geotraverses across the swiss alps the alpine chain marks the collision zone between the european and african lithospheric plates the earth s crust below the alps has been thickened by tectonic activity to form a root of crustal material which extends to a depth of approximately 60 km here we present the initial results of three seismic reflection traverses across the alps which show large scale crustal indentations resulting from collision between continental plates as well as the nappeforming style of deformation produced by compression of attenuated ocean crust the data suggest that the gross structural deformation of the collision zone results from large scale crustal indentations the descending european crust is delaminated and deformed by wedges of the african crust protruding northwards below the alps the nappe forming deformation seems to be restricted to the upper 10 20 km of the penninic domain in the core of the alps

himalayan type escape tectonics along the superior boundary zone in manitoba canada abstract the superior boundary zone separates the neoarchean superior province to the southeast from the paleoproterozoic reindeer zone of the trans hudson orogen to the northwest in northern manitoba late convergence along the zone in the paleoproterozoic has previously been interpreted in terms of a promontory model where the superior province indents the reindeer zone towards the northwest we present a modified promontory model that includes a wnw transport direction of the superior province and lateral escape of a segment of the superior province the split lake block along the northern margin of the promontory the model is based on the kinematics of an array of shear zones along the superior boundary zone that are interpreted as having been active concurrently tectonic escape of the split lake block occurred in a manner similar to the extrusion and rotation of the indochina block along the eastern margin of the himalayas but at a much smaller scale our model explains shear zone kinematics but also the curvilinear nature of some of the shear zones and a high component of along strike stretch along one of the shear zones

observations of the internal tide in monterey canyon abstract data from two shipboard experiments in 1994 designed to observe the semidiurnal internal tide in monterey canyon reveal semidiurnal currents of about 20 cm s 1 which is an order of magnitude larger than the estimated barotropic tidal currents the kinetic and potential energy evidenced by isopycnal displacements of about 50 m was greatest along paths following the characteristics calculated from linear theory these energy ray paths are oriented nearly parallel to the canyon floor and may originate from large bathymetric features beyond the mouth of monterey bay energy propagated shoreward during the april experiment itex1 whereas a standing wave that is an internal seiche was observed in october itex2 the difference is attributed to changes in stratification between the two experiments higher energy levels were present during itex1 which took place near the spring phase of the fortnightly 14 8 days cycle in sea level while itex2 occurred close to the neap phase further evide

nature of the lithosphere across the variscan orogen of sw iberia dense wide angle seismic reflection data 1 two wide angle seismic transects have been acquired across the sw iberian massif they crossed three major geological zones south portuguese zone ossa morena zone and central iberian zone with their tectonic contacts and the pyrite belt being of greatest interest a total of 690 digital seismic recording instruments 650 texans and 40 reftek 3 component units from the iris passcal instrument pool were used the transects a and b are each approximately 300 km long and consist of 3 and 6 shot points respectively with an approximately 60 km shot point interval the charge sizes range from 1000 kg at the edges to 500 kg at the center these recently acquired experiments were designed to provide velocity constraints on the lithosphere and to complement the previously acquired normal incidence seismic profile iberseis both data sets are part of the sw iberia project which was developed within the europrobe program and designed to address fundamental questions about the nature and dynamics of the variscan lithosphere the acquisition parameters provide closely spaced wide angle seismic images of the lithosphere beneath sw iberia in transect a the station spacing was on average 400 m while along transect b the receiver spacing was approximately 150 m because of this close trace spacing the lateral continuity of the seismic arrivals is greatly improved frequency analysis revealed that the recorded events feature relatively low frequencies 6 25 hz after processing the shot records show high amplitude and well defined arrivals the interpreted pmp arrival located at approximately 11 s normal incidence traveltime is characterized by high amplitude and relatively low frequency 6 12 hz a well defined pn arrival appears at offsets beyond 120 km at far offsets greater than 180 km an upper mantle reflection is observed furthermore within the upper crust the shots records feature a relatively high velocity arrival located at 4 5 s normal incidence traveltime the analysis of this arrival indicates that it probably corresponds to the top of the iberian reflective body identified in the iberseis deep seismic profile the velocity models obtained by forward modeling show a complex crust especially in the middle crust the velocity models are the most detailed ones that have been produced in the area and contain a large amount of new features that are relevant to the understanding of the composition of the crust and upper mantle beneath the zone the velocity depth functions derived from the velocity models have higher middle crustal velocities than the average in other continental areas a comparison between laboratory seismic velocity measurements and the velocities of the models was carried out in order to estimate the crustal and the upper mantle composition results indicate that the high middle crust velocities correspond to rocks of a mafic composition the combined data set reveals new aspects related to the lithospheric evolution of this transpressive orogen and allows us to attempt an interpretative cross section of the upper lithosphere in sw iberia

3 d geologic modeling in the flin flon mining district trans hudson orogen canada evidence for polyphase imbrication of the flin flon 777 callinan volcanogenic massive sulfide ore system three dimensional geologic modeling by integrated analysis and interpretation of drill core 2 d and 3 d seismic mine survey and geologic map data provides new insights into the structural setting of the 85 5 million tonne mt flin flon callinan 777 volcanogenic massive sulfide vms ore system hosted in the paleoproterozoic flin flon belt of manitoba and saskatchewan canada the resultant camp scale 3 d geologic model was in addition to the densely drill intersected vms hosting mine horizon constrained by lithostratigraphic reference drill holes intersecting the footwall and hanging wall rock successions of the ore system which were established by relogging 52 drill holes and systematically reconciling the lithofacies classes in their log descriptions with the lithofacies units of the 1 10 000 scale flin flon mining district geologic map the lateral persistence and large stratigraphic range of these drill hole markers supported seismic interpretation and allowed tracing lithostratigraphic horizons and structures in areas with low drill hole density expanding 3 d subsurface insight from the local to the more regional structural setting of the ore system the overall 3 d modeled geometry and topological relationships between lithostratigraphic surfaces and multiple generations of thrust faults suggest that the flin flon mining district is underlain by an e dipping stack of w vergent thrust imbricates that formed during precollisional and collisional stages of the 1 9 to 1 8 ga trans hudson orogeny the imbricate stack was subsequently deformed by e trending ductile thrust faults that internally imbricated the flin flon arc assemblage and the molasse cover rocks of the missi group and brought up rocks of the former over the latter in a northerly direction the vms hosting millrock member has been stacked on at least four structural levels enhancing the vms potential in the footwall and hanging wall of the known ore deposits where both thrust systems intersect

