identification et distribution des grandes masses d eau dans les mers du labrador et d irminger the main deep water masses present at the time of the css hudson cruises in labrador and irminger seas in june 1990 and october november 1991 have been identified using characteristic temperatures t and salinities s the purpose of this study was to establish the transfer functions between micropaleontological assemblages of top sediments and thermohaline characteristics of water masses the water mass at the top of the labrador sea labrador sea water lsw is formed after intense movements of winter convection in the first 900 m depth of the water column below that depth the lsw parameters reach a double minimum s 34 80 and t 2 9 c only the sediments located on the continental slopes of greenland and labrador between depths of 500 and 1500 m are in contact with the lsw below the lsw the superior fraction of the north east atlantic deep water neadw1 is characterized by a temperature maximum 3 3 c and as such is distinguishable from the inferior fraction neadw2 the latter is ch

large bedform generated by the 2011 tohoku oki tsunami at kesennuma bay japan abstract the 11 march 2011 m w 9 0 tohoku megathrust earthquake off the pacific coast of japan was a salient event in the history of japan the resultant huge tsunami the 2011 tohoku oki tsunami inundated a vast coastal area of northeastern japan causing widespread devastation twenty days after the tsunami we analyzed the impact of the tsunami on the sea bottom of the kesennuma inner bay using side scan sonar to explore the damage and bathymetric change in the harbor herein we present the first direct evidence that the sea bottom sediments of around 10 15 m were largely reworked by the tsunami to thickness of a few meters and that large dunes were formed by the tsunami considering that the sea wave influence is as weak as it is inside the inner bay the potential exists that even meter thick paleo tsunami deposits are preserved in shallow sea bottoms with large bedforms this finding will be a stepping stone to future geological studies of tsunami effects in shallow sea regions

identification of tsunami deposits considering the tsunami waveform an example of subaqueous tsunami deposits in holocene shallow bay on southern boso peninsula central japan abstract this study proposes a tsunami depositional model based on observations of emerged holocene tsunami deposits in outcrops located in eastern japan the model is also applicable to the identification of other deposits such as those laid down by storms the tsunami deposits described were formed in a small bay of 10 20 m water depth and are mainly composed of sand and gravel they show various sedimentary structures including hummocky cross stratification hcs and inverse and normal grading although individually the sedimentary structures are similar to those commonly found in storm deposits the combination of vertical stacking in the tsunami deposits makes a unique pattern this vertical stacking of internal structures is due to the waveform of the source tsunamis reflecting 1 extremely long wavelengths and wave period and 2 temporal changes of wave sizes from the beginning to end of the tsunamis the tsunami deposits display many sub layers with scoured and graded structures each sub layer especially in sandy facies is characterized by hcs and inverse and normal grading that are the result of deposition from prolonged high energy sediment flows the vertical stack of sub layers shows incremental deposition from the repeated sediment flows mud drapes cover the sub layers and indicate the existence of flow velocity stagnant stages between each sediment flow current reversals within the sub layers indicate the repeated occurrence of the up and return flows the tsunami deposits are vertically divided into four depositional units tna to tnd in ascending order reflecting the temporal change of wave sizes in the tsunami wave trains unit tna is relatively fine grained and indicative of small tsunami waves during the early stage of the tsunami unit tnb is a protruding coarse grained and thickest stratified division and is the result of a relatively large wave group during the middle stage of the tsunami unit tnc is a fine alternation of thin sand sheets and mud drapes deposited from waning waves during the later stage of the tsunami unit tnd is deposited during the final stage of the tsunami and is composed mainly of suspension fallout cyclic build up of these sub layers and depositional units cannot be explained by storm waves with short wave periods of several to ten seconds common in small bays

paleointensity assisted chronostratigraphy of detrital layers on the eirik drift north atlantic since marine isotope stage 11 1 four piston cores collected in 1999 and 2002 from the eirik drift southern labrador sea off se greenland provide paleomagnetic environmental magnetic and oxygen isotope records back to marine isotope stage 11 age models for the cores are based on a combination of planktonic oxygen isotope data relative geomagnetic paleointensity proxies and the identification of geomagnetic excursions laschamp and iceland basin environmental magnetic data delineate two distinct detrital signals interpreted to reflect the behavior of the surrounding ice sheets greenland and laurentide to orbital and millennial scale climate forcing broad decimeter scale intervals of increased magnetic concentration and grain size occur during the early part of interglacial marine isotopic stages mis 1 5 7 9 and 11 discrete centimeter scale layers recognized by magnetic concentration and grain size sensitive parameters gamma ray attenuation gra bulk density and carbonate content are observed in glacial and interglacial stages as well as during terminations on the basis of glacial reconstructions on greenland during the last termination the broad decimeter scale coarser grained intervals can be attributed to detrital influx associated with the retreat of the terrestrial based greenland ice sheet in the early holocene a similar magnetic signal observed within interglacial mis 5 7 9 and 11 indicates similar greenland ice sheet behavior during these time intervals two types of centimeter scale detrital layers are also recognized back to mis 11 detrital carbonate dc layers reflect predominately ice rafted debris ird deposition while the low detrital carbonate ldc layers reflect mass movement as evidenced by sharp basal contacts graded bedding and traction structures likely from the greenland slope some detrital layers on eirik drift particularly the dc layers can be tentatively correlated to detrital layers observed in the central north atlantic and to those documented on the southern side of the labrador sea at orphan knoll

a comparison of the nw european glaciated margin with other glaciated margins the present paper provides an overview of glacial related seabed features and sedimentary sequences found along the formerly glaciated nw european margin and compare it with those found on contemporary glaciated margins from both the southern and northern hemispheres a brief review of the seabed physiography and strata architecture of the margins under consideration is followed by comparison of the most relevant similarities and differences comparison of the present day bathymetric setting of both former and contemporary glaciated margins reveals no clear link to the effect of neither ice sheet or sediment load three different types of glacially eroded shelf transverse troughs have been identified while marginal troughs seem connected to similar geological settings everywhere beyond the shelf edge interaction between downslope and alongslope processes has occurred resulting amongst others in the formation of large sedimentary mounds on the rise more frequent large scale mass wasting occurs on the former glaciated nw european margin than the greenland and antarctic margins in the latest neogene to recent times a two stage evolution of the shelf prograding wedges is observed on all margins under consideration which may reflect a general development of an ice cover from an initial phase of non to restricted glaciation evolving to a mature stage of expansive glaciation

bed forms in bimodal sand gravel sediments laboratory and field analysis bed forms were studied in goodwin creek and a laboratory flume channel the bed sediment of the field site and flume had median diameters of 8ae3 modes of 0ae4 22ae6 mm and 1ae82 mm modes of 0ae5 5ae6 mm respectively the laboratory andfieldchannelshadsimilarvaluesofbimodalparameters ratiosofflowdepth to median bed material diameter and ratios of shear stress to critical shear stress and were judged to be comparable in the transport of bed load sediment and the resulting bed forms three groupings of bed forms from the laboratory flume experiments ripple like bed forms bed load sheets low relief bed waves were identified using the height and period of the bed forms for the range of flow depths and discharges investigated in the flume bed forms became higher and longer with increasing bed shear stress bed forms from goodwin creek were similar to those from theflume with comparable ratios between bed form length height and flow depth the bed forms in the flume provide a positive link between rate and size fluctuations measured in the field and the bed forms the smaller bed forms identified were sediment starved and are not considered to be dunes while the largest bed forms in which all of the bed material sizes were mobilized in the field and laboratory were judged to be dunes

early diagenetic processes in deep labrador sea sediments reactive and nonreactive iron and phosphorus a sequential extraction procedure was applied to separate the oxides and lithogenous phases of iron and manganese and the organic and inorganic phosphorus phases in four box cores and one piston core from the slopes and rises of the labrador sea sedimentation rate rather than the location in the basin appears as a master variable of the diagenetic transformations of fe mn and p high sedimentation rate characteristic of two of the box cores led to the creation of zones near the redox boundary of partial reprecipitation of dissolved fe mn and p released in the deeper reducing portions of the sediments in contrast surficial sediments from box cores with 10 times lower sedimentation rate only have sufficient reductive capacity to remobilize mn hydroxides while leaving the fe oxyhydroxides intact under these conditions there is evidence for a redistribution of reactive inorganic p leading to the crystallization of carbonate fluorapatite in the top 30 cm of the cores gradual transformation of bur

clay mineral signature of the nw atlantic boundary undercurrent abstract surface sediments were sampled along 2 transects across the iceland and irminger basins and in the labrador sea clay mineral assemblages deduced from x ray analyses of the carbonate free

isotope stratigraphy sedimentation rates deep circulation and carbonate events in the labrador sea during the last 200 ka high resolution stable isotope and accelerator mass spectrometry 14c measurements in 25 box and piston cores from the labrador sea allow the reconstruction of major paleoceanographical changes during the last 200 ka in this basin and also document the links between the interior of the laurentide ice sheet and the north atlantic ocean during this interval two deep circulation regimes are indicated by contrasting sedimentation rates on the slopes i the modern situation is characterized by a gyre of the north atlantic deep water nadw components into the basin which is responsible for the high energy western boundary undercurrent this regime also prevailed during the former true interglacials and possibly during shorter warm intervals e g bolling allerod ii a more frequent nadw free situation during glacial and interstadial intervals is marked by the presence of a vertically homogeneous water mass in the basin sedimentological records also indicate that carbonate events i e pulses of

impact of melting of the laurentide ice sheet on sediments from the upper continental slope off southeastern canada evidence from sm nd isotopesthis article is one of a series of papers published in this special issue on the theme polar climate stability network we present new sm nd isotope data for sediments from a core located on the continental slope of the st pierre bank of canada s east coast the nd analyses indicate that the sediments were derived from two principal sources the north american shield that yields an average early proterozoic isotopic signature and a younger proterozoic signature attributed to appalachian crustal sources the appalachian sourced sediments predominated during the last glacial maximum lgm and were associated with low sedimentation rates 30 cm ka with the exception of a strong north american shield signature present in a detrital carbonate layer that corresponds to heinrich layer 1 h1 the dominance of the appalachian signature decreased subsequent to h1 the appalachian signatures closely follow the distribution of sediments interpreted as locally derived glacial tills while the north american shield signatures follow the distribution of hemipelagic mud that was likely deposited by the labrador current the nd data a

