very preliminary reference moon model abstract the deep structure of the moon is a missing piece to understand the formation and evolution of the earth moon system despite the great amount of information brought by the apollo passive seismic experiment alsep the lunar structure below deep moonquakes which occur around 900 km depth remains largely unknown we construct a reference moon model which incorporates physical constraints and fits both geodesic lunar mass and polar moment of inertia and love numbers and seismological body wave arrivals measured by apollo network data in this model the core radius is constrained by the detection of s waves reflected from the core in a first step for each core radius a radial model of the lunar interior including p and s wave velocities and density is inverted from seismic and geodesic data in a second step the core radius is determined from the detection of shear waves reflected on the lunar core by waveform stacking of deep moonquake apollo records this detection has been made possible by careful data selection and processing including a correction of the gain of horizontal sensors based on the principle of energy equipartition inside the coda of lunar seismic records and a precise alignment of sh waveforms by a non linear inversion method the very preliminary reference moon model vpremoon obtained here has a core radius of 380 40 km and an average core mass density of 5200 1000 kg m 3 the large error bars on these estimates are due to the poorly constrained s wave velocity profile at the base of the mantle and to mislocation errors of deep moonquakes the detection of horizontally polarized s waves reflected from the core and the absence of detection of vertically polarized s waves favour a liquid state in the outermost part of the core all these results are consistent within their error bars with previous estimates based on lunar rotation dissipation williams et al 2001 and on lunar induced magnetic moment hood et al 1999

selenophysical parameter inversion in the lunar southern hemisphere highland based on mutant particle swarm optimization abstract selenophysical parameters can be estimated based on admittance between gravity and topography especially high precision grail gravity and lola topography data these parameters include load ratio between subsurface and surface loads crustal thickness crustal density and effective elastic thickness considering non negligible membrane stress the lunar lithosphere is best modeled as a thin and elastic spherical shell taking into account of the nonlinearity of the governing equation of the shell and premature convergence of pso we introduced an updated algorithm of mpso which considers a self adaptive inertia weight and a mutation operator as commonly used in genetic algorithms ga results indicate that mpso is relatively more flexible in the choice of tuning parameters than the general algorithm of pso a low mutation probability of 0 005 is found to promote globally optimized convergence and a low value of 0 002 is employed in parameters estimation for 20 areas in southern hemisphere highland using the updated algorithm of mpso it is found that a well constrained crustal density for most of the studied regions is less than or equal to the mean crustal density 2550 kg m 3 of the entire lunar highland the relatively small crustal density is likely a result of high porosity of southern hemisphere crust the elastic thickness at studied locations far from mare basins is found to be around 7 km corresponding to the thickness at the stage of formation of highland formed from the crystallization of ancient ferroan anorthosite a large elastic thickness is on the contrary discovered surrounding mare basins the ancient lunar lithosphere developed quite thick as the moon becoming cool and it was able to elastically support new loads during the formation of mare basins the difference of elastic thickness indicates the development of lithospheric thickness at the distinct lunar evolutionary history

lapse time dependence of coda q anisotropic multiple scattering models and application to the pyrenees abstract the coda quality factor of short period s waves q c excited by local earthquakes in the pyrenees has been measured as a function of the length of the coda window l w for different choices of the onset time of the coda t w in the 2 16 hz frequency band we observe a transient regime characterized by an increase of q c with l w followed by a stabilization around a plateau the value of which depends on the central frequency of the signal using monte carlo simulations of wave transport in a variety of random media 1200 models we demonstrate that the lapse time dependence of q c in the pyrenees may be modeled by multiple anisotropic scattering of seismic waves without invoking any depth dependence of the attenuation properties in the crust in our model anisotropic scattering is quantified by the ratio between the transport mean free path and the mean path l l at 6 hz the data require an anisotropy factor l l 5 a transport mean free path l 400 km and an intrinsic quality factor q i 800 from the frequency dependent plateau of q c at large lapse time we infer an intrinsic quality factor of the form q i 400 f 0 4 in the pyrenees we also show how the rapid increase of the lapse time dependence of q c with frequency may be exploited to put constraints on the power spectrum of heterogeneities in the crust

composition and history of giant carbonate seep mounds mesoproterozoic borden basin arctic canada abstract the mesoproterozoic ikpiarjuk formation borden basin nunavut consists of a series of very large 200 m thick kms diameter dolostone mounds that accumulated on the floor of a restricted basin the mounds are isolated from contemporaneous shallow water carbonate rocks accumulated at the same time as black shale in deep water regions of the basin and are geographically limited to the vicinity of basin scale fault zones the mounds contain extensive deposits of benthic thrombolites a microbial texture that is not common in mesoproterozoic carbonate rocks field relationships of individual mounds indicate that mound growth was initiated during regional deposition of organic rich black shale mounds developed significant relief above the basin floor and some mound tops were eventually exposed and karsted during differential uplift the mounds accumulated in a deep water sub photic zone setting as a result of fluid venting along basin scale faults interpreted basin depths indicate that the thrombolitic mound texture is probably not related to cyanobacteria chemosynthetic microbes exploited the chemical gradient in the vicinity of the vents and built a mound framework of thrombolites framework voids contain both carbonate mud and isopachous linings of fibrous cement indicating that the mixing of vent fluid with basin water favoured production of abiogenic carbonate minerals in addition to providing a chemical gradient for microbes to exploit proterozoic deep water carbonates and thrombolites are rare and the ikpiarjuk formation mounds represent microbial buildups that are fundamentally different from other examples in the precambrian rock record

subsurface seepage dynamics and flow types in a messinian paleoseep system maiella mts central italy abstract the subsurface feeder complexes of mud volcanoes and seepage systems potentially provide valuable information on the evolution of seepage dynamics ancient seepage systems in outcrops allow for the observation of expulsion features which are otherwise commonly beyond seismic resolution in the maiella hydrocarbon seep area the evolution of fluid migration through the sedimentary column during the messinian salinity crisis generated distinctive seep plumbing features geological responses and geochemical signatures in the brecciated limestones unit the fluid migration pathways evolved from funnel shaped feeder channels flow mobilized sediments into hydrofractured microbial carbonate buildups limestone buildups and finally into blow out micropipes in the host sediment patchy limestones as overpressure dissipated through the plumbing system the flow mobilized sediments 13c down to 24 5 pdb 1 correspond to the highest flow rates in the whole area whereas the patchy limestones 13c down to 39 3 pdb 1 correspond to the slowest flow rates within the intrusive zone the limestone buildups show different degrees of hydrofracturing that reflect different flow rates 13c down to 27 5 pdb 1 the fluid transport mechanisms evolved from focused venting through neoformed feeder channels where sediments elutriated from depths were carried out the sediment prone response to fluid migration to high rate seepage triggering high hydrofracturation in the microbial buildups while the hydrocarbon rich fluids contemporaneously triggered authigenic precipitation the mineral prone response to fluid migration progressive upward and lateral flow deceleration resulted in gradually weaker hydrofracturing of the microbial buildups and finally only local cementation in the form of carbonate patches within the host sediments

a new crater near insight implications for seismic impact detectability on mars a new 1 5 m diameter impact crater was discovered on mars only 40 km from the insight lander context camera images constrained its formation between 21 february and 6 april 2019 follow up high resolution imaging science experiment images resolved the crater during this time period three seismic events were identified in insight data we derive expected seismic signal characteristics and use them to evaluate each of the seismic events however none of them can definitively be associated with this source atmospheric perturbations are generally expected to be generated during impacts however in this case no signal could be identified as related to the known impact using scaling relationships based on the terrestrial and lunar analogs and numerical modeling we predict the amplitude peak frequency and duration of the seismic signal that would have emanated from this impact the predicted amplitude falls near the lowest levels of the measured seismometer noise for the predicted frequency hence it is not surprising this impact event was not positively identified in the seismic data finding this crater was a lucky event as its formation this close to insight has a probability of only 0 2 and the odds of capturing it in before and after images are extremely low we revisit impact seismic discriminators in light of real experience with a seismometer on the martian surface using measured noise of the instrument we revise our previous prediction of seismic impact detections downward from a few to tens to just 2 per earth year still with an order of magnitude uncertainty

u th systematics and ages of authigenic carbonates from hydrate ridge cascadia margin recorders of fluid flow variations uranium u concentrations and activity ratios 234u of authigenic carbonates are sensitive recorders of different fluid compositions at submarine seeps of hydrocarbon rich fluids cold seeps at hydrate ridge off the coast of oregon usa the low u concentrations mean 1 3 0 4 g g and high 234u values 165 317 of gas hydrate carbonates reflect the influence of sedimentary pore water indicating that these carbonates were formed under reducing conditions below or at the seafloor their 230th 234u ages span a time interval from 0 8 to 6 4 ka and cluster around 1 2 and 4 7 ka in contrast chemoherm carbonates precipitate from marine bottom water marked by relatively high u concentrations mean 5 2 0 8 g g and a mean 234u ratio of 166 3 their u isotopes reflect the 234u ratios of the bottom water being enriched in 234u relative to normal seawater simple mass balance calculations based on u concentrations and their corresponding 234u ratios reveal a contribution of about 11 of sedimentary pore water to the bottom water from the u pore water flux and the reconstructed u pore water concentration a mean flow rate of about 147 68 cm a can be estimated 230th 234u ages of chemoherm carbonates range from 7 3 to 267 6 ka 230th 234u ages of two chemoherms alvin and se knoll chemoherm correspond to time intervals of low sealevel stands in marine isotope stages mis 2 4 5 6 7 and 8 this observation indicates that fluid flow at cold seep sites sensitively reflects pressure changes of the hydraulic head in the sediments the 18o pdb ratios of the chemoherm carbonates support the hypothesis of precipitation during glacial times deviations of the chemoherm 18o values from the marine 18o record can be interpreted as to reflect temporally and spatially varying bottom water and or vent fluid temperatures during carbonate precipitation between 2 6 and 8 6 c