observations of overturning in the thermocline the context of ocean mixing abstract the time sequence of events that lead to internal wave breaking and ocean turbulence is investigated data are obtained from depths 100 400 m with a repeat profiling ctd and a coded pulse doppler sonar the instruments were deployed from r p flip during february march 1995 while stationed 30 km west of point arguello california as an aspect of the marine boundary layer experiment although the water depth at the site is 1500 m both rms shear and diapycnal diffusivity as inferred from the average rate and size of overturning events increase with depth below 250 m a deep source of wave energy is implied depth time series of 6 4 m shear s 2 m strain n2 n2 where n is the buoyancy frequency 6 4 m gradient richardson number ri n2 s2 and 2 m effective strain rate the depth derivative of ctd inferred vertical velocity are obtained at 4 minute intervals over a 9 day 100 400 m domain the occurrence of overturns static instabilities of vertical scale 2 m in the observed density

dynamics of advection driven upwelling over a shelf break submarine canyon 1 the response over a submarine canyon to a several day upwelling event can be separated into three phases an initial transient response a later much longer steady advection driven response and a final relaxation phase for the advection driven phase over realistically steep deep and narrow canyons with near uniform flow and stratification at rim depth we have derived scale estimates for four key quantities observations from 5 real world canyon studies and 3 laboratory studies are used to validate the scaling and estimate the scalar constant for each scale based on 4 geometric parameters of the canyon the background stratification the coriolis parameter and the incoming current we can estimate 1 the depth of upwelling in the canyon to within 15 m 2 the deep vorticity to within 15 and 3 the presence absence of a rim depth eddy can be determined based on laboratory data 4 the total upwelling flux can also be estimated the scaling analysis shows the importance of a rossby number based on the radius of curvature of isobaths at the upstream mouth of the canyon this rossby number determines the ability of the flow to cross the canyon isobaths and generate the pressure gradient that drives upwelling in the canyon other important scales are a rossby number based on the length of the canyon which measures the ability of the flow to lift isopycnals and a burger number based on the width of the canyon that determines the likelihood of an eddy at rim depth generally long canyons with sharply turning upstream isobaths strong incoming flow small coriolis parameter and weak stratification have the strongest upwelling response

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

geomorphological and cryostratigraphical analyses of the zackenberg valley ne greenland and significance of holocene alluvial fans abstract in high arctic northern greenland future responses to climatic changes are poorly understood on a landscape scale here we present a study of the geomorphology and cryostratigraphy in the zackenberg valley in ne greenland 74 n containing a geomorphological map and a simplified geocryological map combined with analyses of 13 permafrost cores and two exposures cores from a solifluction sheet alluvial fans and an emerged delta were studied with regards to cryostructures ice and total carbon contents grain size distribution and pore water electrical conductivity and the samples were ams 14c dated the near surface permafrost on slopes and alluvial fans is ice rich as opposed to the ice poor epigenetic permafrost in the emerged delta ground ice and carbon distribution are closely linked to sediment transport processes which largely depend on lithology and topography holocene alluvial fans on the lowermost hillslopes covering 12 of the study area represent paleoenvironmental archives during the contrasting climates of the holocene the alluvial fans continued to aggrade through the warmer early holocene optimum the colder late holocene and the following climate warming and by 0 45 mm a 1 on average this is caused by three factors sedimentation ground ice aggradation and vegetation growth and is reflected by ams 14c dating and continuously alternating cryostructures highly variable sedimentation rates in space and time at the alluvial fans have been detected this is also reflected by alternating lenticular and microlenticular cryostructures indicating syngenetic permafrost aggradation during sedimentation with suspended and organic matrix cryostructures indicating quasi syngenetic permafrost aggradation in response to vegetation growth in periods with reduced or no sedimentation over time this causes organic matter to become buried indicating that alluvial fans represent effective carbon sinks that have previously been overlooked

climatic impacts of parameterized local and remote tidal mixing abstractturbulent mixing driven by breaking internal tides plays a primary role in the meridional overturning and oceanic heat budget most current climate models explicitly parameterize only the local dissipation of internal tides at the generation sites representing the remote dissipation of low mode internal tides that propagate away through a uniform background diffusivity in this study a simple energetically consistent parameterization of the low mode internal tide dissipation is derived and implemented in the geophysical fluid dynamics laboratory earth system model with gold component gfdl esm2g the impact of remote and local internal tide dissipation on the ocean state is examined using a series of simulations with the same total amount of energy input for mixing but with different scalings of the vertical profile of dissipation with the stratification and with different idealized scenarios for the distribution of the low mode internal tide energy dissipation uniformly over ocean basins co

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

introduction to special issue of canadian journal of earth sciences the alberta basement transect of lithoprobe from outcrops in northeastern alberta to exposures within structural culminations in the canadian cordillera the crystalline basement that lies buried beneath the phanerozoic alberta basin of western canada represents a significant part of the canadian shield ca 750 000 km2 the advent of modern high resolution aeromagnetic data and u pb geochronology have opened the doors for the next era of investigation of the crystalline basement of the alberta basin aeromagnetic data and geochronology provided important physical and temporal links to the exposed canadian shield which allowed its structural framework to be extrapolated into the subsurface the most recent chapter in this evolving story has been the alberta basement transects of lithoprobe a 12 year program which has used multi disciplinary geoscience studies to further elucidate the nature history and geometric characteristics of basement domains beneath the alberta basin this special issue is the second in a three issue set of publications

timing constraints of orogeny to cratonization thermochronology of the paleoproterozoic trans hudson orogen manitoba and saskatchewan canada abstract a comprehensive thermochronometric investigation across a 600 km transect of the paleoproterozoic trans hudson orogen tho in canada has resolved two first order thermal events 1 widespread peak metamorphism at 1 82 1 79 ga associated with terrane amalgamation and 2 a late collisional metamorphic episode at ca 1 77 ga that is characterized by significant strike slip deformation and rapid cooling geophysical observations of the lithosphere beneath the tho reveal crust that is markedly different on either side of the crustal scale tabbernor sturgeon weir tsw strike slip fault system which offsets lower crustal reflectors the tho east of the fault system records u pb titanite and total pb monazite domain ages that are relatively indistinguishable from 40ar 39ar hornblende and mica cooling ages indicating rapid cooling and perhaps exhumation following 1 77 ga metamorphism seismic imaging indicates the eastern orogen is an irregular package of stacked crustal blocks and our thermochronometric data demonstrate it behaved as a single coherent element shortly 20 30 m y following cessation of convergence in contrast rocks located west of the tsw fault system cooled distinctly later preserving 40ar 39ar muscovite and biotite ages between 1 74 and 1 72 ga this crustal architecture delineated from seismic surveys illustrates a more homogeneous slightly 5 km thinner crust in the case of this orogen apparent stabilization and cratonization occurred ca 100 m y after peak terrane amalgamation and notably the orogen was likely cratonized as two blocks east and west of the tsw fault system

evidence for extensive tabular intrusions in the precambrian shield of western canada a 160 km long sequence of bright reflections the trans hudson orogen is the preserved early proterozoic collisional zone between the archean superior and hearne rae cratons and the focus of lithoprobe s trans hudson orogen transect where seismic reflection line s2b was recorded the most intriguing structure in the data is a continuous band of strong reflections in the upper crust herein named the wollaston lake reflector which extends for 160 km across the northwestern hinterland of the trans hudson orogen the reflections range from 2 0 to 4 5 s two way traveltime 6 0 13 5 km depth and show a heterogeneous internal structure with multicyclic reflected arrivals and numerous diffractions our studies indicate that a series of high velocity high density reflectors having lengths of 800 m to a few kilometres and thicknesses from 50 to 150 m most likely form the reflecting elements geologic mapping and dating document diabase intrusions associated with the middle proterozoic mackenzie igneous event sills drilled in the region have thicknesses coinciding with those of our seismic model we conclude that the wollaston lake reflector represents a series of diabase sheetlike intrusions emplaced during mackenzie i e post hudsonian magmatic activity regionally it provides constraints for the middle proterozoic paleo stress field and for the late stage tectonic history of the northwestern hinterland of the trans hudson orogen more generally the detection of the reflector emphasizes the importance of large scale horizontal injection of tabular bodies into the crust over long distances and across tectonic boundaries

