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

deformation of western greece during neogene clockwise rotation and collision with apulia following an early miocene phase of n s extension affecting the entire hellenides 50 clockwise rotation affected western greece modern gps analyses show rapid southwestward motion in southwestern greece over subducting oceanic lithosphere and no motion in the northwest where greece collided with apulia we aim to identify the deformation history of western greece associated with the rotation and the collision with apulia the timing of the various phases of deformation is constrained via detailed analysis of vertical motions based on paleobathymetry evolution of sedimentary sequences overlying the evolving structures the results show that accompanying the onset of rotation compression was re established in western greece in the early langhian around 15 ma subsequently western greece collided with the apulian platform leading in the late miocene to a right lateral strike slip system running from the aliakmon fault zone in northern greece via the kastaniotikos fault and the thesprotiko shear zone to the kefallonia fault zone offshore western greece ne sw compression and uplift of the ionian islands was accompanied by ne sw extension in southwestern greece associated with faster southwestward motion in the south than in the north this led in the middle pliocene around 3 5 ma to collision without further shortening in northwestern greece from then onward nw se to n s extension east of apulia and gradually increasing influence of e w extension in the south accommodated motion of the hellenides around the apulian platform as a result curved extensional basin systems evolved including the gulf of amvrakikos sperchios basin gulf of evia system and the gulf of corinth saronic gulf system

extensional tectonics of northwestern macedonia greece since the late miocene tectonic field studies in the florina ptolemais basin northwestern greece were carried out in an attempt to define the regional stress tensors in selected areas affected by neogene and quaternary faulting using recently proposed quantitative methods the analysis allows us to distinguish two extensional phases in the area a late miocene pliocene one with a ne sw average direction of extension and a pleistocene recent one with a nw se direction of extension we conclude that the principal stress axes 2 and 3 were interchanged in passing from one phase to the other these results are reasonably consistent with results of studies carried out in other parts of the aegean area especially the south aegean back arc domain

strong motion records and synthetic isoseismals of the pyrgos peloponnisos southern greece earthquake sequence of march 26 1993 in this work several seismological observations are presented in order to explain characteristic features of the earthquake sequence which occurred in march 1993 in southwestern greece very close to the city of pyrgos fault plane solutions of the largest fore and aftershocks and the main shock as well as the directions at which the maximum ground accelerations were recorded suggest that this earthquake sequence has been developed by rupturing three distinct focal planes with different focal mechanisms the first focal plane located in the off shore area strikes nw se dips se and includes most of the foreshock activity the foreshock activity migrated to the northeastern part of the city of pyrgos and took place on planes with a predominant direction ne sw the main shock ofm x 5 5 occurred in a focal plane located between the two above mentioned areas strong motion records of significant shocks of the sequence show peak acceleration values on components consistent with the relevant fault plane solutions furthermore the observed macroseismic field has been compared with synthetic isoseismals computed by using a certain velocity model and the focal mechanism parameters of the main shock

dense bottom gravity currents and their impact on pelagic methanotrophy at oxic anoxic transition zones we show that inflows of oxygenated waters into sulfidic layers have a strong impact on biogeochemical transformation at oxic anoxic transition zones taking the pelagic methane dynamics in the gotland basin as an example we performed our studies when one of the largest inflows ever recorded entered the baltic sea in march 2015 an inflowing gravity current transported oxic waters into the sulfidic deep layers and freshly generated a near bottom secondary redox interface at the upper slope where the inflowing water masses were vigorously turbulent and the main and secondary redox interfaces in close contact to each other methane oxidation rates inside the transition zone were found to be higher compared to the weakly turbulent basin interior at the main redox interface in the basin center lateral intrusions of oxygenated waters into intermediate water depth may have stimulated the growth of the methanotrophic community and their activity

experimental study of marine pipelines on unstable and liquefied seabed experimental investigation was carried out in a wave flume to study the stability of marine pipelines on mobile and liquefied seabed a wide range of different pipeline specific gravities and wave condition were examined the results showed that for the given soil the seabed response is governed mainly by liquefaction and the pipeline behaviour on unstable seabed is strongly dependent on its specific gravity

sinking of concrete modules into a sandy seabed a case study abstract three submerged coastal structures on the sandy seabed at santa maria del mar smm beach in southwest spain were monitored during the six months after installation starting in november of 2005 the monitoring evaluated the self burial phenomenon of the 40 precast modular concrete elements of the three structures assessment included scouring around the structures their vertical movement the sinking velocity of the modules and the resulting beach profiles pressure sensors and precision topographies permitted continuous monitoring of the self burial process for the first time in a full scale case comparison of two bathymetries one performed immediately prior to installation and another performed six months after installation indicated slight accretion of the seabed whereas intermediate topographic surveys indicated extensive scouring around the structures the three structures began sinking into the sandy bottom platform immediately after placement and continued until they reached the rocky bottom this study implemented a new methodology using pressure sensors attached to the concrete modules to monitor the structural sinking unexpectedly the average sinking speed was extremely rapid at approximately 3 6 cm day 50 of the height of the element was reached in three to six weeks the results of this study are also compared with the results of other full scale cases among other conclusions data from this study indicated that the sinking rate of the modules in smm beach was one order of magnitude greater than the other values

signification structurale des iles strophades dans la marge hellenique abstract numerous seismic reflection profiles have been recorded on the western margin of the hellenic arc between the peloponnesus and the ionian trench the lack of deep drilling data makes tectonic interpretations ambiguous the existence of diapiric gypsum and bathyal lower pliocene outcrops on the strophades islands now provide more information on the structural interpretation of this active margin

