empirical and theoretical comparisons of the chicxulub and sudbury impact structures chicxulub and sudbury are 2 of the largest impact structures on earth research at the buried but well preserved chicxulub crater in mexico has identified 6 concentric structural rings in an analysis of the preserved structural elements in the eroded and tectonically deformed sudbury structure in canada we identified ring like structures corresponding in both radius and nature to 5 out of the 6 rings at chicxulub at sudbury the inner topographic peak ring is missing which if it existed has been eroded reconstructions of the transient cavities for each crater produce the same range of possible diameters 80110 km the close correspondence of structural elements between chicxulub and sudbury suggests that these 2 impact structures are approximately the same size both having a main structural basin diameter of 150 km and outer ring diameters of 200 km and 260 km this similarity in size and structure allows us to combine information from the 2 structures to assess the production of shock melt melt produced directly upon decompression from high pressure impact and impact melt shock melt and melt derived from the digestion of entrained clasts and erosion of the crater wall in large impacts our empirical comparisons suggest that sudbury has 70 more impact melt than does chicxulub 31 000 versus 18 000 km3 and 85 more shock melt 27 000 km3 versus 14 500 km3 to examine possible causes for this difference we develop an empirical method for estimating the amount of shock melt at each crater and then model the formation of shock melt in both comet and asteroid impacts we use an analytical model that gives energy scaling of shock melt production in close agreement with more computationally intense numerical models the results demonstrate that the differences in melt volumes can be readily explained if chicxulub was an asteroid impact and sudbury was a comet impact the estimated 70 difference in melt volumes can be explained by crater size differences only if the extremes in the possible range of melt volumes and crater sizes are invoked preheating of the target rocks at sudbury by the penokean orogeny cannot explain the excess melt at sudbury the majority of which resides in the suevite the greater amount of suevite at sudbury compared to chicxulub may be due to the dispersal of shock melt by cometary volatiles at sudbury

contradictory correlations of paleoproterozoic glacial deposits local regional or global controls abstract there is little agreement among recently proposed correlation schemes for paleoproterozoic glaciogenic rocks scattered thinly around the globe correlations are hindered by the dearth of tight geochronological control on the ages of glacial deposits which are notoriously difficult to date most attempts at global correlation are based on comparison to the huronian supergroup in canada which contains three glaciogenic formations although the two lower glacial units were deposited in a rift setting and have a restricted distribution even in north america they have been used in attempts to effect international correlations the gowganda formation together with correlatives comprises the thickest and by far the most widespread paleoproterozoic glacial deposits in north america glacial deposits are also reported from south africa western australia and elsewhere where they appear to fall within the same time period as the huronian supergroup 2 45 2 2 ga but attempts to correlate individual diamictite bearing units to the three huronian glaciogenic formations have proved difficult none of the huronian glacial formations has been precisely dated until such geochronological data are available it is practical and prudent to recognize that during the early paleoproterozoic as in the cryogenian the earth was susceptible to glaciations that could be triggered by a variety of local events including uplift related to rifting and compressional orogeny within the 250 million years of the huronian glacial event 2 45 2 2 ga it is commonly assumed that ice sheet fluctuations were globally synchronous but this has not been demonstrated

evidence of saharan dust in upper pleistocene reworked palaeosols of north west sardinia italy palaeoenvironmental implications abstract a multi disciplinary approach was followed to investigate two thick palaeosolstrata that alternate with wind blown dominated deposits developed along thealghero coast north west sardinia italy optically stimulated luminescenceages reveal that both palaeosols were developed during cooler drier periods the rst one at around 70 ka marine isotope stage 4 and the latter around 50 ka marine isotope stage 3 in contrast the pedological features indicate that thepalaeosols underwent heavy weathering processes under warm humid to sub humid conditions characteristic of the sardinian climate during the lastinterglacial stage marine isotope stage 5e to reconcile this apparent datadiscrepancy a range of sedimentological and pedological analyses wereconducted these analyses reveal that the palaeosols possess a complexhistory with accumulation and weathering occurring during marine isotopestage 5e and erosion colluviation and nal deposition taking place during thefollowing cold stages thus even if these reddish palaeosols were last formedduring the glacial period the sediments building up these strata probablyrecord the climate of the last interglacial stage marine isotope stage 5e traceelement and x ray diffraction analyses together with scanning electronmicroscope images reveal the presence of saharan dust in the parentmaterial of the palaeosols however no evidence of any far travelled africandust has been observed in the marine isotope stage 4 3 aeolian deposits it ispossible to conclude that in the west mediterranean islands saharan dustinput even if of modest magnitude is preserved preferentially in soilsaccumulated and weathered during interglacial stages keywords marine isotopic stage mediterranean osl dating trace elementgeochemistry xrd analysis sedimentology 2012 59 917 938

orbital observations of contemporary dune activity in endeavor crater meridiani planum mars 1 although aeolian landforms are pervasive on mars evidence for contemporary activity has been limited the next major campaign for the mars exploration rover opportunity is the investigation of the 20 km diameter endeavor crater 6 km to southeast of the rover s position as of december 2010 we present evidence from orbital imagery that eight aeolian bed forms 14 000 m2 in endeavor crater have been active within the past decade 2001 2009 at a spatial scale that should be directly observable by opportunity from the crater rim two dunes appear to show translational migration 10 20 m but all dunes indicate erosion to be the dominant process with up to 100 sediment removal thermophysical properties of these dunes are consistent with very fine to fine sand sizes the particle sizes most easily moved by the martian atmosphere the dunes that show the most surface change have a rippled appearance without well defined slip faces based on their morphology elliptical shape we classify them as dome dunes mesoscale atmospheric modeling is employed to provide insight into the atmospheric forcing of this aeolian system the major wind regimes from modeling are consistent with observations of wind streaks sand streamers ripples and slip faces of regional dune fields although modeled wind speeds are insufficient to move sand the translation and erosion of these dunes constitutes the largest contemporary movement of sand sized sediment reported on mars to date and demonstrates that endeavor crater has been subject to wind profiles exceeding the threshold velocity at the surface daily seasonally and or episodically in the recent past

