deposit from a giant wave on the island of lanai hawaii limestone bearing gravel the newly named hulopoe gravel blankets the coastal slopes on lanai the deposit which reaches a maximum altitude of 326 meters formerly was believed to have been deposited along several different ancient marine strandlines but dated submerged coral reefs and tide gauge measurements indicate that the southeastern hawaiian islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level evidence indicates that the hulopoe gravel and similar deposits on nearby islands were deposited during the pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of lanai

a tsunami deposit at the cretaceous tertiary boundary in texas at sites near the brazos river texas an iridium anomaly and the paleontologic cretaceous tertiary boundary directly overlie a sandstone bed in which coarse grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple laminated very fine grained sandstone this bed is the only sandstone bed in a sequence of uppermost cretaceous to lowermost paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high the most likely source for such a tsunami at the cretaceous tertiary boundary is a bolidewater impact

the anatomy and provenance of thick volcaniclastic flows in the cretan basin south aegean sea abstract santorini volcano has been the largest source of volcaniclastic sediment in the eastern mediterranean during the late quaternary a dozen cores from the cretan basin south of santorini have sampled two megabeds that consist of gravity emplaced volcaniclastic sequences the uppermost megabed u consists of a succession of five u 5 u 1 base cut out turbiditic units lower megabed a is a single turbiditic event only the uppermost u 2 and u 1 turbidites are separated from the underlying beds by hemipelagic marls the texture and composition of the u and a megabeds closely match the texture and composition of the fine vitric ash of the minoan deposits on santorini islands dating from about 3500 yr bp these megabeds are therefore attributed to rapid accumulation of separate gravity flows fed by the minoan eruption except for the upper u 2 and u 1 turbidites deposited from subsequent gravity flows transporting eroded volcaniclastic sediments with the exception of the margin south of santorini dozens of cores retrieved around the margins of the cretan basin have a continuous late quaternary succession that shows no evidence for massive sediment remobilization into the deeper basin including the passage of the minoan tsunami extensive high resolution 3 5 khz records revealed the acoustic character architecture and distribution of the u and a megabeds and four underlying late quaternary volcanogenic megabeds in the cretan basin the acoustic facies of megabeds are typical of megaturbidites and consist of an upper transparent lower velocity layer that corresponds to the fine grained upper turbiditic silt and clay section and a lower strongly reflective higher velocity section that corresponds to the lowest coarser grained base of the turbidite that is developed over a sharp erosional surface penetration of the high resolution records reveals the existence of at least six megabeds correlation with core lithology and the physical properties of the various lithofacies including down core velocity profiles has allowed us to determine the thickness and volumes of the upper four megabeds which are u 9 m thick volume 3 7 km 3 a 25 m thick volume 12 2 km 3 b 22 m thick volume 10 3 km 3 c 15 m thick volume 8 km 3 these thick megabeds are the uppermost products of repeated explosive eruption of santorini in the late quaternary calculated sedimentation rates from and after the minoan eruption are 9 4 m 1000 yr that rise to over 15 7 m 1000 yr if megabed b was also deposited during this eruption

new findings of bronze age homogenites in the ionian sea geodynamic implications for the mediterranean abstract holocene homogenites similar in character and stratigraphic position to those previously recorded in the ionian basin and related to the gigantic tsunami originating from santorini bronze age eruption are described from a core transect crossing the deformation front of the mediterranean ridge east of victor hensen seahill investigations on grain sizes and carbonate content carried out on three cores from three different areas of the ionian basin encompassing the bronze age homogenite revealed important similarities and some differences the most obvious difference concerns the carbonate content which is minimum at the base of the unit in a core close to the messina abyssal plain whereas it is maximum in cores from the western mediterranean and calabrian ridges characterized by the typical cobblestone topography a terrigenous versus pelagic nature of the components is documented and a distal versus local provenance is inferred homogenites are critically compared with unifites a type of re sediment recently described from the eastern mediterranean comparison includes in particular a source and sediment transport and b triggering mechanism a substantial difference exists between the sedimentation patterns of the ionian and levantine basins seaward of the calabrian and hellenic arcs in the latest quaternary and the difference contains a clear geodynamic message sedimentation rates increase from the late pleistocene to the holocene in the ionian basin whereas they decrease in the levantine basin the glacio eustatic signal is well expressed in the levantine basin where the source areas are situated consistently in the south or on a passive type aseismic continental margin north african margin in the ionian basin on the contrary the glacioeustatic signal is totally obscured by the strong tectonic signal from the active northern continental margin of the mediterranean

discovery of an anoxic basin within the strabo trench eastern mediterranean we report here the discovery of a basin which we call the tyro basin in the eastern mediterranean in which anoxic conditions exist and organic rich sediments are accumulating bottom water samples show extremely high salt concentrations a horizontal midwater sound reflector about 70 m above the basin floor was observed in a seismic reflection profile across the basin from shipboard observations we conclude that dissolution of messinian evaporites exposed by faulting in the sides of the basin causes stagnant bottom conditions this basin provides an opportunity to test some of the hypotheses concerning the formation of sapropels present in cores collected from the same area cores taken in an adjacent similar basin for which we propose the name kretheus basin indicate a recent change from anoxic to oxygenated conditions which was probably caused by tectonic activity associated with the strabo trench

sedimentary signatures and processes during marine bolide impacts a review abstract studies of submarine impact craters resulting from impacts of comets or asteroids demonstrate that the presence of water and the physical properties of target rocks have a major influence on sedimentary processes associated with meteorite impacts this results in difference in sedimentary signature of bolide impacts in marine environments compared to subaerial impact craters in subaerial impacts the targets are commonly hard rocks frequently of igneous and or metamorphic origin whereas in submarine impacts the targets are mostly unconsolidated or poorly lithified sediments or sedimentary rocks with high volumes of pore water such differences result in variability in crater morphology and in sedimentary processes inside and outside the impact area impacts in shallow water marine neritic environments produced craters with low or absent rims and wide and shallow brims as characterize by both the montagnais on the scotian shelf the mjolnir in the barents sea 45 and 40 km in diameter respectively and the chesapeake bay 90 km in diameter lack of elevated rims is thought to be the result of current reworking and resurge of the water back into the excavated cavity as the water in the crater is vaporized during this process resurge gullies can be cut across the rim while mass and debris flows turbidites and other gravity deposits are produced as results of tsunami and crater wall and central high collapse during and after the crater excavation stage such deposits are found both within and outside the crater structure the only difference between gravity deposits triggered by an impact or other rare events such as earthquakes is the admixture of various melt particles and possible enrichments in iridium in the former impacts near the shelf edge may cause partial collapse of the continental margin as shown by the montagnais and chicxulub impacts some of the gravity and debris flows generated by margin collapse may be channelized with final deposits up to several hundred meters thick extending for hundreds of kilometers from the impact site other impact features such as shatter cones tektites spherules and ni spinels shocked quartz isotropication and partial melts are common to both submarine and subaerial impacts theoretical calculations of the destructive forces of mega tsunami waves triggered by meteorite impact in the ocean greatly exceed those based on geologic evidence a dearth of gigantic tsunami evidence for the chicxulub impact outside of the gulf of mexico where from theoretical modelling the maximum near bottom orbital velocity of water flow crossing the deep north atlantic basin should have been 1 m s could be the result of the mitigating effect of the bathymetry of surrounding area causing wave diffraction and interference calculated maximum horizontal orbital velocity near the seafloor at the shelf for the montagnais impact is 22 m s for a 200 m high wave 5 5 m s for a 50 m high wave at 500 km decreasing to 0 5 m s at 1000 km strong enough to scour the deep ocean bottom and produce distinct erosion surfaces and disconformities in marine sedimentary record however lack of cores across impact horizon prevents confirmation of occurrence of such bottom water flows

