fault reactivation in brittle viscous wrench systems dynamically scaled analogue models and application to the rhine bresse transfer zone abstract analogue experiments on oblique rifting and subsequent transpressional reactivation were performed with two layer slabs of sand and silicone in this brittle viscous system transtensional and transpressional wrench faulting was induced by movements of a basal rigid plate the dynamically scaled analogue models are confronted with the structural evolution of the rhine bresse transfer zone rbtz that linked palaeogene rifting in the upper rhine and bresse grabens and that appears to have been transpressively reactivated in neogene to recent times fault patterns produced in the sand layer above the basal silicone layer are compared with structural elements in the sedimentary cover separated from the basement by an evaporitic decollement layer in order to investigate strain rate dependence of fault reactivation and graben inversion transpressional shortening was performed under different displacement rates experimental results suggest that the reactivation of pre existing structures in a brittle cover above a viscous decollement is strongly dependent on the strain rate within the viscous layer under low to intermediate displacement rates 2 6 cm h 1 deformation concentrates within the basal viscous layer and former normal faults within the cover are not reactivated the reactivation at higher displacement rates 5 cm h 1 results in a complete inversion of graben structures within the cover ongoing shortening produces lobed thrust fronts which crosscut pre existing normal faults late pliocene to recent en echelon aligned folds and isolated thrust faults in the cover of the rbtz are attributed to thick skinned reactivation of basement faults a comparison of natural and experimentally obtained structures suggests that fault reactivation occurred under low displacement rates

observations of periglacial landforms in utopia planitia with the high resolution imaging science experiment hirise 1 the region of western utopia planitia 80 105 e 40 55 n displays several types of landforms similar to earth periglacial features including scallop shaped depressions and networks of polygonal terrains the scalloped depressions have been proposed to originate from thermokarstic processes such as sublimation and or melting of near surface ground ice using hirise imagery we characterize these depressions and several associated distinct polygon networks in unprecedented morphologic and topographic detail and investigate support for an ice based degradation process the scalloped depressions and interior polygons and ridges are found to evolve together mainly influenced by sublimation local proximity of ground ice to the surface and obliquity variations

mobility of mo u as and sb within modern turbidites modern turbidites uranium molybdenum arsenic antimony we present and discuss porewaters and sediment data of mn fe mo u as and sb within four recent turbidites from the capbreton canyon sw france the deposition of turbidites on continental margins exerts strong influence on the fate of trace metals causing trace metal migration and or immobilization the down core distribution of the elements here depends entirely of ongoing diagenetic processes rather than the diffusion of o2 the persistence of fe mn oxides under anoxic conditions led to anoxic reoxidation of numerous species as nh4 reduced s compounds and trace metals metal oxides thus control the immobilization of mo and as in the solid phase and the remobilization of u and sb to the porewaters although the low sulphide production prevents anoxic authigenesis of mo and as reducing conditions below each horizon rich in mn fe oxides resulted in u and sb accumulation the exact mechanisms of sb immobilization are not known but it is most certainly different from that of as the profile shapes of mn and u were used to estimate the age of the turbidite deposits which cannot be determined by conventional radionuclide methods our interpretations however depend on calculations of diffusion coefficient particularly for u a simple diffusive model applied to mn suggested that the age of the latest deposit noted t1 was 22 months this date is close to the time elapsed between the core sampling and the last known turbiditic event in the capbreton canyon i e martin storm 18 months using the u data set and depending on diffusion coefficients used the estimated ages of the deeper layers were 4 7 yr for t2 and 7 5 14 yr for t3 the reliability and precision of this new approach to date sediments at short timescales is limited by the ignorance of a precise value for u diffusion coefficient reducing uncertainty on u diffusion coefficient will greatly support application of the proposed approach

extensional forced folding and decollement of the pre rift series along the rhine graben and their influence on the geometry of the syn rift sequences

backward modeling of the rifting kinematics in the upper rhine graben insights from an elastic perfect contact law on the restoration of a multi bloc domain this paper addresses the problem of volume restoration for 3 d sedimentary basin kinematic deformation the primary purpose is methodological and concerns the use of contact mechanics with the finite element method in order to deform a geological multi bloc domain this approach is applied to backward model the later stage of rifting of a segment of the southern upper rhine graben france germany border preliminary results from our modeling demonstrate the ability of the method not only to handle complex geometries but also to successfully perform retro deformation of a complex geological domain in addition they provide or confirm crucial information on the rifting evolution and tectonic features of this segment of the upper rhine graben such as the distribution of deformation the asymmetry of the graben and a significant left lateral strike slip component of displacement

detached neotectonic stress field in the northern jura mountains switzerland geodetically determined recent elevation changes plio pleistocene uplift history and quarternary fault movements suggest that the folded jura is neotectonically active this concept is supported by measurements of in situ rock stress in this region

comparative tertiary stratigraphy of the rhine graben bresse graben and molasse basin correlation of alpine foreland events abstract comparative tectonostratigraphic analysis of the tertiary middle eocene pliocene of the rhine bresse graben system and the western molasse basin demonstrates the occurrence of eleven correlative sequences crf i xi these show a close relationship between intra basinal tectonics and depositional history their punctuated sediment accumulation can be related to phases of extra alpine taphrogenesis and alpine orogenesis and to coeval eustatic changes in sea level apparent simultaneity in rift and foredeep sequence development structural deformation and global change in sea level suggests a common causal control in which the development of the alps played an important role

dynamics of ice ages on mars mars experiences much greater fluctuations in exposure to sunlight than the earth does because of larger variations in astronomical factors such as the tilt of its axis relative to the orbital plane climate change is accordingly more intense on mars than on earth norbert schorghofer has now developed a climate model that accounts for the advance and retreat of the subsurface martian ice sheets over forty major ice ages and five million years this explains the present distribution of subsurface ice on mars in addition lessons learned from the long and relatively simple martian ice age stratigraphy should help when it comes to interpreting the more complicated events here on earth numerical simulation and modelling of the retreat and growth of ground ice on mars demonstrates how the subsurface ice sheets could have evolved and ended up in the state we see them today and also reveals that 40 major ice ages occurred on mars over the past 5 million years unlike earth where astronomical climate forcing is comparatively small mars experiences dramatic changes in incident sunlight that are capable of redistributing ice on a global scale1 2 3 4 5 6 the geographic extent of the subsurface ice found poleward of approximately 60 latitude on both hemispheres of mars7 8 9 coincides with the areas where ice is stable7 10 11 however the tilt of mars rotation axis obliquity changed considerably in the past several million years earlier work3 12 has shown that regions of ice stability which are defined by temperature and atmospheric humidity differed in the recent past from today s and subsurface ice is expected to retreat quickly when unstable11 12 13 here i explain how the subsurface ice sheets could have evolved to the state in which we see them today simulations of the retreat and growth of ground ice as a result of sublimation loss and recharge reveal forty major ice ages over the past five million years today this gives rise to pore ice at mid latitudes and a three layered depth distribution in the high latitudes of from top to bottom a dry layer pore ice and a massive ice sheet combined these layers provide enough ice to be compatible with existing neutron and gamma ray measurements7 8 9

the rhinegraben extension subsidence and shoulder uplift abstract we apply a numerical model of the thermal evolution of a continental lithosphere undergoing extensional deformation to the rhinegraben using reasonable parameters the results of computations are in agreement with the present configuration of the rift and of its shoulders as well as with their evolution since the oligocene contrasting evolutions are reconstructed in the northern and southern rhinegraben whereas the northern history is accounted for by a simple model of homogeneous stretching of the lithosphere the history of the southern rhinegraben cannot be explained without introducing two main periods of heterogeneous stretching the results are locally supported by structural analyses of extensional patterns factors of extension average 1 2 in the axial portion of the rhinegraben and 1 15 for the whole rift section suggesting that the total amount of e w extension reaches 6 km

geological and geophysical evidence for large palaeo earthquakes with surface faulting in the roer graben northwest europe from the analysis of geological geodetic and geophysical data we provide clear evidence of seismogenic faults capable of producing large earthquakes in intraplate europe previous studies paulissen vandenberghe gullentops 1985 van den berg et al 1994 geluk et al 1994 have yielded some constraints on the rate of crustal deformation along the roer valley a graben structure crossing the netherlands belgium and germany and have allowed us to address the fundamental questions can intraplate earthquakes rupture the surface in this part of stable continental europe and if so what is their return period detailed palaeoseismic investigations have been carried out in belgium along a 10 km long fault scarp which is the morphological expression of the feldbiss fault the southwestern border fault of the roer graben camelbeeck meghraoui 1996 the scarp is multiple and the frontal fault scarp offsets young deposits and alluvial terraces field investigations using geological and geomorphological methodologies combined with geophysical prospecting provide evidence of holocene seismic surface faulting from 14c dating it is suggested that the last earthquake along the fault scarp occurred between 610 ad and 890 ad levelling profiles across the scarp suggest that it produced a vertical coseismic displacement of 0 5 1 m along the scarp if we suppose that the last surface faulting earthquake ruptured the whole seismogenic layer 17 km thickness over a minimum length 10 km corresponding to the length of the bree scarp with an average slip of 0 6 m its seismic moment was at least 3 1 1018 n m mw 6 3 for an average rigidity 3 1010 pa by estimating the offset of the main terrace of the maas river by slippage along the feldbiss fault we calculate the average late pleistocene vertical deformation rate as 0 08 0 04 mm yr 1 palaeoseismic information combining the trench and geomorphic observations suggests the occurrence of two surface faulting earthquakes during the last 20 kyr a third dates before 28 35 kyr bp then if the time distribution of earthquakes is uniform a return period of 12 5 ka and a vertical deformation rate of 0 06 0 04 mm yr 1 are inferred

