sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

paleotsunami research along the nankai trough and ryukyu trench subduction zones current achievements and future challenges abstract located near japan s most densely populated and industrially active region the nankai trough subduction zone has long been highlighted as a high risk area for damaging earthquakes and tsunamis in contrast less attention has been paid the adjacent ryukyu trench because historical and geological records are scarce in order to develop better quantitative estimates of the timing and size of the earthquakes and tsunamis generated along these subduction zones comprehensive studies using geological seismological and historical methods have been conducted since the 1990s studies of tsunami deposits in this region have contributed to our current understanding of the history of tsunamis over the last 6000 years following the 2011 t hoku earthquake and tsunami paleotsunami research has especially focused on guiding and enhancing tsunami disaster management and mitigation measures the last nine years have seen a rapid increase in paleotsunami data from the nankai trough and ryukyu trench coasts these recent studies reveal that there are significant differences in the size and recurrence pattern of earthquakes and tsunamis along these subduction zones for instance large earthquakes have repeatedly occurred along the nankai trough every 100 200 years on the other hand large earthquakes and tsunamis may not have occurred over the last few thousand years at the junction between these subduction zones there is also no evidence for the occurrence of large earthquakes along the northern and central ryukyu trench over this time period large earthquakes and tsunamis may have occurred every few hundred years at the southern end of the ryukyu trench nevertheless data on the occurrence of these earthquakes are still insufficient both in quantity and quality to estimate the maximum size or recurrence pattern

the discovery of emerged boring bivalves at cape omaezaki shizuoka japan evidence for the 1361 ce tokai earthquake along the nankai trough abstract this study found several in situ fossil shells of the boring bivalve penitella gabbii exposed in mudstone at an elevation of 1 05 1 35 m above mean sea level in a wave cut platform at cape omaezaki shizuoka central japan this region faces the nankai trough where great earthquakes m 8 occur with a recurrence interval of 90 200 years based on the upper limit of living p gabbii 0 8 m above mean sea level and geodetic data the total uplift of shells since the time of their active is estimated to be up to 2 5 m using 14c dates from the uplifted terrace deposits around the study area and shell fossils we propose that the emerged fossils provide new evidence for the pairing of the 1361 ce shohei koan tokai earthquake rupture of suruga trough and the eastern half of the nankai trough with the 1361 ce shohei koan nankai earthquake rupture of the western half of the nankai trough

stratigraphic evidence of historical and prehistoric tsunamis on the pacific coast of central japan implications for the variable recurrence of tsunamis in the nankai trough abstract to complement historical written records of tsunamis in the nankai trough and reconstruct prehistoric tsunami records we conducted a coring survey at a coastal lowland in mie prefecture central japan we found 10 sand layers deposited from about 4500 to 500 years ago the layers are interpreted as tsunami deposits because of the presence of abundant bioclasts of marine organisms and sedimentary structures such as alternating sub layers of sand and silt rip up clasts and upward fining structures all of which are common in modern tsunami deposits at the study site no substantial seawater inundations and sand depositions have been recorded even for the largest typhoons to ever hit the region there are historical accounts of earthquake and tsunami damage along the nankai trough in 1498 1361 1096 887 and 684 ce estimated ages of the youngest three sand layers overlap well with tsunamis in 1498 1096 and 684 ce our results support the hypothesis suggested by archaeological studies that the 684 ce rupture extended farther eastward than the historical record indicates or that another tsunami occurred at some time close to 684 ce we did not find any sand layers that were definitely correlated with the tsunamis of 1361 and 887 ce which are thought to have occurred by multi segment ruptures of the nankai trough that includes the segment directly offshore from the study site if the sand layers found at the study site were deposited by the tsunamis of 1498 1096 and 684 ce and if the tsunamis of 1361 and 887 ce did not inundate the study site the tsunami recurrence interval during the relevant time period was about 400 years this finding does not support the widely believed hypothesis that earthquakes and tsunamis occur at regular intervals of approximately 100 years in this area in addition similar to the historical tsunamis intervals of geologically recorded prehistoric tsunamis at the study site vary from about 100 to 600 years the hypothesis of variable recurrence of earthquakes and tsunamis along the nankai trough should be tested by future geological and historical studies in unbiased way

tsunami deposits refine great earthquake rupture extent and recurrence over the past 1300 years along the nankai and tokai fault segments of the nankai trough japan abstract study of prehistoric to medieval age tsunami deposits along a riverbank site near the eastern nankai trough central japan show that not only did tokai earthquakes occur with a higher frequency than previously thought but that contemporaneous ruptures of the tokai and nankai fault segments were also more common the site revealed a 1 km long coast normal cross section of the strand plain and exposed four sandy tsunami deposits each of which indicates inundation over 2 km inland of the coast radiocarbon dating of previously studied and newly discovered deposits in the region indicates a shorter recurrence time for tokai earthquakes and clarifies their linkage with nankai earthquakes we attribute the younger two tsunami deposits to the 1498 and 1096 ce tokai earthquakes the older two deposits confirm the occurrence of the tokai earthquakes in 887 ce and in the latest 7th century these events are not reliably recorded in historical documents in the tokai region but were noted in the nankai area the 887 ce earthquake likely represents a full length rupture of the tokai and nankai segments as was the case for the 1707 ce earthquake integrated with the previous studies these new results show that nine tokai earthquakes occurred over the last 1300 years the oldest in the latest 7th century and in 887 1096 1361 1498 1614 1707 1854 and 1944 ce recalculated recurrence intervals range from 90 to 265 years except for the 1498 meio tokai earthquake the tokai earthquakes occurred simultaneously with nankai earthquakes

