a late cretaceous turonian ichthyofauna from lac des bois northwest territories canada with paleobiogeographic comparisons with turonian ichthyofaunas of the western interior seaway a fish fauna from a turonian sequence of the great bear basin at lac des bois is described the fauna includes examples of ichthyodectes cf osmeroides a euteleost and several aulopiforrn fishes such as enchodus cimolichthys and a juvenile that cannot be further identified the fauna of lac des bois most closely resembles other arctic fish assemblages of the western interior seaway based on a upgma unweighted pair group method with arithmetic averages cluster analysis of various north american turonian localities there are also slight differences between eastern and western localities along the seaway the north south differences of the ichthyofauna can be explained by current patterns distributing the fishes in the seaway or transgressive events during the turonian the east west differences may be due to changes in water depth from east to west

dynamical mechanisms for the south china sea seasonal circulation and thermohaline variabilities abstract the seasonal ocean circulation and the seasonal thermal structure in the south china sea scs were studied numerically using the princeton ocean model pom with 20 km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography a 16 month control run was performed using climatological monthly mean wind stresses restoring type surface salt and heat and observational oceanic inflow outflow at the open boundaries the seasonally averaged effects of isolated forcing terms are presented and analyzed from the following experiments 1 nonlinear dynamic effects removed 2 wind effects removed and 3 open boundary inflow outflow set to zero this procedure allowed analysis of the contribution of individual parameters to the general hydrology and specific features of the scs for example coastal jets mesoscale topographic gyres and countercurrents the results show that the pom model has the capability of simulating seasonal variations of the scs circulation and thermoha

high temperature deformation during continental margin subduction exhumation the ultrahigh pressure western gneiss region of norway abstract a new dataset for the high pressure to ultrahigh pressure western gneiss region allows the definition of distinct structural and petrological domains much of the study area is an e dipping homocline with e plunging lineations that exposes progressively deeper more strongly deformed more eclogite rich structural levels westward although eclogites crop out across the wgr scandian deformation is weak and earlier structures are well preserved in the southeastern half of the study area the scandian reworking increases westward culminating in strong scandian fabrics with only isolated pockets of older structures the dominant scandian deformation was coaxial e w stretching the sinistrally sheared more trondelag fault complex and nordfjord mylonitic shear zone bound these rocks to the north and south there was moderate top e amphibolite facies deformation associated with translation of the allochthons over the basement along its eastern edge and the nordfjord sogn detachment zone underwent strong lower amphibolite facies to greenschist facies top w shearing a northwestward increase in exhumation related melting is indicated by leucosomes with hornblende plagioclase and scandian sphene in the western 2 3 of the study area exhumation related amphibolite facies symplectite formation in quartzofeldspathic gneiss postdated most scandian deformation further deformation was restricted to slip along biotite rich foliation planes and minor local folding that the western gneiss region quartzofeldspathic gneiss exhibits a strong gradient in degree of deformation implies that continental crust in general need not undergo pervasive deformation during subduction

strontium isotope correlation of the basal maastrichtian stage in antarctica to the european and us biostratigraphic schemes new 87 sr 86 sr dating allows the correlation of a marker horizon within the prolific late cretaceous gunnarites antarcticus faunal assemblage of the cape lamb member snow hill island formation vega island antarctica with reference sections in europe and the usa this horizon is between 81 5 and 96 5 m above the base of the g antarcticus assemblage replicate analysis of six macrofossils from within it yielded a mean value for 87 sr 86 sr of 0 707 735 9 0 000 004 3 2 s e n 17 this ratio in turn yields a numerical age of 71 0 0 2 ma when compared to the standard 87 sr s6 sr reference curve for the latest cretaceous for which the campanian maastrichtian boundary is placed at 71 3 0 5 ma the value of 0 707 735 9 0 000 004 3 correlates to a level in the belemnella lanceolata belemnite zone of the chalk of northwestern germany that is 2 5 5 m beneath the base of the overlying b pseudobtusa zone and 7 5 m above the campanian maastrichtian belemnite boundary and to an interval within the ammonite zonation of the us western interior that spans the early maastrichtian baculites baculus and b eliasi zones but with a most likely level within the b eliasi zone an earliest maastrichtian age is thereby determined for the antarctic horizon and indeed for the entire g antarcticus assemblage gunnarites sensu lato is an important ammonite marker for the base of the maastrichtian throughout the southern high latitude regions and the associated large heteromorph ammonite diplomoceras may comprise a macrofossil link back to the maastrichtian type sections

zircon geochronology and ca 400 ma exhumation of norwegian ultrahigh pressure rocks an ion microprobe and chemical abrasion study understanding the formation and exhumation of the remarkable ultrahigh pressure uhp rocks of the western gneiss region norway hinges on precise determination of the time of eclogite recrystallization we conducted detailed thermal ionization mass spectrometry chemical abrasion analysis and sensitive high resolution ion microprobe analysis of zircons from four ultrahigh and high pressure hp rocks ion microprobe analyses from the flatraket eclogite yielded a broad range of apparently concordant caledonian ages suggesting long term growth in contrast higher precision thermal ionization mass spectrometry analysis of zircon subject to combined thermal annealing and multi step chemical abrasion yielded moderate pb loss from the first lowest temperature abrasion step possible minor pb loss or minor growth at 400 ma from the second step and a 407 404 ma cluster of slightly discordant 206pb 238u ages most likely free from pb loss from the remaining abrasion steps we interpret the latter to reflect zircon crystallization at 405 400 ma with minor discordance from inherited cores zircon crystallization occurred at eclogite facies possibly post peak conditions based on compositions of garnet inclusions in zircon as well as nearly flat hree profiles and lack of eu anomalies in zircon fractions subjected to chemical abrasion these ages are significantly younger than the 425 ma age often cited for western norway eclogite recrystallization implying faster rates of exhumation 2 5 8 5 km myr and coeval formation of eclogites across the uhp portion of the western gneiss region

