the late devensian glaciation along the western margin of the cheshire shroshire iowland the glacial succession in the western part of the cheshire shropshire lowland records the advance coalescence and subsequent uncoupling of irish sea and welsh ice sheets during the late devensian stage during advance a discontinuous sheet of basal till was emplaced across the floor of the region by subglacial lodgement on retreat compression of the irish sea ice sheet against bedrock obstruction generated a zone of supraglacial sedimentation resulting in the creation of the wrexham ellesmere wem whitchurch moraine system and the formation of a wide range of sedimentary environments including ice marginal sandur troughs ice front alluvial fans proglacial ribbon sandur and subglacial ice contact and proglacial lakes the geometry of sedimentary units and their lithologic and geomorphic characteristics display spatially ordered patterns of sediment landform assemblage which show that the statigraphic succession is a response to rapidly changing depositional conditions at a retreating supraglacial ice margin punctuated by minor still stands and ice front oscillations

three dimensional seismic structure of a mid atlantic ridge segment characterized by active detachment faulting trans atlantic geotraverse 25 55 n 26 20 n we use air gun shots recorded by ocean bottom seismometers obss to generate a three dimensional 3d p wave tomographic velocity model of the trans atlantic geotraverse tag segment of the mid atlantic ridge and to search for evidence of reflections from a shallow crustal fault interface near vertical reflections were observed in some of the seismic records from obss deployed within the active seismicity zone defined by microearthquake hypocenters forward modeling of synthetic seismograms indicates that these reflections are consistent with a fault interface dipping at a low angle toward the ridge axis our observations suggest that the fault zone may extend beneath the volcanic blocks forming the eastern valley wall our 3d tomographic results show that the across axis structural asymmetry associated with detachment faulting extends at least 15 km to the east of the ridge axis indicating that detachment faulting and uplifting of deep lithologies has been occurring at the tag segment for at least the last similar to 1 35 myr the velocity model contains a 5 km by 8 km velocity anomaly within the detachment footwall this anomaly which is present beneath the active tag hydrothermal mound is characterized by a velocity inversion at 1 5 2 0 km below seafloor underlain by reduced p wave velocities similar to 6 2 6 5 km s compared to surrounding areas similar to 7 0 7 2 km s extending down to 3 5 km below seafloor the velocity anomaly likely results from some combination of thermal and or hydrothermal processes and in either case our results suggest that hydrothermal fluids circulate within the upper section of the detachment footwall beneath the active mound

vent type taxa in a hydrocarbon seep region on the louisiana slope recent discoveries on the northern gulf of mexico continental slope have altered our understanding of biological and chemical processes occurring in the deep ocean a biological community of hydrothermal vent type organisms was recently discovered at the base of the florida escarpment1 where the fauna are apparently nourished by hydrogen sulphide rich hypersaline water seeping out onto the sea floor dense colonies of deep living chemosynthetic benthic organisms were first discovered during investigations of warm water anomalies along the axis of the galapagos rift in the pacific ocean in 19772 4 and this first discovery of clusters of clams tube worms and other filter feeders in the immediate proximity of warm water vents has been followed by the discovery of a number of other hydrothermal vent sites for example guaymas basin east pacific rise at 21 n the dense population assemblages at these sites are apparently restricted to small areas of the ocean floor where hydrogen sulphide rich water is escaping from spreading centres but the florida escarpment discovery indicates that these communities can also exist on passive margins here we report the discovery of dense biological communities associated with regions of oil and gas seepage on the louisiana continental slope these communities of large epi and infaunal organisms are similar to those associated with the vents of the pacific and the hypersaline brine seeps of the florida escarpment carbon isotope analyses suggest that these communities are chemosynthetic and derive their energy from hydrogen sulphide and or hydrocarbons similar communities may be widely distributed on the sea floor in other oil producing regions of the ocean

