sedimentary record of recent tsunamis in the huelva estuary southwestern spain abstract the coast of the gulf of cadiz has been repeatedly struck by tsunamis during the late holocene and the historic period historical documents record at least seven catastrophic tsunamis affecting this coast while others have been detected by oceanic instruments nevertheless very few studies have documented the sedimentary record of these tsunamis in the low energy coastal environments of the gulf of cadiz the huelva estuary is located at the central sector of the gulf of cadiz and is a mesotidal estuary fed by the tinto and odiel rivers the mean tidal range of the huelva estuary is ca 2 m and the mean significant wave height is ca 0 5 m the outer part of the estuary is characterized by extensive sand rich sedimentary bodies of marine origin whereas the central and inner parts are infilled by muddy tidally deposited sediment bodies recorded within these estuarine sediment bodies are five laterally continuous shelly units these units display many of the typical characteristics of tsunami deposits each typically comprises an erosional base followed by a fining upwards sequence that begins with the shell accumulation and ends with bioturbated muddy sand the results of 14 c ages and recent radionuclides accumulation rates in this study illustrate that these five tsunami deposits correspond with known events that occurred in ad 1755 1531 949 1033 881 and 395 381 all of which are documented in historical sources

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

tsunami deposits in a lacustrine sequence of the sanriku coast northeast japan abstract lacustrine deposits of the pacific coast of northeast japan consisting mostly of black organic mud contain intercalated thin beds of well sorted medium sand examination of the deposits from a coastal site of sanriku has revealed that sand grains are of marine origin and are fractions of deposits in marshy ponds transported from the littoral environment by a great flooding of seawater the mode of sedimentation shown in the thin beds of sand implies that they were deposited by tsunamis each with a maximum rise of 1 m or more above sea level

first indication of storegga tsunami deposits from east greenland a 2 73 m long sediment sequence from loon lake located at 18m a s l on outer geographical society o east greenland was investigated for its chronology and changes in physical and biogeochemical properties macrofossils and grain size distribution the predominance of marine fossils throughout the sequence dated by 14c ams to between 8630 and 7535 cal yr bp shows that the loon lake at that time was a marine basin which according to existing sea level curves was about 15 35 m deep the sequence mainly consists of fine grained homogeneous sediments which are interrupted by a 0 72 m thick sandy horizon with erosive basis and distinct fluctuations in the grain size distribution and in the physical and biogeochemical properties according to the radiocarbon dates this sandy horizon was deposited after 8500 8300 cal yr bp and is interpreted as originating from the storegga tsunami the record from loon lake provides the first indication of storegga tsunami deposits from east greenland copyright 2006 john wiley sons ltd

sedimentary features of tsunami backwash deposits in a shallow marine miocene setting mejillones peninsula northern chile abstract miocene shoreface sandstones in the caleta herradura half graben northern chile contain an exceptionally coarse deposit that based on sedimentologic and stratigraphic features is regarded as having been laid down during a tsunami event by non cohesive and sediment laden subaqueous density flows interpretations of the principal sediment depositing mechanisms effective in the tsunami surges rely largely on field observations of deposit geometry and internal sedimentary characteristics this example comprises two erosively based sedimentation units that were probably deposited by successive waves in the tsunami wave train the lower unit consists of a clast supported polymodal boulder bearing breccia composed mostly of angular clasts and fewer well rounded clasts framework components are mostly chaotic but may also exhibit either inverse to normal grading or crude normal grading laterally changes in characters of depositional facies are common and abrupt the sand sized bioclastic rich matrix is poorly sorted and very similar to the underlying lower shoreface bioclastic sandstone implying that soft sediments eroded at the lower erosional surface contributed to the tsunami deposit the bulk of the upper unit is a poorly sorted breccia bearing sandstone pebbles and cobbles are scattered massive or normally graded sporadic outsized boulders emplaced as debris fall deposits may occur along the erosional base an array of signatures such as unusually coarse grain size in comparison to the surrounding deposits erosional bases the mixed sources of sediments multiple erosional and depositional events normal size grading or massive texture are all considered distinctive features of tsunamigenic deposits backwash deposition is indicated by the incorporation within the tsunami deposits of sediments derived from mixed sources such as angular clasts from nearby subaerial settings rounded clasts reworked from beach gravels and bioclastic sand eroded from older and unconsolidated shoreface deposits notwithstanding the absence of soft sediment deformation features the marked facies change from a lower shoreface into an upper shoreface environment through the tsunamiites provides directional information about the origin of the tsunami wave it was most likely produced by a sea floor fault displacement associated with an episode of sudden probably coseismic coastal uplift

interregional correlation of disconformities in upper cretaceous strata western interior seaway biostratigraphic and sequence stratigraphic evidence for eustatic change comment in their recent publication walaszczyk et al 2014 made a number of claims about regressive transgressive disconformities in uppermost turonian and lower coniacian upper cretaceous strata of the western interior foreland basin of north america they postulated that two of the disconformities are synchronous extending over a distance of 1650 km along the length of the cretaceous western interior seaway from horseshoe dam alberta canada on the northwestern margin of the basin to pueblo colorado united states near its center they proposed that the disconformities are not just intracontinental but also intercontinental lastly they extended two of the surfaces from north america into central europe and postulated that oscillations in relative sea level with some unknown element of eustatic control were responsible for their formation

shallowly buried enigmatic seismic stratigraphy on the new jersey outer shelf evidence for latest pleistocene catastrophic erosion chirp seismic profiles reveal a prominent seismic facies boundary 0 20 m below the seafloor within an 8 6 10 2 km area of the new jersey outer shelf this irregular boundary separates seismically transparent facies from underlying stratified facies the irregularities form two populations of incisions trending northeast and east northeast stratified blocks within the transparent facies occasionally within presumed incisions together with lithologic evidence indicate that some of the transparent facies was formed by disruption of the stratified facies preservation of steep 50 90 incision flanks implies that deposition of the transparent facies closely followed disruption catastrophic erosion and redeposition following the multiple breaching of glacial lake dams to the north ca 19 12 ka constitute the likeliest mechanisms both for producing facies boundary incisions and emplacing the transparent facies implying that local forcing can generate erosional unconformities on periglacial shelves in the absence of base level change this facies boundary adds complexity to the already complex shallowly buried stratigraphic record of the last glacio eustatic cycle on the new jersey continental shelf long considered typical of periglacial shelves worldwide

the storegga slide tsunami comparing field observations with numerical simulations abstract deposits from the storegga tsunami have been found in coastal areas around the norwegian sea and north sea from the northeast coast of england to beyond the arctic circle in northern norway the tsunami deposits reach onshore elevations of 10 12 m above sea level of their time in western norway 3 6 m in northeast scotland and above 20 m on the shetland islands these elevations are compared with surface wave elevations derived from a numerical simulation of the storegga slide a good agreement is obtained for a retrogressive slide that descends at 25 30 m s and that has short time lags of 15 20 s between each individual slide block

ostracods from a marmara sea lagoon turkey as tsunami indicators abstract a 352 cm long sediment core from hersek lagoon gulf of izmit was investigated for its ostracod species composition in order to evaluate the potential of ostracods to detect tsunami deposits in coastal environments the gulf of izmit is the eastern bay of the marmara sea which is tectonically controlled by the north anatolian fault ostracod shells are rare in the lower third of the core which probably represents a coastal wetland environment according to radiocarbon dating of terrestrial plant remains this unit was deposited between ad 500 and ad 800 above ostracod shells are abundant and dominantly monospecific composed almost exclusively of the widespread brackish water ostracod cyprideis torosa this almost monospecific occurrence indicates the establishment and maintenance of the hersek lagoon after ad 800 three distinct layers of mollusc shells and fragments contain ostracod shells of marine and to a lesser extent non marine origin in addition to those of c torosa the shell layers are further characterized by significant maxima in total ostracod shell numbers the high concentration of ostracod shells the higher species numbers and the mixture of marine lagoonal and non marine ostracod shells shows that shell layers were formed as high energy deposits resulting from tsunamis or large storms in the marmara sea the partial occurrence of non marine ostracod shells in the shell layers possibly indicates that tsunamis with extensive run ups and significant backwash flows caused the high energy deposits rather than large storms the investigated sediments show that lagoonal ostracods can serve as good proxies for tsunamis or large storms through significant variations in total shell numbers species numbers and the mixing of shells of different origin

surfaces with a long history the aptian top shu aiba formation unconformity sultanate of oman discontinuity surfaces in shallow marine carbonate successions may represent significant time gaps in the geological record of ancient epeiric neritic seas understanding the hidden geological information contained in major discontinuities is thus of key significance in palaeo environmental analysis sequence stratigraphy reconstructions of sea level change and basin evolution in the present paper the aptian top lower shu aiba formation discontinuity in the sultanate of oman is taken as a prominent example of a regionally extensive 100 000 km2 surface with a long up to 10 myr and complex geological history the top shu aiba discontinuity formed on the topographically elevated domain of the oman platform and represents in essence the late aptian time interval coeval carbonates in the intrashelf bab basin and oceanic rim indicate forced regression and sequence wise gradual down stepping available regional sedimentological sequence stratigraphic petrographic palaeontological and geochemical evidence from outcrops and cored wells in oman is summarized in part complemented by new data and reviewed in a process oriented context in the field the discontinuity is expressed as a low relief stained surface with evidence for a marine hardground stage being dominant indistinct features that indicate a transient meteoric precursor stage isotope shifts meteoric cements circumgranular cracks etc are present but their interpretation requires careful and detailed work this feature is remarkable as a series of relative sea level falls with amplitudes of up to several tens of metres from the early to late aptian boundary to the end of the aptian are reported from the middle east and elsewhere despite the palaeogeographic position of the study area in the tropical climate zone evidence of deep cutting karst features characteristic for many long term exposure surfaces worldwide is scarce acknowledging the fact that the modern world offers no genuine analogues for the lower aptian carbonate system in oman morphological similarities between actualistic wave eroded coastal terraces and the top shu aiba discontinuity are discussed critically this discussion may imply that during an exposure time of several million years the top shu aiba discontinuity experienced repeated stages of shallow flooding and emergence with each transgression removing portions of the underlying rock record the data shown here exemplify the complexity of hiatal surfaces in epeiric neritic carbonates and may serve as a case example for other major discontinuities

