neoproterozoic sedimentation and tectonics of the laurentian midcontinent detrital zircon provenance of the jacobsville sandstone lake superior basin usa and canada

the labradorian orogeny in the grenville province eastern labrador canada two minor intrusions within the hawke river terrane in the grenville province eastern labrador have upper intercept u pb ages as follows i for a megacrystic intermediate dyke and ii 1622 3 ma for a pegmatite dyke the upper intercepts date time of emplacement and the lower intercepts 508 and 320 ma respectively record the timing of early paleozoic events in the region a third sample a sillimanite bearing pelitic gneiss from the paradise metasedimentary gneiss belt in the hawke river terrane yielded a range of ages between 1647 and 1627 ma from seven single zircon analyses the zircons in the metasedimentary gneiss are interpreted as detrital because of their variation in morphology the range of ages obtained and their extreme variation in u content a detrital origin implies that the sedimentary protolith must have been deposited after 1627 ma and is therefore not the same age as morphologically similar metasedimentary gneiss that occurs as enclaves within pre 1670 ma migmatized quartz d

lithoprobe line 55 integration of out of plane seismic results with surface structure metamorphism and geochronology and the tectonic evolution of the eastern grenville province lithoprobe line 55 in the grenville province of eastern quebec provides unusually good control on the three dimensional 3 d geometry and structural relationships among the major lithological units there archean basement underlies the exposed proterozoic rocks along the entire seismic line and there is a lateral ramp in this basement immediately behind a lobate stack of thrust slices of high pressure metamorphic rocks comprising the manicouagan imbricate zone miz integration of the 3 d geometry with p t and geochronological data allows derivation of a tectonic model for the region the miz was buried to depths 60 km at 1050 ma preservation of its high pressure assemblages and the absence of metamorphism at 990 ma which is characteristic of lower pressure metamorphic rocks that tectonically overlie them indicates the miz rocks were rapidly unroofed early in the tectonic history there were two discrete pulses of crustal thickening during the grenvillian orogeny in this region the first inv

late labradorian metamorphism and anorthosite granitoid intrusion cape caribou river allochthon grenville province labrador evidence from u pb geochronology in the cape caribou river allochthon ccra metaigneous and gneissic units occur as a shallowly plunging synform in the hanging wall of the grand lake thrust system glts a grenvillian structure that forms the boundary between the mealy mountains and groswater bay terranes the layered rocks of the ccra are cut by a stockwork of monzonite dykes related to the dome mountain suite and by metadiabase amphibolite dykes that probably form part of the ca 1380 ma mealy swarm the mafic dykes appear to postdate much of the development of subhorizontal metamorphic layering within the lower parts of the ccra the uppermost least metamorphosed units of the ccra the north west river anorthosite metagabbro and the dome mountain monzonite suite have been dated at 1625 6 and 1626 2 ma respectively an amphibolite unit that concordantly underlies the anorthosite metagabbro and is intruded discordantly by monzonite dykes has given metamorphic ages of 1660 3 and 1631 2 ma granitoid gneisses that form the

surface ocean variability at galapagos from 1936 1982 calibration of geochemical tracers in corals a variety of geochemical tracers has been developed in reef corals as a means of reconstructing the natural variability of the tropical surface ocean over wide ranging time frames the purpose of this paper is to calibrate the performance of five of these tracers in a modern coral colony over an extended period a 47 year growth interval 1936 1982 in a colony of pavona clavus taken from san cristobal island galapagos islands was sectioned into 187 quarterly intervals and analyzed for 18o 13o ba ca cd ca and mn ca the resulting time series are compared with eastern pacific sea surface temperatures one of few instrumental data bases available for calibration over this time period linear least squares regressions of four of the tracers 18o 13o ba ca cd ca against peruvian sst show highly significant correlations p 0 0001 over the annual biennial and enso 3 8 years frequency bands cross spectral comparisons show even stronger coherency with sst frequently accounting for 70 80 of the variance in these tracers these results as well as the phase relationships determined from the spectral analyses suggest that the coupling between sst and 18o and the nutrientlike tracers ba and cd is controlled principally by seasonal upwelling cycles and interannual interruptions of these cycles brought about by el nino and anti el nino phenomena an inverse relationship between sst and 13c has its primary origins in the co occurrence of the warm sst phase with high light levels during the first half of the calendar year the association with sunlight derives from the photosynthetic response of algal symbionts which results in fractionation of light and heavy carbon isotopes between soft tissues and caco3 skeleton the fifth tracer the transition metal mn exhibits poorer correlations against both sst and the other tracers slight shifts in phasing of the historical mn ca annual cycle suggest that the general water column distribution of this tracer which is the reverse of a nutrient may not be stable the erratic behavior of mn illustrates how complex hydrography near galapagos may influence tracers with diverse source signatures

the michael gabbro and other mesoproterozoic lithospheric probes in southern and central labrador the michael gabbro 1426 ma and the shabogamo gabbro 1459 ma represent two iarge diabase intrusive episodes that affected the northwestern margin of the northeastern grenville province both have sustained variable effects of subsequent grenvillian metamorphism other broadly contemporaneous magmatic activity in the region includes the formation of elssnian anorthosite granitoid complexes 1 46 1 29 ga that intruded churchill province and nain province rocks to the north the harp dykes 1 27 ga and mealy dykes 1 25 ga petrologic and geochemical data show that the michael gabbro and shabogamo gabbro are similar with the latter displaying more cumulate rock characteristics and the former having compositions closer to those of rapidly cooled magma both have compositions comparable to those of other continental diabases and to some continental flood basalts sr and nd initial isotopic compositions of michael gabbro 1426 ma 4 7 to 6 0 1 1426 ma 8 7832 0 7w and shabogamo gabbro i459 ma 4 0 to 5 5 1 1459 ma 8 7020 0 7060 are alike and overlap suggesting similar sources and processes of development comparisons with other nearly contemporary mafic suites in central and southern labrador show that only the mealy dykes have a distinctly more radiogenic isotopic signature paradoxically other rnafic suites that intrude older basement rocks north of the grenville front have less enriched nd signatures than do those that intrude younger basement rocks south of the front the argument is made that the subcontinental lithospheric mantle and not crustal contamination played the most influential role in evoiution of the magmas

roots of the labradorian orogen in the grenville province in southeast labrador evidence from marine deep seismic reflection data marine deep seismic reflection data obtained as part of the eastern canadian shield onshore offshore transect ecsoot lithoprobe project from offshore southeast labrador are evaluated using geodynamic and gravity models and a tectonic interpretation is developed the geodynamic model explains the seismic reflection data in terms of doubly vergent tectonism resulting from southward directed underthrusting of mantle and lowermost crust middle and upper crustal seismic reflectors are considered to be proshears and retroshears and correlated through potential field data with major mylonite zones at terrane boundaries mapped onshore as there is little evidence of subsequent severe structural modification apart from strike parallel grenvillian dextral transpression which does not alter the crustal geometry along the line of the seismic transect the seismic reflectors are considered to represent labradorian structures inferred from onshore geochronological data to be mostly related to a 1665 ma labradorian accretionary event the southward directed underthrusting of the mantle and lowermost crust is consistent with existing models for southward labradorian subduction coast parallel gravity and magnetic anomalies are interpreted as an expression of a neoproterozoic to early phanerozoic extensional basin the existence of which had little effect on the underlying crystalline basement other than to downfault it relative to that exposed onshore

emplacement of the santa rita flat pluton as a pluton scale saddle reef comment and reply vines and law 2000 1 interpreted the jurassic santa rita flat pluton in the inyo mountains in east central california as a large scale saddle reef emplaced in the core of a broad south southeast plunging syncline this interpretation however is incompatible with the geometry and probable