geological and morphological setting of 2778 methane seeps in the dnepr paleo delta northwestern black sea abstract the dnepr paleo delta area in the nw black sea is characterized by an abundant presence of methane seeps during the expeditions of may june 2003 and 2004 within the eu funded crimea project detailed multibeam seismic and hydro acoustic water column investigations were carried out to study the relation between the spatial distribution of methane seeps sea floor morphology and sub surface structures 2778 new methane seeps were detected on echosounding records in an area of 1540 km 2 all seeps are located in the transition zone between the continental shelf and slope in water depths of 66 to 825 m the integration of the different geophysical datasets clearly indicates that methane seeps are not randomly distributed in this area but are concentrated in specific locations the depth limit for the majority of the detected seeps is 725 m water depth which corresponds more or less with the stability limit for pure methane hydrate at the ambient bottom temperature 8 9 c in this part of the black sea this suggests that where gas hydrates are stable they play the role of buffer for the upward migration of methane gas and thus prevent seepage of methane bubbles into the water column higher up on the margin gas seeps are widespread but accurate mapping illustrates that seeps occur preferentially in association with particular morphological and sub surface features on the shelf the highest concentration of seeps is found in elongated depressions pockmarks above the margins of filled channels on the continental slope where no pockmarks have been observed seepage occurs along crests of sedimentary ridges there seepage is focussed by a parallel stratified sediment cover that thins out towards the ridge crests on the slope seepage also appears in the vicinity of canyons bottom flanks and margins or near the scarps of submarine landslides where mass wasting breaches the fine grained sediment cover that acts as a stratigraphic seal the seismic data show the presence of a distinct gas front which has been used to map the depth of the free gas within the sea floor sediments the depth of this gas front is variable and locally domes up to the sea floor where the gas front approaches the seafloor gas bubbles were detected in the water column a regional map of the sub surface depth of the gas front emphasises this gas front versus seep relationship the integration of all data sets indicates that the spatial distribution of methane seeps in the dnepr paleo delta is mainly controlled by the gas hydrate stability zone as well as by stratigraphic and sedimentary factors

post miocene rifting and diapirism in the northern red sea abstract rifts and diapirs are the dominant structures in the bathyal zone of the northern red sea where commonly the diapirs ascend along normal faults associated with the rifts in this manner the diapirs form elongated features sometimes exceeding lengths of 30 km and widths of 4 km they also penetrate a sedimentary sequence about 1000 m thickness or less thicknesses generally considered to be barely adequate for the gravity conversion required to initiate diapiric motion we suggest that development of diapirs under these minimal overburden conditions was made possible by the high thermal gradients in the area resulting from the underlying attenuated continental crust and ascending mantle that prevail in the rift system of the northern red sea diapiric evolution was also dependent on the extensional tectonic regime with its numerous normal faults forming weaknesses along which the diapirs could move upwards

contributions to atmospheric methane by natural seepages on the u k continental shelf mar geol 137 1997 165 189 abstract natural gas seepages occur on the united kingdom s continental shelf and although published reports suggest that they are very rare the petroleum industry has identified but not publicly reported many more there is also very little data on the flux of gas from seabed seepages and even less on the contribution of seepages to atmospheric concentrations of gases such as methane potential gas source rocks include quaternary and tertiary peats as well as petroliferous source rocks such as the carboniferous coal measures and the upper jurassic kimmeridge clays there are also other organic rich sediments which are potential source rocks together these cover a considerable part of the u k continental shelf analogue seismic reflection pinger profiles acquired during the british geological survey s regional mapping programme have been reviewed to identify water column targets including fish and plumes of gas bubbles the ability to distinguish targets is critical to an assessment of the distribution of gas seepages both theoretical predictions of target identity and the habits of shoaling fish have been investigated in order to identify a method of distinction data from seabed seepages and measurements of seepage rates have been used to establish likely ranges of gas flux rates and the sizes of gas bubbles the likelihood that a rising bubble will survive and escape into the atmosphere is determined primarily by bubble size and water depth methane the principal constituent of seepage gas is relatively unreactive and sparingly soluble the studies have enabled a new estimate of the distribution of gas seepages on the u k continental shelf and of the contribution to atmospheric methane levels the results suggest that natural gas seepages are significantly more important as a source of methane than had hitherto been established it is estimated that between 120 000 and 3 5 mtonnes of methane per year come from a continental shelf area of about 600 000 km 2 this represents between 2 and 40 of the total united kingdom methane emission it is suggested that similar contributions arise from other continental shelf areas worldwide and that geological sources of atmospheric methane are more significant than is generally acknowledged

contributions to atmospheric methane by natural seepages on the uk continental shelf natural gas seepages occur on the united kingdom s continental shelf and although published reports suggest that they are very rare the petroleum industry has identified but not publicly reported many more there is also very little data on the flux of gas from seabed seepages and even less on the contribution of seepages to atmospheric concentrations of gases such as methane potential gas source rocks include quaternary peats as well as petroliferous source rocks such as the carboniferous coal measures and the upper jurassic kimmeridge clays there are also other organic rich sediments which are potential source rocks together these cover a considerable part of the u k continental shelf analogue seismic reflection pinger profiles acquired during the british geological survey s regional mapping programme have been reviewed to identify water column targets including fish and plumes of gas bubbles the ability to distinguish targets is critical to an assessment of the distribution of gas seepages both theoretical predictions of target identity and the habits of shoaling fish have been investigated in order to identify a method of distinction data from seabed seepages and measurements of seepage rates have been used to establish likely ranges of gas flux rates and the sizes of gas bubbles the likelihood that a rising bubble will survive and escape into the atmosphere is determined primarily by bubble size and water depth methane the principal constituent of seepage gas is relatively unreactive and sparingly soluble the studies have enabled a new estimate of the distribution of gas seepages on the u k continental shelf and of the contribution to atmospheric methane levels the results suggest that natural gas seepages are significantly more important as a source of methane than had hitherto been established it is estimated that between 120 000 and 3 5 mtonnes of methane per year come from a continental shelf area of about 600 000 km2 this represents between 2 and 40 of the total united kingdom methane emission it is suggested that similar contributions arise from other continental shelf areas worldwide and that geological sources of atmospheric methane are more significant than is generally acknowledged

proglacial sediment instability features on the scotian slope at 63 w abstract a small area of the scotian slope has been investigated in detail as a type example of a high latitude continental slope adjacent to a major ice outlet the geologic framework has been defined by airgun seismic profiles which show that late tertiary shales have irregular dips but overlie undisturbed strata these shales form a zone of diapirs at around 1200 m water depth which have ponded the prograding quaternary sediments upslope high resolution sparker profiles seamarc i mid range sidescan imagery and piston cores have been used to investigate the late quaternary sedimentary sequence a prominent gullied horizon about 40 m subbottom that is overlain by acoustically unstratified sediments sands is correlated with the occurrence of an early middle wisconsinan grounded icesheet at the top of the continental slope it is overlain by a thick sequence of proglacial muds and a thin veneer of holocene sediments much of the late wisconsinan sequence has been dissected by a series of closely spaced gullies both sidescan and subbottom profiler data show that slumping is common in the late wisconsinan sequence as a result of high sedimentation rates and local gully erosion piston cores provide evidence for debris flows and turbidity currents depositional sediment mounds in the diapir zone have accumulated sediment at three times the regional sedimentation rate suggesting that large amounts of fine sediment reached the slope in suspension and that much of the proglacial sediment by passed the continental slope

