mass balance of two high arctic plateau ice caps mass balance measurements have been renewed on two small ice caps on north eastern ellesmere island original stake networks were established in 1972 and 1976 since then both ice caps have experienced significant mass losses averaging 70 to 140 kg m2 a i they have also decreased in area the equilibrium line in this area has averaged around 1150 m for the last decade or so the ice caps are remnants of former climatic conditions and are out of equilibrium with contemporary climate

shredding of environmental signals by sediment transport 1 landscapes respond to climate tectonic motions and sea level but this response is mediated by sediment transport understanding transmission of environmental signals is crucial for predicting landscape response to climate change and interpreting paleo climate and tectonics from stratigraphy here we propose that sediment transport can act as a nonlinear filter that completely destroys shreds environmental signals this results from ubiquitous thresholds in sediment transport systems e g landsliding bed load transport and river avulsion this morphodynamic turbulence is analogous to turbulence in fluid flows where energy injected at one frequency is smeared across a range of scales we show with a numerical model that external signals are shredded when their time and amplitude scales fall within the ranges of morphodynamic turbulence as signal frequency increases signal preservation becomes the exception rather than the rule suggesting a critical re examination of purported sedimentary signals of external forcing citation jerolmack d j and c paola 2010 shredding of environmental signals by sediment transport geophys res lett 37 l19401 doi 10 1029 2010gl044638

topoclimatic studies of a high arctic plateau ice cap meteorological observations on and around a small exposed plateau ice cap on north eastern ellesmere island n w t canada were carried out in the northern summers of 1982 and 1983 the objective was to assess the effect of the ice cap on local climate as the melt season progressed in 1982 seasonal net radiation totals were lowest on the ice cap and greatest at the site farthest from the ice cap the ice cap site received only 35 of net radiation totals on the surrounding tundra this reflects a gradient in albedo albedo changed most markedly away from the ice cap as the summer progressed a thermal gradient was observed along a transect perpendicular to the ice cap edge this gradient was greatest at low levels i5 cm and was maximized under cloud free conditions the cooling effect of the ice cap was less at the start of the ablation season than later low level inversions occurred more frequently over the ice cap than over the snow free tundra overall melting degree days on the ice cap were only 40 i5 of those on the adjacent tundra a model of interactions between the atmosphere and a snow and ice cover or a snow free tundra felsenmeer surface is proposed observations indicate that the ice cap has a cooling effect on the lower atmosphere relative to the adjacent snow free tundra this effect is absent when snow cover is extensive as in 1983

holocene turbidites record earthquake supercycles at a slow rate plate boundary ongoing evidence for earthquake clustering calls for records of numerous earthquake cycles to improve seismic hazard assessment especially where recurrence times overstep historical records we show that most turbidites emplaced at the africa eurasia plate boundary off west algeria over the past 8 k y correlate across sites fed by independent sedimentary sources requiring a regional trigger correlation with paleoseismic data inland and ground motion predictions support that m 7 earthquakes have triggered the turbidites the bimodal distribution of paleo events supports the concepts of earthquake supercycles and rupture synchronization between nearby faults 13 paleo earthquakes underpin clusters of 3 6 events with recurrence intervals of 300 600 yr separated by periods of quiescence of 1 6 k y without major events on other faults over the study area this implies broad phases of strain loading alternating with phases of strain release our results suggest that fault slip rates are time dependent and call for revising conventional seismic hazard models

long term 17 ma turbidite record of the timing and frequency of large flank collapses of the canary islands volcaniclastic turbidites on the madeira abyssal plain provide a record of large volume volcanic island flank collapses from the canary islands this long term record spans 17 ma and comprises 125 volcaniclastic beds determining the timing provenance and volumes of these turbidites provides key information about the occurrence of mass wasting from the canary islands especially the western islands of tenerife la palma and el hierro these turbidite records demonstrate that landslides often coincide with protracted periods of volcanic edifice growth suggesting that loading of the volcanic edifices may be a key preconditioning factor for landslide triggers furthermore the last large volume failures from tenerife coincide with explosive volcanism at the end of eruptive cycles many large volume canary island landslides also occurred during periods of warmer and wetter climates associated with sea level rise and subsequent highstand however these turbidites are not serially dependent and any association with climate or sea level change is not statistically significant

rapid rise of sea level 19 000 years ago and its global implications evidence from the irish sea basin supports the existence of an abrupt rise in sea level meltwater pulse at 19 000 years before the present b p climate records indicate a large reduction in the strength of north atlantic deep water formation and attendant cooling of the north atlantic at this time indicating a source of the meltwater pulse from one or more northern hemisphere ice sheets warming of the tropical atlantic and pacific oceans and the southern hemisphere also began at 19 000 years b p these responses identify mechanisms responsible for the propagation of deglacial climate signals to the southern hemisphere and tropics while maintaining a cold climate in the northern hemisphere

