valles marineris dune sediment provenance and pathways abstract although low albedo sand is a prevalent component of the martian surface sources and pathways of the sands are uncertain as one of the principal present day martian sediment sinks the valles marineris vm rift system hosts a diversity of dune field populations associated with a variety of landforms that serve as potential sediment sources including spur and gully walls interior layered deposits ilds and landslides here we test the hypothesis that vm dune fields are largely derived from a variety of local and regional intra rift sediment sources results show several dune fields are superposed on ancient wall massifs and ilds that are topographically isolated from extra rift sand sources spectral analysis of dune sand reveals compositional heterogeneity at the basinal dune field and dune scales arguing for discrete relatively unmixed sediment sources in coprates and melas chasmata mapping is consistent with the principle sand source for dunes being noachian aged upper and lower wall materials composed of primary igneous minerals and glasses some of which show evidence for alteration in contrast dune fields in capri juventae and ganges chasmata show evidence for partial sediment derivation from adjacent early hesperian aged hydrated sulfate bearing ild units this finding indicates that these ilds act as secondary sand sources dunes containing soft secondary minerals e g monohydrated sulfate are unlikely to have been derived from distant sources due to the physical weathering of sand grains during transport isolated extra rift dune fields sand sheets and sand patches are located on the plateaus surrounding vm and the adjoining areas but do not form interconnected networks of sand pathways into the rift if past wind regimes with respect to directionality and seasonality were consistent with more recent regimes inferred from morphological analysis i e dune slip faces wind streaks and were sufficient in strength and duration small dune populations within aurorae chaos and north of eastern vm might have resulted from extended sand pathways into vm however we favor local and regional derivation of dune sand from a variety of intra rift lithologic sources for most cases dune sand sources and the mechanism by which the sand is liberated are discussed in the context of findings described herein but are broadly applicable to analysis of sediment production elsewhere on mars

orthogonal relation between wavefield polarization and fast s wave direction in the val d agri region an integrating method to investigate rock anisotropy 1 wavefield polarization is investigated using 200 seismograms recorded by a network of 20 stations installed on rock outcrops in the val d agri region that hosts the largest oil fields in the southern apennines italy polarization is assessed both in the frequency and time domains through the individual station horizontal to vertical spectral ratio and covariance matrix analysis respectively we find that most of the stations show a persistent horizontal polarization of waveforms with a ne sw predominant trend this direction is orthogonal to the general trend of quaternary normal faults in the region and to the maximum horizontal stress related to the present extensional regime according to previous studies in other areas such a directional effect is interpreted as due to the presence of fault related fracture fields polarization being orthogonal to their predominant direction a comparison with s wave anisotropy inferred from shear wave splitting indicates an orthogonal relation between horizontal polarization and fast s wave direction this suggests that wavefield polarization and fast velocity direction are effects of the same cause the existence of an anisotropic medium represented by fractured rocks where shear wave velocity is larger in the crack parallel component and compliance is larger perpendicularly to the crack strike the latter is responsible for the observed anisotropic pattern of amplitudes of horizontal ground motion in the study area

fluid flow and volume loss during mylonitization an origin for phyllonite in an overthrust setting north carolina u s a abstract in the western blue ridge province of the southern appalachians north carolina granite gneisses are converted to phyllitic mylonites phyllonites along the base of the rector branch thrust sheet the mylonites show evidence for fluid infiltration and large volume losses with decreasing distance from the thrust and local shear zones feldspars undergo grain size reduction by cracking followed by chemical breakdown to muscovite sericite and zoisite the following reaction was important during mylonitization 3 k feldspar 2 h muscovite 2 k 6 sio 2 quartz displays evidence for dynamic recrystallization whereas feldspar deforms brittely which together with the secondary mineral assemblages suggest that deformation occurred at temperatures of between 300 c and 500 c in the presence of a fluid the mylonites are enriched by a factor of at least 2 5 in elements such as tio 2 p 2 o 5 zr y v la ce and depleted in sio 2 in comparison to their protolith gneisses the immobile element enrichments are attributed to enrichment in residual phases such as ilmenite zircon apatite and epidote in the mylonites and are interpreted as due to minimum volume losses of 60 mass balance calculations based on major element chemistry indicate the mylonites lost large amounts of sio 2 and smaller amounts of alkalies and were infiltrated by fluid rock weight ratios of between 10 2 and 10 3 phyllonitization as a process involves several deformation mechanisms including cataclasis and solution of feldspar as well as dislocation creep of quartz and micas reaction enhanced softening was apparently important in strain localization

quaternary evolution of the intermontane val d agri basin southern apennines optically stimulated luminescence osl enables the chronology of the late pleistocene evolution for the val d agri intermontane basin of southern apennines to be defined in the frame of mediterranean geodynamic and climate changes quartz sand from braided floodplain and alluvial fan depositional systems was analyzed using the coarse grained single aliquot regenerative dose sar technique the obtained optical ages are mostly consistent with other assessments radiocarbon tephrochronology and stratigraphic constraints osl allows for the dating to 56 43 ka of an asymmetric subsidence stage that forced alluvial fan progradation filling of a former lacustrine area and development of an axial alluvial plain a short period of mediterranean type pedogenesis recorded at the top of the prograding aggrading fans osl age bracket 43 32 ka corresponds with mis 3 during the subsequent stage of decline of vegetation cover possibly corresponding to mis 2 the latest progradation of alluvial fans occurred the subsequent uplift and breakthrough of the basin threshold during the latest pleistocene and holocene induced entrenchment of the drainage network the results presented here provide an example of the usefulness of osl dating in intermontane continental settings where other geochronological constraints are scarce

quartz microstructures developed during non steady state plastic flow at rapidly decaying stress and strain rate abstract synseismic loading to very high stresses 0 5 gpa and subsequent creep during stress relaxation in the uppermost plastosphere at temperatures of ca 300 350 c near the lower tip of an inferred once seismically active crustal scale fault was proposed based on peculiar microstructures identified in rocks exposed over 100 km 2 in the sesia zone european western alps here we discuss the conspicuous and highly heterogeneous microstructural record of quartz in disseminated small scale shear zones sub basal deformation lamellae and arrays of elongate subgrains on the tem scale indicate an early stage of glide controlled deformation at high stresses distributed brittle failure is indicated by healed microcracks very fine grained recrystallised aggregates with a pronounced crystallographic preferred orientation reflect intense plastic flow by dislocation creep locally a fine grained foam microstructure indicates a final stage of static grain growth at low differential stress for the previously inferred peak stresses of about 0 5 gpa and given temperatures initial strain rates on the order of 10 10 s 1 are predicted by available flow laws for dislocation creep of quartz we emphasise the importance of short term non steady state deformation in the uppermost plastosphere underlying seismically active upper crust the related heterogeneous record of quartz is governed by the local stress history at constant temperature

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

microstructures mineral chemistry and geochronology of white micas along a retrograde evolution an example from the aar massif central alps switzerland abstract this study investigates gneissic tectonites of different mechanical origins and aims at unravelling the link between microstructures white mica chemistry and k ar data the highest temperature mylonitic deformation which is investigated is dominated by dislocation creep in monomineralic quartz and viscous granular flow in polymineralic domains these mylonites show homogenous mineral chemistry resulting in robust and consistent k ar age data the lowest temperature deformation investigated is that of a retrograde brittle deformation producing cohesionless fault gouges within the cohesionless fault gouges frictional granular flow is considered as the main deformation mechanism the k bearing phases inside the fault gouges record no chemical resetting during this brittle overprint but contain mechanically fragmented k bearing micas and significant amounts of newly produced smectite this yields k ar ages inside of a gouge that are in the range of adjacent mylonite ages and may not represent the timing of gouge formation in an effort to understand these uncertainties in k ar ages detailed observations of the microstructural context of k bearing white mica were made microstructural criteria in combination with quantitative element mapping allowed for the discrimination of five important mica related processes 1 fracturing recrystallization of white mica 2 re precipitation of new fine grained white mica inside the deforming rock matrix 3 pseudomorphic replacement of precursor minerals by white mica and chlorite 4 pseudomorphic replacement of pre existing white mica without grain size reduction and 5 remnant grains the combination of these different processes led to a high variability in mineral chemistry and isotope data for tectonites which relates directly to variations in the size of the equilibrium volumes despite the samples being highly deformed in the presence of fluids inherited sheet silicates may survive if inherited sheet silicates are present they contribute to an increase in both the chemical heterogeneity and the apparent k ar ages of a sample

north polar region of mars topography of circumpolar deposits from mars orbiter laser altimeter mola data and evidence for asymmetric retreat of the polar cap we have used high resolution mars orbiter laser altimeter mola data to analyze the topography morphology stratigraphy and geologic history of the martian north circumpolar deposits the present polar deposits are offset about toward 0 w from the rotational pole an arc of irregular topography concentric to olympia planitia and the cap consists of polar material remnants depressions which we interpret to be kettles frost covered and residual ice filled craters and frost patches olympia planitia originally thought to be a flat sand covered plain is characterized by a convex upward topography contiguous with the polar cap we interpret olympia planitia to represent a now dune covered extension of the polar materials together olympia planitia and the outlying deposits delineate a former extent of the polar cap topographic data have clarified relationships among the circumpolar deposits contributors to these deposits include local volcanics fluvial and aqueous sediments from outflow channels and a possible standing body of water pyroclastic ash sublimation lag from the olympia lobe and eolian reworked materials significant events in the history of the region include 1 formation of the northern lowlands 2 emplacement of volcanic plains fluvial and aqueous sedimentation and subsequent desiccation forming polygonal patterns which in part underlie the present polar layered deposits 3 formation of the polar cap composed primarily of layered deposits 4 asymmetric retreat of the olympia lobe resulting in sublimation lag deposits polar remnants and kettles and 5 continued collection and reworking of sediments by eolian processes the cause of the asymmetrical retreat of the olympia lobe is unknown

geochronological evidence for continuous exhumation through the ductile brittle transition along a crustal scale low angle normal fault simplon fault zone central alps 1 major low angle normal faults juxtapose different structural levels of the crust that record both brittle and ductile deformation field relationships alone cannot establish whether these different responses to deformation represent 1 parts of a single process of exhumation along the detachment or 2 two separate events with the later more discrete brittle detachment exhuming a fossil ductile shear zone from depth these two general models are critically assessed for the low angle normal simplon fault zone sfz in the central alps the sfz shows a spatial transition from a broad ductile mylonitic shear zone to a discrete brittle detachment with identical kinematics the age of the ductile shear zone and ductile brittle transition is controversial we present a detailed geochronological study based on fission track 40ar 39ar and rb sr microsampling dating coupled with structural petrological and chemical analyses that provides tight constraints on sfz timing discontinuous mineral cooling ages over a broad range of temperatures across the fault zone argue for fault activity between 20 and 3 ma on the basis of synkinematic white mica in low temperature shear zones and necks of foliation boudinage the brittle ductile transition in the footwall could be dated at 14 5 10 ma overall the data presented here are consistent with a continuous transition from ductile shearing to a more localized zone of brittle deformation within the same geological framework over a period of 15 ma the sfz is therefore an example of a telescoped crustal section within a single major low angle fault involving a continuous period of exhumation rather than a two stage structure

