comparative stratigraphy and subsidence history of mesozoic rift basins of north atlantic mesozoic rift basins around the north atlantic all possess many of the following upper jurassic to lower cretaceous oxfordian to albian stratigraphic elements 1 an early oxfordian hiatus 2 backfill deposits in upper jurassic paleovalleys 3 multiple tithonian transgressive regressive sequences 4 early berriasian regressive sequences 5 a sub valanginian unconformity overlain by coarse siliciclastic sandstones and conglomerates 6 valanginian to hauterivian fining upward sequences 7 condensed barremian sequences and 8 prominent aptian unconformities more local features include abrupt kimmeridgian deepening lusitanian basin portugal albian deepening cantabrian and aquitaine basins northern spain and southern france and late albian early cenom nian source rejuvenation cantabrian basin northern iberia decompaction and backstripping of sediments from well and outcrop sections in six basins also reveal broad similarities in trends of rates of apparent basement subsidence relatively high rates 50 100 m m y characterize onset of rift phases in the triassic and the kimmeridgian locally in the lusitanian basin of portugal kimmeridgian rates reach about 250 m m y in the cantabrian and aquitaine basins a third phase of rapid subsidence characterizes the aptian albian interval after the main phase of continental breakup around iberia this phase may be due to transtensional stresses as iberia continued to rotate relative to europe tensional intraplate stresses or gravity driven partial collapse of the new continental marg n the north atlantic mesozoic basins share many features because they had a common origin controlled by intracontinental rifting and subsequent separation of europe and north america pulses of extension generally are reflected in the stratigraphy of all of the basins superimposed on this record are the effects of eustatic sea level variations the main difference between the canadian jeanne d arc basin and iberian basins is the significantly greater early and middle jurassic basement subsidence rate in the former about 40 m m y vs 0 10 m m y this difference may result from prolonged extension on the canadian side perhaps due to northward transfer of shear stress from left lateral transform motion between the grand banks and northwestern africa

remarkable bathymetric change in the nearshore zone by the 2004 indian ocean tsunami kirinda harbor sri lanka we investigated bathymetric data obtained at kirinda harbor sri lanka one month before and 2 and 11 months after the 2004 indian ocean tsunami our bathymetric surveyed data and numerical modeling results suggest that the first run up tsunami wave transported huge amounts of offshore sea bottom sediment and deposited it in a layer up to 4 m thick along the shoreface slope in some places this accreted sediment was not eroded by the backwash because of the particular arrangement of artificial structures and sand dunes especially the sedimentation process and the volume of the sediment transported by the run up waves can be examined where the influence of the backwash flow was very minor remarkable sedimentation attributable to the run up wave would have occurred mainly by the deposition of the sediment particles along the slope by the run up waves the slope was developed toward the stoss side rather than by the settlement of the sediment from the suspension load we estimated that considerable amounts of sediment were transported by the tsunami from the offshore sea bottom but most were deposited not on land but in the sea eleven months after the tsunami the harbor bathymetry had almost undergone complete reversion to its pre tsunami condition implying that the tsunami impact on permanent geomorphological landforms was limited at this harbor

high pressure 2000 mpa kyanite and glaucophane bearing pelitic schist and eclogite from cordillera de la costa belt venezuela in the cretaceous melange of the cordillera de la costa belt introduction north central venezuela there are knockers of eclogite barroisitetwo belts of high pressure hp low temperature lt bearing eclogite and pelitic glaucophane schist these occur in a metamorphic rocks are exposed in the caribbean mounmetamorphic melange matrix that locally consists of marble sertain system of northern venezuela which is part of the pentinite amphibolite actinolite schist feldspathic schist and gneiss complex east west trending boundary zone between the graphitic schist chloritoid schist and garnet bearing mica schist caribbean and south american plates e g menendez the protoliths for these various rock types exhibit a wide age range 1966 1967 these two belts are the cordillera de la cambrian to early cretaceous recently discovered knockers of costa and villa de cura belts both of which were pelitic glaucophane schist contain mg glaucophane paragonite metamorphosed during the mid cretaceous presumably kyanite garnet talc graphite rutile quartz in a subduction zone related to the mid cretaceous the coexistence of kyanite and mg glaucophane suggests minimum leeward antilles volcanic arc e g pindell 1993 from p 2000 mpa at t 600 c eclogite knockers from the same jurassic to eocene time north and south america were outcrop contain garnet and clinopyroxene which yield 500 c for diverging and new proto caribbean sea floor was created cores 700 c for rims and p 1200 mpa the assemblage between them e g pindell 1993 therefore the leegarnet biotite phengite albite within schists of the melange matrix ward antilles arc as well as the entire caribbean mounof this locality indicates metamorphic conditions of t tain system are allochthonous and formed far to the 450 520 c at p 1800 mpa because all lithologies in this west as part of the farallon north south american plate outcrop record high p conditions this metamorphic melange formed boundary zone e g pindell 1993 before or during peak metamorphism in a mid cretaceous subduction although the two hp lt belts have similar metazone morphic ages they differ greatly in lithology and metamorphic history the cordillera de la costa belt consists of oceanic and passive continental margin rocks intermixed with paleozoic granites and granitic gneisses in this belt the eclogites and blueschists were retrograded to epidote amphiboliteand greenschist facies assemblages following an apparent p t path typical for

a phase resolving cross shore sediment transport model for beach profile evolution abstract a phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the on offshore sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone the vertical variation of the mean undertow and the intra wave sediment concentrations are calculated the net sediment transport rates are calculated and the equation for conservation of sediment is solved to predict the beach profile evolution the results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating in all parts of the surf zone even for eroding beaches suggesting that other contributions should not be neglected the present model also showed that for the same offshore wave energy the time series of the oscillatory motion is important and that the effect of wave groups cannot be disregarded

the cretaceous tertiary boundary cocktail chicxulub impact triggers margin collapse and extensive sediment gravity flows a distinctive mixture of reworked microfossils impact derived materials and lithic fragments occurs in sediments at the cretaceous tertiary boundary in the basinal gulf of mexico and caribbean we have named this mixture the cretaceous tertiary boundary cocktail lithologic and paleontologic evidence suggests that the cocktail was deposited by giant sediment gravity flows apparently triggered by the collapse of continental margins around the gulf of mexico as a result of the chicxulub impact as most microfossils in the gravity flow units are reworked biostratigraphy provides only maximum ages recognition of the cocktail is a reliable way to identify cretaceous tertiary boundary deposits in the basinal gulf of mexico and caribbean

sediment scour and deposition within harbors in california usa caused by the march 11 2011 tohoku oki tsunami abstract tsunamis have caused significant damage to boats and docks within harbors and ports along the california coast sediment scour and deposition within harbors by tsunamis though not extensively studied have produced long term impacts to the recovery and resiliency of affected maritime communities the march 11 2011 tohoku oki teletsunami generated strong tsunami currents up to 7 m s or 14 kn within crescent city and santa cruz harbors that triggered sedimentation problems regulatory issues with sediment disposal and months of delays in the reconstruction process evaluation of video pre and post tsunami bathymetric surveys and harbor sediment analysis data helped develop a better understanding of tsunami flow regime and sediment transport within these harbors in crescent city the scour effects of large tsunami surges were amplified by the narrow entrance to the small boat basin increasing the sediment supply and trapping this material within the basin causing shoaling that made the harbor unusable and creating long term disposal issues within the entire harbor at least 289 400 m3 of sediment was scoured in an area of 0 67 km2 a minimum fill volume of 154 600 m3 was calculated with the sediment covering 55 of that portion of the harbor included in the bathymetric surveys in santa cruz the long constricting layout and shallow nature of the harbor increased current velocities and scour in confined areas and exacerbated sedimentation in between and beneath docks at the harbor entrance estimated scour volumes range from 2550 to 14 800 m3 and fill estimates range from 120 to 8750 m3 depending upon the surveys used to characterize post tsunami conditions while the area of deposition ranges from 6 to 64 of the survey overlap areas about 83 m3 of sediment was scoured in santa cruz north harbor while a minimum of 75 m3 was deposited across 50 of that portion of the harbor common to pre and post tsunami surveys fill estimates are considered minimums due to sediment deposited in locales not covered by the various surveys in general the southern part of the harbor near the entrance jetties was erosional while most of the northern part of the harbor was depositional analyses of tsunami currents observed on videos collected during the tsunami provide excellent support for the bathymetric change analyses and together the two lines of evidence provide a means to predict flow patterns and areas at risk of damage from the tsunami by assessing harbor dimensions and layout and analyzing observations video from past tsunamis reducing constrictions and deepening channels within harbors would greatly reduce tsunami current speeds and the potential for scour the maritime community and state regulatory agencies should work together to streamline the review process to assist recovery efforts after significant tsunamis

formation of a jump by the dam break wave over a granular bed a previously unreported shock feature associated with the scouring of a horizontal granular bed by a dam break wave is discussed near the wave centre the present study shows the free surface breaks backward and a hydraulic jump forms this behaviour is described from the standpoint of shallow water theory suitably extended to deal with non equilibrium sediment transport the shock formation involves a particularly strong coupling between flow free surface evolution and bed morphodynamics support for our conclusions is sought through experimental and numerical approaches in order to magnify the observed phenomena measurements were performed for the case of light bed particles moving in sheet and debris flow modes a detailed picture of the transient two phase flow is presented based on whole field acquisition of the grain motions by particle tracking techniques corresponding shallow water solutions are constructed numerically using a shock capturing scheme finally an interpretation of the jump formation is proposed based on the theory of characteristics

origin of ultramafic hosted magnesite on margarita island venezuela ultramafic hosted deposits of magnesite mgco3 have been studied on margarita island venezuela to elucidate the source of carbon and conditions of formation for this type of ore petrographic mineralogic and 18o data indicate that magnesite precipitated on margarita in near surface environments at low p and t 13c ranges from 9 to 16 pdb within the magnesite and 8 to 10 pdb within some calcite and dolomite elsewhere on the island the isotopically light dolomite fills karst and the calcite occurs as stock work veins which resemble the magnesite deposits these carbon isotopic ratios are consistent with a deep seated source rather than an overlying source from a zone of surficial weathering however there is not much enrichment of precious metals and no enrichment of heavy rare earth elements as would be expected if the carbon had migrated upward as aqueous carbonate ions the carbon probably has risen as a gaseous mixture of co2 and ch4 which partially dissolved in near surface water before leaching cations and precipitating as magnesite and other carbonates the process probably is ongoing given regional exhalation of carbonaceous gases

tsunami deposits from the 1993 southwest hokkaido earthquake and the 1640 hokkaido komagatake eruption northern japan the southwest hokkaido tsunami of july 12th 1993 left continuous onshore sand deposits along the west coast of oshima peninsuka hokkaido northern japan we investigated spatial distribution and lithofacies of the new tsunami deposits for its identification of ancient tsunami deposits an eyewitness acount and bent plants helped our interpretation of the onshore tsunami behavior we regard the following properties as typical of the coastal tsunami sand deposits 1 the deposits cover the surface almost continuously on gentle topography 2 deposit thicknesses and mean grain sizes descrease with distance from the sea 3 deposit thicknesses and lithofacies vary greatly across local surface undulation 4 graded bedding reflecting tsunami runup and backwash is present in thick deposits 5 the deposits are widely distributed along the coast and extend inland several tens of meters to 100 m we examined a candidate for the paleo tsunami deposits associated with the 1640 komagatake eruption and confirmed that the similar patterns are typical of ancient tsunami deposits

field investigation of three dimensional flow structure at stream confluences 2 turbulence stream confluences are among the most highly turbulent locations in fluvial systems this paper examines the three dimensional structure of turbulence at three stream confluences in east central illinois the analysis focuses on the characteristics of turbulence both within the shear layer and in the ambient flow results show that at the upstream end of each confluence the shear layer occupies a limited portion of the flow cross sectional area but turbulence kinetic energy within this layer is 2 3 times greater than the turbulence kinetic energy of the ambient flow which has turbulence characteristics similar to those for flow in straight channels turbulence within the shear layer can be characterized as quasi two dimensional in the sense that large scale turbulence generated by transverse shear is predominantly two dimensional whereas small scale turbulence associated with bed friction is three dimensional spectral analysis suggests that the structure of fluid motion within the shear layer differs for confluences with symmetrical versus asymmetrical planforms the shear layer dissipates rapidly as flow enters the downstream channel even though a well defined mixing interface persists at downstream locations

hydrodynamics and sediment transport in the swash zone a review and perspectives the dominant hydrodynamic forcing and resulting sediment transport mechanisms in the swash zone are reviewed combined with a discussion of future measurement and modelling requirements the importance of swash zone processes in the overall behaviour of the nearshore littoral zone are identified with the paper subsequently focusing on aspects that directly relate to sediment transport on beaches the review considers analytical and numerical modelling work and both field and laboratory data the hydrodynamics of the swash zone are first discussed with reference to the surf zone boundary swash characteristics forcing mechanisms and shoreline oscillations subsequent sections consider more micro scale processes such as the internal flow kinematics turbulence the bed boundary layer and infiltration exfiltration through permeable beds the second part of the paper outlines the fundamental mechanics of sediment transport in the swash zone followed by a more detailed discussion of sediment transport modes induced by the dominant hydrodynamic conditions modelling concepts are reviewed and the strengths and weaknesses of different approaches identified a final summary and future modelling perspectives conclude the paper

h2d morphodynamic model considering wave current and sediment interaction abstract a morphodynamic model for weakly dispersive wave and shallow flows in horizontal two dimensional h2d space is proposed the horizontal density variation and the bottom evolution are incorporated into a fully nonlinear boussinesq equation including vorticity effects by coupling the flow equation with the depth integrated sediment transport equation morphodynamic simulation is made possible a fourth order finite volume method with an approximate riemann solver is used to solve the governing equations for the hydrodynamic test under strong wave current interaction environment the accuracy of the computed velocity and water surface was verified for the three typical morphological benchmark tests such as tsunami regular wave and dam break flow good agreement was obtained when proper parameters were provided therefore the proposed morphodynamic model can be a useful tool for a wide range of shallow and wavy flows under dispersive and nonhydrostatic environments associated with wave current and sediment interaction

numerical models of tsunami sediment transport current understanding and future directions abstract researchers who study tsunami deposits share common ultimate goals of their work which are to better assess the magnitude information of paleotsunamis and to contribute to the assessment of future tsunami risks numerical modeling of tsunami sediment transport is an important piece of interdisciplinary research that fills the gap between geological studies and practical utilization of tsunami deposits forward and inverse numerical models that address tsunami transport of sand and boulders have been developed over the last two decades forward models are capable of delineating the time evolution of tsunami hydrodynamics sediment transport and the resulting morphological changes associated with erosion and deposition inverse models estimate tsunami characteristics such as flow speed and depth from deposits numerical modeling can be used not only to quantify paleotsunamis but also to enhance our understanding of tsunami sedimentology and hydrodynamics to make progress towards the ultimate goal of improved tsunami risk assessment development of an in depth mutual understanding between modelers and geologists of the advantages limitations and uncertainties in both numerical modeling and geological records is an important challenge

basin evolution of the northern part of the northeast german basin insights from a 3d structural model abstract a 3d structural model for the entire southwestern baltic sea and the adjacent onshore areas was created with the purpose to analyse the structural framework and the sediment distribution in the area the model was compiled with information from several geological time isochore maps and digital depth maps from the area and consists of six post rotliegend successions the upper permian zechstein lower triassic middle triassic upper triassic jurassic cretaceous and cenozoic this structural model was the basis for a 3d backstripping approach considering salt flow as a consequence of spatially changing overburden load distribution isostatic rebound and sedimentary compaction for each backstripping step in order to reconstruct the subsidence history in the region this method allows determination of the amount of tectonic subsidence or uplifting as a consequence of the regional stress field acting on the basin and was followed by a correlation with periods of active salt movement in general the successions above the highly deformed zechstein evaporites reveal a thickening trend towards the gluckstadt graben which also experienced the highest amount of tectonic subsidence during the mesozoic and cenozoic two periods of accelerating salt movement in the area has been correlated with the e w directed extension during the late triassic early jurassic and later by the late cretaceous early cenozoic inversion suggesting that the regional stress field plays a key role in halokinesis the final part of this work dealt with a neotectonic forward modelling in an attempt to predict the future topography when the system is in a tectonic equilibrium the result reveals that many of the salt structures in the region are still active and that future coastline will run with a wnw ese trend arguing that the compressional stresses related to the alpine collision are the prime factor for the present day landscape evolution

diachronous evolution of late jurassic cretaceous continental rifting in the northeast atlantic west iberian margin 1 regional 2 d seismic reflection profiles outcrop and borehole data are used to characterize the evolution of deep offshore sedimentary basins in southwest iberia alentejo basin the interpreted data indicate the bulk of late jurassic earliest cretaceous subsidence occurred in the present day continental slope area as shown by 1 significant thickening of synrift strata basinward from a slope bounding fault system sfs west of which the total thickness of sediment can reach more than 9 0 km and 2 relatively thin mesozoic strata east of the sfs where thickening of synrift units against principal faults is limited five principal regressive events and their basal unconformities reflect tectonic uplift and relative emersion in proximal basins which were located on the rift shoulder to subsiding tilt blocks west of the sfs these regressive events are correlated with major rift related events occurring on the deeper margin direct comparisons with the peniche basin of northwest iberia reveal that significant portions of the iberian lower plate margin were uplifted and eroded during the last stages of continental rifting this process was repeated at different times and in different areas as the locus of rifting and continental breakup migrated northward as a result two distinct rift axes are recognized in west iberia a first axis extending from the porto basin to the alentejo basin and a second axis located on the outer proximal margin north of 38 30n in addition the sfs delimited 1 prograding deposits of cretaceous paleogene age and 2 late cenozoic deposits draping the modern continental slope these latter facts demonstrate that on lower plate passive margins the relative position of the continental slope is established during the final rifting episode s preceding continental breakup

computational dam break hydraulics over erodible sediment bed this paper presents one of the first dedicated studies on mobile bed hydraulics of dam break flow and the induced sediment transport and morphological evolution a theoretical model is built upon the conservative laws of shallow water hydrodynamics and a high resolution numerical solution of the hyperbolic system is achieved using the total variation diminishing version of the second order weighted average flux method in conjunction with the hllc approximate riemann solver and superbee limiter it is found that a heavily concentrated and eroding wavefront first develops and then depresses gradually as it propagates downstream in the early stage of the dam break a hydraulic jump is formed around the dam site due to rapid bed erosion which attenuates progressively as it propagates upstream and eventually disappears while the backward wave appears to migrate at the same speed as over a fixed bed the propagation of the forward wavefront shows a complex picture compared to its fixed bed counterpart as a result of the domination of rapid bed erosion initially the density difference between the wavefront and the downstream ambient water in the intermediate period and the pattern of the deformed bed profile in the long term it is also found that the free surface profiles and hydrographs are greatly modified by bed mobility which has considerable implications for flood prediction the computed wave structure in the intermediate period exhibits great resemblance to available experiments qualitatively and yet the existence of a shear wave is found in lieu of a secondary rarefaction postulated in an existing analysis finally the use of the complete rather than simplified conservation equations is shown to be essential for correct resolution of the wave and bed structures which suggests that previous models need reformulating

pooled subsidence records from numerous wells reveal variations in pre break up rifting along the proximal domains of the iberia newfoundland continental margins the iberia newfoundland continental margin is one of the most studied conjugate margins in the world however many unknowns remain regarding the nature of rifting preceding its break up we analyse a large dataset of tectonic subsidence curves created from publicly available well data to show spatial and temporal trends of rifting in the proximal domains of the margin we develop a novel methodology of bulk averaging tectonic subsidence curves that can be applied on any conjugate margin with a similar spread of well data the method does not rely on the existence of conjugate deep seismic profiles and specifically attempts to forego the risk of quantitative bias derived from localized anomalies and uncertain stratigraphic dating and correlation results for the iberia newfoundland margin show that active rift driven tectonic subsidence occurred in the central segment of the conjugate margin from c 227 ma early norian to c 152 1 ma early tithonian in the southern segment from c 208 5 ma early rhaetian to c 152 1 ma early tithonian and in the northern segment from c 201 3 ma early hettangian to c 132 9 ma early hauterivian this indicates that rifting in the stretching phase of the proximal domain of the iberia newfoundland margin does not mirror hyperextended domain rifting trends south to north that ultimately led to break up the insights into broad scale three dimensional spatial and temporal trends produced using the novel methodology presented in this paper provide added value for interpretation of the development of passive margins and new constraints for modelling of the formation of conjugate margins

concurrent correction method for modeling morphological response to dredging an offshore sandpit abstract in modeling the morphological impact of an offshore dredging pit using a process based model the hydrodynamic conditions often derived from regional scale models and sometimes incomplete measurements may not be in equilibrium with the initial bathymetry profile before dredging this lack of equilibrium causes a fast profile adjustment toward an equilibrium which may bias the model results representing the direct effect of the pit in this study a method is described which uses the parallel computing technique and evaluates only the morphological changes due to a single factor i e the dredging of a pit the hydrodynamics and morphodynamics are assumed to be in equilibrium before initial dredging of the pit the morphological evolution is computed based on the change of sediment flux due to the presence of the pit the model can avoid the computational demanding spin up period necessary to reach equilibrium conditions in particular the concurrent correction method is efficient for scenario testing with a large amount of morphological settings and hydrodynamic 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

