ophiolite emplacement by collision between the sula platform and the sulawesi island arc indonesia much of the tectonic complexity displayed in eastern indonesia results from a series of neogene collision events between island arcs continental fragments and the australian continent here we examine the emplacement of a large ophiolite belt resulting from the miocene collision between the sulawesi island arc and a continental fragment the sula platform we present the results of several marine geophysical expeditions to the sw molucca sea and the nw banda sea plus gravity and geology on the east arms of sulawesi the batui thrust separates the ophiolite from sedimentary rocks deformed along the leading edge of the sula platform we mapped this thrust eastward from sulawesi along the southern margin of the gorontalo basin the latter is floored by oceanic crust and its south edge is uplifted against the thrust thus the sulawesi ophiolite can be traced offshore to its origin as basement of the gorontalo basin the ophiolite is composed of harzburgite in the southeast arm and passes upward through a complex of gabbros and diabase dikes in the east arm ophiolite melange underlies the harzburgites on the southeast arm beneath low angle thrust contacts where seen our local observations show the melange to be composed of thrust packets of both serpentine and red shale matrix varieties the packets are several hundred meters thick and the melange where studied has a moderate north to northeast dipping foliation this orientation if regionally representative of the melange fabric is consistent with a significant northward component of movement of the lower plate probably the sula platform or its margin where the ophiolite is in contact with rocks of the central schist belt it dips under the schist but where it encounters melange or mesozoic or paleogene sedimentary rocks the ophiolite is thrust over them the tectonic overlap sequence from west to east is schist over ophiolite over older sediments or melange the ophiolite appears to have been emplaced by oblique convergence of the sula platform along the southern edge of the gorontalo basin we suggest that the gorontalo basin represents a forearc basin and the ophiolite is its basement analogous to a number of other forearc settings deformation of the ophiolite may have occurred in part on the seafloor prior to emplacement but we feel that much of the deformation occurred during emplacement the sulawesi ophiolite is only one of a number of ophiolites in the indonesian region each of which has a very different origin and tectonic history

basal water and high pressure basal ice les expressions sont obtenues pour la pression de l eau dans les chenaux et cavites sous un glacier tempere en etat de regime vitesse de glissement constante ecoulement et production de l eau fixes les calculs sont bases sur un obstacle du lit bimodal simplifie

geochemical reconstruction of pacific decadal variability from the eastern north pacific during the holocene determining climate variations over the holocene requires high resolution records with well developed age models a 40 m long marine sediment core raised from effingham inlet an anoxic fjord on the west coast of vancouver island british columbia canada yields such a record forty six 14c accelerator mass spectrometry ams dates determined from terrestrial plant material form the age model downcore sampling at both 5 cm 20 year and 1 5 cm 7 year resolution indicates that high frequency oceanographic variability has prevailed at this site over the last 10 000 years spectral analysis of wt opal a proxy for diatom productivity in the basin reveals the bidecadal and pentadecadal periods of the pacific decadal oscillation pdo north pacific index npi that are related to changes in the strength of the aleutian low coherence analysis between the effingham inlet data and 18o records from jellybean lake a high elevation site in southwest yukon indicates regional coherence at periods of 45 7

models of seismic anisotropy in the deep continental lithosphere seismological observations sks wave polarizations systematic p residual variations azimuthal dependence of pn and surface wave velocities or a dispersion of surface waves are not consistent with isotropic if laterally heterogeneous upper mantle structure therefore an anisotropy should be considered as an a priori aspect of future large scale studies of mantle structure most studies of anisotropy however have assumed horizontal or vertical axes of symmetry but such orientations cannot explain bipolar patterns of spatial variations of p residuals which we have observed at many seismological stations on the basis of the petrophysical properties of real upper mantle rocks we consider anisotropy formed either by hexagonal or by orthorhombic aggregates composed of olivine orthopyroxene and clinopyroxene rotations of the aggregates about vertical and horizontal axes allow us to find the three dimensional orientations of symmetry axes that fit combinations of both p and s seismological observations in central europe and in western north america the orientations with plunging symmetry axes velocity extremes seem to be consistent across large spatially uniform tectonic units and change abruptly at important suture zones

a simple model of fjord and coastal circulation interaction abstract the dynamical interaction of a narrow fjord with a wind driven coastal regime is investigated using a linear two layer numerical model the coriolis acceleration is important in the coastal regime but assumed to he unimportant in the fjord dynamical because v 0 for a wide variety of wind conditions bottom topography and model parameters the wind forced coastal circulation with its geostrophic alongshore currants has a strong effect on the circulation within the fjord these geostrophic currents control the free surface and pycnocline displacement at the fjord mouth thereby strongly affecting fjord circulation this mechanism is an alternative to the classical idea of hydraulic control at the mouth by sills or constrictions model simulators also show that the free surface slope is a baroclinic effect and that alongshore and across shore winds affect the fjord differently alongshore winds produce flooding while up and down fjord winds simply sat up the surface we find that offshore win

annual record of particle fluxes geochemistry and diatoms in effingham inlet british columbia canada and the impact of the 1999 la nina event abstract sediment traps were deployed inside the anoxic inner basin of effingham inlet and at the oxygenated mouth of the inlet from may 1999 to september 2000 in a pilot study to determine the annual depositional cycle and impact of the 1999 la nina event within a western canadian inlet facing the open pacific ocean total mass flux geochemical parameters carbon nitrogen opal major and minor element contents and stable isotope ratios and diatom assemblages were determined and compared with meteorological and oceanographic data deposition was seasonal with coarser grained terrestrial components and benthic diatoms settling in the autumn and winter coincident with the rainy season marine sedimentary components and abundant pelagic diatoms were coincident with coastal upwelling in the spring and summer despite the seasonal differences in deposition the typical temperate zone thalassiosira skeletonema chaetoceros bloom succession was muted a july 1999 total mass flux peak and an increase in biogenous components coincided with a rare bottom water oxygen renewal event in the inlet likewise there were cooler than average sea surface temperatures ssts just outside the inlet and unusually high abundances of a previously undescribed cool water marine diatom fragilariopsis pacifica sp nov within the inlet each of these occurrences likely reflects a response to the strong la nina that followed the year after the strongest ever recorded el nino event of 1997 1998 by the autumn of 1999 ssts had returned to average and f pacifica had all but disappeared from the remaining trap record indicating that oceanographic conditions had returned to normal oxygenation events were not witnessed in the inlet in the years before or after 1999 suggesting that a rare oceanographic and climatic event was captured by this sediment trap time series the data from this record can therefore be used as a benchmark for identifying anomalous environmental conditions on this coast

