sea ice motion in response to geostrophic winds it is an old rule of thumb that sea ice moves with a speed of about 2 of the surface wind and about 45 to the right of the wind a similar relationship between the ice velocity and the geostrophic wind is examined here it is found that only about half of the long term several month average ice motion is directly related to the geostrophic wind the other half being due to the mean ocean circulation on shorter time scales and in all seasons more than 70 of the variance of the ice velocity in the central arctic ocean is explained by the geostrophic wind within about 400 km of the coasts the geostrophic wind is less successful in explaining the ice motion the spatial variations in ice velocity are also partly explained by the geostrophic wind about half of the variance in the large scale ice vorticity and shear are accounted for on the other hand none of the large scale ice divergence can be explained by the wind the long term average ocean current is estimated by subtracting the share of the ice motion caused by the wind from the total ice motion

radar interferometric mapping of deformation in the year after the landers earthquake although the 1992 landers california earthquake sequence occurred in an area well sampled by geodetic networks1 3 the postseismic deformation in the months following the earthquake has been measured at only 15 geodetic stations4 another shortcoming in the geodetic coverage occurs west of the primary rupture where the existing geodetic observations suggest but cannot resolve sympathetic slip on secondary faults1 such measurements which are needed to place the landers earthquake sequence in the context of a recurring seismic cycle in california can be obtained with the dense spatial coverage provided by satellite radar interferometry5 9 here we present radar maps of the surface deformation field which reveal features that would otherwise have been poorly sampled particularly if the earthquake had occurred in a less accessible area we see triggered slip at the level of several centimetres as far as 100 km from the primary rupture and can resolve the geodetic signal of at least one small magnitude 5 aftershock the amount of surface slip following the main shock is less than a decimetre and is consistent with an exponential decay time of several months for the postseismic deformation

discontinuity surfaces clinoforms and facies architecture in a wave dominated shoreface shelf parasequence abstract detailed outcrop analysis of a wave dominated shoreface shelf parasequence exposed in the book cliffs utah reveals minor stratigraphic discontinuities which define clinoforms two types of discontinuity are recognized each with a distinctive lithologic character and geometry nondepositional discontinuities are marked by an abrupt decrease in the thickness and amalgamation of storm generated event beds and are interpreted to record hiatuses in sedimentation these discontinuities define clinoforms with a concave upward geometry that dip gently 0 02 0 58 over distances of 800 6000 m down depositional dip erosional discontinuities are marked by an abrupt increase in event bed amalgamation grain size and sand content and are interpreted as enhanced storm wave scours these discontinuities define more steeply dipping 0 22 0 95 concave upward clinoforms that extend over 100 1600 m down depositional dip and 500 1500 m along depositional strike the distribution and amalgamation of minor stratigraphic discontinuities defines linear zones of distinctive facies architecture that are oriented parallel to the paleoshoreline trend using the simple assumption that the shoreface shelf equilibrium profile remained approximately constant for each type of discontinuity throughout shoreface migration the bruun rule intra parasequence facies architecture can be speculatively interpreted in terms of shoreline trajectory which reflects the balance between sediment supply and accommodation the resulting interpretations support the notion that shoreline trajectory exerts a strong control on intra parasequence facies architecture and preservation of the shoreface shelf profile

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

orbital control on carbon cycle and oceanography in the mid cretaceous greenhouse we established a new high resolution carbonate carbon isotope record of the albian interval of the marne a fucoidi formation central apennines italy which was deposited on the southern margin of the western tethys ocean bulk carbonate sampled with 10 15 cm spacing was used for the construction of a continuous carbon isotope curve through the albian stage spectral analyses reveal prominent 400 kyr cyclicity in the 13c curve which correlates with milankovitch long eccentricity changes cycles occurring in our record resemble those observed in several cenozoic 13c records suggesting that a link between orbital forcing and carbon cycling existed also under mid cretaceous greenhouse conditions based on comparisons with cenozoic eccentricity carbon cycle links we hypothesize that 400 kyr cycles in the mid cretaceous were related to a fluctuating monsoonal regime coupled with an unstable oceanic structure which made the oceanic carbon reservoir sensitive to orbital variations in the tethys these oceanographic conditions lasted until the late albian and then were replaced by a more stable circulation mode less sensitive to orbital forcing

modelling facies belt distribution in fan deltas coupling sequence stratigraphy and geostatistics the eocene sant llorenc del munt example ebro foreland basin ne spain abstract the eocene sant llorenc del munt fan delta complex developed in the ebro foreland basin the stratigraphy of this succession about 1000 m thick has been described as made up of several transgressive regressive composite sequences each composed of a stack of fundamental sequences in turn made up of a transgressive systems tract and an overlying regressive systems tract systems tracts are composed of several facies belts proximal alluvial fan distal alluvial fan fan delta front carbonate platform and fan delta slope and prodelta a 3d facies model of a 130 m thick stratigraphic succession was built using outcrop data from one of the composite sequences the modelling followed a hierarchical approach a deterministic method was used to reconstruct the surfaces bounding fundamental sequences and their constituent systems tracts data input was outcrop traces digitized on photorealistic terrain models the stacking trend and interfingering of adjacent facies belts within each systems tract was added by means of a geostatistical algorithm and was conditioned to measured stratigraphic logs the analysis of the resultant 3d facies distributions allows revising the architectural interpretation of the studied interval leading to the conclusion that the observed arrangements are accommodation not supply driven furthermore the 3d models were flow simulated in two injector producer scenarios up depositional and down depositional dip waterflooding flow simulation results show that the depositional architecture of the studied succession controls potential recovery efficiencies in that a considerable proportion of moveable oil is trapped at the dead ends in depositional pinch outs of the main potential reservoir fan delta front deposits also that up dip waterflooding predicts better recovery efficiencies than down dip the dataset methods and results herein make the sant llorenc del munt complex a ready for application analogue for marine transitional reservoirs

