new zealand s most easterly palaeotsunami deposit confirms evidence for major trans pacific event abstract sedimentary geochemical geomorphological radiocarbon and numerical modelling data were used to examine the nature extent and age of a boulder scatter at okawa point chatham island new zealand boulders up to 98 t were traced around 800 m inland and comprised both a landward and seaward grouping on either side of a mid holocene high stand storm ridge dated to around 4840 4810 cal bp the landward boulder scatter was linked with an enigmatic coarse sand gravel layer that extends up to 1100 m inland and has been dated to around 3500 4500 cal bp numerical modelling indicated that while the seaward boulders that mainly rest upon the chatham island schist shore platform could have been emplaced by either storm or tsunami waves those landward of the mid holocene storm ridge were most probably transported by a tsunami there are several near contemporaneous palaeotsunami deposits reported from mainland new zealand australia sw pacific and the wider pacific region if some or all of these are associated with the same basin wide palaeotsunami then it appears likely to have been one of the largest holocene pacific palaeotsunamis an analysis of historical and numerically modelled data suggests that the most likely candidate is from within the northern chile seismic gap with early evidence suggesting that a large palaeoseismic and palaeotsunami event may have occurred around 4000 yr bp if correct this has important implications for assessing the largest possible magnitude earthquakes in the northern chile seismic gap and the size of the tsunamis they generate

a strong wind event on the ross ice shelf antarctica a case study of scale interactions abstractin situ observations satellite imagery numerical weather prediction and reanalysis fields are used to investigate the synoptic and mesoscale environment of a strong wind event swe at mcmurdo station ross island region on the ross ice shelf antarctica on 10 october 2003 the swe occurred during the passage of a sequence of three mesoscale low pressure systems from the central ross ice shelf to the southwest ross sea a potential vorticity pv analysis showed that the lows drew air of continental origin down the glacial valleys of the transantarctic mountains and onto the ice shelf as a katabatic drainage flow however the analysis indicated that the air mass associated with the swe was of recurved maritime origin drawn in by the second mesoscale low l2 this air mass approached mcmurdo station from the south where interactions with the orography played a critical role in the early stages of the event when the wind speed was less than 10 m s 1 the air was deflected around the topograph

paleocene adakitic porphyry in the northern qiangtang area north central tibet evidence for early uplift of the tibetan plateau abstract uplift of the tibetan plateau and related crustal shortening are key issues in understanding collisional geodynamics and magmatic rocks that formed in this compressional setting provide clues to the processes involved numerous granitic porphyry dikes have been identified in the angsai area of the northern qiangtang block in north central tibet these dikes were emplaced along nw se striking reverse faults that run parallel or sub parallel to the thrust belt suggesting that they are syn collisional new la icp ms zircon 206pb 238u and magmatic biotite 40ar 39ar results demonstrate that the dikes crystallized at ca 64 ma and the bulk geochemistry of the dikes shows that they are adakitic with high sr y and la yb ratios and low y and yb contents their low mgo ni and cr contents along with positive zircon ehf t and bulk end t values suggest that the adakitic rocks were the result of partial melting of a juvenile thickened lower crust our new data indicate the uplift of north central tibet which started as early as 64 ma synthesizing available geochronological geochemical and structural data it seems that the crustal shortening and uplift of the plateau is a long lived process consisting of a rapid early stage and a slow and more constant later stage collision related magmatic activity peaked at the time of transition between those two stages

geochronology petrogenesis and tectonic significance of the jitang granitic pluton in eastern tibet sw china abstract the jitang granitic pluton which is situated in the southern margin of the north qiangtang block in eastern tibet may provide critical information about the source and derivation of the north qiangtang block during gondwana breakup and dispersion in this paper we report relevant data such as zircon u pb age whole rock major and trace element abundances and sr nd isotopes for the jitang pluton the major rock types of the pluton are granodiorite and biotite granite whole rock major element data reveal that the jitang pluton is a peraluminous s type granitic pluton the u pb age of zircons from the pluton is 219 1 1 7 ma which is 10 ma younger than the age of high pressure metamorphism in the longmu co shuanghu collisional suture between the north and south qiangtang blocks the jitang granitoids show pronounced negative ba eu sr anomalies high initial 87sr 86sr ratios from 0 7266 to 0 7389 and low end t values for from 11 1 to 13 2 which are remarkably similar to the gneisses and meta sedimentary rocks from the indian craton as well as the north qiangtang block the results from this study indicate that the jitang granitoids formed by melts derived from a crustal source with sr nd isotopic compositions similar to those of the indian cratonic crust we concur with the previous interpretation based on detrital zircon records that the north qiangtang block was derived from the indian gondwana

late triassic paleolatitude of the qiangtang block implications for the closure of the paleo tethys ocean abstract to better constrain the late triassic paleolatitude of the qiangtang block and the closure of the paleo tethys ocean a combined paleomagnetic and zircon u pb geochronological study has been conducted on the upper triassic jiapila formation volcanic rocks on the northern edge of the qiangtang block of central tibet 34 1 n 92 4 e these rocks are dated to 204 213 ma progressive thermal or alternating field demagnetization successfully isolated stable characteristic remanent magnetizations chrm that pass both the fold and reversal tests consistent with a primary magnetization these are the first volcanic based paleomagnetic results from pre cretaceous rocks of the qiangtang block that appear to average secular variation well enough to yield a reliable paleolatitude estimate based on our new paleomagnetic data from upper triassic lavas we conclude that the late triassic pole of the qiangtang block was located at 64 0 n 174 7 e with a 95 6 6 n 29 we compile published paleomagnetic data from the qiangtang block to calculate a late triassic latitude for the qiangtang block at 31 7 3 0 n the central paleo tethys ocean basin was located between the north china ncb and tarim blocks to the north and the qiangtang block to the south during late paleozoic early mesozoic a comparison of published early triassic paleopole from the qiangtang block with the coeval paleopoles from the ncb and tarim indicates that the paleo tethys ocean could not have closed during the early triassic and that its width was approximately 32 38 latitude 3500 4200 km however the comparison of our new combined late triassic paleomagnetic result with the late triassic poles of the ncb and tarim as well as numerous geological observations indicates that the closure of the paleo tethys ocean at the longitude of the qiangtang block most likely occurred during the late triassic

palaeotsunamis along canada s pacific coast abstract to fully understand tsunami hazards along canada s pacific coast we must consider all potential sources including local and region wide earthquakes volcanic activity slope failure events and bolide impacts furthermore as climate changes future extreme meteorological conditions will exacerbate slope failures on steep and over steepened slopes and potentially augment the magnitude and frequency of earthquake generated tsunamis there have been numerous reviews of the geological records of palaeotsunamis along the cascadia margin but as yet there has been no attempt made to pull together all data related to palaeotsunamis along the pacific coast of canada we summarise all geological data related to palaeotsunamis reported in the region all relevant non geological data and other information concerning potential tsunamigenic sources evidence for between 10 and 22 palaeotsunamis prior to european arrival have been documented with the cascadia subduction zone y event ad1700 being the most widely recognised geological archaeological and anthropological data all indicate a complex multi sourced prehistory of seismic tsunami activity that is poorly understood a clustering of potential activity off the se coast of vancouver island suggests that we should also attempt to better understand locally generated events along canada s pacific coast

geochronological and geochemical constraints on mesozoic suturing in east central tibet 1 this paper reports isotopic major and minor element geochemistry of igneous and metamorphic rocks from the kokoxili and yushu regions of central and eastern tibet the first region lies along the kunlun suture which separates the bayan har songpan ganze songpan terrane from the tarim and qaidam blocks two kokoxili granitoids yield u pb zircon dates of 217 10 and 207 3 ma late triassic which represent the time of emplacement and rb sr isochron dates of 195 3 and 190 3 ma early jurassic which are interpreted as cooling ages the geochemical signatures of these granitoids suggest that they are related to subduction continuing into the late triassic in the yushu area three samples help constrain the age of the jinsha suture which separates the songpan terranes from the qiangtang blocks a leucocratic granite and an orthogneiss in the suture zone yield u pb zircon dates of 206 7 and 204 1 ma respectively and a paragneiss south of it a u pb monazite date of 244 4 ma the existence of coeval magmatism in both the jinsha and kunlun sutures suggests that the two subduction zones were simultaneously active combining isotopic dating with structural evidence on subduction polarity and paleomagnetic reconstructions we propose that the kunlun and qinling block boundaries which were distinct in the permian subsequently formed a continuous late triassic northward subducting plate margin our data suggest that the jinsha suture correlates with the benzilan and nan uttaradit sutures which together belong to a major late triassic subduction zone

