reflection of linear internal tides from realistic topography the tasman continental slope abstractthe reflection of a low mode internal tide on the tasman continental slope is investigated using simulations of realistic and simplified topographies the slope is supercritical to the internal tide which should predict a large fraction of the energy reflected however the response to the slope is complicated by a number of factors the incoming beam is confined laterally it impacts the slope at an angle there is a roughly cylindrical rise directly offshore of the slope and a leaky slope mode wave is excited these effects are isolated in simulations that simplify the topography to separate the incident from the reflected signal a response without the reflector is subtracted from the total response to arrive at a reflected signal the real slope reflects approximately 65 of the mode 1 internal tide as mode 1 less than two dimensional linear calculations predict because of the three dimensional concavity of the topography it is also less than recent glider estimates likely as a result o

modeling semidiurnal internal tide variability in the southern california bight abstractthe regional oceanic modeling system roms is applied in a nested configuration with realistic forcing to the southern california bight scb to analyze the variability in semidiurnal internal wave generation and propagation the scb has a complex topography with supercritical slopes that generate linear internal waves at the forcing frequency the model predicts the observed barotropic and baroclinic tides reasonably well although the observed baroclinic tides feature slightly larger amplitudes the strongest semidiurnal barotropic to baroclinic energy conversion occurs on a steep sill slope of the 1900 m deep santa cruz basin this causes a forced near resonant semidiurnal poincare wave that rotates clockwise in the basin and is of the first mode along the radial azimuthal and vertical directions the associated tidal mean depth integrated energy fluxes and isotherm oscillation amplitudes in the basin reach maximum values of about 5 kw m 1 and 100 m and are strongly modulated by the sprin

metamorphism at the base of the samail ophiolite southeastern oman mountains metamorphic rocks showing an inverted metamorphic zonation from upper amphibolite facies to greenschist facies occur beneath the samail ophiolite the metamorphic protolith was a section of marine basalts mn rich cherts and argillites garnet clinopyroxene amphibolites occur within 2 m of the contact hornblende clinopyroxene assemblages occur within 80 m of the contact and lower amphibolite facies rocks persist to 130 m from the contact the higher grade rocks show polyphase deformation cataclastic fabrics and partial retrogression to greenschist facies assemblages however lower grade phyllites show evidence of only one episode of metamorphic crystallization unmetamorphosed sediments in contact with the basal metamorphic sheet do not show evidence of polyphase deformation the distribution coefficient kd feo mgo gar feo mgo cpx ranges from 4 4 to 5 3 suggesting a t range of 755 865 c at 200 mpa low jadeite content in clinopyroxene and low glaucophane content of ca amphiboles are consistent with moderate pressures of crystallization the metamorphic sheet is inferred to be of composite origin the highest grade rocks were tectonically transported the greatest distance and the lower grade rocks were successively incorporated into the sheet as the peridotite was thrust over progressively cooler rocks residual heat from the ophiolite is the dominant heat source for the metamorphism and this could have been augmented by a limited amount of frictional heat generated during thrusting these thermal constraints suggest that the metamorphism occurred early in the tectonic transport history of the samail ophiolite

internal tides in a dendritic submarine canyon abstract submarine canyons are a common geomorphological feature along continental slopes worldwide and often found to be hotspots of internal tide activity however the majority of well studied submarine canyons are simple linear incisions or have meandering morphology internal tide energetics in branching dendritic canyons has not previously been investigated here we present a high resolution 500 m numerical modelling study of the internal tide within whittard canyon a large dendritic submarine canyon system that incises the celtic sea continental slope a modified version of the princeton ocean model is used to simulate the m 2 semidiurnal internal tide in the whittard canyon region verified against a hydrographic dataset collected by an autonomous ocean glider much of the internal tide energy entering whittard canyon originates to the southeast along the celtic sea shelf break internal tide generation also occurs within the canyon itself but is in part compensated by areas of negative energy conversion depth integrated internal tide energy fluxes exceed 8 kw m 1 in the eastern limb of the canyon the internal tide is topographically steered through the major limbs and along canyon energy flux is bottom intensified suggesting topographic focusing the down canyon extent of bottom intensification closely corresponds to the point that along canyon slope becomes near critical to the semidiurnal internal tide energetically the multiple limbs of whittard canyon behave differently some are net sources of internal tide energy whilst others are net sinks internal tide energy dissipation also varies between the canyon limbs bulk dissipation rates are 2 1 7 7 10 8 w kg 1 in addition the effect of bathymetric resolution on internal tide generation and propagation is investigated by progressively smoothing the model domain decreasing the bathymetric resolution reduces internal tide generation and energy dissipation in both whittard canyon and the model domain as a whole however internal tide energy flux into the canyon is not consistently changed at least 1 5 km resolution bathymetry is required to adequately resolve the semidiurnal internal tide field in this region of complex topography

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

structure of the musandam culmination sultanate of oman and united arab emirates and the straits of hormuz syntaxis the musandam mountains form a link both in time and space between the late cretaceous ophiolite obduction tectonics of the oman mountains and the late tertiary continental collision tectonics of the zagros fold belt of iran culmination of the musandam shelf carbonates occurred after the turonian maastrichtian thin skinned thrusting of the oman mountains was completed the basal hagab thrust cuts up section to the west from at least mid permian level up to the late cretaceous aruma group and breached up into the overlying previously allochthonous cretaceous hawasina cherts in the hagil window ras al khaimah the shelf carbonates show from 4 to 15 km of westward translation extrapolation of foreland sequences suggests that upper cretaceous aruma group and hawasina complex sediments could occur in the subsurface along the footwall east of the mountain front the hagab thrust and musandam structures plunge south southwest at increasingly greater depth and with decreasing amount of translation and carry all overlying late cretaceous thrust sheets of the oman mountains in a piggy back fashion the eocene lr oligocene pabdeh foredeep developed as a result of loading in front of the musandam thrust sheets wedging out to the south the trailing south eastern edge of the musandam culmination is a hinged listric normal fault downthrowing to the south east up to 2 5 km at bayah and less than 500 m at the western end of batha mahani and is interpreted as a dorsal culmination collapse feature

coastal trapped behavior of the diurnal internal tide at o ahu hawai i the influence of rotation on the structure and propagation of internal tides around o ahu hawai i is investigated using in situ observations and a tidally forced primitive equation model with realistic bathymetry and stratification particular attention is given to the diurnal internal tide which largely has been de emphasized in previous studies of the region because of the dominance of the semidiurnal internal tide but has been determined by recent studies to be a significant contributor to baroclinic variability though both diurnal and semidiurnal internal tides are generated primarily over ka ena ridge to the northwest of the island the diurnal internal tide propagates clockwise around the island as an imperfectly trapped wave while the semidiurnal internal tide propagates away from the ridge unaffected by rotation the diurnal and semidiurnal internal tides fall into the superinertial frequency range however the diurnal frequency apparently is sufficiently close to inertial 1 4f for rotation to affect internal tide propagation the in situ observations support the model finding that diurnal trapping provides the primary source of baroclinic variability along the eastern coast of the island a stretch of coastline otherwise sheltered from the internal tide energy generated over the hawaiian ridge the findings in hawai i suggest that coastal trapping of superinertial internal tides may be a significant source of variability and mixing in other nearshore systems around the world