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

seasonal patterns of coupled flow in the active layer at three sites in northwest north america vertical arrays of temperature and electric potential probes were installed in the upper soil at sites along the mackenzie river valley and on the north slope of alaska time series were obtained at subdiurnal frequencies throughout the year in the active layer and upper permafrost if the data acquisition system is properly configured the time series can be used to infer soil physiochemical processes the electric potential develops primarily in response to soil water solute concentration gradients in the soil column and is a crude surrogate of the soil water electrolytic conductivity summer precipitation can cause rapid penetration of the thaw front when percolating rainwater warmed at the ground surface carries sensible heat downward to the thawing front rates of warming at depth occur significantly faster than those typical of conductive heat transfer in early winter as the freezing front penetrates downward toward the permafrost table ions are excluded from the ice and concentrated in the intermediate unfrozen zone nearly instantaneous warming of the active layer is triggered by spring snowmelt at happy valley in northern alaska temperatures at the 29 cm depth rise from 7 to 3 c in 1 h for several hours during this event the temperature at 29 cm is warmer than that at regions both above and below producing a strong thermal inversion time series of electric potential or a surrogate derived from electric potential suggest rapid transport of meltwater from the snowpack to depth probably through soil cracks serial events hasten active layer warming by 1 2 weeks

permafrost response to last interglacial warming field evidence from non glaciated yukon and alaska abstract we present stratigraphic observations from three sites in eastern beringia ch ijee s bluff in northern yukon and nearby exposures on the old crow river the palisades on the yukon river in alaska and placer mining exposures at thistle creek in west central yukon which provide insight into the response of permafrost to regional warming during the last interglaciation chronology is based on the presence of old crow tephra an important regional stratigraphic marker that dates to late marine isotope stage 6 supplemented by paleoecology and non finite 14c ages on wood rich organic silts old crow tephra overlies several relict ice wedges at the palisades and thistle creek indicating that permafrost at these sites did not thaw completely during the last interglaciation prominent deposits of last interglacial wood rich organic silt are present at multiple sites in eastern beringia and probably represent accumulations of reworked forest vegetation due to thaw slumping or deposition into thermokarst ponds or depressions consistent stratigraphic relations between these deposits old crow tephra and ice wedge pseudomorphs at our three study sites and at least six other sites in eastern beringia suggest that thaw of shallow permafrost was widespread during the last interglaciation limited stratigraphic evidence suggests that thaw was probably on the order of meters rather than 10s of meters the ubiquity of shallow permafrost degradation during the last interglaciation suggests that current ground warming may foreshadow widespread near surface thaw under even modest future warming scenarios however the persistence of relict pre last interglacial ice wedges highlights the potential for the regional antiquity of discontinuous permafrost and provides compelling field evidence for the long term resilience of deep permafrost during sustained periods of warmer than present climate

applications of digital methodology to the natmap shield margin project the natmap shield margin project which began in 1991 straddles the manitoba saskatchewan border and studied a rectangular area with east west and north south extents of approximately 250 and 150

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

continental arc magmatism along the southeast hearne craton margin in saskatchewan canada comparison of the 1 92 1 91ga porter bay complex and the 1 86 1 85ga wathaman batholith abstract detailed mapping coupled with geochronological and geochemical investigations has revealed the presence of a 1917 1913 ma gabbro monzodiorite monzonite suite along the southeast margin of the hearne craton in northern saskatchewan canada the predominantly plutonic suite is also characterised by 1915 ma old trachyandesitic subvolcanic and volcaniclastic inclusions the rocks are hornblende epidote titanite augite bearing and collectively termed the porter bay complex the plutonic rocks cut the 2569 ma lueaza river granitoid suite a component of the hearne craton and are themselves intruded by 1859 ma pegmatitic diorite 1856 ma layered gabbro anorthosite and 1853 ma quartz diorite belonging to the wathaman batholith one of the world s largest paleoproterozoic andean type continental arcs wholerock major element geochemistry characterises the porter bay complex as calc alkalic to alkali calcic metaluminous and variable from ferroan to magnesian trace element concentrations are characterised by negative high field strength element anomalies suggesting emplacement along a destructive plate margin the geochemical signatures of the wathaman batholith and the porter bay complex are largely identical the geographic location map relationships and geochronological geochemical and petrographic constraints are consistent with the porter bay complex having formed in a subduction related continental arc setting the southeastern margin of the hearne craton was therefore a long lived active continental margin with two separate periods of continental arc magmatism between 1 92 1 91 ga and 1 86 1 85 ga

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

tidally forced internal waves and overturns observed on a slope results from home abstract tidal mixing over a slope was explored using moored time series observations on kaena ridge extending northwest from oahu hawaii during the survey component of the hawaii ocean mixing experiment home a mooring was instrumented to sample the velocity and density field of the lower 500 m of the water column to look for indirect evidence of tidally induced mixing and was deployed on a slope in 1453 m water depth for 2 months beginning in november 2000 the semidiurnal barotropic tidal currents at this site have a significant cross ridge component favorable for exciting an internal tidal response a large amplitude response is expected given that the slope of the topography 4 5 is nearly the same as the slope of the internal wave group velocity at semidiurnal frequency density overturns were inferred from temperature profiles measured every 2 min the number and strength of the overturns are greater in the 200 m nearest the bottom with overturns exceeding 24 m present at any depth nearly

intense variable mixing near the head of monterey submarine canyon abstract a microstructure survey near the head of monterey submarine canyon the first in a canyon confirmed earlier inferences that coastal submarine canyons are sites of intense mixing the data collected during two weeks in august 1997 showed turbulent kinetic energy dissipation and diapycnal diffusivity up to 103 times higher than in the open ocean dissipation and diapycnal diffusivity within 10 km of the canyon head were among the highest observed anywhere e 1 1 10 6 w kg 1 k 1 0 10 2 m2 s 1 mixing occurred mainly in an on axis stratified turbulent layer with thickness and intensity increasing from neap to spring tide strain spectra showed a gentler than k 1z rolloff suggesting that critical reflection and scattering may push energy into high wavenumbers dissipation dependence on shear appears to be much weaker in the canyon than in the open ocean with indications that the dependence maybe as low as e s coastal canyons may account for a small but significant fraction of the int

