hydrography and energetics of a cold subpolar fjord andvord bay western antarctic peninsula abstract fjords along the western antarctic peninsula contain rich marine ecosystems and tidewater glaciers potentially sensitive to ocean change but much is unknown about the physical oceanography of these fjords this paper presents a comprehensive description of the physical environment of andvord bay a glacial fjord located in the gerlache strait on the northern end of the peninsula measurements were collected as part of the fjordeco program between november 2015 and march 2017 including during three research cruises and from a number of fixed installations sub surface moorings time lapse cameras and automatic weather stations andvord bay is located just north of a sill in the gerlache strait this sill inhibits the direct influence of warm upper circumpolar deep water from the shelf and deep waters in the fjord are therefore relatively cold as a result glaciers in andvord bay are not subject to the substantial ocean driven retreat observed farther south on the peninsula instead mass flux from the glaciers occurs mainly through calving the influence of meltwater in andvord bay is small compared to glacial fjords in the arctic and in the south shetland islands although summer freshening is evident in the fjord near surface layer likely as a result of glacial inputs the combination of surface freshening and the absence of strong mean wind forcing in the fjord results in salinity stratification extending well into the euphotic zone providing advantageous conditions for phytoplankton blooms andvord bay is generally dynamically quiet compared to the ambient ocean with the exception of during local katabatic wind events exchange with the gerlache strait is weak although the deep waters of the fjord are replenished on an annual scale through slow lateral exchange with the outside in addition deep convection may play a role in ventilating subsurface waters in winter

model for the origin of the troodos massif cyprus and other mideast ophiolites any comprehensive model for the origin of the troodos complex and other mideast ophiolite complexes must explain the geochemical evidence for subduction zone involvement the thin inferred oceanic crust the extensional environment indicated by sheeted dikes the existence of fault zones perpendicular to the inferred spreading axes and the discontinuous nature of ophiolite exposures around the arabian block the andaman sea region of the indian ocean may provide an actualistic model for the origin of these ophiolites there spreading takes place in short segments above a subduction zone in the region of active spreading the andaman sea model substantially accounts for the known geologic and geophysical data from the circum arabian ophiolite belt and it leads to some predictions about the structural and geophysical relationships to be expected in this important belt the model also predicts that andaman sea spreading center magmas may be similar in composition to those found in the mideast ophiolites

multiple opening and closing of the eastern mediterranean and south china basins the eastern mediterranean east of crete and the south china basin are small ocean basins surrounded by continental masses and are currently undergoing closure they were both formed by the rifting of continental fragments away from large continents a comparison of the geological evolution of the two basins indicates a remarkable similarity in the sequence of evolutionary stages that took place in both basins although the age of these stages is probably different for each of the two the formation of the two basins is a consequence of a much larger process in which large lithospheric plates south and north of the basins move toward each other africa including sinai and arabia toward eurasia and india australia toward eurasia and the pacific each basin went through several stages of evolution during which oceanic crust was created and destroyed during each stage the area of the newly formed oceanic crust was smaller than the area formed in the previous stage it appears as if similar evolutionary patterns also occurred in other marginal and small ocean basins formed by continental rifting

a pockmark field in the patras gulf greece and its activation during the 14 7 93 seismic event abstract during a recent oceanographical geophysical survey carried out in the southeastern part of the gulf of patras in western greece for the construction of an outfall an active pockmark field was found the pockmark field was formed in soft layered holocene silts the pockmarks are associated with acoustic anomalies attributed to gas charged sediments the pockmarks vary in size and shape from 25 to 250 m in diameter and from 0 5 to 15 m in depth and are among the largest and deepest observed in the world on july 14th 1993 during the survey a major earthquake of magnitude 5 4 on the richter scale occurred in the area during the 24 hour period prior to the earthquake the bottom water temperature anomalously increased on three occasions whilst for a few days after the earthquake it was noted that the majority of the pockmarks were venting gas bublles it is considered that the three abrupt sea water temperature increases were probably the result of upward migrating high temperature gas bubbles in the water column it is further suggested that the earthquake was the triggering mechanism and that the gas expulsion was caused by the reduction in the pore volume in the sediments resulting from changes in the stress regime prior to the earthquake therefore it can be suggested that in seismic areas adjacent to pockmark fields earthquake prediction may be achieved by monitoring the water temperature and or the rate of gas venting in the pockmark field our analysis indicates that the pockmark field in the patras gulf has formed slowly during the holocene by continuous gas venting which is periodically being interrupted by short duration events of enhanced gas seepage triggered by earthquakes

permian early mesozoic tectonism and continental margin formation in israel and its implications for the history of the eastern mediterranean summary the early mesozoic tectonic reorganization of the tethys region also affected the levant area here two processes were superimposed a the pattern of long wavelength vertical motions of the arabo nubian platform changed in the late permian when israel and nearby areas began to subside b rifting occurred in this subsiding area probably in several phases late anisian and ladinian carnian norian and liassic differential movements reached 2 3 km and magmatism occurred in the liassic and perhaps also in the triassic the tectonism was strongly felt up to 50 km landward of the present coast the crust was thinned and modified under the present continental margin and in the main rifts passive margin conditions were established in late liassic times over the previously faulted area later in the jurassic a carbonate shelf was constructed along this subsiding margin its basinward edge was 1 1 5 km high which shows that the adjacent se mediterranean was already a deep sea hence this basin and its passive margin are considered to have been shaped by the early mesozoic rifting which is recognized in israel the rifting process probably signifies oblique separation of the tauride block from the levant part of gondwana