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

multistage collapse of eight western canary island landslides in the last 1 5 ma sedimentological and geochemical evidence from subunits in submarine flow deposits volcaniclastic turbidites in the madeira abyssal plain provide a record of major landslides from the western canary islands in the last 1 5 ma these volcaniclastic turbidites are composed of multiple fining upward turbidite sands known as subunits the subunits indicate that the landslides responsible for the sediment gravity flows occurred in multiple stages the subunits cannot result from flow reflection or splitting because the compositions of volcanic glasses from each individual subunit in an event bed are subtly different this indicates that each subunit represents a discrete failure as part of a multistage landslide this has significant implications for geohazard assessments as multistage failures reduce the magnitude of the associated tsunami the multistage failure mechanism reduces individual landslide volumes from up to 350 km3 to less than 100 km3 thus although multistage failure ultimately reduce the potential landslide and tsunami threat the landslide events may still generate significant tsunamis close to source

environmental signal propagation in sedimentary systems across timescales abstract earth surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales the geomorphic and stratigraphic products of this source to sink sediment transfer record signals of external environmental forcings as well as internal or autogenic dynamics of the sedimentary system here we evaluate environmental signal propagation across sediment routing systems with emphasis on sediment supply qs as the carrier of up system forcings we review experimental numerical and natural examples of source to sink sediment routing and signal propagation during three timescales 1 historic which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries 2 centuries to several millions of years referred to as intermediate timescale and 3 deep time we discuss issues related to autogenic dynamics of sediment transport transient storage and release that can introduce noise lags and or completely mask signals of external environmental forcings we provide a set of conceptual and practical tools for evaluating sediment supply within a source to sink context which can inform interpretations of signals from the sedimentary record these tools include stratigraphic and sediment routing system characterization sediment budgets geochronology detrital mineral analysis e g thermochronology comparative analog approaches and modeling techniques to measure calculate or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment routing systems

storm generated episodic sediment movements off kahe point oahu hawaii abstract the area off kahe point oahu hawaii has been the focus of recent oceanographic research in preparation for a large scale ocean thermal energy conversion otec project underwater instrument arrays moored to the bottom in this area were damaged shifted or lost during hurricane iwa in 1982 four underwater telephone cables located at greater depths were severed during the same period seamarc ii images show that most of the sea floor in this area is represented by light gray tones cores collected from this smooth sediment cover contain thick sequences of hemipelagic silt and clay darker acoustic reflection patterns trend downslope across this light gray background cores containing coarse sands and gravels and displaced shallow benthic foraminifera were collected from rough bottom represented by these patterns the pattern configurations sediment types within them and their benthic foraminiferal content indicate that these darker tones represent downslope sediment flow telephone cables were damaged and instrument arrays moved during hurricane iwa in places and along trajectories coincident with the orientation of the dark tones

the earthquakes of 29 july 2003 12 february 2007 and 17 december 2009 in the region of cape saint vincent sw iberia and their relation with the 1755 lisbon earthquake abstract the cape saint vincent region is of major seismological interest for its tectonic complexity and for the occurrence of the great 1755 lisbon earthquake no structure capable of generating such a large earthquake has yet been convincingly identified but all authors agree that there is a possibility of a similar earthquake occurring offshore of the cape sometime in the future to shed some light on the region s dynamics we here examine the mechanism of the three largest earthquakes to have occurred in the last 40 years west of the cape 29 july 2003 m w 5 3 12 february 2007 m w 6 1 and 17 december 2009 m w 5 5 by inversion of the body waves and the kinematic slip distribution we estimated the three earthquakes to have had similar characteristics dimensions maximum slip stress drop source time function focal depth and rupture velocity although there were differences in the geometry of the rupture that reflect the great seismotectonic complexity of the zone the focal mechanisms of the 2003 and 2007 earthquakes were similar corresponding to thrusting motion but the 2009 earthquake had a dip slip motion in a vertical plane as deduced from the slip distributions the three shocks show ne sw rupture planes with the energy released propagating to the ne compatible with the regional nw se horizontal compression produced by the convergence of the eurasian and african plates applied to the generation of the 1755 lisbon earthquake this direction of faulting would correspond to a complex rupture along ne sw trending thrust faults at the gorringe bank the horseshoe scarp and the marquis de pombal fault with the rupture propagating to the ne towards the portuguese coast such a model could explain that unusually large and tsunami generating earthquake

frequency and timing of landslide triggered turbidity currents within the agadir basin offshore nw africa are there associations with climate change sea level change and slope sedimentation rates abstract older sequence stratigraphic models suggested that submarine landslide and turbidite activities are greatest during sea level lowstands however growing evidence indicates that many turbidite systems are also active during sea level transgressions and highstands the moroccan turbidite system comprises three depocentres of which agadir basin is closest to the moroccan slope and canary archipelago the very large volumes of sediment transported by individual sediment flows in this system suggest that they are triggered by landslides extensive core coverage and dating control for the agadir basin deposits have provided an excellent opportunity to derive accurate records of turbidite and associated landslide frequency for the last 600 ka previous studies in the more distal madeira abyssal plain depocentre have indicated that large volume 50 km 3 turbidites occurred at oxygen isotope stage ois boundaries this study of agadir basin confirms that two major turbidites beds a5 and a12 occurred during glacial interglacial transitions associated with ois4 and ois6 however this association is based on just two examples and two other large volume turbidites beds a7 and a11 did not occur at a stage boundary the main conclusion of this study is that 90 of turbidites and landslides occurred during rising and high sea level which represents 40 of the total time during the last 600 ka only 10 of the turbidites and landslides occurred during glacials 40 of the time with a paucity of turbidites and landslides at peak glacial lowstands a comparison to sediment accumulation rates in the source area of the turbidite suggests that landslides did not occur preferentially during periods of more rapid sedimentation rate although sedimentation rates in this area only varied from 4 to 6 g cm 2 ka 1