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

structure of the baroclinic tide generated at kaena ridge hawaii repeat transects of full depth density and velocity are used to quantify generation and radiation of the semidiurnal internal tide from kaena ridge hawaii a 20 km long transect was sampled every 3 h using expendable current profilers and the absolute velocity profiler phase and amplitude of the baroclinic velocity pressure and vertical displacement were computed as was the energy flux large barotropically induced isopycnal heaving and strong baroclinic energy flux divergence are observed on the steep flanks of the ridge where upward and downward beams radiate off ridge directly above kaena ridge strong kinetic energy density and weak net energy flux are argued to be a horizontally standing wave the phasing of velocity and vertical displacements is consistent with this interpretation results compare favorably with the merrifield and holloway model

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

cryostratigraphy paleogeography and climate change during the early holocene warm interval western arctic coast canada botanical and cryostratigraphic records from northwest canada indicate that the climate of the early holocene was considerably warmer than today tree line was over 100 km farther north and a thaw unconformity dating from 8000 14c years bp formed at the base of an active layer 2 5 times thicker than at present numerous thermokarst lake basins formed in the preceding millennia both the botanical and cryostratigraphic indices described are products of summer conditions previous reconstructions of early holocene climate have not assessed the significance of paleocoastal location on the seasonality and extent of apparent climate warming at present there is a steep gradient in growing season conditions between cooler sites on the beaufort sea coast and warmer inland locations winter conditions are more uniform because both sea and land are snow covered coastal retreat in the region has been rapid due to sea level rising over a gently sloping shelf containing readily erodible sediments the coastlin

crustal suture preserved in the paleoproterozoic trans hudson orogen canada lithoprobe seismic reflection data acquired in 1994 within the trans hudson orogen include a 180 km profile that crosses the boundary between a collapsed marginal basin kisseynew domain and an older volcanic plutonic arc terrane lynn lake belt the seismic data image a prominent band of northeast dipping anastomosing reflections that extend to 10 s two way traveltime from the surface location of a geological boundary where interpreted oceanic crust is preserved and separate thick crust 16 s of the kisseynew domain from the abruptly thinner crust 12 s of the lynn lake belt highly reflective lower crust 10 16 s of the kisseynew domain dips gently northward and extends laterally for at least 40 km beneath the adjacent lynn lake belt in a manner reminiscent of the western alps complementary gravity modeling shows that the thickness of metasedimentary rocks within the kisseynew domain is 20 3 km the seismic image is interpreted as portraying a crustal scale collisional suture that formed as the end result of northward subduction of backarc basin crust ancestral kisseynew basin floor and subsequent contraction and thrusting of the remnant kisseynew basin fill under the margin of the lynn lake belt

geoelectric structure of the northeastern williston basin and underlying precambrian lithosphereearth science sector ess contribution 20080509 magnetotelluric mt measurements were made in southern manitoba canada as part of the portable observatories for lithosphere analysis and research investigating seismicity polaris project to image the northeastern part of the williston basin and underlying precambrian lithosphere data collected at 21 sites along a 400 km east west profile at 49 5 n and a 300 km north south profile at 100 w were analyzed using robust spectral analysis tensor decomposition and two dimensional inversion the resulting resistivity models allow subdivision of the williston basin into three layers an upper layer of 1 5 m corresponding to mesozoic and upper paleozoic rocks a 20 50 m layer corresponding to lower paleozoic carbonate rocks and a 2 3 m layer corresponding to the ordovician winnipeg formation deeper penetrating mt responses interpreted with other mt data reveal a region in the westernmost superior craton with a southwest northeast geoelectric fabric that is oblique to subprovince boundaries the

geophysical transect across a paleoproterozoic continent continent collision zone the trans hudson orogen a summary and comparison of geophysical data and models for the trans hudson orogen in northern manitoba and saskatchewan are presented magnetic total field and bouguer gravity maps are used to define the along strike extension of geological domains of the orogen exposed on the canadian shield and a two dimensional density model is produced which accounts for the observed variations of the bouguer gravity field across the orogen an 800 km long crustal section across the entire continent continent collision zone including the edges of the bounding cratonic blocks is presented it incorporates seismic reflectivity seismic velocities resistivity and density models key results include 1 evidence for west vergent crustal stacking and exhumation in the eastern trans hudson orogen in the form of preserved moho topography and the presence of higher grade higher velocity rocks in the hanging wall of an east dipping crustal stack 2 definition of the eastward extent of the archean sask craton in the

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

internal tides and mixing in a submarine canyon with time varying stratification abstractthe time variability of the energetics and turbulent dissipation of internal tides in the upper monterey submarine canyon msc is examined with three moored profilers and five adcp moorings spanning february april 2009 highly resolved time series of velocity energy and energy flux are all dominated by the semidiurnal internal tide and show pronounced spring neap cycles however the onset of springtime upwelling winds significantly alters the stratification during the record causing the thermocline depth to shoal from about 100 to 40 m the time variable stratification must be accounted for because it significantly affects the energy energy flux the vertical modal structures and the energy distribution among the modes the internal tide changes from a partly horizontally standing wave to a more freely propagating wave when the thermocline shoals suggesting more reflection from up canyon early in the observational record turbulence computed from thorpe scales is greatest in the bottom 5

flow and mixing in ascension a steep narrow canyon 1 a thin gash in the continental slope northwest of monterey bay ascension canyon is steep with sides and axis both strongly supercritical to m2 internal tides a hydrostatic model forced with eight tidal constituents shows no major sources feeding energy into the canyon but significant energy is exchanged between barotropic and baroclinic flows along the tops of the sides where slopes are critical average turbulent dissipation rates observed near spring tide during april are half as large as a two week average measured during august in monterey canyon owing to ascension s weaker stratification however its average diapycnal diffusivity 3 9 10 3 m2 s 1 exceeded the 2 5 10 3 m2 s 1 found in monterey most of the dissipation occurred near the bottom apparently associated with an internal bore and just below the rim where sustained cross canyon flow may have been generating lee waves or rotors the near bottom mixing decreased sharply around ascension s one bend as did vertically integrated baroclinic energy fluxes dissipation had a minor effect on energetics which were controlled by flux divergences and convergences and temporal changes in energy density in ascension the observed dissipation rate near spring tide was 2 1 times that predicted from a simulation using eight tidal constituents averaged over a fortnightly period the same observation was 1 5 times the average of an m2 only prediction in monterey the previous observed average was 4 9 times the average of an m2 only prediction