saddle dolomite and calcite cements as records of fluid flow during basin evolution paleogene carbonates united arab emirates abstract field observations indicate that tectonic compression anticline formation and concomitant uplift events of marine paleogene carbonates in eastern united arab emirates which are related to the zagros orogeny have induced brecciation karstification and carbonate cementation in vugs and along faults and fractures structural analysis stable isotopes and fluid inclusion microthermometry are used to constrain the origin and geochemical evolution of the fluids fluid flow was related to two tectonic deformation phases initially the flux of moderately 87 sr rich basinal nacl mgcl 2 h 2 o brines along reactivated deep seated strike slip faults have resulted in the precipitation of saddle dolomite in fractures and vugs and in dolomitization of host eocene limestones 18 o v pdb 15 8 to 6 2 homogenization temperatures of 80 115 c and salinity of 18 25 wt eq nacl subsequently compression and uplift of the anticline was associated with incursion of meteoric waters and mixing with the basinal brines which resulted in the precipitation of blocky calcite cement 18 o v pdb 22 to 12 homogenization temperatures of 60 90 c and salinity of 4 5 9 wt eq nacl saddle dolomite and surrounding blocky calcite have precipitated along the pre and syn folding e w fracture system and its conjugate fracture sets the stable isotopes coupled with fluid inclusion micro thermometry homogenization temperatures of 50 c and salinity of 87 sr rich cool meteoric waters this carbonate cementation history explains the presence of two correlation trends between the 18 o v pdb and 13 c v pdb values i a negative temperature dependent oxygen isotope fractionation trend related to burial diagenesis and to the flux of basinal brines and ii positive brine meteoric mixing trend this integrated study approach allows better understanding of changes in fluid composition and circulation pattern during evolution of foreland basins

thrust tectonics of the dibba zone and the structural evolution of the arabian continental margin along the musandam mountains oman and united arab emirates in the northern oman mountains several major thrust sheets of tethyan oceanic rocks dibba zone and a 12km thick complete ophiolite sequence have been thrust westward onto the depressed arabian continental margin musandam zone during the turonian to campanian late cretaceous early thrusting was dominantly a downward foreland propagating sequence as the higher earlier thrust sheets are folded around structurally lower and later culminations breached roof thrusts where imbricate thrusts do not always converge with a major roof thrust but in places actually penetrate up into the overlying duplex are common at outcrop scale affecting adjacent thrust sheets late stage breakback or leap frog thrusts cut through the whole pile of duplexes on to previously higher earlier dulexes late thrusting in the musandam zone affects the deeper previously autochthonous permian cenomanian shelf carbonate sequence and probably also the pre permian basement thrusting these rocks at least 15 km over previously allochthonous hawasina rocks late stage oblique dorsal culmination collapse along the se margin of the musandam mountains has downfaulted dibba zone rocks up to 2 5 km to the se along a hinged listric normal fault strain is transferred from the ne sw trending late cretaceous dibba zone to the n s striking mid tertiary musandam culmination at a major pivot point or transfer zone sw of the shelf carbonate culmination

energetics of m2 barotropic to baroclinic tidal conversion at the hawaiian islands abstract a high resolution primitive equation model simulation is used to form an energy budget for the principal semidiurnal tide m2 over a region of the hawaiian ridge from niihau to maui this region includes the kaena ridge one of the three main internal tide generation sites along the hawaiian ridge and the main study site of the hawaii ocean mixing experiment the 0 01 horizontal resolution simulation has a high level of skill when compared to satellite and in situ sea level observations moored adcp currents and notably reasonable agreement with microstructure data barotropic and baroclinic energy equations are derived from the model s sigma coordinate governing equations and are evaluated from the model simulation to form an energy budget the m2 barotropic tide loses 2 7 gw of energy over the study region of this 163 mw 6 is dissipated by bottom friction and 2 3 gw 85 is converted into internal tides internal tide generation primarily occurs along the flanks of the kaena ridge and

three dimensional double ridge internal tide resonance in luzon strait abstractthe three dimensional 3d double ridge internal tide interference in the luzon strait in the south china sea is examined by comparing 3d and two dimensional 2d realistic simulations both the 3d simulations and observations indicate the presence of 3d first mode semi diurnal standing waves in the 3 6 km deep trench in the strait as in an earlier 2d study barotropic to baroclinic energy conversion flux divergence and dissipation are greatly enhanced when semidiurnal tides dominate relative to periods dominated by diurnal tides the resonance in the 3d simulation is several times stronger than in the 2d simulations for the central strait idealized experiments indicate that in addition to ridge height the resonance is only a function of separation distance and not of the along ridge length that is the enhanced resonance in 3d is not caused by 3d standing waves or basin modes instead the difference in resonance between the 2d and 3d simulations is attributed to the topographic blocking

origin and implications of a thrust bound gypsiferous unit along the western edge of jabal sumeini northern oman mountains abstract the oman mountains comprise a series of thrust sheets of neo tethyan oceanic rocks that were emplaced onto the arabian continental margin during obduction of the semail ophiolite during the late cretaceous three separate groups of anomalous gypsiferous bodies intrude the allochthonous units along faults over a distance of about 150 km in the hawasina window jabal qumayrah and jabal sumeini the bodies at jabal sumeini form a band about 4 km long and up to 100 m wide along a late stage thrust that restacks the allochthon over a post emplacement maastrichtian palaeogene sedimentary succession the gypsum shows evidence of flow folding and contains numerous clasts and rafts of a range of quartzose sandstones but with only a minor component from carbonates from the neo tethyan sumeini group in the hanging wall palaeogene limestones from the footwall succession are essentially absent strontium isotope ratios are high and intersect with the open ocean water reference curve for the late cambrian ordovician and late miocene pliocene they are also noticeably higher than the ratios from the two other gypsiferous outcrop areas in the oman mountains and from outcrops of ediacaran early cambrian salt domes in central oman however the regional stratigraphy points towards a source of the gypsum from either an ediacaran early cambrian ara group salt basin or from the lower fars formation early middle miocene and derivation of the sandstone clasts and rafts from thick lower palaeozoic clastic sequences the discrepancy with the ages inferred from the strontium isotope data can be attributed to deposition of the gypsum in restricted conditions not in equilibrium with the prevailing ocean water two models are presented for an ediacaran early cambrian and an early middle miocene source while the latter cannot be wholly discounted the stratigraphic and structural context point more strongly towards an ediacaran early cambrian ara group source of the gypsum this was extruded along deep rooted late cretaceous thrust faults that were reactivated during a period of cenozoic compression incorporating lower palaeozoic sandstone clasts from adjacent strata during extrusion or during an earlier phase of possible halokinesis this is consistent with existing models for the emplacement of the other two identified groups of gypsiferous bodies in the oman mountains and provides further evidence for the presence of smaller evaporite basins between the major hormuz and central southern oman salt basins