sources of non glacial loess size quartz silt and the origins of desert loess abstract descriptions of peridesertic loess deposits and possible non glacial origins for silt size quartz are reviewed including direct release from weathered bedrock results from salt and frost weathering experiments are presented and methods by which sufficient energy can be imparted to sand size grains to release silt size fragments are identified these fragments may then be entrained by aeolian or fluvial action results from fluvial comminution experiments indicate that high energy mixed sediment fluvial systems may be very effective in generating quartz silt purely aeolian attrition is also seen as a major source of silt size and finer material results from aeolian abrasion experiments performed using crushed quartz sand are complemented by trials using sands from deeply weathered granite and pannonian sands from hungary field and laboratory observations are therefore seen to argue for the existence of deposits that can be classified as desert loess

vredefort sudbury chicxulub three of a kind vredefort sudbury and chicxulub are the largest known terrestrial impact structures all have been cited as multi ring basins the available data indicate that all have some form of multiple ring attributes most commonly structural features chicxulub however is the only example with morphological ring features there are also commonalities in the structural and lithological features of vredefort and sudbury and it is possible to construct a generalized compilation of the character of 200 300 km diameter impact basins on earth it is not clear however that any of these structures had the original morphological characteristics of large lunar multi ring basins additional data and synthesis are required to fully characterize these structures in order to realize their potential to constrain large scale cratering processes if this is not sufficient incentive for further studies the environmental effects of chicxulub aside the vredefort sudbury and chicxulub impact events are also the reason for

controls on the large scale spatial variations of dune field properties in the barchanoid portion of white sands dune field new mexico previous studies have shown that sediment fluxes and dune sizes are a maximum near the upwind margin of the white sands dune field and decrease to first order with increasing distance downwind these patterns have alternatively been attributed to a shear stress overshoot associated with a roughness transition localized at the upwind margin and to the influence of long wavelength topography on the hydrology and hence erodibility of dune field sediments i point out an issue that compromises the shear stress overshoot model and further test the hypothesis that long wavelength topographic variations acting in concert with feedbacks among aerodynamic granulometric and geomorphic variables control dune field properties at white sands building upon the existing literature i document that the mean and variability of grain sizes sand dryness aerodynamic roughness lengths bed shear stresses sediment fluxes and ripple and dune heights all achieve local maxima at the crests of the two most prominent scarps in the dune field one coincident with the upwind margin and the other located 6 7 km downwind computational fluid dynamics cfd modeling predicts that bed shear stresses erosion rates and the supply of relatively coarse poorly sorted sediments are localized at the two scarps due to flow line convergence hydrology and the spatially distributed adjustment of the boundary layer to variations in dune size as a result the crests of the scarps have larger ripples due to the granulometric control of ripple size larger grain sizes and or larger ripples lead to larger dunes and hence larger values of bed shear stress in a positive feedback

sudbury breccia canada a product of the 1850 ma sudbury event and host to footwall cu ni pge deposits abstract the sudbury structure formed by meteorite impact at 1850 ma consists of three major components 1 the sudbury basin 2 the sudbury igneous complex which surrounds the basin as an elliptical collar and 3 breccia bodies in the footwall known as sudbury breccia in general the breccia consists of subrounded fragments set in a dark fine grained to aphanitic matrix a comparison of the chemical composition of host rocks clasts and matrices indicates that brecciation was essentially an in situ process sudbury breccia forms irregular shaped bodies or dikes that range in size from mm to km scale contacts with the host rocks are commonly sharp the aspect ratio of most clasts is approximately 2 with the long axes parallel to dike walls the fractal dimension dr 1 55 although there appears to be some concentration of brecciation within concentric zones small sudbury breccia bodies within and outside these zones have more or less random strikes and steep dips sudbury breccia bodies near an embayment structure tend to be subparallel to the base of the sudbury igneous complex sudbury breccia occurs as much as 80 km from the outer margin of the sudbury igneous complex in an inner zone 5 to 15 km wide breccia comprises 5 of exposed bedrock with an increase in brecciation intensity in embayment structures sudbury breccia may be classified into three types based on the nature of the matrix clastic pseudotachylite and microcrystalline clastic sudbury breccia the dominant type in the southern province is characterized by flow surface structures possibly a sudden rise in pore pressure caused explosive dilation and fragmentation followed by fluidization and flowage into extension fractures pseudotachylite sudbury breccia mainly confined to archean rocks apparently formed by comminution and frictional melting microcrystalline sudbury breccia formed as a result of the thermal metamorphism of the north range footwall by the sudbury igneous complex this produced a zone approximately 1 2 km wide wherein the matrix of the breccia either recrystallized or locally melted an overprint of regional metamorphism obliterated contact effects in the south range footwall the ni cu pge magmatic sulphide deposits may be classified into four types based on structural setting sudbury igneous complex footwall contact footwall offset and sheared deposits sudbury breccia is the main host for footwall deposits e g mccreedy east victor lindsley sudbury breccia locally hosts mineralization in radial e g parkin and copper cliff and concentric e g frood stobie offset dikes

