stabilization of the coupled oxygen and phosphorus cycles by the evolution of bioturbation animal burrowing and sediment mixing bioturbation began during the run up to the ediacaran cambrian boundary1 2 3 initiating a transition4 5 between the stratified precambrian6 and more well mixed phanerozoic7 sedimentary records against the backdrop of a variable8 9 global oxygen reservoir probably smaller in size than present10 11 phosphorus is the long term12 limiting nutrient for oxygen production via burial of organic carbon13 and its retention relative to carbon within organic matter in marine sediments is enhanced by bioturbation14 15 16 17 18 here we explore the biogeochemical implications of a bioturbation induced organic phosphorus sink in a simple model we show that increased bioturbation robustly triggers a net decrease in the size of the global oxygen reservoir the magnitude of which is contingent upon the prescribed difference in carbon to phosphorus ratios between bioturbated and laminated sediments bioturbation also reduces steady state marine phosphate levels but this effect is offset by the decline in iron adsorbed phosphate burial that results from a decrease in oxygen concentrations the introduction of oxygen sensitive bioturbation to dynamical model runs is sufficient to trigger a negative feedback loop the intensity of bioturbation is limited by the oxygen decrease it initially causes the onset of this feedback is consistent with redox variations observed during the early cambrian rise of bioturbation leading us to suggest that bioturbation helped to regulate early oxygen and phosphorus cycles

extreme waves in shallow and intermediate water depths this paper concerns the description of large transient waves in shallow and intermediate water depths it builds upon recent advances in the description of deep water waves and provides the first quantitative comparisons with a new kinematic model which has hitherto only been validated in deep water conditions a new series of experimental observations is presented in which the wave components within a random or irregular sea state are focused to produce a large transient wave group comparisons with both linear and second order solutions suggest that non linear wave wave interactions produce a steeper wave envelope in which the central wave crest is higher and narrower while the adjacent wave troughs are broader and less deep spectral analysis of the measured water surface elevation suggest that in addition to the development of significant long wave energy there is also a transfer of energy to the shorter high frequency harmonics this energy redistribution has a significant effect upon the underlying kinematics in particular the near bed velocities are shown to be in good agreement with the second order solution which includes the long wave or frequency difference terms first identified by longuet higgins and stewart furthermore the near surface kinematics are shown to be highly non linear indeed a linear wave theory based upon a correct representation of the freely propagating linear harmonics is generally found to under estimate the near surface horizontal velocity however if the linear calculations are based upon a measured wave spectrum the kinematic predictions suffer from high frequency contamination and require empirical correction in contrast the non linear numerical model presented by baldock and swan provides a good description of the measured kinematics over the entire water depth

relationship between the tibetan snow in spring and the east asian summer monsoon in 2003 a global and regional modeling study in 2003 a climate extreme accompanying a wet and cool summer over east asia was recorded over the east asian countries including central china korea and japan a possible relation of this record breaking summer in east asia to above normal snowfall over the tibetan plateau in spring has been investigated using the national centers for environmental prediction ncep global and regional models the changes in the simulated east asian summer monsoon circulations in response to snow anomalies over tibet are highlighted the results from both global and regional model experiments suggest that above normal snowfall over the tibetan plateau in may induces a weakening of the tibetan high which leads to the formation of favorable upper level circulations accompanying cyclonic circulation anomalies covering the east asian region in summer these circulation anomalies inresponse tothe snow anomalies over theplateau aremore robust and closer towhat wasobserved in the regionalthan inthe global model results the sensitivity experimentsalso show that the precipitation and lower level circulation anomalies in summer caused by the snow anomalies in spring influence the above normal precipitation in the lower reaches of the yangtze river basin as revealed in previous observational studies however the experiments do not fully explain the observed signals in korea and japan since the spring snow anomaly over tibet plays a role in weakening the western pacific subtropical high in the simulated summer whereas in reality the intensity of the high was stronger than normal in 2003

diastasis cracks mechanically generated synaeresis like cracks in upper cambrian shallow water oolite and ribbon carbonates upper cambrian limestones and dolostones of western newfoundland canada display conspicuous synsedimentary mud cracks cracks occur in carbonate mudstone interbedded with ooid and peloid grainstone unwashed oolite and ribbon rock lithofacies the traditional interpretation is that these are desiccation cracks the weight of evidence supports an alternative e explanation cracks resulted from the differential mechanical behaviour under stress of stiff mud interlayered with loose ooid peloid sand the processes envisaged to cause such diastasis cracks may be applicabl e to a wide variety of both carbonate and terrigenous clastic deposits composed of interlayered sediments of contrasting material properties and may be a viable alternative to synaeresis

microbial mats as bioreactors populations processes and products microbial mats are dynamic and complex ecosystems exhibiting spatial and temporal heterogeneity the physical chemical environment is typified by steep gradients and distinct microenvironments these microenvironments support a great diversity of species with a wide range of metabolic processes these processes often result in coupled reactions and biogeochemical cycles and produce important end products such as trace gases and mineral precipitates the latter can impact the composition and character of the sediment imparting a biosignature these biosignatures can be preserved in the rock record and are useful in the interpretation of fossil record on earth and possibly as an indication of life on other planetary bodies the modern marine stromatolites of the exuma cays bahamas provide an ideal system for studying the populations processes and products in a microbial ecosystem using a multidisciplinary approach in order to acquire redox energy microbial populations need to carry out metabolic reactions at rates faster than the equivalent chemical abiotic reactions as such microbes can be viewed as bioreactors that preferably oxidize carbon to co2 to maximize the energy yield the study of the microbial role in carbonate sedimentation and lithification in these stromatolites provides a picture of microbial mats as bioreactors producing a biosignature

assessment of wave height distributions using an extensive field database abstract the present paper investigates the short term statistical distribution of wave heights specifically some of the most commonly applied wave height distributions are assessed using field measurements the latter comprise of wave radar observations from 10 different locations in the north sea and cover water depths between 7 7 m and 45 m in total the field database includes more than 200 million waves making it one of the largest of its kind in this water depth regime in using these data the accuracy of existing wave height distributions has been examined and guidance is provided concerning the best performing models and their domain of applicability additionally insights concerning the influence of key met ocean parameters are also provided taken together the results in this paper present an overview of the statistical behaviour of wave heights in finite water depths as observed in the field

field measurements of rogue water waves abstractthis paper concerns the collation quality control and analysis of single point field measurements from fixed sensors mounted on offshore platforms in total the quality controlled database contains 122 million individual waves of which 3649 are rogue waves geographically the majority of the field measurements were recorded in the north sea with supplementary data from the gulf of mexico the south china sea and the north west shelf of australia the significant wave height ranged from 0 12 to 15 4 m the peak period ranged from 1 to 24 7 s the maximum crest height was 18 5 m and the maximum recorded wave height was 25 5 m this paper will describe the offshore installations instrumentation and the strict quality control procedure employed to ensure a reliable dataset an examination of sea state parameters environmental conditions and local characteristics is performed to gain an insight into the behavior of rogue waves evidence is provided to demonstrate that rogue waves are not go

