space weathered rims found on the surfaces of the itokawa dust particles on the basis of observations using cs corrected stem we identified three types of surface modification probably formed by space weathering on the surfaces of itokawa particles they are 1 redeposition rims 2 3 nm 2 composite rims 30 60 nm and 3 composite vesicular rims 60 80 nm these rims are characterized by a combination of three zones zone i occupies the outermost part of the surface modification which contains elements that are not included in the unchanged substrate minerals suggesting that this zone is composed of sputter deposits and or impact vapor deposits originating from the surrounding minerals redeposition rims are composed only of zone i and directly attaches to the unchanged minerals zone iii zone i of composite and composite vesicular rims often contains nanophase fe mg s the composite rims and the composite vesicular rims have a two layered structure a combination of zone i and zone ii below which zone iii exists zone ii is the partially amorphized zone zone ii of ferromagnesian silicates contains abundant nanophase fe radiation induced segregation and in situ reduction are the most plausible mechanisms to form nanophase fe in zone ii their lattice fringes indicate that they contain metallic iron which probably causes the reddening of the reflectance spectra of itokawa zone ii of the composite vesicular rims contains vesicles the vesicles in zone ii were probably formed by segregation of solar wind he implanted in this zone the textures strongly suggest that solar wind irradiation damage and implantation are the major causes of surface modification and space weathering on itokawa

establishing resolution limits for tectonic subsidence curves by forward basin modelling abstract a forward model was used to study the relationship between gravitational compaction and tectonic subsidence in an idealized one dimensional sedimentary basin gravitational compaction was modelled by a non linear partial differential equation that gives the sediment porosity as a function of time and burial depth the sediments were described in terms of soil mechanics laws for mechanical compressibility and permeability the sedimentation rate appeared as a boundary condition at the depositional surface tectonic subsidence was coupled to the compaction model via an isostatic balance based on airy s hypothesis parameter studies showed that changes in the sedimentation rate and in the sediment compressibility can lead to variations from 454 to 781 m in the subsidence for sediment thicknesses in the range 6 9 7 9 km the forward model was used to assess how well standard backstripping methods reconstructed subsidence history from present day porosity versus depth data standard backstripping can bias the tectonic subsidence by 100 200 m comparable with inferred eustatic variations this bias results because the porosity depends not only on burial depth but also on time by using deterministic models to describe gravitational compaction mechanical properties can be used to better constrain compaction history thus improving the accuracy of reconstructed tectonic subsidence curves

block distributions on itokawa abstract asteroid 25143 itokawa is a small elongated asteroid with two distinct parts the evolution of this two part body has been the source of speculation the scenarios for the formation of this asteroid include two body capture catastrophic disruption and rapid reaccretion yorp spin up and mass shedding and disruption or partial disruption with two body reaccretion in this paper we use the global and regional analyses of block populations and size frequency distributions as evidence of the probable evolutionary history of itokawa the block sample used in this study is believed to be complete for blocks of size 6 m and consists of a sample more than twice as large as previous known studies although block size frequency distributions hint at different evolutionary paths for the head and the body their differences are not statistically significant the distribution of blocks across each body provides clues as to the histories of each body the head is populated in a spherically symmetric fashion while the body has a distinct equatorial peak when considering that the head and the body may have been separate entities for a period of time and estimating a rotational axis using minimum rotational energy considerations the preferential equatorial distribution becomes even more pronounced we interpret this as excellent evidence for the partial disruption of a proto itokawa subsequent planarization of a debris field and reaccretion of the head and the body into its present configuration

craters boulders and regolith of 101955 bennu indicative of an old and dynamic surface small kilometre sized near earth asteroids are expected to have young and frequently refreshed surfaces for two reasons collisional disruptions are frequent in the main asteroid belt where they originate and thermal or tidal processes act on them once they become near earth asteroids here we present early measurements of numerous large candidate impact craters on near earth asteroid 101955 bennu by the osiris rex origins spectral interpretation resource identification and security regolith explorer mission which indicate a surface that is between 100 million and 1 billion years old predating bennu s expected duration as a near earth asteroid we also observe many fractured boulders the morphology of which suggests an influence of impact or thermal processes over a considerable amount of time since the boulders were exposed at the surface however the surface also shows signs of more recent mass movement clusters of boulders at topographic lows a deficiency of small craters and infill of large craters the oldest features likely record events from bennu s time in the main asteroid belt

sample collection from asteroid 162173 ryugu by hayabusa2 implications for surface evolution the near earth asteroid 162173 ryugu is thought to be a primitive carbonaceous object that contains hydrated minerals and organic molecules we report sample collection from ryugu s surface by the hayabusa2 spacecraft on 21 february 2019 touchdown images and global observations of surface colors are used to investigate the stratigraphy of the surface around the sample location and across ryugu latitudinal color variations suggest the reddening of exposed surface material by solar heating and or space weathering immediately after touchdown hayabusa2 s thrusters disturbed dark fine grains that originate from the redder materials the stratigraphic relationship between identified craters and the redder material indicates that surface reddening occurred over a short period of time we suggest that ryugu previously experienced an orbital excursion near the sun

studying solute and particulate sediment transfer in a small mediterranean mountainous catchment subject to land abandonment the sediment budget of the small research catchment of cal parisa vallcebre eastern pyrenees was studied by hydrological monitoring and assessment of the erosion rates in the major sediment sources this area is characterized by clayey mudrock prone to landsliding and badland erosion but the catchment was selected in an area free of major badland features as a representative of middle mountain regions where a system of terraces and drainage ditches had been built for agricultural use but is now abandoned streamwater chemistry is dominated by ca 2 and hco 3 at concentrations close to calcite saturation total dissolved solids show dilution during runoff peaks and positive hysteresis loops that support a slow contribution of subsurface water relative dissolved ion concentrations are different for each event analysed particulate sediment yield is very low and represents only about 1 per cent of gross erosion in the catchment mineralogical analysis of suspended sediments shows an enrichment in calcite because of precipitation chemical analysis of suspended sediments using common one litre water samples shows higher contents of ca p and mn in transported sediment than in sediment source areas attributed to the precipitation of calcite and enrichment in organic particulate matter during events respectively for the two first elements whereas enrichment in mn remains uncertain solid matter yield is therefore clearly dominated by dissolved transport as a result of both high calcium bicarbonate concentrations in runoff waters and strong suspended sediment conveyance discontinuities land conservation structures are very effective because they are in good condition whereas the soil is covered by dense permanent vegetation nevertheless this state is unstable because the network of drainage ditches needs maintenance its spontaneous breakdown after abandonment may result in the rearrangement of the elementary stream network and gullying of old fields in hollows 1997 john wiley sons ltd

irradiation of olivine by 4 kev he simulation of space weathering by the solar wind 1 we have studied the effects of 4 kev he ion irradiation on olivine while measuring in situ changes in the near infrared nir reflectance and in the chemical composition of the surface the observed changes in reflectance are reddening and the attenuation of the fe 3d absorption bands in the nir spectral reddening of irradiated olivine powder 45 m correlates with the amount of metallic iron formed by ion impact consistent with the idea that space weathering effects in the reflectance of olivine bearing s type asteroids are due to the formation of metallic iron the metallization rate of the powder is about half that of a sectioned rock of olivine which we propose is a consequence of redeposition of sputtered material the nir spectral changes observed in ion irradiation experiments are similar to those observed in our previous experiments on vapor redeposition indicating that different space weathering mechanisms can lead to similar final effects on reflectance finally we estimate that at 1 au the spectral reddening caused by the solar wind saturates approximately 2 orders of magnitude faster than comparable reddening caused by micrometeorite impacts

