paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

influence of water column anoxia and sediment supply on the burial and preservation of organic carbon in marine shales abstract previous work has suggested that the laminated organic rich and bioturbated organic poor shales of the camp run member of the late devonian early mississippian new albany shale formed under anoxic and oxygenated bottomwater conditions respectively and that the interbedding of the two facies was due to the vertical oscillation of a water column anoxic oxic boundary where it impinged on the basin margin we have extended this analysis by examining the chemical and mineralogical differences between the two shale facies in a single borehole core by seeking evidence for deposition of the laminated shales under bottom water oxia or anoxia and by determining whether the laminated shales formed when the carbon supply to the sea floor was higher the results of this study show that the laminated and bioturbated shales are mineralogically and chemically distinct relative to al an index of the aluminosilicate content si ti fe p na ba co cr cu mo ni v zn and zr are all higher whereas mn ca mg and sr are lower in the laminated compared with the bioturbated shales the differences are due to a higher quartz feldspar titanite ilmenite and zircon content in the laminated shales probably indicating a coarser grain size and the greater abundance of manganoan calcite in the bioturbated shales dissolved oxygen was present in bottom waters during the deposition of some of the laminated shale intervals because of the presence of manganoan calcite a phase that can only form in sediments with an oxic surface in addition the organic matter preserved in the two shale types is isotopically different 13corganic values are 1 9z permil lighter on average in the laminated compared with bioturbated intervals possibly indicating a larger fraction of terrestrial organic matter in the latter 15n values are 1 9z permil lighter on average in laminated compared with bioturbated intervals possibly indicating a larger fraction of terrestrial organic matter in the latter 15n values are 1 9z permil lighter on average in laminated compared with bioturbated intervals suggesting that nutrient drawdown was less during the deposition of the organic rich laminated shales the chemical mineralogical and isotopic contrasts between the two shale facies of the camp run member indicate that the conditions of sedimentation were different during their deposition the difference was possibly related to variations in sea level which would have caused the camp run shoreline to move closer to and farther from the core site causing in turn the deposition of coarser and finer grained sediments that contained different mixtures of marine and terrestrial organic matter bottomwater conditions were anoxic during deposition of most laminated intervals bottom water anoxia or dysoxia led to decreased burial and preservation of the essential nutrient phosphorus in the laminated organic rich shales relative to the rocks deposited beneath better oxygenated bottomwaters increased availability of phosphorus in the water column on long timescales leads to increased productivity and a higher settling flux of organic matter causing bottom water oxygen levels to fall this is consistent with the nitrogen isotope evidence suggesting that production was probably higher during the deposition of the organic rich shales thus production variations coupled with enhanced sedimentary regeneration of phosphorus from sediments related to low oxygen bottom water concentrations provide a general mechanism for the formation of the alternating facies of this member of the new albany shale

lack of evidence for enhanced preservation of sedimentary organic matter in the oxygen minimum of the gulf of california a test of the hypothesis that hydrogen rich organic matter accumulates preferentially in sediments under oxygen minima has been carried out by examining the composition of laminated and homogeneous diatomaceous sediments of the guaymas basin in the gulf of california the laminated sediments occur where an intense oxygen minimum intersects the slope around the margins of the basin above and below the depth of the oxygen minimum the sediments are homogenized by a burrowing infauna the two sediment types have very similar bulk chemical and mineral compositions and the organic matter is overwhelmingly marine the total organic carbon contents and rock eval parameters hydrogen and oxygen indices of the two sediment types are not significantly different whereas a road organic carbon maximum in the homogeneous sediments is centered at roughly 1200 m depth on the slope of the basin this maximum lies deeper than the core of the oxygen minimum thus both the concentration and the nature of the organic matter in the sediments of this highly productive marginal marine basin are not related to the concentration of dissolved oxygen in the bottom waters

environmental significance of bedrock jointing in southern ontario canada the bedrock surface of many glaciated areas is obscured by thick drift deposits in southern ontario canada the buried bedrock surface is dissected by channels infilled with glacial deposits as much as 150 m thick that are part of a wider mid continent preglacial fluvial system that predates formation of the modern great lake basins the infills of bedrock channels form major groundwater aquifers influence regional groundwater flows and contaminant migration to lake ontario and may localize the release of thermogenic methane and radon within heavily urbanized surface environments a quantitative comparison of the regional pattern of bedrock joints and the orientation pattern of buried bedrock channels and modern river valleys shows that all these orientation patterns are virtually coincident buried bedrock channels in south central ontario are not part of a simple antecedent drainage system but were likely predesigned by bedrock joint patterns that have subsequently been propagated upward into overlying pleistocene sediments joints in sediments are of considerable environmental significance for example subsurface contaminant and gas migration in fine grained clayey sediments and of many origins stress release desiccation etc but are widely assumed to be a predominantly surface related phenomena the existence of deeper joints has been noted by some authors but their origin is obscure data presented herein from south central ontario confirm that in addition to surface related joints a second population of bedrock related joints reflecting the upward propagation of bedrock fractures is present in pleistocene sediments of south central ontario

an improved estimate of lithospheric thickness based on a reinterpretation of tilt data from pleistocene lake algonquin a reinterpretation of relative uplift data associated with the deformed strandline of pleistocene lake algonquin is presented the new analysis is based on a dynamic model that allows for the finite rate of retreat of the laurentide ice sheet and the viscous relaxation of the earth s mantle attention is also paid to the effects of the shape of the load profile on the interpretation in the context of this model the thickness of the lithosphere is constrained to be not more than 85 km this value is based on the assumption of a model ice sheet with a parabolic cross section if the load has a sharper edge a thickness of 110 km is consistent with the data these revised values slightly exceed walcott s original estimate they are on the other hand distinctly lower than the value of 200 km which has recently been inferred by peltier for the thickness of the north american lithosphere the relations between the different estimates are briefly discussed it is suggested that a reconciliation of the estima

linear zones seismicity and the possibility of a major earthquake in the intraplate western lake ontario area of eastern north america seismic hazard assessments conducted in eastern canada rely on seismological data which are essential but alone inadequate that is because the earthquake record is too short to provide a representative picture of where large earthquakes have occurred in the past consequently seismic hazard may be underestimated in areas such as that encompassing western lake ontario that are devoid of documented large earthquakes to attempt to ascertain the likelihood of a major earthquake occurring in that highly populated and industrialized area three regionally extensive geophysically expressed lineaments were investigated and the results were combined with available seismological information the most conspicuous is the niagara pickering linear zone within which there have been at least two if not three periods of brittle faulting including displacements compatible with the current stress field it also appears to represent the same major structure as the akron magnetic boundary in eastern ohio the site of the mb 4 9 leroy earthquake the second is the georgian bay linear zone which extends from georgian bay to new york state it displays evidence of recent outcrop scale faulting an alignment of earthquakes along its southwestern boundary and a possible spatial relationship to other earthquakes including two of m 5 lastly there is the hamilton lake erie lineament which is parallel and proximal to a possible fault and coincides with a linear array of small to moderate earthquakes all three converge on the western lake ontario area which has a higher frequency of seismicity than the adjacent areas thus the western lake ontario area might have a greater potential to experience a major earthquake than heretofore believed resume les evaluations des risques sismiques dans l est du canada sont fondees sur les donnees sismologiques dont

comparative study of organic matter preservation in immature sediments along the continental margins of peru and oman part i results of petrographical and bulk geochemical data abstract detailed petrographical and bulk geochemical investigations of organic matter om have been performed on sediments deposited below or close to upwelling areas offshore peru odp leg 112 sites 679 681 688 and oman odp leg 117 sites 720 723 724 in order to obtain a quantitative understanding of its accumulation and degradation microscopical as well as nanoscopical investigations reveal that the om in sediments affected by upwelling mechanisms mainly up to 98 consists of unstructured amorphous organic aggregates without any apparent biological structures in sediments which are not or to a lesser extent affected by upwelling site 720 terrestrial om predominates organic carbon toc contents are highly variable and range between 9 8 in sediments deposited below upwelling cells and 0 2 in sediments outside the upwelling zone the toc sulphur ratios of the sediments scatter widely the samples from the deep water locations sites 688 and 720 show c s ratios of normal marine sediments whereas at the other locations no correlation or even a negative correlation between sulphur and toc concentration exists in most of the upwelling influenced sediments om contains a significant amount of sulphur the incorporation of sulphur into the om followed microbial sulphate reduction and occurred in the upper meters of the sedimentary column below om is still present in vast amounts and relatively hydrogen rich but is nevertheless non metabolizable and becomes the limiting factor for bacterial sulphate reduction according to mass balance calculations 90 99 of the om produced in the photic zone was remineralized and 1 3 was consumed by microbial sulphate reduction the aerobic and anaerobic processes have greatly affected degradation and conservation of om

