an examination of the parameters that govern the acoustic behavior of sea bed sediments containing gas bubbles the acoustic properties of sea bed sediments containing occluded gas are dominated by the volume of gas contained in bubbles the size of bubbles and the elastic properties of the soil matrix this study evaluated current theory developed by anderson and hampton to determine the sound speed and resonance frequency of gassy soils and the models they used to determine the elastic properties of the soils it compared calculated sound speeds based on material properties simulated by the models with measured sound speeds on large bubble laboratory soils produced in a similar manner to natural sea bed gassy soils there was some evidence that the anderson and hampton equations accurately predicted sound speed at lower frequencies of bubbles resonance and below but results were sensitive to inappropriate values for the elastic and damping properties of the soil the bounds of sound speed based on the elastic properties of models that simulate compressible fluid or suspension behavior were grossly misl

age of the mousterian industry at hayonim cave northern israel using electron spin resonance and 230th 234u methods abstract electron spin resonance esr analysis was done on teeth excavated at hayonim between 1993 and 1997 230 th 234 u analysis was done on two of these teeth and one calcite speleothem excavated in 1992 small amounts of uranium uptake into teeth provided nearly ideal conditions for esr age determinations the combined esr 230 th 234 u analyses on teeth confirmed that uranium uptake occurred according to values constrained by early eu and linear lu uptake esr model age estimates suggesting that eu and lu esr model ages on other teeth were reliable burial ages a speleothem stratigraphically above all the teeth yielded a 230 th 234 u age of 155 3 2 9 1 4 ka the eu and lu esr mean model ages for teeth in layers just below the speleothem were 177 12 and 182 15 ka respectively teeth in the lowest part of the section in the central area yielded younger ages apparently due to the increase in radioactive potassium content associated with the formation of siliceous aggregate mineral assemblages nearby these results were rejected the ages of the reliably dated portion of the section were contemporaneous with levels at tabun cave containing both tabun c type and d type lithics but they were significantly younger than the levels at tabun which contain only the d type lithics the use of infrared spectroscopy to identify mineral assemblages in close proximity to teeth were important to be able to select only those teeth not affected by changes in radioactive dose rate through time

tidal height and frequency dependence of acoustic velocity and attenuation in shallow gassy marine sediments remote prediction of gassy marine sediment properties is important for geohazard assessment gas bubble resonance theory suggests that gassy sediments exhibit acoustic wave velocity frequency and attenuation frequency relationships that depend on gas bubble size gas content and sediment elastic properties an acoustic monitoring experiment to investigate gas bubble resonance effects was undertaken at an intertidal site at dibden bay southampton united kingdom a vertical hydrophone array was positioned to straddle the top of the gassy zone identified on acoustic reflection profiles at about 1 m below the seabed a miniboomer in the seabed above the array was used to generate broadband 600 hz to 3000 hz acoustic signals every 10 min during a 24 hour period with water depths varying between 0 m subaerial exposure at low tide and 2 35 m at high tide the calculated frequency spectra of compressional wave attenuation coefficient show an attenuation maximum over 200 db m that shifts in frequency from 1050 hz at low tide to 1250 hz at high tide thus for the first time providing direct evidence of in situ gas bubble resonance in marine sediments modeling suggests that effective gas bubble radii of 11 mm to 13 mm are responsible for the attenuation maximum supported by x ray computed tomography scan observations on a pressure core which also indicate that bubble shape depends on sediment type modeling of bubble size fluctuations due to pressure equilibration cannot reproduce the observed frequency shift of the attenuation maximum implying that gas diffusion and nonspherical bubbles are significant

late quaternary terraced marine deposits as tools for wide scale correlation of unconformity bounded units in the volcanic aeolian archipelago southern italy abstract late quaternary raised terraced marine deposits are commonly interlayered with volcanic deposits along the coasts of the aeolian archipelago they mostly reflect the interplay between long term crustal vertical movements and glacio eustatic sea level changes during marine isotope stages mis 5 and 9 key discontinuity surfaces are represented by those bounding terraced marine deposits formed in correspondence of recurrent individual interglacial sea level peaks they are the basal ravinement surface formed during gradual sea level rise at the onset of a sea level peak and the upper surface of subaerial erosion developed during ensuing sea level fall and lowstand the discontinuity surfaces are classified according to their sequence stratigraphic significance field documentation and areal extent mis 5 marine deposits are bounded by the first order ui and uii unconformities the ui unconformity is the ravinement surface formed during mis 5e sea level rise age between 130 and 124 ka the uii unconformity is the surface of subaerial erosion and non deposition developed during sea level lowering after mis 5a age 70 ka unconformities ui and uii are correlated throughout the entire aeolian archipelago thus assuming a regional stratigraphic significance by linking to the global sea level curve they are assigned a relative age and assume a substantial chronostratigraphic significance and potential for dating of volcanic rocks further correlation on most of the aeolian archipelago is provided by the l3 unconformity that is the ravinement surface formed during sea level rise of mis 5c 100 ka moreover the f1 unconformity bounds at the base marine deposits older than the last interglacial i e mis 9 and is ascribed of an inter island stratigraphic outcome these allogenic unconformities driven by sea level fluctuations allow definition of a regional unconformity bounded framework for the aeolian archipelago into which local volcanic successions subdivided by autogenic unconformities of volcanic origin may be arranged

bubble growth and rise in soft sediments the mechanics of uncemented soft sediments during bubble growth are not widely understood and no rheological model has found wide acceptance we offer definitive evidence on the mode of bubble formation in the form of x ray computed tomographic images and comparison with theory natural and injected bubbles in muddy cohesive sediments are shown to be highly eccentric oblate spheroids disks that grow either by fracturing the sediment or by reopening preexisting fractures in contrast bubbles in soft sandy sediment tend to be spherical suggesting that sand acts fluidly or plastically in response to growth stresses we also present bubble rise results from gelatin a mechanically similar but transparent medium that suggest that initial rise is also accomplished by fracture given that muddy sediments are elastic and yield by fracture it becomes much easier to explain physically related phenomena such as seafloor pockmark formation animal burrowing and gas buildup during methane hydrate melting

correlation of shape and size of methane bubbles in fine grained muddy aquatic sediments with sediment fracture toughness abstract gassy sediments contribute to destabilization of aquatic infrastructure air pollution and global warming in the current study a precise shape and size of the buoyant mature methane bubble in fine grained muddy aquatic sediment is defined by numerical and analytical modeling their results are in a good agreement a closed form analytical solution defining the bubble parameters is developed it is found that the buoyant mature bubble is elliptical in its front view and resembles an inverted tear drop in its cross section the size and shape of the mature bubble strongly correlate with sediment fracture toughness bubbles formed in the weaker sediments are smaller and characterized by a larger surface to volume ratio that induces their faster growth and may lead to their faster dissolution below the sediment water interface this may prevent their release to the water column and to the atmosphere shapes of the bubbles in the weaker sediments deviate further from the spherical configuration than those in the stronger sediments modeled bubble characteristics important for the acoustic applications are in a good agreement with field observations and lab experiments

consolidation characteristics of sediments from the peru chile continental margin and implications for past sediment instability abstract one dimensional consolidation tests were performed on eight near surface samples 0 5 to 3 5 m from the peru chile continental margin these tests show that the consolidation behavior of these deposits is strongly influenced by the presence of high concentrations of organic matter resulting from the occurrence of coastal upwelling along this margin of south america organic carbon concentrations as high as 12 are found in samples from an upper slope mud lens between 10 5 to 13 6 s that lies beneath an area of intense upwelling with increasing organic content both the compressibility and rate of secondary compression are found to increase the increase in void ratio with increasing organic content and the ease by which organic matter is deformed appear responsible for these trends outside the mud lens the compressibility also increases as a result of increasing concentrations of clay size material and the abundance of smectite and illite all of the sediments along the margin behave as if they were consolidated under a pressure greater than the present effective overburden pressure evidence of erosion as a cause of the overconsolidation is present only on the upper slope mud lens at 13 6 s where 14 c dating verifies the erosion of 3 5 to 7 m of sediment numerous unconformities and intervals of deformed bedding in a core from 13 6 s attest to the past instability of sediments at this site at the other locations along the margin the increase in the overconsolidation ratio with increasing organic carbon content suggests that the bonding of sediment particles by organic matter may be responsible for the apparent overconsolidation low sedimentation rates on the slope off northern chile may also be a contributing factor to the apparent overconsolidation of sediments in this area

the architectural variability of small scale cycles in shelf and ramp clastic systems the controlling factors many sedimentary successions are composed of metre to decametre scale cycles exhibiting various stratal architectures that depend on the complex interplay among several syndepositional controlling factors these controlling factors may produce extremely different stratal and facies architectures along relatively brief distances in the same basin but in contrast they also may form similar architectures in basins that experience a radically different tectonic setting the recognition of factors that controlled the architecture of small scale cycles therefore is very important to reconstruct the depositional history of sedimentary successions these factors include 1 the interplay between the rate of accommodation development and the rate of sediment supply a s 2 the amplitude and shape of the relative sea level curve 3 the position in the shoreface shelf system 4 the basin physiography 5 the shoreline trajectory 6 the climate driven environmental energy 7 the siliciclastic input vs carbonate production shoreface to shelf small scale cycles can be grouped into three main categories r cycles showing a dominant regressive interval t r cycles with transgressive and regressive intervals of similar thickness t cycles showing a dominant transgressive interval although some depositional settings may favour the deposition of a particular type of cycle these cycle motifs appear to be mainly controlled by the interaction of local and wider scale controlling factors for example t cycles may be present in both subsiding and uplifting settings depending on the interplay between the a s and the other factors cited above as a result r t r and t cycles may be recognized within the same depositional system these evidences suggest that care must be taken to apply general models that predict the stratal architecture of cycles mainly in function of the long term a s the correct prediction of the cycle architecture is important also for hydrocarbon researches as the thickness of potential reservoir deposits is the result of the interplay among factors discussed here

experimental results on the influence of gas on the mechanical response of peats direct observation of gas in peat layers generated by slow degradation in anoxic conditions raised concern in the netherlands about its potential impact on the geotechnical response of dykes foun

vertical variation in porosity of nāri calcrete on chalk galilee israel a new interpretation as a tribute to dan h yaalon abstract n ri calcrete is a calcareous formation common in the semiarid mediterranean region of the levant the profile studied in nazareth galilee is 2 75 m thick and divided into the four conventional layers i e a chalky bedrock a powdery lower n ri an indurated and platy upper n ri and a laminar crust capping the profile in this study mercury intrusion porosimetry mip is used to assess the genetic processes at work in the formation of n ri calcrete based on the former work by yaalon and singer 1974 and mip results various parameters are proposed to describe the different layers total porosity n p trapped porosity n t permeability k and strength c these parameters are compared to each other for each layer as well as with their respective calcium carbonate contents an unexpected relationship shows that the more caco 3 is present the more porous the layer of the n ri consequently the lower n ri is interpreted as a weathering layer of the parent chalk whereas the upper n ri which is the most porous and the richest in caco 3 results from in situ recrystallization the upper n ri permeability precludes it from playing the role of a plugged horizon to explain the formation of the laminar crust in conclusion the n ri calcrete in nazareth questions the conventional model of calcrete genesis as its cementation is due to in situ redistribution of caco 3 rather than its translocation these results strengthen yaalon and singer 1974 s conclusions

initial rise of bubbles in cohesive sediments by a process of viscoelastic fracture 1 an understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid e g magmas and hydrofractures appear not to be applicable to bubbles in soft sediments and this paper presents a new model for gas bubble rise in soft fine grained cohesive sediments bubbles in such sediments are essentially dry little if any free water and grow through a process of elastic expansion and fracture that can be described using the principles of linear elastic fracture mechanics which assume the existence of a spectrum of flaws within the sediment fabric by extending this theory we predict that bubbles initially rise by preferential propagation of a fracture in a sub vertical direction we present a criterion for initial bubble rise once rise is initiated the speed of rise is controlled by the viscoelastic response of the sediments to stress using this new bubble rise model we estimate rise velocities to be of the order of centimeters per second we again show that capillary pressure plays no substantive role in controlling bubble growth or rise

evolution of middle to late pleistocene sandy calcareous paleosols underlying the northwestern negev desert dunefield israel abstract calcareous paleosols in the northwestern nw negev desert dunefield israel at the eastern end of the sinai negev erg were studied in relation to their underlying stabilized dunes and downwind loess deposits using sedimentological analyses spectroscopy and optically stimulated luminescence osl dating during the middle to late pleistocene between the end of mis 7 and through mis 3 several cycles of sand veneer sheet deposition stabilization pedogenesis and erosion formed a spatially variable sequence of sandy calcareous paleosols in the nw negev periods of stability on the order of several thousand years to over ten thousand years characterized by post depositional illuviation of aeolian silts clays and salts enabled the formation of diagnostic often indurated calcareous bk horizons stages i iii with orthic carbonate nodules the primary particle size mode of the paleosol 127 m is intermediate between the modes of the overlying mis 2 dune sand and the mode of primary northern negev mis 6 through mis 2 loess deposits in the dunefield periphery the sand fraction of the paleosols is slightly finer than the dune sand and its spatial sedimentation pattern correlates with the pattern of the subsequent dune incursions these observations suggest that 1 bk paleosol horizons were resistant to mis 6 mis 3 sand veneer aeolian erosion and formed chronologically differentiated and durable surfaces 2 these surfaces remained in equilibrium for extensive periods being intermittently covered and preserved by shifting sand veneers 3 the mis 2 dune incursion episodes followed the same transport routes of the underlying paleosol sand substrate while producing a limited amount of aeolian erosion on the bk horizons and 4 the similar sedimentological and chronological framework of the paleosols and loess deposits suggests a partial genetic connection as for the overlying dunes aeolian sand supply to the parent material of the paleosols was initially controlled by sediment availability originating in the nile delta and probably linked to glacial interglacial eustatic cycles and glacial and cold event windiness the nw negev sand deposition episodes that markedly differ from the ages of a nearby sandy paleosol sequence of coastal origin exemplify the role of sand supply on the development of paleosol sequences in a similar paleoclimate

islands in a stream reconstructing site formation processes in the late middle paleolithic site of ein qashish northern israel abstract information retrieved from open air sites is necessary for a more complete reconstruction of middle paleolithic behaviors which is currently often based mainly on data from caves and rockshelters however open air sites present methodological and analytical challenges that differ from those encountered in cave sites being essentially an integral part of their paleo landscape open air sites are affected by localized as well as landscape scale processes that need to be distinguished from the anthropogenic signatures ein qashish is an open air late middle paleolithic occurrence located in the yizra el valley just east of mt carmel situated on the pleistocene floodplain of the qishon stream the site is found at the interface of the sediments deposited by the qishon stream which drains the yizra el valley and paleo wadi qashish which flowed off mt carmel artifacts and bones are dispersed over a vertical distance of some 90 cm observations in geological trenches located at variable distances from the excavated area indicate that this cluster of finds occurred at a circumscribed locality on the landscape rather than as a part of a continuous distribution on the paleo surface we reverse engineer site formation processes starting with the latest post depositional moving to earlier syn depositional processes and relate them to their most likely causative agents through the examination of a series of explicit models gis techniques were applied in order to parse the variable lines of information which include lithic and faunal taphonomy size distributions and spatial and stratigraphic dispersal of objects fabric analysis and osl results we discuss the implications of the results for distinguishing anthropogenic from non anthropogenic effects and for reconstructing the timeline of depositional events that led to the current distribution of artifacts insights into these questions inform our understanding of human activities at the site suggesting that the excavation samples the margins of an occupation horizon where activities focused on knapping and resource processing rather than task specific behaviors such as hunting

rate of growth of isolated bubbles in sediments with a diagenetic source of methane observation of bubbles in estuarine and coastal sediments indicates that bubbles at or below 10 cm depth grow on seasonal time scales may october in order to determine the controls on this growth rate we have constructed a diffusion reaction model that accounts for the dynamics of methane formation its diffusion through pore waters its incorporation into a bubble and the consequent growth of the bubble the model produces an explicit equation for the radius of a growing bubble r t with time using mean parameter values and under the assumption that the mechanics of the sediment response to growth can be neglected equation where w is the porosity d is the tortuosity corrected diffusivity cg is the concentration of gas in the bubble s is the rate of methanogenesis near the bubble r1 is the half separation distance between bubbles r1 k r c1 is the ambient ch4 concentration c0 is the pore water ch4 concentration at r t is time and r0 is the initial bubble radius if not zero the effects of the source s and supersaturation c1 2 c0 thus appear as separate contributing terms and this formula can then be applied even in those cases where apparently c1 c0 the model is applied to three sediments where bubbles have been previously studied i e cape lookout bight usa white oak river usa and eckernfoorde bay germany in all three cases using the site specific time averaged parameter values the model predicts seasonal growth rates consistent with the observations furthermore the source term dominates the rate of growth at the first of these two sites whereas diffusion from the ambient supersaturation dominates at the german location real bubbles may follow a more complicated growth history than predicted by the above equation because of the mechanical properties of sediments nevertheless the overall growth times are concordant with ultimate diffusion control the effects of rectified diffusion that is the pumping of gas into a bubble by pressure oscillations e g from waves and tides were also examined existing models for that process suggest that it is negligible due to the low frequency of these types of oscillations

eustatic and tectonic controls upon quaternary coastal sedimentation in the corinth basin greece the late quaternary sedimentology and palaeogeography of the corinth isthmus in central greece is re interpreted a series of beach to shoreface sub sequences are seen each characteristically having an overall fining up character these occur within a coastal facies belt which has prograded to the west computer modelling illustrates the interaction of tectonic displacements and eustatic sea level variation as controls of facies patterns late pleistocene holocene facies geometries are predicted on the basis of published sea level data over that time interval on coastlines undergoing tectonic uplift such as the isthmus of corinth depositional patterns may be characterized by transgressive wedges these sub sequences merge basinwards below sea level minima each transgression relates to a major eustatic sea level peak such first order models are modified by variations in the rate of tectonic deformation the second control on relative sea level position modelled facies patterns are tested on the basis of new 230 th 234 u dates obtained from sclerac tinian corals of the corinth canal area dated sub sequence sediments correspond in age to late pleistocene eustatic highs and observed facies patterns correlate with the major late pleistocene holocene eustatic transgressions of c 100 ka periodicity episodes of intrabasinal normal faulting are isolated from a structural history otherwise dominated by uplift across the isthmus quantification of post depositional vertical tectonic displacements is achieved constraining the eustatic base level at the time of deposition of a dated horizon by reference to the global late quaternary sea level curve the original depositional level is then subtracted from the present outcrop level using available 230 th 234 u dates to establish syn depositional base levels minimum uplift rates of the order of 0 3 m ka 1 are calculated across the area averaged through the late pleistocene and holocene

