pancakelike domes on venus the shape of seven large domes on the plains of venus with volumes between 100 and 1000 km3 is compared with that of an axisymmetric gravity current spreading over a rigid horizontal surface both the altimetric profiles and the horizontal projection of the line of intersection of domes on the synthetic aperture radar images agree well with the theoretical similarity solution for a newtonian fluid but not with the shape calculated for a rigid plastic rheology nor with that for a static model with a strong skin as a viscous current spreads it generates an isotropic strain rate tensor whose magnitude is independent of radius such a flow can account for the randomly oriented cracks that are uniformly distributed on the surface of the domes the stress induced by the flow in the plains material below is obtained and is probably large enough to produce the short radial cracks in the surface of the plains beyond the domes the viscosity of the domes can be estimated from their thermal time constants if spreading is possible only when the fluid is hot and lies between 1014 and 1017 pa s laboratory experiments show that such viscosities correspond to temperatures of 610 to 700 c in dry rhyolitic magmas these temperatures agree with laboratory measurements of the solidus temperature of wet rhyolite these results show that the development of the domes can be understood using simple fluid dynamical ideas and that the magmas involved can be produced by wet melting at depths below 10 km followed by eruption and degassing

from greenhouse to icehouse organic walled dinoflagellate cysts as paleoenvironmental indicators in the paleogene abstract dinoflagellates are an important component of the extant eukaryotic plankton their organic walled hypnozygotic cysts dinocysts provide a rich albeit incomplete history of the group in ancient sediments building on pioneering studies of the late 1970s and 1980s recent drilling in the southern ocean has provided a wealth of new dinocyst data spanning the entire paleogene such multidisciplinary studies have been instrumental in refining existing and furnishing new concepts of paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts because dinocysts notably exhibit high abundances in neritic settings dinocyst based environmental and paleoclimatic information is important and complementary to the data derived from typically more offshore groups as planktonic foraminifera coccolithophorids diatoms and radiolaria by presenting case studies from around the globe this contribution provides a concise review of our present understanding of the paleoenvironmental significance of dinocysts in the paleogene 65 25 ma representing earth s greenhouse icehouse transition this episode holds the key to the understanding of extreme transient climatic change we discuss the potential of dinocysts for the reconstruction of paleogene sea surface productivity temperature salinity stratification and paleo oxygenation along with their application in sequence stratigraphy oceanic circulation and general watermass reconstructions

steep sided domes on venus characteristics geologic setting and eruption conditions from magellan data a survey of more than 95 percent of the venus surface reveals 145 steep sided domes which can be subdivided into a variety of morphologic forms the most common being shaped like inverted bowls or flat topped domes results of a preliminary analysis of the distribution and geologic setting of the domes are presented the relation of the domes to analogous terrestrial features is examined and possible models for their mode of emplacement are outlined

dinoflagellate cysts sea level changes and planktonic foraminifers across the cretaceous tertiary boundary at el haria northwest tunisia abstract dinoflagellate cysts and planktonic foraminifers have been studied from the cretaceous tertiary k t boundary interval at el haria northwest tunisia a high resolution integrated biostratigraphy is presented the k t boundary is drawn at the level of extinction of cretaceous planktonic foraminifers and is coincident with the first occurrence of the dinoflagellate cyst species danea californica the final extinction of planktonic foraminifers is foreshadowed by a reduction in their total abundance some 5 kyr earlier at the base of the boundary clay this reduction is coeval with reported anomalies in siderophyle elements and 13 c values in the same area dinoflagellate cysts do not show accelerated rates of extinction at k t time associations of dinoflagellate cysts however change drastically and parallel changes in relative numbers of sporomorphs spores and pollen and in the quantity of land derived organic matter jointly these changes reflect a rapidly falling sea level during the final 17 kyr of the mesozoic which culminates at the level of the k t boundary this steep sea level fall at k t time represents a peak regressive pulse at the end of the well documented latest cretaceous regressive trend this short term sea level fall might show to be a wide spread phenomenon which could have caused an excess shrinking of the already reduced areal extent of marginal seas since deep waters in cretaceous oceans were primarily produced in shallow marginal seas the rate of formation of deep water might have been minimized at k t time minimum rates of formation of deep water might have curtailed the slow upward mixing of relatively cool and nutrient rich deeper water through which the thermocline weakened and surficial waters became depleted in nutrients consequently phytoplankton productivity rapidly diminished which in combination with a weakened thermal gradient pushed the highly depth stratified cretaceous planktonic foraminiferal fauna to extinction over a period of time of some 5 kyr guembelitria cretacea was the sole planktonic foraminifer which could accommodate to the low productivity conditions the oscillating rise in sea level at the beginning of the cenozoic reinforced the upward mixing of relatively cool and nutrient rich deeper water steepened the thermocline and replenished the photic layer with nutrients concomitant niche differentiation in the photic layer progressively stimulated morphological innovation amongst early cenozoic planktonic foraminifers the final return of normally sized planktonic foraminifers and of stable and well balanced dinoflagellate cyst associations at about 125 kyr after the k t boundary seems to indicate that primary productivity and niche differentiation in the photic layer begin to revert to optimum levels the earliest cenozoic planktonic foraminiferal species globoconusa minutula and parvularugoglobigerina fringa are thought to have developed from a benthic foraminiferal species rather than having a planktonic ancestry

age budget and dynamics of an active salt extrusion in iran the hormuz salt of kuh e namak iran began rising through its phanerozoic cover in jurassic times and had surfaced by cretaceous times in miocene times the still active zagros folds began to develop and the salt is still extruding to feed a massive topographic dome and two surface flows of salt which have previously been called salt glaciers but are here called namakiers two crude but independent estimates for the rate of salt extrusion and loss are shown to balance the salt budget if the current salt dynamics are assumed to be in steady state first to replace the extrusive salt likely to be lost in solution in the annual rainfall the salt must rise at an average velocity of about 11 cm a second the foliation pattern shows that the extruding and partially dissolved salt column spreads under its own weight the maximum height of the salt dome is consistent with a viscous fluid with a viscosity of 2 6 x 1017 poises extruding from its orifice at a rate of almost 17 cm a k both estimates are consistent in indicating that salt can extrude onto the surface 42 85 times faster than the average long term rate at which salt diapirs rise to the surface the structure fabrics textures and deformation mechanisms of the impure halite all change along the path of the extrusive salt from the dome down the length of both namakiers such changes tend to occur when the flowing salt encounters changes in its boundary conditions and the recognition of buried namakiers is discussed in the light of such observations episodes of salt flow at a rate of 0 5 m per day have been measured along the margin of the n namakier after significant rain showers such brief episodes of rapid flow alternate with long periods when the namakier is dry and stationary the shape of the colour bands cropping out on the n namakier indicate that the flow over the surface of impure salt with a mylonitic texture obeys a power law with n 3 although the reported annual rainfall has the potential of dissolving both namakiers in about 2000 years a superimposed thin marine cover may protect static parts of them for as long as 30 000 to 300 000 years

