luminescence dating of sediments from buctouche spit new brunswick in this paper we describe our efforts to determine the formation chronology of a sequence of dunes on buctouche spit a holocene deposit on the northeast coast of new brunswick optical dating using infrared stimulation of k feldspar grains yielded ages ranging from 5 30 a for an embryo dune to 765 45 a for the oldest dune thermoluminescence ages although less precise support the recent formation of the dunes the ages exhibit the expected sedation from youngest to oldest and are consistent with historical evidence coupled with an assumed constant sediment aggradation rate the age resolution obtained was very good and we conclude that the optical dating method used here shows great promise

thermodynamic analysis of ocean circulation abstract calculating a streamfunction as function of depth and density is proposed as a new way of analyzing the thermodynamic character of the overturning circulation in the global ocean the sign of an overturning cell in this streamfunction directly shows whether it is driven mechanically by large scale wind stress or thermally by heat conduction and small scale mixing it is also shown that the integral of this streamfunction gives the thermodynamic work performed by the fluid the analysis is also valid for the boussinesq equations although formally there is no thermodynamic work in an incompressible fluid the proposed method is applied both to an idealized coarse resolution three dimensional numerical ocean model and to the realistic high resolution ocean circulation and climate advanced model occam it is shown that the overturning circulation in occam between the 200 and 1000 m depth is dominated by a thermally indirect cell of 24 sverdrups 1 sv 106 m3 s 1 forced by ekman pumping in th

tsunami history of an oregon coastal lake reveals a 4600 yr record of great earthquakes on the cascadia subduction zone bradley lake on the southern oregon coastal plain records local tsunamis and seismic shaking on the cascadia subduction zone over the last 7000 yr thirteen marine incursions delivered landward thinning sheets of sand to the lake from nearshore beach and dune environments to the west following each incursion a slug of marine water near the bottom of the freshwater lake instigated a few year to several decade period of a brackish 4 salinity lake four additional disturbances without marine incursions destabilized sideslopes and bottom sediment producing a suspension deposit that blanketed the lake bottom considering the magnitude and duration of the disturbances necessary to produce bradley lake s marine incursions a local tsunami generated by a great earthquake on the cascadia subduction zone is the only accountable mechanism extreme ocean levels must have been at least 5 8 m above sea level and the cumulative duration of each marine incursion must have been at least 10 min disturbances without marine incursions require seismic shaking as well over the 4600 yr period when bradley lake was an optimum tsunami recorder tsunamis from cascadia plate boundary earthquakes came in clusters between 4600 and 2800 cal yr b p tsunamis occurred at the average frequency of 3 4 every 1000 yr then starting 2800 cal yr b p there was a 930 1260 yr interval with no tsunamis that gap was followed by a 1000 yr period with 4 tsunamis in the last millennium a 670 750 yr gap preceded the a d 1700 earthquake and tsunami the a d 1700 earthquake may be the fi rst of a new cluster of plate boundary earthquakes and accompanying tsunamis local tsunamis entered bradley lake an average of every 390 yr whereas the portion of the cascadia plate boundary that underlies bradley lake ruptured in a great earthquake less frequently about once every 500 yr therefore the entire length of the subduction zone does not rupture in every earthquake and bradley lake has recorded earthquakes caused by rupture along the entire length of the cascadia plate boundary as well as earthquakes caused by rupture of shorter segments of the boundary the tsunami record from bradley lake indicates that at times most recently 1700 yr b p overlapping or adjoining segments of the cascadia plate boundary ruptured within decades of each other

a facies model for a quaternary andesitic composite volcano ruapehu new zealand ruapehu composite volcano is a dynamic volcanic sedimentary system characterised by high accumulation rates and by rapid lateral and vertical change in facies four major cone building episodes have occurred over 250 ka from a variety of summit flank and satellite vents eruptive styles include subplinian strombolian phreatomagmatic vulcanian and dome related explosive eruptions and extrusion of lava flows and domes the volcano can be divided into two parts a composite cone of volume 110 km3 surrounded by an equally voluminous ring plain complementary portions of ruapehu s history are preserved in cone forming and ring plain environments cone forming sequences are dominated by sheet and autobrecciated lava flows which seldom reach the ring plain the ring plain is built predominantly from the products of explosive volcanism both the distal primary pyroclastic deposits and the reworked material eroded from the cone much of the material entering the ring plain is transported by lahars either generated directly by eruptions or triggered by the high intensity rain storms which characterise the region ring plain detritus is reworked rapidly by concentrated and hyperconcentrated streams in pulses of rapid aggradation immediately following eruptions and more gradually in the longer intervals between eruptions

late quaternary history of the mackenzie beaufort region arctic canada from modelling of permafrost temperatures 2 the mackenzie delta tuktoyaktuk coastlands in the mackenzie beaufort region maximum permafrost thickness is 750 m in the pleistocene tuktoyaktuk coastlands less than 100 m in the holocene mackenzie delta and 500 m and anomalously warm in the big lake delta plain between the two areas numerical modelling has been used to derive surface temperature histories that fit ground temperatures and permafrost conditions at 12 wells in the unipkat kumak and taglu hydrocarbon fields the models indicate that the present holocene mackenzie delta was built by fluvial processes into a submarine trough the delta front passed a site presently some 20 km from the coast about 4 5 ka and subsequently 58 m of ice bonded permafrost has aggraded in contrast the big lake delta plain was a subaerial platform for much of the wisconsinan it experienced several thousand years of inundation in the holocene probably due to widespread development of thermokarst lakes at sites 8 12 km from the coast the present subaerial conditions were established 0 5 1 5 ka throu