sequence response to syndepositional regional uplift insights from high resolution sequence stratigraphy of late early pleistocene strata periadriatic basin central italy abstract this paper deals with the depositional sequences that occur within the uppermost part of the plio pleistocene periadriatic basin fill in the southern marche region central italy the succession is an early pleistocene easterly dipping clastic wedge showing an overall shallowing trend from slope clays to shallow marine and non marine deposits comprising two major sequences namely qmb and qmc analysis has provided new insights into i the nature of sedimentary facies and facies associations occurring within the upper part of qmb and qmc ii the gradual contact within qmb between regressive littoral deposits rld and underlying deep marine blue clays iii the composite origin of the emilian surface which is a widespread erosional unconformity separating qmb from qmc iv the cyclothemic pattern of qmc composed of downstepping small scale depositional sequences v the role played by synsedimentary uplift on the stacking pattern of small scale sequences and their internal architecture up to three small scale depositional sequences have been recognised within qmc qmc1 qmc2 and qmc3 they are up to 50 m thick and defined by previously unrecorded lower rank regionally extensive surfaces facies organization indicates that as a rule in ascending stratigraphic order each small scale sequence may includes a distinctive basal unconformity surface that can be traced from incised valleys to associated interfluves an incised valley fill a transgressive surface of marine erosion a transgressive systems tract a highstand systems tract a regressive surface of marine erosion and an attached falling stage systems tract in proximal positions the small scale sequences are dominated by transgressive and highstand systems tracts with incised valley fills and falling stage systems tracts absent or volumetrically much less significant in relatively basinward locations where the regressive surfaces of marine erosion converge with the lower sequence boundary the falling stage systems tract may represent the entire depositional sequence high frequency sequences display a distinctive stacking pattern and form a tectonically induced forced regressive sequence set underlain by a composite tectonically enhanced regressive surface of marine erosion formed by the lateral connection of lower rank sequence boundaries

sequence stratigraphy in active extensional basins implications for the interpretation of ancient basin fills abstract systematic variations in sequences their component units and their stacking patterns exist within rift basins these variations can be related to displacement gradients associated with the large scale 12 50 km segmentation of normal fault zones which control accommodation sediment supply and basin physiography sediment supply is also strongly influenced by the nature of pre rift drainage networks and variations in bedrock lithology high rates of hangingwall subsidence close to the centre of normal fault segments may cancel out the effects of glacio eustatic sea level fall so that accommodation development is normally characterized by the continual addition of new space the resulting sequences lack type 1 sequence boundaries and lowstand systems tracts and stack into aggradational sequence sets the adjacent footwall is subject to uplift which may lead to subaerial exposure and incision generating a composite type 1 sequence boundary away from the fault zone and near segment boundaries slip rates are much lower and hence relative sea level change is dominated by eustasy here falls in relative sea level are important resulting in type 1 sequences sequence stacking patterns reflect not only eustasy and local fault controlled subsidence but also the interaction of these with adjacent uplifting footwalls and or regional uplift tectonic influence on sequence development will be more pronounced during greenhouse times than icehouse times

nari calcrete outcrop contribution to ancient agricultural terraces in the southern shephelah israel insights from digital terrain analysis and a geoarchaeological field survey a field survey revealed that byzantine and early arab ca 5th to 8th century c e agricultural systems in the semi arid region of the shephelah central israel were similar to runoff agricultural systems in the arid region of the negev southern israel this similarity led to the hypothesis that systems in the shephelah also function as runoff farms this hypothesis is not trivial since runoff values in semi arid regions are generally low due to intensive but short rainfall events and due to the presence of sink patches that absorb runoff on slope surface the aim of the current research is to examine whether runoff potential in a representative agricultural system in the shephelah is sufficient for sustaining runoff farming a geoarchaeological field survey and digital terrain analysis show that large nari calcrete outcrops on the footslopes generate high runoff values that improve water potential hydrological simulations and calculations show that 230 mm of direct rainfall generates a water potential equivalent to 300 mm of direct rainfall in view of these results it is reasonable to conclude that the presence of nari enabled runoff agricultural farming in the shephelah region even in drought years

methane bubble growth in fine grained muddy aquatic sediment insight from modeling abstract methane ch 4 is the most abundant hydrocarbon and one of the most important greenhouse gases in the atmosphere ch 4 bubble growth and migration within muddy aquatic sediments are closely associated with sediment fracturing in this paper we present the modeling of buoyancy driven ch 4 bubble growth in fine grained muddy aquatic sediment prior to the beginning of its rise we designed a coupled mechanical reaction transport numerical model that enables a differential fracturing over the bubble front as it occurs in nature when the fracturing increment stays constant at the bubble head and subsides towards bubble tail during bubble growth we show that this differential fracturing over the bubble front controls the bubble shape and size temporal evolution and is significantly affected by the critical stress intensity factor of the muddy sediment the intercalated stages of elastic expansion and fracturing during the bubble growth shorten with time as the bubble approaches its terminal size prior to its ascent our simulations reveal a high asymmetry in the bubble shape growing with time with respect to its initial symmetric penny shaped configuration it was found that the bubble grows allometrically while the importance of the bubble surface area growth with time we also confirmed the earlier predictions about the inverted tear drop bubble cross section just prior to the beginning of its rise modeling of the terminal bubble characteristics will permit prediction of the delivery of gaseous methane from the sediment to the atmosphere via the water column

sediment supply as a control on the variability of sequences an example from the late namurian of northern england currently variations in accommodation space are seen as the major control on facies stacking patterns and stratal geometries this paper emphasizes the importance of the sediment supply variable through the use of a regional stratal surface based interpretation of the late namurian stratigraphy of northern england late highstand palaeogeographies and stacking pattern variations highlight spatial and temporal variations in sediment supply which promote the contemporaneous development of prograda tional aggradational and retrogradational stacking patterns this questions the derivation of relative sea level curves from specific stacking patterns and highlights the potential for miscorrelation in areas with major sediment supply variations

computer tomographic analysis of undisturbed samples of loose sands spontaneous flows of very loose sand deposits pose a serious environmental problem in abandoned lignite mines large areas in eastern germany are not safe for public access slight disturbances have triggered large settlement flows causing loss of lives and structures to better understand the mechanisms of fast settlement flows undisturbed samples from depths between 10 and 15 m below ground level were retrieved using the soil freezing method conventional laboratory and computer tomographic soil analyses were performed on these samples the results reveal a very low degree of saturation and large gas filled macropores responsible for considerable density fluctuations within the phreatic zone these spatial porosity variations are thought to strongly contribute to the collapsibility of loose sands key words spontaneous liquefaction undisturbed sampling soil freezing computer tomography density fluctuations gas inclusions

three dimensional numerical modeling of deltaic depositional sequences 2 influence of local controls abstract we investigate the influence of three local controls sediment supply subsidence and physiography on delta development and sequence variability using the three dimensional numerical model of deltaic deposition presented in a companion paper ritchie et al 2004 independently varying a single local control within geologically constrained limits produces marked differences in three dimensional morphology cross sectional stratal geometry and delta evolution during a cycle of sea level change sediment supply strongly influences not only the timing of transgressive and maximum flooding surface development during sea level rise and hence the diachroneity of lowstand transgressive and highstand systems tracts but also the timing of onset of fluvial incision and the characteristics of incised valleys and forced regressive wedges low sediment supply leads to early drowning of forced regressive and lowstand prograding wedges high magnitude transgressions and the late development of maximum flooding surfaces during relative sea level fall low sediment supply results in early initiation of fluvial incision and development of few but major incised valleys that route sediment to elongate forced regressive lobes at their mouths in contrast high sediment supply leads to early onset of normal regression and late transgression during relative sea level rise and numerous poorly developed incised channels and a broad laterally continuous forced regressive apron during relative sea level fall on basin margins with a shelf slope morphology base of slope deepwater deposits may occur at times of sea level highstand due to sediment bypass across the slope during relative sea level fall fluvial incision is enhanced by the relatively steep gradient of the slope leading to the early onset of incision and rapid headward propagation as a result major deep incised valleys develop that capture sediment and feed it directly to thick shelf edge forced regressive and lowstand prograding wedges the greater water depth ahead of the shelf edge and the steep slope gradients result in limited forced and normal regression compared to a ramp setting in contrast to other controls tectonic subsidence or uplift leads to modification of accommodation so that relative sea level change may vary significantly along a basin margin in high subsidence settings relative sea level may continue to rise even at times of high rates of background sea level fall in such settings deltas lack incised valleys forced regressive delta lobes and prominent sequence boundaries furthermore normal regression and even transgression in high subsidence locations can be contemporaneous with forced regression and incised valley development in adjacent lower subsidence locations the results of this sensitivity analysis suggest that systems tracts and their bounding surfaces are likely diachronous along many basin margins and may locally be absent more than one control can produce a similar stratigraphic response making interpretation of controlling processes from the stratigraphic product equivocal the models provide a framework for understanding the stratigraphy of natural basin fills but further research on the interplay between the controls is required in order to understand the climatic tectonic and sea level signals concealed in the stratigraphic record

the undrained shear strength of soils containing large gas bubbles measurements of undrained shear strength are reported from a series of triaxial tests on reconstituted soil samples containing large bubbles of methane gas the experimental results indicate that the undrained strength can be either increased or reduced by the presence of large gas bubbles depending upon the values of the consolidation pressure and the initial pore water pressure a conceptual model for soils containing large gas bubbles developed in the companion paper is analysed to provide theoretical predictions for the undrained shear strength the analysis leads to theoretical upper and lower bounds for the undrained strength which show good agreement with the experimental data the experimental and theoretical developments have led to a better understanding of the strength of soils containing large gas bubbles this could be of considerable benefit to the offshore construction industry if platforms pipelines and other structures are to be built in areas of gas bearing sediments l article pre

the undrained equilibrium behaviour of gassy sediments gassy soils are defined as those soils which contain a relatively large amount of gas dissolved in the pore fluid examples include the alberta oil sands marine sediments from deep ocean locations