observed near inertial kinetic energy in the northwestern south china sea based on more than 3 years of moored current meter records this study examined seasonal variability of near inertial kinetic energy nike as well as all large greater than one standard deviation from the mean nike events related to storms and eddies in the northwestern south china sea the nike in the subsurface layer 30 450 m exhibited obvious seasonal variability with larger values in autumn herein defined as august september and october all large nike events during the observation period were generated by passing storms most of the nike events had an e folding timescale longer than 7 d the phase velocity vertical wavelength and frequency shift of these events were examined the maximum nike induced by typhoon neoguri was observed in april 2008 normal mode analysis suggested that the combined effects of the first four modes determined the vertical distribution of nike with higher nike below 70 m but lower nike from 30 to 70 m another near inertial oscillation event observed in august 2007 had the longest e folding timescale of 13 5 d moreover the nike propagated both upward and downward during this event a ray tracing model indicated that the smaller brunt vaisala frequency and the stronger vertical shear of horizontal currents in an anticyclonic eddy and the near inertial wave with larger horizontal scale facilitated the unusual propagation of the nike and the long decay timescale although the nike originated from wind the water column structure affected by diverse oceanographic processes contributed substantially to its complex propagation and distribution

structural development and petrofabrics of eclogite facies shear zones bergen arcs western norway implications for deep crustal deformational processes caledonian eclogite facies shear zones developed from grenvillian garnet granulite facies anorthosites and gabbros in the bergen arcs of western norway allow direct investigation of the relations between macroscopic structures and crystallographic preferred orientation cpo in lower continental crust field relations on the island of holsnoy show that the eclogites formed locally from granulite facies rocks by progressive development of 1 eclogite adjacent to fractures 2 eclogite in discrete shear zones 2 m thick 3 eclogite breccia consisting of 80 well foliated eclogite that wraps around rotated granulite blocks and 4 anastomosing subparallel eclogite facies shear zones 30 100 m thick continuous over distances 1 km within the granulite terrane these shear zones deformed under eclogite facies conditions at an estimated temperature of 670 50 c and a minimum pressure of 1460 mpa which corresponds to depths of 55 km in the continental crust detailed investigation of the major shear zones shows the development of a strong foliation defined by the shape preferred orientation of omphacite and by alternating segregations of omphacite garnet rich and kyanite zoisite rich layers a consistent lineation throughout the shear zones is defined by elongate aggregates of garnet and omphacite the cpo of omphacite determined from five axis universal stage measurements shows a strong b axis maximum normal to foliation and a c axis girdle within the foliation plane with weak maxima parallel to the lineation direction these patterns are consistent with deformation of omphacite by slip parallel to 001 and suggest glide along 010 the lineation and cpo data reveal a consistent sense of shear zone movement although the displacement was small localized faulting of high grade rocks accompanied by fluid infiltration can be an important mode of failure in the lower continental crust field relations show that granulite facies rocks can exist in a metastable state under eclogite facies conditions and imply that the lower crust can host differing metamorphic facies at the same depth deformation of granulite and partial conversion to eclogite such as is exposed on holsnoy island may be an orogenic scale process in the lowermost crust of collisional orogens

retrogression of eclogite facies shear zones by short lived fluid infiltration during the caledonian orogeny lofoten islands norway norwegian eclogite facies shear zones in the lofoten islands served as major pathways for short lived pulses of both 40 ar rich and 40 ar poor hot fluids during eclogitization and retrogression events related to the caledonian orogeny the open system for ar affected most of the minerals leading to old 40 ar 39 ar ages particularly in trioctahedral micas 40 ar concentration in the fluids appears to decrease during the amphibolite facies retrogression and ca rich amphiboles yield 40 ar 39 ar ages of c 415 ma scandian event late and post caledonian 40 ar 39 ar muscovite and k feldspar ages and rb sr biotite ages coincide with multiple extensional events fluid infiltration and thermal activity during the final exhumation of the crustal rocks potentially reflecting major tectonic episodes such as rifting of pangaea and seafloor spreading between europe and north america