shapes of venusian pancake domes imply episodic emplacement and silicic composition the main evidence available for constraining the composition of the large circular pancake domes on venus is their gross morphology laboratory simulations using polyethylene glycol show that the height to diameter aspect ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic with more episodes leading to greater cooling and taller domes thus without observations of their emplacement the compositions of venusian domes cannot be uniquely constrained by their morphology however by considering a population of 51 venusian domes to represent a sampling of many stages during the growth of domes with comparable histories and by plotting aspect ratio versus total volume we find that the shapes of the domes are most consistent with episodic emplacement on earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition strengthening earlier inferences about the presence of evolved magmas on venus

effects of eruption history and cooling rate on lava dome growth to better understand the factors controlling the shapes of lava domes laboratory simulations measurements from active and prehistoric flows and dimensional analysis were used to explore how effusion history and cooling rate affect the final geometry of a dome fifty experiments were conducted in which a fixed volume of polyethylene glycol wax was injected into a tank of cold sucrose solution either as one continuous event or as a series of shorter pulses separated by repose periods when the wax cooling rates exceeded a critical minimum value the dome aspect ratios height diameter increased steadily with erupted volume over the course of a single experiment and the rate at which height increased with volume depended linearly on the time averaged effusion rate thus the average effusion rate could be estimated from observations of how the dome shape changed with time our experimental results and dimensional analyses were compared with several groups of natural lava flows the recently emplaced mount st helens and soufriere domes which had been carefully monitored while active three sets of prehistoric rhyolite domes that varied in eruptive style and shape and two sets of holocene domes with similar shapes but different compositions geometric measurements suggest that dome morphology can be directly correlated with effusion rate for domes of similar composition from the same locality and that shape alone can be related to a dimensionless number comparing effusion rate and cooling rate extrapolation to the venusian pancake domes suggests that they formed from relatively viscous lavas extruded either episodically or at average effusion rates low enough to allow solidified surface crust to exert a dominating influence on the final morphology

palynological indicators of palaeoenvironmental perturbations in the basque cantabrian basin during the latest cretaceous zumaia northern spain abstract the latest cretaceous palynological assemblages from the southern margin of the basque cantabrian basin northern spain zumaia are dominated by black opaque equidimensional phytoclasts black opaque blade shaped phytoclasts and translucent gold orange to brown phytoclasts deep water dinoflagellate cysts cannosphaeridium utinensis and pterodinium spp constitutes a part of the assemblages throughout the whole succession this record and previous study suggest deposition of the zumaia section in the marine bathyal conditions in relative close proximity to the land palynofacies analyses yields increased abundance of leiosphaeridia spp and some changes in the palynomorph proportions just before the significant lithological change near the lower upper maastrichtian this signal may either be primary and record an environmental change or taphonomic nevertheless environmental interpretation of the upper maastrichtian palynological assemblage seems to be more consistent with the late maastrichtian marine regression and in consequence a reduction of the distance from the nearby land such conditions may have caused transport of leiosphaerids from shallower water sites

subsidence history and continental margin evolution of the western pyrenean and basque basins abstract we have studied cretaceous sedimentary sequences of four sedimentary basins along the european and north iberian continental margins of the western pyrenean realm and the basque basin the depression intermediaire sare vera basin and ulzama basin in the western pyrenees and the zumaya basin along the southern margin of the bay of biscay the formation of these basins was largely due to upper cretaceous sinistral strike slip tectonics during iberian plate motion resulting in wrench basins oblique slip and pull apart basins a detailed biostratigraphic framework and paleobathymetric calculations based on sedimentologic and benthic foraminiferal data were used to construct decompacted and backstripped subsidence history curves for each basin from these curves two major changes in subsidence history are apparent 1 increased subsidence since late albian and 2 decrease in subsidence and or initial uplift since early campanian these changes are closely related to plate tectonic events namely spreading in the bay of biscay followed by european iberian plate convergence

multitemporal alsm change detection sediment delivery and process mapping at an active earthflow remote mapping and measurement of surface processes at high spatial resolution is among the frontiers in earth surface process research remote measurements that allow meter scale mapping of landforms and quantification of landscape change can revolutionize the study of landscape evolution on human timescales at mill gulch in northern california usa an active earthflow was surveyed in 2003 and 2007 by airborne laser swath mapping alsm enabling meter scale quantification of landscape change we calculate four year volumetric flux from the earthflow and compare it to long term catchment average erosion rates from cosmogenic radionuclide inventories from adjacent watersheds we also present detailed maps of changing features on the earthflow from which we can derive velocity estimates and infer dominant process these measurements rely on proper digital elevation model dem generation and a simple surface matching technique to align the multitemporal data in a manner that eliminates systematic error in either dataset the mean surface elevation of the earthflow and an opposite slope that was directly influenced by the earthflow decreased 14 1 mm yr from 2003 to 2007 by making the conservative assumption that these features were the dominant contributor of sediment flux from the entire mill gulch drainage basin during this time interval we calculate a minimum catchment averaged erosion rate of 0 30 0 02 mm yr analysis of beryllium 10 10be concentrations in fluvial sand from nearby russian gulch and the south fork gualala river provide catchment averaged erosion rates of 0 21 0 04 and 0 23 0 03 mm yr respectively from translated landscape features we can infer surface velocities ranging from 0 5 m yr in the wide upper source portion of the flow to 5 m yr in the narrow middle transport portion of the flow this study re affirms the importance of mass wasting processes in the sediment budgets of uplifting weak lithologies copyright 2011 john wiley sons ltd