geodetic imaging of plate motions slip rates and partitioning of deformation in japan 1 interseismic deformation in japan results from the combined effects of tectonic processes including rotation of crustal blocks and the earthquake cycle process of elastic strain accumulation about upper plate faults and subduction zone interfaces we use spherical linear block theory constrained by geodetic observations from densely spaced global positioning system gps stations to estimate plate motions fault slip rates and spatially variable interplate coupling on the japan kuril sagami and nankai subduction zones the reference model developed in this paper consists of 20 blocks produces a mean residual velocity magnitude of 1 84 mm yr at 950 stations and accounts for 96 of the observed interseismic deformation signal we estimate fault slip rates in excess of 15 mm yr along the niigata kobe tectonic zone and itoigawa shizuoka tectonic line through central japan confirming their hypothesized roles as major tectonic boundaries oblique convergence across the nankai trough is partitioned with 3 4 of the 30 mm yr of trench parallel motion accommodated by strike slip motion on the subduction interface and the remaining 1 4 accommodated by right lateral slip on the median tectonic line in contrast our models suggest negligible slip partitioning in eastern hokkaido where oblique slip on the japan kuril subduction interface accommodates all of the trench parallel component of relative plate motion inferred spatial variations in the rake and magnitude of slip deficit on subduction zone interfaces reflect the influences of megathrust geometry and earthquake cycle processes such as enhanced elastic strain accumulation about seismic asperities and coseismic sense fault motion indicative of silent slip events or afterslip following large earthquakes

jellyfish lake palau early diagenesis of organic matter in sediments of an anoxic marine lake jellyfish lake a meromictic marine lake in the palau islands western pacific ocean is accumulating organic matter rich sediments 46 wt wt below anoxic highly sulfidic bottom water elemental and stable isotope 13c data indicate that the sedimentary organic matter is primarily derived from vascular plant remains 65 90 and would form a type 2 kerogen a bacterial layer at the oxic anoxic interface in the water column may play an important role in the rapid recycling of algal derived organic matter from the highly productive surface waters the major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation as shown by 13c nmr lignin and aliphatic substances are preserved in the sediments dissolved organic matter in pore waters is primarily composed of carbohydrates reflecting the degradation of sedimentary carbohydrates rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10 lower than in other anoxic sediments this may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake elemental results from sediment cores and stable isotope 18o 13c studies of shells from the sediments indicate probable climatic or ecological fluctuations affecting the depositional environment of the lake between 80 and 110 yr ago the high sedimentation rate and stable environment of jellyfish lake make it a possible environment for studies of climatic fluctuations during the holocene

relationship between the maximum extent of tsunami sand and the inundation limit of the 2011 tohoku oki tsunami on the sendai plain japan abstract this paper focuses on the relationship between the maximum extent of sandy tsunami deposits and inundation distance of the 2011 tohoku oki tsunami inundation limits of the tohoku oki tsunami were assessed over seven shore normal transects along the sendai coastal plain inundation distances were found to range from 0 6 to 4 0 km at the maximum extent of the tsunami deposit the sand unit ranged in thicknesses from 0 1 to 4 0 cm the maximum limit of the 0 5 cm thick sand layer extended to over 90 of the inundation distance where the inundation distance was less than 2 5 km this observation is consistent with previous studies that examined characteristics of recent tsunami events that had inundation distances of at least 2 km the maximum limit of the 0 5 cm thick sand layer extended to 3 km 57 76 of the inundation distance where the inundation distance was more than 2 5 km our results are important for estimating paleo tsunami inundation distances based on the landward extent of sand deposits and valuable for the assessment of future tsunami risks in other coastal areas in the world which have been devastated by huge tsunamis in the past

segmentation and supercycles a catalog of earthquake rupture patterns from the sumatran sunda megathrust and other well studied faults worldwide abstract after more than 100 years of earthquake research earthquake forecasting which relies on knowledge of past fault rupture patterns has become the foundation for societal defense against seismic natural disasters a concept that has come into focus more recently is that rupture segmentation and cyclicity can be complex and that a characteristic earthquake model is too simple to adequately describe much of fault behavior nevertheless recognizable patterns in earthquake recurrence emerge from long high resolution spatially distributed chronologies researchers now seek to discover the maximum minimum and typical rupture areas the distribution variability and spatial applicability of recurrence intervals and patterns of earthquake clustering in space and time the term supercycle has been used to describe repeating longer periods of elastic strain accumulation and release that involve multiple fault ruptures however this term has become very broadly applied lumping together several distinct phenomena that likely have disparate underlying causes we divide earthquake cycle behavior into four major classes that have different implications for seismic hazard and fault mechanics 1 quasi periodic similar ruptures 2 clustered similar ruptures 3 clustered complementary ruptures rupture cascades and 4 superimposed cycles segmentation is likewise an ambiguous term we identify master segments and asperities as defined by barriers to fault rupture these barriers may be persistent rarely or never traversed frequent occasionally traversed or ephemeral changing location from cycle to cycle we compile a catalog of the historical and paleoseismic evidence that currently exists for each of these types of behavior on major well studied faults worldwide due to the unique level of paleoseismic and paleogeodetic detail provided by the coral microatoll technique the sumatran sunda megathrust provides one of the most complete records over multiple earthquake rupture cycles long historical records of earthquakes along the south american and japanese subduction zones are also vital contributors to our catalog along with additional data compiled from subduction zones in cascadia alaska and middle america as well as the north anatolian and dead sea strike slip faults in the middle east we find that persistent and frequent barriers rupture cascades superimposed cycles and quasi periodic similar ruptures are common features of most major faults clustered similar ruptures do not appear to be common but broad overlap zones between neighboring segments do occur barrier regions accommodate slip through reduced interseismic coupling slow slip events and or smaller more localized ruptures and are frequently associated with structural features such as subducting seafloor relief or fault trace discontinuities this catalog of observations provides a basis for exploring and modeling root causes of rupture segmentation and cycle behavior we expect that researchers will recognize similar behavior styles on other major faults around the world

fault slip and seismic moment of the 1700 cascadia earthquake inferred from japanese tsunami descriptions 1 the 1700 cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in japan computed coseismic seafloor deformation for hypothetical ruptures in cascadia and tsunami modeling in the pacific ocean reports of damage and flooding show that the 1700 cascadia tsunami reached 1 5 m heights at seven shoreline sites in japan three sets of estimated heights express uncertainty about location and depth of reported flooding landward decline in tsunami heights from shorelines and post 1700 land level changes we compare each set with tsunami heights computed from six cascadia sources each source is vertical seafloor displacement calculated with a three dimensional elastic dislocation model for three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip for the other sources ruptures of ordinary width extend 360 670 km to compute tsunami waveforms we use a linear long wave approximation with a finite difference method and we employ modern bathymetry with nearshore grid spacing as small as 0 4 km the various combinations of japanese tsunami heights and cascadia sources give seismic moment of 1 9 1022 n m equivalent to moment magnitude 8 7 9 2 this range excludes several unquantified uncertainties the most likely earthquake of moment magnitude 9 0 has 19 m of coseismic slip on an offshore full slip zone 1100 km long with linearly decreasing slip on a downdip partial slip zone the shorter rupture models require up to 40 m offshore slip and predict land level changes inconsistent with coastal paleoseismological evidence

