smoke signals from corals isotopic signature of the 1997 indonesian haze event abstract from september to november 1997 most of indonesia was covered by a dense blanket of haze originating from fires on sumatra and borneo specimens of porites lobata were collected from two locations i e the riau archipelago south of singapore where the haze was most dense and the karimunjawa islands north of central java where the effects were less severe all corals exhibited strong kinetic isotope effects kie on plots of 18 o vs 13 c shifts in coral metabolism associated with the haze event could be estimated from the distance individual values are positioned from the theoretical kie line skeletons of corals affected by the haze showed decreased 13 c values perhaps produced by a shift to a more heterotrophic mode of feeding these results suggest that wildfires and major forest fire events on tropical coastlines may be recorded in nearby corals as could temporal variation in frequency of major fires moreover information on coral metabolism may be determined by examining shifts of coral skeletal values in c o space

efficient sequestration of terrigenous organic carbon in the new britain trench abstract the fate of terrigenous organic carbon octerr in the ocean remains an enigma for four decades hadal trenches the deepest ocean realm 6 11 km deep were recently proposed to be oc depocenters but whether and how much octerr was sequestrated there remain elusive here we conducted comprehensive analyses for four sediment cores from the new britain trench nbt close to papua new guinea to assess source translocation and burial of oc the bulk and molecular radiocarbon data suggest that the nbt landward slope and axis sediments mainly receive young and biogenic rather than petrogenic oc the three endmember mixing model based on 14c 13c and oc contents reveals that sediments of the nbt axis 8225 m comprise relatively high oc contents 0 66 0 08 of which biogenic octerr accounts for 62 10 the high proportion of biogenic octerr was attributed to the selective translocation of octerr enriched coarse particles and rapid delivery of sediments supported by unique v shape feature of the trench in contrast the sediment oc at the oceanward slope is primarily of a marine origin suggesting that octerr was efficiently trapped in the trench bottom it is estimated that the burial rate is 2 75 0 32 g c m 2 yr 1 for oc and 1 69 0 41 g c m 2 yr 1 for octerr in the nbt given a fact that many trenches are close to the landmasses we propose that the hadal trenches may contribute significantly to the burial of octerr in the ocean

tropical sea surface temperatures for the past four centuries reconstructed from coral archives most annually resolved climate reconstructions of the common era are based on terrestrial data making it a challenge to independently assess how recent climate changes have affected the oceans here as part of the past global changes ocean2k project we present four regionally calibrated and validated reconstructions of sea surface temperatures in the tropics based on 57 published and publicly archived marine paleoclimate data sets derived exclusively from tropical coral archives validation exercises suggest that our reconstructions are interpretable for much of the past 400 years depending on the availability of paleoclimate data within and the reconstruction validation statistics for each target region analysis of the trends in the data suggests that the indian western pacific and western atlantic ocean regions were cooling until modern warming began around the 1830s the early 1800s were an exceptionally cool period in the indo pacific region likely due to multiple large tropical volcanic eruptions occurring in the early nineteenth century decadal scale variability is a quasi persistent feature of all basins twentieth century warming associated with greenhouse gas emissions is apparent in the indian west pacific and western atlantic oceans but we find no evidence that either natural or anthropogenic forcings have altered el nino southern oscillation related variance in tropical sea surface temperatures our marine based regional paleoclimate reconstructions serve as benchmarks against which terrestrial reconstructions as well as climate model simulations can be compared and as a basis for studying the processes by which the tropical oceans mediate climate variability and change

signature of enso signals in the coral growth rate record of arabian sea and indian monsoons we examine here three sets of recently published data 1 updated indian rainfall irf time series of the entire country covering the time span of 1826 1994 2 coral growth rate time series for a period of 42 years spanning 1948 1990 from the arabian sea and iii nino3 temperature records to investigate the signature of enso response of the indian monsoon multiple spectral techniques e g multi taper method mtm maximum entropy method mem wavelet and cross spectra are used to identify the coherent cyclic and nonstationary modes in these records mtm analysis of irf time series resolves statistically significant variability 90 c i i at multi decadal 66 70 year s scales related to the well known global temperature variability of internal atmospheric ocean origin ii relatively weak signals at 13 and 22 years solar cycles and iii the 2 5 to 7 5 year cycles associated with the enso frequency band the mtm spectra of the coral growth rate record also reveal statistically significant periodicities 90 c i within 1 8 4 2 enso frequency band and a relatively weak signal at 12 8 years mem analysis confirms the stability of above spectral peaks wavelet spectral analyses of the above time series reveal nonstationary localized modes of enso evolution corresponding to 2 7 years and higher order terms although matching periodicities are present in these records cross spectral analysis of irf and nino3 temperature records exhibits significant coherency 80 ci only at periods 5 4 years and 2 7 years suggesting the significant role of enso dynamics in organizing the subtle indian monsoon at these frequencies these results may provide significant implication for the modeling of indian monsoon

improving sst reconstructions from coral sr ca records multiple corals from tahiti french polynesia we reconstruct sst from coral sr ca ratios measured at three coral cores taken from the lagoon of tahiti french polynesia two coral cores were drilled from the same coral colony one horizontally and one vertically and a third core was drilled vertically from another coral growing at a different site we evaluate several sr ca records as proxies for regional sst variations 1 the three single core records from tahiti 2 an average sr ca record computed from the two cores drilled from the same coral colony 3 an average sr ca record computed from all three tahiti cores and 4 an average sr ca record computed from the three tahiti cores and a fourth core taken from a different island rarotonga on a monthly scale the average sr ca record including the four coral cores from tahiti and rarotonga shows the best correlation with regional sst the variance of the sst reconstruction is very realistic and the residual sst is low this suggests that reconstructing sst from average proxy records gives a better representation of regional sst variations of the three tahiti cores the one that was drilled horizontally shows the best correlation with grid sst on an annual mean scale all three tahiti corals show much larger interannual sst variations than that indicated by grid sst

comment on a snapshot of climate variability at tahiti at 9 5 ka using a fossil coral from iodp expedition 310 by kristine l delong terrence m quinn chuan chou shen and ke lin 1 the integrated ocean drilling program iodp expedition 310 recovered drill cores from the drowned reefs around the island of tahiti 17 40 s 149 30 w many of which contained samples of massive corals from the genus porites herein we report on one well preserved fossil coral sample a 13 6 cm long porites sp dated by uranium series techniques at 9523 33 years monthly 18o and sr ca determinations reveal nine clear and robust annual cycles coral 18o and sr ca determinations estimate a mean temperature of 24 3 c 3 2 c colder than modern for tahiti at 9 5 ka however this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved the interannual variability in coral 18o is similar between the 9 5 ka coral record and a modern record from nearby moorea the seasonal cycle in coral sr ca is approximately the same or greater in the 9 5 ka coral record than in modern coral records from tahiti paired analysis of coral 18o and sr ca indicates cold wet warm dry interannual anomalies opposite from those observed in the modern instrumental record

a reconstruction of sea surface temperature variability in the southeastern gulf of mexico from 1734 to 2008 c e using cross dated sr ca records from the coral siderastrea siderea this study uses skeletal variations in coral sr ca from three siderastrea siderea coral colonies within the dry tortugas national park in the southeastern gulf of mexico 24 42 n 82 48 w to reconstruct monthly sea surface temperature sst variations from 1734 to 2008 common era c e calibration and verification of the replicated coral sr ca sst reconstruction with local regional and historical temperature records reveals that this proxy temperature relationship is stable back to 1879 c e the coral sst reconstruction contains robust interannual 2 0 c and multidecadal variability 1 5 c for the past 274 years the latter of which does not covary with the atlantic multidecadal oscillation winter sst extremes are more variable than summer sst extremes 2 2 c versus 1 6 c 2 suggesting that loop current transport in the winter dominates variability on interannual and longer time scales summer sst maxima are increasing 1 0 c for 274 years mc 0 5 c 2 whereas winter sst minima contain no significant trend colder decades 1 5 c during the little ice age lia do not coincide with decades of sunspot minima the coral sst reconstruction contains similar variability to temperature reconstructions from the northern gulf of mexico planktic foraminifer mg ca and the caribbean sea coral sr ca suggesting areal reductions in the western hemisphere warm pool during the lia mean summer coral sst extremes post 1985 c e 29 9 c exceeds the long term summer average 29 2 c for 1734 2008 c e yet the warming trend after 1985 c e 0 04 c for 24 years mc 0 5 2 is not significant whereas caribbean coral sr ca studies contain a warming trend for this interval

composite transform convergent plate boundaries description and discussion abstract the leading edge of the overriding plate at an obliquely convergent boundary is commonly sliced by a system of strike slip faults this fault system is often structurally complex and may show correspondingly uneven strain effects with great vertical and translational shifts of the component blocks of the fault system the stress pattern and strain effects vary along the length of the system and change through time these margins are considered to be composite transform convergent ctc plate boundaries examples are given of structures formed along three ctc boundaries the aleutian ridge the solomon islands and the philippines the dynamism of the fault system along a ctc boundary can enhance vertical tectonism and basin formation this concept provides a framework for the evaluation of petroleum resources related to basin formation and mineral exploration related to igneous activity associated with transtensional processes

pliocene cu au bearing igneous intrusions of the gunung bijih ertsberg district irian jaya indonesia k ar geochronology nine distinct potassic intermediate igneous bodies have been identified during detailed surface and underground mapping of 100 km 2 in the gunung bijih erstberg cu au district in the highlands of irian jaya indonesia west new guinea fourteen biotite k ar ages range from 2 6 to 3 8 ma while another from a small isolated pluton is distinctly older at 4 4 ma these ages represent times of intrusion and crystallization which followed regional kilometer scale folding that resulted from collision at a subduction zone of the northern edge of the australian continental margin with the melanesian oceanic island arc complex the grasberg and ertsberg intrusions are cut by numerous faults with only minor hundreds of meters offset throughout the island of new guinea dated neogene igneous rocks form two clusters separated in age and location a distinct belt of miocene 20 10 ma plutons maramuni arc stretches the entire length of the northern highlands of papua new guinea and recurs in western iri

