sediment dewatering in the makran accretionary prism abstract sediments within the makran accretionary prism are considerably more compacted than the material entering the subduction zone due to the additional tectonic stresses resulting from plate convergence and accretionary processes tectonic compaction of the offscraped sediments has been documented by deriving in situ porosities in the upper 4 km from their seismic velocities wide angle seismic reflection refraction profiles were analysed from a transect crossing both the makran accretionary prism and the undeformed abyssal plain sediments to the south the 6 7 km thick abyssal plain sediments exhibit normal compaction with depth the sediments incorporated into the accretionary prism have higher seismic velocities at all depths corresponding to reductions in porosity of 30 40 mapping the porosity depth gradient across the prism shows that there is a marked change in porosity at the seaward toe of the prism the frontal fold there is then little further change until further folding begins to occur 70 km landward of the toe the dewatering and consolidation of the sediments is an important control on deformation occurring within the sedimentary prism

rate of outward growth of the mediterranean ridge accretionary complex abstract the position as a function time of the deformation front on the southwest flank of the mediterranean ridge accretionary complex is constrained as follows 1 a the deformation front is now active 2 b the site of core ban84 05gc was still near the abyssal plain when displaced shallow water benthic foraminifera of inferred african provenance were redeposited within an upper pliocene age unit 3 c the site of core ban84 05gc on the outer flank of the mediterranean ridge was already within the topographically rugged accretionary complex when a pliocene debris flow was emplaced 4 d dsdp site 125 had already been uplifted into a topographically elevated position when lower pliocene pelagic ooze was deposited 5 e a gypsum bearing breccia in dsdp site 125 requires that the site was either on the abyssal plain or within the tectonically active outer perimeter of the accretionary complex during the messinian salinity crisis 6 f dsdp site 377 had already been uplifted into a topographically elevated position when middle miocene age pelagic marl was deposited 7 g dsdp site 377 was still on or near the abyssal plain when early to lower middle miocene age smectite bearing turbidites of inferred african provenance were deposited and 8 h the mediterranean ridge began to grow by offscraping against a backstop formed by the alpine nappes of the hellenic arc at the time that subduction began 33 ma together these constraints define a range of potential growth curves for the mediterranean ridge with a rate of outward growth of approximately 0 5 to 2 cm yr this growth rate is faster than that inferred for most other modern accretionary prisms both as an absolute value and as a fraction of the subduction velocity an unusually thick incoming section and or an unusually weak evaporitic decollement may contribute to the rapid growth rate the inferred age of accretion does not increase linearly with distance from the deformation front rather there is an apparent acceleration of the rate of outward growth through time this observation may reflect a true acceleration of growth rate in response to the onset of back arc extension in the overriding plate aegean sea and or in response to the development of a weak basal decollement following the introduction of halite into the incoming stratigraphic section alternatively the non linearity of the age vs distance curve may indicate that shortening of the offscraped sediments continues across the breadth of the mediterranean ridge rather than being confined to the outer flank

first evidence of benthic communities based on chemosynthesis on the napoli mud volcano eastern mediterranean abstract some molluscan valves attributed to myrtea sp lucinidae vesicomya sp and another undetermined vesicomydae were sampled in 1993 cruise ttr3 leg2 and 1994 cruise um94 by coring on the top of the napoli dome a mud volcano located on the mediterranean ridge at about 1900 m of water depth these bivalves belong to an unknown apparently rich benthic community associated to the sulphides and methane rich emissions that characterize the napoli dome outside the mediterranean deep sea lucinidae and vesicomyidae are associated with cold seeps and hydrothermal vents and are known to be sustained by bacterial chemosynthetic activity based on sulphide and or methane oxidation the same explanation is given for this newly discovered deep mediterranean fauna firstly described here

sediment deformation and hydrogeology of the nankai trough accretionary prism synthesis of shipboard results of odp leg 131 the main objective of leg 131 was to provide data on the deformational processes and associated hydrogeology of the nankai prism toe drilling succeeded for the first time in the history of ocean drilling in penetrating the complete sedimentary sequence to basaltic basement reaching 1327 mbsf metres below seafloor with good core recovery 55 excellent correlation of the lithology and structure including the frontal thrust and the decollement with seismic reflection images was also determined bedding dips faults and shear bands analyzed in the cores confirm the pattern of deformation to be mainly due to nw se shortening as expected from the plate tectonic convergence vector below the decollement no significant deformation features were observed indicating that the decollement is a sharp discontinuity in stress transmission physical properties data show major discontinuities at the decollement notably an increase in porosity below the later this may indicate excess pore pressure in the subducted section and decollement zone a less marked increase in porosity below the frontal thrust may reflect the youthfulness of this feature attempts to make downhole measurements were severely hampered by unstable hole conditions but useful constraints have been placed on the thermal regime and some calibration of laboratory physical properties toin situ conditions has been provided andin situ stress and pore pressure were measured in the uppermost sediments evidence of channelized fluid flows is inconclusive no sharp geochemical signatures or unequivocal geochemical anomalies indicative of channelized fluid flow were found thermal measurements are not significantly different from those predicted by a purely conductive heat flow model a signature of low chloride pore water near the decollement may partly be related to smectite diagenesis but may also be due to episodic fluid flow events we conclude that dewatering probably occurred dominantly through diffuse flow throughout the accreted sediments at this site

classification of sea floor features associated with methane seeps along the gulf of cadiz continental margin abstract based on recently gathered swath bathymetry high to ultra high resolution seismic and underwater camera data along with dredging and coring samples this paper examines the relationship between sea floor features and the nature of hydrocarbon enriched fluid and gas leaks from degassing of deeply buried sediments along the continental margin of the gulf of cadiz eastern central atlantic a classification into three main groups is proposed on the basis of the morphology and nature of deposits 1 mud volcanoes 2 methane derived authigenic carbonates mdac mounds and 3 crater like pockmarks mud volcanoes are topographically cone shaped sea floor edifices built up from catastrophic mud and fluid degassing intercalated with periods of inactivity so far more than 25 mud volcanoes have been discovered in the gulf of cadiz named in memory of deceased colleagues e g ginsburg and baraza or researchers birth places e g faro cibeles almazan san petersburgh yuma rabat bonjardim coruna gades these structures range from 800 to 2500 m in diameter and tower 150 300 m above the seabed the volcanoes consistently feature a well defined outer ring or circular terrace and an inner dome all mud volcanoes are built up of episodes of mud breccia flows intercalated with deep current deposits with evident indications of gas saturation degassing structures a strong h2s smell and chemosynthetic fauna such as pogonophora sp tube worms and calyptogena sp commonly observed carbonate crusts and slabs overlying some mud volcanoes are thought to have been formed by slow diffuse venting during periods of inactivity or slower rates of fluid venting following the ejection of mud a fermentation process the result of microbial mediated oxidation of hydrocarbon enriched fluids seems to play an important role in the growth of large deep water carbonate mounds and chimneys during periods of low methane seep fluid pressure more than 400 crater like pockmarks a common sea floor feature in the tasyo field have been observed their seabed diameter ranges from 500 to 3000 m with steep slopes ranging from 12 to 35 according to their internal structure pockmarks can be grouped into 1 pockmarks with low central mounds and 2 crater like pockmarks apparently collapse structures lacking central mounds with a flat to slightly undulating sea bottom surrounded by steep slopes up to 25

structural grain mud volcanoes and other features on the barbados ridge complex revealed by gloria long range side scan sonar abstract a long range side scan sonar survey of the broad band of deformed sediments east of the antilles volcanic arc has revealed the detailed structural trends of folds and reverse faults or thrusts in plan view for the first time the prevalent trend lies substantially parallel with the arc and is simplest near to the deformation front at the eastern edge of these deformed sediments these trends are interrupted locally by more or less transverse zones of disturbance associated with ridges in the oceanic basement that are obstructing the relative eastward movement of the deformation front local rough surfaced mounds interpreted as mud volcanoes underlain by diapirs are common and occur much further to the north than the mud diapir field already described near trinidad only one large sediment slide has been identified