seismic codas on the earth and the moon a comparison the phenomenon of the seismic coda which is composed of seismic energy delayed by scattering is seen on both the earth and the moon on the moon the scattered coda is very large relative to body wave arrivals with a delay of the time of maximum energy whereas on earth scattered codas are relatively small and show no delay of the energy maximum in both cases the form of the coda is controlled by three distance scales the mean free path l which is the average distance seismic energy travels before it is scattered the attenuation distance x which is the average distance seismic energy travels before it is attenuated and the source receiver distance r two coda models are discussed based on these parameters a strong scattering diffusion model and a weak scattering single scattering model a discussion of the diffusion scattering model indicates that if x l 1 diffusion scattering is an appropriate model but if x l 1 single scattering is the appropriate model within the appropriate range of r a survey of the literature indicates that for the frequency range 0 5 10 hz diffusion scattering is important in lunar codas but for the frequency range 1 25 hz single scattering is important in terrestrial codas another important effect of attenuation is the elimination of scattering paths much longer than x on the moon this means that seismic energy in the coda can only propagate directly in the near surface strong scattering zone between surface sources and the seismometer for source seismometer separations of the order of x l 12 otherwise scattering is limited to regions near the source and the receiver on earth this effect probably prevents multiple scattering

ch 4 consuming microorganisms and the formation of carbonate crusts at cold seeps to understand the role played by microorganisms in the formation of cold seep carbonates we conducted an integrated microbial mineralogical and organic geochemical study of methane related authigenic carbonate crusts formed on eastern mediterranean mud volcanoes we show that supersaturation with respect to carbonate minerals is induced by microbial anaerobic oxidation of methane combined lipid biomarker analysis and 16s rrna gene surveys identified a highly diversified methane consuming archaeal community possibly comprising novel species implying that the anaerobic oxidation of methane is phylogenetically widespread and directly implicating these organisms in the process of crust precipitation moreover pore water sulphate gradients produced by co occurring methane based sulphate reduction exert the main control on aragonite versus magnesian calcite precipitation we propose that this may be the dominant mode of carbonate crust formation at cold seeps world wide in agreement with aquatic chemistry predictions and explaining carbonate mineralogy

methane derived authigenic carbonates formed by subduction induced pore water expulsion along the oregon washington margin authigenic magnesian calcite dolomite and aragonite are precipitated in the uppermost terrigenous sediments of the washington oregon accretionary prism by subduction induced dewatering these distinctive carbonates are methane derived and occur at sites of concentrated pore water expulsion unique biologic communities that subsist at least indirectly on methane suess et al 1985 are also found at some of these sites the methane which is dominantly biogenic is carried to the uppermost sediments of the prism by fluids and is oxidized by sulfate reducers before being incorporated into a carbonate cement carbonate precipitation occurs below the oxic layer probably no deeper than several centimetres to a few metres below the seabed cementation may be induced by three factors 1 increased carbonate alkalinity resulting from microbial sulfate reduction 2 decreased co 2 solubility resulting from a pressure decrease when the pore water escapes the prism and or 3 the addition of ca 2 and mg 2 ions from sea water near the sediment water interface the convergent margin setting engenders precipitation of authigenic carbonates in several ways compressive stresses induce anomalously rapid compaction and dewatering rates and they may cause overpressuring in migrating pore water thereby delaying precipitation of carbonates until pressure is released near the sediment water interface structural deformation of the accretionary prism creates pathways such as fault zones secondary fracture porosity and dipping permeable layers often exposed by mass movement for efficient advection and expulsion of methane enriched pore water these characteristic conditions which lead to the precipitation of methane derived carbonates may be found at other convergent margins

distribution and height of methane bubble plumes on the cascadia margin characterized by acoustic imaging submersible investigations of the cascadia accretionary complex have identified localized venting of methane gas bubbles in association with gas hydrate occurrence acoustic profiles of these bubble plumes in the water column in the vicinity of hydrate ridge offshore oregon provide new constraints on the spatial distribution of these gas vents and the fate of the gas in the water column the gas vent sites remained active over the span of two years but varied dramatically on time scales of a few hours all plumes emanated from local topographic highs near the summit of ridge structures the acoustic images of the bubble plumes in the water column disappear at water depths between 500 to 460 m independent of the seafloor depth this coincides with the predicted depth of the gas hydrate stability boundary of 510 to 490 m suggesting that the presence of a hydrate skin on the bubble surface prevents them from rapid dissolution the upper limit of the acoustic bubble plumes at 460 m suggests that dissolution of the residual bubbles is relatively rapid above the hydrate stability zone

effects of lateral variations in megaregolith thickness on predicted lunar seismic signals we use a modified phonon synthetic seismogram method to investigate the effects of laterally varying megaregolith thickness on the propagation of seismic energy and on the resulting seismic signals recorded at various epicentral distances from the source we show that receivers located in large impact structures with thin crust and thinner megaregolith can record seismic signals that are less affected by high levels of scattering in particular receivers located away from the basin edge by a distance greater than or equal to the thickness of the surrounding megaregolith can record seismograms in which secondary arrivals containing important information about interior structure can be more readily identified seismic sources located beneath the near surface scattering layer such as deep lunar quakes are also advantageous because the resulting seismograms are less affected by high levels of scattering than those from sources within the scattering layer or surface impacts

the global short period wavefield modelled with a monte carlo seismic phonon method summary at high frequencies 1 hz much of the seismic energy arriving at teleseismic distances is not found in the main phases e g p pp s etc but is contained in the extended coda that follows these arrivals this coda results from scattering off small scale velocity and density perturbations within the crust and mantle and contains valuable information regarding the depth dependence and strength of this heterogeneity as well as the relative importance of intrinsic versus scattering attenuation most analyses of seismic coda to date have concentrated on s wave coda generated from lithospheric scattering for events recorded at local and regional distances here we examine the globally averaged vertical component 1 hz wavefield 10 range for earthquakes recorded in the iris farm archive from 1990 to 1999 we apply an envelopefunction stacking technique to image the average time distance behavior of the wavefield for both shallow 50 km and deep 500 km earthquakes unlike regional records our images are dominated by p and p coda owing to the large effect of attenuation on pp and s at high frequencies modelling our results is complicated by the need to include a variety of ray paths the likely contributions of multiple scattering and the possible importance of p to s and s to p scattering we adopt a stochastic particle based approach in which millions of seismic phonons are randomly sprayed from the source and tracked through the earth each phonon represents an energy packet that travels along the appropriate ray path until it is affected by a discontinuity or a scatterer discontinuities are modelled by treating the energy normalized reflection and transmission coefficients as probabilities scattering probabilities and scattering angles are computed in a similar fashion assuming random velocity and density perturbations characterized by an exponential autocorrelation function intrinsic attenuation is included by reducing the energy contained in each particle as an appropriate function of traveltime we find that most scattering occurs in the lithosphere and upper mantle as previous results have indicated but that some lower mantle scattering is likely also required a model with 3 to 4 per cent rms velocity heterogeneity at 4 km scale length in the upper mantle and 0 5 per cent rms velocity heterogeneity at 8 km scale length in the lower mantle with intrinsic attenuation of q 450 above 200 km depth and q 2500 below 200 km provides a reasonable fit to both the shallow and deep earthquake observations although many trade offs exist between the scale length depth extent and strength of the heterogeneity

variable methane fluxes in shallow marine systems over geologic time abstract carbon cycling is an important but poorly understood process on passive continental margins in this study we use the ionic and stable isotopic composition of interstitial waters and the petrology mineralogy and stable isotopic composition of authigenic carbonates collected from ocean drilling program odp leg 174a sites 1071 and 1072 to constrain the origin of the carbonates and the evolution of methane on the outer new jersey shelf the pore fluids of the new jersey continental shelf are characterized by 1 a fresh brackish water plume and 2 organic matter degradation reactions which proceed through sulfate reduction however only minor methanogenesis occurs the oxygen isotopic composition of the pore fluids supports a meteoric origin of the low salinity fluids authigenic carbonates are found in nodules thin 1 cm layers and carbonate cemented pavements siderite is the most common authigenic carbonate followed by dolomite and calcite the oxygen isotopic composition of the authigenic carbonates i e 1 3 6 5 peedee belemnite pdb indicates an origin in marine pore fluids the carbon isotopic composition of dolomite cements range from 16 4 to 8 8 pdb consistent with formation within the zone of sulfate reduction siderite 13c values show a greater range 17 67 16 4 but are largely positive mean 2 8 and are interpreted to have formed throughout the zone of methanogenesis in contrast calcite 13c values are highly negative as low as 41 7 and must have formed from waters with a large component of dissolved inorganic carbon derived from methane oxidation pore water data show that despite complete sulfate reduction methanogenesis appears not to be an important process presently occurring in the upper 400 m of the outer new jersey shelf in contrast the carbon isotopic composition of the siderites and calcites document an active methanogenic zone during their formation the methane may have been either oxidized or vented from shelf sediments perhaps during sea level fluctuations if this unaccounted and variable methane flux is an areally important process during neogene sea level fluctuations then it likely plays an important role in long term carbon cycling on passive continental margins

methane derived carbonate conduits from the late aptian of salinac marne bleues vocontian basin france petrology and biosignatures abstract peculiar carbonate bodies occur in distinct marl layers of the marnes bleues formation aptian albian vocontian basin southern france the carbonate conduits exhibit pipe or sausage like forms and a central channel their sizes range between 30 and 60 cm in length and 5 10 cm in diameter the conduit carbonates consist of automicrite authigenically formed within the sediment millimeter sized aggregates of framboidal pyrite are abundant within the conduit automicrites probably representing former colonies of sulfate reducing bacteria the central channel reflects former pathways of reduced fluids in the carbonate conduit ni enrichments at the margins of the central cavity are may be due to the activity of methane related metabolism as ni is an important bio element for respective microbes light stable carbon isotope ratios of the conduit automicrites 25 86 to 23 10 vpdb point to carbonate precipitation linked to anaerobic oxidation of methane aom while less depleted stable carbon isotope ratios of microspar in marginal zones of the central opening 8 96 vpdb are in line with microbial sulfate reduction a methane related origin of the conduit carbonates is confirmed by the presence of authigenic lipid biomarkers tentatively sourced by archaea most of which are characterized by strong 13 c depletions 13 c values down to 104 the presence of organically bound sulfur is well in line with microbial sulfate reduction isorenieratane potentially point to the presence of brown pigmented green sulfur bacteria the methane was probably sourced by older oae black shales which are known to contain isotopically 13 c heavy biomarkers of archaea as reported elsewhere

