crack azimuths on europa time sequence in the southern leading face the formation sequence of prominent ridges and other tectonic lineaments on the southern portion of the leading hemisphere of europa is determined from cross cutting relationships these selected features formed fairly recently relative to most of the surface older lineaments no longer retain clear evidence of cross cutting if we assume that this sequence represents the order of formation of cracks that underlie each lineament and that the orientation of each crack was determined by tidal stress whose azimuth varies monotonically counter clockwise with time the azimuth must have rotated more than 740 which would correspond to the change in tidal stress over two periods of nonsynchronous rotation relative to the direction of jupiter however that interpretation is not necessarily compelling because the observed orientations of cross cutting lineaments are not densely spaced over these cycles in fact the sequence would fit nearly as well into an arbitrary model with rotation in the opposite sense from that predicted by theory this tectonic record may have formed over many more rotational cycles such that typically only a few cracks form per cycle which would be consistent with evidence from considerations of cycloidal crack patterns sets of cracks that cluster near certain azimuth orientations appear to be parts of globe encircling lineament systems and may result from other effects perhaps polar wander that occurred rapidly relative to nonsynchronous rotation

patterns of fracture and tidal stresses due to nonsynchronous rotation implications for fracturing on europa this study considers the global patterns of fracture that would result from nonsynchronous rotation of a tidally distorted planetary body the incremental horizontal stresses in a thin elastic or viscous shell due to a small displacement of the axis of maximum tidal elongation are derived and the resulting stress distributions are applied to interpret the observed pattern of fracture lineaments on europa the observed pattern of lineaments can be explained by nonsynchronous rotation if these features formed by tension fracturing and dike emplacement tension fracturing can occur for a small displacement of the tidal axis so that the resulting lineaments may be consistent with other evidence suggesting a young age for the surface

cycloid crack sequences on europa relationship to stress history and constraints on growth mechanics based on cusp angles the original model developed to explain cycloidal cracks on europa interprets cycloids as tensile fractures that grow in a curved path in response to the constantly rotating diurnal tidal stress field cusps form when a new cycloid crack segment propagates at an angle to the first in response to a rotation of the principal tidal stress orientation during a period of no crack growth a recent revised model states that a cycloid cusp forms through the creation of a secondary fracture called a tailcrack at the tip of an existing cycloid segment during shearing motion induced by the rotating tidal stress field as the tailcrack propagates away from the cusp it becomes the next cycloid segment in the chain the qualitative tailcrack model uniquely accounts for the normal and shear stresses that mechanically must resolve onto the tip of an existing cycloid segment at the instant of cusp formation in this work we provide a quantitative framework and test of the hitherto purely conceptual tailcrack model we first present a relative age sequence inferred from geologic mapping of multiply cross cutting cycloids in europa s trailing hemisphere and place this into the context of the global stress history the age sequence requires a cumulative minimum of 630 of shell reorientation due to nonsynchronous rotation to account for the observed range of orientations of cycloids of different ages we determined the back rotated longitudes of formation of two cycloid chain examples and used mathematical modeling of europan tidal stresses to show that the tailcrack model for cusp formation is not only viable but places constraints on the overall development of a cycloid chain by controlling the timing of cusp development within europa s orbit for all cusps analyzed the exact ratio of resolved shear to normal stress required to form the cusp angles by a process of tailcracking as governed by the principles of linear elastic fracture mechanics is produced at the tip of a shearing cycloid segment during europa s orbit cusp formation occurs after the point in the orbit at which the maximum tensile principal tidal stress occurs implying that tensile tidal stresses are not directly responsible for cusp development instead cusps develop when a tailcrack forms at the tip of a cycloid segment in response to the highly perturbed stress field induced during concomitant opening and shearing at the tip of the cycloid segment

large scale erosion rates from in situ produced cosmogenic nuclides in european river sediments abstract we have calculated long term erosion rates of 20 100 mm kyr from quartz contained 10be in the bedload of middle european rivers for catchments ranging from 102 to 105 km2 these rates average over 10 40 kyr and agree broadly with rock uplift incision and exhumation rates historic soil erosion rates and erosion rates calculated from the measured sediment loads of the same rivers moreover our new erosion rate estimates correlate well with lithology and relief however in the regen neckar loire and meuse catchments cosmogenic nuclide derived erosion rates are consistently 1 5 4 times greater than the equivalent rates derived from measured river loads this may be due to the systematic under representation of high magnitude low frequency transport events in the gauging records which cover less than a century alternatively the discrepancy may derive from spatially non uniform erosion and preferential tapping of deeper sections of the irradiation profile a third explanation relates the high cosmogenic nuclide derived erosion rates to inheritance of an elevated pleistocene erosion signal uncertainties associated with the cosmogenic nuclide derived erosion rate estimates are not greater than the potential errors in conventional estimates therefore the cosmogenic nuclide approach is an effective tool for rapid catchment wide assessment of time integrated rates of bedrock weathering and erosion and we anticipate its fruitful application to the quaternary sedimentary record

