salt marsh diatom distributions in ho bugt western denmark and the development of a transfer function for reconstructing holocene sea level changes abstract modern diatom samples and associated environmental variables were collected from the kjelst enge and moserva salt marshes in the northern part of ho bugt western denmark the relationship between diatom assemblages and elevation was investigated in order to assess the potential use of diatoms as sea level indicators diatoms were found to be well preserved across the salt marsh surface a total of 54 diatom taxa were found with relative abundances greater than 3 cluster analysis reveals the presence of three vertical assemblage zones the relationship between diatoms and environmental variables elevation ph salinity was explored using canonical correspondence analysis cca a series of partial ccas shows that 24 of the explained variance can be attributed to elevation relative to tidal levels associated monte carlo permutation tests demonstrate that this relationship is significant p 0 014 we developed weighted averaging wa and weighted averaging partial least squares wa pls transfer functions from 40 surface diatom samples the wa pls transfer function was found to perform best r 2 jack 0 90 root mean square error of prediction jack 0 14 m and was subsequently applied to reconstruct salt marsh surface elevations from the diatom assemblages in a core from kjelst enge salt marsh the results indicate that with appropriate chronologic control it will be possible to establish a high precision record of changing sea level from this core

holocene tidal levels and sedimentation rates using a diatom based palaeoenvironmental reconstruction the tees estuary northeastern england an established diatom based tidal level transfer function is used in combination with the present day relationship between sedimentation rate and altitude to reconstruct holocene tidal sediment accretion for the tees estuary northeastern england the results from five cores reveal two periods of enhanced sedimen tation the earlier of which 8000 6000 cal bp is related to relatively rapid sea level rise and increasing tidal range the later phase of increased tidal sedimentation also reflects an enhanced marine influence after c 3000 cal bp but may also be attributed to climate and human induced changes in terrestrial sediment flux to the coastal zone comparison of the reconstructed sediment accretion rates with actual rates calculated from radi ocarbon and luminescence dated sedimentary horizons reveals that this diatom based approach overestimates sediment accretion by a factor of three this overestimation is considered to be due to the contemporary sediment flux being an inappropriate analogue for the mid to late holocene rather than to any significant methodological flaws in the approach

deciphering the role of solar induced thermal stresses in rock weathering a dearth of direct field observations limits our understanding of individual mechanical weathering processes and how they interact in particular the specific contributions of solar induced thermal stresses to mechanical weathering are poorly characterized here we present an 11 mo data set of cracking using acoustic emissions aes combined with measurements of rock temperature strain and other environmental conditions all recorded continuously for a granite boulder resting on the ground in open sun we also present stresses derived from a numerical model of the temperature and stress fields in the boulder idealized as a uniform elastic sphere experiencing simple solar temperature forcing the thermal model is validated using this study s data most observed cracking coincides with the timing of calculated maximum insolation driven tensile thermal stresses we also observe that most cracking occurs when storms or other weather events strongly perturb the rock surface temperature field at these times we hypothesize that these weather actuated thermal perturbations result in a complex thermal stress distribution that is superimposed on the background stresses arising from simple diurnal forcing these additive stresses ultimately trigger measurable cracking measured locations of observed cracking and surface strain support this hypothesis in that they generally match model predicted locations of maximum solar induced tensile stresses also recorded rock surface strain scales with diurnal temperature cycling and records progressive cumulative extension dilation consistent with ongoing thermal stress driven subcritical crack growth in the boulder our results therefore suggest that 1 insolation related thermal stresses by themselves are of sufficient magnitude to facilitate incremental subcritical crack growth that can subsequently be exploited by other chemical and physical processes and 2 simple insolation can impart an elevated tensile stress field that makes rock more susceptible to cracking triggered by added stress from other weathering mechanisms our observed cracking activity does not correlate simply with environmental conditions including temperature extremes or the often cited 2 c min thermal shock threshold we propose that this lack of correlation is due to both the ever varying ambient stress levels in any rock at earth s surface as well as to the fact that ongoing subcritical crack growth itself will influence a rock s stress field and strength because similar thermal cycling is universally experienced by subaerially exposed rock this study elucidates specific mechanisms by which solar induced thermal stresses may influence virtually all weathering processes

diatom evidence for earthquake induced subsidence and tsunami 300 yr ago in southern coastal washington fossil diatoms from four stratigraphic sections along the tidal niawiakum river southwestern washington provide an independent paleoecological test of a relative sea level rise that has been attributed to subsidence during an inferred earthquake in the cascadia subduction zone about 300 yr ago diatom assemblages in a buried soil and overlying mud indicate a sudden and lasting shift from marshes and forests near or above highest tides to mud flats and incipient tidal marshes with a progressive return to high level tidal marshes by sediment aggradation and perhaps gradual tectonic uplift the amount of coseismic submergence required to generate the paleoecological changes observed at these sites could have ranged from a minimum of 0 8 1 0 m to a maximum of 3 0 m fossil diatoms also provide an independent test of previous inferences that the subsidence was shortly followed by a tsunami the inferred tsunami deposit is a distinct sandy interval that widely overlies the buried marsh and forest soil diatoms from this interval consist of species observed on modern sand flats of the open bay identifying a bayward source for the sand occurrences of the same sand flat species above the buried soil in the farthest up valley outcrop where a sandy interval is not recognizable suggest that the tsunami extended farther landward than was previously inferred from the stratigraphy these data rule out proposed alternatives to the coseismic subsidence model that is climatically induced sea level rise temporary submergence caused by storms and support the hypothesis that a great earthquake struck southwestern washington 300 yr ago

experimental determination of elastic constants of oshima granite barre granite and chelmsford granite employing polyhedral specimens longitudinal and shear wave velocities were measured in various directions of propagation and polarization sound velocities showed orthorhombic elasticity in all of the rocks with the assumption of orthorhombic elasticity the nine stiffness constants of all samples were determined by the sound velocities under atmospheric pressure and kelvin christoffel s equation twenty one stiffness constants of oshima granite determined without assuming any symmetry also showed orthorhombic features directions of the symmetry axes agreed well with the orientation of the preexisting cracks akaike s information criterion showed that the orthorhombic model with nine nonzero elastic stiffnesses was better than the model having 21 nonzero elastic stiffnesses for oshima granite the polyhedrons of two granitic rocks were loaded under hydrostatic pressure all components of the stiffness constants increased with pressure under pressure of more than 120 mpa two granitic rocks were approximately isotropic the results show that oriented microcracks are mainly responsible for the orthorhombic elasticity of the granitic rocks and also indicate that dry oriented cracks can not be a cause for the anisotropic elasticity of granites at depths of more than 6 8 km

influence of surrounding environment on subcritical crack growth in marble abstract understanding subcritical crack growth in rock is essential for determining appropriate measures to ensure the long term integrity of rock masses surrounding structures and for construction from rock material in this study subcritical crack growth in marble was investigated experimentally focusing on the influence of the surrounding environment on the relationship between the crack velocity and stress intensity factor the crack velocity increased with increasing temperature and or relative humidity in all cases the crack velocity increased with increasing stress intensity factor however for carrara marble cm in air we observed a region in which the crack velocity still increased with temperature but the increase in the crack velocity with increasing stress intensity factor was not significant this is similar to region ii of subcritical crack growth observed in glass in air region ii in glass is controlled by mass transport to the crack tip in the case of rock the transport of water to the crack tip is important in general region ii is not observed for subcritical crack growth in rock materials because rocks contain water because the porosity of cm is very low the amount of water contained in the marble is also very small therefore our results imply that we observed region ii in cm because the crack velocity increased in both water and air with increasing temperature and humidity we concluded that dry conditions at low temperature are desirable for the long term integrity of a carbonate rock mass additionally mass transport to the crack tip is an important process for subcritical crack growth in rock with low porosity

scale considerations in using diatoms as indicators of sea level change lessons from alaska this paper assesses variations in quantitative reconstructions of late holocene relative sea level rsl change arising from using modern diatom datasets from different spatial scales applied to case studies from alaska we investigate the implications of model choice in transfer functions using local sub regional and regional scale modern training sets and produce recommendations on the creation and selection of modern datasets for reconstructing rsl change over holocene timescales in tidal marsh environments comparable with those in alaska we show that regional modern training sets perform best in terms of providing fossil samples with good modern analogues and in producing reconstructions that most closely match observations where these are available local training sets are frequently insufficient to provide fossil samples with good modern analogues and may over estimate the precision of rsl reconstructions this is particularly apparent when reconstructing rsl change for periods beyond the last century for reconstructing rsl change we recommend using regional modern training sets enhanced by local samples

subcritical crack growth and other time and environment dependent behavior in crustal rocks stable crack growth strongly influences both the fracture strength of brittle rocks and some of the phenomena precursory to catastrophic failure quantification of the time and environment dependence of fracture propagation is attempted with the use of a fracture mechanics technique we examine some of the difficulties encountered when applying techniques originally developed for simple synthetic materials to complex materials like rocks a picture of subcritical fracture propagation is developed that embraces the essential ingredients of the microstructure a microcrack process zone and the different roles that the environment plays to do this we examine the results of 1 fracture mechanics experiments on five rock types 2 optical and scanning electron microscopy 3 studies of microstructural aspects of fracture in ceramics and 4 exploratory tests examining the time dependent response of rock to the application of water

microfossil analysis of sediments representing the 1964 earthquake exposed at girdwood flats alaska usa abstract diatom pollen foraminifera and thecamoebian assemblages from an outcrop of peat and silt at girdwood flats in the upper turnagain arm of the cook inlet alaska record four phases of relative land and sea level changes the first phase is the development of freshwater swamp above high marsh sediments during relative land uplift caused by strain accumulation along the locked portion of the alaska aleutian subduction zone in second phase the top 2 cm of the peat all microfossil groups record pre seismic relative sea level rise relative land subsidence the third phase is rapid land subsidence 1 7 m during the earthquake of march 1964 that initiated intertidal silt accumulation above the peat the final phase is the colonisation of mudflat by salt marsh communities during post seismic land uplift the microfossil data compare favourably with sequences from washington oregon and british columbia that record late holocene submergence events caused by earthquakes the comparable changes in microfossil assemblages record the different phases of relative land and sea level changes and the magnitude of land subsidence caused by each earthquake expressed relative to the tidal range at the site these results raise the question whether preseismic sea level rise represents any kind of warning of large earthquakes