evidence for paleoproterozoic cap carbonates in north america the early paleoproterozoic snowy pass supergroup of the medicine bow mountains and sierra madre wyoming usa and huronian supergroup ontario canada were deposited along the present day southern flank of the wyoming and superior cratons whereas three discrete levels of glacial diamictite are developed in both successions carbonate strata are known only directly above the middle diamictite vagner and bottle creek formations in medicine bow mountains and sierra madre respectively and espanola formation in southern ontario in these thick correlative siliciclastics dominated strata the carbonates from each succession record negative 13 c values 4 0 to 0 8 v pdb and attenuated carbon isotopic difference between organic and inorganic phases oxygen in carbonates is strongly depleted in 18 o suggesting exchange with hot fluids which is consistent with pervasive recrystallization of carbonates and remobilization of elements however the stratigraphic coherence of carbon isotopic compositions and the general lack of correlation between 13 c and either 18 o values or trace element concentrations supports a primary origin for 13 c depleted carbonates which are interpreted here to reflect anomalous oceanic compositions the intimate association of thick carbonate units containing abundant carbonate debris flows with immediately underlying glacial strata indicates that chemical precipitation resulted from a rapid flux of carbonate alkalinity onto ocean margins during post glacial transgression although these early paleoproterozoic carbonates are similar to neoproterozoic cap dolomites in stratigraphic position and carbon isotopic compositions the older post glacial accumulations begin with limestone and lack many of the sedimentary structures typical of neoproterozoic deposits furthermore it is not understood why carbonates only occur above the middle of the three glacial horizons whereas these deposits are ubiquitous above neoproterozoic diamictites the differences might reflect lower overall carbonate saturation in early paleoproterozoic oceans which contrasts sharply with archean and later paleoproterozoic intervals and higher siliciclastic inputs in rift environments which shut down carbonate deposition geological and geochemical indicators suggest a stepwise increase in atmospheric oxygen across the paleoproterozoic glacial epoch the tempo and mode of atmospheric oxygen rise has significant consequences for the abundance of the important greenhouse gases ch4 and co2 and hence for oceanic acidity if we accept that atmospheric oxidation of methane to carbon

windy mars a dynamic planet as seen by the hirise camera 1 with a dynamic atmosphere and a large supply of particulate material the surface of mars is heavily influenced by wind driven or aeolian processes the high resolution imaging science experiment hirise camera on the mars reconnaissance orbiter mro provides a new view of martian geology with the ability to see decimeter size features current sand movement and evidence for recent bedform development is observed dunes and ripples generally exhibit complex surfaces down to the limits of resolution yardangs have diverse textures with some being massive at hirise scale others having horizontal and cross cutting layers of variable character and some exhibiting blocky and polygonal morphologies reticulate fine polygonal texture bedforms are ubiquitous in the thick mantle at the highest elevations

structural characteristics of the sudbury impact structure canada impact induced versus orogenic deformation a review orogenic deformation both preceding and following the impact event at sudbury strongly hinders a straightforward assessment of impact induced geological processes that generated the sudbury impact structure central to understanding these processes is the state of strain of the sudbury igneous complex the solidified impact melt sheet its underlying target rocks overlying impact breccias and post impact sedimentary rocks this review addresses 1 major structural metamorphic and magmatic characteristics of the impact melt sheet and associated dikes 2 attempts that have been made to constrain the primary geometry of the igneous complex 3 modes of impact induced deformation as well as 4 mechanisms of pre and post impact orogenic deformation the latter have important consequences for estimating parameters such as magnitude of structural uplift tilting of pre impact huronian strata and displacement on major discontinuities which collectively have not yet been considered in impact models in this regard a mechanism for the emplacement of offset dikes is suggested that accounts for the geometry of the dikes and magmatic characteristics as well as the occurrence of sulfides in the dikes moreover re interpretation of published paleomagnetic data suggests that orogenic folding of the solidified melt sheet commenced shortly after the impact uncertainties still exist as to whether the sudbury impact structure was a peak ring or a multi ring basin and the deformation mechanisms of rock flow during transient cavity formation and crater modification

soils in the mediterranean region what makes them different mediterranean climates are characterized by winter rains with some months of excess rainfall over evatranspiration warm and dry summer months with moisutre deficits drying out soils and their annual vegetation xeric moisture regime they are found on western parts of all continents between the cooler temperature zone and the hot dry desert zone the largest mediterranean region surrounding the mediterranean sea extends over 4 300 000 km2 and exhibits a wide variety of soils and geo ecosystems characteristics landscape attributes are the high proportion of mountains with sleep slopes significant additions of saharan desert dust to practically all soils of the region and a large proportion of limestone and other calcareous rocks as soil parent materials characteristics soil behavior features are moderate weathering with pervection leaching lessivage of mostly 2 1 clays into b horizons xeralfs luvisols hematite induced reddening of the clays due to summer dehydration of free iron oxyhydroxides carbonate dissolution and reprecipitation with prevalence of calcic horizons xerolls calcisols in semiarid regions and development of vertisols mostly in lowlands where deep layers of swelling cracking clays have sedimented shallows soils on nearly bare slopes mostly a result of erosion subsequent to deforestation are frequent leptosols cambiosols inceptisols entisols red or brown mediterranean soils are no longer used as a separate classification group in modern well defined soil property controlled taxonomies soil taxonomy fao system but were partially replaced by duchaufour s term fersiallitic soils in some classification systems terra rossa continues to be used in some classification for hard limestone derived red soils mostly shallow the effects of man s past and current interference with the lanscape are pervasive in most regions and predictions for possible future effects on the soils and ecosystems due to greenhouse gas induced warming and rainfall change are partly negative partly still too uncertain

the influence of local topography for wind direction on mars two examples of dune fields in crater basins in this work we perform an analysis of large dark dunes within moreux crater and herschel crater on mars using high resolution imaging science experiment hirise and context camera ctx data sets these data allow us to conduct a detailed analysis of dune morphology and slip faces concluding that the studied dune fields are influenced by topographically controlled complex wind directions our morphological analysis reveals that inside moreux crater in particular the topographic setting dominates the wind flow direction leading to the development of a sand transport pathway encircling the central peak of the crater the dune fields in herschel crater are also affected by winds controlled by variable topography as suggested by the presence of complex dunes and dune fields our analysis indicate that the studied dune systems is not the result of paleo wind regimes furthermore we perform thermal inertia measurements using thermal emission spectrometer tes data which indicate that the studied dune fields consist of medium sand 250 500 mm in diameter