trapped diurnal internal tides propagating semidiurnal internal tides and mixing estimates in the california current system from sustained glider observations 2006 2012 abstract from 2006 2012 along 3 repeated cross shore transects california cooperative oceanic fisheries investigations lines 66 7 80 and 90 in the california current system 33 609 shear and 39 737 strain profiles from 66 glider missions are used to estimate mixing via finescale parameterizations from a dataset containing over 52 000 profiles elevated diffusivity estimates and energetic diurnal d1 and semidiurnal d2 internal tides are found a within 100 km of the coast on lines 66 7 and 80 and b over the santa rosa cortes ridge srcr in the southern california bight scb on line 90 while finding elevated mixing near topography and associated with internal tides is not novel the combination of resolution and extent in this ongoing data collection is unmatched in the coastal ocean to our knowledge both d1 and d2 internal tides are energy sources for mixing at these latitudes the d1 internal tide is subinertial on line 90 d1 and d2 tides are equally energetic over the srcr the main site of elevated mixing within the scb numerous sources of internal tides at the rough topography in the scb produce standing and or partially standing waves on lines 66 7 and 80 the dominant energy source below about 100 m for mixing is the d1 internal tide which has an energy density of the d2 internal tide on line 80 estimated diffusivity estimated dissipation and d1 energy density peak in summer the d1 energy density shows an increasing trend from 2006 to 2012 its amplitude and phase are mostly consistent with topographically trapped d1 internal tides traveling with the topography on their right the observed offshore decay of the diffusivity estimates is consistent with the exponential decay of a trapped wave with a mode 1 rossby radius of 20 30 km despite the variable mesoscale it is remarkable that coherent internal tidal phase is found

temporal variability of the standing internal tide in the browse basin western australia 1 we have investigated the seasonal evolution of the internal tide using a yearlong mooring record in the browse basin on the australian north west shelf using a modal harmonic decomposition technique we studied the modulation of the semi diurnal kinetic energy potential energy energy flux group velocity and sea surface height anomaly for different internal wave modes a very coherent and energetic locally generated internal tide dominated the mooring record during spring tide periods relationships amongst the wave variables suggest that the interaction of multiple waves formed a standing wave pattern to assist in explaining the seasonal variability of this standing wave pattern we used an analytical model of internal wave generation and propagation in a double shelf system representative of the area to highlight the effects of changes in the stratification and barotropic forcing a comparison of the low mode wave energy indicated that the analytical solution overestimated the observed wave energy by a factor of two and failed to detect an apparent seasonal shift in the conversion rate we discuss potential mechanisms for this discrepancy

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

from tides to mixing along the hawaiian ridge the cascade from tides to turbulence has been hypothesized to serve as a major energy pathway for ocean mixing we investigated this cascade along the hawaiian ridge using observations and numerical models a divergence of internal tidal energy flux observed at the ridge agrees with the predictions of internal tide models large internal tidal waves with peak to peak amplitudes of up to 300 meters occur on the ridge internal wave energy is enhanced and turbulent dissipation in the region near the ridge is 10 times larger than open ocean values given these major elements in the tides to turbulence cascade an energy budget approaches closure

role of mesoscale eddies in modulating the semidiurnal internal tide observation results in the northern south china sea abstractthe role of mesoscale eddies in modulating the semidiurnal internal tide sit in the northern south china sea scs is examined using the data from a cross shaped mooring array from novem

permian triassic boundary interval in the middle east iran and n oman progressive environmental change from detailed carbonate carbon isotope marine curve and sedimentary evolution abstract the end permian negative 13c excursion is well known but its cause and chronology are still in question in an attempt to decipher the timing and reasons for this strong decrease we established high resolution sedimentological biostratigraphical and carbonate carbon isotopic studies in four sections in iran abadeh shareeza zal and djulfa and two in oman wadi sahtan the position of the sections on two different margins of the neotethys has allowed us to distinguish between local and global signals this high resolution chemostratigraphy tested for isochrony on the basis of an updated high resolution conodont and ammonoid biostratigraphy allows the discrimination of nine successive isotopic events ie 0 8 for the permian triassic boundary interval ptbi the negative excursion of the ptbi has been separated into four distinct parts a first drop ie 0 occurs in the late wuchiapingian with an amplitude of around 1 3 a second decrease begins ie 1 2 at the base of the dzhulfites ammonoid beds changhsingian and continues gradually until the extinction event top jolfensis conodont interval without important second order variations its amplitude varies between 1 5 and 2 8 and its duration has been estimated around 2 2 ma revealing a non catastrophic phenomenon the lower meishanensis praeparvus conodont zone records stationary to slightly increasing values ie 3 the interval of the curve after the extinction event between the upper meishanensis praeparvus zone and the base of the i isarcica zone records numerous second order variations ie 4 7 its amplitude is of 1 2 3 1 these second order variations are correlatable in iran but with some uncertainty with oman poor correlation of these small peaks with others published sections might be due to a higher sensitivity to local perturbations and a lower buffer capacity of the whole ocean we assume that the processes leading to the extinction event also caused the isotopic decrease before the extinction level with a maximal amplitude of only 2 8 this allows consideration of some possible mechanisms that were rejected as unrealistic to cause a 4 6 excursion

subduction zone polarity in the oman mountains implications for ophiolite emplacement two end member models have been proposed to account for the structure and metamorphism of rocks beneath the semail ophiolite in the oman mountains model a involves a single continuous ne directed subduction away from the continental margin during the late cretaceous the ophiolite and underlying thrust sheets of distal to proximal oceanic sediments were emplaced a minimum of 250 km sw onto the continental margin subduction of triassic jurassic oceanic basalts to c 10 kbar c 39 km depth led to the accretion of amphibolite facies rocks to the base of the ophiolite thrusting propagated towards the continental margin and ended with subduction of the thinned continental crust to c 20 kbar c 78 km depth choking the subduction zone buoyancy forces caused the rapid exhumation of eclogites blueschists and carpholite grade hp rocks along the ne margin of the continental plate during the later phase of foreland propagating thin skinned thrusting in the sw ne facing backfolding and backthrusting occurred in the hinterland with the final exhumation of the hp rocks model b follows recent suggestions that a nascent sw dipping subduction zone dipping beneath the continental margin existed between 130 and 95 ma prior to formation and emplacement of the ophiolite a major ne facing fold nappe structure in the pre permian basement rocks of saih hatat is interpreted as reflecting subduction beneath the margin two high pressure metamorphic events have been suggested the first predating ophiolite emplacement the second caused by ophiolite loading this model is untenable being based on a misinterpretation of the ne facing structures in northern saih hatat and on some dubious older 40ar 39ar cooling ages from the eclogite facies rocks of as sifah we conclude that all structures in northern oman and all the reliable geochronology point to a single emplacement obduction event lasting from cenomanian turonian time c 95 ma when amphibolites were accreted along the metamorphic sole of the ophiolite to campanian time when the continental margin was subducted to the ne producing blueschists and eclogites to the final thin skinned emplacement of all thrust sheets which ended before the late maastrichtian at c 68 ma

