laminated cyanobacterial mats in sediments of solar salt works some sedimentological implications formation of microlaminated sediments in solar salt works along the mediterranean coast in southern france only occurs within a restricted salinity range of 60 150 gl 1 these salinities are associated with development of a laminated cyanobacterial mat composed primarily of the filamentous cyanobacteria microcoleus chthonoplastes interbedded with detrital laminae transplants of the cyanobacterial mat to a less saline zone 36 60 gl 1 indicated that the cyanobacterial mats failed to colonize the less saline waters due to herbivorous snails and competition for light from floating algal masses of cladophora and enteromorpha neither the snails nor the cladophora and enteromorpha masses are tolerant of salinities above 60 gl 1 and therefore the microcoleus mats are restricted to those areas of the solar salt works with these higher salinities analyses of salinity conductivity dissolved oxygen and ph in shallow salt pans with salinities of 60 150 gl 1 established a relationship between the daily development of oxygen supersaturation and cyanobacterial photosynthesis sediments are unlaminated in those portions of the solar salt works where there are no cyanobacterial mats these mats are frequently drained of their overlying water and thus desiccation cracks divide them into polygonal plates the development and translocation of these plates is enhanced by gas bubbles which form under the surface of the mats no correlation between the microlaminae in sections from two cores located approximately 1 m apart was observed this was consistent with the hypothesis that the surface of the desiccation crack polygons can be removed by currents and redeposited on the top of other cyanobacterial mat polygons this process results in a patchwork quilt of young and old cyanobacterial mat polygons with an irregular microlamination pattern the presence of such an irregular pattern of laminae permits an important distinction to be made between sediments associated with stromatolite formation and those associated with the very fine and horizontal varved sediments of stratified meromictic water bodies the sedimentological significance of these observations is reviewed in relation to the processes of stromatolite genesis

detecting geothermal anomalies and evaluating lst geothermal component by combining thermal remote sensing time series and land surface model data abstract this paper explores for the first time the possibilities to use two land surface temperature lst time series of different origins geostationary meteosat second generation satellite data and noah land surface modelling lsm to detect geothermal anomalies and extract the geothermal component of lst the lstgt we hypothesize that in geothermal areas the lsm time series will underestimate the lst as compared to the remote sensing data since the former does not account for the geothermal component in its model in order to extract lstgt two approaches of different nature physical based and data mining were developed and tested in an area of about 560 560 km2 centered at the kenyan rift pre dawn data in the study area during the first 45 days of 2012 were analyzed the results show consistent spatial and temporal lstgt patterns between the two approaches and systematic differences of about 2 k a geothermal area map from surface studies was used to assess lstgt inside and outside the geothermal boundaries spatial means were found to be higher inside the geothermal limits as well as the relative frequency of occurrence of high lstgt results further show that areas with strong topography can result in anomalously high lstgt values false positives which suggests the need for a slope and aspect correction in the inputs to achieve realistic results in those areas the uncertainty analysis indicates that large uncertainties of the input parameters may limit detection of lstgt anomalies to validate the approaches higher spatial resolution images from the advanced spaceborne thermal emission and reflection radiometer aster data over the olkaria geothermal field were used an established method to estimate radiant geothermal flux was applied providing values between 9 and 24 w m2 in the geothermal area which coincides with the lstgt flux rates obtained with the proposed approaches the proposed approaches are a first step in estimating lstgt at large spatial coverage from remote sensing and lsm data series and provide an innovative framework for future improvements

determining soil moisture and sediment availability at white sands dune field new mexico from apparent thermal inertia data 1 determinations of soil moisture and sediment availability in arid regions are important indicators of local climate variability and the potential for future dust storm events data from the advanced spaceborne thermal emission and reflection aster radiometer were used to derive the relationships among potential soil erosion soil moisture and thermal inertia ti at the spatial scale of aeolian landforms for the white sands dune field between may 2000 and march 2008 land surface apparent thermal inertia ati data were used to derive an approximation of actual ti in order to estimate the wind threshold velocity ratio wtr the wtr is a ratio of the wind velocity thresholds at which soil erosion occurs for wet soil versus dry soil the aster derived soil moisture retrievals and the changes through time at white sands were interpreted to be driven primarily by precipitation but the presence of a perched groundwater table may also influence certain areas the sediment availability of dunes active playa surfaces and the margin of the alluvial fans to the west were determined to be consistently higher than the surrounding area the sediment availability can be primarily explained by precipitation events and the number of dry days prior to the data acquisition other factors such as vegetation and the amount of surface crusting may also influence soil mobility but these were not measured in the field this approach showed the highest modeled sediment availability values just days prior to the largest dust emission event at white sands in decades such an approach could be extended to a global monitoring technique for arid land systems that are prone to dust storms and for other regional land surface studies in the sahara

