the metagabbros orthogneisses and paragneisses of the connemara complex western ireland although now largely disappeared within the 400 ma old galway granite the syntectonic connemara metagabbro gneiss complex which crystallized at 490 ma arenig is the largest intrusion into the dalradian rocks it is part of widespread cambro ordovician volcanism and plutonic injection into continental crust in the appalachian caledonide orogenic belt being synchronous in crystallization with the widely obducted 490 ma ophiolites within the orogeny the peridotites and hornblende gabbros were injected broken up and shouldered aside by quartz diorite granodiorite granite and trondhjemite gneisses and it is shown that these orthogneisses are not the in situ differentiation products of the gabbro magma the hornblende in the metagabbros is mainly igneous but is partly metamorphic and replaces olivine fo 75 92 orthopyroxene en 65 92 clinopyroxene wo 48 5 en 50 39 fs 5 14 and plagioclase typically an 80 92 range an 50 96 an aureole at least 10 km wide in the sillimanite zone was imposed and cordierite garnet sillimanite dalradian hornfelses were partially melted at temperatures up to 1000 o c near to the gabbros at 4 5 1 kbar corresponding to c 18 km depth this suggests that the complex forms part of the root of a now eroded batholith of calc alkaline affinities the gabbros corresponding to the transition zone to a basic bottom which is often supposed to underlie many batholiths within the orthogneisses are sheets of paragneiss formed from dalradian metasediments which have been folded up from the floor and down into sides of the magma chamber which process could be illustrative of the means by which basic magma can intimately interact with crustal material the 18 o 16 o d h nd and sr isotope evidence and the existence of inherited zircons in the gneisses indicate that the gabbro and gneiss magmas were significantly contaminated with crustal possibly dalradian material both before and after intrusion with the lowest initial 87 sr 86 sr at 490 ma being 0 708 even in samples far removed from metasediment the metagabbros are tholeiitic to high alumina basalt in character but the gneisses have distinct calc alkaline geochemistry the chemistry igneous hornblende and highly calcic plagioclase match many arc plutons in the western usa the syntectonic nature and the ubiquitous gneissic fabric in the quartz diorites trondhjemites and granites is a consequence of early movements which were probably in part connected with the separation of the connemara massif and which culminated in slicing off the largely inverted complex and carrying it southwards on the mannin thrust which underlies the whole of connemara the complex is thus a fragment of a now disrupted cambro ordovician continental magmatic arc or continent island arc environment which can be traced along the se edge of the laurentian continent

current variability near the southeast newfoundland ridge abstract a cooperative moored array experiment to measure currents and temperatures in the vicinity of the southeast newfoundland ridge was carried out over a 14 manth period starting september 1979 and ending december 1980 measurements were obtained from an incoherent exploratory army of nine moorings instrumented at 500 800 1500 and 4000 m levels the objectives were to explore the amplitude spatial variability and time scales of the eddy field in the decay region of the gulf stream an additional experiment and mooring to examine the influx of norwegian sea overflow water into the western north atlantic basin was imbedded in the array supplementary ctd and xbt profiles and a single current profile were taken during deployment and recovery cruises to aid in interpretation of the moored measurements and identification of water masses a description of the array experiment and preliminary results are reported mean velocities were weak compared with rms eddy velocities and were not determined with st

space and time scales of mesoscale motions in the eastern north atlantic abstract the tourbillon experiment carried out in 1979 80 over the porcupine abyssal plain in the eastern north atlantic is the fist experiment providing data that allow an efficient description of the spatial structure of the mesoscale low frequency flows in an eastern midlatitude basin the eddies appear to scale in the horizontal as the internal rossby radius of deformation and although of an energy level comparable to those observed during mode they are intrinsically more nonlinear because of reduced horizontal scale in much the same way the time scales are less than what is observed in western basin experiments mode polymode iii a b suggesting some kind of turbulent dispersion relation with frequency proportional to wavenumber in the eddy energy containing range we observe in tourbillon an equipartition of eddy kinetic and potential energy the frequency kinetic energy spectra have slopes of order 2 in a log log form hence are more white than in western basins 2 5 3 the distribution of

magmatic epidote and its petrologic significance epidote is a major magmatic mineral in tonalite and granodiorite in a belt coextensive with the mesozoic accreted terranes between northern california and southeastern alaska textural and chemical evidence indicates that epidote crystallized as a relatively late but magmatic mineral that formed through reaction with hornblende in the presence of a melt phase the observed relations concur with experimental data on crystallization of epidote from synthetic granodiorite at 8 kbar total pressure plutonic rocks bearing magmatic epidote must have formed under moderately high pressures corresponding to lower crustal depths under fairly oxidizing conditions

pre grenvillian and grenvillian lithotectonic regions in eastern labrador correlations with the sveconorwegian orogenic belt in sweden the trans labrador batholith groswater bay terrane and lake melville terrane are three major crustal segments located adjacent to or within the grenville province in eastern labrador each crustal segment is a distinct lithotectonic entity displaying contrasts with each other in proportions of rock types structural style and metamorphic imprint together they indicate a unilateral polarity to the region partly reflecting grenvillian tectonism which sliced the region into thrust bound blocks in all three crustal segments an archean or aphebian gneissic basement is inferred onto or adjacent to which ca 1900 1700 ma supracrustal rocks were deposited deformation metamorphism and granitoid pluton emplacement were partly coeval with and partly postdated the supracrustal assemblages in the north tectonothermal effects can be assigned to hudsonian ketilidian orogenesis but their peak was 50 100 ma later farther south post tectonic granitoid plutons and layered mafic intrusions were emplaced at about

