sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

site investigations to evaluate flow liquefaction slides at sand heads fraser river delta l ecoulement par liquefaction spontanee est un processus recurrent dans la progradation du delta du fleuve fraser une portion du delta a ete etudiee au moyen d essais de penetration au cone sismique et de resistivite et au moyen de l analyse spectrale de la methode des ondes de surface et de l echantiollonage de sol et de vapeur dans un effort pour determiner la stratigraphie du site l etat in situ et le degre de saturation afin explorer l enigme de l ecoulement par liquefaction spontanee un ensemble de capteur de pression interstitielle et d inclinaison a ete installe comme partie de l etude pour mesurer les effets de la vidange resultant du reflux de la maree les resultats ont indique que le lit de la mer a faible profondeur etait partiellement sature contenant un volume significatif de gaz methane qui affectait la reponse dynamique de la pression interstitielle durant le jusant une reduction de la contrainte effective atteignant 16 5 kpa a ete mesuree de meme qu un delai de 50 min entre le reflux de la maree et la reaction de la pression interstitielle ceci suggere que les effets de tampon sont un facteur significatif dans le declenchement de la liquefaction spontanee des sables l ches non viellis la ou ils reposent sur des pentes sous marines les resultats des essais in situ montrent que les sables nouvellement deposes du fleuve fraser ont une forte susceptibilite a l ecoulement par liquefaction

tectonic constraints on a deep seated rock slide in weathered crystalline rocks abstract deep seated rock slides dsrss recognised as one of the most important mass wasting processes worldwide involve large areas and cause several consequences in terms of environmental and economic damage they result from a complex of controlling features and processes dsrss are common in calabria southern italy where the complex geo structural setting plays a key role in controlling the geometry of the failure surface and its development this paper describes an integrated multi disciplinary approach to investigate a dsrs in palaeozoic high grade metamorphic rocks of the sila massif it focuses on the definition of the internal structure and the predisposing factors of the serra di buda landslide near the town of acri which is a paradigm for numerous landslides in this area an integrated interdisciplinary study based on geological structural and geomorphological investigations including field observations of weathering grade of rocks minero petrographic characterisations geotechnical investigations and in particular fifteen years of displacement monitoring is presented stereoscopic analysis of aerial photographs and field observations indicate that the serra di buda landslide consists of two distinct compounded bodies i an older and dormant body 7 ha and ii a more recent and active body 13 ha that overlies the previous one the active landslide shows movement linked to a deep seated translational rock slide block slide the velocity scale ranges from slow 1 6 m year during paroxysmal stages to extremely slow

recent localised sulphate reduction and pyrite formation in a fissured chalk aquifer abstract sulphate reduction and pyrite formation are well known diagenetic processes in marine sediments during the early stages of burial sulphate reduction has also been detected in aquifers however the identification of pyrite which was precipitated during the circulation of meteoric water is uncommon here we describe petrographic and sulphur isotope data which show that pyrite was formed in fissures while the aquifer contained meteoric water the occurrence of active sulphate reduction is demonstrated by the recovery of sulphate reducing bacteria srb s and detection of hydrogen sulphide hence organic matter may be metabolished and diagenetic minerals formed during late meteoric water diagenesis of sediments this process affects groundwater quality by removing sulphate fe and trace metals and by altering the redox state of the system

geochemistry and mineralogical residences of trace elements in oil shales from julia creek queensland australia abstract abundances and mineralogical residences have been determined for a comprehensive range of trace elements in julia creek oil shale many trace elements are well above normal abundances in shales of these elements v and mo are potentially useful by products whereas as se mo cd tl and u are of possible environmental or occupational health concern samples from a stratigraphic reference bore core through the toolebuc formation near julia creek in queensland were chemically analysed using the multi element techniques of neutron activation analysis and spark source mass spectrometry inter element correlation techniques selective leaching procedures and electron microprobe analyses were used to establish geochemical associations and specific mineralogical residences for a full range of elements the results provide a definitive chemical and mineralogical characterization of the oil shale and identify the major mineralogical residences of the important trace elements v occurs mainly in a mixed layer mica montmorillonite clay mineral and to a lesser extent in kerogen whereas most trace elements of environmental concern are resident in the sulphide minerals pyrite and sphalerite u is concentrated in the fluorapatite of fish debris a sound basis is established for understanding the inorganic chemistry involved in oil shale processing and waste disposal

large scale seismically induced mass movements in a former glacial lake basin lake temiscouata northeastern appalachians eastern canada abstract disturbed lacustrine deposits of eastern canada have been associated with past seismic events in the intraplate western quebec seismic zone wqz and the charlevoix kamouraska seismic zone cksz with five major earthquakes that occurred during historical times and hundreds of minor earthquakes the cksz is the most active seismic zone in eastern canada here we present new high resolution multibeam bathymetric subbottom profiler and sediment core data collected in lake temiscouata southeastern quebec the largest lake located within the influence of the cksz the occurrence of mass movements in the highly cohesive glaciolacustrine deposits of the lake produced a peculiar lacustrine landscape consisting of steep slide scars and residual mounds and very narrow residual crests our data indicate that postglacial times were marked by recurrent seismically induced mass movement events that cannot be individually identified in the sedimentary record due to the highly disturbed stratigraphy of the lake and to the absence of significant postglacial background sediments between events the most recent recorded mass movement is a distinct debris flow sediment layer on the lake floor that was deposited at 1300 cal bp very shortly after a distinct large scale mass movement event observed across the entire lake basin the presence of silt layers in gyttja overlying these disturbed units suggests that the region was affected by other seismic events following this event although no mmds could be directly related to these layers

submarine canyons and channels in the lower st lawrence estuary eastern canada morphology classification and recent sediment dynamics abstract series of submarine canyons and channels observed in the lower st lawrence estuary lsle provide an opportunity to analyze in great detail the morphology spatial distribution and modern activity of such systems in a relatively shallow 300 m semi enclosed basin based on their geomorphology and physical settings the canyons and channels were classified into four categories according to their feeding sources ancient or recent glacially fed river fed longshore drift fed and sediment starved systems their activity was interpreted based on geomorphological characteristics such as the presence of bedforms related to gravity flows backscatter intensity axial incision and the presence of rapidly deposited layers in surficial sediments river fed deltas were interpreted as inactive mainly because suspended sediment concentrations at river mouths are low preventing the generation of hyperpycnal currents or delta lip failures related to high sediment supply longshore drift fed canyons present where the coastal shelf narrows were found to be episodically active probably due to earthquakes or extreme storm events unlike other longshore drift fed canyons observed elsewhere in the world they are active infrequently because of the modern low rates of sediment supply to their heads the most active canyons are the sediment starved type and were observed near pointe des monts their activity is probably due to slope failures and to the presence of strong hydrodynamic processes therefore sediment supply is not the main mechanism responsible for modern canyon and channel activity in the lsle however sediment supply has been an important factor during the formation of the submarine channels and canyons their quasi exclusive occurrence on the quebec north shore is attributed to its larger watershed and important sedimentary delivery during deglaciation the quebec north shore watershed is 20 times greater than the quebec south shore watershed which favored the transport of greater volumes of sediment during the early holocene moreover the slope proximity to the shore led to the formation of longshore drift fed systems on the north shore when sediment supplied to rivers were transferred on a narrow shelf

holocene sea level change and delta growth fraser river delta british columbia the fraser river has been building its delta into the strait of georgia in southwestern british columbia for about the last 9000 years this period encompassed a relative sea level rise of some 13 m this study concerns the effects of the rise in sea level on the depositional evolution of the delta the lithostratigraphy of the delta was established by a series of drill cores four major lithostratigraphic units were defined peat organic rich silt interbedded silts and sands and massive sands these units were interpreted in terms of the delta s contemporary depositional environments including peat bog floodplain and intertidal zone analysis of the delta s depositional architecture and chronology indicates that the delta continued to prograde during the rise in sea level a marine transgression accompanied by the landward migration of marine and intertidal facies did not occur growth of the delta during the rise in sea level was accomplished by both vertical accretion and lateral progradation ver

late quaternary morpho sedimentology and submarine mass movements of the betsiamites area lower st lawrence estuary quebec canada abstract a complex submarine geomorphology was revealed from multibeam bathymetry and seismic reflection surveys conducted between 2001 and 2007 in the lower st lawrence estuary offshore betsiamites river quebec canada in this paper we describe the submarine morpho sedimentology of an area of 500 km 2 with focus on the consequences of four mass movement events the general morpho sedimentology of the area and submarine features resulting from mass movement processes channel erosion and gas seepage are described a spatio temporal sequence for the occurrence of the mass movements and a chronology for the failures are established we propose dates for four of the observed mass movement deposits a buried paraglacial debris flow deposit is dated as older than 9280 cal bp whereas a major landslide scar characterized by two topographic depressions on the shelf and a sediment lobe in the laurentian channel were dated around 7250 cal bp morphological observations and sediment core analyses allow us to identify a least two different recent i e less than 500 yr old debris flow accumulations associated with two recent earthquakes 1 the ad 1663 m 7 and 2 ad 1860 m 6 or ad 1870 m 6 5 earthquakes in addition to a complex geomorphology influenced by mass movements we have identified several regions on the shelf and on the laurentian channel with evidence of pockmarks which could potentially influence submarine slope stability in the estuary