triggering and dynamic evolution of the lusi mud volcano indonesia abstract mud volcanoes are geologically important manifestations of vertical fluid flow and mud eruption in sedimentary basins worldwide their formation is predominantly ascribed to release of overpressure from clay and organic rich sediments leading to impressive build up of mud mountains in submarine and subaerial settings here we report on a newly born mud volcano appearing close to an active magmatic complex in a backarc sedimentary basin in indonesia the location of the mud volcano close to magmatic volcanoes results in a high background temperature gradient that triggers mineralogical transformations and geochemical reactions at shallow depth the eruption of 100 c mud and gas that started the 29th of may 2006 flooded a large area within the sidoarjo village in northeast java thousands of people have so far been evacuated due to the mud flood hazards from the eruption since the initial eruption the flow rate escalated from 5000 to 120 000 m 3 d during the first eleven weeks then the erupted volume started to pulsate between almost zero and 120 000 m 3 d in the period august 14 to september 10 whereas it increased dramatically following swarms of earthquakes in september before reaching almost 180 000 m 3 d in december 2006 sampling and observations were completed during two fieldwork campaigns on the site the eruption of boiling water is accompanied by mud aqueous vapour co 2 and ch 4 based on geochemical and field results we propose a mechanism where the eruptions started following the 27th of may earthquake due to fracturing and accompanied depressurization of 100 c pore fluids from 1700 m depth this resulted in the formation of a quasi hydrothermal system with a geyser like surface expression and with an activity influenced by the regional seismicity

mud volcanoes at the shelf margin of the east china sea abstract roughly circular sediment mounds varying from tens to hundreds of meters in diameter and from a few meters up to 40 m in height have been mapped for the first time at the shelf edge of the east china sea ecs high resolution seismic profiles together with swath bathymetric and acoustic data indicate that these features are common on the ecs outer shelf and on the upper western slope of the okinawa trough they are associated with unusually large pockmarks up to 40 m in depth and 600 m in diameter on seismic records bright spots phase inversions and other acoustic anomalies indicate that gas and or fluid escape plays an important role in the formation of these mounds they are often associated with normal faults that occur along the western slope of the okinawa trough these faults acting as conduits for migrating fluid based on regional stratigraphic correlation we propose that the source of mud and fluid is deeper older than 235 ka the seepage process is suspected to be very recent and probably still active based on the facts that 1 despite high sedimentation rate the mounds are not buried by recent sediments and 2 last glacial maximum deposits are reworked at the emplacement of the mounds carbonate cemented sediments and deep water reefs possibly associated with fluid seepage could be the origin of local patches of very high backscattering acoustic facies mapped with the swath bathymetric system

mud volcanoes at the front of the makran accretionary complex pakistan abstract conical mounds 1 1 5 km in diameter and up to 65 m high were mapped at the foot of the active makran continental margin the mounds developed seaward of the accretionary front in a relatively planar zone where the beginning of build up of tectonic pressure initiates deformation based on shallow high resolution 4 khz sediment echosounding the sedimentary sequence in this area is generally well stratified as indicated by closely spaced horizontal reflections however in the vicinity of the mounds the sediment is characterised by many acoustically transparent zones which are 100 300 m in diameter and cut near vertically through the horizontal reflectors two sediment cores from the top of the largest cone and a neighbouring acoustically transparent zone reveal small scale post depositional deformation in a stratified sequence and methane concentrations up to 40 000 ng g this deformation and disruption of potential reflectors provides a clue to explain the acoustic transparency we interpret it as caused by the rise of charged fluids and mud leading initially to the slight disturbance of the generally good acoustic reflectors and eventually to the formation of conical mud mounds mud volcanoes mcs data showing a buried mound in an analogous structural position support the idea of tectonically induced mud fluid expulsion seaward of the accretionary front

seabed morphology and hydrocarbon seepage in the gulf of cadiz mud volcano area acoustic imagery multibeam and ultra high resolution seismic data abstract extensive mud volcanism mud diapirism and carbonate chimneys related to hydrocarbon rich fluid venting are observed throughout the spanish portuguese margin of the gulf of cadiz all the mud volcanoes and diapirs addressed in this paper lie in the region of olistostrome accretionary complex units which were emplaced in the late miocene in response to nw directed convergence between the african and eurasian plates the study area was investigated by multibeam echo sounder high and ultra high resolution seismic profiling dredging and coring the structures observed on multibeam bathymetry at water depths between 500 and 1300 m are dominated by elongate mud ridges mud cones mud volcanoes and crater like collapse structures ranging in relief from 50 to 300 m and size from 0 8 to 2 km in diameter the main morphotectonic features named the guadalquivir diapiric ridge gdr and the cadiz diapiric ridge cdr are longitudinally shaped diapirs which trend ne sw and consist of lower middle miocene plastic marly clays the gdr field and the tasyo field which consist of mud volcanoes and extensive fluid venting related to diapiric ridge development are described in this paper the gdr field is characterised by numerous single sub circular mud volcanoes and mud cones the single mud volcanoes are cone shaped features with relatively gentle slopes of 3 6 consisting of several generations of mud breccia deposition with indications of gas saturation degassing structures and the presence of h2s the mud cones have asymmetric profiles with steep slopes of up to 25 and contain large surficial deposits of hydrocarbon derived carbonate chimneys and slabs the tasyo field is characterised by an extensive concentration of small sub circular depressions oval and multi cone mud volcanoes and large sediment slides mud volcanoes in this area are characterised by moderate slopes 8 12 have bathymetric relief ranging from 100 to 190 m and consist of sulphide rich mud breccia calcite chimneys carbonate crusts and chemosynthetic fauna pogonophora tube worms we propose that all these hydrocarbon seepage structures are related to lateral compressional stress generated at the front of the olistostromic accretionary wedge this stress results in the uplifting and squeezing plastic marly clay deposits additionally the compressional stress at the toe of the olistostrome forms overpressurised compartments which provide avenues for hydrocarbon enriched fluids to migrate

mud volcanism by repeated roof collapse 3d architecture and evolution of a mud volcano cluster offshore nigeria abstract using 3d seismic data we document the subsurface architecture of a cluster of 3 mud volcanoes located on the upper continental slope offshore nigeria in a background of gently dipping stratified sediments the subsurface of the cluster contains 8 seismic sequences made of one subcircular syncline 1 3 km in diameter and adjoining unstratified units synclines flatten out upward through intercalation of unstratified concave up lenses between stratified units and are eventually filled by a convex up unstratified lens onlapped by background sediments the lower boundary of each sequence is a 0 5 1 5 km deep bowl shaped unconformity across which high dip strata rest above truncated low dip series we interpret each seismic sequence as a mud volcano system mvs sourced from a connected region and evolving through episodes of roof collapse three are associated with the surface mud volcanoes and another 4 to fossil ones mud volcano systems are dynamic features that record the evolution of 1 the material extruded from one single connected source region depletion zone as it grows downwards and stepwise becomes depleted 2 the basal unconformity which joins strata originally separated by material evacuated in the remobilization process by analogy with salt tectonics we propose to call it a mud weld 3 the conduits and 4 the successive collapsed roofs of the depletion zone the evolution of each mud volcano system in this interpretation records progressive growth of the depletion zone by downbuilding punctuated by episodes of roof collapse and extrusion the geometry and evolution of this type of mvs can be interpreted in the light of analogue models of magmatic caldera development in early stages the thin roof experiences downsagging while remobilized material is extruded through an axial pipe like conduit in later stages the thickened roof undergoes piston like subsidence and mud extrusion occurs along the peripheral fault