sand suspension storage advection and settling in surf and swash zones a time dependent cross shore sediment transport model in the surf and swash zones on beaches is developed to predict both beach accretion and erosion under the assumptions of alongshore uniformity and normally incident waves the model is based on the depth integrated sediment continuity equation which includes sediment suspension by turbulence generated by wave breaking and bottom friction sediment storage in the entire water column sediment advection by waves and wave induced return current and sediment settling on the movable bottom the hydrodynamic input required for this sediment transport model is predicted using the finite amplitude shallow water equations including bottom friction the developed model is compared with three large scale laboratory tests with accretional neutral little and erosional beach profile changes under regular waves the model predicts sediment suspension under the steep front of breaking waves and due to bottom friction in the swash zone the computed depth averaged sediment concentration does not respond to local sediment suspension instantaneously because of the sediment storage and advection the mean sediment concentration becomes large in comparison to the oscillatory concentration with the decrease of the normalized sediment fall velocity the net cross shore sediment transport rate is shown to be the small difference between the onshore transport rate due to the positively correlated oscillatory components of the suspended sediment volume per unit area and the horizontal sediment velocity and the offshore transport rate due to the product of the mean suspended sediment volume and the mean horizontal sediment velocity relatedly the net accretion or erosion rate of the movable bottom is determined by the small difference between the mean sediment settling rate and the mean suspension rate caused by wave breaking and bottom friction the present computation is limited to the initial beach profile change but the numerical model is capable of predicting the accretional erosional and neutral profile changes

reconstruction of tertiary progradation and clinoform development on the new jersey passive margin by 2 d backstripping we have reconstructed the oligocene to middle miocene paleobathymetry and stratigraphy of the new jersey margin using a modified backstripping technique by analyzing the geometry of the margin through time we investigate its response to fluctuating sea level changing climate and variable sediment supply during the tertiary the reconstructions reveal a change in the margin morphology from a more steeply dipping 1 300 to 1 500 carbonate ramp in the eocene to a flatter shelf with a sharp shelf edge at present this was accomplished by an increase in the terrigenous sediment supply that filled available accommodation and caused progradation across the margin we link the increase in sediment flux with climatic cooling rather than tectonic processes the progradation is evidenced by a series of clinoforms whose formation was modulated by sea level and which extend over 100 km across the shelf the height and dip of the clinoforms increased as they extended onto the deeper parts of the earlier ramp the miocene clinoform rollovers at the new jersey margin had water depths of60 130 m and are interpreted as the edge of a new continental shelf built over the older ramp sea level fall was probably insufficient to drive the miocene shorelines past the shelf breaks thus measurements of sea level amplitude based upon coastal onlap over the clinoforms are not reliable 1999 elsevier science b v all rights reserved

hydrodynamic modeling of tsunamis from the currituck landslide article i nfo article history accepted 24 september 2008 tsunami generation fromthe currituck landslide offshore northcarolina and propagation of waves towardthe u s coastline are modeled based on recent geotechnical analysis of slide movement a long and intermediate wave modeling package coulwave based on the non linear boussinesq equations are used to simulate the tsunami this model includes procedures to incorporate bottom friction wave breaking and overland flow during runup potential tsunamis generated from the currituck landslide are analyzed using four approaches 1 tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses 2 a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation 3 wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis and 4 a high resolution 1d model isdeveloped to accuratelymodel wavebreakingand the combined influence of nonlinearity and dispersion during nearshore propagation and runup the primary source parameter that affects tsunami severity for this case study is landslide volume with failure duration having a secondary influence bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation the high resolution 1d model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking generating independent short period waves wave breaking occurs approximately 40 50 km offshore where a tsunami bore is formed that persists during runup these analyses illustrate the complex nature of landslide tsunamis necessitating the use of detailed landslide stability mobility models and higher order hydrodynamic models to determine their hazard published by elsevier b v

sediment transport modeling review current and future developments the use of computational models for solving sediment transport and fate problems is relatively recent compared with the use of physical models several considerations govern the choice between physical and computational models namely the nature of the problem that needs to be solved the available resources and the overall cost associated with the problem solution in some specific problems a combination of physical and computational models can be used to obtain a better understanding of the processes under investigation de vries 1973 using computational hydrodynamic sediment transport models in general involves the numerical solution of one or more of the governing differential equations of continuity momentum and energy of fluid along with the differential equation for sediment continuity an advantage of computational models is that they can be adapted to different physical domains more easily than physical models which are typically constructed to represent site specific conditions another advantage of computational models is that they are not subject to distortion effects of physical models when a solution can be obtained for the same flow conditions identical reynolds and froude numbers same length scale in the three directions etc as those present in the field with the rapid developments in numerical methods for fluid mechanics computational modeling has become an attractive tool for studying flow sediment transport and associated pollutant fate processes in such different environments as rivers lakes and coastal areas representative processes in these environments include bed aggradation and degradation bank failure local scour around structures formation of river bends fining coarsening and armoring of streambeds transport of point source and nonpoint

p t conditions for the eclogitic re equilibration of the metaophiolites from val d ala di lanzo internal piemontese zone western alps abstract a study has been made of the high pressure early alpine re equilibration in the eclogites and metasedimentary cover of the val d ala di lanzo ophiolite all of the main high pressure minerals have been analysed and their compositions used to determine re equilibration temperatures the minimum conditions proposed p 1 3 gpa t 450 460 c are also indicated by the presence of a jadeite quartz bearing metagranite the temperatures are compared with those reported for similar eclogites from the voltri group the aosta valley and the valais comparison of recalculated temperatures shows that the temperature and probably the pressure of the eclogitic re equilibration increased in the aosta valley and the valais in keeping with what has been observed in the internal penninic basement of the gran paradiso and monte rosa crystalline massifs

large scale laboratory observations of wave breaking turbulence over an evolving beach 1 wave breaking turbulence over an evolving beach was observed in a large scale laboratory flume as part of the cross shore sediment transport experiment crosstex the data set included comprehensive measurements of water surface elevation fluid velocity and morphology for irregular waves under erosive and accretive wave conditions for the both conditions the beach reached a quasi equilibrium state defined as when the bar shape was stable wave breaking characteristics such as wave heights average rate of energy dissipation by bores and surf similarity parameter were investigated in response to morphodynamics of the bar turbulent kinetic energy tke was estimated using the method by shaw and trowbridge 2001 as the beach evolved a less amount of tke was observed at the trough for the erosive case while more tke was observed at the trough for the accretive case it was also found that the temporal variation of the time averaged tke were closely associated with the average rate of energy dissipation by bores comparing with the bar trough the vertical distribution of nondimensionalized time averaged tke and turbulence dissipation rate at the bar crest showed a large increase near the bottom probably due to a strong cross shore rms velocity finally in the quasi equilibrium state time averaged tke and turbulence dissipation rate at the bar trough were smaller than those inside the surf zone inside the surf zone significant turbulence intensities were observed due to a second breaking on a shallow water depth

the geodynamic province of transitional lithosphere adjacent to magma poor continental margins two different types of transitional lithosphere have been documented along magma poor rifted margins one consists of apparently subcontinental mantle that has been exhumed brit tlely deformed and serpentinized during late stages of rifting a second is thinned 10 km con tinental crust which in some cases is known to have been supported near sea level at least early in the rift history and thus is interpreted to reflect depth dependent extension in both cases it is typically assumed that oceanic crust forms at the time that the brittle continental crust is breached or soon thereafter and thus that transitional lithosphere has relatively limited width here three representa tive cases of transitional lithosphere are examined one in the newfoundland iberia rift and one at goban spur both exhumed mantle and one off the angola congo margin thin continental crust flanked seaward by apparently exhumed lower continental crust exhumed mantle considering the geological and geophysical evidence it appears that depth dependent extension riftward flow of weak lower continental crust and or upper mantle may be a common phenomenon on magma poor margins and that this can result in a much broader zone of transitional lithosphere than has hitherto been assumed transitional lithosphere in this wide zone may consist of subcontinental mantle lower continental crust or some combination thereof depending on the strength profile of the pre rift continental lithosphere transitional lithosphere ceases to be emplaced i e final break up occurs only when emplacement of heat and melt from the rising asthenosphere becomes domi nant over lateral flow of the weak lower lithosphere this model implies a two stage break up first the rupture of the brittle continental crust and second the eventual separation of the ductile sub continental lithosphere which is coincident with emplacement of normal oceanic crust well defined magnetic anomalies can form in transitional lithosphere that consists of highly serpenti nized exhumed mantle and such anomalies therefore are not diagnostic of oceanic crust where present the anomalies can be helpful in interpreting and dating the rifting history

relative geobarometry from high pressure rocks of quartzofeldspathic composition from the sesia zone western alps italy in the sesia zone of the western alps italy early alpine blueschist to eclogite facies metamorphism of rocks of quartzofeldspathic composition has produced the same high pressure assemblage of quartz na pyroxene na amphibole paragonite phengite zoisite garnet magnetite sphene and fe sulphide the qfs assemblage over an area 150 km2 relative gradients in pressure and temperature over this region are reflected in the variations in mineral chemistries of the individual phases of the quartzofeldspathic assemblage through continuous reactions mineralogical discontinuities do not occur in the qfs assemblage of this region increases in the jadeite content of the pyroxenes xjd 0 48 to xjd 0 93 and in the glaucophane content of the amphiboles xgl 0 89 to xgl 0 96 occur from the southwest to the northeast of the region studied analysis of coexisting garnets and pyroxenes indicate that the compositional variation of amphiboles and pyroxenes is associated with a decrease in the grossular component of the coexisting garnet zoned pyroxenes and garnets together with the regional trends in mineral chemistries suggest that the evolution of the qfs assemblage with increasing pressure may be modelled by pressure sensitive continuous reactions in which amphibole zoisite and the more jadeitic pyroxene constitute the high pressure assemblage chemographic constraints permit the positioning in pressure temperature space of the compositional isopleths of those model continuous reactions involving these phases which meet the textural and chemical criteria observed in the natural assemblages the low dp dt slope 20 bars c of these isopleths causes the continuous reactions to be useful for geobarometric calculations at pressures above the absolute breakdown of albite to jadeite plus quartz in addition the pseudobinary loops for the other continuous reactions which are potentially useful geobarometers and involve either the naalca 1mg 1 exchange or the mgca 1 exchange are calculated comparison of mineral chemistries with the isopleths yields a relative barometric scheme for the localities studied with these barometric observations it is possible to show that the p t path which the sesia body travelled towards the final recorded state was one of increasing pressure other blueschist and eclogite occurrences from syros and sifnos which contain rocks of quartzofeldspathic composition are also examined

on sediment extent and runup of tsunami waves abstract tsunami sediments play an important role in tsunami hazard assessments recent tsunami events and their associated tsunami deposits have produced a wealth of sediment data surveys of recent tsunami events observed that maximum inland tsunami inundation exceeds the maximum inland extent of sand deposition a driving question of tsunami sedimentology is whether the difference between maximum tsunami inundation and inland extent of sand can be employed as a measure of inundation for past events for which only the extent of the sand is known attempts to infer the causative flow characteristics from these sediments often suffer from uncertainties in the data and from restrictive assumptions made in inversion models the latter demonstrates that the interaction between the tsunami flow and the movable bed is not fully understood in our contribution we employ numerical simulations of tsunami propagation and inundation with most and a simple model for deposition in our simulations we vary the onshore slope the initial amplitude which can be interpreted as offshore wave amplitude and the grain size while the initial amplitude and onshore slope influence the difference between maximum inundation and sand extent the grain size has little effect the link between the onshore slope initial amplitude and the difference between the maximum tsunami inundation and inland sediment extent can be employed as a first order quantitative tool to estimate tsunami flow characteristics and maximum inundation from tsunami deposits we anticipate these results will improve tsunami hazard assessments and narrow the gap between field observations and numerical simulations