how depositional conditions control input composition and degradation of organic matter in sediments from the chilean coastal upwelling region abstract in a comprehensive study we compared depositional conditions organic matter om composition and organic carbon turnover in sediments from two different depositional systems along the chilean continental margin at 23 s off antofagasta and at 36 s off concepcion both sites lie within the chilean coastal upwelling system and have an extended oxygen minimum zone in the water column however the northern site 23 s borders the atacama desert while the southern site 36 s has a humid hinterland eight surface sediment cores up to 30 cm long from water depths of 126 1350 m were investigated for excess 210pb 210pbxs activity total organic and total inorganic carbon concentrations toc and tic respectively c n ratios organic carbon isotopic compositions 13c chlorin concentrations chlorin indices ci and sulfate reduction rates srr sediment accumulation rates obtained from 210pb analysis were similar in both regions 0 04 0 15 cm yr 1 at 23 s 0 10 0 19 cm yr 1 at 36 s although total 210pbxs fluxes indicated that the vertical particle flux was higher at 36 s than at 23 s we propose that sediment focusing in isolated deposition centers led to high sediment accumulation rates at 23 s furthermore there were no indications for sediment mixing at 23 s while bioturbation was intense at 36 s 13c values 24 5 to 20 1 vs vpdb and c n ratios molar 8 6 12 8 were characteristic of a predominantly marine origin of the sedimentary om in both investigated areas the extent of om alteration in the water column was partly reflected in the surface sediments as chlorin concentrations decreased and c n ratios and ci increased with increasing water depth of the sampling site srr were lower at 23 s areal srr 0 12 0 60 mmol m 2 d 1 than at 36 s areal srr 0 82 1 18 mmol m 2 d 1 which was partly due to the greater water depth of most of the sediments investigated in the northern region and consistent with a lower quality of the sedimentary om at 23 s reaction rate constants for toc degradation that were obtained from measured srr ksrr 0 0004 0 0022 yr 1 showed a good correspondence to ktoc that were derived from the depth profiles of toc 0 0003 0 0014 yr 1 both ksrr and ktoc reflect differences in om composition at 36 s they were related to the degradation state of bulk om represented by c n ratios whereas near 23 s they were related to the freshness of a small fraction of labile om represented by ci our study shows that although rates of organic carbon accumulation were similar in both investigated sites the extent and kinetics of organic carbon degradation were closely linked to differing depositional conditions

neotectonic faulting in metropolitan toronto implications for earthquake hazard assessment in the lake ontario region persistent small scale seismicity around the western end of lake ontario together with larger events in eastern north america have focused attention on the seismotectonic and neotectonic conditions of southern ontario and adjacent new york state newly discovered normal faults that offset both bedrock and overlying quaternary sediments by as much as 1 25 m were discovered along the rouge valley in metropolitan toronto this location is within a zone marked by the intersection of three major lineaments and an elevated level of seismicity these faults result from reactivation of east west oriented fractures in ordovician shales structures are exposed in section only and have no surface expression suggesting that others may have gone undetected the origin of the faults is not yet well established although they may represent the effects of uplift consequent upon isostatic rebound aided by high horizontal compressive stress nevertheless their development in the recent geologic past has important implications for regional seismic hazard assessment because they occur within 7 km of the pickering nuclear power plant

the analysis and prediction of lateral instability in highly stressed near surface rock strata the potential for lateral instability of highly stressed near surface sedimentary rocks such as the paleozoic deposits of southern ontario and western new york state is investigated analytically the minimum magnitude of the in situ stress required for a pressure ridge to form is easily computed once values are obtained for the stratum thickness and short term young s modulus the weight of overburden and the residual friction with the over and underlying material consideration is also given to the increased likelihood of instability associated with excavations of different widths and depths keywords rock excavations quarries instability pressure ridges mechanisms

coupled primary production benthic foraminiferal assemblage and sulfur diagenesis in organic rich sediments of the benguela upwelling system abstract episodically deposited dark organic rich pleistocene and late pliocene sediments from the lower continental slope off southwest africa reveal complex interactions between changes in primary production benthic foraminiferal assemblage and anaerobic microbial processes the organic rich layers contain diatom assemblages characteristic of intense seasonal coastal upwelling whereas stratigraphically adjacent sediments reflect pelagic primary production coastal upwelling dominated depositional intervals coincide with periods of enhanced carbon flux to the seafloor enhanced organic carbon export during dark layer deposition was accompanied by decreases in the diversity of benthic foraminifera to few opportunistic species adapted to high phytodetritus accumulation rates and low o 2 conditions in all sediments the sulfur isotopic composition of pyrite indicates redox cycling of sulfide close to the sediment water interface the sulfur isotopic evidence and the permanent presence of abundant low o 2 adapted benthic foraminifera throughout the organic rich layers suggest an oxygenated benthic environment efficient oxidation of sulfide and removal of sulfide by sulfidization of organic matter inhibited buildup of toxic hydrogen sulfide from bacterial sulfate reduction at the sediment water interface these data imply that in continental slope sediments underneath productive surface waters benthic dysoxic conditions are maintained by the lateral advection of dissolved oxygen to support a small but well adapted benthic community

glacial isostatic deformation of the great lakes region tilting of ancient shorelines of the great lakes region has been studied for more than a century nevertheless fundamental disagreements exist among both glacial geologists trying to understand the chronology of lake events geophysicists investigating the causes of tilting and glaciologists attempting to reconstruct ice sheet thickness along the southern perimeter of the laurentide ice sheet fundamental to many of these studies is the belief that the southern part of the great lakes region has been geodynamically stable for at least the past 11 000 yr results of our numerical model of the glacio isostatic process for a spherical layered self gravitating viscoelastic earth suggest constraints upon earth models shoreline chronologies and ice sheet thickness as a test of the model predictions were compared to observations of outlet chronology and isobases of both ancient shorelines and modern tilting indicated by lake level gauges earth models with a uniform viscosity mantle resulted in the best fit to observed shorelines earth models with a low viscosity asthenosphere or a high viscosity lower mantle do not predict deformation consistent with known outlet chronologies an ice sheet with thickness of 2 000 m over the region results in an excessive amount of tilting in most instances whereas a much thinner ice sheet 700 m although in better agreement with the data generally resulted in underestimates none of the results suggests stability in the southern great lakes region at any time predictions indicate instead that submergence of ancient shorelines has complicated the record there

sedimentary organic matter preservation a test for selective degradation under oxic conditions the authors report here a test of the hypothesis that the extent of organic matter preservation in continental margin sediments is controlled by the average period accumulating particles reside in oxic porewater immediately beneath the water sediment interface oxygen penetration depths organic element compositions and mineral surface areas were determined for 16 sediment cores collected along an offshore transect across the washington continental shelf slope and adjacent cascadia basin individual amino acid sugar and pollen distributions were analyzed for a 11 to 12 cm horizon from each core and sup 14 c based sediment accumulation rates and stable carbon isotope compositions were determined from depth profiles within a subset of six cores from representative sites sediment accumulation rates decreased and dissolved o sub 2 penetration depths increased offshore along the sampling transect as a result oxygen exposure times oet increased seaward from decades mid shelf and upper slope to more than a thousand years outer cascadia basin organic contents and compositions were essentially constant within individual sediment cores but varied consistently with location in particular organic carbon surface area ratios decreased progressively offshore and with increasing oet three independent compositional parameters demonstrated that the remnant organic matter in farther offshore sediments is more degraded both concentrationmore and compositional patterns indicated that sedimentary organic matter exhibits a distinct and reproducible oxic effect oet helps integrate and explain organic matter preservation in accumulating continental margin sediments and hence provides a useful tool for assessing transfer of organic matter from the biosphere to the geosphere less

deglaciation induced vertical motion of the north american continent and transient lower mantle rheology the last deglaciation event of the current ice age which began approximately 18 000 years ago and ended about 7000 years ago continues to exert a profound influence on the vertical motion of the solid earth in and surrounding the regions which were once ice covered observations of such vertical motions may be employed to constrain the radial viscoelastic structure of the planet and therefore to contribute in an important way to the understanding of geodynamic processes in general in this paper both present day rates of vertical motion as recorded on tide gauges and long time scale records of vertical motion as recorded in 14c controlled relative sea level histories are employed to refine previously constructed models of the radial viscoelastic structure an interesting sidelight to this analysis is the demonstration that the lower mantle viscosity inferred from the vertical motion data could represent a transient rather than the steady state value a fact which would help considerably to reconcile the small viscosity stratification required by the glacial rebound data with the large stratification which seems to be required by some recent analyses of the geoid height anomalies associated with internal density heterogeneity of the mantle which has been revealed by application of seismic tomographic techniques a further product of these new analyses is obtained by the application of the glacial isostatic adjustment model to filter this signal from the secular trends of relative sea level observed on tide gauges from both the east and west coasts of the north american continent these results may be important in the context of recently proposed scenarios of climatic change