magnetic grain size and viscous remanent magnetization of pelagic clay unfossiliferous pelagic clay red clay cores from the pacific generally have unstable remanent magnetization except for tens of centimeters to several meters below the surface the origin of this instability has been considered to be viscous remanent magnetization vrm we conducted a rock magnetic study of a pelagic clay core from the south pacific which has the unstable to stable transition at about 1 5 m below the surface using the suspension method of yoshida and katsura 1985 we determined downcore variation of complete alignment magnetization cam and magnetic moment distribution geometric mean moment mg and log standard deviation log a assuming a lognormal distribution mean magnetic grain diameter was calculated from the mg using the saturation magnetization of magnetite 4 8 105 a m 1 on the assumption that all the magnetic grains are single domain magnetites of spherical shape this assumption is supported by thermomagnetic analyses isothermal remanent magnetization irm acquisition experiments and the ratio of cam to saturation irm the grain diameter ranges from about 0 02 to 0 15 m and decreases with depth below about 1 5 m the derived grain size holds even when the magnetites in the sediments suffered oxidation because the saturation magnetization of maghemite is close to that of magnetite the frequency dependence of magnetic susceptibility showed a downward increase in the amount of superparamagnetic grains on the other hand the magnetic viscosity acquisition coefficient normalized by the cam increases with depth we conclude that magnetic grain size can control the magnitude of the secondary magnetization vrm of pelagic clay it has been proposed that the major source of pelagic clay is atmospherically transported dust intensified global atmospheric circulation by the change of climate would raise the grain size of the magnetic minerals of the eolian component which can cause the unstable to stable transition of the remanent magnetization

origin of stable remanent magnetization of siliceous sediments in the central equatorial pacific abstract siliceous sediments distributed in the central equatorial pacific have a stable remanent magnetization regardless of age or depth this is in contrast with the unstable remanence of unfossiliferous red clay defined as pelagic clay here which accumulates in the middle latitudes of the pacific we have conducted a rock magnetic study of the siliceous sediments to clarify the magnetic carriers of the stable remanence for this purpose we combined magnetic granulometry by the suspension method and observation of magnetic grains with a transmission electron microprobe tem the advantage of the former is that the magnetic extraction procedure is not required for obtaining size distribution of the magnetic grains in sediments the tem observations revealed that most of the magnetic extracts are identical in size and shape to bacterial magnetosomes the suspension method proved that the magnetic assemblages of the siliceous sediments of both quaternary and early miocene age have mean diameters of about 0 05 m which is within the single domain range of magnetite and have narrow size distributions compared with pelagic clay these characteristics can be explained if the magnetofossils observed by tem are the major constituent of the magnetic grains in the sediments and have been preserved for a long period of time the difference in the stability of the remanent magnetization between the siliceous sediments and the pelagic clay can be explained by the difference in the size distribution of magnetic grains which would reflect differences in their sources i e biogenic vs detrital eolian

the role of biophysical cohesion on subaqueous bed form size biologically active fine grained sediment forms abundant sedimentary deposits on earth s surface and mixed mud sand dominates many coasts deltas and estuaries our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt sand and gravel this approach underpins many paleoenvironmental reconstructions of sedimentary successions which rely on analysis of cross stratification and bounding surfaces produced by migrating bed forms here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology the results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships the findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record

high resolution thermal inertia derived from the thermal emission imaging system themis thermal model and applications 1 thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the thermal emission imaging system themis on the mars odyssey spacecraft producing the highest resolution thermal inertia data set to date themis thermal inertia values have an overall accuracy of 20 a precision of 10 15 and are consistent with both thermal emission spectrometer orbital and miniature thermal emission spectrometer surface thermal inertia values this data set enables the improved quantification of fine scale surface details observed in high resolution visible images in the tharsis region surface textures and crater rims observed in visible images have no corresponding variation in the themis thermal inertia images indicating that the dust mantle is pervasive at themis scales and is a minimum of a few centimeters and up to 1 2 m thick the thermal inertia of bed form material indicates particle diameters expected for aeolian sediments and these materials are likely currently saltating variations in the thermal inertia within interior layered deposits in hebes chasma can be distinguished and the thermal inertia is too low to be consistent with bedrock or a lava flow thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation higher resolution themis thermal inertia enables the identification of exposed bedrock on the martian surface in nili patera and ares vallis bedrock material corresponds to distinct compositional and morphologic surfaces indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes

magnetotactic bacteria and their magnetofossils in sediments abstract living magnetotactic bacteria from freshwater environments show under natural and laboratory conditions a great variety of morphological appearances their magnetosomes vary in number shape and size one species of bacteria yields up to 1000 magnetosomes per cell individual particles reach a size of up to 200 nm as a rule they form elongated chains in bacteria which are held under laboratory conditions loop shaped arrangements and nearly unordered clusters are also found during the laboratory experiments different species of bacteria periodically dominated freshwater samples always exhibited a great variety of different magnetosomes on the other hand samples from marine environment clearly showed the preponderance of one type of particle these observations may reflect specific properties of the physico chemical milieu in which the bacteria grew at the end of our experiments north and south seeking bacteria co existed in roughly equal quantities quaternary unconsolidated sediments from the ammersee bavaria and the antarctic quaternary to tertiary deep sea sediments from the atlantic and pacific and jurassic limestones from the sonnwendgebirge tyrol austria were analyzed for fossil magnetosomes we found that fossil magnetosomes were morphologically similar to those from living bacteria but seemed to be corroded in some cases the observed differences in quantity size and shape of magnetosomes from various sediments may be influenced by variations in bacterial viability and particle stability at different sites but are not determined by geographical latitude

rock abundance on mars from the thermal emission spectrometer 1 nighttime infrared spectral observations returned from the mars global surveyor thermal emission spectrometer tes are well suited for determining the subpixel abundance of rocks on the surface of mars the algorithm used here determines both the areal fraction of rocky material and the thermal inertia of the fine grained nonrock component present on the surface rock is defined as any surface material that has a thermal inertia 1250 j m 2 k 1 s 1 2 this can be bedrock boulders indurated sediments or a combination of these on a surface mixed with finer grained materials over 4 9 million observations were compiled to produce the 8 pixels per degree global rock abundance and fine component inertia maps total coverage is 45 of the planet between latitudes 60 and 60 less than 1 of the planet has rock abundances greater than 50 and 7 of the mapped surface has greater than 30 rocks rocky regions on mars correspond primarily to the high inertia surfaces observed in thermal inertia data sets the fine component inertia data set is used to identify high inertia exposures that contain few rocks and more homogeneous materials

