spatangoid produced ichnofabrics bateig limestone miocene spain and the preservation of spatangoid trace fossils a spatangoid produced ichnofabric is described from the miocene bateig limestone se spain this ichnofabric is characterized by the dominant presence of large meniscate burrows bichordites produced by irregular echinoids this constitutes an unusual mode of occurrence for spatangoid bioturbation as their traces are most typically preserved in bases and tops of sandstone event beds in fact despite their important role as burrowers in modern settings that can be extended back to the early cretaceous based on their body fossil record spatangoid trace fossils scolicia and bichordites are comparatively rare several factors play an important role in their preservation mechanism of burrowing sediment characteristics early diagenesis and presence absence of deep tier burrowers spatangoid produced ichnofabrics such as those from the bateig limestone characterize depositional settings with intermittent deposition of event beds where there is an absence of deeper tier bioturbation

the calcarenite di gravina formation in matera southern italy new insights for coarse grained large scale cross bedded bodies encased in offshore deposits excellent outcrops of the upper pliocene lower pleistocene calcarenite di gravina around matera southern italy provide continuous exposure of coarse grained clastic basin margin shoreline to offshore facies among these facies the most conspicuous and volumetrically important are the transition slope deposits that form large scale high angle cross bedded lithosomes these are laterally extensive parallel with the paleoshoreline and show seaward progradation we interpret them to represent avalanches of sediment swept out onto a depositional slope below wave base from the shoreface zone by storm waves and wind driven currents three types of building blocks are recognized based on bedding patterns and facies architecture embryonic parasequences mature parasequences and simple sequences parasequences formed during stillstands of sea level and simple sequences during high frequency cycles of relative change of sea level these building blocks are stacked in a backstepping configuration and onlap onto cretaceous limestone substrate backstepping is believed to be due to a tectonically forced transgression that is punctuated by high frequency cycles of sea level modern analogs for these building blocks are the holocene prograding prisms detected in high resolution seismic lines of the mediterranean shelves the reflection patterns of these seismic units resemble the bedding architecture of the matera simple sequences and parasequences and show similarities of shape size position and orientation of coastal setting and direction of progradation comparison of the holocene prisms and the pliocene pleistocene accretional units in matera indicates that they may represent the same begin page 662 genetic process progradation of clastic prisms below the wave base level the matera accretional units also show similarities with other examples of laterally extensive large scale cross bedded sand bodies encased in offshore deposits such as some sandbanks differentiating between these laterally extensive and seaward prograding cross bedded sand bodies and some coarse grained gilbert type deltas is difficult however if interpretations are based only on two dimensional 2 d outcrops in dip section without high resolution data it is also difficult to distinguish between transition slope and prograding shoreface lithosomes this difficulty may be acute where only seismic or well log data are available however certain other architectural characteristics such as stacking and preservation of facies belts and position of bounding surfaces as well as differences in associated sedimentary structures and fossil content may be used for interpretation the matera example provides a mechanism for emplacement in offshore settings of elongate and strandline parallel sand and gravel deposits that prograde seaward and that preserve a coarsening upward internal succession this article offers an interpretation for other ancient examples of large scale cross bedded lithosomes encased in offshore deposits

three dimensional to two dimensional cross strata transition in the lower pleistocene catanzaro tidal strait transgressive succession southern italy sandstone tidal cross strata are the predominant sedimentary feature of strait fill stratigraphic successions however although widely described in numerous studies tidal strait fill two dimensional and three dimensional cross strata have rarely been reported to occur in discrete intervals which are laterally adjacent or vertically stacked and the meaning of this stratigraphic architecture has not yet been fully investigated understanding of the processes responsible for changes in the internal features of modern and ancient tidal bedforms is essential in order to predict lateral and vertical heterogeneities in analogous reservoir strata this facies based study aims to interpret the three dimensional to two dimensional cross strata transition observed in the lower pleistocene mixed siliciclastic bioclastic sandstone filling the catanzaro strait in southern italy during a continuous phase of tectonically driven marine transgression tidal cross strata disappear in the uppermost interval of the studied succession where mudstone strata prevail this stratigraphic trend is interpreted as the evidence of an important change in the tidal strait hydrodynamics due to a phase of relative sea level rise at the beginning of the transgression three dimensional tidal dunes migrated throughout the ca 3 to 4 km wide and ca 30 km long wnw ese oriented catanzaro strait due to strong tidal currents amplified through the seaway and flowing in semi diurnal phase opposition as the intermediate phase of transgression enlarged the seaway width the tidal current strength decreased as tidal water exchange occurred over a larger cross sectional area the progressive reduction of the bed shear stress modified three dimensional tidal dunes into an extensive two dimensional bedform field at the end of the transgression the further widening of the catanzaro strait into a ca 10 to 12 km wide marine passageway changed the tidally dominated strait into a non tidal open shelf the results of this research suggest the presence of a critical cross sectional area in the narrowest strait centre zone which controls the activation and deactivation of tidal current amplification along a marine seaway

deep water measurements of container ship radiated noise signatures and directionality underwater radiated noise from merchant ships was measured opportunistically from multiple spatial aspects to estimate signature source levels and directionality transiting ships were tracked via the automatic identification system in a shipping lane while acoustic pressure was measured at the ships keel and beam aspects port and starboard beam aspects were 15 30 and 45 in compliance with ship noise measurements standards ansi asa s12 64 2009 and iso 17208 1 2016 additional recordings were made at a 10 starboard aspect source levels were derived with a spherical propagation surface affected or a modified lloyd s mirror model to account for interference from surface reflections surface corrected ship source depths were estimated from spectral differences between measurements at different beam aspects results were exemplified with a 4870 and a 10 036 twenty foot equivalent unit container ship at 40 56 and 87 of service speeds respectively for the larger ship opportunistic ansi i

ecologic interpretation of deep sea trace fossil communities abstract trace fossil types and their vertical arrangement tiering are closely related to the biotope and hence can provide information on ecological conditions especially on oxygenation benthic food content sedimentation rate and substrate consistency however to use the full potential of trace fossils for environmental analyses various ichnologic criteria are necessary in addition to trace fossil taxonomy based on a taxonomically oriented ichnologic evaluation of modern deep sea environments six ichnologic aspects to ecologic changes have been found to be of major importance 1 1 penetration depth of burrows is influenced by oxygenation benthic food availability and substrate consistency 2 2 the number and vertical extension of tiers varies due to environmental changes a decrease in the vertical extension of tiers telescoping indicates a decrease in oxygenation benthic food content and or sedimentation rate if shallow penetrating traces disappear oxygen may be depleted and if the deepest tiers disappear the benthic food content may be lowered 3 3 the size diameter of specific trace fossils can indicate oxygen and benthic food availability 4 4 degree of bioturbation is related to sedimentation rate and benthic food content and the diversity of the whole ichnocoenoses or within a specific tier is affected by oxygenation benthic food content sedimentation rate and substrate consistency 5 5 the type of burrow wall unlined mucus lined pellet lined mainly refers to substrate consistency and subordinately to pore water oxygenation 6 6 the type of sediment displacement by body appendages used for excavation ingestion sideward pressing or outside pumping is related to substrate consistency and grain size

ichnology of a glacially influenced continental shelf and slope the late cenozoic gulf of alaska yakataga formation abstract the study of trace fossils in glaciomarine strata is important because of the low preservation potential of fauna but glaciomarine settings have received little attention from ichnologists widespread biological activity is recorded by ichnofossil assemblages in glaciomarine strata of the late cenozoic 6 ma to present yakataga formation alaska glacial sedimentation began in the gulf of alaska in the miocene along a deep water active margin basin dominated by turbidity currents and debris flows later strata record progradation of the continental slope by mass flow processes and the establishment of a broad shelf influenced by repeated glaciation ice rafting of coarse debris changes in water depth and salinity storms earthquakes and high sedimentation rates yakataga formation strata show overall a limited ichnological diversity and low degree of bioturbation in relation to comparable non glacial settings although certain beds are highly bioturbated twenty four ichnotaxa are identified and grouped into nine assemblages characteristic of different depositional settings and substrate types ichnogenera and body fossil evidence shows that polychaetes arthropods molluscs and echinoderms were the dominant infaunal benthic organisms with deposit feeding being the predominant feeding strategy poorly consolidated muddy sediments excluded suspension feeders and limited the development of the skolithos ichnofacies typical of non glacial shelves characterized by clean shifting sand substrates evidence of rapid sedimentation is given by escape structures fugichnia the presence of diplocraterion and by the mass mortality of bivalves firm ground burrows typical of the glossifungites ichnofacies are associated with erosional surfaces boulder pavements and coquinas diminutive feeding traces may reflect salinities lowered by glacial meltwater inputs the downslope transport of food by turbidity currents and mass flows may explain the development of a diverse cruziana ichnofacies in water depths where in non glacial settings the nereites ichnofacies is found an ichnological summary is presented for the late cenozoic gulf of alaska continental margin similar ecological conditions obtain in the modern setting and provide valuable supportive data ichnofacies identified from the yakataga formation are probably widespread in late paleozoic and late cenozoic glacially influenced marine strata