are outliers of the huronian supergroup preserved in structures associated with the collapse of the sudbury impact crater several outliers of the paleoproterozoic huronian supergroup are preserved in a 20 km wide arcuate belt northwest of the sudbury igneous complex forty years ago it was suggested that these outliers represented the remnants of a discontinuous rim syncline developed around a domal structure thirteen years later it was proposed that they were preserved in grabens formed as a result of collapse of the central uplift of a multi ring impact crater and the simultaneous emplacement of the sudbury igneous complex this interpretation has been accepted by most investigators without question to the extent that the position of the outliers has been used to estimate the size of the supposed crater our observations indicate that huronian strata in the outliers were deposited in a series of paleo valleys on a terrane with considerable topographic relief the asymmetric nature of the fill in some of the outliers suggests deposition may have taken place in half grabens the outliers are preserved in synclines develope

aeolian dunes as ground truth for atmospheric modeling on mars 1 martian aeolian dunes preserve a record of atmosphere surface interaction on a variety of scales serving as ground truth for both global climate models gcms and mesoscale climate models such as the mars regional atmospheric modeling system mrams we hypothesize that the location of dune fields expressed globally by geographic distribution and locally by dune centroid azimuth dca may record the long term integration of atmospheric activity across a broad area preserving gcm scale atmospheric trends in contrast individual dune morphology as expressed in slipface orientation sf may be more sensitive to localized variations in circulation preserving topographically controlled mesoscale trends we test this hypothesis by comparing the geographic distribution dca and sf of dunes with output from the ames mars gcm and at a local study site with output from mrams when compared to the gcm 1 dunes generally lie adjacent to areas with strongest winds 2 dca agrees fairly well with gcm modeled wind directions in smooth floored craters and 3 sf does not agree well with gcm modeled wind directions when compared to mrams modeled winds at our study site 1 dca generally coincides with the part of the crater where modeled mean winds are weak and 2 sfs are consistent with some weak topographically influenced modeled winds we conclude that 1 geographic distribution may be valuable as ground truth for gcms 2 dca may be useful as ground truth for both gcm and mesoscale models and 3 sf may be useful as ground truth for mesoscale models

emplacement of sharp walled sulfide veins during the formation and reactivation of impact related structures at the broken hammer mine sudbury ontario broken hammer is a hybrid cu ni platinum group element pge footwall deposit located in archean basement rocks below the impact induced sudbury igneous complex sic canada the deposit consists

the tectonostatigraphic evolution of the huronian basement and the subsequent basin fill geological constraints on impact models of the sudbury event abstract whereas both meteorite impact and volcanic mechanisms have been proposed to explain the rocks and associated ore deposits within the sudbury structure 1 85 ga few models take into consideration the paleogeographic constraints implied by the history of the region before and following the sudbury event huronian depositional style south of the sudbury structure appears to have been strongly influenced by the early development of transtensional extensional basins these basins were initiated by sinistral strike slip movement along part of a paleoproterozoic continental margin which later evolved into a passive margin transition from a rifted strike slip margin to a passive margin was accompanied by major slope failure and soft sediment deformation south of the murray fault diabase dikes were intruded into unconsolidated sediments at considerable depth producing round stone breccias which are texturally similar to sudbury breccia minor compressional folding occurred prior to emplacement of the nipissing diabase suite at around 2 2 ga the abundance of diabase intrusions near the sudbury structure suggests that the area may have been a focal point for magma emplacement the post event fill of the paleoproterozoic sudbury basin reflects initial deposition in a deep water anoxic setting there is no evidence to suggest that sedimentation was influenced by the steep walls of an impact crater carbonate in the basal vermilion member is of sedimentary exhalative origin and was not derived from a shallow marine shelf turbidites in the chelmsford formation show no evidence of centripetal fill as might be expected from a restricted circular basin they appear to have been emplaced along the depositional axis of an elongate foreland basin developed in front of the rising penokean mountain chain penokean deformation continued after the sudbury event and influenced strata well into the archean craton deformation of huronian strata in paleovalleys north and west of the sudbury structure does not appear to be genetically related to the sudbury event if superfaults were generated around the sudbury structure in response to compression and crustal rebound following a meteorite impact these do not appear to have caused offset of pre existing steeply dipping contacts between the huronian and underlying archean basement a new model consistent with these observations needs to be developed

particle size fractionation of eolian sand along the sinai negev erg of egypt and israel eolian sand fractions along the west east transport system of the northern sinai peninsula northwestern negev erg of egypt and israel were analyzed in this study with regard to source dune geomorphology eolian transport and paleoclimate the studied erg is composed of active linear seif dunes in northern sinai western part and stabilized vegetated linear dunes in the nw negev dune field eastern part linear seif dunes differ from vegetated linear dunes in their vegetation cover linearity internal structure and dynamics sand samples were analyzed for sand grain morphology and particle size distribution although both dune types are continuous landforms with similar orientations and sand grain roundness values the linear dunes of sinai are coarser grained than the negev vegetated linear dunes the vegetated linear dunes have a variable but higher proportion of very fine sand 50 125 m content and a varying but lower sand fining ratio defined as the ratio of fine sand percentage to very fine sand percentage from these observations we infer that fractionation of sand occurred along the studied eolian transport path during periods of enhanced windiness very fine sands are suggested to have been transported by saltation and low suspension from source deposits and sand sheets we suggest that a significant proportion of the very fine sand fraction of nile delta sands has been transported downwind through northern sinai during the late pleistocene especially when linear dunes reached the nw negev due to last glacial period windiness and probably larger sediment supply generally decreasing wind velocities and increasing precipitation along the west east dune transport path enhanced vegetative cover in the northern negev and enabled deposition of the very fine sand component within the dunes and probably further downwind our results suggest that particle size distribution can elucidate much about erg history over time scales of a glacial interglacial cycle especially in cases where the sand provenance is of a single dominant source