tectonic role of ophiolite bearing terranes in the development of the southern apennines orogenic belt new data on ophiolite bearing terranes of the liguride complex together with some information on the terranes of the sicilide complex result in a better understanding of the role and tectonic significance of these units in the construction of the southern apennines orogenic belt the liguride complex is composed of two main tectonic units overlain by a thick turbiditic sequence of late oligocene middle miocene age the uppermost one frido unit is a polydeformed and polymetamorphosed sequence composed of two tectonic subunits of shales and calc schists respectively containing blocks of ophiolite garnet gneiss amphibolites and granitoids this unit is thrust over the un metamorphosed terranes calabro lucano flysch unit consisting of a broken formation with blocks of late jurassic ophiolite and their sedimentary cover cretaceous eocene pelagic sediments and late oligocene volcaniclastic deposits the frido unit underwent hp lt metamorphism p 8 10 kb t 400 500 c resulting in glaucophane and lawsonite assemblages in the ophiolitic rocks and aragonite in the meta limestones and calc schists followed by greenschist fades metamorphism p 4 kb t 300 350 c from a structural point of view units of the liguride complex comprise structures developed at different structural levels indicating progressive non coaxial deformation in response to tectonic transport towards the n ne the ophiolite bearing terranes of the liguride complex can be considered as a remnant of an accretionary complex in which the calabro lucano flysch unit represents the toe of the wedge where frontal accretion processes occur and the frido unit is a deeper portion emplacement of the frido unit is explained as being due to formation of a deep duplex structure during the early stage of continental collision processes the polarity of tectonic transport provides new evidence that the liguride complex represents a suture zone between the apulian and the calabrian blocks the age of collision appears to be not older than late oligocene the allochtonous terranes of the liguride and sicilide complexes therefore represent a complete accretionary wedge which records first subduction of the neotethys ocean beneath the calabrian europe continental margin and later continental collision with the african block

shelf fjord exchange driven by coastal trapped waves in the arctic in this article we show that the class of low frequency subinertial waves known as coastal trapped waves ctws are a significant agent of water volume exchange in a west svalbard fjord and by extension more widely along the west svalbard and east greenland margins where similar conditions prevail we show that ctws generated by weather systems passing across the sloping topography of the shelf break propagate into the fjord steered by the topography of an across shelf trough the ctws have characteristic periods of 2 days set by the passage time of weather systems phase speeds and wavelengths vary seasonally by a factor of two according to stratification winter summer values are cp 0 25 ms 1 0 5 ms 1 and 40 km 84 km ctw induced flow velocities in excess of 0 2 ms 1 at 100 m water depth are recorded observationally scaled ctw model results allow their explicit role in volume exchange to be quantified of the estimated exchange terms estuarine exchange is weakest qest 0 62 103 m3s 1 followed by barotropic tidal pumping qbt 2 5 103 m3s 1 with intermediary exchange dominating qi 2 4 104 m3s 1 oscillatory flows display greatest activity in the 1 5 day period band and ctw activity is identified as the likely source of variability in the 40 60 h period band within that band intermediary exchange driven by ctws is estimated as qictw ave 0 82 104 m3s 1 an exchange rate exceeding both barotropic and estuarine exchange estimates

complexities in the tectonic evolution of the west philippine basin abstract the oceanic west philippine basin can be subdivided into a main basin a northwest sub basin and a southern sub basin these basins have undergone different tectonic histories magnetic anomalies 21 17 are present in the main basin and indicate that it formed by two limbed seafloor spreading the now extinct spreading center is located within a zone of rough topography associated with the northwest trending central basin fault cbf the morphology of the cbf is primarily the result of post spreading tectonism the magnetic anomaly pattern of the main basin does not extend into the southern sub basin or the northwest sub basin geometrical constraints indicate that the southern sub basin did not form as part of the southern limb of the main basin the southern sub basin may have formed immediately before a ridge jump to the main basin spreading axis alternatively possible shallower crustal depth in the southern sub basin may indicate that the sub basin is younger than the main basin and formed separately from it in the northwest sub basin which originated as part of the main basin the dominant topographic trends are perpendicular to those in the main basin this difference as well as higher heat flow and shallower depth in the northwest sub basin indicate that it has undergone a deformational event which did not affect the main basin this deformation may be related to subduction along the east luzon margin in mid tertiary time the gagua ridge an uplifted sliver of oceanic crust along the western edge of the northwest sub basin may have originated during this event

the emplacement of ophiolites by collision ophiolites recognized in most of the world s orogenic belts are generally interpreted to be oceanic crust and upper mantle lithosphere fragments that have been incorporated into continental margins at consuming plate boundaries we suggest that the mechanism for ophiolite emplacement is the same in both the alpine and andean type orogenes in both geological settings obduction of oceanic lithosphere onto the continental lithosphere is caused by the convergence of light buoyant bodies such as oceanic plateaus continental slivers island arcs or old hot spot traces for example the troodos ophiolite complex previously interpreted by some workers as resulting from continental collision may have been emplaced by the collision of cyprus with the eratosthenes plateau embedded in the oceanic eastern mediterranean crust on the other hand the upper jurassic coast range ophiolites of california previously interpreted as resulting from typical oceanic subduction may be the result of a continuous injection of thick nonsubductable packages of light continentally derived sedimentary rocks seamounts and plateaus into the subduction zones many other ophiolite complexes may be similarly related to accreted terranes

gravity signatures of terrane accretion abstract in modern collisional environments accreted terranes are bracketed by forearc gravity lows a gravitational feature which results from the abandonment of the original trench and the initiation of a new trench seaward of the accreted terrane the size and shape of the gravity low depends on the type of accreted feature and the strength of the formerly subducting plate along the central american trench the accretion of gorgona island caused a seaward trench jump of 48 to 66 km the relict trench axes show up as gravity lows behind the trench with minimum values of 78 mgal n of gorgona and 49 mgal s of gorgona respectively these forearc gravity lows have little or no topographic expression the active trench immediately seaward of these forearc gravity lows has minimum gravity values of 59 mgal n of gorgona and 58 mgal s of gorgona respectively in the north the active trench has a less pronounced gravity low than the sediment covered forearc in the mariana arc two cretaceous seamounts have been accreted to the eocene arc the northern seamount is most likely a large block the southern seamount may be a thrust slice these more recent accretion events have produced modest forearc topographic and gravity lows in comparison with the topographic and gravity lows within the active trench however the minimum values of the mariana forearc gravity lows are modest only by comparison to the mariana trench 216 mgal their absolute values are more negative than at gorgona island 145 to 146 mgal we speculate that the forearc gravity lows and seaward trench jumps near gorgona island were produced by the accretion of a hotspot island from a strong plate the mariana gravity lows and seaward trench jumps or thrust slices were the result of breaking a relatively weak plate close to the seamount edifice these gravity lows resulting from accretion events should be preserved in older accreted terranes

a multicomponent coupled model of glacier hydrology 1 theory and synthetic examples 1 basal hydrology is acknowledged as a fundamental control on glacier dynamics especially in cases where surface meltwater reaches the bed for many glaciers at midlatitudes basal drainage is influenced by subaerial englacial and subsurface water flow one of the major shortcomings of existing basal hydrology models is the treatment of the glacier bed as an isolated system we present theoretical and computational models that couple glacier surface runoff englacial water storage and transport subglacial drainage and subsurface groundwater flow each of the four model components is represented as a two dimensional vertically integrated layer that communicates with its neighbors through water exchange governing equations are derived from the law of mass conservation and are expressed as a balance between the internal distribution of water and external sources the numerical exposition of this theory is a time dependent finite difference model that can be used to simulate glacier drainage in this paper we outline the theory and conduct simple tests using an idealized glacier geometry in the companion paper the model is tailored to trapridge glacier yukon territory canada where results are compared with measurements of subglacial water pressure

