assimilation of radiocarbon and chlorofluorocarbon data to constrain deep and bottom water transports in the world ocean a coarse resolution global model with time invariant circulation is fitted to hydrographic and tracer data by means of the adjoint method radiocarbon and chlorofluorocarbon cfc 11 and cfc 12 data are included to constrain deep and bottom water transport rates and spreading pathways as well as the strength of the global overturning circulation it is shown that realistic global ocean distributions of hydrographic parameters and tracers can be obtained simultaneously the model correctly reproduces the deep ocean radiocarbon field and the concentrations gradients between different basins the spreading of cfc plumes in the deep and bottom waters is simulated in a realistic way and the spatial extent as well as the temporal evolution of these plumes agrees well with observations radiocarbon and cfc observations place upper bounds on the northward transports of antarctic bottom water aabw into the pacific atlantic and indian oceans long term mean aabw transports larger than 5 sv sv 10 6 m 3 s 1 through the vema and hunter channels in the south atlantic and net aabw transports across 30 s into the indian ocean larger than 10 sv are found to be incompatible with cfc data the rates of equatorward deep and bottom water transports from the north atlantic and southern ocean are of similar magnitude 15 7 sv at 50 n and 17 9 sv at 50 s deep and bottom water formation in the southern ocean occurs at multiple sites around the antarctic continent and is not confined to the weddell sea a cfc forecast based on the assumption of unchanged abyssal transports shows that by 2030 the entire deep west atlantic exhibits cfc 11 concentrations larger than 0 1 pmol kg 1 while most of the deep indian and pacific oceans remain cfc free by 2020 the predicted cfc concentrations in the deep western boundary current dwbc in the north atlantic exceed surface water concentrations and the vertical cfc gradients start to reverse

trace elements in the north atlantic troposphere shipboard results of precipitation and aerosols samples for trace metals in precipitation rain snow and fog and total aerosols were collected at sea as part of the gce case watox expedition during august and september 1988 in the greater north atlantic between bermuda iceland the azores and barbados the samples were collected using ultra clean equipment and methods for the analysis of the trace elements al fe mn zn cu ni cd and pb including stable isotopes the samples were analyzed by graphite furnace atomic absorption spectrometry and thermal ionization mass spectrometry based on stable lead isotopes and retrospective isentropic air mass analyses four air mass sources were evidenced including 1 temperate u s and 2 boreal canadian westerlies and 3 boreal and northern europe easterlies associated with 4 mediterranean and saharan easterlies lead isotopic signatures clearly distinguished emission source regions over the north atlantic with 206pb 207pb ratios of 1 19 1 22 for north american westerlies 1 10 1 12 for european boreal easterlies and 1 15 1 16 for saharan trade easterlies also the contrasting ratios between precipitation and aerosol demonstrate a vertical mixing of chemical sources in precipitation from contrasting air masses of different origin the air mass trajectories were independently calculated and are in general agreement with the lead isotopic tracers the isotopic tracers allowed more confident conclusions on air mass sources particularly after a few days of oceanic transport also the trajectories appeared to be very useful in explaining the strong variability of the trace metal concentrations during restricted periods of sampling time aboard a moving ship to a lesser extent the atmospheric emission sources were characterized by trace element concentrations the occurrence of large dust loadings in the saharan trade easterlies contributed abundant crustal elements and were also associated with enriched anthropogenic elements from southern europe scavenging ratios were calculated for lead and cadmium during select periods when aerosol and precipitation were collected under the same meteorological regimes the cadmium ratio is much greater than that of lead indicating that cadmium and lead are each transported or scavenged on distinct populations of aerosols for lead the ratio is less in the north atlantic than in the pacific suggesting an aerosol concentration dependence like the pacific the ratios increase for the lead dust and sea salt one may thus conclude that marine scavenging ratios cannot yet be used effectively until factors such as concentration dependency and local conditions of tropospheric processing are better defined

using a cfc effective age to estimate propagation and storage of climate anomalies in the deep western north atlantic ocean 1 1990s chlorofluorocarbon cfc observations are used to estimate an effective age of 20 years for north atlantic deep water nadw at the equator the effective age is found by subtracting a relic age from pcfc 11 age the effective age is several to 10 years younger at the equator than other methods from the effective age equatorward effective spreading rates of 1 2 cm s are found which are similar for the nadw components effective spreading rates take into account recirculation gyres along equator flow and mixing which slow spreading of climate anomalies from the north atlantic to the southern hemisphere the difference between direct velocities and tracer effective spreading rates suggests that the buffering effect due to storage in the western north atlantic and equatorial region is about 20 years even so warming and freshening due to greenhouse gases will be first felt in the deep waters of the western north atlantic

entrainment of trace metal enriched atlantic shelf water in the inflow to the mediterranean sea surface waters of the mediterranean sea have higher trace metal concentrations than open atlantic surface waters1 this observation could be explained by sources within the basin but recent data from the alboran sea2 indicate that trace metals may already be enriched in atlantic waters flowing into the mediterranean through the strait of gibraltar here we present new data documenting the presence of trace metal enriched source waters west of the strait and present a mathematical analysis showing that cu ni cd and zn distributions in the alboran sea can be explained as linear mixtures of four well defined sources 1 spanish coastal waters 2 north atlantic central water 3 atlantic surface water and 4 mediterranean levantine intermediate water in this analysis salinity and trace metals are used for the first time to deconvolve mixing between water masses of different origins

pb isotopes in surficial pelagic sediments from the north atlantic we measured pb isotopic composition and concentration in sediment samples close to the sea water interface in 6 box cores from the ne atlantic 2 box cores from the sargasso sea and one from the us continental shelf the anthropogenic pb input to marine sediments due to the increase of pb contamination over the ocean during the last century can be identified in all these cores in the eastern part of the atlantic i e in regions under aeolian influence from europe pb pollution can be recognized using its distinctive unradiogenic composition clearly different from the upper crustal values commonly found in pre holocene sediments in contrast pb pollution in regions influenced by north american sources can be identified only in detailed concentration profiles because the american pb pollution has an isotopic composition much closer to that of the natural detrital pb input coming from weathering of the continental crust pb excess inventories are in good agreement with fluxes estimated from sedimenttrap data and with the time record of pb contamination increase given by analyses in coral growth bands inventories of pb contamination to the sediments of the mud patch american shelf are tenfold higher 84 g cm2 than those to hatteras and bermuda abyssal plains 4 3 and 2 8 g cm2

ordovician ocean plate stratigraphy and thrust duplexes of the ballantrae complex sw scotland implications for the pelagic deposition rate and forearc accretion in the closing iapetus ocean abstract the ballantrae complex at bennane lea in sw scotland contains important ocean plate stratigraphy basalt chert mudstone sandstone in an accretionary prism that is associated with a classic ordovician ophiolite we used the ocean plate stratigraphy to sub divide the prism into 11 tectonic units to determine the depositional age of bedded cherts zircons were separated from 9 tuff beds from 6 different units all the tuffs have early to middle ordovician ages even though their present positions are mutually distant these ages are consistent with microfossil records of radiolaria and graptolites the stratigraphic structural relationships demonstrate that the ocean plate stratigraphy has been repeated by bedding parallel thrusts this is typical of a modern accretionary duplex we calculated the sedimentation rate of early to middle ordovician bedded cherts at bennane lea on the basis of u pb zircon ages obtained from several tuff beds the data indicate that the depositional rate 0 6 3 m myr was as slow as that of mesozoic cenozoic equivalents defined by radiolaria the age spectra of detrital zircons from ballantrae sandstones show prominent single peaks at ca 467 and 478 ma and a lack of precambrian zircons integration of our new zircon ages with published isotopic data and palaeo geographic maps indicates that the sandstones were deposited near an intra oceanic arc and far from any continent containing precambrian rocks the pelagic to clastic sediments at bennane lea were deposited in the closing iapetus ocean from ca 477 ma to ca 464 ma when they were accreted with the intra oceanic arc of ballantrae

isotopic evidence of contaminant lead in the south atlantic troposphere and surface waters abstract the third intergovernmental oceanographic commission ioc baseline contaminant cruise may june 1996 has established the first lead isotopic compositions in the surface water and the atmosphere of the equatorial and south atlantic ocean these ratios have evidenced both anthropogenic and natural origins of lead along the cruise transect from 33 s to 10 n the isotopic gradients tentatively have been attributed to aeolian as well as surface water advective inputs from a suite of rather local and remote sources to the southern hemisphere relatively low 206pb 207pb ratios x sd were encountered within the south equatorial current between 17 s and 5 s 1 156 0 003 those were bracketed by more radiogenic ratios at higher latitudes in the southern hemisphere 33 s to 23 s within the brazil current and the subtropical gyre 1 163 0 003 and in the northern hemisphere 0 to 10 n 1 165 0 005 the latter were comparable to ratios of surface water in the north atlantic equatorial ocean 1 169 0 006 under a combined contaminant influence of both north american westerlies 1 19 1 20 and european easterlies 1 155 1 165 that predominance of contaminant lead contrasts with the measurable presence of natural lead in surface waters of the equatorial ocean which are attributed to aeolian inputs of saharan dust the ratios of lead in surface waters at higher latitudes in the south atlantic are characteristic of anthropogenic lead aerosols also detected in antarctic ice and could substantiate as well the hypothesized aerosol recycling of lead by sea spray emission in the far southern hemisphere the atmospheric lead isotopic compositions 206pb 207pb in bulk depositions 1 171 0 006 precipitation 1 171 0 006 and aerosols 1 168 0 011 were generally more radiogenic than the surface waters 1 162 0 005 beside a poor representation of a short term atmospheric sampling this difference could reflect a recent evolution in atmospheric lead emissions which have not yet been reflected in oceanic surface waters it may also be due in part to advective lead inputs from surface oceanic circulation of the south equatorial current

from mesozoic rifting to apennine orogeny the gran sasso range italy the apennines are a low temperature accretionary prism generated by the west directed subduction of the adriatic ionian plate whose structural origin is still to be fully understood the highest and best exposed seg ment of the apennines the gran sasso range is here documented to unravel the tectonic history of the northern tip of gondwana it is located along a ne verging salient of thrust sheets decoupling the sedimentary cover of the subducting adriatic lithosphere field mapping and structural analysis along the e w trending left lateral transpressive segment of the salient highlight the interplay of the inherited mesozoic passive margin stratigraph ic and tectonic framework with the neogene contraction the rheological differences between the massive carbonate platform and the well bedded turbiditic and pelagic limestones determined along strike undulations of the thrusts geometries and fold styles during shortening heterogeneities are due to inherited syn and post rift mesozoic tectonics the gran sasso overturned anticline shows a backlimb anomalously tilted toward the foreland and we infer this dip as being related to a deeper back thrust of a triangle zone the pinching out of the foredeep sequence on the growth anticline forelimb dates the contractional phases of the region to the late messinian from the late pliocene to present the area has been uplifted and extended about 2 km by oblique normal faults cross cutting the accretionary prism some of them are seismically active as shown by the 2009 mw 6 3 l aquila earthquake

thermocline ventilation of anthropogenic lead in the western north atlantic massive industrial aerosol emissions from north america have over the past century overwhelmed the natural distribution of lead in the western north atlantic thermocline the resultant features to 2000 m depth have been mapped near bermuda for the year 1984 since earlier reported measurements have largely been rejected on grounds of sample contamination the twentieth century evolution of anthropogenic pb in the oceanic water column is unknown coupling of the 1984 water column pb distribution to historical records in reef building corals and tracer derived thermocline ventilation rates jenkins 1980 has permitted a model reconstruction of pb penetration into the sargasso sea the model is constrained by three distinct pb distributions pb concentration stable pb isotopes and 210pb with adjustable scavenging and regeneration parameters to account for nonconservative behavior the results of the model substantiate the importance of lateral isopycnal ventilation while pointing out the necessity of dissolved particulate exchange i e scavenging of the order of 70 years in the deep thermocline minimum regeneration of 10 particulate pb between surface and 1700 m residual discrepancies between model isotopic predictions and observations below 800 m are likely due to a combination of the following factors 1 presence of nonradiogenic background pb in intermediate depth waters 2 geographic variability in north american industrial source signatures 3 mediterranean pb inputs of european origin and 4 along isopycnal mixing effects