the behavior of loose gassy sand methane gas found in loose deltaic deposits can contribute to the triggering of flow liquefaction of submarine slopes the behavior of loose gassy sand is studied in the laboratory using monotoni

marine and nonmarine deposition in a long term low accommodation setting an example from the middle pleistocene qm2 unit eastern central italy abstract facies anatomy and large scale stratigraphic organization of mid pleistocene strata qm2 unit exposed near the town of ortona eastern central italy have been defined through an integrated outcrop and subsurface dataset and record sedimentation within a long term low accommodation setting the studied interval can be subdivided into nine facies associations reflecting a range of continental marginal marine nearshore and innermost shelf environments and contains a well preserved record of high frequency relative sea level changes in the form of a stack of three unconformity bounded sequences each of the three sequences designated qm23 qm22 and qm21 from oldest to youngest consists of a specific subset of the nine identified facies associations as a function of preserved depositional systems and systems tracts typically the following architectural elements occur in ascending stratigraphic order i a basal unconformity molded by fluvial incision and subaerial exposure during sea level fall and shoreface erosion during subsequent rise ii a maximum regressive surface which is coincident with the sequence boundary iii a transgressive systems tract including braided river conglomerates and floodplain fines within the confines of an incised valley palustrine carbonates and back barrier lagoon mudstones and a deepening and fining upward shoreface to offshore transition facies succession bounded at the base by a wave ravinement surface iv a sharp regressive surface of marine erosion produced by shoreface incision during relative sea level fall and v a prograding downstepping and offlapping sharp based lithofacies assemblage of either beach conglomerates or sandstones ascribed to the falling stage systems tract overlain by a rooted paleosol marking subaerial exposure sequences were deposited on the uplifting palaeo adriatic shelf in response to repeated high frequency and high amplitude eustatic changes in sea level that would promote the creation of accommodation space by subtracting space to deposition the contemporaneous regional uplift of the basin margin may be accounted for the shingled downstepping configuration of individual sequences to form a falling stage sequence set of a larger composite sequence in dip view the erosional contact at the base of the qm2 falling stage sequence set is a composite regressive surface resulting from the downdip convergence and amalgamation of multiple erosional surfaces produced by the progressive basinward translation of successive sequences results from this study have direct implications for the oil and gas field development and exploration when making predictions of reservoir and seal geometries within shallow marine marginal marine and nonmarine sediments emplaced in similar long term limited accommodation settings

strike variability of clastic depositional systems does it matter for sequence stratigraphic analysis current sequence stratigraphic models are two dimensional in nature and predict variability in depositional dip sections strike and dip variability of sediment supply to clastic depositional systems causes significant changes to sequence architecture so that contrasting yet coeval stacking patterns result these changes ultimately affect prediction potential based on fixed systems tract stacking patterns and relation to relative sea level curves identification of key surfaces in sequences rather than stacking patterns is the most reliable indicator of relative sea level history

shallow gas accumulations in the german north sea abstract shallow gas here defined as free gas that is trapped in unconsolidated deltaic and shallow marine siliciclastic sediments of plio pleistocene age is found within the topmost 1000 m of sediment in the southern north sea shallow amplitude anomalies in seismic reflection data are likely due to the presence of gas the most prominent and easy to recognize indicators are high amplitude anomalies or bright spots that are widespread within the southern north sea gas from shallow reservoirs is currently produced offshore the netherlands in this study we determine whether there are analogous shallow gas accumulations within the german north sea therefore we screened 2d and 3d multichannel seismic data for shallow amplitude anomalies several clusters of bright spots are identified above salt domes that closely resemble the economic deposits known in the dutch sector in both size and their characteristic multilayered shape three of these potential gas accumulations occurring in combination with additional hydrocarbon indicators such as seismic attenuation and velocity push downs are investigated in detail and compared to shallow gas fields from offshore the netherlands amplitude anomalies indicate gas seepage on the seafloor that may contribute to the atmospheric methane budget and may have an impact on offshore infrastructure

sedimentation and tectonic geomorphology adjacent to major active and inactive normal faults southern greece the active psatha skinos normal fault is uplifting a contrasting variety of lithologies in its footwall including mesozoic limestones ophiolitic peridotites and poorly consolidated plio pleistocene sediments of the inactive megara basin in the latter basin linear marginal uplands border the sedimentary fill and are interpreted as degraded and segmented scarp lines which exhibit features such as facetted spurs drainage domains are defined as groups of drainage basins sharing a common tectono geological substrate contrasting domains in the footwall of the active fault have given rise to spectacular differences in drainage basin growth and form in the uplifting footwall raised coastal terrace levels are present at about 10 and 40 m the latter have yielded corals dated at between 90 126 ka and have enabled us to calculate uplift and erosional rates extrapolation of these rates indicate that some 350 m of footwall relief has been produced over approximately 1 ma most of the sediment eroded from the uplifting footwall is presumed to have been re sedimented into the alkyonides gulf basin plain during this time the prominent footwall unconformity so produced forms a fine modern analogue to features seen in ancient syn rift tilt blocks such as the viking graben footwall uplift has also backtilted the former depositional surface of the megara basin and caused reversal of flow in its axial drainage domain a variety of depositional environments are documented in the subsiding hangingwall to the coastal fault including syn quake talus cones alluvial fans intra fan marshes and swamps truncated fans transgressive barriers and spits

modeling signal loss in surficial marine sediments containing occluded gas the presence of occluded gas in inland lakes harbor muds and surficial marine sediments is well documented surficial gassy sediments cause underlying beds to be acoustically impenetrable to seismic surveys therefore the modeling of signal loss arising from mudline reflection and transmission absorption is of particular interest the anderson and hampton j acoust soc am 67 1890 1903 1980 model for attenuation in gassy sediments was evaluated against the physical and acoustical properties of eight laboratory silty clay soils containing different amounts of occluded gas in bubbles of 0 2 to 1 8 mm diameter the model was shown to give good agreement with measured data over the lower frequencies of bubble resonance and above resonance it did not agree with measured data at frequencies below resonance for which the model did not simulate the bulk properties of the gassy soils the mackenzie j acoust soc am 32 221 231 1960 model for reflection loss was also examined for the gassy soils the maximum reflection losses of 6 db at a grazing angle of 40 does not wholly support speculation by levin geophysics 27 35 47 1962 of highly reflective pressure release boundaries arising from substantial reflection and absorption losses in gassy sediments it was found that mudlines formed from sediments with significant occluded gas may be successfully penetrated although the substantial absorption loss arising from signal transmission through the sediment prevents penetration of the surficial layers to much beyond a meter in depth

grain displacive gas migration in fine grained sediments support for this research was provided by the kaust endowment g e abelskamp edited the manuscript data sets presented as part of this study are available from the kaust repository http hdl handle net 10754 630965

raw material exploitation around the middle paleolithic site of ein qashish abstract lithic reduction sequences reflect decisions made by ancient tool makers the first stages of a reduction sequence concern raw material procurement and include identifying sources on the landscape testing the quality of raw material knapping on the spot or moving material to other locations the distance from raw material source to a destination location is a significant factor that has implications for artifact life history ein qashish is located in the western yizra el valley the lithic assemblage from the late middle paleolithic site of ein qashish is made exclusively on flint this raw material occurs as several different visual types distinguished by their colors and textures several geological formations some of which are flint bearing are known at various distances from the site which is situated on a distal alluvial fan of a drainage that carried sediments and small flint nodules from mt carmel towards the qishon stream in the east in order to associate archaeological flint from the assemblage of ein qashish to potential geological sources we used visual observations color and texture geochemical icp ms icp aes analyses and statistical methods e g anova and principle component analysis our analysis shows that icp ms and icp aes can be used to differentiate between flints from various geological formations and to assign archaeological artifacts to geological origin areas the inhabitants of ein qashish obtained flints from various distances and integrated on site knapping of flint from relatively closer sources with transport of finished tools from more distant locations the relationship between the distance of potential raw material sources and the distribution of raw materials among technological products from different stages of reduction is addressed in order to discuss mobility patterns and raw material economy

a conceptual model for soils containing large gas bubbles offshore site investigations have indicated the presence of undissolved gas bubbles in the soils forming the sea bed at various locations throughout the world the gas bubbles are typically much larger than the normal void spaces so they cannot be considered as occluded bubbles within the pore water which simply change the compressibility of the pore fluid the effect of these large bubbles on the engineering properties of the soil must be understood if offshore construction is to take place in areas of gas bearing sediments this paper describes a conceptual model for soils containing large gas bubbles the model consists of a matrix of saturated soil surrounding isolated gas filled cavities the cavities forming the bubble sites are fixed within the soil so that gas drainage occurs only by the movement of dissolved gas the behaviour of the model is complicated by the processes of localized consolidation and bubble flooding des recherches conduites en mer ont indique qu il y a partout dans le monde d

middle paleolithic open air industrial areas in the galilee israel the challenging study of flint extraction and reduction complexes abstract during the last dozen years we discovered tested and studied several paleolithic flint extraction and reduction complexes in northern israel these paleolithic industrial areas are assigned based on lithic techno typology to the lower middle paleolithic of the levant however the most conspicuous component in all these complexes is the constant use of the levallois technology the immense scale of these sites and the immense lithic assemblages allowed only preliminary field investigations and analyses such paleolithic industrial areas demand a different research design than the one used at habitation sites or other task specific localities previous work demonstrated the potential of these complexes in understanding patterns of human behavior related to flint economy the organization of quarrying and knapping operations the scale of human exploitation of the natural resources caching behavior and more our investigations thus far are however only the tip of the iceberg of the research potential embedded within these unique archaeological complexes this paper raises questions on methodological and conceptual challenges we are confronted within studying these paleolithic extraction reduction complexes especially their formation processes it also brings up the question of how such sites can be incorporated in the future study of middle paleolithic mousterian in the levant