fossil bacterial magnetite in deep sea sediments from the south atlantic ocean the magnetostratigraphy of deep sea sediment cores has proven to be a powerful and high resolution method of dating and comparing sedimentary records in contrast to this widespread application relatively few attempts have been made to analyse and identify the mineralogy grain size and origin of the carrier of the remanent magnetization1 2 it is widely assumed that dominant ferrimagnetic minerals in deep sea sediments are of lithogenic origin that is that they derive from oceanic or continental detritus volcanic ashfalls micrometeorites hydrothermal precipitation or chemical mineralization processes a very different view was taken by kirschvink and lowenstam3 who suggested that fossil remnants of magnetite mineralizing organisms in particular magnetotactic bacteria might play an important part in the magnetization of sediments deposited in certain detritus poor aquatic systems we have used rock magnetic diagnostic methods to characterize the magnetic phases in deep sea sediments from the south atlantic these phases were then extracted and studied with the electron microscope our results indicate that fossil bacterial magnetite is the main carrier of the natural remanent magnetization in sediments ranging in age from quarternary to eocene different types of bacterial magnetosomes were detected most of them occurring in chains of identical particles and nearly all of them falling into the theoretically determined4 size range of single domain magnetitite

influence of thermophilic bacteria on calcite and silica precipitation in hot springs with water temperatures above 90 c evidence from kenya and new zealand hot and boiling springs in kenya and new zealand that are emitting water with temperatures more than 90 c are commonly characterized by a complex array of caco3 and sio2 precipitates that have been formed through abiogenic and biogenic processes thermophilic bacteria are the only microbes that can survive in the boiling water that is discharged into pools around the spring orifice analysis of modern substrates from various springs in the kenya rift valley and the taupo volcanic zone in new zealand shows that they are inhabited by a diverse array of coccoid and filamentous bacteria in some areas these bacteria produce copious amounts of mucus that coat the substrates although the coccoid and filamentous bacteria provide substrates for caco3 and sio2 precipitation the microbes do not seem to have any direct influence on the morphology of the precipitates that are produced conversely the mucus found in these hot spring pools selectively takes up elements such as si mg al and fe but is not calcifi

signatures of biologically influenced caco3 and mg fe silicate precipitation in hot springs case study from the ruidian geothermal area western yunnan province china hot springs at gongxiaoshe and zhuyuan maximum temperatures of 73 to 84 c respectively are characterized by deposits formed of calcite aragonite non crystalline si mg fe deposits and minor amounts of barite and gypsum the deposits at gongxiaoshe are formed largely of alternating calcite and aragonite laminae whereas those at zhuyuan are formed largely of calcite the calcite is in the form of i pseudodendrites that grew as sub crystals stacked upon each other and ii unattached euhedral and incompletely formed dodecahedral and rhombohedral crystals amorphous caco3 formed of nanoparticles 1 m long is common in some of the zhuyuan deposits but minor in the gongxiaoshe deposits the morphologically diverse arrays of aragonite crystals that lie parallel to bedding were not nucleated on a growth surface many substrates in these deposits are covered with reticulate coatings that are formed largely of si and mg with minor fe and micro granular coatings that are formed largely of si and fe biofilms with their extracellular polymeric substances and microbes are common at both springs the compositionally and crystallographically diverse precipitates at these two springs are attributed to a biologically influenced model with precipitation taking place in micro domains that developed in the extracellular polymeric substances according to this model precipitation varied at the micron scale influenced by the elemental concentrations that developed in the hydrogel of extracellular polymeric substances critically the very low preservation potential of the extracellular polymeric substance and its formative microbes means that the precipitates will rapidly lose evidence of their biotic origin the compositional diversity of the precipitates the crystallographic diversity of the calcite and aragonite with numerous incompletely formed crystals and local concentrations of si mg and fe may however serve as proxies of that biologically influenced precipitation

subaerial exposure and changes in the stability of intertidal estuarine sediments abstract the surface cohesive strength of intertidal sediments at six sites on two estuaries throughout the period of a single diurnal subaerial exposure was investigated stations at different tidal heights were examined at each site hourly measurements were made using a cohesive strength meter which provides an ordinal measure of sediment stability the sediment was most easily eroded immediately after the emersion of the mudflat and there was little difference between the initial stability of the mud at different sites or stations as the subaerial exposure continued the sediment of mid shore and high shore stations began to increase in stability no significant change was found at low shore stations before the return of the tide the surface density of diatom populations was also intermittently measured at each site the greatest increase in sediment stability occurred at high shore stations and this was most extreme where there were also dense populations of epipelic diatoms present at the surface of the sediment this supports laboratory evidence that the extracellular products of diatom populations of sufficient density increase the stability of intertidal sediments

high resolution thermal inertia mapping from the mars global surveyor thermal emission spectrometer abstract high resolution thermal inertia mapping results are presented derived from mars global surveyor mgs thermal emission spectrometer tes observations of the surface temperature of mars obtained during the early portion of the mgs mapping mission thermal inertia is the key property controlling the diurnal surface temperature variations and is dependent on the physical character of the top few centimeters of the surface it represents a complex combination of particle size rock abundance exposures of bedrock and degree of induration in this work we describe the derivation of thermal inertia from tes data present global scale analysis and place these results into context with earlier work a global map of nighttime thermal bolometer based thermal inertia is presented at 1 4 per pixel resolution with approximately 63 coverage between 50 s and 70 n latitude global analysis shows a similar pattern of high and low thermal inertia as seen in previous viking low resolution mapping significantly more detail is present in the high resolution tes thermal inertia this detail represents horizontal small scale variability in the nature of the surface correlation with albedo indicates the presence of a previously undiscovered surface unit of moderate to high thermal inertia and intermediate albedo this new unit has a modal peak thermal inertia of 180 250 j m 2 k 1 s 1 2 and a narrow range of albedo near 0 24 the unit covering a significant fraction of the surface typically surrounds the low thermal inertia regions and may comprise a deposit of indurated fine material local 3 km resolution maps are also presented as examples of eolian fluvial and volcanic geology some impact crater rims and intracrater dunes show higher thermal inertias than the surrounding terrain thermal inertia of aeolian deposits such as intracrater dunes may be related to average particle size outflow channels and valleys consistently show higher thermal inertias than the surrounding terrain generally correlations between spatial variations in thermal inertia and geologic features suggest a relationship between the hundred meter scale morphology and the centimeter scale surface layer

measurement of thermal properties of select intact and weathered granulites and their relationship to rock properties abstractunderstanding the thermal properties of granulites a group of high grade metamorphic rocks representing composition of lower crust of the earth is necessary to arrive at effective crustal heat flow modeling however the thermal conductivity and diffusivity of intact and weathered granulites and parameters that influence them are poorly known the above properties for a few felsic mafic and intermediate granulites and associated soils from the southern granulite terrain india were investigated using a cost effective self fabricated setup the results generated by this technique were precise reproducible and comparable with other published procedures and values because the samples analyzed were of intact in situ specimens the thermal conductivity and diffusivity could be directly used in practical applications among several parameters it was observed that sio2 mgo fe2o3 ratio grain size and bulk density were the principal factors to influence the conductivity and diffusivity of fresh

the paleomagnetic field from equatorial deep sea sediments axial symmetry and polarity asymmetry paleomagnetic data from 89 equatorial deep sea sediment cores indicate that the configuration of the time averaged geomagnetic field depends strongly on polarity state but that it remains within 1 degree of axial symmery throughout the pliocene and pleistocene last 5 million years the relative magnitude of the nondipole field was greater by almost a factor of 2 during reverse than during normal polarity intervals these results thus support earlier suggestions that there may be a standing nonreversing component of the geomagnetic dynamo

lithology discrimination from physical rock properties the estimation of lithology from multiple geophysical survey methods needs to be addressed to develop advanced tomographic methods an initial requirement for lithology discrimination is that lithology should be discriminable from the media properties physically related to the geophysical observations to test this condition for different combinations of the most common crustal rocks we performed several lithology discrimination exercises on rock samples under laboratory conditions the physical properties included mass density compressional velocity shear velocity electric conductivity thermal conductivity and magnetic susceptibility a categorical description of the sample lithology was followed hence the inference consisted of predicting the sample rock category lithotype membership the joint information provided by the physical properties of the rocks allowed us to discriminate the sample lithotype correctly with an overall success rate of 100 in the most favorable situation and over 85 in the least favorable situation we obtained successful classification results for a variety of common lithotypes granite gabbro limestone tuff marble basalt and gneiss using three common classification methods clustering analysis gaussian classification and discriminant analysis although discrimination was positive with each of these multivariate classification techniques discriminant analysis showed some advantages for the classification and graphic analysis of the data these results support our postulate that lithology can be estimated reliably if multiple geophysical observations are considered jointly

a direct link between the china loess and marine δ 18 o records aeolian flux to the north pacific most studies of quaternary climates conducted during the past 150 years have focused on glacial sequences and for the past 25 years marine sediments have provided significant further understanding of glacial and interglacial palaeoclimates an important goal of palaeoclimatology however to link the well known detailed continental records to marine records of similar resolution has yet to be realized the classic loess sequences of china provide an apparently continuous record of continental climate over the past 2 4 million years1 2 the oxygen isotope 18o timescale developed from the marine record3 gives us a global chrono stratigraphy of late pleistocene climates previously it has been suggested in studies of the aeolian component in pelagic sediments that it may be possible to link these two records directly by finding a suitable core from the north west pacific downwind from china4 5 here we report the results of such an effort for core v21 146 fig 1 and tie the last 500 000 years of the chinese loess soil sequence directly to the 18o timescale and in so doing refine the dating of regional loess and soil horizons