architecture of late orogenic quaternary basins in northeastern mediterranean sea abstract in the northeastern mediterranean sea pliocene to quaternary depocentres have formed in extensional basins bounded by splays of the east anatolian transform fault this tectonic regime is superimposed on a miocene and older back arc environment that experienced late miocene compression along the misis kyrenia thrust which now lies in the middle of the extensional zone the thrust zone is now represented by a narrow horst that appears to be bounded by strike slip faults pliocene quaternary extension took place on listric fault fans that are orthogonal to the bounding transform splays and sole at a messinian evaporite horizon and on some deeper soling listric faults parallel to and near the bounding faults the rapid extension has resulted in progressive landward migration of paleoshorelines and low depositional gradients glacio eustatic fluctuations in shoreline positions strongly influenced sediment distribution most sediment dispersion was from deltaic plumes with turbidites of minor significance depocentres landward of the maximum seaward extent of paleoshorelines were formed almost entirely by tectonic subsidence minor deep water depocentres controlled by halokinesis accumulated mud turbidites during extreme low stands of sea level

surface rupture and rupture mechanism of the october 1 1995 m w 6 2 dinar earthquake sw turkey abstract a moderate earthquake m w 6 2 caused substantial damage in the town of dinar at 17 57 ut on october 1 1995 surface rupture has been observed to be discontinuous for 10 km along the nw trending dinar fault segments the surface rupture has consisted of nearly vertical cracks up to several tens of meters long and a meter wide that display linear sigmoidal and anastomosing geometries indicating the mechanism of displacement on the fault plane most of these cracks display a dip slip component of displacement 0 05 0 6 m those with anastomosing geometries indicate a large dip slip 0 25 m sigmoidal crack patterns show both right and left strike slip rotational component of displacement and a small dip slip

lithogenic and biogenic particle deposition in an antarctic coastal environment marian cove king george island seasonal patterns from a sediment trap study abstract particulate suspended material was recovered over a 23 month period using two sediment traps deployed in shallow water 30 m deep off the king sejong station located in marian cove of king george island west antarctica variability in seasonal flux and geochemical characteristics of the sediment particles highlights seasonal patterns of sedimentation of both lithogenic terrigenous and biogenic particles in the coastal glaciomarine environment all components including total mass flux lithogenic particle flux and biogenic particle flux show distinct seasonal variation with high recovery rates during the summer and low rates under winter fast ice the major contributor to total mass flux is the lithogenic component comprising from 88 during the summer months about 21 g m 2 d 1 up to 97 during the winter season about 2 g m 2 d 1 the lithogenic particle flux depends mainly on the amount of snow melt snow accumulation delivered into the coastal region as well as on the resuspension of sedimentary materials these fine grained lithogenic particles are silt to clay sized composed mostly of clay minerals weathered on king george island biogenic particle flux is also seasonal winter flux is 0 2 g m 2 d 1 whereas the summer contribution increases more than tenfold up to 2 6 g m 2 d 1 different biogenic flux between the two summers indicates inter annual variability to the spring summer phytoplankton bloom the maximum of lithogenic particle flux occurs over a short period of time and follows the peak of biogenic particle flux which lasts longer the seasonal warming and sea ice retreat result in change in seawater nutrient status and subsequent ice edge phytoplankton production meanwhile the meltwater input to marian cove from the coastal drainage in january to february plays a major role in transporting lithogenic particles into the shallow water environment although the tidal currents may be the main agents of resuspension in this kind of sheltered bay

an integrated view of the methane system in the pockmarks at vestnesa ridge 79 n accepted manuscript version published version available at https doi org 10 1016 j margeo 2017 06 006 accepted manuscript version licensed cc by nc nd 4 0

polar gravel beach ridge systems sedimentary architecture genesis and implications for climate reconstructions south shetland islands western antarctic peninsula abstract the sedimentary architecture of polar gravel beach ridges is presented and it is shown that ridge internal geometries reflect past wave climate conditions ground penetrating radar gpr data obtained along the coasts of potter peninsula king george island show that beach ridges unconformably overlie the prograding strand plain development of individual ridges is seen to result from multiple storms in periods of increased storm wave impact on the coast strand plain progradation by contrast is the result of swash sedimentation at the beach face under persistent calm conditions the sedimentary architecture of beach ridges in sheltered parts of the coast is characterized by seaward dipping prograding beds being the result of swash deposition under stormy conditions or aggrading beds formed by wave overtopping by contrast ridges exposed to high energy waves are composed of seaward as well as landward dipping strata bundled by numerous erosional unconformities these erosional unconformities are the result of sediment starvation or partial reworking of ridge material during exceptional strong storms the number of individual ridges which are preserved from a given time interval varies along the coast depending on the morphodynamic setting sheltered coasts are characterized by numerous small ridges whereas fewer but larger ridges develop on exposed beaches the frequency of ridge building ranges from decades in the low energy settings up to 1600 years under high energy conditions beach ridges in the study area cluster at 9 5 7 5 5 5 and below 3 5 m above the present day storm beach based on radiocarbon data this is interpreted to reflect distinct periods of increased storminess and or shortened annual sea ice coverage in the area of the south shetland islands for the times around 4 3 c 3 1 1 9 ka cal bp and after 0 65 ka cal bp ages further indicate that even ridges at higher elevations can be subject to later reactivation and reworking a careful investigation of the stratigraphic architecture is therefore essential prior to sampling for dating purposes

anatomy of a glacial meltwater discharge event in an antarctic cove glacial meltwater discharge from antarctica is a key influence on the marine environment impacting ocean circulation sea level and productivity of the pelagic and benthic ecosystems the responses elicited depend strongly on the characteristics of the meltwater releases including timing spatial structure and geochemical composition here we use isotopic tracers to reveal the time varying pattern of meltwater during a discharge event from the fourcade glacier into potter cove northern antarctic peninsula the discharge is strongly dependent on local air temperature and accumulates into an extremely thin buoyant layer at the surface this layer showed evidence of elevated turbidity and responded rapidly to changes in atmospherically driven circulation to generate a strongly pulsed outflow from the cove to the broader ocean these characteristics contrast with those further south along the peninsula where strong glacial frontal ablation is driven oceanographically by intrusions of warm deep waters from offshore the fourcade glacier switched very recently to being land terminating if retreat rates elsewhere along the peninsula remain high and glacier termini progress strongly landward the structure and impact of the freshwater discharges are likely to increasingly resemble the patterns elucidated here this article is part of the theme issue the marine system of the west antarctic peninsula status and strategy for progress in a region of rapid change