petrographic and geochemical study of organic matter in surficial laminated sediments from an upwelling system mejillones del sur bay northern chile a study of recent laminated sediments accumulated in the oxygen minimum zone of mejillones bay northern chile shows that the organic matter is autochthonous and deposited under varying oceanographic conditions sedimentary units dominated by light laminations have low values of total organic carbon total nitrogen and sulphur and chaotoceros content coupled with high values of yellow amorphous organic matter these were deposited under conditions of low primary productivity favoring the recycling of the major part of metabolizable organic matter in the water column and the accumulation only of non metabolizable organic matter in the bottom sediments in contrast a unit rich in dark laminations with high values of total organic carbon total nitrogen and sulphur shows high values of brown and black aom and chaetoceros content this sedimentary unit reflects increased flocculation of organic particles during a period of high productivity and fast transit of organic material through the column water thus diminishing the recycling of metabolizable organic matter and its accumulation with non metabolizable organic matter in the sediments finally a unit characterized by presence of both light and dark laminations was formed by abrupt alternations of the two oceanographic states described previously

a 200 year sedimentary record of progressive eutrophication in lake greifen switzerland implications for the origin of organic carbon rich sediments over the past 200 years lake greifen a small lake in northeastern switzerland has undergone dramatic changes in primary productivity and eutrophication due to increased nutrient supply from agricultural activity and industrialization a 40 year historical record of the water column chemistry indicates that productivity and eutrophication reached a maximum in 1974 after which stricter regulations on the input of nutrients resulted in a progressive decrease collected cores show the sedimentary expression of this anthropogenically induced eutrophication by a well developed annual sedimentation and by enhanced values of total organic carbon organic carbon accumulation rates and hydrogen indices hi of the kerogens analyses of the carbon isotopic composition of sedimentary carbonates and organic matter reveal that the fractionation between these two phases varies with the hi of kerogens this observation is explicable in terms of changing productivity and preservation of the organic matter and the co2 aq budget of the water body we propose that if high primary productivity were primarily responsible for the preservation and accumulation of organic matter then a negative correlation will occur between 13ccalcite organic matter 13ccal om and hi values in an environment with relatively low to moderate productivity but with bottom water anoxia a positive correlation will exist between 13ccal om and hi values this study of lake greifen has implications for understanding paleoenvironmental controls on ancient organic carbon rich sediments

palaeozoic sedimentary sequence as a reflection of deep structure in southwest ireland abstract in county cork southwest ireland the upper devonian tournaisian succession is spectacularly thick maximum approximately 8 km a thick visean carbonate succession exists in the ground around cork city and northward from there but that apart there is only a meagre representation of carboniferous rocks younger than tournaisian namurian and westphalian are better developed in areas to the north and to the south of the locus of maximum thickness of upper devonian tuffisitic intrusions occur close to the trace of a large fracture in the bantry bay area they have been suspected to include material derived from the mantle the whole association is interpreted as a palaeozoic example of an inversion structure the inversion is attributed to heating arising from a lithospheric delamination occasioned by the collision which closed the iapetus ocean early in devonian time the possibly mantle derived intrusions are set within the dome produced during the course of the inversion variscan folding took place during the development of the dome and certain irregularities in the pattern of outcrop of variscan folds can be regarded as interference effects imposed on the folds by late continuation of the doming brief comments are appended on the means of dating the progress of the process of delamination on the outworn notion of a variscan front and on the open question of the state of palaeozoic rocks whether metamorphic or non metamorphic in the celtic sea region a strong causal relationship is demonstrated between the sequence of tectonic events and the regional facies associations the patterns of megafacies from upper devonian to westphalian are described and discussed in this context

quantification of neotectonic stress orientations and magnitudes from field observations in finnmark northern norway abstract fieldwork was conducted in finnmark northern norway with the purpose of detecting and measuring stress relief features induced by quarrying and road works and to derive from them valuable information on the shallow crustal stress orientations and magnitudes two kinds of stress relief features were considered in this study the first consists of drillhole offsets that were found along blasted road cuts and which were triggered by the sudden rock unloading following the actual blasting vertical axial fractures found in the concave remains of boreholes represent the second kind of stress relief feature the axial fractures are tension fractures produced by gas overpressure inside the drillhole when the blast occurs as such their strike reflects the orientation of the ambient maximum horizontal stress axis the borehole offsets show mostly reverse slip displacements to the e se and the axial fractures trend nw se on average in agreement with nw se compression induced by north atlantic ridge push forces mechanical considerations of the slip planes offsetting some of the drillholes lead to the conclusion that the magnitude of the maximum horizontal stress at the surface is in the range 0 1 1 mpa this range of magnitudes is 1 2 orders less than the horizontal stress magnitudes measured at the surface in other post glacial environments e g canada it is suggested that this difference is related to the marked decline in stress that followed the tremendous post glacial burst of earthquake activity that affected fennoscandia but apparently not the canadian shield

a review of evidence of glacially induced faulting and seismic shaking in eastern canada abstract evidence of early postglacial glacially induced seismic activity should be abundant in eastern canada which was formerly covered by the laurentide ice sheet during the late wisconsinan glaciation this review identified only two probable and at most nine possible examples of glacially induced faulting over an area of 4 million km2 a far lower number than that expected from a long term rate of background seismicity the probable sites are the holy grail scarp manitoba and the series of faults buried in the sub bottom of round lake ontario the possible nine glacially induced faults include the aspy fault nova scotia and timiskaming east shore fault ontario but there is little published information on the other seven features despite this low number the common occurrence of subaqueous mass transport deposits interbedded within or immediately overlying glaciolacustrine glaciomarine deposits in many modern lake basins strongly hints at an elevated period of glacially induced seismicity over widespread areas of eastern canada in southern quebec the age of these mass transport deposits suggests that glacially induced earthquake activity began as early as about 13 5 ka cal bp which corresponds to the time of local ice melt back this indicates that glacially induced seismicity began at the time of local deglaciation in southern quebec rather then being delayed as existing fault instability models imply it is anticipated that new candidate glacially induced or younger faults will be identified in eastern canada over the next decade or so because of the increasing availability of new high resolution data imagery sources

records of southern and central baltic sea eutrophication in δ 13 c and δ 15 n of sedimentary organic matter abstract the baltic sea catchment area has seen considerable agricultural and industrial development over the last century but observational evidence of eutrophication is ambiguous we examined organic carbon accumulation rates and the stable isotope signature of 13 c and 15 n in organic matter in four 210 pb dated short sediment cores from the southern and central baltic sea to search for sedimentary records of increased nutrient input and biological production organic carbon accumulation rates vary little through time in the cores from the oder estuary and the arkona basin but increase significantly in the bornholm basin and in the gotland deep records over the last 40 years 15 n in the sediments show distinct increases over the last 80 50 years in the oder estuary arkona basin and bornholm basin with the greatest increase near the mouth of river oder the gotland deep record shows increasing 15 n values from 1900 to 1975 and decreased 15 n values during the last 20 years the 15 n records are interpreted to trace the effects of eutrophication in nearshore and basinal sediments over the last 100 years and the magnitude of 15 n increase may be a measure for its extent the switch to lower 15 n values in the gotland basin sediment core after initially increasing values coincides with increasing abundance of summer blooms of nitrogen fixing cyanobacteria as observed in monitoring programs 13 c toc values of organic matter increase in the oder estuary over the last 80 years and over the last 30 years in the bornholm basin and gotland basin the tendency to heavier 13 c indicates decreasing isotope fractionation during massive plankton blooms that this effect is not well documented in the sediments of the arkona basin may be due to enhanced degradation processes in the permanently mixed water column a comparison of organic carbon concentrations and 13 c toc and 15 n from early litorina stage around 7 000 years bp and modern sediments from the gotland sea suggests that the trophic state of the baltic sea was comparable to that of the modern environment productivity was nitrate based in spring and based on nitrogen fixation in summer much higher organic carbon concentrations and 13 c enrichment in modern sediments are indications of enhanced productivity compared to early litorina times