phase transformations earthquakes and the descending lithosphere abstract the energy dissipated from metastable phase transformations is investigated in this paper in addition to the kinetic energy envisaged by randall at least two other major forms of energy latent heat and metastability energy are involved in a metastable phase transformation the seismic energy density for metastable phase transformation is of the order of 10 24 10 25 erg km 3 for most mantle silicates as an example an earthquake of magnitude m 7 5 would require only 0 01 0 03 or 0 04 km 3 of basalt olivine or pyroxene respectively undergoing metastable phase transformation earthquakes caused by both faulting and phase transformation mechanisms have been observed in high pressure laboratory experiments the energy density associated with a faulting mechanism appears to be four to five orders of magnitude less than that associated with metastable phase transformations of mantle silicates confirming theoretical expectations according to all of the thermal models for the descending lithosphere available in the literature metastable phase transformations almost certainly occur in the descending lithosphere enormous energies would be released suddenly in association with these metastable phase transformations thus earthquakes within the descending lithosphere at depths greater than 100 km may be induced by metastable phase transformations however metastable phase transformations in the descending lithosphere have little or an opposing effect on the tectonic engine driving the motion of plates into the mantle

identifying instrumental and historical earthquake records in the sw iberian margin using 210pb turbidite chronology 1 textural mineralogical and geochemical analyses of near surface sediments from six different stations offshore sw iberian peninsula revealed the presence of thin detrital intervals corresponding to very fine grained turbidites precise dating of the two most recent sedimentary layers based on 210pb and 137cs geochronology provides ages of 1971 3 ad and 1908 8 ad these ages correspond to high magnitude historical and instrumental earthquakes that occurred in the region the 1969 horseshoe earthquake mw 8 0 and the 1909 benavente earthquake mw 6 0 such a good correlation between turbidites and high magnitude mw 6 historical and instrumental seismic events suggests that the record of mass transport deposits can also be used as a paleoseismic indicator in low convergence margins

neogene through quaternary tectonic reactivation of sw iberian passive margin southwest portugal the gulf of cadiz and morocco are under the potential threat of natural hazards linked to seismicity and tsunami generation we report the results of two multi channel seismic mcs surveys carried out in 1992 and 1998 along the continental margin and oceanic crust of sw iberia this mcs data set shows the evidence of the compressional deformation which involves both the continental and the oceanic crust of the study area the area of deformation extends from the southern border of the tagus abyssal plain to the seine abyssal plain encompassing the continental margin of sw portugal most of the structures observed are probably related to a mid miocene phase of africa europe plate convergence in this paper we discuss the recent advances on the identification of the tectonic structures that are still active and that may generate great earthquakes and tsunamis the tectonic structures identified are located respectively at the guadalquivir bank along the eastern border of the horseshoe abyssal plain and along the southern continental slope of sw portugal

storminess and vulnerability along the atlantic coastlines of europe analysis of storm records and of a greenhouse gases induced climate scenario abstract identification of the distinctive circulation patterns of storminess on the atlantic margin of europe forms the main objective of this study dealing with storm frequency intensity and tracking the climatology of the extratropical cyclones that affect this region has been examined for the period 1940 1998 coastal meteorological data from ireland to spain have been linked to the cyclone history for the north atlantic in the analysis of storm records for european coasts the study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the north atlantic oscillation nao results indicate a seasonal shift in the wind climate with regionally more severe winters and calmer summers established this pattern appears to be linked to a northward displacement in the main north atlantic cyclone track an experiment with the echam4 a gcm at high resolution t106 has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region the experiment consists of 1 a 30 year control time slice representing present day equivalent co 2 concentrations and 2 a 30 year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent co 2 concentrations the boundary conditions have been obtained from an atmosphere ocean coupled oa gcm simulation at low horizontal resolution an algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones for most of the northern part of the study region covering ireland and scotland results describe the establishment by ca 2060 of a tendency for fewer but more intense storms the impacts of these changes in storminess for the vulnerability of european atlantic coasts are considered for low lying exposed and soft sedimentary coasts as in ireland these changes in storminess are likely to result in significant localised increases in coastal erosion

seismotectonics of portugal and its adjacent atlantic area abstract a study of focal mechanisms of earthquakes and stress indicators are presented for portugal and its adjacent atlantic margins recently riberio et al 1996 published a work on this subject in this study we introduce new focal mechanisms of nine earthquakes we use these results together with 12 other focal mechanisms and the main tectonic features in the region to define more accurately the type of mechanism and the stress pattern of the region all the focal mechanisms used in this study differ partially but are compatible with the regional stress field the stress indicators resulting from focal mechanisms and other geological and geophysical data show that the portugal continental and its atlantic margins are under horizontal pressure in nnw sse direction with a greater proportion of strike slip and reverse oblique mechanisms for the whole area

different frequencies and triggers of canyon filling and flushing events in nazare canyon offshore portugal submarine canyons are one of the most important pathways for sediment transport into ocean basins for this reason understanding canyon architecture and sedimentary processes has importance for sediment budgets carbon cycling and geohazard assessment despite increasing knowledge of turbidity current triggers the down canyon variability in turbidity current frequency within most canyon systems is not well constrained new ams radiocarbon chronologies from canyon sediment cores illustrate significant variability in turbidity current frequency within nazare canyon through time generalised linear models and cox proportional hazards models indicate a strong influence of global sea level on the frequency of turbidity currents that fill the canyon radiocarbon ages from basin sediment cores indicate that larger canyon flushing turbidity currents reaching the iberian abyssal plain have a significantly longer average recurrence interval than turbidity currents that fill the canyon the recurrence intervals of these canyon flushing turbidity currents also appear to be unaffected by long term changes in global sea level furthermore canyon flushing and canyon filling have very different statistical distributions of recurrence intervals this indicates that the factors triggering and thus controlling the frequency of canyon flushing and canyon filling events are very different canyon filling appears to be predominantly triggered by sediment instability during sea level lowstand and by storm and nepheloid transport during the present day highstand canyon flushing exhibits time independent behaviour this indicates that a temporally random process signal shredding or summation of non random processes that cannot be discerned from a random signal are triggering canyon flushing events