origin and significance of high nickel and chromium concentrations in pliocene lignite of the kosovo basin serbia abstract trace element data from 59 pliocene lignite cores from the lignite field in the kosovo basin southern serbia show localized enrichment of ni and cr 33 304 ppm and 8 176 ppm respectively whole coal basis concentrations of both elements decrease from the western and southern boundaries of the lignite field low temperature ash and polished coal pellets of selected bench and whole coal samples were analyzed by x ray diffraction and scanning electron microscopy with energy dispersive x ray analyses these analyses show that most of the ni and cr are incorporated in detrital and to a lesser degree in authigenic minerals the ni and cr bearing detrital minerals include oxides chromites serpentine group minerals and rare mixed layer clays possible authigenic minerals include ni fe sulfates and sulfides analyses of three lignite samples by a supercritical fluid extraction technique indicate that some 1 11 of the ni is organically bound ni and cr bearing oxides mixed layer clays chromites and serpentine group minerals were also identified in weathered and fresh samples of laterite developed on serpentinized paleozoic peridotite at the nearby glavica and cikatovo ni mines these mines are located along the western and northwestern rim respectively of the kosovo basin where ni contents are highest the detrital ni and cr bearing minerals identified in lignite samples from the western part of the kosovo basin may have been transported into the paleoswamp by rivers that drained the two paleocene laterites some ni may have been transported directly into the paleoswamp in solution or alternatively ni may have been leached from detrital minerals by acidic peat water and adsorbed onto organic matter and included into authigenic mineral phases no minable source of ni and cr is known in the southern part of the lignite field however the mineral and chemical data from the lignite and associated rocks suggest that such a source area may exist

forced regressions and lowstand deltas holocene canadian examples abstract some canadian holocene deltas that formed during and after relative sea level falls of over 100 m are modern examples of forced regressions and lowstand deltas the principal controls on deltaic morphology and stratigraphy are rate of sea level change sediment supply timing type basin physiography and sediment dispersal processes in the receiving basin our observations indicate important alongstrike variability in deposition and erosion that affect facies architecture and stratal geometry during rapid relative sea level fall fluvial channels incise rapidly and do not migrate lateral channel migration which would produce a widespread fluvial unconformity begins once relative sea level fall has slowed and continues through the early part of relative sea level rise parts of he emerging shoreline cut off from the fluvial sediment supply become sites of shoreface incision into prodelta deposits regressive marine erosion and wave cut terraces are developed where sandy sediment is then supplied to the shoreface by rivers or updrift sources sharp based littoral sandbodies directly overlie the shoreface erosion surface other parts of the deltas below wave base that become abandoned through lobe switching can also be eroded by tidal currents deltas that have prograded into deep water show evidence of submarine slope instability such as submarine channel development base of slope turbidites and thick and thin skinned failures that disrupt clinoforms isopach trends reflect the existence of underlying structure with holocene sediments locally either thi ning or pinching over bedrock highs

the effects of historic abstraction of groundwater from the london basin aquifers on groundwater quality abstract the basal sands and chalk aquifers in the lee valley and enfield haringey areaas of north london have considerable potential for artificial recharge having been dewatered by groundwater abstraction since the late 1800s trials have been undertaken periodically since the mid 1950s however one of the drawbacks is the potential for developing poor quality groundwater as a result of pyrite oxidation in the basal sands analysis of pumped groundwaters from the basal sands has confirmed the presence of relatively high concentrations of dissolved so4 along with k ca total fe and li porewater chemistry profiles have been obtained from fresh cores through the basal sands and underlying chalk at four sites the site with the highest so4 concentration up to 33 000 mg 1 1 had a porewater ph of 3 45 and has remained dewatered owing to overpumping for more than 70 a water pumped from the chalk showed little evidence of these extreme conditions there was no overall correlation between the bulk pyrite or gypsum content of the sediment and the porewater so4 concentration within the sediment the principal mechanism governing the generation of so4 is the oxidation of pyrite which is present in small amounts the extremely high concentrations of so4 in the porewaters indicate that the extent of oxidation is controlled by the entry of air rather than the input of dissolved oxygen or nitrate in the groundwater or recharge water abstraction from the chalk aquifer over many decades has resulted in the dewatering of the overlying basal sands aquifer allowing air entry and has led to the localized oxidation of pyrite and the accumulation of poor quality porewater in the basal sands the rate of oxidation is probably greatest near to wells and boreholes which allow ready access of air the solutes produced are only available for abstraction after the water table has risen dilution with native chalk groundwater will tend to minimize potential water quality problems future oxidation will be minimized by maintaining a high water table

results and implications of seismic performance studies for duncan dam screening level studies indicated large zones of the foundation soil beneath duncan dam could be triggered to liquefy under the design earthquake resulting in flow slides that could lead to breaching of the dam in these studies estimates of the key soil parameters were obtained from an indirect procedure using penetration tests and seed s chart which is based on field experience during past earthquakes together with empirical correction factors for high confining stress and static bias this is state of the practice procedure in north america and is used because of the difficulty in retrieving and testing undisturbed samples of sand with the high confining stresses present at the site the indirect approach gave very low values of the key liquefaction properties of the soil and the use of such low values in analyses indicated that major and costly remedial measures were required thus a more direct approach was undertaken this involved both direct and semidirect determination of the key soil parame

sedimentary environments and postglacial history of the fraser delta and lower fraser valley british columbia the fraser river delta which is about 1000 km2 in area above low tide level has been built into the strait of georgia in southwestern british columbia during the holocene present day sedimentary

undrained shear strength of clean sands to trigger flow liquefaction this paper attempts to evaluate the undrained shear strength of sand during flow failures based on both laboratory testing and field observations in the laboratory the minimum shear resistance d

sub decadal submarine landslides are important drivers of deltaic sediment flux insights from the mississippi river delta front submarine mass failures triggered by energetic forcing events such as hurricanes and earthquakes are relatively well studied due to the potential for infrastructure damage and tsunami generation such failures are common on heavily sedimented margins where underconsolidated deposits are preconditioned to fail however studies of seafloor sediment movement between large events remain scarce using repeat bathymetric surveys of the mississippi river delta front mrdf we document substantial seafloor movement in absence of major hurricanes about 1 m yr of deepening was observed within preexisting failures with downslope sediment transport on the order of 10 5 m 3 yr outside failure features seafloor depths remained stable or showed minor 20 cm yr accretion mrdf volumetric sediment flux during hurricane driven mass failures is an order of magnitude greater than the annual flux during a quiescent interval when normalized by time however sediment flux during the quiescent interval 5 5 10 5 m 3 yr was half that of hurricane driven mass failures 1 1 10 6 m 3 yr these observations corroborate our wave modeling results which infer that even waves of 1 yr recurrence interval can generate differential seafloor pressures sufficient to trigger submarine landslides this does not exclude the possibility of river floods also being agents of failure these findings indicate that sub decadal submarine landslides are important to mrdf dynamics comparable to the role of major hurricanes and observation during seemingly quiescent periods is necessary to holistically assess sediment flux the periodicity and prevalence of moderate scale mass transport documented here corroborates similar recent studies offshore other deltas globally indicating that highstand mass and time budgets of shelf to deep sea sediment flux in addition to organic carbon and bioreactive particles may need to be revised

evaluation of the in situ state of fraser river sand les glissements de type coulee par liquefaction sont des phenomenes qui arrivent souvent dans le delta de la riviere fraser du cote de sand heads ces ruptures n ont pas trouve d explication et leurs causes restent du domaine de la speculation l etude d un tel glissement ayant eu lieu en 1985 dans la riviere fraser a proximite de sand heads a ete entreprise en utilisant les concepts d etats stationnaires pour qu un glissement par coulee impliquant la liquefaction de depots de sables puisse prendre place le sable doit presenter un ramollissement lors du cisaillement non draine et les contraintes de cisaillement en place doivent etre superieures a la resistance non drainee mobilisable on a effectue des essais de laboratoire sur des echantillons reconstitues de sable de la riviere fraser de facon a etablir les parametres d etat stationnaire les specimens de sol ont ete prepares par compaction humide et pluviation dans l eau des mesures de vitesse de propagation des ondes de cisaillement ont ete utilisees pour evaluer l etat en place des depots de sable recents et non cimentes on a trouve que l etat en place des depots recents au voisinage de sand heads se situait du cote l che de l etat stationnaire ce qui correspond aux instabilites observees sur le site

evaluation of static liquefaction potential of silty sand slopes the mechanism of instability in granular soils is explained and its requirement as a forerunner to the liquefaction of level or sloping ground is described case histories support the observation t

a delta plain sheet sand in the fraser river delta british columbia canada abstract borehole data in the fraser river delta demonstrate that a nearly continuous sand unit generally 8 to 20 m thick underlies the surficial silts and sands of most of the delta plain the sand unit consists of one or more sharp based fining upward sequences and is interpreted to be a complex of distributary channel deposits distributary channel migration and the resulting accumulation of channel sands has occurred primarily in a tidal flat environment due to the interaction of tidal and fluvial processes and the high proportion of sand in the sediment load this sand unit thus provides a model for sand rich river and tide dominated delta plains jetties now maintain the position of the main channel of the fraser river where it crosses the tidal flats and prevent channel migration and further storage of sand in the lower delta plain as a result more of the available sand is being transported directly to the river mouth where failures transport the sand downslope consequently these structures contribute to instability at the river mouth

