persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

use of psinsar data to infer active tectonics clues on the differential uplift across the giudicarie belt central eastern alps italy abstract the permanent scatterers synthetic aperture radar interferometry psinsar methodology provides high resolution assessment of surface deformations precision ranging from 0 8 to 0 1 mm year over long periods of observation hence it is particularly suitable to analyze surface motion over wide regions associated to a weak tectonic activity for this reason we have adopted the psinsar technique to study regional movement across the giudicarie belt a nne trending trust belt oblique to the southern alpine chain and presently characterized by a low to moderate seismicity over 11 000 ps velocities along the satellite line of sight los were calculated using images acquired in descending orbit during the 1992 1996 time span the psinsar data show a differential uplift of around 1 4 1 7 mm year across the most external wnw dipping thrusts of the giudicarie belt mt baldo mt stivo and mt grattacul thrusts alignment this corresponds to a horizontal contraction across the external part of the giudicarie belt of about 1 3 1 5 mm year

seismotectonics of northeastern taiwan kinematics of the transition from waning collision to subduction and postcollisional extension 1 the northeastern region of taiwan is one of the few places on earth that experienced a transition from collision to subduction and back arc opening in a young orogenic belt this provides us a rare opportunity to study the structural characteristics in such a transition we attempt to analyze the seismicity and stress patterns in this transitional region using data obtained from a dense and high quality seismic network our results show that from south to north fault types change from thrust to strike slip then to normal faulting the transitional domain between ilan and hualien is dominated by left lateral strike slip faulting with a nnw sse minimum principal stress axis consistent with the opening of the okinawa trough to the north the ilan plain is formed by structural activities of a series of normal fault systems to the south the spatial distribution of an earthquake cluster north of taiwan s coastal range appears to parallel the subducting interface between the philippine sea and eurasian plates this implies the northern extension of the coastal range has subducted consequently the opening of the okinawa trough becomes an important tectonic driving force in northeastern taiwan the westernmost ryukyu arc is pushed by the opening okinawa trough and moves southward the northern part of taiwan s central range moves with the arc to bend southeastward and the ilan plain forms in the space north of the range the bending of the central range belt results in bedding plane slip with left lateral strike slip earthquakes in the transitional domain to accommodate the deformation

a 60 000 year record of environmental change for the wet tropics of north eastern australia based on the odp 820 marine core palynomorphs from the odp site 820 marine core have provided a detailed record of terrestrial environmental responses to glacial interglacial forcing over the last 250 000 years in the australian wet tropics the development of an accurate geochronological framework for this key sequence has proved challenging consequently different dominant forcing mechanism s have been proposed to drive environmental change in the low latitudes a new chronology for the last 60 000 years based on accelerator mass spectrometry radiocarbon c dates of pollen concentrate material and the existing marine isotope stage boundaries mis 4 to 1 has been produced this new chronology provides a robust geochronological framework for interpreting environmental records across the region in particular our age model helps to resolve several debates concerning the timing of climatic changes and their impacts on both the marine and the terrestrial systems as well as possible human arrival and associated impacts on the region s ecosystems our findings suggest c dating of terrestrial pollen concentrate in marine sediments is a valuable tool for resolving major chronological uncertainties in potentially diagenetically altered marine caco sediments and should play a role in future multi dating strategies copyright

crustal deformation and block kinematics in transition from collision to subduction global positioning system measurements in northern taiwan 1995 2005 1 we present global positioning system gps measurements for the period 1995 2005 at 125 campaign surveyed sites in northern taiwan based on elastic rotating block modeling analyses derived from the gps data we describe the transitional tectonics from arc continent luzon chinese collision to the converging ryukyu trench subduction and back arc opening along the chinese continental margin station velocities relative to station s01r in the chinese stable continental margin were estimated from coordinate time series of each station by using the weighted least squares technique we found two distinct deformation patterns in two geological areas which are basically separated by the surface projection of the nw trending boundary of the subducting philippine sea plate across northern taiwan 1 a waning collision area to the west and 2 a transition zone to the east in the waning collision area the horizontal velocity field shows vectors of 0 3 7 3 mm yr toward the nw in the foothills and the hsuehshan range of northwestern taiwan the tectonic blocks represent a significant nw se internal contraction along with a small block rotation rate 3 0 myr the transition zone can be further divided into an outer range and inner range with distinguishing rotation rates and deformation behaviors in the outer range of the transition zone velocities of 1 0 7 8 mm yr from south to north rotating from 008 to 143 is found in the northernmost foothills and the hsuehshan range the tectonic blocks within the outer range are characterized by a coherent rotation low internal strain rate of 0 10 strain yr with an angular velocity of 5 1 myr where the euler pole is located near its southeastern boundary in the inner range of transition zone a larger clockwise rotation from west to east with horizontal velocities of 9 3 41 2 mm yr from 053 to 146 are found in the northernmost central range the tectonic blocks of the inner range reveal a remarkable nw se internal extension with an ultrarapid clockwise rotation 47 3 myr where the euler pole is near the southern boundary of the range close to the collision comer with the colliding luzon arc the trench roll back together with back arc opening are interpreted to be substantially superposed on the arc continent collision induced rotation in the transition zone with particular regard to the inner range of the northeast taiwan mountain belt

chronological overlap between humans and megafauna in sahul pleistocene australia new guinea a review of the evidence abstract over 60 faunal species disappeared from the australian continent during the middle late pleistocene most of these animals were large to gigantic marsupials birds and reptiles a terminal extinction date of 46 4 kyr has been proposed for the megafauna with all sites containing younger fossil megafauna dismissed by some researchers because of questions over stratigraphic integrity or chronologies the timing of the extinctions is argued to be broadly coincident with estimates of first colonization of the continent by modern humans and explanatory extinction models involving humans have subsequently gained currency however there is considerable evidence to suggest that in some parts of the continent people and some species of megafauna may have co existed well beyond 46 4 kyr in other places such as tasmania and the north of the continent there is no known record of a human megafauna temporal overlap a review of the available evidence indicates that only 13 species of megafauna were extant on human arrival in australia the archaeology of this period indicates that rather than a focus on big game hunting or firestick farming it was characterized by regional variability in subsistence strategies consistent with the range of environmental zones at the present time there is no substantive argument for a terminal extinction date of 46 4 kyr the current evidence indicating that there is no specific time period that correlates to any single mass extinction event on the basis of available evidence arguments for either human or climatic causation are entirely circumstantial and implicitly require acceptance of many unproven assumptions claims to have eliminated climate as a primary driver are premature and the recent focus on delivering proof of human causation in pleistocene faunal extinctions diverts attention from achieving a better understanding of the differential impacts of climate change and short term climatic flux in a land of environmental extremes