geo archaeological evidence for a holocene extreme flooding event within the arabian sea ras al hadd oman abstract the arabian sea is regarded as one of the least studied regions in terms of coastal hazards such as tropical cyclones and tsunamis parts of the coastline are developing rapidly especially in oman this calls for a proper understanding of the natural processes that act on and affect it this can be done by investigating the magnitude and impact of past events in particular on human settlements by doing this future risks may not only be scientifically predicted and evaluated but the damage caused by future events might even be mitigated evidence of past extreme wave events is preserved in the onshore stratigraphic record in addition to this the coastal zone of oman is rich in archaeological remains presented here are the results of comprehensive mapping and analysis of extreme wave deposits of an archaeological site near ras al hadd suggesting that the early bronze age site hd 6 was inundated at 4450 cal bp an event layer is identified between two settlement phases within the archaeological excavation a contemporaneous sand bed with a maximum thickness of 0 4 m was mapped in the vicinity of the settlement ground penetrating radar surveys allow measurement of the thickness as well as identification of the internal facies architecture of the deposit a high resolution digital elevation model reveals the coastal geomorphology it is concluded that the causative event must have been a tsunami that was most likely generated within the makran subduction zone this interpretation does however remain tentative at the moment archaeological evidence indicates that the site was immediately re occupied after the event which attests to a certain resiliences of the early bronze age coastal communities in the region

deposits flow characteristics and landscape change resulting from the september 2009 south pacific tsunami in the samoan islands the september 29th 2009 tsunami caused widespread coastal modification within the islands of samoa and northern tonga in the south pacific preliminary measurements indicate maximum runup values of around 17 m okal et al 2010 and shore normal inundation distances of up to 620 m jaffe et al 2010 geological field reconnaissance studies were conducted as part of an unesco ioc international tsunami survey team survey within three weeks of the event in order to document the erosion transport and deposition of sediment by the tsunami data collected included a general morphology and geological characteristics of the coast b evidence of tsunami flow inundation flow depth and direction wave height and runup c surficial and subsurface sediment samples including deposit thickness and extent d topographic mapping and e boulder size and location measurements four main types of sedimentary deposits were identified a gravel fields consisting mostly of isolated cobbles and boulders b sand sheets from a few to 25 cm thick c piles of organic mostly vegetation and man made material forming debris ramparts and d surface mud deposits that settled from suspension from standing water in the tsunami aftermath tsunami deposits within the reef system were not widespread however surficial changes to the reefs were observed

sources and petrogenesis of late triassic zhiduo volcanics in the northeast tibet implications for tectonic evolution of the western jinsha paleo tethys ocean abstract the western jinsha suture representing a branch of the paleo tethys makes the junction between the songpan ganzi complex and the north qiangtang block nqb however the triassic tectonic evolution of the western jinsha paleo tethys ocean is poorly constrained this paper shows new la icp ms zircon u pb geochronology major and trace elements and sr nd hf isotopic compositions of the zhiduo dacitic volcanic rocks in the northern margin of the nqb la icp ms zircon u pb dating displays that they erupted between 227 2 and 228 1 ma these rocks exhibit high silica medium k calc alkalic signature and low mgo tio2 p2o5 cr and ni compositions they are enriched in light rare earth elements and large ion lithophile elements with moderate to strong negative eu anomalies eu eu 0 24 0 56 and depleted in heavy rare earth elements and high field strength elements they possess relatively low initial 87sr 86sr ratios 0 7055 0 7084 positive whole rock end t 0 2 to 1 4 and magmatic zircon ehf t values focus on 9 2 2 7 with young nd and hf model ages t2dm nd 885 983 ma t2dm hf 467 1035 ma these features are comparable to those of typical arc volcanic rocks and indicate that they were probably derived from partial melting of a juvenile crust source the eruption of these volcanic rocks could be attributed to southward subduction of the western jinsha paleo tethys ocean in combination with previous studies we propose that the subduction of the western jinsha paleo tethys ocean initiated at the beginning of the late triassic ca 228 ma and closed at the end of the late triassic ca 208 ma in addition there is a universal northeastward younging trend of arc magmas in the northern margin of the nqb which may indicate a model involving the initial shallow subduction and subsequent slab roll back

the earthquake and tsunami of 1865 november 17 evidence for far field tsunami hazard from tonga summary historical reports of an earthquake in tonga in 1865 november identify it as the only event from that subduction zone which generated a far field tsunami observable without instruments run up heights reached 2 m in rarotonga and 80 cm in the marquesas islands hydrodynamic simulations require a moment of 4 1028 dyn cm a value significantly larger than previous estimates of the maximum size of earthquake to be expected at the tonga subduction zone this warrants an upwards re evaluation of the tsunami risk from tonga to the cook islands and the various polynesian chains which had hitherto been regarded as minor

a review of palaeo tsunamis for the christchurch region new zealand abstract recent earthquake activity in and around the christchurch region new zealand has raised concerns about tsunamis inundating the coastline while the occurrence of historical tsunamis is well documented information about palaeo tsunamis is poorly understood this review draws together data from numerous sources to outline our current understanding of palaeo tsunamis for the region six probable and one possible holocene palaeo tsunamis are identified and proxy data are summarised with reference to all potential near contemporaneous sites throughout new zealand the events cover a period of around 6500 years occurring around 6250 6500 yr bp 4800 5350 yr bp 4050 4450 yr bp 3400 3700 yr bp 2200 2300 yr bp 1250 1350ad and in 1604ad the relative exposure of christchurch city to tsunamis has however fluctuated over time this is most notable over the past 2000 years or so since the brighton spit extended south to close off the bay then retreated and formed again causing the avon heathcote estuary ihutai to change from open to closed bay and then from open bay to estuary the relative extent of the tsunami hazard is therefore controlled to a certain extent by the presence or absence of the spit which is in turn governed by interactions between seismic activity and fluvial processes potential palaeo sources vary from local subduction fault rupture nearshore submarine landslide gas hydrate release seamount flank collapse to distant subduction fault ruptures in central and south america candidates in most cases more than one potential source was identified for each palaeo tsunami however it appears that the most likely sources for most if not all of the palaeo tsunamis were from central and south america as opposed to more local alternatives the identification of palaeo sources was largely based upon historically documented events and palaeoseismic research and as such was almost entirely limited to known local and distant fault ruptures a review of other potential palaeo sources with tsunamigenic potential reveals numerous additional candidates that need to be investigated in more detail

different sources involved in generation of continental arc volcanism the carboniferous permian volcanic rocks in the northern margin of the north china block abstract new zircon u pb dating results on the carboniferous permian volcanic rocks in the northern margin of the north china block ncb indicate their eruption during the early carboniferous to late permian from 347 3 ma to 258 1 ma and a slight decrease of the upper limits of the volcanic sequences from west to east they have a main rock association of basalt basaltic andesite andesite dacite rhyolite tuff and tufaceous sandstone most of them have calc alkaline compositions and exhibit variable sio2 contents from 48 2 wt to 77 1 wt there is no significant gap between the mafic and felsic volcanic rocks in major and trace element classification diagrams indicating that they are not bimodal in composition the carboniferous permian volcanic rocks exhibit subduction related geochemical features such as negative nb and ta anomalies of mafic to intermediate rocks on primitive mantle normalized diagrams indicating they were formed in an andean type continental arc during southward subduction of the paleo asian oceanic plate beneath the northern ncb however their wide range of whole rock sr nd and zircon hf isotopic compositions indicate that their source areas are very complex and different sources were involved in generation of these volcanic rocks geochemical and sr nd hf isotopic results show that the basalt and some andesite were produced by fractional crystallization of mafic magma derived from partial melting of mantle wedge and subducted oceanic crust however most of the intermediate to felsic volcanic rocks were derived from partial melting of lower continental crust there is an increasing input of crustal materials from the carboniferous to permian as indicated by increasing volumes of felsic volcanic rocks in the volcanic sequences the results show that origin of the continental arc volcanism is very complex and both materials from the subducted oceanic crust and sediments mantle wedge and arc continental crust could be involved in their generation for the permian andesite dacite and rhyolitic volcanic rocks there is a striking correlation between their sr nd hf isotopic compositions and those of the underlying basement sr nd hf isotopic differences between the permian intermediate to felsic volcanic rocks from either side of the northern boundary fault of the north china craton suggest that mixture and homogenization of the magmas in the melting assimilation storage hybridization mash zone within this continental arc was incomplete and incomplete homogenization of magmas is likely a common feature of many mash zones within continental arcs our results on the volcanic rocks also show that the final closure of the paleo asian ocean along the solonker suture zone has not been finished prior to the middle permian and the decease of the paleo asian oceanic subduction beneath the northern ncb in its middle western parts is a little earlier than that in its eastern part

a case study of antarctic katabatic wind interaction with large scale forcing surface pressure decreases of up to 20 hpa occurred over much of the antarctic continent during a 4 day midwinter period of 1988 the widespread change in the pressure field accompanied intense cyclonic activity to the north of the ice sheet the equatorward mass transport across the antarctic coastline resulted in a redistribution of atmospheric pressure that extended to the subtropics of the southern hemisphere most of the mass flux from antarctica was the result of low level processes and appears tied to the katabatic wind circulation the observed surface pressure decrease over the continent reflects a perturbation of the mean meridional circulation between antarctica and the subpolar latitudes by synoptic scale processes zonally averaged circulations over antarctica were examined using output from the european centre for medium range weather forecasts model results suggest that only a poorly defined return branch of the meridional circulation exists in the middle and upper troposphere this southward directed flow does not compensate for the northward mass transport provided by the katabatic wind outflow in the lower atmosphere isallobaric contours over the antarctic ice sheet roughly match the area of the large scale drainage catchment associated with katabatic wind transport through the ross sea sector an intense extratropical cyclone was present in the circumpolar oceanic belt to the north of the continent the horizontal pressure gradient associated with the cyclone prompted enhanced drainage off the high interior plateau the resulting katabatic flow issued from the continent through a narrow corridor across the ross ice shelf and out over the southern ocean