antarctic dry valleys microclimate zonation variable geomorphic processes and implications for assessing climate change on mars the antarctic dry valleys adv are generally classified as a hyper arid cold polar desert the region has long been considered an important terrestrial analog for mars because of its generally cold and dry climate and because it contains a suite of landforms at macro meso and microscales that closely resemble those occurring on the martian surface the extreme hyperaridity of both mars and the adv has focused attention on the importance of salts and brines on soil development phase transitions from liquid water to water ice and ultimately on process geomorphology and landscape evolution at a range of scales on both planets the adv can be subdivided into three microclimate zones a coastal thaw zone an inland mixed zone and a stable upland zone zones are defined on the basis of summertime measurements of atmospheric temperature soil moisture and relative humidity subtle variations in these climate parameters result in considerable differences in the distribution and morphology of 1 macroscale features e g slopes and gullies 2 mesoscale features e g polygons including ice wedge sand wedge and sublimation type polygons as well as viscous flow features including solifluction lobes gelifluction lobes and debris covered glaciers and 3 microscale features e g rock weathering processes features including salt weathering wind erosion and surface pitting equilibrium landforms are those features that formed in balance with environmental conditions within fixed microclimate zones some equilibrium landforms such as sublimation polygons indicate the presence of extensive near surface ice identification of similar landforms on mars may also provide a basis for detecting the location of shallow ice landforms that today appear in disequilibrium with local microclimate conditions in the adv signify past and or ongoing shifts in climate zonation understanding these shifts is assisting in the documentation of the climate record for the adv a similar type of landform analysis can be applied to the surface of mars where analogous microclimates and equilibrium landforms occur 1 in a variety of local environments 2 in different latitudinal bands and 3 in units of different ages documenting the nature and evolution of the adv microclimate zones and their associated geomorphic processes is helping to provide a quantitative framework for assessing the evolution of climate on mars

active normal faulting in the upper rhine graben and paleoseismic identification of the 1356 basel earthquake we have identified an active normal fault in the epicentral area of the basel switzerland earthquake of 18 october 1356 the largest historical seismic event in central europe the event of 1356 and two prehistoric events have been characterized on the fault with geomorphological analysis geophysical prospecting and trenching carbon 14 dating indicates that the youngest event occurred in the interval 610 to 1475 a d and may correspond to the 1356 basel earthquake the occurrence of the three earthquakes induced a total of 1 8 meters of vertical displacement in the past 8500 years for a mean uplift rate of 0 21 millimeters per year these successive ruptures on the normal fault indicate the potential for strong ground movements in the basel region and should be taken into account to refine the seismic hazard estimates along the rhine graben

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

structural and rheological implications of lower crustal earthquakes below northern switzerland abstract a detailed study of the recent seismicity in the northern alpine foreland of switzerland reveals that earthquakes with magnitudes between 0 9 and 4 2 occur not only in the upper part of the crust but contrary to observations in most other intracontinental settings seismicity extends down to depths of about 30 km in the lower crust observed p wave velocities in the focal region of even the deepest earthquakes are less than 6 3 km s 1 the average value of poisson s ratio for the entire focal depth range 6 30 km lies between 0 23 and 0 24 focal mechanisms are mostly a combination of strike slip and normal faults with consistent orientations of p and t axes but without any systematic dependence on focal depth from geological observations regional strain rates are of the order of 10 13 s 1 two dimensional temperature modelling indicates that temperatures in the lower crustal seismogenic zone are well above 450 c under the assumption of a dry environment the observed p wave velocities and poisson s ratios imply either a granitic or quartz rich gneissic composition or possibly a gabbroic quartz free granulite the deformation would be governed either by the rheology of quartz or of plagioclase the onset of ductility observed in laboratory studies lies around 300 c for quartz and around 450 c for plagioclase thus conditions in the lower crust beneath northern switzerland appear to be incompatible with the occurrence of either brittle failure or plastic instabilities as is implied by the existence of earthquakes alternatively lower crustal earthquakes could be a manifestation of the presence of fluids in the lower crust fluids under near lithostatic pressure either evolved in situ from metamorphic reactions or from infiltration from the mantle would tend to decrease the effective stress on pre existing faults and thus allow brittle friction failure to occur at depths where under dry conditions or low fluid pressures only ductile deformation would be expected

equatorial locations of water on mars improved resolution maps based on mars odyssey neutron spectrometer data abstract we present a map of the near subsurface hydrogen distribution on mars based on epithermal neutron data from the mars odyssey neutron spectrometer the map s spatial resolution is approximately improved two fold via a new form of the pixon image reconstruction technique we discover hydrogen rich mineralogy far from the poles including 10 wt water equivalent hydrogen weh on the flanks of the tharsis montes and 40 wt weh at the medusae fossae formation mff the high weh abundance at the mff implies the presence of bulk water ice this supports the hypothesis of recent periods of high orbital obliquity during which water ice was stable on the surface we find the young undivided channel system material in southern elysium planitia to be distinct from its surroundings and exceptionally dry there is no evidence of hydration at the location in elysium planitia suggested to contain a buried water ice sea finally we find that the sites of recurring slope lineae rsl do not correlate with subsurface hydration this implies that rsl are not fed by large near subsurface aquifers but are instead the result of either small

the current martian cratering rate abstract the discovery of 248 dated impact sites known to have formed within the last few decades allows us to refine the current cratering rate and slope of the production function at mars we use a subset of 44 of these new craters that were imaged before and after impact by mars reconnaissance orbiter s context camera a thoroughly searched data set that minimizes biases from variable image resolutions we find the current impact rate is 1 65 10 6 craters with an effective diameter 3 9 m km2 yr with a differential slope power law exponent of 2 45 0 36 this results in model ages that are factors of three to five below the hartmann hartmann w k 2005 icarus 174 294 320 and neukum et al neukum g ivanov b a hartmann w k 2001 space sci rev 96 55 86 ivanov ivanov b a 2001 space sci rev 96 87 104 model production functions where they overlap in diameter the best fit production function we measure has a shallower slope than model functions at these sizes but model function slopes are within the statistical errors more than half of the impacts in this size range form clusters which is another reason to use caution when estimating surface ages using craters smaller than 50 m in diameter

widespread excess ice in arcadia planitia mars the distribution of subsurface water ice on mars is a key constraint on past climate while the volumetric concentration of buried ice pore filling versus excess provides information about the process that led to its deposition we investigate the subsurface of arcadia planitia by measuring the depth of terraces in simple impact craters and mapping a widespread subsurface reflection in radar sounding data assuming that the contrast in material strengths responsible for the terracing is the same dielectric interface that causes the radar reflection we can combine these data to estimate the dielectric constant of the overlying material we compare these results to a three component dielectric mixing model to constrain composition our results indicate a widespread decameters thick layer that is excess water ice 104 km3 in volume the accumulation and long term preservation of this ice is a challenge for current martian climate models

geodetic measurements of crustal deformation in the western mediterranean and europe geodetic measurements of crustal deformation over large areas deforming at slow rates 5 mm yr over more than 1000 km such as the western mediterranean and western europe are still a challenge because 1 these rates are close to the current resolution of the geodetic techniques 2 inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities we present a new velocity field for western europe and the western mediterranean derived from a rigorous combination of 1 a selection of sites from the itrf2000 solution 2 a subset of sites from the european permanent gps network solution 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy on the order of 1 mm yr or better its analysis shows that central europe behaves rigidly at a 0 4 mm yr level and can therefore be used to define a stable europe reference frame in that reference frame we find that most of europe including areas west of the rhine graben the iberian peninsula the ligurian basin and the corsica sardinian block behaves rigidly at a 0 5 mm yr level in a second step we map recently published geodetic results in the reference frame previously defined geodetic data confirm a counterclockwise rotation of the adriatic microplate with respect to stable europe that appears to control the strain pattern along its boundaries active deformation in the alps apennines and dinarides is probably driven by the independent motion of the adriatic plate rather than by the africa eurasia convergence the analysis of a global gps solution and recently published new estimates for the african plate kinematics indicate that the africa eurasia plate motion may be significantly different from the nuvel1a values in particular geodetic solutions show that the convergence rate between africa and stable europe may be 30 60 slower than the nuvelia prediction and rotated 10 30 counterclockwise in the mediterranean

sharad detection and characterization of subsurface water ice deposits in utopia planitia mars morphological analyses of utopia planitia mars have led to the hypothesis that the region contains a substantial amount of near surface ice this paper tests this hypothesis using ground penetrating radar techniques we have identified an expansive radar reflective region spanning approximately 375 000 km2 in shallow radar sharad data over western utopia planitia the sharad reflective regions coincides with high densities of scalloped depressions and polygonal terrain the reflectors are associated with layered mesas 80 170 m thick we find a value of 2 8 0 8 for the dielectric constant of the material overlying the reflectors this work finds that the dielectric constant is consistent with a mixture of ice air and dust containing a water ice volume up to 14 300 km3 in this unit

modeling the development of martian sublimation thermokarst landforms abstract sublimation thermokarst landforms result from collapse of the surface when ice is lost from the subsurface on mars scalloped landforms with scales of decameters to kilometers are observed in the mid latitudes and considered likely thermokarst features we describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation over periods of tens of thousands of mars years under conditions similar to the present the model produces scallop like features similar to those on the martian surface starting from much smaller initial disturbances the model also indicates crater expansion when impacts occur in surfaces underlain by excess ice to some depth with morphologies similar to observed landforms on the martian northern plains in order to produce these landforms by sublimation substantial quantities of excess ice are required at least comparable to the vertical extent of the landform and such ice must remain in adjacent terrain to support the non deflated surface we suggest that martian thermokarst features are consistent with formation by sublimation without melting and that significant thicknesses of very clean excess ice up to many tens of meters the depth of some scalloped depressions are locally present in the martian mid latitudes climate conditions leading to melting at significant depth are not required

thermokarst lakes and ponds on mars in the very recent late amazonian past the history of water is fundamental to understanding the geological evolution of mars and to questions concerning the possible development of life on the red planet today mars is cold and dry it