decoding the mechanism of formation in marine ooids a review abstract ooid shoals sedimentary structures consisting of carbonate grains are often used as proxies to explore changes in seawater chemistry over earth history despite their importance as contributors to the global carbonate budget and as paleo environmental indicators for water depth ph temperature and water energy the mechanism of formation of these concentric sub spherical concretions of tangentially or radially arranged aragonite or calcite crystals is still the subject of intense debate unlike oncoids whose microbial origins are well acknowledged ooids are traditionally viewed as abiotic grains mainly produced in suspension by agitated warm waters that are supersaturated with respect to caco3 yet there is considerable evidence including geochemical bio signatures and detection of viable microbes capable of mineralization and biofilm production and degradation to suggest otherwise the emergence of new and sophisticated technologies reveals that the level of microbial diversity of these sedimentary grains exceeds that of some microbialite systems these findings have refined our understanding of ooid genesis and ooid accretion processes and argue toward microbial mediation both as a direct result of metabolic activities inducing changes in the environment conducive to precipitation and by a passive mechanism in which mucilaginous extracellular polymeric substances eps act as a template for mineral nucleation furthermore new developments in the field indicate that carbonate mineralization in marine ooids occurs through sequential precipitations that involve an amorphous calcium carbonate phase acc which some argue are of biotic origins herein we discuss the most relevant theories of ooid formation including some of the early pioneering studies that laid the groundwork for new theories attempting to decode the origins of these controversial grains

mantled and exhumed terrains in terra meridiani mars 1 hematite bearing deposits in the terra meridiani region of mars constitute the top stratum of a partially eroded layered complex that covers dissected noachian aged cratered terrain the hematite unit consists of dark plains and dunes covering a bright substrate this substrate is fully exposed beyond the borders of the hematite bearing deposit and consists of polygonal ground separated by ridges or valleys together with layered deposits that have been eroded into a variety of landforms the complex is partially covered by a regional scale aeolian mantle that thickens toward the north the hematite bearing stratum exhibits low albedoes pulse widths and intermediate thermal inertias whereas the underlying unit exhibits high values of these parameters both units have spectral emissivity signatures similar to those for the low albedo cratered terrain to the south with the addition of hematite for the top stratum the complex is interpreted to consist of extensive plains forming lava flows and tephra deposits emplaced during an extensional regime and at least partially buried by an aeolian mantle aeolian stripping of the mantle exposed much of the complex and differentially eroded the deposits to produce the landforms existent today exploration of the hematite bearing deposits by the 2003 mars exploration rover opportunity will allow testing of the hypotheses presented since this stratum has been locally reworked into dunes that only partially cover the underlying brighter portion of the complex in particular the rover based measurements will allow us to test the extent to which the unusual remote sensing properties of the units indicate aqueous alteration

remote sensing of damavand volcano iran using landsat imagery implications for the volcano dynamics abstract remote sensing techniques are applied to retrieve land surface temperature lst radiative heat flux rhf geothermal heat flux ghf and to map hydrothermal alteration zones around the damavand stratovolcano iran landsat enhanced thematic mapper plus etm day and nighttime images are used and merged to available geological data to identify thermal anomaly areas rhf is determined using the stefan boltzmann equation after preprocessing geometric radiometric and atmospheric correction and processing emissivity calculation and lst retrieval of thermal infrared bands in order to estimate ghf from daytime image solar radiation and albedo maps are generated to minimize these effects the ghf values are derived from nighttime image using the background subtraction technique using boolean operation only those pixels with the ghf values greater than 30 w m 2 obtained from daytime image and the ghf values greater than 10 w m 2 estimated from nighttime image are identified as thermal anomalies the geothermal areas are identified by combining the thermal anomaly map and other geological information thermal anomalies have close spatial correlation to faults thermal springs and high heat flow measurements from subsurface data and lithology some of the thermal anomalies and hydrothermal alteration areas also overlap active deformation areas this suggests role of heat and hydrothermal alteration on flank instability processes the thermal anomaly areas show an arc shaped pattern this pattern and the concentration of higher ghf areas in the eastern sector of the volcano are consistent with a release of fluids in a transition zone between a transpressional and a transtensional tectonic regime the combination of thermal infrared data with other geological information layers can be used to detect geothermal areas as well as to analyze the complex relationships among geothermal activity active tectonics and gravity instability processes on volcanoes

electron optical characterization of bacterial magnetite abstract magnetic grains isolated from magnetococcoid bacterial cells were studied by means of transmission electron microscopy electron diffraction and electron microprobe analysis observed in situ the magnetic grains are each surrounded by an organic membrane and are usually found in a random array although chains are also seen electron diffraction confirms the magnetite mineralogy and provides additional evidence in favor of vacancies in the structure electron microprobe analysis shows the magnetite to be slightly titaniferous electron microscopy indicates that the grains rather than being flake shaped are parallelepiped crystals with a mean length of 99 3 8 7nm a mean width of 62 3 6 1nm yielding a width to length ratio of 0 63 these data support the contention that the magnetic bacterial grains are single domain crystals capable of producing a natural remanent magnetization in sediments

olduvai onset polarity transition two detailed paleomagnetic records from north central pacific sediments abstract paleomagnetic analyses of two azimuthally oriented deep sea sediment cores from the north central pacific ocean which contain a record of the onset of the olduvai subchron polarity transition show 1 intermediate directions of magnetization with transitional inclinations reaching values up to 70 2 up to three sequential 180 declination changes two of which imply rapid oscillations of the geomagnetic field before the main reversal and 3 a pronounced drop in intensity of magnetization within the transitional interval the data further indicate that the intensity decay and recovery cycle took longer than the directional changes of the reversal whereas the directional changes lasted about 5000 years the duration of the recorded intensity cycles suggest that the complete onset of the olduvai reversal may have lasted as much as 28 000 years anhysteretic remanent magnetization studies and thermomagnetic analyses indicate that uniform magnetic mineralogy characterizes the transition zones of the cores this further suggests that the j 10 arm 70 ratio may represent a relative paleointensity estimate and may thus indicate a decrease of the intensity of the geomagnetic field during the onset of the olduvai reversal virtual geomagnetic pole paths of the two records are near sided directions in projected d i space indicate that the olduvai onset transitional field geometry possessed a contribution from non axisymmetric terms in addition to the dominating zonal harmonics the analyses also suggest that the transitional field during the onset of the olduvai reversal was dominated by harmonics different from those of the matuyama brunhes boundary jaramillo transitions and upper olduvai reversal