two centuries of variation in coral growth in a massive porites colony from moorea french polynesia a response of ocean atmosphere variability from south central pacific abstract long lived massive corals can contribute to the monitoring of coral reef environments through measurable growth records in the annual density patterns these can provide an historical perspective against which to assess environmental changes and can help to establish limits of coral growth furthermore proxy records from corals may provide information about long term variability in the performance of coral reefs allowing unnatural changes to be distinguished from natural variability a measurement of two centuries 1800 1990 coral growth using computerized tomography has led to a refined record of skeletal extension density and calcification rates in a massive coral head from moorea island french polynesia correlation analysis of coral growth characteristics with climatic instrumental data indicates a link between variations in average annual calcification and variations in annual air temperature linear regression of temperature versus calcification shows a trend in which a rise of 1 c in temperature would increase the calcification rate by about 4 5 moreover these data suggest that calcification has increased over recent decades which differs notable from the 6 14 decline in calcification over the past 100 yr predicted by certain researchers spectral analysis of annual calcification record indicates a strong concentration of variance at the quasi biennial 2 5 yr el nino southern oscillation 4 7 yr and decadal scale variability 21 9 yr frequency bands

reply to comment by cahyarini et al on a snapshot of climate variability at tahiti at 9 5 ka using a fossil coral from iodp expedition 310

stable isotope geochemistry of corals from costa rica as proxy indicator of the el nino southern oscillation enso abstract we analyzed the 18 o and 13 c time series contained in coral skeletons collected from isla del cano costa rica that survived the 1982 1983 el nino warming event coral 18 o give a record of thermal histories with a precision of 0 5 c for this locality we have determined that the average w effect in the coral skeletons is equivalent to 33 of the skeletal 18 o range therefore if w effects are not compensated for the annual skeletal 18 o range displays a temperature range of 1 c lower than actual values the isotopic record of porites lobata skeletons shows simultaneous depletions in 18 o and 13 c at skeletal levels corresponding to 1983 coincident with the el nino southern oscillation enso event therefore the el nino event is not only recorded as negative 18 o anomalies in the skeleton suggesting the warming of ambient waters but also in the 13 c signal as negative anomalies indicating coral bleaching contrary to the predictions of the 13 c insolation model that the annual carbon isotope variation should be attenuated with depth in proportion to the decrease in light intensity variation with depth we found a clear trend where 13 c increases with depth coral bioenergetics which depends on both coral physiology and ecology may adequately explain the unexpected increase in 13 c range with depth without contradicting the seasonal character of 13 c variability with the solar irradiance cycle although some authors have determined the presence of hiatuses in the skeletal record due to severe stress and growth cessation in this study it has been found that skeletal growth was not seriously diminished during the el nino year of 1983 we attribute the good agreement of the 18 o record with the timing and magnitude of the el nino 1982 1983 warming event to the nature of the warming trend in the area as well as to some synergistic implications of coral tolerance to thermal stress

geochronology of the porgera gold deposit papua new guinea resolving the effects of excess argon on k ar and age estimates for magmatism and mineralization abstract mesothermal epithermal gold mineralization at porgera in the highlands of papua new guinea png occurs in structurally controlled veins and disseminations which overprint and cross cut a suite of shallow level comagmatic mafic alkaline stocks and dykes the porgera intrusive complex pic and their sedimentary host rocks conventional k ar apparent ages of twelve hornblende separates from eight different intrusions scatter between 7 and 14 ma but four biotite separates are concordant at 6 02 0 29 ma 2 40 ar 39 ar step heating experiments on six of the hornblende separates reveal saddleshaped age spectra which indicate the presence of excess 40ar one of these samples yields a well defined plateau with an apparent age of 5 96 0 25 ma 2 this age is identical to that of the biotites and suggests an age of 6 0 0 3 ma 2 for emplacement of the pic older apparent ages obtained from conventional k ar and 40 ar 39 ar analyses are explained by excess 40ar contamination conventional k ar analyses of six separates of hydrothermal illite and roscoelite associated with gold mineralization yield apparent ages of between 5 1 and 6 1 ma and indicate that ore deposition occurred within 1 ma of magmatism at porgera evidence for the evolution of a magmatic volatile phase and the presence of excess 40ar both in the intrusives and in hydrothermal fluids associated with the orebody suggest that magmatic fluids may have had some involvement in metallogenesis but the exact nature of this involvement is not yet clear late miocene magmatism and mineralization at porgera are thought to have occurred shortly prior to or during the initiation of continent arc collision and to pre date associated pliocene uplift and foreland deformation in the highlands

chronological control of coral records using luminescent lines and evidence for non stationary enso teleconnections in northeast australia eight multicentury porites coral cores were used to develop a 373 year chronology by cross dating techniques adapted from dendrochronology characteristic patterns of distinct luminescent lines within the coral skeletons were matched between coral cores from inshore and mid shelf reefs in the central great barrier reef australia skeleton plots of luminescent banding were produced for each core and combined into a master chronology back to ad 1615 in addition to improving dating control the luminescence master chronology provides a proxy for burdekin river runoff and queensland summer rainfall variations in the magnitude of the correlation between the luminescence master and the mann et al 2000 nino3 sea surface temperature reconstruction provides insights into the long term stability of el nino southern oscillation enso telecon nections burdekin river runoff was significantly inversely related to enso variability for much of the period from the ad 1650s to 1800 suggesting that enso related te

a coral oxygen isotope record from the northern red sea documenting nao enso and north pacific teleconnections on middle east climate variability since the year 1750 a 245 year coral oxygen isotope record from the northern red sea ras umm sidd egypt 28 n in bimonthly resolution is presented the mean annual coral 18o signal apparently reflects varying proportions of both sea surface temperature and 18oseawater variability in conjunction with instrumental observations of climate the coral record suggests for interannual and longer timescales that colder periods are accompanied by more arid conditions in the northern red sea but increased rainfall in the southeastern mediterranean whereas warmer periods are accompanied by decreased rainfall in the latter and less arid conditions in the northern red sea a 70 year oscillation of probably north atlantic origin dominates the coral time series interannual to interdecadal variability is correlated with instrumental indices of the north atlantic oscillation nao the el nino southern oscillation enso and north pacific climate variability the results suggest that these modes contributed consistently to middle east climate variability since at least 1750 preferentially at a period of 5 7 years

reconstructing enso the influence of method proxy data climate forcing and teleconnections in this study we compare three newly developed independent nino3 4 sea surface temperature sst reconstructions using data from 1 the central pacific corals 2 the texmex region of the usa tree rings and 3 other regions in the tropics corals and an ice core which are teleconnected with central pacific ssts in the 20th century although these three reconstructions are strongly calibrated and well verified inter proxy comparison shows a significant weakening in inter proxycoherenceinthe 19thcentury thisbreakdownin commonsignalcouldberelatedtoinsufficient data dating errors in some of the proxy records or a breakdown in el nino southern oscillation s enso s influence on other regions however spectral analysis indicates that each reconstruction portraysenso likespectralproperties superposedepochanalysisalsoshowsthateachreconstruction shows a generally consistent el nino like response to major volcanic events in the following year while duringyearst 4tot 7 la nina like conditions prevail theseresults suggest thateachofthe series expresses enso like behaviour but this behaviour does not appear to be spatially or temporally consistent this result may reflect published observations that there appear to be distinct types of enso variability depending on location within the tropical pacific future work must address potential dating issues within some proxies i e sampling of multiple coral heads for one location as well as assessing the time stability of local climate relationships with central pacific ssts more emphasis is needed on sampling new and extending old coral proxy records from the crucial central and eastern tropical pacific region copyright 2009 john wiley sons ltd and crown copyright 2009

emplacement of ophiolite in papua new guinea summary the major ophiolite complexes of papua new guinea lie on the northeastern margin of the australian craton and are flanked externally by palaeogene volcanic arcs the ophiolites are segments of oceanic lithosphere which occupied the forearc zone prior to arc continent collision in the case of the easternmost ophiolite the papuan ultramafic belt there is evidence that emplacement was preceded by development of a secondary rupture in the down going plate at some distance from the subduction zone and was followed by extension buoyant emergence and reversed movement of the ophiolite the westernmost ophiolite april ultramafics has more complex structure and probably developed as a series of thrust sheets in a subduction system the thrust sheets were subjected to renewed deformation and thrusting by continued convergence after arc continent collision

deep structure of an arc continent collision earthquake relocation and inversion for upper mantle p and s wave velocities beneath papua new guinea we examine mechanisms of lithospheric growth and modes accommodating subcrustal convergence following the cessation of subduction by analyzing the seismicity and upper mantle velocities in the new guinea arc continent collision earthquakes in the papua new guinea png region from 1967 to 1984 have been relocated in a joint inversion with seismic velocities using p and s wave arrival times recorded by seismographs in png a total of 957 well recorded earthquakes were chosen for use in three dimensional velocity inversions from an initial catalog of 12 960 events based on the stability of initial hypocenter relocations constant velocity blocks were defined as irregular polyhedra to give fine detail in heavily sampled areas without introducing a large number of poorly controlled parameters and to exploit a priori knowledge of the geometry of velocity anomalies spherical geometry was used to accurately calculate long ray paths up to 1500 km in length most of the 700 best located hypocenters from the png data set are in the upper mantle beneath the finisterre huon fh ranges the newly accreted island arc terrane beneath the papuan peninsula and in the new britain seismic zone an oceanic subduction system these hypocenters show a well defined seismic zone dipping vertically or steeply to the north beneath the northern fh ranges from 125 to 250 km depth continuous along strike with the new britain seismic zone to the east which shows earthquakes to 600 km depth the steeply dipping intermediate depth seismicity flattens near 100 km depth beneath the fh ranges and forms a subhorizontal seismic zone beneath the fh ranges by contrast seismicity continues upward to the surface beneath new britain where the arc has not yet collided with new guinea the 100 km deep flat zone does not continue south of the fh ranges but appears to be truncated below the eastern and southern boundaries of the island arc terrane and no clear evidence for a south dipping seismic zone could be found the relationship of the flat part of the slab 100 km beneath the fh ranges and surface faulting is difficult to discern the apparent surface suture bounding the south side of the fh ranges is 100 km directly above the southern termination of intermediate depth seismicity nowhere in png could clear evidence for arc polarity reversal be found from seismicity all of the well located subcrustal earthquakes beneath the papuan peninsula lie in a narrow horizontal line between 125 and 175 km depth that follows the center of the peninsula and are distinctly separated from the fh seismic zone to the north these events do not require a southward subducting plate beneath the papuan peninsula an alternate and reasonable explanation for these events is that they are a result of unstable thickening of the lithosphere information on lateral heterogeneity in the mantle is limited because large variations in crustal velocities dominate the observed pattern of travel time residuals allowing for only crustal heterogeneity reduces travel time residual variances by 40 from a simple one dimensional structure while allowing for additional mantle heterogeneity results in 10 further reduction for the various parameterization s attempted here inversions with several different block geometries show low velocities at 35 to 171 km km depth beneath the bismarck sea back arc basin and high velocities just south of the intermediate depth fh seismic zone the pattern of lateral heterogeneity supports the inference from seismicity of north dipping slabs beneath both northeast new guinea and new britain