characterization of late campanian and maastrichtian planktonic foraminiferal depth habitats and vital activities based on stable isotopes abstract depth habitats of 56 late cretaceous planktonic foraminiferal species from cool and warm climate modes were determined based on stable isotope analyses of deep sea samples from the equatorial pacific dsdp sites 577a and 463 and south atlantic dsdp site 525a the following conclusions can be reached planoglobulina multicamerata de klasz and heterohelix rajagopalani govindan occupied the deepest plankton habitats followed by abathomphalus mayaroensis bolli globotruncanella havanensis voorwijk gublerina cuvillieri kikoine and laeviheterohelix glabrans cushman also at subthermocline depth most keeled globotruncanids and possibly globigerinelliodes and racemiguembelina species lived at or within the thermocline layer heterohelix globulosa ehrenberg and rugoglobigerina pseudotextularia and planoglobulina occupied the subsurface depth of the mixed layer and pseudoguembelina species inhabited the surface mixed layer however depth ranking of some species varied depending on warm or cool climate modes and late campanian or maastrichtian age for example most keeled globotruncanids occupied similar shallow subsurface habitats as rugoglobigerina during the warm late campanian but occupied the deeper thermocline layer during cool climatic intervals two distinct types of vital effect mechanisms reflecting photosymbiosis and respiration effects can be recognized by the exceptional 13c signals of some species 1 photosymbiosis is implied by the repetitive pattern of relatively enriched 13c values of racemiguembelina strongest planoglobulina rosita and rugoglobigerina species pseudoguembelina excolata weakest 2 enriched respiration 12c products are recognized in a mayaroensis gublerina acuta de klasz and heterohelix planata cushman isotopic trends between samples suggest that photosymbiotic activities varied between localities or during different climate modes and may have ceased under certain environmental conditions the appearance of most photosymbiotic species in the late maastrichtian suggests oligotrophic conditions associated with increased water mass stratification

paleo oxygenation in tertiary epeiric seas evidence from dinoflagellate cysts the dinoflagellate cyst record from an epeiric setting in the oligocene of southwest germany exhibits major changes associated with variations in paleo oxygenation inferred from benthic foraminifera dinoflagellate cyst diversity and equitability strongly decline in the case of extreme oxygen depletion the relative abundance of the dinoflagellate cyst thalassiphora pelagica inversely correlates with the availability of benthic oxygen the t pelagica spectrum consists of different morphotypes which are considered to represent different stages within the cystal part of the t pelagica life cycle following the concept of benedek and gocht the distribution of these morphotypes is also linked to oxygen availability horizons with highest t pelagica abundances are characterized by the occurrence of t pelagica specimens representing an early stage in cyst formation a model is proposed that uses t pelagica as a proxy to assess oxygenation both at the sediment surface and in the water column the occurrence of t pelagica specimens representing an early stage in cyst formation is interpreted to reflect the extension of oxygen depletion upwards into the water column because t pelagica is an easily recognized globally distributed element of paleogene and early neogene dinoflagellate cyst assemblages the application of this model may be of importance in the reconstruction of paleo oxygenation in epeiric settings from these times its sensitivity to changes in benthic oxygenation can be as high as if not higher than that of the approach based on foraminifera moreover it is applicable to decalcified sediments

radar topography of domes on planetary surfaces abstract we investigate the possibility of measuring the heights and morphology of viscously emplaced domes using radar imagery we accurately reproduce the known height and shape of a terrestrial salt dome and estimate the heights of several venusian pancake domes to within a factor of two the terrestrial salt dome is consistent with a bingham flow while the much larger venusian pancake domes are consistent with a newtonian flow applying the same techniques to ganesa macula a potential cryovolcanic dome on titan we estimate a height between 2 0 4 9 km additional factors such as variable roughness and composition might account for some of the discrepancies observed

quantifying geomorphic change at ephemeral stream restoration sites using a coupled model approach abstract rock detention structures are used as restoration treatments to engineer ephemeral stream channels of southeast arizona usa to reduce streamflow velocity limit erosion retain sediment and promote surface water infiltration structures are intended to aggrade incised stream channels yet little quantified evidence of efficacy is available the goal of this 3 year study was to characterize the geomorphic impacts of rock detention structures used as a restoration strategy and develop a methodology to predict the associated changes we studied reaches of two ephemeral streams with different watershed management histories one where thousands of loose rock check dams were installed 30 years prior to our study and one with structures constructed at the beginning of our study the methods used included runoff sediment transport and geomorphic modelling and repeat terrestrial laser scanner tls surveys to map landscape change where discharge data were not available event based runoff was estimated using kineros2 a one dimensional kinematic wave runoff and erosion model discharge measurements and estimates were used as input to a two dimensional unsteady flow and sedimentation model nays2dh that combined a gridded flow transport and bed and bank simulation with geomorphic change through comparison of consecutive dems the potential to substitute uncalibrated models to analyze stream restoration is introduced we demonstrate a new approach to assess hydraulics and associated patterns of aggradation and degradation resulting from the construction of check dams and other transverse structures notably we find that stream restoration using rock detention structures is effective across vastly different timescales

morphodynamic signatures of braiding mechanisms as expressed through change in sediment storage in a gravel bed river previous flume based research on braided channels has revealed four classic mechanisms that produce braiding central bar development chute cutoff lobe dissection and transverse bar conversion the importance of these braiding mechanisms relative to other morphodynamic mechanisms in shaping braided rivers has not yet been investigated in the field here we exploit repeat topographic surveys of the braided river feshie uk to explore the morphodynamic signatures of different mechanisms of change in sediment storage our results indicate that when combined the four classic braiding mechanisms do indeed account for the majority of volumetric change in storage in the study reach 61 total chute cutoff traditionally thought of as an erosional braiding mechanism appears to be the most common braiding mechanism in the study river but was more the result of deposition during the construction of diagonal bars than it was the erosion of the chute three of the four classic mechanisms appeared to be largely net aggradational in nature whereas secondary mechanisms including bank erosion channel incision and bar sculpting were primarily net erosional although the role of readily erodible banks in facilitating braiding is often conceptualized we show that bank erosion is as or more important a mechanism in changes in sediment storage than most of the braiding mechanisms and is the most important secondary mechanism 17 of total change the results of this study provide one of the first field tests of the relative importance of braiding mechanisms observed in flume settings

cassini radar views the surface of titan the cassini titan radar mapper imaged about 1 of titan s surface at a resolution of 0 5 kilometer and larger areas of the globe in lower resolution modes the images reveal a complex surface with areas of low relief and a variety of geologic features suggestive of dome like volcanic constructs flows and sinuous channels the surface appears to be young with few impact craters scattering and dielectric properties are consistent with porous ice or organics dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons

combined micro fourier transform infrared ftir spectroscopy and micro raman spectroscopy of proterozoic acritarchs a new approach to palaeobiology abstract micro scale analytical techniques permit correlation of chemistry with morphology of individual proterozoic acritarchs organic walled microfossils and thus provide new approaches for elucidating their biological affinities a combination of micro fourier transform infrared ftir spectroscopy and laser micro raman spectroscopy was used to investigate the organic structure and composition of individual acritarchs well preserved neoproterozoic acritarchs from the tanana formation australia ca 590 565 ma and mesoproterozoic acritarchs from the roper group 1 5 1 4 ga australia and ruyang group china 1 4 1 3 ga age poorly resolved but certainly 1000 ma and h stretching bands in the 2900 cm 1 region relative to the c c aromatic ring stretching band at 1600 cm 1 this ftir spectrum is consistent with the ftir spectra obtained from algaenans isolated from extant chlorophyte and eustigmatophyte microalgae ftir spectra of leiosphaeridia sp from the tanana formation contain a less intense aliphatic c h stretching band relative to the c c aromatic ring stretching band by comparison the spectra acquired from the mesoproterozoic acritarchs were dominated by c c aromatic ring stretching bands at 1600 cm 1 relative to moderate weak ch3 terminal groups 1345 cm 1 c h aliphatic stretching 3000 2700 cm 1 and c o 1710 cm 1 although some differences in biopolymer composition occurred between species curve fitting of the aliphatic c hx stretching region provides greater insight into the aliphatic structures of the acritarchs the ch2 ch3 intensity ratio can be used to assess the relative chain length and degree of branching organic material in the tanarium conoideum consists of straight long chain hydrocarbons while the other acritarchs contain hydrocarbons consisting of short chains that are highly branched in this study it was found that raman spectroscopy does not provide additional information about biopolymer composition of proterozoic acritarchs but rather offers complementary data regarding the aromaticity and degree of saturation of the macromolecular structure of acritarch cysts

cryovolcanic emplacement of domes on europa abstract here we explore the hypothesis that certain domes on europa may have been produced by the extrusion of viscous cryolavas a new mathematical method for the emplacement and relaxation of viscous lava domes is presented and applied to putative cryovolcanic domes on europa a similarity solution approach is applied to the governing equation for fluid flow in a cylindrical geometry and dome relaxation is explored assuming a volume of cryolava has been rapidly emplaced onto the surface nonphysical singularities inherent in previous models for dome relaxation have been eliminated and cryolava cooling is represented by a time variable viscosity we find that at the onset of relaxation bulk kinematic viscosities may lie in the range between 103 and 106 m2 s while the actual fluid lava viscosity may be much lower plausible relaxation times to form the domes which are linked to bulk cryolava rheology are found to range from 3 6 days to 7 5 years we find that cooling of the cryolava while dominated by conduction through an icy skin should not prevent fluids from advancing and relaxing to form domes within the timescales considered determining the range of emplacement conditions for putative cryolava domes will shed light on europa s resurfacing history in addition the rheologies and compositions of erupted cryolavas have implications for subsurface cryomagma ascent and local surface stress conditions on europa

hydrovolcanic tuff rings and cones as indicators for phreatomagmatic explosive eruptions on mars hydrovolcanism is a common natural phenomenon on earth and should be common on mars too since its surface shows widespread evidence for volcanism and near surface water we investigate fields of pitted cones in the nephentes amenthes region at the southernmargin of the ancient impact basin utopia which were previously interpreted as mud volcanoes the cone fields contain pitted and breached cones with associated outgoing flow like landforms based on stratigraphic relations we determined ahesperian or youngermodel age we test the hypothesis of a hydro volcanic origin based on a detailed morphological and morphometrical analysis and an analysis of the regional context an igneous volcanic origin of these cones as hydrovolcanic edifices produced by phreatomagmatic eruptions is plausible several lines of evidence suggest the existence of subsurface water ice the pitted cones display well developed wide central craters with floor elevations below the preeruptive surface their morphometry and the overall appearance are analogous to terrestrial tuff cones and tuff rings mounds that are also observed in the same region resemble terrestrial lava domes the hydrovolcanic interaction between ascending magma and subsurface water and or water ice may explain the formation of the pitted cones although other scenarios such as mud volcanism cannot be ruled out together with the mounds the cones might represent effusive and explosive edifices of amonogenetic volcanic field composed of lava domes tuff rings tuff cones and possibly maars

methodological sensitivity of morphometric estimates of coarse fluvial sediment transport abstract the estimation of fluvial sediment transport rate from measurements of morphological change has received growing recent interest the revival of the morphological method reflects continuing concern over traditional methods of rate determination but also the availability of new survey methods capable of high precision high resolution topographic monitoring remote sensing of river channels through aerial digital photogrammetry is a potentially attractive alternative to labour intensive ground surveys however while photogrammetry presents the opportunity to acquire survey data over large areas data precision and accuracy particularly in the vertical dimension are lower than in traditional ground survey methods this paper presents results of recent research in which digital elevation models dems have been developed for a reach of a large braided gravel bed river in scotland using both digital photogrammetry and high resolution rtk gps ground surveys a statistical level of change detection is assessed by comparing surfaces with independent check points the methodological sensitivity of the annual channel sediment budget 1999 2000 to the threshold is presented results suggest that while the remote survey methods employed here can be used to develop qualitatively convincing moderate precision dems of channel topography rmse 0 21 m the remaining errors imply significant limits on reliable change detection which lead to important information losses tests at a 95 confidence interval for change detection show that over 60 of channel deposition and 40 of erosion may be obscured by the lower level of precision associated with photogrammetric monitoring when compared to ground survey measurements this bias reflects the difficulty of detecting the topographic signature of widespread but shallow deposition on bar tops

the unique radar properties of silicic lava domes 1 silicic lava domes exhibit distinct morphologic characteristics at scales of centimeters to kilometers multiparameter radar observations capture the unique geometric signatures of silicic domes in a set of radar scattering properties that are unlike any other natural geologic surfaces backscatter cross section values are among the highest observed on terrestrial lava flows and show only a weak decrease with incidence angle cross polarization backscatter hv shows a unique behavior increasing with increasing wavelength circular polarization ratios are relatively high in the 0 3 0 95 range and increase with increasing wavelength field measurements of boulder size frequency distributions and microtopography indicate that silicic dome surfaces are among the roughest ever measured rms heights at a 1 m lateral scale range from 13 cm to 50 cm rms slopes at 1 m spacing range from 12 to 43 degrees modeling of the scattering behavior suggests it results from a combination of rough surface facet scattering and scattering from block edges that act as a random collection of dipoles the unusual wavelength dependence of the radar parameters appears to result from a higher component of edge scattering at large wavelengths producing for example higher cross polarized backscatter at p band 68 cm steep sided volcanic domes on venus superficially resemble terrestrial silicic domes in plan view gross morphology but few similarities remain when the radar scattering and three dimensional shapes of the features are compared the unique radar scattering properties suggest that such volcanic surfaces can be identified with multiparameter radar observations in future planetary radar missions and in active terrestrial volcanoes where dome development can represent serious hazards

