flow characteristics of metresa an oligocene seismoturbidite in the dukla unit polish carpathians metresa is a thick distinctive turburdite within the menilite shales in the carpathians of south east poland it was deposited by a se flowing turbidity current derived from the silesian cordillera and can be traced for 55 km downcurrent it has a width of at least 15 km the current contained roughly 3 km3 of sediment and conforms to the definition of a seismoturbidite grain size analyses of samples from the nine localities where metresa is exposed indicate average velocities decreasing from 2 m s 1 to less than 1 m s 1 over the 55 km massive divisions are poorly developed instead the turbidite although graded tends to be laminated throughout flat lamination predominates with intercalated cross lamination and erosion structures at various levels small scale cross lamination presumably associated with ripples occurs at some upper levels an exceptional feature is a large scale wave like structure somewhat resembling hummocky cross stratification the structures are not consistent with the inferred velocities it is suggested that the stability fields relating structures to stream power herein called the allen fields are displaced in respect to deposition from waning turbidity currents

grain size distribution patterns of a point bar system in the usri river india grain size distribution patterns in a point bar system of the usri river india were critically analysed in the light of log normal log hyperbolic and log skew laplace distribution models sand samples were collected from the cross bedding foreset of different sizes of bedform the objectives were to i study whether bedform heights have any role in grain size distribution patterns ii offer a best fit statistical model iii study the downstream variation of size sorting in a point bar system and iv study the mechanism of grain sorting the results indicate that the bedform heights have no role in grain size distribution patterns quantitatively when the errors in three distribution models were analysed it was observed that the log normal distribution is the best fit statistical model and the next one is the log skew laplace however in the upper reaches of the river log normal distribution is the best fit model in the case of large bedforms whereas in the lower reaches the log normal model is the best fit one in the case of small bed forms it is also observed that within a point bar for large and small bedforms there is a tendency for mean grain size to decrease downstream between point bars for large bedforms there is no consistency in decreasing grain size downstream whereas for small bed forms the decrease of grain size downstream is observed except near the confluence at palkia with distance of transport the coarser and finer fractions of sediments are gradually chopped off the coarser fractions are buried below the advancing bedforms on the lee sides and the finer ones are transported further downstream thus the finer admixture giving rise to the fining upward sequence overlies a carpet of coarser materials this mechanism provides a clue to the process of grain sorting in the fluvial environment an interpretation has been offered for the log normality of the grain size distribution pattern during prolonged transportation in a fluvial environment the larger grain size fractions are gradually chopped off and buried below the advancing bedforms on their lee sides on the other hand the finer fractions are transported further downstream in suspension thus the narrow intermediate size fraction takes active part in the distribution patterns leading to the generation of unimodality and a symmetric distribution pattern downstream which are the main criteria for log normality similarly increase of bedform size is the effect of increase of stream power and froude number leading to the selective segregation of bed materials thus the intermediate size fractions take a more active part than the coarser and the finer size fractions in developing log normality besides the hydrodynamic parameters of the usri coarsening of grain size downstream has been attributed to i the aggrading nature of the usri downstream and ii the contribution of coarser materials to the usri by its tributaries and bank erosion copyright 2006 john wiley sons ltd

lithologic and structural controls on natural fracture distribution and behavior within the lisburne group northeastern brooks range and north slope subsurface alaska the carboniferous lisburne group of northern alaska has been deformed into a variety of map scale structures in both compressional and extensional structural settings thus providing a series of natural experiments for observing the formation distribution and behavior of fractures in this thick carbonate unit two fracture sets dominate the lisburne group carbonates of the north slope subsurface and the nearby northeastern brooks range fold and thrust belt north northwest striking regional extension fractures probably formed in front of the northeastern brooks range fold and thrust belt in the north slope subsurface this fracture set overprints east northeast striking fractures related to earlier extensional deformation in contrast in the fold and thrust belt the north northwest striking fracture set is overprinted by younger east northeast striking fractures related to subsequent contractional deformation lithology is the primary control on the fracture density of both sets in mildly deformed lisburne copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 20 1996 revised manuscript received november 25 1996 final acceptance june 5 1997 2geophysical institute university of alaska fairbanks fairbanks alaska 99775 3sandia national laboratories ms 0705 albuquerque new mexico 87185 4department of petroleum natural gas engineering new mexico institute of mining technology socorro new mexico 87801 and sandla national laboratories ms 0705 albuquerque new mexico 87185 this study was supported by a department of energy subcontract administered by sandia national laboratories additional support was provided by arco alaska bp alaska chevron exxon mobil and japan national oil company we would like to thank arco alaska and bp alaska for giving us permission to view selected lisburne group cores w wallace for helpful discussions on deformational styles of detachment folds a j mansure for help in interpreting the interference tests and w wallace k biddle w belfield n hurley and j kelley for helpful reviews of the manuscript