emplacement of the santa rita flat pluton as a pluton scale saddle reef regional mapping indicates that the middle jurassic santa rita flat pluton exposed in the inyo range of eastern california is situated within the core of a south plunging synform defined by bedding in the surrounding metasedimentary wall rocks which dip beneath the pluton however bedding in rocks preserved above the pluton defines a south plunging antiform anisotropy of magnetic susceptibility analysis revealed that magnetic foliation within the pluton also defines a south plunging antiform and the accompanying magnetic lineation plunges subparallel to the axis of this antiform our data indicate that the pluton was initially intruded as a sill in the hinge zone of the enveloping synform subsequent vertical inflation of the sill resulted in upward doming of the overlying roof and formation of the antiform now observed at the current erosion level in the pluton and preserved roof rocks emplacement of the pluton at 164 1 5 ma u pb zircon age overlaps in time with regional thrust faulting and folding ca 185 148 ma recognized in the southern inyo range we speculate that space for initial emplacement of the pluton was produced during folding by layer parallel slip and hinge zone dilation producing a saddle reef like structure

evidence for a volcanic cooling signal in a 335 year coral record from new caledonia although volcanic cooling events have been detected in tree ring records their occurrence in marine records has received much less attention herein we report results from a 335 year oxygen isotope record 1657 1992 from a new caledonia coral indicating that as many as 16 interannual scale cooling events occur within 1 year of a volcanic eruption as determined by ice core records there are also pentadal decadal scale cooling events beginning in 1675 1813 and 1903 that immediately postdate volcanic eruptions however the interannual correspondences are complicated by the fact that some of the cooling events also coincide with el ninos which cause cooling in this part of the western south pacific if our conclusions are substantiated by further work occurrence of distinct volcanic cooling signals may enable refinement of coral chronologies by use of the event stratigraphic approach with the most promising correlation horizons being associated with the following eruptions 1808 unknown 1813 1821 several eruptions 1835 coseguina 1883 krakatau and possibly 1963 agung

daily banding in corals implications for paleoclimatic reconstruction and skeletonization abstract corals have the potential to record several centuries of highly detailed environmental information in the form of chemical proxies such as trace elements and stable isotopes massive corals commonly lay down density bands that are used as annual markers allowing time series records to be produced in addition montastraea faveolata a common caribbean coral species used for proxy records apparently erects its skeleton in two phases with a second phase of skeletonization producing micro scale banding that may reflect daily cycles of carbonate secretion while this raises the possibility of producing proxy records of daily environmental variation it also introduces uncertainty as we seek to sample at progressively finer scales until we better understand the mechanisms and timing of skeletonization a scanning electron microscope sem and backscattered electron imaging bei study of montastraea faveolata reveals that it produces a complex pattern of microbands three orders of magnitude smaller than the density bands commonly used for proxy records etched polished sections of coral skeleton show that the microbands consist of shingled aragonite crystallites oriented at high angles to the main axis of colony growth the microbands are 1 to 10 m in width and suggest a second phase of skeletonization that occurs later than the main axis of corallite extension individual imaged crystallites show a stepped increase in crystal breadth that could either be real or an artifact of sample preparation related to differential solubility bei analysis reveals that the bands of crystallites contain cyclical alternations of elemental abundance high resolution electron microprobe traverses 1 m beam diameter 1 m step size reveal that the elemental alternations are controlled at least in part by variations in sr ca within individual crystallites sr concentration in the microbands ranges cyclically between 9 800 and 10 800 ppm the microbands appear to fill in the pore space between thecae corallite walls and dissepiments corallite floors this secondary skeletonization process appears to be responsible for the production of the larger scale annual high density bands via destruction of pore space the possibility exists that the crystallite microbanding and the chemical alternation within it is driven by external cyclicity such as diurnal temperature variation if this is the case then the direction and timing of this microscale skeletonization could interfere with the collection of proxy data within the high density band the secondary skeletonization would likely cause blurring of the chemical signal and be responsible for chemical noise in proxy patterns produced by analytical techniques such as ion microprobe analysis as the resolution of analytical techniques improves these problems would likely be exacerbated on the other hand the possibility exists for extremely high resolution sampling within the high density band to reveal daily environmental variation and short lived pulse events presently difficult to detect in coral records it is also possible that the chemistry and fabric of the microbanding patterns could be used as an indicator of the degree of diagenetic alteration an important consideration as fossil corals are used increasingly to study paleoclimatic conditions

labradorian and grenvillian crustal evolution of the goose bay region labrador new u pb geochronological constraints major initial crust formation in the northeastern grenville province of labrador occurred during the labradorian orogeny 1710 1620 ma prior to re deformation in the grenvillian orogeny between 10

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

temporal and spatial variability of the oxygen isotopic composition of massive corals from the south china sea influence of the asian monsoon coral colonies of porites lutea and p lobata were collected from areas to the east and south offshore of hainan island south china sea oxygen isotope ratios o 18 o 16 were analyzed along the major axis of growth at a resolution of 25 28 samples within an annual band from three colonies giving data series lengths of 15 20 and 30 years coral delta o 18 correlates well with sea surface temperature sst throughout most years particularly when the asian winter monsoon prevails over the region due to the same seasonal phases of sst and sea surface salinity sss it is estimated that most of the seasonal features of coral delta o 18 are controlled by changes in sst with a significant contribution of sss this indicates the importance of temperature as determined by the asian winter monsoon as a control on seasonal coral delta o 18 variations in the south china sea given the fact that annual sss maxima show minor inter annual changes the inter annual change of annual coral delta o 18 maximum mainly reflects the sst induced by the winter monsoon while the coral delta o 18 is mainly controlled by sst deviations of the delta o 18 from sst correlate statistically with sea surface salinity particularly for summer extreme events when sst reaches its annual maximum with minor inter annual change therefore we suggest that the inter annual variation of the annual coral delta o 18 minima is mainly controlled by seawater composition seawater composition analysis indicates that its delta o 18 and salinity are simultaneously affected by freshwater inputs primarily from precipitation which is mainly supplied by the asian summer monsoon thus seasonal alternations of the winter and summer monsoon mainly control the coral delta o 18 thereby allowing reconstruction of these monsoonal variables the three coral records consistently reveal clear inter decadal trends in delta o 18 a gradual increase from 1968 to 1987 and a subsequent decrease from 1987 to 2003 these inter decadal trends are roughly consistent with salinity changes but not with temperature and precipitation suggesting that seawater composition controlled by freshwater inputs from distant source areas rather than from local precipitation is responsible for the trends in seawater composition and coral delta o 18 over the last 30 years comparison of the three coral records indicates that spatial variations in coral delta o 18 coincide with variations in seawater salinity and local precipitation but not with temperature this confirms the dominant role of seawater composition mainly controlled by monsoonal precipitation on the spatial variability of coral delta o 18 in the south china sea c 2006 elsevier b v all rights reserved

the lithoprobe abitibi grenville transect two billion years of crust formation and recycling in the precambrian shield of canada we summarize the results of lithoprobe studies in the neoarchean southeastern superior province and the mesoproterozoic grenville province in the southeastern precambrian shield of canada through two composite cross sections based on seismic reflection data which define dramatically different styles of crust formation and tectonic accretion in the neoarchean and mesoproterozoic in the neoarchean the structures at the surface are steep with discontinuous and flatter structures at depth much of the crust appears to be juvenile and the predominant process of crustal growth is inferred to have been subduction accretion of primitive crust in a prograding arc system in the mesoproterozoic surface structures are shallow and the seismic character of the crust is continuous over the entire cross section archean parautochthonous rocks and reworked archean crust comprise a very significant proportion of the preserved crust in the mesoproterozoic and provided the backstop to the grenvillian orogeny result

