interface resolved direct numerical simulations of sediment transport in a turbulent oscillatory boundary layer the flow within an oscillatory boundary layer which approximates the flow generated by propagating sea waves of small amplitude close to the bottom is simulated numerically by integrating the navier stokes and continuity equations the bottom is made up of spherical particles free to move which mimic sediment grains the approach allows one to fully resolve the flow around the particles and to evaluate the forces and torques that the fluid exerts on their surface then the dynamics of sediments is explicitly computed by means of the newton euler equations for the smallest value of the flow reynolds number presently simulated the flow regime turns out to fall in the intermittently turbulent regime such that turbulence appears when the free stream velocity is close to its largest value but the flow recovers a laminar like behaviour during the remaining phases of the cycle for the largest value of the reynolds number turbulence is significant during almost the whole flow cycle the evaluation of the sediment transport rate allows one to estimate the reliability of the empirical predictors commonly used to estimate the amount of sediments transported by sea waves for large values of the shields parameter the sediment flow rate during the accelerating phases does not differ from that observed during the decelerating phases however for relatively small values of the shields parameter the amount of moving particles depends not only on the bottom shear stress but also on flow acceleration moreover the numerical results provide information on the role that turbulent eddies have on sediment dynamics

sediment suspension due to waves 1 a simulation of the turbulent flow and sediment dynamics in the boundary layer originated close to the seabed by a first order stokes wave is performed the flow field is obtained by the numerical integration of navier stokes and continuity equations while sediment trajectories are computed via a simplified model that assumes a one way coupling hence the results describe situations characterized by low concentrations and small values of the stokes particle number the investigation of the interaction of turbulent vortex structures with sediment shows that particles are picked up from the bed and carried into suspension when the low speed streaks start to break up and to generate small incoherent vortices that increase mixing effects the low speed streaks are generated close to the seabed at the end of the accelerating phases when the flow velocity is maximum and breakdown during the decelerating phases of the cycle the effects of turbulence structure and sediment characteristics on pickup and deposition rates are investigated and quantified by varying the values of the parameters which control the phenomenon

geochemical and nd isotopic evolution of paleoproterozoic arc type granitoid magmatism in the flin flon belt trans hudson orogen canada granitoid magmatism spans three flin flon belt evolutionary stages i evolved arc 1920 ma plus early juvenile arc 1904 1880 ma plutonism during intraoceanic arc back arc formation ii early 1878 1860 ma and middle 1860 1844 ma successor arc plutonism following accretion and successor arc s development and iii late 1843 1826 ma successor arc plutonism accompanying successor basin formation and waning arc magmatism amphibole bearing mineralogy metaluminous compositions and igneous microgranitoid enclaves indicate derivation from infracrustal sources predominance of intermediate calc alkaline compositions and negative nb anomalies on normalized patterns over a 46 77 wt silica range indicate an arc setting basaltic end members indicate important contributions directly from the mantle e nd t values are predominately in the range 0 to 4 3 reflecting mixing between depleted mantle melts and an archean crustal component preserved in evolved arc plutons 3 9 to 6 temporal variations include the following i early juvenile arc plutons are low k high field strength element hfse depleted with relatively flat rare earth element ree patterns and negative eu anomalies indicative of low pressure partial melting fractionation in the mantle wedge with residual pyroxene and plagioclase ii early and middle successor arc plutonism is medium k with steep ree patterns and no eu anomalies indicative of input from melting of basaltic sources likely subducted back arc oceanic crust under high pressure conditions with residual garnet and or amphibole and no plagioclase iii late successor arc plutons are high k more hfse enriched with both variable ree pattern slopes and eu anomalies indicative of a significant petrogenetic role of recycling of preexisting juvenile arc accretionary complex crust