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

nd isotopic excursion across cretaceous ocean anoxic event 2 cenomanian turonian in the tropical north atlantic late cretaceous fish debris from demerara rise exhibits a dramatic positive excursion of 8 nd units during ocean anoxic event 2 oae2 that is superimposed on extremely low nd t values 14 to 16 5 observed throughout the rest of the studied interval the oae2 nd excursion is the largest yet documented in marine sediments and the majority of the shift is estimated to have occurred over nd values on demerara rise are explained as the nd isotopic signature of the south american craton whereas eruptions of the caribbean large igneous province or enhanced mixing of intermediate waters in the north atlantic could have caused the excursion

correlation of basinal carbonate cycles to nearshore parasequences in the late cretaceous greenhorn seaway western interior u s a upper cretaceous limestone shale couplets developed within the late transgressive stage of the greenhorn cyclothem may be correlated from carbonate dominated basinal sequences in central kansas and colorado westward to clastic cycles in southern utah six such basinal couplets have been traced to corresponding upward coarsening progradational cycles developed on the western margin of the western interior basin in the central basin in colorado and kansas these sedimentary cycles are represented by limestone shale and marlstone shale couplets 0 5 1 0 m in thickness more calcareous parts of these couplets may be correlated westward into condensed fossiliferous concretion and shell beds in proximal offshore lithofacies of arizona and utah these concretion and shell beds are physically traceable farther landward westward into bioturbated fossil rich transgressive lag deposits that bound 10 to 20 m thick coarsening upward progradational strand plain deposits parasequences in southwestern utah thus the progra dational phase of parasequence deposition correlates with accumulation of clay rich sediment in the central basin and the transgressive phase is characterized by reduced terrigenous input and deposition of carbonate rich sediment we consider milankovitch style orbital forcing of climate and tectonically induced fluctuations in rates of foredeep basin subsidence as possible forcing mechanisms for these basinwide events based on the widespread distribution of the limestone shale couplets as well as on estimated sedimentation rates and geochronology it has been widely speculated that these carbonate cycles reflect milankovitch cycles with periodicities on the order of 20 k y to 100 k y if so then stratigraphic data suggest that orbital forcing of climate affected eustasy and or sediment input and biogenic production in the western interior basin alternatively thrusting events in the sevier orogenic belt may have produced episodic changes in the rates of foredeep basin subsidence and consequent changes in base level which could have controlled the deposition of the greenhorn parasequences and carbonate cycles in either case correlation of these units demonstrates a consistent basinwide sedimentary response to high frequency base level or sediment input changes in the western interior epicontinental basin

observations of ice sheet motion in greenland using satellite radar interferometry we present interferometric observations of ice sheet motion in western greenland based on pairs of ers 1 synthetic aperture radar sar images these observations provide the first detailed regional view of ice motion associated with dynamically supported topography near the margin of an ice sheet the interferograms of this area are much more complicated than other interferograms of ice sheets presented to date we devote the largest part of this paper to explaining the source of the complexity in these interferograms a synthetic interferogram based on a simple model helps to illustrate the effects of different components of the ice velocity field in interferometric data and suggests a method for estimating the large scale ice velocity field from such data

tertiary carbonate dissolution cycles on the sierra leone rise eastern equatorial atlantic ocean abstract most of the tertiary section on sierra leone rise off northwest africa consists of chalk marl and limestone that show cyclic alterations of clay rich and clay poor beds about 20 60 cm thick on the basis of biostratigraphic accumulation rates the cycles in oligocene and miocene chalk have periods which average about 44 000 years and those in eocene siliceous limestone have periods of 4000 27 000 years several sections were sampled in detail to further define the cycles in terms of content of caco 3 clay minerals and relative abundances of calcareous nannofossils extending information gained by analyses of pleistocene cores from the continental margin of northwest africa to the tertiary cycles on sierra leone rise both dilution by noncarbonate material and dissolution of caco 3 could have contributed to the observed relative variations in clay and caco 3 however dissolution of caco 3 as the main cause of the carbonate clay cycles on the sierra leone rise rather than dilution by clay is suggested by the large amount of change several thousand percent in terrigenous influx required to produce the observed variations in amount of clay and by the marked increase in abundance of dissolution resistant discoasters relative to more easily dissolved coccoliths in low carbonate parts of cycles the main cause of dissolution of caco 3 was shoaling of the carbonate compensation depth ccd during the early neogene and climatically induced fluctuations in the thickness of antarctic bottom water

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

untangling the palaeocene climatic rhythm an astronomically calibrated early palaeocene magnetostratigraphy and biostratigraphy at zumaia basque basin northern spain abstract the magnetostratigraphy of a 54 m long section above the cretaceous tertiary boundary at the sea cliff section of zumaia in the basque basin northern spain has been established the section encompasses the entire danian and the lower part of the selandian stages as indicated by calcareous plankton biostratigraphy the studied interval consists of hemi pelagic limestone marl alternations in the form of couplets and bundles which range from centimetre decimetre to metre scale respectively and a few thin bedded calcareous turbidites the magnetostratigraphy based on samples from about 200 stratigraphic levels allows the identification of six reversal boundaries from chron c29r to c26r at a bed level the spatial or temporal evolution of periodicities from a lithologically coded series is studied with the continuous wavelet transform technique a preliminary age model based on the standard ck95 gpts indicates that the basic lithologic carbonate marl couplet corresponds to the 19 23 kyr precession cycle 21 31 cm cycle in the depth domain and that a bundle cycle usually groups of four to six basic couplets with global periodicity centred at 1 22 m corresponds to the 110 kyr eccentricity cycle we have tuned the bundle cycles to the va03 r7 eccentricity orbital solution astrophys j 592 2003 620 630 following an initial match of a node of the 2 4 ma eccentricity modulatory cycle in the target time series to particularly carbonate rich bundles from the upper part of the zumaia section that displays significant power of a 4 4 m period cycle corresponding to the 404 kyr eccentricity cycle consistency between lithologic patterns and characteristics in the eccentricity target is reasonably met although the 404 kyr eccentricity cycle is not persistent throughout the tuning however appears robust as it brings the age of the k t boundary at 65 8 ma it is argued that a sea level signal tectonically driven is superimposed on the climatic forcing at the milankovitch band masking the full expression of the low frequency astronomical periods we provide a cycle tuned duration for all intervening early palaeocene polarity chrons and estimate relative ages for bioevents the cycle tuned chronology indicates that the ck95 gpts overestimates the duration of chrons c28 and c27 by 20 and 26 respectively our data may prove useful to better constrain early palaeocene biostratigraphy of calcareous plankton and in the redefinition of the boundary between the danian and selandian stages

orbital cyclicities above and below the cretaceous paleogene boundary at zumaya n spain agost and relleu se spain abstract the rhythmicity of hemipelagic limestone marl successions covering the cretaceous paleogene k pg boundary is investigated and evidence of orbital control is presented three sections were surveyed and sampled in detail two are located near agost and relleu in the province of alicante and one near zumaya in the basque country the distance between agost and relleu is about 30 km between agost and zumaya about 600 km the carbonate content of 2779 samples was determined and used as a proxy to determine cyclicities lithologically all three successions are very similar although in the maastrichtian of the zumaya succession 63 7 m 339 light green siliciclastic turbidite layers varying in thickness between 0 1 and 12 cm intercalate with the calcisiltites conventional paleomagnetic and micropaleontologic datum planes are few and show the usual associated uncertainties power spectra based on the few reliable datum planes available are unstable more datum planes were created in an unconventional way i e by visual correlation of the local maxima and minima of the carbonate curves to those of the relevant part of the theoretical eccentricity curve the validity of the method is based on the assumption that the eccentricity periods are considered practically stable throughout geologic time the results support the hypothesis that the carbonate rhythmicity at agost relleu and zumaya are orbitally controlled most likely orbital forcing and random processes play a role in the frequency of occurrence and the thickness of turbidites in the maastrichtian of zumaya the age of the k pg boundary is estimated at 64 56 0 4 ma