did two massive earthquakes in the holocene induce widespread landsliding and near surface deformation in part of the ottawa valley canada recent evidence based on ages of large landslides and the existence of severely disturbed terrain in champlain sea sediments to the east of ottawa suggests that this area may have been the site of two of the most geologically destructive earthquakes in eastern canada the walls of several paleochannels downcut into sensitive marine clayey silts are scarred by numerous large earthflows of sizes unequaled in historical time while radiocarbon ages of 15 landslides as much as 35 km apart range from ca 1870 to 5130 yr b p the majority of events cluster at ca 4550 yr b p the coincidence of numerous large failures in different paleovalleys occurring concurrently long after channel abandonment and at a time of drier climate suggests that the widespread landsliding was triggered by a strong earthquake close to the landslide area areas of very disturbed terrain in a flat erosional plain show severely deformed bedding and irregular ground subsidence and are attributed to a large earthquake ca 7060 yr b p that strongly shook a thick sequence of sensitive material filling deep steep sided bedrock basins

a case for neotectonic joints along the niagara escarpment in a search for proof that some joints on the appalachian plateau are neotectonic orientation data were collected on more than 1800 fractures in exposures of the lockport dolomite in western new york and southern ontario of greatest interest was a late forming ene joint set present in the central and western portions of the field area these joints increase in abundance with proximity to the niagara escarpment the shape of the east west trending niagara escarpment is defined by a series of asymmetric reentrants with a strong ene linear trend reflecting the bedrock joint pattern the joints appear to have formed near the earth s surface in response to low tensile stresses developed in bedrock adjacent to the retreating escarpment since the current shape and position of the escarpment were controlled by glacial activity during the last 3 m y it is possible that the ene joints and reentrants are neotectonic features

geochemical characteristics of chilean upwelling sediments at 36 s abstract we examined the cycling of c s fe and the trace elements te ag cd mo mn re and se in chilean upwelling sediments from water depths of 127 2744 m at 36 s the sediments are clay rich with moderate total organic carbon toc and low biogenic caco3 contents for the shallow site within oxygen minimum zone omz which shows some thioploca biomass highest observed toc contents correspond to highest productivity induced toc flux and or enhanced preservation under o2 deficient conditions pyrite formation may be restricted by the concurrent presence of elemental s in thioploca and or the availability of reactive iron in the other sediments 370 m water depth pyrite formation is strongly restricted due to the low availability of metabolizable toc for sulfate reduction calculations of the degree of bacterially mediated remineralization suggest that more nitrogen than toc was remineralized by sulfate reduction than expected from redfield c n relationship manganese is significantly depleted due to reductive dissolution of mn hydr oxides within all sediments mo is only significantly enriched vs the lithogenic background in the shallow core implying anoxic conditions contents of re and mo as well as re mo ratios indicate suboxic conditions for the other cores cd and re contents decrease with increasing water depth reflecting decreasing reducing conditions in contrast authigenic ag contents increase with water depth suggesting enrichment controlled by seawater availability and or opaline input and not redox conditions elevated se contents in all cores may be either due to bio detrital input or diffusion from seawater accumulation rates of toc ts and te off chile are in the same order as those from the gulf of california and lower than those off peru distinct seasonality in upwelling and dilution of chilean sediments with terrigenous material lead to rather low metabolizable toc contents and lower te trapping capacity

deep burial of coal bearing strata anthracite region pennsylvania sedimentation or tectonics recent studies of vitrinite reflectance sedimentary compaction and fluid inclusions indicate that coal bearing strata of the pennsylvania anthacite region were once buried at depths ranging from 6 to as much as 9 km vitrinite reflectance anisotropy suggests that anthracite rank was attained by normal geothermal heating largely prior to and during alleghanian folding paleomagnetic ages for the folding and paleobotanical ages of the youngest extant sediments delimit the maximum burial and deformation to a relatively short interval 285 to 270 ma in comparison with typical molasse sequences the implied thicknesses and rates of deposition are excessive suggesting that much of the former overburden was emplaced tectonically or by extremely rapid sedimentation the total implied thickness about 20 km of paleozoic strata in the region is abnormally large for an epicontinental basin an inferred body of mafic rock embedded in the precambrian basement evidenced by the scranton gravity high sgh may have influenced crustal subsidence especially during the allegheny orogeny and produced a large downwarp accounting for the high coal rank the fact that isorank contours paleozoic sediment isopach contours and a large structural sag all lie roughly parallel to the boundaries of the sgh oblique to the principal alleghanian fold trend lends support to this idea

vitrinite reflectance data from the kinsale harbour old head of kinsale area southern ireland and its bearing on the interpretation of the munster basin vitrinite reflectance of the upper devonian carboniferous succession in the kinsale harbour old head of kinsale area ranges from 4 06 5 21 m and 6 21 7 82 max which is indicative of meta anthracite coal rank no correlation is apparent between vitrinite reflectance and stratigraphic position through c 2 km of section suggesting that near maximum temperatures were maintained until after variscan folding low reflectance values of 0 62 and 0 30 0 35 m at the local base of the jurassic succession in the north celtic sea basin well 48 30 1 and onshore at cloyne respectively indicate a major discontinuity in the maturation profile in the region comparison with high reflectance gradients from upper palaeozoic successions in the halen and turnhout boreholes in belgium and the munsterland no 1 borehole in west germany suggests that a thick 5 7 km cover of pre permo tnassic rocks must once have been present in the munster basin to account for the high maturation levels observed whether the cover was emplaced by silesian sedimentation or by late palaeozoic thrusting is unclear

structural evolution of the irish variscides the effects of the variscan orogeny on the upper palaeozoic succession are recognizable throughout central and southern ireland the deformation can be zoned using structural styles and trends which illustrate a northward decrease in deformation intensity coupled with increasing control by pre variscan structures in the basement the most intense deformation occurs to the south of the dingle dungarvan line where shortening approaches 50 as a result of layer parallel shortening followed by buckling and finally thrusting the deformation is considered to have developed above a shallow dipping sole thrust which has been located offshore by the swat seismic reflection profiles cross faults which are common throughout the orogen resulted from n s shear couples this is consistent with their origin as accommodation structures due to differential shortening along strike the original shape of the munster basin has exerted a control on the distribution and overall facing of the major structures the sole thrust extends to the north of the dingle dungarvan line and the structural zonation of the orogen is due to variations in the stratigraphic level of this thrust the leinster massif is considered to be essentially autochthonous slip on the sole thrust decays towards the massif which acted as a rigid passive block and was partially responsible for the arcuate trend of the orogen

multibeam sonar backscatter lineaments and anthropogenic organic components in lacustrine silty clay evidence of shipping in western lake ontario abstract a multibeam sonar survey 95 khz covering more than 500 km 2 of western lake ontario revealed anomalous lineaments of relatively high backscatter the lineaments did not align with or parallel the most prominent structural zones beneath the lake as expected instead the principal lineaments lay on lines between ports on opposite sides of the lake especially between toronto and welland canal and toronto and niagara river mouth as the lineaments underlie current and historical shipping routes used during the steamship era they are interpreted as an acoustic response to shipping debris cumulated in the near surface bottom sediment an exploratory study of the organic components in the silty clay surface sediment using geochemical and petrological techniques shows that the upper 10 cm commonly contains silt sized particles of anthropogenic origin especially combustion residues combustion residues are more abundant on or near the lineaments consistent with an origin related to shipping enhanced acoustic backscatter is evident where silt sized combustion particles are hosted in dominantly clay sized sediment the coarser grained anthropogenic particles increase the acoustic impedance of the lakebed relative to the bottom water as well as the roughness and volume scattering contributions to lakebed backscatter

radiocarbon evidence for extensive plate boundary rupture about 300 years ago at the cascadia subduction zone the cascadia subduction zone a region of converging tectonic plates along the pacific coast of north america has a geological history of very large plate boundary earthquakes1 2 but no such earthquakes have struck this region since euro american settlement about 150 years ago geophysical estimates of the moment magnitudes mw of the largest such earthquakes range from 8 ref 3 to 9 1 2 ref 4 radiocarbon dating of earthquake killed vegetation can set upper bounds on earthquake size by constraining the length of plate boundary that ruptured in individual earth quakes such dating has shown that the most recent rupture or series of ruptures extended at least 55 km along the washington coast within a period of a few decades about 300 years ago5 here we report 85 new 14c ages which suggest that this most recent rupture or series extended at least 900 km between southern british columbia and northern california by comparing the 14c ages with written records of the past 150 years we conclude that a single magnitude 9 earthquake or a series of lesser earthquakes ruptured most of the length of the cascadia subduction zone between the late 1600s and early 1800s and probably in the early 1700s