introduction to special issue of canadian journal of earth sciences the trans hudson orogen transect of lithoprobe dedication dr john f lewry 1939 1999 see saskatchewan geological survey 1999 dedicated his career to investigations of the saskatchewan manitoba segment of the trans hudson orogen tho one of the principal paleoproterozoic orogens associated with the assembly of laurentia indeed one can make a strong case that lithoprobe s trans hudson orogen transect thot was designed to test the tectonic models proposed by john lewry he delineated the distinct tectonic provinces in the western part of the tho predicted the presence of an archean craton trapped within the tho and recognized and interpreted the significance of the pelican thrust between the juvenile paleoproterozoic volcanic arc complex of the western flin flon domain and the archean craton now called the sask craton the research published in lewry and stauffer 1990 and many of his ideas provided the framework for the design of the thot geophysical and geological studies john lewry was co leader of the thot until he passed away in 19

paleoenvironmental changes in the japan sea during the last 85 000 years five distinct changes in the paleoenvironment of the japan sea within the last 85 000 years are revealed from the sedimentary record of a piston core recovered from the oki ridge changes in both surface and deepwater conditions are registered by changes in lithology calcium carbonate content organic carbon content oxygen and carbon isotope ratios and microfossil assemblages including calcareous nannoplankton diatoms radiolaria and foraminifera between 85 and 27 ka the warm tsushima current did not flow into the japan sea and cold surface water conditions prevailed environments at the seafloor fluctuated between dysaerobic to weakly oxic conditions between 27 and 20 ka freshwater input to the japan sea probably from the huang ho river in china stratified the water column and the severe anoxic conditions eliminated most benthic fauna between 20 and 10 ka the cold oyashio current flowed into the japan sea through the tsugaru strait reestablishing deepwater ventilation shallow water benthic assemblages of the north pacific ocean subsequently colonized the japan sea and occupied the vacant niches of the deep basins between 10 and 8 ka the foraminifer compensation level fcl gradually rose to a depth shallower than 1000 m and bottom conditions changed from dysaerobic to oxic at 10 ka the warm tsushima current started to flow into the japan sea through the tsushima strait to establish the modern oceanographic regime which has existed since 8 ka the eustatic sea level during the last glacial maximum was above the sill depths 130 m of the tsushima and tsugaru straits assuming that tectonic movements at these straits were negligible for the last 20 ka

sediment suspension in oscillatory flow measurements of instantaneous concentration at high shear abstract different syphon type suspended load probes were used together with a specially developed carousel sampler for measurements of the instantaneous sediment concentration in turbulent oscillatory flow over a sand bed shields parameters were well above the ripple flat bed transition region resulting in intense sediment transport over a flat bed the measurements were performed at different levels in a large oscillating water tunnel they showed some characteristic features of the temporal concentration variation at fixed levels including a pronounced effect of the orientation of the suction tube relative to the flow the variation with height of the average concentration is reasonably well described assuming a constant turbulent diffusivity and the magnitude of this can be predicted relatively well using simple turbulence arguments two empirical formulae for the extrapolated bed concentration are also presented the analysis is partly based on wilson s finding that in sheet flow the equivalent bed roughness is nearly proportional with the shields parameter resulting in a roughness grain diameter ratio much larger than 2 5 the figure often adopted for a flat bed but without sheet flow

sequence stratigraphy and evolution of the paleoproterozoic intracontinental baker lake and thelon basins western churchill province nunavut canada abstract the baker lake and thelon basins lie along the border between the rae and hearne domains of the western churchill province basin fill comprises the dubawnt supergroup a ca 1 85 1 70 ga succession of predominantly continental clastic and intercalated volcanic rocks that nonconformably and unconformably overlies granitic and supracrustal rocks most of late archean age the dubawnt supergroup comprises three second order sedimentary sequences that record deposition within a rift basin a modified rift basin and a thermal sag basin respectively the baker sequence is inferred to represent the principal phase in the development of baker lake basin a series of generally elongate northeast striking half graben and fault bounded troughs filled with continental redbeds and coeval voluminous ultrapotassic volcanic rocks faults parallel to the basin margin exhibit evidence for strike slip ca 1 83 1 81 ga the nature and timing of basin development and associated magmatism allows that it may be a transtensional basin that formed by lateral escape in response to crustal thickening during the trans hudson orogeny similar to the formation of mesozoic and cenozoic strike slip and associated rift basins on the margins of the tibetan plateau the overlying whart sequence was deposited in small basins formed by block faulting and tilting of the baker sequence basin fill comprises eolian and alluvial redbeds with intercalated rhyolite flows and epiclastic rocks distribution of facies and stratigraphy suggest that faulting occurred throughout deposition of the whart sequence but ceased before deposition of the overlying barrens sequence ca 1 72 ga deformation and basin formation can be linked to a regional episode of granite emplacement and associated thermal metamorphism ca 1 76 1 75 ga the barrens sequence represents deposition over a broader area primarily in thelon basin strata generally are thinner and flatter than underlying sequences and display lateral continuity indicating minimal influence from syndepositional faulting the depositional record reflects progressive upward fining and eventually the first record of marine transgression within the dubawnt supergroup these features suggest that the barrens sequence was deposited over a broad region of thermal subsidence likely related to cooling of previously attenuated continental lithosphere the barrens sequence may be a remnant of a huge cratonic sand sheet that included the thelon athabasca amundsen and elu basins a regional subsidence mechanism to account for these basins may be mantle downwelling linked to the late stage amalgamation of laurentia the tripartite sequence evolution of the baker lake and thelon basins represents a framework for future sequence correlation among late paleoproterozoic basins in laurentia and shares characteristics with the evolution of contemporaneous intracontinental basins from north central australia and southeastern brazil

