geological evaluation of multiple general circulation model simulations of late jurassic palaeoclimate abstract general circulation models gcms are currently used to predict future global change however the robustness of gcms should be evaluated by their ability to simulate past climate regimes their success in retrodiction can then be assessed by reference to the geological record geological evidence provides a database that can be used in the estimation of sea surface temperatures orography and other proxy data useful in palaeoclimatic studies these data can then be used to refine the prescribed boundary conditions for running gcms themselves results from a series of modelling experiments run with late jurassic kimmeridgian boundary conditions and using the uk university global atmospheric modelling programme ugamp gcm and the uk meteorological office gcm are presented simulations from these two quite independently generated models although subtly different confirm a generally warmer jurassic earth with arid zones over the tethys and sw usa parts of gondwana dominated by monsoonal systems and convective rainfall generally higher over the oceans than at present circum polar wetlands are also indicated these results generally conform well to the distributions of known facies in these regions modelled cloudiness is also higher in the jurassic and although unconfirmed geologically such conditions would have contributed to greenhouse conditions at high latitudes and could have influenced both terrestrial biomes and marine ecosystems using one of the gcms ugamp we have also investigated the role of orbital parameters for high latitude climate at times of minimum seasonal forcing comparable with an orbital geometry affecting the earth at 115 ka bp parts of antarctica could have sustained a modest ice sheet over areas exceeding 1 km elevation but such modelled sheets would have been ephemeral features and very dynamic in character

new scaling of fractures in a giant carbonate platform from outcrops and subsurface abstract we scale properties of fractures in the late kimmeridgian carbonate platform of the arabian shelf from outcrop and subsurface strata the platform is flat lying undeformed except from low relief anticlines and domes at which the strata hosts the world s most prolific petroleum reserves the strata exhibit stylolites and veins besides the dominant fractures the fractures are opening mode steep and forming major sets of nw se and ne sw orientations faults are uncommon fracture abundance varies significantly across the platform but it is constrained spatially by inherent variation in mechanical stratigraphy and temporally by anticlinal growth and isotope geochemistry in early burial stages the platform strata were slightly deformed by bed parallel stylolites and mutually crosscutting veins the strata fracturing increased by the anticlinal growth in the late cretaceous fracture spacing is an average of 2 m in the horizontal bedded outcrops in central arabia and 0 30 m in the equivalent subsurface in a dome in eastern arabia the dome is an end member in the deformation spectrum of the platform interior with up to c 5 structural dip and 2 dilational strain expressed in the doming and a few major faults this finding indicates that carbonate platforms can reach fracture oversaturation under such a subtle tectonic extension

analyzing tomographic sar data of a forest with respect to frequency polarization and focusing technique forest canopies are semitransparent to microwaves at both l and p bands thus a number of scattering sources and different types of scattering mechanisms may contribute to a single range cell of a synthetic aperture radar sar image by appropriately combining the sar data of multiple parallel flight paths a large 2 d aperture is synthesized which allows for tomographic imaging of the 3 d structure of such semitransparent media and the underlying ground a separate paper deals with the actual tomographic imaging part that leads to the 3 d data cube in particular three focusing techniques are described and analyzed multilook beamforming robust capon beamforming and multiple signal classification beamforming in this paper the resulting data products obtained by tomographically focusing two airborne multibaseline sar data sets of a partially forested area one at l band and another at p band are subject to a detailed analysis with respect to the location and the type of backscattering sources in particular the following aspects are investigated 1 the forest structure as obtained from the vertical profiles of intensities at sample plot locations within the forest is compared to the height distribution of the top of the forest canopy as derived from airborne laser scanning data and profiles are presented for all polarimetric channels and focusing techniques as well as at both frequencies 2 the type and location of scattering mechanisms are analyzed as functions of height for the two frequencies namely l and p bands and using the polarimetric channels as well as the pauli and cloudepottier decompositions thereof and 3 the accuracy of the ground elevation estimation obtained from the different focusing techniques and the two frequencies is assessed with the help of a lidar derived digital elevation model

origin of the rudstone floatstone beds in the upper jurassic arab d reservoir khurais complex saudi arabia abstract detailed description and analysis of cores from more than 50 wells through the kimmeridgian arab d reservoir arab d member and upper part of the jubaila formation in khurais abu jifan and mazalij oil fields are used to establish a consistent depositional model that represent a shift in the conceptual understanding of the upper jurassic carbonates of saudi arabia the jubaila fm and arab d mb conform to a shallowing upward carbonate evaporite succession in which three main carbonate facies belts occur capped by anhydrite the lower facies belt corresponds to the jubaila formation and consists of a series of eventites triggered by breaking internal waves interbedded peloidal wackestones represents the background sedimentation where neritic lime mud was churned by pellet producing benthonic fauna eventites consist of a lower intraclastic rudstone floatstone interval a middle grainstone packstone interval and an upper barren mudstone interval the middle facies belt is made of microbial coral stromatoporoid buildups the upper facies belt consists of the following shallow water lithofacies with cladocoropsis green algae foraminifers peloids and oolitic grainstones and oolitic cryptomicrobial mudstone to grainstone the stacking patterns of the internalites internal wave deposits in the jubaila fm suggests alternating periods with different internal waves activity namely different strength and bathymetric position of the pycnocline and intermittent production and accumulation of the neritic lime mud this interpretation represents a change to previous interpretations turbidites and tempestites and has important implications in both the perceptions of depositional processes in play and the criteria behind stacking lithofacies into parasequences and sequences