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

granitic plutonism as an indicator of microplates in the palaeozoic of central and eastern maine abstract oxygen and strontium isotope ratios have been used to characterize source regions for granitic magmas for a transect across the northern appalachian orogen in central and eastern maine the northwestern plutons katahdin and seboeis have 18 o values of 10 3 13 3 and initial 87 sr 86 sr ratios of 0 7083 and 0 7066 respectively the central plutons bottle lake and center pond have lower 18 o values 8 2 9 9 and initial 87 sr 86 sr ratios 0 7043 0 7055 the southeastern plutons lucerne and deblois have 18 o values 9 0 11 0 but initial 87 sr 86 sr ratios 0 7077 and 0 7041 respectively which are intermediate between the northwestern and central plutons source models derived from these results and other petrological and geochemical data reflect the juxtaposition of discrete source regions by transcurrent faulting which may be related to oblique plate motions this model illustrates the importance of microplate accretion in the palaeozoic history of the northern appalachian orogen

observations of the antarctic circumpolar current and deep boundary current in the southwest atlantic fourteen month velocity and temperature records from an array of 14 moorings north and west of the falkland plateau and supporting hydrographic and tracer data reveal a narrow boundary current that carries dense antarctic waters the current flows west along the northern flank of the falkland plateau with mean speeds of more than 10 cm s 1 at 5000 m and more than 30 cm s 1 at 2500 m the westward flow extends from the bottom to at least 1000 m but the upper portion of the current is a branch of the antarctic circumpolar current acc following the only deepwater route between the scotia sea and the argentine basin waters colder than 0 2 c are too cold to be associated with the acc at drake passage and must ultimately derive from the weddell sea as part of the deep thermohaline circulation the westward transport of water colder than 0 2 c is 8 2 106 m3 s 1 in the mean the bottom boundary current is similar to that predicted by the stommel arons model but considerable variability is introduced by the meandering of the overlying acc chlorofluorocarbon data suggest that new antarctic water from the georgia basin enters the argentine basin via the deep boundary current which passes beneath the acc some new water is also advected east after being entrained in the acc most of the water in the deep boundary current is recirculated water that has been in residence in the argentine basin for some time water colder than 0 2 c is relatively new to the basin and comprises about 2 5 106 m3 s 1 of the westward flow of the boundary current

the vertical partition of oceanic horizontal kinetic energy to produce an interpretation of the surface kinetic energy as measured by altimeters a survey is made of the vertical structure of kinetic energy profiles in a large number of globally distributed long current meter records although the data are geographically confined primarily to a latitude band in the north pacific to the north atlantic and to a few moorings in the south atlantic the results show generally speaking that most regions are dominated by the barotropic and first baroclinic modes because of the near surface intensification of baroclinic modes altimeters primarily reflect the first baroclinic mode and thus the motion of the main thermocline there is good quantitative agreement with a few exceptions with estimates of the surface kinetic energy obtained from the topex poseidon altimeter and from vertical extrapolations to the surface of the mooring profiles these results are consistent with previous suggestions that barotropic models have little skill in depicting variability as seen in the altimeter data an eof analysis is shown to produce fictitious mode coupling unless the dynamical modes have very different energy levels

mesoscale variability transition from the western to the eastern atlantic along 48 n abstract the north atlantic low frequency variability along 48 n is described from 76 year long velocity temperature records obtained as part of the topogulf project whose main objective was to document the effects of the mid atlantic ridge upon the circulation the eddy energy is thermocline intensified and shows a fivefold decrease eastward from 35 to 10 w west of the ridge it penetrates more easily to the ocean floor between 1500 and 2500 m sudden energetic bursts are observed and we argue that they are associated with the passage of sub mesoscale concave cyclonic lenses depleted of labrador sea water at nearly all locations a negative zonal momentum flux u v is observed which may be linked to an energy transfer from the north atlantic current eddy heat fluxes are also obtained and are directed up down the mean gradient west east of the ridge crest

oliverian syenites of the pliny region northern new hampshire recent field work in the pliny range of northern new hampshire established the existence of two syenite units which predate the igneous activity of the white mountain magma series but postdate the formation of highly foliated units of the oliverian jefferson dome a total of ten syenite samples were analyzed for sr isotopes major elements and selected trace elements the syenites describe a whole rock rb sr isochron of 441 5 m y with initial 87sr 86sr of 0 70453 0 00006 the syenites of the jefferson dome thus formed during the same oliverian activity which produced the rocks of the domes extending along the bronson hill anticlinorium in new hampshire furthermore the structural position of the rocks establishes 441 m y as a minimum age for the taconic deformation in northern new hampshire the syenites have high total alkalis high k2o na2o contents and low mgo and cao concentrations they have extremely fractionated chondrite normalized rare earth element patterns with either small negative or no eu anomalies the magmas which produce the syenites were probably produced from partial melting of eclogite however the composition of the source material either mid ocean ridge basalt morb plus sediments altered morb or island arc tholeiite prior to metamorphism within the eclogite facies is uncertain

