transtensional origin of multi order cross folds in a high grade gneiss complex southwestern grenville province formation during post peak gravitational collapse the well mapped western part of the ottawa river gneiss complex orgc new name a large metamorphic core complex hosts a system of gently plunging cross folds of outcrop to regional scale situated in the ductile detachment zone between the lower grade cover and high grade core of the complex the cross folds are buckle structures that deform the attenuated gneissic layering plunge parallel to the regional elongation lineation range from upright to recumbent and exhibit distinctive hinge parallel elongation lineations all features of extension dominated ductile transtension our l s fabric data are consistent both with kinematic modelling that predicts progressive constrictional strain in the hinge zones of transtensional folds and with dynamic modelling that predicts rotation of flattened fold limbs into moderately dipping attitudes on the basis of petrologic data we show that cross folding postdated the peak ottawan metamorphism and took place during retrogression and exhumation of the thrust sheet stack the cross folds form an inclined system that is principally developed in retrograde melt weakened amphibolite facies rocks with the transtensional origin implying that exhumation and retrogression of the high grade core of the complex took place in an oblique extensional setting a transtensional origin for the cross folds removes the need to appeal to orogen parallel regional shortening an implausible requirement of previous interpretations and is compatible with data indicating that much of the visible fabric and structure of amphibolite facies domains of the orgc developed during post peak exhumation retrogression and gravitational collapse of the thrust sheet stack

wave induced sediment transport and sandbar migration onshore sediment transport and sandbar migration are important to the morphological evolution of beaches but are not well understood here a model that accounts for fluid accelerations in waves predicts the onshore sandbar migration observed on an ocean beach in both the observations and the model the location of the maximum acceleration induced transport moves shoreward with the sandbar resulting in feedback between waves and morphology that drives the bar shoreward until conditions change a model that combines the effects of transport by waves and mean currents simulated both onshore and offshore bar migration observed over a 45 day period

shock capturing boussinesq model for irregular wave propagation abstract in this paper a shock capturing numerical model based on the combined solution of boussinesq and nonlinear shallow water equations is validated with respect to the transformation breaking and runup of irregular waves boussinesq equations are applied where dispersive and nonlinear effects are both relevant assuring an appropriate description of wave propagation from intermediate to shallow waters nonlinear shallow water equations are used where dispersion is negligible their shock capturing features exploited by the application of the finite volume method enable an intrinsic representation of wave breaking and swash zone oscillations no case by case calibration or tracking algorithms are required comparisons with experimental data show that the model is able to simulate wave height variations mean water level setup wave runup and the generation of nearshore currents accurately

heterogeneous amphibolite facies deformation of a granulite facies layered protolith matches island shear system parry sound domain grenville province ontario canada abstract amphibolite facies transposition of granulite facies gneiss resulted in the formation of a nappe bounding km scale shear zone at the margin of the parry sound domain grenville province the matches island shear system illustrates the earlier stages of transposition in which heterogenous retrogression of the well layered mafic felsic granulite facies gneiss along pegmatites orthogonal to layering controlled the location of shear zones and ensured that unretrogressed granulite persisted as strong elements shear zones curve anticlockwise from their original orientation accompanied by rigid rotation of wall rock layering which remains orthogonal to the shear zones this relationship is modified so that wall rock layering form sigmoidal mafic fish where shear zone linkage occurs via i merging of established parallel shear zones by wall rock collapse ii merging of an established shear zone with a new shear zone formed within preexisting wall rock or iii linking of two established zones by an oblique new shear zone all of these wall rock shear zone relations are displayed in the maximally transposed nappe bounding shear zone but contrast with those at the boundary of other nappes where uniform amphibolite facies protolith is transposed with a buckle and shear style

deep crustal ductile extension following thrusting in the southwestern grenville province ontario two lithotectonic assemblages in southern britt domain have different histories of plutonism metamorphism structural development and mafic dyke emplacement these differences are accounted for by postulating that a cryptic grenvillian thrust separates the assemblages amphibolite facies extensional shear along the central britt shear zone cbsz overprinted the thrust obscuring kinematic evidence for its existence the structurally lower bayfield nadeau island assemblage contains orthogneiss suites of disparate age lesser amounts of supracrustal rocks deposited before intrusion of the youngest orthogneiss pre grenvillian and grenvillian metamorphic assemblages and at least three mafic dyke suites the overlying ojibway sand bay assemblage contains only younger orthogneiss with grenvillian metamorphic assemblages volumetrically important supracrustal rocks that are younger than the youngest orthogneiss and lacks cross cutting mafic dykes comparable tectono stratigraphic changes are present acros

turbulence transport vorticity dynamics and solute mixing under plunging breaking waves in surf zone plunging breaking waves generate turbulence and vorticity which are of great importance for the solute and sediment transport in surf zone in this paper the complex breaking processes are simulated by using an accurate numerical model that solves the reynolds equations for the mean flow and modified k e equations for the turbulence field a solute transport model is employed to investigate the solute mixing under plunging waves after validation of the numerical model by comparing numerical results with available experimental data the numerical model is further utilized to study the detailed mechanisms of turbulence transport and vorticity dynamics the differences between spilling and plunging breaking waves are discussed the impact of the wave breaking on solute mixing in the surf zone is also examined

forcing of resonant modes on a fringing reef during tropical storm man yi 1 open basin resonant modes have been observed at tidal frequencies on coastal shelves but their excitation on coral reef platforms has only been suggested the topography of and water depth over most fringing reefs correspond to resonant periods that are the order of tens of minutes and fall outside of the energetic part of the wave spectrum during tropical storm man yi low frequency near resonant oscillations dominated the variance of the sea surface elevation at the shoreline of ipan reef guam the excitation of the resonant modes resulted both from a large increase in water level over the reef due to wave setup which increased the resonant frequencies and the occurrence of wave group forcing with time scales commensurate with these increased resonant frequencies

a new method to estimate the overtopping and overflow discharge at over washed and breached dikes abstract most of the experience collected on wave overtopping is concentrated on emerged or zero freeboard structures and only few experiments are available on over washed dikes the experience on submerged crest conditions is principally related to rubble mound structures and limited to the wave reflection and transmission processes the existing tools for the prediction of the average wave overtopping discharge q at dikes are therefore targeted to represent overtopped structures leading to cautious estimates at over washed dikes and unrealistic overestimations in case of catastrophic scenarios such as breached dikes this paper proposes a new conceptual and practical method for the prediction of q that is valid for both over washed and fully breached dikes it consists of three physically based formulae whose coefficients are fitted on a new numerical database of smooth structures under variable wave attack the predictions are compared with the new numerical results and the data and the tools available from the literature i e experimental data formulae and neural network the new method gives a more realistic representation of the overtopping and overflow processes reducing significantly the overestimation in case of breaching and being at least as accurate as the existing tools in case of over washing

seismic images of the grenville orogen in ontario in 1990 lithoprobe acquired 240 km of seismic reflection data across parts of the central gneiss belt cgb and the central metasedimentary belt cmb within the western grenville province of southern ontario interpretation of these data in conjunction with geological constraints provided by bedrock mapping supports a model of northwest directed thrusting and crustal shortening for the grenville orogen within the cgb the parry sound shear zone is imaged as a 3 km wide zone of reflections dipping southeastward at 20 25 and soling at depths 7 km in the north and 3 km in the south beneath parry sound domain parry sound domain and the immediately adjacent domains are underlain by a gently southeast dipping reflective zone at 4 5 12 0 km depth interpreted as a detachment surface likely associated with the central britt shear zone this zone may have accommodated northwesterly transport of parry sound southern britt and northwestern rosseau domains over britt domain during grenvillian thrusting wit

boussinesq modeling of longshore currents 1 a time domain boussinesq model for nearshore hydrodynamics is improved to obtain the conservation of vertical vorticity correct to second order and extended for use on an open coast using longshore periodic boundary conditions the model is utilized to simulate surface waves and longshore currents under laboratory and field conditions satisfactory agreement is found between numerical results and measurements including root mean square wave height mean water level and longshore current one striking result of the simulations is the prediction of the strong longshore current in the trough shoreward of the bar as observed during the duck experiment on low frequency and incident band longshore and across shore hydrodynamics field campaign the model results give insight into the spatial and temporal variability of wave driven longshore currents and the associated vertical vorticity field under the phase resolving random wave forcing with wave current interaction numerical experiments are carried out to examine the response of the modeled longshore currents to the randomness of surface waves and the cross shore distributions of bed shear stress coefficient we find that both regular and irregular waves lead to very similar mean longshore currents while the input of monochromatic unidirectional waves results in much more energetic shear waves than does the input of random waves the model results favor whitford and thornton s 1996 finding that the bed shear stress coefficient for the area offshore the bar is larger than that in the trough as better agreement with the field data for both regular and irregular waves is found if such coefficients are used in the boussinesq model

influence of microscale weak zones on bulk strength shear zones have different rheological properties than the surrounding rocks indicating that the bulk strength of regions containing shear zone networks cannot be determined by considering the the host rock rheology alone we demonstrate the value of this concept at the microscale we first consider the phase arrangements in naturally deformed rocks and document that weak phases exhibit little interconnection within a microstructure rather three dimensional weak zones analogous to viscous shear zones can interconnect or bridge weak phases these zones typically form at high stress sites comprise multiple minerals and deform by mechanisms independent of those in the surrounding minerals the presence of weak zones strongly affects the bulk strength of the rock disproportionate to the mode of the weak zones for example the development of 1 mode of a weak zone at a high stress site can reduce the bulk strength of the rock nearly an order of magnitude calculation of the bulk strength of the rock by some averaging algorithm of the deformation mechanisms operating outside the weak zones will overestimate strength instead accurate calculations and predictions of bulk strength require accounting for the presence and geometry of weak zones for this reason we advocate use of the scale independent conceptual rheological model of interconnected weak zones or layers rather than that of interconnected weak phases more generally the way forward in improving quantification of the mechanical properties of the lithosphere requires recognizing and explicitly accounting for the spatial and temporal distribution of deformation mechanisms operating throughout a rock this article is protected by copyright all rights reserved