the passive and active nature of ocean heat uptake in idealized climate change experiments the influence of ocean circulation changes on heat uptake is explored using a simply configured primitive equation ocean model resembling a very idealized atlantic ocean we focus on the relative importance of the redistribution of the existing heat reservoir due to changes in the circulation and the contribution from anomalous surface heat flux in experiments in which the surface boundary conditions are changed we perform and analyze numerical experiments over a wide range of parameters including experiments that simulate global warming and others that explore the robustness of our results to more general changes in surface boundary conditions we find that over a wide range of values of diapycnal diffusivity and southern ocean winds and with a variety of changes in surface boundary conditions the spatial patterns of ocean temperature anomaly are nearly always determined as much or more by the existing heat reservoir redistribution than by the nearly passive uptake of temperature due to changes in the surface boundary conditions calculating heat uptake by neglecting the existing reservoir redistribution which is similar to treating temperature as a passive tracer leads to significant quantitative errors notably at high latitudes and secondarily in parts of the main thermocline experiments with larger circulation changes tend to produce a relatively larger magnitude of existing reservoir redistribution and a faster growing effective heat capacity of the system the effective heat capacity is found to be sensitive to both vertical diffusivity and southern ocean wind

the role of vertical eddy flux in southern ocean heat uptake 1 the role of changing vertical eddy heat flux on southern ocean heat uptake is investigated in an idealized eddy permitting ocean model enhanced air sea heat flux drives deep reaching southern warming due to a reduction in the isopycnal meridional temperature gradient and therefore decreased upward eddy heat flux this mechanism is qualitatively similar in models with either permitted or parameterized eddies due to its dependence on the isopycnal temperature gradient rather than the dynamical response of the eddy field in contrast increased wind stress drives mid depth southern ocean cooling through an enhancement of the eddy field and resultant eddy heat divergence the transient cooling extends over multiple decades while the mean flow adjusts to balance the faster eddy response this wind driven cooling mechanism has not been captured by coarse resolution models with fixed eddy parameterizations and is a possible candidate for the recent cooling observed in the southern ocean

sedimentology and event timing of a catastrophic volcaniclastic mass flow volcan hudson southern chile eruption of volcan hudson aisen region southern chile on 12 august 1971 melted up to 80 of ice within the 9 km wide hudson caldera rapid mobilisation of abundant fluvio glacial sediment within the adjacent huemules valley led to the generation of a catastrophic mass flow which swept westwards along the valley eventually entering the fjord some 40 km downstream the mass flow developing from one source and being unaffected by tributary input was characterised by three events within the flood hydrograph 1 a precessional flood possibly linked to breakage of an early formed dammed lake 2 a main mass flow which varied in its rheological behaviour from plug flow to hyperconcentrated flow and 3 a recessional flood at the tail of the main flow which diluted towards a concentrated streamflow the main debris flow displayed characteristics of pulsing internal segregation density stratification significant downstream sediment assimilation cohesive frictional freezing with ensuing fluidisation and development of an advancing runout phase consideration of these sedimentary characteristics and spatial temporal flow transformations are used to propose a schematic model of event timing within this catastrophic volcaniclastic flow

vertical heat transport by ocean circulation and the role of mechanical and haline forcing abstractvertical transport of heat by ocean circulation is investigated using a coupled climate model and novel thermodynamic methods using a streamfunction in temperature depth coordinates cells are identified by whether they are thermally direct flux heat upward or indirect flux heat downward these cells are then projected into geographical and other thermodynamic coordinates three cells are identified in the model a thermally direct cell coincident with antarctic bottom water a thermally indirect deep cell coincident with the upper limb of the meridional overturning circulation and a thermally direct shallow cell coincident with the subtropical gyres at the surface the mechanisms maintaining the thermally indirect deep cell are investigated sinking water within the deep cell is more saline than that which upwells because of the coupling between the upper limb and the subtropical gyres in a broader thermohaline circulation despite the higher salinity of its sinking water the deep cell tr

tertiary quaternary drainage of the pre glacial mackenzie basin abstract pre glacial drainage in the northwestern mackenzie region was established in early tertiary time with the uplift of the mountains during the laramide orogeny and persisted until near the end of the pleistocene rivers arose in the mackenzie and richardson mountains and followed a generally eastward direction across piedmont surfaces from the mountains towards the plains the evidence to support this hypothesis includes geomorphology provenance of sediments reconstruction of paleo surfaces and stratigraphy two major drainage systems developed one to the atlantic ocean and another to the arctic ocean the atlantic drainage is composed of the northwestern tributaries of an integrated drainage system that flowed towards hudson bay traces of this drainage are found in the canyon ranges of the mackenzie mountains iroquois upland and in the norman range of the franklin mountains the arctic drainage included two main basins the porcupine basin that drained from west to east across the richardson mountains and the anderson basin that included the peel and snake rivers as its tributaries late wisconsinan laurentide glaciation deranged these drainage systems establishing the porcupine river as a tributary of the yukon river and integrating the tertiary drainage systems into the mackenzie river system flowing to the arctic ocean

late miocene valley confined subglacial volcanism in northern alexander island antarctic peninsula isolated late miocene volcanogenic sequences in northern alexander island antarctic peninsula form an unusual cogenetic association of volcaniclastic sandy gravelly lithofacies including tillites and volcanic lava hyalocalstite lithofacies using simple lithofacies analysis and theoretical considerations of hydrodynamic effects of subglacial eruptions valley confined volcanic activity beneth thin wet based ice is suggested the alexander island successions are complete enough to be regarded as model sequences for this uncommonly recorded type of eruptive depositional activity the sedimentary lithofacies represent resedimented tuffs and meltout or flow tills which were probably deposited in subglacial ice tunnels eroded or enlarged by volcanically heated meltwater the volcanic lithofacies formed by the interaction of hot magma with the ice tunnel walls generating abundant meltwater and water saturatedsediments resulting in the formation of heterogeneous masses of lava and hyaloclastite there is no obvious sequence organisation in the sedimentary sections this is probably due to a complex interplay of eruption related and environmental hydrodynamic factors affecting the relative proportions of water and entrained sediment