biogenic structure of early sediment fabric visualized by low temperature scanning electron microscopy the accurate visualization of early biogenic sediment fabric is important in the search for modern analogues to relict fossil structure and therefore for the interpretation of past environmental conditions water may have a significant structural role within hydrated material and sample dehydration may be detrimental to the structural interpretation of natural sediments and their associated microbiota water is present in sediments as free water or in the form of bound or hydration water extracellular polymeric substances associated with microbial assemblages have a high content of hydration water and are distorted by dehydration the use of low temperature scanning electron microscopy for the visualization of water saturated sediments and associated biogenic structures is examined low temperature sem allows samples to be examined without the removal of water that is normally associated with the preparatory procedures for traditional ambient sem samples for low temperature sem are first frozen cryofixed and then examined fully hydrated and still frozen at low temperature cf 180 c on the stage of a specially adapted sem the process of low temperature sem for the examination of hydrated sediments is described and several examples of cohesive and mixed flat sediments and their associated biogenic fabrics are given detail of the internal fabric and associated microbiota can be examined by freeze fracture techniques to preserve the natural condition of the sediments

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

a transient method of measuring the thermal properties of rocks the aim of the paper is to describe a new rapid transient method for the determination of thermal diffusivity and thermal conductivity of rocks the present transient method is based on the application of a constant heat flux to the top surface of a block of rock that is insulated on all other surfaces results of a sensitivity analysis of the method indicate that thermal diffusivity can be measured to a best accuracy of about 3 percent and thermal conductivity of saturated rocks can be determined to a best accuracy of about 8 percent the method provides estimates of thermal conductivity that are consistent with estimates made using the steady state divided bar apparatus the method is applied to determine the thermal conductivity of a suite of rocks from western australian sedimentary basins

sediment properties influencing upwelling spectral reflectance signatures the biofilm gel effect microbial communities often produce copious films of extracellular polymeric secretions eps that may interact with sediments to influence spectral reflectance signatures of shallow marine sediments we examined eps associated with microbial mats to determine their potential effects on sediment reflectance properties distinct changes in spectral reflectance signatures of carbonate sediments from the bahamas were observed among several sediment sites which were specifically chosen for their presence of microbial mats and adjacent nonmat sediments the presence of mats greatly reduced sediment reflectance signatures by 10 20 compared with adjacent nonmat areas having similar sediment characteristics decreases in reflectance near 444 and 678 nm could be attributed primarily to absorbance by photopigments however additional nonspecific decreases in reflectance occurred across a wide spectral range 400 750 nm experimental manipulations determined that nonspecific reflectance decreases were due to eps that are produced by biofilm associated microorganisms of the mats microbial eps isolated from natural mat sediments exhibited small but nonspecific absorbances across a broad spectral range when eps was in relatively high concentrations as in microbial mats there was a biofilm gel effect on sediment reflectance properties the effect was twofold first it increased the relative spacing of sediment grains a process that permitted light to penetrate deeper into sediments second it resulted in a more efficient capture of photons because of the change in refractive index of eps gel itself relative to seawater the relatively translucent eps of biofilms therefore influenced the magnitude of reflectance across a broad spectral range in marine sediments

working with natural cohesive sediments summary of stabilizing and destabilizing biotic in uenceson natural cohesive sediment stabilizing destabilizingeps secretion extracellularpolymeric substances bybacteria and microphytobenthosenhances cohesion promotes occulation and hence deposition blistering trapping ofoxygen bubbles in bio lmsincreases buoyancy of thebio lm to such an extentthat it pulls away fromthe sediment sediment compaction burrowingmacrofauna increasesediment densityand hence stability pelletization theformationof faeces and psuedo faeces can enhanceerodibility increased drainage burrowand channel formationpromotes dewatering grazing organismsfeedingon intertidal ats causesphysical disturbance andresuspensionof the sediment andreduces the stabilizingin uence ofmicrophytobenthos network effects filamentous biotaramify through the sediment matrixbinding sediment particles together burrow cleaning somebenthic fauna cleantubes they inhabit inthe sediment giving riseto a localizedbenthic ux flow effects

thermal conductivity estimation in sedimentary basins abstract thermal conductivity is a very important parameter for understanding the present and past thermal regimes of sedimentary basins the bulk thermal conductivity of sedimentary rocks depends mainly on three factors 1 their mineralogic and fluid composition 2 their temperature and 3 their structure as shown by a series of measurements on small scale isotropic samples the effects of mineralogy and fluid content can be estimated quite accurately using the geometric mean model however this estimate does not take into account a possible anisotropy related to various structural effects such as small scale heterogeneity or crystalline orientation this anisotropy effect seems especially important in the case of clayey formations various observations using equilibrium temperature logging together with classical well logs can be interpreted as indicating such an effect the effect appears to depend on depth as would be expected from the major changes occurring in clays during their burial history compaction mineralogical transformation and structural reorganization