expected seismicity and the seismic noise environment of europa seismic data will be a vital geophysical constraint on internal structure of europa if we land instruments on the surface quantifying expected seismic activity on europa both in terms of large recognizable signals and ambient background noise is important for understanding dynamics of the moon as well as interpretation of potential future data seismic energy sources will likely include cracking in the ice shell and turbulent motion in the oceans we define a range of models of seismic activity in europa s ice shell by assuming each model follows a gutenberg richter relationship with varying parameters a range of cumulative seismic moment release between 10 16 and 10 18 nm yr is defined by scaling tidal dissipation energy to tectonic events on the earth s moon random catalogs are generated and used to create synthetic continuous noise records through numerical wave propagation in thermodynamically self consistent models of the interior structure of europa spectral characteristics of the noise are calculated by determining probabilistic power spectral densities of the synthetic records while the range of seismicity models predicts noise levels that vary by 80 db we show that most noise estimates are below the self noise floor of high frequency geophones but may be recorded by more sensitive instruments the largest expected signals exceed background noise by 50 db noise records may allow for constraints on interior structure through autocorrelation models of seismic noise generated by pressure variations at the base of the ice shell due to turbulent motions in the subsurface ocean may also generate observable seismic noise

temporal and spatial evolution of a gas hydrate bearing accretionary ridge on the oregon continental margin a seismic reflection survey on the oregon continental margin conducted in 1989 indicates the widespread presence of gas hydrate beneath the middle and lower slope of this accretionary margin the seismic signature of gas hydrate a bottom simulating reflector bsr with negative polarity that locally cuts across stratigraphic horizons is especially well developed beneath hydrate ridge this anomalously shallow accretionary ridge was drilled during ocean drilling program leg 146 to study fluid venting in this paper we focus on the seismic data from the southern part of hydrate ridge where little evidence of active venting has previously been reported but where the seismic data indicate a complicated subsurface plumbing system apparent disruptions of the bsr beneath the western ridge flank suggest dissociation of gas hydrate in response to slumping a double bsr beneath the southern crest suggests hydrate destabilization in response to tectonic uplift and folding on the basis of these and other observations we propose a qualitative model for the evolution of a hydrate bearing ridge in an active accretionary complex in which gas hydrate initially stabilizes the sea floor permitting construction of large ridges that are then eaten away by slumps along their margins the north to south variation in sea floor venting and subsurface seismic structure along hydrate ridge may reflect different stages in the temporal evolution of one of these ridges

landward vergence and oblique structural trends in the oregon margin accretionary prism implications and effect on fluid flow abstract the central oregon margin spans a regional transition in accretionary structures from seaward verging in the south to landward verging in the north new multichannel seismic mcs data image both landward and seaward vergent provinces along the central and northern oregon margin landward vergence is characterized by a deep decollement with deformation distributed across a broad lower continental slope in a coherent structural style in the landward vergent area virtually all 4 km of incoming trench sediments overthrust the preceding thrust sheet forming fault bend folds and a distinctive ridge trough morphology this style of landward vergence is not explained by existing models in contrast seaward vergence correlates with a shallower decollement approximately 1 4 km above the oceanic crust and a more intense style of deformation within a narrower slope initial thickening of the trench sediments occurs across a well developed protothrust zone the frontal thrust forms a ramp anticline that is cut by a prominent backthrust previously observed seafloor vent sites in both regions correlate with thrusts that exhibit high amplitude reversed polarity reflections suggestive of enhanced porosity along the faults potential fluid sources and migration paths are strongly influenced by changes in the level of the decollement and vergence along the margin abrupt changes in structural style occur both along strike and updip and are bounded by two sets of oblique slip faults three nw striking left lateral faults are imaged in both mcs and seabeam data plunging anticlines developed along the nw striking faults are venting fluids and were previously interpreted as mud volcanoes the deformation front is locally disrupted where these faults intersect the prism but they appear to have limited influence on the structural evolution of the prism in contrast the ne striking right lateral faults are confined to the deforming sediments of the upper plate these faults interact with the thrusts within the prism forming a rhomboidal pattern of three dimensional deformation

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

shallow seismic activity and young thrust faults on the moon the discovery of young thrust faults on the moon is evidence of recent tectonic activity but how recent is unknown seismometers at four apollo landing sites recorded 28 shallow moonquakes between 1969 and 1977 some of these shallow quakes could be associated with activity on the young faults however the epicentre locations of these quakes are poorly constrained here we present more accurate estimates of the epicentre locations based on an algorithm for sparse seismic networks we found that the epicentres of eight near surface quakes fall within 30 km of a fault scarp the distance of the expected strong ground shaking from an analysis of the timing of these eight events we found that six occurred when the moon was less than 15 000 km from the apogee distance analytical modelling of tidal forces that contribute to the current lunar stress state indicates that seven near apogee events within 60 km of a fault scarp occur at or near the time of peak compressional stresses when fault slip events are most likely we conclude that the proximity of moonquakes to the young thrust faults together with evidence of regolith disturbance and boulder movements on and near the fault scarps strongly suggest the moon is tectonically active shallow moonquakes detected at four apollo landing sites between 1969 and 1977 occurred during maximum stress and in close proximity to young faults suggesting that the moon is tectonically active according to reanalyses of the seismic data and tidal force modelling

barrier island arcs along abandoned mississippi river deltas abstract generation of transgressive barrier island arcs along the mississippi river delta plain and preservation of barrier shoreline facies in their retreat paths on the inner shelf is controlled by 1 shoreface translation 2 age of the transgression and 3 the thickness of the barrier island arc sediment package barrier island arcs experience an average relative sea level rise of 0 50 1 00 cm yr 1 and shoreface retreat rates range from 5 15 m yr 1 young barrier island arc sediment packages isles dernieres are thin and have experienced limited landward retreat of the shoreface older barrier island arcs chandeleur islands are thicker and have experienced significant landward movement of the shoreface because of the greater time available for retreat if the transgressed barrier shoreline sediment package lies above the advancing ravinement surface the entire sequence is truncated a thin reworked sand sheet marks the shoreface retreat path the base of the transgressive sediment package can lie below the ravinement surface in older barrier shorelines in this setting the superstructure of the barrier shoreline is truncated leaving the basal portion of the transgressive sequence preserved on the inner shelf a variety of transgressive stratigraphic sequences from sand sheets to truncated barrier islands to sand filled tidal inlet scars have been identified by high resolution seismic profiling across the shoreface retreat paths of mississippi delta barrier island arcs one of these examples the isles dernieres represents a recently detached barrier island arc in the early stages of transgression an older example the chandeleur islands represents a barrier island arc experiencing long term shoreface retreat this paper describes the stratigraphic character and preserved transgressive facies for the isles dernieres and chandeleur islands

fluid flow in accretionary prisms evidence for focused time variable discharge accretionary prisms are wedges of saturated sediment that are subject to intense deformation as a result of lithosphere convergence compressive stress and rapid burial of the accreted deposits result in sediment compaction and mineral dehydration these latter processes in conjunction with fermentation or thermal maturation of entrained organic matter yield hydrocarbon bearing pore fluids that are expelled from the prism regional fluxes of heat and a number of dissolved chemical species most notably carbon are controlled by the advective expulsion of the pore waters numerical modeling observation and monitoring of flow patterns and rates and recent in situ hydrogeological tests quantify the conditions that control rates of fluid flow dispersed intergranular flow 10 8 to 10 11 m s controlled by the vertical permeability of the prism 10 14 to 10 20 m is limited by low permeability lithologies and seems not to vary much from margin to margin focused flow 10 1 to 10 8 m s above the decollement is controlled by fault zones or sedimentary intrusions diapiric structures at low fluid pressures fault zone permeability may be similar to that of adjacent wall rock but as fluid pressure increases from hydrostatic 0 to near lithostatic levels 1 0 fault zones dilate and fracture permeability increases by 2 4 orders of magnitude 10 10 to 10 16 m similarly mud volcanoes and diapirs provide high permeability fluid conduits to the sediment water interface as a result faults and intrusions become primary flow paths and support surface vents at which syntectonic deposits carbonate and gas hydrates accumulate and chemosynthetic organisms cluster models of thermal and chemical anomalies and epigenetic deposits indicate that flow is temporally variable that conclusion has been quantified by extended 1 10 months seafloor and borehole experiments that measured temperature anomalies associated with flow events on the cascadia prism flow estimated velocity 3 10 5 m s 950 m yr confined to a thrust fault that cuts upward through the prism has brought thermogenic hydrocarbons from depths 1 5 km to the surface within the last 400 years

modeling seismic energy propagation in highly scattering environments meteoroid impacts over millions to billions of years can produce a highly fractured and heterogeneous megaregolith layer on planetary bodies such as the moon that lack effective surface recycling mechanisms the energy from seismic events on these bodies undergoes scattering in the fractured layer s and generates extensive coda wave trains that follow major seismic wave arrivals the decay properties of these codas are affected by the planetary body s interior structure to understand the propagation of seismic waves in such media we model the transmission of seismic energy in highly scattering environments using an adapted phonon method in this monte carlo simulation approach we track a large number of seismic wavelets as they leave a source and we record the resulting ground deformation each time a wavelet reaches a surface receiver our method provides the first numerical global modeling of 3 d scattering with user defined power law distributions of scatterer length scales and frequency dependent intrinsic attenuation under the assumption of 1 d background velocity models we model synthetic signals for simple but highly scattering interior models and vary the model parameters independently to assess their individual effects on the coda results show that the magnitude of the decay times is most affected by the background velocity model in particular the presence of shallow low velocity layers the event source depth and the intrinsic attenuation level the decay times are also controlled to a lesser extent by the size frequency distribution of scatterers the thickness of the scattering layer and the impedance contrast at the scatterers

constraints on the shallow elastic and anelastic structure of mars from insight seismic data mars s seismic activity and noise have been monitored since january 2019 by the seismometer of the insight interior exploration using seismic investigations geodesy and heat transport lander at night mars is extremely quiet seismic noise is about 500 times lower than earth s microseismic noise at periods between 4 s and 30 s the recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground transferred wind generated lander noise here we constrain properties of the crust beneath insight using signals from atmospheric vortices and from the hammering of insight s heat flow and physical properties hp3 instrument as well as the three largest marsquakes detected as of september 2019 from receiver function analysis we infer that the uppermost 8 11 km of the crust is highly altered and or fractured we measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the moon which suggests that the crust contains small amounts of volatiles the crust beneath the insight lander on mars is altered or fractured to 8 11 km depth and may bear volatiles according to an analysis of seismic noise and wave scattering recorded by insight s seismometer

