holocene coastal glaciation of alaska holocene uctuations of the three cirque glaciers on the seward peninsula and ve groups of tidewater and land terminating glaciers along the northernmost gulf of alaska provide a proxy record of late holocene climatic change furthermore the movements of the coastal glaciers were relevant to late holocene native american migration the earliest expansion was recorded about 6850 yr bp by hubbard glacier at the head of yakutat bay in the gulf of alaska however its down fjord advance to the bay mouth was delayed until 2700 bp similarly expansions of the icy bay bering and mccarty glaciers occurred near their present termini by 3600 3000 bp compatible with marked cooling and precipitation increases suggested by the alaskan pollen record decrease in glacier activity 2000 bp was succeeded by advances of gulf coastal glaciers between 1500 and 1300 bp correlative with early medieval expansions across the northern hemisphere a medieval optimum encompassing at least a few centuries prior to ad 1200 is recognized by general retreat of land terminating glaciers but not of all tidewater glaciers little ice age advances of land based glaciers many dated with the precision of tree ring cross dating were centered on the middle 13th or early 15th centuries the middle 17th and the last half of the 19th century a d strong synchrony of these events across coastal alaska is evident 2000 elsevier science ltd all rights reserved

mw 8 6 sumatran earthquake of 11 april 2012 rare seaward expression of oblique subduction the magnitude 8 6 and 8 2 earthquakes off northwestern sumatra on 11 april 2012 generated small tsunami waves that were recorded by stations around the indian ocean combining differential travel time modeling of tsunami waves with results from back projection of seismic data reveals a complex source with a significant trench parallel component the oblique plate convergence indicates that 20 50 m of trench parallel displacement could have accumulated since the last megathrust earthquake only part of which has been taken up by the great sumatran fault this suggests that the remaining trench parallel motion was released during the magnitude 8 6 earthquake on 11 april 2012 within the subducting plate the magnitude 8 6 earthquake is interpreted to be a result of oblique subduction as well as a reduction in normal stress due to the occurrence of the sumatra andaman earthquake in 2004

tsunamigenic potential of an incipient submarine slope failure in the northern south china sea abstract tsunamis generated by submarine slope failures have the potential to cause devastating consequences the combination of 1 dense population and infrastructure along the coastline of south china sea scs and 2 frequent slope failures occurring along the marine slopes of the scs points to the vulnerability of china and surrounding countries to submarine landslide related tsunamis a geohazard that is still poorly understood in the scs in this study the tsunamigenic potential of a possible future slope failure along the continental slope of the scs is estimated after being constrained by geophysical data interpretation and numerical modeling results suggest that a slope failure of a scale similar to past events would likely generate a catastrophic tsunami on the numerous islands scattered throughout the northern scs with maximum wave height of 21 8 m furthermore the highly populated coastlines of scs would experience widespread tsunami events with maximum wave height of 6 m and little advance warning this preliminary study suggests that tsunamis generated by submarine slope failure are a potentially significant geohazard to the coastlines of scs and should be considered during the assessment of scs geohazard

a viscoelastic and afterslip postseismic deformation model for the 1964 alaska earthquake 1 we developed a 3 d viscoelastic model in concert with an afterslip model to describe the postseismic deformation following the 1964 alaska earthquake our model incorporates a realistic geometry including an elastic slab with very low dip angle these geometric factors are important and require a reanalysis of the 1964 coseismic model our coseismic model differs from previous models in that the montague island splay fault extends farther along the kenai peninsula coast and as a result slip on the megathrust in that region is smaller we computed postseismic deformation models using a range of mantle viscosities with maxwell relaxation time of 1 to 50 years with a best estimate of 20 years the viscoelastic model explains most of the trenchward motion observed in the present velocity field but has little impact on cumulative 1965 to present uplifts after removing the viscoelastic response the largest residual cumulative uplifts were located downdip from areas of largest coseismic slip area and we explain them using an afterslip model constrained in space by the observed cumulative postseismic uplifts and in time by tide gauge records no single mechanism can explain both the 30 years of cumulative uplift and the present velocities but a combination of viscoelastic relaxation afterslip interseismic elastic deformation and motion of southern alaska relative to north america explains the first order features of the observations forty years after the earthquake the present day velocities contain a significant component of postseismic deformation so very long lived postseismic deformation plays an important role in the subduction zone earthquake cycle for great earthquakes

stratigraphie framework for the cambrian ordovician rift and passive margin successions from southern quebec to western newfoundland the taconian humber zone stretches from western newfoundland to southern quebec the early cambrian slope succession in newfoundland is found in the curling group whereas in quebec various units were deposited during that first time slice biostratigraphic data allow correlation of the curling group with the labrador group in newfoundland and with the newly time constrained slope succession in quebec the end of the rift drift transition is marked by a sea level lowstand at the end of the early cambrian the middle cambrian to latest early ordovician passive margin history recorded five cyclic sea level fluctuations three of these cycles are recorded in the shallow marine middle to late cambrian platform port au port group and slope sediments preserved in the cow head and northern head groups in newfoundland the biostratigraphic information assists correlation with cambrian passive margin units in quebec major sea level lowstands are recognized along the continental margin in early middle late camb