a geodynamic model of the southern apennines accretionary prism the apennines comprise a neogen quaternary accretionary prism that shows several anomalies with respect to classic alpine type mountain belts namely i low elevation ii a shallow new moho below the core of the belt iii high heat flow in the internal parts iv mainly sedimentary cover involved in the prism v a deep foredeep and vi a fully developed back arc basin the suction exerted by a relatively eastward migrating mantle can determine the eastward retreat of the subduction zone and an asthenospheric wedging at the retreating subduction hinge heat flow geochemical and seismological data support the presence of a hot mantle wedge underlying the western side of the apenninic accretionary prism a thermal model of the belt with foreland dipping isotherms fits with deepening of the seismicity toward the east mantle volatiles signatures are also widespread in springs along the apennines

spectral and geological study of the sulfate rich region of west candor chasma mars sulfates have been discovered by the omega spectrometer in different locations of the planet mars they are strongly correlated to light toned layered deposits in the equatorial regions west candor chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates a detailed study coupling mineralogy derived from omega spectral data and geology derived from hrsc imager and other datasets leads to some straightforward issues the monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material it likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments or during hydrothermal alteration at depth because it is typically found on outcrops that are eroded and steep polyhydrated sulfates that match any ca na fe or mg sulfates with more than one water molecule are preferentially present on less eroded and darker outcrops than outcrops of kieserite these variations can be the result of a diversity in the composition and or of the rehydration of kieserite on surfaces with longer exposure the latter possibility of rehydration in the current or recent atmosphere suggests the low surface temperatures preserve sulfates from desiccation and also can rehydrate part of them strong signatures of iron oxides are present on sulfate rich scarps and at the base of layered deposits scarps they are correlated with tes gray hematite signature and might correspond to iron oxides present in the rock as sand size grains or possibly larger concretions that are eroded and transported down by gravity at the base of the scarp pyroxenes are present mainly on sand dunes in the low lying terrains pyroxene is strongly depleted or absent in the layered deposits when mixed with kieserite local observations favor a spatial mixing with dunes over layered deposits sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation either in an intermittent lacustrine environment or by hydrothermal fluid circulation both possibilities require the presence of sulfur rich groundwater to explain fluid circulation the elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2 5 km above datum only 1 km below the plateau surface

earthquake faulting as a structural process abstract structural geology is concerned with the history of movement in the earth s crust and the processes by which displacements occur in the upper one third to one half of deforming continental crust displacement is accommodated largely by seismic slip increments on existing faults it follows that earthquakes and related processes are an integral part of structural geology traditionally structural geologists have been preoccupied with the complexity of the finite deformation within fault zones and with the stress states prevailing at the initiation of faults in intact crust future structural work should be directed more towards understanding the dynamic character of fault reactivation during incremental slip and related effects questions of interest include rheological and geometrical controls on the initiation perturbation and termination of ruptures directivity effects associated with rupture propagation the recognition of structures resulting from repeated stress cycling within seismogenic crust and identification of structural features diagnostic of shear stress levels during faulting structures arising from the inter relationships between slip episodes and induced fluid flow are of special importance because these dynamic fault processes appear influential in the development of much fault hosted mineralization mesothermal gold quartz lodes hosted in high angle reverse shear zones of mixed brittle ductile character form illustrative examples of structures that arguably can only be interpreted by seismo structural analysis embodying the concepts listed above

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

dust haze in valles marineris observed by hrsc and omega on board mars express 1 we present analysis of a bright haze observed inside valles marineris which formed in mid northern spring the data were collected by the high resolution stereo camera hrsc and the imaging spectrometer observatoire pour la mineralogie l eau les glaces et l activite omega aboard mars express this study provides a case example of the power of simultaneous multiple emission angle and hyperspectral imaging for study of aerosols and clouds in the martian atmosphere the haze appeared thinner after three days and disappeared in nine days it was limited to a 2 km layer at the bottom of the canyon the color was redder than the underlying surface the analysis of the omega spectra indicates that this haze was composed of dust particles the dust layer appeared brighter with the hrsc stereo channels than the nadir channel due to longer scattering paths we have estimated the optical depth of the haze by fitting both hrsc and omega data with radiative transfer calculations the retrieval of the optical depth is very sensitive to the aerosol scattering model used and the reflectance of the surface applying an aerosol scattering model derived from sky surveys at a constant elevation by the imager for mars pathfinder the optical depth of the haze is estimated from hrsc data to be within 1 7 to 2 3 at the wavelength of 0 675 m the wavelength dependence is obtained from omega spectrum it increases to 2 2 2 6 at 1 35 m and moderately decreases to 1 2 1 8 at 2 4 m

transitional morphology in west deuteronilus mensae mars implications for modification of the lowland upland boundary abstract west deuteronilus mensae which lies along the lowland upland boundary of mars at 45 latitude 345 longitude exhibits both gradational l a rossbacher 1985 in models in geomorphology woldenberg ed pp 343 372 allen unwin boston and fretted terrain r p sharp 1973 j geophys res 78 4073 4083 boundary types to the west the boundary is gradational and to the east it is defined by fretted terrain the two types of boundaries do not merge with one another within the west deuteronilus mensae region however the gradational boundary materials appear to overlap the fretted terrain by about 500 km contacts between units associated with the gradational boundary and the fretted terrain boundary can both be recognized in the region of overlap the fretted terrain can be identified as much as 300 km north of the gradational boundary in this region lowland units associated with the gradational boundary embay canyons of the fretted terrain in a topographically conformal fashion changes in the fretted terrain across the gradational boundary from uplands to lowlands include a reduction of canyon wall slopes and depths such that the fretted terrain north of the gradational boundary appears mantled but not obscured there are at least two major classes of processes which might explain the lateral overlap 1 erosion of stratified upland terrain and 2 deposition of plains materials onto the sloping upland margin and fretted terrain erosion of stratified upland terrain does not adequately explain the plainward decrease in crater densities across the gradational boundary nor is it consistent with evidence that lowland plains material appears to onlap the sloping upland margin in several places of the possible plains emplacement mechanisms eolian deposition would not produce the sharp apparently topographically conformal gradational unit contacts volcanics plains emplacement would not preserve the complex geometry of the underlying fretted terrain sediment deposition in either a liquid or ice covered sea could produce the draped appearance of the fretted terrain outflow channels along the lowland upland boundary particularly those of the circum chryse and west elysium regions may have flooded the northern lowlands to depths of tens to hundreds of meters the gradational unit contacts may represent the shorelines of such a sea the scale of characteristic morphologies along these contacts may require an unfrozen condition of sufficient duration to allow lacustrine style wave erosion and redistribution of material along the contacts our limited understanding of the martian paleoclimate and h 2 o inventories allows the possibility of clement periods in the past and other geological evidence e g small valley networks and outflow channels strongly suggests an extensive role of liquid water

thermomechanics of an extensional shear zone raft river metamorphic core complex nw utah abstract a detailed structural and microstructural analysis of the miocene raft river detachment shear zone nw utah provides insight into the thermomechanical evolution of the continental crust during extension associated with the exhumation of metamorphic core complexes combined microstructural electron backscattered diffraction strain and vorticity analysis of the very well exposed quartzite mylonite show an increase in intensity of the rock fabrics from west to east along the transport direction compatible with observed finite strain markers and a model of necking of the shear zone microstructural evidence quartz microstructures and deformation lamellae suggests that the detachment shear zone evolved at its peak strength close to the dislocation creep exponential creep transition where meteoric fluids played an important role on strain hardening embrittlement and eventually seismic failure empirically calibrated paleopiezometers based on quartz recrystallized grain size and deformation lamellae spacing show very similar results indicate that the shear zone developed under stress ranging from 40 mpa to 60 mpa using a quartzite dislocation creep flow law we further estimate that the detachment shear zone quartzite mylonite developed at a strain rates between 10 12 and 10 14 s 1 we suggest that a compressed geothermal gradient across this detachment which was produced by a combination of ductile shearing heat advection and cooling by meteoric fluids may have triggered mechanical instabilities and strongly influenced the rheology of the detachment shear zone

microstructural analyses of a giant quartz reef in south china reveal episodic brittle ductile fluid transfer abstract a long lived hydrothermal system at the heyuan fault south china has led to the development of a giant quartz reef now partially exhumed along its length for more than 40 km systematic analyses and focused microstructural studies have been undertaken to unravel a complex formation history of repeated fracturing hydrothermal fluid flow and sealing cycles resulting in a dynamic permeability across the fault zone the change in morphology and decreasing grain size with time further indicates the move from slow ductile opening to fast seismic events quartz reef formation has been estimated to occur within a range of 200 350 c based on evaluation of i quartz deformation microstructures ii chlorite and mica geothermometry and iii review of comparable quartz reef studies additionally a set of physico chemical formation conditions have been identified which compose the quartz reef window these are i significant volume of fluid ii fluid sources from meteoric metamorphic and or from mantle origin iii considerable time integrated fluid fluxes iv sio2 oversaturation due to a temperature change b sudden pressure drop or c chemical change e g fluid mixing v accommodation space to grow the reef vi channel permeability and vii cap rock seal to trap the fluid flow the mechanism of quartz reef growth is here interpreted as the brittle ductile analogue of the brittle fault valve model

the state and future of mars polar science and exploration as the planet s principal cold traps the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of 10 6 km 2 and total as much as 3 4 km thick from the scarcity of superposed craters on their surface these layered deposits are thought to be comparatively young preserving a record of the seasonal and climatic cycling of atmospheric co 2 h 2o and dust over the past 10 5 10 8 years for this reason the martian polar deposits may serve as a rosetta stone for understanding the geologic and climatic history of the planet documenting variations in insolation due to quasiperiodic oscillations in the planet s obliquity and orbital elements volatile mass balance atmospheric composition dust storm activity volcanic eruptions large impacts catastrophic floods solar luminosity supernovae and perhaps even a record of microbial life beyond their scientific value the polar regions may soon prove important for another reason providing a valuable and accessible reservoir of water to support the long term human exploration of mars in this paper we assess the current state of mars polar research identify the key questions that motivate the exploration of the polar regions discuss the extent to which current missions will address these questions and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding

north polar stratigraphy and the paleo erg of mars an accurate self consistent way of coregistering the imaging and topographic data sets of the mars global surveyor mission was developed and used to begin a stratigraphic analysis of the northern polar region a distinct change in the layering style exists at a definite stratigraphic horizon near the base of the north polar layered deposits occurrences of the contact between two distinct layered units can be mapped hundreds of kilometers apart at nearly the same mars orbiter laser altimeter mola elevation the lower layered unit has a consistent association with sand dunes leading to the conclusion that it is an eroding sand rich deposit that predates most of the overlying north polar layered deposits which exhibits the expected features of a dust ice mixture these results suggest that an areally extensive erg was in existence before the present ice cap and that the present circumpolar erg is likely composed of material reworked from this older deposit the volume of this lower unit is estimated to be on the order of 10 5 km 3 the presence of this deposit implies that there existed a period in mars history when there was no icy polar cap a dramatic climatic change leading to the deposition of the upper layered icy unit in the present day polar layered deposits represents a major event in mars history however owing to uncertainties in the mechanics of layered deposits formation such an event cannot be dated at this time

high resolution imaging of the high agri valley basin southern italy with electrical resistivity tomography abstract the first high resolution images of the fault controlled high agri valley basin obtained with the electrical resistivity tomography are presented the agri valley is one of the more complex components of the quaternary fault network of the apennine chain the geometry of the pre quaternary bedrock the location and dip of the master fault and the tectonic evolution of the basin are still a subject of debate therefore deep electrical resistivity tomography integrated with stratigraphic analyses has been carried out to improve knowledge of the geological setting of the basin the high resolution electrical images allow us to reconstruct the complex geometry of the basin the electrical imaging highlights the irregular shape of the basin which is bordered by shallow faults and filled with pleistocene alluvial deposits in longitudinal cross section the basin appears as a mosaic of fault bounded blocks forming three different depocenters separated by intrabasinal highs in transverse cross section the basin is an irregular graben locally asymmetric to the northeast and with secondary grabens due to antithetic faults

