zone in the shallow part of an accretionary prism especially within lithologically homogeneous material

structural characteristics of shallowly buried accretionary prism rapidly uplifted neogene accreted sediments on the miura boso peninsula central japan 1 the upper miocene misaki and nishizaki formations on the miura and boso peninsulas in central japan preserve the deformation features of an off scraped accretionary prism the spatial distribution geometry and style of accretion related deformation with paleotemperature and burial depth estimation are elucidated in this study the deformation structures and textures are similar to those of modern accretionary prisms the low maximum paleotemperature 50 c and high preserved porosity of the sediments 30 50 imply a maximum burial depth of less than 1000 m on the basis of the mode of deformation this off scraped body is divided into an imbricate thrust a thrust unit and an upper coherent unit in ascending order the imbricate thrust corresponds to a branch from the basal decollement zone and is subdivided into a brecciated zone a main gouge zone and a shear band zone the thrust unit hosts a concentration of thrust systems that form various orders of duplex structures while the upper coherent unit is characterized by gravitational instability and earthquake induced deformation without thrust faulting the duplex distribution shear strain and fluid migration associated with the off scraping processes are clearly localized within the imbricate thrust and thrust unit this accretion related deformation occurred before lithification of the sediment and under high fluid pressure induced by shear deformation thickening of the sedimentary sequence and earthquake induced liquefaction these processes are inferred to control the effect on the mode of deformation and the location of thrusting during early deformation of the accretionary prism

timing of the antarctic cold reversal and the atmospheric co2increase with respect to the younger dryas event the transition from the last glacial to the holocene is a key period for understanding the mechanisms of global climate change ice cores from the large polar ice sheets provide a wealth of information with good time resolution for this period however interactions between the two hemispheres can only be investigated if ice core records from greenland and antarctica can be synchronised accurately and reliably the atmospheric methane concentration shows large and very fast changes during this period these variations are well suited for a synchronisation of the age scales of ice cores from greenland and antarctica here we confirm the proposed lead of the antarctic cold reversal on the younger dryas cold event the antarctic cooling precedes the younger dryas by at least 1 8 kyr this suggests that northern and southern hemispheres were in anti phase during the younger dryas cold event a further result of the synchronisation is that the long term glacial interglacial increase of atmospheric co 2 was not interrupted during the younger dryas event and that atmospheric co 2 changes are not necessarily dominated by changes in the north atlantic circulation

towards a climate event stratigraphy for new zealand over the past 30 000 years nz intimate project it is widely recognised that the acquisition of high resolution palaeoclimate records from southern mid latitude sites is essential for establishing a coherent picture of inter hemispheric climate change and for better understanding of the role of antarctic climate dynamics in the global climate system new zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the southern hemisphere westerly circulation zone a critical transition zone between subtropical and antarctic influences new zealand has mountainous axial ranges that amplify the climate signals and consequently the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions since 1995 intimate has through a series of international workshops sought ways to improve procedures for establishing the precise ages of climate events and to correlate them with high precision for the last 30 000 calendar years the nz intimate project commenced in late 2003 and has involved virtually the entire new zealand palaeoclimate community its aim is to develop an event stratigraphy for the new zealand region over the past 30 000 years and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from northern hemisphere records e g last glacial maximum lgm termination i younger dryas an initial outcome of nz intimate has been the identification of a series of well dated high resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal yr bp to the present day high resolution records for the last glacial coldest period lgcp including the lgm sensu stricto and last glacial interglacial transition lgit from auckland maars kaipo and otamangakau wetlands on eastern and central north island marine core md97 2121 east of southern north island speleothems on northwest south island okarito wetland on southwestern south island are presented discontinuous fragmentary records comprising compilations of glacial sequences fluvial sequences loess accumulation and aeolian quartz accumulation in an andesitic terrain are described comparisons with ice core records from antarctica epica dome c and greenland gisp2 are discussed a major advantage immediately evident from these records apart from the speleothem record is that they are linked precisely by one or more tephra layers based on these new zealand terrestrial and marine records a reasonably coherent regionally applicable sequence of climatically linked stratigraphic events over the past 30 000 cal yr is emerging three major climate events are recognised 1 lgcp beginning at ca 28 000 cal yr bp ending at termination i ca 18 000 cal yr bp and including a warmer and more variable phase between ca 27 000 and 21 000 cal yr bp 2 lgit between ca 18 000 and 11 600 cal yr bp including a lateglacial warm period from ca 14 800 to 13 500 cal yr bp and a lateglacial climate reversal between ca 13 500 and 11 600 cal yr bp and 3 holocene interglacial conditions with two phases of greatest warmth between ca 11 600 and 10 800 cal yr bp and from ca 6 800 to 6 500 cal yr bp some key boundaries coincide with volcanic tephras copyright 2007 john wiley sons ltd

bed load grain velocities and sediment transport rates theoretical consideration of the dynamics of bed load sediment transport leads to expressions for bed grain velocity and sediment transport rate as respectively ub a u u c and ib a tan u u c 0 c agreeing in form with many previous analyses the grain velocity equation agrees well with all experimentally determined velocities of single grains moving over fixed rough beds if a is allowed to vary with bed roughness and saltation height values of u c for such overriding grains are substantially less than normally accepted values the sediment transport rate equation predicts plane bed experimental data well over five orders of magnitude of ib values of a tan increase significantly from lower to upper stage plane beds due to an increase in a with suspended sediment concentration but also due to a decrease in tan with increasing transport stage and grain size as predicted by bagnold

precise radiocarbon dating of late glacial cooling in mid latitude south america abstract variability of atmospheric 14c content often complicates radiocarbon based chronologies however specific features such as periods of constant 14c age or steep changes in radiocarbon ages can be useful stratigraphic markers the younger dryas event in the northern hemisphere is one of those periods showing conspicuous 14c wiggles although the origin of those variations is not fully understood we can make practical use of them and determine i whether the younger dryas was global in extent if so ii were the initial cooling and the final warming synchronous worldwide and iii what are the implications of these similarities differences here we report high resolution ams 14c chronologies from the mid latitudes of south america that pinpoint a cool episode between 11 400 and 10 20014c yr b p the onset of the final cool episode of the late glacial in the southern mid latitudes i e the huelmo mascardi cold reversal preceded the onset of the younger dryas cold event by 550 calendar years both events ended during a radiocarbon age plateau at 10 20014c yr b p thus the huelmo mascardi cold reversal encompasses the younger dryas as well as a couple of short term cool warm oscillations that immediately preceded its onset in the north atlantic region

fingerprints and age models for widespread new zealand tephra marker beds erupted since 30 000 years ago a framework for nz intimate abstract the role of tephras in the nz intimate project is a critical one because most high resolution palaeoclimatic records are linked and dated by one or more tephra layers in this review first we document eruptive distributional and compositional fingerprinting data both mineralogical and geochemical for 22 key marker tephras erupted since 30 000 years ago to facilitate their identification and correlation we include new glass compositional data the selected marker tephras comprise 10 from taupo and nine from okataina volcanoes rhyolitic one from tuhua volcano peralkaline rhyolitic and one each from tongariro and egmont volcanoes andesitic second we use four approaches to develop 2 age models for the tephras youngest to oldest 1 calendar ages for kaharoa and taupo y were obtained by wiggle matching log derived tree ring sequences dated by 14c 2 whakaipo v was dated using an age depth model from peat 3 14 tephras in the montane kaipo peat sequence waimihia s unit k whakatane tuhua mamaku rotoma opepe e poronui c karapiti b okupata konini waiohau rotorua rerewhakaaitu were dated by simultaneously wiggle matching stratigraphic position and 51 independent 14c age points against intcal04 using bayesian probability methods via both oxcal and bpeat and 4 the five oldest tephras erupted before ca 18 000 cal yr bp were dated by calibrating limited numbers of 14c ages using intcal04 okareka or comparison curves of the expanded cariaco basin sequence te rere kawakawa oruanui poihipi okaia kawakawa oruanui tephra the most widely distributed marker tephra was erupted probably ca 27 097 957 cal yr bp potential dating approaches for the older tephras include their identification in antarctic ice cores if present or annually laminated sediments for which robust calendar age models have been constructed high precision ams 14c dating on appropriate material from environmentally stable sites systematic luminescence dating or new radiometric techniques e g u th he if suitable minerals are available and errors markedly reduced further application of bayesian age modelling to stratigraphic sequences of 14c ages possibly augmented with luminescence ages may help refine age models for pre holocene tephras with the largest errors finally we discuss the critical role these marker tephras play in the ongoing construction of an event stratigraphy for the new zealand region which is a key objective of australasian and southern hemisphere intimate projects

