lgm ice sheet extent in the weddell sea evidence for diachronous behavior of antarctic ice sheets abstract inaccessibility due to harsh weather conditions and perennial sea ice has resulted in the weddell sea being one of the more under studied regions of antarctica re examination of existing cores and unpublished multibeam bathymetric data provide new insight into the lgm configuration of the ice sheet in the region sediment cores from the eastern continental shelf where the east antarctic ice sheet eais drains display a retreat stratigraphy with distal glacimarine sediments overlying proximal glacimarine sediments and till the distinction between distal and proximal glacimarine sediments is based on degrees of marine influence based on grain size distributions and foraminiferal abundance and diversity glacimarine sediments yielded ams radiocarbon ages that span the past 30 476 cal yr bp indicating that retreat of the eais from the continental shelf occurred prior to the lgm multibeam swath bathymetry data show mega scale glacial lineations in two troughs on the southern continental shelf which indicates the existence of two ice streams draining the west antarctic ice sheet wais more subtle lineations within filchner trough imply more sluggish flow across bedrock and older strata within this trough although there are no radiocarbon ages to absolutely constrain the timing of this grounding event on the southern continental shelf we interpret the lineations as lgm age based on their pristine nature this interpretation is consistent with results from other sectors of the west antarctic continental shelf where compelling evidence for significant wais advance during the lgm exists in the weddell sea this apparent diachronous behavior of the eais and wais is consistent with results from onshore studies

lift off moraines markers of last ice flow directions on the scotian shelf lift off moraines are acoustically incoherent subparallel ridges observed on sidescan sonograms and high resolution reflection seismic profiles on the southeastern continental margin of canada they are up to 3 m high 20 80 m wide and are commonly overlain by stratified proglacial sediments although little is known about them detailed study of high resolution seismic profiles from the emerald basin and the lahave basin on the scotian shelf show that their height width ratio varies with the sounder seabed separation suggesting that the ridges may be narrower than they appear their morphology is similar to degeer moraines or cross valley moraines which form perpendicular to ice flow direction as their orientations can be estimated at the intersection of seismic lines they can be used to estimate ice flow directions since proglacial sediments are draped directly over top of them they are assumed to record the direction of last ice flow this directional data suggests that ice retreated not only

early permian to middle jurassic rifting and sedimentation in east africa and madagascar pre drift sediments of madagascar early permian middle jurassic have been studied palynologically these studies resulted in a more precise dating of individual stratigraphic units and the recognition of minor and major breaks in the succession palynostratigraphic and physical evidence of unconformities have been used to subdivide the pre drift sediments into depositional cycles and to infer rifting events a comparison with equivalent strata of mozambique tanzania kenya ethiopia and somalia shows a general correspondence and provides additional information for the construction of a generalized framework for the east african madagascan region which demonstrates the relationships between rifting and sedimentation and elucidates the prehistory of the break up of gondwana into a western and eastern fragment during the middle jurassic the predrift succession of east africa madagascar can be subdivided into two major sequences a karoo sequence cycles 1 5 asselian early smithian and a transitional sequence cycles 6 9 ladinian early bajocian the two sequences are separeted by a late scythian to anisian hiatus which indicates extensive uplift and erosion before a major rifting event initiated the resumption of sedimentation in the ladinian this middle triassic event marks the transition from the intracratonic rift stage to the pericratonic basin stage and correlates with a significant event in the pangaean history the transition from final coalescence to initial dispersal the onset of the southward drift of madagascar is believed to have occurred about 60 ma later near the aalenian bajocian boundary contemporaneous with or immediately after the deposition of syntectonic sediments of cycle 9

late quaternary stratigraphy of laurentian fan a record of events off the eastern canadian continental margin during the last deglacial period abstract examination and correlation of 10 piston cores from laurentian fan off the eastern canadian continental margin revealed a high resolution stratigraphic record of events since the last glacial maximum lgm the five lithofacies identified in the cores are 1 bioturbated olive grey silty mud with varying amounts of biogenic carbonate 2 olive grey and reddish brown silt laminated mud with rare fine to very fine sand beds 3 poorly sorted light grey and brick red gravelly sandy mud 4 colour banded silty mud with colours alternating at a centimetre scale between olive grey and reddish brown and 5 brown silty mud commonly massive but occasionally silt laminated the dominant depositional processes include hemipelagic sedimentation turbidity currents and ice rafting in these sediments colour is diagnostic of the sediment source area with reddish sediment being delivered to the fan from the gulf of st lawrence and laurentian channel whereas greenish sediment arrives on the fan from st pierre bank through grand banks valley turbidites are the most volumetrically significant facies conversely ice rafted beds are volumetrically minor but they are the most chronostratigraphically significant facies and include heinrich layers h0 h1 and h2 the chronological control provided by radiocarbon dating and stable oxygen isotopes suggests that sedimentation rates for the reddish brown turbidites deposited between the lgm and 14 ka exceeded 10 m kyr 1 mapping of the units together with a simple sediment deposition model suggest that these beds resulted from deposition by turbidity currents over 1 km thick that lasted on the order of weeks less information can be ascertained from the olive grey turbidites that interbed with h2 and directly overlie h1 because of a lack of sampling except that they had a lower sedimentation rate and include sediment derived from newfoundland and the grand banks comparison of the stratigraphy on laurentian fan with that of other deep water areas further north southwest grand banks margin flemish pass and the labrador sea shows striking similarities over the late quaternary with the deglacial period characterized by rapid sediment accumulation however only on laurentian fan does sediment gravity flow deposition occur during the lgm reddish brown turbidites deposited on laurentian fan during the deglacial period have no equivalent facies further north these unique features suggest important glaciological differences between the ice stream occupying laurentian channel and ice streams farther north the onset of widespread hemipelagic deposition occurred after ca 12 ka on laurentian fan and in flemish pass but not until ca 8 2 ka in the labrador sea consistent with the earlier retreat of glacial ice out of laurentian channel as compared to hudson strait

the deglaciation of atlantic canada as reconstructed from the postglacial relative sea level record the post wisconsinan relative sea level record from atlantic canada is used to reconstruct the morphology of late wisconsinan age ice cover during its retreat from the atlantic region the proposed reconstruction has little or no grounded ice in the southern gulf of st lawrence an ice dome over the north shore of the st lawrence and thin ice often less than 1 km thick over much of the rest of the area a sensitivity analysis shows that the proposed reconstruction is not unique in its ability to account for the relative sea level record but that the thickness of ice in any individual area of the reconstruction is unlikely to be in error by more than a factor of two the exact position of the ice margin in some areas is not well constrained by the model an example is in southeastern newfoundland the numerical model used to relate ice morphology to postglacial relative sea level assumes that the ice sheets are isostatically equilibrated at the glacial maximum and therefore that load changes associat

morphology and seismic stratigraphy of the inner continental shelf off nova scotia canada evidence for a 65 m lowstand between 11 650 and 11 250 c14 yr b p abstract nova scotia s position near the margin of large pleistocene ice sheets makes the scotian shelf region critical for evaluation of glaciation models and sea level change the sea floor of the inner scotian shelf was mapped using multibeam bathymetry a combination of conventional seismic and sonar techniques and sampling multibeam bathymetry provides an areal image of the sea floor combining this unique image with sub bottom seismic imaging the relationships between sea floor topography and the underlying strata were explored the inner continental shelf of nova scotia can be subdivided into five major terrain zones these are the 1 truncation zone 2 morainal zone 3 outcrop zone 4 basin zone and 5 scotian shelf end moraine complex the scotian shelf end moraine complex and basin zone are glacial depositional zones at the seaward edge of the inner shelf landward of these zones is a region of high relief bedrock with ridges and valleys largely devoid of surficial sediments extending from 80 to 120 m water depth outcrop zone this zone is interpreted as a relict bedrock surface preserved under frozen bed glacier conditions to the east of the outcrop zone in similar water depths are unmodified till ridges overlying bedrock morainal zone the truncation zone is a region of the inner shelf from 90 m to the present shoreline characterized by muted acoustic topography and planar erosional surfaces truncating bedrock and surficial sediments the truncation zone is subdivided into the valley subzone the transition subzone the platform subzone and the estuarine subzone the valley subzone is typified by sediment infilled valleys occurring in 75 to 90 m water depths these valleys contain seismic facies with a ponded style of deposition planed off at the sea floor or by erosional unconformities near the sea floor the transition subzone is marked by a relatively steep ramp and terraces the ramp at the type section extends from 75 to 65 m water depth the surface of the ramp can be either an erosional unconformity or a depositional surface formed by clinoform beds the 65 m former shoreline is interpreted as the top of the transition subzone ramp surface at one ramp locality clinoform beds form part of a progradational sequence called the sambro delta a mussel valve fragment mytilus edulis was obtained from a core in the foresets and radiocarbon dated an age of 11 650 110 yr b p was obtained adjusted for isotopic fractionation above 65 m the sea floor forms a low relief gently sloping erosional surface platform subzone estuarine deposits have been found above 50 m the new sea level curve constructed with the dated 65 m shoreline and recently published data is at variance with calculated rsl curves based on geophysical models primarily in the amplitudes and rates of rsl change reasons for the discrepancies may be late melting ice and regional variations in lithospheric strength and thickness

binge purge oscillations of the laurentide ice sheet as a cause of the north atlantic s heinrich events ice rafted debris in sediment cores from the north atlantic suggests that the laurentide ice sheet lis periodically disgorged icebergs in brief but violent episodes which occurred approximately every 7 000 years here i propose that heinrich events i e what these episodes are called were caused by free oscillations in the flow of the laurentide ice sheet which arose because the floor of hudson bay and hudson strait is covered with soft unconsolidated sediment that forms a slippery lubricant when thawed the proposed heinrich event cycle has two phases the growth phase occurs when the sediment is frozen and the lis is stranded immobile on a rigid bed the volume of the lis slowly grows during this phase at a rate dictated by snow accumulation the purge phase occurs when the basal sediment thaws and a basally lubricated discharge pathway i e an ice stream such as those which occur in west antarctica today developes through hudson strait the volume of the lis rapidly equilibrates to the reduced basal friction during this phase by dumping icebergs into the labrador sea the periodicity t k sl2g 2 7000 years of the proposed heinrich event cycle is a function of the thermal conductivity and diffusivity of ice k and respectively the atmospheric sea level temperature sl in degrees celsius and the excess geothermal heat flux defined by g g k where is the atmospheric lapse rate and g is the geothermal heat flux agreement between the predicted t and the apparent periodicity implied by the marine record is the main virtue of the free oscillation mechanism i propose an alternative mechanism in which heinrich events are forced by periodic variations in external climate is implausible because periodic atmospheric temperature perturbations are strongly attenuated with depth in an ice sheet

sedimentary framework of the southern maine inner continental shelf influence of glaciation and sea level change abstract although the tidally influenced shoreline of maine is longer than that of virtually any other state almost no research on its geology has been published in order to go some way towards remedying this 1500 km of high resolution seismic reflection data and 800 km of sidescan sonar imagery have been collected on the basis of these data and observations made during ten submersible dives more than 800 bottom samples were collected and evaluated for texture and composition the understanding of the sedimentary framework of the southern maine shelf and the processes that maintain it are summarized and future research directions to evaluate the strategic mineral potential are indicated in the past 14 000 years the maine shelf has experienced a deglaciation and two marine transgressions separated by a regression the deglaciation was accompanied by the first transgression and deposited till interbedded with up to 40 m of glaciomarine sediment the presumpscot formation across the shelf the first transgression culminated about 12 500 yrs b p and its landward limit is marked by large glaciomarine deltas 50 100 km landward of the present day coast sea level fell until about 9500 yrs b p when shorelines were cut at about the 65 m depth and some large lowstand deltas were deposited sea level has risen since then and in the general absence of modern river sediment input marine processes have reworked the older sediment five shelf environments have been defined in terms of their surficial sediment and stratigraphy nearshore ramps are sandy regions extending to about 30 m deep offshore of sandy beaches these may be reworked lowstand deltas and possess the thickest bodies of sand in the region nearshore basins are mud filled troughs seaward of coastal areas lacking significant river input slumping glaciomarine deposits provide most of the holocene mud that floors these basins rocky zones are extensive areas of exposed rock most common in the 30 50 m depth range these are areas of high carbonate productivity and provide shell fragments to adjacent areas the outer basins are muddy regions that begin at the 65 m shoreline and extend beyond the 100 m isobath to the deep gulf of maine finally shelf valleys are former stream courses that connect nearshore ramps and basins to the outer basins these bedrock framed valleys are filled with sand and mud and are apparently still active conduits for the offshore movement of sediment the mineralogy of the shelf sediment is complex and it is not yet clear whether glacial homogenization has obliterated distinctions between river drainage basins and the adjacent shelf studies are continuing into northern maine and analysis of the heavy mineralogy of the shelf sediment utilizing a 2 m humphrey spiral to process large grab samples and cores has begun

antarctic tertiary progonocytheridae the last refuge of majungaella the survivor of a long lineage a geographical and physiological migration from low to high latitudes abstract majungaella grekoff is shown to be the only member of the once dominant ostracod family progonocytheridae progonocytherinae to survive the jurassic and also to survive the cretaceous tertiary boundary event in the jurassic majungaella had a northeastern gondwanine distribution occurring only in india africa and madagascar however during the neocomian it appears in south america where it extends to the maastrichtian while in australia it first appears in the aptian and ranges up to the campanian its last records in africa are in the cenomanian of south africa and the santonian of south western africa this southward shift into higher latitudes was probably due to an increasing cryophilia and although this may have also been prompted by competitive exclusion by better adapted newly evolved taxa it is difficult to demonstrate this due to the universal distribution of most late mesozoic ostracod genera whatever the reason majungaella seems to have become during the cretaceous increasingly adapted to living in high latitude shallow seas and this adaptation is advanced as the prime reason why the genus alone among the progonocytherids was able to survive both the post cretaceous global cooling and antarctic palaeoenvironments into the late neogene eocene oligocene and pliocene occurrences of majungaella in the antarctic are investigated and it is concluded that the genus is in situ in all instances and that especially in the two latter cases it lived in water temperatures very much lower than those of its mesozoic forebears

review of long seabed samplers and criteria for new sampler design a cost efficient way of investigating shallow sediments and for collecting soils data for many offshore geotechnical problems e g anchoring of floating structures with suction piles or evaluation of submarine slope stability is to carry out seabed sampling to say 25 m below seabed and in addition perform seabed cptus to say 40 m based on a review of data collated from the literature and from in house project experience at the norwegian geotechnical institute it was found that kullenberg type piston core samples give poor recovery and samples which are increasingly disturbed as penetration increase this means that laboratory tests on these samples will give results that are not representative of in situ conditions and will give incorrect parameters for foundation design many different factors control the quality of the samples recovered but the need for an effectively stationary piston a core retainer and improvements to the physical sampler parameters e g diameter wall thickness ratio cutting edge angle inside and outside friction are perhaps the most critical the importance of each of these factors is discussed in detail in addition to the need for instrumentation and the way to penetrate the sampler recommendations are given in terms of criteria for the design of a new sampler which the authors feel will give better results than most samplers used in practice today

the laurentide and innuitian ice sheets during the last glacial maximum the late wisconsinan advance of the laurentide ice sheet started from a middle wisconsinan interstadial minimum 27 30 14 c ka bp when the ice margin approximately followed the boundary of the canadian shield ice extent in the cordillera and in the high arctic at that time was probably similar to present ice advanced to its late wisconsinan stage 2 limit in the northwest south and northeast about 23 24 14 c ka bp and in the southwest and far north about 20 21 14 c ka bp in comparison to some previous reconstructions of ice extent our current reconstruction has substantially more late wisconsinan ice in the high arctic where an innuitian ice sheet is generally acknowledged to have existed in the atlantic provinces where ice is now thought to have extended to the continental shelf edge in most places and on eastern baffin island where ice probably extended to the fiord mouths rather than to the fiord heads around most of the ice margin the late wisconsinan maximum ice extent either exceeded the extent of earlier wisconsinan advances or it was similar to the early wisconsinan advance ice marginal recession prior to 14 14 ck a bp occurred mainly in deep water and along the southern terrestrial fringe however heinrich event 1 probably drew down the entire central ice surface at 14 5 14 c ka bp sufficiently to displace the labrador sector outflow centre 900 km eastward from the coast of hudson bay the onset of substantial ice marginal recession occurred about 14 14 c ka bp in the northwest southwest and south but not until about 10 11 14 c ka bp in the northeast and in the high arctic thus the period of maximum ice extent in north america generally encompasses the interval from b24 21 to 14 14 c ka bp or considerably longer than the duration of the lgm defined as occurring during a period of low global sea level as well as during a time of relative climate stability b18 14 c ka bp the interval of advance of much of the laurentide ice sheet to its maximum extent between b27 14 c ka bp and b24 14 c ka bp coincides with a suggested interval of rapid fall in global sea level to near lgmlevels r 2001 elsevier science ltd all rights reserved

early middle jurassic ostracod migration between the northern and southern hemispheres further evidence for a proto atlantic central america connection abstract early to middle jurassic marine ostracod assemblages from the southwestern part of the british isles north african continental margin and south america have yielded taxa which are not known from other parts of britain and europe we discuss the palaeogeographical and stratigraphical distribution of these taxa here arranged into ten informal groups from which we infer that benthonic podocopid ostracoda successfully migrated between northwest europe and the eastern part of tethys during the early and middle jurassic not through the main tethyan seaway but via a proto atlantic central america route supporting previous observations based on macrofossil evidence hispanic corridor of smith 1983 furthermore the fact that these taxa are absent from contemporary european sequences suggests the existence of physical and or chemical barriers limiting benthonic faunal exchange between the western part of the british isles and the rest of north western europe particularly during the late pliensbachian through to aalenian interval