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

partitioning of the cretaceous pan yangtze basin in the central south china block by exhumation of the xuefeng mountains during a transition from extensional to compressional tectonics abstract the formation of a series of intermountain basins is likely to indicate a geodynamic transition especially in the case of such basins within the central south china block cscb determining whether or not these numerous intermountain basins represent a division of the cretaceous pan yangtze basin by exhumation of xuefeng mountains is key to understanding the late mesozoic to early cenozoic tectonics of the south china block scb here we present apatite fission track aft data and time temperature modeling in order to reconstruct the evolution history of the pan yangtze basin fourteen rock samples were taken from a ne sw trending mountain basin system within the cscb including from west to east the wuling mountains wuling shan the south and north mayang basins the xuefeng mountains xuefeng shan and the hengyang basin cretaceous lacustrine sequences are well preserved in the south and north mayang and hengyang basins and sporadically crop out in the xuefeng mountains whereas paleogene piedmont proluvial lacustrine sequences are only found in the south mayang and hengyang basins aft results indicate that the wuling and xuefeng mountains underwent rapid denudation post 84 ma whereas the south and north mayang basins were more slowly uplifted from 67 and 84 ma respectively following a quiescent period from 32 to 19 ma both the mountains and basins have been rapidly denuded since 19 ma both the aft data and sedimentary facies changes suggest that the cretaceous deposits that cover the south north mayang and hengyang basins through to the xuefeng mountains define the cretaceous pan yangtze basin integrating our results with tectonic background for the scb we propose that rollback subduction of the paleo pacific plate produced the pan yangtze basin which was divided into the south north mayang and hengyang basins by the abrupt uplift and exhumation of the xuefeng mountains from 84 ma to present apart from a period of tectonic inactivity from 32 to 19 ma this late late cretaceous to paleogene denudation resulted from movement on the ziluo strike slip fault which formed due to intra continental compression most likely associated with the eurasia indian plate subduction and collision sinistral transpression along the ailao shan red river fault at 34 17 ma probably transformed this compression to the extrusion of the indochina block and produced the quiescent window period from 32 to 19 ma for the mountain basin system in the cscb therefore the initiation of exhumation of the xuefeng mountains at 84 ma indicates a switch in tectonic regime from cretaceous extension to late late cretaceous and cenozoic compression

procedures used for luminescence dating of sediments abstract an account of the procedures for thermoluminescence tl and optically stimulated luminescence osl dating of sediments used at the nordic laboratory for luminescence dating is given the topics discussed include sampling sample preparation separation of quartz and feldspars using heavy liquids dose rate estimation and methods for estimating the equivalent dose special attention is paid to the partial bleach tl technique of mejdahl 1988 which appears to give reliable results for partially bleached sediments optically stimulated luminescence dating using stimulation by infra red ir and green light has been taken up and especially added dose methods using stimulation by ir or green light have been tried with some success some sources of error are discussed including the adverse effect of shallow traps

slow earthquakes and nonvolcanic tremor nonvolcanic tremor is observed in close association with geodetically observed slow slip events in subduction zones accumulating evidence points to these events as members of a family of slow earthquakes that occur as shear slip on the downdip extensions of fault zones in a regime that is transitional between a frictionally locked region above and a freely slipping region below by virtue of their locations and their properties slow earthquakes are certain to provide new insights into the behavior of earthquakes and faulting and into the hazard they embody

tephrochronological study in the quaternary val d agri intermontane basin southern apennines italy in the south eastern depocentre of the val d agri basin southern apennines a volcanic ash layer crops out interbedded within poorly structured alluvial fan deposits of late pleistocene age textural depositional and pedological features of this weathered layer suggest a primary deposition from a pyroclastic fall out of volcanic ash chemical analyses of feldspars show an alkali trachytic composition and accessory minerals association allow to correlate this tephra layer with the regionally dispersed y 7 marine tephra layer tufo verde epomeo eruption ischia volcano dated at 56 4 ka the val d agri tephra here described for the first time was deposited during mis stage 3 its recovery and characterization permit to contribute to regional correlation of the mediterranean climatic and volcanic events from marine to continental successions and to describe landscape evolution of the southern apennines during glacial interglacial cycles

fracturing and hydrothermal alteration in normal fault zones large normal fault zones are characterized by intense fracturing and hydrothermal alteration displacement is localized in a slip zone of cataclasite breccia and phyllonite surrounding corrugated and striated fault surfaces slip zone rock grades into fractured but less comminuted and hydrothermally altered rock in the transition zone which in turn grades abruptly into the wall rock fracturing and fluid flow is episodic because permeability generated during earthquakes is destroyed by hydrothermal processes during the time between earthquakes

detecting young slow slipping active faults by geologic and multidisciplinary high resolution geophysical investigations a case study from the apennine seismic belt italy 1 the southern apennines range of italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics coupled to very recent middle pleistocene onset and slow slip rates of active normal faults as shown by the irpinia fault source of a m6 9 earthquake in 1980 major faults might have small cumulative deformation and subtle geomorphic expression a multidisciplinary study including morphological tectonic paleoseismological and geophysical investigations has been carried out across the extensional monte aquila fault a poorly known structure that similarly to the irpinia fault runs across a ridge and is weakly expressed at the surface by small scarps warps the joint application of shallow reflection profiling seismic and electrical resistivity tomography and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions geophysical data clearly 1 image a fault zone beneath suspected warps 2 constrain the cumulative vertical slip to only 25 30 m 3 delineate colluvial packages suggesting coseismic surface faulting episodes paleoseismological investigations document at least three deformation events during the very late pleistocene 20 ka and holocene the clue to surface rupturing episodes together with the fault dimension inferred by geological mapping and microseismicity distribution suggest a seismogenic potential of m6 3 our study provides the second documentation of a major active fault in southern italy that as the irpinia fault does not bound a large intermontane basin but it is nested within the mountain range weakly modifying the landscape this demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region more in general our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques the proposed multidisciplinary methodology can be effective in regions characterized by young and or slow slipping active faults

laboratory simulated acid sulfate weathering of basaltic materials implications for formation of sulfates at meridiani planum and gusev crater mars 1 acid sulfate weathering of basaltic materials is a candidate formation process for the sulfate rich outcrops and rocks at the mer rover opportunity and spirit landing sites to determine the style of acid sulfate weathering on mars we weathered basaltic materials olivine rich glassy basaltic sand and plagioclase feldspar rich basaltic tephra in the laboratory under different oxidative acid sulfate conditions and characterized the alteration products we investigated alteration by 1 sulfuric acid vapor acid fog 2 three step hydrothermal leaching treatment approximating an open system and 3 single step hydrothermal batch treatment approximating a closed system in acid fog experiments a1 fe and ca sulfates and amorphous silica formed from plagioclase rich tephra and mg and ca sulfates and amorphous silica formed from the olivine rich sands in three step leaching experiments only amorphous si formed from the plagioclase rich basaltic tephra and jarosite mg and ca sulfates and amorphous silica formed from olivine rich basaltic sand amorphous silica formed under single step experiments for both starting materials on the basis of our experiments jarosite formation in meridiani outcrop is potential evidence for an open system acid sulfate weathering regime waters rich in sulfuric acid percolated through basaltic sediment dissolving basaltic phases e g olivine and forming jarosite other sulfates and iron oxides aqueous alteration of outcrops and rocks on the west spur of the columbia hills may have occurred when vapors rich in so 2 from volcanic sources reacted with basaltic materials soluble ions from the host rock e g olivine reacted with s to form ca mg and other sulfates along with iron oxides and oxyhydroxides

fault valve behavior and the hydrostatic lithostatic fluid pressure interface abstract currently deforming regions of continental crust are characterized by seismic activity in a brittle carapace which presumably overlies regions undergoing local or distributed metamorphism one may note in this regard the global correlation between active seismic belts and the distribution of co2 rich springs barnes et al 1984 in regions of moderate to high heat flow 60 100 mw m 2 the seismogenic regime representing the zone of unstable frictional sliding typically extends to depths of 10 15 km marking the onset of greenschist metamorphic conditions sibson 1983 however in regions of rapid thrust convergence 1cm yr 1 seismic activity may extend to significantly greater depths through depression of isotherms as in the thrust front of the himalaya

ground penetrating radar measurements of subsurface structures of lacustrine sediments in the qaidam basin nw china possible implications for future in situ radar experiments on mars abstract the stratigraphic profile of paleolakes on mars preserves a record of past climatic hydrological and sedimentary environment radar could be used to detect the structure and distribution of buried lacustrine sediments but orbiter radar sounders rarely detect the internal structure or the bottom of the ancient martian lake deposits future martian missions will employ ground penetrating radar gpr onboard rovers to investigate the shallow subsurface structure of paleolake basins in this case ground experiments are necessary to test the potential of gpr detection this study reports on gpr experiments operating at 100 mhz and 200 mhz carried out in the qaidam basin one of the analogue sites for martian paleolake environments to detect the subsurface structure of lacustrine sediments and measure the relative permittivity of sediments with both laboratory instrument and gpr data two gpr measurements were performed on top of yardangs representing layered lacustrine sedimentary outcrops another survey site is a polygonal patterned ground which is a common landform in the qaidam basin and on mars the observations revealed by gpr experiments show that 1 sediments of three sites have varied compositions density and porosity and have a wide range of relative permittivity values from 1 56 to 4 56 2 the detection depth of our measurements could reach 20 m 3 the interfaces between sedimentary layers can be seen in radargrams but reflectors in radargrams may not always match with exposed layers of the yardang outcrops due to the undetected change of permittivity values or thin thickness of layers 4 a distinct and continuous reflector is observed beneath the polygonal terrain which we interpret as a subsurface layer with low water brine content our ground experiments suggest that a similar gpr on martian rover could detect the near surface structure of lacustrine sediments e g deposition anomaly interfaces of drastic permittivity change such as buried ice brine considering that the design frequency is close to our equipment