soft sediment deformation structures induced by cyclic stress of storm waves in tempestites miocene guadalquivir basin spain the identification of triggering agents for soft sedimentation structures is an enigmatic geological problem mainly seismic induced soft sediment structures have been recognized in ancient sediments rather than those resulting from storm waves we analyse soft sediment deformation structures in upper miocene calcarenitic tempestites of the guadalquivir basin southern spain the most common structures are load casts which vary in height and width from 10 centimetres to several metres the structures are always restricted to a small part of the stratigraphic sections in exclusive association with tempestites the analysed soft deformation structures are interpreted to be the result of liquidization processes chiefly from their inferred depositional environment and subordinately from the deformation style we have devised basic criteria to identify the trigger mechanism in these soft sediment deformation structures the liquefaction was triggered by pore pressure changes induced by cyclic and residual stress of storm waves

reply to comment by luigi vigliotti on lost tsunami about 8 3 ka ago a devastating tsunami flooded thecoasts of the eastern mediterranean sea pareschi et al 2006c that tsunami was triggered by a landslide from thecollapse of the eastern flanks of mt etna volcano sicily italy in turn inducing 1 a scar on volcano slopes namedvalle del bove 2 inland deposits chiancone and milounits dated 7 6 8 3 ka cal b p calvari and groppelli 1996 calvari et al 1998 and 3 offshorelandslidedeposits pareschi et al 2006a the tsunami had a largeimpact effecting southern italy western greece and northafrica including tunisia to libya egypt southern turkey syria lebanon and israel in israel the tsunami ravaged theneolithic village of atlit yam caused the death of villagersand animals filling a water well and destroying village huts pareschi et al 2006c 2007 an early holocene sea levelrise dated 8 350 8 250 calendar year b p matches thetiming of the mt etna tsunami the consequent flooding ofcoastal areas led to the sudden loss of land favoured byearly farmers and initiated an abrupt expansion of activityacross europe turney and brown 2007

evidence of tsunami sedimentation on the southeastern coast of australia in coastal regions the highest magnitude storms cannot always be invoked to account for large scale anomalous sediment features any coastline in the pacific ocean region can be affected by tsunamis including australia which historically lacks evidence of such events geologically tsunamis along the new south wales coast have deposited a suite of holocene features that consist of anomalous boulder masses either chaotically tossed onto rock platforms and backshores or jammed into crevices highly bimodal mixtures of sand and boulders and dump deposits consisting of well sorted coarse debris in addition many coastal aboriginal middens were distributed by such events within estuaries tsunamis have left a record of stranded run up ridges that have been interpreted mistakenly as cheniers dating of such deposits indicates that several events have affected this coastline since 3000 bp in contrast to storm waves tsunamis can leave a depositional imprint of their passage characterized by chaotic sort

a geophysical interpretation of the 1883 krakatau eruption abstract from the present submarine topography in the vicinity of the krakatau islands it is concluded that the focus of the large explosions was situated to the northwest of the present rakata island the channel between krakatau and sebesi islands was completely blocked by banks of volcanic material immediately after the eruptions and it is suggested that this material was mainly lithic fragments the explosion sequences of krakatau are deduced from the records of sea waves and air waves observed at jakarta the large tsunami was caused by the most violent explosion simultaneously with the largest air waves it is inferred that the origin of the tsunami was a sudden upheaval of the seawater due to a violent explosion and that the height of the tsunami near its source was 30 40 m energy of the explosion is estimated from analyses of the air waves as one order of magnitude greater than that of the 1956 bezymianny eruption thus the 1883 krakatau eruption may have caused explosive removal of more than 10 km3 of material the subsurface structure of krakatau islands after the 1883 eruption is deduced from gravity anomalies it is concluded that at the bottom of the caldera there are deposits of low density in the shape of an inverted cone 8 km in diameter and 1 km in depth from the residual gravity anomaly observed over the caldera one can estimate the mass deficiency there this allows estimates to be made as to the amount of ejecta although large uncertainties remain these data indicate that explosive removal of material was the main process responsible for the disappearance of the northern half of the former rakata krakatau island in the 1883 eruption

sedimentological record of tsunamis on shallow shelf areas the case of the 1969 ad and 1755 ad tsunamis on the portuguese shelf off lisbon one of the aims of the sedport project esf euromargins eurocores program was to investigate the depositional features on the shelf and upper slope of the portuguese margin tagus system during the holocene to fulfill the objectives two shallow box cores and two sedimentary sequences were studied po287 26b and the spliced sequence of sites d13902 po287 26g recovered on the portuguese continental shelf ssw off the tagus river mouth and the box po287 28b and gravity core geob8903 collected towards the w of the river mouth magnetic susceptibility grain size and xrf fe data as well as 210 pb and ams 14 c dating of these sedimentary sequences have allowed the identification of an instantaneous deposit at about 20 cm in the box cores downcore we could establish a hiatus corresponding to 355 yr of sedimentation at both sites a 39 cm instantaneous deposit of coarse material including carbonate broken shells on the ssw site and a 1 5 m instantaneous deposit of fine material on the w site both hiatus and instantaneous deposits are considered to be of tsunamigenic origin the box cores deposit has an estimated age of 1969 ad and it is attributed to the 1969 earthquake caused tsunami the hiatus and deposits found downcore are due to the age limits encountered believed to represent the tsunami related to the 1755 lisbon major earthquake these data further indicate a sediment deposit similar in type and thickness on both ssw and w sites in 1969 while the 1755 ad record indicates a higher energy backwash along the ssw and a preferential deposition of fine suspended matter towards the w c 2007 elsevier b v all rights reserved

an ams radiocarbon method to determine the emplacement time of recent deep sea turbidites abstract this paper reports the evaluation of a novel method based on accelerator mass spectrometer ams radiocarbon dating of planktonic foraminifera to evaluate the times of emplacement of recent deep sea turbidites it assumes that the standing stock of relatively large 150 m planktonic foraminifera in the bioturbated surface mixed layer of box cores represents an integration of the flux from the water column since the turbidite was emplaced and exploits the potential of the ams method to analyse the resultant small samples which can be readily separated the method is evaluated by application to three atlantic turbidites which form the present day sediment surfaces on the horseshoe madeira and tagus abyssal plains the time of emplacement of madeira abyssal plain turbidite is estimated at 1120 730 and 870 years before present each 120 140 years in three different cores the resultant weighted mean emplacement time 930 76 years before present is somewhat older than previous estimates by geochemical methods the times of emplacement for the horseshoe 240 and 140 years before present each 120 years and tagus 300 120 years before present abyssal plains are both consistent with initiation by the lisbon earthquake of 1755

depositional processes of uniform mud deposits unifites hedberg basin northwest gulf of mexico new perspectives structureless mud deposits unifites are a common depositional phenomenon in the intraslope basins of the continental slope of the northwest gulf of mexico high resolution acoustic data and long sediment cores from hedberg basin middle slope were used to provide a better insight into the origin of these enigmatic depositional units the unifite occurring in hedberg basin is structureless under visual observations but x ray radiographs reveal that it consists of three divisions 1 u1 division representing waning sequences of fine grained mud turbidites 2 u2 division characterized by faint normally graded mud layers with occasionally wispy silty interlaminae and 3 u3 division characterized by a uniform appearance with no obvious sedimentological structures other than a faint banding of slightly siltier and slightly more clayey layers high resolution geophysical data reveal that there is no connection between intrabasinal sediment failures and the occurrence of unifites we suggest that unifites have resulted from the deposition of a long lasting 1 53 months pulsating showing internal surges fine grained turbidity current dated at 28 629 ka that originated from the flow transformation of a series of massive sediment failures on the shelf edge and or upper continental slope the fine grained nature of the turbidity current is probably caused by the depositional segregation of the flow by depositing its coarsest material in intraslope basins in more proximal locations we propose that the uniform texture of the unifite is attributed to the development of a stratification interface lower stratified layer generated by the continuous introduction of a turbulent sediment cloud in the intraslope basins the lowest two unifite divisions are considered to develop prior to and during the development of the stratified layer