metamorphic rocks seek meaningful cooling rate interpreting 40ar 39ar ages in an exhumed ultra high pressure terrane 40ar 39ar dating of metamorphic white mica is commonly used to elucidate the timing of cooling and or exhumation of metamorphic terranes in theory so long as the dated mineral originally crystallised above its closure temperature the yielded 40ar 39ar ages should not vary significantly within or between samples and should vary only due to grain size 3 ma variation depending on the estimated cooling rate infra red laser single grain fusion and ultra violet laser spot muscovite and or phengite data from mafic eclogite bodies and their host gneisses in the nordfjord region of the western gneiss complex wgc norway show that the ages yielded both within and between white micas from the same mafic eclogite sample vary by up to 284 ma ages yielded within the same pelitic gneiss sample vary by up to 28 ma overall the 40ar 39ar phengite dates from mafic eclogites range from 750 to 440 ma and are significantly older than the previously reported 405 400 ma u pb zircon age constraining peak metamorphism in the nordfjord wgc the felsic host gneiss samples which recrystalised during a post peak exhumation related amphibolite facies overprint yield single grain fusion and laser spot 40ar 39ar white mica dates spanning 420 to 385 ma encompassing previous estimates of the timing of the entire metamorphic cycle these data suggest that ar is heterogeneously distributed both within grains and between grains on the cm to sub mm scale in all samples and imply restricted ar transport and inefficient removal during the metamorphic cycle open system zero grain boundary ar concentration behaviour is an inherent assumption in the commonly applied closure temperature formulation but unless this can be demonstrated linking 40ar 39ar ages to temperature is no longer trivial the high spatial and chronological precision afforded by uv laser ablation mean that intra grain ar concentration distributions may be used to assess open vs closed system behaviour the data presented here suggest that open system behaviour cannot be assumed in metamorphic systems even those in which the pressure temperature and time conditions in theory allow for efficient diffusion during the metamorphic cycle high spatial resolution 40ar 39ar data and robust comparison with numerical models of open system behaviour provide the greatest future potential for unravelling the complexities of metamorphic exhumation timescales

middle late cretaceous climate of the southern high latitudes stable isotopic evidence for minimal equator to pole thermal gradients a detailed 18 o and 13 c stratigraphy has been generated from analysis of well preserved albian early maastrichtian foraminifera from deep sea drilling project dsdp sites 511 and 327 falkland plateau 58 s 62 s paleolatitude in the southern south atlantic and cenomanian and coniacian santonian foraminifera from dsdp site 258 naturaliste plateau 58 s paleolatitude in the southern indian ocean these results when combined with previously published maastrichtian stable isotope data from ocean drilling program odp site 690 weddell sea 65 s paleolatitude provide new insight into the climatic and oceanographic history of the southern high latitudes during middle late cretaceous time the planktonic foraminifer 18 o curves reveal a gradual warming of surface waters from the albian through the cenomanian followed by extremely warm surface waters from the turonian through the early campanian long term cooling of surface waters began in the late early campanian and continued through the end of the maastrichtian the benthic foraminifer 18 o record generally parallels changes in the oxygen isotopic curves defined by shallow dwelling planktonic foraminifera the vertical oxygen and carbon isotopic gradients were relatively low during the albian cenomanian high from the turonian early campanian and then low during the late campanian and maastrichtian foraminiferal oxygen isotopic data from published sources and this study are averaged for each site corrected for latitudinal changes in salinity based on modern day surface water values and plotted versus paleolatitude for the late albian coniacian santonian and late maastrichtian differences between lowand high latitude surface water paleotemperatures are estimated at 14 c during the late albian and late maastrichtian but the coniacian santonian reconstruction reveals only a 0 4 c latitudinal temperature gradient uncertainty regarding cretaceous salinity gradients and possible diagenetic alteration of 18 o values introduce error into our estimates of paleolatitudinal thermal gradients however apparent low equator to pole temperature differences could indicate much higher poleward heat transport than at present

seasonal thermocline in the china seas and northwestern pacific ocean climatological seasonal variations of the thermocline in the china seas and northwestern pacific ocean were studied using historical data from 1930 through 2001 707 624 profiles the quantitative roles of surface thermal buoyancy b q haline buoyancy flux b p and total buoyancy flux b against the wind induced mixing tau in different seasons and regions were also explored using the buoyancy ratio r b q b p and the monin obukhov depth ratio delta respectively the thermocline has obvious seasonal variations in the study area north of 20 degrees n there is no thermocline along the west coast of the bohai sea bs yellow sea ys and northern east china sea from december to march resulting from surface cooling and wind mixing the significantly different variation of the thermocline strength on and off the chinese shelf is mainly caused by the fact that the thermal stratification is enhanced by bottom tidal mixing on the shelf the delta indicates that the thermocline depth on the chinese shelf is mainly dominated by b in summer while it is dominated by tau in winter it reveals an opposite feature in the kuroshio region the dominating factor is b in winter associated with the large heat buoyancy loss there south of 20 degrees n the dominating factor is similar to that on the shelf with the more obvious b dominant characteristic during the monsoon transition periods the r demonstrates that b is mainly controlled by b q all year round with some sporadically b p dominated regions in the tropical area in winter and in the bs and eastern ys in september

polarity variations of internal solitary waves over the continental shelf of the northern south china sea impacts of seasonal stratification mesoscale eddies and internal tides abstractspatiotemporal variations in internal solitary wave isw polarity over the continental shelf of the northern south china sea scs were examined based on mooring array observations from october 2013 to june 2014 depression isws were observed at the easternmost mooring where the water depth is 323 m then they evolved into elevation isws at the westernmost mooring with a depth of 149 m at the central mooring with a depth of 250 m the isws generally appeared as depression waves in autumn and spring but were elevation waves in winter seasonal variations in stratification caused this seasonality in polarity on the intraseasonal time scales anticyclonic eddies can modulate isw polarity at the central mooring by deepening the thermocline depth for periods of approximately 8 days during some days in autumn and spring depression isws and isws in the process of changing polarity from depression to elevation appeared at time intervals of 10 12 h because of the thermocline deepening caused by in