stress tensor determination in france and neighbouring regions abstract the tectonic behaviour of different seismic regions of france is inferred from the properties of the local stress tensor obtained from focal mechanisms of regional earthquakes polarities of p wave arrivals for several earthquakes are used in the inversion of the stress tensor and individual focal mechanisms the principal axes and the shape of the tensor are closely related to the forces which generate seismic ruptures on pre existing faults we analyse 142 earthquakes of magnitude above 3 7 which occurred between 1965 and 1989 good results are obtained for some regions the northern alps and the southern end of the upper rhinegraben show a quasi compressive strike slip tectonic regime with a maximum stress axis oriented nw se the tectonic regime changes to an extensional strike slip type in the rhenish massif and the lower rhinegraben the direction of the minimum stress axis being nne ssw the central and western regions of france central and armorican massifs exhibit an extensional tectonic regime combined with strike slip faulting the minimum stress axis strikes in a ne sw direction a strongly non homogeneous stress field seems to be present in the southwestern alps and no unique stress tensor could be obtained for that region this problem is likely to be related to a rapid variation of the stress field in space which could be expected given the arc like geometry of the mountain range the pyrenean domain is unresolved due to lack of data and moreover existing focal mechanisms are globaly inconsistent nevertheless those mechanisms which are well constrained suggest a nnw sse to nw se direction of maximum stress in the western part of the pyrenees thus the stress field in france is fairly homogeneous at a regional scale for most of the territory except for the highly deformed belts

geomorphological evidence of localized stagnant ice deposits in terra cimmeria mars the presence of snow and ice at mid latitudes of mars cannot be explained by current climatic conditions as surface ice is unstable however a large variety of debris covered glaciers have been observed at both mid latitudes here we report the presence of local small scale and debris covered stagnant ice deposits on the floor of a valley system in terra cimmeria these deposits termed valley fill deposits vfd have a distribution that is restricted to the host valley floor and to the extent of the ejecta blanket associated with tarq impact crater the vfd are characterized by convex upward morphology various crevasses sublimation pits an average area of a few km2 and occasional ejecta streaks on their surface our model age estimation points to two possible time frames for the tarq impact event thus we suggest two formation scenarios for vfd i distribution of ice due to impact into shallow ice during the middle amazonian ii post impact deposition of vfd due to precipitation in both scenarios ice preservation is most likely due to a lag of dust and debris deposited in the valley s topographic lows scenario i is more consistent with our geomorphological observation of the vfd being overlain by ejecta streaks our results highlight the importance of local geological events and conditions in the distribution and preservation of buried ice deposits on mars and suggest that more small scale and debris covered ice deposits may exist in the mid latitudes than previously thought these deposits are of high importance for future human exploration missions to mars

recent height changes in the central segment of the rhinegraben and its adjacent shoulders abstract zippelt k and malzer h 1981 recent height changes in the central segment of the rhinegraben and its adjacent shoulders in j h illies editor mechanism of graben formation tectonophysics 73 119 123 the height changes in the central segment of the rhinegraben its shoulders included are computed from first order levelling data the network for investigation with regard to recent vertical crustal movements extends the graben segment between karlsruhe and worms and overlaps the shoulders of the pfalzer wald in the west and the kraichgau in the east the investigated area is characterized by negative height changes subsidence in its eastern shoulder and by positive values uplift in its western one in the graben positive height changes were found in its western part but in the eastern part negative values dominate over thick unconsolidated pleistocene sediments tectonically controlled ground motions cannot be separated from atectonic processes like subsidence as caused by changing groundwater levels

forced folds and fractures this volume is concerned with defining the major similarities and difference between forced folds and buckle folds in order that these differences can be used to recognize the type of folding and therefore the expected fracture pattern present in regions of poor exposure or where the geologist has to rely on seismic images an understanding of the differences between the two fold types their 3d geometry spatial organization fracture patterns etc provides an invaluable tool for earth scientists concerned with assessing the possible role of folds and their associated fracture patterns in controlling fluid migration and concentration within the crust the papers presented here are grouped into 4 sections contributions in the first section describe the use of numerical analyses to investigate the formation of fractures in forced folds including compaction folds and the section contains a description of large scale compaction folding in which the associated fracturing has given rise to the development of large sandstone dykes the papers in the second section deal with the formation of forced folds as a result of normal faulting in various geological environments including along a classical graben margin and around a resurgent caldera the third section contains papers relating to forced folding in compressional and strike slip regimes the final section considers the temporal and spatial relationships between forced folds and buckle folds the formation of crustal scale folds and a method of determining the distribution of strain on any folded surface a key parameter controlling the distribution of fractures

do river profiles record along stream variations of low uplift rate environments 1m m yr 1 where climate changes may have erased tectonic features we evaluate the respective contribution of low uplift rate 0 1 mm yr 1 and pleistocene climate oscillations on gradient variations of two comparable river profiles crossing different uplift zones in the southern upper rhine graben we compare the observed points of discontinuity in river profile knickpoints and convex portions knickzones with those predicted by a detachment limited model that includes stochastic short term and cyclic long term variations in climate a bedrock detachment threshold and rock uplift the detachment limited model is chosen as it predicts the development of persistent knickpoints differing values of the shear stress exponent erosion threshold climate variability and uplift pattern have been checked our modeling suggests that climate changes had no significant effects on profiles and that anomalies are more likely due to anticline growth this surprising result arises from the combination of a very low regional uplift rate and the detachment limited assumption the detachment limited model implies an upstream propagation of knickpoints and knickzones generated by uplift at the outlet during dry climate periods of low erosion the greater the uplift rate the larger the variations in river bed elevation thus for high uplift rate knickpoints and knickzones generated by climate oscillations are more likely to hide tectonic features this result seems counterintuitive because it suggests that tectonic knickzones will be better preserved in low uplift rate environments provided that the lithology is homogeneous

stress field determinations in france by hydraulic tests in boreholes the stress field has been determined at eight different sites in france four in crystalline or metamorphic rocks four in sedimentary formations by hydraulic tests in boreholes for seven of these sites the complete stress field has been determined using the hydraulic tests on pre existing fractures htpf inversion method validity of the results is demonstrated by the good fit between a priori and a posteriori values for the data and by the low values of the a posteriori standard deviation on the unknowns for four sites results have been compared with those derived according to the hydraulic fracturing theory the two methods yield comparable results for the orientation of the maximum horizontal principal stress h a generally satisfactory fit for the magnitude of the minimum horizontal principal stress h but a very poor agreement for the magnitude of h this latter misfit has been attributed to the effect of fluid percolation prior to the actual opening of the fractures below a depth of 500 m a homogeneous h direction n150 e has been determined at the crystalline sites auriat echassieres le mayet de montagne chassoles all located in the northern massif central for three of these sites the vertical stress is significantly lower than the weight of overburden as computed from the rock density and the depth of the corresponding measurement at auriat and echassieres the stress field is consistent with a mostly strike slip faulting regime at le mayet de montagne and chassoles the maximum stress is vertical but nearly equal to h the stress field has been found to be much more heterogeneous at two of the four sites in sedimentary rocks because of the large variability in mechanical rock properties in such heterogeneous formations inversion with the htpf method must be limited to those data which pertain to the same rock horizon however because of its structure this heterogeneity does not restrict the possibility of defining large scale uniform principal stress directions all the results are consistent with the local seismotectonics

expanded secondary craters in the arcadia planitia region mars evidence for tens of myr old shallow subsurface ice abstract a range of observations indicates widespread subsurface ice throughout the mid and high latitudes of mars in the form of both pore filling and excess ice it is generally thought that this ice was recently emplaced and is not older than a hundred thousand to a few millions of years old based on ice stability and orbital induced climate change we analyze the distribution of subsurface ice in arcadia planitia located in the northern mid latitudes by mapping thermokarstically expanded secondary craters providing additional evidence for extensive excess ice down to fairly low latitudes less than 40 n we further infer the minimum age of this subsurface ice based on the ages of the four primary craters that are thought to be the source of a large portion of these secondaries which yields estimates on the order of tens of millions of years old much more ancient than anticipated this estimated ancient age suggests that ice can be preserved in the shallow subsurface for long periods of time at least in some parts of arcadia planitia where expanded secondary craters are especially abundant we estimate the amount of ice lost to sublimation during crater expansion based on measurements of expanded secondary craters in hirise digital terrain models the loss is equivalent to a volume of ice between 140 and 360 km 3 which would correspond to a global layer of 1 2 5 mm thick we further argue that much more ice at least 6000 km 3 is likely preserved beneath the un cratered regions of arcadia planitia since significant loss of this excess ice would have caused extensive terrain dissection and the removal of the expanded secondary craters both the loss of ice due to secondary crater expansion and the presence of this ice today have implications for the martian climate

modeling and observational occurrences of near surface drainage in utopia planitia mars during the past 15 years evidence for an ice rich planet mars has rapidly mounted become increasingly varied in terms of types of deposits and types of observational data and has become more widespread across the surface the mid latitudes of mars especially utopia planitia show many types of interesting landforms similar to those in periglacial landscapes on earth that suggest the presence of ice rich permafrost these include thermal contraction polygonal networks scalloped terrains similar to thermokarst pits debris flows small mounds like pingos and rock glaciers here we address questions concerning the influence of meltwater in the utopia planitia up landscape using analogs of near surface melting and drainage along ice wedge troughs on bylot island northern canada in utopia planitia based on the identification of sinuous channel like pits within polygonal networks we suggest that episodic underground melting was possible under severe periglacial climate conditions in up the collapse pattern and morphology of unconnected sinuous elongated pits that follow the polygon crack are similar to underground melting in bylot island nunavut canada based on this terrestrial analogue we develop a thermal model that consists of a thick insulating dusty layer over ice saturated dust during a period of slight climatic warming relative to today s climate in the model the melting point is reached at depths down to 150 m we suggest that small scale melting could have occurred below ground within ground ice polygonal fractures and pooled in underground cavities then the water may have been released episodically causing mechanical erosion as well as undermining and collapse after melting the dry surface dusty layer might have been blown away thus exposing the degraded terrain of the substrate layer

anatomy and kinematics of oblique continental rifting revealed a three dimensional case study of the southeast upper rhine graben germany the upper rhine graben is a north northeast trending small displacement crustal scale rift of tertiary age retrodeformation of its southeastern part demonstrates that it is a product of sinistral oblique rifting early extension was toward 80 later the major stretching axis changed to a 60 direction the modeling results suggest that the eastern main border fault developed first and that faulting later propagated into the evolving graben interior considerable along strike variations in heave throw and displacement are evident displacement partitioning causes warping of the rift floor with a 30 35 km wavelength we consider this to be a characteristic of oblique rifting contact deformation of the wall rocks to the major faults may have caused widespread smaller scale faulting and brecciation and may be the location of later movements close spatial coincidence of the depth projections of some of the faults studied and the hypocenters of recent small earthquakes indicates continuing activity of the fault system apparently three fault segments in the freiburg area are currently active and may be an increased earthquake risk