40ar 39ar constraints on obduction of the seram ultramafic complex consequences for the evolution of the southern banda sea on kaibobo w seram obduction of hot oceanic lithosphere produced high grade metamorphism and granite in overthrust continental crust 40ar 39ar plateau ages of 5 65 6 0 ma and 5 4 ma of muscovite and biotite from the sole among the youngest so far measured on single crystals indicate complete resetting of the ar isotope system chloritized biotite crystals gave disturbed spectra and younger ages single fusion on biotite from the granite gave an age of 5 5 ma time limits for the obduction exhumation history of the kaibobo complex and sole are approximated by simple 1d forward p t t modelling constrained by pt data and 40ar 39ar thermochronology c 400 c at 6 ma c 320 c at 5 5 ma best fit results indicate that the decelerating post emplacement exhumation of ophiolite and sole began 8 ma ago the rate during the first 1 ma of this uplift exceeded 7 5 mm a 1 undoing 8 ma of migration in the sw pacific and australian regimes of motion back tracks kaibobo to the site where obduction emplacement ended near the southeastern corner of the banda sea plate similar compositions and time settings of the kaibobo and n timor ophiolites lead us to postulate that during the early miocene slow rate spreading occurred in the oceanic lithosphere of the southern banda sea south of the current volcanic arc

isotopic evidence of pollutant lead transport from north america to the subtropical north atlantic gyre abstract lead isotope ratios have been measured in aerosols seawater and marine particles collected in 1990 1992 in the subtropical northeastern atlantic ocean as part of the jgofs eumeli program while the atmospheric input has unradiogenic 206 pb 207 pb ratios 1 158 0 006 typical of the tradewinds bringing lead from european countries all the samples collected in the water column have more radiogenic 206 pb 207 pb from 1 170 to 1 196 this demonstrates that lead at the eumeli sites contains a dominant input from american emissions that has been circulated across the north atlantic by the subtropical north atlantic gyre using measurements in sargasso sea surface waters as an estimate of the isotopic composition of this input 206 pb 207 pb 1 195 0 004 we calculate a contribution of 42 57 from america in these waters this demonstrates that american emissions still dominated lead contamination over the north atlantic in the early 1990s in spite of the early reduction of leaded gasoline in the usa these results also give new evidence of the equilibrium between dissolved and particulate phases during scavenging processes

the mean flow field of the tropical atlantic ocean the mean horizontal sow eld of the tropical atlantic ocean is described between 20in and 20is from observations and literature results for three layers of the upper ocean tropical surface water central water and antarctic intermediate water compared to the subtropical gyres the tropical circulation shows several zonal current and countercurrent bands of smaller meridional and vertical extent the wind driven ekman layer in the upper tens of meters of the ocean masks at some places the sow structure of the tropical surface water layer as is the case for the angola gyre in the eastern tropical south atlantic although there are regions with a strong seasonal cycle of the tropical surface water circulation such as the north equatorial countercurrent large regions of the tropics do not show a signi cant seasonal cycle in the central water layer below the eastward north and south equatorial undercurrents appear imbedded in the westward sowing south equatorial current the antarcic intermediate water layer contains several zonal current bands south of 3in but only weak sow exists north of 3in the sparse available data suggest that the equatorial intermediate current as well as the southern and northern intermediate countercurrents extend zonally across the entire equatorial basin due to the convergence of northern and southern water masses the western tropical atlantic north of the equator is an important site for the mixture of water masses but more work is needed to better understand the role of the various zonal under and countercurrents in cross equatorial water mass transfer 1999 elsevier science ltd all rights reserved

the younger dryas relevant in the australian region an assessment of australian climate during the younger dryas chronozone ydc is presented this review focuses on securely dated records from sites of continuous deposition placing greatest emphasis on temperature reconstructions with records of effective precipitation i e the combined effect of precipitation minus evapotranspiration also considered while there is a paucity of australian records covering the last glacial interglacial transition particularly those which directly infer temperature sufficient data exist to examine ydc climate from southern and eastern australia temperature reconstructions from tasmania based on both chironomid and pollen data show no evidence for younger dryas cooling by contrast there is evidence for cooling associated with the antarctic cold reversal from tullabardine dam pollen data and the sediment organic content from eagle and platypus tarns in tasmania records from a number of eastern australian mainland sites provide no evidence of effective precipitation shifts concurrent with the younger dryas chronozone similarly reconstructions of discharge from the murray darling basin which covers a large proportion 14 of the australian continent and dust transport from a larger portion of the continent also show no evidence of climate shifts concomitant with the younger dryas of research published in the past decade only one study located in the great australian bight claims evidence of a ydc cooling andres et al 2003 by contrast this review suggests that there is no conclusive evidence for cooling or indeed any distinctive climate patterning during the younger dryas chronozone in australia

isotopic equilibration between dissolved and suspended particulate lead in the atlantic ocean evidence from 210pb and stable pb isotopes decreased consumption of leaded gasoline in the united states over the past two decades has drastically altered the flux and isotopic composition of pb entering the western north atlantic from the atmosphere here we exploit the resulting temporal changes in the distribution and isotopic composition of oceanic pb to investigate interactions between dissolved and particulate pb in the oceanic water column measurements of dissolved pb isotopic composition on samples collected in 1987 in the upper water column near bermuda demonstrate that surface water 206pb 207pb decreased from 1 203 to 1 192 since 1983 and that a measurable change propagated to 300 500 m since the 1984 profile of shen and boyle 1988 the first accurate measurements of suspended particulate pb in an open ocean profile show concentrations of 1 3 pmol l equal to 2 4 of total pb vertical profiles of 1 the stable lead isotopic composition and 2 the ratio of total pb to 210pb in suspended particles closely track contemporaneous depth variations in these ratios for dissolved pb throughout the upper 2000 m of the sargasso sea near bermuda thus suspended particles reach isotopic equilibrium with ambient sea water pb on a time scale which is shorter than their residence time with respect to vertical removal in agreement with equilibrium scavenging hypotheses based on interpretations of th isotope distributions a simple flux model suggests that the effect of deep ocean scavenging processes on the flux and isotopic composition of pb sinking on large particles was minor throughout the preanthropogenic and most of the anthropogenic era but has become important as surface inputs decrease to pre leaded gasoline levels and may exceed the contribution of surface derived pb flux in the next decade

isotopic evidence for the source of lead in the north pacific abyssal water national science foundation u s oce 0325031 oce 0325031 oce 0220978 oce 0321402 oce 0728930 and arc 0612538

deformation and metamorphism of the aileu formation north coast east timor and its tectonic significance abstract the large block of metamorphic rocks along the north coast of east timor is of special interest as it occurs at the boundary between continental and oceanic crust in an island arc continent collision zone a detailed study of the structure and metamorphic history of 400 km2 of this formation showed it has a complex history of penetrative deformation but the structure is coherent pelites psammites and limestones interlayered with dolerites and amphibolites have been metamorphosed in a medium pressure environment they now form a metamorphic province zoned from low greenschist facies in the southwest to upper amphibolite facies in the east the earliest recognised deformation phase predated the metamorphism and produced a widespread layer parallel schistosity but no recognisable folds the second deformation phase post dated the metamorphic maximum and micropetrological evidence indicates a gradual cooling during this event this deformation produced tight folds with an axial plane schistosity and transposed the earlier structures the progressively weaker third and fourth phases developed crenulation cleavages and related folds under greenschist facies conditions open fifth phase macroscopic folds were probably synchronous with strike slip faulting parallel to the north coast later dip slip faulting juxtaposed the aileu formation with permian and mesozoic sediments of very low metamorphic grade reconnaissance k ar radiometric dating using hornblende and biotite showed the prograde metamorphic maximum occurred before 11 ma ago and implies that the second and strongest deformation phase occurred in the late miocene this young age establishes the relationship of the deformation events to the collision between australia and the inner banda arc the proposed models for the structure of timor must be modified to fit the deformation history of the aileu formation if timor is essentially autochthonous the aileu formation was probably deposited in a palaeozoic graben and the metamorphic maximum may have occurred in the jurassic the overthrusting models must be modified in the light of the close correlation in time between penetrative deformation and emplacement of the proposed thrust sheets the analogy proposed between timor and normal convergent margins is not supported but it may be possible to draw analogies with the molucca sea

size fractionated major particle composition and concentrations from the us geotraces north atlantic zonal transect the concentration and the major phase composition particulate organic matter caco3 opal lithogenic matter and iron and manganese oxyhydroxides of marine particles is thought to determine the scavenging removal of particle reactive teis particles are also the vector for transferring carbon from the atmosphere to the deep ocean via the biological carbon pump and their composition may determine the efficiency and strength of this transfer here we present the first full ocean depth section of size fractionated 1 51 m 51 m suspended particulate matter spm concentration and major phase composition from the us geotraces north atlantic zonal transect between woods hole ma and lisbon portugal conducted in 2010 and 2011 several major particle features are notable in the section intense benthic nepheloid layers were observed in the western north american margin with concentrations of spm of up to 1648 g l two to three orders of magnitude higher than surrounding waters that were dominated by lithogenic material a more moderate benthic nepheloid layer was also observed in the eastern mauritanian margin 44 g l that had a lower lithogenic content and notably significant concentrations of iron and manganese oxyhydroxides 2 5 each an intermediate nepheloid layer reaching 102 g l an order of magnitude above surrounding waters was observed associated with the mediterranean outflow finally there was a factor of two enhancement in spm at the tag hydrothermal plume due almost entirely to the addition of iron oxyhydroxides from the hydrothermal vent we observe correlations between poc and caco3 in large 51 m particles in the upper 2000 m but not deeper than 2000 m and no correlations between poc and caco3 at any depth in small 51 m particles there were also no correlations between poc and lithogenic material in large particles overall there were very large uncertainties associated with all regression coefficients for mineral ballast carrying coefficients suggesting that mineral ballast was not a strong predictor for poc in this section