continental rift to back arc basin jurassic cretaceous stratigraphical and structural evolution of the larsen basin antarctic peninsula the larsen basin developed in jurassic times as a result of continental rifting during the early stages of gondwana break up lower upper jurassic non marine sedimentary and volcanic rocks constitute a syn rift megasequence recording initial largely amagmatic extension and subsequent widespread extension related silicic volcanism a succeeding kimmeridgian early berriasian transgressive megasequence consisting largely of anoxic dysoxic hemipelagic mudstones is thought to have been deposited during a thermal subsidence phase when relative magmatic quiescence and peak jurassic eustatic sea levels served to maximize sediment starvation the fragmentary record for late berriasian barremian times suggests that a regressive megasequence may have developed in the earlier part of this period recording increased sediment yield to the larsen basin from the increasingly emergent antarctic peninsula arc subsequently strata in the southern but not the northern part of the basin underwent relatively intense eastward verging deformation possibly during the formation of a retro arc fold thrust belt where exposed the lower part of the succeeding aptian eocene megasequence consists of a deep marine clastic wedge deposited along the fault bounded western basin margin during a phase of arc uplift and related differential subsidence following partial basin inversion in late cretaceous times regression took place as reduced basinal subsidence rates allowed shallow marine facies to prograde basinward

regional dynamics of seasonal variability in the south china sea abstract dynamics of the seasonal cycle of sea surface height ssh in the south china sea scs are studied using observations as well as numerical and theoretical models seasonal variability of the scs is interpreted in light of large scale dynamics and rossby waves it is found that the seasonal cycle over most of the scs basin is determined predominantly by the regional ocean dynamics within the scs the ssh variability is shown to be forced mainly by surface wind curl on baroclinic rossby waves annual baroclinic rossby waves cross the basin in less than a few months leaving the upper ocean in a quasi steady sverdrup balance an anomalous cyclonic anticyclonic gyre is generated in winter summer by the anomalous cyclonic anticyclonic wind curl that is associated with the northeasterly southwesterly monsoon in addition surface heat flux acts to enhance the wind generated variability the winter surface cooling warming cools warms the mixed layer especially in the central scs reducing

late cretaceous antarctic fish diversity new material from the santa marta formation late coniacian early maastrichtian of james ross island contributes significantly to the current knowledge of late cretaceous antarctic fish diversity the taxon list for the santa marta formation is extended and new records of neoselachians and teleosts are reported the stratigraphic ranges of some previously known taxa are enlarged and the palaeobiogeography and palaeoecology of late cretaceous antarctic fishes are discussed top predators that occupied the higher levels in the food chain along with marine tetrapods dominate the marine faunas from the santa marta and lopez de bertodano formations the only fish adapted to crushing hard shelled invertebrates were the chimeroids rays an important component of marine fish associations as well as fish from lower trophic levels remain unknown from the late cretaceous of antarctica

composition of fluids in the lower crust inferred from metamorphic salt in lower crustal rocks knowledge of the rheological properties of the lower crust and the metamorphic processes that operate there is important for our understanding of orogenic processes and granite genesis the rheological properties critically depend on whether fluids are present in the lower crust1 2 and if present on their composition3 4 5 6 fluid inclusion7 8 9 and phase equilibria4 10 studies of lower crustal granulites have shown that fluids with low water activities due to the presence of dissolved components such as ch4 n2 co co2 and chlorides 11 are present at least episodically in the lower crust here we report the occurrence of a solid salt solution nacl kcl found together with chlorine rich amphibole and biotite in lower crustal granulites a desiccation mechanism explains how salt and chlorine rich minerals formed from an originally water rich fluid through a short lived series of hydration reactions in the granulites during which chlorine was progressively enriched in the fluid consequently it would appear that fluid was present in the lower crust in only small amounts and was not stable over geologically long periods of time leading to the conclusion that the lower crust is devoid of a free fluid phase during most of its history

walvis ridge barrier its influence on palaeoenvironments and source rock generation deduced from ostracod distributions in the early south atlantic ocean the early south atlantic was subdivided latitudinally by the proto walvis ridge which separated early cretaceous open marine conditions in the south from non marine environments to the north changes in the palaeogeography which can be monitored by the distribution of ostracod assemblages determined the establishment of a wide variety of depositional environments including evaporitic and total organic carbon rich facies limited northward marine influxes across the barrier are postulated for mid aptian time while largescale southward migrations of marine ostracods from the northern sector occurred in early cenomanian and or turonian times the latter established cosmopolitan faunas in the southern atlantic and effectively marked the breakdown of the walvis ridge as a physical barrier to north south migrations although possible oceanographic factors militated against longitudinal faunal movements variations in the composition of ostracod assemblages during so called oceanic anoxic events and the production of potential source rocks is briefly reviewed

additions to the diversity of elasmosaurid plesiosaurs from the upper cretaceous of antarctica abstract three specimens of elasmosaurid plesiosaurs sauropterygia plesiosauria from upper cretaceous beds of antarctica are described here these include postcranial remains of a single adult individual recovered from late maastrichtian beds of marambio seymour island possessing a distinctive combination of features cervical vertebrae having centra with a triangular outline in transverse section a vertical groove on the rostral and caudal edge of the neural spines and a deep articulation over the neural arch for the following postzygapophysis while the scapula shows an unusually large and anteriorly recurved dorsal process this combination of features is unknown in any adult postcranial elasmosaurid genus recovered to date in the upper cretaceous of the weddellian biogeographic province and could represent a new form additional specimens from james ross island comprise the first record of an aristonectinae plesiosauria elasmosauridae in late campanian beds being the oldest known record of this sub family finally a third specimen from the same age and locality reveals the presence of very long necked elasmosaurids with affinities to typical representatives from the upper cretaceous of the northern hemisphere these findings add to the known diversity of upper cretaceous elasmosaurids in high latitudes of the southern hemisphere