δ18o values of mudrocks more evidence for an 18o buffered ocean abstract the whole rock 18 o of mudrocks as well as the 18 o of the clay sized silicate fraction does not change in any systematic manner over paleozoic and late proterozoic time therefore the 18 o of the ocean has not changed except a per mil or so as the result of glaciation deglaciation over the last billion years of earth history

challenges of anticipating the 2011 tohoku earthquake and tsunami using coastal geology 1 can the magnitude of a giant earthquake be estimated from paleoseismological data alone attempts to estimate the size of the jogan earthquake of ad 869 whose tsunami affected much of the same coast as the 2011 tohoku tsunami offers an excellent opportunity to address this question which is fundamental to assessing earthquake and tsunami hazards at subduction zones between 2004 and 2010 examining stratigraphy at 399 locations beneath paddy fields along 180 km of coast mainly south of sendai we learned that a tsunami deposit associated with the ad 869 jogan earthquake had run inland at least 1 5 km across multiple coastal lowlands and that one of the lowlands had subsided during the jogan earthquake and an earlier earthquake as well radiocarbon ages just below above sand deposits left by the pre jogan tsunamis suggested recurrence intervals in the range of 500 to 800 years modeling inundation and subsidence we estimated size of the jogan earthquake as moment magnitude 8 4 or larger and a fault rupture area 200 km long we did not consider a longer rupture like the one in 2011 because coastal landform and absence of a volcanic ash layer make any jogan layer difficult to identify along the sanriku coast still sendai tsunami geology might have reduced casualties by improving evacuation maps and informing public awareness campaigns

hydrogen and oxygen isotope ratios of shales and characteristics of formation waters in sedimentary complexes accreted at different times kinki district southwest japan abstract oxygen and hydrogen isotope analyses were made of shale samples from southwest japan to investigate water circulation in sedimentary complexes during burial and low grade metamorphism the sedimentary complexes of the kinki district were accreted to the asian continent at two different times and the geology is characterized by a clear zonal structure hydrogen isotope ratios of the bulk shales become heavier from the older northernmost terrain d smow 105 to 90 to the younger southernmost terrain 60 to 40 hydrogen isotope ratios of illite show two distinctive ranges for the two different accretionary complexes 100 to 60 for the jurassic to early cretaceous complexes and 65 to 45 for the cretaceous to paleogene complexes these hydrogen isotope characteristics of the bulk shales and illite suggest that deeply circulating meteoric water interacted with the jurassic sedimentary formations whereas the original sedimentary isotope ratios were likely retained in the cretaceous to paleogene terrains oxygen isotope ratios of the bulk shales and the constituent minerals are similar for the two accretionary complexes indicating that sediments were constantly supplied from the same hinterland of the asian continent chlorite and illite with normal to high 18o values 5 to 17 and 10 to 21 respectively may have formed during burial diagenesis and low grade metamorphic reactions although a fraction of the minerals are detrital in origin the similar oxygen isotope values of fine quartz 17 to 23 to those previously reported for detrital quartz in shales and soils suggest homogeneity of detrital quartz in the northern hemisphere

holocene tsunami storm and relative sea level records obtained from the southern hidaka coast hokkaido japan abstract on the pacific coast of hokkaido historical documents and seismic detections spanning the last 200 years show that large earthquakes magnitude 7 8 have occurred every 50 100 years along the kuril trench geological reconstructions of past earthquakes in the region show extend records to the last 6000 years and show that unusually large m8 earthquakes occurred at intervals of several hundreds of years however the magnitude and extent of tsunamis induced by these unusually large earthquakes are not fully understood in this study we found nine anomalous sand layers embedded in peat sediments that dated between 5 5 and 1 2 ka on the southern hidaka coast hokkaido paleoenvironments reconstructed from the peat sediments using diatom chemical and mineralogical analyses showed an evolution of the site from a saltmarsh to a supratidal marsh to a back barrier wetland environment radiocarbon dating of peat sediments showed that these environmental changes correspond to a sea level fall following the mid holocene highstand the anomalous sand layers showed inland thinning and shape contacts with the underlying peat amongst the layers the most recent layer 1 7 1 2 ka was designated as a storm deposit due to its limited distribution of less than 100 m from the beach ridge eight additional sand layers from 5 5 to 2 2 ka were distributed more than 300 m away from the beach ridge and displayed a normal grading of sand particles a characteristic typical of tsunami deposits because there was no record of tsunamis striking the hidaka coast from the observed large earthquakes m7 8 that recur every 50 100 years we interpret the sand layers as tsunamis deposited by unusually large earthquakes because the eight inferred tsunami sand layers were deposited during the highstand period prior to 2 2 ka we infer that the inundation area due to tsunamis in the coastal zone has changed with relative sea level rsl in the past we highlight the necessity of evaluating the influence of long term rsl change

oxygen isotope studies of diagenesis in the basal belly river sandstone pembina i pool alberta abstract the oxygen isotope compositions of authigenic clay and carbonate minerals from the pembina i pool basal belly river sandstone provide useful constraints on the diagenesis of this unit early diagenetic chlorite has 18o values 4 2 to 6 3 smow compatible with low temperature crystallization from brackish water the 18o values of diagenetic calcite 11 8 to 14 7 smow and kaolinite 10 4 to 12 8 smow are best explained by crystallization at temperatures of at least 45 to 70 c from pore fluids similar in 18o to the existing formation water 9 smow the implicatio of such temperatures is that the sandstone was much more deeply buried in the past than it is at present at least 1 300 1 400 m of overlying material may have been eroded since maximum burial