sedimentary facies and high resolution primary production inferences from laminated diatomacous sediments off northern chile 23 s the oceanographic conditions at the mejillones bay 23 s are strongly influenced by an important wind driven upwelling cell of the humboldt current system hcs as well as by the presence of the oxygen minimum zone omz in this region laminated diatomaceous sediments in this bay were analysed using different qualitative and quantitative techniques on the sediment cores 33c and 32b to interpret the main physical ocean climate factors driving sedimentation processes the composition of these sediments is dominated by the high concentration of resting spores of the genus chaetoceros sp which denotes the strong influence of the upwelling events and primary production on hemipelagic sedimentation processes within the basin the laminae characterized by thickness ranging from 1 mm to several cm are associated with changes in density porosity due to the different concentration and composition of phytoplankton remains and organic matter dark laminae are generally characterized by higher concentration of chaetoceros r s toc organic matter carbonates and lithic minerals with respect to the adjacent lighter laminae representing periods of strong upwelling events high primary production rates and intensified hypoxia contrarily relatively lighter laminae are characterized by diminished concentration of chaetoceros r s and relative increases of the concentration of centric and pennate diatoms producing a more porous sediment some of these light laminae could be associated with short lived major oceanographic enso like events the variability of the sedimentary fluxes observed in both cores represents mostly ocean climate trends at decadal interdecadal and secular time periods the secular trends of the sedimentary fluxes suggest an intensification of the upwelling events and primary production from the second half of the 19th century as well as intensified processes during the 20th century these changes seem to occur contemporaneously with ocean climate variations in the southwestern tropical pacific ocean suggesting a major basin scale climate change during this period

glacio seismotectonics ice sheets crustal deformation and seismicity abstract the last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity this growth has been driven largely by the emergence of postglacial rebound models pgm constrained by new field observations that incorporate increasingly realistic rheological mechanical and glacial parameters in this paper we highlight some of these recent field based investigations and new pgms and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation the emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern canada and fennoscandia however many of these models neglect important parameters such as topography lateral variations in lithospheric strength and tectonic strain built up during glaciation in glaciated mountainous terrains glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields in general the short term response to ice fluctuations is similar to the earth s response to fluctuations in water reservoirs with the subsequent increase or decrease in seismicity which depends on the pre existing stress state when the ice fluctuations occur on the spatial scale and magnitude of the late pleistocene glaciation and deglaciation however the viscoelastic response of the earth especially the mantle causes significant changes in crustal deformation and earthquake activity that is spatially extensive and temporally complex the regions of greatest ice thickness and the regions marginal to the late pleistocene ice sheets indicate the most dramatic evidence of earthquake faulting the mantle response to these large ice mass fluctuations and the change in mass between the oceans and land caused and continues to cause measureable crustal deformation at hundreds of kilometres from the ice margins for both tectonically active and cratonic regions palaeoseismic investigations of late pleistocene and holocene faults are an important tool in evaluating earthquake hazard the predicted response of the earth over this time however is very dependent on the model assumed for most regions far more carefully designed field observations are needed to constrain the existing rheological and ice models

effects of strong seismic shaking in lake sediments and earthquake recurrence interval temiscaming quebec the magnitude 6 3 timiskaming earthquake of 1935 resulted in discoloration in small lakes in the epicentral region sonar profiles for lac tee have shown that organic rich gyttja has been removed from the sides and redeposited in the deep parts of the lake lake sediment cores from deep basins contain a 2 3 cm uppermost layer which is interpreted as the normal accumulation of sediment since 1935 this is followed by a 20 cm chaotic zone of black gyttja mixed with partly tabular fragments of a previously formed silt layer underlain by a dense 1 2 cm thick silt horizon the latter is interpreted as having formed by rapid settling of the denser silicate portion of the resuspended sediment this 20 cm zone is insufficient to account for the abnormal thickness of gyttja in the basins so events of this kind would have had to have occurred repeatedly since deglaciation the only major prehistoric event revealed by these 100 cm cores is at a depth equivalent to about 1500 years ago based on the amount of sed

seasonal climatology of hydrographic conditions in the upwelling region off northern chile over 30 years of hydrographic data from the northern chile 18os 24os upwelling region are used to calculate the surface and subsurface seasonal climatology extending 400 km offshore the data are interpolated to a grid with sufficient spatial resolution to preserve cross shelf gradients and then presented as means within four seasons austral winter july september spring october december summer january march and fall april june climatological monthly wind forcing surface temperature and sea level from three coastal stations indicate equatorward upwelling favorable winds throughout the year weakest in the north seasonal maximum alongshore wind stress is in late spring and summer december march major water masses of the region are identified in climatological t s plots and their sources and implied circulation discussed surface fields and vertical transects of temperature and salinity confirm that upwelling occurs year round strongest in summer and weakest in winter bringing relatively fresh water to the surface nearshore surface geostrophic flow nearshore is equatorward throughout the year during summer an anticyclonic circulation feature in the north which extends to at least 200 rn depth is evident in geopotential anomaly and in both temperature and geopotential variance fields subsurface fields indicate generally poleward flow throughout the year strongest in an undercurrent near the coast this undercurrent is strongest in summer and most persistent and organized in the south south of 21os a subsurface oxygen minimum centered at 250 m is strongest at lower latitudes low salinity subsurface water intrudes into the study area near 100 m predominantly in offshore regions strongest during summer and fall and in the southernmost portion of the region the climatological fields are compared to features off baja within the somewhat analogous california current and to measurements from higher latitudes within the chile peru current system

assessing the origin and variability of eolian lithic material for high resolution paleoceanographic reconstructions off northern chile 23 s abstract lithic particles in marine laminated sediments provide the opportunity to reconstruct ocean climate processes like wind dynamics from the sedimentary record in mejillones bay 23 s located on the hyperarid coast of the atacama desert marine laminated sediments record paleoceanographic variations related to coastal upwelling and regional south pacific climate conditions in this work we assess the provenance of lithic particles found in these laminated sediments and we analyze the relationship between the variability of lithic transport sedimentation processes and wind we compared the sedimentological morphological and mineralogical characteristics of desert soil particles with those of surface sediments collected at various locations of the bottom of the bay and particles retrieved from marine sediment cores we also compared horizontal fluxes of particles eroded at the surface of the hyperarid plain pampa mejillones and vertical fluxes of lithic material settling through the water column in the marine basin results show that particles retrieved in dust traps mostly quartz and feldspars with some calcite fragments amphiboles and clay minerals are similar to those collected in the marine sediment traps these are characterized by grain size modes finer than 125 150 m and decreasing from the pampa towards the bottom of the bay together with morphological features such as polished surfaces and v shaped impact marks this supports the hypothesis of an eolian origin of these particles with complex transport histories from quaternary uplifted coastal plains towards the marine laminated sediments from in situ measurements and monitoring we observed a close relationship between the variability of wind intensity horizontal fluxes of lithic particles across the surface of the desert and vertical fluxes in the marine water column this supports the idea that not only in mejillones bay but also in other places quantitative paleoclimate reconstructions could be performed from the quantification of the amount of lithic particles with sizes between 50 and 150 m contained in laminated sediments

organic matter preservation on continental slopes importance of mineralogy and surface area abstract theoretical considerations calculations and data reported by keil et al 1994a were used to assess the recent hypotheses that mineral surface roughness controls the specific surface area of continental margin sediments and that the matrix linked organic carbon content of continental margin sediments occurs as a monolayer or monolayer equivalent coating of organic compounds on the surfaces of detrital minerals and other detrital nonorganic grains mayer 1994 results of our analysis indicate that it is not the surface roughness of the terrigenous detrital framework grains that controls the specific surface area of most continental margin sediments even in the sand and silt fractions but rather the presence of nonspherical high surface area to volume particles primarily clays but also oxy hydroxides and ultra structured nonorganic bioclasts such as diatom frustules analysis of the mineralogy organic carbon content surface area and in situ microfabric of continental margin sediments off california in the mendocino and san luis obispo areas and off the state of washington indicate a strong correlation between the amount of matrix linked organic matter present and the suite of clay minerals data indicate that organic carbon appears to be preferentially sequestered in smectite rich sediments compared to those whose clay fractions are dominated by chlorite we suggest that this association is a function of differences in the site density and chemistry of the clays and differences in their flocculation behavior our data also indicate that organic carbon preservation on the three california transects all of which have a suboxic oxygen minimum zone that impinges on the sea floor is not significantly influenced by differences in bottom water oxygen concentration and carbon stable isotope data suggest no preferential preservation of continental organic matter over that of marine origin

distribution of organic carbon in surface sediments along the eastern arabian sea a revisit abstract one hundred twelve surface sediment samples along the western continental margin of india were analyzed for organic carbon oc elevated oc concentrations are associated with sediments deposited in areas where productivity is moderate to high very high oc concentrations as reported in earlier studies even for regions where productivity is comparatively low could not be confirmed the re analysis of selected samples by coulometry shows that oc concentrations determined previously by the wet oxidation method may be too high by up to more than a factor of two a broad similarity in the distribution of oc and bioproductivity is observed which is in accordance with other productivity proxies such as the abundance of planktonic foraminiferal species g bulloides and hydrogen indices hi our results indicate the importance of bioproductivity for oc accumulation along the western continental margin of india even though low dissolved oxygen concentrations in the water column sedimentation rate sediment texture clay mineral content dilution by quartz and carbonate as well as topography are considered responsible for the general oc distribution in this area