effects of check dams reforestation and land use changes on river channel morphology case study of the rogativa catchment murcia spain this work has been financially supported by the project respuesta hidrologica y geomorfologica de los sistemas fluvio torrenciales afectados por proyectos de restauracion hidrologico forestal en cuencas semiaridas del sureste peninsular of the fundacion instituto euromediterraneo de hidrotecnia ce the first author was financially supported by an i3p postdoc contract csic ce and a ramon y cajal contract from the education and science ministry spain gonzalo g barbera also was supported by i3p postdoc contract

clay mineralogical and geochemical expressions of the late campanian event in the aquitaine and paris basins france palaeoenvironmental implications campanian sediments from two french sedimentary basins were studied using clay mineralogy and stable isotope 13c and 18o geochemistry in order to investigate the late campanian event the clay fraction of the campanian sediments from the tercis les bains section aquitaine basin and from the poigny borehole paris basin is mainly composed of smectite this background sedimentation was however interrupted during the upper campanian in the two basins by a substantial increase in detrital inputs including illite kaolinite and chlorite at tercis les bains and illite at poigny this detrital event resulting from the enhanced erosion of nearby continental areas triggered by increasing runoff has also been recognized in the tethys and south atlantic oceans it coincided with a global negative carbon isotope excursion the late campanian event lce carbon isotope stratigraphy was used to correlate the two basins with previously studied sections from distant areas spectral analysis of the bulk 13c from tercis les bains suggests a duration of ca 400 kyr for a pre lce negative excursion and ca 800 900 kyr for the lce sensu stricto the detrital event as characterized by clay mineralogy spans the interval that comprises the pre lce and the lce with a duration of 1 3 myr intensification of continental erosion during the lce may have resulted either from the late campanian polyplocum regression and or from a regional tectonic pulse that triggered the emersion of previous submerged shelf areas and the increase of silicate erosion as the lce seems to be recorded at a large geographic scale it is proposed here that enhanced chemical weathering and an associated decrease in atmospheric pco2 levels could have contributed to the long term late cretaceous cooling trend

evidence for amazonian highly viscous lavas in the southern highlands on mars we have identified small scale volcanic edifices two cones and three domes with associated flows within terra sirenum a region situated in the martian southern highlands based on thermal morphological and morphometrical properties and the determination of absolute model ages we conclude that these features were formed by volcanic activity of viscous lavas in the mid amazonian epoch relatively recently in martian history if our hypothesis is correct this small volcanic field represents rare evidence of young volcanic activity in the martian highlands in which martian equivalents of terrestrial lava domes and coulees might be present on earth such landforms are usually formed by highly viscous evolved lavas i e andesitic to rhyolitic for which observational evidence is sparse on mars hence this field might be one of only a few where martian evolved lavas might be investigated in detail

dinoflagellate based sea surface temperature reconstructions across the cretaceous tertiary boundary abstract quantitative analysis of organic walled dinoflagellate cyst dinocyst assemblages from closely spaced samples across the cretaceous tertiary boundary ktb at el kef nw tunisia caravaca se spain and stevns klint e denmark allows for reconstructions of sea surface temperature sst trends the combined dinocyst based sst curves indicate relatively stable warm conditions during the latest maastrichtian in contrast to strongly fluctuating and on average cooler conditions during the earliest danian in detail the results indicate cooling across the ktb immediately followed by an interval of pronounced warming the latter recorded in all studied sections two more cooling pulses may be recognized in the overlying interval followed by a gradual return to stable relatively warm conditions our data furthermore show that these ktb related climatic changes invoked distinct migration among organic walled cyst producing dinoflagellates a group not pushed to extinction at the ktb recordable in both hemispheres recent models predict periods varying between several months to 8 13 yr of global cooling impact winter and reduced solar transmission as a direct result of the chicxulub ktb impact followed by relatively long term excess co 2 related global warming our results are in line with such models but suggest that the impact related cooling phase may have lasted longer and that marked climatic instability continued to some 100 000 yrs following the ktb event s

submarine analogs to venusian pancake domes abstract the morphology and dimensions of the largediameter steep sided flat topped pancake domes on venusmake them unlike any type of terrestrial subaerial volcano comparisons between images of hawaiian seamounts andpancake domes show similarities in shapes and secondaryfeatures the morphometry of pancake domes is closer to thatof pacific seamounts than subaerial lava domes consideringboth morphology and morphometry seamounts seem a betteranalog to the pancake domes the control of volatileexsolution by pressure on venus and the seafloor can causelavas to have similar viscosities and densities although thelatter will be counteracted by high buoyancy underwater however analogous effects of the venusian and seafloorenvironments alone are probably not sufficient to producesimilar volcanoes rather venusian lavas of variouscompositions may behave like basalt on the seafloor ifappropriate rates and modes of extrusion and planetary thermalstructure are a so considered introduction

the sand seas of titan cassini radar observations of longitudinal dunes the most recent cassini radar images of titan show widespread regions up to 1500 kilometers by 200 kilometers of near parallel radar dark linear features that appear to be seas of longitudinal dunes similar to those seen in the namib desert on earth the ku band 2 17 centimeter wavelength images show 100 meter ridges consistent with duneforms and reveal flow interactions with underlying hills the distribution and orientation of the dunes support a model of fluctuating surface winds of 0 5 meter per second resulting from the combination of an eastward flow with a variable tidal wind the existence of dunes also requires geological processes that create sand sized 100 to 300 micrometer particulates and a lack of persistent equatorial surface liquids to act as sand traps