assessment of scattering mechanism of polarimetric sar signal from mountainous forest areas this study aims to understand the effects of the topographic slope variation on the vegetation backscattering characteristics of polarimetric imaging radar most of the previous studies in modeling microwave backscattering signatures of vegetated area have been carried out over relatively flat areas in order to model vegetation scattering mechanisms of mountainous forests this paper presents an improvement of the radiative transfer model that accounts for the tilted scattering surface beneath a forest canopy an l band polarimetric synthetic aperture radar sar data set acquired by the nasa jet propulsion laboratory airborne sar system was used to test and to assess the vegetation scattering model for a sloping forest area experimental result shows the proposed model to be adequate for evaluating slope induced changes in microwave scattering mechanisms

effects of crustal field rotation on the solar wind plasma interaction with mars the crustal remnant field on mars rotates with the planet at a period of 24 h 37 min constantly varying the magnetic field configuration interacting with the solar wind until now there has been no self consistent modeling investigation on how this varying magnetic field affects the solar wind plasma interaction here we include the rotation of this localized crustal field in a multispecies single fluid mhd model of mars and simulate an entire day of solar wind interaction under normal solar wind conditions the mhd model results are compared with mars global surveyor mgs magnetic field observations and show very close agreement especially for the field strength along almost all of the 12 orbits on the day simulated model results also show that the ion escape rates slowly vary with rotation generally anticorrelating with the strength of subsolar magnetic crustal sources with some time delay in addition it is found that in the intense crustal field regions the densities of heavy ion components enhance significantly along the mgs orbit implying strong influence of the crustal field on the ionospheric structures

hurricane induced sediment transport in open shelf tropical systems an example from st croix u s virgin islands hurricane hugo passed directly over st croix on 17 september 1989 sustained winds in excess of 110 knots gusts to 165 knots and waves 6 7 m in height accompanied the storm along the north coast wave height was lower ca 3 4 m due to the leeward position of the shelf in the deeper reefs at cane bay and salt river damage was confined primarily to the soft bodied benthic community e g sponges gorgonians coral damage was much less severe largely because of the buffering effects of the water column the greatest change observed after the storm was wholesale flushing of sand from shelf edge areas in salt river submarine canyon a minimum of 2 million kg of sediment were flushed into deeper water the transport rate associated with the storm was eleven orders of magnitude above that measured during fair weather and the volume of sediment that was removed from the canyon equalled roughly a century of normal sediment accumulation at cane bay 336 000 kg of sediment were flushed from a single channel with similar amounts removed from adjacent breaks in the shelf edge reef a current meter in salt river submarine canyon provided information on the timing and intensity of the oceanographic processes related to hurricane hugo as the storm approached waves piled water against the shoreface and in salt river bay as the storm passed over st croix the change in wind direction followed by a decrease in wave height triggered a release of water trapped in the bay and along the adjacent shoreline by waves earlier in the storm for a period of 4 6 hours net down canyon currents reaching 2 m s and oscillatory flows up to 4 m s occurred along the base of the western canyon wall removing up to 2 m of sand similar events were likely responsible for the wholesale removal of sand in eastern cane bay the paradoxical concurrence of wholesale sediment transport and low level reef damage is related to the protection from waves but not wind afforded by the north coast of st croix facing away from the direction of storm approach these observations and measurements provide our first opportunity to relate sediment export in such a high energy event to the physical processes that were responsible calculations based on post hugo measurements are in agreement with an earlier sediment budget for salt river canyon sediment export in cane bay exceeded the volume similarly predicted because such events are probably common on all exposed carbonate shelf margins storms like hurricane hugo are among the most important factors in the cycling of sediment through exposed open marine environments both now and in the geologic past the patterns of reef damage and sediment transport are much more complicated than previously envisioned and more thoughtful consideration of their variability and the processes responsible is essential to an understanding of the signature that will be left by major storms

the effect of topography on radar scattering from vegetated areas the ways in which radar scattering from vegetated areas is affected by the topography of the surface underneath the vegetation are discussed it is shown using a discrete scatterer model that the dominant scattering mechanism may change drastically when the ground surface is tilted relative to the horizontal for a horizontal ground surface for example the total scattering may be dominated by scattering off the tree trunks followed by a reflection off the ground surface for a relatively small tilt in the ground surface the ground trunk interaction term may be replaced by scattering from the branches alone as the dominant scattering mechanism the effect of the topography is more pronounced for scattering by longer wavelengths and the implications on algorithms designed to infer forest woody biomass and soil and vegetation moisture using polarimetric sar data are discussed the effect of the topography on the scattering behavior from forested areas is illustrated with images acquired by the nasa jpl three frequency polarimetric sar over the black forest in germany