effect of fire on solute release from organic horizons under larch forest in central siberian permafrost terrain abstract to evaluate the effects of forest fire and post fire stand recovery on the organic layer chemistry and solute release within mound and trough microrelief elements termed earth hummock microtopography that mainly distribute permafrost affected area we chose five fire plots larch forests burned in 1951 1981 1990 1994 and 2005 paired with adjacent control plots in mature larch forests in central siberian permafrost terrain we determined total carbon nitrogen and ash content in solid organic soils and analyzed total carbon nitrogen bases and major anions in water extracts there was a significant correlation between water extracted organic carbon weoc and total carbon kg m 2 in area basis implying that the quantity of total carbon was a major factor in weoc production weoc correlated negatively with ph indicating strong control by organic horizons organic solute leaching on soil acidity and base cation dynamics the sum of water extractable base cations was also correlated significantly to total carbon indicating that cations can be released through organic matter decomposition organic horizons in troughs in burned plots released greater amounts of ca mg and k than those in mounds probably due to greater content of organic matter as a cation source anions including nitrate and phosphate and weoc also accumulated in trough depressions due probably to organic matter degradation the contrasting distribution of solutes between mounds and troughs in burned plots seems to be controlled by organic horizon development via changes in microtopography after forest fires

diagnosing a partly standing internal wave in mamala bay oahu 1 an internal partly standing wave in mamala bay hawaii is studied using new observations and the princeton ocean model pom previous work suggested a convergence in the bay of east and westbound waves emanating from kaena ridge and makapuu point respectively new energy flux measurements with shipboard adcp ctd confirm that makapuu point is the eastern source after validating the pom results against observations the model output is modally decomposed and compared with the expected theoretical patterns of kinetic and available potential energy energy flux and group velocity for a partly standing wave agreement is seen for the first baroclinic mode which also contains most of the energy the results confirm previous suggestions of standing wave dynamics in mamala bay

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

penokean tectonics along a promontory embayment margin in east central minnesota abstract recent geologic investigations in east central minnesota have utilized geophysical data test drilling and high resolution geochronologic dating to produce a significantly improved map of a poorly exposed part of the 1880 1830 ma penokean orogen these investigations have elucidated major changes in the structure of the orogen as compared to its counterparts in northern michigan and northwestern wisconsin foreland basin fold and thrust belt and magmatic terrane components that are recognized to the east extend into east central minnesota but they appear to be deflected southwards and truncated in proximity to archean rocks of the minnesota river valley mrv subprovince in contrast the interior of the mrv subprovince to the southwest shows little sign of penokean tectonism in addition the magmatic and metamorphic rocks of the internal zone of the orogen in east central minnesota are extensively invaded by ca 1785 1770 ma granitic rocks the east central minnesota batholith whereas post orogenic granites of this age occur sparingly to the east these differences in orogenic structure may be related to their location near the juncture of an embayment becker embayment and a promontory mrv promontory that formed the pre penokean continental margin in this scenario the mrv promontory which at the surface consists chiefly of high metamorphic grade mesoarchean gneisses would have formed competent high standing crust that resisted deformation and did not host significantly thick continental margin sequences in contrast the part of the becker embayment adjoining the promontory would have involved relatively weak low standing crust that favored deposition of continental margin sequences and during penokean collision would have accommodated tectonic loading of the cratonic margin through thin skinned deformation thrusting of thick embayment sequences and possibly a block of archean crust marshfield terrane onto the embayment margin may have produced a greatly thickened crust that subsequently promoted crustal melting and generation of the geon 17 granites preliminary gravity and magnetic model studies of the present day crust imply that rocks of the fold and thrust belt may sole out at 5 8 km depth whereas magmatic and high metamorphic grade rocks associated with the internal zone of the orogen could extend to mid crustal depths the tectonic model proposed here implies that a collision between an embayment and an impinging continental mass may enhance tectonic thickening and subsequent generation of post orogenic magmas this and other hypotheses regarding the penokean orogen need to be investigated further in the third dimension of depth which will require a comprehensive suite of geophysical studies

downward water movement into frozen ground western arctic coast canada field studies carried out mainly since 1975 in permafrost areas of alaska canada china and the soviet union have been combined with the results of laboratory investigations to show that in summer water can move from the thawing active layer into the subjacent frozen active layer and under certain conditions even into the top of permafrost direct field evidence discussed includes data from drilling and neutron probe logging which show a summer increase in the ice content of already frozen ground summer heave of heavemeters with heave occurring in the frozen active layer and increase in the ice content of the subjacent frozen ground in both permafrost and non permafrost areas caused by snowmelt infiltration indirect field and laboratory evidence is also added to support the direct lines of evidence the conditions that favor the downward migration of water from thawed to frozen ground are examined in terms of thermally induced hydraulic gradients hydraulic conductivity content of unfrozen pore

impact of a base metal smelter on the geochemistry of soils of the flin flon region manitoba and saskatchewan the regional dispersal patterns of six trace metals as cd cu hg pb zn emitted from the base metal smelter at flin flon were examined in surface soils and at depth using an extensive regiona

mixing in the romanche fracture zone the romanche fracture zone is a major gap in the mid atlantic ridge at the equator which is deep enough to allow significant eastward flows of antarctic bottom water from the brazil basin to the sierra leone and guinea abyssal plains while flowing through the romanche fracture zone bottom water properties are strongly modified due to intense vertical mixing the diapycnal mixing coefficient in the bottom water of the romanche fracture zone is estimated by using the finestructure of ctd profiles the microstructure of high resolution profiler data and by constructing a heat budget from current meter data the finestructure of density profiles is described using the thorpe scaleslt it is shown from microstructure data taken in the bottom water that the ozmidov scale lo is related to lt by the linear relationship lo 5 0 95lt similar to other studies which allows an estimate of the diapycnal mixing coefficient using the osborn relation the thorpe scale and the diapycnal mixing coefficient estimates show enhanced mixing downstream eastward of the main sill of the romanche fracture zone in this region a mean diapycnal mixing coefficient of about 1000 3 1024 m2 s21 is found for the bottom water estimates of cross isothermal mixing coefficient derived from the heat budgets constructed downstream of the current meter arrays deployed in the romanche fracture zone and the nearby chain fracture zone are in agreement with the finestructure estimates of the diapycnal mixing coefficient within the romanche fracture zone although the two fracture zones occupy only 0 4 of the area covered by the sierra leone and guinea abyssal plains the diffusive heat fluxes across the 1 4 8c isotherm in the romanche and chain fracture zones are half that found over the abyssal plains across the 1 88c isotherm emphasizing the role of these passages for bottom water property modifications