structural evolution of shale diapirs from reactive rise to mud volcanism 3d seismic data from the baram delta offshore brunei darussalam two areas of shale diapirism in a deltaic setting were examined using 3d seismic data from offshore brunei to determine the origin evolution and geometry of shale diapirs the study areas cover parts of the egret and ampa fields within the baram delta province the ampa diapir consists of a small bulge of the mobile setap shale around which lies a zone of chaotically disrupted country rock reflections at the crest of this chaotic zone vertical cylindrical shale pipes arise that end in a wider head the diapir heads wear halos of high amplitude reflections probably due to the presence of methane gas the egret data show the same features except that the bulge of the source layer is not detected due to low reflectivity and chaotic reflections at the base of the overburden the bulging of the setap shale on the ampa data is interpreted as modified reactive diapirism in response to differential loading the initial reactive diapir shape was modified by lateral or oblique upward migration of fluidized shales into the hanging wall of the fault controlling the reactive diapir this probably occurred as a network of dykes and sills the presence of some preserved bedding is indicated by weak but coherent reflectivity from the area initially defined as chaotic shale the spreading of overpressure and the injection of shale into the overburden is thought to be a late phenomenon possibly late pliocene or early pleistocene and the mobility of the shale is attributed to overpressure increase due to gas generation within the setap shale and maybe the lower part of the overburden gas migration perhaps ahead of the diapir intrusion probably facilitated the mud injection the ampa and egret diapirs formed in two diapiric phases an early reactive diapirism and a later active diapirism but the phases have little in common they are seperated by about 9 million years of inactivity and differ in process and probably differ in degree of overpressure in overpressure generating mechanism and in properties of the diapiric mud

gas seepage and assumed mud diapirism in the italian central adriatic sea abstract an assemblage of acoustic and topographical features recorded on high resolution 3 5 khz sub bottom profiler records are discussed a close relationship between locally elevated sea bed mounds or ridges and the several acoustic features is found in the adriatic sea off ortona italy these features include acoustically turbid or opaque zones assumed to represent gas charged sediments acoustically transparent sediments assumed to represent sediments with relatively high pressured pore water free of large gas bubbles acoustic fountains assumed to represent 1 2 m wide sediment columns of relatively high pressured pore water where the gas charged pore water may migrate vertically through the sediment acoustic voids assumed to be up to 50 m wide sediment zones near the sea bed containing high pressured gas charged pore water finely layered sediments assumed to represent sediments with sharp density contrasts caused by varying gas concentrations a function of grain size and stagnant pore water gas seepage to the water column originating at the acoustic voids the positive topographical sea bed features are assumed to represent sediment clay diapiric structures the mechanism of diapir formation and its association with the gas charged sediments and gas seepages is discussed diapirism is assumed to result when plastic clay near the sea bed is charged with gas migrating from below bubbles forming and concentrating in the plastic clay causes local density reversals whereby the clay flows upwards due to buoyancy thus forming the elevated topographical features and the associated gas seepages

soil formation in kettle holes from high altitudes in central apennines italy abstract kettle holes are relatively common features of glaciated landscapes and have been widely reported in the literature the work reported here documents the presence of kettle holes at high altitude and low latitude in the central apennines italy and describes the geomorphic and pedogenic processes that originated the soils infilling these depressions the areas selected for this study were located on three of the main massifs of the central apennines italy gran sasso majella and sibillini the kettle holes on these massifs formed at the end of the wurm glaciation appear smaller and shallower than those reported from elsewhere in the northern hemisphere are roughly circular in form and do not contain bogs or lakes in each area the dimensions of 40 kettle holes were measured and three kettle holes were excavated to examine the soils developed inside them the size of the kettle holes was highest in the sibillini massif where the glaciers reached altitudes as low as 1700 m in the very narrow low lying valleys it is hypothesised that at lower elevations the glacier receded more rapidly generating larger blocks of ice and consequently larger kettle holes once formed the kettle hole depressions were very effective as sediment traps and acted as sink for materials washed in from the surrounding slopes or from more distant wind blown sources in the kettle holes from gran sasso and majella massifs small fragments of woody charcoal were found the material filling the kettle holes accumulated inside them in the form of layers soils formed inside the kettle holes showed horizons whose thickness and properties appeared mostly inherited from the amassed layers the only pedogenic process common to the kettle holes of the three massifs was the incorporation of organic matter that as expected from the rather cold climatic conditions was subjected to slow dynamics in the kettle holes of the majella massif the horizons developed from layers rich of materials of volcanic origin and the formation of short range order minerals occurred we conclude that the soils inside the kettle holes are a repository of geomorphic pedogenic and in reference to the source of the charcoal paleo environmental information

integrated petrographic and geochemical record of hydrocarbon seepage on the voring plateau authigenic carbonate crusts nodules and chemoherms were sampled from pockmarks and mud diapirs on the southern part of the voring plateau during the ttr 8 and ttr 10 marine expeditions a petrographic and geochemical study was carried out to investigate their possible relationship with the seepage of hydrocarbon fluids all authigenic carbonates are depleted in 13 c 31 6 13 c 18 o 18 o 4 6 18 o 18 o rich fluid the occurrence of different carbonate mineral phases aragonite calcite dolomite is possibly related to varying dissolved sulphate concentrations in the diagenetic environment fluid inclusion microthermometry and raman spectroscopy indicate the presence of an aqueous hydrocarbon mixture inside the inclusions this seepage mixture was almost certainly immiscible resulting in heterogeneous trapping

seabed morphology and gas venting features in the continental slope region of krishna godavari basin bay of bengal implications in gas hydrate exploration abstract increased oil and gas exploration activity has led to a detailed investigation of the continental shelf and adjacent slope regions of mahanadi krishna godavari kg and cauvery basins which are promising petroliferous basins along the eastern continental margin of india in this paper we analyze the high resolution sparker subbottom profiler and multibeam data in kg offshore basin to understand the shallow structures and shallow deposits for gas hydrate exploration we identified and mapped prominent positive topographic features in the bathymetry data these mounds show fluid gas migration features such as acoustic voids acoustic chimneys and acoustic turbid layers it is interesting to note that drilling coring onboard joides in the vicinity of the mounds show the presence of thick accumulation of subsurface gas hydrate further geological and geochemical study of long sediment cores collected onboard marion dufresne in the vicinity of the mounds and sedimentary ridges shows the imprints of paleo expulsion of methane and sulfidic fluid from the seafloor to understand the origin of the mounds and their relationship with gas hydrate cold seep formation we analyzed the multi channel seismic reflection mcs data close to the mounds the mcs data show that the subsurface layers beneath the mounds are folded below the folded overburden we observe zones of no coherent reflections probably originating from miocene sequence since the study area is located in shale tectonics regime where miocene sequences are known to be overpressured we interpret the zones of no coherent reflections as miocene shale diapirs the upward movement of shale diapirs has folded the overburden layer and resulted in the formation of numerous faults fractures these faults act as permeable pathways for fluid gas movement facilitating the formation of gas hydrate and cold seeps close to shale diapiric mound

environmental changes within kettle holes at borras bog triggered by construction of the a5156 llanypwll link road north wales abstract an unusual cluster of 41 kettle holes occupies 3 km 2 on the surface of the wrexham delta terrace a glacial platform underlain by the singret member of the wrexham formation of pleistocene late devensian age two coalescent kettle holes at borras bog constitute a natural obstacle on the route of the a5156 llanypwll link road and posed difficulties for highway design and construction localised deposits of peat infill the kettle holes at borras bog and prompted concern about a potential subsidence problem within the area of highway construction the method adopted to cross the kettle holes involved driving sheet piling along the boundaries of the construction corridor excavating the peat from between the sheet pile walls and then infilling with granular material post construction monitoring revealed two changes within the mire first the level of the bog has subsided at about 10 mm y and secondly birch woodland has invaded the central part of the mire these changes indicate progressive dewatering of the kettle holes basin breaching of the clay floor of the basin is suspected to have induced drainage of the bog through the core of granular material a remedial strategy is recommended to encourage the bog to recover the main plank of the strategy entails grouting of the granular fill with bentonite slurry to seal the leakage points in addition the birch woodland growth should be cleared however the local community prefer the visual appearance of the flourishing new woodland and vigorously oppose the conservation measures deliberations continue on the optimum way forward

suspected gas associated clay diapirism on the seabed off mid norway abstract on the continental shelf off mid norway at water depths ranging from 150 to 350 m large areas of the seabed consist of plastic clays with a rugged surface topography and an amorphous opaque subsurface acoustic appearance five topographic side scan sonar and shallow seismic examples are presented and discussed many of the mounds and ridges are suspected to be of a clay diapiric nature numerous gas seepages originating from opaque clays have also been found off mid norway a tentative formation model for the ridges and dome shaped features is proposed the model is based on suspected differential gas charging of subsurface sediments and clay diapirism caused by differential clay buoyancy