sediment instability on the portuguese continental margin under abrupt glacial climate changes last 60 kyr abstract it is well established that orbital scale sea level changes generated larger transport of sediments into the deep sea during the last glacial maximum than the holocene however the response of sedimentary processes to abrupt millennial scale climate variability is rather unknown frequency of distal turbidites and amounts of advected detrital carbonate are estimated off the lisbon setubal canyons core md03 2698 at 4602 mwd within a chronostratigraphy based on radiometric ages oxygen isotopes and paleomagnetic key global anomalies we found that 1 higher frequency of turbidites concurred with northern hemisphere coldest temperatures greenland stadials gs including heinrich h events but more than that an escalating frequency of turbidites starts with the onset of global sea level rising and warming in antarctica and culminates during h events at the time when rising is still in its early mid stage and the atlantic meridional overturning circulation amoc is re starting this short time span coincides with maximum gradients of ocean surface and bottom temperatures between gs and antarctic warmings antarctic isotope maximum aim 17 14 12 8 4 2 and rapid sea level rises 2 trigger of turbidity currents is not the only sedimentary process responding to millennial variability land detrital carbonate with a very negative bulk 18o signature enters the deep sea by density driven slope lateral advection accordingly during gs 3 possible mechanisms to create slope instability on the portuguese continental margin are sea level variations as small as 20 m and slope friction by rapid deep and intermediate re accommodation of water masses circulation 4 common forcing mechanisms appear to drive slope instability at both millennial and orbital scales

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

sediment dynamics and post glacial evolution of the continental shelf around the blanes submarine canyon head nw mediterranean abstract the blanes submarine canyon bc deeply incises the catalan continental shelf in the nw mediterranean sea as a consequence of the closeness only 4 km of its head to the coastline and the mouth of the tordera river the canyon has a direct influence on the shelf dispersal system as it collects large amounts of sediment mainly during high energy events multibeam bathymetry backscatter imagery and very high resolution seismic reflection profiles have allowed characterizing the morphology of the continental shelf around the canyon head also identifying sediment sources and transport pathways into the canyon the morphological data have also been used to reconstruct the evolution of the continental shelf during the last sea level transgression so that the current understanding of shelf to canyon sediment exchanges through time could be improved the continental shelf surrounding the bc consists of both depositional and erosional or non depositional areas depositional areas display prominent sediment bodies a generally smooth bathymetry and variable backscatter these include i an area of modern coarse grained sediment accumulation that comprises the inner shelf ii a modern fine grained sedimentation area on the middle shelf offshore tossa de mar and iii a modern sediment depleted area that covers most of the middle and outer shelf to the west of the canyon head erosional and non depositional areas display a rough topography and high backscatter and occur primarily to the east of the canyon head where the arrival of river fed inputs is very small in agreement with this pattern the continental shelf north and west of the canyon head likely is the main source of shelf sediment into the canyon to the north a pattern of very high backscatter extends from the coastline to the canyon head suggesting the remobilization and off shelf export of fines additionally relict near shore sand bodies developed over the barcelona shelf that extend to the canyon head rim constitute a source of coarse sediment high energy processes namely river floods and coastal storms are the main controls over the river shelf canyon sediment exchange river floods increase the delivery of terrigenous particles to the coastal system storms mainly from the east remobilize the sediment temporarily accumulated on the shelf towards the canyon head so that the finer fractions are preferentially removed and a coarse lag is normally left on the shelf floor exceptionally very strong storms also remove the coarse fractions from the shelf drive them into the canyon processes like dense shelf water cascading which is much more intense in canyons to the north of bc and the northern current also contribute to the transport of suspended sediment from far distant northern sources during the last post glacial transgression the bc had a strong influence on the evolution of the inner continental margin as it interrupted the shelf sediment dispersal system by isolating the shelves to its north and south named la planassa and barcelona shelves respectively

evaluating optical lightness as a proxy for carbonate content in marine sediment cores abstract optical lightness is increasingly being used as a proxy for the carbonate content of marine sediment we compared three measurements of optical lightness gray scale brightness and l to carbonate content to test the reliability of these measurements as carbonate content proxies in five piston cores from isotope stages 1 though 6 0 130 ka all measures of optical lightness are reasonable proxies of relative but not absolute changes in carbonate content in contrast in the upper sediments of odp hole 997a which are holocene to pliocene in age lightness values in only the top 10 m of the 180 m analyzed exhibit a strong correlation to carbonate content to better understand which factors control the optical lightness of sediments we analyzed samples in which carbonate content remained constant while the composition of three common clay minerals chlorite illite and kaolinite was varied kaolinite even at a concentration of 20 did not significantly change optical lightness however 20 illite reduced optical lightness by 30 and 20 chlorite reduced lightness by 20 we conclude that regional and temporal changes in the composition of the non carbonate sediment fraction may significantly alter the relationship between lightness and carbonate content we recommend that care must be taken when applying these measures to sediment sequences which span long time intervals or to sediment samples taken over a broad geographical areas