sedimentologic characteristics of a fluvial to aeolian succession in weichselian talsand in the emsland f r g abstract a sedimentologic study of a fluvial to aeolian succession in weichselian talsand in the emsland f r g is presented here from bottom to top two fluviatile units an aeolian bed an aeolian lacustrine unit and a second windborne deposit succeed each other in the investigated exposure the aeolian facies represent two distinct styles of deposition by wind the lower aeolian unit with horizontal alternating bedding presumably results from both a periodic change in mean surface wind strength and the spring thawing of seasonally frozen ground the emerged part of the north sea basin was the principle source of sand and silt for this sediment type the upper aeolian unit is characterised by a low dune or sand sheet topography inclined bedding and the predominance of plane bed lamination it was laid down on depositional surfaces normally too dry for the formation of adhesion stratification surface wind speed was generally high and its distribution over the year had become more uniform than before furthermore sand supply was increasingly from local sources close to the depositional site the deposition of the aeolian lacustrine unit is due to lateral migration of the low dunes mentioned above during this process sand was blown into a pool of still water and then subjected to gravitational slumping the change from fluvial to aeolian depositional regime observable in the talsand is tentatively attributed to the combined effect of intensified wind activity and lowering of the groundwater table as a result of permafrost degradation

mid wisconsinan eolian deposits of the kittigazuit formation tuktoyaktuk coastlands northwest territories canada the kittigazuit formation is a late quaternary sand unit commonly observed throughout the tuktoyaktuk coastlands and in subbottom sediments of the southern beaufort shelf stratigraphic and sedimentology data including sedimentary structures grain surface characteristics and heavy and light mineralogy assist in characterizing the deposit and indicate that it is eolian in origin plant and arthropod macrofossils suggest that although the summer climate during deposition was as warm or slightly warmer than today conditions were likely more arid permafrost is interpreted as being widespread during deposition accelerator mass spectrometry radiocarbon dates indicate that the kittigazuit formation was deposited between 37 and 33 ka bp the unit is therefore interpreted as a mid wisconsinan eolian dune deposit formed by reworking of underlying alluvial sediments of the kidluit formation under nonglacial conditions glaciogenic sediments overlying the kittigazuit formation indicate that glacial ice cover

anatomy hydrodynamics and depositional setting of a westphalian c lacustrine delta complex west midlands england studies spanning a 3 year period of westphalian c strata exposed in an active quarry have enabled three dimensional reconstruction of a lacustrine delta complex the sequence exhibits a complex history of lake infilling by sediment introduced by intermittent high energy low sinuosity distributary channel flows deposition in the small 0 2 km2 lake prior to delta formation was dominated by organic matter and typified rheotrophic swamp conditions large lycopods colonized the swamp floor the lake was filled by a prograding delta which comprised six horizontally and vertically stacked delta lobes the presence of lycopods aided sediment accumulation fluctuations in river discharge and consequent lake level rise and fall exerted a fundamental control on delta progradation and aggradation flooding during low lake levels first produced erosion on the existing lobe followed by a lake level rise which created accommodation for aggradation of a new delta lobe further lobe erosion and low stand lobe formation occurred during lake level fall the area s proximity to alluvial fans resulted in hyperconcentrated flood flow within the distributary channels the occurrence upon in channel surfaces of plant colonization including lycopods testifies to the ephemeral nature of the flow the lacustrine delta complex formed at the front of a terminal alluvial fan northward progradation of the alluvial fan was achieved by the capture and infilling of lakes by northerly flowing distributary channels

a medial to distal volcaniclastic record of an andesite stratovolcano detailed stratigraphy of the ring plain succession of south west taranaki new zealand the 25 ka volcaniclastic ring plain succession in south west taranaki has been remapped to establish a much more detailed understanding of the older stratigraphic record of mt taranaki coastal cliff exposures show a range of volcaniclastic lithofacies including debris avalanche and lahar deposits and allow a detailed chronological reconstruction of past volcanic and sedimentary events five new debris avalanche deposits were identified and their distribution in coastal cross sections mapped in addition four previously described units were renamed and their stratigraphic position and lateral extent redefined chronostratigraphic control of the younger 50 ka sequence was obtained by radiocarbon dating of wood found within or peat interbedded with the deposits emplacement ages of the older units were estimated from their stratigraphic position and underlying marine wave cut surfaces overall at least 14 widespread debris avalanche deposits occur within the 200 ka ring plain record of mt taranaki suggesting one major edifice failure on average every 14 000 years with an increase in frequency since 40 ka the stratigraphic reconstruction of the ring plain succession showed that the same pattern of deposition was repeatedly produced throughout the existence of mt taranaki depending on their sedimentological characteristics the different volcanic and sedimentary lithofacies can be related to phases of edifice construction or collapse events based on the identified cyclic sedimentation pattern we present a new episodic stratigraphy that integrates existing and new lithostratigraphic units into a coherent chronostratigraphic framework that can be applied to the entire volcanic and volcaniclastic succession at mt taranaki this model takes into account the complex geological processes that have taken place on the volcano and provides a more uniform stratigraphic terminology that could be applied to repeatedly collapsing stratovolcanoes elsewhere