a re analysis of the late bronze age eruption and tsunami of santorini greece and the implications for the volcano tsunami hazard the paroxysmal eruption of santorini ca 3500 bp referred to as the late bronze age lba eruption probably generated multiple tsunami their occurrence and impacts being cited frequently in scientific papers and articles this paper examines what is known about any lba tsunami noting possible mechanisms of generation and identifying sedimentological traces firstly the eruption sequence is outlined providing the context in which tsunami genesis may have occurred secondly the arguments forwarded for the tsunami and a summary of the evidence is given thirdly results of a new geological investigation for lba tsunami deposits at 41 coastal sites from crete and kos are presented the data are used to test the hypothesis that the lba eruption generated an east mediterranean wide tsunami it will be seen that no terrestrial geological evidence is identified the paper re examines the original arguments presented for lba tsunami challenging them because their founding assumptions are flawed together the new data and the re analysis of the original tsunami hypothesis indicate that there is insufficient evidence to demonstrate that any significant far field tsunami propagated throughout the entire east mediterranean as frequently purported some terrestrial evidence exists to suggest localised near field tsunami inundation there is good submarine evidence however to suggest that a tsunami was focused to the w and wsw the results have important implications for understanding the volcano related tsunami hazard within the region and elsewhere

a thick holocene homogenite from the ionian abyssal plain eastern mediterranean abstract a homogenite layer thicker than 12 m holocene in age occurs in the ionian abyssal plain the graded sandy base is 1 3 m thick most of the layer is structureless and homogeneous in grain size and mineral composition the most remarkable components are siltsized grains composed of aragonite needles they are interpreted as skeleton fragments of the green alga halimeda sp the homogenite covers an area of at least 1100 km 2 and assuming a minimum thickness of 10 m comprises a volume of 11 km 3 the source of the material of the homogenite is a matter of speculation very likely it has been remobilized from different areas around the ionian abyssal plain as triggering event a tsunami generated by the collapse of the santorini caldera about 3500 yrs b p is assumed

stratigraphy of the western mediterranean and southern calabrian ridges eastern mediterranean abstract the present paper illustrates the stratigraphic results of a transponder navigated coring program carried out in 1978 on the southern calabrian ridge cobblestone area 4 and western mediterranean ridge cobblestone area 3 semi quantitative investigations of over 600 foraminiferal samples and 450 nannofossil slides from forty cores with a total recovery of 333 m comprise the data base of the study most of the sediments recovered are late pleistocene or holocene in age the high resolution nannofossil biostratigraphic scheme recently proposed for the quaternary coupled with sapropel stratigraphy and with tephrachronology resulted in precise correlation of the cores mid pleistocene sediments were recovered in a single core from area 4 and in one core from area 3 both located on basin walls four cores from basin walls in area 4 yielded pliocene sediments no sediments older than approximately 3 m y foraminiferal zone m pl 4 reticulofenestra pseudoumbilica nannofossil zone are exposed on the explored walls from the southern calabrian ridge early and late pliocene sediments were recovered from the walls of the deepest crater like basin explored in area 3 but only in dredges in this latter area also two peculiar lithologies were cored basically unfossiliferous but thought to be pre pliocene in age a mud breccia whose clasts yield a sparse assemblage of mid cretaceous planktonic foraminifera and a dolomitic mudstone which is attributed to the late messinian on the basis of correlation with a similar lithology cored at dsdp site 374 and substantiated by analogy in x ray controlled mineralogical composition the fairly complete record of late pleistocene and holocene sapropels recovered in the southern calabrian ridge discards the hypothesis that the southern part of the ionian sea did not undergo stagnant cycles during the ice ages another hypothesis relating the origin of cobblestone topography to olistostromes is also considered untenable on the basis of the new data the large number of cores precisely located on a previously mapped highly irregular bottom physiography disproves that large scale chaotic sedimentation occurred debris flows recorded in base of slope cores document local slope failures

possible tsunami signatures from an integrated study in the augusta bay offshore eastern sicily italy abstract twelve anomalous layers marked by a high concentration of displaced epiphytic foraminifera species growing in vegetated substrates like the posidonia oceanica and subtle grain size changes were found in a 6 7 m long fine sediment core ms 06 sampled 2 km off the shore of the augusta harbor eastern sicily at a depth of 72 m recording the past 4500 yrs of deposition because concentrations of epiphytic foraminifera are quite common in infralittoral zones but not expected at 72 m we believe that these anomalous layers might be related to the occurrence of tsunamis causing substantial uprooting and seaward displacement of p oceanica blades with their benthic biota our approach involved the study of geophysical data morphobathymetry seismic reflection and seafloor reflectivity and sediment samples including x ray imaging physical properties isotopic dating tephrochronology grain size and micropaleontology correlations between anomalous layers and tsunami events have been supported by a multivariate analysis on benthic foraminifera assemblage and dates of historical tsunami records we found that four out of the eleven layers were embedded in age intervals encompassing the dates of major tsunamis that hit eastern sicily 1908 1693 and 1169 and the broader eastern mediterranean santorini at about bp 3600 one more layer even if less distinct than the others was also defined and may be the evidence for the ad 365 crete tsunami

the augias megaturbidite in the central ionian sea central mediterranean and its relation to the holocene santorini event abstract a thick mud turbidite up to 24 m in thickness termed the augias turbidite is decribed from the ionian and sirte abyssal plains and the adjacent slopes of the calabrian rise and the mediterranean ridge the material of the megaturbidite is derived from the gulf of sirte revealed by its high aragonite content and through erosion from the sirte rise the shallow water sediments making up the turbidite were probably mobilized by a tsunami caused by the minoan santorini collapse around 3500 yr b p the volume of the mobilized sediments is calculated as a minimum of 65 km3 isolated turbidites of the same age deposited on the upper slope of the mediterranean ridge may consist of tsunami mobilized shallow water material as well as of earthquake triggered sediment from the flanks of local depressions

deep sea tsunami deposits in the eastern mediterranean new evidence and depositional models the tsunami wave induced by the collapse of the santorini caldera after the bronze age minoan eruption 3500 bp produced turbidites and large volume mega turbidites in the abyssal plains of the ionian sea as well as on the floor of small basins of the mediterranean and calabrian ridges characterized by the so called cobblestone topography since the first discovery in 1978 a holocene mud layer which has been termed homogenite and which typically shows a graded interval at its base has been identified and correlated in over 50 deep sea cores recovered in the eastern mediterranean four types of homogenite can be distinguished each related to a particular depositional setting 1 a closed cobblestone these are from a few decimetres to several metres thick pelagic turbidites of local provenance exclusively found at the bottom of small sized ponded basins of the mediterranean and calabrian ridges a debris flow may be present at the base of the turbidite where the vertical relief of the basins is over 200 m 2 b abyssal plain a 10 to 20 m thick megaturbidite recorded in the ionian and sirte abyssal plains the source area is the african continental margin possibly the continental shelf it can be easily identified as a transparent acoustic layer that shows recent deformation across the deformation front of the mediterranean ridge accretionary prism the volume of the minoan homogenite in the ionian abyssal plain has been calculated at a minimum of 11 km3 3 c open cobblestone this type is exclusively found on the outer slope of the mediterranean ridge near the deformation front unlike types a and b the base of the turbidite here is erosional instead of depositional this homogenite has been deposited in small basins and occasionally on topographic highs of the mediterranean ridge by the up slope flow of turbidity currents of african provenance that formed the abyssal plain deposit type b 4 d a fourth depositional model has been identified homogenites present in deep anoxic basins of the mediterranean ridge this setting is substantially similar to type a but the vertical relief of the basin is much higher up to 800 m and the deposition occurs in high density anoxic brines which modify the settling rate and hence the resulting sedimentological characters

a scenario of the 1883 krakatau tsunami abstract the 1883 krakatau tsunami provides an important clue for solving the mechanisms of the eruption of krakatau first sea waves of volcanic origin are basically classified the travel times of the crest of the largest tsunami in the 1883 krakatau eruption are recalculated taking the wave heights and the sea depths along the path into consideration as a special case of sea waves air waves coupled with those of the sea are examined and the necessary conditions of their generation are discussed the sea depths must be around 5 km the sea wave paths require long stretches of sea and the magnitudes of volcanic explosions must be large to produce the air sea waves the information collected suggests that the tsunamis registered at batavia jakarta were not air sea waves some results of the recent reflection survey of the subbottom materials and a supplemental gravity survey in the krakatau area are introduced to provide further evidence for explosive mechanisms the origin times of the onset and the crest of the tsunami and the air wave both registered at batavia are calculated from their travel times adopting these origin times the author reconstructs a scenario of the tsunami in order to generate a tsunami as long as about 60 km wave length successive developments of surges and water domes seem to be necessary