the sask craton and hearne province margin seismic reflection studies in the western trans hudson orogen a three dimensional model of the regional crustal architecture of the western trans hudson orogen based on the interpretation of 590 km of deep sounding seismic reflection data and a comparable length of existing seismic reflection information is presented the seismic images identify the regional geometry of the basal detachment zone pelican thrust that separates juvenile allochthonous terranes from the underlying archean microcontinent sask craton the sask craton is inferred to have a minimum spatial extent of over 100 000 km2 with an associated crustal root that extends for 200 km along strike during terminal collision complete convergence of the rae hearne and superior continental blocks was precluded by the presence of the sask craton resulting in the preservation of anomalous amounts of oceanic and associated sedimentary juvenile material along regional tectonic strike consistency of crustal structure across the rae hearne margin reindeer zone boundary is established several phases of

textural and carbon isotopic evidence of monsoonal changes recorded in a composite type speleothem from korea since mis 5a abstract textural and stable isotopic records of a composite type speleothem from gwaneum cave in the eastern part of the korean peninsula show prominent paleoenvironmental changes since mis marine oxygen isotope stage 5a based on 230 th 234 u dating the speleothem experienced growth from 90 9 6 5 ka to 1 2 0 5 ka with several hiatuses four growth phases a b c and d are recognized based on speleothem type and texture very irregular and laterally discontinuous growth laminae in phases b and c indicate that the cave coralloids grew over the stalagmite phase a when the supply of dripping water became limited variations within the 13 c time series of phase a are interpreted as responses to millennial scale fluctuations of the east asian monsoon intensity during mis 5a the monsoonal interpretation is based on the idea that 13 c values reflect the isotopic composition of soil derived co 2 which in turn should relate to monsoon driven changes in terrestrial productivity above the cave during the mis 5a our reconstruction reveals that the significant monsoonal changes on the korean peninsula occurred in conjunction with changes in sea level and or oceanic circulations during the transition period from mis 5a to mis 4

age and origin of the jan lake complex a glimpse at the buried archean craton of the trans hudson orogen the largely buried sask craton is a continental fragment or microcontinent that collided with and underthrust the paleoproterozoic flin flon glennie protocontinent along the pelican decollement zone at 1840 1830 ma rocks of the sask craton are exposed in three tectonic windows those of the pelican window have been named the jan lake complex and comprise 2960 ma arc derived leucocratic orthogneisses migmatitic paragneisses and a tholeiitic within plate igneous suite comprising 2488 ma dioritic to gabbroic rocks and 2450 ma enderbitic and charnockitic rocks including the sahli granite ages of ca 2450 ma are also common from the other two tectonic windows to the sask craton suggesting that emplacement of the igneous suite was widespread and perhaps part of the coeval matachewan igneous event the absence of rocks in the 2960 and ca 2450 ma age ranges on both the adjacent superior and rae hearne cratonic margins makes it improbable that the sask craton was derived by simple fragmentation without large scale tectonic transport the overthrust paleoproterozoic rocks represent a high grade northwestern extension of the flin flon volcanic belt and include 1856 ma leucotonalite and 1843 ma quartz monzodiorite an 1830 ma suite of homogeneous calc alkaline enderbitic rocks which intrude burntwood semipelitic migmatites throughout the kisseynew domain has also been emplaced in mylonites of the pelican decollement zone zircon and monazite ages in the 1812 1803 ma range record a high grade metamorphic event that resulted from collision between the sask craton and flin flon glennie complex