age variation in the source of the diapiric mud breccia along and across the axis of the mediterranean ridge accretionary complex abstract pleistocene or younger mud diapirism is recorded along the arcuated crest of the mediterranean ridge accretionary complex over a distance of more than 450 km the extruded mud supported breccia named mud breccia is poorly fossiliferous but the matrix may be dated as late aptian to albian and late burdigalian to langhian in age based on the calcareous plankton content calcareous nannofossils and planktonic foraminifera diagnostic of other ages are sparse within the two above mentioned major assemblages they indicate the presence of sediments attributable 1 to the santonian and cenomanian which occur in association with the mid cretaceous assemblages toronto unnamed and aros domes and 2 to the serravallian which occur in association with the late burdigalian langhian assemblages in the gelendzhik dome aptian albian to late cretaceous sediments are pelagic in origin and are similar to the scisti a fucoidi and scaglia rossa formations well known from continental italy mixed dolomitic clasts and crystals also occur within the matrix indicating the presence of portions of the evaporitic sequence of messinian age in four cores from the western locations single very rare plankton specimens indicative of other ages different from those mentioned above also occur within the matrix at various places they are interpreted as reworked primarily within the late burdigalian langhian sediments the age of the emplacement of the breccia should be older than the middle pleistocene as supported by the occurrence of clasts of this age in the mud breccia and is still an ongoing process at least in the napoli dome

cold seeps at the salt front in the lower congo basin i current methane accumulation and active seepage abstract active high intensity gas seepage is documented for the first time at the seaward edge of the salt occurrence in the southern lower congo basin microbial methane release from the seafloor occurs on the crests of two 800 m high ridges formed by fault propagation folding intense uplift is documented since the end of the miocene by distinct onlapping reflections on the landward flank of these ridges a paleo pockmark structure suggests an onset of seepage coincident with this deformation period high resolution seismic imaging reveals methane migration along strata from oligocene miocene fan deposits towards the ridge crests where large gas accumulations form beneath a discontinuous bottom simulating reflection bsr detailed mapping revealed that free gas and gas hydrate occurrences below and above the base of the gas hydrate stability zone are closely linked to sedimentary strata in the flanks of topographic ridges gas transport through the gas hydrate stability zone originates from the shallowest area of the bsr directly beneath the seafloor seep sites suggesting pressure controlled venting these sites represent the most seaward salt related gas seepage features documented in the area and illustrate the initiation of long lasting seepage at the front of an area of compressional tectonics at a passive continental margin

shallow gas transport and reservoirs in the vicinity of deeply rooted mud volcanoes in the central black sea abstract the principal objective of this paper is to understand the gas migration process and the structures of mud volcanoes in the central black sea multichannel seismic lines were acquired across 6 mud volcanoes in the central black sea msu yuzhmorgeologiya malyshev kornev goncharov and vassoevitch based on a high resolution seismic processing we analyzed acoustic anomalies and studied near surface sediment structures of these mud volcanoes four types of pathways for gas and fluid migration and three types of gas reservoirs were recognized a regional bottom simulating reflection bsr seems to be absent in most parts of the study area however a clear bsr was observed in one of the seismic profiles the free gas migrating upwards along these pathways were sealed by gas hydrates or fine grained sediments in the gas hydrate stability zone four seismic units were separated according to a suggested age model and identified seismic facies combining with the possible sedimentary processes of the central black sea we try to reveal the active mechanism of these mud volcanoes these mud volcanoes reveal two to three major active stages these active stages might be related to distinct sea level falls which seem to be one of the main trigger factors of the mud volcano eruptions in the central black sea a structural model for the msu mud volcano was presented with respect to mechanisms of gas migration and the origin of the gas

sedimentary succession and evolution of the mediterranean ridge western sector as derived from lithology of mud breccia clasts abstract rock fragments from mud breccia extruded by mud volcanoes discovered during the ttr 4 cruise of the r v gelendzhik on the western mediterranean ridge are represented by a number of different lithologies they provide important information on the composition genesis and age of the deep seated sedimentary series of the basin lithological description and age determination of the main rock types obtained as clasts from mud breccia were made on the basis of a study of ninety seven samples depositional processes and environments of their accumulation were determined using sedimentological criteria the sedimentary section through which mud volcanoes erupted on the western mediterranean ridge includes aptian albian claystones late cretaceous limestones paleogene siliciclastic rocks and a variety of miocene limestones and mudstones the rock clasts studied throw insight into the evolution of the western sector of the eastern mediterranean basin from at least aptian time the aptian albian clayey series have been deposited in the marine conditions of a relatively narrow basin with a high input of terrigenous clayey material during the late cretaceous the basin enlarged terrigenous input into deep parts of the basin decreased and carbonate pelagic sedimentation became prevalent regression in paleogene time led to the deposition of thick terrigenous siliciclastic series of deltaic prodeltaic sediments extensive turbidite systems were emplaced in the western sector of the eastern mediterranean during the miocene along with predominantly carbonate pelagic sedimentation

martian mud volcanism terrestrial analogs and implications for formational scenarios the geology of mars and the stratigraphic characteristics of its uppermost crust mega regolith suggest that some of the pervasively occurring pitted cones mounds and flows may have formed through processes akin to terrestrial mud volcanism a comparison of terrestrial mud volcanism suggests that equivalent martian processes likely required discrete sedimentary depocenters volatile enriched strata buried rheological instabilities and a mechanism of destabilization to initiate subsurface flow we outline five formational scenarios whereby martian mud volcanism might have occurred a rapid deposition of sediments b volcano induced destabilization c tectonic shortening d long term load induced subsidence and e seismic shaking we describe locations within and around the martian northern plains that broadly fit the geological context of these scenarios and which contain mud volcano like landforms we compare terrestrial and martian satellite images and examine the geological settings of mud volcano provinces on earth in order to describe potential target areas for piercement structures on mars our comparisons help to evaluate not only the role of water as a functional component of geological processes on mars but also how martian mud volcanoes could provide samples of otherwise inaccessible strata some of which could contain astrobiological evidence

wide angle seismic data reveal extensive overpressures in the eastern black sea basin summary we present new data that explores the link between pore pressure and seismic velocity to estimate the magnitude of the overpressure within the deep sediments of the eastern black sea basin new wide angle seismic data combined with coincident reflection data have been modelled simultaneously using the seismic tomography code jive3d to provide a wellconstrained seismic velocity model of the sediments our models reveal a widespread lowvelocity zone at the depth of 5 5 8 5 km which is characterized by a velocity decrease from 3 5 to 2 5 km s 1 using two separate methods that relate changes in seismic velocity to changes in effective stress we estimate pore pressures of at least 160 mpa within the lowvelocity zone these pore pressures give values of 0 8 0 9 within the centre of the basin and above the mid black sea high the low velocity zone occurs within the maikop formation an organic rich mud layer identified as the source of mud volcanism in the black sea and south caspian sea

mud volcanoes along the inner deformation front of the calabrian arc accretionary wedge ionian sea abstract we present geophysical data integrated with the analysis of well targeted sediment samples in order to contribute to a better understanding of fluid circulation in the calabrian arc accretionary wedge two cores bs81 ii 5 and bs81 ii 10 collected on a swell in the hangingwall of the inner deformation front show upper pleistocene mud breccias that include cretaceous to late miocene rock fragments mechanically incorporated into the eruption deposit by the upward transport of overpressured fluids an additional core cala 21 came from the summit of a topographic high in the footwall of the inner deformation front of the accretionary wedge and contains a mud breccia patchy cloudy facies where sediment disturbance is caused by fluid expulsion integration of the entire data set provides evidences of the interplay among tectonics fluid emissions and sedimentation and enables the identification of two new volcanoes in the accretionary prism where overpressuring due to pliocene and pleistocene sediment accumulation and the evolution of active fault systems triggered fluid circulation and the formation of those structures

coseimic massive methane release from a submarine mud volcano abstract we report here the discovery of two methane enriched plumes in a water column above the kumano knoll 5 submarine mud volcano kk 5 in nankai trough during 2004 a slight methane enrichment was observed in this region in 2000 and 2010 the deeper of the two plumes spread horizontally at depths near the top of kk 5 whereas a shallow plume spread at a height of 300 m from the top of kk 5 the end member 13 c values of methane in both plumes 46 1 4 8 and 51 4 5 8 in the deep and shallow plumes respectively and methane extracted from sediment in kk 5 52 2 are statistically indistinguishable we conclude that the plumes were created by massive release of methane from kk 5 and that this event probably occurred in response to the large earthquakes m w 7 5 that occurred shortly before our observation in 2004 the discharge rates from submarine mud volcanoes smvs in subduction zones may be highly variable in response to major earthquakes