semidiurnal internal tide incoherence in the equatorial pacific the jets in the equatorial pacific ocean of a realistically forced global circulation model with a horizontal resolution of 1 12 5 cause a strong loss of phase coherence in semidiurnal internal tides that propagate equatorward from the french polynesian islands and hawaii this loss of coherence is quantified with a baroclinic energy analysis in which the semidiurnal band terms are separated into coherent incoherent and cross terms for time scales longer than a year the coherent energy flux approaches zero values at the equator while the total flux is 500 w m the time variability of the incoherent energy flux is compared with the internal tide travel time variability which is based on along beam integrated phase speeds computed with the taylor goldstein equation the variability of monthly mean taylor goldstein phase speeds agrees well with the phase speed variability inferred from steric sea surface height phases extracted with a plane wave fit technique on monthly time scales the loss of phase coherence in the equatorward beams from the french polynesian islands is attributed to the time variability in the vertically sheared background flow associated with the jets and tropical instability waves on an annual time scale the effect of stratification variability is of equal or greater importance than the shear variability is to the loss of coherence in the model simulations low frequency equatorial jets do not noticeably enhance the dissipation of the internal tide but merely decohere and scatter it

alkaline peridotite pyroxenite and gabbroic intrusions in the oman mountains arabia high level intrusions of highly undersaturated alkalic ultrabasic and gabbroic rocks occur in four areas of the oman mountains they all intrude either the haybi volcanic oman exotic limestone permo triassic thrust slice immediately beneath the semail ophiolite cenomanian or the uppermost thrust slice of the underlying hawasina permian to cenomanian tethyan sediments detailed structural mapping indicates that the sills were all emplaced prior to the late cretaceous thrusting of the oman allochthon onto the mesozoic continental margin of arabia and therefore in an oceanic setting these differentiated sills consist of biotite wehrlites at the base and kaersutite bearing jacupirangites above with kaersutite gabbros at the top olivine occurs only at the base titanaugite kaersutite titanium phlogopite apatite and opaque iron titanium oxides are common mineral phases fractional crystallization and gravity differentiation processes and a rapid increase in volatile components at decreasing press

sedimentological and structural evolution of the arabian continental margin in the musandam mountains and dibba zone united arab emirates the northernmost extremity of the oman mountains the musandam peninsula is composed of an allochthonous sequence of permian to middle cretaceous shelf carbonates these are separated from ophiolitic rocks to the south by a northeast southwest trending belt known as the dibba zone this structurally complex belt is composed of allochthonous slope and basin facies sediments haybi volcanic rocks oman exotic limestones sub ophiolitic metamorphic rocks and ultra mafic slices lithofacies correlation confirms that fragmentation and rifting of a vast east facing carbonate platform occurred in middle to late triassic time resulting in the establishment of a shelf edge and small ocean basin this margin was typified from northwest to southeast by ooid skeletal lime sand shoals or small bioherms on the shelf edge a bypass foreslope of well laminated periplatform ooze and basin margin accumulations of carbonate turbidites or debris flows the shelf edge now coincides with the northern boundary of the dibba zone and appears to have remained stationary from middle triassic to late jurassic time periods of arrested carbonate sedimentation on the platform either because of exposure late triassic and middle cretaceous or because of drowning late jurassic are represented in the basin by starved sedimentation and deposition of radiolarian cherts a spectacular platform margin collapse occurred in the middle and late cretaceous as represented by massive conglomerates with clasts as young as albian above an unconformity that progressively removed all of the lower cretaceous the tethyan basinal and ophiolitic rocks of the dibba zone were emplaced from the east southeast during the turonian to lower maastrichtian after emplacement of these allochthonous units compressional deformation in the mid tertiary resulted in large scale open whaleback folds with wavelengths as much as 15 km generally with north south axes in places these folds which affect the complete shelf and allochthonous sequences are overturned toward the west and thrusting has caused previously lower tectonic units of the late cretaceous stacking order to be thrust over previously higher tectonic units thus reversing the late cretaceous tectonostratigraphy the maximum amount of translation on the later thrusts is in excess of 5 km on the hagab thrust where the complete shelf carbonate sequence of the musandam mountains has been thrust west northwest over the previously higher hawasina and haybi thrust sheets the tertiary folding and thrusting can be correlated in time and space with the zagros fold belt of southwestern iran

the geology of the dibba zone northern oman mountains a preliminary study the dibba zone is a narrow structurally complex ne sw trending part of the oman mountains thrust front it comprises a series of imbricated and folded thrust sheets of shelf edge and slope facies mesozoic carbonates basinal facies sediments and a sedimentary melange overlain by a thrust sheet of sub ophiolitic greenschist and amphibolite facies metamorphic rocks and the basal part of the upper cretaceous semail ophiolite nappe thrusting during the late cretaceous was directed towards the w and nw across the former continental margin it is postulated that during the mesozoic the area lay on a se facing probably transform fault controlled section of the ne arabian continental margin there is no evidence for major post early mesozoic high angle faulting along the dibba zone as has previously been postulated in tectonic syntheses of the area

global observations of open ocean mode 1 m2internal tides abstracta global map of open ocean mode 1 m2 internal tides is constructed using sea surface height ssh measurements from multiple satellite altimeters during 1992 2012 representing a 20 yr coherent internal tide field a two dimensional plane wave fit method is employed to 1 suppress mesoscale contamination by extracting internal tides with both spatial and temporal coherence and 2 separately resolve multiple internal tidal waves global maps of amplitude phase energy and flux of mode 1 m2 internal tides are presented the m2 internal tides are mainly generated over topographic features including continental slopes midocean ridges and seamounts internal tidal beams of 100 300 km width are observed to propagate hundreds to thousands of kilometers multiwave interference of some degree is widespread because of the m2 internal tide s numerous generation sites and long range propagation the m2 internal tide propagates across the critical latitudes for parametric subharmonic instability 28 8 s n

