deposit from a giant wave on the island of lanai hawaii limestone bearing gravel the newly named hulopoe gravel blankets the coastal slopes on lanai the deposit which reaches a maximum altitude of 326 meters formerly was believed to have been deposited along several different ancient marine strandlines but dated submerged coral reefs and tide gauge measurements indicate that the southeastern hawaiian islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level evidence indicates that the hulopoe gravel and similar deposits on nearby islands were deposited during the pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of lanai

growth and collapse of the reunion island volcanoes this work presents the first exhaustive study of the entire surface of the reunion island volcanic system the focus is on the submarine part for which a compilation of all multibeam data collected during the last 20 years has been made different types of submarine features have been identified a coastal shelf debris avalanches and sedimentary deposits erosion canyons volcanic constructions near the coast and seamounts offshore criteria have been defined to differentiate the types of surfaces and to establish their relative chronology where possible debris avalanche deposits are by far the most extensive and voluminous formations in the submarine domain they have built four huge submarine bulges to the east north west and south of the island they form fans 20 30 km wide at the coastline and 100 150 km wide at their ends 70 80 km offshore they were built gradually by the superimposition and or juxtaposition of products moved during landslide episodes involving up to several hundred cubic kilometers of material about 50 individual events deposits can be recognized at the surface the landslides have recurrently dismantled piton des neiges les alizes and piton de la fournaise volcanoes since 2 ma about one third are interpreted as secondary landslides affecting previously emplaced debris avalanche deposits on land landslide deposits are observed in the extensively eroded central area of piton des neiges and in its coastal areas analysis of the present day topography and of geology allows us to identify presumed faults and scars of previous large landslides the submarine bulges are dissected and bound by canyons up to 200 m deep and 40 km long filled with coarse grained sediments and generally connected to streams onshore a large zone of sedimentary accumulation exists to the north east of the island it covers a zone 20 km in width extending up to 15 km offshore volcanic constructions are observed near the coast on both piton des neiges and piton de la fournaise volcanoes and are continuations of subaerial structures individual seamounts are present on the submarine flanks and the surrounding ocean floor a few seem to be young volcanoes but the majority are probably old eroded seamounts this study suggests a larger scale and frequency of mass wasting events on reunion island compared to similar islands the virtual absence of downward flexure of the lithosphere beneath the island probably contributes to this feature the increased number of known flank failure events has to be taken into consideration when assessing hazards from future landslides in particular the probability of landslide generated tsunamis

chaotic deposition by a giant wave molokai hawaii a coral basalt breccia conglomerate is exposed 60 m above present sea level and nearly 2 km inland from the present shoreline on the southwest side of east molokai volcano molokai the conglomerate is preserved mantling interfluves between gullies and forms a blanket like deposit 0 5 to 3 m thick no evidence of a wavecut terrace either within the blanket or at its upper or lower limits of exposure can be found no coral was found in growth position unsorted basalt clasts as large as boulder size are subrounded to angular randomly oriented and vary from 2 3 to 50 volume of the deposit the size of the largest basalt and coral fragments shows almost no systematic variation with elevation distance inland or lateral position parallel to the shore two indistinct rock units are present in a few places a lower carbonate rich unit that we interpret as an onwash facies and an upper basalt rich unit an offwash facies the carbonate rich onwash facies is dominated by biogenic debris especially fragments of coral and beach rock and gastropod and bivalve shells the offwash facies contains 40 to 90 basalt cobbles and boulders in a matrix of finely broken biogenic fragments where the distinct facies are lacking the proportion of basalt clasts increases crudely from the lower to the upper part of the conglomerate at a single place and from lower to higher elevation out crops where the deposit overlies a cinder cone several carbonate bearing elastic dikes extend from the conglomerate as much as 10 m down into the basalt cinders this deposit was apparently laid down by a giant wave that broke over an outer reef similar to the present fringing reef and advanced as a turbulent bore over the back reef flat picking up a slurry of carbonate rich debris and depositing it on the slopes inland as the wave advanced the offwash picked up loose basalt debris on its return flow u series dating of coral fragments indicates that the age of this deposit is 240 200 ka indicating the wave is distinct from that which produced a similar deposit on lanai about 100 ka this giant wave was most likely caused by one of the many large submarine landslides that have been identified on the lower slopes of the major hawaiian islands

geomagnetic field intensity and reversals during the past four million years a long and continuous record of the geomagnetic field intensity shows that intensity variations are dominated by two modes major episodes of field regeneration prevail on timescales of a few thousand years immediately after most reversals whereas stable polarity states are characterized by a slow 0 5 myr relaxation process reversals can be seen as the consequence of a progressive degradation of the dipole field

giant blocks in the south kona landslide hawaii a large field of blocky sea floor hills up to 10 km long and 500 m high are gigantic slide blocks derived from the west flank of mauna loa volcano on the island of hawaii these megablocks are embedded in the toe of the south kona landslide which extends 80 km seaward from the present coastline to depths of nearly 5 km a 10 15 km wide belt of numerous smaller 1 3 km long slide blocks separates the area of giant blocks from two submarine benches at depths of 2600 and 3700 m depth that terminate seaward 20 to 30 km from the shoreline similar giant blocks are found on several other major submarine hawaiian landslides including those north of oahu and molokai but the south kona blocks are the first to be examined in detail using high resolution bathymetry dredging and submersible diving dredging of two of the giant blocks brought up pillowed tholeiitic lava observations from the u s navy submersible sea cliff on the asymmetrically steep eastern flank of one block 10 km long and 300 m high revealed a succession of fractured massive basalt laminar lava flows hyaloclastite and pillow lavas chemical analyses of dredged lava identified 19 units that overlap compositionally with lavas from the south rift zone ridge of mauna loa sulfur content indicates that most of the lavas were erupted in subaerial and shallow submarine

observations and simulations of wave runup during a laboratory dune erosion experiment abstract xbeach a process based numerical model designed to simulate morphologic change during extreme storm events was calibrated and compared to observations from a large scale laboratory dune erosion experiment wave conditions along the tan wave runup at the beach and 3 dimensional position of the dune were measured throughout the experiment seiching modes in the tank were simulated and matched the observations once the model was calibrated simulated waves were sensitive to the ratio of wave height to water depth and cf the coefficient of friction simulated runup explained 50 87 of the observed variance in observations however the magnitude of simulated wave runup was underestimated throughout the experiment errors in simulated runup were composed of a high bias and gain error in mean water level low bias in the infragravity swash and low bias and gain errors in incident swash observed probability density functions of swash were statistically consistent between times when swash was confined to the foreshore and times when swash interacted with the dune however simulated probability density functions of swash were statistically different during the collision regime despite the systematic underestimation of wave runup modeled dune erosion compared well with observations after the sediment transport parameters were calibrated modeled dune erosion was sensitive to the critical slope parameters over the wet and dry regions of the beach the depth of the interface between the wet and dry regions of the beach and the threshold depth for sediment transport and return flow

the off shore continuation of an active basaltic volcano piton de la fournaise reunion island indian ocean structural and geomorphological interpretation from sea beam mapping abstract in 1984 a sea beam survey of the submarine east flank of piton de la fournaise was performed with r v jean charcot three main types of volcanic or volcano tectonic features have been identified 1 1 the subaerial ne and se volcanic rift zones of piton de la fournaise do not extend more than about five kilometers offshore unlike typical hawaiian rift zones which form narrow 2 4 km ridges extending tens of kilometers from the summit the active rift zones of piton de la fournaise widen downslope attaining more than 10 km at their front 2 2 the submarine extension of the grand brule slide is larger than the subaerial portion the entire slide forms a 7 24 km scar bounded by two ramparts to the north and south the slumped material may have moved as a debris flow forming a large talus downslope of the slide however the submarine counterpart of the south area of the grand brule seems to be composed by a slumped block whose structure is apparently not disturbed 3 3 another prominent feature is a conspicuous topographic high that occupies nearly all the center of the surveyed zone this cast flank submarine plateau cannot be associated with any active structure of piton de la fournaise its surface generally dips gently 2 3 and its northern and southern flanks are extensively cut by landslides cones of variable dimensions are observed on the plateau and farther to the east three hypotheses are examined to account for the origin of this morphology a remnant flank of an ancestral fournaise volcano associated with a large buried intrusion found by drilling beneath the grand brule b distinct volcanic massif or c material of a huge and ancient landslide the geophysical data show that the western part of this submarine plateau is reversely magnetized and associated with a moderate positive gravity anomaly this confirms that as suggested by the bathymetric analysis this part of the plateau is relatively coherent conversely the eastern portion of the plateau appears to be poorly magnetized and composed of low density material probably chaotic materials derived from landslides the reversed magnetization of the western part shows that the whole structure is older than 0 7 ma these results show that the volcanic history of piton de la fournaise is more complex than previously thought

improvements in long core measurement techniques applications in palaeomagnetism and palaeoceanography we report on new developments in the long core measurement techniques using u channels in connection with new small access cryogenic magnetometers with these new instruments u channel samples allow us to measure a wide range of magnetic parameters along entire core length with a spatial resolution and accuracy virtually equivalent to that obtained using discrete cubic samples an additional advantage is that the sediment disturbance when sampling is significantly less when using u channels we present comparisons of results from both continuous and discrete measurements and examine the effectiveness of minimal deconvolution using various techniques examples of continuous measurements of low field susceptibility nrm arm irm hrc from north atlantic deep sea cores show that it is possible to generate logs of combination of parameters related to rock magnetic characteristics of the sediments useful in palaeoceanography in particular the continuous method allows us to rapidly detect core regions with fast changing magnetic parameters useful for correlation between cores and also for understanding changes in palaeo environmental conditions the fast scan also allows us to detect regions of the core where the rock magnetic parameters are suitable or not suitable for palaeomagnetic studies related to changes in the geomagnetic field such as the relative changes in palaeointensity

non axisymmetric behaviour of olduvai and jaramillo polarity transitions recorded in north central pacific deep sea sediments the causes of the reversals of the earth s magnetic field can be investigated by studying the palaeomagnetic record preserved in rocks a proper documentation of reversal phenomena should yield valuable information about the generation of the field deep sea sediments provide a globally and temporally distributed set of polarity transition records our studies2 4 of the olduvai 1 88 1 72 myr 1 and jaramillo 0 94 0 88 myr 1 subchrons using deep sea sediments showed that the time averaged behaviour of the geomagnetic field during these reversals proved to be reliably recorded independent of the latitude and longitude of the sample site here we test some phenomenological transition models and present directional data virtual geomagnetic poles vgps and related directions in rotated declination inclination d i space5 using two records of the olduvai reverse normal reverse r n r and two records of the jaramillo r n r polarity transitions these data are better explained by the flooding rather than the standing field model but they also indicate a degree of asymmetry of the transitional field

mega tsunami conglomerates and flank collapses of ocean island volcanoes abstract marine conglomerates at high elevation on the flanks of ocean islands are usually interpreted as evidence of mega tsunamis generated by volcano flank collapses although their origin is sometimes debated elevated littorals vs tsunami in this review we introduce case studies of well documented examples of tsunami conglomerates in hawaii pacific ocean the canary and cape verde islands atlantic ocean and mauritius island indian ocean other less documented marine conglomerates are also presented as tsunami candidates then we build a comprehensive picture of the general characteristics of these conglomerates and the different methods that can be applied to date them different perspectives of research are proposed especially on the use of tsunami conglomerates as proxies for better constraining numerical models of ocean island flank collapses and associated tsunamis we also discuss the possible links between volcano growth flank instability and climate

the giant submarine alika debris slide mauna loa hawaii probably represent multiple subsidence events before during and after the debris avalanches lower slopes of the slide contain distinctive lobate terraced deposits that are interpreted as having been emplaced more slowly prior to the debris avalanches estimated thicknesses of 50 200 m suggest volumes of 200 600 km 3 for the two lobes the combined volume of the entire slide and slump terrane is probably 1500 2000 km 3 the slide deposits predate a 13 ka coral reef and probably postdate the block faulted ninole basalt roughly dated as a few hundred thousand years old the alika slide or a similar deposit recognized on gloria images further north along the hawaiian ridge probably triggered a giant wave that washed 325 m high on lanai at about 100 ka slumping on mauna loa has been most intense adjacent to the large arcuate bend in its southwest rift zone as the rift zone migrated westward away from the growing kilauea volcano slumping events were probably triggered by seismic activity accompanying dike injection along the rift zone such massive slumps landslides and distal submarine turbidity flows appear to be widespread on the flanks of hawaiian volcanoes

the influence of glacier surface processes on the short term evolution of supraglacial tree vegetation the case study of the miage glacier italian alps supraglacial debris cover allows vegetation to colonize glacier surface and whenever it is enough stable and thick also shrubs and trees can germinate and grow supraglacial tree growth and distr

uplift caused by lithospheric flexure in the hawaiian archipelago as revealed by elevated coral deposits the presence of definitive indicators of sea level such as corals found in growth position coralline beach deposits wave cut notches and wave eroded terraces all at elevations above known levels of eustatic sea level during the past 500 ka provides strong evidence that uplift has occurred in the central high hawaiian islands lithospheric flexure is proposed as the mechanism for uplift the modelled wavelength and amplitude of flexure roughly correspond to the distance and height of elevated coral rich deposits a trend of increasing age of coralline beach deposits with elevation on oahu and molokai adds support to the uplift hypothesis data and observations presented in this paper are inconsistent with a tsunami origin for most elevated deposits on lanai molokai and oahu a giant wave origin may only apply to scattered and localized deposits concentrated in low lying gulches 100 m such as those on lanai

eruptive response of oceanic islands to giant landslides new insights from the geomorphologic evolution of the teide pico viejo volcanic complex tenerife canary large sector collapses are a major component of oceanic islands evolution here we show that voluminous events such as the icod landslide on tenerife canary islands cause dramatic changes on the magma feeding system and control the subsequent volcanic and geomorphologic evolution of the eruptive complex over a period of more than 150 kyr instantaneous unloading by the icod landslide is marked by the development of a large phonolitic explosive eruption dated at 175 3 ka and interpreted as reflecting the immediate emptying of a shallow pre existing magma chamber geochronological geomorphological and geochemical analyses carried out on the post landslide volcanic succession sampled in a 4 4 km long underground water recovery gallery provide further evidence for an enhanced extrusion of primitive lavas starting in the 10 kyr time interval following the failure rapid construction 40 kyr of a thick basaltic volcano in the landslide scar at high eruptive rates up to 8 km3 kyr 1 increased the lithostatic pressure which then favored the intermittent storage of basic magma under the edifice this resulted in more episodic construction evidenced by a significant decrease in output rates and the increasing occurrence of lavas with intermediate composition from 117 7 to 52 7 ka an apparent volcanic gap is observed between 52 7 and 18 1 ka after which highly differentiated lavas have been dominantly erupted we propose that part of the gap can be explained by the individualization of a shallow magma reservoir a few kilometers below the base of the teide volcano during recent periods vertical and lateral extrusions of trachytic and phonolitic viscous bodies from this storage area contributed to increase the slope of the main edifice up to 35 overall favoring its present day instability

origin and depositional environment of clastic deposits in the hilo drill hole hawaii volcaniclastic units cored at depths of about 87 164 178 226 and 246 m below sea level and carbonate units located between depths of 27 and 53 m below sea level in the hilo drill core were found to be deposited at or near sea level four of these units are hydroclastic deposits formed when subaerially erupted mauna loa lava flows entered the ocean and fragmented to produce quenched glassy fragments during hydrovolcanic explosions ash units 24 and 26 at 178 m depth accumulated at sea level in a freshwater bog they contain pyroxenes crystallized from tholeiitic magma that we infer erupted explosively at the summit of kilauea volcano two carbon rich layers from these ashes have a weighted average radiocarbon age of 38 6 0 9 ka the ashes probably correlate with the oldest and thickest part of the pahala ash ash unit 44 at the transition from mauna kea to mauna loa lava flows was probably nearly 3 2 m thick and is inferred to be equivalent to the lower thick part of the composite homelani ash mapped in hilo and on the flanks of mauna kea the age of this part of homelani ash is between 128 33 and 200 10 ka it may have erupted subglacially during the pohakuloa glacial maxima on mauna kea beach sand units 12 and 22 were derived from nearby mauna loa and mauna kea lava flows the middle of beach sand unit 38 was derived mainly from lava erupted near the distal end of the subaerial east rift zone of kilauea volcano these sands were transported about 33 km northwest to hilo bay by prevailing longshore currents combined age depth and sea level markers in the core allow us to determine that lava flow recurrence intervals averaged one flow every 4 kyr during the past 86 kyr and one flow every 16 kyr between 86 and 200 ka at the drill site and that major explosive eruptions that deposit thick ash in hilo have occurred only twice in the last 400 kyr these recurrence intervals support the moderate lava flow hazard zonation zone 3 for coastal hilo previously determined from surficial mapping

submarine geology of the hilina slump and morpho structural evolution of kilauea volcano hawaii abstract marine geophysical data including sea beam bathymetry hawaii mr1 sidescan and seismic reflection profiles along with recent robot submersible observations and samples were acquired over the offshore continuation of the mobile kilauea volcano south flank this slope comprises the three active hot spot volcanoes mauna loa kilauea and loihi seamount and is the locus of the hawaiian hot spot the south flank is the site of frequent low intensity seismicity as well as episodic large magnitude earthquakes its sub aerial portion creeps seaward at a rate of approximately 10 cm year the hilina slump is the only large submarine landslide in the hawaiian archipelago thought to be active and this study is one of the first to more highly resolve submarine slide features there the slump is classified into four distinct zones from nearshore to the island s base estimates of size based on these data indicate a slumped area of 2100 km 2 and a volume of 10 000 12 000 km 3 equivalent to about 10 of the entire island edifice the overall picture gained from these data sets is one of mass wasting of the neovolcanic terrain as it builds upward and seaward though reinforcement by young and pre hawaii seamounts adjacent to the pedestal is apparent extensive lava delta deposits are formed by hyaloclastites and detritus from recent lava flows into the sea these deposits dominate the upper submarine slope offshore of kilauea with pillow breccia revealed at mid depths along the lower flanks massive outcrops of volcanically derived sedimentary rocks were found underlying kilauea thus necessitating a rethinking of previous models of volcanic island development the morphologic and structural evolutionary model for kilauea volcano and the hilina slump proposed here attempts to incorporate this revelation a hazard assessment for the hilina slump is presented where it is suggested that displacement of the south flank to date has been restrained by a still developing northeast lateral submarine boundary when it does fully mature the south flank may be more subject to land slips triggered by large long duration earthquakes and thus kilauea may undergo more frequent episodes of failure with increased displacements

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

a map of the pacific geomagnetic anomaly during the brunhes chron abstract the persistence of an anomaly of the geomagnetic field in the central pacific ocean has been suggested by many authors however the amplitude and the extent of this feature remain poorly constrained due to insufficient spatial and temporal coverage of the volcanic database records from marine sediments are appropriate to document the long term behavior of the geomagnetic field we studied 11 piston cores from the central and southwestern pacific in order to document the anomaly during the past 800 kyr ten records were retained after applying selection criteria dealing with physical disturbances deformations and any possible sources of inclination errors the results have been integrated into a new data set for the pacific ocean and the eastern indian ocean which combines sedimentary and volcanic records a strong negative inclination anomaly 10 in the southwestern pacific is the main characteristic of the new map in contrast the sedimentary records from the hawaiian area do not indicate any stable feature but rather alternating positive and negative anomalies the new inclination map of the brunhes chron bears striking similarities with the configuration of the historical field particularly the presence of a negative anomaly centered in the eastern indian ocean and southwestern pacific ocean detailed records constraining the archeological period in the southwestern pacific and documenting the spatial extension of the anomaly are now needed to establish a direct link with the present field

volcanic spreading on mauna loa volcano hawaii evidence from accretion alteration and exhumation of volcaniclastic sediments a transect of submersible dives across the submarine west flank of mauna loa volcano yields compelling evidence for volcanic spreading and associated hydrothermal circulation during volcano growth a frontal bench at the toe of the flank formerly thought to be a downdropped block of mauna loa contains a mix of volcaniclastic lithologies including distally derived siltstone mudstone and hyaloclastite the bench is overlain by bedded gravels and subaerially erupted pillow flows derived from local shoreline crossing lava flows the volcaniclastic strata in the bench were offscraped uplifted and accreted to the edge of the flank as it plowed seaward into the surrounding moat the accreted strata underwent significant diagenesis through deep burial and circulation of hydrothermal fluids expelled from porous sediments beneath the volcano timing constraints for bench growth and breakup suggest that catastrophic failure of the subaerial edifice ca 250 200 ka triggered volcanic spreading by reducing stresses resisting basal sliding and rift zone inflation increased eruptive activity and westward migration of mauna loa9s southwest rift zone gradually rebuilt the massive flank arresting slip prior to detachment of the alika 2 debris avalanche ca 120 ka

frozen bed fennoscandian and laurentide ice sheets during the last glacial maximum the areal extents of the laurentide and fennoscandian ice sheets during the last glacial maximum about 20 000 years ago are well known1 but thickness estimates range widely from high domed2 to thin3 with large implications for our reconstruction of the climate system regarding for example northern hemisphere atmospheric circulation and global sea levels this uncertainty stems from difficulties in determining the basal temperatures of the ice sheets and the shear strength of subglacial materials4 a knowledge of which would better constrain reconstructions of ice sheet thickness here we show that in the absence of direct data the occurrence of ribbed moraines in modern landscapes can be used to determine the former spatial distribution of frozen and thawed bed conditions we argue that ribbed moraines were formed by brittle fracture of subglacial sediments induced by the excessive stress at the boundary between frozen and thawed bed conditions resulting from the across boundary difference in basal ice velocity maps of glacial landforms from aerial photographs of canada and scandinavia reveal a concentration of ribbed moraines around the ice sheet retreat centres of quebec keewatin newfoundland and west central fennoscandia together with the evidence from relict landscapes that mark glacial areas with frozen bed conditions the distribution of ribbed moraines on both continents suggest that a large area of the laurentide and fennoscandian ice sheets was frozen based and therefore high domed and stable during the last glacial maximum

lateglacial nunataks in central scandinavia biostratigraphical evidence for ice thickness from lake flafattjonn tynset norway abstract this study reveals for the first time biostratigraphical evidence of nunataks emerging from the late weichselian ice sheet in central scandinavia almost 1 m of minerogenic basal layers from lake flafattjonn 1110 m a s l at tynset norway was deposited in the lateglacial possibly as early as 16 000 cal yr bp the sediments contain well preserved remains of plants diatoms and chironomids and indicate 1 a mosaic pioneer vegetation of dwarf shrub tundra snow bed vegetation and xerophytes on wind blown ridges 2 an ice free lake during summers with clear water at low ph due to little inwash 3 a continental climate with summers slightly warmer than today ca 10 c and most probably with very cold winters according to indications of permafrost and 4 a hiatus reduced sedimentation during at least the first half of the younger dryas when the lake was sealed by a more or less permanent ice cover the existence of lateglacial nunataks indicates a thin and multi domed lateglacial ice sheet in scandinavia early migration of arctic alpine plants to nunataks could explain their centric distribution in s norway furthermore vegetation establishment on the flafatet lateglacial nunatak indicates that s norway could have been vegetated by successions along the retreating ice from alpine nunataks and from coastal and southern areas the upland and lowland vegetation met at the final deglaciation

north kona slump submarine flank failure during the early tholeiitic shield stage of hualalai volcano abstract the north kona slump is an elliptical region about 20 by 60 km 1000 km 2 area of multiple geometrically intricate benches and scarps mostly at water depths of 2000 4500 m on the west flank of hualalai volcano two dives up steep scarps in the slump area were made in september 2001 using the rov kaiko of the japan marine science and technology center jamstec as part of a collaborative japan usa project to improve understanding of the submarine flanks of hawaiian volcanoes both dives at water depths of 2700 4000 m encountered pillow lavas draping the scarp and bench slopes intact to only slightly broken pillow lobes and cylinders that are downward elongate dominate on the steepest mid sections of scarps while more equant and spherical pillow shapes are common near the tops and bases of scarps and locally protrude through cover of muddy sediment on bench flats notably absent are subaerially erupted hualalai lava flows interbedded hyaloclastite pillow breccia and or coastal sandy sediment that might have accumulated downslope from an active coastline the general structure of the north kona flank is interpreted as an intricate assemblage of downdropped lenticular blocks bounded by steeply dipping normal faults the undisturbed pillow lava drape indicates that slumping occurred during shield stage tholeiitic volcanism all analyzed samples of the pillow lava drape are tholeiite similar to published analyses from the submarine northwest rift zone of hual lai relatively low sulfur 330 600 ppm and water 0 18 0 47 wt contents of glass rinds suggest that the eruptive sources were in shallow water perhaps 500 1000 m depth in contrast saturation pressures calculated from carbon dioxide concentrations 100 190 ppm indicate deeper equilibration at or near sample sites at water depths of 3900 to 2800 m either vents close to the sample sites erupted mixtures of undegassed and degassed magmas or volatiles were resorbed from vesicles during flowage downslope after eruption in shallow water the glass volatile compositions suggest that the tholeiitic lavas that drape the slump blocks were erupted either 1 early during shield stage tholeiitic volcanism prior to emergence of a large subaerial edifice or alternatively 2 from submarine radial vents during subaerial shield building because no radial vents have been documented on land or underwater for the unbuttressed flanks of any hawaii volcano alternative 1 is favored in comparison to other well documented hawaiian slumps and landslides north kona structures suggest a more incipient slump event with smaller down slope motions and lateral displacements

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

lake store finnsjoen a key for understanding lateglacial early holocene vegetation and ice sheet dynamics in the central scandes mountains the lateglacial lg deglaciation and vegetation development in the scandes mountains has been debated for a century here we present new evidence from microfossils radiocarbon dated plant macrofossils and sedimentary ancient dna from laminated sediments in lake store finnsjoen 1260 m a s l at dovre central norway combined with previous results from three other dovre lakes this allows for new interpretations of events during and immediately after the lg deglaciation the finnsjoen sediments present the first uninterrupted record of local vegetation development in the scandes mountains from the late younger dryas yd ca 12 000 cal years bp to the early holocene around 9700 cal years bp the local vegetation in late yd early holocene was extremely sparse with pioneer herbs e g artemisia norvegica beckwithia campanula cf uniflora koenigia oxyria papaver saxifraga spp and dwarf shrubs betula nana salix including salix polaris from 11 300 cal years bp local vegetation rapidly closed with dominant dryas saxifraga spp and silene acaulis from ca 10 700 cal years bp open birch forests with juniper empetrum nigrum and other dwarf shrubs developed pine forests established within the area from 10 300 cal years bp we identified the cold preboreal oscillation pbo not earlier described from pollen data in south norway around 11 400 cal years bp by a regional pollen signal distinct local vegetation changes were not detected until the post pbo warming around 11 300 cal years bp apparently the earlier warming at the yd holocene transition at 11 650 cal years bp was too weak and short lived for vegetation closure at high altitudes at dovre for the first time we demonstrate a regional glacier readvance and local ice cap formations during the yd in the scandes mountains in two of the deep lakes with small catchments yd glaciation blocked sedimentation without removing old sediments and caused a hiatus separating sediments of the ice free lg interstadial lgi from those of the ice free holocene period both regional glaciers and local ice caps caused hiati ice free pre yd conditions at dovre followed by a yd readvance point to a scenario that is intermediate between the maximum ice model postulating a thick glacier during the entire lg and the minimum ice model postulating thin and multi domed early lg ice

causal link between quaternary paleoclimatic changes and volcanic islands evolution 1 giant landslides and resulting tsunamis represent the main geologic hazards linked to volcanic island evolution from offshore and onland studies flank failures have been identified around numerous islands in most geodynamic contexts however the triggering conditions are still poorly understood and several causes may act simultaneously to reach a critical threshold here we show that most large volume 10 km3 landslides occur at glacial stages termination and we propose that a causal relationship between flank collapse of volcanic islands and global climatic changes has existed at least since 900 kyr moreover ages reported here favour the hypothesis that major collapses occurred during the onset of glacial to interglacial transitions when sudden influx of melt water from polar ice caps causes rapid sea level rise we propose that rapid sea level rise induces enhanced coastal erosion and sudden changes of pore pressure conditions within basal layers which favour edifice failure

the origin of mauna loa s nīnole hills evidence of rift zone reorganization in order to identify the origin of mauna loa volcano s n nole hills bouguer gravity was used to delineate density contrasts within the edifice our survey identified two residual anomalies beneath the southwest rift zone swrz and the n nole hills the n nole hills anomaly is elongated striking northeast and in inversions both anomalies merge at approximately 7 km above sea level the positive anomaly modeled as a rock volume of 1200 km3 beneath the n nole hills is associated with old eruptive vents based on the geologic and geophysical data we propose that the gravity anomaly under the n nole hills records an early swrz orientation now abandoned due to geologically rapid rift zone reorganization catastrophic submarine landslides from mauna loa s western flank are the most likely cause for the concurrent abandonment of the n nole hills section of the swrz rift zone reorganization induced by mass wasting is likely more common than currently recognized

olduvai onset polarity transition two detailed paleomagnetic records from north central pacific sediments abstract paleomagnetic analyses of two azimuthally oriented deep sea sediment cores from the north central pacific ocean which contain a record of the onset of the olduvai subchron polarity transition show 1 intermediate directions of magnetization with transitional inclinations reaching values up to 70 2 up to three sequential 180 declination changes two of which imply rapid oscillations of the geomagnetic field before the main reversal and 3 a pronounced drop in intensity of magnetization within the transitional interval the data further indicate that the intensity decay and recovery cycle took longer than the directional changes of the reversal whereas the directional changes lasted about 5000 years the duration of the recorded intensity cycles suggest that the complete onset of the olduvai reversal may have lasted as much as 28 000 years anhysteretic remanent magnetization studies and thermomagnetic analyses indicate that uniform magnetic mineralogy characterizes the transition zones of the cores this further suggests that the j 10 arm 70 ratio may represent a relative paleointensity estimate and may thus indicate a decrease of the intensity of the geomagnetic field during the onset of the olduvai reversal virtual geomagnetic pole paths of the two records are near sided directions in projected d i space indicate that the olduvai onset transitional field geometry possessed a contribution from non axisymmetric terms in addition to the dominating zonal harmonics the analyses also suggest that the transitional field during the onset of the olduvai reversal was dominated by harmonics different from those of the matuyama brunhes boundary jaramillo transitions and upper olduvai reversal

assessing glacier features supporting supraglacial trees a case study of the miage debris covered glacier italian alps the number of debris covered glaciers featuring supraglacial trees is increasing worldwide as a response of high mountain environments to climate warming generally their distribution on the glacier surface is not homogeneous thus suggesting that some glacier parameters influence germination and growth of trees in this study we focused our attention on the widest italian debris covered glacier the miage glacier mont blanc massif we analyzed the ablation area in the range from 1730 to 2400 m a s l where continuous debris coverage is present and trees are found using data obtained by remote sensing investigations and field surveys we defined a record of glacier parameters to be analyzed with respect to the presence and abundance of trees we found that supraglacial trees are present at the miage glacier 1 whenever exceeding a debris thickness threshold 19 cm 2 with a gentle slope 10 3 with a low glacier surface velocity 7 0 m yr and 4 where the vertical changes due to glacier

support for the giant wave hypothesis evidence from submerged terraces off lanai hawaii the origin of subaerial coral conglomerate deposits on the hawaiian islands of lanai and molokai is controversial primarily because these deposits are difficult to interpret and the vertical motion of these islands is poorly constrained based on bathymetry dive observations sedimentary and radiocarbon data from coralline algal dominated deposits from two submerged terraces at 150 and 230 m off lanai lanai has experienced relatively little vertical movement over the last 30 ka using internally consistent age versus depth relationships paleowater depths and published sea level data we estimate that lanai has experienced maximum rates of uplift of 0 1 m kyr or subsidence of 0 4 m kyr over this period our analysis of possible uplift mechanisms published geophysical numerical modelling and recent tide data suggests that this is also the maximum uplift rate for the last several hundred thousand years taken together these data support the interpretation that coral conglomerates at elevations higher than 35 m on lanai are tsunami deposits with a minimum wave run up 170 m rather than shoreline deposits formed during the last two interglacials then uplifted to their present elevations

correlation frequency of emplacement and source directions of megaturbidites on the madeira abyssal plain abstract this paper describes the sediments of the whole madeira abyssal plain including the madcap area to the south previous studies have centred on the central sub basin which occupies most of the plain and which has become one of the most studied areas of seafloor the plain is made up of a series of large turbidites separated by thin pelagic layers which can be used to provide a high resolution stratigraphy back to about 750 000 years many of the turbidites were deposited close to oxygen isotope stage boundaries suggesting a strong relationship to sea level climate change although the exact initiation mechanism for the flows is not known data from the northern and southern extensions of the plain shows the effects of different entry points for the four main turbidite groups volcanic rich turbidites enter from the ne and e calcareous turbidites from the w one group of organic rich turbidites enters from the se and one group from the ne and e different turbidite sources operate for limited periods before switching to one of the other source areas it is very rare for two sources to provide turbidites at the same isotope stage boundary

catastrophic flank collapses and slumping in pico island during the last 130 kyr pico faial ridge azores triple junction abstract the pico island constitutes the easternmost sub aerial domain of a steep wnw ese volcanic ridge which has developed within the nubia eurasia diffuse plate boundary azores triple junction the island comprises three volcanic systems from older to younger the topo volcano the fissural system and the pico stratovolcano from a high resolution digital elevation model 10 m and new bathymetric stratigraphic structural and high precision k ar data we reconstruct the main successive stages of growth and partial destruction of the island over the last 200 kyr we especially concentrate on the central sector of the island which has recorded gradual movements through slumping and catastrophic flank collapses since ca 130 kyr the remmants of the topo volcano are partly exposed on pico s se flank and are here dated between 186 5 and 115 4 ka topo was significantly destroyed by n and s directed large scale flank collapses between ca 125 and 70 ka on pico s n flank collapse seems to have removed all the unstable material but in the s the collapse structure is composite including a major flank collapse and a remnant slump complex that is still active a first episode of deformation occurred between ca 125 and 115 ka along the master fault of the slump between ca 115 and 69 ka most of the unstable material was removed by a major flank collapse leaving behind a still considerable volume of unstable material that comprises the active slump this first collapse was catastrophic and generated a large debris deposit recognized on the high resolution bathymetry with a minimum run out of ca 17 km the scar was partially filled by volcanic products erupted from volcanic cones developed within the slump depression and possibly also from the early wnw ese fissural system subsequent deformation in the slump area affected in part the filling units leading to the individualization of secondary curved faults younger volcanic products have gradually masked the mass wasting scars unlike the well known hilina slump hawaii pico s slump evolution might be controlled by an active regional tectonics

englacial and proglacial glaciotectonic processes at the snout of a thermally complex glacier in svalbard many glaciers in svalbard which tend to be thermally complex with both warm and cold ice produced complex push moraines or thrust moraine complexes at the time of their maximum neoglacial advance and during their subsequent recession uv rsbreen which nearly reaches the coast of northwest spitsbergen has a push moraine 50 m high comprising gravel and sand of fluvial origin and diamicton derived from basal ice as well as thrust masses of dead ice the push moraine is almost entirely a product of the tectonic processes especially thrusting that occurred in the snout of the glacier and in the frozen sediments immediately in journal of quaternary science front thrusting is probably initiated where the glacier switches from a sliding mode to a state of being frozen to the bed thrusting in the foreland is an extension of the same processes that occur within the ice itself and a sole thrust probably extends from the frozen sediment that underlies the base of the glacier near its snout thrusting results in subglacial sediment being uplifted to a high level within the glacier or even to the surface subsidiary near horizontal thrusts parallel to the bedding plane link thrusts dipping up glacier and result in local thickening of individual subglacial sedimentary units gravels incorporated in this way retain their integrity but sands are folded whereas uplifted debris rich basal ice is intensely folded the distinctive tectonic style of low dip bedding in gravels truncated by high angle 30 40 thrusts and only localised folding in less competent material differs from most descriptions of such ridges but may be typical of many push moraines composed principally of fluvial material

upslope flow of turbidity currents a comparison among field observations theory and laboratory models field observations from the marine realm indicate that turbidity currents are capable of transferring detritus considerable distances upslope onto bathymetric highs upslope deposition occurs because of the combined effects of flow thickness tilting of the cross flow surface slope and a vertical shift in the flow s center of gravity numerical analysis and laboratory experiments indicate that the maximum run up elevation of a subcritical turbidity current is approximately equal to 1 53 times the flow thickness

direct u th dating of marine sediments from the two most recent interglacial periods a knowledge of the age of marine sediments is necessary to determine the timing of events and rates of processes in the marine realm and the relationships among marine and other climatically sensitive records the establishment of an accurate chronology for pleistocene marine sediments beyond the range of radiocarbon dating approximately the past 45 kyr has therefore been a goal of palaeoceanographers for decades early attempts1 2 based on measurements of the radionuclides 230th and 231pa were beset with problems and subsequent studies focused on tying fluctuations in marine sediment oxygen isotope records to events such as the formation of coral reef terraces and changes in the earth s magnetic polarity3 4 and tuning the resultant chronologies to the earth s orbitally driven insolation variations5 8 but these chronologies especially the age and duration of the last interglacial period have been challenged by several studies9 12 raising questions about the fundamental cause of pleistocene climate fluctuations here we report the direct u th dating of aragonite rich marine sediments from the bahamas and present an accurately dated marine oxygen isotope record for the last two interglacials we obtain dates of 120 127 kyr bp for the last interglacial and 189 190 kyr bp for the late stage 7 interglacial these dates are in accord with the general theory of orbitally forced climate fluctuations and demonstrate the potential of our direct dating approach for developing an absolute chronology for the pleistocene marine oxygen isotope record

woody vegetation fuel and fire track the melting of the scandinavian ice sheet before 9500 cal yr bp abstract new studies indicate the presence of early holocene ice free areas far north in scandinavia post glacial fire and vegetation were investigated based on sedimentary charcoal and pollen from two small lakes in northern sweden accumulation of organic sediment started around 10 900 and 9200 cal yr bp showing that both lake valleys were ice free extremely early given their northerly location fire events started after 9600 cal yr bp and became less common around the 8 2 ka event woody vegetation provided fuel that contributed to fires the first vegetation in our pollen record consisted of hippophae dryas grasses and sedges subsequently broadleaved trees betula salix increased in abundance and later pinus alnus ferns and lycopodium characterized the vegetation pollen from larix picea and malus were also found the change in vegetation composition was synchronous with the decrease in lake water ph in the region indicating ecosystem scale processes this occurred during a period of net global and regional warming the changes in fire frequency and vegetation appear independent of regional trends in precipitation the reconstructed fire history and vegetation support the scenario of early ice free areas far north in scandinavia during early holocene warming creating favorable conditions for woody plants and wildfires

fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model the evolution of ice sheet configuration and flow pattern in fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model i e a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets the model uses mapped flow traces and deglacial melt water landforms as well as relative chronologies derived from cross cutting striae and till lineations as input data flow trace systems were classified into four types i time transgressive wet bed deglacial fans ii time transgressive frozen bed deglacial fans iii surge fans and iv synchronous non deglacial event fans using relative chronologies and aggregation of fans into glaciologically plausible patterns a series of ice sheet configurations at different time slices was erected a chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume geological evidence exists for several discrete ice sheet configurations centred over the scandinavian mountain range during the early weichselian the build up of the main weichselian fennoscandian ice sheet started at approximately 70 ka and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern norway this configuration had a flow pattern which is poorly reproduced by current numerical models of the fennoscandian ice sheet at the last glacial maximum the main ice divide was located overthe gulf of bothnia a major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the scandinavian mountain chain widespread areas of preserved pre late weichselian landscapes indicate that the ice sheet had a frozen bed core area which was only partly diminished in size by inward transgressive wet bed zones during the decay phase

deglaciation of the eurasian ice sheet complex the eurasian ice sheet complex eisc was the third largest ice mass during the last glacial maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea level lowering whilst recent terrestrial and marine empirical insights have improved understanding of the chronology pattern and rates of retreat of this vast ice sheet a concerted attempt to model the deglaciation of the eisc honouring these new constraints is conspicuously lacking here we apply a first order thermomechanical ice sheet model validated against a diverse suite of empirical data to investigate the retreat of the eisc after 23 ka bp directly extending the work of patton et al 2016 who modelled the build up to its maximum extent retreat of the ice sheet complex was highly asynchronous reflecting contrasting regional sensitivities to climate forcing oceanic influence and internal dynamics most rapid retreat was experienced across the barents sea sector after 17 8 ka bp when this marine based ice sheet disintegrated at a rate of 670 gigatonnes per year gt a 1 through enhanced calving and interior dynamic thinning driven by oceanic atmospheric warming and exacerbated by eustatic sea level rise from 14 9 to 12 9 ka bp the eisc lost on average 750 gt a 1 peaking at rates 3000 gt a 1 roughly equally partitioned between surface melt and dynamic losses and potentially contributing up to 2 5 m to global sea level rise during meltwater pulse 1a independent glacio isostatic modelling constrained by an extensive inventory of relative sea level change corroborates our ice sheet loading history of the barents sea sector subglacial conditions were predominately temperate during deglaciation with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network moreover the maximum eisc and its isostatic footprint had a profound impact on the proglacial hydrological network forming the fleuve manche mega catchment which had an area of 2 5 106 km2 and drained the present day vistula elbe rhine and thames rivers through the seine estuary during the bolling allerod oscillation after c 14 6 ka bp two major proglacial lakes formed in the baltic and white seas buffering meltwater pulses from eastern fennoscandia through to the younger dryas when these massive proglacial freshwater lakes flooded into the north atlantic ocean deglaciation temporarily abated during the younger dryas stadial at 12 9 ka bp when remnant ice across svalbard franz josef land novaya zemlya fennoscandia and scotland experienced a short lived but dynamic re advance the final stage of deglaciation converged on present day ice cover around the scandes mountains and the barents sea by 8 7 ka bp although the phase lagged isostatic recovery still continues today

turbidites from giant hawaiian landslides results from ocean drilling program site 842 pliocene to pleistocene volcanic sand turbidites recovered 320 km west of the island of hawaii at ocean drilling program site 842 contain fragments off fresh weakly vesicular glass and tests of pleistocene and eocene radiolarians this sand is probably related to turbidity currents generated from debris avalanches produced by giant landslides on the flanks of the hawaiian islands on their way to site 842 the currents flowed over the m bigh ha waiian arch indicating that the turbidity currents were at least 325 m thick similar sand has been reported 930 km south of the islands thus hawaiian giant landslides play a significant role in central pacific deep sea sedimentary processes

alpine debris covered glaciers as a habitat for plant life debris covered glaciers represent a significant increasing fraction of glaciers and can host plant life on their surface the goal of this work was to evaluate the suitability of supraglacial debris as a habitat for plant life and to discuss its ecological and biogeographic role the research was carried out on the miage glacier mont blanc massif western alps italy vegetation cover was sampled using a regular sampling grid recording plant species and number of individuals in 71 plots detailed glaciological parameters surface temperature debris thickness glacier surface velocity were recorded or derived from published data relationships between vegetation and environmental variables were assessed through generalized linear models principal components analysis and canonical correspondence analysis the glacier surface hosted a high biodiversity with 40 vascular plant species including trees and shrubs plant cover was arranged along an altitude glacier velocity gradient whilst debris thickn

growth of plants on the late weichselian ice sheet during greenland interstadial 1 unglaciated forelands and summits protruding from ice sheets are commonly portrayed as areas where plants first establish at the end of glacial cycles but is this prevailing view of ice free refug

accumulation rates chemical partitioning and q mode factor analysis of metalliferous sediments from the north fiji basin abstract in order to assess recent hydrothermal contributions to pelagic sediments from active back arc spreading surface samples collected from the north central north fiji basin and the vanuatu archipelagic apron were chemically and mineralogically analyzed including phase and size partitioning and q mode factor analysis of the chemical data sediment cores were analyzed for accumulation rates by the excess 230 th method using alpha track autoradiography the north central north fiji basin sediments are largely carbonate oozes in which the non carbonate material is dominated by volcanic detritus in the 2 m fraction and by fe montmorillonite amorphous ferromanganese oxides and fine grained volcanic ash in the m fraction phase and size partitioning indicate that metal concentrations in the m fraction approach those for metalliferous sediments from the eastern pacific and that the metalliferous material in the majority of these sediments is concentrated in the oxide portion of the m fraction suggesting potential widespread colloidal dispersion from the source areas iron accumulation rates are similar to those of metalliferous sediments from the east pacific rise the mean mn accumulation rate is about twice the global authigenic rate whereas al is accumulating about ten times faster than in eastern and equatorial pacific pelagic sediments because of volcanic ash contributions from the vanuatu island arc and possible intra basin volcanism q mode factor analysis of the compositional data produced three major factors hydrothermal authigenic and detrital which together account for 90 of the sample variance in both size fractions of the non carbonate material the aerial distribution of the m fraction factor components reveals a major hydrothermal source associated with the south pandora ridge spreading center in general agreement with the mn and as accumulation rate patterns two smaller hydrothermal sources were revealed by the factor analysis which are not associated with any known active tectonic features suggesting that back arc rifting and associated hydrothermal activity in this portion of the north fiji basin may follow both ordered and complex regional modes

hawaiian xenolith populations magma supply rates and development of magma chambers hawaiian volcanoes pass through a sequence of four eruptive stages characterized by distinct lava types magma supply rates and xenolith populations magma supply rates are low in the earliest and two latest alkalic stages and high in the tholeiitic second stage magma storage reservoirs develop at shallow and intermediate depths as the magma supply rate increases during the earliest stage magma in these reservoirs solidifies as the supply rate declines during the alkalic third stage these magma storage reservoirs function as hydraulic filters and remove dense xenoliths that the ascending magma has entrained during the earliest and latest stages no magma storage zone exists and mantle xenoliths of lherzolite are carried to the surface in primitive alkalic lava during the tholeiitic second stage magma storage reservoirs develop and persist both at the base of the ocean crust and 3 7 km below the caldera only xenoliths of shallow origin are carried to the surface by differentiated lava during the alkalic third stage magma in the shallow subcaldera reservoir solidifies and crustal xenoliths including oceanic crustal rocks are carried to the surface in lava that fractionates in an intermediate depth reservoir worldwide xenolith populations in tholeiitic and alkalic lava may reflect the presence or absence of subvolcanic magma storage reservoirs

a chronological framework for the holocene vegetational history of central minnesota the steel lake pollen record abstract paleorecords from minnesota and adjacent areas have often been used to evaluate large scale climatic processes in the mid continent of north america however most of these records are compromised by chronological flaws making problematic any comparisons with climatic interpretations based on other records e g gisp2 in greenland we report here a high resolution pollen record with a secure chronology constrained by 26 14 c dates on terrestrial macrofossils from steel lake central minnesota about 11 2 ka cal bp 11 000 calibrated yr before present the late glacial picea forest near steel lake was succeeded abruptly by pinus banksiana and or resinosa the pinus forest began to open 9 4 ka cal bp with the expansion of prairie taxa and a pine parkland or savanna prevailed until about 8 ka cal bp when quercus replaced pinus to become the dominant tree in the prairie areas for 4500 yr the close chronological control permits the correlation of key vegetational changes with those at other reliably dated sites in the eastern dakotas and in minnesota suggesting that the abrupt decline of the spruce forest was time transgressive from southwest to northeast during 2000 yr and that the development of prairie was time transgressive in the same direction over 2600 yr correlation of key pollen horizons at steel lake with those in the high resolution pollen profiles of elk lake ca 50 km northwest of steel lake suggests that the well known elk lake varve chronology for the early holocene is about 1000 yr too young

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

stratigraphic constraints on the timing and emplacement of the alika 2 giant hawaiian submarine landslide abstract previous work has found evidence for giant tsunami waves that impacted the coasts of lanai molokai and other southern hawaiian islands tentatively dated at 100 and 200 ka by u series methods on uplifted coral clasts seafloor imaging and related work off hawaii island has suggested the alika phase 2 debris avalanche as the source of the 100 ka giant wave deposits although its precise age has been elusive more recently a basaltic sand bed in odp site 842 300 km west of hawaii estimated at 100 20 ka has been suggested to correlate with this or another large hawaiian landslide our approach to the timing and linkage of giant submarine landslides and paleo tsunami deposits is a detailed stratigraphic survey of pelagic deposits proximal to the landslide feature beginning with a suite of seven piston gravity and box cores collected in the vicinity of the alika 2 slide we used u series dating techniques including excess 230 th and 210 pb profiling high resolution paleomagnetic stratigraphy including continuous u channel analysis 18 o stratigraphy visual and x ray sediment lithology and the petrology and geochemistry of the included turbidites and ash layers minimum ages for the alika phase 2a slide from detailed investigation of two of the cores are 112 15 ka and 125 24 ka 2 based on excess 230 th dating a less precise age for the alika phase 1 and or south kona slide is 242 80 ka 2 consistent with previous geological estimates oxygen isotope analyses of entrained planktonic foraminifera better constrain the alika phase 2a maximum age at 127 5 ka which corresponds to the beginning of the stage 5e interglacial period it is proposed that triggering of these giant landslides may be related to climate change when wetter periods increase the possibility of groundwater intrusion and consequent phreatomagmatic eruptions of shallow magma chambers our study indicates the contemporaneity of the alika giant submarine landslides and distal deposits from enormous turbidity currents as well as coral clasts reported to be tsunami deposits on lanai and molokai through direct dating and compositional analysis of the landslide deposits

giant submarine landslides submarine landslides can generate enormous turbidity currents that carry that carry 500 km3or more of sediment down to the oceans abyssal plains the slides can cause tsunamis and may release large amounts of methane to the air

fossiliferous lana i deposits formed by multiple events rather than a single giant tsunami giant tsunamis generated by submarine landslides in the hawaiian islands have been thought to be responsible for the deposition of chaotic gravels high on the southern coastal slopes of the islands of lana i and moloka i hawaii here we investigate this hypothesis using uranium thorium dating of the hulopoe gravel on lana i and a study of stratigraphic relationships such as facies changes and hiatuses within the deposit the hulopoe gravel contains corals of two age groups representing marine isotope stages 5e and 7 135 000 and 240 000 years ago respectively with significant geographical and stratigraphic ordering we show that the hulopoe gravel was formed by multiple depositional events separated by considerable periods of time thus invalidating the main premise of the giant wave hypothesis instead the gravels were probably deposited during interglacial periods when sea level was relatively high by typical hawaiian shoreline processes such as seasonal wave patterns storm events and possibly normal tsunamis and reached their present height by uplift of lana i

olduvai termination detailed palaeomagnetic analysis of a north central pacific core summary a high resolution record of the termination of the olduvai normal to reverse subchron 1 77 myr polarity transition was obtained from a fully azimuthally oriented deep sea sediment piston core recovered at a northern mid latitude site 37 22 4 n 179o36 l w the n r olduvai reversal was continuously sampled at 3 to 5 mm intervals across 130 cm of section this continuous sampling was achieved by staggering the 1 cc plastic boxes incrementally so that offset segments corresponding to sampling windows of 3 to 5 mm were obtained the reversal is well defined and at least 10 truly intermediate directions have been recorded displaying a definite directional change of moo with a pronounced decrease in intensity of magnetization the decrease of magnetization and the directional change coincide closely the inclination record during the transition is characterized by a brief steepening trend early in the reversal passing through high positive values followed by a gradual shallowing trend this time passing through the horizontal from this point on the inclinations show a final settling about the reversed polarity mean this record is characterized by full normal and reverse polarity directions which are in good agreement f2 with those predicted by the geocentric axial dipole field model for the core site latitude the estimated duration of the directional change was about 10 ooo yr whereas that of the intensity decrease was between 12 ooo and 16 ooo yr anhysteretic remanent magnetization arm studies and thermomagnetic analyses indicate that a uniform magnetic mineralogy characterizes the transition zone of the core this further suggests that the j10 arm70 ratio may represent a relative palaeointensity estimate and may thus indicate a decrease of the intensity of the geomagnetic field during the reversal the virtual geomagnetic pole vgp path of the record is far sided directions in projected d 1 space indicate that the n r olduvai reversal transition field geometry had contributions from both non axisymmetric and axisymmetric terms the results based on this single record show that 1 the palaeofield at this locality during the olduvai transition was characterized by contributions from both zonal and non zonal terms but the contribution of non zonal quadrupolar terms was predominant this is in contrast to the observation by herrero bervera et al 1991 based on four deep sea records in which the vgps show general confinement within the longitude band of the americas and their antipode that the transitional field may be dominated by a dipolar component 2 the field intensity dropped to about 22 per cent of its initial or final recovered value during the transition it stayed at or close to this minimum for approximately half or less of the overall intensity change

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr