abyssal serpentinites as gigantic factories of marine salts and oil abstract serpentinites occur worldwide in various geological settings such as in magma starved oceanic basins abyssal serpentinites are long term storage for chlorine and carbon the latter forming dominantly reduced and subordinately oxidized compounds hence serpentinites salts and reduced carbon phases coexist in an abyssal association although huge reservoirs of salts and reduced carbonaceous matter in abyssal serpentinites are thought to be lacking this may be more a reflection of intrinsic limits in research methods than an indication of their absence on the other hand shallow seated hydrocarbon rich mud volcanoes and diapirs consisting of salts hydrocarbons oils and gases and clayey muds including mudded serpentines can provide evidence for such an oceanic association here we search for scientific data in support of the oceanic association and hence we propose a reappraisal of exploitable worldwide salt hydrocarbon reservoirs even gigantic in size abyssal serpentinites are well known source rocks of abiotic gaseous hydrocarbons via fischer tropsch type reaction ftt whereas macromolecular carbonaceous matter mostly bitumen found in serpentinites is postulated to be biogenic this inference is based mainly on three assumptions i ftt in nature does not yield oils ii hydrocarbons derive essentially from the thermal alteration of microbial molecules iii the presence of biomarkers traditionally considered evidence of the biological origin of oils nevertheless some lines of strong evidence disprove these accepted conventions i lab experiments demonstrated that ftt can synthesize significant quantities of liquid hydrocarbons oils under conditions compatible with the deeper and more reduced level of serpentinite hosted hydrothermal systems ii macromolecules generally thought to derive from microbial activity can be abiotically generated as documented in extraterrestrial bodies iii biomarkers are evidence for the proliferation of microbial communities which subsist on serpentinization and ftt products thus they are biological pollutants moreover seawater driven serpentinization consumes water producing huge amounts 11 kg halite m 3 of peridotite of salts that can be stored in the deeper zone of abyssal type hydrothermal systems thus the origin of shallow sited salt deposits even gigantic in size can be related to either the advective upwelling of hot hydrothermal brines due to the dehydration of abyssal serpentinites or to the passive upwelling of buoyant saline geobodies piercement structures are indeed seismically imaged in several localities such as south atlantic the gulf of mexico the serpentinite belt extending from cuba to hispaniola the north sea trench and the zagros orogenic belt similar lines of evidence at the microscopic scale have been found in some hyblean serpentinite xenoliths south eastern sicily being representative of the unmetamorfosed in situ relic of the palaeo tethys ocean upon which sicily and its off shore areas lie in spite of the accepted stereotype of hydrocarbons as fossil fuels and hence finite resources reduced carbon compounds abiotically produced in abyssal serpentinites may be copious protracted over time and thus renewable

tsunami deposits in a lacustrine sequence of the sanriku coast northeast japan abstract lacustrine deposits of the pacific coast of northeast japan consisting mostly of black organic mud contain intercalated thin beds of well sorted medium sand examination of the deposits from a coastal site of sanriku has revealed that sand grains are of marine origin and are fractions of deposits in marshy ponds transported from the littoral environment by a great flooding of seawater the mode of sedimentation shown in the thin beds of sand implies that they were deposited by tsunamis each with a maximum rise of 1 m or more above sea level

marine incursions of the past 1500 years and evidence of tsunamis at suijin numa a coastal lake facing the japan trench sandy deposits of marine origin underlie the floor of suijin numa a coastal lake midway along the subduction zone marked by the japan trench the deposits form three units that are interbedded with lacustrine peat and mud above a foundation of marine probably littoral sand unlike the lacustrine deposits all three sandy units contain marine and brackish diatoms the middle unit b contains in addition graded beds sug gestive of multiple waves of long wavelength and period the uppermost unit c probably dates to a time in the area s written history when the lake was separated from the sea by a beach ridge plain at least 0 5 km wide and several metres high units a and b postdate ad 540 870 and unit c postdates ad 1030 1640 as judged from radiocarbon dating of leaves and seeds unit b pre dates ad 915 and unit c postdates that year as judged from a tephra within the peat that separates units b and c the age constraints permit correlation of unit b with a tsunami in ad 869 that reportedly devastated at least 100 km of coast approximately centred on sendai unit c may represent a later catastrophic tsunami in 1611 or perhaps a storm surge that inundated much of sendai the lake lacks obvious signs of tsunamis from the region s largest twentieth century earthquakes which were centred to the north in 1933 m 8 1 and directly offshore in 1936 m 7 5 and 1978 mw 7 6

a record of local storms and trans pacific tsunamis eastern banks peninsula new zealand this study of five sand units at lavericks bay new zealand reports on the sedimentary evidence for three trans pacific tsunamis and two local storms the 1868 arica 1877 iquique and 1960 valdivia tsunamis from chile were the largest distantly generated events in new zealand s history but have never before been identified at the same location it is also the first time that the 1877 iquique tsunami deposit has been found in new zealand two further sand units were identified as local storm deposits laid down in 1869 1870 and 1929 the identification and chronology of these events were established through the use of geochemistry palynology diatoms charcoal abundance and historical documents their relative magnitudes were estimated through the use of grain size parameters and lateral extent of the recognisable sand layers the recognisable sandy tsunami deposits extend about 60 of the inundation distance while the storm sediments are finer and less extensive there were two notable geochemical diffe

salt tectonics in the atlantic margin of morocco the offshore basins of morocco s atlantic margin represent the westernmost exploration frontier area in north africa figure 1 whereas the presence of an active petroleum system is very well established onshore e g essaouira basin only promising oil shows and one minor oil accumulation have been found to date offshore e g tarfaya basin however all previous exploration effort concentrated only on the shelfal region and therefore it should not be very surprising that several blocks were licensed in the last few years covering large offshore acreage in water depths to almost 3000 m figure 1 as the reconnaissance licenses for these permits are in the process of being converted to exploration licenses a shift from regional scale 2 d seismic reflection data acquisition to prospect scale 2 d and even 3 d is under way figure 1 index map of the atlantic margin of morocco showing location of a regional cross section figure 2 and simplified salt tectonics map figure 3 an active petroleum system is not proven in the deepwater region although a broad world class salt basin stretches along the coastline creating spectacular structural traps the first deepwater well might be spudded as early as next year to test one of these salt related structures a potential target zone within the deepwater salt basin is at the westernmost leading edge of the salt deformational front where a very well developed toe thrust zone formed during the mid tertiary the salt tectonics of offshore morocco may provide some very specific analogs for exploration efforts in other salt basins of the world perhaps the easiest way to understand the scale of the salt basin offshore morocco is to compile regional seismic transects figure 2 shows a line drawing of a regional composite seismic profile across the ras tafelney and safi haute mer permits figure 1 note that the atlantic passive margin of

high resolution p cable 3d seismic imaging of gas chimney structures in gas hydrated sediments of an arctic sediment drift the newly developed p cable 3d seismic system allows for high resolution seismic imaging to characterize upper geosphere geological features focusing on geofluid expressions gas chimneys shallow gas and gas hydrate reservoirs seismic imaging of a geofluid system of an arctic sediment drift at the vestnesa ridge offshore western svalbard provides significantly improved details of internal chimney structures from the seafloor to not vert similar500 m bsf below seafloor the chimneys connect to pockmarks at the seafloor and indicate focused fluid flow through gas hydrated sediments the pockmarks are not buried and align at the ridge crest pointing to recent topography controlled fluid discharge chimneys are fuelled by sources beneath the base of gas hydrate stability zone ghsz that is evident at not vert similar160 170 m bsf as indicated by a bottom simulating reflector bsr conduit centres that are not vertically straight but shift laterally by up to 200 m as well as discontinuous internal chimney reflections indicate heterogeneous hydraulic fracturing of the sediments episodically active pressure driven focused fluid flow could explain the hydro fracturing processes that control the plumbing system and lead to extensive pockmark formation at crest of the vestnesa ridge high amplitude anomalies in the upper 50 m of the chimney structures suggest formations of near surface gas hydrates and or authigenic carbonate precipitation acoustic anomalies expressed as high amplitudes and amplitude blanking are irregularly distributed throughout the deeper parts of the chimneys and provide evidence for the variability of hydrate and or carbonate formation in space and time

mud volcanism in the gulf of cadiz results from the ttr 10 cruise a new deep water mud volcano field between 2000 and 3500 m water depth was discovered in the deep south portuguese margin as well as several new mud volcanoes in the south spanish and western moroccan margins of the gulf of cadiz during the ttr 10 training through research unesco ioc cruise in july august 2000 this work followed the discovery of a large mud volcano field in the gulf of cadiz first investigated during the ttr 9 cruise gardner 2001 geophys res lett 28 339 342 kenyon et al 2000 ioc technical series no 56 the discoveries were made based on a seamap side scan sonar mosaic and multibeam bathymetry seabeam collected in the area by the naval research laboratory nrl washington dc usa in 1992 kindly released for this purpose single channel seismics long range side scan sonar okean tv controlled grab hull mounted 3 5 khz profiler and coring were used to investigate several seafloor features observed on the side scan sonar imagery in the south iberia spanish and moroccan margins of the gulf of cadiz which were confirmed to be mud volcanoes the typical structures related to fluid venting in the gulf of cadiz are essentially represented by conical mud volcanoes with diameters ranging from several tens of meters to 4 km and heights that can reach 200 m some of these structures appear to be aligned along major conjugate ne sw and nw se trending faults that can be identified on the side scan sonar imagery the new field discovered in the south portuguese margin is the deepest in the gulf of cadiz area and includes three new mud volcanoes bonjardim olenin and carlos ribeiro which seem to be quite active with near surface gas hydrate occurrence and a high saturation in h2s and hydrocarbon gases mainly methane in the mud breccia and overlying pelagic sediments gas hydrates were recovered from the bonjardim mud volcano an intensely gassified mud breccia with one fragment of semi consolidated claystone with a thin bituminous veneer at the surface was recovered from the carlos ribeiro mud volcano the fauna recovered consists mainly of pogonophoran worms belonging to several species and undetermined species of foraminifera three new mud volcanoes were also discovered in the nw moroccan margin rabat student and jesus baraza these show a richer fauna that includes several species of molluscs polychaetes pogonophoran worms crustaceans echinoderms and some fragments of dead coral madrepora and lophelia carbonate crusts were recovered from the student mud volcano the ginsburg mud volcano discovered during the previous ttr 9 cruise was revisited and gas hydrates recovered once again a new mud volcano was also discovered in the spanish margin tasyo where evidence was found of coral build ups on the hard substratum of the mud volcanic edifice