vertical structure of surface gravity waves propagating over a sloping seabed theory and field measurements 1 theoretical predictions of the vertical structure of wave motion over a sloping seabed are compared with field observations close to the bed in the nearshore zone of particular interest is the effect of the local slope on the magnitude and phase of the vertical velocity field measurements of near bed velocity profiles on a 2 bed slope were obtained using a coherent doppler profiler the surface elevation was measured by a colocated upward looking acoustic sounder results are presented from two intervals of different wave energy levels during a storm event for wave height water depth ratios smaller than 0 3 and for ursell numbers smaller than 0 6 the local comparisons of magnitude and phase between the vertical velocity and surface elevation measurements are in good agreement with linear theory for a sloping bed but differ greatly from that for a horizontal bottom especially in the lower water column the sloping bottom however has little effect on the horizontal velocity linear theory appears to adequately describe the transfer function between the surface elevation and the near bed velocities not only at the peak frequencies but also at their harmonics however in relatively shallow water the local transformations of free and forced waves at the harmonic frequencies are indistinguishable in the lower water column therefore given surface elevation measurements at a particular location which reflect the integrated effects of nonlinearities associated with wave shoaling the vertical structure of the third moments of velocity fields estimated from linear theory is in reasonable agreement with the observations both theory and observations show that the skewness and asymmetry of the vertical velocity are subject to significant bottom slope effects whereas those of horizontal velocity are not index terms 4211 oceanography general benthic boundary layers 4203 oceanography general analytical modeling 4219 oceanography general continental shelf processes 4546 oceanography physical nearshore processes 4560 oceanography physical surface waves and tides 1255 keywords shoaling waves bottom slope vertical structure skewness asymmetry boundary layers citation zou q a e hay and a j bowen vertical structure of surface gravity waves propagating over a sloping seabed theory and field measurements j geophys res 108 c8 3265 doi 10 1029 2002jc001432 2003

relationships between sulfide oxidizing bacterial mats and their carbon sources in northern gulf of mexico cold seeps abstract chemical and isotopic characterization of microbial mats collected from methane and petroleum seeps in the gulf of mexico suggest microbial mat color is related to carbon utilization a survey of white and orange colored microbial mats collected in the northern gulf of mexico from the brine pool nr 1 bp and a hydrate mound site in green canyon 234 gc 234 during johnson sea link submersible dives was conducted to explore the bacterial utilization of different carbon sources sedimentary organic matter at bp is predominantly derived from biogenic methane whereas organic material available in sediments at gc 234 originates from a mixture of methane and non methane hydrocarbons interstitial sulfide concentrations were significantly elevated in porewater fluids below white mats collected from bp 1 2 0 2 mm and below orange mats at gc 234 6 1 0 7 mm sulfate reduction rates ranging from 0 4 to 3 8 mol so 4 cm 3 d 1 indicate rapid sulfate consumption below gc 234 orange mats a model based on carbon isotopes was used to delineate possible inorganic and organic carbon sources to bp white mats and gc 234 orange mats the results suggest the white mats are chemoautotrophic and that the orange mats may employ either heterotrophy or autotrophy

recent accelerating mass loss of southeast tibetan glaciers and the relationship with changes in macroscale atmospheric circulations the mass balance history 1980 2010 of a monsoon dominated glacier in the southeast tibetan plateau is reconstructed using an energy balance model and later interpreted with regard to macroscale atmospheric variables the results show that this glacier is characterized by significant interannual mass fluctuations over the past three decades with a remarkably high mass loss during the recent period of 2003 2010 analysis of the relationships between glacier mass balance and climatic variables shows that interannual temperature variability in the monsoonal season june september is a primary driver of its mass balance fluctuations but monsoonal precipitation tends to play an accentuated role for driving the observed glacier mass changes due to their covariation concurrence of warm dry and cold wet climates in the monsoon influenced southeast tibetan plateau analysis of the atmospheric circulation pattern reveals that the predominance of anticyclonic cyclonic circulations prevailing in the southeastern northern tibetan plateau during 2003 2010 contributes to increased air temperature and decreased precipitation in the southeast tibetan plateau regionally contrasting atmospheric circulations explain the distinct mass changes between in the monsoon influenced southeast tibetan plateau and in the north tibetan plateau tien shan mountains during 2003 2010 the macroscale climate change seems to be linked with the europe asia teleconnection

detection of coastlines in sar images using wavelet methods to monitor map and model sediment transport in big river estuaries complete maps of bottom topography are needed this information is obtained by extracting shorelines from synthetic aperture radar sar images of the european remote sensing satellites ers 1r tide gauge information and heights from a dynamic tide model the aim of this paper is to show how coastlines can be derived from sar images by using wavelet and active contour methods in a first step an edge detection method suggested by mallat et al 1992 is applied to ers sar images to detect all edges above a certain threshold a blocktracing algorithm ba then determines the boundary area between land and water a refinement is achieved by local edge selection in this coastal area and by propagation along the wavelet scales in a final step the refined edge segments are joined by an active contour algorithm a model solution for land water segmentation is constructed from a sar image by visual inspection the error is estimated by comparing the results from the algorithms to this model solution the area under investigation is the elbe estuary which is located in the intertidal zone of the german bight due to high rates of sediment transport in this area local government agencies have to spend large amounts of money to keep shipping lanes open the demonstrated method is shown to be suitable for operational use by applying it to a data set of 24 sar images covering a time span of approximately five years

wrinkle structures microbially mediated sedimentary structures common in subtidal siliciclastic settings at the proterozoic phanerozoic transition sedimentary structures produced by microbial activity are well known from ancient carbonate facies but little is known about equivalent microbial structures in ancient siliciclastic facies wrinkle marks and kinneyia ripples are closely related sedimentary structures that are commonly found in ancient siliciclastics and they may represent microbial activity to evaluate this possibility these structures were studied in vendian cambrian strata of north america and compared to structures formed by modern microbial mat communities in redfish bay texas striking similarities in sedimentologic petrographic and morphologic characteristics of modern and ancient occurrences suggest that the enigmatic but widespread ancient structures could have been formed by microbial processes the relative abundance of these structures in siliciclastic facies of this interval further suggests that prior to the onset of relatively intense bioturbation in the ordovician microbial mats could have played a significant role in the evolution and diversification of early life in a broad variety of sea floor environments

offshore stereo measurements of gravity waves stereo video techniques are effective for estimating the space time wave dynamics over an area of the ocean indeed a stereo camera view allows retrieval of both spatial and temporal data whose statistical content is richer than that of time series data retrieved from point wave probes to prove this we consider an application of the wave acquisition stereo system wass for the analysis of offshore video measurements of gravity waves in the northern adriatic sea in particular we deployed wass at the oceanographic platform acqua alta off the venice coast italy three experimental studies were performed and the overlapping field of view of the acquired stereo images covered an area of approximately 1100 m2 analysis of the wass measurements show that the sea surface can be accurately estimated in space and time together yielding associated directional spectra and wave statistics that agree well with theoretical models from the observed wavenumber frequency spectrum one can also predict the vertical profile of the current flow underneath the wave surface finally future improvements of wass and applications are discussed

response of karakoram himalayan glaciers to climate variability and climatic change a regional climate model assessment the karakoram and the himalayan mountain range accommodate a large number of glaciers and are the major source of several perennial rivers downstream to interactively describe to response of glaciers to climate change a glacier parameterization scheme has been developed and implemented into the regional climate model remo the scheme simulates the mass balance as well as changes of the areal extent of glaciers on a subgrid scale the parameterization scheme is for the first time applied to the region a regional glacier inventory is compiled and is used to initialize glacier area and volume over the highly complex and data sparse region the simulated mass balance largely agrees with observations including the positive karakoram anomaly the simulated equilibrium line altitude is well captured although a systematic underestimation is apparent remo simulates the glacier climate interaction reasonably well it has clear potential to be used for future climate assessments

