radon 222 as a tracer for mixing in the water column and benthic exchange in the southern california borderland the concentrations of222rn and226ra in the water column and in the sediments of santa barbara and san nicolas basins have been measured semi annually over the last four years approximately one third of excess radon profiles obtained in the water column in these basins can be adequately fit with a one dimensional eddy diffusion decay model exponential profiles in the center of san nicolas basin yield a vertical eddy diffusivity of 26 16 cm2 s and 3 4 1 0 cm2 s for santa barbara basin the application of a two dimensional eddy diffusion decay model to profiles obtained in the center and on the margins of san nicolas basin produces a better fit than is found using a one dimensional vertical eddy diffusivity the two dimensional model for san nicolas basin predicts a vertical eddy diffusivity of 17 cm2 s and a horizontal eddy diffusivity of 105 cm2 s these values are in reasonable agreement with those predicted from the vertical buoyancy gradient and the horizontal length scale the vertically integrated radon excess standing crop in the water column of santa barbara basin averages 53 23 atoms m2 s this is in good agreement with the flux across the sediment water interface of 60 15 atoms m2 s calculated by measuring radon emanation in the sediments as a function of depth and applying a molecular diffusion reaction model hence one dimensional molecular diffusion accurately predicts the flux of radon from the laminated santa barbara basin sediments in san nicolas basin the integrated radon excess in the water column is 376 143 atoms m2 s but the diffusive randon flux from san nicolas basin sediments averages only 190 53 atoms m2 s this descrepancy indicates that a non diffusive process probably macrofaunal irrigation supplies much of the flux of radon from san nicolas basin sediments

kinematics of a growth fault raft system on the west african margin using 3 d restoration abstract the ability to quantify the movement history associated with growth structures is crucial in the understanding of fundamental processes such as the growth of folds or faults in 3 d in this paper we present an application of an original approach to restore in 3 d a listric growth fault system resulting from gravity induced extension located on the west african margin our goal is to establish the 3 d structural framework and kinematics of the study area we construct a 3 d geometrical model of the fault system from 3 d seismic data then restore six stratigraphic surfaces and reconstruct the 3 d geometry of the system at six incremental steps of its history the evolution of the growth fault raft system corresponds to the progressive separation of two rafts by regional extension resulting in the development of an intervening basin located between them that evolved in three main stages 1 the rise of an evaporite wall 2 the development of a symmetric basin as the elevation of the diapir is reduced and buried and 3 the development of asymmetric basins related to two systems of listric faults the main fault f1 and the graben located between the rollovers and the lower raft important features of the growth fault raft system could only be observed in 3 d and with increments of deformation restored the rollover anticline associated with the listric fault f1 is composed of two sub units separated by an e w oriented transverse graben indicating that the displacement field was divergent in map view the rollover units are located within the overlap area of two fault systems and displays a mock turtle anticline structure the seaward translation of the lower raft is associated with two successive vertical axis rotations in the opposite sense clockwise then counter clockwise by about 10 this results from the fact that the two main fault systems developed successively fault system f1 formed during the upper albian and the graben during the cenomanian using a new approach of 3 d restoration this study suggests a consistent solution for 1 the processes of deformation of a fault system 2 the faulting kinematics and 3 the incremental steps of deformation

sedimentary flattening and multi extensional deformation along the west african margin abstract the structural world is usually divided into compressional and extensional zones and this tectonic style is representative of the regional deformation which leads to shortening or extension along the west african margin there is no evidence of crustal extension since 100 my ago but the post salt series are intensely deformed by gravity and sedimentary loading normal faults as well as reverse faults are present the modes of deformation of such an area are described using large 3d seismic data sets analogue models and cross section and map restorations results show that 1 surface rotations are large at a regional scale 2 plane deformation is not a valid hypothesis across the margin the amount of extension parallel to the coast being on the same order of magnitude as the extension perpendicular to the margin 3 the surface area of the beds are not preserved the data indicate that the deformation of the shale in such a context is a ductile flow due to body forces and sedimentary loading here called sedimentary flattening competent layers sand prone such as sheet sand lobes or channels constitute passive markers which follow the ductile flow in a brittle mode resulting in boudinage

advances in marine chemistry 1979 1982 these four years saw advances in many areas further developments in sampling and analytical techniques have opened new avenues of exploration for trace elements and particulate matter the impact of the geosecs expedition was further felt in the field of marine chemistry as the results were still being published a major field effort occurred as a follow on to the geosecs work tto and intensive sampling was performed in the newly discovered submarine hydrothermal vent fields an important and unresolved controversy has arisen regarding the ability to measure preformed co2 in the seawater system in many respects the field of marine chemistry appears to be gaining a momentum spurred by both improvements in analytic techniques and an increasing social and economic relevance

remobilization of authigenic uranium in marine sediments by bioturbation uranium behaves as a nearly conservative element in oxygenated seawater but it is precipitated under chemically reducing conditions that occur in sediments underlying low oxygen bottom water or in sediments receiving high fluxes of particulate organic carbon sites characterized by a range of bottom water oxygen bwo and organic carbon flux ocf were studied to better understand the conditions that determine formation and preservation of authigenic u in marine sediments our study areas are located in the mid latitudes of the northeast pacific and the northwest atlantic oceans and all sites receive moderate 0 5 g cm2 kyr to high 2 8 g cm2 kyr ocf to the sediments bwo concentrations vary substantially among the sites ranging from 3 to 270 m a mass balance approach was used to evaluate authigenic u remobilization at each site within each region studied the supply of particulate nonlithogenic u associated with sinking particles was evaluated by means of sediment traps the diffusive flux of u into sediments was calculated from pore water u concentration profiles these combined sources were compared with the burial rate of authigenic u to assess the efficiency of its preservation a large fraction one third to two thirds of the authigenic u precipitated in these sediments via diffusion supply is later regenerated even under very low bwo concentrations 15 m bioturbating organisms periodically mix authigenic u containing sediment upward toward the sediment water interface where more oxidizing conditions lead to the remobilization of authigenic u and its loss to bottom waters

sediment fluxes re suspension and accumulation rates at two wind exposed coastal sites and in a sheltered bay abstract sediment fluxes measured by sediment traps placed at different heights above the sea bed at two near coastal sites and in a sheltered bay are analysed in relation to wave and current conditions traps were deployed for 13 15 coastal sites and 6 months and recovered with a mean period of 16 6 14 0 and 30 days respectively the traps with an aspect ratio of 5 were placed at 0 3 0 5 0 8 1 0 2 0 4 0 6 0 8 0 and 10 0 m above the sea bed at one location whereas an aspect ratio of 2 3 was used at the second coastal location with similar trap intervals the trap in the sheltered bay was placed at 1 0 m above the sea bed results showed that sediment fluxes varied between 505 0 and 38 9 g m 2 day 1 at 0 3 m above the sea bed at a coastal site whereas only small flux variations occurred in the sheltered bay accumulation rates were measured by 210 pb at the three sites and was 2 4 g m 2 day 1 at the same site where fluxes varied between 505 0 and 38 9 g m 2 day 1 at 0 3 m above the sea bed this shows that re suspension here is high and frequent a similar pattern was found at the other coastal site whereas accumulation rate and sediment flux were very similar in the sheltered bay analyses showed that re suspension was induced both by surface wave activity related to periods of high wind speeds and by current shear stress in more calm periods re suspension is quantified as a time series by applying the introduced depth integrated re suspension flux dirf high dirf occurred during periods of high surface wave activity and one re suspension event accounted for about 25 of the total re suspension flux at the site although the event had a very low frequency of occurrence less than 5 of the time about 50 of the total re suspension flux occurred in the interval between 0 0 and 20 0 g m 2 day 1 comparison of different time scales for measuring sediment fluxes and re suspension using sediment traps shows that a time scale of 24 12 h gives an adequate resolution

budgets and behaviors of uranium and thorium series isotopes in santa monica basin sediments abstract nine natural decay series isotopes were measured in six box cores collected from a transect across the santa monica basin the 210 pb derived sedimentation rate decreases from 80 mg cm 2 yr at the slope to 20 mg cm 2 yr in the deep central basin sediment mixing prevails in sites underlying oxic waters but is subdued in the anoxic deep basin below the sill depth uranium contents in sediments are controlled by levels of authigenic u which are higher in the more reduced condition in the deep basin most of the authigenic u results from precipitation within the sediments the 232 th 228 th disequilibrium in sediments indicates that 228 ra is lost from the sediments from a depth of 10 cm upward modelling the distribution of excess 228 th and 234 th in the surficial layers of the deep basin sediments results in a mean sediment mixing coefficient of 0 2 cm 2 yr and a sedimentation rate close to that based on 210 pb there is no evidence of changing sedimentation rate in the central basin during the past century fluxes of excess 210 pb 230 th and 231 pa to the central santa monica basin sediments are much higher than what can be predicted from local supply advective input of open ocean waters coupled with enhanced scavenging of these reactive nuclides at the ocean margin is considered to be the primary cause