magnetofossil dissolution in a palaeomagnetically unstable deep sea sediment magnetofossils1 the fossil remains of bacterial magneto somes2 are found in various deep sea sediments and have been linked to the preservation of stable natural remanent magnetization in many of them1 3 5 they have also been extracted and identified from lithified carbonates of jurassic5 and precambrian6 age showing that magnetotactic bacteria have been a sedimentary source of fine grained magnetite for much of geological time some clay rich deep sea sediments however do not record a stable remanent magnetization for unknown reasons here we report results from a high resolution transmission electron microscope study on samples of this type collected by the deep sea drilling project dsdp the material contains a complex mixture of single domain magnetic minerals well preserved magnetofossils show the same crystal structures as those found in magnetosomes from recent bacteria7 10 whereas others in these same preparations display a wide range of dissolution corrosion and aggregation effects rock magnetic measurements are consistent with the presence of these alterations in many dsdp sediments including those that preserve reliable palaeomagnetic directions as we were unable to fina authigenic magnetic minerals in our sample and as the magnetic fraction is dominated by well preserved magnetofossils we suggest that the poor preservation of the magnetization is a result of diagenetic interactions between the magnetofossils and the clay minerals in the matrix

the identification and biogeochemical interpretation of fossil magnetotactic bacteria magnetotactic bacteria which most commonly live within the oxic anoxic transition zone oatz of aquatic environments produce intracellular crystals of magnetic minerals specifically magnetite or greigite the crystals cause the bacteria to orient themselves passively with respect to the geomagnetic field and thereby facilitate the bacteria s search for optimal conditions within the sharp chemical gradients of the oatz the bacteria may also gain energy from the redox cycling of their crystals because magnetotactic bacteria benefit from their magnetic moments natural selection has promoted the development of traits that increase the efficiency with which the intracellular crystals impart magnetic moments to cells these traits also allow crystals produced by magnetotactic bacteria called magnetofossils when preserved in sediments to be distinguished from abiogenic particles and particles produced as extracellular byproducts of bacterial metabolism magnetofossils are recognizable based on their narrow size and shape distributions distinctive morphologies with blunt crystal edges chain arrangement chemical purity and crystallographic perfection this article presents a scheme for rating magnetofossil robustness based on these traits the magnetofossil record extends robustly to the cretaceous and with lesser certainty to the late archean because magnetotactic bacteria predominantly live in the oatz the abundance and character of their fossils can reflect environmental changes that alter the chemical stratification of sediments and the water column the magnetofossil record therefore provides an underutilized archive of paleoenvironmental information several studies have demonstrated a relationship between magnetofossil abundance and glacial interglacial cycles likely mediated by changes in pore water oxygen levels more speculatively a better developed magnetofossil record might provide constraints on the long term evolution of marine redox stratification more work in modern and ancient settings is necessary to explicate the mechanisms linking the abundance and character of magnetofossils to ancient biogeochemistry

a rock magnetic study of giant piston core ll44 gpc3 from the central north pacific and its paleoceanographic implications previous magnetostratigraphic studies of nonfossiliferous pre pliocene age pelagic clay cores from the central north pacific have proven unsuccessful because of the unstable behavior of the natural remanent magnetization the inability to obtain a reliable magnetostratigraphy has severely limited the temporal resolution that can be achieved in paleoceanographic studies of these nonfossiliferous pelagic clays we carried out a rock magnetic study of core ll44 gpc3 which spans the interval 0 70 m y ago to determine whether rock magnetic parameters can be used to construct a high resolution stratigraphic framework for paleoceanographic studies of central north pacific pelagic clays despite the instability of the natural remanence in addition we tested the ability of rock magnetic methods to detect and characterize the paleoceanographic changes that are recorded in the sediments of ll44 gpc3 stratigraphic variations in rapid and nondestructive rock magnetic parameters and related ratios reflect changes in the concentration mineralogy and grain size of the magnetic minerals within the sediments rock magnetic parameters exhibit coherent fluctuations within both the stable and unstable sections of ll44 gpc3 this result suggests the potential use of these parameters for regional correlation and relative dating of the nonfossil bearing pelagic clays of the central north pacific gyre major fluctuations in rock magnetic parameters plotted as accumulation rates correspond to intervals of paleoenvironmental change that have been previously detected by other paleoceanographic methods in addition variations in a parameter proportional to the concentration of goethite hematite correlate remarkably well with the mass accumulation rate of the total eolian component suggesting that in some situations it can be used as a proxy indicator for eolian activity

modern diatom distribution in mangrove swamps from the kaw estuary french guiana modern diatom assemblages were analyzed in 85 surface sediment samples collected in the kaw estuary and adjacent mangrove swamps samples were collected according to seasonal variations wet versus dry and mudbank stability phases from fluid mudflat to mangrove swamps overgrown with vegetation according to the diatom species habitat and salinity affinities the modern distribution shows three main diatom assemblages more related to the sediment stability than the seasonal variations the fluid mudflat was primarily dominated by marine planktonic species coscinodiscus centralis cyclotella stylorum thalassionema nitzschioides carried by oceanic waters these species also dominated the samples located in the estuarine channel of the kaw river and in adjacent mangrove swamp areas in the upstream portion of the estuary the occurrence of these marine planktonic species suggests a deep penetration of oceanic water into the estuary the fluid mudflat was characterized by epipelic species mostly dominated by species from the genera gyrosigma which are characterized by a high motility inside the sediments this autochthonous epipelic assemblage could be considered as a biological indicator of the fluid mudflat stability in the mangrove swamp stabilized by vegetation the diatom assemblages are more diverse and dominated by species from the genera nitzschia and navicula