syneresis cracks subaqueous shrinkage in argillaceous sediments caused by earthquake induced dewatering abstract syneresis cracks often confused with subaerial desiccation phenomena are traditionally ascribed to subaqueous shrinkage whereby salinity changes caused deflocculation of clay this and other previously proposed mechanisms fail to account for their occurrence in low energy typically non evaporitic facies stratigraphically sporadic distribution intrastratal formation under shallow burial depths variation in morphology degree of contraction generation of sedimentary dikelets as crack fills and deformation of dikelets and enclosing layers instead it is suggested that ground motion from strong synsedimentary earthquakes caused argillaceous sediments to dewater interbedded sands and silts to be almost simultaneously liquefied and injected into the resulting fissures and then these dikelets to be distorted comparative rarity of syneresis cracks in phanerozoic versus precambrian marine strata is considered to be primarily an evolutionary consequence of theological changes caused by increased organic binding of clay flocs in the water column greater input of organic matter into the sediment and the diversification of sediment dwelling bacteria and meiofauna in phanerozoic deposits

terminal proterozoic mid shelf benthic microbial mats in the centralian superbasin and their environmental significance abstract a combined sedimentological and biogeochemical study has been conducted on several terminal proterozoic mid shelf microbial mat facies from the centralian super basin isotopic and organic geochemical analysis of the bitumen and kerogen indicated that two sources of organic matter from planktonic and benthic microbial mat populations contributed to the sediment the planktonic source provided a suite of n alkanes with c20 whereas the benthic source contributed an overlay of n alkanes c20 with a strong even preference together with mid chain methyl alkanes kerogen and biomarkers derived from the microbial mat were found to be depleted in 13c relative to planktonic material pyrite in the micorbial mats was also found to be depleted in 34s compared to surrounding facies the combination of these observations suggested that the mats may have been at least partly composed of sulfide oxidising bacteria these organisms have specific environmental tolerances that set limits on palaeo environment their requirement for oxygen indicates that the water column above the mid shelf could not have been anoxic accordingly from the results and age determinations reported here it would appear that mid shelf environments of the centralian superbasin of australia were seeing significant levels of oxygen through the ediacarian

possible indicators of microbial mat deposits in shales and sandstones examples from the mid proterozoic belt supergroup montana u s a abstract it has been suspected for some time that microbial mats probably colonized sediment surfaces in many terrigenous clastic sedimentary environments during the proterozoic however domination of mat morphology by depositional processes post depositional compaction and poor potential for cellular preservation of mat building organisms make their positive identification a formidable challenge within terrigenous clastics of the mid proterozoic belt supergroup a variety of sedimentary structures and textural features have been observed that can be interpreted as the result of microbial colonization of sediment surfaces among these are a domal buildups resembling stromatolites in carbonates b cohesive behaviour of laminae during soft sediment deformation erosion and transport c wavy crinkly character of laminae d bed surfaces with pustular wrinkled appearance e rippled patches on otherwise smooth surfaces f laminae with mica enrichment and or randomly oriented micas g irregular curved wrinkled impressions on bedding planes h uparched laminae near mud cracks resembling growth ridges of polygonal stromatolites and i lamina specific distribution of certain early diagenetic minerals dolomite ferroan carbonates pyrite although in none of the described examples can it irrefutably be proven that they are microbial mat deposits the observed features are consistent with such an interpretation and should be considered indicators of possible microbial mat presence in other proterozoic sequences

an experimental study of large waves in intermediate and shallow water depths part i wave height and crest height statistics abstract this paper describes a series of laboratory observations undertaken in a purpose built wave flume the objective of the study was to simulate a range of realistic ocean spectra evolving over a number of mild bed slopes m the chosen sea states allowing a systematic investigation of the role of local water depth spectral peak period significant wave height spectral bandwidth and bed slope the focus of the present paper lies in the statistical distribution of both the wave height h and the wave crest elevation c the laboratory data being used to provide both an understanding of the importance of the various parameters and an assessment of the commonly adopted design distributions the results of the study have shown that both the wave height and the crest height distributions are primarily dependent upon the effective water depth k p d where k p is the wave number corresponding to the spectral peak and d the water depth and the sea state steepness 1 2 h s k p where h s is the significant wave height conversely the distributions are independent of the mild bed slope for m 1 100 and the spectral bandwidth the latter result being very different to that which arises in deep water following detailed comparisons across a wide parameter range the wave height distributions in the deeper water depths k p d 1 0 are shown to be in reasonable agreement with the forristall 1978 and glukhovskii 1966 distributions the latter becoming more important as the proportion of breaking waves increases as the water depth reduces the mendez et al 2004 distribution as well as the battjes groenendijk 2000 composite weibull distribution cwd become increasingly applicable however comparisons between sea states of varying steepness but with all other parameters held constant suggest that the empirical parameters on which the latter solution is based may not be universally applicable finally in the shallowest water depths k p d 0 5 none of the existing distributions provide a good description of the measured data all leading to an over estimate of the largest wave heights

sedimentology digging deeper the cambrian evolution of burrowing species is thought to have facilitated sediment mixing however sediment fabrics suggest that bioturbation remained insignificant until the appearance of more efficient sediment mixers in the silurian

spring snow albedo feedback analysis over the third pole results from satellite observation and cmip5 model simulations the snow albedo feedback is a crucial component in high altitude cryospheric change but is poorly quantified over the third pole encompassing the karakoram and tibetan plateau here we present an analysis of present day and future spring snow albedo feedback over the third pole using a 28 year satellite based albedo and the latest climate model simulations we show that present day spring snow albedo feedback strength is primarily determined by the decrease in albedo due to snow metamorphosis rather than that due to reduced snow cover in the karakoram but not found in southeastern tibet we further demonstrate an emergent relationship between snow albedo feedback from the seasonal cycle and that from climate change across models combined with contemporary satellite based snow albedo feedback from seasonal cycle this relationship enables us to estimate that the feedback strength for the karakoram with a relatively high glaciated area is 2 42 0 48 k 1 under an unmitigated scenario which is much stronger than that for southeastern tibet 1 64 0 48 k 1 and for the third pole 0 89 0 44 k 1 respectively moreover it is noteworthy that the magnitude of the constrained strength is only half of the unconstrained model estimate for the third pole suggesting that current climate models generally overestimate the feedback of spring snow change to temperature change based on the unmitigated scenario

on the average shape of the largest waves in finite water depths abstractthis paper investigates the average shape of the largest waves arising in finite water depths specifically the largest waves recorded in time histories of the water surface elevation at a

trace fossil preservation and the early evolution of animals abstract the trace fossil record is an important element in discussions of the timing of appearance of bilaterian animals a conservative approach does not extend this record beyond about 560 555 ma crucial to the utility of trace fossils in detecting early benthic activity is the preservational potential of traces made close to the sediment water interface our studies on the earliest cambrian sediments suggest that shallow tiers were preserved to a greater extent than typical for most of the phanerozoic this can be attributed both directly and indirectly to the low levels of sediment mixing the low levels of sediment mixing meant that thin event beds were preserved the shallow depth of sediment mixing also meant that muddy sediments were firm close to the sediment water interface increasing the likelihood of recording shallow tier trace fossils in muddy sediments preservation of surficial trace fossils in this type of setting remains problematic but the above factors suggest that also these can be expected to have left a reasonable record overall the trace fossil record can be expected to provide a sound record of the onset of bilaterian benthic activity the lack of convincing trace fossils significantly before the cambrian supports models of late appearance of macroscopic benthic bilaterians

conditional second order short crested water waves applied to extreme wave episodes a derivation of the mean second order short crested wave pattern and associated wave kinematics conditional on a given magnitude of the wave crest is presented the analysis is based on the second order sharma and dean finite water wave theory a comparison with a measured extreme wave profile the draupner new year wave shows a good agreement in the mean indicating that this second order wave can be a good identifier of the shape and occurrence of extreme wave events a discussion on its use as an initial condition for a fully nonlinear three dimensional surface wave analysis is given