predicting reach specific properties of fluvial terraces to guide future fieldwork a case study for the late quaternary river allier france with the fluver2 model numerical models have not yet systematically been used to predict properties of fluvial terrace records in order to guide fieldwork and sampling this paper explores the potential of the longitudinal profile model fluver2 to predict testable field properties of the relatively well studied late quaternary allier system in france for the allier terraces an overlapping 14c and u series chronology as well as a record of 10be erosion rates exist the fluver2 modelling exercise is focused on the last 50 ka of the upper allier reach because for this location and period the constraints of the available dating techniques are tightest a systematic calibration based on terrace occurrence and thicknesses was done using three internal parameters related to 1 the sediment erodibility 2 the sediment transport distance and 3 the sediment supply derived from the surrounding landscape as external model inputs the best available reconstructed tectonic climatic and base level data were used calibrated model outputs demonstrate a plausible match with the existing fluvial record validation of model output was done by comparing the modelled and measured timing of aggradation and incision phases for the three locations the modelled range of landscape erosion rates showed a reasonably good match with existing erosion rate estimates derived from 10be measurements of fluvial sands the quasi validated model simulation was subsequently used to make new testable predictions about the timing and location of aggradation and erosion phases for three locations along the allier river the validated simulations predict that along the allier reach specific dynamics of incision and aggradation related to the variations in sediment supply by major tributaries cause relevant differences in the local fluvial terrace stratigraphy numerical models have not yet systematically been used to predict properties of fluvial terrace records in order to guide fieldwork and sampling this paper explores the potential of the longitudinal profile model fluver2 to predict testable field properties of the relatively well studied late quaternary allier system in france for the allier terraces an overlapping 14 c and u series chronology as well as a record of 10 be erosion rates exist the fluver2 modelling exercise is focused on the last 50 ka of the upper allier reach because for this location and period the constraints of the available dating techniques are tightest a systematic calibration based on terrace occurrence and thicknesses was done using three internal parameters related to 1 the sediment erodibility 2 the sediment transport distance and 3 the sediment supply derived from the surrounding landscape as external model inputs the best available reconstructed tectonic climatic and base level data were used calibrated model outputs demonstrate a plausible match with the existing fluvial record validation of model output was done by comparing the modelled and measured timing of aggradation and incision phases for the three locations the modelled range of landscape erosion rates showed a reasonably good match with existing erosion rate estimates derived from 10 be measurements of fluvial sands the quasi validated model simulation was subsequently used to make new testable predictions about the timing and location of aggradation and erosion phases for three locations along the allier river the validated simulations predict that along the allier reach specific dynamics of incision and aggradation related to the variations in sediment supply by major tributaries cause relevant differences in the local fluvial terrace stratigraphy copyright 2016 john wiley sons ltd

strike slip faults on europa global shear patterns driven by tidal stress abstract diurnal tides due to orbital eccentricity may drive strike slip motion on europa through a process of walking in which faults open and close out of phase with alternate right and left lateral shear mapping of five different regions on europa has revealed 121 strike slip faults including astypalaea linea a 800 km long fault with 42 km of right lateral offset at high southern latitudes near astypalaea linea all of the strike slip faults identified were right lateral europa appears to preferentially form right lateral faults in the southern hemisphere and left lateral faults in the northern hemisphere consistent with tidal walking at the five locations nonsynchronous rotation explains the azimuthal orientations and distribution of sense of shear which fit formation 60 to 90 west of their current positions alternatively stress due to differential rotation might also explain the observed shear patterns nearly all identified strike slip faults were associated with double ridges or bands but few were detected along ridgeless cracks even older ones thus cracks without ridges may not have penetrated to a decoupling layer consistent with the models for ridge formation that require cracks to penetrate to a liquid water ocean

the implications of tides on the mimas ocean hypothesis we investigate whether a present day global ocean within mimas is compatible with the lack of tectonic activity on its surface by computing tidal stresses for ocean bearing interior structure models derived from observed librations we find that for the suite of compatible rheological models peak surface tidal stresses caused by mimas high eccentricity would range from a factor of two smaller to an order of magnitude larger than those on tidally active europa thermal stresses from a freezing ocean or a past higher eccentricity would enhance present day tidal stresses exceeding the magnitudes associated with europa s ubiquitous tidally driven fractures and in some cases the failure strength of ice in laboratory studies therefore in order for mimas to have an ocean its ice shell cannot fail at the stress values implied for europa furthermore if mimas ocean is freezing out the ice shell must also be able to withstand thermal stresses that could be an order of magnitude higher than the failure strength of laboratory ice samples in light of these challenges we consider an ocean free mimas to be the most straightforward model best supported by our tidal stress analysis

rotation of europa constraints from terminator and limb positions abstract tidal torques on europa due to jupiter would tend to drive europa s rotation to a rate slightly faster than synchronous unless synchroneity is maintained by a permanent asymmetry in europa s mass distribution moreover global fracture patterns on europa s surface as well as the complex fine scale tectonics revealed by galileo high resolution imagery may be evidence of stress due to nonsynchronous rotation a direct measurement of europa s rotation rate is made from the positions of surface features relative to the terminator in a galileo image and comparing the results with similar measurements of the positions of the same features relative to the terminator in a voyager 2 image taken 17 years earlier any nonsynchronous rotation must be slower than a few tenths of a degree in 17 years a complete rotation in 10 4 years relative to the direction of jupiter

long term behaviour of continental hydrothermal systems u series study of hydrothermal carbonates from the french massif central allier valley abstract u series dating of hydrothermal carbonates deposited by co2 rich thermo mineral waters of the french massif central provides new insights on the long term behaviour of a continental hydrothermal system dating of aragonite veins and travertines impregnating old terrace levels of the allier river allowed identification of the main episodes of surface deposition and thus factors likely to influence these circulations fifteen layers from three veins and four travertines from two separate areas were analysed sr isotope compositions were also measured on vein samples the results show that this region was subjected to at least 3 main episodes of surface or near surface hydrothermal deposition 253 to 208 ky 135 to 100 ky and less than 8 ky comparison of these ages with a global climatic curve indicates that preferential deposition of carbonates occurs during warm periods suggesting a strong influence of climatic conditions on the hydrothermal system it is suggested that this climatic influence does not necessarily imply the absence of carbonate deposition during cold and dry periods but rather that carbonate precipitation might occur at depth before the geothermal fluids reach the surface in addition the isotope compositions of fluids recorded by the 87sr 86sr and 234u 238u initial ratios in the aragonite veins from coudes remained remarkably constant over 250 ky ranging from 0 71360 to 0 71371 and from 3 10 to 3 39 respectively the two samples coming from saladis show a slightly higher 234u 238u initial ratio around 3 95 the constancy of these ratios over such a long period suggests a hydrothermal system in a near steady state with respect to water rock interaction we thus propose a possible model allowing a conservative steady state despite variations in the water recharge rates in response to the climatic variations the difference between 234u 238u initial ratios measured in the coudes and saladis systems suggests the existence of two separate reservoirs and constrains their lateral extension to a few km at most