paleoproterozoic 1 90 1 86 ga arc volcanism in the flin flon belt trans hudson orogen canada geochemical and isotopic nd sr data are reported on paleoproterozoic 1904 1864 ma maficintermediate 1870 ma collision and subsequent intra arc deformation

regional mapping of precambrian basement beneath phanerozoic cover in southeastern trans hudson orogen manitoba and saskatchewan the northern edge of phanerozoic platformal rocks of the western canada sedimentary basin overlies the flin flon belt trans hudson orogen in manitoba and saskatchewan a program of regional mapping of the phanerozoic covered basement has been undertaken involving the integration of high resolution aeromagnetic and gravity data with extensive drill core information several major domains are recognized in the buried basement each with a distinct lithotectonic character and potential field anomaly pattern three lithotectonic domains in the buried basement clearwater athapapuskow and amisk lake domains are characterized by northerly trending positive gravity and aeromagnetic anomalies and correlate with the 1 92 1 83 ga volcanic and plutonic rocks of the exposed flin flon belt amisk collage and snow lake assemblage an upper amphibolite grade orthogneiss complex namew gneiss complex containing calc alkaline intrusive rocks ranging in age from 1 88 to 1 83 ga and screens derived from the older v

intraoceanic tectonics and the development of continental crust 1 92 1 84 ga evolution of the flin flon belt canada the flin flon belt is a complex amisk collage of distinct tectono stratigraphic assemblages that was brought together at a relatively early stage in the tectonic evolution of the paleoproterozoic trans hudson orogen four main tectono stratigraphic assemblage types are recognized isotopically juvenile oceanic arc 1 90 1 88 ga ocean floor ca 1 90 ga oceanic plateau ocean island and isotopically evolved arc 1 92 1 90 ga oceanic arc assemblages include tholeiitic calc alkaline and lesser shoshonitic volcanic and volcaniclastic rocks as well as turbidites and arc rift volcanic rocks the tectono stratigraphic assemblages were juxtaposed in an accretionary complex amisk collage at ca 1 88 1 87 ga probably as a result of arc arc collision collisions accretionary collage structures are largely obliterated by subsequent deformation and metamorphic events but can be inferred where cut by calc alkaline plutons related to a 1 866 1 838 ga arc coeval subaerial volcanism is recorded in ca 1 87 1 85 ga calc alkaline to shoshonitic volcaniclastic sequences unroofing of the accretionary collage development of a paleosol and deposition of continental alluvial fluvial sedimentary rocks occurred ca 1 85 1 84 ga coeval with the waning stages of post accretion arc magmatism stabilization of the flin flon belt by 1 85 1 84 ga as part of a philippines or japan like microcontinent is attributed to both tectonic and magmatic thickening of the lithosphere

introduction to special issue 2 on the natmap shield margin project the flin flon belt trans hudson orogen manitoba and saskatchewan the shield margin project of the national geoscience mapping program natmap resulted in a new understanding of the paleoproterozoic flin flon belt manitoba and saskatchewan in four dimensions

