one hundred million years of geomagnetic polarity history since 1968 absolute ages have been assigned to the late cretaceous cenozoic geomagnetic reversal time scale by fixing the ages of two or more calibration points in a composite marine magnetic anomaly profile and interpolating between or extrapolating beyond these points assuming constant spreading rates in each interval previously no more than 4 calibration points were used but it is now possible to specify 11 calibration points in addition to the 0 m y datum this improvement is based on magnetostratigraphic studies in italian pelagic limestones these studies closely tie the geomagnetic reversal sequence to the foraminiferal and coccolith zonations absolute ages of calibration points are provided by the best available dates on stage boundaries which are located from the biostratigraphic zonation the greatest changes from previous scales come in the late paleocene early eocene where the new ages are as much as 3 m y younger than in the 1977 scale of labrecque and others and as much as 1 8 m y younger than in the 1980 scale of ness and others

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

onset of recent rapid sea level rise in the western atlantic ocean a high resolution record of sea level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt marsh peat sequence at chezzetcook nova scotia canada former mean tide level positions are reconstructed with a precision of 0 055 m using a transfer function derived from distributions of modern salt marsh foraminifera our age model for the core section older than 300 years is based on 19 ams 14c ages and takes into account the individual probability distributions of calibrated radiocarbon ages the past 300 years is dated by pollen and the isotopes 206pb 207pb 210pb 137cs and 241am between ad 1000 and ad 1800 relative sea level rose at a mean rate of 17 cm per century apparent pre industrial rises of sea level dated at ad 1500 1550 and ad 1700 1800 cannot be clearly distinguished when radiocarbon age errors are taken into account furthermore they may be an artefact of fluctuations in atmospheric 14c production in the 19th century sea level rose at a mean rate of 1 6 mm yr between ad 1900 and ad 1920 sea level rise accelerated to the modern mean rate of 3 2 mm yr this acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming 2005 elsevier ltd all rights reserved

rupture process of the 2002 mw 7 9 denali earthquake alaska using a newly devised hybrid blind deconvolution method this paper investigates the kinematics of the rupture process of the main event of the mw 7 9 denali alaska earthquake of 3 november 2002 a newly devised hybrid blind deconvolution method is applied to deconvolve teleseismic broadband s wave displacement recordings of the earthquake so as to determine the apparent source time functions astfs at 10 stations located around the epicenter the derived azimuthal angle of slip strongly indicates that the event ruptured unilaterally in an east southeasterly direction as determined by the calculated astfs the total duration of the rupture process was about 74 sec based on the images of the static slip dis tribution three slip concentrated areas were located at depths of less than 10 km maximum slip was about 13 4 m centered at 170 km east of the hypocenter and the average slip on the observed rupture area reached 4 1 m one concentrated rupture velocity area located at 160 180 km east of the hypocenter coincided with a slip concentrated area of maximum slip amplitude strongly suggesting that seismic energy was released rapidly a region of the fault along the strike direction with high rupture velocity 80 120 km also had very low levels of slip indicating that this portion of the fault may well have been relatively weak maximum and minimum rupture velo cities were respectively 3 32 and 2 64 km sec while the average rupture velocity was about 2 95 km sec based on the average rupture velocity and the source duration it is suggested that the principal rupture length of the denali fault must have been greater than 210 km

benthonic foraminiferal distributions and quantitative transfer functions for the northwest european continental margin abstract a database of benthonic foraminiferal data from 298 sediment surface samples from the northwest european ireland to svalbard and iceland margin has been compiled samples deeper than 500 m on the continental slope and shallower than 30 m in coastal areas are not included bottom water temperatures at the sites range between 1 and 12 5 c and salinity between 33 5 and 35 5 detrended correspondence analyses of percentage values of 65 benthonic foraminifera taxa from 260 of the samples show a strong statistically significant relationship between modern foraminiferal assemblages and summer temperature and salinity utilising weighted averaging partial least square regression transfer functions for summer bottom water temperature ts and salinity ss have been developed the transfer functions have relatively low root mean square errors of prediction expressed as a percentage of the range of the modern environmental gradient sampled for ts 3 9 and for ss 9 02 compared to transfer functions developed for other proxies which commonly range from 8 to 20 the distributions of benthonic foraminifera species are dependent on other factors than salinity and temperature such as nutrients substrate turbidity current regime different biological factors different depth related factors etc the present analyses demonstrate that for this group as for most other groups there is an overall but not necessarily direct relationship with distribution and abundance and temperature and salinity conditions the transfer functions have been tested on a late glacial holocene data set and an eemian early weichselian data set from the eastern north sea region these experiments suggest that transfer functions on benthonic foraminifera can be a useful new tool in palaeoceanographic and palaeoenvironmental work along the european north atlantic seaboard

the barremian aptian arid phase in western europe abstract evidence is presented from nine areas in western europe speeton yorkshire southern north sea channel and weald basins southern england jeanne d arc lusitanian and aquitanian basins of the north atlantic continental margins lower saxony basin north germany the paris basin and southern france for a phase of aridity which began during the hauterivian middle barremian and continued to dominate the climate of the region until the mid aptian although conditions during this period were not uniformly dry throughout criteria for recognising arid environments include the occurrence of evaporites abundances of carbonate rich sediments red beds firmgrounds carbonate nodules and pyrite concretions depletion of kaolinite spore assemblages of limited morphological diversity and the presence of numerous coniferalean and cheirolepidiacean pollen grains the change from generally humid to dry climates during the barremian is thought to have been linked to a lowering of sea level the arid phase clearly falls within the time span of the first cretaceous oceanic anoxic event

temporal spatial rupture process of the 1999 chi chi earthquake from iris and geoscope long period waveform data using aftershocks as empirical green s functions a large earthquake m w 7 6 occurred near chi chi taiwan on 20 september 1999 utc and was followed by many moderate size aftershocks in the following days the two largest aftershocks with magnitudes m w 6 1 and 6 2 respectively were used as empirical green s functions egfs to retrieve the source time functions stfs and further image the temporal spatial rupture process of the mainshock for each station two types of stfs were retrieved one from p phases and another from s phases a total of 178 stf individuals were retrieved for source process analysis of the event from the stfs retrieved firstly similarities appeared on the stfs from most stations except that several stfs in special azimuths looked different or odd because of the focal mechanism difference between the mainshock and the egf aftershocks and secondly systematic shape variation with azimuth appeared the analysis of the stfs indicated that this event consisted of two subevents on the average the second event was about 7 sec later than the first one and the first event was about 15 larger than the second one in the moment release rate the total duration time of earthquake rupture process was about 26 sec from the image of the static slip distribution there were two slip concentrated areas on the fault plane and their centers were about 45 km away from each other the maximum slip of about 6 5 m appeared on the northern one the rupture area with the slip greater than 0 5 m was about 80 km long and 60 km wide the maximum stress drop was about 25 mpa 250 bar and the average stress drop on the entire fault was 9 2 mpa 92 bar from the snapshots of the temporal spatial variation of slip and slip rate the rupture initiated at the southern end and stopped at the northern end of the fault which suggested an overall unilateral rupture at a rupture velocity of about 2 5 km sec the depth of the initiation locus was about 20 km the rupture duration times on the subfaults were estimated a good correlation was noticed between the rupture duration time and slip amplitude of the subfaults the larger the slip amplitude the longer the rupture duration time of the subfault the maximum duration time for the subfaults was 16 sec which was about two thirds the total duration time of the earthquake rupture process in the beginning and near the end of the source process the rupture propagated like a self healing pulse of slip manuscript received 21 may 2001

teleseismic time functions for large shallow subduction zone earthquakes broadband vertical p wave records are analyzed from 63 of the largest shallow subduction zone earthquakes which have occurred in the circum pacific in the last 45 yr most of the records studied come from a common instrument the pasadena california benioff 1 90 seismometer propagation and instrument effects are deconvolved from the p wave records using a damped least squares inversion to obtain the teleseismic source time function the inversion has the additional constraint that the time function be positive everywhere the period band over which the time functions are considered reliable is from 2 5 to 50 sec fourier displacement amplitude spectra computed for each of the 1 90 p wave trains indicate spectral slopes measured between 2 and 50 sec of 1 0 to 2 25 with an average value of 1 5 these values assume an average attenuation of t 1 0 the seismic moments derived from the p wave time functions compare well with other published values for earthquakes having moments smaller than 2 5 10 28 dyne cm m w 8 2 because the 1 90 seismometer has little response at very long periods this technique underestimates the moments of the very largest events the time functions are characterized using five parameters 1 spectral slope between 2 and 50 sec 2 roughness of the time function 3 multiplicity of sources 4 pulse widths of individual sources and 5 overall signal duration the 63 earthquakes studied come from 15 subduction zones with a wide range in the ages of subducted lithosphere convergence rates and maximum size of earthquakes comparing the time function parameters with age rate and m w of the subduction zone does not yield obvious global trends however most of the subduction zones do behave characteristically and can be grouped accordingly