euphotic zone bacterioplankton sources major sedimentary bacteriohopanepolyols in the holocene black sea abstract bacteriohopanepolyols bhps are lipid constituents of many bacterial groups geohopanoids the diagenetic products are therefore ubiquitous in organic matter of the geosphere to examine the potential of bhps as environmental markers in marine sediments we investigated a holocene sediment core from the black sea the concentrations of bhps mirror the environmental shift from a well mixed lake to a stratified marine environment by a strong and gradual increase from low values 30 g g 1 toc in the oldest sediments to 170 g g 1 toc in sediments representing the onset of a permanently anoxic water body at about 7500 years before present bp this increase in bhp concentrations was most likely caused by a strong increase in bacterioplanktonic paleoproductivity brought about by several ingressions of mediterranean sea waters at the end of the lacustrine stage 9500 years bp 15n values coevally decreasing with increasing bhp concentrations may indicate a shift from a phosphorus to a nitrogen limited setting supporting growth of n2 fixing bhp producing bacteria in sediments of the last 3000 years bhp concentrations have remained relatively stable at about 50 g g 1 toc the distributions of major bhps did not change significantly during the shift from lacustrine or oligohaline to marine conditions tetrafunctionalized bhps prevailed throughout the entire sediment core with the common bacteriohopanetetrol and 35 aminobacteriohopanetriol and the rare 35 aminobacteriohopenetriol so far only known from a purple non sulfur proteobacterium being the main components other bhps specific to cyanobacteria and pelagic methanotrophic bacteria were also found but only in much smaller amounts our results demonstrate that bhps from microorganisms living in deeper biogeochemical zones of marine water columns are underrepresented or even absent in the sediment compared to the bhps of bacteria present in the euphotic zone obviously the assemblage of molecular fossils in the sediments does not represent an integrated image of the entire community living in the water column remnants of organisms living in zones where effective transport mechanisms such as the fecal pellet express exist are accumulated while those of others are underrepresented our work shows a high stability of bhps over geological time scales largely uniform distributions and only minor changes in structures like an increasing prevalence of saturated over unsaturated bhps with time were observed consequently sedimentary bhp distributions are less suitable as markers for in situ living bacteria but are useful for paleoreconstructions of bacterioplanktonic communities and productivity changes

underthrusting and exhumation a comparison between the external hellenides and the hot cycladic and cold south aegean core complexes greece 1 after their emplacement in the course of the late mesozoic and the cenozoic the hellenic nappes became fragmented during late orogenic extension since the late eocene here we focus on the transition of underthrusting during nappe emplacement to exhumation during late orogenic extension to this end we compared previously published data on the structural geological and metamorphic history of the underthrusted parts of the tripolitza and ionian nappes which were exhumed in the cycladic and south aegean windows with newly obtained data on the sedimentary stratigraphic and structural development of the part of these nappes in the foreland in front of the subduction thrust the results allow the identification of two major events event 1 took place around the eocene oligocene transition and marks the onset of underthrusting of the tripolitza nappe below the pindos nappe and the ionian nappe below the tripolitza nappe respectively this led to the uplift and erosion of the pindos unit and the onset of deposition of the tripolitza and ionian flysch in front of the pindos thrust together with the formation of mylonites at the base of the metamorphosed portions of the pindos unit related to the underthrusting of the tripolitza unit event 2 occurred in the latest oligocene to earliest miocene and marks the decoupling of the ionian unit from the underthrusting plate the accretion of the tripolitza and ionian units to the overriding plate and the onset of late orogenic extension and exhumation in the overriding plate this led to the formation of the south aegean and cycladic core complexes and the subsidence of the klematia paramythia half graben throughout the early miocene

paleobathymetry in the backstripping procedure correction for oxygenation effects on depth estimates abstract this paper aims to provide a straightforward and easily applicable method for estimating the depositional depth evolution of marine basins vertical movements of the basin floor can be reconstructed from the sedimentary record and more accurately constrained when information from the sedimentary history is combined with palaeodepth estimates derived from fauna to this end we propose to extend an existing method based on the percentage of planktonic foraminifera with respect to the total planktonic and benthic foraminiferal association which is expressed as the percentage planktonics p the ratio between planktonic and benthic foraminifera is related to water depth and the p generally increases with increasing distance to shore however next to water depth the oxygen level of bottom waters has a profound effect on the abundance of benthic foraminifera and as such influences the p depending on basin configuration the oxygen level at the sea floor can vary on milankovitch time scales and is reflected by the fraction of benthic foraminiferal species that indicate an effect of oxygen stress on the biotic system these species can be used as stress markers and their percentage with respect to the total benthic population is here expressed as s to assess whether the effect of sea floor oxygenation impairs depth reconstructions we studied the percentage of planktonic foraminifera p in five well dated sedimentary successions from the lower pliocene of crete corfu and milos in greece additionally we assessed whether different foraminiferal size fractions and counting methods affect the determination of the percentage of planktonic foraminifera the palaeobathymetric evolution calculated for each basin was confirmed for all successions by an independent check on depth related occurrences of benthic foraminifera after correction for bathymetry changes of the basin due to sedimentation compaction and eustatic sea level variations the vertical movement history of the basin floor was inferred we propose a standard methodology for reconstructions of palaeobathymetry of marine sedimentary successions from foraminiferal associations

mechanics of the scouring and sinking of submerged structures in a mobile bed a physical model study abstract wave induced flow velocity and turbulence may cause scouring in the seabed around coastal structures depending on the wave climate and tidal water depth a 3 d physical modelling study was conducted to investigate the possible causes of the sinking of two submerged coastal structures on the santa maria del mar smm beach spain the experimental investigation was conducted by employing a froude similarity law with a geometric scale of 1 20 and the submerged modular structure was subjected to different wave climates and tidal water levels the combinations of the significant wave height and peak period were chosen from in situ real wave conditions that were monitored during the sinking of the prototype structures linking and unlinking conditions for the modules in the structure were investigated in this study the results show that the modules sank to approximately 48 of their height at the end of the tests with storm waves and semi linking conditions of low water depth most of the experimental results were compatible with the prototype monitoring results tests with proper linking among the modules and tests with an appropriate gravel foundation resulted in a sustainable solution because they presented much less or almost no scouring and sinking

new constraints on the provenance of hopanoids in the marine geologic record bacteriohopanepolyols in marine suboxic and anoxic environments abstract the abundance and structural diversity of bacteriohopanepolyols bhps was examined in three marine pelagic environments that are characterized by strong vertical redox gradients and water column suboxia or anoxia the abundance and in most instances structural diversity of bhps was highest at depths where conditions were suboxic or anoxic however the majority of the bhp structures that were identified are environmentally cosmopolitan and their biological sources are presently not well constrained an isomer of bacteriohopanetetrol denoted bht ii was observed at all three study sites in association with anoxic and suboxic conditions within the water column based on the absence of bht ii from terrigenous and oxic marine environments studied to date and its strong association with suboxic and anoxic marine pelagic environments we propose that bht ii is a promising candidate biomarker for water column suboxia and anoxia in the marine geologic record the molecular fingerprint of bhps in suspended and sinking particles and core top sediments indicates that hopanoids produced within the water column are exported to marine sediments and that their biological source is most likely associated with settling particles and not the free water phase based on our observations bhps likely represent an important input to the sedimentary hopanoid inventory particularly in upwelling environments characterized by pelagic oxygen minimum zones omz and anoxic marine basins