emplacement of a passive margin evaporitic allochthon in the betic cordillera of spain the triassic section of the external domain of the betic cordillera is rootless and thus allochthonous the frontal accretionary wedge of the guadalquivir allochthon consists dominantly of triassic evaporites and red beds forming a melange with upper cretaceous paleogene deep water sedimentary rocks throughout the unit jurassic rocks are absent it is here proposed that the widespread triassic evaporites of the guadalquivir allochthon were originally emplaced as gravitational allochthonous masses in a passive margin setting much like the widespread allochthonous salt of the texas louisiana gulf of mexico thus on the betic passive margin allochthonous evaporites were first emplaced during the late cretaceous paleogene later during neogene time these evaporites were overthrusted as an accretionary wedge to form the guadalquivir allochthon a schematic reconstructed position of the guadalquivir allochthon places the original passive margin allochthon in its continental slope setting

mud volcanoes revealed and sampled on the western moroccan continental margin we surveyed and sampled two active and 3 inactive mud volcanoes on the atlantic continental margin of morocco the active mud volcanoes named yuma and ginsburg are each about 4 km in diameter rise between 150 250 meters above the seafloor and are the first active methane related mud volcanoes to be identified in this region the inactive volcanoes range in diameter from 1 3 km with relief between 50 and 80 meters gravity cores from the crest of the active mud volcanoes yielded methane hydrates and mud breccia deposits chemosynthetic communities of pogonophora worms and the bivalve solemya were found on the surface of the active mud volcanoes sediment cores from the inactive volcanoes contained hemipelagic sediments rich in foraminifera and ahermatypic coral debris overlying mud breccia

structure of mud volcano systems and pockmarks in the region of the ceuta contourite depositional system western alboran sea abstract new high resolution seismic and swath bathymetry data reveal the detailed structure of nine mud volcanoes and two large fields of pockmarks at water depths of 400 1100 m in the western alboran sea these features are related to episodes of focused fluid flow through pliocene quaternary contourite deposits of the ceuta drift we describe nine mud volcano systems composed of two key structural elements i extrusive edifices comprising cones bicones and low dip mudflows interfingering with adjacent drift sediments and ii intrusive feeder complexes comprising pipes and unstratified downward tapering cones underlying the extrusive edifices the mud volcano systems are grouped into four types i complex edifices ii stacked single edifices iii single edifices fed by buried bicones and iv single edifices all except the last record episodic extrusive activity since the pliocene the timing of which is constrained by correlation between the main mud extrusion episodes and dated unconformities within the ceuta drift complex mud volcanoes composed of twin to multiple seabed cones are the longest lived systems with at least six extrusive episodes since the mid pliocene most of the mud volcanoes appear to have been reactivated in the mid pleistocene 0 9 ma mpr discontinuity and all at mis12 0 4 ma while the onset of focused fluid flow was triggered by mid pliocene tectonically driven diapirism of lower miocene shales that form the rooting zone of the mud volcanoes we suggest that some of the pleistocene phases of mud extrusion might be related to erosion of the contourite drift during major sea level falls in addition to vertical focused fluid flow we propose that leakages from the mud volcano feeder complexes into high permeability contourite sediments may cause lateral fluid migration and form gas accumulations lateral fluid flow in the near surface sediments could be responsible of forming subsurface reservoirs and consequently random pockmarks by fluidification and or liquefaction of the non consolidated shallow sediments stacked buried paleo pockmarks indicate that this mechanism has been persistent along recent times at least after the mid pleistocene

horizontal and vertical variation of 2004 indian tsunami deposits an example of two transects along the western coast of thailand abstract we investigated horizontal and vertical variations in modern tsunami deposits along two transects at nam khem and khao lak western coast of thailand deposited by the large tsunami associated with the earthquake magnitude 9 0 of 26 december 2004 off sumatra indonesia tsunami waves 6 10 m high struck the area approximately 2 h after the earthquake tsunami deposits cover the low lying coastal plains and extend more than 1 km inland from the shoreline no landward decrease in sediment thicknesses was found clearly at either transect terrace scarps and a steep slope behind the coastal plain probably stopped tsunami deposition further inland causing substantial sediments to be deposited in front of these features very clear vertical variations in grain size and multiple layers are found in the deposits to about 600 m inland at nam khem fine grained sediments overlie the coarse grained sediments of the basal layer of the tsunami deposits at some sites the fine grained sediments are overlain by another layer of coarse grained sediments suggesting deposits laid down in succession by multiple waves the basal coarse grained sediments at nam khem fine landward the up flow waned inland based on the assumption that the grain size of the basal deposits relates to the strength of the up flow these results are potentially useful in disaster prevention and coastal environmental change management as well as for interpreting paleotsunami deposits in geological records

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

seafloor instabilities and sediment deformation processes the need for integrated multi disciplinary investigations abstract in this paper we present the current practice of investigations of seafloor instabilities and deformation processes based on extensive research conducted over the last years which sets the scene for future research activities in this field the mapping of the continental margins and coastal areas with ever increasing resolution systematically reveals evidence of instabilities and deformation processes both active and palaeo features in order to properly assess the hazards and risks related to these features an integrated and multi disciplinary approach is essential but challenging such an approach consists of combining field data geophysics geology sedimentology geochemistry and geotechnical data with numerical simulations constrained by results from laboratory data as such it is of paramount importance to build a common knowledge base and understanding that unify these disciplines into more complete and conceptual models constrained by all the data we review the status of this integrated approach adapted to palaeo landslides e g storegga ana vesteralen and recent deformations finneidfjord nice gulf of guinea allowing to identify gaps in our knowledge at these sites by reviewing these case studies one can conclude that each case remains highly site specific in which both the regional and local geological tectonic settings have a distinct effect of the type of instability or deformation taking place or that can take place our knowledge on the actual triggers remains poorly constrained and there is even ambiguity for historic landslides e g finneidfjord also our knowledge of the preconditioning factors is incomplete there is a general lack of geotechnical data both in situ and from laboratory and therefore modelling the dynamics e g rheology of the instabilities relies on a number of assumptions rather than facts in addition excess pore pressure and its evolution is one of the key parameters driving instabilities despite this fact in situ excess pore pressure is rarely measured or monitored much work remains to be done to relate and integrate geotechnical data with geophysics e g through inversion and rock physical models in order to obtain additional quantitative information from the sub surface but also with respect to partial saturation free gas hydrate and pore pressure behaviour or lithologies it is of critical importance to be able to identify the different processes which can lead to hazardous situations which include establishing recurrence intervals timing and frequencies through event recognition and age control and magnitudes so that proper mitigation measures can be developed in this perspective the smaller scale instabilities deserve much attention as there are many instances where such features had far reaching consequences for society e g nice finneidfjord in that perspective human interferences e g exploitation drilling blasting loading must be one of the factors that should be taken into consideration

structure and evolution of the olistostrome complex of the gibraltar arc in the gulf of cadiz eastern central atlantic evidence from two long seismic cross sections reflection profiles characterize the structure and the upper mesozoic to cenozoic deposits of the gulf of ca diz region two long ene wsw multichannel seismic lines ca 400 500 km long are analyzed to study the evolution of the area from the continental shelf to the horseshoe and seine abyssal plains the huge allochthonous deposits emplaced in this region the socalled olistostrome of the gulf of cadiz are described in terms of three different domains on the basis of the seismic architecture the main tectonic features and the nature of the basement oceanic or continental the eastern domain extends along the continental shelf and upper and middle slope and corresponds to the offshore extension of the betic rifean external front it is characterized by salt and shale nappes later affected by extensional collapses the central domain develops along the lower slope between the betic rifean front and the abyssal plains and is characterized by a change in dip of the allochthonous basal surface and the basement the allochthonous masses were emplaced by a combined gravitational and tectonic mechanism the northern boundary of this domain is marked by the occurrence of an outstanding wnw ese trending thrust fault with a strike slip component termed here as the gorringe horseshoe fault the westernmost domain corresponds to the abyssal plains where the distal emplacement of the allochthonous body takes place it is characterized by thrust faults affecting both the sedimentary cover and the oceanic basement the allochthonous masses show a less chaotic character and the thickness decreases notably these domains represent different evolutionary steps in the mechanisms of emplacement of the allochthonous units the eastern domain of the allochthonous units was emplaced as part of the pre messinian orogenic wedge related to the collision that gave rise to the betic rifean belt whereas the allochthonous wedge of the central and western domains were emplaced later as a consequence of the ne sw late miocene compression that continues in present times

sediments deposited by the 2004 indian ocean tsunami along the malaysia thailand peninsula stratigraphy grain size distribution and foraminiferal assemblages of pre tsunami and tsunami sediment from the indian ocean tsunami at five sites along the malaysia thailand peninsula were analyzed to gain information on tsunami sediment source and deposition style between three and five stratigraphic units were identified at each site and contained between one and three fining upward sequences reflecting waning flow or pre backwash deposition coarser sand layers reflecting uprush high energy flow separated the fining upward sequences with the exception of one site sungai burong which contained a coarsening upward sequence all contacts between the pre tsunami and tsunami sediment were sharp or erosional medium and coarse sand dominated all of the tsunami sediment deposits and often contained shell fragments foraminiferal assemblages were able to differentiate pre tsunami sediment from tsunami sediment where no lithological or grain size distribution change was evident between two and four foraminiferal zones were identified at each of the five sites and provided estimates of sediment source and wave characteristics

the tohoku tsunami of 11 march 2011 the key event to understanding tsunami sedimentation on the coasts of closed bays of the lesser kuril islands the tohoku tsunami of 11 march 2011 manifested in the region of the south kuril islands although as a rule the run up heights in this region did not exceed 3 m in closed bays that were covered with ice before the tsunami the eroding capacity of tsunami waves was aggravated by the ice fragments they carried here mud sheets formed reaching up to 106 m inland the 2012 studies have shown well preserved tsunami deposits evident 1 5 years after the event a comparative analysis of tsunami deposits from the periphery and from the near field area close to the tsunami source was performed this was important for understanding the deposition mechanism during the event as it had different strengths on different shores the difference in run up heights determined the considerable differences in erosion sedimentation distribution of tsunami deposits the formation of sedimentary structures grain size composition and diatom and foraminifera assemblages the sources of the material also varied significantly from each other the material came from offshore in closed bays located in the tsunami source periphery while in the near field region close to the epicenter the most active erosion occurred in the inundation area in the latter area the main sources of sand were beaches and dunes while soil erosion was the source of mud studies of the tohoku tsunami on the coasts of the lesser kuril islands demonstrated that mud layers in the sections of coastal lowlands in closed bays could contain preserved detailed geological records of paleotsunamis even those with a small height run up in the sections of coastal peatlands of closed bays on shikotan island up to 7 9 layers of mud and silty sands were found these can easily be traced for more than 500 m inland the grain size composition of the mud is similar to the deposits of the 2011 tohoku tsunami the marine origin of these deposits is confirmed by the diatom analysis data

tsunamis and tectonic deformation at the northern cascadia margin a 3000 year record from deserted lake vancouver island british columbia canada three layers of sand occur within a sequence of muddy gyttja in a 3 m core recovered from deserted lake which lies at the head of a fjord on the central west coast of vancouver island british columbia canada the sedimentology and microfossil assemblages of these layers are consistent with deposition by tsunamis radiocarbon ages suggest that the tsunamis were generated by plate boundary earthquakes at the cascadia subduction zone about 2600 1600 and 300 years ago diatom and protozoan contents of the gyttja layers indicate that relative sea level fell in the periods between tsunamis the sea level changes are probably a product of interseismic uplift of the north america plate margin post tsunami diatom and protozoan assemblages are generally more marine than their pre tsunami counterparts suggesting that the study site subsided during earth quakes estimates of interseismic and coseismic deformation during one earthquake cycle indicate that less than half of the interseismic uplift was recovered during the earthquake leading to cumulative or permanent uplift of the area