structural evidence for the permo triassic tectonic evolution of the yidun arc eastern tibetan plateau abstract deformation across the yidun arc occurred as a two phase process i early triassic deformation of paleozoic sequences resulting from closure of the jinsha jiang suture and ii late triassic deformation of middle to late triassic rocks as a result of final basin closure deformation in the western yidun arc is dominantly west vergent a north south striking west directed thrust the jinsha thrust forms the boundary between the western yidun arc and the eastern qiangtang block the jinsha thrust incorporates within it ophiolitic material of the jinsha jiang suture and the structural geometry across the jinsha thrust suggests that early triassic subduction was east dipping along the jinsha jiang suture deformation within middle to late triassic sequences of the eastern yidun arc eastern qiangtang block and western songpan garze fold belt is thin skinned being restricted largely to a single generation of upright folds and associated thrusts late triassic westwards subduction underneath the combined western yidun arc qiangtang block resulted in arc volcanism in the eastern yidun arc coeval arc volcanics in the northern margin of the qiangtang block suggest that the suture along the northern margin of the qiangtang block may be correlated with the garze litang suture rather than the jinsha jiang suture

a case study of a ross ice shelf airstream event a new perspective abstract a case study illustrating cloud processes and other features associated with the ross ice shelf airstream ras in antarctica is presented the ras is a semipermanent low level wind regime primarily over the western ross ice shelf linked to the midlatitude circulation and formed from terrain induced and large scale forcing effects an integrated approach utilizes moderate resolution imaging spectroradiometer modis satellite imagery automatic weather station aws data and antarctic mesoscale prediction system amps forecast output to study the synoptic scale and mesoscale phenomena involved in cloud formation over the ross ice shelf during a ras event a synoptic scale cyclone offshore of marie byrd land draws moisture across west antarctica to the southern base of the ross ice shelf vertical lifting associated with flow around the queen maud mountains leads to cloud formation that extends across the ross ice shelf to the north the low level cloud has a warm signature in thermal infrare

factors controlling the near surface wind field in antarctica abstract using data from the regional atmospheric climate model racmo ant1 the momentum budget of the antarctic atmospheric surface layer sl taken as the lowest model layer located at 6 7 m above the surface is presented in july winter the katabatic pressure gradient force pgf dominates the sl momentum budget over the steep coastal slopes which results in strong 10 15 m s 1 and directionally constant katabatic winds farther inland where surface slopes are more gentle the large scale pgf may become equally important with the circumpolar pressure trough north of the antarctic coastline the large scale pgf acts along with the katabatic pgf in the downslope direction in wilkes land dronning maud land and on the western ross ice shelf the large scale pgf causes equivalent geostrophic winds in excess of 10 m s 1 thermal wind effects that oppose the downslope acceleration are especially strong in areas where large scale forcing is weak which allows cold air to pile up over the flat ice she

three large tsunamis on the non subduction western side of new zealand over the past 700years abstract the tasman sea between australia and new zealand is rarely considered as an important source for tsunamis we review the past 1000 years of unusual events and find evidence for three possibly four large tsunamis one historical and two during the period of m ori occupation prior to european arrival event 1 appears to have affected the town of westport new zealand on the 12th august 1870 and event 2 occurred in the south taranaki bight between 1470 and 1510 ad although it may extent farther south along new zealand s west coast there are currently insufficient data to determine whether the west coast sites represent a separate event or are associated with event 2 event 3 occurred between 1320 and 1450 ad along the west waikato coast of the north island new zealand in attempting to identify possible tsunamigenic sources for these large events we note the importance of considering a range of potential tsunamigenic options such as complex subduction zone earthquakes and a range of slope failure scenarios in order to better understand the threats posed not only by tasman sea sources but for similar geographical locations around the world

distribution and characteristics of mesoscale cyclones in the antarctic ross sea eastward to the weddell sea abstract the mesoscale cyclone activity observed in the portion of antarctica that faces the south pacific ocean and weddell sea area is summarized from a study of 1991 in general area normalized results reveal much greater mesoscale cyclonic activity over the ross sea ross ice shelf and southern marie byrd land than on both sides of the antarctic peninsula more than 50 of the observed mesoscale vortices are of the comma cloud type the average diameter of mesoscale vortices is approximately 200 km near terra nova bay 270 km near byrd glacier and 280 km near siple coast near the antarctic peninsula the average diameter is about 370 km over the bellingshausen sea and 380 km on the weddell sea side the largest percentage of deep vortices occurs over the bellingshausen sea sector 38 of all cases where convective instability frequently occurs over the ross sea ross ice shelf and weddell sea sectors the majority of the mesoscale vortices are low cloud features that probably do not exceed the 700

modeling the enso modulation of antarctic climate in the late 1990s with the polar mm5 abstract the polar fifth generation pennsylvania state university ncar mesoscale model mm5 is employed to examine the el nino southern oscillation enso modulation of antarctic climate for july 1996 june 1999 which is shown to be stronger than for the mean modulation from 1979 to 1999 and appears to be largely due to an eastward shift and enhancement of convection in the tropical pacific ocean this study provides a more comprehensive assessment than can be achieved with observational datasets by using a regional atmospheric model adapted for high latitude applications polar mm5 the most pronounced enso response is observed over the ross ice shelf marie byrd land and over the weddell sea ronne filchner ice shelf in addition to having the largest climate variability associated with enso these two regions exhibit anomalies of opposite sign throughout the study period which supports and extends similar findings by other investigators the dipole structure is observed in surface temperature meridio

coral reefs as buffers during the 2009 south pacific tsunami upolu island samoa abstract the coral reef bordering the coastline of samoa affected by the 29 september 2009 tsunami provides a variety of ecosystem services from nurseries for fisheries and inshore source of food for local communities to aesthetics for tourists and the width of the lagoon may have been a factor in reducing the onshore wave height to understand the complex interactions between the onshore human population and the offshore coral we formed an interdisciplinary survey team to document the effects the tsunami had on the nearshore coral reef and how these changes might affect local inhabitants the scale of reef damage varied from severe where piles of freshly killed coral fragments and mortality were present to areas that exhibited little impact despite being overrun by the tsunami we found that many coral colonies were impacted by tsunami entrained coral debris which had been ripped up and deposited on the fore reef by repeated cyclones and storm waves in other places large surface area tabular coral sustained damage as the tsunami velocity increased as it was funneled through channels areas that lacked debris entrained by the waves as well as areas in the lee of islands came through relatively unscathed with the exception of the delicate corals that lived on a sandy substrate in the lagoon on the south coast with its steep topography coral colonies were damaged by tsunami generated debris from onshore entrained in the backwash despite the potential for severe tsunami related damage there were no noticeable decreases in live coral cover between successive surveys at two locations although algal cover was higher with the increased nutrients mobilized by the tsunami while there was an immediate decrease in fish takes in the month following the tsunami when supporting services were likely impacted both volume and income have rapidly increased to pre tsunami levels long term monitoring should be implemented to determine if nursery services were affected

numerical simulation of winter katabatic winds from west antarctica crossing siple coast and the ross ice shelf abstract twenty four hour numerical simulations of wintertime surface winds under clear sky conditions over the west antarctic ice sheet and its vicinity are performed using a hydrostatic three dimensional primitive equation model two initial states are examined a state of rest and a prescribed pressure field associated with katabatic winds from west antarctica propagating across the ross ice shelf the antarctic katabatic winds are mainly due to the strong radiative cooling of the ice slopes the west antarctic terrain is different from that of east antarctica in two respects its mean elevation is much lower and the slope in the interior is steeper than near the margin at siple coast the simulated surface wind regime reveals confluence zones just inland from the coast and diffluence zones around the crest of the terrain the model results suggest that the continuation of katabatic winds beyond coastal confluence zones which are sustained by cold air drainage in the interior has an important impa

the mixing of magmas in plutonic and volcanic environments analogies and differences abstract magma mixing processes have been widely recognized in both the plutonic and volcanic environments but the quality and quantity of information that can be extracted from the two environments are substantially different understanding the advantages and limits associated with the study of plutonic and volcanic rocks is essential to establish precise methodological approaches to build the most complete conceptual model by merging information from these two complementary igneous environments in this work we review magmatic interaction processes in the plutonic and volcanic environments by considering several aspects of these geological phenomena in particular we first briefly report on the structural and geochemical evidence for magma mixing in both plutonic and volcanic rocks with the aim to provide a general picture of this natural phenomenon successively we discuss some recent results about magma mixing achieved using the concepts from chaos theory and discuss their potential impact on magma differentiation finally we attempt to build a general picture of this igneous process by merging present day information from both the plutonic and volcanic environments it emerges from the general picture that the time spent by the magmatic system in the molten or partially molten state is the crucial factor for the preservation of the fingerprints of magma mixing in the two environments we propose a conceptual model that may be useful to understand what kind of information we can obtain from volcanic and plutonic rocks and ultimately to maximize our knowledge about magma mixing

tectonic evolution of the early mesozoic blueschist bearing qiangtang metamorphic belt central tibet this is the published version copyright 2003 american geophysical union all rights reserved