a unified depth averaged approach for integrated modeling of surface and subsurface flow systems abstract a two dimensional depth averaged continuum framework is developed for simulating the interaction of flows outside and within porous media a unique set of generalized equations applicable to both surface and subsurface systems is derived originating from conservation laws of microscopic variables with first volume averaging and then integrating vertically the model is free of ad hoc coupling as interface conditions are satisfied implicitly owing to the generalized nature of the governing equations the set of depth integrated equations unconditionally hyperbolic is resolved by employing a total variation diminishing maccormack scheme the developed model is validated with four one dimensional experimental test cases containing both darcy and non darcy regimes and applied to a demonstrative two dimensional scenario having various interface conditions results obtained from the proposed framework highlights the potential applicability of the generalized model for diverse time scales and vertical sloping interface conditions

rans modelling applied to random wave interaction with submerged permeable structures abstract this paper is the second part of the work presented by garcia et al garcia n lara j l losada i j 2004 2 d numerical analysis of near field flow at low crested breakwaters coastal engineering 51 10 991 1020 in the mentioned paper flow conditions at low crested rubble mound breakwaters under regular wave attack were examined using a combination of measured data of free surface bottom pressure and fluid velocities from small scale experiments and numerical results provided by a vof type model cobras based on the reynolds averaged navier stokes rans equations this paper demonstrates the capability of the cobras model to reproduce irregular wave interaction with submerged permeable breakwaters data provided by the numerical model are compared to experimental data of laboratory tests and the main processes of wave structure interaction are examined using both experimental and numerical results the numerical model validation is carried out in two steps first the procedure of irregular wave generation is verified to work properly comparing experimental and numerical data of different cases of irregular wave trains propagating over a flat bottom next the validation of the numerical model for wave interaction with submerged rubble mound breakwaters is performed through the simulation of small scale laboratory tests on different incident wave spectra results show that the numerical model adequately reproduces the main aspects of the interaction of random waves with submerged porous breakwaters especially the spectral energy decay at the structure and the spectrum broadening past the structure the simulations give good results in terms of height envelopes mean level spectral shape root mean square height for both free surface displacement and dynamic pressure inside the breakwater moreover large scale simulations have been conducted on both regular and irregular incident wave conditions the overall pattern of the wave interaction with a large scale submerged breakwater is adequately reproduced by the numerical model the processes of wave reflection shoaling and breaking are correctly captured the good results achieved at a near prototype scale are promising regarding the use of the numerical model for design purposes

observations and predictions of run up for a significant range of offshore wave conditions and foreshore slopes run up observations are compared to semiempirical formulations and predictions of an existing numerical model based on the depth averaged one dimensional nonlinear shallow water equations with bore like breaking wave dissipation and quadratic bottom friction the numerical model is initialized with time series of sea surface elevation and cross shore velocity observed in 80 cm mean water depth approximately 50 m offshore of the mean shoreline on a gently sloping beach and in 175 cm water depth 100 m offshore of the shoreline on a steep concave beach run up was measured with a stack of resistance wires at elevations 5 10 15 20 and 25 cm above and parallel to the beach face at sea swell frequencies nominally 0 05 f 0 18 hz run up energy is limited by surf zone dissipation of shoreward propagating waves so that increasing the offshore wave height above a threshold value does not substantially increase the predicted or observed sea swell run up excursions e g run up is saturated existing semiempirical saturation formulations are most consistent with the observations and numerical model predictions of run up excursions nearest the bed in contrast at infragravity frequencies 0 004 f 0 05 hz where surf zone dissipation is relatively weak and reflection from the beach face is strong e g saturation formulas are not applicable the run up excursions increase approximately linearly with increasing offshore wave height the numerical model also accurately predicts that the tongue like shape of the run up results in sensitivity of run up measurements to wire elevation for instance run up excursions and mean vertical superelevation above the offshore still water level increase with decreasing wire elevation and continuous thinning of the run up tongue during the wave uprush can result in large phase differences between run up excursions measured at different wire elevations numerical model simulations suggest that run up measured more than a few centimeters above the bed cannot be used to infer even the sign of the fluid velocities in the run up tongue

effects of wave shape on sheet flow sediment transport 1 a two phase model is implemented to study the effects of wave shape on the transport of coarse grained sediment in the sheet flow regime the model is based on balance equations for the average mass momentum and fluctuation energy for both the fluid and sediment phases model simulations indicate that the responses of the sheet flow such as the velocity profiles the instantaneous bed shear stress the sediment flux and the total amount of the mobilized sediment cannot be fully parameterized by quasi steady free stream velocity and may be correlated with the magnitude of local horizontal pressure gradient or free stream acceleration a net sediment flux in the direction of wave advance is obtained for both skewed and saw tooth wave shapes typical of shoaled and breaking waves the model further suggests that at critical values of the horizontal pressure gradient there is a failure event within the bed that mobilizes more sediment into the mobile sheet and enhances the sediment flux preliminary attempts to parameterize the total bed shear stress and the total sediment flux appear promising

can the rayleigh distribution be used to determine extreme wave heights in non breaking swell conditions abstract a reliable set of tools for prediction of low exceedance design waves is of high importance when designing coastal protection structures the significant wave parameters are typically obtained from buoys or numerical wave propagation models and design values are found by extreme analysis statistical wave height distributions are used to transform the significant wave height to lower exceedance wave heights these extreme single waves will cause the highest loads and wave overtopping volumes on structures and thereby represent the design conditions an under prediction of the design maximum wave height causes unsafe designs while an over prediction causes too conservative and thus expensive designs the wave height distribution by longuet higgins 1952 rayleigh distribution for deep water non breaking waves is in the present paper evaluated against data from numerical tests with long period and long crested swell waves the numerical model is validated against data from physical model tests generally it is concluded that the rayleigh distribution is under predicting the low exceedance wave heights in irregular swell waves this is expected to be caused by wave non linearity and thus a new modified wave height distribution is suggested where the shape parameter in the distribution is dependent on the wave non linearity represented by the ursell number the new proposed wave height distribution for non linear and non breaking waves is highly applicable for practical engineering design of both near shore and offshore structures under influence of swell waves

relevance of infragravity waves in a wave dominated inlet this study investigates the relevance of infragravity ig waves at albufeira lagoon inlet a shallow wave dominated inlet located on the western coast of portugal a field experiment carried out in september 2010 revealed the occurrence of low frequency oscillations i e 25 300 s in water levels and current velocities while these fluctuations were present over the ebb tidal delta along the whole tidal cycle they only appeared between the beginning of the flood and up to 2 h after high tide inside the lagoon the xbeach modeling system was applied to albufeira lagoon inlet and reproduced the generation and propagation of ig waves and their blocking during the ebb this behavior was explained by blocking due to opposing tidal currents reaching 2 5 m s 1 in shallow water depths numerical results suggest that the breakpoint mechanism and the long bound wave shoaling mechanisms contributed significantly to the generation of ig waves in the inlet ig waves induced fluctuations in flood currents inside the lagoon reaching temporarily 100 of their magnitude the fact that these fluctuations occur mostly at flood and not at ebb could promote flood dominance in the lagoon this hypothesis will have to be verified namely under storm wave conditions

observations and predictions of fluid velocities in the surf and swash zones 1 surfzone and swashzone water level fluctuations and cross shore fluid velocities observed at seven cross shore locations for 139 51 min periods on a low sloped fine grained sandy beach are shown to be modeled well by the depth averaged nonlinear shallow water equations the model initialized with observations about 150 m from the shoreline in 300 cm water depth accurately predicts the observed decrease in sea swell wave heights and orbital velocities with decreasing water depth across the surf zone and the observed maxima in infragravity orbital velocities and offshore directed mean flows near the outer edge of the swash zone in the surf zone both the observed and predicted velocity fluctuations are dominated by sawtoothed shaped pitched forward asymmetrical sea swell waves in the swash zone infragravity waves contribute substantially to the total velocity variance and asymmetry shoreward of the outer swash zone observed and predicted total and infragravity velocity asymmetry decrease onshore changing sign from positive to negative in the upper swash

the influence of swash based reflection on surf zone hydrodynamics a wave by wave approach abstract a detailed understanding of the behaviour of waves in the nearshore is essential for coastal engineers as these waves cause beach erosion coastal flooding and damage to coastal structures significantly the influence of reflected waves is often neglected in surf zone studies although they are known to influence wave properties and circulation in the nearshore in this paper a phase resolving model is rigorously applied to model conditions from the prototype scale bardexii experiment in order to examine and assess the influence of swash based reflection on surf zone hydrodynamics at both the individual wave and time averaged timescales surface elevation is separated into incoming and outgoing signals using the radon transform and a crest tracking algorithm is used to extract incident and reflected wave properties it is found that on steep beaches tan 1 9 the swash based reflection the reflection generated in the swash during the backwash contributes significantly to the intrawave variability of individual wave properties such as the wave height to water depth ratio through the generation of quasi nodes antinodes system for expressed with individual wave heights variations up to 25 and 40 are obtained for the modelled regular and irregular wave tests whereas it reaches 15 when it is based on the significant wave height the outgoing wave field induced hydrodynamics is also found to affect time averaged parameters undertow and horizontal velocity skewness the undertow is mainly strengthened particularly in the shoaling region where the outgoing component dominates over the contribution from the incoming wave field offshore of the bar an onshore directed flow streaming close to the bed is also generated under the outgoing wave field and is suspected to help in stabilising the bar position this along with the influence of the outgoing wave field on the horizontal velocity skewness and the presence of quasi standing waves suggests a complex contribution of the hydrodynamics induced by swash based reflection into sediment transport rates and nearshore bar generation migration