bacteriohopanepolyols preserved in silica sinters from champagne pool new zealand indicate a declining temperature gradient over the lifetime of the vent siliceous sinters from champagne pool cp a geothermal vent in the taupo volcanic zone north island new zealand contained exceptionally well preserved bacteriohopanepolyol bhp distributions bhps were present in a range of sinters deposited over the lifetime of cp 900 yr before present the distributions correlated well with the presence of members of bhp producing bacterial orders known to inhabit cp for example acidothiobacillales burkholderiales and pseudomonadales are known sources of composite bhps with a more complex functional group at c 35 such as bacteriohopanetetrol cyclitol ether found in high relative abundance in each cp sinter analysed the bhp distributions preserved in cp sinters were different from those described previously for any other environmental setting with pentafunctionalised bhps accounting for up to 55 of the total assemblage furthermore composite bhps were the most abundant compound type in each sample and accounted for up to 80 of the total bhp distribution as the age of sinter increased a general increase in bhp abundance was observed similarly in older sinters the complexity of the bhp compounds increased the observations are consistent with a higher temperature of vent water in the past the excellent preservation of bhps in this setting over the lifetime of the vent highlights the usefulness of bhps as biomarkers for reconstructing modern and ancient geothermal vent bacterial communities 2014 published by elsevier ltd

establishment of a continuous gps network across the kephalonia fault zone ionian islands greece abstract we report on the establishment of a continuous gps network across the kephalonia fault zone kfz central ionian islands greece the kfz is an important segment of the boundary zone between the rapidly moving aegean microplate and the apulian platform italy repeated gps measurements carried out between the northern ionian islands and the island of crete have shown rates of crustal motion of the aegean reaching 35 mm a oriented sw relative to southern italy the kfz coincides with a maximum shear strain rate 180 nano strain a and a very high level of seismicity in order to monitor the ongoing deformation across the kfz and correlate the strain accumulation with earthquakes a continuous gps network has been installed operating at a sampling rate of 5 s this paper describes the instrumental set up the data logging strategy and first preliminary results

variability in aerobic methane oxidation over the past 1 2 myrs recorded in microbial biomarker signatures from congo fan sediments methane ch4 is a strong greenhouse gas known to have perturbed global climate in the past especially when released in large quantities over short time periods from continental or marine sources it is therefore crucial to understand and if possible quantify the individual and combined response of these variable methane sources to natural climate variability however past changes in the stability of greenhouse gas reservoirs remain uncertain and poorly constrained by geological evidence here we present a record from the congo fan of a highly specific bacteriohopanepolyol bhp biomarker for aerobic methane oxidation amo 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol that identifies discrete periods of increased amo as far back as 1 2 ma fluctuations in the concentration of aminopentol and other 35 aminobhps follow a pattern that correlates with late quaternary glacial interglacial climate cycles with highest concentrations during warm periods we discuss possible sources of aminopentol and the methane consumed by the precursor methanotrophs within the context of the congo river setting including supply of methane oxidation markers from terrestrial watersheds and or marine sources gas hydrate and or deep subsurface gas reservoir compound specific carbon isotope values of 30 to 40 for bhps in odp 1075 and strong similarities between the bhp signature of the core and surface sediments from the congo estuary and floodplain wetlands from the interior of the congo river basin support a methanotrophic and likely terrigenous origin of the 35 aminobhps found in the fan sediments this new evidence supports a causal connection between marine sediment bhp records of tropical deep sea fans and wetland settings in the feeding river catchments and thus tropical continental hydrology further research is needed to better constrain the different sources and pathways of methane emission however this study identifies the large potential of aminobhps in particular aminopentol to trace and once better calibrated and understood quantify past methane sources and fluxes from terrestrial and potentially also marine sources

biomarkers for aerobic methanotrophy in the water column of the stratified gotland deep baltic sea filter samples from the oxic zone and suboxic zone of the physically stratified water column and sediment samples of the gotland deep baltic sea were analyzed for bacteriohopanepolyol bhp and phospholipid fatty acid plfa concentrations in total eight bhps were identified with the greatest diversity in the suboxic zone there 35 aminobacteriohopane 31 32 33 34 tetrol aminotetrol and 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol whose concentrations decreased concurrently from the lower to the upper suboxic zone indicated type i methanotrophic bacteria and thus aerobic oxidation of methane the presence and activity of type i aerobic methanotrophic bacteria was further supported by the presence of 13c depleted plfas specifically 16 1 8c and 16 1 5c 13c as low as 41 2 however the relative amount of methanotroph specific compounds was low aminopentol 0 2 of total bhps 16 1 8c ca 0 5 of total plfas suggesting a minor contribution of aerobic methanotrophic bacteria to the particulate organic matter the distinctive bhp pattern in the suboxic zone including aerobic methanotroph biomarkers and a tentative marker for a pelagic redoxcline putative 22s isomer of the ubiquitous 22r bacteriohopanetetrol bht was mirrored in the sediment samples our data indicate that a major portion of the sedimentary hopanoids of the gotland deep is sourced from the suboxic part of the water column via an effective but unknown transport mechanism

gps derived strain rate field within the boundary zones of the eurasian african and arabian plates we use the gps velocity field 1988 1998 for eastern mediterranean and asia minor to determine the crustal deformation strain rate field in an area bounded by 35 n and 43 n and 20 e and 48 e we calculate the normal and shear strain rate components associated with the major faults and compare these qualitatively with seismological data uncertainties in the calculation of the strain rates reach 50 nstrain yr 1 in sparsely observed parts of anatolia whereas we estimate errors 20 nstrain yr 1 in the aegean and marmara regions the largest compressional strain rate components in the eastern part of the study area occur along the greater caucasus mountain front reaching 70 nstrain yr 1 1 nstrain yr 1 0 0317 10 15 s 1 the north anatolian fault zone is the clearest feature in the shear strain rate field it is expressed as a pronounced dextral strike slip fault zone reaching rates of up to 170 nstrain yr 1 this holds true also for the izmit area where the august 17 1999 earthquake occurred central anatolia is almost strain free whereas extension prevails in western anatolia the principal axes of extension vary around the n s direction with strain rates of up to 85 nstrain yr 1 these extensional areas coincide with graben features and normal faulting earthquakes the central and southwestern aegean sea is strain free with values far below 40 nstrain yr 1 the seismic cluster around the dodekanissa islands southeastern aegean sea coincides with nw se oriented extension attaining strain rates of up to 90 nstrain yr 1 this area of extension also exhibits recent active volcanism the entire hellenic arc shows compressional strain rates perpendicular to the arc the pliny strabo troughs along the eastern segment of the arc show left lateral shear strain rates reaching 80 nstrain yr 1 significant extension is found in central greece with a nne ssw oriented maximum of 120 nstrain yr 1 centered around the gulf of corinthos the kephalonia fault zone in nw greece is a distinct dextral fault zone separating apulia from the rapidly moving aegean microplate right lateral shear strain rates reach 150 nstrain yr 1