characterisation and correlation of active hydrocarbon seepage using geophysical data sets an example from the tropical carbonate yampi shelf northwest australia abstract for the first time in australia active present day hydrocarbon seepage has been imaged on the tropical carbonate yampi shelf in 50 and 90 m water depth seepage is evidenced by gas plumes in the water column that are associated with seabed features such as clusters of reflective blocks hard grounds pockmark fields and mounds seepage activity and intensity seems to vary with changes in pressure related to macro tidal cycles the seabed features coincide with sub surface features such as areas of seismic signal attenuation under high amplitude reflectors seismic discontinuities and bright spots hydrocarbon migration seepage pathways appear to be controlled by the reactivation of pre existing fractures and dykes within the basement the types of seabed features and their preservation on a tropical carbonate shelf are strongly influenced by the coarse bioclastic nature of sediments and the high energy of macro tidal currents and storm reworking

hydrography of potter cove a small fjord like inlet on king george island south shetlands abstract the hydrography of potter cove king george island south shetlands is described in detail for one summer season recorded data are wind air temperature water temperature salinity and water colour from these information on surface circulation patterns and dynamics of suspended sediments are derived possible sources of sediment input are discussed as a result a complex interaction between wind forcing circulation and seasonal melt of high glacier surfaces emerges

iron cycling and stable fe isotope fractionation in antarctic shelf sediments king george island iron fe fluxes from reducing sediments and subglacial environments are potential sources of bioavailable fe into the southern ocean stable fe isotopes 56fe are considered a proxy for fe sources and reaction pathways but respective data are scarce and fe cycling in complex natural environments is not understood sufficiently to constrain respective 56fe endmembers for different types of sediments environmental conditions and biogeochemical processes we present 56fe data from pore waters and sequentially extracted sedimentary fe phases of two contrasting sites in potter cove king george island antarctic peninsula a bay that is affected by fast glacier retreat sediments close to the glacier front contain more easily reducible fe oxides and pyrite and show a broader ferruginous zone compared to sediments close to the icefree coast where surficial oxic meltwater streams discharge into the bay pyrite in sediments close to the glacier front predominantly derives from eroded bedrock for the high amount of easily reducible fe oxides proximal to the glacier we suggest mainly subglacial sources where fe liberation from comminuted material beneath the glacier is coupled to biogeochemical weathering processes likely pyrite oxidation or dissimilatory iron reduction dir our strongest argument for a subglacial source of the highly reactive fe pool in sediments close to the glacier front is its predominantly negative 56fe signature that remains constant over the whole ferruginous zone this implies in situ dir does not significantly alter the stable fe isotope composition of the accumulated fe oxides the nonetheless overall light 56fe signature of easily reducible fe oxides suggests pre depositional microbial cycling as it occurs in potentially anoxic subglacial environments the strongest 56fe depletion in pore water and most reactive fe oxides was observed in sediments influenced by oxic meltwater discharge the respective site showed a condensed redox zonation and a pore water 56fe profile typical for in situ fe cycling we demonstrate that the potential of pore water 56fe as a proxy for benthic fe fluxes is not straight forward due to its large variability in marine shelf sediments at small spatial scales 2 4 at the site proximal to oxic meltwater discharge vs 0 9 at the site proximal to the marine glacier terminus both at 2 cm sediment depth the controlling factors are multifold and include the amount and reactivity of reducible fe oxides and organic matter the isotopic composition of the primary and secondary ferric substrates sedimentation rates and physical reworking bioturbation ice scraping the application of 56fe geochemistry may prove valuable in investigating biogeochemical weathering and fe cycling in subglacial environments this requires however similarly to the use of 56fe for the quantification of benthic fluxes that the spatial and temporal variability of the isotopic endmember is known and accounted for since geochemical data from subglacial environments are very limited further studies are needed in order to sufficiently assess fe cycling and fractionation at glacier beds and the composition of discharges from those areas

physical properties and state of the crust and upper mantle of the eastern mediterranean sea deduced from geophysical data abstract by evaluating the geophysical information available for the eastern mediterranean sea ems a crustal thickness map and some conclusions as to the nature of the crustal type were drawn it was found that the ionian abyssal plain is floored by an oceanic type of crust which is 14 km thick and covered by sediments of the order of 8 km thick the herodotus abyssal plain in the levantine sea is floored by a crust 22 km thick and covered by sediments ranging between 10 and 15 km thick the eastern mediterranean rise extending more or less continuously from the apulian plateau to rhodes and the south of the antalya basin is of a thickness ranging between 28 and 34 km the thickness of its sedimentary cover is of the order of 10 km the borders of the eastern mediterranean sea are built up of thick continental crust for example the hellenides of western greece range between 40 and 44 km thick and western turkey has a similar crustal thickness the crust of sicily also exceeds 40 km whereas the southern and eastern borders of the ems are approximately 30 32 km thick tectonically the northern border of the ems is built up of active continental margins defined by the calabrian hellenic and cyprus antalya arcs whereas the southern border represents a passive continental margin controlled mainly by subsidence and stretching to the east the dead sea megashear limits the area the deep basins of the eastern mediterranean sea are tectonically controlled by subsidence and partial stretching the mediterranean ridge or rise is still an area of dispute regarded by some authors as a subsiding continental fragment and separated from the hellenic arc by the hellenic trench whereas others consider it to be a zone of crustal shortening thickened mainly by thrusting both the western and southwestern borders of the mediterranean rise and the hellenides are controlled by compressional processes similar to those deforming the calabrian arc the stravo and pliny trenches to the east southeast border of the hellenic arc are partly affected by strike slip movements various plate tectonic models of the area have been proposed by several authors though the complexity of the deformation hardly permits reliable reconstructions the lack of reliable paleomagnetic information and the absence of linear magnetic anomalies do not favour the application of plate tectonic concepts vertical processes due to the uprising of lithothermal systems below the hellenic and calabrian arcs may also be regarded as the driving force controlling the present day deformation