mud volcanoes the most important pathway for degassing deeply buried sediments abstract this paper discusses the nature of the phenomenon of mud volcanism with respect to degassing of deeply buried sediments mud volcanoes are defined as geological structures and their main elements are described based on the nature of activity mud volcanoes are grouped in to three main types and the relationship between each type and corresponding morphological expression is discussed the presented up to date data of the world geographical distribution of mud volcanoes show that they approximate to 1800 individuals a detail overview of geological environments in which they occur helps to deduce some necessary conditions for mud volcano formation the basic mechanisms of mud volcano formation are discussed specifically the fluid pressure hypothesis and some triggering events are identified the most common investigation approach and some criteria for recognizing of a submarine mud volcano on side scan sonar records and seismic sections are given mud volcanism in the mediterranean ridge an accretionary complex and black sea abyssal plane a back ark basin with tectonic regime of extension are described as case studies to show variety in morphology and common factors in development of mud volcanoes the manifestation of continuous gas migration through mud volcanoes is clarified and the attempt made to quantify the gas release shows that mud volcanoes are one of the significant natural sources of atmospheric methane emitting a total amount of about 10 3 to 12 6 tg annually

multifrequency geoacoustic imaging of fluid escape structures offshore costa rica implications for the quantification of seep processes quantification of fluid fluxes from cold seeps depends on accurate estimates of the spatial validity of flux measurements these estimates are strongly influenced by the choice of geoacoustic mapping tools multibeam bathymetry side scan sonar and chirp subbottom profiler data of several mound shaped cold seeps offshore central costa rica show great variety in morphology and structure although the features are only a few kilometers apart mound 11 a 35 m high and 1000 m in diameter structure situated in the se of the study area has an irregular morphology but a smooth surface on side scan sonar data while mound 12 30 m high 600 m across is a cone of more regular outline but with a rough surface and mound grillo 5 m high 500 m across shows the same rough surface as mound 12 but without relief video observations and sediment cores indicate that the structures are formed by the precipitation of authigenic carbonates and indications for extensive mud extrusion are absent except for one possible mudflow at mound 11 different sonar frequencies result in variable estimates of the extent of these mounds with low frequencies suggesting much wider cold seeps consequently overestimating fluid fluxes the absence of mud volcanism compared to accretionary prisms where mud volcanism occurs is related to different tectonic styles strong sediment overpressure and thrust faulting in typical accretionary prisms can generate mud volcanism while subduction erosion and normal faulting extension of the overriding plate at the costa rican margin result in fluid venting driven by only slight fluid overpressures

reply to comment by g etiope and g martinelli pieve santo stefano is not a mud volcano comment on structural controls on a carbon dioxide driven mud volcano field in the northern apennines

acoustic evidence for shallow gas accumulations in the sediments of the eastern black sea the black sea contains immense gas accumulations exploration of gas accumulations is geologically and economically important because migration of methane in sediments may cause massive slope failures and the methane seeps may indicate deeper hydrocarbon reservoirs human activity both in and on the seafloor oil industry and natural activity earthquakes cyclones trigger mechanisms for seafloor failure and gas release that may have a local and possibly global environmental impact recently sonar and high resolution seismic surveys were carried out to obtain information about the effects of gas and gas filled sediments throughout the turkish margin of the eastern black sea and shallow gas was detected on the subbottom profiler records it continues about 25 65 m below the sea floor and is marked by bright and cloudy spots sometimes pockmarks and acoustic voids the lower section of the turkish shelf is an extensive pockmarked plateau the pockmarks are seen as circular structures with high backscattering on the sonar records

significance of mud volcanism 1 mud volcanism and diapirism have puzzled geoscientists for 2 centuries they have been described onshore and offshore in many places on earth and although they occur in various tectonic settings the majority of the features known to date are located in compressional tectonic scenarios this paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described mud volcanoes show variable geometry up to tens of kilometers in diameter and several hundred meters in height and a great diversity regarding the origin of the fluid and solid phases gas predominantly methane water and mud may be mobilized at subbottom depth of only a few meters but in places can originate from several kilometers depth with minor crustal or mantle input the possible contribution of mud extrusion to global budgets both from quiescent fluid emission and from the extrusive processes themselves is important in regions where mud volcanoes are abundant such as the collision zones between africa and eurasia fluid flux through mud extrusion exceeds the compaction driven pore fluid expulsion of the accretionary wedge also quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and hence to greenhouse climate

structural features of mud volcanoes and the fold system of the mediterranean ridge south of crete abstract new information on the geometry of the mud volcanoes folds and faults located in the central part of the mediterranean ridge is provided from long range and deep tow sidescan sonar images high resolution seismic and low frequency echosounder profiles and gravity cores obtained on the r v gelendzhik during the 1993 unesco esf training through research cruise symmetrical gentle folds with a mean wavelength of 750 m deform predominantly pliocene quaternary sediments but also perhaps as old as messinian in most areas of the mediterranean ridge the north northeast directed subduction of the african plate below the eurasian plate at the hellenic arc produces folds with hinge lines subparallel to the trend of the ridge however the hinge lines of the folds curve around the southern part of the area with highest concentration of mud volcanoes and produce an irregular u shape fold belt some of the folds show an intrusive nucleus and in some of them mud breccia appears to have flowed from the flanks of the folds into the troughs the mud volcanoes consist of domes of interlayered pelagic sediments and mud breccias containing sediments and rock fragments of late aptian to pleistocene ages mud breccia flows are mainly extruded radially from vents although rare fissure extrusions are also observed the mud volcanoes have an irregular to elliptical shape with diameters up to 16 km the distribution of mud volcanoes in the area is irregular but they are more frequent in an area called the olimpi field faults in the uppermost part of the mediterranean ridge are rare most of the faults are normal and subparallel to fold limbs in addition n20 e and n100 e subvertical faults are found controlling the shape of the mud volcanoes

archaeal lipids and anaerobic oxidation of methane in euxinic water columns a comparative study of the black sea and cariaco basin abstract the black sea and the cariaco basin are both large euxinic marine basins in which methane concentrations are high and where anaerobic oxidation of methane aom is an important part of the carbon cycle aom can be recognized by lipid biomarkers that are specific to methanotrophic archaea involved and by strongly 13c depleted isotope compositions consistent with uptake of 13c depleted methane derived carbon the working hypothesis for our investigation was that aom in both the black sea and cariaco basin would generate measurable diagnostic biomarkers and isotope depletions to test this hypothesis we analyzed particulate matter and surface sediments for intact glycerol dialkyl glycerol tetreaethers gdgts components of archaeal membrane lipids and measured stable carbon isotope compositions of their constituent biphytanes several gdgts and strongly 13c depleted biphytanes indicative of aom were present in the deep anoxic region of the black sea 700 m unexpectedly this biomarker signal was not detected in the upper anoxic zone of the black sea or in the entire water column of the cariaco basin even though previous studies had shown high rates of aom to occur in both basins it is possible that the aom derived biomarker signal is masked by archaeal lipids derived from non methanotrophic archaea which utilize 13c enriched carbon substrates alternately we speculate that the methanotrophic community may be highly diverse in euxinic basins possibly producing another suite of biomarkers that we did not measure this conclusion will require further testing by coordinated organic geochemical microbial ecology studies

comparative characteristics of the black sea and mediterranean ridge mud volcanoes morphological and structural characteristics of the black sea and mediterranean ridge mud volcanoes studied during several unesco esf cruises of the r v gelendzhik 1991 1994 are compared on the basis of single and multi channel seismic and sidescan sonar observations morphologically three types of mud volcanoes were distinguished in the black sea and six types in the mediterranean they differ in size shape and presence of the mud flows some types from both localities are very similar to each other but in any case their deep structure is very distinctive this difference in deep structure is explained by their development in different geological conditions under an extensional regime with high terrigenous input in the black sea and under strong lateral compression on the mediterranean ridge

seal bypass at the giant gjallar vent norwegian sea indications for a new phase of fluid venting at a 56 ma old fluid migration system highlights the giant gjallar vent is still active in terms of fluid migration and faulting the base pleistocene unconformity acts as a seal to upward fluid migration seal bypass in at least one location leads to a new phase of fluid venting the giant gjallar vent ggv located in the voring basin off mid norway is one of the largest 5 3 km vent systems in the north atlantic the vent represents a reactivated former hydrothermal system that formed at about 56 ma it is fed by two pipes of 440 m and 480 m diameter that extend from the lower eocene section up to the base pleistocene unconformity bpu previous studies based on 3d seismic data differ in their interpretations of the present activity of the ggv describing the system as buried and as reactivated in the upper pliocene we present a new interpretation of the ggv s reactivation using high resolution 2d seismic and parasound data despite the absence of geochemical and hydroacoustic indications for fluid escape into the water column the ggv appears to be active because of various seismic anomalies which we interpret to indicate the presence of free gas in the subsurface the anomalies are confined to the kai formation beneath the bpu and the overlying naust formation which are interpreted to act as a seal to upward fluid migration the seal is breached by focused fluid migration at one location where an up to 100 m wide chimney like anomaly extends from the bpu up to the seafloor we propose that further overpressure build up in response to sediment loading and continued gas ascent beneath the bpu will eventually lead to large scale seal bypass starting a new phase of venting at the ggv

interrelations of mud volcanism fluid venting and thrust anticline folding examples from the external northern apennines emilia romagna italy 1 the present work aims to provide an example of connection between fluid seepage and fault fracture zones associated with compressional thrust folds surface fluid seepage along the pede apennine margin consists of mud volcanism and methane rich emissions showing an intimate link with thrust related folds dominant gaseous or ch4 bearing fluid emissions characterize thrust fold settings in which fluid escape from the main reservoir and source rock i e the marnoso arenacea flysch is not impeded by a seal layer conversely remarkable mud volcanism is closely linked to the presence of the impermeable ligurian units sealing the marnoso arenacea reservoir structural analyses focused on selected thrust folds exhibiting clear relations between surface seepage and brittle elements associated with the fold various scenarios potentially explaining mud volcanism and venting over the crestal region of the thrust related folds are discussed with respect to fluid pressure state and the development of second order fault and fracture sets that are observed to control surface fluid expulsion it is proposed that mud volcanism can be potentially triggered by first order fault failure cycles during which the overpressured fluid is released during faulting events past anomalous eruptions associated with strong earthquakes seem to support this hypothesis the relatively quiescent but continuous activity of the current pede apennine mud volcanoes could instead reflect a short lived leakage of overpressured fluids along permeable fractures faults expansion of methane contained in the rising mud may assist this process fundamentally

mud volcanoes in the alboran sea evidence from micropaleontological and geophysical data during the basacalb ttr9 cruise of the r v professor logachev 1999 two mud volcanoes called marrakech and granada were discovered in the southern sector of the mud diapir province in the west alboran basin wab this paper presents micropaleontological and geophysical data on these mud volcanoes from gravity core samples sidescan sonar okean images and high resolution seismic lines mud breccia recovered from the granada mud volcano is matrix supported with well consolidated clasts of limestone marlstone claystone siltstone sandstone and mudstone whereas mud breccia from the marrakech mud volcano contains unconsolidated clasts the mud breccia matrix contains abundant miocene calcareous nannofossils cn together with pliocene pleistocene species and reworked late cretaceous and paleocene eocene species cn dating indicates that clasts in the mud breccia derive from late cretaceous paleocene eocene and probable miocene sediments these data suggest that the mud diapirs and mud volcanoes in the wab can be derived from the olistostromes of unit vi the basal stratigraphic sequence in the alboran sea basin unit viconsists of lower miocene sediments that incorporated late cretaceous and paleocene eocene materials and basement derived rock fragments the mud volcanic deposits are covered by a thin drape of pelagic marls suggesting that these two volcanoes are currently inactive structures determined on highresolution seismic profiles across mud volcanoes and surrounding diapirs correspond to the late stage pliocene toquaternary diapir development this stage is thought to have developed during a compressional tectonic setting that produced folding and wrench tectonics throughout the basin mud ascent at that time resulted in active diapirism and mud volcanoes on the seafloor 2002 elsevier science b v all rights reserved

unmixing detrital geochronology age distributions despite recent advances in quantitative methods of detrital provenance analysis there is currently no widely accepted method of unmixing detrital geochronology data we developed a mixing model that determines mixing proportions for source samples through inverse monte carlo modeling wherein mixed samples are compared to randomly generated combinations of source distributions and a range of best mixing proportions are retained results may then be used to constrain a forward optimization routine to find a single best fit mixture quantitative comparison is based on the kolmogorov smirnov ks test d statistic and kuiper test v statistic for cumulative distribution functions and the cross correlation coefficient for finite mixture distributions probability density plots or kernel density estimates we demonstrate the capacity of this model through a series of tests on synthetic data sets and a published empirical data set from north america mixed in known proportions this proof of concept testing shows the model is capable of accurately unmixing highly complex distributions we apply the model to two published empirical data sets mixed in unknown proportions from colombia and central china neither data set yields perfect model fits which provides a cautionary note of potentially inadequate characterization of source and or mixed samples and highlights the importance of such characterization for accurate interpretation of sediment provenance data set size appears to be a major control on mixture model results small n 100 detrital data sets may lead to misinterpretation of sediment provenance the model is available as a matlab based stand alone executable exe file graphical user interface

three dimensional seismic investigations of the sevastopol mud volcano in correlation to gas fluid migration pathways and indications for gas hydrate occurrences in the sorokin trough black sea new 3 d seismic investigations carried out across the sevastopol mud volcano in the sorokin trough present 3 d seismic data of a mud volcano in the black sea for the first time the studies allow us to image the complex three dimensional morphology of a collapse structured mud volcano and to propose an evolution model the sevastopol mud volcano is located above a buried diapiric structure with two ridges and controlled by fluid migration along a deep fault system which developed during the growth of the diapirs in a compressional tectonic system overpressured fluids initiated an explosive eruption generating the collapse depression of the sevastopol mud volcano several cones were formed within the depression by subsequent quiet mud extrusions although gas hydrates have been recovered at various mud volcanoes in the sorokin trough no gas hydrates were sampled at the sevastopol mud volcano a bsr bottom simulating reflector is missing in the seismic data however high amplitude reflections bright spots observed above the diapiric ridge near the mud volcano at a relatively constant depth correspond to the approximate depth of the base of the gas hydrate stability zone bghsz thus we suggest that gas hydrates are present locally where gas fluid flow occurs related to mud volcanism i e above the diapir and close to the feeder channel of the mud volcano depth variations of the bright spots of up to 200 ms twt might be caused by temperature variations produced by variable fluid flow

high resolution deep tow multichannel seismic and sidescan sonar survey of the submarine mounds and associated bsr off nicaragua pacific margin bathymetric and conventional multichannel seismic surveys offshore nicaragua and costa rica have revealed numerous mud mounds beneath which the generally widespread bsr is not well imaged however many of the mounds are partially capped by patches of authigenic carbonate crusts so it was not clear if the semitransparent seismic facies and the apparent gaps in the bsr beneath the mounds are real or due to poor normal incidence seismic penetration through the cap rocks to address these problems a high resolution seismic survey was carried out over the continental slope of the nicaraguan pacific margin using a deep towed multichannel seismic streamer dtmcs along with a sidescan sonar system dts to image submarine mud mounds and the associated bsr the proximity of the very short 39 m active length but high resolution 17 channel streamer to the seafloor of the deep towed system allows greatly improved lateral resolution whereas the relatively large source receiver offset allows the undershooting of the cap rocks for the first time our data show that the bsr in many cases continues but rises beneath the mounds this is consistent with the advection of deep warm fluids and thus increased heat flow through the mounds the occurrence of mud mounds seems to be controlled by the locations of faults

