elemental compositions and monazite age patterns of core sediments in the changjiang delta implications for sediment provenance and development history of the changjiang river core from a continuous borehole in the changjiang delta to a depth of 318 7 m dated back to the pliocene 3 58 ma and was selected for geochemical measurements and determinations of th u pb ages of monazite in order to investigate the changing sediment provenance and development history of the changjiang river geochemical proxies including fractionation parameters of rare earth elements cerium and europium anomalies and elemental ratios cr th nb co and th co suggest that the pliocene and quaternary sediments have remarkably different provenances six peak ages of monazite grains dated at 25 50 200 200 400 400 550 800 1000 and 1800 2000 ma are consistent with the main tectonic and magmatic events in the yangtze craton the data imply that the pliocene sediments were mostly derived from proximal and more silicic sources whereas the quaternary sediments were sourced from distal and more basic provenances including the emeishan basalt province in the upper changjiang valley we propose that during the pliocene the paleo changjiang or its eastern equivalent was a locally small river draining today s lower changjiang valley whereas during the early pleistocene not later than 1 18 ma it changed its drainage pattern and developed into a large river that originated from the eastern tibetan plateau this time matches well with many previous studies based upon geomorphologic geographic and tectonic observations in the jinshajiang valley and the three gorges

downfan transformation from turbidity currents to debris flows at a channel to lobe transitional zone the lower pleistocene otadai formation boso peninsula japan transformation of turbidity currents into debris flows across a channel to lobe transition zone was recognized on the basis of lateral mapping of a falling stage systems tract deposit in the lower pleistocene otadai formation submarine fan sequence on the boso peninsula japan the most proximal outcrops comprise 1 to 4 m thick turbidites which are laterally equivalent to debrites encased in turbidites in outcrops farther down flow such turbidites and encased debrites were deposited from single flow events the most distal outcrops comprise only thinner 2 to 40 cm thick turbidites debrites contain many siltstone clasts and finer grained sediments which are characterized by deep water faunas and clay mineral composition similar to those of interbedded hemipelagites therefore the transformation of turbidity currents into debris flows is interpreted to have occurred in response to the incorporation of many siltstone clasts and finer grained sediment particles into the precursor turbidity currents through erosion of muddy substrates subsequently turbulence in the precursor turbidity currents was suppressed and near bed flow with higher sediment concentration developed intense erosion of muddy substrates is interpreted to have occurred in response to the increase in intensity of turbulence in the precursor turbidity currents at the mouths of middle fan channels the precursor turbidity currents or turbidity currents generated by dilution of debris flows produced a turbidite deposit which was subsequently overrun by the debris flow in a proximal lobe environment the debris flows are interpreted to have subsequently been transformed into turbidity currents which are recorded by turbidite deposition in the more distal lobe environment debrites can characterize the proximal portion of an attached lobe deposit in a channel to lobe transition zone such debrites can be significant heterogeneities for fluid flows in sand prone successions from middle fan channel to attached lobe deposits

benthic foraminiferal evidence of deep sea sediment transport by the 2011 tohoku oki earthquake and tsunami abstract benthic foraminiferal assemblages within turbidites recovered from two upper slope stations off sendai bay northeast japan have been analyzed to estimate the source area of the turbidites resulting from the 2011 tohoku oki earthquake and tsunami the turbidite at one station st 5 893 m water depth is composed of a surface layer that contains foraminiferal species living on the outer shelf or inner bay and a lower part with bathyal species in the turbidite at the second station st 6 1446 m the assemblage consists of only bathyal species living in 800 1000 m the composition of the st 6 assemblage gradually changes from the base to the top of the turbidite consistent with the upward fining graded structure i e thin walled tiny species are increased in the upper layer the lower part of the turbidites at both sites st 5 and st 6 are considered to have originated from turbidity currents triggered by earthquake shaking in contrast the most probable generation mechanism for the turbidity current that formed the surface layer at st 5 is the tsunami related agitation of sediment in shallow water the relatively good preservation of benthic foraminiferal tests in the turbidites suggests transport processes with minimal internal friction and or collision of grains within the turbidity current these results show that benthic foraminifera are useful in turbidite paleoseismology

large submarine landslides in the japan trench a new scenario for additional tsunami generation 1 we describe in detail possible large submarine landslides several tens of kilometers in length and width on the trench landward slope of the japan trench on the basis of high resolution topographic surveys and detailed seafloor observations these slides stopped at the toe of the trench slope after initial movement of the toe along a basal decollement or thrust of the trench landward slope wedge during an earthquake the basal frictional condition s might change drastically from static to dynamic thus reducing the frictional strength as a result rapid submarine landsliding push downward on the toe generating large horizontal displacements for tsunamis this hypothesis should explain suitably the relation between large displacement of the thrust fault and tsunami generation by the 2011 tohoku earthquake as well as tsunami generation by the 1896 tohoku earthquake

a slump in the trench tracking the impact of the 2011 tohoku oki earthquake we present differential bathymetry and sediment core data from the japan trench sampled after the 2011 tohoku oki offshore japan earthquake to document that prominent bathymetric and structural changes along the trench axis relate to a large 27 7 km 2 slump in the trench transient geochemical signals in the slump deposit and analysis of diffusive re equilibration of disturbed so 4 2 profiles over time constrain the triggering of the slump to the 2011 earthquake we propose a causal link between earthquake slip to the trench and rotational slumping above a subducting horst structure we conclude that the earthquake triggered slump is a leading agent for accretion of trench sediments into the forearc and hypothesize that forward growth of the prism and seaward advance of the deformation front by more than 2 km can occur episodically during a single event large mega thrust earthquake

erosional response of south china to arc rifting and monsoonal strengthening a record from the south china sea abstract ocean drilling program sampling of the distal passive margin of south china at sites 1147 and 1148 has yielded clay rich hemipelagic sediments dating to 32 ma oligocene just prior to the onset of seafloor spreading in the south china sea the location of the drill sites offshore the pearl river suggests that this river or its predecessor may have been the source of the sediment in the basin which accounts for only 1 8 of the total neogene sediment in the asian marginal seas a mean erosion depth of 1 km over the current pearl river drainage basin is sufficient to account for the sediment volume on the margin two dimensional backstripping of across margin seismic profiles shows that sedimentation rates peaked during the middle miocene 11 16 ma and the pleistocene since 1 8 ma nd isotopic analysis of clays yielded nd values of 7 7 to 11 0 consistent with the south china block being the major source of sediment more positive nd values during and shortly after rifting compared to later sedimentation reflect preferential erosion at that time of more juvenile continental arc rocks exposed along the margin as the drainage basin developed and erosion shifted from within the rift to the continental interior nd values became more negative a rapid change in the clay mineralogy from smectite dominated to illite dominated at 15 5 ma synchronous with middle miocene rapid sedimentation mostly reflects a change to a wetter more erosive climate evidence that the elevation of the tibetan plateau and erosion in the western himalaya both peaked close to this time supports the suggestion that the asian monsoon became much more intense at that time much earlier than the 8 5 ma age commonly accepted

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

neodymium isotopic variations of the late cenozoic sediments in the jianghan basin implications for sediment source and evolution of the yangtze river abstract the yangtze river originates from eastern asia and is one of the most important components of the east asia river system in this study we applied bulk nd isotopic analysis to identify the sediment provenance in the jianghan basin middle yangtze river and tried to provide useful information on the evolvement of the yangtze river the fine grained

sr and nd isotopes in river sediments from the ganga basin sediment provenance and spatial variability in physical erosion 1 sr and nd concentrations and isotope compositions in sediment of the ganga river from gangotri to rajmahal and its tributaries have been measured to determine provenance and the spatial variability in physical erosion among the ganga subbasins sr and nd in silicates range from 37 to 138 and from 10 to 36 g g with 87sr 86sr and nd of 0 7474 0 8428 and 25 5 to 15 5 respectively the results suggest that 65 of ganga mainstream sediments are derived from the higher himalayan crystallines highlighting intense physical erosion in this region the 87sr 86sr values of sediments in the gangetic plain show nearly identical trends during two seasons with a sharp and significant decrease at barauni downstream of gandak confluence this brings out the major impact of the sediment contribution from the gandak to the ganga mainstream model calculation suggests that about half of the ganga sediment at rajmahal is sourced from the gandak the erosion rates in the himalayan subbasins of the ganga range between 0 5 and 6 mm a where a is years with the gandak having the highest erosion rate high relief and intense precipitation over the headwater basins of the gandak appear to drive the rapid and focused erosion of this basin the results of this study and those in literature suggest that the eastern syntaxis brahmaputra the western syntaxis indus and the gandak have much higher physical erosion rates than the other himalayan basins focused erosion in the hot spots of these river basins contributes significantly to the global riverine sediment budget and influence regional tectonics

tracing sr isotopic composition in space and time across the yangtze river basin abstract variation of dissolved 87 sr 86 sr in the yangtze river is poorly documented compared to other tibetan sourced rivers here we trace the sr isotopic composition in space and time across the yangtze river basin using a systematic sampling strategy the 87 sr 86 sr values of samples collected at different depths within the water column at three gauge stations located in the upper middle and lower reaches of the river are very similar indicating a well mixed water body at a given location data from basin wide samples shows low 87 sr 86 sr values in the upper reaches while higher 87 sr 86 sr values in the middle lower reaches which mainly reflect the controls of source rocks a time series record at the lowermost reaches of the river indicates a temporal variation of 87 sr 86 sr values from 0 7101 to 0 7109 with a discharge weighted value of 0 7106 we suggest that temporal variations of the isotopic composition result from changes in the relative contributions from different terrains associated with spatial variability of rainfall within the basin a mixing model based on sr values deduced from basin wide sampling from different seasons yields similar temporal variations of sr isotopic composition compared to experimental data calculation of sr fluxes indicates that the upper reaches contribute 3 times as much as the middle and lower reaches to total sr flux the annual sr flux of the yangtze river to the east china sea is estimated to be 1 9 10 9 mol a 1 which is one magnitude higher than that of the brahmaputra and ganges

seasonal phytodetritus deposition and responses of bathyal benthic foraminiferal populations in sagami bay japan preliminary results from project sagami 1996 1999 the seasonal carbon cycle was studied in the bathyal environment of sagami bay japan to determine whether benthic pelagic coupling takes place in this eutrophic marginal oceanic setting both japanese sea color observation satellite adeos photography and sediment trap moorings have been used since 1996 for monitoring sea surface primary production video records at a real time deep sea floor observatory off hatsushima island in sagami bay were also used to monitor the deposition of phytodetritus on the sea floor at this location a spring bloom starts in mid february and ends in mid april about 2 weeks after the start of the spring bloom phytodetrital material is deposited on the sea floor video records clearly show that phytodetritus deposition has taken place in the spring of every year since 1994 even though the exact timing is different from year to year the population size of benthic foraminifera is highly correlated to this phytodetritus deposition the phytodetritus triggers rapid opportunistic reproduction of the shallow infaunal taxa bolivina pacifica stainforthia apertura and textularia kattegatensis shallow infaunal species mainly occur in the phytodetrital layer or just below this layer during the spring this indicates that such opportunistic species are key indicators of phytodetrital deposition the deep infaunal taxa globobulimina affinis and chilostomella ovoidea show less pronounced seasonal fluctuations in population size but nevertheless exhibit some response to phytodetrital deposition thus the seasonal flux of organic matter is the most important determinant of population size microhabitats and reproduction of benthic foraminifera in sagami bay