bottom current controlled sand deposits a review of modern shallow to deep water environments abstract different examples of modern marine sand accumulations generated or strongly influenced by the action of bottom currents are here presented they are drawn from a variety of tectonic and morphological settings and grouped into three water depth zones deep water 2000 m mid water 300 2000 m and outer shelf upper slope 50 300 m deposits in the first two of these depth zones are normal contourites according to their original definition heezen and hollister 1971 being those sediments that have been transported and deposited by contour currents in deep water environments those deposited at shallower depths under the influence of surficial geostrophic currents combined with other hydrodynamic factors shelf currents induced by wind tide and waves gyres internal waves etc are more properly referred to as outer shelf upper slope bottom current sands or shallow water bottom current sands we have elaborated a facies model for each bathymetric zone deep water sandy contourites are relatively rare thin and very thin bedded highly bioturbated and mainly of bioclastic composition they are interbedded with muddy contourites and pelagites or in some areas with turbidites in the latter case thin bottom current reworked sandy tops of turbidites provide a different and distinct facies mid water sandy contourites are more common ranging up to a metre in thickness and may form extensive sandy sheets in a variety of slope bank and channel settings they are mainly of mixed siliciclastic bioclastic composition typically bioturbated and associated with muddy silty contourites in coarsening up fining up complete or truncated sequences shallow water bottom current sands occur in particular outer shelf upper slope settings where they may develop relatively thick 1 20 m laterally extensive sheets covered by fields of sandwaves megaripples and ribbons internal structures may be preserved along with much bioturbation their composition varies from mainly siliciclastic to bioclastic and they may be interbedded with both inner shelf facies and slope hemipelagites the principal factors that control the deposition of sandy contourites and shallow water bottom current sands are the hydrodynamic regime of the basin the availability of coarse grained sandy sediments and the physiographic context of the area swept by the currents the greater the depth the finer and rarer the bottom current or sandy contourite deposits global sea level and climatic changes and the time involved in the depositional history play an ultimate role in the development of important sand accumulations of this sort by controlling the ocean circulation pattern and its long term persistence from the present analysis we conclude that mid depth sandy contourites are the most commonly found in modern environments and that shallow water bottom current sands constitute the most significant potential oil reservoirs to be found in the geological record

lithostratigraphy and deep water setting of the upper nanaimo group upper cretaceous outer gulf islands of southwestern british columbia the upper cretaceous nanaimo group consists of extensive shaly units and lenticular bodies of sandstone and conglomerate deposited in neritic to bathyal marine paleoenvironments single sandstone and conglomerate lenses cannot be traced throughout the basin but instead tend to concentrate at particular stratigraphic levels defining crudely sheet like composite units of coarse grained rocks many of the lenticular coarse grained units rest in major channels as deep as about 550 m sand and gravel were generally transported to the west and northwest by sediment gravity flows through these channels into the basin centre recognition of widespread channeling is critical to the definition of formal lithostratigraphic units four formations and two informal members are defined here for the upper nanaimo group the top of the nanaimo group is probably truncated by a major unconformity with local relief of at least 2 km the effect of the unconformity can only be seen by mapping the orientation of offshore rid

deformed cross stratified deposits in the early pleistocene tidally dominated catanzaro strait fill succession calabrian arc southern italy triggering mechanisms and environmental significance abstract the early pleistocene catanzaro strait fill succession consists of large scale tidal sets accumulated in a tectonically confined basin during a phase of rapid relative sea level rise it crops out mainly in the present day catanzaro trough where numerous field sections supported the characterization of the vertical and lateral facies variations and the documentation of a variety of soft sediment deformation structures exposed throughout their vertical and lateral extents the soft sediment deformation structures ssds are the result of liquefaction and fluidization processes that deformed cross laminations and other primary structures into folds fluid escape structures and structureless expanses three different groups of ssds have been documented in the cross stratified deposits of the catanzaro strait the detailed description of these soft sediment deformation structures in a depositional context established by facies analysis enables interpretation in terms of possible trigger mechanisms consistent relationships between the occurrence of distinctive ssds and specific tidally dominated facies have been established indicating a probable autogenic origin for the soft sediment deformations liquefaction and fluidization features are interpreted as the result of increases in water pore pressure induced by overloading in particular two types of overloading agents are hypothesized which affect the lee and stoss sides of the migrating dunes in distinct events and inducing the deformation of foreset laminae or sets of cross strata respectively

heavy metal pollution in the quaternary garza basin a multidisciplinary study of the environmental risks posed by mining linares southern spain abstract in the metallogenic district of linares jaen spain intense deep mining associated with vein type deposits of pb and cu has been conducted for centuries and has generated large mine waste accumulations the objective of this study was to elucidate the influence of these mine wastes on the quality of the soil the surface water and the groundwater for this purpose a sedimentary endorheic basin in the mining district was selected as the study location the quaternary garza basin the characterisation of the basin geometry and the tailings dams in the area was conducted by electrical resistivity imaging eri which was supported with data provided by mechanical probing the eri data indicated that the basin is bounded by fractures that cause sudden changes in the thickness of the sedimentary cover and the wedging of the layers toward the edges of the basin furthermore the resistivity profiles allowed the morphological identification of the deposits associated with the tailings dams in addition zones of weakness preferential groundwater flow paths and the contact between the slimes deposits and the substratum were identified these results confirmed the absence of impervious barriers at the tailings sites which is a situation that poses a high pollution risk for soils and waters a geochemical characterisation of the tailings dams and the surrounding soils indicated the presence of a high concentration of metals and metalloids of the 19 elements analysed at the dams it is important to highlight the following values expressed in mg kg 1 19 913 for pb 418 for cu 4149 for mn 43 for as 190 for zn and 26 200 for fe furthermore the hydrochemical data showed the mobilisation through the aqueous media of certain heavy elements fe mn and pb that originate from lixiviation at these ancient tailings impoundments and from the adits that drain mine waters

a facies based depositional model for ancient and modern tectonically confined tidal straits modern and ancient tidal straits are the least well understood of all tide dominated depositional systems to provide an increased understanding of these systems a facies based depositional model is assessed by comparing multibeam surveys of three present day tidally dominated seaways with a number of superbly exposed neogene to quaternary strait fill successions of calabria south italy the model points out the existence of four depositional zones laterally adjacent from the narrowest strait centre to its terminations distributed along symmetrical or asymmetrical seaways these zones whose signature is recorded in four facies associations in the calabrian tidal straits are as follows i the strait centre zone associated with the tidal current maxima and where sediments are scarce or absent ii the dune bedded zone where sediments form dune complexes due to tidal flow expansion iii the strait end zone where currents decelerate accumulating thinly bedded fine grained deposits and iv the strait margin zone where sediment massflows descend tectonically active steep margins towards the strait axis in ancient tectonically confined narrow seaways these facies generate a distinctive deepening upward vertical succession where tidal currents are the dominant process in the sediment distribution

waveform analysis of scholte modes in ocean sediment layers summary in an effort to determine the characteristics of seismic noise on the ocean bottom and its relationship to the structure of the sea floor we have adapted the method of nonlinear waveform fitting to accommodate multidimensional models shear velocity j and shear damping qs and have applied it to invert several records of interface waves scholte 1958 from the thumper experiment off southern california waveform fitting is a very powerful tool to determine the s velocity in the top few metres of the sediment starting from 30 m s l at the top clay layer the s velocity increases with a gradient of 2 8 m sk1 m over the first 150 m of sediment a theoretical estimation of the source strength gives coherent estimates of qs as a function of depth for distances between 400 and 1070m from the source the qs models are characterized by very low values 10 20 in the top three metres but by values in excess of 100 below that level the results confirm the identification of the noise as harmonics of interface waves in the area of this experiment the largest noise amplitudes belong to the fundamental mode and penetrate to a depth of about 20 m into the sediment the overtone energy can be appreciable too and is noticeable to about 80m depth the qs structure confirms the strong influence that the sea floor structure has on the noise spectrum the high attenuation at frequencies above 3 4 hz suppresses noise propagation and produces low noise at higher frequencies similarly high attenuation in the asthenosphere suppresses noise propagation below 0 1 hz