a proxy for determining solar wind dynamic pressure at mars using mars global surveyor data 1 we develop a method to infer the upstream solar wind pressure at mars using data from the mars global surveyor mgs magnetometer instrument the method assumes magnetic field pressure in the magnetic pileup region balances the incident solar wind dynamic pressure newtonian pressure balance conditions are imposed for positions off of the subflow point proof of concept exists from the mapping phase of the spacecraft mission when the orbital geometry at a constant altitude allows fits to magnetic field data as a function of solar zenith angle during the elliptical orbit phase of mgs when the spacecraft passes through a large range of altitudes such fits are not possible however the measured magnetic pressure in the magnetic pileup region is scaled by the same means as derived for the mapping orbits and reasonable upstream solar wind pressure is obtained we compare the distribution of solar wind pressure calculated using mgs data with the solar wind pressure measured upstream of the earth during the same time period and find good agreement further supporting this algorithm as a valid proxy for the incident solar wind pressure the response of the position of the magnetic pileup boundary to the inferred solar wind pressure also validates the method high solar wind ram pressure depresses the altitude of the magnetic pileup boundary

production and cycling of calcium carbonate in a shelf edge reef system st croix u s virgin islands applications to the nature of reef systems in the fossil record abstract geologic reefs are the end products of not only constructive processes that produce calcium carbonate but also of destructive processes e g bioerosion and wave action that reduce solid substrate to sediment and of physical processes that rework the reef fabric and transport sediment a study was conducted at cane bay on the island of st croix u s virgin islands to quantify the suite of processes that have influenced holocene reef development data on carbonate production reef accretion bioerosion and sediment transport were used to construct a detailed carbonate budget and to apply the findings of this study to the character of reefs observed in the fossil record total carbonate production on the reef ranged from 0 to 5 78 kg m2 per year with a reef wide average of 1 21 kg m2 per year 1 13 by corals 0 02 by coralline algae 0 06 by primarily molluscs forams and echinoderms based on 7 cores only 0 91 kg m2 per year of this have been retained within the reef interior the remaining 0 24 kg m2 per year of sediment along with the 0 06 kg m2 per year contributed directly by molluscs etc are deposited within reef channels and are probably flushed from the reef by major storms of the material recovered in the cores 58 was either loose sediment and rubble or open void space much of the recognizable coral material was demonstrably reworked and out of place accretion rates across the shelf generally increased with water depth as a result of active slumping along the steepening reef face over the past 2 000 3 000 years the importance of detrital material in the reef fabric and the major role played by secondary processes that constantly rework the substrate have resulted in a reef whose interior is more of a garbage pile than an in place assemblage of corals cemented together into a rigid framework the physical similarities between the detrital fabric of the reef at cane bay and those found in many ancient deposits imply that the general processes operating along the cane bay shelf have persisted during much of the evolution of ancient reefs it is proposed that our modern models overemphasize the importance of in place framework as a criterion for an ecologic reef

phenomenology of ground scattering in a tropical forest through polarimetric synthetic aperture radar tomography this paper aims at characterizing the scattering mechanisms occurring at the ground level in a tropical forest illuminated by a p band synthetic aperture radar sar the analysis is carried out based on the multibaseline fully polarimetric data set collected by onera over paracou french guyana in the frame of the european space agency campaign tropisar the favorable baseline distribution of this data set results in the possibility of removing most contributions from the vegetation layer by tomographic techniques thus allowing the generation of a new fully polarimetric single look complex sar image relative to scattering contributions from the ground level only such a ground layer image is then analyzed by considering the variation of its polarimetric signature with respect to terrain local slope and radar look angle two major conclusions are drawn 1 double bounce scattering from trunk ground interactions is observed to be the dominant scattering mechanism at the ground level on flat terrains whereas it rapidly tends to vanish as the topographic slope increases and 2 the characteristic parameter that rules trunk ground scattering is not the tree height but rather the available free path facing the tree as a result of the presence of nearby trees undulating topography or understory preventing double bounce scattering from taking place whenever the ground bounce occurs too far away from the considered tree the mean free path length resulting from the analysis of this data set is found to be l 7 m finally we discuss how the concept of free path length can be accounted for in simple terms by assuming an equivalent extinction model characterized by a variation along the horizontal dimension