resolving spatial heterogeneities in exhumation and surface uplift in timor leste constraints on deformation processes in young orogens although exhumation and surface uplift are important parameters in understanding orogenesis the opportunity to measure both in close proximity is rare in timor leste east timor deeply exhumed metamorphic rocks and piggyback deepwater synorogenic basins are only tens of kilometers apart permitting direct relation of uplift and exhumation by comparing micropaleontology to thermochronology interpreted through one dimensional thermal modeling foraminifera in two deepwater synorogenic basins suggest basin uplift from depths of 1 2 km to depths of 350 1000 m between 3 35 and 1 88 ma thermochronologic sampling was conducted in the central mountain belt between these basins of four muscovite 40ar 39ar samples one provides a reset age of 7 13 0 25 ma in the aileu high grade belt that suggests 9 16 km of exhumation since that time eighteen zircon u th he samples contain a group of reset ages in the aileu complex ranging from 4 4 to 1 5 ma which suggest exhumation rates of 1 0 3 1 mm yr with 2 7 7 8 km of exhumation since these ages thirteen apatite u th he ages in the gondwana sequence range from 5 5 to 1 4 ma suggesting 1 2 km of exhumation and defining a pattern of exhumation rates ranging from 0 2 to 1 3 mm yr that positively correlates with average annual rainfall seven apatite fission track samples display varying degrees of partial resetting with greatest resetting where apatite u th he ages are youngest together these data demonstrate extreme variability in surface uplift and exhumation over small spatial scales we propose ongoing subsurface duplexing driven by subduction and underplating of australian continental crust as the predominant driver for surface uplift and uplift induced exhumation

elevated trace metal content of prokaryotic communities associated with marine oxygen deficient zones little is known about the trace metal content of marine prokaryotes in part due to their co occurrence with more abundant particulate phases in the upper ocean such as phytoplankton and biogenic detritus lithogenic minerals and authigenic mn and fe oxyhydroxides we attempt to isolate these biomass signals in particulate data from the us geotraces eastern pacific zonal transect cruise gp16 in the eastern tropical south pacific etsp which exhibited consistent maxima in p and other bioactive trace metals and minima in particulate mn in the oxygen deficient zones odzs of 13 stations nitrite maxima and nitrate deficits indicated the presence of denitrifying prokaryotic biomass within etsp odzs and deep secondary fluorescence maxima at the upper odz boundaries of 10 stations also suggested the presence of low light autotrophic communities odzs were observed as far west as 99 w more than 2300 km from the south american coast where eolian lithogenic and lateral resuspended sedimentary inputs were negligible presenting a unique opportunity to examine prokaryotic metal stoichiometries odz particulate p maxima can rival gyre mixed layer biomass concentrations are highly sensitive to oxygen and are in excess of amounts scavengable by local fe oxyhydroxides and acid volatile sulfides even after correction for lithogenic and ferruginous scavenged metals odz p maxima are often enriched in cd co cu ni v and zn exhibiting particulate trace metal ratios to p that exceed mixed layer biomass ratios by factors of 2 9 odz prokaryotic communities may be largely hidden tm rich pools involved in the marine cycles of these bioactive trace metals

the structural evolution of the timor collision complex eastern indonesia abstract the structural style of timor is consistent with foreland fold belt processes and zones of frontal accretion and underplating can be recognized in the australian parautochthonous sequence the parautochthon is overlain by an allochthonous sequence which corresponds to the pre collisional oceanic forearc in northern timor the parautochthon has been underplated directly beneath the allochthonous basement unlike previous interpretations of timor in terms of foreland fold belt processes the timor foldbelt is here interpreted as having evolved in a fairly straightforward way from the pre collisional forearc by the sequential addition of thrust slices of australian continental crust to the front and base of the developing collision complex

sunda banda arc transition incipient continent island arc collision northwest australia the eastern sunda arc represents one of the few regions globally where the early stages of continent arc collision can be studied we studied along the western limit of the collision zone at the sunda banda arc transition where the australian margin collides with the banda island arc causing widespread back arc thrusting we present integrated results of a refraction wide angle reflection tomography gravity modeling and multichannel reflection seismic imaging using data acquired in 2006 southeast of sumba island the composite structural model reveals the previously unresolved deep geometry of the collision zone changes in crustal structure encompass the 10 12 km thick australian basement in the south and the 22 24 kmthick sumba ridge in the north where backthrusting of the 130 km wide accretionary prism is documented the structural diversity along this transect could be characteristic of young collisional systems at the transition from oceanic subduction to continent arc collision citation shulgin a h kopp c mueller e lueschen l planert m engels e r flueh a krabbenhoeft and y djajadihardja 2009 sunda banda arc transition incipient continent island arc collision northwest australia geophys res lett 36 l10304 doi 10 1029 2009gl037533

stable lead isotopic ratios trace thermohaline circulation in the subarctic north atlantic abstract vertical profiles of lead concentrations in the subarctic north atlantic attest to the predominance of anthropogenic lead inputs to those waters while variations in their lead isotopic ratios 204 pb 206 pb 207 pb 208 pb show the multiplicity of those industrial lead inputs spatial gradients in the isotopic ratios are consistent with the thermohaline circulation of different water masses which seemingly have relatively discrete isotopic signatures these include characteristic 206 pb 207 pb ratios of the north atlantic drift 1 183 1 187 iceland scotland overflow water 1 173 1 176 denmark straits overflow water 1 179 1 182 and labrador sea water 1 190 1 120 based on parallels between these initial isotopic data and t s measurements it is proposed that stable lead isotopic compositions may be employed as complementary tracers of the mixing of source waters in the nordic seas as they overflow the iceland scotland ridge and denmark strait mixing into the labrador sea to form north atlantic deep water

pb and sr isotopic compositions of snowpack from quebec canada inferences on the sources and deposition budgets of atmospheric heavy metals elemental concentrations of al ba cd cu mg mn pb rb sr and zn as well as pb and sr isotopic compositions were determined in samples of snowpack obtained along two main transects from the province of quebec canada one north south between 47 n and 55 n 1994 and the other within the st lawrence valley 1997 median enrichment factors relative to upper crustal abundances for cd cu mn pb and zn for all samples range from 300 to 42 000 and are indicative of an anthropogenic origin pb isotope ratios for snow samples retrieved in 1994 are highly variable 206pb 207pb 1 148 to 1 193 and are characterized by the most radiogenic sr isotope values 87sr 86sr 0 710 in contrast the pb and sr isotope results for 1997 snow samples collected along the st lawrence valley below latitude 47 n yield the most radiogenic pb isotope ratios 206pb 207pb 1 180 to 1 190 and 87sr 86sr ratios between 0 708 and 0 710 the former indicate that the atmospheric pollution in this region of quebec is dominated by a mixture of anthropogenic emissions from u s 206pb 207pb 1 20 and canadian 206pb 207pb 1 15 sources pb isotope ratios 206pb 207pb 1 160 to 1 180 for 1997 samples collected north of latitude 47 n indicate input of an additional anthropogenic component possibly that of eurasian pollution being transported over the high arctic during the winter season a comparison of the pb isotope results between lichens and snow samples from identical sample locations indicate that these either overlap along st lawrence valley or are significantly different north south transect the latter discrepancy may be attributed to either 1 different time scales for the integration of the atmospheric signal months for snow vs years for lichens 2 recording of the atmospheric signal at substantially different altitudes or 3 the presence of an important local point source of atmospheric pollution annual depositional budgets have been estimated for pb cd zn cu and mn and average values g km 2 yr 1 are 1500 130 196 000 1900 and 6400 respectively compared to previous depositional fluxes 1993 1994 estimated from adjacent regions in north america those reported here are slightly lower with the exception of mn and zn the nondecrease in depositional fluxes of mn may be attributed to combustion of mn bearing fossil fuels by automotive vehicles the exact cause for the elevated annual depositional values for zn however remains enigmatic

mantle flow induced crustal thinning in the area between the easternmost part of the anatolian plate and the arabian foreland e turkey deduced from the geological and geophysical data abstract eastern anatolia consisting of an amalgamation of fragments of oceanic and continental lithosphere is a current active intercontinental contractional zone that is still being squeezed and shortened between the arabian and eurasian plates this collisional and contractional zone is being accompanied by the tectonic escape of most of the anatolian plate to the west by major strike slip faulting on the right lateral north anatolian transform fault zone natfz and left lateral east anatolian transform fault zone eatfz which meet at karliova forming an east pointing cusp the present day crust in the area between the easternmost part of the anatolian plate and the arabian foreland gets thinner from north ca 44 km to south ca 36 km relative to its eastern eahp and western sides central anatolian region this thinner crustal area is characterized by shallow cpd 12 16 km very low pn velocities

evidence for the jurassic arc volcanism of the lolotoi complex timor tectonic implications abstract we report the first sensitive high resolution ion microprobe shrimp u pb zircon ages with geochemical data from metavolcanic rocks in the lolotoi complex timor the zircon u pb ages of two andesitic metavolcanic rocks yield a permissible range of the middle jurassic extrusion from 177 ma to 174 ma the geochemical data indicate that the origins of the basaltic and andesitic metavolcanic rocks are products of prolonged oceanic crust and arc magmatism respectively they are originated from partial melting of lherzolites providing an insight into the tectonic evolution of the forearc basements of the banda volcanic arc thus parts of the banda forearc basement are pieces of allochthonous oceanic basalts and jurassic arc related andesites accreted to the sundaland during the closure of mesotethys and are incorporated later into the great indonesian volcanic arc system along the southeastern margin of the sundaland

water mass analysis for the u s geotraces ga03 north atlantic sections we present the distributions of hydrographic properties potential temperature salinity dissolved oxygen and micromolar level inorganic macronutrients along two sections occupied in the subtropical north atlantic as part of the first u s geotraces ga03 survey during 2010 and 2011 the purpose of this work is to place subsequent papers in this special issue in a general context and to provide a framework in which the observed distributions of trace elements and isotopes can be interpreted using these hydrographic properties we use a modified optimum multiparameter water mass analysis method to diagnose the relative contributions of various water types along the sections and rationalize their distributions the water mass compositions appear largely consistent with what is understood from previous studies about the large scale circulation and ventilation of the north atlantic with perhaps one exception we found that the north atlantic deep water both east and west of the mid atlantic ridge is more strongly influenced by iceland scotland overflow water relative to denmark straits overflow water about 3 1 than inferred from other tracer studies typically 2 1 it remains unclear whether this is an artifact of our calculation or a real change in deep water composition in the decades between the determinations

accretion of the southern banda arc to the australian plate margin determined by global positioning system measurements global positioning system geodetic measurements at thirteen locations in indonesia and four in australia reveal that the australian continent has accreted the banda island arc to its margin small relative velocities of five sites on west java south kalimantan bali and south sulawesi define a rigid sunda shelf that moves relative to northern australia in a manner consistent with pole locations from nuvel 1 australia eurasia but at a rate that is about 7 slower block like northward motion of the southern banda arc toward the sunda shelf at nearly the same rate as australia suggests that the timor trough is now inactive as a thrust little of the convergence of australia with eurasia is accommodated by strain within the banda arc structure most of the convergence appears to occur as northward translation of the rigid arc with shortening on the flores and wetar thrusts and possibly on faults within the back arc basin