changes in the western boundary undercurrent outflow since the last glacial maximum from smectite illite ratios in deep labrador sea sediments high resolution mineralogical studies were performed on late glacial and deglacial sediments from two deep piston cores from the labrador sea located at the inlet sw greenland rise and outlet labrador rise of the western boundary undercurrent wbuc gyre at the two sites smectites transported from the eastern iceland and irminger basins by the wbuc are observed clay mineral changes are used as proxies for the paleointensity reconstruction of the wbuc on the greenland rise a clay mineral index smectite illite s i ratio is defined a s i ratio of 1 characterized the last glacial maximum it increased after 17 ka and reached a maximum value of 4 during the early holocene the mineralogical changes are gradual and do not show any reversal during the younger dryas this pattern which is confirmed by first order estimations of smectite and illite fluxes suggests gradually increasing sedimentary fluxes and wbuc intensity since the last glacial maximum a peak in the velocity of the wbuc at 9 ka as recorded by clay assemblages is consistent with other regional studies based on pollen foraminifera or grain size measurements a massive dilution of smectites by illite and chlorite s i 3 occurs at 8 5 ka it corresponds to a period of rapid sediment accumulation and reflects an intensified illite rich detrital supply by meltwaters from the southern greenland ice margin on the labrador rise the smectite content varies between 20 and 60 with no obvious trend through time the mineralogical composition is strongly influenced by ice rafted deposition and by the abundance of fast deposit units cf heinrich layers in the north atlantic which contain abundant detrital carbonates spilled over from the north west atlantic mid ocean channel in such layers smectites are present but are diluted by the addition of illites chlorites and kaolinites this provides evidence for a discrete and continuous wbuc supply of fine particles from the irminger and iceland basins as far as the southeastern part of the labrador basin early deglacial smectite rich layers up to 60 are also observed at this site they indicate an increase in the outflow of the wbuc at 13 5 ka bolling allerod as previously reported from grain size or foraminiferal assemblage studies

relationship between the maximum extent of tsunami sand and the inundation limit of the 2011 tohoku oki tsunami on the sendai plain japan abstract this paper focuses on the relationship between the maximum extent of sandy tsunami deposits and inundation distance of the 2011 tohoku oki tsunami inundation limits of the tohoku oki tsunami were assessed over seven shore normal transects along the sendai coastal plain inundation distances were found to range from 0 6 to 4 0 km at the maximum extent of the tsunami deposit the sand unit ranged in thicknesses from 0 1 to 4 0 cm the maximum limit of the 0 5 cm thick sand layer extended to over 90 of the inundation distance where the inundation distance was less than 2 5 km this observation is consistent with previous studies that examined characteristics of recent tsunami events that had inundation distances of at least 2 km the maximum limit of the 0 5 cm thick sand layer extended to 3 km 57 76 of the inundation distance where the inundation distance was more than 2 5 km our results are important for estimating paleo tsunami inundation distances based on the landward extent of sand deposits and valuable for the assessment of future tsunami risks in other coastal areas in the world which have been devastated by huge tsunamis in the past

horizontal and vertical variation of 2004 indian tsunami deposits an example of two transects along the western coast of thailand abstract we investigated horizontal and vertical variations in modern tsunami deposits along two transects at nam khem and khao lak western coast of thailand deposited by the large tsunami associated with the earthquake magnitude 9 0 of 26 december 2004 off sumatra indonesia tsunami waves 6 10 m high struck the area approximately 2 h after the earthquake tsunami deposits cover the low lying coastal plains and extend more than 1 km inland from the shoreline no landward decrease in sediment thicknesses was found clearly at either transect terrace scarps and a steep slope behind the coastal plain probably stopped tsunami deposition further inland causing substantial sediments to be deposited in front of these features very clear vertical variations in grain size and multiple layers are found in the deposits to about 600 m inland at nam khem fine grained sediments overlie the coarse grained sediments of the basal layer of the tsunami deposits at some sites the fine grained sediments are overlain by another layer of coarse grained sediments suggesting deposits laid down in succession by multiple waves the basal coarse grained sediments at nam khem fine landward the up flow waned inland based on the assumption that the grain size of the basal deposits relates to the strength of the up flow these results are potentially useful in disaster prevention and coastal environmental change management as well as for interpreting paleotsunami deposits in geological records

x ray tomography of tsunami deposits towards a new depositional model of tsunami deposits x ray computed microtomography is used to obtain high resolution imagery of a historical tsunami deposit in andalusia spain 1755 lisbon tsunami the technique allows characterization of grain size distribution structures component analysis and sedimentary fabric of fine grained unconsolidated tsunami deposits at resolutions down to particle scale the results are validated by comparing to data obtained using other techniques such as laser diffraction anisotropy of magnetic susceptibility and x ray microfluorescence on the same deposits specific technical details such as sampling scanning and image processing methods and further improvements are addressed the use of x ray computed microtomography provides new insights into the stratigraphy of the deposits and gives access to significantly more detailed view of key sedimentary features such as mudlines rip up clasts crude laminations convolutions floating outsized clasts and contacts between successive units this analysis of the 1755 tsunami deposits using x ray computed microtomography allows the proposal of new hypotheses for the sedimentary processes forming tsunami deposits deposition by settling is limited and the section analysed here is dominated by a high shear stress leading to the development of traction carpets with laminated mudlines corresponding to the basal frictional region of these carpets the onset of the tsunami backwash is marked by a micro vortex resembling kelvin helmoltz instabilities

smectite composition as a tracer of deep circulation the case of the northern north atlantic abstract the link between smectite composition in sediments from the northern north atlantic and labrador sea and deep circulation is being further investigated through detailed studies of the x ray pattern of smectites and cation saturations this allows clear distinction of dominant terrigenous sources associated to the main components of the modern western boundary undercurrent time variations of smectite characteristics in two piston cores from the inlet and outlet of the western boundary undercurrent gyre in the labrador sea indicate 1 a more southern circulation of north east atlantic deep water during the late glacial 2 a step by step transition to the modern pattern of deep circulation during the late glacial holocene transition with intensification of north east atlantic deep water and davis strait overflow 3 an expansion of davis strait overflow and labrador sea water circulation in relation to ice surges and deposition of detrital layers 4 an intensified circulation of north east atlantic deep water during the younger dryas and 5 a very recent increased influence of denmark strait overflow water beginning between 4 4 and

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

sea ice cover sea surface salinity and halo thermocline structure of the northwest north atlantic modern versus full glacial conditions abstract seasonal sea ice develops along the eastern continental margins in the northern north atlantic where freshwater and or meltwater outflow are responsible for relatively low salinity in surface waters and very pronounced water mass stratification sea ice constitutes a major parameter in the marine ecosystem since the duration and extent of its seasonal spreading constrain the plankton distribution and the related microfossil assemblages on the sea floor organic walled dinoflagellate cysts that are highly resistant to dissolution were recovered from surface sediments of the northern north atlantic and used to develop transfer functions best analogue method for the reconstruction of the seasonal spreading and duration of sea ice cover in addition to salinity and temperature of the warmest month of the year application of the best analogue approach to cores from the labrador sea reveals large variations in sea ice cover and sea surface conditions throughout the last glacial stage and during the early holocene isotopic analyses in epipelagic and mesopelagic planktonic foraminifers also suggest important changes in salinity and temperature gradients between the surface and sub surface water masses specific study of the last glacial maximum lgm time slice 16 20 ka on a 14 c time scale in the northwestern north atlantic shows much more extensive sea ice than at present with perennial sea ice lying along the continental margins of eastern canada seasonal spreading of the cover of sea ice offshore was accompanied by large seasonal contrasts in temperature with very cold winters but relatively warm summers a pattern linked to strong stratification between a buoyant low saline surface layer having a low thermal inertia and the underlying intermediate oceanic waters

using magnetic fabric to reconstruct the dynamics of tsunami deposition on the sendai plain japan the 2011 tohoku oki tsunami abstract the magnetic fabric and grain size of sand deposits emplaced during the 2011 tohoku oki tsunami were studied in five trenches along a 1800 m long shore normal transect on the sendai plain as well as in a near shore sedimentary infill of a scour depression the magnetic susceptibility in all deposits is due to ferromagnetic minerals mainly magnetite making the anisotropy of magnetic susceptibility magnetic fabric suitable for fabric analyses the dominant magnetic fabric is planar in all trenches and stronger in finer grained inland deposits than in the coarser sediments this planar fabric is related to tractive shearing of the bedload basal portion of the tsunami flow that led to the deposition of traction carpet layers among the various fabric parameters used for this study the vertical evolution of the shape factor q of the magnetic ellipsoid in each trench follows the evolution of the magnetic lineation l and foliation f these parameters provide information on the hydrodynamic energy flow speed fluctuations during the emplacement of the tsunami deposit for the most proximal deposits characterized by well sorted reworked beach sand with minor fluctuations in grain size distribution the magnetic fabric is sensitive to hydrodynamic energy variations during sedimentation reconstruction of tsunami flow orientation in the sediments based on the orientation of the mean k max calculated for each trench appears to be unambiguous only for the sandy infills of small topographic depressions the variations in flow direction indicators elsewhere could be related to local variation of the flow and to micro topographic effects these findings are encouraging for the use of the magnetic fabric proxy in the study of paleotsunami deposits

glacial interglacial instabilities of the western boundary under current during the last 365 kyr from sm nd ratios of the sedimentary clay size fractions at odp site 646 labrador sea we present 40 sm nd isotope measurements of the clay size 2 m fractions of sediments from the sout hern greenland rise odp 646 that span the last 365 kyr these data track changes in the relative supply o f fine particles carried into the deep labrador sea by the western boundary under current wbuc back to the fourth glacial interglacial cycles earlier studies reveal ed three general sources of particles to the core s ite i precambrian crustal material from canada greenland and or scandinavia north american shield nas ii palaeozoic or younger crustal material from east gr eenland nw europe and or western scandinavia young crust yc and iii volcanic material from iceland and the mid atlantic ridge mar clay size fractions from glacial sediments have the lowest nd isotopic ratios supplies of young crustal particles were si milar during glacial oxygen isotope stages ois 2 6 and 10 i n contrast the mean volcanic contributions decrease d relative to old craton material from ois 10 to ois 6 and the n from ois 6 to ois 2 the glacial ois 8 interval d isplays a mean sm nd ratio similar to those of interglacials ois 1 5 and 9 compared with other interglacials ois 7 was marked by a higher yc contribution but a similar 3 0 mar supply the overall nas contribution dropped by a factor of 2 during each glacial interglacial tran sition with the mar contribution broadly replacing it during interglacials to decipher between higher supplies and or dilution particle fluxes from each end memb er were estimated glacial nas fluxes were systematically h igher than interglacial fluxes during the time int erval examined fine particle supplies to the labrador se a were strongly controlled by proximal ice margin e rosion and thus echoed the glacial stage intensity in con trast the wbuc carried mar supplies from the eastern basins did not change significantly throughout the last 36 5 kyr except for a marked increase in surface sedi ments that suggests unique modern conditions distal wbuc controlled inputs from the northern and ne north atlant ic seem to have been less variable than proximal suppl ies linked with glacial erosion rate