shear deformation and eclogite formation within granulite facies anorthosites of the bergen arcs western norway the anorthosites of the bergen arcs contain two distinct metamorphic mineral assemblages which are stable under different p t conditions a granulite facies assemblage which equilibrated at t 800 900 c p 10 kbar is defined by the minerals plagioclase al rich diopside cpx i garnet gnt i scapolite orthopyroxene dark brown hornblende this assemblage is linked by corona structures to a primary magmatic mineralogy where coexistence of olivine and plagioclase limits the maximum crystallization pressure of the anorthosites to 8 kbar at 1200 c the anorthosites are transected by a series of fine grained shear zones in which the granulite facies assemblage is replaced by an eclogite mineralogy defined by omphacite cpx ii jd40 50 garnet kyanite epidote clinozoisite phengite quartz amphibole with plagioclase sometimes remaining in the marginal parts mineral compositions indicate equilibration conditions for the eclogite paragenesis of t 700 800 c p 16 19 kbar a series of textural and mineralogical changes which can be observed as the strain increases into the shear zones demonstrates that the eclogite mineralogy is formed at the expense of the granulite facies minerals during the early stages of shear zone development the eclogite mineralogy defines a strong mylonitic fabric which again is truncated by centimetres thick secondary shear zones containing clasts of both granulite and eclogite minerals these latter fine grained ultramylonites may be connected to uplift of this deep seated complex the eclogite shear zones are highly oblique to the granulite structures indicating that the eclogite shear zones formed under a new stress regime rb sr dating shows that the granulite facies assemblage formed in sveconorwegian time or earlier while minerals from shear zones define ages around 400 ma indicating a caledonian formation of the eclogites this work demonstrates the critical role of deformation in triggering metamorphic reactions whether the shear stress also was important in stabilizing the eclogite assemblages is not clear from the available data

chlorine stable isotope composition of granulites from lofoten norway implications for the cl isotopic composition and for the source of cl enrichment in the lower crust abstract the cl isotopic composition of lower crustal rocks as revealed from granulites from the lofoten islands northern norway centres around the value of standard mean ocean chloride smoc the investigated rocks and mineral separates of cl amphibole and cl biotite have 37 cl values 37 cl 35 cl normalized to smoc of 1 12 to 0 79 with most values concentrated in the range of 0 3 to 0 11 and an average of 0 15 samples from gabbroic and from dry granitic rocks magmatic mangerites and charnockites with highly cl enriched hydrosilicates and from a later amphibolite with low cl amphiboles show no distinct differences in their 37 cl values the results indicate that there was only minor involvement of mantle derived cl in fluid involving processes in the middle and lower crust assuming a 37 cl of 4 7 for the undegassed mantle 1 cl isotopic values of the granulites do not support the influx of significant amounts of mantle derived cl the maximum possible mantle contribution to the sample with the highest 37 cl is about 33 thus the common occurrence of cl enriched minerals in granulite facies terrains is regarded as a product of remobilized crustal cl either during magmatism or during later fluid activity the results support the hypothesis that the crust can be regarded as a reservoir with cl isotopic values very similar to smoc

excess 40ar transport scale and mechanism in high pressure phengites a case study from an eclogitized metabasite of the dora maira nappe western alps application of the bulk separate furnace heating laser step heating and in situ laser agemapping 40ar 39ar techniques reveals that high pressure phengites from an alpine eclogite of the dora maira basement nappe western alps were pervasively contaminated with excess 40ar to yield ages 130 ma spot fusion dating of individual grains with the 40ar 39ar laserprobe reveals concentric radial patterns with core ages as high as 320 ma showing that this excess component was trapped at an early stage and subsequently remobilized by volume diffusion during a late greenschist thermal pulse the single grains and population from this hand sample retain major differences in apparent ages indicating that the extent of the excess 40ar contamination varies from grain to grain attempt to model these differences in terms of grain size dependent fractional loss falls short and demonstrates that strong cm scale argon isotopic gradients locally prevailed during syn kinematic high pressure metamorphism on petrostructural grounds a model of internal isotopic buffering is outlined whereby the excess 40ar is argued to have been internally derived from within the eclogite protolith itself low intergranular ar diffusion rates due to reduced water activity buffered below unity by the phengite assemblage resulted in the local segregation and partitioning of the excess 40ar along grain boundaries during ongoing ductile deformation supporting evidence for this model comes from the recent literature on fluid and stable isotope behaviour in alpine eclogites and very high pressure metasediments which shows that volatile recycling during high pressure metamorphism may occur on a very limited scale