numerical simulation of swash zone fluid accelerations 1 a volume of fluid navier stokes solver incorporating a k closure model numerical water flume newflume lin and xu 2005 is used to investigate the temporal and spatial structure of accelerations in the swash zone of steep beaches for surging plunging and nearly spilling waves simulations for idealized swash over planar slopes show that shoreward directed local accelerations exist only for up to 22 of the swash cycle depending on wave type in general shoreward directed local accelerations were predicted to occur only near the wave run down limit baldock and holmes 1997 similarly convective accelerations had the largest magnitudes during this time and tended to be either near zero or shoreward directed for the remainder of the swash cycle this finding is in direct contrast to a modified ballistic theory for swash motion arising as a particular solution to the depth averaged nonlinear shallow water equations peregrine and williams 2001 that predicts the convective acceleration maintains the sign of the fluid velocity near bed pressure gradients are found to be poorly correlated to both the depth averaged and near bed local acceleration these numerical findings indicate that local fluid accelerations are not a proxy for pressure gradients in the swash zone for enhanced sediment transporting mechanisms or parameterizations however the numerical results require corroboration with highly resolved swash zone data

modelling of velocity and turbulence fields around and within low crested rubble mound breakwaters abstract a description of the progress achieved within delos environmental design of low crested coastal defence structures eu project in the modelling of wave interaction with low crested structures lcs is presented in this paper emphasis is put on the description of the near field flow especially the velocity and turbulence distribution around and inside lcs as required by other researchers in the project two dimensional varans and three dimensional les numerical modelling has been considered the two dimensional model has been extensively validated with delos laboratory data as shown in garcia et al garcia n lara j l losada i j 2004 2 d numerical analysis of near field flow at low crested breakwaters coastal engineering elsevier 51 10 991 1020 a system of flow recirculation is included in both the experimental and numerical set ups for a correct description of the 2dv velocity field in the vicinity of the structure further validation is presented in this paper laboratory tests on two values of crest width have been simulated in order to analyse relevant near field flow features related to a variation of the geometric configuration of the structure the width of the breakwater crest is seen to significantly influence the wave breaking induced flow pattern at the structure magnitudes such as turbulent kinetic energy tke tke dissipation rate shear stresses and reynolds stresses are computed around and inside the breakwater the three dimensional model numerical results are compared with results of wave basin experiments showing a good agreement for instantaneous free surface numerical results of the flow over the breakwater and around the breakwater head are also presented

synconvergent ductile flow in variable strength continental crust numerical models with application to the western grenville orogen 1 we present results from numerical models for a convergent orogen with laterally variable lower crustal strength representing a simplified orogenic system in which a strong craton flanked by progressively weaker terranes collides with another continent with progressive convergence crustal thickening and thermal relaxation lower crust becomes decoupled from upper and middle crust forming a ductile orogenic infrastructure beneath a stronger superstructure collision with strong external crust results in uplift and expulsion of ductile nappes from the orogenic core creating allochthonous terranes overlying a lower crustal indentor the extent of transport and exhumation of lower crustal nappes over the indentor reflects the amount of convergence and the erosion rate the western grenville orogen displays across strike variations in age tectonic history and protolith association suggesting a systematic variation in precollision crustal strength the laurentian craton margin and accreted terranes were variably reworked at synorogenic depths of 25 35 km during the ottawan orogeny deformation propagated from younger monocyclic rocks in the southeast into older polycyclic rocks flanking the craton on the northwest a comparison between numerical model results and crustal scale cross sections from the georgian bay and montreal val d or transects shows close correspondence between crustal structure and model geometry this indicates that the models produce geologically realistic results and provides a context for interpreting the tectonic evolution of the western grenville orogen contrasts between the results of homogeneous channel flow models and the present ductile nappe models suggest that the effects of different styles of ductile flow can be distinguished in the geologic record

three stage evolution of lower crustal gneiss domes at breaksea entrance fiordland new zealand 1 new structural analyses reveal the presence of several kilometer scale gneiss domes and many subdomes within an exhumed section of cretaceous lower crust in sw fiordland the domes are defined by complex nearly concentric trajectories of foliations and steep high strain zones in migmatitic granulite and eclogite facies orthogneiss structural patterns combined with evidence of deformation that was synchronous with partial melting and high grade metamorphism steep mineral lineation orientations sense of shear indicators and near isothermal decompression suggest that buoyancy driven diapiric flow of hot partially molten crust aided initial dome formation mafic intermediate magmatism appears to have enhanced this process superimposed on all high grade structures are upper amphibolite facies shear zones that record a change in the style and conditions of lower crustal flow lineation orientations sense of shear evidence of cooling with decompression and other patterns suggest that the retrograde shear zones record bulk horizontal flow and crustal thinning driven by regional tectonic forces a preferred sequence begins with the initial emplacement of mafic intermediate magma into the lower crust at depths up to 70 km d1 diapirism and initial dome formation occurred during a period of waning arc magmatism and episodic partial melting and high grade metamorphism d2 following melt crystallization dominantly horizontal flow of a cooler strain hardened lower crust occurred during late cretaceous continental extension d3 this example highlights the interplay between mechanisms of horizontal and vertical flow at the root of a continental arc and illustrates their roles in the formation of gneiss domes

efficient computation of surf zone waves using the nonlinear shallow water equations with non hydrostatic pressure abstract a numerical method for non hydrostatic free surface irrotational flow governed by the nonlinear shallow water equations including the effects of vertical acceleration is presented at the aim of studying surf zone phenomena a vertical boundary fitted grid is used with the water depth divided into a number of layers a compact finite difference scheme is employed for accurate computation of frequency dispersion requiring a limited vertical resolution and hence capable of predicting the onset of wave breaking a novel wet dry algorithm is applied for a proper handling of moving shoreline mass and momentum are strictly conserved at discrete level while the method only dissipates energy in the case of wave breaking the numerical results are verified with a number of tests and show that the proposed model using two layers without ad hoc assumptions enables to resolve propagating nonlinear shoaling breaking waves and wave run up within the surf and swash zones in an efficient manner

deep crustal deformation textures along megathrusts from newfoundland and ontario implications for microstructural preservation strain rates and strength of the lithosphere lithospheric scale thrusts from the west newfoundland ophiolite belt white hills peridotite shear zone and the south western grenville province parry sound shear zone involve rocks of lower crustal and or upper mantle origin that exhibit intense crystal plastic deformation of plagioclase k feldspar orthopyroxene and clinopyroxene minerals that are commonly viewed as representative of low ductility phases the occurrence of this extreme deformation in shear zones that exhibit similar lower crustal syntectonic p t conditions suggests a phenomenological link between the megathrust environment and both the generation and subsequent preservation of the observed deformation microstructures an empirical homologous parameter is constructed in an attempt to characterize conditions for similar behaviour among different minerals and to explore the feasibility of refining a threshold recovery preservation condition within the megathrusts studied this parameter predicts at the estimated syntectonic temper

networking of shear zones at the brittle to viscous transition cap de creus ne spain a crustal scale shear zone network at the fossil brittle to viscous transition exposed at cap de creus ne spain evolved by coeval fracturing and viscous mylonitic overprinting of an existing foliation initial fracturing led to mylonitic shearing as rock softened in ductilely deformed zones surrounding the fractures mylonitic shear zones widened by lateral branching of fractures from these shear zones and by synthetic rotation of the existing foliation between the fractures and shear zones shear zones lengthened by a combination of fracturing and mylonitic shearing in front of the shear zone tips shear zones interconnected along and across their shearing planes separating rhomb shaped lozenges of less deformed rock lozenges were subsequently incorporated into the mylonitic shear zones by widening in the manner described above in this way deformation became homogeneous on the scale of initial fracturing metre to decametre scale in contrast the shear zone network represents localisation of strain on a decametre length scale the strength of the continental crust at the time of coeval fracturing and viscous shearing is inferred to have decreased with time and strain as fracturing evolved to mylonitic shearing and as the shear zones coalesced to form a through going network subparallel to the shearing plane crustal strength must therefore be considered as strain and scale dependent

can field data constrain rock viscosities abstract in the 1960s it looked as though the ratio of wavelength to thickness of folds along shortened competent single layers might allow constraint of the viscosity ratios between the layers and their hosts when they deformed together in the 1970s the possibility arose that simple field measurements of boudins and mullions might also constrain rock viscosity ratios and thereby distinguish deformation facies and map rock viscosities in pressure temperature time space even more potential tools for constraining rock viscosities appeared in the 1980s but since then progress appears to have stagnated in a welter of problems an attempt is made to refocus attention on direct retrospective measurements of rock rheologies during natural deformations by reviewing the potential field tools for constraining rock viscosities discussing some of their problems and by a crude application of the most developed approach further advances are likely to come from iteration between modellers and structural geologists working in a variety of tectonic settings as well as constraining the pressure temperature time paths of our rocks we should also be attempting to measure their viscosities

transect across the northwestern grenville orogen georgian bay ontario polystage convergence and extension in the lower orogenic crust the grenville orogenic cycle between 1190 and 980 ma involved accretion of magmatic arcs and or continental terranes to the laurentian craton a transect across the western central gneiss belt georgian bay ontario which crosses the boundary between parautochthonous and allochthonous units at an inferred orogenic depth of 20 30 km offers some insights on the thermal and mechanical behavior of the lower crust during the development of the grenville orogen prior to grenvillian metamorphism this part of laurentia consisted largely of meso proterozoic 1450 ma granitoid orthogneisses granulites and subordinate mafic and supracrustal rocks grenvillian convergence along the transect began with transport of the previously deformed and metamorphosed 1160 ma parry sound domain over the craton sometime between 1120 ma and 1080 ma this stage of transport was followed by out of sequence thrusting and further convergence along successively deeper foreland propagating ductile thrust zones a major episode of extension at 1020 ma resulted in southeast directed transport of allochthonous rocks along the midcrustal shawanaga shear zone the final stage of convergence involved deformation and metamorphism in the grenville front tectonic zone at 1000 980 ma peak metamorphism along most of the transect at 1065 1045 ma followed initial transport of allochthonous rocks over the craton by 15 35 m y regional cooling which postdated peak metamorphism by 70 m y was probably delayed by the combined effects of late stage extension and convergence transport of allochthons at least 100 km over the craton was accomplished along a weak migmatitic decollement further propagation of the orogen into the craton followed partial melting and weakening of parautochthonous rocks below this decollement extensional deformation was associated with distributed ductile flow the formation of regional transverse folds with axes parallel to the stretching direction and reactivation of the allochthon parautochthon thrust boundary as an extensional decollement the extensional lower crustal flow was likely the primary cause of the subhorizontal attitude of many structures and seismic reflectors in this part of the central gneiss belt

