uncertainties in the relative positions of the australia antarctica lord howe and pacific plates since the late cretaceous we determined parameters that describe finite rotations and their uncertainty regions for relative plate motion at the spreading centers between the pacific and antarctica plates between australia and antarctica and between the lord howe rise and australia we combined these to yield a range of possible finite rotations describing the relative positions of the pacific australia antarctica and lord howe plates since the late cretaceous if the pacific australia plate boundary has had its present trend since anomaly 18 time reconstructions show 330 110 km of motion of the pacific plate relative to the lord howe rise since anomaly 5 time 9 8 m y 420 110 km since anomaly 6 time 19 5 m y 770 330 km since anomaly 13 time 35 6 m y and 820 260 km since anomaly 18 time 43 0 m y we examined two cases for times prior to anomaly 18 assuming a late cretaceous age of australia antarctica separation if a plate boundary existed between the lord howe rise and pacific plates since the late cretaceous with no plate boundary in antarctica reconstructions with the lord howe rise fixed predict 610 200 km of westward motion of the pacific plate between the times of anomalies 31 and 22 followed by 260 100 km of northward motion between the times of anomalies 22 and 18 if the lord howe rise was fixed to the pacific plate until the eocene but a plate boundary existed between east and west antarctica reconstructions show very little motion across this boundary between the times of anomalies 31 and 22 followed by convergence between the times of anomalies 22 and 18 this second case also brings 70 80 m y paleomagnetic poles from the pacific and east antarctica plates into better agreement than the first case but large uncertainties in the reconstructions do not allow the first case to be conclusively eliminated

late cretaceous cenozoic tectonic development of the southwest pacific region abstract a new model of the plate tectonic development of the southwest pacific integrates the continental geology of new zealand with the age structure of the surrounding oceanic crust revealed previously from magnetic anomaly lineations the model differs from previous ones in that the onland geology of new zealand is used to constrain the tectonic development in two important ways 1 the modern australia pacific plate boundary did not transect the new zealand sector until 23 million years ago 2 there has been a total of only c 500 km of dextral displacement on the plate boundary through new zealand the model is described with reference to a series of paleotectonic maps drawn to represent the setting at the times of anomalies 32 24 7 and 5 novel interpretations based on these reconstructions include the following during the late cretaceous the campbell fault was a continental transform fault between the tasman sea spreading centre and the bounty rift its 330 km of dextral displacement accompanying 25 of counterclockwise rotation of a campbell plateau block when the eastward propagating southeast indian ridge broke into the south tasman sea 57 million years ago it continued to propagate directly into southern south island and generated late eocene oligocene continental rifting through western new zealand at the same time back arc spreading in the norfolk basin caused continental rifting along a similar trend in western north island the australia pacific plate boundary originated as a transform fault between the southeast indian ridge and the pre existing kermadec trench it developed in response to the sudden cessation of spreading on the segment of the southeast indian ridge east of a fracture zone here named fracture zone z two implications arise from this model regarding the integrity of antarctica 1 1 during the cretaceous marie byrd land was probably no more than 200 km northwest of its present position 2 2 the proposition made in some earlier plate tectonic reconstructions that if the alpine fault did not form until after the late eocene there must be a late cretaceous early tertiary plate boundary within antarctica is most probably valid

fission track analysis reveals character of collisional tectonics in new zealand during the late cenozoic the pacific plate has been obliquely converging with the australia plate in south island new zealand this has resulted in westward obduction of continental crust of the pacific plate and consequently a major mountain range the southern alps has formed east of the alpine fault and within the leading edge of the pacific plate we have applied the apatite and zircon fission track dating technique to a suite of outcrop samples from three transects across the southern alps starting at the alpine fault to better understand the uplift age and structure of the continental collision the results show the following 1 uplift was underway at 7 ma in the south at haast pass and by 5 ma in the north at arthur s pass 2 profiles of the total amount of late cenozoic uplift show an exponential increase toward the alpine fault adjacent to the alpine fault there has been 14 5 to 21 5 km of uplift in the vicinity of haast pass 14 5 to 21 km near mt cook and 12 5 to 15 5 km in the arthur s pass transect adjacent to the alpine fault in the mount cook region the average uplift rate from 5 5 ma to 1 ma was 2 3 to 2 5 mm yr between 1 ma and the present it has averaged 6 2 mm yr the strongly asymmetric uplift pattern is responsible for the exposure of a 13 25 km wide belt of greenschist to midamphibolite facies rocks immediately east of the alpine fault known as the alpine schists 3 late cenozoic uplift of torlesse greywackes and alpine schists was preceeded during the jurassic early cretaceous by 5 8 km of uplift the otago schist belt to the south was uplifted much more during this interval and in addition western parts of the otago schists were uplifted 5 6 km during the late cretaceous 4 the fission track data do not support the notion of significant late cenozoic shear heating about the alpine fault as previously suggested from spatial variations in k ar ages of the otago and alpine schists