lineament azimuths on europa implications for obliquity and non synchronous rotation abstract lineaments are thought to form as tensile cracks due to tidal stress which is driven mainly by europa s eccentric orbit however this model would not produce the wide range of lineament azimuths observed on europa unless the stress in a given region or the conditions for fault failure change over time in this work we test the ability of two mechanisms that would alter the stress field over time to account for the observed lineament azimuths non synchronous rotation and spin pole precession first we revisit previous analysis of lineaments and find that an underlying assumption used to predict their azimuths was inconsistently applied after revising these predictions we incorporate the effects of a non zero obliquity which has been shown to influence the formation of other tidal tectonic features we then expand our analysis to include the effects of the time variable phenomena spin pole precession and non synchronous rotation of the ice shell we also consider additional failure assumptions to those used in previous work on lineament azimuths we test our models against the azimuths of observed lineaments in the bright plains region of europa without obliquity we find that non synchronous rotation is insufficient to explain the wide range of azimuths observed in this region in the presence of obliquity we find that either spin pole precession or non synchronous rotation could produce wide variations in lineament azimuths however neither model can independently account for the observed distribution of azimuths in the bright plains region in fact a model in which all of the lineaments are assumed to form at random orientations outperforms the non synchronous rotation model in our statistical tests the model with the highest likelihood of producing the observations is one in which 45 of the lineaments formed as predicted in the precession model 55 formed at random orientations and older lineaments are less represented in the tectonic record given the relative timescales expected for spin pole precession and non synchronous rotation it makes sense that the signal of precession is more apparent in the tectonic record these results are in good agreement with assessments of strike slip faults modeling of both types of features indicates a large obliquity the same spin pole direction during the most recent epoch of tectonic activity a similar percentage of features that are not well explained by the tidal model and little evidence of non synchronous rotation

patterns of fracture and tidal stresses on europa abstract the hypothesis that lineaments on europa are fractures produced by tidal distortion and planetary volume change is examined by comparing the orientations of dark bands triple bands and cuspate ridges to fracture patterns predicted for tidal distortion due to orbital recession and orbital eccentricity if short reticulate dark band nnear the anti jove point are tension cracks which formed in response to tidal distortion they could only have been produced by orbital eccentricity long arcuate dark band and triple bands peripheral to the anti jove point orientations which suggest that they are strike slip faults which formed in response to orbital recession if cuspate ridges are compressional features their orientations and distribution suggest that they formed in response to combined orbital recession and a decrease in planetary volume stresses due to orbital eccentricit could have produced tension cracks near the anti jove point only if tensile failure occurred either prior to the accumulation of orbital recession stresses or after they had relaxed surface fracturing if a consequence of tidal deformation places important constraints on the orbital evolution of europa

polar wander and surface convergence of europa s ice shell evidence from a survey of strike slip displacement two global issues regarding europa are addressed by a survey of strike slip faults first a common type of terrain that appears to represent convergent sites of surface removal which may help compensate for substantial widespread dilation along tectonic bands elsewhere thus helping resolve the problem of conserving global surface area is identified second evidence for polar wander may provide the first confirmation of that theoretically predicted phenomenon these results among others come from an extensive survey of strike slip faults over the portion of the surface where galileo images at 200 m pixel resolution were obtained for regional mapping purposes the images cover two broad swaths that run from the far north to the far south one in the leading hemisphere and the other in the trailing hemisphere among the faults that have been mapped are a fault 170 km long with a strike slip offset of 83 km the greatest yet identified on europa and a quasi circular strike slip fault that surrounds a 500 km wide plate which has undergone rotation as a rigid unit reconstruction of specific examples of strike slip reveals sites of lateral convergence because europa is unique in many ways these sites are not similar to compression features on other bodies which may explain why they had previously been difficult to identify the distribution of strike slip in both hemispheres when compared with predictions of the theory of tidal walking provides evidence for polar wander the crust of europa appears to have slid as a single unit relative to the spin axis such that the site on the crust that was previously at the north rotational pole has wandered probably during the last few million years to a location currently in the leading hemisphere about 30 away from the spin axis such polar wander probably also explains symmetry patterns in the distribution of chaotic terrain pits and uplift features

constraints on europa s rotational dynamics from modeling of tidally driven fractures abstract cycloids arcuate features observed on europa s surface have been interpreted as tensile cracks that form in response to diurnal tidal stress caused by europa s orbital eccentricity stress from non synchronous rotation may also contribute to tidal stress and its influence on cycloid shapes has been investigated as well obliquity fast precession and physical libration would contribute to tidal stress but have often been neglected because they were expected to be negligibly small however more sophisticated analyses that include the influence of jupiter s other large satellites and the state of europa s interior indicate that perhaps these rotational parameters are large enough to alter the tidal stress field and the formation of tidally driven fractures we test tidal models that include obliquity fast precession stress due to non synchronous rotation and physical libration by comparing how well each model reproduces observed cycloids to do this we have designed and implemented an automated parameter searching algorithm that relies on a quantitative measure of fit quality which we use to identify the best fits to observed cycloids we then apply statistical techniques to determine the tidal model best supported by the data by incorporating obliquity fits to observed southern hemisphere cycloids improve and we can reproduce equatorial and equator crossing cycloids furthermore we find that obliquity plus physical libration is the tidal model best supported by the data with this model the obliquities range from 0 32 to 1 35 the libration amplitudes are 0 72 2 44 and the libration phases are 6 04 to 17 72 with one outlier at 84 5 the variability in obliquity is expected if europa s ice shell is mechanically decoupled from the interior and the libration amplitudes are plausible in the presence of a subsurface ocean indeed the presence of a decoupling ocean may result in feedbacks that cause all of these rotational parameters to become time variable