gas charged sediments in the aegean and ionian seas greece abstract during the last fifteen years marine seismic surveys in the aegean and ionian seas have revealed numerous acoustic anomalies i e acoustic turbid zones gas pockets gas plumes enhanced reflectors columnar disturbances wipe outs and meso to micro morphological features such as pockmarks domes mud volcanoes and elongated depressions these are attributed to the presence of gas in sediment interstices the gas charged sediments are found in pleistocene and present day fjord like environments pleistocene and present day deltaic environments lakes and open sea environments the gas found in the quaternary fjord like and deltaic depositional environments is assumed to be of biogenic origin the gas found in the pre quaternary open sea environments is associated with faulting and salt doming and may therefore be of thermogenic origin although the sediment grain size is favourable for the formation of pockmarks the lack of them is probably due to the high seismicity which characterises these regions

structurally controlled hydrocarbon seeps on a glaciated continental margin hecate strait offshore british columbia abstract this paper describes structurally controlled gas seeps and their influence on seafloor morphology at sites within queen charlotte basin qcb a sedimentary basin situated offshore british columbia western canada numerous surficial and shallow sediment features related to both ice cover and shallow gas have been identified in high resolution multichannel seismic huntec deep towed seismic multibeam bathymetry and backscatter and piston core data that were acquired over a 10 km by 10 km grid in an eastern part of qcb pockmarks seafloor mounds and iceberg ploughmarks are visible in the multibeam data small scale folds vertical blank zones and acoustic turbidity are observed in the huntec data the multichannel seismic data show a faulted anticline phase reversed bright spots zones of low instantaneous frequency and velocity pull ups one seafloor mound lies directly above a shallow fault that offsets an asymmetric fold the remaining mounds lie either above or in close proximity to asymmetric folds that are faulted bright spots are observed along some fault traces and within a cut and fill sequence at two way travel times between 0 42 and 1 0 s velocity pull ups are observed in the multichannel data below gas expansion voids present in piston cores backscatter data show that seafloor mounds are highly reflective compared to the surrounding seafloor these observations indicate that gas has been migrating upward through the rock column and expelled into the shallow sediments the shallow gas has been biologically mediated to form carbonate sediments within and around seafloor mounds shallow gas has also deformed surficial sediments into positive relief mounds and negative relief pockmarks

fluid sediment interactions at eastern mediterranean mud volcanoes a stable isotope study from odp leg 160 abstract pore fluids from two odp sites at eastern mediterranean mud volcanoes have been analyzed for their cl concentration and their 18o and d isotopic composition the cl data span a wide range of concentrations from extremely depleted with respect to seawater as low as 60 mm at the crest of milano dome site 970 to strongly enriched up to 5 4 m at napoli dome site 971 chloride enrichment is known to be due to dissolving messinian evaporites whereas the source of the low cl fluid is deduced from stable isotope data presented here the isotopic composition of the endmember fluid is found to be 10 for 18o and 32 for d for low as well as for high cl waters from this signature it can be concluded that neither gas hydrates nor meteoric water play a significant role in the freshening of the pore water several other processes altering the 18o d composition of pore waters are discussed and considered to be of only negligible influence the process characterizing the isotopic composition of the fluid is found to be clay mineral dehydration mainly smectite illite transformation corresponding to a depth range of 3 5 7 km and an elevated temperature of about 120 165 c a quantitative estimate shows that this reaction is capable of producing the observed extreme cl depletion

evaluation of the simple settling theory for predicting sediment deposition by overland flow experiments were conducted in the laboratory to evaluate the influence of sediment concentration sediment grain size distribution bed slope and flow discharge on sediment deposition rates and patterns associated with a reduction in bed slope the experimental data clearly indicate that sediment deposition by overland flow is a very selective process fine particles remain almost entirely in suspension and coarse particles are deposited quickly analysis of the data shows that up to a critical unit discharge a simple settling equation without a transport term assuming continuous mixing of the sediment and water gives a good prediction of the overall sediment delivery ratio and the grain size distribution of the deposited and the exported sediment however there are some discrepancies for the clay the coarse silt and the sand fractions the assumption of continuous mixing is tested by investigating the sedimentation patterns of very narrow size classes the observed decrease of sediment concentration versus distance from the inflow point for these individual sediment size classes closely agrees with the prediction assuming continuous mixing when the critical unit discharge is exceeded hydraulic properties of the overland flow do influence the sediment delivery outcomes at discharges exceeding the threshold value the simple settling theory underpredicts the sediment delivery ratio in these hydraulic conditions a transport term needs to be incorporated into the simple settling theory it is shown that the transport capacity and the re entrainment model yield similar expressions for the description of sediment transport by overland flow over an area of net deposition the experimental data indicate that the re entrainment of previously deposited sediment is non selective copyright 1999 john wiley sons ltd

redox conditions and trace metal cycling in coastal sediments from the maritime antarctic abstract redox sensitive trace metals mn fe u mo re nutrients and terminal metabolic products no 3 nh 4 po 4 3 total alkalinity were investigated for the first time in pore waters of antarctic coastal sediments the results of this study reveal a high spatial variability in redox conditions in surface sediments from potter cove king george island western antarctic peninsula particularly in the shallower areas of the bay the significant correlation between sulphate depletion and total alkalinity the inorganic product of terminal metabolism indicates sulphate reduction to be the major pathway of organic matter mineralisation in contrast dissimilatory metal oxide reduction seems to be prevailing in the newly ice free areas and the deeper troughs where concentrations of dissolved iron of up to 700 m were found we suggest a combination of several factors to be responsible for the domination of metal oxide reduction over sulphate reduction in these areas these include the increased accumulation of fine grained material with high amounts of reducible metal oxides a reduced availability of metabolisable organic matter and an enhanced physical and biological disturbance by bottom water currents ice scouring and burrowing organisms based on modelled iron fluxes we calculate the contribution of the antarctic shelf to the pool of potentially bioavailable iron feb to be 6 9 103 to 790 103 t yr 1 consequently these shelf sediments would provide an feb flux of 0 35 39 5 mg m 2 yr 1 median 3 8 mg m 2 yr 1 to the southern ocean this contribution is in the same order of magnitude as the flux provided by icebergs and significantly higher than the input by aeolian dust for this reason suboxic shelf sediments form a key source of iron for the high nutrient low chlorophyll hnlc areas of the southern ocean this source may become even more important in the future due to rising temperatures at the wap accompanied by enhanced glacier retreat and the accumulation of melt water derived iron rich material on the shelf