tectonic and metamorphic events in the westernmost grenville province central ontario new results from high precision u pb zircon geochronology the u pb isotopic ages of metamorphic zircons from deformed amphibolitized metadiabase dykes and associated unstrained anatectic pegmatites have been determined to constrain the times of postdyke ductile flow related recrystallization and deformation samples from the central gneiss belt of the grenville province in the southern georgian bay region provide a means of linking areas formed during common episodes of ductile flow three zircon fractions from one attenuated dyke in the moon river domain gave identical concordant ages of 1062 1065 and 1064 2 ma while those from another gave identical concordant ages of 1052 1051 and 1050 2 ma for the time of metamorphism zircons from a folded dyke from the go home domain gave identical concordant ages of 1049 1047 and 1046 2 ma while a single overgrowth fragment from an unstrained anatectic pegmatite in the fold hinge gave a concordant age of 1047 2 ma as if folding metamorphic zircon growth and postfolding pegmatite are part of the same proc

numerical analysis of wave loads for coastal structure stability abstract the numerical model cobras uc losada i j lara j l guanche r gonzalez ondina j m 2008 numerical analysis of wave overtopping of rubble mound breakwaters coastal engineering vol 55 1 47 62 is used to carry out a two dimensional analysis of wave induced loads on coastal structures the model calculates pressure forces and moments for two different cross sections corresponding to a low mound and a conventional rubble mound breakwater with a crown wall under regular and irregular incident wave conditions predicted results are compared with experimental information provided in losada et al losada i j lara j l guanche r gonzalez ondina j m 2008 numerical analysis of wave overtopping of rubble mound breakwaters coastal engineering vol 55 1 47 62 and lara et al lara j l losada i j guanche r 2008 wave interaction with low mound breakwaters using a rans model ocean engineering 35 pp 1388 1400 doi 10 1016 j oceaneng 2008 05 006 on a 1 20 scale good agreement is found and the differences between both typologies are explained in detail additionally numerical results are also compared with several semi empirical formulae recommended for design at both the 1 20 model scale and two prototype cross sections results suggest that cobras uc is able to provide realistic stability information that can be used to complete the approach based on currently existing methods and tools

crustal architecture and tectonic assembly of the central gneiss belt southwestern grenville province canada a new interpretation the central gneiss belt southwestern grenville province is characterized by parautochthonous crust in the north and allochthonous lithotectonic domains in the south despite nearly two decades of study the basal decollement to allochthonous domains transported from the southeast known as the allochthon boundary thrust has not been precisely located throughout much of the belt between lake nipissing and georgian bay where its surface trace is known it separates 1 24 ga sudbury metadiabase in the footwall from eclogite remnants and 1 17 1 15 ga coronitic olivine metagabbro confined to its hanging wall on the premise that this relationship can be used to trace the allochthon boundary thrust elsewhere in the central gneiss belt we have sought to extend the known distribution of these mafic rock types making use of field petrographic and geochemical criteria to identify them new occurrences of all three mafic types are identified in a region extending from south of lake nipissing to western quebec

diagnostic investigation of impulsive pressures induced by plunging breakers impinging on gravel beaches abstract this paper presents an integrated investigation of physical processes generating impulsive pressures under the action of plunging breakers impinging on gravel beaches this work is an extension of a recent investigation which suggested that wave impacts from plunging breakers acting on gravel beaches may be a key mechanism to enhance sediment mobilisation in particular comparisons of full scale laboratory measurements against model results from a well validated phase depth resolving numerical model based on the reynolds averaged navier stokes rans equations are presented this represents the first attempt at comparison with such a tool against observed hydrodynamics on steep slope 1 8 gravel beaches at prototype scale in order to understand how impulsive pressures are generated under plunging waves the numerical model is used to carry out a detailed investigation to examine the role of each of the acceleration terms in the momentum balance consistent with prior studies numerical results show that under plunging breakers the local acceleration u t alone cannot be used as a proxy for pressure gradients however the contribution of the third term w u z of total acceleration is recognized for the first time and indicates that this term has an important role in both the induced pressure gradient and sediment mobilisation as induced by this particular type of breaking furthermore results suggest that a parameterisation of the pressure gradient in terms of u t u u x may not suffice when dealing with plunging breakers and hence there is a lack of a suitable parameterisation of this process in the present literature thus for different types of breaking it may be necessary to consider a different characterisation of the pressure gradient toward the parameterisation of sediment transport inside the surf zone

nucleation and initial growth of a shear zone network within compositionally and structurally heterogeneous granitoids under amphibolite facies conditions abstract in the neves area the pre alpine intrusive protolith of the zentralgneise unit tauern window eastern alps is well preserved in a kilometric scale low strain domain without pervasive alpine deformation it is compositionally heterogeneous consisting predominantly of granodiorites with lesser leucocratic granites and different generations of lamprophyres and aplites the intrusive rocks are crosscut by fractures that were locally infiltrated by fluids and surrounded by alteration haloes incipient alpine amphibolite facies ductile deformation is strongly localized on these precursor fractures and on lithological planar heterogeneities resulting in the development of several different types of shear zones fractures without alteration haloes initially accommodate slip entirely on the fracture itself with increasing deformation a foliation is progressively developed in the adjacent host rock eventually producing a single heterogeneous ductile shear zone with the typical sigmoidal foliation pattern strong layers aplite dykes and bleached alteration haloes developed to either side of precursor fractures localize shear on their boundaries to produce characteristic paired shear zones shearing is more evenly distributed within weak layers lamprophyres and quartz veins with a marked discontinuity in shear strain against the adjacent little deformed granodiorite shear zone development was accompanied by the formation of new fractures and quartz rich veins in the host rock which in turn also localized shear magmatic contacts fractures and quartz veins are mostly steeply dipping and effectively span the complete range of strike orientations the kinematics of the overprinting strike slip shear zones was determined by the orientation of the initial discontinuities relative to the local principal compressive stress axis 1 here oriented ca 345 discontinuities of almost all orientations show shear reactivation even in the case of very low resolved shear stress indicating an overall viscous response of the system without a specific yield stress the geometry and kinematics of the shear zone network suggest that the overall deformation in low strain domains was close to coaxial during deformation along the shear zone network compatibility was maintained by fracturing with the development of new quartz veins and by distributed ductile deformation of the host rock especially within contractional domains of the shear network and at shear zone intersections deformation never propagates into the undeformed homogeneous granodiorite as discrete ductile shear zones but is limited by the original extent of the precursor discontinuities shear zone development in intact rock is always preceded by fracturing which localizes subsequent shear reactivation

remote sensing of the correlation between breakpoint oscillations and infragravity waves in the surf and swash zone a novel remote sensing methodology to determine the dominant infragravity mechanism in the inner surf and swash zone in the field is presented video observations of the breakpoint motion are correlated with the shoreline motion and inner surf zone water levels to determine the relationship between the time varying breakpoint oscillations and the shoreline motion the results of 13 field data sets collected from three different beaches indicate that inside the surf zone the dominance of bound wave or breakpoint forcing is strongly dependent on the surf zone width and the type of short wave breaking infragravity generation by bound wave release was stronger for conditions with relatively narrow surf zones and plunging waves breakpoint forcing was dominant for wider surf zones and spilling breaker conditions

breaking waves over a mild gravel slope experimental and numerical analysis 1 an experimental and numerical study of the effects of a gravel slope on wave shoaling and breaking is presented herein in the laboratory experiments fluid velocities pressure and water surface elevations were measured experiments were conducted for both spilling and plunging breakers and for gravel slopes with different gravel sizes since gravel slopes caused additional energy dissipation wave heights in the shoaling zone as well as at the breaking point were reduced on the other hand the mean free surface setup inside the surf zone increased it was also observed that the gravel slope had a stronger influence on the vertical profile of undertow under spilling breaker than on that under a plunging breaker moreover the undertow became weaker over a gravel slope with a larger gravel size outside the surf zone turbulent velocities near the gravel slope were relatively high because of the bottom roughness and percolation inside the surf zone turbulence generated by wave breaking dominated over the gravel bed generated turbulence the vertical flow induced by the gravel slope changed the turbulence pattern only at cross sections very close to the shoreline numerical simulations of the wave breaking processes over a gravel slope were performed the numerical model was tested by comparing numerical results with experimental data the model accurately simulated the mean flow quantities the magnitude of turbulence and turbulence characteristics were also simulated reasonably well

2 d numerical analysis of near field flow at low crested permeable breakwaters abstract this paper describes the capability of a numerical model named cornell breaking waves and structures cobras lin p liu p l f 1998 a numerical study of breaking waves in the surf zone journal of fluid mechanics 359 239 264 liu p l f lin p chang k a sakakiyama t 1999 numerical modeling of wave interaction with porous structures journal of waterway port coastal and ocean engineering 125 322 330 liu p l f lin p hsu t chang k losada i j vidal c sakakiyama t 2000 a reynolds averaged navier stokes equation model for nonlinear water wave and structure interactions proc coastal structures 99 169 174 based on the reynolds averaged navier stokes rans equations to simulate the most relevant hydrodynamic near field processes that take place in the interaction between waves and low crested breakwaters the model considers wave reflection transmission overtopping and breaking due to transient nonlinear waves including turbulence in the fluid domain and in the permeable regions for any kind of geometry and number of layers small scale laboratory tests were conducted in order to validate the model with different wave conditions and breakwater configurations in the present study regular waves of different heights and periods impinging on a wide crested structure are considered three different water depths were tested in order to examine the influence of the structure freeboard the experimental set up includes a flow recirculation system aimed at preventing water piling up at the lee of the breakwater due to overtopping the applicability and validity of the model are examined by comparing the results of the numerical computations with experimental data the model is proved to simulate with a high degree of agreement all the studied magnitudes free surface displacement pressure inside the porous structure and velocity field the results obtained show that this model represents a substantial improvement in the numerical modelling of low crested structures lcs since it includes many processes neglected previously by existing models the information provided by the model can be useful to analyse structure functionality structure stability scour and many other hydrodynamic processes of interest