formation of ripples in erodible channels formation of ripples and dunes in erodible channels is analyzed by using the hydrodynamic model developed by kobayashi and madsen this issue applying the continuity equation of sediment the propagation velocity of the wavy bed is expressed in terms of the net fluxes of bed load along the wavy bed and suspended sediment out of the bed load transport layer the spatial variation of the bed load transport rate is derived by analyzing the balance of forces acting on a representative bed load particle on a sloping bed the net flux of the suspended sediment out of the bed load transport layer is obtained by solving the diffusion equation for the suspended sediment near the bed the stability analysis predicts that a perturbation that is either fairly short or long relative to the depth of flow will initially grow depending on whether the flow is hydraulically smooth or fully rough thus the model explains why ripples are not observed in experiments involving fairly coarse sediments since in these cases the flow is rough turbulent

loose boundary hydraulics and fluid mechanics selected advances since 1961 s u m m a r y a maj or and acknowledged role in the advance o f sedimentological knowledge is played by the methods of physics as expressed through fluid mechanics and loose boundary hydraulics turbulence is increasingly being seen as involving orderly flow structures and these are significant for the origin of several sedimentary structures and for suspension transport recent advances in sediment transport theory are rooted in the concept of the sediment load as a downward acting force and in the notion of the flow as a transporting machine laboratory experiments are increasing our understanding of bedforms due to rivers and waves but there is a need for well framed field studies to clarify the influence of change in natural environments physical explanations are being proposed for tidal bedforms field studies in both modern environments and the stratigraphic record suggest that tidal patterns and strengths are recognizable from the internal features of cross bedded units formed by sand waves tidal patterns are complex however and a wider range of situations needs to be explored than has hitherto been the case mathematical modelling could help to define the expectable bedding patterns although successful mathematical models have been constructed of flow and sedimentation in channel bends secondary flow in real bends and the evolution of those bends are not yet well understood turbidity currents on a geologically significant scale have not been observed directly but valuable insights into their character and processes have come from laboratory experiments recent laboratory work points to the limitations of lock exchange experiments and emphasizes the various ways in which turbidity currents mix with the ambient medium these studies seem to have implications yet to be worked out for the internal features and some sole marks of turbidites

multiscale statistical characterization of migrating bed forms in gravel and sand bed rivers received 14 october 2010 revised 24 october 2011 accepted 25 october 2011 published 20 december 2011 1 migrating bed forms strongly in uence hydraulics transport and habitat in river environments their dynamics are exceedingly complex making it difcult to predict their geometry and their interaction with sediment transport acoustic instrumentation now permits high resolution observations of bed elevation as well as ow velocity we present a space time characterization of bed elevation series in laboratory experiments of sand and gravel transport in a large 84 m long 2 75 m wide ume we use a simpleltering and thresholding methodology to estimate bed form heights and report that the shape of their probability density function pdf remains invariant to discharge for both gravel and sand and has a positive tail slightly thicker than gaussian using a wavelet decomposition we quantify the presence of a rich multiscale statistical structure and estimate the scale dependent celerity of migrating bed forms showing the faster movement of smaller bed forms relative to the larger ones the nonlinear dynamics of gravel and sand bed forms is also examined and the predictability time i e the interval over which one can typically forecast the system is estimated our results demonstrate that ow rate as well as bed sediment composition exert a signicant in uence on the multiscale dynamics and degree of nonlinearity and complexity of bed form evolution

comment on magnetostratigraphic study of the kuche depression tarim basin and cenozoic uplift of the tian shan range western china baochun huang john d a piper shoutao peng tao liu zhong li qingchen wang rixiang zhu earth planet sci lett 2006 doi 10 1016 j epsl 2006 09 020 abstract the recent publication of magnetostratigraphic study of the kuche depression tarim basin and cenozoic uplift of the tian shan range western china by b c huang j d a piper s t peng t liu z li q c wang r x zhu earth planet sci lett 2006 doi 10 1016 j epsl 2006 09 020 discusses the cenozoic uplift history of the tianshan mountains by studying the magnetostratigraphy of paleogene to neogene continental sediments from two sections located in the kuche basin at the northern edge of the tarim basin to support their conclusion they reinterpreted a magnetostratigraphic study of the yaha section which lies 10 km south of their sections we previously published j charreau s gilder y chen s dominguez j p avouac s sen m jolivet y li and w wang magnetostratigraphy of the yaha section tarim basin china 11 ma acceleration in erosion and uplift of the tianshan mountains geology 34 3 2006 181 184 here 1 we argue that the interpretations of the sedimentation rate changes they proposed for the kuche sections are partially invalid 2 we disagree with their reinterpretation of the age of the yaha section and 3 we think that the way they interpret their ams data is incorrect

changes in el nino southern oscillation enso conditions during the greenland stadial 1 gs 1 chronozone revealed by new zealand tree rings the warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in greenland greenland stadial 1 or gs 1 and europe younger dryas stadial or yd this reversal to glacial like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain whilst the wider atlantic region has a network of high resolution proxy records spanning gs 1 the pacific ocean suffers from a scarcity of sub decadally resolved sequences here we report the results from an investigation into a tree ring chronology from northern new zealand aimed at addressing the paucity of data the conifer tree species kauri agathis australis is known from contemporary studies to be sensitive to regional climate changes an analysis of a historic 452 year kauri chronology confirms a tropical pacific teleconnection via the el nino southern oscillation enso we then focus our study on a 1010 year sub fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring width downturn between 12 500 and 12 380 cal bp within gs 1 wavelet analysis shows a marked increase in enso like periodicities occurring after the downturn event comparison to low and mid latitude pacific records suggests a coherency with enso and southern hemisphere atmospheric circulation change during this period the driver s for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and or increased expression of enso across the mid latitudes of the pacific seemingly independent of the atlantic and polar regions

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

basin evolution in the arc arc izu collision zone mio pliocene miura group central japan a comparative study of the present collision zone between the izu bonin ridge island arc with mainland japan honshu arc and the mio pliocene of onshore se japan suggests that arc arc collision processes and the resulting stratigraphic successions may be repetitious and predictable arc arc collision has led to the incremental accretion of segments of delaminated izu bonin arc crust onto the honshu arc associated with the sequential southward migration in jumps of the plate boundary and trench prior to accretion of a segment of izu bonin arc crust the leading edge underwent uplift to generate an approximately trench parallel topographic high the zenisu ridge being the present example with the hayama mineoka uplift zone as a mio pliocene example the ridge separated a northern trench or trough from a southern intra oceanic arc basin during collision accretion the trench received both honshu arc derived terrigenous and izu bonin arc derived volcaniclastic sediments whereas the arc basin tended to receive only arc deposits during the final stages of accretion the arc basin began to receive ever increasing volumes of terrigenous honshu arc derived detritus fed through basement controlled canyons the accretionary process was accompanied by intense deformation and the residual deep marine basin was then infilled above an angular unconformity