initiation and growth of martian ice lenses abstract water ice in the upper meters of the martian regolith is a major volatile reservoir although the geographic extent burial depth and thermal stability of this shallow ice are well understood its origin history and stratigraphy are not over the past decade a growing body of observational evidence has indicated that shallow ground ice exceeds the pore volume of its host soil over large regions of both martian hemispheres this is confounding given that 1 the physical theory that accurately predicts the location of ground ice also assumes that ice should be pore filling in the upper meter of regolith and 2 the phoenix spacecraft uncovered far more pore filling ice than excess ice at its landing site in the northern hemisphere the development of ice lenses by low temperature in situ segregation analogous to the processes that generate frost heave on earth has been hypothesized to explain shallow excess ice on mars we have developed a numerical model of ice lens initiation and growth in the martian environment and used it to test this hypothesis for the first time we carried out a large suite of numerical simulations in order to place quantitative constraints on the timing and location of ice lens initiation and on the magnitude of ice lens growth in a variety of host soils we find that ice lens initiation is a ubiquitous process in the martian high latitudes but the ultimate magnitude of lens growth or frost heave is sensitive to the properties of the host soil depending on the specific properties of martian soils in situ segregation may be a very slow process sufficient to explain the excess ice observed in the dodo goldilocks trench at the phoenix landing site but without regionally significant effects alternatively if clay sized particles or perchlorate salts are present in situ segregation may be a vigorous process that has significantly affected the stratigraphy of ground ice in the upper meter of regolith throughout the high latitudes

high latitude patterned grounds on mars classification distribution and climatic control patterned grounds such as polygonal features and slope stripes are the signature of the presence of ground ice and of temperature variations in cold regions on earth identifying similar features on mars is important to understand its past climate as well as the ground ice distribution in this study young patterned grounds are classed and mapped from the systematical analysis of mars observer camera high resolution images these features are located poleward of 55 latitude which fits the distribution of ground ice found by the neutron spectrometer onboard mars odyssey thermal contraction due to seasonal temperature variations is the predominant process of formation of polygons formed by cracks which sizes vary from 15 to 300 m the small 40 m widespread polygons are very recent and degraded by the desiccation of ground ice from the cracks which enhances the effect of ice sublimation the large polygons 50 to 300 m located only around the south co2 polar cap indicate the presence of ground ice and thus outline the limit of the co2 ice cap they could be due to the blanketing of water ice deposits by the advances and retreats of the residual co2 ice cap during the last thousand years large 50 250 m and homogeneous polygons similar to ice wedge polygons hillslope stripes and solifluction lobes may indicate that specific environments such as crater floors and hillslopes could have been submitted to freeze thaw cycles possibly related to higher summer temperatures in periods of obliquity higher than 35 these interpretations must be strengthened by higher resolution images such as those of the hirise mission of the mars reconnaissance orbiter because locations with past seasonal thaw could be of major interest as potential landing sites for the phoenix mission

determination of displacements in the upper rhine graben area from gps and leveling data the upper rhine graben is a north northeast trending rift system which belongs to the european cenozoic rift system today the southern part of the graben is seismically still active earthquakes of magnitude 5 have a recurrence time of approximately 30 years in order to monitor and to determine the displacements in the study area gps measurements have been carried out in two campaigns 1999 and 2000 and observations of the available permanent stations have been processed in 2002 owing to the small size of deformations expected high accuracy requirements must be met by the gps processing in order to achieve these requirements precise antenna modeling has been introduced into the processing as expected the short time span has not enabled to detect significant displacements from the gps measurements the deformation analysis shows that the horizontal displacement rates do not exceed 1 mm year which is compatible with the geological information owing to the fact that the accuracy of positioning with gps for the vertical coordinates is lower than for the horizontal coordinates the determination of vertical displacements has been carried out using the leveling technique in the area of freiburg first order and second order leveling lines have been chosen for the detection of local displacements on the weinstetten on the lehen schonberg and on the main border fault mbf some sections of these faults are still active today significant vertical displacements have been observed at the weinstetten fault in the area of bad krozingen and on the mbf in freiburg the displacement rates 1925 1984 are 0 17 0 01 mm year and 0 25 0 02 mm year respectively the results agree very well with the results of seismotectonic investigations and show that ongoing displacements can be found on the northern part of the lehen schonberg fault in the vicinity of eichstetten and on the mbf in the vicinity of freiburg

interplay between tectonic fluvial and erosional processes along the western border fault of the northern upper rhine graben germany abstract the northern upper rhine graben situated in the central part of the european cenozoic rift system is currently characterized by low intra plate seismicity historical earthquakes have not been large enough to produce surface rupturing moreover the records of quaternary surface processes and human modifications are presumably better preserved than the record of the relatively slow tectonic deformation in order to gain information on the neotectonic activity and paleoseismicity in this setting the geological and geomorphological records of fault movements along a segment of the western border fault wbf were studied using an integration of techniques in paleoseismology structural analysis and shallow geophysics the wbf segment investigated follows a 20 km long linear scarp of unclear origin a series of geophysical measurements were performed and the results suggested that near surface deformation structures are present at the segments southern end several trenches opened at this location revealed fault structures with consistent extensional style and a maximum vertical displacement of 0 5 m in one trench the deformation structures were dated between 19 and 8 ka assuming the deformation has been caused by an earthquake a m w 6 5 earthquake would be implied aseismic deformation would point to a fault creep rate 0 04 mm yr a reconstruction of the sequence of events at the trench site from middle pleistocene to present demonstrates that the morphology at the base of the scarp is the result of interplay between tectonic activity and fluvial and erosional processes at the regional scale a mixed origin for the wbf scarp is proposed combining the effects of fluvial dynamics erosion regional uplift and localized tectonic activity on the wbf

kinematic evolution of a tectonic wedge above a flat lying decollement the alpine foreland at the interface between the jura mountains northern alps and the upper rhine graben we estimate strain rates of three parameters that describe the buildup of a tectonic wedge jura front france the uplift rate on frontal ramps decreases with the slip on the ramps and the coeval increase of vertical loads the migration rate of the tip of the sole thrust appears to be episodic and faster than the translation rate of the backstop the long term tilting rate appears to be constant whereas the short term rate is slightly slower we propose a model of wedge growth that proceeds without underthrusting in a prefractured medium the wedge would activate the frontal ramp with a weaker frictional resistance than the forward decollement an instantaneous forward jump of the deformation front would occur when the resistance on the ramp equals the resistance of the frontal decollement this model differs from those proposed for accretionary zones and relates to the backstop of a single tapered orogenic belt

geomorphic evidence for the distribution of ground ice on mars high resolution viking orbiter images show evidence for quasi viscous relaxation of topography the relaxation is believed to be due to creep deformation of ice in near surface materials the global distribution of the inferred ground ice shows a pronounced latitudinal dependence the equatorial regions of mars appear to be ice poor while the heavily cratered terrain poleward of 30 latitude appears to be ice rich the style of creep poleward of 30 varies with latitude possibly due to variations in ice rheology with temperature the distribution suggests that ice at low latitudes which is not in equilibrium with the present atmosphere has been lost via sublimation and diffusion through the regolith thereby causing a net poleward transport of ice over martian history

surveys on environmental tectonics abstract until now research on neotectonics and related seismicity has mostly focused on active plate boundaries characterized by generally high earthquake activity current seismic hazard estimates for intraplate areas are commonly based on probabilistic analyses of historical and instrumental earthquake data the accuracy of these hazard estimates is limited by the nature of the data e g ambiguous historical sources and by the restriction of available earthquake catalogues to time scales of only few hundred years which are geologically insignificant and not suitable to describe the tectonic processes causing earthquakes this is especially relevant to intraplate regions where faults show slow slip rates resulting in long average recurrence times for large earthquakes 10 3 10 6 yr the alpine orogen and intraplate sedimentary basins and rifts of its northern foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that the northern alpine foreland is being actively deformed this has major implications for the assessment of their natural hazards and environmental degradation the nw european lithosphere has undergone a polyphase evolution with an intensive interplay of upper mantle thermal perturbations and stress induced intraplate deformation a number of recent findings point to an important role of lithospheric folding in thermally weakened lithosphere of the northwestern european foreland the eu funded interdisciplinary environmental tectonics research network entec addresses relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland its objectives are to quantify the effects of ongoing alpine collision on nw european foreland intraplate deformation and its impact on surface geomorphology and natural hazards three natural laboratories have been selected 1 the lower rhine graben lrg 2 the upper rhine graben urg and 3 the vienna basin vb these three areas record the manifestation of neotectonics within the alpine orogen vb at its front urg and in the far field area lrg

sharad sounding radar on the mars reconnaissance orbiter 1 sharad shallow radar is a sounding radar provided by agenzia spaziale italiana asi as a facility instrument on the mars reconnaissance orbiter mission its 20 mhz center frequency and 10 mhz bandwidth complement the lower frequency relatively narrower bandwidth capability of the marsis sounding radar a joint italian u s team has guided the experiment development and is responsible for data analysis and interpretation the radar transmits signals at a 700 hz pulse repetition frequency prf and collects reflections from both the surface and near subsurface of mars vertical and horizontal resolutions are respectively 15 m free space and 3 6 km cross track by 0 3 1 km along track the scientific objective of sharad is to map in selected locales dielectric interfaces to at least several hundred meters depth in the martian subsurface and to interpret these results in terms of the occurrence and distribution of expected materials including competent rock soil water and ice a signal to noise ratio of 50 db for a specular surface return is achieved with 10 w of radiated power by using range and azimuth focusing in ground data processing preprocessed data as well as range and azimuth focused data will be formatted according to planetary data system pds standards and be made available from the asi science data center asdc and from the geosciences node of the planetary data system pds important targets for sharad include the polar layered deposits sedimentary stacks especially in terra meridiani buried channel systems buried impact craters volcanic complexes and shallow ice deposits in equilibrium with the atmosphere