210 po and 210 pb distribution dissolved particulate exchange rates and particulate export along the north atlantic us geotraces ga03 section vertical profiles of 210po and 210pb in the water column were measured in the dissolved phase 51 m particles at seven stations along the us geotraces north atlantic zonal transect ga03 mass balance calculations were employed to assess nuclide exchange rates at the dissolved small particle interface and between small and large particles and to quantify export with settling large particles in the surface ocean 210po scavenging is linearly correlated with the concentration of particulate organic carbon poc in large particles supporting the role of biogenic particle in 210po bioaccumulation and export in stations near the coast this link is more complex due to the variable source of biogenic material and temporal changes in the surface biogeochemical and physical conditions at depth 210po exhibits significant widespread deficit with respect to 210pb that could in part be attributed to in situ 210po scavenging and may be related to surface biological productivity as previously reported the 210pb scavenging rates in the surface ocean were higher at ocean margins at depth 210pb scavenging increases with depth and eastward due to the increase of adsorption sites available in the benthic layers and to a regional contribution of benthic 210pb scavenging and or particle flux respectively the benthic nepheloid layer bnl and the hydrothermal tag plume distinctly enhance 210pb scavenging due to increased surface adsorption in association with resuspended or freshly formed particles in contrast 210po is not seen to be significantly scavenged in these environments due to its relatively short half life and the long residence time of particles

blueschists eclogites and subduction zone tectonics insights from a review of late miocene blueschists and eclogites and related young high pressure metamorphic rocks abstract in this paper late miocene blueschist and eclogite belts including the world s youngest blueschist belt in timor tanimbar island chain eastern indonesia and the world s youngest coesite bearing eclogite papua new guinea together with selected cenozoic high pressure and ultrahigh pressure metamorphic rocks are reviewed from a synthesis of the geology metamorphism and chronology of these rocks the formation and exhumation process are evaluated and the significance on tectonics at convergent plate boundaries is discussed

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

rise and fall of the eastern great indonesian arc recorded by the assembly dispersion and accretion of the banda terrane timor abstract new age petrochemical and structural data indicate that the banda terrane is a remnant of a jurassic to eocene arc trench system that formed the eastern part of the great indonesian arc the arc system rifted apart during eocene to miocene supra subduction zone sea floor spreading which dispersed ridges of banda terrane embedded in young oceanic crust as far south as sumba and timor in timor the banda terrane is well exposed as high level thrust sheets that were detached from the edge of the banda sea upper plate and uplifted by collision with the passive margin of nw australia the thrust sheets contain a distinctive assemblage of medium grade metamorphic rocks overlain by cretaceous to miocene forearc basin deposits new u pb age data presented here indicate igneous zircons are less than 162 ma with a cluster of ages at 83 ma and 35 ma 40ar 39ar plateau ages of various mineral phases from metamorphic units all cluster at between 32 38 ma these data yield a cooling curve that shows exhumation from around 550 c to the surface between 36 28 ma after this time there is no evidence of metamorphism of the banda terrane including its accretion to the edge of the australian continental margin during the pliocene these data link the banda terrane to similar rocks and events documented throughout the eastern edge of the sunda shelf and the banda sea floor

lead concentrations in the northeast pacific evidence for global anthropogenic perturbations lead concentrations were determined by isotope dilution mass spectrometry in 34 surface and deep water samples collected in the northeast pacific between hawaii and california and off the california coast using a deep water sampler protected against fouling by contamination from the ship and hydrowire measured concentrations lie more than one order of magnitude below previously published open ocean values and they show that in most cases 90 or more of the total lead is in a dissolved form lead concentrations are about 10 fold higher in surface and thermocline waters than in deep waters values drop as low as 1 ng kg 5 pmol kg below 3500 m depth lead profiles thus appear different compared to those of most trace metals which show enrichment in deep waters compared to surface concentrations lead concentrations in surface waters increase from 5 to 15 ng kg 25 to 75 pmol kg along a transect starting from a location 200 km off the california coast and continuing towards the center of the north pacific gyre this increase is congruent with that observed for 210 pb concentrations in the same waters sampled at the same time lead is supplied to the open north pacific largely from the atmosphere at a rate of about 60 ng cm 2 yr which exceeds the prehistoric oceanic output flux of authigenic lead recorded in pelagic sediments about tenfold this excess originates from emissions from smelters and combustion of leaded gasoline overwhelming natural lead inputs that entered the ocean during prehistoric time probably largely through rivers vertical lead concentration profiles below the surface mixed layer are probably not in steady state there concentrations must be increasing in response to the increase of anthropogenic inputs because the estimated lead residence times are more than 20 years in the thermocline and about 80 years in deep waters based on an estimated 10 fold input and concentration increase since the mid eighteenth century in the surface mixed layer in the central northeast pacific it is calculated that the 10 ng kg average concentration between 100 and 900 m is 2 to 5 times larger and the 1 8 ng kg average concentration between 900 and 5000 m depth is about 2 times larger than it was in the mid eighteenth century profiles of lead concentrations in the north atlantic are expected to be shifted generally to larger values by a factor of 2 to 3 compared to those in the north pacific because of the effects of greater industrial lead contamination while lead concentration profiles in the south pacific are expected to be shifted generally to lower values compared to the north pacific by about this same factor because of the effects of lesser industrial lead contamination

temporal variability of lead in the western north atlantic consumption of alkyl leaded gasoline has decreased considerably in the united states over the last 15 years in order to evaluate the chemical response of the ocean to decreased atmospheric deposition of anthropogenic lead new 210pb and stable pb data have been obtained near bermuda june 1983 to december 1984 concentrations of these tracers in the mixed layer are highly variable during the period of observations 25 from june through september soluble eolian deposits accumulate in the shallow mixed layer because mixing and productivity are inhibited by the seasonal thermocline in the fall these enriched surface waters mix with upper thermocline waters and surface pb concentrations decrease in the winter storms from the east coast of north america cause local episodes of high pb and 210pb input into the ocean surface the resulting areally limited high pb concentrations are dispersed within less than 2 weeks by vertical and horizontal mixing pb 210pb ratios in surface waters are almost invariant over this period averaging 669 pmol dpm ranging from 564 to 718 pmol dpm surface pb 210pb appears to have declined by a factor of 2 since 1979 similar to the 2 6 fold decrease in u s leaded gasoline consumption during this period a substantial fraction on the order of 10 of gasoline pb is transported into the ocean pb concentrations in the upper thermocline may have declined by about 15 from 1979 to 1984 the helium tritium thermocline ventilation model of jenkins 1980 coupled with boundary conditions appropriate for pb and 210pb shows that the supply of pb and 210pb to the thermocline is dominated by lateral isopycnal ventilation the shape of the vertical profile is dominated by this physical ventilation near surface biological removal processes in situ scavenging and for stable lead time dependent input vertical transport by particles is responsible for minimal transport of dissolved lead into the upper ocean similar processes are likely to account for the plutonium maximum in the thermocline of the north pacific observations of pb and other reactive species in winter surface outcrops of thermocline isopycnals would provide valuable constraints on chemical processes within the thermocline

lead concentrations and isotopes in corals and water near bermuda 1780 2000 abstract the history of the oceanic anthropogenic lead pb transient in the north atlantic ocean for the past 220 yr is documented here from measurements of pb concentration and isotope ratios from annually banded corals that grew in coastal seawaters near bermuda and from seawater samples collected during the last 20 yr of the 20th century anthropogenic pb emissions in this area have been dominated by the industrialization of north america beginning in the 1840s the introduction of leaded gasoline beginning in the 1920s and its phase out that began in the mid 1970s the phase out of leaded gasoline was largely completed by the late 1990s coral pb concentrations occur at a constant low level of about 5 nmol pb mol ca 15 pmol kg in seawater from the late 1700s to 1850 from 1850 to 1900 there is a small increase rising to a plateau at 25 nmol pb mol ca 80 pmol kg in seawater in the 1930s until the late 1940s at which point pb concentrations rapidly increase to 60 nmol pb mol ca 200 pmol kg in seawater in the mid 1970s pb began to decline to 25 nmol pb ca 40 pmol kg in seawater by the end of the 20th century comparable to levels occurring in the early 20th century pb isotope ratios pb i r show maximum 206pb 207pb 1 21 and 208pb 207pb 2 49 in the middle of the 19th century we conclude that this signal is a reflection of the early dominance of upper mississippi valley pb ore in the united states as previously seen in the estuarine sediments of rhode island after 1900 pb i r decrease only slightly until the 1960s when there is a significant local maximum in the 1970s to 206pb 207pb 1 19 and 208pb 207pb 2 45 as low pb i r sources were phased out in the united states then as us leaded gasoline utilization decreased more rapidly than european pb gas utilization which has lower pb i r western north atlantic pb i r decreased to 206pb 207pb 1 17 and 208pb 207pb 2 44 their lowest values in the past two centuries

spatial and temporal evolution of lead isotope ratios in the north atlantic ocean between 1981 and 1989 29 68 w in the early 1980s 206 pb 207 pb ratios in the north african basin averaged 1 193 0 005 1 s similar radiogenic ratios within the level of analytical precision average 0 29 were found in the labrador and iceland basins 1 198 0 006 and in the norwegian sea 1 196 0 008 these radiogenic mixed layer signatures along with atmospheric global lead emission patterns suggest that most north atlantic lead in the early 1980s was derived from north american leaded gasoline samples in the east iberian basin near portugal and france showed lower 206 pb 207 pb ratios between 1 167 and 1 182 indicating a significant influence of less radiogenic atmospheric lead transported from europe and possibly the influence of the rio tinto acid mine drainage very close to shore in the gulf of cadiz pb across the entire north atlantic basin ranged between 54 and 145 pmol kg with the lowest values 54 74 pmol kg found at high latitudes 65 n in the late 1980s surface waters in the western subtropical north atlantic north american basin sargasso sea 47 w and in the eastern subtropical north atlantic north african basin central iberian basin 53 these elemental and isotopic results demonstrate the strongly variable isotopic and elemental signatures of north american and european lead throughout the north atlantic ocean frequently dominated by high 206 pb 207 pb and pb north

a dual doubly vergent orogen in the banda arc continent arc collision zone as observed on deep seismic reflection profiles new deep seismic reflection profiles across the banda arc of indonesia reveal reflectors in the uppermost 50 km of the lithosphere combined with existing earthquake hypocenter locations and focal mechanisms the new structural geometries inferred from the reflectors yield a more complete analysis of deformation during the past 10 m y and provide insights into how strain is partitioned across an orogenic belt in which volcanic arcs and continents converge a clearly defined wadati benioff zone and recent deformation of shelf sediments observed on older shallow seismic profiles indicated to previous workers that substantial convergence occurred at the timor trough a few focal mechanisms seafloor escarpments and recent geodetic surveying indicate that convergence at 7 cm yr 1 currently last 200 kyr occurs at the northern margin of the now inactive volcanic arc the wetar thrust zone reflectors on the new seismic profiles are interpreted as thrust faults and folds that occur throughout the crust and within the uppermost mantle between the timor trough and wetar thrust specifically basement reflectors beneath the toe of the accretionary complex have reverse sense offsets that imply blind thrusts the whole crust is horizontally shortened not only the sedimentary cover rocks that previously deformed into duplexes above a decollement reflectors dipping away from both margins of the forearc basin and at the northern margin of the volcanic arc are interpreted as evidence of thrusting thus each arc represents a doubly vergent fold and thrust belt but only the northern one is currently active crustal thicknesses inferred from seismic velocities reflectors and gravity anomalies are consistent with the merging of a thinned continental shelf margin with oceanic lithosphere to form an orogenic belt with at present 3 4 km of topographic relief in the region of eastern timor