multidirectional synchronously triggered seismo turbidites and debrites revealed by x ray computed tomography ct on 21 april 2007 a mw 6 2 earthquake struck aysen fjord chilean patagonia and caused onshore and offshore mass movements which triggered tsunamis and density flows in the fjord to better understand the facies successions in and the intercalation of the density flow deposits a study was made of the 2007 deposits in 22 short sediment cores taken in the inner aysen fjord by combining grain size analysis with x ray computed tomography scanning it was possible to demonstrate that the encountered facies correspond to classical divisions of debrites and turbidites the single event deposits consist of a succession of several sub deposits deposited under different flow directions and can be interpreted as stacked turbidites orientations of i folds ii imbricated mud clasts iii backsets and foresets of climbing ripples and iv asymmetrical convolute lamination were used to determine relative flow directions at the location of the cores by assigning the basal flow of the stacked debrites and turbidites to the closest principal mass flow the absolute flow directions of the sub deposits were determined which in combination with multibeam basin floor morphology allowed reconstruction of the 2007 density flow successions in aysen fjord furthermore alternating flow directions provide evidence for a seiche induced by the density flows it was concluded that x ray computed tomography scans provide crucial information for reconstructing palaeoflows and can be a useful tool in marine and lacustrine sedimentology and palaeoseismology the multidirectionality of sub deposits in turbidites is next to differences in mineralogy a new criterion to identify stacked turbidites these multidirectional stacked turbidites are an indication of simultaneous triggering of density flows and can therefore in most cases be attributed to earthquakes ruling out other triggers such as floods storms or other sediment failures this article is protected by copyright all rights reserved

sand drift and soil formation along an exposed north atlantic coastline 14 000 years of diverse geomorphological climatic and human impacts this paper sets out the history of aeolian deposition and soil formation over the last 14 15 000 calendar years along the exposed and gale prone atlantic coastlines of the southern isles of the outer hebrides of scotland detailed palaeoenvironmental interpretation and chronological control have been provided by field mapping soil micromorphological analyses and radiocarbon and optically stimulated luminescence osl dating programmes two dominant types of aeolian sands are described in this region quartzose sands are shown to originate mainly as periglacial wind blown sands derived from glacial and periglacial deposits of late devensian age which were formerly exposed on the present continental shelf this aeolian deposition did however continue into the early holocene with re working perhaps by slope wash taking place as recently as the 4th millenniumbp quartzose sands mantle valley floors and hillslopes by the end of the devensian and early holocene a variety of soil types with extensive horizonation had developed upon them including podzolic brown earths peaty gleys and peat soils radiocarbon and osl dating demonstrate that the carbonate sands of the machair sand sheets which characterize the present atlantic shorelines began to accumulate very early for a european shoreline from approximately 8700 calendar years ago on benbecula and north uist whereas further south deposition began later osl dating suggests that non sequences and diastems are common in greater part these machair sand sheets are best interpreted as a composite of separate slivers of sand reflecting small scale and local episodes of sand drift rather than distinct layers of region wide distribution which might reflect past major storms or significant palaeoclimatic fluctuations the new evidence presented here provides little support for the following explanatory geomorphic or stratigraphic models which have previously sought to explain the development of these coastal machair landscapes continuous development layer cake or step wise prograding coastal barrier qualified support is given for the explanations that emphasize i the long term spasmodic input and re cycling of sands and ii that the present smoothed landscapes and distinctive machair grassland vegetation are essentially recent in age and reflect the interactions of natural and human processes in a stormy environment characterized by re working widespread layers of thick organic materials within the carbonate sands in the study area which have previously been regarded as dune palaeosols dating to the bronze age and iron age are suggested by soil micromorphological analysis to be in significant part anthropogenic in origin they are organically enriched layers or midden soils the consequence of human activities notably the disposal of organic wastes and other forms of soil modification during times of significant settlement in these coastal sands these periods of relatively intense human activity are therefore shown to be associated at least locally with periods of soil formation and stability not universal instability and dune drift along these shorelines in general these extensive layers of midden soil do not necessarily imply periods of decreased storminess relatively widespread soil formation in these coastal dunes did however take place in the period between 400 and 100 years ago essentially within the period of increased storminess associated with the little ice age it is suggested that at some point s within the following periods of time broadly defined in calendar yearsbp notable sand drift affecting the quartzose sands the carbonate sands or both took place within the study area 13 700 13 000 11 000 10 500 9000 8300 7500 7000 6900 6400 5800 4200 one of the most notable episodes of drift in the outer hebrides as well as elsewhere on the coast of north west europe 3800 3300 1700 1300 600 200 with individual great storms being recorded in the 17th and 18th centuries and 100 present day limited drift associated with machair stratification

possible submarine tsunami deposits on the outer shelf of sendai bay japan resulting from the 2011 earthquake and tsunami off the pacific coast of tohoku abstract although it is accepted that large tsunami waves impact the sea floor the response of surface sediments to tsunami is not yet fully understood tsunami by the 2011 off the pacific coast of tohoku earthquake caused considerable damage to northeast japan surface sediments on the outer shelf of sendai bay also show evidence of strong ground motion and agitation by the subsequent tsunami sediments in the hemipelagic mud below the erosional surface contain vein like structures providing evidence of strong ground motions induced by the earthquake two turbidite sequences are present above the erosional surface in which 134 cs and 137 cs only occur in the upper turbidite unconsolidated mud on the inner mid sendai shelf was agitated and resuspended by the high frictional velocities associated with the tsunami waves the high concentration of suspended sediment in the water column above the shelf is likely to have generated turbidity currents and have made the lower turbidite after the release of 134 cs by the accident at the fukushima no 1 nuclear power plant the second turbidity current generated and created the upper turbidite

advances in the study of mega tsunamis in the geological record abstract extreme geophysical events such as asteroid impacts and giant landslides can generate mega tsunamis with wave heights considerably higher than those observed for other forms of tsunamis in this paper we review recent advances in the study of mega tsunamis in the geological record focusing on well documented examples that have captured particular attention over the past decade we provide up to date background on the source mechanisms of tsunami generation during asteroid impacts and ocean island landslides which are the largest landslides on earth we also discuss the main sources of uncertainty for modelling such mega tsunamis and for addressing associated hazards

magnitudes and source areas of large prehistoric northern alpine earthquakes revealed by slope failures in lakes we identify evidence for three large paleo earthquakes in central switzerland with moment magnitudes m 6 5 7 0 significantly exceeding historically known values these earthquakes occurred during the past 15 k y and were strong enough to simultaneously affect a large region that includes the present day major cities of lucerne and zurich we reconstruct the chronology magnitudes and epicenters of these prehistoric earthquakes using temporal and spatial correlation of multiple subaqueous landslide deposits in lake zurich and lake lucerne through high resolution seismic surveys radiocarbon dated sediment cores and spatial calculations using an empirical seismic attenuation model our data indicate ongoing alpine deformation that generated and could potentially generate destructive events in heavily populated regions that have been unaccustomed to seismic activity during historic time

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

a common opportunistic foraminiferal species as an indicator of rapidly changing conditions in a range of environments abstract long term biological and environmental time series several decades to centuries are essential for distinguishing between anthropogenically and naturally induced environmental change as well as for monitoring environmental change over time irrespective of the causes since such long time series are virtually non existent for most areas other methods have to be explored which can provide the best possible analogues numerous investigations have shown that benthic foraminifera meiofaunal protists which leave a fossil record in most marine sediments are well suited for this purpose a prerequisite for performing sound interpretations is an optimal understanding of their biology and ecology stainforthia fusiformis williamson is one of the most common benthic foraminiferal species in nw european waters and living stained populations have been recorded in all clastic soft bottom intertidal to outer shelf and slope areas with sediments consisting of at least some fines 4 28 its predominance in ephemerally dysoxic anoxic areas has caused it to be used as a proxy for severe oxygen depletion a strong dominance even 90 of this species is however also reported from well oxygenated coastal and shelf settings and consequently high abundance of this species occurs in habitats with very different environmental characteristics a closer examination of these areas suggests that they can be roughly grouped into three categories 1 beneath hydrographic frontal areas 2 physically disturbed areas of sediment and 3 ephemerally dysoxic anoxic basins the main characteristic feature that these highly different environments have in common is that they experience rapidly changing conditions it is concluded that the opportunistic life strategy of s fusiformis makes it highly adapted to cope with environmental stress and that this rather than tolerance to a particular environmental parameter causes it to predominate in areas subject to rapidly changing environmental conditions

quartz electron spin resonance signal intensity of al and ti li centers as a provenance indicator an example from the yangtze river basin abstract the quartz electron spin resonance esr signal intensity si of the al and ti li centers in sediment samples collected from the mainstream and major tributaries of the yangtze river basin were measured to determine whether they can be used as fluvial sediment provenance indicators the results show significant spatial variation in the esr si between the bulk coarse 200 355 m and fine 75 154 m grain size fractions for all three size fractions the esr sis of sediment from the mid lower reaches of the basin were higher than those of the upper reaches demonstrating that the esr si can be used to distinguish between quartz contributed by the upper and mid lower reaches of the basin furthermore the quartz esr si of the major tributaries exhibited distinct spatial variation according to the distribution of the type of bedrock thus the quartz esr si can be used to trace the provenance of fluvial sediments even in large river systems additionally the upper yangtze river basin contributed a large amount of material to the lower mid mainstream and even the fine fraction of sediment in the lower yangtze river originated mainly from the upper yangtze river basin

sedimentology of seismo turbidites off the cascadia and northern california active tectonic continental margins northwest pacific ocean abstract holocene turbidites from turbidite channel systems along the active tectonic continental margins of the cascadia subduction zone offshore vancouver island to mendocino triple junction and the northern san andreas transform fault the triple junction to san francisco bay have been analyzed for sedimentologic features related to their seismic origin centimeter thick silt sand beds turbidite base capped by mud layers turbidite tail and interbedded with hemipelagic silty clay intervals with high biogenic content have been characterized by visual core descriptions grain size analysis x ray radiographs and physical properties along the northern california margin in upstream single tributary canyons and channels most turbidites are uni pulsed classic fining up whereas downstream below multiple tributary canyon and channel confluences most deposits are stacked turbidites because each set of stacked turbidites has no hemipelagic sediment between each turbidite unit and each unit has a distinct mineralogy from a different tributary canyon we interpret that a stacked turbidite is deposited by several coeval turbidity currents fed by multiple tributary canyons and channels with synchronous triggering from a single san andreas fault earthquake the cascadia margin is characterized by individual multi pulsed turbidites that contain multiple coarse grained sub units without hemipelagic sediment between pulses because the number and character of multiple coarse grained pulses for each correlative multi pulsed turbidite is almost always constant both upstream and downstream in different channel systems for 600 km along the margin we interpret that the earthquake shaking or aftershock signature is usually preserved for the much stronger cascadia 9 mw compared to weaker california 8 mw earthquakes which result in upstream uni pulsed turbidites and downstream stacked turbidites consequently both the strongest 9 mw great earthquakes and downstream confluences cause multi pulsed and stacked turbidites that are typical for seismo turbidites generated by a single great earthquake along both margins earthquake triggering and multi pulsed or stacked turbidites become an alternative explanation for amalgamated turbidite beds in active tectonic margins and show that multiple grain size pulses and reverse grading are not unique criteria for hyperpycnites thalweg levee turbidites or mini basin margin turbidites the analyses of the turbidites along the cascadia and northern california margins reveal common sedimentologic characteristics of turbidites triggered by great earthquakes that can be used to distinguish seismo turbidites in other active tectonic margins around the world

sedimentary and foraminiferal evidence of the 2011 tōhoku oki tsunami on the sendai coastal plain japan abstract the 2011 t hoku oki megathrust earthquake mw 9 0 generated a tsunami that reached the sendai coastal plain with flow heights of 2 to 11 m above tp tokyo peil we examined the tsunami deposit exposed in 14 shallow trenches along a 4 5 km transect perpendicular to the coast we primarily document the stratigraphical sedimentological foraminiferal and geochemical characteristics of the t hoku oki tsunami deposit and perform a preliminary comparison with sediments deposited by the j gan tsunami of a d 869 in the coastal forest and rice fields inundated by the t hoku oki tsunami a poorly sorted dark brown soil is buried by a poorly sorted brown medium grained sand deposit in some trenches located more than 1 2 km inland the sand is capped by a thin muddy sand layer the tsunami deposit although highly variable in thickness is generally thickest 25 cm near the coastal dune and thins to less than 5 mm at 4 5 km inland the tsunami deposit was discriminated from the underlying soil by the appearance of recent and fossil foraminifera and a pronounced increase in grain size that fined upward and landward the recent foraminifera preserved in the sandy facies of the deposit are rare and showed evidence of prolonged subaerial exposure e g pitting corrosion fragmentation recent foraminifera likely originated from coastal dune and beach sediments that were breached by the tsunami calcified and sediment in filled fossil foraminifera are abundant and were eroded from sedimentary units and transported by fluvial or wave activity to sendai bay trends associated with test size e g decreasing concentration of large test sizes with distance inland are in agreement with grain size data at two locations a decrease in total organic carbon and an increase in 13c were found in the tsunami sand compared with the underlying soil supporting a beach to intertidal origin for the upper unit

sm nd studies of archaean metasediments and metavolcanics from west greenland and their implications for the earth s early history metasedimentary and metavolcanic rocks from the archaean of west greenland have been examined for evidence of crustal components greater than 3 8 ga in age and for their compatibility with the presently adopted bulk earth sm nd parameters sm nd isotopic data have been obtained for the garbenschiefer metagabbro unit metasediments from the isua supracrustal belt gneisses interior to the isua belt and metasediments from the malene supracrustal belt using estimates of emplacement age t of between 3 77 and 3 67 ga for the parental volcanics to the garbenschiefer unit initial143nd 144nd ratios yield positiveendt values between 1 0 and 3 1 relative to the chur parameters for seven out of eight samples model sm nd ages for the isua gneisses and metasediments are only compatible with their estimated stratigraphic ages if their sources were ca 2end relative to chur at those times similarly model sm nd ages for the malene samples are only compatible with stratigraphic age constraints when based on a source evolution with positiveendt implications of these results for the early development of the earth s mantle are discussed

centennial climate variability in the british isles during the mid late holocene abstract multi millennial climate changes were relatively minor over the mid late holocene in the british isles because orbitally forced insolation changes were smaller than those at higher latitudes centennial climate variability is thus likely to have exerted a greater influence on the environment and human society of the region proxy climate records from the british isles covering the last 4500 years are assembled and re evaluated with the aim of identifying centennial climate variability reflected by multi proxy indicators the proxies include bog oak populations peatland surface wetness flooding episodes from fluvial deposits speleothem annual band width and oxygen isotopes chironomids from lake sediments and sand and dune deposition most proxies reflect water balance rather than temperature alone and records predominantly reflect warm season climate a series of 12 key periods of enhanced precipitation evaporation p e are identified by their presence in two or more proxy records variability in p e is much greater than that shown by temperature proxies and there is no necessary association between warm cool and dry wet periods although the data for temperature are less robust than those for p e a series of key temperature changes are proposed based on speleothem 18o and chironomid inferred july temperature records relatively cool before c 3100 years bp warmer 3100 2000 years bp cool 2000 1250 cal years bp warm 1250 650 cal years bp and cool 650 cal years bp onwards some key increases in p e 2750 1650 550 cal years bp show a strong correspondence with bond cycles in ocean proxy records for increased ice rafted debris decreased summer sea surface temperatures and sometimes decreased north atlantic deep water circulation other higher frequency changes in p e are also strongly related to sst variability whilst some of the main changes to cooler ssts and increased p e are approximately coincident with reduced solar output most are not and thus must be the result of the internal dynamics of the ocean and atmosphere future work should concentrate on firmly establishing the pattern of temperature change improving chronological accuracy and precision in existing records and improving process based understanding of proxies

chronology and provenance of the yichang gravel layer deposits in the jianghan basin middle yangtze river valley china implications for the timing of channelization of the three gorges valley abstract the three gorges valley linking the upper and the middle lower yangtze river areas is a key area for understanding the geomorphological evolution of the yangtze river valley especially the timing of its formation which remains controversial and occurred following the authors to from the pre miocene to late pleistocene periods the 100 m thick yichang gravel layer ygl extending over an area 100 km2 is immediately observed downstream of the three gorges valley in the middle yangtze river basin also named jianghan basin studying heavy minerals assemblage and chronology of the ygl deposits can shed lights not only on the geological origin of the sediments and the morphological evolution of the three gorges valley but also the formation of the yangtze river valley in this study 18 sediment samples carried out from six representative sections of the unconsolidated ygl and 2 samples from the underlying neogene and paleogene bedrocks were analyzed in order to examine their heavy mineral assemblage compositions these assemblages were compared with modern yangtze river sediments sampled in yichang area n 5 and present day sediments from other rivers of the jianghan basin n 6 to further identify the sediment provenance of the ygl the statistic results indicate that the heavy minerals identified the ygl dominated by zircon epidote titanite hematite limonite and ilmenite are similar to the assemblages observed in the 5 modern yangtze river sediment samples but differ obviously from both underlying bedrock assemblages containing kyanite garnet rutile and monazite and other modern river sediments jianghan basin including hornblende chlorite tourmaline rutile anatase spinel and garnet in addition 8 sandy samples from the ygl were dated by electron spin resonance esr method using ti li center showing a deposition age ranging between 1123 139 and 734 183 ka based on these observations we propose that the ygl sediments derived from the upper yangtze river basin above the three gorges valley indicating that the three gorges valley was channelized before 1 12 ma ago this result is consistent with previous provenance tracing studies of continuous deposited late cenozoic sediment from central jianghan basin since 3 0 ma which also constrains the incision time of the three gorges to 1 1 ma

evidence from sites in western ireland of late holocene changes in coastal environments the presence of sand layers interleaved with biogenic material in coastal sedimentary sequences from back barrier areas has often been used as evidence of storm surge or tsunami action during the holocene this paper discusses such stratigraphies from two adjacent sites in western ireland in order to assess the validity of this inference detailed examination of the sand layers indicates that while some of the sand beds at one of the sites were deposited by overwash other processes including aeolian deposition and fluvial reworking of aeolian sediments were also important in sand redistribution in the back barrier areas in these cases local controls including site drainage characteristics barrier morphology and available sediment supply appear to have been important in site evolution a regional signal of storm frequency was not detected

on the river lake relationship of the middle yangtze reaches abstract the geological and meteorological setting of the jianghan dongting lake area leads to high precipitation and siltation but poor water discharge thus the area is frequently flooded in the past the river lake relationship of the middle yangtze has been variable but has deteriorated recently under increasing human influence the jianghan plain of the middle yangtze becomes a waterlogged lowland under the constant threat of flooding from the perched jingjiang river due to siltation and land reclamation the dongting lake has lost most of its regulatory function for the river and has become increasingly vulnerable to flood disasters the middle yangtze river has been undergoing siltation resulting from a downstream decline of sediment transport capacity resulting in the elevation of the flood level above the lowlands heightening of the levees has caused further siltation of the channel the three gorges reservoir will provide a buffering period of 50 80 years during which much of the silt will be trapped in the reservoir and scouring downstream may occur we should utilize this period to work out an overall resolution to the problem construction of a water and silt diversion project in the honghu lake and surrounding areas may resolve this problem in the dangerous chenglingji wuhan segment of the yangtze widening the canals connecting the middle yangtze and han rivers may function as a discharge dividing channel of the yangtze which may prove to be beneficial

testing solar forcing of pervasive holocene climate cycles the temporal and spatial extent of holocene climate change is an area of considerable uncertainty with solar forcing recently proposed to be the origin of cycles identified in the north atlantic region to address these issues we have developed an annually resolved record of changes in irish bog tree populations over the last 7468 years which together with radiocarbon dated bog and lake edge populations extend the dataset back to 9000 yr ago the irish trees underpin the internationally accepted radiocarbon calibration curve used to derive a proxy of solar activity and allow us to test solar forcing of holocene climate change tree populations and age structures provide unambiguous evidence of major shifts in holocene surface moisture with a dominant cyclicity of 800 yr similar to marine cycles in the north atlantic indicating significant changes in the latitude and intensity of zonal atmospheric circulation across the region the cycles however are not coherent with changes in solar activity both being on the same absolute timescale indicating that holocene north atlantic climate variability at the millennial and centennial scale is not driven by a linear response to changes in solar activity copyright 2005 john wiley sons ltd