unraveling the timing of the caviahue depression andean southern volcanic zone insights from the sedimentary infill the caviahue copahue volcanic complex in the southern volcanic zone of the andes is composed of the pliocene pleistocene caviahue depression and the active copahue volcano this volcanic complex is located in a zone of profuse volcanic and tectonic activity and thus the origin of the depression includes both tectonic and volcanic hypothesis e g formation of a collapse caldera and a pull apart basin according to current knowledge the oldest rocks filling the depression are lavas and ignimbrites of the pleistocene las mellizas formation however clastic sedimentary deposits underlying this unit have been recognized here we document the characteristics of these deposits at the south shore of the caviahue lake using field data and digital outcrop models dom we have concluded that the deposits are deltaic and alluvial in origin and made up by a prodelta distal deltaic front delta front deposits delta plain sediments and alluvial deposits an unconformity separates the deltaic deposits from overlying alluvial deposits indicating the decrease in the stratigraphic base level probably associated with a sudden coarse grained clastic input and a drop in the lake level our study has implications on the timing and evolution of the caviahue depression and indicates that the depression precedes the las mellizas formation thus las mellizas ignimbrite should not be interpreted as the main unit related to the caviahue caldera as it has been proposed by some authors if the depression had indeed been formed by a collapse caldera this event would be previous to the described sediments

control of lower limb overturning circulation in the southern ocean by diapycnal mixing and mesoscale eddy transfer a simple model is developed of the lower limb of the meridional overturning circulation in the southern ocean based on residual mean theory it is hypothesized that the strength of the lower limb overturning is strongly controlled by the magnitude of abyssal diapycnal mixing and that of mesoscale eddy transfer k in particular it is argued that k the scaling and associated theory find support in a suite of sensitivity experiments with an idealized ocean general circulation model this study shows that intense diapycnal mixing is required to close the buoyancy budget of the lower limb overturning circulation in contrast to the upper limb where air sea buoyancy fluxes can provide the required diabatic forcing

the energetics of southern ocean upwelling abstractthe ocean s meridional overturning circulation is closed by the upwelling of dense carbon rich waters to the surface of the southern ocean it has been proposed that upwelling in this region is driven by strong westerly winds implying that the intensification of southern ocean winds in recent decades may have enhanced the rate of upwelling potentially affecting the global overturning circulation however there is no consensus on the sensitivity of upwelling to winds or on the nature of the connection between southern ocean processes and the global overturning circulation in this study the sensitivity of the overturning circulation to changes in southern ocean westerly wind stress is investigated using an eddy permitting ocean sea ice model in addition to a suite of standard circulation metrics an energy analysis is used to aid dynamical interpretation of the model response increased southern ocean wind stress enhances the upper cell of the overturning circulation through creation of avail

oceanic isopycnal mixing by coordinate rotation abstract current numerical models of oceanic circulation differentiate between the eddy diffusion and viscosity transport along the geopotential horizontal and vertical directions only in order to model the effect of anisotropic turbulence as diffusive transport along and across density surfaces the isopycnal mixing tensor has been transformed from a diagonal second rank tensor in the isopycnal coordinate system to a tensor containing off diagonal elements in the geopotential coordinate system

fluvial and lacustrine palaeoenvironments of the miocene siwalik group khaur area northern pakistan the miocene siwalik group upsection the chinji nagri and dhok pathan formations in northern pakistan records fluvial and lacustrine environments within the himalayan foreland basin thick 5 m to tens of metres sandstones are composed of channel bar and fill deposits of low sinuousity 1 08 1 19 single channel meandering and braided rivers which formed large low gradient sediment fans or megafans river flow was dominantly toward the south east and likely perennial palaeohydraulic reconstructions indicate that chinji and dhok pathan rivers were small relative to nagri rivers bankfull channel depths of chinji and dhok pathan rivers were generally 15 m and up to 33 m for nagri rivers widths of channel segments including single channels of meandering rivers and individual channels around braid bars were 320 710 m for chinji rivers 320 1050 m for nagri rivers and 270 340 m for dhok pathan rivers mean channel bed slopes were on the order of 0 000056 0 00011 bankfull discharges of channel segments for chinji and dhok pathan rivers were generally 700 800 m3s 1 with full river discharges possibly up to 2400 m3s 1 bankfull discharges of channel segments for nagri rivers were generally 1800 3500 m3s 1 with discharges of some larger channel segments possibly on the order of 9000 32 000 m3s 1 full river discharges of some of the largest nagri braided rivers may have been twice these values thin decimetres to a few metres sandstones represent deposits of levees crevasse channels and splays floodplain channels and large sheet floods laminated mudstones represent floodplain and lacustrine deposits lakes were both perennial and short lived and likely less than 10 m deep with maximum fetches on the order of a few tens of kilometres trace fossils and body fossils within all facies indicate the former existence of terrestrial vertebrates molluscs bivalves and gastropods arthropods including insects worms aquatic fauna e g fish turtles crocodiles trees bushes grasses and aquatic flora palaeoenvironmental reconstructions are consistent with previous palaeoclimatic interpretations of monsoonal conditions

the removable cap suction corer an inexpensive and durable device to extract unconsolidated wet sediments obtaining sediment samples in unconsolidated sediment presents many challenges the locale substrate can be soft penetration of the sediment may be limited preservation of the sedimentary fabric may be incomplete and extraction of the sample may be difficult some of these issues are overcome with vibracore or suction core techniques vibracoring requires heavy bulky and relatively expensive equipment which is costly to ship to the remote field study locations and difficult to use in muddy settings such as muddy tidal flats or coastal marshes the van der staay suction corer van de meene et al 1979 is cost effective and fixes logistical problems but sample extraction has to be done in the field the tess 1 suction corer mendez et al 2003 was designed on the basis of the van der staay suction corer and allows recovering intact sediment samples for further laboratory analysis but it requires custom machinery with more man hours and uses small diameter core tubes with a high possibility of disturbance of sedimentary structures in unconsolidated and waterlogged deposits here we present a new removable cap suction corer that is inexpensive to construct light in weight highly portable and can be designed to extract any core diameter the corer can be used for coarse and fine grained wet sediments tidal flats riverine and estuarine bars coastal marshes and shallow subaqueous environments lakes rivers shallow shoreface