on the orbital forcing of martian water and co2 cycles a general circulation model study with simplified volatile schemes 1 variations in the martian water and co2 cycles with changes in orbital and rotational parameters are examined using the geophysical fluid dynamics laboratory mars general circulation model the model allows for arbitrary specification of obliquity eccentricity and argument of perihelion as well as the position and thickness of surface ice exchange of co2 between the surface and atmosphere is modeled generating seasonal cycles of surface ice and surface pressure water is allowed to exchange between the surface and atmosphere cloud formation is treated and both cloud and vapor are transported by modeled winds and diffusion exchange of water and co2 with the subsurface is not allowed and radiative effects of water vapor and clouds are not treated the seasonal cycle of co2 is found to become more extreme at high obliquity as suggested by simple heat balance models maximum pressures remain largely the same but the minima decrease substantially as more co2 condenses in the more extensive polar night vapor and cloud abundances increase dramatically with obliquity the stable location for surface ice moves equatorward with increasing obliquity such that by 45 obliquity water ice is stable in the tropics only ice is not spatially uniform but rather found preferentially in regions of high thermal inertia or high topography eccentricity and argument of perihelion can provide a second order modification to the distribution of surface ice by altering the temporal distribution of insolation at the poles further model simulations reveal the robustness of these distributions for a variety of initial conditions our findings shed light on the nature of near surface ice rich deposits at midlatitudes and low latitudes on mars

phyllonitization and development of kilometer size extension gashes in a continental scale strike slip shear zone north goias central brazil abstract several km scale vertical extension gashes occur in a low metamorphic grade strike slip shear zone in central brazil these mega gashes show many of the characteristics commonly found in en echelon extension gashes of cm and outcrop scale reflecting a wide range of scale invariance for this phenomenon the gashes are filled with quartz veins which commonly host gold mineralization microstructures show a progressive deformation of the original cavity infilling vein structures towards the gash margins logarithmic plots of length vs thickness for gashes from thin section outcrop and air photograph scales define a power law l 11 4 t 0 96 logarithmic plots of cumulative frequency define curves with power law segments whose slopes indicate fractal dimensions d around 1 4 1 5 for both length and thickness the phyllonite zones adjacent to the mega gashes are interpreted to exert a crucial role in their development calculations show that the amount of quartz depleted in the phyllonite zones correspond to the amount of quartz precipitated in the mega gashes 7 10 6 m 3 volumes of fluid in the order of 10 10 m 3 must have been channelled through the opened fractures to precipitate such an amount of quartz we conclude that these mega gashes have developed from continuous propagation and opening of tension fractures in zones relatively preserved from phyllonitization protomylonites it is suggested that the development of kilometric extension gashes in the non phyllonitic domains produces a volume gain in response to the volume loss produced in the phyllonite zones the whole shear zone is envisaged therefore as an isovolumetric system with alternating lateral zones of volume loss phyllonites and volume gain extension gashes

the effects of a tectonic stress regime change on crustal scale fluid flow at the heyuan geothermal fault system south china abstract the south china heyuan fault zone provides unique crustal exposure to study the meso macroscale architecture of evolving fracture networks in response to a change in tectonic stress regime and associated changing fluid flow pathways multiple generations of fracturing across the fault zone reveal its structural evolution related to the change in stress regime from extensional since the mesozoic to transpressive in the cenozoic which coincides with generations of growth and fracturing on the microscale low angle mode i fractures quartz veining and a giant quartz reef 75 m wide and 40 km long were formed due to a combination of chemo mechanical mechanisms including a crucial phyllonite cap rock during the extensional phase this evolved through to a predominately sub vertically aligned shear fracture network exhibiting only minor quartz precipitation these open fractures are attributed to the transpressive regime experienced since the cenozoic in which strike slip faults cross cut the heyuan fault we propose that this sub vertical fracture network provides the fluid flow pathway supplying the present day hot springs by penetrating through the phyllonite seal which previously enabled sio2 accumulation additionally further quartz reef building would likely be reduced due to i lack of seal integrity and ii an unfavourable tectonic setting to channel the flow and provide accommodation space

climatic and tectonic controls on pedogenesis and landscape evolution in a quaternary intramontane basin val d agri basin southern apennines italy abstract paleopedological studies of alluvial systems in intramontane valley settings provide useful tools for understanding the interaction of tectonics climate and local base level changes in controlling alluvial dynamics an example is reported from the quaternary alluvial deposits of the val d agri basin in southern italy which were accreted in response to cycles of deposition pedogenesis and erosion several buried weathering profiles representative of the main stratigraphic unconformities were characterized by field description and micromorphological analyses the profiles appear to be truncated at the top by intense erosion the main pedological features and their formative processes occurred polycyclically attesting to different and relict pedogenetic phases that are not in equilibrium with present day environmental conditions we interpret the weathering profiles as paleosols that developed mainly during pleistocene interglacial periods the peri glacial phases mainly caused erosion of devegetated slopes and soil truncation processes all of the paleosols in the val d agri basin offer useful information on the chronological reconstruction of climatic phases and the associated sequence of pedogenetic events during the quaternary in the mediterranean region

tectonic and climatic control on geomorphological and sedimentary evolution of the mercure basin southern apennines italy abstract the morpho tectonic and sedimentary evolution of the mercure intramontane basin calabria lucania boundary southern apennines has been assessed through facies analysis morphostratigraphy and geomorphological correlation with adjacent areas the mercure basin one of the most active seismogenic zones of the southern apennines is a favorable area for reconstructing the main stages of landscape evolution of the axial zone because of its capability to record changes in base level during the quaternary in addition the presence of both erosional and depositional palaeosurfaces is a useful marker for reconstructing tectonic and morphogenetic events and hence to detect the role played by tectonics and climate in its genesis evolution and extinction the present study identifies the key role of tectonics and denudation combined with high frequency floods as mechanisms controlling alluvial sedimentation in the study area during endorheic conditions denudational processes driven by pulses of extensional deformation of the basin margin caused strong alluvial inputs that resulted in the development of alluvial fans alluvial facies are mainly characterized by turbulent subaerial hyperconcentrated flood flows deposited during the glacial semi arid conditions of mis 14 the retrogradational stacking pattern of the alluvial system indicates decreasing rates of tectonic activity along with declining river gradients the mercure coalescing alluvial fans were inundated by lake transgression during mis 13 in response to i abrupt tectonic subsidence at the basin margins and ii large decrease of coarse sediment supply due to the interplay among climate tectonics and catchment size changes in this regard it is suggested that tectonic control on the drainage network along with climate and long term slope evolution may have caused marked pulses in sediment supply thus influencing the arrangement of facies associations in the sedimentary succession in addition the study points out that the main tectonic landforms developed during each period of the landscape evolution well correspond with some active fault segments

a systematic mapping procedure based on the modified gaussian model to characterize magmatic units from olivine pyroxenes mixtures application to the syrtis major volcanic shield on mars clenet et al 2011 have developed an adapted version of the modified gaussian model mgm the improvements allow the characterization of spectra of olivine pyroxene s mixtures addressing both modal composition and individual minerals chemical composition this version of mgm is fully automated and operational with large amounts of hyperspectral imaging data two natural cases are considered the first one is the sumail massif in the oman ophiolite earth based on our approach applied to hymap data two contrasted lithologic units are mapped the mantle which is harzburgite dominated and the crust made of gabbros and clinopyroxene rich cumulates with spectral variations interpreted in terms of pyroxenes chemical compositions once this new mgm mapping approach has been validated on a controlled natural situation we map the distribution of mafic assemblages across the syrtis major volcano on mars using a visible and near infrared vnir short wave infrared swir observatoire pour la mineralogie l eau les glaces et l activite omega mars express mex mosaic our results are in agreement with previous work but olivine appears to be more abundant than previously estimated in the central part of the volcanic edifice especially in ternary mafic assemblages augite olivine enstatite based on these results we propose a possible scenario for the igneous and thus thermal evolution of the syrtis major region surrounding terrains have formed first and local heterogeneity can be observed between northern and southern areas of the noachian crust we also observe variations in the mineral assemblages within syrtis major lavas which can be interpreted in terms of differentiation from a common parent melt and or of a progressive evolution of the mantle source composition and temperature key points mgm systematic mapping on syrtis major to characterize mafic minerals mixtures olivine and pyroxenes mixture is detected in the central lavas of the volcano pyroxenes have chemical compositions spanning the enstatite augite range

planetary science ancient equatorial ice on mars nasa s opportunity rover found enigmatic sulphate deposits at meridiani planum on mars a proposal that the deposits are sublimation leftovers of large ice fields similar in scale to those at the present day polar caps adds to the existing hypotheses

a few remarks on the kinetics of static grain growth in rocks static grain growth is a relatively simple transformation in which grain size increases under driving forces caused by grain and interphase boundary curvature given the relative simplicity of the protocol for grain growth experiments measurements of grain boundary mobility show surprising variations boundary mobilities during grain growth are affected by solute and impurity chemistry chemical fugacity of trace and major elements pore size and number pore fluid chemistry the presence of melts and the presence of solid second phases as well as temperature and pressure all of these factors may exert influence on grain growth of rocks in natural situations and many are also present during the laboratory experiments provided that the necessary kinetics parameters are known bounds may be placed on the interface mobility when pores partial melts or solutes are present to predict the rate of grain growth in natural situations will require improved laboratory data and careful consideration of the thermodynamic conditions likely to be encountered in nature

dark material in the polar layered deposits and dunes on mars viking infrared thermal mapping and bistatic radar data suggest that the bulk density of the north polar erg material is much lower than that of the average martian surface or of dark dunes at lower latitudes we have derived a thermal inertia of 245 280 j m 2 s 1 2 k 1 5 9 6 7 10 3 cal cm 2 s 1 2 k 1 for the proctor dune field and 25 150 j m 2 s 1 2 k 1 0 6 3 6 10 3 cal cm 2 s 1 2 k 1 for the north polar erg the uniqueness of the thermophysical properties of the north polar erg material may be due to a unique polar process that has created them the visible and near infrared spectral reflectance of the erg suggests that the dark material may be composed of basalt or ferrous clays these data are consistent with the dark material being composed of basaltic ash or filamentary sublimate residue fsr particles derived from erosion of the layered deposits dark dust may be preferentially concentrated at the surface of the layered deposits by the formation of fsr particles upon sublimation of water ice further weathering and erosion of these areas of exposed layered deposits may form the dark saltating material that is found in both polar regions dark fsr particles may saltate for great distances before eventually breaking down into dust grains re mixing with the global dust reservoir and being recycled into the polar layered deposits via atmospheric suspension