documentation of earthquake induced disturbance of lake sediments using subbottom acoustic profiling subbottom acoustic profiling in lakes on the canadian shield and in the canadian cordillera has revealed disruptions in deltaic and lacustrine sediments that can be attributed to large historical earthquakes the timiskaming earthquake of 1935 magnitude 6 25 and the vancouver island earthquake of 1946 magnitude 7 2 triggered extensive slumping and flow of postglacial sediments in lakes located within a few tens of kilometres of the epicentres of these events there is some evidence in one of the surveyed lakes for in situ mobilization of sediment on relatively gentle slopes with minimal horizontal displacement this may be a product of liquefaction induced by coseismic shaking or displacements along faults beneath the basin in another lake widespread coseismic slumping resuspended large amounts of fine sediment which then settled out onto the lake floor to produce a texturally anomalous layer features similar to those produced by the 1935 and 1946 earthquakes can also result from a variety of non

anchovy population and ocean climatic fluctuations in the humboldt current system during the last 700 years and their implications a marine sedimentary record collected from 87 m water depth in a coastal environment of the humboldt current system mejillones bay 23 s northern chile was used to reconstruct the past 700 years of ocean climatic conditions and to study the influence of any changes on anchovy population dynamics we analyzed quartz organic carbon total nitrogen alkenones and fish scales four stratigraphic units in the sediment column correspond with fluctuations in these and other proxies low scale deposition rate sdr values from 1330 to 1420 suggest a low abundance of anchovy in this coastal environment three subsequent cycles of ca 170 years each showed an increase and decrease of anchovy populations which is in agreement with changes in the wind regime sea surface temperature and primary productivity since ca 1840 marked fluctuations of sdr have been observed probably as a consequence of the onset of a different oceanographic regime characterized by intensified southern winds and upwelling colder surface waters higher primary productivity and enhanced la nina like interdecadal variability an increase of the anchovy population was observed until halfway through the 20th century followed by a decrease even though water temperature decreased and primary productivity increased this situation is likely the consequence of the increased fishery activity that developed in this zone during the last 60 years after analyzing the results obtained for anchovy sdr we can determine that there is a relation between the abundance of this species and phases of the pacific decadal oscillation pdo in which an increase in the sdr coincides with a pdo cold phase while a decline coincides with a warm phase fast fourier transformation analysis applied to the time series obtained from the mejillones sediment core and to the north atlantic oscillation nao the pdo and the solar irradiance index time series shows three different decadal cycles 80 100 years 61 75 years and 45 48 years approximately furthermore the results of this study suggest that both the pdo and the nao and the biogeochemical markers of mejillones exhibit periodicities that fall within the 80 to 100 year gleissberg solar cycle indicating that global solar radiation plays a key role in the local ocean climatic processes and confirming teleconnection linkages between widely separated regions

liquefaction features on the fraser delta evidence for prehistoric earthquakes sand dykes and sills and vented sand boils on the fraser river delta and adjacent serpentine river floodplain in southwestern british columbia record one or more major liquefaction events the source of the dykes is a shallow subsurface saturated sand unit that was deposited in foreslope and distributary channel environments during holocene progradation of the fraser delta the dykes cut steeply through a crust of delta topset muds and locally flatten out as sills in overlying peaty sediments at two sites evidence was found for venting of sand onto a subaerial or intertidal surface liquefaction and upward movement of sand and water locally deformed the intruded sediments causing some subsidence and uplift of the delta surface all observed liquefaction features are younger than ca 3500 bp and at least some are younger than 2400 bp it is not clear however whether they formed during one or several separate events a review of possible causes suggests that the liquefaction features probably are seis

the use of varved clay chronology for dating paleoseismic events the erstavik record in the stockholm area south sweden abstract geological structures suggest that the fennoscandian shield was subjected to a higher seismicity at the end of the last glaciation than today this article demonstrates the use of varved clay chronology for dating paleoseismic events it is argued that the deposited annually layered glacial varves were sensitive to past ground movements in the stockholm area the erstavik varved clay chronology suggests four paleoseismic events a first i dating from varve year 10 473 to 10 468 bp a second ii 10 451 to 10 445 bp a third iii 10 429 to 10 425 bp and a fourth iv 10 409 to 10 404 bp in de geer s old 1940 chronology the first i dating corresponds with 1117 to 1112 the second ii with 1095 to 1089 the third iii with 1073 to 1069 and the fourth iv with 1053 to 1048 the most pronounced event was the one at around varve year 10 429 bp varve 1073 in de geer s old chronology the recurrence time of about 20 years suggests a totally different seismic regime at the time of deglaciation than what exists today it coincided with the period of maximum isostatic uplift the complexity of the varved clay response to seismic events is also discussed

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

organic matter preservation on the pakistan continental margin as revealed by biomarker geochemistry in order to assess whether the oxygen minimum zone omz in the arabian sea has an eaect on the preservation and composition of organic matter in surface sediments we investigated samples from three diaerent transects on the pakistan continental margin across the omz in addition to determining the total amount of organic carbon toc we analyzed the extractable lipids by gas chromatography combined gas chromatography mass spectrometry and compound specific stable carbon isotope measurements the extractable lipids are dominated by marine organic matter as indicated by the abundance of lipids typical of marine biota and by the bulk and molecular isotopic composition sediments from within the omz are enriched in organic carbon and in several extractable lipids i e phytol n alcohols total sterols n c35 alkane relative to stations above and below this zone other lipid concentrations such as those of total n fatty acids and total n alkanes fail to show any relation to the omz only a weak correlation of toc with mineral surface area was found in sediments deposited within the omz in contrast sediments from outside the omz do not show any relationship between toc and surface area among the extractable lipids only the n alkane concentration is highly correlated with surface area in sediments from the hab and makran transects in sediments from outside the omz the phytol and sterol concentrations are also weakly correlated with mineral surface area the depositional environment of the indus fan oaers the best conditions for an enhanced preservation of organic matter the omz together with the undisturbed sedimentation at moderate rates seems to be mainly responsible for the high toc values in this area overall the type of organic matter and its lability toward oxic degradation the mineral surface area the mineral composition and possibly the secondary productivity by sedimentary bacteria also appear to have an influence on organic matter accumulation and composition 2000 elsevier science ltd all rights reserved

a study of joints and stress release buckles in palaeozoic rocks of the niagara peninsula southern ontario joint sets in palaeozoic bedrock of the niagara peninsula occur at 005 045 085 and 135 orientations there is no consistent change in joint orientation with lithology rock age or location within the area drainage pattern analysis using airphotos and topographic maps indicates that glacial drift effectively masks underlying joint systems rare calcite and gypsum mineralization occurs along joints of 085 and 135 trend stress relief buckles indicate a contemporary maximum principal stress along an 050 trend joint systems in the niagara peninsula are similar in trend to those on the appalachian plateau

seasonal and spatial variations in the source and transport of sinking particles in the strait of georgia british columbia canada three sequential sediment traps were deployed at 150 m in the strait of georgia from march 1996 to february 1998 one at the southern end of the strait one located centrally opposite the main channel of the fraser river and one to the north of the fraser river channels subsequently all three traps were moored at the central site on a single mooring 150 225 and 300 m from february 1998 to january 1999 the highest total flux in the b500 am fraction 2 2 g cm 2 a 1 was recorded at the southern station and the lowest at the northern station 0 044 g cm 2 a 1 an annual flux peak at all three stations coincided approximately with the fraser river freshet may june and the southern station exhibited a second flux peak in september which seemed not to be directly associated with the river s discharge lithogenic particles dominated the flux at all three stations representing about 85 of the total flux at the southern and central stations and 60 at the northern station although that proportion varied widely throughout the year at all three stations according to stable isotope composition y 13 c and y 15 n the majority of the biogenic material was marine derived particularly at the northern station approximately 80 of organic matter marine derived with much of the variation in the trap samples explained by variation in the proportions of marine and terrigenous organic matter however a second source of variation was evident in the isotopic composition of the marine derived organic matter probably because of seasonal changes in nutrient availability productivity and the length of the local food chain as a result the sinking organic matter in the strait of georgia can be described as a mixture of three end members terrigenous marine bloom and marine non bloom the flux and compositional data together with data from sediment cores collected at the same locations imply that most of the particles settle in the southern strait where they may then be transported northward along the bottom toward the central and northern stations d 2005 elsevier b v all rights reserved