the continuity of active fault systems in greece summary evidence from geomorphology the distribution of large earthquakes and geodetic measurements suggests that the active faulting in mainland greece and the north aegean sea is concentrated into a small number of discrete linear zones that bound relatively rigid blocks on land the zones are most clearly identified where the faulting is associated with large escarpments particularly in hard footwall rocks the zones can become indistinct and diffuse near their ends sometimes because they enter high unstable topography where landsliding obscures the fault morphology but mostly because the extension rates decrease along strike as a consequence of the relative rotation of the blocks they bound the main graben systems of chalkidiki southern thessaly and the north gulf of evia all seem to connect with the strike slip faulting in the offshore aegean and to die out in the west a configuration related to clockwise rotations in east central greece by contrast the gulf of corinth which is the fastest opening graben system in greece opens more rapidly in the west than the east both these features of the gulf of corinth are consequences of the motion of the south aegean and peloponnese as a single block late pliocene and quaternary geology and geomorphology indicate that the boundaries of the rigid blocks in central greece have changed over that time with faulting migrating into the hanging walls sometimes changing in orientation these changes are probably related to the way faulting in the seismogenic layer adapts to block rotation so as to maintain the general features of a velocity field that is controlled by larger scale effects such as buoyancy forces and the seaward migration of the subducting slab beneath crete the image of greece as a mosaic of rigid blocks whose boundaries change with time is a useful framework for seismic hazard evaluation but we emphasize that some moderate sized earthquakes do occur away from the main fault zones within the relatively rigid blocks and especially near their diffuse ends

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

wave induced dynamics of marine pipelines in liquefiable seabed abstract this paper presents a simple but workable modeling method to simulate the wave induced liquefaction scenarios around a marine pipeline within the framework of the biot s theory incorporating the main features such as relation for the consolidation describing the pore volume reduction hysteretic stress strain behavior of soil skeleton and soil pipe contact effect in this context special attention is paid to the implementation of a well calibrated cyclic soil model for hysteretic and nonlinear stress strain behavior i e strain softening and cyclic degradation associated with a semi empirical shear volume coupling equation for capturing the accumulative volumetric change which links the increment of volumetric strain per cycle of wave with the shear strain occurring during that particular cycle the proposed modeling framework is then incorporated into an explicit time matching finite difference analysis procedure allowing a full non linear dynamic analysis of the intensive interactions between the pipeline and the seabed undergoing buildup of pore pressure and residual liquefaction retrospective simulation of the wave flume test performed by sumer et al 2006c using the proposed model shows good agreement calibrating the reliability of the modeling method for the prediction of wave induced liquefaction of sandy seabed and failure process of the buried pipelines finally the liquefaction mechanism around a buried pipeline under a nonlinear wave loading is investigated by numerical examples the obtained results interpret the cause of liquefaction and the resulting consequence for pipeline stability in wave environment

uplift of immersed tunnel in liquefiable seabed under wave and current propagation abstract in ocean environments wave usually propagates in association with a current the paper presents a cyclic characterization framework for elastoplastic consolidating behavior of liquefiable seabed around the immersed tunnel under combined wave and current loading based on the biot dynamic consolidation theory special attention is placed on modeling the nonlinear wave current interaction the cyclic plasticity behavior of marine deposits and the soil structure contact effect the paper extends an existing masing model to large strain regime in the order of 10 2 in the framework of cyclic plasticity for capturing the liquefaction induced nonlinear behavior of marine deposits then the proposed cyclic plasticity model is implanted into an explicit time matching finite difference analysis platform permitting a comprehensive simulation of the intensive response of the immersed tunnel in the seabed experiencing the excess pore pressure accumulation and residual liquefaction retrospective simulation of a well documented centrifuge test by the proposed framework indicates satisfactory agreement validating the reliability for capturing the excess pore pressure accumulation and residual liquefaction during wave propagation finally the influences of current on the wave induced liquefaction in the vicinity of an immersed tunnel are investigated by a numerical example the results indicate that the ocean current significantly changes the original characteristics of wave induced liquefaction as well as the induced uplift of the immersed tunnel especially with consideration of the cyclic plasticity behavior of marine deposits the mechanisms of seabed liquefaction and the induced uplift of the immersed tunnel under wave and current actions are also interpreted

miocene detachment in crete and exhumation p t t paths of high pressure metamorphic rocks a major problem posed by the geology of crete is the horizontal contact of an upper unit without miocene metamorphism onto a metamorphosed lower one with early miocene high pressure low temperature hp lt parageneses this very sharp contact is roughly parallel to the major oligo miocene thrust planes which were reactivated as a large scale detachment which allowed exhumation of high pressure units we describe the extensional deformation and the metamorphic evolution of the lower plate most first order deformation features relate to the retrogression from high pressure to low pressure conditions a n s pervasive stretching is observed everywhere often associated with a top to the north sense of shear the extreme variation of thickness of the phyllite quartzite nappe upper part of the lower plate is probably the result of large scale boudinage similar to the one seen in large outcrops the most important observation is the systematic occurrence of fresh carpholite immediately below the base of the tripolitza nappe except in northwestern crete where a late extensional shear zone is present deeper in the nappe pile carpholite is systematically retrograded this observation reveals a drastically different pt history for the upper part of the phyllite quartzite nappe it also suggests that the late extensional shear zone found along the northern side of crete cuts inside the metamorphic structure and brings the nonmetamorphosed tripolitza nappe directly in contact with the deeper parts of the phyllite quartzite nappe pt t paths suggest a fast temperature decrease in the top of the phyllite quartzite during retrogression and hence during the top to the north shear the deeper part of the phyllite quartzite nappe shows a low temperature regime throughout but its pt path includes an isothermal decompression in the first stage we produce a tentative map of domains having experienced similar pt trajectories during decompression the overall cool regime is related to the continuous underthrusting of cola continental units during exhumation isothermal decompression observed in the core of the phyllite quartzite nappe implies fast exhumation during extension and the faster cooling of the upper part is related to a continuous displacement toward the north of a cooler unit during exhumation single grain 39ar 40ar ages obtained on phengites 15 25 ma in various structural sites are in good agreement with these conclusions and with the geological context suggesting that underthrusting of cold units at the front the accretionnary complex occurred contemporaneously with unroofing below a north dipping detachment near the top of the wedge the age of this detachment is bracketed between the end of the high pressure event 20 ma and the deposition of the breccia early to middle miocene in the neogene basins