gravity currents facilitate formation of high frequency internal solitons and bores at the base of the fraser delta in the southern strait of georgia

siliceous microfossil record of late holocene oceanography and climate along the west coast of vancouver island british columbia canada diatoms silicoflagellates and biogenic silica bsi were analyzed from two piston cores recovered from effingham inlet british columbia relatively productive marine conditions from 4850 to 4000 cal yr bp were followed by a transition to the modern ocean climate regime marked by a decreased siliceous microfossil production since 2800 cal yr bp this change in the northeast pacific climate was characterized by an apparent cooling associated with higher rainfall and lower light levels the reduced abundance of most spring summer bloom diatom taxa skeletonema thalassiosira chaetoceros was coupled with a decreased abundance of diatoms normally associated with incursions of offshore water into coastal inlets this pattern reflected a weaker summer upwelling along vancouver island associated with the insolation related increase in the strength of the aleutian low and a weakened north pacific high after ca 2800 cal yr bp diatom assemblages also indicated more frequent periods of relatively low spring summer surface water salinity and a disruption of the typical bloom sequence indicative of increased climatic variability a period of warmer and drier climate conditions and possibly increased coastal upwelling offshore occurred ca 1450 1050 cal yr bp the most recent 500 yr are marked by reduced diatom production and the appearance of three distinct diatom biomarkers in the stratigraphic record rhizosolenia setigera ca ad 1940 minidiscus chilensis ca ad 1860 thalassionema nitzschioides morphotype a ca ad 1550 the oceanographic changes recorded in effingham inlet are correlative with other marine and terrestrial paleoenvironmental records in the northeast pacific ocean

seasonal waves on glaciers seasonal waves accompanying annual changes in the sliding velocity of ice travel down glacier at speeds much faster than the ice itself a simple explanation for these waves in terms of the passage of a pressure wave through the subglacial drainage system is given drainage by both distributed and localized systems is explored with the sliding velocity governed by a dependence on the effective pressure waves are caused by drainage through a slow distributed system but may be damped if this is well connected to an efficient channelized system a possible connection between these waves and high velocity spring events is discussed

a coupled marine ice stream ice shelf model theorie des variations climatiques du pleistocene a aujourd hui liees a la dynamique des couvertures marines de glace couplee aux glaces libres flottantes on neglige les effets thermodynamiques et on etudie les processus de flottaison en relation avec les rapports de densite entre la place et l eau de mer

hydraulics of subglacial cavities modele theorique du comportement a l etat stationnaire des cavites remplies d eau et interconnectees sur le lit du glacier

collisional processes in the eastern mediterranean in the eastern mediterranean the collision of the erastosthenes and the anaximander seamounts with the cyprus arc results in a unique tectonic setting due to the small size of the eastern mediterranean basin as a result of the collision some of the motion between the african plate and the eurasian plate is taking place by thrust faulting along the north african passive margin it seems that the stress at the plate boundary along the cyprus arc may be transmitted southward to cause the reactivation of a pre existing fault zone along the passive margin of eastern north africa

the rate of inflow and mixing during deep water renewal in a sill fjord we obtained high resolution data on a deep water renewal in the basin of gullmar fjord sweden using an autonomous profiling platform in the middle of the fjord where the platform is anchored renewal starts with the passage of a gravity current front and continues with a steady thickening of the new oxygen rich low nitrate bottom layer and an associated lifting of the old oxygen depleted high nitrate bottom water the basin continuously fills to sill level during a period of 10 d at the mouth of the fjord a three layer structure develops renewal is driven by the density difference between the intermediate water inside and the new deep water outside the fjord the volume flux is well predicted by a hydraulic exchange model in which the upper layer plays a passive role local upwelling and downwelling of the upper halocline cause fluctuating baroclinic currents during renewal but these seem to have little influence on the average volume flux of new deep water entrainment rates are small and the associated volume flux increase seems to be balanced by detrainment

modeling and observations of deep water renewal and entrainment in a swedish sill fjord a baroclinically forced deep water renewal event in a small swedish sill fjord is investigated using a one dimensional numerical model and a dataset that resolves temporal variations in salinity and oxygen the observations indicate an almost complete renewal of the basin water within a period of 2 3 weeks the details of the renewal process are emphasized by modeling the sill flow as well as the resulting dense bottom plume with various rates of entrainment it is found that sill mixing is relatively unimportant but that entrainment increases the deep water inflow by a factor of 2 4 different formulas for calculating plume entrainment are compared and the model s sensitivity to variations in sill flow and bottom friction is investigated it is shown that even weak entrainment occurring at shallow depths where the density difference between the plume and the resident water is large has a significant impact entrainment prolongs the time it takes for a complete renewal i e to flush out all resident water and on the moderate timescales considered here yields lower post renewal salinity and oxygen concentrations this implies that entrainment and mixing during renewal may be as important as basin water diffusion in setting the timescale for forthcoming renewal events

late holocene paleofish populations in effingham inlet british columbia canada abstract paleontological studies of fish remains in laminated sediments provide a proxy relationship between fish populations and ocean climate this study examines climate variability from approximately 500 y b p to 4000 y b p as recorded in fish remain abundances primarily scales collected from laminated sediments within effingham inlet on the west coast of vancouver island british columbia the study also discusses technical issues involving fish remains from laminated sediments including sampling resolution sediment volume identification of remains and appropriate abundance considerations the dominant species in the assemblage include northern anchovy and pacific herring with lesser percentage abundances from rockfish hake elasmobranches and surfperch the data indicate that northern anchovy experienced a shift in scale deposition abundance at approximately 2800 y b p with not only a greater total abundance but also a greater consistency of deposition with time pacific herring underwent cyclical deposition that changed little through time statistical analysis reveals that none of these species is directly responding to climatic signals as indicated in the lithological and palynological record but that this could have been partially due to the sampling resolution of the piston core analysis indicates a lack of correlation between the two dominant species as might be expected on the basis of their opposing lifestyle strategies with respect to sea surface temperatures with appropriate sampling strategies paleohistorical fish remains from laminated sediments reflect changes in population structure and behaviour for some species illustrate basic secondary trophic information and provide potential clues to basin scale oceanographic climatological variability