are reefs and mud mounds really so different although both ecologic reefs and mud mounds are demonstrably rigid framework reefs they are still considered to be distinct in terms of their dominant processes of formation and preferred environmental settings this distinction has rested largely upon the assumption that ecologic reefs are dominated by skeletal metazoans growing in shallow waters in contrast to the complex autochthonous micrite supported cavity systems that characterise deep water mud mounds now considered to represent either organomineralic deposits where carbonate precipitation has taken place in association with nonliving organic substrates to form automicrite or various types of microbialite where carbonate forms as a direct result of the physiological activity or decay of benthic microorganisms yet such autochthonous micrite is increasingly recognised as an important component of many ancient shallow ecologic reefs as well as some modern coral reefs and indeed may contribute locally up to 80 of the reef rock these observations raise doubts as to the validity of current fabric based definitions used to distinguish between mud mounds and ecologic reefs whether the autochthonous micrite in mud mounds proves to be dominated by either automicrite or microbialite both require particular environmental conditions for their formation automicrites form where surplus organic matter from metazoans has degraded to release quantities of acidic amino acids with a significant ability to bind ca 2 and microbialite formation also often requires either unusual marine chemistries or ecological conditions such conditions might include changes in terrigenous influx ground water seepage local anoxia and increases in the ph of interstitial reef waters or in nutrient concentration d 2001 elsevier science b v all rights reserved

magnetic lineations in the ancient crust of mars the mars global surveyor spacecraft in a highly elliptical polar orbit obtained vector magnetic field measurements above the surface of mars altitudes 100 kilometers crustal magnetization mainly confined to the most ancient heavily cratered martian highlands is frequently organized in east west trending linear features the longest extending over 2000 kilometers crustal remanent magnetization exceeds that of terrestrial crust by more than an order of magnitude groups of quasi parallel linear features of alternating magnetic polarity were found they are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on earth but with a much larger spatial scale they may be a relic of an era of plate tectonics on mars

low vhf band backscatter from coniferous forests on sloping terrain low frequency synthetic aperture radar sar is a promising technique for stem volume retrieval particularly for dense forests due to the good penetration of forest canopies however it is well known that the dominant scattering mechanism the trunk ground dihedral interaction decreases rapidly on sloping terrain in this paper we use low vhf band sar data collected with carabas over dense coniferous forests in sweden to examine the effect of topography using flight passes with different headings the effect of slope and aspect angle on backscatter is characterized for tall trees spl sim 30 m on the steepest slopes in the test site up to spl sim 12 spl deg differences of up to 8 db are observed between images acquired with different look directions relative to the slope a physical model is developed to investigate the different scattering mechanisms and their sensitivity to terrain slopes the model shows that the trunk ground scattering still dominates the response for large trees on moderate slopes and a semiempirical model for the effect of topography on backscatter is proposed the model shows good agreement with measurements indicating the possibility of using it to compensate for the effects of sloping terrain when retrieving stem volume in coniferous forest

arabian carbonate reservoirs a depositional model of the arab d reservoir in khurais field saudi arabia the upper jurassic arab formation in the arabian peninsula the most prolific oil bearing interval of the world is a succession of interbedded thick carbonates and evaporites that are defined stratigraphically upsection as the arab d arab c arab b and arab a the arab d reservoir is the main reservoir in khurais field one of the largest onshore oil fields of the kingdom of saudi arabia in khurais field the arab d reservoir is composed of the overlying evaporitic arab d member of the arab formation and the underlying upper part of the jubaila formation it contains 11 lithofacies listed from deepest to shallowest 1 hardground capped skeletal wackestone and lime mudstone 2 intraclast floatstone and rudstone 3 pelletal wackestone and packstone 4 stromatoporoid wackestone packstone and floatstone 5 cladocoropsis wackestone packstone and floatstone 6 clypeina and thaumatoporella wackestone and packstone 7 peloidal packstone and grainstone 8 ooid grainstone 9 crypt microbial laminites 10 evaporites and 11 stratigraphically reoccurring dolomite the arab d reservoir lithofacies succession represents shallowing upward deposition which from deepest to shallowest reflects the following depositional environments offshore submarine turbidity fans lithofacies 1 and 2 lower shoreface settings lithofacies 3 stromatoporoid reef lithofacies 4 lagoon lithofacies 5 and 6 shallow subtidal settings lithofacies 7 and 8 peritidal settings lithofacies 9 and sabkhas and salinas lithofacies 10 the depositional succession of the reservoir represents a prograding shallow marine reef rimmed carbonate shelf that was subjected to common storm abrasion which triggered turbidites

a 50 degree spherical harmonic model of the magnetic field of mars this paper presents a 50 degree and order spherical harmonic model of the magnetic field of mars derived at 120 km altitude using the three orthogonal components of the vector magnetic field data acquired by the mars global surveyor within the 80 to 200 km altitude range the downward continued vector magnetic field components to the surface of mars delineate details of the martian magnetic field the strong magnetic anomalies in the southern hemisphere do not show compelling evidence for magnetic lineations similar to those associated with the seafloor spreading on earth the anomalies are more or less equidimensional the magnetic signatures surrounding the impact basins hellas argyre and isidis show that the prominent magnetic anomalies are older than the impact events an average magnetization of 2 a m is estimated for the upper crust surrounding hellas basin four isolated magnetic anomalies are modeled by vertical prisms with circular cross sections of 170 to 190 km radius and 20 to 30 km thickness the magnetization of the model prisms is 5 a m more than that of the surroundings