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

shallow seismicity of arc continent collision near lae papua new guinea abstract in northeastern new guinea the narrow ramu markham valley rmv separates island arc rocks to the north from those of continental origin to the south and appears to be the western onland extension of the new britain trench to explore the tectonic processes at the leading edge of the island arc during collision we operated a portable seismic network for six weeks near the city of lae at the eastern end of the rmv we observed a narrow near vertical belt of seismicity between 10 and 30 km depth that we call the lae seismic zone lsz starting at the rmv in the southwest and trending northeasterly cutting across surface geologic structure the truncation of the lsz along a steep plane by the ramu markham fault zone rmfz and earthquake first motions suggest that the earthquakes occur in the hanging wall of a steep n dipping fault that crops out at the rmfz we also consider that the lsz is within the lower plate of a gently dipping thrust below 20 km depth the microearthquake zone is truncated by a gently ne dipping plane coinciding in depth and dip with nodal planes of recent large mb 5 6 and 6 0 thrust earthquakes we suggest that the huon peninsula is being emplaced onto the australian plate along a gently 25 dipping thrust fault that is 20 km deep beneath lae the rmfz may be a steeply dipping thrust fault that connects with this gently n dipping thrust but accommodates little convergence at present the lsz trends nearly perpendicular to an anticlinal range which appears to be sheared in a left lateral sense p wave first motions for earthquakes in the lsz with steep 70 to 90 dip nodal planes that strike parallel to the lsz suggest a component of south side up displacement also hence the crustal block south of the lsz may be rising relative to the huon peninsula and the rapid quaternary uplift rates estimated for the lae coastal region may be higher than the uplift rate of the huon peninsula as a whole we suggest that the lsz reveals a tear of small offset in the huon terrane but may be similar to a structure that produced a magnitude 7 earthquake near madang in 1970

seismicity of the indo australian solomon sea plate boundary in the southeast papua region abstract seismicity and earthquake focal mechanism plots of the southeast papua and woodlark basin region for the period january 1960 to may 1979 show that 1 a the west woodlark basin spreading centre extends from the deep west woodlark basin through dawson strait into goodenough bay southeast papua 2 b a southeast seismic trend in the west woodlark basin is associated with a left lateral transform fault but a gap exists between this zone and the seismic east woodlark basin spreading centre 3 c southeast papua seismicity divides into a shallow earthquake zone in which the earthquakes occur mainly in the northeast side of the owen stanley range and an intermediate depth southwest dipping benioff zone which extends almost from mt lamington to goroka the benioff zone indicates the presence of a southwest dipping slab of solomon sea plate beneath the indo australian plate in the southeast papua and ramu markham valley region this subduction zone has collided with the new britain subduction zone of the solomon sea plate along the ramu markham valley the solomon sea plate is now hanging suspended in the form of an arch beneath ramu markham valley inhibiting further subduction beneath southeast papua

imaging continental breakup using teleseismic body waves the woodlark rift papua new guinea this study images the upper mantle beneath the d entrecasteax islands papua new guinea providing insight into mantle deformation beneath a highly rifted continent adjacent to propagating spreading centers differential travel times from p and s wave teleseisms recorded during the 2010 2011 cdpapua passive seismic experiment are used to invert for separate vp and vs velocity models of the continental rift a low velocity structure marks the e w axis of the rift correlating with the thinnest crust high heat flow and a linear trend of volcanoes this slow region extends 250 km along strike from the oceanic spreading centers demonstrating significant mantle extension ahead of seafloor breakup the rift remains narrow to depth indicating localization of extension perhaps as a result of mantle hydration a high vp structure at depths of 90 120 km beneath the north of the array is more than 6 5 faster than the rift axis and contains well located intermediate depth earthquakes these independent observations place firm constraints on the lateral thermal contrast at depth between the rift axis and cold lithosphere to the north that may be related to recent subduction although the polarity of subduction cannot be resolved this geometry is gravitationally unstable downwelling or small scale convection could have facilitated rifting and rapid lithospheric removal although this may require a wet mantle to be realistic on the required time scales the high v structure agrees with the maximum p t conditions recorded by young ultra high pressure rocks exposed on the rift axis and may be implicated in their genesis

high resolution isotopic records from corals using ocean temperature and mass spawning chronometers abstract we present a 6 year long 1978 1984 18 o and 13 c record from a great barrier reef pandora reef porites lutea coral based on near weekly sample intervals a sampling technique was designed to minimise any smoothing or distortion of the isotopic record due to complex coral growth calyx architecture and calcification at depth within the tissue layer the arrival time of the mid winter minimum sea surface temperature is very consistent 2 weeks near pandora reef and provides an annual time marker offering more precision than the traditional density band chronometer the improved chronology and high resolution record demonstrate that signal distortion in porites due to calcification within the tissue layer and variable intra annual coral extension is generally negligible also confirmed is that the arrival time of monsoonal floods is precisely preserved 1 week within the skeleton of porites the sensitivity of weekly sampling allows the detection of a subtle warm to cool sea surface temperature anomaly which preceded by more than one year a similar temperature anomaly associated with the 1982 83 el nin o in the east pacific sharply higher 13 c values coincide with the time of the annual coral mass spawning event in the great barrier reef recognition of this mass spawning signal should simplify the interpretation of coral 13 c records and provides an additional precise time marker with which to adjust chronologies when intra annual coral extension is not constant

assessing spatial variability in el nino southern oscillation event detection skill using coral geochemistry 1 the el nino southern oscillation enso drives interannual climate variability but evidence of its preinstrumental expression is limited to proxy data and model inference we develop a skill assessment technique using instrumental records of sea surface temperature sst and sea surface salinity sss and apply it to a suite of 23 coral 18o records a common enso proxy we compare coral proxy skill with pseudoproxy records constructed from instrumental data to establish the expected proxy response to enso events and constrain proxy sensitivity the central pacific has a balanced response toward enso events the western pacific warm pool favors el nino expression and the south pacific convergence zone preferentially records la nina events however all three regions display high sensitivity to enso variability presenting promising targets for future coral paleoclimate reconstructions eastern pacific coral records display surprisingly low enso sensitivity despite the presence of large enso related sst anomalies suggesting nonclimatic influences comparisons between the pseudoproxy and coral skill ratings provide a test to highlight where these nonclimatic impacts that may affect coral record skill networks of proxy data skill ratings may better delineate the spatial structure of the sst and sss response to enso variability a feature of the climate system that is currently poorly reproduced in climate models

the tertiary arc chain in the western pacific abstract the arcs bordering the pacific plate on the western and southwestern pacific rim are reconstructed since their initiation in the eocene and oligocene they occur in a zone forming an arc chain from the western pacific tropics to the eastern margin of australia they are the bonin mariana yap palau halmahera north new guinea west melanesia solomon vanuatu and tonga kermadec arcs designated here the tertiary arc chain they are associated with the formation and consumption of backarc basins reversals of arc polarity and episodic subduction has occurred in some of them the tertiary arc chain is characterized by four major stages in its evolution which can be seen characteristically in some of the arcs the first stage is the occurrence of the arc chain from the middle eocene to earliest oligocene the second stage is the formation of the backarc basins from the early to late oligocene the third stage is the occurrence of double arcs on the inner side of the arc chain in the early to middle miocene and the fourth stage is the reversal of arc polarities due to collisions since the late miocene the backarc basins associated with the arcs of the tertiary arc chain have fixed limits of duration in their evolution the backarc basins initially form 15 million years after the initiation of the volcanic arc several to 10 million years after the initial opening backarc spreading terminates approximately 20 million years after the cessation of the backarc spreading a second phase of opening occurs in the backarc region in the case of arc collision reversal of the arc polarity occurs if there is oceanic crust on the backarc side and opening of a backarc basin occurs within several million years these occurrences and durations have a variation of ca 3 5 million years

reconstructing organic matter sources and rain rates in the southern west pacific warm pool during the transition from the deglaciation period to early holocene abstract transient features in the organic carbon content of deep sea sediment cores resulting from changes in the flux and or quality of sedimentary organic matter are not uncommon we examined the geochemical characteristics of sediments retrieved with a gravity corer from the northwestern solomon sea 3908 m water depth southern west pacific warm pool wpwp 13c and 15n of sedimentary organic matter together with toc tn data suggest that the organic material is characterized by a mixture of marine and terrestrial origins with a higher contribution from marine algae the data were analyzed with an inverse non steady state reaction transport model to examine the variability and magnitude of particulate organic carbon poc flux to the seafloor during the transition between the deglaciation period and early holocene measured poc content and porewater no3 nh4 dic and so42 concentrations were used to constrain the model hindcast results revealed that poc flux decreased from 75 to 37 5 g cm 2 yr 1 during the deglaciation early holocene transition the rate of poc degradation in the present setting is slightly lower compared to that in the pre holocene setting the synchronous decline in the relative contribution of terrestrial organic matter input and rapid sea level rise during this transition suggest that sea level rather than surface productivity is the dominant factor controlling the poc deposition flux in the solomon sea this is conceivable because the sampling site is proximal to high relief islands with high rainfall a well developed submarine canyon system and narrow and steep continental margins consequently we suggest that deep water basins in proximity to similar high relief mountainous islands in the tropical pacific may represent important sinks for terrestrial organic material especially during sea level lowstands