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

the distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz implications for dating young sediments abstract we noted recently murray et al 1995 that quartz samples taken from in channel fluvial deposits have apparent doses ranging over several orders of magnitude we suggested that these dose distributions are best explained by a mixture of a small number of poorly bleached grains and a larger number of well bleached grains in this paper we examine the distribution of apparent dose in small aliquots each composed of 2000 grains of different particle size fractions 63 90 m 90 125 m 125 180 m 180 212 m 212 250 m diameter from two samples collected from the murrumbidgee river new south wales australia the samples are of known burial age the first being 70 years old and the second being its modern equivalent 0 2 gy the difference in the lowest apparent dose in the two samples is considered to be the result of their different burial times we suggest a method for dating recently deposited

kinematics of convergence deformation and stress distribution in the taiwan collision area 2 d finite element numerical modelling abstract using a 2 d plane stress finite element model with elastic and elasto plastic rheologies appropriate for deformation within the brittle upper crust we analyse the relationship between kinematics of convergence deformation and stress distribution in the present taiwan collision occurring between the ryukyu and luzon subduction zones the distribution of stress trends calculated in our models is compared with a synthetic map of actual stress trajectories based on the most recent data available in the collision zone these data combine present day sources from borehole breakouts and earthquake focal mechanism with the reconstruction of quaternary palaeostress from fault slip data analyses resulting in a complete map of compressional stress trajectories which is used to constrain our models we show that the distribution of stress trajectories in the active taiwan collision is principally controlled by 1 the geometric configuration of the boundary between eurasia and the philippine sea plate 2 the shape and rheological properties of major structural units 3 the direction of convergence of the philippine sea plate relative to eurasia and 4 the influence of the opening of the okinawa trough the study of a two dimensional elastic and elasto plastic finite element modelling of the subduction collision in and around taiwan allows us to estimate the influences of these different parameters in the stress pattern taking into account both the simplifying assumptions of the numerical modelling and the angular uncertainties of field determinations the fit between the calculated stress pattern of the finite element model and that determined based on the geometrical synthesis of field analyses is rather good in general indicating that our model is valid to first approximation misfits remain minor and can be explained by data uncertainties and simplifying modelling assumptions for instance the shape of the corner of the collision zone is critical but is not accurately known also limited decoupling in the longitudinal valley collision zone was not considered in our models although it certainly plays a role some interesting features of our model are 1 the greater influence of the shape of the collision zone in comparison with that of the direction of convergence 2 the requirement for a trench retreat related to suction force in the ryukyu arc and 3 the crucial role of the interaction between okinawa trough opening and collision at the sharp northwestern corner of the philippine sea plate including its influence on the geological evolution of northeastern taiwan

geomagnetic field intensity north atlantic deep water circulation and atmospheric δ14c during the last 50 kyr we present simulated records of past changes in the atmospheric 14c for the last 50 kyr due to changes in geomagnetic field intensity and in the strength of the north atlantic deep water nadw a new geomagnetic record was used largely based on the napis 75 record laj et al phil trans r soc london a 358 2000 1009 1025 which has been extended for the 0 20 kyr interval using archeomagnetic and volcanic data past changes of the nadw were derived from a mineral magnetic study of the cores used in the construction of napis 75 two box models of different complexity 4 and 17 boxes were used to simulate the carbon cycle calculated records of 14c are consistent with experimental determinations for the last 24 kyr for older ages the records calculated with variable oceanic circulation conditions reach values as high as 600 with an average of 500 between 20 and 40 kyr with maxima around 21 30 and 38 kyr gisp2 age model while low values are observed prior to 42 kyr although large inconsistencies in experimental data preclude precise comparison the average record simulated with the 17 box model is overall consistent with the icelandic sea record voelker et al radiocarbon 40 1998 517 534 42 2000 437 452 except for the extremely high peak observed in this record at 40 5 kyr on the other hand the results recently reported from a stalagmite recovered from a submerged cave in the bahamas beck et al science 292 2001 2453 2458 are inconsistent with all our model simulations in the 20 45 kyr interval the improved geomagnetic record combined with the new nadw profile allows us to give a modeled evaluation of the relative contribution of these factors to changes in atmospheric 14c the average simulation provides a first order modeled correction for conventional radiocarbon ages older than 25 kyr for which no calibration curve is available as yet