the foreslope hills large scale fine grained sediment waves in the strait of georgia british columbia abstract the foreslope hills are a set of 20 m high 5 km long ridges at 230 350 m water depth in the south central strait of georgia occupying a 60 km 2 area at the base of the fraser river delta foreslope they are composed of clay silt and fine sand previous authors have interpreted them as 1 a single mass slide deposit 2 mud diapirs 3 in situ rotational failures and 4 creep deformation features but collaborative evidence for these interpretations is lacking seafloor surface morphological renders derived from recent multibeam sonar bathymetry data show linear evenly spaced symmetrical ridges with ridge bifurcation resembling wave ripples but on a much larger scale detailed multichannel and single channel seismic reflection data show sinusoidal internal reflections suggesting upslope migration the ridges occur within the uppermost portion of the holocene section in a very high sedimentation rate environment consequently they are probably less than 3000 years old moored current meter records for the region show reversing currents largely oriented normal to the ridge crests averaging 10 cm s with a maximum of 50 cm s this evidence combined with increasing documentation of large scale sedimentary bedforms in slope and rise environments suggests that the foreslope hills should be re interpreted as sediment waves upslope migration is typical of many large scale fine grained sediment waves the preferred physical interpretation for the creation and maintenance of the foreslope hills as sediment waves is the lee wave model requiring a phase shift in density stratified flow as it passes over the wavy topography maximum measured bottom currents are easily strong enough to entrain silt and clay delivered to the site by turbidity currents or by sediment plume fallout from fraser river outflow either strong flood tides or severe biannual density intrusions due to their intense stratification may be susceptible to lee wave formation and the creation of sediment waves leading to the observed pattern of upslope migration

the hydrogeochemistry of methane evidence from english groundwaters the presence of methane ch4 in groundwater is usually only noticed when it rises to high concentrations to date rather little is known about its production or natural baseline conditions evidence from a range of non polluted groundwater environments in england including water supply aquifers aquicludes and thermal waters reveals that ch4 is almost always detectable even in aerobic conditions measurements of potable waters from cretaceous jurassic and triassic carbonate and sandstone aquifers reveal ch4 concentrations of up to 500 g l but a mean value of 10 g l however aquiclude and thermal waters from the carboniferous and triassic typically contain in excess of 1500 g l such high concentrations have so far only been found at redox eh potentials below 0 mv but in general ch4 concentration and eh value are poorly correlated this suggests a lack of thermodynamic equilibrium which is confirmed by comparing pe values calculated from the redox couple c 4 c 4 with those derived from eh genesis of ch4 appears to occur on two timescales a rapid if low rate of production from labile carbon in anaerobic microsites in the soil and a much longer millennium scale of production from more refractory carbon methane is rarely measured in groundwater there is no single ionic determinand which acts universally as a proxy but a combination of high hco3 and low so4 concentrations or the reverse is an indication that high amounts of ch4 may be present

determination of easily accessible metal fractions in rocks by batch leaching with acid cation exchange resin the easily accessible fraction of metals in rocks is derived from leaching experiments aliquots of rock powders are mixed with ion exchange resin and distilled water the ph self adjusts to a value of 3 after batch leaching times of 2 48 hr at 70 c the resin is quantitatively separated from the rock powder and eluted with 4 n hno3 the metal contents of the leachates are determined and related to the respective contents of the whole rock the leaching kinetics of each element is related to that of a reference element aluminium is most commonly chosen as a reference element because it is considered to represent the dissolution behaviour of the main rock forming minerals the easily accessible trace element fraction eat is given as the percentage of leached element at 1 al dissolution these eat values are reproducible and independent from grain size and sample resin ratio the procedure is tested on basaltic glass and variably altered gneisses the glass shows congruent release of all metals a slightly crystalline glass of the same chemical composition displays heterogeneous leaching behaviour the leaching kinetics of variably altered gneisses provide insight into the mineralogical siting of elements and their accessibility to fluids consequences for rb sr dating of rocks are discussed

late glacial stratigraphy and history of the gulf of st lawrence reply the three dimensional configuration of the quaternary sediments in the gulf of st lawrence is described based on analysis of 8000 km of high resolution seismic reflection data complemented by anal

geochemical study of a crater lake lake pavin puy de dome france constraints afforded by the particulate matter distribution in the element cycling within the lake abstract suspended particles concentrations and settling particle fluxes collected by sediment traps were analyzed along a vertical profile in lake pavin france at the same time as dissolved element concentrations which are reported elsewhere viollier et al 1995 results for iron manganese cobalt vanadium molybdenum uranium barium rubidium and cesium are presented here particulate concentrations of all elements increase significantly just above the sediment water interface manganese iron and barium particulate concentrations exhibit a peak just above the oxic anoxic boundary molybdenum and uranium particulate concentrations increase drastically below the oxic anoxic boundary manganese and cobalt fluxes are at a maximum at 55 m depth above the oxic anoxic boundary for all other elements fluxes are at a maximum at 85 m depth just above the bottom of the lake in all cases settling particles fluxes are greater than buried fluxes indicating that a dissolution reaction occurs at the bottom of the lake particulate iron is essentially present as fe iii oxides in the mixolimnion as fe ii phosphates in the monimolimnion and as pyrite in the sediment the change in the fe bearing mineral leads to either important remobilisation or immobilisation of trace element into or from solution comparison of fluxes in the sediment trap at 85 m depth with dissolved concentrations gradients above the bottom leads to the rejection of the previous hydrodynamic model of the lake the fluxes and gradient data are consistent with the tritium data only if the arrival of sublacustrine waters occurs in the mixolimnion residence times of waters in monimolimnion in the model derived from the present study are about 20 times greater than the previous values the dissolved element concentrations profiles are explained only by eddy diffusion with a coefficient varying from about 20 m2 a at the bottom of the lake to 0 2 m2 a 1 at the mixolimnion monimolimnion boundary transport parameters obtained in this way allow a quantitative description of the element cycles within the lake and an estimation of the elemental ratio sedimentation versus exportation by the outlets

morphodynamics in sediment starved inner shelf submarine canyons lower st lawrence estuary eastern canada abstract the contemporaneous activity and sedimentary processes in a series of inner shelf submarine canyons located in the lower st lawrence estuary were examined using high resolution multibeam bathymetry and backscatter data the presence of crescent shaped bedforms csbs displaced upslope at the bottom of the canyons between 2007 and 2012 indicates that they are currently active through the remobilization of sediment by gravity flows however the shelf and shores of the region are characterized by the absence of sediment our results indicate that gravity flows currently eroding the canyon floors do not transport new material downslope coming from the shelf but rather remobilize in situ deglacial sediments within the canyon thalweg we suggest that slope failures and internal tides waves are responsible for sediment remobilization in these canyons although their role in the upslope migrating csbs is unclear this paper provides evidence that sediment supply is not a prerequisite for the modern activity of inner shelf submarine canyons when processes such as slope failures and internal tides waves are frequent enough to remobilize in situ sediments

large scale subaerial and submarine holocene and recent mass movements in the betsiamites area quebec canada abstract at least three major landslide events formed the submarine and subaerial betsiamites quebec canada landslide complex and mobilized an estimated total volume of 2000 million m3 2 km3 linkage between offshore and onshore geophysical investigations with borehole data and in situ testing allows reconstruction of the architecture of the betsiamites river delta area and leads to the identification of the main failure events the submarine scar of the betsiamites landslide complex may have resulted from a first failure dated at about 9250 cal bp which mobilized a minimum volume of 200 million m3 a second landslide dated at 7250 cal bp mobilized a volume of 1300 million m3 over an area of 54 km2 the betsiamites submarine landslide event dated at 7250 cal bp left the largest scar yet identified on the st lawrence estuary seafloor furthermore this paper demonstrates that the subaerial scar of the betsiamites landslide complex is a result of the colombier landslide event which was initiated by the 1663 earthquake and involved four successive failure phases one submarine and three subaerial the february 5th 1663 earthquake triggered a submarine landslide event which reached the shoreline and led in a short period of time successively to two subaerial flowslides in sensitive clayey material and a subaerial lateral spread the four failure phases mobilized a possible total volume of about 530 million m3 over an area of 20 km2 the colombier landslide event is among the largest documented historic landslides in canada the presence of submarine scars left by the early holocene events acted as predisposition factors for the development of the failure while the earthquake of 1663 was the main triggering factor of the first submarine failure

evaluation of preconsolidation pressure and the overconsolidation ratio from piezocone tests of clay deposits in quebec the preconsolidation pressure and overconsolidation ratio profiles are the most important factors related to the mechanical behaviour of clay deposits they are interpreted on the basis of a limited number of laboratory tests but the near continuous information provided by the piezocone can allow local data to be extrapolated to an entire site numerous methods have been proposed for relating piezocone data to preconsolidation pressure and the overconsolidation ratio but their validity is still uncertain in this paper nine methods are compared on the basis of data collected on 31 sensitive clay sites in quebec whose preconsolidation pressure profiles are well known each method is briefly presented and the most promising are identified the simplest method which directly relates preconsolidation pressure to net tip resistance also appears to be the most effective key words clay preconsolidation pressure overconsolidation ratio piezocone correlations