quasi quadrennial and quasi biennial variability in the equatorial pacific evaluation of competing el nino southern oscillation enso theories requires one to identify separate spectral peaks in equatorial wind and sea surface temperature sst time series to sharpen this identification we examine the seasonal to interannual variability of these fields by the data adaptive method of multi channel singular spectrum analysis m ssa m ssa is applied to the equatorial band 4 n 4 s using 1950 1990 data from the comprehensive ocean and atmosphere data set two major interannual oscillations are found in the equatorial sst and surface zonal wind fields u the main peak is centered at about 52 months we refer to it as the quasi quadrennial qq mode quasi biennial qb variability is split between two modes with periods near 28 months and 24 months a faster 15 month oscillation has smaller amplitude the qq mode dominates the variance and has the most distinct spectral peak in time longitude reconstructions of this mode the sst has the form of a standing oscillation in the eastern equatorial pacific while the u field is dominated by a standing oscillation pattern in the western pacific and exhibits also slight eastward propagation in the central and western pacific the locations of maximum anomalies in both qb modes are similar to those of the qq mode slight westward migration in sst across the eastern and central and eastward propagation of u across the western and central pacific are found the significant wind anomaly covers a smaller region than for the qq the qq and qb modes together represent the enso variability well and interfere constructively during major events the sharper definition of the qq spectral peak and its dominance are consistent with the devil s staircase interaction mechanism between the annual cycle and enso

eastern pacific sea surface temperature since 1600 a d the δ18o record of climate variability in galapagos corals we measured stable oxygen isotope ratios and skeletal growth rates in the massive corals pavona clavus and p gigantea from the west coast of isabela island galapagos to assess interannual to decadal climate variability in the eastern pacific comparisons of instrumental data sets show that sea surface temperatures sst in the galapagos region are representative of a broad portion of the eastern equatorial pacific the site is especially well suited for long term studies of the el nino southern oscillation enso phenomenon as it lies within the eastern pacific center of action for thermal anomalies associated with enso the p gigantea isotope record is nearly monthly in resolution spans the period 1961 1982 and shows strong correlation with a galapagos instrumental sst record r 0 90 for annual averages cross spectral analysis shows that sst can explain greater than 80 of the variance in 18o at both the annual cycle and within the high frequency portion of the enso band 3 5 years the p clavus record is annual in resolution extends from 1587 to 1953 a d and was obtained from a 10 m diameter colony preserved within the urvina bay uplift because seawater 18o variations in the region are very small we interpret the urvina bay coral 18o record in terms of annual average sst the isotopic record appears to be a very good but not perfect indicator of enso events and shows good correspondence with the historical enso reconstruction of quinn et al 1987 a number of low 18o excursions that we observe during the 17th and 18th centuries very likely represent enso events that are missing from the historical tabulations most interannual 18o variations between 1607 and 1953 a d represent annual average temperature excursions of 1 to 2 5 c during the little ice age the annual 18o series correlates well with many north american tree ring records and shows low temperatures during the early 1600s and early 1800s and relatively warmer conditions during the 1700s unlike most northern hemisphere tree ring and instrumental records we see no evidence at this site for warming between 1880 and 1940 but rather observe a slight cooling 28 of the total variance the main enso mode is centered at 4 6 years and accounts for 12 of the total variance additional significant oscillations occur at periods of 3 3 6 8 11 17 22 and 34 years both annual growth rate and 18o show variance at periods equivalent to the solar and solar magnetic periods e g 11 and 22 years respectively in addition the amplitude of the 11 year 18o cycle generally varies with the amplitude of the solar cycle supporting previous suggestions that the solar cycle may modulate interannual to decadal climate variability in the tropics the dominant oscillatory modes both within the enso and interdecadal frequency bands shift to shorter periods from the early to middle 1700s and again from the middle to late 1800s this may reflect major reorganizations within the tropical ocean atmosphere system and suggests that tropical pacific climate variability is linked across timescales ranging from years to decades

evaluating the use of the massive coral diploastrea heliopora for paleoclimate reconstruction 1 to date coral based paleoclimate research in the pacific has primarily utilized core samples from the genus porites and has been most successful reconstructing past variability on interannual timescales particularly the el nino southern oscillation enso the indo pacific coral genus diploastrea however owing to its slower extension rate denser structure and longer lifespan can potentially preserve geochemical proxy records 2 3 times longer than porites cores of the same length before its potential can be realized diploastrea must first be calibrated and its climate signal assessed we present oxygen isotope 18o and sr ca results from two diploastrea cores collected in fiji 16 49 s 179 14 e that allow for simultaneous evaluation of this coral s paleoclimatic utility and the reproducibility of each tracer at this site comparison to a porites record from the same location allows for further evaluation of diploastrea as a paleoclimatic archive we demonstrate that diploastrea s septal and columellar material yield similar 18o sst relationships and that despite some sacrifice of the seasonal 18o amplitude bulk sampling of either region is satisfactory for resolving interannual and lower frequency modes of climatic variability therefore paleoclimate reconstructions employing either a septal or columellar sampling regime of this genus may be useful at filling in spatial and temporal sampling gaps which currently hinder the reconstruction of long term changes in major climate fields in the western pacific

deep seismicity and modes of deformation in tonga subduction zone the geometry of deep 400 km earthquakes in the subducting western edge of the pacific plate when related to the local distribution of seismic activity reveals a complex pattern of planes of shear failure enabling the modes of deformation by which the descending plate shortens and thickens to be identified the deepest part of the slab is displaced laterally suggesting that it fails to penetrate the discontinuity at 670 km

continental breakup and uhp rock exhumation in action gps results from the woodlark rift papua new guinea we show results from a network of campaign global positioning system gps sites in the woodlark rift southeastern papua new guinea in a transition from seafloor spreading to continental rifting gps velocities indicate anticlockwise rotation at 2 2 7 myr relative to australia of crustal blocks north of the rift producing 10 15 mm yr of extension in the continental rift increasing to 20 40 mm yr of seafloor spreading at the woodlark spreading center extension in the continental rift is distributed among multiple structures these data demonstrate that low angle normal faults in the continents such as the mai iu fault can slip at high rates nearing 10 mm yr extensional deformation observed in the d entrecasteaux islands the site of the world s only actively exhuming ultra high pressure uhp rock terrane supports the idea that extensional processes play a critical role in uhp rock exhumation gps data do not require significant interseismic coupling on faults in the region suggesting that much of the deformation may be aseismic westward transfer of deformation from the woodlark spreading center to the main plate boundary fault in the continental rift the mai iu fault is accommodated by clockwise rotation of a tectonic block beneath goodenough bay and by dextral strike slip on transfer faults within and surrounding normanby island contemporary extension rates in the woodlark spreading center are 30 50 slower than those from seafloor spreading derived magnetic anomalies the 0 5 ma to present seafloor spreading estimates for the woodlark basin may be overestimated and a reevaluation of these data in the context of the gps rates is warranted

evidence for active subduction at the new guinea trench 1 recent seismic tomography imaging shows clear evidence for southwestward subduction along the entire length of the new guinea trench ngt in indonesia and papua new guinea viewed in conjunction with the occurrence of large mw 7 thrust earthquakes that are known to have occurred on the trench this confirms conclusions of earlier studies that the ngt is an active inter plate boundary the 650 km long slab is visible to a depth of about 300 km and subducts with a dip angle that varies from 30 at 136 e to 10 at 143 e the improved clarity of the seismic tomography in this region stems from the use of a more accurate data set of p and s wave arrival times and hypocentral locations

new views of tropical paleoclimates from corals abstract corals offer a rich archive of past climate variability in tropical ocean regions where instrumental data are limited and where our knowledge of multi decadal climate sensitivity is incomplete in the eastern equatorial pacific coral isotopic records track variations in enso related changes in sea surface temperature further west corals record variability in sea surface temperature and rainfall that accompanies zonal displacement of the indonesian low during enso events these multi century records reveal previously unrecognised enso variability on time scales of decades to centuries outside the enso sensitive equatorial pacific long term trends towards recent warmer wetter conditions suggest the tropics respond to global forcings new coral paleothermometers indicate that surface ocean temperatures in the tropical southwestern pacific were depressed by 4 6 c during the younger dryas climatic event and rose episodically during the next 4000 yr high temporal resolution measurements of sr ca and 18 o in corals provide information about the surface ocean hydrologic balance and can resolve the seasonal balance between precipitation and evaporation radiocarbon measurements in corals coupled with ocean circulation models may be used to reconstruct near surface ocean circulation past mixing rates and the distribution of fossil fuel co2 in the upper ocean most recently seasonal to interannual variations in the radiocarbon of corals from the equatorial pacific have been linked to the redistribution of surface waters associated with the enso

a snapshot of climate variability at tahiti at 9 5 ka using a fossil coral from iodp expedition 310 1 the integrated ocean drilling program iodp expedition 310 recovered drill cores from the drowned reefs around the island of tahiti 17 40 s 149 30 w many of which contained samples of massive corals from the genus porites herein we report on one well preserved fossil coral sample a 13 6 cm long porites sp dated by uranium series techniques at 9523 33 years monthly 18o and sr ca determinations reveal nine clear and robust annual cycles coral 18o and sr ca determinations estimate a mean temperature of 24 3 c 3 2 c colder than modern for tahiti at 9 5 ka however this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved the interannual variability in coral 18o is similar between the 9 5 ka coral record and a modern record from nearby moorea the seasonal cycle in coral sr ca is approximately the same or greater in the 9 5 ka coral record than in modern coral records from tahiti paired analysis of coral 18o and sr ca indicates cold wet warm dry interannual anomalies opposite from those observed in the modern instrumental record

a 173 year stable isotope record from a tropical south pacific coral 0 we have generated a 173 year long time series a d 1806 to 1979 of changes in the 18 o and 13 c composition of a coral head platygyra lamellina to investigate environmental change in the climatologically sensitive region of the tropical south pacific little is known about decadal and centennial scale climate change at sea level in this region our coral is from near the south coast of espiritu santo island 15 s 167 e republic of vanuatu the stable isotope record from this coral is consistent with meteorological and oceanographic records during the period of overlap in the records 1964 1978 18 o values positively correlate with sst r 0 77 and 13 c values are highly coherent with rainfall r 0 82 at the annual cycle these relations suggest that the 18 o signal in this coral is a function of variations in sst and rainfall induced changes in sss whereas the 13 c signal may be related to rainfall and cloud cover modulation of photosynthesis in the coral 18 o and 13 c values are positively correlated over the entire length of the record r 0 65 a relation that is even stronger between 1806 and 1866 r 0 81 i e prior to the time of possible anthropogenic influence on the 13 c record because of the positive correlation between temperature and rainfall in this region we interpret the long term record of 18 o in terms of joint variations of these two variables the most significant cool dry excursion in the santo record occurs during the nineteenth century 1832 1866 and ends abruptly in 1866 with a change to modern values superimposed on this pattern is a slight 0 2 cooling drying toward the end of the twentieth century cross spectral analysis of the 18 o and 13 c records indicates a strong concentration of variance at the quasi biennial 2 years and el nino southern oscillation enso 4 5 years frequency bands in addition to a 15 year peak found also in global temperature records cross spectral analysis of coral isotope records from santo and the philippine sea indicate a concentration of variance at enso 4 5 years frequency bands however comparison of the santo coral isotope record with high latitude northern hemisphere temperature records indicates that the major cool dry excursion in the santo record 1832 1866 is not seen in the northern hemisphere record if verified in other tropical south pacific coral records the results have implications concerning the global scale of cooling for little ice age events