distribution and interplay of geologic processes on titan from cassini radar data abstract the cassini titan radar mapper is providing an unprecedented view of titan s surface geology here we use synthetic aperture radar sar image swaths ta t30 obtained from october 2004 to december 2007 to infer the geologic processes that have shaped titan s surface these sar swaths cover about 20 of the surface at a spatial resolution ranging from 350 m to 2 km the sar data are distributed over a wide latitudinal and longitudinal range enabling some conclusions to be drawn about the global distribution of processes they reveal a geologically complex surface that has been modified by all the major geologic processes seen on earth volcanism tectonism impact cratering and erosion and deposition by fluvial and aeolian activity in this paper we map geomorphological units from sar data and analyze their areal distribution and relative ages of modification in order to infer the geologic evolution of titan s surface we find that dunes and hummocky and mountainous terrains are more widespread than lakes putative cryovolcanic features mottled plains and craters and crateriform structures that may be due to impact undifferentiated plains are the largest areal unit their origin is uncertain in terms of latitudinal distribution dunes and hummocky and mountainous terrains are located mostly at low latitudes less than 30 with no dunes being present above 60 channels formed by fluvial activity are present at all latitudes but lakes are at high latitudes only crateriform structures that may have been formed by impact appear to be uniformly distributed with latitude but the well preserved impact craters are all located at low latitudes possibly indicating that more resurfacing has occurred at higher latitudes cryovolcanic features are not ubiquitous and are mostly located between 30 and 60 north we examine temporal relationships between units wherever possible and conclude that aeolian and fluvial pluvial lacustrine processes are the most recent while tectonic processes that led to the formation of mountains and xanadu are likely the most ancient

late cretaceous to late eocene palaeogeographic evolution of southwest europe abstract a synthesis of personal research concerning the peri pyrenean region and previously published data is presented as a series of palaeogeographic reconstructions subsequent to the progressive regression at the end of the cretaceous the sea invaded three times parts of the earlier senonian marine domain on both sides of the eastern palaeo pyrenees pre cuisian climatic rewarming combined with cuisian continental epeirogenic deformations resulted in major biogeographic modifications during the cuisian local tectonics forced the sea from the northern pyrenean basin whereas in the southern pyrenean basin the sea retreated much later as a consequence of the pyrenean tectonic phase however the pyrenean tectogenesis seems to have affected a much larger region including the alps shoreline migrations are compared and related to the geodynamic behaviour of the meridional and septentrional european provinces in order to distinguish between tectonic and eustatic causes

venus topography and kilometer scale slopes during the first 8 months of the magellan mission the radar altimeter has made some three million measurements of the surface of venus covering the latitude range from 85 n to 80 s methods involving range correlation doppler filtering multi burst summation and range migration are used to focus the observations and to achieve high surface resolution results are presented as maps of the global distribution of topography meter scale roughness and power reflection coefficient the results are similar to those reported in previous experiments surface heights exhibit a unimodal distribution with more than 80 of the surface lying within 1 km of the 6051 84 km mean radius but the higher resolution of the magellan altimeter has disclosed several surprisingly steep features e g the southwest face of the maxwell montes the southern face of the danu montes and the chasmata to the east of thetis regio where average kilometer scale slopes of greater than 30 are not uncommon this conclusion is corroborated by close inspection of synthetic aperture radar imagery

oxygen as a factor controlling palynological record an example from the cenomanian turonian transition in the rybie section polish carpathians abstract palynology constitutes a useful tool for biostratigraphical and palaeoenvironmental analyses and is commonly used in academic and applied research however the palynological signal can be significantly influenced by both intra and post depositional oxidizing processes to estimate the dependence of the palynological record on the oxygen level near the sediment water interface the palynofacies have been analysed from shale and marlstone of the cenomanian turonian c t transition in the rybie section carpathians poland and correlated to previously obtained ichnological record and interpretation the results show abrupt and intense palynofacies fluctuations from samples rich in organic matter to almost barren only the short middle to upper cenomanian interval yields well preserved and diversified organic walled dinoflagellate cysts the whole section reflects palaeoenvironmental fluctuations within a deep water basin including mesotrophic conditions and environment deterioration interval 1 extreme oligotrophic conditions hyperoligotrophy influencing oxydation of organic matter interval 2 reduction of oxygen content enhanced organic productivity increased production of organic carbon and deposition of amorphous organic matter bonarelli level comprising the late cenomanian oceanic anoxic event oae 2 rapid increase in oxygenation above the bonarelli level interval 3 the hyperoligotrophy recorded within the interval 2 is likely associated with the plenus cold event and coeval enhanced oxygenation of bottom waters prior to the oae 2 the results yield the enhanced environmental fluctuations near the c t transition and emphasise the sensibility of palynological record to near bottom oxygen content

early maastrichtian carbon cycle perturbation and cooling event implications from the south atlantic ocean published stable isotope records in marine carbonate are characterized by a positive 18o excursion associated with a negative 13c shift during the early maastrichtian however the cause and even the precise timing of these excursions remain uncertain we have generated high resolution foraminiferal stable isotope and grey scale records for the latest campanian to early maastrichtian 73 68 ma at two ocean drilling program sites 525 walvis ridge and 690 weddell sea we demonstrate that the negative 13c excursion is decoupled from the 18o increase with a lag of about 600 kyr our 13c records both planktic and benthic show an amplitude for the negative excursion of 0 7 that falls between about 72 1 and 70 7 ma our planktic 18o records indicate an overall increase of 1 2 from 73 to 68 ma at site 690 whereas at site 525 they record a slightly smaller increase 1 that peaks around 70 1 ma with decreasing values thereafter our benthic 18o data indicate an increase of 1 5 at site 525 and 0 7 at site 690 between about 71 4 and 69 9 ma benthic 18o values show different baseline values at the two sites before and after the excursion but the larger increase at site 525 means that the values attained at the peak of the excursion are similar at the two sites we interpret this observation in terms of water mass changes the excursion is interpreted to reflect a cooling of bottom waters in response to the strengthening contribution of intermediate to deep water production in the high southern latitudes rather than increased ice volume the associated carbon cycle perturbations that we observe are interpreted to reflect a weakening of surface water stratification and increased productivity as supported by our grey value data

