transformation of debris flows into turbidity currents mechanisms inferred from laboratory experiments three sets of lock exchange experiments were run to look at the generation of turbidity currents from debris flows the flows ranged from reasonably dilute 4 volumetric concentration to dense 40 volumetric concentration with cohesive non cohesive and mixed cohesive non cohesive sediment concentration was measured at one height using an ultrasonic high concentration meter velocity was measured using ultrasonic doppler velocimetry profiling at 10 different heights in each run the resulting flows range from plug flows to well mixed flows comparison of the concentration profiles velocity time height plots and vertical profiles of downstream velocity and root mean square velocity showed several different transformation mechanisms depending on the concentration and composition of the flow transformation took place through one or more of the following processes erosion of material from the dense mass breaking apart of the dense underflow breaking of internal waves and turbulent mixing the extent of transformation depends on the viscosity and density of the flow initially very dense and viscous flows experience minor transformation only at the surface resulting in a dilute turbidity current flows that are initially not so dense and viscous are churned up entirely undergoing the different transformation processes for these flows transformation processes work throughout the entire flow not just at the surface transformation of the less dense flows is efficient with all or most material ending up in the resulting turbidity current

erosion of tephra from the 1980 eruption of mount st helens erosion of tephra on hillslopes north of mount st helens was measured at intervals of several months between 1980 and 1983 using large arrays of stakes rill erosion was initially greater than sheetwash but its importance decreased comparatively quickly both rill erosion and sheetwash decreased by one to two orders of magnitude over the three year period because a stable rill network developed and more permeable and less erodible substrates were created or exposed the decrease occurred prior to recovery of plants the causes for the rapid decline in erosion at mount st helens explain patterns of erosion following several other recent tephra eruptions basin wide annual rates of erosion were computed by mapping the surface cover the hillslope gradient and the texture and thickness of tephra and by using statistical relations developed between them and erosion rates annual erosion decreased from 26 mm between may 1980 and may 1981 to 1 8 mm between may 1982 and may 1983 projecting this rate of decline into the future indicated that only about one sixth of the tephra on hillslopes will be removed by water erosion before soil creep and other forms of mass wasting again dominate hillslope evolution

bmpix and peak tools new methods for automated laminae recognition and counting application to glacial varves from antarctic marine sediment we present tools for rapid and quantitative detection of sediment lamination the bmpix tool extracts color and gray scale curves from images at pixel resolution the peak tool uses the gray scale curve and performs for the first time fully automated counting of laminae based on three methods the maximum count algorithm counts every bright peak of a couplet of two laminae annual resolution in a smoothed curve the zero crossing algorithm counts every positive and negative halfway passage of the curve through a wide moving average separating the record into bright and dark intervals seasonal resolution the same is true for the frequency truncation method which uses fourier transformation to decompose the curve into its frequency components before counting positive and negative passages we applied the new methods successfully to tree rings to well dated and already manually counted marine varves from saanich inlet and to marine laminae from the antarctic continental margin in combination with ams14c dating we found convincing evidence that laminations in weddell sea sites represent varves deposited continuously over several millennia during the last glacial maximum the new tools offer several advantages over previous methods the counting procedures are based on a moving average generated from gray scale curves instead of manual counting hence results are highly objective and rely on reproducible mathematical criteria also the peak tool measures the thickness of each year or season since all information required is displayed graphically interactive optimization of the counting algorithms can be achieved quickly and conveniently