late quaternary history of the marmara sea and black sea from high resolution seismic and gravity core studies abstract lithologic and multi proxy paleoenvironmental data from 21 dated cores have been used to define three allostratigraphic units allounits within the late quaternary successions of the marmara sea and black sea allounits are bounded by unconformities and their correlative conformities in both regions allounit a extends from the seafloor downward to a 12 11 ka sequence boundary which is a major shelf crossing unconformity in water depths less than 100 110 m in deep basins of the marmara sea the lower part of allounit a designated subunit a2 is a laminated sapropel m1 on the shelf subunit a2 consists of backstepping delta lobes and early transgressive barrier islands and sand sheets allounit b has only been recovered in marmara sea cores collected at water depths greater than 90 m and represents basinal or prodeltaic deposition during the 23 12 ka late pleistocene lowstand during the last glacial maximum the shelves surrounding the marmara sea were subaerially exposed and deltas of allounit b accumulated along the present day shelf edge following the post glacial rise of global sea level to 75 m at 12 ka the marmara sea quickly became inundated and thereafter rose in synchroneity with the mediterranean by 10 ka the black sea rose to start spilling into the marmara sea leading to establishment of a brackish water lid that has persisted to the modern day the strongest black sea outflow began at 10 ka and persisted to 6 ka promoting the accumulation of sapropel m1 in the deep marmara sea and progradation of an overflow delta just south of the exit from the bosphorus strait allounit c is a laminated sapropel m2 in basinal cores dated at 30 23 ka like m1 it is believed that m2 accumulated during a period of increased brackish water input into the marmara sea mainly from the black sea in the black sea wave erosion kept the shelf stripped of unconsolidated sediments during the falling sea level associated with the last glaciation and subsequent early stages of the post glacial holocene transgression this erosion created a major unconformity shelf edge deltas of allounit b received their sediment during the last lowstand from small rivers that likely coalesced into a single system toward the shelf edge at modern water depths of 100 to 110 m these deltas were active until 11 10 5 ka subsequently sea level in the black sea rose to 40 m by 10 ka and a set of backstepping barrier islands developed on the shelf as part of the associated transgressive systems tract once water level reached 40 m continued sea level rise stalled until 9 ka as the black sea began to spill across the bosphorus strait into the marmara sea

comparison of four meteorite penetration funnels in the campo del cielo crater field argentina abstract more craters may be discovered in the future but as it is currently known the campo del cielo crater field is 18 km long by 4 km at its widest point such a distribution of craters suggests that the parent meteoroid entered and traversed the atmosphere at a very low angle relative to horizontal the crater field contains at least 20 small craters produced by the larger fragments of the parent meteoroid four of these are explosion analog craters and the rest are penetration funnels during four field seasons we have constructed topographic and magnetic maps of four of the penetration funnels as found and then dug trenches across them to learn their original structures and recover meteorites preserved within them structures of these penetration funnels indicate very low angles of impact i e 9 16 relative to horizontal this supports the idea that the parent meteoroid traversed the atmosphere at a low angle data given here for the four penetration funnels include projectile masses lengths widths depths and estimates of impact angles and azimuths one of the penetration funnels described here no 6 can almost be classified as an explosion analog crater

visible ir and raman microspectroscopic investigation of three itokawa particles collected by hayabusa mineralogy and degree of space weathering based on nondestructive analyses hayabusa returned samples offer a unique perspective for understanding the link between asteroids and cosmomaterials available in the laboratory and provide insights on the early stages of surface space weathering this study characterizes the mineralogy and the extent of space weathering of the three itokawa particles ra qd02 0163 ra qd02 0174 and ra qd02 0213 provided by jaxa to our consortium we report here a series of results based on nondestructive analyses through visible near infrared reflectance and raman spectroscopy results were obtained on the raw particles both in their original containers and deposited on diamond windows identification of the minerals characterization of their elemental compositions and measurements of their relative abundances were led through raman spectroscopy in punctual and automatic mode reflectance spectra in the visible and near ir wavelengths constrain the mineralogy of the grains and allow direct comparison with the surface of itokawa the spectra reflect the extent of space weathering experienced by the three particles particle ra qd02 0163 consists of a heterogeneous mixture of minerals olivine fo76 dominates an assemblage with both ca rich en50 wo50 and ca poor en85 pyroxenes the elemental compositions of the silicates are consistent with those previously reported for distinct hayabusa particles particles ra qd 0174 and ra qd02 0213 are solely composed of olivine whose chemical composition is similar to that observed in ra qd02 0163 it has been previously shown that the s type asteroid 25143 itokawa is a breccia of poorly equilibrated ll4 and highly equilibrated ll5 and ll6 materials the three particles studied here can be related to the least metamorphosed lithology ll4 based on the high forsterite content of the olivine neither carbonaceous matter nor hydrated minerals were detected through raman on the three allocated particles the nir vis reflectance incidence 45 light collection at e 0 spectra of the three particles in particular the 1 m band are consistent with the presence of both olivine and pyroxene detected via raman the spectra of particles ra qd02 0163 and ra qd02 0213 are also fully compatible with the ground based observations of asteroid 25143 itokawa in terms of both spectral features and slope by contrast particle ra qd02 0174 has a similar 1 m band depth but higher redder spectral slope than the surface of itokawa this probably reveals a variable extent of space weathering among the regolith particles ra qd02 0174 may contain a higher amount of nanophase metallic iron and nanophase fes such phases are products by space weathering induced by solar wind previously detected on other itokawa particles

smectite dehydration its relation to structural development and hydrocarbon accumulation in northern gulf of mexico basin a comparison of clay diagenesis data obtained from a study of tertiary shales from the brazos colorado river system of texas the mississippi river system of louisiana and the niger river system of nigeria illustrates significant differences in temperature intervals over which smectite diagenesis occurs the threshold temperature required to initiate diagenesis ranges from about 160 f 71 c in mississippi river sediments to more than 300 f 150 c in the niger delta water expelled from smectite into the pore system of the host shale during the process of diagenesis may migrate out of the shale early or may be totally or partially trapped and released slowly through time in either situation the water can act as a vehicle for hydrocarbon migration p ovided hydrocarbons are present in a form and in sufficient quantities to be transported observations from the northern gulf of mexico basin indicate a close relation between buildup of high fluid pressure and the smectite illite transformation process abnormal pressures exert partial control on the type and quantity of hydrocarbons accumulated because pressure potential determines the direction of fluid flow and overpressuring partly controls the geometry of growth faults and related folds in basins where shale structures are the dominant type formed the depths to which growth faults can penetrate and the angle of dip that these faults assume at depth are largely dependent on fluid pressure in the sedimentary section at the time of faulting dips of some faults in texas have been observed to change abruptly within the interval of smectite diagenesis and some faults formed in the overpressured miocene and younger sections become beddingplane types at depths where the temperature is near that required for thermal generation of petroleum although these faults may be important for fluid redistribution in shallow sandstone shale sections they are a minor factor in moving hydrocarbons out of shale below the faults in much of the texas offshore area fluid movement upward through microfracture systems in the deeply buried overpressured section overlying and extending upward from fault trends in the sub tertiary section is proposed as a mechanism for flushing hydrocarbons from the deeper portion of the northern gulf of mexico basin this flushing process would be enhanced by smectite diagenesis because water derived from smectite that was trapped during basin subsidence would cause the flushing process to continue for longer periods of time and to extend to greater depths than could be attained if only remnants of original pore water were present shale tectonism is also the primary mechanism for structural development in the tertiary section of the niger delta however seismic data indicate that the rate of dip change of seaward dipping listric growth faults is commonly less than that observed in texas where dips as low as 10 15 can occur at depths as shallow as 10 000 15 000 ft 3 048 4 572 m syndepositional faults in nigeria are formed in sandstone shale sections where the clay composition of shale is primarily kaolinite and where little water of smectite diagenesis has been added to the pore system of the host sedimentary section subtle differences in structural styles in the tertiary sections of texas and nigeria are probably the result of differences in clay composition of the shaly sections being deformed