asian summer monsoonal variations during the holocene revealed by huguangyan maar lake sediment record abstract high resolution records of summer monsoonal evolution in the holocene are essential to paleoclimate reconstruction but are hard to obtain here we provide a continuous well dated high resolution record from huguangyan maar lake located in the west pacific climate regime multi proxies including chlorophyll a toc sr rb ratio and magnetic susceptibility have been used to reconstruct the monsoon variations in the holocene higher chlorophyll a values are related with stronger summer monsoon and vice versa high temporal resolution radiocarbon dating enables us to divide summer monsoon evolution stages summer monsoon in zhanjiang area was strongest in the early holocene but began to decline at 6080 yr bp and weakened substantially since about 3600 yr bp the transition around 6080 yr bp supported by our high resolution dating lags the previous estimates by 1700 years the decreasing summer solar radiation at 30 n through the holocene is probably responsible for gradually weakened summer monsoon the anti phased co variation of summer monsoon intensity and enso activity throughout the holocene suggests that they could be interlinked driven together by solar radiation at orbital scale

cooling and uplift patterns in the lepontine alps south central switzerland and an age of vertical movement on the insubric fault line 96 new fission track ft apatite and zircon k ar and rb sr biotite and muscovite ages are presented for 19 samples mainly acid gneisses from a 40 km traverse through the lepontine alps in the maggia valley south central switzerland plotting measured mineral ages against assumed system closure temperatures yields cooling rates for each sample the entire profile shows a fairly uniform late neogene recent mean uplift rate of 0 5 mm a confirmed by a gradient of ft apatite age with elevation cooling from higher temperatures occurred earlier in the south where uplift rates of 2 2 mm a in the steep belt root zone indicate 9 km early miocene uplift of the northern pennine block this uplift started before 23 ma and is interpreted as resulting from a major phase of backthrusting along the insubric line and as dating the formation of the mylonite belt estimated cooling rates constrain the timing of lepontine mid tertiary metamorphism 3 schematic models are proposed which also consider published rb sr k ar mica and hornblende and u pb monazite ages slow cooling differential initial heating and subsequent cooling of different parts of the central alps and post 38 ma cooling with syntectonic metamorphism at 27 ma are postulated as alternative interpretations of isotopic data and geologic evidence from extrapolation between k ar and rb sr mica ages and apatite ft ages 240 50 c is proposed as the closure temperature for the retention of fission tracks in zircon

the indian monsoon and its variability for over 300 years the monsoon has been viewed as a gigantic land sea breeze it is shown in this paper that satellite and conventional observations support an alternative hypothesis which considers the monsoon as a manifestation of seasonal migration of the intertropical convergence zone itcz with the focus on the indian monsoon the mean seasonal pattern is described and why it is difficult to simulate it is discussed some facets of the intraseasonal variation such as active weak cycles break monsoon and a special feature of intraseasonal variation over the region namely poleward propagations of the itcz at intervals of 2 6 weeks are considered vertical moist stability is shown to be a key parameter in the variation of monthly convection over ocean and land as well as poleward propagations special features of the bay of bengal and the monsoon brought out by observations during a national observational experiment in 1999 are briefly described

vegetation and climate history inferred from a qinghai crater lake pollen record from tengchong southwestern china abstract a palynological investigation of a 514 cm long continuous core section from qinghai crater lake western yunnan province southwestern china was performed in order to reconstruct regional vegetation and climate from 15 8 cal kyr bp to the present the results show that the area was covered with deciduous broadleaved forest dominated by deciduous quercus between 15 8 and 12 8 cal kyr bp suggesting slightly cold and dry conditions from 12 8 to 8 3 cal kyr bp the vegetation continued to be dominated by deciduous broadleaved forest but there was also a sudden increase in castanopsis lithocarpus and a slight drop in deciduous quercus and alnus reflecting a gradual increase in both temperature and humidity during the period 8 3 4 6 cal kyr bp the mixed deciduous forests became more diverse and dense with thermophilous and hygrophilous species expanding to their maximum extents implying a warm and rather humid climate from 4 6 to 0 5 cal kyr bp the vegetation was succeeded by open mixed deciduous forest dominated by alnus with a retreating evergreen broadleaved forest indicating a cool and slightly dry climate after 0 5 cal kyr bp the vegetation became less diverse and more open but evergreen broadleaved trees increased their spread markedly suggesting that the climate had become warmer and drier in recent decades human activity resulted in a large increase in alnus and pinus around this lake basin specifically we concluded that the warm and moist climate detected between 8 3 and 4 6 cal kyr bp may have occurred in response to the high sea surface temperatures and high sea levels in the bay of bengal existent at that time

late oligocene pacific wide tectonic event stratigraphic and structural changes radiometrically and biostratigraphically dated from basins and basement across new zealand indicate that the modern australia pacific plate boundary including the alpine fault sector formed between 28 and 24 ma this age range coincides with changes at about 25 ma in the trends of the hawaiian and louisville hotspot chains and a 27 25 ma reorganization of spreading on the antarctic pacific spreading ridge it also follows closely the 28 5 ma initiation of subduction of the east pacific rise south of mendocino fracture zone that lead to formation of the san andreas continental transform the late oligocene pacific wide tectonic reorganization may have been triggered by this ridge trench collision