stratigraphic and tectonic setting of early proterozoic volcanogenic massive sulfide deposits flin flon manitoba volcanogenic massive sulfide deposits in the flin flon metavolcanic belt occur in an early proterozoic island arc setting that includes arc tholelite back arc ocean floor and shoshonitic assemblages near the town of flin flon manitoba these volcanic assemblages are structurally juxtaposed in a tectonic collage nearly all of the volcanogenie massive sulfide deposits at flin flon are associated with the arc tholeiite assemblage and occur in complex stratigraphic sequences which represent volcanic constructs and associated intravolcanic basins within the former magmatic arc back arc or ocean floor basalts in the flin flon belt host only a few small cu rich massive sulfide deposits and consequently have a lower exploration potential than the arc tholeiite assemblage within the arc tholeiite assemblage volcanogenie massive sulfide deposits occur in association with felsic volcanic units at major stratigraphic and compositional breaks in the volcanic sequence the breaks can be recognized by contrasting major element trace element and isotopic characteristics of the underlying and overlying mafic rocks most volcanogenie massive sulfide deposits are underlain by coarse mafic intermediate or felsic volcaniclastic rocks the best documented examples including the flin flon cuprus and white lake deposits discussed in this paper are clearly localized in basinal structures that vary widely in size the flin flon deposit 62 4 mt occurs in a proximal volcanic environment it lies on the upper flank of a shallow subaqueous basalt volcano possibly in a fault bounded depression the massive sulfides are emplaced within a rhyolite flow complex and are underlain by a disconformable chloritic hydrothermal alteration zone developed in footwall basalt breccia the massive sulfides were overlain by a thick 3 km subaqueous basalt basaltic andesite succession compositionally unrelated to basalts in the stratigraphic footwall the cuprus and white lake deposits total 1 3 mt occur in a 5 5 km thick sequence dominated by more than 3 km of basaltic andesitc interpreted as a subaqueous shield volcano this volcano contains a collapse caldera within which an intracaldera subaqueous rhyolite flow and coeval felsic and intermediate basin filling volcaniclastic rocks were deposited massive sulfides accumulated in subbasins within the caldera hosted by a thin unit of graphitic mudstone and chert overlying formations are laterally extensive unlike the wedgeshaped caldera filling deposits and were deposited in a large deep water basin these rocks are chemically and isotopically unrelated to formations underlying the massive sulfide deposit

oceanographic variations over the last 150 000 yr in the japan sea and synchronous holocene with the northern hemisphere abstract the paleo hydrography in the japan sea called a mini ocean was reconstructed based on the high resolution analysis of diatom assemblages over the period of 150 000 yr the decrease of diatom fertilization in the japan sea when it was isolated from surrounding seas due to the drop of sea level during the glacial to stadial phase resulted in dissolution and or extremely low diatom production in the northern cores in the subarctic water masses the annual td derived paleo ssts c were controlled by the fluctuations of 2 kyr and 4 kyr periods at intervals of 20 kyr and 40 kyr over the last 160 kyr bp respectively a 23 kyr cycle is recognized during the periods from 140 ka to 100 ka according to the wavelet analysis after temperature and sea level increased both at 133 128 ka 60 53 ka and 15 10 ka oceanic warm water diatom species predominated at 127 119 ka and after 9 cal ka in the interstadial phase at 21 3 16 9 ka and 12 9 9 8 ka sea level and salinity increased as the transgression developed at 10 0 7 0 ka the oceanic association shifted from cold water species in the stadial period to warm water ones in the interstadial phase the fluctuations of td derived ssts c on century to millennial time scales during the holocene are well correlated with abrupt climatic events that different paleoclimatic proxies record in many regions of the northern hemisphere

u pb geochronology of late neoarchean tonalites in the flin flon belt trans hudson orogen surprise at surface the flin flon volcanic belt of the trans hudson orogen in northern manitoba comprises magmatic rocks 1 88 1 90 ga generated in an intra oceanic arc and identified as one of the best examples of juvenile paleoproterozoic crust in the flin flon athapapuskow lake area the belt consists of a series of fault bounded blocks each having distinct stratigraphic and magmatic affinities juxtaposed to form an accretionary collage two tonalitic bodies within the northeast arm shear zone a major deformation corridor separating two of the most important blocks in the area have been dated by the u pb zircon method at and these results indicate the presence of fragments of late neoarchean crust within the flin flon belt possibly related to ca 2 5 ga granitic bodies found in terranes beyond the western limit of the belt the presence of ca 2 5 ga tonalites within the flin flon belt herein reported for the first time has major implications for basement involvement in the early tectonic evolution of the f