cenozoic evolution of the eastern black sea a test of depth dependent stretching models abstract subsidence analysis of the eastern black sea basin suggests that the stratigraphy of this deep extensional basin can be explained by a predominantly pure shear stretching history a strain rate inversion method that assumes pure shear extension obtains good fits between observed and predicted stratigraphy a relatively pure shear strain distribution is also obtained when a strain rate inversion algorithm is applied that allows extension to vary with depth without assuming its existence or form the timing of opening of the eastern black sea which occupied a back arc position during the closure of the tethys ocean has also been a subject of intense debate competing theories called for basin opening during the jurassic cretaceous or paleocene eocene our work suggests that extension likely continued into the early cenozoic in agreement with stratigraphic relationships onshore and with estimates for the timing of arc magmatism further basin deepening also appears to have occurred in the last 20 myr this anomalous subsidence event is focused in the northern part of the basin and reaches its peak at 15 10 ma we suggest that this comparatively localized shortening is associated with the northward movement of the arabian plate we also explore the effects of paleowater depth and elastic thickness on the results these parameters are controversial particularly for deep water basins and margins but their estimation is a necessary step in any analysis of the tectonic subsidence record stored in stratigraphy

permeability controls on aquathermal pressuring aquathermal pressuring refers to fluid pressures in excess of the hydrostatic which have been created by fluid thermal expansion against a less expansive sediment matrix two commonly stated objections to this mechanism are 1 hydraulic gradients and the finite but very low permeabilities now existing in the gulf of mexico are sufficient to dissipate aquathermal pressures and 2 the increasing temperatures decrease fluid viscosity at a rate so that hydraulic conductivity increases fast enough to dissipate these pressures evaluation of the momentum transport equations in the eulerian frame of reference indicates the first objection is not applicable because it treats the problem as steady flow and not transient flow furthermore existing data indicate that under no mal diagenetic conditions the decrease in intrinsic permeability caused by consolidation is greater than the viscosity effect therefore the two commonly stated objections to aquathermal pressuring do not by themselves prove the mechanism is ineffective in settings such as the gulf of mexico permeability increases by fracturing and faulting may however be sufficient to bleed off aquathermally produced excess pressures the measured very low permeabilities of gulf coast fine grained sediments indicate that aquathermal pressuring is a potentially important mechanism if the fine grained sediments do control the hydraulic response

does crater saturation equilibrium occur in the solar system abstract similarity is found in crater densities on the most heavily cratered surfaces throughout the solar system this is hypothesized to result from a steady state saturation equilibrium being approached or achieved by cratering processes this hypothesis conflicts with some recent interpretations however it accounts for 1 a similarity in maximum relative crater density below certain theoretically predicted values on all heavily cratered surfaces 2 a leveling off at this same relative density among 100 m scale secondary craters in populations on lunar maria and other sparsely cratered lunar surfaces 3 the approximate uniformity of maximum relative densities on saturn satellites in spite of dramatic variations predicted from nonsaturation models assuming heliocentric impactors the lunar frontside upland crater population sometimes described as a well preserved production function useful for interpreting other planetary surfaces is found not to be a production function it was modified by intercrater plains formed at least partly by early upland basaltic lava flooding recently confirmed spectrophotometrically consistent with this counts in pure uplands those lacking intercrater plains match the proposed saturation equilibrium density variations among large d 64 km crater populations are found but these may involve several hypothesized mechanisms that rapidly obliterate large craters especially on icy surfaces recent models in which different populations of interplanetary bodies hit different planets need further appraisal

vertic features in a soil catena developed on eocene marls in the inner depression of the central spanish pyrenees scientific interest in marls has expanded in recent years especially in regard to erosion rates weathering processes and stabilization of the resulting sediments however information regarding the properties and evolution of overlying soil is relatively scarce this work analyzes the relationship between mechanical properties and standard properties of soils developed on eocene marls in mountainous regions of the southern central spanish pyrenees it also examines whether these soils have the vertic features traditionally ascribed to them and how these features may vary along a catena the water holding capacity of the soils exhibits a typical catena related trend that increases progressively from low values in upper slope profiles to higher values for the middle slope and valley the soils have a high percentage of silt sized particles quartz and calcite are the main mineralogical components of the fine earth fraction illite represents the major component of the clay fraction the linear extensibility and atterberg limits are positively and significantly correlated to clay content low liquid limit usually less than 30 low soil aggregate stability lower than 25 in ap horizons and high subsidence values n 0 7 are likely factors in the high dispersivity and sliding risk observed for the soils these factors also explain the presence of buried soils and lithological discontinuities in lower slope profiles as well as the relatively limited degree of soil evolution despite a relatively humid climate low porosity mainly of vesicular type and a poor structure facilitate saturation in the wet season and lead to soil reduction processes especially within deep soil horizons along lower parts of hillslopes simulated wetting and freezing treatments were shown to fracture the unaltered marls into small fragments demonstrating the soil s susceptibility to physical weathering given moderate clay content absence of smectites and moderate soil extensibility cole 0 06 cm cm 1 in most horizons topsoil cracking in lower slope profiles is apparently caused by high rates of evaporation during the dry season the soils described here did not meet the requirements of vertic horizons but most meet the diagnostic criteria of having a protovertic horizon despite the absence of swelling and shrinking clays

inverse modelling and seismic data constraints on overpressure generation by disequilibrium compaction and aquathermal pressuring application to the eastern black sea basin summary pore pressure above the hydrostatic overpressure is common in deep basins it plays an important role in pore fluid migration represent a significant drilling hazard and is one of the factors controlling slope stability and deformation in seismically active areas here we present an inverse model to calculate overpressure due to disequilibrium compaction and aquathermal pressuring we minimize a function that contains the misfits between estimates from our forward model and observed values using a non linear least squares approach the inverse model allows the introduction of observed seismic and geological constraints such as p wave velocity vp and density data and depth of the layer boundaries for a better pore pressure prediction the model output also provides estimates of 1 surface porosity 2 compaction factor 3 intrinsic permeability at surface conditions 4 a parameter controlling the evolution of the intrinsic permeability with porosity 5 the ratio between horizontal and vertical permeability and 6 uncompacted thickness so sedimentation rate assuming known time intervals for each sedimentary layer we apply our inverse approach to the centre of the eastern black sea basin ebsb where the vp structure has been inferred from wide angle seismic data first we present results from a 1 d inverse model and an uncertainty analysis based on the monte carlo error propagation technique to represent the observed rapid change from low vp to normal vp below the maikop formation we impose a zero overpressure bottom boundary and subdivide the layer below the maikop formation into two sublayers an upper layer where the rapid change is located and a lower layer where the vp is normal secondly we present the results from a 2 d inverse model for the same layers using two alternative bottom boundary conditions zero overpressure and zero flow we are able to simulatetheobserved vp suggestingthatthelowvelocityzone lvz at 3500 6500mdepth below the seabed mbsf can be explained by overpressure generated due to disequilibrium compaction 90 per cent and to aquathermal pressuring 10 per cent our results suggest thattheuppersublayer belowthemaikopformation behavesasasealduetoitslowpermeability 0 3 2 10 14 ms 1 this seal layer does not allow the fluids to escape downwards and hence overpressure develops in the maikop formation and not in the layers below this overpressure was mainly generated by the relatively high sedimentation rate of 0 29 m ka 1 of the maikop formation at 33 9 20 5ma and an even higher sedimentation rate of 0 93 m ka 1 at 13 11 ma we estimate a maximum ratio of overpressure to vertical effective stress in hydrostatic conditions o f 0 62 at 5200 mbsf associated with an overpressure