fundamentals of desiccation cracking of fine grained soils experimental characterisation and mechanisms identification this paper presents the results of a comprehensive experimental study of the desiccation of fine grained soils air drying of initially saturated soil slabs in controlled conditions is investigated by performing three kinds of tests free desiccation tests constrained desiccation tests prevented shrinkage and crack pattern tests strains suction water con tent and crack geometry are investigated results reveal that unconstrained drying exhibits two stages a domain with large mostly irrecoverable deformations and degree of saturation close to 100 followed by a domain with lower defor mations at a decreasing degree of saturation homogeneous soil macroscopic cracking is possible only in the presence of boundary constraints and or moisture gradients inducing the build up of tensile stresses results also show that for the initially saturated remoulded soils tested here in the whole sample and near a crack initiation point the degree of satura tion remains very close to 100 until cracking while cracking onset the air entry suction and the shrinkage limit are close to each other cavitation nuclei and the formation of an irregular drying front at cracking initiation are commented upon in light of this observation finally results suggest that the crack pattern geometry is the result of energy redistribu tion a quantification of the process is proposed resume cet article presente les resultats d une etude experimentale complete de la dessiccation de sols fins le sechage de sols initialement satures est etudiedans des conditions controlees et atemperature ambiante trois types d essais ont eteeffectues essais de dessiccation libre essais de dessiccation avec contraintes le retrait est empechedans une direc tion et essais de plans de fissures les deformations la succion la teneur en eau et la geometrie des fissures ont eteinves tiguees les resultats demontrent que le sechage sans contrainte presente deux etapes un domaine durant lequel les deformations sont grandes et irreversibles et le degrede saturation reste pres de 100 suivi d un domaine durant lequel les deformations sont plus faibles et le degrede saturation diminue pour un sol homogene des fissures macroscopiques apparaissent seulement lorsqu il y a des contraintes aux frontieres et ou des gradients d humidite ce qui induit des contraintes en tension les resultats montrent aussi que pour les silts et argiles remanies initialement satures utilises dans cette etude le degrede saturation reste tres pres de 100 jusqu ala fissuration de plus la fissuration l entree d air et la limite de retrait sont proches les unes des autres suite a ces observations l existence de germes de cavitation et la forma tion d un front de sechage irregulier lors de l initiation des fissures sont discutees finalement les resultats suggerent que la geometrie des fissures resulte d une redistribution de l energie a travers le corps une quantification du processus est proposee mots cles dessiccation initiation de fissure succion succion a l entree d air geometrie des fissures

seaglider surveys at ocean station papa circulation and water mass properties in a meander of the north pacific current a seaglider autonomous underwater vehicle augmented the ocean station papa osp 50 n 145 w surface mooring measuring spatial structure on scales relevant to the monthly evolution of the moored time series during each of three missions from june 2008 january 2010 a seaglider made biweekly 50 km 50 km surveys in a bowtie shaped survey track horizontal temperature and salinity gradients measured by these surveys were an order of magnitude stronger than climatological values and sometimes of opposite sign geostrophically inferred circulation was corroborated by moored acoustic doppler current profiler measurements and aviso satellite altimetry estimates of surface currents confirming that glider surveys accurately resolved monthly scale mesoscale spatial structure in contrast to climatological north pacific current circulation upper ocean flow was modestly northward during the first half of the 18 month survey period and weakly westward during its latter half with rossby number 0 01 this change in circulation coincided with a shift from cool and fresh to warm saline oxygen rich water in the upper ocean halocline and an increase in vertical finestructure there and in the lower pycnocline the anomalous flow and abrupt water mass transition were due to the slow growth of an anticyclonic meander within the north pacific current with radius comparable to the scale of the survey pattern originating to the southeast of osp this article is protected by copyright all rights reserved

the criteria for the biogeneicity of microbially induced sedimentary structures miss in archean and younger sandy deposits abstract the identification of fossils or biogenic sedimentary structures in rocks of archean age is difficult because similar lithological features could rise from purely physical or chemical processes alone therefore it is important to define criteria that serve the secure definition of a fossil or structure in question as of biological origin such criteria have been established for stromatolites and microfossils this contribution discusses the 6 criteria of biogeneicity of microbially induced sedimentary structures miss those structures are found in sandy deposits of early archean age to the present and rise from the interaction of benthic microbiota with physical sediment dynamics the six criteria for their biogeneicity are i miss occur in rocks of not more than lower greenschist facies ii in stratigraphic sections miss correlate with turning points of regression trangressions iii miss correlate with a characteristic depositional facies that enhances the development and the preservation of microbial mats iv the distribution of miss correlates with the ancient average hydraulic pattern v the geometries and dimensions of fossil miss correspond to that of the modern ones vi the miss include at least one of 9 specific microtextures

statistical analysis and intercomparison of wam model data with global ers 1 sar wave mode spectral retrievals over 3 years ocean wave spectra were retrieved from a set of ers i synthetic aperture radar sar wave mode swm spectra between january 1993 and december 1995 an assessment is given of the swm data quality and the retrieval performance as well as the operational feasibility of the retrieval algorithm sensitivity studies are performed to demonstrate the weak residual dependence of the retrieval on the first guess input spectrum the mean spectral parameters of the swm retrievals are compared with spectral parameters from collocated wave model wam spectra the time series of swm retrieved and wam derived monthly mean significant wave heights hs in various ocean basins show good overall agreement but with a small systematic underestimation of hs by the wam a decomposition of the wave spectra into wind sea and swell reveals an average 10 overprediction of the wind sea by the wam while swell is underpredicted by 20 30 the positive wind sea bias exhibits no clear wave height dependence while the negative swell bias decreases with swell wave height this could be due to a too strong damping in the wam at low frequencies detailed regional investigations point to the existence of smaller scale phenomena which may not be adequately reproduced by the wam at the present resolution of the wind forcing finally an intercomparison is made of the observed and modeled azimuthal cutoff length scales and global distributions are investigated ratios of the observed azimuthal cutoff wavenumber to the mean azimuthal wavenumber component indicate that about 75 of the swell can be directly resolved by the sar while about 70 of the wind sea lies at least partially beyond the cutoff

a scale comparison of waves breaking on a beach abstract a measurement programme conducted in a small scale wave flume which comprised the breaking of periodic and random waves on a gently sloping beach was partly repeated in a large scale wave flume the results are used here to make a scale comparison the quantities considered in the comparison are wave heights set up and vertical profiles of maximum seaward maximum shoreward and time mean horizontal velocities it appears that both qualitatively and quantitatively scale effects in these quantities are virtually absent in the wave height range of 0 1 m to 1 5 m

a short history of ocean station papa and line p abstract this short article summarises the origins of observations at ocean station papa the evolution into line p and the subsequent history of observations along that line