modeling winter circulation under landfast ice the interaction of winds with landfast ice 1 idealized models and a simple vertically averaged vorticity equation illustrate the effects of an upwelling favorable wind and a spatially variable landfast ice cover on the circulation beneath landfast ice for the case of no along shore variations in ice upwelling favorable winds seaward of the ice edge result in vortex squashing beneath the landfast ice leading to 1 large decreases in coastal and ice edge sea levels 2 cross shore sea level slopes and weak 05 m s 1 under ice currents flowing upwind 3 strong downwind ice edge jets and 4 offshore transport in the under ice and bottom boundary layers of the landfast ice zone the upwind under ice current accelerates quickly within 2 4 days and then slows as cross shore transport gradually decreases the cross shore sea level slope near the ice edge bottom boundary layer convergence produces ice edge upwelling cross ice edge exchanges occur in the surface and above the bottom boundary layer and reduce the under ice shelf volume by 15 in 10 days under ice along shore pressure gradients established by along and cross shore variations in ice width and or under ice friction alter this basic circulation pattern for a landfast ice zone of finite width and length upwelling favorable winds blowing seaward of and transverse to the ice boundaries induce downwind flow beneath the ice and generate vorticity waves that propagate along shore in the kelvin wave direction our results imply that landfast ice dynamics not included explicitly herein can effectively convert the long wavelength forcing of the wind into shorter scale ocean motions beneath the landfast ice

north and northeast greenland ice discharge from satellite radar interferometry ice discharge from north and northeast greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3 5 times that estimated from iceberg production the satellite estimates obtained at the grounding line of the outlet glaciers differ from those obtained at the glacier front because basal melting is extensive at the underside of the floating glacier sections the results suggest that the north and northeast parts of the greenland ice sheet may be thinning and contributing positively to sea level rise

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

growth faults at the prodelta to delta front transition cretaceous ferron sandstone utah cliff exposures of synsedimentary growth faults at the base of the cretaceous ferron sandstone in central utah represent outcrop analogs to subsurface growth faults delta front sands prograded over and deformed less dense prodelta muds of the underlying tununk shale detailed fault patterns and associated facies changes demonstrate a complex fault history and style for growth fault development rather than a simple progressive development of faults in a basinward position the most proximal and most distal fault sets were the earliest active faults growth faulting was initiated by deposition of cross bedded distributary channel and mouth bar sandstones that reach 9 m thick in the hangingwalls of the faults curvature of the beds in the hangingwall of the faults nucleates smaller conjugate fault sets cross bed sets in the hangingwalls of faults decrease from meter to decimeter scale away from the faults suggesting decreasing flow velocity or decreased preservation of cross sets as a result of decreasing accommodation in distal hangingwalls shifts in depositional loci including upstream and downstream accretion of mouth bar sands contribute to the complex faults history and internal heterogeneity and development of potentially isolated sandy reservoir compartments

effects of climate tectonics and sea level changes on rhythmic bedding patterns in the niobrara formation upper cretaceous u s western interior regional correlation of interbedded pelagic hemipelagic limestones and calcareous shales of the fort hays limestone member of the niobrara formation confirms development of at least two levels of cyclicity occurrence of time parallel rhythmically deposited beds that can be correlated over distances exceeding 800 km lends strong support to the hypothesis that these cycles were induced by milankovitch type climatic forcing however visual observation and fourier analysis of variations in shale and limestone thickness demonstrate that the pattern of fort hays cyclicity lacks regional uniformity complications in the cyclic pattern may have resulted from the influence of orbital parameters having differing periodicities additionally departures from simple cyclical patterns resulted from sedimentary effects of the sevier orogeny and from erosional events associated with sea level changes documentation of thickness variations within the regionally persistent fort hays bedding sequence furnishes a basis for fine scale analysis of cretaceous crustal movements within the western interior seaway

water mass circulation on demerara rise during the late cretaceous based on nd isotopes abstract circulation in the north atlantic during the late cretaceous has implications for poleward heat transport and nutrient distribution during an extreme greenhouse interval with episodes of ocean anoxia nd isotopes of fossil fish teeth and debris represent one of the few water mass tracers that can be used to reconstruct deep ocean circulation we present nd isotopic data interpreted as bottom water values for 290 samples from three ocean drilling program sites on demerara rise sites 1258 1260 and 1261 along with 102 analyses from four other north atlantic sites cape verde goban spur bermuda rise and blake nose that provide additional geographic and bathymetric control our results confirm the presence of a water mass with low end values 14 to 17 that are believed to be influenced by continental material during local water mass formation at low latitudes this demerara bottom water dbw is the primary water mass in the region from the cenomanian to coniacian and from the late campanian through early maastrichtian following a hiatus of 10 my a positive 8 end unit excursion occurs during ocean anoxic event 2 oae2 that cannot be explained by changes in weathering inputs diagenesis or magmatic sources of nd instead it appears to represent an influx of bottom waters sourced from the tethys or north atlantic this replacement of dbw during oae2 argues for decreased production of dbw or enhanced production of tethys north atlantic waters during peak greenhouse conditions from the late campanian through early maastrichtian dbw becomes the only water mass recorded at demerara rise and it appears to expand to abyssal depths at cape verde in the campanian this water mass is ultimately replaced by waters that appear to be sourced from the north atlantic starting in the late maastrichtian observed variations in circulation in the tropical north atlantic during the late cretaceous can account for extensive deposition of black shales in the region prior to the hiatus as well as local warming during a global cooling event in the maastrichtian

open water production in arctic sea ice satellite measurements and model parameterizations sequential synthetic aperture radar sar images from the ers 1 spacecraft were routinely used as input to the geophysical processor system at the alaska sar facility from 1992 through 1994 to produce sea ice displacement vectors on a 5 km grid we have combined some 5000 of these products consisting of nearly 700 000 displacement vectors into a set of 914 strips or mosaics of ice motion that span mostly 3 day intervals for each strip we compute the opening and closing of leads based on the change in area of the 5 km grid cells we also compute the area averaged deformation or strain invariants of the motion the small scale several kilometer lead activity can be parameterized fairly well in terms of the large scale several hundred kilometer strain invariants sea ice models implicitly contain such a parameterization through their constitutive equations the well known model of hibler 1979 that uses a viscous plastic rheology and an elliptical yield curve is in good agreement with our data the variance in the data about this theoretical relationship is less than that suggested by a random model of sea ice motion the data also indicate that shearing deformation contributes to the opening and closing of leads models with two categories or levels of ice thickness generally do not take shearing deformation into account in the evolution of the ice concentration nor do they redistribute ice as a result of ridging we show how to add these features to two level models however we argue that three level models consisting of open water thin ice and thick ice are much better suited to the proper treatment of open water production and we present such a model

bottom water anoxia inoceramid colonization and benthopelagic coupling during black shale deposition on demerara rise late cretaceous western tropical north atlantic 1 the bulk rock geochemistry and inoceramid isotopic composition from cenomanian to santonian finely laminated organic rich black shales recovered during ocean drilling program leg 207 on demerara rise western tropical north atlantic suggest persistent anoxic free h2s conditions within the sediments and short term variations within a narrow range of anoxic to episodically dysoxic bottom waters over a 15 ma time interval in addition to being organic rich the 50 90 m thick sections examined exhibit substantial bulk rock enrichments of si p ba cu mo ni and zn relative to world average shale these observations point to high organic burial fluxes likely driven by high primary production rates which led to the establishment of intensely sulfidic pore waters and possibly bottom waters as well as to the enrichments of cr mo u and v in the sediments at the same time the irregular presence of benthic inoceramids and foraminifera in this facies demonstrates that the benthic environment could not have been continuously anoxic the 13c and 15n values of the inoceramid shell organics provide no evidence of chemosymbiosis and are consistent with pelagic rain as being a significant food source demerara rise inoceramids also exhibit well defined regularly spaced growth lines that are tracked by 13c and 18o variations in shell carbonate that cannot be simply explained by diagenesis instead productivity variations in surface waters may have paced the growth of the shells during brief oxygenation events suitable for benthic inoceramid settlement these inferences imply tight benthopelagic coupling and more dynamic benthic conditions than generally portrayed during black shale deposition by invoking different temporal scales for geochemical and paleontological data this study resolves recent contradictory conclusions e g sulfidic sedimentary conditions versus dysoxic to suboxic benthic waters drawn from studies of either sediment geochemistry or fossil distributions alone on demerara rise this variability may be relevant for discussions of black shales in general

the contribution of alaskan siberian and canadian coastal polynyas to the cold halocline layer of the arctic ocean numerous arctic ocean circulation and geochemical studies suggest that ice growth in polynyas over the alaskan siberian and canadian continental shelves is a source of cold saline water which contributes to the maintenance of the arctic ocean halocline the purpose of this study is to estimate for the 1978 1987 winters the contributions of arctic coastal polynyas to the cold halocline layer of the arctic ocean the study uses a combination of satellite oceanographic and weather data to calculate the brine fluxes from the polynyas then an oceanic box model is used to calculate their contributions to the cold halocline layer of the arctic ocean this study complements and corrects a previous study of dense water production by coastal polynyas in the barents kara and laptev seas recurrent polynyas form on the canadian and alaskan coasts from banks island to the bering strait and on the siberian coast from the bering strait to the new siberian islands in the bering sea polynyas form in norton sound south and west of st lawrence island and in the gulf of anadyr two regions that account for almost 50 of the total dense water production are the siberian coastal polynyas in the adjacent regions of the gulf of anadyr and anadyr strait and the alaskan coastal polynyas which occur along the coast from cape lisburne to point barrow for all of the western arctic coastal regions examined the mean annual total brine flux is 0 5 0 2 sv combination of this flux with the contribution from the barents kara and laptev seas which is recalculated from data in the earlier study shows that over the entire arctic coastal polynyas generate about 0 7 1 2 sv of dense water this compares well with the theoretical estimates of 1 1 5 sv because an unknown fraction of the barents kara and laptev brine flux must go to the eurasian basin deep water the coastal polynyas alone cannot renew the halocline layer other potential brine generation mechanisms include overall freezing on the shelves and the response of the ice to infrequent violent storms for example during february 1982 an intense storm generated a large region of low ice concentration in the eastern chukchi sea over barrow canyon the refreezing of the region was followed by the flow of a dense plume down barrow canyon although the ocean dynamical response to this refreezing needs to be established the possible response of a barrow canyon flow to this refreezing event suggests that the overall refreezing in response to infrequent violent storms may be a potential source of the additional brine needed to maintain the arctic ocean halocline

distribution of discontinuous mudstone beds within wave dominated shallow marine deposits star point sandstone and blackhawk formation eastern utah deposits of wave dominated shorelines are typically considered to act as relatively simple hydrocarbon reservoirs and are commonly modeled as tanks of sand however important heterogeneities that can act as barriers to fluid flow occur at the parasequence bedset and bed scales especially in viscous oil or low permeability oil fields heterogeneities at the parasequence and bedset scales have been well studied but discontinuous mudstone beds occurring within the shoreface have received little attention the book cliffs and wasatch plateau are among the best exposed and best studied deposits of wave dominated shallow marine systems in the world two parasequences within these outcrops have been studied in detail to investigate the distributions of intrashoreface shales and to propose models for the controls on their distribution a data set consisting of 30 km 18 6 mi of virtual outcrops derived from oblique helicopter mounted light detection and ranging lidar scanning with supporting stratigraphic sections makes it possible to collect a large quantity of accurate geometric data of depositional elements from inaccessible cliffs nine hundred and twenty one discontinuous mudstone beds were measured these occur as ellipses with long axes oriented normal to the paleoshoreline lengths and widths of these mudstone beds exhibit a lognormal distribution with means of 21 9 and 13 8 m 71 9 and 45 3 ft respectively within the shoreface succession the number of mudstone beds increases downward whereas size does not vary significantly with stratigraphic height an average of 100 m 328 ft cumulative length of shale exists per 100 m 328 ft of horizontal outcrop this increases threefold near both wave dominated deltas and bedset boundaries that reflect minor sea level fluctuations during progradation

transgressive regressive cycles and the occurrence of coal in some upper cretaceous strata of utah cenomanian santonian strata contain about 60 of the known cretaceous coal resources of utah the areal and temporal distribution of these resources can be related to the transgressive regressive history of the western shoreline of the interior cretaceous seaway two orders of transgressive regressive cycles the larger of which corresponds to third order cycles of vail et al are deemed important in analyzing the distribution of coal in utah the largest coal fields are associated with extensive vertical stacking of the deposits of what are here termed fourth order cycles at the transgressive and regressive maxima of third order cycles deposits of transgressive and regressive phases of third order cycles contain only minor amounts of coal this genetic relationship may prove useful in predicting areas of important cretaceous coal resources in deeper parts of structural basins in the rocky mountain region

mapping arctic landfast ice extent using l band synthetic aperture radar interferometry in recent years methods have been developed to extract the seaward landfast ice edge from series of remote sensing images with most of them relying on incoherent change detection in optical infrared or radar amplitude imagery while such approaches provide valuable results some still lack the required level of robustness and all lack the ability to fully automate the detection and mapping of landfast ice over large areas and long time spans this paper introduces an alternative approach to mapping landfast ice extent that is based on coherent processing of interferometric l band synthetic aperture radar sar data the approach is based on a combined interpretation of interferometric phase pattern and interferometric coherence images to extract the extent and stability of landfast ice due to the low complexity of the base imagery used for landfast ice extraction significant improvements in automation and reduction of required manual interactions by operators can be achieved a performance analysis shows that l band interferometric sar insar data enable the mapping of landfast ice with high robustness and accuracy for a wide range of environmental conditions

lidar based digital outcrops for sedimentological analysis workflows and techniques f rarity x m t van lanen d hodgetts r l gawthorpe p wilson i fabuel perez j redfern

high resolution sequence stratigraphic correlation between shallow marine and terrestrial strata examples from the sunnyside member of the cretaceous blackhawk formation book cliffs eastern utah the sunnyside member of the upper cretaceous blackhawk formation in the book cliffs of eastern utah provides an ideal opportunity to investigate high resolution sequence stratigraphic correlation between shallow marine and terrestrial strata in an area of outstanding outcrop exposure the thick laterally extensive coal seam that caps the sunnyside member is critical for correlating between its shallow marine and terrestrial components petrographic analysis of 281 samples obtained from 7 vertical sections spanning more than 30 km 18 mi of depositional dip enabled us to recognize a series of transgressive regressive coal facies trends in the seam on this basis we were able to identify a high resolution record of accommodation change throughout the deposition of the coal as well as a series of key sequence stratigraphic surfaces the stratigraphic relationships between the coal and the siliciclastic components of the sunnyside member enable us to correlate this record with that identified in the time equivalent shallow marine strata and to demonstrate that the coal spans the formation of two marine parasequences and two high frequency fourth order sequence boundaries this study has important implications for improving the understanding of sequence stratigraphic expression in terrestrial strata and for correlating between marine and terrestrial records of base level change it may also have implications for improving the predictability of vertical and lateral variations in coal composition for mining and coalbed methane projects

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

discrimination of geophysical phenomena in satellite radar interferograms various geophysical phenomena are recorded in the interference patterns formed by differencing two synthetic aperture radar sar images the fringes generated by the topographic relief can be removed using a digital elevation model dem the remaining fringes map the change in satellite to ground range which occurred between the acquisition times of the two images by comparing different pairs of images spanning different intervals of time it is possible to discriminate between geophysical signal and interferometric artifact here we apply this pair wise logic to the area around the 1992 landers california earthquake using sar images acquired by the ers 1 satellite the range varies with time as a constant step impulsive or sloping function examples of each type include a dem error an aftershock two atmospheric perturbations and postseismic afterslip respectively their signatures are identified and separated using the pair wise logic

contrasts in arctic shelf sea ice regimes and some implications beaufort sea versus laptev sea the winter ice regime of the 500 km from the mainland than in the beaufort sea as a result the annual freeze up does not incorporate old deep draft ice and with a lack of compression such deep draft ice is not generated in situ as on the beaufort sea shelf the laptev sea has as much as 1000 km of fetch at the end of summer when freezing storms move in and large 6 m waves can form also for the first three winter months the polynya lies inshore at a water depth of only 10 m turbulence and freezing are excellent conditions for sediment entrainment by frazil and anchor ice when compared to conditions in the short fetched beaufort sea we expect entrainment to occur yearly different from the intensely ice gouged beaufort sea shelf hydraulic bedforms probably dominate in the laptev sea corresponding with the large volume of ice produced more dense water is generated in the laptev sea possibly accompanied by downslope sediment transport thermohaline convection at the midshelf polynya together with the reduced rate of bottom disruption by ice keels may enhance benthic productivity and permit establishment of open shelf benthic communities which in the beaufort sea can thrive only in the protection of barrier islands indirect evidence for high benthic productivity is found in the presence of walrus who also require year round open water by contrast lack of a suitable environment restricts walrus from the beaufort sea although over 700 km farther to the south we could speculate on other consequences of the different ice regimes in the beaufort and laptev seas but these few examples serve to point out the dangers of exptrapolating from knowledge gained in the north american arctic to other shallow arctic shelf settings

surface displacement of the 17 may 1993 eureka valley california earthquake observed by sar interferometry satellite synthetic aperture radar sar interferometry shows that the magnitude 6 1 eureka valley earthquake of 17 may 1993 produced an elongated subsidence basin oriented north northwest parallel to the trend defined by the aftershock distribution whereas the source mechanism of the earthquake implies a north northeast striking normal fault the 3 millimeter accuracy of the radar observed displacement map over short spatial scales allowed identification of the main surface rupture associated with the event these observations suggest that the rupture began at depth and propagated diagonally upward and southward on a west dipping north northeast fault plane reactivating the largest escarpment in the saline range

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

quantitative outcrop data for flow simulation abstract an architectural analysis documents variations in bedding geometry and rock properties within a tide influenced deltaic sandstone exposed in the cretaceous frontier formation of central wyoming usa digital maps of bedding lithofacies and diagenetic cements as well as vertical logs of grain size lithofacies and permeability describe rock properties that potentially influence fluid flow behavior these records are used to construct simulation models that assess the relative importance of different types of geologic variability on prediction of subsurface fluid flow two 25 meter thick tide influenced deltaic sandstone bodies coarsen upward and contain inclined beds that reflect episodic delta front progradation decimeters to meters thick beds within bodies alternate between cross stratified sandstones formed during rapid flows and shales deposited during more quiescent conditions down depositional dip bed draping shales are more continuous and lithofacies within sandstone beds become finer grained and increasingly heterolithic as sandstone beds fine down dip mean permeability values decrease and coefficients of variation increase permeability values change from nearly normal distributions to highly right skewed and permeability values become more strongly spatially correlated nodular cements also affect permeability all of these variations were modeled using stratigraphic cornerpoint grids that preserve stratal geometry and gridblocks with properties assigned using a combination of rock property maps and statistical models based on rock property logs simulations predict effects on fluid flow of geologic heterogeneity at different scales the influences of process variables and the effects of different methods of grid construction and rock property assignment flow simulations of water flooding through a 22 m thick by 360 m long segment of a deltaic sandstone oil reservoir predict that 1 rapid flow through coarser grained deposits at the top of the sandstone body tends to draw water upward 2 thin shales draping sandstone beds shunt downdip directed flow downward and updip directed flow upward 3 cement nodules cause more tortuous flow patterns but have little effect on recovery efficiency 4 methods of predicting intrafacies correlation of permeability have little effect on flow behavior at this scale a simulation model constructed using a high resolution cartesian grid did not resolve the effects of inclined shales demonstrating the usefulness of stratigraphic cornerpoint grids for modeling flow through complex geologic deposits flow simulations of tracer flow through a meter thick cross stratified bed within the deltaic sandstone body showed that at this scale shale drapes and models of the intrafacies distribution of permeability have statistically significant effects

studies of multibaseline spaceborne interferometric synthetic aperture radars the authors have utilized a set of seasat synthetic aperture radar sar data that were obtained in nearly repeat ground track orbits to demonstrate the performance of spaceborne interferometric sar insar systems an assessment of the topography measurement capability is presented a phase measurement error model is described and compared with the data obtained at various baseline separations and signal to noise ratios finally the implications of these results on future spaceborne insar design are discussed

limestone marl alternations as environmental archives and the role of early diagenesis a critical review limestone marl alternations and other micritic calcareous rhythmites have long appealed to sedimentologists as they appeared to directly reflect high frequency environmental change in particular when orbital forcing gained popularity amongst sedimentologists and paleoclimatologists in 1980s such rhythmites seemed to offer an ideal tool for high resolution chronostratigraphy and environmental reconstruction however in spite of the fact that orbital forcing has become a routine interpretation of calcareous rhythmites and that the processes of formation of calcareous rhythmites are considered well understood research in the past 10 years again has questioned their primary origin and their direct interpretability detailed petrographic paleontological and geochemical data from numerous successions through geological time provided the basis for testing whether or not the regular alternation of limestone beds and marl or shale interlayers represents bimodally fluctuating environmental conditions in a direct way in particular these data supplemented by box model simulations imply that post depositional alteration diagenesis has the potential to not only seriously distort primary environmental signals but also to mimic primary signals this questions the use of micritic calcareous rhythmites for high resolution chronostratigraphy and for environmental interpretations where independent data of diagenetically inert parameters are not available diagenetic changes appear to have a yet widely underestimated influence on the appearance of limestone marl alternations and other calcareous rhythmites the aim of the present review is to summarize new approaches and give an overview of our research results in this field of the past decade this review also aims at pointing to still enigmatic aspects that need to be addressed before the interpretation of micritic calcareous rhythmites can be considered a reliable tool for high resolution chronostratigraphy and paleoenvironmental interpretation

an overview of the post messinian paleoenvironmental history of the western mediterranean a review of the pliocene pleistocene paleoenvironmental history of the western mediterranean is presented based on micropaleontological and geochemical studies of ocean drilling program odp leg 107 material and marine outcrops in southern italy the calcareous plankton biochronology proposed for the mediterranean by rio et al 1990 and 1991a provides the necessary age control for determining the timing of major climatic and oceanographic changes in the region the early pliocene period in the mediterranean was not a time of warm stable climate rather it was marked by relatively high amplitude climatic oscillations in marginal areas these climatic oscillations resulted in the rhythmic deposition of limestone marl couplets which have an average duration of approximately 19 000 years it is proposed that these sedimentary couplets are the result of precessionally induced changes in monsoon intensity which in turn cause variability in coastal divergence and upwelling the 18o and the calcareous plankton foraminifera and coccoliths records for tyrrhenian sea odp site 653 reveal a cooling of surface waters at 3 1 ma coincident with this cooling is an increase in the frequency of diatomite formation in southern italy bianco section the global cooling at 2 4 ma and the associated expansion of northern hemisphere glaciation resulted in a shift to more arid conditions in the mediterranean region this climate change may have altered the mediterranean water balance resulting in the establishment of antiestuarine water exchange with the atlantic at this time the 18o record for site 653 is also marked by a sharp cooling across the pliocene pleistocene boundary in the boundary stratotype section at vrica this cooling is manifested as an increase in the abundance of the planktonic foraminifer neogloboquadrina pachyderma

fast ice distribution in east antarctica during 1997 and 1999 determined using radarsat data 1 we present the first detailed maps of fast ice around east antarctica 75 e 170 e using an image correlation technique applied to radarsat scansar images from november in 1997 and 1999 this method is based upon searching for and distinguishing correlated regions of the ice covered ocean which remain stationary in contrast to adjacent moving pack ice within the overlapping longitudinal range of 86 e 150 6 e the total fast ice area is 141 450 km2 in 1997 and 152 216 km2 in 1999 calibrated radar backscatter data are also used to determine the distribution of two fast ice classes based on their surface roughness characteristics these are smooth fast ice 25 4 db to 13 5 db and rough fast ice 13 5 db to 2 5 db the former comprises 67 of the total area with rough fast ice making up the remaining 33 an estimate is made of fast ice volume on the basis of fast ice type as a proxy measure of ice thickness and area results suggest that although fast ice forms 2 16 of the total november sea ice area for this sector of east antarctica in 1997 and 1999 average 8 3 across maps it may comprise 6 57 of the total ice volume average 28 across maps grounded icebergs play a key role in fast ice distribution in all regions apart from 150 e 170 e these are snapshot estimates only and more work is required to determine longer term spatiotemporal variability

anatomy of a transgressive lag panther tongue sandstone star point formation central utah the panther tongue of the star point formation in central utah contains a variety of transgressive lag deposits that when mapped regionally show a sensitive dependence upon pre existing topography of the palaeoshoreline the panther tongue consists of a coarsening upward sandstone wedge that prograded into the western interior seaway during late cretaceous santonian time high resolution sequence stratigraphic analysis revealed that this member was deposited during the long distance 50 km regression and transgression of a delta into shallow marine environments containing basal highstand forced regression lowstand and transgressive systems tracts based on grain size clast composition lateral extent and stratigraphic position the coarse sandstones on top of the panther tongue were classified into four types 1 simple 2 dispersed 3 oxidized and 4 local lags the simple lag is composed of dark grey coarse sandstone with oyster fragments and shark teeth this lag is typically extensively bioturbated and massive laminated and cross bedded units are also common this type of coarse sandstone is interpreted as a typical transgressive lag the dispersed lag differs in that it contains abundant mud and commonly occurs as multiple beds in thick intervals of muddy sandstone mixing of bay estuarine and shallow marine mud with simple lag sand may be responsible for deposition of this type of coarse sandstone the oxidized lag is distinctive in its reddish colour with extensive bioturbation and is commonly overlain by a simple lag the local lag is composed of thin bedded dark grey coarse sandstone occurring locally between the mouth bar and distributary channel the variation in types grain size and bed thickness of the coarse grained lags was mainly controlled by antecedent topography as suggested by immediately underlying lithofacies relatively thick 30 cm simple lags are present on top of mouth bar sandstones whereas dispersed lags are common on top of the distributary channel sandstone and in bay estuarine and shallow marine mudstones erosion of topographic highs mouth bar resulted in relatively thick accumulation of simple lags in topographic low areas such as distributary channel estuary bay and shallow marine environments fine grained muddy sands that were eroded from the nearby topographic highs were redeposited intermittent storm waves transported coarse sands both landward and seaward forming a dispersed lag the net effect was reworking of local topographic relief during overall transgression forming an apparently planar transgressive surface of erosion

proximate environmental forcing in fine scale geochemical records of calcareous couplets upper cretaceous and palaeocene of the basque cantabrian basin eastern north atlantic abstract calcareous couplets are key elements in reconstructing the evolution of a sedimentary basin due to the influence of forcing mechanisms such as climate sea level and tectonism on their depositional patterns proposed forcing mechanisms however are often not mutually exclusive and even constraining the relative importance of different processes is problematic added to the question of discriminating forcing mechanisms a major challenge is to produce high sampling density so that observations lie within temporal resolutions equal to or finer than the timescales on which different forcing operates here we show fine scale 1 sample 2 cm caco3 18o and 13c records and sedimentological observations from three different sites isla de castro sopelana ma and sopelana da with calcareous couplets in the basque cantabrian basin eastern north atlantic to illustrate the potential of fine sampling strategies to help distinguish proximate environmental forcing partial redistribution of carbonate during burial diagenesis has been proposed for these sediments our caco3 18o and 13c data could thus be dismissed as diagenetic signals if only one sample was collected from each bed detailed observations of the fine scale geochemical records however challenge purely diagenetic explanations combined with sedimentology the caco3 18o and 13c values partially altered by diagenesis are interpreted to have resulted from alternating climates the proximate forcing through which alternating climates caused the geochemical patterns though was different in each section due to their specific palaeogeographic positions in the basin and the properties of the seawater masses the proximity of continental areas of high relief to the isla de castro section supported a high continental influence during its deposition the sopelana ma sediments are assigned to a transgressive system tract a condition that is interpreted to have promoted a high influence of oceanic processes in its depositional setting finally a relatively cool oxygen rich water mass with high oxidation potential influenced the geochemical and depositional patterns of sopelana da beyond the climatic and oceanographic dynamics inferred for a basin that linked the western tethys with boreal domains during major marine transgressions of the late cretaceous to palaeocene an implication of our work is that if similar fine scale geochemical records were applied to calcareous couplets spanning major events in earth s history e g ocean anoxic events alternative forcing scenarios leading to and out of these events could be discriminated

topographic mapping using radar interferometry processing techniques a new processing algorithm for the nasa jpl topsar topographic radar mapper is described it incorporates extensive motion compensation features as well as accurate three dimensional target location algorithm the processor applies an algorithm to resolving the absolute phase ambiguity this allows rectified height maps to be generated without any use of ground reference points the processor was tested using data acquired with extreme aircraft motion so that performance could be evaluated under adverse conditions the topographic maps generated by the radar were compared to digital elevation models dems derived using conventional optical stereo techniques in one region the rms elevation deviations measured were less than the specified dem accuracy and in the region covered by the more accurate dem errors varied from 2 2 m rms in relatively flat terrain up to 5 0 m in mountainous area the rms difference between radar and dem elevation over the 6 5 km by 22 km area covered by the more accurate dem was 3 6 m

sedimentary vs diagenetic control on rhythmic calcareous successions pliensbachian of asturias spain the diagenetic overprint in rhythmic hemipelagic successions can either enhance or change the original distribution of caco3 but it is difficult to evaluate its effect because in most field examples it is not possible to distinguish between sedimentary and diagenetic features the rhythmic succession of the pliensbachian of asturias spain shows alternation of bioclastic and laminated burrowed intervals the original content of carbonate brought by storms from shallow areas was larger in the bioclastic horizons however there is a widespread mismatch between facies alternations and the observed lithological rhythms the diagenetic redistribution of caco3 resulted in successive limestone marl clay couplets that do not match either in number or in the location of the boundaries the sedimentary cycles defined by facies alternations we conclude that interpreting the limestone marl rhythms as a direct response to primary changes is highly questionable unless there is unequivocal proof of a sedimentary origin of the alternation of the two lithologies

assessing small scale deformation and stability of landfast sea ice on seasonal timescales through l band sar interferometry and inverse modeling abstract rapid environmental change and increases in use of shorefast ice by industry and coastal communities highlight the need for an approach to accurately assess landfast sea ice stability on seasonal timescales while stability can sometimes be inferred from field measurements current methods are lacking robustness and the ability to be automated and applied over large areas and long time scales to ensure safety and document change in the context of transportation indigenous ice uses and industrial development this paper introduces an inverse model capable of reconstructing three dimensional deformation fields from one dimensional interferometric l band synthetic aperture radar sar phase patterns we apply this method at three landfast ice locations on the alaska beaufort sea coast near barrow and prudhoe bay we find the small scale displacements estimated from the model consistent with regional patterns of ice motion our study suggests that interferometry can provide planning and decision support information for ice road development and structures operating within ice moreover insar can potentially increase our understanding of sea ice on a fundamental level in terms of large scale stability and long term changes in ice dynamics

overlapping faults and their effect on fluid flow in different reservoir types a lidar based outcrop modeling and flow simulation study in this article we focus on the potential of fault overlap zones as conduits for fluid flow in a variety of reservoir types light detection and ranging lidar technology were applied to collect a three dimensional spatially constrained data set from a well exposed fault overlap zone that crops out in the devil s lane area of the canyonlands national park in utah a virtual outcrop was generated and used to extract structural and stratigraphic data that were taken into a reservoir modeling software and reconstructed the outcrop based model was flow simulated and used to test fluid flow through a real world fault overlap zone a structural framework was built based on collected outcrop data and combined with a series of nine different facies models the different facies models included an eolian model based on the outcrop and a range of synthetic fluvial and shallow marine systems results show that for certain depositional models cross fault reservoir communication may be poor despite the geometric connectivity of the relay beds this was the case for low net gross fluvial models and shoreface models conversely high net gross fluvial systems and eolian systems show good communication through the same relay zone overall the results show that in the presence of a fault overlap zone pressure communication across a relay ramp may still be poor depending on the scale of the faults and relay ramp as well as the geometry and volume of the sands