response of lead cycling in the surface sargasso sea to changes in tropospheric input lead and its stable isotopes have been analyzed in surface water samples 0 600 m and trapped particles collected at the bermuda atlantic time series station u s joint global ocean flux study in april and november 1989 these results are compared with wet atmospheric lead deposition as determined from precipitation continuously collected in bermuda since august 1988 as pan of the atmosphere ocean chemistry experiment program despite an expected seasonal variability lead concentrations in surface waters have clearly decreased by 30 to 40 since 1979 in response to a corresponding decline by a factor of 5 to 8 of the tropospheric deposition this result is corroborated by stable lead isotope measurements with 206pb 207pb ratios which are significantly less radiogenic 1 18 1 20 in the first 500 m of the 1989 profile than those measured in 1984 1 20 1 21 this isotopic shift reflects changes of lead ore supply in the united states as well as a relative increase of the eurafrican contribution to lead input in the northwest atlantic that is likely due to the reduction of lead emissions from gasoline consumption in north america this fast response of lead to interannual variations of the tropospheric input into surface waters is related to its efficient bioreactivity as demonstrated with a sediment trap deployed at 150 m in april 1989 sediment trap results show the rapid penetration of lead into the first 200 m associated with large particles during a period of high plankton activity retrospective isentropic air mass trajectories in three dimensions coupled with the precipitation events collected in bermuda in 1988 1989 show that 30 to 40 of the annual lead deposition originates from the trade easterly meteorological regime this input is clearly evidenced with lead isotopic signals observed in surface waters 0 100 m in april and november 1989 we show that lead accumulated in the seasonal mixed layer 0 50 m reflects this atmospheric input taking into account the isotopic signal measured in this mixed layer 1 178 0 001 as well as the respective contribution of the temperate westerlies and trade easterlies to atmospheric lead deposition to the sargasso sea we calculate that the isotopic signature from the eurafrican regions is 1 155 0 004 based on these results we calculate that the actual 206pb 207pb average ratio in surface waters of the sargasso sea is 1 188 0 004

impact of anthropogenic pb and ocean circulation on the recent distribution of pb isotopes in the indian ocean abstract pb and pb isotope ratios in the modern ocean have been altered significantly by anthropogenic pb inputs over the past century most studies of anthropogenic pb in the ocean have focused on the north atlantic and north pacific oceans and the impact of anthropogenic pb inputs to the indian ocean and processes controlling the distribution of pb in the indian ocean are poorly known this study presents the pb and pb isotopic composition 206 pb 207 pb 208 pb 207 pb of 11 deep stations from the indian ocean japanese geotraces cruise kh 09 5 from the bay of bengal and arabian sea to the southern ocean 62 s the pb isotope ratios of the indian ocean range 1 140 1 190 for 206 pb 207 pb and 2 417 2 468 for 208 pb 207 pb with lower ratios appearing in the shallow waters of the northern indian ocean and higher ratios appearing in the deep layers of the southern ocean this result agrees with a previous study on pb concentrations echegoyen et al 2014 showing that the indian ocean particularly its northern part is largely perturbed by anthropogenic pb inputs 206 pb 207 pb and 208 pb 207 pb of the indian sector southern ocean are still lower than natural pb showing this region was also affected by anthropogenic pb anomalously low or high 206 pb 207 pb and 208 pb 207 pb were observed in the thermocline and shallow waters of the southern indian ocean and the arabian sea which are ascribed to water mass distribution e g subantarctic mode water and evolving pb isotope ratios of this region as dominant anthropogenic pb sources change 206 pb 207 pb and 208 pb 207 pb in the bay of bengal are higher than those in the arabian sea which might be the result of the anthropogenic pb inputs from different provenance or seawater exchanging pb isotopes with natural particles derived from rivers and or sediments at the basin boundaries

younger dryas in southernmost south america an update abstract high resolution pollen data from a peat section in southern tierra del fuego documents high paleoenvironmental variability between 11 ka and 9 ka detailed analysis of plant macro remains in the same section showed that the repeated high amplitude changes in pollen taxa were related to repeated fire disturbance burning at least once even the surface of the mire in many peat sections from southernmost patagonia and tierra del fuego charcoal particles have been found intermittently since about 13 ka and in great abundance especially after 11 ka this suggests that the environmental changes previously interpreted to imply a return to colder climates comparable to the north atlantic younger dryas event instead are in response to local and regional disturbances by fires

deformation and exhumation in timor distinct stages of a young orogeny abstract timor island in the outer banda arc bordering the timor sea preserves the orogenic product of an arc continent collision between the australian plate and the banda arc that commenced after 10 9 9 8 ma gts2004 but emerged above sea level only 3 1 ma ago the orogenic pile includes large tracts of material from the australian margin including the permian to middle jurassic gondwana megasequence and the late jurassic to early late miocene australian margin megasequence which occur in thrust slices in addition material from the banda arc side of the plate margin referred to as the banda terrane occurs throughout the island and includes both seafloor metamorphosed igneous material and cover sediments also in thrust sheets however the distribution of thrust slices is unclear in many areas perhaps because only the uppermost nappes of the thrust pile are currently emergent and also because the thrust piles have been disrupted by later high angle faulting evidence from east timor suggests that the major break between deformed pre collisional strata and the relatively undeformed overlying deposits was during the late miocene 9 8 5 5 ma we present evidence for the timing of three distinct phases of orogenic development as determined from east timor including initial collision and emplacement of the early nappes creating loading and diapirism within the 9 8 5 5 ma interval a tectonic quiet interval 5 5 ma 4 5 ma that extended for about a million years during the middle of the collision and may represent the time of locking of the subduction system and a post 4 5 ma phase of uplift unroofing and further diapirism in response to isostatic rebound our conclusions offer an alternative model for the evolution of this part of the banda arc

rates of neogene and quaternary tectonic movements in the southern banda arc based on micropalaeontology it is generally considered that the outer banda arc islands are composed in part of strongly deformed sediments that accumulated at the north australian continental margin the onset and completion of folding nappe emplacement imbrication and uplift that produced the islands of the outer banda arc have been dated by means of planktonic foraminifera the dating of the onset of uplift of timor from a deep submarine position at the end of the neogene nappe emplacement to mountains now reaching nearly 3 km high indicates the rate of post collision uplift to have been initially 3 mm yr then it slowed to about 1 5mm yr where the australian continental margin meets the eastern end of the present java trench there are indications that the australian margin has overridden the trench in the timor region by 240 km micropalaeontological dating of the neogene collision between the australian continental slope proximal rise and the trench provides constraints for checking the overriding hypothesis by calculating rates of convergence derived from plate motions 7 5cm yr against the rates based on the tectonic model 7 4cm yr after nappe emplacement possibly faster than 6 25 cm yr shortening of the continental crust appears to have migrated towards the australian continent so that the shelf itself has become involved in the imbrication with shortening of the cover rocks between the nappes and the present shelf edge amounting to about 40 km during the last 2 ma

cordierite bearing schists and gneisses from timor eastern indonesia p t conditions of metamorphism and tectonic implications in the boi massif of western timor the mutis complex which is equivalent to the lolotoi complex of east timor is composed of two lithostratigraphical components various basement schists and gneisses and the dismembered remnants of an ophiolite cordierite bearing pelitic schists and gneisses carry an early mineral assemblage of biotite garnet plagioclase al silicate but contain no prograde muscovite sillimanite occurs in a textural mode which suggests that it replaced and pseudomorphed kyanite at an early stage and some specimens of pelitic schist contain tiny kyanite relics in plagioclase textural relations between and mineral chemistries of ferro magnesian phases in these pelitic chists and gneisses suggest that two discontinuous reactions and additional continuous compositional changes have been overstepped possibly with concomitant anatexis as a result of decrease in pload during high temperature metamorphism the simplified reactions are garnet and or biotite sillimanite quartz cordierite hercynite ilmenite excess components p t conditions during the development of the early mineral assemblage in the pelitic gneisses are estimated to have been p 10 kbar and t 750 c based upon the plagioclase garnet al silicate quartz geobarometer and the garnet biotite geothermometer p t conditions during the subsequent development of cordierite bearing mineral assemblages in the pelitic gneisses are estimated to have been p 5 kbar and t 700 c with xh2o 0 5 based upon the fe content of cordierite occurring in the assemblage quartz plagioclase sillimanite biotite garnet cordierite coexisting with melt final equilibration between some of the phases suggests that conditions dropped to p 2 3 kbar and t 600 c a similar exhumation p t path is suggested for the pelitic schists with early metamorphic conditions of p 6 2 kbar and t 745 c and subsequent development of cordierite under conditions in the range p 3 4 kbar and t 600 700 c the tectonic implications of these p t estimates are discussed and it is concluded that the p t path followed by these rocks was caused by decompression during rifting and synmetamorphic ophiolite emplacement resulting from processes during the initiation and development of a convergent plate junction located in southeast asia during late jurassic to cretaceous time

world s youngest blueschist belt from leti island in the non volcanic banda outer arc of eastern indonesia abstract the timor tanimbar region constitutes part of the non volcanic outer banda arc of eastern indonesia here the world s youngest a type high pressure metamorphic belt crops out with different stages of evolution whereas an advanced domal uplift stage is seen in timor island the high pressure hp metamorphic belt is still in the first stage of tectonic extrusion on the eastern small islands of kisar leti moa sermata and laibobar the metamorphic rocks on leti are among the best exposed in the islands they are tectonically juxtaposed against overlying ultramafic rocks and underlying unmetamorphosed continental shelf sediments bound by normal and reverse faults respectively the leti metapelites display four progressive metamorphic zones chlorite biotite garnet chloritoid staurolite and kyanite zones with increasing grade zonation in leti metabasite unit is comparable and progressively changes from blueschist greenschist transition bs gs through epidote amphibolite ea to amphibolite am facies with increasing grade the highest grade metapelites and metabasites occupy structurally intermediate levels overprinting mineral relationships in bs gs transition schists indicate that decompression occurred from 5 5 7 kbar to the protoliths of leti metamorphic rocks are originally permo triassic the younger sediments and igneous rocks at the margin of the northward advancing australian continent entered the subduction zone immediately prior to the commencement of the banda arc australia collision in the pliocene burial reached a maximum depth of 30 35 km at the main stage of peak p t conditions and was related to the main stage of the collisional event slab break off at depth in the collision zone facilitated rapid uplift by wedge extrusion and active erosion during the exhumation stage the tectonic juxtaposition of the schist units at mid crustal levels and hydration may correspond to the final stage of barrovian overprinting which continued through transportation from depth the leti island belongs to the eastern portion of the world s youngest blueshist belt which has not yet entered the second stage mountain building and is slightly younger than the western timor which evolved to the extensive mountain building stage by doming

seeing a mountain in a grain of garnet the collision of continents which results in mountain formation takes place through subduction in which one slab of crust is pushed below another the rock that is subducted is put under high pressure and new mineral phases can form as discussed in the perspective by liou et al a report by darling et al in the same issue p 91 1 describes a low pressure mineral cristobalite that was found in high pressure rocks understanding how this low pressure form of silicate was created and preserved may lead to better understanding of the process of subduction and how deep material is brought to the surface 1 lookup doi 10 1126 science 276 5309 91