transition from partly standing to progressive internal tides in monterey submarine canyon monterey submarine canyon is a large sinuous canyon off the coast of california the upper reaches of which were the subject of an internal tide observational program using moored profilers and upward looking moored adcps the mooring observations measured a near surface stratification change in the upper canyon likely caused by a seasonal shift in the prevailing wind that favoured coastal upwelling this change in near surface stratification caused a transition in the behaviour of the internal tide in the upper canyon from a partly standing wave during pre upwelling conditions to a progressive wave during upwelling conditions using a numerical model we present evidence that either a partly standing or a progressive internal tide can be simulated in the canyon simply by changing the initial stratification conditions in accordance with the observations the mechanism driving the transition is a dependence of down canyon supercritical internal tide reflection from the canyon floor and walls on the depth of maximum stratification during pre upwelling conditions the main pycnocline extends down to 200 m below the canyon rim resulting in increased supercritical reflection of the up canyon propagating internal tide back down the canyon the large up canyon and smaller down canyon progressive waves are the two components of the partly standing wave during upwelling conditions the pycnocline shallows to the upper 50 m of the watercolumn above the canyon rim resulting in decreased supercritical reflection and allowing the up canyon progressive wave to dominate

evidence for early proterozoic plate tectonics from seismic reflection profiles in the baltic shield plate tectonics provides the linking framework for all tectonic and magmatic activity seen today but it is not known when plate tectonics first developed on earth new deep seismic reflection and

structure propagation and mixing of energetic baroclinic tides in mamala bay oahu hawaii abstract large semidiurnal vertical displacements 100 m and strong baroclinic currents 0 5 m s 1 several times as large as barotropic currents dominate motions in mamala bay outside the mouth of pearl harbor hawaii during september 2002 the authors sought to characterize them with a 2 month mclane moored profiler deployment and a 4 day intensive survey with a towed ctd adcp and the research vessel r v revelle hydrographic sonar spatial maps and time series of turbulent dissipation rate diapycnal diffusivity k isopycnal displacement velocity u energy e and energy flux f are presented dissipation rate peaks in the lower 150 m during rising isopycnals and high strain and shows a factor of 50 spring neap modulation the largest k values in the western bay near a submarine ridge exceed 10 3 m2 s 1 the m2 phases of and u increase toward the west implying a westward phase velocity cp 1 m s 1 and horizontal wavelength 60 km consistent with theoretical mode 1 values these phase

tracing variability of run off generation in mountainous permafrost of semi arid north eastern mongolia the headwaters of mountainous discontinuous permafrost regions in north eastern mongolia are important water resources for the semi arid country but little is known about hydrological processes there run off generation on south facing slopes which are devoid of permafrost has so far been neglected and is totally unknown for areas that have been affected by recent forest fires to fill this knowledge gap the present study applied artificial tracers on a steppe vegetated south facing and on two north facing slopes burned and unburned combined sprinkling and dye tracer experiments were used to visualize processes of infiltration and water fluxes in the unsaturated zone on the unburned north facing slope rapid and widespread infiltration through a wet organic layer was observed down to the permafrost on the burned profile rapid infiltration occurred through a combusted organic and underlying mineral layer stained water seeped out at the bottom of both profiles suggesting a general tendency to subsurface stormflow ssf ongoing ssf could directly be studied 24 h after a high intensity rainfall event on a 55 m hillslope section in the burned forest measurements of water temperature proved the role of the permafrost layer as a base horizon for ssf repeated tracer injections allowed direct insights into ssf dynamics a first injection suggested rather slow dispersive subsurface flow paths whereas 18 h later a second injection traced a more preferential flow system with 20 times quicker flow velocities we speculate that these pronounced ssf dynamics are limited to burned slopes where a thermally insulating organic layer is absent on three south facing soil profiles the applied tracer remained in the uppermost 5 cm of a silt rich mineral soil horizon no signs of preferential infiltration could be found which suggested reduced biological activity under a harsh dry and cold climate instead direct observations distributed tracers and charcoal samples provided evidence for the occurrence of overland flow copyright 2014 john wiley sons ltd

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

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

lithoprobe new perspectives on crustal evolution lithoprobe is canada s national collaborative multidisciplinary earth science research program directed toward an enhanced understanding of how the north american continent evolved research in i

correlation chart of the proterozoic assembly of the northeastern canadian greenland shield chart 1 correlation chart of the proterozoic assembly of the northeastern canadian greenland shield including a location map and reference list

propagation and dissipation of the internal tide in upper monterey canyon 1 submarine canyons are sites of intense turbulence and mixing monterey canyon cuts into the continental shelf off california and is defined by its sinuous nature temperature salinity and current velocity measurements were made over 21 days in april 2009 with a depth cycling towed body to understand internal tide propagation and dissipation through the canyon bends cross canyon transects reveal complex flow patterns that follow large scale bathymetry on scales greater than 5 km changes in thalweg direction deflect baroclinic energy flux but the bends in the measurement region are too sharp for the flux to follow the thalweg ridges that form the bends in the canyon act as obstacles to the flow and turbulent dissipation rates greater than 1 10 5 m2 s 3 were observed on their flanks especially at the largest meander the gooseneck the canyon integrated baroclinic energy flux increased from 2 7 mw at the most western section to 3 7 mw at the gooseneck ridge which has a nearly critical bottom slope with respect to the semidiurnal baroclinic tide on the western side baroclinic energy flux was 50 less on the eastern side of the ridge while measured dissipation near the gooseneck meander was sufficient to explain the flux divergence turbulence near the gooseneck may have been undersampled between the gooseneck ridge and the most eastern cross canyon transect dissipation may account for the decrease in the energy flux though a local energy balance does not hold the energy budget is balanced over the larger scale of the measurement region east of the gooseneck ridge

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

internal wave reflection on shelf slopes with depth varying stratification abstractreflection of internal waves from sloping topography is simple to predict for uniform stratification and linear slope gradients however depth varying stratification presents the complication that regions of the slope may be subcritical and other regions supercritical here a numerical model is used to simulate a mode 1 m2 internal tide approaching a shelf slope with both uniform and depth varying stratifications the fractions of incident internal wave energy reflected back offshore and transmitted onto the shelf are diagnosed by calculating the energy flux at the base of slope with and without topography and at the shelf break for the stratifications topographies considered in this study the fraction of energy reflected for a given slope criticality is similar for both uniform and depth varying stratifications this suggests the fraction reflected is dependent only on maximum slope criticality and independent of the depth of the pycnocline the majority of the reflected energy flux is in

chronology of crustal growth and recycling in the paleoproterozoic amisk collage flin flon belt trans hudson orogen canada u pb zircon ages have been compiled for magmatic and sedimentary rocks from the low metamorphic grade portion of the flin flon greenstone belt now recognized as a paleoproterozoic tectonic collage

thermokarst dynamics in western siberia insights from dendrochronological research abstract thermokarst dynamics and their underlying causes are investigated and reconstructed on the basis of muzhy weather station records western siberia of air temperature precipitation and snow cover and a tree ring chronology analysis of siberian stone pine pinus sibirica du tour the results indicate that the development of thermokarst over the last 50 years has depended primarily on increasing precipitation rather than increasing air temperature reconstruction of past thermokarst borderlines shows that the rate of thermokarst expansion in the second half of the 20th century increased to 7 4 cm year as compared to past rates ranging from 4 to 8 1 cm year