reconstructing seawater δ18o from paired coral δ18o and sr ca ratios methods error analysis and problems with examples from tahiti french polynesia and timor indonesia we compare several statistical routines that may be used to calculate delta o 18 and sss from paired coral sr ca and delta o 18 measurements typically the delta o 18 coral sst relationship is estimated by linear regression of coral delta o 18 vs sst if this method is applied evidence should be given that at a particular site sst and sss do not co vary in the tropical oceans sst and delta o 18 sw sss often co vary and this will bias the estimate of the regression slope of delta o 18 coral sst using a stochastic model we show that covariance leads to a bias in the coefficients of the univariate regression equations as the slope of the delta o 18 coral sst relationship has known we propose to insert this value for gamma 1 in the regression models this requires that the constants of the regression equations are removed to omit the constants we propose to center the regression equations i e to remove the mean values from the variables the statistical error propagation is calculated to assess our ability to resolve past variations in delta o 18 sw sss at tahiti we find that the combined analytical uncertainties of coral delta o 18 and sr ca equal the amplitude of the seasonal cycle of delta o 18 sw sss therefore we cannot resolve the seasonal cycle of sss at tahiti at timor the error of reconstructed delta o 18 sw sss is lower than the magnitude of seasonal variations of delta o 18 sw sss and the seasonal cycle of delta o 18 sw sss can be resolved c 2008 elsevier ltd all rights reserved

stratigraphic constraints on the development and timing of arc continent collision in northern papua new guinea abstract the finisterre mountains of northern papua new guinea are the site of an active southeast propagating collision between the finisterre terrane and the australian continental margin the clastic sedimentary sequence on the southern flank of the range records the history of the collision the age of initial collision can be deduced from the second of two provenance shifts that occur in the sequence as revealed by a study of 69 dated sandstones the first shift at about 16 18 ma was from volcanolithic sediments to mixed provenance sediments rich in quartz and metasedimentary lithic fragments these latter sediments were probably derived from the orogenic belt active along the australian continental margin at that time at 3 0 3 7 ma the volcanic source was rejuvenated initial collis on at this time uplifted the finisterre terrane causing the provenance shift here we break the stratigraphic sequence into three units the sarawaget beds the erap structural complex and the leron formation the sarawaget beds are middle eocene to early miocene volcanolithic sandstones that were deposited as clastic aprons un the flanks of the finisterre volcanic are volcanic activity ceased in the early miocene the erap complex is divided into two clastic subunits the sukurum and nariawang units and one basaltic subunit the gorambampan unit the sukurum unit consists of turbidites deposited south of the extinct finisterre arc from the latest early miocene through the early pliocene much of the sediment in the unit was derived from low to medium grade metasedimentary units on the active northern margin of the australian continent renewed subduction i the late miocene or pliocene occurred along the new britain trench just south of the remnant finisterre arc closing an eastward widening small ocean basin the sukurum unit probably represents an accretionary prism that formed at this subduction zone scattered seamounts that were scraped off the downgoing plate are preserved as the gorambampan unit initial collision of the finisterre terrane with the continental margin at 3 0 3 7 ma uplifted the paleogene volcanic rocks which were rapidly eroded and deposited as the volcanolithic turbidites of the nariawang unit southeastward propagation of the collision tip caused incorporation of the nariawang unit into the accretionary wedge rapid uplift raised the terrane foreland above sea level sometime after 1 3 mo the fluvial lacustrine and marginal marine deposits of the leron formation accumulated in a terrane foreland basin that developed south of the collision zone further propagation of the thrust front toward the foreland incorporated the leron formation into the fold and thrust belt rapid uplift of the finisterre range and voluminous volcanolithic sedimentation continue to the present in the finisterre range arc continent collision is marked by a provenance shift from metasedimentary and quartzose detritus to volcanic detritus in another modern arc continent collision on taiwan collision has caused a shift from volcanic to metasedimentary detritus we attribute this discrepancy to the presence of the finisterre terrane an extinct arc in the forearc region of the finisterre arc continent collision and the absence of a similar terrane in the forearc area on taiwan the very different evolution of sandstone provenance in the active taiwan and finisterre collision zones shows that local factors can profoundly influence the provenance histories of collision zones no one model of sediment provenance evolution can characterize all collision zones whether modern or ncient

deuterium excess record from central greenland over the last millennium hints of a north atlantic signal during the little ice age a stacked water isotope record for summit central greenland has been established covering approximately the last 900 years measurements of 18o and d in the grip deep ice core and the 230 m core s93 allow the reconstruction of a millennial record of the deuterium excess in a near annual resolution a short period of particularly high values of the deuterium excess at the beginning of the fourteenth century may be associated with the medieval warm period mwp the little ice age lia might be represented by a 100 year period of very low excess values in the sixteenth and seventeenth centuries using a simple isotope model 18o and deuterium excess are interpreted in terms of surface temperature variations over central greenland and over the subtropical north atlantic greenland s principal vapor source region an estimated cooling of 0 7 c of subtropical sea surface temperatures ssts during the little ice age and a warming of 0 6 c during the short warm period in the medieval is in agreement with previous studies over periods of about 100 years an antiphasing between gradually decreasing 18o and increasing deuterium excess is observed interannual to decadal scale variability associated to the north atlantic oscillation may be responsible for this anti phase relationship an alternative explication is a north south oscillation in north atlantic sea surface temperatures associated with short term changes in the thermohaline circulation

el nino and related monsoon drought signals in 523 year long ring width records of teak tectona grandis l f trees from south india abstract we present a 523 year a d 1481 2003 tree ring width index chronology of teak tectona grandis l f from kerala southern india prepared from three forest sites dendroclimatological investigations indicate a significant positive relationship between the tree ring index series and indian summer monsoon rainfall ismr and related global parameters like the southern oscillation index soi a higher frequency of occurrence of low tree growth is observed in years of deficient indian monsoon rainfall droughts associated with el nino since the late 18th century prior to that time many low tree growth years are detected during known el nino events probably related to deficient indian monsoon rainfall the general relationship between ismr and el nino is known to be negative and the spatial correlations between our kerala tree ring chronology and sea surface temperatures ssts over the nino regions follow similar patterns as those for ismr this relationship indicates strong enso related monsoon signals in the tree ring records these tree ring chronologies with a high degree of sensitivity to monsoon climate are useful tools to understand the vagaries of monsoon rainfall prior to the period of recorded data

environmental controls on coral skeletal δ13c in the northern south china sea in this paper we investigate the relationship between seasonal climatic and environmental variables and the skeletal c 13 of modern and mid holocene porites lutea corals from the southern coast of hainan island in the northern south china sea no significant correlations were observed between c 13 in the modern coral and solar insolation or sea surface temperature however seasonal variability of c 13 in the modern coral covaries with rainfall on hainan island furthermore the seasonal variations of c 13 in both the modern and mid holocene coral are synchronous with those of the coral o 18 which is a proxy for seawater o 18 and in turn largely controlled by local rainfall these observations suggest that coral c 13 variations are closely associated with rainfall in this region given that river runoff contains dissolved inorganic carbon dic with a negative c 13 we suggest that periods of high rainfall on hainan island deliver increased amounts of c 13 depleted dic to coastal seawater resulting in an enhanced negative c 13 in the corals our findings together with previous studies appear to demonstrate that in coastal environments coral skeletal c 13 levels are controlled mainly by terrestrial carbon input and are significantly influenced by terrestrial river runoff consequently the geochemical interpretation of coral c 13 records may differ between coastal areas and offshore areas or the open ocean

evaluation of sampling resolution in coral stable isotope records a case study using records from new caledonia and tarawa we have generated a 40 year long monthly stable isotope record from a porites lutea coral collected offshore of amedee new caledonia 22 s 167 e to investigate the relation between sampling resolution in coral isotope studies and retrieval of sea surface environmental information we interpret the high correlation between our oxygen isotope record and a twenty year long sea surface temperature record at the monthly timescale r 0 88 to indicate that our coral isotope record is an accurate monitor of environmental conditions offshore of amedee the character of the signal and the percent variance explained in the record at the annual band at the quasi biennial oscillation band qbo 2 0 2 4 years and at the el nino southern oscillation band enso 3 8 years changes little in response to a reduction in sampling density from monthly to bimonthly to quarterly similar results have been obtained in a reanalysis of a coral isotope record from tarawa kiribati our results indicate that a significant amount of the information obtained from high density sampling can also be retrieved from lower density sampling in particular bimonthly sampling yields virtually no drop off in variance explained and quarterly sampling is satisfactory for resolving interannual and decadal scale trends in time series the proposed sampling approach may enable a more rapid filling in of numerous spatial holes in coral sampling sites needed for reconstruction of long term decadal scale variations in climate