the kephalonia transform fault and the rotation of the apulian platform evidence from satellite geodesy this paper describes a collaborative gps project to determine recent crustal movements and deformations across the ne ionian sea this region is characterized by rifting in the african foreland pelagian sea subduction along the calabrian and west hellenic arcs rotation of the italian peninsula and distributed normal faulting in central greece from gps campaigns on the ionian islands and in nw greece performed in 1989 and 1991 a kinematic field is deduced which is controlled by the deep trough following the nw coast of kephalonia island it is concluded that this prominent bathymetric feature resembles an active fault system kephalonia fault which has the signature of a right lateral transform fault

microbial biomarkers support organic carbon transport from methane rich amazon wetlands to the shelf and deep sea fan during recent and glacial climate conditions abstract we have investigated the delivery of terrestrial organic carbon oc to the amazon shelf and deep sea fan based on soil marker bacteriohopanepolyols bhps adenosylhopane and related compounds and branched glycerol dialkyl glycerol tetraethers gdgts as well as on 14c dating of bulk organic matter the microbial biomarker records show persistent burial of terrestrial oc evidenced by almost constant and high bit values 0 6 and soil marker bhp concentration 80 230 g g toc total oc on the late holocene shelf and even higher bit values 0 8 0 9 but lower and more variable soil marker bhp concentration 40 100 g g toc on the past glacial deep sea fan radiocarbon data show that oc on the shelf is 3 4 kyr older than corresponding bivalve shells emphasizing the presence of old carbon in this setting we observe comparable and unexpectedly invariant bhp composition in both marine sediment records with a remarkably high relative abundance of c 35 amino bhps including compounds specific for aerobic methane oxidation on the shelf avg 50 of all bhps and the fan avg 40 notably these marine bhp signatures are strikingly similar to those of a methane producing floodplain area in one of the amazonian wetland varzea regions the observation indicates that bhps in the marine sediments may have initially been produced within wetland regions of the amazon basin and may therefore document persistent export from terrestrial wetland regions with subsequent re working in the marine environment both during recent and past glacial climate conditions

a new particulate mn fe p shuttle at the redoxcline of anoxic basins abstract pelagic redoxclines of anoxic basins and deeps form the suboxic transition between oxygenated surface and anoxic or even sulfidic bottom waters intense element cycling favoured by elevated microbial activity causes steep gradients of physico chemical parameters nutrients and redox sensitive trace metals this study presents a conceptual model for authigenic particle formation at pelagic redoxclines which is based on the tight coupling of mn fe and p cycles besides the well known occurrence of mn oxides textural sem edx and geochemical icp oes icp ms analyses of particles from the redoxclines of the black sea and the baltic sea gotland basin landsort deep evidence the existence of earlier postulated fe oxyhydroxo phosphates and emphasize mixed phases consisting of mn oxides and fe oxyhydroxo phosphates as a new solid species most of the analyzed particles are star shaped of about 5 m in size and occur as single particles or aggregates without any morphological differences between mn oxides fe oxyhydroxo phosphates and mixed phases throughout the redoxcline these minerals show a general succession with maximum abundance of mn oxides above the redoxcline followed by mixed phases and almost pure fe phosphates within and below the redoxcline respectively molar fe p ratios of single particles argue against the formation of known pure fe phosphates like vivianite or strengite at the lower end of the redox transition zone but are consistent with recent experimental findings for colloidal p bearing hydrous ferric oxides moreover morphological similarities suggest the formation of irregular fe oxyhydroxo coatings due to oxidation of upward diffusing fe 2 by oxygen and stepwise replacement of mn iv by fe iii on sinking mno x particles followed by immediate adsorption or even co precipitation of phosphate batch type experiments using biogenic mno x particles demonstrate the efficient potential of fe 2 oxidation by sinking mno x particles when entering sulfidic waters mno x particles are progressively reduced leading to an increasing relative abundance of fe and p rich particles in deeper parts of the water column these particles are also reductively dissolved thereby releasing fe 2 and phosphate to the water column this mn fe p shuttle likely affects phosphate transport throughout the water column and thus impacts primary production at least over longer time scales furthermore the particulate mn fe p shuttle must have played an important role for the cycling of p and certain trace metals in ancient ocean basins e g during certain periods of cretaceous black shale formation and should be considered in future mass balances and modeling approaches dealing with oxic anoxic interfaces of aquatic ecosystems

vertical mixing in the baltic sea and consequences for eutrophication a review abstract in the transition area between the north sea and the baltic sea entrainment processes dominate the vertical mixing in the inflowing saline bottom water the hot spots of these processes are located at the darss sill and the bornholm channel in the western baltic sea in the central baltic sea the horizontal advection of saline water in deep layers below the permanent halocline dominate the temporal changes and associated transports this is accompanied by the turbulent vertical transport through the halocline into the surface layers the related vertical salt transport into the entire surface mixed layer estimated by various methods is slightly above 30 kg m 2 a during stagnation periods the residence time of the deep water in the eastern gotland basin increases roughly by a factor of five vertical mixing through the halocline is drastically reduced when inflows are lacking the potential processes of diapycnal mixing are discussed to the present knowledge the turbulent motion resulting from breaking internal waves is capable of turbulent transports through the halocline corresponding to the estimates of the salt transport into the surface mixed layer the actual knowledge about boundary mixing due to internal waves in the baltic sea is poor mesoscale eddies may contribute to the vertical mixing but it is not known whether they really do and which of the possible direct and indirect mixing mechanisms is most effective near bottom currents induced by inflow events likely enhance vertical mixing coastal upwelling certainly contributes to the vertical transport but the depth of its origin and the volume transport are hard to determine for large scale quantifications the short spatiotemporal scale of turbulent transports through the halocline resulting in a weakening of the halocline during summer together with the mixing of the entire surface layer down to the halocline in winter form a consistent description of the vertical salt transport it is hypothesised that the longer residence time of the deep water during stagnation periods results from the lack of energy imported by the inflows and directly or indirectly feeding the diapycnal mixing processes the vertical transport of nutrients such as the phosphate is quantitatively not sufficiently understood and needs further interdisciplinary research activities