giant irregular pockmark craters in the palaeogene of the outer moray firth basin uk north sea a cluster of irregular pockmark craters of palaeogene age in block 15 18 in the outer moray firth uk north sea have been mapped on 3d seismic data with well control the craters range from 0 5 to 4 km in diameter between 50 and 200 m in depth and have been buried by tertiary subsidence and sedimentation to present day depths of between 1000 and 1400 m sub sea they are circular to elliptical in plan view and are located in a delta front and upper pro deltaic slope position on the dornoch delta the structures are confined to the top of the lower eocene balder formation and regional mapping across the moray firth basin shows they are restricted to an area of ca 15 15 km2 well data show that the craters are sand filled and have excavated an argillaceous and tuffaceous unit the crater filling sands are sealed by overlying mudstone units planar wing like features emanate from the margins of the craters well control indicates that these seismically identified wings consist of sandstone suggesting that the craters have been modified by an episode of sand remobilisation and injection the proposed mechanism for the formation of these structures is large scale fluid eruption probably shallow gas at the early eocene seafloor these craters are significantly larger in size than those typically observed on contemporary sea floors we argue that the gas is more likely to have been sourced from deeper jurassic or carboniferous sediments within the witch ground graben than from shallow biogenic origins these structures rank in scale alongside the largest known pockmarks and demonstrate that natural fluid and hydrocarbon seeps have a long ancestry in this basin

evidence of fluid seepage in gronfjorden spitsbergen implications from an integrated acoustic study of seafloor morphology marine sediments and tectonics abstract this study integrates high resolution surface and sub surface geophysical data to investigate possible fluid gas and or liquids migration pathways to the seafloor in gronfjorden west spitsbergen gronfjorden is an n s aligned tributary fjord located in the western part of the isfjorden fjord system pockmarks were identified on the bathymetric data in the southern and northern parts of the fjord three types of shallow seep related acoustic features have been identified in the marine sediments i enhanced reflections ii acoustic turbid zones and iii acoustic blankings they occur beneath some of the pockmarks and circular patches of high backscatter on the seafloor in the central part of the fjord which are potential seep related seafloor features 6 8 km long nnw sse striking ridges have been identified in the southern part of the study area thrust faults were interpreted on 2d multichannel seismic data truncating the triassic jurassic and cretaceous successions of western isfjorden located north of gronfjorden a possible link has been found between these fault systems and the seafloor ridges which strike in a similar direction further a normal fault has been identified within the shallow marine sediments which drapes the bedrock of the fjord the fractured bedrock of the fjord and faults associated with the west spitsbergen fold and thrust belt could possibly represent major conduits for fluid migration from deeper stratigraphy to shallow marine sediments and the seafloor

thermogenic hydrocarbons in unconsolidated sediment of eel river basin offshore northern california thermally produced hydrocarbons were recovered from unconsolidated sediment ponded within a bathymetric depression on the surface of a shale diapir in the offshore eel river basin of northern california evidence that the hydrocarbons are thermogenic consists of the following 1 very high concentrations of hydrocarbon gases particularly ethane through butanes c2 c4 2 methane having a carbon isotopic composition relative to the pdb standard of 43 and 44 per mil 3 presence of gasoline range c5 hydrocarbons and 4 presence of a complex mixture of heavy hydrocarbons c15 with n alkanes having a petroleumlike distribution this mixture of gaseous and liquid hydrocarbons likely originated deep within the basin an migrated to the surface through fractures and faults developed during the emplacement of the diapir the presence of thermogenic hydrocarbons in unconsolidated surface sediment indicates that conditions for petroleum generation have existed within this offshore basin