upper crustal fluids in a large fault system microstructural trace element and oxygen isotope study on multi phase vein quartz at the bavarian pfahl se germany fault systems are zones of crustal weakness and are used as pathways for ascending hydrothermal fluids one impressive example is the more than 150 km long bavarian pfahl system at the sw boundary of the bohemian massif dextral ductile shearing of moldanubian basement has shaped a several hundred meter wide zone of mylonites and ultramylonites this setting was reactivated under brittle conditions and infiltrated by fluids resulting in a multi phase quartz lode structural analysis using scanning electron microscopy cathodoluminescence sem cl images has been carried out in combination with trace element and oxygen isotope analysis on quartz along the system three successive quartz phases have been distinguished due to their structural details and trace element contents cryptocrystalline quartz fabric in the first quartz phase results from crystallization from a silica gel whereas in phases ii and iii quartz precipitation is characterized by repeated fragmentation and sealing visible due to strongly varying cl intensities the 18o of bavarian pfahl quartz decreases from 13 8 in the nw to 8 5 in the se whereas quartz from the close by situated wolsendorf fluorite deposit shows 18o between 15 9 and 18 5 vs smow flat shale normalized rare earth element patterns point towards an upper crustal origin of the hydrothermal fluids the southeastern part of the bavarian pfahl is interpreted to represent a deeper crustal level with higher mineralization temperatures about 350 c compared to the rest of the pfahl 250 c

seismic imaging of a mid crustal low velocity layer beneath the northern coast of the south china sea and its tectonic implications abstract low velocity layer lvl within the continental crust is usually closely associated with tectonic events thus it may reflect ongoing processes or offer a chance to backtrack the evolutional history mid crustal lvl has been reported in the northern coast of the south china sea scs by several geophysical studies but the 3d distribution of lvl in the whole coastal area is still poorly known here we perform a receiver function study based on 67 broadband seismological stations we use the common conversion point method to construct structures of the moho as well as intra crustal interfaces we image sharp intra crustal negative velocity gradient broadly distributed in the eastern cathaysia block with depth increasing from 10 km in the nw to 12 16 km in the se the corresponding amplitude of the negative interface shows variable values from 0 03 to 0 1 with an evidential trend of strengthening eastwards we interpret the negative gradient as top of the lvl produced by accumulation of fluids from dehydration of the paleo pacific subduction plate the mid crustal lvl tends to act as weak domains during continental rift and the lateral variation of the lvl may be one possible reason explaining the along strike variation in crustal stretching in the northern scs rifted margin

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

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

thermal and albedo mapping of the polar regions of mars using viking thermal mapper observations 1 north polar region we present the first maps of the apparent thermal inertia and albedo of the south polar region of mars the observations used to create these maps were acquired by the infrared thermal mapper irtm instruments on the two viking orbiters over a 30 day period in 1977 during the martian late southern summer season the maps cover the region from 60 s to the south pole at a spatial resolution of 1 of latitude thus completing the initial thermal mapping of the entire planet the analysis and interpretation of these maps is aided by the results of a one dimensional radiative convective model which is used to calculate diurnal variations in surface and atmospheric temperatures and brightness temperatures at the top of the atmosphere for a range of assumptions concerning dust optical properties and dust optical depths the maps show that apparent thermal inertias of bare ground regions decrease systematically from 60 s to the south pole in unfrosted regions close to the south pole apparent thermal inertias are among the lowest observed anywhere on the planet on the south residual cap apparent thermal inertias are very high due to the presence of co2 frost in most other regions of mars best fit apparent albedos based on thermal emission measurements are generally in good agreement with actual surface albedos based on broadband solar reflectance measurements however in the frost free region poleward of 75 s best fit apparent albedos are significantly higher than measured lambert albedos implying that measured brightness temperatures in this area are up to 15 k colder than would be expected for surfaces with the same measured albedos during this season the one dimensional atmospheric model calculations also predict anomalously cold brightness temperatures close to the pole during late summer and after considering a number of alternatives it is concluded that the net surface cooling due to atmospheric dust is the best explanation for this phenomenon the observed systematic decrease in apparent thermal inertia from 60 s to the south pole during this season is also consistent with the predictions of atmospheric model calculations the region of lowest apparent thermal inertia close to the pole which includes the south polar layered deposits is interpreted to be mantled by a continuous layer of aeolian material that must be at least a few millimeters thick the low thermal inertias mapped in the south polar region imply an absence of surface water ice deposits which is consistent with viking mars atmospheric water detector mawd measurements which show low atmospheric water vapor abundances throughout the summer season however these observations do not necessarily imply a complete absence of water thermal model calculations that can reproduce observed diurnal temperature variations in the south polar region show that annual maximum subsurface temperatures at depths ranging from 4 to 20 cm are cold enough to permit the stability of ground ice deposits even if they are in excellent diffusive contact with the atmosphere therefore the presence of near surface ground ice in the south polar region is not inconsistent with the viking irtm and mawd observations

quaternary uplift vs tectonic loading a case study from the lucanian apennine southern italy abstract uplift rates have been calculated for a large sector of the lucanian apennine axial zone of the southern apennines italy using both geomorphological observations elevation values ages and arrangement of depositional and erosional landsurfaces and other morpho tectonic indicators and stratigraphical and structural data sea level related facies fault kinematics and offset estimations these data have been compared with those derived from clay mineralogy of mesozoic pelagic successions lagonegro units outcropping in the same sector of the chain which gave information on tectonic loading the values of the quaternary uplift rates of the southern apennines axial zone vary from a minimum of 0 2 mm yr to a maximum of about 1 2 mm yr intermediate values 0 5 0 7 mm yr have been calculated for the other studied areas using geomorphological features and late pliocene to pleistocene successions involved in the genesis of erosional and depositional landsurfaces the same rates 0 6 mm yr have been obtained for a large time span about 2 ma in the melandro basin and adjacent maddalena mts therefore during the last 2 ma the total uplift amount of the axial zone of the lucanian apennine is about 1 2 1 3 km with local peaks of 1 5 km on the other hand the mesozoic pelagic units experienced a tectonic loading of 4 5 km as estimated by means of illite crystallinity in the range 0 6 1 1 2 percentage of illitic layers in illite smectite mixed layers 60 90 and white mica polytypes in the range of 10 35 the quaternary uplift and the related erosion rates of the southern apennines are unquestionably due to strike slip faulting and above all due to extensional tectonics coupled with thermal isostatic regional raising the gap of several kilometres derived from the comparison between uplift rates and tectonic loading values may be explained only by different exhumation modalities starting from late miocene time

temperature micro mapping in oscillatory zoned chlorite application to study of a green schist facies fault zone in the pyrenean axial zone spain oscillatory compositional zoning in minerals has been observed in hydrothermal magmatic and metamorphic environments and is commonly attributed to chemical or physical cyclical changes during crystal growth chemical zoning is a common feature of solid solutions which has been rarely reported in phyllosilicates in this study oscillatory zoning in chlorite is described in samples from the pic de port vieux thrust a minor thrust fault associated to the major gavarnie thrust fault zone central pyrenees spain the pic de port vieux thrust sheet comprises a 1 20 m thick layer of triassic red pelite and sandstone thrust over mylonitized cretaceous dolomitic limestone the thrust fault zone deformation comprises secondary faults and cleavage affecting the triassic pelite and sandstone an important feature responsible to this deformation is a set of veins filled by quartz and chlorite chlorite is present in crack seal extension veins and in shear veins both structures opened under the same stress conditions in some shear veins chlorite occurs as pseudo uniaxial plates arranged in rosette shaped aggregates these aggregates appear to have developed as a result of radial growth of the chlorite platelets oscillatory zoning has been imaged by backscattered scanning electron microscopy and by x ray quantitative micro mapping these oscillations correspond to chemical zoning with alternating iron rich and magnesium rich bands the chlorite composition ranges from a fe rich pole to a mg rich pole fe 3 fe values were measured in chlorite using xanes spot analyses and vary from 0 23 to 0 44 the highest values are in the fe rich area temperature maps built from standardized microprobe x ray images and redox state using the program xmaptools indicate oscillatory variations from about 310 to 400 50 c during chlorite crystallization these temperature variations are correlated with a fe 3 fe variation by al 3 fe 3 1 and di trioctahedral substitutions highlighted by mg and fe tot contents fe mg zoning chemical variations could be then explained by alternation of cooling times and cyclical pulses of a fluid hotter than the host rock it is however not excluded that kinetic effects influence the incorporation of mg or fe during chlorite crystallization

repeated hydrothermal quartz crystallization and cataclasis in the bavarian pfahl shear zone germany abstract field and microstructural data of the pfahl shear zone in north eastern bavaria germany reveal the intimate spatial temporal connection between fragmentation fluid influx and quartz crystallization these processes and their interaction led to complex structured quartz units i a dense network of early quartz veins ii two domains of fine grained reddish to grayish quartz masses iii an extended central zone of massive white quartz and iv late cross cutting closely spaced parallel fractures and partly open quartz veins the fine grained quartz domains result from repeated and coeval cataclasis fluidization and quartz precipitation material transport in these domains is at least partly governed by the flow of mobile fluid quartz particle suspensions the complex internal meso to microstructures of the massive white quartz are generated by repeated processes of fragmentation and grain growth in general the brittle part of the pfahl shear zone represents a key example of cyclic dissolution precipitation and fragmentation on large scale

archean geodynamics and the abitibi pontiac collision implications for advection of fluids at transpressive collisional boundaries and the origin of giant quartz vein systems abstract giant quartz vein systems of all ages from the archean to cenozoic are characterised by similarities of geodynamic setting local structure paragenesis metal budget p t t paths and chemical fluid dynamic and isotopic properties that collectively imply a singular hydrothermal process such quartz vein provinces form in regional brittle ductile shear zones that define terrane boundaries including closure of back arc basins and arc continent or continent continent collisions examples include the svz of the archean abitibi belt the norseman wiluna belt yilgarn block kolar schist belt india foothills metamorphic belt california and coast ranges megalineament in the cordillera and the cenozoic monte rosa district insubric line evidence for an archean collisional environment comes from the abitibi and pontiac subprovince tectonic boundary which hosts giant quartz vein systems in this region the amphibolite facies lacorne tectonic block in the archean abitibi greenstone belt is anomalous with respect to the prevalent low grade supracrustal sequences in neighbouring blocks the lacorne block has mature clastic sediments with a zircon provenance age spectrum from 3040 2691 ma and two granitic magma series a late syntectonic monzodiorite monzonite granodiorite syenite series formed over 2685 2670 ma similar to phanerozoic volcanic arc granites and post tectonic garnet muscovite granites emplaced at 2650 2630 ma which compositionally resemble phanerozic collisional s type granites the pontiac subprovince to the south of the abitibi greenstone belt shares all the above features with the lacorne block and collided with and was locally thrust under the abitibi belt with differential uplift of the lacorne block following collision to generate a tectonic window following collision of allochthonous terranes the conjuction of large volumes of subcreted oceanic crust and sediments between accreted terranes displaced isotherms rise and metamorphic dehydration are all necessary conditions for forming giant quartz vein systems metamorphic fluids are expelled along the terrane boundary structures at deep levels and focussed into second and higher order splays at mid crustal levels where quartz and au precipitation occurs hydrothermal fluids that formed the giant quartz veins are remarkably uniform in h o c and sr isotopic compositions albeit with small provincial variations the veins and gold precipitated at 270 360 c from fluids with low salinity and moderate co2 at 2 3 kbar in the brittle ductile transition