regolith migration and sorting on asteroid itokawa high resolution images of the surface of asteroid itokawa from the hayabusa mission reveal it to be covered with unconsolidated millimeter sized and larger gravels locations and morphologic characteristics of this gravel indicate that itokawa has experienced considerable vibrations which have triggered global scale granular processes in its dry vacuum microgravity environment these processes likely include granular convection landslide like granular migrations and particle sorting resulting in the segregation of the fine gravels into areas of potential lows granular processes become major resurfacing processes because of itokawa s small size implying that they can occur on other small asteroids should those have regolith

effective stress coefficient in shales and its applicability to eaton s equation pore pressure within formations determines the mud weight required to build a balancing fluid pressure downhole an improper understanding of the subsurface geology and the formation pressures may result in fracturing the formation if the mud weight is too high in contrast if mud weight is too low then formation fluids can flow into the well potentially leading to well blowouts if not controlled complex geological settings make pore pressure prediction difficult and often inaccurate due to uncertainty in pressure generating mechanisms estimation of proper pore pressures is necessary for designing stable holes and an optimized casing program in exploration knowledge of pore pressures can assist in assessing seal effectiveness and in high grading reservoir sweet spots it also provides useful calibration information for basin modeling hence it becomes very important to accurately predict pore pressures

weathering of a gypsum calcareous mudstone under semi arid environment at tabernas se spain laboratory and field based experimental approaches the weathering of a late miocene gypsum calcareous mudstone outcropping in large badland areas of se spain under a semi arid mediterranean climate was studied by means of two experimental approaches field and laboratory experiments were carried out to reproduce though in accelerated form some of the weathering conditions of the consolidated mudstone in the laboratory three sequences of 5 10 and 20 wetting drying cycles were produced on undisturbed blocks of fresh mudstone samples at the end of the three sequences samples were analysed for their micromorphology elemental and soluble salt chemistry and total mineralogy unweathered dry samples as blanks and permanently wet samples were also analysed in the field two small plots of freshly exposed mudstone were monitored over 3 years for their response to natural weathering in terms of morphological changes and sediment output the porosity was increased by a few wetting drying cycles as assessed by significant increases in water absorption capacity of the mudstone a combination of three factors is responsible for mudstone weathering repeated cycles of wetting drying the presence of geologically induced cracks and fissures and dissolution crystallisation of relatively soluble minerals gypsum being the most abundant within this category a few wetting drying cycles were sufficient to reveal ion migration specially na ca mg so4 hco and cl within the mudstone explaining mineral dissolution in the field surface weathering rates from 0 7 to 8 mm year 1 were measured weathering rates were found to be proportional to the number of rainfall events during the sampling periods confirming what was found in laboratory conditions namely that the number of wetting drying cycles has the greatest influence on weathering these weathering rates might be considered as the probable range of incision rates under present semi arid conditions

comparative characteristics of the black sea and mediterranean ridge mud volcanoes morphological and structural characteristics of the black sea and mediterranean ridge mud volcanoes studied during several unesco esf cruises of the r v gelendzhik 1991 1994 are compared on the basis of single and multi channel seismic and sidescan sonar observations morphologically three types of mud volcanoes were distinguished in the black sea and six types in the mediterranean they differ in size shape and presence of the mud flows some types from both localities are very similar to each other but in any case their deep structure is very distinctive this difference in deep structure is explained by their development in different geological conditions under an extensional regime with high terrigenous input in the black sea and under strong lateral compression on the mediterranean ridge

episodic fluid expulsion from geopressured sediments numerical simulation of fluid explusion from geopressured sediments using a one dimensional finite difference model shows that large volumes of fluid can be transported through a fractured seal during short lived 100 year expulsion events in this model abnormal fluid pressures are maintained by an impermeable seal when the fluid pressure exceeds 85 of the lithostatic pressure a vertical fracture opens in the seal providing a permeable pathway from the geopressured sediments into the overlying section fluid pressure in the seal decreases as fluid flows through the fracture closing the fracture as sediments in the seal compact once the fracture closes the seal remains impermeable until fluid flowing from deeper in the section increases fluid pressure to the fracture criteria a process that takes 10 000 500 000 years fractures emplaced in relatively incompressible seals such as compacted and or cemented sediments remain open for 20 50 years fluid fluxes through the seal integrated over the life of these events are 1 5 107 kg m2 and temperatures in the overlying sediments are increased by 5 20 c these temperature anomalies decay to less than half their original value in 300 years suggesting that the thermal anomalies observed in wells that are attributed to fluid expulsion formed in response to a very recent or currently active event

geomorphic agents versus vegetation spreading as causes of badland occurrence in a mediterranean subhumid mountainous area abstract previous evidence on the chief role of physical weathering on badland development in the vallcebre area south eastern pyrenees led to the study of the amounts of energy available for the main geomorphic agents and to analyze the results in the light of the patterns of vegetation cover and species distribution in order to explain both the occurrence of these badland forms and their preference for north facing shady hillslopes results showed that the weathering potential provided by freezing is about two orders of magnitude greater than rainfall kinetic energy and that the former strongly depends on hillslope aspect the study of vegetation demonstrated that vegetation is poorer in cover and species composition on shady hillslopes than on sunny ones spontaneous revegetation of these surfaces being restrained by cold thermal conditions rather than by water availability these results show that the occurrence of these badland areas depends on montane climatic attributes that control geomorphic and biological processes and that are different from those that promote the occurrence of badlands in dry mediterranean areas the preference for northern aspects provides evidence for these differences

shrinkage and atterberg limits in relation to other properties of principal soil types in israel abstract soil samples collected from 32 sites across israel representing major types were analyzed for their pedological characteristics and mechanical properties correlative relationships between shrinkage measured by the coefficient of linear extensibility cole atterberg limits liquid and plastic and the physical and chemical properties were established and indicate possibilities of estimating mechanical properties from known pedological data strong correlations were noted between mechanical properties and the pedological characteristics reflecting clay mineralogy and texture e g cation exchange capacity specific surface area hygroscopic moisture and clay content these relationships are useful inasmuch as clay mineralogy is usually evident from soil classification sodicity and salinity common in dry soils of semi arid regions may introduce complicating factors such as raising or lowering atterberg limits respectively shrinkage is similarly affected being accentuated at high sodium low salt levels and reduced in highly saline sodic soils organic matter was correlated with liquid and plastic limits but no relationship with shrinkage was noted calcium carbonate also had little influence on atterberg limits the relationships presented may serve as first approximations mechanical properties of the soil groups illustrate the range of values encountered among regions with differing environmental conditions