sediment transport processes on an active submarine fault escarpment gulf of corinth greece abstract sediment transport processes on the escarpment of a listric fault in the tectonically active and terrigenous sediment dominated corinth graben in greece are studied using 3 5 khz and airgun profiles and sidescan sonar images the whole of the slope area is affected by gravitational mass movements slumps debris mud flows and liquified and turbidity flows in canyon fan systems large volumes of sediment are transported through slumping debris mud and turbidity flows into the basin here they build coalescing fans which consist of intercalations of debris flow deposits and turbidites in delta front slope fan apron systems sediments are transported radially downslope through slumping debris mud flows liquified flows and high density turbidity flows into the basin where they build coalescing fan aprons these consist of massive homogenized deposits fluxoturbidites in shelf slope systems retrogressive rotational slumping is the dominant instability feature however due to the sharp increase in the slope gradient caused by the slumping debris and turbidity flows are triggered the major factors responsible for triggering gravitational mass movements in the region are earthquakes high sedimentation rates off the river mouths and heavy rainfalls and high seas these mass movements appear to occur at least once every 2 yrs as indicated by the failure of submarine cables

rates of tectonic uplift in the corinth and megara basins central greece we present evidence of the rates of late quaternary tectonic uplift that have affected parts of central greece during this period of active extension and basin formation dual lines of evidence indicate upper pleistocene to holocene uplift rates of the order of 0 3 mm yr 1 for the corinth and megara basins first u series disequilibrium ages of acropora sp corals from uplifted marine sediments are used to derive minimum average rates of vertical displacement since deposition second the geometries of cyclical transgressive sequences and of erosional terraces are consistent with the radiometric evidence and the known history of late quaternary sea level fluctuations two types of uplift are distinguished on the basis of structural relationships 1 fault block rotation about a horizontal axis tilting in response to footwall uplift on the active normal fault bounding the alkyonides gulf and 2 a more regional uplift which affects the corinth basin and peloponnesos to the south the results of u series dating are discussed in the light of initial 234u 238u activity ratios derived from the coral samples which are higher than for average marine waters 1 17 1 31 compared to 1 14 these values may be related to a variable freshwater input to the structurally confined gulf of corinth or alternatively they may reflect a previously higher global 234u 238u activity ratio in marine waters or post mortem enrichment in 234u although the mechanism of the latter is not yet understood

aggradation incision transition in arid environments at the end of the pleistocene an example from the negev highlands southern israel abstract one of the most significant environmental processes that occurred at the transition from the last glacial phase into the present inter glacial phase in arid regions was the shift from aggradation to incision in the drainage systems this is evident by the sharp transition from a fluvial regime depositing fine grained sediment within the wadis to intensive incision which formed gullies and narrow channels that dissected the late pleistocene sediments in order to investigate this transition we studied three small scale basins in the arid region of the negev highlands southern israel although the selected basins drain toward different base levels their geomorphological parameters particle size distribution of alluvial units and their osl ages are similar sediments from the penultimate glacial cycle are found in patches in the bigger catchments fluvial loess was widely deposited since at least 67 ka until after 28 ka covering valleys and slopes between 28 and 24 ka loess was washed from the slopes into the channels exposing the underlying colluvium at 24 ka erosion began with the transport of slope colluvium as gravels into the valleys that eroded the underlying loess sediments incision became dominant at 12 ka and is still ongoing and intensifying dust and reworked loess continued to be deposited during the main incision stages it is proposed that the transition from aggradation to incision was controlled by rates of loess supply and removal until 24 ka dust choked the drainage system and only after reduction in dust supply was erosion and incision possible it began first on the slopes and then in the channels our results show that an increase in precipitation is not a prerequisite for initiation of incision as is often assumed similar processes are described in other arid zones around the world

effect of gas hydrates melting on seafloor slope instability we present a theoretical study of the thermodynamic chemical equilibrium of gas hydrate in soil by taking into account the influence of temperature pressure pore water chemistry and the mean pore size distribution the model uses a new formulation based on the enthalpy form of the law of conservation of energy the developed model shows that due to a temperature and pressure increase hydrates may dissociate at the top of the hydrate occurrence zone to ensure a chemical equilibrium with the surrounding bulk water this original result confirms what has been already shown through experiments the second part of the paper presents an application of the model through a back analysis of the giant storegga slide on the norwegian margin two of the most important changes during and since the last deglaciation hydrostatic pressure due to the change of the sea level and the increase of the sea water temperature were considered in the calculation simulation results show that melting of gas hydrate due to the change of the gas solubility can be at the origin of a retrogressive failure initiated at the lower part of the storegga slope once again the developed model leads to predictions which are supported by laboratory experiment results but contradictory to previous interpretations and beliefs considering that hydrate dissociation occurs only at the bottom of the gas hydrate stability zone

tidal strait to embayment seismic stratigraphy and evolution of a rock bounded embayment in the context of holocene sea level change abstract elongate rock framed santa catarina island partly encloses a low energy marine embayment that communicates with the ocean via narrow rock bounded inlets with ebb and flood tide deltas the bay shoreline consists of low energy sandy beaches strandplains mangroves and bayhead deltas while the exposed atlantic shoreline comprises a series of headland embayment littoral cells in a linked north directed longshore drift system new and previously published seismic stratigraphic investigations enable assessment of the palaeogeographic geomorphic evolution of the area since the early holocene at a sea level of ca 50 m a sandy mainland attached shoreline complex dune and beach developed on a coastal plain setting some 6 7 km offshore of the present shoreline north of the island a barrier island and tombolo were formed in a coastal re entrant adjacent to the northern entrance to florianopolis bay the open coast beach dune system was overstepped by rapid sea level rise during mwp 1b whereas the barrier island and tombolo continued to accrete until mwp 1c when they too were overstepped the back island embayment contains up to 40 m of sediment overlying an irregular bedrock surface it was initially flooded during mwp 1c and the early muddy sedimentation suggests a distal sheltered marine embayment the subsequent development of many large bioherms on bedrock and mud suggests a change to more fully marine conditions as sea level continued to rise in the north bay these were subsequently enveloped by tidal dunes migrating north from the mid bay the vertical stacking of 3 d and 2 d sandy bedforms suggests that a tidal strait had developed with strong tidal currents radiating from a constriction in the vicinity of modern florianopolis city the strong tidal currents may be linked to the holocene sea level high that is well documented for this region a fall in sea level from this highstand coupled with accumulation of tidal strait sediments reduced the tidal prism and strength of tidal currents in the bay at the same time regressive beachridge plains developed in open coast and bay environments this coincided with development of the contemporary tidal inlet complexes at the north and south outlets of the bay as a consequence the upper surface of the tidal strait sand deposits experienced tidal ravinement and the bay switched to a sheltered back barrier environment dominated by deposition of mud and silt which blanket the contemporary bay floor the tidal inlets sequestered sand from the littoral drift system in ebb and flood tide deltas which created breaks in the longshore drift system causing littoral sediment to accumulate at the north of the island in a series of spits and promoting strandplain development south of the island

estimating the free gas content in baltic sea sediments using compressional wave velocity from marine seismic data a 2 d high resolution velocity field was obtained from marine seismic data to quantify free gas content in shallow muddy sediments at in situ pressure and temperature the velocities were acquired applying migration velocity analysis on prestack time migrated data compressional wave velocities are highly sensitive to free gas as very small amounts of gas can cause a significant decrease in the medium velocity the analyzed profile crosses a depression filled with organic rich holocene mud in the bornholm basin baltic sea the interval velocity field reveals two low velocity patches which extend from the reversed polarity reflections marking the top of the gassy sediment layer down to the base of the holocene mud average interval velocities within the gassy mud are lower than the seafloor migration velocity by up to 500 m s this decrease using a geoacoustic model is caused by an average 0 046 gas volume fraction the interval velocities in individual cells of the velocity field are reduced to 200 m s predicting up to 3 4 gas content the velocity field is limited in resolution due to velocity determination at and between reflections however together with the stratigraphic interpretation geological units containing free gas could be identified shallow gas occurs vertically throughout most of the holocene mud in the gassy area comparison with biogeochemical studies at other baltic sea sites suggests that the distribution of free gas is likely to be patchy in the sediment but the gas concentration may peak below the sulfate methane transition zone and gradually decrease below

morphometric and geomorphic approaches for assessment of tectonic activity dead sea rift israel a series of 31 short parallel steep channels mostly of first or second order occur at intervals of 300 500 m along 16 km of the western margin of the northern dead sea rift israel the analysis of tectonic and geometric activity along the marginal faults between the various segments is based on morphometric parameters such as sinuosity of the mountain front channel gradients drainage basin elongation ratio planimetric ratio facet areas hypsometric curves and integrals longitudinal profiles of the channels were studied in relation to the underlying lithology and the presence of marginal faults despite the great differences in climatic and geomorphologic settings comparison with other studies worldwide showed morphometric values similar to other tectonically active regions the southern segments of the study area which face the hula deep depression indicate enhanced geomorphic and tectonic activity the northern segment proved dissimilar to the others and is explained by its different tectonic setting six sedimentary fan like units composed of polymictic conglomerates were deposited along the mountain piedmont at the channel mouths the units were dated by osl k ar and archaeology to 1 1 ma q 1 and q 1 1 0 56 ma unit q 2 120 ka unit q 3 and 10 ka units q 4 and qs the morphology and structure of the sedimentary units indicate pulses of depositional activity followed by periods of quiescence and calcicsoil development no major faulting occurred along the naftali escarpment during the upper pleistocene despite the high tectonic morphometric values obtained for the study area the marginal faults displaced unit q 2 during the mid pleistocene and since then tectonic activity has shifted from the western marginal faults eastward to younger faults deeply buried in the center of the graben the field data calibrate the morphometric analysis carbonate limestone and dolomite hillslopes developed in the mediterranean climate have maintained active tectonic class morphology since the last major faulting events during the mid pleistocene

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

seismic stratigraphy of the gulf of cadiz continental shelf a model for late quaternary very high resolution sequence stratigraphy and response to sea level fall

effect of gas bubbles on pore pressure response in peat beneath a railway embankment this paper presents the pore pressure behaviour observed within peat beneath a newly constructed railway embankment piezometers installed at different depths beneath the structure showed episodic increases in pore pressure above hydrostatic pressure followed by a rapid pore pressure decrease it was postulated that this fluctuation in pore pressure was due to the movement and expulsion of gases within the peat investigations were conducted in the laboratory to replicate this pore pressure response the peat specimens were subjected to isotropic consolidation within a triaxial cell at constant confining pressure while measuring the change in the specimen s pore pressure and volume the results of this investigation indicate that the gas bubbles move through the channeled network of voids towards the drainage boundary where they restrict the flow of water which results in the increase of pore pressure towards an upper limit or escape pressure ultimately causing an expulsion of gas bubbles this expuls

the terraces of corinth gerrce a detailed record of eustatic sea level variations during the last 500 000 years abstract between corinth and xylokastro 20 marine terraces reflect the interaction of the northern peloponnese uplift and the global eustatic sea level fluctuations during the last 500 000 years correlation of the terraces with oxygen isotope records in deep sea cores allowed accurate dating of these fossilized transgressive shorelines curves of altitude versus age have been plotted they show a regular decrease of the uplift rate and a frequent return of the sea level very close to the present day one not only during the interglacial periods 5 7 9 11 13 but also during glacial periods 3 1 3 3 6 8 the alternative would be to suppose very complicated and highly improbable vertical movements of the substratum to explain the regularity of the curves the rhythm of these high sea levels is around 20 30 ka since at least 330 000 years ago

mechanical behaviour of gas charged marine plastic sediments understanding how free gas modifies the mechanical behaviour of marine plastic sediments remains a challenging issue special triaxial tests were carried out on natural sediments recovered from the gulf of guinea special attention was devoted to the laboratory preparation procedure involving saturation of natural marine sediment samples with carbonated water and generation of free gas following undrained unloading experimental data show that soil destructuration and damage generated by gas expansion and exsolution are at the origin of a the increase in the isotropic compressibility and decrease in the preconsolidation pressure and b the decrease in the peak undrained strength and abrupt increase of the pore pressure during undrained shearing the experimental data also show that flooding of gas bubbles and dissolution of free gas do not imply a complete strength recovery of natural sediments

partially saturated tailings sand below the phreatic surface an opportunity to re examine the liquefaction potential of hydraulically placed tailings sand has been provided by the canadian liquefaction experiment canlex as part of this experiment undisturbed samples of tailings sand were recovered after freezing the tailings in situ examination of undisturbed cores of frozen tailings sand clearly showed that the specimens were not fully saturated this was confirmed by both physical measurements and laboratory tests in which gas was recovered from thawing specimens and analysed by gas chromatography the gas was mainly air although a small amount of microbial gas was also present cryogenic scanning electron microscopy and confocal laser scanning microscopy were used to further confirm the existence of occluded gas bubbles triaxial undrained compression tests were carried out on undisturbed tailings specimens that were not back saturated prior to shearing in order to preserve the in situ degree of saturation occluded air bubbles within the tailings sand ev

morphology of molar tooth structures in precambrian carbonates influence of substrate rheology and implications for genesis abstract molar tooth mt is an enigmatic carbonate fabric composed of variously shaped cracks and voids filled with a characteristically uniform equant microspar mt is both abundant and widespread in mesoproterozoic and early neoproterozoic strata where void filling microspar comprises up to 90 of individual beds and 5 25 of preserved carbonate the temporal restriction of this fabric suggests a potential link between mt formation and the biogeochemical evolution of marine environments detailed petrographic relationships among mt crack morphology distribution of mt microspar and composition of the surrounding substrate suggest that crack formation and microspar precipitation are intimately linked to the decomposition of sedimentary organic matter in the presence of supersaturated proterozoic seawater laboratory experiments have shown that gas generated within unconsolidated mud can reproduce a variety of mt crack morphologies yet current gas expansion and migration models do not explicitly consider the role of substrate variability in determining morphologies of mt cracks a detailed petrographic examination of mt structures from the mesoproterozoic belt supergroup montana permits interpretation of the microscale relationship between crack morphology and lithologic and potentially rheologic variability of the surrounding substrate by tracing the distribution of petrographically distinctive mt microspar observations of lateral offset of mt cracks at bedding planes or within coarser grained siltstone or sandstone layers termination of cracks beneath clay or organic rich horizons grain collapse into underlying mt cracks and the presence of mt microspar as a pore filling precipitate suggest that grain size substrate lithology and substrate cohesion all play critical roles in the development of mt cracks by contrast the presence of a wide range of mt crack morphologies within petrographically homogeneous substrates and an apparent relationship between crack diameter and sinuosity suggest that the void forming process itself also played a role in determining the final morphology of mt cracks together these petrographic observations are used to define a model of microscale gas sediment interactions that can be used to interpret crack morphology in terms of gas pressure and the strength of sedimentary substrates the presence of characteristic void filling microspar is integral to preservation of mt structures cathodoluminescence cl identification of this characteristic microspar within mt voids in pore space of coarse grained facies and interstitially within fine grained facies adjacent to mt voids suggests that mt voids and cement share a common genesis because microspar cores are similar in size and morphology to vaterite precipitated experimentally in the presence of a variety of dissolved organic molecules we suggest that precipitation of mt microspar was intimately linked with gas production during organic decomposition within the host substrate in this scenario gas production would result in pore fluids with elevated concentrations of dissolved organic molecules which would initiate precipitation of mt microspar when the pore fluids come in contact with supersaturated proterozoic seawater restriction of mt largely to mesoproterozoic and early neoproterozoic strata likely reflects a critical level of carbonate saturation that limited early substrate lithification thereby allowing void production but remained high enough that organic catalysts were able to initiate precipitation of mt microspar

tectonic controls on sequence stacking pattern and along strike architecture in the pleistocene mejillones formation northern chile implications for sequence stratigraphic models abstract in the mejillones formation a shallow marine pleistocene succession of northern chile the cyclic stratigraphic record is the result of the complex interaction of regional uplift glacio eustasy local tectonics sediment supply and sedimentary processes stratal geometries characteristics of sedimentary facies and nature of sequence bounding unconformities have been investigated to evaluate the influence of i intrabasinal short term normal faulting on both along strike variations in sequence architecture and genetic complexity of key stratal surfaces and ii long term regional uplift on sequence stacking pattern the stratigraphic succession dissected by small displacement few meters normal faults striking obliquely with respect to the palaeo shoreline trends displays systematic variations in sequence architecture and the nature of bounding surfaces across them indeed depending on position with respect to the fault plane two basic types of internal organisation can be recognised in the examined shallow marine almost clastic starved sequence within grabens it consists of a siliciclastic rich transgressive systems tract tst which is bounded beneath by a transgressively modified glossifungites demarcated sequence boundary sb rs overlain by a mollusc bearing falling stage systems tract fsst the erosional downlap surface that separates the tst from the fsst is the regressive surface of marine erosion rsme on the footwall crests the combination of marine regressive erosion during falls in relative sea level and uplift has resulted in complete removal of the sediments of the tst from these sites leading to the formation of a tectonically enhanced basal unconformity composed of the rsme superimposed onto the previous sb rs sb rs rsme the prominent lateral change in component units systems tracts and nature of bounding surfaces within the studied sequence is directly related to the presence of normal faults and indicates that fault activity had a major impact on the sequence stratigraphic evolution of the mejillones formation enhancing subsidence within the grabens and promoting unconformities in the horsts overall the mejillones formation records a long term sea level fall driven by the contemporaneous regional uplift punctuated by repeated high frequency eustatic sea level changes the effect of this superimposition was that glacio eustatic sequences were displaced progressively downward and basinward and stacked in a distinct downstepping tectonically enhanced falling stage sequence set which reflects basin wide loss in accommodation space the sequence set is underlain by a composite rsme that becomes progressively younger basinward and is made up by the lateral and down dip connection of a series of lower rank sequence boundaries including hanging wall sb rss and footwall sb rs rsmes of successive sequences

mechanical behaviour of unsaturated marine sediments experimental and theoretical approaches abstract the costa target areas exhibit different slope failure events which reflect different triggering mechanisms including gas hydrates dissociation gas hydrates stability law depends on temperature pore pressure gas chemistry and pore water salinity any change in the equilibrium parameters may convert the hydrate to gas plus water causing significant weakening of the sediment and generating a rise of pore pressure a significant consequence of the hydrate melting is the gas production which alters significantly the behaviour and mechanical properties of the marine sediments and could be very hazardous when the sediment is unloaded in undrained conditions the behaviour of the unsaturated marine sediment has to be accurately identified in order to quantify the geological risks associated to the hydrate dissociation see for instance sultan n cochonat p foucher j p mienert j this volume effect of gas hydrates melting on seafloor slope instability thus in this work five tests were carried out on synthetic marine sediments in order to identify the gas effect on the hydro mechanical behaviour of unsaturated marine sediments based on the experimental results obtained from this study on previous constitutive models alonso e e gens a josa a 1990 a constitutive model for partially saturated soils geotechnique 40 3 405 430 gens a alonso e e 1992 a framework for the behaviour of unsaturated expansive clays can geotech j 29 1013 1032 and on the relationship of van genuchten van genuchten m th 1980 a closed form equation for predicting the hydraulic conductivity of unsaturated soils soil sci soc am j 44 892 898 a new mathematical formulation was proposed to simulate the behaviour of the unsaturated soil qualitative comparison between experimental results and model predictions shows the capacity of the proposed model to reasonably reproduce the essential features of the hydro mechanical behaviour of marine unsaturated sediment experimental and simulation results show that unloading tidal cycles erosion natural slope instabilities excavation a submarine unsaturated sediment slope in shallow water is much more hazardous than unloading the same submarine slope in deep water