new insights on the 1 7 1 0 ga crustal evolution of the central grenville province from the manicouagan baie comeau transect abstract integrated field relationships and u pb geochronology of rocks exposed along the southern part of the manicouagan reservoir central grenville province quebec provide insights into protolith formation and thermal events that range in age from ca 1 7 to 0 9 ga and share common features with the rest of the grenville province and beyond from presently lower to higher structural levels main findings include the recognition of a ca 1 70 1 75 ga granitic magmatism and metamorphism in the southern part of the parautochthonous gagnon terrane correlative in age with late stages of magmatism in the makkovik orogen to the northeast b a ca 1 69 gabbro anorthosite suite island domain which is inferred to represent the southwesternmost exposure of labradorian crust in the central grenville province c a 1 4 ga volcaniclastic sequence and associated plutonic rocks canyon domain which based on lithological association and age is inferred to represent the nne extension of the montauban island arc and d a ca 1 2 ga bimodal felsic mafic volcanic to intermediate volcaniclastic sequence banded complex inferred to have originated in an intra continental rift system contemporaneously with the composite arc belt southwestern grenville province and with widespread extensional magmatism elsewhere in the canadian shield in addition 1 3 ga granitoid plutons are documented to intrude labradorian units at the nw boundary of canyon domain the significance of these plutons is ambiguous as they may represent either stitching plutons marking the accretion of the 1 4 ga canyon domain to the laurentian margin or the first stage in the development of the ca 1 2 ga continental rift system the hinterland units island domain canyon domain and banded complex were metamorphosed under medium pressure granulite facies conditions during the culmination of the grenvillian orogeny between 1 08 and 1 04 ga this metamorphism was accompanied by ca 1 07 ga a type granitic magmatism in canyon domain in addition locally abundant ca 0 98 ga late tectonic felsic pegmatite and ultrapotassic dykes occur in canyon domain this event is coeval with titanite ages documented in a wide range of units the data on the grenvillian evolution suggest mantle derived magmatism and associated metamorphism in the hinterland during both the culmination and the waning stages of the grenvillian orogeny

paleomagnetism of pre grenvillian mafic intrusions from the grenville province southeast labrador paleomagnetic results are reported for middle proterozoic layered intrusions and dykes from within the grenville province of coastal southeastern labrador rock units studied include the little gra

the importance of late and post orogenic crustal growth in the early proterozoic evidence from smnd isotopic studies of igneous rocks in the makkovik province canada abstract sm nd isotopic studies suggest that large tracts of 1900 1700 ma old crust in laurentia baltica is of juvenile origin this crust has generally been ascribed to arc magmatism sustained over long periods and most conceptual models for crustal growth emphasize this process the late to post orogenic granitoid rocks that areally dominate many ancient orogenic belts are commonly viewed as anatectic derivatives of the earlier arc type crust however in regions of short crustal residence the time resolution of isotopic tracers such as the sm nd system does not permit discrimination between this model and continued growth of the crust during post orogenic magmatism the relative contributions of recycled crust and new mantle derived material in late to post orogenic magmas can only be assessed where they also transect much older crustal blocks the nd isotopic signatures of 1800 1720 ma igneous suites in the makkovik province define such a boundary between an archean craton and a juvenile proterozoic domain in the juvenile domain the nd signatures of most igneous suites are equivocal initial nd 0 to 2 and they could be anatectic derivatives of slightly older orthogneisses however addition of new mantle derived material is documented by a type granites with initial nd up to 4 in the cratonic domain temporally and compositionally equivalent igneous suites mostly have initial nd of 7 to 3 significantly above local archean basement which has nd of 15 at 1800 ma conservative calculations suggest that most of these suites contain more than 50 new mantle derived material these results suggest significant crustal growth via late stage magmatism and direct interaction of mantle derived magmas and lower crustal rocks in contrast 1650 ma igneous suites lack clear systematic variation in nd and are interpreted as representing crustal growth via later distal arc type magmatism with crust mantle mixing mainly facilitated by sediment subduction crustal growth in this area thus involved significant addition of new material through late to post orogenic magmatism this process may partially explain the unusually high growth rates calculated for some segments of proterozoic crust which approach or exceed modern global arc addition rates this stage 3 crustal growth may have been proportionally more important in early earth history due to higher ambient mantle temperatures

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

crustal formation in the grenville province nd isotope evidence ninety eight new nd isotope analyses are presented for gneissic rocks from the grenville province when combined with over 250 published nd analyses and some unpublished analyses these data can be used to establish a first order crustal formation age map for most of the grenville parautochthon and allochthonous polycyclic belt in particular the geographic extents of a juvenile labradorian arc labradoria and a juvenile 1 5 ga arc quebecia are defined each with an area probably in excess of 100 000 km2 in addition pre 1 75 ga arcs are identified in ontario barilia and labrador makkovikia this work largely fills the last major gap in the continent wide crustal formation age map of the precambrian shield of north america

lithoprobe reflection studies of archean and proterozoic crust in canada abstract lithoprobe canada s national collaborative earth science research project established to develop a comprehensive understanding of the evolution of the north american continent is a multidisciplinary program spearheaded by seismic reflection studies five recently recorded seismic lines discussed in this paper are located in precambrian regions the mesoproterozoic grenville province the paleoproterozoic trans hudson orogen tho the paleoproterozoic archean basement of alberta and the archean superior province data acquired across the grenville orogen in eastern quebec show strong reflectivity throughout the crust upper crustal reflections can be correlated with exposed structural elements including extensional shear zones and packages of deformed high pressure rocks eclogites in a marine survey across the grenville orogen off southeastern labrador seismic images show variably dipping reflections and a structural high associated with a major gravity anomaly data acquired across central alberta show crustal scale thrust stacking and imbrication of the archean hearne craton to the east across the trans hudson orogen images of similar collisional features are observed geochronologic constraints indicate contemporaneity of tectonic activity between the two regions at 1 8 ga suggesting that collisional tectonic activity was coeval over a broad crustal region ca 1000 km across strike in the superior province seismic data across a collision zone involving the northern abitibi greenstone belt and the arc related opatica plutonic belt show spectacular crustal reflectivity and dipping reflections that extend 8 s 30 km into the mantle the latter feature is interpreted as representing a relict 2 69 ga old suture associated with subduction providing the first direct evidence that plate tectonics was active in the late archean these five examples supported by other lithoprobe results refute a number of generalizations about crustal reflectivity that have been made in the past and illustrate how reflection studies combined with other geoscience studies can lead to a better understanding of precambrian tectonics reflectivity persists throughout the crust there is no general separation into a poorly reflective upper crust and a reflective lower crust crustal reflectivity in archean and proterozoic regions is as pervasive as that in areas of more recent tectonism the precambrian reflection moho is generally well defined but shows a range of characteristics relative ages of reflectors can be discerned and tectonic significance can be attached to characteristic features of the crustal reflectivity