bedform distribution and inferred sand transport on georges bank united states atlantic continental shelf four bedform provinces have been identified on georges bank using sidescan sonar and echo sounding techniques large sand waves superimposed on sand ridges small sand waves megaripples and featureless seafloor the large sand waves and sand ridges are found on the bank crest where the surface tidal currents are strongest areas of small sand waves and megaripples formed where tidal currents are moderate in strength border the area of large sand waves to the north and south featureless seafloor is found farthest from the bank crest where surface tidal currents are weakest sand wave asymmetry and surface sediment texture have been used to infer bedload transport paths on georges bank in the large sand wave area bedforms indicate a clockwise transport around each of the linear north west striking sand ridges with slight convergence of the sand waves on the ridge crests this transport pattern implies erosion from the troughs and accumulation on the sand ridges the asymmetry of the small sand waves along the south side of georges bank indicates that sand is also transported southward away from the linear sand ridges on top of the bank although the asymmetry of megaripples could not be determined the occurrence of megaripples between the small sand wave province and areas of featureless seafloor suggests a decreasing effectiveness of sand transport away from the bank crest this sand dispersal pattern is further supported by the surface sediments which become progessively finer to the north and sw away from the crest of georges bank

structural and geomorphological constraints on active normal faulting and landscape evolution in calabria italy calabria is one of the fastest uplifting and most seismically active regions in the mediterranean yet the time averaged c 10 6 years rates of normal faulting remain poorly constrained here we use digital elevation model analysis geological cross sections and a compilation of published data to quantify systematically along strike the fault throws and time averaged throw rates of the serre cittanova armo east crati and west crati faults we show that regional uplift has uplifted both their hanging wall and footwall blocks by c 200 400 m and the aspromonte massif by up to c 1150 1300 m we find that these faults have throws between c 640 and 1430 m and throw rates between c 0 6 and 1 4 mm a 1 their footwall ranges have variable proportions of inherited relief up to c 300 800 m the channels draining these ranges reflect the active normal faulting and relief in their steepness indices becoming c 5 8 m 0 9 steeper for each 0 1 mm a 1 throw rate increment and each 100 m relief increase finally the presence of knickpoints suggests that these channels are transiently responding to changes in relative base level which could be due to fault linkage or regional strain rate increases for the southern calabrian faults and to regional uplift acceleration in the case of the crati faults supplementary material topographic profiles of the marine terraces and long profiles of rivers are available at https doi org 10 6084 m9 figshare c 3689464

on the use of the norwegian geotechnical institute s prototype seabed coupled shear wave vibrator for shallow soil characterization i acquisition and processing of multimodal surface waves summary pure shear wave data are only very rarely acquired for offshore site investigations and exploration here we present details of a novel seabed coupled shear wave vibrator and field data recorded by a densely populated multicomponent ocean bottom cable to improve shallow soil characterization the prototype shear wave vibrator uses vibroseis technology adopted for marine environments through its instalment on top of a suction anchor assuring seabed coupling in combination with self weight penetration the prototype is depth rated to 1500 m water depth and can be rotated while installed in the seabed the philosophy is to acquire fully complementary seismic data to conventional p and p to s converted waves in particular for 2 d profiling vsp vertical seismic profiling or monitoring purposes thereby exploiting advantages of shear waves over compressional waves for determining for example anisotropy small strain shear modulus and excess pore pressures effective stress the source was primarily designed for reservoir depths however significant energy is emitted as surface waves which provide detailedgeotechnicalinformationthroughmappingofshearwavevelocitiesinpotentiallyhigh resolution of the upper soil units to fully utilize pure shear wave content a proper analysis of surface waves is paramount due to the proximity of surface wave propagation speed with shear wave velocities the experiment was carried out in the northern north sea in 364 m water depth cable dragging was necessary to obtain close receiver spacing 2 5 m effective spacing with total line length of 600 m frequency waveform transforms reveal both scholte and love waves up to six surface wave modes are identified that is fundamental mode and several higher surface wave modes the occurrence of these two different dispersive surface wave types with well resolved higher modes allows for a unique analysis and inversion scheme for highresolution mapping of physical properties in the shallow subsurface as well as anisotropy which is discussed in an accompanying paper the data presented in this paper are thus a unique long and densely populated receiver array allows for multimodal love and scholte surface waves from the marine environment but challenging marine operations marine data set

present day kinematics of the plate boundary zone between africa and europe from the azores to the aegean anticlockwise rotation of africa relative to europe around an euler pole in the eastern atlantic causes plate convergence in the central mediterranean towards n20 w at rate considered a priori to be 5 10 mm yr 1 however previous summaries of the present day deformation sense in the central mediterranean are inconsistent with observations in southern italy recent investigations of italy and adjacent parts of north africa enable local deformation sense observed to be reconciled with sense predicted from relative plate motions suggested angular velocity of the african plate relative to europe is 0 07 myr 1 around a pole near 21 n 21 w this predicts 2 6 mm yr 1 maximum extension rate towards n64 e near the azores consistent with the minimum local accretion of new oceanic crust in the past few millions of years and 4 3 mm yr 1 plate convergence towards n20 w in the central mediterranean at 13 e further east the northern margin of the african plate can be regarded as the gargano seismic zone in the central adriatic sea the northern adriatic sea is a microplate rotating anticlockwise relative to europe at 0 3 myr 1 around a pole in northwestern italy causing northeastward shortening in yugoslavia and up to 4 mm yr 1 extension in central and northern italy the african plate is deforming internally in tunisia and northern libya extending obliquely in direction e10 s at rate up to 5 5 mm yr 1 the resultant velocity relative to europe in the ionian and southern adriatic seas 5 mm yr 1 towards n50 e explains the observed relative velocity across southern italy kinematic consistency requires present day shortening rate east of calabria associated with subduction on the tyrrhenian sea benioff zone and tyrrhenian sea extension rate to be both zero or equal to within 1 mm yr 1

attenuation mechanisms in sands laboratory versus theoretical biot data the velocity and attenuation of compressional q 1p vp respectively and shear waves q 1s vs respectively determined with the pulse transmission technique at a frequency of about 100 khz are compared with the grain size shape porosity density and static frame compressibility of dry and water saturated sands except for vs all the quantities vp q 1p and q 1s are dependent on grain size and are higher in coarser grains than in finer grains q 1s decreases significantly with increasing differential pressure in coarse grained sediments but the same sediments show an anomalous increase with differential pressure in q 1p at low pressures we have also modeled the vp vs q 1p and q 1s of these samples to understand the mechanisms governing the observed changes the contact radius model with surface force effects predicts both vp and vs to be dependent on grain size frictional losses in unconsolidated coarse grained sands must also be considered at small strains 10 7 velocity and losses measured

shear wave velocities and anisotropy in the barbados accretionary complex s wave velocities at the base of the barbados accretionary wedge were determined from mode converted s waves in two vertical seismic profiles in ocean drilling program boreholes at hole 949c the profile extends from 92 to 397 m below seafloor mbsf ending 17 m into the decollement zone separating the wedge from the underthrust sediment on the subducting plate beneath at hole 948d the profile extends from 105 to 471 mbsf ending 19 m above the decollement zone s wave velocities are 303 549 m s at hole 949c and 453 679 m s at hole 948d the profiles show that the lowest 70 m of the accreted sediment just above the decollement has lower s wave velocity 379 26 m s at hole 949c and 453 11 m s at hole 948d and higher ratio of p wave to s wave velocity vp vs 4 59 0 31 at hole 949c and 3 99 0 10 at hole 948d than in the overlying layer this coincides with high clay content that has a high proportion of smectite shear wave splitting observed in records from the lowest 100 m of the accretionary wedge at both sites indicates little or no anisotropy in the low velocity zone a single measurement at hole 949c of the horizontal component of polarization of the leading split s wave from an ocean bottom shot is n68 e 20 at hole 949c split shear wave delays in the downward propagating s wave originating at a fault at 275 mbsf indicate strong anisotropy in the range 275 306 mbsf and little or no anisotropy in the range 306 380 mbsf the rate of increase of delay between 275 and 306 mbsf 0 52 0 16 ms m can be modeled by either a hudson cracked medium with crack density 0 186 0 054 or preferably a hornby model of shale with 44 of clay particles aligned within 5 of the symmetry plane this strong anisotropy is attributed to scaly fabric alignment of clay particles by pervasive shear in the fault zone which is observed in core the low anisotropy in the remainder of the section shows that there is very little overall alignment of pore space in the lower part of the accreted sediments supporting the hypothesis that the sediments are undercompacted rather than hydrofractured the low s wave velocities and high vp vs ratios indicate undercompaction and low effective stress despite the tectonic burial of the lowermost accreted sediments