late quaternary paleolimnology of onepoto maar auckland new zealand implications for the drivers of regional paleoclimate abstract a high resolution record of lacustrine environments spanning ca 30 9 cal ka bp was obtained from onepoto maar northern north island new zealand the multi proxy record of environmental change is constrained by tephrochronology and ams 14 c ages and provides evidence for episodes of rapid environmental change during the last glacial coldest period lgcp 28 5 18 cal ka bp and late glacial interglacial transition lgit from northern new zealand the onepoto pollen record indicates that the lgcp was cold dry and windy in the auckland region with vegetation dominated by herbs and grasses in a beech forest mosaic at the same time the diatom record indicates oligotrophic conditions with low lakes levels and turbulence whilst cladocerans indicate low water temperatures the inference of cold dry and windy conditions during the lgcp is supported by geochemical evidence for increased sediment influx charcoal and co 2 limiting conditions for terrestrial macrophytes rapid climate amelioration and forest expansion after ca 18 cal ka bp corresponds with reduced sediment influx diatom and cladoceran inferred higher lake levels indicating increasing moisture availability and temperature diatom flora indicates that an oligotrophic circumneutral lake was becoming established during the lgit but conditions were still variable between ca 13 8 and 12 5 cal ka bp two brief drier and possibly cooler episodes are apparent ca 13 8 13 2 and 13 12 5 cal ka bp followed by a warm phase combined with generally stable high lake levels between ca 12 5 and 10 5 cal ka bp subsequently the lake water chemistry became more alkaline and eutrophic possibly because sea level had risen high enough by this time to influence ground water chemistry

seasonal variations in aridity and temperature characterize changing climate during the last deglaciation in new zealand abstract new multiproxy records of aridity from northern new zealand assess the seasonality and overall pattern of wetness through the last glacial coldest period lgcp to the early holocene in the subtropical southwest pacific biomass burning indicators based on terrestrial biomarkers and 13 c of individual plant leaf wax carbon compounds n alkanoic acids from a maar lake were used to track aridity in combination with published sea surface temperatures and new pollen based temperature estimates from the same core seasonal climatological changes in the auckland area were determined from 27 to 9 cal ka bp these proxies document a shift from cold and dry conditions in the last glacial maximum to seasonally wetter conditions through the deglaciation spring became warmer first and possibly wetter while summers remained drier and initially cooler the progression from cold dry to warm wet was punctuated by the antarctic cold reversal acr which stands out as having wetter conditions in both spring and summer and mild cooling largely concentrated in spring the seasonal climate trends observed here can be plausibly explained by a rapid change from a subpolar climate to one with subtropical control in this region of the southwest pacific across the last glacial to interglacial transition a southerly shift and decreasing intensity of the westerly wind belt after the lgcp is considered to have driven the early deglacial warming and pulse of wetness whereas a northward shift without a commensurate increase in intensity of the westerlies may explain conditions in the acr

geometry and kinematics of dunes during steady and unsteady flows in the calamus river nebraska usa the geometry and kinematics of river dunes were studied in a reach of the calamus river nebraska during day long surveys dune height length steepness migration rate creation and destruction were measured concurrently with bedload transport rate flow depth flow velocity and bed shear stress within a survey individual dune heights lengths and migration rates were highly variable associated with their three dimensional geometry and changes in their shape through time notwithstanding this variability there were discernible changes in mean dune height length and migration rate in response to changing discharge over several days changes in mean dune height and length lagged only slightly behind changes in discharge therefore during periods of both steady and unsteady flow mean dune lengths were quite close to equilibrium values predicted by theoretical models mean dune steepnesses were also similar to predicted equilibrium values except during high falling flows when the steepness was above that predicted variations in mean dune height and length with discharge are similar to those predicted by theory under conditions of low mean dune excursion and discharge variation with a short high water period and long low water period however the calculated rates of change of height of individual dunes vary considerably from those measured rates of dune creation and destruction were unrelated to discharge variations contrary to previous results instead creations and destructions were apparently the result of local variations in bed shear stress and sediment transport rate observed changes in dune height during unsteady flows agree with theory fairly well at low bed shear stresses but not at higher bed shear stresses when suspended sediment transport is significant

reply to the comment by j charreau et al on magnetostratigraphic study of the kuche depression tarim basin and cenozoic uplift of the tian shan range western china earth planet sci lett 2008 doi 10 1016 j epsl 2008 01 025

vegetation history and palaeoclimate of the last glacial period at lago grande di monticchio southern italy a high resolution palynological study of a 51 m core from lago grande di monticchio southern italy has provided a palaeonvironmental record for the last glacill a annual lamination based chronology supported by radiometric and tephrochronological dates provides an absolute timescale for this record that spans 76 300 years correlations are established between the pollen stratigraphy the grip ice core 18o record and foraminiferal assemblages from atlantic core v23 81 both dansgaard oeschger and heinrich events are reflected by changes in the pollen stratigraphy revised dates are estimated for heinrich events h1 h6 a quantitative palaeoclimate reconstruction based upon the pollen data provides evidence of the climate changes in southern italy associated with these and other fluctuations during the last glacial

flow structure and resistance over subaquaeous high and low angle dunes a prominent control on the flow over subaqueous dunes is the slope of the downstream leeside while previous work has focused on steep 30 asymmetric dunes with permanent flow separation little is known about dunes with lower lee slope angles for which flow separation is absent or intermittent here we present a laboratory investigation where we systematically varied the dune lee slope holding other geometric parameters and flow hydraulics constant to explore effects on the turbulent flow field and flow resistance three sets of fixed dunes lee slopes of 10 20 and 30 were separately installed in a 15 m long and 1 m wide flume and subjected to 0 20 m deep flow measurements consisted of high frequency vertical profiles collected with a laser doppler velocimeter we show that the temporal and spatial occurrence of flow separation decreases with dune lee slope velocity gradients in the dune leeside depict a free shear layer downstream of the 30 dunes and a weaker shear layer closer to the bed for the 20 and 10 dunes the decrease in velocity gradients leads to lower magnitude of turbulence production for gentle lee slopes aperiodic strong ejection events dominate the shear layer but decrease in strength and frequency for low angle dunes flow resistance of dunes decreases with lee slope the transition being nonlinear over the 10 20 and 30 dunes shear stress is 8 33 and 90 greater than a flat bed respectively our results demonstrate that dune lee slope plays an important but often ignored role in flow resistance

experimental deformation of synthetic magnetite bearing calcite sandstones effects on remanence bulk magnetic properties and magnetic anisotropy we have quantified effects of experimental deformation on the magnetic properties of a set of synthetic calcite sandstone samples containing magnetite the deformation was carried out in a microcomputer controlled apparatus that adjusted the applied differential stress as needed to maintain a constant strain rate of 10 5 s 1 most samples were deformed under dry conditions but a few were deformed with a pore fluid present the samples deformed under dry conditions required substantially higher differential stresses macroscopically ductile shortening strains of up to 25 produced the following irreversible changes in magnetic properties 1 increased bulk coercivity remanence coercivity and mean anhysteretic remanence susceptibility 2 decreased mean low field susceptibility 3 decreases in the component of remanence parallel to shortening 4 smaller decreases for most samples in the component normal to shortening resulting in a net rotation of the remanence away from the shortening axis 5 larger decreases in the normal component in a few samples resulting in a net rotation of the remanence towards the shortening axis 6 increased magnetic anisotropy and 7 increased deformation of initial magnetic ellipsoids a comparison of data for samples deformed under dry and wet conditions higher and lower differential stresses respectively indicates that remanence reorientation and susceptibility anisotropy are controlled primarily by bulk strain i e rotation and displacement of particles whereas coercivity and anhysteretic anisotropy are controlled dominantly by microstrain or intragranular stress

unsteady flow in straight alluvial streams part 2 transition from dunes to plane bed the effect of suspended sediment on the modification of individual dunes in unsteady channel flow is analyzed the model is an extension of that developed by fredsoe 1979 in which the change of the dune dimensions was analyzed assuming that the transport of sediment mainly occurs as bed load by including suspended sediment it is possible to describe dune behaviour at high sediment transport rates for which the dunes are washed out so the bed at sufficiently high bed shear stress becomes plane the model is compared with laboratory experiments and the agreement is reasonable the effect of temperature variations on dune dimensions is incorporated in the analysis