ancient lacustrine hyperpycnites a depositional model from a case study in the rayoso formation cretaceous of west central argentina abstract hyperpycnal flows originate when sediment laden fluvial discharges enter standing lower density water because of their excess density the flows plunge near the river mouth and continue to travel basinward as a quasi steady and fully turbulent underflow the related deposits are hyperpycnites and constitute a particular type of turbidite with poorly known facies and facies tracts although hyperpycnal flows seem to be quite common in present times their occurrence in fossil strata is poorly documented this paper addresses the characteristics and depositional processes of shallow lacustrine sandy hyperpycnites on the basis of the field analysis of well exposed lower cretaceous strata rayoso formation in the neuquen basin of west central argentina the rayoso formation is composed of clastic and minor evaporitic red beds up to 1200 m thick deposited in a shallow perennial lake of variable salinity affected by long lived hyperpycnal flows main clastic facies are composed of fine grained sandstones with climbing ripples and plane beds other common sandstone facies include massive beds and low angle cross stratification most sandstone facies are related to traction plus fallout processes and often show a vertical fluctuation between sedimentary facies originated under different traction plus fallout conditions within single beds these fluctuations are interpreted to be evidence of deposition from flow fluctuations in sustained hyperpycnal flows most beds internally show the existence of three depositional phases acceleration ap erosion plus bypass ep and deceleration dp which record the complete evolution of a single long lived hyperpycnal flow at a fixed point additionally the depositional evolution of a single long lived hyperpycnal flow with distance records initially the progressive basinward migration of the ap and ep phases and finally an overall deposition under the dp phase both in proximal and distal areas this evolution provides an adequate explanation for the basinward extension of channelized features and for the occurrence of fine grained sandstones with climbing ripples both in proximal and distal positions within the same hyperpycnal system consequently facies analysis derived from application of the bouma sequence is not valid for deposits of quasi steady hyperpycnal flows

volcano tectonic interactions during rapid plate boundary evolution in the kyushu region sw japan evolution of the local plate tectonic and volcanic system relationship at kyushu island is defined by major changes in tectonics and volcanic style at ca 15 10 6 and 2 ma plate reconstructions presented here suggest that prior to 15 ma the pacific plate subduction dominated kyushu tectonics from 15 to 6 ma the evolving relative plate motions shifted the triple junction between the pacific plate philippine sea plate and southwest japan northwards so that the philippine sea plate was subducted beneath kyushu we suggest that a lack of subduction related volcanism from 10 to 6 ma is due to shallow subduction of the young shikoku basin lithosphere by 6 5 ma changes in the philippine sea plate motion led to more rapid nearly trench normal subduction of the eocene west philippine basin crust beneath kyushu this model is supported by an increase in arc like geochemistry of lavas since ca 6 5 ma subduction of fluid rich features such as the kyushu palau ridge introduced large volumes of fluids into the kyushu arc system leading to voluminous volcanism across kyushu focused particularly in areas where the ridge subduction occurs in tandem with local extensional tectonics key issues such as the timing of izu arc collision with central japan and the history of motion of the philippine sea plate are reassessed here resulting in a model that favors izu arc central japan collision at ca 8 6 ma rather than the more widely accepted date of ca 15 ma

bed thickness frequency distributions and recurrence intervals of sediment gravity flow deposits intercalated in lacustrine varved diatomite examples from the middle pleistocene hiruzenbara formation southwest japan

advance of east antarctic outlet glaciers during the hypsithermal implications for the volume state of the antarctic ice sheet under global warming we present the first circum east antarctic chronology for the holocene based on 17 radiocarbon dates generated by the accelerator method marine sediments from around east antarctica contain a consistent high resolution record of terrigenous ice proximal and biogenic open marine sedimentation during holocene time this record demonstrates that biogenic sedimentation beneath the open marine environment on the continental shelf has been restricted to approximately the past 4 ka whereas a period of terrigenous sedimentation related to grounding line advance of ice tongues and ice shelves took place between 7 and 4 ka an earlier period of open marine biogenic sedimentation conditions following the late pleistocene glacial maximum is recognized from the prydz bay ocean drilling program record between 10 7 and 7 3 ka clearly the response of outlet systems along the periphery of the east antarctic ice sheet during the mid holocene was expansion this may have been a direct consequence of climate warming during an antarctic hypsithermal temperature accumulation relations for the antarctic indicate that warming will cause a significant increase in accumulation rather than in ablation models that predict a positive mass balance growth of the antarctic ice sheet under global warming are supported by the mid holocene data presented herein