imaging of small scale features on 433 eros from near evidence for a complex regolith on 25 october 2000 the near earth asteroid rendevous near shoemaker spacecraft executed a low altitude flyover of asteroid 433 eros making it possible to image the surface at a resolution of about 1 meter per pixel the images reveal an evolved surface distinguished by an abundance of ejecta blocks a dearth of small craters and smooth material infilling some topographic lows the subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter sized blocks

erosion quantification in the small marly experimental catchments of draix alpes de haute provence france calibration of the etc rainfall runoff erosion model abstract erosion rates measured for 15 years in the small ranging from 0 13 ha to nearly 1 km2 and steep 30 75 mountainous marly basins of draix south alps france are over 100 tons ha year in a badland area devoid of vegetation in a similar basin reforested at the end of the 19th century the sediment yield is considerably reduced less than 3 tons ha year the analysis of the sediment yield of these torrents reveals the importance of the erosion processes on slopes at the scale of the elementary gully and the influence of deposition transport and scouring processes as soon as the channel network of the basin is developed these processes were modelled by a hydrosedimentologic model developed by cemagref for flood torrent erosion and called etc etc is an integrated spatialized and global model working at the event scale the rainfall runoff component and the solid transport component which involves scouring deposition and armouring are well developed on the other hand the erosion component is not yet a physically based model as the knowledge on the elementary processes is not enough quantitative the etc model was used on a badland basin of 86 ha in area the laval and has shown its ability to simulate both water and sediment flows in mountainous and steep basins the erosion modelling highlighted the need for a better representation of the slope processes and for more information on the storing of sediments in the channel network observations carried out on the influence of the vegetation cover patterns and the links between slopes and channels should be taken into account to improve the model

fractal scaling of surface roughness in artificially weathered smectite rich soil regoliths abstract laboratory trials were established to simulate under controlled conditions the natural weathering sequence of smectite rich soil regoliths from a highly degraded badland area at vallcebre eastern pyrenees range spain experiments were carried out to deepen the knowledge on the response of the bulk materials to experimental freezing thawing and wetting drying cycles and the role of the mineral components in the path of surface structure detachment during the experiments variation of surface roughness was determined by measuring consecutive transects of the artificially weathered samples with a noncontact laser profile meter and data were analysed with a program written for this purpose the analysis of data was based on the calculation of the fractal dimension according to the richardson equation of sequential surface profiles of samples in frozen thawed wetted and dried conditions in order to achieve a dynamic description of surface aggregate shape arrangement along the whole sequence and at different scale ranges the hurst exponent of selected bulk data was also calculated in order to find added evidence of the nature of surface which in some cases appeared to be multifractal with the richardson diagram the fractal model applied allowed to obtain fractal dimension values of surface roughness which were used to explain how the pedological characteristics of a given material containing clay and carbonate association may react to applied climatic extremes thereby showing differential surface arrangement and weathering paths freezing and thawing as well as wetting and drying events modified the sample s surface and these effects describe the material susceptibility to weathering against individual climatic components and may be useful in erosion modelling at the catchment scale

the recurring cycles of biancana badlands erosion vegetation and human impact abstract the biancana badlands a typical element of the southern tuscany landscape were in expansion for centuries until bulldozers began erasing them for land reclamation purposes over the last 10 15 years some of the scattered remnants of biancanas have been placed under protection in order to preserve their biodiversity and their particular cultural and geomorphological landscapes rural abandonment and the lack of appropriate management practices have contributed to vegetation encroaching on biancana badland slopes causing a loss of elements of high ecological and cultural values as well as eroded spots the aim of this paper is to explore the direction and rate of change in land use of the biancana badland landscapes over the last 50 years evaluating the erosion vegetation dynamics and examining the processes involved in two biancana badlands lucciola bella and crete di camposodo crete di leonina which are sites of community importance first we analysed the landscape changes that occurred in the biancana areas from 1954 to 2005 comparing old and recent land use maps twinspan classification was applied on selected plots of a plant dataset to distinguish vegetation types and identify the indicator species of each different type we then evaluated soil erodibility on the eroded biancana surfaces regosols and well developed vertisols which represent the coexisting extremes of the soil situation within the biancana badlands we empirically assessed the effects of a few roots on saturated soil shear strength to introduce direct links between plants and soil processes our results showed a decrease in bare or scarcely vegetated spots of 0 9 ha y 1 if the encroachment continues to progress at this rate in 35 40 years from now all the biancana domes will be completely re vegetated encroachment on the most eroded biancanas was mainly ascribed to generalist ruderal species such as avena fatua and dactylis glomerata we showed that rills and subsurface micropipes are characterized by the same erosion processes meaning that they can be contrasted and eventually halted by the same means and we observed a clear positive trend that will substantially suppress rilling at very low plant cover no more than 20 badlands were previously kept alive by limited but nonetheless devastating grazing activities if this picture is correct then mimicking traditional badland grazing practices seems to be a necessary step towards saving the landscape and biodiversity that the protected areas were established to preserve

small basin response in a mediterranean mountainous abandoned farming area research design and preliminary results abstract a 36 ha basin named cal parisa has been studied since early 1988 in the eastern pyrenees spain this basin was selected as a representative of extensive areas on clayey bedrock formerly used for farming nowadays almost abandoned where badlands are of great importance as far as sediment production is concerned as we are interested in the hydrological behaviour of terraced areas and badland areas could strongly modify the hydrological and sediment response the basin is devoid of badlands but has some bedrock scars and small gullies severe geoecological disturbances were produced in it by agricultural land use in the past the basin was deforested topography was terraced and the drainage net was increased by ditching monitoring design is based on two measuring stations one at the main outlet and the other in a 16 ha sub basin and two sampling stations at the outlets of the two main sub basins a weather station and four rain recorders preliminary data show a hydrological response fully controlled by antecedent moisture conditions suggesting that soils have high infiltration capacities and that runoff is generated by saturation overland flow delayed flow being less significant stream water samples show relatively high dissolved solids concentrations dominated by calcium bicarbonate and suspended sediments concentrations about ten times less than dissolved ones as a consequence of the strong sediment conveyance discontinuities observed in the field

clay mineralogy as a crucial factor in badland hillslope processes abstract comprehensive and important work has been done in understanding badland processes on both the big scale and more recently on smaller scale in order to understand the subtle differences between sites however most studies lack important information regarding clay mineralogy and their importance for weathering processes type and rate of weathering depend on material physico chemical properties climatic regimes and slope characteristics as weathering progresses the surface conditions change influencing erosion processes usually badland lithologies are reported as sodium rich highly dispersive materials but that is not invariably true the primary objective of this study is to show that clay minerals have an important role in defining surface and subsurface processes on badland hillslopes field studies conducted in dinosaur park badlands alberta canada chinguacousy badlands ontario canada and sestino badlands tuscany italy have shown that there are two dominant clay rich lithologies smectite rich and smectite poor mudrocks different surface crust and weathering profiles were observed on smectite rich mudrocks during two field years with distinct precipitation inputs after a dry fall winter season the popcorn surface was very well developed 2 3 cm the subsurface layer 10 15 cm thick overlaid the layer of smaller shards followed by the unweathered material after a very wet fall winter season the surface layer was denser and thinner 0 5 cm with wider cracks and a thin subsurface layer attached to the crust weathering profiles on smectite poor lithologies did not show any differences with variable climatic conditions a thin surface layer was composed of soft thin and small 0 5 0 3 0 1 cm shards a layer of larger shards overlying unweathered material was beneath it in order to better understand the described occurrences badland materials were monitored in controlled laboratory conditions during an incremental weathering experiment six samples of each material were subjected to 10 cycles of simulated rainfall which duration ranged 10 60 min very short rainfalls 10 20 min can cause swelling of clay minerals in smectite rich materials and formation of popcorn surface during drying periods during subsequent wetting drying periods the crust becomes flatter and denser and desiccation cracks become wider and deeper samples subjected to 50 and 60 min of rainfall showed maximum swelling after only one cycle of rainfall after this swift swelling samples became unstable and dispersive during subsequent wetting dispersion became dominant resulting in flatter surfaces thinner crust and narrower desiccation cracks smectite poor mudrocks appeared to be resistant to variable wetting and drying large shards broke down into smaller due to differential swelling of illite and chlorite once they were reduced to tiny flaky shards the surface became compacted the surface cracks served as the initial pathways for sediment and water movement knowing if the material is smectite rich or smectite poor can help in prediction of processes and the erosion rates the amount intensity and duration of precipitation will determine not only the rate of weathering but also the type of the weathered surface on smectite rich surfaces smectite poor materials appear to be more resistant to change in precipitation