role of increased marine silica input on paleo pco2 levels changing the supply of silica to the ocean may alter pco2 levels the increase in dust delivered to the ocean during glacial times increased the availability of silica for biological uptake the increased silica levels shifted species composition diatom populations increased and coccolith populations decreased decreasing the population of coccoliths decreased the flux of calcite to the sediments which in turn lowered pco2 levels enough to explain the glacial interglacial pco2 transition furthermore the contemporary increase in dust delivered to the ocean s mixed layer may be removing significant amounts of carbon dioxide from the atmosphere at present to set the stage this silica hypothesis is compared with the iron fertilization and nitrogen fixation hypotheses

submarine slides in glaciomarine sediments in some western norwegian fjords abstract submarine slides from four western norwegian fjords fjaerlandsfjord and ardalsfjord in the sognefjord and nordfjord and romsdalsfjord are studied sparker and high resolution seismic profiles are used to illustrate the thickness morphology and internal structure of the primary material as well as of the accumulated slides sediment cores are studied to calibrate the acoustic signals acoustic lamination is thought to represent sequences of variable density or some of the zones of fine sand and silt laminae which have acted as sliding planes these rapidly deposited layers constitute underconsolidated zones that are susceptible to liquefaction causing sliding of the overlying material along bedding planes or faults the morphology and structure of the slides are in some cases very similar to that of the mass movements described from continental slopes a 25 m deep and 1 km 2 wide plunge pool is formed in the sognefjord at the bottom of a 800 m high and 25 steep slide path down from the fjaerlandsfjord most of the slides are ancient but one slide increasing the fjord depth in an area of the inner nordfjord by 55 m most probably took place in 1967 the volumes of the slides are in the order of 3 30 10 6 m 3

rupture process of the 1964 prince william sound alaska earthquake from the combined inversion of seismic tsunami and geodetic data 1 four great earthquakes 1952 1960 1964 and 2004 have occurred since seismic monitoring began and only two since the installation of a global seismic network a reexamination of the 1964 m 9 2 prince william sound pws alaska earthquake is timely due to the 2004 sumatra earthquake because it adds constraints to the potential range of source parameters for these types of infrequent events and aids in the ability to predict the ground motions for other subduction zone including cascadia we first measured the durations of high frequency energy radiation from teleseismic p wave codas recorded by short period world wide standardized seismographic network wwssn sp instruments to put constraints on the earthquake rupture length the durations ranged between 250 and 600 s and are shorter in time between azimuths of 190 and 260 the fault length is estimated to range from 540 to 740 km rupturing at average speeds of 1 4 2 km s in a 220 238 direction we developed a multiple time window kinematic rupture model for the pws earthquake from the least squares inversion of teleseismic p waves tsunami tide gauge records and geodetic leveling survey observations based on the green s function technique we assume three major fault segments for the subduction zone dipping 6 12 based on geologic data the subfault size on the megathrust was set to 50 50 km the patton bay fault pbf imbricate thrust was assigned a 60 dip with a subfault size of 20 20 km we estimated a seismic moment of 5 52 1022 n m mw9 12 we identified three areas of major moment release on the pws segment near montague and middleton islands extending out to the trench beneath the portlock anticline on the cook segment between 58 n fracture zone and the kodiak bowie seamount chain and finally on the katmai segment off the coast of kodiak island extending to the trench our preferred rupture model has a peak slip of 14 9 m along the megathrust and 17 4 m along the pbf the addition of the pbf resulted in an 8 improvement in residuals and also had a significant effect on the overall slip distribution moment release occurred as deep as 50 km depth slab contour near the 350 c isotherm and mantle fore arc wedge which is about 10 20 km deeper than previous coupling depths

slip distribution of the 1952 tokachi oki earthquake m 8 1 along the kuril trench deduced from tsunami waveform inversion 1 we inverted 13 tsunami waveforms recorded in japan to estimate the slip distribution of the 1952 tokachi oki earthquake m 8 1 which occurred southeast off hokkaido along the southern kuril subduction zone the previously estimated source area determined from tsunami travel times hatori 1973 did not coincide with the observed aftershock distribution our results show that a large amount of slip occurred in the aftershock area east of hatori s tsunami source area suggesting that a portion of the interplate thrust near the trench was ruptured by the main shock we also found more than 5 m of slip along the deeper part of the seismogenic interface just below the central part of hatori s tsunami source area this region which also has the largest stress drop during the main shock had few aftershocks large tsunami heights on the eastern hokkaido coast are better explained by the heterogeneous slip model than previous uniform slip fault models the total seismic moment is estimated to be 1 87 1021 n m giving a moment magnitude of mw 8 1 the revised tsunami source area is estimated to be 25 2 103 km2 3 times larger than the previous tsunami source area out of four large earthquakes with m 7 that subsequently occurred in and around the rupture area of the 1952 event three were at the edges of regions with relatively small amount of slip we also found that a subducted seamount near the edge of the rupture area possibly impeded slip along the plate interface