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

geologic setting field survey and modeling of the chimbote northern peru tsunami of 21 february 1996 whereas the coast of peru south of 10 s is historically accustomed to tsunamigenic earthquakes the subduction zone north of 10 s has been relatively quiet on 21 february 1996 at 21 51 gmt 07 51 local time a large tsunamigenic earthquake harvard estimate m w 7 5 struck at 9 6 s 79 6 w approximately 130 km off the northern coast of peru north of the intersection of the mendana fracture zone with the peru chile trench the likely mechanism inferred from seismic data is a low angle thrust consistent with subduction of the nazca plate beneath the south american plate with relatively slow rupture characteristics approximately one hour after the main shock a damaging tsunami reached the peruvian coast resulting in twelve deaths we report survey measurements from 7 7 s to 11 s on maximum runup 2 5 m between 8 and 10 s maximum inundation distances which exceeded 500 m and tsunami sediment deposition patterns observations and numerical simulations show that the hydrodynamic characteristics of this event resemble those of the 1992 nicaragua tsunami differences in climate vegetation and population make these two tsunamis seem more different than they were this 1996 chimbote event was the first large m w 7 subduction zone interplate earthquake between about 8 and 10 s in peru since the 17th century and bears resemblance to the 1960 m w 7 6 event at 6 8 s together these two events are apparently the only large subduction zone earthquakes in northern peru since 1619 est latitude 8 s est m w 7 8 these two tsunamis also each produced more fatalities than any other tsunami in peru since the 18th century we concur with pelayo and wiens 1990 1992 that this subduction zone in northern peru resembles others where the subduction zone is only weakly coupled and convergence is largely aseismic subduction zone earthquakes when they occur are slow commonly shallow and originate far from shore near the tip of the wedge thus they are weakly felt and the ensuing tsunamis are unanticipated by local populations although perhaps a borderline case the chimbote tsunami clearly is another wake up example of a tsunami earthquake

flow conditions of the 2004 indian ocean tsunami in thailand inferred from capping bedforms and sedimentary structures the 2004 indian ocean tsunami deposited a sheet of sand with surficial bedforms at the andaman coast of thailand here we show the recognition of bedforms and the key internal sedimentary structures as criteria of the tsunami supercritical flow condition the presence of well preserved capping bedforms implied a dominant tsunami inflow sets of internal sedimentary structures including parallel lamination seaward and landward inclined laminations and downstream dipping laminae indicated antidune structures that were generated by a supercritical flow current in a depositional stage during the inflow a set of seaward dipping cross laminations containing sand with mud drape on the surface of one depositional layer are a unique indication of an outflow structure a majority of deposits show normal grading but in some areas localized reverse grading was also observed the recognition of these capping bedforms and determination of the internal sedimentary structures provides new key criteria to help derive a better understanding of tsunami flow conditions

submersible study of mud volcanoes seaward of the barbados accretionary wedge sedimentology structure and rheology abstract in 1992 the nautile went to a mud volcano field located east of the barbados accretionary wedge near 13 50n using nannofossil analysis on cores we determined the sedimentation rate and provided a new estimation of the age of the mud volcanoes 750 000 years for the oldest one six structures have been explored with the submersible nautile and manifestations of fluid venting chimneys carbonate cementation and chemosynthetic communities were observed on all sedimentological analysis identifies two sources of diapiric mud most mud volcanoes expel mud containing late miocene to quaternary faunae that have the same composition as sediments drilled above the barbados wedge decollement one volcano also contains older oligocene taxa with a mud composition corresponding to the sedimentary sequence below the decollement we use diving observations to map the fine scale morphology the distribution of chemosynthetic fauna and define two end member types of structures mud pies flat topped mud volcanoes and conical mounds mud pies atalante and cyclops are characterised by the presence of a lake of highporosity mud 70 to 75 in their central parts chemosynthetic benthic communities calyptogena colonies and sponge bushes are concentrated in the outer parts contrasting morphologies of the two mud pies indicate different stages of activity cyclops is growing whereas atalante is collapsing expulsion of water and methane occurs mostly through the mud lake and may be stronger during the collapse phase on conical mounds there are no mud lakes fluid venting concentrates near the summit and occurs through carbonate cemented chimneys which form within the sediment viscosity measurements have been carried out on mud samples from the two mud pies and one conical mound all mud samples have a plastic fluid behaviour the plastic threshold decreases with porosity and thixotropy is observed for a porosity of more than 70 an analogue experiment shows that for this thixotropic mud shearing in the feeding conduit liquefies the mud which then spreads to form a mud pie conical mounds form when the mud remains plastic we show that the dissociation of methane hydrate is the cause of the high porosity in mud pies and confirm that these structures are a consequence of large scale dissociation of methane hydrate at the base of its stability field dissociation of hydrates before and during ascent is only slightly contributing to the pore fluid in conical mounds but solid hydrates still present in the mud may contribute to its buoyancy

large scale slope failure involving triassic and middle miocene salt and shale in the gulf of cadiz atlantic iberian margin sheets of salt and ductile shale advancing beyond the thrust front of the gibraltar arc iberian moroccan atlantic continen tal margin triggered downslope movements of huge allochth onous masses these allochthons represent the cadiz nappe which detached from the gibraltar arc along low angle normal faults and migrated downslope from the iberian and moroccan continental margins towards the atlantic ocean extensional tectonics initiated upslope salt withdrawal and downslope diapirism during large scale westward mass wasting from the shelf and upper slope low angle salt and shale detachments bound by lateral ramps link extensional structures in the shelf to folding thrusting and sheets of salt and shale in the gulf of cadiz from backstripping analyses carried out on the depo centres of the growth fault related basins on the shelf we infer two episodes of rapid subsidence related to extensional collapses these were from late tortonian to late messinian 200 400 m myr 1 and from early pliocene to late pliocene 100 150 m myr 1 the extensional events that induced salt movements also affected basement deformation and were probably associated with the westward advance of frontal thrusts of the gibraltar arc as a result of the convergence between africa and eurasia the complexities of salt and or shale tectonics in the gulf of cadiz result from a combination of the deformations seen at convergent and passive continental margins

diatom assemblages in tsunami deposits associated with the 2004 indian ocean tsunami at phra thong island thailand abstract diatom assemblages in sandy deposits of the 2004 tsunami at phra thong island thailand may provide clues to flow conditions during the tsunami the tsunami deposits contain one or more beds that fine upward commonly from medium sand to silty very fine sand diatom assemblages of the lowermost portion of the deposit predominantly comprise unbroken beach and subtidal species that live attached to sand grains the dominant taxa shift to marine plankton species in the middle of the bed and to a mix of freshwater brackish and marine species near the top these trends are consistent with expected changes in current velocities of tsunami through time during high current velocities medium sand is deposited only beach and subtidal benthic diatoms attached to sediment can be incorporated into the tsunami deposit high shear velocity keeps finer material including planktonic diatoms in suspension with decreasing current velocities finer material including marine plankton can be deposited finally during the lull between tsunami waves the entrained freshwater brackish and marine species settle out with mud and plant trash low numbers of broken diatoms in the lower medium sand implies rapid entrainment and deposition whilst selective breakage of marine plankton thalassionema nitzschioides and thalassiosira and coscinodiscus spp in the middle portion of the deposit probably results from abrasion in the turbulent current before deposition

coseismic slip and afterslip of the great mw 9 15 sumatra andaman earthquake of 2004 we determine coseismic and the first month postseismic deformation associated with the sumatra andaman earthquake of 26 december 2004 from near field global positioning system gps surveys in northwestern sumatra and along the nicobar andaman islands continuous and campaign gps measurements from thailand and malaysia and in situ and remotely sensed observations of the vertical motion of coral reefs the coseismic model shows that the sunda subduction mega thrust ruptured over a distance of about 1500 km and a width of less than 150 km releasing a total moment of 6 7 7 0 10 22 n m equivalent to a magnitude m w 9 15 the latitudinal distribution of released moment in our model has three distinct peaks at about 4 n 7 n and 9 n which compares well to the latitudinal variations seen in the seismic inversion and of the analysis of radiated t waves our coseismic model is also consistent with interpretation of normal modes and with the amplitude of very long period surface waves the tsunami predicted from this model fits rela tively well the altimetric measurements made by the jason and topex satellites neither slow nor delayed slip is needed to explain the normal modes and the tsunami wave the near field geodetic data that encompass both coseismic deformation and up to 40 days of postseismic deformation require that slip must have continued on the plate interface after the 500 sec long seismic rupture the postseismic geodetic moment of about 2 4 10 22 nm mw 8 8 is equal to about 30 5 of the coseismic moment release evolution of postseismic deformation is consistent with rate strengthening frictional afterslip online material summary of geodetic data used in this study

tectonics and mud volcano development in the gulf of cadiz many structures associated with fluid escape including mud volcanoes mud carbonate mounds pockmarks and slides have been identified and characterized in the gulf of cadiz most of the mud volcanoes following ne sw and nw se main trends are found at 350 2000 m depth in the eastern domain of the gulf of cadiz which corresponds to the betic rifean margin scattered mud volcanoes have also been recognized on the lower slope at 2300 3900 m depth the major tectonic structures are thrust faults extensional faults strikeslip faults and diapirs all these tectonic structures have provided escape pathways for overpressured material and fluids or have favoured upward fluid movement along the sedimentary column and eventually the build up of mud volcanoes in this work we present images of the mud volcano plumbing systems and the relationship between regional tectonics and mud volcano development seismic profiles acquired during the tasyo 2000 and mvseis ttr 15 cruises are used to image and interpret the link between the mud volcano edifices and the subsurface tectonic structures

evidence for three north sea tsunamis at the shetland islands between 8000 and 1500 years ago abstract coastal fen and lake deposits enclose sand layers that record at least three holocene tsunamis at the shetland islands the oldest is the well known storegga tsunami ca 8100 cal yr bp which at the shetlands invaded coastal lakes and ran up peaty hillsides where it deposited sand layers up to 9 2 m above present high tide level because sea level at ca 8100 cal yr bp was at least 10 15 m below present day sea level the runup exceeded 20 m in two lakes we also found deposits from a younger tsunami dated to ca 5500 cal yr bp the sediment facies are similar to those of the storegga tsunami rip up clasts sand layers re deposited material and marine diatoms runup was probably more than 10 m yet another sand layer in peat outcrops dates to ca 1500 cal yr bp this sand layer thins and fines inland and was found at two sites 40 km apart and traced to ca 5 6 m above present high tide the oldest tsunami was generated by the storegga slide on the norwegian continental slope we do not know what triggered the two younger events