the role of second phases for controlling microstructural evolution in polymineralic rocks a review abstract we present a state of the art review of the microstructural evolution in rocks under static and deformational conditions first the general concepts and processes are introduced using monomineralic aggregates then they are expanded into the more complex context of polymineralic rocks with a dominant matrix phase the first part of this contribution delivers information on sample strategies to quantify polymineralic microfabrics based on comparisons between microfabrics of monomineralic and polymineralic rocks we use the common knowledge collected over the past decades for monomineralic systems and discuss the differences to polymineralic ones in terms of microstructures modal compositions spatial distribution of phases crystallographic preferred orientations and associated processes the article puts particular emphasis on the effect of coupled grain growth mass transfer processes and deformation mechanisms we speculate on the effect of mineral reactions during the evolution of microstructures and rheology in polymineralic aggregates at different metamorphic conditions at the end of the article we demonstrate the great potential of grain size evolution maps as microstructural tool to unravel the geological history of polymineralic rocks that evolved under a variety of geodynamic situations

stratigraphic architecture and quaternary evolution of the val d agri intermontane basin southern apennines italy abstract the sedimentary record of the val d agri basin is of great importance for understanding the quaternary tectonic activity and climatic variability in the southern apennines changes in tectonic controls sediment supply and climatic input have been identified the interval from 56 to 43 ka was associated with asymmetric subsidence restricted to the north eastern actively faulted margin of the basin and development of axial braided river and transverse alluvial fan systems short lasting mediterranean type pedogenesis between 43 and 32 ka mis stage 3 coexisted with progradation aggradation of the southern alluvial fan deposits and southwards tilting of the basin floor aggradation ended with consumption of accommodation space after 32 ka during a subsequent stage of decline of vegetation cover possibly as a consequence of climatic cooling probably mis stage 2 active progradation of alluvial fans occurred breakthrough of the basin threshold and entrenchment of the drainage network must therefore be attributed to a latest pleistocene to holocene age the first stages of basin opening and fill predating 56 ka have only been inferred by stratigraphic considerations the earliest lacustrine sedimentation should be middle pleistocene or older in age the following south eastward basin widening allowed progradation of alluvial fan systems which completely filled the lacustrine area tentatively late middle pleistocene pedogenesis in mediterranean like climate conditions caused the final development of a highly mature fersiallitic paleosol at the top of the fan surfaces in areas of morpho tectonic stability plausibly during mis stage 5 the study results demonstrate the potential of applying a multidisciplinary approach in an intermontane continental settings marked by a relative rapid and constant tectonic subsidence and a high rate of sediment supply during the pleistocene glacial interglacial cycles

p t deformation fe3 fe2 mapping at the thin section scale and comparison with xanes mapping application to a garnet bearing metapelite from the sambagawa metamorphic belt japan quantitative x ray maps of composition from a chlorite k white mica albite quartz and garnet bearing thin section from a sambagawa blueschist facies metapelite were combined with a multiequilibrium calculation method to calculate a p t fe3 fe2 deformation map at the millimetre scale the studied sample was chosen because elongated chlorite crystallization tails pressure shadows rimmed by phengite are present which is an appropriate assemblage for the quantification of the p t evolution chlorite temperature and fe3 content maps were calculated by successive iterations for each pixel analysis of fe3 until convergence of the four chlorite quartz h2o equilibria that can be written using the fe and mg amesite clinchlore daphnite and sudoite chlorite end members the calculated map of fe2 fe3 in chlorite is in good qualitative agreement with the in situ mapping of this ratio using xanes x ray absorption near edge structure techniques the temperature map indicates that high temperature chlorite zones with low fe3 contents alternate with lower temperature zones and higher fe3 contents in the crystallization tail late fractures perpendicular to the elongation axis of the tail are filled by very low temperature chlorite 250 c showing fe3 fetotal up to 0 4 groups of chlorite and mica pixels were then identified based on compositional and structural criteria and a p tdeformation map was calculated using representative analyses of these groups the calculated p tdeformation map suggests that in contrast to chlorite the composition of most mica did not change significantly during exhumation mica reequilibrated in late ew shear bands only ew shearing was already active at 0 1 gpa 500 c which corresponds to the peak temperature and probably pressure conditions at reduced redox conditions the intensity of deformation probably decreased with decrease in temperature to 350 400 c at this temperature a second main deformation event corresponding to a further ew stretching occurred and was still active below 250 c and more oxidizing conditions these results indicate that the scale at which p t data can be obtained is now close to the scale of observation of structural geologists a close link between deformation and mineral reaction is therefore possible at the microscopic scale which provides information about the relationship between deformation and mineral reactivity the modalities of deformation with time and the p t conditions at which it occurred

determining the origin circulation path and residence time of geothermal groundwater using multiple isotopic techniques in the heyuan fault zone of southern china abstract medium low temperature geothermal resources are abundant in southern china but their heat source and link to fault zones is poorly understood consequently geothermal energy is only used at small scale in order to broaden the footprint of geothermal energy use in southern china it is first necessary to understand and track the geothermal groundwater circulation pattern associated with fault zones the heyuan fault zone serves as a typical medium low temperature geothermal system of south china here we show that the geothermal groundwater circulation pattern can be traced by using stable hydrogen and oxygen isotopes helium and neon isotopes carbon 13 and carbon 14 as well as hydrochemical parameters the results show that in the heyuan fault zone the main hydrochemical type of the hot springs is hco3 na k while the shallow cold groundwater is mainly enriched in hco3 ca the results of the helium isotope and neon isotope indicate that the geothermal groundwater of this area is derived from the crust thus excluding the possibility of extremely deep paths of groundwater tapping into mantle helium sources furthermore the characteristics of the stable hydrogen and oxygen isotopes imply that geothermal groundwater is of local meteoric origin and the recharge area located at the hilly area of the hanging wall of the heyuan main fault with the recharge elevations ranging from about 440 m to 670 m the hot spring geothermometer shows that the highest reservoir temperature is about 157 c and the deepest circulation depth is about 6500 m carbon 14 isotope age dating suggests that the geothermal groundwater ages are mostly from 9 9 kyr bp to 12 3 kyr bp according to the geological structural characteristics of the study area the main upward channel for geothermal groundwater is the heyuan main fault generally the hot springs in this area are mixed with shallow cold groundwater and surface water which raises the ratio of the ca2 in water and dilutes the heavy hydrogen and oxygen isotopes

p t t estimation of deformation in low grade quartz feldspar bearing rocks using thermodynamic modelling and 40ar 39ar dating techniques example of the plan de phasy shear zone unit brianconnais zone western alps pressure temperature time p t t estimates of the syn kinematic strain at the peak pressure conditions reached during shallow underthrusting of the brianconnais zone in the alpine subduction zone was made by thermodynamic modelling and 40ar 39ar dating in the plan de phasy unit se of the pelvoux massif western alps the dated phengite minerals crystallized syn kinematically in a shear zone indicating top to the n motion by combining x ray mapping with multi equilibrium calculations we estimate the phengite crystallization conditions at 270 50 c and 8 1 2 kbar at an age of 45 9 1 1 ma combining this p t t estimate with data from the literature allows us to constrain the timing and geometry of alpine continental subduction we propose that the brianconnais units were scalped on top of the slab during ongoing continental subduction and exhumed continuously until collision

optically stimulated luminescence dating of a stratigraphic late glacial holocene sequence in the po plain bubano quarry bologna italy abstract quartz and k feldspars from an exposed 14 m thick undisturbed succession of silty clay late glacial holocene sediments in the po plain bubano quarry bologna province italy were optically dated for part of the sequence three radiocarbon ages and palynological dating provide an independent age control the separation procedures whose effectiveness was checked at each step by means of quantitative x ray powder analysis qxrpd and single aliquot regenerative dose protocols adopted are discussed in general the quartz optically stimulated luminescence osl ages are systematically younger than those obtained with feldspars probably due to the presence of medium component in the osl decay the evidence of contribution from the low sensitivity light traps has been checked using lm osl measurements and the equivalent doses have been calculated considering only the contribution of fast components moreover a residual presence of feldspars in the quartz separated fraction even if not detected by qxrpd could account for the observed underestimation the osl ages were consistent with the radiocarbon chronology

the last interglacial pedocomplexes in the litho and morpho stratigraphical framework of the central northern apennines central italy recently in italy a great deal of effort has been devoted to the mapping of quaternary continental deposits several unconformity bounded stratigraphic units ubsu have been defined the unconformities indicate important phases of changing dynamics linked to quaternary climatic changes and have been related to valley downcutting simultaneous with paleosol formation during interglacials however glacial periods are characterised by deposition of thick continental sequences we suggest that the ubsu s belonging to the late middle pleistocene mis 6 and late pleistocene can also be defined under a pedostratigraphic point of view locally at the top of the ubsu attributed to mis 6 buried or relict paleosols are preserved the paleosols developed in calcareous fluvial and moraine gravels with minor flints the pedocomplexes are made of three paleosols separated by erosion surfaces and or stonelines the older paleosol mis 5e is severely truncated and is characterised by a ck horizon overlain by strongly leached reddish bt horizons with flinty rock fragments with a diagnostic wavy lower boundary in some sites subsequent secondary precipitation of carbonates transformed this horizon into a btk this paleosol is buried by a younger paleosol mis 5c with less leached reddish btk horizons quartz of aeolian origin and very small and scarce calcareous clasts the main pedofeatures are associated with colluvial processes biological activity and carbonate precipitation this paleosol is also truncated and buried under a similar paleosol mis 5a therefore the lower paleosol of the pedocomplex can be attributed to the eemian and constitutes a valid marker for the definition and mapping of the underlying and overlying sedimentary units in other parts of the apennines no sedimentary units have been found that correspond to the unconformities separating different pedostratigraphical units in order to map the different ubsu s due to the poor lateral continuity of the preserved paleosols morpho and litho stratigraphical investigations and correlation are always recommended