seismic attenuation from recordings of ambient noise abstractwe applied seismic interferometry to data from an ocean bottom survey offshore norway and found that ambient seismic noise can be used to constrain subsurface attenuation on a reservoir scale by crosscorrelating only a few days of recordings by broadband ocean bottom seismometers we were able to retrieve empirical green s functions associated with surface waves in the frequency range between 0 2 and 0 6 hz and acoustic waves traveling through the sea water between 1 0 and 2 5 hz we discovered that the decay of these surface waves cannot be explained by geometrical spreading alone and required an additional loss of energy with distance we quantified this observed attenuation in the frequency domain using a modified bessel function to describe the cross spectrum in a stationary field we averaged cross spectra of equally spaced station couples and sorted these azimuthally averaged cross spectra with distance we then obtained frequency dependent estimates of attenuation by minimizing the misfit

fossil contourites a critical review abstract despite three decades of study there is still great controversy over the recognition and interpretation of fossil contourites exposed in ancient series on land in order to best examine this problem we briefly review the evidence from modern systems including the many examples of cenozoic contourites that have been recovered from dsdp odp drilling on major drifts in the present day oceans the range of contourite facies described from both deep water 2000 m and mid water 300 2000 m drifts are mostly fine grained bioturbated and homogeneous often with a distinct bedding cyclicity and with some coarser grained sandy contourites developed under higher energy bottom currents there are also a number of current controlled sediment bodies that have formed in outer shelf upper slope settings 50 300 m under the influence of counter currents underflows and major surface currents these are not considered contourites sensu stricto but may be mistaken as such in ancient examples the most commonly described fossil contourites in the literature have been interpreted by the authors concerned as bottom current reworked turbidites however a critical review suggests that these are the facies most subject to misinterpretation and many of the sediments claimed as fossil contourites are almost certainly fine grained turbidites whereas others were more likely formed under outer shelf upper slope current systems there remain very few ancient examples that are more closely comparable to modern contourites these include the cretaceous talme yafe formation in israel the ordovician jiuxi drift in china and parts of the paleogene lefkara formation cyprus and the neogene misaki formation in japan we present a set of possible criteria for the recognition of fossil contourites and bottom current reworked turbidites

an ichnofabric approach to the depositional interpretation of the intensely burrowed bateig limestone miocene se spain abstract the foraminiferal rich pelagic bateig limestone forms several varieties of the important building stones quarried at bateig hill in southeastern spain three principal ichnofabrics bichordites mottled palaeophycus and mottled ophiomorpha are recognized which are present in at least two possibly up to four repeated successions cycles each succession begins with an erosional event the bichordites ichnofabric represents a new type of facies formed as thin turbidity grain flow stratiform units derived from sediment slips off a fault into deep water each slipped unit became almost completely bioturbated by infaunal echinoids colonizing by lateral migration because of the thinness of the units successive colonizations tended to truncate the underlying burrows giving rise to a pseudo stratification as the bichordites ichnofabric accumulated on the fault apron thus reducing the effective height of the fault scarp the substrate gradually came under the influence of currents traversing the shelf this led to a change in hydraulic regime and to the mottled palaeophycus and mottled ophiomorpha ichnofabrics in sediment deposited under bed load transport and associated with laminar and cross stratified beds and local muddy intervals reactivation of the fault triggered erosion and channeling and a return to grain flow sedimentation and to the bichordites ichnofabric of the succeeding cycle the highest unit of the bateig limestone is formed entirely of cross stratified calcarenites with occasional ophiomorpha ophiomorpha primary lamination ichnofabric and is similar to many shallow marine facies but they still bear a significant content of pelagic foraminifera the sedimentary setting bears resemblance with that described for the pleistocene monte torre paleostrait and the modern strait of messina italy where the narrow morphology of the depositional area enhanced tidal currents and allowed for high energy sandy deposition in relatively deep areas more data on the miocene paleogeography of the bateig area should provide further testing for this hypothesis the ichnofacies and stacking of the bateig limestone differ from the classic seilacherian model in that they reflect changes in hydraulic process and are associated with faulting and subsidence and changes in sediment supply recognition of the unusual ichnofabrics and their relationships provides a clear indication of the overall dynamic setting

widespread syn eruptive volcaniclastic deposits in the pleistocenic basins of south western calabria abstract since late tortonian depositional sequences developed along the southern calabrian forearc inside the half graben depressions of the mesima gioia tauro and reggio calabria basins in these basins volcaniclastic sedimentation took place during lower to middle pleistocene volcaniclastic deposits consist of isolated pumice swarms ash layers and thick successions of lapilli and ash in this paper we describe and discuss the depositional characteristics of these volcanogenic sediments and the morphology mineralogy and chemistry of pumices shards lithics and crystal fragments these deposits all have the characteristics of a proximal tephra fall deposit from a plinian plume which has been reworked in a shore environment in the mesima basin the deposits reach 6 m in thickness and in the gioia tauro plain 21 m of pumiceous sediments have been cored in a drill hole the compositional homogeneity of fragments and the absence of non volcanic detritus as well as of soil or organic matter suggest that the deposits were quickly reworked after their primary emplacements all the tephra deposits exhibit calc alkaline affinity and dacitic to rhyolitic composition the mineralogical assemblage including orthopyroxene as phenocryst indicates provenance from magmatic arc volcanism icp ms and la icp ms analyses of crystals and glass point to a common origin probably from a single eruption this makes these volcaniclastic layers a very useful tool for stratighaphic reconstructions at a regional scale the geological setting of the deposits their petrological and geochemical signature and the occurrence of large size clasts suggest a provenance from explosive eruptions preceding the emplacement of the 50 ka dacitic lava dome of the island of panarea aeolian archipelago however a provenance from a different calc alkaline volcanic system cannot be excluded these deposits can therefore represent the only evidence of a large explosive eruption in the southern tyrrhenian sea whose very proximal equivalent is not preserved

detrital modes of the ionian forearc basin fill oligocene quaternary reflect the tectonic evolution of the calabria peloritani terrane southern italy abstract during oligocene neogene time the calabria peloritani terrane cpt a small block of continental lithosphere rifted from the southern margin of the eurasian continent and drifted southeastward to collide with the african continent along the leading edge of the cpt a late oligocene to quaternary mostly siliciclastic succession 2 000 meters thick was deposited in the ionian forearc basin the detritus forming the succession was derived directly from the erosion of the nearby cpt composed of hercynian plutons intruding metasedimentary host rocks contrary to most modern and ancient forearc basins penecontemporaneous volcanic detritus is virtually absent this results from rift related topographic barriers which separated the forearc basin from the associated volcanic arc in spite of an overall quartzofeldspathic continental block provenance the analysis of a large sandstone and conglomerate petrological dataset 228 samples points to three discrete detrital inputs of aphanitic lithic fragments in i late oligocene early miocene ii late messinian and iii quaternary times these petrological variations can be linked to independently determined tectonic events in the western mediterranean which likely modified the lithologic composition of the sediment source terranes input i documents the progressive widespread unroofing of the continental basement of the southern european margin when northwestward subduction of the remnants of the ligurian ocean began input ii is related to widespread intra messinian tectonism possibly due to out of sequence thrusting induced by isostatic readjustments of the perimediterranean orogenic wedges following the messinian drawdown input iii reflects the rapid vertical uplift experienced by the cpt since mid pleistocene time possibly the result of slab detachment along the ionian subduction zone this study indicates that detailed statistical analysis of the detrital modes of ancient terrigenous deposits can be used to identify the tectonic events affecting somewhat petrologically monotonous sediment source areas within small lithospheric terranes

modeling of long period ground motions in the nankai subduction zone model simulation using the accretionary prism derived from oceanfloor local s wave velocity structures the accretionary prism in the subduction zone which consists of thick low velocity oceanic sediments significantly affects the propagation of seismic waves for shallow offshore earthquakes including large interplate earthquakes in order to simulate long period 5 s ground motions in the nankai subduction zone we constructed a three dimensional 3d seismic velocity structure model of the accretionary prism by interpolation extrapolation of local s wave velocity structures beneath 46 oceanfloor seismic stations donet which are deployed just above the accretionary prism off the southern kii and eastern shikoku regions we modeled local s wave velocity structures using a simple two parameter depth varying velocity function to investigate the effects of the accretionary prism on ground and seafloor motions we conducted numerical simulations of seismic wave propagation for three local earthquakes that occurred in southwestern japan the simulations reasonably reproduced the observed seismograms not only for the period ranges of the moment tensor inversion 50 s but also for the strong long period ground motions in the sedimentary basins 5 s especially in the region where donet stations are densely deployed since depth varying local s wave structures significantly improve the reproducibility of long period ground motions our modeling procedure is useful for modeling long period ground motions of local and regional offshore subduction zone earthquakes