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

a revised model for the crustal structure of the sw grenville province ontario canada the grenville province forms the exhumed remnants of a 1 1 ga collisional orogeny that telescoped an older continental margin terranes with distinct crustal formation ages can be mapped using nd isotopes revealing a ramp flat thrust structure the ramp is identified by the presence of retrogressed eclogites and its trajectory is refined using nd model ages the main allochthon is locally overlain by the parry sound klippe but is also underlain by a tectonic duplex northwest directed nappes represent remnants of a corrugated thrust sheet but a ring shaped remnant was also preserved where the thrust sheet was down buckled under the dense rocks of parry sound domain

dating ductile deformation using u pb geochronology examples from the gilbert river belt grenville province labrador canada the gilbert river belt in the grenville province in southeastern labrador is a distinctive west northwest trending zone of locally intense deformation and voluminous granitoid plutonism up to 30 km in width in an attempt to directly quantify the timing of deformation in ductile shear zones within the belt rocks interpreted as having been intruded synchronously with ongoing deformation were sampled for u pb isotopic analysis three of these samples are 2 m wide granitic veins that have sharp intrusive contacts that truncate ductile deformation fabrics but are themselves deformed at metamorphic conditions similar to their host rocks and are therefore interpreted as having intruded after the initiation of deformation and fabric development but prior to cessation of this deformation the first vein is syntectonic with respect to amphibolite facies deformation and yielded a zircon age of the second vein intruded synchronously with the development of a zone of amphibolite facies straight gneisses wh

hydrology of lake eyre australia el nino link abstract all major ephemeral rivers of australia lie in the lake eyre basin dry for years on occasions they carry enormous floods with annual volumes of 40 km 3 and instantaneous discharges of the order of 30 000 m 3 s 1 mean annual runoff of the basin is 4 km 3 or 3 5 mm significantly less than the 57 mm for the whole of australia this paper examines lake eyre and its drainage basin describing the historical hydrology of the catchment both in terms of instrument records and inflows hindcast using a model based on the technique of coral fluorescence palaeohydrological reconstruction coral fluorescence is a function of nearby river discharge and can be used to reconstruct annual river outputs reconstruction coral fluorescence is a function of nearby river discharge and can be used to reconstruct annual river outputs beyond the instrument period the burdekin river catchment runoff history is strongly paralleled by the volumes of lake eyre inflows during the period of common reliable instrument gaugings the burdekin runoff data have been extended back to 1735 a d using the correlation between river discharge and annual growth band fluorescence in an old coral from pandora reef off the north queensland coast for the instrument period 1952 to 1980 73 of the variance between coral fluorescence and burdekin discharge is common during the period 1949 1980 41 of the variance between coral fluorescence and lake eyre inflow data is common modelled inflows to lake eyre for the period 1885 1948 are based on the latter data set

el nino southern oscillation events recorded in the stratigraphy of the tropical quelccaya ice cap peru snow accumulation measured during 1982 1983 on the quelccaya ice cap peru was 70 percent of the average from 1975 through 1983 inspection of 19 years 1964 through 1983 of accumulation measured near the summit of quelccaya reveals a substantial decrease 30 percent in association with the last five el nino southern oscillation enso occurrences in the equatorial pacific the enso phenomenon is now recognized as a global event arising from large scale interactions between the ocean and the atmosphere understanding this extreme event with the goal of prediction requires a record of past occurrences the quelccaya ice cap which contains 1500 years of annually accumulated ice layers may provide a long and detailed record of the most extreme enso events

lateral ramps as an aid to the unroofing of deep crustal rocks seismic evidence from the grenville province we suggest that lateral ramps in the basement to orogenic wedges may be important agents in the rapid unroofing of deeply buried continental crust our suggestion is based on a study of the distribution of high pressure metamorphosed continental rocks in the mesoproterozoic grenvillian orogen in eastern quebec these rocks were buried to depths of more than 50 km through crustal thickening during a continental collision and were then rapidly unroofed they are currently exposed in a 100 km 60 km lobate embayment north of the manicouagan reservoir using a combination of surface structural data and seismic reflection data from lithoprobe line 55 we reconstruct the three dimensional form of the high pressure rocks our reconstruct ion methods are based on demonstrable correlations between the attitudes of gneissic layering at the surface and the attitudes of reflectors on the seismic profile they make extensive use of the fact that much of the seismic reflectivity on line 55 comes from outside the vertical plane of the seismic line because of the sinuous nature of the line and its obliquity to tectonic strike the validity of the reconstructions is demonstrated by the generation of a synthetic seismogram from the interpreted geometry that is very similar to the observed seismogram our reconstruction shows that a steep lateral ramp extends to the base of the crust immediately behind the broad lobe of high pressure rocks at the surface the lateral ramp probably provided a favorable pathway for the extrusion of deep seated rocks from the deep crust and their transport onto the foreland

a group of rifting events in the terminal paleoproterozoic in the north china craton abstract rifting events of the terminal paleoproterozoic are well preserved in the north china craton they include an aulacogen and cratonic marginal rift basins mafic dyke swarms two anorthosite suites and rapakivi granites all of these events took place after metamorphism deformation and magmatism of the late paleoproterozoic between 2 0 ga and 1 85 ga or 1 80 ga the rifting events belong to an anorogenic event group reflecting breakup of a late paleoproterozoic united north china craton an intracratonic rift basin in the center of the north china craton is named the yanshan taihangshan aulacogen a stratigraphic thickness of 9193 m was deposited within the basin including three groups and twelve formations with time range ca 1 8 ga to 0 85 ga the oldest changcheng group of the sequence was deposited in a graben and is mainly composed of alluvial basal conglomerates terrestrial clastic rocks and shallow marine sandstone and carbonates with super high potassium basalt trachyte the marginal basins occur around the northern western and southern margins of the north china craton respectively located in langshan baiyun obo helanshan mountain and the adjacent regions between henan shanxi and shaanxi provinces the stratigraphic sequences of the basins are generally made up of clastic rocks in the lower parts and carbonates in the upper part with a thick volcanic sequence with u pb age of 1840 14 ma exposed in the southern marginal regions based on stratigraphic sequences isotopic data and volcanic features the initial rifts took place at about 1 85 ga to 1 80 ga mafic dyke swarms are largely developed in central parts of the north china craton where they intrude archean granulite and high amphibolite rocks a new single zircon u pb isotopic age of 1769 2 5 ma has been reported from a mafic dyke in east henshan mountain northwestern shanxi province an anorthosite suite agms is exposed along two deep fault belts in northern hebei province isochron ages of 1683 193 ma by rb sr and 1735 239 ma by sm nd were measured from an anorthosite body the rapakivi granites crop out along the miyun qiangzilu xinglong fault in an e w direction and are characterized by megacrysts of alkali feldspars mantled by plagioclase thus showing many of the petrographic features of classic rapakivi granites worldwide a typical rapakivi body preserved in shachang of miyun county beijing has a u pb age of 1716 31 ma super high potassium volcanics located in the upper changcheng group have been dated at 1683 67 ma and 1625 6 ma the time range for all magmatic events is between 1 72 ga and 1 62 ga

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

spatial correlations of interdecadal variation in global surface temperatures we have analyzed spatial correlation patterns of interdecadal global surface temperature variability from an empirical perspective using multi taper coherence estimates from 140 yr records we find that correlations between hemispheres are significant at 95 confidence for non randomness for most of the frequency band 0 06 f 0 24 cyc yr coherence estimates of pairs of 100 yr grid point temperature data series near 5 yr period reveal teleconnection patterns consistent with known patterns of enso variability significant correlated variability is observed near 15 year period with the dominant tele connection pattern largely confined to the northern hemisphere peak to peak t 0 5 with simultaneous warming and cooling of discrete patches on the earth s surface a global average of this pattern would largely cancel

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

carbon and oxygen isotopic composition of a guam coral and their relationships to environmental variables in the western pacific we examine the high resolution 32 samples year carbon and oxygen isotopic composition 13ccoral and 18ocoral in a coral core porites lobata from double reef guam over the years 1980 2000 the 13ccoral shows clear seasonal variations with mean seasonal amplitude of 1 89 which roughly corresponds with seasonal variations in solar radiation the seasonal amplitude of 18ocoral variations are small 0 23 0 57 but they are significantly correlated with sea surface temperature sst and salinity sss the 18ocoral and sst are more strongly correlated during el nino southern oscillation enso warm phases r 0 81 p 28 c and lower values of 18osw at guam these differences in oceanic parameters result from movements of the western pacific warm pool wpwp during the different phases of enso anomalies in 18osw inferred from the 18ocoral and instrumental sst are consistent with sss anomalies for the years 1980 2000 these 18osw anomalies may reflect changes in sss and evaporation precipitation due to movements of the wpwp this detailed analysis of a coral from guam suggests that it may contain an excellent archive of past enso events