modeling sublimation of ice exposed by new impacts in the martian mid latitudes abstract new impacts in the martian mid latitudes have exposed near surface ice this ice is observed to slowly fade over timescales of months in the present martian climate exposed surface ice is unstable during summer months in the mid latitudes and will sublimate we model the sublimation of ice at five new impact sites and examine the implications of its persistence even with generally conservative assumptions for most reasonable choices of parameters it is likely that over a millimeter of sublimation occurred in the period during which the ice was observed to fade the persistence of visible ice through such sublimation suggests that the ice is relatively pure rather than pore filling such ice could be analogous to the nearly pure ice observed by the phoenix lander in the dodo goldilocks trench and suggests that the high ice contents reported by the mars odyssey gamma ray spectrometer at high latitudes extend to the mid latitudes our observations are consistent with a model of the martian ice table in which a layer with high volumetric ice content overlies pore filling ice although other structures are possible

height changes and recent vertical crustal movements in western german areas instrumental improvements abstract the working group recent height changes of the german geodetic commission dgk in co operation with the departments of ordnance survey has published a map of height changes for western german areas the scale of the map is 1 1 000 000 and the height changes resulting from first order levellings are described by isolines of 0 1 mm year instrumental improvements with regard to the observation of recent vertical crustal movements have been achieved the influences of scale errors and insufficient temperature registration on the results of precise levellings are reported

martian pedestal craters marginal sublimation pits implicate a climate related formation mechanism 1 pedestal craters on mars are defined by an outward facing scarp forming a plateau perched tens of meters above the surrounding terrain their origin has been attributed to impact armoring of the surface and subsequent removal of inter crater terrain by either eolian deflation or sublimation of an ice rich substrate we identified 2696 pedestal craters between 60 n and 60 s latitude 98 are poleward of 33 n and 40 s the majority of pedestal crater margins are smoothly sloped but 3 concentrated in utopia planitia and malea planum display distinctive marginal pits these pedestal crater scarps are anomalously tall usually 80 100 m and the pits resemble sublimation depressions seen on earth and elsewhere on mars providing evidence for sublimation of volatiles in the scarp where the armored surface has tapered the pitted scarps provide insight into the origin of the general pedestal crater population favoring formation via deposition of a volatile rich substrate impact armoring and sublimation of intervening volatiles crater densities and overlapping pedestal craters suggest multiple periods of emplacement and loss of these climate related latitude dependent deposits throughout the amazonian

upper rhine graben role of preexisting structures during rift evolution 1 the evolution of the cenozoic upper rhine graben was controlled by a repeatedly changing stress field and the reactivation of a complex set of crustal discontinuities that had come into evidence during permo carboniferous times a comparison of the spatial and temporal thickness distribution of synrift deposits with preexisting fault patterns permits to infer a sequence of distinct basin subsidence phases that can be related to changes in the ambient stress field reactivation of a system of late palaeozoic fault systems outlining troughs and highs controlled the nucleation of initially separated middle and late eocene basins the depocenters of which coincided with a preexisting wsw ene trend during oligocene crustal extension the individual basins coalesced resulting in the development of the ssw nne striking upper rhine graben during the late oligocene chattian change in stress field the upper rhine graben was probably reactivated as a dextral strike slip system with the central graben segment forming a releasing bend during the early miocene aquitanian a major reorientation of the regional stress field is held responsible for the main subsidence phase of the northern parts of the upper rhine graben this is reflected by a counterclockwise rotation and northeastward shift of the depocenter axis and later by the middle miocene uplift and erosion of the southern parts of the upper rhine graben during the plio quaternary the upper rhine graben was reactivated as a sinistral strike slip system with the central graben segment forming a restraining bend

the growth of geological structures by repeated earthquakes 1 conceptual framework in many places earthquakes with similar characteristics have been shown to recur if this is common then relatively small deformations associated with individual earthquake cycles should accumulate over time to create geological structures following this paradigm we show that existing models developed to describe leveling line changes associated with the seismic cycle can be adapted to explain geological features associated with a fault in these models an elastic layer containing the fault overlies a viscous half space with a different density fault motion associated with an earthquake results in immediate deformation followed by a long period of readjustment as stresses relax in the viscous layer and isostatic equilibrium is restored deformation is also caused as a result of the loading and unloading due to sediment deposition and erosion in this paper the parameters that control the growth of dip slip structures are identified we find that the flexural rigidity of the crust or the apparent elastic thickness provides the main control of the width of a structure the loading due to erosion and deposition of sediment determines the ratio of uplift to subsidence between the two sides of the fault the flexure due to sediment load is much more important in this respect than whether the fault is normal or reverse in character we find that in general real structures are associated with apparent elastic thicknesses of 4 km or less and thus with very low flexural rigidities

apparent thermal inertia and the surface heterogeneity of mars abstract thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters consequently surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season to investigate these temporal variations we processed three mars years of mars global surveyor thermal emission spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia these maps show broad regions with diurnal and seasonal differences up to 200 j m 2 k 1 s 1 2 at mid latitudes 60 s to 60 n and 600 j m 2 k 1 s 1 2 or greater in the polar regions we compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5 resolution delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials the thermal behavior of most regions on mars appears to be dominated by layering with upper layers of higher thermal inertia e g duricrusts or desert pavements over fines prevailing in mid latitudes and upper layers of lower thermal inertia e g dust covered rock soils with an ice table at shallow depths prevailing in polar regions less common are regions dominated by horizontal mixtures such as those containing differing proportions of rocks sand dust and duricrust or surfaces with divergent local slopes other regions show thermal behavior that is more complex and not well represented by two component surface models these results have important implications for mars surface geology climate modeling landing site selection and other endeavors that employ thermal inertia as a tool for characterizing surface properties

new observations of martian southern mid latitude recurring slope lineae rsl imply formation by freshwater subsurface flows abstract southern mid latitude sml recurring slope lineae rsl are narrow 0 5 5 m dark albedo features that emanate from bedrock and incrementally lengthen down steep slopes that preferentially face the equator we observe that sml rsl begin lengthening prior to southern summer at a solar longitude ls of 245 11 when mars global surveyor thermal emission spectrometer tes derived near maximum surface temperatures are 296 5 k and mars reconnaissance orbiter mars climate sounder mcs and mars odyssey thermal emission imaging system themis derived mid afternoon surface temperatures are 273 k sml rsl continue to lengthen for 104 38 sols with an average near maximum surface temperature of 298 5 k the sml rsl then stop lengthening at ls 314 12 when mid afternoon surface temperatures drop below 273 k they remain dark for another 116 41 sols until ls 16 14 as surface temperatures continue to fall although the rsl recharge mechanism remains unknown our observation that the vast majority of rsl lengthen only when mid afternoon surface temperatures are 273 k supports the hypothesis that they are formed by shallow subsurface liquid water flows without significant freezing point depression the number and length of rsl at multiple sites increased dramatically following the mars year 28 globe encircling dust storm we interpret this increase to be due to warmer subsurface temperatures created by a dust laden greenhouse effect that may be unique to the southern mid latitudes near ls 270 therefore sml rsl flow is quite sensitive to ground temperature and may only occur under favorable orbital parameters when mean insolation during the rsl lengthening season is above that of the current southern mid latitude mean insolation value this value is currently at a peak that has not been attained for the last 100 ka meanwhile the rsl poor northern mid latitude mean insolation is near a minimum and has a value 27 lower than the southern value if sml rsl are indeed formed by shallow subsurface freshwater flows then they may be some of the best locations on mars to explore for extant life

hirise observations of new impact craters exposing martian ground ice twenty small new impact craters or clusters have been observed to excavate bright material inferred to be ice at mid latitudes and high latitudes on mars in the northern hemisphere the craters are widely distributed geographically and occur at latitudes as low as 39 n stability modeling suggests that this ice distribution requires a long term average atmospheric water vapor content around 25 precipitable micrometers more than double the present value which is consistent with the expected effect of recent orbital variations alternatively near surface humidity could be higher than expected for current column abundances if water vapor is not well mixed with atmospheric co2 or the vapor pressure at the ice table could be lower due to salts ice in and around the craters remains visibly bright for months to years indicating that it is clean ice rather than ice cemented regolith although some clean ice may be produced by the impact process it is likely that the original ground ice was excess ice exceeding dry soil pore space in many cases observations of the craters suggest small scale heterogeneities in this excess ice the origin of such ice is uncertain ice lens formation by migration of thin films of liquid is most consistent with local heterogeneity in ice content and common surface boulders but in some cases nearby thermokarst landforms suggest large amounts of excess ice that may be best explained by a degraded ice sheet

mars odyssey neutron data 2 search for buried excess water ice deposits at nonpolar latitudes on mars 1 global maps of hydrogen abundance near the surface of mars interpreted as the mass percent of water equivalent hydrogen weh have been generated from measurements of neutron leakage fluxes from mars although these data provide an unambiguous indicator of the presence of weh quantitative details of its magnitude and burial depth depend on the model of the host regolith that is used to interpret the data previous models assumed a spatially uniform surface cover layer having a one to two mass percent of weh and thickness d covering a semi infinite ice rich deposit these assumptions allowed the derivation of the relative proportions of ice and regolith in the lower layer which had been used to create global maps of weh in the near surface in this paper we develop a new method that determines from the mars odyssey neutron spectrometer mons data a self consistent model of the weh content of both the upper and lower layers as well as the thickness d of the upper layer the results of our model suggest that large areas at nonpolar latitudes may contain water ice deposits that have abundances that are larger than can be held by normal pore volumes these deposits are buried less than about 1 m below the surface and may represent buried water ice or high concentrations of hydrous minerals intriguingly the most definitive mons evidence at intermediate latitudes for excess ground ice corresponds to a region of arcadia planitia within which high resolution imaging science experiment hirise has observed fresh icy craters