factors controlling shelf sediment dispersal along the southeast african continental margin abstract four major factors control sediment dispersal along the southeast african continental margin 1 morphology of the upper continental margin 2 wave regime and wind driven circulation 3 influence of the agulhas current and 4 sediment supply these factors interact on various scales to produce a unique regional sediment dispersal pattern the continental shelf is very narrow and the adjacent slope extremely steep the shelf platform is interrupted by a number of structural offsets and locally the shelf break is dissected by numerous submarine canyons the nearshore zone down to about 60 m waterdepth is dominated by a high energy swell regime and in most places is underlain by a thin wedge of sandy sediment this wedge appears to have achieved dynamic equilibrium with the prevailing energy regime and additional sediment is rapidly dispersed and fed into a sandstream situated on the central shelf where the agulhas current dominates sediment transport along some parts of the coast the sediment wedge is dammed behind a drowned coastal dune ridge within the sandstream sediment is transported alongshelf until a structural offset is reached where sediment spills over the shelf break four major localities for off shelf transport are recognized between maputo and port elizabeth most of the suspended load appears to be expelled from the system without being deposited on the shelf in the lee of each offset a clockwise gyre is developed which produces return flow currents capable of moving sediment northward thereby creating bedload partings in the vicinity of these partings depositional features are observed that are similar to those normally associated with tidal regimes e g bedforms migrating in opposite directions most of the bedload sediment entering the system is eventually deposited in well defined sinks situated in the lee of structural offsets this model applies only to inter glacial high sea level situations accompanied by strong western boundary flow of the agulhas current

relationships between fault controlled subsidence and preservation of shallow marine small scale cycles example from the lower pliocene of the crotone basin southern italy abstract the northern part of the crotone basin southern italy was characterized by the activity of pliocene growth faults bounding half graben sub basins the thickest unit deposited during growth fault activity is the lower pliocene belvedere formation up to 450 m thick which shows a small scale highly regular rhythmic cyclicity this sandstone unit was deposited in a shallow marine environment and its accumulation was mostly influenced by storm processes and locally by flows in tectonically confined areas the meter scale cycles are represented by rhythmic alternations between shell rich intervals characterized by storm structures or large scale cross sets and shell poor sandy intervals that are commonly burrowed and poorly stratified the better preserved cycles commonly show a fining upward trend with minor progradation in their upper part and may be bounded at the base by a shell lag the deposition of large scale cross sets is thought to be the consequence of the creation of fault scarps which led to tectonic confinement in the half graben basins in the tectonically confined areas tidal currents were enhanced and large subaqueous dunes migrated the evidence suggests that the observed cyclicity was generated by sea level and climatic variations that controlled the sediment input into the basin the relationship between large scale cross sets and tectonic confinement demonstrates that local extensional tectonics significantly influenced the sedimentation the excellent preservation of the observed small scale cycles is thought to be the consequence of deposition in the highly subsiding half graben sub basins on the structural highs this cyclicity is amalgamate and less appreciable the data presented may be significant for a better understanding of the role of subsidence in preserving sedimentary successions in these growth faulted settings

coexistence of gravity waves and elastic waves in unconsolidated sediments based on a linear viscoelastic model we study the coexistence and transition of gravity waves and surface elastic waves in a half space of unconsolidated sediment the dispersion relation and surface response are calculated as a function of the period and rigidity of the system the dispersion relation shows two branches one branch corresponds to a rayleigh wave for short wave periods and it becomes a leaky surface wave as the period increases the second branch shows a linear dependence of the phase velocity with period as expected for gravity waves as the period increases this branch evolves into a leaky surface wave joining the first branch the surface response function which is related to the vertical displacement is also calculated two distinct peaks are present in the surface response function one corresponds to a classical rayleigh wave while the second is a gravity driven mode whose amplitude is strongly dependent on the wave period and soil rigidity

paleoecology of the marine endobenthos endobenthic animals which reside within the sea bottom include stationary suspension feeders mobile deposit feeders and both stationary and mobile carnivores their activities especially with regard to dwelling feeding walking crawling and resting nesting are recorded as trace fossils abundance diversity and density of some kinds of trace fossils allow interpretation of the population strategies of the trace makers in terms of opportunistic r selected and equilibrium k selected strategies opportunistic ichnotaxa tend to be faciesbreaking traces which are highly localized in low diversity high density trace fossil associations in rocks representing environmental extremes e g variable salinities harsh temperatures low oxygen levels or shifting substrates equilibrium ichnotaxa usually are restricted to particular sedimentary facies and are characteristic of high diversity low dominance trace fossil associations in sediments reflecting stable predictable environmental conditions the most important environmental factors influencing the composition of trace fossil assemblages in marine settings are bathymetry substrate oxygen and hydrodynamic energy the four factors are closely interrelated because as water depth increases there is a general decrease in sediment grain size and hydrodynamic energy of the depositional environment as depth below the water sediment interface increases the firmness of the sediment due to compaction and dewatering increases and the oxygen content of interstitial waters drops drastically marine ichnofacies are largely substrate controlled soupgrounds are water saturated incompetent substrates typified by highly compressed and usually unidentifiable burrows softgrounds commonly contain numerous distinctive burrows and are zoned bathymetrically by the skolithos cruziana zoophycos and nereites ichnofacies firmgrounds are characterized by stiff compacted sediments in which traces of the glossifungites ichnofacies are excavated hardgrounds are cemented substrates in which bioerosion traces of the trypanites ichnofacies are bored woodgrounds are woody materials that have been exposed to the sea and bored by bivalves which produce characteristic traces of the teredolites ichnofacies tiering of endobenthic communities is common and is related to substrate preference of the burrowers and oxygen stratification of interstitial waters

jasper seamount structure seafloor seismic refraction tomography the velocity structure of jasper seamount was modeled using one and three dimensional inversions of p wave travel times the results represent the first detailed seismic images of a submerged intraplate volcano two seismic refraction experiments were completed on jasper seamount incorporating ocean bottom seismometers and navigated seafloor shots the p wave travel times were first used to compute a one dimensional velocity profile which served as a starting model for a three dimensional tomographic inversion the seamount p velocities are significantly slower than those observed in typical oceanic crust at equivalent subbasement depths this suggests that jasper seamount is constructed predominantly of extrusive lavas with high average porosity the velocity models confirm morphological predictions jasper seamount is a shield volcano with rift zone development high seismic velocities were detected beneath the large radial ridges while low velocities characterize the shallow summit and flanks comparisons between p velocity models of jasper seamount and the island of hawaii reveal that these two shield volcanoes are not structurally proportional jasper seamount is far smaller than hawaii yet both volcanoes exhibit an outer extrusive layer of similar thickness this suggests that seamount size influences the intrusive extrusive proportions density equilibrium between melt and country rock may explain this behavior

threshold of erosion of submarine bedrock landscapes by tidal currents since sea level stabilized 7000 yr bp shelf seas experiencing semi diurnal tides will have been affected by streaming four times per day if tidal erosion of bedrock were even only marginally efficient the 10 million streamings since then should have left geomorphological imprints we examine high resolution multibeam sonar data from three areas with extreme tidal currents the minas passage bay of fundy experiencing 8 knot surface tidal currents was surveyed in 2007 with a multibeam sonar in an area near to transverse dunes which are evidence for bedload transport the data show local overhanging surfaces near to the sediment rock contact potentially created by abrasion by saltating particles however they are uncommon in the straits of messina where surface currents reach 10 knots surveying revealed ridges lying oblique to the flow that are not obviously broken into separate outcrops by erosion in the bristol channel uk sonar data collected where currents reach 3 4 knots at 1 5 m above the bed reveal outcrops of limestone with superimposed sand dunes but only minor rounding of blocks holocene tidal currents have apparently been generally ineffective at eroding bedrock we examine this issue further by compiling extreme tidal streams around the uk and from them estimate shear stresses representing a macro tidal environment where peak surface currents reach 9 7 knots those data are compared with shear stresses in mountainous rivers where long term rates of erosion are comparable with tectonic uplift rates and are thus geomorphologically significant whereas river stresses reach 102 103 pa the largest tidal stresses are generally 101 and only rarely approach 102 pa too small for quarrying to operate generally however the vertical faces in the minas passage may represent the onset of abrasion given this limited evidence for abrasion we explore conditions in the geological past for tides that may have locally eroded bedrock