pipe soil interaction model for current induced pipeline instability on a sloping sandy seabed as offshore exploitation moves to deeper waters ocean currents become the prevailing hydrodynamic loads on pipelines and at the same time a sloping seabed is always encountered the prediction of lateral soil resistance is vital in evaluating pipeline on bottom stability unlike previous pipe soil interaction models used mainly for horizontal seabed conditions a pipe soil interaction model for current induced downslope and upslope instabilities is proposed by using the limit equilibrium approach the coulomb s theory of passive earth pressure for the sloping seabed is incorporated in the derivation the model verification with existing full scale tests shows good agreement between the experimental results and predicted ones parametric study indicates that the effect of slope angle on pipeline lateral soil resistance is significant in the examined range of slope angle from 15 to 15 the critical pipeline embedment and corresponding passive pressure decrease approximately linearly with increasing slo

intracontinental wedging and post orogenic collapse in the mesohellenic trough the mesohellenic trough is a 130 km long and about 30 km wide subsiding area which contains a thick sequence of well exposed late cenozoic post orogenic sediments this intermontane basin located at the contact between the apulian and pelagonian collided margins provides a good example of the characteristics needed to study the chronology of late orogenic intracontinental structures

an analog experiment for the aegean to describe the contribution of gravitational potential energy the southern aegean seafloor exhibits clear evidence of internal deformation stretching as shown by tectonics seismology and space geodesy we use an analog three layer laboratory experiment of sand silicone putty and honey to investigate the deformation of the southern aegean lithosphere the model is installed in a box and confined by a vertical wall we open a gate in the wall and observe the deformation of the two upper layers due to buoyancy forces the general pattern of the deformation of the southern aegean is found in the analog model we observe the formation of an arc spreading outward with time the extension is radial in the inner part but parallel to the arc in the external part and of comparable importance at both ends of the gate we observe strike slip motion dextral in the western part sinistral in the eastern part rotation clockwise in the western part counterclockwise in the eastern part of up to 40 is seen on both sides of the gate but is also present with a smaller amplitude far in the internal region partially due to distributed shear the spreading is associated with the thinning of the two upper layers and affects a region of dimensions comparable to the length of the free boundary this spreading does not propagate inward with time some pieces of material located near the active boundary remain undeformed during the experiment

decoupling of bio and geohopanoids in sediments of the benguela upwelling system bus abstract geohopanoids derive from bacteriohopanepolyol bhp precursors however knowledge of the specific sources and diagenetic fate of both compound classes in marine sediments is fragmentary we studied the relationship between bhps and geohopanoids in a sediment core from the central benguela upwelling system bus including deposits over the last 75 ka the bus is a palaeo oceanographically stable setting where primary production is largely controlled by variation in upwelling intensity and therefore nutrient supply marine production in the bus was generally higher during glacial than during interglacial times as reflected in the levels of sedimentary total organic carbon geohopanoids at the study site consisted mainly of extractable hopanes and hopanols and occurred in the highest amounts during glacial periods a minor but still considerable fraction of geohopanoids was sulfur linked to geomacromolecular organic matter among these s bound hopane moieties 17 h 21 h trishomohopane c33 was the predominant compound suggesting a diagenetic overprint of bhps before linkage among the bhps a rare bacteriohopanetetrol with likely 22s configuration was observed this structural feature was lacking in the geohopanoids which all had the 22r configuration different behaviour of bhp and geohopanoid concentrations as well as 13c discrepancies indicate a decoupling of bio and geohopanoids geohopanoids most likely reflect laterally transported fossil organic matter whereas bhps are indigenous to the upper water column of the study site and may relate to past upwelling intensity nutrient levels hence care has to be taken using geohopanoids and other biomarkers for palaeoreconstruction in settings where sedimentation processes are not fully understood

bacteriohopanepolyols in tropical soils and sediments from the congo river catchment area the congo river basin drains the second largest area of tropical rainforest in the world including a large proportion of pristine wetlands we present the bacteriohopanepolyol bhp inventory of a suite of tropical soils and from comparison with published data propose some initial ideas on bhp distribution controls strong taxonomic controls on bhp production are evident in wetland sediments dominant within the suite were 35 aminobacteriohopane 31 32 33 34 tetrol aminotetrol and 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol indicating aerobic methanotrophy a narrow range and low mean relative abundance of 30 5 adenosyl hopane adenosylhopane and related compounds collectively termed soil marker bhps were observed in congo soils mean 17 range 7 9 36 of total bhps n 22 compared with literature data from temperate surface soils and arctic surface soils mean 36 range 0 66 of total bhps n 28 suggesting a greater rate of conversion of these bhp precursors to other structures

sinking floatation of pipelines and other objects in liquefied soil under waves abstract this paper presents the results of an experimental study where the sinking and floatation of a pipeline and other objects namely a sphere and a cube in a silt bed was investigated the bed was exposed to progressive waves two kinds of experiments were made the undisturbed flow experiments and the experiments with the structure model a pipeline a sphere and a cube in the former experiments the pore water pressure was measured across the soil depth the pore water pressure built up as the waves progressed the soil was liquefied for wave heights larger than a critical value regarding the experiments with the structure model the displacement of the structure sinking or floatation was measured simultaneously with the pore water pressure the influence of various parameters such as the initial position of the object the specific gravity the soil layer thickness and the wave height was investigated it was found that while the pipe sank in the soil to a depth of 2 3 times the pipe diameter the sphere sank to even larger depths the pipe with a relatively small specific gravity initially buried floated to the surface of the soil the drag coefficients for the objects sinking in the liquefied soil were obtained

wave induced liquefaction of beds of sand in a centrifuge the behaviour of beds of fine grained sand under fluid wave trains was investigated using centrifuge modelling three sets of centrifuge wave tank tests with viscous scaling were performed such that time scaling laws for wave propagation as well as consolidation were matched the test programme consisted of either progressive or standing wave tests on loosely packed fresh deposits of soil as well as repeated travelling wave tests with intervening periods of consolidation the results from the progressive and standing wave tests indicate that for each of the wave loading regimes there exists a critical cyclic stress ratio below which liquefaction does not occur the critical value for the progressive wave loading series was found to be considerably smaller than that for the standing wave loading series moreover the wave induced liquefaction of the sand beds was of a progressive nature in fact under the action of severe travelling waves liquefaction was first induced in the uppermost layer of the