improved accuracy of u series and radiocarbon dating of ostrich eggshell using a sample preparation method based on microstructure and geochemistry a study from the middle stone age of northwestern ethiopia abstract the middle stone age msa is important to studies of human evolution because it witnessed the origin of modern homo sapiens and its dispersal out of africa and across the rest of the old world obtaining accurate ages for these and other events that occurred during this time interval is of critical importance ostrich eggshell oes is commonly found in msa sites and oes calcite can be dated by radiocarbon and u series geochronologic techniques it is important to understand how both techniques are potentially compromised when the eggshell s pore clusters and intercrystalline microporosity are infilled with younger calcite and or soil derived detrital materials we investigated this question by using high resolution x ray computed tomography hrxct to reveal the extent and three dimensional structure of the pore clusters and element mapping to evaluate concentrations of detrital elements in modern versus ancient oes within the pore clusters and the crystal outer and cone inner layers relative to the palisade central layer hrxct results support earlier findings that oes pores are generally composed of one to several openings on the cone surface that develop into a complex three dimensional cluster of anastomosing and branching pores that extend through the palisade layer to exit on the crystal surface these hollow pore clusters provide a considerable total volume for the potential ingress of detrital materials element mapping revealed high concentrations of detrital mineral indicator elements al mg in ancient relative to modern oes and in the cone and crystal layers relative to the palisade layer within the palisade layer of ancient oes there are relatively high detrital mineral indicator element concentrations within filled pore clusters extracted pore cluster infill from the palisade layer yields significantly higher and more variable concentrations of 232th 2 200 10 000 ppt and 238u 35 54 ppb relative to the non porous palisade layer 150 3 100 ppt 232th and 19 25 ppb 238u based on these results we developed a mechanical preparation method that combines the removal of the pore cluster infill with the more common removal of the cone and crystal layers using this method u th analyses of four oes from an msa archaeological site in nw ethiopia yielded a mean age of 75 7 4 7 ka 2 sd the inclusion of the pore cluster infill with the palisade in a different oes from the same site produced a much younger age of 53 1 2 ka 1 se splits of several of these same oes samples prepared by this new method yield ams 14c ages that are beyond the range of 14c dating 50 ka while 60 of the oes analyses of the palisade layer that retained the pore cluster infill yielded much younger ages 27 38 ka our results demonstrate that dating oes that retains the pore cluster infill shifts both u th and 14c analyses to younger ages in order to obtain more precise and accurate ages we recommend that preparation of oes for both u series and 14c dating include the mechanical removal of both the pore cluster infill and the cone and crystal layers in order to more fully account for the incorporation of th u and c from detrital and authigenic minerals within the oes structure

the 2005 ilan earthquake doublet and seismic crisis in northeastern taiwan evidence for dyke intrusion associated with on land propagation of the okinawa trough summary northern taiwan underwent mountain building in the early stage of the taiwan orogeny but is currently subjected to post collisional crustal extension it may be related to gravitational collapse or to the rifting of the okinawa trough which lies offshore northeastern taiwan the ilan plain northeastern taiwan which is bounded by the normal fault systems and filled up with thick pliocene pleistocene sedimentary sequences formed under such an extension environment over there on 2005 march 5 two earthquakes with about the same magnitude m l 5 9 occurred within 68 s and produced intense aftershocks activity according to the records of central weather bureau seismic network of taiwan we relocated the earthquake sequence by the three dimension earthquake location algorithm with the newly published 3d vp and vp vs velocity model and determined the first polarity focal mechanisms of the earthquake doublet one major cluster of aftershocks which trends e w and dips steeply to the south can be identified and picked up as a potential fault plane the focal mechanisms of the two main shocks are both classified as normal type by first polarity but strike slip by centroid moment tensor inversion however two methods both yield consistent e w strike static coseismic deformation was additionally determined from global positioning system gps daily solutions at a set of continuous gps stations and from strong motion seismographs these data show nw se extension at high angle to the fault plane which cannot be explained from a simple strike slip double couple mechanism on the other hand the small vertical displacements and steep fault plane cannot be explained from a simple normal event as well we present from elastic dislocation modelling that the geodetic data are best explained by significant component of tensile source with centimetre scale of opening on a 15 km long fault extending from 1 to 13 km depth we therefore interpret the crisis as the result of dyke intrusion at the very tip of the okinawa trough which is reasonably driven by backarc spreading

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

velocity field of gps stations in the taiwan area abstract the 131 stations of the taiwan gps network were surveyed 4 6 times from 1990 to 1995 with dual frequency geodetic receivers the standard deviation of an observed baseline length with its linear trend removed is in the range of 6 10 mm for a 3 120 km long baseline the average rates of length change for all baselines of the network and those from nine continuously monitoring permanent stations are used in a least squares adjustment to estimate the velocities of the gps stations relative to paisha penghu situated at the chinese continental margin to the south of fengping in the northern coastal range the velocity vectors of stations in lanhsu lutao and the coastal range trend in the directions of 306 322 with rates of 56 82 mm yr in contrast there is a dramatic decrease in the rates to the north of fengping this may be caused by the motion along the ne sw trending thrusts which obliquely cut the northern coastal range a discontinuity of about 30 mm yr in the rates along with a remarkable change in the directions of station velocity is observed across the longitudinal valley then the moving directions gradually shift to the west for the stations in the western foothills in the kaohsiung pingtung coastal area the station velocities are even directed toward the southwest to the north of the peikang high the velocity vectors of the stations change direction from the west gradually to the north and finally to the east and southeast significant nw se extensional deformation is found in the ilan plain and northern taiwan in general the pattern of the velocity field for gps stations in the taiwan area is quite consistent with the directions of present day tectonic stress

neotectonic architecture of taiwan and its implications for future large earthquakes the disastrous effects of the 1999 chi chi earthquake in taiwan demonstrated an urgent need for better knowledge of the island s potential earthquake sources toward this end we have prepared a neotectonic map of taiwan the map and related cross sections are based upon structural and geomorphic expression of active faults and folds both in the field and on shaded relief maps prepared from a 40 m resolution digital elevation model augmented by geodetic and seismologic data the active tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the eurasian continental margin have created two neotectonic belts in taiwan in the southern part of the orogen both belts are in the final stage of consuming oceanic crust collision and suturing occur in the middle part of both belts and postcollisional collapse and extension dominate the island s northern and northeastern flanks both belts consist of several distinct neotectonic domains seven domains kaoping chiayi taichung miaoli hsinchu ilan and taipei constitute the western belt and four domains lutao lanyu taitung hualien and ryukyu make up the eastern belt each domain is defined by a distinct suite of active structures for example the chelungpu fault source of the 1999 earthquake and its western neighbor the changhua fault are the principal components of the taichung domain whereas both its neighboring domains the chiayi and miaoli domains are dominated by major blind faults in most of the domains the size of the principal active fault is large enough to produce future earthquakes with magnitudes in the mid 7 values