implications of carbon flux from the cascadia accretionary prism results from long term in situ measurements at odp site 892b a 403 day in situ field experiment at ocean drilling program site 892b sought to quantify the flux of methane along a fluid active fault and to experimentally determine rates of methane hydrate and authigenic carbonate deposition associated with fluid expulsion from the borehole an instrument package was deployed that osmotically sampled fluid measured borehole pressure and flow rates and contained reaction chambers in which deposition of gas hydrates and carbonates was anticipated and from which microbial communities might be extracted flow is highly variable in the three phase water methane system that exists at site 892b flow rates fluctuate over two orders of magnitude in response to tidally induced pressure variations and gas hydrate formation and dissociation hydrate formation began 45 days into the experiment and reduced the initial flow 2 l day to 20 ml day unexpectedly the hydrate destabilized after about 125 days tidally induced flow reversals are common 25 of time in this setting characterized by overpressured pore waters these reversals pump sulfate rich bottom water into near surface sediments where archaea anaerobically oxidize ch4 and induce carbonate precipitation at the sediment water interface authigenic carbonates are undergoing dissolution methanotrophs dominated the microbial community where fluid is discharged to ambient seawater all expelled methane is apparently oxidized in the water column

iron oxyhydroxide and sulphide mineralization in hydrocarbon seep related carbonate submarine chimneys gulf of cadiz sw iberian peninsula this paper aims to investigate the iron mineralization hosted in the submarine hydrocarbon seep related carbonate chimneys from the gulf of cadiz continental slope sw iberia chimneys are made of a general fine groundmass of major fe rich dolomite ankerite and calcite small grains of quartz and phyllosilicates and some foraminifer tests and ostracod shells primary porosity is frequently generated inside foraminifer chambers and ostracod shells and is filled with closely packed microcrystals of iron oxyhydroxide and sulphide minerals forming framboids some extremely peculiar multiframboidal textures are also detected corresponding to microcrystal groups spherical framboids and euhedral crystals without framboidal texture the mineralogy observed is mainly goethite pyrite pseudomorphs traces of tiny grains of pyrite were also observed cubic octahedral and pyritohedral are the habits observed in both minerals chemical analyses of framboids and euhedral crystals display high often erratic amounts of as co ni and mo in oxyhydroxides and mo pb v and co in sulphides versus almost always negligible concentrations of cu and zn a textural geochemical and mineralogical evolution is proposed to explain the coexistence of different morphologies in the multiframboidal texture a growth and aggregation of microcrystals as typical framboidal type mineralogical associations b development of euhedral habits c coalescence and homogenization of the microcrystal into large size euhedral to anhedral crystals and d formation of euhedral crystals or polycrystalline masses with complete loss of framboidal texture along this process an increase of the concentration of fe s mn and ti linked to a decrease in mg si al as p ca and v was observed the study of the iron mineralization in the gulf of cadiz is a first and can give clues to understand the complex geobiological interactions in this and other similar extreme hydrocarbon bearing submarine ecosystems

contrasting hydrogeologic regimes along strike slip and thrust faults in the oregon convergent margin evidence from the chemistry of syntectonic carbonate cements and veins samples of carbonate cemented sedimentary rocks were collected during 11 alvin dives in two regions along the cascadia margin a northern strike slip fault zone and a southern thrust fault zone second ridge we characterized 35 samples petrographically and chemically northern area samples are dominantly sandstones second ridge samples are all mudstones vugs and high percentages of carbonate cement in the mudstones suggest that these rocks were never deeply buried the abundance of veins and brecciation in samples from both regions attests to their proximity to faults northern area cements are dominantly calcite or magnesian calcite whereas second ridge cements generally are more dolomitic oxygen and sr isotopic values of carbonate cements indicate the involvement of two very different fluid reservoirs during cementation one reservoir generally has low 18 o very low 13 c and high 87 sr 86 sr ratios but the other has high 18 o moderately negative 13 c and 87 sr 86 sr ratios lower than modern seawater values in the northern area diagenetic carbonates are subdivided into two populations of coupled oxygen and carbon isotopic values population i has 18 o pdb values of 3 to 5 and 13 c pdb values of 55 to 45 population ii has 18 o values of 13 to 4 and 13 c values of 25 to 1 such common low 18 o values in carbonate cements have not been observed at any other accretionary wedge 87 sr 86 sr ratios of northern area samples range from 0 7128 to 0 7088 oxygen and sr isotopic values show a correlation between increasing 87 sr 86 sr ratios and decreasing 18 o values oxygen and carbon isotopic values of most diagenetic carbonates from the second ridge range from 3 to 10 and 55 to 38 respectively enrichments of 18 o probably result from a combination of dolomitic mineralogy cold bottom water temperatures and the presence of decomposing gas hydrate in the subsurface 87 sr 86 sr ratios of carbonates from the second ridge range from 0 7086 to 0 7091 the geochemical signatures of diagenetic cements from the northern area suggest that fluids were derived from greater than 2 km depth perhaps from the decollement prominent gullies throughout the northern area are probably underlain by strike slip faults that provide conduits for upward fluid migration cements at the second ridge precipitated from shallowly derived fluids the difference in fluid source depth is related to proximity to the fluid conduits and different orientations of minimum principal stress and resultant hydrofractures in the two fault regimes

u th dating and post depositional alteration of a cold seep carbonate chimney from the campos basin offshore brazil abstract dating authigenic cold seep carbonates allows determining the timing of active seepage of hydrocarbon rich fluids at continental margins and ultimately the detection of the geological factors affecting it u th dating has been selected in this study the method having been successfully used before however incorporation of initial thorium in substantial amounts of detrital material due to the precipitation of carbonates within the seabed and post depositional alteration potentially pose a major problem violating the basic assumptions of the method here we report results from several samples from the campos basin off the coast of brazil they are unusual in their high 13 c values mean of 10 0 vpdb high detrital contents and being dominantly dolomite elevated 230 th 238 u activity ratios indicate that most of the carbonates lost uranium during diagenesis isochrones are obtained from the unaffected samples yielding an age of 140 4 3 1 ka vertical growth of the chimney must have been short and rapid since results from the top and bottom parts of the chimney concur within analytical uncertainties furthermore profiles of u th radioisotope specific activity 234 u and 232 th specific activity on two quarter slices of a carbonate chimney reveal the occurrence of three distinct diagenetic processes u loss u exchange with seawater and th gain

broadening of seismogram envelopes in the randomly inhomogeneous lithosphere based on the parabolic approximation southeastern honshu japan analyzing horizontal component seismograms of small earthquakes with intermediate hypocentral distances in southeastern honshu japan we found that time widths of seismogram envelopes around direct s waves are much longer than source duration times estimated from their magnitudes the time lags of the maximum amplitude and the half maximum after the peak were measured from the onset of the direct s wave arrival from band pass filtered seismograms from 2 to 32 hz even though there is considerable scatter both the time lags are found to increase with increasing hypocentral distance up to 305 km we hypothesize that pulse shape broadens and the maximum amplitude is reduced after propagating through the random structure of the lithosphere the parabolic approximation theoretically predicts that the long wavelength component of velocity inhomogeneities compared with the wavelength of seismic waves produces diffraction fluctuations and makes seismogram envelopes broaden with increasing travel distance in the saturated regime supposing a gaussian autocorrelation function for the randomness and an empirical frequency dependent attenuation we propose a formula for the temporal change in the power spectral density of seismic waves applying this formula to the observed data we statistically evaluated the scale of random inhomogeneities the mean square fractional velocity fluctuation was estimated to be 10 3 times the correlation distance a in kilometers

radiometric dating of submarine hydrocarbon seeps in the gulf of mexico massive abiotic carbonates and calcareous shells of the chemosynthetic mytilid bathymodiolus sp containing a detailed history of hydrocarbon seepage were investigated using radiocarbon and u series isotopes stable carbon isotopes and 87 sr 86 sr ratios were also determined in order to provide insights on the carbon source and the nature of the hydrocarbon rich fluids samples from five seepage sites on the northern gulf of mexico sea floor overlying subsurface salt diapirs and encompassing depths from 125 to 2000 m were selected as representative of the spectrum of active and extinct seeps examined from submersible dives in general paired 14 c and 230 th dates of carbonate buildups consisting of aragonite high mg calcite and dolomite mineralogies are highly discordant the cause of the discordance established on the basis of paired 14 c and 13 c values 14 c 898 to 992 13 c 9 5 to 53 3 for n 27 lies with the impairment of the radiocarbon dates resulting from dilution of the 14 c pool with fossil hydrocarbon derived carbon the validity of the ionium dates based on u rich 2 4 7 6 ppm samples is demonstrated by the concordance between 234 u 238 u and 230 th 234 u evolution in time and by the 234 u 238 u o activity ratios that are generally within the range of sea water value of 1 14 0 04 2 sigma some dolomite rich samples are exceptional because their 234 u 238 u o ratios are significantly higher 1 22 1 38 than sea water suggesting deposition from anoxic pore waters where the soluble u reached anomalous 234 u 238 u ratios the formation of the carbonates from sea water derived fluids rather than from formation fluids advecting from deep aquifers is supported by the 87 sr 86 sr composition of the samples mean 0 709145 19 10 6 n 14 that compares well with modern nonseep marine carbonates and the ambient gulf of mexico sea water 0 709171 8 10 6 calcareous shells the 13 c values of which indicate a carbon source in sea water 13 c 4 3 to 1 1 yield valid radiocarbon ages and show fair concordancy between their radiocarbon and ionium dates isotope migration attested by the observed u uptake in the fossil shells is likely to affect the accuracy of their ionium dates radiometric ages from extinct and senescent seep sites at upper bathyal depths indicate that hydrocarbon seepage occurred there during late pleistocene time 195 13 ka ages derived from nascent seep sites at mid bathyal and abyssal depths 12 3 0 0 ka indicate that currently vigorous seepage was initiated at the end of the last deglaciation these radiometric ages most likely reflect the time of sedimentary loading and associated salt diapirism that activated the fault conduits to the sea floor