solar wind interaction with the martian upper atmosphere crustal field orientation solar cycle and seasonal variations a comprehensive study of the solar wind interaction with the martian upper atmosphere is presented three global models the 3 d mars multifluid block adaptive tree solar wind roe upwind scheme mhd code mf mhd the 3 d mars global ionosphere thermosphere model m gitm and the mars exosphere monte carlo model adaptive mesh particle simulator m amps were used in this study these models are one way coupled i e the mf mhd model uses the 3 d neutral inputs from m gitm and the 3 d hot oxygen corona distribution from m amps by adopting this one way coupling approach the martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation solar cycle and martian seasonal conditions the calculated ion escape rates are compared with mars express observational data and show reasonable agreement the variations in solar cycles and seasons can affect the ion loss by a factor of 3 3 and 1 3 respectively the crustal magnetic field has a shielding effect to protect mars from solar wind interaction and this effect is the strongest for perihelion conditions with the crustal field facing the sun furthermore the fraction of cold escaping heavy ionospheric molecular ions 2 and or 2 total are inversely proportional to the fraction of the escaping ionospheric and corona atomic ion o total whereas 2 and 2 ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path

effects of the crustal magnetic fields on the martian atmospheric ion escape rate eight years 2007 2015 of ion flux measurements from mars express are used to statistically investigate the influence of the martian magnetic crustal fields on the atmospheric ion escape rate we combine all aspera 3 ima measurements taken during nominal upstream solar wind and solar extreme ultraviolet euv conditions to compute global average ion distribution functions individually for the north south hemispheres and for varying solar zenith angles sza of the strongest crustal magnetic field escape rates are subsequently calculated from each of the average distribution functions the maximum escape rate 4 2 1 2 1024s 1 is found for sza 60 80 while the minimum escape rate 1 7 0 6 1024s 1 is found for sza 28 60 showing that the dayside orientation of the crustal fields significantly affects the global escape rate p 97 however averaged over time independent of sza we find no statistically significant difference in the escape rates from the two hemispheres escape from southern hemisphere 46 18 of global rate

control of mars global atmospheric loss by the continuous rotation of the crustal magnetic field a time dependent mhd study we present a time dependent mhd study of the controlling effects of the mars crustal field on atmospheric escape we calculate globally integrated planetary ion loss rates under quiet solar conditions considering the continuous rotation of crustal anomalies with the planet it is found that the rotating crustal field plays an important role in controlling atmospheric escape significant time variation of 20 and 50 is observed during the entire rotation period for o and for o2 and co2 respectively the control is exerted mainly through two processes first the crustal magnetic pressure over the subsolar regime controls solar wind penetration and mass loading and therefore the escaping planetary ion source there is a strong negative correlation between the magnetic pressure and ion loss with a time lag of 1 h for o and 2 5 h for o2 and co2 second the crustal magnetic pressure near the terminator region controls the cross section area between the induced magnetospheric boundary and 100 km altitude at the terminator the change in day night connection regulates the extent to which planetary ions created on the dayside can be ultimately carried away by the solar wind and escape mars there is a strong positive correlation between the cross section area and ion loss with no significant time lag as the planet rotates the dayside process and the terminator process work together to control the total amount of escaping planetary ions however their relative importance changes with the local time of the strong crustal field region

hydrocarbon habitat in main producing areas saudi arabia current hydrocarbon production in saudi arabia is from reservoirs of cretaceous and jurassic age geochemical studies of the sediments and oils suggest that the hydrocarbons were derived from two separate source rock provinces oil production from the large fields in the southern part of the area is from jurassic carbonate reservoirs most of these oils were derived from thermally mature thinly laminated organic rich carbonate rocks of jurassic age callovian oxfordian these source rocks were deposited in an intrashelf basin which is limited to the southern part of the main producing areas extensive vertical migration of oils originating in these sediments is prevented by superjacent evaporite seals deposited during the late jurassic fields in the northern producing areas appear to have derived their hydrocarbons from a source rock province on the north production from cretaceous clastic and carbonate reservoirs is limited to the northeastern part of the producing areas this distribution may be explained by limitation of thermally mature cretaceous source rocks to the northeastern areas or by the local lack of subjacent evaporite seals to separate these reservoirs from jurassic source rocks thermal maturation studies indicate that the hydrocarbons in mesozoic reservoirs migrated into the present traps during the early tertiary