detailed japan sea paleoceanography during the last 25 kyr constraints from ams dating and δ18o of planktonic foraminifera abstract we have reconstructed paleoceanographic changes in the japan sea for the period from the last glacial maximum lgm to the present using expanded paleoclimate proxy records from two cores together with previously published results from three others a suite of new accelerated mass spectrometer ams 14 c dates provides chronologies that differ from earlier age models and suggest correlation between conditions in the japan sea changes in the north pacific and global sea level and climate changes we present evidence that reduced salinity of the japan sea surface water during the late pleistocene was due primarily to the increased importance of the precipitation evaporation balance at a time when lowered sea level had reduced water exchange with the pacific to a few percent of the present value

flin flon belt seismic anisotropy elastic symmetry heterogeneity and shear wave splitting laboratory measurements of compressional and shear wave velocities and shear wave splitting have been carried out on a set of upper greenschist lower amphibolite facies of metasediments and metavolcanics and plutonic rocks from two ductile shear zones in the flin flon belt ffb of the trans hudson orogen tho selected metamorphic rocks vary in composition from felsic to mafic test sites with outcrops of sheared metamorphic rocks were correlated with a series of inclined seismic reflectors possibly extending from the midcrust and intersecting a well mapped shear zone at the surface determination of the lithological and physical properties of highly deformed metamorphic rocks is essential for proper interpretation of the nature of observed seismic reflectors to investigate the anisotropic properties of the rocks compressional velocity was measured at confining pressure up to 300 mpa in three mutually orthogonal directions aligned with respect to visible textural features in addition on selected

plagioclase preferred orientation and induced seismic anisotropy in mafic igneous rocks fractional crystallization and crystal segregation controlled by settling or floating of minerals during the cooling of magma can lead to layered structures in mafic and ultramafic intrusions in continental and oceanic settings in the lower crust thus the seismic properties and fabrics of layered intrusions must be calibrated to gain insight into the origin of seismic reflections and anisotropy in the deep crust to this end we have measured p and s wave velocities and anisotropy in 17 plagioclase rich mafic igneous rocks such as anorthosite and gabbro at hydrostatic pressures up to 650 mpa anorthosites and gabbroic anorthosites containing 80 vol plagioclase and gabbros consisting of nearly equal modal contents of plagioclase and pyroxene display distinctive seismic anisotropy patterns vp z vp y 1 and vp z vp x 1 for anorthosites while 0 8 vp y than the gabbros laminated anorthosites with vp x vp y vp z display a strong crystal preferred orientation cpo of plagioclase whose 010 planes and 100 and 001 directions parallel to the foliation for the gabbros and amphibolites characterized by vp x vp y vp z and vp x vp y vp z respectively pyroxene and amphibole play a dominant role over plagioclase in the formation of seismic anisotropy the poisson s ratio calculated using the average p and s wave velocities from the three principal propagation polarization directions x y and z of a highly anisotropic anorthosite cannot represent the value of a true isotropic equivalent the cpo induced anisotropy enhances and decreases the foliation normal incidence reflectivity at gabbro peridotite and anorthosite peridotite interfaces respectively

kisseynew metasedimentary gneiss belt trans hudson orogen canada back arc origin and collisional inversion the kisseynew metasedimentary gneiss belt initially developed in a back arc setting the ages of detrital zircons and crosscutting plutons constrain turbidite sedimentation to 1 855 1 841 ga postdating early deformation and metamorphism associated with arc arc and arc continent collisions affecting much of the trans hudson orogen these turbidites are interpreted to have been deposited in a back arc basin behind a retreating subduction boundary the kisseynew domain and its southern flank are marked by 1 84 1 83 ga magmatic rocks that may be related to subduction of back arc basin oceanic crust collapse of the kisseynew basin by ductile fold and thrust deformation began during 1 84 1 83 ga magmatism and continued through peak metamorphism at ca 1 820 1 805 ga from authors

alluvial eolian and lacustrine sedimentology of a paleoproterozoic half graben baker lake basin nunavut canada the northeast trending baker lake sub basin was a volcanically active half graben during deposition of ca 1 85 1 76 ga baker lake group drainage was oriented along transverse and axial directions with flow to playa lake and deeper perennial lacustrine depocentres basin marginal streamflow dominated alluvial fans were concentrated along the southern margin and provided sediment from archean crystalline basement rocks these fed transverse gravel and sand bed braided streams alluvial dynamics were characterized by channel aggradation and abandonment abandoned channel belts were sites of floodplain and eolian deposition basin axial braided streams fed northeast and southwest to a depocentre near christopher island where eolian playa and lacustrine environments were intimately linked felsic minette flows were initially erupted from localized centres contemporaneous sedimentary deposits typically contain minor volcaniclastic components that increase in abundance basinward voluminous and widespread younger minette flows prograded outward from volcanic centres contributing significant additional basin infill