near bottom particulate matter dynamics in the nazare submarine canyon under calm and stormy conditions two mooring lines equipped with near bottom sediment traps were deployed in the axis of the nazare submarine canyon at similar to 1600 and similar to 3300 m depth respectively we studied time series of particle flux composition biogenic silica carbonates organic matter and lithogenic fractions granulometry mineralogy and pb 210 concentration of particulate matter over five sediment trap deployments between october 2002 and december 2004 current meters equipped with turbidimeters were also deployed at trap depths to monitor the water flow temperature salinity and suspended particle concentration the composition of the collected particles was fairly constant year round dominated by the lithogenic fraction and with oc n ratios in the range 11 21 suggesting an important terrigenous influence inside the canyon the results show contrasting dynamic environments in the upper 1600 m depth and middle 3300 m depth canyon high current speeds spring tides up to 80 cm s 1 and high apparent mass fluxes of particulate matter mean 65 g m 2 d 1 maximum 265 g m 2 d 1 are permanent at the shallowest station at the deepest site fluxes were below 10 g m 2 d 1 most of the time and the annual flux was governed by events of sharp flux increase storms affecting the continental shelf during autumn and winter are a major driver of down canyon dispersal of sediments to the middle canyon and beyond important nepheloid activity developed inside the canyon in response to storms with significant wave heights between 4 and 6 m as testified by turbidimeters deployed in midwater and near the seabed at 1600 m water depth on three occasions during the study period significant wave heights of incident storms surpassed 7 m leading to notable episodes of down canyon transport that were clearly observed in the middle canyon during one of these stormy periods january 2003 a sediment gravity flow transporting unusual quantities of sand and coastal plant debris was observed at 3200 m however a storm with significant wave heights as low as 5 m was apparently able to trigger a sediment gravity flow reaching beyond the middle canyon the role of storms in the offshore dispersal of sediments is clearly relevant but seems to be modulated by synergic factors such as river flooding

in situ measurements of velocity structure within turbidity currents 1 turbidity currents are thought to be the main mechanism to move 500 000 m3 of sediments annually from the head of the monterey submarine canyon to the deep sea fan indirect evidence has shown frequent occurrences of such turbidity currents in the canyon but the dynamic properties of the turbidity currents such as maximum speed duration and dimensions are still unknown here we present the first ever in situ measurements of velocity profiles of four turbidity currents whose maximum along canyon velocity reached 190 cm s two turbidity currents coincided with storms that produced the highest swells and the biggest stream flows during the year long deployment

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 new attenuation relation for peak horizontal acceleration of strong earthquake ground motion in japan abstract a new attenuation relation for peak horizontal acceleration applicable to the near source region in japan is developed the data base consists of 1372 horizontal components of peak ground acceleration from 28 earthquakes in japan and 15 earthquakes in the united states and other countries coefficients describing the decrease in acceleration with increasing distance found by most previous studies of japanese data are significantly smaller than those found by analyzing individual earthquakes this phenomenon is examined and found to result from use of general nonstratified multiple regression analyses the present analysis uses a two step stratified regression procedure and an attenuation model that accounts for geometrical spreading and anelastic attenuation but has magnitude independent shape at very short distances the resulting relation in japan is log 10 a 0 41 m log 10 r 0 032 10 0 41 m 0 0034 r 1 30 where a is the mean of the peak acceleration from two horizontal components at each site cm sec 2 r the shortest distance between site and fault rupture km and m the surface wave magnitude the median estimate of peak horizontal acceleration at the source region is 620 cm sec 2 independent of earthquake magnitude effects of four different ground condition rock hard medium and soft soils on the attenuation relation are also examined average peak horizontal accelerations for the rock and the soft soil sites are 60 and 140 per cent respectively of the value predicted from the equation

across shelf sediment transport since the last glacial maximum southern california margin correlation of continental shelf slope stratigraphy in santa monica bay southern california with ocean drilling program records for nearby slope basin sites has illuminated the timing and scale of terrigenous sediment dispersal on margin since the last glacial maximum lgm marine flooding surfaces preserved in a transgressive sequence on the santa monica shelf provide a key link between base level elevation and sediment transport across shelf sediment accumulation rates at slope basin sites were maximal ca 15 10 ka well after the lgm decreased during the 12 9 ka transition from fluvial estuarine to fully marine conditions on the shelf and decelerated throughout the holocene to 30 75 of their values at the lgm the deceleration is interpreted to manifest a landward shift in the margin depocenter with the onset of transgressive sedimentation beginning when sea level surmounted the shelf edge ca 13 ka as predicted by sequence stratigraphic models however the records make clear that factors other than base level modulated slope basin accumulation rates during the deglaciation

the record of historic earthquakes in lake sediments of central switzerland deformation structures in lake sediments in central switzerland can be attributed to strong historic earthquakes the type and spatial distribution of the deformation structures reflect the historically documented macroseismic intensities thus providing a useful calibration tool for paleoseismic investigations in prehistoric lake sediments the swiss historical earthquake catalogue shows four moderate to strong earthquakes with moment magnitudes of mw 5 7 to mw 6 9 and epicentral intensities of i0 vii to i0 ix that affected the area of central switzerland during the last 1000 years these are the 1964 alpnach 1774 altdorf 1601 unterwalden and 1356 basel earthquakes in order to understand the effect of these earthquakes on lacustrine sediments four lakes in central switzerland sarner see lungerer see baldegger see and seelisberg seeli were investigated using high resolution seismic data and sediment cores the sediments consist of organicand carbonate rich clayey to sandy silts that display fine bedding on the centimeter to millimeter scale the sediments are dated by historic climate and environmental records 137 cs activity and radiocarbon ages deformation structures occur within distinct zones and include large scale slumps and rockfalls as well as small scale features like disturbed and contorted lamination and liquefaction structures these deformations are attributed to three of the abovementioned earthquakes the spatial distribution of deformation structures in the different lakes clearly reflects the historical macroseismic dataset lake sediments are only affected if they are situated within an area that underwent groundshaking not smaller than intensity vi to vii we estimate earthquake size by relating the epicentral distance of the farthest liquefaction structure to earthquake magnitude this relationship is in agreement with earthquake size estimations based on the historical dataset d 2004 elsevier b v all rights reserved