using image based size analysis for determining the size distribution and flux of eolian particles sampled in coastal northern chile 23 s the aim of this study was to determine the size distribution and flux of the mineral fraction collected in marine sediment traps in mejillones bay 23 degrees s using image based size analysis in this bay the material settling in the water column is a mixture of biogenic particles and lithic grains the sediments analyzed correspond to four samples collected in the austral spring of 2008 we used image based size analysis because it presents several advantages which makes it an ideal method to study fine marine sediments this analysis also yielded important information about the aspect and the morphology of the particles in order to analyze the lithic fraction only different pretreatments were applied and size analyses were carried out with and without image information besides the main lithic components quartz feldspar amphiboles and micas some nonlithic particles corresponding mainly to organic matter remains were observed in the images showing that the pretreatment was not fully effective biogenic silica and unexpected dark particles of probable anthropogenic origin were also detected to avoid the influence of nonlithic grains in the analysis the images were filtered based on the aspect of the particles using various discrimination tools before and after this removal the size distributions of the samples were estimated and used to calculate the total flux as compared to the flux of lithic particles this total flux displays a systematic overestimation of up to 12 as a consequence using image based size analysis allows not only enhancing the determination of the size distribution and flux but also controlling and improving the pretreatments protocols

role of a strong oxygen deficient zone in the preservation and degradation of organic matter a carbon budget for the continental margins of northwest mexico and washington state rates of organic carbon oxidation in marine sediments were determined for the continental margins of northwest mexico and washington state with the goal of assessing the role of oxygen in the preservation of organic matter on a margin with a strong oxygen deficient zone and on a typical western continental margin total carbon oxidation rates including rates for individual electron acceptors o2 no3 and so4 were determined at depths ranging from 100 to 3000 m on both margins carbon oxidation rates were generally higher on the washington margin than on the mexican margin the relative importance of the different electron acceptors varied across the two margins and was related primarily to the availability of o2 and no3 from the overlying water the relative contribution of o2 consumption increased in deeper sediments 2000 m as aerobic processes began to dominate the total carbon oxidation rate denitrification rates were highest in washington sediments however denitrification represented a larger fraction of the total carbon oxidation rate in the mexican sediments 40 for mexico vs 30 for washington sulfate reduction accounted for as much as 79 of the total carbon oxidation rate in shallow sediments and less than 20 in deep sediments on both margins the offshore trends in carbon oxidation rate appeared to be related to the organic carbon input rate pore water o2 and no3 penetration depths were shallowest in nearshore stations and increased offshore regeneration ratios of c n p reveal non redfield behavior on both margins carbon budgets for the two margins demonstrate that off mexico a much greater percentage of the organic matter produced in the surface ocean reached the sediments 15 vs 8 for mexico and washington respectively on the mexican margin 8 of the primary production escaped oxidation in the surface sediments to be permanently buried as compared with only 1 2 of the primary production on the washington margin this suggests that oxygen deficient conditions on mexican margin are linked to enhanced carbon preservation

enhancement of coastal upwelling and interdecadal enso like variability in the peru chile current since late 19th century art no l13607

organic matter preservation through the oxygen deficient zone of the ne arabian sea as discerned by organic carbon mineral surface area ratios abstract it is debated whether there is a causal or even correlative relationship between the presence of a minimum in bottom water oxygen bwo concentration and the preservation of organic matter in underlying marine sediments one relationship that has not been examined in this regard is the relationship between sedimentary organic carbon content and mineral surface area normalization of organic matter content to mineral surface area eliminates the mass based problems associated with traditional weight percent carbon measurements and thus may allow better evaluation of carbon preservation we measured organic carbon to mineral surface area ratios oc sa on 26 sediment samples from along the ne edge of the arabian sea and on 21 hydrodynamically sorted fractions using split flow lateral transport thin splitt fractionation from three of these stations samples spanned from above to well below the minimum in local bwo concentration sediments deposited under the oxygen minimum had oc sa ratios in excess of 1 1 mg oc m 2 indicative of enhanced preservation a bioturbated sediment at the edge of the oxygen minimum bwo 35 m also had a high oc sa ratio with the exception of the anomalous sample along the slope all samples from shallower and deeper than the oxygen depleted water mass bwo 35 m have oc sa ratios that fall within the typically observed range 0 5 1 1 mg oc m 2 while further work will be necessary to discern what causes this relationship our data indicate that organic matter preservation as estimated by oc sa is enhanced within the general locale of the bwo minimum in ne arabian sea sediments if this relationship proves to be robust repeatable and stable over time in other modern bwo minimum zones surface area normalized organic carbon loadings may be a useful paleoceanographic proxy for past bwo levels

geochemical study of organic matter rich cycles from the kimmeridge clay formation of yorkshire uk productivity versus anoxia abstract in this contribution we study two meter scale cycles from the kimmeridge clay formation cored near marton yorkshire which shows cyclic organic matter om distribution our aim is to try to understand the factors responsile for om accumulation the first cycle called lower cycle shows a total organic carbon toc content between 1 and 10 whereas the second called upper cycle shows a toc content varying between 5 and 35 the geochemical composition major elements and trace elements the organic geochemistry toc hi palynofacies and mineralogy of the sediments have been determined in both cycles the cyclicity is expressed through variations in the nature and in the relative abundance of the various types of organic matter constituents furthermore dilution effects by inorganic components of the sediment cannot account for the toc cyclicity for lower cycle the mo v and u content is low and little variable as is the intensity of the oxidation which om suffered from this indicates that variations in phytoplanktonic productivity may be held responsible for the cyclicity in steady and mildly reducing redox conditions in the upper cycle cyclicity also appears to depend on productivity but variations in the concentration of mo v and u and in the oxidation state of the om suggest the environment was temporarily more reducing it is proposed that larger amounts of h 2 s were released into marine bottom waters as a result of initial om decomposition forced the oxic anoxic boundary to rise in the water column and thus favoured om storage the main driving force for variations in the om concentration was the productivity of organic matter walled phytoplankton redox conditions of the depositional environment could have had a positive action but only by acting as a positive feedback effect

multiple late holocene earthquakes along the reelfoot fault central new madrid seismic zone the reelfoot fault is an east vergent reverse fault underlying the lake county uplift a low amplitude late holocene anticline bordered on the east by the 32 km long reelfoot scarp fluvial deposits across the scarp define an 8 m high east facing monocline most near surface deformation along the scarp is accommodated via folding rather than faulting we interpret the scarp as a fault propagation fold developed over a wcst dipping reverse fault interpreted from shallow seismic reflection data trench exposurcs provide evidence for three episodes of deformation along the reelfoot fault within thc past approximately 2400 years between a d 780 and 1000 between a d 1260 and 1650 and during a d 1812 our best estimate of the average recurrence interval for deformation along the scarp is 400 500 years each episode of deformation had a slightly different style the third most recent event produced a small graben a few tens of centimeters deep in the hanging wall of the reverse fault the second most recent earthquake produced about 1 3 m of throw in the graben as well as folding along the updip projection of the reverse fault and development of the scarp thesc relations suggest that graben development increased through time concomitant with growth of the monocline or that the events are of different magnitude the 1811 1812 episode of deformation produced abundant liquefaction prominent folding of fluvial strata along the scarp and minor faulting in the graben

postglacial faulting in eastern canada nature origin and seismic hazard implications abstract at more than 70 locations in southeastern canada and the adjacent united states tiny bedrock faults displace glacial striations that are about 10 000 years old these reverse faults mostly of small displacement occur in a broad arc from western ontario to newfoundland the faults lie near the margin of the laurentian ice sheet strike generally tangential to it and imply compression nearly normal to the ene directed contemporary regional stress these observations and some age relationships suggest that the faults formed very soon after deglaciation perhaps in the first few thousand years after ice melting in each place and probably represent the release of stresses caused by flexural deformation of the upper crust although the individual offsets are small the faults are believed to be pervasive and individual outcrops reflect amounts of stress relief consistent with stresses implied by the postglacial tilt of nearby lake shorelines

suppression of earthquakes by large continental ice sheets the interior regions of antarctica and greenland are aseismic no earthquake larger than body wave magnitude 4 5 5 0 is known for either except along coastal zones or continental shelves here i advance an explanation for this lack of seismic activity in terms of pressure effects produced by the continental ice sheets that mantle both continents