emplacement mechanism and lateral correlation of pyroclastic flow and surge deposits in northen st kitts lesser antilles thick accumulations of pyroclastic deposits have emanated from the mt misery volcano on st kitts lesser antilles during two major eruptive episodes 2 3000 and 41000 a bp systematic logging of coastal sections in the northern part of the island has revealed a variety of deposits including pyroclastic flows surges and intermittent air fall palaeosols and one laterally persistant surge deposit provide important marker horizons permitting correlation of the intervening and less persistent flow deposits block and ash flows traditionally termed nuee ardentes can be subdivided into andesitic pelean type and basaltic andesite st vincent type deposits closely corresponding to the products of historic pyroclastic eruptions in the lesser antilles finer grained ash flows are equally voluminous and comprise scoria semi vesicular andesite and mixed magma and ash deposits a significant pyroclastic surge component has been recognized with characteristic bedforms field evidence suggests that there is a continuous gradation between flow and surge deposits collectively the pyroclastic flow deposits are all of the small volume type and are commonly stratified with poor to moderate sorting and coarse tail grading where thickly developed they show an internal depositional sequence compatible with the standard ignimbrite flow unit well developed bedforms include steeply incised u shaped gullies eroded by the infilling flows the depositional characteristics of these pyroclastic flows appears to be a function of the physical properties of the magma on eruption initial flow magnitude potential energy and degree of topographic channel formation in general grain size and the erosive potential of the flow increases with increasing channel formation whilst sorting and the degree of stratification decrease the development of graded bedding is however apparently unaffected

tsunami sedimentation associated with the lisbon earthquake of 1 november ad 1755 boca do rio algarve portugal a description is given of a distinctive marine deposit at boca do rio on the algarve coast of portugal it is proposed here that the sediment accumulation was deposited by the tsunami generated by the lisbon earthquake of 1 november ad 1755 the deposit exhibits sedimentary characteristics quite unlike other coastal sediment accumulations that are deposited by more moderate wave regimes these include laterally continuous sand layers chaotic pebble horizons large amounts of gravel sized shell debris and distinctive assemblages of marine microfossils a preliminary attempt is made here to use the empirical field and laboratory data to define more clearly the processes of coastal sedimentation that characterize tsunami runup the use of tsunami sediments as time synchronous marker horizons is also discussed

characterization and interpretation of discontinuity surfaces in a jurassic ramp setting high atlas morocco discontinuity surfaces are widely recognized but often poorly understood features of epeiric carbonate settings in sedimentary systems these features often represent hiatus surfaces below biostratigraphic resolution and may represent a considerable portion of the time contained in the sediment record from an applied perspective discontinuities may represent horizontal flow barriers and result in reservoir compartmentalization here a total of 80 condensed surfaces s1 firmgrounds s2 and hardgrounds s3 from a jurassic middle and upper bajocian assoul formation ramp setting of the high atlas in morocco are carefully documented with respect to their morphology their secondary impregnation by fe and mn oxides and phosphates and their palaeoecological record a statistical frequency distribution of two surfaces of the s1 type 1 1 surfaces of the s2 type and 0 4 surfaces of the s3 type per 10 section metres is observed along a 220 m long carbonate succession based on two stratigraphically and spatially separated study windows and correlative sections the stratigraphic frequency distribution the lateral extent and the nature of facies change across discontinuities are documented in a quantitative manner specific features of the study site include the considerable stratigraphic thickness of the assoul formation and the conspicuous absence of subaerial exposure related features based on the data presented here firmground and hardground surfaces are best interpreted as maximum regression related features relative sea level lowstand results in a lowered wave base and wave orbitals and currents result in sea floor omission and lithification care must be taken to avoid overly simplistic interpretations as differences in bathymetry and carbonate facies result in marked changes in discontinuity characteristics in proximal distal transects the data shown here are of significance for those concerned with the interpretation of shoal water carbonate environments and are instrumental in the building of more realistic carbonate reservoir flow models

ground penetrating radar facies of inferred tsunami deposits on the shores of the arabian sea northern indian ocean abstract the occurrence of tsunami waves that affected the shores of the arabian sea including the gulf of oman coastline has been proven by historical reports and sedimentological investigations the damaging effect of such extensive events should not be underestimated in this region in our study we present an investigation of coarse to fine grained marine tsunami deposits in the vicinity of fins sultanate of oman using ground penetrating radar gpr the sedimentary setting along the beach section preserves evidence boulder block deposits as well as trenching results for possible high energy wave impacts the investigated area s environment is representative of conditions which lead to the best possible gpr data quality arid conditions no interference due to electrical power lines and an elevated study area 5 10 m a m s l which eliminates the low frequency noise of the ground and the possibility of salt water in the gpr data 3d visualisation of gpr results from four study areas show e g wedging out of sediments and fining inland features as well as several erosion features at the base of the deposit these findings corroborate the hypothesis of inferred tsunami deposits furthermore the presented gpr investigation technique provides new insights regarding the spatial distribution and internal architecture of palaeo tsunami deposits in comparable tsunami prone regions worldwide

holocene relative sea level changes on the margin of a glacio isostatically uplifted area an example from northern caithness scotland evidence is presented for holocene relative sea level changes on the margin of a glacio isostatically uplifted area the lower wick river valley northern caithness scotland lithostratigraphic b

lateglacial and holocene relative sea level changes and first evidence for the storegga tsunami in sutherland scotland we reconstruct one of the longest relative sea level rsl records in northwest europe from the north coast of mainland scotland using data collected from three sites in loch eriboll sutherland that we combine with other studies from the region following deglaciation rsl fell from a late glacial highstand of 6 8 m od ordnance datum c mean sea level at c 15 k cal a bp to below present then rose to an early holocene highstand and remained at c 1 m od between c 7 and 3 k cal a bp before falling to present we find no evidence for significant differential holocene glacio isostatic adjustment between sites on the northwest lochinver loch laxford north loch eriboll and northeast wick coast of mainland scotland this suggests that the region was rapidly deglaciated and there was little difference in ice loads across the region from one site at the head of loch eriboll we report the most westerly sedimentary evidence for the early holocene storegga tsunami on the scottish mainland the presence of the storegga tsunami in loch eriboll is predicted by a tsunami wave model which suggests that the tsunami impacted the entire north coast of scotland and likely also the atlantic coastline of northwest scotland

ichnology of a subaqueously prograding clastic wedge late pliocene morne l enfer formation fullarton trinidad implications for recognition of autogenic erosional surfaces and delineation of stress factors on irregular echinoids abstract the morne l enfer formation outcrops near fullarton trinidad expose an erosional surface between the shelf deposits below and a prograding clastic wedge of the late pliocene paleo orinoco system above the surface exhibits similarities as well as dissimilarities with examples of regressive surfaces of marine erosion rsmes in wave influenced shelf settings and also with incised valleys inherited from fluvial incision of shelf during a forced regression episode however detailed ichnological studies reveal that the surface is a subaqueous autogenically controlled erosional surface on a shelf dominated by the hyperpycnal and hypopycnal discharges with transient wave influence integration of ichnological and sedimentological characteristics also suggests complicated interrelationships among different stress factors affecting the infauna in different subenvironments especially the irregular echinoids the delta prograded subaqueously through autogenically establishing its lobe on the open shelf without stratigraphically significant erosional removal of sediments in the subaqueously prograding clastic wedge the fluvial influence pertains high stress conditions not only for the adult infauna but also for their larvae within the water column especially in and near the subaqueous distributary channels

stratigraphic evidence for earthquakes and tsunamis on the west coast of south andaman island india during the past 1000 years abstract stratigraphic records from west coast of south andaman island revealed evidence of three historical earthquakes and associated transoceanic tsunamis during past 1000 yrs in addition to the mw 9 3 tsunamigenic earthquake of 26 december 2004 our finding suggests that along with sumatran arc segment the andaman arakan segment is also capable of generating mega subduction zone earthquakes and transoceanic tsunamis to study the near sub surface stratigraphic succession we excavated shallow trenches and obtained geoslices from two sites around collinpur sites 1 and 2 the exposed succession comprised 11 lithounits unit a youngest and k oldest of alternating sequence of coarser units overlain by peaty soils and some of these are indicative of deposition during paleo tsunami events event i that predated ad 800 and is marked by a 35 40 cm thick deposit of fine gravel to coarse sands along with broken shell fragments unit k event ii dated around ad 660 800 is represented by 20 25 cm thick coarse sand and broken shell fragments unit i based on stratigraphic evidences of land level changes this event is attributed to a near source rupture along andaman arakan segment accompanied by a transoceanic tsunami event iii occurred around ad 1120 1300 is marked by a 50 cm thick sand deposit unit g the 2004 tsunami resulted in deposition of 15 cm thick medium to coarse sand at the same location we infer that the 2004 tsunami and event iii resulted in different styles of sedimentation at the same site four events at collinpur along with the record of a subsidence event of ad 1679 from the east coast of andaman close to port blair malik et al 2011 suggest that mega subduction zone earthquakes and associated tsunamis recur at an interval of 300 500 years at variable locations along the sumatra andaman subduction zone

heavy mineral assemblages of the storegga tsunami deposit abstract this study applies heavy mineral analysis to the storegga tsunami deposit across a range of locations whale firth maggie s kettle loch and scatsta voe in shetland scotland the usefulness of this proxy is tested in the identification and characterization of these palaeotsunami units furthermore provenance relationships are established based on the mineralogical content of tsunami deposits and their potential source finally the capability of identifying different phases of tsunami inundation in an 8200 years old tsunami deposit is attempted our results show that overall tsunamigenic samples presented a clear dominance of garnets and amphiboles while whale firth presented a more balanced distribution between these two mineral groups in maggie s kettle loch and scatsta voe the tsunamigenic samples are dominated by amphiboles 90 of transparent heavy minerals focusing on the two dominant heavy minerals garnets and amphiboles and their vertical variation one could observe that garnets mimic the heavy mineral concentration variability higher values at the base and decreasing values to the top this effect of concentration of the heaviest of the heavy minerals assemblage presents similarities with the formation of beach placer deposits in fact based on the heavy mineral vertical variation of the tsunami deposits in maggie s kettle loch scatsta voe and whale firth it is possible to conclude that hornblende most likely amphibole of the assemblage has the lowest concentration factor indicating that its transport process is more efficient and consequently most of its particles eventually may have moved offshore in the backwash phase of the tsunami furthermore the more platy shape of amphiboles also favours a slower deposition the opposite can be observed for garnets which require more energy to be transported i e they are more difficult to entrain by the tsunami waves and tend to be more easily preserved in the formation of a tsunamigenic placer deposit the work presented here is of particular relevance for future high resolution sedimentological studies aiming to distinguish different inundation phases of the storegga tsunami and assess the degree of preservation of these deposits especially considering the specific geomorphological and stratigraphic depositional setting of scotland