outwash plains and thermokarst on mars abstract the spatial distribution of different types of rampart craters on mars suggests a hemispheric asymmetry in the distribution of ground ice the northern plains especially major topographic depressions near the terminations of outflow channels have high percentages of rampart craters two of these basins acidalia and utopia planitiae received extraordinarily large amounts of water and sediment from the chryse and elysium outflow channels in both regions the analysis of high resolution viking pictures 12 m pixel indicates a concentration of kilometer scale depressions that are similar in size and form to thermokarstic features in yakutia siberia and parts of the arctic coastal plain of north america accordingly we infer that 1 utopia planitia and acidalia planitia may contain thick laterally continuous ice rich sedimentary deposits related to outflow channel forming floods and 2 these areas of mars may have experienced thermokarstic processes similar to modern thermokarstic processes in some periglacial regions of earth

shallow radar sharad pedestal craters and the lost martian layers initial assessments 1 since their discovery martian pedestal craters have been interpreted as remnants of layers that were once regionally extensive but have since been mostly removed pedestals span from subkilometer to hundreds of kilometers but their thickness is less than 500 m except for a small equatorial concentration in the medusae fossae formation the nearly exclusive occurrence of pedestal craters in the middle and high latitudes of mars has led to the suspicion that the lost units bore a significant fraction of volatiles such as water ice recent morphological characterizations of pedestal deposits have further supported this view here we employ radar soundings obtained by the shallow radar sharad to investigate the volumes of a subset of the pedestal population in concert with high resolution imagery to assist our interpretations from the analysis of 97 pedestal craters we find that large pedestals diameter 30 km are relatively transparent to radar in their majority with sharad being able to detect the base of the pedestal deposits and possess an average dielectric permittivity of 4 0 5 in one of the cases of large pedestals in malea planum layering is detected both in sharad data and in high resolution imagery of the pedestal margins we find that clutter is a major issue in the analysis of radar soundings for smaller pedestals and tentative detection of the basal reflection occurs in only a few of the cases examined these detections yield a higher average permittivity of 6 the permittivity value derived for the larger pedestals for which a basal reflection is unambiguous is higher than that of pure water ice but lower than that of most silicate materials a mixture of ice and silicates or an ice free porous silicate matrix can explain a permittivity of 4 and radar alone cannot resolve this nonuniqueness data from the compact reconnaissance imaging spectrometer crism tentatively confirms a mafic component in at least one pedestal in malea planum interpretation of sharad results can support either a mixture of ice and silicates or a porous silicate the former is compatible with a model where nonpolar ice is periodically deposited in the midlatitudes as a result of obliquity variations the latter is compatible with ash deposits at least in where pedestals appear in volcanic centers such as malea planum

subsurface ice on mars with rough topography high latitude ground ice on mars discovered by the gamma ray spectrometer suite is thought to be thermally stable owing to the presence of vapor in the martian atmosphere however local slopes can alter surface and subsurface temperatures substantially and hence allow ground ice to persist at locations where it would otherwise be unstable global statistics of the topography of mars are computed processed and extrapolated to derive a description of surface roughness on spatial scales to which ground ice should be sensitive this slope distribution is convolved with a new thermal model for the dependence of subsurface ice on slope to produce a prediction of the global ice distribution that includes the effect of topographic roughness in the highest latitudes slopes reduce the amount of buried ice while in lower latitudes the ice fraction increases widening the geographic boundary of the ice table at the high latitudes where ice is stable beneath horizontal ground the estimated reduction of ice is small compared to the existing ice volume areas in the midlatitudes with high surface roughness that have previously been predicted to be ice free are predicted to contain quantities of ice that may be detectable at present and accessible in the future slopes cause ground ice to be stable to latitudes of about 25 degrees in both hemispheres including for example areas within the northern olympus mons aureole deposits hecates tholus and hellas basin ice is unstable at equatorial latitudes even when accounting for surface slopes

radar evidence for ice in lobate debris aprons in the mid northern latitudes of mars 1 subsurface radar sounding data indicate that lobate debris aprons found in deuteronilus mensae in the mid northern latitudes of mars are composed predominantly of water ice the position in time delay and the relatively low amount of signal loss of the apparent basal reflectors below the debris aprons indicate that aprons contain only a minor component of lithic material the current presence of large ice masses at these latitudes has important implications for the climate evolution of mars and for future targets for in situ exploration

an inventory and population scale analysis of martian glacier like forms abstract martian glacier like forms glfs indicate that water ice has undergone deformation on the planet within its recent geological past but the driving mechanisms behind the origin evolution and dynamics of these landforms remain poorly understood here we present the results of a comprehensive inventory of glfs derived from a database of 8058 context camera ctx images to describe the physical controls on glf concentration and morphometry the inventory identifies 1309 glfs 727 glfs in the northern hemisphere and 582 in the southern hemisphere clustered in the mid latitudes centred on a mean latitude of 39 3 in the north and 40 7 in the south and in areas of rough topography morphometric data show inter hemispheric similarity in glf length mean 4 66 km and width mean 1 27 km suggesting a common evolutionary history and a poleward orientation of glfs in both hemispheres indicating a sensitivity to climate and insolation on a local scale elevation is shown to be the most important control on glf location with most glfs occurring above an altitude threshold of 3000 m aod and in areas of moderate but not high relief we propose therefore that martian glfs may not exhibit accumulation or ablation areas as is the norm for terrestrial glacial systems but reflect ice motion in response to local relief within a widely distributed reservoir of ice deposited within prescribed latitudinal and elevational ranges

geochemical discrimination of clastic sedimentary rock sources abstract factors controlling the geochemistry of a clastic sedimentary rock can include 1 composition of source terrain 2 chemical weathering 3 hydraulic sorting 4 diagenesis 5 metamorphism and 6 hydrothermal alteration a linear solution inferring source terrain composition from geochemistry of the sediment is impossible in this multivariate system as several unknowns will commonly be present the use of graphical analysis of element pairs circumvents the problem chemically immobile elements will maintain invariant ratios during rock mass change caused by either addition or depletion of mobile elements this results in chemically immobile element scattergrams exhibiting linear trends along radians extending from the origin if the major mineral phases of the immobile elements have behaved in a hydrodynamically similar manner as chemically mobile element plots will produce a scatter of points this relationship can be used to test chemical immobility and similarity in hydrodynamic sorting history the constraint on analysis is that the source area must be compositionally uniform or the sediment well mixed prior to delivery to the basin a second technique using sio2 plots has also been developed to investigate element mobility and hydrodynamic behaviour of the mineral phases containing the elements sio2 immobile element plots result in a linear arrangement of points extending towards either 0 or 100 sio2 the 0 intercept position occurs for elements with major mineral phases concentrated in sand the 100 intercept for those concentrated in clays plotting chemically mobile elements produces different patterns and this can be used to gain information on alteration and sorting history elemental ratios for chemically immobile elements with similar hydrodynamic behaviour will be the same as those for the weighted average composition of the source material this provides a powerful tool for deducing source terrain from sediment geochemistry techniques outlined above were tested on archaean metasandstones from superior province canada immobile element ratio diagrams for nb al ti and zr al ti indicate that a calc alkaline extrusive intrusive suite lying to the north of the study area was the source and not five other volcanic suites in the region this conclusion agrees with previous clast lithology studies and accentuates the applicability of the geochemical techniques

distribution and evolution of scalloped terrain in the southern hemisphere mars abstract scalloped depressions are a unique martian surface morphology found in the northern and southern hemisphere latitude dependent dust and ice rich surface mantles these features exhibit a distinct asymmetric north south slope profile characterized by steep pole facing scarps flat floors and gentle equator facing slopes we examined high resolution stereo camera hrsc images of the southern hemisphere to determine their longitudinal distribution which revealed that a majority of scalloped terrain is located in the region of the southern wall of the hellas basin and northern malea planum a detailed map of this area was produced where scallops were found to contour the southern wall of the basin and where the ice rich mantle was seen to be thickest scalloped terrain is concentrated along the topographic highs near the amphitrites and peneus paterae and areal extent and depth decreases with increasing depth into the basin we also examined existing hypothesis for the formation and evolution of scalloped depressions using high resolution imaging science experiment hirise images and data from the thermal emission imaging system infrared themis ir and the thermal emission spectrometer tes our approach provides regional context for the development of scalloped terrains within the southern hemisphere and offers detailed evidence of scallop depressions forming around small cracks presumably caused by thermal contraction morphometric measurements show that scalloped depressions can be as much as 40 m deep with typical depths of between 10 and 20 m our observations of scallop formation and development in the southern hemisphere support a solar insolation model proposed by previous researchers e g morgenstern a hauber e reiss d van gasselt s grosse g schirrmeister l 2007 j geophys res 112 citeid e06010 lefort a russell p s thomas n mcewen a s dundas c m kirk r l 2009a j geophys res 114 e04005 lefort a russell p s thomas n 2009b icarus in press observations made using hirise images suggest that scalloped depressions most likely form from small cracks in the mantle which become larger and deeper through sublimation of interstitial ice from within the mantle sublimation is likely enhanced on equator facing slopes because of increased solar insolation which accounts for the asymmetric slope profile and hemispherical orientation and is demonstrated by themis ir images we suggest that sublimation lag deposits can possibly be removed by dust devils or strong slope winds related to the hellas basin offering an explanation as to why scalloped terrain is so abundant only in this area of the southern hemisphere daytime maximum summer temperatures suggest that sublimation in the study area of malea planum is possible under current conditions if the sublimation lag is removed while it cannot be ruled out that scalloped terrain in malea planum is presently evolving we attribute the extensive distribution to geologically recent obliquity excursions when conditions were more conducive to mesoscale modification of the ice rich mantle

scalloped terrains in the peneus and amphitrites paterae region of mars as observed by hirise abstract the peneus and amphitrites paterae region of mars displays large areas of smooth geologically young terrains overlying a rougher and older topography these terrains may be remnants of the mid latitude mantle deposit which is thought to be composed of ice rich material originating from airfall deposition during a high obliquity period less than 5 ma ago within these terrains there are several types of potentially periglacial features in particular there are networks of polygonal cracks and scalloped shaped depressions which are similar to features found in utopia planitia in the northern hemisphere this area also displays knobby terrain similar to the so called basketball terrains of the mid and high martian latitudes we use recent high resolution images from the high resolution imaging science experiment hirise along with data from previous mars missions to study the small scale morphology of the scalloped terrains and associated polygon network and knobby terrains we compare these with the features observed in utopia planitia and attempt to determine their formation process while the two sites share many general features scallops in peneus amphitrites paterae lack the diverse polygon network i e there is little variation in the polygon sizes and shapes and large curvilinear ridges observed in utopia planitia this points to a more homogeneous ice content within the substrate in the peneus amphitrites paterae region and implies that scallop formation is independent of polygon formation this work shows that as in utopia planitia sublimation of interstitial ice is a likely process explaining the formation of the scalloped depressions in the region of peneus amphitrites paterae therefore we provide a simplified scallop formation model based on sublimation of interstitial ice as proposed for utopia planitia we also show that the differences in scallop morphologies between the two regions may be explained by differences in near surface ice content sublimation rates and age of formation of the scalloped terrains