characteristics of pleistocene climate cycles identified in cerna valley loess paleosol section vertesacsa hungary abstract a climate cycle model was calculated using different methods e g paleomagnetic sedimentological and heavy mineral studies on the loess sequence containing four paleosol and five loess layers in cerna valley the model is based on the development of the sediment sequence created by the influence of the climatic geological and geomorphological phenomena and contains the following cycles the homogeneous non laminated loess was developed during the semiarid 350 400 mm y and cold periods in the pleistocene the magnetic fabric was built up by multidomain ferromagnetic minerals and reflects the direction of dust deposition or and the paleoslope the accumulation period of dust was followed by a more humid 650 mm y pedogenic period indicated by the enrichment of superparamagnetic minerals and by the disturbed or inverse magnetic fabric developed during pedogenesis by different processes e g leaching bioturbation the third period following the pedogenic period is a humid erosional phase indicated by the fine layered reworked loess the magnetic fabric built up by multidomain ferro and superparamagnetic minerals was characterized by better aligned directions of principal susceptibilities than in the wind blown material sheet wash and other water logged surface processes appeared in the fabric of these layers this process is possibly connected to non periodic sudden events with high precipitation and absence of the vegetation the next cycle started with the following dust accumulation period

curie temperatures of synthetic titanomagnetites in the fe ti o system effects of composition crystal chemistry and thermomagnetic methods 1 the present study is aimed at improving the calibration of the compositional dependence of the curie temperature tc of titanomagnetite tmt on the basis of temperature dependent magnetic susceptibility c t curves measured on synthetic tmts in the fe ti o system in order to assess the possible influence of high temperature cation vacancies onto the tc values we have synthesized two types of assemblages in subsolidus conditions at 1 bar 1100c and 1300c under controlled oxygen fugacity conditions tmts synthesized in equilibrium with ilmenite hematitess ilmss are expected to have the highest vacancy concentrations those in equilibrium with wustite wus the lowest the composition and homogeneity of the synthetic tmts were carefully checked with a scanning electron microscope sem and an electron microprobe emp tc was determined from c t curves using a kappabridge and for comparison from ms t curves measured with a variable field translation balance our data set shows systematically higher tc values for tmt coexisting with ilmss than for tmt coexisting with wus most c t curves are nonreversible whereby the largest dtc 40 k concern tmt ilmss o f intermediate compositions synthesized at 1300c nonreversibility is interpreted as reflecting cation reordering in tmt during the high temperature c t measurements tc values obtained from ms t curves are higher than those obtained from the c t curves whereby the difference regularly increases up to 40 k with increasing ti content up to xusp 0 6 our new calibration curves are suitable to retrieve tmt compositions in basalts that were rapidly cooled and not oxidized by deuteric or hydrothermal fluids citation lattard d r engelmann a kontny and u sauerzapf 2006 curie temperatures of synthetic titanomagnetites in the fe ti o system effects of composition crystal chemistry and thermomagnetic methods j geophys res 111 b12s28

interpreting flash flood palaeoflow parameters from antidunes and gravel lenses an example from montserrat west indies the wavelength of stationary water surface waves and their associated antidune bedforms are related to the mean velocity and depth of formative flow in sand bed flume experiments alexander et al 2001 found that lens structures were preserved during antidune growth and change and the dimension of the lenses were empirically related to antidune wavelength and thus could be used to estimate flow velocity and depth this study is the first to compare observations of formative flow conditions and resulting sedimentary structures in a natural setting testing the alexander et al 2001 relationship at a field scale trains of stationary and upstream migrating water surface waves were prevalent during the flash flood in october 2012 in the belham valley montserrat west indies wave positions and wavelengths were assessed at 900 s intervals through the daylight hours of the event within a monitored reach the wave data indicate flow depths up to 1 3 m and velocity up to 3 6 m s 1 sedimentary structures formed by antidune growth and change were preserved in the event deposit these structures include lenses of clast supported gravel and massive sand with varying internal architecture the lenses and associated low angle strata are comparable to sand bed structures formed from stationary and upstream migrating waves in flume experiments confirming the diagnostic value of these structures using mean lens length in the event deposit underestimated peak flow conditions during the flood and implied that the lenses were preserved during waning flow

magnetic fabric evidence for rapid characteristic changes in the dynamics of the 2011 tohoku oki tsunami abstract low field anisotropy of magnetic susceptibility ams and rock magnetic measurements were applied to sediments deposited by the 2011 tohoku oki tsunami to reveal the dynamic of the tsunami run up and the character of the sedimentation along the misawa coast aomori prefecture northern japan in the tsunami deposits studied elongated coarse grained multi domain titanomagnetite and magnetite minerals were the carriers of the ams signal two main types of sedimentary environment are described a higher energy tangential stress dominated environment with imbrication and traction rolling transportation and a calmer post peak wave environment ruled by gravitational stress rapid characteristic changes in the tsunami dynamics are also described the tsunami began with erosion of the pre tsunami surface caused by rapidly increasing energy bedload features such as ripple stratification were developed by the repeated accelerations and decelerations of the tsunami wave during run up the arrival of the peak wave was indicated by high density flow slurry like sediments following the peak wave the decreasing energy was marked by a change in magnetic fabric mf the study showed that quite similar tendencies in the character of tsunami dynamics can be identified in tsunami deposits despite their materials being deposited in currents with quite different energy levels

inflow and outflow facies from the 1993 tsunami in southwest hokkaido abstract we describe in detail the sedimentary facies provenance and grain size distributions of the 1993 tsunami deposits in the lower reaches of usubetsu river only two lithofacies were recognized a gravel lobe facies glf and a sand sheet facies ssf the gravel lobe facies was deposited rapidly by a hydraulic jump in contrast the sand sheet facies which contains both current ripples and dunes was deposited by a traction current under subcritical flow conditions we identified four stratigraphic units unit 1 unit 2 unit 3 and unit 4 in ascending order we interpreted units 1 and 2 as having been deposited by the inflow and outflow events of the first run up and units 3 and 4 by the inflow and outflow events of the second run up respectively units 3 and 4 were more widely distributed and coarser grained than units 1 and 2 because the second run up was larger than the first run up furthermore unit 4 was more widely distributed than unit 3 because the outflow eroded the inflow deposits grain size distributions of the inflow and outflow deposits were clearly different unit 4 deposits had a peak at 2 5 phi p 1 population in contrast unit 3 deposits had a bimodal distribution with peaks at 0 5 1 5 phi p 2 population and at 2 5 phi p 1 population a comparison of the tsunami deposits with other sedimentary deposits near the study area showed that the tsunami deposits were mainly derived from the seabed at depths below 5 5 m in the offshore area where the marine sands are about 2 2 5 phi in size and thus are the source of the p 1 population the p 2 population is derived from coarse 0 5 2 phi fluvial materials eroded during the tsunami run up according to our calculations benthic foraminiferal tests were entrained from the comparatively deep seabed at depths up to 100 m during the tsunami run up and included in the tsunami deposits

deep circulation changes in the labrador sea since the last glacial maximum new constraints from sm nd data on sediments sm nd concentrations and nd isotopes were investigated in the fine fraction of two labrador sea cores to reconstruct the deep circulation patterns through changes in sedimentary supply since the last glacial stage three sources are involved the north american shield palaeozoic rocks from northeastern greenland and mid atlantic volcanism the variable input of these sources provides constraints on the relative sedimentary supply in conjunction with inception of deep currents during the last glacial stage a persistent but sluggish current occurred inside the labrador basin an increasing discharge of volcanic material driven by the north east atlantic deep water is documented since 14 3 kyr signaling the setup of a modern like deep circulation pattern throughout the labrador irminger and iceland basins during the last deglacial stage the isotopic record was punctually influenced by erosion processes related mainly to ice sheet instabilities especially 11 4 10 2 and 9 2 kyr ago

local variation of inundation sedimentary characteristics and mineral assemblages of the 2011 tohoku oki tsunami on the misawa coast aomori japan abstract the 2011 tohoku oki tsunami caused severe damage to the coastal regions of eastern japan and left a sediment veneer over affected areas we discuss differences in depositional characteristics of the 2011 tohoku oki tsunami from the viewpoint of the sediment source coastal topography and flow height the study area on the misawa coast northern tohoku includes a 20 km long coastline with sandy beaches coastal dunes and a gently sloping lowland this landscape assemblage provides an opportunity to examine the effects of topography on the characteristics of the tsunami deposit during field surveys conducted from april 10 to may 2 2011 we described the thickness facies and structure of the tsunami deposit we also collected sand samples at approximately 20 m intervals along 13 shore perpendicular transects extending up to 550 m inland for grain size and mineral assemblage analysis the tsunami flow height was estimated by measuring the elevation of debris found in trees broken tree limbs or water marks on buildings the nature of the coastal lowland affected the flow height and inundation distance in the southern part of the study area where there is a narrow 100 m wide low lying coastal strip the run up height reached 10 m on the landward terrace slopes to the north the maximum inundation reached 550 m with a run up height of 3 2 m on the wider low lying coastal topography the average flow height was 4 5 m the tsunami eroded coastal dunes and formed small scarps along the coast immediately landward of the coastal dunes the tsunami deposit was more than 20 cm thick but thinned markedly inland from this point close to the dunes the deposit was composed largely of medium sand 1 2 with planar and parallel bedding but with no apparent upward fining or coarsening the grain size was similar to that of the coastal dune and we infer that the dunes were the local source material for the tsunami deposit at this point the mineral assemblage of the tsunami deposit was dominated by orthopyroxene and clinopyroxene and was also similar to the dune and beach sand at sites more than half the inundation distance inland the thinner tsunami deposit consisted mainly of fine sand 2 375 with some upward fining the difference in grain size and sedimentary characteristics was probably caused by differences in sediment transportation and depositional processes we infer that the well sorted finer sediments were deposited out of suspension whereas the relatively coarse sands were laid down from traction flows the depositional characteristics of the 2011 tohoku oki tsunami deposit appeared to have been affected mainly by the coastal topography and the extent of erosion at any one point as opposed to flow height