postglacial deltaic sediments southern fraser river delta british columbia the fraser river delta the largest delta on the west coast of canada has been built into the strait of georgia during the holocene drill hole and seismic reflection records reveal a succession of sedimentary units deposited during early holocene progradation of the delta these overlie an irregular surface developed on pleistocene drift mud and silt similar to sediments presently accumulating off the mouth of fraser river in the southern strait of georgia are conformably overlain by a thick unit of sandy foreset beds dipping gently to the south southwest into boundary bay and deposited in a foreslope environment the foreset unit is sharply overlain by a much thinner topset sequence comprising silt and sand deposited in intertidal fluvial channel and overbank environments and peat deposited in swamps and bogs fifteen accelerator mass spectrometry radiocarbon dates on shell and wood indicate that most of the deltaic sediments south of the main channel of fraser river were deposited between ca 7

geomorphology and potential slope instability on the fraser river delta foreslope vancouver british columbia le delta du fleuve fraser est localise dans une des regions ayant les plus hauts risques sismiques au canada et comprend pour une bonne part des sables fluviaux meubles tres connus comme possedant un potentiel eleve de liquefaction sismique des etudes recentes de la rive ouest du delta du fraser indiquent que la liquefaction cyclique durant un fort tremblement de terre est possible engendrant potentiellement des deformations incluant des extensions laterales un ramollissement cyclique et possiblement une coulee l on presente une evaluation preliminaire de la stabilite statique des pentes apres secousse dans laquelle les analyses ont ete limitees aux valeurs estimees des resistances au cisaillement ultimes ou a l etat d equilibre deduites de correlations avec les donnnees du terrain et aux contraintes de cisaillement calculees en partant de la bathymetrie du lit de mer existant l on a trouve que le coefficient postliquefaction de securite contre le glissement etait inferieur a l unite pour la pente de la terrasse superieure roberts en supposant une limite inferieure de resistance au cisaillement ultime equivalente a 0 06 p 0 les donnees pour evaluer la validite de cette hypothese sont insuffisantes cependant il y a abondance de depots de rupture le long de la base de la pente du delta

large scale mass wasting events on the fraser river delta front near sand heads british columbia although the fraser river delta front supports coastal structures including ports a lighthouse jetties submarine power cables and sewage pipelines the stability of the delta front is little understood five large scale mass wasting events at the mouth of the main channel near sand heads have been detected by comparing successive bathymetric surveys conducted by public works canada between 1970 and 1986 these events can involve the downslope movement of more than 1 106 m3 of silty sand and the landward retrogression of the delta front crest of up to 350 m or more morphologic and sedimentologic evidence suggests that these events are slope failures which result from the liquefaction of silty sand rapid deposition at the river mouth is likely a prerequisite for failure although interstitial gas tidal currents waves and earthquakes also may contribute to failure these results have important implications for the foundation stability of the sand heads lighthouse and future coastal structures in t

seabed instability due to flow liquefaction in the fraser river delta les ruptures par liquefaction de depots de sables l ches peuvent representer une menace importante pour les structures cotieres on a evalue a partir des concepts d etats stationnaires les contributions possibles de divers mecanismes de declenchement lors d une rupture par liquefaction qui a eu lieu en 1985 a l embouchure du chenal principal de la riviere fraser parmi les mecanismes qui ont pu declencher le glissement par liquefaction en 1985 on a etudie la sedimentation les vagues de surface et les marees basses l analyse montre qu une sedimentation rapide genere des contraintes de cisaillement dans la pente mais ne pourrait pas faire demarrer des ruptures par liquefaction lorsqu on evalue l effet des vagues de surface et leur capacite a causer des glissements de type coulee profonde on trouve qu il ne s accumule pas de pressions interstitielles significatives dues aux vagues de surface pouvant exister dans la region les marees basses ne peuvent pas non plus declencher de rupture dans des sables submerges et completement satures l apparition de gaz provoque cependant la desaturation des sediments ce qui peut induire des pressions interstitielles residuelles pendant les marees basses on emet donc l hypothese que c est la combinaison de sediments l ches de faibles quantites de gaz et de marees basses qui favorise les ruptures par coulees liquefiees dans le delta ces ruptures conduisent a des glissements regressifs

low temperature sulphate reduction biological versus abiological sulphate is considered to have been a major source of sulphide in strata bound and stratiform base metal sulphide deposits many of these deposits however appear to have been formed at moderate temperatures 200 c which poses the question by what mechanism s was sulphate reduced to sulphide two modes of reduction have been established experimentally 1 catalysis by sulphate reducing bacteria which at present is only known to occur below ca 100 c and 2 abiological reduction by ferrous iron or organic matter which has only been clearly shown above ca 250 c several attempts have been made to demonstrate abiological reduction below 200 c and some new data are presented here although the results do not exclude the possibility that such a reaction may be geochemically significant there has been no unequivocal demonstration of nett sulphide formation from sulphate at these temperatures recent studies of the microbiology of hydrothermal regions have opened up the prospect of bacterial sulp

liquefaction flow of submarine slopes under partially undrained conditions an effective stress approach the stability of submarine slopes is commonly assessed based on undrained soil response liquefaction flow may occur when pore pressure rise in soil elements under constant shear stress causes a reduction in effective stresses recent experimental studies have shown that a small net flow of water into an element results in additional pore pressure generation and further reduces its strength as a result soil elements can liquefy due to expansive volumetric strains that cannot be predicted by undrained analysis submarine deposits of the fraser river delta are known to contain high concentrations of methane gas tidal variations can cause unequal pore pressure generation with depth and time in these soils such changes reduce the effective stresses during low tides and may induce liquefaction flow of slopes due to partial drainage conditions an effective stress approach based on an elastic plastic stress strain relationship is presented to model liquefaction flow of sand a fully coupled analysis is carr

an in hole shotgun source for engineering seismic surveys we have conducted several source comparisons involving 12 gauge and 8 gauge buffalo guns a 7 3 kg sledgehammer and a 75 kg weight drop the results are strongly site dependent we found that when the near surface consisted of fine grained water saturated sediments the 12 gauge buffalo gun produced up to two orders of magnitude more energy than the conventional hammer across a broad frequency range under such conditions the gun produced the greatest improvement in energy between 200 and 400 hz where it yielded up to ten times more energy than the 75 kg weight drop this indicates that the buffalo gun may be particularly useful as a shallow reflection seismic source however at sites where the near surface materials were coarse grained and the water table was well below the ground surface the advantages of using an in hole shotgun source as opposed to a hammer or weight drop were minimal nevertheless in many areas we believe that the buffalo gun is an excellent source for engineering seismic surv

palaeohydrogeological reconstructions of the north lincolnshire chalk uk for the last 140 000 years abstract the influence of climatic change on hydrogeology is investigated by studying the evolution of the north lincolnshire chalk aquifer system during the last 140 000 years a numerical modelling approach is adopted using a density coupled finite difference model to reconstruct past groundwater environments two major controls on groundwater circulation are considered the position of sea level which determines the base level condition and the amount of recharge associated with different climates the quaternary history of the region is used to define aquifer boundary conditions and climate analogue data are used to determine likely recharge amounts model results cannot be compared against groundwater flow volumes or head other than for the present day situation and so hydrochemical evidence is used to constrain the model simulations the main finding is that recharge to the chalk aquifer during the last 140 000 years has been restricted to periods when the climate and sea level position have been similar to those of the present day the devensian cold period experienced very minor recharge with no chalk permeability development forest clearance since about 5000 years ago is predicted to have permitted an increase in the volume of freshwater recharge which increased the rate of chalk permeability development the presence of saline water at depth in the aquifer is argued on the basis of the model behaviour to be contributed by a component of upward cross formational flow

an assessment of the megathrust earthquake potential of the cascadia subduction zone the active tectonic setting of the southwest coast of canada and the pacific northwest coast of the united states is dominated by the cascadia subduction zone the zone can be divided into four segments where oceanic lithosphere is converging independently with the north american plate the winona and the explorer segments in the north the larger juan de fuca segment that extends into both canada and the united states and the gorda segment in the south the oceanic lithosphere entering the cascadia subduction zone in all segments is extremely young less than 10 ma of the other six zones around the pacific where young 20 ma lithosphere is being subducted five have had major thrust earthquakes megathrust events on the subduction interface in historic time an estimation based on potential area of rupture gives maximum possible earthquake magnitudes along the cascadia subducting margin of 8 2 for the winona segment 8 5 for the explorer segment 9 1 for the juan de fuca segment and 8 3 for the so