new perspectives on the flin flon belt trans hudson orogen manitoba and saskatchewan an introduction to the special issue on the natmap shield margin project part 1 a new tectonic framework for the flin flon belt in southeastern reindeer zone of the trans hudson orogen has emerged in recent years through four dimensional studies bedrock and subsurface mapping

comparisons between sediment transport models and observations made in wave and current flows above plane beds as a part of the mast2 g8 m coastal morphodynamics project the predictions of four sediment transport models have been compared with detailed laboratory data sets obtained in the bottom boundary layer beneath regular waves asymmetrical waves and regular waves superimposed co linearly on a current each data set was obtained in plane bed sheet flow conditions and each of the four untuned numerical models has provided a one dimensional vertical 1dv time varying representation of the various experimental situations comparisons have been made between the model predictions and measurements of both time dependent sediment concentration and also wave averaged horizontal velocity and concentration for the asymmetrical waves and for the combined wave current flows comparisons have been made with vertical profiles of the cycle averaged sediment flux and also with the vertically integrated net sediment transport rate each of the turbulence diffusion models gives an accurate estimate of the net transport rate invariably well within a factor of 2 of the measured value in contrast none of the models provides a good detailed description of the time dependent suspended sediment concentration due mainly to the inability of conventional turbulence diffusion schemes to represent the entrainment of sediment into suspension by convective events at flow reversal however in the cases considered here this has not seriously affected the model predictions of the net sediment flux due to the dominance of the near bed transport the comparisons in this paper are aimed not only at testing the predictive capability of existing sediment transport modelling schemes but also at highlighting some of their deficiencies

geochemistry of 1 9 ga morb and oib like basalts from the amisk collage flin flon belt canada evidence for an intra oceanic origin subaqueously erupted basalts that occur in kilometre scale allochthons within the 1 9 ga flin flon belt canada appear to have been generated at oceanic ridges and possibly oceanic plateaus remote from archean cratons the ocean floor basalts fall into two categories 1 n type resembling n morbs and mariana type back arc basin basalts depleted to flat ree patterns high zrnb variable thnb and initial nd 3 3 to 5 4 2 e type resembling transitional and plume morbs slightly enriched ree patterns lower zrnb initial nd 3 1 to 4 5 in the largest and best studied allochthon the elbow athapapuskow assemblage mixing between depleted n morb and enriched oib sources or melts coupled with variable addition of a subduction lile component can explain the chemical variations in the basalts zircon u pb dates of 1904 ma for a syn volcanic diabase sill and 1901 6 5 ma for a gabbro peridotite cumulate complex demonstrate that crystallization of the ocean floor basalts overlapped with in part eruption of the tectonically juxtaposed 1 90 1 88 ga arc volcanic rocks the elbow athapapuskow allochthon is interpreted as back arc basin crust that developed simultaneously with flin flon arc magmatism subaerially erupted basalts that chemically resemble tholeiitic oibs 8 14 mgo relative hree depletion initial nd 2 2 to 3 4 occur in tectonic contact with the elbow athapapuskow assemblage the oibs may have been generated by deeper garnet residue melting of enriched mantle tapped during extension in the elbow athapapuskow back arc basin and were possibly erupted onto a remnant arc deeper mantle melting is also indicated by the presence of the lree enriched oceanic plateau like basalts of the sandy bay assemblage the back arc 01b and plateau volcanic assemblages were jux taposed against ca 1 9 ga arc assemblages in a philippines like intraoceanic accretionary complex by 1 87 ga