three dimensional kinematic modeling of reversible fault and fold development in the current context of continuous supply of energy the discovery and development of new prospects will rely on our ability to detect reserves in deeper and structurally more complex formations these exploration areas stretch the capabilities of currently available three dimensional 3 d exploration software which cannot accommodate a realistic geometrical description of present day geological structures and the tectonic deformation steps correctly handling the kinematics of structural deformation and evaluating the pressure regime and temperature history at the scale of exploration will remain as challenges for several years to come in this article we focus on geometric aspects using a reversible kinematic approach to deform and restore faulted and folded structures kinematic modeling is a good alternative to the complexity of a mechanical approach and is sufficiently representative of the natural processes involved sedimentation erosion and compaction its reversibility ensures that the basin parameters need to be defined only once for both the restoration and the deformation steps the model describes the incremental development of the basin in space and time it is based on a hexahedral discretization process that is fully adapted and appropriate for thermal and fluid transfer different deformation modes flexural slip and vertical shear are mixed to integrate natural deformation more effectively the algorithm is validated using different geological examples of growing complexity up to curved normal and thrust faults the approach offers various prospects for improvement integrating both kinematic and mechanical constraints considering the challenges that the industry needs to overcome in future exploration the results of this approach are very encouraging and can be considered as a solution for solving the structural part of 3 d basin modeling in complex areas

mesoscale forcing of a boundary layer jet along the california coast mesoscale numerical model simulations were examined to investigate the thermal and topographic forcing of a boundary layer jet along the northern california coast from 0000 utc may 2 to 1200 utc may 3 1990 routine surface and upper air observations satellite and higher resolution coastal observations r v point sur and doppler wind profiler data documented the diurnal evolution of a coastal marine atmospheric boundary layer mabl coastal cloud structure and mesoscale features such as the coastal jet and land sea breeze circulations that were reasonably well forecast by the numerical model sensitivity model simulations to coastal baroclinicity showed that the diurnal development and intensification of the coastal mabl jet located north of the san francisco bay area was a result of thermal forcing due to differential land sea heating simulations in which the coastal baroclinicity was held fixed in time at a minimal strength showed no diurnal development of the mabl jet the strength of the jet was approximated well by the thermal wind relationship with the jet core located in the sloping marine inversion layer within one rossby radius of deformation from the coastline the steepness of the marine inversion at the coastline was enhanced by regions of strong mabl divergence just offshore and strong convergence onshore resulting from the sea breeze circulation modifications to coastal terrain in two separate sensitivity model simulations illustrated that the primary effect of coastal topography was to act as a barrier to the onshore intrusion of higher momentum offshore air this blocking was due to a topographically forced vertical circulation with a strong descending branch located at the coast this downslope flow and adiabatic warming steepened the mabl inversion at the coast and enhanced the coastal baroclinicity and the coastal jet simulations without coastal terrain showed a jet structure that was spatially diffuse across the coastline and displaced more shoreward simulations in which coastal valleys were removed and replaced by a larger coastal mountain range resulted in little modification to the coastal jet intensity or offshore displacement

review of methods to measure short time scale sediment accumulation this review paper aims at providing a list of methods available to measure sediment accumulation in underwater or intertidal environments over short term periods in the order of hours to months at the most both in situ and under laboratory conditions methods are classified based on two criteria a whether they measure sediment accumulation or sediment elevation change and b whether they allow continuous or discontinuous measurements the main characteristics of each method are outlined along with its vertical resolution its accuracy its temporal resolution its spatial coverage capacity and an indication of its relative cost typical examples of applications are also provided the purpose of this review is to be a starting point for readers who need an overview of existing techniques that measure short term sediment accumulation in order to guide and facilitate for instance the selection of an appropriate technique for a given application with set requirements

the contrasting biogeochemistry of iron and manganese in the pacific ocean abstract vertical and horizontal distributions of dissolved and suspended particulate fe and mn and vertical fluxes of these metals obtained with sediment traps were determined throughout the pacific ocean in general dissolved fe is low in surface and deep waters 0 1 to 0 7 nmol kg with maxima associated with the intermediate depth oxygen minimum zone 2 0 to 6 6 nmol kg vertical distributions of dissolved mn are similar to previous reports exhibiting a surface maximum a subsurface minimum a mn maximum layer coincident with the oxygen minimum zone and lowest values in deep waters near shore removal processes are more intense for dissolved fe than for dissolved mn dissolved mn in the surface mixed layer remains elevated much farther offshore than dissolved fe elevated near surface dissolved mn concentrations occur in the north pacific equatorial current suggesting transport from the eastern boundary near surface mixed layer dissolved mn concentrations are higher in the north pacific gyre reflecting enhanced northern hemisphere aeolian sources residence time estimates for the settling of refractory paniculate fe and mn from the upper water column are 62 220 days fe and 105 235 days mn in contrast residence times for the scavenging of dissolved fe and mn are 2 13 years fe and 3 74 years mn scavenging residence times for dissolved mn based on horizontal mixing in the surface mixed layer of the northeast pacific are 0 4 years nearshore to 19 years 1000 km offshore there is no evidence for in situ fe redox dissolution within sub oxic waters in the eastern tropical north pacific dissolved fe appeared to be controlled by dissolution from sub oxic sediments with oxidative scavenging in the water column or upper sediment layers however in situ mn dissolution within the oxygen minimum zone was evident

application of a three dimensional finite element method to strain field analyses abstract i have programmed a three dimensional finite element model to spatially integrate distributed strains the mathematics is based on cobbold and percevault 1983 the method finds the pre strain configuration of a region by unstraining rectangular prisms into parallelepipeds then rotating and translating them iteratively to minimize the interelement deviations a numerical singular value decomposition calculates the necessary rotations and the final cycle of further strains to make a best fit of the elements the deviation of elements from holes formed by their nearest neighbors indicates the degree of compatibility of strain measurements the program reproduces the rotations required in examples with analytic solutions even though only a single horizontal layer of elements is used the fitting procedure correctly calculates rotations in all three dimensions from the constraints of strain compatibility three dimensional strains measured in an archean greenstone belt of northeastern minnesota were integrated using a layer of nearly equant finite elements rotations calculated from the pre tectonic configuration accord with field observations of fabrics indicating variable amounts of shear rotations about horizontal axes are minimal precluding large vertical shears an estimate of 40 true horizontal north south shortening across the belt can be made from the undeformed configuration

map restoration of folded and faulted late cenozoic strata across the oak ridge fault onshore and offshore ventura basin california the ventura basin lies within the east west trending active fold and thrust belt of the western transverse ranges california this basin has been the site of significant earthquakes on structures within it and bordering it the purpose of our study is to identify the main structures in the basin and its borders and to quantify their rate of deformation our study includes the onshore and offshore ventura basin the arcuate basin bounding oak ridge reverse fault and the oxnard shelf to the south shortening fault slip and crustal block motions were studied using a three dimensional map restoration technique structure contour maps on the 6 ma surface and other horizons were digitized and restored to the initial horizontal state by unfolding them using the computer program unfold and then fitting the unfolded surfaces across faults comparing the restored and present configuration allows us to estimate total net finite displacements relative to a fixed horizontal reference line average post 5 ma shortening rates estimated from our restoration are slower than both post 1 ma rates and present rates determined by global positioning systems most shortening due to folding in the onshore basin is post 1 ma although slip on the oak ridge fault has occurred both before and after 1 ma displacement due to faulting and folding includes left lateral strike slip motion on the northeast southwest coastal segment of the oak ridge fault and associated clockwise rotation of the adjacent ventura basin the oxnard shelf is bordered to the south by mountains and islands that have been previously interpreted as folds above thrust fault ramps this onshore offshore block moves as one continuous thrust sheet similarly beyond the well studied onshore fault a kinematically continuous offshore oak ridge mid channel left oblique fault system is interpreted to continue at least an additional 100 km westward beneath the santa barbara channel

wind related resuspension of sediments in the peel harvey estuarine system resuspension of bottom sediments accounted for 69 92 of mean deposition rates 11 6 69 3 gm 2 day 1 measured at 5 sites in the peel harvey estuarine system western australia deposition rates at all but one of the sites were found to be correlated p 0 05 with a function of wind combining a fetch factor with the number of hours of winds greater than 5 ms 1 weighted by the third power of wind velocity the exception was the only site with a cover of benthic algae cladophora during the study wind related resuspension greatly affects the forms and amounts of productivity in this system

nicolas and eel submarine fans california continental borderland nicolas and eel submarine fans occur in the san nicolas basin an outer basin of the california continental borderland that has a low sedimentation rate nicolas fan lies southeast of san nicolas island and the broad san nicolas bank the upper fan is characterized by numerous channels the midfan region may be divided into three distinct areas a central midfan and two subfans the central midfan depositional system is typical of normark s suprafan the subfans are essentially flat sandy lobes eel fan lies west of san clemente island and is fed by an erosional valley its midfan region may also be characterized as a flat sandy lobe box core data show that holocene turbidity currents have occurred on the central nicolas fan whereas the subfans and eel fan are nearly nactive the local tectonic regime influences these fans by determining slope trends creating bathymetric obstacles controlling canyon location and triggering mass movements sea level changes affect sedimentation patterns of the fans by increasing the mean grain size and the amount of sediment delivered to the fan during lowstands these changes may in turn affect the morphology of the fan the characteristics of these fans represent variations of the generalized fan models described in the literature