crack azimuths on europa sequencing of the northern leading hemisphere 1 nonsynchronous rotation of europa should result in a periodic change in stress azimuths at any given location which may result in a corresponding change in crack azimuths an early study seemed to provide evidence for such variation within a crack sequence in the northern trailing hemisphere however more recent work with higher resolution imagery resulted in a more complete sequence of cracks in the region and showed that the azimuth variation with time was not systematic similar results were found in the southern leading region here we investigate whether the northern leading region contains a crack record on the basis of crosscutting relationships that is adequate to indicate nonsynchronous rotation as in the previous studies of other regions we find no clear evidence of nonsynchronous rotation within crack azimuth patterns however there are other lines of evidence in support of nonsynchronous rotation therefore the lack of a continuous pattern of azimuth change with time is likely due to only a few cracks forming per cycle thus hiding any discernable signal from nonsynchronous rotation in those regions in that case the cracks would have formed over numerous cycles of nonsynchronous rotation the study also reveals a distinctive distribution of crack azimuths with gaps at certain values this distribution may reflect a combination of observation selection due to illumination and less favorable cracking orientations

tidal reorientation and the fracturing of jupiter s moon europa the most striking characteristic of europa is the network of long linear albedo markings over the surface suggestive of global scale tectonic processes various explanations for the fractures have been proposed freezing and expansion of an early liquid water ocean1 planetary expansion due to dehydration of hydrated silicates2 localization by weak points in the crust generated by impacts3 and a combination of stresses due to planetary volume change and tidal distortions from orbital recession and orbital eccentricity4 5 calculations by yoder6 and greenberg and weidenschilling7 have shown that europa may rotate slightly more rapidly than the synchronous rate with a rotation period reorientation through 360 ranging from 20 to 103 yr if a liquid mantle is present or up to 1010 yr if the satellite is essentially solid7 helfen stein and parmentier8 modelled the stresses due to nonsynchronous rotation and concluded that this could explain the long fractures in part of the anti jovian hemisphere in this note i present a global map of lineaments with long arc lengths 20 or 550 km and compare the lineament orientations to the tensile stress trajectories due to tidal distortions changes in the lengths of three principal semiaxes and to nonsynchronous rotation longitudinal reorientation of two of the principal semiaxes an excellent orthogonal fit to the lineaments is achieved by the stresses due to nonsynchronous rotation with the axis radial to jupiter located 25 east of its present position this fit suggests that nonsynchronous rotation occurred at some time in europa s history

the interior and orbital evolution of charon as preserved in its geologic record abstract pluto and its largest satellite charon currently orbit in a mutually synchronous state both bodies continuously show the same face to one another this orbital configuration is a natural end state for bodies that have undergone tidal dissipation in order to achieve this state both bodies would have experienced tidal heating and stress with the extent of tidal activity controlled by the orbital evolution of pluto and charon and by the interior structure and rheology of each body as the secondary charon would have experienced a larger tidal response than pluto which may have manifested as observable tectonism unfortunately there are few constraints on the interiors of pluto and charon in addition the pathway by which charon came to occupy its present orbital state is uncertain if charon s orbit experienced a high eccentricity phase as suggested by some orbital evolution models tidal effects would have likely been more significant therefore we determine the conditions under which charon could have experienced tidally driven geologic activity and the extent to which upcoming new horizons spacecraft observations could be used to constrain charon s internal structure and orbital evolution using plausible interior structure models that include an ocean layer we find that tidally driven tensile fractures would likely have formed on charon if its eccentricity were on the order of 0 01 especially if charon were orbiting closer to pluto than at present such fractures could display a variety of azimuths near the equator and near the poles with the range of azimuths in a given region dependent on longitude east west trending fractures should dominate at mid latitudes the fracture patterns we predict indicate that charon s surface geology could provide constraints on the thickness and viscosity of charon s ice shell at the time of fracture formation

viscous relaxation as a prerequisite for tectonic resurfacing on ganymede insights from numerical models of lithospheric extension abstract ganymede s bright terrain formed during a near global resurfacing event or events that produced both heavily tectonized and relatively smooth terrains the mechanism s by which resurfacing occurred on ganymede e g cryovolcanic or tectonic and the relationship between the older dark and the younger bright terrain are fundamental to understanding the geological evolution of the satellite using a two dimensional numerical model of lithospheric extension that has previously been used to successfully simulate surface deformation consistent with grooved terrain morphologies we investigate whether large amplitude preexisting topography can be resurfaced erased by extension i e tectonic resurfacing using synthetically produced initial topography we show that when the total relief of the initial topography is larger than 25 50 m periodic groove like structures fail to form instead extension is localized in a few individual isolated troughs these results pose a challenge to the tectonic resurfacing hypothesis we further investigate the effects of preexisting topography by performing suites of simulations initialized with topography derived from digital terrain models of ganymede s surface these include dark terrain fresh relatively deep impact craters smooth bright terrain and a viscously relaxed impact crater the simulations using dark terrain and fresh impact craters are consistent with our simulations using synthetic topography periodic groove like deformation fails to form in contrast when simulations were initialized with bright smooth terrain topography groove like deformation results from a wide variety of heat flow and surface temperature conditions similarly when a viscously relaxed impact crater was used groove like structures were able to form during extension these results suggest that tectonic resurfacing may require that the amplitude of the initial topography be reduced before extension begins we emphasize that viscous relaxation may be the key to enabling tectonic resurfacing as the heat fluxes associated with groove terrain formation are also capable of reducing crater topography through viscous relaxation for long wavelength topography large craters viscous relaxation is unavoidable we propose that the resurfacing of ganymede occurred through a combination of viscous relaxation tectonic resurfacing cryovolcanism and at least in a few cases band formation variations in heat flow and strain magnitudes across ganymede likely produced the complex variety of terrain types currently observed