diatoms as an aid in identifying late holocene tsunami deposits diatoms bacillariophyta help identify the onshore deposits of tsunamis from earthquakes on the cascadia subduction zone along the pacific coast of oregon washington and british columbia and on faults high in the north american plate in the puget sound area of washington at the copalis river washington diatom analyses suggest that a tsunami deposit about 300 calendric years old 300 yr bp originated from sandy shoals of the lower estuary rather than nearby beaches or coastal dunes at cultus bay and west point washington well preserved benthic estuarine diatoms in sand sheets overlying tidal marsh peat indicate that the deposits came from intertidal or nearshore areas of puget sound on an abruptly uplifted mudflat at the landward end of hood canal at lynch cove washington tidal flat diatoms refute the possibility of a terrestrial source for the sand diatoms in 300 yr bp tsunami deposits on the niawiakum river washington confirm that the sand in these deposits had a marine source and help

inflow and outflow facies from the 1993 tsunami in southwest hokkaido abstract we describe in detail the sedimentary facies provenance and grain size distributions of the 1993 tsunami deposits in the lower reaches of usubetsu river only two lithofacies were recognized a gravel lobe facies glf and a sand sheet facies ssf the gravel lobe facies was deposited rapidly by a hydraulic jump in contrast the sand sheet facies which contains both current ripples and dunes was deposited by a traction current under subcritical flow conditions we identified four stratigraphic units unit 1 unit 2 unit 3 and unit 4 in ascending order we interpreted units 1 and 2 as having been deposited by the inflow and outflow events of the first run up and units 3 and 4 by the inflow and outflow events of the second run up respectively units 3 and 4 were more widely distributed and coarser grained than units 1 and 2 because the second run up was larger than the first run up furthermore unit 4 was more widely distributed than unit 3 because the outflow eroded the inflow deposits grain size distributions of the inflow and outflow deposits were clearly different unit 4 deposits had a peak at 2 5 phi p 1 population in contrast unit 3 deposits had a bimodal distribution with peaks at 0 5 1 5 phi p 2 population and at 2 5 phi p 1 population a comparison of the tsunami deposits with other sedimentary deposits near the study area showed that the tsunami deposits were mainly derived from the seabed at depths below 5 5 m in the offshore area where the marine sands are about 2 2 5 phi in size and thus are the source of the p 1 population the p 2 population is derived from coarse 0 5 2 phi fluvial materials eroded during the tsunami run up according to our calculations benthic foraminiferal tests were entrained from the comparatively deep seabed at depths up to 100 m during the tsunami run up and included in the tsunami deposits

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

stratigraphic evidence for pre 2004 tsunamis in southwestern thailand abstract the 2004 sumatra andaman earthquake and the associated indian ocean tsunami vastly exceeded the size of their predecessors from the previous two centuries or more we sought clues on how often large tsunamis occur by taking 9 shallow cores 0 5 2 0 km inland from the modern shore on a holocene beach ridge plain of phra thong island 125 km north of phuket we tentatively correlated one sand sheet among these cores and found a second sand bed beneath in one of the cores we infer that these deposits represent two pre 2004 tsunamis the island s setting precludes river floods and tends to rule out storms as causes of the sand deposition establishment of the beach ridge plain requires that both the inferred tsunamis occurred after holocene sea levels approached their present position radiocarbon ages of bulk soil samples are consistent with this conclusion though root penetration into soil samples probably makes the ages appear younger one inferred tsunami occurred before ad 1300 and the other occurred before ad 1900 based on the age estimates the tsunamis probably originated along the sunda megathrust from where tsunamis can travel directly to the thailand coast

expanding the proxy toolkit to help identify past events lessons from the 2004 indian ocean tsunami and the 2009 south pacific tsunami article i nfo some of the proxies used to identify palaeotsunamis are reviewed in light of new findings following the 2004 indian ocean tsunami and the 2009 south pacific tsunami and a revised toolkit provided the new application of anisotropy of magnetic susceptibility ams to the study of tsunami deposits and its usefulness to determine the hydrodynamic conditions during the emplacement of tsunami sequences together with data from grain size analysis are presented the value of chemical proxies as indicators of saltwater inundation associated marine shell and or coral high energy depositional environment and possible contamination is demonstrated and issues of preservation addressed we also provide new findings from detailed studies of heavy minerals new information gathered during the unesco international oceanographic commission ioc international tsunami survey of fine onshore sediments following the 2009 south pacific tsunami is presented and includes grain size chemical diatom and foraminifera data the tsunami deposit varied ranging from fining upward sand layers to thin sand layers overlain by a thick layer of organic debris and or a mud cap grain size characteristics chemical data and microfossil assemblages provide evidence for marine inundation from near shore and changes in flow dynamics during the tsunami

diatom assemblages within tsunami deposit from the 2011 tohoku oki earthquake along the misawa coast aomori prefecture northern japan abstract this paper reports variations in the diatom assemblages within the deposit from the 2011 tohoku oki tsunami along the misawa coast aomori prefecture northern japan the landward extent of the tsunami deposit was as much as 400 m inland the deposit contained mixed assemblages of marine brackish and freshwater diatoms the mixed assemblages indicated that the tsunami deposit was composed of not only beach and dune sand but also soil from the coastal forest marine brackish species were predominant in the seaward tsunami deposit however the relative abundance of marine brackish species rapidly decreased in the samples about 150 to 250 m inland from the shoreline a decrease in marine brackish diatoms at inland locations suggests that the eroded terrestrial soil was incorporated into the tsunami deposit the composition of marine brackish species in the tsunami deposit was different from that of modern inter to supra tidal sediments one possible interpretation for this discrepancy is that the 2011 tsunami deposit were sourced from multiple environments including supra inter and sub tidal locations

nine unusually large tsunami deposits from the past 4000 years at kiritappu marsh along the southern kuril trench abstract large earthquakes along the kuril subduction zone in northern japan are known to have caused damaging tsunami although there is a little information on historical earthquakes and tsunami in this area because no documents exist before the 19th century that might refer to tsunami events to determine the likely timing and size of future events we need information on their recurrence intervals and to do this for the prehistoric past we have investigated sediments located in the kiritappu marsh in eastern hokaido that we interpret as laid down by tsunami using reliable multiple lines of evidence from sedimentological geomorphological micropaleontological and chronological results we identify 13 tsunami sands two of these lie within a peat bed above a historical tephra ta a ad 1739 the upper one probably corresponds to the ad 1843 tempo tokachi oki earthquake m 8 2 tsunami and the lower to either the ad 1952 tokachi oki earthquake m 8 2 tsunami or the ad 1960 chilean earthquake m 9 5 tsunami underlying are 11 prehistoric tsunami sand beds nine large sand beds and two smaller sand beds deposited during the past 4000 years because of the wide spatial distribution of the large sand beds and inundation distances inland of between 1200 to 3000 m we suggest that they record unusually large tsunamis along the kuril subduction zone according to our analyses these tsunami sands were derived from the coastal area and although they do not show clear graded bedding they commonly have gradational upper boundaries and erosional bases and include internal sedimentary structures such as plane beds dunes and current ripples reflecting bedload transportation based on our results we calculate the recurrence interval of unusually large earthquakes probably m 8 6 along the kuril subduction zone as about 365 553 years and estimate the youngest large event to have occurred in the 17th century

contamination of tsunami sediments in a coastal zone inundated by the 26 december 2004 tsunami in thailand tsunami sediments deposited in a coastal zone of thailand by the 26 december 2004 tsunami wave were sampled within 50 days after the event all surface and ground waters in tsunami inundated zone revealed significant salinity at that time the tsunami sediments composed mainly of fine to medium sand contain significantly elevated contents of salts na k ca 2 mg 2 cl and so4 2 in water soluble fraction and of cd cu zn pb in the bioavailable fraction and as in the exchangeable fraction in relation to the reference sample the origin of contaminants is marine as well as litho and anthropogenic the salts and pb zn and cu reveal high correlation to each other and to the mean grain size pore size and porosity serious environmental hazard exists in that region because due to gentle morphology there is a risk of migration of the contaminants into ground waters and food chain

predecessors to the 2009 south pacific tsunami in the wallis and futuna archipelago abstract multi proxy studies of trench sediments from futuna island in the wallis and futuna archipelago have produced a record of two palaeotsunamis dated to around 1860 2000 bp and c 470 bp one of the most useful proxies in this study has been the archaeological data associated with occupations that immediately underlie the deposits associated with both palaeotsunamis the reworking of the archaeological material into the palaeotsunami deposits and the additional chronological control provided by artefacts have added value to interpretations based upon more conventional earth science proxies the identification of tsunamigenic sources for these events is tentative and based upon known potential sources based upon a comparison between the effects of the 2009 south pacific tsunami and those recorded in the trenches event 1 1860 2000 bp appears most likely to be associated with a large tsunami sourced from the tonga kermadec trench region there are only rare contemporaneous events reported from around the region although this appears to be largely due to a lack of similar research as opposed to a lack of evidence event 2 c 470 bp is markedly larger than event 1 with sedimentary evidence indicating significant inland inundation and runup around the entire island there are several lines of evidence for a contemporaneous event in the south pacific around 470 bp although much of this needs further verification determining a source for this event is problematic because it must take in to account the regional signal and the significant impacts recorded on futuna we propose that the source for this younger event was either a larger tonga kermadec trench related earthquake or the kuwae caldera collapse in 1452 1453 ad we recognise that as further research is carried out in the pacific we will greatly improve our abilities to identify past sources and the magnitude and frequency of past events from these areas this can only serve to improve our understanding of the regional risk from tsunamis

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

tsunami sources of the november 2006 and january 2007 great kuril earthquakes abstract along the northern kuril trench a great interplate earthquake occurred in november 2006 followed by an outer rise normal fault event in january 2007 surface wave magnitudes m s 7 8 and 8 2 indicate that the 2007 event was larger while the global cmt solutions m w 8 3 and 8 1 indicate that the 2006 event was larger tsunamis from both events were recorded at tide gauge stations in japan russia and the united states as well as deep ocean assessment and reporting of tsunamis dart systems and cabled tsunami sensors installed on deep ocean bottom inversion of 52 tsunami waveforms indicates that the 2006 tsunami source was about 200 km long extending from the epicenter to northeast the largest slips of 4 7 m are estimated on the northeastern subfaults for the 2007 event inversion of 32 waveforms shows that the tsunami source was about 120 km long with the largest slip of 3 5 m on the northeastern subfault the agreements between the observed and synthetic tsunami waveforms are generally good for both events not only within the inversion time windows but also for the later phases which were not used in inversions the slip distributions yield the seismic moment of m w 8 1 for the 2006 event and m w 7 9 for the 2007 event the seismic moment of the 2006 event was larger than the 2007 event from comparison of tsunami data regardless of fault model