provenance analysis of the mesozoic hoh xil songpan ganzi turbidites in northern tibet implications for the tectonic evolution of the eastern paleo tethys ocean 1 mesozoic strata of the hoh xil songpan ganzi complex in northern tibet are exposed in a vast 370 000 km2 triangle shaped orogenic belt bound by the longmen shan thrust belt in the east the kunlun terrane and north china block in the north and the qiangtang terrane and yidun arc in the south these strata consist of middle upper triassic submarine fan and deep marine facies rocks that were deposited in the paleo tethys ocean late triassic early jurassic contractional deformation in the eastern hoh xil songpan ganzi complex marks the demise of the paleo tethys ocean basin and the accretion of the gondwana derived qiangtang terrane to eurasia we conducted geological mapping regional stratigraphic analyses and u pb geochronology of detrital zircons n 4128 on the mesozoic sequences exposed in the hoh xil songpan ganzi complex kunlun terrane and qiangtang terrane we identify for the first time marine silciclastic sandstone and shale of jurassic age in the northwestern hoh xil songpan ganzi complex that unconformably overlie upper triassic turbidites zircon age data indicate that the middle upper triassic marine gravity flow deposits of the hoh xil songpan ganzi complex were shed from the north and south china blocks and middle late triassic ultrahigh pressure qinling dabie orogenic belt as well as the kunlun and qiangtang terranes in addition the detrital zircon results suggest vast sediment source to sink distances 1500 km for the middle upper triassic hoh xil songpan ganzi strata which is consistent with tectonic models for the paleo tethys ocean basin that incorporate significant components of horizontal tectonic transport like opening of large back arc basins in response to oceanic slab rollback

predecessors to the 2009 south pacific tsunami in the wallis and futuna archipelago abstract multi proxy studies of trench sediments from futuna island in the wallis and futuna archipelago have produced a record of two palaeotsunamis dated to around 1860 2000 bp and c 470 bp one of the most useful proxies in this study has been the archaeological data associated with occupations that immediately underlie the deposits associated with both palaeotsunamis the reworking of the archaeological material into the palaeotsunami deposits and the additional chronological control provided by artefacts have added value to interpretations based upon more conventional earth science proxies the identification of tsunamigenic sources for these events is tentative and based upon known potential sources based upon a comparison between the effects of the 2009 south pacific tsunami and those recorded in the trenches event 1 1860 2000 bp appears most likely to be associated with a large tsunami sourced from the tonga kermadec trench region there are only rare contemporaneous events reported from around the region although this appears to be largely due to a lack of similar research as opposed to a lack of evidence event 2 c 470 bp is markedly larger than event 1 with sedimentary evidence indicating significant inland inundation and runup around the entire island there are several lines of evidence for a contemporaneous event in the south pacific around 470 bp although much of this needs further verification determining a source for this event is problematic because it must take in to account the regional signal and the significant impacts recorded on futuna we propose that the source for this younger event was either a larger tonga kermadec trench related earthquake or the kuwae caldera collapse in 1452 1453 ad we recognise that as further research is carried out in the pacific we will greatly improve our abilities to identify past sources and the magnitude and frequency of past events from these areas this can only serve to improve our understanding of the regional risk from tsunamis

momentum budget of the east antarctic atmospheric boundary layer results of a regional climate model output of a regional atmospheric climate model is used to quantify the average january and july momentum budget of the atmospheric boundary layer abl over the east antarctic ice sheet and the surrounding oceans results are binned in nine elevation intervals over the ice sheet and six distance intervals over the ocean in january when surface cooling is weak the large scale pressure gradient force dominates the abl momentum budget in july under conditions of strong surface cooling a shallow katabatic jet develops over the gentle slopes of the interior ice sheet and a strong deep jet over the steep coastal slopes in the coastal regions the abl thickens considerably caused by the piling up of cold air over the adjacent sea ice and ice shelves this represents the main opposing force for the katabatic winds horizontal and vertical advection are generally small in the cross slope direction the momentum budget represents a simple balance between surface drag and coriolis turning intraseasonal variability of the large scale wind field in the abl can be explained in terms of the strength of the polar vortex the background baroclinicity and the topography of the ice sheet subsidence is found over the interior ice sheet and rising motion in the coastal zone reflecting the acceleration and deceleration of the katabatic circulation however vertical velocities are generally small because the downslope mass flux in the abl is confined to a shallow layer below the wind speed maximum

dating tsunami deposits present knowledge and challenges abstract dating approaches for fine sediment tsunami deposits can be divided into two categories 1 dating directly using materials from within a tsunami deposit and 2 dating indirectly using materials from above and below it for the former optically stimulated luminescence osl dating has a possible advantage in that is can directly date the burial age of sediments laid down by a tsunami however because of methodological limitations osl dating cannot always provide a reliable age although 14c and u th dating of reworked material from within a tsunami deposit are possible means of determining the age of the event the results merely represent a maximum age of deposition for these reasons dating is commonly achieved indirectly from 14c dates taken from samples in sections immediately above and below a tsunami deposit however indirectly dated results do not provide a precise timing of the event therefore there are distinct limitations in the ability to obtain high precision dating of past tsunamis recent methodological developments including the application of bayesian statistical analysis to radiocarbon dating results and the selection of appropriate dating materials has significantly improved the accuracy of age determination by reducing errors this review presents several methodological improvements that have enhanced tsunami deposit age estimation the most important points for a more precise tsunami age estimation are the numbers of 14c samples dated coupled with the use of bayesian statistical analysis these points are applicable not only to tsunami deposits but also to many other past geohazard events

the late triassic rift related volcanic rocks from eastern qiangtang northern tibet china age and tectonic implications abstract the late triassic nadi kangri volcanic rocks with nearly ew trending outcrops within the qiangtang basin northern xizang tibet china are composed mainly of acid tuff dacite rhyolite and minor basic volcanic rocks there exists a significant depositional hiatus between the nadi kangri volcanic rocks and underlying strata therefore the nadi kangri volcanic rocks represent a new evolution history of the mesozoic qiangtang basin the magma emplacement age of the nadi kangri volcanic rocks in the geladaindong area is 220 4 2 3 ma representing the onset of the mesozoic qiangtang basin the nadi kangri basalts have high nb zr 0 049 0 058 ta hf 0 12 0 15 and zr y 4 95 6 01 ratios in the tectonic discrimination diagrams such as zr vs zr y and th hf vs ta hf the nadi kangri basaltic rocks mostly plot in the within plate setting field the geological background and the geochemical characteristics suggest that the nadi kangri volcanic rocks were formed in a continental rift setting

triassic nb enriched basalts magnesian andesites and adakites of the qiangtang terrane central tibet evidence for metasomatism by slab derived melts in the mantle wedge new chronological geochemical and isotopic data are reported for triassic 219 236 ma adakite magnesian andesite nb enriched basaltic rock associations from the tuotuohe area central qiangtang terrane the adakites and magnesian andesites are characterized by high sr y 25 45 la yb 14 42 and na2o k2o 12 49 ratios high al2o3 15 34 18 28 wt and moderate to high sr concentrations 220 498 ppm and end t 0 86 to 1 21 values low enrichments of th rb relative to nb and subequal normalized nb and la contents and enrichments of light rare earth elements combine to distinguish a group of nb enriched basaltic rocks nebs they have positive end t 2 57 to 5 16 values positive correlations between th la and nb and an absence of negative nb anomalies on mantle normalized plots indicate the nebs are products of a mantle source metasomatized by a slab melt rather than by hydrous fluids a continuous compositional variation between adakites and magnesian andesites confirms slab melt interaction with mantle peridotite the spatial association of the nebs with adakites and magnesian andesites define an adakitic metasomatic volcanic series recognized in many demonstrably subduction related environments e g mindanao arc philippines kamchatka arc russia and southern baja california arc mexico the age of the touhuohe suite and its correlation with triassic neb to the north indicates that volcanism derived from subduction modified mantle was abundant prior to 220 ma in the central qiangtang terrane

late triassic batang group arc volcanic rocks in the northeastern margin of qiangtang terrane northern tibet partial melting of juvenile crust and implications for paleo tethys ocean subduction the batang group btg volcanic rocks in the zhiduo area with nw trending outcrops along the northeastern margin of the qiangtang terrane northern tibet are mainly composed of volcaniclastic rocks dacite and rhyolite major and trace element sr and nd isotope zircon u pb and hf isotope data are presented for the btg dacites laser ablation inductively coupled plasma mass spectrometry zircon u pb dating constrains the timing of volcanic eruption as late triassic 221 1 ma major and trace element geochemistry shows that the btg volcanic rocks are classified as calc alkaline series all samples are enriched in large ion lithophile elements and light rare earth elements with negative slightly positive eu anomalies eu eu 0 47 1 15 and depleted in high field strength elements and heavy rare earth elements in addition these rocks possess less radiogenic sr 87sr 86sr i 0 7047 0 7078 much radiogenic nd end t 4 2 to 1 3 and hf ehf t 4 0 6 6 isotopes suggesting that they probably originated from partial melting of a crustal source containing a mantle derived juvenile component the inferred magma was assimilated by crustal materials during ascending and experienced significant fractional crystallization by combining previously published and the new data we propose that the btg volcanic rocks were genetically related to southwestward subduction of the ganzi litang ocean a branch of paleo tethys in the northeastern margin of the qiangtang terrane given the coeval arc affinity magmatic rocks in the region we envisage that the ganzi litang ocean may extend from the zhongdian arc through the yidun terrane to the zhiduo area probably even further northwest to the tuotuohe area