momentum balance under breaking waves closure to discussion by t e baldock of laboratory investigation of pressure gradients induced by plunging breakers abstract this paper replies to observations put forward by prof t e baldock baldock t e 2012 discussion of laboratory investigation of pressure gradients induced by plunging breakers by pedrozo acuna et al coastal engineering vol 66 august 2012 pages 1 2 regarding a laboratory investigation of pressure gradients induced by plunging breakers firstly we focused on clarifying the inconsistencies and present the revised figures which do not change the conclusions reached in the study moreover in order to confirm and extend the derived conclusions in the aforementioned investigation we conduct a numerical study of momentum balance in the surf zone for different types of breaking the analysis incorporates results from a well validated rans model which enables the assessment of the fluid acceleration and pressure gradients it is demonstrated that the type of wave breaking controls the relative importance of pressure gradients and bed shear stresses in the sediment transport within the surf zone

numerical modelling of short and long wave transformation on a barred beach abstract this work aims to demonstrate an advancement towards the integrated modelling of surf zone hydrodynamics by means of a vof type numerical model cobras uc based on the reynolds averaged navier stokes equations in this paper the numerical model is adapted and validated for the study of nearshore processes on a mildly sloping beach the model prediction of wave energy transformation and higher order statistics skewness and asymmetry are in good agreement with detailed laboratory observations from a barred beach boers m 1996 simulation of a surf zone with a barred beach report 1 wave heights and wave breaking tech rep 96 5 comm on hydrol and geol eng dept of civil engineering delft university of technology moreover the numerical model allows us to study the low frequency motions inside the surf zone it is found that in order to achieve a satisfactory simulation of both short and long wave transformation the numerical model must achieve i the simultaneous second order wave generation and absorption ii the energy transfer between triad of components iii the short and long wave energy dissipation inside the surf zone and iv the wave reflection at the shoreline comparisons between numerical and experimental results demonstrate the model capability to satisfactorily simulate all the aforementioned processes

zircon u pb and trace element zoning characteristics in an anatectic granulite domain insights from lass icp ms depth profiling abstract understanding the geochemical characteristics of metamorphic zircon and how they may be modified by recrystallization processes is fundamental to defining the timescales of tectonic processes affecting continental lithosphere we utilize laser ablation split stream lass icp ms depth profiling analysis to obtain a continuous rim to core record of the u pb ages and trace element composition preserved within variably recrystallized zircon from different rock types within a well studied granulite domain in the western grenville province canada detailed analysis of the depth resolved signal enables definition of chemically distinct homogeneous internal domains and heterogeneous intervening zones that can generally be correlated with textural features observed in cl three age populations have been distinguished within the 35 m deep profiles that correlate well with the established timing of protolith formation granulite facies metamorphism and amphibolite facies shearing respectively the u pb isotopic system and th u ratios in much of the crystal interiors have undergone considerable modification as evidenced by a linear correlation between 207pb 206pb age and th u ratio interior and rim domains commonly contain blurred or faded oscillatory zoning patterns suggesting that solid state recrystallization is at least partially responsible for the modified u th pb composition a number of systematic trends in trace element composition are also observed between interior domains and recrystallized rims including 1 decreased th u to 0 1 2 tighter clustering of hf concentrations 3 decreased total ree 4 unchanged eu anomalies and 5 a widened spread of hree enrichment values ybn gdn both ybn gdn vs th u and u ce vs th plots show increasing degree of compositional differentiation from protolith zircon as a function of metamorphic reworking processes i e sample type the transition zones between interior and rim domains exhibit textural features consistent with solid state recrystallization and migration of a transgressive recrystallization front the main compositional characteristics of the transition zones are 1 spikes in u and ta 2 steady to abrupt increases in hf toward maximum values in the rims 3 steady to abrupt decreases in th toward minimum values in the rims and 4 variable ree patterns that include spikes troughs and montonic decreases most of these characteristics are consistent with the purging of larger ions from the crystal lattice during recrystallization with local bands of high concentration associated with recrystallization fronts

numerical analysis of wave overtopping of rubble mound breakwaters abstract the paper describes the results of a two dimensional 2 d numerical modelling investigation of the functionality of rubble mound breakwaters with special attention focused on wave overtopping processes the model cobras uc is a new version of the cobras cornell breaking waves and structures based on the volume averaged reynolds average navier stokes varans equations and uses a volume of fluid technique vof method to capture the free surface the nature of the model equations and solving technique provides a means to simulate wave reflection run up wave breaking on the slope transmission through rubble mounds overtopping and agitation at the protected side due to the combined effect of wave transmission and overtopping also two dimensional experimental studies are carried out to investigate the performance of the model the computations of the free surface and pressure time series and spectra under regular and irregular waves are compared with the experimental data reaching a very good agreement the model is also used to reproduce instantaneous and average wave overtopping discharge comparisons with existing semi empirical formulae and experimental data show a very good performance the present model is expected to become in the near future an excellent tool for practical applications

wave transformation across the inner surf zone sea and swell wave heights observed on transects crossing the mid and inner surf zone on three beaches a steep concave up beach a gently sloped approximately planar beach and a beach with an approximately flat terrace adjacent to a steep foreshore were depth limited i e approximately independent of the offshore wave height consistent with previous observations the wave evolution is well predicted by a numerical model based on the one dimensional nonlinear shallow water equations with bore dissipation the model is initialized with the time series of sea surface elevation and cross shore current observed at the most offshore sensors located about 50 to 120 m from the mean shoreline in mean water depths 0 80 to 2 10 m the model accurately predicts the cross shore variation of energy at both infragravity nominally 0 004 f 0 05 hz and sea swell here 0 05 f 0 18 hz frequencies in models of surf zone hydrodynamics wave energy dissipation is frequently parameterized in terms of s the ratio of the sea swell significant wave height to the local mean water depth the observed and predicted values of s increase with increasing beach slope and decreasing normalized by a characteristic wavenumber k water depth kh and are well correlated with kh a measure of the fractional change in water depth over a wavelength errors in the predicted individual values of s are typically less than 20 it has been suggested that infragravity motions affect waves in the sea swell band and hence s but this speculation is difficult to test with field observations numerical simulations suggest that for the range of conditions considered here s is insensitive to infragravity energy levels

mega scale moho relief and the structure of the lithosphere on the eastern flank of the viking graben offshore southwestern norway the international lithosphere project deep reflection seismic survey in the norwegian sector of the north sea has been reprocessed particularly focusing on the deep crust the reflection moho and the upper mantle the data display shifting reflection patterns of the crust and the upper mantle parallel to the eastern margin of the viking graben in the upper crust which is mainly seismically transparent by the processing techniques utilized here large scale structural features like detachment shear zones and master faults can be identified several of the major onshore faults and shear zones match seismic features in the seismic lines many of these structures acted as extensional shear zones in the devonian the middle crust is of variable reflectivity whereas the lower crust is generally strongly reflective and is particularly so in the southern domain the reflection moho is identified throughout the study area but is of variable character the presence of a s e dipping structure hardanger moho offset that displaces the moho by approximately 10 km extends deep into the mantle below the 50 km line depth is positioned where the shallower hardangerfjord shear zone which flattens on the level of the middle crust is situated the hardangerfjord shear zone hardanger moho offset system coincides with change of the crustal thickness depth to moho a change that also coincides with the transition from thin to thick skinned caledonian deformation intramantle reflections are common in the study area some of which are interpreted as shear zones whereas others most likely represent magmatic intrusions

geologic transect across the grenville orogen of ontario and new york revised cross sections of the western grenville province incorporate new geologic results and reprocessed seismic reflection data the geology is presented in terms of three tectonic elements 1 pre grenvillian laurentia and its margin with ca 1740 and 1450 ma continental arc plutons and associated supracrustal rocks 2 composite arc belt of allochthonous 1300 1250 ma volcanic arcs and sedimentary rocks and 3 frontenac adirondack belt characterized by supracrustal and granitoid rocks and anorthosites of uncertain affinity that may represent a distinctive part of the composite arc belt or an offshore micro continent rocks of the composite arc and frontenac adirondack belts were amalgamated with each other by ca 1160 ma were then thrust over laurentia during ca 1080 1035 ma and ca 1010 980 ma phases of convergence and were dissected and exhumed by 1040 ma normal faults penetrative deformation was restricted to that part of the pre grenvillian laurentian margin that lies to the southeast of the grenville front and parts of the accreted composite arc and frontenac adirondack belts the laurentian rocks in the grenville province are bounded to the northwest and southeast by southeast dipping ductile thrust and or normal shear zones the composite arc and frontenac adirondack belts to the southeast are bounded by ductile and brittle ductile thrust and or normal faults that separate domains with contrasting cooling histories despite a long pre grenvillian tectonic and plutonic history the present crustal architecture and much of the seismic reflectivity were acquired during 1080 980 ma phases of compression and extension

structural analysis of high pressure shear zones bacariza formation cabo ortegal nw spain abstract high pressure granulites of the bacariza formation cabo ortegal complex nw spain exhibit spectacular examples of ductile shear zones developed at different scales in rocks containing pre existing foliations a detailed structural analysis was carried out on these shear zones in order to unravel and compare the role of various parameters controlling the deformation process i e heterogeneous simple shear components of homogeneous deformation heterogeneous volume change and degree of non coaxiality although heterogeneous simple shear largely dominated negligible deviations from the ideal simple shear model were detected involving shortening along the structural directions perpendicular to the stretching axis within the foliation plane of the finite strain ellipsoid the relationship between displacement parallel to a half shear zone and the normal distance from its boundary provided the basis for the estimation of the stress exponent in the power law constitutive flow equation associated with each shear zone which is interpreted as a rheological indicator these geometric and rheological results and the thermobaric conditions of high pressure shear zone deformation indicate that these shear zones accommodated dominant plastic rock flow coeval with high pressure and high temperature deformations under moderate stress levels concomitant with elevated strain rates