mud volcano field seaward of the barbados accretionary complex a deep towed side scan sonar survey a 30 km2 diapiric field has been identified near 13 50 n up to 12 km seaward of the deformation front of the barbados accretionary complex using a deep towed side scan sonar with a 3 5 khz profiler we identified 31 different diapiric structures based on seismic stratigraphy we show that this field has been active for 200 000 years and that it is a transient feature triggered by the seaward propagation of the high pore fluid pressure associated with the decollement beneath the accretionary complex both basement and decollement in this area are anomalously shallow due to the presence of a n110 basement ridge the height of the diapirs above seafloor does not exceed 40 50 m and can be related to the pressure head of the mud below the decollement two types of structures are identified mud volcanoes and massively emplaced diapirs and ridges on the one hand enigmatic circular very flat mud pies and conical mounds on the other hand the second type of structures has steeper slopes and appears to be associated with very active venting as confirmed by a submersible exploration reported in a companion paper le pichon et al this issue b the venting results in the formation of a stiff carbonate crust and of large subsiding basins around the mud pies continuous active fluid expulsion through these structures indicates that an efficient piping system still connects them to the zone of anomalously high pore pressure below the protodecollement

mud diapirism and subcretion in the barbados ridge accretionary complex the role of fluids in accretionary processes mud diapirism has recently been recognized in several modern accretionary wedges it provides an important means of dewatering accretionary wedges and should be regarded as an important process for producing the melanges found in both modern and ancient accretionary terranes mud diapirism affects a large area of the barbados ridge accretionary complex the distribution of the mud diapirs appears to be primarily controlled by the presence of underconsolidated terrigenous submarine fan deposits that are being accreted to the complex the frequency of diapir occurrence decreases northward as the fan becomes thinner mud diapirs are absent from the very eastern most part of the complex formed from sediments accreted at its toe with the exception of a few mud volcanoes on the ocean floor in front of the complex the initiation of diapirism appears to be spatially coincident with the onset of subcretion or underplating of sediment to the base of the complex at a ramp between two levels of decollement it is proposed that the release of mud and pore water from the subcreted sediments is a direct or indirect cause of most of the mud diapirism in the accretionary complex there is a range of diapiric form dependent on the viscosity of the mud from mud volcanoes fed by low viscosity mud to higher viscosity mud ridges the diapirs in the eastern areas of the complex are generally mud volcanoes with narrow conduits feeding a surface mound mud ridges are prominent in the western parts of the complex this is interpreted as reflecting a general westward decrease in the fluid content of the accretionary complex bottom simulating seismic reflectors formed by gas hydrate are commonly developed in the areas of mud volcano occurrences the presence of the hydrate indicates that large volumes of methane are being generated at depth in these regions the generation of methane may be contributing to zones of overpressuring in the wedge methane may also be partly responsible for driving the diapiric material to the surface to form mud volcanoes ridges in the subducting oceanic crust beneath the accretionary complex locally enhance diapirism above their crests and southern flanks faults formed later in the development of the complex are more commonly associated with diapirism than those resulting from accretion at the toe of the wedge these later faults play an important role in controlling the sites of individual mud volcanoes chains of mud volcanoes and mud ridges

authigenic carbonate precipitates from the ne black sea a mineralogical geochemical and lipid biomarker study carbonate precipitates recovered from 2 000 m water depth at the dolgovskoy mound shatsky ridge north eastern black sea were studied using mineralogical geochemical and lipid biomarker analyses the carbonates differ in shape from simple pavements to cavernous structures with thick microbial mats attached to their lower side and within cavities low 13c values measured on carbonates 41 to 32 v pdb and extracted lipid biomarkers indicate that anaerobic oxidation of methane aom played a crucial role in precipitating these carbonates the internal structure of the carbonates is dominated by finely laminated coccolith ooze and homogeneous clay layers both cemented by micritic high magnesium calcite hmc and pure botryoidal yellowish low magnesium calcite lmc grown in direct contact to microbial mats 18o measurements suggest that the authigenic hmc precipitated in equilibrium with the black sea bottom water while the yellowish lmc rims have been growing in slightly 18o depleted interstitial water although precipitated under significantly different environmental conditions especially with respect to methane availability all analysed carbonate samples show lipid patterns that are typical for anme 1 dominated aom consortia in the case of the hmc samples with significant contributions of allochthonous components of marine and terrestrial origin reflecting the hemipelagic nature of the primary sediment

seabed morphology and gas venting in the black sea mudvolcano area observations with the mak 1 deep tow sidescan sonar and bottom profiler abstract the central part of the black sea was investigated with the mak 1 deep tow acoustic system providing sidescan observations and acoustic profiling subsequently underwater tv recordings and bottom sampling was done in an area with extensive mudvolcanism the mud volcanoes can be divided into three types according to their dimensions and morphology the first type has a seabed diameter of more than 2 km reaches a height of 100 150 m has a complex top with a crater like structure and gentle slopes and reflects massive mudflows in the crater and at its flanks the second type has smaller dimensions is more conical in cross section almost without relief on its relatively steep slopes and is characterised by small radial mudflows the third type is made up by the only mud volcano with a partially collapsed rim and with massive and liquid mudflows the first type expectedly is in a mature relatively passive stage the latter two types seem to be younger and more active various types of low relief slides are found in the area and are related to the presence of shallow subbottom gas 40 100 m below the seafloor or mudvolcano activity evidence for the presence of gas in the mudvolcano area is shown by gas venting acoustic turbidity acoustic masking numerous pockmarks acoustic voids and acoustic windows gashydrates do occur associated with some of the mudvolcanoes

the geochemistry and origin of the hydrothermal water erupted at lusi indonesia abstract the spectacular lusi mud eruption started in northeast java the 29th of may 2006 despite extensive research the origin of the erupted water remains elusive and poorly constrained here we present a comprehensive study of the geochemistry of lusi waters compared with those collected from surrounding areas all collected between 2006 and 2013 including data from mud volcanoes and volcano hosted hydrothermal springs within this broad context the geochemical characteristics of the fluids expelled in the lusi region suggest that we can classify the waters in three groups 1 meteoric waters expelled in cold springs and artesian wells 2 hydrothermal waters typically mixed with meteoric waters and 3 formation water from marine sediments altered by diagenetic processes such as clay mineral dehydration samples collected from the lusi crater are cl and na dominated up to 527 mm and 471 7 mm respectively similar to seawater indicating that altered sedimentary formation waters are predominant in this system in addition they are enriched in sr up to 808 4 m and other elements commonly associated with hydrothermal systems such as li up to 877 6 m compared to 26 m in seawater some of these elements are up to ten times enriched compared to seawater values high temperature fluid mineral interactions in the subsurface appear to have facilitated the transfer of li and other mobile elements into the fluids high temperature fluid mineral interaction reactions are also supported by si concentrations significantly higher compared to other sampled mud volcanoes in the island crater samples also show the highest 18o values 5 after correction for evaporation compared to 1 at the mv localities 87sr 86sr ratios vary between of 0 7077 and 0 7083 and seem to reflect a general mixture of fluids from clay mineral dehydration carbonate recrystallization alteration of volcanic rocks and hydrothermal imprint eight years of geochemical monitoring indicate that the composition of the deep sourced lusi fluids remain fairly constant through time thus our findings show that the lusi crater waters represent a regional geochemical anomaly and we suggest that a combination of high temperatures in the source region and fluid rock interactions with silicates and possibly carbonate rich lithologies can explain the data this is consistent with a model where the emitted gases migrate from a deep seated 4 km source region likely associated with the presence of hot igneous intrusions and or high t reactions related to the presence of neighbouring active volcanoes

nature and distribution of deformation across the banda arc australian collision zone at timor recently acquired seismic reflection and seamarc ii side scan and swath bathymetry profiles near timor show that the banda arc australia collision zone has a tectonic framework similar to that of a typical oceanic subduction system deformation is occurring at present most intensely at the foot of the inner slope of the timor trough this deformation front is discontinuously advancing southward as new thrust slices develop within the subducted australian margin strata in contrast present deformation is apparently negligible in the savu basin the complex fore arc basin north of timor a possible significant exception is a postulated right lateral northeast trending fault zone offsetting the outer arc high between savu and roti although back arc thrusting has been documented north of the volcanic arc this component of convergence is minor compared with the scale of ongoing deformation in the timor trough the detailed nature of these surveys has also led to the recognition of along strike variations in deformation in the timor trough and in the savu basin these variations may be related to the variable degree of involvement of the australian continental margin along the arc