detection of geothermal anomalies using advanced spaceborne thermal emission and reflection radiometer aster thermal infrared images at bradys hot springs nevada usa abstract surface temperature anomalies associated with geothermal activity at bradys hot springs churchill county nevada were mapped using advanced spaceborne thermal emission and reflection radiometer aster thermal infrared tir image data in order to highlight subsurface contributions of geothermal heat the aster images were processed to minimize temperature variations caused by the diurnal heating effects of the sun surface temperature variations caused by changes in albedo were corrected with visible and near infrared aster bands and a 10 meter smoothed digital elevation model dem was used to correct for topographic slope effects field measurements of ground surface temperatures made over 24 hour periods were used to design a thermal inertia correction incorporating day and night thermal infrared images in the resulting processed image background temperature variations were reduced 30 50 without reducing the intensity of geothermal anomalies thus making it easier to distinguish geothermal activity from false anomalies caused by non thermal springs topographic effects and variable rock soil and vegetation compositions

thermal infrared remote sensing detection of thermal information associated with faults a case study in western sichuan basin china abstract using enhanced land surface temperatures lsts image retrieved from landsat etm this article shows that thermal information associated with faults have been detected these anomalies may be provided by geothermal natural convection through faults and partially influence the ground surface thermal environment the study area in southern segment of longmen mountains thrust belt of western sichuan basin contains complex faults and folds with recent earthquake activity in order to study the faults for future oil exploration we use lst data retrieved from landsat thermal infrared band to detect the thermal information associated with faults the lsts are enhanced by filtering out anthropogenic activity and influence land cover classes and interpolating to contour map the spatial patterns of the enhanced images revealed the spatial correspondence between the thermal information and the dip planes of faults when compared with the explanation profiles and geologic features obtained from the 3d seismic geophysical data the thermal affected ranges calculated and the statistically significant of regression model also indicate the result that the thermal information located near the faults are consistent with the faults dip planes

temperature dependent thermal inertia of homogeneous martian regolith 1 past studies of the thermophysical properties of the martian surface layer have assumed temperature independent thermal inertia which is a function of the material density specific heat and bulk conductivity in this paper we evaluate the temperature driven variations of these quantities for particulated and cemented material under martian conditions of atmospheric pressure and temperature temperature driven density variations are negligible the specific heat of a basaltic material is strongly influenced by the temperature 75 increase from 150 to 315 k inducing significant variations of the thermal inertia the thermal conductivity of uncemented martian regolith is weakly controlled by the solid phase conductivity and strongly controlled by the gaseous phase conductivity as a result the conductivity of the solid phase i e composition temperature is unimportant whereas medium to large variations 30 50 of the bulk conductivity are associated with temperature induced fluctuations of the pore filling gas conductivity overall the thermal inertia of uncemented martian soils is predicted to vary significantly 80 throughout the range of the observed surface temperatures in the case of cemented soils the contribution of the gas conductivity is generally small and the solid phase i e grains and cement conductivity i e composition temperature becomes more important consequently the magnitude of the thermal inertia change for cemented soils is variable and smaller than that predicted for uncemented materials 10 50 large diurnal and seasonal temperature variations only occur within the top material and most of the near surface regolith does not experience large thermal inertia variations the shapes of modeled diurnal temperature curves are not significantly modified e g the 0200 lt martian local time apparent thermal inertia of uncemented regolith is up to 15 lower than the average daily inertia of the top material thermally derived grain sizes are usually based on conductivity measurements operated at room temperature or above where the thermal inertia and specific heat are higher than on mars implying that grain size predictions for mars are currently underestimated however in situ observations by the mars exploration rovers and thermal conductivity modeling suggest that this underestimation is not significant

ultrafine grained magnetite in deep sea sediments possible bacterial magnetofossils a new extraction technique now permits ultrafine magnetite crystals to be separated from a variety of deep sea sediments morphologic characterization of these particles with transmission electron microscopy reveals the presence of several distinct crystal types some of which closely resemble those formed by the magnetotactic bacteria the apparently biogenic magnetite particles are of single domain size and dominate the population in calcareous deep sea sediments bacterially precipitated magnetite may therefore be a major source of the stable magnetic remanence in some marine sediments these objects possibly constitute the smallest mineral fossils yet recovered from the sedimentary record

temporal radiative heat flux estimation and alteration mapping of tendurek volcano eastern turkey using aster imagery abstract tendurek volcano is a polygenetic basaltic shield volcano formed by successive alkaline basalt flows it is one of the youngest volcanoes of turkey both historical and holocene activities have been reported for the volcano continuous hydrothermal and fumarole activity has been observed on the twin summit craters located 4 5 km apart aster daytime and nighttime satellite imagery acquired between 2001 and 2014 are used to calculate surface temperature surface temperature anomaly and relative radiative heat flux from the craters to determine a base value for the current thermal emission surface temperature and surface temperature anomaly calculations yield a heat flux between 14 4 and 35 5 w m 2 at the western crater and between 7 72 and 28 3 w m 2 at the eastern crater these values are well correlated with other known low level activity volcanoes the annual and long term consistency of the thermal pattern is investigated the location and extent of surficial hydrothermal alteration within and surrounding the tendurek craters is identified by band ratioing and indexing using aster visible through shortwave infrared bands spectral identification of gypsum hydroxides sulfates hydrated sulfates and clay mineralisation indicates pervasive acid sulfate alteration due to the activity of fumarole vents around tendurek craters