empirical green s function study of the january 17 1994 northridge california earthquake the january 17 1994 northridge main shock was analyzed using an empirical green s function approach to estimate the spatial and temporal distribution of fault slip far field source time functions obtained from seismograms recorded by the berkeley digital seismic network bdsn and terrascope stations reveal the distributed nature of the source and the presence of a second large subevent the location of the fault beneath the san fernando valley as well as the updip directivity of the rupture contributed to the locally heavy damage due to this earthquake

palaeoclimate analysis using spectral gamma ray data from the aptian cretaceous of southern england and southern france abstract the abundance and half lives of potassium k uranium u and thorium th make these three elements the dominant sources of gamma rays detected in rocks both at outcrop and in the subsurface with the advent of the spectral gamma ray tool sgr the variation shown by these three elements in rocks has been considered to reflect sorting at flooding surfaces and changes in the weathering regime of sediment source lands k and u are considered to be more soluble than th thus elevated th to k or u ratios in soils and eroded clays can reflect hot humid climates and palaeoclimates this study makes an assessment of the usefulness of sgr data to palaeoclimate studies by comparing changing th k and th u ratios from a known period of palaeoclimate change to extensive published and new data from other analytical methods new sgr data from the cretaceous of southern england and southern france compare favourably to outcrop sedimentological facies interpretations and laboratory geochemical data palaeoclimate data from two other sections northern germany northern italy are compared as controls to the study together these analyses suggest that there was a gradual change from semi arid climate in the barremian and early aptian to a semi humid climate in the mid aptian superimposed on this long term rise in humidity were a number of short term ammonite zone length changes in th k and th u ratios and the abundance of climate sensitive materials this study shows that sgr data are more useful than originally thought when problems of overprinting from heavy minerals and diagenesis are overcome outcrop and borehole spectral gamma ray logs from mudstones or the clay rich beds of mixed successions may be used to interpret past patterns of hinterland weathering

recent coastal evolution and sea level rise setiu wetland peninsular malaysia abstract sea level reconstructions based on foraminiferal assemblage data are common for temperate salt marsh settings in comparison the widespread mangrove swamps of equatorial to subtropical settings have received considerably less attention due to enhanced taphonomic loss of specimens extensive bioturbation abundant infaunal foraminifera and irregular intertidal topography the tropics however provide the best possible estimate of eustatic function and thus are important for testing earth ice models in this paper we use foraminiferal data in a chronologic framework provided by optically stimulated luminescence radiocarbon and pb 210 age estimates to determine coastal evolution and rates of sea level rise in the setiu wetland of northeastern peninsular malaysia on the western margin of the southern south china sea over the past ca 200 years foraminiferal data from three surface transects across fringing mangrove swamps were used to interpret four cores from mid to high mangrove swamp settings patterns of foraminiferal distribution were determined by correspondence analysis canonical correspondence analysis and detrended canonical correspondence analysis of dead assemblage data we used weighted averaging as the transfer function model to reconstruct sea level curves for the cores and to provide a composite reconstruction for the last ca 200 years based on one c 14 estimate sea level rose during the 19th century at 1 26 mm yr 1 the rate increased to 3 2 0 6 mm yr 1 around 1900 ce roughly coincident with rate increases recorded globally however the 20th century rate in the setiu wetland is considerably greater than that of global estimates ca 1 8 mm yr 1 for this period rates of sea level rise in the gulf of thailand immediately to the north of the setiu wetland determined from gps corrected tide gauge data and multi satellite altimetry are geographically variable but also greater than the global rate the data from the setiu wetland provide the first foraminifera based sea level reconstruction of the past few hundred years from the southeastern south china sea scs and they represent the first time the early 20th century increase in rate of sea level rise has been identified using proxy foraminiferal data in an equatorial setting

evidence of nonlinear elasticity of the crust from the mw7 6 manyi tibet earthquake satellite synthetic aperture radar sar interferometry shows that the magnitude 7 6 manyi earthquake of 8 november 1997 produced a 170 kilometer long surface break with up to 7 meters of left lateral slip reactivating a n76 e quaternary fault in western tibet the radar interferometric map reveals asymmetric along strike displacement profiles between the two sides of the surface rupture a pattern that cannot be explained with linear elastic theory this observation suggests that the elastic moduli of the crust in tension and in compression are different because of the presence of cracks in the crust at shallow depth a model indicates that a ratio of 2 between compressive and tensile elastic moduli can account for the observed asymmetry a ratio that is consistent with laboratory and borehole measurements

palaeoenvironmental significance of storm coquinas in a lower cretaceous coastal lagoonal succession vectis formation isle of wight southern england thin bioclastic limestone beds coquinas in the vectis formation wealden group lower cretaceous of the isle of wight southern england exhibit a range of biofabrics and internal stratigraphies these features are attributed to both simple and complex storm deposition of allochthonous biogenic and siliciclastic materials in coastal lagoons and on adjacent mudflats these modes of deposition facilitated preservation of dinosaur trackways desiccation cracks shallow tier trace fossils and in situ bivalve colonies through rapid burial the coquinas thus preserve a record of surficial muds commonly lost through reworking the principal components of the coquinas comprise dispersed elements from within the argillaceous background facies some of these beds are laterally traceable for up to 27 km providing the foundations for a high resolution event stratigraphic framework

recognising subtidal foraminiferal assemblages implications for quantitative sea level reconstructions using a foraminifera based transfer function microfossil based transfer function models are increasingly used to provide decimeter scale sea level change reconstructions in this paper i demonstrate that in the tropical location of northern australia problems arise in selecting the appropriate elevation range for the modern training set used to calibrate fossil calcareous foraminiferal assemblages most calcareous foraminiferal species found in cores occur in both modern intertidal and shallow subtidal environments a lack of independent measures to indicate whether fossil assemblages come from intertidal environments forces use of a training set that includes intertidal and subtidal environments this results in decreased precision compared to using a training set solely from intertidal environments the widely used method of assessing model fit to fossil assemblages modern analogue technique often fails to discriminate between acceptable and unacceptable reconstructions it is important to investigate a number of different measures including modern analogue technique canonical correspondence analysis and changing bootstrapped sample specific transfer function errors to fully understand the level of similarity between modern and fossil foraminiferal samples to judge the reliability of transfer function predicted sea level reconstructions copyright 2008 john wiley sons ltd

early to mid cretaceous tectonics and unconformities of the wessex basin southern england sediment distribution patterns time subsidence plots seismic data and outcrop analysis of the lower cretaceous ryazanian albian of the wessex basin southern england suggest that a number of unconformable horizons exist and that there is no single late cimmerian unconformity surface a tectonic change from areally restricted deposition in the weald and channel sub basins to extensive sedimentation across the whole of southern england began in the mid aptian this change ended with transgression of basement highs in the early albian of the dorset area and later albian of the devon and london platform basin margin areas its onset can be linked to the austrian tectonic phase of europe the onset of marine deposition in the aptian is coincident with periodic transgression of the margins of the wessex basin throughout the aptian albian mid late aptian and early mid aibian transgressions were preceded by periods of erosion the aptian albian lower greensand is characterized by transgressive regressive phases suggesting a short term controlling process third order eustatic changes or intra plate mechanisms tectonic changes in the mid aptian include uplift followed by widespread subsidence this change coincides with a time of plate reorganization in the european and north atlantic areas

stability of rapid finite fault inversion for the 2014 mw6 1 south napa earthquake local seismograms are useful for rapidly reconstructing kinematic finite fault sources but the results often depend not only on the data coverage but also on uncertainties of parameters e g hypocentral location and fault geometry used as a priori information during the inversion an automatic scheme was applied to offline tests for the 2014 south napa earthquake in the case of retrospective full waveform inversions a network with station spacing of 10 km within the epicentral distance of 30 km is able to provide adequate stable key source parameters if the preestimated hypocenter and fault orientation are accurate of 5 km and 15 respectively in simulated real time inversions the magnitude reaches mw6 0 at 13 s and the slip distribution matches that from the retrospective inversion at about 22 28 s after the origin time of the earthquake these results are meaningful for estimating the lead time of a catastrophic seismic event