the orogenic superstructure infrastructure concept revisited quantified and revived the historical superstructure infrastructure concept s i expressed contrasts in structural style and metamorphic grade between shallow and deep orogenic levels two dimensional thermal mechanical models provide a quantitative explanation in terms of progressive crustal shortening and thickening phase 1 thermal relaxation and rheological weakening phase 2 and ductile flow at depth phase 3 results predict an upper crustal superstructure dominated by early steep structures separated across a subhorizontal high strain zone from a ductile infrastructure with late gently dipping structures this is consistent with observations from the western superior province these models can account for contrasts in structural style metamorphic grade seismic reflectivity and age between upper and lower crustal levels in contrast to conventional thrust tectonics models the revived s i model shows how young structures can form beneath older ones during progressive convergence thereby encouraging reassessment of standard seismic reflection interpretations

a boussinesq model for waves breaking in shallow water abstract a simple description of wave breaking in shallow water is incorporated in the boussinesq equations by using the concept of surface rollers the roller is considered as a volume of water being carried by the wave with the wave celerity the effect of the roller is included in the vertical distribution of the horizontal velocity which leads to an additional convective momentum term the breaking criterion is related to the local slope of water surface and the thickness of the roller is determined from simple geometrical considerations although the model is simple it is capable of representing a variety of processes such as the initiation and cessation of wave breaking the evolution of wave profiles before during and after wave breaking the initial conversion of potential energy into forward momentum flux and the associated horizontal shift between the break point and the point where the setup in mean water level is initiated results are presented for regular and irregular wave trains and comparison with measurements shows good agreement

early mesoproterozoic tectonic history of the southwestern grenville province ontario constraints from geochemistry and geochronology of high grade gneisses

structural and metamorphic inheritance controls strain partitioning during orogenic shortening kalak nappe complex norwegian caledonides abstract the occurrence of pre collisional structural and metamorphic fabrics may control the development of new structures during subsequent orogenic deformation structural petrological and geochronological analyses have been performed on selected samples collected along a nw se cross section of the kalak nappe complex knc exposed on kvaloya island finnmark norway in order to define pre caledonian or caledonian affinity of deformation fabrics nappes within the knc experienced different pre collisional tectonometamorphic histories resulting in contrasting pre caledonian fabrics which in turn controlled orogen scale strain partitioning and metamorphic re equilibration during caledonian shortening caledonian deformation during top to se directed thrusting occurred at 550 675 c and 0 8 1 0 gpa in the presence of fluids suitably oriented pre collisional fabrics were firstly exploited as zones of localized shearing internal to the knc and subjected to metamorphic re equilibration during shortening fold geometry during caledonian thrusting was also controlled by the orientation of pre caledonian fabrics se verging asymmetric folds were developed after minor tilting of pre caledonian upright folds with orogen parallel hinge in the hinterland consistently with top to se shearing shear parallel folds displaying orogen perpendicular hinge lines resulted from top to se general shearing of pre collisional upright folds showing pre collisional orogen perpendicular hinge lines caledonian metamorphism appears to have been accompanied by infiltration of radiogenic 40ar rich fluids which affected the ar isotopic system in synkinematic micas

numerical experiments of swash oscillations on steep and gentle beaches a weakly non linear boussinesq model with a slot type shoreline boundary is used to simulate swash oscillations on beaches numerical simulations of swash were compared with laboratory measurements and in general good agreement found less than 15 root mean square error of surface elevation except in regular waves a series of numerical experiments on shoreline movement were then performed for a range of beach slopes and incident wave conditions the resulting swash characteristics are then discussed in terms of their physical nature and spectral properties on steep slopes both individual bores and infragravity waves are equally significant in driving the swash while infragravity waves alone drive them on mild slopes swash excursions on any given slope are found to be highest when individual bores from a partially saturated surf zone ride on top of low frequency waves this is confirmed by the relationship found between swash excursion and wave groupiness in the surf zone swash excursions increase with increasing incident wave energy even in fully saturated surf zones however a poor correlation is found between swash excursion and the surf similarity parameter due to the involvement of infragravity wave energy in the swash

nd isotope mapping of the allochthon boundary thrust on the shores of georgian bay ontario significance for grenvillian crustal structure and evolution nearly 50 new nd isotope analyses are presented for the shawanaga region of georgian bay ontario to study crustal evolution in the grenvillian central gneiss belt depleted mantle t dm nd model ages are used to map a major grenvillian tectonic boundary the allochthon boundary thrust abt which in the shawanaga area separates gneisses with t dm ages above and below 1 65 ga this is lower than the 1 8 ga age cut off observed further north and is attributed to a southward increase in mesoproterozoic magmatic reworking of an original palaeoproterozoic continental margin causing a progressive southward decrease in nd model ages between shawanaga island and franklin island nd isotope mapping yields an abt trajectory that closely matches published geological mapping and passes within 100 m of four retrogressed eclogite bodies typically associated with the thrust boundary this validation of the method gives confidence in the mapped trajectory south of snake island where sparse outcrop inhibits lithological mapping the new results suggest that published 1 7 1 9 ga t dm ages in the lower go home domain of the central gneiss belt further south are also indicative of parautochthonous crust hence we propose that the main ramp of the abt is located in the immediate hangingwall of the go home domain much further south than generally recognized this has important implications for the large scale crustal structure of the sw grenville province suggesting that the abt ramp has a similar curved trajectory to the grenville front and the central metasedimentary belt boundary thrust

spectral evolution of shoaling and breaking waves on a barred beach field observations and numerical model predictions are used to investigate the effects of nonlinear interactions reflection and dissipation on the evolution of surface gravity waves propagating across a barred beach nonlinear interactions resulted in a doubling of the number of wave crests when moderately energetic about 0 8 m significant wave height narrowband swell propagated without breaking across an 80 m wide nearly flat 2 m depth section of beach between a small offshore sand bar and a steep slope 0 1 beach face where the waves finally broke these nonlinear energy transfers are accurately predicted by a model based on the nondissipative unidirectional i e reflection is neglected boussinesq equations for a lower energy wave height about 0 4 m bimodal wave field high frequency seas dissipated in the surf zone but lower frequency swell partially reflected from the steep beach face resulting in significant cross shore modulation of swell energy the combined effects of reflection from the beach face and dissipation across the sand bar and near the shoreline are described well by a bore propagation model based on the nondispersive nonlinear shallow water equations boussinesq model predictions on the flat section where dissipation is weak are improved by decomposing the wave field into seaward and shoreward propagating components in more energetic wave heights greater than 1 m conditions reflection is negligible and the region of significant dissipation can extend well seaward of the sand bar differences between observed decreases in spectral levels and boussinesq model predictions of nonlinear energy transfers are used to infer the spectrum of breaking wave induced dissipation between adjacent measurement locations the inferred dissipation rates typically increase with increasing frequency and are comparable in magnitude to the nonlinear energy transfer rates

timing and duration of melting in the mid orogenic crust constraints from u pb shrimp data muskoka and shawanaga domains grenville province ontario the central gneiss belt in the grenville province ontario exposes metaplutonic rocks orthogneisses and minor paragneisses that were deformed and metamorphosed at crustal depths of 20 35 km during the mesoproterozoic grenvillian orogeny we present sensitive high resolution ion microprobe shrimp u pb zircon data from eight samples of migmatitic orthogneiss granite and pegmatite from the muskoka and shawanaga domains that constrain the age and duration of partial melting in the mid orogenic crust our results support earlier interpretations that the protoliths to these migmatitic orthogneisses formed at ca 1450 ma emplacement and crystallization of granite and pegmatite in the shawanaga domain took place at ca 1089 ma apparently coevally with deformation and high grade metamorphism leucosomes in the muskoka and shawanaga domains yield ages of 1067 and 1047 ma respectively interpreted as the ages of melt crystallization the geochronological data and field observations suggest that melt was pr

nappe emplacement direction in the central gneiss belt grenville province ontario canada evidence for oblique collision abstract the proterozoic grenville province in canada is widely regarded as a compressional orogen in which thrust transport occurred towards the northwest perpendicular to the orogenic front new structural data from an area near parry sound ontario lead to a re evaluation of this interpretation nappe structures in this area are consistent with northeast rather than northwest directed thrusting and imply that the southwestern part of the province experienced an early sinistral oblique collision which predated the emplacement of the 1 24 ga sudbury dike swarm two nappe piles which contain different rock types and have distinct stacking sequences are separated by a lateral ramp or ductile tear fault that coincides with the interior of the parry sound domain of davidson et al 1982 early nappes and associated structures f 1 are overprinted by nw se striking upright folds f 2 that formed between about 1 16 and 1 12 ga these later folds partially reorient rotated feldspar porphyroclast systems that formed during nappe emplacement and have axes that are consistently parallel to a well developed mineral lineation the orientation of this lin lineation reflects the two stage deformation history of the area rather than the thrusting direction during a single orogenic event

the offshore boundary condition in surf zone modeling abstract numerical models predicting surfzone waves and shoreline runup in field situations are often initialized with shoreward propagating sea swell and infragravity waves at an offshore boundary in 10 30 m water depth we develop an offshore boundary condition based on fourier analysis of observations with co located current and pressure sensors that accounts for reflection and includes nonlinear phase coupling the performance of additional boundary conditions derived with limited or no infragravity observations are explored with the wave resolving nonlinear model swash 1d in some cases errors in the reduced boundary conditions applied in 11 m depth propagate shoreward whereas in other cases errors are localized near the offshore boundary boundary conditions that can be implemented without infragravity observations e g bound waves do not accurately simulate infragravity waves across the surfzone and could corrupt predictions of morphologic change however the bulk properties of infragravity waves in the inner surfzone and runup are predicted to be largely independent of ig offshore boundary conditions and dominated by ig generation and dissipation

non hydrostatic modelling of infragravity waves under laboratory conditions the non hydrostatic wave model swash is compared to flume observations of infragravity waves propagating over a plane slope and barred beach the experiments cover a range of infragravity wave conditions including forcing by bichromatic and irregular waves varying from strongly dissipative to strongly reflective so that model performance can be assessed for a wide range of conditions the predicted bulk wave parameters such as wave height and mean wave period are found to be in good agreement with the observations moreover the model captures the observed breaking of infragravity waves these results demonstrate that swash can be used to model the nearshore evolution of infragravity waves including nonlinear interactions dissipation and shoreline reflections