2004 indian ocean tsunami inflow and outflow at phuket thailand at bangtao beach phuket the 2004 indian ocean tsunami produced a repeated sequence in which rapid inflow of turbulent water was followed by ponding and then by gradual outflow photographs and eyewitness accounts show an initial withdrawal followed by series of inflows the tsunami left behind a sand sheet as much as 25 cm thick that contains parallel inclined landward and seaward lamina in addition to the normal grading commonly reported from tsunami deposits the sheet contains evidence for two times of vigorous inflow each of these is marked by mud rip ups medium to coarse sand that grades upward to fine landward inclined laminae and a sharp basal contact the top of the sand sheet when observed in the first days after the tsunami abounded in current dune and ripple bedforms of mostly landward orientation the tsunami s first positive wave left noonshore sedimentary record in this pitting area the second wave deposited sand that is much less extensive and slightly finer than that of the third wave the deposit of both these waves contains multiple fining upward sequences possibly due to multiple surges in one wave train the depth averaged flow velocity estimated from thickness and grain size are in the range 7 21 m s whereas a near bottom threshold velocity calculated from bedforms reveals the order of magnitude difference from 1 74 to 1 03 m s 2007 elsevier b v all rights reserved

historical tsunamis and storms recorded in a coastal lowland shizuoka prefecture along the pacific coast of japan four sand units deposited by tsunamis and one sand unit deposited by storm surge s were identified in a muddy marsh succession in a narrow coastal lowland along the pacific coast of central japan tsunamis in ad 1498 1605 1707 and 1854 that were related to large subduction zone earthquakes along the nankai trough and storm surges in 1680 and or 1699 were responsible for the deposition of these sand units these sand units are distinguished by lithofacies sedimentary structures grain size and mineral composition and radiocarbon ages their ages are supported by events in local historical records the tsunami deposits in the study area are massive or parallel laminated sands with associated intraclasts gravels draping mud layers and rarely a return flow subunit the storm surge deposits are devoid of these characteristics and are composed of groups of thin current ripple laminated sand layers the differences in sedimentary structures between the tsunami and storm surge deposits are attributed to the different characteristics of tsunami and storm waves

linked halokinesis and mud volcanism at the mercator mud volcano gulf of cadiz mud volcanoes are seafloor expressions of focused fluid flow that are common in compressional tectonic settings new high resolution 3 d seismic data from the mercator mud volcano mmv and an adjacent buried mud volcano bmv image the internal structure of the top 800 m of sediment at both mud volcanoes revealing that both are linked and have been active episodically the total volumes of extruded mud range between 0 15 and 0 35 km3 and 0 02 0 05 km3 for the mmv and the bmv respectively the pore water composition of surface sediment samples suggests that halokinesis has played an important role in the evolution of the mud volcanoes we propose that erosion of the top of the vernadsky ridge that underlies the mud volcanoes activated salt movement triggering deep migration of fluids dissolution of salt and sediment liquefaction and mobilization since the end of the pliocene since beginning of mud volcanism in this area the mud volcanoes erupted four times while there was only one reactivation of salt tectonics this implies that there are other mechanisms that trigger mud eruptions the stratigraphic relationship of mudflows from the mmv and bmv indicates that the bmv was triggered by the mmv eruptions this may either be caused by loading induced hydrofracturing within the bmv or due to a common feeder system for both mud volcanoes this study shows that the mud volcanoes in the el arraiche mud volcano field are long lived features that erupt with intervals of several tens of thousands of years

evidence for 17th century tsunamis generated on the kuril kamchatka subduction zone lake tokotan hokkaido japan abstract in the seventeenth century two tsunamis that were generated by earthquakes on the kuril kamchatka subduction zone inundated the eastern coast of hokkaido northern japan stratigraphic evidence for these two tsunamis and related land level change in coastal hokkaido consists of two landward thinning sand layers in the sediments of lake tokotan a coastal lagoon on the hokkaido coast the marine origin of these sand layers is indicated by the presence of brackish marine diatoms the rarity and high degree of fragmentation of diatom valves suggests that the sands were transported in a short time over a considerable distance tsunamis at this site were probably generated by great earthquakes along the kuril kamchatka trench volcanic ash deposits lying just above the sands suggest that tsunamis occurred in the late 17th century tsunamis during the historic period are not recorded in lake tokotan which suggests that the sand layers were deposited by tsunamis substantially larger than historic tsunamis

traces of tsunami preserved in inter tidal lacustrine and marsh deposits some examples from northeast japan the japan sea earthquake of may 26 1983 triggered a large scale tsunami that surged over the coast of ne japan and caused considerable damage the tsunami resulted in peculiar sedimentary processes on the coast depending on the hydraulic scale of the tsunami three kinds of sedimentary processes were recognized each of which left unique deposits such deposits are expected to remain in sedimentary sequences preserving remarkable sedimentary facies borehole samples drilled at different localities in coastal regions have been examined to detect traces of ancient tsunamis sedimentological and geochemical studies of the samples reveal that layered deposits similar to those developed by the tsunami of the japan sea earthquake are common in the drilled cores estimated ages of these deposits are exactly equivalent to the dates of ancient tsunamis documented in historical records these results show that the invasion of tsunamis is recorded in coastal depositional sequences from analyses of long borehol

coastal sedimentation associated with the june 2nd and 3rd 1994 tsunami in rajegwesi java abstract this paper presents the second detailed study of sediments deposited by modern tusnamis the first being that of the flores indonesia tsunami of december 1992 shi et al 1995 sediment cores were collected from areas in which eyewitnesses reported sediment deposition grain size analysis shows pronounced vertical variations in grain size as well as changes in standard deviation skewness and kurtosis that appear to be indicative of complex tsunami flooding vertical variations in grain size in individual cores are greater than spatial variations between cores taken along a transect completed perpendicular to the coastline the java tsunami deposited sediments do not show unequivocal evidence of local erosion but instead evidence for sediment transport and deposition is clear and is characterised by dominantly unimodal sediments with fine tailed distributions

the holocene storegga slide tsunami in the united kingdom all currently known sites in the united kingdom with evidence for the holocene storegga slide tsunami are described information on the altitude distribution stratigraphical context age particle size profile and microfossil characteristics of the deposits is presented the tsunami involved a greater area than previously described reaching a coastline over 600 km long the ubiquitous sand layer which forms the main deposit associated with the event is shown to exhibit a consistent morphology and a particle size profile marked by fining upwards sequences an analysis of new and previously published radiocarbon dates indicates that from evidence in the united kingdom the event took place sometime around 7100 radiocarbon years bp 7900 calibrated years bp a new isobase model for mainland scotland and adjacent areas providing a preliminary estimate of land uplift since the tsunami is presented the model estimates contemporary sea surface level offshore at 14 m below the present day mean high water spring tides tsunami sediment run up is greatest in inlets where it reaches at least 25 m on shetland and at least 5 m along the mainland coastline to the south and run up of the tsunami would have exceeded these values the tsunami sediments identified here are considered particularly valuable as a synchronous marker horizon

the sedimentology of middle holocene tsunami facies in northern sutherland scotland uk abstract lagoonal sediments attributed to the main holocene marine transgression in strath halladale northern sutherland contain a complex coarser layer believed to have been deposited during the tsunami associated with the second storegga slide off south west norway the coarser sequence is dated at between 7590 50 and 7290 50 radiocarbon years bp 6507 6260 cal bc and 6228 6029 cal bc detailed stratigraphical analysis has determined a distinctive suite of sedimentary sub units within the coarser layer in marked contrast to the sediments which occur above and below a pronounced erosional unconformity with the underlying sediments is recorded with the base of the tsunami layer characterised by eroded material from the underlying peat the presence of a mixed diatom assemblage although fragmentary indicates a chaotic accumulation of the deposit with all habitats represented variations in particle size within the sequence disclose striking similarities with those from contemporary tsunami deposits the run up of the tsunami sediments is calculated at a minimum of 4 6 m this is the first occasion on which a deposit of the second storegga slide tsunami has been found outside the north sea basin and indicates that the area affected by the tsunami may have been larger than has been previously described

geophysical evidence of gas hydrates in shallow submarine mud volcanoes on the moroccan margin 1 gas hydrates inside mud volcanoes have been observed in several locations but are generally found at water depths of 1000 m and deeper we present the first observation of the base of a gas hydrate stability zone within a shallow mud volcano in the el arraiche mud volcano field on the moroccan atlantic margin the mud volcano base is located at about 475 m and is over 125 m high on high resolution seismics we observed an anomalous but coherent reflection under the slopes of the mud volcano the event was interpreted as the base of a gas hydrate stability zone because of its inverse polarity and its morphology far from the crater the event is nearly parallel to the seafloor closer toward the crater the event shallows inside the mud volcano crater no event is observed a stability model using thermogenic gas compositions is applied to local p t conditions indicating that thermogenic gas hydrates can be stable at this depth the high modeled heat flow in the crater of the mud volcano indicates a focused flow of warm fluids below the slopes of the mud volcano the inferred heat flow is also elevated but less high in areas of thermogenic gas production gas hydrates can occur at shallow water depths even in areas with high heat flow this also suggests that dewatering of the accretionary wedge complex is mainly focused along fault surfaces and through seafloor structures such as mud volcanoes

esr in the 21st century from buried valleys and deserts to the deep ocean and tectonic uplift abstract electron spin resonance esr dating can date many materials including hydroxyapatite in enamel and some fish scales aragonite and calcite in corals molluscs some travertine and calcrete and quartz from ash fluvial deposits and some flint dating studies using these materials have numerous potential applications in many varied quaternary settings esr dating uses signals resulting from trapped charges created by radiation in crystalline solids ages are calculated by comparing the accumulated radiation dose in the dating sample with the internal and external radiation dose rates produced by natural radiation in and around the sample and produced by cosmic radiation when compared to other dating techniques age agreement has been excellent for teeth corals molluscs and quartz recent improvements have included using a more complex modelling technique to calculate the cosmic dose rates and more detailed modelling techniques for dealing with variable external dose rates methods in development include using quartz from buried fluvial valleys to date geomorphic surfaces and using the signals in barnacles and benthic foraminifera for dating fossils or their associated sediment new chronometer applications recently developed include using coral and mollusc dates to build sealevel curves and to monitor volcanic activity and tectonic uplift using tooth and mollusc dates to assess water availability in deserts and using isochron data to assess u uptake processes into teeth when coupled with other geochemical and geomorphological techniques esr can provide the chronometric control to build paleoclimatic and other paleoenvironmental records many other applications are possible from heating studies for artefacts to dating sulphates and other minerals on distant planets