diatom assemblages within tsunami deposit from the 2011 tohoku oki earthquake along the misawa coast aomori prefecture northern japan abstract this paper reports variations in the diatom assemblages within the deposit from the 2011 tohoku oki tsunami along the misawa coast aomori prefecture northern japan the landward extent of the tsunami deposit was as much as 400 m inland the deposit contained mixed assemblages of marine brackish and freshwater diatoms the mixed assemblages indicated that the tsunami deposit was composed of not only beach and dune sand but also soil from the coastal forest marine brackish species were predominant in the seaward tsunami deposit however the relative abundance of marine brackish species rapidly decreased in the samples about 150 to 250 m inland from the shoreline a decrease in marine brackish diatoms at inland locations suggests that the eroded terrestrial soil was incorporated into the tsunami deposit the composition of marine brackish species in the tsunami deposit was different from that of modern inter to supra tidal sediments one possible interpretation for this discrepancy is that the 2011 tsunami deposit were sourced from multiple environments including supra inter and sub tidal locations

sources of labrador sea sediments since the last glacial maximum inferred from nd pb isotopes pb isotopes have been measured in the clay size fraction of late glacial and holocene deep sea sediments recovered from two labrador sea piston cores that have been previously analyzed for nd isotopes the newly acquired pb isotopic data allow us to better constrain the different source areas that supplied clay size material during the last deglaciation until 8 6 kyr calendar ages nd pb data can be modeled mainly as a mixture between a precambrian crust and lower paleozoic material originating from the denudation of the pan african orogen the old material originates mainly from the archean lower proterozoic or both terranes of greenland and also probably corresponding terranes of labrador although minor input of other precambrian material is recorded in some detrital carbonate rich deglacial samples from orphan knoll the phanerozoic crustal end member consists of sediment material mainly originating from northwestern europe this source area is found to be the only significant source of young crustal material in early holocene sediments from the greenland rise no significant input from the mid atlantic volcanism is apparent this study puts further constraints on the deep circulation pattern during the last deglaciation it is concluded that at that time european phanerozoic material was carried from the norwegian sea through the wyville thompson ridge into the iceland basin by the north east atlantic deep water no evidence for an overflow is found either south of the iceland iceland scotland ridge or through the denmark strait

examination of relation with tsunami behavior reconstructed from on site sequence photographs topography and sedimentary deposits from the 2011 tohoku oki tsunami on the kamikita plain japan abstract this report presents an examination of tsunami behavior for the misawa coast of northeastern japan based on interpretations of sequential digital photographs of the 2011 tohoku oki tsunami spatial distribution of tsunami deposits and topographical conditions reconstructed using the digital elevation model dem in the study area run up flow and then backwash flow occurred only once run up flow reached maximum inundation height several minutes after tsunami flooding started topographic features such as terraces dissected valleys coastal lowlands and artificial seawall constrained the tsunami flow the sandy tsunami deposit distribution is limited to several hundred meters from the shoreline deposits show inland thinning and fining they also indicate thinning and fining in the direction of higher surfaces thick deposits which are distributed locally in the basin area between the beach ridge and the seawall exhibited multiple layers of inverse and normal grading formed by repeated acceleration and deceleration for several minutes during the run up flow in the area with concentrated backwash flow after the tsunami struck the sedimentation for tsunami deposits was affected not only by the run up flow but also by the backwash flow

erosion deposition and landscape change on the sendai coastal plain japan resulting from the march 11 2011 tohoku oki tsunami case studies of recent tsunami impacts have proven to be extremely useful in understanding the geologic processes involved during inundation and return flow and refining the criteria used to identify paleotsunami deposits in the geologic record here we report on erosion deposition and associated landscape change resulting from the march 11 2011 tohoku oki tsunami along a nearly 4 5 km shore normal transect on the coastal plain near sendai japan the study area on the broad low relief prograding coastal sendai plain comprised a sand beach backed by 3 m high sand dunes and a forest a wetland the teizan canal agricultural rice fields buildings and roads field observations focused on measurements of tsunami flow characteristics height and direction mapping of erosion features and assessing sediment deposition based on shallow trenches at 50 100 m spacing recorded tsunami inundation heights reached up to about 11 m above mean sea level within the first 500 m from the shoreline and then ranged between 3 and 5 m for the next 2 km gradually decreasing to about 3 m close to the inundation limit the tsunami deposit generally thinned landward from an average maximum 30 cm thick sand deposit in the coastal forest to a thin mud drape several mm thick near the inundation limit a discontinuous sand dominated sheet was prevalent to about 2800 m from the shoreline where mud content then gradually increased further landward eventually resulting in a mud dominated deposit ranging from 3 5 cm to a few mm thickness the overall thinning and fining of the deposit was often interrupted by localized features that led to complex sedimentological relationships over short distances satellite imagery taken on 14 march 2011 3 days after the tohoku oki tsunami shows prominent foreshore incisions with 100 s meters spacing alongshore a foredune ridge that underwent severe erosion and development of a prominent shore parallel elongated scour depression our field survey in early may 2011 revealed that the foreshore recovered quickly with rapid post tsunami sediment deposition from incident waves whereas the dune ridge complex had undergone only minor re working from eolian processes

the regional and temporal significance of primary aeolian magnetic fabrics preserved in alaskan loess abstract the anisotropy of magnetic susceptibility ams data presented herein underscore the resolving power magnetic anisotropy has in non lithified poorly consolidated sediments we turn our attention to primary aeolian sedimentary magnetic fabrics preserved along two coeval loess profiles in central alaska at the halfway house hh3 and gold hill steps ghs2 sites we first demonstrate that published preliminary results along hh1 and hh2 are reproducible moreover the new sample suite the first ever at ghs collected at a higher temporal resolution and statistical confidence permits a better evaluation of the significance of the inferred paleowind directions and their temporal variability the data demonstrate that the resolvability of the magnetic lineation is independent of both the eccentricity of the ams ellipsoid and the strength of the magnetic foliation furthermore the orientations and temporal variability of the most significant magnetic lineations are not artifacts of the data filtering process developed to isolate them we conclude that the temporal variations of inferred paleowind directions along hh3 track paleoclimatic glacial interglacial cycles as well as provide additional constraints to the geochronology of the loess deposit along ghs2 the limited coeval primary magnetic fabrics suggest an influence from a local microclimate not present at the hh site complicating the interpretation of small scale variability in paleowind directions however the overall average paleowind directions are similar to those inferred along hh3 confirming a regional spatial consistency of past surface air circulation

2004 indian ocean tsunami inflow and outflow at phuket thailand at bangtao beach phuket the 2004 indian ocean tsunami produced a repeated sequence in which rapid inflow of turbulent water was followed by ponding and then by gradual outflow photographs and eyewitness accounts show an initial withdrawal followed by series of inflows the tsunami left behind a sand sheet as much as 25 cm thick that contains parallel inclined landward and seaward lamina in addition to the normal grading commonly reported from tsunami deposits the sheet contains evidence for two times of vigorous inflow each of these is marked by mud rip ups medium to coarse sand that grades upward to fine landward inclined laminae and a sharp basal contact the top of the sand sheet when observed in the first days after the tsunami abounded in current dune and ripple bedforms of mostly landward orientation the tsunami s first positive wave left noonshore sedimentary record in this pitting area the second wave deposited sand that is much less extensive and slightly finer than that of the third wave the deposit of both these waves contains multiple fining upward sequences possibly due to multiple surges in one wave train the depth averaged flow velocity estimated from thickness and grain size are in the range 7 21 m s whereas a near bottom threshold velocity calculated from bedforms reveals the order of magnitude difference from 1 74 to 1 03 m s 2007 elsevier b v all rights reserved

smnd signature of modern and late quaternary sediments from the northwest north atlantic implications for deep current changes since the last glacial maximum abstract nd isotopes and sm nd concentrations have been investigated in the clay size fraction of surface and late quaternary sediments of the northern north atlantic four sources of nd have been identified in the surface sediments 1 a radiogenic nd typical of the iceland volcanism 2 a pan african nd issued from eastern greenland 3 a variscan nd derived from the arctic ocean 4 an old unradiogenic nd related to the north american shield in the iceland and irminger basins the major sources of nd are the variscan nd derived from the arctic ocean and the iceland nd except in the western irminger basin where the pan african nd originating from eastern greenland is dominant and labels sedimentary supplies linked to the denmark strait overflow water nd derived from icelandic volcanism is never clearly dominant even on the reykjanes ridge and the nd derived from the american shield becomes dominant only in the labrador sea sediments lying in the pathway of the western boundary undercurrent have nd isotopic compositions which are shifted towards more radiogenic values indicating an input of material from the eastern basins carried by this deep current late quaternary sediments were cored from the southern greenland rise core 90 013 013 and eastern labrador rise orphan knoll core 91 045 094 in core 90 013 013 nd values during the last glacial maximum are as low as 20 but subsequently rose to 9 in the modern sediments indicating that the sedimentary material during the last glacial maximum was dominated by unradiogenic nd from the north american shield this may be related to a lesser outflow of the western boundary undercurrent in core 91 045 094 located along the labrador current trajectory a dominant supply of north american shield nd is recorded perhaps originating at least partially from the hudson strait the sm nd data are compatible with smectite vs illite studies at the same sites which suggest a continuous but more modest western boundary undercurrent supply during last glacial maximum

experiments on the production of transverse grain alignment in a sheared dispersion a series of experiments was designed to investigate grain orientation in flows with concentrations of granular solids in the range from 0 5 to 15 fourteen experiments were carried out in which sand sized material was dispersed in liquid plaster of paris and the dispersion allowed to flow down a slope until it came to rest the preferred orientation of the grains was then estimated by measuring the anisotropy of magnetic susceptibility of specimens cut from the solidified flows five of the experiments showed signs of deformation both in the gross characteristics of the flow and in the grain alignment the remaining nine had grain alignment dependent on grain concentration at concentrations of 1 2 and less and 11 1 and more by volume alignment of long axes was parallel to flow these observations were consistent with the existing theories for low concentrations in which preferred alignment is shown to result from the varying rate of rotation of grains in a shearing flow and for high concentrations in which preferred alignment results from the transfer of angular momentum between colliding grains at some intermediate concentrations transverse alignment was observed a theoretical explanation combining the theories of the extreme cases is suggested the observation of transverse alignment is compared with a similar observation in some turbidites