inflow and outflow facies from the 1993 tsunami in southwest hokkaido abstract we describe in detail the sedimentary facies provenance and grain size distributions of the 1993 tsunami deposits in the lower reaches of usubetsu river only two lithofacies were recognized a gravel lobe facies glf and a sand sheet facies ssf the gravel lobe facies was deposited rapidly by a hydraulic jump in contrast the sand sheet facies which contains both current ripples and dunes was deposited by a traction current under subcritical flow conditions we identified four stratigraphic units unit 1 unit 2 unit 3 and unit 4 in ascending order we interpreted units 1 and 2 as having been deposited by the inflow and outflow events of the first run up and units 3 and 4 by the inflow and outflow events of the second run up respectively units 3 and 4 were more widely distributed and coarser grained than units 1 and 2 because the second run up was larger than the first run up furthermore unit 4 was more widely distributed than unit 3 because the outflow eroded the inflow deposits grain size distributions of the inflow and outflow deposits were clearly different unit 4 deposits had a peak at 2 5 phi p 1 population in contrast unit 3 deposits had a bimodal distribution with peaks at 0 5 1 5 phi p 2 population and at 2 5 phi p 1 population a comparison of the tsunami deposits with other sedimentary deposits near the study area showed that the tsunami deposits were mainly derived from the seabed at depths below 5 5 m in the offshore area where the marine sands are about 2 2 5 phi in size and thus are the source of the p 1 population the p 2 population is derived from coarse 0 5 2 phi fluvial materials eroded during the tsunami run up according to our calculations benthic foraminiferal tests were entrained from the comparatively deep seabed at depths up to 100 m during the tsunami run up and included in the tsunami deposits

historical nankai suruga megathrust earthquakes recorded by tsunami and terrestrial mass movement deposits on the shirasuka coastal lowlands shizuoka prefecture japan geological investigations of coastal sediment sequences play a key role in verifying earthquake and tsunami characteristics inferred from historical records in this paper we present a multi proxy investigation of a coastal lowland site facing the nankai suruga megathrust and appraise evidence for tsunamis and earthquake triggered terrestrial mass movements occurring over the last 800 years combining a high resolution chronology with x ray computed tomography and analyses of particle size diatoms pollen non pollen palynomorphs and aerial photographs we present the most compelling geological evidence of the 1361 ce koan also known as shohei tsunami reported to date from any site along the megathrust this finding is consistent with either of two recent hypotheses a single larger rupture of both the nankai and tnankai regions or two smaller ruptures separated by a few days enhancing the site chronology using bayesian age modelling we verify evidence for inundation during the 1498 ce mei tsunami while previous investigations identified evidence for historically recorded tsunamis in 1605 1707 and 1854 ce and a storm surge in 1680 or 1699 ce we encountered a thick sand layer rather than discrete extreme wave deposits in this interval the overprinting of evidence highlights the potential for geological records to underestimate the frequency of these events a terrestrial mass movement also deposited a sand layer at the site radionuclide dating and aerial photographs provide independent confirmation that this may have been triggered by intense shaking in 1944 ce during the most recent great nankai suruga megathrust earthquake

erosion deposition and landscape change on the sendai coastal plain japan resulting from the march 11 2011 tohoku oki tsunami case studies of recent tsunami impacts have proven to be extremely useful in understanding the geologic processes involved during inundation and return flow and refining the criteria used to identify paleotsunami deposits in the geologic record here we report on erosion deposition and associated landscape change resulting from the march 11 2011 tohoku oki tsunami along a nearly 4 5 km shore normal transect on the coastal plain near sendai japan the study area on the broad low relief prograding coastal sendai plain comprised a sand beach backed by 3 m high sand dunes and a forest a wetland the teizan canal agricultural rice fields buildings and roads field observations focused on measurements of tsunami flow characteristics height and direction mapping of erosion features and assessing sediment deposition based on shallow trenches at 50 100 m spacing recorded tsunami inundation heights reached up to about 11 m above mean sea level within the first 500 m from the shoreline and then ranged between 3 and 5 m for the next 2 km gradually decreasing to about 3 m close to the inundation limit the tsunami deposit generally thinned landward from an average maximum 30 cm thick sand deposit in the coastal forest to a thin mud drape several mm thick near the inundation limit a discontinuous sand dominated sheet was prevalent to about 2800 m from the shoreline where mud content then gradually increased further landward eventually resulting in a mud dominated deposit ranging from 3 5 cm to a few mm thickness the overall thinning and fining of the deposit was often interrupted by localized features that led to complex sedimentological relationships over short distances satellite imagery taken on 14 march 2011 3 days after the tohoku oki tsunami shows prominent foreshore incisions with 100 s meters spacing alongshore a foredune ridge that underwent severe erosion and development of a prominent shore parallel elongated scour depression our field survey in early may 2011 revealed that the foreshore recovered quickly with rapid post tsunami sediment deposition from incident waves whereas the dune ridge complex had undergone only minor re working from eolian processes

historical tsunamis and storms recorded in a coastal lowland shizuoka prefecture along the pacific coast of japan four sand units deposited by tsunamis and one sand unit deposited by storm surge s were identified in a muddy marsh succession in a narrow coastal lowland along the pacific coast of central japan tsunamis in ad 1498 1605 1707 and 1854 that were related to large subduction zone earthquakes along the nankai trough and storm surges in 1680 and or 1699 were responsible for the deposition of these sand units these sand units are distinguished by lithofacies sedimentary structures grain size and mineral composition and radiocarbon ages their ages are supported by events in local historical records the tsunami deposits in the study area are massive or parallel laminated sands with associated intraclasts gravels draping mud layers and rarely a return flow subunit the storm surge deposits are devoid of these characteristics and are composed of groups of thin current ripple laminated sand layers the differences in sedimentary structures between the tsunami and storm surge deposits are attributed to the different characteristics of tsunami and storm waves