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

u pb constraints for the plutonic and tectonometamorphic evolution of lake melville terrane labrador and implications for basement reworking in the northeastern grenville province abstract along the northeastern margin of the grenville province in canada crust of labradorian age 1 71 1 62 ga was variably reworked during northward present day coordinates propagation of the 1 20 1 00 ga grenvillian orogen to provide constraints on the nature of grenvillian reworking we describe previously unreported field relationships and present ten new u pb ages from a transect across lake melville terrane lmt which forms the leading edge of the allochthonous polycyclic belt in the study area exhumation of granulites on the northern margin of lmt along the rigolet thrust zone occurred during the interval 1617 1610 ma and was therefore a late labradorian feature approximately 120 m y after the labradorian orogeny during the interval 1489 1474 ma dioritic to granitic plutons inferred to be related to pinwarian 1 51 1 47 ga magmatism were emplaced in northern lmt this together with a revised u pb baddeleyite and zircon age of 1472 27 21 ma for the michael gabbro suggests that pinwarian ensialic arc magmatism was coeval with the emplacement of the michael and shabogamo gabbro dyke swarms the data also indicate that pinwarian magmatism was not limited to the pinware terrane but occurred throughout the entire grenville province in eastern labrador implying that the region was already accreted to the laurentian margin prior to the grenvillian orogeny the principal phase of grenvillian deformation and uppermost amphibolite facies metamorphism in lmt occurred between 1 08 and 1 05 ga and appears to have been focused between the rigolet shear zone and the anorthosite dominated mealy mountains terrane grenvillian amphibolite facies reactivation of the rigolet shear zone was limited to its upper structural levels only with the central and lower levels preserving labradorian fabrics and granulite facies assemblages high grade grenvillian deformation within lmt was dominated by tight to isoclinal folding and belt parallel transposition minor thrusting followed by localized strike slip shearing at the northeastern and southwestern margins

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

the chief lake complex revisited and the problem of correlation across the grenville front south of sudbury ontario abstract south of sudbury the boundary between the southern and grenville provinces the grenville front is placed along the faulted southeastern edge the ca 1 46 ga chief lake complex clc a southeast dipping thrust sense mylonite zone lies in the immediate hanging wall of the grenville front boundary fault gfbf separating the clc in the southern province from metasedimentary granitoid anorthositic and amphibolitic gneiss in the grenville province to the southeast the gfbf also coincides with an abrupt break in the continuity of southeast trending diabase dykes of the 1 24 ga sudbury swarm the northern clc is a composite intrusion whose units include and are separated by large rafts of the early paleoproterozoic huronian supergroup in which relict stratigraphy outlines engulfed folds mafic rocks along the northwest contact of the clc previously interpreted as metasomatized nipissing gabbro 2 22 ga are in fact a phase of the chief lake intrusive suite commingled with granite the northwest contact coincides in part with a steep southeast side down pre intrusion fault that was later reactivated with reverse sense of displacement the chief lake granitoid rocks become increasingly foliated southeast toward the grenville front but two features suggest that at least some of the deformation of the chief lake intrusive suite was syn emplacement 1 the granitoid component of commingled rocks may be strongly foliated in places where the mafic component is undeformed and 2 included huronian metasedimentary rocks in general lack the constrictional fabric of their enveloping plutonic rocks sudbury dykes cut across the fabric of the clc but the facts that they are themselves buckled locally metamorphosed to greenschist facies and are offset by faults marked by ultramylonite and cataclasite attest to tectonism of grenvillian age in the footwall for a limited distance northwest of the gfbf granitoid rocks dated at 1 74 and 1 47 ga southwest of the study area and archean tonalitic rocks and 2 47 ga anorthositic gabbro to the northeast occur on both sides of the grenville front in the study area units of paragneiss in the hanging wall of the gfbf cannot be assigned to specific huronian formations in the southern province footwall however although not proven it is reasonable to correlate other hanging wall rocks namely mylonitic gabbroic anorthosite amphibolite and granitic gneiss to the 2 47 ga east bull lake intrusive suite nipissing gabbro and chief lake granite respectively in the southern province whereas sudbury dykes do not intrude the mylonitic rocks immediately above the gfbf they do reappear to the southeast as dyke segments and pods within mylonite bounded panels where they cut earlier isoclinal folds and exhibit a progressive increase in metamorphic grade across a gradient shallower than that in the enclosing gneissic rocks they document that much of the tectonic history recorded by their host rocks is pre grenvillian even so there is no evidence that the grenville front was ever the locus of a suture

depositional and tectonic setting of the paleoproterozoic lower aillik group makkovik province canada evolution of a passive margin foredeep sequence based on petrochemistry and u pb tims and lam icp ms geochronology abstract the paleoproterozoic lower aillik group is a deformed metasedimentary metavolcanic succession located in the makkovik province of labrador eastern canada the group is situated near the boundary between reworked archaean gneiss of the nain north atlantic craton and juvenile paleoproterozoic crust that was both tectonically accreted and formed on or adjacent to this craton during the ca 1 9 1 78 ma makkovikian orogeny the lower aillik group is structurally underlain by archaean gneiss and structurally overlain by ca 1860 1807 ma bimodal dominantly felsic volcanic and volcaniclastic rocks of the upper aillik group we present geochemical data from metavolcanic rocks and u pb geochronological data from several units of the lower aillik group in order to address the depositional and tectonic history of this group u pb data were obtained using both thermal ionization mass spectrometry tims and laser ablation microprobe inductively coupled plasma mass spectrometry lam icp ms two quartzite units near the structural base of the lower aillik group contain detrital zircons only of archaean age and are interpreted to have been deposited on the nain craton during post 2235 ma rifting and initiation of a passive continental margin overlying mafic metavolcanic rocks contain thin horizons of intermediate tuff one of which is dated at 2178 4 ma this relatively old age and an inferred stratigraphic relationship with underlying sedimentary units suggest that the volcanic rocks represent transitional oceanic crust consistent with their geochemical similarity to tholeiitic rifted margin sequences of mesozoic age in eastern north america a package of interlayered psammitic and semipelitic metasedimentary rocks that appears to stratigraphically overlie the mafic volcanic unit is dominated by paleoproterozoic detrital zircons but also contains archaean grains this package was deposited after 2013 ma the age of the youngest concordant zircon the u pb data imply a minimum 165 m y time gap between mafic volcanism and sedimentation and are consistent with deposition of the psammite semipelite unit in an evolving foredeep that heralded the approach of a paleoproterozoic arc terrane accretion of this terrane to the nain cratonic margin at ca 1 9 ga initiated the makkovikian orogeny although the lower aillik group is highly deformed and may contain internal tectonic boundaries or be incomplete the u pb and geochemical data allow quantitative assessment of a prolonged rift drift basin closure cycle that characterized the early paleoproterozoic evolution of the southern nain cratonic margin

a multicentury stable isotope record from a new caledonia coral interannual and decadal sea surface temperature variability in the southwest pacific since 1657 a d a 335 year stable isotope record from a new caledonia coral 22 s 166 e helps fill a large gap in historical climate reconstructions although the long term coral 18o based sea surface temperature sst trend is one of warming there are notable decadal fluctuations especially in the early 18th and early 19th centuries mean annual ssts between 1658 and 1900 are estimated to be 0 3 c lower than the 20th century average with interdecadal excursions of 0 5 0 8 c time series analyses of the coral isotope record reveals significant concentrations of variance in the el nino band an inderdecadal spectral peak is present but its robustness requires additional statistical evaluation a secular but irregular decrease in coral 13c values begins in the mid 1800s and may reflect the anthropogenic perturbation of the carbon reservoir these and other results indicate that the new caledonia coral isotope record is a valuable source of information on southwest pacific climate history