a record of aerobic methane oxidation in tropical africa over the last 2 5 ma abstract methane and co 2 are climatically active greenhouse gases ghg and are powerful drivers of rapid global warming comparable to the arctic the tropics store large volumes of labile sedimentary carbon that is vulnerable to climate change however little is known about this labile carbon reservoir in particular the behaviour of high methane producing environments e g wetlands and their role in driving or responding to past periods of global climate change in this study we use a microbial biomarker approach that traces continental aerobic methane oxidation amo from sedimentary organic matter in deep sea fan sediments off the congo river to reconstruct the link between central african methane cycling and continental export during key periods of global pleistocene warmth we use 35 amino bacteriohopanepolyols bhps specifically aminobacteriohopane 31 32 33 34 tetrol aminotetrol and 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol as diagnostic molecular markers for amo ch 4 oxidation markers and the prevalence of continental wetland environments bhps were analysed in sediments from the congo fan odp 1075 dated to 2 5 ma high resolution studies of key warm marine isotope stages mis 5 11 and 13 are included to test the relationship between ch 4 oxidation markers in sediments at different levels of elevated global atmospheric ghg this study presents the oldest reported occurrence to date of 35 amino bhps up to 200 m below sea floor 2 5 ma with no strong degradation signature observed low concentrations of ch 4 oxidation markers identified between 1 7 ma and 1 ma suggest a reduction in wetland extent in tropical africa in response to more arid environmental conditions correlation of high resolution ch 4 oxidation marker signatures with global atmospheric ghg concentrations during mis 5 11 and 13 further emphasize periods of enhanced tropical c cycling however subsequent analysis would be required to further extrapolate the relative importance of tropical methane sources as a driver of global methane concentrations during the pleistocene

an integrated numerical model for the stability of artificial submarine slope under wave load abstract the stability evaluation of artificial submarine slope under wave load is a primary concern in the construction of offshore structures such as submarine pipelines and immersed tunnels aiming at this issue an integrated finite element method fem model of wave seabed interaction is proposed to investigate the effects of wave action on the wave induced slope stability of the temporary trench the reynolds averaged navier stokes rans equations are adopted to describe the wave motion in the fluid domain while the seabed domain is described using the mohr coulomb constitutive model the wave induced seepage pressure near the slope is determined by darcy s law and considered as an external load in the analysis the stability of the temporary slope is evaluated by the means of shear strength reduction the present numerical model is firstly validated through the comparison with the analytical solution and the experimental data available in the literature the integrated numerical model is then applied to a practical engineering application including a new evaluation method of stability for the trench slope excavated temporarily for the fully buried submarine pipelines at an actual site the results indicate that the stability of submarine slope is closely related to the dynamic wave pressure from the upper seawater the minimum of fos factor of safety corresponding to the most dangerous situation is introduced as the stability index for the slope with specific slope ratio in the whole process of dynamic wave loading additionally the wave induced seepage pressure should be considered as external load in the design for the seabed with large permeability such as sandy soils

preservation and diagenesis of hopanoids in recent lacustrine sediments of priest pot england abstract absolute concentrations of various bio and geohopanoids have been determined in a 24 cm long core from anoxic recent sediments of priest pot a small highly productive lake in the english lake district samples were soxtherm extracted derivatised by methods targeted at specific hopanoid groups and quantified by gc ms periodic acid sodium borohydride treatment was used to cleave the side chains of highly functionalised hopanoids producing products more amenable to our detection methods biohopanoids are extremely abundant totalling up to 3000 g g dry sediment particularly those with composite or highly penta and hexa functionalised side chains suggesting that these are important precursors to sedimentary hopanoids in priest pot downcore biohopanoid abundance profiles show a general diagenetic decline with a marked dip at 5 8 cm which we interpret as a change in bacterial input since this is most marked in the composite hopanoids rather than bacteriohopanetetrol we suggest that these two hopanoid groups have at least partly different sources and may thus have potential as environmental markers the geohopanoids are also abundant totalling up to 1700 g g dry sediment being dominated by the and bishomohopanoic acids and bishomohopanol and hop 17 21 ene downcore plots show no apparent conversion of free bio to geohopanoids with depth which suggests that incorporation into kerogen may be commencing at an early diagenetic stage in the sediments

the depth dependency of planktonic benthic foraminiferal ratios constraints and applications abstract study of the ratio between planktonic and benthic foraminifera in a great number of areas shows that variation of this ratio with depth can be described using organic matter flux equations essentially the share of benthic foraminifera in the total association is inversely proportional to depth as is the amount of organic matter resulting from primary productivity reaching the sea bottom variation in the p b ratio from area to area appears to be strongly dependent on the amount of inbenthic living foraminifera if the ratios are corrected for this the regressions between the proportion of planktonic foraminifera p and depth appear to be near identical in the gulf of mexico the gulf of california the west coast of the usa and the adriatic sea this regression can be described by depth e 3 58718 0 03534 p a study of the behaviour of this function in nine cores from the adriatic upper quaternary reveals that the palaeodepth reconstructions are not influenced by fluctuations in productivity and temperature but that they are significantly influenced by redeposition of fine grained deposits

bacteriohopanepolyol distribution in yenisei river and kara sea suspended particulate matter and sediments traces terrigenous organic matter input abstract bacteriohopanepolyols bhps are ubiquitous bacterial membrane lipids encountered in soils river and marine suspended particulate matter spm and sediments their abundance and distribution provides a direct means to identify bacterial inputs and can be used to trace soil derived bacterial organic matter om and in some cases the presence of bacterial groups and their activities in aquatic systems we have studied the bhp distribution in the spm of a major siberian river yenisei river that crosses a large latitudinal gradient draining a large part of mongolia and siberian russia the yenisei river is the main river to flow into the kara sea a shelf sea of the arctic ocean we show that the bhp distribution and concentration of spm and surface sediments of the yenisei outflow in the kara sea allow to trace soil marker bhps and evaluate the performance of the r soil index a proxy developed to trace bacterial soil derived om soil marker bhps are present in the yenisei river and their concentration decreases from the yenisei river outflow into the offshore marine sediments the r soil correlates well with an independent proxy for bacterial om the bit index r2 0 82 and has a moderate correlation with the 13corg values a bulk om proxy for terrigenous input r2 0 44 consequently the r soil index performs well in the kara sea strengthening its application for tracing bacterial om in the arctic ocean both in modern and downcore sediments furthermore a suite of bhps that are characteristic for methanotrophic bacteria i e 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol and 35 aminobacteriohopane 31 32 33 34 tetrol aminotetrol is encountered in the yenisei outflow sediments these components are partly sourced from terrigenous sources but are likely also produced in situ in the marine sediments the distribution of the pentafunctionalized cyclitol ether bhp in the marine systems is noteworthy and indicates that it can possibly be applied as a marker for cyanobacterial biomass in marine sediments