the structural relationship between the east anatolian and dead sea fault zones in southeastern turkey abstract the complex structural relationship between the east anatolian and dead sea fault zones is examined mostly based on field observations in southeastern turkey where the two fault zones are close together several faults previously poorly documented can be traced to connect either to the east anatolian fault zone or to the dead sea fault zone one of these faults connects the dead sea fault zone to the east to the amanos fault to the west the amanos fault a n trending normal fault is a part of the east anatolian fault zone since it is apparently a left step fault between the main and southern strands of the east anatolian fault zone the dead sea fault zone also is connected to the east anatolian fault zone northeast of the town of narli and or northeast of the hazar lake therefore we suggest that the two fault zones can be considered as one broad fault system in southeastern turkey although they are well recognized as two different fault zones this fault system is responsible for several complex neogene structural features of the western part of the southeastern turkey one of these is the hatay graben which can be divided into southern central and northern parts the graben contains down to the west normal faults in its southern part the central part of the graben is a divergent strike slip basin and the northern part is a half graben

active faults in the gulf of izmit on the north anatolian fault nw turkey a high resolution shallow seismic study the northern strandof the north anatolian fault enters the sea of marmara through the gulf of izmit which was affectedby the mw 7 4 i zmit earthquake on august 17 1999 a significant segment of the fault rupturedin between the area west of go lcu k andeast of lake sapanca d uring the earthquake in the southeastern corner of the gulf andfrom go lcu k westwardthe active trace plunges into the sea andis lost to view we investigatedthe gulf of i zmit by means of high resolution shallow seismic data acquired during a post august 17 1999 earthquake to locate and map the active faults in the area considering the neotectonic features around the gulf two different sets of faults were differentiated an earlier and now mostly inactive set of faults that are responsible for the formation of the large pull apart depression in which the gulf of izmit is locatedanda younger secondset of active faults in the gulf that cut through the former set the second set was further divided into two groups the main fault and the secondary faults the main fault which extends roughly in an e w direction as rather throughgoing and longer segments was tracedbetween the southeast endof the gulf in the east andsouth of dar ca in the west where it joins the sea of marmara fault the secondary faults on the other hand lie along the main fault they are shorter and their strikes are controlled by the bathymetry two main seismic sequences were identified in the gulf according to the seismic profiles and existing borehole data holocene marine sediments and pre holocene fluvio lacustrine sediments 2002 elsevier science b v all rights reserved

geophysical evidence for gas geohazards off iskenderun bay se turkey abstract high resolution seafloor and sub surface data were acquired as part of a site survey in iskenderun bay se turkey to characterize the geohazards at the location of the proposed drilling site a 3 km 3 km geophysical study reveals a pockmark field which trends ne and nne similar to the trend of major fault systems in the area the pockmarks with an average diameter of 35 m reach their highest density in the northern part of the detailed survey area with 13 features km2 acoustic anomalies in the seismic records acoustic turbidity blanking enhanced reflectors below the proposed drilling site indicated potential shallow gas beneath it the local seismic anomalies amplitude and frequency parallel to stratigraphy were assigned a low gas risk as a result of the active neotectonics in the area the pockmark field presented a potential hazard for drilling at the original location the geohazard study resulted in moving the proposed drilling site eastward to an area of fewer pockmarks less sub surface seismic anomalies and thus a location interpreted as a lower geohazard environment

magnetic anomalies over the central levant continental margin abstract the magnetic field over the central levant continental margin off northern israel and southern lebanon and the adjacent levant basin has two distinct trends mount carmel and its offshore continuation carmel nose which are the surface expression of a large subbottom structure that extends from the land area across the continental shelf to the continental slope form a dividing zone between the two magnetic trends south of the carmel structure the magnetic field trends east west while north of the carmel structure it trends northeast and north northeast several pronounced magnetic anomalies exist mainly north of the carmel structure the majority of which trend north northeast and northeast parallel and sub parallel to the trend of the magnetic field in this area some also trend northwest perpendicular to the trend of the magnetic field in several cases the magnetic anomalies indicate large lithological elements which continue from land to sea gravity and seismic refraction data show that the two magnetic domains north and south of the carmel structure are associated with areas of different crustal structure south of the carmel structure the continetal oceanic crustal transition zone is located beyond the continental margin at the base of the continental slope while north of the carmel structure it is located under the continental shelf near the shore on land there are also differences in the structure of the crust north and south of the carmel structure the crust being much thinner north of the structure than south of it we suggest that some of the large magnetic anomalies off the central levant were formed during the rifting phase of the eastern mediterranean

wake capture effects observed in a comparison of methods to measure particle settling velocity beyond stokes range abstract a comparison is presented of three methods currently used to measure particle settling velocity beyond stokes range contrasting natural sediments are analyzed in a settling tube and in a modified bottom withdrawal tube and velocities which are estimated to represent single particle behavior are calculated empirically from separate measures of particle size and density and shape velocities calculated empirically for aggregated sediments are lower than measured by either sedimentation method due primarily to aggregate breakdown that occurs during measurement of size by a wet sieve method for all sediment types multi particle velocities measured in a settling tube are very close to calculated single particle velocities but multi particle velocities measured in a modified bottom withdrawal tube are higher the increased velocities measured during this progressive or batch settling are attributed primarily to hydrodynamic wake capture that occurs at reynolds numbers 0 1 when particles of different sizes and velocities settle together in a polydisperse suspension for particles that settle in a polydisperse suspension temperature correction based on single particle behavior appears to be inadequate