lithology controls the regional distribution and morphological diversity of montane mediterranean badlands in the upper llobregat basin eastern pyrenees abstract badlands are pervasive in a wide range of environmental conditions across the mediterranean region including arid semiarid and humid environments on montane cold subhumid and humid mediterranean landscapes harsh thermal conditions on north facing hillslopes favour intense bedrock weathering by freezing and impose serious constraints on plant colonization the above are the customary arguments to explain the high abundance of montane badlands on north exposed shady aspects we studied the distribution and morphological diversity of badlands in the upper llobregat basin catalan pyrenees ne spain using remote sensing information high resolution orthophotos and complementary landsat 8 imagery digital elevation data and regional information on lithology badlands extend over about 200 ha in the upper llobregat basin and occur on two different parent materials swelling smectite rich continental garumnian lutites of late cretaceous age and nonswelling illitic marine eocene marls vegetation assessed by remote sensed vegetation greenness is less developed on north facing badland slopes however badland slope aspect distribution varies considerably with lithology while badlands on eocene marls show preferential distribution on north facing shady slopes badland occurrence on garumnian lutites does not reveal clear slope aspect anisotropy patterns lithology also affects slope gradient with badlands on eocene marls showing rougher topography 30 40 average slope angle than on garumnian lutites 20 30 badland morphological differences induced by lithology are discussed in terms of the greater weathering susceptibility and slope instability of the swelling smectite rich garumnian lutites than of the nonswelling eocene marls elevation which broadly controls annual precipitation and winter air temperature within the region shows no clear influence on badland distribution overall our results reveal lithology as the main factor controlling badland distribution and morphological diversity under the montane mediterranean conditions of the upper llobregat basin

a survey of possible impact structures on 25143 itokawa abstract we determined the morphologies and dimensions of possible impact craters on the surface of asteroid 25143 itokawa from images taken by the hayabusa spacecraft circular depressions circular features with flat floors or convex floors and circular features with smooth surfaces were identified as possible craters the survey identified 38 candidates with widely varying morphologies including rough smooth and saddle shaped floors a lack of raised rims and fresh material exposures the average depth diameter ratio was 0 08 0 03 these craters are very shallow relative to craters observed on other asteroids these shallow craters are a result of 1 target curvature influencing the cratering process 2 raised rim not being generated by this process and 3 fines infilling the craters as many of the crater candidates have an unusual appearance we used a classification scheme that reflects the likelihood of an observed candidate s formation by a hypervelocity impact we considered a variety of alternative interpretations while developing this scheme including inherited features from a proto itokawa spall scars created by the disruption of the proto itokawa spall scars following the formation of a large crater on itokawa itself and apparent depressions due to random arrangements of boulders the size frequency distribution of the crater candidates was close to the empirical saturation line at the largest diameter and then decline with decreasing diameter

cratering efficiency on coarse grain targets implications for the dynamical evolution of asteroid 25143 itokawa abstract remote sensing observations made by the spacecraft hayabusa provided the first direct evidence of a rubble pile asteroid 25143 itokawa itokawa was found to have a surface structure very different from other explored asteroids covered with coarse pebbles and boulders ranging at least from cm to meter size the cumulative size distribution of small circular depressions on itokawa most of which may be of impact origin has a significantly shallower slope than that on the moon small craters are highly depleted on itokawa compared to the moon this deficiency of small circular depressions and other features such as clustered fragments and pits on boulders suggest that the boulders on itokawa might behave like armor preventing crater formation the armoring effect this might contribute to the low number density of small crater candidates in this study the cratering efficiency reduction due to coarse grained targets was investigated based on impact experiments at velocities ranging from 70 m s to 6 km s using two vertical gas gun ranges we propose a scaling law extended for cratering on coarse grained targets i e target grain size projectile size we have found that the crater efficiency reduction is caused by energy dissipation at the collision site where momentum is transferred from the impactor to the first contact target grain and that the armoring effect can be classified into three regimes 1 gravity scaled regime 2 reduced size crater regime or 3 no apparent crater regime depending on the ratio of the impactor size to the target grain size and the ratio of the impactor kinetic energy to the disruption energy of a target grain we found that the shallow slope of the circular depressions on itokawa cannot be accounted for by this new scaling law suggesting that obliteration processes such as regolith convection and migration play a greater role in the depletion of circular depressions on itokawa based on the new extended scaling law we found that the crater retention age on itokawa is 3 33 myr in the main belt which is in good agreement with the cosmic ray exposure ages for returned samples from itokawa which may reflect the age of material a few meters beneath the surface these ages strongly suggest that the global resurfacing that reset the 1 10 m deep surface layer may have occurred in the main belt long after the possible catastrophic disruption of a rigid parent body of itokawa suggested by ar degassing age 1 3 gyr

cratering experiments in sands and a trial for general scaling law we report results of vertical impacts of aluminum projectiles into quartz sand the impacts were performed at velocities of 35 to 830 m sec with a single stage powder gun morphology of craters formed in loose sands is generally conical whereas morphology of craters formed in self compacted sands varies from a flat floor type to a double ring type with increasing impact velocity the present data together with previous experimental data and dienes and walsh s late stage equivalence indicate that crater diameter is expressed by a function of the late stage effective energy but not of the impact kinetic energy the diameter of a crater formed in a noncohesive sand was found to be proportional to one fourth the power of the late stage effective energy for a general impact cratering in a target with a finite strength the diameter d versus impact velocity v relation is written as follows vv vv 2 k dd 4 dd 5 2 where v and d are normalizing values of the impact velocity and diameter and k is a constant related to target and projectile properties the relation suggests that there are four regimes in crater diameter versus the kinetic energy relation

erosion and sediment transport on steep marly hillslopes draix haute provence france an experimental field study abstract despite a thin regolith layer measured sediment yields indicate denudation rates of more than 10 to 20 mm yr 1 on strongly denuded slopes in black marl terres noires near draix alpes de haute provence overland flow and rainfall simulation experiments were conducted on three slopes in the draix erosional research basin to determine the nature and intensity of hillslope erosion processes the experiments showed that during a single storm sediment transport includes water solid mixtures with a wide range of concentrations from highly charged rill flow up to 400 g l 1 to hyperconcentrated flow up to 800 g l 1 to debris flows up to 1400 g l 1 miniature debris flows mdfs strongly controlled sediment transport as long as the sediment store was not depleted slope surfaces were completely reworked in the winter and the regolith layer was rebuilt temperature records from nine recent winter periods indicate that conditions are favourable for soil frost processes