lithofacies and seismic reflection interpretation of temperate glacimarine sedimentation in tarr inlet glacier bay alaska abstract high resolution seismic reflection profiles of sediment fill within tarr inlet of glacier bay alaska show seismic facies changes with increasing distance from the glacial termini five types of seismic facies are recognized from analysis of huntec and minisparker records and seven lithofacies are determined from detailed sedimentologic study of gravity vibro and box cores and bottom grab samples lithofacies and seismic facies associations and fjordfloor morphology allow us to divide the fjord into three sedimentary environments ice proximal iceberg zone and ice distal the ice proximal environment characterized by a morainal bank depositional system can be subdivided into bank back bank core and bank front subenvironments each of which is characterized by a different depositional subsystem a bank back subsystem shows chaotic seismic facies with a mounded surface which we infer consists mainly of unsorted diamicton and poorly sorted coarse grained sediments a bank core depositional subsystem is a mixture of diamicton rubble gravel sand and mud seismic reflection records of this subsystem are characterized by chaotic seismic facies with abundant hyperbolic diffractions and a hummocky surface a bank front depositional subsystem consists of mainly stratified and massive sand and is characterized by internal hummocky facies on seismic reflection records with significant surface relief and sediment gravity flow channels the depositional system formed in the iceberg zone environment consists of rhythmically laminated mud interbedded with thin beds of weakly stratified diamicton and stratified or massive sand and silt on seismic reflection profiles this depositional system is characterized by discontinuously stratified facies with multiple channels on the surface in the proximal zone and a single channel on the largely flat sediment surface in the distal zone the depositional system formed in the ice distal environment consists of interbedded homogeneous or laminated mud and massive or stratified sand and coarse silt this depositional system shows continuously stratified seismic facies with smooth and flat surfaces on minisparker records and continuously stratified seismic facies which are interlayered with thin weakly stratified facies on huntec records

planktonic foraminiferal assemblages in surface sediments from the southwest african continental margin abstract the relative abundance and distribution of planktonic foraminifera species on the southwest african continental margin have been determined from 152 surface sediment samples of the 23 recorded taxa only 8 make a significant contribution to the foraminiferal assemblages individual species proportions are closely related to the surface water hydrography of the benguela system and the associated upwelling phenomena three foraminiferal assemblages can be distinguished by correlation analysis on the abundances of the major taxa species composition of these assemblages range from polar taxa in the upwelling area left coiling neogloboquadrina pachyderma and globigerina quinqueloba to transitional taxa in the offshore oligotrophic environment globorotalia inflata and globorotalia truncatulinoides globigerina bulloides and right coiling neogloboquadrina pachyderma are preferentially distributed in the highly productive intermediate zone of the benguela system where upwelled and oligotrophic offshore waters mix variability of the hydrological processes upwelling intensity strength of the frontal features may be inferred from frequency variations of individual species and diversity patterns

a 400 kyr record of combustion oxygen demand in the western equatorial pacific evidence for a precessionally forced climate response we have developed a combustion analysis technique for sediments which measures the amount of o2 consumed by the reduced species we have measured this quantity which we call combustion oxygen demand cod on a carbonate rich sediment core from the ontong java plateau in the western equatorial pacific back to marine oxygen isotope stage 11 the precision of the cod technique is 6 3 mol o2 g 1 which corresponds to 0 0076 wt corg assuming oxidation of organic carbon dominates the signal the cod time series is characterized by values which are about twice as high during glacials as during interglacials the largest shift occurring from 401 mol o2 g 1 in midstage 6 to 144 mol o2 g 1 at 5e and is coherent with the oxygen isotope curve of globigerinoides sacculifer in the same core at the milankovitch frequencies of 100 and 41 kyr pronounced variations in the 19 23 kyr band suggest that the climate of the western equatorial pacific is sensitive to precessional forcing a response not apparent from other records obtained in this region

the 1964 prince william sound earthquake joint inversion of tsunami and geodetic data the 1964 prince william sound alaska earthquake mw 9 2 ruptured a large area beneath the continental margin of alaska from prince william sound to kodiak island a joint inversion of tsunami waveforms and geodetic data consisting of vertical displacements and horizontal vectors gives a detailed slip distribution two areas of high slip correspond to seismologically determined areas of high moment release the prince william sound asperity with average slip of 18 m and the kodiak asperity with average slip of 10 m the average slip on the fault is 8 6 m and the seismic moment is estimated as 6 3 1022 n m or over 75 of the seismic moment determined from long period surface waves

source and progression of a submarine landslide and tsunami the 1964 great alaska earthquake at valdez like many subduction zone earthquakes the deadliest aspects of the 1964 m 9 2 alaska earthquake were the tsunamis it caused the worst of these were generated by local submarine landslides induced by the earthquake these caused high runups engulfing several coastal towns in prince william sound in this paper we study one of these cases in detail the port valdez submarine landslide and tsunami we combine eyewitness reports preserved film and careful posttsunami surveys with new geophysical data to inform numerical models for landslide tsunami generation we review the series of events as recorded at valdez old town and then determine the corresponding subsurface events that led to the tsunami we build digital elevation models of part of the pretsunami and posttsunami fjord head delta comparing them reveals a 1500 m long region that receded 150 m to the east which we interpret as the primary delta landslide source multibeam imagery and high resolution seismic reflection data identify a 400 m wide chute with hummocky deposits at its terminus which may define the primary slide path using these elements we run hydrodynamic models of the landslide driven tsunamis that match observations of current direction maximum inundation and wave height at valdez old town we speculate that failure conditions at the delta front may have been influenced by manmade changes in drainage patterns as well as the fast retreat of valdez and other glaciers during the past century

remobilized cordon caulle 2011 tephra deposits in north patagonian watersheds resedimentation at deltaic environments and its implications abstract the argentinean side of the andean north patagonia is drained by several fluvio lacustrine systems flowing eastwards from their headwaters at the andes mountains towards large glacial lakes these watersheds are recurrently affected by the deposition of tephra erupted from the many active andean volcanos located in the southern volcanic zone this research focusses on two fluvial systems pireco and totoral pt located in nahuel huapi national park which were severely impacted by the cordon caulle 2011 eruption cc2011 we investigate particularly the resedimentation of pyroclastic materials on their lacustrine deltas and its potential implications considering 1 the deltas morphology and 2 mass wasting processes developing at the delta fronts original tephra fall deposits were registered at nahuel huapi national park in 2011 based on the isopach map we performed a gis based volume estimation of the deposit for the studied watersheds delta plain progradation from 2011 to 2017 was analyzed from satellite images we studied the temporal evolution of the subaqueous morphology and mass wasting processes at the delta fronts using high resolution bathymetric grids registered in 2011 2014 and 2017 during june 2011 the studied watersheds received a tephra input of 72 x 106m3 the significant progradation experienced by both deltas especially during the first month of the eruption was favored by 1 abundant precipitation at the watersheds concomitant to heavy tephra deposition and 2 the pre existing subaqueous morphology characterized by a wide shallow terrace bordering pt delta plains about six years after the beginning of cc2011 6 of the tephra fallen over the entire basins had been resedimented at the delta environments terrace and delta front totalizing 3 x 106t evidence of pre eruption and or co eruptive mass wasting processes occurring at pt delta fronts was found on november 2011 up to 30 m thick pyroclastic deposits were accumulated at pt delta fronts since november 2011 burying mass wasting features at the upper delta fronts a suspended sediment collector installed at the prodelta in 2012 detected hyperpycnal currents transporting pyroclastic materials these currents probably explain the development of mass movements at high depths such as the one that displaced and filled up the bottom sediment trap this frontally confined landslide initiated at a depth of 60 m and involved tephra and organic materials deposited at the lower part of totoral delta front because of their recent deposition and loose consolidation we propose that fresh tephra deposits at pt delta fronts could become particularly unstable and represent a potential hazard to failure especially if a strong earthquake affects the study area in the next years a landslide induced tsunami wave generated at these deltas would impact rural settlements located along the coasts of brazo rincon and probably reach the coastal city of villa la angostura

on the reconstruction of upwelling history namibia upwelling in context abstract eastern boundary upwelling is an important aspect of the modern ocean despite the relatively small area involved consequences of increased upwelling during the neogene as a result of intensifying trade winds include increased heat transport by the ocean increased mixing increased fractionation of phosphate from silicate and opportunities for evolution of new species coastal upwelling has been studied since the first decade of the 20th century the processes involved are complex and differ depending on geographic setting off namibia upwelling history has been studied by a number of drilling expeditions the last of these was odp leg 175 which occupied seven sites on the continental slope between walvis ridge and cape town during september and october of 1997 productivity proxies all along southwestern africa suggest the presence of increased upwelling and organic matter supply to the sea floor during glacial periods at the same time there is a decrease in the supply of diatoms and other siliceous plankton remains this is the walvis opal paradox established through the contrasting results of studies by diester haass 1985 and oberhansli 1991 we propose that the walvis opal paradox is fundamental to the understanding of glacial interglacial productivity fluctuations on a global scale furthermore a central feature of the history of late neogene upwelling off namibia is the matuyama opal maximum centered between gauss and olduvai magnetic chrons wefer et al proc odp 175 1998 it is due to the fact that diatom supply first increases during the gauss when the planet cools and then decreases again during additional cooling on entering the quaternary on a 400 000 year scale peak productions are coincident with or slightly lag maximum seasonal contrast potential in the high latitude insolation curve we suggest that this is further evidence that the nutrient content of thermocline waters was diminished during glacial periods the reasons why this should be so remain to be discovered

combined effects of tectonic and landslide generated tsunami runup at seward alaska during the mw 9 2 1964 earthquake we apply a recently developed and validated numerical model of tsunami propagation and runup to study the inundation of resurrection bay and the town of seward by the 1964 alaska tsunami seward was hit by both tectonic and landslide generated tsunami waves during the m rm w 9 2 1964 megathrust earthquake the earthquake triggered a series of submarine mass failures around the fjord which resulted in landsliding of part of the coastline into the water along with the loss of the port facilities these submarine mass failures generated local waves in the bay within 5 min of the beginning of strong ground motion recent studies estimate the total volume of underwater slide material that moved in resurrection bay to be about 211 million m3 haeussler et al in submarine mass movements and their consequences pp 269 278 2007 the first tectonic tsunami wave arrived in resurrection bay about 30 min after the main shock and was about the same height as the local landslide generated waves our previous numerical study which focused only on the local landslide generated waves in resurrection bay demonstrated that they were produced by a number of different slope failures and estimated relative contributions of different submarine slide complexes into tsunami amplitudes suleimani et al in pure appl geophys 166 131 152 2009 this work extends the previous study by calculating tsunami inundation in resurrection bay caused by the combined impact of landslide generated waves and the tectonic tsunami and comparing the composite inundation area with observations to simulate landslide tsunami runup in seward we use a viscous slide model of jiang and leblond j phys oceanogr 24 3 559 572 1994 coupled with nonlinear shallow water equations the input data set includes a high resolution multibeam bathymetry and lidar topography grid of resurrection bay and an initial thickness of slide material based on pre and post earthquake bathymetry difference maps for simulation of tectonic tsunami runup we derive the 1964 coseismic deformations from detailed slip distribution in the rupture area and use them as an initial condition for propagation of the tectonic tsunami the numerical model employs nonlinear shallow water equations formulated for depth averaged water fluxes and calculates a temporal position of the shoreline using a free surface moving boundary algorithm we find that the calculated tsunami runup in seward caused first by local submarine landslide generated waves and later by a tectonic tsunami is in good agreement with observations of the inundation zone the analysis of inundation caused by two different tsunami sources improves our understanding of their relative contributions and supports tsunami risk mitigation in south central alaska the record of the 1964 earthquake tsunami and submarine landslides combined with the high resolution topography and bathymetry of resurrection bay make it an ideal location for studying tectonic tsunamis in coastal regions susceptible to underwater landslides

assessment of the high resolution paleoseismicity record from sediment gravity flows in prince william sound alaska abstract located along the aleutian megathrust boundary south central alaska is one of the most seismically active areas in the world central to this region prince william sound is a glacially carved basin that receives abundant sediment from multiple sources primary inputs include the columbia glacier and the copper river which have diagnostic signatures of sr pb cu pb k ca rb sr and rb ca as a result earthquake induced sediment gravity flows originating from different locations deposit event layers that have distinct provenance signatures a previous study kuehl et al 2017 identified five such event layers preserved in two cores from the southern part of the deep central channel of prince william sound that were attributed to large historical earthquakes to better understand the spatial continuity of these event layers along the entire length of the central channel seven new gravity cores were collected in a north south transect sedimentation rates were determined by 210pb 137cs and 239 240pu geochronology and cores were assessed for variations in elemental content grain size patterns bulk organic and stable isotopic signatures c n 13c 15n based on a spatial analysis of these cores local earthquakes of mw 7 0 including an event layer from the 1964 great alaskan earthquake have mixed signatures resulting from the widespread generation of numerous flows throughout prince william sound complete gravity flow records are captured within deep ponded sediment basins and the area spanning the southern end of the central channel considering the thick 100 m late holocene sequence the approach utilized in this study has the potential to provide a rich record of earthquake recurrence intervals to 4 ka

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

holocene glacier fluctuations in alaska abstract this review summarizes forefield and lacustrine records of glacier fluctuations in alaska during the holocene following retreat from latest pleistocene advances valley glaciers with land based termini were in retracted positions during the early to middle holocene neoglaciation began in some areas by 4 0 ka and major advances were underway by 3 0 ka with perhaps two distinct early neoglacial expansions centered respectively on 3 3 2 9 and 2 2 2 0 ka tree ring cross dates of glacially killed trees at two termini in southern alaska show a major advance in the ad 550s 720s the subsequent little ice age lia expansion was underway in the ad 1180s 1320s and culminated with two advance phases respectively in the 1540s 1710s and in the 1810s 1880s the lia advance was the largest holocene expansion in southern alaska although older late holocene moraines are preserved on many forefields in northern and interior alaska tidewater glaciers around the rim of the gulf of alaska have made major advances throughout the holocene expansions were often asynchronous with neighboring termini and spanned both warm and cool intervals suggesting that non climatic factors were important in forcing these advances however climatic warming appears to have initiated most rapid iceberg calving retreats large glaciers terminating on the forelands around the gulf of alaska may have had tidewater termini early in the holocene but have progressively become isolated from the adjacent ocean by the accumulation and subaerial exposure of their own sediments

seismic reflection characteristics of glacial and glacimarine sediment in the gulf of alaska and adjacent fjords abstract glaciation together with tectonism have been dominant factors affecting sedimentation in the gulf of alaska area from at least the late miocene throughout the quaternary the effects of tectonism are apparent in high mountains that border the gulf raised terraces of middleton island and the eastern gulf coastal zone and numerous active faults and related earthquakes glacial evidence includes magnificent glaciers and their onshore deposits spectacular fjords large sea valleys incised in the continental shelf submarine morainal ridges at mouths of bays and sea valleys and thick glacimarine sedimentary sequences diamicts that are exposed onshore and at the sea floor along the outer shelf seismic reflection profiling and sampling of the uppermost marine sedimentary sequences in the gulf of alaska and adjacent fjords and bays have allowed identification of three discrete glacially related stratigraphic units these units were delineated on the basis of seismic signature geometry physiographic location stratigraphic position and sedimentologic characteristics the oldest unit a quaternary diamict is portrayed on seismic profiles by irregular discontinuous reflections this unit probably includes till outwash and glacimarine sediment a geographically restricted unit one incorporating holocene end moraines at bay mouths and associated with some sea valleys consists of jumbled masses of discontinuous reflections and very irregular surface morphology the youngest unit a blanket of holocene sand to clayey silt prograding as a sediment wedge across the shelf contains nearly horizontal parallel reflections except where disrupted by mass movement although seismic reflection data alone cannot provide definitive proof of the presence of glacial sediment when combined with sea floor sampling seismic profiling is a powerful tool for determining the continuity of marine sedimentary units and relationships to past and modern glaciers

tree ring dated little ice age histories of maritime glaciers from western prince william sound alaska tree ring studies at 13 glacier forefields in western prince william sound show little ice age glacial fluctuations were strongly synchronous on decadal timescales cross dated glacially overrun trees at eight sites indicate ice margins advanced in the early late twelfth through thirteenth centuries and middle seventeenth to early eighteenth centuries little ice age tree ring dates of 22 moraines at 13 glaciers show two main periods of stabilization the earlier of these in the first decades of the eighteenth century overlaps with the second period of glaciers overrunning trees and marks culmination of this middle little ice age expansion stabilization of moraines on nine of the study forefields in the latter part of the nineteenth century delineates a third interval of little ice age glacial advance the detailed little ice age record from land terminating glaciers in western prince william sound is consistent on a timescale of decades with four other tree ring dated glacial histories from across the northern gulf of alaska this coastal northeastern pacific glacial record reveals the structure of the little ice age in the region and provides a strong basis for comparison with other proxy climate records spanning the past 1000 years

morphology of a submarine slide kitimat arm british columbia a digitally acquired scale corrected side scan sonar survey yielded high resolution imagery of a submarine landslide in british columbia the landslide in a fjord head setting at kitimat was last active in 1975 and created a wide area of deformed sea floor the sediment failure involved shallow rotational movements on the slopes of a fjord head delta marginal tearing translational sliding compressional folding and block gliding of fjord bottom marine clays the slide is shallow and elongate and appears to have been produced by failure in mobile low strength sediments

glacimarine processes and inductive lithofacies modelling of ice shelf and tidewater glacier sediments based on quaternary examples abstract three variables control the type of glacial debris source and where and when debris is introduced to an ocean 1 type of glacial ice source ice sheet or valley glacier 2 condition of a grounded glacier melting freezing or frozen base and cold or warm internal ice and 3 type of glacier front ice shelf or tidewater using these variables in different combinations eight glacimarine regimes are postulated to exist by integrating information from holocene sediment and pleistocene glacimarine sequences with the eight inductive regimes lithofacies relationships are predicted and modelled the models show a complexity of glacimarine lithofacies the importance of recognizing this complexity lies in realistic interpretations of ancient sequences ice shelf sediment may be limited in the geologic record because of tectonic and climatic constraints required for ice shelf formation alternatively in some tidewater glacier regimes larger volumes of glacimarine sediment are produced than in ice shelf regimes ice proximal sediment is distinctive especially near subglacial meltwater stream effluxes ice shelves and tidewater glaciers may produce similar ice proximal lithofacies e g morainal bank associations and laminites in certain regimes however details of lithofacies may aid in distinguishing ice shelf from tidewater regimes ice shelf and tidewater iceberg zone sediment can be distinguished from each other if basal and high level englacial debris can be distinguished ice shelf zone sediment out from the grounding line has a basal debris source high level englacial debris is deposited in more distal ice shelf zones resulting in sediment by pass in corresponding positions of a tidewater glacier regime iceberg rafted debris comprises mixed basal and high level englacial debris deeper water zones receive large volumes of sediment when a melting freezing base grounding line is at the edge of a continental shelf when the grounding line retreats sediment supply may be drastically reduced because of a back sloping continental shelf and trapping by morainal banks cool water bioclastic carbonates may accumulate once a grounding line has retreated although ice shelf iceberg zones are more extensive than those in tidewater regimes ice shelf icebergs have low debris content and resulting ice rafted debris may be scarce the smallest volume of sediment is produced by a frozen base ice sheet ending as a tidewater front and the largest volume by a melting freezing base valley tidewater glacier glacimarine sediment has a relatively high preservation potential near continental interiors or margins however at continental margins mass flow olistostrome and tectonic melange deposits may be preserved with glacimarine diamictites these deposits may be difficult to distinguish from each other especially if metamorphosed such as at a convergent margin the models presented do not fully represent the glacimarine environment because many other variables are omitted however the principal concepts of generating glacimarine lithofacies associations are considered continued research will verify if each regime exists and will provide data on those regimes that exist today to compare and modify these models

varve formation during the past three centuries in three large proglacial lakes in south central alaska the sediments stored in the large deep proglacial lakes of south central alaska are largely unstudied we analyzed sediments in 20 cores up to 160 cm long from eklutna kenai and skilak lakes using a combination of repeated lamination counting radionuclide dating event stratigraphy and tephrochronology we show that the characteristically rhythmic layers were deposited annually most of these glacial varves consist of one coarse grained base and a fine grained top but varves composed of multiple coarse grained turbidite pulses are common too they are likely related to successive episodes of high sediment discharge during flooding and they become more frequent in all three lakes along with increased sedimentation rates during the nineteenth century late phase of the little ice age these flood turbidites were generated by rain events and intense melting of snow and ice other mega turbidites are a result of earthquake triggered slope collapses e g a d 1964 some event layers are present in all three lakes in addition the annual time series of varve thickness normalized annual sedimentation rate are significantly correlated among the three lakes p 0 27 p 0 001 differences between the varve thickness records can be attributed partly to the dam construction at eklutna lake and outbursts from an ice dammed lake at skilak lake geomorphologic differences among the catchments result in further differences in sedimentation patterns in the three lakes

paleoproductivity from benthic foraminifera abundance glacial to postglacial change in the west equatorial pacific surface productivity is correlated with the rate of accumulation of benthic foraminifera on the deep sea floor as a rule of thumb for each 1 mg of organic carbon arriving at the sea floor one benthic foram shell 150 m is deposited the correlation can be used to reconstruct organic flux to the sea floor in the past and hence the productivity of past oceans applying the appropriate equations to box core data from the ontong java plateau in the western equatorial pacific we found that productivity during the last glacial maximum exceeded present productivity by a factor of between 1 5 and 2 0 with intermediate values for the mid transition period accumulation of benthic foraminifera was depressed on top of the plateau during the glacial and transitional period presumably because increased winnowing removed part of the food supply

recognition classification and mechanical description of debris flows abstract various types of flow or mass movement involving water and sediments occur on steep slopes in mountainous areas among them debris flows are peculiar events during which a large volume of a highly concentrated viscous water debris mixture flows through a stream channel throughout the world these phenomena cause considerable damage but remain poorly understood although a basic knowledge is already available concerning their recognition and propagation firstly a synthesis of the useful practical criteria of recognition is proposed debris flows must be seen as intermediate phenomena between hyperconcentrated flows intense bed load transport and landslides separated from them by sharp transitions of some characteristics celerity deposit nature and flow type two parameters solid fraction and material type thought to be appropriate for a sound and practical classification are brought out and the corresponding complete classification of flow and mass movements in mountain areas is presented two extreme debris flow types are thus distinguished muddy debris flows and granular debris flows a critical review of recent advances in debris flow dynamic is then proposed it is pointed out that adequate work must be carried out in the field of non newtonian fluid mechanics in particular one fundamental rheological property of debris flow materials is the yield stress which explains thick deposits on steep slopes and can be inferred from field measurements furthermore it can be used to estimate viscous dissipation within the bulk during flow relevant models predicting muddy debris flow dynamics are already available whereas further progress is needed concerning granular flows