bedforms record the flow conditions of the 2011 tohoku oki tsunami on the sendai plain northeast japan abstract this article describes the bedforms formed by the 2011 tohoku oki tsunami on the southern sendai plain ne japan integrated analyses of satellite images field survey data and x ray radiographs revealed the natural shapes of these bedforms the dominant bedforms are dunes and antidunes about 20 cm thick high and relatively flat because of their meter scale wavelengths their morphologies reflect mainly the tsunami run up flow on the flat lowland and the return flow in a narrow steep valley flow depth changed at sites where the level of the ground surface changed along the tsunami flow path causing the flow velocity to fluctuate flow velocity decreased in depressed deep water sections and increased in raised shallow water sections the types and positions of the tsunami deposit bedforms were thus strongly controlled by local ground surface roughness such as raised roadbeds and levees as a result the observed thickness distribution of the tsunami deposits fluctuates it is important to consider the possible existence of bedforms in paleotsunami surveys especially for accurate determination of the thickness distribution of the tsunami deposits because thickness data are essential information for reconstruction of the tsunami inundation limit as well as its flow speed

geochemical signatures up to the maximum inundation of the 2011 tohoku oki tsunami implications for the 869 ad jogan and other palaeotsunamis abstract the geochemical signature of the tohoku oki tsunami deposit and underlying soil was assessed two months five months and seven months after the 11 march 2011 tsunami inundated the sendai plain the extent of the recognisable sand deposit was traced up to 2 9 km inland while a mud deposit was found up to 4 65 km inland representing 60 and nearly 95 of the maximum tsunami inundation respectively the limit of tsunami inundation was identified 4 85 km from the shore using geochemical marine markers s and cl two months after the tsunami in the absence of any sedimentological evidence concentrations of other geochemical markers k ca sr indicative of the marine incursion and associated minerals were found to decrease landward 13 c and 15 n and c n ratios suggested a mixture of terrestrial and marine organic sources in the sediment while 34 s of sulphate reflected the marine source of water soluble salts the chemical composition of the 869 ad jogan tsunami sand deposit was characterised by high sr and rb concentrations and was comparable to that of the tohoku oki tsunami deposit suggesting that the sources of sediment may be similar marked decreases in s and cl with time indicated that rainfall resulted in the leaching of salts from the sandy sediments however both s and cl markers as well as sr were still well preserved in the muddy sediments and underlying soil beyond the limit of the recognisable sand deposit seven months after the tsunami this suggests that geochemical indicators may well be useful in identifying the extent of historical and palaeotsunamis by determining the marine origin of fine grained sediments beyond the limit of recognisable sand deposition in particular when marine microfossils are sparse or lacking as is the case on the sendai plain this would allow researchers to redraw palaeotsunami inundation maps and re assess the magnitude of events such as the jogan tsunami and other palaeotsunamis not only on the sendai plain but also elsewhere around the world this has important implications for tsunami risk assessment hazard mitigation and preparedness

carbon sulfur iron systematics of the uppermost deep water sediments of the black sea box cores recovered during leg 4 of the 1988 r v knorr black sea oceanographic expedition from deep water regions of the basin were dominated by coccolith rich microlaminated unit 1 sediment and muddy gray turbidite layers both organic carbon oc and pyrite sulfur values for unit 1 display narrow ranges with mean concentrations of 5 3 1 1 1 wt and 1 3 0 3 wt respectively unit 1 is not enriched in pyrite s relative to sediments deposited under oxygenated bottom waters normal marine sediments with comparable oc concentrations carbon sulfur relationships evaluated on a calcium carbonate free basis to avoid spurious correlations resulting from dilution effects demonstrate that oc and pyrite s are essentially decoupled these observations combined with the persistence of elevated pore water sulfide to depth and a strong correlation between pyrite s and the detrital fe component argue strongly for limitation of pyrite formation in unit 1 by the availability of reactive fe unit 1 fe limitation is further indicated by degree of pyritization dop studies a measure of the extent to which the original potentially reactive fe has been transformed to pyrite these studies show sulfidation of reactive fe ranging from 57 to 78 with dop values independent of oc concentration unit 1 dop profiles suggest that the majority of the pyrite is formed in the sulfidic water column and or very close to the sediment water interface pyrite s concentrations of unit 1 when compared with the particulate reduced sulfur fluxes measured in time series sediment traps are compatible with predominantly water column pyrite formation because of the limitations in the supply of reactive fe associated with the comparatively high supply of oc the microlaminated sediment is characterized by c s ratios greater than those typical of holocene oxically deposited sediments the turbidite muds of the deep basin display high reduced s values relative to holocene normal marine sediments in samples with low oc concentrations low c s ratios this reflects pyrite formation under anoxic sulfidic bottom water conditions in a probable upper slope source region as well as during transport and final deposition intermediate dop values for the turbidites in part a product of their rapid rate of deposition reveal that fe limitation is ultimately not a factor and that further pyrite should form during burial however the very rapid rate at which unit 1 pyrite forms suggests fundamental differences between the overall reactivities of the fe phases associated with the microlaminated and turbiditic sediments the signature of water column anoxia with regard to sedimentary pyrite formation is clearly indicated by the high dop values of unit 1 and the comparatively high levels of s associated with the low concentrations of oc of the turbidite muds this agrees with similar conclusions based on studies of ancient sedimentary rocks

isotopic geochemistry of burial metamorphosed volcanogenic sediments great valley sequence northern california isotopic and mineralogic data from an 8500 m thick section of the great valley sequence northern california indicate that changes in the 18o values of authigenic minerals resulted from the conversion of smectite to a 10 a clay mineral as temperature increased with burial in the jurassic cretaceous outer arc basin the clay mineral assemblage in mudstone is characterized by a proportional increase of the 10 a clay mineral with increasing stratigraphic depth and by a depletion in the 18o value of the mixed layer smectite 10 a clay mineral with descending stratigraphic position from 21 9 to 15 5 smow modeling of the oxygen isotopic data from authigenic phases based on equilibrium fractionation during clay mineral diagenesis indicates that 18o values of calcite in mudstones and of calcite cements in sandstone precipitated along a temperature gradient of about 25 c km during maximum burial to about 6 7 km d values of the mixed layer smectite 10 a clay mineral range between 69 to 44 smow using temperatures calculated from the oxygen isotopic data the deuterium and oxygen isotopic data indicate that the smectite underwent late stage dehydration and probably buffered the composition of formation waters from sea water values to isotopic compositions of 18o 8 smow and d 25 smow the 13c values of calcite from mudstone and sandstone imply that crystallization of authigenic calcite was linked to organic diagenesis during which dissolved hcot 3 was continuously enriched in 13c as temperature increased with burial at the base of the sequence and immediately overlying the ophiolitic basement rocks several hundred meters of strata were altered by more oxygen depleted 18o 4 to 5 hydrothermal fluids emanating from the ophiolitic rocks probably at maximum burial depth