opening of the central atlantic ocean implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup study of the deep structure of conjugate passive continental margins combined with detailed plate kinematic reconstructions can provide constraints on the mechanisms of rifting and formation of initial oceanic crust in this study the central atlantic conjugate margins are compared based on compilation of wide angle seismic profiles from nw africa nova scotian and u s passive margins the patterns of volcanism crustal thickness geometry and seismic velocities in the transition zone suggest symmetric rifting followed by asymmetric oceanic crustal accretion conjugate profiles in the southern central atlantic image differences in the continental crustal thickness while profiles on the eastern u s margin are characterized by thick layers of magmatic underplating no such underplate was imaged along the african continental margin in the north two wide angle seismic profiles acquired in exactly conjugate positions show that the crustal geometry of the unthinned continental crust and the necking zone are nearly symmetric a region including seismic velocities too high to be explained by either continental or oceanic crust is imaged along the canadian side corresponding on the african side to an oceanic crust with slightly elevated velocities these might result from asymmetric spreading creating seafloor by faulting the existing lithosphere on the canadian side and the emplacement of magmatic oceanic crust including pockets of serpentinite on the moroccan margin after isochron m25 a large scale plate reorganization might then have led to an increase in spreading velocity and the production of thin magmatic crust on both sides

currents drag and sediment transport induced by a tsunami 1 we report observations of water surface elevation currents and suspended sediment concentration ssc from a 10 m deep site on the inner shelf in northern monterey bay during the arrival of the 2010 chile tsunami velocity profiles were measured from 3 5 m above the bed mab to the surface at 2 min intervals and from 0 1 to 0 7 mab at 1 hz ssc was determined from the acoustic backscatter of the near bed profiler the initial tsunami waves were directed cross shore and had a period of approximately 16 min maximum wave height was 1 1 m and maximum current speed was 0 36 m s during the strongest onrush near bed velocities were clearly influenced by friction and a logarithmic boundary layer developed extending more than 0 3 mab we estimated friction velocity and bed shear stress from the logarithmic profiles the logarithmic structure indicates that the flow can be characterized as quasi steady at these times at other phases of the tsunami waves the magnitude of the acceleration term was significant in the near bed momentum equation indicating unsteady flow the maximum tsunami induced bed shear stress 0 4 n m2 exceeded the critical shear stress for the medium grained sand on the seafloor cross shore sediment flux was enhanced by the tsunami oscillations of water surface elevation and currents continued for several days the oscillations were dominated by resonant frequencies the most energetic of which was the fundamental longitudinal frequency of monterey bay the maximum current speed hourly timescale in 18 months of observations occurred four hours after the tsunami arrived

the continent ocean boundary at the rifted margin off eastern canada new results from deep seismic reflection studies seismic reflection data were collected and processed to 20 s two way travel time along four lines which cross the rifted continent ocean boundary off the grand banks region of eastern canada specifically to examine the origin age and nature of this fundamental boundary this represents the first regional study of its kind the most important result is the presence of landward dipping reflectors near the foot of the continental slope these occur where oceanic crust appears to terminate against the continent we suggest that the dipping reflectors mark the continent ocean boundary and that they may represent magmatic material which has underplated or intruded the rifted and thinned lower continental crust adjacent to the boundary sedimentary basins lie just landward of the continent ocean boundary their subsidence history suggests significant heating and thinning of the lower lithosphere during rifting and this may be an important stage leading to continental breakup rift basins formed further landward on the grand banks do not exhibit this thinning other significant seismic results include the presence of strongly reflective zones in the lower continental crust near the continent ocean boundary also the oceanic crust exhibits a complexity of reflections some of which may be due to compositional zonation during magmatic crystallization finally our results may have important consequences for continental predrift reconstruction as oceanic crust appears to extend farther landward in the newfoundland basin than some recent studies have indicated

riemann wave description of erosional dam break flows this work examines the sudden erosional flow initiated by the release of a dam break wave over a loose sediment bed extended shallow water equations are formulated to describe the development of the surge accounting for bed material inertia a transport layer of finite thickness is introduced and a sharp interface view of the morphodynamic boundary is adopted approximations are sought for an intermediate range of wave evolution in which equilibration of the sediment load can be assumed instantaneous but momentum loss due to bed friction has not yet been felt the resulting homogeneous hyperbolic equations are mathematically tractable using the riemann techniques of gas dynamics dam break initial conditions give rise to self similar flow profiles the wave structure features piecewise constant states two smoothly varied simple waves and a special type of shock an erosional bore forming at the forefront of the wave profiles are constructed through a semi analytical procedure yielding a geomorphic generalization of the stoker solution for dam break waves over rigid bed for most flow properties the predictions of the theoretical treatment compare favourably with experimental tests visualized using particle imaging techniques

three dimensional numerical modeling of dam break flows with sediment transport over movable beds abstracta three dimensional 3d numerical model has been developed to simulate dam break flows with sediment transport over movable beds the hydrodynamic model solves the 3d reynolds averaged navier stokes equations using a finite volume method on collocated hexahedral meshes the volume of fluid vof technique with the compressive interface capturing scheme for arbitrary meshes is used to track the water surface boundary the sediment transport model solves the nonequilibrium transport equations of suspended load and bed load separately and in turn calculates the resulting bed change a moving mesh technique is adopted to track the time evolution of bed topography the grid moving velocity and computational cell volume change due to the moving mesh are taken into consideration when the hydrodynamic and sediment transport equations are discretized the developed model has been tested using several experimental dam break flows over movable beds the calculated temporal and spatial variations of water a

a phase of transient subsidence sediment bypass and deposition of regressive transgressive cycles during the breakup of iberia and newfoundland abstract seismic outcrop and well data from west iberia and newfoundland are used to investigate sediment stacking patterns during continental breakup as a function of tectonic subsidence in west iberia two breakup sequences are revealed on seismic data by marked strata offlap oceanwards from the present day continental shelf this character is similar to newfoundland where correlative strata comprise lower cretaceous cenomanian coarse grained siliciclastics accumulated around local sediment source areas the interpreted data reveal that the two breakup sequences 1 materialise sediment bypass onto continental slope depocentres that experienced important tectonic subsidence during continental breakup but without showing typical syn rift growth packages 2 generate specific forced regressive stratigraphic intervals that relate to uplift and exhumation of the proximal margin subsidence and sediment stacking patterns in both west iberia and newfoundland reflect similar continental breakup processes as they evolved from the upper lithosphere to their mantle breakup stages on both margins coarse grained siliciclastic units on the proximal margin give rise to thick shaley successions in deep water basins this work also confirms that in a setting dominated by a significant sediment influx yet lacking the burial rates of continental slope basins in newfoundland west iberia comprised accommodation driven basins during continental breakup not necessarily sediment starved as a corollary of our analysis we classify breakup sequences around the world based on the characteristic lithologies of their regressive transgressive depositional cycles

the predictability of cross shore bed evolution of sandy beaches at the time scale of storms and seasons using process based profile models deterministic and probabilistic profile models have been compared with hydrodynamic and morphodynamic data of laboratory and field experiments on the time scale of storms and seasons the large scale laboratory experiment is a pure 2d case and offers and ideal test case for cross shore profile models as disturbing alongshore non uniformities are absent the field experiments are performed at the egmond site the netherlands during the eu coast3d project and represent storm time scale oct nov 1998 as well as seasonal time scale conditions may 1998 sep 1999 the objective of the paper is to present information of coastal processes on these time scales and to assess the predictive capabilities coastal process based profile models with respect to hydrodynamics and morphodynamics at sandy beaches on the time scales of storms and seasons profile models can quite accurately errors smaller than 10 represent the cross shore significant wave height distribution in the surf zone if the wave breaking model is properly calibrated the wave breaking coefficient should be a function of local wave steepness and bottom slope for most accurate results profile models can reasonably represent the cross shore and longshore currents undertow in a pure 2d case and in 3d field conditions profile models including cross shore mixing effects and breaker delay effects do not produce better predictions of the longshore and cross shore current velocities profile models using default settings can quite reasonably simulate the behaviour of the outer and inner bars on the storm time scale the behaviour of the beach cannot be modelled with sufficient accuracy on the storm time scale profile models can reasonably simulate the post storm onshore bar migration provided that the near bed orbital velocities and wave asymmetry related sand transport are represented in a sufficiently accurate way using non linear wave theories profile models cannot simulate the beach recovery processes on the post storm time scale because these essentially 3d processes are not sufficiently known to be included in the models profile models using default settings cannot simulate the behaviour of the outer and inner bars and the beach on the seasonal time scale the behaviour of the outer bar on the seasonal time scale can only be represented properly after tuning using measured bed profiles the simulation of the inner bar and beach morphology on the seasonal time scale could not be improved by tuning

implications to garnet clinopyroxene geothermometry of non ideal solid solution in jadeitic pyroxenes garnet clinopyroxene geothermometry has been applied to numerous rock types from the blueschist and eclogite terrain of the sesia zone in the western alps discrepancies in apparent temperatures of up to 600 c have been found suggesting substantial deviation from ideal behaviour of the garnet clinopyroxene equilibria in certain assemblages assemblages containing jadeitic pyroxenes rather than omphacitic or diopsidic pyroxenes yield very low kd 2 0 values and correspondingly high apparent temperatures 1 000 c the garnets coexisting with high na pyroxenes have compositions similar to those coexisting with omphacitic pyroxenes departure from ideal behaviour of these garnets is likely to be minor and is accomodated in the formulation of the geothermometer numerous examples of coexisting garnet clinopyroxene pairs indicate that there is no obvious relationship of kd with jadeite content in pyroxenes with jadeite content less than 70 but at higher values kd varies inversely with the jadeite content the dependence of kd upon the jadeite content in the high na pyroxenes is believed to be due to the preference of m2 sites for fe2 in the enstatite jadeite substitution fe2 mgna 1al 1 this substitution is usually very limited and has no demonstrable effect upon x fe cpx when the m1 fe2 mg content of the pyroxenes is high as in omphacitic and diopsidic pyroxenes however when the m1 fe2 mg content is low as in jadeitic pyroxenes the non ideality of the enstatite type exchange has a marked effect on x fe cpx and consequently on garnet clinopyroxene calculations

observations and modeling of tsunami induced currents in ports and harbors abstract tsunamis or harbor waves in japanese are so named due to common observations of enhanced wave heights currents and damage in harbors and ports however dynamic currents induced by these waves while regularly observed and known to cause significant damage are poorly understood observations and modeling of the currents induced by the 2011 tohoku and 2004 indian ocean tsunamis allows us to show that the strongest flows in harbor basins are governed by horizontally sheared and rotational shallow features such as jets and large eddies when examining currents in harbors this conclusion will generally require a simulation approach that both includes the relevant physical processes in the governing equations and uses a numerical scheme that does not artificially damp these features without proper representation of the physics associated with these phenomena predictive models may provide drag force estimates that are an order of magnitude or more in error the immediate implementation of this type of analysis into tsunami hazard studies can mean the difference between an unaffected port and one in which 300 m long container vessels are detached from their moorings and drift chaotically

quantification and restoration of extensional deformation along the western iberia and newfoundland rifted margins 1 many recent papers describe the structure of the iberia and newfoundland rifted margins however none of them propose kinematic restorations of the complete rift system to quantify the amount of extension necessary to exhume mantle and initiate seafloor spreading in our study we use two pairs of cross sections considered as conjugate lines one across the galicia bank flemish cap and the other across the southern iberia abyssal plain flemish pass both transects have been imaged by reflection and refraction seismic methods and have been drilled during ocean drilling program legs 103 149 173 and 210 drilling penetrated parts of the rift stratigraphy and the underlying basement the cross sections can therefore be considered as the best documented conjugate transects across present day hyperextended magma poor rifted margins the aim of this paper is threefold 1 provide a detailed description of the crustal architecture of the two conjugate sections 2 define the extensional structures and their ages and 3 quantify the amount of strain and strain rate accommodated along these lines this paper proposes a quantitative description of extension along the iberia newfoundland rift system and discusses the limitations and problems in quantifying extensional deformation along hyperextended rifted margins

tectonic evolution of the north sea basin crustal stretching and subsidence summary the lithospheric stretching model for the formation of sedimentary basins was tested in the central north sea by a combined study of crustal thinning and basement subsidence patterns a profile of crustal structure was obtained by shooting a long range seismic experiment across the central graben the main axis of subsidence a seabed array of 12 seismometers in the graben was used to record shots fired in a line 530 km long across the basin the data collected during the experiment were interpreted by modelling synthetic seismograms from a laterally varying structure and the final model showed substantial crustal thinning beneath the graben subsidence data from 19 exploration wells were analysed to obtain subsidence patterns in the central north sea since jurassic times changes in water depth were quantified using foraminiferal assemblages where possible and observed basement subsidence paths were corrected for sediment loading compaction and changes in water depth through time the seismic model is shown to be compatible with the observed gravity field and the small size of observed gravity anomalies is used to argue that the basin is in local isostatic equilibrium both crustal thinning and basement subsidence studies indicate about 70 km of stretching across the central graben during the mid jurassic to early cretaceous extensional event this extension appears to have occurred over crust already slightly thinned beneath the graben and the seismic data suggest that total extension since the early permian may have been more than 100km the data presented here may all be explained using a simple model of uniform extension of the lithosphere

stratification effects by cohesive and noncohesive sediment this study focuses on stratification effects induced by the interaction between suspensions of fine grained cohesive and noncohesive sediment and the turbulent flow in estuarine and coastal environments a concise literature review reveals that this interaction may cause an appreciable modification of the vertical profiles of velocity vertical eddy viscosity diffusivity and reynolds stresses this interaction is further studied with a one dimensional vertical 1dv numerical model which includes the standard k turbulence model with buoyancy destruction terms application of this model to the experimental results by coleman 1981 shows that the measured changes in the velocity profile can be explained entirely by sediment induced buoyancy effects it is argued that capacity for cohesive sediment is cc e a fluid mud layer is formed upon the deposition of the cohesive sediment flocs contrary to the case with noncohesive sediment where the depositing grains immediately form a rigid bed thus a two layer fluid system develops causing significant damping of the vertical mixing processes decreasing the carrying capacity further this positive feed back results in a catastrophic collapse of the turbulence field and the concentration profile a scaling law for this saturation behavior is derived from classical stratified flow theory this law is sustained with a series of numerical experiments with the 1dv model it also predicts the suspended sediment concentrations observed in the yellow river to the right order of magnitude it is concluded that sediment induced buoyancy yields appreciable stratification effects at already moderate suspended sediment concentrations in the case of cohesive sediment these stratification effects can result in a catastrophic collapse of the turbulent flow field and the vertical profile of suspended sediment concentration

stable numerical model for transcritical flow and sediment transport on uneven bathymetry a stable and well balanced finite volume method was proposed to solve the shallow water equations coupled with a sediment transport equation an approximate riemann solver with a monotone upstream centered schemes for conservation laws muscl reconstruction was used for the computation of the flux terms a special but relatively simple treatment of source terms made it possible to ensure numerically and physically balanced computational results on very steep sloped beds various numerical simulations conducted on rigid beds have demonstrated that the proposed numerical scheme could provide stable computational results in the cases of flat and nonflat bottoms from the comparisons of experiments on erodible beds in one and two dimensional channels good agreement was obtained when proper parameters for turbulent flow and sediment transport were provided lastly the effects of the parameters in relation to hydraulic characteristics included in the flow and the sediment transport models were investigated

timing of initial seafloor spreading in the newfoundland iberia rift broad areas of subcontinental lithospheric mantle are commonly exposed along ocean continent transition zones in magma poor rifts and are thought to be exhumed along lithospheric scale detachment faults during the final stages of rifting however the nature of the transition from final rifting to seafloor spreading is controversial we present the first high precision u pb zircon geochronologic and hf isotopic data from gabbros that intrude exhumed mantle at ocean drilling program odp sites 1070 and 1277 in the newfoundland iberia rift north atlantic the sites are conjugate to one another within crust that is commonly considered to have been emplaced during early seafloor spreading magnetic data suggest that crustal accretion occurred at both sites during magnetic polarity chrons m3 m0 130 126 ma however our data indicate that asthenospheric melts were emplaced over brief intervals 1 m y prior to or coeval with mantle exhumation at 124 ma at odp site 1070 and 115 ma at odp site 1277 we suggest that this discrepancy is the result of continued mantle exhumation along large west dipping detachment faults until lithospheric breakup the breakup location is likely coincident with the large amplitude magnetic j anomaly and our 115 ma date for magmatism within this anomaly provides the best available age constraint for breakup along the studied transect

the eclogite bearing series of isla margarita venezuela geochemistry of metabasic lithologies in the la rinconada and juan griego groups abstract xrf analysis for major and minor elements in 94 samples of the metabasic la rinconada group and in 28 samples of metabasic lithologies in the predominantly metasedimentary overlying juan griego group of isla margarita venezuela has been carried out to compare the bulk compositions of the two eclogite bearing metabasic suites the two units differ in the age and geological setting of the protolith the la rinconada group has a monotonous basaltic character but shows irregular variations in bulk composition which are interpreted to reflect variations in the type of protolith ranging from basaltic lava flow to gabbroic cumulitic dyke as a whole the la rinconada group is related to a source of tholeiitic composition in a morb type volcanic hypabyssal environment the juan griego metabasic rocks are compositionally more homogeneous and uniformly basaltic in their major elements again reflecting a tholeiitic source and a morb type environment despite their contrasting geological setting the two suites of metabasic rocks can be inferred to have had a similar source and have probably developed in a passive atlantic type continental margin setting we infer that the la rinconada group represents early oceanic crust later covered by the siliceous continent derived clastics of the juan griego group in which the minor basaltic intrusions represent the last stages of waning magmatic activity

kinematic evolution of the southern north atlantic implications for the formation of hyperextended rift systems we focus on the southern north atlantic rifted margins to investigate the partitioning and propagation of deformation in hyperextended rift systems using plate kinematic modeling the kinematic evolution of this area is well determined by oceanic magnetic anomalies after the cretaceous normal polarity superchron however the rift and early seafloor spreading evolution 200 83 ma remains highly disputed due to contentious interpretations of the j magnetic anomaly on the iberia newfoundland conjugate margins recent studies highlight that the j anomaly is probably polygenic related to polyphased magmatic events and therefore does not correspond to an isochron we present a new palinspastic restoration without using the j magnetic anomaly as the chron m0 we combine 3 d gravity inversion results with local structural stratigraphic and geochronological constraints on the rift deformation history the restoration of the southern north atlantic itself is not the primary aim of the study but rather is used as a method to investigate the spatiotemporal evolution of hyperextended rift systems we include continental microblocks that enable the partitioning of the deformation between different rift segments which is of particular importance for the evolution of the iberia eurasia plate boundary our modeling highlights the following 1 the segmentation of the iberia newfoundland rift system during continental crust thinning 2 the northward v shape propagation of mantle exhumation and seafloor spreading 3 the complex partitioning of deformation along the iberia eurasia plate boundary and 4 a three plate propagation model which implies transtension

cross shore sediment transport under breaking solitary waves 1 laboratory experiments were performed to examine the cross shore sediment transport processes under breaking solitary waves on a fine sand beach the initial beach slope of 1 12 was exposed to a positive solitary wave eight times the beach was rebuilt and exposed to a negative solitary wave eight times the wave motion and sediment transport were not affected much by the beach profile change from the initial profile the positive solitary wave plunged violently near the shoreline and suspended a considerable volume of sand the plunging wave with no seaward flow impeding its run up caused large run up on the foreshore the strong downrush following the large run up resulted in erosion on the foreshore and deposition seaward of wave run down on the other hand the negative solitary wave collapsed against the seaward flow induced by the free surface slope of the negative wave and caused less sediment suspension the wave run up against the seaward flow was much smaller the weak downrush following the small run up resulted in deposition on the foreshore and erosion near the wave collapsing point these limited laboratory experiments indicate the importance of the initial wave profile for swash sediment dynamics and the capacity of a single wave in causing noticeable beach profile changes

rifted margin architecture and crustal rheology reviewing iberia newfoundland central south atlantic and south china sea abstract crustal rheology controls the style of rifting and ultimately the architecture of rifted margins here we review the formation of three magma poor margin pairs iberia newfoundland the central segment of the south atlantic rift and the south china sea by integrating observational data into a numerical forward modelling framework we utilise a 2d version of the finite element code slim3d which includes nonlinear temperature and stress dependent elasto visco plastic rheology and is able to reproduce a wide range of rift related deformation processes such as flexure lower crustal flow and faulting extension in cold strong or thin crust is accommodated by brittle faults and ductile shear zones that facilitate narrow rifts with asymmetric fault geometries hot weak or thick continental crust is dominated by ductile deformation and often extends symmetrically into a wide rift system this simple recipe provides the standard framework to understand initial rift geometry however it is insufficient to account for the dynamics of intermediate and late rift stages that shape the final margin architecture asymmetric conjugate margins where one side is wide and the other narrow can be formed via both wide and narrow rift styles which we reproduce with weak and strong crustal rheologies respectively exemplified by the iberia newfoundland conjugates and the central south atlantic we define three characteristic rift phases an initial phase of simultaneous faulting an intermediate phase of rift migration that involves sequential fault activity and finally the breakup phase crustal rheology plays an overarching role in governing the dynamics of these asymmetric margins we illustrate that weak rheologies generally prolong the phase of simultaneous faulting while rift migration is enabled by initial fault asymmetry as well as relatively weak crust formation of the predominantly symmetric and wide margins of the south china sea was controlled by extraordinarily weak crust that extended the phase of simultaneous faulting until breakup the weak crustal rheology of this region relates to the south china sea s pre rift history where plate convergence lead to crustal thickening and magmatic additions in a back arc regime shortly before the onset of rifting

magmatic breakup as an explanation for magnetic anomalies at magma poor rifted margins during continental breakup the onset of seafloor spreading is thought to be marked by the first occurrence of a magnetic anomaly analysis of seismic and magnetic data from the iberia newfoundland continental rift system suggests that the first magnetic anomaly observed here instead represents a magmatic event that pre dates seafloor spreading

observed and modeled currents from the tohoku oki japan and other recent tsunamis in northern california we investigate the currents produced by recent tsunamis in humboldt bay and crescent city california the region is susceptible to both near field and far field tsunamis and has a historic record of damaging events crescent city harbor located approximately 100 kms north of humboldt bay suffered us 28 million in damages from strong currents produced by the 2006 kuril islands tsunami and an additional us 26 million from the 2011 japan tsunami in order to better evaluate these currents in northern california we deployed a nortek aquadopp 600 khz 2d acoustic doppler current profiler adcp with a 1 min sampling interval in humboldt bay near the existing national oceanic and atmospheric administration noaa national ocean service nos tide gauge station the instrument recorded the tsunamis produced by the mw 8 8 chile earthquake on february 27 2010 and the mw 9 0 japan earthquake on march 11 2011 one other tsunami was recorded on the humboldt bay tide gauge during the period of adcp operation but was not visible on the adcp suggesting a threshold water level value of about 0 2 m to produce an observable adcp record the 2010 tsunami currents persisted in humboldt bay for approximately 30 h with peak amplitudes of about 0 35 m s the 2011 tsunami signal lasted for over 40 h with peak amplitude of 0 84 m s the strongest currents corresponded to the maximum change in water level approximately 67 min after the initial wave arrival no damage was observed in humboldt bay for either event in crescent city currents for the first three and one half hours of the 2011 japan tsunami were estimated using security camera video footage from the harbor master approximately 70 m away from the noaa nos tide gauge station the largest amplitude tide gauge water level oscillations and most of the damage occurred within this time window the currents reached a velocity of approximately 4 5 m s and six cycles exceeded 3 m s during this period measured current velocities both in humboldt bay and in crescent city were compared to calculated velocities from the method of splitting tsunamis most numerical model the frequency and pattern of current amplification and decay at both locations are replicated by the most model for the first several hours after the tsunami onset most generally underestimates 2011 peak current velocities by about 10 30 with a few peaks by as much as 50 at humboldt bay most predicted attenuation of the signal after 4 h but the actual signal persisted at a nearly constant level for at least twice as long the results from this project demonstrate that adcps can effectively record tsunami currents for small to moderate events and can be used to calibrate and validate models i e most in order to better understand hazardous tsunami conditions within harbors

a mechanism to thin the continental lithosphere at magma poor margins crustal thinning where continental plates break apart can be accomplished by a system of conjugate concave downward faults instead of multiple normal faults through exhumation of mid crustal and mantle material where continental plates break apart slip along multiple normal faults provides the required space for the earth s crust to thin and subside1 after initial rifting however the displacement on normal faults observed at the sea floor seems not to match the inferred extension2 here we show that crustal thinning can be accomplished in such extensional environments by a system of conjugate concave downward faults instead of multiple normal faults our model predicts that these concave faults accumulate large amounts of extension and form a very thin crust 10 km by exhumation of mid crustal and mantle material this transitional crust is capped by sub horizontal detachment surfaces over distances exceeding 100 km with little visible deformation our rift model is based on numerical experiments constrained by geological and geophysical observations from the alpine tethys and iberia newfoundland margins3 4 5 6 7 8 9 furthermore we suggest that the observed transition from broadly distributed and symmetric extension to localized and asymmetric rifting is directly controlled by the existence of a strong gabbroic lower crust the presence of such lower crustal gabbros is well constrained for the alpine tethys system4 9 initial decoupling of upper crustal deformation from lower crustal and mantle deformation by progressive weakening of the middle crust is an essential requirement to reproduce the observed rift evolution this is achieved in our models by the formation of weak ductile shear zones

rb sr record of fluid rock interaction in eclogites the marun keu complex polar urals russia abstract rb sr internal mineral isochrons in the eclogite facies marun keu metamorphic complex polar urals russia date periods of fluid rock interaction and record the metamorphic reaction history the marun keu complex consists of late proterozoic to early ordovician mostly igneous rocks that experienced a subduction related non pervasive eclogite facies metamorphism followed by a local decompression related amphibolite facies overprint during the uralian orogeny field observations show that metamorphic reactions as well as ductile deformation are controlled by local availability of a free fluid phase isotopic data reveals that availability of fluids similarly exerts control on isotope distribution from a relic gabbro which has never been infiltrated by free fluids a premetamorphic rb sr age of 467 39 ma was obtained rb sr isochron ages for 14 samples of eclogite and amphibolite facies assemblages sampled from within or close to metamorphic fluid veins range from 352 5 ma to 360 3 ma a sm nd isochron for a metagranite yields an age of 354 4 ma taken together the ages for both prograde and retrograde metamorphic assemblages overlap within analytical uncertainty and yield an average value of 355 5 1 4 ma indicating that the metamorphic evolution and incipient exhumation of the marun keu complex proceeded rapidly the results demonstrate that assemblages preserve their rb sr isotopic signatures as long as they remain devoid of free fluids and that only fluid rock interaction may cause sr isotope redistribution in addition the data suggest local fluid rock equilibrium low fluid rock ratios with overall fluid deficiency and limited fluid mobility at depth however some fluids must have been mobile on the km scale since they can be traced into the suprasubduction zone mantle wedge metasomatic veins in the rai iz ophiolite yield a rb sr mineral isochron age of 373 1 5 4 ma they are interpreted as evidence for suprasubduction zone metasomatism in an oceanic setting prior to subduction of the east european margin and associated formation of eclogites in the marun keu complex we propose that rb sr mineral isochron ages provide hygrochronological rather than thermochronological constraints they define the cooling history only in combination with zircon and apatite fission track data the straightforward interpretation of rb sr mineral ages as cooling ages is obsolete

abrupt plate accelerations shape rifted continental margins rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved it is well known that strain rate dependent processes control rift evolution yet quantified extension histories of earth s major passive margins have become available only recently here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions we find that rifted margins feature an initial slow rift phase less than ten millimetres per year full rate and that an abrupt increase of plate divergence introduces a fast rift phase plate acceleration takes place before continental rupture and considerable margin area is created during each phase we reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions the extension models suggest that the two phase velocity behaviour is caused by a rift intrinsic strength velocity feedback which can be robustly inferred for diverse lithosphere configurations and rheologies our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force this mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes offering new insights into the balance of plate driving forces through time

one dimensional modeling of dam break flow over movable beds a one dimensional model has been established to simulate the fluvial processes under dam break flow over movable beds the hydrodynamic model adopts the generalized shallow water equations which consider the effects of sediment transport and bed change on the flow the sediment model computes the nonequilibrium transport of bed load and suspended load the effects of sediment concentration on sediment settling and entrainment are considered in determining the sediment settling velocity and transport capacity in particular a correction factor is proposed to modify the van rijn formulas of equilibrium bed load transport rate and near bed suspended load concentration for the simulation of sediment transport under high shear flow conditions the governing equations are solved by an explicit finite volume method with the first order upwind scheme for intercell fluxes the model has been tested in two experimental cases with fairly good agreement between simulations and measurements the sensitivities of the model results to parameters such as the sediment nonequilibrium adaptation length manning s roughness coefficient and the proposed correction factor have been verified the proposed model has also been compared to an existing model and the results indicate the new model is more reliable

quantitative subsidence analysis of the mesozoic evolution of the lusitanian basin western iberian margin abstract quantitative subsidence analysis of 26 wells in the lusitanian basin provides new constraints on the western iberian mesozoic passive margin development backstripped tectonic subsidence curves show a three fold subdivision of vertical motions from late triassic onward continental rifting was initiated during the late triassic and early jurassic from middle jurassic onward a distinct different behaviour is expressed in the subsidence curves for the north and the south lusitanian basin during the middle jurassic the south lusitanian basin records a stretching episode with stretching factors of about 1 08 while the north lusitanian basin typically has a middle jurassic hiatus this different development is also expressed in the late jurassic and early cretaceous sedimentary sequence when both the north and south lusitanian basin are subjected to another stretching episode with a more pronounced development of the southern than of the northern part of the basin the stretching factors for this last phase are about 1 03 for the northern part and 1 08 for the southern part of the area this north south difference during the middle jurassic to early cretaceous for which the transition roughly coincides with the location of the nazare fault zone is probably a result of differences in pre rift crustal composition or thickness late cretaceous sediments are mostly absent in the analysed wells in the southern part of the basin the absence of the cretaceous record is a consequence of erosion due to cenozoic inversion of the basin the generally low estimates for stretching factors suggest that the analysed eastern part of the lusitanian basin forms the distal part of the mid cretaceous continental breakup a comparison with subsidence curves of neighbouring basins of iberia reflects general patterns in mesozoic basin development and confirms the generally held view that the extension leading to continental breakup migrated from south to north during the middle jurassic to early cretaceous in west iberia

plate tectonics and basin subsidence history tectonic setting exerts fi rst order control on basin formation as refl ected in basin subsidence history while our approach ignores the effects of fl exural loading and eustatic sea level change consistency of backstripped subsidence histories i e with local loading effects of sediment removed suggests consistent tectonic driving mechanisms in each tectonic setting with the possible exception of forearc basins based on published subsidence curves and open fi le stratigraphic data we show the subsidence characteristics of passive margins strike slip basins intracontinental basins foreland basins and forearc basins passive margin subsidence is characterized by two stages rapid initial synrift subsidence and slow post rift thermal subsidence with increasing subsidence rates toward the adjacent ocean basin subsidence of intracontinental basins is similar in magnitude to that seen in passive margin settings but the former is generally slower longer lived and lacks initial subsidence long lived subsidence for many intracontinental basins is consistent with cooling following thermal perturbation of thick lithosphere found beneath old parts of continents basins associated with strike slip faults are usually short lived with very rapid subsidence changes in local stress regimes as strike slip faults evolve and migrate over time coupled with three dimensional heat loss in these small basins likely explain this subsidence pattern foreland basin subsidence rates refl ect the fl exural response to episodic thrust loading resultant subsidence curves are punctuated by convex up accelerating segments forearc basins have the least consistent subsidence patterns subsidence histories of these basins are complex and may refl ect multiple driving mechanisms of subsidence in forearc settings second order deviations in subsidence suggest reactivation or superimposed tectonic events in many basin settings the effects of eustatic sea level change may also explain some deviations in curves for many of these settings subsidence histories are suffi ciently distinctive to be used to help determine tectonic setting of ancient basin deposits

retrograde evolution of eclogite facies rocks from ne oman evidence from fluid inclusions and petrological data eclogite facies rocks from eastern saih hatat oman metamorphosed under peak conditions of p 12 kbar and t of 550 580 c have several types of fluid inclusions in quartz clinopyroxene and garnet most of these inclusions are two phase at room t and contain an aqueous fluid belonging to the system nacl mgcl2 h2o final melting temperatures for most inclusions range from 4 to 0 c but values as low as 13 c have been recorded indicating salinities of 490 c inclusions with three phases at room t also contain a predominantly low salinity aqueous fluid with xco2 12 kbar to 4 kbar or less at t 500 550 c this conclusion is supported by the scatter in homogenization temperatures for these inclusions and their large variety of shapes and sizes which range from irregular with hair like fractures surrounded by satellite inclusions to negative crystals the replacement of ferroan dolomite ankerite and quartz by calcite talc and of rutile calcite by titanite or rutile glaucophane by ilmenite albite in these eclogites are also consistent with a stage of isothermal decompression following near isothermal decompression to depths of 10 15 km brittle deformation prevailed leading to the formation of layer parallel and crosscutting fractures that were filled by quartz calcite this stage was followed by near isobaric cooling recorded by the isochores for fluid inclusions in vein quartz and by the occurrence of dendritic networks of decrepitated and imploded fluid inclusions in these veins

aspects of the structural evolution of the lusitanian basin in portugal and the shelf and slope area offshore portugal abstract the study provides a regional seismic interpretation and mapping of the mesozoic and cenozoic succession of the lusitanian basin and the shelf and slope area off portugal the seismic study is compared with previous studies of the lusitanian basin from the late triassic to the cretaceous the study area experienced four rift phases and intermittent periods of tectonic quiescence the triassic rifting was concentrated in the central part of the lusitanian basin and in the southernmost part of the study area both as symmetrical grabens and half grabens the evolution of half grabens was particularly prominent in the south the triassic fault controlled subsidence ceased during the latest late triassic and was succeeded by regional subsidence during the early early jurassic hettangian when deposition of evaporites took place a second rift phase was initiated in the early jurassic most likely during the sinemurian pliensbachian this resulted in minor salt movements along the most prominent faults the second phase was concentrated to the area south of the nazare fault zone and resulted here in the accumulation of a thick sinemurian callovian succession following a major hiatus probably as a result of the opening of the central atlantic resumed deposition occurred during the late jurassic evidence for late jurassic fault controlled subsidence is widespread over the whole basin the pattern of late jurassic subsidence appears to change across the nazare fault zone north of the nazare fault fault controlled subsidence occurred mainly along nnw sse trending faults and to the south of this fault zone a nne ssw fault pattern seems to dominate the oxfordian rift phase is testified in onlapping of the oxfordian succession on salt pillows which formed in association with fault activity the fourth and final rift phase was in the latest late jurassic or earliest early cretaceous the jurassic extensional tectonism resulted in triggering of salt movement and the development of salt structures along fault zones however only salt pillow development can be demonstrated the extensional tectonics ceased during the early cretaceous during most of the cretaceous regional subsidence occurred resulting in the deposition of a uniform lower and upper cretaceous succession marked inversion of former normal faults particularly along ne sw trending faults and development of salt diapirs occurred during the middle miocene probably followed by tectonic pulses during the late miocene to present the inversion was most prominent in the central and southern parts of the study area in between these two areas affected by structural inversion fault controlled subsidence resulted in the formation of the cenozoic lower tagus basin northwest of the nazare fault zone the effect of the compressional tectonic regime quickly dies out and extensional tectonic environment seems to have prevailed the miocene compressional stress was mainly oriented nw se shifting to more n s in the southern part

process based modeling of tsunami inundation and sediment transport 1 the infrequent and unpredictable nature of tsunamis precludes the use of field experiments to measure the hydrodynamic and sediment transport processes that occur instead these processes are often approximated from laboratory numerical and theoretical studies or inferred from observations of the resultant sediment deposits here delft3d a three dimensional numerical model is used to simulate the inundation and sediment transport of a tsunami similar in magnitude to the 26 december 2004 indian ocean tsunami over one measured and three idealized morphologies the model is first shown to match well the observations taken at kuala meurisi sumatra and then used to examine in detail the processes that occur during the tsunami the model predicts that at a given cross shore location the onshore flow accelerates rapidly to a maximum as the wavefront passes and then gradually decelerates before reversing direction and flowing offshore the onshore flow does not tend to zero everywhere at maximum inundation but instead flow reversal occurs near the shoreline even as the wavefront continues to inundate landward while some sediment is eroded by the passing wavefront the suspension of sandy sediment is dominated by the long duration high velocity backwash that occurs along the beach face and offshore of the shoreline some of the sediment suspended during backwash is advected shoreward by the subsequent wave creating large spatial gradients in the suspended sediment concentrations which may not be in equilibrium with the local hydrodynamics the inundation and transport of sediment during a tsunami can be affected by complexities in the morphological profile and interactions between multiple waves and many of the hydrodynamic and sediment transport processes predicted here are similar to analogous processes previously observed in the swash zone

jurassic tectono sedimentary evolution of the northern lusitanian basin offshore portugal abstract the lusitanian basin is one of a series of rift related basins developed during the rifting that led to the break up of iberia and canada the strong influence of halokinesis on the depositional evolution of its northern sector provides an analogue for the development of other evaporite prone rift basins on atlantic type passive margins in this paper the pre valanginian evolution of the northern lusitanian basin is documented based on regional seismic stratigraphy isochron and time structure maps tied with sonic and stratigraphic data from 10 exploration wells the pre salt structure of the study area is marked by two sets of faults i a n s to ne sw striking set active throughout the jurassic period and ii a nw se striking set active during the late jurassic the latter defines five late jurassic sub basins northeast of a basin margin structure the marinha grande fault the development of half graben basins in the northern lusitanian basin during the jurassic was overprinted by halokinesis over the marinha grande fault and other major marginal basement faults halokinesis climaxed during the oxfordian kimmeridgian rifting with the formation of a 10 km long salt ridge over the marinha grande fault the ridge limited the southward progradation of fluvial deltaic units derived from hanging wall drainage systems and restricted the syn rift sediments to a 15 km long 5 km wide bowl shaped depocentre located 10 km west of the present coastline in order to better characterise the jurassic tectono sedimentary evolution of the northern lusitanian basin the interpreted seismic data is compared with physical models for extensional forced folds above active normal faults and with stratigraphic information from well and outcrop

uniform sense normal simple shear of the continental lithosphere geophysical studies suggest that the thin crust characteristic of the basin and range province extends eastward beneath the west margin of the colorado plateau and rocky mountain regions in arizona and utah zones perhaps over 100 km wide may be defined bounded on the west by the east limit of upper crustal normal faults that account for more that 10 extension and on the east by the east limit of thinning beneath the colorado plateau a discrepancy exists within these zones between the negligible extension measurable in the upper crust and the substantial extension apparent from crustal thinning assuming the discrepant zone crust was as thick as or thicker than the colorado plateau rocky mountain crust prior to extensional tectonism if various theories appealing to crustal erosion are dismissed mass balance problems evident in the discrepant zones are most easily resolved by down to the east normal simple shear of the crust moving lower and middle crustal rocks that initially were within the zones up and to the west to where they now are locally exposed in the basin and range province west of the discrepant zones in both arizona and utah east directed extensional allochthons with large displacement are exposed these geophysical and geological observations complement one another if it is accepted that the entire crust in both arizona and utah failed during extension on gently east dipping east directed low angle normal faults and shear zones over a region several hundred kilometres wide large scale uniform sense normal simple shear of the crust suggests the entire lithosphere may do the same such a hypothesis predicts major lithospheric thinning without crustal thinning will occur in plateau areas in the direction of crustal shear in the case of the arizona utah and red sea extensional systems and possibly the death valley extensional terrain a broad topographic arch typically 1500 2000 m higher than the extended terrain is present suggesting lithospheric thinning in areas predicted by the hypothesis

tsunami deposits in a super large wave flume abstract understanding the process of sediment transport under tsunami inundation is essential to providing credible information about potential tsunamis from tsunami deposits in this study a super large wave flume 205 m long and 3 4 m wide was used to investigate the hydraulic process of tsunami inundation and sedimentary features of the resulting tsunami deposit a uniformly sloping topography 1 50 with a sand dune 0 2 m high was built in the flume and the topography change induced by a solitary wave was measured the maximum wave height at the shoreline was 0 6 m and the horizontal velocity reached up to 3 5 m s resulting in a sediment concentration of up to 5 by volume the inundation and return flow completely eroded the dune and caused deposition which showed landward and seaward thinning and fining the vertical distribution of grain size and density in the inundation flow indicated upward fining and an upward decrease in density and the deposits showed inverse grading at the base in addition to normal grading therefore the inverse grading was attributed to the depositional process instead of the vertical distribution of grain size in the flow such as via a traction carpet the inundation flow was classified into two phases the first phase flow which appeared at the front of the inundation flow was governed by the wave speed at the shoreline the second phase flow which occurred near the dune was controlled by the difference in wave levels in front of and behind the dune the deposits caused by the first phase flow near the inundation limit were constant regardless of the presence of the dune indicating that the effect of the dune on the deposits was limited in the nearshore region the deposits near the inundation limit showing rapid fining and different chemical compositions were carried by muddy foam floating on the water surface the sediment supply from offshore to onshore over the dune was small and the erosion of the sand dune accounted for 36 of the onshore deposits the offshore deposits were mainly caused by wave motion and the contribution of the onshore sediment brought by the return flow was small 24 however the return flow had a large effect on the sedimentary structure of the offshore deposits such as seaward fining our results will help to examine the physical processes resulting in the empirically established common sedimentary characteristics of tsunami deposits and will provide a detailed data set to validate sediment transport models used in numerical simulations

sedimentologic and geomorphologic tsunami imprints worldwide a review abstract tsunami events with extreme effects on sedimentary transport or considerable alterations of the coastal configuration are rather rare regarding human history but considering geological timescales they occur frequently at least 100 megatsunami in different parts of the world have been recorded in the past 2000 years but presumably far more have failed to be noticed during historical times and are not mentioned either in written or oral ancient records therefore the topic of paleotsunami requires inevitable sedimentological and geomorphological research however field research concerning paleotsunami is astonishingly rare within the scientific approach and only 5 of the existing tsunami literature is related to this subject future efforts in paleotsunami research should focus on the geological evidence of these mega events to clarify their contribution to coastal forming processes this paper reviews the state of the art knowledge of sedimentologic and geomorphic imprints of tsunami along the world s coastlines in order to highlight the need for more detailed studies of paleotsunami depositional and geomorphological traces

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

oscillatory zoning in eclogitic garnet and amphibole northern serpentinite melange cuba a record of tectonic instability during subduction exotic blocks of eclogite from distant localities along the northern serpentinite melange of cuba have comparable p t histories that include high pressure prograde sections 450 600 c 15 kbar associ ated with subduction of oceanic lithosphere and retrograde sections within the albite epidote amphibolite facies 500 c 10 kbar related to melange uplift 40 ar 39 ar and rb sr cooling ages 118 103 ma of one of the blocks indicate pre aptian subduction and aptian albian uplift detailed x ray imaging and profiling further reveals that minerals in these eclogite blocks notably garnet and amphibole display subtle but well defined oscillatory zoning that developed along the prograde trajectory of the rocks previous to attainment of peak eclogitic conditions the chemistry e g coupled changes of mg and mn in garnet and of si ti al and na in amphibole and geometry euhedral to anhedral shapes of the oscillations can be interpreted in terms of subtle fluctuations in p t during the general prograde subduction related metamorphic path a near equilibrium model is presented for the formation of oscillations at near peak conditions by means of recurrent dissolution growth reaction processes this model for near peak conditions and the chemical signatures of earlier oscillations notably in amphibole suggest that episodes of retrogression upward movement affected parts of the subducting slab it is proposed that these retrograde episodes record the tectonic rupture of the subducting slab and probably of the upper plate mantle either due to the intrinsic dynamic behaviour of subduction systems or to the effects of the plate tectonic rearrangement of the caribbean region during the early cretaceous

structural comparison of archetypal atlantic rifted margins a review of observations and concepts abstract in this study we compare three pairs of conjugate rifted margins that are often referred to as archetypes of rift systems despite numerous differences a remarkable first order structural similarity appears between the magma poor iberia newfoundland the magma rich mid norway east greenland and the sediment rich angola brazil rifted margins typical is the seaward arrangement of distinct domains proximal necking distal and outer that each present specific comparable structural characteristics our study also suggests that magma rich systems may go through a stage of hyper extension indicating that extreme crustal thinning does not preclude a magmatic breakup in this contribution we clarify the definition of a number of terms introduced recently in rifted margin studies we review the major features constitutive of these key referenced systems discuss their similarities and differences and examine how the related deformation modes develop in the life cycle of a rift that goes to seafloor spreading we conclude that the distinct domains observed in the margin architecture represent distinct stages in the evolution of rifted margin independently of their later evolution into magma poor or magma rich environments

measurements and modelling of the advection of suspended sediment in the swash zone by solitary waves novel laboratory experiments and numerical modelling have been performed to study the advection scales of suspended sediment in the swash zone an experiment was designed specifically to measure only the sediment picked up seaward of the swash zone and during bore collapse the advection scales and settling of this sediment were measured during the uprush along a rigid sediment free beach face by a sediment trap located at varying cross shore positions measurements were made using a number of repeated solitary broken waves or bores approximately 25 of the pre suspended sediment picked up by the bores reaches the mid swash zone 50 of the horizontal run up distance indicating the importance of the sediment advection in the lower swash zone the pre suspended sediment is sourced from a region seaward of the shoreline still water line which has a width of about 20 of the run up distance an eulerian lagrangian numerical model is used to model the advection scales of the suspended sediment the model resolves the hydrodynamics by solving the non linear shallow water equations in an eulerian framework and then solves the advection diffusion equation for turbulence and suspended sediment in a lagrangian framework the model provides good estimates of the measured mass and distribution of sediment advected up the beach face the results suggest that the correct modelling of turbulence generation prior to and during bore collapse and the advection of the turbulent kinetic energy into the lower swash is important in resolving the contribution of pre suspended sediment to the net sediment transport in the swash zone c 2009 elsevier b v all rights reserved

the betic orogen and the iberian african boundary in the gulf of cadiz geological evolution central north atlantic abstract the study of the gulf of cadiz on the basis of multichannel seismic profiles and wells illustrates the stratigraphy and tectonics the evolution of the southern iberian margins was more complex than in most north atlantic margins since it entailed several phases of rifting convergence and strike slip motions three main tectonic provinces surround the internal zones of the gibraltar arc orogenic belt these include in the iberian margin of the gulf of cadiz the flysch units of the campo de gibraltar complex the betic external zones and the neogene basins of the guadalquivir valley fault bounded blocks of flysch and subbetic units crops out over large areas of the southeastern iberian shelf the basement of the northwestern area in contrast is represented by the paleozoic rocks of the hercynian massif of iberia half graben structures determined the main structural trends of the margin during the mesozoic which were affected by inversion structures during the neogene compressional stages the mesozoic and lower cenozoic units are best observed in wells and seismic profiles from the northern area these units are either obscure below a thick olistostrome deposit or are absent in most of the rest of the gulf of cadiz seven lithoseismic units from triassic to upper oligocene and another seven neogene and quaternary units are identified based on the relationship to the depositional sequence and the emplacement of the olistostrome the first tectonic phase was characterized by a passive margin which was controlled by the development of half graben extensional structures and carbonate platforms this evolution comprises the mesozoic and early cenozoic ocean spreading in the north atlantic induced extensional tectonics which deformed the cretaceous syn tectonic post aptian deposits increased amounts of terrigenous materials were supplied to the margin from aptian to albian times controlling depositional patterns while terrigenous siliciclastic facies replaced the jurassic carbonate platforms from middle eocene to early miocene the margin was influenced by the relative motions of iberia and africa and the development of the alpine orogeny the iberian african boundary in the gulf of cadiz experienced transpression and the mesozoic basins probably underwent subduction the emplacement of an olistostrome took place in the gulf of cadiz towards the central atlantic basin plains during the tortonian the end of the olistostrome emplacement during the late miocene coincides with accelerated tectonic subsidence while thick progradational and aggradational depositional sequences were developed the occurrence of closely juxtaposed regions of compression and extension during the miocene may reflect the westwards progression of the gibraltar arc mountain front over a subducting thinned tethys crust when the motion between iberian and africa was n s to nnw sse oriented the migration of the arcuate mountain front into the eastern gulf of cadiz is attributed to a mechanism of collision induced delamination of the mantle lithosphere in contrast to the betic rif belts however there is no geophysical evidence to postulate that continental collision took place in the gulf of cadiz during the cenozoic

the ecologite bearing metabasaltic sequence of isla margarita venezuela a geochemical study abstract xrf analyses for twenty elements in 41 samples and rnaa for eight ree in ten samples have been carried out as part of a continuing project to elucidate the geological history of the la rinconada group metabasites of margarita island venezuela through the study of continuous and discontinuous metamorphic reactions the study of variations in amphibole composition and by means of a large scale survey of bulk rock geochemistry all together twelve sampling points taken along a continuous metamorphic profile were considered with grade increasing from chlorite bearing amphibolites to paragonite bearing amphibolites to end up into amphibole bearing eclogites the entire section lies within the p t field of conditions of the epidote amphibolite facies the la rinconada group as a whole has a basaltic character although sio 2 may reach as much as 54 despite being macroscopically monotonous the metabasites are chemically variable with fractionation indices i e feo mgo varying by a factor of 5 from 0 48 to 2 66 there is no correlation between the zonation in the metamorphic mineral assemblages and the bulk rock chemistry so that this zonation must reflect only variations in the intensive parameters of metamorphism a definitive distinction between morb and iat or the pia classification of donnelly and rogers 1978 is not yet possible on the basis of the present partial data set the lil elements which are notoriously mobile suggest an iat affinity however the relatively immobile elements ti cr zr and y favour morb ree patterns and enrichment factors which are also considered fairly reliable criteria display characteristics between those typical of morb and pia

magnetic evidence for slow seafloor spreading during the formation of the newfoundland and iberian margins there is considerable debate concerning the nature and origin of the thin crust within the ocean continent transition oct zones of many passive non volcanic continental margins located between thinned continental and true oceanic crust this crust is usually found to be underlain by upper mantle material of 7 2 7 4 km s velocity at shallow depths 1 2 km it has been proposed that such crustal material could have originated either by exhumation of upper mantle material during rifting of continents or by slow seafloor spreading one of the examples of occurrence of such a crust are the conjugate margins of newfoundland and iberia here we present an interpretation of magnetic data from these regions to show that their oct zones are underlain by crustal material formed by slow seafloor spreading 6 7 mm yr soon after iberia separated from the grand banks of newfoundland in the late jurassic similarities in the magnetic anomalies and velocity distributions from these regions with those from the sohm abyssal plain a region lying immediately south of the newfoundland basin and formed by seafloor spreading at a similar rate of spreading give further support to such an interpretation the idea that these regions were formed by unroofing of upper mantle during rifting of iberia from newfoundland may be likely but the presence of weak magnetic anomalies in these regions which bear all the characteristics of seafloor spreading anomalies makes it difficult to ignore the possibility that these regions could be underlain by oceanic crust formed during slow seafloor spreading the similarities in velocity structure and the presence of small amplitude magnetic anomalies both across this pair of conjugate margins of the north atlantic and that of the labrador sea suggest that this oct velocity structure may be the norm rather than the exception across those passive non volcanic margins where the initial seafloor spreading was slow furthermore the existence of similar velocity distributions along a few active spreading centers raises the possibility of formation of similar crust across slow spreading ridges fl 2000 elsevier science b v all rights reserved

tsunamis as geomorphic crises lessons from the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract large tsunamis are major geomorphic crises since they imply extensive erosion sediment transport and deposition in a few minutes and over hundreds of kilometres of coast nevertheless little is known about their geomorphologic imprints the december 26 2004 tsunami in sumatra indonesia was one of the largest and deadliest tsunamis in recorded human history we present a description of the coastal erosion and boulder deposition induced by the 2004 tsunami in the lhok nga bay located to the west of banda aceh northwest sumatra the geomorphological impact of the tsunami is evidenced by beach erosion some beaches have almost disappeared destruction of sand barriers protecting the lagoons or at river mouths numerous erosion escarpments typically in the order of 0 5 1 5 m when capped by soil and more than 2 m in dunes bank erosion in the river beds the retreat along the main river is in the order of 5 15 m with local retreats exceeding 30 m large scars typically 20 50 cm deep on slopes dislodgement of blocks along fractures and structural ramps on cliffs the upper limit of erosion appears as a continuous trimline at 20 30 m a s l locally reaching 50 m the erosional imprints of the tsunami extend to 500 m from the shoreline and exceed 2 km along riverbeds the overall coastal retreat from lampuuk to leupung was 60 m 550 000 m 2 and locally exceeded 150 m over 276 000 m 3 of coastal sediments were eroded by the tsunami along the 9 2 km of sandy coast the mean erosion rate of the beaches was 30 m 3 m of coast and locally exceeded 80 m 3 m the most eroded coasts were tangent to the tsunami wave train which was coming from the southwest the fringing reefs were not efficient in reducing the erosional impact of the tsunami the 220 boulders measured range from 0 3 to 7 2 m large typically 0 7 1 5 m with weights from over 50 kg up to 85 t we found one boulder less than 1 m large at 1 km from the coastline but all the others were transported less than 450 m 30 m and the moderate tsunamis height