the geomorphic effectiveness of a large flood on the rio grande in the big bend region insights on geomorphic controls and post flood geomorphic response abstract since the 1940s the rio grande in the big bend region has undergone long periods of channel narrowing which have been occasionally interrupted by rare large floods that widen the channel termed a channel reset the most recent channel reset occurred in 2008 following a 17 year period of extremely low stream flow and rapid channel narrowing flooding was caused by precipitation associated with the remnants of tropical depression lowell in the rio conchos watershed the largest tributary to the rio grande floodwaters approached 1500 m 3 s between a 13 and 15 year recurrence interval and breached levees inundated communities and flooded the alluvial valley of the rio grande the wetted width exceeding 2 5 km in some locations the 2008 flood had the 7th largest magnitude of record however conveyed the largest volume of water than any other flood because of the narrow pre flood channel conditions record flood stages occurred we used pre and post flood aerial photographs channel and floodplain surveys and 1 dimensional hydraulic models to quantify the magnitude of channel change investigate the controls of flood induced geomorphic changes and measure the post flood response of the widened channel these analyses show that geomorphic changes included channel widening meander migration avulsions extensive bar formation and vertical floodplain accretion reach averaged channel widening between 26 and 52 occurred but in some localities exceeded 500 the degree and style of channel response was related but not limited to three factors 1 bed load supply and transport 2 pre flood channel plan form and 3 rapid declines in specific stream power downstream of constrictions and areas of high channel bed slope the post flood channel response has consisted of channel contraction through the aggradation of the channel bed and the formation of fine grained benches inset within the widened channel margins the most significant post flood geomorphic changes have occurred at and downstream from ephemeral tributaries that contribute large volumes of sediment

mountains on titan observed by cassini radar abstract the cassini titan radar mapper has observed elevated blocks and ridge forming block chains on saturn s moon titan demonstrating high topography we term mountains summit flanks measured from the t3 february 2005 and t8 october 2005 flybys have a mean maximum slope of 37 and total elevations up to 1930 m as derived from a shape from shading model corrected for the probable effects of image resolution mountain peak morphologies and surrounding diffuse blankets give evidence that erosion has acted upon these features perhaps in the form of fluvial runoff possible formation mechanisms for these mountains include crustal compressional tectonism and upthrusting of blocks extensional tectonism and formation of horst and graben deposition as blocks of impact ejecta or dissection and erosion of a preexisting layer of material all above processes may be at work given the diversity of geology evident across titan s surface comparisons of mountain and blanket volumes and erosion rate estimates for titan provide a typical mountain age as young as 20 100 million years

radar scattering properties of steep sided domes on venus abstract more than 100 quasi circular steep sided volcanic domes with diameters ranging from 6 to 60 km have been observed on the surface of venus by the magellan radar mapper assuming that they have the shape of a solidified high viscosity newtonian fluid their radar scattering properties can be studied in detail from magellan images since a typical radar swath resolves each dome into several tens of thousands of measurements of radar cross section at incidence angles varying from 15 to 55 through examination of 20 domes in detail it appears that many of those situated on lava plains scatter radar in a manner that is indistinguishable from that of the surrounding material suggesting that either 1 they were formed of a relatively high density high viscosity material e g andesite rather than a lower density one e g rhyolite or dacite or 2 that their surfaces share a common origin with those of their surroundings e g through in situ weathering or aeolian deposition

disturbance stream incision and channel evolution the roles of excess transport capacity and boundary materials in controlling channel response abstract channel incision is part of denudation drainage network development and landscape evolution rejuvenation of fluvial networks by channel incision often leads to further network development and an increase in drainage density as gullies migrate into previously non incised surfaces large anthropogenic disturbances similar to large or catastrophic natural events greatly compress time scales for incision and related processes by creating enormous imbalances between upstream sediment delivery and available transporting power field examples of channel responses to antrhopogenic and natural disturbances are presented for fluvial systems in the mid continent and pacific northwest usa and central italy responses to different types of disturbances are shown to result in similar spatial and temporal trends of incision for vastly different fluvial systems similar disturbances are shown to result in varying relative magnitudes of vertical and lateral widening processes and different channel morphologies as a function of the type of boundary sediments comprising the bed and banks this apparent contradiction is explained through an analysis of temporal adjustments to flow energy shear stress and stream power with time numerical simulations of sand bed channels of varying bank resistance and disturbed by reducing the upstream sediment supply by half show identical adjustments in flow energy and the rate of energy dissipation the processes that dominate adjustment and the ultimate stable geometries however are vastly different depending on the cohesion of the channel banks and the supply of hydraulically controlled sediment sand provided by bank erosion the non linear asymptotic nature of fluvial adjustment to incision caused by channelization or other causes is borne out in similar temporal trends of sediment loads from disturbed systems the sediments emanating from incised channels can represent a large proportion of the total sediment yield from a landscape with erosion from the channel banks generally the dominant source disturbances that effect available force stream power or flow energy or change erosional resistance such that an excess of flow energy occurs can result in incision channel incision therefore can be considered a quintessential feature of dis equilibrated fluvial systems

the spreading of variable viscosity axisymmetric radial gravity currents applications to the emplacement of venusian pancake domes the magellan images of venus have revealed a number of intriguing volcanic features including the steep sided or pancake domes these volcanic domes or flows have morphologies that suggest formation by a single continuous emplacement of lava with a higher viscosity than that of the surrounding basaltic plains numerous investigators have suggested that such high viscosity is due to high silica content leading to the conclusion that the domes are evidence of evolved magmatic products on venus however viscosity depends on crystallinity as well as on silica content high viscosity could therefore also be due to a cooler and therefore higher crystal content lava models of dome emplacement which include both cooling and composition factors are thus necessary in order to determine the ranges of crystallinity and silica content which might lead to the observed gross dome morphologies accordingly in this study domes are modelled as radial viscous gravity currents with an assumed cooling induced viscosity increase to include both effects analytical and numerical results indicate that pancake dome formation is feasible with compositions ranging from basaltic to rhyolitic therefore observations of gross dome morphology alone are insufficient for determining composition and the domes do not necessarily represent strong evidence for evolved magmatism on venus

late cretaceous campanian carbon isotope events sea level change and correlation of the tethyan and boreal realms abstract carbon stable isotope stratigraphy provides unique insights into environmental change during the campanian the longest 83 5 71 3 ma but least well understood stage of the late cretaceous a new carbon isotope 13c profile for a 500 m thick campanian basal maastrichtian tethyan pelagic hemipelagic section near el kef northern tunisia is calibrated using data from a biostratigraphically well constrained succession at kalaat senan the general shapes of the tunisian 13c reference curve and published tethyan 13c profiles from elles tunisia and bidart sw france and a boreal curve for the trunch borehole eastern england are remarkably similar in all three areas a positive carbon isotope event of 0 2 13c in the mid campanian dated at 78 7 ma and a negative excursion of 0 4 in the upper campanian at 74 8 ma can be correlated between tunisia and england a positive excursion of 0 3 at 83 7 ma spans the santonian campanian boundary these isotope events enable precise inter regional correlations that are consistent with published nannofossil data review of campanian sea level data from north africa the middle east and northern europe indicates that major shifts in 13c profiles coincide with changes in eustatic sea level relatively stable 13c values in the lower campanian and their long term fall through the upper campanian reflect high and then falling eustatic sea levels and increased carbonate production short term 600 kyr positive excursions record greater organic productivity and or organic matter preservation and decreased carbonate fluxes during periods of rapid sea level rise and the drowning of carbonate platforms excursions were terminated by falling nutrient supply and increased carbonate deposition associated with epicontinental sea expansion and renewed carbonate platform growth during the late transgression and highstand negative excursions are linked principally to reworking of marine and terrestrial organic matter during rapid sea level fall carbon isotope stratigraphy is a powerful tool for correlation which can be used to test the validity of campanian global biostratigraphic frameworks and improve our understanding of the nature and timing of late cretaceous sea level change