tsunami induced sediment transport in the abyssal mediterranean sea an unusual stratigraphic unit nicknamed homogenite fills topographic lows in the complex ridge and trough bathymetry at two survey sites on the western mediterranean ridge and the calabrian ridge on near bottom 4 khz seismic reflection profiles this unit us an acoustically transparent near surface flat lying layer whereas in cores it is a homogeneous gray marl as much as 7 m thick grain size decreases upcore within the unit implying that it was deposited in a single event controlled by gravitational settling the stratigraphic position of the homogenite relative to a firmly dated sapropel bed suggests emplacement between 4400 and 3100 yr b p the source of the homogenite is inferred to be the nearby basin walls farther east two other sites with similar rugged topography lack homogenite entirely a triggering mechanism is required which is capable of initiating massive sediment transport simultaneously in many separate basins at the western two survey sites but which is not effective at the eastern sites a large archeologically recorded earthquake of the correct age is considered and rejected because its epicenter is closer to the nonhomogenite bearing sites than to the sites where this sediment type was observed and because several other earthquakes of comparable magnitude have since been recorded in the area whereas the homogenite is unique the 3 500 yr b p collapse of the caldera of the volcano of santorini caused a huge tsunami which is recorded archeologically and geologically around the eastern mediterranean because of refraction of the tsunami by the bathymetry and because the caldera collapsed in its southwest corner a disproportionate amount of tsunami energy was directed toward the western area where homogenite is observed in contrast the homogenite free sites were relatively sheltered an order of magnitude calculation shows that the near bottom oscillating currents accompanying the santorini tsunami were at or above the threshold erosion velocity at the homogenite bearing sites in addition the near bottom pressure pulse under the tsunami at the homogenite bearing sites was sufficient to cause liquefaction of sediments neither mechanism was adequate to cause sediment transport or slope failure at the homogenite free sites

historical and pre historical tsunamis in the mediterranean and its connected seas geological signatures generation mechanisms and coastal impacts abstract the origin of tsunamis in the mediterranean region and its connected seas including the marmara sea the black sea and the sw iberian margin in the ne atlantic ocean is reviewed within the geological and seismotectonic settings of the region a variety of historical documentary sources combined with evidence from onshore and offshore geological signatures geomorphological imprints observations from selected coastal archeological sites as well as instrumental records eyewitnesses accounts and pictorial material clearly indicate that tsunami sources both seismic and non seismic e g volcanism landslides can be found in all the seas of the region with a variable tsunamigenic potential local regional and basin wide tsunamis have been documented an improved map of 22 main tsunamigenic zones and their relative potential for tsunami generation is presented from west to east the most important tsunamigenic zones are situated offshore sw iberia in the north algerian margin in the tyrrhenian calabria and messina straits in the western and eastern segments of the hellenic arc in the corinth gulf of central greece in the levantine sea offshore the dead sea transform fault and in the eastern side of the marmara sea important historical examples including destructive tsunamis associated with large earthquakes are presented the mean recurrence of strong tsunamis in the several basins varies greatly but the highest event frequency 1 96 years is observed in the east mediterranean basin for most of the historical events it is still unclear which was the causative seismic source and if the tsunami was caused by co seismic slip by earthquake triggered submarine landslides or by a combination of both mechanisms in pre historical times submarine volcanic eruptions i e caldera collapse massive pyroclastic flows volcanogenic landslides and large submarine landslides caused important tsunamis although little is known about their source mechanisms we conclude that further investigation of the tsunami generation mechanisms is of primary importance in the mediterranean region inputs from tsunami numerical modeling as well as from empirical discrimination criteria for characterizing tsunami sources have been proved particularly effective for recent well documented aseismic landslide tsunamis e g 1963 corinth gulf 1979 cote d azur 1999 izmit bay 2002 stromboli volcano since the tsunami generation mechanisms are controlled by a variety of factors and given that the knowledge of past tsunami activity is the cornerstone for undertaking tsunami risk mitigation action future interdisciplinary research efforts on past tsunamis are needed

gelatinous pellicles in deep anoxic hypersaline basins from the eastern mediterranean abstract gelatinous pellicles have been observed in three out of ten cores recovered from the bannock basin or bacino bannock and in two dredges from its flanks during a cruise of the r v bannock in the eastern mediterranean similar pellicles have also been detected in two cores recovered from the tyro basin the bannock and tyro basins are brine filled depressions which are presently characterized by anoxic sedimentation in the bannock basin also gypsum precipitation occurs the gelatinous pellicles some millimeters thick and dark grey to greenish in color are always found in very dark colored sediments of quaternary age these pellicles have been investigated by optical microscopy by scanning electron and transmission electron microscopy and by flash pyrolysis gas chromatography and flash pyrolysis gas chromatography mass spectrometry to decipher their nature abundant skeletal tests of siliceous and calcareous planktonic organisms radiolaria diatoms silicoflagellates formainifera and nannofossils are observed together with amorphous organic matter the pellicles enclosing these remains consist of organic matter they foliate into submillimetric undulating and anastomosing microlaminae cellular structures are never observed neither in the pellicles nor in the microlaminae organic geochemical analyses point to a high contribution of terrestrial material the organic matter of the pellicles investigated consists of a coal like material it is suggested that the pellicles are originally formed at the brine seawater interface but subsequently sink to the bottom due to increasing load of entrapped biogenic and non biogenic detritus

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

proximal impact deposits at the cretaceous tertiary boundary in the gulf of mexico a restudy of dsdp leg 77 sites 536 and 540 restudy of deep sea drilling project sites 536 and 540 in the southeast gulf of mexico gives evidence for a giant wave at cretaceous tertiary boundary time five units are recognized 1 cenomanian limestone underlies a hiatus in which the five highest cretaceous stages are missing possibly because of catastrophic k t erosion 2 pebbly mudstone 45 m thick represents a submarine landslide possibly of k t age 3 current bedded sandstone more than 2 5 m thick contains anomalous iridium tektite glass and shocked quartz it is interpreted as ejecta from a nearby impact crater reworked on the deep sea floor by the resulting tsunami 4 a 50 cm interval of calcareous mudstone containing small cretaceous planktic foraminifera and the ir peak is interpreted as the silt size fraction of the cretaceous material suspended by the impact generated wave 5 calcareous mudstone with basal tertiary forams and the uppermost tail of the ir anomaly overlies the disturbed interval dating the impact and wave event as k t boundary age like beloc in haiti and mimbral in mexico sites 536 and 540 are consistent with a large k t age impact at the nearby chicxulub crater

a tsunami about 1000 years ago in puget sound washington water surged from puget sound sometime between 1000 and 1100 years ago overrunning tidal marshes and mantling them with centimeters of sand one overrun site is 10 kilometers northwest of downtown seattle another is on whidbey island some 30 kilometers farther north neither site has been widely mantled with sand at any other time in the past 2000 years deposition of the sand coincided to the year or less with abrupt probably tectonic subsidence at the seattle site and with landsliding into nearby lake washington these findings show that a tsunami was generated in puget sound and they tend to confirm that a large shallow earthquake occurred in the seattle area about 1000 years ago

impact of the minoan tsunami of santorini simulated scenarios in the eastern mediterranean 1 we have simulated the impact of the tsunami generated by the late bronze age lba volcanic eruption of santorini on the eastern mediterranean two different tsunami triggering mechanisms were considered a caldera collapse and pyroclastic flows surges entering the sea simulations include the worst input conditions in order to evaluate the maximum possible impacts but also lighter input conditions compatible with the lack of any tsunami trace on the northern coasts of crete in all the simulations tsunami propagation is mainly confined to the southern aegean outside the aegean the tsunami impact was negligible and not responsible for the slide slumping of fine grained pelagic and or hemipelagic sediments considered the sources of the sporadically located sea deposits in the ionian sea and of the widespread megaturbidite deposits localized in the ionian and sirte abyssal plains