mud volcano field seaward of the barbados accretionary complex a submersible survey we describe a 0 55 km2 semicircular mud pie and three adjacent diapiric mounds explored using the submersible nautile near 13 50 n 12 km seaward of the barbados accretionary complex deformation front this diapiric field had been previously explored with an acoustically navigated deep towed side scan sonar thus providing an accurate base map the mud pie is situated at a depth of 4938 m in addition to visual observations water rock sediment and biological sampling we measured temperature gradients and made geochemical analyses of the samples fluid venting associated with chemosynthetic animal communities is widespread on all four structures but is maximal in the central third of the mud pie the chemosynthetic life distribution on the mud pie displays a concentric zonation which we relate to an increase in venting activity toward the center as evidenced by thermal gradients recent mud flows are present in the centralmost part of the mud pie the simplest interpretation of the structure is that it is a mud lake covered by a mechanically resistant carbonate crust we determine that approximately 106 m3 of fluid are advected upward through the crust of the mud lake every year this large amount of fluid implies large scale lateral transport

the mediterranean ridge and related mud diapirism a background abstract the mediterranean ridge stretching from the calabrian rise to the florence rise is the largest structural unit of the eastern mediterranean sea it is directly related to ongoing convergence and collision of the african and eurasian plates starting in the oligocene and is considered to be a giant accretionary complex consisting of intensively folded and faulted rocks of the african margin since its origin in the late miocene the ridge continued to grow up and outward experiencing more deformation because of the developing collision the mud diapirism and mud volcanism are usual and wide spread phenomena for the mediterranean ridge that developed as a result of an intensive tectonic overburden due to stacking of rock units by thrusting and strong lateral compressional stress pressing up and squeezing plastic sedimentary series out onto the seafloor

palaeo methane seepage history traced by biomarker patterns in a carbonate crust nile deep sea fan eastern mediterranean sea abstract we investigated lipid biomarkers in three depth intervals of a methane derived carbonate crust collected from a pockmark in the nile deep sea fan sampled during the nautinil cruise of the r v l atalante a diverse set of 13 c depleted archaeal and bacterial lipids were detected along this crust with 13 c values as low as 118 this provides evidence that anaerobic oxidation of methane was the main process that induced the formation of this carbonate crust archaeal lipid biomarker distributions revealed the presence of archaea belonging both to the anme 1 and anme 2 phylogenetic clusters with the former predominating the distribution and compound specific 13 c values of aom derived lipid biomarkers showed no significant variations with depth these results infer that the archaeal community structure and thus the local seepage environment remained relatively stable during the 5000 kyr period of the carbonate crust precipitation

spatial transition from compression to extension in the western mediterranean ridge accretionary complex the mediterranean ridge has been described since 1982 as an accretionary prism related to the hellenic subduction zone however little attention has been paid to the actual mechanical boundary between the sedimentary wedge and the crustal backstop of the outer hellenic arc using seismic velocity structures from recent esp s pasiphae cruise we propose a new interpretation of existing geological and geophysical data around the western hellenic trenches the velocity structure of the inner unit of the mediterranean ridge suggests that the late neogene to quaternary sequences were deposited above a high velocity rigid body we propose to correlate the boundary of this rigid body backstop of the accretionary wedge with a series of oblique reflectors dipping to the southwest near dsdp sites 126 and 377 the backstop extends further south than previously thought and decreases by one third the total width of the compressional wedge it has thus major implications on the volume of accreted material the short wavelength folding of plio quaternary sediments observed on the outer wall of the south matapan trench is probably a consequence of gravity gliding layers above the high velocity body gently dipping 2 to the northeast using the messinian evaporite as a decollement on the other hand the hellenic trenches appear to be narrow half grabens affected by the widespread extensional deformation active on the outer hellenic arc they are situated on the landward boundary of a wider and poorly sedimented fore arc basin we conclude that extensional deformation extends at least over the width of the hellenic trenches on the continental side of the backstop whereas compressional deformation stops near the edge of the backstop itself 100 km to the southwest

complex plumbing systems in the near subsurface geometries of authigenic carbonates from dolgovskoy mound black sea constrained by analogue experiments targeted sampling on the dolgovskoy mound northern shatsky ridge revealed the presence of spectacular laterally extensive and differently shaped authigenic carbonates the sampling stations were selected based on sidescan sonar and profiler images that show patchy backscatter and irregular and discontinuous reflections in the near subsurface the interpretation of acoustic data from the top part of the mound supports the seafloor observations and the sampling that revealed the presence of a complex subsurface plumbing system characterized by carbonates and gas the crusts sampled consist of carbonate cemented layered hemipelagic sedimentary unit 1 associated with several centimetres thick microbial mats three different carbonate morphologies were observed a tabular slabs b subsurface cavernous carbonates consisting of void chambers up to 20 cm3 in size and c chimney and tubular conduits vertically oriented or forming a subhorizontal network in the subsurface the methanogenic origin of the carbonates is established based on visual observations of fluids seepage structures 13c depletion of the carbonates 13c varying between 36 7 and 27 4 and by thin carbonate layers present within the thick microbial mats laboratory experiments with a hele shaw cell were conducted in order to simulate the gas seepage through contrasting grain size media present on the seafloor combined petrography visual observations and sandbox simulations allowed a characterization of the dynamics and the structures of the plumbing system in the near subsurface based on sample observations and the experiments three observed morphologies of authigenic carbonates are interpreted respectively as a darcian porous flow through the finely laminated clayey coccolith rich layers b gas accumulation chambers at sites where significant fluid escape was impeded by thicker clayey layers forming the laminated unit1 and c focussed vertical fluid venting and subhorizontal migration of overpressured fluids released from b the hele shaw cell experiments represent a promising tool for investigating shallow fluid flow pathways in marine systems

timing and origin for sand dunes in the green river lowland of illinois upper mississippi river valley usa abstract the recent increase in dune studies in north america has been heavily focused in the great plains while less attention has historically been given to the dune fields east of the mississippi river here we report ages and suggest a potential sediment source for sand dunes in the green river lowland illinois which may provide a better understanding of the dynamic interactions between eolian glacial lacustrine and fluvial processes that shaped the landscapes of the upper midwest seven coherent optically stimulated luminescence ages osl or optical ages obtained from four sites suggest that major dune construction in the green river lowland occurred within a narrow time window around 17 500 ago this implies either an enhanced aridity or an episodic increase of sediment supply at 17 500 years ago or combination of the both contrary to previous assertions that dune sand was sourced from the deflation of the underlying outwash sand deposited when the lake michigan lobe retreated from the area we propose that green river lowland dunes sand originated from the green bay lobe through the rock river specifically sediment supply increased in the rock river valley during drainage of glacial lake scuppernong which formed between 18 000 and 17 000 years ago when the green bay lobe retreated from its terminal moraine the lake drained catastrophically through the rock river valley providing glacial sediment and water to erode the preexisting sandy sediments throughout the remainder of the late pleistocene the laurentide ice sheet drained into larger more northerly glacial lakes that in turn drained through other river valleys therefore the dunes in the green river lowland formed only during the catastrophic drainage of glacial lake scuppernong but were stabilized through the remainder of the pleistocene this scenario explains the abrupt dune construction around 17 500 years ago and explains the lack of later dune activity up to the pleistocene holocene transition osl and radiocarbon ages also indicate that dunes were reactivated during the early middle and late holocene some eolian activation occurred within well defined dry intervals in the upper midwest suggesting that increased aridity may have been the primary driver in mobilizing sand however many ages do not correspond to drier periods in contrast to the relative coherency of the pleistocene osl ages from multiple study sites the holocene osl ages do not overlap from one site to another suggesting that increased aridity alone cannot explain the multiple phases of dune reactivation in the holocene therefore we conclude that the combined effect of localized disturbances and greater aridity acted in concert to increase eolian sand activity in the holocene the multiple periods of eolian activity during the holocene suggest a high potential for future sand activation in the region and these results are informative for environmental prediction and potential future mitigation