paleomagnetic history of the mealy dykes of labrador canada paleomagnetic analysis of the mealy diabase dykes of labrador reveals magnetizations that predate the grenville event at about 1000 ma these dykes intrude the mealy mountains anorthositic complex in the grenville structural province they are well south of the grenville front tectonic zone but were apparently never subjected to temperatures as high as 500 c during their post consolidation history four distinct magnetic components were uncovered by thermal and alternating field treatments and a fifth remained unresolved the major magnetic mineral present titanomagnetite is thought to record two magnetic directions acquired during cooling from magmatic temperatures these are b d 305 i 76 n 18 sites 12 95 11 and a d 095 i 52 n 20 sites 46 95 5 component b has much within site dispersion the other two components c d 274 i 47 n 10 sites 15 95 13 and d d 292 i 74 5 95 31 probably reside in magnetite and pyrrhotit

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

exploration of the eddy field in the midlatitude north pacific abstract fourteen moorings were deployed across the midlatitude north pacific 165 e to 152 w for approximately 2 years during 1983 85 ten mooring sites had previously been occupied at similar latitudes 30 40 n nominal for roughly two years 1980 82 along 152 e taken together these observations form the basis for the first systematic basinwide zonal exploration of the eddy field based on moored instrument techniques in the midlatitude north pacific along the kuroshio extension system and north pacific drift eddy kinetic energy ke at abyssal depths decays sharply moving east from 152 e and has decreased by a factor of 4 by 165 e there is a plateau in abyssal ke of about 10 cm2 s 2 across the emperor seamounts from 165 to 175 e abyssal ke drops to roughly 5 cm2 s 2 at 175 w and 1 cm2 s 2 at 152 w for a total decay of a factor of about 50 across the midlatitude north pacific upper level ke decreases by a total of roughly two orders of magnitude approximately 103 to 101 from 152 e to 152 w

geophysical and geochemical evidence for a hercynian magmatic arc maryland to georgia the distribution of hercynian granitic plutons in the central and southern appalachians is compatible with their being generated in a continental magmatic arc environment isotopic and geochemical data show a consistent pattern of lesser degree of crustal involvement in the most easterly plutons both gravity and aeromagnetic anomaly data suggest that the plutons were either synchronous with or postdate the development of the geophysical anomalies and are unlikely to be a part of any major allochthon

regional differences in pb isotopic compositions of feldspars in plutonic rocks of the northern appalachian mountains u s a and canada a geochemical method of terrane correlation feldspar pb isotopic compositions from paleozoic tonalitic to leucogranitic caledonian plutons from the northern appalachian mountains of the u s a and canada range from nonradiogenic to radiogenic relative to the evolution curve of stacey and kramers 1975 pb isotopic values in the feldspars are generally independent of modal and major and trace element contents of the plutons plutons with the least radiogenic pb isotopic signatures northern group have intruded allochthonous rocks closest to the north american craton and plutons with the most radiogenic pb southern group have intruded avalonian basement feldspars from plutons in the central group have intermediate pb isotopic compositions between the northern and southern groups and do not define an isotopically unique group the predominant source of the felsic magmas was the continental lithosphere as indicated by the general pb isotopic similarity of the plutonic feldspars with either grenville or chain lakes basement in the case of the northern group and with avalonian basement rocks in the case of the southern group the source region for plutons in the central group may have contained a mixture of grenvillian and avalonian components plutons in the northern appalachians are as a group more evolved in their pb isotopic compositions relative to caledonian plutons in the british isles

on the kuroshio extension near the emperor seamounts in june july 1982 and november 1983 studies were carried out of the vertical structure of the kuroshio extension along 167 e and the path of the current as it approached the emperor seamount chain in addition records from moored current meters at three locations two at 167 e and one in the main gap of the emperor seamount chain were obtained the kuroshio extension in both 1982 and 1983 turned cyclonically meander wave length of 450 km as it approached the chain the axis of the surface current was located in deep water 3 5 km in 1982 and in relatively shallow water 0 5 km in 1983 in 1982 the horizontal temperature gradient decreased and the density surfaces down to 2000 m ascended as the kuroshio extension flowed over the emperor seamounts in neither year was there evidence of current splitting as it crossed the seamounts in 1983 in contrast to 1982 there was no weakening of the horizontal temperature gradient and the kuroshio extension went over a very shallow portion of kinmei seamount 500 m the current measurements made at the time of the hydrographic section show that the instantaneous kuroshio extended to the bottom abyssal eastward current of 2 cm s 1 the deep low frequency eddy kinetic energy values are intermediate between those measured at 152 e and those at 158 w suggesting a large scale eastward decrease in deep eddy activity zonal mean flow near 3500 m at 167 e was essentially zero 0 1 cm s 1 the mean meridional components were larger 2 1 and 0 7 cm s 1 at the southern side of the gap the deep flow was unusually steady ke km 1 and directed northeastward into the eastern basin of the north pacific low ratios o 1 were also observed in the lower thermocline compared with those at 167 e o 10 100 the frequency content of the gap kinetic energy differed from that measured at 167 e the highest frequency band 2 hours p 2 days was the most energetic whereas at 167 e the mesoscale band 20 days p 150 days was the most energetic the flow in the gap resembles in many of its characteristics that observed in two other channel flows the vema channel and the charlie gibbs fracture zone

gulf stream flow field and events near 68 w the synoptic ocean prediction synop experiment was designed to provide an accurate understanding of the energetic mesoscale processes in the gulf stream the central array measured velocity and temperature throughout the water column with horizontal extent large enough nearly to span the meander envelope and eulerian mean structure of the jet at 68 w the 55 to 70 km mooring spacing resolved mesoscale eddy interactions with the gulf stream and the 26 month duration allowed stable estimation of long term mean fields six steep meander troughs propagated into or developed within the array each lasting around 30 60 days thus impressing a small mean trough near 68 w in the predominantly eastward currents at jet level 1000 m and above at the deep level 3500m the mean flow was southwest at the shoreward sites shallower than 4300 m but it flowed cyclonically around a mean low pressure anomaly affecting all the deeper offshore sites the eddy kinetic energy per unit mass e k decreased by a factor of about 2 5 with each depth increment from 400 to 700 to 1000 m but was only a factor of 2 smaller at 3500 m than at 1000 m values of e k in the upper central jet 400 m were 100 to 230 mj kg 1 and were 4 13 mj kg 1 at 3500 m overall e k in the upper 1000m at 68 w was higher than previously published values at 55 w two extended case studies of meander propagation through the array demonstrate the development and intensification of deep cyclonic and anticyclonic flows beneath the gulf stream the cyclonic flow at 3500m associated with amplifying meander troughs often exceeded 0 35 ms 1 which was much larger than the typical 0 05 ms 1 deep mean velocities

modal decomposition of the low frequency currents and baroclinic instability at drake passage abstract recently collected hydrographic data show that each of the four water mass zones previously identified in drake passage is characterized by a distinctly different vertical profile of brunt vaisala frequency stratification in drake passage is rather weak resulting in small values of the first baroclinic radius of deformation varying from 17 3 km for the subantarctic zone in the north to 7 7 km for the continental zone in the south using current meter records collected in 1979 at nine moorings the vertical structure of the low frequency currents is described in terms of dynamic normal and empirical modes dominance of the barotropic and first baroclinic modes was evident irrespective of mooring location accounting for typically 83 98 of record variance the first empirical mode which explains more than 90 of record variance at most moorings is surface intensified and appears to be a superposition of the barotropic and first baroclinic modes due to the observed modal coupling between the b

a note on the barotropic response of sea level to time dependent wind forcing this study examines the extent to which sea level variations at periods between 30 days and 1 year and spatial scales greater than 1000 km can be described by the wind driven linear barotropic vorticity dynamics the topex poseidon altimetric observations of sea level and the wind products of the national meteorological center are used as the database for the study each term of the linear barotropic vorticity equation was evaluated by averaging over regions of 10 10 in most of the open ocean the result of the analysis suggests that the sea level variabilities at the scales considered cannot be fully described by the equation the apparent net vorticity change is more than what can be explained by the local wind stress curl in the few regions where the wind stress curl is strong enough to balance the vorticity budget predominantly in the northeast pacific and the southeast pacific the balance is basically achieved in terms of the time dependent topographic sverdrup relation namely the balance between the advection of the planetary vorticity plus the topography induced vorticity and the forcing by the wind stress curl

low frequency eddy variability at 28 n 152 w in the eastern north pacific subtropical gyre abstract a current meter mooring maintained for over three years at 28 n 152 w in the eastern north pacific has yielded velocity and temperature data throughout the water column with particularly good thermocline resolution the flow is characterized by weak primarily westward mean velocities with a superimposed eddy field having rms velocities ranging from 10 cm s 1 in the upper thermocline to 3 cm s 1 at 1000 m depth the eddy energy is divided into two main bands the low frequency eddies have spatial scales of 250 300 km and periods of 100 200 days propagate southwestward and have slightly more zonal than meridional energy the high frequency eddies also propagate southwestward have spatial scales of 150 175 km and periods of 40 80 days and are strongly meridionally oriented vertical eof structure calculated in the frequency domain suggests that the low frequency eddies are more wavelike linear in nature than are the high frequency the entire band appears to derive energy baroclinically fro

proterozoic metamorphism in the grenville province a study in the double mer lake melville area eastern labrador a regional metamorphic gradient from upper greenschist to granulite facies is identified south of the grenville front in the double mer lake melville area of eastern labrador mineral assemblages in politic granitic gneiss amphibole bearing quartzo feldspathic gneiss and coronitic metagabbro allow three major metamorphic domains to be established these are collectively divisible into 11 subdomains geothermobarometry applied to the higher grade domains suggests that each is characterized by specific p t conditions which achieved 1000 1100 mpa and 700 800 c in the deepest level rocks the problem of reconciling geochronological data which record a major orogenic event at 1650 ma with the occurrence of high grade mineral assemblages in 1426 ma metagabbro which suggests a pervasive grenvillian event is discussed in terms of three models the preferred model envisages crustal stabilization at 1650 1600 ma to give high grade mineral assemblages seen in the host rocks and with which mineral assemblage

progressive metamorphism of pelitic and quartzofeldspathic rocks in the grenville province of western labrador tectonic implications of bathozone 6 assemblages aphebian metapelites and quartzofeldspathic rocks from the grenville province south of the labrador trough display progressive changes in mineral assemblages as a result of grenvillian metamorphism consistent with variation in grade from greenschist to upper amphibolite facies the following metamorphic zones have been delineated i chlorite muscovite ii chlorite muscovite biotite iii chlorite muscovite biotite garnet iv muscovite staurolite kyanite v muscovite garnet biotite kyanite vi muscovite garnet biotite kyanite granitic veins vii k feldspar kyanite granitic veins viii k feldspar sillimanite granitic veins reactions linking the lower grade metamorphic zones are interpreted to be dehydration phenomena whilst anatectic reactions occur at higher grades at lower metamorphic grades ah2o was high but it declined progressively as water entered the melt phase during higher grade anatectic reactions with the onset of vapour absent anatexis the restite assemblage became essenti

structural implications of some radiometric ages of igneous rocks in southeastern new england u th pb zircon rb sr whole rock and k ar hornblende isotopic ages reveal two major episodes of igneous activity in southeastern new england one in late proterozoic z time 600 650 m y ago and the other in devonian to ordovician time 375 450 m y ago the dated rocks are discussed in the context of several individual structural provinces that evolved more or less independently of each other prior to middle to late paleozoic assembly these provinces generally are bounded by major faults and or abrupt changes in metamorphic grade and from east to west include i the milford dedham zone ii the putnam nashoba zone iii the merrimack synclinorium and iv the bronson hill zone from the present and other recently published studies reasonably accurate ages representative of the two major episodes can now be assigned to many of the igneous rocks other units remain less well constrained but probably may be placed into one or the other of the general age groupings case by case examination of the geochronologic data makes us cautious in accepting some apparent fine structure age resolution within each grouping until factors such as inherited zircon and metamorphic overprinting can be better evaluated with the above mentioned qualifications in mind igneous rock ages summarized according to structural province are as follows i milford dedham zone a late proterozoic z dedham granite and related rocks 630 15 m y 595 15 m y 612 646 m y milford granite 630 15 m y 591 50 m y hope valley alaskite gneiss and scituate granite gneiss ages uncertain unnamed granite near assonet 600 650 m y b devonian to ordovician alkalic rocks including quincy cape ann and peabody granites wenham monzonite and nahant gabbro ii putnam nashoba zone a late proterozoic z no plutonic rocks identified but may include some metavolcanic rocks b devonian to ordovician sharpners pond diorite 430 5 m y andover granite 408 22 m y 450 22 m y muscovite granite near west berlin age uncertain preston gabbro 424 5 m y ill merrimack synclinorium a late proterozoic z granitic orthogneiss unit of the massabesic gneiss complex 600 620 m y metavolcanic unit of the massabesic gneiss complex 646 m y or older b devonian to ordovician fitchburg complex at maiden hill 402 11 m y fitchburg complex at rollstone quarry 390 15 m y newburyport complex 450 15 m y ayer granite 433 5 m y chelmsford granite age uncertain muscovite biotite granite at millstone hill 372 7 m y canterbury gneisses 395 10 m y 392 9 m y iv bronson hill zone a late proterozoic z dry hill gneiss of the pelham dome 600 m y b devonian to ordovician monson gneiss 440 10 m y these distinctive age patterns together with contrasts in petrography and texture of the igneous rocks in stratigraphy of the country lock and in metamorphic grade accentuate the separate geologic development of each structural province no correlation involving preassembly geology should be attempted across province boundaries without due consideration of the exotic character of each province

seasonal variations of the large scale geostrophic flow field and eddy kinetic energy inferred from the topex poseidon and jason 1 tandem mission data 1 geostrophic surface velocity anomalies are used to analyze the annual variations of the large scale geostrophic currents and of the eddy kinetic energy eke field of the ocean circulation the underlying geostrophic currents were estimated from the jason 1 topex poseidon jtp tandem altimetric sea surface height data using the parallel track approach with a 10 km along track resolution however because of the given separation of the tracks of the two satellites only large mesoscale eddies are resolved by the tandem measurements the analysis covers the entire 3 year period of the tandem mission 109 repeat cycles from september 2002 to september 2005 the analysis of the seasonal flow changes reveals annual changes of all major current systems but especially of the zonal flow field in low latitudes leading to zonal jets on the annual cycle in the southern pacific atlantic and indian oceans in middle and high latitudes indications of a seasonally modulated strength of the sverdrup circulation emerge from the analysis the eke field also shows changes in its amplitude on the annual period in low latitudes those can be rationalized as resulting from seasonally modulated currents in middle and high latitudes changes in the wind driven barotropic circulation loom large which are not represented in other altimetric velocity products results shown suggest that velocity time series of the jtp tandem mission should be continued through similar constellations e g of jason 1 and jason 2

reconstructing the ocean s interior from surface data a new method is proposed for extrapolating subsurface velocity and density fields from sea surface density and sea surface height ssh in this the surface density is linked to the subsurface fields via the surface quasigeostrophic sqg formalism as proposed in several recent papers the subsurface field is augmented by the addition of the barotropic and first baroclinic modes whose amplitudes are determined by matching to the sea surface height pressure after subtracting the sqg contribution an additional constraint is that the bottom pressure anomaly vanishes the method is tested for three regions in the north atlantic using data from a high resolution numericalsimulation the decomposition yields strikinglyrealistic subsurfacefields it is particularly successful in energetic regions like the gulf stream extension and at high latitudes where the mixed layer is deep but it also works in less energetic eastern subtropics the demonstration highlights the possibility of reconstructing three dimensional oceanic flows using a combination of satellite fields for example seasurfacetemperature sst andssh andsparse orclimatological estimatesoftheregionaldepthresolveddensity themethodcouldbefurtherelaboratedtointegrateadditionalsubsurfaceinformation such as mooring measurements

acadian synorogenic mafic intrusions in the maine appalachians two belts of syn acadian mafic intrusions the central maine belt is progressively more altered and metamorphosed toward the southwest at the northeast end the moxie pluton represents the least altered and most important example in the belt forsterite contents of the most primitive olivines are consistent with the derivation of the earliest magma from a largely unfractionated mantle melt the coastal maine belt is spatially associated with the siluro devonian coastal volcanics the age difference however between the volcanics and plutonics suggests that they may not be directly related the important pocomoonshine gabbro appears to represent the well layered roof zone of a major fractionated body mineral compositions are similar to those in the moxie pluton and suggest a similar primary magma intrusions in both belts have complex contacts pronounced contact aureoles and were all deformed by late acadian deformation modified journal abstract

isopycnal empirical orthogonal functions eofs in the north and tropical atlantic and their use in estimation problems we investigated the vertical variability of the thermal dynamical structure of the north and tropical atlantic ocean from a set of historical hydrographic data reynaud et al 1998 the analysis was performed in 10 geographic bins in terms of vertical empirical orthogonal functions eofs in isopycnal coordinates as first proposed by gavart and de mey 1997 hereinafter referred to as gdm97 in the isopycnal coordinate system the state vector is made up of isopycnal displacements and the compensated potential temperature along isopycnals gdm97 showed that in the azores madeira region the isopycnal eofs consistently help to better separate physical processes in the water column and to better project the dynamic height anomaly downward in comparison with the classical eof analysis in depth coordinates in the present study we extended their work geographically and the connection with state estimation and data assimilation was more formalized from our results smooth spatial variations of isopycnal eofs were found in the north atlantic and confirmed the large scale relevance of isopycnal eofs in the ocean north of 20 n the dominant isopycnal eof was associated with a quasihomogeneous vertical displacement of the isopycnal surfaces 1 with a quasiconservation of compensated potential temperature on those surfaces 0 that mode was strongly modified by thermocline intensified baroclinic effects along the path of the gulf stream up to 40 w some physical interpretations of the vertical eofs were also suggested in several areas as far as the isopycnal formulation was concerned e g some thermal fronts the mediterranean outflow water lenses or meddies this work confirmed the validity of the ideas of gdm97 over the entire north atlantic ocean the potential use of the isopycnal eofs in state estimation problems was discussed they are possible candidates to reduce the order of state estimation problems provided that they have good observability properties these observability properties were studied in the case of satellite altimetry that is we examined how the dominant isopycnal eofs were connected to sea level anomalies in most bins it was found that the order of an estimation problem could be truncated to one primarily north of 20 n or two modes the dominant eof was found to account for most of the surface dynamic height variability with a rather normally distributed error of only a few centimeters dynamically more robust results were also presented performing a univariate isopycnal analysis in leaving coherent thermal effects out as a result the dominant character of mode 1 was further enhanced everywhere these univariate isopycnal eofs can be used for purely dynamical state estimation more generally we believe that our results can be used to set up reduced order data assimilation schemes in the north atlantic or in other regions with good historical data

near surface mean circulation and kinetic energy in the central north atlantic from drifter data an analysis of a large drifting buoy data set is presented the objective is to obtain a self contained description of the properties of the near surface circulation drogue depth 100 m in the central north atlantic ocean independent of hydrographic data a necessary preanalysis step was the removal of all data from undrogued buoys from the data set the physical parameters of the circulation were deduced by averaging the remaining data in 2 3 boxes the minimum amount of data which is necessary to get statistically stable results was determined by an empirical quality criterion all important mean currents in the investigation area are reproduced by the near surface mean velocity field a separation of the mean velocity field into a nondivergent and an irrational part shows that the flow field is almost nondivergent the distribution of eddy kinetic energy is concentrated along the mean currents and provides the largest part of the total kinetic energy but there are regional variations energy from inertial movements dominates the high frequency part of the kinetic energy its distribution is very patchy the analysis of the reynolds stress terms shows an energy transfer from the eddy field to the mean circulation in the vicinity of the north atlantic current

estimates from altimeter data of barotropic rossby waves in the northwestern atlantic ocean abstract a dynamical model representing linear barotropic rossby waves is combined with geosat data from the northwest atlantic ocean the model is too simple to be very realistic in this complex area but the problem of combining any model with real data raises a number of issues that we address the combination method used is sequential estimation in the form of a filtering smoothing operation a fraction of the total signal variance 5 to 15 in the area over several spacecraft repeat cycles is demonstrated to be consistent with five rossby waves that the result is robust is demonstrated by recovering known signals added synthetically to the real data

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

tidal and lower frequency currents above fieberling guyot an intensive yearlong deployment of current meter moorings was made over and around fieberling guyot 32 5 n 127 75 w in the north pacific the measurements are used to investigate tidal currents the mean flow and subinertial current fluctuations the k1 and o1 diurnal tides were greatly amplified over the seamount apparently through dynamics resembling nonlinear seamount trapped waves the diurnal tides interacted nonlinearly to induce constituents at the sum frequency m2 and difference frequency fortnightly above the summit diurnal amplification was strongest at about 450 m and it extended from the seamount center out over the flanks the s2 semidiurnal tide was not substantially amplified over the seamount the mean flow was primarily along isobaths and was strongest about 50 m above the seamount rim it was driven by tidal rectification so that mean along isobath velocity at a given location correlated well with the amplitude of the local fortnightly tide at that location accompanying the mean flow was a cold dome over the seamount that was presumably maintained by a balance of mean downward advection and eddy tidal radial heat transport lower frequency current fluctuations were enhanced near the seamount and were apparently driven by fluctuations in the ambient flow

seasonal and interannual changes in the north atlantic subpolar gyre from geosat and topex poseidon altimetry sea surface slopes from the altimetric satellites geosat and topex poseidon are used to calculate eddy kinetic energy of the north atlantic subpolar gyre 40 65 n 60 5 w using two years of data from each satellite december 1986 to december 1988 and october 1992 to september 1994 respectively interannual differences in the north atlantic current nac are revealed in regions of strong currents the eddies are driven by baroclinic instability of the mean flow are not seasonally varying and may therefore be used as a surrogate for the mean flow itself wind stress curl fields for the same periods show that the northward and southward shifts in the current branches across the mid atlantic ridge are related to interannual differences in the winter wind stress curl pattern when the zero in wind stress curl is well defined and wind stress is at a maximum outside the nac the eddies are driven primarily by wind stress indicated by a significant seasonality time series of eddy kinetic energy and wind stress are generated for the 4 years and the magnitude phase and significance of annual and semiannual signals are determined interannual changes in the timing of the maximum eddy kinetic energy are associated with that of the maximum wind stress with each being shifted by a month or two later or earlier throughout much of the northern north atlantic a significant annual signal in eddy kinetic energy is observed lagging the wind stress by on average 6 weeks a negligible lag is found in the region of the east greenland current and irminger sea whereas the greatest lag about 2 months is found in the labrador sea

paleomagnetism of pre grenvillian mafic rocks from the northeast grenville province labrador implications for the grenville track a paleomagnetic study of mafic plutonic rocks in the northeast grenville province found five magnetizations interpreted as grenvillian and later overprints components a b and c with the highest unblocking temperatures and distinct regional distributions have paleopoles that appear to lie on the grenville track component c with pole at 348 e 11 s p m 2 4 and mostly distributed in lower grade mafic rocks in the groswater bay terrane near the grenville front is interpreted as a post ca 970 ma grenville overprint predating components a and b the latter components nearly coextensive in distribution in the groswater bay and sandwich bay regions farther south have respective poles at 326 e 02 n n 9 sites p m 8 11 and 348 e 13 n n 13 sites p m 6 8 component b could be interpreted either as a grenville overprint or more likely as a later overprint of late neoproterozoic 615 ma to cambrian age due to rifting in the lake melville region if so many other so

paleomagnetism of the lac st jean anorthosite and related rocks grenville province quebec alternating field and thermal demagnetization study of the lac st jean anorthosite and related rock units in the central portion of the exposed grenville province reveals two components of magnetization one of reversed and the other of normal polarity both components are thought to have been acquired during the last regional metamorphism which was sufficiently intense in this area mostly amphibolite grade to reset any earlier magnetization corresponding paleopoles at 193 w 8 s dm 7 3 dp 4 6 and 213 w 19 s dm 10 5 dp 8 5 lie along the 950 900 ma segment of the recently calibrated grenville track of the north american apparent polar wander path a track that has thus far been defined largely by results from rock units of the western grenville

seasonal variability of the tyrrhenian sea surface geostrophic circulation as assessed by altimeter data abstractnew insights into the structure and variability of the tyrrhenian sea s surface circulation are obtained through the analysis of a very long series of altimetric observations 1993 2010 in late winter and part of spring a consistent mean flow is individuated in the eastern tyrrhenian sea formed by a stream of atlantic water that meanders around four anticyclonic structures located along the italian coast which have smaller cyclonic companions offshore the signatures of these vortices are also found in images of chlorophyll and sea surface temperature as well as in modeling results both from a high resolution operational model of the tyrrhenian sea s circulation and from a dedicated numerical simulation analysis of the energy exchange between eddies and mean flow together with numerical evidence suggests that this winter spring circulation pattern may result from basin scale instability of the atlantic stream in summer the dynamic is dominated by a well known dipole located to the east

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

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

direct observations of the mean circulation at 48 n in the atlantic ocean abstract eulerian velocity measurements carried out along 48 n in the atlantic ocean provide averaged velocities with definite large scale structure this warrants an analysis of these mean velocity vectors within the framework of steady and large scale dynamics the dominant part played by the bottom forcing in the planetary vorticity balance is demonstrated combined use of vertical velocities derived from fills balance and the mean velocity spirals allows us to estimate advection in the heat equation and residual cros isopycnal velocities at the westernmost mooring site 35 w heat losses to the atmosphere account for these residuals while at the other sites 20 25 and 30 w lateral heat fluxes induced by mesoscale eddues must be invoked the hydrology of the region provides elements of comparison with the set of averaged velocities qualitative through our knowledge of the motions of watermasses at this latitude then more quantitative using geostrophic calculations beta spiral inversions are ca

observations and eof analysis of low frequency variability in the western part of the gulf stream recirculation abstract this study of low frequency oceanic variability is based on data collected during the long term upper ocean study lotus which was a two year program of mainly moored meteorological and oceanographic measurements the mooring arrays were centered at 34 n 70 w over the hatteras abyssal plain with a distance of about 300 km to the mean gulf stream axis and the continental slope lotus was the most northern and western long term mooring site in the gulf stream recirculation region to date the observed low frequency variability is dominated by zonally elongated motions of the secular time scale periods 100 days even great depths 4000 m in contrast to observations in other parts of the recirculation region the spectral shapes are strongly depth dependent the vertical structure of the variability was examined by eof analysis different kinds of eofs were tested the best representation of the observed variability was obtained by an eof representing a undirectional nonrotating with depth

parameterization of mixed layer eddies part ii prognosis and impact abstract the authors propose a parameterization for restratification by mixed layer eddies that develop from baroclinic instabilities of ocean fronts the parameterization is cast as an overturning streamfunction that is proportional to the product of horizontal buoyancy gradient mixed layer depth and inertial period the parameterization has remarkable skill for an extremely wide range of mixed layer depths rotation rates and vertical and horizontal stratifications in this paper a coarse resolution prognostic model of the parameterization is compared with submesoscale mixed layer eddy resolving simulations the parameterization proves accurate in predicting changes to the buoyancy the climate implications of the proposed parameterization are estimated by applying the restratification scaling to observations the mixed layer depth is estimated from climatology and the buoyancy gradients are from satellite altimetry the vertical fluxes are comparable to monthly mean air sea fluxes in large areas of

eddy kinetic energy in the north atlantic from surface drifters one hundred ten satellite tracked freely drifting buoys measured velocities and trajectories of the near surface currents in the north atlantic mean velocity values and the velocity variance about the mean were calculated for different regions a horizontal map of eddy kinetic energy was prepared on a 2 2 grid between latitudes 20 and 55 n maximum eddy energy 3000 cm2 s 2 coincides with the high speed gulf stream jet where it begins large amplitude meanders near 37 n 67 w a tongue of high eddy energy coincides with the stream s path eastward and around the grand banks into the newfoundland basin where values of 1000 cm2 s 2 are found a weaker tongue extends eastward across the mid atlantic ridge near 45 n a second weak extension reaches southeastward from the stream and crosses the mid atlantic ridge between 30 and 35 n north and south of the stream eddy energy diminishes rapidly reaching an e folding at 300 km from the axis values of 200 cm2 s 2 were observed in the mid gyre region and 100 cm2 s 2 in the eastern north atlantic and north equatorial current although the gross distribution of eddy energy is similar to that determined from ship drift measurements there are significant differences eddy energy from drifters amounts to about twice the value measured by ship drift in the gulf stream and one half the ship drift values in the mid gyre it is suggested that these differences are due to the horizontal averaging of mesoscale motion and the errors in navigation both of which are problems with the ship drift technique

some characteristics of internal gravity waves in the equatorial pacific one year moored current and temperature measurements made in the central equatorial pacific ocean at subthermocline depths display spectral characteristics at internal gravity wave frequencies which are distinct from those found at mid latitudes these characteristics are meridional orientation of current ellipses kinetic energy scaling proportional to buoyancy frequency 1 2 and coherence of zonal current and temperature at phases significantly different then 0 or 180 characteristics vary over as little as 100 m vertically but not over 40 km horizontally low frequency flow is predominantly zonal and shares similar spatial structure suggesting internal waves are influenced by it although horizontal internal wave fluxes cannot be calculated directly from the observations models provide a framework in which to interpret internal wave spectral characteristics models of internal waves near the equator in a resting ocean an ocean with a uniform zonal current and an ocean with depth dependent zonal current all require wave flux to be horizontally anisotropic in order to obtain current ellipses and zonal current temperatures similar to those observed the model with vertical shear is the most realistic of these three observed shears are sufficiently strong to allow the possibility of internal wave critical layers which in turn are a likely source of both horizontal anisotropy and vertical asymmetry of wave fluxes

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 global frequency wavenumber spectrum of oceanic variability estimated from topex poseidon altimetric measurements two years of altimetric data from the topex poseidon spacecraft have been used to produce preliminary estimates of the space and time spectra of global variability for both sea surface height and slope the results are expressed in terms of both degree variances from spherical harmonic expansions and in along track wavenumbers simple analytic approximations both in terms of piecewise power laws and pade fractions are provided for comparison with independent measurements and for easy use of the results a number of uses of such spectra exist including the possibility of combining the altimetric data with other observations predictions of spatial coherences and the estimation of the accuracy of apparent secular trends in sea level