design of tunnel lining in rock for long term time effects excavation of underground openings in rock relieves the in situ state of stresses providing an initiating mechanism for time dependent deformation in shaly rocks to occur the construction of a permanent lining restrains the rock movement resulting in an increase with time of pressure acting on the lining closed form solutions for this problem of rock structure time interaction of circular tunnels have been developed taking into account a the state of initial stresses b the time dependent properties of the lining as well as the rock and c the time lapsed between excavation and lining expressions for lining pressures stresses thrusts and moments are given for both no slip and full slip interface conditions the effects of material parameters lining flexibilities and time lapse on quantities of engineering interest are studied and their implications on design illustrated the results of analysis are compared with the field observations made in three tunnels it is shown that the theoret

stress relief buckles in the mcfarland quarry ottawa six quarry floor buckles in a west end ottawa bedrock quarry are described and a semi quantitative estimate of the stress field is inferred from them the maximum principal stress component is hori

influence of water column anoxia on the burial and preservation of carbon and phosphorus in marine shales abstract organic p and organic c concentrations were measured in several well characterized phanerozoic marine shale sequences with the primary focus being the camp run member of the devonian mississippian new albany shale sequences were selected with close spatial association of bioturbated and laminated sediments which reflect deposition from oxic and anoxic waters respectively average organic c p mole ratios calculated from the data are 150 for bioturbated shales and 3900 for the laminated shales of the new albany differences in the extent and mechanisms of early diagenesis related to the oxygenation of waters at the sediment water interface can account for the c p ratios of buried organic matter low c p ratios of bioturbated sediments are attributed to 1 1 the increased ability of bacteria to store p in well oxygenated environments which leads to the production of low c p ratio bacterial biomass and 2 2 the extensive oxidation of sedimentary organic matter resulting in the formation of residual organic phases with low c p ratios high organic c p ratios of laminated sediments are explained by a combination of 1 1 the limited ability of bacteria to store p under anoxic conditions 2 2 extensive p regeneration from sedimentary organic matter 3 3 enhanced c preservation relative to the bioturbated shales it is also shown that relative to organic c laminated shales are not as effective a p sink as are bioturbated shales this provides a mechanism in anoxic environments for burying large quantities of organic matter without simultaneously sequestering the p needed to sustain further productivity

organic geochemistry of recent marine sediments from the nansha sea china recent marine sediments from two cores collected on the continental slope of the nansha sea china have been analyzed for organic matter content n alkane and isoprenoid hydrocarbons fatty acids n alkanols and sterols the organic carbon contents of the two sediment cores average 0 7 and 0 53 respectively and are higher than those of other sedimentary environments in this region the distributions of various lipid compounds indicate that most of the sedimentary organic matter in the two cores is derived from marine plankton and bacteria with land derived organic matter present in relatively small amounts the decrease in relative abundances of shorter chain lipids n alkanes n fatty acids and n alkanols with depth is evident as is the biochemical conversion of stenols to stanols in some samples the low pristane phytane ratios may result primarily from microbial activity and reflect the occurrence of significant diagenetic alteration of organic matter in the two cores

a history of neotectonic studies in ontario abstract first observations of geologically young rock faults and folds in new york in the late nineteenth century were shortly followed by others in ontario remapping of the paleozoic rocks began in the 1930s and quaternary geology mapping became organized in the 1950s leading to further discoveries of faults and folds in the bedrock engineering works in the niagara and hamilton areas from the 1890s to the 1970s encountered repeated problems of rock squeeze the separate geological and engineering experiences were linked in the 1970s and with heightened awareness discoveries of rock disturbances mainly popups greatly increased in the 1970s and 1980s understanding centered on high horizontal stress in the bedrock which became quantified through rock testing and modeling the creation of the multi agency group for neotectonics in eastern canada magnec in 1986 brought together a diverse group interested in all aspects of neotectonics including the distribution and causes of rock stress and the potential implications for seismic risk the existence of nuclear power plants sensitive to variations in the stress environment and high population densities near the great lakes provided motivation for further attention and prince edward county was designated for special study recent suggestions of reduced seismic activity under ice sheets and increased activity associated with isostatic uplift during their retreat lead to the question whether seismic risk is slowly decreasing as uplift rates decline

interplay between sedimentary organic matter and dissolved oxygen availability in a coastal zone of the humboldt current system mejillones bay northern chile abstract geochemical and petrographical analyses were done in 26 surficial sediment samples from mejillones bay northern chile to investigate the processes that participate in the preservation of sedimentary organic matter annual variability of chlorophyll a and dic 13 c measured in surface waters of three different parts of mejillones bay did not show any significant spatial variability in biological productivity on the other hand bottom dissolved oxygen showed strong changes associated with water depth and season surface sediment composition was statistically analyzed displaying organic facies which are in agreement with the principal zones of bottom oxygenation annual mean condition identified in this bay in the oxic coastal zone 1 ml l 1 the total carbon tc total nitrogen tn total organic carbon toc hydrogen index hi and oxygen index oi were 1 3 0 1 0 4 355 8 mg hc g toc and 237 6 mg co 2 g toc respectively these results and the presence of almost exclusively dispersed amorphous organic matter suggest an environment where most metabolizable organic matter is degraded within the water column and or in the sediment water interface in the microxic hemipelagic zone 1 located deeper than 65 m the tc tn toc hi and oi were 10 5 1 0 6 6 529 7 mg hc g toc and 103 1 mg co 2 g toc respectively these values and the presence of abundant agglomerated amorphous organic matter suggest a better preservation of metabolizable and non metabolizable compounds we can conclude that biological productivity and dissolved oxygen exert a similar influence on the sedimentary organic matter but the characteristics and quantity of organic material preserved in bottom sediments of this bay are controlled principally by the availability of dissolved oxygen at the sediment water interface according to this conclusion we suggest that the sedimentary record of mejillones bay must be interpreted in paleoceanographic terms primarily in relation to the temporal variability of dissolved oxygen more than biological productivity the oi seems to be a good proxy of paleoxygenation in this coastal system

the oxygen and carbon isotope distribution in the mediterranean water masses abstract the oxygen and carbon stable isotope compositions of the present day mediterranean waters have been measured in order to evaluate their variability which is related to the specific climatic and hydrological conditions within the basin the experimental equation between the 18 o value and the salinity of water based on 300 measurements on surface intermediate and deep waters sampled during the vicomed 2 and 3 cruises in the western central and eastern mediterranean has a slope of 0 27 a value which is significantly lower than the slope of 0 45 as defined in the northeast atlantic ocean this difference in the 18 o salinity relationship which occurs immediately in the alboran basin is basically a characteristic of the climatic regime of the mediterranean i e of an excess evaporation over fresh water input the largest variations of these two parameters 18 o of water and 13 c of co 2 are observed in the surface waters mostly in the western mediterranean this evolution mirrors the progressive eastward restriction which separates the less evaporated and more productive western basins from the more evaporated and less productive eastern basins the intermediate waters constitute a homogeneous layer however their 18 o values decrease eastward by 0 35 at maximum due to progressive dilution by mixing with overlying and underlying water masses their 13 c values decrease also eastward by 0 35 at maximum due to an increasing input of nutrients issued from the regeneration of sinking organic particles the deep waters have similar 18 o values but slightly higher 13 c values often by less than 0 1 than the overlying intermediate waters indicating generally well ventilated conditions due to active winter convection

modeling of the thermo hydro mechanical chemical response of sedimentary rocks to past glaciations abstract thermo hydro mechanical chemical thmc coupled processes that have resulted from long term past climate changes and glaciation cycles in the sedimentry rocks of southern ontario are investigated a conceptual numerical model has been developed to solve four coupled partial differential equations pdes which represent hydraulic thermal mechanical and chemical processes the finite element method is used to solve the pdes under transient surface boundary conditions imposed by past glaciation cycles to predict the hydraulic mechanical thermal and geochemical responses of the geological system the results show that past glaciations have a significant impact on the hydraulic gradient and pressure vertical effective stress and salinity profiles and a limited effect on the permafrost depth the predicted results show good agreement when compared with the field data for the total dissolved solid rock strength and quality the results show relatively good agreement with the anomalous pore water pressure profile in the field the modeling results indicate that the infiltration depth of glacial melted water is less than 300 m and are consistent with the field observation of total dissolved solids at the level of a deep geological repository dgr for low and intermediate level radioactive wastes being planned in these rock formations a safety factor of 6 9 is predicted against failure by using hoek brown failure envelopes while a low safety factor of 0 83 is predicted at the shallower level of the silurian salina formation it is found that solute transport at the middle and upper ordovician formations are diffusion dominated at depths of 300 m or more and controlled by diffusion advection above 300 m based on the results obtained the modeling of a past glaciation can be used with reasonable confidence in predicting the impact of future glaciations related to the long term safety and stability of the proposed dgr in the sedimentry formation however for site specific conditions thmc modeling is very sensitive to material properties and sensitivity analysis is required for future model development