tsunami sedimentary facies deposited by the storegga tsunami in shallow marine basins and coastal lakes western norway sedimentary successions in small coastal lakes situated from 0 to 11 m above the 7000 year bp shoreline along the western coast of norway contain a distinctive deposit very different from the sediments above and below the deposit is interpreted to be the result of a tsunami inundating the coastal lakes an erosional unconformity underlies the tsunami facies and is traced throughout the basins with most erosion found at the seaward portion of the lakes the lowermost tsunami facies is a graded or massive sand that locally contains marine fossils the sand thins and decreases in grain size in a landward direction above follows coarse organic detritus with rip up clasts here termed organic conglomerate and finer organic detritus the tsunami unit generally fines and thins upwards the higher basins 6 11 m above the 7000 year shoreline show one sand bed whereas basins closer to the sea level 7000 years ago may show several sand beds separated by organic detritus these alternations in the lower basins may reflect repeated waves of sea water entering the lakes in basins that were some few metres below sea level at 7000 years bp the tsunami deposit is more minerogenic and commonly present as graded sand beds but also in some of these shallow marine basins organic rich facies occur between the sand beds the total thickness of the tsunami deposit is 20 100 cm in most studied sites an erosional and depositional model of the tsunami facies is developed

diatom assemblages in tsunami deposits associated with the 2004 indian ocean tsunami at phra thong island thailand abstract diatom assemblages in sandy deposits of the 2004 tsunami at phra thong island thailand may provide clues to flow conditions during the tsunami the tsunami deposits contain one or more beds that fine upward commonly from medium sand to silty very fine sand diatom assemblages of the lowermost portion of the deposit predominantly comprise unbroken beach and subtidal species that live attached to sand grains the dominant taxa shift to marine plankton species in the middle of the bed and to a mix of freshwater brackish and marine species near the top these trends are consistent with expected changes in current velocities of tsunami through time during high current velocities medium sand is deposited only beach and subtidal benthic diatoms attached to sediment can be incorporated into the tsunami deposit high shear velocity keeps finer material including planktonic diatoms in suspension with decreasing current velocities finer material including marine plankton can be deposited finally during the lull between tsunami waves the entrained freshwater brackish and marine species settle out with mud and plant trash low numbers of broken diatoms in the lower medium sand implies rapid entrainment and deposition whilst selective breakage of marine plankton thalassionema nitzschioides and thalassiosira and coscinodiscus spp in the middle portion of the deposit probably results from abrasion in the turbulent current before deposition

the application of diatoms to reconstruct the history of subduction zone earthquakes and tsunamis abstract earthquake and tsunami records on centennial and millennial temporal scales are necessary to understanding long term subduction zone behavior and the occurrences of large but infrequent events microfossils such as diatoms incorporated into coastal stratigraphy provide some of the most detailed reconstructions of the history of earthquakes and tsunamis we explore qualitative and quantitative techniques that employ the relation between diatoms and salinity tidal elevation and life form to 1 reconstruct records of vertical land level change associated with large earthquakes and 2 identify anomalous sand and silt beds deposited by tsunamis a global database shows that diatoms have been successfully employed in the reconstruction of earthquake and tsunami histories in chile the indian ocean japan new zealand the north sea the pacific northwest of north america and the south pacific we use case studies from some of these locations to highlight advancements in the field and new capabilities that diatoms have enabled examples from the pacific northwest of north america illustrate the evolution of quantitative diatom based reconstructions of earthquake related land level change in alaska and japan diatoms have documented land level changes throughout the earthquake deformation cycle including possible preseismic land level change signals and postseismic deformation diatoms helped identify coseismic uplift along the central chile subduction zone coast and uplift and subsidence along the alaska aleutian megathrust expanding our knowledge of the variability of slip in megathrust ruptures in tsunami studies diatoms help determine the provenance of anomalous sands and silts found in low energy coastal stratigraphic sequences in japan allochthonous marine and brackish diatoms within sand deposits signaled repeated marine incursions into a coastal lake helping identify a possible predecessor to the 2011 tohoku tsunami in the pacific northwest of north america and chile diatoms were used to estimate tsunami run up beyond the landward limit of tsunami sedimentation examples from the north sea thailand and japan show how the fragmentation and sorting of diatom valves may provide evidence of high energy transport during the rapid turbulent flow of a tsunami to conclude we emphasize the importance of studying the modern diatom response to changes in land level and or tsunami inundation to improve diatom based records of prehistoric earthquakes and tsunamis

sedimentary features observed in the tsunami deposits at rikuzentakata city abstract the march 11 2011 tohoku oki tsunami triggered by an earthquake off the east coast of northeastern honshu island tohoku region japan deposited large amounts of sediment on land including the sendai plain and sanriku coast this study reports on the characteristics of the tsunami deposits in rikuzentakata city southeastern iwate prefecture northeastern japan a field survey identified the inundation pattern of the tsunami in this region and the facies model of the tsunami deposits at the bay head deltas of estuarine systems the tsunami deposits in rikuzentakata city generally consist of one to four units that represent a discrete runup or backwash flow each unit is characterized by initial inverse grading and successive normal grading that correspond to the accelerating and decelerating stages of the flow respectively an internal erosional surface often developed between the inverse graded and normal graded units it corresponds to the maximum shear velocity of the flow and truncates the underlying inverse graded unit in the case of the runup unit silty fine grained drapes overlay the graded sandy interval a correlation of the sedimentary structures and grain fabric analysis revealed that the tohoku oki tsunami inundated rikuzentakata city at least twice and that the flow velocity exceeded 2 4 m s paleontological analysis of the sediment and kriging estimation of the total volume of the tsunami deposit implied that the sediments were sourced not only from eroded beach sands but also from the seafloor of hirota bay or more offshore regions

subduction zone slip variability during the last millennium south central chile abstract the arauco peninsula 37 38 s in south central chile has been proposed as a possible barrier to the along strike propagation of megathrust ruptures separating historical earthquakes to the south 1960 ad 1837 1737 and 1575 and north 2010 ad 1835 1751 1657 and 1570 of the peninsula however the 2010 mw 8 8 earthquake propagated into the arauco peninsula re rupturing part of the megathrust that had ruptured only 50 years earlier during the largest subduction zone earthquake in the instrumental record mw 9 5 to better understand long term slip variability in the arauco peninsula region we analyzed four coastal sedimentary sections from two sites tirua 38 3 s and quidico 38 1 s located within the overlap of the 2010 and 1960 ruptures to reconstruct a 600 year record of coseismic land level change and tsunami inundation stratigraphic lithologic and diatom results show variable coseismic land level change coincident with tsunami inundation of the tirua and quidico marshes that is consistent with regional historical accounts of coseismic subsidence during earthquakes along the valdivia portion of the subduction zone 1960 ad and 1575 and coseismic uplift during earthquakes along the maule portion of the subduction zone 2010 ad 1835 1751 in addition we document variable coseismic land level change associated with three new prehistoric earthquakes and accompanying tsunamis in 1470 1570 ad 1425 1455 and 270 410 the mixed record of coseismic subsidence and uplift that we document illustrates the variability of down dip and lateral slip distribution at the overlap of the 2010 and 1960 ruptures showing that ruptures have repeatedly propagated into but not through the arauco peninsula and suggesting the area has persisted as a long term impediment to slip through at least seven of the last megathrust earthquakes 600 years

diatoms as an aid in identifying late holocene tsunami deposits diatoms bacillariophyta help identify the onshore deposits of tsunamis from earthquakes on the cascadia subduction zone along the pacific coast of oregon washington and british columbia and on faults high in the north american plate in the puget sound area of washington at the copalis river washington diatom analyses suggest that a tsunami deposit about 300 calendric years old 300 yr bp originated from sandy shoals of the lower estuary rather than nearby beaches or coastal dunes at cultus bay and west point washington well preserved benthic estuarine diatoms in sand sheets overlying tidal marsh peat indicate that the deposits came from intertidal or nearshore areas of puget sound on an abruptly uplifted mudflat at the landward end of hood canal at lynch cove washington tidal flat diatoms refute the possibility of a terrestrial source for the sand diatoms in 300 yr bp tsunami deposits on the niawiakum river washington confirm that the sand in these deposits had a marine source and help

evidence for three north sea tsunamis at the shetland islands between 8000 and 1500 years ago abstract coastal fen and lake deposits enclose sand layers that record at least three holocene tsunamis at the shetland islands the oldest is the well known storegga tsunami ca 8100 cal yr bp which at the shetlands invaded coastal lakes and ran up peaty hillsides where it deposited sand layers up to 9 2 m above present high tide level because sea level at ca 8100 cal yr bp was at least 10 15 m below present day sea level the runup exceeded 20 m in two lakes we also found deposits from a younger tsunami dated to ca 5500 cal yr bp the sediment facies are similar to those of the storegga tsunami rip up clasts sand layers re deposited material and marine diatoms runup was probably more than 10 m yet another sand layer in peat outcrops dates to ca 1500 cal yr bp this sand layer thins and fines inland and was found at two sites 40 km apart and traced to ca 5 6 m above present high tide the oldest tsunami was generated by the storegga slide on the norwegian continental slope we do not know what triggered the two younger events