strike slip fault patterns on europa obliquity or polar wander abstract variations in diurnal tidal stress due to europa s eccentric orbit have been considered as the driver of strike slip motion along pre existing faults but obliquity and physical libration have not been taken into account the first objective of this work is to examine the effects of obliquity on the predicted global pattern of fault slip directions based on a tidal tectonic formation model our second objective is to test the hypothesis that incorporating obliquity can reconcile theory and observations without requiring polar wander which was previously invoked to explain the mismatch found between the slip directions of 192 faults on europa and the global pattern predicted using the eccentricity only model we compute predictions for individual observed faults at their current latitude longitude and azimuth with four different tidal models eccentricity only eccentricity plus obliquity eccentricity plus physical libration and a combination of all three effects we then determine whether longitude migration presumably due to non synchronous rotation is indicated in observed faults by repeating the comparisons with and without obliquity this time also allowing longitude translation we find that a tidal model including an obliquity of 1 2 along with longitude migration can predict the slip directions of all observed features in the survey however all but four faults can be fit with only 1 of obliquity so the value we find may represent the maximum departure from a lower time averaged obliquity value adding physical libration to the obliquity model improves the accuracy of predictions at the current locations of the faults but fails to predict the slip directions of six faults and requires additional degrees of freedom the obliquity model with longitude migration is therefore our preferred model although the polar wander interpretation cannot be ruled out from these results alone the obliquity model accounts for all observations with a value consistent with theoretical expectations and cycloid modeling

nonsynchronous rotation evidence and fracture history in the bright plains region europa abstract a geologic map for the bright plains in the conamara chaos region of europa is presented and is used to unravel a detailed fracture sequence using cross cutting relationships and fracture mechanics principles fracture orientations in the bright plains region rotated with time consistently in a clockwise sense this conclusion agrees with the observations of other researchers northern europan hemisphere investigations and points strongly toward the fracture sequence being controlled by the effect of nonsynchronous rotation whereby the outer ice crust of europa rotates slightly faster than the satellite s interior this is convincing evidence that europa s crust has been decoupled from the interior possibly due to the presence of a liquid ocean beneath the crust tidal stresses induced in the ice crust by the combined effects of nonsynchronous rotation and diurnal tidal flexing can be calculated using the assumption that the crust behaves elastically over relatively short time scales i e no viscous relaxation of stresses the fracture orientations in the bright plains area were compared to a global scale tidal stress field to determine the longitudes at which each fracture set developed the fracture sequence points strongly to the bright plains region of the crust having rotated at least 720 and perhaps up to 900 with respect to the satellite s interior during the visible fracture history this amount exceeds previously published estimates of nonsynchronous rotation the orientations of the most recent surface fractures are incompatible with the current state of stress in the bright plains region implying a period of a few thousand years since the most recent fracturing events based on existing nonsynchronous rotation rate estimates

modelling long term 300 ka upland catchment response to multiple lava damming events landscapes respond in complex ways to external drivers such as base level change due to damming events in this study landscape evolution modelling was used to understand and analyse long term catchment response to lava damming events palaeodem reconstruction of a small turkish catchment 45km 2 that endured multiple lava damming events in the past 300ka was used to derive long term net erosion rates these erosion rates were used for parameter calibration and led to a best fit parameter set this optimal parameter set was used to compare net erosion landscape time series of four scenarios i no uplift and no damming events ii no uplift and three damming events iii uplift and no damming events and iv uplift and three damming events spatial evolution of net erosion and sediment storage of scenario iii and iv were compared simulation results demonstrate net erosion differences after 250 000years between scenarios with and without dams initially trunk gullies show less net erosion in the scenario with damming events compared with the scenario without damming events this effect of dampened erosion migrates upstream to smaller gullies and local slopes finally an intrinsic incision pulse in the dam scenario results in a higher net erosion of trunk gullies while decoupled local slopes are still responding to the pre incision landscape conditions sediment storage differences also occur on a 100ka scale these differences behaved in a complex manner owing to different timings of the migration of erosion and sediment waves along the gullies for each scenario although the specific spatial and temporal sequence of erosion and deposition events is sensitive to local parameters this model study shows the manner in which past short lived events like lava dams have long lasting effects on catchment evolution copyright c 2014 john wiley sons ltd

multistage evolution and variable motion history of agenor linea europa abstract europa the second galilean moon of jupiter is composed of a silicate mantle and an ice shell which overlies a supposed subsurface ocean the surface of europa is scarred with fractures varying in morphology dimensions and geometry we focus on agenor linea a 1500 km bright band that extends across europa s antijovian to trailing southern hemisphere agenor linea is morphologically a band like strike slip fault however it experienced at least three evolutionary growth phases marked by three zones of varying albedo each with a different geological history structures within the band material and kinematic indicators are consistent with formation through oblique left lateral dilation followed by normal dilation and right lateral strike slip movement or combinations thereof these motions produced a cumulative maximum right lateral offset of 29 5 km and a maximum band width of 34 km we interpret agenor linea to have formed primarily in response to the combined effects of nonsynchronous rotation stress and diurnal tidal flexing if so its orientation is optimal for right lateral oblique opening in the current global stress field consistent with its most recent kinematic behavior a small amount of offset of relatively young tension fractures that postdate cryospheric disruption by lenticulae suggest the possibility of ongoing activity along agenor in contrast to a previously published model in which strike slip duplexing was the primary process of band formation this study shows that initial dilation of three distinct morphological zones under disparate stress orientations preceded strike slip motion that resulted in both localized and distributed deformation features within the zones across the width of the band

the formation of enceladus tiger stripe fractures from eccentricity tides abstract enceladus has a young tectonically active south polar region which is erupting material from a prominent set of fractures called tiger stripes no comparable activity is observed at the north pole which is heavily cratered with limited tectonism given the many lines of evidence supporting a global ocean under enceladus icy shell the reason for the dichotomy in geologic activity is unclear we model the formation of the tiger stripes as tidally driven fractures and examine the magnitudes of tidal stresses with different ice shell structures in order to explore whether and how tidal stress might explain enceladus distribution of tectonic activity we find that eccentricity driven tidal stresses would produce fractures of nearly identical orientations to the observed tiger stripe fractures and that a 10 km difference in ice shell thickness between the north and south poles can result in substantially different tidal stress magnitudes providing a natural explanation for the hemispheric dichotomy in tectonic activity on enceladus finally we synthesize these results with enceladus global geologic record to offer insight into the evolution of this enigmatic moon

distribution of strike slip faults on europa study of four different regions on europa imaged by the galileo spacecraft during its first 15 orbits has revealed 117 strike slip faults europa appears to form preferentially right lateral faults in the southern hemisphere and left lateral faults in the northern hemisphere this observation is consistent with a model where diurnal tides due to orbital eccentricity drive strike slip motion through a process of walking in which faults open and close out of phase with alternating right and left lateral shear lineaments that record both left and right lateral motion e g agave linea may record the accommodation of compression in nearby chaotic zones nearly all identified strike slip faults were associated with double ridges or bands and few were detected along ridgeless cracks thus the depth of cracks without ridges does not appear to have penetrated to the low viscosity decoupling layer required for diurnal displacement but cracks that have developed ridges do extend down to such a level this result supports a model for ridge formation that requires cracks to penetrate to a decoupling layer such as a liquid water ocean

the climate in western europe during the last glacial interglacial cycle derived from pollen and insect remains using the pollen sequence of la grande pile xx france we review problems with the application of transfer functions in paleoclimatic reconstructions one of them is to find modern analogues for the herbaceous vegetation of the cold periods we propose a method to distinguish between steppes and tundra vegetations for which the moderns are only partial analogues of the glacial periods another method to solve these problems is based on constraining by insect remains the two methods provide coherent reconstructions the results are also compared with other paleodata there is a good correlation with the six cold heinrich events between 70 and 15 ka b p a cooling event during the eemian period marked by high percentages of taxas at about 125 ka b p needs still to be correlated with high resolution ocean and ice cores

stresses generated in cooling viscoelastic ice shells application to europa 1 a cooling viscoelastic ice shell overlying an ocean develops stresses due to two effects thermal contraction of the ice due to cooling and the expansion of the shell due to the ice water volume change the former effect generates near surface compression and deeper extension the second effect generates extension only in both cases stresses are smaller at depth due to viscous creep the resulting combined stresses are extensional except at shallow 1 km depths in thin ice shells for ice shells thicker than 45 km stresses are extensional throughout the extensional stresses exceed 10 mpa for shells thicker than 20 km and thus dominate all other likely sources of stress as long as shell cooling occurs the dominantly extensional nature of the stresses may help to explain the puzzling lack of compression observed on europa and other large icy satellites however after 100 myr of conductive cooling the maximum theoretical elastic strains for europa are 0 35 which are probably insufficient to explain the total amount of observed extension

modelling centennial sediment waves in an eroding landscape catchment complexity sediment flux dynamics in fluvial systems have often been related to changes in external drivers of topography climate or land cover it is well known that these dynamics are non linear recently model simulations of fluvial activity and landscape evolution have suggested that self organization in landscapes can also cause internal complexity in the sedimentary record in this contribution one particular case of self organization is explored in the sabinal field study area spain where several dynamic zones of sedimentation and incision are observed along the current river bed whether these zones can be caused by internal complexity was tested with landscape evolution model lem lapsus landscape process modelling at multi dimensions and scales during various 500 year simulations zones of sedimentation appear to move upstream and downstream in eroding river channels waves these waves are visualized and characterized for a range of model settings under constant external forcing and the self organizing process behind their occurrence is analysed results indicate that this process is not necessarily related to simplifications in the model and is more generic than the process of bed armouring that has recently been recognized as a cause for complexity in lem simulations we conclude that autogenic sediment waves are the result of the spatial propagation in time of feedbacks in local transport limited deposition and detachment limited erosion conditions

evolution of lineaments on europa clues from galileo multispectral imaging observations abstract four distinct classes of lineaments can be described on the basis of galileo s improved spectral and spatial coverage of europa 1 incipient cracks are narrow the morphologies spectral properties and orientations of the lineaments vary systematically with age suggesting that these four classes represent different stages of development in an evolutionary sequence lineament formation appears to be the dominant resurfacing mechanism on europa and every landscape that has escaped erasure by heating from below is imprinted with generation after generation of intersecting ridges at various scales and orientations relatively recent fractures expose coarse grained clean ice in the shallow subsurface possibly accounting for the distinctive color of the satellite in comparison to the other icy moons of jupiter the process of lineament formation may be continuing today the bright band agenor linea is among the leading candidates for current activity

europa s rate of rotation derived from the tectonic sequence in the astypalaea region abstract the most recent visible tectonic features in the astypalaea region in the southern hemisphere of europa are a set of cycloidal ridges three of which have cross cutting relationships that define a time sequence for their formation the longitudes at which each of these features formed which may be different from the current location due to rotation of europa are constrained by models of their formation reconciling the time sequence with the inferred longitudes of formation appears to require that

shell tectonics a mechanical model for strike slip displacement on europa we introduce a new mechanical model for producing tidally driven strike slip displacement along preexisting faults on europa which we call shell tectonics this model differs from previous models of strike slip on icy satellites by incorporating a coulomb failure criterion approximating a viscoelastic rheology determining the slip direction based on the gradient of the tidal shear stress rather than its sign and quantitatively determining the net offset over many orbits this model allows us to predict the direction of net displacement along faults and determine relative accumulation rate of displacement to test the shell tectonics model we generate global predictions of slip direction and compare them with the observed global pattern of strike slip displacement on europa in which left lateral faults dominate far north of the equator right lateral faults dominate in the far south and near equatorial regions display a mixture of both types of faults the shell tectonics model reproduces this global pattern incorporating a small obliquity into calculations of tidal stresses which are used as inputs to the shell tectonics model can also explain regional differences in strike slip fault populations we also discuss implications for fault azimuths fault depth and europa s tectonic history