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

paleoseismicity of the cascadia subduction zone evidence from turbidites off the oregon washington margin cores from cascadia deep sea channel contain sequences of turbidites that can be correlated and dated by the first occurrence of volcanic glass from the mount mazama eruption 6845 50 radiocarbon yrbp turbidity currents from the tributaries appear to have occurred synchronously to form single deposits in the main channel there being only 13 turbidite deposits in the lower main channel since the mazama eruption instead of the twice as many expected if the tributaries had behaved independently in addition to the cascadia channel 13 post mazama turbidites have been deposited in the astoria canyon and at two sites off cape blanco sample locations that span 580 km of the oregon washington margin pelagic intervals deposited between the turbidites suggest that in each place the turbidity currents occurred fairly regularly every 590 170 years on average the best explanation of the spatial and temporal extent of the data is that the turbidity currents were triggered by 13 great earthquakes on the cascadia subduction zone the variability of turbidite timing is similar to that for great earthquake cycles the thickness of the topmost pelagic layer suggests the last event was 300 60 years ago from three places along the margin but this number may be a biased underestimate it is however consistent with the youngest sudden subsidence event on the washington coast the turbidite data demonstrate that the near term hazard of a great earthquake on the cascadia subduction zone is of the order of 2 10 in the next 50 years

late quaternary lacustrine paleo seismic archives in north western alps examples of earthquake origin assessment of sedimentary disturbances abstract the late quaternary sedimentary fills of several lakes of the north western alps are revealed to be possible paleo seismological archives in a moderately active seismo tectonic region the strongest historically reported events can be correlated with specific layers whose textures result from different processes i mass failures of sub aqueous slope deposits especially delta foresets evolving into hyperpycnal currents influenced by seiche effects and or multiple reflections on lake basin slopes ii in situ liquefaction and flowage and iii micro fracturing based on identification of the sedimentary signature of a well documented historical earthquake the paleoseismic interpretation can be extrapolated back to 16 000 yrs bp with a reconstruction of a time series and textural identification of slope failure related turbidites the most frequent earthquake signature the obtained time series are compatible with historical seismicity in terms of recurrence interval

field expressions of the transformation of debris flows into turbidity currents with examples from the polish carpathians and the french maritime alps various transformation mechanisms can generate turbidity currents from subaqueous debris flows different transformation mechanisms have been described and interpreted in the past from laboratory experiments and from deposits but the two approaches have not generally been linked this has made the genetic interpretation and comparison of deposits difficult in this paper a generic classification scheme of debrite turbidite couplets is proposed based on transformation mechanisms inferred from laboratory experiments five different flow types called a e herein and their resulting deposits are detailed but they are all part of a continuous spectrum and a mixture of types is likely to be found in the field type a flows are strong dense debris flows that undergo little transformation their deposit will be a debrite overlain by a thin turbidite which is separated from it by a clear grain size break type b flows are weaker and can develop waves at the debris flow turbidity current interface the deposit will be a debrite with a wavy top overlain by a turbidite that is thicker than for type a flows for type c flows the interfacial waves will grow so much that the debris flow disintegrates into separate parts the deposit will consist of debrite lenses encased in a turbidite type d flows will undergo even more mixing than type c flows so that the debrite parts will be mixed their deposit will be a turbidite with laterally varying areas of debrite characteristics near the bed type e flows will be so transformed that the debris flow character has disappeared and the flow is a turbidity current with high sediment concentration the deposit will be largely turbiditic the flow types and deposits will be illustrated with some examples from two field areas the polish carpathians and the french maritime alps

regionality of deep low frequency earthquakes associated with subduction of the philippine sea plate along the nankai trough southwest japan abstract the fukuoka district meteorological observatory recently logged three possible deep low frequency earthquakes lfes beneath eastern kyushu japan a region in which lfes and low frequency tremors have never before been identified to assess these data we analyzed band pass filtered velocity seismograms and relocated lfes and regular earthquakes using the double difference method the results strongly suggest that the three events were authentic lfes each at a depth of about 50 km we also performed relocation analysis on lfes recorded beneath the kii peninsula and found that these lfes occurred near the northwest dipping plate interface at depths of approximately 29 38 km these results indicate that lfes in southwest japan occur near the upper surface of the subducting philippine sea phs plate to investigate the origin of regional differences in the occurrence frequency of lfes in western shikoku the kii peninsula and eastern kyushu we calculated temperature distributions associated with phs plate subduction then using the calculated thermal structures and a phase diagram of water dehydration for oceanic basalt the water dehydration rate wt km which was newly defined in this study was determined to be 0 19 0 12 and 0 08 in western shikoku the kii peninsula and eastern kyushu respectively that is the region beneath eastern kyushu has the lowest water dehydration rate value considering that the kyushu palau ridge that is subducting beneath eastern kyushu is composed of tonalite which is low in hydrous minerals this finding suggests that the regionality may be related to the amount of water dehydration associated with subduction of the phs plate and or differences in lfe depths notable dehydration reactions take place beneath western shikoku and the kii peninsula where the depth ranges for dehydration estimated by thermal modeling agree well with those for the relocated lfes the temperature range in which lfes occur in these regions is estimated to be 400 500 c