deep sea records from the southeast labrador sea ocean circulation changes and ice rafting events during the last 160 000 years 1 results from two deep sea cores from northeast of newfoundland at 1251 and 2527 m water depth respectively indicate that during the time period from 160 000 to 10 000 years bp ice rafting events in the labrador sea were accompanied by rapid variations in deep and surface water circulation twelve ice rafting events occurred each coinciding with high concentrations of detrital carbonate and oxygen isotopic depletion of both surface and bottom waters eleven of these can be correlated with the north atlantic heinrich events h1 h11 the remaining very conspicuous ice rafting event took place early in mis substage 5e at a time when the planktic faunal assemblage suggests marked warming of the sea surface in the shallower core benthic delta 13 c values rise from a minimum during the deglaciation to peak substage 5e values following the last ice rafting event indicating that the ventilation of intermediate depths was renewed after the deglaciation was complete and continued throughout substage 5e the benthic foraminifera suggest that this well ventilated water mass was comparable to the modern labrador sea water lsw the benthic faunas suggest that a relatively warm intermediate water mass entered the se labrador sea during heinrich events generally low benthic delta 13 c values indicate that this water mass was poorly ventilated and rich in inorganic nutrients isotope data and benthic faunal distributions indicate that north atlantic deep water nadw formed in the norwegian greenland sea reached the se labrador sea between the heinrich events

transient well flow in leaky multiple aquifer systems abstract a previously developed eigenvalue analysis approach to groundwater flow in leaky multiple aquifers is used to derive exact solutions for transient well flow problems in leaky and confined systems comprising any number of aquifers equations are presented for the drawdown distribution in systems of infinite extent caused by wells penetrating one or more of the aquifers completely and discharging each layer at a constant rate since the solution obtained may be regarded as a combined analytical numerical technique a type of one dimensional modelling can be applied to find approximate solutions for several complicating conditions numerical evaluations are presented as time drawdown curves and include effects of storage in the aquitard unconfined conditions partially penetrating wells and stratified aquifers the outcome of calculations for relatively simple systems compares very well with published corresponding results the proposed multilayer solution can be a valuable tool in aquifer test evaluation as it provides the analytical expression required to enable the application of existing computer methods to the determination of aquifer characteristics

response of leaky aquifers to earth tides interpreted with numerical simulation abstract the response of aquifers to earth s solid tides earth tides has increasingly been used as a tool for monitoring the hydraulic properties of groundwater systems recent studies of the tidal response of the arbuckle aquifer opened to a usgs deep well in oklahoma wang et al 2018 barbour et al 2019 which has been injected with an enormous amount of toxic wastewater showed evidence that this aquifer may be leaking quantitative interpretation of the tidal response of this aquifer was made with a one dimensional analytical solution wang et al 2018 that showed that substantial leakage is occurring however the analytical model has inherent simplifications such as conductivity isotropy small aquifer thickness absence of aquitard storage and no basement leakage in this study we revisit the tidal response of leaky aquifers with a finite element multi layered model where such simplifications are removed we found that the simplifications in the analytical model lead to overly conservative estimates of leakage we revisit the tidal response of the arbuckle aquifer in oklahoma with the numerical simulation and estimate an average vertical hydraulic conductivity of 2 10 6 t o 7 10 5 m s for the aquitard overlying the arbuckle thus the aquitard above the arbuckle is not confining at this location but is as conductive as the aquifer itself given the fast rise of fluid level in many arbuckle wells in response to the injection of hundreds of millions of barrels of wastewater into this aquifer across oklahoma and kansas the present result calls for vigilant monitoring of leakage of wastewater from the arbuckle aquifer into the overlying freshwater reservoirs and the surface environment plain language summary earthquakes can damage the confinement of groundwater aquifers and thus can cause seismic hazard by letting freshwater in some aquifers to be contaminated or stored toxic wastewater in other aquifers to leak out into the environment thus it is important to monitor possible leakage of aquifers in earthquake countries analysis of the aquifer response to earth s solid tides in a usgs deep well in oklahoma wang et al 2018 barbour et al 2019 which has been used as the repository of an enormous amount of injected toxic wastewater shows that the aquifer may be leaking an analytical solution wang et al 2018 that contains several simplifications was used to quantify the aquifer leakage from the tidal response here we use a two dimensional multilayered numerical simulation without these simplifications to explore the limitations of the analytical model we find that aquitard storage and basement leakage have important effects on the tidal response of aquifers and the omission of these factors in the analytical solution may have caused underestimation of the aquifer leakage we then apply the numerical model to interpret the tidal response of water level documented in a usgs deep monitoring well installed in the arbuckle aquifer in oklahoma where an enormous amount of toxic wastewater has been stored with reasonable estimates of the aquitard storage our simulations yield an estimate of 2 10 6 t o 7 10 5 m s for the vertical hydraulic conductivity of the aquitard thus the aquitard is not at all confining but is as conductive as the aquifer itself given the fast rise of fluid level in many arbuckle wells in response to the injection of hundreds of millions of barrels of wastewater into this aquifer across oklahoma and kansas the present result calls for vigilant monitoring of leakage of wastewater from the arbuckle aquifer into the overlying freshwater reservoirs and the surface environment

evolution of the northeast labrador sea during the last interglaciation 1 boreal summer insolation during the last interglaciation lig generally warmed the subpolar to polar northern hemisphere more than during the early holocene yet regional climate variations between the two periods remain we investigate northeast labrador sea subsurface temperature and hydrography across terminations t i and ii and during the lig to assess the impact of two different magnitudes of boreal summer insolation increase on the northeast labrador sea we use mg ca ratios in neogloboquadrina pachyderma sinistral as a proxy of calcification temperature to document changes in subsurface temperatures over eirik drift our corresponding record of d 18 o of seawater documents changes in water mass salinity mg ca calcification temperatures peak early in the holocene coincident with peak boreal summer insolation in contrast lig temperatures are relatively constant through the interglaciation and are no warmer than peak holocene temperatures during the first half of the lig d 18 o of seawater remains depleted likely from southern greenland ice sheet retreat and enhanced arctic freshwater and sea ice export to the labrador sea the consequent stratification of the labrador sea and attendant suppressed convection explains delayed deep ocean ventilation and a cooler subsurface in the northeast labrador sea during the lig

high resolution rock magnetic study of a late pleistocene core from the labrador sea a high resolution rock magnetic study of a late pleistocene core from the labrador sea north of the eirik ridge on the greenland rise reveals three main features in the downcore variation of the

directional petrological characterisation of deep marine sandstones using grain fabric and permeability anisotropy methodologies theory application and suggestions for integration abstract different methods for quantifying preferred grain orientation or grain shape fabric in sandstones are reviewed and their value for the reconstruction of palaeocurrent direction and preferred direction of pore fluid flow is reassessed critically based on existing knowledge from literature and new grain fabric data it is shown that petrographic analysis has distinct merits because grain fabric can be determined with low equipment costs and population statistics are based on the orientation of individual grains several recommendations are given how to standardise procedures for acquisition of grain fabric through microscopy these recommendations include 1 the careful selection of cross section orientations to acquire apparent long grain axes that are representative of true long grain axes 2 the preferred measurement of the coarsest grains in cross section and 3 a new statistically founded method to select a subset of grains that is representative of the total population of grains in a sandstone sample magnetic techniques that use anisotropy of magnetic susceptibility ams as a proxy for grain orientation require specialised equipment and are more restricted in statistical evaluation but these methods benefit greatly from being able to measure a large number of grains in a three dimensional space in a short amount of time and with a lower sensitivity to user bias of the two magnetic techniques discussed in this paper the new enhanced ams method in which rock magnetic properties are enhanced by introducing magnetite into the pores and as precipitates on grain surfaces is regarded to be an improvement over the traditional natural ams method in which only the natural assemblage of magnetite particles present in the rock is analysed enhanced ams measures the preferred orientation of essentially all grains in a rock sample thus providing the shape fabric of a hydrodynamically more accurate representation of framework grains than natural ams through a small technical modification the enhanced ams method can be used to obtain a magnetic cast of the pore network of a rock sample so that the resulting ams is controlled by the shape anisotropy of the individual pores it is commonly assumed that long axes of sand grains in sedimentary deposits parallel the direction of the flows that formed the deposits this concept is challenged by a new systematic study of grain fabric in deep marine turbidites it indeed appears that grains in ripple cross laminated divisions of turbidites dominantly attain a preferred orientation parallel to the palaeoflow direction but grains in plane parallel laminated divisions have an additional flow perpendicular mode which suggests a contribution of rolling grain transport three different fabric modes occur in massive structureless sandstones and massive divisions in turbidites apart from flow aligned and flow perpendicular modes there is a statistically significant but hydrodynamically enigmatic flow oblique mode with an average azimuthal deviation of 40 this large variation of fabric types suggests that a similar variation exists in preferred paths of pore fluid flow within turbidites controlled to at least some degree by depositional process this is confirmed by independent laboratory measurements of permeability anisotropy on samples for which grain fabric data are available and thus defines grain fabric analysis as a viable alternative to traditional permeametry techniques

the warm marine isotope stage 31 in the labrador sea low surface salinities and cold subsurface waters prevented winter convection surface and subsurface conditions in the labrador sea during marine isotope stage mis 31 at the integrated ocean drilling program iodp site u1305 off southwest greenland are reconstructed based on dinocyst and foraminifer assemblages isotopic compositions of planktonic neogloboquadrina pachyderma np and benthic cibicides wuellerstorfi cw and oridorsalis umbonatus ou foraminifera provide further information about water properties in the mesopelagic layer as well as at seafloor dinocyst proxy reconstructions indicate low salinities 32 34 5 cool winters 3 6 c and mild summers 10 15 c in the surface water layer during the mis 31 optimum however planktonic foraminifer assemblages largely dominated by np suggest relatively cold subsurface conditions in winter 2 0 c and summer 2 4 c lower 13c values in np vs cw further suggest either a lesser ventilated mesopelagic layer than the bottom one or high organic matter oxidation rates at np habitat depth the dinocyst and planktonic foraminifer records together suggest a strong stratification between the surface and subsurface water layers isotopic and micropaleontological data thus converge towards paleoceanographical conditions unsuitable for convection and intermediate or deep water formation in the labrador sea during the warm mis 31 interglacial a situation similar to the one which prevailed during the warm mis 5e

distribution of organic walled dinoflagellate cysts in surface sediments from transects across the polar front offshore southeast greenland the polar front along the southeast greenland margin denotes the contrasting hydrographic properties of the polar and atlantic water masses on either side the remains of planktonic organisms in underlying sediments are expected to reflect these contrasts to test this we quantitatively analysed the organic walled dinoflagellate cyst dinocyst assemblages in surface sediments from transects across the present day polar front on the southeast greenland margin proportional differences are found between the composition of the dinocyst assemblages on either side of the polar front the influence of polar water can be traced in the dinocyst record as high abundances of algidasphaeridium minutum and the presence of pentapharsodinium dalei the influence of atlantic water is reflected in the presence of operculodinium centrocarpum and selenopemphix quanta all samples include taxa from both environments but the quantitative composition of the cyst assemblages clearly reflects the hydrographic features of the overlying surface water masses copyright 2001 john wiley sons ltd