proterozoic southward accretion and grenvillian orogenesis in the interior grenville province in eastern labrador evidence from u pb geochronological investigations abstract this study is a fascinating example from the eastern grenville province of unraveling the triple challenges inherent in the geochronological investigation of any multi orogenic region namely inheritance emplacement and subsequent metamorphism the existence of hitherto unknown pre labradorian crust within allochthonous grenvillian terranes is demonstrated formerly unrecognized spatial relations between labradorian and pinwarian crust are outlined and a new perception of mid grenvillian magmatic and metamorphic events is presented the pre labradorian crust has an age range of 1800 1770 ma and consists of calc alkaline plutonic rocks intruding earlier supracrustal assemblages containing archean and early paleoproterozoic inherited zircons evidence is provided from dated enclaves and inheritance in younger rocks that similar aged pre labradorian crust once existed farther south the geochronologically defined geographic extent of early labradorian crust having a 1680 1655 ma age range is expanded this crust is intruded by the mid labradorian mealy mountains intrusive suite for which new results confirm its 1650 1630 ma time of emplacement pinwarian orthogneiss dated between 1513 and 1496 ma and previously unknown in the region is now recognized to be common sufficient data exist to define for the first time a boundary between labradorian and pinwarian orthogneiss cryptic in the field establishing the presence of pinwarian aged crust to the southwest lacking labradorian inheritance except close to the boundary a belt of layered mafic anorthositic and monzogranitic intrusions is situated close to the boundary current data favour a pinwarian age for emplacement of these rocks mid grenvillian plutonism is demonstrated by 1043 ma ages from two k feldspar megacrystic granodiorite bodies they are situated on either flank of a crustal scale northeast trending northeast closing fold the fold which is 40 km wide and at least 160 km long and exposes pinwarian orthogneiss in its core post dates emplacement of the 1043 ma intrusions the fold probably formed at the peak of grenvillian tectonism in the region between 1030 and 1015 ma and certainly before intrusion of weakly deformed granitoid rocks at 992 ma final activity included the emplacement of late to post grenvillian granitoid plutons between 964 and 951 ma a pluton having a 951 ma age is the youngest known in the eastern grenville province cooling and stabilization was completed by ca 940 ma broader implications of the results in conjunction with existing data are that i the northeasternmost part of the eastern grenville province was only peripherally affected by grenvillian orogenesis ii an east northeast offshore extrapolation of the grenville front as a major tectonic feature does not exist iii high grade metamorphic mineral assemblages in the groswater bay and hawke river terranes are pre grenvillian rather than an eastward expression of a grenvillian high pressure belt and iv the north shore of the eastern st lawrence estuary represents across orogen exposure rather than orogen parallel as previously supposed

the southern oscillation part viii model sensitivity to sst anomalies in the tropical and subtropical regions of the south pacific convergence zone abstract we show by means of a general circulation model experiment that the atmospheric circulation over the south pacific ocean is sensitive to sea surface temperature anomalies in the tropical and subtropical regions of the south pacific convergence zone the possible implications for understanding the life cycle of an extreme event in the southern oscillation are discussed

proterozoic orogens of the northeastern canadian shield new information from the lithoprobe ecsoot crustal reflection seismic survey as part of the eastern canadian shield onshore offshore transect ecsoot lithoprobe acquired 1250 km of deep seismic reflection data along the coast of labrador and across ungava bay to image evidence of proterozoic crustal accretion to the archean nuclei of the nain and superior provinces of the canadian shield the relatively pristine archean crust of the nain province has low reflectivity and generally lacks systematic reflector orientations reworking of archean crust on the margins of the makkovik province has little effect on this weak signature in contrast the archean crust in the eastern churchill rae province appears to have been overprinted by a strongly developed whole crustal easterly dipping reflection fabric interpreted to result from proterozoic collision of the nain and superior provinces in the paired new quebec and torngat orogens juvenile proterozoic crust in the makkovik and grenville provinces also shows strong whole crustal dipping reflection fabrics interpretable as outw

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

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

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

metamorphic conditions and 40ar39ar geochronologic contrasts across the grenvile front zone coastal labrador canada the grenville front zone on the eastern labrador coast transects lower and middle proterozoic metamorphic and plutonic rocks and embodies elements of a protracted metamorphic history that involved two periods of pre grenvillian metamorphism onto which grenvillian effects were superimposed the earliest event minimum age 1 8 ga was a granulite facies metamorphism ca 650 750 c and minimum pressure between 4 0 and 6 0 kbar that occurred prior to emplacement of plutons of the benedict mountains intrusive suite bmis and produced the white bear islands granulite complex these rocks were subsequently affected by a progressive amphibolite facies retrogression from about 700 to 550 c at 5 kbar this event was synchronous with the intrusion and or deformation of the bmis which yields rb sr isochron crystallization ages of 1 7 1 8 ga hornblende within deformed units of the bmis north of the grenville front record 40ar39ar plateau ages of 1 66 1 64 ga interpreted to date cooling through temperatures needed for intracrystalline retention of 40ar following the pre grenvillian metamorphism following the intrusion of the michael gabbro ca 1 4 ga grenvillian orogenesis was superimposed on the area during the grenvillian orogeny the area was sliced into three thrust bound blocks which contain contrasting metamorphic mineral assemblages ranging from greenschist facies in the north to lower amphibolite facies maximum 560 630 c moderate pressures in the south collectively these represent a thrust induced telescoped metamorphic sequence precise 40ar39ar dating of individual grenvillian tectonothermal events in this area is precluded by the widespread incorporation of extraneous excess 40ar components within various mineral phases

paleomagnetism and geochemistry of carboniferous sandwich bay dykes from coastal labrador paleomagnetic petrographic and geochemical data are used to characterize a suite of dykes in the sandwich bay area south of cartwright labrador these dykes are carboniferous in age and their separate identity is indicated by the following i distinct paleomagnetic signatures ii homogeneous geochemistry iii cross cutting relations with other dated rock units in the area and iv a whole rock k ar date of 327 13 ma the dikes have a soft present earth9s field component superposed on a stable magnetization at d 325 5 i 26 9 n 14 k 91 6 95 4 6 with the corresponding paleopole at 16 2 n 157 6 e dp dm 2 8 5 2 the stable magnetization is shown to be primary from baked contact tests no kiaman overprint is present the paleopole determined for the dykes suggests emplacement of the dykes at equatorial latitudes during the carboniferous times

upb geochronology of labradorian and later events in the grenville province eastern labrador u pb dating of selected rock units in the hawke river and groswater bay terranes of the grenville province in eastern labrador has refined the timing of metamorphism and magmatism during the labradorian orogeny 1710 1620 ma in the northern part of the hawke river terrane a major migmatization event is confirmed between 1671 4 3 ma for a tonalitic gneiss and a newly determined age of 1662 3 ma for a granite dyke that cross cuts the migmatized fabric of its host this event can be correlated with similar coeval activities in the lake melville terrane to the south and labradorian thrusting at the grenville front in the paradise metasedimentary gneiss belt high grade metamorphism has been dated in two localities in pillowed mafic volcanic flows associated with the metasedimentary gneisses which produced new zircon growth at 1645 ma in a garnet amphibolite assemblage and in pegmatitic melt pods hosted in high grade pelitic gneiss at 1638 11 3 ma the time of this metamorphic event places a minimum depositional age on the supracrustal assemblage in the paradise metasedimentary gneiss belt that conflicts with a previously reported age for sedimentation at 1627 ma the 1645 ma metamorphic event was coeval with emplacement of a layered mafic intrusion 1644 2 ma in the groswater bay terrane a large granite body between the groswater bay terrane and the hawke river terrane 1645 7 5 ma which is a minimum age for juxtaposition of the two terranes but inferred from other data to be 1665 ma and leucogabbro from the white bear arm complex 1640 ma which is adjacent to the paradise metasedimentary gneiss belt the faulted contact between the white bear arm complex and the paradise metasedimentary gneiss belt is intruded by the 100 km long paradise arm pluton at 1639 2 ma indicating contact between the two domains at this time pegmatitic phases in the white bear arm complex indicate later magmatism at 1629 3 2 ma current geological models argue for accretion of terranes never widely separated at 1665 ma followed by crustal thickening and uplift between 1645 and 1639 ma deformation in the hawke river terrane during the pinwarian event ca 1500 1470 ma is suggested by complex data for monazite and baddeleyite from the white bear arm complex and from titanite data for rocks elsewhere in the hawke river terrane grenvillian metamorphic effects are present in the region but do not appear to have had a major impact