the relationship between annual varve thickness and maximum annual discharge 1909 1971 annually laminated varved sediments from the river angermanalven mid central sweden have been used to construct an annual 2000 year long record of varve thickness maximum daily annual discharge and mean varve thickness for the years 1909 1971 are significantly correlated r 0 87 a relationship between maximum daily annual discharge for the observed period 1909 1971 and varve thickness was determined the return time of two exceptionally thick varves in the 2000 year long record at the years 658 and 492 ad were estimated and their likelihood estimated based on a gumbel frequency analysis c 2002 elsevier science b v all rights reserved

turbidites as records of intense palaeoearthquakes in lake biwa japan abstract some 20 turbidites were collected in the uppermost 3 m of surface sediments in lake biwa southwest japan these turbidites correlate in age to historical earthquakes that caused severe loss of lives and property near lake biwa the age of each turbidite was estimated precisely based on sedimentation rate by weight and the age of tephra markers below the turbidites the magnitudes and epicentres of major historical earthquakes during the last 1300 years are available from historical documents empirical equations relating intensity distance to the epicentre and magnitude enable us to calculate the ground shaking at lake biwa from these historical earthquakes earthquakes having intensity stronger than grade iv l on the japan meteorological agency jma earthquake scale that is 44 gal acceleration at lake biwa all coincide with the turbidite ages this intensity is apparently the lower threshold for turbidity current initiation in lake biwa

long term river discharge and multidecadal climate variability inferred from varved sediments southwest alaska abstract sedimentological analyses of 289 years ad 1718 2006 of varved sediment from shadow bay southwest alaska were used to investigate hydroclimate variability during and prior to the instrumental period varve thicknesses relate most strongly to total annual discharge r2 0 75 n 43 p

miocene pleistocene volcanism and tectonics in southern korea and their relationship to the opening of the japan sea abstract miocene pleistocene volcanism and tectonics in southern korea are discussed the miocene volcanism and related tectonics are represented by the eoil orogeny which occurred in the yangnam and pohang basins in the southeastern corner of the korean peninsula the yangnam and pohang basins represent the uplifted central part of the pohang ulsan graben which was rifted between the proto korean peninsula and paleo ulleung land probably in late oligocene early miocene times the eoil orogeny is correlated with the green tuff orogeny in japan evidence of pliocene volcanism is observed on ulleung island located in the western part of the central japan sea volcanic and tectonic events represented on ulleung island are in chronological order 1 volcanic eruption 2 subsidence and marine transgression 3 dome like uplift and 4 volcanic eruption evidence of pleistocene volcanism is present on cheju island located at the southwestern entrance to the korea tsushima strait volcanic and tectonic events represented on cheju island are in chronological order 1 volcanic eruption 2 subsidence and marine transgression 3 uplift and volcanic eruption and 4 doming and volcanic eruption three grabens namely the pohang ulsan graben the ulleung basin and the yamato basin were formed in the southern half of the japan sea which was above sea level in early miocene times paleo ulleung land was present between the pohang ulsan graben and the ulleung basin in miocene pliocene times these three grabens are active rifts and the tectonic events that occurred in this region originated from the action of rising magma the extension and deepening of the southern half of the japan sea resulted from the tectonic movements of these active rifts and their surrounding regions thus it is suggested that the opening of the japan sea progressed by diapiric tectogenesis

a revised earthquake chronology for the last 4 000 years inferred from varve bounded debris flow deposits beneath an inlet near victoria british columbia

annually laminated lake sediments and the study of quaternary environmental changes a review abstract annually laminated lake sediments non glacial varves have in recent years been discovered in increasing abundance especially since the development of in situ freezer samplers so far the majority of examples have been found in three main areas eastern north america northern and central europe and east and central africa a much more widespread distribution seems highly probable however the formation of annual laminations in freshwater lakes is governed by a number of factors the most important of which appears to be morphometry seasonality of sediment supply which may be controlled by physical biological or even cultural processes in the lake or in its catchment is also clearly significant four main types of laminations here termed ferrogenic calcareous biogenic and clastic have so far been recorded although it is quite clear that others exist special field and laboratory techniques are needed in order that the particular properties of varved sediments may be fully exploited annually laminated sediments have so far been applied to the investigation of a number of aspects of the quaternary these include the study of a geochronology b climatic change c vegetation history especially the role of fire in forest ecosystems d the calculation of rates of sediment influx to lakes and of rates of erosion from their catchments and e the monitoring of processes in the modern environment such as heavy metal pollution eutrophication and acid rain annually laminated lake sediments combine an internal independent chronology with the preservation of discrete visible increments of seasonal and annual sedimentation given this unique property and the likelihood that many more examples will be discovered the prospects for further applications of studies of these sediments to the investigation of the quaternary seem very good indeed

lacustrine turbidites as a tool for quantitative earthquake reconstruction new evidence for a variable rupture mode in south central chile understanding the long term earthquake recurrence pattern at subduction zones requires continuous paleoseismic records with excellent temporal and spatial resolution and stable threshold conditions south central chilean lakes are typically characterized by laminated sediments providing a quasi annual resolution our sedimentary data show that lacustrine turbidite sequences accurately reflect the historical record of large interplate earthquakes among others the 2010 and 1960 events furthermore we found that a turbidite s spatial extent and thickness are a function of the local seismic intensity and can be used for reconstructing paleo intensities consequently our multilake turbidite record aids in pinpointing magnitudes rupture locations and extent of past subduction earthquakes in south central chile comparison of the lacustrine turbidite records with historical reports a paleotsunami subsidence record and a marine megaturbidite record demonstrates that the valdivia segment is characterized by a variable rupture mode over the last 900 years including i full ruptures mw 9 5 1960 1575 1319 9 1127 44 ii ruptures covering half of the valdivia segment mw 9 1837 and iii partial ruptures of much smaller coseismic slip and extent mw 7 5 8 1737 1466 4 also distant or smaller local earthquakes can leave a specific sedimentary imprint which may resolve subtle differences in seismic intensity values for instance the 2010 event at the maule segment produced higher seismic intensities toward southeastern localities compared to previous megathrust ruptures of similar size and extent near concepci n

holocene flood frequency across the central alps solar forcing and evidence for variations in north atlantic atmospheric circulation the frequency of large scale heavy precipitation events in the european alps is expected to undergo substantial changes with current climate change hence knowledge about the past natural variability of floods caused by heavy precipitation constitutes important input for climate projections we present a comprehensive holocene 10 000 years reconstruction of the flood frequency in the central european alps combining 15 lacustrine sediment records these records provide an extensive catalog of flood deposits which were generated by flood induced underflows delivering terrestrial material to the lake floors the multi archive approach allows suppressing local weather patterns such as thunderstorms from the obtained climate signal we reconstructed mainly late spring to fall events since ice cover and precipitation in form of snow in winter at high altitude study sites do inhibit the generation of flood layers we found that flood frequency was higher during cool periods coinciding with lows in solar activity in addition flood occurrence shows periodicities that are also observed in reconstructions of solar activity from 14 c and 10 be records 2500 3000 900 1200 as well as of about 710 500 350 208 suess cycle 150 104 and 87 gleissberg cycle years as atmospheric mechanism we propose an expansion shrinking of the hadley cell with increasing decreasing air temperature causing dry wet conditions in central europe during phases of high low solar activity furthermore differences between the flood patterns from the northern alps and the southern alps indicate changes in north atlantic circulation enhanced flood occurrence in the south compared to the north suggests a pronounced southward position of the westerlies and or blocking over the northern north atlantic hence resembling a negative nao state most distinct from 4 2 to 2 4 kyr bp and during the little ice age south alpine flood activity therefore provides a qualitative record of variations in a paleo nao pattern during the holocene additionally increased south alpine flood activity contrasts to low precipitation in tropical central america cariaco basin on the holocene and centennial time scale this observation is consistent with a holocene southward migration of the atlantic circulation system and hence of the itcz driven by decreasing summer insolation in the northern hemisphere as well as with shorter term fluctuations probably driven by solar activity