stress field variations in the swiss alps and the northern alpine foreland derived from inversion of fault plane solutions 1 this study is devoted to a systematic analysis of the state of stress of the central european alps and northern alpine foreland in switzerland based on focal mechanisms of 138 earthquakes with magnitudes between 1 and 5 the most robust feature of the results is that the azimuth of the minimum compressive stress s3 is generally well constrained for all data subsets and always lies in the ne quadrant however within this quadrant the orientation of s3 changes systematically both along the structural strike of the alpine chain and across it the variation in stress along the mountain belt from ne to sw involves a progressive counterclockwise rotation of s3 and is most clear in the foreland where it amounts to 45 50 this pattern of rotation is compatible with the disturbance to the stress field expected from the indentation of the adriatic block into the central european plate possibly together with buoyancy forces arising from the strongly arcuate structure of the moho to the immediate west of our study area across the alps the variation in azimuth of s3 is defined by a progressive counterclockwise rotation of about 45 from the foreland in the north across the helvetic domain to the penninic nappes in the south and is accompanied by a change from a slight predominance of strike slip mechanisms in the foreland to a strong predominance of normal faulting in the high parts of the alps the observed rotation can be explained by the perturbation of the large scale regional stress by a local uniaxial deviatoric tension with a magnitude similar to that of the regional differential stress and with an orientation perpendicular to the strike of the alpine belt the tensile nature and orientation of this stress is consistent with the spreading stress expected from lateral density changes due to a crustal root beneath the alps

numerical backward and forward modelling of the southern upper rhine graben france germany border new insights on tectonic evolution of intracontinental rifts abstract this paper presents numerical models based on finite elements and contact theories of a segment of the southern upper rhine graben urg both forward and backward models are presented the results demonstrate the possibility to successfully model a complex multi block geological domain with finite element methods in addition they provide crucial information on the tectonic evolution of this segment of the urg they document the distribution of deformation and the possibility of a strike slip component of displacement during rifting they also evidence tectonic features that might be characteristic of oblique rifting such as a zone of high strain and brittle behaviour that follows the graben axis this zone coincides with the surface trace of the present day rhine river fault which is probably a major structure for the rifting history of the urg

formation of recurring slope lineae by liquid brines on present day mars 1 recurring slope lineae rsl are small scale seasonal flow features identified by mars reconnaissance orbiter that present several interesting characteristics such as an albedo contrast seasonal dependence and a strong preference for equator facing slopes all of these characteristics strongly suggest a thermally driven mechanism such as a liquid triggered or dominated flow here we investigate the possibility that these features are formed by melting of brines of various compositions via a combination of thermodynamic and kinetic numerical models results suggest that a solution with a freezing temperature of 223 k can best reproduce the observed seasonality relatively high surface evaporation rates at the rsl locations make the flows quickly disappear over a single season our model reproduces well the seasonality of rsl and can explain the preference for equator facing slopes suggesting that brine flows and therefore liquids are possible on a small time and space scale today on mars however if the rsl are indeed formed by brines it may indicate that a recharge mechanism is active in order to maintain a source of brine over even short geological timescales which would have important implications for the martian water cycle

latitude dependence of martian pedestal craters evidence for a sublimation driven formation mechanism we report on the results of a survey to document and characterize pedestal craters on mars equatorward of similar to 60 degrees n and 65 degrees s latitude the identification of 2696 pedestal craters reveals a strong latitude dependence with the vast majority found poleward of 33 degrees n and 40 degrees s this latitudinal extent is correlated with many climate indicators consistent with the presence of an ice rich substrate and with climate model predictions of where ice is deposited during periods of higher obliquity in the amazonian we have measured key physical attributes of pedestal craters including the farthest radial extents of the pedestals pedestal heights and the circularity of the pedestal margins in conjunction with the geographic distribution our measurements strongly support a sublimation related formation mechanism this is in contrast to previous hypotheses which have relied on eolian deflation to produce the elevated plateaus the identification of marginal pits on the scarps of some pedestal craters interpreted to be sublimation pits provide direct evidence for the presence of ice rich material underlying the armored surface of pedestal craters on the basis of our findings we propose a formation mechanism whereby projectiles impact into a volatile rich dust snow ice substrate tens to hundreds of meters thick overlying a dominantly fragmental silicate regolith the area surrounding the resulting crater becomes armored pedestals extend to a distance of multiple crater radii farther than typical ejecta deposits necessitating an armoring mechanism that is capable of indurating the surface to a distance greater than the reach of the ejecta return to low obliquity causes sublimation of the volatile rich layer from the intercrater plains lowering the elevation of the regional terrain this yields generally circular pedestal craters elevated above the surrounding plains as a result the armored surfaces of pedestal craters have preserved a significant record of amazonian climate history in the form of ice rich deposits

active tectonics of the southeastern upper rhine graben freiburg area germany the upper rhine graben has two plio quaternary depocentres usually interpreted as resulting from tectonic reactivation the southern basin near freiburg im breisgau germany contains up to 250 m of sediments beneath the younger alluvial deposits related to the current drainage system a former river network deeply entrenched in the substratum reveals a very low regional base level of early pleistocene age the offset of channels at faults allows us to infer a pleistocene reactivation of the syn rift fault pattern and the estimation of slip rates maximum vertical movements along the faults have not exceeded 0 1 mm yr since the middle pleistocene current activity is concentrated along the westernmost faults morphologic markers indicate late pleistocene reactivation of the rhine river fault and geophysical prospecting suggests a near surface offset of young sedimentary deposits the size of the fault segments potentially reactivated suggests that earthquakes with magnitude larger than mw 6 3mw 6 3 could be expected in the area with a return interval of about 8000 years extrapolated to the duration of the plio pleistocene the strain rate estimates reveal that the tectonic forcing may account for only one third to one half of the whole thickness of the plio pleistocene sediments of the basin fill thus other processes must be invoked to understand the growth of the plio pleistocene basin especially the piracy of the rhine river to the north during the early pleistocene could explain these effects

formation of glaciers on mars by atmospheric precipitation at high obliquity surface conditions on mars are currently cold and dry with water ice unstable on the surface except near the poles however geologically recent glacierlike landforms have been identified in the tropics and the midlatitudes of mars the ice has been proposed to originate from either a subsurface reservoir or the atmosphere we present high resolution climate simulations performed with a model designed to simulate the present day mars water cycle but assuming a 45 obliquity as experienced by mars a few million years ago the model predicts ice accumulation in regions where glacier landforms are observed on the western flanks of the great volcanoes and in the eastern hellas region this agreement points to an atmospheric origin for the ice and reveals how precipitation could have formed glaciers on mars

sparse subsurface radar reflectors in hellas planitia mars abstract geomorphological features potentially related to subsurface ice such as scalloped depressions expanded craters pedestal craters and banded terrain are present in and around hellas planitia mars we present a radar survey of the region using the shallow radar sharad instrument on board the mars reconnaissance orbiter mro to identify candidate subsurface reflectors that may be due to the presence of potentially ice rich deposits we found that the majority of radar returns are likely from off nadir surface topography clutter arising from the rough topography of the region there is no widespread radar return from any subsurface interfaces however we identify a group of six reflectors adjacent to each other on a plateau in malea patera in which we have higher confidence landforms associated with a likely ice rich mantle are associated with the plateau but the thickness of this mantle does not correspond to the expected depth of the reflectors however layers beneath the mantle and marginal pitting at the edge of the plateau are similar to those associated with pedestal craters which may be ice rich and are a similar thickness to the expected depth of the reflectors malea patera has been interpreted to be a volcanic caldera so the reflectors may be associated with a volcanic deposit within the plateau although the evidence for this is inconclusive because this radar detection is localized and its origin ambiguous we cannot use it to make conclusions about the thickness of subsurface deposits in the hellas region as a whole the lack of widespread radar reflectors in this region as compared to the northern mid latitudes where extensive radar reflections have been mapped may be due in part to higher surface roughness which creates radar clutter that may obscure subsurface reflectors however on the southern rim of the basin and south of the basin the lack of reflectors may indicate that the possible ice rich deposits observed geomorphologically in this region are too thin to be resolved by sharad are dielectrically similar to the underlying unit or have a gradual vertical transition in ice content that is not reflective for the radar this would imply that recent climate processes may have favored widespread thick ice deposition or preservation in the northern hemisphere as compared to the southern hemisphere

thermal contraction crack polygons on mars classification distribution and climate implications from hirise observations morphology is shown to be consistent with thermal contraction cracking of an ice rich mantling unit consistent with observations of sediment wedge thermal contraction crack polygons forming in ice cemented sediment at the phoenix landing site polygon groups are distributed symmetrically in both northern and southern hemispheres suggesting strong climate controls on polygon morphology northern hemisphere polygonally patterned surfaces are found to decrease in age from low to high latitude spanning surface ages from 1 to 0 1 ma suggesting more recent deposition of ice rich material at high latitudes than at low latitudes six of the seven classes of polygons are interpreted to be capable of forming because of the combined effects of thermal contraction cracking and differential sublimation suggesting that sublimation and sand wedge polygons dominate martian high latitudes gully polygon systems present at midlatitudes suggest that small amounts of liquid water may have been involved in thermal contraction crack polygon processes producing composite wedge polygons no evidence is found for the presence of pervasive small scale ice wedge polygons