40ar 39ar thermochronology of late and postorogenic extension in the caledonides of north central norway abstract we report 40ar 39ar mineral cooling data that elucidate the timing and style of devonian late orogenic extensional collapse and permian triassic postorogenic continental rifting in the north central norwegian caledonides 40ar 39ar mineral cooling ages from ductile extensional shear zones that have either excised or reactivated caledonian thrust faults along the western flanks of two major basement domes indicate that late orogenic extensional deformation in this region occurred during the early ca 409 388 ma and late devonian ca 371 355 ma these extensional pulses are consistent with events recently identified by workers investigating areas to the south of our study area the timing and style of the early devonian event supports the northern continuation of the devonian orogen parallel scoop shaped extensional deformation documented in the central norwegian caledonides late devonian extension on the other hand was orogen orthogonal this late devonian event is similar in timing and ki

fine scale isotopic heterogeneities and fluids in the deep crust a40ar 39ar laser ablation and tem study of muscovites from a granulite eclogite transition zone spectacular exposures on holsnoy island western norway reveal that eclogites formed in situ from adjacent anhydrous granulites as a result of the localized infiltration of fluids stepwise and laser40ar 39ar experiments on muscovite from the eclogites have been used in conjunction with electron microprobe and transmission electron microscopy tem analysis to examine the behavior of argon under high pressure metamorphism and subsequent cooling muscovites with 0 10 0 17na na k yield40ar 39ar plateau and integrated ages in the range 450 465 ma 20 35 myr older than40ar 39ar muscovite plateau ages from adjacent eclogite samples laser40ar 39ar analyses on 75 m spots across two single muscovite grains from these samples are approximately uniform at 444 2 1 9 21 spots and 443 3 1 7 ma 26 spots however incremental heating of high sodic 0 18 0 32 na na k muscovite failed to yield a plateau laser40ar 39ar analyses of 100 areas from two single grains from this sample reveal complex two dimensional patterns with variable apparent ages in the range of 445 625 ma electron microprobe measurements obtained from one of the grains reveal that the paragonite content is also highly variable both parallel and perpendicular to 001 all the tem bright field images obtained from this mica yield information consistent with a single homogeneous phyllosilicate phase yet several of the selected area electron diffraction saed analyses document locally intergrown muscovite and sodic muscovite possibly in an exsolution relationship on a unit cell scale analytical electron microscopy aem analyses obtained over a 5 100 nm scale on the same sample reveal great range and heterogeneity inna k including pure muscovite although no separate paragonite domains were found in contrast muscovite grains with consistent laser spot fusion and plateau ages show little heterogeneity inna k at the microprobe level these data provide evidence of variable fluid mediated incorporation of excess40ar under high pressure eclogite facies conditions at the time of the development of the sodic muscovite compositions the data indicate that fine scale heterogeneities in argon isotopic compositions were generated during eclogite facies equilibration and were preserved as the rocks were cycled back to the surface despite the influx of free fluids in the rocks at high pressure the heterogeneities are best reconciled with local buffering and limited mobility of the fluids at least during the final stages of equilibration

fossil marine actinopterygian fishes from the kaskapau formation upper cretaceous turonian near watino alberta turonian fossil marine fishes occur at several localities near watino alberta in sandstones and in shale concretions of the vimy member kaskapau formation the actinopterygian fossils in the san

the silurian to permian history of a metamorphic core complex in lofoten northern scandinavian caledonides 1 the lofoten archipelago exposes precambrian baltic basement and caledonian allochthonous sequences within a 1000 km long chain of gravity and magnetic highs and structural culminations along the extended british and norwegian continental shelf previous regional geophysical studies indicate that post caledonian extension and development of the northern norwegian shelf occurred during broadly defined carboniferous permian cretaceous jurassic and early tertiary events structures related to these events are known to young westward we report field structural and 40ar 39ar thermochronologic data from rocks exposed in lofoten that further define the history and style of post caledonian extension the islands of southwest lofoten also represent the most outboard exposures of caledonian basement in northern norway that presumably formed the middle to deep crustal core of the orogen metasedimentary rocks and penetratively deformed basement in lofoten record high grade silurian devonian metamorphism and top to the east hereinafter tops east thrusting followed by episodes of late devonian to early carboniferous tops west ductile extension which progressed into oblique left slip movements the structural style and timing of silurian contraction in this area are remarkably similar to that determined for the more forelandward areas on the mainland 120 km to the east supporting the inference that distal parts of the baltic continental margin that were once deeply subducted are presently exposed in lofoten the timings of post devonian structural events that affected rocks in lofoten are partially constrained by the ages of unconformities and strata known to be preserved in graben flanking the lofoten culmination the radiometric age and structural data presented in this study in combination with stratigraphic constraints suggest a westward progression through time of extensional deformation over a protracted interval of silurian to permian time the latest permian extension in lofoten is largely characterized by brittle structures that formed at conditions substantially less than 300 c compared to the exhumation history of the southern western gneiss region the depth of caledonian continental a type subduction and subsequent unroofing of lofoten are of lesser magnitude and the present erosional level remained in the middle crust for a much longer interval of time the permian 40ar 39ar mineral ages documented in this study are the youngest such ages yet identified in scandinavia these ages relate to episodes of deformation and cooling in response to extensional tectonic events that occurred roughly 100 m y after comparable effects identified on the caledonian mainland our preferred explanation for the carboniferous permian radiometric ages structural evolution and stratigraphic data for lofoten is that they all developed in the context of a long lived cordilleran style metamorphic core complex