microearthquake seismicity and active tectonics of northwestern greece we carried out a microearthquake survey lasting for six weeks in northwest greece using 18 portable seismograph stations to examine a region in which normal and thrust faulting have been reported in close proximity to one another with this array we located 148 events and determined fault plane solutions for eight events using only rays radiated upwards the seismicity of the region is diffuse with events extending to depths of nearly 30 km and there is a minimum in activity near a depth of 15 km the fault plane solutions exhibit a wide spectrum of fault types and orientations and are not consistent with simple zones of shortening or extension neither tractions applied to the edges or bottom of the region nor deviatoric stresses that compensate for lateral variations in crustal thickness can account for the variety of fault plane solutions we think that the complicated behavior is a manifestation of inhomogeneous deformation due at least in part to a pre existing complicated juxtaposition of structures and formations

distribution of methane in the water column of the baltic sea the distribution of dissolved methane in the water column of the baltic sea was extensively investigated a strong correlation between the vertical density stratification the distribution of oxygen hydrogen sulfide and methane has been identified a widespread release of methane from the seafloor is indicated by increasing methane concentrations with water depth the deep basins in the central baltic sea show the strongest methane enrichments in stagnant anoxic water bodies max 1086 nm and 504 nm respectively with a pronounced decrease towards the pelagic redoxcline and slightly elevated surface water concentrations saturation values of 206 and 120 respectively in general the more limnic basins in the northern part of the baltic are characterized by lower water column methane concentrations and surface water saturation values close to the atmospheric equilibrium between 106 and 116 in contrast the shallow western baltic sea is characterized by high saturation values up to 746

reconstructing oxygen deficiency in the glacial gulf of alaska combining biomarkers and trace metals as paleo redox proxies abstract marine anaerobic oxidation of ammonium anammox plays a central role in the nitrogen cycle of modern oxygen deficient zones odzs the newly developed bacteriohopanetetrol stereoisomer bht x biomarker for anammox which is largely unaffected by early diagenesis allows for the reconstruction of the presence and dynamics of past odzs from the sedimentary record of continental margins in this study we investigate the development and dynamics of the odz in the gulf of alaska goa between 60 and 15 cal ka bp using records of redox sensitive trace metals tm and the bht x anammox biomarker from iodp site u1419 700 m water depth the biomarker record indicates that the odz in the goa was in concert with global climate fluctuations in the late pleistocene anammox was more pronounced during warmer periods and diminished during cooler periods as indicated by correlation with the 18o signal obtained by the north greenland ice core project ngrip trace metal enrichments however do not match the trend in bht x systematic metal enrichments in intervals where biomarkers point to more intense water column deoxygenation are not observed we suggest that this proxy discrepancy was caused by environmental factors other than water column redox conditions with opposing effects on the tm and biomarker records two of the most widely used redox indicators mo and u are not significantly enriched throughout the sediment record at site u1419 site u1419 experienced some of the highest sedimentation rates 100 1000 cm ka 1 ever reported for late pleistocene continental margin sediments leading to a continuous and rapid upward migration of the sediment water interface we suggest that despite water column and seafloor oxygen depletion significant sedimentary enrichments of these redox sensitive trace metals were prevented by a limited time for their diffusion across the sediment water interface and subsequent enrichment as authigenic phases thus depositional conditions were ideal for biomarker preservation but prevented significant authigenic trace metal accumulations similar discrepancies between organic and inorganic redox proxies could exist in other high sedimentation rate environments potentially putting constraints on paleo redox interpretations in such settings if they are based on trace metal enrichments alone

long chain alkenones in baltic sea surface sediments new insights abstract c 37 alkenones produced by certain haptophytes of the isochrysidales are valuable sedimentary biomarkers used to estimate sea surface temperature sst in the open ocean however in coastal seas the role of salinity gradients on alkenone producing species and sst estimates is poorly known alkenones were analyzed in surface sediments from the marine skagerrak region and the entire brackish baltic sea three types of alkenone distribution patterns were identified type a distribution which resembles the distribution in emiliania huxleyi type b distribution which is similar to ruttnera lamellosa isochrysis galbana and pseudoisochrysis paradoxa distributions although these haptophytes are absent from the baltic sea and type c distribution which is also found in worldwide lake sediments these types of distribution are apparent in the percentage of c 37 4 alkenone c 37 4 which is significantly negatively correlated to sea surface salinity sss the distribution of alkenones very likely results from distinct alkenone producing haptophytes whose spatial distribution is ultimately related to sss as supported by the hydrogen isotope fractionation between alkenones and water u 37 k and u 37 k correlate more significantly than u 37 k with both sst and sss probably due to the superimposed effect of changing alkenone producing species the application of u 37 k and u 37 k as sst proxies results in unrealistic holocene temperature records for the southern baltic sea but c 37 4 as a sss proxy reveals reasonable salinity changes interestingly a c 32 hopanoic acid was found abundantly as the methyl ester in the ketone fractions and may represent a marker for cyano bacterial biomass in the baltic sea

unfluidized soil responses of a silty seabed to monochromatic waves abstract a flume experimental study on unfluidized responses of a silty bed d 50 0 05 mm to monochromatic water waves had shown that pore pressure variations were generally poro elastic in the bulk body and displayed two other characteristic features not found in previous laboratory sand tests they were an immediately fluidized thin surface layer induced by wave stresses inside the seabed s boundary layer and a porous skeleton with internally suspended sediments due to channeled flow motions the analyses verified that on soils beneath the measurement points both features resulted in relatively small step pore pressure build ups while the former played a primary role besides laboratory observations confirmed that there were some near bed sediment suspensions during wave actions resulting in a flat bed form over a silty bed compared to small scaled ripples over a sandy bed with no clearly identified suspended sediments these characteristic silt responses suggest that sediment transport is critically associated with the internal soil responses and some field observed sediment suspensions near above sandy beaches can further be approached in the laboratory by utilizing fine grained soils

holocene history of the baltic sea as a background for assessing records of human impact in the sediments of the gotland basin sediment cores from the gotland basin were studied for their siliceous microfossil assemblages and organic carbon content to compare recent environmental changes in the baltic sea with its natural

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin