eggs of titanosaurid sauropods from the upper cretaceous of auca mahuevo argentina we provide a detailed description of the sauropod eggs from the late cretaceous nesting site of auca mahuevo neuquen province argentina the only eggs that are unequivocally associated with titanosaurid dinosaurs these eggs are subspherical averaging 132 by 115 mm well preserved specimens display a pronounced eggshell ornamentation that consists mostly of single nodes averaging 0 58 mm in diameter and 0 28 mm in height base to apex with internodular values of 0 52 to 0 87 mm the pore canal network consists of vertical and horizontal canals intersecting at the bases of eggshell units vertical canals may fork defining a y pattern and their diameters vary between 0 08 and 0 2 mm their surficial apertures of 0 15 to 0 29 mm are funnel like and located between the surficial nodes in pristine specimens the eggshell thickness equals 1 31 mm and radial sections exhibit a single structural horizontal layer composed of juxtaposed shell units consisting of acicular calcite crystals radiating from an organic core relying only on taxonomically identified oological material we regard this character also shared in the innermost layer layer 1 of deinonychus antirrhopus oviraptorid theropods and observed during an early oogenetic stage in extant bird as primitive for saurischians the eggshell morphology advocates that these eggs were likely incubated in moist nesting environments perhaps such as nests covered with vegetal matter examination of the south american megaloolithid eggshells reveals that the titanosaurid eggs from auca mahuevo are mostly similar to those described as megaloolithus patagonicus and megaloolithus pseudomamillare

gas hydrate systems in petroleum provinces of the sw barents sea abstract 3d seismic data of the sw barents sea provided information about the existence of structure ii gas hydrates and shallow gas in marine sediments gas hydrates and shallow gas exist in the sw barents sea in conjunction with deep hydrocarbon reservoir leakage available conventional 3d seismic data show acoustic chimneys that extend to depths 1700 ms two way travel time below the seafloor the location of the chimneys coincides with structural boundaries and fault complexes cutting through mostly jurassic and triassic strata vertical fluid flow through these chimneys transports thermogenic gas to the gas hydrate stability zone causing the formation of a bottom simulating reflector bsr in addition variations of fluid flux across deep seated fault complexes cause changes in heat flow which explains the shoaling of the bsr and the formation of a tilted bsr tbsr at the border between the ringvassoya fault complex and the loppa high the stability model using thermogenic gas composition type i and ii shows gas hydrates are stable at 225 m 345 m depth corresponding to variation in the geothermal gradient for upper bsr 28 7 c km and 37 c km and lower bsr levels 23 4 c km and 28 3 c km these lateral changes in the temperature gradient can be reconciled with changes in upward fluid flow rates of 1 8 2 2 mm yr 1 such gas hydrate and fluid flow systems on arctic continental margins especially in shallow water depths are potential gas emitters due to their sensitivity to warming ocean temperatures

seismic evidence for shallow gas escape features associated with a retreating gas hydrate zone offshore west svalbard active gas venting occurs on the uppermost continental slope off west svalbard close to and upslope from the present day intersection of the base of methane hydrate stability bmhs with the seabed in about 400 m water depth in the inter fan region between the kongsfjorden and isfjorden cross shelf troughs from an integrated analysis of high resolution two dimensional pre stack migrated seismic reflection profiles and multibeam bathymetric data we map out a bottom simulating reflector bsr in the inter fan region and analyze the subsurface gas migration and accumulation gas seeps mostly occur in the zone from which the bmhs at the seabed has retreated over the recent past 1975 2008 as a consequence of a bottom water temperature rise of 1 c the overall margin parallel alignment of the gas seeps is not related to fault controlled gas migration as seismic evidence of faults is absent there is no evidence for a bsr close to the gas flare region in the upper slope but numerous gas pockets exist directly below the predicted bmhs while the contour following trend of the gas seeps could be a consequence of retreat of the landward limit of the bmhs and gas hydrate dissociation the scattered distribution of seeps within the probable hydrate dissociation corridor and the occurrence of a cluster of seeps outside the predicted bmhs limit and near the shelf break indicate the role of lithological heterogeneity in focusing gas migration

bottom characterization of lagoa das furnas on sao miguel azores archipelago abstract lagoa das furnas is a crater lake located in an area exposed to geohazards from earthquakes and volcanic activity on the island of sao miguel in the azores archipelago geophysical mapping of lagoa das furnas reveals a previously undiscovered volcanic dome this dome is comprised largely of subaquatic pyroclastic debris of trachytic composition sedimentological petrological geochemical and geochronological studies of pyroclastic deposits from the dome link it to the historically documented furnas 1630 eruption the chemistry of glass and crystal fragments sampled from the dome suggests that it is comprised of more evolved magma than that of the main furnas 1630 dome located 1400 m away this suggests that the dome was formed during a final phase of the 1630 eruption in the lagoa das furnas area

seafloor geomorphology of the sw barents sea and its glaci dynamic implications abstract three dimensional 3d reflection seismic imaging techniques provide a unique means of identifying large scale submarine geomorphic features produced by former ice sheets we have used such techniques to image the geomorphology of the sw barents sea but using a dense grid of 2d seismic covering a 240 000 2 km large study area supplemented with 3d seismic from selected areas the study area is located at the convergence of ice flow from the former fennoscandian barents sea and svalbard ice sheets the morphology of the major cross shelf troughs is characterized by elongated ridge groove features interpreted to be glacial bedforms produced by fast flowing grounded glaciers mega scale glacial lineations have been grouped into distinct flow sets related to three specific ice flow events these events document the last glacial maximum lgm and two readvances during deglaciation of specific interest is a detailed and well preserved set of seafloor imprints in the bjornoyrenna trough which acted as the main pathway for ice streams draining the surrounding ice sheets the geomorphic features indicate that bjornoyrenna hosted six separate ice stream lobes that diverged fan like at their margins but were not all active simultaneously an end moraine zone 68 km wide up to 85 m high and 300 km long filled the whole width of this major glacial trough as a result of high sediment flux within sub ice stream deformable beds the imprint of this ice stream system can be followed on our seabed images for 500 km however detailed geomorphologic elements demonstrate that these imprints reflect time transgressive behaviour and do not indicate the length or width of single ice streams the seismic derived seafloor geomorphology demonstrates that the barents sea ice behaved in a much more dynamic way during the last glaciation than previously assumed with major shifts between ice originating from the fennoscandian spitsbergen and barents sea ice sheets

late quaternary evolution and sea level history of a glaciated marine embayment bantry bay sw ireland ireland experienced a spatially complex pattern of relative sea level rsl changes and shoreline development caused by the interplay of isostatic and eustatic ice equivalent sea level processes since the last glacial maximum lgm using a combination of high resolution marine geophysical data vibrocores foraminiferal analysis and 10 ams radiocarbon dates we reconstruct the late quaternary evolution and rsl history of bantry bay a large 40 km long 5 10 km wide embayment in sw ireland the data indicate two infill phases one before and one after the lgm separated by glacial and lowstand sediments the pre lgm history is not dated and the depositional history is inferred a large sediment lobe formed at the outer edge of bantry bay as a lowstand ice proximal glacimarine outwash system as the ice retreated after the lgm at a sea level ca 80 m lower than present iceberg scour immediately west of this location likely relate to the break up of the local kerry cork ice cap long curvilinear ridges seen both offshore and on top of the sediment lobe probably formed as shoreface ridges under stronger than present tidal currents during a period of rsl stability pre 14 6 ka cal bp a subsequent infill phase is characterised by a basin wide erosional ravinement surface and the deposition of inter and sub tidal estuarine sediments although our data support the general trends our stratigraphic and radiocarbon data suggest a higher sea level between 11 and 13 5 ka cal bp than predicted by existing glacial isostatic adjustment models

process related classification of acoustic data from the hudson river estuary acoustic surveying provides valuable information on the distribution of sedimentary environments in subaqueous settings frequently differences in acoustic backscatter strength are used to distinguish sedimentary environments on the basis of their grain size composition here we are presenting acoustic backscatter data from the haverstraw bay section of the hudson river estuary that has been mapped using sidescan sub bottom profiling and multibeam bathymetry as part of the benthic mapping project of the hudson river estuary program funded by new york state in addition hundreds of gravity cores and grab samples provide ground truth for a classification of the river bottom into discrete substrate types analyses of sedimentary environments reveal patterns in backscatter strength beyond those that can be related to the sediment grain size distribution alone an integrated interpretation of sidescan sub bottom profiling and high resolution bathymetry data indicates that the backscatter pattern can be attributed to spatial variations in the modern depositional environments which cause differences in bottom roughness and sediment compaction based on an integrated interpretation of the acoustic and sample data sets we distinguished eight different sedimentary classes many of the classes can be linked to dynamic processes including contemporary deposition erosion and sediment migration in sand waves the results provide a better understanding of the dynamic processes of the hudson river estuary and improve the interpretation of the acoustic backscatter data from fine grained sedimentary environments

paleobiogeography of africa how distinct from gondwana and laurasia abstract although africa was south of the tethys sea and originally belonged to the gondwana its paleobiogeographical history appears to have been distinct from those of both gondwana and laurasia as early as the earliest cretaceous perhaps the late jurassic this history has been more complex than the classical one reconstructed in the context of a dual world gondwana vs laurasia geological and paleobiogeographical data show that africa was isolated from the mid cretaceous albian aptian to early miocene i e for ca 75 million years the isolation of africa was broken intermittently by discontinuous filter routes that linked it to some other gondwanan continents madagascar south america and perhaps india but mainly to laurasia interchanges with gondwana were rare and mainly out of africa dispersals whereas interchanges with laurasia were numerous and bidirectional although mainly from laurasia to africa despite these intermittent connections isolation resulted in remarkable absences poor diversity and emergence of endemic taxa in africa mammals suggest that an african faunal province might have appeared by late jurassic or earliest cretaceous times i e before the opening of the south atlantic during isolation africa was inhabited by vicariant west gondwanan taxa i e taxa inherited from the former south american african block that represent the african autochthonous forms and by immigrants that entered africa owing to filter routes nearly all or all immigrants were of laurasian origin trans tethyan dispersals between africa and laurasia were relatively frequent during the cretaceous and paleogene and are documented as early as the earliest cretaceous or perhaps late jurassic i e perhaps by the time of completion of the tethys between gondwana and laurasia they were permitted by the mediterranean tethyan sill a discontinuous route that connected africa to laurasia and was controlled by sea level changes interchanges first took place between southwestern europe and africa but by the middle eocene a second eastern route the iranian route involved southeastern europe and southwestern asia the iranian route was apparently the filtering precursor of the definitive connection between africa and eurasia the relationships and successive immigrations of mammal mostly placental clades in africa allow the recognition of five to seven phases of trans tethyan dispersals between africa and laurasia that range from the late cretaceous to the eocene oligocene transition these dispersal phases involve dispersals toward laurasia and or toward africa immigrations the immigrations in africa gave rise to faunal assemblages the african faunal strata afss all successful and typical african radiations have arisen from these afss we recognize four to six afss each characterized by a faunal association even major old african clades such as paenungulata or the still controversial afrotheria which belong to the oldest known afs involving placentals ultimately originated from a laurasian stem group africa was an important center of origin of various placental clades their success in africa is probably related to peculiar african conditions endemicity weak competition although strongly marked by endemicity the african placental fauna did not suffer extinctions of major clades when africa contacted eurasia the present geographic configuration began to take shape as early as the mid cretaceous at that time the last connections between africa and other gondwanan continents began to disappear whereas africa was already connected to eurasia by a comparatively effective route of interchange

natural variability of benthic foraminiferal assemblages and metal concentrations during the last 150 years in the ingoydjupet trough sw barents sea abstract while today the sw barents sea is a relatively un impacted and uncontaminated area industrial activities related to the petroleum industry are projected to increase in the coming decades this makes the area a valuable natural laboratory to establish pre impacted baselines as a precursor for future seabed monitoring programs here we present benthic foraminiferal assemblages and metal concentrations in four sediment cores from the ingoydjupet trough sw barents sea covering approximately the last 150 years this information supports the application of foraminiferal assemblages as a bio monitoring tool applicable in high latitudes at all stations metal concentrations in the sediment correspond to no effect concentrations the downcore metal concentrations are mainly attributed to natural variability of the clay fraction and total organic content of the sediments agglutinated foraminifera are poorly preserved down core patterns in the calcareous foraminiferal assemblages suggest an enhanced food supply as a result of increased atlantic water inflow through the region during the last 150 years at near shore stations the norwegian coastal current additionally influences assemblages decadal scale climatic oscillations are indicated by increased calcareous fluxes and are attributed to variability in the food rich atlantic water this study serves as an important baseline data set prior to increasing industrial activities in the sw barents sea and thereby contributes to a better understanding of natural environmental variability

pockmark like depressions near the goliat hydrocarbon field barents sea morphology and genesis abstract pockmarks are observed worldwide along the continental margins and are inferred to be indicators of fluid expulsion in the present study we have analysed multibeam bathymetry and 2d 3d seismic data from the south western barents sea in relation to gas hydrate stability field and sediment type to examine pockmark genesis seismic attributes of the sediments at and beneath the seafloor have been analysed to study the factors related to pockmark formation the seabed depths in the study area are just outside the methane hydrate stability field but the presence of higher order hydrocarbon gases such as ethane and or propane in the expelled fluids may cause localised gas hydrate formation the selective occurrence of pockmarks in regions of specific seabed sediment types indicates that their formation is more closely related to the type of seabed sediment than the source path of fluid venting such as faults the presence of high acoustic backscatter amplitudes at the centre of the pockmarks indicates harder coarser sediments likely linked to removal of soft material the pockmarks show high seismic reflection amplitudes along their fringes indicating deposition of carbonates precipitated from upwelling fluids high seismic amplitude gas anomalies underlying the region away from the pockmarks indicate active fluid flow from hydrocarbon source rocks beneath which is blocked by overlying less permeable formations in areas of consolidated sediments the upward flow is limited to open fault locations while soft sediment areas allow diffused flow of fluids and hence formation of pockmarks over a wider region through removal of fine grained material

giant sandwaves in the hola glacial trough off vesteralen north norway abstract seabed data acquired from the hola glacial trough off vesteralen north norway reveal the morphology of spectacular sandwave fields and large sandwaves in great detail the sandwave fields are among the deepest known occurring in water depths of 200 260 m multibeam bathymetry and backscatter shallow seismic sediment samples and video data collected by the mareano programme and bottom current modelling results have been used to interpret morphology transport and distribution of the seabed sediments sand supply to the hola trough was initially from wave and current reworking of glacial and glaciomarine deposits during the eustatic sea level lowstand and sea level rise after the last glaciation more recently deposited bioclastic sand dominates the upper part of the sand unit which locally reaches 10 m thickness sand predominantly accumulates behind ridges where current strength decreases and in topographic lows straight crested and barchan type sandwaves up to 3 km long and 7 m high are interpreted to form by tidal and geostrophic currents with bottom current speeds reaching 0 7 0 8 m s 1 a large cluster of coral reefs occur immediately east of the barchan type sandwaves where modelling shows bottom current velocities up to c 1 m s 1 sandwaves occur in four major sandwave fields strong variation in the nature of sandwaves over short distances e g migration direction between neighbouring sandwave fields point to important local variations in current regime and sedimentary processes the present work demonstrates how local topography and interaction of several current systems may produce complex depositional patterns on a local scale detailed multibeam mapping and video inspection of open shelf troughs in other narrow shelf settings worldwide may reveal similar sandwave fields

late weichselian iceberg surface melt and sediment production from the eurasian ice sheet results from numerical ice sheet modelling abstract results from a numerical ice sheet model were matched with geological evidence detailing the extent and timing of the late weichselian ice sheet in the eurasian arctic through simple adjustments in the model s environmental inputs the numerical model predicts the spatial and temporal variation in 1 subglacial sediment transport and deposition 2 rates of iceberg calving and 3 rates of supraglacial melting over the past 30 000 yr the ice sheet is characterised by a series of ice streams occupying bathymetric troughs in the barents sea and west of norway which act as sources for glacial sediment build up and iceberg production our model indicates that significant volumes of sediment are deposited over the bear island fan 3000 km 3 in 12 000 yr franz victoria trough fan 500 km 3 in 8000 yr and a series of smaller fans west of norway which combine to yield 4000 km 3 in 12 000 yr the norwegian channel ice stream operated for only 4000 yr during which time 400 km 3 of sediments were deposited on the adjacent fan the ice sheet experienced two major periods of iceberg production where the rate of calving increased by 50 at about 15 000 and 12 500 yr ago however the time dependent response of iceberg calving to sea level rise for individual ice streams is shown to be more complicated than the generalised ice sheet response the marine portions of the ice sheet decayed after 15 000 yr ago resulting in several embayments at the mouths of bathymetric troughs a second pulse of enhanced iceberg calving at 12 500 yr ago caused further decay of the marine ice sheet and the ice margin retreated back to the shorelines of island archipelagos in the northern barents sea ice loss through surface melting was restricted mostly to the southern margin of the ice sheet

geophysical evidence of deep keeled icebergs on the rockall bank northeast atlantic ocean high resolution multibeam swath bathymetric data acquired from the rockall bank reveal an abundance of linear to slightly sinuous seabed incisions these features interpreted as relict iceberg scours provide for the first time evidence that the rockall bank was intensively scoured by iceberg keels while the shallower portion of the rockall bank lacks evidence of iceberg scouring on the western and southern flanks between 250 and 450 m water depth the seabed is almost completely covered by thousands of cross cutting scours more isolated scours up to 800 m wide and 25 km long are also observed down to nearly 600 m water depth based on a full glacial sea level low stand of 120 m these isolated scour marks must have been carved bygigantic icebergs with keels up to 500 m deep and able to create incisions up to 15 m deep in the seabed analysis of scour orientation length width and depth indicates that these mega icebergs were likely calved from large fast flowing ice sheet outlets draining circum north atlantic ice sheets prevailing scour orientations suggest a number of possible ice sheet sources including southeast and southern greenland and the donegal barra ice stream of the last british irish ice sheet the bimodal distribution of the scour depth observed across the rockall bank suggest either different icebergs provenances or physical and climatic controlson icebergs draft

description and numerical model of pleistocene iceberg scours and ice keel turbated facies at toronto canada near toronto in southern ontario canada glaciolacustrine muds and shoreface sands of late pleistocene age early wisconsin glaciation 45 ka were deformed by icebergs ploughing the floor of an ancestral ice dammed lake ontario outcrop mapping and a ground penetrating radar survey identify ice scour structures up to 4 m deep up to 10 m wide and at least several hundred metres long with high standing lateral margins berms ploughing of lake floor sediment is also recorded by ice keel turbated facies in which storm deposited shoreface sands have been mechanically mixed with underlying muds palaeoenvironmental information for one prominent scour such as water depths estimates of the mass and draft of the ice mass and scouring forces can be determined using a simple finite element numerical model a mass of 0 04 million tonnes a keel draft of between 10 and 30 m and a scouring force of 5 103 kn is consistent with scouring by a small iceberg bergy bit or pressure ridged lake ice the former is preferred because of the considerable depth of the scour and the overall glacial depositional setting estimates of ice mass dimensions agree with independent reconstructions of palaeobathymetry no greater than 20 m derived from storm deposited hummocky and swaley cross stratified facies that fill the scour data presented here aid the identification of ice scour structures and turbated sediment in the ancient record despite being a common process on modern high latitude shelves descriptions of ancient structures and facies are few

giant iceberg plow marks at more than 1 km water depth offshore west greenland abstract during a recent 2006 cruise of rv dana high resolution side scan sonar and sub bottom profiling was carried out on selected shelf and slope transects offshore disko bugt central west greenland available commercial seismic data from the margin indicate here irregular seabed morphology with erosional features locally extending down to c 1100 m water depth the newly acquired side scan sonar data reveal the presence of giant iceberg plow marks extending sub parallel to the slope between about 800 and 1085 m water depth the height difference between bottom of the scours and rim crest is up to 40 m the largest plow marks are about 750 m wide to date no observed modern icebergs including those from antarctica have drafts in excess of c 500 m taking into account maximum glacial sea level lowering of c 120 m the paleo iceberg keel depth was at least 950 m due to the presence of the relatively shallow 1000 m and dimensions of the plow marks are concluded to be exceptional and comparable to glacial scouring features reported from the arctic ocean

a possible egg of the dromaeosaur deinonychus antirrhopus phylogenetic and biological implications a unique find of a partial egg in contact with articulated gastralia from a known specimen of the dromaeosaurid deinonychus antirrhopus amnh 3015 is described much of the original taphonomic context of the specimen was lost during the 1931 excavation and preparation but enough information is preserved to provide strong evidence for a parental association between the adult skeleton and egg the articulated nature of the gastralia suggests that the adult skeleton was at least partially articulated and had not suffered from either extensive subaerial exposure or postmortem transport and the egg preservation also indicates in situ burial and postburial lithogenic crushing additional support stems from the presence of limey claystone matrix that indicates a low energy depositional event phylogenetic characteristics of the eggshell microstructure are consistent with a theropod origin and skeletochronological analysis suggests that amnh 3015 was an adult and thus of breeding age bolstering the interpreta

bottom currents interpreted from iceberg ploughmarks revealed by multibeam data at tromsoflaket barents sea abstract multibeam data have been acquired on eastern tromsoflaket a bank in the southwestern barents sea comprising a plateau detailed examination of the multibeam backscatter data however reveals a high variability of sediments especially in and around iceberg ploughmarks we observe coarser sediments on the levees either side of the ploughmarks than inside the furrows moreover we frequently note asymmetries in the distribution of fine sediments across these ploughmark features drawing inspiration from previous studies of bottom currents which use the distribution of sediments across bedforms e g sand waves we have interpreted the direction of bottom currents on tromsoflaket by examining the local distribution of fine sediments across iceberg ploughmarks which are the most prominent bedform in this area further integration of our results with existing grain size current speed models have allowed estimates of the bottom current speeds to be obtained such interpretations are particularly valuable in this area where availability of bottom current measurements sparse our approach makes valuable and novel use of multibeam data and results show good agreement with the limited set of available current data and models we can identify near bottom pathways for the norwegian atlantic current and norwegian coastal current the two major current systems in this region and the patterns of circulation help to explain the sedimentation regime and identify recent erosion and deposition areas

understanding biomineralization in the fossil record abstract biomineralization the formation of minerals by organisms is a key aspect in the understanding of the fossil record knowing how biominerals form and their properties is important in the correct use of fossils in geochemistry the understanding of evolution and in the interpretation of how geological events have influenced the fossil record throughout the phanerozoic the focus of this contribution rather than a conventional review on the status of this research field is on the importance of highlighting the traditional link between paleontology and biomineralization

chronostratigraphic synthesis of the latest cretaceous dinosaur turnover in south western europe abstract in south western europe the uppermost cretaceous continental deposits in the different sedimentary basins of iberia portugal and north and central spain the pyrenees spain and france as well as languedoc and provence southern france provide one of the few terrestrial records that allow a comprehensive study of the campanian maastrichtian dinosaur assemblages for the last years the southern pyrenees has been the target of intense geological palaeontological and geochronological research hundreds of fossil localities are now framed in high resolution lithological sections the succession of these sites most of them located in the tremp syncline is based on the physical correlation of rock bodies as permitted by the general outcropping conditions outside this syncline correlation is supported by geochronologic and biostratigraphic data mainly magnetostratigraphy and planktic foraminifera biostratigraphy the integration of the entire dataset sheds new light on the maastrichtian dinosaur turnover characterized by a shift from a sauropod dominated to a hadrosauroid dominated faunal assemblage this turnover was progressive and involved immigrants from north america eurasia and gondwana which probably reached the study area after a sea level drop this faunal change was mainly triggered by the arrival of lambeosaurine hadrosauroids a group that rapidly displaced the rest of the herbivorous clades of the region some of the extinction events suffered by the pre turnover faunas during the maastrichtian coincide with marine isotopic and sea level drop events suggesting that faunal competition was not the only cause of the observed changes in dinosaur composition despite this faunal replacement the resulting ecosystem after the turnover shows no major loss of biodiversity before the cretaceous paleogene extinction event

contour current driven continental slope situated sandwaves with effects from secondary current processes on the barents sea margin offshore norway abstract seabed data acquired from the southern barents sea continental margin offshore norway reveal detailed morphology of large sandwave fields multibeam echosounder bathymetry and backscatter shallow seismic sediment samples and seabed video data collected by the mareano program have been used to describe and interpret the morphology distribution and transport of the sandwaves the bedforms lie on a slope dominated by relict glacial forms and muddy sandy gravelly sediments sandwave migration across small gravity mass failures of the glacial mud constrains the field initiation as early post glacial or later the contour parallel nature of the fields and crestlines normal to the bathymetry contours and the geostrophic norwegian atlantic current nwac demonstrate that the nnw flowing oceanographic circulation is the primary driving current the fields coincide with the depth range at which a transition between warm saline and underlying cooler less saline waters fluctuate across the seabed statistically rigorous measurements of height width and various parameters of slope and symmetry confirm a tendency to downstream nnw sandwave migration but with significant exceptions anomalous bedform symmetry domains within the fields are tuned to meso scale topography along relict glacial debris flow chutes indicating current focusing upstream and upper slope derived winnowed sand transport eroded from the glacial sediments is the supposed source sandwave flank slope values are comparable to the regional slope such that the gravitational vector would have a cumulative downslope migration affect unless balanced by upslope drivers perpendicular cross cutting of stoss face 3 d ripples by linear 2 d ripples in the sandwave troughs and lee faces is evidence for non synchronous episodic current variations though deep ekman transport and internal wave action are unproven here these could explain chute related tuning of bedform symmetry through funneling in the debris flow chutes and favor sand recycling thus contributing to long term maintenance of the sandwave field

formation of a large submarine crack during the final stage of retrogressive mass wasting on the continental slope offshore northern norway laberg jan sverre baeten nicole jeanne lagstad petter arthur forwick matthias vorren tore ola formation of a large submarine crack during the final stage of retrogressive mass wasting on the continental slope offshore northern norway marine geology 2013 volum 346 s 73 78

high resolution 3d seismic study of pockmarks and shallow fluid flow systems at the snohvit hydrocarbon field in the sw barents sea accepted manuscript version published version available at https doi org 10 1016 j margeo 2018 06 012 accepted manuscript version licensed cc by nc nd 4 0

sandwaves and other large scale bedforms as indicators of non tidal surge currents in the skagerrak off northern denmark abstract results from side scan sonar surveys made at two sites in the skagerrak off hanstholm and hirtshals show that transverse and longitudinal current induced bedforms are widespread in both areas down to a water depth of 70 m a maximum sandwave height of 7 m is found off hanstholm comet marks have a maximum length of near 50 m off hanstholm wave action markedly affects the seabed at depths of less than 25 m this can cause significant deformation of current induced bedforms the bedforms are not relict structures they demonstrate that maximum bottom flow velocities associated with the jutland current can locally reach a magnitude of at least 70 100 cm s bedform configuration and sediment distribution off hansholm indicate continuation of the jutland current bottom flow axis in a northeast direction diverging from the coastline this may favour sand transport in greater water depths than is usually found elsewhere in the area as an exception at one occasion at the site off hirtshals megaripples were found to have southwest facing leeside slopes and small comet marks were also directed towards the southwest this must have resulted from exceptional outflow conditions with bottom current speed in excess of 60 cm s

bottom currents sedimentation and ice sheet retreat facies successions on the mac robertson shelf east antarctica abstract measurements of water turbidity currents seafloor sediment samples and geophysical data document the sedimentary processes and the late quaternary sedimentary history of a continental shelf valley system on the east antarctic continental margin the valley is up to 1200 m in depth and strikes across the shelf it is interpreted as having formed by glacial erosion processes on the outer shelf sill of the valley northwestward offshore currents with speeds of up to 0 47 m s referenced to 100 cm above the seabed were recorded over a 10 month period such currents are competent to initiate bedload transport of medium sand and formation of small ripple sized bedforms which explains the occurrence of ripple cross bedding observed in some x radiographs of cores a nepheloid layer with concentrations of up to 3 5 mg l was noted at two stations and the available evidence suggests that density flows resulting from the sea ice brine rejection mechanism are competent to entrain shelf bottom sediments episodically sediment cores taken from this environment document the succession of facies resulting from retreat of glacial ice from the shelf during the holocene transgression under low sea level glacial conditions the ice sheet is interpreted to have been grounded on the outer shelf where it deposited a grounding line moraine rising sea level and global warming caused the ice shelf to retreat leaving a sub ice shelf glacial marine mud this is overlain by a laminated to massively bedded ice rafted debris rich facies interpreted as being deposited at the glacial calving front above this is a siliceous mud and ooze facies having a basal age of about 10 000 years bp characterising modern open marine conditions two types of iceberg keel marks on the outer part of the shelf valley are recognised from sidescan sonographs one relict arcuate type formed during the retreat of the ice shelf prior to 10 000 years bp and a second modern elongate type that is presently being formed near the shelf break by iceberg grounding processes this facies succession has been described from other antarctic shelf environments and is probably representative of facies deposited during holocene glacial retreat from the antarctic shelf

the effects of fine scale surface roughness and grain size on 300 khz multibeam backscatter intensity in sandy marine sedimentary environments abstract high frequency acoustic backscatter intensity that is returned from sediment is affected by a number of seabed characteristics including sediment grain size distribution the nature and magnitude of seabed surface roughness and volume scattering by subsurface scatterers in order to develop quantitative remote sediment classification techniques it is important to determine the relative and combined effects of the dominant variables to which the acoustic signal is sensitive data used in this study were collected at two sandy sites off the south shore of long island new york and include 300 khz multibeam simrad em 3000 backscatter intensity data as well as grab samples and stereo bottom photographs multivariate statistical analyses were used to investigate the relationships between grain size properties seabed roughness and backscatter intensity at a number of sample locations at each study site encompassing a moderate range of backscatter intensities from 32 5 to 24 db the results of this study demonstrate that the relative importance of variables that affect backscatter intensity varies at different sites suggesting that backscatter intensity alone cannot be used to quantitatively predict seabed characteristics however our study indicates that in sandy sediments the median grain size the standardized magnitude of seabed roughness and the sorting of sediment can together be used to predict 300 khz backscatter intensity with high significance and that the relative importance of these variables varies from site to site we present an empirical model derived from a combined dataset that includes two sites of similar sedimentary and hydrodynamic conditions to predict the magnitude of seabed roughness based on backscatter intensity and sediment grain size characteristics the spatially coherent patterns in predicted seabed surface roughness revealed through the use of this kind of model greatly improve our understanding of variations in backscatter intensity in sandy marine sedimentary environments as a result the multivariate statistical approach that we employ improves our overall ability to remotely assess the details of the sedimentary environment that are significant with respect to benthic habitats and physical processes and are applicable to other geophysical datasets including sidescan sonar data

dinosaur eggshell and tooth enamel geochemistry as an indicator of mongolian late cretaceous paleoenvironments the late cretaceous fossiliferous beds of mongolia s gobi desert have yielded spectacular articulated remains of a remarkable diversity of fossil mammals lizards turtles birds and non avian dinosaurs paleoenvironmental interpretations of the deposits at these localities have ranged from arid wind blown dune fields to more mesic moist environments among the diversity of fossils dinosaur eggshells and teeth are commonly found at these localities dinosaur eggs like modern avian eggs are constructed of biomineralized calcite caco3 and proteins allowing carbon and oxygen stable isotopes to be quantified to provide information about the environment in which the egg laying animals were living here it is shown that dinosaur eggshell and teeth from the djadokhta and nemegt formations have not been significantly altered and reflect an environment of dry dunes during deposition of the djadokhta formation and a more mesic stream environment for conditions in the nemegt formation carbonate nodules from the same eggshell bearing layers also independently reflect a similar environmental signal this study represents the first geochemical analysis of dinosaur remains from the cretaceous of mongolia and illustrates the potential of utilizing dinosaur fossil geochemistry of both eggs and teeth to reconstruct mesozoic environments

taphonomical and palaeoecological investigation of the late cretaceous maastrichtian tustea vertebrate assemblage romania haţeg basin insights into a unique dinosaur nesting locality abstract the tustea vertebrate locality at oltoane hill northwestern part of the ha eg basin romania has provided a rich and diverse assemblage of late cretaceous maastrichtian continental vertebrates more than 800 vertebrate fossils were recovered from this locality the isolated and associated remains represent 21 different taxa including amphibians turtles lizards snakes crocodyliforms pterosaurs dinosaurs and mammals the local assemblage is overwhelmingly dominated by dinosaurs with the rhabdodontid zalmoxes as the most abundant taxon the bonebeds that yielded this fossil material occur in a stacked series of mudstone calcrete units belonging to the middle member of the densus ciula formation the taphonomical investigations suggest that the tustea assemblage is made up of attritionally accumulated politaxic remains and that it is a parautochthonous assemblage with no evidence for significant bone transport or reworking according to the synthesis of all available field data two outstanding fossiliferous levels can be identified within the tustea locality where megaloolithus eggs and hadrosauroid hatchling material are preserved together recognized here as two superposed nesting grounds such co occurrence was considered controversial since there is a long standing and quasi general consensus that eggs of the megaloolithus oogenus were laid by titanosaurian sauropods we present several alternative scenarios to account for the co occurrence of telmatosaurus hatchling remains and megaloolithid eggs in the nesting horizons and explore these alternative hypotheses by weighing the arguments supporting or contradicting them the burden of evidence derived from our sedimentological taphonomical and palaeoecological investigations at tustea is still in favour of the autochthony of the hatchlings preserved within their own nesting grounds whereas there is no such support for a titanosaurian origin of the tu tea megaloolithid eggs

description of the first lithostrotian titanosaur embryo in ovo with neutron characterization and implications for lithostrotian aptian migration and dispersion abstract although titanosaurs represent one of the most diverse radiations of non avian dinosaurs during the cretaceous our knowledge of their early developmental stages was restricted to the auca mahuevo argentina embryos in ovo here we present the first complete lithostrotia titanosaur embryo in ovo the relatively small spherical 87 07 to 91 1 mm egg was discovered at the lower cretaceous locality algui ulaan tsav in mongolia and is to date the smallest positively identified titanosaur egg through taphonomic processes the egg was transformed into a calcite geode at the bottom of which the embryonic bones settled down and are now partially exposed on the lower egg surface neutron tomography characterization reveals a fully developed embryo fossilized within a thin 7 6 mm 8 6 mm calcite layer ebsd a sem based diffraction technique which measures the complete crystallographic orientation of the crystal lattice from a submicron area on the sample surface is used for the first time on an extinct dinosaur eggshell observations of the egg and its embryo combined with eggshell microcharacterizations suggest that this new embryo was a lithostrotia titanosaur with an intermediate robusticity index that shares a mosaic of skeletal characters with diamantinasaurus matildae from queensland australia and the nemegtosaurid rapetosaurus krausei madagascar more than with any other titanosaurs the early cretaceous age of algui ulaan tsav implies that this specimen greatly predates the previously described lithostrotian titanosaurs from the late cretaceous sediments of mongolia in addition the recognized amount of similar eggs that has been recovered during the last 70 years at algui ulaan tsav suggests that a well established population of lithostrotian titanosaurs used this site as a nesting site the combined observations provide an important addition to mongolian fossil richness and alter our understanding of the paleodispersion of this sauropod group it now appears that lithostrotian sauropods would have reached mongolia during the aptian albian thus suggesting the existence of a passage before the complete separation of the laurasian and gondwanan continents possibly the lithostrotian north and eastward migration could have occurred between north africa spain and the rest of europe prior to its fragmentation in large islands during the cretaceous thus justifying the presence of lithostrotians in the cretaceous romanian hateg island

iceberg crater marks on the sea floor labrador shelf abstract sidescan sonograms of the labrador seabed show evidence of numerous subcircular iceberg generated impact craters some of these craters are found in linear associations crater chains having been formed by a single iceberg keel alternately impacting and rotating free of the seabed a three degrees of freedom iceberg model is used to generate crater chain configurations an unstable trapezoid shaped iceberg of 6 million t with a draft of 140 m in a water depth of 160 m is used in the simulations soil pressures acting on the penetrating keel introduce a vertical heave motion which depending on phase relationships with the swinging motions of the iceberg results in a variety of noncoherent crater depths and crater chain morphologies including chains with skips where craters appear to be missing on sidescan sonograms depending on the position of the final static orientation of the iceberg keel it may generate a crater chain if the keel comes to rest above the seabed or a crater chain may lead into a normal scour if the keel remains below the seabed both configurations are observed in nature

submarine landforms and the reconstruction of fast flowing ice streams within a large quaternary ice sheet the 2500 km long norwegian svalbard margin 57 80 n morphological interpretation of regional and detailed bathymetric data sets on the 2500 km long norwegian shelf from the north sea 57 n to svalbard 80 n has revealed a dynamic ice flow pattern along the western marginof the scandinavian and barents svalbard ice sheets about 20 cross shelf troughs with megascale glacial lineations msgl elongate ridges and grooves oriented parallel to trough long axes are interpreted as former pathways for fast flowing ice streams studies of large scale margin morphology and seismic profiles have identified large submarine fans at the mouths of several major cross shelf troughs less dynamic ice probably existed on shallower banks the two largest paleo ice streams were the norwegian channel ice stream and bear island trough ice stream each 150 200 km wide at the mouth the lengths of individual msgl vary from hundreds of meters to several tens of kilometers and the distance between ridges varies from 0 1 to 3 km msgl amplitudes reach 15 m but are commonly 10 m the onset of msgl and hence fast ice flow is generally close to the outer coast at the border zone between crystalline rocks and softer sedimentary rocks transverse submarine ridges on various scales commonly parallel to the shelf edge reflect either the maximum ice sheet position or the recessional pattern of the ice sheet lateral ice stream moraines several tens of kilometers long have also been mapped along the sides of several cross shelf troughs identifying the border zone between fast ice flow and stagnant or slow flowing ice on intervening banks

net sediment transport patterns inferred from grain size trends based upon definition of transport vectors reply abstract a new approach to the analysis of the grain size trends associated with net sediment transport directions in shallow marine environments is developed here two specific trends modified from mclaren and bowles 1985 on the basis of a literature review are used to define a grid of trend vectors such vectors are filtered and transformed into transport vectors it is suggested that an ordered pattern of the transport vectors represents net transport paths the orderliness of the derived pattern is examined on the basis of a significance test using the average length of the transport vectors as a criterion both the filtering operation and the significance test procedure are based upon the assumption that the trend vectors which are not associated with net transport have the same probability of being in any direction the technique is applied to data from yangpu harbour southern china the technique can be applied to inner continental shelf and coastal environments for such an analysis the area under investigation should be sampled at an interval large enough to reflect the real grain size trends resulting from net sediment transport but small compared with the dimensions of the sedimentary environment the time scale of the results depends upon the sampling depth applicability of the technique is likely to be somewhat limited where the environment is highly variable over short distances furthermore due to its statistical character the analysis may fail to identify net transport patterns

ice sheet grounding and iceberg plow marks on the northern and central yermak plateau revealed by geophysical data abstract we present new evidence for a grounded ice sheet and subsequent erosion by large fields of coherent icebergs for the central and northern yermak plateau 80 6 n to 82 2 n sediment echosounder and swath bathymetry data were combined with seismic reflection profiles and reveal at least three different glacial events marked by erosional unconformities i an erosional unconformity was observed at 70 90 m below seafloor down to depths of more than 850 m present water depth extending to 82 n the erosional unconformity is overlain by an acoustically chaotic layer of 50 m thickness interpreted as a diamicton originating from a grounded ice sheet the erosional unconformity and the overlying diamicton can be correlated to the overconsolidated sediments found at odp site 910 at a sediment depth between 19 and 70 95 m the oldest sediments just above the overconsolidated sediments are of late early pleistocene age mis19 20 and provide a minimum age for the grounding event ii parallel to sub parallel mega scale lineations are observed on large parts of the plateau west and northeast of the sverdrup bank at water depths between 725 and 850 m these lineations are mainly oriented nne ssw and were quite likely formed by the keels of deep draft mega scale tabular icebergs entrapped in a coherent mass of icebergs and sea ice the lineations are of late middle pleistocene age iii smaller scale curvilinear plow marks were found in the southernmost part of our study area at water depths between 640 and 775 m these were possibly caused by single icebergs and are of late pleistocene age iceberg scours are also found on three basement heights on the yermak plateau these however cannot be assigned to specific events they might as well originate from additional glacial phases the western at 850 m water depth and eastern at 1000 1200 m water depth flanks of the yermak plateau are relatively featureless and indicate the maximum depth of a grounded ice sheet and of iceberg armadas probably entrapped in sea ice

glacigenic sediments on a passive continental margin as exemplified by the barents sea abstract reflection seismics data borehole data and gravity cores have been used to map the sedimentary facies of the epicontinental southwestern barents sea its continental margin and adjacent coastal areas an upper unconformity with a glacially eroded morphology extends over most of the continental shelf up to 300 m of stratiform glacigenic sediments overlie this unconformity these sediments can be grouped into seismic units which are separated by smooth or irregular erosional surfaces each sequence may be up to 150 m thick normally with a lateral extent of 100 300 km three dominant seismic signatures may be discerned semi transparent stratified and chaotic reflection patterns these sediments are partly glacifluvial in origin but on the whole they represent more or less tectonized glacimarine deposits the deeper troughs on the continental shelf contain an undeformed postglacial glacimarine marine trough fill the greatest thickness up to 1000 m of glacigenic sediments occurs at the shelf break and below the upper slope the depocentres are situated at trough mouth fans the sediments comprise several prograding sequences with a complex sigmoid oblique character indicating alternating upbuilding and depositional bypass erosion in the topset segment small and large scale slide scars are observed on the upper slope and debris lobes on the lower slope a marked progradation seems to have occurred during the plio pleistocene glacial periods this progradation also resulted in an unstable slope with various types of sediment gravity flows currents flowing along the slope were established during interglacials and gullying by cold dense shelf water and downslope transport occurred maximum net sedimentation rates are 0 2 m ka continental slope 0 4 m ka shelf break 0 1 m ka shelf stratiform diamictons 1 m ka shelf trough fills and 60 m ka fjord trough fills

laurentide ice sheet dynamics in the bay of fundy canada revealed through multibeam sonar mapping of glacial landsystems abstract recent multibeam sonar data collected in the bay of fundy canada interpreted in conjunction with geophysical profiling and sediment sampling reveal in unprecedented detail a suite of glacial landforms associated with the southwest margin of the laurentide ice sheet these landforms constitute four glacial landsystems 1 subglacial landsystem i in southwestern bay of fundy the elongated grand manan basin contains ice contact sediments of possible mid wisconsinan age overlain by late wisconsinan ice contact sediments strongly imprinted by iceberg furrows and pits in places possible mid wisconsinan glaciomarine sediments have been eroded by late wisconsinan ice creating streamlined landforms eroded bedrock and megafluted ice contact sediment on the flanks of grand manan basin indicate the southwest direction of topographically steered ice 2 subglacial landsystem ii along the southern margin of the bay of fundy an array of drumlins with superimposed esker complexes was formed by glacial ice that emanated northwest from the interior of nova scotia and was deflected to the southwest by the ice flowing out of the bay of fundy to the gulf of maine the esker complexes formed later when the nova scotia ice sheet stagnated and meltwater escaped northwest via topographic gaps 3 ice marginal landsystem i in northern bay of fundy both small de geer moraines and larger basin bounding moraines were created when retreating late wisconsinan ice became grounded in relatively shallow water new radiocarbon ages show that the owen basin moraine in this landsystem was abandoned prior to c 14 600 14 c yr bp cal bp 17 015 17 270 0 7 17 286 17 405 0 3 4 ice marginal landsystem ii this distinctive landsystem consists of numerous arcuate moraines commonly superimposed on one another this landsystem was formed by thin 170 m lightly grounded ice that retreated northeast into the bay of fundy the splayed pattern of the ice margin was a response to a large accommodation space and velocity variations within the ice the isle haute moraine is a large lobate moraine its age is poorly constrained by shells from glaciomarine sediments 13 750 60 14 c yr bp cal bp 15 970 15 996 0 03 16 047 16 665 0 97 but the moraine may be coeval with the onset of a terrestrial ice margin established at the head of the bay of fundy by c 14 300 14 c yr bp cal bp 16 824 17 013

late cenozoic environmental changes along the norwegian margin abstract our ability to understand the rates and consequences of contemporary climate change is limited by the insufficient duration of instrumental records thus we are not able to fully understand the processes that provide a fundamental control in driving climate changes across different timescales palaeo climate archives like those preserved offshore norway provide our only real window through which to observe long term rates and styles of climate change this paper reviews the extensive geological and geophysical data available from the late cenozoic atlantic margin of norway along the margin periods of erosion and deposition have been controlled by agents including fluvial glacial and oceanographic processes current controlled sedimentation along the margin provides insight into the connection of the arctic and atlantic oceans from the miocene onward plio pleistocene shelf edge progradation of up to 150 km can be linked to the grounding of ice sheets on the continental shelf through observations of buried grounding zone wedges and mega scale glacial lineations the margin is also important for understanding the ability of glaciation to cause topographic relief changes and generate offshore geohazards such as the storegga slide which mobilised some 3000 km 3 of sediments during the holocene whilst the processes operating along the norwegian margin are well understood through the late cenozoic there is little geochronological control with which to constrain the environmental changes that have been observed concomitant with the wealth of knowledge and the extensive data that are currently available we propose that the norwegian margin is an ideal location to be considered for future ocean drilling the observations of multiple processes acting independently and together means ocean drilling could yield information of global significance due to the bridging location of norway s atlantic margin between the arctic and lower latitudes

quaternary sea levels northern spencer gulf australia abstract five marine transgressions inundated spencer gulf during the late quaternary the oldest encountered deposits are correlated with stage 7 ca 220 ka of the marine oxygen isotope record sediments of the last interglacial maxima mambray formation isotope stage 5e ca 125 ka occupied a gulf of greater lateral extent than the present and sea level reached 1 m above present low water maximum sea levels associated with isotope stages 5c ca 105 ka and 5a ca 82 ka only reached to levels of 8 and 14 m respectively the holocene sea inundated the gulf between 7000 and 8000 yrs b p and subsequently was at least 2 5 m above present level tectonism has had little long term effect on shoreline elevation other than vertical movements of a few metres