late glacial allerod younger dryas buried organic deposits nova scotia canada a contribution to the north atlantic seaboard programme of igcp 253 termination of the pleistocene abstract numerous deposits of organic shallow pond sediments and wetland peat accumulations buried by minerogenic sediments have been discovered throughout nova scotia they are interpreted as representing a late glacial climatic oscillation correlative with the allerod younger dryas event of europe and the north atlantic ocean the organic deposits began forming during the warm or warming interval following deglaciation and often record a transition to colder conditions the climatic reversion recorded in many deposits began about 10 8 ka bp and continued or sustained cooling culminated in the burial of the organic deposits by minerogenic sediments indicative of solifluction and mass wasting processes some deposits provide strong evidence for regeneration or rejuvenation of local glaciers as the organic deposits are not as susceptible as lake sediments to contamination by old carbon they provide a more reliable chronological framework for deglaciation and late glacial vegetational history palynological evidence shows that pioneer herb tundra communities colonized some areas shortly after 13 ka bp willow and birch shrubs followed soon after spruce woodlands had migrated into the region prior to 10 8 ka bp but had not yet reached the northeast mainland and cape breton island cooling after 10 8 ka bp decimated tree populations and favoured a return to shrub and herb communities the record in the buried deposits was then truncated by deposition of minerogenic sediments and lake sediment sequences from deeper basins with continuous sedimentation are required to complete the record

comparison of the jurassic and cretaceous sedimentary cycles of somalia and madagascar implications for the gondwana breakup the jurassic and cretaceous sedimentary history of northern somalia and the morondava basin of south western madagascar have been studied both regions display an independent facial development however a comparison of the sequential evolution of the mesozoic sedimentary successions in these two presently widely separated areas reveals a surprisingly high level of similarity which probably reflects major events during the disintegration of eastern gondwana during the jurassic and cretaceous although in jurassic times the onset of transgressions and regressions in both areas compares well with eustatic development major deviations in combination with the tectonic activities of different degrees are observed in the early and late cretaceous synchronously in both regions transgressions are observed in toarcian bajocian not dated in northern somalia callovian valanginian madagascar only aptian and campanian times tectonism is noted before the aptian and campanian transgressions in northern somalia and the morondava basin of south western madagascar

late quaternary sediment sediment mass flow processes and slope stability on the scotian slope canada the study area just to the west of the verrill canyon on the scotian slope eastern canada exhibits both large and small scale sediment mass movement features study of high resolution seismic reflection and sidescan sonar data shows that a large portion approximately 70 of the near surface sediment 20 m in the area has undergone erosion rotational slumping and internal deformation remoulded sediment observed in physical properties profiles of piston cores and sediment deformation structures are further evidence of slumping small scale mass flow events are recorded by abundant turbidites and debris flow deposits noted in piston cores sediment physical properties are highly dependent on sediment type lithofacies frequent facies changes both temporally and spatially make correlation between cores difficult although the small scale mass movement events correlate with glacial recession on the continental shelf and lower relative sea levels the triggering mechanisms for the large scale events are less obvious slope stability analyses indicate that at present the seabed is stable the most plausible explanation for large scale slope failures in this region are ground accelerations related to earthquake shock our analyses demonstrate that it is unlikely that large magnitude distant earthquakes such as those previously proposed in the laurentian slope seismic zone lsp model could initiate failure of sediment in the study region our data support the interpretation that more frequent lower magnitude earthquakes closer to the study region as previously proposed in the eastern slope experimental source zone esx model are the likely causes of large scale slope failures furthermore excess pore pressures resulting from shallow gas and or high sedimentation rates during deglaciation contribute to slope failure

modeling surface waves from aboveground and underground explosions in alluvium and limestone the may 2012 humble redwood iii hriii experiment series in new mexico provides a unique dataset to study surface wave generation from explosions conducted above and underground for different rock types four 90 6 kg trinitrotoluene equivalent explosions were detonated either at 2 m height of burst hob or 7 m depth of burial dob at separate alluvium and limestone test sites for the alluvium site data from a temporary seismoacoustic network show that fundamental mode surface waves graphic 1 from the 7 m dob in alluvium shot were four to five times larger than the above alluvium shot the graphic 2 amplitudes from the 7 m dob limestone shot were 15 times larger than graphic 3 recorded from the collocated 2 m hob shot to model these differences in graphic 4 we generated 1d velocity models for both test sites using observed surface wave dispersion we considered two different methods for synthetic seismogram generation for the aboveground shots we have coupled near field blast wave pressures and shapes with source medium properties to model seismic data at distance for the underground shots we use explosion source theory to estimate a moment for scaling explosion synthetics for both above and underground shots the synthetics provide excellent fits to the observed 1 5 hz graphic 5 data this modeling provides a viable technique to predict peak particle velocities for surface and aboveground explosions in different rock types that can be used to estimate combined seismoacoustic yields online material movies of four explosions studied in this paper 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif 4 embed inline graphic 4 gif 5 embed inline graphic 5 gif

sedimentary and rock magnetic signatures and event scenarios of deglacial outburst floods from the laurentian channel ice stream abstract eastern canadian margin sediments bear testimony to several catastrophic deglacial meltwater discharges from the retreating laurentide ice sheet the reddish brown plumite layers deposited on the levees of the laurentian fan valleys have been recognized as indications of multiple outburst floods between heinrich events 2 and 1 five event layers have been consistently recorded in three new gravity cores retrieved on the sw grand banks slope and comply with the previously published laurentian fan core md95 2029 the apparently huge extent of these outburst plumes around the laurentian fan as well as their causes and consequences are investigated in this study using physical properties rock magnetic and grain size analyses together with seismoacoustic profiling we provide the first detailed 14c ages of the outburst event sequence and discuss their recurrence intervals in the context of regional ice retreat compared to the hemipelagic interlayers event layers have overall uniform and systematic changes of rock magnetic properties hematite contents increase over time and proximally while magnetite grain sizes fine upwards and spatially away from the fan based on the sediment composition and load we argue that these plumites were formed by recurrent erosion of glacial mud deposits in the laurentian channel by meltwater outbursts three alternative glaciological scenarios are evaluated in each case the provenance of the transported sediment is not an indicator of the precise source of the meltwater

late quaternary calcareous nannofossil biostratigraphy and sedimentation patterns fram strait arctica sediment cores from the fram strait are dated by means of calcareous nannofossil biostratigraphy and are shown to represent at the most the last 300 kyr oxygen isotope stages 1 8 differences in sedimentation rates are mainly controlled by the bottom topography and the intensity of ice rafted deposition sedimentation rates are normally in the order of a few centimeters per kiloyear in the central fram strait but increase to over 10 cm kyr in cores located on the continental slope the highest sediment accumulation rates occurred on the shelf several tens of centimeters per kiloyear

palaeoecology and palaeobiogeography of the middle jurassic ostracods of southern tunisia abstract the results of a palaeoecological biostratigraphical and palaeobiogeographical analysis of jurassic ostracods from southern tunisia are presented the shallow to marginal marine deposits of bajocian bathonian krachoua and techout formations and callovian oxfordian age tataouine formation which accumulated under predominantly warm humid climatic conditions yielded diverse ostracod faunas from limnic brackish and marine environments which have been analysed statistically a qualitative cluster analysis yielded fourteen associations and two assemblages which are characterised by different percentages of marine brackish and freshwater species the distribution of the associations in the middle jurassic reflects temporal and spatial salinity gradients which are interpreted to reflect climatic variations humid arid and global eustatic sea level changes in the callovian the ostracods and macrofaunas probably also reflect minor relative sea level changes in accordance with other biostratigraphical data the ostracods support a bajocian bathonian age for the upper krachoua and the lower techout formations and a callovian age for the lower tataouine formation the palaeobiogeographical relationships suggest faunal exchange between southern tunisia and europe southern france sardinia england in the bajocian bathonian and an isolation of the south tunisian ostracod faunas from the european faunas in the callovian probably due to the deepening of the central western tethys predominantly in the bajocian bathonian but also in the callovian brackish conditions resulted in an endemicity of the ostracod faunas as a consequence of the eustatic sea level rise in the callovian species from the eastern north gondwana shelf israel jordan egypt saudi arabia respectively the ethiopian province invaded southern tunisia palaeobiogeographically the ostracods from southern tunisia are intermediate between the ostracods from the arabic northeast african region and northwest africa morocco

in situ geotechnical characterization of sediments on the nova scotian slope eastern canadian continental margin abstract a seabed 2 m long cone penetrometer and coring system geotechnical module has been used at 17 stations in four transects on the scotian slope to characterise in situ shear strength and induced pore pressure on several different types of late pleistocene and early holocene failure study sites were selected using the sar high resolution deep towed acoustic system equipped with a digital 160 190 khz sidescan sonar and a 3 5 khz subbottom profiler several distinctive types of geotechnical signature were recognised from plots of cone resistance and induced pore pressure with depth in the sediment normally consolidated sediments show a progressive increase in cone resistance with depth to about 75 kpa at 2 m subbottom holocene surficial muds show spectacular apparent overconsolidation reaching a peak of 250 kpa at about 50 cm subbottom and then decreasing down to 1 5 m this overconsolidation is associated with zoophycos burrows late pleistocene sediments exhumed by bedding plane slides show strong true overconsolidation consistent with the original depth of burial inferred from high resolution seismic stratigraphy debris flows show only a slight shear stress gradient with depth 40 45 kpa over 0 5 1 m subbottom with under consolidation due to remoulding of sediment

reconstructed ice flow patterns and ice limits using drift pebble lithology outer nachvak fiord northern labrador discussion on the basis of their analysis of pebble lithologies and age estimates of marine shells the authors presented an interpretation for late quaternary events in outer nachvak fiord that they sav is incom atible with the late wisconsinan ice model of f k k and osh josenhans et al 1986 clark 1988 we believe that much of their data when reinterpreted do not conflict with our reconstruction and in fact can be accommodated by our reconstruction in contrast our data from nachvak fiord and the adjacent continental shelf are not compatible with their hypotheses nor have they directly addressed these data in their hypotheses in this discussion we will evaluate the clast morphologic and chronologic data used by the authors to develop their hypotheses we also summarize our work related to the glacial history of nachvak fiord and the adjacent shelf for the purpose of discussion and comparison with their hypotheses

proposed younger dryas glaciation of the eastern scotian shelf a refined synthesis of the stratigraphy of the scotian shelf is presented based on recently published borehole and seismic reflection data and detailed correlation along high resolution seismic profiles between the outer banks and the central basins one of the new stratigraphic units of the outer bank region is of glacigenic origin and represents the last glacial event near the margin of the shelf these deposits appear to be part of a morainal bank complex formed at a tidewater front a younger dryas age is proposed for the glacial deposits and the ice may have been widely distributed across the eastern scotian shelf evidence for the late glaciation is expressed in the central shelf area by an unconformity which on the bank areas is associated with subglacial meltwater channels 14c dates for the basin sediments of this region provide the most reliable chronology for the shelf stratigraphy the origin of sable island is closely related to the depositional history of the moraine and its surface has be

mid core flow in implications for stretched stratigraphic sections in piston cores stratigraphic disruption of piston cores known as flow in often occurs in basal portions of cores but also can form within a core between undisturbed sediment layers or at the top of cores flow in is caused by piston movement upwards either abruptly during corer penetration or slowly during corer pull out from the sea floor sedimentary structures indicative of flow in are usually noticeable by vertical streaking of sediments in contrast to horizontal layers that result from natural depositional processes if however piston movement is brief or the cored sediment has no obvious layering smeared and disrupted sections may not be apparent resulting in unnaturally thick sediment layers in the middle or top of the core such stretched stratigraphic sections could be difficult to detect and consequently could lead to misinterpretation of stratigraphic data

characterization of seismic sources from military operations in urban terrain mout examples from baghdad abstract on 10 october 2006 a mortar attack on u s forward operating base falcon south of the iraqi capital baghdad ammunition supply point resulted in an ammunition cook off accompanied by numerous explosions the explosions shook the base and damaged surrounding structures and they were both felt by baghdadi residents and seismically recorded at the single broadband seismometer at the baghdad seismic observatory bhd the mortar activity ensuing explosions and accompanying military activities provided a wealth of information on the nature of seismic and acoustic wave generation and propagation resulting from nearby battlefield sources seismic records from the observatory show a variety of waveforms that can be qualified as different types of battlefield related sources including weapon rounds mortars rockets mines improvised explosive devices vehicle borne improvised explosive devices and airborne vehicles these different kinds of military operations in urban terrain are characterized and quantified by correlating their recorded military activity with observed seismic records and various aspects of the signals wave propagation

sedimentation rates in baffin island fiord cores from comparative radiocarbon dates five accelerator tams system university of arizona radiocarbon dates on small 30 50 mg paired bivalves or shell fragments have been obtained on two piston cores these dates are compared with conventional and accelerator 14c dates on the total organic fraction 2 m size fraction from similar levels in the two cores the shell dates are always younger by several thousands of years we argue that the shell dates are the more reliable for example we demonstrate that pre quaternary pollen is abundant in the lowermost 6 m in core hu77 159 from frobisher bay since the occurrence of shells is rare in piston cores we have developed an empirical relation that enables us to change dates on organic matter to a more probable true age if this correction is applied to dates on the total organic fraction that we obtained on an additional five cores from fiord and shelf sites a consistent pattern of sedimentation rate variations is shown this indicates that sedimentation rates were highest between ca 9

late quaternary sedimentation on the southwestern scotian slope eastern canada relationship to glaciationgeological survey of canada contribution 20070176 the sedimentary record on continental slopes has the potential to preserve a record of glacial retreat on the adjacent continental shelf the glacial history of the southwestern part of the scotian shelf is poorly known air gun and high resolution sparker profiles and numerous sediment cores up to 10 m long have been used to determine the character of sedimentation on the southwestern scotian slope since the last glacial maximum lgm seismic reflection profiles show that glacial till was deposited at shallow depths on the upper continental slope and correlation to dated piston cores farther downslope show that this till dates from the lgm slope sedimentation at this time was dominated by local ice and deposited as plume fallout and turbidites progressively increasing importance of red brown sediment derived from glacial supply to laurentian channel indicates retreat of ice from the shelf edge and diminishing supply of proglacial sediment from the calving embayment in the mid scotian shelf with the

the marine record of deglaciation from the continental margin off nova scotia continental margin sediments off nova scotia accumulate at high rates up to 360 cm kyr 1 and contain a history of millennial scale environmental changes which are dominated by the proximity of the laurentide ice sheet during the latest quaternary using stable isotope ratios of oxygen accelerator mass spectrometer radiocarbon dating micropaleontology and sedimentology we document these changes in six piston cores ranging in water depth from 450 to 4300 m we find that maximum 18o in n pachyderma occurred about 15 ka and preceded the maximum abundance of this species in these cores by 1000 years between 13 and 14 ka we find a second peak in abundance of n pachyderma minimum 18o and two pulses of ice rafting the sediment lithology supports terrestrial studies which indicate that there was a general withdrawal of ice beyond the upper paleozoic and mesozoic red beds by 14 ka in southeastern canada so the ice rafting events between 13 and 14 ka probably reflect ice stream activity in the st lawrence valley the younger dry as event is recognized as a peak in abundance of n pachyderma and ice rafting dated as 11 3 ka but meltwater discharge to the gulf of st lawrence was either too small or occurred over too long a time to leave a distinct 18o minimum off nova scotia at 7 1 ka in the middle of holocene warming we find a third peak in abundance of n pachyderma and another 18o minimum but no ice rafting we interpret these data as evidence of a late occurring meltwater event which if correct could have originated in the great lakes in the labrador ungava region or in both the final millennial scale phenomenon off nova scotia is the onset of neoglaciation marked by increased ice rafting and increased n pachyderma beginning about 5 kyr ago

initiation and development of the laurentide and cordilleran ice sheets following the last interglaciation abstract fossil records from sites overridden by or adjacent to the laurentide ice sheet indicate that the climate of the last interglaciation oxygen isotope substage 5e ca 130 116 ka was warmer than today following the last interglaciation the laurentide ice sheet first developed during stage 5 over keewatin quebec and baffin island along its northern margin the ice sheet reached its maximum extent of the last glaciation during stage 5 the ice sheet advanced across baffin island onto the continental shelf early during stage 5 5d whereas the advance into the western canadian arctic occurred late during stage 5 5b the ice sheet also may have advanced into the st lawrence lowland during substage 5b although this event may be younger stage 4 the hudson bay lowland became ice free during substage 5a retreat of the ice sheet on baffin island occurred during late stage 5 probably substage 5a the exact timing of retreat from the western canadian arctic is unknown but it occurred before 48 ka the southern sector including the st lawrence lowland was ice free during late stage 5 the hudson bay lowland may have remained ice free through stage 4 and much of stage 3 because of conflicting chronologies however it is more likely that this area was glaciated throughout stage 3 and perhaps stage 4 nevertheless the data demonstrate that the lowland was ice free during part of the last glaciation an independent ice cap developed over the appalachian uplands and advanced across nova scotia during stage 4 perhaps as far as the edge of the continental shelf the ice cap remained active over nova scotia as a setellite to the laurentide ice sheet throughout the remainder of the last glaciation the ice sheet advanced into the st lawrence lowland during stage 4 and subsequently overwhelmed the local ice cap in the appalachian uplands advancing perhaps into northern new england but not farther south the lowland remained covered by the ice sheet until late stage 2 the ice sheet may also have advanced into the lake ontario basin during stage 4 the position of the northern margin of the laurentide ice sheet during stage 4 is not known but it remained an unknown distance behind its maximum position reached during stage 5 cores from baffin bay indicate a substantial decrease in high latitude glaciation during stage 4 following retreat the keewatin sector of the ice sheet may have remained over much of northwestern canada as a quasi stable ice mass until it readvanced during stage 2 similarly the baffin island sector of the ice sheet may have remained largely intact the southern margin of the ice sheet may have advanced into the lake ontario basin and upper mississippi valley during the middle of stage 3 ca 50 ka reaching its maximum extent of the last glaciation during stage 2 ca 18 21 ka advance of the northern margin was younger ca 8 13 ka than that of the southern margin this advance was less extensive than the penultimate advance stage 5 paleoenvironmental records indicate that the last interglaciation in areas covered by and near the cordilleran ice sheet was as warm as or warmer than present the cordilleran ice sheet appears to have developed during stage 5 or 4 at that time it advanced over southern british columbia and into the northern puget lowland there is no record of this event in northern areas that were later covered by the ice sheet the ice sheet disappeared before 59 ka at the beginning of a lengthy nonglacial interval paleoenvironmental records indicate that climate was similar to the present during part of this interval the ice sheet was absent and glaciers probably were confined to mountain areas throughout stage 3 climatic deterioration marking the end of this nonglacial interval may have begun as early as 29 ka by 14 15 ka the ice sheet had achieved its maximum extent of the last glaciation because there are few suitable dating methods capable of resolving events beyond the radiocarbon limit and because sites that preserve a record of events from the last glaciation are spatially restricted we consider this synthesis as tentative and subject to significant revision as dating methods improve nevertheless this perspective of the north american ice sheets through the last glaciation demonstrates their complex and dynamic behavior and attendant rapid fluctuations in ice volume

seismic models for near surface explosion yield estimation in alluvium and sedimentary rock author s templeton dc rodgers aj ford sr harben pe ramirez al foxall w reinke re abstract 2018 seismological society of america all rights reserved seismic ground motion data provide valuable constraints on explosion characteristics such as yield and height of burst depth of burial hob dob this study investigated a range of seismic amplitude features and their efficacy in minimizing errors associated with yield estimation using a set of explosion recordings from experiments conducted in alluvium and sedimentary rock geologies we investigated the effectiveness of three different seismic feature types over a range of different frequencies using both velocity and displacement data we investigated the zero to peak ztp amplitude of the first arriving p wave the peak to peak ptp amplitude of the first arriving p wave and the prms amplitude over various time windows starting with the p wave these three basic features were measured on both vertical component only data and the vertical radial vector sum in total there were 56 different combinations investigated our seismic models combine the effects of scaled range and scaled hob dob on the observed seismic features the results show that the vertical radial vector sum of the ztp amplitudes measured on displacement seismograms most consistently produce models with the smallest difference between predicted amplitude values and observed amplitude values when accounting for both alluvium and sedimentary rock lithology the improvement in fit to the data when incorporating the difference in source lithology is significant if an alluvium lithology is assumed for a sedimentary rock lithology the difference in yield could be up to 3 0 times the appropriate yield in the far field

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

gondwana to asia plate tectonics paleogeography and the biological connectivity of the indian sub continent from the middle jurassic through latest eocene 166 35 ma abstract using the most up to the date information available we present a considerably revised plate tectonic and paleogeographic model for the indian ocean bordering continents from gondwana s middle jurassic break up through to india s collision with asia in the middle cenozoic the landmass framework is then used to explore the sometimes complex and occasionally counter intuitive patterns that have been observed in the fossil and extant biological records of india madagascar africa and eastern eurasia as well those of the more distal continents although the paleogeographic model confirms the traditional view that india became progressively more isolated from the major landmasses during the cretaceous and paleocene it is likely that at various times minor physiographic features principally ocean islands provided causeways and or stepping stone trails along which land animals could have migrated to from the sub continent aside from a likely link albeit broken by several marine gaps to africa for much of this time it is notable that the present day recent biota of madagascar indicates that the ancestors of five land mammal orders plus bats crossed the 400 km wide mozambique channel at different times in the cenozoic it is possible that the kerguelen plateau connected india and australia antarctica in the mid cretaceous approximately 115 90 ma later the seychelles mascarene plateau and nearby elevated sea floor areas could have allowed faunas to pass between southern india and madagascar in the late cretaceous from around 85 65 ma with an early cenozoic extension to this path forming as a result of the reunion hot spot trace islands growing on the ocean floor to the ssw of india the modelling also suggests that india s northward passage towards asia with eventual collision at 35 ma involved the ne corner of the sub continent making a glancing contact with sumatra followed by burma from 57 ma late paleocene onwards a scenario which is compatible with the fossil record indicating that india asia faunal exchanges began occurring at about this time finally we contend that a number of biologically based direct terrestrial migration routes that have been proposed for last 15 m y of the cretaceous asia to india antarctica to madagascar and or india can probably be dismissed because the marine barriers likely varying from 1000 up to 2500 km were simply too wide

seismo acoustic energy partitioning at near source and local distances from the 2011 sayarim explosions in the negev desert israel the january 2011 calibration explosions at the sayarim military range in the negev desert israel provide a unique dataset to study seismic and acoustic partitioning for surface sources at near source and local distances we present an analysis of the seismic and overpressure acoustic signals generated from two explosions which included 10 240 and 102 080 kg of mainly anfo with some composition b detonated on the surface on 24 and 26 january respectively at different times of the day a temporary seismo acoustic overpressure network was deployed at distances between 0 1 and 39 km to supplement data from permanent stations in israel the near source data confirm the explosions produced overpressure signals consistent with complete and simultaneous surface detonation of 7 4 and 76 8 metric tons of tnt equivalent explosives we observe acoustic amplification at local distances 5 km south of the larger explosion that can be explained by a low altitude southward flowing wind at the detonation time for the smaller shot the southward flow was not present and amplification was not observed in the pressure data we present results of modeling these overpressure data with blast pressure scaling models with and without meteorological data seismic phases generated by the surface shots include p waves fundamental and higher mode rayleigh waves and love waves that appear to have been generated at or very near the explosion source the seismic ground motion is less than would be expected for fully coupled explosions of 7 6 and 76 8 tons and at near source distances 10 km can be modeled well by reducing ground motion predictions from the fuis et al 2001 model by a factor of 4 the results from the sayarim explosions combined with past and future experimental datasets will lead to an improved understanding of the seismo acoustic source function for explosions and energy partitioning between seismic and acoustic waves

late wisconsinan deglaciation of emerald basin scotian shelf emerald basin is a glacially overdeepened basin located on the central scotian shelf where quaternary sediments form a thin veneer over tertiary bedrock nineteen piston cores and 1200 line km of seismic data were obtained from the basin from which seven acoustic facies were recognized i cambro ordivician metasediments ii tertiary sediments iii scotian shelf drift till iv acoustically stratified emerald silt v acoustically unstratified emerald silt vi lahave clay vii diffused gas six depositional sequences were recognized in the emerald silt and lahave clay facics and were correlated with sediments recovered in piston cores depositional sequence 0 is a strongly stratified package which drapes over the scotian shelf drift it is correlated with stiff unbioturbated slightly gravelly sandy muds with no in situ molluscs and is characterised by an ice marginal foraminiferal assemblage depositional sequence 1 drapes over depositional sequence 0 and shows onlap on topographical highs it is correlated with slightly gravelly muds which are characterised by alternating bioturbated and unbioturbated hands and monospecific molluscan and foraminiferal assemblages depositional sequence 2 asymmetrically drapes over and onlaps onto depositional sequence 1 and is correlated with bioturbated slighty gravelly muds with monospecific molluscan and foraminiferal assemblages depositional sequence 3 infills the basin deeps erosionally truncating reflections of depositional sequence 2 it is correlated with bioturbated muds which are characterised by a monospecific foraminiferal assemblage and a slightly diverse molluscan assemblage depositional sequence 4 drapes over the erosional upper surface of depositional sequence 3 and is correlated with bioturbated muds which are characterised by a diverse molluscan assemblage depositional sequence 5 onlaps onto depositional sequence 4 infilling the basin deeps and is correlated with soft bioturbated sandy silts which are characterised by diverse molluscan and foraminiferal assemblages the present day seafloor in emerald basin is marked by small gas escape structures intepreted as pockmarks buried pockmards are observed in depositional sequences 4 and 5 buried iceberg scours are observed on the upper surface of depositional sequence 0 and within depositional sequences 1 and 2 small ridges interpreted as lift off moraines are formed on the upper surface of the scotian shelf drift and are oriented transverse to ice flow directions during glacial retreat wedge shaped acoustically unstratified features interpeted as till tongues are rooted in moraines on the basin flanks and were deposited simultaneously with depositional sequences 0 1 and 2 detailed interpretation of the seismic and core data suggest that glacial ice advanced across emerald basin reaching the shelf edge at approximately 24 ka melting of the ice sheet resulted in deglaciation of emerald basin at 17 5 ka by lift off of the grounded ice sheet to form a floating ice shelf of 10 100 yr duration sediment beneath the ice shelf was primarily supplied by subglacial meltwater streams prior to lift off till was squeezed into basal crevasses in the ice to form features known as lift off moraines the ice shelf calved at approximately 17 4 ka causing intense scouring of the seafloor by in situ icebergs and isolating ice rises on the banks surrounding emerald basin these ice rises disintegrated rapidly except for the rise on emerald bank which contributed sediment to emerald basin until 12 ka sediment was primarily supplied by subglacial meltwater and deposited out of suspension except near the ice margin where ice rafting and gravity flow mechanisms were important iceberg scouring occurred until about 14 ka the main ice margin remained on the northern flank of the basin until 15 4 ka at which time it retreated landward a widespread erosive event caused by storm driven currents occurred at 13 ka rain out from suspended sediment plumes was the dominant depositional mechanism until 12 ka lahave clay is primarily derived from inner shelf sediments reworked by rising sea level storm generated currents have created an erosional surface at the present day seafloor around the flanks of the basin

oversampling of sedimentary series collected by giant piston corer evidence and corrections based on 3 5 khz chirp profiles 1 the depth scale accuracy of marine sedimentary series collected by coring is of key importance for the precise calculation of sedimentation rates and fluxes for three giant piston cores collected during the interpole md99 114 international marine past global changes study images v cruise md99 2227 md99 2246 and md99 2251 the 3 5 khz chirp profiles recorded on board are compared to synthetic seismograms computed from physical property logs measured on cores in each case the perfect match of main deep reflectors requires a significant upward shift of the water sediment w s interface in the synthetic seismograms with respect to the 3 5 khz profiles since no drastic perturbation of the physical property logs is observed this upward shift is interpreted as resulting from a significant sediment oversampling in the upper part of the cores the affected depth intervals are consistent with the thickness of the perturbed zones observed in penetrometry and anisotropy of magnetic susceptibility records 10 15 m to retrieve the true in situ sediment thickness a linear depth correction is applied between consecutive acoustic reflectors to achieve a perfect match between the synthetic seismogram and the corresponding 3 5 khz profiles depth correction laws amount of material excess as a function of initial depth are deduced from this resynchronization procedure first estimations of upper core oversampling rates range from 30 core md99 2227 to 37 core md99 2246 moreover we observe that some undersampling may also exist in the lower part of the sediment cores

palynological records of red tide producing species in canada past trends and implications for the future abstract increases in red tides and other harmful algal blooms habs during the past 50 yr on both the atlantic and pacific coasts of canada suggest that global scale factors such as climate change and increased international shipping trade are the driving forces because the historical record is too short to understand the long term dynamics of habs the holocene history of harmful phytoplankton species was examined using ultra high resolution studies annual to decadal scale of dinoflagellate cysts as a proxy for red tide production paleoecological transfer functions were then applied to the cyst assemblage data to determine correlations with changes in sea surface temperature and salinity pacific records were obtained from varved marine sediments in saanich inlet british columbia and in the santa barbara basin off california comparison of annual cyst production and historical plankton data provides cyst theca ratios from which the magnitude of past bloom size can be evaluated the 10 500 yr pacific record clearly shows that the largest blooms correspond to cysts of protoceratium reticulatum and gonyaulax spinifera during the early holocene sporadic blooms of potentially toxic alexandrium spp lingulodinium polyedrum and gymnodinium spp also occurred from ca 7000 to 5000 yr bp and more frequently from ca 2000 to 3000 yr bp individual holocene blooms were up to 10 times larger than in the historical record but they almost always occurred sequentially without overlap of red tide species in pre historical times the bloom cycles started and stopped abruptly in 10 yr or less and they persisted for about 100 1000 yr in contrast the variability and near concurrence of species blooms in the modern past 60 yr record is unmatched in the past and suggests disequilibrium of the natural ecosystem structure atlantic records from la have and emerald basins on the scotian shelf are less precise because bioturbation limits time resolution to ca 25 yr however cyst abundances of cf alexandrium protoceratium reticulatum gonyaulax spinifera and lingulodinium polyedrum were also an order of magnitude larger in the early holocene where they correspond to a summer sea surface warming of 2 5 c lesser peaks also appear during the past 2000 yr where they apparently correspond to a slight increase in winter temperature there is no evidence of much lower salinity that would support stronger stratification the similarity of pre industrial age cyst records of red tide histories in the oceanographically different pacific and atlantic regions of canada indicates that climate change including surface temperature and storminess is the main driving force stimulating blooms this implies that habs will reoccur regardless of efforts to limit spreading however reduced pollution may decrease the hab diversity thereby stabilizing the population dynamics and increasing the predictability of bloom occurrences

a reconstruction of glacial events in southeastern new brunswick sedimentological and petrographical data obtained from five sections located north and south of the caledonian highlands in southeastern new brunswick demonstrate the existence of three main till units and one glaciofluvial unit which have been grouped in four distinct lithostratigraphic units the lower till was deposited by a glacier that overrode the caledonian highlands from northwest to southeast and advanced as far as nova scotia during middle to late wisconsinan times the overlying middle till from the north provides evidence that ice continued to advance across the highlands from northwest toward southeast and then was partially overwhelmed by another glacier that was advancing southwest along the southern border of the highlands this glacier deposited a coeval middle till during late wisconsinan deglaciation ice separated into two masses a residual ice cap with radial outflow from the highlands and a lobe in the chignecto bay retreating toward the northeast the existence of a plateau

a 2000 year geomagnetic field record from the gulf of papua abstract a high resolution holocene record of geomagnetic field direction and intensity in the gulf of papua was constructed using paleomagnetic data from eight piston cores collected in the region the chronology of the cores was based largely on radiocarbon dates from benthic foraminifera correlation of seismic reflectors imaged in subbottom data between nearby cores was consistent with the chronostratigraphic framework based on radiocarbon dates and provided additional confidence of the age model in other regions where cores sampled different depositional settings associated with the three dimensional prograding lobes reflectors could not be confidently correlated between cores furthermore radiocarbon ages from the bottoms of trigger cores and tops of co located piston cores revealed varying amounts of overpenetration of the piston core below the seafloor the relative paleointensity and a general eastward trend in the declination and steepening of the inclination in our new record are generally compatible with the closest 4300 km existing records our record does not agree well with global field models cals3k and pfm9k likely reflecting the lack of existing data contributing to field models in the region

application of ostracoda and charophyta from the late jurassic to early cretaceous tendaguru formation at tendaguru tanzania east africa biostratigraphy palaeobiogeography and palaeoecology abstract revisitation of the famous late jurassic early cretaceous dinosaur locality of tendaguru by a german tanzanian expedition in summer 2000 resulted in a new standard section micropalaeontologic samples from this section yielded a marine and nonmarine partially mixed ostracod fauna consisting of 40 taxa and some charophyte gyrogonites and utriculi a few marine taxa provided biostratigraphic information although comparable faunas from the west indian madagascan east african faunal province are stratigraphically older middle late jurassic fully marine and strongly endemic an middle oxfordian age is suggested for the lower part of the tendaguru formation nodosoclavatoroid utriculi charophyta suggest that the jurassic cretaceous boundary may be located lower in the section than supposed previously i e in the trigonia smeei member rather than in the upper saurian member in biogeographical terms the marine ostracod fauna is relatively endemic and has most similarities with that known from eastern tanzania only a few faunal links to madagascar northwest india and somalia exist and there are no links to south africa ostracods and charophytes also provided palaeoecological data for specific horizons in the lower part of the middle saurian member a regression is documented while the nonmarine late jurassic early cretaceous ostracods of tendaguru are not applicable to biostratigraphy so far they are important because the nonmarine setting is unique in this area of the tethys

chronology of late wisconsinan glaciation emerald basin scotian shelf eight new accelerator mass spectrometry ams radiocarbon dates from proglacial sediments in emerald basin indicate that the previously proposed chronology based on dates of total organic matter is much too old the new chronology indicates that grounded ice occupied emerald basin in the late wisconsinan

processes controlling the accumulation of diatoms in sediments a model derived from british columbian fjords the transformation of biocoenosis to taphocoenosis of diatom assemblages was examined using monthly sediment traps over a 3 year period at four sites in the fjords of british columbia the fjords were chosen as a natural laboratory where productivity is high and seasonally variable and where geological rates of sediment accumulation approach the biological rates of production and flux the composition of trap samples from different depths was quantified and compared with the surface sediment recovered by box cores fragmentation caused by zooplankton grazing preferentially destroys 20 50 of the early spring and 50 75 of the late spring and early summer production grazing activity and incorporation into pellets does not otherwise affect preservation differential dissolution occurs during settling through the water column taxa with a high surface to volume ratio are preferentially lost low level lateral advection tends to concentrate heavy robust taxa while strong advection affects all particles equally and has no net biasing effect the interaction of these processes results in a sediment assemblage in which winter and fall taxa are more common than they are in the plankton while the early spring bloom is badly underrepresented multivariate analyses indicate that the sediment is dominated by the early summer bloom but caution must be exercised in this interpretation because the bloom is characterized by a species skeletonema costatum which is common at all seasons of the year and therefore is not a reliable indicator of a single period of production the end result is a decrease in seasonal contrast and at some sites a reordering of seasonal proportion in the sediment while the seasonal composition can still be identified there is also evidence of homogenization of sediment assemblages with some of the original spatial variability obscured taken to an extreme a unique fossil assemblage may be produced which cannot be statistically related to any combination of seasons of production three factors which might affect preservation of deep sea assemblages water depth accumulation rate and degree of bioturbation do not have a measurable effect in fjord environments strong modification of assemblages can occur within the upper 500 m deep sea monitoring programs which do not include this interval may lead to erroneous conclusions concerning production and flux to the sediments

analysis and modelling of gravity and piston coring based on soil mechanics the effects of gravity and piston corers on the dimensional accuracy of marine sediment cores is analysed using principles of soil mechanics a model for the coring process is built around the feedback that arises and develops between the core barrel and the sampled sediment this model for sediment response is applied to different hypothetical coring scenarios which are then compared to real examples providing insights into the specific effects of each sampling method and the development of these effects down core four cores from a single location on the iberian margin are found to contain stratigraphically intact successions that differ in length by a factor of up to 2 7 due solely to the different effects of each coring method these dimensional discrepancies are attributed to the combined effects of over sampling in the upper portions of the piston cores due to cable rebound causing upward piston acceleration and under sampling dominant in the basal portions of the open barrel gravity type cores it is suggested that heavier piston corers deployed on longer lighter cables are prone to greater over sampling ratios over longer stratigraphic intervals due to the increased likelihood and extent of cable rebound cable rebound may also give rise to double penetration of gravity corers resulting in repeated stratigraphic intervals knowledge of the dimensional accuracy of marine sediment cores is essential to an evaluation of past sedimentation rates and hence interpretations of past depositional processes it is therefore essential that we recognise the sampling effects of each coring method and their variability down core lest coring artefacts be interpreted as sedimentary signals different core types may be more suited to different palaeoceanographic investigations hence failing the development of a practical cable deployed recoilless piston corer a combination of a variety of core types will permit the best acquisition of the in situ stratigraphic truth our results suggest that a large diameter dc 20 30 cm square barrel gravity corer for the top 10 12 m combined with a cylindrical piston corer below 10 m may provide the least deformed material

alkane distributions in arctic ocean sediments reply to alkane and pah biomarkers as tracers of terrigenous organic carbon in arctic ocean sediments by mark b yunker robie w macdonald lloyd r snowdon brian r fowler comment by vera petrova and co authors

sediment accumulation in low sedimentation wave dominated glaciated inlets abstract many fjords situated in lowland areas of resistant bedrock are characterized by a comparatively low fluvial sediment flux and are often dominated by wave processes several such fjords in eastern canada are used as examples to develop a generalized sediment distribution model physiographically the fjords can be subdivided into nearshore platforms basin slopes and basin floors where there has been marine transgression the principal sediment source is shoreline erosion of glacial till in areas of crustal rebound late glacial and early holocene muds deposited on highs are eroded as they come within the zone of wave erosion with the falling sea level storm waves resuspend fine grained sediment in water depths of many tens of metres and produce near bottom turbid water zones within basins fine sand and silt settle out rapidly leading to the deposition of graded beds on the basin floors residual sand and gravel accumulate on the near shore platforms while silt and mud prograde over or are advected beyond basin slopes burying older basin fill sediment

middle and upper jurassic ostracods from western kachchh gujarat india biostratigraphy and paleobiogeography abstract this paper presents a study of the middle and upper jurassic ostracods from western kachchh india the first part discusses the biochronological importance of the ostracod assemblages while the second part reports the paleobiogeographical results benthic foraminiferal biozones are used to calibrate the biostratigraphical distribution of ostracod species and genera from sections in the aalenian tithonian interval located in western kachchh or kutch mundham anticline jumara dome jhurio dome and habo dome and on pachchham island khavda nala gujarat india a total of 71 species are listed including 32 previously published species and 38 species in open nomenclature belonging to 23 genera the ostracod assemblages indicate that faunal communication was first established during the bathonian and callovian middle jurassic and continued until the early cretaceous these faunal exchanges occurred between laurasia usa europe russia and siberia and the indo east african province extending along the western tethyan carbonate shelves bordering west and east gondwana through to the pacific ocean margin of west gondwana

coring disturbances in iodp piston cores with implications for offshore record of volcanic events and the missoula megafloods piston cores collected from iodp drilling platforms and its predecessors provide the best long term geological and climatic record of marine sediments worldwide coring disturbances affecting the original sediment texture have been recognized since the early days of coring and include deformation resulting from shear of sediment against the core barrel basal flow in due to partial stroke loss of stratigraphy fall in sediment loss through core catchers and structures formed during core recovery and on deck transport the most severe disturbances occur in non cohesive sandy facies which are particularly common in volcanogenic environments and submarine fans although all of these types of coring disturbances have been recognized previously our contribution is novel because it provides an easily accessible summary of methods for their identification this contribution gives two specific examples on the importance of these coring disturbances we show how suck in of sediments during coring artificially created very thick volcaniclastic sand layers in cores offshore montserrat and martinique lesser antilles we then analyze very thick structureless sand layers from the escanaba trough inferred to be a record of the missoula mega floods these sand layers tend to coincide with the base of core sections and their facies suggest coring disturbance by basal flow in destroying the original structure and texture of the beds we conclude by outlining and supporting iodp led initiatives to further reduce and identify coring disturbances and acknowledge their recent successes in drilling challenging sand rich settings such as during iodp expedition 340

paleoflow history determined from mudwave migration argentine basin abstract a mudwave site in the central argentine basin was investigated to determine its present and past mudwave activity site 7 on the south flank of the ewing drift in the northern argentine basin has mudwaves that have migrated primarily throurgh preferential deposition resulting in a relatively complete sediment on both wave flanks thus a history of mudwave migration can be determined for this site the mudwave studied shows migration from before 420 ka until 32 ka with paleocurrent speeds near 15 cm s 1 and with minor changes in current speeds around 110 120 ka the wave migration rate became less from 32 ka to 26 ka with paleospeeds of 9 cm s 1 wave migration ceased about 26 ka suggesting a cessation in flow this study indicates that bottom water velocities at this site were high during the last glacial period but dropped abruptly near the end of the last glacial period however bottom current velocities appear to have been moderately high during the previous interglacial period 120 ka suggesting that there is no simple relationship between flow speed and paleoclimate at this site

quaternary history of sea ice and paleoclimate in the amerasia basin arctic ocean as recorded in the cyclical strata of northwind ridge the 19 middle early pleistocene to holocene bipartite lithostratigraphic cycles observed in high resolution piston cores from northwind ridge in the amerasia basin of the arctic ocean provide a detailed record of alternating glacial and interglacial climatic and oceanographic conditions and of correlative changes in the character and thickness of the sea ice cover in the amerasia basin glacial conditions in each cycle are represented by gray pelagic muds that are suboxic laminated and essentially lacking in microfossils macrofossils trace fossils and generally in glacial erratics interglacial conditions are represented by ochre pelagic muds that are oxic and bioturbated and contain rare to abundant microfossils and abundant glacial erratics the synglacial laminated gray muds were deposited when the central amerasia basin was covered by a floating sheet of sea ice of sufficient thickness and continuity to reduce downwelling solar irradiance and oxygen to levels that precluded photosynthesis maintenance of a biota and strong oxidation of the pelagic sediment except during the early part of 3 of the 19 synglacial episodes when it was periodically breached by erratic bearing glacial icebergs the floating arctic ocean sea ice sheet was sufficiently thick to block the circulation of icebergs over northwind ridge and presumably other areas of the central arctic ocean interglacial conditions were initiated by abrupt thinning and breakup of the floating sea ice sheet at the close of glacial time which permitted surges of glacial erratic laden icebergs to reach northwind ridge and the central arctic ocean where they circulated freely and deposited numerous and relatively thick erratic clast rich beds breakup of the successive synglacial sea ice sheets initiated deposition of the interglacial ochre mud units under conditions that allowed sunlight and increased amounts of oxygen to enter the water column resulting in photosynthesis and biologic productivity and strong oxidization of the pelagic sediment the lithostratigraphy of northwind ridge suggests that during at least late pleistocene time glacial conditions in the arctic ocean were initiated abruptly and continued unabated until terminated also abruptly by onset of the succeeding interglacial warming variations in abundance of glacial erratics within the interglacial units of the late pleistocene indicate that during at least most interglacial episodes northern north america was glaciated but with generally diminishing severity until onset of the succeeding continental glaciation magnetostratigraphy suggests that the glacial interglacial cycles on northwind ridge had an average periodicity of approximately 93 5 k y during the brunhes normal and approximately 105 k y during the latter part of the matuyama reverse polarity zone these average periodicities are close to the 100 k y temperature cycles found in north atlantic deep water sediments of the brunhes normal polarity chron which have been ascribed to forcing by a milankovitch eccentricity cycle they are also close however to the average interval 101 k y between the aperiodic glacial terminations in the 500 k y pleistocene continental climate record from devil s hole nevada which have been ascribed to nonlinear feedbacks within the earth s atmosphere ice sheet ocean system

gt0 explosion sources for ims infrasound calibration charge design and yield estimation from near source observations three large scale on surface explosions were conducted by the geophysical institute of israel gii at the sayarim military range negev desert israel about 82 tons of strong high explosives in august 2009 and two explosions of about 10 and 100 tons of anfo explosives in january 2011 it was a collaborative effort between israel ctbto usa and several european countries with the main goal to provide fully controlled ground truth gt0 infrasound sources monitored by extensive observations for calibration of international monitoring system ims infrasound stations in europe middle east and asia in all shots the explosives were assembled like a pyramid hemisphere on dry desert alluvium with a complicated explosion design different from the ideal homogenous hemisphere used in similar experiments in the past strong boosters and an upward charge detonation scheme were applied to provide more energy radiated to the atmosphere under these conditions the evaluation of the actual explosion yield an important source parameter is crucial for the gt0 calibration experiment audio visual air shock and acoustic records were utilized for interpretation of observed unique blast effects and for determination of blast wave parameters suited for yield estimation and the associated relationships high pressure gauges were deployed at 100 600 m to record air blast properties evaluate the efficiency of the charge design and energy generation and provide a reliable estimation of the charge yield the yield estimators based on empirical scaled relations for well known basic air blast parameters the peak pressure impulse and positive phase duration as well as on the crater dimensions and seismic magnitudes were analyzed a novel empirical scaled relationship for the little known secondary shock delay was developed consistent for broad ranges of anfo charges and distances which facilitates using this stable and reliable air blast parameter as a new potential yield estimator the delay data of the 2009 shot with imi explosives characterized by much higher detonation velocity are clearly separated from anfo data thus indicating a dependence on explosive type this unique dual sayarim explosion experiment august 2009 january 2011 with the strongest gt0 sources since the establishment of the ims network clearly demonstrated the most favorable westward eastward infrasound propagation up to 3 400 6 250 km according to appropriate summer winter weather pattern and stratospheric wind directions respectively and thus verified empirically common models of infrasound propagation in the atmosphere

regional significance of pre wisconsinan till from nantucket island massachusetts abstract a major pre wisconsinan glacial event is the only possible source of the lower till on nantucket island massachusetts the till occurs near the late wisconsinan drift border and below fossiliferous marine beds of oxygen isotope stage 5 sangamonian age it is considered to be illinoian in age but the evidence is tenuous the till is correlated with the lower till of new england and its presence supports the view that the new england upper and lower tills represent two glaciations the pre wisconsinan lower till in new england may correlate with older tills elsewhere in the northeastern united states and in southeastern canada that are considered to be early wisconsinan or older in age

blast waves from violent explosive activity at yasur volcano vanuatu 1 infrasonic and seismic waveforms were collected during violent strombolian activity at yasur volcano vanuatu averaging 3000 seismic events showed stable waveforms evidencing a low frequency 0 1 0 3 hz signal preceding 5 6 s the explosion infrasonic waveforms were mostly asymmetric with a sharp compressive 5 106 pa onset followed by a small long lasting rarefaction phase regardless of the pressure amplitude the ratio between the positive and negative phases was constant these waveform characteristics closely resembled blast waves infrared imagery showed an apparent cold spherical front 20 m thick which moved between 342 and 405 m s before the explosive hot gas fragments cloud we interpret this cold front as that produced by the vapor condensation induced by the passage of the shock front we suggest that violent strombolian activity at yasur was driven by supersonic dynamics with gas expanding at 1 1 mach number inside the conduit

a conceptual model of the deglaciation of atlantic canada abstract we present a conceptual model for the deglaciation of atlantic canada in which a role is played by ice streams the ice margin lay close to the edge of the continental shelf at the last glacial maximum ice streams occupying shelf troughs comprised 1 a major ice stream in the laurentian channel 2 secondary streams in the bay of fundy gulf of maine trinity trough and notre dame channel and 3 lesser ice streams elsewhere early retreat in the northeast notre dame bay and in the southwest bay of fundy gulf of maine was mainly by calving along embayments by 18 ka radiocarbon years a calving embayment had opened on emerald basin scotian shelf retreat along channels marooned ice on intervening banks a major calving episode beginning just before 14 ka removed ice from the gulf of st lawrence triggering re advances down secondary troughs isolation of a newfoundland ice cap produced radial drainage via fiords and more extensive flow into the st george s bay lowlands on the west coast by 13 ka most ice was on land and was ablating by melting rather than calving shelf ice caps persisted until 11 ka

the orientation of buried iceberg scours and other linear phenomena abstract the average orientations of surficial iceberg scours can be obtained from sidescan sonograms using certain assumptions the average orientation of similar buried phenomena can be estimated from a pattern of intersecting seismic profiles two possible solutions are generated at each intersection of two seismic profiles each of which is oriented at an angle i from the profile which encounters the fewer scours where i tan 1 sin i r cos i and r is the ratio of the number of scours observed on the two seismic lines several pairs of solutions are required to determine which solution of each pair is significant iceberg scours observed on aerial photographs of the floor of glacial lake agassiz demonstrate that the estimates provided by this technique correspond with the average orientation of the population applying this method to buried iceberg scours in emerald basin scotian shelf gives orientations which are parallel to paleo bathymetric contours

lithostratigraphie et dynamique glaciaires au wisconsinien ile d anticosti golfe du saint laurent the laurentide ice sheet deposited three tills on anticosti island the oldest the riviere a la patate till was formed by southeastward flowing ice as determined from till fabrics the till has an estimated age of 85 000 years bp based on the aminoacid racemization of shell fragments in overlying marine sediments thus it is probably early wisconsinan in age the middle wisconsinan riviere jupiter till and the late wisconsinan ile d anticosti till are the result of the southwest flowing laurentide ice the ice flowed without restriction though without accomplishing deep erosion of the bedrock as indicated by glaciotectonic structures and till fabrics however striated blocks and pebbles in the tills reveal that basal shearing occurred the ice limit in the gulf of st lawrence from about 36 000 years bp onwards was located along the south coast of the island this was the result of active calving at the margin of the relatively slow moving ice sheet during retreat of the ice sheet an ice cap became

the quaternary stratigraphy of southwest sable island bank eastern canada three boreholes ten vibrocores and high resolution seismic reflection records were analyzed to reconstruct the stratigraphy of the topmost 50 m of the sedimentary column of southwest sable island bank the sequence is complex owing to the effects of two low stands of sea level two periods of ice influence and two periods of open water during the past 40 000 yr a low stand at 98 m occurred at 28 000 to 32 000 yr b p a second low stand occurred at 110 m between 13 000 and 15 000 yr b p ice covered the region prior to 32 000 yr b p and from 11 000 to 10 000 yr b p open water prevailed at other times the sequence of sediments follows the formational subdivision of king and the member subdivision of amos and knoll the sable island sand and gravel formation is subdivided into three members trough bedded sand cross bedded sand and conformably bedded sand the conformably bedded sand formed under heavy sea ice and represents the younger dryas event the uppermost two members result from shelf sediment reworking the emerald silt formation is subdivided into four members channel gravel upper stratified sand fines barren gravelly sand and lower stratified sand fines and two regional discontinuities r1 and r2 the coarser grained facies of the channel gravel and barren gravelly sand members are the result of reworking during late and mid wisconsinan transgressions of sable island bank the upper stratified sand fines member is interpreted as an open water marine deposit formed during the scotian stade the lower stratified sand fines member is interpreted as a glacio marine deposit formed during the digby stade

problems with piston core sampling mechanical and geochemical diagnosis abstract a series of sampling experiments using a piston corer equipped with data logging instruments has demonstrated that representative stratigraphic intervals of soft marine sediments may never be obtained with piston corers that use a non reference triggering system incidents of sediment by passing and flow in can occur throughout a single core resulting in both foreshortening and stretching of sedimentary units these problems are difficult to recognize by standard visual core logging techniques most of these problems are initiated by accelerations in the lowering cable that occur after tripping with resultant accelerations in the piston and fluctuations in the cavity pressure inside the core liner the non representative sampling can result in more than 1 0 m of missing stratigraphic units below the sediment interface and as much as 1 3 m of sediment flow in these problems can lead to miscalculations of sediment deposition rates by as much as a factor of two and can result in obtaining samples that are of no value for geotechnical analyses

the maastrichtian danian maimara tracksite yacoraite formation salta group quebrada de humahuaca argentina environments and ichnofacies implications fil console gonella carlos alfredo consejo nacional de investigaciones cientificas y tecnicas centro cientifico tecnologico conicet tucuman instituto superior de correlacion geologica universidad nacional de tucuman facultad de ciencias naturales e instituto miguel lillo departamento de geologia catedra geologia estructural instituto superior de correlacion geologica argentina

petrographic evidence from the eastern canadian margin of shelf crossing glaciations abstract it is difficult to evaluate when and where glaciers extended across the outer continental shelf off eastern canada the outer shelf and upper slope are commonly hard bottomed or have a great thickness of post glacial sediment in either case making direct sampling and dating of ice margin sediment impossible the timing and extent of glacier ice is important for understanding continental slope sedimentation and ice sheet dynamics we have therefore determined the lithologic components of the 1 4 mm granule fraction of over 100 well dated samples from 40 cores from the more distal parts of the deep water margin off nova scotia and newfoundland this fraction is demonstrably ice rafted in these cores and geographic variation in component results from input of icebergs at different calving margins the samples show that heinrich layers have a distinctive granule fraction that shows some areal variation as a result of dilution by sources other than hudson strait heinrich event 2 ca 21 ka is widespread as far southwest as the west scotian slope but by the last glacial maximum lgm numerous discrete sources of ice rafted granules are recognised implying that calving ice margins were present in several places off newfoundland and nova scotia including off banquereau a distinctive purplish lgm gravelly mud is recognised on the eastern newfoundland margin derived from a calving margin on the ne newfoundland shelf at the time of heinrich event 1 ca 14 ka there was a calving ice outlet somewhere on the grand banks and another in halibut channel retreat of ice from the gulf of st lawrence can be tracked by changing granule petrology from the lgm to 13 ka these data suggest that final ice retreat from many parts of the outer shelf was later than is shown in many recent ice margin reconstructions