estimation of gas hydrate concentration from multi component seismic data at sites on the continental margins of nw svalbard and the storegga region of norway high resolution seismic experiments employing arrays of closely spaced four component ocean bottom seismic recorders were conducted at a site off western svalbard and a site on the northern margin of the storegga slide off norway to investigate how well seismic data can be used to determine the concentration of methane hydrate beneath the seabed data from p waves and from s waves generated by p s conversion on reflection were inverted for p and s wave velocity vp and vs using 3d travel time tomography 2d ray tracing inversion and 1d waveform inversion at the nw svalbard site positive vp anomalies above a sea bottom simulating reflector bsr indicate the presence of gas hydrate a zone containing free gas up to 150 m thick lying immediately beneath the bsr is indicated by a large reduction in vp without significant reduction in vs at the storegga site the lateral and vertical variation in vp and vs and the variation in amplitude and polarity of reflectors indicate a heterogeneous distribution of hydrate that is related to a stratigraphically mediated distribution of free gas beneath the bsr derivation of hydrate content from vp and vs was evaluated using different models for how hydrate affects the seismic properties of the sediment host and different approaches for estimating the background velocity of the sediment host the error in the average vp of an interval of 20 m thickness is about 2 5 at 95 confidence and yields a resolution of hydrate concentration of about 3 if hydrate forms a connected framework or about 7 if it is both pore filling and framework forming at nw svalbard in a zone about 90 m thick above the bsr a biot theory based method predicts hydrate concentrations of up to 11 of pore space and an effective medium based method predicts concentrations of up to 6 if hydrate forms a connected framework or 12 if hydrate is both pore filling and framework forming at storegga hydrate concentrations of up to 10 or 20 were predicted depending on the hydrate model in a zone about 120 m thick above a bsr with seismic techniques alone we can only estimate with any confidence the average hydrate content of broad intervals containing more than one layer not only because of the uncertainty in the layer by layer variation in lithology but also because of the negative correlation in the errors of estimation of velocity between adjacent layers in this investigation an interval of about 20 m thickness equivalent to between 2 and 5 layers in the model used for waveform inversion was the smallest within which one could sensibly estimate the hydrate content if lithological layering much thinner than 20 m thickness controls hydrate content then hydrate concentrations within layers could significantly exceed or fall below the average values derived from seismic data

marine volcaniclastics of the hidden lake formation coniacian of james ross island antarctica an enigmatic element in the history of a back arc basin

late pliocene early pleistocene athalassa formation north central cyprus carbonate sand bodies in a shallow seaway between two emerging landmasses the late pliocene early pleistocene athalassa formation accumulated within the neogene mesaoria basin of northern cyprus bordered by two subdued but rising landmasses the kyrenia range to the north and the troodos ophiolitic massif to the south in the eastern part of the basin the formation is dominated by cross stratified bioclastic rich sandstones interpreted as shallow marine carbonate sand bodies the sediments are described in terms of six calcarenite facies and subfacies and one sandstone fades palaeocurrent analysis indicates that the carbonate sand bodies formed near the southern margin of the kyrenia landmass and then migrated southwards across a shallow marine platform the driving force is believed to have been storms generated by strong winds such winds during the late pliocene early quaternary were probably stronger than today in this area other factors influencing deposition of the formation include minor tectonic instability and probable eustatic sea level changes study of the athalassa formation thus provides insights into late pliocene pleistocene palaeoenvironments in the easternmost mediterranean

defect microdynamics in minerals and solid state mechanisms of seismic wave attenuation and velocity dispersion in the mantle the propagation of seismic waves in the earth s mantle can be significantly affected by relaxation processes causing attenuation and velocity dispersion reduction this paper reviews the solid state mechanisms of relaxation processes based on the theory of defect microdynamics in solids together with some experimental observations on defects in minerals particularly in olivine for a given mechanism to have a significant effect on seismic wave propagation both the density and the mobility of the defects must be in an appropriate range the examination of the densities and geometry and mobilities of defects in olivine shows that dislocation and or grain boundary mechanisms can have a significant effect on seismic wave propagation although wide distributions of geometrical factors such as spacing of pinning points and of mobilities are required to explain all available data point defect mechanisms however are unlikely to be important because their densities are too small and or their mobilities are too large since the dislocation density and or grain size are determined in most cases by the long term tectonic stress seismic wave attenuation and velocity dispersion reduction involving these defects are likely to depend on the magnitude of the tectonic stress as well as the temperature theoretical considerations suggest a wide range of dependence of seismic wave attentuation and velocity dispersion on the long term tectonic stress this is particularly the case for dislocation mechanisms and warrants careful experimental investigation dislocations and or grain boundaries cause anelastic behavior relaxation peaks when they are pinned or blocked at some points pinning or blocking becomes ineffective at high temperatures and or low frequencies causing a transition to viscoelastic behavior both laboratory and seismological observations of internal friction are dominated by the high temperature background where internal friction increases monotonically with temperature which can be interpreted as a gradual transition to viscoelastic behavior or to a wide distribution of relaxation times however in most experimental studies to date the dislocation densities or the grain sizes were not well controlled making it difficult to identify the attenuation mechanisms and preventing any quantitative applications to earth the need for better characterization of defect microstructures in experimental specimens is emphasized

coupled seismoacoustic modes on the seafloor 1 wave to wave coupling arises when an acoustic pulse selects a rayleigh mode of the same speed and both travel together swapping energy across an interface ewing et al 1957 a distinctive signal is observed at the hawaii 2 observatory for purely oceanic paths from earthquakes on the blanco and mendocino fracture zones off the coast of north america the signal appears to be a composite of undispersed higher rayleigh modes propagating along the ocean floor both in the sediments and in the water the new coupled modes are identified by their frequency composition and their phase and group velocities seismoacoustic coupling at the seafloor is conditioned on a the presence of a low velocity interface at the ocean floor and b the wavelength of the rayleigh component being shorter than the depth of the water layer

interplay of tidal and fluvial processes in an early pleistocene delta fed strait margin calabria southern italy abstract the architecture and morphodynamics of modern and ancient tidal straits and in particular the deposits of strait margin zones have been significantly understudied compared to other marginal marine settings even though many reservoirs in the north sea and the norwegian continental shelf are developed in narrow grabens or seaways this paper presents a detailed sedimentological and stratigraphic analysis of an early pleistocene marginal marine succession deposited along the northern margin of the siderno paleostrait southern italy this area represents an excellent case study of sedimentation along a tidal strait margin interpreted to record the interaction of fluvial and tidal processes here syn depositional tectonics produced a complex coastal morphology significantly influencing sedimentation and hydrodynamic processes along the strait margin the emplacement of an isolated tectonic high piano fossati created a ca 3 5 km wide local passageway this morpho structural element induced interplays between fluvio deltaic processes fed from the northern strait margin and tidal current reworking active within the marine strait the field based facies analysis reported here documents an initial stage of non tidal shallow marine sedimentation across the strait a subsequent regression caused river generated hyperpycnal flows and the transfer of large volumes of pebbly and shelly sandstones into deeper water tidal currents became amplified in the strait and in the delta front area they were able to rework river derived sediments generating large dune fields following the local tidal transport pathway strong tidal currents skewed the delta front causing it to be asymmetrical and elongated sand bodies in a direction parallel to the marine strait axis differently from the classical tide influenced deltas in which onshore offshore tidal flow predominates coast parallel deflection and strong asymmetry of delta front deposits is a typical feature of deltas entering tide dominated seaways and straits where strong tidal currents are capable of dispersing large volumes of sand for significant distances along the coast and along the strait axis this process became progressively enhanced during the following transgression when tide modulated currents reworked biocalcarenitic sands over the previous delta deposits generating southeasterly migrating dunes at the end of the transgression strandplain deposits formed in this area this last stage of sedimentation was followed by a dramatic regional scale structural uplift which ended any marine circulation within the strait this work provides new insights on sedimentation in a tide dominated strait and helps to predict sandbody distribution along the strait margin and axis these findings can be applied to any other setting characterized by a narrow possibly structurally confined basin dominated by tidal currents