holocene moisture variations across china and driving mechanisms a synthesis of climatic records based on the review of 33 holocene moisture reconstructions that passed quality scrutiny temporal and spatial patterns of regional moisture variations are delineated the regionally averaged moisture index from xinjiang demonstrates that the moisture index has been persistently climbing since 10 ka cal bp and that the period between 4 and 0 ka cal bp is the holocene moisture optimum comparison of the moisture index of xinjiang region with the winter climate of northern europe leads us to propose that the holocene moisture variations in xinjiang region have been controlled by the winter temperature variations in the north atlantic region the regionally averaged moisture index from the tibetan plateau shows that the moisture has been persistently declining since 11 ka cal bp and that the period between 11 5 and 7 5 ka cal bp was the holocene moisture optimum the parallel trends between the moisture level in the tibetan plateau and the indian summer monsoon strength retrieved from the arabian sea suggest that the tibetan plateau has been under influence of the indian summer monsoon throughout the holocene the regionally averaged moisture index curves from northern china and southern china are the delayed reflections of the east asian summer monsoon strength to the solar radiation that is the peak insolation was responded by the holocene oceanic thermal optimum with significant time lags and the oceanic thermal optimum was then responded by the holocene moisture optimum in southern china and northern china also with some time lags the differences in the moisture index curve shapes and in the durations of the holocene moisture optimum between northern china and southern china suggest that the strength of the east asian summer monsoon had gradually transgressed northward in the early holocene and gradually regressed southward in the late holocene

a 20 000 year high resolution pollen record from huguangyan maar lake in tropical subtropical south china abstract a high resolution pollen record from huguangyan maar lake near the south china sea spanning the past 20 400 yr bp has been presented aimed to provide an improved understanding of the response of the regional vegetation in tropical subtropical south china to climatic variations since the late last glacial maximum the results reveal the strong control of the asian summer monsoon asm strength on vegetation via orbitally induced variations in northern hemisphere summer solar insolation the trend of climatic evolution of the region consists of change from a warm temperate northern subtropical climate 20 400 18 700 cal yr bp to a southern subtropical climate 16 500 11 500 cal yr bp during the last deglaciation followed by a stepwise environmental shift from a tropical climate 11 500 8200 cal yr bp to a southern subtropical climate 8200 6600 cal yr bp and finally to a middle northern subtropical climate the bolling allerod warming is characterized by the highest percentages of evergreen quercus but the lowest percentages of xerophytic gramineae throughout the record suggesting intensified warm wet conditions during 15 000 13 000 cal yr bp by contrast the younger dryas is characterized by a marked decrease in subtropical evergreen broad leaved plants but a significant increase in herbaceous taxa representing a brief cold reversal during 13 000 12 000 cal yr bp the occurrence of two major cooling events at 8 2 and 6 6 kyr bp both of which are characterized by dramatic decreases in tropical evergreen broad leaved plants is supposed to be linked to a distinct weakening of the asm and southward migration of the intertropical convergence zone associated with marked declines in atlantic meridional overturning circulation the subsequent brief intervals of high herbaceous pollen percentages but low percentages of tropical taxa correspond to high el nino southern oscillation enso activity supporting a link between the weakening of solar isolation driven asm strength and a gradual intensification of enso

late holocene vegetation and climate change in jeju island korea and its implications for enso influences abstract several recent studies suggest the hypothesis that the el nino southern oscillation enso is an important factor controlling the holocene east asian monsoon eam however the mechanism underlying this influence remains unclear due to the lack of high resolution paleoclimate records from the coast of east asia here we provide a new record of late holocene climate change in coastal east asia based on multi proxy evidence pollen organic content magnetic susceptibility grain size obtained from a sediment core from jeju island south korea as jeju island is strongly influenced by the kuroshio flow our sediment proxy records contain enso signals from the tropical pacific the study area was affected by dry cool conditions in the western tropical pacific wtp between 4350 and 1920 cal yr bp when el ninos were frequent and by rapid warming wetting and forestation since 1920 cal yr bp when la ninas were more common jeju island was relatively dry cool between 2100 and 1600 1300 1200 1100 1000 800 650 and 300 50 cal yr bp as opposed to the galapagos islands which were relatively wet warm reflecting the enso related negative correlation between eastern and western margins of pacific wet conditions may have prevailed during the early little ice age lia 620 280 cal yr bp despite consistent cooling this period of high precipitation may have been associated with the increased landfall of typhoons and with warmer kuroshio currents under la nina like conditions according to our results eam on the east asian coastal margin was predominantly driven by enso activity rather than by the precession effect paleoclimatic data from jeju island with its insular position and closeness to warm kuroshio currents provide clear evidence of these enso influences