aeolian processes in proctor crater on mars mesoscale modeling of dune forming winds 1 both atmospheric modeling and spacecraft imagery of mars are now of sufficient quality that the two can be used in conjunction to acquire an understanding of regional and local scale aeolian processes on mars we apply a mesoscale atmospheric model adapted for use on mars the mars mm5 to proctor crater a 150 km diameter crater in the southern highlands proctor crater contains numerous aeolian features that indicate wind direction including a large dark dune field with reversing transverse and star dunes containing three different slipface orientations small and older bright bedforms that are most likely transverse granule ripples and seasonally erased dust devil tracks results from model runs spanning a martian year with a horizontal grid spacing of 10 km predict winds aligned with two of the three dune slipfaces as well as spring and summer winds matching the dust devil track orientations the primary most prevalent dune slipface orientation corresponds to a fall and winter westerly wind created by geostrophic forces the tertiary dune slipface orientation is caused by spring and summer evening katabatic flows down the eastern rim of the crater influencing only the eastern portion of the crater floor the dunes are trapped in the crater because the tertiary winds enhanced by topography counter transport from the oppositely oriented primary winds which may have originally carried sand into the crater the dust devil tracks are caused by light spring and summer westerly winds during the early afternoon caused by planetary rotation the secondary dune slipface orientation is not predicted by model results from either the mars mm5 or the geophysical fluid dynamics laboratory mars general circulation model the reason for this is not clear and the wind circulation pattern that creates this dune slipface is not well constrained the mars mm5 model runs do not predict stresses above the saltation threshold for dune sand of the appropriate size and composition as with previous work the calculated wind velocities are too low which may be caused by too large of a grid spacing

present day aeolian activity in herschel crater mars abstract in this report we show evidence for ripple and dune migration in herschel crater on mars we estimate an average dune migration of 0 8 m and a minimum ripple migration of 1 1 m in a time span of 3 7 earth years these dunes and ripples are mainly shaped by prevailing winds coming from the north however we also report the presence of secondary winds which elongate the barchans horns such a complex wind scenario is likely caused by the influence of winds blowing off the western crater rim as suggested by the mars regional atmospheric modeling system mrams an atmospheric mesoscale model a multi directional wind regime at the local scale is also supported by the observed bimodal distribution of the ripple trends for the first time a survey integrating the assessment of dune and ripple migration is presented showing how dune topography can influence the migration patterns of ripples and how underlying topography appears to control the rates of dune migration

the potential influence of dust flux and chemical weathering on hillslope morphology convex soil mantled carbonate hillslopes in the eastern mediterranean abstract convex soil covered hillslopes are ubiquitous in various tectonic and climatic settings and their morphologic characteristics can be significantly altered by dust flux and chemical weathering carbonate hillslopes across the eastern mediterranean display a classic convex morphology despite high rates of dust deposition which are apparently similar in magnitude to denudation rates and despite a highly soluble bedrock lithology these high rates of dust flux and bedrock dissolution result in soil composition which is strikingly different from the underlying bedrock in this study we apply a modified regolith mass balance equation which includes dust input and chemical depletion and utilize a combination of field work and geochemical methods immobile and major elements xrd to estimate the fraction of dust derived materials in the soil and the fraction of the soil that was lost via dissolution soil and bedrock were sampled at 7 eastern mediterranean study sites across a prominent north to south gradient in both precipitation 250 to 900 mm yr 1 and dust flux 150 to 40 g m 2 yr 1 and compared with dust composition our results indicate that the dust fraction in the soil correlates with modern measurements of dust deposition rates and decrease from nearly 100 of the 2 mm indicating that mechanical weathering of the underlying bedrock contributes to regolith formation and plays a role in shaping carbonate hillslopes using a commonly used soil transport model we show that the observed dust fraction and chemical weathering can potentially account for a 50 change in hillslope curvature furthermore the predicted steady state hilltop curvature based on our results fits well the observed curvature based on high resolution lidar derived topographic data our results highlight the potential importance of dust and chemical weathering in soil production formulations and hillslope evolution models and we propose that these contributors to soil mass balance could also be relevant for silicate terrain in addition we also demonstrate that the source material of mediterranean soils varies with environmental factors such as rainfall dust deposition rates and bedrock mechanical properties

dune migration and slip face advancement in the rabe crater dune field mars 1 eight overlapping images of a dune slip face in rabe crater 35 e 44 s from the mars global surveyor mars orbiter camera show changes interpreted to be multiple grainflow events that would indicate present day sand saltation and dune migration new occurrences of these features appear sporadically throughout late southern summer and early fall and then no further changes occur throughout winter by the following summer the pattern of old streaks had been almost completely covered by new dark streaks assuming that this activity is typical from year to year migration rates are estimated to be on the order of 1 2 cm per martian year produced by south to southeasterly winds that blow mostly during the southern spring and early summer this slow migration rate is consistent with a present day sediment state that is either transport or availability limited

active aeolian processes on mars a regional study in arabia and meridiani terrae 1 we present evidence of widespread aeolian activity in the arabia terra meridiani region mars where different kinds of aeolian modifications have been detected and classified passing from the regional to the local scale we describe one particular dune field in meridiani planum where two ripple populations are distinguished by means of different migration rates moreover a consistent change in the ripple pattern is accompanied by significant dune advancement between 0 4 1 meter in one martian year that is locally triggered by large avalanche features this suggests that dune advancement may be common throughout the martian tropics

late glacial and holocene aeolian deposits and geomorphological features near roccaraso abruzzo central italy abstract aeolian deposits and geomorphological features due to wind erosion have been recorded in the aremogna plain near roccaraso central apennines at this site three different aeolian deposits can be distinguished 1 silty loess deposits composed mainly of quartz 2 aeolian sand deriving from the reworking of tephra which lies on a peat level dated to 12 850 200 bp and 3 aeolian silt coming from the deflation of the deposits 2 which is associated to deflation geomorphological features in part still active the onset of these processes is more recent than 4690 200 bp the first and the second aeolian deposits are related to cold and dry phases of the late glacial period the third set of aeolian deposits and deflation features corresponds to wind erosion on a denudated landscape as a consequence of a dry climatic phase the effect of which was amplified by winter freezing thawing activity