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

a synthesis of the geologic evolution of taiwan abstract the island arc of taiwan is composed of cenozoic geosynclinal sediments more than 10 000 m thick lying on a pre tertiary metamorphic basement pleistocene to miocene andesitic islands surround the main island and are related mostly to arc magmatism the penghu island group in the taiwan strait is covered with pleistocene flood basalt neogene shallow marine clastic sediments are exposed mainly in the western foothills with pleistocene andesitic extrusives at the northern tip and the northeastern offshore islands a thick sequence of paleogene to miocene argillitic to slaty metaclastic rocks underlies the western central range and forms the immediate sedimentary cover on the pre tertiary metamorphic complex to the east which represents an older mesozoic arc trench system the coastal range in eastern taiwan is a neogene andesitic magmatic arc including also a large variety of volcaniclastic and turbiditic sediments cenozoic taiwan is the site of arc continent collision where the luzon arc on the philippine sea plate overrides the chinese continental margin on the eurasian plate east and northeast of taiwan the polarity of subduction changes whereby the oceanic philippine sea plate is subducting beneath the ryukyu arc system on the eurasian plate continent arc collision in taiwan island is anomalous and may occur in a broad belt of deformation rather than along a well defined plate boundary or subduction zone

stratigraphy sedimentology chronology and palaeohydrology of quaternary lacustrine deposits at madigan gulf lake eyre south australia abstract madigan gulf is a large bay at the southern end of lake eyre north a major ephemerally flooded playa in arid central australia at the southwestern margin of a vast 1 300 000 km2 internal drainage basin the stratigraphy and chronology of the quaternary sequence in the gulf is described from 8 cores and a cliff exposure at the gulf margin a number of depositional environments are recognised and their distinctive sedimentary components are described facies recognised include deep and shallow water lacustrine environments dominated by surface water processes and dry or ephemerally flooded playa environments dominated by groundwater controlled processes sedimentary components include terrigenous clastics from river inflow and shoreline erosion carbonates of detrital inorganic or biological origin and gypsum and halite evaporites carbonates and gypsum evaporites precipitated within the basin are frequently reworked as clastic components the establishment of a preliminary chronology for the sequence by the application of thermoluminescence uranium thorium disequilibrium amino acid racemization and radiocarbon dating techniques has allowed a reconstruction of the last 130 ka of lake eyre palaeohydrology the wettest phase occurred during the last interglacial early in oxygen isotope stage 5 when an enlarged lake eyre was up to 25 m deep subsequently there has been a number of dry periods separating successively less effective wet phases culminating in the deposition of a substantial halite salt crust around the time of the glacial maximum the dry interludes are characterised by deflation of salts and sediment from the basin a process controlled by lowering of the watertable the record from madigan gulf demonstrates the dramatic and repetitive impact of lake deflation on the quaternary record of lake eyre in the early holocene a minor but mostly perennial lacustrine event was terminated at about 3 4 ka when the modern ephemeral playa regime was established the major catchment of lake eyre is located in the monsoon watered areas of northern australia as demonstrated by large floodings of the modern ephemeral regime major lacustrine episodes must indicate enhanced monsoon precipitation in northern australia in the holocene the lake has not risen to levels achieved during the early stage 5 lacustral phase indicating a marked reduction in the effectiveness of the monsoon in the present interglacial by comparison with its predecessor

radiocarbon dating of organic and carbonate carbon in genyornis and dromaius eggshell using stepped combustion and stepped acidification abstract a technique for determining the radiocarbon age of both organic carbon and carbonate carbon in the eggshell of the large flightless birds genyornis newtoni now extinct and dromaius novaehollandiae extant emu is presented here stepped combustion for organic carbon and stepped acidification for carbonate carbon were used to obtain multiple age determinations for each sample from which an assessment of the reliability of the ages is possible analysis of a genyornis newtoni eggshell fragment known to have an age considerably beyond the limit of radiocarbon dating has indicated that the backgrounds obtainable using this approach are 0 122 0 033 pmc for the organic carbon fraction and 0 070 0 025 pmc for the carbonate carbon fraction these backgrounds suggest that finite ages up to 50 000 55 000 bp are readily achievable on eggshell using stepped combustion acidification analysis of a single fragment of genyornis eggshell from williams point central south australia suggests that significant contamination of the organic carbon fraction of the eggshell is possible while ages for the carbonate fraction appear more reliable and indicate that the eggshell has an age of at least 49 000 2000 bp a total of six analyses of single genyornis newtoni and dromaius novaehollandiae eggshell fragments from the wood point deposit in southern south australia suggest ages for the samples of 41 000 800 and 37 900 700 bp respectively while an optically stimulated luminescence osl sample from a location very close to the genyornis sample has an age of 55 5 ka 1 the osl and calibrated radiocarbon ages for the genyornis sample and the sand matrix overlap at two standard deviations suggesting the most likely age for the eggshell and the sand matrix is 45 cal ka bp or earlier