late wisconsinan erosion and eolian deposition summer island area pleistocene mackenzie delta northwest territories optical dating and implications for glacial chronology the summer island area of the pleistocene mackenzie delta western canadian arctic is thought to have been last glaciated during the early wisconsinan 35 ka with a suggested late wisconsinan 13 ka glacial limit located 80 100 km to the south cryostratigraphic observations in the summer island area identify eolian and fluvial sediments overlying an erosion surface on summer island eolian sand occurs within sand wedges the tops of which are contiguous with an eolian sand sheet deposited on a formerly bare ice surface this paleo ice surface is attributed to fluvial erosion and that in turn is attributed to proglacial meltwater activity the age of erosion is inferred to be shortly before 14 ka determined by optical dating using infrared stimulation of luminescence from feldspar of the eolian sand wedges this 14 ka meltwater erosion is significantly north of the generally accepted limit of late wisconsinan glaciation in this coastal area suggesting that ice last covered the whole of rich

vertical heat flux in the ocean estimates from observations and from a coupled general circulation model the net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically generally it is necessary to rely on global climate models to study these processes in detail in the present study it is shown that a key component of the vertical heat flux namely that associated with the large scale mean vertical circulation can be diagnosed over extra tropical regions from global observational data sets this component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance combined with estimates of absolute geostrophic flow results are compared with the output of a non eddy resolving coupled atmosphere ocean general circulation model reasonable agreement is found in the latitudinal distribution of the vertical heat flux as well as in the area integrated flux below about 250 m depth the correspondence with the coupled model deteriorates sharply at depths shallower than 250 m due to the omission of equatorial regions from the calculation the vertical heat flux due to the mean circulation is found to be dominated globally by the downward contribution from the southern hemisphere in particular the southern ocean this is driven by the ekman vertical velocity which induces an upward transport of seawater that is cold relative to the horizontal average at a given depth the results indicate that the dominant characteristics of the vertical transport of heat due to the mean circulation can be inferred from simple linear vorticity dynamics over much of the ocean

turbidites and iron formations beardmore geraldton ontario application of a combined ramp fan model to archaean clastic and chemical sedimentation sandy turbidites grain flows conglomeratic mass flows and oxide facies iron formation are present in the late archaean beardmore geraldton terrain a metasedimentary belt which extends for at least 80 km in an e w direction the marine portion of this basin contains four lithofacies associations la 1 thinbedded iron formation clastic sediment association this association represents a continuum of deposit types containing iron formation subtypes are defined on the basis of bedding attributes and the proportion of iron formation to sand silt 2 thin bedded turbidite dominated association these sediments consist mostly of silt sand beds which either show no vertical trends or thin and fine upwards over a few metres 3 medium bedded turbidite dominated association most of these sediments are medium to coarsegrained vertically unstructured sand sequences with occasional structured intervals 4 thick bedded association this is dominated by poorly graded sands up to 7 8 m in thickness sand beds are characterised by a thin basal zone of coarse sand and pebbles a large central interval containing a mixture of medium and coarse sand and a thin upper zone of fine sand silt the overall depositional system was initiated by transport of sediment by braided streams to the strand area where it accumulated in distributary mouth bars we infer a nearshore break in slope locally with large channels la 4 extending from close to the strand line across deltaic surfaces to the deeper portions of submarine fans structured portions of la 3 however many deltaic surfaces probably were not tapped by major channels but merged downslope into a submarine ramp sediment was transported across the ramp by slump events and sheet like grain flows unstructured portions of la 3 iron formation and la 2 sediments probably accumulated both in upper mid ramp areas with low sediment delivery rates and distal to fan ramp successions as major streams on the braid plain changed position associated submarine channels and slump fed ramp deposits also would have shifted laterally this produced overlap of different facies associations in both the fan and ramp environments which may explain why observed vertical trends in bedding are limited to several metres we suggest that on narrow active archaean cratonic margins additional non regular processes such as variations in sediment supply related to periods of heightened pyroclastic activity and seismic activity associated with the arc also contributed to the lack of vertically structured sequences turbidite sequences in such environments in general may contain important contributions from both submarine ramp and submarine fan sedimentation

deposits and physical properties of pyroclastic density currents during complex subplinian eruptions the ad 472 pollena eruption of somma vesuvius italy small scale pyroclastic density currents pdcs associated with the ad 472 pollena eruption of somma vesuvius italy were generated by both magmatic and phreatomagmatic explosive fragmentation the resulting deposits were emplaced under flow boundary conditions dominated by varying combinations of grain interaction fluid escape and traction processes stratigraphic and lithofacies analysis of these pdcs offers a new perspective on the en masse versus progressive aggradation debate for pdc deposition in particular the analyses indicate that pdcs were density stratified with a basal underflow dominated by grain interactions the underflows comprised trains of self organized granular pulses of variable thickness and magnitude depending on the overall particle concentration and fluid turbulence a change in gradient between the upper and lower slopes of the volcano promoted deposition and the different pulses aggraded sequentially stepwise in this model each pulse stops en masse and the whole deposit aggrades progressively particle concentration density mean velocity and flow height were assessed for the studied pdcs using differaent methods for massive and stratified deposits the calculated mobility of the flows was 0 2 to 0 3 in the expected range for small scale pdcs