mathematical removal of regional ductile strains in central brittany evidence for wrench tectonics abstract hercynian deformation in central brittany is responsible for folding of paleozoic and earlier sediments with concurrent development of cleavage essentially e w and vertical and stretching lineation essentially horizontal in the past the regional motion was inferred to be a n s shortening more recent studies emphasize e w transcurrent motions associated with major crustal faults values and orientations of ductile strain at 29 localities in central brittany show that the regional deformation is basically a horizontal plane strain with local three dimensional perturbations we first remove the perturbations rendering the problem two dimensional then a selected domain is divided into an array of finite elements parallel to strain trajectories using strain values extant at element centroids each element is unstrained independently of its neighbours resulting gaps and overlaps are minimized using a least squares technique which allows elements to translate and rotate rigidly thus we obtain the configuration of the domain in the undeformed state to within an unknown but constant rigid rotation the domain has undergone a heterogeneous dextral simple shear with vertical shearing plane striking n125 and horizontal shear direction a band of low strain running through guer is flanked by two zones of more intense strain the banding is approximately parallel to a major transcurrent fault in the area the south armorican shear zone

structural evolution of the witch ground graben the witch ground graben is a nw se trending extensional basin in the central part of the northern north sea lying between the moray firth and the viking graben ne sw extension occurred from triassic to cretaceous times extension took place on listric normal faults along the sw margin with downthrow to the ne giving rise to the asymmetry of the basin one of the principal phases of fault controlled subsidence occurred in the lower cretaceous from the valanginian to albian compilation of biostratigraphic data from this interval shows the development of an increasing number of stratigraphic breaks across the basin from sw to ne these breaks increasing in time span also in this direction this is a result of rotation of the subsiding fault block on the listric extensional faults the rotation is recorded in dipmeter data and occurred in several distinct episodes the triassic the volgian and the valanginian to aptian in reconstructing a cross section of the basin the interpreted fault curvature is constrained by the observed rotation of bedding surfaces and the amount of extension across the listric faults is constrained by the observed basin subsidence a depth to decollement for the faults of 4 km below sea level and an extension across the basin of 40 are estimated

a three dimensional numerical investigation of a carolina coastal low level jet during gale iop 2 abstract the pennsylvania state university ncar mesoscale model is used to examine the structure and dynamics of three low level jets lljs observed during the second intensive observation period of the genesis of atlantic lows experiment 1 a piedmont llj along the east slope of the appalachians 2 a coastal llj the focus of this study along the carolina coastline and 3 an llj to the rein of a cold frontal system positioned over the gulf stream geostrophic forcing was important for the formation of the lljs shallow local baroclinity near the top of the cold dome associated with the cold air dammed to the east of the appalachian mountains forced the piedmont llj an analysis of the model momentum tendencies reveals that the coastal llj developed and was maintained by strong geostrophic forcing associated with the coastal baroclinic zone and its strength was modulated by strong inertial accelerations significant horizontal structure in the coastal llj developed during the daytime as a result of

sequential restoration and unstraining of structural cross sections applications to extensional terranes we restore cross sections using a strain minimization strategy that concentrates displacement on known faults and on slip systems within fault blocks growth strata are used to sequentially restore cross sections and the misfit of rigidly restored fault blocks is used to determine the internal strain within each fault block texture mapping allows data e g seismic profile photograph of an analog model or outcrop to be imaged onto the restored state and the image is translated rotated and unstrained during the restoration growth strata are stripped layer by layer to sequentially restore a cross section this approach determines the history of deformation including the activity of faults and the internal strain accumulated during each growth increment during each increment of growth a cross section is initially restored to a horizontal datum assuming that deformation is by rigid body translations and rotations of fault blocks fault blocks are unstrained by dividing them into smaller triangular elements that accommodate the internal deformation within each fault block translations and rotations of the smaller rigid elements within each fault block produce a least squares minimized best fit after attaining a best fit of rigid elements continuity is regained by moving initially coincident triangle vertices to a common centroid the change in shape of the triangular elements in regaining continuity is a measure of strain at that location assuming homogeneous strain within each triangular element sequential restoration and unstraining determines the spatial variation and temporal evolution of strain orientations and magnitudes calculated at each vertex during each increment of restoration the method is tested on an analog sandbox model of deformation in the hanging wall of a listric normal fault and on two seismic profiles a listric normal fault system from the gulf of mexico and a graben developed over salt from the north sea the sequential restoration accurately determines the sequence of faulting in the analog model and provides insights into the development of the natural examples the restoration method determines the orientations and magnitudes of strain which can be used to predict the orientation intensity and timing of small scale deformation features

tectonic significance of fault slip data abstract the statistical analysis of populations of minor faults is commonly used by structural geologists working in areas of brittle rock it is based on measurements of fault attitude direction and sense of slip at individual sampling localities results are classically interpreted as indicators of stress or strain rate fields assuming a homogeneous stress or strain rate tensor respectively however fault patterns are expected to vary with time because of displacements rigid rotations and internal strains which generally occur along boundaries of fault bounded blocks as deformation proceeds thus in the general situation where early faults accumulate displacements and rigid rotations and where new faults develop during progressive deformation fault slip data can be rather complex and variable in space and reflect neither local stress or strain rate tensors nor finite strains and finite rotations in a simple way we use two examples of faulted regions to illustrate the spatial variability of fault slip data this can be due to local complications at the edges of fault blocks or to complex kinematic conditions at regional boundaries such complications may make it difficult to deduce a consistent and simple pattern of either stresses or strain rates instead our results suggest that information contained in fault slip data can be pertinent to finite deformation in particular the principal axes that we have deduced from the analysis of fault slip data are consistent with the finite displacements at block boundaries that we have calculated by numerical restoration

radial gravitational gliding on passive margins abstract gravitational gliding of uppermost sediments down a passive margin is possible if there is a basal layer of evaporite or other soft material to allow detachment in examples from the gulf of mexico and the brazilian margin gliding has produced three main structural domains an uppermost domain of downdip extension an intermediate domain of rigid gliding and a lowermost domain of downdip contraction domain boundaries are established by changes in slope in this paper we examine three kinds of gravitational gliding depending on the paths followed by material particles in ideal parallel gliding particle paths are parallel straight lines trending downslope this should occur where the margin is perfectly straight in ideal radial gliding particle paths are radii of a circle and the margin is shaped like a circular cone natural margins will not have ideal shapes but divergent gliding will tend to occur off coastal salients convergent gliding off coastal re entrants a simple kinematic model based on ductile behaviour illustrates some essential features of radial gliding changes in radius during divergent gliding produce strike parallel extension during convergent gliding they produce strike parallel contraction vertical strains also differ divergent gliding produces an uppermost domain of strong vertical thinning balanced by extensions in all horizontal directions similarly convergent gliding produces a lowermost domain of strong vertical thickening balanced by contractions in all horizontal directions these deformed states cannot be restored by simple techniques based on section balancing we have done three experiments using analogue materials sand to model the brittle behaviour of sediments silicone putty to model the ductile behaviour of basal layers of evaporite the experiments were properly scaled to account for gravitational forces experiment i reproduced convergent gliding above a basement with a conical upper surface strike parallel contraction was responsible for radial folds on the lower slopes the lowermost domain had a complex fold pattern indicating contraction in all horizontal directions experiment 2 reproduced divergent gliding above a basement with a pyramidal upper surface strike parallel extension produced radial rifts on the upper slopes the uppermost domain had a complex polygonal pattern of normal faults indicating extension in all horizontal directions experiment 3 also reproduced divergent gliding but due to non uniform sediment thickness we have examined the many seismic profiles both downdip and alongstrike available for the brazilian margin alongstrike profiles show structures which we attribute to strike parallel strains around the santos re entrant syn sedimentary growthfolds indicate strike parallel contraction increasing downslope this argues for a mechanism of convergent gliding in contrast around the campos salient normal growth faults and associated salt rollers indicate strike parallel extension decreasing downslope this argues for a mechanism of divergent gliding the pattern of oil fields in the campos area including the giant marlim field seems to be closely controlled by divergent gravitational gliding and associated processes radial gliding should occur on other passive margins as well especially where the coastline is sinuous structures around the western gulf of of mexico seem to indicate convergent gliding at the scale of the entire gulf structures at a smaller scale around the mississippi delta seem to indicate divergent gliding

compatibility constraints on folded and faulted strata and calculation of total displacement using computational restoration unfold program abstract a balanced surface method is proposed that allows one to test the reliability of the interpretation of the structural geometry of folded and faulted strata it also estimates both the finite total displacement field linked to the folding and faulting processes and the finite displacement field linked to the folding the method describes a thin competent folded and faulted sedimentary layer using rigid triangular elements their sizes depending on the curvature of the surface the elements are laid flat and are automatically fit to form a horizontal surface which represents the initial state of the layer the degree of compatibility given by different indicators tests the reliability of the geometric fitting of the layer if folding and faulting occur without bed stretching or if this change is known and introduced as a parameter in the code a plausible interpretation can be perfectly retrodeformed just as a folded and torn sheet of paper may be smoothed with an iron the method has been applied to two natural examples in oil field regions using three or two dimensional depth migrated seismic data the main results reveal in general that the petroleum company s interpretations of the data were nonoptimal a careful reinterpretation of the seismic data was necessary to obtain balanced folded and faulted surfaces the estimation of the finite displacement fields revealed the compatibility between fold and fault deformation and also the strike slip movement or rotation associated with the deformation