setting and tectonic evolution of some eastern mediterranean deep sea basins abstract nine discrete deep sea basins seven from the calabrian and mediterranean ridges and two from the strabo trench were explored geologically during several cruises carried out from 1978 to 1984 in the eastern mediterranean the seven basins displaying similar geological features calabrian and mediterranean ridges may be divided into three groups on the basis of their size 1 very small basins botticelli and raffaello basins whose area ranges from 1 1 to 4 3 km 2 2 small basins ares aphrodite and katia basins from 7 to 13 km 2 and 3 large basins bannock and cleft basins from 22 to 74 km 2 the two basins from the strabo trench tyro and kretheus basins whose areas range from 16 to 20 km 2 are considered separately tectonics is the most important element affecting basin formation processes progressive folding and faulting of messinian pliocene and quaternary sediments in the calabrian and mediterranean ridges allows the infiltration of water into the subbottom and dissolution of messinian evaporites so that collapse of the overlying unconsolidated plio quaternary cover creates local distensive tectonics superimposed on the regional compressive tectonic setting the size of the basins reflects different steps in this process very small basins are related to the fracturing occurring at the top of anticlines small basins originate when anticlines are faulted and large amounts of water are able to reach the evaporites and increase the intensity of leaching finally large basins are related to regional tectonic lineaments both compressive large reverse faults overthrusts and strike slip salt diapirism may be associated with some of these situations the process responsible for the tyro and kretheus basins formation is the pull apart mechanism connected with the strike slip motion occurring in that area the geometric position of subaqueously dissolved evaporites seems to influence the environment on the basin floor brines originating from the dissolution of buried evaporites are thought to disperse in the subbottom whereas brines originating from dissolution of evaporites cropping out on the basin walls can flow to the floor and cause stagnation only if the shape of the basin prevents the action of bottom currents

the origin of the tsunami excited by the 1906 san francisco earthquake lawson et al 1910 reported a tsunami observed at fort point in san francisco bay fig la during the 1906 san francisco earthquake m 8 this observation is curious because the san francisco earthquake is generally believed to be a strike slip earthquake for which tsunamis are not usually expected

stratigraphy and sedimentation in the anoxic bannock basin eastern mediterranean abstract ten gravity and or piston cores raised from the floor and the eastern flank of the bannock basin and from nearby plateaus were investigated lithologically and biostratigraphically the bannock basin is a large rimmed depression with a vertical relief of over 600 m containing deep seated brines the brines are derived from submarine dissolution of messinian evaporites in a physiographic setting deep rimmed basin that does not permit dilution and removal by bottom currents plateau cores range in age from holocene emiliania huxleyi acme zone to middle pleistocene pseudoemiliania lacunosa zone they consist of low sedimentation rate pelagic sediments with sapropels and tephras as minor isochronous lithologies two cores on the flanks recovered pliocene pelagic sediments one of these cores displays an unconformable contact between holocene anoxic sediments and early pliocene reticulofenestra pseudoumbilica zone marls the other core is entirely pliocene consisting of a debris flow with a matrix that is referred to the discoaster tamalis subzone cores from the deeper part of the basin consist of laminated non bioturbated poorly oxygenated dark sediments rich in h 2 s and containing large gypsum crystals organic carbon content is higher than in normal eastern mediterranean pelagic sediments but lower than in true sapropels the kerogen is dominated by amorphous organic matter although the oxygen content of the bottom waters was not measured sedimentary evidence suggests that poorly oxygenated but not entirely anoxic conditions exist in the basin at the sediment water interface in particular benthic foraminifers would be much less abundant than they actually are and org c content would be higher if bottom waters were anoxic poor oxygenation started to develop in the bannock basin some 180 ka b p after the deposition of sapropel s 6 as documented in core 84 02 this long lasting period of anoxia strongly differs from the short anoxic episodes in the eastern mediterranean that were controlled by glacial interglacial changes the bannock basin anoxia is a result of brine formation causing strong density stratification with a density contrast 20 that is much higher than the density contrast derived from changes in thermohaline circulation during glacial interglacial times during these eastern mediterranean basin wide euxinic episodes the boundary between oxygenated and anoxic waters was much shallower than the 3200 m interface recorded in the bannock basin reworked and displaced foraminiferal faunas were found in the pliocene sediments recovered in the flank cores in particular the occurrence of abraded tests of the shallow water form elphidium spp of bulimina costata and of other displaced taxa does suggest that the area was subject to deposition by turbidity currents originating on the african margin and that in pliocene times no rimmed basin was in existence

acquisition of detrital magnetization in four turbidites turbiditic events are mostly avoided in paleomagnetic studies and therefore their remanence and magnetic properties are poorly described turbidites are exempt of bioturbation and potentially provide pertinent information about depositional remanence we studied four quaternary turbidites of different origins in marine sediment cores upward fining of both magnetic and sedimentary fractions indicates that coarser grains reached the bottom first we observe a progressive shallowing of the magnetic inclinations between the upper and bottom layers of the turbidites that increases with the size of the events and obeys a simple linear scaling law measurements of magnetic anisotropy suggest that hydrodynamic conditions prevailing during deposition seem to be dominant for the alignment of the magnetic grains we suggest that small spherical grains are randomly oriented with zero resultant magnetization in presence of strong turbulent conditions while the alignment of elongated grains is constrained by the competition between gravity and magnetic forces a possible scenario is that under turbulent conditions they tend to rest at the bottom with their long axes parallel to the sediment surface and therefore with shallow inclinations whereas weakly turbulent conditions like during the smallest 26 cm thick event do not disturb the magnetic alignment and therefore do not generate inclination shallowing this article is protected by copyright all rights reserved

acoustic facies of holocene megaturbidites in the eastern mediterranean abstract the acoustic facies of holocene megaturbidites in the central western abyssal plains of the eastern mediterranean sea is analysed combining core lithology and synthetic seismograms produced on the basis of p wave velocity profiles derived by multi sensor core logging from a core in the western herodotous trough the acoustic facies of the megaturbidite is divided in two layers 1 an upper transparent low velocity layer corresponding to structureless mud 2 a lower highly reflective high velocity layer corresponding to the graded sandy base correlation with sub bottom profiler data allowed us to estimate in about 21 23 m the maximum total thickness of the two layer megaturbidite in the ionian abyssal plain these results demonstrate that thicknesses traditionally computed on the basis of the acoustically transparent layer alone may produce a relevant underestimation of the total volume of the deposit the total volume of the megaturbidite extending over the ionian and sirte abyssal plains including the western herodotous trough is therefore estimated in about 162 10 km 3

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

model simulations of tsunamis generated by the storegga slides abstract a mathematical model based on the hydrodynamic shallow water equations is developed for numerical simulation of water waves generated by the submarine storegga slides on the norwegian continental slope the equations are solved numerically by a finite difference technique computations of wave amplification effects reveal run up heights for the second storegga slide between 3 and 5 m in exposed areas along the eastern coast of greenland iceland and scotland and the western coast of norway the calculated run up heights agree remarkably well with possible tsunami wave heights deduced from geological evidences along the eastern coast of scotland the generated wave heights are strongly dependent on the acceleration of the slide the effects of shear stress at the interface between the water and the slide body has turned out to be important