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

does extrusion occur at both tips of the taiwan collision belt insights from active deformation studies in the ilan plain and pingtung plain regions abstract we analyse the present day deformation in two key areas of the taiwan collision belt the ilan plain to the nw and the pingtung plain to the sw our approach is mainly based on consideration of horizontal displacement revealed by recent geodetic gps surveys derived strain rate tensors indicating horizontal deformation and three dimensional seismotectonic stress regimes issued from inversion of focal mechanisms of earthquakes we reconstruct a consistent albeit complex tectonic pattern involving non rigid rotations clockwise in ne taiwan anticlockwise in sw taiwan transitions from pure compression near the mountains to transtension near the sea and simple shear affecting the deforming domain nw se left lateral in ne taiwan nne ssw right lateral in sw taiwan these tectonic patterns reflect lateral extrusion processes towards mechanically weak domains with respect to collision zone i e adjacent subduction zones ryukyu to the ne manila to the sw the extrusion of the ilan plain area occurs towards the se whereas that of the pingtung plain area occurs towards the sw the extrusion in ne taiwan is facilitated by the opening of the okinawa trough so that velocity and deformation rates are higher than in sw taiwan despite less active collision in this northern area the symmetry of the extrusion patterns is altered by differences in relative positions and orientations of collision belt and adjacent subduction zones which depend on the plate tectonic configuration and tectonic history of the taiwan region

the crustal deformation of the ilan plain acted as a westernmost extension of the okinawa trough abstract we analyze the current deformation in ilan plain of northeastern taiwan considered as the western extension of okinawa trough based on 34 geodetic sites observed between 2002 and 2006 the station velocities are between 1 9 mm yr and 43 0 mm yr in a direction between 38 and 143 relative to stable continent margin of eurasian plate this largest velocity is moving southeastward 143 at a rate of 43 mm yr was enhanced by a seismic doublet that occurred on march 6 2005 the station velocities at the northern margin of ilan plain are insignificant with a magnitude of 1 9 mm yr to 7 5 mm yr on the contrary the station velocities increase approximately southward along the southern margin of ilan plain the stations are moving roughly e w with a magnitude of 5 8 mm yr to 21 8 mm yr further southward the station velocities increase to a value of 43 0 mm yr in a direction of 143 the most prominent feature of the strain distribution patterns in ilan plain are the remarkable extensional strain rates observed in central and southern flank of the ilan plain the largest extensional rate is found 2 66 strain yr in 147 with a shortening rate in the perpendicular direction 1 28 strain yr in 57 indicating transtensional deformation mode in the northeastern flank of ilan plain insignificant or minor deformations are observed overall the extensional rates in this area clearly increase from north to south the extension directions in study area mostly trend e w to nw se directions using the velocity field of 34 gps stations and its strain rate filed we suggest the lateral extrusion process towards mechanically weak domain adjacent ryukyu subduction zone the lateral extrusion is facilitated by the opening of the okinawa trough we conclude that the northeast taiwan is subjected to both the compressional force exerted by the indentation of philippine sea plate and the tensile force induced by trench retreat related to the suction force at the ryukyu trench due to the interaction of two forces the stress regime rapidly changes from pure compression in the taiwan collision belt to transtension near ilan plain and its offshore area

modern vertical deformation rates and mountain building in taiwan from precise leveling and continuous gps observations 2000 2008 1 to characterize the present day vertical displacement field in the active taiwan orogenic belt 1843 precise leveling and 199 continuous gps measurements from 2000 to 2008 are collected and analyzed in this study vertical velocities derived from the leveling data are placed in a reference frame of the chinese continental margin using continuous gps observations at nearby sites the leveling and gps vertical velocities generally reveal a dome shaped pattern with uplift of 0 2 18 5 mm yr in the interior of the mountain range and subsidence on the flanks of the mountains and coastal plains modern uplift rates in the active fold and thrust belt are generally consistent with geologic uplift rates however present day uplift rates in the central range are faster than the million years averaged exhumation rates the modern subsidence rates are generally consistent with geologic rates except for the rates in western coastal areas due to groundwater pumping present day subsidence in the southern central range and northern coastal range is however inconsistent with long term uplift which may reflect interseismic elastic strain accumulation across faults present day subsidence in northern taiwan occurs in a region of postcollisional orogenic collapse we model the present day and geologic vertical velocities and published gps horizontal velocity data across southern taiwan using a 2 d lithospheric model the model suggests a combined slip rate of 40 mm yr on the frontal thrusts and 45 mm yr on the longitudinal valley fault the model requires an additional source of crustal thickening under the central range to match the observed present day uplift rates

calibration of the 14c time scale to 40 ka by 234u 230th dating of lake lisan sediments last glacial dead sea a new comparison of 14c dates with 234u 230th ages is presented of aragonites from lake lisan the last glacial dead sea between 20 52 cal ka bp the lisan data are coincident with the coral based 14c calendar age calibration through the continuous portion of the curve to 23 5 cal ka bp and with the additional checkpoints at 30 and 40 cal ka bp the agreement with the corals provides evidence for the accuracy of the u th and 14c ages and indicates that lisan aragonites can potentially be used to generate a nearly continuous record of the atmospheric 14c variations through this crucial time interval the lisan data are compared with other records older than 25 cal ka bp from lake suigetsu japan north atlantic foraminifera south african cave deposits and tufa from spain over some age intervals the records show broad agreement over other intervals they diverge all agree that 14c ages were 2 5 0 5 ka younger than calendar ages between 20 32 cal ka bp for ages 32 cal ka bp the lake suigetsu data indicate small differences between 14c ages and calendar ages of less than 1 5 ka the other records broadly agree that 14c ages are too young by 3 1 ka from 32 39 cal ka bp at 40 cal ka bp the foraminifera show equal 14c and calendar ages while the corals lisan aragonites and the spanish tufa indicate a large age difference of 4 5 ka a recent paleomagnetic study of the lisan formation indicates that the high calendar 14c age difference at 40 cal ka bp may be associated with the laschamp paleomagnetic excursion

dating north asian surface assemblages with ostrich eggshell implications for palaeoecology and extirpation east asian ostrich struthio anderssoni lowe was thought to have become extinct sometime in the late pleistocene petroglyphs portray ostrich with pleistocene animals and ostrich eggshell oes fragments and ornaments from holocene sites were considered to be older fossils here we summarize previous radiometric dates for ostrich eggshell oes and present 15 new calibrated accelerator mass spectrometry ams dates indicating that ostrich survived in mongolia and northern china until at least 8 9 ka bp the dates in our sample population suggest a correlation between struthio and warm steppe environments with extirpation probably related to essential changes in holocene steppe ecosystems including human expansion this study assesses the usefulness of asian oes for archaeological dating by ams constrains the date of asian ostrich extirpation and investigates palaeoenvironmental implications of ostrich survival and extinction