identifying coseismic subsidence in tidal wetland stratigraphic sequences at the cascadia subduction zone of western north america tidal wetland stratigraphy reveals that great plate boundary earthquakes have caused hundreds of kilometers of coast to subside at the cascadia subduction zone however determining earthquake recurrence intervals and mapping the coastal extent of past great earthquake ruptures in this region are complicated by the effects of many sedimentologic hydrographic and oceanographic processes that occur on the coasts of tectonically passive as well as active continental margins tidal wetland stratigraphy at many cascadia estuaries differs little from that at similar sites on passive margin coasts where stratigraphic sequences form through nonseismic processes unrelated to coseismic land level changes methods developed through study of similar stratigraphic sequences in europe provide a framework for investigating the cascadia estuarine record five kinds of criteria must be evaluated when inferring regional coastal subsidence due to great plate boundary earthquakes the suddenness and amount of submergence the lateral extent of submerged tidal wetland soils the coincidence of submergence with tsunami deposits and the degree of synchroneity of submergence events at widely spaced sites evaluation of such criteria at the cascadia subduction zone indicates regional coastal subsidence during at least two great earthquakes evidence for a coseismic origin remains equivocal however for the many peat mud contacts in cascadia stratigraphic sequences that lack 1 contrasts in lithology or fossils indicative of more than half a meter of submergence 2 well studied tsunami deposits or 3 precise ages needed for regional correlation paleoecologic studies of fossil assemblages are particularly important in estimating the size of sudden sea level changes recorded by abrupt peat mud contacts and in helping to distinguish erosional and gradually formed contacts from coseismic contacts reconstruction of a history of great earthquakes for the cascadia subduction zone will require rigorous application of the above criteria and many detailed investigations

motion of the philippine sea plate consistent with the nuvel 1a model summary we determine euler vectors for 12 plates including the philippine sea plate ph relative to the fixed pacific plate pa by inverting the earthquake slip vectors along the boundaries of the philippine sea plate gps observed velocities and 1122 data from the nuvel 1 and the nuvel 1a global plate motion model respectively this analysis thus also yields euler vectors for the philippine sea plate relative to adjacent plates our results are consistent with observed data and can satisfy the geological and geophysical constraints along the caroline cr ph and pa cr boundaries the results also give insight into internal deformation of the philippine sea plate the area enclosed by the ryukyu trench nankai trough izu bonin trench and gps stations s102 s063 and okino torishima moves uniformly as a rigid plate but the areas near the philippine trench mariana trough and yap palau trench have obvious deformation

flaser and wavy bedding in ephemeral streams a modern and an ancient example abstract flaser and wavy bedding are sedimentary structures characterized by alternating rippled sand and mud layers these structures often are considered to form mostly in tidally influenced environments published examples from fluvial environments are rare flaser and wavy bedding were found in two ephemeral stream deposits the jurassic kayenta formation and the modern wash in seven mile canyon both located in southeastern utah usa these examples demonstrate that flaser bedding can form and be preserved in ephemeral streams

a systematic review of geological evidence for holocene earthquakes and tsunamis along the nankai suruga trough japan the nankai suruga trough the subduction zone that lies immediately south of japan s densely populated southern coastline generates devastating great earthquakes magnitude 8 characterised by intense shaking crustal deformation and tsunami generation forecasting the hazards associated with future earthquakes along this 700 km long fault requires a comprehensive understanding of past fault behaviour while the region benefits from a long and detailed historical record palaeoseismology has the potential to provide a longer term perspective and additional crucial insights in this paper we summarise the current state of knowledge regarding geological evidence for past earthquakes and tsunamis along the nankai suruga trough incorporating literature originally published in both japanese and english and enhancing available results with new age modelling approaches we summarise and critically evaluate evidence from a wide variety of sources palaeoseismic evidence includes uplifted marine terraces and biota marine and lacustrine turbidites liquefaction features subsided marshes and tsunami deposits in coastal lakes and lowlands while 75 publications describe proposed evidence from 70 sites only a limited number provide compelling well dated evidence the best available records enable us to map the most likely rupture zones of twelve earthquakes that occurred during the historical period this spatiotemporal compilation suggests that the 1707 ce earthquake ruptured almost the full length of the subduction zone and that earthquakes in 1361 ce and 684 ce may have been predecessors of similar magnitude intervening earthquakes were of lesser magnitude highlighting the variability in rupture mode that characterises the nankai suruga trough intervals between ruptures of the same seismic segment range from 450 years during the historical period over longer timescales palaeoseismic evidence suggests intervals between earthquakes ranging from 100 to 700 years however these figures reflect a range of thresholds controlling the creation and preservation of evidence at any given site as well as the genuine intervals between earthquakes at present there is no geological data that suggest the occurrence of a larger magnitude earthquake than that experienced in 1707 ce however few studies have sought to establish the relative magnitudes of different earthquake and tsunami events along the nankai suruga trough alongside the lack of research designed to quantify the maximum magnitude of past earthquakes we emphasise issues over alternative hypotheses for proposed palaeoseismic evidence the paucity of robust chronological frameworks and insufficient appreciation of changing thresholds of evidence creation and preservation over time as key issues that must be addressed by future research

clay mineral formation and transformation in rocks and soils three mechanisms for clay mineral formation inheritance neoformation and transformation operating in three geological environments weathering sedimentary and diagenetic hydrothermal yield nine possibilities for the origin of clay minerals in nature several of these possibilities are discussed in terms of the rock cycle the mineralogy of clays neoformed in the weathering environment is a function of solution chemistry with the most dilute solutions favouring formation of the least soluble clays after erosion and transportation these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size clays undergo little reaction in the ocean except for ion exchange and the neoformation of smectite therefore most clays found on the ocean floor are inherited from adjacent continents upon burial and heating however dioctahedral smectite reacts in the diagenetic environment to yield mixed layer illite smectite and finally illite with uplift and weathering the cycle begins again