miocene shallow marine cold seep carbonate in fold and thrust western foothills sw taiwan a mound shaped authigenic carbonate buildup 50 m wide and 5 m high occurred in the middle part of the late miocene shallow marine succession the hunghuatzu formation exposed along the nantzuhsien river sw taiwan the carbonate concretions are classified into four types based on morphology which appeared to develop in upward sequence with vague boundaries 1 flat pipe shaped nodules highly dolomitic small pipes or nodules subparallel to the host strata 2 bulb shaped nodules discrete or combined small mesoclots with subspherical to irregular shapes 3 mushroom shaped concretions large mushroom like or irregular shaped blocks with chimney or vent structures and 4 carbonated layers with sedimentary structures these concretions are mainly composed of dolomite micrites quartz feldspar muscovite and clay minerals ubiquitously interweaved with blackish brown colored low magnesium calcite lmc veins low delta c 13 vpdb values 51 8 parts per thousand to 29 8 parts per thousand of all types of the carbonates reveal that the carbonates were mainly derived from anaerobic oxidation of hydrocarbons many samples are also o 18 depleted delta o 18 vpdb 11 5 parts per thousand to 1 00 parts per thousand due to the mixture with isotopically light lmc veins likely precipitated from meteoric waters there are numerous chemosymbiotic bivalve fossils genus monitilora diameter 3 4 cm in growth position just above the carbonate buildup according to the geological and isotopic signatures the hunghuatzu carbonates are related to a cold seep pseudobioherm which formed in a very shallow marine environment like tidal flat in a passive margin setting exposures of the hunghuatzu pseudobioherm may provide clues for tracking and comparing the evolution history of gas reservoir systems and hints of active tectonics of the sw taiwan region c 2012 elsevier ltd all rights reserved

a search for clustering among the meteoroid impacts detected by the apollo lunar seismic network abstract we examined temporal clustering of meteoroid impacts detected by the apollo lunar seismic network and found a distinct difference between small meteoroids masses smaller than about 1 kg and large meteoroids masses larger than about 1 kg small meteoroids show strong clustering many of which are identified with showers known from terrestrial meteor studies in contrast little clustering is found for large meteoroids suggesting that they represent meteoroids of type and origin different from those of the small meteoroids overall 28 of the small events and 15 of the large events occur as clusters the small meteoroids appear to be mostly cometary while the large meteoroids may be derived from near earth asteroids and short period comets two swarms of large meteoroids detected in june 1975 and january 1977 possibly contain high density meteoritic objects and thus may represent meteorite streams

pore fluid constraints on the temperature and oxygen isotopic composition of the glacial ocean pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical atlantic indicate that the oxygen isotopic composition 18 o of seawater at this site during the last glacial maximum was 0 8 0 1 per mil higher than it is today combined with the 18 o change in benthic foraminifera from this region the elevated ratio indicates that the temperature of deep water in the tropical atlantic ocean was 4 c colder during the last glacial maximum extrapolation from this site to a global average suggests that the ice volume contribution to the change in 18 o of foraminifera is 1 0 per mil which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from barbados corals and terrestrial climate proxies

geological imprint of methane seepage on the seabed and biota of the convergent hikurangi margin new zealand box core and grab carbonate results abstract short box cores to 30 cm bsf and seafloor carbonate grab samples were acquired at mapped hydrocarbon seep sites 600 1200 m water depths during the 2007 rv sonne so191 cruise on the hikurangi margin offshore eastern north island new zealand to evaluate the influence of methane seepage on sedimentologic biotic mineralogic and stable isotopic attributes of seabed sediments sedimentary horizons in the box cores consist of siliciclastic silts and sands shell beds and nodular microcrystalline aragonite bands up to 15 cm thick the megafauna is dominated by infaunal to semi infaunal chemosymbiotic bivalves calyptogena lucinoma and acharax as well as associated worms and carnivorous and grazing gastropods burrows in silts some occupied by worms or juvenile acharax mainly have simple morphologies more typical of high energy nearshore settings than deep sea environments while a few are large and sparsely branched with wall scratch marks inferred to be of decapod crustacean origin the box core silts and nodular carbonate samples vary in toc content from 0 2 to 0 9 wt carbonate content from 4 to 78 and 13 c and 18 o values from 50 3 to 0 6 pdb and 0 77 to 3 2 pdb respectively low carbonate content silt samples have the most enriched 13 c values implying a seawater source for their pore water bicarbonate negative 13 c and positive 18 o values typify the nodular microcrystalline aragonite bands indicating formation during microbially mediated sulphate dependent anaerobic oxidation of methane aom in a cold near seafloor environment as is also supported by lipid biomarker data a clear isotopic mixing trend of decreasing 13 c and increasing 18 o and carbonate content in the fine seafloor grab carbonate samples show greater textural variability and are divided into two types fresh appearing grey to white blocks yield similar mineralogic isotopic and biomarker signatures to the nodular carbonate bands in the cores a largely seep related epifauna affiliated with these grab samples include chemosymbiotic bathymodiolin mussels siboglinid tube worms methanotrophic suberitid sponges and grazing limpets which in places are entombed within the carbonate by contrast some dark reddish to brown iron stained microcrystalline dolomitic slabs and tubular concretions support abundant non seep epifaunal encrusters from the surrounding deep sea indicative of long exposure on the seafloor distinct stable isotopic signatures of these exhumed dolostones 13 c c 20 pdb 18 o up to 7 pdb suggest derivation from an oxidised methane pool and pore fluid freshening by gas hydrate dissociation or from mobilized burial fluids that have undergone clay mineral dehydration

lateral variations of lunar crustal thickness from the apollo seismic data set seismic waves generated by meteoroid impacts have been detected by the apollo lunar seismic network these waves are sensitive to the crustal structure beneath both the seismic stations and the impact sites we use a markov chain monte carlo algorithm in order to invert for lateral variations of crustal thickness on the moon the inversion uses travel times of seismic waves originating from multiple meteoroid impact locations previous seismic investigations constrained the crustal thickness solely for apollo stations 12 14 and 16 whereas our approach enables to estimate the crustal thickness at locations far from the apollo network and to build a first crustal thickness map based on seismic data here we compare our crustal thickness estimates based on seismic travel times to those based on inversions of the topography and gravity field both methods turn out to be coherent in the sense that highland sites possess a thicker crust than mare sites

fluid venting in the eastern aleutian subduction zone fluid venting has been observed along 800 km of the alaska convergent margin the fluid venting sites are located near the deformation front are controlled by subsurface structures and exhibit the characteristics of cold seeps seen in other convergent margins the more important characteristics include 1 methane plumes in the lower water column with maxima above the seafloor which are traceable to the initial deformation ridges 2 prolific colonies of vent biota aligned and distributed in patches controlled by fault scarps over steepened folds or outcrops of bedding planes 3 calcium carbonate and barite precipitates at the surface and subsurface of vents and 4 carbon isotope evidence from tissue and skeletal hard parts of biota as well as from carbonate precipitates that vents expel either methane or sulfide dominated fluids a biogeochemical approach toward estimating fluid flow rates from individual vents based on oxygen flux measurements and vent fluid analysis indicates a mean value of 5 5 0 7 l m 2 d 1 for tectonics induced water flow wallmann et al 1997b a geophysical estimate of dewatering from the same area von huene et al 1997 based on sediment porosity reduction shows a fluid loss of 0 02 l m 2 d 1 for a 5 5 km wide converged segment near the deformation front our video guided surveys have documented vent biota across a minimum of 0 1 of the area of the convergent segment off kodiak island hence an average rate of 0 006 l m 2 d 1 is estimated from the biogeochemical approach the two estimates for tectonics induced water flow from the accretionary prism are in surprisingly good agreement

farside deep moonquakes and deep interior of the moon 1 an effort to find farside deep moonquakes among the recently discovered nests of deep moonquakes has identified about 30 nests that are likely to be on the farside although only a few of them are locatable with currently available data and those few provide little new information about the deep interior of the moon the inferred distribution of the rest of these nests indicates that either the region of the moon s deep interior within about 40 degrees from the antipode of the moon is nearly aseismic or alternatively the very deep interior of the moon severely attenuates or deflects seismic waves since this has important bearing on the origin and evolution of the moon future missions to the moon need to be oriented toward resolving this uncertainty some limited data favor the attenuation deflection hypotheses

hydrate ridge a natural laboratory for the study of microbial life fueled by methane from near surface gas hydrates hydrate ridge cascadia convergent margin is characterized by abundant methane hydrates at and below the seafloor active venting of fluids and gases chemosynthetic communities composed of giant sulfide oxidizing bacteria and clams authigenic carbonates and some of the highest methane oxidation rates ever found in the marine environment fluid flow rates vary over six orders of magnitude among closely spaced settings at the crest of hydrate ridge the distribution of benthic communities is mainly related to the sulfide flux from the subsurface sediments produced by anaerobic oxidation of methane aom even at high flux rates aom removes most of the methane seeping from the subsurface less than 50 of the methane escapes from bacterial mats from calyptogena fields 15 and from acharax beds no methane is emitted to the water column the precipitation of carbonate derived from aom is a significant and permanent carbon sink hence compared to the amount of gas hydrates and methane derived carbonates stored at the summit of hydrate ridge the emission of methane is relatively low due to the efficient filtering capacity of methanotrophic microbial communities this present review updates current knowledge of the geology of hydrate ridge summarizes recently published data on geomicrobiology and biogeochemistry and derives a local methane budget

formation of carbonate chimneys in the mediterranean sea linked to deep water oxygen depletion marine sediments at ocean margins vent substantial amounts of methane1 2 microbial oxidation of the methane released can trigger the precipitation of carbonate within sediments and support a broad diversity of seafloor ecosystems3 4 the factors controlling microbial activity and carbonate precipitation associated with the seepage of submarine fluid over geological time remain poorly constrained here we characterize the petrology and geochemistry of rocks sampled from metre size build ups of methane derived carbonate chimneys located at the amon mud volcano on the nile deep sea fan we find that these carbonates comprise porous structures composed of aggregated spherules of aragonite and closely resemble microbial carbonate reefs forming at present in the anoxic bottom waters of the black sea5 using u series dating we show that the amon carbonate build ups formed between 12 and 7 thousand years ago contemporaneous with the deposition of organic rich sediments in the eastern mediterranean the so called sapropel layer s1 we propose that the onset of deep water suboxic or anoxic conditions associated with sapropel formation resulted in the development of intense anaerobic microbial activity at the sea floor and thus the formation of carbonate chimneys