the obliquely convergent plate boundary in the south island of new zealand implications for ancient collision zones abstract the alpine fault of new zealand forms the western boundary of a zone of distributed deformation formed by the oblique convergence of continental crust belonging to the pacific and australian plates structural and geodetic data from the alpine fault show that a large proportion of the total plate displacement is accommodated by rapid oblique slip on the fault the remaining displacement is distributed over a 200 km wide zone to the east the collision may be modelled as a two sided deforming orogen with the partitioning of deformation being controlled by erosional differences between the narrow high strain inboard and broad low strain outboard sides in ancient collision zones little evidence may remain of the nature and amount of displacement on the inboard side partitioning of deformation among pre existing structures complicates interpretation of the outboard zone radiometric ages may post date collision by several tens of millions of years and indicate slow isostatic uplift and unroofing collision ages if preserved may be recognized by high uplift rates calculated from muscovite biotite pairs

anthropogenic and climate driven environmental change in the songnen plain of northeastern china over the past 200 years abstract multi proxy records pollen particle size loss on ignition c n ratios and radioisotopes 210pb and 137cs of natural and anthropogenic environmental change are reported for sediment cores from three lakes in the songnen plain of northeastern china these data provide high resolution records of vegetation history and catchment dynamics for the region over the past 200 years records show that vegetation initially responded to a cooler and drier climate during the little ice age with high values of pinus ephedra and amaranthaceae and low values of cyperaceae as anthropogenic activity increased in northeastern china pinus gradually declined while broad leaved deciduous vegetation increased in the region from 1900 ce aquatic taxa also increased from 1900 ce as the wetlands responded to changing lake water levels and agricultural activities land policy implementation had a profound impact on the vegetation with arboreal pollen in keqin and hongyan lakes declining from 1900 ce as marginal land was reclaimed and agricultural activities increased vegetation diversity increased as agricultural activities caused environmental disturbance with pollen taxa indicating human disturbance including humulus polygonum and xanthium silt and organic content increased and c n ratios declined after 1940 ce as erosion in the catchment and productivity in the lakes increased re vegetation strategies introduced in the late 1990s caused an increase in arboreal taxa in the pollen record this multi proxy palaeoenvironmental study improves understanding of the long term relationship between natural and anthropogenic environmental change in northeastern china

asynchronous marine terrestrial signals of the last deglacial warming in east asia associated with low and high latitude climate changes a high resolution multiproxy record including pollen foraminifera and alkenone paleothermometry obtained from a single core dg9603 from the okinawa trough east china sea ecs provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka on land the deglacial stage was characterized by rapid warming as reflected by paleovegetation and it began ca 15 kabp consistent with the timing of the last deglacial warming in greenland however sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20 19 kabp as in the western pacific warm pool wpwp sea surface temperatures in the okinawa trough were influenced mainly by heat transport from the tropical western pacific ocean by the kuroshio current but the epicontinental vegetation of the ecs was influenced by atmospheric circulation linked to the northern high latitude climate asynchronous terrestrial and marine signals of the last deglacial warming in east asia were thus clearly related to ocean currents and atmospheric circulation we argue that i early warming seawater of the wpwp driven by low latitude insolation and trade winds moved northward via the kuroshio current and triggered marine warming along the ecs around 20 19 kabp similar to that in the wpwp and ii an almost complete shutdown of the atlantic meridional overturning circulation ca 18 15 kabp was associated with cold heinrich stadial 1 and delayed terrestrial warming during the last deglacial warming until ca 15 kabp at northern high latitudes and hence in east asia terrestrial deglacial warming therefore lagged behind marine changes by ca 3 4 ka

mode of crustal shortening adjacent to the alpine fault new zealand the late cenozoic episode of crustal shortening in the south island new zealand which has caused present day uplift rates of greater than 10 mm yr and has formed the southern alps may have also caused clockwise rotation of the alpine fault by up to 20 in contrast to the northern end of the alpine fault which appears to have remained fixed relative to the australian plate increasing westward movement of the fault trace has occurred southward along the fault this westward movement may exceed 100 km where the fault crosses the coastline in northern fiordland most shortening adjacent to the southern end of the alpine fault has occurred within australian plate continental crust which has been thrust beneath pacific plate continental crust this zone of continental underthrusting merges with the fiordland subduction zone further south where australian plate oceanic crust is being subducted gravity modelling of the continental collision zone beneath the southern alps indicates that the leading edge of underthrust australian plate crust may be close to a relatively sharp 10 km change in moho depth inward dipping thrust faults on both plates mark the outer limits of the collision zone which is over 300 km wide near the southern end of the alpine fault the probable increase in crustal thickness due to the late cenozoic shortening suggests that the amount of crustal thickening is similar in size to the amount of eroded crust

solar forcing of holocene summer sea surface temperatures in the northern north atlantic mounting evidence from proxy records suggests that variations in solar activity have played a significant role in triggering past climate changes however the mechanisms for sun climate links remain a topic of debate here we present a high resolution summer sea surface temperature sst record covering the past 9300 yr from a site located at the present day boundary between polar and atlantic surface water masses the record is age constrained via the identification of 15 independently dated tephra markers from terrestrial archives circumventing marine reservoir age variability problems our results indicate a close link between solar activity and ssts in the northern north atlantic during the past 4000 yr they suggest that the climate system in this area is more susceptible to the influence of solar variations during cool periods with less vigorous ocean circulation furthermore the high resolution sst record indicates that climate in the north atlantic regions follows solar activity variations on multidecadal to centennial time scales