shallow marine deposits associated with the 2011 tohoku oki tsunami in sendai bay japan little is known about offshore tsunami deposits although they have the potential to improve palaeotsunami reconstructions especially in areas with limited preservation of onshore tsunami deposits we analysed 44 sediment cores collected in 2012 at water depths of 14 30 m in sendai bay north eastern japan to identify the deposits of the 2011 tohoku oki tsunami with the aid of 134cs released from the fukushima daiichi nuclear plant the preserved tsunami deposits in the inner shelf are interbedded with very fine sand and mud showing similar features to storm deposits in the shoreface a distinct layer of coarse sand overlies fine sand appearing to have originated as beach sand transported offshore by the tsunami backwash the coarse sand fades offshore around the boundary between the shoreface and inner shelf many of the core sites show evidence that surface sediment was reworked probably by post tsunami storm waves suggesting that further reworking would make the ultimate preservation of the tsunami deposits unlikely

benthic foraminiferal record of ecosystem variability in the eastern mediterranean sea during times of sapropel s5 and s6 deposition high resolution benthic foraminiferal and geochemical investigations were carried out across sapropels s5 and s6 from two sediment cores in the levantine sea to evaluate the impact of climatic and environmental changes on benthic ecosystems during times of sapropel formation the faunal successions indicate that eutrophication and or oxygen reduction started several thousand years prior to the onset of sapropel formation suggesting an early response of the bathyal ecosystems to climatic changes severest oxygen depletions appear in the early phases of sapropel formation the initial reduction of deep water ventilation is caused by a warming and fresh water induced stratification of eastern mediterranean surface waters during the late phase of s5 formation improved oxygenation is restricted to middle bathyal ecosystems indicating that at least some formation of subsurface water took place during s6 formation oxygen depletions and eutrophication were less severe and more variable than during s5 formation estimated oxygen contents were low dysoxic at middle bathyal to anoxic at lower bathyal depths during the early phase of s6 formation but never dropped to anoxic values in its late phase the high benthic ecosystem variability during s6 formation suggests that water column stratification at deep water formation sites was in a very unstable mode and susceptible to minor temperature fluctuations at a millennial time scale 5 2002 elsevier science b v all rights reserved

submarine earthquake geology along the north anatolia fault in the marmara sea turkey a model for transform basin sedimentation abstract the submerged portions of the north anatolia fault system beneath the marmara sea were studied with high resolution multibeam bathymetry subbottom profiling and sediment cores the major objectives were to learn about the seismic and tectonic history of the fault from the stratigraphic record at a scale similar to paleoseismic studies on land and to develop tools for submarine earthquake geology that can be applied to fault controlled basins in general we focused on holocene sediment in several marmara sea basins of different sizes the approach was to test whether 1 the depocenters of the larger basins contain a record of all historic ms 7 earthquakes within the marmara sea region 2 the small transform basins record earthquakes that rupture through them 3 vertical and strike slip holocene deformation can be quantified and 4 the effects of an earthquake generally includes both primary structural features due to rupture of the sea floor such as strata offset scarps and tilting as well as secondary effects due to shaking such as mass wasting and gravitational flows we found evidence of earthquakes that we correlate with historic events in 181 ad 740 ad 1063 ad 1343 ad 1509 ad 1766 ad 1894 ad and 1912 ad the geologic evidence is primarily from those basins adjacent to the rupture as inferred from historic data this suggests that coseismic deformation of the sea floor along the rupture is a critical factor in the sedimentary record we propose a qualitative sedimentation model that relates this coseismic deformation to mass wasting of the slope scour of the basin floor seiche motions and homogenite deposition frequent earthquake activity sheds sediments from the flanks contributes to the much thicker sediment on the basin floor and decreases the likelihood of sediment failures in response to normal marine gravity driven processes the surveying techniques and approaches used have therefore the potential of documenting earthquake ruptures of fault segments and to extend the earthquake record far before the known history thus improving hazard evaluations and the fundamental understanding of earthquake process

a decadal scale holocene sea surface temperature record from the subpolar north atlantic constructed using diatoms and statistics and its relation to other climate parameters 1 a sediment core from reykjanes ridge has been studied at 10 to 50 year time resolution to document variability of holocene surface water conditions in the western north atlantic and to evaluate effects of holocene ice rafting episodes diatom assemblages are converted to quantitative sea surface temperatures sst using three different transfer functions spectral and scale space methods are also applied on the records to explore variability at different timescales diatom assemblage and sst records clearly show that decaying remnants of the laurentide ice sheet strongly influenced early holocene climate in the western north atlantic this overrode the predominance of milankovitch forcing which played a key role in the development of holocene climate in the eastern north atlantic and nordic seas superimposed on general holocene climate change is high frequency sst variability on the order of 1 3 c the record also documents climatic oscillations with 600 to 1000 1500 and 2500 year periodicities with a time dependent dominance of different periodicities through the holocene a clear change in variability occurred about 5 ka bp the sst record also provides evidence for holocene cooling events hce that in some cases correlate to documented southward intrusions of ice into the north atlantic

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

sedimentary features of seismoturbidites triggered by the 1983 and older historical earthquakes in the eastern margin of the japan sea abstract both mass failure deposits and turbidites are widely distributed in the epicentral area of the 1983 earthquake mw 7 9 in the eastern margin of the japan sea this basin is semi enclosed with no active conduits for the entrance of coarse detrital sediments seismic reflection surveys and sediment cores reveal that mass failure deposits which are distributed on the continental slopes merge into turbidites in the basin plain hence the mass wasting process is a major transportation process in this region one gravity core gh93 816 was recovered from the southeastern margin of the japan basin close to the epicentral area of the 1983 japan sea earthquake sedimentological results show that five turbidite beds are intercalated in the top 68 cm of the column occurrence of the b tm tephra at the depth of 68 71 cm indicates that these turbidite beds were developed during the last 1000 years the high 137cs concentration in the top 20 cm of the core implies that the uppermost turbidite bed was deposited after 1954 based on these age limits for the top and the bottom of the studied interval we estimate the recurrence intervals of turbidites as 160 330 years we suggest that these turbidites were generated by submarine slides which were triggered by the 1983 and older historical earthquakes in this region these seismoturbidites are characterized by amalgamated beds irregular structure sequences grain size breaks fluctuations abrupt changes in composition within bed and variable composition among beds from these features we infer that deposition resulted from a series of turbidity currents associated with multiple or line sources for example multiple shallow slides that were regionally initiated by the same earthquake the sedimentary features described herein may be useful as criteria for identifying modern seismoturbidites in other settings as well as seismoturbidites in the geologic record however further study is needed for the distinction of this type of turbidites from other types e g tempestites reflected turbidites

nd isotopes of siliciclastic rocks from tibet western china constraints on provenance and pre cenozoic tectonic evolution nd isotope data from pre cenozoic siliciclastic rocks from tibet are used to determine variations of source regions with time and hence tectonic history on average the tdm and tchur ages of the tibetan samples are up to 1 83 0 36 ga and 1 25 0 45 ga respectively indicating that tibet is underlain by lower proterozoic basement and has close affinity with the himalayas an nd isotope crisis occurred at the early permian with older samples defining a trend of slight decrease in end values with time while the lower permian rocks sharply increasing 6 5 end units this is related to the coeval widespread basaltic magmatism in tibet which could be responsible for tibet rifting away from northern gondwanaland the central qiangtang meta sedimentary samples have distinct nd isotope characteristics end 0 19 87 1 51 tdm 2 07 0 13 ga tchur 1 78 0 21 ga from the songpan ganzi samples end 0 12 77 2 87 tdm 1 49 0 18 ga tchur 1 08 0 23 ga suggestive that these two groups were derived from differentsourcesandthatthe former werenot theequivalents ofthe latterthat wasunderthrust fromthe jinsasuture andmayrepresent subducted continental crust the mid jurassic flysch rocks in northern lhasa have typical upper crust nd isotopic signatures and could have formed under a passive margin environment their bangong counterparts averagely 6 35 units higher in end values unveil derivations from a likely magmatic arc along the northern bangong margin basaltic pebblewith low nd content and endvalue from the berriasian valanginian rocks in central tibet along with the samples with generally high end values shows that the bangong ophiolites could have been a main source of sediments during the earliest cretaceous time a significant transition of sediment sources occurred at the beginning of the hauterivian stage 120 ma sedimentary basaltic tuff end t 2 27 in the hauterivian lower cenomanian samples in central tibet and common nd signatures for input of mantle like materials in these rocks indicate that mantle derived magmatic rocks could have constituted a significant source the huge hauterivian lower cenomanian sediments in central tibet are thus inferred to have been accumulated under a back arc rifting setting 2007 elsevier b v all rights reserved

enhanced global continental erosion and exhumation driven by oligo miocene climate change surface erosion is the most significant process responsible for the recycling of continental crust into the upper mantle and controls both exhumation in mountain belts and the long term global climate via chemical weathering earlier studies have highlighted the importance of climate instability since the onset of northern hemispheric glaciation similar to 3 ma as being the primary influence causing high erosion rates since that time here i show that synchronous pulses of erosion and exhumation occurred across eurasia in north america and in africa starting after 33 ma with a prominent peak around 16 ma correlation of these erosional events with changes in global climate suggests that they are controlled by surface processes because these climate events involve both cooling and warming periods the importance of increased seasonality is emphasized as being the key factor in controlling global erosion and exhumation throughout the cenozoic citation clift p d 2010 enhanced global continental erosion and exhumation driven by oligo miocene climate change geophys res lett 37 l09402 doi 10 1029 2010gl043067

evidence for an earthquake triggered basin collapse in saguenay fjord canada abstract on february 5 1663 perhaps the largest earthquake ever witnessed in eastern north america struck the saguenay fjord basin with such force that landslides and submarine slides were triggered over a wide region over 3 km 3 of clayey holocene sediments collapsed from the margins of the fjord resulting in amalgamated debris flow and slide deposits that covered much of the basin floor these deposits reached thicknesses of up to 100 m and extended over an area of 100 km 2 the ambient seafloor was compressed under the impact and load of these debris masses and or liquefied under the cyclic stress of the seismic wave a 0 2 km 3 landslide also occurred at this time blocking the saguenay river and possibly facilitating an extra large spring freshet discharge biotracers planktonic and benthic foraminifera arcellaceans pollen and wood in conjuction with mass physical properties of sediment cores and high resolution seismic and sidescan profiler data have been used to identify local and distal sediment sources including their original water depth of deposition and their subsequent mode of mass gravitational transport the landslide material was eroded by the river and super elevated sediment concentrations are considered responsible for a long lasting 28 days turbidity current that entered the saguenay fjord depositing a single 0 3 km 3 turbidite the 2 to 10 m thick turbidite is considered to have been self igniting having eroded into the surface of the collapsed basin debris paleo hydraulic calculations suggest that this turbid flow averaged 0 45 m s and reached a flow thickness of 30 m