infaunal holothurian distributions and their traces in the fraser river delta front and prodelta british columbia canada abstract holothurians sea cucumbers constitute one of the largest and most abundant infaunal groups inhabiting the fraser river delta front 0 to 150 m water depth and prodelta greater than 150 m water depth the spatial distribution and density of animals reveal their preferred substrate grain sizes and their tolerance or sensitivity to various stress factors including salinity fluctuations available food resources sedimentation rate and pollution in the delta front below 25 m water depth below storm wave base holothurians are asymmetrically distributed with respect to the main distributary channel population densities primarily reflect asymmetry in grain size distributions across the delta front holothurians are absent or occur in low density in the sand dominated southern delta front sdf whereas the mud dominated northern delta front ndf is more heavily colonized sedimentation rate and nutrient content are equally important in holothurian distribution population densities of certain holothurians show significant increase where there are moderate sedimentation rates 2 4 cm yr 1 and river derived nutrient supply several subsurface traces and their surface expressions are attributed to holothurians subsurface traces include diminutive and robust artichnus thalassinoides and u shaped bio deformation structures on the sediment surface bio topographic structures such as mounds and funnel shaped depressions are produced by the activity of sea cucumbers of the holothurian generated traces only artichnus can conclusively be attributed to sea cucumbers based on the distributions of the trace makers of artichnus we hypothesize that in the rock record this trace fossil can be used as evidence of stable euhaline salinity conditions and sediment deposition and colonization below storm wave base artichnus occurs mainly in mud dominated 55 mud substrates

mineralogy and trace element geochemistry of gas shales in the united states environmental implications abstract this paper presents a compilation of published mineralogic and trace element data from nine gas shales in the united states formations analyzed include the antrim bakken barnett eagle ford haynesville marcellus new albany utica and woodford these mineralogic and trace element data can be used to assess the potential for environmental impacts during hydraulic fracturing impacts addressed in this study include 1 the potential for acid rock drainage generation during gas shale weathering 2 the distribution of trace elements in gas shales and comparison with regulatory guidelines and 3 the implications for environmental management of well cuttings the use of the mineralogic data to assess the fracability of the gas shales is also considered compilations of the mineralogy and geochemistry of gas shales can be a valuable resource for managing real and perceived environmental problems associated with their exploitation comprehensive environmental assessment to fully address these issues in addition to other potential environmental impacts will require collection and collation of additional data on the mineralogy and trace element geochemistry of gas and other hydrocarbon producing shales

proprietes caracteristiques des argiles de l est du canada the compilation of numerous geotechnical data has allowed the definition of the main physical mechanical and hydraulic properties of marine and lacustrine clays of eastern canada as well as the establishment of correlations between some of these properties the possible uses of these correlations are described this study shows that the clays of eastern canada exhibit a behaviour similar to that of other clays but that they are characterized by a higher degree of structuration keywords physical properties mechanical properties hydraulic properties clays canada correlations journal translation

chronologie th u des concretions calcaires des varves du lac glaciaire de deschaillons wisconsinien inferieur late pleistocene lake deschaillons varves from the central st lawrence lowlands represent a lithostratigraphic unit whose upper limit is defined by the overlying gentilly till which was laid down

diagenesis in oxidising and locally reducing conditions an example from the triassic skagerrak formation denmark abstract diagenetic changes in red and white parts of the skagerrak formation triassic from onshore wells in denmark were analysed by scanning electron microscope electron microprobe and petrographic microscope in reflected and transmitted light the diagenetic sequences of the red and white parts of the skagerrak formation are in many ways the same early infiltration clays followed by precipitation of caliche calcite dolomite mixed layer illite smectite quartz feldspar kaolin minerals illite chlorite and anhydrite with increasing burial differences between the red and white parts of the skagerrak formation comprise oxidation stage in detrital minerals oxidation of glauconite in the red part and reduction of biotite in the white part the presence of eogenetic authigenic minerals pyrite and poikilotopic calcite in the white part hematite and red coatings in the red part the amount of mesogenetic authigenic kaolin minerals larger in the white part the chemistry of mesogenetic authigenic chlorite mg rich in the red part and fe rich in the white part and the preservation stage of detrital opaque minerals magnetite hematite chromite ilmenite show none or minor alteration in the red part whereas they have been almost completely altered in the white part as the differences between red and white areas are found both in early eogenetic and in mesogenetic authigenic minerals different oxidising conditions must have prevailed immediately after the deposition and continued into burial oxidising conditions were dominant in the arid triassic climate and the widespread red colour of the skagerrak formation was probably formed during early diagenesis due to precipitation of iron oxides or hydroxides locally reducing areas were formed probably by oxidation of organic material precipitation of oxidised iron minerals was thus prevented and the original white colour was preserved reducing conditions prevailed until the reducing agent was exhausted then an outer rim of the reduction spot might locally have been secondarily oxidised these changing redox conditions explain the occurrence of hematized authigenic pyrite and crandallite group minerals in red areas

a massive sensitive clay landslide quyon valley southwestern quebec canada and evidence for a paleoearthquake triggering mechanism abstract a landslide debris field covering 31 km2 the presence of large sediment blocks up to hundreds of meters long and the exposure of deposits of a single landslide along the incised course of the quyon river are evidence of a massive failure of sensitive champlain sea glaciomarine sediments along the lower quyon valley southwestern quebec canada seventeen radiocarbon ages indicate that the failure occurred between 980 and 1060 cal yr bp twenty four additional radiocarbon ages reveal that nine landslides within a 65 km belt in the quyon ottawa area also occurred at approximately this time in combination the contemporaneous occurrence of ten landslides between 980 and 1060 cal yr bp the setting or morphology of five of the other failures and the close proximity of two of the failures to the quyon valley landslide provide circumstantial evidence of a paleoearthquake triggering mechanism the paleoearthquake is estimated to be mw 6 1 or larger with the epicenter within the west quebec seismic zone a common earthquake triggering mechanism for the three largest landslides in eastern canada suggests a close link between massive failures of sensitive glaciomarine sediments and the regional seismicity

effects of mass wasting on the stratigraphic architecture of a fjord valley fill correlation of onshore shear wave seismic and marine seismic data at trondheim norway abstract a combined record of onshore high resolution shear wave seismic and marine p wave seismic data shows the near shore stratigraphic organisation of a fjord valley fill at trondheim central norway the overall stratigraphy shows a typical fjord valley fill of up to 160 m in thickness that is composed of glaciomarine and fjord marine sediments overlain by deltaic deposits which in the onshore section are draped by an anthropogenic fill an interval characterised by low shear wave velocities below the onshore anthropogenic fills is shown by sampled drillings to comprise part clay and part organic deposits the seismic record reveals evidence of recurrent mass wasting events that include landslide debris turbidite deposits and channel features a chronological framework for the stratigraphy is provided by existing radiocarbon dates for local deglaciation and mass wasting events the combined onshore offshore datasets document the lateglacial to holocene development of an emerging fjord and delta system affected by major mass wasting events the architectural development of the younger part of the stratigraphy is interpreted as particularly affected by two known mass wasting events each involving several million m 3 of debris a thick layer of debris from a 3500 cal yr event probably resulted in a blockage of the subaqueous channels diversion of turbidity currents and deposition of lateral accretion packages whereby local fjord sedimentation temporarily increased a 2200 cal yr event resulted in a sudden reorganisation of the distributary system whereby distal delta sedimentation abruptly shifted north to northeastwards to an area temporarily subjected to marine erosion during fall of relative sea level the study adds to the understanding of landslides and low stiffness zones in the area of importance for near shore geohazard assessment the study also provides insight into the stratigraphic variability of fjord valley fills and highlights the interplay between fjord marine sedimentation marine abrasion delta progradation and mass wasting during late stages of fjord filling

a high resolution holocene paleomagnetic secular variation and relative paleointensity stack from eastern canada abstract a high resolution holocene paleomagnetic secular variation psv and relative paleointensity rpi stack was constructed using u channel paleomagnetic data from six radiocarbon constrained marine sedimentary sequences raised along the main axis of the laurentian channel eastern canada from its head to its mouth centennial to millennial scale declination and inclination features of the eastern canadian stack can be correlated within the dating uncertainties with other holocene north american icelandic and european psv records suggesting a common possibly hemispheric in character geomagnetic origin both magnetic inclination and declination of the eastern canadian stack are generally consistent with the time varying spherical harmonic model of the geomagnetic field cals7k 2 notably during the last 4000 cal bp in addition the eastern canadian holocene rpi stack reveals similar millennial and even centennial time scale variations consistent with some virtual axial dipole moment vadm reconstructions derived from absolute paleointensity data as well as with north american lacustrine rpi records accordingly these results suggest that the holocene paleomagnetic secular variation in north america is significantly driven by large scale 5000 km geomagnetic field changes at these timescales

detection of large prehistoric earthquakes in the pacific northwest by microfossil analysis geologic and palynological evidence for rapid sea level change 3400 and 2000 carbon 14 years ago 3600 and 1900 calendar years ago has been found at sites up to 110 kilometers apart in southwestern british columbia submergence on southern vancouver island and slight emergence on the mainland during the older event are consistent with a great magnitude m 8 earthquake on the cascadia subduction zone the younger event is characterized by submergence throughout the region and may also record a plate boundary earthquake or a very large crustal or intraplate earthquake microfossil analysis can detect small amounts of coseismic uplift and subsidence that leave little or no lithostratigraphic signature

small and large scale soft sediment deformations in a triassic lacustrine delta caused by overloading and seismicity in the ordos basin central china abstract the instability of an upper triassic lacustrine deltaic system in the southwestern ordos basin central china is examined based mainly on detailed measurements and descriptions of core data nine lithofacies associations are identified including undeformed and deformed channel deposits sandy and muddy slumps sandy debrites sandy dykes undeformed and deformed fringe silty deposits and muddy deposits quantification of the vertical and horizontal spatial distribution of these sediments reveals the deformed sediments can comprise more than one third of the entire cored interval in more than half of the wells indicating the significance of soft sediment deformation structures as essential components of this deltaic system a depositional model is constructed which highlights the location of deformed and remobilized sediments and their relationships with undeformed sediments in the proximal part of the delta the undeformed and deformed channel deposits and sandy slumps dominate the sandy sediments which are interbedded to form thick amalgamated sandstones in areas distant from these massive sandstones undeformed and deformed fringe fine grained deposits are well developed which could generate muddy slumps in the distal part of the delta besides undeformed and deformed fringe fine grained deposits sandy debrites are present as isolated sandbodies large scale sandy dykes formed between thick sandstones and adjacent mudstones two possible trigger mechanisms for initial deformation development are identified sediment overloading induced by sudden deposition of remobilized sediments and seismicity which caused large scale remobilization in the study area the high percentage of soft sediment deformation structures in this delta influences the reservoir heterogeneity of the three types of sandstones undeformed channel deposits sandy slumps and sandy debrites porosity permeability analysis reveals that reservoir quality of these three types varies significantly and thus distinguishing deformed sediments from undeformed deltaic sediments is essential for hydrocarbon development in this area

numerical modelling of tsunamis generated by hypothetical landslides in the strait of georgia british columbia a modified and corrected version of the viscous slide model of jiang and leblond 1994 is used to assess the tsunami risk associated with hypothetical underwater slope failures in two coastal areas of british columbia having potentially unstable sediment deposits a malaspina strait separating the mainland coast and texada island in the central strait of georgia and b roberts bank on the foreslope of the fraser river delta in the southern strait of georgia the intent of this study is to demonstrate the capability of the model for tsunami risk assessment and to improve upon previous studies of tsunami risk in the region based on reasonable submarine landslide scenarios the potential risk from tsunamis associated with slide failures has been examined but the likelihood of failure events themselves was not considered for the malaspina strait scenarios simulated tsunamis are generated by failure of a lobe of perched sediment situ ated on the slope of eastern texada island failure as a flow slide of the estimated 1 250 000 m3 of sediment generates wave troughs reaching 4 9 m and trough to crest heights of 6 to 8 m along the coast of texada island at cape cockburn on the opposite side of the strait wave heights of 1 5 to 2 0 m are produced for roberts bank simulated waves are examined for two separate failure scenarios the larger slide case 1 involves the failure of a sediment lobe with lateral dimensions of 7 3 km2 and volume of 0 75 km3 while the smaller slide case 2 fails a sediment lobe with dimensions of 4 2 6 km2 and volume of 0 23 km3 computations were made both for high 3 m and low 3 m tide conditions for both failure volumes maximum wave amplitudes up to 18 m for case 1 and 8 m for case 2 occur on the coasts of mayne and galiano islands opposite the source area wave amplitudes are much smaller 1 to 4 m on the mainl and coast because of the reflection of the initial waves from roberts bank additional numerical experiments were conducted for both regions to estimate the sensitivity of the computed tsunami wave heights to input parameters such as slide viscosity bulk density and slide position

identification and dating of a key late pleistocene stratigraphic unit in the st lawrence estuary and gulf eastern canada abstract a recently acquired 8 m long sediment core along with high resolution seismic reflection and subbottom profiler sections allowed the identification characterization and dating of a widespread seismic unit extending from the head of the laurentian channel lower st lawrence estuary to honguedo strait gulf of st lawrence eastern canada this seismic unit labelled unit 2 is characterized by a series of parallel high amplitude reflections with thicknesses ranging from 68 m near the head of the laurentian channel to 250 m in the st lawrence estuary leaving it very difficult to be reached by conventional coring operations here we reveal how we were able to trace and core this seismic unit in an area where it lays closer to the seafloor near the southern wall of the laurentian channel in the lower st lawrence estuary this seismic unit consists of two sedimentary facies sandy mud including ice rafted debris ird underlying faintly laminated to homogenous and plastic silty clays based on the sedimentary facies we interpret the upper clays as ice distal glaciomarine sediments and the lower sandier sediments as ice proximal glaciomarine sediments this interpretation is further supported by the fact that no seismic nor sediment facies present above seismic unit 2 throughout the estuary and gulf of st lawrence can be linked to glacial i e ice contact sediments such as till moraines esker etc sediments seismic unit 2 is highly disturbed by iceberg scouring in the gulf of st lawrence where it is found at shallower depths indicating that it was deposited during deglaciation the available ams 14c dates obtained in the ice proximal glaciomarine sediments indicate that the lower part of seismic unit 2 was deposited during local re advances or stillstands of the laurentide ice sheet margins in the goldthwait sea that began at or before the younger dryas cold event 11 100 10 000 yr bp and that seismic unit 2 can be used as a chronostratigraphic marker throughout the st lawrence estuary and northwestern gulf of st lawrence

evidence for a large earthquake and tsunami 100 400 years ago on western vancouver island british columbia abstract a peaty marsh soil is sharply overlain by a sand sheet and intertidal mud at tidal marshes near tofino and ucluelet vancouver island british columbia foraminifera and vascular plant fossils show that the buried soil was submerged suddenly and was covered quickly by sand radiocarbon ages place this event between 100 and 400 yr ago the coastal subsidence suggested by the submergence occurred in an area of net late holocene emergence perhaps during the most recent great earthquake on the northern part of the cascadia subduction zone the sand sheet overlying the peaty soil records the tsunami triggered by this earthquake similar stratigraphic sequences of about the same age have been reported from estuaries along the outer coasts of washington and northern oregon suggesting that hundreds of kilometers of the cascadia subduction zone may have ruptured during one or a series of plate boundary earthquakes less than 400 yr ago

release of selected chemical elements from shale drill cuttings to aqueous solutions of different ph abstract the effect of ph changes on leachability of light and heavy metals from shale drill cuttings generated from unconventional shale gas production was investigated cuttings being the primary byproduct generated from drilling operations belong to the potentially hazardous type of wastes due to presence of heavy and radioactive elements and remains of drilling fluid in this regard assessment of potentially dangerous components pdcs from rock waste materials was performed by application of batch leaching tests which has provided information on the sensitivity of leaching under externally imposed changes in ph natural or caused by treatment in specific scenarios the description of shale rocks mineralogical and chemical properties was performed by means of x ray fluorescence spectroscopy diffractometry as well as scintillation spectrometry the concentrations of released constituents due to the leaching tests were measured by atomic absorption spectrophotometry results were compared and discussed accordingly with the waste acceptable criteria of elution limits analysis of the substrate revealed that the elemental composition was dominated by light elements whereas heavy metals were present in trace amounts however noticeable release of barium 2 0 4 6 was also recorded which has originated from not only rock material but also drill mud minor mobility was observed for transition elements such as cr co fe mn ni zn cu and pb results revealed that drill cuttings follow the requirements for other than hazardous and municipal type of deposition with exception for barium moreover content of radioactive isotopes fulfill the requirements range of acceptable concentrations

the origin and isotopic composition of dissolved sulfide in groundwater from carbonate aquifers in florida and texas the 34s values of dissolved sulfide and the sulfur isotope fractionations between dissolved sulfide and sulfate species in floridan ground water generally correlate with dissolved sulfate concentrations which are related to flow patterns and residence time within the aquifer the dissolved sulfide derives from the slow in situ biogenic reduction of sulfate dissolved from sedimentary gypsum in the aquifer in areas where the water is oldest the dissolved sulfide has apparently attained isotopic equilibrium with the dissolved sulfate 34s 65 per mil at the temperature 28 c of the system this approach to equilibrium reflects an extremely slow reduction rate of the dissolved sulfate by bacteria this slow rate probably results from very low concentrations of organic matter in the aquifer in the reducing part of the edwards aquifer texas there is a general down gradient increase in both dissolved sulfide and sulfate concentrations but neither the 34s values of sulfide nor the sulfide sulfate isotope fractionation correlates with the ground water flow pattern the dissolved sulfide species appear to be derived primarily from biogenic reduction of sulfate ions whose source is gypsum dissolution although upgradient diffusion of h2s gas from deeper oil field brines may be important in places the sulfur isotope fractionation for sulfide sulfate about 38 per mil is similar to that observed for modern oceanic sediments and probably reflects moderate sulfate reduction in the reducing part of the aquifer owing to the higher temperature and significant amount of organic matter present contributions of isotopically heavy h2s from oil field brines are also possible