a sediment trap intercomparison study in the santa barbara basin four sediment traps of radically different design were deployed in the santa barbara basin for approximately 45 days the measured fluxes ranged from 370 to 774 g m 2 yr 1 for the different designs these values lie within flux measurements previously determined for the basin compared to the 25 year record 920 g m 2 yr 1 however all fluxes determined in this experiment are somewhat low because this experiment was conducted during a general period of high storm activity and runoff measurement of greater than average flux was expected it is probable that the higher flux recorded by the sediments results from a significant input of detritus into the basin by near bottom transport the chemical composition of trapped material was nearly identical in all four trap designs the deep cone design however had a significantly lower mn content since this trap was the only one in which reducing conditions were produced in the sample container reduction and mobilization of manganese after collection is believed to have occurred in spite of the very different designs tested the factor of two agreement in flux determination and the compositional similarity of the material collected is encouraging for future attempts to directly measure the flux of particulates in the ocean

the trace metal composition of suspended particles in the oceanic water column near bermuda trace metal partitioning between seawater and particles both suspended and sinking must be determined to understand and model oceanic trace metal scavenging processes in order to improve the oceanic particulate trace metal data base a newin situ pump was developed and deployed to collect suspended particles from 0 4000 m in the sargasso sea near bermuda these particles were analyzed for al fe mn co zn cu ni cd and pb major particulate carrier phases were estimated from ca opaline si and p cd is the only trace element of this group with a particulate maximum in near surface waters the other metals have low particulate concentrations mol l in near surface waters and increase with depth into the upper thermocline particulate al and fe are then uniform with depth below about 1000 m until increasing in the bottom nepheloid layer the remaining elements mn co zn cu ni and pb decrease from the mid thermocline values to lower and relatively uniform concentrations in deep waters the similarities among the vertical profiles for these metals suggest that authigenic mn oxides influence their uptake from the dissolved pool although an important or dominant role for other host phases specifically particulate organic matter is not ruled out by the data mean intermediate and deep water concentrations are al 3600 fe 1200 mn 146 co 1 5 zn 7 4 cu 15 ni 6 0 cd 0 06 and pb 2 1 pmol l these particulate al and mn values agree with previous measurements in this region but the other elements are lower by a factor of 3 fe co to 30 zn suggesting that earlier data were compromised by contamination the suspended metal data are used in a simple steady state two flux model to evaluate the role of suspended particles in determining the vertical flux of metals in the sargasso sea the model calculations indicate that removal of suspended particles in the deep 500 m water column contributes less than half of the total deep flux for all of the elements investigated except for cd this result implies that uptake of these metals onto particles in the deep central ocean is a minor factor in their oceanic mass balance if this finding is generally true for oligotrophic ocean environments whole ocean residence times for these elements must be governed largely by processes occurring either in near surface waters or at ocean margins

an inverse method for determining three dimensional fault geometry with thread criterion application to strike slip and thrust faults western alps and california abstract in order to draw geological structures such as faults interpolation is generally needed between scattered data the use of an approximation criterion integrating the kinematic properties of the faults helps to document the fault surfaces by adding a compatibility criterion to the data set assuming that two jointed blocks of rocks slipping on each other generate a thread surface an approximation method has been developed which integrates a thread criterion this approximation method is used to solve an inverse problem with least squares criteria including proximity to data points smoothness and thread criteria the aim is to find a smooth surface which is as close as possible to a thread and as close as possible to the observed data set applications to two corrugated fault surfaces with a dense data set located in the western alps france and in the transverse ranges california confirm the validity of the thread assumption despite their difference in mean corrugation wavelength 5 m and 10 km respectively in the type of fault strike slip and thrust fault respectively and in the nature of the faulted rocks limestones and sandstones respectively very similar results are obtained in both cases the observed data fit well with a thread surface and the computed fault displacement fits well with the measured displacement on the fault striae seismic focal mechanism geodetic data restoration the conclusion is that treating a fault as a thread is a valid physical description which gives the slip direction independently of other kinematic indicators the advantage of using a thread criterion in addition to classical proximity and smoothness criteria is that this physical insight allows information from areas where data are relatively dense to help constrain areas where data are relatively sparse these last areas being those that are usually not well constrained by proximity and smoothness criteria

anomalous isotopic concentrations in the sea off southern california measurements are reported of the 10be concentrations in 15 sediments from the sea off southern california the sedimentation patterns are modelled with a two component system one component having the high 10be concentration of pelagic sediment and the other the low concentration of continental runoff the pelagic component brought to the region by the california current with the pacific ocean as reservoir is very likely the source not only of anomalously high 10be deposition but also of similar effects with 2101pb 239 240pu and 241pu

variations in amount and direction of seafloor spreading along the northeast atlantic ocean and resulting deformation of the continental margin of northwest europe the ne atlantic ocean opened progressively between greenland and nw europe during the cenozoic seafloor spreading occurred along three ridge systems the reykjanes ridge south of iceland the mohns ridge north of the jan mayen fracture zone jmfz and the aegir and kolbeinsey ridges between iceland and the jmfz at the same time compressional structures developed along the continental margin of nw europe we investigate how these compressional structures may have resulted from variations in the amount and direction of seafloor spreading along the ridge system assuming that greenland is rigid and stationary we have used a least squares method of palinspastic restoration to calculate differences in direction and rate of spreading along the reykjanes kolbeinsey aegir and mohns ridges the restoration generates relative rotations and displacements between the oceanic segments and predicts two main periods of left lateral strike slip along the main oceanic fracture zones 1 early eocene to late oligocene along the faeroe fracture zone and 2 late eocene to early oligocene and during the miocene along the jmfz such left lateral motion and relative rotation between the oceanic segments are compatible with the development of inversion structures on the faeroe rockall plateau and norwegian margin at those times and probably with the initiation of the fugloy ridge in the faeroe shetland basin during the eocene and oligocene the iceland mantle plume appears to have been in a position to generate differential seafloor spreading along the ne atlantic and resulting deformation of the european margin

vertical axis rotation in the bolivian orocline south america 2 kinematic and dynamical implications an analysis is presented of the kinematic consequences and dynamical causes of paleomagnetically determined rotations about a vertical axis documented in the central andes south america between 15 s and 25 s at these latitudes there is a pronounced bend in the topographic and structural trends defining the bolivian orocline the observed vertical axis rotations during the last 10 myr are used in conjunction with observations of horizontal dilatation to calculate the finite strain and displacement field in a network of triangles spanning the bolivian orocline assuming that the rotations represent the rotational component of finite strain this shows that rotation during the last 10 myr has accommodated bending of the bolivian andes increasing the curvature of the eastern margin of the bolivian orocline by 10 to 27 with a systematic variation in strains around the oroclinal hinge which is consistent with the observed pattern of upper miocene to recent deformation vertical axis rotations greater than that inferred for regional oroclinal bending can be explained in terms of simple kinematic models of vertical axis rotation and reverse faulting in margin parallel zones of sinistral and dextral shear the dynamical controls of vertical axis rotation are analyzed using a simple thin sheet model of viscous flow in a narrow channel this model suggests that in general regional bending is controlled by a combination of along strike gradients of 1 boundary normal stresses at the subduction zone 2 bulk lithospheric viscosity 3 gravitational potential energy buoyancy stress contrasts and 4 width of the fluid like channel if along strike gradients of boundary normal stresses and viscosity are small then the pattern of vertical axis rotation can be explained as a consequence of along strike gradients in buoyancy stress for a bulk lithospheric viscosity in the bolivian andes 7 1021 pa s in detail the organization of vertical axis rotation and horizontal shortening suggests that there are both horizontal and vertical gradients of velocity and rheology in the lithosphere

balancing and restoration of piercement structures geologic insights from 3d kinematic models abstract restoration of cross sections and map surfaces of volume balanced 3d flexural slip models are presented to provide insight into the structural interpretation and validation of highly 3d structures like faulted salt domes 2d restoration results in apparently unbalanced cross sections most sections show apparent thickening on dome flanks because the section line is oblique to the dip except the radial cross section that bisects a flank horst or graben along the slip direction a section is corrected by adjusting the thickness according to the true dip as determined in map view a cross section from the flank of a 3d piercement structure is best restored by flexural slip unfolding between pin lines placed at each edge of the section parallel flexural slip unfolding is a reasonably good and practical restoration method for 3d piercement structures small gaps nearly always exist along every fault trace restored in the model this systemically distributed small inconsistency does not however indicate a problem in the interpretation these small gaps are due to the use of the same unfolding direction for every restored block insights from model dome restoration are applied to test the interpretation of natural salt dome examples from eastern texas and northern germany

restoration of transpression transtension by generating the three dimensional segmented helical loci of deformed lines across structure contour maps abstract in transpression transtension zones the strain is three dimensional and rotational this causes material to move through the plane of cross section often invalidating balancing and restoration within this plane methods are presented which allow the three dimensional segmented irregular helical locus of an originally straight line to be constructed in any direction on a structure contour map of a folded and faulted surface this construction depends on a knowledge of the kinematics of folding and faulting and can be modified to suit local conditions the ratio of the length of the cylindrical envelope bounding this helical locus to the sum of the lengths of the helical fragments between faults gives the true stretch in the direction of the envelope when the traces of the segmented helices are constructed in different directions on a deformed surface the sectional finite strain ellipse can be found for that surface knowledge of the dimensions of this ellipse and its orientation with respect to the kinematic axes of the transpression zone allows the tensor components to be constrained this permits the three dimensional boundary conditions to be determined and thus restored the methods are applied to the ardross fault zone in central scotland the solutions suggest this fault zone underwent a phase of dextral transpression along a nw zone boundary during hercynian e w compression in the scottish midland valley contemporaneous e w dyke swarms and n s regional flexures support these kinematics