first evidence of a mid holocene earthquake triggered megaturbidite south of the chile triple junction abstract megaturbidites have been the focus of many paleoseismic and paleoenvironmental studies because they can provide evidence for catastrophic and or hazardous events with potentially major environmental implications during a recent research cruise in baker fjord chile 47 54 s 74 30 w a megaturbidite was described between the northern and southern patagonian icefields here we aim to determine the depositional processes of the megaturbidite and identify its origin based on the turbidite s location a possible origin was the early holocene drainage of paleo lake general carrera which was recently proposed in the literature as having produced a glacial lake outburst flood glof that drained through baker fjord due to the fjord s location in a subduction zone and close to the chile triple junction however seismic activity must also be considered as a potential triggering mechanism to achieve our goals we undertook a multi proxy analysis of sediment core md07 3121 including sedimentology grain size loss on ignition foraminifera counts magnetic properties bulk organic geochemistry and radiocarbon dating and we analysed bathymetric maps and sub bottom profiles our grain size results display a diagnostic fining upward trend and show evidence of seiching in the 733 cm thick megaturbidite the age of the event 5513 5211 cal yr bp contradicts the hypothesis of an early holocene glof origin bulk organic geochemical results indicate that the sediments that compose the turbidite are clearly of marine origin which further goes against a glof origin in addition the megaturbidite is underlain by a 1136 cm thick mass transport deposit mtd also composed of marine sediments according to the sub bottom profiles the mtd and the megaturbidite originate from the reworking of thick packages of sediment previously deposited on nearby sills and on the fjord s flanks furthermore similar coeval deposits are found in an adjacent sub basin we therefore interpret these deposits to be triggered by an earthquake during the late mid holocene while megathrust and intraslab earthquakes are possible in the region we argue that a crustal earthquake is the most likely seismic trigger in the study area this study reveals the first earthquake triggered megaturbidite south of the chile triple junction

the 2011 tohoku oki earthquake displacement reaching the trench axis we detected and measured coseismic displacement caused by the 11 march 2011 tohoku oki earthquake moment magnitude mw 9 0 by using multibeam bathymetric surveys the difference between bathymetric data acquired before and after the earthquake revealed that the displacement extended out to the axis of the japan trench suggesting that the fault rupture reached the trench axis the sea floor on the outermost landward area moved about 50 meters horizontally east southeast and 10 meters upward the large horizontal displacement lifted the sea floor by up to 16 meters on the landward slope in addition to the vertical displacement

paleoseismicity along the southern kuril trench deduced from submarine fan turbidites abstract large m 8 damaging interplate earthquakes occur frequently in the eastern hokkaido region northern japan where the pacific plate is subducting rapidly beneath the okhotsk north american plate at approximately 8 cm yr 1 with the aim of estimating the long term recurrence intervals of earthquakes in this region seven sediment cores were obtained from a submarine fan located on the forearc slope along the southern kuril trench japan the cores contain a number of turbidites some of which can be correlated among the cores on the basis of the analysis of lithology chronology and the composition of sand grains foraminiferal assemblages and the composition of sand grains indicate that the upper middle slope 1000 m water depth is the source of the turbidites the deep sea origin of the turbidites is consistent with the hypothesis that they were derived from slope failures initiated by strong shaking associated with earthquake events the recurrence intervals of turbidite deposition are 113 439 yr for events that occurred over the past 7 kyr the short intervals are recorded in the cores obtained from levees on the middle fan although many large earthquakes 150 cm s 2 of peak ground acceleration at the inferred slump sources occurred during the 19th and 20th centuries the pilot core from the upper fan contains only three turbidites located stratigraphically above layers of 17th century volcanic ash the results of 210pbex and 137cs dating combined with simulations of the ground accelerations of historical earthquakes enable correlation of the three turbidites with known historical earthquakes the 1952 tokachi oki and the 1961 and 1973 nemuro oki earthquakes the turbidites within the sampled cores potentially record about half of the large earthquakes known to have occurred over the interval covered by the cores the fact that any single core records only a portion of the known seismic events suggests that the recurrence interval of earthquakes in this region is less than 113 yr during holocene

late cenozoic evolution of the eastern margin of the tibetan plateau inferences from 40ar 39ar and u th he thermochronology high topography in central asia is perhaps the most fundamental expression of the cenozoic indo asian collision yet an understanding of the timing and rates of development of the tibetan plateau remains elusive here we investigate the cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the sichuan basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed temperature time paths inferred from 40 ar 39 ar thermochronology of biotite multiple diffusion domain modeling of alkali feldspar 40 ar release spectra and u th he thermochronology of zircon and apatite imply that rocks at the present day topographic front of the plateau underwent slow cooling 30 50 c m y coincident with exhumation from inferred depths of 8 10 km at denudation rates of 1 2 mm yr samples from the interior of the plateau continued to cool relatively slowly during the same time period 3 c m y suggesting limited exhumation 1 2 km however these samples record a slight increase in cooling rate from 1 to 3 c m y at some time during the middle tertiary the tectonic significance of this change remains uncertain regardless late cenozoic denudation in this region appears to have been markedly heterogeneous with the highest rates of exhumation focused at the topographic front of the plateau margin we infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable sichuan basin and thus marks the onset of deformation related to the development of the tibetan plateau in this region the present margin of the plateau adjacent to and north of the sichuan basin is apparently no older than the late miocene or early pliocene 5 12 ma

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

decoupling of erosion and precipitation in the himalayas the hypothesis that abrupt spatial gradients in erosion can cause high strain rates in active orogens has been supported by numerical models that couple erosional processes with lithospheric deformation via gravitational feedbacks1 2 3 most such models invoke a stream power rule in which either increased discharge or steeper channel slopes cause higher erosion rates spatial variations in precipitation and slopes are therefore predicted to correlate with gradients in both erosion rates and crustal strain here we combine observations from a meteorological network across the greater himalaya nepal along with estimates of erosion rates at geologic timescales greater than 100 000 yr from low temperature thermochronometry across a zone of about 20 km length spanning the himalayan crest and encompassing a more than fivefold difference in monsoon precipitation significant spatial variations in geologic erosion rates are not detectable decreased rainfall is not balanced by steeper channels instead additional factors that influence river incision rates such as channel width and sediment concentrations must compensate for decreasing precipitation overall spatially constant erosion is a response to uniform upward tectonic transport of greater himalayan rock above a crustal ramp

annual growth banding in a cave stalagmite the presence of microscopic luminescence banding in cave calcite deposits speleothems has recently been reported1 3 the luminescence seems to be caused by excitation of humic and fulvic acids derived from the overlying soil and subsequently incorporated into the calcite3 4 we have tested whether such luminescence corresponds to annual growth layers using high precision thermal ionization mass spectrometric 238u 234u 230 th ages from banded sections of a holocene stalagmite we report here that the timespans yielded by counting bands on the assumption that they are annual agree within error limits with those obtained by our uranium thorium dating this demonstration that the banding is annual should make banded speleothems valuable resources for providing high resolution records of past climate in which precipitation can be estimated from growth rates5 6 and temperatures from stable isotope measurements7 and solar terrestrial correlations as the luminescence intensity can be related to the solar sunspot cycle1 3

detrital zircon evidence from burma for reorganization of the eastern himalayan river system the first in situ hf and u pb isotope analyses of detrital zircons from upper miocene sandstone in the inner burma tertiary basin together with data of igneous zircons from the eastern transhimalayan batholith from southern tibet to burma enable us to study the sedimentary source to sink relation and river evolution around the eastern himalayas among 47 out of 62 dated zircons from the miocene sandstone that exhibit cretaceous and paleogene 206pb 238u ages 24 grains have positive ehf t isotope values up to 16 whilst zircons of such ages are common in the transhimalayan plutons those showing high ehf t values have been observed so far only in the gangdese batholith our results therefore support the notion that by late miocene time the yarlu tsangpo which flows past the gangdese batholith in southeastern tibet drained into the irrawaddy river we attribute this river routing to not only regional topographic control but also the dextral movement of the jiali gaoligong sagaing fault system that appears most active during the middle miocene subsequent reorganization of these mountain rivers was affiliated with headward erosion of the brahmaputra river that eventually cut across the namche barwa syntaxis and captured the yarlu tsangpo drainage to form the modern eastern himalayan river system

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

turbidite paleoseismology in the calabrian arc subduction complex ionian sea 1 the calabrian arc subduction system is part of the africa eurasia plate boundary is one of the most seismically active regions in the mediterranean sea and has been struck repeatedly by destructive historical earthquakes in this study we investigate the effects of historical earthquakes on abyssal marine sedimentation through the analysis of the turbidite record we collected gravity cores in tectonically controlled basins where the eastern mediterranean pelagic sequence is interbedded with resedimented units textural micropaleontological geochemical and mineralogical signatures reveal three turbidite events in the last millennium we dated the turbidite sequences from two different cores using different radiometric methods whereas the average time interval between successive turbidite beds was estimated from pelagic sediment thickness and sedimentation rates chronologies were refined through age modeling that provided age ranges 2 of each turbidite bed the results suggest that turbidite emplacement was triggered by three historical earthquakes recorded in the area i e the 1908 1693 and 1169 events their magnitude epicentral location and associated tsunamis support causative faults located in the ionian sea the source for all the turbidites as inferred from their mineralogy is the metamorphic basement outcropping in southern calabria and or northeastern sicily turbidite composition and cable breaks for the 1908 event have been used to infer likely traveling paths and seismogenic faults in the subduction system our findings suggest that ionian sea turbidites represent more than 80 of sedimentation and may be seabed archives of paleo earthquakes capable of reconstructing seismicity back in time during several earthquake cycles

a sensitive high resolution record of late holocene climatic change from a raised bog in northern england proxy climatic data in the form of plant macrofossils have been analysed from a 5 m core from bolton fell moss cumbria uk detailed analysis of peat from the upper 50 cm of this core is used to demonstrate a strong correlation between changes in the relative proportion of taxa and known climatic changes over the last 1000 years the record of changes in bog vegetation contained within the peat profile is used to reconstruct changes in bog surface wetness for the latter half of the holocene as bog surface wetness is directly controlled by the prevailing climatic conditions this reconstruction can be viewed as a proxy climate record twelve radiocarbon age estimates on the 5m core suggest that between 50 and 500 cm peat accumulated at a relatively constant rate of 12 4 yr cm 1 the regular sampling intervals thus provide a time series of past bog surface wetness spectral analyses of this series indicates that wetness changes are cyclic with a ca 800 year periodicity