microhabitats of salt marsh foraminifera st catherines island georgia usa abstract salt marsh foraminifera of st catherines island georgia occupy a range of epibenthic to deep infaunal to 30 cm micro habitats freshly collected specimens of arenoparrella mexicana from 27 to 30 cm below the marsh surface extruded pseudopodial nets and actively collected foreign material about the aperture salt marsh foraminifera may be primarily epibenthic 0 1 cm epibenthic to intermediate infaunal 0 10 cm or deep infaunal 0 30 cm most of the twelve commonly occurring species in st catherines island marshes are epibenthic to intermediate infaunal species distributional patterns differ with regard to maximum depth of infaunal occurrences infaunal microhabitat utilization in different marsh zones and environments and the presence or absence of subsurface population maxima selective preservation impacts both calcareous and agglutinated foraminifera intense bioturbation primarily by halophytes and decapod crustaceans may contribute to the deep infaunal occurrences of foraminifera in these environments

lagoonal sedimentation and fluctuating salinities in the vectis formation wealden group lower cretaceous of the isle of wight southern england abstract sedimentation in the shepherd s chine member of the vectis formation is characterised by a cyclicity of four principal facies on which a strong asymmetry has been imprinted by erosional events the four lithofacies are 1 very fine to fine sandstones 2 heterolithic sand silt and mudstones 3 parallel laminated pinstripe mudstones and 4 black mudstones the biota principally associated with lithofacies 2 and 3 as shelly partings and coquinas can be grouped into five molluscan associations which range from freshwater to quasi marine these associations are poorly correlated with the lithofacies but fluctuate within and between cycles salinity and storm frequency increase towards the top of the formation heralding the main marine aptian transgression lithofacies and biotas indicate deposition in a lagoon that was shallow and temporarily emergent the cyclicity is thought to represent the more distal phases of the advance and retreat of deltaic sand bodies derived from a westerly direction into the lagoon major storm events broke the symmetry of the cycles a deltaic facies represented by the barnes high sandstone member is thought to be laterally linked reworked deltaic sandstone lobes

departures from the local inverse barometer model observed in altimeter and tide gauge data and in a global barotropic numerical model sea level data from the topex poseidon altimeter satellite and from subsets of the global tide gauge and bottom pressure recorder networks have been employed to study the worldwide distribution of departures from the simple local inverse barometer lib model from a combination of measurement techniques the lib model was found to provide a reasonable representation of the data within 5 10 outside of the tropics for timescales from several days to several weeks for most locations however several parts of the southern ocean and other higher latitude areas were seen from the altimetry to contain significant departures across the range of timescales accessible for study by the technique within the tropics the response of sea level to air pressure forcing was observed to be typically 50 of that of the lib model at timescales of several days with considerable spatial variation and to approximate the lib model more closely at timescales of several weeks a coarse grid global barotropic numerical model was found to reproduce qualitatively the global average response as a function of frequency to simulate many of the characteristics of the spatial variation of the response and to demonstrate the relative importance of air pressure and wind forcing at different timescales data sets from the permanent service for mean sea level and u k meteorological office were used to investigate lib departures at intraseasonal and longer timescales along continental coastlines and at ocean islands increasingly large departures were observed along many parts of the world coastline as timescales increased from months to seasons

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

development of a foraminifera based transfer function in the basque marshes n spain implications for sea level studies in the bay of biscay abstract in order to reconstruct former sea level we have developed a foraminifera based transfer function using three models based on a modern dataset of 59 samples and 23 species obtained from four basque marshes in northern spain the relationship between observed and foraminifera predicted elevation illustrated the strong performance of the transfer function r 2 jack ranges from 0 74 to 0 81 these results indicated that precise reconstructions of former sea levels are possible error ranges from 0 11 to 0 19 m the transfer function was used to calibrate the foraminiferal assemblages collected from a 50 cm salt marsh core we placed the foraminifera based reconstructions into a temporal framework using 137 cs pb concentrations and 210 pb derived sediment accumulation rates the resulting relative sea level curve is in good agreement with regional tide gauge data both instrumental data and microfossil records suggest a rate of relative sea level rise of approximately 2 mm yr 1 for the 20th century

recent large earthquakes near cape mendocino and in the gorda plate broadband source time functions fault orientations and rupture complexities the northward migration of the mendocino triple junction is associated with complex faulting within the gorda plate and in the convergent zone between the gorda and north american plates this region has experienced substantial recent large earthquake activity and quantification of these faulting processes is essential for understanding the evolution of the triple junction using an empirical green function deconvolution method for teleseismic and regional surface waves and body waves we obtain relative source time functions for the april 25 1992 cape mendocino thrust earthquake m w 7 2 its two large strike slip aftershocks on april 26 1992 m w 6 5 6 6 and two large strike slip events in the gorda plate that occurred july 13 1991 m w 6 8 and august 17 1991 m w 7 1 the removal of propagation effects using empirical green functions provides unusually detailed source rupture information and indicates that all the ruptures are less than 16 s in duration analyzing the directivity effects observed in the source time functions we resolve rupture directions and corresponding fault orientations for the four largest events and place some constraints on the smaller aftershock significant differences in the rupture duration and stress drop are observed between the cape mendocino mainshock and its two largest aftershocks the mainshock which ruptured westward on a shallow dipping plane either on or paralleling the interplate contact between the gorda and north american plates had a smooth 9 s long rupture with a 0 9 4 6 mpa static stress drop the two largest aftershocks occurred within the uppermost mantle of the gorda plate and have more complex ruptures with total durations of 14 15 s and static stress drops of less than 0 3 mpa perhaps reflecting a difference between mantle and crustal earthquakes in this region the aftershocks appear to have ruptured conjugate strike slip faults accounting for differences in their damage patterns the august 17 1991 gorda plate event ruptured a southwest striking fault while the july 13 1991 event ruptured a southeast striking fault with both events relieving north south compression within the deforming gorda plate the existence of multiple active faults in the region constitutes a significant earthquake hazard associated with the complex stress environment of the migrating triple junction

environmental constraints of foraminiferal assemblages distribution across a brackish tidal marsh caminha nw portugal abstract foraminiferal living assemblages from a brackish tidal marsh were studied across three sampling transects under spring and autumn conditions foraminiferal analysis was also extended to the dead assemblages of spring samples altimetric control of each sampling point was acquired through the connection to the national datum by gps differential positioning combined with a regional geoid model the influence of the geochemical characteristics on the assemblages including chemical composition of the estuarine and marsh surface sediments in addition to salinity ph and calcite saturation of estuarine and marsh interstitial waters was evaluated a high affinity was found between spring and autumn living assemblages probably related to the low number of representative species the affinity also found between living and dead assemblage was seen as a consequence of low ph and calcite undersaturation that prevent the accumulation effect of several generations of foraminifera salinity appears as a clear constraint to the foraminiferal assemblages composition that is enhanced by calcite undersaturation in brackish marshes interstitial waters and sediments generally abundant marsh species like trochammina inflata jadammina macrescens and the calcareous foraminifera are limited to an episodic presence foraminiferal assemblages distribution across brackish tidal marsh can be assumed as an elevation proxy the high marsh ib sub zone is dominated by haplophragmoides sp and haplophragmoides manilaensis low marsh zone ii is characterised by the dominance of miliammina fusca but can be subdivided in an iia upper part where is followed by pseudothurammina limnetis and in a iib lower part defined by a subsidiary presence of psammosphaera sp haplophragmoides manilaensis dominance between 1 55 m and 1 67 m at living as well as dead assemblages suggests this species as a potential sea level indicator for the brackish tidal marshes