seismic energy release of the moon previous estimates of the seismic energy released by lunar events have not properly accounted for instrument bandwidth variations in corner frequency and the effects of intense scattering in this paper equations are developed that include all of these effects and give realistic estimates for source parameters these equations are applied to seismograms and displacement spectra from near surface and deep moonquakes to obtain m0 seismic moment s seismic energy release eyr seismic energy released annually by each lunar event class stress drop and mb body wave magnitude the calculations yield m0 3 1021 dyn cm s 2 1017 ergs 400 bars and mb 5 0 for the largest shallow moonquakes and m0 5 1020 dyn cm s 1 1013 ergs 0 1 bars and mb 3 0 for large deep events the average energy released annually is eyr 2 1017 erg yr and eyr 8 1013 erg yr by shallow and deep events respectively overall lunar energy release is dominated by the shallow events the energy released by the deep events may be accounted for by tidal dissipation and deep event stress drops are comparable to and smaller than the calculated tidal stresses a comparison of the above values with those observed terrestrially eyr 1025 ergs and with the energy available from heat flow and tidal dissipation emphasizes the importance of tectonic style e g plate tectonics in determining the characteristics of planetary seismicity

composition and origin of authigenic carbonates in the krishna godavari and mahanadi basins eastern continental margin of india abstract the mineralogical and stable isotopic composition of authigenic carbonates from the krishna godavari kg and mahanadi basin provide a deeper insight into the processes inducing carbonate formation in the sediments of the eastern continental margin of india in the bay of bengal authigenic carbonate cements micro nodules bioturbation casts and tubes from 12 core locations drilled during the indian national gas hydrate program nghp expedition 01 were investigated for this study three main processes responsible for authigenic carbonate precipitation are identified organoclastic sulfate reduction anaerobic oxidation of methane and methanogenesis evidence of vigorous methane seepage is indicated in carbonates recovered at sites 7 10 12 kg basin and 19 mahanadi basin these methane derived carbonates display typical paragenetic carbonate mineralogies aragonite high mg calcite with 15 mol mgco 3 ca rich dolomite two separate horizons of methane derived carbonates are correlated between 4 drill holes up to 16 km apart the upper horizon has been dated with 14 c 40 100 51 600 a bp 1950 and clearly indicates that methane seepage has been much more vigorous in the past possibly due to the effect of lower sea level on the gas hydrate stability zone across the margin

authigenic carbonates from seeps on the northern continental slope of the south china sea new insights into fluid sources and geochronology seep carbonates represent excellent archives of seepage activities near seafloors in order to provide insights on sources of seeping fluids stable carbon and oxygen isotopes and sr 87 sr 86 ratios were applied to seep carbonates from shenhu sw dongsha and ne dongsha on the northern continental slope of the south china sea u th dating was selected to constrain the time involved in carbonate formation and the potential driving force the delta c 13 values of the shenhu and ne dongsha carbonates vary from 52 3 parts per thousand to 32 6 parts per thousand v pdb indicating that biogenic methane is the primary carbon source at both locations the delta c 13 values of the sw dongsha carbonates are much higher ranging from 18 8 parts per thousand to 11 parts per thousand v pdb suggesting that thermogenic methane is the predominant carbon source in this region a relatively deep origin of thermogenic methane for the sw dongsha seeps is also supported by somewhat lower sr 87 sr 86 ratios of the samples from 0 709025 to 0 709097 the delta o 18 values of the shenhu and ne dongsha carbonates vary from 1 4 to 5 1 v pdb while the delta o 18 values of the sw dongsha carbonates range from 2 5 to 3 4 v pdb many samples from shenhu and ne dongsha demonstrate an o 18 enriched fluid source that most likely originated from waters released from the dissociation of locally abundant gas hydrate u th ages of the shenhu carbonates show a large range from 330 ka to 152 ka bp and the ne dongsha carbonates have ages from 77 ka to 63 ka bp interestingly u th ages of most samples are either within times of sea level lowstands or correspond to periods when the sea level was falling taken together our data suggest that in the south china sea gas hydrate dissociation during sea level lowstands or falling stages resulted from reduced hydrastastic pressures which in turn enhanced the seep activities and promoted the formation of authigenic carbonates close to the seafloor c 2013 elsevier ltd all rights reserved

cretaceous methane seep deposits from new zealand and their fauna abstract six cretaceous methane seep deposits are reported from the raukumara peninsula eastern north island new zealand dinoflagellate dating indicates a late albian to mid cenomanian age for three deposits from port awanui and a mid campanian age for two deposits from waipiro bay and for one from owhena stream the dominant petrographic fabric of the carbonates is detrital micrite and the numerous fenestrae and vugs are filled with various cements including two types of non detrital micrite and botryoidal and banded fibrous calcites these petrographic features in combination with negative 13c values of early diagenetic micrites as low as 29 2 vs v pdb and 13c depleted molecular fossils such as the archaeal biomarkers pentamethylicosane 97 vs v pdb and biphytane 99 and the bacterial biomarker anteiso c15 fatty acid 47 reveal that sulfate dependent anaerobic oxidation of methane aom induced the formation of these deposits the carbonates preserve a typical mollusk dominated late mesozoic deep water seep fauna including the large modiomorphid bivalve caspiconcha the lucinid bivalve ezolucina and limpets hokkaidoconchids and a large abyssochrysoid among the gastropods with close biogeographic relationships to north pacific seep faunas of cretaceous age in contrast to the general marine mollusk fauna of new zealand which shows a high degree of endemism in both the cenozoic and recent new zealand s cretaceous to present day seep faunas consist largely of taxa known from coeval seeps around the world thus while deep water seeps in new zealand were repeatedly or continuously colonized by members of the global seep fauna the general mollusk fauna of the new zealand region developed a considerable degree of endemism during this time

radiative transfer and diffusion of waves in a layered medium new insight into coda q summary this paper is devoted to the study of the seismic coda in inhomogeneous media exhibiting a discontinuity of physical properties at a given depth we focus on the problem of a layer overlying a half space and analyse the precise effect of a contrast of wave velocities and or scattering strengths between them in order to model s codawave envelopes we solve the radiative transfer equation by the monte carlo method thereby neglecting the polarization i e the acoustic approximation we pay special attention to the transition towards the diffusion regime under the assumption of an almost isotropic intensity field a diffusion equation can be derived from the radiative transfer equation and we accurately determine the boundary conditions associated with our models analytical solutions of the diffusion equation have been obtained and systematically compared to the numerical solutions of the radiative transfer equation we identify the domain of validity of the diffusion approximation which provides a simple analytical form for the decay in the late coda we apply our theoretical investigations to the continental lithosphere if the scattering strengths of the mantle and the crust are assumed to be of the same order a velocity contrast at the moho will according to our theory amplify the coda signal since part of the energy is trapped in the crust an amplification factor is defined and given explicitly as a function of the reflection coefficients and the velocity contrast at the moho the shape of the long time decay is of the algebraic form f 3 2 like that of a uniform half space on the other hand if the scattering strength of the mantle is small with respect to that of the crust the decay in the diffusive regime is predicted to be of the form r i exp 2nft qa where q is a function of the reflection coefficients at the moho the mean free path of waves in the crust and frequencyf the coefficient q quantifies the rate at which the partially trapped energy leaks from the crust into the mantle this formula has the same form as that proposed by aki chouet 1975 to fit coda observations which has since been widely used to deduce the qc parameter with realistic model parameters we find that q roughly equals the parameter qc deduced from observations this shows that the effect of partial trapping of energy in the crust may be significant consequently seismic albedos of the crust may have been underestimated in previous studies in our theory the energy decay of seismic coda waves is determined by the layered structure of the earth that is a highly heterogeneous crust overlying a rather homogeneous mantle such structure is confirmed by geological and geochemical studies

methane hydrate and free gas on the blake ridge from vertical seismic profiling seismic velocities measured in three drill holes through a gas hydrate deposit on the blake ridge offshore south carolina indicate that substantial free gas exists to at least 250 meters beneath the bottom simulating reflection bsr both methane hydrate and free gas exist even where a clear bsr is absent the low reflectance or blanking above the bsr is caused by lithologic homogeneity of the sediments rather than by hydrate cementation the average methane hydrate saturation above the bsr is relatively low 5 to 7 percent of porosity which suggests that earlier global estimates of methane in hydrates may be too high by as much as a factor of 3

mineralogy geochemistry and petrography of methane derived authigenic carbonates from enza river northern apennines italy abstract a remarkable exposure of carbonate pipe like and slab concretions occurs along the enza riverbanks on the northern apennines foothills italy based upon geochemical and field evidences their genesis has been attributed to microbial governed carbonate precipitation from hydrocarbon enriched fluids the pipe like concretions are thus interpreted as former conduits chimneys marking sites of methane ascent onto the seafloor the resulting enza river chimney field is arranged in a palisade fashion a rare example of such mineralogical and petrographic analyses of some chimneys and slabs document that the dominant cement is dolomite although the chimneys show a rather homogeneous texture a clear zonation is observed in the relative distribution of major and minor elements in their internal and external parts the occurrence of sulphide minerals in the stratigraphically upper samples indicates possible renewal of fluids leakage after a major erosive event

envelope broadening characteristics of crustal earthquakes in northeastern honshu japan summary in short period seismograms of microearthquakes s wave envelopes are found to broaden with hypocentral distance increasing for crustal events envelope broadening is caused not only by multiple scattering due to velocity inhomogeneities but also by the contribution of guided waves and head waves intrinsic absorption is also an important parameter to truncate the time duration microearthquakes of focal depth less than 40 km and magnitude range from 1 5 to 4 5 which took place in northeastern honshu japan are used for the study of envelope broadening digital data acquired by hi net are used for the analysis we estimated the 90 per cent time duration t90 and the root mean square rms time duration trms from the rms traces of horizontal component seismograms for frequency bands 1 2 2 4 4 8 8 16 and 16 32 hz the estimated time duration increases with hypocentral distance increasing in both sides of the volcanic front which runs from south to north in the study area at reference distance of 100 km the time duration in the backarc side decreases with frequency however that in the forearc side has the minimum at 4 hz the time duration at a reference distance in the backarc side is shorter than that in the forearc side especially for frequencies higher than 4 hz which can be interpreted by strong intrinsic absorption in the backarc side