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

structure and variability of semidiurnal internal tides in mamala bay hawaii 1 moored current meter and temperature observations and results from a three dimensional primitive equation model are used to examine the energetic semidiurnal internal tides present in mamala bay on the south coast of oahu hawaii the steady harmonic component of the internal tide is characterized by large vertical displacements in the central region of the bay 35 m amplitude for the m2 constituent and enhanced alongshelf baroclinic currents at the headlands on either end of the bay 0 27 m s 1 seasonal changes in amplitude and phase are observed the model captures the qualitative spatial structure of the observations baroclinic energy flux estimates from the mooring observations and the numerical simulations suggest that internal tide energy propagates into the bay and does not originate within the bay the model indicates that internal wave generation occurs over the flanks 500 1000 m depth of the ridge predominantly on the east side with perhaps some additional contribution on the west from an energetic internal tide generated north of oahu wave superposition is believed to account for the alongshelf spatial structure of currents and displacements incoherent modulations of the internal tide occur that are not related to local changes in stratification at least on superannual timescales factors contributing to this signal may include stratification variations at the deep generation sites mesoscale activity and or the shoaling of a random internal wave field into the bay from the open ocean

a structural record of the emplacement of the pozanti karsanti ophiolite onto the menderes taurus block in the late cretaceous eastern taurides turkey abstract the aladag region of eastern taurides turkey is characterized by an imbricated thrust structure developed during late stage emplacement of the pozanti karsanti ophiolite onto the menderes taurus block in the late cretaceous the mid to late cretaceous dynamothermal metamorphic sole and the underlying unmetamorphosed melange here named the aladag accretionary complex were accreted to the base of the pozanti karsanti ophiolite during intra oceanic subduction transport and final obduction of the ophiolite onto the menderes taurus block in the dynamothermal metamorphic sole intensity of deformation and degree of metamorphism increase from the base to the top and at least three episodes of foliation lineation and fold development are recognized the asymmetry of quartz c axis fabrics tightness and asymmetry of folds of the same generation and curvature of fold hinge lines increase from base to top indicating that non coaxial progressive deformation prevailed during the development of the metamorphic sole the melange is divided into three major thrust fault bounded tectonic slivers each of which is characterized by distinctive types of matrix and block lithologies structures and deformation style kinematic analyses of the dynamothermal metamorphic sole and the melange reveal that the tectonic transport direction of the pozanti karsanti ophiolite during its emplacement was from north northwest to south southeast suggesting that the pozanti karsanti ophiolite was derived from a neo tethyan ocean to the north of the menderes taurus block

model estimates of m2 internal tide energetics at the hawaiian ridge 1 a primitive equation model is used to examine the structure and energetics of m 2 internal tides generated at the hawaiian ridge recent estimates based on altimeter data suggest that 20 gw of barotropic tidal dissipation occurs at the ridge with conversion to internal tides believed to be the dominant dissipation mechanism the model simulates an internal tide that accounts for 9 7 gw of radiated energy away from the ridge in the northeast and southwest directions the strongest generation occurs at three sites where enhanced barotropic currents flow across elongated topographic features the depth integrated baroclinic energy flux and energy densities at these sites are on the order of 10 4 w m 1 and 10 4 j m 2 respectively a modal decomposition indicates that 62 of the outgoing energy flux is accounted for by the first internal mode 15 is accounted for by the second mode and less than 5 is accounted for by each subsequent higher mode the tidal dissipation due to bottom friction along the ridge is estimated to be 0 1 gw the level of turbulent dissipation near the ridge owing to tidal energy conversion remains to be determined to assess fully the barotropic baroclinic energy budget

structure and sequence of thrusting in deep water sediments during ophiolite emplacement in the south central oman mountains abstract sedimentological and stratigraphical investigations of the deep water passive margin sediments of the oman neo tethys the hawasina ocean when allied with structural relationships between duplexes of these units emplaced on to the oman margin during late cretaceous ophiolite obduction allow the reconstruction of sediment distribution in the hawasina ocean from this starting point and the observed stacking order of duplexes the sequence of thrusting of the oceanic sediments can be deduced imbrication proceeded through foreland propagating thrusts whilst the assembled thrust stack was modified at a late stage of emplacement by out of sequence thrusting related to sequential locking of thrust planes towards the hinterland and gravity sliding off the flanks of a major anticline that developed in the underlying autochthonous shelf and basement two main factors governed duplex and imbricate fan formation and distribution firstly two contrasting sedimentary basins were present along the central oman margin the duru basin distal to the al ayn basin secondly competent sedimentary successions were bulldozed ahead of the semail ophiolite whilst less competent shale and chert units were overridden by the ophiolite or imbricated along its leading edge

barotropic and baroclinic m2 tides in the monterey bay region abstract a high resolution 250 m primitive equation model is used to simulate the depth averaged and baroclinic m2 tides in the monterey bay region the model shows a high level of skill in comparisons with sea level observations adcp current observations within the submarine canyon are reasonably well reproduced the modeled depth averaged currents have a complex spatial pattern with magnitudes in excess of 0 1 m s 1 near moss landing during the second half of flood ebb tide the flow is into out of the bay through the canyon but out of into the bay over the shelf regions this depth averaged flow pattern is not evident in a diagnostic run implying a feedback between the internal tides and the pressure gradient in the bay the depth integrated baroclinic total minus depth averaged energy fluxes show a complex beamlike pattern due to the interaction of energy from multiple sources the beams have magnitudes up to 1 kw m 1 interspersed with regions of near zero depth integrated flux energy en

long range propagation of the semidiurnal internal tide from the hawaiian ridge abstract the northeastward progression of the semidiurnal internal tide from french frigate shoals ffs hawaii is studied with an array of six simultaneous profiling moorings spanning 25 5 37 1 n 1400 km and 13 yr long ocean topography experiment topex poseidon t p altimeter data processed by a new technique the moorings have excellent temporal and vertical resolutions while the altimeter offers broad spatial coverage of the surface manifestation of the internal tide s coherent portion together these two approaches provide a unique view of the internal tide s long range propagation in a complex ocean environment the moored observations reveal a rich time variable and multimodal internal tide field with higher mode motions contributing significantly to velocity displacement and energy in spite of these contributions the coherent mode 1 internal tide dominates the northeastward energy flux and is detectable in both moored and altimetric data over the entire array phase and group prop