untangling the palaeocene climatic rhythm an astronomically calibrated early palaeocene magnetostratigraphy and biostratigraphy at zumaia basque basin northern spain abstract the magnetostratigraphy of a 54 m long section above the cretaceous tertiary boundary at the sea cliff section of zumaia in the basque basin northern spain has been established the section encompasses the entire danian and the lower part of the selandian stages as indicated by calcareous plankton biostratigraphy the studied interval consists of hemi pelagic limestone marl alternations in the form of couplets and bundles which range from centimetre decimetre to metre scale respectively and a few thin bedded calcareous turbidites the magnetostratigraphy based on samples from about 200 stratigraphic levels allows the identification of six reversal boundaries from chron c29r to c26r at a bed level the spatial or temporal evolution of periodicities from a lithologically coded series is studied with the continuous wavelet transform technique a preliminary age model based on the standard ck95 gpts indicates that the basic lithologic carbonate marl couplet corresponds to the 19 23 kyr precession cycle 21 31 cm cycle in the depth domain and that a bundle cycle usually groups of four to six basic couplets with global periodicity centred at 1 22 m corresponds to the 110 kyr eccentricity cycle we have tuned the bundle cycles to the va03 r7 eccentricity orbital solution astrophys j 592 2003 620 630 following an initial match of a node of the 2 4 ma eccentricity modulatory cycle in the target time series to particularly carbonate rich bundles from the upper part of the zumaia section that displays significant power of a 4 4 m period cycle corresponding to the 404 kyr eccentricity cycle consistency between lithologic patterns and characteristics in the eccentricity target is reasonably met although the 404 kyr eccentricity cycle is not persistent throughout the tuning however appears robust as it brings the age of the k t boundary at 65 8 ma it is argued that a sea level signal tectonically driven is superimposed on the climatic forcing at the milankovitch band masking the full expression of the low frequency astronomical periods we provide a cycle tuned duration for all intervening early palaeocene polarity chrons and estimate relative ages for bioevents the cycle tuned chronology indicates that the ck95 gpts overestimates the duration of chrons c28 and c27 by 20 and 26 respectively our data may prove useful to better constrain early palaeocene biostratigraphy of calcareous plankton and in the redefinition of the boundary between the danian and selandian stages

atlantic eocene planktonic foraminiferal historical biogeography and paleohydrographic indices abstract analysis of a quantitative and synoptic data base of eocene atlantic planktonic foraminifera has illuminated many facets of foraminiferal faunal structure and composition reflective of bioprovince and useful for empirical establishment of ecologic and paleohydrographic indices tropical indigenes such as the morozovellids turborotaliids subquadrate acarininids and some globigerinathekids dissolve most rapidly along with juveniles of most species tropical faunas are high in diversity and dominance include oxygen minimum indices such as the biserial heterohelicids only in high productivity times such as the middle eocene are dominated by genera with high numbers of species and species consistently typical of warm water regions until the late eocene when faunas include a higher number of middle than lower latitude types truly tropical genera are replaced by subtropical eutrophic indicators such as the globigerinathekids and contract to the florida current region prior to their extinctions at the end of the middle eocene atlantic late paleogene tropical forms first appear in the gulf of mexico at the end of the middle eocene middle latitude faunas include high numbers of chiloguembelinids pseudohastigerinids small and biconvex morozovellids round and globigerinid form acarininids low spired subbotinids in the late middle eocene high spired subbotinids large and typical globigerinids in the late eocene these forms have intermediate dissolution susceptibilities middle latitude faunas are often high in diversity in midddle latitude frontal regions dominance is low even in warm intervals when tropical indigenes increase in number in middle latitude faunas especially in boundary currents low latitude species penetrate temperate areas also during cool eutrophic periods of vigorous circulation such as the late middle eocene typical of temperate slope faunas are high abundances of high spired subbotinids and small sized catapsydracids high latitude faunas are usually low in diversity except in the middle to late eocene when frontal regions were located in the southern labrador sea and over rockall bank typical forms are the low spired subbotinids until the late middle eocene globorotaloids catapsydracids tenuitellids and in the late eocene the biserial heterohelicids indigenous species are the most solution resistant and many are mesopelagic during warmings rare low latitude indices penetrate high latitudes subpolar faunas have greatest affinities with middle latitude faunas at these times

time dependent brittle creep in darley dale sandstone 1 the characterization of time dependent brittle rock deformation is fundamental to understanding the long term evolution and dynamics of the earth s crust the chemical influence of pore water promotes time dependent deformation through stress corrosion cracking that allows rocks to deform at stresses far below their short term failure strength here we report results from a study of time dependent brittle creep in water saturated samples of darley dale sandstone initial porosity 13 under triaxial stress conditions results from conventional creep experiments show that axial strain rate is heavily dependent on the applied differential stress a reduction of only 10 in differential stress results in a decrease in strain rate of more than two orders of magnitude however natural sample variability means that multiple experiments must be performed to yield consistent results hence we also demonstrate that the use of stress stepping creep experiments can successfully overcome this issue we have used the stress stepping technique to investigate the influence of confining pressure at effective confining pressures of 10 30 and 50 mpa while maintaining a constant 20 mpa pore fluid pressure our results demonstrate that the stress corrosion process appears to be significantly inhibited at higher effective pressures with the creep strain rate reduced by multiple orders of magnitude the influence of doubling the pore fluid pressure however while maintaining a constant effective confining pressure is shown to influence the rate of stress corrosion within the range expected from sample variability we discuss these results in the context of microstructural analysis acoustic emission hypocenter locations and fits to proposed macroscopic creep laws

influences of electrolyte concentration on subcritical crack growth in sandstone in water abstract information on subcritical crack growth in rock is essential to ensure the long term stability of structures in a rock mass subcritical crack growth in rock is known to be affected by its surrounding environment in most cases rock found underground is saturated by water the underground water can be fresh water or salt water with variable electrolyte concentrations however the influence of electrolyte concentration on subcritical crack growth in rock has not been fully elucidated in this study subcritical crack growth in berea sandstone and shirahama sandstone was measured when saturated with distilled water and with sodium chloride solutions of differing concentrations crack velocity in berea sandstone changed very little with different electrolyte concentrations by contrast in the shirahama sandstone crack velocity became lower with increased electrolyte concentrations up to 1 0 mol l with increasing electrolyte concentration the width of the electric double layer on the surface of mineral grains decreased which caused a decrease in the repulsive force acting on the crack surface leading to a decrease in crack velocity up to concentrations of 1 0 mol l however when the electrolyte concentration was higher than 1 0 mol l crack velocity increased due to the nucleation of microscopic defects on the boundary between clays and stiff mineral grains thus electrolyte concentration affects subcritical crack growth by decreasing the width of the electric double layer and the condensation of clay minerals

the palaeocene top chron c27n transient greenhouse episode evidence from marine pelagic atlantic and peri tethyan sections terra nova 24 477 486 2012 abstract the early cenozoic which is punctuated by several negative carbon isotope excursions cies was a time of climatic and oceanographic transition from greenhouse to icehouse conditions the occurrence of a 0 5 cie starting at the top of chron c27n tc27n is reconfirmed with stable isotope data from zumaia spain and bjala bulgaria localities spectral analysis on respective carbonate magnetic susceptibility proxy records substantiates the orbital cyclostratigraphy allowing correlation to a high resolution benthic foraminifera isotope record from odp pacific site 1209 that indicates a coeval 2 c transient warming the hyperthermal event lasts 200 ka contrasting with other short lived events from the eocene and displays a relatively rapid onset and a longer tailing back to pre event values similar to the palaeocene eocene thermal maximum petm though lower in amplitude that a causal trigger for the tc27n event may be the onset of volcanism in the north atlantic igneous province naip can be inferred from a 200 m thick lava pile erupted during c27n c26r polarity transition in the e greenland margin

black shale formation during the latest danian event and the paleocene eocene thermal maximum in central egypt two of a kind abstract the paleocene eocene thermal maximum petm 55 8 ma is considered as the most severe of a series of transient warming events hyperthermals that occurred during the early paleogene however the extent and magnitude of environmental changes during the short lived warming events pre and post dating the petm are still poorly constrained in this study we focus on the latest danian event lde 61 7 ma and compare it to the petm we present high resolution micropaleontological geochemical and mineralogical data of the petm and the lde in two adjacent sections from the gebel qreiya area in egypt there both events are characterized by a distinct set of event beds overlying an unconformity they are associated with intense carbonate dissolution and substantial changes in the benthic foraminifera fauna moreover both show an abrupt drop of siliciclastic input sediment starvation correlative to the onset of black shale formation and a strong enrichment in redox sensitive trace elements the evidence for enhanced detrital input during the onset of the petm and a longer recovery phase with enhanced phosphorus sedimentation during the petm attests a stronger environmental impact of this event compared to the lde according to rock eval and elemental analysis the petm as well as the lde event beds have up to 4 wt organic carbon small amounts of volatile hydrocarbons but high amounts of highly weathered and inert organic matter black carbon during pyrolysis the extremely high temperatures for the maximum release of hydrocarbons of the petm and lde samples correspond to thermal heating of 170 c which is incompatible with the sediment burial history therefore we suggest that the organic matter in both event deposits does not reflect well preserved marine biomass but predominantly represents a mixture of heavily weathered autochthonous marine material and allochthonous combustion residues differences in preservation and or type of organic matter are also likely to account for the divergent stable isotope anomalies of organic carbon the well known negative carbon isotope anomaly at the petm and a positive anomaly at the lde although warming water column stratification and enhanced nutrient input may have promoted anoxic conditions on the shelf during the lde as well as during petm our results support rapid sea level rise and clastic starvation as one important mechanism for black shale formation and carbon sequestration for both events this result underlines the similarity of both hyperthermal events in terms of environmental changes recorded on the southern tethyan margin with the petm showing an additional early phase of strong detrital input not revealed at the lde