paleosols provide sedimentation relative age and climatic information about the alluvial fan of the river tirso central western sardinia italy four representative paleosols in the plio pleistocene alluvial fan of the river tirso central western sardinia italy were studied for paleoenvironmental information to describe the sedimentology of the alluvial fan and to define a relative chronological framework for the fan the representative depositional units and associated paleosols were characterised by fieldwork physical chemical and mineralogical analyses pedogenesis was mostly driven by the time and climate factors in the proximal fan location pedogenesis was initially influenced by a warm subtropical tropical climate of the late pliocene and subsequently by warm and humid interglacial phases of the pleistocene these phases were also responsible for soil formation in the middle fan in the distal reaches of the fan pedogenesis was driven by the different climatic pulses of the late pleistocene tyrrhenian interglacial mis 5 pleistocene eustatic sea level changes directly influenced the lowest elevations of the middle fan and the distal fan erosion and soil truncation mainly occurred in the proximal fan and at the highest elevations of the middle fan during glacial phases

the mars regional atmospheric modeling system model description and selected simulations the mars regional atmospheric modeling system mrams is introduced and selected model results are presented and compared with landed meteorological data when possible mrams is descended from a nonhydrostatic earth mesoscale and cloud scale model that is widely used for forecasting weather and simulating atmospheric systems over complex terrain mesoscale models such as mrams are ideal tools for making use of the high resolution data sets arriving from mars global surveyor experiments simulation of the mars pathfinder mpf landing site at lsd 142 using 1 2 degree mars orbiter laser altimeter mola derived topography and thermal emission spectrometer thermal inertia is shown to be in good agreement with observed near surface temperature pressure and wind direction simulations of topographically induced thermal circulations and mountain induced gravity waves are shown to be consistent with theory and earlier studies that tie large amplitude mountain waves to strong winds capable of producing dust streaks and local dust lifting events a large eddy simulation of the convective boundary layer provides estimates of vertical profiles of heat flux momentum flux turbulent kinetic energy and vertical velocity variance the model results suggest that the martian atmosphere is roughly two to three times more turbulent than the terrestrial atmosphere during the afternoon but fluxes are roughly an order of magnitude smaller due to the lower density dust devillike circulations are also predicted in the large eddy simulation finally a simulation that examines atmosphere surface interactions near big crater is discussed predicted surface wind stress patterns are consistent with aeolian processes inferred through mars orbiter camera imagery of big crater located near the mpf landing site c 2001 academic press

eolian dust deposition on the giara di gesturi basalt plateau sardinia mineralogical study of samples from depression fills on an isolated basalt plateau in central sardinia showed that although the basalt is free of quartz and mica fair amounts of these minerals occur in the finer fractions results from x ray analyses of silt fractions and morphoscopical analyses of sand fractions indicate that the bulk of the quartz and mica is of eolian origin the eolian quartz is predominantly of medium and coarse silt size and in the upper 10 cm of the depression fills constitutes about 20 per cent of the soil mass approx 20 kg m2 eolian mica is present in smaller amounts and is of medium silt or smaller size the provenance of the eolian material could not be established with certainty although a local origin can be excluded

late quaternary eolian deposition in central italy abstract records of eolian quartz from two continuous sediment sequences drilled in lagaccione and lago di vico volcanic lakes in central italy contribute to the knowledge of eolian deposition in the central mediterranean during the last 100 000 years the chronology is based on 14 c and 40 ar 39 ar dating and tephra analysis pollen data provide the paleoenvironmental framework and enable correlation between the cores eolian inputs were high during the steppe phases corresponding to oxygen isotope stages 4 and 2 low inputs correspond to the forest phases of the last interglacial and the middle holocene eolian inputs have increased in the late holocene patterns of eolian deposition in central italy resemble the antarctic dust record from the vostok ice core the italian patterns may also correspond with hydrological changes registered in north africa the main source of dust loading over the mediterranean now north africa may have played an important role in dust supply throughout the last climatic cycle

variation in plagioclase clouding intensity in matachewan dykes evidence for the exhumation history of the northern margin of the sudbury igneous complex early proterozoic matachewan mafic dykes that cut the archean cartier granite levack gneiss complex north of the sudbury igneous complex sic canada are generally metamorphosed to lower amphibolite facies but exhibit locally unaltered plagioclase these plagioclase feldspars display a clouding similar to that found in the same swarm in the vicinity of the kapuskasing uplift about 200 km to the northwest where the clouding intensity is due to magnetite exsolution and displays a positive correlation with the depth of dyke emplacement in the sudbury area the clouding intensity obtained by image analysis of thin sections increases away from the sic opposite to the direction of increasing regional metamorphism in the archean basement this suggests that the levack gneiss complex north of the sic was exhumed prior to the intrusion of 2 47 ga matachewan dykes and therefore predates the formation of the sic and associated impact event the southward tilting of the crust inferred from the plagioclase clouding data appears to have involved uplift along the benny deformation zone but the exact age of this deformation is unknown it may be associated with the 1 8 1 9 penokean orogen 1 85 ga sudbury impact crater or 2 2 2 4 ga blezardian orogen resume les dykes mafiques de matachewan proterozoique precoce qui recoupent le complexe de granite cartier gneiss levack archeen au nord du complexe igne de sudbury sic sont generalement metamorphoses au facies inferieur des amphibolites mais ils montrent par endroits du plagioclase inaltere ces feldspaths presentent un embrouillage semblable ce que l on retrouve dans le meme essaim aux environs du bloc sureleve de kapuskasing environ 200 km au nord ouest ou l intensite de l embrouillage est causee par de l exsolution de la magnetite et demontre une correlation positive avec la profondeur de la mise en place du dyke dans la region de sudbury l intensite de l embrouillage obtenue par l analyse d images de sections minces augmente en s eloignant du sic soit dans la direction opposee du metamorphisme regional croissant dans le socle archeen cela suggere que le complexe de gneiss levack au nord du sic a ete exhume avant l intrusion des dykes mafiques de matachewan 2 47 ma et donc qu il est plus vieux que la formation du sic et associe a l evenement d impact l inclinaison vers le sud de la croute deduite a partir des donnees d embrouillage du plagioclase semble impliquer un soulevement le long de la zone de deformation de benny mais l ge exact de cette deformation est inconnu la deformation peut etre associee a l orogene penokeen 1 8 1 9 ga au cratere d impact de sudbury 1 85 ga ou a l orogene blezardien vers 2 2 2 4 ga traduit par la redaction siddorn and halls 942