anatomy of a fringing reef around grand cayman storm rubble not coral framework abstract our fair weather perception of modern reefs has led to the implicit assumption that their development is controlled by processes that govern the siting of in place coral growth yet more ephemeral processes such as storms and hurricanes assume much greater importance over longer time scales because few reefs escape their influence to discover the importance of storms on reef development we analyze the zonation anatomy and architecture of a fringing reef complex around grand cayman we find that the surface zonation of in place corals is merely a facade and the reef core is in fact composed of meter thick layers of coral cobble rudstone capped by crusts of coralline algae the large size and abraded condition of the rudstone clasts shows that these layers are not the product of f ir weather processes but the result of destruction and deposition during hurricanes as hurricane waves cross coral mantled zones of the inner shelf they destroy live coral stands and deposit the clasts as a rubble layer covering the entire reef complex between storms this rubble foundation is stabilized by coralline algal crusts and recolonized by rapidly growing corals leading eventually to full reef regeneration before the next hurricane this cyclic pattern of destruction and regeneration consequently produces a fringing reef complex with a core composed of hurricane generated rubble not coral framework as previously assumed in addition to explaining reef anatomy hurricane control also explains the variation in reef architecture along shelf uniform reef location across shelf and reef absence along certain shelf sections as hurricane waves cross a mid shelf scarp they start to break and destroy coral growth over most of the inner shelf coral rubble generated by these waves is deposited 350 50 m from the mid shelf scarp on margins exposed to the largest waves but only 250 50 m on semi protected margins that experience smaller fetch limited waves in areas where the width of the inner shelf is 250 m hurricane waves throw rubble ashore and a fringing reef does not develop during sea level rise this influence of shelf width on rubble deposition controls the timing of reef nitiation and that in turn controls reef architecture reefs initiate first on low gradient coasts with wide shelves and gradually extend around higher gradient coasts as sea level rises and shelf width increases thus older reefs are located farther offshore front deeper lagoons and have thicker and narrower profiles than younger reefs

magnetic field and plasma observations at mars initial results of the mars global surveyor mission the magnetometer and electron reflectometer investigation mag er on the mars global surveyor spacecraft has obtained magnetic field and plasma observations throughout the near mars environment from beyond the influence of mars to just above the surface at an altitude of 100 kilometers the solar wind interaction with mars is in many ways similar to that at venus and at an active comet that is primarily an ionospheric atmospheric interaction no significant planetary magnetic field of global scale has been detected to date 2 1021 gauss cubic centimeter but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of mars is reported

variability of the altitude of the martian sheath received 31 march 2005 revised 18 august 2005 accepted 25 august 2005 published 24 september 2005 1 using electron energy spectra we identify time periods when the mars global surveyor mgs spacecraft is in or above the martian magnetic pileup boundary mpb we use more than five years of data to develop a statistical picture of the location of the mpb relative to the mgs mapping altitude near 400 km we show for the first time that the mpb location is sensitive to interplanetary magnetic field imf orientation and to martian season and confirm a dependence upon solar wind pressure we confirm that crustal magnetic sources raise the altitude of the mpb and demonstrate that sheath electrons populate magnetic cusp regions in the southern hemisphere during southern summer strong crustal fields near the subsolar point raise the altitude of the mpb over the entire dayside implying that martian crustal fields modify the solar wind interaction globally citation brain d a j s halekas r lillis d l mitchell r p lin and d h crider 2005 variability of the altitude of the martian sheath geophys res lett 32 l18203

multibaseline polarimetric sar tomography of a boreal forest at p and l bands longer wavelength synthetic aperture radars sars are precious in the remote sensing of forested areas being sensitive to contributions from the whole vegetation layer and from the ground below the electromagnetic properties of such contributions are retrieved from multipolarimetric acquisitions whereas their vertical structure is retrieved from multibaseline acquisitions through tomographic imaging combining baseline and polarization diversity provides most information allowing the decomposition of the sar signal into ground and volume only contributions a formal treatment of this problem is provided with the algebraic synthesis technique which extends the concepts of polinsar the decomposition however is shown to be ambiguous in that different solutions are equally consistent with the data the main goal of this paper is to discuss this topic in light of the experimental results from a tomographic and polarimetric analysis of the boreal forest within the krycklan river catchment northern sweden investigated at p and l bands during the esa campaign biosar 2008 different solutions to the decomposition problem will be discussed by examining the corresponding vertical structures accessible through tomographic techniques elements are shown supporting the idea that ground volume interactions play a nonnegligible role at p band and a solution is proposed to isolate contributions from direct volume backscattering the retrieval of forest top height is discussed as well leading to the conclusion that such parameter is robust against erroneous choices in the identification of volume only contributions thus corroborating the polinsar approach for the analysis of single baseline data