holocene cyclic climatic variations and the role of the pacific ocean as recorded in varved sediments from northeastern china we present an n alkane and compound specific carbon isotope record of the past 9 ka from the annually laminated sedimentary sequence of lake xiaolongwan northeastern china the n alkane distribution suggests that lake xiaolongwan has undergone a shift from an oligotrophic state with low algal production and little emergent submerged macrophytes in the early holocene to a eutrophic state with high algal production and abundant emergent submerged macrophytes since the middle holocene the pattern of variation observed in the biomarker proxies acl the n alkane average chain length paq aquatic macrophyte versus aquatic macrophyte and terrestrial plant ratio and lptp lake productivity terrigenous organic production is throughout the record similar to that of the total organic carbon the variation of compound specific carbon isotopic values in the middle and short chain alkanes was mainly regulated by lake productivity and the accumulating organic pool through time in this forested region where the vegetation is dominated by c 3 plants the long chain n alkanes c27ec31 are predominantly derived from leaf wax lipids the compound specific d 13 c27e31 value is sensitive to effective precipitation and therefore represents a useful indicator of regional monsoonal precipitation spectral analysis on the d 13 c27e31 time series reveals significant periodicities of 87e89 205e212 1020e1050 and 1750e2041 years on the centennial timescale the quasi periodicities around 88 and 210 years suggest a strong link between solar activity and monsoon rainfall the millennial monsoon cycle in northeastern china is associated with sea surface temperature sst variations in two active centers of the summer monsoon the western pacific subtropical high wpsh and the okhotsk high increasing sst in the subtropical sea may cause a northwards shift of the wpsh which extends the monsoon rain band meiyu to northeastern china and thus increasing rainfall in that region meanwhile decreasing sst in the okhotsk sea may strengthen the okhotsk high bringing more moisture into northeastern china we suggest that the pacific ocean is a main regulator for summer monsoon rainfall in northeastern china at present and at different time scales during the holocene

searching for ancient forests a 2000 year history of land use in northeastern french forests deduced from the pollen compositions of closed depressions evidence of the agricultural use during roman or medieval times of forested areas formerly considered to be ancient as well as legacies of this former land use on plant biodiversity and soil pro

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

asynchronous evolution of the indian and east asian summer monsoon indicated by holocene moisture patterns in monsoonal central asia abstract the numerical meta analysis of 92 proxy records 72 sites of moisture and or temperature change confirms earlier findings that the dominant trends of climatic evolution in monsoonal central asia since the last glacial roughly parallel changes in northern hemisphere summer insolation i e the period following the last glacial maximum was characterized by dry and cold conditions until 15 cal kyr bp followed by a warm wet period coincident with the bolling allerod warm period and terminated by a cold dry reversal during the younger dryas period after an abrupt increase at the start of the holocene warm and wet conditions prevailed until ca 4 cal kyr bp when moisture levels and temperatures started to decrease ordination of moisture records reveals strong spatial heterogeneity in moisture evolution during the last 10 cal kyr the indian summer monsoon ism areas northern india tibetan plateau and southwest china exhibit maximum wet conditions during the early holocene while many records from the area of the east asian summer monsoon indicate relatively dry conditions especially in north central china where the maximum moisture levels occurred during the mid holocene we assign such phenomena to strengthened hadley circulation centered over the tibetan plateau during the early holocene which resulted in subsidence in the east asian monsoonal regions leading to relatively dry conditions our observations of the asynchronous nature of the two asian monsoon subsystems on millennial time scales have also been observed on annual time scales as well as implied through the spatial analysis of vertical air motion patterns after strong ascending airflows over the tibetan plateau area that were calculated from ncep ncar reanalysis data for the last 30 years analogous with the early holocene the enhancement of the ism in a future warming world will result in an increase in the asynchronous nature of the monsoon subsystems this trend is already observed in the meteorological data from the last 15 years

tectonic development of the alpine fault zone new zealand a fission track study fission track dating of zircons from the alpine fault zone in new zealand and associated granites and gneisses reveals at least three stages in the development of the present fault zone mylonites northwest of the fraser fault give ages of ca 80 ma zircons from the fraser formation bounded by the fraser and alpine faults give ages of ca 9 ma samples east of the alpine fault give ages below 5 ma these youngest ages result from the currently active uplift of the alpine schists against the alpine fault the 9 ma ages record a rapid uplift of the fraser formation owing to the onset of compression across the plate boundary mylonites to the west of the mapped fraser fault that give zircon fission track ages of ca 80 ma indicate a third much earlier phase of fault movement structural and other geologic evidence supports these conclusions the observation that the present plate boundary was located along a preexisting zone of weakness suggests that mylonite zones may merit greater attention as possible sites for initiation of rifting and or continental transform faults 26 references