geoscience impact a synthesis of studies of the sudbury structure geophysical probing results are synthesized into a three dimensional framework necessary for understanding the genesis of the sudbury structure based primarily on seismic reflection results centred on the sudbury igneous complex remnants of crustal melting from a catastrophic meteorite impact are superimposed on the juxtaposition of mid crustal rocks exhumed during the archean against deformed paleoproterozoic sedimentary rocks sedimentation metamorphism deformation and metasomatic overprints are all part of the post impact history of sudbury and tend to dominate the geophysical response of the structure pre impact deformation although certainly preserved in some aspects of sudbury geology is not clearly expressed in the geophysical data nor are any elements of impact induced deformation geophysical views of the sudbury igneous complex are thus somewhat biased in representing mostly the post impact but pre grenvillian history of the region with the exception of igneous events establishing th

contribution of saharan dust to mediterranean soils assessed by sequential extraction and pb and sr isotopes abstract measurements of the concentrations and isotopic composition of pb and sr in al silicates and fe oxides of two soil profiles developed in the guadalquivir river basin andalusia southwestern spain are used in order to estimate the significance of local versus foreign sources lead concentrations are 10 6 mg kg in deep more than 100 cm soil samples and reach 30 60 mg kg near the surface 206 pb 207 pb values range from 1 200 to 1 206 in deep samples and from 1 186 to 1 191 in the upper most samples sr concentrations range from 30 to 69 mg kg showing no systematic trend with depth 87 sr 86 sr ratios range from 0 71753 to 0 72526 also with no systematic changes with depth in the fe oxide fraction but with a systematic increase in values with depth in the al silicate fraction of one of the soil profiles in all the samples the isotopic composition of pb in the al si fraction is slightly more radiogenic than its value in the fe oxide fraction the isotopic composition of sr exhibits the opposite behavior and 87 sr 86 sr values in the fe oxide fraction are always higher than in the al silicate fraction based on our data we calculate that al silicates in the fine soil fraction less than 5 m in both sites contain 33 86 of saharan dust and that the fe oxides contain less saharan dust and more material released by the weathering of basement granitoid type rocks in the case of pb a third source is present in the upper part of the soil i e anthropogenic pb probably added to the soil over millennia the results of the present study suggest that saharan dust makes up a significant fraction in al silicates and fe oxides of mediterranean soils but that local sources both natural rock derived and anthropogenic are not trivial

origins of outliers of the huronian supergroup within the sudbury structure abstract the spatial relations between outliers of huronian metasediment and the current outline of the sudbury igneous complex sic have been used previously to constrain the original size of the meteorite impact crater despite uncertainty regarding their structure and origin the outliers are tight to isoclinal gently plunging synclines with northeast southwest trending axes slightly overturned to the northwest major deformation of the huronian supergroup preceded the 1849 ma sudbury meteorite impact event by sufficient time to permit peneplanation of the region impact occurred in a foredeep related to the subduction of the laurentia plate under the wisconson magmatic terranes faults truncate the northwest margins of most of the outliers where examined at several localities the northwest margin bounding faults are invariably occupied by pseudotachylite structural considerations provide evidence for thousands of meters of slip along these surfaces each of which was apparently accomplished in

carbon isotope record for the onset of the lomagundi carbon isotope excursion in the great lakes area north america carbonate units of the chocolay group in the lake superior area usa and the gordon lake formation of the correlative upper huronian supergroup ontario canada were deposited after the last paleoproterozoic glacial event and an episode of intense chemical weathering the huronian supergroup contains at the base 2 45 ga volcanics and is intruded by the 2 22 ga nipissing diabase dykes and sills while the chocolay group is bracketed in age between 2 29 and 2 20 ga the lomagundi 2 22 2 1 ga carbon isotope excursion started after the paleoproterozoic glacial epoch and before a plume breakout event at 2 22 ga therefore the chocolay and upper huronian carbonates were deposited either before or during the onset of the lomagundi event notably thin carbonates of the basal gordon lake formation and thick carbonate succession of the kona dolomite in the northeastern exposures of the chocolay group record 13 c values as high as 9 5 versus v pdb similar to other successions deposited during the lomagundi event both units contain pseudomorphs and molds after sulfates this observation suggests that seawater sulfate contents rose dramatically in association with the onset of the lomagundi event and the rise of atmospheric oxygen carbonates in the western and southern exposures of the chocolay group randville and bad river dolomites and saunders formation previously assumed to be equivalent to the gordon lake formation and kona dolomite have carbon isotope values close to 0 based on basin analysis we infer that these carbonate units were deposited during a negative carbon isotope excursion after the lomagundi event started and are slightly younger than the kona dolomite and gordon lake formation this interpretation implies that the carbonate platform in the great lakes area transgressed to the west over shallow marine and fluvial deposits the negative carbon isotope excursion in the lake superior area might correspond to similar 13 c values of the mooidraai dolomite in the griqualand west basin south africa supporting correlation between paleoproterozoic successions of north america and south africa and the notion of three global glaciations in the paleoproterozoic era carbonates of the mille lacs group trout lake glen township and denham formations in minnesota have 13 c values ranging from 1 2 to 2 5 combined with geochronologic constraints these data suggest that these units were deposited after the lomagundi excursion and are related to the rifting event that led to development of the so far unrecognized 2 0 ga passive margin in the lake superior area 2006 elsevier b v all rights reserved