mt pelee martinique may 8 and 20 1902 pyroclastic flows and surges abstract the distribution stratigraphic relationships and fragmental components of the may 8 and 20 1902 pyroclastic flows from mt pelee martinique together with eyewitness accounts suggest the following explanation for those eruptions the eruptions were vertically directed magmatic perhaps initiated phreatically and contained abundant juvenile lithics from congealed magma of the dome and neck this resulted in a two part eruption column having 1 a dense lithic charged part which collapsed into the crater and flowed out of a pre existing notch in its side giving rise to pyrochlastic flows and 2 a magmatically derived column containing gases juvenile vitric material and crystals which largely by passed the neck and dome and escaped into the atmosphere all of the energy of the flows was apparently focused through the notch they emerged fully turbulent and flowed down riviere blanche gravity segregation of large and abundant fragments soon resulted in a dense high concentration poorly fluidized block and ash flow confined to the valley leaving above a fully turbulent high energy ash cloud surge as the ash cloud surge moved down the mountain it continued to expand outward the process of gravity segregation continued as the ash cloud surge expanded resulting in secondary block and ash underflows toward st pierre the secondary block and ash flows developed on a gently sloping upland surface 100 m or more above the valley of riviere blanche the turbulent fragment depleted surges above the secondary block and ash flows maintained sufficient energy to devastate the landscape outward to about 3000 m including st pierre the surges refracted around obstacles and in one place moved up a small valley in a direction opposite to the main flows

patterns of holocene relative sea level change in the north of britain and ireland temporal and spatial patterns of relative sea level rsl change in the north of britain and ireland during the holocene are examined four episodes each defined by marked changes in the rsl trend are identified each episode is marked by a rise to a culminating shoreline followed by a fall episode hrsl 1 dates from the younger dryas to early in the holocene hrsl 2 to hrsl 4 occurred later in the holocene there is extensive evidence for each episode and on this basis the spatial distribution of the altitude data for three culminating shorelines and a shoreline formed at the time of the holocene storegga slide tsunami ca 8110 100 cal bp is analysed ordinary kriging is used to determine the general pattern following which gaussian trend surface analysis is employed recognising that empirical measurements of rsl change can be unevenly distributed spatially a new approach is introduced which enables the developing pattern to be identified the patterns for the most widely occurring shorelines were analysed and found to be similar and common centre and axis models were developed for all shorelines the analyses described provide models of the spatial pattern of holocene rsl change in the area between ca 8100 cal bp and ca 1000 cal bp based on 2262 high resolution shoreline altitude measurements these models fit the data closely no shoreline altitude measurement lying more than 1 70 m or 1 82 m from the predicted value the models disclose a similar pattern to a recently published glacial isostatic adjustment model for present rsl change across the area indicating that the overall spatial pattern of rsl change may not have varied greatly during the last ca 8000 years

local variation of inundation sedimentary characteristics and mineral assemblages of the 2011 tohoku oki tsunami on the misawa coast aomori japan abstract the 2011 tohoku oki tsunami caused severe damage to the coastal regions of eastern japan and left a sediment veneer over affected areas we discuss differences in depositional characteristics of the 2011 tohoku oki tsunami from the viewpoint of the sediment source coastal topography and flow height the study area on the misawa coast northern tohoku includes a 20 km long coastline with sandy beaches coastal dunes and a gently sloping lowland this landscape assemblage provides an opportunity to examine the effects of topography on the characteristics of the tsunami deposit during field surveys conducted from april 10 to may 2 2011 we described the thickness facies and structure of the tsunami deposit we also collected sand samples at approximately 20 m intervals along 13 shore perpendicular transects extending up to 550 m inland for grain size and mineral assemblage analysis the tsunami flow height was estimated by measuring the elevation of debris found in trees broken tree limbs or water marks on buildings the nature of the coastal lowland affected the flow height and inundation distance in the southern part of the study area where there is a narrow 100 m wide low lying coastal strip the run up height reached 10 m on the landward terrace slopes to the north the maximum inundation reached 550 m with a run up height of 3 2 m on the wider low lying coastal topography the average flow height was 4 5 m the tsunami eroded coastal dunes and formed small scarps along the coast immediately landward of the coastal dunes the tsunami deposit was more than 20 cm thick but thinned markedly inland from this point close to the dunes the deposit was composed largely of medium sand 1 2 with planar and parallel bedding but with no apparent upward fining or coarsening the grain size was similar to that of the coastal dune and we infer that the dunes were the local source material for the tsunami deposit at this point the mineral assemblage of the tsunami deposit was dominated by orthopyroxene and clinopyroxene and was also similar to the dune and beach sand at sites more than half the inundation distance inland the thinner tsunami deposit consisted mainly of fine sand 2 375 with some upward fining the difference in grain size and sedimentary characteristics was probably caused by differences in sediment transportation and depositional processes we infer that the well sorted finer sediments were deposited out of suspension whereas the relatively coarse sands were laid down from traction flows the depositional characteristics of the 2011 tohoku oki tsunami deposit appeared to have been affected mainly by the coastal topography and the extent of erosion at any one point as opposed to flow height

correlation of ash flow tuffs discrimination and correlation of ash flow sheets is important in structurally complex long lived volcanic fields where such sheets provide the best keys to the regional stratigraphic framework three dimensional complexities resulting from pulsatory eruptions sectorial emplacement mechanical sorting during outflow thermal and compositional zoning of magmas the physical zoning of cooling units and structural and erosional disruption can make such correlation and discrimination difficult when lithologic magnetic petrographic chemical and isotopic criteria for correlating ash flow sheets are critically evaluated many problems and pitfalls can be identified distinctive phenocrysts pumice clasts and lithic fragments are among the more reliable criteria as are high precision k ar ages and thermal remanent magnetization trm directions in unaltered welded tuff chemical correlation methods should rely principally upon welded or nonwelded pumice blocks not upon the ash flow matrix which is subject to fractionation mixing and contamination during emplacement compositional zoning of most large sheets requires that many samples be analyzed before phenocryst glass or whole rock chemical trends can be used confidently as correlation criteria

large scale washover sedimentation in a freshwater lagoon from the southeast australian coast sea level change tsunami or exceptionally large storm a distinct lens of marine sand up to 90 cm thick confined vertically by peat is found in the upper fill of a closed freshwater back barrier lagoon on the southeast australian coast coring of the deposit suggests it extends continuously up to 600 m inland and tapers landward rising to 1 6 m above principle datum in places the sand is overlain by accumulations of organic rich silt that contain charophytes indicating re estab lishment of lagoon conditions hypotheses considered for the deposition of the sandsheet are higher holocene sea level storms and tsunami ground penetrating radar transects of the seaward dune system suggest a penecontemporaneous erosional contact between a series of truncated pre event dunes and several small over lying post event dunes dating the sandsheet was problematic but it is confined to the last 800 years the young age combined with a lack of associated beach deposits and evidence of wave scouring suggest that a higher sea level hypothesis is unlikely this sand lens is attributed to a large scale washover event from the southeast based on comparisons with modern storm deposits from the same coast and sedimentological diagnostic crite ria derived from studies of modern storm and tsunami deposited sandsheets it is concluded that this sand deposit is the product of a short lived large scale overwash event attributed to a late holocene tsunami

overlapping paleoichnology paleoecology and taphonomy analysis of tooth traces in a late pleistocene early holocene megafaunal assemblage of brazil and description of a new ichnotaxon in hard substrate abstract tooth traces are key evidence in vertebrate taphonomy paleoecology and paleoichnology they are product of feeding behavior of vertebrates and can also be evaluated in biostratinomic perspective regarding the quaternary fossil record of vertebrates in brazil the taphonomic paleoecological information of tooth traces has been underexplored recently features of this sort were identified in quaternary mammals fossils recovered from lajedo da escada caves state of rio grande do norte northeastern brazil consisting in an opportunity to unveil taphonomic paleoichnological and paleoecological aspects of the quaternary megafauna the ichnospecies machichnus bohemicus and m fatimae are recorded in the late pleistocene early holocene age the latter is a new ichnospecies of machichnus described herein the traces m fatimae and m bohemicus observed in glyptotherium sp were generated outside the cave by an adult individual of the large sized canid protocyon troglodytes during event of predation nonetheless m bohemicus recognized in eremotherium laurillardi and smilodon populator was generated by either a juvenile individual of p troglodytes or an adult of the small sized canid cerdocyon thous in a scavenging context outside the cave probably other tooth traces previously reported to the quaternary of brazil in the states of ceara and minas gerais can be assigned to machichnus

moss growth patterns and timing of human exposure to a mesolithic tsunami in the north atlantic the storegga tsunami triggered 8150 yr ago by one of the largest submarine slides on earth flooded margins of the north sea and the norwegian sea that were occupied by mesolithic peoples sand deposits of storegga age overlie the remains of coastal settlements in norway and scotland the resulting casualties however depend on the season when the tsunami struck human exposure would have been least in summer and early autumn when mesolithic peoples went to the mountains to hunt reindeer the hunters returned to the coast in late autumn to settle into their winter quarters here we use moss stems to show that the storegga tsunami happened in late autumn the storegga tsunami deposits contain samples of the moss hylocomium splendens some of these stems retain green color and chlorophyll that imply burial alive h splendens has a characteristic growth cycle where new segments branch off from previous year s growth the storegga mosses have segments more mature than those of modern july and august samples but as mature as those from october through december the enormous storegga tsunami thus occurred late enough in the year to have reached a large fraction of the people then inhabiting western norway and northeast scotland for those who survived the tsunami the loss and destruction of dwellings boats equipment and supplies must have made the following winter very difficult

petrography and environmental controls on the formation of phanerozoic marine carbonate hardgrounds early marine seafloor lithification of carbonate sediments leads to the formation of hardgrounds and is known from rocks as old as the proterozoic hardground surfaces however are more commonly recorded in the phanerozoic sedimentological archive while ecological studies of hardground biota abound the environmental and physico chemical parameters leading to the development of seafloor lithification remain in many cases poorly understood and documented this paper reviews published evidence on the petrography mineralogy and geochemistry of phanerozoic carbonate hardgrounds within a process oriented context of their environmental controls hardgrounds typically develop in warm and shallow agitated tropical waters that are saturated with respect to caco3 but are also reported from hemi pelagic to bathyal realms and from cool water temperate settings a range of early marine cement types are documented from present day hardgrounds whereas preserved cement fabrics and related mineralogies are less diverse in early phanerozoic hardgrounds carbonate hardgrounds are widespread during calcite sea periods e g ordovician and cretaceous as opposed to some preservation bias ancient aragonite seas e g permian and triassic obviously the relation between seawater chemistry and hardground abundance and attributes is not an easy one here the concept of aragonite versus calcite seas serves as a first order template for the sake of a structured discussion whereas modern aragonite mode oceans document a significant diversity in spatial and bathymetric seawater properties this spatio temporal complexity is perhaps reflected in the scarce record of calcite sea hardgrounds from the devonian or paleogene rock record contrasted by the abundance in aragonite holocene and recent seas holocene hardgrounds allow for the direct assessment of rates of and reasons for early subaquatic lithification and in most cases escaped subsequent non marine diagenetic overprint conversely studies of ancient hardgrounds are often biased by early biological and mechanical erosion the degree of diagenetic overprint and tectonic to orogenic processes the formation distribution and physical properties of hardgrounds depend on the global climatic context greenhouse icehouse modes on sea level changes on ocean stratification on the spatial extent of epicontinental seas and carbonate depositional environments and on the spatially different mineralogies and rates of carbonate production the fabrics and mineralogies of early hardgrounds cement seem to substantially hinge on variations in atmospheric co2 thus the application of lessons from modern to ancient hardground case examples is not straightforward a holistic model explaining the full variability of controls on submarine hardground formation and their cement petrography throughout the phanerozoic is as yet lacking a more critical view on secular changes in hardground formation patterns is clearly needed future work should rely on the combination of sedimentological stratigraphic palaeoecological petrographic and geochemical approaches specific emphasis should be given to time intervals triassic carboniferous cambrian etc where the bulk of reported case studies is at best scarce