the taxonomic distribution of asteroids from multi filter all sky photometric surveys abstract the distribution of asteroids across the main belt has been studied for decades to understand the current compositional distribution and what that tells us about the formation and evolution of our solar system all sky surveys now provide orders of magnitude more data than targeted surveys we present a method to bias correct the asteroid population observed in the sloan digital sky survey sdss according to size distance and albedo we taxonomically classify this dataset consistent with the bus and binzel bus s j binzel r p 2002 icarus 158 146 177 and bus demeo et al demeo f e binzel r p slivan s m bus s j 2009 icarus 202 july 160 180 systems and present the resulting taxonomic distribution the dataset includes asteroids as small as 5 km a factor of three in diameter smaller than in previous work such as by mothe diniz et al mothe diniz t carvano j m a lazzaro d 2003 icarus 162 march 10 21 because of the wide range of sizes in our sample we present the distribution by number surface area volume and mass whereas previous work was exclusively by number while the distribution by number is a useful quantity and has been used for decades these additional quantities provide new insights into the distribution of total material we find evidence for d types in the inner main belt where they are unexpected according to dynamical models of implantation of bodies from the outer solar system into the inner solar system during planetary migration levison h f bottke w f gounelle m morbidelli a nesvorn d tsiganis k 2009 nature 460 july 364 366 we find no evidence of s types or other unexpected classes among trojans and hildas albeit a bias favoring such a detection finally we estimate for the first time the total amount of material of each class in the inner solar system the main belt s most massive classes are c b p v and s in decreasing order excluding the four most massive asteroids 1 ceres 2 pallas 4 vesta and 10 hygiea that heavily skew the values primitive material c p types account for more than half main belt and trojan asteroids by mass most of the remaining mass being in the s types all the other classes are minor contributors to the material between mars and jupiter

how mudrock and soil physical properties influence badland formation at vallcebre pre pyrenees ne spain abstract soils regoliths and their parent materials were investigated in relation to the development of badlands in the pre pyrenees in ne spain on late cretaceous mudrocks under a mountain mediterranean climate whilst all the soils in the area which are developed on mudrocks show a good structure and support a dense plant cover the bare parent materials slake very rapidly giving rise to badlands characterized by high erosion rates several physical chemical mineralogical and micromorphological properties of soils regoliths and related parent materials were analyzed in order to explain their different susceptibility to erosion and to determine which of all these properties are better related to such erosive behaviour only micromorphological and porosity properties were able to explain the erosion susceptibility whilst mineralogical chemical and physico chemical specific surface area properties were not among the aggregate stability tests performed to estimate the relationships of soil components with the susceptibility to erosion the emerson test for macroaggregate evaluation was particularly well suited although no good correlation was found between the emerson test classes and organic matter content we observed that the degree of slaking in organic rich horizons was always lower than in subsurface horizons and regoliths consequently as far as organic rich aggregates are present in the soil surface the influence of water in producing slaking swelling and then erosion will be minimum however when regoliths and rocks are uncovered the influence of water in these particular materials through freeze drying and swell shrinking will give rise to mudrock desintegration leading to accelerated erosion

regolith behaviour and physical weathering of clayey mudrock as dependent on seasonal weather conditions in a badland area at vallcebre eastern pyrenees abstract studies on badland areas in the vallcebre basin pyrenees suggest that erosion rates are controlled by the weathering rate of mudrocks to obtain the temporal pattern of physical weathering and its control on the erosive processes monitoring of regolith temperatures at different aspect depth and lithology and periodical determination of regolith moisture and bulk density were carried out changes in surface regolith have also been monitored by means of photographic techniques using an especially designed tripod finally the hydrological and erosive response of the regolith trough the seasons were studied using rainfall simulations the results obtained support and confirm previous knowledge on the role of frost action in mudrock weathering and the role of subsequent regolith development and wetness status on infiltration and runoff generation these seasonal changes of behaviour are so important that they raise serious questions about the validity of observations or experiments carried out in only one season this work confirms that erosion processes are controlled by regolith formation during winter and regolith depletion by storm rainfall erosion during summer spring and early autumn it also raises important points about annual trends of infiltration and erodibility that should be used as guidelines for modelling runoff and sediment production

the rubble pile asteroid itokawa as observed by hayabusa during the interval from september through early december 2005 the hayabusa spacecraft was in close proximity to near earth asteroid 25143 itokawa and a variety of data were taken on its shape mass and surface topography as well as its mineralogic and elemental abundances the asteroid9s orthogonal axes are 535 294 and 209 meters the mass is 3 51 1010 kilograms and the estimated bulk density is 1 9 0 13 grams per cubic centimeter the correspondence between the smooth areas on the surface muses sea and sagamihara and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting itokawa is considered to be a rubble pile body because of its low bulk density high porosity boulder rich appearance and shape the existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re agglomeration into a rubble pile object

preliminary study of the erosion mechanisms in a biancana badland tuscany italy abstract italian badlands are present along the appennini mountains with an annual precipitation which ranges from 400 to 1200 mm the genesis of these badlands has often been studied whereas current processes and erosion rates have only rarely been examined and measured this paper describes a preliminary study on a badland developed in temperate mediterranean climate and located in sw tuscany italy the selected site is characterized by biancane dome shaped features a few meters in height generally having a vegetated nne aspect and severely eroded ssw slope with a sub horizontal basal pediment field rainfall and runoff experiments were carried out field results were substantiated by data collected in specially devised laboratory tests it was concluded that near surface pipes which develop at the point of contact between a surficial layer of weathered and severely fractured regolith and the less fractured and weathered regolith underneath are the main drainage channels while rills play a secondary role soil detachment is largely due to mechanical and chemical slaking of the regolith during infiltration the role of runoff is almost solely transport in particular it was found that the runoff detachment rate is limited by the rate at which the water front penetrates into the regolith

40ar 39ar age of material returned from asteroid 25143 itokawa the hayabusa mission to asteroid 25143 itokawa brought back 2000 small particles which most closely resemble material found in ll4 6 chondrites we report an 40ar 39ar age of 1 3 0 3 ga for a sample of itokawa consisting of three grains with a total mass of 2 g this age is lower than the 4 0 ga ages measured for 75 of ll chondrites but close to one for y 790964 and its pairs the flat 40ar 39ar release spectrum of the sample suggests complete degassing 1 3 ga ago recent solar heating in itokawa s current orbit does not appear likely to have reset that age solar or impact heating 1 3 ga ago could have done so if impact heating was responsible then the 1 3 ga age sets an upper bound on the time at which the itokawa rubble pile was assembled and suggests that rubble pile creation was an ongoing process in the inner solar system for at least the first 3 billion years of solar system history

quantification of rock control in geomorphology abstract rock control the influence of rock properties on landform development has for long been a relatively under researched topic but numerous techniques have been developed especially by geotechnical engineers and stone conservationists that are now being applied to geomorphological issues by geomorphologists these techniques range in scale from the quantification of major discontinuities through to analysis of micro pores rock control studies that have taken place over the last few decades have contributed important insights into our understanding of such diverse phenomena as 1 river terraces bedrock channel forms and gradients pot hole development drainage density and gully badland development 2 slope forms and failures especially with respect to rock mass strength 3 the form of glacial troughs and of subglacial erosional landforms 4 weathering controls on rock durability and the association of weathering with porosity 5 classic karst features including various types of karren 6 sandstone landforms 7 inselbergs and tors and 8 cliffs and shore platforms