climatic variability in the southwest pacific during the last termination 20 10 kyr bp the degree to which palaeoclimatic changes in the southern hemisphere co varied with events in the high latitude northern hemisphere during the last termination is a contentious issue with conflicting evidence for the degree of teleconnection between different regions of the southern hemisphere the available hypotheses are difficult to test robustly however because there are few detailed palaeoclimatic records in the southern hemisphere here we present climatic reconstructions from the southwestern pacific a key region in the southern hemisphere because of the potentially important role it plays in global climate change the reconstructions for the period 20 10 kyr bp were obtained from five sites along a transect from southern new zealand through australia to indonesia supported by 125 calibrated c 14 ages two periods of significant climatic change can be identified across the region at around 17 and 14 2 cal kyr bp most probably associated with the onset of warming in the west pacific warm pool and the collapse of antarctic ice during meltwater pulse 1a respectively the severe geochronological constraints that inherently afflict age models based on radiocarbon dating and the lack of quantified climatic parameters make more detailed interpretations problematic however there is an urgent need to address the geochronological limitations and to develop more precise and quantified estimates of the pronounced climate variations that clearly affected this region during the last termination c 2005 elsevier ltd all rights reserved

geohazards in coastal areas near the northernmost sagami trough central japan review of neotectonic activity in onshore and offshore areas of the izu island arc collision subduction zone

towards characterising rhyolitic tephra layers from new zealand with rapid non destructive μ xrf core scanning abstract tephra layers are of importance for the construction of reliable age control in late quaternary paleoenvironmental and volcanic hazard studies especially in volcanically active settings such as the north island of new zealand however their identification involves time consuming and destructive processing steps making the application of non destructive xrf core scanners potentially advantageous for tephra identification here we investigate the potential of the itrax xrf core scanner to differentiate between rhyolitic tephra layers sourced from various northern new zealand rhyolitic volcanic centres deposited in maar lakes of the auckland volcanic field in their macroscopic form these tephra layers are usually visibly distinct when surrounded by a dark organic rich sediment matrix although their attribution to source volcanic centre and eruption typically requires examination of their mineral assemblages combined with chemical fingerprinting of the rhyolite glass shards we demonstrate that xrf core scanning of rhyolitic tephra layers from the taupo volcanic zone and tuhua volcanic centre can also allow identification and sometimes differentiation of the tephra using xrf derived elemental counts especially high si k ca and very low br and ti different rhyolite tephra layers vary in their relative abundances of major minor and trace elements as is evident from electron microprobe and la icp ms analyses of their glass shards mo tube based xrf cannot detect na nor mg and is of lower reliability for the lighter elements ca al which play an important role in traditional tephra fingerprinting nevertheless we are able to demonstrate that xrf core scanning data can distinguish between previously identified tephra layers using multivariate statistics furthermore the study emphasises the need for a standard protocol for xrf core scanning of tephra layers for this approach to be more widely applicable especially to aid or be a substitute for conventional geochemical approaches used for tephra fingerprinting

seasonal controls on sediment transport and deposition in lake ohau south island new zealand implications for a high resolution holocene palaeoclimate reconstruction laminated sediments in lake ohau mackenzie basin new zealand offer a potential high resolution climate record for the past 17 kyr such records are particularly important due to the relative paucity of detailed palaeoclimate data from the southern hemisphere mid latitudes this paper presents outcomes of a study of the sedimentation processes of this temperate lake setting hydrometeorological limnological and sedimentological data were collected over a 14 month period between 2011 and 2013 these data indicate that seasonality in the hydrometeorological system in combination with internal lake dynamics drives a distinct seasonal pattern of sediment dispersal and deposition on a basin wide scale sedimentary layers that accumulate proximal to the lake inflow at the northern end of the lake form in response to discrete inflow events throughout the year and display an event stratigraphy in contrast seasonal change in the lake system controls accumulation of light winter and dark summer laminations at the distal end of the lake resulting in the preservation of varves this study documents the key processes influencing sediment deposition throughout lake ohau and provides fundamental data for generating a high resolution palaeoclimate record from this temperate lake

the two step shape and timing of the last deglaciation in antarctica the two step character of the last deglaciation is well recognized in western europe in greenland and in the north atlantic for example in greenland a gradual temperature decrease started at the bolling b around 14 5 ky bp spanned through the allerod a and was followed by the cold younger dryas yd event which terminated abruptly around 11 5 ky bp recent results suggest that this ba yd sequence may have extended throughout all the northern hemisphere but the evidence of a late transition cooling is still poor for the southern hemisphere here we present a detailed isotopic record analyzed in a new ice core drilled at dome b in east antarctica that fully demonstrates the existence of an antarctic cold reversal acr these results suggest that the two step shape of the last deglaciation has a worldwide character but they also point to noticeable interhemispheric differences thus the coldest part of the acr which shows a temperature drop about three times weaker than that recorded during the yd in greenland may have preceded the yd antarctica did not experienced abrupt changes and the two warming periods started there before they started in greenland the links between southern and northern hemisphere climates throughout this period are discussed in the light of additional information derived from the antarctic dust record

collision of the izu arc with honshu and the effects of oblique subduction in the miura boso peninsulas abstract collision of the izu arc in central japan is discussed with a focus on its tectonic effects to the east of the arc in the miura boso peninsulas of honshu the tectonics are the combination of the following events philippine sea plate spreading in the late oligocene to early miocene opening of the sea of japan in the middle miocene obduction of ophiolitic rocks in the northeasternmost corner of the philippine sea plate and forearc sedimentation between the honshu and izu arcs oblique subduction has shifted the plate boundary from northeast to southwest from the present mineoka tectonic belt through the miura fold belt to the sagami trough since the miocene remarkable right lateral transpressional deformation occurred throughout this period of the oblique collision and subduction

magnetic fabric development in the tertiary accretionary complex in the boso and miura peninsulas of central japan it has been demonstrated that the anisotropy of magnetic susceptibility ams is a sensitive indicator for distinguishing various processes that had acted during and after the deposition of sediments recently much attention has been focused on proving its usefulness in distinguishing early deformation signatures in sediments which show no visible grain scale deformation here we present the ams results of the neogene miura group of central japan which was formed by arc arc collision tectonics with subdivisions of two contrasting tectonic provinces the southern province a highly deformed accretionary prism and slope basin and the northern province a gently deformed forearc basin samples were collected from 21 sites in both tectonic settings we obtained from axes orientations three typical fabric domains considered to represent sedimentary tectonically deformed and their intermediate types the shape parameters of ams also revealed distinctions clearly sedimentary fabrics are more foliated and anisotropic deformed fabrics show a more prolate shape and are closer to being isotropic the sedimentary fabrics predominate in the northern forearc basin sequence whereas the intermediate and deformed fabrics occur predominantly in the southern province the general trend of the shape of the magnetic fabric in studied sediments reveals a clear evolution in the pattern of the isotropic tectonic fabric constructed from foliated sedimentary fabric

asynchronous climate change between new zealand and the north atlantic during the last deglaciation climatic fluctuations recorded in antarctica and greenland during the last deglaciation 18 10 ka differ markedly in their timing it remains controversial whether local climate fluctuations recorded in southern mid latitudes relate primarily to northern or southern polar records we present multiproxy results from new zealand that show strong evidence for a minor cooling or slowdown in the rate of warming at the time of the north atlantic late glacial interstadial the younger dryas chronozone in new zealand was a period of resumed warming and increased westerly airflow differences between the hemispheres at this time were probably due to a reorganization of the thermohaline circulation system and associated changes in the meridional temperature gradient