analysis of observed and predicted tsunami travel times for the pacific and indian oceans i have examined over 1500 historical tsunami travel time records for 127 tsunamigenic earthquakes that occurred in the pacific and indian oceans after subjecting the observations to simple tests to rule out gross errors i compare the remaining reports to simple travel time predictions using huygens method and the long wave approximation thus simulating the calculations that typically take place in a tsunami warning situation in general i find a high correspondence between predicted and reported travel times however significant departures exist some outliers imply significantly slower propagation speeds than predicted many of these are clearly the consequences of observers not being able to detect the possibly weak first arrivals other outliers imply excessively long predicted travel times these outliers reflect peculiar geometric and bathymetric conditions that are poorly represented in global bathymetric grids leading to longer propagation paths and consequently increased travel times analysis of t the difference between observed and predicted travel time yields a mean t of 19 minutes with a standard deviation of 131 minutes robust statistics being less sensitive to outliers yield a median t of just 18 seconds and a median absolute deviation of 33 minutes care is needed to process bathymetry to avoid excessive travel time delays in shallow areas i also show that a 2 2 arc minute grid yields better results that a 5 5 arc minute grid the latter in general yielding slightly slower propagation predictions the largest remaining source of error appears to be the inadequacy of the point source approximation to the finite tsunami generating area

note on the 1964 alaska tsunami generation by horizontal displacements of ocean bottom numerical modeling of the runup in chenega cove alaska a numerical model of the wave dynamics in chenega cove alaska during the historic m w 9 2 megathrust earthquake is presented during the earthquake locally generated waves of unknown origin were identified at the village of chenega located in the western part of prince william sound the waves appeared shortly after the shaking began and swept away most of the buildings while the shaking continued we model the tectonic tsunami in chenega cove assuming different tsunami generation processes modeled results are compared with eyewitness reports and an observed runup results of the numerical experiments let us claim the importance of including both vertical and horizontal displacement into the 1964 tsunami generation process we also present an explanation for the fact that arrivals of later waves in chenega were unnoticed

upwelling intensification as part of the pliocene pleistocene climate transition a deep sea sediment core underlying the benguela upwelling system off southwest africa provides a continuous time series of sea surface temperature sst for the past 4 5 million years our results indicate that temperatures in the region have declined by about 10 c since 3 2 million years ago records of paleoproductivity suggest that this cooling was associated with an increase in wind driven upwelling tied to a shift from relatively stable global warmth during the mid pliocene to the high amplitude glacial interglacial cycles of the late quaternary these observations imply that atlantic ocean surface water circulation was radically different during the mid pliocene

a submarine landslide source for the devastating 1964 chenega tsunami southern alaska abstract during the 1964 great alaska earthquake m w 9 2 several fjords straits and bays throughout southern alaska experienced significant tsunami runup of localized but unexplained origin dangerous passage is a glacimarine fjord in western prince william sound which experienced a tsunami that devastated the village of chenega where 23 of 75 inhabitants were lost the highest relative loss of any community during the earthquake previous studies suggested the source of the devastating tsunami was either from a local submarine landslide of unknown origin or from coseismic tectonic displacement here we present new observations from high resolution multibeam bathymetry and seismic reflection surveys conducted in the waters adjacent to the village of chenega the seabed morphology and substrate architecture reveal a large submarine landslide complex in water depths of 120 360 m analysis of bathymetric change between 1957 and 2014 indicates the upper 20 50 m 0 7 km3 of glacimarine sediment was destabilized and evacuated from the steep face of a submerged moraine and an adjacent 21 km2 perched sedimentary basin once mobilized landslide debris poured over the steep 130 m high face of a deeper moraine and then blanketed the terminal basin 465 m water depth in 11 5 m of sediment these results combined with inverse tsunami travel time modeling suggest that earthquake triggered submarine landslides generated the tsunami that struck the village of chenega roughly 4 min after shaking began unlike other tsunamigenic landslides observed in and around prince william sound in 1964 the failures in dangerous passage are not linked to an active submarine delta the requisite environmental conditions needed to generate large submarine landslides in glacimarine fjords around the world may be more common than previously thought

earthquake and flood induced turbidites in the saguenay fjord quebec a holocene paleoseismicity record abstract a 38 m long piston core from the deep basin of the saguenay fjord quebec recorded rapidly deposited layers rdl interpreted to represent major floods and earthquakes over the past 7200 years high resolution physical magnetic and sedimentological analyses revealed at least 14 rdl generally with a sandy base and a light gray color interbedded with hemipelagic sediments digital x radiography and grain size analyses at