glaciomarine sedimentation and its paleoceanographic implications along the fjord margins in the south shetland islands antarctica during the last 6000 years abstract two 3 m long cores were collected from maxwell and admiralty bays on king george island one of the south shetland islands west antarctica these cores were examined for their benthic foraminifer globocassidulina biora 18o and 13c records diatom abundance counts and biogenic constituents carbon and silica these high resolution data were used to reconstruct the paleoceanography of the bays and to link the marine record with deglaciation of the south shetland islands ice cap in maxwell bay extremely low diatom abundance the depletion of total organic carbon toc and biogenic silica biosi and enriched 18o between 6200 and 4000 bp indicate that this period was characterized by cold conditions with deposition of waterlain till unit 1 just seaward of the grounding line low sedimentation limitation of primary production on surface water and lack of meltwater supply deglaciation along the maxwell bay margin was dated from about 4000 bp until at least 2700 bp with increasing toc biosi and diatom abundance and decreasing the c n ratio up core at this time subglacial meltwater streams began to emanate from the glacier front sediment laden meltwater plumes from these streams deposited interlaminated sand and mud unit 2 in the ice proximal zone deglaciation was followed by marked climatic warming at around 2700 bp with evidence of toc and biosi maxima depleted 18o and markedly increased diatom valves with further glacier recession diatomaceous pebbly mud unit 3 was deposited in open marine conditions a large influx of organic materials by enhanced production during this period caused both rapid depletion of caco3 in sediment and resulted in marked increase in sedimentation since 2700 bp at 200 m water depth along the maxwell bay margin core s 19 in contrast the shallower platform along the admiralty bay margin core s 2 was deglaciated later about 1900 bp that is 2000 years after the maxwell bay margin this is possible as core s 19 is situated 200 m water depth more distal to the fjord head glacier while core s 2 in admiralty bay lies on a shallower platform

sedimentology of a late cenozoic collisional sequence the misis complex adana southern turkey abstract this study is concerned with miocene sequences formed within part of the cukurova basin of southern turkey a major downwarp created during the early stages of collision between the afro arabian plate and the tauride anatolian microplate assemblage we report here the results of a combined stratigraphical sedimentological structure and geochemical study of the misis complex a structurally elevated segment of cukurova basin fill this analysis has demonstrated the structurally imbricated nature of the misis sequences and the tectonic juxtaposition of originally well separated coeval facies the initial discernible phase of basin filling pre burdigalian was marked by deep marine conditions and marginal tectonic instability probably related to a late phase of tauride nappe advance the subsequent phase of crustal extension burdigalian early tortonian produced expansion of the cukurova basin limits and an upwards shoaling succession in which sediment transport towards the southwest gradually became dominant as a result of earlier suturing and uplift in northeasterly sectors of the collision zone the miocene arenites of the misis complex are petrographically diverse with common siliciclastic and carbonate detrital admixtures and mineralogically immature and their position in petrotectonic fields indicates a compound provenance from both recycled orogen and magmatic arc sources a noteworthy petrographic feature is the compositional similarity of arenites from both shallow and deep marine facies the general succession of neogene facies observed in the cukurova basin and misis complex is consistent with their evolution within a perisutural foreland basin but this interpretation is complicated by petrographic and geochemical features attributed to remnants of an older magmatic arc later stages of basin filling are also marked by the local occurrence of anomalous palaeoenvironmental associations including olistostromic units attributed to contemporaneous intra basinal tectonism

distal enhanced sedimentation from volcanic plumes insights from the secondary mass maxima in the 1992 mount spurr fallout deposits some tephra fallout deposits show an increase of mass and thickness at distances from the source 100 km areas of secondary mass maximum asmm which demonstrates distal enhanced sedimentation from volcanic plumes we explore development of the asmms during the 1992 august and september mount spurr eruptions usa by combining eld data on the spatial distribution of mass and grain size with 1 simulations of individual particle settling through a homogeneous and horizontally strati ed atmosphere and 2 mesoscale models of the three dimensional wind eld that include the effect of the underlying topography the crosswind and downwind variations of deposit characteristics indicate that the increase of sedimentation at the asmms is not formed solely because of preferential settling of small ash particles 125 m as commonly assumed in aggregation models instead asmm grain sizes correspond to the ne modes of the bimodal total grain size distributions there also appears to be a link between the asmm and the topography the mass local minima occur across the windward ank of 2 km high mountain ranges while the asmms spread on the leeward ank mesoscale models of the three dimensional wind eld show vertical oscillations in the wind over mountainous regions which may enhance mechanisms of en masse sedimentation aggregation hydrometeor formation and particle boundary layers as well as strong spatial variations of the horizontal wind eld in the lower troposphere our study demonstrates the importance of using grain size as well as mass data to constrain the complex processes responsible for particle sedimentation from volcanic plumes

structure and tectonics of the eastern cyprean arc abstract the geometry and nature of the eastern segment of the cyprean arc are little understood several hypotheses have been put forward to explain the tectonic situation there recent marine geophysical data for this region mapped several deep and shallow structural elements the most prominent element is a ridge the latakia ridge which extends from the syrian coast near latakia south westward to meet with an east west trending bathymetric escarpment east of the hecateus ridge the new seismic profiles suggest that these two elements mark the present plate boundary along the eastern cyprean arc the latakia ridge is a young and still active feature it was formed by southward migration of the plate boundary the ridge probably originated as a large thrust sheet which later when the convergence direction was changed became a zone of wrench faulting the ridge is still forming today and serves as a dam to the sediments north of it the wrench faulting activity is more pronounced in the eastern segment of the ridge