impact of arc continent collision on the conditions of burial and exhumation of uhp lt rocks experimental and numerical modelling abstract a 2 d physical and finite element numerical modelling of arc continent collision was performed to study the deformation and failure of the overriding lithosphere the experimental technique allowed us to model the whole subduction collision process from oceanic subduction to deep subduction of the continental crust with the numerical approach we have modelled the deformation of the overriding plate only through initial stages of its failure and studied the influence of different parameters on this process the results obtained by both techniques are coherent and mutually complementary they show that the failure of the overriding plate is physically quite plausible or even inevitable during subduction the conditions for such a failure the weakening of this plate are prepared during oceanic subduction the weakening occurs due to the interaction between the subducting lithosphere and the asthenosphere in the mantle corner between the two plates and due to back arc spreading in oceanic subduction zones with a compressional regime no back arc opening thick and strong back arc lithosphere the weakest zone is volcanic arc area when weakening becomes sufficient during subduction the lithosphere fails in this area the failure occurs along a fault dipping under the arc in either of two possible directions and results either in subduction reversal or subduction of the fore arc almost half of the presently active subduction zones are characterised by a tensional subduction regime with back arc spreading in such subduction zones the weakest place is not the volcanic arc but the back arc spreading centre when a subduction regime changes from tensional to compressional failure occurs in the vicinity of the extinct spreading centre this process can occur during oceanic subduction again along either a trench vergent or trenchward dipping fault but the formation of a trench verging fault is most likely in this latter case which is a principal subject of our study the failure is followed by partial subduction of the arc plate complete subduction occurs during arc continent collision subduction of the continental margin when tectonic compression of the lithosphere increases rapidly and becomes sufficient to push the arc plate into the mantle the arc itself can be subducted completely or be partially or completely scraped off and accreted a deeply subducted material including continental margin is preserved at relatively low temperatures between the lithospheric mantle and the cold subducted arc plate to about 150 km depth subduction of the arc plate is a major phenomenon which affects all processes associated with continental subduction from deep burial and hp lt metamorphism to exhumation of subducted material does this process occur in nature future investigations will allow us to answer this question in this paper we analyse the conditions of emplacement of a very young oceanic lithosphere samail ophiolite on the continental crust in oman in the late cretaceous and argue that this lithosphere formed in a back arc basin it reached and overthrust the arabian continent after complete subduction of the arc plate

sediment resuspension mechanisms associated with internal waves in coastal waters 1 large amplitude vertically trapped internal waves can induce sizable velocities and trigger hydrodynamic instabilities in the bottom boundary layer thereby contributing to the resuspension of sediments and the maintenance of sediment concentration in the water column we discuss numerical simulations of several different situations in which the boundary layer in the wave footprint undergoes hydrodynamic instability with a resultant increase in the incidence of spatiotemporal structures that could facilitate sediment resuspension for the case of internal solitary waves we provide bounds in parameter space separating regions in which internal waves can be expected to efficiently resuspend sediment from those in which the boundary layer in the wave footprint is both laminar and stable a notable finding is that the onset of instability is a strong function of the background current the lagrangian transport of passive particles due to the instability is explored and some quantitative measures of the efficiency of the particle transport process are provided we subsequently discuss the evolution of the power spectra of the bottom shear stress with time and find that while the general characteristics of the instability are robust lowering either the reynolds number or the strength of the background current leads to an increase in the typical length scales associated with the mature instability finally we discuss instabilities during the internal wave generation process and alternative instability mechanisms when the bottom is not flat

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

the breaking and scattering of the internal tide on a continental slope abstracta strong internal tide is generated in the luzon strait that radiates westward to impact the continental shelf of the south china sea mooring data in 1500 m depth on the continental slope show a fortnightly averaged incoming tidal flux of 12 kw m 1 and a mooring on a broad plateau on the slope finds a similar flux as an upper bound of this 5 5 kw m 1 is in the diurnal tide and 3 5 kw m 1 is in the semidiurnal tide with the remainder in higher frequency motions turbulence dissipation may be as high as 3 kw m 1 local generation is estimated from a linear model to be less than 1 kw m 1 the continental slope is supercritical with respect to the diurnal tide implying that there may be significant back reflection into the basin comparing the low mode energy of a horizontal standing wave at the mooring to the energy flux indicates that perhaps one third of the incoming diurnal tidal energy is reflected conversely the slope is subcritical with respect to the semidiurnal tide and the observed

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

hamrat duru group revised stratigraphy of a mesozoic deep water passive margin in the oman mountains the stratigraphy of the hawasina complex is redefined and rationalized to conform with standard stratigraphical nomenclature previously proposed tectono stratigraphical units are abandoned in favour of a system that relies on the lateral correlation of lithofacies between structural units to this end the dibba dhera wahrah and al ayn formations are incorporated into an expanded hamrat duru group this group is divided into five formations the zulla guweyza sandstone guweyza limestone sid r and nayid and spans triassic to mid cretaceous cenomanian time it locally passes up into the syn orogenic sediments of the riyamah member of the muti formation the nomenclature of the deeper water chert dominated formations is left unaltered

sources of baroclinic tidal energy in the gaoping submarine canyon off southwestern taiwan 1 a three dimensional model driven by tidal constituents o1 k1 m2 and s2 was adopted to evaluate the sources of baroclinic tidal energy in the gaoping submarine canyon gpsc off southwestern taiwan the model domain covered the probable primary generation sites including the luzon strait ls and the southeastern taiwan strait ts the simulated baroclinic tides agreed with the observations of tidal current velocity isotherm vertical displacement and baroclinic tidal energy flux fbc in the gpsc the depth integrated seven day averaged fbc computed from the model result was 2 2 kw m 1 in the gpsc and the corresponding area integrated fbc reached 189 4 mw the results obtained from the model suggest that the baroclinic tides lead to strong turbulent mixing near the canyon head with a vertical diffusivity of 3 5 10 3 m2 s 1 baroclinic tidal energy in the gpsc is mainly generated on the western ridge in the ls and on the steep topography in the southeastern ts the local generation of baroclinic energy only accounts for 4 4 of the total value the other 95 6 of the baroclinic tidal energy is remotely generated at the ls and the southeastern ts of which 31 9 and 8 8 are directly emanated respectively into the gpsc the northwestward and southeastward baroclinic energy beams radiating from the ls and the southeastern ts respectively meet each other and form internal partial standing tides outside the gpsc the transverse baroclinic energy from the internal partial standing tides accounts for the remaining 54 9 of the baroclinic tidal energy in the gpsc

the beysehir hoyran hadim nappes genesis and emplacement of mesozoic marginal and oceanic units of the northern neotethys in southern turkey the beysehir hoyran hadim nappes crop out over 700 km from nw to se above a regionally autochthonous tauride carbonate platform the beysehir hoyran nappes begin with a thrust sheet c 400 m of mainly redeposited carbonates quartzose sandstones and mudstones of mid late triassic age interpreted as a proximal slope base of slope succession above is a thrust sheet c 1 km of middle upper triassic intermediate acidic extrusive rocks volcaniclastic rocks and minor pelagic carbonates interpreted as a continental rift thin