eustatic control of turbidites and winnowed turbidites global changes in sea level primarily the results of tectonism and glaciation control deep sea sedimentation during periods of low sea level the frequency of turbidity currents is greatly increased episodes of low sea level also cause vigorous contour currents which winnow away the fines of turbidites in the rock record the occurrence of most turbidites and winnowed turbidites closely corresponds to global lowstands of paleo sea level this observation may be useful in predicting the occurrence of deep sea reservoir facies in the geologic record

linking continental slope failures and climate change testing the clathrate gun hypothesis it has been suggested that the release of clathrates rather than expansion of wetlands is the primary cause of the rapid increases observed in the ice core atmospheric methane record during the pleistocene because submarine sediment failures can involve as much as 5000 gt of sediment and have the capacity to release vast quantities of methane hydrates one of the major tests of the clathrate gun hypothesis is determining whether the periods of enhanced continental slope failure and atmospheric methane correlate to test the clathrate gun hypothesis we have collated published dates for submarine sediment failures in the north atlantic sector and correlated them with climatic change for the past 45 k y more than 70 by volume of continental slope failures during the past 45 k y was displaced in two periods between 15 and 13 ka and between 11 and 8 ka both these intervals correlate with rising sea level and peaks in the methane record during the bolling allerod and preboreal periods these data support the clathrate gun hypothesis for glacial interglacial transitions the data do not however support the clathrate gun hypothesis for glacial millennial scale climate cycles because the occurrence of sediment failures correlates with heinrich events i e lows in sea level and atmospheric methane a secondary use of this data set is the insight into the possible cause of continental slope failures glacial period slope failures occur mainly in the low latitudes and are associated with lowering sea level this finding suggests that reduced hydrostatic pressure and the associated destabilization of gas hydrates may be the primary cause the bolling allerod sediment failures were predominantly low latitude suggesting an early tropical response to deglaciation e g enhanced precipitation and sediment load to the continental shelf or warming of intermediate waters in contrast sediment failures during the preboreal period and the majority of the holocene occurred in the high latitudes suggesting either isostatic rebound related earthquake activity or reduced hydrostatic pressure caused by isostatic rebound causing destabilization of gas hydrates

recent sediment transport and deposition in the nazare canyon portuguese continental margin processes pathways and fluxes of sediment transport and deposition in the nazare submarine canyon portuguese continental margin were investigated by water column profiling of suspended particulate matter recording of near bottom currents and suspended particulate matter fluxes with benthic landers and by analysis of surface sediment cores the results show that fine grained suspended sediment from the adjacent shelf is captured in the upper canyon and actively transported through the canyon to the abyssal plain under influence of tidal currents and intermittent sediment gravity flows tidal currents are actively resuspending and transporting sediment in the upper to middle canyon as reflected by high concentration of suspended particles in bottom waters high horizontal and vertical sediment fluxes in the bottom water layer and high sediment accumulation rate on the seabed diminishing strength of tidal currents leads to focussed sediment deposition in the middle canyon further transport of sediments toward the lower canyon takes place predominantly by sediment gravity flows occurring on yearly or longer timescale turbidity currents strong enough to transport sand sized material to the lower canyon occur only on centennial or longer timescales

determination of turbidity current erosional characteristics from reworked coccolith assemblages canary basin north east atlantic turbidites contain mixtures of sediments of various ages these sediments can include both material that was eroded to form the initial turbidity current plus additions derived from erosion of the sea floor during transport it has been possible to interpret the age range of sediments incorporated into individual turbidites from the madeira abyssal plain by examining the proportions of microfossil coccolith species that they contain the pelagic record of coccoliths is well known for the quaternary period and shows a succession of dominant species or acmes each lasting a few tens of thousand years hence erosion of sediment representing more than a few tens of thousand years will produce coccolith mixtures not seen in the pelagic record but dependent upon the age range of the sediments that were eroded this age range can be estimated by comparison with synthetic ratios of coccolith species created by combining ratios of species from successively older layers in the pelagic record these can then be compared with the ratios found in individual turbidites until a match is found the results show age ranges of 54 500 kyr for the sediment mixture in seven turbidites from the madeira abyssal plain since the volumes of these turbidites are also known and accumulation rates in their source areas can be estimated it is possible to determine both the thickness and the area of the eroded sediment mass that generated the turbidity current minimum depths of erosion on the north west african continental margin vary from 8 to 50 m and minimum areas eroded from 1600 to 5800 km2 none of the turbidites examined contains a significant excess of surface sediment suggesting that once formed the turbidity currents that transported them were virtually non erosional and that they travelled several hundred kilometres in this state

comparison between holocene and marine isotope stage 11 sea level histories the exceptionally long interglacial warm period known as marine isotope stage 11 mis 11 428 397 ky ago vs ky vs kyr is often considered as a potential analogue for future climate development in the absence of human influence we use a new high resolution sea level record a globally integrated ice volume signal to compare mis 11 and the current interglacial holocene it is found that sea level rise into both interglacials started over similar timescales relative to the respective insolation increases and progressed up to 50 m at similar rates of 1 0 1 2 m per century subsequent weak insolation changes anomalously prolonged the mis11 deglaciation over more than 20 ky the main sea level highstand was achieved at the second mis 11 insolation maximum with a timing closely equivalent to that of the holocene highstand compared to its single insolation maximum consequently while mis 11 was an exceptionally long period of interglacial warmth its ice volume minimum sea level highstand lasted less than 10 ky which is similar to the duration of other major interglacials comparison of the ends of mis 11 and the holocene based on timings relative to their respective maxima in mean 21 june insolation at 65 n suggests that the end of holocene conditions might have been expected 2 0 2 5 ky ago instead interglacial conditions have continued with co2 temperature and sea level remaining high or increasing this apparent discrepancy highlights the need to consider that a comparisons may need to focus on other orbital control indices in which case the discrepancy can vanish and or b the feedback mechanisms that dominate the planetary energy balance may have become decoupled from insolation during the past 2millennia