postcollision extension in arc continent collision zones eastern indonesia postcollisional extension superimposed on arc continent collision complexes is a common feature in the orogenic belts of eastern indonesia in the southern banda arc the arc continent collision event is essentially a pliocene and younger feature but already an element of extension is being superimposed on the compressional structures of the collision complex it is thus likely that the extension commences within a very short period 5 m y after the initiation of collision related compressional deformation a similar history of fold belt development immediately followed by extension can be inferred for the lengguru fold belt and the adjacent wandamen wondiwoi terranes of irian jaya and for the gulf of bone in sulawesi it is suggested that the extension results from decoupling of the subducting oceanic lithosphere from the unsubductable continental lithosphere and that the superimposition of extension is a virtually unavoidable consequence of the arc continent collision

buoyancy driven rapid exhumation of ultrahigh pressure metamorphosed continental crust abstract preservation of ultrahigh pressure uhp minerals formed at depths of 90 125 km require unusual conditions our subduction model involves underflow of a salient 250 150 km wide 90 125 km long of continental crust embedded in cold largely oceanic crust capped lithosphere loss of leading portions of the high density oceanic lithosphere by slab break off as increasing volumes of microcontinental material enter the subduction zone buoyancy driven return toward midcrustal levels of a thin 2 15 km thick low density slice finally uplift backfolding normal faulting and exposure of the uhp terrane sustained over 20 million years rapid 5 mm year exhumation of the thin aspect ratio uhp sialic sheet caught between cooler hanging wall plate and refrigerating downgoing lithosphere allows withdrawal of heat along both its upper and lower surfaces the intracratonal position of most uhp complexes reflects consumption of an intervening ocean basin and introduction of a sialic promontory into the subduction zone uhp metamorphic terranes consist chiefly of transformed yet relatively low density continental crust compared with displaced mantle material otherwise such complexes could not return to shallow depths relatively rare metabasaltic metagabbroic and metacherty lithologies retain traces of phases characteristic of uhp conditions because they are massive virtually impervious to fluids and nearly anhydrous in contrast h2o rich quartzofeldspathic gneissose schistose more permeable metasedimentary and metagranitic units have backreacted thoroughly so coesite and other uhp silicates are exceedingly rare because of the initial presence of biogenic carbon and its especially sluggish transformation rate uhp paragneisses contain the most abundantly preserved crustal diamonds

pb and sr isotopic evidence for sources of atmospheric heavy metals and their deposition budgets in northeastern north america concentrations of al ba cd cu mg mn pb rb sr and zn as well as pb and sr isotopic compositions were determined in samples of snowpack obtained during the 1998 winter season from northeastern north america median enrichment factors relative to upper crustal abundances for cd cu mn pb and zn for all samples range from ca 50 to 36 000 and are indicative of an anthropogenic origin the pb isotope ratios correlate with geographic location because snowpack from eastern ontario and the northeastern usa are characterized by the most radiogenic 206pb 207pb ratios ca 1 18 1 19 and these decrease systematically in an easterly direction towards the atlantic coast ca 1 16 the pb isotope data for the 1998 samples of snowpack indicate that atmospheric pollution in this region of north america is dominated solely by a mixture of anthropogenic emissions from us 206pb 207pb ca 1 20 and canadian 206pb 207pb ca 1 15 sources this result contrasts with that obtained for 1997 snowpack from similar geographic regions because the pb isotope data for the latter suggest the involvement of an additional anthropogenic component possibly that of eurasian pollution transported over the high arctic this difference in the distribution pattern of atmospheric pollution over northeastern north america between the 1997 and 1998 winter seasons may be related to the el nino phenomenon sr isotope data for all the 1998 snowpack samples define a large range in 87sr 86sr values but most are between 0 709 to 0 710 similar to the value of present day seawater ca 0 7092 however the majority of snowpack samples from eastern ontario are characterized by lower 87sr 86sr ratios 0 709 and these correlate negatively with their enrichment factors of pb such trends suggest the presence of a relatively unradiogenic source of anthropogenic sr possibly related to emissions from coal fired power plants located in the western and midwestern regions of the usa annual depositional budgets estimated from 1998 snowpack indicate that those for pb cd and cu are highest in eastern ontario and significantly lower in the remaining regions the former reflect a meteorological corridor in northeastern north america which coincides with heavily industrialized and densely populated areas depositional budgets of zn are extremely high in all areas investigated and their exact source s remains enigmatic these may reflect either an increase in atmospheric industrial emissions since the 1980s a lower residence time in the atmosphere or particular chemical speciation that affects the deposition of zn from the lower troposphere depositional budgets for mn are also high and may be related to the combustion of mn bearing fossil fuels by automotive vehicles

sediment discharge and export of fluvial carbon and nutrients into the arafura and timor seas a regional synthesis abstract the arafura and timor seas ats are a crucial link between the indian and pacific oceans and play a vital role in global ocean circulation and climate some high standing islands in the ats are globally significant sources of sediment here we derive a synthesis of river catchments and their role as sources of water sediment carbon and nutrients to estimate the pathways magnitude and fate of exported riverine materials the edge of the australian continental shelf and slope receives riverine sediment from asia as isotopes suggest a mixing of sediment sources with some overlap between the australian and non australian material including evidence of significant input of volcanic material from indonesia the catchments bordering both the arafura and timor seas account for 12 of sediment and 35 of water discharged from tropical asia northern australia discharges a volume of freshwater comparable to southwest new guinea but 50 65 of total sediment 754 mt dic 61 1 mt poc 7 9 mt doc 3 5 mt tn 2 88 mt and tp 254 264 t delivered annually to the ats come from new guinea the island of timor discharges much smaller amounts of water 170 km 3 yr 1 and sediment 133 mt yr 1 but area specific rates of dic 1150 t km 2 yr 1 poc 238 t km 2 yr 1 doc 94 t km 2 yr 1 tn 61 t km 2 yr 1 and tp 4 4 t km 2 yr 1 are higher reflecting very high rates of deforestation and land degradation compared to other tropical rivers carbon export into the ats is dominated by dic the ats catchments are being increasingly affected by human activities and material discharge to the continental margins will likely increase impacting shelf communities and highly diverse reef mangrove and seagrass habitats

deformation of the cablac mountain range east timor an overthrust stack derived from an australian continental terrace the cablac mountain range in central east timor comprises a thrust stack of gondwana megasequence rocks of mainly triassic to jurassic age this southerly directed thrust stack occurs in structural contact with the underlying lolotoi formation and both the lolotoi formation and the overlying gondwanan thrust stack appear to be structurally emplaced upon younger mid eocene units to the south in addition the cablac thrust stack is bound to the north by a high angle fault along which a crush breccia comprising clasts from both the gondwana megasequence and asian banda terrane occurs this interpretation of the cablac mountain range differs significantly from previous interpretations in which the cablac limestones were suggested to be massive miocene limestones that occurred in depositional contact with underlying units

middle jurassic radiolaria from a siliceous argillite block in a structural melange zone near viqueque timor leste paleogeographic implications abstract thin bedded siliceous argillite forming a large block within a structural melange zone at viqueque timor leste has yielded a middle jurassic late bathonian early callovian radiolarian assemblage belonging to unitary association zone 7 fifty five species are recognized and illustrated forming the most diverse radiolarian fauna yet documented from the jurassic of timor the fauna shows little similarity in species content to the few other assemblages previously listed from the middle or late jurassic of timor and also has few species in common with faunas known elsewhere in the region from rotti sumatra south kalimantan and sula based on lithofacies similarities and age the siliceous argillite succession in the melange block at viqueque is included in the noni group originally described as the lower part of the palelo series in west timor in terms of lithofacies the noni group is distinct from other stratigraphic units known in timor it may be associated with volcanic rocks but age relationships are uncertain although some of the radiolarian cherts in the noni group in west timor have been reported to include tuffaceous sediment the deep water character of the siliceous hemipelagite pelagite facies the probable volcanic association and an age close to that of continental breakup in the region suggest deposition in a newly rifted indian ocean in timor s tectonostratigraphic classification scheme the noni group is here placed in the indian ocean megasequence

cycling of lithogenic marine particles in the us geotraces north atlantic transect in this paper we present describe and model the first size fractionated 0 8 51 m 51 m water column particulate trace metal results from the us geotraces north atlantic zonal transect in situ pumping survey with a focus on the lithogenic tracer elements al fe and ti this examination of basin wide full depth distributions of particulate elements elucidates many inputs and processes some for bulk lithogenic material others element specific which are presented via concentration distributions elemental ratios size fractionation dynamics and steady state inventories key lithogenic inputs from african dust north american boundary interactions the mediterranean outflow hydrothermal systems and benthic nepheloid layers are described using the refractory lithogenic tracer ti we develop a 1 d model for lithogenic particle distributions and test the sensitivities of size fractionated open ocean particulate ti profiles to biotically driven aggregation disaggregation rates vertical sinking speeds and dust input rates we discuss applications of this lithogenic model to particle cycling in general and to poc cycling specifically

thallium isotope variations in seawater and hydrogenetic diagenetic and hydrothermal ferromanganese deposits results are presented for the first in depth investigation of tl isotope variations in marine materials the tl isotopic measurements were conducted by multiple collector inductively coupled plasma mass spectrometry for a comprehensive suite of hydrogenetic ferromanganese crusts diagenetic fe mn nodules hydrothermal manganese deposits and seawater samples the natural variability of tl isotope compositions in these samples exceeds the analytical reproducibility 0 05 by more than a factor of 40 hydrogenetic fe mn crusts have 205tl of 10 to 14 whereas seawater is characterized by values as low as 8 205tl represents the deviation of the 205tl 203tl ratio of a sample from the nist srm 997 tl isotope standard in parts per 104 this 2 difference in isotope composition is thought to result from the isotope fractionation that accompanies the adsorption of tl onto ferromanganese particles an equilibrium fractionation factor of 1 0021 is calculated for this process ferromanganese nodules and hydrothermal manganese deposits have variable tl isotope compositions that range between the values obtained for seawater and hydrogenetic fe mn crusts the variability in 205tl in diagenetic nodules appears to be caused by the adsorption of tl from pore fluids which act as a closed system reservoir with a tl isotope composition that is inferred to be similar to seawater nodules with 205tl values similar to seawater are found if the scavenging of tl is nearly quantitative hydrothermal manganese deposits display a positive correlation between 205tl and mn fe this trend is thought to be due to the derivation of tl from distinct hydrothermal sources deposits with low mn fe ratios and low 205tl are produced by the adsorption of tl from fluids that are sampled close to hydrothermal sources such fluids have low mn fe ratios and relatively high temperatures such that only minor isotope fractionation occurs during adsorption hydrothermal manganese deposits with high mn fe and high 205tl are generated by scavenging of tl from colder more distal hydrothermal fluids under such conditions adsorption is associated with significant isotope fractionation and this produces deposits with higher 205tl values coupled with high mn fe