delayed delivery from the sediment factory modeling the impact of catchment response time to tectonics on sediment flux and fluvio deltaic stratigraphy the sediment flux from a catchment is driven by tectonics and climate but is moderated by the geomorphic response of the landscape system to changes in these two boundary conditions consequently catchment response time and the non linear behavior of landscapes in response to boundary condition change control the downstream propagation of climatic or tectonic perturbations from catchments to neighboring basins in order to investigate the impact of catchment response time on sediment flux we integrated a spatially lumped numerical model pacmod with new routines simulating the evolution of landscape morphology and erosion rates under tectonic and climatic forcing we subsequently applied the model to reconstruct the sediment flux from a tectonically perturbed catchment in central italy finally we coupled our model to deltasim a process response model simulating fluvio deltaic stratigraphy and investigated the impact of catchment response time on stratigraphy using both synthetic scenarios and a real world system fucino basin central italy our results demonstrate that the differential response of geomorphic elements to tectonic and climatic changes induces a complex sediment flux signal and produces characteristic stratigraphic architectures and shoreline trajectories copyright 2014 john wiley sons ltd

tectonic processes on europa tidal stresses mechanical response and visible features abstract europa s orbital eccentricity driven by the resonance with io and ganymede results in diurnal tides 3 5 day period and possibly in nonsynchronous rotation both diurnal variation and nonsynchronous rotation can create significant stress fields on europa s surface and both effects may produce cracking patterns and time sequences of apparent tectonic features on europa include lineaments that correlate with both sources of stress if we take into account nonsynchronous rotation after initial crack formation by amounts ranging up to several tens of degrees for example the crosscutting time sequence of features in the cadmus and minos linea region is consistent with a combined diurnal and nonsynchronous tensile stress field as it evolves during tens of degrees of nonsynchronous rotation constraints on the rotation rate from comparing voyager and galileo images show that significant rotation requires 104yr but could be fast enough to have allowed significant rotation since the last global resurfacing even if such resurfacing was as recent as a few million years ago once cracking is initiated diurnal tides work cracks so that they open and close daily although the daily effect is small over 105yr double ridges could plausibly be built along the cracks with sizes and morphologies consistent with observed structures according to a model in which underlying liquid water fills the open cracks partially freezes and is extruded during the daily closing of the cracks thus several lines of observational and theoretical evidence can be integrated if we assume nonsynchronous rotation and the existence of a liquid water layer

a revised model for cycloid growth mechanics on europa evidence from surface morphologies and geometries although a single model currently exists to explain the development of curved europan cycloids there have been no systematic studies of the range of morphologies and quantifiable geometric parameters of cycloidal features we address variations in geometry along individual cycloid segments characterizing differences in cusp styles and angles and addressing the morphologic aspects of cycloid segments and cusps in so doing we illustrate how geometric and morphologic evidence imply a formation mechanism that differs from the existing model in several aspects the current model states that cycloids are initiated as tensile fractures that grow in a curved path in response to rotating diurnal tidal stresses on europa however the geometry of a cycloid cusp necessitates that shear stress was resolved onto the existing cycloid segment by the rotating diurnal stresses at the instant of cusp formation furthermore we observe that cycloid cusps have a strikingly similar geometry to tailcracks that developed at the tips of many ridge like strike slip faults on europa in response to shearing at the fault tip we suggest that this similarity in geometries can be attributed to an identical formation mechanism whereby cycloid cusps form by a tailcracking process we therefore present a revised mechanically based model for cycloid formation that retains the basic premise that crack growth is governed by diurnal stresses but describes the development of cycloid cusps in response to resolved shear stresses at the tips of existing cycloid segments the ratio of normal to shear stress at the time of tailcrack formation dictates the cusp angle and over longer time periods influences the morphologic evolution of the cycloid segment as it is repeatedly reworked by tidal stresses

geologic mapping of the northern leading hemisphere of europa from galileo solid state imaging data the northern leading hemisphere of europa was imaged at regional mapping resolution 230 m pixel by the galileo spacecraft ssi camera we produced geologic maps from a regional scale mosaic and a high resolution inset of this region twelve geologic units were sufficient to produce correlative geologic maps at both regional and local scales stratigraphic relationships indicate four major episodes in the geologic history of this area the first episode includes background plains formation and modification followed by a second period of extensive lineament formation the third episode included extensive chaotic disruption of the surface at low and middle latitudes the final episode includes the formation of new sets of ridges and bands especially at high latitudes the low crater density indicates that all these episodes in europa s geologic history are geologically recent the latitudinal distribution of chaos areas broadly matches that of areas of crustal thinning from models of tidal heating we show that stress directions rotated clockwise with time which is consistent with predictions from global stress models involving tidal deformation and nonsynchronous rotation of europa s crust on the basis of the change in lineament orientation with time the reconstructed longitudinal positions of the studied area indicate that europa s crust completed a full rotation relative to the tidally deformed interior

modelling the impact of regional uplift and local tectonics on fluvial terrace preservation abstract a terrace formation model terrace combined with a longitudinal river profile model fluver was used to simulate fluvial terrace formation and preservation in the northwest iberian lower mino river basin under the influence of three tectonic conditions namely regional vertical uplift local basin subsidence and localised differential uplift the simulation results were compared against mapped terrace altitudes and deposit thicknesses the best results were achieved by combining all three tectonic factors indicating that specific terrace formation is a complex interplay of regional and local tectonics the best fit regional uplift rate of 0 10 m ka 1 over the past 600 ka is higher than the 0 08 m ka 1 previously estimated for a section farther to the west which can be attributed to an increase in tectonic uplift from the nw iberian atlantic margin toward the east local relative subsidence causes sediment accumulation in the local basin and less sedimentation in the fluvial terraces on the surrounding uplifting blocks different uplift rates on both sides of the valley caused preservation of unpaired terraces which are fill terraces on one side of the valley and strath terraces on the other side usually the formation of fill or strath terraces is considered to be only climate dependent our results indicate that local tectonics can be important in the terrace formation and preservation this suggests that terrace correlations in other river systems based on deposit thicknesses only might be over simplified