holocene sedimentation in the shallow nearshore zone off nauset inlet cape cod massachusetts abstract present conditions and sedimentary evolution of the shallow offshore region near nauset inlet on cape cod massachusetts were clarified using high resolution seismic reflection profiles sidescan sonar records surface grab samples and current meter measurements the study area contains three provinces 1 a nearshore province shallower than 18 m with a relatively steep slope 0 6 and a cover of medium sand 2 a northern offshore province covered with coarse sand gravel and boulders interpreted to be glacial drift and 3 a southern offshore province with a gentle seaward dipping slope 0 3 and a surface sediment of coarse sand the glacial drift exposed in the northern offshore province can be traced southward under the coarse sand province the overlying fill is comprised of either outwash sediment derived from the pleistocene south channel ice lobe to the east or holocene aged marine sediments eroded from seacliffs to the north latest holocene sediment appears to be limited to the zone shoreward of 18 m where the medium sand occurs near bottom mean flows measured over two winter months in 10 m water depth average 6 cm sec 1 to the south mean flows exceeded 20 cm sec 1 approx 23 of the time ninety percent of the flows exceeding 20 cm sec 1 were directed to the south reflecting the dominant atmospheric forcing during these winter months waves had an average variance of 650 cm 2 with variance exceeding 5000 cm 2 3 of the time indicating moderate wave activity present processes are actively reshaping the nearshore province which is characterized by many east to northeast trending shore oblique channels that do not extend seaward of the 18 m contour coarse sand in the floors of these channels suggests they may be erosional features and the presence of megaripples oriented perpendicular to the channel axes indicates active transport in these channels megaripple orientation and the current and wave regime of the study area support a rip current origin for these channels

t phase observations in northern california acoustic to seismic coupling at a weakly elastic boundary plans for a hydroacoustic network intended to monitor compliance with the ctbt call for the inclusion of five t phase stations situated at optimal locations for the detection of seismic phases converted from ocean borne t phases we examine factors affecting the sensitivity of land based stations to the seismic t phase the acoustic to seismic coupling phenomenon is described by upslope propagation of an acoustic ray impinging at a sloping elastic wedge we examine acoustic to seismic coupling characteristics for two cases the first in which the shear velocity of the bottom is greater than the compressional velocity of the fluid i e vp vs vw the second is a weakly elastic solid in which vs vw vw we show that acoustic energy couples primarily to shear wave energy except at very high slope angles we show that the weakly elastic solid i e vs vw behaves nearly like a fluid bottom with acoustic energy coupling to both p and s waves even at low slope angles

the record of tidal cycles in mixed silici bioclastic deposits examples from small plio pleistocene peripheral basins of the microtidal central mediterranean sea the pliocene pleistocene peripheral marine basins of the mediterranean sea in southern italy from basilicata and western calabria to northern and eastern sicily represent tectonically formed coastal embayments and narrow straits here units of cross stratified mixed silici bioclastic sand 25 to 80 m thick record strong tidal currents the central mediterranean sea has had a microtidal range of ca 35 cm and the local amplification of the tidal wave is attributed to tides enhanced in some of the bays and to the out of phase reversal of the tidal prism in narrow straits linking the tyrrhenian and ionian basins the siliciclastic sediment was generated by local bedrock erosion whereas the bioclastic sediment was derived from the contemporaneous foramol type cool water carbonate factories the cross strata sets represent small to medium sized 10 to 60 cm thick two dimensional dunes with mainly unidirectional foreset dip directions these tidalites differ from the classical tidal rhythmites deposited in mud bearing siliciclastic environments firstly the foreset strata lack mud drapes and instead show segregation of siliciclastic and bioclastic sand into alternating strata secondly the thickness variation of the successive silici bioclastic strata couplets measured over accretion intervals of 2 to 3 m and analysed statistically reveal only the shortest term diurnal and semi diurnal tidal cycles thirdly the record of diurnal and semi diurnal tidal cycles is included within the pattern of neap spring cycles differences between these sediments and classical tidal rhythmites are attributed to the specific palaeogeographic setting of a microtidal sea with the tidal currents locally enhanced in peripheral basins it is suggested that this particular facies of mud free silici bioclastic arenite rhythmites in the stratigraphic record might indicate a specific type of depositional sub tidal environment of straits and embayments and the shortest term tidal cycles

sediment characterization at the equatorial mid atlantic ridge from p to s teleseismic phase conversions recorded on the pi lab experiment accurate marine sediment characteristics for example thickness and seismic velocity are important for constraining sedimentation rates with implications for climate variations and for seismic imaging of deeper structures using ocean bottom seismic deployments we analyze p to s seismic phase conversions from the sediment crust boundary recorded by the passive imaging of the lithosphere asthenosphere boundary pi lab experiment to infer the sediment thickness across the mid atlantic ridge covering 0 to 80 myr old seafloor we find p d s p delay times of 0 04 0 37 s or 5 to 82 m thickness sediment thickness increases with age thickness agrees with global estimates for young 15 20 myr seafloor but is thinner on older lithosphere our result may represent a lower limit on sediment thickness given that several of our stations are on topographic highs the sedimentation rate decrease observed from 5 to 1 2 mm kyr at 10 myr suggests a recent increase in productivity related to climate change eolian dust fluxes and or biogenic marine activity

transverse and linear dunes in an upper pleistocene marine sequence corinth basin greece a range of large scale dunes of oolitic calcarenite composition are exposed in the corinth basin of central greece these transverse dunes and a very large linear dune 15 m high lie within an upper pleistocene transgressive marine sequence tidal flow accelerated by constriction through a narrow fault bounded seaway is interpreted to have generated the current velocities necessary to produce the dunes marine facies in the upper pleistocene sequence include beach to offshore conglomerates and sandstones with wave modified sedimentary structures and herringbone cross stratification an offshore facies association comprises variably bioturbated siltstones and sandstones with a varied marine fauna that includes thermophile species such as scleractinian corals and strombus bubonius oolitic sandstone facies also occur oolitic sands were apparently produced in shoal environments subject to tidal and wave action and transported by dominant southerly currents over the southern part of the basin oolites accumulated in a linear dune 2 7 km long and 15 20 m high and in three dimensional transverse dunes up to 10 m high having a variety of compound and simple internal geometries the isolated wsw ene trending linear form exhibits angle of repose sedimentary dips up to 35 of avalanche sets on its se flank and sets typically with dips of 15 20 to the nw internal high angle discontinuities are developed in the se dipping lee face it is proposed that a dominant north to south flow crossed over the crest obliquely resulting in both net erosional and depositional processes on the lee flank a subordinate tidal current may have locally and or periodically crossed the dune crest in a westwards direction a string of transverse dunes which were located adjacent to a fault marine terrace scarp is interpreted to have originally coalesced to form the linear dune the distribution of transverse and linear dunes together with the palaeogeographical reconstruction suggest that a marine connection periodically existed across the corinth isthmus during the late pleistocene due to a combination of active faulting and glacio eustatic highstands of sea level

p and s wave delays beneath intraplate volcanic ridges and gravity lineations near the east pacific rise the gravity lineations intraplate melting petrology and seismic expedition glimpse explored the origin of two intraplate non hot spot ridge systems associated with gravity lineations in the south central pacific using the 11 month ocean bottom seismometer obs deployment of the glimpse experiment we determined the average p and s station delays for the region across the array station delays varied by 1 22 s for p waves and 2 13 s for s waves the presence of ultraslow shear velocity