powerful unconfined turbidity current captured by cabled observatory on the fraser river delta slope british columbia canada turbidity currents are one of the main sediment transport processes on earth yet are notoriously difficult to monitor directly this article presents the first direct and high bandwidth observation of a turbidity current using a cabled sea floor observatory on 5 june 2012 a platform on ocean networks canada located in 107 m of water on the fraser river delta slope was displaced downslope and severed from its data cable the platform weighed ca 1000 kg in water the event took place during high river discharge high tides and rapid sediment accumulation on adjacent upslope areas of the sea floor data recorded as it tumbled downslope allow a reconstruction of the flow which is inferred to have been an unconfined turbidity current lines of evidence indicate that the flow came in as a bed hugging wedge and built up to between 1 m and 4 m in height as the head passed through comparison with laboratory data suggest that the flow was initially supercritical while the adjacent slope offset to the north clearly exhibits change over an annual resurvey period the bathymetry directly at the event location show no resolvable change over a period from seven months before the event to one month after sediment cores collected after the event were pervasively biototurbated and they contain no obvious deposit connected with this event the remarkable aspects of this research follow the flow was powerful enough to carry a 1 tonne platform and sever a heavily armoured cable the current occurred on the unchannelized open slope this powerful event failed to cause discernible seabed elevation change the flow was triggered by tidal conditions the event was detected by a purpose designed cabled observatory thus providing high bandwidth data and also alerting researchers in real time to mount follow on investigations

sediment transport by tidal currents and implications for slope stability fraser river delta british columbia tidal currents on the sandy southern slope of fraser river delta have generated dunes with heights of 0 5 3 5 m and lengths of 11 108 m dune geometry and migration measurements indicate net sediment transport to the northwest in the direction of flood tidal currents two current meters moored in the dune field showed greater frequencies of occurrence and higher mean current speeds in the flood direction compared with the ebb predictions from two bed material load models indicate sediment transport is overwhelmingly dominated by flood currents there is no obvious source of sand to replace sediment transported in the dune field suggesting net erosion of the surface a previous analysis of bathymetric data also shows recent erosion of the lower slope and overall slope steepening these patterns of erosion could lead to slope failure and damage to coastal structures

a river mouth submarine channel and failure complex fraser delta canada abstract high resolution seismic and side scan sonar surveying combined with coring of the fraser delta slope seaward of the main fluvial distributary has revealed a complex suite of morphologic units which include undisturbed delta slope sediments shallow rotational slides relict and active slope channels debris accumulations and ponded turbidites sediment transport through the main submarine channel is thought to be primarily by debris flows rather than by turbidity currents although this is a seismically active region the instability related features described here are probably due primarily to rapid sediment deposition on the upper delta slope at the river mouth

anomalous iron distribution in shales as a manifestation of non clastic iron supply to sedimentary basins relevance for pyritic shales base metal mineralization and oolitic ironstone deposits in previous investigations nearshore pyritic shale horizons in the mid proterozoic newland formation were interpreted to be due to non clastic colloidal iron supply by streams new data on the chemical composition of shales in the newland formation support this interpretation in these shales fe and al show a positively correlated trend that intercepts the fe axis above the origin these relationships suggest control of fe by clays via iron oxide coatings on clay minerals and the presence of an additional non clastic iron component shales from stratigraphic intervals during which pyritic shale horizons were deposited plot above the fe al trend typical for the remainder of the newland formation

post liquefaction stability and deformation analysis of duncan dam duncan dam is a 39 m high zoned embankment and is founded on a deep deposit of unconsolidated sediments consisting of sands silts and gravels that are susceptible to liquefaction during earthquake loading a comprehensive program of field laboratory and analytical investigations was conducted to evaluate the liquefaction potential of the foundation soils and performance of the dam during an earthquake this paper describes the evaluation procedures and analyses and presents results of the post liquefaction stability and deformation analysis of the dam analyses were carried out based on the total stress approach using two methods namely the lab method and seed s method the lab method is a site specific direct laboratory based approach utilizing soil parameters from laboratory tests on undisturbed soil samples obtained in situ after freezing the ground seed s method is indirect and is based on field penetration data and past experience from earthquakes the lab method indicates that the residual

modern sedimentary processes at the heads of martinez channel and steffen fjord chilean patagonia abstract chilean fjord sediments constitute high resolution archives of climate and environmental change in the southern andes to interpret such records accurately it is crucial to understand how sediment is transported and deposited within these basins this issue is of particular importance in glaciofluvial martinez channel and steffen fjord 48 s due to the increasing occurrence of glacial lake outburst floods glofs originating from outlet glaciers of the northern patagonian icefield hence the bathymetry of the head of martinez channel and steffen fjord was mapped at high resolution and the grain size and organic carbon content of grab sediment samples were examined results show that the subaquatic deltas of baker and huemules rivers at the head of martinez channel and steffen fjord respectively are deeply incised up to 36 m by sinuous channels the presence of sediment waves and coarser sediments within these channels imply recent activity and sediment transport by turbidity currents although several triggering mechanisms are possible we argue that elevated river discharge and the associated relatively high suspended sediment loads is the main cause of the occurrence of turbidity currents at the head of these fjords and are of key importance in shaping the fjord s subaquatic morphology this study shows that the heads of martinez channel and steffen fjord are dynamic sedimentary environments with rapidly migrating channels it highlights the importance of site selection and multi coring in any future project aimed at reconstructing environmental change using the sediments of either fjord

recent localised sulphate reduction and pyrite formation in a fissured chalk aquifer reply reduction oxidation reactions in the london basin aquifer system how may they be investigated

influence of placement method on the in situ density of hydraulic sand fills the range of densities achievable by hydraulic placement of sand straddles the boundary between values giving acceptable potential performance and those giving unacceptable potential performance this has led to concerns over the safety of structures using hydraulic fills such as the artificial drilling islands in the canadian beaufort sea liquefaction failures of hydraulically placed sand have occurred at four or more of these islands until recently the factors affecting in situ density were little understood data obtained from several artificial islands are presented and these are used to demonstrate the overwhelming influence of method of placement on in situ density the possible reasons for this influence and the implications for design are discussed recommendations are made for research that together with conclusions drawn in the paper should allow hydraulic fills to be used with more confidence in the future key words sand hydraulic fill liquefaction cone penetration test

stability of the fraser river delta front the distributary front deposits of the delta consist mainly of interlayered sand and silt and lie in one of the most seismically active zones in canada subsurface deposits at the north tend to be siltier than those at the south sediments on the surface of the delta slope range from clayey silts at the north to pure sands at the south slope angles vary from 23 at the head of the slope to 1 2 within 2 km beyond the tidal flats hydraulic bedforms observed on the sandy slopes southeast of the main channel gradually increase in size from small ripples to large asymmetric sand waves 2 3 m high and approximately 30 m long they are generated primarily by flood tidal currents which scour the seabed to a water depth in excess of 100 m formation of gullies which crease the delta slope probably is initiated principally by failure of oversteepened deposits at a channel mouth previous studies have suggested that the large hummocks or ridges at the base of the slope off the main channel have been formed by the co

hydrochemical evolution of the east midlands triassic sandstone aquifer england a detailed hydrogeochemical interpretation has been made of the red bed sherwood sandstone triassic aquifer of the east midlands of england on which a radiocarbon model has been used to establish a chronology of groundwaters along the flow line groundwater evolution is dominated by carbonate and sulphate mineral solution and precipitation and by redox reactions cation exchange reactions are negligible and the hydrogeochemistry has evolved in the absence of residual saline water three distinct zones are recognised 1 i recent groundwater mainly 100 y oxidising dominated by congruent dissolution of dolomite and by inputs from atmospheric and anthropogenic sources 2 ii groundwater age 103 104 y predominantly reducing dominated by incongruent dissolution of dolomite 3 iii groundwater age 104 y reducing conditions approach to isotopic and chemical equilibrium in the carbonate system dominance of gypsum dissolution the minor and trace element variation can be interpreted in relation to the principal geochemical reactions and recharge history na cl f and b are controlled by atmospheric inputs sr2 and mn2 trends can be explained by carbonate and sulphate mineral dissolution ba2 is derived from carbonates but controlled by barite equilibrium fe so42 no3 and u are strongly influenced by redox reactions the concentrations of transition metals and other elements remain very low only li and k are considered to represent additions by reaction of silicate minerals the extent of direct anthropogenic influence is probably limited to enhanced so4 no32 and possibly cu zn and pb in zone i

hydrochemical trends palaeorecharge and groundwater ages in the fissured chalk aquifer of the london and berkshire basins uk the hydrochemical radiochemical stable isotope 14c and dissolved noble gas composition of groundwaters has been determined along two profiles across the confined fissured chalk aquifer of the london basin of southern england and for selected sites in the adjacent berkshire basin during downgradient flow in the london basin aquifer the groundwater chemistry is modified by water rock interactions congruent and incongruent reaction of the carbonate lithology resulting in enhanced mg ca and sr ca ratios and 13c contents with increased residence times redox and ion exchange reactions and towards the centre of the basin mixing with a residual saline connate water stored in the chalk matrix there is evidence from anomalous water chemistries for a component of vertical leakage from overlying tertiary beds into the confined aquifer as a result of historical dewatering of the aquifer dissolved noble gas contents indicate the climate was up to 4 5 c cooler than at present during recharge of the waters now found in the centres of both basins stable isotope 2h and 18o depletions correspond to this recharge temperature change for evolved waters having 13c 8 pdb a negative linear correlation is demonstrated between derived recharge temperatures and 13c values which is interpreted as mixing between relatively warm light isotopic fracture borne waters and cooler stored waters of the matrix having a 13c signature more or less equilibrated with the chalk from geochemical 14c 4he age estimates the abstracted water is interpreted as being either of wholly holocene post devensian glacial origin or an admixture of holocene and late pleistocene pre glacial cold stage interstadial recharge devensian pleniglacial stage waters of the last glacial maximum are not represented