strain partitioning across a subduction thrust fault near the deformation front of the hikurangi subduction margin new zealand a magnetic fabric study on iodp expedition 375 site u1518 abstract understanding the distribution of strain along thrust and splay faults in active accretionary systems is crucial to understand the mechanical properties of the sediments and the strength of the fault zone and its slip behavior this paper investigates the distribution of strain through sediment compaction and texture development across the p paku fault a major splay fault near the deformation front of the hikurangi subduction margin new zealand using the anisotropy of magnetic susceptibility technique ams international ocean discovery program site u1518 penetrated hanging wall fault zone and footwall sequences to a maximum depth of 484 9 meters below seafloor a total of 330 discrete samples was subjected to ams measurements and magnetic remanence data used to reconstruct the axial orientation of each sample in a geographic reference frame the ams display distinct fabric differences between hanging wall through the fault zone and footwall domains demonstrating that strain is partitioned across the fault zone hanging wall sequences show a strike parallel northeasterly lineation of kmax and weakly prolate shapes typical for a component of northeast southwest lateral shortening in contrast footwall sequences are more oblate and show a clustering of kmax in northerly direction this demonstrates that strain in the footwall is dominated by gravitational loading however a component of sub horizontal east westerly strain parallel to the convergence direction of the pacific plate exists strain decoupling between hanging and footwall sequences occurs near the top of the p paku fault zone differences in the degree of magnetic susceptibility between footwall sediments incorporated into the fault zone and the underlying undeformed footwall sequences are indicative for the progressive dewatering of the underconsolidated footwall sequences

distal record of multi sourced tephra in onepoto basin auckland new zealand implications for volcanic chronology frequency and hazards we have documented 80 tephra beds dating from ca 9 5 to 50 ka contained within continuously deposited palaeolake sediments from onepoto basin a volcanic explosion crater in auckland new zealand the known sources for distal 190 km from vent tephra include the rhyolitic taupo volcanic centre 4 and okataina volcanic centre 14 and the andesitic taranaki volcano 40 and tongariro volcanic centre 3 the record provides evidence for four new events between ca 50 and 28 ka mangaone subgroup suggesting okataina was more active than previously known the tephra record also greatly extends the known northern dispersal of other mangaone subgroup tephra ten rhyolitic tephra pre date the rotoehu eruption ca 50 ka and some are chemically dissimilar to post 50 ka rhyolites some of these older tephra were produced by large magnitude events however their source remains uncertain eight tephra from the local basaltic auckland volcanic field avf are also identified interpolation of sedimentation rates allow us to estimate the timing of 12 major explosive eruptions from taranaki volcano in the 27 5 9 5 ka period in addition 28 older events are recognised the tephra are trachytic to rhyolitic in composition all have high k2o contents 3 wt and there are no temporal trends this contrasts with the proximal lava record that shows a trend of increasing k2o with time by combining the onepoto tephra record with that of the previously documented pukaki crater 15 avf basaltic fall events are constrained at 34 6 30 9 29 6 29 6 25 7 25 2 24 2 23 8 19 4 19 4 15 8 and 14 5 ka and three pre 50 ka events this provides some of the best age constraints for the avf and the only reliable data for hazard recurrence calculations the minimum event frequency of both distal and local fall events can be estimated and demonstrates the auckland city region is frequently impacted by ash fall from many volcanoes

a sharp view on river dune transition to upper stage plane bed sandy river beds are dominated by rhythmic features known as dunes experimental investigations of turbulent flow and sediment transport over dunes have predominantly focused on equilibrium flows that are rare in natural rivers using a novel acoustic instrument over migrating dunes in a laboratory setting we quantify a number of dynamical properties that are crucial in our understanding and modeling of dune morphology and kinematics particularly under nonequilibrium flows during dune transition to upper stage plane bed measured sediment transport distributions reveal a positive spatial lag between dune crest and maximum sediment transport rate that eventually caused washing out of dunes bed load was entirely captured in dune troughs contributing to dune translation where most of suspended load was advected further downstream contributing to dune deformation measured bypass fraction was about 76 which means that only 24 of the total sediment load at the dune crest contributed to dune migration

evidence for early postglacial warming in mount field national park tasmania abstract situated between the western pacific warm pool to the north and antarctica to the south tasmania is an ideal location to study both postglacial and holocene paleoclimates few well dated quantitative temperature reconstructions exist for the region so that important questions about the occurrence and magnitude of events such as the antarctic cold reversal and younger dryas in tasmania remain unanswered here we provide chironomid based reconstructions of temperature of the warmest quarter twarm for two small subalpine lakes eagle and platypus tarns mount field national park shortly after deglaciation twarm reached modern values by approximately 15 000 cal a bp and remained high until 13 000 cal a bp after which temperatures began to cool steadily reaching a minimum by 11 100 10 000 cal a bp these results are consistent with sea surface temperature sst reconstructions from south of tasmania but are in stark contrast to temperature inferences drawn from vegetation reconstructions based on pollen data that indicate cool initial temperatures followed by a broad warm period between 11 600 6800 cal a bp 10 000 6000 14c a bp the chironomid record broadly matches the summer insolation curve whereas the vegetation record and associated climate inferences mirror winter insolation the antarctic cold reversal and younger dryas cold events are not evident in the chironomid inferred temperatures but the antarctic cold reversal is evident in the loss on ignition curves

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

rapid change in early holocene environments inferred from lake pupuke auckland city new zealand sediment cores from lake pupuke in auckland city new zealand contain a high resolution millennial to centennial scale record of changing climate and catchment hydrology spanning the past ca 10 000 years here we focus on the period between 9500 25 and 7000 155 cal yr bp during which grain size diatom palaeoecology biogenic silica concentrations sediment elemental and carbon isotope geochemistry reflect changes in sediment sources and lake conditions with a significant event commencing at ca 8240 cal yr bp commensurate with a lowering of lake level faster erosion rates and increased sediment influx with a duration of ca 360 yrs however the changes in the lake are not reflected in the terrestrial vegetation where the pollen record indicates that podocarp forest dominated the auckland region with apparent environmental stability during this part of the early holocene the synchronous change in most of the proxies between ca 8240 and 7880 cal yr bp at lake pupuke indicates the presence of a sustained episode of relatively low lake level and concomitant increased rate of erosion in the early holocene that appears to be at least partly coeval with the 8200 cal yr bp meltwater event proposed for the north atlantic region copyright 2008 john wiley sons ltd

vegetation and climate of auckland new zealand since ca 32 000 cal yr ago support for an extended lgm auckland occupies a climatically sensitive position close to a major biogeographic boundary in the southern mid latitudes a new pollen record from kohuora maar crater auckland displays vegetation and climatic changes for the past ca 32 000 years of particular interest are the inferred climatic patterns for the first part of the interval encompassing the last glacial maximum lgm the kohuora record corresponds closely with pollen records from other auckland sites indicating that the patterns observed are at least regional in extent it is also broadly consistent with a variety of palaeoenvironmental evidence from across new zealand including the glacial record from westland other palynological records from north island other palaeoecological records from the south island and aeolian quartz sequences from western north island these records show that glacial conditions prevailed across most if not all of new zealand during the interval ca 29 19 k cal yr bp longer and earlier than the lgm sensu stricto we suggest that the term extended lgm elgm may be more appropriate for the new zealand region within this predominantly cold interval the auckland pollen records indicate a climatic amelioration for the interval ca 26 24 k cal yr bp also consistent with other palaeocological data from canterbury that fall within a period of climate amelioration recognised between the first two elgm glacial advances in westland we refer to this warming interval as the elgm interstadial the ca 27 k cal yr bp kawakawa oruanui tephra is instrumental in most of these inter site comparisons and occurs after the first peak of elgm cooling in a short lived comparatively mild phase a subsequent return to apparently colder climate in the auckland records may indicate a volcanic cooling effect or more likely widespread landscape disturbance following this major eruption event strong correspondence between biotic responses glacial fluctuations and aeolian quartz deposition linked to major shifts in strength and latitudinal extent of the southern westerlies suggest that both the elgm and elgm interstadial may be more widely registered at least across the southern ocean support for this assertion comes from parallel investigations in western and southernmost south america and isotopic and palaeoecological records from southern ocean marine cores recent reconstructions of the globally averaged ice equivalent sea level history are in line with this evidence from the southern hemisphere suggesting that the elgm may have a global registration in light of these observations we suggest a re examination of the defined timing of the lgm along with renewed effort to establish climatic patterns during this period and understand their causes copyright 2007 john wiley sons ltd