analysis of partially emerged corals and reef terraces in the central vanuatu arc comparison of contemporary coseismic and nonseismic with quaternary vertical movements in the central vanuatu arc living and recently deceased reef corals act as natural tide gauges which have allowed us to map vertical tectonic deformation patterns as corals grow the density of the aragonite coral skeletons varies on an annual cycle producing annual growth bands similar to tree rings using coral growth bands we can determine the year coral surfaces died due to emergence we interpret four major coral emergence events as coseismic uplifts that occurred near the epicenters and times of large shallow earthquakes on january 5 1946 ms 7 3 august 11 1965 ms 7 5 october 27 1971 ms 7 1 and december 29 1973 ms 7 5 the 1965 and 1973 events caused maximum uplifts of 120 and 60 cm respectively in the frontal arc also related to these events are uplifts of 10 cm and 6 cm in the back arc on pentecost and maewo islands which lie east of the volcanic chain and the primary forearc zones of uplift and subsidence similar secondary zones of uplift occurred with the great 1960 chile and 1964 alaska earthquakes the amplitude of these secondary uplifts is significantly larger than that predicted by models having a single fault in an elastic half space however the amount of secondary uplift is comparable to that predicted if the fault occurs in a plate of constant thickness overlying a viscoelastic half space at various places in 1957 1969 1970 1977 and 1978 1981 there was about 5 10 cm of emergence not associated with major earthquakes which may indicate nonseismic tectonic uplift however oceanographically lowered sea levels as in el ninos may have determined the times when corals died and recorded these events nevertheless the accumulation of emergence its persistence the limited geographic extent of each event and occurrence in areas of rapid holocene uplift suggest that the causes of the uplifts are tectonic these events suggest that in some areas a third or more of the total accumulated uplift in central vanuatu takes place as aseismic motion however in some areas we find only coseismic emergence in central vanuatu contemporary coseismic vertical deformation holocene uplift and topography have remarkably similar patterns this suggests that the mechanisms and processes causing vertical deformation have varied little over the last 106years apparently the topography structure and seismotectonics are controlled by the subduction of the d entrecasteaux ridge a major bathymetric feature underthrusting this part of the arc the influence of this ridge may have been especially extensive because it migrates very slowly along the arc trend and thus it interacts for a long time with a single portion of the arc system our previous studies of reef terraces indicated the existence of at least four seismotectonic arc segments or blocks along the santo malekula interval of the arc and our present results further support this conclusion each block has uplifted at different times by different amounts at different rates and tilted in a different direction boundaries between the north santo and the south santo segment and between the north malekula and the south malekula segment correlate with the north and south flanks of the d entrecasteaux ridge as does the absence of a physiographic trench west of santo

oxygen isotopic evidence for decrease in calcification rate of porites coral from the lakshadweep island abstract reef building corals are under tremendous physiological stress due to the changing climate and industrial pollution several studies have documented rapidly declining coral cover and reduced coral diversity in indo pacific regions the main threats to coral reefs are caused by increasing sea surface temperature sst and ocean acidification however land based sources of pollution in coastal regions can also contribute in rapid decline of coral cover we report here a significant decrease in calcification rate 10 15 in a scleractinian coral porites lutea collected from a lakshadweep kavaratti island in the southeast arabian sea our observation is mainly based on high resolution oxygen isotopic record and x radiography of coral to investigate seasonal changes a monthly scale sst record was developed by using oxygen isotopes the observed reduction in the calcification rate of porites coral from 1989 to 2003 a d is attributed to climate change and anthropogenic activity in the vicinity of coral growth this decrease in calcification rate is consistent with the decline in growth rate of genus porites from the great barrier reef gbr such a reduction in calcification of porites lutea appears to have been caused by the temperature stress ocean acidification and local environmental pollution however it is difficult to assign any one particular reason for the observed change

carbon isotopic records of middle holocene corals and environmental causes in northern south china sea two high resolution delta c 13 records of similar to 5 4 and similar to 4 4 ka coral colonies porites lutea from east coast of hainan island in the northern south china sea scs provide insights into the complex links between coral carbon isotopes and environment changes the delta c 13 of the similar to 5 4 ka coral offered a 40 year growth history with an average of 2 62 parts per thousand and amplitude of 2 96 parts per thousand the similar to 4 4 ka coral s revealed a 55 year growth history with an average of 3 12 parts per thousand and amplitude of 4 21 parts per thousand which revealed higher coral delta c 13 and increased seasonality in the middle holocene our analysis suggests that the higher coral delta c 13 was the combined result of higher radiation salinity and nutrient level and lower atmosphere co2 concentration which might increase coral delta c 13 through strengthening photosynthesis of symbiont zooxanthella in the context of kinetic and metabolic fractionations the increased seasonality was mostly produced by strengthened radiation the decreasing standard deviation of the similar to 5 4 ka coral annual delta c 13 revealed weakened interannual changes of atmospheric co2 salinity and nutrient by contrast the increasing deviation of the similar to 4 4 ka coral delta c 13 suggests strengthened interannual changes of these variables the similar to 5 4 ka coral delta c 13 showed a long term increasing trend at a rate of 0 33 increase y 1 which was attributed to natural decrease in atmospheric co2 and increasing salinity and nutrient level however the similar to 4 4 ka coral delta c 13 showed a long term decreasing trend at a rate of 0 25 decrease y 1 which was ascribed to unusual increase in atmospheric co2 and decreasing salinity and nutrient level c 2014 elsevier ltd and inqua all rights reserved

interannual and decadal variability of the western pacific sea surface condition for the years 1787 2000 reconstruction based on stable isotope record from a guam coral 1 we present a monthly resolved 213 year stable isotope time series from a coral from guam 13 n 145 e which is located on the northern edge of the western pacific warm pool oxygen isotopic composition of the coral skeleton 18ocoral shows seasonal interannual and decadal variability which documents significant oceanographic changes related to thermal and hydrologic variations in this region the 18ocoral anomaly reflects sea surface temperature sst anomaly and sea surface salinity sss anomaly with significant r values of 0 69 and 0 49 respectively which are strongly linked to oceanographic changes that occur during el nino southern oscillation enso warm and cool phases we identified 46 enso warm el nino and 53 cool phases la nina in the coral record which are consistent with those phases reconstructed by nino 3 4 sst anomaly spectral analyses of the 18ocoral anomaly record for the years 1790 1999 identified significant peaks around 3 to 7 years these results indicate that the guam coral has recorded enso periodicity the 18ocoral anomaly shows decadal variability of 15 to 45 year periodicity with significant shifts 0 2 from warmer to cooler condition and vice versa an accumulative decrease in 18ocoral time series may imply 0 75 c warming of sst and 0 23 freshening of seawater 18o corresponding to a decrease of sss by 0 85 in the northwestern tropical pacific over the last 2 centuries

origin of the south pacific convergence zone abstract the importance of the presence of south america and australia to the existence and orientation of the south pacific convergence zone spcz during january is explored using the ecmwf t21 model each of the continents is removed from the model and replaced with an ocean surface and the resulting precipitation and circulation associated with the spcz are then compared to a perpetual january control run results show that the presence of south america and the equatorial pacific upwelling zone does not appear to be crucial to the spcz but that the removal of australia destroys the southern monsoon and substantially weakens the western part of the spcz this suggests that the northwest southeast orientation of the spcz during southern summer is more dependent on interactions with the midlatitude westerlies over the south pacific than on the distribution of sea surface temperature and land over the southern hemisphere