changes in deep sea benthic foraminiferal fauna caused by turbidites deposited after the 2011 tohoku oki earthquake abstract the impact of the 2011 tohoku oki earthquake and subsequent turbidites on the deep sea environment was investigated by conducting sedimentological radionuclide and benthic foraminiferal analyses of core sediments collected from water depths of 3230 and 3570 m 5 and 17 months after the earthquake sedimentological profiles and patterns of excess 210pb 134cs and 137cs indicate that the analyzed sediment core records deposits before the earthquake turbidite deposits just after the earthquake and deposits after the fukushima daiichi nuclear power plant fnpp1 accident which caused the release of a large amount of radioactive material four days after the earthquake core 4w 2012 f rn was collected at 3585 m water depth 17 months after the earthquake within this core an event deposit layer 6 5 cm thick consisting of turbidites contains highly diverse and possibly reworked foraminiferal assemblages overlying these turbidites are sediments with high 134cs concentrations that were deposited after the fnpp1 accident overall foraminiferal and species abundances show a marked decrease in the sediments above the deposited turbidites the abundance of opportunistic and competitive species shows a gradual upward increase in the uppermost sediment layers and these species are dominant in the top 1 cm of the core our findings demonstrate that although foraminiferal assemblages in the sediment overlying the turbidites related to the 2011 earthquake might include allochthonous assemblages turbidites deposited after the earthquake caused a marked decrease in benthic foraminiferal diversity and allowed opportunistic species to colonize in a low diversity assemblage within 17 months these foraminiferal faunal changes together with analysis of sedimentological structure provide valuable information for identifying these types of sedimentation events in core sediments from the deep sea floor

evaluating the evolution of the red river system based on in situ u pb dating and hf isotope analysis of zircons 1 the red river originates from sw china and se tibet and has a total length 1000 km in this study we present new u pb dating and hf isotopic analysis of zircon grains from both modern and paleoriver sands in order to constrain the provenance of the modern river and to decipher drainage evolution through time our data show that the yangtze and songpan garze blocks are the most important sources for sediment although this material is mostly reworked via younger sedimentary rocks in the upper reaches of the red river sands in the da river and to a lesser extent the lo river have zircon ages indicating that they are minor contributors to the net flow consistent with rock uplift which is strongest in the upper reaches of the red river rather than precipitation being the primary control on erosion sediments eroded from the metamorphic rocks along the red river fault zone appear to have made a greater contribution during the miocene zircon ages suggest that the red river flowed north of the day nui con voi in the middle late miocene the red river appears to have had a largely stable provenance since at least the late miocene upper miocene sedimentary rocks ne of the red river indicate the presence of a separate large river in the late miocene hf isotope data indicate that the irrawaddy river was never part of the red river system although we do not exclude the salween mekong and yangtze rivers from having been part of the red river any connection must have been pre middle miocene

high resilience of harpacticoid copepods in the landward slope of the japan trench against disturbance of the 2011 tohoku earthquake

yangtze river of china historical analysis of discharge variability and sediment flux hydrological records covering a 100 year period from the upper middle and lower yangtze river were collected to examine the temporal and spatial distribution of discharge and sediment load in the drainage basin the yangtze discharge as expected increases from the upper drainage basin downstream only an estimated 50 of the discharge is derived from the upper yangtze with the rest being derived from the numerous tributaries of the middle and lower course however the distribution of sediment load along the yangtze is the reverse of that observed for discharge with most of the sediment being derived from the upper basin a dramatic reduction in sediment load by 0 8 108 tons year occurs in the middle yangtze because of a marked decrease in slope and the change to a meandering pattern from the upper yangtze rock sections considerable siltation also occurs in the middle yangtze drainage basin as the river cuts through a large interior dongting lake system sediment load in the lower yangtze while significantly less than that of the upper river is somewhat higher than the middle yangtze because of additional load contributed by adjacent tributaries a strong correlation exists between the discharge and sediment load along the yangtze drainage basin during the dry season as lower flows carry lower sediment concentration during the wet season a strong correlation is also present in the upper yangtze owing to the high flow velocity that suspends sand on the bed however a negative to poor correlation occurs in the middle and lower yangtze because the flow velocity in these reaches is unable to keep sand in suspension transporting only fine grained particles downstream hydrological data are treated for 30 years 1950 1980 when numerous dams were constructed in the upper yangtze drainage basin at yichang and hankou hydrological stations records revealed a decreasing trend in annual sediment load along with slightly reduced annual discharge at the same stations this can be interpreted as the result of water diversion primarily for agriculture sediment load at datong further downstream is quite stable and not influenced by slightly reduced discharge furthermore sediment concentration at the three hydrological stations increased which can be attributed to sediment loss in association with intensifying human activity especially in the upper drainage basin such as deforestation and construction of numerous dams mean monthly sediment load of these 30 years pulses about 2 months behind discharge implying dam released sediment transport along the entire river basin during the high water stage

late cenozoic uplift of southeastern tibet the age of surface uplift in southeastern tibet is currently unknown but the initiation of major river incision can be used as a proxy for the timing of initial uplift the topographically high eastern plateau and gently dipping southeastern plateau margin are mantled by an elevated low relief relict landscape that formed at a time of slow erosion at low elevation and low tectonic uplift rates prior to uplift of the eastern tibetan plateau thermochronology from deep river gorges that are cut into the relict landscape shows slow cooling between ca 100 and ca 10 20 ma and a change to rapid cooling after ca 13 ma with initiation of rapid river incision at 0 25 0 5 mm yr between 9 and 13 ma a rapid increase in mean elevation of eastern tibet beginning at this time supports tectonic climate models that correlate the lateral eastern expansion of high topography in tibet with the late miocene intensification of the indian and east asian monsoons

history of yellow river and yangtze river delivering sediment to the yellow sea since 3 5 ma tectonic or climate forcing abstract reconstructing the plio pleistocene sedimentary history of the yellow sea is important for understanding the long term influence of the yellow river huanghe and or yangtze river changjiang on the asian marginal seas and to further constrain any links between river development regional paleoenvironmental change tectonic deformation and or global climate change here we present the first high resolution clay mineral record combined with sr nd isotopic compositions from a 300 m long sediment core recovered in the western south yellow sea our study suggests that large scale transgression in the yellow sea occurred after 0 8 ma possibly related to tectonic subsidence of eastern china coast and the min zhe uplift in contrast the sedimentary environment of bohai and yellow seas was mainly dominated by fluvial lacustrine deposits at 3 5 0 8 ma provenance analysis suggests a major change in sediment provenance from the yangtze river to the yellow river at 0 8 ma which corresponds to the timing of the final integration of the yellow river in its present form at the same time the major channels of the yangtze river migrated from the south yellow sea to the modern yangtze river delta due to the subsidence of east china coast the consistence in timing of the provenance transition and large scale regional marine transgression suggests that tectonic deformation rather than climate change is the first order control on the evolution of the yellow and yangtze rivers and sedimentary environmental change in the bohai and yellow seas

numerical modeling of the 2011 tohoku oki tsunami in the offshore and onshore of sendai plain japan abstract this paper examines the results of a numerical modeling of the 2011 tohoku oki earthquake tsunami to investigate its offshore propagation and inundation along a shore normal transect located in the center of the sendai plain the inundation distance flow depth and flow speed were compared with the available data measured during a post tsunami field survey and estimated from the video records the calculated inundation distance reached 4 5 5 5 km from the coastline which is comparable to the actual inundation distance the variation of tsunami heights from 2 4 6 m and flow speeds from 3 4 6 2 m s along the transect is generally consistent with the measured heights and estimated speeds the waveform on the beach showed that the wave train was composed of a high 10 11 m first wave followed by low 4 m waves considering the waveform and the topographic change the erosion of the beach and the sedimentation inland are explained mainly by the first wave in addition the calculated flow speed and friction velocities in the offshore may account for the formation of the possible tsunami deposits which were reported recently by a sea bottom survey the modeling results are generally consistent with the available data and are considered to be useful for understanding the inundation pattern and sedimentation process of the tohoku oki tsunami on the sendai plain

yangtse river sediments and erosion rates from source to sink traced with cosmogenic 10be sediments from major rivers abstract estimates of regional erosion and sediment mixing from different sources in the yangtse river system are presented based on sand samples collected from major tributaries and the trunk stream at 23 sites between western sichuan and the yangtse delta mixing is estimated from concentrations of mg ca sr ti mn and fe which are substantially higher in sand from major tributaries in the western yangtse river catchment than from tributaries in the eastern catchment intermediate concentrations occur in sand from the yangtse delta both for modern samples from the surface and for early holocene samples from drill holes mixing ratios indicate that 35 5 of sand in the delta came from eastern sources a similar result was obtained using cosmogenic 10be in quartz grains as a tracer of mixing regional erosion rate estimated from 10be in sand grains from high mountain catchments of the western yangtse river are mostly similar to rates based on sediment gauging but are sometimes higher and range to over 700 m ma 1 while 10be measured at upper yangtse river tributaries on the northeast tibetan plateau gave rates of 20 30 m ma 1 for the eastern catchments 10be measurements from quartz sand and sediment gauging both gave rates of 30 70 m ma 1 eroding at this rate the eastern catchments could not supply more than 20 of the sediment in the delta in contrast with 35 estimated from geochemical fingerprints the relative input from eastern sources may have been higher in late pleistocene times under a different climatic regime and reworking of pleistocene deposits may still be in progress

multivariate statistical and multiproxy constraints on earthquake triggered sediment remobilization processes in the central japan trench understanding the impact of earthquakes on subaqueous environments is key for submarine paleoseismological investigations seeking to provide long term records of past earthquakes for this purpose event deposits e g turbidites are among others identified and stratigraphically correlated over broad areas to test for synchronous occurrence of gravity flows hence detailed spatiotemporal petrographic and geochemical fingerprints of such deposits are required to advance the knowledge about sediment source and the underlying remobilization processes induced by past earthquakes in this study we develop for the first time in paleoseismology a multivariate statistical approach using x ray fluorescence core scanning magnetic susceptibility and wet bulk density data that allow to test confirm and enhance the previous visual and lithostratigraphic correlation across two isolated basins in the central japan trench the statistical correlation is further confirmed by petrographic heavy grain analysis of the turbidites and additionally combined with our novel erosion model based on previously reported bulk organic carbon 14c dates we find surficial sediment remobilization a process whereby strong seismic shaking remobilizes the uppermost few centimeters of surficial slope sediment to be a predominant remobilization process which partly initiates deeper sediment remobilization downslope during strong earthquakes at the japan trench these findings shed new light on source to sink transport processes in hadal trenches during earthquakes and help to assess the completeness of the turbidite paleoseismic record our results further suggest that shallow buried tephra on the slope might significantly influence sediment remobilization and the geochemical and petrographic fingerprints of the resulting event deposits

the occurrence of paleodictyon in shallow marine deposits of the upper cretaceous mikasa formation hokkaido island northern japan implications for spatiotemporal variation of the nereites ichnofacies abstract the trace fossil paleodictyon is characterized by a regular hexagonal network and has been widely considered to be a characteristic of the nereites ichnofacies indicative of a deep marine environment recently however some researchers have reported paleodictyon occurrences in relatively shallow settings leading to suggestions that the habitat of these burrowers was not restricted to deep marine environments a new occurrence of this trace fossil is presented in this study from a shallow marine succession of upper cretaceous deposits in northern japan paleobathymetric and temporal variations in the habitat range of shallow marine examples of this ichnotaxon are also discussed based on a compilation of previous works the new paleodictyon specimens discussed here are from the lowermost part of the mikasa formation within the yezo group interpreted as a deposit representing the lower shoreface through to the inner shelf transitional zone this paper presents the first record of a shallow marine paleodictyon from the pacific region combined with data from previous studies records suggest that shallow marine paleodictyon are observable from paleozoic to mesozoic shelf deposits although no reliable records of their occurrences have so far been reported from the cenozoic increasing bioturbation intensity and predation pressure during the mesozoic and cenozoic may have been significant factors preventing the preservation of this ichnogenus in post mesozoic shallow marine settings the paleodictyon bearing interval of the mikasa formation also preserves evidence for low intensity bioturbation which may account for preservation of the traces in this case