coherence scales of wave induced suspended sand concentration fluctuations multifreqiiency acoustic backscatter measurements made in the nearshore zone are analyzed to determine the correlation structure of the instantaneous suspended sediment concentration field at horizontal separations of 20 cm large amplitude backscatter fluctuations representing suspended sediment concentrations more than a factor of 10 greater than the mean and with vertical coherence scales many times greater than the logarithmic wave boundary layer thickness are shown to be spatially correlated at horizontal separations less than the wave orbital amplitude over successive wave cycles the time lag between the appearance of fluctuations in different acoustic beams is inversely proportional to the fluid velocity showing that the fluctuations in backscatter amplitude contain real information on fluctuations in suspended sediment concentration advected with the fluid it is found that the instantaneous suspended sediment field in shore normal cross section is punctuated by spatially discrete clouds extending well above the logarithmic wave boundary layer the fluctuations appear to be present even in the absence of small scale ripples it is suggested that the sediment clouds may be due to vortex shedding from megaripples other bed forms of intermediate scale or coherent structures in combined wave current flows

land ocean linkages over orbital and millennial timescales recorded in late quaternary sediments of the japan sea late quaternary sediments of the japan sea are characterized by centimeter to meter scale alternations of dark and light layers which are synchronous basinwide high resolution analyses of the sediments from ocean drilling program site 797 reveal that deposition of the meter scale alternations reflect variations in paleoceanographic conditions which were closely associated with glacio eustatic sea level changes through the modulation of the volume and character of the influx to the sea through the tsushima strait the centimeter to decimeter scale alternations reflect millennial scale variations which are possibly associated with dansgaard oeschger d o cycles with each dark layer appearing to correspond to an interstadial this variability is attributed to the development of a humid climate in central to eastern asia and the consequent increase in discharge from the huanghe and changjiang rivers during interstadials this caused expansion of the east china sea coastal water ecscw which penetrated more strongly into the japan sea the increased influence of the lower salinity nutrient enriched ecscw reduced deep water ventilation and enhanced the surface productivity leading to the development of anoxic bottom waters and deposition of the dark layers thus the centimeter to decimeter scale alternations of the dark and light layers record wet and dry cycles in central to eastern asia possibly associated with d o cycles

structural evolution of the eastern amisk collage trans hudson orogen manitoba deformation recorded in the amisk collage in the central part of the paleoproterozoic flin flon belt southeastern trans hudson orogen is divided into pre early late and post hudsonian orogeny distinguished by significant changes in metamorphic conditions and the orientation of structures detailed structural analysis petrography and high precision geochronology combined with previous mapping and geochemical studies indicate a structural history spanning 180 ma in the amisk collage and the database provides an excellent opportunity to study the structural evolution of precambrian greenstone belts accretion of the 1 92 1 88 ga tectono stratigraphic assemblages in the amisk collage began prior to 1 868 ga the deformational history records six generations of ductile structures f1 f6 followed by development of brittle ductile and brittle structures f7 which may have continued as late as 1 690 ga during exhumation of the collage the steep generally north northeast macroscopic structural g

stable isotope and lithologic evidence of late glacial and holocene oceanography of the northwestern pacific and its marginal seas abstract stable isotopes geochemical lithological and micropaleontological results from cores from the far northwest fnw pacific and the okhotsk and bering seas are used to reconstruct the regional environment for the last glaciation the deglacial transition and the holocene 18 o records of planktonic foraminifera of the region show two light shifts during deglacial time provoked by the freshening of the surface water and climate warming these north pacific terminal events t1anp and t1bnp with ages of 12 500 and 9300 yr b p respectively occur almost simultaneously with two episodes of accelerated glacier melting around the north atlantic along with the isotopic shifts the caco 3 content in regional sediments increased abruptly 1a and 1b carbonate peaks probably due to changes of productivity and pore water chemistry of surface sediments organic matter and opal concentration increased during the transition between t1anp and t1bnp events in the sediments of the fnw pacific and the southern part of the bering sea and opal content increased in the holocene in the bering and okhotsk seas 13 c records of cores from the okhotsk and bering seas and the fnw pacific do not contradict the hypothesis of increased intermediate water formation in the region during glaciation during deglaciation accumulation of the coarse terrigenous component decreased in sediments of the bering sea and the fnw pacific before the t1anp event probably as a result of rising sea level and opening of the bering strait