time and size of a giant earthquake in cascadia inferred from japanese tsunami records of january 1700 geological evidence shows that great earthquakes have occurred in the recent prehistoric past in the cascadia subduction zone off the pacific coast of north america the most recent event or series of events is dated at about 300 years ago1 4 but the precise date and magnitude have not been determined geological investigations have not been able to distinguish a single giant earthquake from a series of great earthquakes occurring over a timespan of a decade or two4 although this information is important for the assessment of future hazard5 we have found several tsunami records in japan from ad 1700 with no indication of a local cause historical earthquake records and palaeoseismic evidence indicate the absence of a large earthquake in 1700 in south america alaska or kamchatka leaving cascadia as the most likely source of this tsunami the estimated time of the earthquake is the evening about 21 00 local time of 26 january 1700 the magnitude is estimated as 9 from the tsunami heights in which case the earthquake ruptured the entire length of the cascadia subduction zone2 these estimates are consistent with native american legends that an earthquake occurred on a winter night6

unexpected fast rate of morphological evolution of geologically active continental margins during quaternary examples from selected areas in the italian seas abstract in the last few decades seafloor imagery systems have drastically changed our vision of a mostly regular and depositional marine landscape evidencing how erosive and mass wasting processes are widespread in the marine environments with particular reference to geologically active areas most of the previous studies have focused on the characterization of these features whereas a very few ones have tried to estimate what is the extent and order of magnitude of erosion rates in these areas in this paper we show several examples from some of the most geologically active margins off southern italy aimed to a quantify the spatial extent of such processes b better understand the role of submarine erosion in the morphogenesis of the coastal sector and c try to roughly estimate the order of magnitude of erosion rates in these areas the results are impressive with mass wasting features widespread from coast down to 2600 affecting from the 52 up to 97 of the whole continental slope because of the narrow or totally lacking shelves in these areas mass wasting processes often occur close to the coast and match embayment of the coast so indicating a key role in the morphogenesis of coastal sector with significant implication on the related geohazard finally based on a morphological approach integrated by available stratigraphic constraints we have roughly estimated average erosion rates in these areas ranging from at least some mm year to a few cm year i e some hundreds of meters up to kilometers eroded in each eustatic cycle despite the large uncertainties of these estimates as well as their spatial and temporal variability in response to regional and local factors the obtained values are very high and they should be considered for future model of margin evolution source to sink computation and marine coastal geohazard assessment

holocene paleomagnetic records from the st lawrence estuary eastern canada centennial to millennial scale geomagnetic modulation of cosmogenic isotopes two long holocene piston cores md99 2220 and md99 2221 were raised from the st lawrence estuary eastern canada because of the expanded holocene sediment sequence this location provides a u channel based paleomagnetic study supported by an accelerator mass spectrometry ams 14c chronology rock magnetic and sedimentological data indicates that these sediments provide a paleomagnetic directional secular variation psv and relative paleointensity rpi proxy records for the last 8500 cal bp sedimentation rates vary from 1 2 to 4 2 m kyr comparison of inclination and declination features with other north american holocene psv records are generally consistent and temporal offsets are within chronological uncertainties the normalized natural remanent magnetization intensity record a rpi proxy from the postglacial sediments of core 2220 compares favorably with north american and european holocene rpi records at millennial and even some centennial timescales comparisons between core 2220 rpi proxy and the 10be flux record from the greenland summit gisp2 ice core finkel and nishiizumi j geophys res 102 1997 26699 26706 and a 14c production rate record bond et al science 294 2001 2130 2136 suggest that geomagnetic modulation may control the millennial and even some centennial scale variability within cosmogenic isotope records this implies that the core 2220 rpi record reflects changes in global scale geomagnetic field at these timescales

seismotectonic characteristics of the lower st lawrence seismic zone quebec insights from geology magnetics gravity and seismics the estuary of the st lawrence river between baie comeau and sept iles is an area where 50 to 100 earthquakes are detected yearly this study defines the major lineaments of the precambrian basement and compares them with mapped faults where possible and examines their possible correlation with the local earthquakes onshore aerial photographs remote sensing images and field mapping are used to identify the geological structures of the precambrian basement while offshore they are interpreted from potential field magnetic gravity and a published synthesis of seismic reflection profiles the precambrian basement dips towards the southeast under the appalachian nappes with normal faults with kilometre scale throw and east west or ene wsw strikes onshore a system of normal brittle faults with a complex history of movements crosscuts both the precambrian basement and the overlying ordovician sedimentary cover most earthquakes occur beneath the st lawrence river at focal depths between about 7 and

groundwater sources and geochemical processes in a crystalline fault aquifer the origin of water flowing in faults and fractures at great depth is poorly known in crystalline media this paper describes a field study designed to characterize the geochemical compartmentalization of adeep aquifer system constituted by a graben structure where a permeable fault zone was identified analysesof the major chemical elements trace elements dissolved gases and stable water isotopes reveal theorigin of dissolved components for each permeable domain and provide information on various watersources involved during different seasonal regimes the geochemical response induced by performinga pumping test in the fault zone is examined in order to quantify mixing processes and contributionof different permeable domains to the flow reactive processes enhanced by the pumped fluxes are alsoidentified and discussed the fault zone presents different geochemical responses related to changes in hydraulic regime theyare interpreted as different water sources related to various permeable structures within the aquifer during the low water regime results suggest mixing of recent water with a clear contribution of olderwater of inter glacial origin recharge temperature around 7 c suggesting the involvement of watertrapped in a local low permeability matrix domain or the contribution of large scale circulation loops during the high water level period due to inversion of the hydraulic gradient between the major permeablefault zone and its surrounding domains modern water predominantly flows down to the deep bedrockand ensures recharge at a local scale within the graben pumping in a permeable fault zone induces hydraulic connections with storage reservoirs the overlaidregolith domain ensures part of the flow rate for long term pumping around 20 in the present case during late time pumping orthogonal fluxes coming from the fractured domains surrounding the majorfault zone are dominant storage in the connected fracture network within the graben structure mainlyensures the main part of the flow rate 80 in the present case reactive processes are induced by mixingof water from different sources and transfer conditions a specific approach is applied to quantify thereaction rate involved along the pumping time autotrophic denitrification coupled with iron mineralsoxidation is highlighted and water rock interaction is clearly enhanced by the flux changes induced bypumping

liquefaction and flow failure during earthquakes two aspects of seismically induced liquefaction are discussed which are of vital engineering significance the triggering condition and the consequences of liquefaction the triggering condition is examined with respect to liquefaction analysis note being taken of the onset condition which is governed by cyclic strength consequences of liquefaction are discussed with respect to post seismic stability analysis in which the residual strength plays a major role procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced and the applicability of this method for estimating associated ground settlements is discussed the evaluation of residual strength requires a better understanding of undrained sand behaviour results of extensive laboratory rests on japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better the results of laboratory tests on silty sands are examined in the same way ah the results are

baseline geochemical conditions in the chalk aquifer berkshire u k a basis for groundwater quality management the chalk aquifer is the most important british aquifer and is also important over much of northern europe aquifer protection requires a sound knowledge of the baseline conditions and how these might vary or have varied with time this detailed geochemical study of a representative area of chalk in berkshire u k includes a consideration of several components 1 the inputs from the atmosphere 2 the interstitial water of the soil and the unsaturated zone 3 the interstitial water in the confined and unconfined sections of the aquifer and 4 the saturated mainly fissure flow along the hydraulic gradient which forms an important water supply of the thames valley region atmospheric inputs form an important source of some elements but the dominant chemical characteristics of the chalk groundwater are acquired during percolation through the soil and the upper unsaturated zone during saturated flow downgradient the chemistry is modified mainly by incongruent reactions of the carbonate matrix and by redox reactions and only to a minor extent by exchange reactions and mixing with residual saline connate water the incongruent reaction of carbonate results in a marked increase in the mg ca ratio and the sr and 13c contents of the groundwater with increased residence time oxygen concentrations are reduced mainly by oxidation of fe2 and the onset of reducing conditions allows dissolved fe2 to increase and rapid denitrification to occur the salinity profile through the confined chalk confirms that residual connate water up to one fifth sea water concentration still remains at depth and this accounts for some salinity increase in the confined groundwater resulting from fissure water pore water diffusional exchange timescales for groundwater movement have been established using tritium radiocarbon and indirectly using inert gas ratios and stable isotope ratios on balance it is concluded that all abstracted water is of holocene age although inert gas temperatures indicate cooler climatic conditions for recharge for some of the confined groundwater the implications for development and aquifer protection are discussed especially the prospect of natural in situ denitrification problems of fe solubility and the recognition of groundwater of different maturities