holocene vegetation and climate dynamics of ne china based on the pollen record from sihailongwan maar lake abstract high resolution palynological analysis on annually laminated sediments of sihailongwan maar lake shl provides new insights into the holocene vegetation and climate dynamics of ne china the robust chronology of the presented record is based on varve counting and ams radiocarbon dates from terrestrial plant macro remains in addition to the qualitative interpretation of the pollen data we provide quantitative reconstructions of vegetation and climate based on the method of biomization and weighted averaging partial least squares regression wa pls technique respectively power spectra were computed to investigate the frequency domain distribution of proxy signals and potential natural periodicities pollen assemblages pollen derived biome scores and climate variables as well as the cyclicity pattern indicate that ne china experienced significant changes in temperature and moisture conditions during the holocene within the earliest phase of the holocene a large scale reorganization of vegetation occurred reflecting the reconstructed shift towards higher temperatures and precipitation values and the initial holocene strengthening and northward expansion of the east asian summer monsoon easm afterwards summer temperatures remain at a high level whereas the reconstructed precipitation shows an increasing trend until approximately 4000 cal yr bp since 3500 cal yr bp temperature and precipitation values decline indicating moderate cooling and weakening of the easm a distinct periodicity of 550 600 years and evidence of a mid holocene transition from a temperature triggered to a predominantly moisture triggered climate regime are derived from the power spectra analysis the results obtained from shl are largely consistent with other palaeoenvironmental records from ne china substantiating the regional nature of the reconstructed vegetation and climate patterns however the reconstructed climate changes contrast with the moisture evolution recorded in s china and the mid latitude semi arid regions of n china whereas a clear insolation related trend of monsoon intensity over the holocene is lacking from the shl record variations in the coupled atmosphere pacific ocean system can largely explain the reconstructed changes in ne china

holocene vegetation history precipitation changes and indian summer monsoon evolution documented from sediments of xingyun lake south west china we present a pollen based precipitation reconstruction and multi proxy records from a 485 cm long sequence from a sediment core from xingyun lake yunnan plateau south west china which depicts the evolution of the indian summer monsoon ism during the last 8500 years pollen and other palaeoenvironmental records document several stages of vegetation history and climate change the warmest and wettest climate in the xingyun lake catchment occurred before 5500 cal a bp and subsequently the climate became gradually drier after 2000 cal a bp the regional environmental conditions became unstable and a wet medieval warm period is probably recorded our reconstruction of the ism is similar to that portrayed by holocene speleothem o 18 records from southern china but is distinctly different from the east asian summer monsoon easm evolution which features a mid holocene maximum our results support the hypothesis that the ism and easm evolved asynchronously during the holocene and imply that the chinese speleothem o 18 records from southern china may principally reflect changes in moisture source from the indian monsoon domain and thus record the history of the ism rather than the easm

time transgressive onset of the holocene optimum in the east asian monsoon region abstract the east asian summer monsoon affects precipitation and hence vegetation in the densely populated northwest pacific region yet a long standing controversy exists concerning the spatial and temporal dynamics of the holocene optimum ho in the east asian monsoon region here we use a detailed 14 000 year record reconstructing vegetation variations from a strategically selected crater lake from northeast china as well as a compilation of previous paleoclimatic studies to show that the ho began around 6 000 cal a bp in northeast china significantly later than generally recognized by comparing our paleoenvironmental data with holocene vegetation records from other regions of east asia we identified a marked northward shift for the onset of the ho from 10 260 cal a bp in south china to 6 000 cal a bp in northeast china the gradual northward transgression of the vegetation change could be caused by both the temperature and precipitation changes in different regions finally we fitted a regression model of the start of the ho period versus latitude which allowed us to make predictions for the beginning of the ho at different geographical locations this study reveals a strong relationship between latitude and the initiation of the ho and provides a window towards better understanding the forcing of vegetation changes in the east asian monsoon region

continental underthrusting beneath the southern alps of new zealand both the inferred thermal regime and the variation in crustal thickness beneath the southern alps suggest that the mode of crustal shortening changes substantially along the length of the alpine fault north of mt cook crustal shortening is being accommodated predominantly by uplift and erosion of pacific plate continental crust as postulated in the wellman adams tectonic model however south of mt cook the absence of high heat flow and a large crustal root that is not in isostatic equilibrium may have resulted from underthrusting of as much as 100 km of indian plate continental crust

an exact analytical solution for steady seepage from a perched aquifer to a low permeable sublayer kirkham brock s legacy revisited an analytical solution is obtained for steady 2 d potential seepage flow from a nonclogged and nonlined soil channel into a highly permeable porous layer with phreatic surfaces tapering toward a horizontal interface with a subjacent low permeable formation along this boundary a vertical component of the darcian velocity vector equals the formation saturated hydraulic conductivity the image of the physical flow domain in the hodograph plane is a circular polygon a triangle or digon in a limiting case of a phreatic jet impinging on the low permeable substratum the polygon is mapped onto an auxiliary half plane where the complex physical coordinate and complex potential are reconstructed by the polubarinova kochina method i e by solution of a riemann bvp the seepage flow rate from the channel free surfaces and a saturated water logged area are found for different thicknesses of the top layer channel widths and conductivity ratios of the two strata in particular the earlier results of brock kirkham and youngs which are based on a numerical solution dupuit forchheimer df approximation and approximate potential model are confirmed in the full 2 d models sufficiently far from the channel the phreatic surface and interface make a wedge for a sufficiently deep substratum three zones are analytically distinguished an almost vertical 1 d descending flow an almost wedge configured 1 d flow and an essentially 2 d zone in between where neither a standard infiltration theory nor df analysis are valid