accumulation of organic matter in cretaceous oxygen deficient depositional environments in the central pacific ocean abstract complete records of organic carbon rich cretaceous strata were continuouslycored on the flanks of the mid pacific mountains and southern hess rise in the central north pacific ocean during dsdp leg 62 organic carbon rich laminated silicified limestones were deposited in the western mid pacific mountains during the early aptian a time when that region was south of the equator and considerably shallower than at present organic carbon rich laminated limestone on southern hess rise overlies volcanic basement and includes 136 m of stratigraphic section of late albian to early cenomanian age this limestone unit was deposited rapidly as hess rise was passing under the equatorial high productivity zone and was subsiding from shallow to intermediate depths the association of volcanogenic components with organic carbon rich strata on hess rise in the mid pacific mountains is striking and suggests that there was a coincidence of mid plate volcanic activity and the production and accumulation of organic matter at intermediate water depths in the tropical pacific ocean during the middle cretaceous pyrolysis assays and analyses of extractable hydrocarbons indicate that the organic matter in the limestone on hess rise is composed mainly of lipid rich kerogen derived from aquatic marine organisms and bacteria limestones from the mid pacific mountains generally contain low ratios of pyrolytic hydrocarbons to organic carbon and low hydrogen indices suggesting that the organic matter may contain a significant proportion of land derived material possibly derived from numerous volcanic islands that must have existed before the area subsided the organic carbon in all samples analyzed is isotopically light 13 c 24 to 29 per mil relative to most modern rine organic carbon and the lightest carbon is also the most lipid rich there is a positive linear correlation between sulfur and organic carbon in samples from hess rise and from the mid pacific mountains the slopes and intercepts of c s regression lines however are different for each site and all are different from regression lines for samples from modern anoxic marine sediments and from black sea cores the organic carbon rich limestones on hess rise the mid pacific mountains and other plateaus and seamounts in the pacific ocean are not synchronous but do occur within the same general middle cretaceous time period as organic carbon rich lithofacies elsewhere in the world ocean particularly in the atlantic ocean strata of equivalent age in the deep basins of the pacific ocean are not rich in organic carbon and were deposited in oxygenated environments this observation together with the evidence that the plateau sites were considerably shallower and closse to the equator during the middle creataceous suggests that local tectonic and hydrographic conditions may have resulted in high surface water productivity and the preservation of organic matter in an oxygen deficient environment where an expanded mid water oxygen minimum developed and impinged on elevated platforms and seamounts

modis terra observed seasonal variations of snow cover over the tibetan plateau 1 seasonal variations of snow cover fraction sfc over the tibet plateau tp are examined using the data acquired from the moderate resolution imaging spectroradiometer modis on the terra spacecraft in this study we first evaluate the accuracy of the modis high resolution snow cover data by comparing the data with in situ chinese snow observations results show that overall accuracy of modis snow data is about 90 over the tp area statistical analysis is then performed over the modis snow data during 2000 2006 it is found that the most persistent snow cover is located in the southern and western edges of the tp within large mountain ridges and western part of yarlung zangbo valley the higher scfs are mostly concentrated in the regions where the elevation is higher than 6000 m the duration for snow persistence varies in different elevation ranges and generally becomes longer with increases in the terrain elevation

statistical properties of mechanically generated surface gravity waves a laboratory experiment in a three dimensional wave basin a wave basin experiment has been performed in the marintek laboratories in one of the largest existing three dimensional wave tanks in the world the aim of the experiment is to investigate the effects of directional energy distribution on the statistical properties of surface gravity waves different degrees of directionality have been considered starting from long crested waves up to directional distributions with a spread of 30 at the spectral peak particular attention is given to the tails of the distribution function of the surface elevation wave heights and wave crests comparison with a simplified model based on second order theory is reported the results show that for long crested steep and narrow banded waves the second order theory underestimates the probability of occurrence of large waves as directional effects are included the departure from second order theory becomes less accentuated and the surface elevation is characterized by weak deviations from gaussian statistics

a wavelet based algorithm to estimate ocean wave group parameters from radar images in recent years new remote sensing techniques have been developed to measure two dimensional 2 d sea surface elevation fields the availability of these data has led to the necessity to extend the classical analysis methods for one dimensional 1 d buoy time series to two dimensions this paper is concerned with the derivation of group parameters from 2 d sea surface elevation fields using a wavelet based technique wave grouping is known to be an important factor in ship and offshore safety as it plays a role in dangerous resonance phenomenons and the generation of extreme waves synthetic aperture radar sar data are used for the analysis the wavelet technique is introduced using synthetic ocean surfaces and simulated sar data it is shown that the group structure of the ocean wave field can be recovered from the sar image if the nonlinear imaging effects are moderate the method is applied to a global dataset of european remote sensing satellite ers 2 wave mode data different group parameters including the area covered by the largest group and the number of groups in a given area are calculated for over 33 000 sar images global maps of the parameters are presented for comparison classical 1 d grouping parameters are calculated from colocated wave model data showing good overall agreement with the wavelet derived parameters ers 2 image mode data are used to study wave fields in coastal areas waves approaching the island of sylt in the north sea are investigated showing the potential of the wavelet technique to analyze the spatial wave dynamics associated with the bottom topography observations concerning changes of wavelength and group parameters are compared to linear wave theory

reynolds stresses under wind waves this paper describes a series of wave measurements taken from an oceanographic tower concerning water particle kinematics attention is focused on the phase relationship between surface elevation and the velocity components large phase shifts with respect to the expected values are found under active wave conditions while swell behavior closely follows the linear theory the reliability of the measurements is analyzed in detail possible physical reasons for the findings are indicated in the final discussion

on the distribution of wave height in shallow water abstract the statistical distribution of the height of sea waves in deep water has been modelled using the rayleigh longuet higgins 1952 and weibull distributions forristall 1978 depth induced wave breaking leading to restriction on the ratio of wave height to water depth requires new parameterisations of these or other distributional forms for shallow water glukhovskiy 1966 proposed a weibull parameterisation accommodating depth limited breaking modified by van vledder 1991 battjes and groenendijk 2000 suggested a two part weibull weibull distribution here we propose a two part weibull generalised pareto model for wave height in shallow water parameterised empirically in terms of sea state parameters significant wave height h s local wave number k l and water depth d using data from both laboratory and field measurements from 4 offshore locations we are particularly concerned that the model can be applied usefully in a straightforward manner given three pre specified universal parameters the model further requires values for sea state significant wave height and wave number and water depth so that it can be applied the model has continuous probability density smooth cumulative distribution function incorporates the miche upper limit for wave heights miche 1944 and adopts h s as the transition wave height from weibull body to generalised pareto tail forms accordingly the model is effectively a new form for the breaking wave height distribution the estimated model provides good predictive performance on laboratory and field data

remarkable preservation of microbial mats in neoproterozoic siliciclastic settings implications for ediacaran taphonomic models abstract it is beyond doubt that the appearance of infaunal bioturbation and metazoan biomineralization across the ediacaran cambrian transition irreversibly affected the nature of marine sediment architecture and biogeochemistry here we review those changes in relation to their likely effect upon the processes of fossil preservation especially within siliciclastic sediments processes of soft tissue preservation in siliciclastic settings from the ediacaran period including microbes and microbial mats as well as ediacaran macrofossils are here reviewed within this context highlighted examples include the exceptional preservation of microbes found in association with wrinkle structures and ediacaran macrofossils in england and newfoundland replicated by silicate minerals and in the white sea region of russia replicated by iron sulphide these occurrences show that soft tissue preservation in siliciclastic settings went well beyond that typical for ediacaran macrofossils alone and also extended to similar modes of preservation in associated microbes using these new observations it can be argued that several existing explanations for ediacaran fossil preservation can be united within a biogeochemical model that involves evolution of the sediment mixed layer across this transition

the average shape of large waves in the coastal zone abstract the ability of the newwave focused wave group the scaled auto correlation function to represent the average shape in time of large waves in a random sea state makes it a useful tool for the design of offshore structures however the profile has only been validated against field data for waves on deep and intermediate water depths a similar validation is advisable when applying newwave to shallow water problems where waves are less dispersive and more nonlinear for this purpose data recorded by two channel coastal observatory cco wave buoys during two large storms in january 2014 are analysed to assess the ability of newwave to replicate the average shape of large waves in shallow water a linear newwave profile is shown to successfully capture the average shape of the largest waves from the perranporth and porthleven wave buoys during these large storm events the differences between the measurements obtained by a surface following buoy and a fixed sensor become important when considering the ability of a second order corrected newwave profile to capture weakly nonlinear features of the measured data a general expression for this effect is presented for weakly nonlinear waves on intermediate water depths leading to lagrangian second order sum corrections to the linear newwave profile a second order corrected newwave profile performs reasonably well in capturing the average features of large waves recorded during the january storms these findings demonstrate that the newwave profile is valid in relatively shallow water kpd values less than 0 5 and so may have potential for use as a design wave in coastal engineering applications