rates of processes in magmatic arcs implications for the timing and nature of pluton emplacement and wall rock deformation abstract the construction of arcs and in many cases the emplacement of plutons occur in tectonically active regions it is critical therefore to evaluate the rates of structural and magmatic processes when trying to understand the evolution of arcs and the associated pluton wall rock systems our best estimates of average rates or durations of processes in shallow to moderate level arc environments are the following 1 crystal growth rates in magma of 10 4 cm year 1 2 growth rates of metamorphic porphyroblasts between 10 5 and 10 2 cm year 1 3 long term magma supply rates of 10 1 km 3 year 1 and short term rates of up to 350 km 3 year 1 4 diapiric ascent rates for mafic plutons of 1 3 m year 1 5 cooling of plutons to ambient wall rock temperatures in 10 5 10 6 years 6 final crystallization of plutons in a small fraction of the time needed for complete cooling 7 fault displacements of 3 cm year 1 8 development of cleavages in fault zones in less than 10 6 years at strain rates of 10 13 s 1 or higher and 9 the development of regional cleavages in 10 6 years at strain rates of 10 14 s 1 these rates indicate that processes operating in magmatic arcs are relatively rapid pluton emplacement cleavage development etc occur over time spans of tens of thousands to no more than a few million years however the rate of ascent and crystallization of plutons at shallow levels is generally shorter than that needed to get large displacements on faults or widespread cleavages developed at deeper levels or in zones undergoing faster strain rates the time spans of the various processes approach one another thus plutons with otherwise similar characteristics emplaced in regions undergoing fast strain rates or at deeper crustal levels may appear quite different structurally from those emplaced at shallow levels or in regions undergoing slower strain rates comparison of these data also suggests that the rate at which wall rock deforms is the limiting factor controlling the rates of other structural processes during emplacement of plutons unless fast strain rates or multiple deformation mechanisms are considered thus emplacement mechanisms that rely on the transport of magma over 10 5 to 10 6 years are favored and need further consideration finally we argue that the structural and other characteristics of pluton wall rock systems will depend on rates of various processes involved and that these rates at the very least influence and sometimes invalidate the timing criteria previously published by us and others

wide angle seismic imaging of pristine archean crust in the nain province labrador a detailed refraction wide angle reflection seismic experiment was carried out in northern labrador to determine the velocity structure of relatively unaltered archean crust in the nain province six 3 component land seismometers were used to record an airgun source along a profile parallel to the coast forward modeling of traveltimes and amplitudes yields a p and s wave velocity model that shows two crustal blocks separated by a fault magnetic data suggest but do not prove that the fault is the offshore continuation of the handy fault a southwards thickening of the lower crust across the fault indicates that a transcurrent component might have been associated with the faulting the total crustal thickness is 33 km to the north and 38 km to the south of the fault the presence of pms reflections imply a sharp transition at the moho upper crustal velocities of 5 8 6 3 km s and poisson s ratios of 0 20 and 0 24 north and south of the fault respectively are consistent with a gneissic composition

continuous reef growth during the last 23 cal kyr bp in a tectonically active zone vanuatu southwest pacific abstract at urelapa island vanuatu sea level rise and a tectonic uplift of 3 mm yr 1 have controlled water depth and the colonization and reef development on a substrate from 23 until 6 cal kyr bp analysis of coralgal assemblages offers insights on the mode of reef growth and on water depth over the reef for the studied period those assemblages precisely dated by the 230 th 234 u method give valuable information on the rate and timing of sea level rise since the last glacial maximum the urelapa reef sequences are characterized by upwards replacement of reef frameworks which indicates changes in wave energy through time the sudden acceleration of sea level rise associated with meltwater pulse 1b at around 11 3 cal kyr bp is marked by a change in reef growth strategy from a keep up mode to a catch up mode we examine the delay in timing of the occurrence of suitable substrates the role of paleoceanographic factors and the influence of possible jumps in sea level

seasonal growth bands in famennian rugose coral scruttonia kunthi and their environmental significance abstract large colonies of rugose coral scruttonia kunthi occurring in the upper famennian of sudetes southern poland reveal distinct growth banding in their skeletons they were investigated for internal structural characteristics and stable isotopic composition the skeletal tissue consists of alternating light and dark bands which differ in thickness density and morphology of structural elements and in occurrence of corallite contraction and rejuvenescense darker parts with densely arranged thick skeletal elements are thin in comparison to lighter parts in addition they include frequently offsets and contraction of corallites a couplet of dense and less dense bands is interpreted to represent most probably an annual cycle the calculated growth rate for scruttonia kunthi varied from 6 mm yr to 12 mm yr growth band formation was influenced environmentally oxygen isotopic data provide an evidence that high density bands were formed in the season of higher environmental stress with relatively warmer temperatures and higher sedimentation rates carbon isotopic signatures are very uniform and thus enigmatic they indicate that at least growth rate of the skeleton and seawater temperature had no influence on the coral 13 c

crustal evolution in eastern labrador constraints from precise u pb ages abstract new u pb ages for rocks of eastern labrador complement previous u pb dates for the grenville and makkovik provinces and substantiate the following conclusions eastern labrador consists of two distinct crustal blocks that are different in age as well as magmatic metamorphic and structural overprint the northern block includes archaean to lower proterozoic basement rocks 1900 ma and two distinct episodes of rhyolitic volcanism at 1860 and 1807 ma high grade metamorphism deformation and anatexis affected this block between 1860 and 1760 ma ago makkovikian orogeny the southern block comprises the trans labrador batholith and the various terranes of the grenville province in contrast to the northern region the southern block shows no proof for the existence of continental crust older than 1710 ma this suggests that large amounts of juvenile material were added between 1710 and 1630 ma ago as dated by a large series of precise rock ages at least towards its end this crust forming event was associated with high grade metamorphism deformation and anatexis labradorian orogeny the 1710 1630 ma period of activity was followed by three distinct phases of anorogenic plutonism causing the emplacement of pegmatites 1500 ma a widespread suite of cotonitic metagabbros michael gabbro 1426 ma and granitic syenitic bodies 1296 ma during the grenvillian orogeny the region achieved its present structural configuration including the emplacement of granitoid plutons the structurally highest regions the mealy mountains and the hawke river terranes were thrust over the lake melville terrane and part of the groswater bay terrane and they were only marginally affected by grenvillian metamorphism the more deeply buried lake melville and groswater bay terranes however were significantly modified during tectonothermal events at 1030 ma and 980 960 ma respectively

the effect of colony topography on climate signals in coral skeleton the stable oxygen isotope composition of the aragonitic skeleton of hermatypic corals is a potential archive of paleotemperature and rainfall data biological processes also influence coral 18o although it has been difficult to determine which processes are involved and whether or not they dominate the stable isotope signal we show here that colony topography or surface bumpiness is associated with significant differences in 18o 13c and the timing of high density band formation between same age corallites in the central and fastest growing region of a coral colony these differences reflect changes experienced by individual corallites as they grow from the summit of a bump toward the bottom of a valley corallites on the bump record isotopic temperatures more than 1 c higher and accrete high density skeleton about 2 months earlier than their valley counterparts just 20 mm away we propose that these changes are not caused by corallite aging but rather by changes in the overall rate and timing of light enhanced calcification which is lower and occurs later in shaded valleys than it does on exposed bumps although we conclude that sea temperature is the dominant influence on 18o values in our coral our results show that significant isotopic variations may be expected over a small surface area in a single colony the production of accurate and reproducible coral based climate records thus requires an understanding of the complexities of coral growth processes and incorporation of this knowledge into sampling strategies and interpretation of data