experimental validation of terzaghi s effective stress principle for gassy sand abstractgassy soils are a special case of unsaturated soils for which the gas phase exists in the form of occluded bubbles of a size that allows the bubbles to fit within the void spaces without d

the physics of bubbles in surficial soft cohesive sediments abstract this paper reviews current understanding of the physics of bubbles in soft unlithified cohesive sediments certainly in the top 100 m from the sediment water interface but likely much deeper experimental evidence primarily ct scans and internal pressure records indicate that near surface bubbles grow by elastically compressing and fracturing these sediments which results in thin irregular disks of gas these data do not suggest either plastic or fluid behavior on the part of the bulk sediment in addition there is no hint of capillary invasion of gas into the pores of fine grained sediments the growth rate of an elastic fracturing disk shaped bubble can vastly exceed that of a spherical bubble depending on the eccentricity of the bubble this effect results from the far more favorable surface to volume ratio of flattened bubbles the initial rate of rise of bubbles in cohesive sediments also appears to be governed by a fracture process which is driven by pseudo buoyancy the rate of bubble rise could be controlled by various possible mechanisms but only the predictions from a visco elastic fracture propagation model seem to produce rise velocities that are not ballistic experimental evidence demonstrates that a rising bubble can deviate from its path to the surface if it encounters a zone of sediment with lower lateral fracture toughness such a bubble will begin to move in a lateral direction but stall because pseudo buoyancy is no longer operative subsequent bubbles will do the same and accumulate in the low fracture toughness zone this explains the occurrence of shallow sub seafloor domes of gas and modeling of this process predicts only modest over pressures in such structures

depositional bias and environmental change important factors in sequence stratigraphy abstract differences among depositional systems here called depositional bias strongly influence sequence patterns siliciclastics and shallow water carbonates for instance shed most of their sediment during opposite phases of a sea level cycle lowstand shedding and highstand shedding respectively furthermore the two systems generate their own system specific relief on the sea floor disperse their sediment load along different avenues and differ in the way they are deactivated reefs and carbonate platforms can be drowned whereas siliciclastic deposition can be shut off and renewed at any depth as a consequence of these differences pronounced unconformities drowning unconformities develop where carbonate platforms are terminated and buried by siliciclastics the siliciclastic to carbonate transition tends to be more gradual drowned platforms and drowning unconformities appeared world wide in great abundance in the miocene cretaceous valanginian turonian jurassic toarcian and devonian frasnian famennian examples of drowning unconformities interpreted as sequence boundaries include those of the early cretaceous platforms off new jersey and off morocco the mid cretaceous unconformity in the gulf of mexico and miocene unconformities on top of reefs in the far east the eustatic cycles postulated from sequence stratigraphy are a very unlikely cause for the mass drownings of reefs and platforms either the rates of rise are an order of magnitude lower than the growth potential of platforms or cycle amplitudes are too small or the cycles are too short and subsidence too slow to remove platforms permanently from the photic zone the critical element in the mass drowning seems to be environmental stress that reduces the growth potential of carbonate systems thus drowning unconformities demonstrate the importance of environmental change as a control on sequence development other examples of dominantly environment controlled sequences include slope deposits shaped by shifting currents e g florida and blake plateau and basin fills that were controlled by changes in sediment input related to tectonic alteration of the drainage in the hinterland e g gulf of mexico environmental change must be considered as a third independent factor that competes with eustatic and tectonically driven regional changes of sea level for control of sequences the definition of sequences and sequence boundaries should be broad enough to include the possibility of non sea level controls

clay distribution over the landscape of israel from the hyper arid to the mediterranean climate regimes abstract the current study evaluates clay distribution in modern surface sediments mainly soils to which desert dust is a major contributor the mineralogical composition of the clay fraction of seventy seven samples was analyzed by x ray diffraction twenty nine soil and dust samples were also analyzed for their bulk chemical composition the samples are settled dust soils developed on various sedimentary rocks stream and lake sediments they were collected along a climate gradient from hyper arid to mediterranean regimes in israel the purpose of the study is to decipher the main factors that control variable clay distribution along this gradient including annual precipitation substrate type and topography the common clay composition for most samples of all sources is illite smectite is kaolinite illite trace amounts of chlorite palygorskite goethite and quartz might be present pedogenic processes are recognized even under arid climate where loessial soils display kaolinite depletion and more illitic is phases than dust two main processes shape clay composition under a mediterranean climate regime regardless of the parent material a smectitization process occurs in leached low permeable clayey soils and reaches optimum evolution with 90 smectite or smectitic is this evolutionary trend is also recognized in poorly drained soils of catenary chains that are related to other soil types like terra rossa hamra and pale rendzina kaolinitization and apparently illite pedogenic formation occur in well drained red mediterranean soils of the terra rossa and hamra types to the detriment of smectitic is phases of parent materials in the most evolved terra rossa and hamra soils kaolinite becomes the principal mineral and illite is significantly enriched pedogenic evolution of the clay fraction mineralogical composition affects bulk chemical composition of most soil types clay inheritance from the bedrock is rather limited in leached soils it is widely recognized in pale rendzina soils by the presence of smectite or smectite and palygorskite derived from late cretaceous or eocene chalks respectively streams clay composition like that of dust is fairly uniform as streams average various sources across their drainage basins however composition variations can be attributed to local contribution from certain sources

cyclic liquefaction of loose gassy sand gas can be found in many soils but none more common than in seabed soils gas charged sediments are known to be widely distributed throughout the world s oceans numerous research programs have studied saturated soil response to cyclic loading however little is known about the behavior of gassy soils subjected to cyclic loading the response of loose gassy specimens subjected to cyclic loading was studied in a laboratory program triaxial tests were performed on specimens of reconstituted ottawa sand prepared to various gas contents and densities the specimens were consolidated and then sheared under undrained cyclic loading gas content was measured at the beginning and end of each test using time domain reflectometry the response of the gassy specimens has been shown to be influenced by the soil state and grain characteristics and the intensity duration and frequency of the cyclic loading the propensity of a soil to liquefy is represented by a cyclic resistance ratio defined as the cyclic stres

timing of relay ramp growth and normal fault linkage upper galilee northern israel we investigate a kilometer scale steep relay rampstructure in the galilee northern israel the data indi cate an asymmetric fold above the buried tip of thesouthern boundary fault as well as at the lower partof the ramp structural analysis suggests that the buriedtip of the bounding fault is only a few hundred metersbelow the surface a sequence of colluvial wedges exposed at the base of the southern flank of the relayramp over the blind tip of the boundary fault presentssuccessively decreasing angles from 67 at the bottomto 30 at the top the lower three wedges rest at anglesgreater than the angle of repose suggesting tilting dur ing and after deposition we suggest that the increasingangle of the wedges is the result of the development ofthe monocline over the buried tip ofthe boundaryfault which in turn reflects the development of the entirerelay ramp structure paleomagnetic measurements testthis hypothesis samples from three of the four lowerwedges and the carbonate fill in the fractured bedrockyield northerly declination and positive inclination inclination anomalies are 19 4 3 3 and 11 3 1 8 for the fractured bedrock and the wedges respec tively these anomalies reflect part of the tilt paleo magnetic measurements and optically stimulatedluminescence osl constrain the time of initial defor mation of the monocline above the southern boundaryfault between 780 ka and 461 75 ka osl age ofwedge 1 and the termination of deformation to 176 22 ka osl age of wedge 5 these bounding agessuggest tilting rates that range between 1 16 kyrand 1 8 kyr termination of tilting along the south ern flank of the relay ramp and the fact that the tipof the buried normal fault is only a few hundreds ofmeters below the surface suggest that the relay rampmay be close to being breached by a connecting fault

mineralogical and chemical variability of mountain red brown mediterranean soils the purpose of the current study was to quantitatively explore the dynamics of clay pedogenesis in red brown soils of the terra rossa type and associated soils mainly rhodoxeralfs of the mediterranean region with respect to bedrock and dust composition and the impact of the vegetation translocated elements silicon and potassium fifteen non cultivated shallow and leached mountain pedons were sampled in israel along three transects that represent various rainfall ranges and bedrock lithologies bulk and clay fraction chemical and mineralogical compositions as well as grain size were determined quantitative relative analysis of clay minerals displayed a large variability that was largely affected by leaching leaching was dependent on rainfall amount and bedrock soil permeability in general if the better soils were drained and leached the higher were the amounts of both kaolinite and illitic phases soil clay assemblages lay between two mineralogical end members one with dominance of smectite and the second with high values of kaolinite and illitization parameters potassium and silicon were mobile in soils relative to aluminum but under high rainfall or certain vegetation translocation by vegetation reached a degree that promoted illite or smectite formation local combinations of rainfall bedrock soil permeability and vegetation translocation of potassium and silicon dictated a large variability in clays including illite formation within a restricted group of red brown mediterranean soils