campanian maastrichtian cretaceous stratigraphy of the james ross island area antarctica one of the most important outcrops of uppermost cretaceous campanian maastrichtian sedimentary rocks in the southern high latitudes occurs within the james ross island group northeastern antarctic peninsula these rocks comprise a 1500 2000 m thick sequence of predominantly shallow marine clastic sediments that were deposited within a retro arc basin they are virtually undeformed and have yielded prolific invertebrate and vertebrate faunas and a wide range of plant taxa campanian maastrichtian strata are contained within two component formations of the upper cretaceous lower tertiary marambio group the lower santa marta formation is approximately 1100m thick and has three constituent members ammonites within the santa marta formation indicate an early to late campanian age assignment dinoflagellates suggest that the lower levels of the formation may range into the santonian stage in the northern james ross island to vega island region there is a conformable transition into the overlying lopez de bertodano formation here the basal cape lamb member is unconformably overlain by the sandwich bluff member although there are some lithological and fauna1 discrepancies which are attributed to marked lateral facies changes across the basin it is believed that the cape lamb member can be correlated with the lower to middle regions of the 1200 m thick sequence of undifferentiated lopez de bertodano formation lithologies exposed on seymour island molluscan data indicate a late campanian palaeocene age range for this upper formation dinoflagellates again suggest that the lowest beds may be slightly older the correlation presented provides the basis for a formal subdivision of the campanian and maastrichtian stages in the southern high latitudes it has also revealed two major basin shallowing events in the late campanian early maastrichtian and latest maastrichtian respectively and the existence of a major fault fault zone across southeastern james ross island the improved temporal framework will aid late cretaceous palaeoclimatic and palaeobiological studies in antarctica

mesoscale eddies in the south china sea mean properties spatiotemporal variability and impact on thermohaline structure we investigated mean properties and the spatiotemporal variability of eddies in the south china sea scs by analyzing more than 7000 eddies corresponding to 827 eddy tracks identified using the winding angle method and 17 years of satellite altimetry data eddies are mainly generated in a northeast southwest direction and southwest of luzon strait there is no significant difference between the numbers of two types of eddies anticyclonic and cyclonic in most regions the mean radius and lifetime of eddies are 132 km and 8 8 weeks respectively both depending on where the eddies are formed anticyclonic and cyclonic eddies tend to deform during their lifetimes in different ways furthermore eddy propagation and evolution characteristics are examined in the northern scs eddies mainly propagate southwestward along the continental slope with velocities of 5 0 9 0 cm s 1 while in the central scs eddies tend to move with slight divergence but still in a quasi westward direction with velocities of 2 0 6 4 cm s 1 eddy propagation in the western basin to the east of vietnam is quite random with no uniform propagate direction investigation of 38 long lived eddies shows that eddies have a swift growing phase during the first 12 weeks and then a slow decaying phase that affects the eddy radii and eddy energy densities nevertheless vorticity has less variability in addition the effect of eddies on the thermocline and halocline is analyzed using 763 argo temperature profile data cyclonic eddies drive the thermocline shallower and thinner and significantly strengthen the thermocline intensity whereas anticyclonic eddies cause the thermocline to deepen and thicken and weaken the thermocline intensity to a certain degree the halocline impacted by cyclonic eddies is also shallower and thinner than that impacted by anticyclonic eddies finally eddy temporal variations are examined at seasonal and interannual scales eddy activity is sensitive to the wind stress curl and in the northern scs it is also related with the strength of the background flows

seasonal and intraseasonal thermocline variability in the central south china sea seasonal and intraseasonal variability of thermo cline and relative surface height in the central south china sea scs are investigated using time series data of tem perature from three buoys and sea surface height anomaly data from topex poseidon and ers 1 ers 2 satel lites t p ers from feb 1998 through mar 1999 we found that the thermocline becomesdeeper and thinner in winter owing to a great loss of the heat on the sea surface thisfeature ismore evident in the northern than the s outh ern part of the central scs the intraseasonal variation of the thermocline ismainly controlled by the geos trophic vor ticity and is out of phase with sea surface height ssh fur thermore we find a double thermocline phenomenon occurs in the scs in spring owing to maximum net downward heat flux at the surface with the new thermocline appear ing above 80 m and the old thermocline keeping under 80 m deep

a new hesperornithiform aves specimen from the late cretaceous canadian high arctic with comments on high latitude hesperornithiform diet here we describe a new hesperornithiform specimen from the upper cretaceous kanguk formation of devon island nunavut canada this specimen nuvf 286 is referred to cf hesperornis sp based on size and shape of femora and teeth preserved with other skeletal elements previous osteohistologic analyses indicate a subadult ontogenetic stage at the time of death this new cf hesperornis specimen includes the first teeth associated with a high latitude hesperornithiform allowing for comments on the trophic behavior of these birds paleoecological reconstructions based on current knowledge of polar assemblages and comparisons to modern birds suggest that high latitude hesperornithiform birds may have had more varied diets than previously assumed

eddy effects on sea surface temperature and sea surface wind in the continental slope region of the northern south china sea 1 warm and cold sea surface temperature sst tongues on weather timescales are detected in the continental slope region of the northern south china sea nscs and their effects on sea surface wind are studied using satellite observations crossing the basin scale sst front geostrophic currents between cyclonic and anticyclonic eddies induce the warm and cold sst tongues during the northeast monsoon corresponding to the warm and cold sst tongues the sea surface wind is highly uneven in spatial distribution its speed is faster slower over the warm cold sst tongues than the surrounding areas the sst and sea surface wind non uniformity in space shifts southwestward with eddy motion along the continental slope these new findings from satellite observations give us an opportunity to study oceanic eddy s roles in ocean atmosphere interaction on weather timescales

definition of late cretaceous stage boundaries in antarctica using strontium isotope stratigraphy abstract new 87sr 86sr analyses of macrofossils from 13 key marker horizons on james ross and vega islands antarctica allow the integration of the antarctic late cretaceous succession into the standard biostratigraphic zonation schemes of the northern hemisphere the 87sr 86sr data enable late cretaceous stage boundaries to be physically located with accuracy for the first time in a composite southern hemisphere reference section and so make the area one of global importance for documenting late cretaceous biotic evolution particularly radiation and extinction events the 87sr 86sr values allow the stage boundaries of the turonian coniacian coniacian santonian santonian campanian and campanian maastrichtian as well as other levels to be correlated with both the united kingdom and united states these correlations show that current stratigraphic ages in antarctica are too young by as much as a stage immediate implications of our new ages include the fact that inoceramus madagascariensis a useful

late cretaceous extinction patterns in antarctica new correlations of marine clastic sedimentary rocks exposed within the james ross basin antarctica have shown that the mid to late cretaceous succession is in excess of 5 km thick plotting the ranges of the principal molluscan macrofossils against the revised stratigaphy indicates that inoceramid bivalves are totally absent and dimitobelid belemnites extremely rare throughout an extensive 1400 m thick maastrichtian succession these early extinction patterns are interpreted to be due to both a regional shallowing event and a pronounced phase of high latitude campanian maastrichtian cooling cool polar bottom waters may have been forming by as early as mid to late campanian times

an airborne expendable bathythermograph survey of the south china sea may 1995 an extensive airborne expendable bathythermograph survey of the south china sea scs conducted in may 1995 and historical data are used to analyze and infer the upper layer 300 m synoptic structure and general circulation the primary thermal feature observed was a central scs warm pool surrounded by several cool pools the size of the warm pool decreased with depth from approximately 200 000 km2 at 50 m depth to about 70 000 km2 at 300 m depth the maximum temperature of the warm pool was 30 c appearing near the surface at the depth of 50 m the temperature of the central scs warm pool was 29 c and the temperature of the five surrounding cool pools ranged from 26 c to 22 c a three dimensional estimate of the absolute velocity field was obtained from the observed temperature field and a climatological salinity field using the spiral method striking circulation features were the existence of dual anticyclonic eddies in the central scs warm pool and the existence of cyclonic eddies associated with the cool pools in the upper layer the tangential velocity of the dual central scs anticyclonic warm core eddies is around 30 40 cm s and that of the five cyclonic cool core eddies varies from 10 cm s to 40 cm s the tangential velocity of all the eddies decreased with depth at 300 m depth it became less than 5 cm s for all the eddies

stratigraphy and vertebrate paleoecology of upper cretaceous lowest paleogene strata on vega island antarctica the upper cretaceous maastrichtian sandwich bluff member of the lopez de bertodano formation is well exposed on vega island in the james ross basin off the northeastern coast of the antarctic peninsula although this unit is one of the richest sources of end cretaceous vertebrate fossils in antarctica it is also one of the least sedimentologically and stratigraphically characterized units in the basin new facies and stratigraphic analyses of the sandwich bluff member and the underlying cape lamb member of the snow hill island formation were performed in tandem with intensive prospecting for fossil vertebrates and stratigraphic assessment of historic paleontological localities on vega island this effort has led to a revised stratigraphy for the sandwich bluff member and the precise stratigraphic placement of important terrestrial and marine vertebrate fossil localities facies analysis reveals a fining and shallowing upward trend through the section that culminates in a newly recognized sequence boundary near the top of the sandwich bluff member followed by the deposition of a previously unrecognized 6 m thick matrix supported pebble cobble conglomerate of probable alluvial origin immediately overlying this unit well developed thalassinoides burrow networks in fine grained transgressive sandstones and siltstones indicate a rapid return to marine conditions a similar stratigraphic pattern is well documented at the top of the lopez de bertodano formation and the base of the overlying paleocene sobral formation on seymour island in the southern part of the basin although no fossils were recovered to constrain the age of the upper 10 15 m of the succession on vega island that preserves the newly recognized upper sequence boundary strata below this level can be confidently placed within the manumiella bertodano interval zone which extends to a short distance below the k pg boundary on seymour island hence based on sequence stratigraphic and lithostratigraphic evidence the uppermost 10 15 m of the succession on vega island may encompass the cretaceous paleogene boundary together with a few meters of the paleocene sobral formation

an exceptional anticyclonic eddy in the south china sea in 2010 the highest sea level near the xisha islands in recent 20 years occurred during august 2010 satellite altimeter data indicated that the extreme event was largely due to an anticyclonic eddy whose amplitude exceeded 20 cm and size exceeded 400 km on 11 august 2010 cruise observations showed the eddy raised the center temperature by 7 7 degrees c at 75 m and vertically extended to 500 m eddy tracking showed it had a life span of more than 8 months and propagated far from the south of xisha islands such strong and long lasting eddy that moved northward for such a long distance was observed for the first time in the south china sea scs observational data from ctd xbt and the reconstructed three dimensional temperature and salinity were used to explore the eddy s features and vertical structure our analyses show the 2010 summer monsoon and current in the western boundary of the scs were largely altered after the 09 10 el nino event from may onward the wind blew northward and strengthened over the northwestern scs such wind drove a strong northward current along the western boundary which carried the eddy northward by advection from may to july energy budget showed during the eddy northward propagation the boundary current passed energy to the eddy which led to the continuing growth of the eddy in both strength and size