crustal structure of the levant basin eastern mediterranean abstract a seismic refraction wide angle reflection experiment was undertaken in the levant basin eastern mediterranean two roughly east west profiles extend from the continental shelf of israel toward the levant basin the northern profile crosses the eratosthenes seamount and the southern profile crosses several distinct magnetic anomalies the marine operation used 16 ocean bottom seismometers deployed along the profiles with an air gun array and explosive charges as energy sources the results of this study strongly suggest the existence of oceanic crust under portions of the levant basin and continental crust under the eratosthenes seamount the seismic refraction data also indicate a large sedimentary sequence 10 14 km thick in the levant basin and below the levant continental margin assuming the crust is of cretaceous age this gives a fairly high sedimentation rate the sequence can be divided into several units a prominent unit is the 4 2 km s layer which is probably composed of the messinian evaporites overlying the evaporitic layer are layers composed of plio pleistocene sediments whose velocity is 2 0 km s the refraction profiles and gravity and magnetic models indicate that a transition from a two layer continental to a single layer oceanic crust takes place along the levant margin the transition in the structure along the southern profile is located beyond the continental margin and it is quite gradual the northern profile north of the carmel structure presents a different structure the continental crust is much thinner there and the transition in the crustal structure is more rapid the crustal thinning begins under western galilee and terminates at the continental slope the results of the present study indicate that the levant basin is composed of distinct crustal units and that the levant continental margin is divided into at least two provinces of different crustal structure

late tertiary subsidence history of the southern levant margin eastern mediterranean sea and its implications to the understanding of the messinian event the late tertiary subsidence history of the southern levant continental margin situated in the southeastern mediterranean sea was quantitatively analyzed paleodepth reconstruction across the margin off ashdod suggests the existence of a deep basin in pre messinian time which resembles the present one this implies that the deposition of the evaporites in the study area during the messinian desiccation of the mediterranean sea occurred in a deep basin the path of the tectonic subsidence of the basement since early tertiary is generally smooth as expected from the nature of the thermal subsidence the unconformity beneath the messinian indicates erosion of 50 200 m at the coastal plain in the pliocene the tectonic subsidence in the coastal plain and shelf area diverts from the expected thermal path and increases from 250 m to 450 m respectively in the quaternary the rate of tectonic subsidence nearly resumed the predicted thermal subsidence sedimentation and subsidence rates decrease but are still higher than those of the pre messinian we suggest that the evolution of the southern levant margin is most probably influenced by three main causes 1 the messinian event in late miocene 2 the deposition of large volumes of nile derived sediments since the pliocene and 3 the flexural response of the lithosphere to the load from the nile delta and or from the uplift of the judea mountains the western shoulder of the dead sea transform we interpret the latter to be the cause of the anomalous subsidence of the southern levant margin during the pliocene

distribution and dispersal pattern of suspended particulate matter in maxwell bay and its tributary marian cove in the south shetland islands west antarctica abstract water property casting data spm and ctdt have been obtained from ice influenced fjords maxwell bay and marian cove in the south shetland islands antarctica to describe the configuration of turbid meltwater plumes in detail and to elucidate the dispersal pattern of the plumes in the areas of the primary sediment pathways only ice contact processes are unique in ice influenced fjords the effect of glaciofluvial discharges has been overwhelmed by the influences of subglacial discharge and ice front melting fluvial discharge from side entry glaciers that commonly end on land and or supraglacial discharge from ice surface are however more responsible for the overflow plumes in maxwell bay and marian cove subglacial meltwater discharge which is almost always in the form of vertically rising buoyant jets is considered rare active glaciofluvial and or supraglacial input from marian cove causes most suspended particulate matter to be concentrated near the mid point of maxwell bay thus even though closer to fjord head trunk glaciers spm concentration in collins bay is comparatively low largely due to clean tidewater glaciers and absence of meltwater streams around collins bay strong bottom current flowing along the continental shelf off the south shetland islands may import and export sediment from the outside of maxwell bay influencing the distribution of bottom sediment as well as benthic community

macroscopic seismic anomalies and submarine pockmarks in the corinth patras rift greece prior to the aigion earthquake m 6 2 of 15 june 1995 in the western gulf of corinth people in the area observed anomalous phenomena including bubbling of the sea extraordinary behavior of animals earthquake lights ground deformation and the sound of wind immediately before the shock some precursory phenomena of this kind might be understood as symptoms of gas venting before an earthquake sonar observations made in 1988 showed a chain of submarine pockmarks tracing the aigion fault and evidently produced by the expulsion of fluids under pressure t hasiotis et al mar geol 130 333 344 reported that hot gas erupted from a field of giant submarine pockmarks in the neighboring bay of patras several hours prior to an earthquake in 1993 automated monitoring of bottom water temperature in submarine pockmark fields may detect outgassing events prior to earthquakes in this region

structures and kinematics in the northeastern mediterranean a study of an irregular plate boundary abstract extensional structures are prominent in the northeastern mediterranean a unique sector of the africa eurasia plate convergence zone to explain this paradoxical situation we analyse here the young tectonics of this region by examining its structural elements and plate kinematics offshore multichannel seismic reflection profiles and onland geology show that the stuctural settings are different on the two sides of the northeastern mediterranean triple junction afr arb ana on the east stuctures controlled by strike slip and by compression coexist whereas on the west compression is not very conspicuous here deep basins separated by a partly submerged ridge are prominent we interpret the ridge which comprises the kyrenia misis andirin unit at its core as a large flower structure which extends from southeastern turkey to cyprus the adana cilicia and the iskenderun latakia mesaoria basins on its flanks are interpreted as due to extension this interpretation agrees with the relative motions between the africa arabia eurasia and anatolia plates in this region analysis of the local plate kinematics reveals that strike slip predominates along the southern boundary of the anatolia plate in this region as a result of anatolia s westward escape east of the triple junction this motion is associated with comparable shortening transverse to the plate boundary whereas west of the triple junction the motion transverse to the plate boundary varies between slight compression to extension depending mainly on the local strike of the plate boundaries these variations calculated from regional data correlate well with the observed structural changes along the northeastern mediterranean sector of the plate convergence zone the structural kinematic analysis explains both the lateral changes in the deformation style and the existence of local extension in the northeastern mediterranean

a seeping sea floor in a ria environment ria de vigo nw spain the occurrence of gas accumulations in the ria de vigo nw spain have been characterized by the authors in previous research pockmarks frequently appear on seismic and sonar records covering ca 45 of the sea floor of the study area which indicates that gas expulsion is not an uncommon phenomena in the coastal ria environment here we report the occurrence of gas seepage for the first time along the coast of nw spain side scan sonar echo sounder and high resolution seismic techniques were used for mapping gas expulsion features some expulsion pockmarks sit over elongated features that represent bottom marks created by anthropogenic activity thus these anthropogenic sites may act as preferential venting zones for gas as well as being potential hazards on a muddy sea bed such as that of the ria where gas accumulates just below the surface of the sea floor

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

faulting processes along the northern dead sea transform and the levant margin the northern dead sea transform is markedly different from the southern segments of the transform the strike of the transform changes in this area that forms a restraining bend and the displacement on it is much less than that on the southern and central dead sea transform the structure and evolution of the northern dead sea transform was simulated using a rheological model of a visco elastic material that takes into consideration the crustal structure variations in this area and the proximity to the collisional belts along the cyprean arc and the taurus mountains the simulation can explain the formation of the restraining bend known in this area as the yammuneh fault and the faulting along the northern levant continental margin providing that a simultaneous propagation of the dead sea transform from the north and south took place this suggests that restraining bends in general which are common features along continental transform faults are formed when two segments of a transform propagate toward each other

the structure of the africa anatolia plate boundary in the eastern mediterranean new marine deep seismic reflection data from south of cyprus to the syrian coast provide images of the upper crustal structure of the cyprean arc indicating that the deformation is partitioned along strike slip fault systems distributed over a wide zone rather than forming a sharp plate boundary between african and anatolian plates three major submarine strike slip fault systems tens of kilometers in length are mapped which follow bathymetric features and merge together toward the east these structures exhibit the three dimensional characteristics typical of strike slip deformation zones throughout the seven pre stack depth migrated sections including several sets of positive flower structures forming bathymetric ridges and the intervening contemporaneous subbasins beneath the plio quaternary sediments 500 m thick that are blanketing the whole area and that reflect only the main surface traces of the fault systems the subbasins are of varied dimensions and have rapid lateral changes in the thickness of the sedimentary fill they include two major unconformities that have been correlated throughout the data marked by the m and k reflections the m reflection is well imaged above varied thickness of messinian evaporites and the k reflection commonly appears at the base of syntectonic tertiary age sediments within the eastern cyprean arc the k reflection corresponds to the basement cover contact indicating that the strike slip tectonic scenario may have been active since the uppermost cretaceous or lowermost paleogene times to present the active deformation front of the alpine belt in the eastern mediterranean corresponds to a strike slip fault system that forms a 110 arc and coincides at the southern slope of the hecateaus rise continuing along the latakia ridge to the syrian coast the mapped structures fit within a general kinematic framework of left lateral transcurrent deformation that transfers slip from the subduction zone southwest of cyprus into the dead sea transform system in the east this change in the mode of deformation at the africa anatolia plate boundary occurs toward the junction between african anatolian and arabian plates

quaternary sedimentary history of adana cilicia and iskenderun basins northeast mediterranean sea detailed single channel airgun and 3 5 khz profiles from the northeastern mediterranean sea show that the continental shelf is formed by superimposed deltaic successions depositional sequences separated by major erosional unconformities each depositional sequence is composed of a sigmoid prograding package overlain by an oblique prograding package representing respectively delta progradation during high and low sea levels of interglacial and subsequent glacial stages during the glacio eustatic lowstands of sea level deltas prograded seaward the present day shelf break denotes the topset to forest transition at maximum progradation during the last glacial period during post glacial transgressions the deltas initially lost their dynamic equilibrium with the environment and rapidly retreated landward leading to the deposition of a thin veneer of sediments originating from reworking of formerly coastal sediments at the highstand position the deltas were re established in the ancestral adana bay and foreset progradation started chronology suggests that the cilicia and iskenderum basins are subsiding at rates of 0 38 m 1000 yr 1 and 0 33 m 1000 yr 1 respectively seismic reflection profiling shows that delta architecture in the adana cilicia and iskenderun basins is mainly controlled by glacio eustatic sea level fluctuations and continuous basin subsidence

constrains on the origin and history of the eastern mediterranean basin abstract the basin formed along the northern passive margin of gondwanaland as a relict of the mesozoic neotethys in early mesozoic time though direct information from the basin itself is meagre the geology of its passive margins and the regional framework of the tethys evolution constrain the formation and history of the basin the eastern mediterranean and its passive margins are interpreted to have formed as a result of several faulting and continental breakup phases from early permian to middle jurassic times before pangaea s complete disintegration this led to the detachment of the eratosthenes and tauride blocks from the margins of the levant and herodotus basins respectively the latter merged in the northeast with the cyprus basin that extended along arabia s northern margin the main rifting probably occurred in the triassic leading to seafloor spreading in the herodotus and cyprus basins while along the levant margin important rifting also occurred in the jurassic during the initial rifting stages extension perpendicular to the levant margin was important but subsequently the tauride block drifted mainly northward the existence of the passive margins and slopes of the eastern mediterranean is documented at least from the end of the middle jurassic until then the basin was probably narrow 200 300 km but during the main phase of the africa laurasia separation it grew to twice its present width or more this scenario depends critically on the interpretation that the tauride block was originally located next to northeastern africa on the western side of the eratosthenes block plate convergence and consumption of the northern portion of the basin have taken place since mid cretaceous times but the active convergent boundary on its northern side formed only in the neogene by modification of earlier structures some intra plate deformation also took place especially in the neogene but it hardly changed the original configuration of the remaining portion of the basin