tidal data inversion interpolation and inference initial efforts in applying inverse methods to studies of ocean tides have focused on making the best use of a small number of observations to map tidal fields in a large area as such inversion can be viewed as an objective analysis scheme which uses a dynamically appropriate spatial covariance derived from the shallow water equations to interpolate and smooth a sparse data set data from recent altimetry missions are not sparsely distributed relative to tidal wavelengths in the open ocean apparently reducing the need for complicated dynamically based interpolation schemes altimetric data sets are also quite large making application of rigorous inversion methods to global tidal modeling a challenging computational problem we describe here a new iterative solution scheme which allows us for the first time to fit the full set of topex poseidon cross over differences the resulting solution tpxo 3 fits validation tide gauges significantly better than previous inverse solutions tpxo 3 also reduces residual cross over variances relative to other recent inverse and empirical solutions particularly in shallow water where improvements are dramatic with the new solution approach very significant improvements in global tidal models should be possible in shallow areas and in the vicinity of complex bathymetry where high accuracy tidal modeling remains a challenging problem with the recent improvements in the definition of tidal elevations in the open ocean it should now also be possible to resolve some long unanswered questions about tidal energetics and dynamics inverse methods provide a natural framework for addressing these issues and making inferences about tidal dynamics in particular by bringing data and dynamics together in a single solution we can rigorously test the consistency of the two we present results of global and local inversions which suggest that over elongated bathymetric features oriented perpendicular to tidal flows energy dissipation in the open ocean is significantly enhanced presumably due to conversion of barotropic tidal motions into baroclinic modes for the m2 tide our preliminary results suggest that perhaps as much as 0 5 tw of energy is dissipated in this manner however due to the simplified linear dynamics and limited spatial resolution used for our inversion there are significant uncertainties associated with these results a more careful application of inverse methods to make more rigorous inferences about tidal energetics including use of more reasonable prior dynamics and the highest possible spatial resolution should allow for closure of the tidal energy budget within the next few years

the generation of internal tides at the hawaiian ridge previous analyses of altimeter and acoustic data indicate that the hawaiian ridge is a significant generation site for semidiurnal m2 period internal waves owing to tidal flow over topography such waves likely play an important role connecting the dissipation of tidal energy to ocean mixing here a primitive equation numerical model with realistic stratification bathymetry and tidal forcing is used to simulate the generation of these waves in a manner consistent with altimeter sea surface observations the highest amplitude waves originate at three generation sites located at both the island and seamount portions of the chain these sites have in common both enhanced flows across ridge shaped topography and maxima in model calculated body force which couples barotropic and baroclinic motions the model vertical structure suggests the presence of multiple dynamical modes within 100 km of the ridge and not just the lowest modes that have been detected at the sea surface

turbulent convection of suspended sediments due to flow reversal 1 we investigate the ejection of sediments from the near bed region of a pulsating boundary layer over a flat bottom the boundary layer flows were generated using large eddy simulation les while the motion of individual particles was calculated using a modified version of the maxey and riley equation the suspension rate of near bed sediment particles sharply increases during decelerating flow phase and peaks near the time of local flow reversals this suspension pattern of sediments was closely related to the near bed turbulent vortex structures which evolve during a wave cycle during period of maximum flow rate the horizontally aligned vortex cores retarded settling of sediment particles as the flow decelerates vertically organized vortices induce an upward flux of particles vertical velocity fluctuations are strongest at the time of flow reversal leading to maximum sediment suspension at this time these results are shown to be incompatible with simple eddy diffusivity models for sediment transport

sumeini group oman evolution of a mesozoic carbonate slope on a south tethyan continental margin abstract deposition of the mostly mesozoic sumeini group occurred on the slope between the shallow marine arabian carbonate platform and the deep oceanic hawasina basin or south tethys sea these strata record the evolution of the northeast arabian continental margin from permian and triassic rifting to ocean basin closing with the late cretaceous obduction of the semail ophiolite platform margin type and its evolution can be inferred from exposures of these slope sediments at jebel sumeini in the western oman mountains in the lower permian base of the sequence bedded spicular limestones suggest deep marine conditions this is followed by an enigmatic thick sequence of bedded dolomite in the early to middle triassic small carbonate submarine fans formed along a distally steepened slope a subsequent interval of terrigenous clastic sedimentation was followed by development of a steep escarpment margin during ladinian to norian time with coralgal reefs at the shelf break and a debris apron at the base of the scarp the late triassic is marked by another influx of terrigenous sediment which accompanied widespread emergence of the platform in the jurassic a thick apron of thin bedded limestone formed on the slope this apron was cut by channelized gullies that now include blocks of older reefal material and oolitic sands a well documented submergence of the platform during the tithonian and early cretaceous led to the deposition of radiolarian cherts on the slope and basin upper lower cretaceous megabreccias up to 200 m thick suggest an interval of localized slope instability and or tectonism continued deposition of bedded limestone and marl with lesser calcirudite marks the top of stratigraphic sequence at jebel sumeini the early to middle triassic carbonate submarine fan deposits occur as discrete lenticular sequences of bedded calciturbidite modified grain flow and debris flow deposits which were derived from mostly slope sources the ladinian to norian base of slope debris apron deposits were derived from both slope and shallow marine sources including reefs and appear to form a laterally extensive but narrow belt of thick lenticular to sheet like beds of debris which accumulated over a long interval of time coarse limestones in the jurassic gullied slope deposits are distinct in that they occur randomly as individual channelized beds in a sequence dominated by thin bedded lime mudstones thick lower cretaceous megabreccias are distinguished by their great lateral distribution and general lack of matrix

sensitivity of internal tide generation in hawaii energy from the barotropic tide is transferred into the baroclinic tide over topographic gradients which provides a mechanism for the ocean boundaries to communicate with the deep ocean to close energy budgets and as a source of flux affecting nutrient supply and larval transport understanding the temporal variability of the conversion from barotropic to baroclinic tides is critical to our understanding of these processes using a numerical model and its adjoint we examine the sensitivity of tidal conversion at kaena ridge in hawaii we find a sensitivity to changes in the upper ocean due to a phase difference between the pressure anomaly and tidal velocity caused by internal waves generated on the opposite slope of the ridge however we also find that conversion is equally as sensitive to local deep stratification changes

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

interference pattern and propagation of the m2 internal tide south of the hawaiian ridge abstract most of the m2 internal tide energy generated at the hawaiian ridge radiates away in modes 1 and 2 but direct observation of these propagating waves is complicated by the complexity of the bathymetry at the generation region and by the presence of interference patterns observations from satellite altimetry a tomographic array and the r p flip taken during the farfield program of the hawaiian ocean mixing experiment home are found to be in good agreement with the output of a high resolution primitive equation model simulating the generation and propagation of internal tides the model shows that different modes are generated with different amplitudes along complex topography multiple sources produce internal tides that sum constructively and destructively as they propagate the major generation sites can be identified using a simplified 2d idealized knife edge ridge model four line sources located on the hawaiian ridge reproduce the interference pattern of sea surface height and energy fl

internal tide dynamics in a topographically complex region browse basin australian north west shelf 1 field observations and numerical circulation modeling revealed the spatial variability of the tidally driven dynamics in the topographically complex continuously stratified macrotidal environment of the browse basin on the australian north west shelf internal wave generation occurred at a number of discrete topographic features and the resultant interaction of multiple waves led to a spatially variable internal wave climate the generation of baroclinic energy was most intense in regions where the barotropic tide was aligned with steep topography generation of low mode internal waves occurred at the inner shelf break where the ratio of tidal excursion distance to topographic length scale was large in contrast generation of high mode beam like internal waves occurred at the outer shelf break where the ratio of tidal excursion distance to topographic length scale was very small the most efficient conversion from barotropic to baroclinic energy occurred at the outer shelf break the internal waves generated at the inner and outer shelf breaks interacted to produce a partly standing internal wave resulting in a large along shelf energy flux and discrete locations with small ratios of horizontal kinetic energy to available potential energy this phenomenon is likely to occur in other regions with semienclosed topography and multiple generation sites

observations of internal tides on the oregon continental slope abstracta complex superposition of locally forced and shoaling remotely generated semidiurnal internal tides occurs on the oregon continental slope presented here are observations from a zonal line of five profiling moorings deployed across the continental slope from 500 to 3000 m a 24 h expendable current profiler xcp survey and five 15 48 h lowered adcp ladcp ctd stations the 40 day moored deployment spans three spring and two neap tides during which the proportions of the locally and remotely forced internal tides vary baroclinic signals are strong throughout spring and neap tides with 4 5 day long bursts of strong cross slope baroclinic semidiurnal velocity and vertical displacement energy fluxes exhibit complex spatial and temporal patterns throughout both tidal periods during spring tides local barotropic forcing is strongest and energy flux over the slope is predominantly offshore westward during neap tides shoaling remotely generated internal tides dominate and energy flux is pr

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

structure and metamorphism of blueschist eclogite facies rocks from the northeastern oman mountains the northern part of the saih hatat window oman shows high pressure metamorphic rocks derived from shelf sediments and pre premian continental basement and is atypical of sub ophiolite metamorphism elsewhere the high pressure rocks are divided into structural units originally bounded by foreland propagating thrusts formed during ophiolite obduction although now many contacts are backthrusts normal faults or extensional shear zones metamorphic breaks exist across many unit boundaries the deepest unit as sifah has eclogite facies assemblages in metabasites and metapelites which record evolution of p t conditions along a clockwise path culminating al 23 2 5kbar 540 75 c contrasting markedly with overlying units 5 10 kbar 200 500 c although separated by 40 ar 39 ar apparent ages our tectonic model relates all the high p units to a single convergent event in the late cretaceous the as sifah eclogites were exhumed in two stages i tectonic emplacement against other units at c 20 25 km depth and ii exhumation of the entire high p zone by culmination collapse after obduction

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

sequence of thrusting and origin of culminations in the northern and central oman mountains abstract detailed mapping and structural analysis of three large scale culminations sumeini and asjudi half windows and haybi hawasina window in the oman mountains shows a considerably more complex history of deformation than a simple foreland or downward sequence of thrust development early thrusting processes tended to create a regular stacking order of imbricate slices and major thrust sheets complying with the rules of thrust propagation assembled progressively downwards and forwards in the direction of translation out of sequence thrusts can also be demonstrated in places by truncation of footwall structures folds imbricate slices etc gross strain differences between thrust sheets downward facing structures in footwall units and elimination of thrust sheets beneath late stage thrusts frequently cut up section through the previously assembled stack putting previously younger lower thrust sheets over previously older higher ones many of the culminations in the northern and central oman mountains were formed by ramping associated with this late stage leap frog rethrusting event

standing internal tides in the tasman sea observed by gliders abstractlow mode internal tides are generated at tall submarine ridges propagate across the open ocean with little attenuation and reach distant continental slopes a semidiurnal internal tide beam identified in previous altimetric observations and modeling emanates from the macquarie ridge crosses the tasman sea and impinges on the tasmanian slope spatial surveys covering within 150 km of the slope by two autonomous underwater gliders with maximum profile depths of 500 and 1000 m show the steepest slope near 43 s reflects almost all of the incident energy flux to form a standing wave starting from the slope and moving offshore by one wavelength 150 km potential energy density displays an antinode node antinode node structure while kinetic energy density shows the opposite mission mean mode 1 incident and reflected flux magnitudes are distinguished by treating each glider s survey as an internal wave antenna for measuring amplitude wavelength and direction incident fluxes are 1 4 and 2 3 k

oman exotics oceanic carbonate build ups associated with the early stages of continental rifting the so called oman exotic limestones form isolated masses from boulder size to 1 000 m thick of middle to upper permian and upper triassic fossiliferous limestones and crop out within imbricated thrust slices beneath the semail ophiolite in the oman mountains permian exotics are of dominantly reef and forereef facies whereas triassic exotics are more typically of back reef and lagoonal facies they are commonly associated with a substrate of alkalic and transitional tholeiitic basalts and are interpreted as a series of reef associated carbonate buildups deposited in part on oceanic islands or seamounts close to the site of initial rifting of the oman continental margin

an ocean facing aptian albian carbonte margin oman a high energy aptian albian platform margin in northern oman fronted onto an open oceanic basin making the area a valuable analogue for coeval guyot margins most similar aged carbonate margins described in the literature faced either intracratonic or minor oceanic basins the studied margin is characterized by a stabilized outer rim which although it did not rise discernibly above the adjacent lagoonal deposits flanked a steep upper slope 32 40 basinwards with a relief of at least 30 m two main facies provided the rigidity of the outer margin lithocodium boundstones that constituted up to 50 of the rock volume and marine fibrous cements that occluded up to 35 of primary pore space in contrast coral rudist patches and other shelly sessile benthos were distributed irregularly and the rudist bioherms of the outer margin were often disrupted with shells being transported and redeposited the inner margin is characterized by wedge shaped storm layers that radiate from the platform top lagoonwards where they interdigitate with carbonate sands and small rudist bioherms polygenetic discontinuity surfaces that bear evidence of both marine hardground and subaerial exposure stages are prominent features of the margin throughout the latest aptian to middle albian the platform succession recorded some 30 relative sea level falls of which seven reached amplitudes of many tens of metres these seven high amplitude falls in sea level are recorded across the entire south eastern portion of the arabian craton and are probably of eustatic origin

petrochemistry and origin of sub ophiolitic metamorphic and related rocks in the oman mountains the semail ophiolite complex of the northern oman mountains was obducted during cenomanian to campanian upper cretaceous times onto the arabian continental margin during this time span schistose metamorphic rocks of amphibolite and greenschist facies exhibiting polyphase deformation were formed and accreted below the ophiolite slice whole rock and mineral analyses confirm that the amphibolites were originally tholeiitic basalts comparable to present day occurrences at mid ocean ridges a comparison of trace element geochemistries however suggests that the protoliths were not equivalent to the haybi alkaline and transitional tholeiites found in the underlying structural slice or to the semail ophiolite volcanic rocks which lie structurally higher in the sequence it is therefore suggested that the amphibolites may have been derived from jurassic or lower cretaceous oceanic basalts not recognized elsewhere in the oman mountains structurally beneath the amphibolites within the metamorphic sheet greenschist facies metasedimentary rocks including quartzites and marbles are interbanded with metabasite horizons containing actinolite and less commonly blue crossitic amphiboles it is suggested that the sedimentary and volcanic protoliths were metamorphosed in a subduction zone environment during initial ophiolite displacement and were accreted to the base of the ophiolite during progressive underthrusting