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

comment on mixed layer deepening during heinrich events a multi planktonic foraminiferal delta18o approach rashid and boyle reports 19 october 2007 p 439 analyzed oxygen isotopes in planktonic foraminera from marine sediments and concluded that heinrich events massive iceberg discharges into the north atlantic ocean caused upper water masses to deepen we question the robustness of this interpretation and argue that a strongly stratified mixed layer characterized by dense sea ice cover and production of oxygen 18 depleted brines likely prevailed during such events

determining flow patterns and emplacement dynamics from tsunami deposits with no visible sedimentary structure in the absence of eyewitness reports or clear sedimentary structures it can be difficult to interpret tsunami deposits or reconstruct tsunami inundation patterns the emplacement dynamics of two historical tsunami deposits were investigated at seven transects in okains bay new zealand using a combined geospatial geomagnetic and sedimentological approach the tsunami deposits are present as layers of sand and silt intercalated between soils and become finer and thinner with distance inland the deposits are attributed to the 1960 and possibly the 1868 tsunamis based on radiometric dating and correlation with historical records measurements of magnetic fabric mf anisotropy of magnetic susceptibility and particle size were used to reconstruct the evolution of flow dynamics laterally and vertically a combination of statistical methods including spatial autocorrelation testing spearman s rank order correlation principal component analysis pca and k means cluster analysis was applied to examine relationships between mf parameters and sediment texture and infer depositional hydrodynamics flow patterns deduced from mf show the estuary channel acted as a conduit for inundation with flow commonly aligned sub perpendicular to the estuary bed mf and sediment data suggest deposition occurred from settling during laminar flow evidence of both uprush and backwash deposition as well as wave reflection from infrastructure was found statistical analysis of data showed significant relationships between grain size parameters and mf parameters associated with flow speed and magnetic fabric type pca and cluster analysis differentiated samples into two primary hydrodynamic groups 1 samples deposited from laminar flow and 2 samples deposited close to the limit of inundation which includes samples deposited further inland those affected by flow convergence and those in the upper part of tsunami deposits this approach has potential as a tool for reconstructing hydrodynamic conditions for palaeotsunamis and by combining spatial and statistical analyses large scale investigations can be more easily performed this article is protected by copyright all rights reserved

clay mineral evidence of nepheloid layer contributions to the heinrich layers in the northwest atlantic abstract the clay fraction of four cores drilled in the north atlantic ocean was studied at a very high resolution over the last 150 ka in order to record the mineralogical signature of heinrich events factor analysis of clay mineralogy establishes that three independent factors represent the main variations a detrital factor illite chlorite kaolinite a smectite factor and a mixed layer factor ivml illite vermiculite mixed layered clay the clay mineral fraction of core su90 38 drilled in the northeastern atlantic basin did not record any heinrich event whereas large changes in the clay mineral fraction occurred during heinrich events h1 h2 h4 and h5 in the three cores from the northwestern atlantic basin cores su90 08 su90 11 and su90 12 heinrich layers are characterized by increases in the detrital factor in cores su90 08 and su90 11 and sharp increases in the mixed layer factor in cores su90 11 and su90 12 the geographical setting of the cores the pattern of surface intermediate and deep water circulation and the main sources of clay minerals allow recognition of two major mechanisms involved in the deposition of the heinrich layers 1 an increased supply of detrital clay minerals by the icebergs and 2 a specific input of illite vermiculite mixed layer clay minerals by a nepheloid layer

paleoclimatic significance of the temperature dependent susceptibility of holocene loess along a nw se transect in the chinese loess plateau we have conducted mineral magnetic investigations of samples of modern dune sand pristine loess and present day loess along a nw se transect from the northern to the central loess plateau in china the methods used include the temperature dependence of susceptibility tds before and after citrate bicarbonate dithionite cbd treatment as well as x ray diffraction xrd analysis the xrd analyses demonstrate that magnetite and hematite both exist in the chinese loess paleosol sequence and its modem source area but the tds measurements show that magnetite is the predominant contributor to magnetic susceptibility maghemite is present in the pristine loess and the present day loess due to pedogenesis the pedogenic processes that produce the maghemite are closely linked to paleoclimate and for this transect precipitation appears to be the most important climatic variable we suggest that tds can be used as a useful method for the analysis of pedogenesis and climatic change

temperature dependence of magnetic susceptibility in an argon environment implications for pedogenesis of chinese loess palaeosols summary temperature dependence of magnetic susceptibility t has been widely used to determine changes in mineralogy of natural samples during heat treatment we carried out integrated rock magnetic experiments to interpret the t curves of the chinese loess palaeosols in argon we used both raw materials and heated samples in addition we also investigated the magnetic properties of magnetic extracts and residues to quantify contributions from each fraction to the bulk magnetic properties for the heating curves the susceptibility loss 30 per cent between 300 400 c is caused by the inversion from pedogenic fine grained maghemite to haematite suggesting that the susceptibility loss can be used as a new concentration index of the pedogenic fine grained superparamagnetic sp particles in the chinese loess palaeosols unlike the warming curves the cooling curves are dominated by newly formed fine grained magnetites with a dominant size of 35 nm the onset for the new production of these fine grained magnetic particles occurs at 400 c it is interesting that the room temperature magnetic susceptibility ph of the samples heated after a 700 c run is independent of the degree of pedogenesis and saturates at approximately 33 35 10 7 m3 kg 1 indicating that the susceptibility enhancement is controlled only by the reduction of fe bearing aeolian minerals during heating it appears that the 700 c thermal treatment in argon could be in some sense an analogue to the pedogenic processes thus we predict that 33 35 10 7 m3 kg 1 is the maximum susceptibility that pedogenesis can generate for the last interglacial palaeosol unit s1 in practice ph would be useful to quantify the aeolian inputs to the chinese loess plateau

new aspects of the interpretation of the loess magnetic fabric cerna valley succession hungary abstract anisotropy of magnetic susceptibility ams is a frequently applied method in sedimentology especially in the determination of the orientation of transport processes we present an analysis of magnetic fabric mf studies on loess new aspects of fabric development reveal i the deposition of the aeolian sediments was controlled by gravity low energy transport and local geomorphology hence no clarified wind direction can be defined ii the influence of phyllosilicates is also significant among the magnetic components iii while the primary mf is relatively well defined the secondary mf is influenced by several processes the analysis of stereoplots combined with the q diagram and photostatistics showed encouraging results during the characterization of various secondary mf such as redeposited mf and pedogenic fabric iv changes in processes from aeolian to water lain deposition and the increasing transportation energy were reflected by the connection between ams and observed micro scale sedimentary features v a relationship was obvious between the degree of pedogenesis and the transformation of sedimentary mf into a vertical mf typical for paleosols vi the significant role of very fine grained magnetite on the formation of inverse mf could not be excluded

transient well flow in vertically heterogeneous aquifers abstract a solution for the general problem of computing well flow in vertically heterogeneous aquifers is found by an integration of both analytical and numerical techniques the radial component of flow is treated analytically the drawdown is a continuous function of the distance to the well the finite difference technique is used for the vertical flow component only the aquifer is discretized in the vertical dimension and the heterogeneous aquifer is considered to be a layered stratified formation with a finite number of homogeneous sublayers where each sublayer may have different properties the transient part of the differential equation is solved with stehfest s algorithm a numerical inversion technique of the laplace transform the well is of constant discharge and penetrates one or more of the sublayers the effect of wellbore storage on early drawdown data is taken into account in this way drawdowns are found for a finite number of sublayers as a continuous function of radial distance to the well and of time since the pumping started the model is verified by comparing results with published analytical and numerical solutions for well flow in homogeneous and heterogeneous confined and unconfined aquifers instantaneous and delayed drainage of water from above the water table are considered combined with the effects of partially penetrating and finite diameter wells the model is applied to demonstrate that the transient effects of wellbore storage in unconfined aquifers are less pronounced than previous numerical experiments suggest other applications of the presented solution technique are given for partially penetrating wells in heterogeneous formations including a demonstration of the effect of decreasing specific storage values with depth in an otherwise homogeneous aquifer the presented solution can be a powerful tool for the analysis of drawdown from pumping tests because hydraulic properties of layered heterogeneous aquifer systems with partially penetrating wells may be estimated without the need to construct transient numerical models a computer program based on the hybrid analytical numerical technique is available from the author

a simple model for calculating tsunami flow speed from tsunami deposits abstract this paper presents a simple model for tsunami sedimentation that can be applied to calculate tsunami flow speed from the thickness and grain size of a tsunami deposit the inverse problem for sandy tsunami deposits where grain size and thickness vary gradually in the direction of transport tsunami sediment transport is modeled as a steady spatially uniform process the amount of sediment in suspension is assumed to be in equilibrium with the steady portion of the long period slowing varying uprush portion of the tsunami spatial flow deceleration is assumed to be small and not to contribute significantly to the tsunami deposit tsunami deposits are formed from sediment settling from the water column when flow speeds on land go to zero everywhere at the time of maximum tsunami inundation there is little erosion of the deposit by return flow because it is a slow flow and is concentrated in topographic lows variations in grain size of the deposit are found to have more effect on calculated tsunami flow speed than deposit thickness the model is tested using field data collected at arop papua new guinea soon after the 1998 tsunami speed estimates of 14 m s at 200 m inland from the shoreline compare favorably with those from a 1 d inundation model and from application of bernoulli s principle to water levels on buildings left standing after the tsunami as evidence that the model is applicable to some sandy tsunami deposits the model reproduces the observed normal grading and vertical variation in sorting and skewness of a deposit formed by the 1998 tsunami

an analytical solution for leakage rate and depletion of aquitard influenced by the delayed yield phenomenon delayed yield phenomenon dyp occurs when the drawdown of an aquitard is no longer in equilibrium owing to previous changes in the level of water in adjacent aquifers in this study an analytical solution to determine the distribution of the drawdown at any time and at any point in an aquitard in which the water level was not in equilibrium at the initial time and the water level of the aquifers immediately above and below the aquitard was time dependent was developed the analytical solution for the flow rate at any time and location was presented based on variations in drawdown in the aquitard in addition the effects of the dyp on the leakage rate and depletion of the aquitard were studied subsequent comparison of the proposed analytical and numerical solutions revealed that they were in good agreement the results of this study will be useful to future studies of groundwater flow and environmental problems such as water budgets rising sea levels solute transport heat conduction and ground subsidence

geochemical and micropaleontological impacts caused by the 2011 tohoku oki tsunami in matsushima bay northeastern japan abstract we present stratigraphic geochemical cns elemental analysis and micropaleontological ostracode assemblages evidence for the 2011 tohoku oki tsunami impact in matsushima bay northeastern japan and examine the recovery process after the impact to the bay environment using short sediment cores from two different topographic settings at a water depth of approximately 4 m at both sites tsunami deposits are composed of two sedimentary layers that recorded the first tsunami run up and backwash at the western site near the channel that connects the bay with the pacific ocean the first tsunami wave eroded the bay floor sediments and left the tsunami deposits composed of medium sand rich in shell fragments but with sparse numbers of meiobenthic ostracodes by contrast at the eastern site which is surrounded by many small islands the first wave eroded very little of the bay floor sediments and left tsunami deposits consisting of sandy mud rich in exotic ostracodes such as phytal species shallow marine sand dwelling species and brackish water species overlying post tsunami deposits are composed mainly of organic rich mud in which organic matter was derived primarily from marine plankton ostracode assemblages in the tsunami deposits lack the offshore species that live in water depths 50 m and are dominated by the species from matsushima bay and its adjacent nearshore upper sublittoral areas and brackish water environments the distance from deep water offshore areas to the core sites is too far to transport ostracode valves by tsunami waves

new insights of tsunami hazard from the 2011 tohoku oki event we report initial results from our recent field survey documenting the inundation and resultant deposits of the 2011 tohoku oki tsunami from sendai plain japan the tsunami inundated up to 4 5 km inland but the 0 5 cm thick sand deposit extended only 2 8 km 62 of the inundation distance the deposit however continued as a mud layer to the inundation limit the mud deposit contained high concentrations of water leachable chloride and we conclude that geochemical markers and microfossil data may prove to be useful in identifying the maximum inundation limit of paleotsunamis that could extend well beyond any preserved sand layer our newly acquired data on the 2011 event suggest that previous estimates of paleotsunamis e g 869 ad j gan earthquake and tsunami in this area have probably been underestimated if the 2011 and 869 ad events are indeed comparable the risk from these natural hazards in japan is much greater than previously recognized

an approximate analytical solution for well flow in anisotropic layered aquifer systems abstract the mathematical problem of steady groundwater flow toward a pumping well in an aquifer system consisting of layers or aquifers with anisotropy of the horizontal conductivity is solved analytically for the first time the solution is an approximation for relatively weak anisotropy if more than one layer is horizontally anisotropic the method requires that the principal directions of anisotropy are the same in all layers the presented solution is based on a first order perturbation technique comparison with numerical calculations shows a good agreement as long as tmin is nowhere less than 0 6tmax layers with stronger anisotropy are also allowed provided these are embedded in a system with layers of weaker anisotropy

flow speed estimated by inverse modeling of sandy tsunami deposits results from the 11 march 2011 tsunami on the coastal plain near the sendai airport honshu japan abstract tsunami deposits contain information about the flow that created them which can be interpreted to estimate tsunami magnitude sandy deposits near sendai airport are modeled using an inverse sediment transport model to explore the spatial and temporal variation of tsunami flow speed in the 11 march 2011 tohoku oki tsunami the 2011 deposits contain grain size signatures of both sediment transport convergences and sediment settling out of suspension sediment transport convergences form massive or inversely graded intervals sediment falling out of suspension forms a specific type of normal grading termed suspension grading the jaffe and gelfenbaum 2007 inverse sediment transport model which relates the thickness and bulk grain size of suspension graded intervals to tsunami flow speed was applied to 24 suspension graded intervals ranging in thickness from 2 to 4 cm at 7 trenches located from about 250 to 1350 m inland from the shoreline modeled tsunami flow speeds range from 2 2 to 9 0 m s and were strongly dependent on the choice of manning s n roughness parameterization flow speeds were highest from about 75 300 m landward of the forested sand dunes where the tsunami encountered lower roughness in a low lying area as it traveled downslope and decreased by 16 as the tsunami moved inland over the subsequent 596 m as many as 5 suspension graded intervals interpreted as forming during the onshore flow of up to 5 waves were identified at each location with a tendency for an inland decrease in the number of suspension graded intervals suggesting fewer waves inland tsunami flows tended to be fastest in the lower two intervals earlier waves and slowest in the uppermost interval last wave of the deposits modeled reconstructions of the suspension graded intervals at a vertical resolution of 1 cm reproduced observed upward fining of the distributions reasonably well supporting the use of the inverse model estimates of the time required to form 99 of the thickness of the suspension graded intervals ranged 2 to 5 min allowing that sediment falling from suspension could have formed these portions of the deposits in the time between waves application of the inverse model to determine paleotsunami flow speeds from deposits although now possible is complicated by uncertainty in roughness as inverse approaches to estimating roughness and tsunami flow speed improve the magnitude of paleotsunamis will be better understood and the ability to assess tsunami hazard from paleotsunami deposits will improve

steady groundwater flow in leaky multiple aquifer systems abstract the hydraulic properties of stratified formations usually vary from layer to layer within the area of influence of a pumped well drain or section of a river the subsoil can often be schematized into a limited number of aquifers each separated by less pervious layers a general method has been developed for the analytical solution of steady flow problems in leaky multiple aquifer systems comprising any number of aquifers this method has been used to investigate potential distributions in multilayered aquifers of infinite extent being pumped or recharged at a constant rate using completely penetrating wells and drains in one or more of the aquifers the same approach is applicable to groundwater flow problems with more complicated boundary conditions such as the influence of a wide river partially penetrating the leaky top layer the well flow solution has been applied to evaluate hydraulic properties of several aquifers and aquitards from pumping tests in a six layer leaky aquifer system in a general sense the method presented may be regarded as a combined analytical numerical technique

analytical solutions for pressure perturbation and fluid leakage through aquitards and wells in multilayered aquifer systems 1 large scale groundwater pumping or deep fluid injection in a multilayered subsurface system may generate pressure perturbation not only in the target formation s but also in over and underlying units hydraulic communication in the vertical direction may occur via diffuse leakage through aquitards and or via focused leakage through leaky wells existing analytical solutions for pressure perturbation and fluid flow in such systems consider either diffuse leakage or focused leakage but never in combination with each other in this study we developed generalized analytical solutions that account for the combined effect of diffuse and focused leakage the new solutions solve for pressure changes in a system of n aquifers with alternating leaky aquitards in response to fluid injection extraction with any number ni of injection pumping active wells and passive leakage recharge in any number nl of leaky wells the equations of horizontal groundwater flow in the aquifers are coupled by the vertical flow equations in the aquitards and by the flow continuity equations in the leaky wells the solution methodology described in detail in this paper involves transforming the transient flow equations into the laplace domain decoupling the resulting ordinary differential equations odes coupled by diffuse leakage via eigenvalue analysis solving a system of nl n linear algebraic equations for the unknown rates of flow through leakage wells and superposing the solution of pressure buildup drawdown in aquifers and aquitards resulting from flow in the ni active and nl leaky wells verification of the new methodology was achieved by comparison with existing analytical solutions for diffuse leakage and for focused leakage and against a numerical solution for combined diffuse and focused leakage application to an eight aquifer system with leaky aquitards and one leaky well demonstrates the usefulness and efficiency of the approach and illustrates the pressure behavior over a spectrum of leakage scenarios and parameters

structure of the upper water column in the northwest north atlantic modern versus last glacial maximum conditions 1 during the last glacial maximum the northwestern north atlantic constituted a major conduit for labrador and greenland ice sheet meltwaters vertical density gradients in its upper water masses have been reconstructed by combining information from transfer functions based on dinocysts and from oxygen isotope measurements 18o in planktonic foraminifera transfer functions yield temperature and salinity and thus potential density for the warmest august and coldest february months in the photic zone the 18o values in different size fractions of epipelagic globigerina bulloides and mesopelagic neogloboquadrina pachyderma left coiled npl foraminifera allow us to assess gradients through the pycnocline between surface and intermediate waters based on the calibration of a versus 18o relationship from transfer function reconstructions the size and density of npl shells provide further constraints on these gradients the results show the development of a very strong pycnocline during the lgm with a difference of about 3 summer to 1 5 winter units between surface and underlying waters they indicate conditions unfavorable for vertical convection and support the hypothesis of the spreading of a shallow low salinity buoyant layer over the northern north atlantic this layer depicted a strong e w gradient with maximum seasonal contrast and minimum absolute values westward

use of anisotropy of magnetic susceptibility ams in the study of tsunami deposits application to the 2004 deposits on the eastern coast of banda aceh north sumatra indonesia abstract we studied emplacement dynamics of the december 26 2004 tsunami deposits in artificial shallow ponds and in shallow lagoons along the northern coast of sumatra in banda aceh area successive tsunami waves inundated topographic lows which acted as sediment traps and favored preservation of deposits individual waves led to the deposition of fining upwards sedimentary sequences this multiple normal grading deposit with a thickness ranging from 2 to 80 cm constitutes a site of major interest for the study of the deposits emplaced by a tsunami wave train the main interest lies in the characteristics of the deposits that can be correlated to the behavior of the waves attested by numerous testimonies in this setting we aimed at testing the applicability of the ams anisotropy of magnetic susceptibility technique as a proxy of unconsolidated sediment fabric the combination of this proxy and traditional sedimentary analysis helped reconstructing the hydrodynamic conditions particularly the flow direction prevailing during sedimentation we applied the ams technique on eight sections stretching inland from 1 5 km to 2 2 km from the pre tsunami coastline grain size and ams data from these deposits provide similar and partially complementary information traction dominates in the basal parts of the deposits and occurs mainly for the basal layers of the sequences whereas settling dominates for the upper layers of these sequences the vertical evolution of the ams parameters within the deposits is related to the arrival of the successive waves with variations in the traction and decantation processes during deposition variations of current strength during sedimentation are related to the wave s momentum and to the progressive infill of topographic depressions the vertical change of the fifth coarsest percentile vs the median grain sizes of the deposits suggests strong variations of the energy of the currents and confirms the evolution of the ams parameters in the present study the fabric of the deposits which developed exclusively during the uprush phase of the cycle also allows the reconstruction of flood directions that are both normal and parallel to the shoreline with variations related to flow dynamics mean grain size and local topographic control due to the absence of backwash in between the waves and low velocity of the final backwash information about the sedimentation conditions of the tsunami deposits appears to be better preserved in topographic depressions in areas located remote from the seashore the ams proxy appears to be a promising tool for further studies of recent and paleo tsunami deposits

