the 1996 ad delta collapse and large turbidite in lake brienz abstract in spring 1996 ad the occurrence of a large mass transport was detected by a series of events which happened in lake brienz switzerland turbidity increase and oxygen depletion in deep waters release of an old corpse into surface waters and occurrence of a small tsunami like wave this mass transport generated a large turbidite deposit which is studied here by combining high resolution seismic and sedimentary cores this turbidite deposit correlates to a prominent onlapping unit in the seismic record attaining a maximum of 90 cm in thickness it is longitudinally graded and thins out towards the end of the lake basin thickness distribution map shows that the turbidite extends over 8 5 km2 and has a total volume of 2 72 106 m3 which amounts to 8 7 yr of the lake s annual sediment input it consists of normally graded sand to silt sized sediment containing clasts of hemipelagic sediments topped by a thin white clay sized layer the source area the exact dating and the possible trigger of this turbidite deposit as well as its flow mechanism and ecological impact are presented along with environmental data river inflow wind and lake level measurements the combined results indicate that no particular cause i e earthquake explosion flood wind storm lake level change seiche or sediment dredging triggered the 1996 ad large turbidite deposit instead it was due to a delta slope failure most likely caused by normal sediment accumulation

submarine landforms in the fjords of southern chile implications for glacimarine processes and sedimentation in a mild glacier influenced environment abstract chilean fjords are the lowest latitude at which glaciers reach the sea today high accumulation and mass throughput sustain tidewater glacier margins in this relatively mild climatic and oceanographic setting 27 000 km 2 of swath bathymetry allow mapping of sea floor landforms and inferences on glacimarine sediments and sedimentation tidewater glaciers are present in several fjords beyond retreating tempano glacier a terminal moraine marks the limit of probable little ice age advance with smaller transverse ridges closer to the glacier beyond advancing pio xi glacier there are few signs of organised submarine landforms older moraine ridges along several fjords formed at still stands during deglaciation elsewhere meltwater fed braided rivers connect the glacial and marine sedimentary systems swath imagery shows glacifluvial and fluvial deltas with small channels and chutes that develop into long and sinuous turbidity current channels few iceberg ploughmarks and submarine slope failures were observed but several fields of pockmarks were present the fjords of chile are dominated by sediment delivery from turbid meltwater which distributes fine grained debris widely producing sorted and laminated fine grained ice proximal wedges and draping ice distal seismic architecture to give a predominantly smooth sea floor turbidity currents also transfer sediments to some ice distal environments the chilean fjordlands represent the mildest climatic and oceanographic end member of a continuum of glacier influenced marine settings similar to south east alaska in the northern hemisphere components of a landform assemblage model for climatically mild meltwater dominated fjords include ice contact moraine ridges glacifluvial and fluvial deltas and turbidity current channels full glacial and deglacial streamlined subglacial landforms are likely to have been buried in many areas by subsequent glacimarine sedimentation

the quaternary geology of the labrador shelf the regional distribution of glacial and postglacial sediments on the labrador shelf was mapped by medium and high resolution seismics and shows a succession of tills that extend to the continental shelf edge at approximately 600 m the uppermost of these tills is less laterally extensive and does not occur on the labrador shelf bank tops in water depths less than 160 m we infer that the last glacial episode was less extensive than the preceding ones glaciomarine stratified silts and postglacial muds are found overlying the upper till in the deep basins that separate the banks the upper till glaciomarine silts and postglacial muds are interpreted to constitute one complete deglacial cycle radiocarbon age determination suggests this deglacial sequence began at approximately 20 000 years bp on the northernmost labrador shelf and hudson strait seismic evidence indicates a late glacial readvance locally deposited a till that overlies the glaciomarine sediments associated with the last glacial advance