rupture characteristics of the three m 4 7 1992 1994 parkfield earthquakes slip on the san andreas fault was determined for three m 4 7 earthquakes using a tomographic inverse system beroza and spudich 1988 to invert seismic source time functions stfs from s waves stfs were obtained by deconvolving mainshock accelerograms by those from collocated smaller earthquakes accelerograms were from the u s geological survey parkfield small aperture array upsar and from a distributed array of digital accelerometer stations at parkfield eight or nine stfs are used in each of the three inversions stfs are typically symmetrical pulses with a duration of about 0 3 0 5 s in the inversion mainshock rise time was set to 0 05 s and we allowed the rupture time to vary slightly from a constant rupture velocity of approximately 0 85 rupture for all three events which are located in or close to the middle mountain preparation zone or box mmb quickly reaches a local maximum in slip and then propagates outward to peaks ridges or plateaus in the slip distribution slip for the october 20 1992 event located just inside the southern edge of the mmb propagates from an initial spike north and updip along a curving ridge for about 2 km the initial spike continued to grow in the november 14 1993 event located north of the october 20 1992 event just beneath the hypocenter of the 1966 parkfield earthquake which shows little directivity although there is a smaller patch of slip updip and to the south in contrast rupture for the december 20 1994 event located just south of the october 20 1992 event propagated north and slightly updip creating a rough plateau in slip a few kilometers wide on a side directivity for this event also is to the north directivity for all three events points in the approximate direction of the 1966 hypocenter small pulses which comprise a coda are found on the stfs for several seconds after the initial impulsive event several tests based on the assumption that the average of all stfs from upsar for each event is an estimate of the true slip at the source suggest that the codas in the stfs are s waves from a long duration source rather than uncorrected site response an initiation phase is found on the array average for the november 14 1993 and december 20 1994 events these precursory phases are the result of a spike in slip at the hypocenter a value of 2 4 4 mm is obtained for d c the slip weakening distance by interpreting the initial spike as a critical patch the few aftershocks for the october 20 1992 event are distributed to the north and updip of the mainshock but the november 14 1993 event had a strong burst of aftershock activity that propagated to the north of its hypocenter at roughly the same depth aftershocks of the december 20 1994 event are mostly updip the november 14 1993 event had the simplest slip distribution appeared to be the most impulsive and had the most active aftershock sequence and the greatest depth if the eventual parkfield earthquake initiates near the 1966 hypocenter then the directivity of the three events studied here will have pointed to it however it is certainly possible that both the initiation of characteristic parkfield shocks and the directivity of smaller events are controlled by fault properties on a larger scale such as by fault bends or jogs

fossil wood carbon isotope stratigraphy of the non marine wealden group lower cretaceous southern england fossil wood carbon isotope data are presented for the wessex formation a non marine unit within the lower cretaceous valanginian barremian wealden group of the isle of wight and dorset southern england the carbon isotope values have a range 13 c c 26 6 to 19 8 that is consistent with that expected for mesozoic c 3 plants consideration of the isle of wight fossil wood carbon isotope data together with data from dorset allows construction of a composite fossil wood carbon isotope curve for almost the entire wealden group the new carbon isotope curve is in smooth continuity with data previously published from the overlying lagoonal vectis formation and marine lower greensand group of aptian age a tentative correlation with a tethyan reference carbon isotope curve allows the provisional application of stage level chronostratigraphy to the wealden group correlations suggest that the wealden group sediments are dominantly of hauterivian and barremian age and that the valanginian is either condensed or partially missing the carbon isotope data presented indicate that even during times of relative carbon cycle quiescence atmosphere co 2 faithfully tracks the carbon isotopic composition of the oceanic reservoir

lateglacial and holocene coastal evolution in the minho estuary n portugal implications for understanding sea level changes in atlantic iberia the absence of accurate sea level index points in sw europe has long precluded the development of holocene sea level curves and the correct understanding of tectonic activity in order to understan

source process of the 4 june 2000 southern sumatra indonesia earthquake source parameters of the 4 june 2000 southern sumatra indonesia earthquake m s 8 0 were estimated from teleseismic body waves recorded by long period seismograph stations of the global seismic network the analysis shows that the earthquake had a mechanism with a strike of 199 a dip of 82 and a rake of 5 and ruptured unilaterally from the northeast to the southwest nearly perpendicular to the java trench the focal mechanism of mainly left lateral strike slip with a small thrust component explains well the reason why no tidal waves were generated by this great earthquake the double couple component of this earthquake was 1 5 10 21 nm the compensated linear vector dipole component was 1 2 10 20 nm and the explosion component was 5 9 10 19 nm the analysis indicates that the source duration was about 16 sec the fault area is about 95 km in length and 60 km in width the average static slip is estimated to be about 11 m and the average static stress drop 90 mpa

techniques for estimation of tidal elevation and con nement salinity histories of sheltered harbours and estuaries using benthic foraminifera examples from new zealand techniques for estimating tidal elevation and con nement proxy for salinity using modern benthic foraminiferal census data from new zealand harbours and lower salinity estuaries are described and assessed for their utility for reconstructing the depositional settings of late holocene sequences we describe a simple modern analogue technique for estimating tidal or subtidal elevation of holocene fossil faunas utilizing the modern data set most applicable to the holocene setting sheltered tidal harbours and inlets or lower salinity estuaries canonical correspondence analysis was used to extract a synthetic con nement gradient from for aminiferal census data in transects down ve new zealand estuaries this gradient was used to develop a new zealand con nement index that can be computed for new zealand modern and holocene estuarine and harbour samples based on their foraminiferal composition the value of the method for estimating holocene elevational and con nement palaeosalinity histories was

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

arctic planktic foraminiferal assemblages implications for subsurface temperature reconstructions abstract earlier reconstructions of the inflow of atlantic water to arctic and subarctic oceans based on foraminiferal proxy data have been obstructed by uncertain quantitative reconstructions of sea surface and subsurface temperatures in this study surface sediment samples with undisturbed sediment water interface from polar north atlantic and barents sea were retrieved and prepared at the size fractions from 100 m to 1000 m the foraminiferal analyses show that neogloboquadrina pachyderma constitutes 96 99 of the fauna in arctic and polar surface water masses the same result is obtained when investigating the 150 m size fraction however in arctic areas influenced by atlantic water additional faunal information is obtained when using the smaller 100 m size fraction in these areas n pachyderma is reduced to about 50 and the relatively small species turborotalita quinqueloba becomes very frequent this also applies to the coastal water masses which are dominated by neogloboquadrina incompta and globigerinita uvula transfer functions using the current dataset based on the 100 m size fraction were developed and assessed different statistical models were tested using both seasonal and annual temperature data from 0 m 10 m 50 m and 100 m water depth the most precise reconstructions of subsurface temperatures were found when using summer temperatures from the 100 m depth level the transfer function was tested on holocene foraminiferal records and compared to previous reconstructions the results show that our new transfer function based on the 100 m fraction generally yields lower temperatures at both 10 and 100 m water depth than earlier reconstructions e g hald et al 2007 this could be due to the increased number of samples containing both small species and or the presence of more small specimens representing cold conditions

source pulse enhancement by deconvolution of an empirical green s function observations of the earthquake source time function are enhanced if path recording site and instrument complexities can be removed from seismograms assuming that a small earthquake has a simple source its seismogram can be treated as an empirical green s function and deconvolved from the seismogram of a larger and or more complex earthquake by spectral division when the deconvolution is well posed the quotient spectrum represents the apparent source time function of the larger event this study shows that with high quality locally recorded earthquake data it is feasible to fourier transform the quotient and obtain a useful result in the time domain in practice the deconvolution can be stabilized by one of several simple techniques in this paper the method is implemented and tested on high quality digital recordings of aftershocks of the jan 9 1982 miramichi new brunswick earthquake in particular seismograms from a jan 17 aftershock 017 13 33 gmt local mag 3 5 exhibit path or site effects which complicate the determination of source parameters after deconvolution the apparent far field source of this event is a simple pulse in displacement with duration 0 07 second for both p and s

investigation of the rupture process of the 28 june 1992 landers earthquake utilizing terrascope abstract displacement seismograms recorded by terrascope for the 28 june 1992 landers earthquake m w 7 3 are deterministically modeled using a forward point source summation technique although the data set is sparse it was possible to robustly determine important rupture parameters such as gross slip distribution rupture velocity rise time and total source duration the relatively simple approach lends itself to rapid application following large earthquakes provided that a catalog of green9s functions appropriate for the region is available the fault used in the modeling of the landers mainshock has a length of 70 km along strike and a width of 15 km along dip a model was found in which the distribution and amplitude of slip at the surface matches the observed surface slip and provides a very good level of fit to the seismic data seismically the landers earthquake is characterized as two subevents the peak slip of the first subevent is 10 km north of the epicenter and the second is 40 km northwest along strike from the epicenter the seismic moment is distributed as 2 10 26 dyne cm to the first and 6 10 26 to the second subevent respectively it was assumed in our modeling that the distribution of seismic moment along strike was the same at all depths this assumption implies that slip at depth is 69 of that at the surface as a result of differences in the material properties in the velocity model the sensitivities of the source model to rupture velocity and dislocation rise time were examined a rupture velocity of 2 9 km sec 80 of the shear wave velocity and a rise time of 1 to 3 sec were found to satisfy the data the rise time is only a fraction of the total source process time of 24 sec and implies that slip on the fault occurred within a narrow band 3 to 10 km at any instant during the rupture

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

recent global sea level acceleration started over 200 years ago 1 we present a reconstruction of global sea level gsl since 1700 calculated from tide gauge records and analyse the evolution of global sea level acceleration during the past 300 years we provide observational evidence that sea level acceleration up to the present has been about 0 01 mm yr2 and appears to have started at the end of the 18th century sea level rose by 6 cm during the 19th century and 19 cm in the 20th century superimposed on the long term acceleration are quasi periodic fluctuations with a period of about 60 years if the conditions that established the acceleration continue then sea level will rise 34 cm over the 21st century long time constants in oceanic heat content and increased ice sheet melting imply that the latest intergovernmental panel on climate change ipcc estimates of sea level are probably too low

the dynamics of a one dimensional fault in the presence of friction summary the tearing and healing of a one dimensional crack in a solid in the presence of external tectonic forces pre stress static friction cohesion and dynamic friction is investigated it is found that cohesive forces have a strong influence on the velocity of rupture the velocity of rupture is always less than or equal to the velocity of sound the extension of the crack ceases either when the crack enters a region with too high a cohesive force or when the difference between the tectonic stress and the dynamical shear stress becomes negative over a substantial region of space for one simple model a high displacement high energy release event has been found while in another model of the same fault length a low displacement low energy release event with the same stress drop takes place the difference between the two models is in the mode of healing and in particular whether the fault breaks out at the free surface of the earth

holocene sea levels and palaeoenvironments malay thai peninsula southeast asia sedimentological and palynological investigations of great songkhla lakes east coast of the malay thai peninsula southeast asia reveal sedimentary sequences rich in palynomorph assemblages dominated by pollen of mangroves and freshwater swamps compared with other regions in southeast asia the assemblages are of relatively low diversity geochronological data indicate that the great songkhla lakes record one of the earliest mangrove environments in southeast asia 8420 8190 cal yr bp which are subsequently replaced by a freshwater swamp at 7880 7680 cal yr bp owing to the decline of marine influence sea level observations from great songkhla lakes and other areas of the malay thai peninsula reveal an upward trend of holocene relative sea level from a minimum of 22 m at 9700 9250 cal yr bp to a mid holocene high stand of 4850 4450 cal yr bp which equates to a rise of c 5 5 mm yr the sea level fall from the high stand is steady at c 1 1 mm yr geophysical modelling shows that hydroisostasy

rupture characteristics and tomographic source imaging of ml 3 earthquakes near anza southern california the rupture characteristics of several ml 3 earthquakes near anza california are determined from time domain analysis of path corrected displacement pulses these pulses are corrected for propagation effects apparent attenuation scattering site resonance using the waveforms of adjacent small events ml 2 1 as empirical green s functions the earthquakes studied occurred during two swarm sequences near cahuilla in an area characterized by swarm activity at shallow depth 5 km the data consist of seismograms recorded by the anza seismic network a high dynamic range local array with digital telemetry the waveforms of adjacent small events ml 2 1 are deconvolved from those of the ml 3 events to yield the source time functions of the larger earthquakes the ml 3 earthquakes display a variety of rupture modes similar to those reported for large shocks but over much shorter time scales and distances events with single and multiple ruptures are observed relative locations of the subevents are obtained from azimuthal differences in the time separation of pulses in the deconvolved displacement waveforms some events as small as ml 2 4 display unilateral rupture propagation as manifested by azimuthal variations in the pulse widths of the deconvolved displacement pulses a tomographic back projection technique is applied to the deconvolved displacement pulses to image the slip velocity on the fault as a function of time after nucleation and distance along the fault using a one dimensional fault model the tomographic inversion for one of the events ml 2 4 reveals a unilateral rupture with rupture velocity about equal to the shear wave velocity vs and fault length of 300 m a similar inversion for an ml 3 7 event resolves two subevents separated by about 200 m and yields an average rupture velocity of 0 8vs these rupture velocities are similar to those reported for large earthquakes indicating that rupture velocity is independent of seismic moment down to 3 1 1019 dyn cm the smallest event studied there are clear variations in pulse width for neighboring events with similar seismic moments implying significant differences in static stress drops factor of five variations in stress drop 11 61 bars are calculated for events within 200 m of each other thus the stress and or strength along this fault zone varies considerably over distances of hundreds of meters

revised and synthetic apparent polar wander paths of the african eurasian north american and indian plates and true polar wander since 200 ma we have reviewed paleomagnetic data available for the eurasian african north american and indian plates over the last 200 ma selection criteria are those generally accepted with an emphasis on evidence for lack of remagnetization accurate dating and proper structural analysis this results in 23 35 51 and 2 poles for eurasia africa north america and india respectively we believe that this limited set of higher quality data is more likely to reveal key features of apparent polar wander apw paths than averaging of larger data sets involving less stringent selection criteria we propose and describe revised apw paths but more importantly we next use relative motion models to transfer all data in a common reference frame we find good agreement between transferred data when they are averaged separately for each plate in independent 20 ma windows this is a check on consistency of paleomagnetic data kinematic models and of the geocentric dipole hypothesis transferred data from all plates are averaged in 20 ma windows to generate synthetic apw paths for all plates studied these synthetic paths are in agreement with the original revised apw paths that use only data from a single plate moreover both geographic and time resolution are improved spatial confidence intervals are of the order of 5 the synthetic paths display interesting features such as a previously ill recognized apw loop for eurasia paleomagnetic and hotspot apw are next compared and a determination of true polar wander tpw is derived we find significant tpw amounting to over 20 in the last 200 ma tpw appears to be episodic with a standstill between 180 and 110 ma there is general agreement with a previous study of livermore et al 1984 the tpw standstill appears to correlate with a time of decreasing reversal frequency ending with the cretaceous long normal superchron other periods of fast tpw would seem to correspond to increasing reversal frequency however it is suggested that the major tpw hairpin at 50 ma might correspond to the collision of india with eurasia tentative correlations with core or mantle indicators can be understood as a result of couplings between the core mantle and lithosphere we believe primarily related to episodic evolution of the d layer

sequence stratigraphic analysis of the aptian albian lower greensand in southern england abstract facies analysis and its use in sequence stratigraphy is described using the lower greensand of southern england as an example and the resulting interpretations are outlined this work forms an independent test of sequence stratigraphic techniques and the exxon cycle chart sequence stratigraphy is a very powerful tool in the analysis of problematic successions although some modification is made here in emphasizing the use of the transgressive surface changing palaeoenvironmental conditions and the effect that palaeoceanography has on the recognition of sequence boundaries are also discussed broad agreement is found between these results and the cycle chart although changing tidal conditions alter the criteria available for analysis of the aptian albian lower greensand succession comparison between this study and sequence stratigraphic analyses conducted in the more condensed type sections of england and france shows that further sequence boundaries are recognizable

a 20th century acceleration in global sea level rise 1 multi century sea level records and climate models indicate an acceleration of sea level rise but no 20th century acceleration has previously been detected a reconstruction of global sea level using tide gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea level rise but no significant acceleration over this period here we extend the reconstruction of global mean sea level back to 1870 and find a sea level rise from january 1870 to december 2004 of 195 mm a 20th century rate of sea level rise of 1 7 0 3 mm yr 1 and a significant acceleration of sea level rise of 0 013 0 006 mm yr 2 this acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed if this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm consistent with projections in the ipcc tar

the plant debris beds of the early cretaceous barremian wessex formation of the isle of wight southern england their genesis and palaeontological significance abstract the early cretaceous barremian wessex formation of the isle of wight primarily represents high sinuosity fluvial but also lacustrine and terrestrial deposition on a low relief floodplain occupying half grabens with active normal faults immediately to the north plant debris beds form a very small proportion of the succession but are the main source of vertebrate fossils including dinosaurs these conspicuous but thin grey units are distributed randomly throughout the wessex formation and are of limited lateral extent the lower part of most plant debris beds comprises a poorly sorted matrix supported conglomerate the upper part of most consists of structureless mudstone which usually grades up into colour mottled but predominantly red and purple floodplain mudstones the plant debris beds contain an unusual mixture of freshwater molluscs diverse aquatic and terrestrial vertebrates and mainly terrestrial plants with a variable quality of preservation we conclude that each plant debris bed represents a locally generated sheetflood which was then transformed on the floodplain into a debris flow by the acquisition of surface material the debris flows surged into and were deposited in depressions on the alluvial plain including abandoned chute and cut off channels oxbows and ponds these units are therefore intrabasinal and interfluvial and the fossils that they contain are locally derived similar deposits of palaeontological significance have not been reported elsewhere in the literature in view of this their origin and sedimentology their palaeontological significance and the taphonomy of the flora and fauna they contain are discussed