late quaternary climatic changes in northern cilento southern italy an integrated geomorphological and paleopedological study abstract this paper reports a contribution to the knowledge of the local morphodynamic and pedogenetic response to late quaternary climatic changes in northern cilento southern italy three representative geomorphological units and associated paleosols have been characterised in detail by field work chemical and mineralogical analyses and micromorphological observations of thin sections the data confirm an intense degree of weathering and a complex history of soil formation often representing different environments in contrast with the present pedoclimatic regime two of the three profiles reveal a polygenetic character recording typical interglacial conditions characterised by high temperatures and humidity with important soil development followed by the occurrence of periglacial conditions possibly occurring during cold glacial stages namely the last glacial at mid latitude coastal regions of southern italy the third paleosol appears essentially monogenetic and developed under interglacial like conditions

sulfur bearing phases detected by evolved gas analysis of the rocknest aeolian deposit gale crater mars the sample analysis at mars sam instrument suite detected so2 h2s ocs and cs2 from 450 to 800 c during evolved gas analysis ega of materials from the rocknest aeolian deposit in gale crater mars this was the first detection of evolved sulfur species from a martian surface sample during in situ ega so2 3 22 mol is consistent with the thermal decomposition of fe sulfates or ca sulfites or evolution desorption from sulfur bearing amorphous phases reactions between reduced sulfur phases such as sulfides and evolved o2 or h2o in the sam oven are another candidate so2 source h2s 41 109 nmol is consistent with interactions of h2o h2 and or hcl with reduced sulfur phases and or so2 in the sam oven ocs 1 5 nmol and cs2 0 2 1 nmol are likely derived from reactions between carbon bearing compounds and reduced sulfur sulfates and sulfites indicate some aqueous interactions although not necessarily at the rocknest site fe sulfates imply interaction with acid solutions whereas ca sulfites can form from acidic to near neutral solutions sulfides in the rocknest materials suggest input from materials originally deposited in a reducing environment or from detrital sulfides from an igneous source the presence of sulfides also suggests that the materials have not been extensively altered by oxidative aqueous weathering the possibility of both reduced and oxidized sulfur compounds in the deposit indicates a nonequilibrium assemblage understanding the sulfur mineralogy in rocknest materials which exhibit chemical similarities to basaltic fines analyzed elsewhere on mars can provide insight in to the origin and alteration history of martian surface materials

optical dating of young modern sediments using quartz results from a selection of depositional environments abstract equivalent dose ed evaluations for quartz grains extracted from a number of modern or young samples collected from a range of depositional environments are reported the signal used was optically stimulated luminescence osl with an argon ion laser tuned to 514 nm as a light source typical equivalent dose values were 0 05 0 3 gy for the given samples which is substantially less than equivalent doses expected for similar sediments by conventional thermoluminescence tl the non zero equivalent dose exhibited by the samples may be a product of relict osl from incompletely bleached traps sample pre treatment procedures or due to signal recuperation following bleaching during antiquity the potential significance of each are discussed a number of modifications to sample pre treatment and processing are also described

dehydration of dioctahedral aluminous phyllosilicates thermodynamic modelling and implications for thermobarometric estimates we propose a solid solution model for dioctahedral aluminous phyllosilicates accounting for the main compositional variations including hydration observed in natural smectites interlayered illite smectite illites and phengites from diagenetic to high grade metamorphic conditions the suggested formalism involves dehydrated micas and hydrated pyrophyllite like thermodynamic end members with these end members the equilibrium conditions of quartz water k bearing mica like phyllosilicates of fixed 2 1 composition are represented by a line in p t space along which the interlayer water content varies the relevant thermodynamic properties required for the calculation of equilibrium conditions were derived using a set of 250 natural data of known maximal temperature and pressure conditions which covers a range between 25 c and few mpa to 800 c and 5 gpa the temperatures calculated at fixed pressure with our model are in fair agreement with those reported in the literature for the 250 natural data at low temperature and pressure the amount of interlayer water in k deficient phengite and illite is predicted to reach 100 of the apparent vacancies which is consistent with previous values reported in the literature although the amount of interlayer water is predicted to decrease with pressure and temperature it is calculated to be significant in k deficient phengite from lt hp pelites metamorphosed at about 350 c 10 kbar the presence of molecular water in the interlayer site of such phengites has been confirmed by ftir mapping its implications for p t estimates are discussed

effect of mica on the grain size of dynamically recrystallized quartz in a quartz muscovite mylonite abstract quartz ribbons in a quartz muscovite mylonite from the sunchang shear zone of south korea show a variation in the average size 25 107 m of dynamically recrystallized quartz depending on the fraction and dispersion of muscovite within the ribbons micas within the quartz ribbons occur both inside quartz grains and along their boundaries having a strong preferred orientation with the basal planes parallel to the mylonitic foliation micas or mica aggregates inside the quartz show a size range of 1 25 m whereas those along the quartz grain boundaries range from 2 to 98 m the average quartz grain size d calculated from three dimensional grain size distribution decreases drastically with increasing mica volume fraction f m up to f m 3 in the ribbons and further increases in the mica fractions above 3 result in only a little decrease with some fluctuation in the quartz grain size generating the equation of d 20 11 ln f m 9 64 with almost the same fraction of mica however the quartz ribbons with dispersed mica show a smaller quartz grain size than those with clustered mica indicating the importance of dispersion as well as fraction of second phase particles to the grain size of dynamically recrystallized quartz quartz c axes tend to have a random orientation with an f m 3 presumably due to the greater contribution to the total deformation of grain boundary sliding for quartz with a smaller grain size d

giant quartz vein formation and high elevation meteoric fluid infiltration into the south armorican shear zone geological fluid inclusion and stable isotope evidence giant quartz veins associated with the south armorican shear zone record important fluid circulation during the hercynian period regional scale mapping of veins allows two groups of veins to be identified on the basis of their geometric relationship with the south armorican shear zone veins in the first group are parallel to the shear zone whereas those in the second group developed in a direction oblique to it the former probably record infiltration of fluids along permeable pathways in highly deformed zones the latter may represent crustal scale tension gashes in the regional context most quartz veins have 18 o values between 10 and 16 indicating a mid crustal origin for the fluids microthermometry on fluid inclusions from euhedral quartz indicates that late fluids were mostly aqueous with very low salinity 0 1 7 wt eq and with homogenization temperatures ranging between 150 and 270 c together with very low 18 o values of some euhedral quartz down to 2 these features argue for a surface origin corresponding 18 o fluid values estimated near 11 are probably related to the high palaeo elevation of meteoric precipitation scarce but significant h 2 o co 2 fluid inclusions in euhedral quartz indicate a metamorphic contribution these were probably sourced from the exhumed metamorphic basement in the southern part of the region

summer evolution of the north polar cap of mars as observed by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega visible infrared imaging spectrometer extensively observed regions of mars with latitudes above 70 n in late 2004 heliocentric longitude from ls 93 to ls 127 the extent of water ice at the surface and the size of ice grains were monitored as a function of time bright small grained frost which initially covered a large fraction of the polar cap waned in favor of large grained ice in outlying regions dominated by large grained ice the albedo increased over the period evaluating the dust content was model dependent however contamination of ice by dust was low

sulfates in the north polar region of mars detected by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer observed the northern circumpolar regions of mars at a resolution of a few kilometers an extended region at 240 e 85 n with an area of 60 kilometers by 200 kilometers exhibits absorptions at wavelengths of 1 45 1 75 1 94 2 22 2 26 and 2 48 micrometers these signatures can be unambiguously attributed to calcium rich sulfates most likely gypsum this region corresponds to the dark longitudinal dunes of olympia planitia these observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains

analysis of a spectrally unique deposit in the dissected noachian terrain of mars 1 we have analyzed a spectrally anomalous dark intracrater deposit and an adjacent lighter toned fan shaped deposit in the dissected noachian terrain of mars using a combination of high spatial and spectral resolution remote sensing data sets the spatial proximity of these two deposits and their dust free spectral character make these prime targets for 1 determining whether the dark toned deposit is derived from the fan shaped deposit and 2 constraining the nature and mineralogy of the fan shaped deposit stereo observations and derived digital elevation models of the of the fan shaped deposit show a set of three flows lobes calculations of the yield strength based on morphometry of the lobes indicate yield strengths consistent with those of other volcanic flows on mars although an aqueous origin cannot be discounted the dark deposit consists of a mantle that forms dunes at its thickest portions and extends as a thinner veneer we find no obvious morphologic association between the dark deposit and adjacent fan multispectral imaging from the themis vis and ir instruments show that the two deposits have different spectral characteristics probably caused by differences in their mineralogy rather than their physical properties finally modeling of mgs tes spectra of the combined deposits indicates a feldspar rich composition that is possibly complemented by smaller quantities of alteration products such as carbonates and possibly sulfates and clays these results indicate that 1 there is no association between these deposits and 2 the combined deposits have a primarily igneous mineralogy although some aqueous alteration may have occurred

iron sulfur mineralogy of mars magmatic evolution and chemical weathering products models for the evolution of sulfide minerals on mars and reaction pathways to their oxidative weathering products in martian regolith have been proposed based on petrogenetic associations between komatiitic rock types viking geochemical data snc meteorites and terrestrial fe ni sulfide deposits to test the weathering model komatiitic pyrrhotites and olivines were exposed to sulfuric acid solutions with and without dissolved ferric iron added to simulate deep weathering processes and the reaction products were identified by mossbauer spectroscopy secondary fes sub 2 pyrite or marcasite feooh goethite and possibly jarosite were formed from pyrrhotite while olivine was oxidized to nanophase goethite these results suggest that on mars acidic groundwater induced pyrrhotite yields fes sub 2 yields feooh jarosite oxidative weathering reactions particularly in the presence of dissolved fe sup 3 such gossaniferous materials occurring in martian regolith were derived mainly from fe ni sulfides associated with komatiitic basalts and not from sulfides occurring in calc alkaline porphyry copper deposits granitic hydrothermal veins sediment hosted pbs zns ores etc which presumably did not evolve on mars due to the virtual lack of plate tectonic activity there

microfabric memory of vein quartz for strain localization in detachment faults a case study on the simplon fault zone abstract this manuscript deals with the adaptation of quartz microfabrics to changing physical deformation conditions and discusses their preservation potential during subsequent retrograde deformation using microstructural analysis a sequence of recrystallization processes in quartz ranging from grain boundary migration recrystallization gbm over subgrain rotation recrystallization sgr to bulging nucleation blg is detected for the simplon fault zone sfz from the low strain rim towards the internal high strain part of the large scale shear zone based on i the retrograde cooling path ii estimates of deformation temperatures and iii spatial variation of dynamic recrystallization processes and different microstructural characteristics continuous strain localization with decreasing temperature is inferred in contrast to the recrystallization microstructures crystallographic preferred orientations cpo have a longer memory cpo patterns indicative of prism and rhomb glide systems in mylonitic quartz veins overprinted at low temperatures 400 c suggest inheritance of a high temperature deformation in this way microstructural textural and geochemical analyses provide information for several million years of the deformation history the reasons for such incomplete resetting of the rock texture is that strain localization is caused by change in effective viscosity contrasts related to temporal large and small scale temperature changes during the evolution of such a long lived shear zone the spatially resolved quantitative investigation of quartz microfabrics and associated recrystallization processes therefore provide great potential for an improved understanding of the geodynamics of large scale shear zones

dynamic recrystallization of quartz correlation between natural and experimental conditions quartz veins in the eastern tonale mylonite zone italian alps were deformed in strike slip shear due to the synkinematic emplacement of the adamello pluton a temperature gradient between 280 c and 700 c was effected across this fault zone the resulting dynamic recrystallization microstructures are characteristic of bulging recrystallization subgrain rotation recrystallization and grain boundary migration recrystallization the transitions in recrystallization mechanisms are marked by discrete changes of grain size dependence on temperature differential stresses are calculated from the recrystallized grain size data using paleopiezometric relationships deformation temperatures are obtained from metamorphic reactions in the deformed host rock flow stresses and deformation temperatures are used to determine the strain rate of the tonale mylonites through integration with several published flow laws yielding an average rate of approximately 10 14s 1 to 10 12s 1 the deformation conditions of the natural fault rocks are compared and correlated with three experimental dislocation creep regimes of quartz of hirth tullis linking the microstructures of the naturally and experimentally deformed quartz rocks a recrystallization mechanism map is presented this map permits the derivation of temperature and strain rate for mylonitic fault rocks once the recrystallization mechanism is known

analysis of phyllosilicate deposits in the nili fossae region of mars comparison of tes and omega data abstract diverse phyllosilicate deposits discovered previously in the nili fossae region with near infrared reflectance data are a window into the complex history of aqueous alteration on mars in this work we used thermal infrared data from the thermal emission spectrometer tes in combination with near infrared data from the observatoire pour la mineralogie l eau les glaces et l activite omega to better constrain the mineralogy and geologic origin of these deposits we developed a tes spectral index for identification of clay minerals which correctly identifies the phyllosilicates in the nili fossae area and points to several other interesting deposits in the syrtis major region however detailed inspection of the tes spectral features of nili fossae phyllosilicates shows a feature at low wavenumbers 350 550 cm 1 that is not an exact match to any specific fe 3 al or mg rich phyllosilicate phase instead the feature is more similar to basaltic glass and may indicate that the phyllosilicates in this region are 1 rich in fe 2 based on similarity to trends seen in laboratory data of clay minerals 2 poorly crystalline extremely disordered and or 3 present within a matrix of actual basalt glass this feature is similar to spectral features seen in altered rocks in the columbia hills region of gusev crater by previous authors by calibrating measured spectral index values against mathematical spectral mixtures of typical martian dark surfaces and known abundances of alteration minerals we are able to estimate an enrichment in abundance of alteration minerals in the altered surfaces many dark noachian deposits in the nili fossae area are enriched phyllosilicates by 20 30 10 15 relative to dark volcanic surfaces in the same region the distribution and abundance of these phases indicates that alteration in the region was pervasive but did not completely erase the original mineralogy of what was likely an fe rich basalt protolith as a group the nili fossae phyllosilicate deposits are fundamentally different from those found in the mawrth vallis region nili fossae deposits have strong thermal infrared features related to admixed pyroxene plagioclase and occasionally olivine whereas the mawrth vallis deposits contain no mafic minerals comparison of tes and omega data also illustrates some more general differences between the datasets including the impact of physical character of the martian surface on detectability of minerals in each spectral range

hydrogen isotope analyses of alteration phases in the nakhlite martian meteorites abstract secondary alteration phases such as carbonates smectite clays and fe oxides are found within the martian meteorites if these meteorites were seen to fall the assumption can be reasonably made that the secondary phases have a martian origin however for martian meteorite finds this is not the case deuterium hydrogen d h ratio analysis can be used to distinguish between terrestrial and martian secondary alteration phases the martian atmosphere is currently five times enriched in deuterium compared to terrestrial seawater producing a deuterium enrichment in the martian alteration phases large enough to be detected with modern ion microprobe techniques we aimed to measure the d h ratio of the iddingsite like alteration veins in the nakhlite martian meteorites nakhla mil 03346 mil 090030 and y 000593 to help confirm the martian origin of this material and determine the relative amounts of terrestrial contamination in each meteorite as an observed fall nakhla is nominally uncontaminated by terrestrial alteration and shows elevated d values in its alteration veins however even the highest of these values is much below that of the martian atmosphere indicating that terrestrial contamination probably combined with fractionation effects between the martian atmosphere and the alteration material have reduced the d values of these veins the speed of hydrogen isotope exchange in the nakhlite iddingsite like alteration veins is demonstrated by the purely terrestrial d values in the veins of nakhla 110 a thin section exposed to the terrestrial atmosphere since its preparation in 1998 mineralogical heterogeneity also affects the hydrogen isotope exchange rate in these veins the wide variation in d within the veins of nakhla and y 000593 appears to be due to the heterogeneous nature of the vein material where some phases exchange hydrogen with the atmosphere at a faster rate than others

long term fluid circulation in extensional faults in the central catalan coastal ranges p t constraints from neoformed chlorite and k white mica the neoformation of chlorite and k white mica in fault rocks from two main faults of the central catalan coastal ranges the valles and the hospital faults has allowed us to constrain the p t conditions during fault evolution using thermodynamic modeling crystallization of m1 and m2 muscovite and microcline occured as result of deuteric alteration during the exhumation of the pluton 290 c t 370 c in the permian after that three tectonic events have been distinguished the first tectonic event attributed to the mesozoic rifting is characterized by precipitation of m3 and m4 phengite together with chlorite and calcite c1 at temperatures between 190 and 310 c the second tectonic event attributed to the paleogene compression has only been identified in the hospital fault with precipitation of low temperature calcite c2 the shortcut produced during inversion of the valles fault was probably the responsible for the lack of neoformed minerals within this fault finally the third tectonic event which is related to the neogene extension is characterized in the valles fault by a new generation of chlorite associated with calcite c4 and laumontite formed at temperatures between 125 and 190 c in the absence of k white mica differently the hospital fault is characterized by the precipitation of calcite c3 during the syn rift stage at temperatures around 150 c and by low temperature fluids precipitating calcites c5 c6 and pc1 during the post rift stage during the two extensional events mesozoic and neogene faults acted as conduits for hot fluids producing anomalous high geothermal gradients 50 c km minimum

deformation at the frictional viscous transition evidence for cycles of fluid assisted embrittlement and ductile deformation in the granitoid crust abstract mid crustal deformation is classically characterized by the transition from ductile to brittle deformation defining the frictional to viscous transition fvt here we investigate an exhumed continental mid crustal basement section in order to envisage the relationship between ductile and brittle deformation at the fvt our detailed study from km to micro scale shows that under greenschist metamorphic conditions deformation is accommodated by a dense network of highly localized ductile shear zones in the investigated case it is not quartz which defines the overall ductile deformation behavior but the viscous granular deformation in shear zones with an ultrafine grained polymineralic matrix consisting of quartz feldspar sheet silicates and epidote during viscous granular flow mass transfer processes under the presence of fluids promote a chemo mechanical mixing resulting in grain size reduction and reaction softening coeval with this ductile deformation fluid assisted embrittlement occurs as indicated by biotite coated fractures cataclasites and injection of non cohesive polymineralic gouge material into secondary fractures inside the host rock the embrittlement during predominant ductile deformation occurs in cycles i e prolonged periods of slow viscous granular flow are interrupted by rapid brittle deformation we interpret this fluid assisted cyclic embrittlement evidenced by injection of the fluidized material into off fault fractures as an alternative equivalent to pseudotachylites and as a microstructural indicator for paleo seismic activity with exhumation and associated cooling localized deformation persists in the ultrafine grained polymineralic shear zones but progressively transitions to cataclastic flow and finally to pressure dependent frictional flow always showing cycles of slow interseismic flow and fast seismic injection events overall in the granitic crust of the aar massif brittle and ductile deformation coexist up to deformation temperatures of minimum 450 c indicating that the fvt has to be placed in a rather wide range from 8 km up to 18 20 km in the granitoid crust

active extension in val d agri area southern apennines italy implications for the geometry of the seismogenic belt summary integration of geologic geomorphologic and seismologic data sets is used to reconstruct the recent tectonic evolution and active deformation pattern in the val d agri area located in the seismically active axial sector of the southern apennines italy the western portion of the apennines thrust belt has been affected by pliocene quaternary extension during easterly roll back and crustal delamination of the adriatic slab the bulk of quaternary extension has been accommodated by sw dipping oblique and normal faults which have attained mature morphologic and structural features and nowadays separate mountain ranges from intermontane basins however in the present seismogenic belt coseismic faulting locally occurs on ne dipping structures which might cut the inherited pleistocene landscape in the val d agri basin in spite of the large early middle pleistocene displacement occurred on sw dipping faults bordering its eastern flank our investigations show that the recent basin evolution has been controlled by a ne dipping fault system monti della maddalena fault system mmfs this fault system cuts across the monti della maddalena range west of the agri valley and has not yet created an evident tectonic landscape notwithstanding fault motion since the middle pleistocene might explain geomorphologic and hydrographic anomalies of the agri river and its valley where fault controlled subsidence has captured the river course and produced an aggrading plain within a regional uplift context recent and ongoing motion is documented by fault scarplets in loose deposits 14c ages of palaeosols and the spatial relation with low to moderate instrumental seismicity results from fault kinematic analysis are compatible with fault plane solutions of local and regional seismic events and indicate ne sw oriented extension recognition of the mmfs as a potential seismogenic fault increases the longitudinal extent of the ne dipping morphologically immature seismic sources in the southern apennines and argues against the range bounding fault model for active extension in the region the regional size of the ne dipping seismogenic belt may result from impingement of a mantle wedge beneath the apenninic chain and possibly track the external front of crustal delamination

claritas rise mars pre tharsis magmatism claritas rise is a prominent ancient noachian center of tectonism identified through investigation of comprehensive paleotectonic information of the western hemisphere of mars this center is interpreted to be the result of magmatic driven activity including uplift and associated tectonism as well as possible hydrothermal activity coupled with its ancient stratigraphy high density of impact craters and complex structure a possible magnetic signature may indicate that it formed during an ancient period of mars evolution such as when the dynamo was in operation as tharsis lacks magnetic signatures claritas rise may pre date the development of tharsis or mark incipient development since some of the crustal materials underlying tharsis and older parts of the magmatic complex respectively could have been highly resurfaced destroying any remanent magnetism here we detail the significant characteristics of the claritas rise and present a case for why it should be targeted by the mars odyssey mars reconnaissance orbiter and mars express spacecrafts as well as be considered as a prime target for future tier scalable robotic reconnaissance