between scylla and charybdis part 2 the sedimentary dynamics of the ancient early pleistocene messina strait central mediterranean based on its modern analogue abstract the 3 km wide messina strait divides sicily from the italian peninsula representing one of the most impressive examples of tide dominated marine passageway of the central mediterranean sea the tidal hydrodynamics governing the strait results from a semi diurnal phase inversion between two interlinked wider basins i e the tyrrhenian sea to the north and the ionian sea to the south due to the presence of a nodal tidal point in the centre of the strait this condition associated with coastal narrowing causes continuous water exchanges and a local phenomenon of tidal amplification producing collinear tidal currents up to 3 m s 1 in velocity in the point of tidal maxima of the strait centre currents follow bi directional patterns across the strait decelerating towards either opposite peripheries because of the progressive enlargement of the cross sectional areas tides exert a relevant influence on the strait bottom shaping characteristic erosional features governing the main sediment transport routes and promoting the migration of distinctive bedforms the textural and dimensional attributes of these bottom features vary according to the current velocity trends and main directions indicating a specific partition of the strait in individual sedimentary zones in the early pleistocene analogous conditions established across the same area and huge quantities of siliciclastic and bioclastic deposits accumulated in the ancient messina strait under a similar tidal hydrodynamics the 250 m thick strait fill succession which is magnificently exposed across the two opposite margins i e scylla and charybdis of the modern passageway represents a crucial correlative element in supporting the reconstruction of the sedimentary dynamics of the past strait based on the observation of the modern system in this work which represents the second part of a first article focused on the modern messina strait previous stratigraphic data are reviewed and integrated with new sedimentological observations carried out in both onshore and offshore key areas in particular outcrop analysis allows distinguishing a number of facies associations which are described and interpreted by taking into account the correspondent modern depositional strait setting the results of this study highlight a mutual correlation between the depositional zones detected in the modern messina strait and the individual facies associations recognised in the onshore margins the strait centre zone represented a bedload parting sector in the ancient system this zone which is one of the most difficult environment to detect in ancient straits due to a condensed sedimentary record is suggested to coincide with a structural palaeo high exposed in the southern sector of the investigated onshore area and continuing offshore in the modern strait this tectonic horst symmetrically separated two opposite highly depositional zones to the north and to the south hosting gravel and sand size siliciclastic and bioclastic deposits exhibiting diffuse motifs of large scale tidal cross stratification and a specific vertical facies stacking these characteristic tidal deposits which are believed to record the migration of several generations of tidal dunes forming extensive bedform fields in the strait reflect a tidal asymmetry between flood and ebb currents tidal asymmetry is referable to the oceanographic setting observable nowadays in the messina strait and deriving from a marked density driven water mass stratification between the two opposite flows in the ancient system tidal dunes transited down current to highly bioturbated fines including sporadic small scale tidal cross strata representing the distal periphery of the early pleistocene strait here bedforms followed migration pathways not always reflecting mutually evasive net gross sediment transport routes due to local conditions of current rotation occurring during each tidal phase inversion during these stages similar to slack water periods currents were weak enough to allow fine sediments to be settled from suspension reproducing a signature typical of other tide dominated coastal systems e g estuaries tidal flats etc these sedimentary zones of the ancient messina strait were laterally bounded by tectonically active margins where fan deltas clastic aprons and carbonate wedges developed under the constant interplay between mass transport processes and tidal currents the resulting architectural and sedimentary features observable in outcrop reveal impressive similarities with the morpho bathymetric features nowadays documented in the correspondent strait margin modern environments these considerations allow deciphering a general palaeo environmental reconstruction of the ancient strait which although suffering of limitations due to a partial preservation of the whole rock record discloses sedimentary processes and depositional environments of the ancient messina strait the process based analysis of this field based case study is crucial in predicting long term environmental changes and facies migration pathways and improves the state of knowledge on tidal straits which are the less understood among the most common tidal depositional systems

sedimentary facies during early stages of flooding in an extensional basin the breche rouge de carboneras late miocene almeria se spain the intramontane basins of the betic cordil leras se spain formed subsequent to the main phase of orogenic deformation during the middle miocene in a close genetic relation to the trans alboran shear zone left lateral movements along a local branch carboneras fault zone cf strike ne sw of this zone played a major role in controlling the formation and dynamics of the nijar carboneras basin to the south of the fault a major phase of strike slip faulting is recorded during the late tortonian the expression of this event is the brche rouge de carboneras brc which seals a deep denudational surface on top of dislocated fault blocks formed by volcanics of the cabo de gata complex and early tortonian shallow marine calcarenite the sedi mentary facies of this widely distributed unit in the carboneras subbasin mirror the submarine topography and the distribution of the fault zones along strike slip fault zones autoclastic breccias and neptunian dikes preferentially oriented nw se and ne sw occur which are interpreted to represent the near surface expression of the faults red limestone forms the groundmass of the autoclastic breccia and infills of neptunian dikes which exhibit multiple phases of opening of fissures gravita tional sedimentary infill lithification and renewed cre ation of cracks steep relief probably along fault scarps was mantled by epiclastic volcanic conglomerate with a red carbonate matrix well lithified coarse skeletal lime stone rich in planktonic foraminifera formed pavements along sediment starved rocky surfaces in deep water laterally within topographic depressions the pavement limestone grades into thick accumulations of skeletal rudstone composed of fragmented azooxanthellate corals and stylasterid hydrozoans which were concentrated by powerful bottom currents and gravitiy flows within the shallow water zone of dip slope ramps cross bedded calcarenite and calcirudite formed based on textures fabrics and biota rocks of the brc were grouped into nine genetic lithofacies which document cryptic deep aphotic and shallow photic environments typical of a sediment starved extensional basin

bioclastic sediment lobes on a supply dominated upper cretaceous carbonate platform margin montagna della maiella italy a thick bioclastic sediment wedge was deposited on the slope of the maiella carbonate platform margin in the late campanian to late maastrichtian the wedge consists of lobate depositional units laterally and vertically convex structures the complex internal geometries of the lobes combine characteristics of unidirectional sandwaves and the alternating point sources of deltas excellent outcrop permits a detailed documentation and discussion of the depositional processes the sediment wedge constitutes a supersequence which prograded along the platform margin as a result of high sediment supply and forced regression within the supersequence a hierarchy of higher order stratigraphic units sequence sets and sequences are developed the individual bioclastic sediment lobes are interpreted as systems tracts and parasequences of the sequences within the sequence sets

sand waves echinocardium traces and their bathyal depositional setting monte torre palaeostrait plio pleistocene southern italy stacked cross sets up to 2 5 m thick produced by sand wave migration and meniscate trace fossils produced by echinocardium cordatum both considered in the literature as typical of shallow water marine depositional settings commonly occur in the bathyal plio pleistocene deposits of monte torre calabria southern italy the plio pleistocene sediments form two coarsening upward depositional sequences separated by an unconformity and by a palaeobathymetric gap of at least 300 m the lower sequence passes upwards from hemipelagic marls and thin bedded turbidites to thick bedded sandy turbidites then to sand wave deposits alternated with sandy turbidites and finally to base of slope megabreccias facies characteristics and relationships and the occurrence of deep sea faunal associations indicate deposition in the bathyal zone the facies of the upper sequence reflect a fan delta environment no deeper than a few tens of metres the depositional setting of the lower sequence where the sand wave deposits and meniscate trace fossils occur appears to have been a tectonically controlled seaway connecting the tyrrhenian and ionian seas this seaway became progressively narrower with time evolving into a strait the overall coarsening upward trend reflects the upward transition from a low to a high energy environment possibly caused by the tectonic narrowing of the seaway deposition and erosion from high concentration turbidity currents and from tidal bottom currents were important processes periods of tectonic activity producing first the uplift of the seaway margins and culminating with the uplift of the strait sequence itself are marked by scattered rockfall deposits the strait setting causing the development of powerful oxygenated bottom currents produced optimal conditions in the bathyal zone for the colonization of sandy bottoms by a single infaunal r selected species echinocardium sp

anatomy of a late pleistocene clinoformal sedimentary body le castella calabria southern italy a case of prograding spit system abstract the le castella marine terrace is the smallest and youngest terrace of the crotone area southern italy and formed after a rapid marine ingression due to a glacio eustatic rise outpacing the regional uplift of the area the most prominent feature of the terrace deposits is a seaward accreting clinoform about 10 m thick inferred to be formed during forced regressive conditions this prograding body is mostly composed of bioclastic material and shows an internal complexity consisting of alternating oblique and sigmoid elementary units inferred to be produced mainly by changes of accommodation development foreset avalancing was due to sediment accumulation by gravity flow processes while topsets were characterized by the migration of medium to large scale dunes showing a unimodal palaeocurrent pattern oblique with respect to the dip direction of the large scale clinoform foresets the le castella clinoform starts to develop from a topographic step on the basement due to tectonics which also controlled the palaeoshoreline trend the recognized stratigraphic and facies architectures the palaeocurrent pattern and the inferred palaeogeographic setting during deposition all suggest that the le castella clinoform is an example of spit system attached to the mainland and accreted due to longshore transport the present example contributes to establish criteria allowing the recognition of ancient spit systems which still are poorly known and rarely documented in the pre quaternary geological record

a comparison between p wave and s wave propagation characteristics in the southern part of the gulf of california mexico abstract we performed a regional study of p seismic wave attenuation and source excitation from moderate size earthquakes recorded at distances ranging from 23 to 120 km off the coast of la paz baja california sur from a remarkably productive earthquake sequence that occurred in 2007 data were recorded from four strong motion seismic stations using the la paz seismic network and two broadband stations located close to the bay of la paz we compared our results with a previously reported study in the same region with virtually the same method from peninsular earthquakes using s lg seismic waves the regional attenuation was carried out by measuring the maximum amplitude of the p waves after separating the excitation and site terms from the propagation term d r f our best model of the p quality factor is q p f 53 f 0 32 in addition offshore s and scholte modes in ocean sediment layers are discussed in this article