caldera development during the minoan eruption thira cyclades greece the well known caldera of thira santorini greece was not formed during a single eruption but is composed of two overlapping calderas superimposed upon a complex volcanic field that developed along a ne trending line of vents before the minoan eruption of 1400 b c thira consisted of three lava shields in the northern half of the island and a flooded depression surrounded by tuff deposits in the southern half andesitic lavas formed the overlapping shields of the north and were contemporaneous with and in many places interbedded with the southern tuff deposits although there appears to be little difference between the composition of magmas erupted differences in eruption style indicate that most of the activity in the northern half of the volcanic field was subaerial producing lava flows whereas in the south eruptions within a flooded depression produced a sequence of mostly phreatomagmatic tuffs many of these tuffs are plastered onto the walls of what appears to have been an older caldera most probably associated with an eruption of rhyodiacitic tephra 100 000 years ago the minoan eruption of about 1400 b c had four distinct phases each reflecting a different vent geometry and eruption mechanism the minoan activity was preceded by minormore eruptions of fine ash 1 the eruption began with a plinian phase from subaerial vent s located on the easternmost of the lave shields 2 vent s grew toward the sw into the flooded depression subsequent activity deposited large scale base surge deposits during vent widening by phreatomagnetic activity 3 the third eruptive phase was also phreatomagmatic and produced 60 of the volume of the minoan tuff this activity was nearly continuous and formed a large featureless tuff ring with poorly defined bedding less

development of a tsunami inundation map in detecting tsunami risk in gulf of fethiye turkey namidance tsunami simulation and visualization tool is used to create tsunami inundation maps showing quantitative maximum tsunami flow depths in fethiye the risk of an extreme but likely earthquake generated tsunami is estimated at fethiye bay for 14 probabilistic earthquake scenarios the bay is located 36 39 5 n 29 7 23 e southwestern turkey which has coastline to the eastern mediterranean sea the tsunami simulation and inundation assessment are performed in three stages 1 formation of a digital elevation model of the region from the best available topography bathymetry dataset 2 estimation of a maximum credible tsunami scenario for the region and determination of related earthquake parameters 3 high resolution tsunami simulation and computation of near shore and overland tsunami dynamics in the study area using tsunami simulation and visualization code namidance 4 determination of spatial distributions of tsunami characteristics maximum water elevations water velocities flow depths under the critical tsunami condition the results are based on the most recent descriptions of potential tsunami sources topographic and bathymetric databases and tsunami numerical models we present an innovative study concentrating on preparation of quantitative flow depths and inundation maps with a very high resolution bathymetry topographic dataset in the eastern mediterranean inundation maps will be used to analyze the effects of possible tsunamis the presented research is crucial to raising the awareness of government officials the public and other stake holders about the high probability of a tsunami event in turkey moreover the results of this study will help to plan for evacuation routes establish safe zones and assist in preparation for the tsunami creating public awareness and planning evacuation routes before the actual tsunami event happens

low sea level stand emplacement of megaturbidites in the western and eastern mediterranean sea piston cores from the balearic and herodotus abyssal plains in the mediterranean sea show that the late pleistocene to holocene sedimentary sequence is dominated by turbidite muds on each plain one turbidite bed is conspicuous by its thickness and this bed can be correlated basinwide on the basis of geochemical compositional analysis and its apparent correspondence with a distinct acoustically transparent layer on high resolution seismic records these megabeds on the two plains represent megaturbidites of very large volume 300 600 km3 each and are shown by ams radiocarbon dating to have been emplaced during the last low stand of sea level at the height of the last glacial maximum the megabed on the balearic abyssal plain is derived from the southern european margin and is the main sedimentation event over the last 120 ka it emplaced as much material as was deposited by smaller flows during the previous 25 ka sedimentation rate curves for the balearic abyssal plain show that falling sea level correlates with increased terrigenous deposition and that gross sedimentation rates in the basin increased as sea level fell from 120 18 ka due to more frequent emplacement of distal turbidites the herodotus abyssal plain megabed is derived from the libyan egyptian continental shelf west of the nile delta and was the dominant sedimentation event in this basin during the past 60 kyr high resolution seismic profiles from the ionian and sirte abyssal plains in the central mediterranean also suggest possible low sea level emplacement of megabeds in these regions available evidence suggests widespread emplacement of megaturbidites throughout the mediterranean at the last glacial maximum although the triggering mechanisms for these events remain speculative catastrophic destabilisation of the margin after a long period of accumulation with an increased rate of sediment supply is suggested

holocene sedimentation in the tectonically active tekirdag basin western marmara sea turkey abstract the effects of various depositional conditions and active tectonics on the late holocene sedimentation in the tekirdag basin west of the marmara sea were investigated in 11 gravity cores and on 3 seismic profiles representing shelf to slope to deep basin floor environments except for the two coarser grained avg 60 sand and gravel and calcareous avg 25 caco 3 shelf cores sediments in the slope and basin floor cores constitute low calcareous avg 12 caco 3 and terrigenous mud 90 silt and clay the occurrences of relatively higher total organic carbon contents in sediments from the southern slope 1 14 1 38 compared to that from the northern slope 0 37 1 2 indicate significant input from the southern rivers the presence of silty sandy laminations within the mud matrix of the cores and chaotic and mounded reflection configurations on the seismic profiles from the slope and basin floor environments all suggest the effects of gravity mass movements of sediments slides slumps turbidites most likely due to seismotectonic events earthquakes however it was difficult to establish a basin wide correlation between the historical earthquake events in the region and the positions of silty sandy laminations in dated deep sea sediment cores due to complicated other events such as repeated river run off and floods increased sediment load and slope failure the water contents of sediments from the basin floor avg 10 30 are significantly lower than those from the slope sediments avg 32 46 the former can be explained by the influences of synsedimentation with tectonics and compaction between the north and south boundary sub faults of the naf system whereas the latter shows fluidization of slope sediments during sliding and slumping radiocarbon dated base sections from three cores revealed that sediment deposition at these sites commenced about 4700 bp when the late holocene depositional conditions changed from the formation of upper sapropels to the present state the increases of organic carbon contents at or near the base sections of the cores support this contention

modelling of tsunami generated by the giant late bronze age eruption of thera south aegean sea greece summary tsunami generated by the late bronze age lba eruption of thera were simulated using synthetic tide records produced for selected nearshore 20 m depths sites of northern crete the cyclades islands sw turkey and sicily inundation distances inland were also calculated along northern crete modelling was performed by incorporating fully non linear boussinesq wave theory with two tsunamigenic mechanisms the first involved the entry of pyroclastic flows into the sea assuming a thick 55 m 30 km3 flow entering the sea along the south coast of thera in three different directions all directed towards northern crete then a thin pyroclastic flow 1 m 1 2 km3 entering the sea along the north coast of thera directed towards the cyclades islands flows were modelled as a solid block that slowly decelerates along a horizontal surface the second mechanism assumed caldera collapse of 19 km3 and 34 km3 modelled as a dynamic landslide producing rapid vertical displacements calculated nearshore wave amplitudes varied from a few metres to 28 m along northern crete from pyroclastic flows and up to 19 m from caldera collapse 34 km3 volume inundation distances on crete were 250 450 m waves produced by pyroclastic flows were highly focused however as a function of sea entry direction smaller volume pyroclastic flows produced nearshore wave amplitudes up to 4 m in the cyclades islands north of thera wave amplitudes in the cyclades from smaller volume caldera collapse 19 km3 were up to 24 m whereas in sw turkey were as low as 2 1 and 0 8 m didim and fethye where lba tsunami deposits have been found wave amplitudes for the larger volume caldera collapse 34 km3 were generally 2 5 3 times larger than those generated by the smaller volume collapse 19 km3 these results provide estimates for understanding possible consequences of tsunami impact in lba coastal zones thus providing criteria at archaeological sites for detecting inundation damage as well as for contemporary hazard assessment they also provide additional criteria for deciphering homogenite layers in the abyssal stratigraphy of the ionian and eastern mediterranean seas