analysis of coseismic surface displacement gradients using radar interferometryc new insights into the landers earthquake the map of the coseismic displacement field generated by interferometric processing of synthetic aperture radar lsarr images taken before and after the june 28 1992 landers earthquake sequence brings new insights into the nature of deformation caused by these earthquakes we use the interferometric map generated by massonnet et al l1993r to analyze the surface displacement field in the vicinity of the fault trace complexities in the fringe pattern near the fault reflect shorthwavelength variations of the surface rupture and slip distribution and attest to large displacement gradients along two sections of the fault characteristic fringe patterns can be recognized contrasting in density and direction with patterns observed away from the rupture in order to understand the observed fringe patterns we compute synthetic interferograms in three simple cases l1r rigidhbody rotations about a vertical axis l2r about a horizontal axis ltiltr and l3r distributed simple shear the orientation and spatial separation of interferometric fringes predicted by these models help constrain nearhfield deformation and rupture parameters where the kickapoo fault connects with the homestead valley fault the interferogram shows a clear pattern of parallel n20 w fringes separated by about 160 m this pattern and vertical offsets measured along the kickapoo fault suggest that the block between this fault and the johnson valley fault may have been tilted down to the west a 5hkm block lifted by l m on one side would be tilted by an angle of 0 01 l190 radr producing fringes separated by about 160 m parallel to the tilt axis such a tilt parallel to a n20 w direction would account for the gradual northward increase of the vertical slip component observed along the kickapoo fault this tilt may also explain the 1 m of reverse slip observed along the slip gap section of the homestead valley break between the southern end of the johnson valley fault and the eureka peak fault where no surface rupture has been mapped the dense pattern of fringes implies distributed shear probably resulting from fault slip at depth the density and direction of the fringes in the gap are consistent with a righthlateral slip of 1 2 3 8 m on a blind fault locked above the depth of 1 5 2 km such observations of small wavelength features in the sar interferogram bring new insights into the nearhfield displacement gradient and thus on response of the uppermost crust to seismic rupture

ice flow dynamics of the greenland ice sheet from sar interferometry synthetic aperture radar sar interferograms produced from esa s ers 1 satellite provide the first synoptic view of ice flow dynamics of the western sector of the greenland ice sheet glacial motion is detected in the radar ranging direction at millimetric scales across a complete sequence of snow accumulation and melting regimes despite significant variations in their radar scattering properties ice flow evolves from a slow regular motion at the higher elevations at lower elevations motion is strongly convoluted by meter scale undulations in surface topography which have a unique interferometric signature that enables a novel approach for retrieving flow direction inferred flow directions combined with surface displacements in the radar ranging direction yield ice velocity estimates that are within 6 of in situ measurements gathered along a 40 km survey line application of repeat pass sar interferometry to the entire greenland ice sheet should enable precise mapping of its ice flow dynamics at an unprecedented level of spatial detail

meso and microscale sea ice motion in the east siberian sea as determined from ers 1 sar data synthetic aperture radar sar derived ice motion vectors and sar interferometry were used to study the sea ice conditions in the region between the coast and 75 n 560 km in the east siberian sea in the vicinity of the kolyma river ers 1 sar data were acquired between 24 december 1993 and 30 march 1994 during the 3 day repeat ice phase of the satellite the time series of the ice motion vector fields revealed rapid 3 day changes in the direction and displacement of the pack ice longer term 1 month trends also emerged which were related to changes in large scale atmospheric circulation on the basis of this time series three sea ice zones were identified the near shore stationary ice zone a transitional ice zone and the pack ice zone three 3 day interval and one 9 day interval interferometric sets amplitude correlation and phase diagrams were generated for the end of december the begining of february and mid march they revealed that the stationary ice zone adjacent to the coast is in constant motion primarily by lateral displacement bending tilting and rotation induced by atmospheric oceanic forcing the interferogram patterns change through time as the sea ice becomes thicker and a network of cracks becomes established in the ice cover it was found that the major features in the interferograms were spatially correlated with sea ice deformation features cracks and ridges and major discontinuities in ice thickness

the spreading of a buoyant plume beneath a landfast ice cover abstractidealized numerical simulations using the regional ocean modeling system demonstrate the effects of an immobile landfast ice cover that is frictionally coupled to an underice buoyant plume established by river discharge the discharge rapidly increases and decreases over a 30 day period and has a maximum of 6000 m3 s 1 this study examined the response to a landfast ice cover of 26 km width and one that encompasses the entire shelf width the model setting mimics spring conditions on the alaskan beaufort sea abs shelf in comparison with the ice free case subject to the same discharge scenario underice plumes are broader and deeper and the downwave freshwater flux is substantially decreased and delayed multiple anticyclonic bulges form in the ice free case but only a single large bulge forms when ice is present these differences are because of the frictional coupling between the ice and plume which results in an ekman like underice boundary layer a subsurface velocity maximum and fricti

arctic sea ice as a granular plastic an important consideration in understanding sea ice mechanics is the integration of observed sea ice behavior on a floe neighborhood scale 1 10 km into ice dynamics on a regional scale o 50 km we investigate sea ice kinematics from october 1993 through april 1994 using relative motions from 13 drifting buoys with global positioning system navigation in a 20 km array centered on the sea ice mechanics initiative ice camp and we compare these motions to synthetic aperture radar sar derived ice velocities over a 100 by 500 km region in the beaufort sea there is excellent correspondence between the deformation of the buoy array and that from the sar inferred ice dynamics from analysis of the two major northerly wind convergence events of the winter are consistent with a granular hardening plastic conceptual model for beaufort sea ice under continued northerly winds the ice from the alaskan shore to the camp failed in shear and convergence in a progressive manner away from the coast the continuum scale o 10 km is an order of magnitude larger than the grain i e floe size o 1 km the ice motion often forms aggregates of 20 200 km separated by narrow 10 km shear zones similar to granular materials at moderate forcing i e wind stress multiplied by fetch the ice appears to fail along slip lines that occur at an acute angle to each other and to the direction of the wind forcing characteristic of a plastic material at critical state with longer fetch the ice appears to fail in compression perpendicular to the wind direction sea ice appeared to harden on a regional scale after the first event during the second northerly wind event there was a sea ice breakout toward the west apparently due to a lack of lateral confining stress our observations suggest that the ice floes advect through relatively stationary stress fields created by the wind forcing and coastal boundaries for example while the sar and advanced very high resolution radiometer images indicated the presence of the shear feature at the same geographic location for nearly a week buoys would show shearing only for several days as they transited across the region of shear there is a high correspondence between the major internal ice deformation events and persistent weather patterns on a 3 to 5 day temporal scale this implies that sar data collection and analysis for regional sea ice dynamics should be consistent with the wind forcing and have a sampling of less than 3 days