weibull vs lognormal distributions for fluvial gravels abstract krumbein and tisdel 1940 suggested that the particle size distribution of a weathered source rock tends to follow the rosin distribution whereas with distance downstream fluvially transported sediment tends to follow the lognormal distribution this issue can be illuminated somewhat by recognizing that the rosin distribution is the same as the well studied weibull distribution however it can be difficult to distinguish the lognormal rosin weibull and even gamma distributions in particle size distribution curves brennan and durrett 1987 suggest that differences in splitting rates can give rise to the lognormal vs weibull distributions but the geological implications of these concepts and the integration of the effects of sorting by fluvial transport remain to be addressed

hydraulic controls of grain size distributions of bedload gravels in oak creek oregon usa grain size distributions of gravels transported as bedload in oak creek oregon show systematic variations with changing flow discharges at low discharges the gravel distributions are nearly symmetrical and gaussian as discharges increase the distributions become more skewed and follow the ideal rosin distribution the patterns of variations are established by goodness of fit comparisons between the measured and theoretical distributions and by q mode factor analysis two end members are obtained in the factor analysis having respectively almost perfect gaussian and rosin distributions and the percentages of the two end members within individual samples vary systematically with discharge transformation from gaussian to rosin distribution with increasing discharge may be explained by processes of selective entrainment of grains from a bed of mixed sizes samples of bed material in oak creek follow the rosin distribution at high discharges the transported bedload approaches the grain sizes of that bed material source and mimics its rosin distribution random selection processes must be more important to grain entrainment at lower discharges so that the resulting gaussian distributions of transported bedload reflect similar distributions of bed stresses exerted by the stream flow the results from oak creek demonstrate that the competence of the flow is reflected in the entire distribution of transported gravel sizes a sequence of layers of fluvial gravels modern or ancient might show systematic variations between coarse rosin and finer grained gaussian distributions and these could be used to infer frequencies of various discharges and to establish a relationship to the source sediment with further study analyses of changing bedload grain size distributions and their transport rates will lead to a better understanding of downstream variations in grain sizes of bed sediments and how their distributions reflect the progressive development of textural maturity

the benefit of hh and vv polarizations in retrieving extreme wind speeds for an ascat type scatterometer the wind retrieval performance of a fixed fan beam scatterometer operating at c band in vv polarization advanced scatterometer ascat type is well established in the range of 0 25 m s this work evaluates prospective extensions with hh and vh polarized beams aimed at improving retrievals at extreme wind speeds from 25 to 65 m s the geophysical model functions for c band vv hh and vh polarized backscatter used in the wind retrieval simulations are defined along with an objective assessment of the quality scores ascribed to the optional beam configurations our study finds that the introduction of a vh capability in the midbeam improves the determination of wind speed over the entire scatterometer swath with wind speed root mean square rms errors of about 0 5 m s the introduction of hh beams in the fore aft antennas improves the determination of the ocean surface wind vector wind speed and direction but over a more limited portion of the outer swath with wind vector rms errors as low as 6 m s but conditioned to a priori information to resolve the directional ambiguity if the determination of wind speed primes over the determination of wind vectors at high wind speeds then the introduction of a single vh capability in the midbeam antenna comes forth as the most simple and cost effective manner to extend the wind retrieval capabilities of an ascat type scatterometer into the domain of extreme winds

quantitative evaluation of fractures on monkshood anticline a detachment fold in the foothills of western canada monkshood anticline is a well exposed surface anticline located in the foothills in northeastern british columbia extension fractures are well developed in the prophet formation a carbonate shale chert sequence throughout this fold virtually all of these fractures are filled with some combination of calcite and quartz cements the fractures formed and the mineral cements were deposited during the fold development most fractures on monkshood anticline have formed at high angles to bedding and they commonly fall into two to three distinct orientation sets the dominant fracture trend is aligned with the fold axis through the backlimb of the fold but there is considerable variance in the dominant orientation in the forelimb an order of magnitude variation is found in fracture densities across this fold and over two orders of magnitude variation occur in mean fracture aperture these variations in density and aperture do not correlate with particular structural positions fracture trace lengths exhibit power law distribution patterns suggesting fractal character fracture aperture displays a roughly linear correlation to volumetric fracture strain but shows no consistent association with either density or trace length stochastic modeling of the fracture networks on monkshood anticline suggests density is the primary factor affecting fracture network connectivity but fracture size also can play an important supporting role the occurrence of a dominant fracture orientation set can impart a significant directional bias to connectivity measurement stations on monkshood anticline that have both high fracture densities for connectivity and substantial fracture apertures for conductance occur primarily in midlimb positions

cross polarization geophysical model function for c band radar backscattering from the ocean surface and wind speed retrieval the wind speed sensitivity of cross polarization cross pol radar backscattering cross section vh from the ocean surface increases toward high winds the signal saturation problem of vh if it exists occurs at a much higher wind speed compared to the copolarization copol vv or hh sea returns these properties make vh a better choice over vv or hh for monitoring severe weather combined with high spatial resolution of the synthetic aperture radar sar the development of hurricane wind retrieval using vh is advancing rapidly this paper describes a cross pol c band radar backscattering geophysical model function gmf with incidence angle dependence for the full wind speed range in the available data sets up to 56 m s the gmf is derived from radarsat 2 r2 dual polarization dual pol scansar modes with 300 and 500 km swaths the proposed gmf is compared to other published algorithms the result shows that the simulated vh cross section and the retrieved wind speed with the proposed gmf is in better agreement with measurements with careful treatment of noise the vh retrieved wind speeds may extend to mild or moderate conditions the higher fraction of non bragg contribution in vh can be exploited for analysis of surface wave breaking

on bayesian scatterometer wind inversion in a quest for a generic unbiased scatterometer wind inversion method the different inversion procedures currently in use are revisited in this paper a careful examination of both the errors in the wind and in the measurement domain combined with the nonlinear shape of the geophysical model function gmf leads to a generic and novel bayesian wind retrieval approach in the measurement domain in this approach the shape of the gmf solution manifold in measurement space is more important than the specified noise this shape is related to the system wind direction sensitivity and when this sensitivity is uniform realistic and precise wind direction distributions are retrieved even when measurements lie far from the gmf manifold a simplified measurement space transformation that produces such uniform sensitivity for the european remote sensing satellite ers scatterometer is presented and shown to have reduced wind direction bias compared to the more traditional measurement noise normalized inversion for ers moreover the simplified wind inversion reveals a similar performance to the current operational ers wind inversion but is potentially more generally applicable the simplified method is then applied to seawinds but is ineffective in this case the instrument geometry results in a low sensitivity to wind direction at a few specific directions as a consequence certain wind direction solutions remain favored in the seawinds inversion

fetch and duration limited nature of surface wave growth inside tropical cyclones with applications to air sea exchange and remote sensing abstractthe 2d wavenumber spectra collected by an airborne scanning radar altimeter in hurricane hunter missions are used to investigate the fetch and duration limited nature of wave growth inside hurricanes despite the much more complex wind forcing conditions the dimensionless growth curves obtained with the wind wave triplets reference wind velocity significant wave height and dominant wave period inside hurricanes except near the eye region are comparable to the reference similarity counterparts constructed with the wind wave triplets collected in field experiments conducted under ideal quasi steady fetch limited conditions in dimensionless terms the youngest waves are in the back quarter of the hurricane in the northern hemisphere the dimensionless frequency decreases systematically counterclockwise ccw and the most mature waves are in the left hand sector except for those waves near the eye region the dominant wave phase speeds are about 0 32 to 0 71 times of the local wind speed

dual polarized c and ku band ocean backscatter response to hurricane force winds 1 airborne ocean backscatter measurements at c and ku band wavelengths and h and v polarizations at multiple incidence angles obtained in moderate to very high wind speed conditions 25 65 m s 1 during missions through several tropical cyclones are presented these measurements clearly show that the normalized radar cross sections nrcs response stops increasing at hurricane force winds for both frequency bands and polarizations except for high incidence angles at c band and h polarization the results also show the mean nrcs departing from a power law behavior for all the presented frequency bands polarizations and incidence angles suggesting a reduction in the drag coefficient the overall flattening of the azimuthal response of the nrcs is also very apparent in all cases a new set of geophysical model functions gmfs at c and ku band are developed from these direct ocean backscatter observations for ocean surface winds ranging from 25 to 65 m s 1 the developed gmfs provide a much more accurate characterization of the nrcs versus wind speed and direction and their implementation in operational retrieval algorithms from satellite based scatterometer observations would result in better wind fields the differences between these measurements and other currently available gmfs such as quikscat nscat2 cmod4 and cmod5 are reported the implementation of these gmfs in retrieval algorithms will result in better wind fields from satellite based scatterometers measurements

modelling approaches to understanding fold development implications for hydrocarbon reservoirs a mechanics based approach to the evolution of buckle folds is proposed existing analytic and simple numerical models are used to demonstrate that dramatic changes in layer parallel stress occur in developing folds and that the bulk effective rheology of folding rocks is strongly reduced in relation to neighbouring rocks with no folds a methodology for estimating regions of folds more or less likely to suffer fracture is set out in this methodology a simple abstraction of the natural fold is identified and the stress history during its development is calculated using linear viscosity as a proxy for competence this simple and computationally cheap approach allows all salient features of natural multilayer folds to be recreated in numerical experiments the final step in the method is to use the stress conditions for three types of fracture failure tensile failure dilatant shear failure and grain crushing to define potential functions that indicate increased or decreased probability of failure results give predictions that agree well with observation in the simple cases studied a novel method for approximating three dimensional deformations is used to model the propagation of folds in the axial direction and it is found that this occurs rapidly and allows constructive and destructive interference of propagating folds below a certain amplitude this provides a means by which perturbations may interact over a certain distance such a mechanism was an implicit requisite of classic fold theories but its identity has been obscure for three decades it is shown that many small perturbations are needed to give patches of coherent folds and that few large perturbations give single arc folds

silver abyssal plain carbonate turbidite flow characteristics approximately 20000 years ago the main part of a large turbidity current was channeled between the caicos outer ridge and the bahama escarpment until it spread fanwise across the central silver abyssal plain floor unusual grain size and compositional changes in the turbidite appear to have been produced by surges superimposed on the main flow sharp decreases in the thickness and grain size of the turbidite on the slopes of the caicos outer ridge indicate that the depth of the current was approximately 35 m as deposition began at the first abyssal plain core site estimates based on the fall velocity of the fastest settling particles deposited from suspension suggest that the flow velocity was approximately 3 m sec as the current began to move across the abyssal plain floor the transition from deposition of turbidite sediments with graded bedding to deposition of parallel laminated sediments appears to have occurred at similar or slightly lower flow velocities than those predicted for the transition fr

lateral variations of strain in experimental forced folds abstract packages of rock layers deformed under confining pressure by the uplift and rotation of a steel block forcing assembly translate both towards and away from the margin of the principal uplifted block the resulting asymmetric forced folds and especially their long planar limbs exhibit along layer variations in strain alternations of layer elongation and contraction occur along profiles extending away from the antiform synform couplet layer normal strains are mostly nil so the longitudinal strains largely equate to volume strains in these plane strain models spaced anomalies in outcrops indicating either increased cementation or erosional weakness may suggest that similar processes operate in nature to produce variations in damage caused during the flexural slip process two non exclusive explanations are offered to account for the patterns of strain observed in the experiments 1 they may be caused by decaying wavetrains of small scale flexural deflections and their local strain patterns related to the bending of the major forced folds or 2 they may be caused by a patchy development of layer parallel slip and the consequent spatial variability in displacements

patterns of grain size distribution in some point bars of the usri river india abstract the patterns of grain size distribution of point bar sediments on the usri river india were compared to log normal log hyperbolic and log skew laplace distribution models sediment samples were collected from a specific size of bedform ranging in foreset thickness from 23 to 40 cm from the source to the mouth of the river over a distance of about 90 km the hydrodynamic parameters of the river were also measured at four point bars the results indicate that a the log normal distribution is the best fitted distribution model among the three distribution models b after a certain distance of transport the log normal distribution becomes log hyperbolic and c though there is a tendency for grain size to decrease downstream within each point bar together with improvement of sorting this pattern is not consistent along the entire course of the usri river from one equivalent bar position to the next or from the source to its mouth

comparison of composite bragg theory and quad polarization radar backscatter from radarsat 2 with applications to wave breaking and high wind retrieval 1 depolarized de pol radar backscatter is now produced by many spaceborne satellites analysis of radarsat 2 r2 quad polarization quad pol data with collocated in situ ocean wind measurements reveals that the de pol radar backscatter does not saturate in high winds this is a significant development for radar wind sensing because wind retrieval with copolarized co pol backscatter suffers from problems of incidence and azimuth angle dependent signal saturation and dampening in high winds we present a study comparing satellite quad pol measurements with the composite surface bragg cb theory of radar backscattering from the ocean surface the co pol data are in good agreement with the cb theory de pol data are more sensitive to wind speed compared to theoretical prediction thus retrieval of high winds is more accurate using the de pol return the cubic wind speed dependence of de pol returns in high winds reflects the significant breaking wave contributions the relationship can be used to obtain wave breaking properties from space

muddled or mixed inferring palaeoclimate from size distributions of deep sea clastics abstract one of the outstanding problems of palaeoclimate reconstruction from physico chemical properties of terrigenous deep sea sediments stems from the fact that most basin fills are mixtures of sediment populations derived from different sources and transported to the site of deposition by different mechanisms conventional approaches to palaeoclimate reconstruction from deep sea sediments do not distinguish between provenance and dispersal related variations and therefore often fail to recognise the true significance of variations in sediment properties we formulate a set of requirements that each proposed palaeo environmental indicator should fulfil and focus on the intrinsic coupling between grain size and chemical composition a critical review of past achievements in grain size analysis serves to introduce a conceptual model of spatio temporal grain size variation based on dynamic populations each dynamic population results from a characteristic combination of production and transport mechanisms that corresponds to a distinct subpopulation in the data analysed the mathematical statistical representation of the conceptual model can be obtained by means of the end member modelling algorithm emma applications of the model to several ocean basins are discussed as well as methods to examine the validity of grain size based palaeoclimate reconstructions palaeoclimate reconstructions of a high and low latitude basin illustrate the common degree of complexity of deep sea grain size records

hydraulic interpretation of grain size distributions using a physical model for bedload transport abstract grain size distributions of bedload sediment are modelled by considering the time variation of sediment transport in a unidirectional turbulent flow a frequency distribution of instantaneous bed shear stress is divided into a large number of shear stress ranges with mean values of oi each oi is capable of transporting a range of sediment sizes as bedload the maximum size is just at its entrainment threshold the minimum size is just too large to be suspended rates of bedload transport are calculated for each size range using a theoretical bedload function and the proportion of time that these rates occur is obtained by integrating the frequency distribut on between the boundaries of each shear stress range the relative weights of sediment transported in particular size ranges determined for all oi values constitutes the grain size distribution obtained from bedload sampling at a fixed point on the bed cumulative grain size curves have been simulated using the model in order to demonstrate the effects of the various model parameters e g mean bed shear stress viscosity all curves show a distinct break in slope which represents the maximum grain size transportable in suspension when the shear stress attains its maximum fluctuating value examination of many natural bedload distributions shows close qualitative and quantitative agreement with the model and reasons for discrepancies can be fully explained typical grain size distributions of deposited sediments can be obtained by mixing of different flow related bedload distributions in various proportions thus although deposited sediments may primarily result from bedload transport during a steady flood flow flow unsteadiness also plays a part the effects of some deposition directly from suspended load can also be surmised

numerical modelling of finite amplitude similar folds developing under general deformation histories abstract a simple model of similar folds in homogeneous materials with anisotropic properties is proposed and it is shown that the model is applicable to a wide range of natural examples of folds a mathematical derivation is given which allows the instantaneous deformation of the folds to be calculated for any imposed bulk deformation a means of projecting the effects of the deformation over a finite time interval is described the modelling is illustrated by simulations of folds observed in the morcles nappe western switzerland based on the assumption that the folds formed under simple shear bulk deformation folds with geometrical features remarkably similar to those natural folds are produced in the modelling by varying the parameters

dual polarization measurements at c band over the ocean results from airborne radar observations and comparison with envisat asar data this paper presents an analysis of measurements of the normalized radar cross section nrcs in vertical and horizontal polarizations over the ocean obtained from the c band airborne radar storm the dataset was collected during the experiment called validation with a polarimetric airborne radar of envisat sar over the ocean valpareso which took place during the calibration validation phase of the envisat advanced synthetic aperture radar asar from this dataset the properties of the polarization ratio are discussed and in particular its dependencies with radar geometry incidence and azimuth angle as well as with meteorological conditions wind and sea state the polarization ratio is found to be dependent on incidence and azimuth angles its dependence with incidence angle is found to be significantly different from empirical models previously proposed in the literature it also exhibits some correlation with surface conditions wind and wave with a more important correlation with significant wave steepness two new analytical formulations are proposed to model the polarization ratio one as a function of incidence angle only the second one with additional dependence with azimuth angle it is shown that it is necessary to consider an azimuth dependent polarization ratio for incidence angles larger than 30 spl deg comparisons with the polarization ratio from envisat asar images are used to assess this model