application of inventory data for estimating characteristics of and regional climate change effects on mountain glaciers a pilot study with the european alps a parameterization scheme using simple algorithms for unmeasured glaciers is being applied to glacier inventory data to estimate the basic glaciological characteristics of the inventoried ice bodies and simulate potential climate change effects on mountain glaciers for past and potential climate scenarios glacier changes for assumed mass balance changes are calculated as step functions between steady state conditions for time intervals that approximately correspond to the characteristic dynamic response time a few decades of the glaciers in order to test the procedure a pilot study was carried out in the european alps where detailed glacier inventories had been compiled around the mid 1970s total glacier volume in the alps is estimated at about 130 km3 for the mid 1970s strongly negative mass balances are likely to have caused a loss of about 10 20 of this total volume during the decade 1980 90 backward calculation of glacier length changes using a mean annual mass balance of 0 25m w e a 1 since the end of the little ice age around 1850 ad gives considerable scatter but satisfactory overall results as compared with long term observations the total loss of alpine surface ice mass since 1850 can be estimated at about half the original value an acceleration of this development with annual mass losses of around 1 m a 1 or more as anticipated from ipcc scenario a for the coming century could eliminate major parts of the presently existing alpine ice volume within decades

geologic and paleomagnetic evidence for a possible miocene collision in western panay central philippines the palawan metamorphic terrane represented by paleozoic basement on the northwestern tip of panay central philippines collided with the remainder of the island between late oligocene and middle miocene time subduction continued north and south of the collision zone along the manila and negros trenches respectively evidence for the collision is 1 the juxtaposition along a major fault of old melange terrane against highly metamorphosed paleozoic continental sediments similar to those exposed on palawan island itself and 2 miocene thrusting in the melange terrane oriented parallel to the suture paleomagnetic studies show that since the early miocene the island of panay has rotated 20 clockwise declination 20 9 inclination 22 1 for six sites whereas the northern philippines has rotated counterclockwise these contrasting rotations are consistent with a collision of the philippine arc with a northeastward converging palawan block

origin and assembly of the tethyside orogenic collage at the expense of gondwana land abstract the tethysides are a superorogenic complex flanking the eurasian continent to the south and consisting of the cimmerides and alpides products of palaeo and neo tethys respectively we here review their evolution mainly on the basis of new maps showing the distribution of sutures magmatic rocks certain palaeobiogeographically and palaeoclimatologically significant taxa and facies and fragments of pan african 900 450 ma orogenic system forming the basement of many tethyside blocks these are supplemented by palaeomagnetic data reported in the literature a fundamental tenet of this paper is that major sutures which contain ophiolite fragments represent tectonic sections between continental blocks where oceanic crust has been subducted palaeo tethys came into existence largely in late carboniferous time coevally it began to be consumed by both internal and peripheral subduction zones which continued into the permian some of these had been inherited from pre tethyan times in the later permian rifting subparallel with the northern margin of gondwana land began between the zagros and malaysia separating a cimmerian continent from n gondwana land and thus heralding the opening of neo tethys and other smaller oceans that were back arc basins of palaeo tethys this rifting possibly also extended farther west into crete and mainland greece however the north china block yangtze block huanan block the eastern moity of the qangtang block north tibet and annamia all originally pieces of the end proterozoic early palaeozoic gondwana land had already separated from it in pre late carboniferous times possibly during the devonian all of these blocks and the cimmerian continent were characterized by cathaysian floral elements in late palaeozoic time palaeomagnetic and palaeontological data showing the original gondwana land affinity of these continental blocks are supplemented by correlating late proterozoic early palaeozoic pan african sutures orogenic belts and sedimentary basin fragments across tethyside sutures late permian foraminiferal provinces are related to this palaeogeographical interpretation by triassic times most cimmeride subduction zones were already in existence the cimmerian continent accelerated its separation from gondwana land and locally in the late permian began disintegrating internally along the waser rushan pshart banggong co nu jiang mandalay ocean by late triassic time all of the chinese blocks except lhasa and annamia had collided with each other and with laurasia the resulting enormous orogenic collage had a soft cushion between itself and laurasia in the form of the enormous accretionary complex of the songpan ganzi this connection enabled laurasian land vertebrates to reach south east asia by late triassic time in late triassic to middle jurassic times most major cimmeride collisions were completed widespread aridity in central asia occurred in late jurassic time probably in the rain shadow of the newly formed cimmeride mountain wall neo tethyan subduction systems formed along the s margin of the cimmerides or within neo tethyan oceanic lithosphere during the jurassic most if not all were north or east dipping they continued the northerly migration of the tethyside blocks evolution of the tethysides influenced the distribution of marine and terrestrial organisms and affected sea level changes and patterns of atmospheric circulation during much of the mesozoic and cainozoic it is likely to have reflected the surface expression of a persistent trend in the large scale convective circulation in the mantle that continuously transported material northward into the tethyan domain

the link between glacier velocity and the drainage of ice dammed lakes comment on a paper by knight and tweed the interesting suggestion by knight and tweed 1991 that a link exists between glacier velocity changes and the filling and draining of a marginal ice dammed lake at solheimajokull southern iceland is examined the main problem lies not with plausibility but with a lack of field data to substantiate the argument some pertinent hydrological glaciological and meteorological data from the area are presented here many of which do not entirely support certain inferences and observations made in their paper it is shown that this very small lake is likely to have limited quantitative significance in the operation of the glacio hydrological or solute and sediment transfer systems in this basin further specific difficulties include the absence of crucial observations on glacier velocity variations and the precise timing and pattern of lake drainage in relation to such velocity changes the lack of evidence for a significant relationship between precipitation receipt and ice velocity here a component of the knight and tweed 1991 proposition and the occurrence of the lake drainage event in a rain free period contrary to the authors suggestion the opportunity is also taken to correct some incidental errors

processes of allochthonous terrane evolution mindoro island philippines on mindoro two tectonostratigraphic terranes the north palawan block and the mindoro block are separated by a steeply dipping shear zone the north palawan block was rifted off southern china in the oligocene and comprises most of the shallow southern end of the south china sea the eastern part of this terrane exposed on mindoro includes jurassic and paleogene strata probable rift basalts of oligocene age and oligo miocene graben fill deposits in the late oligocene and early miocene the eastern north palawan block underwent crustal stretching with grabens oriented at a high angle to synchronous spreading anomalies in the south china basin we hypothesize that grabens formed in an overall transtensional environment near a transform boundary at the eastern margin of the opening south china basin the mindoro block consists of a pre upper cretaceous low grade metamorphic basement overlain by upper cretaceous and upper eocene strata the mindoro block records several episodes of intense deformation of mesozoic and tertiary age and contrasts with the north palawan block both in terms of stratigraphy and structural evolution the mindoro suture which separates the mindoro and north palawan blocks is a complex structural boundary comprising slices of diverse lithologies separated by steeply dipping anastomosing faults deformed tectonic slices in the suture zone include serpentinized ultramafic rock amphibolite and rocks derived from both of the bounding terranes we interpret this suture as a zone of mostly transcurrent faulting that was active through much of mid tertiary time paleogeographic considerations for early and middle miocene time support the premise that the west side of the central philippine archipelago was a left lateral transform boundary the mindoro and north palawan blocks were initially juxtaposed along the transcurrent mindoro suture by late miocene time subsequent deformation on mindoro includes crustal shortening associated with the southern end of the manila trench which projects onshore on southwest mindoro the onset of shortening here probably reflects a late miocene change in philippine eurasian plate motion the mindoro suture zone is now locked and it acts as a rigid buttress against which strata of the north palawan block have been structurally stacked the mindoro suture zone is similar to other terrane boundaries in the northern philippines the history of terrane transport in this region was apparently dominated by strike parallel shuffling of terranes along major transcurrent boundaries within the philippine arc transcurrent motion has taken place in extensional and compressional regimes and it is ongoing today this may be a dominant process by which complex island arc systems are disrupted prior to accretion onto a continental margin