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

sediment sources and sedimentation processes of 2011 tohoku oki tsunami deposits on the sendai plain japan insights from diatoms nannoliths and grain size distribution abstract the 11th march 2011 tohoku oki tsunami inundated the low lying sendai plain japan more than 5 km inland leaving sand and mud deposits over most of the area in order to establish the sources of the tsunami deposits and interpret processes of their sedimentation samples were collected from the deposits underlying soils and the beach along a shore perpendicular transect and analysed for grain size diatom assemblages and nannoliths the fining inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland more specifically there was a slight fining of the coarse to medium sand mode within the sandy deposits and an increased contribution of the coarse and very coarse silt fraction in the mud deposits the tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening fining upward trends few diatoms were present in beach sediments soils and tsunami deposits within 1 km of the coastline while diatoms were more abundant farther inland diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater brackish habitats while no typically marine species were encountered nannoliths were generally absent in the studied sediments except for few specimens our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami the sandy tsunami deposits within 1 km of the coastline were mostly derived from beach and dune erosion from 1 to 2 km landward the contribution of these sources decreased while sources comprising local soil erosion and the entrainment of sediments from the teizan bori canal increased farther inland local soil erosion was the major sediment source for the mud deposits the tsunami deposits were most likely deposited during at least two inundations mostly out from suspension resulting in an upward grain size fining trend however bed load deposition was also important in the sandy deposits as suggested by a common grain size upward coarsening position on c m diagrams and frequent horizontal lamination the present study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin marine diatoms foraminifera nannoliths marine sediments may be of limited use

the holocene storegga slide tsunami in the united kingdom all currently known sites in the united kingdom with evidence for the holocene storegga slide tsunami are described information on the altitude distribution stratigraphical context age particle size profile and microfossil characteristics of the deposits is presented the tsunami involved a greater area than previously described reaching a coastline over 600 km long the ubiquitous sand layer which forms the main deposit associated with the event is shown to exhibit a consistent morphology and a particle size profile marked by fining upwards sequences an analysis of new and previously published radiocarbon dates indicates that from evidence in the united kingdom the event took place sometime around 7100 radiocarbon years bp 7900 calibrated years bp a new isobase model for mainland scotland and adjacent areas providing a preliminary estimate of land uplift since the tsunami is presented the model estimates contemporary sea surface level offshore at 14 m below the present day mean high water spring tides tsunami sediment run up is greatest in inlets where it reaches at least 25 m on shetland and at least 5 m along the mainland coastline to the south and run up of the tsunami would have exceeded these values the tsunami sediments identified here are considered particularly valuable as a synchronous marker horizon

ignimbrite depositional facies the anatomy of a pyroclastic flow a model is presented for the depositional regimes in a pyroclastic flow to explain the origin of facies in the taupo ignimbrite and to compare these with other published examples in this model a pyroclastic flow consists of a head a body and a tail the head which is where fluidization caused by air ingestion occurs generates layer 1 deposits on lithological grounds these are divided into layers 1 p which is fines depleted and rich in pumice and 1 h which is fines depleted and rich in lithics and crystals layer 1 p represents material thrown forwards from the flow head and is termed the jetted deposits layer 1 h represents material sedimented from within the flow head and is termed the ground layer the body represents the bulk of the flow and the tail is its trailing part which is slowed by ground friction these parts generate the layer 2 deposits which include the valley pond ignimbrite and its associated ignimbrite veneer deposit localized depositional modes within the body and tail generate distinctive coarse pumice concentration zones and pumiceous lee side lenses behind obstacles at its outer limits all of the flow on interfluves is affected by air ingestion fluidization producing the distant facies which combines features of both layer 1 and 2 deposits one important conclusion of this work is that the thicknesses and compositions of the various facies are not related in any simple way to the thickness and composition of the parent flow

the sedimentology of middle holocene tsunami facies in northern sutherland scotland uk abstract lagoonal sediments attributed to the main holocene marine transgression in strath halladale northern sutherland contain a complex coarser layer believed to have been deposited during the tsunami associated with the second storegga slide off south west norway the coarser sequence is dated at between 7590 50 and 7290 50 radiocarbon years bp 6507 6260 cal bc and 6228 6029 cal bc detailed stratigraphical analysis has determined a distinctive suite of sedimentary sub units within the coarser layer in marked contrast to the sediments which occur above and below a pronounced erosional unconformity with the underlying sediments is recorded with the base of the tsunami layer characterised by eroded material from the underlying peat the presence of a mixed diatom assemblage although fragmentary indicates a chaotic accumulation of the deposit with all habitats represented variations in particle size within the sequence disclose striking similarities with those from contemporary tsunami deposits the run up of the tsunami sediments is calculated at a minimum of 4 6 m this is the first occasion on which a deposit of the second storegga slide tsunami has been found outside the north sea basin and indicates that the area affected by the tsunami may have been larger than has been previously described

geological records of western pacific tsunamis in northern taiwan ad 1867 and earlier event deposits abstract located in the western circum pacific seismic zone taiwan is an ideal area for recording tsunamis that originate in the tectonically and volcanically active systems of the ryukyu arc okinawa trough and luzon arc however because of taiwan s short historical record there is only credible evidence for one disastrous tsunami which occurred in northern taiwan in ad 1867 to better understand the western pacific tsunamis an upper holocene deposit of a coastal plain inundated by the ad 1867 tsunami was investigated to search for geological evidence of tsunamis based on facies characteristics and sediment composition we identified two sharp based decimetre thick marine quartzose sandy layers that fine upward and landward intercalated with floodplain marsh sand and mud the fluvium are rusty red rich in volcanic clasts and fe and comparable to modern riverine sediments of local andesitic provenance extending 0 8 km inland the marine quartzose sandy layers are light coloured and rich in quartz and si have high ca ti values and are comparable to the modern beach dune sediments of regional siliciclastic provenance radiocarbon dating indicates that the marine sandy layers are correlated with the ad 1867 tsunami and an older event at the boundary between the 17th and 18th centuries both events were probably associated with reported earthquakes involving normal faulting in addition the distribution patterns of the two marine sandy layers are similar suggesting that the inundation distances run ups and flow heights of the two events are comparable this indicates that the disastrous tsunamis were frequent in the area between northern taiwan and the okinawa trough of the western circum pacific seismic zone

a 600 year long stratigraphic record of tsunamis in south central chile the stratigraphy within coastal river valleys in south central chile clarifies and extends the region s history of large earthquakes and accompanying tsunamis our site at quidico 38 1 s 73 3 w

palaeoecology and evolution of marine hard substrate communities abstract marine organisms have occupied hard substrates since the archaean shells rocks wood and sedimentary hardgrounds offer relatively stable habitats compared to unconsolidated sediments but the plants and animals which inhabit them must develop means to gain and defend this premium attachment space hard substrate communities are formed by organisms with a variety of strategies for adhering to and or excavating the substrates they inhabit while mobile grazers organically attached and even soft bodied organisms may leave evidence of their former presence in ancient hard substrate communities a superior fossil record is left by sessile encrusters with mineralised skeletons and by borers which leave trace fossils furthermore encrusters and borers are preserved in situ retaining their spatial relationships to one another and to the substrate spatial competition ecological succession oriented growth and differential utilisation of exposed vs hidden substrate surfaces can all be observed or inferred hard substrate communities are thus excellent systems with which to study community evolution over hundreds of millions of years here we review the research on modern and ancient hard substrate communities and point to some changes that have affected them over geological time scales such changes include a general increase in bioerosion of hard substrates particularly carbonate surfaces through the phanerozoic this is at least in part analogous to the infaunalisation trends seen in soft substrate communities encrusting forms show an increase in skeletalisation from the palaeozoic into the mesozoic and cenozoic which may be a response to increasing levels of predation hard substrate communities considering borers and encrusters together show a rough increase in tiering through the phanerozoic which again parallels trends seen in soft substrate communities this extensive review of the literature on living and fossil hard substrate organisms shows that many opportunities remain for large scale studies of trends through time at the community and clade levels palaeontologists will especially benefit by closer integration of their work with that of neontologists particularly in aspects of ecology such as larval recruitment competition and succession

geomorphological effects of tsunami run up and backwash abstract geomorphological processes associated with tsunami run up and backwash are highly complex to date most studies have considered the sedimentology of palaeo tsunamis while almost no detailed studies have been undertaken in areas known to have been affected by tsunamis in recent times research on contemporary tsunamis show that coastal landscapes may be greatly altered not only by direct tsunami run up orthogonal to the shoreline but also by episodes of vigorous backwash and by water flow sub parallel to the coastline the combined effect of these processes produces hitherto unrecognised coastal landforms that are dominated by the effects of high magnitude erosion and deposition deposition of large boulders is also associated with severe tsunamis while in adjacent areas run up processes often result in the deposition of continuous and discontinuous sediment sheets in many instances the upper limit of sediment deposition lies well below the upper limit of wave run up which is frequently marked by a well defined zone of stripped vegetation and soil the processes described have considerable implications for models of coastal evolution it may even be the case that the evolution of particular stretches of coastline are dominated by such high magnitude low frequency events