a description of the ross ice shelf air stream ras through the use of self organizing maps soms 1 the low level wind field across the ross ice shelf region antarctica is studied through the method of self organizing maps soms emphasis is placed on identifying and characterizing the ross ice shelf air stream ras the ras is a dominant northward stream of air resulting in significant transport of atmospheric mass from the interior of antarctica two soms are created for the lowest model level 13 m and the 5th lowest model level 150 m from archived real time numerical weather prediction output of the antarctic mesoscale prediction system amps a verification of the som for the lowest model level is completed by comparing select nodes to automatic weather station wind rose plots the winds depicted in the lowest model level som are dominated by the position of the cyclone in the ross sea and the changes in wind speeds on the antarctic plateau the 5th lowest model level provides a better depiction of the ras the ras is found to be present primarily when associated with a cyclone in the ross sea there is a strong seasonality to the ras with the ras occurring frequently during the winter months and rarely during the summer months the structure and position of the ras is strongly dependent on the position of the ross sea cyclone

late silurian early devonian adakitic granodiorite a type and i type granites in nw junggar nw china partial melting of mafic lower crust and implications for slab roll back abstract late silurian early devonian magmatism of the nw junggar region in the central asian orogenic belt provides a critical geological record that is important for unraveling regional tectonic history and constraining geodynamic processes in this study we report results of zircon u pb ages and systematic geochemical data for late silurian early devonian largely granitic rocks in nw junggar aiming to constrain their emplacement ages origin and geodynamic significance the magmatism consists of a variety of mafic to felsic intrusions and volcanic rocks e g adakitic granodiorite k feldspar granite syenitic granite gabbro and rhyrolite u pb zircon ages suggest that the granitoids and gabbros were emplaced in the late silurian early devonian 420 405 ma adakitic granodiorites are calc alkaline characterized by high sr 407 532 ppm low y 12 2 14 7 ppm yb 1 53 1 77 ppm cr mostly

dynamical constraints on katabatic wind cessation in adelie land antarctica the katabatic wind events observed in the coastal zone of adelie land antarctica on 27 november and 3 december 1985 are simulated with a hydrostatic mesoscale atmospheric model coupled to a snow moder the diurnal cycle of insolation is strong the main difference in the forcing between the two events is the large scale wind which is weak on 27 november and moderate on 3 december in both cases temperature and wind are characterized by well marked diurnal cycles in particular katabatic winds blow during nighttime and upslope winds during daytime in both cases the katabatic airstream slows down progressively over the ocean consequently continental air piles up and this generates a pool of cold air responsible for a pressure gradient force opposing the katabatic wind an amplification of the slowing down results when in the morning insolation increases the surface inversion weakens but the influence of the cold air pool increases the katabatic how starts to decay over the coastal zone and then retreats progressively toward the ice sheet interior when the large scale wind is weak the surface warming is sufficient for generating an additional upslope bouyancy force and anabatic flow develops over the ice sheet in the afternoon when the large scare wind is moderate and downslope the pilling up of cold air is important and this has a dramatic impact on the flow a sharp spatial transition is generated between downslope and upslope winds over the ocean this discontinuity moves toward the ice sheet interior in the morning and is responsible for the sudden cessation of the katabatic flow seen by static observers the results of the simulations are used in order to refine a simple parameterization of antarctic katabatic winds

understanding the history of extreme wave events in the tuamotu archipelago of french polynesia from large carbonate boulders on makemo atoll with implications for future threats in the central south pacific abstract numerous large carbonate boulders up to 164 tonnes in mass were investigated on the reef flat and beaches of makemo atoll in the tuamotu archipelago of french polynesia to reveal the past occurrence and to anticipate the future potential threat of extreme wave events possibly generated by tropical cyclones and tsunamis the modern reef edge and emerged mid holocene coastal landforms were identified as sources of boulders mobilized during extreme wave events in the past the minimum flow velocities produced by extreme wave events were estimated to exceed 5 4 15 7 m s at the reef edge on different parts of the atoll comparison of uranium thorium ages of boulder coral fabric with written historical records indicates that two large boulders 77 and 68 tonnes were possibly emplaced on the reef flat by a powerful cyclone in february 1878 although most boulder dates are older than the earliest historical cyclone and tsunami records in french polynesia their ages concur with the following a periods of storminess i e increased cyclone activity compared to today in the central south pacific over the last millennium and b periods of high sea surface temperature sst at the great barrier reef possibly associated with higher than normal ssts pacific wide that facilitated the generation of cyclones affecting the central south pacific ocean none of the boulders on makemo were dated younger than ce1900 implying that the last century has not experienced extreme waves of similar magnitude in the past nevertheless the findings suggest that waves of comparable magnitudes to those that have transported large boulders on makemo may recur in the tuamotus and threaten island coasts across the central south pacific in the future

u pb dating geochemistry and sr nd isotopic composition of a granodiorite porphyry from the jiadanggen cu mo deposit in the eastern kunlun metallogenic belt qinghai province china abstract the jiadanggen porphyry cu mo deposit is newly discovered and located in the eastern kunlun metallogenic belt of qinghai province china here we present a detailed study of the petrogenesis magma source and tectonic setting of the mineralization causative granodiorite porphyry the new data indicate that the granodiorite porphyry is characterized by high sio 2 68 21 70 41 wt and al 2 o 3 relatively high k 2 o low na 2 o and low mgo and cao concentrations and is high k calc alkaline and peraluminous the granodiorite porphyry has low mg 38 46 values that are indicative of no interaction between the magmas and the mantle the samples that we have examined have low nb ta 9 17 10 3 and rb sr 0 28 0 39 ratios which are indicative of crustal derived magmas source region discrimination diagrams indicate that the magmas that formed the granodiorite porphyry were derived from melting of a mixed amphibolite source in the lower crust the samples have i sr values of 0 70954 0 70979 e nd t values of 8 3 to 7 9 and t 2dm ages ranging from 1644 to 1677 ma these indicate that the magmas that formed this intrusion were generated by melting of mesoproterozoic lower crustal material higher k rb contents of the samples indicate that the magma source is high potassium basaltic material in the lower crust which could be derived from an enriched mantle source la icp ms zircon u pb dating of the granodiorite porphyry yields a late indosinian age concordia age of 227 1 ma mswd 0 31 which is close to the molybdenite re os isochron age 227 2 1 9 ma indicating further the close relationship between the granodiorite porphyry and the cu mo mineralization these samples are lree and lile e g rb k ba and sr enriched and hfse e g nb ta p and ti depleted especially in p and ti similar to the characteristics of volcanic arc magmas this intrusion most likely formed during the later stage of indosinian deep subduction of oceanic slab this was associated with underplating of mantle derived magmas which provided heat for crustal melting similar to the jiadanggen granodiorite porphyry indosinian hypabyssal intermediate felsic intrusive rocks formed under subduction tectonism or a transitional regime from subduction to syn collision make up the most important targets for porphyry cu mo deposits in the eastern kunlun metallogenic belt

empirical building fragilities from observed damage in the 2009 south pacific tsunami abstract this manuscript presents empirical building fragility functions that were developed based on data obtained from the 29th september 2009 south pacific tsunami a multi disciplinary reconnaissance team involving topographic surveyors tsunami hydrology modellers structural engineers and risk analysts collected observational and quantitative data on building damage and the tsunami demand a diverse range of collected data which included a topographic survey observed water depths predominant flow directions inundation limits building damage and eyewitness reports were used to recreate the peak tsunami induced demands on structures at each of the survey locations using the interpreted data fragility functions were developed for a variety of building classes using logistic regression it was observed that residential timber structures were more fragile i e have a higher likelihood of damage for a given water depth than masonry residential structures for severe and collapse damage states conversely residential reinforced concrete structures were observed to be less fragile than residential masonry structures for severe and collapse damage states the influence of shielding and entrained debris effects on fragility functions were also quantified using the empirical data other parameters such as velocity or impact duration were not considered due to the paucity of data the results of this study contribute to the ongoing development of robust methods for explicitly estimating tsunami induced risk to coastal communities