biomarker and 16s rdna evidence for anaerobic oxidation of methane and related carbonate precipitation in deep sea mud volcanoes of the sorokin trough black sea many mud volcanoes were recently discovered in the euxinic bottom waters of the sorokin trough ne black sea three of them i e nioz odessa and kazakov were selected for a detailed biogeochemical investigation four methane related carbonate crusts covered with microbial mats and sediments dmud brecciat from these mud volcanoes were collected during the 11th training through research cruise ttr 11 in 2001 the first finding of methanotrophic microbial mats associated with authigenic carbonates in the deep black sea we measured the concentrations and 13c values of methane and specific archaeal and bacterial lipids and determined archaeal and bacterial 16s rrna gene sequences the 13c of the microbial lipids reflected the carbon isotopic values of the methane indicating that methane was the main carbon source for microorganisms inducing carbonate formation anaerobic oxidation of methane aom in these settings was performed by archaea affiliated with the so called anme 1 group none of the identified archaeal sequences were closely related to known methanogens the combined 16s rrna gene sequence and biomarker data revealed a distinct difference in archaeal assemblage between the carbonate crusts and mud breccias besides gene sequences of sulfate reducing bacteria dna analysis of bacterial communities revealed a diversity of bacteria with apparent contrasting metabolic properties the methane utilization via aom processes was detected in the uppermost sediments where it subsequently induces authigenic carbonate precipitation most probably below seafloor the results of integrated biomarker and 16s rrna gene study reveal a crucial role of aom processes in formation of authigenic carbonates in methane seep environments

morphology and activity of the helgoland mud volcano in the sorokin trough northern black sea abstract morphological change and activity of submarine mud volcanoes mvs are still poorly understood in this study we integrated acoustic subbottom profiles autonomous underwater vehicle auv high resolution bathymetric and backscatter data remotely operated vehicle rov seafloor observations bottom water temperatures bwt and compositions of gas samples collected from three research expeditions to study the morphology and activity of the helgoland mud volcano helgoland mv in the sorokin trough of the black sea based on the micro bathymetric and backscatter maps we conducted a geomorphological analysis which differentiates the helgoland mv into five regions which are the active center the inner crest the inner moat the outer crest and an outer moat special seafloor features such as gas bubble emissions mud breccia and mud pools were observed in different regions by rov observations they indicate a heterogeneous distribution of materials and activities at the helgoland mv active mud extrusion from the center was inferred from bwt elevations up to 1 652 c that showed the same orientation as a major fault nw se at the location methane stable carbon isotopes 58 1 63 6 and molecular compositions of light hydrocarbons c1 c2 2836 ch4 99 545 c2h6 0 033 c3h8 0 002 co2 0 417 suggest a predominance of biogenic hydrocarbons with an admixture of thermogenic gas circular faults surrounding the helgoland mv as observed in the bathymetric and sub bottom profiles are speculated to be formed due to subsidence of the mv caldera and gravity driven sediment movement a conceptual model is proposed to explain the interrelationship between the seafloor morphology and activity of the helgoland mv combining multidisciplinary data especially from the application of rovs and auvs broaden the scope in which the activity and morphology of submarine mud volcanoes can be investigated

natural oil seepage at kobuleti ridge eastern black sea abstract analysis of advanced synthetic aperture radar satellite images in combination with water column and seafloor investigations documented natural oil seepage from pechori mound and colkheti seep in 1000 1200 m water depth in the eastern black sea offshore georgia hydroacoustic imaging of the water column using multibeam echosounder evidenced numerous gas emissions from both structures gas bubbles rose as high as 45 m below sea surface it is proposed that oil coatings around gas bubbles hamper their dissolution allowing them to reach the sea surface where widespread oil slicks are formed slow rise velocities 14 1 cm s 1 of bubbles with radii of 2 6 0 3 mm n 101 derived from video data obtained with the remotely operated vehicle marum quest4000 corroborate the assumption that bubbles are oil coated high resolution seafloor mapping with the autonomous underwater vehicle marum seal5000 at colkheti seep revealed a crater strewn morphology whose formation is explained by frequent rafting of shallow gas hydrate deposits satellite imaging of oil slicks on the sea surface above both sites indicates that oil seepage is rather persistent since 2003 an order of magnitude estimation of minimum oil seepage rates suggests discharge rates of 40 liters per hour from both sites the data presented are the first comprehensive description of oil seepage in the black sea

fluid venting from a mud volcano in the mediterranean ridge diapiric belt direct observation of active emission of fluids and mud from a submarine mud volcano were made for the first time in an extensive field of mud diapirs and mud volcanoes on the mediterranean ridge using a video camera towed 2 m above the seafloor in 1800 m of water this recent research using both long range and deep towed sidescan sonar systems indicates also that diapirism and eruption of mud along the crest of the ridge is more common than previously thought the southwards increase in age of rock fragments carried within the erupted mud supports the hypothesis that the fluid mud becomes overpressured within a southward dipping backthrust from the inner deformation front of this accretionary prism

geological evidence for mud diapirism on the mediterranean ridge accretionary complex abstract a mud breccia has been repeatedly cored from four mud diapir fields located on the crest of the mediterranean ridge this breccia is composed of subrounded clasts supported by a clay rich matrix and ranges in age from cretaceous to early miocene sedimentological analysis allows identification of a primitive intrusive and a reworked mud breccia the latter being formed by mud extrusion and gravitational reworking of the former homogeneous mud sorted by grain size which occurs at the top of the diapirs has been interpreted as a lake deposit based on composition and carbon isotopic ratios gases present within the diapiric material suggest a partial thermogenic origin and gas escape structures have been identified in the mud breccia and host sediments carbonate crusts occurring in the host sediments are not related to bacterial oxidation of methane and consequent authigenic calcite precipitation their carbon and oxygen isotopic ratios reveal that they are characteristic of early deep sea lithification in the mediterranean sea the presence of a marker bed composed of mn nodules and bacterial colonies the mud lake deposits showing lower carbonate content than primitive mud breccia and the gas escape structures suggest the presence of active fluid vents in the vicinity of the diapiric structures evidence of active mud diapirism can be found from about 300 000 yrs b p to the present

spatial distribution of mud flows chemoautotrophic communities and biogeochemical habitats at hakon mosby mud volcano marine mud volcanoes are significant source locations contributing to the marine methane cycle enhanced heat flow unique chemoautotrophic communities occurrence of massive gas hydrates and large gas plumes are direct evidences of elevated methane concentrations and the dynamic environment of mud volcanoes related to the high concentrations and large inventories of ch4 in surface sediments only a fraction of the methane is exported to the bottom water this is mainly due to chemoautotrophic communities oxidizing methane and proving a microbial filter reducing ch4 fluxes although these processes were studied for several mud volcanoes still little is known about the spatial pattern and the areas covered by chemoautotrophic communities or by present mud flows for this purposes the hakon mosby mud volcano hmmv which is located at the continental slope of the barents sea was studied by several dives with the remotely operated vehicle victor6000 during these dives a high resolution microbathymetric map with a footprint of 25 25 cm and a vertical resolution of better than 10 cm was derived furthermore video streams of the bottom camera were converted into georeferenced mosaics providing a detailed image about the spatial distribution of seafloor features as bacterial mats pogonophorans both indicating methane oxidation or mud flows based on visual inspection of 2310 georeferenced mosaics covering an area of 46 160 m 2 different biogeochemical habitats were identified and quantified on a m 2 basis by application of geostatistic techniques as indicator kriging the distribution of different biogeochemical habitats was quantified and mapped for the entire hmmv considering the flat and hummocky area of hmmv approximately 16 115 165 m 2 of the flat centre is nearly void of any benthic communities this area is considered as a region of high methane discharge into bottom water an area of 5 38 244 m 2 located in the south eastern part is densely inhabited by beggiatoa the hummocky outer part is colonised dominantly by pogonophoran tube worms 37 3 276 121 m 2 and only occasional by beggiatoa source locations and drainage directions for current mud flows were identified by computation of trend surfaces and consideration of temperature data this suggests that present mud flow ascend close to the northern edge of the flat unit of hmmv and that the drainage pattern of mud flows shifted from a westward to a south south eastern direction 2007 elsevier b v all rights reserved