okinawa trough backarc basin early tectonic and magmatic evolution the okinawa trough lying between japan and taiwan is a backarc basin formed by extension within the continental lithosphere behind the ryukyu trench arc system stress directions associated with the two last extensional phases in the southwestern okinawa trough have been deduced from a comparison with analog modeling the direction of extension is n 150 o for the pleistocene phase of extension 2 0 1 ma and n 170 o for the late pleistocene holocene phase of extension 0 1 0 ma the present day ryukyu volcanic arc a narrow continuous feature extending from japan to taiwan is located on the eastern side of the okinawa trough 80 100 km above the wadati benioff zone the minimum depth for emplacement of arc magmatism scarce present day backarc volcanism appears in the middle and southern okinawa trough within linear en echelon bathymetric depressions a n045 o oriented seamount volcanic chain cuts across obliquely the southwestern okinawa trough and lies in the direct line of extension of the gagua ridge a n s linear volcanic feature of the philippine sea plate associated with this extension of the gagua ridge a large reentrant located at the base of the ryukyu prism the uplift of part of the nanao forearc basin and the deformation of the sedimentary arc suggest that the voluminous cross backarc volcanism could be tied to the subduction of the gagua ridge located there at a depth of 80 100 km beneath the backarc basin a second area of anomalous volcanism has been identified in the middle okinawa trough in the ene extension of the daito ridge a wnw ese 400 km long volcanic feature of the philippine sea plate we suggest that the gagua and daito ridges initially induced stress at the base of the arc which is still brittle and cracks propagated through the overlying brittle lithosphere allowing magmas with arc affinities to erupt at the seafloor this excessive magmatism reaches the seafloor through conduits which preferentially follow in their shallowest portion the crustal normal faults of the backarc rifts the okinawa trough is consequently still in an early stage of evolving from arc type to backarc activity

present day kinematics of active mountain building in taiwan from gps observations during 1995 2005 1 we characterize the kinematics of modern crustal deformation in taiwan and evaluate the potential for large earthquakes by computing tectonic block motions and fault slip rates from 531 gps horizontal velocities these new gps velocity field indicates that lateral extrusion in the southern transition from collision to subduction is primarily achieved by motion along several major reverse faults and internal distortion of blocks the northern transition is characterized by asymmetric opening of the okinawa trough and collision induced rotation between the ryukyu trench and okinawa trough we suggest that the differences in style of deformation in northern and southern taiwan are a result of differences in trenchward motions between the overriding plate and forearc sliver along strike variations in basin thickness and the presence of foreland basement obstacles in central taiwan result in clockwise rotation with sinistral motion on faults and counterclockwise rotation with dextral motion on faults north and south of the obstacle respectively in eastern taiwan high slip rate of 43 mm yr on the southern longitudinal valley fault lvf is responsible for the full collision of taiwan orogeny e w syn orogenic extension in the southern central range has been inferred by our model patches with high slip rate deficits on the lvf and the chelungpu fault from our model respectively mainly correspond to the source areas of the 1951 m 7 1 longitudinal valley earthquake sequence and of the 1999 mw 7 6 chi chi earthquake

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

extremely large variations of atmospheric 14c concentration during the last glacial period a long record of atmospheric 14c concentration from 45 to 11 thousand years ago ka was obtained from a stalagmite with thermal ionization mass spectrometric 230th and accelerator mass spectrometric 14c measurements this record reveals highly elevated 14c between 45 and 33 ka portions of which may correlate with peaks in cosmogenic 36cl and10be isotopes observed in polar ice cores superimposed on this broad peak of 14c are several rapid excursions the largest of which occurs between 44 3 and 43 3 ka between 26 and 11 ka atmospheric 14c decreased from 700 to 100 per mil modulated by numerous minor excursions carbon cycle models suggest that the major features of this record cannot be produced with solar or terrestrial magnetic field modulation alone but also require substantial fluctuations in the carbon cycle

monitoring interseismic activity on the ilan plain ne taiwan using small baseline ps insar gps and leveling measurements partitioning from arc continent collision and backarc extension

application of sar interferometry to a large thrust deformation the 1999 mw 7 6 chichi earthquake in central taiwan summary application of the interferometric method to four ers2 sar images acquired before and after the 1999 chichi earthquake has allowed determination of the coseismic surface displacement in the footwall area of the chelungpu fault the interferometric results revealed a relative shortening in the round trip distance between the radar antenna and the ground of the footwall side of chelungpu fault during the earthquake this shortening progressively increased from the west to the east and reaches the maximum amount of approximately 26 cm near the central segment of the chelungpu fault our interferometric results have been precisely examined using a dense gps network in the investigated area we mapped the gps coseismic measurements into the radar line of sight and implemented a forward simulation of sar interferogram from this synthesized result to control our unwrapping performance in this study these two observations are compared with a 3 d dislocation model of the fault finally a deformation analysis based on our interferometric result has indicated that a segment with irregular deformation behaviour can be distinguished in the footwall area of the chelungpu fault this segment may result from either the influence of inherited basement faults or the presence of a structural terrace that provide local opportunities for superficial deformation