tectonic and chemical implications of cathodoluminescent microstructures in quartz parry sound domain ontario canada cathodoluminescence cl imaging of quartz in orthogneiss of the parry sound domain grenville province ontario canada reveals four dark microstructures medium dark grains mantles sinuous lines and straight lines the parry sound domain experienced granulite facies deformation and metamorphism followed by variable degrees of amphibolite facies retrogression associated with the development of retrograde shear zones we integrate our observations of cl visible quartz microstructures with structures observable with optical and scanning transmission electron microscopy analyses of water species concentration and trace element distribution in quartz as well as with microstructures in plagioclase to determine their characteristics and elucidate their timing and mechanisms of formation relative to the deformational history medium dark grains are primarily located in and near kilometer scale shear zones at the margins of the parry sound domain have notably darker cores than most samples in the interio

geochemical geochronological and isotopic constraints on the origin of members of the allochthonous shawanaga and basal parry sound domains central gneiss belt grenville province ontario abstract the sand bay and lighthouse lower and upper and armer bay gneiss associations comprise metasupracrustal rocks within respectively the shawanaga and basal parry sound domains elements of deep crustal thrust sheets of the central gneiss belt of the grenville province in ontario new and published geochemical isotope and detrital zircon data for metavolcanic and metasedimentary rocks of these gneiss associations suggest origin in one or more late mesoproterozoic laurentian margin back arcs mean nd values for the sand bay lower and upper lighthouse gneiss associations and the armer bay metavolcanic amphibolites are with the exception of sand bay close to dm values for their estimated time of eruption 2 8 5 6 5 0 and 4 2 respectively taken in conjunction with extant and new geochemical analyses and field relations these data are compatible with protoliths of all the units originating in rifted arcs or back arcs deposited on thin sand bay armer bay to vanishingly thin lighthouse pre existing crust detrital zircon data indicate the sand bay units are younger than ca 1260 ma the lower lighthouse unit formed after ca 1234 ma and metasediments close to the base of the upper lighthouse gneiss association formed at or after ca 1350 ma whereas deposition age at the top of the unit is estimated at less than ca 1249 ma a metasediment layer within the armer bay amphibolites has detrital ages clustered at 1251 ma similar to the upper lighthouse metasediments a quartz rich metasediment from the top of armer bay gneiss association is estimated to have a maximum age of deposition of ca 1322 ma the units represent one or more rifting events of the andean type laurentian margin in a post 1 35 ga episode s distinct from that documented in the muskoka ojibway arc at 1 45 ga as such they may be the tectonically reworked equivalents of rifted arcs and back arcs related to parry sound domain arc s and related to magmatic units of similar age in the composite arc belt

kwangsian crustal anatexis within the eastern south china block geochemical zircon u pb geochronological and hf isotopic fingerprints from the gneissoid granites of wugong and wuyi yunkai domains abstract gneissoid granites were traditionally thought to be the components of the precambrian basement in the eastern south china block but twenty four gneissoid granite samples from the wugong northern wuyi southern wuyi and yunkai domains gave zircon u pb ages of 424 456 ma 410 457 ma 426 438 ma and 415 450 ma respectively the existence of the abundant kwangsian gneissoid granites which have incorrectly been assigned to the precambrian basement indicates that the so called precambrian stratigraphic sequence of the cathaysia block should be termed complex rather than group these gneissoid granites are peraluminous granites with relatively high al 2 o 3 mgo tio 2 feot and cao na 2 o but low cao al 2 o 3 mgo feot and rb sr ratios they exhibit strongly negative ba sr nb p and ti and positive pb anomalies in primitive mantle normalized diagrams and have initial 87 sr 86 sr ratios ranging from 0 70924 to 0 72935 and negative end t values from 6 4 to 11 4 similar to those of paragneissic enclaves and precambrian sedimentary rocks in the eastern south china block the zircons crystallized in the kwangsian gneissoid granites gave ehf t values ranging from 2 4 to 19 4 with the peak at 4 almost all grains clustering at 1 to 12 and hf model ages of 1 1 2 1 ga the synthesis of these geochemical and in situ zircon hf isotopic data indicates that the kwangsian gneissoid granites dominantly originated from proterozoic metapelitic and meta igneous components with insignificant input of juvenile mantle derived magmas a model of two stage crustal anatexis is proposed for the kwangsian granitic magma in the eastern south china block with 1 the formation of 460 430 ma granite through the breakdown of hydrous minerals under the condition of the doubly thickened crust and 2 the generation of the 430 400 ma granite accompanying promoted melting along a path of isothermal decompression due to the increasing thermal weakening for the collapse of the thickened crust the crustal anatexis has probably occurred in an intracontinental tectonic regime that was geodynamically linked to the far field response to the assembly of the australian indian plate with the cathaysia block during middle paleozoic kwangsian time

evolution of stretching lineations in granulite hosted ductile shear zones eastern ghats province india role of temperature strain rate and pre existing stretching lineations abstract shear zone kinematics are interpreted from sections x z parallel to the stretching lineation x direction and perpendicular to the mylonitic foliation x y the stretching lineation is a product of finite strain defined by minerals or mineral aggregates that deform plastically in quartzofeldspathic rocks deformed below 600 c rheological contrasts between quartz and feldspar are amplified and the mesoscopic stretching lineation in the shears may be indistinct in outcrop as quartz ribbons anastomose around relatively competent feldspar clasts in high strain rate zones rheological contrasts between these minerals are reduced and a stretching lineation suitable for kinematic interpretation develops in late amphibolite and greenschist facies shear zones transecting pre lineated quartzofeldspathic granulites of the eastern ghats province india the stretching lineation represents the resultant of pre existing stretch and superposed increments of later shearing until the stretch accumulated in the x direction of the later deformation exceeds the earlier finite stretch the pre existing stretching lineation progressively rotates towards the later x direction with decreasing aspect ratio these intermediate lineation orientations have no kinematic relevance to either earlier or later deformations this example highlights the importance of temperature strain rate and orientation of pre existing stretching lineations in the appearance and kinematic interpretation of stretching lineations in ductile shear zones

how ductile are ductile shear zones three premises of ductile deformation in the middle and lower crust are widely accepted 1 rocks flow with power law viscous rheology 2 localization in ductile shear zones involves strain softening and 3 fluid flows into and is channelized within ductile shear zones ductile viscous shear zones should therefore initially develop along planes of maximum shear stress strain soften and rotate as material planes into the field of progressive extension however the mean stress or pressure within a weak elongate viscous band being stretched is higher than the surrounding matrix and this is difficult to reconcile with premise 3 in contrast mohr coulomb brittle faults always have lower pressure within the fault zone flow of fluid and melt into high temperature shear zones therefore implies that ductile shear zones are not perfectly viscous but have a pressure dependent viscoplastic rheology the continued pressure dependence may reflect significant microcracking on the grain scale even when localized deformation does not produce larger scale discrete fractures

himalayan tectonics explained by extrusion of a low viscosity crustal channel coupled to focused surface denudation recent interpretations of himalayan tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the tibetan plateau1 2 3 and that ductile extrusion of high grade metamorphic rocks between coeval normal and thrust sense shear zones can explain exhumation of the greater himalayan sequence4 5 6 7 here we use coupled thermal mechanical numerical models to show that these two processes channel flow and ductile extrusion may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low viscosity material our models provide an internally self consistent explanation for many observed features of the himalayan tibetan system8 9 10

solar signature in sedimentary cycles from the late precambrian elatina formation australia climatic cyclicity is recorded by regular variations in the thickness of varves in the elatina formation a late precambrian periglacial lake deposit in south australia earlier conclusions that the climatic cycles reflect solar variability are strongly supported by a complexity of periods revealed through study of drill cores of the varved sequence the new data promise to contribute significantly to our understanding of solar processes

wave transformation in the nearshore zone comparison between a boussinesq model and field data abstract a numerical model based on the boussinesq equations was developed to simulate wave transformation in the nearshore zone with emphasis on describing the effects of wave breaking two different formulations for estimating additional momentum due to depth limited wave breaking namely one proposed by watanabe and dibajnia watanabe a dibajnia m 1988 a numerical model of wave deformation in the surf zone proceedings of the 21st coastal engineering conference asce pp 578 587 and another one by schaffer et al schaffer h a madsen p a deigaard r 1993 a boussinesq model for waves breaking in shallow water coastal engineering 20 185 202 were incorporated and tested in the numerical wave model detailed high quality data from duck nc collected during the duck85 and superduck field experiments using photographic means were employed to evaluate the applicability of the boussinesq model to surf zone conditions also comparison with the field data allowed for an assessment of how well the two formulations could describe the effects of wave breaking on the evolution of the waveform model simulations were compared with measured time series of water surface elevation as well as with derived statistical quantities such as the skewness kurtosis and root mean square wave height overall the model results were satisfactory although the boussinesq model failed to accurately reproduce the strong nonlinear shoaling that occurred prior to breaking the roller model developed by schaffer et al produced somewhat better agreement with the data than the model proposed by watanabe and dibajnia however the difference was small and both formulations are judged to yield acceptable results although improvements are needed before the predictions can be used for calculating the sediment transport rate in intra wave models

toward modeling turbulent suspension of sand in the nearshore 1 we present two depth and phase resolving models based on single and two phase approaches for suspended sediment transport under water waves both models are the extension of a wave hydrodynamic model cornell breaking wave and structure cobras in the two phase approach dilute two phase mass and momentum equations are calculated along with a fluid turbulence closure based on balance equations for the fluid turbulence kinetic energy k f and its dissipation rate f in the single phase approach the fluid flow is described by the reynolds averaged navier stokes equations while the sediment concentration is calculated by an advection diffusion equation for the conservation of sediment mass the fluid turbulence is calculated by k f f equations that incorporate the essential influence of sediment which can also be consistently deduced from the two phase theory by adopting a commonly used sediment flux boundary condition near the bed the proposed models are tested against laboratory measurements of suspended sediment under nonbreaking skewed water waves and shoaling broken waves although the models predict wave averaged sediment concentrations reasonably well the corresponding time histories of instantaneous sediment concentration are less accurate we demonstrate that this is due to the uncertainties in the near bed sediment boundary conditions in addition we show that under breaking waves the near bed sediment pickup cannot be solely parameterized by the bottom friction suggesting that other effects may also influence the near bed sediment boundary conditions