stratigraphic variations in lacustrine sediment gravity flow deposits intercalated in varved diatomite an example from the hiruzenbara formation okayama prefecture southwest japan abstract the hiruzenbara formation which is distributed within the hiruzenbara basin of southwest japan includes a section of varved diatomite representing ca 8000 y of deposition in a dammed lake formed during the middle pleistocene the varve on average ca 1 5 mm thick consists of light and dark green laminae sets and is predominately composed of planktonic diatoms several facies types of sediment gravity flow deposits are intercalated in the varved diatomite in this study we examined the sedimentary facies lateral changes and stratigraphic variations of these sediment gravity flow deposits in addition we also analyzed a time series of varve thickness fluctuations based on their sedimentary facies composition and diatom species sediment gravity flow deposits in the varved diatomite can be classified as flood generated or slope failure generated sedimentary facies analysis indicates that the slope failure deposits were deposited by slope failure within the lake since no significant segregation of rip up clasts is observed in the deposits a proximal depositional setting at the base of the lake slope is suggested the flood generated deposits have eroded lower contacts which indicate deposition by hyperpycnal flows in contrast deposits with no basal erosion indicate deposition by homopycnal or hypopycnal flows the thickness time series of the varve shows a thickening upward trend indicating an increase in diatom production or in diatom shells sizes running mean thicknesses show non stationary periodicities of 200 500 y the frequency of the deposit varies but is approximately 10 events per 400 y flood deposits in the middle part of the section are dominated by volcaniclastic silt this suggests that vegetation around the lake was reduced by ash fall resulting in frequent flood events during this interval the frequency and thickness of slope failure deposits increases in the lower part of the succession together with the occurrence of slump scars the frequency of the deposits in the upper part of the section is approximately 100 500 y similar to the postulated interval at activity of the nearby yamasaki fault system the results of this study improve our knowledge of paleoenvironmental changes in the study site and also provide new criteria for classifying sediment gravity flow deposits in lacustrine sedimentary cores

initiation of turbidity currents outcrop evidence for eocene hyperpycnal flow turbidites abstract the most widely used although not as widely documented explanation for initiation of turbidites is the conversion of catastrophic sediment failures into turbidites such instantaneous sediment failures generate short lived surge type flows that deposit turbidite beds described as bouma sequences in this communication we present data from the eocene central basin of spitsbergen that shows turbidite systems that are volumetrically dominated by thick ungraded and laminated sandy turbidite beds deposited by gradual aggradation from sustained flows sustained flows are long lived and more or less continuous they can be generated by a variety of mechanisms e g 1 instability during volcanic eruptions and the consequent remobilisation of unconsolidated material 2 seismically triggered subaerial sliding within the drainage 3 storm surges 4 retrogressive slope failure 5 breaching and 6 hyperpycnal flows our database shows that in the eocene central basin the sustained flows were generated by hyperpycnal flows i e by direct river effluent the hyperpycnal flow turbidites have been recognized on the basis of 1 physical connection between fluvial and turbidite channels at the shelf edge 2 abundance of thick turbidite sandstone beds 3 sand prone nature of the turbidite systems 4 downslope changes of individual thick sandy turbidite beds and their collapsed pinch out segments 5 great abundance of continental material leaves coal fragments in turbidite beds 6 low abundance of associated slumped or debris flow beds and 7 the occurrence of turbidites in systematically accreted shelf margins these features strongly suggest that hyperpycnal flow generated by direct river effluent deposited significant number of turbidite beds in the documented slope and basin floor turbidite successions we also argue that the hyperpycnal flows are preferentially fed into the deepwater slopes beyond the shelf edge during the falling stage and lowstand of relative sea level the turbidite beds were studied in the context of seismic scale 1 15 km dip oriented outcrops by measuring detailed vertical sections following individual beds and packages of beds downslope for distances over 5 km lateral mapping and helicopter taken photomosaics