seismotectonics of new guinea a model for arc reversal following arc continent collision the structure and evolution of the northern new guinea collision zone is deduced from international seismological center isc seismicity 1964 1985 new and previously published focal mechanisms and a reexamination of pertinent geological data a tectonic model for the new guinea margin is derived which illustrates the sequential stages in the collision and suturing of the bewani toricelli adelbert finisterre huon new britain arc to central new guinea followed by subduction polarity reversal in the west east of 149 e the solomon plate is being subducted both to the north and south bringing the new britain and trobriand forearcs toward collision west of 149 e the forearcs have collided and together they override a fold in the doubly subducted solomon plate lithosphere which has an axis that is parallel to the strike of the ramu markham suture and that plunges westward at an angle of 5 beneath the coast ranges of northern new guinea active volcanism off the north coast of new guinea is related to subduction of the solomon plate beneath the bismarck plate active volcanism of the papuan peninsula and quaternary volcanism of the new guinea highlands are related to slow subduction of the solomon plate beneath the indo australian plate along the trobriand trough and the trough s former extension to the west respectively from 144 148 e seismicity and focal mechanisms reveal that convergence between the sutured bismarck and indo australian plates is accommodated by thrusting within the finisterre and adelbert ranges and compression of the new guinea orogenic belt together with basement involved foreland folding and thrusting to the south the finisterre block overthrusts the new guinea orogenic belt whereas the adelbert block is sutured to new guinea and overthrusts the oceanic lithosphere of the bismarck sea along the new guinea trench west of 144 e seismicity defines a southward dipping wadati benioif zone and focal mechanisms indicate oblique subduction only this oldest westernmost portion of the collision has progressed past suturing to a full reversal in subduction polarity

the opening of the woodlark basin subduction of the woodlark spreading system and the evolution of northern melanesia since mid pliocene time abstract magnetic anomaly and seismological data define segments of active seafloor spreading and associated magnetic lineations trending ene in the woodlark basin the total opening rate has been approximately 6 cm yr for the last 1 m y spreading rates diminish by over 10 from east to west along the woodlark spreading system implying a pole of current opening 15 20 to the west commencement of seafloor spreading in the basin has apparently been time transgressive beginning prior to 3 5 m y in the east and at successively later times to the west earthquake focal mechanisms and geological evidence suggest that the land areas bounding the western end of the woodlark basin are undergoing tensional deformation we believe that eventually the woodlark basin plate boundary will propagate westward through the d entrecasteaux islands into the papuan peninsula hitherto unreported shallow seismicity associated with the northern margin of the ne trending section of the woodlark rise probably reflects partial decoupling of the woodlark and solomon basins possibly due to mechanical difficulties in subducting the young woodlark lithosphere analysis of the relative motions between the solomon indo australian and pacific plates shows that the woodlark spreading system has been subducted at high rates 10 cm yr beneath the solomon islands during the opening of the woodlark basin several tectonic and geological features limited to the region of interaction of the woodlark basin with the solomon trench and arc may be symptomatic of ridge subduction these features include high heat flow in the solomon trench which shoals to 4 km low levels of seismicity and only shallow hypocenters and voluminous eruptions of high k 2 o tio 2 olivine basalts and basaltic andesites extremely close to the trench axis this close association in space and time of an unusual volcanic suite with ridge subduction implies a strong dependence of the petrogenesis on the tectonic regime a combination of this study of the woodlark basin and the previous study of the bismarck basin taylor 1979 provides a reconstruction of the positions of the continents ocean basins and island chains in northern melanesia for mid pliocene time in accepting the existence of a solomon plate we can explain the trench like structure off the trobriand margin of new guinea the occurrence of late cenozoic calc alkaline volcanism along the papuan peninsula and the presence of intermediate depth seismicity beneath the north papuan peninsula the rapid changes in relative motions along or across the new ireland solomons chain over the past 3 5 m y may explain the spatial and temporal changes in igneous activity observed on these islands

sea surface temperature and salinity reconstruction from coral geochemical tracers massive scleractinian corals secrete an aragonitic skeleton which incorporates a large array of chemical tracers corals present several advantages for palaeoclimate research they grow continuously and can live up to 1000 years they are easy to date and they can be sampled at high resolution weekly to monthly resolution both live and fossil corals can be collected in the field in the past two decades significant efforts have been made to identify robust tracers of sea surface temperature sst and salinity sss in corals to date sr ca and 18o are considered to be the most reliable sst tracers although changes in seawater 18o can significantly alter sst reconstructed from coralline 18o because these variations in seawater 18o can be linked to sss changes this initial problem can in fact be turned into an advantage and provide us with an sss tracer the sst component in the coral 18o signal can either be evaluated through sr ca measurements or in some case simply filtered out however there is still much uncertainty concerning the exact mode of incorporation of trace elements and stable isotopes into the coral skeleton the effects of growth rate light intensity feeding habits ph and water chemistry are still poorly documented a review of the strength and weaknesses of sr ca and 18o is presented together with some examples of sst and sss reconstructions other potential sst tracers are also reviewed it is expected that the ability to grow corals in aquarium under controlled conditions and that the development of sophisticated analytical techniques at the micrometric level should help us understand better the robustness of each tracers and the factors controlling their incorporation in coral aragonite

long term variability in the stable carbon isotopic composition of porites corals at the northern gulf of aqaba red sea abstract to study long term variations in surface ocean 13c we investigated coral skeletal 13c records of 20 colonies of the shallow water coral porites spp from the northern gulf of aqaba and the northern red sea the coral colonies represent different water depths a wide range of different periods last interglacial holocene the last centuries the last decades and various growth rates records from modern and fossil corals show irregular seasonal cycles attributed mainly to the seasonal cycle of light no attenuation in the amplitude of the seasonal skeletal 13c cycle with depth is evident and no significant correlation between mean annual coral 13c and water depth was observed in the modern corals the mean coral extension rates show no clear relationship with mean skeletal 13c values the average skeletal 13c value of modern corals was 2 74 0 49 offset from both calcite and aragonite equilibrium values by about 5 22 and 6 26 respectively modern corals reveal a clear trend toward lighter skeletal 13c values since the year 1974 at longer timescales the skeletal 13c values from last interglacial and holocene corals and from coral records extending back to the mid to late 18th century reveal much heavier 13c values compared to values from 1960 to the present the trend toward lighter skeletal 13c values over the last decades can be attributed to changes in the 13c of the dissolved inorganic carbon of the ambient seawater due to the addition of anthropogenically derived co2 13c suess effect to the atmosphere other factors such as the metabolic effects of corals may account for the modulation of skeletal 13c on shorter timescales a centuries long coral record from the northern red sea reveals a magnitude of decrease in skeletal 13c comparable to global trends 1960 1990 whereas a centuries long coral record from the northern gulf of aqaba indicates a larger decrease over the same period probably due to local effects in conclusion the combined carbon isotope records obtained from porites spp corals from the northern red sea seem to be suited to provide information on long term world wide changes in atmospheric co2

a calibration of the oxygen isotope paleothermometer of coral aragonite from porites the oxygen isotopic composition 18oaragonite of coral aragonite is dependent upon two parameters temperature and water oxygen isotopic composition this tracer allows temperature reconstruction in tropical zones different published 18o temperature relationships show a slope derived from the regression 18o against t c which varies between 0 16 and 0 23 for porites genus this implies greater uncertainty for paleoclimatic reconstruction the calibrations were generated differently they were obtained from several colonies collected in different locations or the formula was derived from the same coral head following seasonal variations of temperature the relationships took into account of 18osw fluctuation or 18osw were estimated from salinity or were not considered we show by using isotopic data from weber and woodhead 1972 and assessing the 18osw value by two different methods that a thermodynamically significant formula is generated

atmospheric and oceanic evidences of el nino southern oscillation events in the south central pacific ocean from coral stable isotopic records over the last 137 years we measured 18o and 13c in porites lutea collected in the moorea lagoon where the instrumental records show that an el nino southern oscillation enso event implies both a cloud cover decrease and a weak sea surface temperature sst increase two proxies allow an enso record to be reconstructed at moorea the annual 13c anomaly associated with the south pacific convergence zone motion and an annual 18o anomaly showing increased sst the frequency bands exhibited by the singular spectral analysis ssa and the multitaper method of the annual 18o and 13c records are centered on 2 5 and 5 2 years and 2 4 and 3 2 years respectively which are the main enso modes we used ssa to reconstruct enso events at moorea over the past 137 years results indicate that climate variability at this site is strongly affected by enso events

h2o2 treatment of recent coral aragonite oxygen and carbon isotopic implications coral skeletons contain relatively little organic material and inorganically precipitated carbonate cement although these quantities are enough to bias geochemical measurements preliminary treatment is therefore often necessary to remove these materials hydrogen peroxide seems to be the most efficient reagent this strong oxidant destroys organic matter and its acid ph promotes dissolution of carbonate cements that precipitate after the coral skeleton has formed we tested the isotopic effects both on 18o 16o and 13c 12c ratios of such a chemical treatment on coral aragonite we demonstrate that only one treatment is necessary to eliminate different contents without alteration of coral aragonite and we verified that there is no isotopic exchange between the oxygen atoms from cac03 and h2o2 we measured carbon and oxygen isotopic compositions from samples that cover 2 5 years of coral growth and that were split in two ways untreated and h2o2 treated the h2o2 treated subsamples reveal a clear seasonal oscillation that is not evident in the untreated isotopic record therefore hydrogen peroxide treatment should be systematically carried out before isotopic analyses in order to perform palaeoclimatic reconstructions

the effect of accessory minerals on the redistribution of lead isotopes during crustal anatexis a model abstract the initial pb isotopic composition of anatectic granites is modelled as a mixture of pb derived from major minerals that have characteristically low 238 u 204 pb and 232 th 204 pb ratios i e feldspars biopyroboles etc with pb contributed from dissolved accessory minerals with characteristically high 238 u 204 pb and 232 th 204 pb ratios i e zircon monazite etc the initial pb isotopic composition of anatectic granites is a function of a the age type modal distribution and heterogeneity in the initial u and th content of the accessory minerals b variation in melt composition and temperature during anatexis c the fraction of the source melted and d the extent to which the melt was homogenized prior to crystallization the differential behavior of accessory minerals during anatexis can explain the common yet enigmatic decoupling of the pb isotopes from other chemical and isotopic systems in granite rocks granitic plutons derived by anatexis of the same source material are not required to have the same initial pb isotopic composition low temperature peraluminous granites are more likely to exhibit homogeneous initial pb isotopic compositions dominated by the pb contained within the major mineral assemblage of the source material in contrast the initial pb isotopic composition of higher temperature metaluminous or peralkaline anatectic granites is more likely to be heterogeneous unless the melts are homogenized during emplacement and will record a larger fraction of the radiogenic pb component contained in the accessory mineral assemblage of the source material heterogeneity in the initial pb isotopic composition of individual granites or granitic suites can preserve the weighted average age of the radiogenic pb present in the accessory mineral assemblage of the source region even if these minerals are entirely dissolved during anatexis the use of isotopic tracer studies in terrane analysis will be optimized by the isotopic characterization of granitic suites