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

impact of mesoscale eddy transfer on heat uptake in an eddy parameterizing ocean model abstractusing a set of experiments with an eddy parameterizing ocean model it is found that the strength of the atlantic meridional overturning circulation amoc intensifies with the decrease of

cryostructures in permafrost tuktoyaktuk coastlands western arctic canada the shape and distribution of ice and sediment within frozen ground constitute its cryostructure observations on perennially frozen sediments in the tuktoyaktuk coastlands enable six cryostructures to be identified 1 structureless 2 lenticular 3 layered 4 reticulate 5 crustal and 6 suspended these cryostructures can be transitional or composite five cryofacies types can also be identified according to volumetric ice content and grain size they can be grouped into cryofacies assemblages the utility of the descriptive classification of ice rich sediments is illustrated from a palaeothaw layer at crumbling point

hydrodynamic behaviour of taupo 1800a pumice implications for the sedimentology of remobilized pyroclasts large scale explosive eruptions from silicic caldera volcanoes can generate huge volumes of pyroclastic material in terrestrial and marine environments on land erosion remobilization and redeposition of this debris is predominantly carried out by running water in the form of precipitation run off conversely in the submarine realm both primary emplacement and subsequent remobilization are influenced by the presence of water as a transporting medium despite this and the number of studies devoted to volcaniclastic sedimentation relatively little attention has been paid to the hydrodynamic behaviour of the particles themselves which ought to underpin any assessment of transport or depositional process this is crucial as many volcanic particles exhibit variable density according to composition and as functions of differing degrees of vesiculation and the extent to which pore space is filled by water and or gaseous phases during transport and deposition investigation of the physical and hydrodynamic properties of taupo 1800a pumice with reference to sedimentary facies developed during the eruption aftermath shows that although buoyant when dry when sufficiently waterlogged cool pumice clasts will sink and behave more like quartzo feldspathic material saturation is apparently achieved by a combination of rapid capillary flooding of large interconnected vesicles and slower diffusional air water exchange in smaller pores low saturated pumice densities result in lower settling velocities and easier entrainment by tractional currents than those for equivalent sized quartzo feldspathic or crystal lithic particles fine grained pumice is conversely harder to entrain because of the frictional interlocking of angular particles these unusual properties of temporary buoyancy variable saturation low density and size dependent cohesion complicate interpretations of the depositional setting and energy of pumiceous sediments and give rise to several unique facies these findings have implications not only for the analysis of remobilized pyroclastic facies in terrestrial and marine environments but also for primary depositional processes during subaqueous explosive volcanism

a conceptual model of ocean heat uptake under climate change abstracta conceptual model of ocean heat uptake is developed as a multilayer generalization of gnanadesikan the roles of southern ocean ekman and eddy transports north atlantic deep water nadw formation and diapycnal mixing in controlling ocean stratification and transient heat uptake are investigated under climate change scenarios including imposed surface warming increased southern ocean wind forcing with or without eddy compensation and weakened meridional overturning circulation moc induced by reduced nadw formation with realistic profiles of diapycnal mixing ocean heat uptake is dominated by southern ocean ekman transport and its long term adjustment controlled by the southern ocean eddy transport the time scale of adjustment setting the rate of ocean heat uptake increases with depth for scenarios with increased southern ocean wind forcing or weakened moc deepened stratification results in enhanced ocean heat uptake in each of these experiments the role of diapycnal mixing in settin

sedimentology of proximal to distal volcaniclastics dispersed across an active foldbelt ellensburg formation late miocene central washington late miocene volcaniclastics of the ellensburg formation washington northwestern usa are exposed in basins within an integrated palaeodrainage over the depositional reach from 15 to 120 km eastward from a cascade range source area two facies associations are recognized the first is composed of laterally restricted well sorted polymictic conglomerates representing a gravel bedload regime during inter eruption periods the second comprises laterally extensive sheets bounded by deeply developed paleosols composed of monomictic pebbly pumiceous dacitic sandstones with intercalated debris flow and hyperconcentrated flood flow deposits these sheets aggraded in response to eruptive events that are sometimes recorded by air fall tephras at the bases of sequences debris flow and hyperconcentrated flood flow deposits occur as far as 120 km from source but are uncommon beyond 50 km hyperconcentrated flood flow deposits initially increase in abundance away from source as debris flow deposits diminish suggesting formation of hyperconcentrated flood flows by dilution of debris flows sandy facies form broad sheets dominated by scour fill bedding in proximal and medial settings and grade to narrower trough cross bedded sheets in distal settings suggesting moderation of flood discharges with distance base level changes associated with episodic sediment influx caused incision aggradation cycles in mainstream settings and episodic impoundment of tributaries to form lakes or rapidly aggrading poorly drained floodplains although volcanism was the primary control on depositional style concurrent development of the yakima fold belt produced a structure consequent drainage pattern that determined sediment dispersal and basin subsidence permitted preservation of both syn eruption and inter eruption facies detritus from rising anticlines was generally diluted by the volumetrically superior extrabasinal volcaniclastics but dominates deposits of small tributary streams flowing toward rather than from the cascades

the blue emission of k feldspar coarse grains and its potential for overcoming tl age underestimation abstract this paper presents preliminary tl ages on k feldspar coarse grains from raised shallow marine sediments of nw europe and southern italy comparisons between tl ages using different optical filters suggest the use of the blue transmitting corning 7 59 filter allows measurement of an apparently stable tl component in k feldspar which could overcome the problem of age underestimation in the 75 300 ka range