structural controls on seepage of thermogenic and microbial methane since the last glacial maximum in the harstad basin southwest barents sea the harstad basin is a structural block on the continental shelf of sw barents sea where gas hydrates likely occurred below the grounded ice sheet during the last glaciation and it hosts active gas seepage at numerous seafloor sites we present an integrated study of fluid flow systems in the harstad basin by combining seismic profile interpretations and gas flare mapping data with the geochemical results obtained on seafloor seeping gas and methane derived carbonate crusts more than 190 acoustic gas flares were registered in water column many of them in association with pockmarks and carbonate crust fields however weak or absent seepage observed during remotely operated underwater vehicle transects across many pockmarks and crust fields suggests that seepage activity may have decreased since the last deglaciation in the western harstad basin seeps of microbial methane occur mainly above tertiary formations that are pinching out below the glacial sediments high amplitude seismic anomalies suggest the presence of gas pockets at the base of the glacial sediments and within tertiary deposits in contrast gas seeping in the eastern harstad basin originates from a biodegraded thermogenic source tentatively connected to the deeply faulted mesozoic rocks occurring below glacial sediments this spatial variability in fluid sources is also recorded in the carbon isotope data of seafloor carbonate crusts with 13 c values typically between 55 and 42 and 40 and 20 vpdb for carbonate crusts associated with microbial and thermogenic fluids respectively u th chronology combined with the stable isotope data suggests that this discrepancy in fluid sources over a distance of about 20 km has been stable since the last glaciation and highlights the significance of regional underlying geology in mediating fluid supply to the seafloor

scattering attenuation profile of the moon implications for shallow moonquakes and the structure of the megaregolith abstract we report measurements of the attenuation of short period seismic waves in the moon based on the quantitative analysis of envelope records of lunar quakes our dataset consists of waveforms corresponding to 62 events including artificial and natural impacts shallow moonquakes and deep moonquakes recorded by the four seismometers deployed during apollo missions 12 14 15 and 16 to quantify attenuation and distinguish between elastic scattering and inelastic absorption mechanisms we measure the time of arrival of the maximum of energy t max and the coda quality factor q c the former is controlled by both scattering and absorption while the latter is an excellent proxy for absorption consistent with the strong broadening of seismogram envelopes in the moon we employ diffusion theory in spherical geometry to model the propagation of seismic energy in depth dependent scattering and absorbing media to minimize the misfit between predicted and observed t max for deep moonquakes and impacts we employ a genetic algorithm and explore a large number of depth dependent attenuation models quantified by the scattering quality factor q sc or equivalently the wave diffusivity d and the absorption quality factor q i the scattering and absorption profiles that best fit the data display very strong scattering attenuation q sc 10 or equivalently very low wave diffusivity d 2 km2 s in the first 10 km of the moon these values correspond to the most heterogeneous regions on earth namely volcanic areas below this surficial layer the diffusivity rises very slowly up to a depth of approximately 80 km where q sc and d exhibit an abrupt increase of about one order of magnitude below 100 km depth q sc increases rapidly up to approximately 2000 at a depth of about 150 km a value similar to the one found in the earth s mantle by contrast the absorption quality factor on the moon q i 2400 is about one order or magnitude larger than on earth our results suggest the existence of an approximately 100 km thick megaregolith which is much larger than what was previously thought the rapid decrease of scattering attenuation below this depth is compatible with crack healing through viscoelastic mechanisms using our best attenuation model we invert for the depth of shallow moonquakes based on the observed variation of t max with epicentral distance on average they are found to originate from a depth of about 50 km 20 km which suggests that these earthquakes are caused by the failure of deep faults in the brittle part of the moon

a methane derived carbonate build up at a cold seep on the crimean slope north western black sea abstract a unique chimney shaped carbonate build up was produced by microbially mediated anaerobic oxidation of methane at a deep sea cold seep the build up was sampled from 1600 m water depth in the area of the lomonosov rise nw black sea crimean shelf slope the carbonate chimney grew free into the anoxic water column with its base attached to a steep slope composed of plagiogranite and void of sediments the perfectly preserved 1 5 m high chimney stores reliable records of the diversity of mineralogy geochemistry and stable isotope composition of deep sea methane related carbonates never studied before the build up consists of mg calcite mgco 3 9 13 mol with minor aragonite the carbonate matrix encloses organic matter and emiliania huxleyi coccoliths as well as minor framboidal pyrite gypsum barite and diatomite fragments the contribution of detrital silicate material is negligible micritic mg calcite in the inner zone of the chimney forms obtuse rhombohedrons clustered in hemispherical aggregates clots and hosts isolated prismatic aragonite 1 vol in the outer zone mg calcite exists as foliated crystals and spherulites while aragonite spherulites are restricted to the top surface the carbon isotope compositions of carbonates 13 46 5 to 33 0 vpdb and remnant bacterial mats 13 76 9 to 81 6 vpdb provide evidence of a biogenic methane source for the build up formation oxygen came mainly from sea water judging by a narrow range of 18 o values in carbonates 0 2 to 1 3 vpdb the prevalence of mg calcite throughout the build up indicates an anme 2 sbr consortium being the main component of the bacterial mats living at the seep aragonite grew mostly late in the seep history which hints to environmental changes and the ensuing predominance of the anme 1 sbr consortium the observed relationship between the prokaryotic communities and the main carbonate phases is common to the microbial mats of the black sea but is actually opposed to the pattern of aom community and aom related carbonates found in sediments different morphologies of carbonates in the outer and inner zones of the build up point to variations in the methane flux gradient which controlled the biomass density of the aom consortia the ree y patterns of mg calcite from the inner zone are typical of carbonates crystallised in a freshened sea water environment while both mg calcite and aragonite from the outer zone show distinct sea water signatures inasmuch as the time span of build up growth radiocarbon ages from 9000 180 to 7500 180 year bp overlaps the period when the black sea lake reconnected to the mediterranean sea the progressive arrival of sulphate rich waters can be inferred to be another possible control of ree y patterns in seep carbonates besides the methane flux gradient and related activity of aom consortia

formation of methane related authigenic carbonates within the bioturbated zone an example from the upwelling area off vietnam abstract in the biologically high productive area off vietnam authigenic carbonates formed in the bioturbated zone while methane was oxidized microbially under anaerobic conditions open crustacean burrows spongeliomorpha connected to the seafloor acted as conduits for methane as suggested by intense cementation of burrow walls having a light c isotope signature although seawater circulated within these open inhabited tubes conditions favorable for anaerobic oxidation of methane aom occurred trypanites cementation started at several spots that coalesced later to form the nodule carbon isotopes indicate a biogenic methane source 13 c carb reaching 49 to 40 v pdb while higher 13 c values imply mixing with carbon from other sources that is very likely within the bioturbated zone the cement is generally fine grained 18 o values of 5 1 reflect the general 18 o enriched isotope signature of the bottom water in south china sea especially during glacial times but influence of water released from decaying gas hydrate cannot be excluded the studied nodule was found on top of a slump that displaced it

3d morphology and timing of the giant fossil pockmark of beauvoisin se basin of france in the se basin of france drome fossil cold seep structures made of fossil rich carbonate lenses were identified in the oxfordian late jurassic terres noires formation about 30 years ago to date all seep sites have generally been studied individually without consideration of any link to neighboring or more distant sites based on a detailed fieldwork in the beauvoisin area and comparison with the modern active giant regab pockmark and sandbox experiments we suggest that this site can now be considered as a 800 m wide fossil analogue of a giant pockmark it comprises several 4 6 m deep 80 120 m wide coalesced sub seep sites a spatio temporal 3d reconstruction of the position of these sub sites shows that the carbonate lenses are organized in clusters with only one cluster active at a given period two periods of seep activity are separated by a period of quiescence due to the lateral shift of the feeder conduit beneath the structure this suggests that even if a seafloor pockmark appears to be inactive this could be due to the lateral shift of the feeder conduit meaning that the sub seafloor is still charged in gas

numerical modeling of carbonate crust formation at cold vent sites significance for fluid and methane budgets and chemosynthetic biological communities at many cold vent sites authigenic carbonates precipitate due to the release of carbonate alkalinity during the anaerobic oxidation of methane carbonate precipitation often induces the formation of massive crusts at the sediment surface or within surface sediments the range of physical and biogeochemical conditions allowing for the formation of carbonate crusts is largely unknown so that the significance of these widespread manifestations of fluid flow is unclear here we use numerical modeling to investigate the conditions that induce carbonate crust formation in the sediment and the effect of crust formation on sediment porosity and fluid flow rate starting with the conditions prevailing at a previously investigated reference site located on hydrate ridge off oregon several parameters are systematically varied in a number of numerical experiments these parameters include coefficients of bioturbation and bioirrigation sedimentation rate fluid flow velocity methane concentration in the ascending vent fluids and ph and saturation state at the sediment water interface the simulations show that carbonate crusts in the sediments only form if the fluids contain sufficient dissolved methane 50 mm and if bioturbation coefficients are low 50 cm ka 1 inhibit crust formation bioirrigation induces a downward displacement of the precipitation zone and accelerates the formation of a solid crust crusts only form over a rather narrow range of upward fluid flow velocities 20 60 cm a 1 which is somewhat enlarged up to 90 cm a 1 if the overlying bottom waters are supersaturated with respect to calcite at higher flow rates methane is rapidly exported into the water column so that methane oxidation and carbonate precipitation cannot proceed within the surface sediment the formation of a several centimeters thick carbonate crust in surface sediments is typically completed after a few hundred years 100 500 a crust formation reduces the supply of methane to surface sediments which imposes a strong resistance against diffusive and advective methane transport therefore rates of anaerobic methane oxidation and sulfide production are diminished and thus the density and metabolism of chemosynthetic biological communities is limited by crust formation due to the moderate flow rates and the slow diffusive transport only very little methane escapes into the bottom water overlying carbonate encrusted vent areas