structural tectonic and glaciological controls on the evolution of fjord landscapes abstract the fjord landscape of south america stretching 1500 km between golfo corcovado 43 s and tierra del fuego 56 s is the largest continuous fjord landscape on earth this paper presents the results of new structural geological and geomorphological mapping of this landscape using optical satellite images and digital elevation models first order geological structures are represented by strike slip faults forming lineaments up to hundreds of kilometres long the strike slip faulting has been active since late cretaceous times and is responsible for the presence of a conspicuous structural cleavage visible as lineaments up to 10 km long a detailed analysis of these second order lineaments from digital image data was carried out in three sectors in sector 1 located northwest of the north patagonian icefield there are three distinct mean orientations characterized by a main nearly orogen parallel orientation az 145 and two orogen oblique secondary orientations az 20 and az 65 in sector 2 located west of the south patagonian icefield there are also three separate mean orientations with most of the lineaments concentrated between azimuths 0 and 80 mean at 36 and two other orogen oblique means at azimuth 122 and 163 in sector 3 around the cordillera darwin there is a single main orogen parallel mean at 100 115 in all three sectors mapped fjord orientations bear a striking similarity to the structural data with fjords orientated preferentially in the same direction as structural lineaments we infer that successive glaciations followed the same ice discharge routes widening and deepening pre existing geological structures at the expense of the surrounding terrain to create the fjord landscape this study has broader implications for ice sheet reconstructions and landscape evolution beneath ice sheets because we demonstrate that the primary control on fjord development in glaciated areas is geological and not glaciological

thick and fast sedimentation in a pleistocene fiord lake of british columbia canada the central interior plateau of british columbia canada is dissected by numerous elongate glacially overdeepened lake basins akin to coastal fiords an air gun seismic reflection investigation 242 km of trackline of okanagan lake 120 km long 3 5 km wide shows that the pleistocene sediment fill is up to 792 m thick and that bedrock has been excavated by repeated pleistocene glacial erosion to nearly 650 m below sea level the depth of bedrock incision below the surrounding plateau is more than 2000 m exceeding that of the grand canyon in arizona the total volume of sediment infill within the narrow trenchlike basin is more than 90 km 3 and several lines of evidence suggest that this fill accumulated rapidly during a single phase of glaciolacustrine sedimentation during late wisconsin deglaciation of the region after 15 ka similar fiord lake basins up to 100 km long are common in the interior of british columbia if the data from okanagan are representative these basins may represent a major previously unrecognized component of the total glacial sediment flux to the ocean overdeepening below sea level and the focusing of large volumes of glacial sediment and meltwater into such basins are of considerable glaciologic significance and may record the fast unstable flow of ice streams during deglaciation of the cordilleran ice sheet

widespread deformation of basin plain sediments in aysen fjord chile due to impact by earthquake triggered onshore generated mass movements abstract the 2007 mw 6 2 earthquake in aysen fjord caused widespread basin plain deformation and has had prehistorical predecessors both superficial and buried deformed basin plain deposits are mapped using multibeam bathymetry and seismic reflection sparker profiling the seismic signature of the sediment was ground truthed with short cores on key locations deformed basin plain deposits induced by the 2007 earthquake can be divided in frontally emergent and confined deposits with both a deep and shallow basal shear surface all deformed basin plain deposits with a deep basal shear surface are induced by the weight and impact of a slope adjacent mass flow wedge the frontally emergent most mobile basin plain deformation is triggered by mass flows originating from onshore mass movements i e debris flows rock slides and avalanches propagating into the fjord this basin plain deformation results in vertical seafloor offsets of up to 20 m therefore it might be even more important for far field tsunami propagation than the impact of the onshore mass movements on the sea surface in the depressions created by the basin plain deformation megaturbidites occur while more distally sandy density flow deposits cover the seafloor the data also indicates that these density flows propagate slower than the basin plain deformation based on correlations with the two main eruptions of the hudson volcano we hypothesize that during the holocene three to four similar events have struck the fjord the small variability of the structural characteristics of the liquine ofqui fault zone in the northern patagonian fjordland and historical seismic swarms in this area make us conclude that similar hazards should be taken into account for most of the fjords in this region