onshore tsunami deposits caused by the 1993 southwest hokkaido and 1983 japan sea earthquakes onshore tsunami deposits resulting from the 1993 southwest hokkaido and 1983 japan sea earthquakes were described to evaluate the feasibility of tsunami deposits for inferring paleoseismic events along submarine faults tsunami deposits were divided into three types based on their composition and aerial distribution a deposits consisting only of floating materials b locally distributed siliclastic deposits and c widespread siliclastic deposits the most widely distributed tsunami deposits consist of the first two types type c deposits are mostly limited to areas where the higher tsunami runup was observed the scale of tsunami represented by vertical tsunami runup is an important factor controlling the volume of tsunami deposits the thickest deposits about 10 cm occur behind coastal dunes to produce thick siliclastic tsunami deposits a suitable source area such as sand bar or dune must be available in addition to sufficient vertical tsunami runup estimation of the amounts of erosion and deposition indicates that tsunami deposits were derived from both onshore and shoreface regions the composition and grain size of the tsunami deposits strongly reflect the nature of the sedimentary materials of their source area sedimentary structures of the tsunami deposits suggest both low and high flow regimes consequently it seems very difficult to identify tsunami deposits based only on grain size distribution or sedimentary structure of a single site in ancient successions

bivalve trace fossils in an early miocene discontinuity surface in patagonia argentina burrowing behavior and implications for ichnotaxonomy at the firmground hardground divide abstract ichnofossils developed in a firmground at the contact between the middle eocene lower miocene continental sarmiento formation and the lower miocene marine chenque formation in central eastern patagonia argentina are assigned to gastrochaenolites ornatus kelly and bromley kelly s r a bromley r g 1984 ichnological nomenclature of clavate borings palaeontology 27 793 807 and interpreted as dwelling structures of suspension feeding bivalves these record the activities of pholadids most likely belonging to the pholadinae bivalves are usually preserved as casts and external molds within the biogenic structures the details of the internal ornamentation in g ornatus allow identification of two sets of scratch patterns permitting comparison with the boring behavior of modern pholadids in terms of ichnotaxonomy when the same organism is able both to excavate and to bore and the excavation technique is identical to the mechanical perforation technique the same name should be used accordingly gastrochaenolites whilst more commonly assigned to bioerosion structures in hard substrates is herein regarded as available also for bivalve burrows in firm but unlithified substrates the firmground studied here represents a co planar surface of lowstand erosion and transgressive erosion that produced exhumation of deposits belonging to the sarmiento formation providing appropriate conditions for the development of the glossifungites ichnofacies differential erosion of the apertural necks the heterogeneity of the available casting material and the wide size range of ichnofossils suggest a complex history of colonization and erosion for this surface

sedimentary record of late holocene seismicity and uplift of hersek restraining bend along the north anatolian fault in the gulf of izmit abstract the north anatolian fault naf in the gulf of izmit eastern marmara sea consists of three subsegments linked by bends the present study focuses on the hersek peninsula which is a ridge of pleistocene and holocene deposits emerged by tectonic uplift at a left stepping 7 restraining double bend between the karamursel and darica segments of the naf the hersek bend has acted as a local barrier to westward rupture propagation whereby the marine substrate was deformed by transpressional thrusting combined with underwater slumping the record of the hersek ridge emergence has been analyzed in excavation trenches by the methods of sedimentology geomorphology and radiocarbon dating the time of initial emergence is unknown but the highest recognized palaeoshoreline terrace indicates that around 2250 yrs bc a narrow ridge was already standing at least 13 m above the sea level the uplift rate of the ridge is about 3 5 m kyr for the past 4250 years the development of the three lower lying successively younger palaeoshoreline terraces involved episodes of uplift accompanied and or followed by tsunami events the ridge s stepwise uplift above the sea level amounted to at least 28 m on the basis of radiocarbon dates the deciphered seismotectonic events have been tentatively correlated to the region s historical earthquakes which allowed the fault bend s behavior to be reconstructed and time constrained the study gives new insights into the dynamics of an naf restraining bend and the non characteristic behavior of the naf segments in the quake stricken region of eastern marmara sea

distribution geomorphology and lithofacies of cliff top storm deposits examples from the high energy coasts of scotland and ireland abstract cliff top storm deposits ctsds occur on cliffs at elevations of up to 50 m above sea level at exposed sites on the deep water coasts of the british isles this study examines the distribution geomorphology and lithofacies of ctsds at sites from shetland orkney caithness and the outer hebrides in scotland and from the aran islands in galway bay in ireland ctsds are generated largely by the quarrying of blocks from the cliff top and transported by green water bores across cliff top platforms and ramps to be deposited in backing ridges or as debris spreads maximum boulder sizes reach 48 m 3 but it is likely that much larger blocks can be quarried prior to disintegration during transport eye witness accounts and field mapping demonstrate that formation and modification of ctsds has continued during major storms over recent decades recent ctsds bury a range of man made debris but older deposits lack this and instead show weathering effects that indicate a longer residence time in shetland osl dates on intercalated sands suggest that the oldest ctsds date from 800 ad radiocarbon dates on shell buried inside ctsd ridges relate to major storms between 1700 and 1900 ctsds represent an overlooked archive of storm sedimentation that has great potential for the elucidation of local storm chronologies ctsds also provide evidence of wave impacts on any part of the cliff face or top in fundamental contrast to the concentration of wave action at the cliff foot implicit in traditional models of the erosion of rock coasts

bathymetry sediment texture and substrate cohesiveness their impact on modern glossifungites trace assemblages at willapa bay washington abstract glossifungites demarcated discontinuities have been demonstrated to have stratigraphic significance unfortunately their stratigraphic utility commonly eclipses the palaeoecological information derived from such surfaces this paper attempts to identify factors that influence the nature of trace assemblages observed in modern firmgrounds in particular it focuses on the causes of lateral variability and erosional topography inherent to glossifungites surfaces the extensive pleistocene database at willapa bay is used to test the interpretations striking heterogeneity in glossifungites assemblages is documented from modern firmgrounds at willapa bay this variability is related to intertidal zonation sediment texture the absolute firmness of the firmground and the presence or absence of a sediment veneer generally subtidal and lower to middle intertidal firmgrounds are colonized by crustaceans the upogebia association or the bivalve petricola the petricola association these surfaces are characteristically burrowed with thalassinoides and gastrochaenolites like traces the upper intertidal is dominated by the polydora association the burrows of which include diminutive diplocraterion and arenicolites like traces sandy and heterolithic substrates are avoided by burrowing crustaceans and polychaetes alike in contrast petricola is observed in muddy sandy mud and heterolithic substrates therefore where colonized sandier substrates are dominated by the clavate gastrochaenolites like burrows produced by these bivalves the absolute firmness of exhumed firmgrounds is quite variable the upogebia association is absent in substrates that exceed 10 9 pa polydora dominated assemblages are poorly developed in similar firmgrounds the petricola association however is well developed in relatively firm substrates finally the morphologic characteristics of exhumed modern firmgrounds show that the history of a glossifungites demarcated surface can be extremely dynamic firmground surfaces are exposed to an array of physico chemical conditions as they are exhumed colonized and pass into the geological record these surfaces are commonly re exhumed due to auto and allocyclic processes

geological and historical records of tsunami in australia abstract the indian ocean tsunami iot of 2004 has resulted in significant interest within australia about the record of tsunami for the continent because an understanding of tsunami hazard begins with a catalogue of past events here a preliminary catalogue of tsunami affecting australia is presented the catalogue contains entries for 57 tsunami events the oldest event is dated at 3 47 ga the most recent is the july 17th 2006 forty four tsunami were recorded on the new south wales coast although the nw coast of western australia records a significant number of events forty seven events have affected australia since ad1858 maximum run up for an historic event is 6 m asl whilst the maximum run up for a palaeotsunami event is reported at an elevation of at least 100 m asl twenty three percent of historic australian tsunami were generated by unknown causes and papua new guinea the solomon islands and indonesia collectively represent the most important source area of historic tsunami for australia geological records for palaeo and historic tsunami are identified and summarised the geological record of tsunami represents a potentially important source of information for australian tsunami however at the present time the geological record is both limited and controversial and future research should seek to re examine proposed geological evidence of tsunami from an analysis of this preliminary catalogue of australian tsunami a series of key research priorities have been identified to guide future research in the region

volcanic hazards on st kitts and montserrat west indies pyroclast flows constitute the main potential hazard on both st kitts and montserrat radiocarbon dating indicates that the last major series of eruptions on st kitts occurred about 2000 years ago although a more recent phase of activity 1620 50 years b p produced the pyroclast surge and blast deposits of the steel dust series on montserrat the last major eruptive episode occurred about 19000 years ago and there is rather uncertain evidence for a small near historic eruption pyroclast flow material tends to have a basaltic andesite composition on st kitts and that of a more siliceous andesite on montserrat at mt misery st kitts the present configuration of the summit region has exercised considerable control over the distribution of pyroclast flows and the western side of the volcano remains the most vulnerable to future activity of this kind the summit morphology of the soufriere hills montserrat is more complex and appears to have changed during relatively recent times making the preferred pathway down the eastern slopes over the less populated side of the island pyroclast falls regarded as a negligible hazard on montserrat may attain a critical destructive thickness of c 50 cm once every few thousand years on st kitts lava flows which may be considered unimportant on montserrat are also likely to be a minor and very infrequent hazard on st kitts