pleistocene periglacial eolian deposits in southwestern alaska sedimentary facies and depositional processes abstract pleistocene periglacial eolian sediments are widespread in the nushagak holitna and upper kuskokwim lowlands of southwestern alaska these sediments comprise mainly sand sheet deposits and sand loess intergrades with subordinate sand dune deposits and loess sand sheet deposits range from 1 sharply defined parallel low angle laminae formed by migrating wind ripples to 2 irregular subhorizontal strata which reflect migration of poorly segregated wind ripples accumulation on a sparsely vegetated surface adhesion on a quasi planar bed and or niveo eolian deposition sand loess intergrades represent alternating bed load and suspension deposition related mainly to the stochastic and seasonal variability of former wind systems the dominance of sand sheet deposits over deposits of well formed dunes in the pleistocene eolian record of southwestern alaska reflects the limited availability of loose dry sand in this former periglacial environment immobilization of sand after deposition as low relief sheets resulted from a seasonally variable combination of ice cementation sparse vegetation high water tables and snow cover

vertical heat transport in eddying ocean models 1 the effect of mesoscale eddies on the vertical heat transport of the ocean is examined using two eddy resolving numerical models the global heat transport by the mean flow and diffusion are both downwards and are balanced by an upward eddy heat flux mean and eddy advective heat fluxes dominate the subpolar regions while diffusive flux is important primarily in the subtropics in the subtropical abyss the mean advective heat flux is balanced by a combination of eddy and diffusive fluxes and the classical munk type advective diffusive heat balance must be modified the munk and wunsch 1998 expression for the vertical turbulent diffusivity over estimates the diffusivity by as much as a factor of four near the base of the main thermocline this implies that the mixing required to close the meridional overturning circulation determined by munk and wunsch 1998 may be an over estimate due to the neglect of mesoscale eddies

dating young geomorphic surfaces using age of colonizing douglas fir in southwestern washington and northwestern oregon usa dating of dynamic young 500 years geomorphic landforms particularly volcanofluvial features requires higher precision than is possible with radiocarbon dating minimum ages of recently created landforms have long been obtained from tree ring ages of the oldest trees growing on new surfaces but to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores 1 the time interval between stabilization of the new landform surface and germination of the sampled trees germination lag time or glt and 2 the interval between seedling germination and growth to sampling height if the trees are not cored at ground level the sum of these two time intervals is the colonization time gap ctg such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the cascade range where significant eruption induced lateral shifting and vertical aggradation of channels can occur over years to decades and where timing of such geomorphic changes can be critical to emergency planning earliest colonizing douglas fir pseudotsuga menziesii were sampled for tree ring dating at eight sites on lowland 750 m a s l recently formed surfaces of known age near three cascade volcanoes mount rainier mount st helens and mount hood in southwestern washington and northwestern oregon increment cores or stem sections were taken at breast height and where possible at ground level from the largest oldest looking trees at each study site at least ten trees were sampled at each site unless the total of early colonizers was less results indicate that a correction of four years should be used for glt and 10 years for ctg if the single largest and presumed oldest douglas fir growing on a surface of unknown age is sampled this approach would have a potential error of up to 20 years error can be reduced by sampling the five largest douglas fir instead of the single largest a glt correction of 5 years should be added to the mean ring count age of the five largest trees growing on the surface being dated if the trees are cored at ground level this correction would have an approximate error of 5 years if the trees are cored at about 1 4 m above the ground surface breast height a ctg correction of 11 years should be added to the mean age of the five sampled trees with an error of about 7 years published in 2006 by john wiley sons ltd

the origin of horizontal alternating bedding in weichselian aeolian sands in northwestern europe abstract periglacial acolian sands of weichselian age are widespread in the lowlands of western and central europe one facies of this sediment type corresponding to the coversand sensu stricto is characterised by a wavy parallel bedding and a generally horizontal position of the strata since this layering results from an alternation of finer and coarser grained beds horizontal alternating bedding is the appropriate designation for it by a detailed analysis of representative lacquer peels eight characteristic stratification types could be distinguished these units are the smallest fundamental building blocks constituting the sediment under consideration an idealised annual cycle of sedimentation is proposed in summer light and variable winds carry silt in suspension to the site of deposition whilst the sandy saltation load is left behind in a throughput zone farther upwind upon settling the fines adhere to the surface which is wet or damp due to the thawing of the seasonally frozen ground in winter wind strength is generally greater so that deposition of sand prevails in the area whereas the fine grained suspension load settles downwind deposition by snow free winds results in the accretion of patches of well sorted sand snow flurries on the other hand produce niveo aeolian strata of generally more poorly sorted sand in the cycle it is implied that 1 the aeolian sedimentation basin must have been large and uniform enough to permit areal separation of sand and loess like material and 2 a seasonal shift in the centres of sand and silt deposition was inherent to the atmospheric pressure system of the formative period the exposed part of the northern and eastern north sea floor as it existed around the middle weichselian glacial climax assumedly was the principal source area for the deposits the relationships between the periglacial aeolian sands with horizontal alternating bedding loess and their integrades as described from the belgian lowlands and niedersachsen can be interpreted in the context of the proposed depositional cycle

bottom enhanced diapycnal mixing driven by mesoscale eddies sensitivity to wind energy supply abstractit has been estimated that much of the wind energy input to the ocean general circulation is removed by mesoscale eddies via baroclinic instability while the fate of this energy remains a subject of research arguments have been presented suggesting that a fraction of it may get transferred to lee waves that upon breaking result in bottom enhanced diapycnal mixing here the authors propose several parameterizations of this process and explore their impact in a low resolution ocean climate model focusing on their impact on the abyssal meridional overturning circulation moc of antarctic bottom water this study shows that when the eddy energy is allowed to maintain diapycnal mixing the abyssal moc generally intensifies with increasing wind energy input to the ocean in such a case the whole system is driven by the wind wind steepens isopycnals and generates eddies and the parameterized eddies generate small scale mixing driving the moc it is also demonstrated that if the model diapycn