the seismic stratigraphy of okanagan lake british columbia a record of rapid deglaciation in a deep fiord lake basin this paper presents the first detailed data regarding the newly discovered deep infill of okanagan lake okanagan lake 50 00 n 119 30 w is 120 km long 3 5 km wide and occupies a glacially overdeepened bedrock basin in the southern interior of british columbia this basin and other elongate lakes of the region e g shuswap kootenay kalamalka canim and mahood lakes mark the site of westward flowing ice streams within successive cordilleran ice sheets an air gun seismic survey of okanagan lake shows that the bedrock floor is nearly 650 m below sea level more than 2000 m below the rim of the surrounding plateau the maximum thickness of pleistocene sediment in okanagan lake basin approaches 800 m forty six seismic reflection traverses and an axial profile show a relatively simple stratigraphy composed of three seismic sequences argued to be no older than the last glacial cycle 30 ka a discontinuous basal unit sequence i characterized by large scale diffractions and up to 460 m thick infills the narrow v shaped bedrock floor of the basin and is interpreted as a boulder gravel deposited by subglacial meltwaters overlying seismic sequence ii is composed of two sub sequences sub sequence iia is a chaotic to massive facies up to 736 m thick lakeshore exposures close to where this unit reaches lake level show deformed and chaotically bedded glaciolacustrine silts containing gravel lens and large ice rafted boulders the surface topography of this sub sequence is irregular and in general mimics the form of the underlying bedrock as a result of compaction this sequence passes laterally into stratified facies sub sequence iib at the northern end of the basin seismic sequence ii appears to record rapid ice proximal dumping of glaciolacustrine silt as the okanagan glacier backwasted upvalley in a deep lake a thin 60 m max laminated seismic sequence iii drapes the hummocky surface of sequence ii and represents postglacial sedimentation from fan deltas the extreme thickness of sequences i and ii in okanagan lake reflects the focussing of large volumes of meltwater and sediment into the basin during deglaciation pre existing sediments that pre date the last glacial cycle appear to have been completely eroded glaciological conditions during sedimentation may have been similar to marine based outlet glaciers calving in deep water in fiord basins in contrast to marine settings where ice bergs are free to disperse large volumes of dead ice were trapped within the basin structural evidence for sedimentation around dead ice blocks has been previously used to argue that the cordilleran ice sheet downwasted in situ we emphasize in contrast the trapping of dead ice left behind by rapidly calving lake based outlet glaciers

fjords as temporary sediment traps history of glacial erosion and deposition in muir inlet glacier bay national park southeastern alaska glacimarine sedimentary deposits within the basins of muir inlet a 48 km long silled fjord are interpreted from complimentary sets of high resolution seismic reflection profiles using known glacial advance and retreat history two prominent glacial erosion surfaces are identified the lowest attributed to the last glacial maximum lgm advance and the upper coincident with the little ice age lia advance the lgm ice sheet which advanced onto the continental shelf was 1700 m thick in muir inlet and eroded bedrock whereas the thinner lia ice did not lgm deposits 300 m thick occur beneath the lia erosion surface in the deepest basins evidence for earlier neoglacial advances is present in subaerial deposits however neoglacial sediments preserved within the marine record are restricted to one depositional package on the entrance sill volumes of lia retreat sediments were calculated within basins an average annual sediment flux was calculated by modeling the duration of sediment contributed from muir glacier and from tributary glaciers and side entry sources the annual sediment flux ranged from 1 3 10 6 m 3 yr to 4 6 10 7 m 3 yr and increases logarithmically with increasing drainage basin area similar to fluvial systems this sediment flux does not only represent bedrock erosion additional sediment is contributed from persistent tributary glaciers and from lgm sediment stored within deeper basins basin wide reflections characterize the most common seismic facies and indicate that strata are horizontal and continuous across each basin confirming the importance of sediment gravity flows originating from sills and sloping fjord walls

dust production by abrasion of eolian basalt sands analogue for martian dust dust is nearly ubiquitous on mars covering much of the planet s surface having been redistributed by dust storms analysis of dust via landed instrumentation indicates a basaltic composition for its protolith the same is interpreted for the dark dune sands encountered at rover field sites in this paper we used samples of aeolian sands derived from basaltic volcanoes in an experiment to simulate dust production from basalt dune sands within an abrasion chamber in addition we used samples from gypsum dunes because gypsum is found within dune fields on the northern plains of mars the results expressed as weight of sample reduced to dust show a remarkably broad range over four orders of magnitude aeolian abrasion of basalt sands can produce similar amounts of dust as is the case for some desert sands on earth some plausible mars analogue materials can produce large amounts of dust suggesting that aeolian movement of basaltic sand and volcanic sediments on the surface of mars is a potential source of fine grained sediment or dust

fjord stratigraphy and processes evidence from the ne atlantic fensfjorden system fjords commonly hold sediment basins with high temporal resolution that mirror land and marine based processes and depositional environments during a glacial interglacial cycle here we present topas seismic profiles with a vertical resolution of 30 cm bathymetric records and a gravity core from fensfjorden west norway which allow a detailed study of sedimentary processes and depositional environments in a ne atlantic fjord system fensfjorden hosts a sediment volume of 0 70 km3 and the sediment basins evolved reach a maximum thickness of 100 m the basins are characterized by a lower acoustically well laminated glacimarine unit of allerod and younger dryas age this unit is overlain by several acoustically transparent lenses interpreted to be slide debrites we suggest these slide debrites to be a result of recurrent mass failures that occurred between 11 500 and 2100 cal a bp a thin late holocene hemipelagic unit drapes the slide debrites during the late holocene the sedimentation rates in fensfjorden decreased from 0 110 to 0 040 cm a 1 and two turbidity currents occurred in the 2040 1190 cal a bp time period this ability to map fjord processes in more detail has furthermore made it possible to revise the established stratigraphical framework for ne atlantic fjords copyright 2013 john wiley sons ltd

western norwegian fjord sediments age volume stratigraphy and role as temporary depository during glacial cycles abstract the sediments in the western norwegian fjords are described chronologically qualitatively and quantitatively by means of seismic profiling and correlation with dated terrestrial sediments along the fjords five chronostratigraphic units i v are proposed for the fjord sediments using the well established quaternary stratigraphy in the area sediment volumes of the main fjords are calculated using a dense seismic grid combined with map analyses approximately 150 km 3 of sediments are present in the fjords between 59 63 n ninety percent of this material is considered to be deposited during deglaciation of the last weichselian ice sheet less than ten percent of the fjord sediments in this area is older than the last glacial weichselian maximum both glacial and glaciofluvial processes are active in emptying the fjord basins and transporting the sediments to the continental shelf and slope during glaciations

the sedimentary record of glacial retreat marinelli fjord patagonia regional correlations and climate ties abstract the inland passage of chile comprises the most continuous latitudinal transect of ice fields ice caps and alpine glaciers in the southern hemisphere providing an excellent natural laboratory for the study of glacial response to climate change during the holocene here we report results from a marine geological investigation of marinelli fjord tierra del fuego 54 25 s 69 35 w and ainsworth fjord which merges with marinelli fjord data acquired during july 2005 onboard the rv ib nathaniel b palmer include high resolution seismic data multibeam swath bathymetry data and sediment cores post cruise analyses include detailed seismic facies and lithofacies analysis and radiocarbon dating the results indicate that a major transition in the glacimarine record from ice proximal facies to ice distal facies occurred in the outer basins of the fjord at 15 5 kyr to 12 5 kyr the ice proximal facies consists of pebbly mud with abundant laminations and is characterized by high average sedimentation rates 28 mm yr in contrast an ice distal facies is dominantly bioturbated mud with low average sedimentation rates 0 56 mm yr this transition marks the retreat of marinelli glacier from the outer basins with no evidence for glacial re advance subsequently during the mid to late holocene ainsworth glacier retreated and exposed ainsworth fjord our results are consistent with the climatic trends for southern south america where the final deglaciation of the region ended at 12 5 ka during the holocene stable ice conditions persisted until the mid 1960s when marinelli glacier began rapidly retreating to its modern day position

postglacial sequence stratigraphy of lake melville labrador abstract in lake melville labrador the quaternary glacimarine sediments reflect a single retreat phase of the laurentide ice sheet during the early holocene based on extensive airgun and high resolution seismic surveys sediment deposits are subdivided into thirteen units that are associated with glacial paraglacial and postglacial styles of deposition their distribution patterns reflect paleo positions of a retreating ice margin during the period between 10 000 and 9000 years before present formation of paraglacial deltas during the early to mid holocene 6 9 ka and postglacial tidal influenced deposition during the late holocene

erosion and infill of new york finger lakes implications for laurentide ice sheet deglaciation a comprehensive seismic reflection profile investigation of the new york finger lakes has revealed the extent of bedrock erosion and nature of sediment fill beneath the lakes bedrock deepens to the south where gorgelike profiles have been eroded to as much as 304 m below sea level and infilled with up to 275 m of late quaternary age 14 ka sediment we propose a working hypothesis that invokes ice streaming and pressurized subglacial meltwater and sediment to account for regional geomorphology this working hypothesis is consistent with recent concepts of the collapse of continental ice sheets via ice streaming and the marine isotopic record for a meltwater spike at 13 14 ka the finger lakes may provide a critical testing ground for deglaciation models of the southern laurentide ice sheet because they contain a thick well preserved and now seismically defined record of the deglaciation process

sedimentation in chilko lake a record of the geomorphic environment of the eastern coast mountains of british columbia canada abstract chilko lake is the largest and deepest lake draining the coast mountains of british columbia a sedimentary record from the 60 km long lake was constructed by using 3 5 khz subbottom acoustic profiles and short cores of surface sediments sediment accumulation since deglaciation is remarkably thin averaging less than 10 m except in the central deep part of the lake despite extensive activity of holocene and modern glaciers in the 1960 km 2 contributing watershed sediment focusing of silts and clays in the main part of the lake occurs mainly by overflow interflow processes from the edmond and nine mile deschamps drainages sandy turbidites from these drainages and other smaller streams however extend for several kilometers into the lake basin distinct laminae in short cores from the central lake suggest that modern rates of deposition reach a maximum of 2 2 mm a 1 210 pb dating and inferences from the acoustic results however indicate a lake wide long term average rate of less than 1 mm a 1 which is equivalent to a specific sediment yield of about 80 t km 2 a 1 this specific yield is amongst the lowest for glacier fed lakes of the southern canadian cordillera a low sediment supply can be related to three factors 1 a much drier climate on the leeward side of the coast mountains producing lower specific discharges 2 fewer autumn rainstorms that affect mainly lakes west of the coast mountains and 3 opportunities for storage of sediment in the lower 20 km of edmond river which drains the most heavily glacierized portion of the watershed

geomorphological criteria for identifying pleistocene ice streams ice streams are critical regulatory mechanisms in contemporary ice sheets it has been inferred that they also had a significant effect on the dynamics of former ice sheets subsequently many people have invoked their widespread occurrence from a variety of formerly glaciated areas hypothesised locations however have often outweighed meaningful evidence this paper addresses the problem using the characteristics of contemporary ice streams as a basis for their identification from former ice sheet beds a convergence of knowledge gained from contemporary ice stream research coupled with theories of glacial geomorphology allows several geomorphological criteria to be identified as suggestive signatures of ice stream activity it is envisaged that the geomorphological criteria developed here will introduce a more objective approach to the study of former ice streams the criteria are used to construct conceptual land system models of the beds of former ice streams and it is hoped such models can provide an observational template upon which hypotheses of former ice streams can be better based

megaturbidite deposits in the holocene basin fill of lake como southern alps italy abstract for the first time limnogeological investigations have been carried out in lake como the deepest lake of the alps combining a bathymetric survey multibeam simrad 3000 with a high resolution seismic reflection study single channel 3 5 khz sub bottom profiler and a coring campaign gravity corer this data set enables detailed characterization of the sedimentary subsurface in the western branch of the lake the como branch which has a typical fjord morphology this paper focuses on the deepest part of the como branch argegno basin in which up to 3 5 m thick turbidite deposits are identified the basin fill of the como branch is characterized by well layered draping and onlapping pelagic sediments that are locally affected by creeping and that are intercalated with mass wasting deposits in particular with two large debris flow deposits evolving into megaturbidites in the deepest part of the basin the multibeam data together with the acoustic facies distributions and the volumes of these two major sedimentary deposits mt1 3 106 m3 and mt2 10 5 106 m3 indicate that they resulted from large slides at the northern tip of the como branch along the steep slopes of a sub lacustrine plateau the estimated ages of these events around the mid 12th mt1 and early 6th mt2 centuries are extrapolated from mean sedimentation rates based on radiocarbon 14c and radionuclide 137cs analyses from short cores in the argegno basin possible trigger mechanisms leading to these catastrophic events in the como branch include a combination of steep slope overloading with significant lake level fluctuations related to holocene climate change and or earthquake shaking the tentative age assignment places the age of both major mass movements near two other events mt1 near the occurrence of a major earthquake in the po plain in 1222 ad intensity ix mcs macroseismically derived magnitude 6 2 and mt2 near a megaturbidite triggered in 700 ad in a proglacial lake in southeastern switzerland blass a anselmetti f grosjean m sturm m 2005 the last 1300 years of environmental history in the sediments of lake sils engadine switzerland eclogae geologicae helvetiae 98 319 332 since dangerous tsunami like waves seiches can be generated by large sub aqueous landslides leading to such megaturbidites in this fjord like basin future studies are required 1 to constrain the age of these catastrophic events 2 to document the stabilities of the steep slopes in the como branch 3 to assess the expected frequency of such catastrophic events and 4 to model the propagation of large waves in the como branch and their potential damage along the highly populated lake shore

freshwater outbursts to the oceans from glacial lake agassiz and their role in climate change during the last deglaciation abstract lake agassiz was the largest lake in north america during the last deglaciation as the laurentide ice sheet lis retreated large volumes of water stored in this proglacial lake were episodically released into the oceans these waters were variably routed to the gulf of mexico arctic ocean north atlantic ocean and hudson bay during this period the three largest cooling events in the northern hemisphere closely followed 4 of the 5 largest outbursts from lake agassiz 1 the younger dryas which was preceded by a release of 9500 km 3 2 the preboreal oscillation preceded by releases of 9300 km 3 and 5900 km 3 and 3 the 8 2 ka cold event preceded by a 163 000 km 3 outburst these are respectively fluxes of 0 30 sv 0 29 sv 0 19 sv and 5 2 sv if released in 1 year because the influx of freshwater reaching the north atlantic ocean can inhibit thermohaline circulation partly depending on whether the ocean was in a glacial interglacial or transitional mode of circulation we believe that at least these large outbursts from lake agassiz may have provided the triggers for changes in ocean circulation and in turn for widespread climate change

geophysical surveys of the sediments of loch ness scotland implications for the deglaciation of the moray firth ice stream british irish ice sheet we present results from three geophysical campaigns using high resolution sub bottom profiling to image sediments deposited in loch ness scotland sonar profiles show distinct packages of sediment providing insight into the loch s deglacial history a recessional moraine complex in the north of the loch indicates initial punctuated retreat subsequent retreat was rapid before stabilisation at foyers rise formed a large stillstand moraine here the calving margin produced significant volumes of laminated sediments in a proglacial fjord like environment subsequent to this ice retreated rapidly to the southern end of the loch where it again deposited a sequence of proglacial laminated sediments sediment sequences were then disturbed by the deposition of a thick gravel layer and a large turbidite deposit as a result of a jo kulhlaup from the spean roy ice dammed lake these sediments are overlain by a holocene sheet drape data indicate i a former tributary of the moray firth ice stream migrated back into loch ness as a major outlet glacier with a calving margin in a fjord like setting ii there was significant sediment supply to the terminus of this outlet glacier in loch ness and iii that jo kulhlaups are important for sediment supply into proglacial fjord lake environments and may compose 20 of proglacial sedimentary sequences

buried preglacial fluvial gorges and valleys preserved through quaternary glaciations beneath the eastern laurentide ice sheet the geomorphology geometry and sedimentary infill of buried gorges and v shaped valleys observed at the base of major river valleys in the formerly glaciated southeastern canadian shield region have been revealed from excavation and drilling data acquired during the construction of hydro electric dams and seismic data collected on lakes and offshore compilation of these previously published and unpublished data provided an exceptional opportunity to examine the morphology and spatial distribution of buried bedrock gorges and the mechanical processes responsible for their erosion in some valleys detailed observations of deep gorges have been allowed by their exhumation over large areas archive photographs show deep and large potholes natural pillars furrows flutes and scallops on the well polished bedrock walls of the gorges they also reveal that gorges and valleys have a sharp ending v shape and very narrow base and are superimposed by a u shaped valley forming a buried valley within valley topography the narrow and deep cross profile of these gorges their well polished slopes and the type of bedforms observed within them are typical features of fluvial bedrock channels drilling operations at many sites have also provided data on bedrock topography of these gorges within valleys and on the nature of their sedimentary infill the different lines of evidence presented in this paper indicate that gorges and v shaped valleys of the region were not eroded by the laurentide ice sheet during quaternary glaciations but are relics of a preserved preglacial fluvial system eroded during a lower base level this paleofluvial system is interpreted to be linked to fluvially cut channels observed on the seafloor of the estuary and gulf of st lawrence

a multidisciplinary overview of the lower mino river terrace system nw iberian peninsula abstract the mino river basin represents one of the main fluvial catchments draining the atlantic side of the iberian peninsula the extensive sedimentary deposits of this basin have been documented since the 19th century but limited research has been undertaken on these features historically and the quaternary record of the basin has remained understudied until recently research carried out over the last decade on the spanish margin of the mino river has enabled more detailed classification and mapping of the main fluvial landforms as well as numerical luminescence electron spin resonance cosmogenic dating of some of the deposits associated with palaeolithic archaeological sites here we synthesise the existing quaternary fluvial record for the basin and present new geospatial and chronological analyses for the lower catchment area our latest examination has enabled the identification of nine fluvial terrace levels and other regionally significant sedimentary features e g alluvial fans formed in response to tectonics eustatic changes and associated global climate changes the chronological data and calculated incision rates indicate that the various fluvial terraces were formed during the early to late pleistocene numerous palaeolithic sites have been found in association with the middle terrace levels between 40 and 13 m above present day river level primarily these archaeological sites preserve assemblages that feature large flake acheulean lfa tools though a number of middle palaeolithic sites have also been documented direct dating of these sites together with morphostratigraphic correlations across the terrace system suggest that the basin has been extensively occupied by human populations during the last 300 thousand years

generation and migration of coarse grained sediment waves in turbidity current channels and channel lobe transition zones large scale sediment waves composed of gravels and sands have been studied using deep water sidescan systems new data are presented from submarine channels off the canary islands and from canyon mouths off portugal data from other areas are briefly reviewed including a re interpretation of data from laurentian fan in order to summarise the varied morphology and setting of these bedforms coarse grained sediment waves are found in the proximal dominantly bypassing areas of deep water turbidite systems within canyons channels and channel lobe transition zones wave heights are in the region of 1 10 m and wavelengths are up to several hundred metres the distribution of waves and sparse sedimentological evidence from modern and ancient sediment wave fields suggests that initial transport and deposition of coarse sediment occurs within a high density turbidity current and not as a non newtonian debris flow in some cases the development of pronounced wave asymmetry and evidence of wave disruption and reworking suggests that the wave morphology is at least partially controlled by a later phase of low density turbidity flow grain size also appears to exert some control on wave morphology for example gravel rich waves have a greater height for the same wavelength than sand rich waves coarse grained sediment waves are often difficult to recognise on the seafloor because of reworking or burial by younger turbidity currents and are equally difficult to recognise in outcrop because of their large size

sedimentary processes and depositional environments in glaciated fjord systems evidence from nordfjord norway abstract fjords situated in past or present glacial regimes represent important repositories between land masses source systems and the open oceans sink systems newly collected topas high resolution seismic profiles from the previously glaciated nordfjord system on the west coast of norway reveal sedimentary processes and depositional environments within fjords in more detail than before the seismic data show that the fjord basins are characterised by a well laminated lower unit that is overlain by acoustic transparent lensoidal bodies we infer the lower unit which is up to 350 m thick to be composed of glacimarine sediments the transparent bodies represent up to 0 25 km 3 large slide debrites that comprise 14 c yr bp c 15 000 cal yr bp during the last deglaciation the entire nordfjord system was ice free for a short time period before the 1000 year long younger dryas readvance halted the main fennoscandian deglaciation and over ran the eastern part of nordfjord in contrast to the last glacial maximum we suggest that the sediments in the ice covered fjord basins were preserved during younger dryas the rapid isostatic adjustments accompanying the withdrawal of the younger dryas ice sheet promoted conditions for failures we relate the identified nordfjord slide bodies to this paraglacial environment this implies that the acoustic well laminated glacimarine fjord unit has been deposited in about 2000 yr and that sediment rates as high as 20 cm yr have existed during deposition

abrupt deglaciation events and holocene palaeoceanography from high resolution cores cartwright saddle labrador shelf canada the uppermost quaternary sediments in cartwright saddle labrador shelf are acoustically laminated with reflectors that can be traced over long distances two piston cores from the saddle record changes in sediment and meltwater delivery from the northeast margin of the laurentide ice sheet lis during deglaciation variations in sediment properties indicate a similar history of sediment accumulation over the last 12 kyr the temporal sampling interval reaches decadal resolution in the last deglacial period 7 9 ka analyses of total carbonate content sediment magnetic variables foraminiferal species and stable isotope measurements on planktic foraminifers show that abrupt changes occurred ca 10 9 9 2 8 8 7 9 and 7 ka with 450 yr correction there was no distinct change in sediment character during much of the younger dryas chronozone in the 18o record the 8 8 ka event is a dramatic 1 shift toward lower values which we associate with the noble inlet glacial event within hudson strait we do not see the pronounced low 18o event at 7 1 ka reported off nova scotia but surprisingly neither the nova scotia records nor other records in the labrador sea capture the impressive 8 8 ka change serious consideration must be given to the final collapse of the lis as the cause of the 8 2 cal ka cold event recorded in greenland and northwest europe copyright 1999 john wiley sons ltd

ice sheet grounding zone wedges gzws on high latitude continental margins abstract grounding zone wedges gzws are asymmetric sedimentary depocentres which form through the rapid accumulation of glacigenic debris along a line source at the grounding zone of marine terminating ice sheets during still stands in ice sheet retreat gzws form largely through the delivery of deforming subglacial sediments the presence of gzws in the geological record indicates an episodic style of ice retreat punctuated by still stands in grounding zone position moraine ridges and ice proximal fans may also build up at the grounding zone during still stands of the ice margin but these require either considerable vertical accommodation space or sediment derived from point sourced subglacial meltwater streams by contrast gzws form mainly where floating ice shelves constrain vertical accommodation space immediately beyond the grounding zone an inventory of gzws is compiled from available studies of bathymetric and acoustic data from high latitude continental margins the locations and dimensions of gzws from the arctic and antarctic alongside a synthesis of their key architectural and geomorphic characteristics are presented gzws are only observed within cross shelf troughs and major fjord systems which are the former locations of ice streams and fast flowing outlet glaciers typical high latitude gzws are less than 15 km in along flow direction and 15 to 100 m thick gzws possess a transparent to chaotic acoustic character which reflects the delivery of diamictic subglacial debris many gzws contain seaward dipping reflections which indicate sediment progradation and wedge growth through continued delivery of basal sediments gzw formation is inferred to require high rates of sediment delivery to a fast flowing ice margin that is relatively stable for probably decades to centuries although the long term stability of the grounding zone is controlled by ice sheet mass balance the precise location of any still stands is influenced strongly by the geometry of the continental shelf the majority of high latitude gzws occur at vertical or lateral pinning points which encourage grounding zone stabilisation through increasing basal and lateral drag and reducing mass flow across the grounding zone

signatures of slope failures and river delta collapses in a perialpine lake lake lucerne switzerland historical reports from the 17th century document two destructive tsunamis with runups exceeding 5 m affecting proximal basins of lake lucerne switzerland one event in ad 1601 is coeval with a strong nearby earthquake mw ca 5 9 which caused extensive slope failures in many parts of the lake the second event in ad 1687 is associated with an apparently spontaneous partial collapse of the muota river delta this study combines high resolution bathymetry reflection seismic and lithological data in order to document the sedimentary and morphological signatures of the two subaqueous mass movements that probably generated the observed tsunamis such mass movements are significant as a common sedimentation process and as natural hazard in fjord type lakes and similar environments the deposits covering large parts of the basins with thicknesses reaching 10 m consist of two subunits a lower massflow deposit contains variably deformed sediments from the source areas its emplacement affected pre existing sediments incorporating thin sediment slices into the deposit and increasing its volume deep reaching deformation near this is an accepted article that has been peer reviewed and approved for publication in the sedimentology but has yet to undergo copy editing and proof correction

what controls the location of ice streams ice streams influence ice sheet mass balance and stability but key aspects of their behaviour remain poorly understood this paper reviews and discusses one very important aspect what controls their location in an ice sheet seven potential controls on ice stream location are identified from the literature topographic focusing topographic steps macro scale bed roughness calving margins subglacial geology geothermal heat flux and subglacial meltwater routing for each control the theoretical basis for its link to rapid ice flow is introduced followed by discussion of the evidence of its influence on the location of both contemporary and palaeo ice streams based on this new synthesis topographic focusing subglacial geology meltwater routing and calving margins appear to be most commonly associated with fast ice flow it is clear that rather than a single control however there exist a number of potential controls of varying influence we propose a hierarchy of factors with those occurring at the top of the hierarchy exerting a stronger influence on ice stream location and where present beneath an ice sheet are very likely to be associated with fast flow those factors occurring lower down the hierarchy are less commonly associated with ice streaming but appear to be influential in the absence of more common controls in such a hierarchy topographic focusing in the presence of a calving margin is the primary control in the absence of this ice streams will preferentially occur in areas with favourable subglacial meltwater routing and subglacial geology in the absence of these bed roughness geothermal heat flux and topographic steps may promote ice streaming significantly the primary controls on a given ice stream location are likely to influence its spatial and temporal dynamics ice streams governed by the presence of meltwater routing and or calving processes might exhibit more variable behaviour because these controls can vary over relatively short time scales compared to controls that vary over longer time scales e g geothermal heat flux subglacial roughness geology and topography identifying the controls on ice stream location is therefore of paramount importance when understanding ice stream longevity and their past and future activity