exploring the continental shelf for low geological risk nuclear waste repository sites using petroleum industry databases a uk case study abstract site selection for deep disposal of intermediate and high level radioactive waste in the uk to date has not taken full advantage of oil industry databases that cover offshore areas the shallow water area of the uk continental shelf is twice that of the onshore area and due to variations in regional geology many geological settings occur that are not found onshore the geology and hydrogeology of the uk continental shelf contrast in many respects with that of onshore areas the geology of the north sea in particular is constrained by over 3000 deep 2 km exploration wells 50 000 km 2 of 3d seismic data and several million line kilometres of 2d seismic data vastly more than the coverage of data constraining the deep geology onshore combined with detailed studies of oil and gas fields this data has led to a greater technical understanding of many aspects of offshore geology relative to that onshore these data represent an original investment of 20bn by oil and gas companies but are now in the public domain these databases are used here to compare onshore and offshore settings in terms of criteria such as structural geology fault activity and uplift subsidence clear differences emerge such as risk of seismicity exhumation and the variety of hydrogeological systems the distribution and geometry of candidate repository sites throughout the north sea salt structures shale basins sealed sandstone reservoirs and basement highs are illustrated several lines of petroleum related research have yielded lessons that may be useful in assessing deep repository locations such as migration of hydrocarbons through shale seals the exceptional combination of seismic data and well control means that offshore areas on the continental shelf and the north sea in particular can now be thoroughly explored in this context and contribute candidate sites into a nationwide portfolio of deep geological disposal options in the event of site selection being pursued in the uk an example framework for this process is presented here

sedimentology of the december 26 2004 sumatra tsunami deposits in eastern india tamil nadu and kenya the december 26 2004 sumatra tsunami caused severe damage at the coasts of the indian ocean we report results of a sedimentological study of tsunami run up parameters and the sediments laid down by the tsunami at the coast of tamil nadu india and between malindi and lamu kenya in india evidence of three tsunami waves is preserved on the beaches in the form of characteristic debris accumulations we measured the maximum run up distance at 580 m and the maximum run up height at 4 85 m flow depth over land was at least 3 5 m the tsunami deposited an up to 30 cm thick blanket of moderately well to well sorted coarse and medium sand that overlies older beach deposits or soil with an erosional unconformity the sand sheet thins inland without a decrease of grain size the deposits consist frequently of three layers the lower one may be cross bedded with foresets dipping landward and indicating deposition during run up the overlying two sand layers are graded or parallel laminated without indicators of current directions thus it remains undecided whether they formed during run up or return flow thin dark laminae rich in heavy minerals frequently mark the contacts between successive layers benthic foraminifera indicate an entrainment of sediment by the tsunami from water depths less than ca 30 m water depth on the indian shelf these depths are present at distances of up to 5 km from the coast in kenya only one wave is recorded which attained a run up height of 3 m at a run up distance of ca 35 m from the tidal water line at the time of the tsunami impact only one layer of fine sand was deposited by the tsunami it consists predominantly of heavy minerals supplied to the sea by a nearby river the sand layer thins landward with a minor decrease in grain size benthic foraminifera indicate an entrainment of sediment by the tsunami from water depths less than ca 30 m water depth reaching down potentially to ca 80 m the presence of only one tsunami related sediment layer in kenya but three in india reflects the impact of only one wave at the coast of kenya as opposed to several in india grain size distributions in the indian and kenyan deposits are mostly normal to slightly positively skewed and indicate that the detritus was entrained by the tsunami from well sorted pre tsunami deposits in nearshore swash zone and beach environments

flandrian relative sea level changes in the ythan valley northeast scotland relict flandrian estuarine deposits in the ythan valley are confined to an area in the lower valley around the present estuary they rest upon a discontinuous layer of peat over an irregular surface of sand and gravel and consist for the most part of a grey silty clay or carse deposit which forms terraces or small areas of carseland at the seaward end of the estuary the grey silty clay contains a layer of grey micaceous silty fine sand which tapers into the basal peat whilst in places the surface of the grey silty clay is covered by peat and or blown sand the vegetational context and age of these deposits have been determined at waterside near the mouth of the present estuary here the grey silty clay accumulated as the result of a marine transgression which began in the early flandrian and culminated between about 6189 95 and some time prior to 4000 80 radiocarbon years b p the carseland surface produced by this phase of accumulation is the highest flandrian estuarine surface in the valley at about 4 5 m o d and is correlated with the main postglacial shoreline elsewhere in eastern scotland withdrawal of the sea from this level may have been interrupted by the formation of a lower carseland surface before present levels were reached though this is far from certain the grey micaceous silty fine sand layer is dated at approximately 6850 140 radiocarbon years b p and is correlated with similar layers that may have been deposited following a storm surge the paper concludes with some considerations on the age and distribution of the main postglacial shoreline in eastern scotland

tsunami and palaeotsunami depositional signatures and their potential value in understanding the late holocene tsunami record in recent years much research on modern and palaeotsunami deposits has been published from these studies a range of signature types has been identified identifying and dating such deposits is an important element in understanding late holocene tsunami hazard and risk however important questions such as do modern and palaeotsunami leave similar or dissimilar traces do tsunami leave the same signatures all around the world or are there significant variations and what is the actual record of tsunami in different parts of the world still remain answering these questions is not an easy task but examining megatsunami flood deposits should shed some light on these questions because such high magnitude events should leave very clear and detailed traces within the coastal landscape the coast of se australia is reported to have been affected by numerous palaeomegatsunami in the late holocene as such the coast of new south wales offers an important natural laboratory to examine in detail deposits associated with such events here we summarize the published characteristics of modern and palaeotsunami deposits globally and within australia we briefly outline the tsunami risk to australia before examining a site called minnamurra point on the coastline of se australia south of sydney that has previously been described as containing evidence for a palaeomegatsunami of an unknown age we describe the results of a detailed coastal survey field stratigraphic investigation and various standard laboratory analyses surprisingly we are unable to replicate the previously reported findings of tsunami deposits whilst we prefer the interpretation that the sequence is an in situ soil the sediment sequence examined contains none of the usually reported lines of evidence to demonstrate tsunami provenance we recognize and discuss the significance and difficulty of identifying tsunami deposits in the field and consider the implications of our findings to the wider debate about the preservation of tsunami deposited sediments

bivalve bioerosion in cretaceous neogene amber around the globe with implications for the ichnogenera teredolites and apectoichnus abstract amber samples with bivalve borings from six localities around the world ranging in age from hauterivian to miocene have been studied the possible assignment to teredolites or gastrochaenolites is discussed considering the type of substrate as an ichnotaxobase it is proposed to regard amber or similar resins as a variant of xylic substrates and to maintain the separation between the two ichnogenera and their different paleoecological implications the amber borings are assigned to teredolites clavatus leymerie 1842 and apectoichnus longissimus kelly and bromley 1984 respectively the presence of bioglyphs in a few borings suggests a mechanical production process with pholadid bivalves such as martesia preserved inside many of the samples representing the producer in general the amber producing trees mostly grew along a forested coastline where they were occasionally flooded by seawater or even transported from rivers into the sea and later deposited

propagation of the storegga tsunami into ice free lakes along the southern shores of the barents sea this paper is part of anders romundset s doctoral thesis which is available in munin at http hdl handle net 10037 2703

sedimentologic and geomorphologic tsunami imprints worldwide a review abstract tsunami events with extreme effects on sedimentary transport or considerable alterations of the coastal configuration are rather rare regarding human history but considering geological timescales they occur frequently at least 100 megatsunami in different parts of the world have been recorded in the past 2000 years but presumably far more have failed to be noticed during historical times and are not mentioned either in written or oral ancient records therefore the topic of paleotsunami requires inevitable sedimentological and geomorphological research however field research concerning paleotsunami is astonishingly rare within the scientific approach and only 5 of the existing tsunami literature is related to this subject future efforts in paleotsunami research should focus on the geological evidence of these mega events to clarify their contribution to coastal forming processes this paper reviews the state of the art knowledge of sedimentologic and geomorphic imprints of tsunami along the world s coastlines in order to highlight the need for more detailed studies of paleotsunami depositional and geomorphological traces

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

shallow marine tsunami deposits in teluk banten nw java indonesia generated by the 1883 krakatau eruption teluk banten tb is a tropical shallow marine embayment with coral reef islands close to the krakatau volcanic complex the 1883 krakatau eruption generated a tsunami which had a devastating effect on the neighboring coastal areas the effects of the 1883 krakatau eruption and the associated tsunami on the bottom sediments in tb are assessed using textural compositional and 210 pb geochronological data an important diagnostic criterion consists of the occurrence of tephra conform descriptions of the 1883 eruption tephra the tsunamite consists of a sandy layer with abundant reworked shell and other carbonate fragments coarse components in the tsunamite consist of locally derived material eroded from the seabed land derived components are incorporated in the tsunamite only in close proximity to the coast the tsunamite is thickest in localized areas of the central part of the bay along the northern open sea facing slope of tb the tsunamite is relatively thin 6 7 cm thick but well preserved as little postdepositional modifications have occurred in the eastern bay area recent erosion since the redirection of the ciujung river in the 1920s has removed the krakatau tsunamite along the west coast of tb the only signature of the 1883 krakatau eruption consists of tephra and evidence for a high energy event is lacking presumably the western area was sheltered from the tsunami wave coming from the northwest at the shallower stations with low accumulation rates the tephra has been thoroughly mixed by bioturbation 2003 elsevier science b v all rights reserved

evaluation of tsunami impacts on shallow marine sediments an example from the tsunami caused by the 2003 tokachi oki earthquake northern japan abstract a combined approach of field geology and numerical simulation was conducted for evaluating the tsunami impacts on the shelf sediments the 2003 tokachi oki earthquake m 8 0 that occurred on 25 september 2003 off southeastern hokkaido northern japan generated a locally destructive tsunami maximum run up height of the tsunami waves reached 4 m above sea level in order to estimate the tsunami impacts on shallow marine sediments we compared pre and post tsunami marine sediments in water depths of 38 112 m in terms of grain size sedimentary structure and microfossil content decreases of fine fractions especially finer than very fine sand which led to coarsen the mean grain size were detected in the inner shelf of the northern part of the study area foraminiferal assemblages also changed in the coarsened sediments on the other hand the other shelf sediments largely unchanged or slightly fined we also simulated the tsunami wave velocity and direction and grain size entrained by the modeled tsunami the numerical simulation resulted in that the 2003 tsunami could transport very fine sand in water depths shallower than 45 95 m at the northern part of the study area this is comparable with the actual grain size changes after the tsunami had passed however some storms and tidal currents might also be possible to stir the surface sediments after the pre tsunami survey so we could not conclude that the grain size changes had been caused only by the tsunami nevertheless a combined approach of sampling and modeling was powerful for estimating the tsunami impacts under the sea

an amalgamated meter thick sedimentary package enabled by the 2011 tohoku tsunami in el garrapatero galapagos islands abstract tsunamis and storms instigate sedimentological and geomorphological changes to the coastal system both long term and ephemeral to accurately predict future coastal hazards one must identify the records that are generated by the processes associated with these hazards and recognize what will be preserved using eyewitness accounts photographs and sedimentology this study documents pre and post tsunami conditions and constrains the timing and process of depositional events during and following the 11 march 2011 tohoku tsunami in the coastal system at el garrapatero galapagos islands while the tsunami acted as both an erosional and depositional agent the thick fan like sand sheet in el garrapatero was primarily emplaced by overwash deposition during high tide from swell waves occurring between 19 25 march and 17 22 april 2011 the swell waves were only able to access the terrestrial coastal system via a channel carved by the 2011 tohoku tsunami through the barrier sand dune this combined deposit could result in an overestimation of the hazard if interpreted to be the result of only one event either tsunami or wind generated waves an analogous sand layer younger than 1390 1530 cal yr bp may record a similar prior event