fabric based criteria to distinguish tectonic from sedimentary melanges in the shimanto accretionary complex yakushima island sw japan abstract fabric analyses based on the anisotropy of magnetic susceptibility ams provide a criterion with which to distinguish tectonic from sedimentary melanges in the tertiary shimanto accretionary complex yakushima island sw japan sedimentary melanges are characterized by fabric overprinting associated with compaction and diagenesis the magnetic ellipsoids for such melanges represent a cleavage bedding parallel magnetic foliation similar to that obtained for coherent sedimentary layers in nearby rocks the tectonic melanges and tectonically formed duplex structure are characterized by grain rotation whereby the grain short axis is rotated about axes oriented parallel to the intersection between s and c planes and the long axis of pencil cleavage perpendicular to the shear direction the ams data obtained for tectonic melanges and duplex structure show a less intense magnetic foliation compared with the sedimentary melanges with kmax the maximum magnetic susceptibility axes oriented parallel to the intersection between s and c planes and the long axis of pencil cleavage and kmin the minimum magnetic susceptibility axes showing a girdle distribution about kmax these contrasting paths of fabric development may reflect different stages of melange formation during the overall history of sediment deposition burial accretion and uplift sedimentary melanges are likely to be strongly compacted given that they formed soon after sedimentation in contrast tectonic melanges and duplex structure contain a shear induced fabric because they develop at a relatively late stage once the sediments have been sufficiently compacted for such a fabric to develop possibly at levels near the maximum burial depth

reconstructing a millennial scale record of flooding in a single valley setting the 2011 flood affected lockyer valley south east queensland australia this paper reconstructs past flooding from a range of settings in lockyer creek a key tributary of the mid brisbane river which experienced extreme flood events in ad 2011 and ad 2013 optically stimulated luminescence samples n 110 were collected from alluvial material preserved in within channel benches and floodplains age distributions from material in the bedrock reaches confirm an event 300 years ago which stripped the valley alluvium to bedrock in the unconfined reaches floodplain deposits indicate lateral stability over the past 6000 years marked differences in the inundation patterns of the ad 2011 event highlighted changes in downstream channel geometry the age distribution of alluvium in reaches not inundated during ad 2011 was older 12 000 years with no preserved evidence of deposition during the past 1000 years a relatively continuous record of floodplain deposition in reaches which were inundated in ad 2011 identifies a major peak in flood activity also around 300 years ago ad 1730 with five additional peaks occurring at approximately ad 1962 ad 1897 ad 1300 ad 550 and 5400 bc the main climatic driver of changes in flooding over this timescale is oscillations in el nino southern oscillation and although proxy records are scarce for this region some correlations with high resolution records of rainfall variability are apparent

magnetostratigraphy of the kelasu section in the baicheng depression southern tian shan northwestern china abstract in order to better constrain chronology of the cenozoic sediments in the foreland basin of the southern tian shan we carried out a magnetostratigraphic study along the kelasu river in the baicheng depression northwestern china this is the basis for future studies of the tectonic shortening history and paleoclimatic changes stepwise thermal demagnetization was used to isolate the high temperature characteristic component chrm from 1521 oriented samples collected along two overlapped sections the chrm directions are interpreted to be acquired at or close to the time of rock formation a composite magnetostratigraphic column composed of 86 45 normal and 41 reversed polarity chrons can correlate with gpts ck95 from 54 ma to 7 6 ma the basal ages of the kumugeliemu suweiyi jidike and the kangcun formations are 54 ma 46 ma 34 ma and 9 7 ma respectively the changes of anisotropy of magnetic susceptibility ams parameters p j and t cannot be used to reflect the cenozoic uplift of the southern chinese tian shan due to the parameters have a significant linear positive correlation with the bulk magnetic susceptibility k m suggesting a sedimentary provenance control based on the alignments of the ams we concluded that the paleo river channel flowed from north to south being similar to the present river flowing direction suggesting that there was still a residue relief of the tian shan orogen after the long term mesozoic denudation or the reactivation of the tian shan may have been initiated as early as 54 ma

strain removal applied to paleomagnetic directions in an orogenic belt the permian red slates of the alpes maritimes france abstract detailed investigations of relationships between strain and directions of characteristic remanent magnetization chrm have been conducted on the permian red series of the alpes maritimes france the analysis of the results obtained by structural and paleomagnetic studies on 14 sites leads to the following observations in most sites the mean direction of the strain shortening axis is close to the expected permian paleomagnetic direction in this case we observe a large scatter of the chrm directions within each site which is interpreted as an increase of an initial dispersion due to strain moreover this dispersion more or less increases with strain intensity in other cases where the angle between the shortening axis and the paleomagnetic direction is high the whole population is deflected towards the cleavage xy plane these observations lead us to assume a material line like behaviour of the chrm vectors and consequently an attempt has been made to recalculate these directions by strain removal these calculations give positive results at two levels 1 a statistically significant improvement in the clustering of the within site distributions and 2 after tilt correction using unstrained bedding planes a significant improvement in the clustering of the between site distribution the formation mean direction after strain removal is in good agreement with known permian results for stable europe

late holocene climate variability from lake pupuke maar auckland new zealand abstract spectral analyses of quasi annual organo diatomaceous laminae couplets in an auckland maar lake indicate brief sub decadal scale episodes with strong spectral power and long periods of weak to no spectral power between c 1700 to c 550 cal yr bp laminae couplet thickness appears to be a function of changes in wind flow over the basin with enhanced wind flow deepening the mixing zone and providing additional nutrients for laminae formation aeolian dust from australia amplifies the wind signal spectral signals in the high power episodes are focused in

magnetostratigraphic study of the kuche depression tarim basin and cenozoic uplift of the tian shan range western china abstract magnetostratigraphic and rock magnetic results from 1006 horizons in paleogene and neogene sediments between the upper kumugeliemu formation and the base of the kuche formation within the kuche depression of the tarim basin nw china are used to evaluate postcollisional uplift and deformation in the tian shan range characteristic remanences with both normal and reversed polarity were isolated by thermal demagnetization generally between 300 and 690 c and a composite magnetostratigraphy is constructed from data at 969 accepted levels correlating with polarity chrons c12n to c3r dated between 31 0 and 5 5 ma on the ck95 geomagnetic polarity time scale observed height dependent changes of rock magnetic parameters km and ams ellipsoid parameters indicate that these sediments were influenced by weak deformation with the succession accumulated before 15 ma recording the effects of compressive deformation this finding together with two substantial increases in accumulation rate at 16 17 and 7 ma define a framework for cenozoic uplift and deformation of the tian shan range we argue that thrusting in the south of the range was probably initiated at 20 ma and followed by rapid uplift at 16 17 ma on the assumption that sediment accumulation in western china was still predominately tectonically controlled at 7 ma another later pulse of rapid uplift with a much larger regional influence is also recognized in the tian shan the kuche depression was subjected to two postcollisional phases of rotational deformation with clockwise rotation prior to 12 ma 1 36 ma succeeded by counterclockwise rotation at 1 64 ma after 12 ma and possibly continuing to the present day this rotational deformation is not temporally related to the history of basin formation resolved from the magnetostratigraphy and may be linked to block interactions with adjoining terranes