influence of sea level and basin physiography on emplacement of the late pleistocene herodotus basin megaturbidite se mediterranean sea radiocarbon 14c dates from pelagic intervals above a megaturbidite in the herodotus basin give direct evidence of emplacement at the beginning of the last glacial period approximately 27 125 calendar years before present as sea level lowered rapidly and entered a low stand phase the herodotus basin megaturbidite is a basinwide deposit that forms a recognisable acoustically transparent layer on 3 5 khz high resolution seismic profiles and covers an area of approximately 40 000 km2 it thins from about 20 m in thickness proximally to some 10 m distally over a basin length in excess of 400 km the total volume is estimated at around 400 km3 which is significantly more than the volume of sediment that could have been displaced from its most likely source area the funnel shaped marginal embayment of the gulf of salum to the west of the nile cone the additional material may have been derived in part from synchronous failures on other parts of the libyan egyptian shelf and slope but most is believed to have come from large scale erosion at the base of the very large volume turbidity current that was generated from the original slide detailed sedimentary analyses of cores recovered from the megaturbidite show its distinctive characteristics graded sand silt mud and bioturbated mud units poorly developed structures proximally becoming more distinct and ordered distally variation in grain size and structures that suggest either flow separation reflection around topographic highs and or an inherently unstable flow and a mixed source bioclastic terrigenous composition these features together with its size and lateral extent would make any similar megabed an excellent marker horizon in basin analysis a combination of factors was responsible for triggering the initial slide debris flow event that evolved downslope into this mega turbidity current these include lowered sea level that destabilised the outer shelf upper slope sediments tectonic oversteepening of the margin relatively high rates of sedimentation and seismic activity

scale of tsunami generated sedimentary structures in deep water to date no attempt has been made to explore possible constraints on maximum water depths for tsunami generated sedimentary structures of various sediment grain sizes in terms of estimated wavelength and amplitude of potential bedforms this paper explores some possible quantitative limits on threshold velocities for sediment movement at specified water depths assuming airy wave theory which treats tsunami waves as shallow water small amplitude long wavelength waves such a treatment suggests that the passage of tsunami waves is unlikely to entrain sediment coarser than line sand to coarse silt in water depths in excess of 200 mm although fraught with theoretical difficulties and a lack of observations of modern sedimentary bedforms attributable to known tsunamis this paper is presented to stimulate debate rather than provide definitive answers

storms versus tsunamis dynamic interplay of sedimentary diagenetic and tectonic processes in the cambrian of montana the upper cambrian deadwood formation of north central montana is composed mainly of fine grained calcareous sandstone and intercalated silty shale and contains scattered intraclastic flat pebble conglomerate these rocks typical of many mixed carbonate siliciclastic subtidal shelf successions of proterozoic through early ordovician age are distal storm deposits in which the conglomerates are conventionally thought to record occasional very high energy events that scoured incipiently cemented layers in the deadwood formation most sandstone beds have a linear to crudely reticulate pattern of vertical cracks filled with injected silt and clay the cracks exhibit a consistent northwest southeast trend and are very shallow burial deformation structures caused by the passage of seismic waves possibly originating from strong earthquakes in idaho most conglomerates are composed of angular to subangular sandstone intraclasts the polygonal plan view of which is similar in outline to the areas between cracks in the sandstones the deformation implied by the cracks sporadic distribution of conglomerates high degree of scouring indicated and angularity of the intraclasts argue that rather than storms the conglomerates were generated by occasional tsunamis the sweep of these tsunamis across the shallow intracratonic sea created extraordinarily strong oscillating bottom currents at the deeper reaches of storm wave base tsunamites are therefore identified with confidence virtually for the first time in shallow subtidal shelf deposits

catastrophic wave erosion on the southeastern coast of australia impact of the lanai tsunamis ca 105 ka sand barriers along the coast of southern new south wales dating from the last interglacial have been almost completely destroyed most probably by a catastrophic tsunami evidence for catastrophic wave erosion can also be traced to heights of at least 15 m above present sea level on coastal abrasion ramps these erosional features lie above the range of effective erosion by contemporary storm waves and cannot be attributed to either eustatic fluctuations or local uplift chronological evidence for the timing of the destruction of the last interglacial barriers suggests that tsunamis generated by the submarine slide off lanai in the hawaiian islands 105 ka traveled across the pacific and eroded this coast

tsunami and seiche triggered deformation within offshore sediments abstract most studies of tsunami and seiche related deposits have focussed on coastal and near coastal zones which are most readily accessible with few investigations of deeper water settings and the potential soft sediment deformation effects of such waves the late pleistocene lisan formation outcropping to the west of the dead sea contains superb examples of sedimentary slump folds formed in water depths of

tsunamis of volcanic origin summary of causes with particular reference to krakatoa 1883 known tsunamis of volcanic origin are reviewed and classified according to their causes earthquakes accompanying eruptions excluding tectonic events which apparently triggered eruptions pyroclastic flows and submarine explosions have each accounted for about 20 of cases ten causes of volcanic tsunamis are discussed from the risk point of view those due to landslides are particularly dangerous eruptions at calderas are more likely to generate tsunamis than eruptions elsewhere of those killed directly by volcanic eruptions nearly a quarter have died as a result of tsunamis by transfer of energy to sea waves a violent eruption which would be comparatively harmless on land extends greatly the radius over which destruction occurs

impacts tsunamis and the haitian cretaceous tertiary boundary layer the marker bed at the cretaceous tertiary boundary of the beloc formation southern haiti contains abundant coarse grained microtektites and minor amounts of shocked quartz grains in the basal part the upper part is composed of medium grained marl with amalgamated microtektite lenses and finer grained marl lenses disseminated throughout field and petrographic observations and the distribution of planktonic foraminifera suggest that the bed formed from a complex sequence of events a bolide impact nearby produced microtektites that sett1led to form a nearly pure layer at the base vaporized materials with anomalously high extraterrestrial components settled last along with carbonate sediments the entire bed became sparsely consolidated subsequently another major disruptive event perhaps a giant tsunami partly reworked the initial deposit cohesive fragments of the original marker bed mixed with exotic materials were redeposited as lenticular bodies this process also may have caused further mixing of cretaceous and tertiary microfossils as observed at beloc and elsewhere

the storegga slides evidence from eastern scotland for a possible tsunami abstract the second storegga slide on the continental slope off western norway has been dated at between 8000 and 5000 yrs b p a prominent sand layer in flandrian holocene deposits along the coast of eastern scotland and dated at approximately 7000 yrs b p may have been deposited by a tsunami generated by the slide the altitude and stratigraphy of the layer allow estimates to be made of the magnitude of the earthquake which initiated the slide

late quaternary co seismic sedimentation in the sea of marmara s deep basins the deep northern part of the sea of marmara northwestern turkey is composed of several aligned actively subsiding basins which are the direct structural and morphological expression of the north anatolian fault s northern branch the last 20 kyr of their sedimentary fill lacustrine before 12 kyr bp have been investigated through giant piston coring onboard r v marion dufresne marmacore cruise 2001 and chirp subbottom profiler onboard r v atalante during marmarascarps cruise 2002 especially during the lacustrine stage the infilling of the deep basins tekirda central kumburgaz and cinarcic basins up to 1250 m depth was dominated by turbidites with coarse mixed siliciclastic and bioclastic basal part intercalated in hemipelagic type finegrained calcareous and slightly siliceous clays often especially in the thickest ones the turbidites show strong segregation and a sharp boundary between coarse part and suspendedload part in the central basin 8 m of a unique sedimentary event include a 5 to 8m thick homogenite well imaged on seismic profiles the latter is interpreted as related to a major possibly triggered tsunami effect as described in the eastern mediterranean by kastens and cita 1981 in the marine holocene upper part of the sedimentary fill repeated to and from structures affecting silt or fine sand are evidencing seiche like effects and thus earthquake triggering detailed correlations between two deep coring sites 1250 and 1200 m indicate more than 100 overthickening in the deepest one this implies specific processes of distribution of terrigenous input by dense hyperpycnal currents high kinetic energy seiche effect complex reflections on steep slopes the peculiar sedimentary infilling of the sea of marmara s central basin and by extrapolation of the whole set is tentatively interpreted as a direct consequence of the strong seismic activity the imprint of the latter is more obvious prior to the base of the holocene as environmental conditions favoured marginal accumulation especially on the southern shelf of large amounts of erosion products available for mass wasting