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

relative sea level change and evidence for the holocene storegga slide tsunami from a high energy coastal environment cocklemill burn fife scotland uk a site in the cocklemill burn valley on the north shore of the firth of forth scotland provides evidence of relative sea level changes during the holocene from ca 7970 to ca 5090 radiocarbon years bp and of the holocene storegga slide tsunami dated here as having taken place after ca 7215 radiocarbon years bp marine sediments associated with two shorelines widely present in mainland scotland the main postglacial shoreline and the blairdrummond shoreline are recorded the holocene storegga slide tsunami deposits are unique here in the record of such sediments in eastern scotland in that they occur within marine sands of which the upper horizons are intertidal sandflat deposits the tsunami deposits probably accumulated shortly after a period of accelerated relative sea level rise the pattern and timing of which could have played a role in triggering the holocene storegga slide

the application of ichnology to palaeoenvironmental and stratigraphic analysis it has been increasingly realized by sedimentologists in the petroleum industry and academia that integration of ichnological information into sedimentological models and vice versa is one of the main means by which we can improve our understanding of ancient depositional environments this volume aims to provide an analytical review of the ichnology of all major depositional environments and the use of ichnology in biostratigraphic and sequence stratigraphic analysis as well as highly refined palaeoenvironmental studies the remit of the book is achieved through a combination of review articles and novel research papers that outline methodologies and protocols for improving our understanding of ancient palaeoenvironments trace fossils from microscopic borings to dinosaur footprints are considered the comprehensive coverage of ancient depositional environments means that the book will be of use as a course text for undergraduates as well as an invaluable reference text for all students of ichnology whether they are ichnologists sedimentologists or petroleum geologists by trade

characteristics of dune bedded pyroclastic surge bedsets abstract the grainsize characteristics of dune bedded pyroclastic surge bedsets are surveyed the variance between coarsest and finest beds ranges from 1 to 6 phi in different surge bedsets and it increases as the grainsize of the coarsest bed increases reflecting an increasing velocity of emplacement deposits of wet surges identified as those which contain accretionary and ash coated lapilli tend to be finer and show less variance this partly because wet ash is cohesive but mainly because wet surges tend to be weaker dry surge bedsets are strongly fines depleted wet ones less so the lack of erosion of underlying ash layers shows that the environment is a strongly depositional one individual bedsets are demarcated by thin intervening fine ash fall layers which are the complementary ash cloud deposits settled or flushed out after the passage and decay of each turbulent surge surge deposits are generally less coarse than the coarsest associated airfall deposits which shows that they are formed by generally weaker events this study helps interpret the dune bedded parts of the landscape mantling may 18th 1980 blast deposit of mount st helens the blast was a very violent event but the variance and the grainsize of the coarsest bed are those of a relatively weak surge this suggests that the dune bedding was produced by a weak effect such as minor turbulence in a thin pyroclastic flow coming to rest in a mountainous terrain roughened by tree stumps and fallen logs

a late holocene record of environmental changes from coastal wetlands abel tasman national park new zealand abstract article size organic content loss on ignition loi geochemistry radiocarbon and 137cs analyses were carried out on paired cores taken from wainui totaranui and awaroa inlets abel tasman national park a 1700 year record of long and short term environmental changes was produced representing a sedimentary and geochemical sequence from tidal flat to mature salt marsh the sequence is punctuated by a series of short term environmental changes namely tsunami establishment of salt marsh and european settlement long term environmental changes include fluctuating accretion rates and relative sea level rise tsunami signatures include i a peak in fines ii contemporaneous or delayed peak in organic content and or loi iii contemporaneous peaks in fe and or s iv dilution of anthropogenic contaminants and v visible change in the sediments ruptures of the wellington and west wairarapa faults are considered to be the tsunamigenic sources pre european sediment accretion rates in abel tasman national park range from 0 5 to 1 7 mm a with post european settlement rates increasing to 1 6 2 7 mm a in the past 30 years rates have increased to 2 3 3 3 mm a the component of relative sea level rise is estimated to be about 1 3 2 2 mm a which compares favourably with the nearest tidal records from wellington

substrate controlled ichnofacies along a marine sequence boundary the intra valanginian discontinuity in central neuquen basin argentina abstract the intra valanginian discontinuity in the neuquen basin argentina marks a dramatic sea level fall within lower cretaceous strata and can be mapped for tens of kilometers both along depositional strike and dip in the proximal region of the lowstand configuration the subaerial segment of the sequence boundary is demarcated by alluvial conglomerates basal mulichinco formation onto deep marine black shales vaca muerta formation in the distal marine realm the time equivalent marine sequence boundary separates black shales and marls beneath from shallow marine carbonate deposits above this paper documents and discusses substrate controlled trace fossils demarcating the marine sequence boundary across more than 30 km in a proximal distal transect in order to shed light onto processes affecting the sea floor during the generation biogenic modification and preservation of this regionally extensive omission surface the downdip expression of the marine sequence boundary is well exposed across a 20 km long strike oriented outcrop everywhere in this region the discontinuity is demarcated by robust thalassinoides with well defined walls and circular cross sections suggesting that the marly substrate was relatively firm during excavation the burrow system is filled with bioclasts of echinoids and bivalves not present in underlying strata up to pebble size intraclasts that were eroded from the underlying succession and authigenic minerals glauconite phosphates this trace fossil suite illustrates the glossifungites ichnofacies the updip expression of the marine sequence boundary in the study area was recorded in a cored well located about 20 km from the outcrops as in the distal region a first generation of passively filled thalassinoides excavated into a firm marly substrate is attributed to the glossifungites ichnofacies however this suite is cross cut at the top by gastrochaenolites and other unidentified borings bored intraclasts also occur above the omission surface this trace fossil suite represents the trypanites ichnofacies the intra valanginian discontinuity records a complex history after the onset of the dramatic sea level fall extensive erosion and exhumation of previous sediments as well as early cementation combined to produce different types of substrates during the generation of the omission surface firmgrounds and hardgrounds colonization of firm substrates probably started firstly in proximal regions when relative sea level was still falling during early transgression firmgrounds were occupied in distal regions and borers colonized the hardgrounds developed in proximal regions thus the surface demarcates a composite surface involving a sequence boundary plus a transgressive surface draped in turn by a mixing of sediments suggesting siliciclastic starvation the generation and preservation of the features associated with the intra valanginian discontinuity are thought to result from the combination of a ramp type pre existing morphology coupled with a high amplitude sea level fall and a relatively deep marine setting prior to the formation of the omission surface

tsunamis as geomorphic crises lessons from the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract large tsunamis are major geomorphic crises since they imply extensive erosion sediment transport and deposition in a few minutes and over hundreds of kilometres of coast nevertheless little is known about their geomorphologic imprints the december 26 2004 tsunami in sumatra indonesia was one of the largest and deadliest tsunamis in recorded human history we present a description of the coastal erosion and boulder deposition induced by the 2004 tsunami in the lhok nga bay located to the west of banda aceh northwest sumatra the geomorphological impact of the tsunami is evidenced by beach erosion some beaches have almost disappeared destruction of sand barriers protecting the lagoons or at river mouths numerous erosion escarpments typically in the order of 0 5 1 5 m when capped by soil and more than 2 m in dunes bank erosion in the river beds the retreat along the main river is in the order of 5 15 m with local retreats exceeding 30 m large scars typically 20 50 cm deep on slopes dislodgement of blocks along fractures and structural ramps on cliffs the upper limit of erosion appears as a continuous trimline at 20 30 m a s l locally reaching 50 m the erosional imprints of the tsunami extend to 500 m from the shoreline and exceed 2 km along riverbeds the overall coastal retreat from lampuuk to leupung was 60 m 550 000 m 2 and locally exceeded 150 m over 276 000 m 3 of coastal sediments were eroded by the tsunami along the 9 2 km of sandy coast the mean erosion rate of the beaches was 30 m 3 m of coast and locally exceeded 80 m 3 m the most eroded coasts were tangent to the tsunami wave train which was coming from the southwest the fringing reefs were not efficient in reducing the erosional impact of the tsunami the 220 boulders measured range from 0 3 to 7 2 m large typically 0 7 1 5 m with weights from over 50 kg up to 85 t we found one boulder less than 1 m large at 1 km from the coastline but all the others were transported less than 450 m 30 m and the moderate tsunamis height

diatom biostratigraphy of tsunami deposits examples from the 1998 papua new guinea tsunami abstract distinctive diatom assemblages may be associated with tsunami sediments and may often contrast with the assemblages found within sediments underlying the tsunami deposit as well as those associated with the modern coastal environment sediments associated with the 1998 tsunami that destroyed much of the sissano lagoon area in northern papua new guinea have been investigated surface sediments from three transects across the sediment spit near warapu have been examined for diatom content and preservation the preservation is variable and the data show an often chaotic assemblage that can be attributed to the tsunami waves incorporating and depositing diatoms from distinctive habitat zones during their runup and subsequent backwash the diatoms identified within the warapu sediments indicate an origin from within the inter tidal and offshore area rather than from the beach sand spit complex the sand deposits disclose a high percentage in excess of 75 of broken diatom valves and a predominance of centric circular species due to preferential preservation the study demonstrates that the application of diatom biostratigraphy to modern tsunami deposits can be used in conjunction with other stratigraphical lines of evidence to interpret the source and provenance of historical and palaeo tsunami deposits