restoration of cross sections to constrain deformation processes of extensional terranes abstract restoring balanced cross sections constrains the possible deformation processes affecting extensional terranes with a ductile substratum such as salt and syndeformational sedimentation cross sections are divided into fault blocks and shear domains each of which can be undeformed with a different set of parameters the success of restorations is judged by compatibility between the blocks and the reasonableness of the restored structures fault blocks in physical models restore with simple shear at about 60 dipping in the direction which removes extension corresponding to an antithetic orientation in the hangingwalls of normal growth faults and subparallel to the fault in the footwall other components of the deformation are rigid rotation translation and decompaction shear angles inferred from natural examples are more varied ranging from vertical to moderately inclined nearly always dipping in a direction that removes extension

quantifying simultaneous discrete and distributed deformation most natural deformation involves simultaneous discrete deformation e g faults and distributed deformation e g penetrative strain in order to properly understand the bulk kinematics of a given deformation the discrete and distributed components must be evaluated simultaneously the displacement diagram method has previously been utilized to quantify strain accommodated by faults or other discrete surfaces the same method is applicable to distributed deformation such as ductilely deformed conglomerates which are typically evaluated by finite strain analysis by mathematically combining the gradients in the displacement fields of both the discrete and distributed components of deformation the bulk deformation can be quantified we apply this method to several examples that contain both distributed and discrete components and characterize the bulk displacement field and finite strain for these deformed systems

non annual laminations and expansion of anoxic basin floor conditions in santa monica basin california borderland over the past four centuries sediments from box cores in the deep portion of santa monica basin have been examined by x radiography and the upper 10 20 cm are characterized by laminations 1 5 mm in thickness age dating of 9 cores by 210pb analysis has shown that accumulation rates on the central basin floor have been remarkably constant during the past century averaging 16 0 0 4 mg cm2 yr densitometer analysis of the x radiography films from 7 cores and spectral analysis of the resulting time series indicates that most lamination couplets have a periodicity in the 3 7 year range a range matching that of the el nino southern oscillation periodicity the median periodicity appears to have decreased slightly during the past 3 centuries from 7 0 years during 200 300 yrs b p to 5 2 yrs during 0 100 yrs b p this trend could be due to a decreasing sedimentation rate an increasing forcing frequency or an increasingly faithful response of the basin in more recent years multiple processes have contributed to creation of the laminations in santa monica basin the principal factors appear to be 1 variations in porosity due to the relative abundance of organic filaments probably formed by beggiatoa mats and 2 compositional variations that reflect variations in carbonate lithogenous ratios and in grain size both of these are expected to respond to enso events the presence of near anoxic bottom waters has prevented bioturbation permitting laminations to be preserved basin bottom waters became nearly anoxic about 350 years ago at the onset of warming as the little ice age waned expansion of the near anoxic area during the past century may have been augmented by 20th century anthropogenic effects the style of these non annual laminations in santa monica basin matches that of the annual laminations in the adjacent santa barbara basin and demonstrates the need for caution in interpreting all laminations as representing annual varves

displacements strains and rotations within the afar depression djibouti from restoration in map view within the afar depression djibouti the stratiform basaltic lava flows emplaced between 4 ma and 1 ma cover the two thirds of the depression because of the desert climate they are almost non eroded the topography can then be used as a reference surface to measure the vertical offset of younger faults using a detailed map the southeastern part of the depression showing the fault pattern and the vertical offset on each fault obtained from stereoparts of spot images we have restored the topography in map view we have computed the fields of finite displacement rotation and strain the field of horizontal displacements shows vectors trending to the ne on average this direction is compatible with the displacement to the ne of the arabian plate with reference to the african plate in detail however displacement vector trend from nne ssw to ne sw major axes of strain ellipse trend ne sw suggesting that major faults n120 are dominantely extensional strain intensities and magnitudes of block rotations are increasing from southwest to northeast of the restored area magnitudes of block rotations are very small compared with those obtained from paleomagnetic measurements therefore we computed a second restoration that covers a smaller area where the true vertical offset of the major faults taking into account the sedimentary fill of basins were avalaible this second model gives rotation magnitudes in better agreement with paleomagnetic data but still underestimates we discuss these results with the available kinematic models of the southeastern part of the depression

restoration in plan view of faulted upper cretaceous and oligocene horizons and its bearing on the history of salt tectonics in the campos basin brazil abstract in the campos basin atlantic margin of brazil cretaceous and tertiary sediments show abundant evidence for thin skinned deformation above a layer of aptian salt near the coast there is a domain of downslope extension further offshore a domain of donwslope contraction thus we attribute the domainal pattern to gravitational gliding on the salt layer gravitational gliding appears to be driven primarily by surface slopes each material particle tends to move in the direction of steepest slope if topography is irregular particle paths diverge or converge deformation then differs from a plane strain and vertical cross sections cannot be individually balanced or restored we have therefore developed a method for restoring non plane deformation in extensional domains assuming that blocks between faults are rigid we restore stratigraphic horizons in plan view by least squares minimization of distances across fault separations cut off lenses obtaining fields of finite horizontal displacements for selected areas in the extensional domain of the campos basin where divergent gravitational gliding has led to extension in various horizontal directions we have restored two stratigraphie markers an upper cretaceous and an oligocene horizon for each horizon displacement vectors diverge seawards forming a fanlike pattern with a degree of mirror symmetry nevertheless there are major differences between the upper cretaceous and oligocene patterns both for faults and for displacements we infer that this resulted from the development during the tertiary of a propagating deltaic front whose sediment load drove the divergent gravitational gliding and induced a new fault pattern

the influence of mesoscale orography on a coastal jet and rainband abstract the role of mesoscale orography along the central california coast in the development and evolution of a coastal jet and rainband is investigated using a high resolution triply nested nonhydrostatic numerical model comparison of the model simulations which use horizontal grid increments of 5 and 2 km on the inner computational meshes with a coastal mesoscale observation network indicates that the finescale structure of the jet and rainband dynamics are adequately simulated although phase and orientation errors occur the observed and simulated near surface winds have maximum speeds that exceed 22 m s 1 and a direction nearly parallel to the coastline and topography force balance analysis indicates that blocking in the lowest 500 m and flow over the coastal range above this layer contribute to mesoscale pressure perturbations including pressure ridging upstream of the coastal mountains which forces the ageostrophic dynamics of the coastal jet pressure perturbations associated with the to

influence of boundary scavenging and sediment focusing on 234th 228th and 210pb fluxes in the santa barbara basin abstract sediment trap samples were collected from the santa barbara basin to examine the flux of 234 th 228 th and 210 pb mean ratios of measured to predicted fluxes are 2 10 and 21 for 234 th 228 th and 210 pb respectively boundary scavenging may supply a portion of all three radionuclides however sediment focusing supplies additional 228 th and 210 pb but little 234 th sediment temporarily deposited on the shelf around the basin contains little excess 234 th due to its short half life 228 th and 210 pb fluxes to the sediments in the santa barbara basin are several times greater than predicted from their supply in the overlying water column these enhanced fluxes require lateral transport of 228 th and 210 pb to the basin through boundary scavenging and sediment focusing 234 th flux is poorly correlated with 228 th and 210 pb fluxes because individual radionuclide sources to the basin differ i e water column production boundary scavenging and or sediment focusing correlations between 228 th and 210 pb fluxes are high due to the strong influence of sediment focusing on both radionuclides there is a strong correlation between both the 228 th and 210 pb flux and total mass flux and lithogenic flux but a weak correlation with the other major sediment components e g organic carbon carbonate and biogenic opal in the santa barbara basin a large fraction of the total mass flux is lithogenic material 50 80 hence the strong correlation between 228 th and 210 pb fluxes and both total mass and lithogenic fluxes 234 th flux is poorly correlated with total mass and major sediment component fluxes

structural restoration of seismic and geologic sections in extensional regimes seismic sections from extensional basins can be structurally transformed to produce restored seismic sections showing subsurface geology of the past restoration is achieved using a simple and effective algorithm which is suited for use in an interactive seismic interpretation environment seismic data are resampled along paleovertical trajectories which are the deformed equivalents of what were originally closely spaced vertical lines paleoverticals are generated within the present day section as follows 1 origin points are equally spaced along a reference horizon that corresponds to an original depositional surface 2 paleovertical segments are vertical within fault blocks 3 paleoverticals are offset across faults by the reference horizon slip and 4 restor d depth is equated to distance down a paleovertical these rules can be modified to conform with such styles of extensional deformation as vertical simple shear inclined shear or rigid rotation and to account for compaction structures with complex fault patterns readily are restored several examples from the gulf of mexico and offshore west africa show that seismic restoration is useful for 1 unravelling structural and stratigraphic history 2 revealing tectonically masked features and 3 checking interpretations across faults for seismic correlation and structural balance geologic sections can be restored in similar fashion

least squares palinspastic restoration of regions of normal faulting application to the campos basin brazil we have developed an iterative least squares method for palinspastic restoration of regions of normal faulting the method closes the gaps cut off lenses across normal faults on a structure contour map of a given stratigraphie horizon such data are often available for sedimentary basins covered by seismic surveys before restoration we first produce a fault block map where each block is completely surrounded by faults whether real or artificial we then apply an algorithm to minimize d the sum of the squares of the distances across cut off lenses with respect to unknown rigid block translations and rotations minimization results in non linear equations which we solve by an iterative method we deem the solution to have converged when d falls below a given critical level in general restoration not only closes the original gaps but also results in strike slip displacements between blocks thus the deformation need not be a plane strain and displacement vectors need not be parallel we have applied the method to an area of the campos basin on the atlantic margin of brazil where the stratigraphy and structure are well known from seismic surveys and from wells cretaceous and tertiary sediments have glided downslope on a lubricating layer of aptian evaporites producing an uppermost domain of normal faulting the normal faults occupy a strip lying between undisturbed continental crust to the west and relatively unstructured sediments to the east assuming the western boundary to be stationary we have restored an upper oligocene stratigraphie level the marco azul convergence was achieved rapidly and the degree of fit is good according to our restoration the eastern boundary of the area has bowed out seawards since the oligocene block displacement vectors form a fan like pattern with an element of mirror symmetry about a line trending nw se maximum displacements occur in an apical domain bounded by a horseshoe pattern of faults there is a general pattern of block rotations counterclockwise in the northeast clockwise in the southwest some notable exceptions to this general pattern are due to local domino motions we attribute the overall displacement field to divergent gravitational gliding off a local salient in the sea bottom topography because of the three dimensional nature of the displacement field restoration of vertical cross sections alone would yield gross errors this demonstrates the value of palinspastic methods such as ours

chronologic modeling of faulted and fractured reservoirs using geomechanically based restoration technique and industry applications we have developed a geomechanically based restoration method to model reservoir deformation the approach founded on the finite element method simulates the physical behavior of the rock mass and considers heterogeneous material properties bedding slip and the mechanical interaction of faults to demonstrate the method s potential we analyze the deformation and fault growth in the hanging wall of a synsedimentary listric normal fault from a sand box model which provides an analog for evaluating complex faulted reservoirs the numerical model results are then analyzed to investigate the chronology of faulting the numerical model corresponds well to the physical model and provides additional insights about reservoir evolution and deformation the approach is also tested on a natural example of folding using outcrop data to study contractional deformation these examples illustrate how undetected faults and fractures reservoir compartmentalization hydrocarbon migration pathways and hydrocarbon traps can be understood in the context of tectonic processes and how this understanding can be exploited in decision making and reducing risk we conclude that the geomechanically based restoration of faulted and fractured reservoirs has significant potential for industry applications compared to common geometric restoration techniques which lack a mechanical basis

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

least squares restoration of tertiary thrust sheets in map view tajik depression central asia the tajik depression located west of the pamirs and south of the tien shan is a compressional intermontane basin bounded by basement overthrusts and filled with mesozoic and cenozoic sediments the internal structure is typical of a thin skinned tbld and thrust belt kinematic data available in the literature suggest that indentation of the pamirs into asia durino the cenozoic collision of india and asia has been accommodated in various ways within the depression including westward extrusion thickening combined with wrenching along n s tblds and thrusts and counterclockwise rotations these various detbrmation processes can be analyzed and quantified by reconstruction of the predeformed state of the depression however the combina tion of thrusting wrenching and block rotations implies a nonplane deformation which cannot be restored properly using balanced cross sections alone we have therefore developed a numerical method for restoration of stratigraphic surfaces designed for regions of nonplane compressional tectonics the deformed region is represented in map view as a mosaic of fault bounded blocks overlapping each other along the faults blocks are separately unfolded and then numerically packed together by least squares minimization of overlaps yielding fields of finite horizontal translations and rotations about vertical axes to analyze the deformation postdating the collision of india and asia we have restored a stratigraphic surface at the base of the cenozoic first in order to test the numerical method we restored a map that had previously been restored by a purely manual method restoration of a second map drawn from newly available subsurface data leads to geometrical inconsistencies overlaps and gaps which cannot be reduced remain in the restored state after correction of these inconsistencies restoration yields a complex mode of deformation for the depression individual thrust slices have undergone counterclockwise rotations about verti cal axes the magnitudes increasing from west to east up to a maximum of 40 o near the pamirs horizontal shortening is 150 km 35 in the center of the depression and 240 km 85 in the northeastern part between the pamirs and the tien shan strike slip motions commonly not revealed by balancing cross sections are associated with thrusting on faults striking n s inde pendent paleomagnetic data and slip directions on small scale faults provide positive checks on the results of our restoration

particulate iron and manganese in the santa barbara basin california abstract particulate fe and mn may be important trace metal scavengers in the water column as well as being probable indicators of biologically mediated redox processes a study has been made of suspended particulate composition in the santa barbara basin a shallow near shore basin off southern california with sub oxic conditions below sill depth observations have revealed several interesting phenomena relating to the geochemistry of fe and mn most striking is a profound enrichment of particulate fe in samples from the bottom two hundred meters these particulates have a constant fe p mole ratio of about three and may originate at the sediment water interface or may be transported to the basin from local marshes for particulate mn enrichments are observed both in the sub sill waters and near the base of the euphotic zone a consideration of particle removal rates suggests that the sub photic zone enrichment has a biogenic origin in the sub sill waters enrichment in mn is apparently due to the precipitation of dissolved mn diffusing from the anoxic basin sediments a simple mass balance suggests that most of the mn lost from the sediments is transported from the santa barbara basin in dissolved form

towards an integrated inversion of geoscientific data what price of geology abstract the inversion of multiple geoscientific datasets to define structures in hard rock terrains has for the most part been limited to geophysical methods supported by rock property constraints in this paper we expand the range of constraints available to geological modellers by defining a series of misfit functions that are used to define the quality of a given geological model with respect to the available geological data these misfit functions encompass both spatial and temporal observations and include primary data such as the location of an outcrop or bore hole location of a given rock type the orientation of its different generations of foliations as well as secondary geologic observations such as age relationships when we combine geologic conditions with geophysical misfit functions which already exist for many geophysical measures we have the potential to better constrain two and 3d models of the earth as a first test a subset of these misfit functions are applied to a set of synthetic three dimensional volumetric models built with an implicit surface modelling scheme by perturbing the input structural data within a narrow range we can simulate a range of significantly different three dimensional models for which we can then apply both geological and geophysical misfit functions several joint geological geophysical inversion schemes may be developed based on this methodology with the ultimate goal being an inversion scheme that simultaneously minimizes both geological and geophysical misfit

kinematic analysis of a growth fault system in the niger delta from restoration in map view by restoring six stratigraphic markers in map view we have studied the kinematics of a growth fault system involving a major fault its antithetic and a faulted roll over located within the niger delta offshore nigeria restoration yields for each marker the horizontal displacements due to normal faulting and the associated fields of block rotation about vertical axes as expected for a continuous history of growth faulting the amount of extension computed for each stratigraphic marker increases with depth from the fields of finite displacement and block rotation we find that horizontal extension perpendicular to fault traces is associated with a minor amount of bulk left lateral wrenching accommodated by counterclockwise rotation of blocks because the overall deformation differs from a plane strain balancing of cross sections alone would lead to some errors we also computed incremental displacement fields for time intervals between successive stratigraphic markers according to our results during the first stages of growth faulting displacement occurred only on the major faults whereas during later stages larger horizontal displacements were accommodated by numerous small faults probably responsible for the collapse of the roll over

copper isotope signatures in modern marine sediments abstract the development of metal stable isotopes as tools in paleoceanography requires a thorough understanding of their modern marine cycling to date no cu isotope data has been published for modern sediments deposited under low oxygen conditions we present data encompassing a broad spectrum of hydrographic and redox regimes including continental margin and euxinic sulphide containing settings taken together with previously published data from oxic settings these data indicate that the modern oceanic sink for cu has a surprisingly homogeneous isotopic composition of about 0 3 65cu relative to nist srm976 we suggest that this signature reflects one of two specific water column processes 1 an equilibrium isotope fractionation between soluble isotopically heavy cu complexed to strong organic ligands and an isotopically light pool sorbed to particles that deliver cu to the sediment or 2 an equilibrium isotope fractionation between the same isotopically heavy ligand bound pool and the particle reactive free cu2 species with the latter being scavenged by particulates and thereby delivered to the sediment an output flux of about 0 3 into sediments is isotopically light relative to the known inputs to the ocean at around 0 6 and the seawater value of 0 6 to 0 9 suggesting the presence of an as yet unidentified isotopically light source of cu to the oceans we hypothesize that this source may be hydrothermal or may result from the partial dissolution of continentally derived particles

numerical simulations of the boundary layer jet off the southeastern coast of china abstracta strong coastal boundary layer jet cblj 8 m s 1 off the southeastern coast of china around 28 n 122 e is found from the july 2006 11 hourly model data simulated by the advanced research weather research and forecasting model wrf arw with a 9 km horizontal grid the southerly cblj has a jet core at the 925 hpa level located along the western periphery of the west pacific subtropical high wpsh the cblj is mainly contributed by large scale enhancement by diurnal forcing and orographic effects by the coastal terrain along the southeastern china coast and the terrain of taiwan although the geostrophic winds offshore are faster in the afternoon due to the larger east west pressure gradient caused by land surface heating over the china plain the cblj has a nocturnal 0200 lst maximum in the afternoon hours easterly ageostrophic winds driven by differential land sea thermal heating develop at low levels after sunset with the disappearance of land surface heating the ageostrophic win

balancing sub and supra salt strain in salt influenced rifts implications for extension estimates the structural style of salt influenced rifts may differ from those formed in predominantly brittle crust salt can decouple sub and supra salt strain causing sub salt faults to be geometrically decoupled from but kinematically coupled to and responsible for supra salt forced folding salt influenced rifts thus contain more folds than their brittle counterparts an observation often ignored in extension estimates fundamental to determining whether sub and supra salt structures are kinematically coherent and the relative contributions of thin i e gravity driven and thick skinned i e whole plate stretching deformation to accommodating rift related strain is our ability to measure extension at both structural levels we here use published physical models of salt influenced extension to show that line length estimates yield more accurate values of sub and supra salt extension compared to fault heave before applying these methods to seismic data from the halten terrace offshore norway we show that given the abundance of ductile deformation in salt influenced rifts significant amounts of extension may be ignored leading to the erroneous interpretations of thin skinned gravity gliding if a system is kinematically coherent supra salt structures can help predict the occurrence and kinematics of sub salt faults that may be poorly imaged and otherwise poorly constrained

map view retrodeformation of an arcuate fold and thrust belt the jura case 1 the mechanism of arcuate mountain range formation is a matter of debate here we perform a map view restoration of a detailed three dimensional model of the jura arc a typical arcuate mountain range in the foothills of the swiss and french alps this retrodeformation is performed using the unfold surface balanced program based on a block mosaic method it results in a displacement field divergent toward the deformation front this displacement field suggests counterclockwise rigid rotations in the horizontal plane up to 30 in the southern internal jura and a corresponding vertical axis rotation or shear strain of the savoie molasse basin hinterlandward we also predict a 10 clockwise vertical axis rotation of the molasse basin in switzerland all these rotations agree with those documented by paleomagnetic data the former are taken to result from a substantial decrease in shortening at the southern jura end while the divergence of displacements is interpreted to result from variations in the detachment level distribution

examination of the impact of a coupled atmospheric and ocean wave system part i atmospheric aspects abstract to take into account the change of surface roughness length induced by ocean waves a coupled atmospheric and ocean wave model system is developed a two way coupling is done between a mesoscale atmospheric model mc2 and an oceanic wave model a regional version of wam cycle 4 two different approaches based on the wave age of smith et al and the wave induced stress of janssen are used to compute a coupling parameter called the charnock parameter expressed as the nondimensional surface roughness length the coupling between the two models is accomplished by the use of this parameter which is a function of sea state instead of the constant value obtained from empirical studies using the well known charnock relation the coupled atmospheric and ocean wave system was applied to four intense storms in the western atlantic to examine the impact of the two way interaction using real midlatitude storm cases in part i the atmospheric forecasts resulting from this two way coupling are discusse

3 d palinspastic restoration of normal faults in the inner moray firth implications for extensional basin development abstract balanced cross section techniques and the construction of a restored section permit 2 dimensional palinspastic restorations to be made in both compressional and extensional terraines in 3 dimensions an equivalent restoration can be made by assuming conservation of bedding plane area and considering the volume of a stratigraphic interval rather than its cross sectional area extensional basins displaying upper crustal listric normal faulting are particularly amenable to this approach computerised 3 d restorations have been made of the inner moray firth basin offshore scotland this basin is not isostatically compensated and was produced by 7 8 post triassic extension of which 2 5 3 is post jurassic above a detachment surface at 20 25 km depth close to the base of the crust limited lower crustal thinning and lithospheric stretching has affected the eastern part of the basin but this can account for no more than half of the measured upper crustal extension some of this shallow extension is probably coupled by low angle faults or shear zones into major zones of lithospheric stretching such as the north sea grabens where it may help account for discrepancies between estimates of lithospheric thinning and upper crustal extension

southern california inner basin sediment trap calibration the deployment of particle interceptor traps pits in the three inner basins of the southern california bight santa barbara santa monica and san pedro where preserved laminated bottom sediments occur provides a natural calibration between the parameters determined with the pits and those derived from the historical sedimentary deposits the accumulation rates and chemical composition of the pit materials compare favorably with these recently deposited bottom sediments the ratio of the measured particle collection rate to the sediment accumulation rate for these three basins averaged0 93 0 20 radionuclide 210pb 228th 232th and trace element fe cu zn cd pb compositions of the pit materials and surface sediments agree within generally 30 in each basin an application of pits as a sampling system in an outer basin san nicolas where the sedimentary record has been obscured by bioturbation is also presented to further demonstrate the utility of pits for spatial and temporal studies of various aspects of particle transport and sediment deposition based on the calibration of the pits in the three inner basins we conclude from the comparison of the radionuclide and trace element compositions between the pit materials and surface sediments from the san nicolas basin that recently deposited sedimentary material has been mixed by bioturbation with older material from the last several hundred years excess210pb and the228th 232th activity ratio in the pit material are 6 and 15 times higher than in the surface sediment total pb and1n hno3 leachable pb are 4 and 8 fold higher in the pit material

in situ calibration of a sediment trap1 2 a relatively small self contained sediment trap with a timed closing system was deployed in dabob bay washington for 1 year samples were collected representing 326 trap exposure days an in situ calibration was obtained by comparing the capture and retention of unsupported sup 210 pb by the traps with the steady state acccumulation rate of unsupported sup 210 pb in the underlying bottom the efficiency of the traps to collect a representative sample of the sedimenting material is 118

mechanism of thin skinned detachment in the amazon fan assessing the importance of fluid overpressure and hydrocarbon generation abstract since about 10 ma a wedge of clastic sediment up to 10 km in thickness has accumulated near the mouth of the amazon river forming the amazon fan thin skinned extensional and contractional structures root into a common basal detachment hundreds of kilometers long extensional faults have formed landward of the prograding delta slope and contractional folds and faults have formed seaward of it by plan view restoration we show that extension and contraction balance we therefore infer that slope instability has provided the driving force for thin skinned deformation on seismic data the detachment appears as a sharp surface within late cretaceous strata however there is no evidence at that level for soft layers such as evaporites or muds abnormal fluid pressure provides a more reasonable mechanism for the detachment at depths of several thousand meters deep wells have encountered fluid overpressures amongst the possible causes of abnormal fluid pressures are compaction and hydrocarbon generation although compaction may have contributed to fluid overpressures encountered in wells we argue that hydrocarbon generation provides the best explanation for detachment in cretaceous rocks which were old and lithified when it occurred in particular the broadly triangular area of detachment coincides with an inferred pod of cenomanian turonian source rock which is interpreted to have been in the gas window during detached deformation we have developed new techniques of sandbox modelling to investigate the geometries of fault patterns produced by fluid flow through porous media for the amazon fan we have been able to reproduce the structural pattern on the assumption that fluid overpressures existed over a broadly triangular area beneath the detachment

mixing and cycling of uranium thorium and 210pb in puget sound sediments abstract activity profiles of excess 234 th excess 210 pb 232 th 230 th 234 u and 238 u and 228 232 th ratios determined in eight box cores of sediment from six sites in central puget sound provide new insights into the dynamic nature of solid phase mixing in surface sediments the exchange of 228 ra and other soluble species across the sediment water interface and the cycling of u th and 210 pb in this coastal zone comparison of excess 234 th inventories in sediments with its production rate in the overlying water column indicates a mean residence time of at most 14 days for particles in the central puget sound water column surface sediment horizons with excess 234 th have no excess 228 th which might be used to ascertain sediment accumulation rates over the past decade instead deficiencies of 228 th due to loss of soluble 228 ra from pore water to the overlying water persist to 20 30 cm revealing that exchange of soluble chemicals between pore and overlying waters reaches these depths in the extensively bioturbated sediments of puget sound solid phase u isotope concentrations tend to increase by up to a factor of two with depth in sediments as a result of dissolved u being biologically pumped down into sediments where it is partially removed when conditions become mildly reducing 232 th and 230 th activities and 230 232 th ratios are constant with depth in sediments indicating constant detrital phase compositions and essentially no authigenic 230 th steady state 210 pb depositional activities in and fluxes to puget sound sediments average only about onehalf those for sediments of the open washington coast north of the columbia river mouth primarily because of a much lower supply of dissolved 210 pb in sea waters adverting into puget sound excess 234 th profiles in sediments reveal much more detail about the depth dependency dynamic nature and recent history of solid phase mixing processes than excess 210 pb profiles at least six of eight 234 th profiles show that mixing within the 210 pb defined surface mixed layer is depth dependent in three profiles 234 th derived mixing rates are fastest several centimeters below the sediment water interface indicating greater macro benthic activity at these depths depth dependent mixing coefficients derived from the best fit of a four layer advection diffusion decay model to the 234 th data are consistent with 210 pb profiles determined for the same sediments strongly suggesting that 234 th and 210 pb are mixed equivalently and in a multilayered manner

el nino in santa barbara basin diatom radiolarian and foraminiferan responses to the 1983 el nino event abstract santa barbara basin box cores collected in august of 1985 were sub sampled and processed in search of microfossil evidence of the 1983 el nino microplankton and microbenthos indicate the presence of that el nino bounded by non el nino conditions specifically the event is recognized by an increase in diatom diversity and the presence of several warm water taxa e g coscinodiscus plicatoides hemidiscus cuneiformis nitzschia kolaczekii pseudoeunotia doliolus thalassiosira lineata thalassiosira nodulolineata an increase in polycystine radiolarian flux and the presence of the eastern tropical pacific species spongaster pentas an increase in the diversity of planktonic foraminifera and the occurrence of the warm water species globoturborotalita rubescens there is also evidence for an oxygenation of the basin during the 1983 el nino as suggested by the increase in the abundance of the benthic foraminifera bolivina vaughani and by the decrease in the preservation of phaeodarian radiolarian spines which are best preserved under anoxic conditions a new onboard procedure for sampling of box cores and freezing of subcores is described

finite deformation and displacement fields on the southern yemen margin using satellite images topographic data and a restoration method abstract geological interpretations of processed satellite images and structural field measurements were used to calculate the amount of extension and the finite displacement field of two stretched areas located on the northern margin of the gulf of aden in yemen this calculation was done by a comparison between the deformed and the undeformed states of each studied area the structural setting established from satellite image interpretations and fieldwork yields a detailed geometry of the deformed state the undeformed state was reconstructed from reference layers chosen on satellite images from folded and faulted geological markers the strike and dip of those layers were computed directly from dip indicator measurements identified on three dimensional 3d realistic views of the sites derived from spot stereoscopic views and topographic data and controlled by field measurements from the previous structural data a numerical model of the deformed state was prepared with respect to the structural setting the two stretched areas were then restored to their undeformed state successively by 1 an unfolding method use of the unfold program on each folded piece bounded by faults and 2 a best fit method fitting along the boundary of the unfolded pieces the comparison between the deformed and undeformed states leads to quantifying the amount of strain and to establishing the total finite displacement field the results point to differences in the amount of extension and in the finite displacement field between the two areas studied within the regional context of the afar triple junction kinematics this leads to the conclusion that there was an early extensional tectonic phase recorded on the southern yemen margin probably linked to the earlier opening of the gulf of aden

sensitivity of the phosphate cadmium carbon isotope relation in the ocean to cadmium removal by suboxic sediments reconstructions of past deep ocean nutrient concentrations rely largely on the carbon isotopic composition and cadmium content of shells of benthic foraminifera when comparing records of these two paleonutrient tracers a relation similar to the phosphate cadmium carbon isotope relation in the water column today is generally assumed we present new water column sediment and pore water data from the california continental margin which demonstrate that cd accumulation is enhanced in suboxic sediments these results suggest that the oceanic cd inventory is sensitive to changes in the areal extent and redox intensity of suboxic sediments and thus that the phosphate cadmium relation in the ocean could have been different in the past the magnitude of this effect and its evolution through time is presently hard to quantify because the oceanic cd budget is poorly constrained

extension displacement and block rotation in the larger gullfaks area northern north sea determined from map view restoration numerical map view restoration of the larger gullfaks area on the western side of the viking graben reveals a late jurassic apparent displacement field that is slightly divergent with displacement vectors trending east northeast west southwest to east southeast west northwest the predominant extension direction is east west in the gullfaks field changing to east southeast west southwest in the gullfaks sor area we relate the divergent pattern to extensional collapse over low angle extensional detachments in the eastern part of the area the detachments also explain the anomalously high extensions in this same area total extension in the horizontal plane is estimated to be 19 on average in the larger gullfaks area whereas it is 42 and 33 in gullfaks and gullfaks so respectively block rotations about vertical axes are minor mostly 5 calculated fault slip directions indicate that major north south striking faults are mostly dip slip whereas accommodation faults or transfer faults oriented at high angles to the major faults tend to be oblique slip in general numerical or manual map view restoration is useful before choosing and balancing vertical sections in most of the gullfaks area strain is close enough to plane strain and block rotations are small enough for section balancing to be reliable east west sections should be chosen across the main gullfaks field and east southeast west northwest sections in the gullfaks sor area

variabilities of particulate flux and 210pb in the southern east china sea and western south okinawa trough abstract variabilities of the particulate mass flux and associated 210 pb activity were examined on samples collected from time series sediment traps deployed in the continental slope area of the east china sea off northeast taiwan and in the western south okinawa trough sot as a part of the keep program the particulate flux decreases laterally from the continental slope toward the trough increases vertically toward the bottom at most of the mooring sites and shows fairly synchronous temporal variations among the traps in each mooring for most of the deployments the temporal variation of 210 pb is generally smaller than that of the particulate flux in terms of relative change as expressed in standard deviation of the mean of each trap in the lower slope area the mean particulate flux varies between 9 5 and 79 g m 2 d and the mean 210 pb varies between about 44 and 81 dpm g in the trough the mean particulate flux has the smallest values from 0 06 to 5 7 g m 2 d while the mean 210 pb has the highest from 82 to 192 dpm g the particulate flux decreases while the 210 pb activity increases from the slope toward the trough in the trough 210 pb increases with depth while the particulate flux may show a mid depth maximum of a nepheloid layer although the 210 pb activity increases from the slope toward the trough the 210 pb flux decreases toward the trough because of much greater particulate flux in the slope area within the trough the 210 pb flux as determined from the traps is comparable to that determined from the underlying sediments but on the lower slope the 210 pb flux determined from the traps is much higher than that obtained from the underlying sediments thus a large portion of the particulates and the associated 210 pb may have been transported laterally from elsewhere to the slope area in transit without depositing onto the underlying sediments plots of the mean 210 pb flux versus the mean mass flux for each of the traps show positive linear correlation with four distinctive slopes each representing a mean 210 pb activity of a particular area or a group of traps in the mien hua canyon the mean activity is about 40 dpm g in the sot the mean value is about 130 dpm g on the lower slope the mean values fall in between those of the canyon and the trough in the middle traps where the mass flux is higher in a nepheloid layer the mean activity is about 47 dpm g while the remaining traps yield a mean of about 65 dpm g taking the mean activity of the canyon and that of the trough as the two end member values the slope with a nepheloid layer is a mixture of about 90 canyon and 10 trough materials indicating the canyon as the major particulate provider for the nepheloid layer the slope without a nepheloid layer is a mixture of about 70 canyon and 30 trough materials

effect of the andes cordillera on precipitation from a midlatitude cold front the effects of the andes cordillera the major mountain range in south america on precipitation patterns of baroclinic systems approaching from the southeast pacific remain largely unstudied this study focuses on a case in late may 2008 when an upper level trough and surface cold front produced widespread precipitation in central chile the primary goal was to analyze the physical mechanisms responsible for the structure and evolution of the precipitation weather research and forecasting wrf model simulations indicate that as an upper level trough approached central chile midtropospheric flow below 700 hpa was blocked by the high topography and deflected poleward in the form of a barrier jet this northerly jet had wind maxima in excess of 15 m s 21 was centered around 925 hpa and extended westward 200 km from the mountains it intersected the cold front which approached from the south near the coast thereby increasing convergence along the frontal surface slowing its equatorward progress and enhancing rainfall over central chile another separate region of heavy precipitation formed over the upwind slopes of the cordillera a trajectory analysis confirmed that the barrier jet moved low level parcels from their origin in the moist southeast pacific boundary layer to the coast when model topography was reduced to twenty percent of its original height the cold front advanced more rapidly to the northeast generated less precipitation in central chile between 338 and 368s and produced minimal orographic precipitation on the upwind andean slopes based on these findings the high topography appears responsible for not only orographic precipitation but also for substantially increasing precipitation totals over the central coast and valley

recent crustal deformation in southern california deduced from the restoration of folded and faulted strata a rigid element method of restoration unfold is used to restore competent folded and faulted layers of the ventura and los angeles basins to their initial horizontal state comparison of initial undeformed state with present deformed state allows one to estimate both the finite crustal deformation and its associated horizontal displacement field relative to an arbitrary fixed line including data from the santa barbara channel basin the total finite displacement field for the western transverse ranges and vicinity within the pacific plate is inferred from this map restoration and is modeled as a double fan closure this model implies a 10 clockwise rotation of the northeen boundary of the western transverse ranges and a 5 counterclockwise rotation of its northeast boundary lateral variation of the deformation reveals the heterogeneity of the subsurface deformation most of the major thrusts appear to initiate as en echelon structures along the left lateral northern margin and the right lateral northeastern margin of the studied area the resulting deformation and displacement values closely match those derived by other geological methods section balancing techniques or fault slip measurements and by geophysical methods geodetic paleomagnetic and focal mechanism data map restoration thus is a method that can independently quantify both local and regional deformation including folds and faults this method also reveals the zones where problems of compatibility appear with the available geological and geophysical data and thus where the next studies might be focused

paleogene building of the bolivian orocline tectonic restoration of the central andes in 2 d map view using available information on the magnitude and age of tectonic shortening as well as paleomagnetically determined tectonic rotations we have run a series of 2 d map view restorations of the central andes neogene shortening in the foreland belt induced only slight orogenic curvature of the central andes the constraints on the ages of the large observed fore arc rotations average of 37 counterclockwise in southern peru and 29 clockwise in northern chile indicate that the bolivian orocline formed during the eocene oligocene as a consequence of differential shortening focused in the eastern cordillera to minimize local block rotations along the fore arc the restoration that best fits the central andean rotation pattern requires about 400 km of total paleogene plus neogene shortening near the arica bend this value corresponds to the upper bound of estimates of maximum horizontal shortening for the central andes along strike variations in horizontal shortening in the back arc induced bending of the continental margin block rotations with fore arc along strike extension and or orogen parallel transport of upper crustal material toward the symmetry axis of the orocline