secular variation in late cretaceous carbon isotopes a new δ13c carbonate reference curve for the cenomanian campanian 99 6 70 6 ma carbon stable isotope variation through the cenomanian santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven chalk successions in england the sections show consistent stratigraphic trends and 13c values that provide a basis for highresolution correlation positive and negative 13cexcursions and inflection points on the isotope profiles are used to define 72 isotope events key markers are provided by positive 13c excursions of up to 2 the albian cenomanianboundary event mid cenomanian event i thecenomanian turonian boundary event the bridgewick hitch wood and navigation events of late turonian age and the santonian campanian boundary event isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons an age calibrated composite 13c reference curve and an isotope event stratigraphy are constructed using data from the english chalk the isotope stratigraphy is applied to successions in germany france spain and italy correlation with pelagic sections at gubbio central italy demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the cenomanian turonian stages confirming established relationships between tethyan planktonic foraminiferal and boreal macrofossil biozonations correlation of the coniacian santonian stages is less clear cut magnetostratigraphic evidence for placing the base of chron 33r near the base of the upper santonian is in good agreement with the carbon isotope correlation but generates significant anomalies regarding the placement of the santonian and campanian stage boundaries with respect to tethyan planktonic foraminiferal and nannofossil zones isotope stratigraphy offers a more reliable criterion for detailed correlation of cenomanian santonian strata than biostratigraphy with the addition of campanian 13c data from one of the english sections a composite cenomanian campanian age calibrated reference curve is presented that can be utilized in future chemostratigraphic studies the cenomanian campanian carbon isotope curve is remarkably similar in shape to supposedly eustatic sea level curves increasing 13c values accompanying sea level rise associated with transgression and falling 13c values characterizing sea level fall and regression the correlation between carbon isotopes and sea level is explained by variations in epicontinental sea area affecting organic matter burial fluxes increasing shallow sea floor area and increased accommodation space accompanying sea level rise allowedmore efficient burial ofmarine organic matter with the preferential removal of 12c from the marine carbon reservoir during sea level fall reduced seafloor area marine erosion of previously deposited sediments and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter causing falling 13c values additionally drowning of carbonate platforms during periods of rapid sea level rise may have reduced the global inorganic relative to the organic carbon flux further enhancing 13c values while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition variations in nutrient supply changing rates of oceanic turnover and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon isotope ratios

stream bed stabilization using boulder check dams that mimic step pool morphology features in northern italy during the last 10 years the check dams made of boulders have been fully employed for torrent management particularly for high gradient stream stabilization the analysis of this typology is shown in relation to three aspects building features field of use and design according to geomorphologic principles the maso di spinelle torrent located in the province of trento italy north italian alps is an example where a sequence of low check dams made of boulders have been used for bed stabilization the design criteria are taken from the step pool morphology features and the results are encouraging for further applications the artificial step pool grade control structures in the maso di spinelle torrent have been successfully tested by floods events with return periods of about 7 10 and 20 25 years

cryovolcanic features on titan s surface as revealed by the cassini titan radar mapper abstract the cassini titan radar mapper obtained synthetic aperture radar images of titan s surface during four fly bys during the mission s first year these images show that titan s surface is very complex geologically showing evidence of major planetary geologic processes including cryovolcanism this paper discusses the variety of cryovolcanic features identified from sar images their possible origin and their geologic context the features which we identify as cryovolcanic in origin include a large 180 km diameter volcanic construct dome or shield several extensive flows and three calderas which appear to be the source of flows the composition of the cryomagma on titan is still unknown but constraints on rheological properties can be estimated using flow thickness rheological properties of one flow were estimated and appear inconsistent with ammonia water slurries and possibly more consistent with ammonia water methanol slurries the extent of cryovolcanism on titan is still not known as only a small fraction of the surface has been imaged at sufficient resolution energetic considerations suggest that cryovolcanism may have been a dominant process in the resurfacing of titan

cassini radar images at hotei arcus and western xanadu titan evidence for geologically recent cryovolcanic activity 1 images obtained by the cassini titan radar mapper radar reveal lobate flowlike features in the hotei arcus region that embay and cover surrounding terrains and channels we conclude that they are cryovolcanic lava flows younger than surrounding terrain although we cannot reject the sedimentary alternative their appearance is grossly similar to another region in western xanadu and unlike most of the other volcanic regions on titan both regions correspond to those identified by cassini s visual and infrared mapping spectrometer vims as having variable infrared brightness strengthening the case that these are recent cryovolcanoes citation wall s d et al 2009 cassini radar images at hotei arcus and western xanadu titan evidence for geologically recent cryovolcanic activity geophys res lett 36 l04203 doi 10 1029 2008gl036415

pyrenean orogeny and plate kinematics 1 the evolution of the pyrenees a mountain range between iberia and eurasia has remained the subject of many debates between geologists and geophysicists for a long time by combining the identification of seafloor spreading anomalies a33o to m0 in the bay of biscay with those in the north atlantic we have derived a position of a mean pole of rotation for the entire opening of the bay of biscay four hundred kilometers of shortening took place between the iberian and eurasian plates in the pyrenean domain during the opening of the bay of biscay from chrons m0 to a33o time 118 to 80 ma the deep seismic etude continentale et oceanique par reflexion et refraction sismique ecors profile shot across the pyrenees and teleseismic data show the presence of two distinct slabs which dip to the north the southern slab is linked to the subduction of the neo tethys ocean which was created from late jurassic to early aptian simultaneously elongated back arc basins formed along the future pyrenean domain this slab was active from at least 118 ma early aptian to 100 ma late albian the northern slab active since 85 ma is linked to the subduction of the lower continental crust located south of the pyrenean domain in the upper crust normal faults as well as the north pyrenean fault became reverse faults and former back arc basins were inverted giving rise to the uplift of the pyrenees as a double asymmetrical wedge