tsunamis and submarine landslides in suruga bay central japan caused by nankai suruga trough megathrust earthquakes during the last 5000 years abstract magnitude 8 megathrust earthquakes that have generated large tsunamis with wave heights of 5 m in coastal areas of southwestern japan have occurred every 100 150 years along the nankai suruga trough which marks the convergent boundary between the eurasian and philippine sea plates using sedimentological geochemical and paleontological analyses as well as 14c dating we examined tsunami deposits in 12 sediment cores collected from the hamatome lowland yaizu plain shizuoka which faces the suruga trough four sandy tsunami deposits sands 1 4 are identified in sediments deposited during the last 5000 years sand 1 was deposited between 805 and 405 bc suggesting that only one tsunami left a sedimentological imprint in the hamatome lowland lagoon during the period of 4000 years between 3090 and 2913 bc and the ad 1096 eicho tokai earthquake this very low frequency of tsunami inundation may suggest that this tsunami was larger than those typically associated with megathrust earthquakes sands 2 4 are correlated with tsunamis associated with the eicho tokai ad 1361 shohei koan and ad 1498 meio tokai earthquakes respectively our data indicate that a sand spit which had previously protected the lagoon from oceanic waves was abruptly destroyed following the ad 1096 eicho tokai earthquake and did not re form at the same location this disappearance of the sand spit is inferred to have involved an earthquake induced submarine landslide the data presented in this paper together with information obtained from historical documents indicates that m8 megathrust earthquakes in ad 1096 and ad 1498 caused submarine landslides in the study area resulting in coastal subsidence and damage to coastal areas additional to that caused by the tsunamis

recrystallization of dolomite evidence from the monterey formation miocene california dolomites from the upper calcareous siliceous member of the miocene monterey formation exposed west of santa barbara california were analysed for geochemical isotopic and crystallographic variation the data clearly document the progressive recrystallization of dolomite during burial diagenesis in marine pore fluids recrystallization is recognized by the following compositional and crystallographic variations dolomites have decreasing 18o and 13c compositions decreasing sr contents and increasing mg contents with increasing burial depths and temperatures from east to west in the study area 18o values vary from 5 3 in the east to 5 5 pdb in the west and are interpreted to reflect the greater extent and higher temperature of dolomite recrystallization in the west 13c values correlate with 18o and decrease from 13 6 in the east to 8 7 pdb in the west sr concentrations correlate positively with 18o values and decrease from a mean of 750 ppm in the east to a mean of 250 ppm in the west mol mgco3 values inversely correlate with 18o values and increase from a minimum of 41 0 in the east to a maximum of 51 4 in the west rietveld refinements of powder x ray diffraction data indicate that the more recrystallized dolomites have more contracted unit cells and increased cation ordering the fraction of the ca sites in the dolomites that are occupied by ca atoms increases slightly with the approach to stoichiometry the fraction of the mg sites occupied by mg atoms strongly correlates with mol mgco3 even in early diagenetic non stoichiometric dolomites there is little substitution of mg in ca sites during recrystallization the amount of mg substituting for ca in ca sites decreases even further most of the disorder in the least recrystallized non stoichiometric dolomites is related to substitution of excess ca on mg sites

nodular chert from the arbuckle group slick hills sw oklahoma a combined field petrographic and isotopic study nodular chert from the middle and upper arbuckle group early ordovician in the slick hills sw oklahoma was formed by selective replacement of grainstones burrow fillings algal structures and evaporite nodules chert nodules are dominantly microquartz with minor fibrous quartz both quartzine and chalcedony megaquartz and microflamboyant quartz lepisphere textures of an opal ct precursor are preserved in many especially in finely crystalline chert nodules the 18o values of microquartz chert range from 23 4 to 28 80 00 smow significantly lower than those of cenozoic and mesozoic microquartz chert formed both in the deep sea and from near surface sea water the 18o values of chert decrease with increasing quartz crystal size silicification in the arbuckle group occurred during early diagenesis with the timing constrained by the relative temporal relationships among silicification burial compaction and early dolomite stabilization silica for initial chert nucleation may have been derived from both dissolution of sponge spicules and silica enriched sea water chert nucleation appears to have been controlled by the porosity permeability and organic matter content of precursor sediments this conclusion is based on the fact that chert selectively replaced both porous grainstones and burrows and algal structures enriched in organic matter growth of chert probably occurred by a maturation process from opal a to opal ct to quartz as indicated by the presence of opal ct precursor textures in many chert nodules although field and petrographic evidence argues for an early marine origin for chert in the arbuckle group the light 18o values are inconsistent with this origin meteoric resetting of the 18o values of the chert during exposure of the carbonate platform best explains the light 18o values because i the 18o values of chert nodules decrease with decreasing 18o values of host limestones and ii chert nodules from early dolomite which underwent more extensive meteoric modification than associated limestones have lighter 18o values than chert nodules from limestones increasing recrystallization of chert nodules by meteoric water resulted in progressive 18o depletion and quartz crystal enlargement

18o16o and 13c12c in lower paleozoic articulate brachiopods implications for the isotopic composition of seawater three hundred and eleven articulate brachiopods with extensive geographic coverage spanning the cambrian to silurian stratigraphic interval were analyzed for oxygen and carbon isotopic composition cambrian samples have 18o 7 ordovician samples 2 4 and silurian samples 1 9 confirming the previously established trend towards lighter isotopic compositions with increasing age throughout the lower paleozoic forty nine best preserved ordovician and silurian samples were identified based on scanning electron microscopy and trace element analysis they were found to bracket the isotopic compositions of over 85 of specimens from these stratigraphic intervals supporting widespread preservation of the isotopic signal some latest ordovician and lower ludlovian samples associated with shale sequences are apparently enriched in 18o these are interpreted as an environmental phenomenon perhaps related to water temperature and glaciation a number of silurian samples of varying genera and stratigraphic levels are highly enriched in 13c up to 6 some are shale related but some are associated with carbonate bearing basins these are also thought to represent near original compositions but a single environmental cause is unknown the present data show that luminescence is not a decisive criterion for evaluating the degree of brachiopod preservation whole shell values were isotopically similar to their nonluminescent portions for both oxygen and carbon