foraminifera in a new zealand salt marsh and their suitability as sea level indicators abstract vertical distributions of live and dead foraminiferal abundances are investigated in a salt marsh at pounawea in southeastern new zealand for potential use in holocene sea level reconstructions statistical analyses are conducted to determine whether dead foraminiferal abundances can be utilised as a proxy for elevation in southeastern new zealand it is concluded that dead salt marsh foraminifera which can predict elevations to within 5 cm or better are precise sea level proxies holocene sea level reconstructions along the tectonically stable catlins coast based on fossil salt marsh foraminifera can therefore serve as a potential baseline tool to estimate relative vertical tectonic displacement along tectonically active coasts in new zealand

timing and magnitude of recent accelerated sea level rise north carolina united states we provide records of relative sea level since a d 1500 from two salt marshes in north carolina to complement existing tide gauge records and to determine when recent rates of accelerated sea level rise commenced reconstructions were developed using foraminifera based transfer functions and composite chronologies which were validated against regional twentieth century tide gauge records the measured rate of relative sea level rise in north carolina during the twentieth century was 3 0 3 3 mm a consisting of a background rate of 1 mm a plus an abrupt increase of 2 2 mm a which began between a d 1879 and 1915 this acceleration is broadly synchronous with other studies from the atlantic coast the magnitude of the acceleration at both sites is larger than at sites farther north along the u s and canadian atlantic coast and may be indicative of a latitudinal trend

carbon isotope analysis of fossil wood and dispersed organic matter from the terrestrial wealden facies of hautrage mons basin belgium pedogenic nodules calcitic shells dispersed organic carbon and bulk rocks affected by low diagenesis are judged to be reliable tools for carbon isotope chemostratigraphy up to now no systematic study has been carried out to check the reliability of fossil wood material for carbon isotope chemostratigraphy in terrestrial settings the 235 m thick wealden facies sediments of the danube bouchon quarry at hautrage hautrage clays formation mons basin belgium encompass dark to grey clays and sands rich in organic matter and coalified charcoalified fragments of fossil wood deposited in an alluvial plain during middle barremian to earliest aptian we measured and compared the carbon isotope ratios of 110 levels of the stratigraphic succession for dispersed organic carbon delta c 13 doc and fossil wood delta c 13 wood collected in the same geological level in the whole succession the averages of delta c 13 doc and delta c 13 wood have a significant difference of about 0 9 the delta c 13 wood is usually heavier than the delta c 13 doc which is consistent with measurements on different constituents of modern trees branches versus leaves and tissues in one single stratigraphic level the variability of delta c 13 wood is much higher up to 7 3 parts per thousand than that of delta c 13 doc 0 4 parts per thousand four main causes may explain these results firstly the delta c 13 doc averages the isotopic signal of different compounds and tissues such as leaves seeds cuticles as they become mixed and dispersed the delta c 13 wood reflects the carbon isotope ratio of a small part only of one single tree which is a complex system with delta c 13 variations over a range of 4 parts per thousand secondly there is strong delta c 13 variability between different species of plants in hautrage several gymnosperm genera were collected including podocarpoxylon taxodioxylon brachyoxylon and thujoxylon and numerous fern taxa thirdly coalification and charcoalification can affect the delta c 13 of the doc and the various kinds of woods in a different way fourthly the wood fragments may be reworked several times from more ancient geological levels especially in the alluvial plain environment of hautrage where thick levels of fluviatile coarse sand deposits are observed however in the whole succession both delta c 13 wood and delta c 13 doc curves show similar trends this suggests that carbon isotope curves on fossil wood can be matched to carbon isotope curves on doc for the whole trend fossil wood is a relatively good chemostratigraphic tool when sufficient samples are measured in the succession whenever possible both control of the wood taxa and estimation of degree of char coalification are however recommended in one single level charcoal has more stable delta c 13 wood values than delta c 13 wood of coalified fragments the delta c 13 positive trend can be due to several causes including global pco 2 variations and or regional changes and or local environmental conditions in the alluvial plain if global the dating of the hautrage succession may be refined to the late early barremian early late barremian by matching palynological and carbon isotope chemostratigraphical data c 010 elsevier b v all rights reserved

shear wave splitting and earthquake forecasting seismic shear wave splitting sws monitors the low level deformation of fluid saturated microcracked rock we report evidence of systematic sws changes recorded above small earthquakes monitoring the accumulation of stress before earthquakes that allows the time and magnitude of impending large earthquakes to be stress forecast the effects have been seen with hindsight before some 15 earthquakes ranging in magnitude from an m1 7 seismic swarm event in iceland to the ms7 7 chi chi earthquake in taiwan including a successfully stress forecast of a m5 0 earthquake in sw iceland characteristic increases in sws time delays are observed before large earthquakes which abruptly change to deceases shortly before the earthquake occurs there is a linear relationship between magnitudes and logarithms of durations of both increases and decreases in sws time delays before large impending earthquakes however suitably persistent swarms of small earthquakes are too scarce for routine stress forecasting reliable forecasting requires controlled source cross hole seismics between neighbouring boreholes in stress monitoring sites sms it would be possible to stress forecast damaging earthquakes worldwide by a global network of sms in real time

a cretaceous and jurassic geochronology an integrated geomagnetic polarity and geologic time scale for the jurassic and cretaceous periods is presented based on various methods according to the availability of definitive isotopic ages an age calibrated sea floor spreading model is used to interpolate the ages of the kimmeridgian to barremian and the campanian to maestrichtian stages numerical age estimates for the aptian to santonian stage boundaries follow published isotopic age determinations the hypothesis of equal duration of ammonite zones is employed as a vernier to apportion time for the hettangian to oxfordian stages the new scale results in ages of 208 ma for the base of the jurassic 144 ma for the jurassic cretaceous boundary and 66 5 ma for the top of the cretaceous the integrated biostratigraphic magnetostratigraphic and geochronometric record serves as a working hypothesis for geologic correlation of jurassic and cretaceous strata

marsh benthic foraminifera response to estuarine hydrological balance driven by climate variability over the last 2000 yr minho estuary nw portugal abstract a high resolution study of a marsh sedimentary sequence from the minho estuary provides a new palaeoenvironmental reconstruction from nw iberian based on geological proxies supported by historical and instrumental climatic records a low salinity tidal flat dominated by trochamminita salsa haplophragmoides spp and cribrostomoides spp prevailed from ad 140 1360 roman warm period dark ages medieval climatic anomaly this sheltered environment was affected by high hydrodynamic episodes marked by the increase in silt clay ratio decrease of organic matter and poor and weakly preserved foraminiferal assemblages suggesting enhanced river runoff the establishment of low marsh began at ad 1380 this low salinity environment marked by colder and wet conditions persisted from ad 1410 1770 little ice age when foraminiferal density increased significantly haplophragmoides manilaensis and trochamminita salsa mark the transition from low to high marsh at ad 1730 since ad 1780 the abundances of salt marsh species jadammina macrescens trochammina inflata increased accompanied by a decrease in foraminiferal density reflecting climate instability when droughts alternate with severe floods sw europe marsh foraminifera respond to the hydrological balance controlled by climatic variability modes e g nao and solar activity thus contributing to the understanding of ne atlantic climate dynamics

magnetostratigraphy of the lower cretaceous vectis formation wealden group on the isle of wight southern england magnetostratigraphic results are described from two sections within the lower cretaceous vectis formation formerly wealden shales of the isle of wight southern england the sections are located at shepherd9s chine and yaverland respectively in both of these sections a reliably established reverse polarity magnetozone herein defined as the vectis magnetozone occurs within the shepherd9s chine member this magnetozone has a thickness of some 15 m and its upper boundary is well defined in the yaverland section but is obscured in the shepherd9s chine section due to cliff slumping the lower boundary is well established in both sections and lies some 15 m above the barnes high sandstone member in the shepherd9s chine section and 12 m above this unit at yaverland this boundary provides a useful chron stratigraphic datum a comparison with established geomagnetic polarity timescales for the cretaceous indicates that the vectis magnetozone may be correlated either with lower aptian reverse polarity chron cm 0 or with lower barremian chron cm 1 with the former being the more likely an important implication of this interpretation is that the base of the aptian stage as defined from tethyan foraminiferal zones must lie within the vectis formation at least 25 30 m beneath the top of the shepherd9s chine member rather than at the top of this member as hitherto commonly accepted beds characterized by anomalously high intensities of magnetization which occur at the base of the vectis formation and a few metres above the barnes high sandstone in the two sections are tentatively interpreted as having a volcanogenic origin