holocene evolution of deep circulation in the northern north atlantic traced by sm nd and pb isotopes and bulk sediment mineralogy 1 bulk mineralogy sm nd and pb elemental and isotopic compositions of the clay size fraction of holocene sediments were analyzed in three deep north atlantic cores to trace the particle provenance the aims of the present paper are to identify the origin of the particles driven by deep currents and to reconstruct deep circulation changes over the holocene in the north atlantic the three cores are retrieved in fracture zones two of them are located in the island basin along the gyre of north atlantic deep water and the third core is located off the present deep circulation gyre in the labrador sea whereas sedimentary supplies in the labrador sea were constantly derived from proximal sources the geochemical mixing trends in the iceland basin samples indicate pronounced changes in the relative contribution of continental margin inputs over the past 6 kyr supplies from western european margin that sharply increased at 6 kyr were progressively diluted by a larger contribution of scandinavian margins over the last 3 kyr changes in composition of the particles imply significant reorganization of paleocirculation of the deep north atlantic components in the eastern basins mainly reorganizations for both iceland scotland overflow water and norwegian sea overflow water moreover the unusual pb isotopic composition of the oldest sediments from the southern iceland basin indicates that distal supplies from greenland margin were driven into the iceland basin supporting a deep connection between labrador sea and iceland basin through the charlie gibbs fracture zone prior the holocene transition period

sm nd isotope systematics in deep sea sediments clay size versus coarser fractions sm nd studies were carried out on last glacial and holocene sediments from the labrador sea three grain size fractions were analyzed for each sediment the clay size fraction 2 m the fine cohesive silts 2 10 m and the coarse silts 10 63 m in most cases sm nd s ignatures are different from one grain size to anot her in addition different sm nd signatures are derived fr om the clay size fractions compared to the cohesive silt fraction indicating that the cohesive fraction is heterogeneous and that distinct origins in terms of source areas are implied silt fractions record the influence of supplies from the north american precambrian shield whereas clay size fractions 2 m are more sensitive to s edimentary input from the eastern basins in relati on with deep currents coupling sm nd studies on silt and c lay fractions may be a powerful tool to unravel the evolution of deep circulations versus detrital supplies

the influence of high latitude flux lobes on the holocene paleomagnetic record of iodp site u1305 and the northern north atlantic 1 paleomagnetic analysis and radiocarbon dating of an expanded holocene deep sea sediment sequence recovered by integrated ocean drilling program iodp expedition 303 from labrador sea site u1305 lat 57 28 5 n long 48 31 8 w water depth 3459 m provides insights into mechanisms that drive both paleomagnetic secular variation psv and magnetization acquisition in deep sea sediments seventeen radiocarbon dates on planktonic foraminifera define postglacial ca 8 ka sedimentation rates as ranging from 35 to 90 cm kyr alternating field af demagnetization of u channel samples show that these homogeneous sediments preserve a strong stable and consistently well defined component magnetization normalized remanence records pass reliability criteria for relative paleointensity rpi estimates assuming that the age of magnetization is most accurately defined by well dated psv records with the highest sedimentation rates allows us to estimate and correct for temporal offsets at site u1305 interpreted to result from postdepositional remanence acquisition at a depth of 20 cm comparisons indicate that the northern north atlantic psv and rpi records are more consistent with european than north american records and the evolution of virtual geomagnetic poles vgp are temporally and longitudinally similar to global reconstructions though with much larger latitudinal variation the largest deviations from a geocentric axial dipole gad are observed during times of the highest intensities in contrast to the usual assumption these observations are consistent with the idea that psv in the north atlantic and elsewhere during the holocene results from temporal oscillations of high latitude flux concentrations at a few recurrent locations

an experimental study into the geometry of supply limited dunes the relationship between dune geometry and the volume of mobile sediment was studied in flume experiments in these flume experiments the volume of mobile sediment on top of an immobile coarse sediment layer was increased stepwise and the bedform characteristics were observed a strong relationship was found between the volume that is mobile and therefore available for bedform formation and the dune dimensions and regularity if the sediment supply is limited dunes are smaller and more regular series of experiments with a decreasing supply limitation were conducted for different flow velocities and water depths the relationship between the dune dimensions and the available volume is different for each series the observed relationships between dune dimensions and layer thickness collapse to one relationship for height and one for length if scaling parameters are introduced current models for bedform dimensions under alluvial conditions can be extended to partial transport conditions using this relationship

nd and pb isotope signatures of the clay size fraction of labrador sea sediments during the holocene implications for the inception of the modern deep circulation pattern holocene on the basis of sediment supply variations for the last 12 kyr three sources have contributed to the sediment mixture the north american shield the pan african and variscan crusts and the mid atlantic ridge clay isotope signatures indicate two mixtures of sediment sources the first mixture 12 2 6 5 ka is composed of material derived from the north american shield and from a young crustal source from 6 5 ka onward the mixture is characterized by a young crustal component and by a volcanic component characteristic of the midatlantic ridge since the significant decrease in proximal deglacial supplies the evolution of the relative contributions of the sediment sources suggests major changes in the relative contributions of the deep water masses carried by the western boundary undercurrent over the past 8 4 kyr the progressive intensification of the western boundary undercurrent was initially associated mainly with the transport of the northeast atlantic deep water mass until 6 5 ka and with the denmark strait overflow water thereafter the establishment of the modern circulation at 3 ka suggests a reduced influence of the denmark strait overflow water synchronous with the full appearance of the labrador seawater mass our isotopic data set emphasizes several changes in the relative contribution of the two major components of north atlantic deep water throughout the holocene index terms 4267 oceanography general paleoceanography 4558 oceanography physical sediment transport 1040 geochemistry isotopic composition chemistry 9325 information related to geographic region atlantic ocean 9604 information related to geologic time cenozoic keywords clay size fraction sedimentary mixings deep circulation nd and pb isotopes north atlantic labrador sea

the future of tsunami research following the 2011 tohoku oki event abstract in this paper we summarize the regional setting our previous understanding of historical and pre historical tsunamis on the pacific coast of tohoku japan prior to the 2011 tohoku oki tsunami and our current understanding of the sedimentological geochemical and paleontological features of the onshore and offshore deposits of the event post tsunami surveys revealed many new insights such as 1 the maximum extent of the sand deposit is sometimes only 60 of the inundation distance 2 the inundation limit can be estimated by geochemical analysis even a few months after the event 3 a minor amount of marine sediment was transported inland by the tsunami on the sendai and adjacent plains with the major sediment sources being from beach and dune erosion or vented sediments from liquefaction although nearshore and offshore surveys revealed that there was a significant amount of sediment transport on the seafloor 4 coarse gravel deposits 1 m in thickness were usually thicker than the sand ones 30 cm in thickness and 5 beach erosion was minimal in some places while severe in others another important aspect of this event is that it was a large infrequent tsunami that took place where possible predecessors e g ad869 j gan were already known to have occurred based on historical and geological evidence the ad869 j gan tsunami deposits are noticeably similar to the 2011 tohoku oki sands therefore suggesting that the j gan and its source mechanism may have been larger than previously thought while we have learned many lessons from the 2011 tohoku oki event more research is needed to provide reliable tsunami risk assessments around the world

bedforms record the flow conditions of the 2011 tohoku oki tsunami on the sendai plain northeast japan abstract this article describes the bedforms formed by the 2011 tohoku oki tsunami on the southern sendai plain ne japan integrated analyses of satellite images field survey data and x ray radiographs revealed the natural shapes of these bedforms the dominant bedforms are dunes and antidunes about 20 cm thick high and relatively flat because of their meter scale wavelengths their morphologies reflect mainly the tsunami run up flow on the flat lowland and the return flow in a narrow steep valley flow depth changed at sites where the level of the ground surface changed along the tsunami flow path causing the flow velocity to fluctuate flow velocity decreased in depressed deep water sections and increased in raised shallow water sections the types and positions of the tsunami deposit bedforms were thus strongly controlled by local ground surface roughness such as raised roadbeds and levees as a result the observed thickness distribution of the tsunami deposits fluctuates it is important to consider the possible existence of bedforms in paleotsunami surveys especially for accurate determination of the thickness distribution of the tsunami deposits because thickness data are essential information for reconstruction of the tsunami inundation limit as well as its flow speed

instabilities in the labrador sea water mass structure during the last climatic cycle in the modern labrador sea the north atlantic deep water components are found below the 2 km deep intermediate labrador sea water lsw mass which is renewed locally through winter convective mixing this water mass structure remained relatively stable since 9 5 14 c ka bp as indicated by isotopic studies of foraminifer assem blages from deep sea cores almost constant differences in 18 o values are observed between major species these av erage 0 5 between the epipelagic species globigerina bulloides and the mesopelagic species neogloboquadrina pachyderma left coiled and 1 between neogloboquadrina pachydermaand the benthic species cibicides wuellerstorfi after correction for cibicides wuellerstorfi specific fractionation these isotopic compositions represent thermohaline conditions in surface waters in the pycnocline with the lsw and in the deep component of the north atlantic deep water respectively a drastically different structure characterized the glacial labrador sea differences in 18 o values of 2 to 2 5 are then observed between globigerina bulloides and benthic species indicative of a strong halocline between the corresponding water masses thus for reduced production of intermediate waters during the same interval neogloboquadrina pachydermashows 13 c and 18 o fluctuations of 1 to 1 5 amplitude in phase with heinrich bond events and higher frequency climate oscillations the 18 o values in neogloboquadrina pachyderma vary between those of globigerina bulloides and of benthic foraminifers suggesting large amplitude bathymetric fluctuations of the halo thermocline above and below the bathymetric range occupied by neogloboquadrina pachyderma minimum 18 o values in neogloboquadrina pachydermamatch intervals of maximum ice rafting deposition such as the late heinrich events thus intervals with a deeper more dilute buoyant surface water layer

groundwater flow to a well in a layered porous medium 1 steady flow analytical solutions of steady multiple aquifer problems usually assume the flow of groundwater to be essentially horizontal in aquifers and vertical in aquitards these assumptions yield formulae that are economical to evaluate the simplifications however ask for a theoretical check this paper is dealing with the derivation of an analytical formula that may serve as such it considers steady flow of groundwater to a partially screened well in a layered porous medium both horizontal and vertical flow components are taken into account