crater morphology and evolution at the phoenix landing site insights into timing of modern geological processes and subsurface ice abstract we report results of an in depth study of the morphology of small km scale and smaller craters over a 4000 km2 region on mars that includes the phoenix landing ellipse focused on the nature and timing of geological processes that have been active in the region the study seeks to constrain regolith depositional rates thickness of ground ice layer abundance of ice in the subsurface and the rate of crater degradation measurements of the size of ejecta blocks around craters show that the region has not been a net depositional site over the last billion years most craters smaller than 200 350 m lack ejecta blocks regardless of age indicating that there is a layer approximately 20 35 m deep that either does not form or does not retain ejecta blocks this layer is expressed both within and outside the extended ejecta blanket of heimdal crater implying that it is not associated with the ejecta blanket we propose that this unconsolidated layer consists dominantly of ice cemented soil which raises questions about the emplacement of ice at depth we also note clear progression in crater degradation morphology which allows us to place constraints on the rate and style of crater degradation small craters 20 to 200 m in diameter appear to lose their relief due to slow infilling of the bowl over time scales of 5 100 kyr the infilling of small craters perhaps by a combination of ice and dust presents a mechanism by which ice is buried down to a few tens of meters on the other hand larger craters 200 m to 1 km do not exhibit evidence for infilling but do exhibit concentric sets of fractures within and outside the rim we propose that loss of relief of the larger craters is due to viscous creep over time scales of a few to tens of myr this latter interpretation would require the presence of water ice in abundances greater than pore filling down to depths of at least tens of meters

high resolution chemostratigraphy of quaternary distal turbidites a case study of new methods for the analysis and correlation of barren sequences

distribution of mid latitude ground ice on mars from new impact craters new impact craters at five sites in the martian mid latitudes excavated material from depths of decimeters that has a brightness and color indicative of water ice near infrared spectra of the largest example confirm this composition and repeated imaging showed fading over several months as expected for sublimating ice thermal models of one site show that millimeters of sublimation occurred during this fading period indicating clean ice rather than ice in soil pores our derived ice table depths are consistent with models using higher long term average atmospheric water vapor content than present values craters at most of these sites may have excavated completely through this clean ice probing the ice table to previously unsampled depths of meters and revealing substantial heterogeneity in the vertical distribution of the ice itself

kinematic analysis of the upper rhine graben boundary fault system this paper presents a new set of kinematic data for the central part of the upper rhine graben fault slip measurements were gathered covering the near field of a 200 km long segment of the graben boundary faults on both sides the resulting kinematic analysis shows a strong predominance of strike slip faulting and some oblique slip and pure normal faulting overall there is a regional coherence in the orientations of the extensional and shortening axes associated with both types of faulting throughout the entire study area the data set is best interpreted as the result of more or less continuous sinistrally transtensive kinematics with a nw se to nnw sse oriented or subvertical shortening and a ne sw to e w oriented extensional direction local transpressive overprints are not reflected in the pattern of brittle deformation in the near field of the boundary fault system we conclude that the opening history of the rhine graben may be less complex than hitherto assumed

evidence for recent climate change on mars from the identification of youthful near surface ground ice ground ice in the crust and soil may be one of the largest reservoirs of water on mars1 2 3 near surface ground ice is predicted to be stable at latitudes higher than 40 ref 4 where a number of geomorphologic features indicative of viscous creep and hence ground ice have been observed5 mid latitude soils have also been implicated as a water ice reservoir6 the capacity of which is predicted to vary on a 100 000 year timescale owing to orbitally driven variations in climate7 it is uncertain however whether near surface ground ice currently exists at these latitudes and how it is changing with time here we report observational evidence for a mid latitude reservoir of near surface water ice occupying the pore space of soils the thickness of the ice occupied soil reservoir 1 10 m and its distribution in the 30 to 60 latitude bands indicate a reservoir of 1 5 6 0 104 km3 equivalent to a global layer of water 10 40 cm thick we infer that the reservoir was created during the last phase of high orbital obliquity less than 100 000 years ago and is now being diminished

ice rich periglacial vs icy glacial depressions in the argyre region mars a proposed cold climate dichotomy of landforms on mars so called scalloped depressions are widely observed in utopia planitia up and malea planum mp typically they are rimless metres to decametres deep incised sharply tiered inwardly polygonised and sometimes pitted the depressions seemingly incise terrain that is icy and possibly thermokarstic i e produced by the thermal destabilisation of the icy terrain agewise the depressions are thought to be relatively youthful originating in the late amazonian epoch here we report the presence of similar depressions in the argyre region ar 30 60 s 290 355 e more importantly we separate and differentiate these landforms into two groups ice rich periglacial depressions type 1 and icy glacial depressions type 2a c this differentiation is presented to the mars community for the first time based on a suite of morphological and geological characteristics synonymous with ice complexes in the lena peninsula eastern russia and the tuktoyaktuk coastlands northwest territories canada we propose that the type 1 depressions are ice rich periglacial basins that have undergone volatile depletion largely by sublimation and as the result of thermal destabilisation in keeping with the terms and associated definitions derived of terrestrial periglacial geomorphology ice rich refers to permanently frozen ground in which ice lenses or segregation ice collectively referenced as excess ice have formed we suggest that the depressions are the product of a multi step cold climate geochronology 1 atmospheric precipitation and surface accumulation of an icy mantle during recent high obliquities 2 regional or local triple point conditions and thaw evaporation of the mantle either by exogenic forcing i e obliquity driven rises of aerial and sub aerial temperatures or endogenic forcing i e along argyre impact related basement structures 3 meltwater migration into the regolith at least to the full depth of the depressions 4 freeze thaw cycling and the formation of excess ice 5 sublimation of the excess ice and depression formation as high obliquity dissipates and near surface ice becomes unstable the type 2 depressions exhibit characteristics suggestive of supra glacial dead ice basins and snow ice suncups observed in high alpine landscapes on earth e g the swiss alps and the himalayas like the type 1 depressions the type 2 depressions could be the work of sublimation however the latter differ from the former in that they seem to develop within a glacial like icy mantle that blankets the surface rather than within an ice rich and periglacially revised regolith at near the surface interestingly the type 2 depressions overlie the type 1 depressions at some locations if the periglacial glacial morphological and stratigraphical dichotomy of depressions is valid then this points to recent glaciation at some locations within the ar being precursed by at least one episode of periglaciation this also suggests that periglaciation has a deeper history in the region than has been thought hitherto moreover if the hypothesised differences amongst the argyre based depressions are mirrored in utopia planitia and malea planum then perhaps this periglacial glacial dichotomy and its associated geochronology are as relevant to understanding late period landscape evolution in these two regions as it is in the ar

metastability of liquid water on mars abstract a simple model of local heat transport on mars demonstrates that transient melting of ice may occur in depressions and gullies nearly anywhere on the planet where thin ice is illuminated by normal incidence insolation an experiment has been performed to confirm the model of evaporation rate at low pressure reduction of radiative cooling due to gully geometry is shown to be important since appropriate meteorological topographic and optical conditions may occur on slopes nearly anywhere on the planet hydrological features such as gullies would likely form only where such ice might accumulate notably in sheltered locations at high latitudes it is suggested that cold trapping of winter condensation could concentrate a sufficient amount of ice to allow seasonal melting in gullies

the presence and stability of ground ice in the southern hemisphere of mars abstract we calculate new estimates of ground ice stability and the depth distribution of the ice table the depth boundary between ice free soil above and ice cemented soil below and compare these theoretical estimates of the distribution of ground ice with the observed distribution of leakage neutrons measured by the neutron spectrometer instrument of the mars odyssey spacecraft s gamma ray spectrometer instrument suite our calculated ground ice distribution contains improvements over previous work in that we include the effects of the high thermal conductivity of ice cemented soil at and below the ice table we include the surface elevation dependence of the near surface atmospheric humidity and we utilize new high resolution maps of thermal inertia albedo and elevation from mars global surveyor observations results indicate that ground ice should be about 5 times shallower than in previous predictions while results are dependent on the atmospheric humidity depths are generally between a few millimeters and a few meters with typical values of a few centimeters results are also geographically similar to previous predictions with differences due to the higher resolution of thermal inertia and the inclusion of elevation effects on humidity comparison with the measured epithermal neutron count rates in the southern hemisphere indicate that the geographic distribution of the count rate is best correlated with ground ice in equilibrium with 10 to 20 pr m precipitable micrometers column abundance of atmospheric water assuming a uniform distribution with co2 however given the uncertainties 5 to 30 pr m also may be viable this water abundance represents a longer term average over 100 to 1000 yr there is a high degree of correlation between the depth of the ice table and the epithermal count rate that agrees remarkably well with predicted count rates as a function of ice table depth these results indicate that ground ice in the upper meter of the martian soil is in diffusive equilibrium with the atmosphere since ground ice in this depth zone is expected to undergo saturation desiccation cycles with orbital variations this ice should be younger than about 500 kyr and was emplaced under similar cold and dry climate conditions of today remaining differences between the predicted depths of the ice table and those inferred from the neutron data are likely to be due to subpixel heterogeneity in the martian surface including the presence of rocks slopes and patches of soil with varying thermophysical properties

deposition and degradation of a volatile rich layer in utopia planitia and implications for climate history on mars 1 we investigate the surface morphology of a study area in western utopia planitia mars which is characterized by a variety of landforms that resemble those of terrestrial periglacial landscapes polygonally fractured ground and thermokarst like depressions are found to be located in a young mantling deposit with a thickness of several tens of meters we observe a latitudinal dependence of the degradation of this mantling deposit larger depressions whose floors reveal the underlying basement rocks cover a higher fraction of the total terrain in the southern part of the study area than in the northern part indicating a more intense degradation of the mantle in the south all depressions have an asymmetric cross section in north south direction interpreted to be the result of the different solar radiation on differently oriented slopes on the basis of our morphological observations we develop a conceptual model for landscape evolution in western utopia planitia it involves subaerial deposition of a layered ice rich mantle and its subsequent degradation by polygon formation and sublimation a terrestrial analog to the polygonally fractured mantling deposit and its thermokarst like depressions is the siberian ice complex or yedoma which consists of subaerial ice rich deposits and is connected to nonglaciated landscapes with highly continental cold climatic environmental conditions our comparison suggests that no unusual or exotic processes need to be invoked to explain the current morphology of western utopia however the young age of the deposition and degradation implies climatic excursions in the very recent past on mars