forced regressive wedges on a neoproterozoic siliciclastic shelf chandarpur group central india abstract outcrop based sequence analysis across the transition from the chaporadih to the kansapathar formation of chandarpur group chattisgarh supergroup central india resolved a long standing uncertainty on occurrence of depositional discontinuity through undoubted identification of a forced regressive wedge and associated intraformational unconformity process based facies analysis identified eleven different facies types that are grouped into five different facies associations paleoenvironments range from shelf shoreface foreshore and beach tide influenced estuary and delta bounded between the surface of marine erosion at its base and subaerial unconformity marked by paleosol development at its top the coarse grained wedges of shoreface sandstone is interpreted as forced regressive in origin the basinward downstepping of two such regressive wedges bears evidence for lowering of wavebase in connection with relative fall in sea level the valley created during the falling sea level was filled by sediments in lowstand transgressive and highstand depositional motif the aggradational to weakly progradational bedsets of foreshore beach sediments record the history of early slow rise in base level with steepening in the rate of relative sea level rise the coastline transformed from wave dominated to tide dominated wide variability in the balance between sediment supply and accommodation is recorded in the facies types and stacking motif of transgressive estuarine sections at different studied locations the highstand tidal delta is a supply driven normal regressive product at stable or marginally rising base level

liquefaction response of partially saturated sands ii empirical model partial saturation in sands attributable to the presence of gas bubbles not capillarity can be encountered naturally in the field be cause of the decomposition of organic matter or it can be induced for liquefaction mitigation an empirical model rupss was developed to predict the excess pore pressure ratio ru in partially saturated sands subjected to earthquake induced shear strains the model is based on experimental test results on partially saturated sands cyclic simple shear strain tests were performed on specimens prepared and tested in a special liquefaction box excess pore pressures were measured for a range of degrees of saturation 40 s 90 relative densities dr 520267 and cyclic shear strains g50 0120 2 the test results demonstrated that partially saturated sands achieved a maximum excess pore pressure ratio ru max when large enough cycles of shear strain were applied the excess pore pressure ratio ru that partially saturated sand can achieve under a given earthquake induced peak shear strain and the number of equivalent cycles of application can be significantly smaller than ru max therefore the empirical model was developed in two stages in the first stage ru max was related to s dr and shearstrain g in thesecondstage amodelwasdevelopedrelatingru toru max shearstrainamplitude g effectivestress s9 andearthquake magnitude m thispaperpresentstheequationsthatdefinethepredictivemodelsforru max andru throughtheseequations plotsforru max and ru are provided for ranges of soil and earthquake parameters for ease of use in engineering applications to illustrate the implementation of the empirical model for predicting ru max and ru an example is presented in which a partially saturated sand layer experiencing a peak earthquake induced shear strain was analyzed and the pore pressure response of the sand was evaluated using both the predictive equations and the plots doi 10 1061 asce gt 1943 5606 0000816 2013 american society of civil engineers ce database subject headings soil liquefaction soil treatment saturated soils pore pressure empirical equations sand soil type author keywords soil liquefaction soil treatment saturation pore pressure empirical equations induced partial saturation liquefaction mitigation empirical model soil model

stress dilatancy behaviour of bubbled fine grained sediments abstract although the strength and stiffness of fine grained gassy soil have been relatively well characterised its dilatancy remains poorly understood this study aimed to understand and formulate the stress dilatancy behaviour of fine grained gassy soil through a series of triaxial tests 19 in total conducted on fine grained gassy specimens where different initial gas volume fractions 0 and initial pore water pressures uw0 were considered compared to the stress dilatancy relation of saturated fine grained soil the addition of gas bubbles was found to result in more contractive or dilative soil behaviour depending on the combination of 0 and uw0 these distinct features cannot be captured by the existing stress dilatancy functions for fine grained saturated soils which solely depend on the stress ratio therefore a new stress dilatancy function is proposed within the framework of critical state soil mechanics to quantify the distinct modification effects of bubbles which either suppress or enhance dilatancy on the dilatancy of gassy soils with different 0 and uw0 values in a unified manner this new function has been validated and can be readily implemented in critical state based constitutive models for predicting the shear behaviour of fine grained gassy soil and therefore the response of various offshore structures i e foundations and pipelines founded on a gas bearing seabed

hayonim cave a tl based chronology for this levantine mousterian sequence the thermoluminescence dating method was applied to 77 heated flints from the mousterian layers of hayonim cave in order to provide a precise tl based chronology for this important levantine sequence a detailed dosimetric study was performed by using 76 dosimeter capsules and revealed strong spatial dose rate variations in parallel fourier transform infrared spectrometry enabled the identification of various mineral assemblages in the sediments of the cave and to localize the boundaries of these assemblages by comparing these two data sets it is shown that low dose rate values w500 mgy a are systematically recorded in areas where the calcite dahllite cd assemblage is preserved whereas higher values up to 1300 mgy a are associated with the leucophosphite montgomeryite variscite and siliceous aggregates lmvs assemblage the dosimetric and mineralogical information was combined in order to assess where possible the dose rate experienced by each flint during its burial some of the flint samples analyzed were too close to mineral assemblage boundaries and were therefore discarded this rigorous selection led to tl ages ranging from 230 to 140 ka for the lower part of the mousterian sequence layers f and lower e which contains lithic industries characterized by blade production using the laminar method 2006 elsevier ltd all rights reserved

facies and cycle architecture of a pleistocene marine terrace crotone southern italy a sedimentary response to late quaternary high frequency glacio eustatic changes abstract cyclic late pleistocene shallow marine deposits such as those forming the sedimentary cover of some marine terraces allow a detailed study of the architecture of nearshore to offshore cycles deposited under the influence of high amplitude glacio eustatic changes the capo colonna marine terrace located near crotone southern italy is composed of two cycles recording a low frequency retrogradational trend which is thought to be the result of a generalized base level rise during a late pleistocene interglacial stage superimposed on regional uplift cycles of the capo colonna marine terrace are composed of coarse grained lags siliciclastic shoreface deposits and mostly carbonate shelf deposits and their general stratigraphic architecture evidences relatively thin transgressive and thick regressive intervals the latter can be top truncated due to wave ravinement during a subsequent erosional transgression the architectural style of the capo colonna marine terrace cycles is thought to be linked to very rapid base level rises related to the late pleistocene high amplitude glacio eustatic changes climatic variations controlling the sediment supply rate are considered less effective in the present context present results allow a comparison with other cyclic successions developed under icehouse climatic regimes showing a discrete variability in their stratal architecture

flint workshop affiliation chronology technology and site formation processes at giv at rabbi east lower galilee israel abstract salvage excavations at the middle paleolithic flint workshop giv at rabi east lower galilee israel aimed at obtaining chronometric ages for the site s exploitation reconstructing the process of its formation and collecting an assemblage of diagnostic flint items for testing the conjectured connection with nearby qafzeh cave the excavations revealed two archaeological units the lower one directly overlaying the calcrete bedrock formation and separated from the upper one by a sterile layer of clay sediments the sequence of four osl ages fall within the time range of the levantine middle paleolithic and correspond to mis 6 and most of mis 5 the assemblage of flint artefacts included hundreds of levallois debitage items alongside bifacial fossiles directeurs of the lower paleolithic acheulian found mostly in the lower archaeological unit while parameters reflecting the degree of core exploitation i e size number of scars and amount of cortex support the hypothesized connection between the workshop and qafzeh cave osl dates suggest that the beginning of the workshop s existence predates that cave s occupation moreover the possibility that the upper archaeological unit in gre represents re deposited part of the original accumulation of flint artefacts reduces even more the likelihood of the connection between the workshop and the cave these results suggest that additional and more remote sites were probably involved in the workshop formation and allow for a variety of scenarios concerning acquisition and management of flint resources during the middle paleolithic in the lower galilee chronometric dates within the sequence of the middle paleolithic the indication of nearly in situ deposition of the lower archaeological unit alongside physical condition of different artefact groups suggest that the bifacial type fossils of the lower paleolithic acheulian may have been recycled by middle paleolithic hominids

effect of initial pore pressure on undrained shear behaviour of fine grained gassy soil many of the world reserves of fossil fuels are located at various water depths in fine grained sediment under the seabed the fine grained sediment contains relatively large biogas bubbles which has been posing challenges to the stability of offshore foundations supporting oil and gas platforms although fine grained gassy soil was found to exhibit different undrained shear strengths cu by altering the initial pore pressure ui relevant to water depth systematic studies concerning the effect of ui on undrained shear behaviours of the soil are still lacking this study reports a series of undrained triaxial tests aiming to compare and investigate the responses of reconstituted fine grained gassy soil with the same consolidation pressure p c but at a wide range of varying ui 0 1000 kpa the shearing induced excess pore pressure u in the gassy specimens highly depends on ui it can be either smaller than that of the saturated specimen with the same p c due to partial dissipation of u int

stability of bubbles in a linear elastic medium implications for bubble growth in marine sediments 1 methane bubbles in muddy fine grained sediments grow initially through a process of elastic expansion punctuated by discrete fracture events lefm growth the ability of the surrounding sediments to support a stress and actively resist expansion can under conditions of low gas production or high sediment toughness result in the cessation of growth and the presence of stable bubbles thus it is possible for a bubble to stop growing despite the presence of a source in the sediments that continues to produce gas this contrasts with growth of bubbles in a fluid medium which cannot support a stress and so will continue to grow as long as a surrounding source provides gas this no growth condition is the result of the coupling between gas supply methane production or supersaturation and the sediment mechanics here we quantify this condition and present a criterion for the switch between no growth and the lefm growth regimes we apply this theory to the sediments of eckernforde bay in the kiel bight germany and despite the absence of measurements for the key sediment mechanical properties we can provide a qualitative explanation for the sizes and shapes of the observed bubble population with depth in the sediment we also show how the release of hydrostatic pressure can stimulate growth by pushing otherwise stable bubbles into the lefm growth regime this could provide a mechanism for the release of bubbles during periods of low water such as during low tide or wave events