global dynamics of a temperate valley glacier mer de glace and past velocities deduced from forbes bands transverse profiles and velocities which have been measured on the ablation zone of mer de glace more or less continuously since 1891 contradict the weertman nye theory of glacier kinematic waves faint broad waves which undoubtedly result from fluctuations in the balance travel down the glacier faster than this theory predicts this theory having first been completed by taking changes in width with time and with distance down the glacier into account on the other hand velocity fluctuations are synchronous and more or less the same over the entire length studied 6 km these discrepancies result from bottom friction being of the solid type i e independent of sliding velocity friction should also be almost insensitive to discharge in subglacial waterways since in the steady state energy for keeping them open not entirely flooded and at atmospheric pressure is superabundant the sliding velocities at all cross profiles are thus controlled by some areas where the body of the glacier suffers strong deformation because the valley shape is far from cylindrical one such controlling zone exists on mer de glace owing to the existence of a subglacial transverse shoulder a new perturbation equation and a new rough expression for wave velocity are given intervals between forbes bands were plotted on seven aerial surveys between 1939 and 1979 progressive tilting of the slices of blue dusty ice from the position from which these dark bands proceed and progressive lowering of their exposed edge must be taken into account this analysis confirms the validity of our simple model for velocity fluctuations and allows us to estimate the entire series since the year 1888

seismotectonics of the southern boundary of anatolia eastern mediterranean region subduction collision and arc jumping the pattern of seismicity and fault plane solutions of earthquakes are used to outline the tectonic features of the southern boundary of anatolia in the eastern mediterranean and southeastern turkey the results of this study show that this boundary is composed of two distinct parts one in southeastern turkey and syria is a wide and complex zone of continental collision the other in the levantine basin of the eastern mediterranean is a zone of oceanic subduction in the region of continental collision three zones of seismicity are observed most of the seismic activity in this region follows the bitlis zone and is associated with a zone of thrusting and mountain building this appears to be the zone of most active deformation and plate consumption in the plate boundary region between arabia and turkey a less active zone of seismicity to the north of the bitlis zone is interpreted to have been more active in the past whereas another active zone of seismicity to the south is interpreted to be a zone which may be more active in the future as the main zone of plate consumption jumps to the south in the subduction zone of the eastern mediterranean the depth of the subducted slab and the rate of seismicity generally increase from east to west the zone of present day convergence between africa and turkey in the levantine basin can be best outlined by the northern edge of the mediterranean ridge the subduction zone in this area sequentially jumps to the south as small continental fragments collide with existing zones of subduction deep seismic activity near the gulf of antalya is associated with a detached subducted slab north of the anaximander mountains that is distinctly different from the seismic trend which is associated with present day active subduction the plate boundary between africa and turkey at the center of the levantine basin appears to have shifted to the south of the anaximander mountains and florence rise most of the focal mechanisms of the earthquakes along the entire southern boundary of anatolia indicate that n to nnw thrusting is the dominant mode of seismic deformation the present set of data is inconsistent with a major transform fault in the cyprean arc east of cyprus and in southeastern turkey

ogasawara plateau multi beam sonar bathymetry and possible tectonic implications the ogasawara plateau bathymetry in the northwest pacific ocean is presented by u s naval oceanographic office multi beam sonar data the plateau is significant in that it separates the izu and bonin trenches and may be obducted onto the overriding plate and or jamming the subduction zone the high resolution bathymetry suggests morphologic evidence of faulting within and possible uplifting on the approximately 20 000 km 2 features

effects of co2 h2o and oblique collision on orogenesis the european hercynides as an example abstract the european hercynides are considered the collisional result of baltica and the microcontinents of southern europe after subduction destroyed the intervening rheic ocean during the early paleozoic their geotectonic development is assumed to consist of four overlapping stages 1 1 lithospheric thinning upwelling of hot asthenospheric material subsidence along listric faults and basinal and geosynclinal development on the opposing shelves of the rheic ocean starting in pre devonian time 2 2 intermittent subduction of the rheic ocean interspersed with episodes of fracturing volcanism local uplift and subsidence and basement reactivation as a result of compression with dextral megashear particularly since the earliest devonian 3 3 several phases of folding with a northward vergence and thrusting and overthrusting along listric surfaces the true orogenic stage 4 4 post orogenic stage of massive granite intrusions and subsequent volcanism in the permo triassic the high clastic content as opposed to carbonates of the sedimentary sequences involved in the subduction and folding processes and the consequent release of large amounts of meteoric water are held responsible for the synorogenic and post orogenic magma rise and for the wide zone of anatectic granites and migmatites the dominant dextral megashear the constant re adjustment of the microcontinents of southern europe oblique collision and the scarcity of back arc basins oceanic plateaus and microcontinents led to the poor preservation of ophiolites and ultrabasic rocks and to a wide over 1500 km hercynian foldbelt during the paleozoic the depositional center of the rhenish massif shifted from south polar latitudes in the early ordovician to tropical positions within a period of about 100 m y the sediment facies reflects this paleogeographic development

remote alongshore winds drive variability of the california undercurrent off the british columbia washington coast the california undercurrent transports warm salty nutrient rich oxygen depleted water along the continental slope from the equatorial pacific to the aleutian islands we use multiyear acoustic doppler current profiler records collected simultaneously at two mooring sites off vancouver island to detail the regional structure of the undercurrent and to show that much of its variability is attributable to the passage of remotely forced coastal trapped waves we also document two subsurface currents missed by earlier current measurements the undercurrent becomes evident in spring intensifies through summer and fall and merges with the wind driven poleward surface flow in winter during intensification at the southern mooring site a1 the undercurrent shoals from 250 50 m in early summer to 150 50 m depth in late fall at the northern site bp2 225 km to the northwest of a1 the current is weaker and maintains a year round depth of 150 50 m temporal variability in the undercurrent velocity attains highest coherence with winds along the southern oregon northern california coast with peak coherence occurring for synoptic 10 40 day period alongshore winds off cape blanco in southern oregon the undercurrent lag of 3 2 days relative to the cape blanco winds at synoptic periods is consistent with low mode poleward propagating coastally trapped waves for periods 40 days the wind current coherence remains high for winds off the oregon california coast but lags are often negative indicating possible forcing by alongshore baroclinic pressure gradients at interannual time scales the undercurrent variations have links to climate scale processes in the equatorial pacific