magnetic remanence in the chalk of eastern england an unusually resistant vrm a single component natural remanent magnetization nrm is carried largely by pseudosingle domain magnetite in the cretaceous lower chalk and red chalk of eastern england the red chalk also records the same direction in haematite most of the ferro magnetic minerals occur as primary clastic or early diagenetic grains a stable remanence component is resistant to demagnetization and is carried by both magnetite and haematite nevertheless it has a steep inclination close to the present earth s field and it is too steep for the previously reported palaeolatitude of these rocks at the time of sedimentation a postglacial slump breccia scatters the chrm but also provides some evidence of viscous partial magnetic overprinting during slumping despite its resistance to thermal and alternating field demagnetization the characteristic remanent magnetization chrm is probably a young bruhnes epoch viscous remanent remagnetization vrm

source process of the 1990 gonghe china earthquake and tectonic stress field in the northeastern qinghai xizang tibetan plateau the m s 6 9 gonghe china earthquake of april 26 1990 is the largest earthquake to have been documented historically as well as recorded instrumentally in the northeastern qinghai xizang tibetan plateau the source process of this earthquake and the tectonic stress field in the northeastern qinghai xizang plateau are investigated using geodetic and seismic data the leveling data are used to invert the focal mechanism the shape of the slipped region and the slip distribution on the fault plane it is obtained through inversion of the leveling data that this earthquake was caused by a mainly reverse dip slipping buried fault with strike 102 dip 46 to ssw rake 86 and a seismic moment of 9 4 1018 nm the stress drop strain and energy released for this earthquake are estimated to be 4 9 mpa 7 4 10 5 and 7 0 1014 j respectively the slip distributes in a region slightly deep from nww to see with two nuclei i e knots with highly concentrated slip located in a shallower depth in the nww and a deeper depth in the see respectively

automatic imaging of earthquake rupture processes by iterative deconvolution and stacking of high rate gps and strong motion seismograms by combining the complementary advantages of conventional network inversion and backprojection methods we have developed an iterative deconvolution and stacking ids approach for imaging earthquake rupture processes with near field complete waveform data this new approach does not need any manual adjustment of the physical empirical constraints such as restricting the rupture time and duration and smoothing the spatiotemporal slip distribution therefore it has the ability to image complex multiple ruptures automatically the advantages of the ids method over traditional linear or nonlinear optimization algorithms are demonstrated by the case studies of the 2008 wenchuan and 2011 tohoku earthquakes for such large earthquakes the ids method is considerably more stable and efficient than previous inversion methods additionally the robustness of this method is demonstrated by comprehensive synthetic tests indicating its potential contribution to tsunami and earthquake early warning and rapid response systems it is also shown that the ids method can be used for teleseismic waveform inversions for the two major earthquakes discussed here the ids method can provide without tuning any physical or empirical constraints teleseismic rupture models consistent with those derived from the near field gps and strong motion data

carbon isotope composition of lower cretaceous fossil wood ocean atmosphere chemistry and relation to sea level change the carbon isotope composition of fossil wood fragments collected through a biostratigraphically well constructed aptian lower cretaceous shallow marine siliciclastic succession on the isle of wight southern britain shows distinct variations with time the results indicate that the stratigraphic signature of delta sup 13 c sub wood through the aptian was influenced primarily by fluctuations in the isotopic composition of co sub 2 in the global ocean atmosphere system as registered in marine carbonates elsewhere and was not governed by local paleoenvironmental and or paleoecological factors negative and positive excursions in delta sup 13 c sub wood through the lower aptian occur in phase with inferred transgressions and regressions respectively a pattern that contrasts with that observed in many previous studies for different time intervals the relationship between delta sup 13 c variations and relative sea level change is tentatively interpreted as a response to various climatic and eustatic factors relating to rapid sea floor spreading thermal uplift of ocean floor emplacement of plateaus volcanic co sub 2 emissions weathering and sedimentary rate

recognition and documentation of depositional sequences from outcrop an example from the aptian and albian on the eastern margin of the wessex basin stratigraphic data relating to the aptian and albian sediments around folkestone in southeast england on the eastern margin of the wessex basin are plotted graphically to illustrate biostratigraphic gaps and condensed intervals these are then used to suggest candidate sequence boundaries notated lg1 4 and gl 3 which are named after the lower greensand and gault the biostratigraphic subzones apparently unrepresented in the area are lg1 obsoletus and bodei lg2 gracite and debile lg3 schrammeni gl bulliensis candidate sequence boundaries g2 cristatum subzone and g3 auritus subzone are erosion surfaces correlating with probable biostratigraphic gaps elsewhere in the basin the age of lg4 is uncertain but must lie within the mammillatum superzone all candidate sequence boundaries correspond closely to those predicted by recent global sea level cycle charts and additionally there is a close match between predicted maximum flooding surfaces and the occurrence of condensed intervals most of the candidate sequence boundaries could have been formed as a result of rapid and at least regionally extensive relative sea level falls but the sedimentological contexts of lg3 and gl suggest that these may have been generated by transgression related sediment condensation the minor sequence boundary in the loricatus zone intermedius subzone illustrated in the cycle charts cannot be unambiguously recognized at outcrop in the folkestone area additional sequence boundaries not shown in the cycle charts may also be present in the wessex basin

assessing the performance of a foraminifera based transfer function to estimate sea level changes in northern portugal a b s t r a c t a r t i c l e i n f o article history received 14 april 2010 available online 15 december 2010 we assessed the performance of a transfer function model for sea level studies using salt marsh foraminifera from two estuaries of northern portugal an independent data set of 12 samples and 13 sub fossil samples from a core were used to evaluate if reconstructions and errors derived from current models are adequate initial transfer function models provided very strong results as indicated by cross validation component 2 r 2 0 80 0 82 rmsep ranged from 10 7 to 12 3 cm and improved its performance by ca 10 when sample size reached ca 50 results derived using an independent test data set indicate that cross validation is a very effective approach and produces conservative errors when compared to observed errors we additionally explored the possible effect of transforming the concentration data into percent in the error estimations by comparing the results obtained based on the use of both concentration and compositional data results indicate that this type of transformation does not affect the performance of the transfer function results derived from a reconstruction of sub fossil samples from a core indicate that high resolution sea level reconstructions are possible but show that depositional environments have to be selected carefully in order to minimize the impact of possible taphonomical loss

a time domain inversion technique for the tempo spatial distribution of slip on a finite fault plane with applications to recent large earthquakes in the tibetan plateau a time domain inversion technique is proposed to invert for the tempo spatial distribution of slip on an earthquake fault plane this technique is based on the idea that a finite fault plane can be divided into several subfaults each of which can be treated as a point source and that the source time function stf of the finite fault is the weighted sum of the stfs of all the subfaults this technique is applied to deduce the source processes of three recent large earthquakes in the qinghai xizang tibetan plateau the 1990 april 26 gonghe qinghai earthquake ms6 9 ruptured on a fault plane with a strike of 113 a dip of 68 and a rake of 89 the fault has a length of 45 km a width of 15 km and a total moment release of 9 4 1018 n m the rupture initiated at the wnw end of the fault and propagated unilaterally towards the ese end of the fault in total the rupturing lasted for 45 s and was divided into two episodes the first 9 s long and the second 16 s long with 20 s quiescence in between there are two distinct rupture regions nuclei on the fault plane these two nuclei with maximum slips of about 62 and 55 cm are about 25 km apart in the wnw ese direction the 1996 february 3 lijiang yunnan earthquake ms7 0 has a focal mechanism with a strike of 157 a dip of 48 and a rake of 102 the earthquake fault is about 45 km with a width of 20 km and a total moment release of 9 8 1018 n m the total duration of the rupture was 16 s is divided into two episodes the first 8 5 s long and the second 7 5 s long the inverted final slip distribution of the lijiang earthquake also shows two nuclei one nucleus with a maximum slip of 40 cm is located on the nnw portion of the fault at a shallower depth and the other with a maximum slip of 50 cm is located on the sse portion of the fault at a greater depth the 1997 november 8 mani xizang tibet earthquake ms7 9 has a focal mechanism with a strike of 250 a dip of 88 and a rake of 19 and a moment release of 3 4 1020 n m the total duration of the rupture was about 15 s the inverted final slip distribution of the mani earthquake shows three nuclei on the fault plane the first nucleus with a maximum slip of 956 cm is located at the wsw end of the fault at 10 km in depth the second with a maximum slip of 743 cm is located at the ene end of the fault 55 km away from the wsw end of the fault and at 35 km depth the third with a maximum slip of 1060 cm is about 30 km away from the wsw end of the fault and at about 40 km depth these three nuclei form a total rupture area of about 70 km in length and 60 km in depth