trench normal variation in observed seafloor displacements associated with the 2011 tohoku oki earthquake 1 seafloor geodetic measurements using the gps acoustic technique just above the rupture area of the 2011 tohoku oki earthquake revealed strong trench normal variation in the horizontal crustal displacement associated with the earthquake one set of observations at a site only 50 km away from the trench yielded the most trench ward data ever reported with an accuracy better than 1 m it showed a coseismic displacement of up to 31 m whereas another set of observations 100 km away from the trench showed a 15 m displacement these horizontal data as well as vertical data from pressure gauges and tsunami observations strongly indicate that the seismic slip reached the trench they are also likely to contribute quantitatively to further investigations that reveal the coseismic behavior of the frontal wedge of the overriding plate in the source region along the japan trench

episodic subsidence and active deformation of the forearc slope along the japan trench near the epicenter of the 2011 tohoku earthquake abstract to investigate the present day geological deformation occurring off the pacific coast of tohoku japan we obtained high resolution multichannel seismic reflection and bathymetric data in 2007 the study area is located along the japan trench near the epicenter of the 2011 off the pacific coast of tohoku earthquake the seismic profiles do not show active structures indicative of compressional stress on the forearc slope instead recent tectonic deformation is characterized by extensional subsidence and the occurrence of normal faults within a series of small basins on the slope to a water depth of 3000 m these isolated basins are thickest 525 m 0 7 s two way travel time in regions underlying areas of flat bathymetry the isolated basins range in width from several to 40 km and are covered by stratified sediments onlapping at the termination of concave down reflectors the seismic units below the basins show continuous subparallel internal reflectors suggesting that the subsidence related deformation started abruptly and recently the thickness of sediments overlying the unconformity at the top of the cretaceous is roughly constant in the upper slope area however lenticular internal reflection patterns occur locally the lenticular sedimentary units are similar to the isolated basins in terms of their widths and internal reflection patterns we infer that episodes of extensional deformation of the overriding plate in the form of isolated basins have occurred over geological time we suggest that the geological structures of the forearc slope along the japan trench are typical of those resulting from subduction erosion and propose that the episodic subsidence accompanied by normal faulting is the most recent deformation

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

himalayan tectonics explained by extrusion of a low viscosity crustal channel coupled to focused surface denudation recent interpretations of himalayan tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the tibetan plateau1 2 3 and that ductile extrusion of high grade metamorphic rocks between coeval normal and thrust sense shear zones can explain exhumation of the greater himalayan sequence4 5 6 7 here we use coupled thermal mechanical numerical models to show that these two processes channel flow and ductile extrusion may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low viscosity material our models provide an internally self consistent explanation for many observed features of the himalayan tibetan system8 9 10

displacement above the hypocenter of the 2011 tohoku oki earthquake the moment magnitude m w 9 0 2011 tohoku oki mega thrust earthquake occurred off the coast of northeastern japan combining global positioning system gps and acoustic data we detected very large sea floor movements associated with this event directly above the focal region an area with more than 20 meters of horizontal displacement that is four times larger than those detected on land stretches several tens of kilometers long along the trench the largest amount reaches about 24 meters toward east southeast just above the hypocenter furthermore nearly 3 meters of vertical uplift occurred contrary to observed terrestrial subsidence

tsunami triggered dispersal and deposition of microplastics in marine environments and their use in dating recent turbidite deposits microplastics have become widely dispersed throughout the marine environment in and around japan since the 1960s which correspond to the onset of mass plastic production and use in this country our study documents a possible abrupt microplastics depositional event in continental shelf and deep sea environments triggered by a tsunami the sediment layers contaminated by microplastics correspond with sedimentary horizons where 137cs signals were measured indicating deposition after 1960s nuclear tests the microplastics were observed in the 2011 tohoku oki tsunami deposits tsunamis can thus contribute to the wide dispersal of microplastics from coastal to deep sea areas and these anthropogenic particles can be used to date very recent turbidite deposits

conditions for the ignition of catastrophically erosive turbidity currents abstract the basic impediment to a clear understanding of eroding and depositing turbidity currents has been the lack of a proper formulation of bed sediment entrainment this problem is addressed herein a detailed analysis indicates that the bagnold criterion is necessary but insufficient for self sustaining turbidity currents the analysis reveals two possible equilibrium states a relatively low velocity ignitive state and a high velocity dense catastrophic state a stability analysis indicates that the ignitive state is unstable flows below it invariably die out and flows above it ignite i e accelerate and entrain sediment to the catastrophic state which is stable the ignitive state thus defines the criterion for a self sustaining turbidity current estimates of the catastrophic state suggest that it is highly erosive and competent to scour out submarine canyons

geomorphic evolution of the yangtze gorges and the time of their formation abstract the three gorges of the yangtze link its upper rocky valley to downstream alluvial sections a series of stepped landforms exist in the three gorges area the sichuan basin upstream and the jianghan basin downstream these landforms are characterized by two planation surfaces one erosional surface and up to seven terraces the higher planation surface named the exi surface 1800 2000 m a s l and the lower planation surface 1200 1500 m were probably formed in the tertiary prior to 3 4 3 6 ma b p no correlation seems to exist between the drainage networks of earlier period with the present yangtze system it is suggested that the erosional surface found in the study area at 800 1200 m in elevation above sea level was formed in late pliocene of early pleistocene during this period following the last planation event the ancestral yangtze might have begun to adjust its drainage network the seven terraces well developed along the eastern sichuan basin and the three gorges date from early to late pleistocene 1 16 0 01 ma b p the chronostratigraphic evidence and diagnostic sediments are generally comparable in time and space from the sichuan basin through the three gorges to the jianghan basin therefore the present study proposes that the three gorges were cut not later than the initiation of the earliest terrace the fluvial landforms in the yangtze gorges are characterized also by valley in valley cross sections i e an older u shaped valley cut by a younger v shaped valley a tectonic rise accompanied by a rapid downcutting of the river channels predominated in the region

time and space distribution of coseismic slip of the 2011 tohoku earthquake as inferred from tsunami waveform data a multiple time window inversion of 53 high sampling tsunami waveforms on ocean bottom pressure global positioning system coastal wave and tide gauges shows a temporal and spatial slip distribution during the 2011 tohoku earthquake the fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface a very large slip approximately 25 m in the deep part off miyagi at a location similar to the previous 869 jogan earthquake model was responsible for the initial rise of tsunami waveforms and the recorded tsunami inundation in the sendai and ishinomaki plains a huge slip up to 69 m occurred in the shallow part near the trench axis 3 min after the rupture initiation this delayed shallow rupture extended for 400 km with more than a 10 m slip at a location similar to the 1896 sanriku tsunami earthquake and was responsible for the peak amplitudes of the tsunami waveforms and the maximum tsunami heights measured on the northern sanriku coast 100 km north of the largest slip the average slip on the entire fault was 9 5 m and the total seismic moment was 4 2 1022 n m m w 9 0 the large horizontal displacement of seafloor slope was responsible for 20 40 of tsunami amplitudes the 2011 deep slip alone could reproduce the distribution of the 869 tsunami deposits indicating that the 869 jogan earthquake source could be similar to the 2011 earthquake at least in the deep plate interface the large tsunami at the fukushima nuclear power station is due to either the combination of a deep and shallow slip or a triggering of a shallow slip by a deep slip which was not accounted for in the previous tsunami hazard assessments online material table of estimated slip for all subfaults at 0 5 min invervals

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

ar ar muscovite dating as a constraint on sediment provenance and erosion processes in the red and yangtze river systems se asia in this study we applied 40ar 39ar dating methods to muscovite grains in sands from the modern red and yangtze rivers in order to constrain palaeo and modern erosion patterns and sediment transport processes micas in the headwaters of the red river and its southern da river tributary are dominantly cenozoic while the northern lo river tributary shows a typical 160 220 ma population the lower reaches of the red river comprise 53 of such triassic grains indicating that the lo river is the most important net contributor to the modern delta however this contrasts with zircon u pb data indicating that the upper reaches of the red river dominate that mineral group we suggest that the mismatch reflects the rapid transport of mica relative to zircon in the river and the fact that the red river is not in equilibrium we hypothesize that the zircons were eroded 8 ka under a regime of stronger monsoon that enhanced erosion in the northern drainage basin while modern erosion is focused in the south especially in the song chay massif micas from the upper yangtze river are resolvably older than those in the red river 230 250 ma so that this method could be used to test for drainage capture in palaeo delta sediments micas in the modern yangtze delta are generally much younger than those in the upper reaches and indicate that erosion in the longmen shan sichuan and neighbouring regions is more important than the upper yangtze in supplying sediment reflecting the stronger monsoon rains in those areas

increased marine sediment suspension and fluxes following an earthquake earthquakes are commonly cited as one possible triggering mechanism for turbidity flows dense sediment water plumes that can transport large volumes of sediment great distances down slope in both marine and lacustrine settings1 2 3 4 5 6 heezen and ewing1 were the first to make such a suggestion attributing breaks in a sea floor telephone cable in the north atlantic ocean to turbidity flows generated by the 1929 grand banks earthquake anumber of workers have consequently used sedimentary turbidite records to reconstruct the earthquake histories of various regions2 7 8 here we present direct observations of a seismically induced turbidity flow measurements of light scattering and sediment fluxes in the cariaco basin indicate that the earthquake that occurred along the coast of northern venezuela on 9 july 1997 resulted in considerable downslope displacement of sediments probably 105 tonnes into the deep part of the basin in such a seismically active region this mechanism of sediment transport may be responsible for a significant component of the long term sediment accumulation in the basin furthermore this process may result in the sequestration in deep sea sediments of large amounts of carbon initially deposited at shallow depths