paleomagnetism and the motion of large and small plates the focus of paleomagnetic research during past decades has varied greatly the first generation in paleomagnetism might be defined as beginning with the pioneering studies aimed at discovering whether the geomagnetic field has been a reliable reference frame for measuring and timing continental displacements an enormous effort followed in the form of individual paleomagnetic studies of cratonic rocks culminating with the construction of apw apparent polar wander paths for the continents which could be used to test paleogeographic reconstructions coupled with parallel research in marine geophysics and geology the refined apwp which result from this effort have helped to develop a reasonable first order history of cenozoic mesozoic paleogeography for the major plates

deep water renewal in the upper basin of loch sunart a scottish fjord abstract recording current meters were deployed near the surface and bottom in the upper basin of loch sunart during the summers of 1987 1989 and 1990 the measurements revealed frequent though irregular deep water renewal events when the basin water was replaced by density driven intrusions the data suggested that these events were induced by wind enhanced estuarine circulation during periods of low fresh water runoff a semi implicit laterally integrated estuarine model was modified to allow variable vertical grid spacing and to permit the sea surface to move vertically through the grid both modifications being necessary in order to apply the model to the sea loch environment a turbulence closure scheme was also incorporated the model can simulate the evolution of the salinity field over periods of several weeks and was used to examine the mechanisms that induce deep water renewal model results suggested that very weak stratification in the basin is required for renewal to occur and indicated

oceanic plateaus the fragmentation of continents and mountain building many anomalous rises in today s oceans may be submerged continental fragments detached from previous continents ancient island arcs or basaltic piles formed by hot spots and spreading centers these rises are embedded in their respective moving oceanic plates and are fated to be consumed at active margins where such rises are being consumed at present e g the nazca ridge they cause cessation of volcanism disruption of the downgoing slab and possible shifts in plate boundary configuration many past rises including numerous continental fragments have been recognized within mountain belts as allochthonous terranes they constitute a large portion of the orogenic belts in the north pacific from mexico through western north america alaska east siberia japan and in new zealand the orogenic deformation in these belts is possibly the result of the accretion of the allochthonous terranes many terranes have been accreted with substantial deformation also in the alpine chain well before major continent continent collisions it is suggested therefore that the accretion of fragments may be the common process of the deformation phase of mountain building subduction of normal oceanic crust may be insufficient for deformation whereas full continent continent collision may not be necessary the general validity of this conclusion depends critically on whether allochthonous terranes caused orogenic deformation in the andes or not most of the accreted fragments with continental affinities in the mesozoic cenozoic orogenic belts of the world can be traced back to the breakup of gondwana beginning with a pacifica domain in the permian through a larger india domain in the early mesozoic and continuing through the separation of the somalia plate in the near future the reasons for this 250 million year breakup process are not known but some kind of thermal process possible of mantle wide scale is implied

an introductory overview to the concept of displaced terranes on land much of the pacific margin is composed of allochthonous terranes which are of continental and noncontinental origins in the oceans numerous oceanic rises some of which are submerged continental fragments are presently embedded in the oceanic plates these oceanic rises are probably future accreted terranes they thus represent one stage in the development of allochthonous terranes found in orogenic zones minerals found in these terranes were formed at locations that in the past could have been thousands of kilometres away this is because some oceanic terranes were split into several parts that moved with their respective plates in different directions also faulting at the continental margins caused large scale concurrent and post accretionary horizontal translations of hundreds of kilometres of the allochthonous terranes studying the allochthonous terranes may provide important information about the paleozoic and early mesozoic history of the pacific ocean because most of the oceanic crus

a numerical model of interactions between a polar ice stream and the ocean application to ice stream e west antarctica a time dependent numerical model has been developed to study the dynamics of a polar ice stream grounded below sea level the model was applied to ice stream e one of the two most active ice streams draining the ross sea sector of the west antarctic ice sheet the retarding force or back stress from the floating ross ice shelf needed to hold the model grounding line in dynamic equilibrium was found to compare closely with retarding force mapped from field data by earlier investigators this implies that the grounding line of ice stream e is in fact close to dynamic equilibrium neither advancing nor retreating rapidly if the ice stream and its catchment area are approximately in mass balance sensitivity tests showed that the model ice stream is more sensitive to changes in back stress from the ice shelf than to changes in the accumulation rate changes in back stress can be caused by changes in the average thickness of the ice shelf the model was used to simulate retreat of the ice stream from the edge of the continental shelf in the ross sea during the holocene period of rising sea level the sea floor was assumed to be isostatically depressed but to remain rigid during retreat the effect of the assumed retreat history of the ross ice shelf on the computed timing of grounding line retreat was investigated by considering several alternative ice shelf histories the results support the conclusion of earlier investigators that the ross ice shelf caused the grounding line to stop retreating near its present position after extensive retreat during the holocene in addition the timing of retreat of the calving front of the ross ice shelf exerted major influence on the timing of retreat of the ice stream grounding line

tectonostratigraphic evolution of cenozoic marginal basin and continental margin successions in the bone mountains southwest sulawesi indonesia abstract the bone mountains located in southwest sulawesi along the se margin of sundaland are composed of oligocene to possibly lower miocene marginal basin successions bone group that are juxtaposed against continental margin assemblages of eocene miocene age salokalupang group three distinct units make up the latter i middle upper eocene volcaniclastic sediments with volcanic and limestone intercalations in the upper part matajang formation reflecting a period of arc volcanism and carbonate development along the sundaland margin ii a well bedded series of oligocene calc arenites karopa formation deposited in a passive margin environment following cessation of volcanic activity and iii a series of lower middle miocene sedimentary rocks in part turbiditic which interfinger in the upper part with volcaniclastic and volcanic rocks of potassic affinity baco formation formed in an extensional regime without subduction the bone group consists of morb like volcanics showing weak to moderate subduction signatures kalamiseng formation and a series of interbedded hemipelagic mudstones and volcanics deko formation the deko volcanics are in part subduction related and in part formed from melting of a basaltic precursor in the overriding crust we postulate that the bone group rocks formed in a transtensional marginal basin bordered by a transform passive margin to the west sundaland and by a newly initiated westerly dipping subduction zone on its eastern side around 14 13 ma an extensional tectonic event began in sw sulawesi characterized by widespread block faulting and the onset of potassic volcanism it reached its peak about 1 ma year later with the juxtaposition of the bone group against the salokalupang group along a major strike slip fault walanae fault zone the latter group was sliced up in variously sized fragments tilted and locally folded potassic volcanism continued up to the end of the pliocene and locally into the quaternary

basal water film basal water pressure and velocity of traveling waves on glaciers la theorie de nye et weertman des ondes cinematiques est etendue pour couvrir le cas ou la presence d une abondante quantite d eau au fond ou une pression croissante d eau accroit la vitesse de glissement d un glacier sur son lit on trouve que le rapport entre la vitesse de l onde et la vitesse superficielle du glacier est independante de la quantite d eau ou de sa pression au fond