global trench migration velocities and slab migration induced upper mantle volume fluxes constraints to find an earth reference frame based on minimizing viscous dissipation sincetheadventofplatetectonicsdifferentglobalreferenceframeshavebeenusedtodescribethemotionofplatesandtrenches thedifferencein plate motion and trench migration between different reference frames can be substantial up to 4 cm yr this study presents an overview of trench migration velocities for all the mature and incipient subduction zones on earth as calculated in eight different global reference frames calculations show that irrespective of the reference frame 1 trench retreat always dominates over trench advance with 62 78 of the 244 trench segments retreating 2 the mean and median trench velocity are always positive retreating and within the range 1 3 1 5 cm yr and 0 9 1 3 cm yr respectively 3 rapid trench retreat is only observed close to lateral slab edges b1500 km and 4 trench retreat is always slow far from slab edges n2000km thesecalculationsarepredictedbygeodynamicmodelswithavaryingslabwidth inwhichplatemotion trenchmotionandmantleflow result from subduction ofdense slabs suggesting that trenchmotion is indeedprimarily drivenby slab buoyancyforces andthat proximity to alateral slab edge exerts a dominant control on the trench migration velocity despite these four general conclusions significant differences in velocities between such reference frames remain it is therefore important to determine which reference frame most likely describes the true absolute velocities togetanunderstandingoftheforcesdrivingplatetectonicsandmantleconvection itishereproposedthat basedonfluiddynamicconsiderationsand predictions from geodynamic modelling the best candidate is the one which optimises the number of trench segments that retreat minimizes the trench perpendicular trench migration velocity vt in the centre of wide n4000 km subduction zones maximizes the number of retreating trench segments located within 2000 km of the closest lateral slab edge minimizes the average of the absolute of the trench perpendicular trench migration velocity vt forallsubductionzonesonearth andminimizestheglobaluppermantletoroidalvolumeflux to thatresultsfromtrenchmigration and associated lateral slab migration i e slab rollback or slab roll forward calculations show that these conditions are best met in one particular indo atlantic hotspot reference frame where 75 of the subduction zones retreat vt in the centre of wide subduction zones ranges between 3 5 and 1 8 cm yr 83 of the trench segments located within 2000 km of the closest lateral slab edge retreat the average of vt is 2 1 cm yr and to 456 km 3 yr lower limit and 539 km 3 yr upper limit inclusion of all the incipient subduction zones on earth results in slightly greater fluxes of 465 km 3 yr lower limit and 569 km 3 yr upper limit it is also found that this reference frame is close to minimizing the total sub lithospheric uppermantlevolumeflux k associatedwithmotionofcontinentalkeelslocatedbelowthemajorcratons itisstressed however that kisanorder of magnitude smaller than to and thus of subordinate importance in conclusion the indo atlantic hotspot reference frame appears preferable for calculating plate velocities and plate boundary velocities

a strategy to improve the contribution of coral data to high resolution paleoclimatology abstract various geochemical tracers measured in massive coral skeletons have the potential to compliment other sources of high resolution proxy climate information e g tree rings ice cores by providing paleoclimatic data from shallow water tropical ocean regions twenty previously published coral records 19 18o and one sr ca series between 54 and 346 years in length were examined for their local and larger scale relationships el nino southern oscillation with climate series were examined in a consistent manner over the same time periods and relationships were tested for stability through time the results demonstrate a spectrum of climatic interpretation ranging from 1 no significant relationship of the coral record with either local or larger scale climate variables 2 significant relationship of the coral record with climate but the relationship is not stable through time and 3 the coral record shows a significant and temporally stable relationship with climate which explains a significant and useful proportion of climate variance it is concluded that reliance to date on analyzing only one long coral core from a site has prevented identification of coral records or parts of coral records where non climatic factors are dominating the geochemical signal various factors may cause these non climatic signals to dominate more process studies into how corals of particular species with various growth rates and from various environmental settings incorporate geochemical tracers into their skeleton are required to understand exactly what is being measured in addition it is recommended that some level of replication ideally three separate corals of geochemical tracers will ensure accurate dating of the record identification of periods when non climatic factors dominate and thus enhance the reliability of the paleoclimatic record such an approach will allow the rich archive of environmental information contained in massive coral skeletons to make a significant contribution to high resolution paleoclimatology and improve our understanding of the nature and causes of past climate variability

toward a semantic web of paleoclimatology 1 the paleoclimate record is information rich yet significant technical barriers currently exist before this record can be used to answer scientific questions here we make the case for a universal format to structure paleoclimate data a simple example demonstrates the scientific utility of such a self describing way of organizing coral data and meta data this example is generalized to a universal ontology that may form the backbone of an open source open access and crowd sourced paleoclimate database the format is designed to enable semantic searches and is expected to accelerate discovery on topical scientific problems like climate extremes the characteristics of natural climate variability and climate sensitivity to various forcings

coral oxygen isotope records of interdecadal climate variations in the south pacific convergence zone region 1 the south pacific convergence zone spcz a region of high rainfall is a major feature of subtropical southern hemisphere climate and contributes to and interacts with circulation features across the pacific yet its past temporal variability and forcing remain only partially understood here we compare coral oxygen isotopic 18o series spanning a d 1997 1780 and a d 2001 1776 from two genera of hermatypic corals in fiji located within the spcz to examine the fidelity of these corals in recording climate change and spcz interdecadal dynamics one of these coral records is a new 225 year subannually resolved 18o series from the massive coral diploastreaheliopora diploastrea s use in climate reconstructions is still relatively new but this coral has shown encouragingly similar interannual variability to porites the coral genus most commonly used in pacific paleoclimate studies in fiji we observe that interdecadal 18o variance is also similar in these two coral genera and diploastrea contains a larger amplitude interdecadal signal that more closely tracks instrumental based indices of pacific interdecadal climate change and the spcz than porites both coral 18o series record greater interdecadal variability from 1880 to 1950 which is consistent with the observations of folland et al 2002 who reported higher variability in spcz position before 1945 these observations indicate that diploastrea will likely provide a significant new source of long term climate information from the spcz region

calibration of stable oxygen isotope signatures in galapagos corals a 2 year 1993 1994 study was conducted in the galapagos islands ecuador to determine the relationship between 18o in skeletal carbonate and sea surface temperature sst in three species of reef building corals pavona clavus pavona gigantea and porites lobata coral samples were grown at 3 10 and 3 m depth at bartolome island champion iisland and urvina bay isabela island respectively hourly measurements of sst and sea surface salinity sss were taken at each site immediately adjacent to colonies which were stained biannually to establish the chronology of growth in addition surface waters were sampled periodically bimonthly to monthly at each site to determine variation in 18o seawater results indicate the mean annual ssts were similar between sites varying from 22 9 c at champion to 23 8 c at urvina bay comparisons of monthly sst averages between instrumental and remote sensing satellite 1 1 grid data show a high correspondence r2 ranging from 0 84 to 0 94 indicating that remote sensing data are useful for interpreting the 18o record in corals when instrumental data are lacking here 18ocoral analyses of eight specimens show that coralline aragonite is a reliable indicator of sst in galapagos in general higher resolution coral sampling year resolved more of the monthly variation in sst up to 97 at a sampling resolution of 1 4 samples per millimeter of linear skeletal growth comparisions of the 18ocoral signal among and between species at the same site showed consistent seasonal patterns of variation closely tracking sst in addition comparisons between sites were highly concordant with some differences reflecting local variation in sst seasonal patterns however were essentially the same over the entire region thus we conclude that the 18ocoral signal from coral skeletons in galapagos can be used to interpret regional changes in sst variation

coral climate proxy data from a marginal reef area kuwait northern arabian persian gulf we present the first coral climate proxy data sr ca 18o 13c from the persian arabian gulf using a porites lutea coral collected offshore kuwait both oxygen isotope and sr ca ratios of the coral core investigated are statistically correlated with instrumental sea surface temperatures sst for the area from 1980 2002 however the temperature calibration curve for sr ca differs from other published curves in that its slope is much lower the correlation coefficient between 18ocoral and instrumental sst is at the lower limit as compared to other sites these differences most likely relate to insufficient data representation of cold winters and hot summers and indicates that much higher sampling resolution is needed in marginal reef areas such as kuwait with extreme environmental fluctuations i e intra annual sst variation of 16 34 c as compared to low latitude locations with relatively low sst variation variations of carbon isotopes of the coral skeleton do not exhibit climate control however a negative excursion in 1991 might be attributed to the massive oil field fires of the ii gulf war

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

variability of skeletal growth and δ13c in massive corals from the south china sea effects of photosynthesis respiration and human activities the delta c 13 skeletal density and extension rates were analyzed along same growth axes of massive coral colonies collected from the shallow sea to the east and south of hainan island northern south china sea seasonal changes of delta c 13 extension and calcification rates of porites lutea and porites lobata are in phase and correlated with solar radiation in addition annual high delta c 13 values extension and calcification rates occur in spring and low values and rates occur in late autumn or early winter the annual highest density band of p lutea formed in spring and the lowest ones in early winter whereas r lobata shows only a weak seasonal density change we suggest that the seasonal features of the coral delta c 13 extension and calcification rates are modulated by light induced photosynthesis determined by solar radiation reaching the top of the atmosphere and by cloud coverage the results also support the suggestion that photosynthesis promotes both the extension growth and skeleton thickening for p lutea but that it mainly promotes the extension growth for p lobata remarkable inter decadal trends are evident in the coral records these trends are progressive decreases of skeletal delta c 13 density and calcification rate and an increase of the extension rate over the last 30 years which are marked by abrupt changes at about 1987 these trends are ascribed to intensified coral respiration arising from rising temperature together with the effects of declining nutrient levels caused by the destruction of the coastal ecosystem in the sampling regions c 2008 elsevier b v all rights reserved