cryptic meteoric diagenesis in freshwater bivalves implications for radiocarbon dating shells of freshwater bivalves are commonly used for radiocarbon dating late pleistocene archaeological and vertebrate fossil sites thus providing important constraints on late pleistocene human dispersal and megafauna extinction hypotheses the reliability of bivalve shells for dating rests partly on the ease with which subsequent diagenetic alteration can be recognized typically wherein original shell aragonite is replaced by calcite in meteoric environments here we document late pleistocene freshwater bivalve shells wherein meteoric diagenesis involved syntaxial overgrowth of aragonite cement on original aragonite shell biocrystals aragonite cement was identified in situ using raman microspectroscopy and formed rather than calcite as a result of unusually high mg ca ratios in local groundwaters thus altered shells contain diagenetic 14c rendering their dates unreliable but they may slip past common vetting techniques because 1 epitaxial cements are not readily apparent petrographically because they are in optical continuity with adjacent biocrystals 2 x ray diffraction indicates that no calcite is present 3 alteration is not apparent in cathodoluminescence studies and 4 stable isotopes of c and o are difficult to interpret in shells that originate in terrestrial meteoric environments hence although freshwater with a high mg ca ratio is not common groundwater chemistry should be considered before accepting bivalve based radiocarbon dates uncritically more broadly meteoric diagenesis in carbonate rocks is generally characterized by the dissolution of aragonite or its conversion to calcite our data show that such is not invariably the case even in fully terrestrial freshwater systems

the determination of late quaternary paleoenvironments at equus cave south africa using stable isotopes and amino acid racemization in ostrich eggshell abstract the stable carbon and nitrogen isotopes from organic compounds and stable oxygen and carbon isotopes from inorganic carbonate in modern and fossil ostrich eggshell oes at equus cave south africa were used to determine relative changes in c 3 and c 4 vegetation rainfall and temperature throughout the last 17 ka amino acid racemization and three new radiocarbon dates were used to assign ages to the individual oes fragments analyzed for stable isotopes and to evaluate the stratigraphic integrity of the samples the amino acid racemization and radiocarbon data indicate that most of the oes fragments are not in correct stratigraphic context and may have been upwardly and downwardly mixed thus each fragment was placed in chronological sequence using radiocarbon calibrated amino acid racemization the stable carbon isotope data from the fossil oes do not change systematically through the last 17 ka the ostriches primarily consumed c 3 plants between 70 and 90 and smaller quantities of c 4 plants between 30 and 10 indicating that a mixture of c 3 and c 4 plants has been in the vicinity of equus cave for the last 17 ka stable nitrogen isotope data from oes indicate that at 17 ka mean annual precipitation map was at a minimum 190 50 mm yr increased steadily to modern values by 6 ka 600 150 mm yr and remained relatively unchanged until present stable oxygen isotope data coupled with nitrogen isotope data indicate that paleotemperatures were at a minimum between 14 and 17 ka and reached their maximum in the latest holocene this study demonstrates the plethora of paleoenvironmental information that can be derived from analysis of three different stable isotopes carbon nitrogen and oxygen in the same sample type oes and presents a new tool with wide applicability for reconstructing paleoenvironments in semi arid and arid regions of africa

present day surface deformation and tectonic insights of the extensional ilan plain ne taiwan abstract taiwan s mountain belt is an ideal location to address major questions regarding mechanisms of lithospheric deformation in convergent settings mountain building processes from oceanic subduction to continental subduction and post orogenic extension in the northeast of this belt the ilan plain is a triangular deltaic plain characterized by a flat topography close to the sea level and surrounded by the high mountains of the hsuehshan range to the northwest and the central range to the southeast its eastern coast faces the western tip of the okinawa trough the back arc basin of the ryukyu subduction zone in this study we analyzed the present day surface deformation of the ilan plain aiming at deciphering its relationships with basement faults and the regional geodynamic setting our approach is mainly based on surface vertical displacements revealed by persistent scatterer interferometry synthetic aperture radar psi which indicate that there is an area of active subsidence 18 mm yr located in the southern part of the plain in probable connection with active basement faults and in agreement with previous geodetic measurements and existing geophysical data our psi results also suggest that the subsidence occurring in the ilan plain has moved from north to south during quaternary in relation with extrusion of the belt due to the westward propagation of the okinawa trough through the taiwan mountains

dating surface assemblages using pottery and eggshell assessing radiocarbon and luminescence techniques in northeast asia the vast majority of known archaeological sites in arid northeast asia are surface assemblages containing few or no organic remains the lack of stratified sites and a relative absence of organic remains in surface assemblages hinders our ability to date sites create local chronologies and contextualize technological and socio economic change such problems are common in arid regions around the world new radiocarbon and luminescence dates on collections from the gobi desert of mongolia and china are used here to assess the potential for direct dating of commonly occurring artefacts like ostrich eggshell and pottery direct dating also allows for the identification and sorting of mixed age assemblages here we compare dates derived from accelerator mass spectrometry ams on ostrich eggshell ams on pottery and luminescence on pottery our findings show that ams and luminescence are highly complementary methods and produce results consistent with expected archaeological ages while ostrich eggshell dates were older than the associated site assemblages

230th u burial dating of ostrich eggshell abstract obtaining precise and accurate dates for late quaternary terrestrial sequences containing middle stone age or middle paleolithic archaeological materials ca 30 300 ka can be challenging many such sequences lie beyond the limit of radiocarbon dating 50 ka and lack volcanic ashes suitable for 40ar 39ar dating we report a dating approach with about ten times the range of radiocarbon dating 500 ka based on a novel protocol for 230th u dating of ostrich eggshell a common component of african near eastern and asian archaeological sequences uranium in ostrich eggshell typically at levels of tens to hundreds of ppb is acquired after burial however accurate burial ages can be determined from measured 230th u ages when corrected for uranium uptake via diffusion using ostrich eggshells from a pleistocene holocene east african site we have 1 characterized the spatial distribution of uranium and common thorium 232th concentrations in ostrich eggshell by laser ablation icp ms 2 determined apparent 230th u ages on outer and inner layers of eggshells by solution icp ms analyses of selectively abraded eggshells and 3 calculated 230th u burial ages using a simple model for diffusive uptake of uranium we assess our method by comparing the 230th u burial ages median uncertainty 2 3 1 sd with radiocarbon dates on carbonate from the same eggshells we find good agreement in seven out of nine eggshells confirming the accuracy of their 230th u model ages eggshells that fail to yield reliable 230th u ages may be recognized by anomalous patterns of apparent 230th u ages providing a reliability criterion innate to the 230th u data ostrich eggshells are resistant to diagenesis simplifying 230th u dating compared to bones and teeth eggshells of ostrich emu rhea and other living and extinct ratites found on six continents share similar structure and composition suggesting our new approach to 230th u dating of eggshell may be applicable in diverse late quaternary terrestrial settings

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

lake eyre palaeohydrology from 60 ka to the present beach ridges and glacial maximum aridity lake eyre is presently an ephemeral playa lake in an extremely large 1 3 million km2 internal drainage basin with most of its inflow derived from monsoon watered northern australia the hydrologic state of the lake has varied in the past in response to climate change from a perennial lake up to 25 metres deep to a groundwater controlled playa marked by substantial sediment deflation this paper is concerned with the stratigraphic record of the last 60 ka of that hydrologic history particularly the character and age of a playa marginal unit formed by deflation from the playa and of stranded high beach ridges a major deflation episode between 60 and 50 ka excavated the present lake eyre basin and deposited a gypsum and clay rich aeolian phase the williams point aeolian unit at a number of sites around the lake after deflation ceased a thick secondary gypsum profile developed on the dune early in oxygen isotope stage 3 evidence for the state of lake eyre at this time is equivocal preliminary results from a substantial suite of amino acid racemization aar analyses of mollusc shell and bird eggshell samples from beach ridges at 5 and 10 m australian height datum ahd suggest that they are oxygen isotope stage 5 in age sedimentologic evidence suggests that it is unlikely that the shells are reworked from older deposits these aar results apparently conflict with early oxygen isotope stage 3 thermoluminescence tl dates from the 5 m ahd beach ridge nanson et al this volume however the age difference is not substantial the calibration of the aar is still at a preliminary stage and only one site was sampled for both techniques further stratigraphic and chronologic work is required to fully assess the apparent discrepancy between about 30 000 and 12 000 yr b p lake eyre was at least as dry as it is today at many sites around madigan gulf a lunette like playa marginal aeolian unit the shelly island unit was deposited during this period formed by material deflated from the playa floor forty ams radiocarbon dates span the period 35 000 to 10 000 yr b p from the shelly island unit 11 and from aeolian sediment close to playa level 29 indicating that the lake was dry during this period this evidence conflicts strongly with 2 tl dates from latest oxygen isotope stage 3 and oxygen isotope stage 2 from the 5 and 10 m ahd beach ridges nanson et al this volume additionally the aar results from the high beach ridges cannot be reconciled with these tl dates after 10 000 yr b p a minor lacustral phase occurred until the modern ephemeral playa regime became established at 3000 4000 yr b p

seismotectonics of taiwan abstract high quality seismicity data and focal mechanism solutions obtained during 1973 1983 by the permanent taiwan telemetered seismographic network and several temporary local seismographic networks are used for a detailed study of the seismotectonics of the taiwan area seismicity distribution in southern taiwan clearly reveals an east dipping benioff zone which has a thickness of about 30 km and begins to deepen along 121 e at a dip angle of 55 60 the leading edge of this benioff zone reaches a depth of about 180 km between 21 n and 22 n but tapers off to a shallower depth of about 100 km from 22 n to 23 n the presence of this seismic zone implies that subduction of the south china sea plate under the philippine sea plate extends from luzon northward to about 23 n the position of the northern boundary of the south china sea plate as tentatively defined according to the seismicity distribution passes through southern taiwan from the offshore area in the taiwan strait west of kaohsiung in an east northeast direction to the taitung area where a triple junction probably lies seismicity is found to disappear abruptly below a certain depth in many parts of taiwan this phenomenon may be attributed to the frictional to quasiplastic transition in the crust or upper mantle comparison of shallow seismicity with surface faults and fractures shows that all areas of active shallow seismicity are marked by densely developed faults and fractures however the converse is not necessarily true this may be partly due to the relatively short duration of seismicity data and partly due to excessive weakening of some of the severely faulted and fractured areas finally focal mechanism solutions for west central taiwan and the kuangfu fuli area in eastern taiwan predominantly show a maximum horizontal compression in the se nw direction which can be related to collision between the eurasian and philippine sea plates however focal mechanism solutions for both the hualien area in eastern taiwan and the tainan area in southwestern taiwan show remarkable irregularities which may result from local tectonic complexities

indentation of the philippine sea plate by the eurasia plate in taiwan details from recent marine seismological experiments abstract we analyze in this study a new set of marine data including 3d local tomography 1992 2008 relocated earthquakes and two recent multichannel seismic lines to characterize the deformation style in the collision area offshore east taiwan we have mapped in detail the mohos of the converging plates as well as the subduction interface with a resolution never reached before we show that the sharp continental subduction of the eurasia plate beneath the middle part of the central range indents the philippine sea plate psp as attested by intra oceanic slicing and incipient subduction of the psp beneath the east coast of taiwan the westernmost part of the psp slab is probably experiencing a beginning of break off as attested by nw trending en echelon shear zones beneath the southern slope of the southern ryukyu arc sra these en echelon shear zones have a sinistral component favored by the collision free subduction of the psp north of 24 30 n the down faulting of the subduction interface forms ramps along which earthquakes clusterize three m7 subduction earthquakes occurred offshore suao city along these ramps with a recurrence interval of about 40 years 1920 m w 7 7 1963 m w 7 2 and 2002 m w 7 1 events the 1966 m w 6 0 7 5 earthquakes sequence likely outlines a wnw ese left lateral intra slab shear zone the sra upper plate accommodates the complex geometry and deformation of the subducting psp through seismic deformation shallow high velocities fringing the luzon volcanic arc lva beneath the longitudinal valley and north of the southernmost ryukyu forearc basins are interpreted as relics of the lva forearc basement squeezed in the collision zone based on the accommodation of a large part of the convergence through shortening within the psp and the subsequent segmentation of the shallow subduction interface we consider that the nucleation of a m w 8 earthquake along the southernmost ryukyu megathrust is unlikely