conditions for a crustal block to be sheared off from the subducted continental lithosphere what is an essential factor to cause features associated with collision 1 crustal blocks are detached from the subducting lithosphere at various depths i call such phenomena shearing off and investigate the mechanical conditions for shearing off to occur in the continental lithosphere the buoyancy of the crustal block does not work selectively as a driving force until it has been sheared off and i suppose that shearing off occurs when the shear traction at the thrust whose maximum value is calculated from the strength along the thrust overcomes the strength of the boundary faults of the block and determine the depth of the leading edge of the subducted crustal block when shearing off occurs the temperatures of the slab and at its surface are calculated by the steady state formula of molnar and england 1990 as a function of the surface heat flow dip angle and convergence velocity of the subducted continental plate as the shear stress and temperature at the ductile part of the thrust zone are consistent with the flow law the shear stress at the brittle part is a strong function of the pore fluid pressure ratio i show that shearing off of an upper crustal block is possible only for a small value of such as 0 4 when the surface heat flow value is 70 mw m2 i suggest that the essential factor to cause shallow offscraping of crustal blocks in collision zones is not a buoyancy of the continental crust but a low value of which would result from a little amount of dehydration from the subducted continental plate

the 2011 tohoku tsunami generated major environmental changes in a distal canadian fjord 1 tsunamis triggered by powerful earthquakes cause extensive damage and loss of life within many regions of the world ocean although coastal inundation from major tsunamis is becoming increasingly well understood we know little about the broader aspects of such events on distal marine systems here we use time series from moored oceanic sensors to show that the tohoku tsunami generated by the magnitude 9 0 earthquake off eastern japan in march 2011 caused days of surge like currents and turbulent mixing in the inner basin of an anoxic canadian fjord located over 7000 km from the seafloor rupture zone mixing combined with the inflow of more oxygen rich water from the adjoining outer basin led to abrupt changes in the hydrodynamics bottom sedimentation and zooplankton behavior in the basin these findings help define mechanisms by which major transoceanic tsunamis can significantly alter coastal marine environments located far from the source area

a current velocity index of ocean variability we use daily time series of the longshore component of residual detided current velocity z t measured at several depths at a single location on the continental slope to construct a current velocity index i s z z of coastal ocean variability here z is depth t is time and sgn f f2 2 1 is a normalization factor constructed from the local coriolis parameter f a friction parameter and the standard deviation of the near surface current velocity where s is the fluctuation about the time series mean sgn f 1 for the northern hemisphere and 1 for the southern hemisphere the time series of vertical shear z z is derived from the velocity difference between simultaneous current meter records separated by a vertical distance z within the upper half of the water column the index characterizes low frequency baroclinic variability over the continental margin and is linked through use of the thermal wind relation to instability processes that effect the transfer of potential energy stored in the mean cross slope density field to the kinetic energy of mesoscale meanders and eddies for eastern boundary regions the index ranges from large positive values during summer upwelling conditions to large negative values during winter downwelling conditions the transition seasons spring and fall are characterized by i 0 we demonstrate use of the index by applying it to the continental margin of southwest vancouver island using current velocity data collected from october 1989 to march 1995 at depths of 35 100 175 and 400 m at a long term mooring site results enable us to specify the start and end times of the oceanic seasons and to quantify the summer upwelling and winter downwelling intensities for the region gaps in the current meter time series prompted us to examine records of coastal sea level sea surface temperature sea surface salinity and bakun upwelling index the wind driven cross shore component of surface ekman transport as possible surrogates for the velocity index none of these time series were acceptable although the bakun index is a logical substitute for the velocity index differences between the two indices are significant and suggest that current velocity data are needed for accurate delineation of seasonal oceanic variability along continental margins

coastal trapped waves alongshore pressure gradients and the california undercurrent abstractthe california undercurrent cuc a poleward flowing feature over the continental slope is a key transport pathway along the west coast of north america and an important component of regional upwelling dynamics this study examines the poleward undercurrent and alongshore pressure gradients in the northern california current system ccs where local wind stress forcing is relatively weak the dynamics of the undercurrent are compared in the primitive equation navy coastal ocean model and a linear coastal trapped wave model both models are validated using hydrographic data and current meter observations in the core of the undercurrent in the northern ccs in the linear model variability in the predominantly equatorward wind stress along the u s west coast produces episodic reversals to poleward flow over the northern ccs slope during summer however reproducing the persistence of the undercurrent during late summer requires additional incoming energy from sea level variability applied south

distribution of diatom surface sediment assemblages within effingham inlet a temperate fjord on the west coast of vancouver island canada abstract twenty nine surface sediment samples from effingham inlet a small fjord on the west coast of vancouver island british columbia were analyzed for diatoms this fjord has been selected for paleoceanographic investigation due to the presence of laminated sediments resulting from the dysoxic to anoxic bottom water conditions in the inner and outer basins of the inlet distributional patterns of the diatom microflora reflected proximity to littoral regions phytoplankton production and marine influence from outside the fjord principal components and cluster analyses of the microflora established four diatom assemblages with a clear separation between the inner and outer basin diatom floras inner basin stations were characterized by elevated absolute abundance with assemblages dominated by spring early summer bloom taxa including skeletonema costatum thalassiosira nordenskioeldii and thalassiosira pacifica chaetoceros spp resting spores were abundant throughout effingham inlet with the exception of the stations closest to the fjord head stations located in the outer basin and towards the fjord mouth had relatively lower absolute abundance yet showed a higher relative and absolute abundance of thalassionema nitzschioides rhizosolenia setigera coscinodiscus radiatus ditylum brightwellii odontella longicruris and paralia sulcata in relation to the inner basin many of these latter taxa are often associated with late summer and autumn conditions in fjords along coastal british columbia oceanographic data for effingham inlet suggest that increased offshore penetration is more likely to occur from summer to early fall with a more restricted offshore influence in the inner basin diatom surface sediment assemblages in effingham inlet appear to reflect incursions of offshore waters into the fjord absolute abundance estimates and the preservation of lightly silicified taxa suggest excellent preservation of fossil material in the sediments of the predominantly anoxic inner basin preservation in the outer basin is reduced reflecting more frequent recharge by oxygenated waters spilling over the outer sill into the basin our findings suggest the inner basin should be an optimal site for reconstruction of diatom production with records from the outer basin providing more consistent information about offshore influence and coastal upwelling conditions over the holocene estimates of diatom abundance within the inner basin sediment may serve as a good proxy of production although proxy tracers of bottom water conditions and sedimentological analyses must be coupled to the diatom record to ensure depositional conditions were not influencing valve preservation or abundance our results suggest that fjords can serve as good environments for paleoceanographic reconstructions of both inshore and offshore conditions although careful site selection and understanding of processes affecting the microfossil record are essential

coefficients for sea surface wind stress heat flux and wind profiles as a function of wind speed and temperature surface layer coefficients for wind profiles wind stress and heat flux in typical open sea conditions are briefly reviewed businger dyer flux gradient relationships and a charnock wind stress formula fit the empirical data and are dimensionally consistent these have been solved by an iterative method and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data