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

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

relations between air and surface temperature in discontinuous permafrost terrain near mayo yukon territory the association of site characteristics with the n factor a ratio of air to ground surface temperature was investigated at five sites in the boreal forest near mayo yukon territory permafrost was in equilibrium with surface conditions at three sites was degrading at another and was absent from the fifth air and near surface ground temperatures were recorded by data loggers between september 2000 and april 2002 and mean daily temperatures were accumulated to calculate n factors for the freezing nf and thawing nt seasons air temperature did not vary between the sites so inter site differences in nf and nt were because of variations in surface temperature variations in nf between the sites over the two winters were primarily because of differences in snow depth but at sites with similar snow cover the surface temperatures were relatively high when the site was underlain by unfrozen ground during summer daily mean surface temperatures were initially less than air temperatures however once

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

flow and mixing in juan de fuca canyon washington we report breaking internal lee waves strong mixing and hydraulic control associated with wind driven up canyon flow in juan de fuca canyon washington unlike the flow above the canyon rim which shows a tidal modulation typical on continental shelves the flow within the canyon is persistently up canyon during our observations with isopycnals tilted consistent with a geostrophic cross canyon momentum balance as the flow encounters a sill near the canyon entrance at the shelf break it accelerates significantly and undergoes elevated mixing on the upstream and downstream sides of the sill on the downstream side a strong lee wave response is seen with displacements of o 100 m and overturns tens of meters high the resulting diffusivity is o 10 2 m2 s 1 sufficient to substantially modify coastal water masses as they transit the canyon and enter the salish sea estuarine system

turbulent mixing and exchange with interior waters on sloping boundaries abstractmicrostructure measurements along the axes of monterey and soquel submarine canyons reveal 200 300 m thick well stratified turbulent near bottom layers with average turbulent kinetic energy dissipation rates e 4 10 8 w kg 1 and eddy diffusivities k 16 10 4 m2 s 1 assuming mixing efficiency 0 2 to at least thalweg depths of 1200 m turbulent dissipation rates are an order of magnitude lower in overlying waters whereas buoyancy frequencies are only 25 higher well mixed bottom boundary layer thicknesses hn are an order of magnitude thinner than the stratified turbulent layer hn he because well stratified turbulent layers are commonly observed above slopes arguments that mixing efficiency should be reduced on sloping boundaries do not hold in cases of energetic internal wave generation or interaction with topography an advective diffusive balance is used to infer velocities and transports predicting horizontal upslope flows of 10 50 m day 1 extrapolating this estimate globa

deep seismic profile across a proterozoic collision zone surprises at depth collisions between continents generate the world s most striking mountains the deep structure of these collision zones inferred from seismic reflection profiles1 3 can be equally dramatic if less well understood improved knowledge of the structure of ancient collisional belts now known to have developed through plate tectonic processes4 5 can provide important new insights into the mechanisms of crustal growth although many such belts have been partly destroyed by severe post collisional deformation6 7 or magmatism8 some have been preserved in the stable interiors of continents9 one example is the early proterozoic trans hudson orogen9 10 in western canada here we present seismic reflection images across the entire orogen which reveal a broadly symmetric structure with reflections linked to island arc rocks dipping beneath both bounding archaean cratons the observed reflection geometries imply a doubling of crustal thickness during the collision along crust penetrating faults the presence of a significant amount of archaean crust at depth the extent of which could not have been determined from surface mapping suggests the need for caution in inferring crustal growth rate from the surface area of juvenile crust11 12

comment on ground surface temperature history in central canada inferred from 10 selected borehole temperature profiles by laurent guillou frottier jean claude mareschal and julien musset

internal tide convergence and mixing in a submarine canyon abstractobservations from eel canyon located on the north coast of california show that elevated turbulence in the full water column arises from the convergence of remotely generated internal wave energy the incoming semidiurnal and bottom trapped diurnal internal tides generate complex interference patterns the semidiurnal internal tide sets up a partly standing wave within the canyon due to reflection at the canyon head dissipating all of its energy within the canyon dissipation in the near bottom is associated with the diurnal trapped tide while midwater isopycnal shear and strain is associated with the semidiurnal tide dissipation is elevated up to 600 m off the bottom in contrast to observations over the flat continental shelf where dissipation occurs closer to the topography slope canyons are sinks for internal wave energy and may have important influences on the global distribution of tidally driven mixing

observations of nonlinear internal wave run up to the surfzone abstractthe cross shore evolution of nonlinear internal waves nliws from 8 m depth to shore was observed by a dense thermistor array and adcp isotherm oscillations spanned much of the water column at a variety of periods at times nliws propagated into the surfzone decreasing temperature by 1 c in 5 min when stratification was strong temperature variability was strong and coherent from 18 to 6 m depth at semidiurnal and harmonic periods when stratification weakened temperature variability decreased and was incoherent between 18 and 6 m depth at all frequencies at 8 m depth onshore coherently propagating nliw events had associated rapid temperature drops t up to 1 7 c front velocity between 1 4 and 7 4 cm s 1 and incidence angles between 5 and 23 front position t and two layer equivalent height ziw of four events were tracked upslope until propagation terminated front position was quadratic in time and normalized t and ziw both decreased collapsing as a linearly decaying funct

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

diamonds exploration mines and marketing abstract the beauty value and mystique of exceptional quality diamonds such as the 603 carat lesotho promise recovered from the letseng mine in 2006 help to drive a multi billion dollar diamond exploration mining and marketing industry that operates in some 45 countries across the globe five countries botswana russia canada south africa and angola account for 83 by value and 65 by weight of annual diamond production which is mainly produced by four major companies de beers alrosa rio tinto and bhp billiton bhpb which together account for 78 by value and 72 by weight of annual diamond production for 2007 during the last twelve years 16 new diamond mines commenced production and 4 re opened in addition 11 projects are in advanced evaluation and may begin operations within the next five years exploration for diamondiferous kimberlites was still energetic up to the last quarter of 2008 with most work carried out in canada angola democratic republic of the congo drc and botswana many kimberlites were discovered but no new economic deposits were outlined as a result of this work except for the discovery and possible development of the bunder project by rio tinto in india exploration methods have benefitted greatly from improved techniques of high resolution geophysical aerial surveying new research into the geochemistry of indicator minerals and further insights into the formation of diamonds and the relation to tectonic structural events in the crust and mantle recent trends in diamond marketing indicate that prices for rough diamonds and polished goods were still rising up to the last quarter of 2008 and subsequently abruptly sank in line with the worldwide financial crisis most analysts predict that prices will rise again in the long term as the gap between supply and demand will widen because no new economic diamond discoveries have been made recently the disparity between high rough and polished prices and low share prices of publicly traded diamond companies may be due to investors losing patience with the slow pace or absence of new promising discoveries and switching into shares of base metals and fertilizers for agriculture potash and phosphates