oligo miocene magnetostratigraphy and rock magnetism of the xishuigou section subei gansu province western china and implications for shallow inclinations in central asia magnetostratigraphy of 222 remanent directions together with late oligocene to early miocene mammal and charophyte paleontology suggest that 2179 m of the xishuigou section subei gansu province china were deposited from 26 to 19 ma stratigraphic patterns of bulk susceptibility anisotropy of magnetic susceptibility parameters and natural and anhysteretic remanent magnetization intensities demonstrate that 1 faulting does not significantly affect the record 2 sediment deposition was relatively continuous 3 sediment source changed around 23 ma and 4 rapid uplift near subei occurred at 21 ma subei rotated 27 5 counterclockwise with respect to the 20 ma pole from the eurasian synthetic apparent polar wander path folding and rotation of the section took place after 19 ma the paleolatitude of subei is 14 less than at present and 19 3 less than predicted from the reference pole both rock magnetic and paleomagnetic data sets suggest that the unusually low paleolatitude is the result of synsedimentary inclination shallowing a phenomenon which has likely affected other paleomagnetic data from central asia

glacial and deglacial climatic patterns in australia and surrounding regions from 35 000 to 10 000 years ago reconstructed from terrestrial and near shore proxy data abstract this study forms part of a wider investigation of late quaternary environments in the southern hemisphere we here review the terrestrial and near shore proxy data from australia indonesia papua new guinea png new zealand and surrounding oceans during 35 10 ka an interval spanning the lead up to the last glacial maximum lgm the lgm proper 21 2 ka and the ensuing deglaciation sites selected for detailed discussion have a continuous or near continuous sedimentary record for this time interval a stratigraphically consistent chronology and one or more sources of proxy climatic data tropical australia indonesia and png had lgm mean annual temperatures 3 7 c below present values and summer precipitation reduced by at least 30 consistent with a weaker summer monsoon and a northward displacement of the intertropical convergence zone the summer monsoon was re established in northwest australia by 14 ka precipitation in northeast australia was reduced to less than 50 of present values until warmer and wetter conditions resumed at 17 16 ka followed by a second warmer wetter phase at 15 14 ka lgm temperatures were up to 8 c lower than today in mainland southeast australia and up to 4 c cooler in tasmania winter rainfall was much reduced throughout much of southern australia although periodic extreme flood events are evident in the fluvial record glacial advances in southeast australia are dated to 32 2 5 19 1 1 6 and 16 8 1 4 ka with periglacial activity concentrated towards 23 16 ka deglaciation was rapid in the snowy mountains which were ice free by 15 8 ka minimum effective precipitation in southern australia was from 14 to 12 ka in new zealand the glacial advances date to 28 21 5 and 19 ka with the onset of major cooling at 28 ka or well before the lgm there is no convincing evidence for a younger dryas cooling event in or around new zealand but there are signs of the antarctic cold reversal in and around new zealand and off southern australia there remain unresolved discrepancies between the climates inferred from pollen and those inferred from the beetle and chironomid fauna at a number of new zealand sites one explanation may be that pollen provides a generalised regional climatic signal in contrast to the finer local resolution offered by beetles and chironomids sea surface temperatures ssts were up to 5 c cooler during the lgm with rapid warming after 20 ka to attain present values by 15 ka the increase in summer monsoonal precipitation at or before 15 ka reflects higher insolation warmer ssts and steeper thermal gradients between land and sea the postglacial increase in winter rainfall in southern australia is probably related to the southward displacement of the westerlies as ssts around antarctica became warmer and the winter pack ice and antarctic convergence zone retreated to the south

the southern hemisphere westerlies in the australasian sector over the last glacial cycle a synthesis abstract the southern hemisphere westerlies in the southwest pacific are known to have waxed and waned numerous times during the last two glacial cycles though even semi continuous histories of the westerlies extend back no more than about 20 000 years we have good evidence for at least three scales of events a westerly maximum occurs at the last glacial maximum there is less conclusive evidence for another westerly maximum in the late holocene and for a minimum at ca 11 ka it is too early to ascribe even a cycle to these data but there are grounds to suggest that milankovitch precessional forcing may underlie the observed pattern there is also a quasi 2600 year cycle present in antarctic ice cores that appears to correlate to variation in westerly flow there is strong centennial scale variability in historical times the little ice age lia ca 1400 1850 was associated with a poleward shift in the circumpolar trough in the southern ocean strengthened westerly circulation over tasmania and a strengthening of southwesterly circulation and neoglaciation in southern new zealand while the preceding period 800 1400 ad was less certainly marked by reduced westerly flow from modern records we know that decadal and inter annual variability is important e g pacific decadal oscillation high latitude mode also known as the antarctic oscillation el nino southern oscillation only a minority of the proxies examined can identify changes on these temporal scales but data from tree rings ice cores and laminated lake sediments do indicate systematic changes in these phenomena through time rossby wave patterns are shown to play a critical role in long duration events as well as at the synoptic scale we conclude that westerly circulation is as strong now as at any time in the last glacial cycle in addition changes in latitudinal boundaries in the westerlies may be nearly as large in inter annual zonal shifts ca 2 maximum as in glaciation interglaciation movements ca 3 4 there is however reasonable evidence of strengthening weakening across much of the westerly belt at westerly maxima minima such as the lia early holocene

tectonic record of convergence changes in a collision area the boso and miura peninsulas central japan abstract late cenozoic formations in boso and miura have been affected by several tectonic events tectonic analysis enables us to reconstruct six different paleostress types 1 early extension affecting the oligocene early miocene mineoka group 2 and 3 relatively minor compressional and extensional events probably early pliocene in age 4 major nne ssw compression dominating prior to 2 or 3 ma ago and 5 and 6 more recent major nnw sse compression to the west and wnw ese extension to the east both types affecting the pleistocene and prevailing since 1 2 ma ago the counterclockwise change from nne ssw to nnw sse compression is not accurately dated but very likely occurred between 2 and 3 ma ago it is compared to similar evolutions in other areas of the izu collision zone we conclude that it corresponds to a major counterclockwise change in the direction of plate convergence from sse nnw to se nw the relationships between the directions of convergence and the distributions of plio quaternary compressional paleostresses in and around the collision zone are described through a simple analogy for the two stages of plio quaternary collision this counterclockwise change in stress fields and relative motions also described in the taiwan collision zone along the same philippine sea plate eurasia boundary is interpreted as a major event at the scale of the plate the possible significances of the other paleostress types identified in boso are discussed we conclude that tectonic analysis in and along collision boundaries provides a key for understanding kinematic evolution

sedimentary structures exposed in bar tops in the brahmaputra river bangladesh the brahmaputra river is one of the world s largest sand bed braided rivers with a channel belt up to 15 km wide a mean channel depth of 5 m and maximum scour depths of up to 40 m the recorded discharge varies by around 60 000 cumecs every year following the annual monsoon producing dramatic stage fluctuations with the water level falling between 7 and 8 m from bankfull to low flow stage in the dry season large areas of bar top and channel bed are exposed and low flow channels cut natural sections through bar tops exposing the internal stratification elements of upstream downstream and lateral accretion are identified although the high width depth ratio of channels up to 500 1 results in extremely low depositional dips on bed bounding surfaces within the accretionary elements vertical and lateral changes in sedimentary structures are ubiquitous and varied but some patterns can be discerned channel deposits are dominated by sinuous crested dunes and trough cross stratification upper stage plane bed lamination often with a very low angle depositional dip has been observed in beds up to 4 m thick and is generally found at the base of the exposed bar top sections trough cross stratification in bar tops occurs in sets from 0 1 m to 3 m thick with rapid vertical and lateral changes in set thickness very large sets of trough cross stratification 3 m thick do not occur in the bar top sections current ripple lamination is most abundant on the tops of bars with very high rates of climb associated with high rates of sediment deposition from these observations a generalised vertical sequence of bar top origin might include trough cross stratification overlain by upper stage plane bed lamination isolated sets of trough cross stratification truncated and capped by current ripple lamination this sequence which is considered to represent the deposits of a single flood may occur within the upstream downstream or lateral accretion elements however it should be noted that vertical and lateral changes in facies are extremely abundant with many changes in sedimentary structures and reactivation surfaces within each depositional episode