coastal sedimentation associated with the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract with wave heights of 30 m and runups reaching 50 m a s l and 6 km inland the december 26 2004 tsunami in sumatra was one of the largest tsunamis in recorded human history in this paper we present a description of the event in the lhok nga bay west coast of banda aceh and an interpretation of the tsunami sand deposits mostly based upon grain size analysis the 3 5 km long transect of lampuuk displays two landward fining thinning and sorting sequences the thickest cross sections of the first sequence of deposits 0 1 5 km inland suggest a deposition by three consecutive runups inflows and a final backwash return flow or outflow from 1 5 to 3 5 km inland the record is dominated by the second and highest wave 15 30 m normally graded couplets or triplets of layers were used to identify the runup of each wave the topmost layers interpreted as the backwash deposition describe a seaward sequence of increasing mean grain size and decreasing degree of sorting the local effects of the topography could be identified thickest deposits in the topographic lows 50 80 cm great spatial variations in thickness and upper laminated texture when the sedimentation was limited by steep slopes landward coarsening and very poor sorting at the wave breaking point bimodal grain size distributions reflecting different sources of sediments finally by coupling the longitudinal and vertical trends of the 26 cross sections we propose a model of sediment transport and deposition in a large tsunami wave

stratigraphy and paleoceanography of a topography controlled contourite drift in the pen duick area southern gulf of cadiz abstract the northern part of the gulf of cadiz has and still is receiving a lot of attention from the scientific community due to among others the recent iodp expedition 339 in contrast its southern part or the moroccan margin has received far less attention although mud volcanoes diapiric ridges and cold water corals are present in this region the el arraiche mud volcano field is characterized by a compressive regime creating several ridges and assisting the migration of hydrocarbon fluids towards the seabed surface this study presents seismic and multibeam evidence for the existence of a contourite drift at water depths between 550 and 650 m along the southwestern flank of the pen duick escarpment and gemini mud volcano within the el arraiche mud volcano field from the onset of the quaternary when the escarpment started to lift and the local mud volcanism initiated contouritic deposition was initiated as well at the foot of both topographic obstacles initially fairly low velocity bottom currents gave rise to sheeted drift deposits affected by the uplift of the escarpment or mud extrusion from the middle pleistocene onwards separated mounded drift deposits were formed due to intensified bottom currents an antarctic intermediate water origin is inferred as driving mechanism for the drift development although glacial conditions are not yet well constrained the influence of mediterranean outflow water mow cannot be substantiated here moreover the changes recorded within this contourite drift differ from the mow dominated contourite depositional system in the northern gulf of cadiz as drift deposits only occur as early as the base of the quaternary compared to the early pliocene for the north and mounded drift deposits only occur from the middle pleistocene onwards compared to the early pleistocene cold water coral mounds have been observed within and on top of the sedimentary sequence at the foot of the pen duick escarpment this implies that environmental conditions in which cold water corals thrive were not necessarily restricted to the top of the pen duick escarpment

implications of passive salt diapir kinematics for reservoir segmentation by radial and concentric faults abstract reservoirs associated with salt diapirs that are circular or elliptical in plan view can be segmented by radial faults concentric faults both or neither explanations for this variation are offered based on integration of fault kinematics published studies and seismic examples strata around diapirs can be divided into three structural domains with characteristic fault styles 1 roof zone between the present day depositional surface and crest of a buried inactive diapir this zone is characterised by doming radial faults and occasionally conic graben doming is usually caused by differential compaction and increases with depth 2 a steeply dipping sheath of strata surrounds the diapir out to a distance of less than one diapir radius recording near surface diapir growth in poorly lithified sediments these contain early gravity slumps and late concentric extensional faults regional layer bound polygonal fault systems form radial faults within approximately one diapir radius the only significant radial faulting mechanism below the roof zone 3 diapir root zone of strata whose structural architecture records the diapirs initiating mechanism typically rim synclines or graben that detach on the salt source layer concentric faults at radial distances of a kilometre or more have been found only in root zone rim synclines and sheared sheath strata these models and observations can assist seismic interpretation and structural model building in areas of poor geophysical imaging for instance below overhanging salt

isotopic evidence 87sr 86sr δ7li for alteration of the oceanic crust at deep rooted mud volcanoes in the gulf of cadiz ne atlantic ocean the chemical and isotopic composition of pore fluids is presented for five deep rooted mud volcanoes aligned on a transect across the gulf of cadiz continental margin at water depths between 350 and 3860 m generally decreasing interstitial li concentrations and sr 87 sr 86 ratios with increasing distance from shore are attributed to systematically changing fluid sources across the continental margin although highest li concentrations at the near shore mud volcanoes coincide with high salinities derived from dissolution of halite and late stage evaporites clayey terrigenous sediments are identified as the ultimate li source to all pore fluids investigated light delta li 7 values partly close to those of hydrothermal vent fluids delta li 7 11 9 parts per thousand indicate that li has been mobilized during high temperature fluid sediment or fluid rock interactions in the deep sub surface intense leaching of terrigenous clay has led to radiogenic sr 87 sr 86 ratios similar to 0 7106 in pore fluids of the near shore mud volcanoes in contrast non radiogenic sr 87 sr 86 ratios similar to 0 7075 at the distal locations are attributed to admixing of a basement derived fluid component carrying an isotopic signature from interaction with the basaltic crust this inference is substantiated by temperature constraints from li isotope equilibrium calculations suggesting exchange processes at particularly high temperatures 200 degrees c for the least radiogenic pore fluids of the most distal location advective pore fluids in the off shore reaches of the gulf of cadiz are influenced by successive exchange processes with both oceanic crust and terrigenous fine grained sediments resulting in a chemical and isotopic signature similar to that of fluids in near shore ridge flank hydrothermal systems this suggests that deep rooted mud volcanoes in the gulf of cadiz represent a fluid pathway intermediate between mid ocean ridge hydrothermal vent and shallow marginal cold seep due to the thicker sediment coverage and slower fluid advection rates the overall geochemical signature is shifted towards the sediment diagenetic signal compared to ridge flank hydrothermal environments c 2009 elsevier ltd all rights reserved

effects of landforms on tsunami flow in the plains of banda aceh indonesia and nam khem thailand abstract mapping on high resolution satellite images and in the field shows differences in landforms and characteristics of tsunami flow on two contrasting coastal plains following the giant earthquake on december 26 2004 the plain of banda aceh on the northern tip of the sumatra island indonesia and the nam khem plain in the andaman sea coast of thailand the landforms of the banda aceh coastal plain are characterized as deltaic lowland with tidal plains in the western and central parts and strand plain with beach ridges in the eastern part the run up tsunami flow invaded areas about 3 4 km from the coast strong tsunami flow severely damaged the tidal plain and the landforms along the coast except coastal dunes in the east most of the landforms except sand dunes along the coast had almost no effect on the protection against the tsunami but the higher micro landforms such as beach ridges and natural levees prevented the flow of the tsunami from its invasion into the inland near the end of tsunami inundation the tsunami inundation spread out over the entire nam khem coastal plain with an average depth of 4 5 m the direction of run up flow was almost perpendicular to the coastline whereas backwash flow directions were controlled by topography backwash flow was concentrated in the lower portions of the plain for example in small stream channels wedge shaped channels in the lower parts of the streams were formed due to the concentration of backwash flow the existence of the swales between parallel beach ridges corresponds well with the distribution of thick tsunami deposits coastal erosion of the plain was caused by the direct attack of tsunami waves and the lower reaches of small rivers were eroded by strong backwash flow

high resolution geochemical and grain size analysis of the ad 1755 tsunami deposit insights into the inland extent and inundation phases abstract in the study of palaeotsunamis it is crucial to decipher the sedimentological record to derive intensity of past events and to infer different inundation phases to achieve this goal it is important to apply high resolution techniques that allow magnifying intra deposit details at a sub centimetric scale that otherwise would not be perceived consequently valuable information could be overlooked in this work we applied successfully high resolution geochemical and grain size analyses xrf core scanning and image analysis respectively to the ad 1755 tsunami deposit this quartz sand enriched in bioclast deposit exhibiting high si al and ca ti was recognized in the coastal stratigraphic sequence of salgados lagoon due to its contrasting composition when compared with the under and overlying mud layers with scarce bioclasts exhibiting low si al and ca ti in the absence of textural evidence the identification of peaking concentrations of cl s and br all major constituents of sea salt in a continuous muddy sequence allowed slightly extending farther inland the limit of inundation in addition grain size analysis data attested the fining inland of the deposit furthermore despite the macroscopic massive structure of the tsunami deposit throughout the lagoon grain size results revealed more complexity and allowed inferring up to four depositional sequences directly associated with the ad 1755 tsunami inundation

sources of mud volcano fluids in the gulf of cadiz indications for hydrothermal imprint mud volcanism in the gulf of cadiz occurs over a large area extending from the shelf to more than 3500 m water depth and is triggered by compressional stress along the european african plate boundary affecting a deeply faulted sedimentary sequence of locally more than 5 km thickness the investigation of six active sites shows that mud volcano mv fluids on average are highly enriched in ch4 li b and sr and depleted in mg k and br the purity of the fluids is largely controlled by the intensity of upward directed flow flow rates could be constrained by numerical modelling and vary between 0 05 and 15 cm yr 1 application of d 18o systematics identifies clay mineral dehydration most likely within mesozoic and tertiary shales and marls as the major source of fluids hence cl and na in the pore fluids are mostly depleted below seawater values following a general trend of dilution however deviations from this trend occur and are likely caused by the dissolution of halite in evaporitic deposits other secondary processes overprinting the original fluid composition may occur along the flow path such as dissolution of anhydrite or gypsum and or the formation of calcite and dolomite different sources of fluids are also indicated by variations in 87sr 86sr which range from 0 7086 to 0 7099 at the different sites dehydration may be induced primarily by overburden and tectonic compression however very high concentrations of li and b specifically at captain arutyunov mv camv indicate additional leaching at temperatures above 150 c which could be explained by the injection of hot fluids along deep penetrating major e w strike slip fault systems this hypothesis is supported by the occurrence of generally thermogenic but significantly ch4 enriched light volatile hydrocarbon gases at camv which cannot be explained by shallow microbial methanogenesis li and li b ratios from different types of hot and cold vents are used to infer that high temperature signals seem to be preserved at various cold vent locations and indicate a closer coupling of both systems in continental margin environments than outlined in previous studies

the el arraiche mud volcano field at the moroccan atlantic slope gulf of cadiz the el arraiche field is a new mud volcano field discovered near the moroccan shelf edge in the gulf of cadiz that consists of 8 mud volcanoes in water depths from 200 to 700 m the largest mud volcano in the field al idrissi mud volcano is 255 m high and 5 4 km wide the cluster was discovered during a survey with the rv belgica and studied further during leg 2 of the ttr 12 survey onboard the r v prof logachev the 2002 surveys yielded detailed multibeam bathymetry over a 700 km 2 study area dense grids of high resolution seismic data deep tow sub bottom profiles sidescan sonar mosaics over the major structures selected video imagery lines video guided grab samples dredge samples gravity cores and box cores were collected for groundtruthing purposes eight mud volcanoes in water depths from 200 to 700 m cluster around two sub parallel anticlines and associated active extensional faults rock clasts and regional seismic data locate the el arraiche field over a late miocene pliocene extensional basin the onset of mud volcanic activity is estimated at about 2 4 ma and probably roots in the cretaceous miocene accretionary wedge stacked outflows are visible up to a depth of about 500 m below the sea floor the occurrence of long lived mud volcanoes bear witness to continued overpressure generation at depth either by in situ oil and gas generation or by focussed flow and accumulation in the area geochemical analyses of pore water from cores demonstrate the presence of thermogenic hydrocarbon processes the activity of the mud volcanoes is indicated by the thickness of hemi pelagic sediments covering extruded mud breccia the