an interpretation of surface and borehole seismic surveys for mine planning at the millennium uranium deposit northern saskatchewan canada abstractthe millennium uranium deposit is located within the athabasca basin in northern saskatchewan canada the deposit is hosted within moderately dipping paleoproterozoic gneisses that are unconformably overlain by more than 500 m of flat lying porous paleoproterozoic to late mesoproterozoic athabasca group sandstones the deposit is associated with the sandstone basement unconformity post athabasca structure and hydrothermal alteration these features combine to create a complex 3d hydrogeologic setting that presents challenges with respect to mine development production and safety in 2007 as part of a prefeasibility study for potential mine development a seismic program consisting of a 3d surface survey vertical seismic profiling moving source profiling and side scan surveys was undertaken to map the complex geology the geometry and resolution of these different seismic surveys allowed for direct imaging of the geologic targets of interest regardless of orientation and size after int

the response 1958 1997 of permafrost and near surface ground temperatures to forest fire takhini river valley southern yukon territory forest fires in permafrost areas often modify ground surface conditions causing deepening of the active layer and thawing of near surface permafrost takhini river valley lies in the discontinuous permafrost zone of southern yukon territory the valley floor is covered by glaciolacustrine deposits which are locally ice rich in 1958 extensive forest fires burned most of the vegetation and the soil organic horizon in the valley but 50 km west of whitehorse 1 km2 of spruce forest adjacent to the alaska highway escaped burning permafrost beneath this stand of trees is in equilibrium with surface conditions the active layer is 1 4 m thick the base of permafrost is at 18 5 m the annual mean temperature at the top of permafrost 1 5 m is 0 8 c and the temperature gradient in permafrost is constant with depth at burned sites nearby there has been little regeneration of forest vegetation since the fire and long term permafrost degradation has occurred at one burned site the permafrost table is mor

internal tide reflection and turbulent mixing on the continental slope abstract observations of turbulence internal waves and subinertial flow were made over a steep corrugated continental slope off virginia during may june 1998 at semidiurnal frequencies a convergence of low mode onshore energy flux is approximately balanced by a divergence of high wavenumber offshore energy flux this conversion occurs in a region where the continental slope is nearly critical with respect to the semidiurnal tide it is suggested that elevated near bottom mixing k 10 3 m2 s 1 observed offshore of the supercritical continental slope arises from the reflection of a remotely generated low mode m2 internal tide based on the observed turbulent kinetic energy dissipation rate the high wavenumber internal tide decays on time scales o 1 day no evidence for internal lee wave generation by flow over the slope s corrugations or internal tide generation at the shelf break was found at this site

a reflecting steepening and breaking internal tide in a submarine canyon submarine canyons are common features of the coastal ocean although they are known to be hotspots of turbulence that enhance diapycnal transport in their stratified waters the dynamics of canyon mixing processes are poorly understood most studies of internal wave dynamics within canyons have focused on a handful of canyons with along axis slopes less steep than semidiurnal d2 internal wave characteristics subcritical here we present the first tidally resolving observations within a canyon with a steeply sloping axis supercritical a process study consisting of two 24 hour shipboard stations and a profiling mooring was conducted in the la jolla canyon off the coast of la jolla ca baroclinic energy flux is oriented up canyon and decreases from 182 18 w m 1 at the canyon mouth to 46 5 w m 1 near the head the ratio of horizontal kinetic energy to available potential energy and the observed group speed of each mode are lower than expected for freely propagating d2 internal waves at each station indicating partial reflection harmonic analysis reveals that variance is dominated by the d2 tide moving up canyon the relative importance of d2 decreases and its higher harmonics are needed to account for a majority of the observed variance indicating steepening steep internal tides cause large isopycnal displacements 50 m in 100m water depth and high strain events these events coincide with enhanced o 10 7 10 5 m2 s 3 dissipation of turbulent kinetic energy at mid depths

initial seismic observations from a deep borehole drilled into the canadian shield in northeast alberta the availability of a deep borehole in northeastern alberta provides an unprecedented opportunity to study the in situ metamorphic craton rocks this borehole reaches a depth of 2 4 km with 1 8 km in the crystalline rocks and is the only known borehole allowing access into the deeper rocks of the metamorphic canadian shield in 2011 a zero offset vertical seismic profile vsp was acquired to assist in the interpretation of seismic reflection data and geophysical logs three sets of upgoing tube waves interpreted from the raw profile correspond to the small scale fluctuations in the borehole diameters and fracture zone in the crystalline rocks a comparison between sonic log velocities and vsp velocities reveals a zone with increased velocity that could be due to the change in rock composition and texture in the basement rocks the final processed profile is used to generate corridor stacks for differentiating between primary reflections and multiples in the seismic reflection profile analysis of the zero offset vsp verifies existing log interpretation on the presence of fractures and the possible lithological changes in the metamorphic rocks of the canadian shield

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

cryostratigraphic record of permafrost degradation and recovery following historic 1898 1992 surface disturbances in the klondike region central yukon territory we present a detailed cryostratigraphic reconstruction of the degradation and recovery of near surface permafrost in the southern klondike goldfields central yukon territory two ice rich layers a

suture zone geometry along an irregular paleoproterozoic margin the superior boundary zone manitoba canada lithoprobe acquired a 190 km long deep seismic reflection profile across the superior boundary zone at the eastern margin of the paleoproterozoic trans hudson orogen the profile is located 250 km south of a major promontory along the ancient margin of the superior craton and complements earlier profiles closer to the promontory the new data image the remnants of a craton verging thrust belt younger than 1864 ma within the superior boundary zone extending to a maximum depth of 15 km above a shallowly west dipping basal decollement across the surface suture zone a dip reversal to east dipping reflections occurs within the adjacent reindeer zone where a crustal scale imbricate stack is imaged reindeer zone lower crust and upper mantle extend eastward beneath the superior craton margin for 40 100 km preservation of a foreland thrust belt within the superior boundary zone is explained as a result of reduced collisional convergence and subsequent exhumation within a reentrant flanking the thompson promontory

internal tide radiation from mendocino escarpment abstract strong semidiurnal internal tides are observed near mendocino escarpment in full depth profile time series of velocity temperature and salinity velocity and density profiles are combined to estimate the internal tide energy flux divergence of this flux demonstrates that its source is the barotropic tide interacting with the escarpment a baroclinic energy flux of 7 kw m 1 radiates from the escarpment corresponding to 3 of the 220 kw m 1 fluxing poleward in the surface tide energy and energy flux are concentrated in packets that emanate from the flanks of the ridge surmounting the escarpment and one site 90 km north of the escarpment coherent beamlike structure along semidiurnal ray paths remains identifiable until the first surface reflection beyond the first surface reflection north of the escarpment the energy flux drops by 2 kw m 1 and beams are no longer discernible turbulence as inferred from finescale parameterizations is elevated by over two orders of magnitude relative to th