a cosmogenic nuclide chronology of the last glacial transition in north west nelson new zealand new insights in southern hemisphere climate forcing during the last deglaciation we present a new glacial chronology for the last glacial interglacial transition c 20 to 10 ka from the cobb valley nw nelson new zealand based on a suite of 10be and 26al cosmogenic exposure ages this chronology describes one of the most comprehensive deglaciation sequences from a late quaternary valley system in the southern hemisphere we chronicle the decay from the last local glacial maximum as follows onset of the last deglaciation that commenced no earlier than 18 19 ka followed by numerous short term still stands and or minor re advances over the ensuing 3 4 kyr and complete evacuation of ice by 14 ka we find no evidence to indicate a late glacial re advance commensurate with the northern hemisphere younger dryas chronozone the absence of a major glacial re advance in this valley during the latter stages of the last glacial interglacial transition lgit precludes a thermal decline in excess of about 3 c and suggests no decline the absence of late lgit re advances in the mountains of north west nelson while deglacial readvances occurred in the main ranges of the southern alps can be best explained if westerly wind forcing rather than large scale thermal decline is the primary control on glacier fluctuations at least during the deglaciation these findings challenge models of global climate change predicated on synchrony of millennial scale glacial transitions due to thermal changes between northern and southern hemispheres

a sand wave field in the entrance to bahia blanca estuary argentina abstract sand waves in the mouth of the bahia bllanca estuary show differences in wavelength crestlength and crest shape characteristics between two sectors of the field these differences may be explained by assuming that the residual ebboriented currents are stronger in the southern sector crest bifurcations on the centerline are suggestive of intermediate energy conditions and the development of secondary flows oblique to the main current direction the large lee slopes and the presence of megaripple fans are indicative of flow separation a condition seldom mentioned for subtidal sand waves boundaries of the sand wave field may be controlled by the thickness of the surficial sand layer rapid reduction of the water depth as produced by a large marginal shoal and variations in grain size an average migration rate of 33 m yr 1 was calculated from repeated bathymetric surveys assuming that sand waves preserve shape and size the established net sediment flux over the crests is 0 025 cm3 cm 1 s 1 current measurements made during four individual tidal cycles yielded a net bedload sediment transport of 0 048 cm3 cm 1 s 1

sedimentary structures sorby and the last decade henry clifton sorby pioneered in the last century the description and especially the hydrodynamic interpretation of sedimentary structures together with their use as palaeocurrent indicators research completed since the last syntheses were published a decade ago shows that work along these lines continues to be necessary and relevant particularly as regards the physical explanation of structures and to present significant challenges and opportunities perhaps the most pressing needs are for a better understanding of 1 bedforms in gravels silts and carbonate sediments 2 tidal and especially sand wave bedding 3 hummocky and swaley cross stratification and 4 soft sediment and dewatering structures in turbidites many sedimentary structures present a little exploited opportunity to quantify process rates and define short time periods from the rock record

neogene uplift of the tian shan mountains observed in the magnetic record of the jingou river section northwest china the tian shan mountains constitute central asia s longest and highest mountain range understanding their cenozoic uplift history thus bears on mountain building processes in general and on how deformation has occurred under the influence of the india asia collision in particular in order to help decipher the uplift history of the tian shan we collected 970 samples for magnetostratigraphic analysis along a 4571 m thick section at the jingou river xinjiang province china stepwise alternating field and thermal demagnetization isolate a linear magnetization component that is interpreted as primary from this component a magnetostratigraphic column composed of 67 polarity chrons are correlated with the reference geomagnetic polarity timescale between 1 ma and 23 6 ma with some uncertainty below 21 ma this correlation places precise temporal control on the neogene stratigraphy of the southern junggar basin and provides evidence for two significant stepwise increases in sediment accumulation rate at 16 15 ma and 11 10 ma rock magnetic parameters also undergo important changes at 16 15 ma and 11 10 ma that correlate with changes in sedimentary depositional environments together with previous work we conclude that growth history of the modern tian shan mountains includes two pulses of uplift and erosion at 16 15 ma and 11 10 ma middle to upper tertiary rocks around the tian shan record very young 5 ma counterclockwise paleomagnetic rotations on the order of 15 to 20 which are interpreted as because of strain partitioning with a component of sinistral shear that localized rotations in the piedmont

variability of the atmospheric circulation in the southern hemisphere during the last glacial maximum 1 a high resolution atmospheric climate model has been used to investigate short term variability of the atmospheric circulation in the southern hemisphere during the last glacial maximum lgm the model was forced at the lower boundary by sea surface temperatures ssts and sea ice fields from a lower resolution coupled model simulation of the lgm although the semiannual oscillation sao in the control simulation showed a different annual cycle than in the national centers for environmental prediction ncep reanalysis the lgm sao was similar to that of today albeit slightly weaker with the onset of the second peak delayed by a month nearly one third of the interannual variability of monthly mean 500 hpa height anomalies was accounted for by the southern annular mode empirical orthogonal function analysis showed that the next two most important modes looked similar to those associated with el nino southern oscillation enso however correlations of the associated time series with those of the coupled model s tropical sea surface ssts were much smaller than for the observed present day enso correlations

evidence for slow late glacial ice retreat in the upper rangitata valley south island new zealand abstract a suite of cosmogenic radionuclide ages taken from boulders on lateral and latero terminal moraines in the rangitata valley eastern south island new zealand demonstrates that relatively thick ice occupied valley reaches inland of the rangitata gorge until c 21 ka thereafter ice began to thin and by c 17 ka it had retreated 33 km up valley of the rangitata gorge to the butler brabazon downs a structurally created basin in the upper rangitata valley despite its magnitude this retreat represents a minor ice volume reduction from 21 ka to 17 ka and numerous lateral moraines preserved suggest a relatively gradual retreat over that 4 ka period in contrast to records from adjacent valleys there is no evidence for an ice collapse at c 18 ka we argue that the rangitata record constitutes a more direct record of glacial response to deglacial climate than other records where glacial dynamics were influenced by proglacial lake development such as the rakaia valley to the north and the major valleys in the mackenzie basin to the south west our data supports the concept of a gradual warming during the early deglaciation in the south island new zealand

a consideration of the dune antidune transition in fine gravel hydraulic data defining the dune antidune transition in fine gravel are compared with potential flow theory and information is drawn from published experiments and field based studies attention is given to both transitional bedforms and the development of downstream migrating antidunes in the latter case most data pertain to sand beds and not to gravel empirical data provide some weak support for the theoretical notion that the transition occurs at progressively lower froude numbers at greater relative depths although a critical froude number of 0 84 may reasonably be applied for the beginning of the dune to antidune transformation lag effects and a possible depth limitation ensure that transitional bedforms may persist across a broad range of froude numbers from 0 5 to 1 8 this latter observation has great relevance for palaeohydraulic estimates derived from outcrop data whereas the application of theoretical bedform existence fields based upon potential flow theory to fine gravel was previously purely speculative the addition of experimental and field data to these plots provides a degree of confidence in applying stability theory to practical geological problems for the first time laboratory data pertaining to downstream migrating gravel antidunes are compared with theory these bedforms have been reported from certain experimental near critical flows above sand or gravel beds but have been observed infrequently in natural streams however there are no detailed studies from natural rivers and only a few contentious identifications from outcrops nevertheless the limited hydraulic data conform to theoretical expectations

possible enso signals prior to the last glacial maximum during the last deglaciation and the early holocene from new zealand annually laminated lake sediments from a maar crater in auckland new zealand were analyzed spectrally for three time slices just prior to the last glacial maximum lgm during the deglaciation and during the early holocene strong spectral power in 2 7 year 9 30 year and a centennial 80 120 year timescale prior to the lgm and during two brief intervals in the deglaciation contrasts with virtually no spectral power during the rest of the deglaciation and during the early holocene the antarctic cold reversal acr appears to be the younger deglacial event the results indicate that el nino southern oscillation enso and possibly the inter decadal pacific oscillation ipo operated in a modern mode prior to the lgm pulsed on and off during the deglaciation and were suppressed or absent from northern new zealand during the early holocene the acr was a period of enhanced southwesterly flow over northern new zealand