millennial scale asian summer monsoon variations in south china since the last deglaciation abstract characterizing spatiotemporal variability of the asian summer monsoon asm is critical for full understanding of its behavior dynamics and future impacts the present knowledge about asm variations since the last glaciation in south china largely relies on several precisely dated speleothem stable oxygen isotope 18 o records although these speleothem 18 o signals provide useful evidence for regional past environmental changes their validity for denoting asm intensity remains a great controversy the huguangyan maar lake hml provides one of the most complete archives of environmental and climatic changes in the tropical subtropical south and east asia since the last glaciation here we document a continuous centennial to millennial scale asm record over the past 16 ky bp from the high sedimentation rate hml sediments in contrast with the low amplitude variations of chinese speleothem derived 18 o signals and the chinese loess based monsoon precipitation proxy indexes our multi proxy records reveal a pattern of high amplitude regional climatic fluctuations including fine scale oscillations during the bolling allerod warming the 8 2 ka cooling event and an abrupt climate shift from 6 5 5 9 ka the existence of bond like cold dry events indicates a distinct influence of the north atlantic circulation on low latitude monsoon changes the broad comparability between the hml paleo proxies chinese speleothem 18 o records and the northern hemisphere summer insolation throughout the holocene suggests that solar insolation exerts a profound influence on asm changes these findings reinforce a model of combined insolation and glacial forcing of the asm

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

pollen record of the centennial climate changes during 9 7 cal ka bp in the changjiang yangtze river delta plain china we reconstructed the centennial climate changes for the period of 9 7 cal ka bp in the upper region of the changjiang yangtze river delta plain a general warming and wetting trend from 8560 to 7220 cal yr bp was indicated by the decrease in quercus deciduous and increases in quercus evergreen pinus and polypodiaceae spores however there were several brief climate fluctuations a notable palynological change from regional assemblages dominated by arboreal pollen to local assemblages mainly consisting of nonarboreal pollen reflects climate fluctuations the key indices of quercus deciduous pinus herbs fern spores and palynological concentrations showed similar signs of centennial climate fluctuations we suggest that the climate changes of the dongge cave and yangtze river delta regions were mainly affected by the east asian summer monsoon easm during the period of 9 7 cal ka bp the general warming trend may be associated with an intensified easm and solar activity may be one of the important factors driving the centennial climate changes the 8 2 ka event was also recorded in the yangtze river delta region which suggests that there was a close relationship between the easm and greenland climate during the early holocene

tectonic architecture of the mountain front foreland basin transition south island new zealand assessed by fission track analysis oblique continental convergence across the alpine fault since the mid miocene has loaded the australia plate with the leading edge of the pacific plate and formed a foreland basin the basin occurs mostly offshore beneath the continental shelf but remnants of the marine basin fill overlie ordovician basement in a narrow coastal strip 10 20 km wide in westland between the tasman sea and the alpine fault the results of fission track analyses of apatite and zircon separates from this basement integrated with the regional structure and stratigraphy indicate that the foreland basin formerly extended across the whole of westland and that its succession increased in thickness eastward toward the alpine fault reaching a maximum of about 4 km continuing covergence across the main thrust alpine fault has caused its footwall to thicken by reverse fauting in a transitional zone 10 20 km wide immediately west of the mountain front southern alps consequently the inner margin of the foreland basin has been inverted and the succession almost completely eroded in the southern part of westland upper crustal shortening in the australia plate amounted to about 2 km associated uplift started about 5 m y ago and involved only one major fault bounded block in northern westland upper crustal shortening amounted to about 12 km two major fault bounded blocks were involved and uplift was underway by 10 ma assuming a preuplift geothermal gradient of 25 c km the long term rate of uplift ranged between 0 8 and 2 0 mm yr in southern westland and between 0 4 and 1 2 mm yr in different parts of northern westland

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

two sided orogen collision and erosion from the sandbox to the southern alps new zealand in continental collision zones the indentor is of approximately the same vertical dimension as the material being deformed thereby allowing material to move over the indentor and out of the deforming orogen this simple constraint on the height of the indentor differs from that imposed by the bulldozer model of wedge deformation and results in the formation of an orogen with two opposite dipping topographic slopes these two wedges are mechanically coupled and the mechanics are strongly influenced by the erosion conditions imposed on the wedge where the growing mountains perturb prevailing moisture laden winds the erosion pattern is highly asymmetric erosional work being concentrated at the toe of the steep wedge facing the indentor the inboard wedge concentration of erosional energy results in concentration of mechanical energy in the same region and produces the distinctive geological and geophysical patterns associated with continental collision these include rapid uplift and exposure of deep crustal assemblages adjacent to the indentor accompanied by high crustal heat flow and anomalously low seismicity the outcrop pattern along the inboard wedge evolves from that of a crustal cross section currently exposed in the southern alps to one dominated by repetitive nappe structures consisting predominantly of lower crustal units as in the western alps of europe the other wedge the outboard wedge undergoes relatively little erosion is broad with a more gentle surface slope and maintains an outcrop pattern consisting of upper crustal material