a complete terrestrial radiocarbon record for 11 2 to 52 8 kyr b p radiocarbon 14c provides a way to date material that contains carbon with an age up to 50 000 years and is also an important tracer of the global carbon cycle however the lack of a comprehensive record reflecting atmospheric 14c prior to 12 5 thousand years before the present kyr b p has limited the application of radiocarbon dating of samples from the last glacial period here we report 14c results from lake suigetsu japan 35 35 n 135 53 e which provide a comprehensive record of terrestrial radiocarbon to the present limit of the 14c method the time scale we present in this work allows direct comparison of lake suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels

turbidite depositional architecture across three interconnected deep water basins on the north west african margin the moroccan turbidite system mts on the north west african margin extends 1500 km from the head of the agadir canyon to the madeira abyssal plain making it one of the longest turbidite systems in the world the mts consists of three interconnected deep water basins the seine abyssal plain sap the agadir basin and the madeira abyssal plain map connected by a network of distributary channels excellent core control has enabled individual turbidites to be correlated between all three basins giving a detailed insight into the turbidite depositional architecture of a system with multiple source areas and complex morphology large volume 100 km3 turbidites sourced from the morocco shelf show a relatively simple architecture in the madeira and seine abyssal plains sandy bases form distinct lobes or wedges that thin rapidly away from the basin margin and are overlain by ponded basin wide muds however in the agadir basin the turbidite fill is more complex owing to a combination of multiple source areas and large variations in turbidite volume a single very large turbidity current 200 300 km3 of sediment deposited most of its sandy load within the agadir basin but still had sufficient energy to carry most of the mud fraction 500 km further downslope to the map large turbidity currents 100 150 km3 of sediment deposit most of their sand and mud fraction within the agadir basin but also transport some of their load westwards to the map small turbidity currents 35 km3 of sediment are wholly confined within the agadir basin and their deposits pinch out on the basin floor turbidity currents flowing beyond the agadir basin pass through a large distributary channel system individual turbidites correlated across this channel system show major variations in the mineralogy of the sand fraction whereas the geochemistry and micropalaeontology of the mud fraction remain very similar this is interpreted as evidence for separation of the flow with a sand rich erosive basal layer confined within the channel system overlain by an unconfined layer of suspended mud large volume turbidites within the mts were deposited at oxygen isotope stage boundaries during periods of rapid sea level change and do not appear to be specifically connected to sea level lowstands or highstands this contrasts with the classic fan model which suggests that most turbidites are deposited during lowstands of sea level in addition the three largest turbidites on the map were deposited during the largest fluctuations in sea level suggesting a link between the volume of sediment input and the magnitude of sea level change

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

seismicity source mechanisms and tectonics of the azores gibraltar plate boundary abstract a study and partial revision of the seismicity and source mechanisms of earthquakes are presented for the oceanic plate boundary of eurasia and africa from the azores islands to the strait of gibraltar focal mechanisms of 36 earthquakes wave form modelling of 4 and seismic moments and dimensions of 28 have been calculated these results indicate that the boundary is divided into three sections with different characteristics the azores the central section and the east section the azores section has high seismicity of moderate magnitude and a low slip rate 0 76 cm yr the predominant mechanism is normal or transform faulting with horizontal tensions on average in a n25 e direction in the central section large earthquakes occur with strike slip right lateral motion along faults in an e w direction there is a high slip rate 3 39 cm yr the east section is of more complex nature large earthquakes also occur but the predominant mechanism is reverse faulting with a horizontal pressure axis in the n30 w direction resulting in underthrusting of africa from the slip vectors the pole of rotation for the african plate is located at 28 2 n 21 1 w nearer to the boundary than previous locations close to the continent there is a continuation in the ocean crust of some structural features of the iberian peninsula

northern hemisphere ice sheet responses to past climate warming during periods of glaciation the northern hemisphere was swathed by large ice sheets a review of ice sheet retreat during the last two deglaciations shows that land based ice sheets responded rapidly to rising summer insolation whereas marine based ice sheets underwent a delayed but more abrupt response

radiation and cloud observations on a high arctic plateau ice cap transmission du rayonnement solaire sous differentes conditions de nebulosite au n e des iles ellesmeres

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

near synchronous and delayed initiation of long run out submarine sediment flows from a record breaking river flood offshore taiwan subsea fiber optic telecommunication cables can break under fast sediment flows that travel 100s of kilometers through the deep ocean in response to earthquakes and submarine landslides similar flows are inferred to form from major river floods whose sediment laden waters plunge and travel along the seabed however the complex initiation of flood related flows and their hazard potential have not been observed until now here we use cable fault data from the gaoping canyon manila trench off taiwan to show that a major river flood formed during typhoon morakot 2009 generated two long run out destructive sediment flows one during peak flood and the other 3 days later the latter flow was more damaging with speeds and run out similar to that of landslide triggered turbidity currents formed in the same catchment if the second flow was due to remobilized canyon sediment it occurred during low earthquake mw 2 0 activity suggesting other triggering mechanisms