detection of ocean wave groupiness from spaceborne synthetic aperture radar 1 in recent years a number of remote sensing techniques capable to provide two dimensional information of the sea surface have been applied to describe sea states this information is obtained from the estimation of the directional wave number spectrum however the wave number spectrum is not sufficient for a complete description of sea states the analysis of some phenomena such as wave grouping detection of individual waves maximum wave heights etc needs a complementary study which has been carried out historically in the temporal domain from buoy records in two dimensions e g the spatial domain the complementary analysis of those phenomena can be carried out in the spatial domain rather than the temporal domain in this work two methods to analyze wave groupiness in the spatial domain from sea surface images are presented the first method is based on the two dimensional generalization of the smoothed instantaneous wave energy history siweh function which had been originally developed to analyze wave groupiness for wave elevation time series the second method uses the estimation of the wave envelope in two dimensions to extract wave grouping parameters assuming that the wave fields are gaussian stochastic processes both methods are applied to ers 2 synthetic aperture radar sar and envisat advanced sar asar images of the sea surface where only cases with almost range traveling waves are considered in order to avoid strong nonlinearities in the sar imaging mechanisms the obtained results shown that spaceborne sar can be used to extract wave grouping information on global scale

the dynamic pressure in deep water extreme stokes waves in this paper we consider the dynamic pressure in a deep water extreme stokes wave while the presence of stagnation points introduces a number of mathematical complications maximum principles are applied to analyse the dynamic pressure in the fluid body by means of an excision process it is shown that the dynamic pressure attains its maximum value beneath the wave crest and its minimum beneath the wave trough while it decreases in moving away from the crest line along any streamline this article is part of the theme issue nonlinear water waves

microbial mats implicated in the generation of intrastratal shrinkage synaeresis cracks intrastratal shrinkage often termed synaeresis cracks are commonly employed as diagnostic environmental indicators for ancient salinity stressed transitional fluvial marine or marginal marine depositional environments despite their abundance and use in facies interpretations the mechanism of synaeresis crack formation remains controversial and widely accepted explanations for their formation have hitherto been lacking sedimentological ichnological petrographic and geochemical study of shallow marine mudstone beds from the ordovician beach formation of bell island newfoundland has revealed that crack development cf synaeresis cracks on the upper surface of mudstone beds is correlated with specific organic geochemical and sedimentological parameters contorted sinuous sand filled cracks are common at contacts between unbioturbated mudstone and overlying sandstone beds cracks are absent in highly bioturbated mudstone and are considered to pre date firmground assemblages of trace fossils that include planolites and trichophycus the tops of cracked mudstone beds contain up to 2 1 wt total organic carbon relative to underlying mudstone beds that contain around 0 5 wt total organic carbon high resolution carbon isotope analyses reveal low 13corg values 27 6 on bed tops compared with sandy intervals lacking cracks 24 4 to 24 9 cracked mudstone facies show evidence for microbial matgrounds including microbially induced sedimentary structures on bedding planes and carbonaceous laminae and tubular carbonaceous microfossils in thin section non cracked mudstone lacks evidence for development of microbial mats microbial mat development is proposed as an important prerequisite for intrastratal shrinkage crack formation both microbial mats and intrastratal shrinkage cracks have broad palaeoenvironmental distributions in the precambrian and early phanerozoic in later phanerozoic strata matgrounds are restricted to depositional environments that are inhospitable to burrowing and surface grazing macrofauna unless evidence of synaeresis i e contraction of clay mineral lattices in response to salinity change can be independently demonstrated the general term intrastratal shrinkage crack is proposed to describe sinuous and tapering cracks in mudstone beds

theory of synthetic aperture radar ocean imaging a marsen view this paper reviews basic synthetic aperture radar sar theory of ocean wave imaging mechanisms using both known work and recent experimental and theoretical results from the marine remote sensing marsen experiment several viewpoints that have contributed to the field are drawn together in a general analysis of the backscatter statistics of a moving sea surface a common focus for different scattering models is provided by the mean image impulse response function which is shown to be identical to the spatially varying frequency variance spectrum of the local complex reflectivity coefficient from the analysis has emerged a more complete view of the sar imaging phenomenon than has been previously available a new generalized imaging model is proposed

protracted development of bioturbation through the early palaeozoic era mobile organisms first appeared in the fossil record prior to the precambrian cambrian transition sediment textures indicate that the degree of sediment mixing by animal activity remained low for 120 million years following the transition

production and preservation of organic matter the significance of iron 1 iron fertilization has been previously recognized as a potential mechanism for enhanced organic matter burial in marine sediments however the singular view of iron as a control on primary production overlooks its role in sedimentary diagenesis a factor that must be evaluated when considering organic matter accumulation this study examines the role of iron as a buffer of pore water sulfide and its implications for marine organic matter burial biogeochemical model experiments indicate that dissolved sulfide buildup in surficial marine sediments is highly sensitive to reactive iron concentration a reduction in reactive iron concentration can initiate dissolved sulfide accumulation the consequences of which include inhibition of bioturbation bioirrigation a decrease in oxygen exposure time and enhanced organic matter burial alternatively an increase in reactive iron concentration can serve to decrease organic matter burial the coupling of iron and phosphorous cycling within marine sediments provides an important positive feedback and therefore this mechanism is designated the sulfide buffer phosphorous trap hypothesis given sufficient organic carbon supply carbonate rich and opal rich sediments should be especially prone to the development of sulfidic conditions because of a deficiency in terrigenous iron widespread chalk and marl deposition during the cretaceous in association with the evolutionary expansion of calcareous plankton may have predisposed many benthic marine environments to the accumulation of toxic hydrogen sulfide and fostered the development of oceanic anoxic events comparison of model results with proxy data from oceanic anoxic event ii middle cretaceous suggests a complex role of iron as a control on both organic matter production and preservation

wave height distributions on shallow foreshores wave height distributions on shallow foreshores deviate from those in deep water due to the effects of the restricted depth to height ratio and of wave breaking laboratory data of wave heights on shallow foreshores of different slopes have been analysed to determine these effects and to derive generalised empirical parameterisations a model distribution is proposed consisting of a rayleigh distribution or a weibull distribution with exponent equal to 2 for the lower heights and a weibull with a higher exponent for the higher wave heights the parameters of this distribution have been estimated from the data and expressed in terms of local wave energy depth and bottom slope yielding a predictive model that is found to be significantly more accurate than existing expressions

accuracy of bathymetry and current retrievals from airborne optical time series imaging of shoaling waves a sequence of visual images of shoaling ocean waves collected from an aircraft can be used to retrieve maps of water depth and or currents the data are mapped to rectilinear coordinates on the mean ocean surface and three dimensional 3d cubes of these data typically 2 min dwell and 256 m spl times 256 m square area are fourier transformed to provide the 3d frequency wavenumber spectrum of the modulations the spectrum is fitted by the theoretical two dimensional dispersion surface for linear gravity waves with the depth and current vector as free parameters and the errors determined by comparison with simultaneously collected in situ data very little attention has been focused on the limitations and inherent errors in this approach for retrieving these parameters in the past this paper examines the dependence of these errors upon various instrumental and collection geometry parameters in order to estimate the achievable retrieval accuracy and provide collection guidelines significant errors occur when the mapping is inaccurate and when the data cubes are too small either spatially or temporally data cubes of the size given above or larger are required to contain the relative errors within 5 to 10 of the ground truth values the spatial resolution and temporal sampling rate are less critical and pixel sizes of spl sim 3 4 m and framing rates of spl sim 0 5 hz for depth and 1 2 hz for currents are sufficient for providing adequate results with the data examined here finally we show that the covariance matrix from the functional fit provides a quantitative measure of the retrieval accuracy independent of in situ data