holocene climate dynamics derived from pollen record of jiulongchi wetland in fanjing mountain southwest china abstract an alpine wetland core was obtained to a depth of 4 0 m from the fanjing mountain in southwest china sections of the core were dated with 14c data obtained with high resolution mass spectrometry ams and holocene climate changes were inferred by categorizing predominant tree and fern vegetation identified from pollen and spore counts at various core depths the temperature increased during 11 9 8 0 cal ka bp and the warmest period was during 8 0 4 6 cal ka bp then it gradually became cooler during the late holocene our temperature estimates were in good agreement with the previous studies of the holocene temperature in the asian monsoon areas there were two relatively wet periods of 10 7 8 0 cal ka bp and 4 6 2 6 cal ka bp there was an asynchronous precipitation trend in the south north and southwest china which was probably due to the different monsoon impacts in east asian summer monsoon easm area the monsoon precipitation gradually transgressed northward during the early to middle holocene and regressed southward during the late holocene our results will be useful to improve the understanding of the coherent spatio temporal patterns of climate evolution in easm region in china

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

a users guide to fission track dating calibration abstract misconceptions regarding the fission track dating method prompt the description of five handling procedures and the derivation of commonly used system calibrations problems of registration geometry inhomogeneous uranium distribution accumulated radiation damage and anisotropic etching largely invalidate all but the population and external detector methods and impose strict limitations upon even their routine application complexities of unique absolute thermal neutron dosimetry are illustrated by the calibration and use of the nbs pre irradiated glass srm 962 the 20 disparity in measured f decay constant values cannot be isolated from neutron fluence measurement and calibration frequently a calibration ratio f is evaluated against an age standard and then split into its component parts to illustrate this interdependence of f and zircon fission track ages in agreement with independent k ar ages are obtained by calculating the same track count data with each of the preferred values of f f 7 03 10 17 yr 1 and8 46 10 17 yr 1 together with appropriate selected neutron dosimetry schemes an alternative approach is presented formally relating unknown ages of samples to known ages of standards either by direct comparison of standard and sample track densities or by the repeated calibration of a glass against age standards practical recommendations are given for the reporting and critical assessment of fission track data

vegetation response to holocene climate change in east asian monsoon margin region abstract fossil pollen records from 20 sites with reliable chronologies and high resolution data in the east asian monsoon margin region were synthesized to document holocene vegetation and climate change and to understand the large scale controls the vegetation experienced different changes over the holocene in various sub regions 1 near the boundary between modern forest and temperate steppe in northeast china forest showed clear expansion in the middle holocene 2 in central china near the boundary between steppe forest and desert vegetation showed various patterns at different sites 3 further west on the tibetan plateau near the boundary between highland meadow steppe and semi desert desert forest expanded at most sites during the early and middle holocene our synthesis indicates that climate in the margin region was slightly moist in the early holocene wettest in the middle holocene and dry in the late holocene though there are regional differences as reflected by vegetation change this general pattern is very different from either monsoon or westerly dominated regions the maximum moisture occurred during the early holocene in the monsoon region while the arid central asia dominated by the westerlies was driest in the early holocene and wettest in the mid holocene the interplay of the asian summer monsoon westerlies topography and regional vegetation factors might have contributed to this spatial complexity

latest pleistocene and holocene vegetation and climate history inferred from an alpine lacustrine record northwestern yunnan province southwestern china abstract reconstructing past changes of the summer monsoon in southwestern china is key to understanding the paleoclimatic dynamics of the indian summer monsoon southwest monsoon a major tropical system with impacts beyond the region high resolution pollen and conifer stoma data are presented from a sediment core tiancai lake located just below treeline in the hengduan mountains northwestern yunnan province of china these data record changes in vegetation and climate for the latest pleistocene and holocene c the last 12 230 cal yr bp and by comparing these results with the pollen records from the nearby erhai lake and lugu lake a regional climate history in yunnan province can be inferred during the period of 12 230 11 510 cal yr bp open alpine meadow around tiancai lake indicates a relatively cold and dry climate corresponding to the younger dryas cold event yd between 11 510 and 10 000 cal yr bp the vegetation types around tiancai lake changed into picea and abies forest and alpine rhododendron shrubland reflecting increases in the temperature and humidity from 10 000 to 6100 cal yr bp tsuga forest expanded persistently toward tiancai lake indicating further climate changed towards warmer and wetter conditions between 6100 and 3410 cal yr bp tsuga forest was the dominant vegetation type nearest to tiancai lake denoting warm and humid climatic conditions corresponding to the holocene climatic optimum in the northwestern yunnan province tsuga forest in mountains around lugu lake shrank quickly at 3410 cal yr bp reflecting significant decline of humidity since 2930 cal yr bp tsuga forest around tiancai lake shrank gradually indicating a fluctuating decrease of temperature these climatic changes reflect changes of the southwest monsoon namely warm and humid climate indicating strong southwest monsoon cold and dry climate denoting weak southwest monsoon