softening the lower crust modes of syn transport transposition around and adjacent to a deep crustal granulite nappe parry sound domain grenville province ontario canada 1 the parry sound domain is a granulite nappe stack transported cratonward during reactivation of the ductile lower and middle crust in the late convergence of the mesoproterozoic grenville orogeny field observations suggest the following with respect to the ductile sheath 1 formation of a carapace of transposed amphibolite facies gneiss derived from and enveloping the western extremity of the parry sound domain and separating it from high strain gneiss of adjacent allochthons this ductile sheath formed dynamically around the moving granulite nappe through the development of systems of progressively linked shear zones 2 transposition initiated by hydration amphibolization of granulite facies gneiss by introduction of fluid along cracks accompanying pegmatite emplacement shear zones nucleated along pegmatite margins and subsequently linked and rotated the source of the pegmatites was most likely subjacent migmatitic and pegmatite rich units or units over which parry sound domain was transported comparison of gneisses of the ductile sheath with high strain layered gneiss of adjacent allochthons show the mode of transposition of penetratively layered gneiss depended on whether or not the gneiss protoliths were amphibolite or granulite facies tectonites before initiation of transposition resulting in e g folding before shearing no folding before shearing respectively meter scale truncation along high strain gradients at the margins of both types of transposition related shear zones observed within and marginal to parry sound domain mimic features at kilometer scales implying that apparent truncation by transposition originating in a manner similar to the ductile sheath may be a common feature of deep crustal ductile reworking

interplay between folding and ductile shearing in the proterozoic crust of the muskoka parry sound region central ontario grenville gneiss of the central georgian bay region was subjected to ductile deformation that produced narrow mylonite zones as well as three sets of superimposed folds differing greatly in structural signature size and orientation some mylonite zones are concordant to gneissosity and are repeatedly folded others cut gneissosity and postdate the folding gneissosity was generated as a regionally subhorizontal feature either by crustal thinning or like the early mylonite zones by low angle reverse shearing an attempt is made to account for the initially subhorizontal gneissosity the mylonite zones and the folds in a regime of large scale reverse shearing that strikes parallel to the grenville front upright northwest southwest to north south buckle folds dominate the map pattern and are subperpendicular to the reverse grenville front boundary fault these set 2 folds cannot be attributed to reverse simple shearing but require a large component of east west compression such stress could have been

buckle folding and deep crustal shearing of high grade gneisses at the junction of two major high strain zones central gneiss belt grenville province ontario low plunging transport parallel f3 folds are common at all scales in the central gneiss belt of the grenville province but few of these folds are sheath folds where the d1 d2 parry sound shear zone intersects the d3 shawanaga shear zone ssz at a high angle f3 folds formed at several scales centimetre to greater than outcrop scale in layered d1 d2 straight gneisses at the start of their evolution the f3 folds formed just beyond the ssz with hinges near orthogonal to the d3 shear direction and with typical buckle features e g wavelengths vary with layer thickness and hinges are discontinuous and bifurcate the buckle folds evolved within the ssz by rotation of hinges towards the shear direction even though hinges initiated at a high angle to the shear direction sheath folds were not produced in addition to tightening the buckles the ductile reorientation produced thin thick extended shortened limb pairs and very straight ridge like fold hinges and removed small folds from the extended

magnitude of weakening during crustal scale shear zone development we describe and apply a field based approach for calculating the bulk strength of a heterogeneous material to a crustal scale shear zone defining the margin of the ma parry sound domain in the grenville province of southeastern ontario using a numerical method we calculate bulk strength defined as effective viscosity as the ratio between the surface traction needed to deform a square block in simple shear and the velocity gradient across that block we use natural shear zone geometries to define the internal block structure and assign internal relative viscosities based primarily on textural criteria the margin of the parry sound domain developed into the km scale twelve mile bay shear zone accommodating several tens of km of transport while the domain interior remained rigid fracturing and fluid infiltration drove development of an amphibolite facies meter scale shear zone network that evolved into the twelve mile bay structure we analyzed three sites across the w5 km wide strain gradient from near the granulitic domain to the large scale shear zone the rocks at the shear zone margin weakened by approximately 30 those in the core weakened by at least 77 and probably by an order of magnitude these values lie between but differ substantively from the isostress and isostrain rate bounds indicating that a numerical approach such as presented here markedly improves the accuracy of bulk strength calculations

quantitative estimation of exponents of power law flow with confidence intervals in ductile shear zones abstract talbot journal of structural geology 21 1535 1551 1999b introduced a new model for ductile shear zones as counterflow boundaries in pseudoplastic power law fluids and demonstrated that natural shear zones empirically fit theoretical curves generated by his model thus estimates of the power law exponent relating stress and strain are deduced it is shown here how application of standard non linear statistical techniques to shear zone displacement data allows quantitative estimation of the power law exponent together with confidence intervals of the calculated value application to natural shear zones verifies the method and also validates the applicability of the model it is hoped that this will encourage field geologists to apply the model of talbot to natural examples thereby a database of power law exponents for a wide variety of lithologies and metamorphic grades may be assembled

swash on a gently sloping beach waves observed in the inner surf and swash zones of a fine grained gently sloping beach are modeled accurately with the nonlinear shallow water equations the model is initialized with observations from pressure and current sensors collocated about 50 m from the mean shoreline in about i m depth and model predictions are compared to pressure fluctuations measured at five shoreward locations and to run up run up was measured with a vertical stack of five wires supported parallel to and above the beach face at elevations of 5 10 15 20 and 25 cm each 60 m long run up wire yields time series of the most shoreward location where the water depth exceeds the wire elevation as noted previously run up measurements are sensitive to the wire elevation owing to thin run up tongues not measured by the more elevated wires as the wire elevation increases the measured mean run up location moves seaward low frequency infragravity energy decreases and higher frequency sea swell energy increases these trends as well as the variation of wave spectra and shapes e g wave skewhess across the inner surf zone are well predicted by the numerical model

surf zone dynamics simulated by a boussinesq type model part i model description and cross shore motion of regular waves abstract this is the first of three papers on the modelling of various types of surf zone phenomena in this first paper part i the model is presented and its basic features are studied for the case of regular waves the model is based on two dimensional equations of the boussinesq type and it features improved linear dispersion characteristics possibility of wave breaking and a moving boundary at the shoreline the moving shoreline is treated numerically by replacing the solid beach by a permeable beach characterized by an extremely small porosity run up of nonbreaking waves is verified against the analytical solution for nonlinear shallow water waves the inclusion of wave breaking is based on the surface roller concept for spilling breakers using a geometrical determination of the instantaneous roller thickness at each point and modelling the effect of wave breaking by an additional convective momentum term this is a function of the local wave celerity which is determined interactively the model is applied to cross shore motions of regular waves including various types of breaking on plane sloping beaches and over submerged bars model results comprise time series of surface elevations and the spatial variation of phase averaged quantities such as the wave height the crest and trough elevations the mean water level and the depth averaged undertow comparisons with physical experiments are presented the phaseaveraged balance of the individual terms in the momentum and energy equation is determined by time integration and quantities such as the cross sectional roller area the radiation stress the energy flux and the energy dissipation are studied and discussed with reference to conventional phase averaged wave models the companion papers present cross shore motions of breaking irregular waves swash oscillations and surf beats part ii and nearshore circulations induced by breaking of unidirectional and multidirectional waves part iii

bars bumps and holes models for the generation of complex beach topography in shallow water any two waves of the same frequency are shown to produce complex patterns of drift velocity above the sea bed if the longshore components hi h of the wave numbers of the two waves are different these steady flow patterns exhibit a longshore periodicity of wave number hi h irrespective of whether the waves propagate in the same direction say hi he positive or in opposite directions he negative the interaction of two edge wave modes is examined in detail the drift velocities are calculated and a simple sediment transport model is used to predict the beach topography that would be in equilibrium with these flow patterns as expected crescentic sand bars are produced by the special case of standing edge waves hi h intriguingly for all other cases a combination of complex transverse bars plus meandering or straight offshore bars result patterns that are surprisingly reminiscent of many published descriptions of complex rhythmic topography the extension of the model to three or more waves produces topography that appears to be very irregular although the pattern should repeat over sufficiently long distances along the beach even with only three waves these distances may be very large compared to the scale of the bars

origin and incremental evolution of brittle ductile shear zones in granitic rocks natural examples from the southern abitibi belt canada abstract metre scale shear zones developed in the mooshla granitic pluton exhibit a plethora of internal mesoand microstructures revealing their mode of nucleation growth and termination the subvertical e w brittle ductile shear zones are developed in the most isotropic part of the intrusion and consist of phyllonites characterized by mylonitic fabrics and well developed down dip mineral lineations they are exposed on a single large and flat outcrop perpendicular to the mineral lineation these brittle ductile shear zones are in close spatial association with a fracture system along which they have nucleated and propagated joints fractures and brittle faults contain abundant evidence of ductilely deformed and recrystallized minerals suggesting that they underwent ductile shearing after their formation the deformation was accompanied by the influx of a metasomatic fluid which altered original fe mg bearing minerals and plagioclase into quartz epidote chlorite sericite and carbonate that precipitated in dilatant fractures and narrow breccia zones we recognize two different types of lateral terminations i shear zones that terminate into joints and fractures that are parallel or oblique to the shear direction and ii curved segments of shear zones that connected with neoformed splay fractures at high angle to the shear direction in the latter case sharp bending and severe perturbation of the shear zone orientation occur at the shear zone termination where ductile shearing is transfered into an adjacent shear zone via dilatational fractures this demonstrates that shear zones tended to grow towards each other and coalesce to form a well developed anastomosing network we propose that narrow dilatational fractures and joints acted as paleo weakness planes along which fluid rock interaction and resulting reaction softening occurred the deformation scenario involves episodic fluid drawn into dilatant sites responsible for cyclic fluid pressure fluctuation in the system dilatancy related fracturing and reaction softening lead to deformation under brittle to plastic conditions and to shear strain localization