paleoenvironmental change at the danian selandian transition in tunisia foraminifera organic walled dinoflagellate cyst and calcareous nannofossil records abstract in the present study we document paleoenvironmental change across the danian selandian transition planktic foraminiferal interval p2 p3b calcareous nannofossil zone np4 subzones ntp6 ntp8a 61 59 ma in nw tunisia diversifications of paleogene planktic foraminifera with the evolution of the muricate and photosymbiotic lineages morozovella acarinina and igorina and of the biostratigraphically important nannofossils genus fasciculithus are recorded within this interval the present study aims to understand early paleogene environmental changes in the southern tethys by analyzing the evolution of surface water and to a lesser extent seafloor conditions three localities were investigated ain settara elles and el kef all representing outer neritic deposition in the same basin the tunisian trough paleoenvironmental changes are explored by combining planktic foraminiferal organic dinocyst and calcareous nannofossils assemblages and several proxy parameters planktic benthic ratio numbers of planktic foraminifera per gram peridinioid gonyaulacoid ratio terrestrial marine palynomorph ratio in addition also some geochemical parameters calcite content and stable isotopes are examined our records indicate that the environment evolved from an initially oligotrophic open marine deep outer neritic setting in p2 p3a towards a shallower and nutrient rich setting from the base of subzone p3b this change is seen in the foraminiferal assemblages with the substitution of praemurica by morozovella among the planktic foraminifera and an upward decrease in deeper benthic taxa also the organic dinocyst assemblages show a peak of peridinioid cysts cerodinium and lejeunecysta associated to these dinocyst assemblages the lowest occurrence of apectodinium is recorded which seem to have evolved in this region possibly in response to enhanced nutrient levels on the shelf additionally a distinct change in calcareous nannofossil assemblages is also described marked by the lowest appearance of chiasmolithus edentulus the lowest consistent occurrence of fasciculithus and a slight increase in near shore taxa essentially pontosphaera this project provides an accurate understanding of paleoenvironmental change across the danian selandian transition in tunisia especially integrating different proxies demonstrates a paleobathymetric shallowing from the danian to the selandian associated to increase surface paleoproductivity furthermore the results are compared with those from other localities along the southern tethyan margin egypt and jordan and a more regional paleoclimatic paleoceanographic perturbation in the southern tethys is suggested

tidal marsh stratigraphy sea level change and large earthquakes i a 5000 year record in washington u s a abstract many of the estuaries of the pacific northwest of the u s a and canada contain stratigraphic sequences typified by alternating peat mud couplets recent studies in this region interpret such couplets as the product of repeated large magnitude s or 9 earthquakes on the cascadia subduction zone the resultant pattern of land level movements is described by a model the earthquake deformation cycle of coseismic land subsidence followed by land uplift during interseismic strain accumulation however peat mud couplets similar to those recorded in the pacific northwest are found on other less tectonically active temperate latitude coasts such as northwest europe and the atlantic coast of the u s a where they have been interpreted as the product of non seismic coastal processes in this paper we apply the methods and scientific framework common to sea level investigations in northwest europe to a sequence of peat mud couplets recorded in the lower johns river an estuary in southern washington to provide a test of the earthquake deformation cycle stratigraphic investigations of the intertidal sediments along the lower johns river using lithological pollen diatom and foraminiferal data show evidence for eight coastal submergence events during the last 5000 years to evaluate the earthquake deformation cycle we assess the lateral extent of peat mud couplets the synchroneity of submergence the presence of tsunami deposits accompanying submergence and the suddenness and amount of submergence each submergence is shown to be accompanied by changes in coastal sedimentation broadly commensurate with those predicted by the earthquake deformation cycle demonstrating the continued intermittent seismic activity of the cascadia subduction zone throughout the mid and late holocene quantitative analyses of contemporary and fossil biostratigraphic data using twinspan and detrended correspondence analysis enable us to estimate the magnitude of submergence accompanying each peat mud couplet one event was accompanied by submergence of about 1 5 m or more four events by intermediate submergence of about 1 0 5 m and a further three events by submergence of

thermal stress weathering and the spalling of antarctic rocks using in situ field measurements laboratory analyses and numerical modeling we test the potential efficacy of thermal stress weathering in the flaking of millimeter thick alteration rinds observed on cobbles and boulders of ferrar dolerite on mullins glacier mcmurdo dry valleys mdv in particular we examine whether low magnitude stresses arising from temperature variations over time result in thermal fatigue weathering yielding slow crack propagation along existing cracks and ultimate flake detachment our field results show that during summer months clasts of ferrar dolerite experience large temperature gradients across partially detached alteration rinds 4 7 c mm 1 and abrupt fluctuations in surface temperature up to 12 c min 1 the latter are likely due to the combined effects of changing solar irradiation and cooling from episodic winds the results of our thermal stress model coupled with subcritical crack growth theory suggest that thermal stresses induced at the base of thin alteration rinds 2 mm thick common on rocks exposed for 105 years may be sufficient to cause existing cracks to propagate under present day meteorological forcing eventually leading to rind detachment the increase in porosity observed within alteration rinds relative to unaltered rock interiors as well as predicted decreases in rind strength based on allied weathering studies likely facilitates thermal stress crack propagation through a reduction of fracture toughness we conclude that thermal stress weathering may be an active though undervalued weathering process in hyperarid terrestrial polar deserts such as the stable upland region of the mdv

a complete high resolution paleocene benthic stable isotope record for the central pacific odp site 1209 1 we have compiled the first stratigraphically continuous high resolution benthic foraminiferal stable isotope record for the paleocene from a single site utilizing cores recovered at pacific odp site 1209 the long term trend in the benthic isotope record suggests a close coupling of volcanic co2 input and deep sea warming over the short term the record is characterized by slow excursions with a pronounced periodic beat related to the short 100 kyr and long 405 kyr eccentricity cycle the phase relationship between the benthic isotope record and eccentricity is similar to patterns documented for the oligocene and miocene confirming the role of orbital forcing as the pace maker for paleoclimatic variability on milankovitch time scales in addition the record documents an unusual transient warming of 2 c coeval with a 0 6 carbon isotope excursion and a decrease in carbonate content at 61 75 ma this event which bears some resemblance to eocene hyperthermals marks the onset of a long term decline in 13c the timing indicates it might be related to the initiation of volcanism along greenland margin

isolation basin records of late quaternary sea level change central mainland british columbia canada isolation basin records from the seymour belize inlet complex a remote area of central mainland british columbia canada are used to constrain post glacial sea level changes and provide a preliminary basis for testing geophysical model predictions of relative sea level rsl change sedimentological and diatom data from three low lying 4 m elevation basins record falling rsls in late glacial times and isolation from the sea by 11 800 11 200 14c bp a subsequent rsl rise during the early holocene 8000 14c bp breached the 2 13 m sill of the lowest basin woods lake but the two more elevated basins sill elevations of 3 6 m remained isolated at 2400 14c bp rsl stood at 1 49 0 34 m above present mtl falling rsls in the late holocene led to the final emergence of the woods lake basin by 1604 36 14c bp model predictions generated using the ice 5g model partnered with a small number of different earth viscosity models generally show poor agreement with the observational data indicating that the ice model and or earth models considered can be improved upon the best data model fits were achieved with relatively low values of upper mantle viscosity 5 1019 pa s which is consistent with previous modelling results from the region the rsl data align more closely with observational records from the southeast of the region eastern vancouver island central strait of georgia than the immediate north bella bella bella coola and prince rupert kitimat and areas to the north west queen charlotte sound hecate strait underlining the complexity of the regional response to glacio isostatic recovery

the distribution of salt marsh foraminifera at little dipper harbour new brunswick canada implications for development of widely applicable transfer functions in sea level research a stepwise linear regression analysis was carried out on both 0 1 and 0 10 cm surface samples from a transect across the marsh at little dipper harbour new brunswick only the 0 1 cm surface samples produce statistically reliable results r 2 0 705 r 02 0 609 these results are in sharpcontrast to those obtained from british columbia marshes where infaunal habitat and taphonomic biasing result in 0 10 cm samples producing the best results using stepwise linear regression the fundamental difference in the apparent preferred habitats of marsh foraminifera in these areas pose difficulties for researchers attempting to develop transfer function training sets that can be applied over wide areas in paleo sea level research r 2004 elsevier ltd and inqua all rights reserved

brittle creep in basalt and its application to time dependent volcano deformation time dependent brittle deformation is a fundamental and pervasive process operating in the earth s upper crust its characterization is a pre requisite to understanding and unraveling the complexities of crustal evolution and dynamics the preferential chemical interaction between pore fluids and strained atomic bonds at crack tips a mechanism known as stress corrosion allows rock to fail under a constant stress that is well below its short term strength over an extended period of time a process known as brittle creep here we present the first experimental measurements of brittle creep in a basic igneous rock a basalt from mt etna volcano under triaxial stress conditions results from conventional creep experiments show that creep strain rates are highly dependent on the level of applied stress and can be equally well fit by a power law or an exponential law with a 20 increase in stress producing close to three orders of magnitude increase in creep strain rate results from stress stepping creep experiments show that creep strain rates are also influenced by the imposed effective confining pressure we show that only part of this change can be attributed to the purely mechanical influence of an increase in effective pressure with the remainder interpreted as due to a reduction in stress corrosion reactions the result of a reduction in crack aperture that restricts the rate of transport of reactive species to crack tips overall our results also suggest that a critical level of crack damage is required before the deformation starts to accelerate to failure regardless of the level of applied stress and the time taken to reach this point the experimental results are discussed in terms of microstructural observations and fits to a macroscopic creep law and compared with the observed deformation history at mt etna volcano c 2011 elsevier b v all rights reserved

palaeoenvironmental changes across the danian selandian boundary in the north sea basin abstract the danian selandian boundary 60 ma marks the cessation of 40 million years of carbonate deposition in the north sea basin and a shift to siliciclastic deposition on the basis of variations in lithology benthic and planktonic foraminifera and calcareous nannofossils in three cores from storebaelt in the eastern part of the north sea basin we have reconstructed the palaeoenvironmental changes across the boundary the benthic foraminiferal faunas belong to the midway type fauna they are extremely rich and more than 260 taxa have been recognized q mode cluster analysis groups the benthic assemblages into four biofacies which correspond fairly closely to lithological units correlation of the storebaelt records with marine palaeorecords from the danish basin and the north sea basin indicate that the transformation of the north sea from a carbonate to a siliciclastic basin occurred in four steps separated by relatively long stable periods the most important external factors involved in the change are firstly a drop in the relative sea level during the late danian leading to the disappearance of bryozoans from the north sea basin and to non deposition and erosion in many areas secondly coinciding with the danian selandian boundary an uplift of the scotland shetland area resulting in a massive input of siliciclastic deposits to the north sea basin thirdly during the early selandian inversion of the sorgenfrei tornquist zone and mesozoic basins in the southern and eastern part of the north sea basin resulted in a huge influx of reworked cretaceous chalk and an almost complete stop of carbonate production finally later in the early selandian in connection to a general sea level rise and a reduction in the gateway between the north sea basin and the tethys sea the sea bottom conditions became colder and more acidic this resulted in partial dissolution of the carbonates and the deposition shifted from marl to clay comparison with records from the western pyrenees the nile basin and the eastern north america suggests that sea level changes across the danian selandian boundary are primarily of eustatic nature

diatoms as an aid in identifying late holocene tsunami deposits diatoms bacillariophyta help identify the onshore deposits of tsunamis from earthquakes on the cascadia subduction zone along the pacific coast of oregon washington and british columbia and on faults high in the north american plate in the puget sound area of washington at the copalis river washington diatom analyses suggest that a tsunami deposit about 300 calendric years old 300 yr bp originated from sandy shoals of the lower estuary rather than nearby beaches or coastal dunes at cultus bay and west point washington well preserved benthic estuarine diatoms in sand sheets overlying tidal marsh peat indicate that the deposits came from intertidal or nearshore areas of puget sound on an abruptly uplifted mudflat at the landward end of hood canal at lynch cove washington tidal flat diatoms refute the possibility of a terrestrial source for the sand diatoms in 300 yr bp tsunami deposits on the niawiakum river washington confirm that the sand in these deposits had a marine source and help

influence of temperature on brittle creep in sandstones the characterization of time dependent brittle creep promoted by chemically active pore fluids is fundamental to our understanding of the long term evolution and dynamics of the earth s crust here we report results from a study of the influence of temperature on both short term strength and time dependent brittle creep in three sandstones under triaxial stress conditions we show that an increase in temperature from 20 degrees to 75 degrees c significantly enhances stress corrosion cracking in all three sandstones leading to 1 a systematic reduction in strength during constant strain rate experiments and 2 an increase by several orders of magnitude in brittle creep strain rates during stress stepping creep experiments we also show that a conventional creep experiment performed at 75 degrees c exhibits a qualitatively similar three stage brittle creep curve as that observed at ambient temperature extrapolation of our results suggests that temperature is likely to be the dominant influence on the evolution of creep strain rate with depth in the shallow crust citation heap m j p baud and p g meredith 2009 influence of temperature on brittle creep in sandstones geophys res lett 36 l19305 doi 10 1029 2009gl039373

an integrated stratigraphic record of the palaeocene lower eocene at gubbio italy new insights into the early palaeogene hyperthermals and carbon isotope excursions a high resolution integrated stratigraphic framework stable isotope stratigraphy standard calcareous nannofossil and foraminiferal biostratigraphy magnetostratigraphy together with geochemical and rock magnetic properties analyses of a complete and well preserved succession at contessa valley gubbio central italy have offered an excellent opportunity to identify and constrain the palaeocene to early eocene hyperthermals and carbon isotope excursions cies in addition we provide the first evidence in the tethys ocean of cies previously identified in the pacific atlantic and southern oceans highlighting their global significance and of some unknown cies their characteristics are compared with those reported for deep sea cores and other land based sections to test whether the signature associated with cies documented in our composite section might give evidence for tracing them over wider areas the contessa composite section thus represents a reference succession also for insight into the magnetobiochronostratigraphy and the magnitude of early palaeogene hyperthermals and cies

testing the mid holocene relative sea level highstand hypothesis in north wales uk accurate holocene relative sea level curves are vital for modelling future sea level changes particularly in regions where relative sea level changes are dominated by isostatically induced vertica

assessing sea level data from connecticut usa using a foraminiferal transfer function for tide level concerns surrounding possible future climate change sea level rise and their potential impacts on coastal environments have stimulated research seeking to elucidate the relationship between ocean levels and climate at the sub century scale the need for increasingly precise reconstructions of relative sea level change has in turn driven the development of new methodologies capable of resolving fine scale variability within salt marsh sedimentary sequences the use of salt marsh foraminifera as precise indicators of past tide levels has played a central role in this process and is exemplified by a number of detailed studies conducted in connecticut usa in this paper we apply the most recent methodological advance in the reconstruction of relative sea levels using salt marsh foraminifera we develop a foraminiferal transfer function for tide level derived from the modern foraminiferal distributions of four connecticut salt marshes in contrast to existing approaches that employ site specific interpolations of local vertical foraminiferal assemblage zones this transfer function can provide objective quantitative and reproducible estimates of palaeomarsh surface elevation with explicitly stated error terms for marshes throughout connecticut irrespective of differences in tidal range we demonstrate the foraminiferal transfer function approach by employing it to reconstruct changes in palaeomarsh surface elevation from three cores recovered from hammock river marsh connecticut the resulting reconstructions which are precise to f0 09 m are tested using an independent dataset from the neighbouring state of maine and are used to assess a pivotal record of mean high water mhw change from this site we conclude that the transfer function reconstructions show good general agreement with previous records of palaeomarsh surface elevation but with the advantages of quantified error terms and a transparent reproducible methodology this replicability will assist in the comparison or combination of local records of mhw change to infer large scale regional sea level variations d 2003 elsevier b v all rights reserved

sheet gravel evidence for a late holocene tsunami run up on beach dunes great barrier island new zealand abstract a semi continuous sheet of granule to cobble size clasts forms a distinctive deposit on sand dunes located on a coastal barrier in whangapoua bay great barrier island new zealand the gravel sheet extends from the toe of the foredune to 14 3 m above mean sea level and 200 m landward from the beach clasts are rounded to sub rounded and comprise lithologies consistent with local bedrock terrestrial sources for the gravel are considered highly unlikely due to the isolation of the dunes from hillslopes and streams the only source for the clasts is the nearshore to inner shelf of whangapoua bay where gravel sediments have been previously documented the mechanism for transport of the gravel is unlikely to be storm surge due to the elevation of the deposit maximum recorded storm surge on this coast is 0 8 m above mean high water spring tide aeolian processes are also discounted due to the size of clasts and the elevation at which they occur tsunami is therefore considered the most probable mechanism for gravel transport minimum run up height of the tsunami was 14 3 m based on maximum elevation of gravel deposits optical ages on dune sands beneath and covering the gravel allow age bracketing to 0 4 7 ka within this time frame numerous documented regional seismic and volcanic events could have generated the tsunami notably submarine volcanism along the southern kermadec arc to the east southeast of great barrier island where large magnitude events are documented for the late holocene radiocarbon ages on shell from maori middens that appear to have been reworked by tsunami run up constrain the age of this event to post ca 1400 ad regardless of the precise age of this event the well preserved nature of the whangapoua gravel deposit provides for an improved understanding of the high degree of spatial variability in tsunami run up

diatom based tidal level transfer functions as an aid in reconstructing quaternary history of sea level movements in the uk this research analyses the diatom asssemblages recorded from six uk coastal sites and relates these diatom assemblages to tidal levels the relationship between diatom assemblages and tidal levels is examined statistically in order to develop a diatom based tidal level transfer function the results suggest that there is highly significant correlation between the diatom assemblages and water levels from mean high water of neap tides to highest astronomical tide p 0 01 99 random permutations a weighted average wa transfer function is thus established and the predictive ability of this transfer function is highly satisfactory finally this transfer function is applied successfully to estimate palaeotidal levels from fossil diatom data recorded in late holocene coastal sequences copyright 1999 john wiley sons ltd

characterization of granite matrix porosity and pore space geometry by in situ and laboratory methods summary most available studies of interconnected matrix porosity of crystalline rocks are based on laboratory investigations that is work on samples that have undergone stress relaxation and were affected by drilling and sample preparation the extrapolation of the results to in situ conditions is therefore associated with considerable uncertainty and this was the motivation to conduct the in situ connected porosity experiment at the grimsel test site central swiss alps an acrylic resin doped with fluorescent agents was used to impregnate the microporous granitic matrix in situ around an injection borehole and samples were obtained by overcoring the 3 d structure of the porespace represented by microcracks was studied by u stage fluorescence microscopy petrophysical methods including the determination of porosity permeability and p wave velocity were also applied investigations were conducted both on samples that were impregnated in situ and on non impregnated samples so that natural features could be distinguished from artefacts the investigated deformed granites display complex microcrack populations representing a polyphase deformation at varying conditions the crack population is dominated by open cleavage cracks in mica and grain boundary cracks the porosity of non impregnated samples lies slightly above 1 per cent which is 2 2 5 times higher than the in situ porosity obtained for impregnated samples measurements of seismic velocities vp on spherical rock samples as a function of confining pressure spatial direction and water saturation for both non impregnated and impregnated samples provide further constraints on the distinction between natural and induced crack types the main conclusions are that 1 an interconnected network of microcracks exists in the whole granitic matrix irrespective of the distance to ductile and brittle shear zones and 2 conventional laboratory methods overestimate the matrix porosity calculations of contaminant transport through fractured media often rely on matrix diffusion as a retardation mechanism

late cretaceous deep water agglutinated foraminiferal assemblages from the north atlantic and its marginal seas the stratigraphic and biogeographic distribution of more than 170 species of deep water agglutinated benthic foraminifers dwaf from the north atlantic and adjacent marginal seas has been compared with paleoenvironmental data e g paleobathymetry oxygenation of the bottom waters amount of terrigenous input and substrate disturbance six general types of assemblages in which deep water agglutinated taxa occur are defined from the turonian to maastrichtian times 1 high latitude slope assemblages 2 low to mid latitude slope assemblages 3 flysch type assemblages 4 deep water limestone assemblages scaglia type 5 abyssal mixed calcareous agglutinated assemblages 6 abyssal purely agglutinated assemblages latitudinal differences in faunal composition are observed the most important of which is the lack or extreme paucity of calcareous forms in high latitude assemblages east to west differences appear to be of comparatively minor importance most dwaf species occur in all studied regions and are thus considered as cosmopolitan biostratigraphic turnovers in the taxonomic content of assemblages are observed in the lowermost turonian mid campanian and in the upper maastrichtian to lowermost paleocene these datum levels correspond to inter regional and time constant paleooceanographic events which probably also affected the deep water benthic biota this allows us to use deep water agglutinated foraminifers for biostratigraphy in the north atlantic sequences deposited below ccd and to geographically extend the currently used zonal schemes which have been established in the carpathian and alpine areas

paleogeography glacially induced crustal displacement and late quaternary coastlines on the continental shelf of british columbia canada abstract subsequent to the last glacial maximum lgm complex isostatic adjustments resulted from deglaciation eustatic sea level change tectonic faulting and a relatively thin flexible lithosphere in the queen charlotte islands qci region a geostatistical interpolation model charts the sequence of evolving landscapes and displays temporal changes in the magnitudes and extent of crustal flexure that accompanied forebulge development on the late quaternary northeast pacific continental shelf between 14 2 and 8 7 ka bp wavelength and forebulge amplitude are consistent with thermal modeling implying low upper mantle viscosity and thin elastic lithospheric thickness beneath queen charlotte qc sound and hecate strait glacial ice 690 m thick began retreating from dixon entrance after 14 5 ka bp 14c years ago and prior to 12 6 ka bp permitting over 100 m of crustal uplift in northern hecate strait a forebulge persisted in hecate strait and qc sound from 13 2 until after 9 7 ka bp implying fixed glacial ice on the british columbia bc mainland until 10 ka bp paleogeographic reconstructions show two emergent ice free terrains one extending eastward from the qci and the other in qc sound by 11 7 ka bp a landbridge connected the bc mainland and the qci

the danian selandian boundary at site 1262 south atlantic and in the tethyan region biomagnetostratigraphy evolutionary trends in fasciculiths and environmental effects of the latest danian event abstract a high resolution calcareous nannofossil analysis of the danian selandian boundary was conducted at site 1262 walvis ridge south atlantic to pinpoint the lowest occurrence of fasciculiths and to unravel the evolutionary trends throughout nannofossil zone np4 using quantitative analyses numerous primary and secondary bioevents were identified improving the biostratigraphic resolution of this interval the main events recorded at site 1262 were also identified at the zumaia section global stratotype section and point gssp of the base of the selandian and at the qreiya section egypt the lowest occurrence of fasciculiths represented by the lo of gomphiolithus magnicordis and gomphiolithus magnus was observed in the middle part of chron c27r above the lo of toweius pertusus and prior to the lo of the genus sphenolithus the synchroneity of the lo of fasciculiths was also verified at various latitudes such as dsdp site 384 nw atlantic odp site 761b indian ocean and dsdp site 577a pacific ocean the first and second diversification events steurbaut and sztrakos 2008 or radiation events bernaola et al 2009 of fasciculiths have been thoroughly discussed and well characterized by a succession of events the occurrence of the latest danian event lde and several paleoenvironmental changes recognized during this time interval coupled with an ecological competition with sphenolithus appear to be the probable causes of the first and second radiations and the fasciculith barren interval between them the occurrence of new morphostructures and taxa suggests evolutionary trends and a strict link between morphological evolution and paleoclimate

mid and late holocene sea level changes in roudsea marsh northwest england a diatom biostratigraphical investigation diatoms vascular vegetation sediment data and water salinity from contemporary intertidal environ ments in roudsea marsh northwest england are used to define altitudinal relationships between diatom assem blages and reference water levels comparison of these data with the high resolution diatom biostratigraphy of a fossil marsh sequence allows identification of fluctuations of relative sea level in the mid and late holo cene two oscillations in relative sea level are recorded a rise in sea level 0 6 m led to the inundation of the site after 6000 bp and was followed by a fall in sea level c 1 m around 4700 bp a second rise in sea level 0 5 m occurred before 2420 bp and was followed by a relatively stable or smaller rise of sea level during the last millennium the use of diatom groups based on marsh altitude was successful

foraminiferal evidence for the amount of coseismic subsidence during a late holocene earthquake on vancouver island west coast of canada abstract foraminiferal data from two sites 6 km apart on the shores of an inlet near tofino on the west coast of vancouver island british columbia allow estimates to be made of the amount of coseismic subsidence during a large earthquake 100 400 years ago the sampled sediment succession at the two sites is similar peat representing a former marsh surface is abruptly overlain by intertidal mud grading upward into peat of the present marsh at one of the sites a layer of sand interpreted to be a tsunami deposit locally separates the buried peat from the overlying intertidal mud the abrupt peat mud contact records sudden crustal subsidence during the earthquake the paleoelevation of each fossil sample was estimated by comparing its foraminiferal assemblage with modern assemblages of known elevation the modern assemblages were obtained from surface samples collected along transects across the marsh near the fossil sample sites comparisons were made statistically using transfer functions estimates of coseismic subsidence based on differences in paleoelevations just above and below the top of the buried peat range from 20 cm to 1 m with the most likely value in the 55 70 cm range post seismic crustal rebound began soon after the earthquake and may have been largely complete a few decades later

stress corrosion cracking of quartz a note on the influence of chemical environment abstract tensile mode i stress corrosion growth of cracks on the a plane of quartz in a direction normal to z has been studied in de ionized water in 2n hcl and in 2n naoh solutions at 20 c the double torsion testing method was used to obtain crack velocity v stress intensity factor ki curves the stress corrosion index n where v kin was 19 3 for 2n hcl 12 8 for deionized water and 9 5 for 2n naoh the degree of influence of reagent chemistry on crack velocity was most marked at low ki values at 0 5 kic 3 orders of magnitude increase in crack velocity results from substituting 2n naoh for 2n hcl as the corrosive medium but decreased monotonically on raising ki so that close to kic there was no clearly discernible influence on crack growth rates ca 10 3 m s 1 these observations are explained in terms of a model of crack propagation in which at low ki values the chemistry of the bulk fluid environment controls the corrosion reaction the rate of crack growth is enhanced by increasing environmental oh concentration at high ki or velocity however the chemical composition of the quartz surface may control crack propagation rates through its influence on the chemistry of the crack tip fluid as the ph of natural pore fluids is likely to vary widely in different geological environments these results should be noted when invoking stress corrosion to explain geophysical phenomena

late holocene great earthquakes and relative sea level change at kenai southern alaska kenai located on the west coast of the kenai peninsula alaska subsided during the great earthquake of ad 1964 regional land subsidence is recorded within the estuarine stratigraphy as peat overlain by tidal silt and clay reconstructions using quantitative diatom transfer functions estimate co seismic subsidence relative sea level rise between 0 28 0 28 m and 0 70 0 28 m followed by rapid post seismic recovery stratigraphy records an earlier co seismic event as a second peat silt couplet dated to 1500 1400 cal yr bp with 1 14 0 28 m subsidence two decimetre scale relative sea level rises are more likely the result of glacio isostatic responses to late holocene and little ice age glacier expansions rather than to co seismic subsidence during great earthquakes comparison with other sites around cook inlet at girdwood and ocean view helps in constructing regional patterns of land level change associated with three great earthquakes ad 1964 950 850 cal yr bp and 1500 1400 cal yr bp each earthquake has a different spatial pattern of co seismic subsidence which indicates that assessment of seismic hazard in southern alaska requires an understanding of multiple great earthquakes not only the most recent all three earthquakes show a pre seismic phase of gradual land subsidence that marked the end of relative land uplift caused by inter seismic strain accumulation copyright 2005 john wiley sons ltd

gradient analysis of diatom assemblages in a puget sound salt marsh can such assemblages be used for quantitative paleoecological reconstructions abstract taphonomy is important to coastal paleoecologists because processes acting on diatom thanocoenoses tend to work towards obscuring original ecological relationships between diatom assemblages and the environment the purpose of this paper is to briefly describe diatom taphonomy and present a method for quantitative reconstruction of environmental parameters from salt marsh diatom assemblages the main hypothesis for this study is that major environmental and taphonomic processes e g tides act in predictable ways to distribute living and dead diatoms along environmental gradients to test this hypothesis a modern transect was established across a large salt marsh in southwestern puget sound for the purpose of determining modern species environment gradients and calibrating species assemblages to environmental variables canonical correspondence analysis cca relates modern species assemblages to environmental gradients and weighted averaging calibration is used to develop transfer functions for predicting environmental information cca showed that the effect of salinity and elevation on the species distributions is significant indicating that environmental processes control the distribution of sedimentary diatoms across the salt marsh surface in predictable ways salinity was strongly correlated with cca axis 1 and elevation with axis 2 the calibration results indicate that although mixing of allochthonous and autochthonous diatoms does occur salt marsh diatom assemblages reflect major environmental gradients in puget sound salt marshes and can be effectively used for quantitative reconstructions of former environmental conditions

in search of the latest danian event in a paleobathymetric transect off kasserine island north central tunisia danian lower paleocene sequences in north central tunisia are dominantly composed of marls and shales but a conspicuous indurated glauconite bearing marker bed is associated with the p3a p3b transition this glauconite bed is considered to correlate with the latest danian event lde described from the nile basin in egypt with the top chron c27n event atlantic and pacific oceans and with the cie ds1 zumaia spain the lde is thought to reflect a short period of global warming similar to the paleocene eocene thermal maximum but of lesser magnitude the presence of a glauconitic bed at the p3a p3b transition in tunisia suggests that the sequence is condensed which is confirmed by planktic foraminifer and nannofossil biostratigraphy and by the absence of the typical lde beds found in most egyptian sections benthic foraminiferal assemblages were quantitatively analyzed in three sections in north central tunisia sidi nasseur garn halfaya elles in order to characterize the paleoenvironmental evolution during the late danian and compare this with sections in egypt the benthic foraminiferal assemblages indicate that the tunisian sections were located along a depth and a paleoenvironmental gradient on the shelf north of kasserine island the reconstructed depth range is comparable with sections in egypt and encompasses middle neritic sidi nasseur section to shallow upper bathyal depths elles section with up to 16 gavelinella beccariiformis below the p3a p3b like in egypt assemblage shifts across the p3a p3b subzonal transition indicate shallowing and a transition to a more eutrophic paleoenvironment characterized by relatively high abundances of buliminids and stainforthia sp the 13c and 18o records generated on well preserved specimens of the ostracode species bairdia failed to demonstrate the presence of the carbon isotope excursion cie associated with the lde at the base of subzone p3b a condensed section or a hiatus associated with the glauconite bed would explain why the cie is not recorded in the tunisian sections

characterization of the latest danian event by means of benthic foraminiferal assemblages along a depth transect at the southern tethyan margin nile basin egypt abstract the latest danian event lde has been recognized on the southern tethyan margin egypt tunisia and in the atlantic zumaia spain and pacific oceans odp site 1209 based on a supraregional carbon isotope excursion and a negative shift in oxygen isotopes in the pacific it has been suggested that the lde is an early paleogene transient warming event so far the environmental effects of the lde have been observed in few sections and details on its impact and duration are scarce we present a quantitative study of benthic foraminiferal assemblages retrieved from five sections along a depth transect on the paleocene southern tethyan shelf nile basin egypt to assess paleoenvironmental change during the lde the lithologic sequences and foraminiferal assemblages indicate that the onset of the lde is related to widespread shelf dysoxia the organic rich laminated marls of lower lde bed i contain levels devoid of benthic foraminifera during the later stage of the lde dark gray shales of bed ii the shelf is repopulated by a neoeponides duwi benthic assemblage occurring in all sections initiating a gradual restoration of normal marine shelf environments q mode and r mode correspondence analysis assist in the interpretation of the n duwi assemblage which is related to disturbed conditions at the sea floor following oxygen depletion and increased organic loading the sharp lithologic boundary at the base of the lde suggests that the event coincides with a rapid transgression following a sea level fall with an estimated amplitude of 50 m or less comparison with the dan c2 and elpe mpbe two proposed transient warming episodes preceding and postdating the lde shows that the three paleocene events have several characteristics in common however the duration of the lde 200 kyr exceeds the estimated duration of the other events and a sea level cycle is only reported from the lde

stratigraphy of the paleocene continental sedimentary succession of the northern pyrenean basin corbieres southern france using δ13corg isotopes continental dominated successions are often poorly constrained stratigraphically due to a lack of robust biostratigraphic markers this study provides the first dataset of 13corg together with magnetostratigraphic and biostratigraphic data from a thick continental dominated succession at lairiere northern pyrenees france this section encompasses the latest cretaceous up to the paleocene eocene thermal maximum interval and is characterized by fluvial deposits occasionally intercalated with continental carbonates lacustrine deltaic deposits and shallow marine sediments this work identifies 13corg events and assigns them to global 13c geochemical events defined in pyrenean and tethyan marine successions in which the stage boundaries are well calibrated as the isotopic measurements are performed on dispersed organic matter in sedimentary rocks with a low organic content we propose that analyses of the signal should take into consideration the depositional environment because variations in the organic matter content might affect the signal we establish a high resolution chronostratigraphy in terrestrial paleocene deposits in the ne pyrenean zone recognize a late selandian interval and define the paleocene eocene thermal maximum event supplementary material palaeomagnetic results geochemistry details and palynological analysis are available at https doi org 10 6084 m9 figshare c 4871214

subcritical dyke propagation in a host rock with temperature dependent viscoelastic properties summary in this paper we examine the effects of temperature dependent viscoelastic properties of the host rock on the subcritical growth of a dyke from a magma chamber a theoretical relationship between the velocity of subcritical dyke growth and dyke length is established using a perturbation solution of stress intensity factor at the dyke tip and a viscoelastic crack growth theory in which the temperature dependent creep properties are taken into account the temperature field around the dyke is calculated using an analytic solution the numerical results for a dyke subcritically propagating from a magma chamber indicate that while the general dyke growth characteristics are similar to those with constant creep properties the subcritical dyke growth velocity is increased by an order of magnitude by considering the temperature dependence of the creep properties hence the subcritical growth duration before the dyke reaches the unstable growth state is significantly shortened

fracture toughness and subcritical crack growth during high temperature tensile deformation of westerly granite and black gabbro abstract the double torsion testing method has been used to determine catastrophic and subcritical crack propagation parameters for pre cracked specimens of westerly granite and black gabbro under a number of environmental conditions the critical stress intensity factor for catastrophic crack propagation fracture toughness of granite and gabbro has been measured at temperatures from 20 to 400 c in a vacuum at 20 c the fracture toughness of westerly granite was 1 79 0 02 mpa m 1 2 and for two blocks of black gabbro it was 3 03 0 08 mpa m 1 2 and 2 71 0 15 mpa m 1 2 respectively these values are very close to those reported by other investigators for tests conducted in air of ambient humidity at room temperature for both rocks fracture toughness at first increased slightly and then decreased steadily on raising the temperature above ambient conditions this behaviour is explained in terms of the density and distribution of thermally induced microcracks as determined by quantitative optical microscopy subcritical crack growth behaviour has been studied at temperatures up to 300 c and under water vapour at pressures of 0 6 to 15 kpa both the load relaxation and incremental constant displacement rate forms of the double torsion testing method were utilised to generate stress intensity factor crack velocity diagrams crack growth was measured over the velocity range 5 10 3 to 10 7 m s 1 increasing both temperature and water vapour pressure resulted in substantially higher crack growth rates the overall effect of raising the temperature over the range studied here 20 300 c was to increase the crack growth rate in granite and gabbro by 5 and 7 orders of magnitude respectively at constant stress intensity factor and vapour pressure of water for both rocks the slopes of stress intensity factor crack velocity curves were sensitive to changes in both temperature and water vapour pressure at low values of the latter parameter slopes fell substantially on raising the water vapour pressure but were relatively insensitive to changes in temperature at these higher pressures no subcritical crack growth limit was encountered estimates of the uncertainty in our experimental data are given from the results of multiple load relaxation experiments on westerly granite specimens we estimate the uncertainty in position of stress intensity factor crack velocity curves along the stress intensity axis to be c 10 of the fracture toughness and the uncertainty in slope of such curves to be c 12 problems associated with the extrapolation of our experimental data to regions of higher effective confining pressure in the earth s crust are discussed

permanent strain of thermal expansion and thermally induced microcracking in inada granite 1 i made measurements of the permanent strain of thermal expansion compressional wave velocity and density of microcracks of inada granite which was subjected to slow and homogeneous temperature change under atmospheric pressure the permanent strain implying the cumulative amount of newly generated microcracks and the opening of preexisting microcracks appeared distinctly at a temperature between 100 and 125 c and increased almost exponentially in the range from 200 c to immediately before the temperature of transition in quartz 573 c as the peak temperature of the thermal cycle was elevated at 600 c the strain increased further the density of the microcracks was heightened as the peak temperature increased moreover the said trend coincided with that of the crack density parameter estimated from the compressional wave velocity at the same time the maximum width of the microcracks which was determined by microscopic observation and the average width increment of the microcracks calculated from the permanent strain and microcrack density showed a similar trend using the mercury intrusion porosimetry method the average width increment of the microcracks coincided with the equivalent width of the microcracks measured there are two causes of thermally induced microcracking the mismatching of the coefficients of thermal expansion between the adjacent mineral grains and the decrepitation of the fluid inclusions the density of the fluid inclusion microcracks showed a remarkable increase starting from the peak temperature of 300 c at temperatures equal to or higher than 400 c the fluid inclusion microcracks accounted for approximately 35 of all the intragranular cracks

high resolution iridium δ13c δ18o foraminifera and nannofossil profiles across the latest paleocene benthic extinction event at zumaya spain in the expanded upper paleocene lower eocene section 30 m of zone p5 sediments at zumaya northern spain the highest occurrence of many late paleocene deep sea benthic foraminifera species 40 extinction coincides with a transition from marl to calcite free clay our high resolution studies chemical elements 613c 6180 calcareous nannofossils planktic and benthic foraminifera show that below the marl clay transition there is a 40 50 cm thick interval corresponding to 10 20 kyr containing a detailed record of a gradual succession of faunal and geochemical events culminating in the benthic extinctions planktic foraminiferal and nannofossil changes e g the onset of demise in fasciculithus genus occur a few meters below the marl clay transition in the limestone 50 cm below the base of the clay a prominent glauconite maximum indicates that sea floor oxygenation suddenly decreased glauconite continues to be common until the onset of clay deposition a whole rock negative 613c shift 1 6 0 most likely reflecting an original sea water trend is gradually developed over the 40 cm of greenish brown marls immediately below the clay at the base of these marls there is a small significant iridium anomaly of 133 ppt ir compared with an average background of 38 ppt in the marls the demise of the fasciculithus species accelerates gavelinella beccariiformis becomes extinct and the abundance of acarinina species begins to increase the superjacent 4 m of clay is devoid of original calcite in its lower part and has a low calcareous content higher up at calcareous levels in the clay an unusual planktic foraminifera fauna occurs dominated by acarinina species when marl deposition returns 613c gradually increases and then stabilizes at values about 0 5 o lower than before the isotopic excursion the 613c excursion spans in total 5 m probably corresponding to 200 400 kyr the fasciculiths disappear shortly after the stabilization of 613c here we also present a whole rock 6 3c profile through the entire paleocene section at zumaya the profile is very similar to previous profiles registered in well preserved deep sea material suggesting that whole rock 613c at zumaya can be used for correlation

effects of relative humidity and temperature on subcritical crack growth in igneous rock abstract effects of relative humidity and temperature on subcritical crack growth in igneous rock have been investigated experimentally on samples of kumamoto andesite and oshima granite stress intensity factors and crack velocities were measured using the double torsion technique and all experiments were conducted in moist air our results show that in experiments conducted under the same relative humidity crack velocity increased with increasing temperature in agreement with previous studies our results also show that in experiments conducted at the same temperature crack velocity increased dramatically with increasing relative humidity a three to fourfold increase in relative humidity resulted in an increase in crack velocity of between one and four orders of magnitude such an increase is larger than that predicted by classical stress corrosion theory it is suggested that capillary condensation of water vapour close to crack tips of small aperture influences the rate of crack growth it is concluded that relative humidity needs to be controlled to avoid time dependent weakening and extend the lifetime of structures in a rock mass

high resolution intra and interbasinal correlation of the danian selandian transition early paleocene the bjala section bulgaria and the selandian gssp at zumaia spain abstract the danian selandian d s boundary has been identified for the first time in the black sea coast at bjala bulgaria based on a new integrated bio magneto and cyclostratigraphic study several correlation criteria as established for the basal selandian gssp from zumaia basque basin are evaluated noteworthy is the almost complete lack of calcareous nannoplankton species braarudosphaera bigelowi in the bulgarian sections a sharp decrease of which was indicated as suitable criteria for defining the d s boundary as it occurred both at zumaia and in the classical locations of the north sea basin conversely the second evolutionary radiation of the calcareous nannofossil genus fasciculithus together with the occurrence of fasciculithus tympaniformis that define the np4 np5 zonal boundary seem to be reliable criteria to approximate the d s boundary in detail however the best approach is to integrate biostratigraphic data within a magnetostratigraphic and or cyclostratigraphic framework refinements on the placement of chron c27n at zumaia and robust bed by bed correlation between several basque sections and bjala indicates that the d s boundary is located 30 precession cycles 630 ky above c27n in addition to the precession related marl limestone couplets and 100 ky eccentricity bundles recognized in the studied sections expression of the stable 405 ky long eccentricity allows direct tuning to the astronomical solutions a correlation of the land based sections with previously tuned data from odp site1262 from the southern atlantic is challenged our choice is consistent with original tuning at zumaia but shifts one 100 ky cycle older previous tuning from site 1262 along the interval above c27n under the preferred tuning scheme the d s boundary can be given an age of 61 641 0 040 ma on the la04 orbital solution

high resolution calcareous nannofossil biostratigraphy and paleoecology across the latest danian event lde in central eastern desert egypt abstract a detailed study of the calcareous nannofossil assemblages of latest danian to early selandian age from wadi qena the qreiya 1 qreiya 2 and araas sections in the central eastern desert and the gebel duwi section at the red sea coast has been carried out to understand the local phytoplankton paleocommunities for the first time in egypt four calcareous nannofossil zones ntp6 ntp7 ntp8 ntp9 and five subzones ntp7a ntp7b ntp8a ntp8b and ntp8c were distinguished subdividing the standard np4 and np5 zones the calcareous nannofossil zones were correlated with nannofossil zonations from the tethyan region e g tunisia and the zumaia section the gssp for the danian selandian boundary the calcareous nannofossil assemblages are moderately to well preserved the event beds are characterized by a dark brown shaley marl bed rich in organic carbon and coprolites three main assemblages are distinguished a pre event assemblage a transitional assemblage and a post event assemblage the paleoenvironments vary from cool eutrophic water below and above the event to warm oligotrophic conditions during the event the result of this study concludes that the latest danian event lde may represent an early paleocene hyperthermal

distribution of living and dead diatoms in tidal wetlands of northern japan relations to taphonomy abstract this paper presents the results of a survey of the contemporary diatom distributions in four tidal marshes of eastern hokkaido northern japan distribution of living diatom cells as defined by cluster analysis have relations to vegetation and substratum and clearly to tide level comparison between living and dead diatoms in each cluster provides synecological information relating to diatom taphonomy in the tidal wetland environments four assemblages are recognized and they are summarized as follows 1 an upland assemblage consisting of autochthonous freshwater diatoms adapted to relatively dry conditions 2 a high marsh assemblage formed at or slightly above mean high tide level mhtl with only few allochthonous components 3 a low marsh assemblage formed below mhtl dead valves within this assemblage are repeated widely redistributed by tidal processes this assemblage is therefore a mixed assemblage comprising a combination of allochthonous and autochthonous diatoms 4 a tidal flat assemblage on death diatom valves in tidal flat are immediately redistributed by tidal currents and the dead diatom assemblage here has the characteristics of an autochthonous or residual assemblage autecological perspectives based on the distribution patterns can advance these interpretations dead valves of the epiphytic diatom cocconeis scutellum which possesses a raphid valve r valve and a rapheless valve p valve are common on two transects but only p valves are widely distributed beyond the seaweed zone which represents the actual habitat of this species such selective processes are related mainly to the life form characteristics of monoraphid species only r valves remain attached to their substratum on death the tychoplankton paralia sp is also a widely distributed species in the case of paralia their long chains float more readily than other specimens are transported easily by tidal currents and then trapped in entire tidal environments these observations suggest it is likely that concentrations of only p valves of c scutellum or paralia in the tidal marsh deposits should be treated as allochthonous components in the diatom assemblage

amount of subsidence during a late holocene earthquake evidence from fossil tidal marsh foraminifera at vancouver island west coast of canada abstract fossil foraminifera in intertidal deposits beneath a marsh near tofino on west central vancouver island british columbia provide a basis for estimating the amount of subsidence during a large earthquake less than 400 years ago we compared the fossil foraminiferal assemblages with present day assemblages along a surveyed transect across the marsh and we estimated paleo elevation by means of both subjective and quantitative methods the comparisons suggest that the site subsided at least 0 2 m and perhaps more than 1 m during the earthquake most of the subsidence was tectonic for the deposits rest on a pleistocene substrate unlikely to have compacted much when shaken soon after the earthquake the land began to rebound tectonically most of the 0 2 1 m of recorded subsidence was recovered during deposition of the first 6 cm of sediment above the buried marsh surface probably within a few decades after the earthquake because of the speed at which the land rebounded some recovery may have occurred before the first post earthquake sediments were deposited if so the actual amount of subsidence is larger than the foraminiferal data indicate

relation of fracture resistance to fabric for granitic rocks double torsion specimens of two granitic rocks were prepared in several directions with reference to microcracks fabric even for the same rock and at the same stress levels the observed crack velocities in two granitic rocks were dependent on both the propagation direction and the opening direction the maximum difference by several orders of magnitude was found for both rocks the highest crack velocity was observed when the subcritical crack was parallel to most of the preexisting cracks the maximum critical stress intensity factor was about twice as high as the minimum one in different directions an analysis for a thin plate having anisotropic elasticity under torsional load showed that the observed difference in the crack velocity and the critical stress intensity factor was not an error due to conventional equations derived on the assumption of isotropic elasticity but the true material s property as the preferred orientation of microcracks has been pointed out for many granitic rocks we can conclude that the anisotropic nature of the fracture resistance of the two granitic rocks used in this study was not exceptional a region of a transport limited velocity was not found for rocks even at the velocity of 10 2 m s that is almost equal to the theoretical limit of the stress corrosion cracking

inferred pseudo cryptic speciation in the coccolithophore species braarudosphaera bigelowii gran and braarud during the early paleocene danian abstract pseudo cryptic speciation occurs commonly in living oceanic plankton in the coccolithophores recent genetic studies have revealed that braarudosphaera bigelowii has a number of unique genotypes that correlate well with pentalith size indicating that this coccolithophore species actually contains multiple pseudo cryptic taxa in order to look for evidence of pseudo cryptic speciation in the past we measured the radii of 2800 b bigelowii pentaliths from the braarudosphaera rich limestones that contain the gssp for the lower middle paleocene danian selandian boundary at zumaia spain analysis of the radius measurements using the expectation maximization algorithm yielded two size groups herein termed form x

the indicative meaning of diatoms pollen and botanical macro fossils for the reconstruction of palaeoenvironments and sea level fluctuations along the coast of lower saxony germany abstract interdisciplinary studies carried out on marine and terrestrial deposits such as tidal flats lagoonal deposits and salt marshes have provided the basis for interpreting holocene sea level fluctuations along the southern north sea coast radiocarbon dating provides the timeframe for the studies the employed palaeoecological techniques include analysis of pollen diatoms and botanical macro remains benefits and constraints of each technique are discussed using examples of sediment cores from around the southern north sea sea level index points have been defined using the results of these interdisciplinary studies and then employed to reconstruct the sea level oscillations of the last two millennia

palaeoenvironmental changes during the danian selandian boundary interval the ichnological record at the sopelana section basque basin w pyrenees abstract ichnological analysis was conducted in the danian selandian d s boundary interval from the sopelana section basque basin northern spain to improve characterization of the recently defined global stratotype section and point of the base of the selandian stage middle paleocene in the nearby zumaia section and to interpret the danian selandian boundary event with its associated palaeoenvironmental changes the trace fossil assemblage of the boundary interval is relatively scarce and shows low diversity consisting of chondrites planolites thalassinoides trichichnus and zoophycos which cross cut a diffuse burrow mottled background typical of a normal burrowing tiered community distribution of trace fossils shows local drops in abundance and diversity just above the d s boundary and about half a metre upwards into the succeeding selandian generally the selandian part of the section has slightly lower trace fossil diversity and abundance this is interpreted as due to a higher detrital food supply corresponding to a sea level fall in contrast to a decreased food supply during the selandian sea level rise smaller scale fluctuations of trace fossil diversity and abundance are also interpreted as due more to food content fluctuations in the sediment than to oxygenation of pore waters results reveal the minor influence of an extreme warming event hyperthermal conditions at the d s boundary which affected the whole benthic habitat contrarily a probable major effect of sea level fluctuations can be envisaged which determined variations in siliciclastic input and food content

modern distribution of salt marsh foraminifera and thecamoebians in the seymour belize inlet complex british columbia canada foraminifera and thecamoebian distribution along two marsh transects in the waump wir 16 and wawwat l wir 12 indian reserves in the seymour belize inlet complex north coastal british columbia were investigated based on q and r mode cluster analysis of the faunal distributions three high abundance low diversity faunal assemblages were identified the freshwater brackish and high salt marsh assemblages the freshwater assemblage is dominated by the soil thecamoebian species cyclopyxis kahli a significant presence of centropyxids and nebela collaris the brackish assemblage is characterized by abundant centropyxids and less than 10 foraminifera the high salt marsh assemblage is characterized by the dominance of balticammina pseudomacrescens the results of this study show the high potential of combined thecamoebian foraminifera analyses for paleo sea level research under lower salinity marsh conditions

integrated bio chemostratigraphical correlations and climatic evolution across the danian selandian boundary at low latitudes abstract the global boundary stratotype section and point for the base of the selandian stage is defined in the zumaia section spain at an abrupt change in lithology base of itzurun formation which coincides with the onset of a negative carbonate carbon isotope shift however this lithological change is not always very well expressed in other sections in order to document the stratigraphic position of the danian selandian boundary dsb on a more global scale we have investigated three sections across the dsb the zumaia reference section gssp the loubieng section auxiliary dsb reference section france and the sidi nasseur section tunisia the danian selandian boundary interval is subdivided and correlated throughout low latitudes from the altlantic bay of biscay to the southern tethys on the basis of seven calcareous nannofossil and planktonic foraminiferal events e events the base of the selandian is proved to coincide with the end of the braarudosphaera acme which correlates with the lowest consistent occurrence lcso of lithoptychius aff bitectus fasciculithus janii sensu steurbaut and sztrakos 2008 event e4 but which is slightly posterior to the second radiation of the fasciculiths up to now considered to represent the primary correlation tool of the dsb a short term 13 c org negative excursion associated with an increase in p co 2 is recorded at the very base of the selandian it is interpreted as a short period of global warming hyperthermal the duration of which is estimated at 30 kyr it is followed in all the three studied sections by a long term decoupled carbon isotope event marked by increasing 13 c org and decreasing 13 c carb values it may reflect a period of climatic cooling of a few 100 kyr interpreted as a possible precursor of the global cooling event marking the late paleocene in the north atlantic realm the integration of the biostratigraphic and the isotope data indicates major differences in sedimentation rates during the early selandian in the studied sections but there is no evidence of substantial breaks in sedimentation in any of the sections during this interval the lithological shift at the base of the selandian points to an abrupt palaeoenvironmental reorganisation although our integrated bio chemostratigraphical investigation does not allow for estimating its duration nor the presence of a hiatus at that time

foraminiferal and δ13c isotopic event stratigraphy across the danian selandian transition at zumaya northern spain chronostratigraphic implications unconformity characterized by a ma jor lithological shift from greyish white oxic limestone chalk of the danskekalk fm upper danian to suboxic glauconitic green sand of the lellinge greensand fm lower selan dian overlain by grey marl and clay of the kerteminde marl fm middle selandian this unconformity was correlated with the sequence bound ary between cycles ta 1 3 and ta 1 4 abstract the zumaya section northern spain is a suitable candidate to define the global stratotype section and point for the base of the selandian stage palaeocene because of its excellent accessibility exposure and stratigraphic continuity uncertain ties exist however with regard to the stratigraphic horizon where to place the danian selandian d s boundary five potential stratigraphic horizons hds1 to hds5 to define the d s boundary have been identified at zumaya based on integrated stratigraphic studies that include quantitative plank tic and benthic foraminiferal results as well as d 13 c isotopic and lithological data two of these horizons hds2 and hds4 placed in zone c26r appear to have particularly good potential for serving as the d s boundary marker because they may represent significant global palaeoceanographic palaeoclimatic and eustatic events

biostratigraphic and magnetostratigraphic intercalibration of latest cretaceous and paleocene depositional sequences from the deep water basque basin western pyrenees spain abstract latest cretaceous late maastrichtian and paleocene depositional sequences from the deep water basque basin have been calibrated with published 1 2 and newly acquired magnetostratigraphic data sequences mostly consist of hemipelagic marls and limestones and their relative ages are well constrained with planktic foraminifera they accumulated during a phase of tectonic tranquillity and reduced clastic input into the basin and therefore they can be attributed to eustatic sea level changes with reasonable confidence on the basis of the planktic foraminifera zonation a good match has been observed previously between the depositional sequences of the basque basin and specific sea level cycles of the 1988 version of the exxon global cycle chart gcc 3 here a new attempt at correlation using their respective magnetostratigraphic data has failed to confirm such a match the disagreements observed may indicate that for the studied interval 1 the current planktic foraminifera biostratigraphy lacks the necessary level of resolution to ensure synchrony between sequences of different basins and or 2 the magnetostratigraphy of the gcc needs to be revised whatever the case the new findings lend support for some criticism on the use of the gcc for interregional correlations

microfossil evidence for land movements associated with the ad 1964 alaska earthquake microfossil diatom and pollen data from a number of cores at coastal marshes at girdwood flats and kenai flats in cook inlet alaska suggest that there was a phase of gradual land subsidence prior to the main shock of the ad 1964 earthquake this phase followed a long period of gradual land uplift since the last large earthquake which occurred about 730 900 years ago caesium 137cs records indicate that subsidence started approximately 15 years before the 1964 earthquake this pre seismic subsidence is evident in the coastal marsh sediment sequences in changes in diatom and pollen assemblages that indicate changes in tidal marsh environments or a change from raised bog to marsh conditions the microfossil evidence indicates 0 15 m pre seismic land subsidence at both girdwood flats and kenai flats and co seismic subsidence of 1 8 m and 0 2 m respectively

interaction between local tectonics and glacial unloading on the pacific margin of canada abstract variations in late quaternary coastal deformation along the pacific margin of canada reflect not only differences in glacial history but also local non glacial tectonics a forebulge developed to the north in the queen charlotte basin qcb from 13 2 until after 9 7 ka bp resulting in exposure of the currently submerged shelf whereas similar exposure was not evident to the south in the georgia basin a semi quantitative effective elastic lithosphere thickness of between 10 and 20 km is estimated for the qcb we propose that this warm relatively thin lithosphere combined with tectonic movement influenced crustal displacement particularly the decoupling of the north american plate along the queen charlotte qc fault which may have allowed the qcb to behave like a hinge in response to glacial unloading this would explain large magnitude crustal tilting 2 1 m km 1 observed adjacent to the qc fault the 50 m of depression observed in the early and mid holocene may imply that the western edge of the north america plate flexed down below present elevation producing a second wave of response to ice loading and unloading

contemporary distributions of saltmarsh diatoms in the seymour belize inlet complex british columbia canada implications for studies of sea level change article i nfo surface diatom samples were collected from two saltmarshes in the seymour belize inlet complex on the mainland coast of british columbia to examine the controls on diatom distribution and provide training sets for regional studies of sea level change cluster analysis and detrended correspondence analysis dca were used to examine diatom distributions within and between the two marshes whilst canonical correspondence analysis cca and partial canonical correspondence analysis pcca were used to analyse species environment relationships the diatom assemblages were shown to be quite different between the two marshes waump and wawwat l q mode cluster analysis separated the diatom assemblages from waump into three zones corresponding to recognized vegetation zones diatom zone c corresponds to the high marsh and is dominated by pinnularia obscura caloneis bacillum and diploneis ovalis zone b spans the high and mid marsh and is characterised by fragilaria exigua nitzchia palea and d ovalis whilst zone a from the low marsh tidal flat includes high frequencies of diploneis smithii ctenophora pulchella and f exigua three different diatom zones were recognised at wawwat l two upper zones e and f corresponding to the mid marsh which are dominated by mixed abundances of n palea and fragilaria construens var venter navicula peregrina and navicula clementis and zone d from the low marsh tidal flat with increased frequencies of f exigua and achnanthes delicatula at waump the major controls on diatom distribution were found to be elevation and to a lesser extent ph whilst at wawwat l the primary controls were grain size organic content conductivity and elevation the results confirm that saltmarsh diatoms may have potential for future sea level studies in this region however caution must be exercised as the significant difference in the diatom assemblages between the two marshes suggests that the diatoms are responding to a number of environmental variables on a local scale some of this variation may reflect highly seasonal changes in sedimentation and salinity resulting from the proximity of the marshes to adjacent streams which are subject to spring freshet local differences in elevation between the collected samples may also account for some of the assemblage variability the results emphasize the great diversity and high sensitivity of intertidal diatom species to environmental controls

late holocene relative sea level changes and the earthquake deformation cycle around upper cook inlet alaska abstract multiple peat silt couplets preserved in tidal marsh sediment sequences suggest that numerous great plate boundary earthquakes caused the coast around cook inlet alaska to subside over the past 3500 years field and laboratory analyses of the two youngest couplets record the well documented earthquake of ad 1964 and the penultimate one approximately 850 cal yr bp diatom assemblages from a range of modern day estuarine environments from tidal flat through salt marsh to acidic bog produce quantitative diatom transfer function models for elevation reconstructions based on fossil samples only nine out of 124 fossil assemblages analysed including previously published data for the ad 1964 earthquake have a poor modern analogue calibration of fossil samples indicate co seismic subsidence of 1 50 0 32 m for ad 1964 similar to measurements taken after the earthquake and 1 45 0 34 m for the 850 cal yr bp earthquake elevation standard errors for individual fossil samples range from 0 08 m in peat layers to 0 35 m in silt units lack of a chronology within fossil silt units prevents identification of changes in the rate of recovery and land uplift between the post seismic and inter seismic periods however preservation of multiple peat silt couplets indicates no net emergence over multiple earthquake cycles glacio isostatic movements from little ice age glacier advance and retreat explains a 0 15 m relative sea level oscillation recorded within the peat layer subsequently submerged as a result of the ad 1964 earthquake before both this and the 850 cal yr bp earthquake diatom assemblages suggest pre seismic relative sea level rise of 0 12 0 13 m representing possible precursors to great earthquakes

depositional changes during the danian selandian transition in loubieng france zumaia spain and sidi nasseur tunisia insights from and limits of rock magnetism depositional changes are studied in three sections encompassing the danian selandian transition loubieng france zumaia spain and sidi nasseur tunisia using magnetic susceptibility as a proxy additional rock magnetic analyses are used to avoid ambiguous interpretation of magnetic susceptibility the magnetic susceptibility measured on 90 to 270 samples per section is mainly controlled by paramagnetic minerals and linked to detrital input major increases in the detrital input are correlated to the end of the latest danian event a hyperthermal and to the danian selandian boundary in loubieng two gradual increases in magnetic susceptibility within limestones beds precede the major detrital input increases and start synchronously with the beginning of the latest danian event and the onset of haematite deposition around the danian selandian boundary respectively this haematite is suspected to be of primary origin based among other things on low magnetic viscosity values which is used here as an indicator of diagenetic origin in haematite and goethite the red levels where haematite is interpreted to be of primary origin could be linked to the hyperthermal event previously hypothesized for the basal selandian the comparison of the magnetic susceptibility chemo and biostratigraphic data between the three sections highlights the condensed nature of the sedimentation around the danian selandian boundary in the sections of the atlantic realm the lower part of the selandian shows a particularly low sedimentation rate at zumaia compared to loubieng and sidi nasseur the latter displays the most complete record of the three

tidal marsh stratigraphy sea level change and large earthquakes ii submergence events during the last 3500 years at netarts bay oregon usa abstract this is the second investigation where we apply the methods and scientific framework common to sea level investigations in northwest europe to test a model of coseismic land subsidence followed by land uplift during interseismic strain accumulation used to explain alternating peat mud couplets of late holocene age found in many of the estuaries of the pacific northwest of the usa and canada recent studies in this region interpret such couplets as the product of repeated large magnitude 8 or 9 earthquakes on the cascadia subduction zone stratigraphic investigations of the intertidal sediments at netarts bay oregon using lithological pollen and diatom analyses reveal different types of submergence associated with peat mud couplets during the last 3500 yr three peat mud couplets record gradual sedimentation changes within an infilling body of water four other couplets record rapid submergence burial of tidal marshes and their replacement by low marsh environments in three of the events rapid submergence is small 0 0 5 m the most recent marsh submergence event around ad 1700 was 0 4 0 3 m most of the buried peats contain microfossil evidence for a gradual increase in marine influence before the rapid change from organic to minerogenic sedimentation similar gradual changes are common in comparable palaeoenvironments on non seismic coasts and are strong evidence against a simple interseismic strain accumulation coseismic subsidence model one hypothesis is that the gradual increase in marine influence before each submergence represents pre seismic relative sea level rise caused by a reduction in the rate of land uplift the microfossil analyses provide evidence of three stages within an earthquake deformation cycle coseismic subsidence interseismic land uplift and pre seismic reduction in the rate of land uplift at present the microfossil data do not differentiate between rapid post seismic land uplift and rapid sedimentation

using foraminiferal transfer functions to produce high resolution sea level records from salt marsh deposits maine usa quantitative analyses of foraminiferal distributions along the coast of maine are used to provide transfer functions for reconstruction of sea level changes from fossil foraminiferal assemblages the indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration not height as the predictor variable sea level records are produced for two sites in maine usa a middle marsh site in scarboro and a high marsh site in machiasport these records offer temporal resolution of five to seven years and span the past century they are compared with instrumental data from a nearby tidal station to assess their accuracy strong correlations are found between the geologic records and the observational data in particular between the foraminiferal record from machiasport and the tide gauge record from eastport r2 0 83 p 0 005 thus a foraminifera based transfer function approach offers great potential for reso