oxygen and hydrogen isotope geochemistry of cretaceous bentonites and shales from the disturbed belt montana the mineralogy o18 and d of the 0 1 m fraction of 22 cretaceous bentonites and the mineralogy and o18 of the 0 1 m fraction of 14 adjacent shales collected from outcrops in the sweetgrass arch and disturbed belt montana have been determined mixed layer illite smectite i s is the dominant mineral in the bulk bentonite and usually the only mineral in the 0 1 m fraction i s is also the major clay mineral in the shales the diagenetic grade in bentonite is qualitatively given by the percentage of illite layers in i s which varies from 2 to 25 sweetgrass arch to as high as 95 disturbed belt o18 of 0 1 m bentonite generally decreases from about 20 to about 13 with increasing diagenetic grade on a plot of d versus o18 data for the 0 1 m bentonite define a field that generally parallels but falls on the meteoric water line side of the smectite water line savin and epstein 1970 o18 of bulk bentonite is 1 to 3 more negative than the o18 of the 0 1 m fraction due to the presence of volcanic quartz and feldspar o18 of several size fractions of clay sized quartz separated from the bentonite varies from 11 to 24 and in a given bentonite generally increases with decreasing grain size among the different bentonites the o18 range of the different grain sizes decreases as the percentage of illite layers in the coexisting i s increases the o18 of 0 1 0 5 m shale quartz is generally 1 to 4 more positive than clay sized quartz from an adjacent bentonite and the o18 of 0 1 m i s concentrate of shales is generally 1 to 4 more negative than the 0 1 m i s from an adjacent bentonite isotopic temperatures interpreted to be maximum burial temperatures range between about 160 c shale to about 250 c bentonite the isotopic data can be interpreted using the stages 1 1 deposition of volcanic glassy ash containing some quartz and feldspar 2 2 devitrification into mostly 100 expandable smectite with a o18 of about 20 and d of 60 to 80 3 3 tectonic burial beneath thrust sheets in the disturbed belt region which induced elevated temperatures that allowed oxygen and hydrogen isotope reequilibration as the percentage of illite layers in i s increased and diagenetic quartz formed and 4 4 exhumation of the strata with preservation of o18o16 and d h attained during burial

detailed coseismic slip distribution of the 1944 tonankai earthquake estimated from tsunami waveforms coseismic slip distribution on the fault plane of the 1944 tonankai earthquake is estimated from inversion of tsunami waveforms three improvements from a previous study satake 1993 are made these are 1 smaller subfaults are used to resolve detailed slip distribution 2 the sub faults fit better to the plate interface geometry and 3 finer and more accurate bathymetry data is used the inversion result shows that a maximum slip of about 3 m occurred on the plate interface off shima peninsula the total seismic moment is estimated to be 2 0 1021 nm mw 8 2 the result confirms that the 1944 tonankai earthquake did not rupture the plate interface beneath the tokai region and supports the existence of the seismic gap in the tokai region suggested by ishibashi 1981 the slip of about 1 5 m on the plate interface beneath atsumi peninsula northeast of the large slip area is necessary to explain the observed tsunami waveforms although no seismic moment release was estimated from strong motion data by kikuchi et al 1999 this may suggest that the rupture beneath atsumi peninsula was slow

microfossil evidence for recurrent coseismic subsidence around lake hamana near the nankai suruga trough central japan abstract we reconstructed recurrent coseismic subsidence during the middle holocene from analyses of sedimentary facies and fossil diatom assemblages in a small drowned valley the shinjo lowland bordering lake hamana near the nankai suruga trough central japan the lake hamana region is known for coseismic subsidence during the 1707 hoei m8 6 and 1854 ansei tokai m8 4 earthquakes along the nankai suruga trough subduction zone a coring survey revealed three widely distributed peat layers in the lowland with a mud layer overlying each of the two lower peats with a sharp contact we traced the alternating peat mud beds for over 300 m along the long axis of a valley the fossil diatom assemblage analysis revealed that the peat layers were deposited in a freshwater pond marsh environment which changed abruptly to an estuarine to inner bay environment recorded by the mud layers from the sudden environmental change at the two peat mud contacts and our radiocarbon dating results we inferred that coseismic subsidence followed by an invasion of seawater into the lowland occurred at least twice during a great earthquake that occurred between 5645 and 6635 cal yr bp and during another great earthquake at ca 5700 cal yr bp within the mud layers the dominant diatom species changed gradually upward from nitzschia frustulum and cocconeis scutellum in the lower part to cyclotella striata and achnanthes submarina in the upper part these changes suggest that water depth and salinity gradually increased after the coseismic subsidence a possible cause of this gradual subsidence is postseismic subsidence following great nankai suruga trough earthquakes

wavefield decomposition using ml probabilities in modelling single site 3 component records summary this paper presents a new approach to the analysis of three component digital seismograms earlier approaches used techniques such as principal components to estimate particlemotion using models of p and s waves in this paper the maximum likelihood ml estimator is preferred because this allows the use of x2 probabilities to test whether energy of a specific wave type p s love or rayleigh is present in addition this analysis allows the joint estimation of azimuth of approach and in cases of p and sv waves also apparent angle of incidence and hence information on apparent velocity for a single three component seismogram the covariance matrix provides only six independent observations thus restricting analysis to rather simple wave models the technique works satisfactorily for p waves whereas shear and surface wave models sometimes prove cumbersome to handle due to correlation between radial and transverse components reflecting complex propagation characteristics in inhomogeneous media this technique has been tested on synthetic data and in such cases works perfectly for all wave types an important aspect of this work has been the visual display of the probability and velocity information as functions of time and azimuth displaying the data in this form provides information on the ray path in a manner similar to analysis performed by seismic arrays practical examples on a variety of siesmic data are given to illustrate the viability of the technique the data cover a broad spectrum of frequencies and applications from broad band teleseismic data 1 hz regional seismic data 10 40 hz seismic profiling data 125 hz and vsp 500 hz recordings