a process based analysis of ocean heat uptake in an aogcm with an eddy permitting ocean component about 90 of the anthropogenic increase in heat stored in the climate system is found in the oceans therefore it is relevant to understand the details of ocean heat uptake here we present a detailed process based analysis of ocean heat uptake ohu processes in higem1 2 an atmosphere ocean general circulation model with an eddy permitting ocean component of 1 3 resolution similarly to various other models higem1 2 shows that the global heat budget is dominated by a downward advection of heat compensated by upward isopycnal diffusion only in the upper tropical ocean do we find the classical balance between downward diapycnal diffusion and upward advection of heat the upward isopycnal diffusion of heat is located mostly in the southern ocean which thus dominates the global heat budget we compare the responses to a 4xco2 forcing and an enhancement of the windstress forcing in the southern ocean this highlights the importance of regional processes for the global ocean heat uptake these are mainly surface fluxes and convection in the high latitudes and advection in the southern ocean mid latitudes changes in diffusion are less important in line with the cmip5 models higem1 2 shows a band of strong ohu in the mid latitude southern ocean in the 4xco2 run which is mostly advective by contrast in the high latitude southern ocean regions it is the suppression of convection that leads to ohu in the enhanced windstress run convection is strengthened at high southern latitudes leading to heat loss while the magnitude of the ohu in the southern mid latitudes is very similar to the 4xco2 results remarkably there is only very small global ohu in the enhanced windstress run the wind stress forcing just leads to a redistribution of heat we relate the ocean changes at high southern latitudes to the effect of climate change on the antarctic circumpolar current acc it weakens in the 4xco2 run and strengthens in the wind stress run the weakening is due to a narrowing of the acc caused by an expansion of the weddell gyre and a flattening of the isopycnals which are explained by a combination of the wind stress forcing and increased precipitation

vibracoring a new method for coring deep lakes abstract a major limitation facing lacustrine researchers is an inability to take long 6 to 18 m continuous sediment cores in water depths greater than several metres at a low cost these problems have limited the advancement of palaeolimnology and quaternary stratigraphy working from a frozen lake surface new developments make it possible to take 18 m long vibracores in water depths of at least 55 m high frequency low amplitude vibrations are transferred down a series of 6 m long 7 6 cm diameter core tubes 3 inch aluminum irrigation pipe rigidly coupled end to end vibrations liquify sediment adjacent to the core tube walls thus allowing penetration of the sediment a core catcher prevents sediment from extruding out of the tube end during extraction this cost effective and labour efficient two persons coring system has been achieved by developing rigid core tube couplers a hand powered drum cable hoist and a set of operation procedures the hoist cable end is attached to a clamp 1 m above the core catcher and at each coupler along the pipe string at 6 m intervals lifting or lowering using a drum cable hoist allows for quick coupling and decoupling of core tubes although vibracoring is an improvement over other systems it still has portability limitations because of the bulk and weight of the equipment and large amount of pipe required for deep coring three sleds are required to transport equipment from the nearest vehicle access to the coring sites

the structure and genesis of weichselian to early hologene aeolian sand sheets in western europe abstract weischselian to early holocene aeolian sands are widespread in the lowlands of western europe to a large extent these deposits occur in the form of sheet like coversands with slipfaced dunes being much rarer whereas the latter type of landform corresponds to a single facies with dune foreset cross bedding aeolian facies 1 two structurally different facies are distinguishable in the sand sheets this paper concentrates on the two sand sheet facies which are referred to as aeolian facies 2 and aeolian facies 3 data on these two types are based on 1 a survey of existing literature and 2 a detailed analysis of lacquer peels and larger scale exposures in england the netherlands and the federal republic of germany aeolian facies 2 is defined by the spatial position of its beds which may be either horizontal inclined or oppositely dipping in the case of structures formed by fluctuating winds horizontal bedding is by far the most common type inclined bedding is related either to small isolated dome dunes or to scoop shaped deflation surfaces the structures resulting from fluctuating winds are rare and do not represent an inherently large measure of directional variability of the wind regime the internal structure of the beds is dominated by aeolian planebed lamination with or without concordantly infilled wind scours degradation of this stratification type because of interference by coarse particles is discussed aeolian facies 3 is uniquely typified by the alternation of coarser and finer grained horizontal thin beds that are either wavy or even in shape depositional models of facies 3 are given at both the local and regional scales in both cases the coarser grained layers result from tractional deposition of saltating and creeping grains whilst the finer grained strata were laid down by settling from suspension periodic changes in surface wind speed the presence of a damp depositional surface and the availability of both sand and silt in the source area are necessary conditions for the working of the models the large scale model is associated with specific environmental conditions of the weichselian upper pleniglacial the local scale model accounts for the fact that facies 3 is also found in units of weichselian late glacial or early holocene age the regional scale model involves stepwise tractional transport over long distances so that grains of distant provenance were mixed with material from sources nearer to the receiving site this process was an important control on the mineralogical composition of the resultant deposits the prevalence of aeolian planebed lamination in both facies 2 and the coarser grained layers of facies 3 is attributed to the interaction of three factors viz the rarity of topographic barriers the sparseness of vegetation cover and a high ratio between wind energy and sand availability during the processes of transport and deposition in the lowlands of europe sand sheets are gradually replaced in an easterly direction by coeval wind dunes the possible causes of this phenomenon are considered