lithostratigraphy of the cambrian lower ordovician bell island and wabana groups of bell little bell and kellys islands conception bay eastern newfoundland the upper cambrian arenigian succession of bell little bell and kellys islands conception bay eastern newfoundland consists of at least 1500 m of interbedded micaceous sandstones siltstones shales and ironstones the succession has previously been formally subdivided into only two groups namely a lowermost bell island group and an overlying wabana group the existing lithostratigraphic nomenclature below group level has to date only been informally proposed and is therefore herein formally revised the lowermost bell island group comprises from base to top the kellys island little bell island beach redmans ochre cove and dominion formations of these the ochre cove and dominion formations are newly proposed and the beach formation is considerably revised from its historical usage the beach formation contains two newly proposed members the mcgraw and eastern head members both of which in previous nomenclature were informally referred to as beds the disconformably overlying wabana

on estimating extremes in an evolving wave field abstract observations of waves as a time series from a fixed or moored sensor are shown to underestimate the extreme waves occurring in the vicinity the underestimate arises because of the difference in phase and envelope propagation of surface water waves so that the highest crest for example is recorded only when the crest coincides with the envelope maximum at the location of the wave recorder in addition the dispersive nature of water waves can lead to the coalescence of groups of waves as longer waves catch up to shorter slower waves so that the group shape changes markedly as the waves propagate moored accelerometer buoys introduce another error that exacerbates the underestimate of the highest crest the quasi lagrangian motion of the buoy leads to flattening of the crests and sharpening of the troughs so that apparent mean water level is raised and thus the height of crests above it is reduced an analysis approach to correct these underestimates is outlined and tested with observed data against the predictions of extreme values based on narrow banded random wave theory

earth s earliest microbial mats in a siliciclastic marine environment 2 9 ga mozaan group south africa this study provides evidence for the existence of filamentous cyano bacteria forming sediment stabilizing mats in shelf environments at 2 9 ga the oldest known occurrence of microbial mats in siliciclastic rocks the mesoarchean mozaan group south africa features fine grained quartzites of an ancient shallow shelf environment these sandstones contain wrinkle structures which in thin section reveal filamentous textures forming carpet like microbial mat fabrics the textures resemble the trichomes of modern cyanobacteria chloroflexi or sulfur oxidizing proteobacteria mineralogical geochemical and isotopic analyses acre consistent with a biological origin of the filament like textures carbon filaments with biogenic isotopic signatures 1 3 c 24 2 0 5 are closely associated with hematite goethite and chert minerals which may derive from the former presence of oxygen within the microbial mats detrital quartz zircon and rutile in the mats could indicate baffling trapping and binding of the bacterial communities

santa ana winds of southern california their climatology extremes and behavior spanning six and a half decades santa ana winds saws are an integral feature of the regional climate of southern california northern baja california region but their climate scale behavior is poorly understood in the present work we identify saws in mesoscale dynamical downscaling of a global reanalysis from 1948 to 2012 model winds are validated with anemometer observations saws exhibit an organized pattern with strongest easterly winds on westward facing downwind slopes and muted magnitudes at sea and over desert lowlands we construct hourly local and regional saw indices and analyze elements of their behavior on daily annual and multidecadal timescales saws occurrences peak in winter but some of the strongest winds have occurred in fall finally we observe that saw intensity is influenced by prominent large scale low frequency modes of climate variability rooted in the tropical and north pacific ocean atmosphere system

microbial signatures in peritidal siliciclastic sediments a catalogue a catalogue of microbial structural signatures is presented based upon the coupling of fundamental biogeochemical microbial processes and local morphogenetic determinants it summarizes a collection of sedimentary structures obtained from two modern siliciclastic peritidal environments in different climatic zones temperate humid mellum island southern north sea subtropical arid coast of southern tunisia textural geometries reveal a high structural diversity but their determinants are primarily based upon six major parameters 1 intrinsic biofactors structural diversification of sedimentary microbial films and mats inherent in the organisms i e their construction morphology growth taxis and behaviour and local abundance of specific morphotypes most prominent are the ensheathed filamentous cyanobacteria microcoleus chthonoplastes and lyngbya aestuarii and the sheathless filamentous cyanobacterium oscillatoria limosa 2 biological response to physical disturbances sediment supply erosion and fracturing of surface layers resulting from desiccation cause growth responses of biofilms and microbial mats 3 trapping binding effects physicobiological processes give rise to grain orientations and wavy to lenticular lamina lamina specific grain arrangements and sucrose calcium carbonate accumulations 4 secondary physical deformation of biogenic build ups mechanical stresses acting upon sediments overgrown and biostabilized by biofilms and mats produce erosional and overthrust structures 5 post burial processes textural fabrics that evolve from mechanical effects of gas formation from decaying mats and features related to the formation of authigenic minerals calcium carbonates calcium sulphates pyrite 6 bioturbation and grazing post depositional structures such as skolithos type dwellings traces of burrowing insects gastropod grazing traces and faecal pellets in synopsis the catalogue firstly comprises a sound set of ubiquitous signatures this uniformity in architectural characteristics is attributed to the presence and local dominance of certain microbes throughout the different settings the catalogue secondly documents signatures that are extremely sensitive to tidal position hydrodynamic regime and overall climatic conditions these kinds of signature indicate narrow facies zones which often coincide with the activity or dominance zones of certain organisms an overview of structures of microbial origin from the fossil record underlines the potential of many of the signatures included in this catalogue to become fossilized and provide strong indicators of former siliciclastic tidal settings

observations of the shape and group dynamics of rogue waves surface elevation records from two locations in the northeast pacific are used to examine rogue waves and the relationship to wave groups three hundred individual rogue waves with heights greater than 2 2 times the significant wave height are found in analyzing 2 106 wave groups in contrast to recent nonlinear modeling results we do not find that rogue waves occur at the front of wave groups there is a tendency for steep waves to occur at the front of a group but these are not the largest waves of the group and do not meet the rogue wave criterion rogue waves are most commonly located in the center of the group but their height ratio to the neighboring crest is greater than in the average wave group assessing group dynamics in terms of spectral width suggests that random superposition of nonlinear waves is sufficient to explain the observations of individual rogue waves

observation of extreme sea waves in a space time ensemble abstractin this paper an observational space time ensemble of sea surface elevations is investigated in search of the highest waves of the sea state wave data were gathered by means of a stereo camera system which was installed on top of a fixed oceanographic platform located in the adriatic sea italy waves were measured during a mature sea state with an average wind speed of 11 m s 1 by examining the space time ensemble the 3d wave groups have been isolated while evolving in the 2d space and grabbed when and where they have been close to the apex of their development thus exhibiting large surface displacements the authors have selected the groups displaying maximal crest height exceeding the threshold adopted to define rogue waves in a time record that is 1 25 times the significant wave height hs the records at the spatial positions where such large crests occurred have been analyzed to derive the empirical distributions of crest and wave heights which have been compared against standar

the velocity field beneath wind waves observations and inferences an extensive set of measurements taken from a fixed tower is used to study the velocity field under wind waves velocity measurements made with miniature drag spheres are compared with linear theory estimates of the orbital velocities obtained from measured surface elevation results are presented in the context of how well linear theory is able to predict wave induced forces on cylindrical structural members linear theory is seen to predict the flow velocities to within about 7 furthermore both the inertial and drag forces are generally well predicted by linear theory although small scale turbulent motions not accounted for by linear theory can result in significantly higher inertial forces on smaller structural members