formation of cycloidal features on europa cycloidal patterns are widely distributed on the surface of jupiter s moon europa tensile cracks may have developed such a pattern in response to diurnal variations in tidal stress in europa s outer ice shell when the tensile strength of the ice is reached a crack may occur propagating cracks would move across an ever changing stress field following a curving path to a place and time where the tensile stress was insufficient to continue the propagation a few hours later when the stress at the end of the crack again exceeded the strength propagation would continue in a new direction thus one arcuate segment of the cycloidal chain would be produced during each day on europa for this model to work the tensile strength of europa s ice crust must be less than 40 kilopascals and there must be a thick fluid layer below the ice to allow sufficient tidal amplitude

crack azimuths on europa the g1 lineament sequence revisited abstract the tectonic sequence in the anti jovian area covered by regional mapping images from galileo s orbit e15 is determined from a study of cross cutting relationships among lineament features the sequence is used to test earlier results from orbit g1 based on lower resolution images which appeared to display a progressive change in azimuthal orientation over about 90 in a clockwise sense such a progression is consistent with expected stress variations that would accompany plausible non synchronous rotation the more recent data provide a more complete record than the g1 data did we find that to fit the sequence into a continual clockwise change of orientation would require at least 1000 5 cycles of azimuthal rotation if due to non synchronous rotation of europa this result implies that we are seeing back further into the tectonic record than the g1 results had suggested the three sets of orientations found by geissler et al now appear to have been spaced out over several cycles not during a fraction of one cycle while our more complete sequence of lineament formation is consistent with non synchronous rotation a statistical test shows that it cannot be construed as independent evidence other lines of evidence do support non synchronous rotation but azimuths of crack sequences do not show it probably because only a couple of cracks form in a given region in any given non synchronous rotation period

linking europa s plume activity to tides tectonics and liquid water abstract much of the geologic activity preserved on europa s icy surface has been attributed to tidal deformation mainly due to europa s eccentric orbit although the surface is geologically young 30 80 myr there is little information as to whether tidally driven surface processes are ongoing however a recent detection of water vapor near europa s south pole suggests that it may be geologically active initial observations indicated that europa s plume eruptions are time variable and may be linked to its tidal cycle saturn s moon enceladus which shares many similar traits with europa displays tidally modulated plume eruptions which bolstered this interpretation however additional observations of europa at the same time in its orbit failed to yield a plume detection casting doubt on the tidal control hypothesis the purpose of this study is to analyze the timing of plume eruptions within the context of europa s tidal cycle to determine whether such a link exists and examine the inferred similarities and differences between plume activity on europa and enceladus to do this we determine the locations and orientations of hypothetical tidally driven fractures that best match the temporal variability of the plumes observed at europa specifically we identify model faults that are in tension at the time in europa s orbit when a plume was detected and in compression at times when the plume was not detected we find that tidal stress driven solely by eccentricity is incompatible with the observations unless additional mechanisms are controlling the eruption timing or restricting the longevity of the plumes the addition of obliquity tides and corresponding precession of the spin pole can generate a number of model faults that are consistent with the pattern of plume detections the locations and orientations of these hypothetical source fractures are robust across a broad range of precession rates and spin pole directions analysis of the stress variations across the fractures suggests that the plumes would be best observed earlier in the orbit true anomaly 120 our results indicate that europa s plumes if confirmed differ in many respects from the enceladean plumes and that either active fractures or volatile sources are rare

late cenozoic landscape development and its tectonic implications for the guadalhorce valley near alora southern spain abstract landscape evolution is the result of a variety of geomorphological processes and their controls in time in southern spain tectonics climate and sea level fluctuations have been some of the main variables controlling long term late cenozoic landscape evolution in the guadalhorce valley malaga geomorphological reconstructions can be undertaken using sedimentary evidence from marine and fluvial deposits as well as erosional evidence such as terrain form and longitudinal profile analysis data are obtained and analysed from the upper miocene to present these allow reconstructions which add information and constraints to the uplift history and landscape development of the area main sedimentation phases are the late tortonian early pliocene and pleistocene important erosional hiatus are found for the middle miocene messinian and late pliocene to early pleistocene these phases of erosion and sedimentation resulted in a relative large and elongated tortonian marine valley filled with complex sedimentary structures next a prolonged stage of erosion of these deposits and incision of the major valley system took place during the messinian in the pliocene a short palaeo guadalhorce in a narrow and much smaller valley existed this valley was partly filled with marine sediments and prograding fan delta complexes during the pleistocene a wider and larger incising river system resulted in rearrangements of the drainage network evaluating the uplift history of the area we found that rates of tectonic activity were higher during the tortonian messinian and upper pleistocene while tectonic activity was lower during the pliocene relative uplift rates for the study area range for the messinian between 160 and 276 m ma 1 for the pliocene between 10 and 15 m ma 1 and for the pleistocene between 40 and 100 m ma 1

the influence of obliquity on europan cycloid formation tectonic patterns on europa are influenced by tidal stress an important well recognized component is associated with the orbital eccentricity which produces a diurnally varying stress as jupiter s apparent position in europa s sky oscillates in longitude cycloidal lineaments seem to have formed as cracks propagated in this diurnally varying stress field maps of theoretical cycloid patterns capture many of the characteristics of the observed distribution on europa however a few details of the observed cycloid distribution have not been reproduced by previous models recently it has been shown that europa has a finite forced obliquity so jupiter s apparent position in europa s sky will also oscillate in latitude we explore this new type of diurnal effect on cycloid formation we find that stress from obliquity may be the key to explaining several characteristics of observed cycloids such as the shape of equator crossing cycloids and the shift in the crack patterns in the argadnel regio region all of these improvements of the fit between observation and theory seem to require jupiter crossing europa s equatorial plane 45 to 180 after perijove passage suggestive of complex orbital dynamics that locks the direction of europa s pericenter with the direction of the ascending node at the time these cycloids were formed