use of stable lead isotopes to characterize the sources of anthropogenic lead in north atlantic surface waters stable lead isotopes are used to illustrate the impact of surface water circulation on dissolved lead distribution in north atlantic surface waters during oligotrophic conditions using stable lead isotopic signatures from 1 the sargasso sea and 2 direct tropospheric deposition to the north atlantic we estimate that 10 40 of the lead accumulated in surface waters of the european basin is transported from the western north atlantic by the north atlantic current south of 50 n lead appears to be primarily distributed by the subtropical north atlantic gyre that extends well beyond the western basins to 30 w in the north african basin at 30 40 n there are different lead isotopic signatures between the subtropical gyre to the guiana and western guinea basins which suggests that the inter tropical convergence zone acts as an efficient barrier limiting chemical exchanges between the gyre and the equatorial currents

provenance of permian triassic gondwana sequence units accreted to the banda arc in the timor region constraints from zircon u pb and hf isotopes abstract analysis of zircons from australian affinity permian triassic units of the timor region yield age distributions with large age peaks at 230 400 ma and 1750 1900 ma which are similar to zircon age spectra found in rocks from ne australia and crustal fragments now found in tibet and se asia it is likely that these terranes which are now widely separated were once part of the northern edge of gondwana near what is now the northern margin of australia the cimmerian block rifted from gondwana in the early permian during the initial formation of the neo tethys ocean the zircon age spectra of the gondwana sequence of ne australia and in the timor region are most similar to the terranes of northern tibet and malaysia further substantiating a similar tectonic affinity a large 1750 1900 ma zircon peak is also very common in other terranes in se asia hf analysis of zircon from the aileu complex in timor and kisar islands shows a bimodal distribution both radiogenically enriched and depleted in the gondwana sequence at 300 ma the magmatic event from which these zircons were derived was likely bimodal i e mafic and felsic this is substantiated by the presence of permian mafic and felsic rocks interlayered with the sandstone used in this study similar rock types and isotopic signatures are also found in permian triassic igneous units throughout the cimmerian continental block the permian triassic rocks of the timor region fill syn rift intra cratonic basins that successfully rifted in the jurassic to form the nw margin of australia this passive continental margin first entered the sunda trench in the timor region at around 7 8 ma causing the permo triassic rocks to accrete to the edge of the asian plate and emerge as a series of mountainous islands in the young banda collision zone eventually the australian continental margin will collide with the southern edge of the asian plate and these gondwanan terranes will rejoin

quaternary hinterland evolution of the active banda arc surface uplift and neotectonic deformation recorded by coral terraces at kisar indonesia abstract coral terrace surveys and u series ages of coral yield a surface uplift rate of 0 5 m ka for kisar island which is an emergent island in the hinterland of the active banda arc continent collision based on this rate kisar first emerged from the ocean as recently as 450 ka these uplifted terraces are gently warped in a pattern of east west striking folds these folds are strike parallel to more developed thrust related folds of similar wavelength imaged by a seismic reflection profile just offshore this deformation shows that the emergence of kisar is influenced by forearc closure along the south dipping kisar thrust however the pinnacle shape of kisar and the protrusion of its metamorphic rocks through the forearc basin sediments also suggest a component of extrusion along shear zones or active doming coral encrusts the island coast in many locations over 100 m above sea level terrace morphology and coral ages are best explained by recognizing major surfaces as mostly growth terraces and minor terraces as mostly erosional into older terraces all reliable and referable coral u series ages determined by mc icp ms correlate with marine isotope stage mis 5e 118 128 ka the only unaltered coral samples are found below 6 m elevation however an unaltered tridacna giant clam shell in growth position at 95 m elevation yields a u series age of 195 31 ka which corresponds to mis 7 this age agrees with the best fit uplift model for the island loose deposits of unaltered coral fragments found at elevations between 8 and 20 m yield u series ages of

role of oceanic circulation on contaminant lead distribution in the south atlantic abstract both the relatively high lead concentrations and their characteristic anthropogenic isotopic compositions attest to the widespread contamination of industrial lead in the western equatorial and south atlantic ocean spatial gradients in those isotopic signatures evidence the conservative lateral transport of lead in oceanic water masses while the discrete isotopic signatures in deep oceanic waters substantiate the complementary hypothesis that the release of lead from settling particles is relatively small on a decadal time scale specifically the relatively low radiogenic lead e g 206pb 207pb 1 148 0 009 in the lower north atlantic deep water l nadw south of 10 north is primarily attributed to us industrial lead emitted in the northern hemisphere prior to 1965 and the more radiogenic lead e g 206pb 207pb 1 180 0 006 in the upper north atlantic deep water u nadw is primarily attributed to subsequent industrial lead emissions in that hemisphere in contrast the relatively radiogenic lead e g 206pb 207pb 1 186 0 007 in the antarctic bottom water aabw seemingly reflects a mixture of natural and anthropogenic lead sources within the southern hemisphere and its isotopic dissimilarity with that e g 206pb 207pb 1 159 0 002 of antarctic intermediate water aaiw and the aabw may be due to differences in either their aeolian or water mass inputs

the transfer of bomb radiocarbon and anthropogenic lead to the deep north atlantic ocean observed from a deep sea coral abstract deep ocean c 14 pb concentrations and pb isotopes were reconstructed from a deep sea coral enallopsammia rostrata from 1410 m depth off of bermuda our high resolution time series is created from closely spaced radial cross sections with samples taken from the center of concentric coral growth bands that we show to be the oldest portion of the section prebomb radiocarbon ages from the coral demonstrate that the vertical growth rate of the coral is linear and the age of the coral is estimated to be 560 630 yr old based on the growth rate using this age model to reconstruct c 14 in deep seawater we first detect bomb radiocarbon at the coral growth site around 1980 and show that c 14 increased from 80 1 average 1930 1979 to a plateau at 39 3 1999 2001 pb ca of the coral ranges between 1 1 4 5 nmol mol during the 16th and 17th centuries and pb isotope ratios 206pb 207pb 1 21 208pb 207pb 2 495 in this period agree with pre anthropogenic values found in the pelagic sediments of the north atlantic ocean basin coral pb ca is slightly elevated to 6 2 0 9 nmol mol between the 1740s and the 1850s and then increases to 25 1 0 2 nmol mol in the 1990s the increase in coral pb ca is accompanied by a decrease in coral 206pb 207pb and 208pb 207pb indicating that the increase was caused by the infiltration of anthropogenic pb to the coral growth site comparing our data to the surface coral c 14 and pb records from bermuda reveals a time scale of tracer transport from the surface ocean to the coral growth site some characteristic features e g the bomb derived c 14 increase appear in the deep ocean approximately 25 yr later than the surface but the overall increase of c 14 and pb in the deep ocean is smaller and slower than the surface showing the importance of mixing during the transport of these tracers

absence of cooling in new zealand and the adjacent ocean during the younger dryas chronozone as the climate warmed at the end of the last glacial period a rapid reversal in temperature the younger dryas yd event briefly returned much of the north atlantic region to near full glacial conditions the event was associated with climate reversals in many other areas of the northern hemisphere and also with warming over and near antarctica however the expression of the yd in the mid to low latitudes of the southern hemisphere and the southwest pacific region in particular is much more controversial here we show that the waiho loop advance of the franz josef glacier in new zealand was not a yd event as previously thought and that the adjacent ocean warmed throughout the yd

climate space bioclimatic envelopes and coexistence methods for the reconstruction of past climates a method using australian beetles and significance for quaternary reconstruction abstract if quaternary palaeoclimatic reconstructions are to be adequately contextualised it is vital that the nature of modern datasets and the limitations this places on interpreting quaternary climates are made explicit such issues are too infrequently considered this paper describes a coexistence method for the reconstruction of past temperature and precipitation parameters in australia using fossil beetles it presents the context for quaternary palaeoclimatic reconstruction in terms of climate space bioclimatic envelope data derived from modern beetle distributions and the palaeoclimatic limitations of bioclimatic envelope based reconstructions tests in modern climate space using bioclimatic envelope data for 734 beetle taxa and 54 site based assemblages from across the continent indicate that modern seasonal especially summer temperatures and precipitation are accurately and in the case of temperature precisely reconstructed the limitations of modern climate space especially in terms of the limited seasonal variation in thermal regimes and subsequent lack of cold winters in the australian region renders winter predictions potentially unreliable when applied to the quaternary record

on the driving processes of the atlantic meridional overturning circulation because of its relevance for the global climate the atlantic meridional overturning circulation amoc has been a major research focus for many years yet the question of which physical mechanisms ultimately drive the amoc in the sense of providing its energy supply remains a matter of controversy here we review both observational data and model results concerning the two main candidates vertical mixing processes in the ocean s interior and wind induced ekman upwelling in the southern ocean in distinction to the energy source we also discuss the role of surface heat and freshwater fluxes which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state we conclude that both wind driven upwelling and vertical mixing are likely contributing to driving the observed circulation to quantify their respective contributions future research needs to address some open questions which we outline

a new petrogenetic grid for low grade metabasites abstract we have used internally consistent thermodynamic data to present calculated phase equilibria for the system na2o cao mgo al2o3 sio2 h2o ncmash in the range 0 500 c and 0 1 10 kbar involving the phases anorthite glaucophane grossular heulandite jadeite laumontite lawsonite paragonite prehnite pumpellyite stilbite tremolite wairakite zoisite with excess albite clinochlore quartz and pure water average activity terms derived from published mineral chemical data were included for clinochlore glaucophane prehnite pumpellyite tremolite and zoisite the new petrogenetic grid delineates stability fields and parageneses of common index minerals in zeolite prehniteactinolite prehnite pumpellyite pumpellyite actinolite blueschist and greenschist facies metabasites the stability fields of mineral assemblages containing prehnite pumpellyite epidote actinolite albite chlorite quartz were analysed in some detail using activity data calculated from five specific samples for example the prehnite actinolite facies covers a p t field ranging from about 220 to 320 c at pressures below 4 5 kbar the transition from the prehnite actinolite and pumpellyite actinolite to greenschist facies occurs at about 250 300 c at 1 3 kbar and at about 250 350 c at 3 8 kbar p t fields of individual facies overlap considerably due to variations in chemical composition

dynamic variability of dissolved pb and pb isotope composition from the u s north atlantic geotraces transect abstract this study presents dissolved pb concentration and isotopic composition distributions from geotraces ga03 the u s north atlantic transect pb in the ocean is primarily derived from anthropogenic sources and pb fluxes into the north atlantic ocean have been steadily decreasing following the phase out of alkyl leaded gasoline usage in north america and europe between 1975 and 1995 a compilation of dissolved pb profiles from three stations occupied repeatedly during the last three decades reveals a dramatic decrease in concentrations within the surface layers and the thermocline maxima although elevated concentrations greater than 60 pmol kg are still observed in the center of the north atlantic gyre where ventilation timescales are longer than at the western boundary the evolution of stable pb isotopes at these stations shows a shift from dominantly north american like composition in surface waters in the early 1980s towards a more european like composition in later years the most recent shallow signatures at the bermuda atlantic time series station bats show an even more recent trend returning to higher 206pb 207pb ratios after the completed phase out of leaded gasoline in europe presumably because recently deposited pb is more strongly influenced by industrial and incineration pb than by residual alkyl leaded gasoline utilization in surface waters trends toward a more prominent european influence are also found in the middle of the basin and toward the european coast coincident with higher concentrations of surface dissolved pb scavenging of anthropogenic pb is observed within the tag hydrothermal plume and it is unclear if there is any significant contribution to deep water by basaltic pb leached by hydrothermal fluids in the upper water column many stations along the transect show pb concentration maxima at 100 m depth coincident with a low 206pb 207pb isotopic signature that is typical of european emission sources although pb ores from the united states historically tend to carry 206pb 207pb signatures 1 17 hurst 2002 subsurface signatures as low as 1 1563 in 206pb 207pb were observed in this feature this signature appears to be carried westward within saline subtropical underwater stuw that ventilates from the central eastern part of the north atlantic subtropical gyre where the lowest surface isotope 206pb 207pb ratios are observed along the western boundary deep water masses of different ages carry distinct isotope ratios corresponding to their respective times of ventilation finally a low 206pb 207pb signature in bottom water along the eastern margin suggests that there may be some mobilization of european derived anthropogenic pb from recent surface deposits on the ocean floor