multiple sources for late holocene tsunamis at discovery bay washington state usa nine muddy sand beds interrupt a 2500 yr old sequence of peat deposits beneath a tidal marsh at the head of discovery bay on the south shore of the strait of juan de fuca washington an inferred tsunami origin for the sand beds is assessed by means of six criteria although all the sand beds contain marine diatoms and almost all the beds display internal stratification the areal extent of the oldest beds is too limited to confirm their origin as tsunami deposits the ages of four beds overlap with known late holocene tsunamis generated by plate boundary earthquakes at the cascadia subduction zone diatom assemblages in peat deposits bracketing these four beds do not indicate concurrent change in elevation at discovery bay diatoms in the peat bracketing a tsunami bed deposited about 1000 cal yr bp indicate a few decimeters of submergence suggesting deformation on a nearby upper plate fault other beds may mark tsunamis caused by more distant upper plate earthquakes or local submarine landslides trigg

origin of light volatile hydrocarbon gases in mud volcano fluids gulf of cadiz evidence for multiple sources and transport mechanisms in active sedimentary wedges widespread mud volcanism across the thick 7000 between sites mixing of shallow biogenic and deep thermogenic gases cannot account for the observed compositions which instead result mainly from extensive migration of thermogenic gases in the deeply buried sediments possibly associated with biodegradation of c2 homologues and secondary methane production at captain arutyunov and carlos ribeiro mvs at the deep water bonjardim olenin and carlos ribeiro mvs generation of c2 enriched gases is probably promoted by high heat flux anomalies which have been measured in the western area of the wedge at porto mv gases are highly enriched in ch4 having delta c 13 ch4 similar to 50 parts per thousand as at most sites but markedly lower delta h 2 ch4 values 250 parts per thousand suggesting that it is not generated by thermal cracking of n alkanes but rather that it has a deep archaeal origin the presence of petroleum type hydrocarbons is consistent with a thermogenic origin and at sites where ch4 is predominant support the suggestion that gases have experienced extensive transport during which they mobilized oil from sediments similar to 2 4 km deep these fluids then migrate into shallower thermally immature muds driving their mobilization and extrusion at the seafloor at porto mv the limited presence of petroleum in mud breccia sediments further supports the hypothesis of a predominantly deep microbial origin of ch4 c 2009 elsevier b v all rights reserved

fluid evolution and authigenic mineral paragenesis related to salt diapirism the mercator mud volcano in the gulf of cadiz the formation of mud volcanoes in the gulf of cadiz is closely linked to diapirism in the deep subsurface the mercator mud volcano mmv is a rare example where diapiric emplacement in addition to being key for upward fluid migration is also an important zone for fluid and mineral diagenesis the most intriguing findings in the near surface muds of the mmv are extremely high salinities of up to 5 2 m of nacl from diapiric and evaporitic halite dissolution and the occurrence of authigenic gypsum and anhydrite crystals both of which have not been observed to date in the gulf of cadiz employing a thermodynamic model we elucidate how the interplay of temperature pulses strong salinity gradients and fluid flow dynamically drive mineral dissolution and re formation the strong increase in salinity in the pore fluids has important implications for thermodynamic equilibria by significantly lowering the activity of water thereby raising the gypsum anhydrite transition zone from 1 km to about 400 m sediment depth at the mmv this transition is further shifted to immediately below the seafloor during intervals of active mud and fluid expulsion when the mv surface temperature is heated up to at least 30 c as a consequence precipitation of authigenic gypsum near the sediment surface 1 2 mbsf has been linked to the dissolution of evaporites below the mmv more precisely the mechanisms generating supersaturation in the ascending gypsum saturated mmv fluids are 1 the slow and constant cooling of these fluids along the geothermal gradient during their ascent leading to formation of ubiquitous micro crystals and 2 the more rapid cooling after a heat pulse or transport from greater and warmer depth during an active mud volcano phase leading to the precipitation of cm scale gypsum crystals or even fist size concretions the mmv fluids approaching the salt diapir from farther below have experienced a genesis similar to those of other mud volcanoes in the gulf of cadiz located above deep rooted faults these processes include clay mineral dewatering thermogenic degradation of organic matter and deep high temperature leaching of terrigenous sediments or continental crust

new insights of tsunami hazard from the 2011 tohoku oki event we report initial results from our recent field survey documenting the inundation and resultant deposits of the 2011 tohoku oki tsunami from sendai plain japan the tsunami inundated up to 4 5 km inland but the 0 5 cm thick sand deposit extended only 2 8 km 62 of the inundation distance the deposit however continued as a mud layer to the inundation limit the mud deposit contained high concentrations of water leachable chloride and we conclude that geochemical markers and microfossil data may prove to be useful in identifying the maximum inundation limit of paleotsunamis that could extend well beyond any preserved sand layer our newly acquired data on the 2011 event suggest that previous estimates of paleotsunamis e g 869 ad j gan earthquake and tsunami in this area have probably been underestimated if the 2011 and 869 ad events are indeed comparable the risk from these natural hazards in japan is much greater than previously recognized

seafloor expression of sediment extrusion and intrusion at the el arraiche mud volcano field gulf of cadiz 1 the el arraiche mud volcano field consists of eight mud volcanoes up to 255 m high and 5 4 km wide located in the moroccan margin of the gulf of cadiz at water depths between 700 and 200 m available data include detailed swath bathymetry over the entire area dense grids of high resolution seismic data very high resolution deep tow subbottom profiles side scan sonar mosaics over the major structures selected underwater video lines and sediment samples the main morphological aspects of the mud volcanoes are from the margin toward the center a subsidence rim or moat the mud volcano slope in some cases a deep crater and a recent central mud dome at the top the slope is characterized by radial outward sediment flow deposits or by a concentric pattern of terraces and steps the sediment flow deposits can be divided into elongate outflows that accumulate at the base of the slope and short bulky outflow deposits that freeze on the steep slope the crater hosts extruded sediment ranging from fluidized sand to mud breccia with centimeter to meter sized rock clasts issued from several vents within the crater the concentric slope terraces and the central mud dome are interpreted to result from several phases of uplift caused by sediment intrusion or shallow diapirism the mud volcano growth is thus interpreted to result from a combination of extrusive and intrusive processes

salt tectonics and mud volcanism in the latakia and cyprus basins eastern mediterranean salt tectonics and mud volcanism in the latakia and cyprus basin eastern mediterranean is investigated by means of swath sounding reflection seismics and side scan data as well as by camera and video sledge observations both basins are located east of cyprus and are associated with the collision front between the african and anatolian plate the pliocene quaternary sediment succession is underlain by up to 1 km thick messinian evaporites both thick skinned plate tectonic and thin skinned salt tectonic control fluid dynamics and associated mud volcanism in the latakia and cyprus basin as well as at the troodos latacia culmination which separates both basins an end member model is proposed which explains the presence of elongated topographic highs and trenches along the troodos larnaca culmination and south of it by gravity gliding of the messinian evaporites and associated fluid migration thin skinned extension in the troodos larnaca culmination and boudinage respectively facilitate fluid flow through and out of the evaporites the fluid or mud flow dissolutes the salt layer and creates elongated trenches mud intrudes into the pliocene quaternary sediments above the trenches consequently the overburden is thickened and forms morphological ridges south of the culmination the evaporites and overburden are folded due to thin skinned shortening of the evaporites in one instance fluid extrusion out of the evaporites is inferred from seismic data interpretation the outflow caused a volume reduction and collapse of the evaporites mud volcanoes and fold anticlines align above deep rooted transpressional fault systems which are associated with the african anatolian collision zone the faults may act as conduits for rising fluids in the western part of the survey area where the cyprus arc strikes almost west east and the collision occurred more frontal and stress was highest mud volcanoes emerged further to the east where the cyprus arc runs sw ne and sinistral strike slip has been proposed fold anticlines evolved particular mud volcanoes and folds emerged prior to the deposition of the messinian evaporites the undisturbed upper pleistocene sequences as well as the absence of significant mud outflow on the seafloor strongly suggest that the main fluid dynamic ceased

emplacement of giant mud volcanoes in the south caspian basin 3d seismic reflection imaging of their root zones exceptional quality 3d data for the largest mud volcano yet described provide the first detailed imaging of the plumbing architecture that connects a major volcanic edifice to its source layer at depth the volcano is in the south caspian basin and consists of an extruded submarine mud bicone 10 km wide and 1 4 km thick overlying an oval caldera 1 2 1 6 km in width and 0 5 km in depth the caldera narrows downwards into a zone of collapsed country rock forming a downward tapering cone 1 km in height the vertex of which is located close to the top of the mud source layer the imaged structural elements lead to an evolutionary model a narrow steep fluidization pipe fed the oldest pioneer cone we propose that numerous additional fluidization pipes injected the country rock forming a densely intruded cylindrical zone similar to gryphon swarms observed at outcrop onshore wall rock erosion and compaction of the intruded zone led to collapse of the downward tapering cone that linked upwards into ring faults that define the caldera margins later mud flowage focused on the conical sheared margins volumetric contraction of the extruded volcanic cone led to an unusual concentric system of minor outward facing normal faults this model has many similarities to syntheses of igneous maar diatreme caldera systems for which it may be analogous

microfossils from coastal environments as indicators of paleo earthquakes tsunamis and storms abstract coastal risk assessment and hazard mitigation require datasets on centennial and millennial temporal scales to capture natural variability and multiple occurrences of the largest but least frequent events coastal sediments from low energy depositional environments archive geologic evidence of paleo earthquakes tsunamis and storms many of the best reconstructions of these events are derived from changes in microfossil diatoms foraminifera and pollen assemblages in this review we explain how microfossils are used to reconstruct records of paleoearthquakes by quantifying the amount of coseismic and interseismic vertical land movements along tectonically active coastlines examples from the united states alaska and the pacific northwest japan and chile show that microfossil based transfer functions may provide continuous records of vertical land movement during earthquake deformation cycles we discuss how microfossil habitat preferences and taphonomic character are used to constrain sediment provenance e g beach nearshore or offshore sources and identify overwash deposits and how this information can be used to reconstruct the recurrence of tsunamis and storms analysis of overwash deposits from thailand and malaysia indicates the ability of microfossils to resolve individual waves within tsunami sediments and an example from the sendai coastal plain in japan uses foraminifera to ascribe a beach to nearshore provenance for the 2011 tohoku tsunami deposit finally we present recent examples from the gulf of mexico on the use of foraminifera to estimate the volume and distance of transport of storm overwash from hurricanes