modern to late holocene deposition in an anoxic fjord on the west coast of canada implications for regional oceanography climate and paleoseismic history laminated sediments preserved in the anoxic inner basin of effingham inlet on the pacific coast of vancouver island british columbia canada yield a high resolution sediment deposition record spanning about 6000 yr the varying thickness of diatom terrigenous mud varves in sediment cores from the basin can be interpreted in terms of annual changes in surface productivity and freshwater input within the inlet similarly the occurrence of unlaminated mud units homogenites intercalated amongst the laminated sediments can be interpreted in terms of oceanic and climatic changes these units appear to be associated with coastal upwelling events that result infrequently in highly oxygenated oceanic water penetrating to the bottom of the inner and outer basins of the inlet the sedimentary record also contains massive and graded mud units considered to arise from debris flows and turbidity currents some of which were probably initiated by seismic events including a major event about 4500 14 c yr bp which may be earthquake related a total of seventeen oceanographic surveys of the inlet beginning in 1995 characterize the modern seasonal coastal upwelling regime and a unique bottom water oxygenation event which was

accreted terranes in the northern part of the philippine archipelago the philippine archipelago consists of a complex array of ophiolites continental fragments and island arc elements that can be identified as accreted terranes similar to those increasingly recognized as components of orogenic zones the northern philippines including luzon mindoro and nearby smaller islands can be divided into at least six of these tectonic elements from west to east across central luzon there are the neogene accretionary prism of the west luzon arc the eocene zambales ophiolite the cretaceous angat ophiolite and a late cretaceous early paleogene volcanic arc built on an older metamorphic basement this arc terrane is repeated by offset along the philippine fault to the south the western luzon terranes are juxtaposed against the metamorphic basement block of mindoro which itself is colliding with the north palawan microcontinental fragment the ophiolites appear to have originated in back arc basins rather than in oceanic plateaus and the metamorphic belts have protoliths indicating deformation along active margins perhaps deep within accretionary prisms the philippine terranes are interpreted as fragments that originated within the complex pacific eurasian plate boundary rather than as intra pacific basin units these terranes have been assembling at least since the oligocene by strike slip and convergent displacements strike slip displacement either along transcurrent faults or as a component of convergence played a very important if not dominant role in this assembly most terranes identified in the northern philippine appear to be plate fragments with attached crust and upper mantle their characteristics contrast with those usually interpreted for terranes in the north american cordillera where near orthogonal convergence and shallow dipping terrane sutures are favored

a numerical study of the tidal circulation and buoyancy effects in a scottish fjord loch torridon 1 the tidal and buoyancy driven circulation in loch torridon a scottish fjord is investigated using a three dimensional hydrostatic primitive equation model the predictions from the model have been quantitatively compared to available data gathered between 1998 and 2001 the model performed well in reproducing the tidal characteristics and density evolution of the fjord over the 3 month simulation period results show that tidal currents are dominated by the constraint imposed on the flow by the shallow sill separating the upper and middle basins the flow is strongly accelerated during flood and ebb tides and significant residual currents are generated that may influence exchange and residence times of the middle basin a strong baroclinic response to the flow over the sill is predicted throughout the fjord with a propagating linear m2 tide displacing isopycnals vertically by up to 32 m at the sill the formation of stationary lee waves on both flood and ebb tides is predicted with the wave generated during flood tide being notably larger as the growth of the ebb wave is inhibited by deep dense water this allows more energy to transfer into the seaward propagating internal tide as the tidal flow weakens the lee waves propagate over the sill and upstream estimates of the total vertical turbulent buoyancy flux in the fjord are made and the distribution of mixing over a tidal cycle is shown vertical mixing is seen to be highly spatially and temporally variable and strongly linked to the presence and dissipation of lee waves near the sill

accretionary nature of the crust of central and east java indonesia revealed by local earthquake travel time tomography abstract reassessment of travel time data from an exceptionally dense amphibious temporary seismic network on and offshore central and eastern java meramex confirms the accretionary nature of the crust in this segment of the sunda subduction zone 109 5 111 5e traveltime data of p and s waves of 244 local earthquakes were tomographically inverted following a staggered inversion approach the resolution of the inversion was inspected by utilizing synthetic recovery tests and analyzing the model resolution matrix the resulting images show a highly asymmetrical crustal structure the images can be interpreted to show a continental fragment of presumably gondwana origin in the coastal area east of 110e which has been accreted to the sundaland margin an interlaced anomaly of high seismic velocities indicating mafic material can be interpreted to be the mantle part of the continental fragment or part of obducted oceanic lithosphere lower than average crustal velocities of the java crust are likely to reflect ophiolitic and metamorphic rocks of a subduction melange

remote forcing of subsurface currents and temperatures near the northern limit of the california current system local and remote wind forcing of upwelling along continental shelves of coastal upwelling regions play key roles in driving biogeochemical fluxes including vertical net fluxes of carbon and nutrients these fluxes are responsible for high primary productivity which in turn supports a lucrative fishery in these regions however the relative contributions of local versus remote wind forcing is not well quantified or understood we present results of coherence analyses between currents at a single mooring site 48 5 n 126 w in the northern portion of the california current system calcs from 1989 2008 and coincident time series of north america regional reanalysis narr 10 m wind stress within the calcs 36 54 n 120 132 w the two decade long current records from the three shallowest depths 35 100 and 175 m show a remote response to winds from as far south as 36 n in contrast only temperatures at the deepest depth 400 m show strong coherences with remote winds weaker local wind influence is observed in both the currents and 400 m temperatures but is mostly due to the large spatial coherence within the wind field itself lack of coherence between distal winds and the 400 m currents suggests that the temperature variations at that depth are driven by vertical motion resulting from poleward travelling coastal trapped waves ctws understanding the effects of remote forcing in coastal upwelling regions is necessary for determining the occurrence and timing of extreme conditions in coastal oceans and their subsequent impact on marine ecosystems this article is protected by copyright all rights reserved

mantle flow at oceanic spreading centers models derived from ophiolites abstract the internal structures of eleven ophiolite complexes have been structurally investigated the attitude of the foliation and the lineation in the peridotites is related to asthenospheric flow in the uppermost mantle at an oceanic spreading center from the orientation of these structures with respect to the paleohorizontal plane two oceanic situations are distinguished the horizontally spreading asthenosphere illustrated by the table mountain massif newfoundland is characterized by 1 a homogeneous regular and sub horizontal plastic flow pattern over large distances 2 b flat paleo mono and absence of large scale folding 3 c rare economical chromite deposits and depleted mantle the diapirically spreading asthenosphere illustrated by the acoje type philippines displays 1 a inhomogeneous and sub vertical plastic flow pattern 2 b deformed paleo moho and large scale folds 3 c important economical chromite deposits and less depleted mantle presumably due to secondary magmatic impregnation this leads to vogt s model of asthenospheric flow beneath an oceanic ridge the direction of which being equated with the dike swarm in this model the horizontally spreading asthenosphere is derived from the diapirically spreading one in the following way the vertical mantle flow at the diapir center diverges horizontally in every direction including that parallel to the ridge at about 50 km from the diapir center the mantle flow becomes progressively perpendicular to the ridge due to the damming effect of transform faults an important economical consequence of this model is that large chromite deposits are expected preferentially in the diapiric type of ophiolite because chromite is preferentially precipitated at the diapir center from pristine magma