impact induced seismic activity on asteroid 433 eros a surface modification process high resolution images of the surface of asteroid 433 eros revealed evidence of downslope movement of a loose regolith layer as well as the degradation and erasure of small impact craters less than 100 meters in diameter one hypothesis to explain these observations is seismic reverberation after impact events we used a combination of seismic and geomorphic modeling to analyze the response of regolith covered topography particularly craters to impact induced seismic shaking applying these results to a stochastic cratering model for the surface of eros produced good agreement with the observed size frequency distribution of craters including the paucity of small craters

impacts into coarse grained spheres at moderate impact velocities implications for cratering on asteroids and planets abstract the surfaces of many planets and asteroids contain coarsely fragmental material generated by impacts or other geologic processes the presence of such pre existing structures may affect subsequent impacts particularly when the width of the shock is comparable to or smaller than the size of pre existing structures reasonable theoretical predictions and low speed

experimental investigation of the impact fragmentation of blocks embedded in regolith abstract we present results of a set of impact experiments designed to examine the effects of impacts onto rocky blocks resting on and embedded within regoliths the targets were approximately 500 g granodiorite blocks struck with one eighth inch aluminum spheres at nominal speeds of approximately 5 km s 1 the granodiorite blocks were emplaced in 20 30 grade silica sand to simulate an asteroidal or lunar regolith block burial depths ranged from resting flush on the surface to submerged completely below the surface we observe a trend for largest remnant mass to increase with block burial depth documentary still image and high speed video of the resulting block fragments and surrounding regolith reveal new insights into the morphologies of blocks and secondary craters observed on asteroids like 433 eros

structure and porosity of smectitic mudrocks as affected by experimental wetting drying cycles and freezing thawing cycles abstract the erosion rates in the vallcebre basin pyrenees are controlled predominantly by the physical weathering rate of bare regolith i e mudrocks to obtain information on the influence of thermic and moisture regimes on the weathering dynamics laboratory experiments were carried out to investigate how freezing thawing or wetting drying cycles under controlled conditions affect structure and porosity three different clayey mudrocks were selected to represent materials more susceptible to erosion in the studied area the three lithologies identified as ca1r ca2r carr differed mainly in mineral constituents type and quantity of the clay minerals and cation exchange capacity an automated non contact laser profile meter was used to analyse surface microtopography in order to monitor random roughness variations and to calculate bulk density porosity and pore size distribution were carried out with image analysis freezing thawing cycles were the most active in modifying soil surface and bulk structure roughness of ca1r and ca2r was more than doubled at the end of freezing thawing cycles this variation was mostly associated with the whole surface elevation related to the bulk volume increase roughness variations in carr were less pronounced and related to a modification of the microtopography micromorphological observations revealed a platy structure formation induced by repeated ice lensing also porosity was increased by freezing thawing cycles with the formation of a large number of irregular and rounded pores wetting drying cycles did not affect surface roughness and modified bulk density very little in all samples they increased porosity by the formation of large cracks and fissures overall data from wetting drying cycles showed that changes in water content alone did not produce deep structural modifications a mechanism of alteration of soil structure during freezing thawing cycles is proposed

petroleum geology of the black sea abstract the black sea comprises two extensional basins formed in a back arc setting above the northward subducting tethys ocean close to the southern margin of eurasia the two basins coalesced late in their post rift phases in the pliocene forming the present single depocentre the western black sea was initiated in the aptian when a part of the moesian platform now the western pontides of turkey began to rift and move away to the south east the eastern black sea probably formed by separation of the mid black sea high from the shatsky ridge during the palaeocene to eocene subsequent to rifting the basins were the sites of mainly deep water deposition only during the late miocene was there a major sea level fall leading to the development of a relatively shallow lake most of the margins of the black sea have been extensively modified by late eocene to recent compression associated with closure of the tethys ocean gas chromatography mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the black sea can be explained by generation from an oil prone source rock of most probably late eocene age although a wider age range is possible in the basin centres burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post rift basin a palaeozoic source rock may have generated gas condensate in the gulf of odessa in bulgarian waters the main plays are associated with the development of an eocene foreland basin kamchia trough and in extensional structures related to western black sea rifting the latter continue into the romanian shelf where there is also potential in rollover anticlines due to gravity sliding of neogene sediments in the gulf of odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures small gas and oil discoveries around the sea of azov point to further potential offshore around the central azov high in offshore russia and georgia there are large culminations on the shatsky ridge but these are mainly in deep water and may have poor reservoirs there are small compressional structures off the northern turkish coast related to the pontide deformation these may include eocene turbidite reservoirs the extensional fault blocks of the andrusov ridge mid black sea high are seen as having the best potential for large hydrocarbon volumes but in 2200 m of water

distribution of boulders and the gravity potential on asteroid itokawa abstract the small asteroid itokawa was visited in 2005 by the japanese spacecraft hayabusa the images of the surface showed a scenario different to previously visited asteroids itokawa has a small number of large craters and many large boulders randomly distributed on most of the surface we analyse images taken at different surface resolution and configurations corresponding to several regions on the asteroid s surface by overlapping visual images and maps of the total potential and surface gravity we observe a correlation between the distribution of boulders and these parameters the boulders on the surface were identified by visual inspection of several images after fitting ellipses to every boulder we computed their size and the size distribution from decimeters to several meters at different locations in the surface we found that the size distribution is correlated with the total potential and the surface gravity a steeper size distribution shifted towards the small objects is observed in the low negative total potential high surface gravity which corresponds to the muses c region meanwhile in the head and bottom regions of high potential low surface gravity we obtain a shallower size distribution shifted towards the large boulders we confirm there is a size segregation that is correlated with the gravity field which can be explained under the action of the brazil nut effect there is a global relocation of boulders with large ones going into the high potential regions and small ones into the low potential ones a shape segregation is also observed on the location of the boulders more rounded ones are found in the regions of high potential while more elongated ones are frequent in regions of low potential

timescale of asteroid resurfacing by regolith convection resulting from the impact induced global seismic shaking abstract a model for the asteroid resurfacing by regolith convection is built to estimate its timescale in the model regolith convection is driven by the impact induced global seismic shaking the model consists of three steps i intermittent impact of meteoroids ii impact induced global vibration seismic shaking and iii vibration induced regolith convection in order to assess the feasibility of the resurfacing process driven by regolith convection we estimate the resurfacing timescale as a function of the size of a target asteroid in the estimate a set of parameter values is assumed on the basis of previous works however some of them e g seismic quality factor q seismic efficiency and seismic frequency f are very uncertain although these parameter values might depend on asteroid size we employ the standard values to estimate the representative behavior to clarify the parameter dependences we develop an approximated scaling form for the resurfacing timescale according to the estimated result we find that the regolith convection based resurfacing timescale is shorter than the mean collisional lifetime in most of the parameter uncertainty ranges these parameter ranges are within those reported by previous works for small asteroids this means that the regolith convection can be a possible mechanism for the asteroid resurfacing process

an artificial impact on the asteroid 162173 ryugu formed a crater in the gravity dominated regime the hayabusa2 spacecraft investigated the small asteroid ryugu which has a rubble pile structure we describe an impact experiment on ryugu using hayabusa2 s small carry on impactor the impact produced an artificial crater with a diameter 10 meters which has a semicircular shape an elevated rim and a central pit images of the impact and resulting ejecta were recorded by the deployable camera 3 for 8 minutes showing the growth of an ejecta curtain the outer edge of the ejecta and deposition of ejecta onto the surface the ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface the crater formed in the gravity dominated regime in other words crater growth was limited by gravity not surface strength we discuss implications for ryugu s surface age