evidence of volcanic and glacial activity in chryse and acidalia planitiae mars abstract chryse and acidalia planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water ice rich geologic history these landforms include giant polygons bounded by kilometer scale arcuate troughs bright pitted mounds and mesa like features to investigate the significance of the last we have analyzed in detail the region between 60 n 290 e and 10 n 360 e utilizing hirise high resolution imaging science experiment images as well as regional scale data for context the mesas may be analogous to terrestrial tuyas emergent sub ice volcanoes although definitive proof has not been identified we also report on a blocky unit and associated landforms drumlins eskers inverted valleys kettle holes consistent with ice emplaced volcanic or volcano sedimentary flows the spatial association between tuya like mesas ice emplaced flows and further possible evidence of volcanism deflated flow fronts volcanic vents columnar jointing rootless cones and an extensive fluid rich substratum giant polygons bright mounds rampart craters allows for the possibility of glaciovolcanic activity in the region landforms indicative of glacial activity on chryse acidalia suggest a paleoclimatic environment remarkably different from today s climate changes on mars driven by orbital obliquity changes or giant outflow channel activity could have resulted in ice sheet related landforms far from the current polar caps

acoustic evidence of shallow gas accumulations and active pockmarks in the izmir gulf aegean sea abstract based on high resolution chirp seismic multibeam bathymetry and side scan sonar data collected in the izmir gulf aegean sea in 2008 and 2010 gas related structures have been identified which can be classified into three categories 1 shallow gas accumulations and gas chimneys 2 mud diapirs and 3 active and inactive pockmarks on the chirp profiles shallow gas accumulations were observed along the northern coastline of the outer izmir gulf at 3 20 m below the seabed they appear as acoustic turbidity zones and are interpreted as biogenic gas accumulations produced in organic rich highstand fan sediments from the gediz river the diapiric structures are interpreted as shale or mud diapirs formed under lateral compression due to regional counter clockwise rotation of anatolian microplate furthermore the sedimentary structure at the flanks suggests a continuous upward movement of the diapirs several pockmarks exist close to fault traces to the east of hekim island most of them were associated with acoustic plumes indicating active degassing during the survey period in 2008 another chirp survey was carried out just over these plumes in 2010 to demonstrate if the gas seeps were still active the surveys indicate that the gas seep is an ongoing process in the gulf based on the chirp data we proposed that the pockmark formation in the area can be explained by protracted seep model whereby sediment erosion and re distribution along pockmark walls result from ongoing or long lasting seepage of fluids over long periods of time the existence of inactive pockmarks in the vicinity however implies that gas seepage may eventually cease or that it is periodic most of the active pockmarks are located over the fault planes likely indicating that the gas seepage is controlled by active faulting

seafloor gas seeps triggered by a northern california earthquake abstract a series of marine surveys using high resolution seismic reflection and side scan sonar profiling was conducted on the klamath river delta from 1977 to 1985 in november 1980 near the middle of this 8 year time period a major earthquake magnitude 7 occurred in the area the earthquake caused liquefaction of shelf deposits off the klamath river and while mapping the sediment failures we observed an inordinate number of gas vents and acoustic anomalies in the sediment gas charging and water column gas clouds our analyses indicate that a change in gas seepage occurred after the earthquake there was a marked increase in gas abundance immediately after the earthquake a gradual decrease over the next year and stabilization at pre earthquake gas levels within five years or less the acoustic anomalies were observed in pre quaternary rocks as well as in surficial holocene deposits and gas seeps overlay truncated anticlines faults and syncline exposures thus the gas released may have been in part thermogenic in origin a large area 20 km 2 on the delta failed during the earthquake and the abundance of gas seeps and craters in the area suggests that sediment degassing may have been an important process contributing to failure

salt related deformations in the deep antalya basin preliminary results of the mac gan cruise abstract seismic investigation of the deep antalya basin shows the contribution of halokinesis of messinian salt in shaping the shallow morphological setting of the area the causes of such salt related deformations are difficult to firmly establish the plio quaternary overburden 200 250 ms seems too little to be responsible for the extensive diapirism so widespread in the antalya basin extensional tectonics may therefore be involved to some degree there are indications that the messinian of the deep antalya basin bears two separate salt layers in this case a significant overburden in the form of the sum of plio quaternary sediments and the younger evaporites may be present with the older salt layer responsible for most of the observed doming