sea level changes forced ice breakouts in the last glacial cycle new results from coral terraces abstract sea level cycles recorded by coral terraces at huon peninsula hp in papua new guinea match rapid climate changes that occurred between 30 000 and 65 000 years ago seen in greenland ice cores and marine sediments each cycle of 6000 7000 years ended with a sea level rise of 10 15 m lasting 1000 2000 years following a longer period of falling sea level precise dating shows that each rise corresponds to a heinrich episode of ice rafted detritus in north atlantic signalling massive ice outbreak from north america sea level may be the trigger that forced near synchronous breakouts of ice from north america and eastern greenland the hp sea level changes also correspond to similar cycles in benthic oxygen isotopes reported from the north atlantic which are too large to be explained entirely in terms of ice volumes jointly the sea level and isotope records suggest that the north atlantic deep ocean cooled as sea level fell and warmed as sea level rose in each 6000 year cycle

topography climate and ice masses a review topography acts as a filter between regional climate and the consequent response of a glacier or ice sheet it influences the mass and energy inputs and modifies the ice dynamics the evolution of the ice sheet surface and over longer time scales of the bed topography modulates the climatic forcing until we have a better understanding of these topographic linkages the use of geophysical signals from former ice masses to determine palaeoclimates must be regarded as fundamentally flawed

recent sediment transport and deposition in the lisbon setubal and cascais submarine canyons portuguese continental margin abstract recent sediment transport and deposition in the lisbon setubal and cascais submarine canyons portuguese continental margin were investigated on the basis of water column profiles of suspended particulate matter records of near bottom currents and settling fluxes of particulate matter obtained with benthic landers and analysis of surface sediments the results show that fine grained predominantly lithogenic sediment derived from adjacent shelf areas accumulates in the upper reaches of the canyons sediment deposited further down in the middle and lower reaches of the canyons is essentially similar to the hemipelagic sediment found on the adjacent continental slope indicating that down canyon transport of sediment from the upper to the lower canyon is limited tidal currents measured at various depths in the lisbon setubal canyon appear sufficiently strong to resuspend and transport sediment but net up canyon flow of the bottom water may retain shelf derived lithogenic sediment in the upper canyon sediment gravity flows which in the nearby nazare canyon are an effective mechanism for down canyon sediment transport appear rare in the lisbon setubal canyon and probably also in the cascais canyon turbidity current events recorded in the sedimentary record of the canyons may correspond to seismic events of 1969 and 1755 ad

calculating erosion by deep sea turbidity currents during initiation and flow turbidity currents transport massive amounts of sediment from continental margins to the deep sea individual flows can catastrophically remove and redeposit as turbidites many hundreds of cubic kilometres of material1 2 with the larger events reaching the bottom of the continental slope to form the abyssal plains3 here we show that the age range of sediments in individual turbidites can be used directly to estimate both the thickness of failed sediment in the source region even when its exact location is unknown and the extent to which the turbidity current caused erosion of the sea bed our method involves the comparison of the abundance ratios of microfossil coccolith species in turbidites with those in the ocean margin sediments of the source region analysis of a recently emplaced turbidite on the madeira abyssal plain shows that it contains a mixture of sediments with an age range of about 200 000 years equivalent to the failure of a block of sediment about 15 m deep radiocarbon dating and coccolith ratios show that the turbidite contains only about 12 of recent near surface sediment indicating that this turbidity current caused surprisingly little erosion en route

seismic triggering of landslides and turbidity currents offshore portugal 1 sediments in deep water basins often include turbidites that record sediment input from adjacent continental margins in seismically active areas where turbidity currents are triggered by earthquakes the basinal turbidite sequence may thus contain a record of palaeoseismicity which can be used to infer the frequency of earthquakes affecting the margins of the basin this is particularly useful where large earthquakes have a recurrence interval than is greater than the historical record however turbidity currents can be triggered by several processes and it is often difficult to trace individual turbidites to their precise source areas and to assign a definite trigger to a particular turbidite here we demonstrate that turbidites emplaced at 6600 and 8300 cal yr bp in the tagus abyssal plain off portugal correlate with erosional hiatuses in two submarine canyons on the continental margin the turbidites are sourced from simultaneous landsliding in both canyons requiring regional triggers interpreted as earthquakes an earthquake recurrence interval for the continental margin of 4000 years is estimated by extrapolation to deeper turbidites in the basin sequence however the example of the 1755 earthquake which caused widespread devastation in southwest iberia shows that palaeoseismic interpretations must be made with caution the 1755 earthquake had a magnitude 8 5 and yet the associated turbidite in the abyssal plain is typically 5 cm thick while older turbidites can be 1 m thick given the large 1755 earthquake magnitude the difference in turbidite thickness is unlikely to be related to the relative size of triggering earthquakes instead we suggest that the offshore location of the 1755 earthquake coupled with low sedimentation rates during the holocene may have limited the size of the associated turbidite

can turbidites be used to reconstruct a paleoearthquake record for the central sumatran margin turbidite paleoseismology aims to use submarine gravity flow deposits turbidites as proxies for large earthquakes a critical assumption being that large earthquakes generate turbidity currents synchronously over a wide area we test whether all large earthquakes generate synchronous turbidites and if not investigate where large earthquakes fail to do this the sumatran margin has a well characterized earthquake record spanning the past 200 yr including the large magnitude earthquakes in 2004 mw 9 1 and 2005 mw 8 7 sediment cores collected from the central sumatran margin in 2009 reveal that surprisingly few turbidites were emplaced in the past 100 150 yr and those that were deposited are not widespread importantly slope basin deposits preserve no evidence of turbidites that correlate with the earthquakes in 2004 and 2005 although recent flow deposits are seen in the trench adjacent slope basins and adjacent pairs of slope basin and trench sites commonly have different sedimentary records and cannot be correlated these core sites from the central sumatran margin do not support the assumption that all large earthquakes generate the widespread synchronous turbidites necessary for reconstructing an accurate paleoearthquake record