the role of wave reworking on the architecture of storm sandstone facies bell island group lower ordovician eastern newfoundland stacked shallow marine cycles in the lower ordovician bell island group of bell island newfoundland show upward thickening and upward coarsening sequences which were deposited on a storm affected shelf in the beach formation each cycle has a facies sequence comprised from base to top of dark grey mudstones light grey mudstones tabular sandstones and mudstones lenticular sandstones and mudstones and thick bedded lenticular sandstones reflecting a progressive increase of wave orbital velocities at the sediment surface the mudstones and tabular sandstones reflect an environment in which the sea floor lay in the lower part of the wave orbital velocity field and in which tempestites were deposited as widespread sheets from weak combined flow currents the lenticular sandstones in the succeeding facies are wave reworked sands commonly lying in erosional hollows and having erosional tops and internal hummocky cross stratification planar lamination is relatively uncommon and sole marks are mainly absent in this facies oscillatory currents were dominant and accumulated sand in patches generally 10 30 m in diameter the facies formed on the inner shelf where the oscillatory currents generated by storm waves had powerful erosional effects and also determined the depositional bedforms mud partings and second order set boundaries within sandstone beds are believed to separate the products of individual storms so that many lenticular sandstone beds represent the amalgamation of several event beds this interpretation has important implications for attempts to estimate event frequency by counting sandstone beds within a sequence and for estimates of sand budgets during storm events the thick bedded lenticular facies appears to have been formed by erosion of the mud beds between the lenticular sands leading to nearly complete amalgamation of several lenticular sand bodies except for residual mud partings in the overlying redmans formation the process of amalgamation progressed even further so that nearly all the mud partings were removed resulting in the formation of thick bedded tabular sandstones sequence stratigraphic analysis of the cyclical sequence suggests that the cycles were eustatically controlled the rising limb of the sea level curve produced only the dark grey mudstone part of the cycle while the remainder of the cycle was deposited on the falling limb there is a gradational but rapid facies transition from the tabular to the lenticular sandstone facies which is interpreted as occurring at the inflexion point on the falling limb the thick bedded facies of the beach formation and the thick bedded tabular facies of the redmans formation represent periods of maximum sea level fall the stacked cycles in the beach formation are interpreted as an aggradational high frequency sequence or parasequence set bounded at the top by a sequence boundary and succeeded by the three aggradational parasequences of the redmans formation the recognition of storm facies with sandstone beds of very different bed length has important implications for the reservoir modelling of such facies

on the expected structure of extreme waves in a gaussian sea part ii swade scanning radar altimeter measurements abstract in a previous paper phillips et al an approximate theory was developed that predicted that the expected configuration of extreme waves in a random sea or the average configuration of an ensemble of extreme waves is proportional to the space time autocorrelation function of the surface displacement of the wave field as a whole this result is tested by examination of scanning radar altimeter measurements made during swade in four different sea states including a unimodal mature wave field a short fetch a wind generated sea crossing swell a very broad directional spectrum and a fetch limited wind sea with opposing swell in each of these the spatial autocorrelation function was found directly from the sra data the highest waves in each dataset were selected and their configurations averaged with respect to the crest these averaged configurations were in each case found to be consistent with the autocorrelation function

biomats biofilms and bioglue as preservational agents for arthropod trackways abstract due to divergent taphonomic selection corresponding body and trace fossils are rarely found in the same rocks in addition to this general rule arthropod trackways are preferentially preserved in particular settings 1 lithographic limestones where toxic bottom waters account for the exceptional preservation of body fossils at the end of their mortichnial trackways 2 estuarine and lacustrine biolaminites that yield blurred surface tracks as well as the sharper undertracks and 3 cambrian intertidal sands before the precambrian cambrian substrate revolution had reached this environment in all these ichnotopes the original presence of protective microbial films can be inferred from sedimentary structures by analogy it is hypothesised that microbes bioglue may have been involved in the preservation of trackways in eolian dune sands the absence of arthropod tracks in ediacaran sands and silts means either that arthropods had not yet evolved or that they were as yet too tiny to pierce the tougher biomats of the time

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

can rogue waves be predicted using characteristic wave parameters rogue waves are ocean surface waves larger than the surrounding sea that can pose a danger to ships and offshore structures they are often deemed unpredictable without complex measurement of the wave field and computationally intensive calculation which is infeasible in most applications consequently there a need for fast predictors here we collate quality control and analyse the largest dataset of single point field measurements from surface following wave buoys to search for predictors of rogue wave occurrence we find that analysis of the sea state parameters in bulk yields no predictors as the subset of seas containing rogue waves sits within the set of seas without however spectral bandwidth parameters of rogue seas display different probability distributions to normal seas but these parameters are rarely provided in wave forecasts when location is accounted for trends can be identified in the occurrence of rogue waves as a function of the average seas state characteristics at that location these trends follow a power law relationship with the characteristic sea state parameters mean significant wave height and mean zero up crossing wave period we find that frequency of occurrence of rogue waves and their generating mechanism is not spatially uniform and each location is likely to have its own unique sensitivities which increase in the coastal seas we conclude that forecastable predictors of rogue wave occurrence will need to be location specific and reflective of their generation mechanism therefore given location and a sufficiently long historical record of sea state characteristics the likelihood of occurrence can be obtained for mariners and offshore operators

the california coastal wave monitoring and prediction system abstract a decade long effort to estimate nearshore 20 m depth wave conditions based on offshore buoy observations along the california coast is described offshore deep water directional wave buoys are used to initialize a non stationary linear spectral refraction wave model model hindcasts of spectral parameters commonly used in nearshore process studies and engineering design are validated against nearshore buoy observations seaward of the surfzone the buoy driven wave model shows significant skill at most validation sites but prediction errors for individual swell or sea events can be large model skill is high in north san diego county and low in the santa barbara channel and along the southern monterey bay coast overall the buoy driven model hindcasts have relatively low bias and therefore are best suited for quantifying mean e g monthly or annual nearshore wave climate conditions rather than extreme or individual wave events model error correlation with the incident offshore wave energy and between neighboring validation sites may be useful in identifying sources of regional modeling errors

wave enhanced sediment gravity flows and mud dispersal across continental shelves reappraising sediment transport processes operating in ancient mudstone successions recent studies of marine shelf sediment dispersal show that wave enhanced sediment gravity flows are widespread phenomena and can transport large volumes of fluid mud rapidly across low gradient shelves flow evolution is controlled by sediment supply seabed gradient and spatial distribution of wave energy at the seabed using existing flow models we predict that such flows in mud dominated sediments will develop a three part microstratigraphy produced by changing flow conditions beginning with wave induced turbulent resuspension then development of a wave enhanced sediment gravity flow prior to lutocline collapse and suspension settling petrographic examination of modern flow deposits collected from the eel shelf reveals that resultant beds possess a microstratigraphy consistent with our hypothesis a silt rich basal subunit with curved ripple laminae abruptly overlain by a subunit composed of continuous intercalated silt clay laminae and an upper clay rich drape analyses of beds from ancient mud rich outer shelf and basinal successions cleveland ironstone jurassic uk and mowry shale cretaceous united states show that they too contain beds with this three part organization suggesting that such flows were active in these ancient settings too recognition of these microstructures in these ancient mud dominated successions demonstrates that sediment in these settings was commonly reworked and transported advectively downslope by high energy events contrasting with previous interpretations of these units that deposition was dominated by quiescent suspension settling identification of these recognition criteria now allows the products of this newly recognized sediment dispersal mechanism to be identified in other shale dominated successions