the central sudetic ophiolites sw poland petrogenetic issues geochronology and palaeotectonic implications abstract the central sudetic ophiolites cso including the largest and best studied leza ophiolite are relatively well preserved complete palaeozoic ophiolitic sequences at the ne margin of the bohemian massif near the eastern edge of the variscan belt in central europe despite a detailed study and a well documented morb type affinity the geochemical complexity of these ophiolites has only recently been appreciated allowing construction of petrogenetic models we review here petrological and geochemical data indicating a contrast between the plutonic and volcanic members of the leza ophiolite this contrast was previously interpreted in terms of a model of two stage incremental melting of a depleted asthenospheric source producing basaltic magmas and subsequent melts crystallizing as gabbros however we argue that the geochemical differences between the plutonic and volcanic members can be explained by differentiation and cumulation processes of broadly similar parental magmas preliminary interpretation of new shrimp zircon age data from plutonic and volcanic members are consistent with earlier u pb zircon ages and provide evidence for magmatic crystallization of the leza ophiolite at c 400 ma the cso interpreted as traces of the rheic ocean are key for reconstructing the early to mid palaeozoic rifting processes distinct similarities exist with time equivalent ophiolitic units in the western variscan segment of the nw iberian massif the cso represent c 400 ma oceanic crust fragments and their structural position delineates likely major variscan tectonic sutures and tectonic mosaic domains within the variscan accretionary prism

deep mid water bacterial mats from anoxic basins of the eastern mediterranean peculiar pellicles have been recorded in the extant anoxic hypersaline basins of the bannock area and the western strabo trench eastern mediterranean discrete layers of pellicles were found in 29 cores they are oriented parallel to bedding planes or are folded within the sandy base of turbidites and within slumped sediments in addition similar pellicles occur at the surface of or interlocked within gypsum crystals recovered from the bannock area the pellicles are 0 5 3 mm thick and dark greenish grey in colour they foliate into very small 1 mm undulating and anastomosing microlaminae entrapping abundant biogenic and inorganic particles the amorphous organic matter of the pellicles is most probably produced by bacterial masses linked to mineralization processes of the organic debris anaerobic sulphate reducing bacteria desulphovibrio are abundant and the presence of methane bacteria is likely detailed analyses with the light microscope and scanning electron microscope yielded differences and similarities concerning ultrastructure content abundance and morphotypes of the bacterial pellicles from the bannock area and the western strabo trench a consistently well developed ultrastructure comprising thin microlaminae characterizes the bannock pellicles whereas the ultrastructure of the tyro and poseidon pellicles is usually not organized siliceous microfossils are abundant in samples from both sites but centrate diatoms prevail in the bannock pellicles whereas pennate diatoms are overwhelmingly dominant in the tyro and poseidon pellicles calcareous micro and nannofossils together with pyrite framboids are more abundant in samples from the bannock area bacteria are extremely abundant in samples from the bannock area and three different morphological types have been distinguished only one type of bacteria was commonly observed in pellicles from the western strabo trench basins pellicles form at the normal seawater brine interface as substantiated by transmittance profiles and bacteriological investigations therefore the term deep mid water bacterial mats is proposed herein for these peculiar layers after bacterial mats grow at the interface they are included within the sediments by following one of two different paths a when pelagic sedimentation prevails pellicles sink to the basin floor due to the increasing load of biogenic and inorganic detritus and b under a tectonically active regime turbidity currents and slumps can disrupt the interface and destroy the floating mats in the latter case fragments of pellicles are transported to the bottom within the gravity flows

low cloud transitions across the kuroshio front in the east china sea abstractthe east china sea kuroshio ecsk flows in the east asian monsoon region where the background atmospheric circulation varies significantly with season a sea surface temperature sst front associated with the ecsk becomes narrower and sharper from winter to spring the present study investigates how low clouds respond to the ecsk front in different seasons by synthesizing spaceborne lidar and surface visual observations the results reveal prominent cross frontal transitions in low clouds which exhibit distinct behavior between winter and spring in winter cloud responses are generally confined below 4 km by the strong background descending motion and feature a gradual cloud top elevation from the cold to the warm flank of the front the ice clouds on the cold flank of the ecsk front transform into liquid water clouds and rain on the warm flank the springtime clouds by contrast are characterized by a sharp cross frontal transition with deep clouds reaching up to 7 km over the ecsk in both

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

tsunamis generated by eruptions from mount st augustine volcano alaska during an eruption of the alaskan volcano mount st augustine in the spring of 1986 there was concern about the possibility that a tsunami might be generated by the collapse of a portion of the volcano into the shallow water of cook inlet a similar edifice collapse of the volcano and ensuing sea wave occurred during an eruption in 1883 other sea waves resulting in great loss of life and property have been generated by the eruption of coastal volcanos around the world although mount st augustine remained intact during this eruptive cycle a possible recurrence of the 1883 events spurred a numerical simulation of the 1883 sea wave this simulation which yielded a forecast of potential wave heights and travel times was based on a method that could be applied generally to other coastal volcanos

the tsunamite problem the genetic term tsunamite is used for a potpourri of deposits formed from a wide range of processes overwash surges backwash flows oscillatory flows combined flows soft sediment deformation slides slumps debris flows and turbidity currents related to tsunamis in lacustrine coastal shallow marine and deep marine environments tsunamites exhibit enormous variability of features e g normally graded sand floating mudstone clasts hummocky cross stratification etc these sedimentary features may also be interpreted as deposits of turbidity currents turbidites debris flows debrites or storms tempestites however sedimentary features play a passive role when these same deposits are reinterpreted as tsunamites on the basis of historical evidence for tsunamis and their triggering mechanisms e g earthquakes volcanic explosions landslides and meteorite impacts this bipartite sedimentological vs historical approach which allows here classification of the same deposit as both turbidite and tsunamite has blurred the distinction between shallow marine and deep marine facies a solution to this problem is to classify deposits solely by a descriptive sedimentological approach the notion that tsunami waves can directly deposit sediment in the deep sea is unrealistic because tsunami waves represent transfer of energy and they are sediment starved during tsunamis and major storms submarine canyons serve as the physical link between shallow water and deep water environments for sediment transport tsunami related deposition involves four progressive steps 1 triggering stage offshore 2 tsunami stage incoming waves 3 transformation stage near the coast and 4 depositional stage outgoing sediment flows in this progression deep water deposition can commence only after the demise of incoming tsunami waves due to their transformation into outgoing sediment flows deposits of these sediment flows already have established names e g debrite and turbidite therefore the term tsunamite for these deposits is obsolete

brine formation and gypsum precipitation in the bannock basin eastern mediterranean abstract sixty kilograms of gypsum crystals were collected at two dredging stations within a small anoxic hypersaline basin named the bannock basin close to the sirte abyssal plain the basin was investigated in some detail by means of ten precision positioned piston and gravity cores one nansen bottle hydrocast and three ctd stations the sediments of the basin floor are dark h 2 s rich and commonly laminated and contain centimetric crystals of gypsum the water column above the basin has normal salinity down to a depth of 3150 m below this depth the basin is filled with hypersaline brines formed from the dissolution of messinian evaporites outcropping on the steep eastern wall when the brines reach the necessary concentration in ca and in so 4 gypsum may precipitate along the steep eastern wall and within the sediments on the basin floor the very recent age of the gypsum is proved by the inclusions of quaternary planktonic fauna formainifera and pteropods and by radiometric techniques

late quaternary sedimentation in the tyro and kretheus basins southeast of crete abstract this paper summarizes micropaleontologic foraminifera calcareous nannoplankton radiolaria pteropods and pollen grains and sedimentologic piston core data from the eastern mediterranean tyro and kretheus basins 14 c datings indicate a holocene age for the tyro basin cores the latter show anoxic bottom conditions throughout while the kretheus basin core indicates anoxic conditions prior to 3000 years ago and oxic conditions after that time resedimentation through slumps turbidity currents and from suspension resulted in high sediment accumulation rates in both basins reworking in the tyro basin predominantly originated from the basin flanks while the presence of common to abundant metamorphic clastics in the kretheus basin points to a more distant source the minoan eruption of santorini ca 3350 yrs b p which is supposed to have caused a gigantic tsunami is linked to the presence of turbidites and a thick homogenite in the tyro basin the same event may be responsible for the initiation of oxic conditions in the kretheus basin