paleoclimate of the kimmeridgian tithonian late jurassic world ii sensitivity tests comparing three different paleotopographic settings moore g t sloan l c hayashida d n and umrigar n p 1992 paleoclimate of the kimmeridgian tithonian late jurassic world ii sensitivity tests comparing three different paleotopographic settings palaeogeogr palaeoclimatol palaeoecol 95 229 252 topography and location of continents largely determine present day climate we conclude that in the geologic past paleotopographic expression was equally important however in the geologic record paleotopography is difficult to assess and compile because it is largely a self destructive environment without record and is rarely addressed in the literature an objective of this study is to test the sensitivity of paleoclimate to paleotopography by comparing three different late jurassic scenarios paleotopography influences many paleoclimate parameters to varying degrees to test the sensitivity of paleoclimate to modeled paleotopography for simulations incorporating a late jurassic reconstruction we ran three simulations using the same boundary conditions of paleogeography land and ocean and atmospheric co2 concentration 4x the pre lndustrial level 1120 ppm one simulation contained mountain ranges of variable height to 3 kin in another all the mountain ranges were reduced to 1 km highlands the third simulation used a constant 500 m height for all land grid cells the sensitivity tests indicate that paleotopography is an important boundary condition without realistic paleotopography flat or idealized continents surrounded by bodies of water do not produce realistic pateoclimate results we conclude that in paleogeographic reconstructions the location and extent of mountain ranges and highlands should be recognized and given suitable elevations consistent with their plate tectonic origins settings and geologic ages

depositional cycles and source rock development in an epeiric intra platform basin the hanifa formation of the arabian peninsula abstract the upper oxfordian to lower kimmeridgian hanifa formation was deposited in an intra platform basin on the broad epeiric shallow water carbonate platform that extended over much of the middle east during the mesozoic the formation consists of organic rich carbonate mudstones bioturbated mudstones and sulphates the organic rich mudstones are considered to be one of the major hydrocarbon source rocks in the middle east oil province the correlation of sedimentary facies shows a hierarchical stacking pattern of transgressive regressive depositional cycles within the hanifa formation since these cycles occur at a basin wide scale it is assumed that they are related to relative changes of sea level the superimposed scales of cyclicity determine the occurrence of source rock and sulphates major source rock development occurs in transgressive dominated cycles sulphates on the other hand are more common during periods of overall regression

sedimentary evolution of a shallow carbonate ramp kimmeridgian ne spain unravelling controlling factors for facies heterogeneities at reservoir scale abstract the facies evolution of a late jurassic latest kimmeridgian shallow carbonate ramp was reconstructed after the analysis and correlation of 21 logs in a 20 30 km outcrop area located south of zaragoza northeast spain the studied succession belongs to the higueruelas formation which is of potential use as an analogue for understanding facies heterogeneities in certain hydrocarbon carbonate reservoirs e g the arab formation persian gulf the studied succession is arranged in nine sedimentary units bounded by discontinuity surfaces that can be traced over kilometres facies analysis permitted the reconstruction of two sedimentary models showing the transition from inner ramp subenvironments i e intertidal lagoon backshoal washover shoal sand blanket to the mid ramp foreshoal and offshore domains an oncolitic peloidal oolitic and an oolitic peloidal dominated ramp the oncolitic peloidal oolitic dominated ramp is characterized by peloidal oolitic and oncolitic dominated shoal sand blankets that developed in higher energy inner areas protecting peloidal oolitic backshoal and oncolitic lagoon domains including a mosaic of stromatoporoid carpets peloidal facies with fenestral porosity accumulated in an intertidal belt or as patches on top of the shoal sand blankets and washover deposits offshore from the shoal sand blankets chaetetid stromatoporoid coral rich buildups grew on the more proximal mid ramp surrounded by peloidal and peloidal bioclastic grain to mud supported facies an oolitic peloidal dominated ramp developed in a second stage of the evolution of the platform characterized by the presence of a wide restricted peloidal bioclastic oolitic lagoon on the inner ramp grading into a backshoal area dominated by storm related intraclastic peloidal deposits stromatoporoid carpets disappeared and oncolitic dominated deposits were constrained to the foreshoal and backshoal domains and locally to local ponds that developed in the intertidal belt or the restricted lagoon internal and external factors controlling facies heterogeneity and the sedimentary evolution of the carbonate ramp include resedimentation topographic relief and long to short term sea level fluctuations

martian magnetic storms the response of mars to the major space weather events called interplanetary coronal mass ejections icmes is of interest for both general planetary solar wind interaction studies and related speculations on their evolutionary consequences especially with respect to atmosphere escape various particle and field signatures of icmes have been observed on phobos 2 mars global surveyor mgs mars express mex and now mars atmosphere and volatile evolution maven of these maven s combined instrumentation and orbit geometry is particularly well suited to characterize both the event drivers and their consequences however maven has detected only moderate disturbances at mars due in large part to the general weakness of the present solar cycle nevertheless the strongest event observed by maven in march 2015 provides an example illustrating how further insights can be gained from available models here we first look more closely at what previously run bats r us mhd simulations of the combined maven observations tell us about the march 2015 event consequences we then use analogous models to infer those same responses including magnetic field topology changes and ionospheric consequences to a hypothetical extreme icme at mars based on stereo a measurements in july 2012 the results suggest how greatly enhanced yet realistic solar wind pressure magnetic field and convection electric field combine to produce strong magnetospheric coupling with important consequences for upper atmosphere and ionosphere energization