late cenozoic evolution of the central longmen shan eastern tibet insight from u th he thermochronometry 1 this article presents u th he thermochronological data from the longmen shan belt eastern tibet located between the songpan garze terrane and the yangtze craton this mountain range is one of the steepest margins of the tibetan plateau and an important area for the comprehension of the mechanisms that control the dynamics of such plateau borders in terms of spatial distribution of deformation or timing of topographic building we describe several age elevation transects and perform forward modeling of our data to derive quantitative information on the exhumation of the range a major phase of exhumation started at 8 11 ma with an average rate of 0 65 mm a a1 comparison of zircon and apatite ages indicates that the eastern part of the range may have experienced a significant decrease in exhumation since 2 3 ma we use the distribution of finite exhumation across the major faults of the area to quantify their dip slip throw rate over the last 10 ma the beichuan fault which was activated during the 2008 sichuan earthquake is the major active structure of the longmen shan since the late miocene with an average thrusting slip rate between 0 4 and 1 mm a a1 conversely over the same time period only minor dip slip activity occurred on the wenchuan fault zone this distribution in space and time of exhumation and deformation is discussed and compared to the different proposed models for the geodynamical evolution of the eastern tibetan margin it also provides an important long term perspective to put in context the destructive 2008 sichuan earthquake that struck the central longmen shan

provenance of detrital k feldspar in jianghan basin sheds new light on the pliocene pleistocene evolution of the yangtze river the yangtze river is the largest fluvial system draining the tibetan plateau yet its time of formation pre miocene versus pleistocene has been debated for more than a century with a particular focus on the incision of the three gorges in this study we used laser ablation multiple collector inductively coupled plasma mass spectrometry la mc icp ms to measure pb isotope compositions of detrital k feldspars from pliocene pleistocene sediments in the jianghan basin located just downstream of the three gorges our new pb results indicate that feldspars from the songpan ganzi terrane were already being delivered to the jianghan basin by ca 3 4 ma therefore we suggest that the three gorges was incised prior to the late pliocene moreover the pb isotopic data also record the first delivery of detritus from the hanjiang river one of the yangtze s largest tributaries in the middle reaches into the jianghan basin at ca 1 8 ma most k feldspar grains from the mid late pleistocene samples have similar pb isotopic compositions to those from the major tributaries in the upper reaches i e minjiang and jialingjiang rivers indicating that the eastern tibetan plateau as the major sediment supplier to the jianghan basin and mid lower yangtze river has played a key role in the sediment source to sink transport of this river this study sheds light on the factors that control the supply of detrital k feldspar in large scale drainage systems

late cenozoic to holocene deformation in southwestern sichuan and adjacent yunnan china and its role in formation of the southeastern part of the tibetan plateau from at least 2 4 ma to present crust in the southeastern part of the tibetan plateau west of the convex east xianshuihe xiaojiang fault system has deformed internally and rotated clockwise around the eastern himalayan syntaxis the northwest striking ganzi fault zone bounds the rotating crust on the north and has a total left slip of 78 100 km of which 60 km is transferred to the xianshuihe fault zone across a diffuse transfer zone and 22 40 km is absorbed by bending of older structures and crustal shortening crustal shortening is expressed along and east of the eastern end of the ganzi fault zone by mountains capped by permanent glaciers locally rising nearly 1000 m above the average elevation of the tibetan plateau a similar transfer of left slip into shortening occurs farther south across the xianshuihe fault in the high mountains around and east of gongga shan 7556 m the northwest striking convex east left lateral litang fault zone lies southwest of the ganzi xianshuihe xiaojiang fault zone and appears to be less well developed but otherwise similar to the ganzi fault zone the batang chenzhi and other northeast striking right lateral faults of small displacement occur within the rotating crustal fragment together with the left slip faults they accommodate east west shortening northeast of the eastern himalayan syntaxis south of this region of shortening the crust is extending to form grabens within the dali and southern xiaojiang fault systems and in the tengchong volcanic province the progressive change from shortening southward into extension is related to variations in strain that characterize the region from northeast to southeast of the eastern himalayan syntaxis the assemblage of structures in southwestern sichuan geometrically resembles structures of eocene to miocene age in southern yunnan that were positioned northeast of the eastern himalayan syntaxis similar to present day southwestern sichuan at the time of their development the similarity in the structural development in the two areas indicates that crust northeast of the syntaxis underwent a common evolution as the syntaxis migrated northward during the past 50 m y structures in sichuan are less fully developed than older structures in southwestern yunnan and can serve as a guide to reconstruct the progressive tectonic development in the region of the syntaxis deformation in these areas indicates that plateau formation has been complex inhomogeneous and diachronous at scales from 1000 km to less than 100 km

large scale drainage capture and surface uplift in eastern tibet sw china before 24 ma inferred from sediments of the hanoi basin vietnam current models of drainage evolution suggest that the non dendritic patterns seen in rivers in se asia reflect progressive capture of headwaters away from the red river during and as a result of surface uplift of eastern asia mass balancing of eroded and deposited rock volumes demonstrates that the red river catchment must have been much larger in the past in addition the nd isotope composition of sediments from the hanoi basin vietnam interpreted as paleo red river sediments shows rapid change during the oligocene before similar to 24 ma we interpret this change to reflect large scale drainage capture away from the red river possibly involving loss of the middle yangtze river reorganization was triggered by regional tilting of the region towards the east this study constrains initial surface uplift in eastern tibet and southwestern china to be no later than 24 ma well before major surface uplift and gorge incision after 13 ma

contrasting geochemical and sm nd isotopic compositions of archean metasediments from the kongling high grade terrain of the yangtze craton evidence for cratonic evolution and redistribution of ree during crustal anatexis abstract twenty three clastic metasediments from the kongling high grade terrain of the yangtze craton south china were analyzed for major trace and rare earth elements and sm nd isotopic ratios associated dioritic tonalitic trondhjemitic dtt and granitic gneisses as well as amphibolites were also analyzed in order to constrain provenance the results show that the clastic metasediments can be classified into 3 distinct groups in terms of mineralogical geochemical and sm nd isotopic compositions group a is characterized by having no to slight negative eu anomalies eu eu 0 82 1 07 being high in cr 191 396 ppm and ni 68 137 ppm and low in th 3 3 7 8 ppm and ree ree 99 156 ppm these characteristics are similar to those of metasediments from archean greenstone belts in addition the group a metasediments have the value of the chemical index of alteration ciw close to felsic gneisses their sm nd isotopic ree and trace element compositions can be interpreted by mixtures of the dtt gneisses and amphibolites dating of detrital zircons from 2 group a samples by shrimp reveals a major concordant age group of 2 87 3 0 ga which is identical to the age of the trondhjemitic gneiss these results strongly suggest that group a was principally the first cycle erosion product of the local kongling dtt gneiss and amphibolite moreover the higher than amphibolite cr content and slight eu depletion exhibited by some samples from this group infer that ultramafic rocks like komatiite and granite of probably 3 0 3 3 ga in age also played a role group b is characterized by the presence of graphite and shows a more evolved composition similar to post archean shales with a prominent negative eu anomaly eu eu 0 48 0 77 and high ciw on paired cr th vs la co and co th plots group b samples conform to a two end member mixing line of the kongling granitic gneiss and amphibolite however data on nd model age and ciw suggest that the granite component should be younger than the sampled granitic gneiss and derived from a distal source both groups a and b exhibit a clear positive correlation between ciw and tdm and a negative one between ciw and eu eu these correlations point to the crustal evolution of the yangtze craton towards coupled increasing ciw and eu depletion with decreasing age this in turn reflects the change of granitoid magmatism from local na rich dioritic tonalitic trondhjemitic rocks to widespread k feldspar granite the change led to the intracrustal differentiation stabilization and growth of the craton group c is restite and contains abundant sillimanite and garnet and unusually high ilmenite 7 11vol which can be seen to be dehydration melting products of biotite under the microscope this group shows extremely varied ree distributions from lree enriched to depleted and from negative to strong positive eu eu 1 63 eu anomalies compared to groups a and b group c is severely depleted in na2o k2o lree rb and ba whereas tio2 co v sc and hree and y are considerably enriched this is accompanied by anomalous high sm nd 0 21 0 28 147sm 144nd 0 1361 0 1738 and 143nd 144nd 0 511589 0 511958 ratios tdm correlates clearly with sm nd ratio and 2 out of 3 samples give significantly older to unrealistic tdm 3 9 4 9 ga the results document redistribution of ree and an open behavior of the sm nd isotope system during the biotite dehydration melting of metasediments

differential exhumation in response to episodic thrusting along the eastern margin of the tibetan plateau abstract thermochronological data from the songpan ganze fold belt and longmen mountains thrust nappe belt on the eastern margin of the tibetan plateau in central china reveal several phases of differential cooling across major listric thrust faults since early cretaceous times differential cooling indicated by distinct breaks in age data across discrete compressional structures was superimposed upon a regional cooling pattern following the late triassic indosinian orogeny 40ar 39ar data from muscovite from the central and southern longmen mountains thrust nappe belt suggest a phase of differential cooling across the wenchuan maouwen shear zone during the early cretaceous the zircon fission track data also indicate differential cooling across a zone of brittle re activation on the eastern margin of the wenchuan maouwen shear zone during the mid tertiary between 38 and 10 ma apatite fission track data from the central and southern longmen mountains thrust nappe belt reveal differential cooling across the yingxiu beichuan and erwangmiao faults during the miocene forward modelling of apatite fission track data from the northern longmen mountains thrust nappe belt suggests relatively slow regional cooling through the mesozoic and early tertiary followed by accelerated cooling during the miocene beginning at ca 20 ma to present day regional cooling is attributed to erosion during exhumation of the evolving longmen mountains thrust nappe belt lmtnb following the indosinian orogeny differential cooling across the wenchuan maouwen shear zone and the yingxiu beichuan and erwangmiao faults is attributed to exhumation of the hanging walls of active listric thrust faults thermochronological data from the longmen mountains thrust nappe belt reveal a greater amount of differential exhumation across thrust faults from north to south this observation is in accord with the prevalence of proterozoic and sinian basement in the hanging walls of thrust faults in the central and southern longmen mountains the two most recent phases of reactivation occurred following the initial collision of india with eurasia suggesting that lateral extrusion of crustal material in response to this collision was focused along discrete structures in the lmtnb

dynamic process of turbidity generation triggered by the 2011 tohoku oki earthquake 1 we analyzed the distribution of turbidity in seawater near the epicenter of the 2011 tohoku earthquake mw 9 0 as well as the mineral composition and grain size distribution of suspended particles and of shallow sediments in cores from the same area one month after the earthquake in an area where large changes in bathymetry accompanied the earthquake we observed a strong turbidity anomaly above the seafloor maximum 5 mg l that greatly exceeded turbidity measured several years before the earthquake average 0 59 mg l the suspended particles were composed of material similar to the surface material of the sediment cores and we inferred that they were generated locally by a disturbance due to slope failure we estimated slope stability on the basis of the geophysical characteristics of the sediment cores as well as the acceleration of the earthquake our results showed that a submarine landslide could have been induced by the very large ground acceleration of the tohoku earthquake as high as 10 15 m s2 even if the sediment layer on the sliding surface was thin we interpreted the turbidity anomaly observed one month after the tohoku earthquake as the result of shallow submarine landsliding and stirring up of unconsolidated sediment around the epicentral area