petrogenesis and tectonic implications of the triassic volcanic rocks in the northern yidun terrane eastern tibet abstract triassic paleo tethyan subduction related volcanic rocks are extensively distributed in the xiangcheng and changtai regions northern yidun terrane eastern tibet the 228 ma volcanic rocks in the xiangcheng region have intermediate felsic composition 60 1 to 64 7 wt sio 2 with relatively low y 14 18 ppm and high sr 630 1830 ppm yielding high sr y ratios 43 94 they have lree enriched and hree depleted ree patterns la yb 19 26 typical of adakites sr nd isotopic compositions of these volcanic rocks are similar to those of the contemporaneous high silica adakitic rocks in the southern yidun terrane the 231 230 ma volcanic rocks in the changtai region are composed of basalts andesites dacites and rhyolites with sio 2 ranging from 47 7 to 81 0 wt basalts in the changtai region have initial 87 sr 86 sr ratios from 0 7052 to 0 7058 and e nd t from 1 1 to 1 5 they display oib like geochemical signatures and were likely derived from low degrees of partial melting of an oib like mantle source with subordinate input of subduction components indicated by increasing th content andesites and dacites show elemental and isotopic compositions that evolved from the basalts indicative of derivation via crustal contamination and fractional crystallization afc of basaltic magmas rhyolites have lower initial 87 sr 86 sr ratios and higher e nd t values than andesites dacites inconsistent with an afc process and are suggested to have been derived from anatexis of crustal materials emplacement of volcanic rocks in the changtai and xiangcheng regions could be attributed to the subduction of the ganzi litang ocean a branch of the paleo tethys ocean volcanic rocks in the changtai and xiangchang regions have zircon u pb ages about 4 6 myr older than that of arc granites in the eastern yidun terrane the spatio temporal distribution of the volcanic rocks indicates that the subduction was initiated under the southern yidun terrane in the middle triassic and extended to the northern yidun terrane at the beginning of the late triassic

middle to late jurassic felsic and mafic magmatism in southern hunan province southeast china implications for a continental arc to rifting abstract extensive middle to late jurassic felsic and mafic magmatism occurred in the southern hunan province southeast china shrimp zircon u pb dating mineral chemical element geochemical and sr nd hf isotopic data have been determined for these rocks the results indicate that the middle jurassic 178 170 ma changchengling and ningyuan basaltic rocks belong to tholeiitic series and alkaline series respectively and were formed by fractional crystallization of the parent magmas that were derived from partial melting of asthenospheric mantle triggered by the slab released fluids of the subducted paleo pacific plate the late jurassic 152 146 ma daoxian basalts and guiyang lamprophyre dikes are low ti high mg potassic rocks they were derived directly by partial melting of shallower 60 100 km lithospheric mantle composed of amphibole and phlogopite bearing lherzolite in response to thermal perturbations associated with the rifting of continental arc the middle jurassic 164 ma tongshanling granitic rocks belong to calc alkaline series and are strongly peraluminous they were formed by partial melting of palaeoproterozoic metasedimentary basement in the lower crust plus additional input from coeval basaltic magma the late jurassic 156 ma jinjiling and xishan granitic rocks show a2 subtype affinity they were generated by partial melting of granulitized palaeoproterozoic metamorphic basement in the lower crust in response to injection of coeval low ti high mg potassic magmas a moderate degree 56 58 of fractionation of these pure crustal melts could account for more felsic end member of granitic rocks detailed petrologic and geochemical data for the middle to late jurassic felsic and mafic rocks from the southern hunan imply that during the middle jurassic time se china on the southeast of the shi hang zone was a continental arc coupled with the subduction of the palaeo pacific plate and since the beginning of late jurassic time an intra arc rift has been formed along the shi hang zone as a consequence of slab roll back

a synthesis of warm air advection to the south polar plateau surface temperature and wind chronologies of varying length and 10 m snow temperatures have been used to produce a synthesis of airflow into antarctica this synthesis shows relatively warm air over ellsworth land which appears to enter the south polar plateau through a slightly lower lying trough between the summit of the transantarctic mountains and the polar plateau comparison of recent automatic weather station aws records from mount howe 88 5 s 150 w with four aws surrounding south pole at 89 s show that this upslope inflow is a frequent and persistent phenomenon

formation of wulong mafic dikes via mixing of enriched lithospheric mantle derived and crustal magmas eastern north china craton abstractzircon u pb age and geochemical data are reported for the wulong dike swarms from the liaodong peninsula ne china the studied dikes include diorite lamprophyre and dolerite together with previous dating the diverse rocks have a peak age of ca 120 125 ma they are marked by inversely zoned phenocrysts with mg and cr rich rims and they exhibit mantle like signatures i e high mg cr ni associated with prominent subduction type element enrichments the early diorites have relatively radiogenic sr 0 7143 and less radiogenic nd to 11 0 isotopes coupled with high and variable mgo cr ni contents indicating that they were mainly derived from ancient lower crust with subordinate contributions of enriched lithospheric mantle the transitional lamprophyres are characterized by high rb sr ratios 0 22 0 54 but low initial 87sr 86sr ratios 0 7069 0 7093 moderate negative end t values 14 4 to 12 6 and low promantle elements such as mg cr ni reflecting that juvenile lower crust

seismic driving of nationwide changes in geomorphology and prehistoric settlement a 15th century new zealand example abstract we propose a model for the seismic driving of environmental changes and illustrate it using a case study from new zealand dated to the 15th century ad a seismic staircase shows a chronological progression of environmental outcomes that includes tsunami rock avalanches vegetation disturbance rapid coastal dune building river aggradation and abandonment of prehistoric coastal settlements the 15th century event appears to be unique in the past millenium and is most notable for its period of rapid coastal dune building the coincidence of a catastrophic el nino episode in the mid 15th century ad may have served to move sediments rapidly through the terrestrial system thus delimiting clearly separate geomorphological after effects we contend that seismic driving is a major factor in determining paleoenvironmental change in tectonically active areas during the holocene and provides the palaeoenvironmental context within which smaller scale events operate

long term perspectives on giant earthquakes and tsunamis at subduction histories of earthquakes and tsunamis inferred from geological evidence aid in anticipating future catastrophes this natural warning system now influences building codes and tsunami planning in the united states canada and japan particularly where geology demonstrates the past occurrence of earthquakes and tsunamis larger than those known from written and instrumental records under favorable circumstances paleoseismology can thus provide long term advisories of unusually large tsunamis the extraordinary indian ocean tsunami of 2004 resulted from a fault rupture more than 1000 km in length that included and dwarfed fault patches that had broken historically during lesser shocks such variation in rupture mode known from written history at a few subduction zones is also characteristic of earthquake histories inferred from geology on the pacific rim

palaeotsunamis and their influence on polynesian settlement the 11 march 2011 t hoku oki tsunami caused widespread devastation to coastal communities in japan this event however was merely the latest yet largest of several similar occurrences in the pacific that include the 2007 solomon islands 2009 south pacific and 2010 chilean tsunamis all have had their predecessors and a growing data base of palaeotsunamis in the pacific suggests recurrent events comparable with and of larger magnitude than their recent historical counterparts here we show that evidence for regional palaeotsunamis provides an opportunity to re evaluate hypotheses used to explain the punctuated history of human settlement patterns across the pacific in particular the almost two millennia long pause in eastward migration and the abandonment of long distance sea voyaging in the 15th century may be related to palaeotsunamis with potential sources including the tectonically active tonga kermadec trench the kuwae caldera collapse and the more distant pacific wide ring of fire

triassic granitoids in the eastern songpan ganzi fold belt sw china magmatic response to geodynamics of the deep lithosphere the songpan ganzi fold belt sgfb sw china was developed from a passive continental margin into an orogenic belt with the consumption of the paleo tethys during the evolution of the sgfb numerous late triassic granitic plutons formed and exhibited a progressive development from adakite i type granite high ba sr granite a type granite and monzonite representative late triassic plutons were studied to unravel the bewildering evolution of the eastern sgfb the menggu pluton 224 3 ma consists of granites with high alkali k2o na2o 7 85 10 4 wt and adakitic characteristics sr y 19 38 the endt values 2 77 to 5 03 initial 87sr 86sr ratios 0 7050 0 7063 and low nb ta ratios 8 10 are indicative of an origin by partial melting of amphibolitic lower crust rocks from the niuxingou pluton 215 3 ma are richer in k than na k2o na2o 1 1 1 5 and contain high sr 1006 1662 ppm and ba 1277 2009 ppm typical of shoshonite and high ba sr granite they have less enriched endt values 0 08 to 2 04 and less radiogenic 87sr 86sri ratios 0 7047 0 7048 and formed from a mixed melt derived from upwelling asthenosphere and the overlying metasomatised lithospheric mantle the taiyanghe pluton 205 3 ma consists of monzonites with high al2o3 20 wt but low mgo 0 94 1 39 wt the rocks are richer in na than k k2o na2o 0 7 contain high large ion lithophile element lile 681 834 ppm sr and 2142 9453 ppm ba and display strongly fractionated ree patterns la yb n 35 63 these features together with their enriched nd sr isotopic compositions endt 4 78 to 6 50 87sr 86sri 0 7074 0 7090 suggest that the monzonite probably formed from low degrees of partial melting of metasomatised lithospheric mantle although a continuous compressional regime during the mid and late triassic has been invoked for the sgfb the generation of crustally derived adakitic and shoshonitic plutons reflect thickening in response to an arc continental collision accompanied by fracturing of the lithosphere and an extensional regime in the deep lithosphere in the late triassic the 205 ma taiyanghe pluton was emplaced simultaneously with a rapid uplift of the lithosphere when surface deposits changed from deep water turbidite to tidal flat sediments it was therefore generated during decompression probably related to the rapid removal of the overthickened lithospheric mantle the triassic magmatism in the eastern sgfb is therefore important for probing geodynamic processes in the deep lithosphere