lithospheric deformation within the molucca sea arc arc collision evidence from shallow and intermediate earthquake activity this paper presents the results of a local earthquake survey in the molucca sea arc arc collision zone of eastern indonesia although intermediate depth earthquakes define zones dipping to the west beneath the sangihe arc and to the east beneath the halmahera volcanic arc only shallow activity less than 60 km depth occurred beneath the central part of the collision zone where the majority of activity is observed the concentration of earthquake foci in the 10 to 50 km depth range in a limited region beneath the talaud mayu ridge suggests that convergence between the arcs proceeds by shortening within basement of the intervening molucca sea plate rather than by slip along shallow dipping planes between the arcs and the subducted slabs published focal mechanism solutions suggest that high angle reverse faulting beneath the talaud mayu ridge generates almost all of the seismic energy release within the collision zone the predominance of shallow reverse and strike slip faulting at the axis of the bilaterally subducting molucca sea lithosphere suggests that stresses are not due to bending alone and have a large horizontal regional component perpendicular to the island arcs the geometry and state of stress within the molucca sea lithosphere requires an external driving force for the convergence between the two arcs and a strong degree of coupling between the island arcs and the subducting molucca sea plate at least at the present stage of collision

western irian jaya the end product of oblique plate convergence in the late tertiary abstract the island of new guinea is the surface expression of the deformed northern margin of the australian continental block to the south undeformed continental crust is overlain by flat lying platform sediments that form a conformable sequence from late palaeozoic to late tertiary along the new guinea cordillera these platform sediments have been tightly folded and overthrust to the south as a result of crustal shortening caused by convergence between the australian plate and the pacific plate the earth movements resulting from this convergence started at the end of the miocene and continue to the present day it is postulated that all the major structures of western irian jaya were caused by this orogeny and can be explained by the convergence directed southwest northeast between the australian and pacific plates it is further postulated that the convergence has remained essentially constant since the start of the earth movements this convergence is consistent with that postulated in the circum pacific plate tectonic map aapg 1981 of 12 5 cm yr directed about 15 south of west only if the effects of the sorong yapen fault system are taken into account this complex east west trending fault system forms the southern boundary of the pacific plate and has responded to the convergence by left lateral strike slip displacement of at least 370 km since the late miocene as a consequence south of the sorong yapen fault system the convergence has been directed more to the south i e at least 45 south of west in this region south of the fault zones the north south component of the convergence has been accommodated in the east by folding and overthrusting over a wide zone of interaction called the new guinea mobile belt dow 1977 in the west on the other hand the australian continental crust has been a stable buttress kepala burung fig 2 which following convergence has protruded into the pacific plate its northeastern margin has therefore been exposed to the full brunt of collision with the pacific plate and large segments of continental crust have been broken off and rafted westwards in order to accommodate the difference in crustal shortening between the new guinea mobile belt and kepala burung two fundamental crustal fractures formed in the intervening region the waipoga and wandamen faults these fractures make angles of about 65 with the regional structural trend fig 2 and they were the focus of most of the resulting differential crustal displacement two of the more spectacular examples of this differential movement have been the thrusting of large slabs of crustal rocks tens of kilometres southwards over the australian continental crust weyland overthrust and lengguru fold belt

possible coseismic large scale landslide off the northern coast of papua new guinea in july 1998 geophysical and geological results from sos cruises the epicentral area of the 1998 papua new guinea earthquake and tsunami off sissano lagoon northern coast of papua new guinea m 7 1 17 july 1998 was surveyed by the research vessel kairei in january 1999 precise bathymetric survey by use of seabeam 2112 and other geophysical surveys bottom reflectivity sub bottom profiling surface ship gravity and geomagnetic surveys were carried out and four piston core samples were collected during the nine days survey the area was also surveyed by use of the japanese deep sea research rov dolphin 3k and research submersible shinkai 2000 after the regional geophysical survey in order to locate the possible seismic faults and or underwater landslides as the source of tsunami and to study the process which took place off sissano lagoon and the driving force of the event the study area is characterised by substantial fan sediment supply from sissano lagoon straight small scale submarine canyons and valleys are eroding the shelf slope constructed by the fan sediment topographic features of arcuate slumps caused by landslides are recognised at numerous sites of the study area most of them are old and the most recent is located 25 km northeast off the sissano lagoon two major topographic depressions on the shelf were located off sissano lagoon the western is a depression of about 10 km width and the eastern is a meandering deep sea canyon amphitheatre topographic features with slumps caused by landslides that were discovered by kairei s cruise were extensively surveyed in the study area six dives by dolphin 3k and seven dives by shinkai 2000 revealed that a fresh crack of about 15 km in total length is located along the slope of the amphitheatre the crack is apparently the upper slope of a large scale slumping on the amphitheatre characterised by tensional stress on it the easternmost part of the fresh crack is accompanied by living chemosynthetic organisms such as mussels and tube worms the chemosynthetic community is apparently associated with cold seepage along the crack suggesting that the crack was constructed very recently the areas other than the crack were rather old with bioturbation

geochemistry of the end permian extinction event in austria and italy no evidence for an extraterrestrial component the end permian mass extinction 251 ma was the largest in earth s history and the great extent of biospheric perturbation is recorded as dramatic shifts in carbon isotope ratios of sedimentary materials both terrestrial and extraterrestrial events are commonly invoked as causative mechanisms for the crisis and the primary reason for the event remains the subject of controversy geochemical indicators sensitive to the influence of extraterrestrial material involve platinum group elements and osmium and helium isotope ratios analyses of extinction levels in two sections from austria and italy reveal no evidence of an extraterrestrial impact the end permian crisis it appears was a homegrown catastrophe

on the evolution of marginal basins this paper presents a critique of the models proposed to explain the formation of back arc basins those marginal basins located behind active or inactive trench systems and whose origin is inferred to be subduction related several marginal basins are not generically back arc but rather are related to the initiation of subduction continental rifting or plate boundary readjustments models of back arc basin formation must be consistent with the observed characteristics of back arc basins which include the following 1 the crustal structure and magnetic lineation patterns of back arc and major ocean basins are similar implying that the processes of crustal accretion in both tectonic environments are also similar 2 arc trench systems without currently spreading back arc basins are in the majority 3 although petrographically similar to and within the compositional range of midocean ridge basalts morb back arc basin basalts babb show consistent geochemical differences from n type morb and are in many respects transitional toward island arc tholeiites iat 4 distinct babb and iat mantle sources may be in extremely close proximity during the initial rifting of an island arc 5 rifting of the volcanic arc may occur on either side of the line of active volcanoes 50 km and may vary from one side to the other along strike 6 a remnant arc is not always developed 7 back arc spreading may be initiated above subducted lithosphere but with time the center of spreading migrates away from the arc and no longer overlies a benioff zone and 8 there is no simple correlation between the timing of global plate reorganizations and the formation of back arc basins the three main classes of models proposed to explain back arc basin formation are mantle diapirism induced aesthenospheric convection and global plate kinematics because the driving mechanism for the first two classes of models is provided by the local subducting slab these models fail to explain the temporal and spatial distribution of back arc basins the third class of models proposes that back arc basins should form whenever global plate interactions require divergence between the overriding plate and the trench line the latter being observed to move only in a seaward direction with respect to a hot spot reference frame however the tectonic setting of several back arc basins suggests that they represent more than just a passive response to kinematic boundary conditions for example some dynamic back arc force seems required to move the new hebrides tonga and south sandwich forearc plates seaward neither the local nor the global models adequately specify the necessary and or sufficient conditions for back arc basin formation a better understanding of the processes associated with the initiation of rifting and of subduction is required arc rifting and back arc spreading are both secondary phenomena to subduction but they are also primary extensional phenomena fundamentally analogous to continental rifting and the initial spreading of major ocean basins

far field contractional polarity changes in models and nature abstract a change in contractional polarity occurs when the direction of tectonic transport switches along strike this switch is conditioned by lateral variations in rheology or inherited asymmetries such as contrasts in structure or changes in the polarity of subduction zones the parameters controlling contractional polarity changes are less understood in situations when the strain is transferred at large distances from indenters analysing this type of strain transfer is critical for understanding the mechanics of thrusting in fore or back arc settings of orogenic areas comparison of crustal scale analogue modelling with the inversion of the black sea back arc and the formation of the new guinea new britain fore arc suggest that far field changes in contractional polarity are related to rheological contrasts across inherited normal faults the initial extension creates rheological weak zones that localize the subsequent far field contractional deformation along groups of thrusts with opposite vergence along the strike of the system the largest amount of far field contractional deformation is recorded in the transfer zone located between the two indenters moving in opposite directions and is particularly high when inverting oblique extensional systems

arc continent collisional orogenesis in the sw pacific and the nature source and correlation of emplaced ophiolitic nappe components abstract southwest pacific ophiolitic nappes emplaced upon the former margin of eastern australia provide a record of cyclical episodes of arc continent collisional orogenesis that occurred throughout the paleogene cenozoic nappes in papua new guinea new caledonia and northland new zealand consist of two key components 1 a basal and apparently older late cretaceous eocene metamorphosed normal to weakly enriched morb like basaltic ocean floor terrane and 2 an uppermost supra subduction zone ssz ophiolite that represents basement of the associated magmatic forearc a detailed comparison of geochemical characteristics of unequivocal ssz basalts with those considered as representative of the basaltic ocean floor terranes illustrates that formation of the majority of the latter is consistent with melting of a source transitional to normal n and enriched e morb these slight ree enriched or transitional t morb have generally been considered as the result of seafloor spreading in a back arc basin bab or basins to the east of australia in the late cretaceous paleocene 85 55 ma the enrichment recorded by the bab basalts is likely a result of upwelling plumes associated with initial fragmentation of eastern gondwana that left their signature on the mantle source consequently tapped by the bab basalts a subset of slightly more enriched basalts may owe their enrichment to source contamination minor assimilation of thinned gondwana derived continental crust associated lree depleted n mor basalts previously considered as part of the basaltic ocean floor terranes on the other hand are similar to ssz basalts of the northland and papuan ultramafic belt ophiolites refinement of existing tectonic models is hindered by ambiguities in the stratigraphic relationships of the underlying basaltic ocean floor terranes with the overlying ssz ophiolites a paucity of age data and uncertainties in the tectonomagmatic affinities of the underlying basalts nonetheless the geochemical characteristics displayed by lree depleted basalts of the basaltic ocean floor terranes suggest that these may instead represent younger magmatic forearc basement components subsequently overthrust by lower sections of a genetically related ophiolite whether these and for that matter the majority of basalts of the basaltic ocean floor terranes indeed represent complementary forearc crust to the ssz ophiolite as opposed to a slice of late cretaceous eocene bab floor backthrust beneath the ssz ophiolite upon emplacement will have to await the acquisition of corresponding radiometric age data