methane derived carbonates and authigenic pyrite from the northwestern black sea abstract methane seeps in the northwestern black sea are accompanied by carbonate and pyrite precipitates sediments were sampled at locations on the romanian 120 m depth and ukrainian 180 200 m depth shelf and slope layered carbonate crusts are formed of i carbonate cemented siliciclastic sediment containing dreissenoid bivalves ii microcrystalline high mg calcite or aragonite and iii aragonitic cement the dreissena sediment is subrecent and was deposited during the freshwater phase of the black sea it has been affected by seepage of methane rich fluids which induced intergranular precipitation of authigenic carbonates the microcrystalline carbonates exhibit an intense autofluorescence high mg calcite contains 11 14 mol mgco3 the aragonitic cement 8300 9500 ppm sr forms either isopachous layers or botryoids microbial filaments about 10 20 m in diameter and up to 900 m in length are preserved within and on carbonate crusts the carbonates are depleted in 13c microcrystalline carbonate ranges from 27 to 41 pdb and botryoidal aragonite ranges from 26 to 38 pdb the 13c depletion indicates that the carbonates predominantly derive from the microbial oxidation of methane carbonate deposits do not project up into the oxic water column they are restricted to the anoxic water column and to anoxic sediments revealing the crucial role of anaerobic methane oxidation for carbonate precipitation 14c contents give apparent radiocarbon ages of 20 640 180 a bp for a sample of botryoidal aragonite and 19 110 180 a bp for a sample of microcrystalline carbonate compatible with minimum ages of carbon derived from a fossil hydrocarbon source the 18o values of methane derived carbonates show a narrow range from 1 2 to 0 2 pdb 87sr 86sr ratios of microcrystalline carbonate mean 0 70927 and aragonitic cement mean 0 70918 are indistinguishable from ambient seawater mean 0 70917 and thus indicate a shallow sr source higher 87sr 86sr ratios of the dreissena sediment mean 0 71005 are probably caused by sr derived from detrital mica carbonates are accompanied by blocks and crusts composed of pyrite the framboidal sulphide exhibits a palisade like fabric with framboids arranged to parallel pillars sulphur isotopic ratios 34s ranging from 16 8 to 19 7 cdt indicate that the sulphur derives not from the 34s depleted h2s of the water column or the uppermost sediment layers most likely pyrite formed in the lacustrine sediments after the first incursion of mediterranean seawater

u th chronology and formation controls of methane derived authigenic carbonates from the hola trough seep area northern norway abstract we investigated methane derived authigenic carbonate mdac crusts and nodules from a cold seep site on the northern norwegian continental shelf in ca 220 m water depth to determine the timing and mode of their formation gas bubbling observed during remotely operated vehicle rov assisted sampling of mdac crusts revealed ongoing seep activity authigenic carbonates were present as crusts on the seafloor and as centimetre size carbonate cemented nodules at several intervals within an adjacent sediment core aragonite dominated mineralogy of the mdac crusts suggests formation close to the seafloor at higher rates of sulphate dependent anaerobic oxidation of methane aom in contrast dolomite cemented nodules are consistent with the formation at the sulphate methane transition zone deeper within the sediment at lower rates of aom the 13c carbonate values of bulk rock and of micro drilled aragonite samples vary between 22 2 and 34 6 vpdb we interpret the carbon in aragonite to be mainly derived from the anaerobic oxidation of thermogenic methane with a minor contribution from seawater dissolved inorganic carbon dic aom activity is supported by high concentrations of aom related biomarkers of archaea archaeol and 2 sn hydroxyarchaeol and sulphate reducing bacteria iso and anteiso c15 0 fatty acids in the crusts the dolomite nodules exhibit higher 13c carbonate values 12 vpdb suggesting a smaller amount of methane derived carbon presumably due to the contribution of dic migrating from depth and lower aom rates the latter is supported by orders of magnitude lower concentrations of archaeol and sn 2 hydroxyarchaeol in the sediment interval containing the largest dolomite nodules 18o values of pure aragonite samples and dolomite nodules indicate the precipitation of carbonate close to isotopic equilibrium with seawater and no influence of gas hydrate derived water u th dating of two mdac crusts shows that they formed between 1 61 0 02 and 4 39 1 63 ka bp and between 2 65 0 02 and 4 32 0 08 ka bp we infer both a spatial and temporal change in methane flux and related mdac formation at this seep site these changes might be caused by regional seismic events that can affect pore pressure or re activation of migration pathways thus facilitating fluid flow from deep sources towards the seabed

investigation of scattering in lunar seismic coda 1 we investigate the intrinsic attenuation and scattering properties of the moon by parameterizing the coda decay of 369 higher quality lunar seismograms from 72 events via their characteristic rise and decay times we investigate any dependence of the decay times on source type frequency and epicentral distance intrinsic attenuation scattering and possible focusing of energy in a near surface low velocity layer all contribute to the coda decay although it is not possible to quantify the exact contribution of each of these effects in the seismograms results suggest that scattering in a near surface global layer dominates the records of shallow events 0 200 km depth particularly at frequencies above 2 hz and for increasing epicentral distance we propose that the scattering layer is the megaregolith and that energy from shallow sources encounters more scatterers as it travels longer distances in the layer increasing the coda decay times a size distribution of ejecta blocks that has more small scale than large scale scatterers intensifies this effect for increasing frequencies deep moonquakes 700 1100 km depth exhibit no dependence of the decay time on epicentral distance we suggest that because of their large depths and small amplitudes deep moonquakes from any distance sample a similar region near a given receiver near station structure and geology may also control the decay times of local events as evidenced by two natural impact records this study provides constraints and testable hypotheses for waveform modeling of the lunar interior that includes the effects of intense scattering and shallow low velocity layers

an explanation of the effect of seawater carbonate concentration on foraminiferal oxygen isotopes abstract stable oxygen isotope ratios of foraminiferal calcite are widely used in paleoceanography to provide a chronology of temperature changes during ocean history it was recently demonstrated that the stable oxygen isotope ratios in planktonic foraminifera are affected by changes of the seawater chemistry carbonate system the 18 o of the foraminiferal calcite decreases with increasing co 3 2 concentration or p h this paper provides a simple explanation for seawater chemistry dependent stable oxygen isotope variations in the planktonic foraminifera orbulina universa which is derived from oxygen isotope partitioning during inorganic precipitation the oxygen isotope fractionation between water and the dissolved carbonate species s h 2 co 3 hco 3 co 3 2 decreases with increasing p h provided that calcium carbonate is formed from a mixture of the carbonate species in proportion to their relative contribution to s the oxygen isotopic composition of caco 3 also decreases with increasing p h the slope of shell 18 o vs co 3 2 of orbulina universa observed in culture experiments is 0 0022 mol kg 1 1 spero et al 1997 whereas the slope derived from inorganic precipitation is 0 0024 mol kg 1 the theory also provides an explanation of the nonequilibrium fractionation effects in synthetic carbonates described by kim and o neil 1997 which can be understood in terms of equilibrium fractionation at different p h the results presented here emphasize that the oxygen isotope fractionation between calcium carbonate and water does not only depend on the temperature but also on the p h of the solution from which it is formed

a late miocene methane seep deposit bearing methane trapping silica minerals at joetsu central japan abstract the modern japan sea is characterized by active methane seeps associated with gas hydrates but their ancient counterparts are not fully understood this study describes a newly discovered methane seep carbonate block the nakanomata seep deposit from the upper miocene nodani formation in joetsu city central japan the age of this deposit is constrained to 7 5 6 5 ma based on its fossil diatom assemblage the deposit contains molluscan fossils typical of methane seeps including vesicomyid and bathymodiolin bivalves and provannid gastropods and it retains an almost entirely aragonitic mineralogy despite its miocene age it is composed of clotted microcrystalline aragonite containing nodules and intraclasts and is crosscut by vein like networks of voids and cavities rimmed with acicular aragonite the 13c values of the carbonate phases are as low as 41 1 and the presence of lipid biomarkers pentamethylicosane and crocetane suggests that the deposit originated from the anaerobic oxidation of methane it is suggested that an initially diffuse methane seepage formed the micritic nodules followed by a more rapid and intense methane seepage that led to the development of abundant voids in the sediment finally the sediment was cemented by microcrystalline aragonite and void lining acicular aragonite the seep deposit also contains peculiar globular silica minerals and authigenic quartz during their precipitation these globular silica minerals may have trapped methane gas bubbles and the minerals may be pseudomorphs after silica clathrate sufficient increase in ph and supersaturation of silica which led to the dissolution and subsequent precipitation of these silica minerals could have resulted from the degassing of carbon dioxide promoted by an effective supply of methane and its supersaturation thus forming gas bubbles

chemoherms on hydrate ridge unique microbially mediated carbonate build ups growing into the water column two active chemoherm build ups growing freely up into the oceanic water column the pinnacle and the south east knoll chemoherms have been discovered at hydrate ridge on the cascadia continental margin these microbially mediated carbonate formations rise above the seafloor by several tens of meters and display a pinnacle shaped morphology with steep flanks the recovered rocks are pure carbonates dominated by aragonite based on fabric and mineralogic composition different varieties of authigenic aragonite can be distinguished detailed visual and petrographic investigations unambiguously reveal the involvement of microbes during the formation of the carbonates the fabric of the cryptocrystalline and fibrous aragonite can be described as thrombolitic fossilized microbial filaments in the microcrystalline aragonite indicate the intimate relationship between microbes and carbonates the strongly 13c depleted carbon isotope values of the samples as low as 48 1 pdb are characteristic of methane as the major carbon source for the carbonate formation the methane rich fluids from which the carbonates are precipitated originate most probably from a gas reservoir below the bottom simulating reflector bsr and rise through fault systems the 18o values of the aragonitic chemoherm carbonates are substantially higher as high as 5 0 pdb than the expected equilibrium value for an aragonite forming from ambient seawater 3 5 pdb as a first approximation this indicates formation from glacial ocean water but other factors are considered as well a conceptual model is presented for the precipitation of these chemoherm carbonates based on in situ observations and the detailed petrographic investigation of the carbonates this model explains the function of the consortium of archaea and sulfate reducing bacteria that grows on the carbonates performing anaerobic oxidation of methane aom and enabling the precipitation of the chemoherms above the seafloor surrounded by oxic seawater beggiatoa mats growing on the surface of the chemoherms oxidize the sulfide provided by sulfate dependent anaerobic oxidation of methane within an oxic environment the contact between beggiatoa and the underlying microbial consortium represents the interface between the overlying oxic water column and an anoxic micro environment where carbonate formation takes place