aeolian dust transport and deposition over crete and adjacent parts of the mediterranean sea monitoring of dust deposition at several stations on crete over a three year period has shown that the present day depositional flux is of the order of 10 100 gm 2 yr 1 most of the dust deposition takes place during a few annual dust events which typically last for 1 3 days dust haze episodes are usually associated with southerly or southwesterly winds which transport fine sediment from north africa dust is raised by a wide variety of meteorological conditions which generate strong near surface winds in the source areas but major long range transport events are often associated with cold fronts linked to the passage of deep mid latitude depressions during winter and spring dust haze frequency and deposition rates are highest in western crete and decrease towards the east suggesting that transport from tunisia and neighbouring parts of north africa is particularly important the measured rate of dust deposition is well below the minimum level required for loess formation deposits which have previously been identified as loess are shown to be uncemented marine marls of tertiary age laboratory analysis of red soils surface sediments and bedrock samples has confirmed that many of the soils contain an important aeolian dust component but it is concluded that a more important source of soil parent material is provided by weathering of local rocks many of the soils contain significant amounts of quartz sand which cannot have been transported across the sea from north africa reworking of weathered material and deposited dust is extensive and is accomplished by both aeolian and fluvial processes tectonically controlled depressions in the mountains and parts of the coastal lowlands have acted as long term sinks in which a thickness of several metres of sediment and soil has accumulated during the quaternary

mars global digital dune database and initial science results 1 a new mars global digital dune database mgd3 constructed using thermal emission imaging system themis infrared ir images provides a comprehensive and quantitative view of the geographic distribution of moderate to large size dune fields area 1 km2 that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of mars mgd3 extends from 65 n to 65 s latitude and includes 550 dune fields covering 70 000 km2 with an estimated total volume of 3 600 km3 this area when combined with polar dune estimates suggests moderate to large size dune field coverage on mars may total 800 000 km2 6 times less than the total areal estimate of 5 000 000 km2 for terrestrial dunes where availability and quality of themis visible vis or mars orbiter camera narrow angle moc na images allow we classify dunes and include dune slipface measurements which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification for dunes located within craters the azimuth from crater centroid to dune field centroid referred to as dune centroid azimuth is calculated and can provide an accurate method for tracking dune migration within smooth floored craters these indicators of wind direction are compared to output from a general circulation model gcm dune centroid azimuth values generally correlate to regional wind patterns slipface orientations are less well correlated suggesting that local topographic effects may play a larger role in dune orientation than regional winds

ripple migration and dune activity on mars evidence for dynamic wind processes 1 in this report we show evidence of widespread ripple migration over the stoss side of dark barchan dunes in nili patera on mars the measured average migration of 1 7 meters in less than 4 terrestrial months clearly indicates that active sand saltation is occurring in the study area in addition we document widespread changes in the dune base ground surface contact and in the slip face structures showing that not only the ripples but the whole dunes are actually migrating in the present day atmospheric setting these results provide unequivocal evidence of recent aeolian activity and suggest that other dunes and ripples on mars may also be active

multidisciplinary characterization of the middle holocene eolian deposits of the elsa river basin central italy abstract in temperate regions eolian deposits of different natures are often pedogenically altered and mixed with underlying sediments the research reported in this paper identifies for the first time the presence of eolian deposits in soils of central tuscany and investigates the characteristics and origin five relict polycyclic paleosol profiles were studied p1 was situated in a natural dust trap a doline on top of an isolated limestone hill p2 and p3 were both situated on a limestone plateau and p4 and p5 on a mid and foot slope on schist the profiles were sampled for routine analyses iron forms heavy minerals major and trace elements and pollen spores and non pollen palynomorphs undisturbed samples were taken for micromorphological and sem analyses nine soil horizons were sampled for osl dating eolian deposits were dominant or abundant in the first layers of p1 p2 and p3 osl age determinations of soil horizons deriving from eolian parent material were middle holocene chemical and heavy mineral analyses indicated different possible sources including bare slopes alluvial fans and wide channels coming from the nearby streams that drain the middle tuscany ridge and the mounts of chianti marginal contribution of volcanic ashes was only found in p1 the research demonstrated that wind soil erosion accompanied water erosion and colluvial deposition during the middle holocene in the elsa river basin pollen spectra in particular indicated that soil degradation occurred in an environment showing signs of incipient desertification resulting from an increase of aridity in a land already strongly influenced by humans although central italy is currently considered to be only marginally affected by wind soil erosion a climate change which would imply increased arid conditions could trigger a new cycle of slope denudation wind erosion and loess deposition

earth like sand fluxes on mars strong and sustained winds on mars have been considered rare on the basis of surface meteorology measurements and global circulation models raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process recent studies showed sand activity but could not determine whether entire dunes were moving implying large sand fluxes or whether more localized and surficial changes had occurred here we present measurements of the migration rate of sand ripples and dune lee fronts at the nili patera dune field we show that the dunes are near steady state with their entire volumes composed of mobile sand the dunes have unexpectedly high sand fluxes similar for example to those in victoria valley antarctica implying that rates of landscape modification on mars and earth are similar

a unifying model for planform straightness of ripples and dunes in air and water abstract geologists physicists and mathematicians have studied ripples and dunes for more than a century but despite considerable effort no general model has been proposed to explain perhaps the most fundamental property of their morphology why are some bedforms straight continuous parallel and uniform in planform geometry i e two dimensional whereas others are irregular three dimensional here we argue that physical coupling along the crest of a bedform is required to produce straight crests and that along crest flow and sand transport provide effective physical mechanisms for that coupling ripples and dunes with the straightest and most continuous crests include longitudinal and oblique dunes in unidirectional flows wave ripples dunes in reversing flows wind ripples and ripples migrating along a slope at first glance these bedforms appear quite different ripples and dunes air and water transverse oblique and longitudinal orientations relative to the net sand transport direction but they all have one property in common a process that increases the amount of along crest sand transport that lengthens and straightens their crests relative to the across crest transport that makes them migrate and take the more typical and more three dimensional planform geometry in unidirectional flows that produce straight bedforms along crest transport of sand is caused by along crest flow non transverse bedform orientation gravitational transport along an inclined crest or ballistic splash in air bedforms in reversing flows tend to be straighter than their unidirectional counterparts because reverse transport across the bedform crest reduces the net across crest transport that causes the more typical irregular geometry relative to the along crest transport that smoothes and straightens planform geometry