idealized simulations of the antarctic katabatic wind system with a three dimensional mesoscale model the katabatic wind system represents a key factor for the near surface wind field of the antarctic region idealized simulations with a three dimensional mesoscale model are performed to investigate the development of the antarctic katabatic wind system and its sensitivity to physical boundary conditions in particular channeling effects and the thermodynamic forcing close to the coastline the simulated cases represent wintertime cases with complete sea ice coverage and no sea ice as well as a realistic summertime situation for the wintertime situations a large impact of the presence of open water on the three dimensional structure of the wind field close to the coast can be shown whereas the effects on the katabatic wind over the continent are relatively small near surface wind speeds over the continental slope for the summertime case have strengths comparable to those of the wintertime cases but reveal a distinct daily cycle due to the daily course of the radiation fluxes the formation of shallow mesoscale circulations is simulated after 2 4 days of simulation in ice free coastal areas in these regions low level convergence diabatic heating and the cold air advection associated with the katabatic flow leads to low level baroclinicity and cyclonic vorticity production

mesoscale cyclone activity over antarctica during 1991 1 marie byrd land a 1 year statistical study of mesoscale cyclonic activity over southern marie byrd land west antarctica was conducted using high resolution satellite imagery collected insitu during 1991 at the u s mcmurdo and palmer stations results indicate that on average one or two mesoscale cyclones can be observed each week over the southernmost part of marie byrd land siple coast and adjacent areas where cold katabatic winds from the high plateau of east antarctica and relatively warm katabatic airflows from west antarctica interact forming a boundary layer baroclinic zone in the form of a stationary front the 1991 annual mesoscale cyclone behavior exhibits maximum activity in march and minimum in september analysis of the large scale pattern for these months suggests that the higher activity in march is associated with synoptic scale conditions that support the cold katabatic drainage from east antarctica and favor warm air advection into west antarctica a situation that can form and or enhance the boundary layer baroclinic zone more than half 70 of the mesoscale vortices observed near siple coast were of comma cloud type with an average diameter of about 250 km their satellite signature characteristics show that these cyclonic perturbations were stratiform low cloud features indicating that most of them developed within the lower troposphere more than likely below 700 hpa according to a cloud top temperature evaluation

new insights of tsunami hazard from the 2011 tohoku oki event we report initial results from our recent field survey documenting the inundation and resultant deposits of the 2011 tohoku oki tsunami from sendai plain japan the tsunami inundated up to 4 5 km inland but the 0 5 cm thick sand deposit extended only 2 8 km 62 of the inundation distance the deposit however continued as a mud layer to the inundation limit the mud deposit contained high concentrations of water leachable chloride and we conclude that geochemical markers and microfossil data may prove to be useful in identifying the maximum inundation limit of paleotsunamis that could extend well beyond any preserved sand layer our newly acquired data on the 2011 event suggest that previous estimates of paleotsunamis e g 869 ad j gan earthquake and tsunami in this area have probably been underestimated if the 2011 and 869 ad events are indeed comparable the risk from these natural hazards in japan is much greater than previously recognized

petrogenesis of late triassic granitoids and their enclaves with implications for post collisional lithospheric thinning of the liaodong peninsula north china craton abstract major and trace element sr nd and hf isotope zircon u pb and hf isotope data are reported for mafic microgranular enclaves and host granitoids from the xiuyan pluton in the liaodong peninsula of the eastern north china craton in order to investigate their sources petrogenesis and tectonic implications the zircon u pb age of the enclaves 211 1 ma is identical to that of the host granite 210 1 ma establishing that the mafic and felsic magmas were coeval the enclaves have high mgo concentrations at low silica contents and positive ehf t values they are enriched in large ion lithophile and light rare earth elements and depleted in high field strength elements which can be explained as melts derived from a depleted asthenospheric mantle with some crustal contamination the host granitoids have high sio2 contents variable initial 87sr 86sr ratios and highly negative end t and ehf t values suggesting they were mainly derived from an ancient crustal source heated by the input of asthenospheric mantle derived magmas field observations geochronology geochemistry sr and nd isotopic and zircon hf isotopic compositions point to a complex petrogenesis where asthenospheric mantle and crust derived magma mixing was coupled with crystal fractionation thus explaining the genetic link between enclaves and host rocks identification of an asthenospheric mantle component in the xiuyan granitoids suggests asthenospheric mantle upwelling and decompressional melting of the mantle indicating that post collisional lithospheric thinning in the liaodong peninsula was initiated in the late triassic

characteristics of the ross ice shelf air stream as depicted in antarctic mesoscale prediction system simulations 1 streamlines of the mean annual near surface winds over the antarctic continent suggest a confluent channeling of the drainage flows off the ice sheets and onto the ross ice shelf a persistent cyclonic circulation to the north of the ice shelf supports a large scale pressure field that reinforces the continental drainage flows owing to these two processes an enhanced low level airflow is present along the southern and western sections of the ross ice shelf the resulting air stream known as the ross ice shelf air stream ras is one of the persistent and prominent low level wind features seen in the antarctic real time mesoscale simulations of the antarctic atmosphere and high southern latitudes using a modified version of the pennsylvania state university national center for atmospheric research mesoscale modeling system have been ongoing since the 1999 2000 austral field season model results from the 1 year period november 2001 to october 2002 have been analyzed to investigate the mean structure and modulation of the ross ice shelf air stream analyses of model results show the low level air stream over the western ross ice shelf has a wind speed maxima that is linked to the steep topography to the west individual cases of strong wind events appear to contain a significant barrier wind component that arises from cold air damming against the transantarctic mountains cyclones that frequently form in the ross sea are shown to establish conditions that promote barrier wind dynamics and thus significantly modulate the intensity of the ras

the dynamics of idealized katabatic flow over a moderate slope and ice shelf summary a non hydrostatic numerical weather prediction model has been employed to simulate idealized katabatic flows over a moderate slope and adjoining ice shelf the topography of coats land and the adjoining brunt ice shelf antarctica has been used this is typical of much of the antarctic coastline the regional atmospheric modeling system version 4 3 has been adapted for simulations over compacted snow most notably through changes to the multi layer soil model the simulations are initialized using clear sky conditions and at rest on the slope a shallow katabatic flow develops the winds becoming approximately steady on the slope by 12 h the peak downslope winds are about 7 m s 1 at 30 m above the snow surface the katabatic flow depth ranges from 50 to 100 m down the slope over the ice shelf the katabatic flow peters out while a pool of cold air develops primarily through sensible heat loss into the surface and partially balancing the net radiative heat loss to space near surface and sounding data from the model simulations compare well with archetypal and typical katabatic flow observations especially after some tuning of the model s turbulence parametrization an analysis of the downslope flow dynamics shows the buoyancy force is generally balanced by the inertial force except towards the foot of the slope where it is balanced by upslope forces related to gradients in the potential temperature deficit and katabatic layer height caused by the pool of cold air over the ice shelf over time the cooling of the ice shelf boundary layer leads to an apparent retreat of the katabatic flow from the ice shelf and some way up the slope the dynamical analysis explains the surface climatology observed such that the persistent katabatic winds of coats land rarely reach the brunt ice shelf the simulated katabatic flow moves from shooting to tranquil towards the foot of the slope this transition acts to trigger a train of internal gravity waves which propagate energy upwards away from the katabatic flow jump previous studies have also found shooting to tranquil katabatic flow transitions so to generalize these findings would suggest that internal gravitywave generation is ubiquitous around much of coastal antarctica and greenland

petrogenesis of late triassic intrusive rocks in the northern liaodong peninsula related to decratonization of the north china craton zircon u pb age and hf o isotope evidence abstract major and trace element whole rock sr nd and hf isotopes and zircon u pb age and hf o isotope data have been determined for mafic to felsic intrusive rocks from the late triassic mayihe myh longtou chaxinzi xiaoweishahe lcx and nankouqian xidadingzi nx intrusions in the northern liaodong peninsula ne china in order to investigate their sources and petrogenesis related to decrationization of the north china craton the rocks include clinopyroxene diorite monzodiorite quartz diorite granodiorite monzogranite and mafic microgranular enclaves laser ablation inductively coupled plasma mass spectrometry la icpms and secondary ion mass spectrometer sims u pb analyses of zircon from myh lxc to nx intrusions yield late triassic ages of 224 218 ma establishing that the mafic and felsic magmas were coeval the clinopyroxene diorites from the myh pluton have high mgo concentrations at low silica contents with positive whole rock e nd t up to 3 8 and e hf t up to 6 2 and zircon e hf t values and some mantle like 18 o values they are enriched in large ion lithophile liles and light rare earth elements lrees and depleted in high field strength elements hfses which can be explained as melts derived from a depleted mantle with some subsequent crustal contamination however the diorites from the lxc and nx intrusions are high k rocks and have high mgo concentrations and mantle like 18 o values but with negative whole rock e nd t 12 9 to 7 6 and e hf t 14 0 to 5 6 and zircon e hf t values distinct from those of myh pyroxene diorites indicating that their parental magmas were derived from partial melting of an ancient lithospheric mantle the granitoids from three plutons have high sio 2 contents and low mgo concentrations suggesting they were mainly derived from crustal sources however the myh monzogranite and granodiorite have positive whole rock e nd t and e hf t up to 3 0 and zircon e hf t values indicating a juvenile crustal source whereas the lxc and nx granitoids have strong negative and variable whole rock e nd t and e hf t and zircon e hf t values indicating that they were derived from partial melting of ancient lower crustal materials with involvement of mantle components field observations geochronology geochemistry sr nd hf isotopic and zircon hf o isotopic compositions point to a complex petrogenesis where mantle and crust derived magma mixing was coupled with crystal fractionation thus explaining the genetic link between mafic and felsic rocks identification of four components i e depleted and enriched mantle and juvenile and ancient crust in the late triassic magmatism in the northern liaodong peninsula suggests a strong mantle crust interaction process related to decratonization of the north china craton