lead and aluminum in atlantic surface waters 50 n to 50 s reflecting anthropogenic and natural sources in the eolian transport lead and aluminum were measured with a 40 100 km resolution in surface water on two transects across the atlantic ocean one in may 1990 from cape town to the north sea the other in november 1990 from the north sea to the strait of magellan samples were drawn 14 m below surface at normal speed from a 2 m long snorkel system mounted on the bottom of the ship directly into a clean room area in the tropics both pb and al show maximum concentrations in the intertropical convergence zone itcz correlated with each other and with minimum salinities indicating wet deposition as their common source even in this area characterized by large inputs of mineral aerosols the pb al ratio shows that the major source of soluble lead 95 is anthropogenic at higher latitudes al is low throughout 10 20 nmol kg whereas enhanced pb values show the anthropogenic inputs off south africa northern argentina and especially western europe very low pb and especially al concentrations in the upwelling areas associated with the canary and benguela currents show that the enhanced biogenic particle fluxes cause an efficient scavenging of both lithogenic particles known to arrive here by dry deposition and of the adhering reactive trace metals

microearthquake seismicity and fault plane solutions related to arc continent collision in the eastern sunda arc indonesia the collision of australia with the eastern sunda and banda arcs of indonesia represents a modern example of the early stages of arc continent collision in order to obtain a more detailed view of the tectonics of the collision zone a microearthquake survey was conducted around the savu sea the region that encompasses the transition from subduction of indian ocean lithosphere on the west to collision or subduction of australian continental litho sphere on the east intermediate depth earth quakes were concentrated near pantar island the easternmost active volcano of the sunda arc and outline a northwest dipping zone that strikes n65oe from 70 to 150 km depth the seismic zone probably marks the western edge of the collision zone and its more northerly strike and the orientations of nodal planes from fault plane solutions indicate a 25 o bend in the subducted slab to a depth of at least 150 km because the convergence rate and the timing of collision from geologic observations on timor suggest that the oart of the slab now at 150 km depth was at the trench when australia first collided with timor we infer that continental crust or at least rifted continental margin crust caused the bend in the convergent margin and has been subducted to 150 km depth fault plane solutions of several events show nearly vertical nodal planes that trend parallel to the strike of the seismic zone along which a northwest side down sense of dis placement is indicated these events are concentrated at the southern top side of the seismic zone and suggest that the subducted lithosphere is presently detaching in the 50 100 km depth range beneath the eastern savu sea fault plane solutions for earthquakes within the upper part of the detaching slab 70 100 km depth have p and t axes whose trends lie parallel to the strike of the seismic zone and horizontal southeast trending b axes these earthquakes are interpreted as due to stresses caused by the bend in the subducting plate

water masses and currents in the upper tropical northeast atlantic off northwest africa recent current measurements in the tropical eastern north atlantic reproduce the components of the large scale flow field however the observations as well as the 1 12 flame model computations indicate that a lot of eddy scale variability is superimposed on the mean flow field despite of the disturbance by variability the signature of the guinea dome is well present in november 2002 the guinea dome transport from direct observations was about 2 8 sv above 25 8 kg m3 and 4 sv between 25 8 and 27 1 kg m3 the oxygen minimum in the shadow zone comprises the central water and the antarctic intermediate water aaiw layers and is located between the equatorial current system and the north equatorial current the north equatorial counter and undercurrents at 3 to 6 n are major oxygen sources for the central water layer of the low oxygen regions in the northeastern tropical atlantic a second northern north equatorial countercurrent nnecc band exists at 8 to 10 n the nnecc carries oxygen rich water from the southern hemisphere eastward but with an admixture of water from the northern hemisphere a float at 200 m depth was spreading eastward in the north equatorial undercurrent neuc at 28 w it shifted northward into the nnecc and then was trapped in the guinea dome region for more than 3 years the model indicates the region 22 to 32 w as the area of exchange between the necc neuc and the nnecc bands in the aaiw layer the northern intermediate countercurrent acts as oxygen source for the oxygen minimum zone

on going orogeny in the outer arc of the timor tanimbar region eastern indonesia abstract the timor tanimbar islands of eastern indonesia form a non volcanic arc in front of a 7 km deep fore arc basin that separates it from a volcanic inner arc the timor tanimbar islands expose one of the youngest high p t metamorphic belts in the world providing us with an excellent opportunity to study the inception of orogenic processes undisturbed by later tectonic events structural and petrological studies of the high p t metamorphic belt show that both deformation and metamorphic grade increase towards the centre of the 1 km thick crystalline belt kinematic indicators exhibit top to the north sense of shear along the subhorizontal upper boundaries and top to the south sense in the bottom boundaries of the high p t metamorphic belt overall configuration suggests that the high p t metamorphic rocks extruded as a thin sheet into a space between overlying ophiolites and underlying continental shelf sediments petrological study further illustrates that the central crystalline unit underwent a barrovian type overprint of the original high p t metamorphic assemblages during wedge extrusion and the metamorphic grade ranged from pumpellyite actinolite to upper amphibolite facies quaternary uplift marked by elevation of recent reefs was estimated to be about 1260 m in timor in the west and decreases toward tanimbar in the east in contrast radiometric ages for the high p t metamorphic rocks suggest that the exhumation of the high p t metamorphic belt started in western timor in late miocene time and migrated toward the east thus the tectonic evolution of this region is diachronous and youngs to the east we conclude that the deep seated high p t metamorphic belt extrudes into shallow crustal levels as a first step followed by doming at a later stage the so called mountain building process is restricted to the second stage we attribute this quaternary rapid uplift to rebound of the subducting australian continental crust beneath timor after it achieved positive buoyancy due to break off of the oceanic slab fringing the continental crust in contrast tanimbar in the east has not yet been affected by later doming a wide spectrum of processes starting from extrusion of the high p t metamorphic rocks and ending with the later doming due to slab break off can be observed in the timor tanimbar region

mechanism and tectonic implications of the great banda sea earthquake of november 4 1963 abstract the banda sea earthquake of november 4 1963 h 100 km mb 7 8 is probably one of the largest intermediate depth shocks to have occurred worldwide this century the mechanism of this earthquake is studied in detail on the basis of p wave first motion surface wave and aftershock data from the analysis of long period multiple surface waves a seismic moment of 3 1 1028 dyn cm is obtained which is the largest reported so far for any intermediate or deep focus shock this value together with the estimated fault area of 90 70 km2 gives an average dislocation of 7 0 m and a stress drop of 120 bar this event represents an oblique thrust movement on a plane with dip direction n170 e dip 48 and rake 52 a geometrical consideration for the fault plane and the configuration of the inclined seismic zone beneath the banda arc suggests almost definitely that the large scale faulting took place within the subducted plate and offset it further repetition of such large scale faulting might eventually break the subducted plate the 1963 banda sea earthquake thus represents a seismological manifestation of the large scale deformation of the subducted plate in the mantle

thermobaric structure of the franciscan complex in the pacheco pass region diablo range california examination of the thermobaric structure of jadeite glaucophane bearing franciscan rocks in the pacheco pass region of the diablo range show that they are subhorizontal and the structurally intermediate horizon has the highest metamorphic grade mineral parageneses of more than 700 metagraywackes plus 38 metagraywacke samples from up to 1200 vertical feet of drill core were examined modal compositions of about 100 metagraywackes were determined and more than 2600 microprobe analyses were completed to quantify compositions of jadeitic pyroxene from about 80 metagraywackes the jadeite jd zone is defined by the assemblage jadeitic clinopyroxene quartz pm albite lawsonite pm sodic amphibole pm aragonite this zone occurs at an intermediate structural position sandwiched between subhorizontal jadeitic clinopyroxene free albite ab zones transition zones occur both above and below the jd zone the jd zone covers an area 20 km wide and 400 m thick the nearly flat lying boundaries betwee

re evaluation of the cablac limestone at its type area east timor revision of the miocene stratigraphy of timor abstract the cablac limestone widely recorded in timor has its type area on cablac mountain where it was regarded as a lower miocene shallow marine carbonate platform succession the bahaman like facies placed in the cablac limestone are now known to belong to the upper triassic lower jurassic rather than the lower miocene on the northern slopes of cablac mountain a crush breccia formerly regarded as the basal conglomerate of the formation is now considered to have developed along a high angle fault separating banda terrane units of asian affinity from an overthrust limestone stack containing units belonging to the gondwana and australian margin megasequences the cablac breccia includes rock fragments that were probably derived locally from these tectonostratigraphic units after terrane emplacement and overthrusting clasts include peloid and oolitic limestones of the upper triassic lower jurassic derived from the gondwana megasequence deep water carbonate pelagites of the cretaceous and paleogene derived from the australian margin megasequence upper oligocene lower miocene te letter stage shallow water limestone derived from the banda terrane and a younger neogene calcarenite containing clasts of mixed tectonostratigraphic affinity there is no evidence for significant sedimentary or tectonic transport of clasts that form the breccia the clast types and the present understanding of the geological history of timor suggest that the crush breccia formed late in the plio pleistocene uplift history of timor it is not the basal conglomerate of the cablac limestone however the clasts of an upper oligocene lower miocene limestone found in the breccia suggest that a shallow marine limestone unit of this age either outcrops in the region and has not been detected in the field or has been eroded completely during late neogene uplift the clasts are similar in age and lithology to an upper oligocene lower miocene formation that unconformably overlies a metamorphic complex in the booi region of west timor similar to the lolotoi metamorphic complex banda terrane that is juxtaposed against the crush breccia of cablac mountain the cablac limestone at its type area includes a mixed assemblage of carbonate rock units ranging in age from triassic to plio pleistocene and representing diverse facies as a formation the name cablac limestone should be discarded for a cenozoic unit the upper oligocene lower miocene shallow water limestone unit that is typified by outcrops in the booi region of west timor and that has contributed to clasts in the cablac breccia is informally named the booi limestone it is considered part of the allochthonous banda terrane of asian affinity and represents the only shallow marine lower miocene unit known from timor the only other miocene sedimentary unit known from timor includes carbonate pelagites designated the kolbano beds probably deposited on an australian continental terrace at water depths between 1000 and 3000 m on the northeastern edge of cablac mountain oolitic limestone and associated units of the gondwana megasequence the kolbano beds of the australian margin megasequence and the booi limestone and associated metasediments of the banda terrane were juxtaposed by a plio pleistocene high angle fault along which the cablac crush breccia formed