origin of salt giants in abyssal serpentinite systems worldwide marine salt deposits ranging over the entire geological record are generally considered climate related evaporites derived from the precipitation of salts mainly chlorides and sulfates from saturated solutions driven by solar evaporation of seawater this explanation may be realistic for a salt thickness 100 m being therefore inadequate for thicker 1 km deposits moreover sub seafloor salt deposits in deep marine basins are difficult to reconcile with a surface evaporation model marine geology reports on abyssal serpentinite systems provide an alternative explanation for some salt deposits seawater driven serpentinization consumes water and increases the salinity of the associated aqueous brines brines can be trapped in fractures and cavities in serpentinites and the surrounding country rocks successive thermal dehydration of buried serpentinites can mobilize and accumulate the brines forming highly saline hydrothermal solutions these can migrate upwards and erupt onto the seafloor as saline geysers which may form salt saturated water pools as are currently observed in numerous deeps in the red sea and elsewhere the drainage of deep seated saline brines to seafloor may be a long lasting effective process mainly occurring in areas characterized by strong tectonic stresses and or igneous intrusions alternatively brines could be slowly expelled from fractured serpentinites by buoyancy gradients and hence separated salts brines could intrude vertically into surrounding rocks forming salt diapirs serpentinization is an ubiquitous exothermic long lasting process which can modify large volumes of oceanic lithosphere over geological times therefore buried salt deposits in many areas of the world can be reasonably related to serpentinites

a tsunami ca 6300 years bp and other holocene environmental changes northern hawke s bay new zealand abstract sediment cores collected in a coastal lagoon a few kilometres east of wairoa northern hawke s bay new zealand were examined using sedimentological geochemical palynological and micropaleontological analyses a distinct short lived catastrophic saltwater inundation csi about 6300 years bp and possibly other minor marine incursions are preserved in the coastal estuarine to lagoonal freshwater sedimentary sequences which have been deposited in the last 6500 years the csi is characterised by a gravel unit that thins landward and decreases in particle size to sand within a sequence consisting mainly of brackish estuarine muds diatom assemblages indicate a marked change from the shallow brackish estuarine muds to marine gravels and sands to brackish estuarine muds the marine influence in the gravel and sand is also shown by the presence of marine dinoflagellates and a peak in na rb sedimentological chemical and paleontological in particular diatoms evidence indicates it is a csi we conclude that this was a tsunami and propose the most likely propagating mechanisms marine influence decreases upcore and totally freshwater conditions are evident in the upper section of the cores the geochemistry of the sediments mainly reflects the change in stratigraphy with distinct signatures for tephra na fe cr organic rich and peat units as br and the coarse gravel sand csi unit na rb cr fe but it is also indicative of changes in depositional environment the change in chemistry na rb in the csi event is indicative of a saltwater influence whereas a marked change in s content suggests a sudden change from brackish to freshwater conditions shortly after 4800 years bp another peak in s and br content about 3200 years bp may indicate another temporary change to brackish conditions

validating velocities in the geoclaw tsunami model using observations near hawaii from the 2011 tohoku tsunami the ability to measure predict and compute tsunami flow velocities is of importance in risk assessment and hazard mitigation substantial damage can be done by high velocity flows particularly in harbors and bays even when the wave height is small moreover advancing the study of sediment transport and tsunami deposits depends on the accurate interpretation and modeling of tsunami flow velocities and accelerations until recently few direct measurements of tsunami velocities existed to compare with model results during the 11 march 2011 tohoku tsunami 328 current meters were in place around the hawaiian islands usa that captured time series of water velocity in 18 locations in both harbors and deep channels at a series of depths we compare several of these velocity records against numerical simulations performed using the geoclaw numerical tsunami model based on solving the depth averaged shallow water equations with adaptive mesh refinement to confirm that this model can accurately predict velocities at nearshore locations model results demonstrate tsunami current velocity is more spatially variable than waveform or height and therefore may be a more sensitive variable for model validation

quaternary stratigraphic stacking patterns on the continental shelves of the southern iberian peninsula their relationship with global climate and palaeoceanographic changes abstract a quaternary stratigraphic stacking pattern on the continental shelves of the southern iberian peninsula has been determined by analysing and comparing a dense network of low medium high and very high resolution mono channel and multi channel reflection seismic lines and well log data four major low resolution depositional sequences related to a 3rd order cycle at 1 4 1 6 ma have been recognised in the pliocene quaternary sedimentary record m p1 p2 p3 q i and q ii they are separated by four discontinuities corresponding to the most drastic changes in climate and palaeoceanography affecting the atlantic and mediterranean linkage and especially to the most prominent sea level falls in the messinian m at 5 5 ma in the lower pliocene at 4 2 ma in the upper pliocene at 2 4 ma and in the mid pleistocene at 900 920 ka mpr these major sequences were built up by asymmetrical sea level cycles the regressive and lowstand system tracts are the best developed deposits controlling the main progradation of the shelf basinwards as well the quaternary shelf stratigraphy can be divided into asymmetric 3rd order sequences of 800 ka q i and q ii and into 4th order asymmetric sequences of approximately 400 ka q1 q4 200 ka a h and 100 ka on low medium and high resolution seismics the overall architectural stacking of the shelf shows a change after the mpr discontinuity characterised by well differentiated sequences of shelf break wedges with progradational sigmoid configurations assumed to be related to approximately 100 ka sea level cycles this change in the configuration of the shelf wedges during the quaternary is attributed to the onset of the 100 ka eccentricity orbital cycles which abruptly increased the amplitude of sea level variations 100 120 m during the last 900 920 ka

the betic orogen and the iberian african boundary in the gulf of cadiz geological evolution central north atlantic abstract the study of the gulf of cadiz on the basis of multichannel seismic profiles and wells illustrates the stratigraphy and tectonics the evolution of the southern iberian margins was more complex than in most north atlantic margins since it entailed several phases of rifting convergence and strike slip motions three main tectonic provinces surround the internal zones of the gibraltar arc orogenic belt these include in the iberian margin of the gulf of cadiz the flysch units of the campo de gibraltar complex the betic external zones and the neogene basins of the guadalquivir valley fault bounded blocks of flysch and subbetic units crops out over large areas of the southeastern iberian shelf the basement of the northwestern area in contrast is represented by the paleozoic rocks of the hercynian massif of iberia half graben structures determined the main structural trends of the margin during the mesozoic which were affected by inversion structures during the neogene compressional stages the mesozoic and lower cenozoic units are best observed in wells and seismic profiles from the northern area these units are either obscure below a thick olistostrome deposit or are absent in most of the rest of the gulf of cadiz seven lithoseismic units from triassic to upper oligocene and another seven neogene and quaternary units are identified based on the relationship to the depositional sequence and the emplacement of the olistostrome the first tectonic phase was characterized by a passive margin which was controlled by the development of half graben extensional structures and carbonate platforms this evolution comprises the mesozoic and early cenozoic ocean spreading in the north atlantic induced extensional tectonics which deformed the cretaceous syn tectonic post aptian deposits increased amounts of terrigenous materials were supplied to the margin from aptian to albian times controlling depositional patterns while terrigenous siliciclastic facies replaced the jurassic carbonate platforms from middle eocene to early miocene the margin was influenced by the relative motions of iberia and africa and the development of the alpine orogeny the iberian african boundary in the gulf of cadiz experienced transpression and the mesozoic basins probably underwent subduction the emplacement of an olistostrome took place in the gulf of cadiz towards the central atlantic basin plains during the tortonian the end of the olistostrome emplacement during the late miocene coincides with accelerated tectonic subsidence while thick progradational and aggradational depositional sequences were developed the occurrence of closely juxtaposed regions of compression and extension during the miocene may reflect the westwards progression of the gibraltar arc mountain front over a subducting thinned tethys crust when the motion between iberian and africa was n s to nnw sse oriented the migration of the arcuate mountain front into the eastern gulf of cadiz is attributed to a mechanism of collision induced delamination of the mantle lithosphere in contrast to the betic rif belts however there is no geophysical evidence to postulate that continental collision took place in the gulf of cadiz during the cenozoic

authigenic barite records of methane seepage at the carlos ribeiro mud volcano gulf of cadiz submarine mud volcanoes mvs are dynamic features that episodically expel gas charged fluids and mud onto the seafloor transferring various chemical constituents into the overlying water column the temporal variability in mv activity is however poorly understood so their importance as a source of methane ch4 and higher hydrocarbons for the oceanic carbon budget although thought to be significant cannot be properly constrained in this study the history of fluid and gas seepage at the carlos ribeiro mv gulf of cadiz is assessed via geochemical analyses and transport reaction modelling of pore fluids and barium ba rich layers ba fronts in sediment cores recovered along a transect from the eye to the periphery of the mv x ray fluorescence data reveal that ba fronts are absent at the eye while a single front with up to 1740 ppm ba is present at the margin of the summit three ba fronts occur at 45 85 and 130 cm depth within a mudflow to the southeast of the crater spectrometric analyses indicate that barite is the ba rich mineral in these layers upward advecting pore fluids are enriched in barium but depleted in calcium ca2 relative to seawater modelling of the ba2 and ca2 pore fluid profiles indicates that the positions of the ba fronts reflect both the present day hydrodynamic conditions as well as higher fluxes of methane in the past fluid advection appears to have decreased since 340 cal yr before present but degassing of the mudflow is ongoing and is potentially an important source of ch4

holocene coastal evolution and evidence for paleotsunami from a tectonically stable region tasmania australia stratigraphic investigations of three coastal waterbodies in southeastern tasmania reveal major paleoenvironmental phases related to sea level change and anomalous deposits consistent with tsunami

diatom biostratigraphy of tsunami deposits examples from the 1998 papua new guinea tsunami abstract distinctive diatom assemblages may be associated with tsunami sediments and may often contrast with the assemblages found within sediments underlying the tsunami deposit as well as those associated with the modern coastal environment sediments associated with the 1998 tsunami that destroyed much of the sissano lagoon area in northern papua new guinea have been investigated surface sediments from three transects across the sediment spit near warapu have been examined for diatom content and preservation the preservation is variable and the data show an often chaotic assemblage that can be attributed to the tsunami waves incorporating and depositing diatoms from distinctive habitat zones during their runup and subsequent backwash the diatoms identified within the warapu sediments indicate an origin from within the inter tidal and offshore area rather than from the beach sand spit complex the sand deposits disclose a high percentage in excess of 75 of broken diatom valves and a predominance of centric circular species due to preferential preservation the study demonstrates that the application of diatom biostratigraphy to modern tsunami deposits can be used in conjunction with other stratigraphical lines of evidence to interpret the source and provenance of historical and palaeo tsunami deposits