an analysis of low level jets in the greater ross ice shelf region based on numerical simulations abstract an analysis of the presence and location of low level jets lljs across the ross ice shelf region in antarctica is presented based on the analysis of archived output from the real time antarctic mesoscale prediction system amps the method of self organizing maps soms is used to objectively identify different patterns in column averaged wind speed over the approximately lowest 1200 m of the atmosphere as an identifier to the location of lljs the results indicate three primary lljs in the region the largest and most dominant llj is along the transantarctic mountains by the siple coast and the southern end of the ross ice shelf the second llj extends from the base of byrd glacier and curves to the north passing by the eastern extremes of ross island the third llj extends from the base of reeves glacier and curves to the north across the western ross sea a strong seasonality is observed in the frequency and intensity of the lljs with the highest values for wind speed and the size of the

petrogenesis and geodynamics of late archean magmatism in eastern hebei eastern north china craton geochronological geochemical and nd hf isotopic evidence abstract the eastern part of the north china craton contains large volumes of late archean hornblenditic tonalitic dioritic granodioritic and granitic rocks la icpms zircon u pb dating of three plutons from eastern hebei eastern north china craton record emplacement ages of 2526 2515 ma and metamorphic ages of 2500 2490 ma for the diorite granodiorite and monzogranite and 2440 ma for the k feldspar granite hornblendites have high mgo 8 6 10 6 wt cr 674 1126 ppm ni 125 159 ppm and v 224 315 ppm at low basic silica contents sio2 45 7 49 0 wt they are enriched in light rare earth elements lrees and large ion lithophile elements liles and depleted in high field strength elements hfses with positive nd t values 1 2 to 2 0 indicating they were derived from an enriched mantle source the monzogranites have high sr and ba contents and sr y and la yb ratios low y and hrees abundances and positive nd t and zircon hf t values with nd and hf model ages less than 3 0 ga reflecting that they were derived from partial melting of a juvenile lower crust at high pressure however the k feldspar granites with low sr and ba concentrations and high hree and y contents are considered to have originated from partial melting of juvenile crustal materials at shallow crustal levels the diorites and granodiorites have variable major and trace element concentrations magmatic zircons from these rocks have heterogeneous hf t values but record uniform homogeneous u pb ages indicating they resulted from mixing of mafic and felsic magmas coupled with fractional crystallization because of the widespread distribution of late archean magmatism and evidence for magma mixing possibly related to mafic magma underplating it appears likely that this event in the eastern north china craton may relfect mantle plume activity that resulted in significant growth of continental crust during the late archean

multi proxy records of regionally sourced tsunamis new zealand abstract a multi proxy study of sediment cores from kaituna bay mimiwhangata in northern new zealand has produced a record of three palaeotsunamis dated to around 6500 cal yr bp 2800 cal yr bp and 1450 ad these events punctuate a coastal palaeoenvironmental history spanning the last 8000 years or more in which the site progressed from a semi open lagoon to a freshwater swamp proxies used included stratigraphy geochemistry palynology diatoms foraminifera geomorphology and a regional palaeotsunami synthesis the identification of tsunamigenic sources for these events is tentative we propose that the two oldest events are associated with a source in the tonga kermadec trench region with the most recent possibly associated with the kuwae caldera collapse in 1452 1453 ad palaeotsunami deposits contemporaneous with the estimated age of the three events identified in this study were used to assist in identifying possible source regions the development of regional and national palaeotsunami databases is in its infancy but as more data become available the ability to determine the source magnitude and frequency of past events will improve this will greatly enhance our understanding of the regional risk from tsunamis

a type granite and adakitic magmatism association in songpan garze fold belt eastern tibetan plateau implication for lithospheric delamination abstract the songpan garze fold belt covers a huge triangular area 200 000 km2 confined by the south china yangtze north china and tibetan plateau continental blocks in the songpan garze fold belt triassic adakitic granitoids have been identified however whether there are triassic a type granites is unclear here we report our first finding of an a type granite nianbaoyeche which occurs in the central part of the songpan garze fold belt the nianbaoyeche granite 820 km2 is characterized by arfvedsonite in its mineral assemblage using both la icpms and tims u pb zircon dating methods we obtain a magma crystallization age of 211 1 ma which is slightly younger than triassic adakitic granitoids 216 221 ma in the songpan garze fold belt the nianbaoyeche granite is enriched in si k na rb ree hfse nb ta zr hf with elevated feotot feotot mgo and ga al ratios but is depleted in al mg ca ba and sr the ree compositions show moderately fractionated patterns with la yb n 2 67 7 54 and eu eu 0 09 0 34 these geochemical characteristics indicate that the nianbaoyeche granite has an a type affinity geochemical data and u pb zircon age combined with regional studies show that the nianbaoyeche granite formed in a post collisional tectonic setting sr nd isotopic data for the granite exhibit isr 0 7090 0 7123 and end t 2 72 to 4 26 with tdm 1 15 1 51 ga suggesting that the magma has a dominantly crustal source though a minor contribution from the mantle cannot be ruled out melting to produce an a type granite may have resulted from triassic lithospheric delamination after triassic crustal thickening of the songpan garze fold belt due to convergence between the yangtze north china and north tibet continental blocks the lithospheric delamination model also helps to explain the triassic adakitic magma generation in the songpan garze belt we conclude that association of a type granite and adakitic granitoids in post collisional environment could be a useful indicator of lithospheric delamination

the origin and pre cenozoic evolution of the tibetan plateau different hypotheses have been proposed for the origin and pre cenozoic evolution of the tibetan plateau as a result of several collision events between a series of gondwana derived terranes e g qiangtang lhasa and india and asian continent since the early paleozoic this paper reviews and reevaluates these hypotheses in light of new data from tibet including 1 the distribution of major tectonic boundaries and suture zones 2 basement rocks and their sedimentary covers 3 magmatic suites and 4 detrital zircon constraints from paleozoic metasedimentary rocks the western qiangtang amdo and tethyan himalaya terranes have the indian gondwana origin whereas the lhasa terrane shows an australian gondwana affinity the cambrian magmatic record in the lhasa terrane resulted from the subduction of the proto tethyan ocean lithosphere beneath the australian gondwana the newly identified late devonian granitoids in the southern margin of the lhasa terrane may represent an extensional magmatic event associated with its rifting which ultimately resulted in the opening of the songdo tethyan ocean the lhasa northern australia collision at similar to 263 ma was likely responsible for the initiation of a southward dipping subduction of the bangong nujiang tethyan oceanic lithosphere the yarlung zangbo tethyan ocean opened as a back arc basin in the late triassic leading to the separation of the lhasa terrane from northern australia the subsequent northward subduction of the yarlung zangbo tethyan ocean lithosphere beneath the lhasa terrane may have been triggered by the qiangtang lhasa collision in the earliest cretaceous the mafic dike swarms ca 284 ma in the western qiangtang originated from the panjal plume activity that resulted in continental rifting and its separation from the northern indian continent the subsequent collision of the western qiangtang with the eastern qiangtang in the middle triassic was followed by slab breakoff that led to the exhumation of the qiangtang metamorphic rocks this collision may have caused the northward subduction initiation of the bangong nujiang ocean lithosphere beneath the western qiangtang collision related coeval igneous rocks occurring on both sides of the suture zone and the within plate basalt affinity of associated mafic lithologies suggest slab breakoff induced magmatism in a continent continent collision zone this zone may be the site of net continental crust growth as exemplified by the tibetan plateau c 2012 international association for gondwana research published by elsevier b v all rights reserved

mesozoic plutons of the yidun arc sw china u pb geochronology and hf isotopic signature abstract the yidun arc is a triassic volcanic arc located between the songpan garze fold belt and the qiangtang block southwest china to constrain the age of a number of the major granitic plutons from the yidun arc laser ablation icp ms u pb analysis of zircon was conducted hafnium isotope data was also acquired through laser ablation multicollector icpms analysis of zircon with the aim of gaining insight into the age and nature of the source region of the plutons three age groups have been identified from seven granite samples early middle triassic 245 to 229 ma late triassic 219 to 216 ma and cretaceous 105 to 95 ma hafnium analysis shows the triassic granites to have negative and variable e hf values and mesoproterozoic 1 6 ga depleted mantle model ages which is interpreted to reflect derivation from an isotopically heterogeneous largely crustal source the cretaceous granite shows higher and less variable e hf values and slightly younger model ages 1 3 ga and is interpreted to be derived from melting of a more homogeneous crustal source a depleted mantle model age of 1 5 ga is calculated from the pooled triassic and cretaceous samples the source region for these magmas may be tentatively correlated with mesoproterozoic material of the yangtze craton which has been suggested to underlie the yidun arc however further work is necessary to demonstrate this suggestion