kinematic model for the opening of the sea of japan and the bending of the japanese islands we have analyzed paleomagnetic data from japan reported over the past 25 years in combination with marine geophysical and on land geologic data to reconstruct the opening of the sea of japan and the bending of honshu from these data we propose that the sea of japan opened by a two stage back arc spreading event 1 in the early to middle tertiary japan began to rift off the asian coast as a single rigid block rotated clockwise approximately 25 and formed the japan basin 2 in the miocene the yamato and tsushima basins opened and shortly thereafter 19 ma the japan arc collided with another island arc in central hokkaido at this stage honshu began to behave as two rigid blocks southwest honshu and northeast honshu southwest honshu continued to rotate clockwise approximately 45 as the yamato and tsushima basins continued to open northeastern honshu rotated counterclockwise approximately 40 as hokkaido was held fixed by the arc collision while the yamato basin continued to open these two events the opening of the tsushima and yamato basins and the arc collision in hokkaido resulted in the early to middle miocene bending of the japan arc observed in the paleomagnetic data after 12 ma back arc spreading ceased

flood stratigraphies in lake sediments a review abstract records of the frequency and magnitude of floods are needed on centennial or millennial timescales to place increases in their occurrence and intensity into a longer term context than is available from gauged river flow and historical records recent research has highlighted the potential for lake sediment sequences to act as a relatively untapped archive of high magnitude floods over these longer timescales abyssal lake sediments can record past floods in the form of coarser grained laminations that reflect the capacity for river flows with greater hydrodynamic energy to transport larger particles into the lake this paper presents a framework for investigating flood stratigraphies in lakes by reviewing the conditioning mechanisms in the lake and catchment outlining the key analytical techniques used to recover flood records and highlighting the importance of appropriate field site and methodology selection the processes of sediment movement from watershed to lake bed are complex meaning relationships between measureable sedimentary characteristics and associated river discharge are not always clear stratigraphical palaeoflood records are all affected to some degree by catchment conditioning fluvial connectivity sequencing of high flows delta dynamics as well as within lake processes including river plume dispersal sediment focussing re suspension and trapping efficiency with regard to analytical techniques the potential for direct e g laser granulometry and indirect e g geochemical elemental ratios measurements of particle size to reflect variations in river discharge is confirmed we recommend care when interpreting fine resolution geochemical data acquired via micro scale x ray fluorescence xrf core scanning due to variable down core water and organic matter content altering x ray attenuation we also recommend accounting for changes in sediment supply through time as new or differing sources of sediment release may affect the hydrodynamic relationship between particle size and or geochemistry with stream power where these processes are considered and suitable dating control is obtained discrete historical floods can be identified and characterised using palaeolimnological evidence we outline a protocol for selecting suitable lakes and coring sites that integrates environmental setting sediment transfer processes and depositional mechanisms to act as a rapid reference for future research into lacustrine palaeoflood records we also present an interpretational protocol illustrating the analytical techniques available to palaeoflood researchers to demonstrate their utility we review five case studies of palaeoflood reconstructions from lakes in geographically varied regions these show how lakes of different sizes and geomorphological contexts can produce comprehensive palaeoflood records these were achieved by consistently applying site validated direct and proxy grain size measurements well established chronologies validation of the proxy process interpretation and calibration of the palaeoflood record against instrumental or historical records

sg06 a fully continuous and varved sediment core from lake suigetsu japan stratigraphy and potential for improving the radiocarbon calibration model and understanding of late quaternary climate changes abstract the high potential of the varved sediments of lake suigetsu central japan to provide a purely terrestrial radiocarbon calibration model and a chronology of palaeoclimatic changes has been widely recognised for the last two decades however this potential has not been fully realised since the only available long sediment core from the lake sg93 was extracted from a single bore hole and was therefore interrupted by gaps of unknown duration between successive core sections in the summer of 2006 a new sediment core sg06 was recovered from the lake four separate boreholes were drilled and the parallel sets of cores recovered were found to overlap completely without gaps between segments this new record provides the ability to test existing atmospheric radiocarbon calibration models as well as to assess the scale of inter regional leads and lags in palaeoclimatic changes over the last glacial interglacial cycle multi disciplinary analyses from sg06 are still ongoing but a reliable description of the sedimentary sequence needs to be provided to the wider science community before major outputs from the project are released thereby allowing fully informed critical evaluation of all subsequent releases of data based on the sg06 record in this paper we report key litho stratigraphic information concerning the sg06 sediment core highlighting changes in the clarity of annual laminations varves with depth and possible implications for the mechanism of the climate change we also discuss the potential of the sg06 record to meet the fundamental goals of the inqua intimate project