precambrian to jurassic rocks of arabian gulf and adjacent areas their facies depositional setting and hydrocarbon habitat the first sediments to onlap the metamorphosed precambrian arabian shield were infracambrian proterozoic to middle cambrian carbonates clastics and evaporites the oldest arabian reservoir rocks occur in the precambrian to lower paleozoic ara salt of the huqf group which forms the birba field of oman the middle cambrian sequence was followed by late cambrian through early permian marine sandstones and continental to littoral siltstones and variegated shales the first commercial oil discovered in the arabian gulf region occurs in fluvial sands of the ordovician to permian haima and haushi groups of the marmul field in south oman these strata are also productive in other fields and are sealed by unconformable contact with the al khlata formation or beneath shale of he albian nahr umr formation the deeply buried kerogen sediments of the huqf group to the southeast are believed to be the source rocks for these fields of south oman the late permian to triassic deposits of the arabian peninsula are mainly widespread carbonates and evaporites that were deposited during a period of relative tectonic stability their deposition on an epeiric shelf was punctuated by a series of transgressions and regressions significant gas reserves have been proven in deep wells in the arabian gulf these wells penetrate large deep structures in the permian khuff shelf carbonates these carbonates have developed secondary porosity and lie beneath interbedded shale and dolomites of the sudair or suwei formation the source of gas in the khuff is unknown but could lie in more deeply buried formations the large deep structures of the khuff are considered to be among the most attractive for gas potential in the region today the stable shelf depositional environment established during the permian and triassic continued through the mesozoic jurassic rock units of the arabian gulf formed a sedimentary megacycle of epeiric shelf carbonates these include relatively deep water mudstones and wackestones to shallow water grainstones and packstones with the greatest facies variations occurring in the post dhruma to arab d rocks some of the best and most extensive reservoirs of the area occur in the primary and secondary porosity of the upper jurassic arab formation and in the middle jurassic araej and dhruma formations of saudi arabia qatar and abu dhabi the sources for hydrocarbons in these jurassic sediments are thought to be in the dhruma and lower hanifa formation diyab equivalent of the gulf area n general the jubailah is a source in qatar and some of the offshore gulf the most common seals are the argillaceous carbonate at the top of the dhruma and the hith anhydrite the latter also marking the termination of jurassic deposition across the arabian platform the upper jurassic cycles of marine limestones and anhydrites of the arab and hith formations accumulated in response to changes of sea level caused either by regional epeirogenic movements or by eustasy

carbonate platform scale correlation of stacked high frequency sequences in the arab d reservoir saudi arabia abstract the late jurassic arab formation contains a number of hydrocarbon bearing carbonates the most important of which is the lowermost arab d reservoir the reservoir lithofacies in khurais field are couplets of 1 lime mud and 2 intraclastic lithofacies representing basinal turbidites 3 pelletal lithofacies representing lower shoreface sands and silts 4 stromatoporoid lithofacies representing a reef 5 cladocoropsis and 6 dasyclad lithofacies representing a lagoon 7 peloidal and 8 oolitic lithofacies representing shore attached sand sheets 9 cryptomicrobial lithofacies representing supratidal flats 10 anhydrites representing sabkha followed by salina deposits and 11 stratigraphically reoccurring dolomite these are arranged in two partially preserved third order sequences the upper of which represents the arab d member and the lower of which represents the upper jubaila formation within these sequences lie six fourth order high frequency sequences composed of fifth order parasequences and parasequence scale cycles the preserved upward shallowing trend of the arab d reservoir is manifested laterally by a regional eastward thickening interpreted to be the result of an eastward progradation across the shallow late jurassic epeiric shelf and into the relatively deep arabian intrashelf basin this study presents a correlation model that explains the drastic thickening and downward climb of the reservoir lithofacies that is observed between the outcrops south of riyadh and the subsurface in ghawar field this model is different from the one currently used and predicts an eastward porosity improvement in the upper part of the reservoir accompanied by a porosity reduction in the lower part assuming a null diagenetic modification effect

first demonstration of airborne sar tomography using multibaseline l band data in synthetic aperture radar sar interferometry the phase differences between two different sensor positions are used to estimate the terrain topography although it is possible in this way to find a three dimensional 3d surface representation the distribution of the different scatterers in the height direction at a fixed range and azimuth position remains unknown contrary to this tomographic techniques enable a real geometric resolution capability in the height direction and introduce new possibilities for many applications and inversion problems even misinterpretations in sar images caused by layover and foreshortening effects can be solved by the tomographic processing in this paper the successful experimental realization of polarimetric airborne sar tomography is demonstrated for the first time the authors present the concept of aperture synthesis for tomographic imaging for the case of a multibaseline imaging geometry and discuss the constraints arising from the limited number of flight tracks they propose a method for reduction of the height ambiguities associated to the irregular and undersampled spatial distribution of the imaging positions finally they address the experimental requirements for polarimetric airborne sar tomography and show experimental results using a multibaseline data set acquired in l band by dlr s experimental sar e sar of a test site near oberpfaffenhofen germany