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

gyre scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise 1 most of the long tide gauge records in the north atlantic and north pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800 s early 1900 s compared to the latter half of the 20th century the rates of sea level rise tend to be lower in the 19th compared to 20th century we show this behavior may be related to long term gyre scale surface pressure variations similar to those associated with the northern annular mode as sea level pressure increases decreases at decadal and longer timescales at the centers of the subtropical atmospheric gyres sea level trends along the eastern margins in each ocean basin decrease increase this is not an isostatic response the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism rather it appears to be the result of large possibly gyre scale changes in ocean circulation some evidence is also presented indicating slow 2 cm sec westward propagation of sea level changes in the atlantic from the west coast of europe to the east coast of the u s which produce the decadal variability seen there

reprint of arctic planktic foraminiferal assemblages implications for subsurface temperature reconstructions abstract earlier reconstructions of the inflow of atlantic water to arctic and subarctic oceans based on foraminiferal proxy data have been obstructed by uncertain quantitative reconstructions of sea surface and subsurface temperatures in this study surface sediment samples with undisturbed sediment water interface from polar north atlantic and barents sea were retrieved and prepared at the size fractions from 100 m to 1000 m the foraminiferal analyses show that neogloboquadrina pachyderma constitutes 96 99 of the fauna in arctic and polar surface water masses the same result is obtained when investigating the 150 m size fraction however in arctic areas influenced by atlantic water additional faunal information is obtained when using the smaller 100 m size fraction in these areas n pachyderma is reduced to about 50 and the relatively small species turborotalita quinqueloba becomes very frequent this also applies to the coastal water masses which are dominated by neogloboquadrina incompta and globigerinita uvula transfer functions using the current dataset based on the 100 m size fraction were developed and assessed different statistical models were tested using both seasonal and annual temperature data from 0 m 10 m 50 m and 100 m water depth the most precise reconstructions of subsurface temperatures were found when using summer temperatures from the 100 m depth level the transfer function was tested on holocene foraminiferal records and compared to previous reconstructions the results show that our new transfer function based on the 100 m fraction generally yields lower temperatures at both 10 and 100 m water depth than earlier reconstructions e g hald et al 2007 this could be due to the increased number of samples containing both small species and or the presence of more small specimens representing cold conditions

an upper cretaceous paleomagnetic pole for stable europe from aix en provence france abstract a paleomagnetic study of continental deposits limestones sandstones from the upper cretaceous basin of aix en provence campanian to danian 43 5 n 5 5 e gives a mean paleomagnetic direction of d 9 5 i 46 8 n 10 k 33 95 8 3 and a mean pole 73 n 156 e n 10 k 24 a95 10 the fold test is positive as is the reversal test this pole is not significantly different from other cretaceous or lower tertiary poles from stable europe

variable slip rupture model of the great 1923 kanto japan earthquake geodetic and body waveform analysis abstract the available geodetic and teleseismic data sets for the 1923 kanto earthquake m s 8 1 have been combined into a joint inversion for both temporal and spatial slip variations we assumed an initial faulting model to be consistent with the geometry determined by kanamori 1971 on the basis of first motion data aftershock area and the amplitude of surface waves at teleseismic distances and also to enclose the slipped area estimated by matsu9ura et al 1980 from the geodetic data employed here we then inverted for a heterogeneous distribution of slip of the fault plane the leveling routes and triangulation stations used consisting of 225 bench marks and 31 triangulation points are from matsu9ura et al 1980 we chose to first determine the overall static slip distribution by inverting the geodetic data alone we then proceeded to gradually increase the importance of the teleseismic data always requiring a good fit to the geodetic leveling and horizontal displacements in this way we could provide a constraint on the overall static slip characteristics from the geodetic data and provide stability for the teleseismic inversion yet determine the degree of slip heterogeneity and time history most suitable for matching the waveform data and for simulating strong ground motions our analysis yields a seismic moment of 7 to 8 10 27 dyne cm m w 7 8 to 7 9 with a maximum slip of approximately 8 m the most concentrated slip is in the shallow central and western portion of the fault the location of the concentrated slip on the fault plane has important consequences for the amplitude duration and frequency content of the resulting ground motions as documented by takeo and kanamori 1993

the distribution of contemporary intertidal foraminifera at cowpen marsh tees estuary uk implications for studies of holocene sea level changes abstract foraminiferal assemblages were collected at 2 weekly intervals over a period of 12 months from the intertidal zone of cowpen marsh statistical analyses indicate that the foraminiferal distributions for this site are controlled predominantly by altitude furthermore the contemporary foraminiferal assemblages from cowpen marsh broadly reflect vertical floral zones based on vascular plants cluster analysis separates foraminiferal assemblages into four zones two high and middle marsh zones consisting of differing abundances of jadammina macrescens and trochammina inflata a low marsh zone dominated by jadammina macrescens and miliammina fusca and a mudflat zone dominated by calcareous foraminiferal species notably elphidium williamsoni haynesina germanica and quinqueloculina spp the altitudinal ranges of the faunal zones are employed to identify the vertical relationship of the local environment in which the assemblage accumulated to a reference tide level

rupture directivity and slip distribution of the m 4 3 foreshock to the 1992 joshua tree earthquake southern california details of the m 4 3 foreshock to the joshua tree earthquake were studied using p waves recorded on the southern california seismic network and the anza network deconvolution using an m 2 4 event as an empirical green s function corrected for complicated path and site effects in the seismograms and produced simple far field displacement pulses that were inverted for a slip distribution both possible fault planes north south and east west for the focal mechanism were tested by a least squares inversion procedure with a range of rupture velocities the results showed that the foreshock ruptured the north south plane similar to the mainshock the foreshock initiated a few hundred meters south of the mainshock and ruptured to the north toward the mainshock hypocenter the mainshock m 6 1 initiated near the northern edge of the foreshock rupture 2 hr later the foreshock had a high stress drop 320 to 800 bars and broke a small portion of the fault adjacent to the mainshock but was not able to immediately initiate the mainshock rupture

the temporal and spatial evolution of the 19 september 1985 michoacan earthquake as inferred from near source ground motion records abstract a frequency domain inversion technique is employed to image the rupture process of the 19 september 1985 michoacan mexico earthquake a linear system is derived from the elastodynamic representation theorem and is solved for the spatial slip velocity distribution in the frequency bandwidth 0 0 to 0 32 hz the temporal behavior of slip velocity on the fault plane is then recovered by fourier synthesis model complexity is penalized by seeking a solution that propagates with the most nearly constant rupture velocity and that produces the most nearly constant spatial slip distribution at 0 hz the inversion of surface static displacements as inferred from strong motion recordings of the guerrero accelerograph array gives an estimate of the static offset on the fault plane coastal uplift data inferred from the mortality of intertidal organisms bodin and klinger 1986 is also used to further constrain the spatial slip distribution a low frequency image of the rupture process of the earthquake has been obtained using full space green9s functions two areas of large slip amplitude are discernible one located downdip of the reported hypocenter and the other updip of the projection on the fault plane of station la union their separation is approximately 100 km assuming that full space green9s functions underestimate static offset values at the surface of a half space by a factor of 0 5 the inferred seismic moment is 10 6 10 27 dyne cm 90 per cent of which is released in these two areas sustaining the largest slip the total inferred rupture duration is approximately 56 sec from the hypocenter the rupture front proceeds with an average velocity estimated at 2 8 km sec there are indications of bilateral propagation both from the hypocentral area and from an area surrounding the projection on the fault plane of the strong motion station la union an upper bound on rupture duration at the two principal subevents is 8 sec

single station decomposition of seismograms for subevent time histories we have adapted an iterative lseast squares inversion with positivity constraints to the problem of deconvolving the recordings of a small earthquake from the recordings of a large composite earthquake the inversion uses an f test to minimize the number of non zero amplitudes or subevents in the solution set by requiring each added subevent to reduce the variance significantly we apply this inversion to the analysis of strong motion recordings of a set of moderate sized 4 0m l 6 4 aftershocks of the 1976 friuli earthquake

geomagnetic polarity in the early cretaceous and jurassic knowledge of the polarity history of the earth s magnetic field during the mesozoic stems primarily from oceanic m sequence magnetic anomalies certain of these anomalies have been biostratigraphically dated from sediments immediately overlying basaltic basement at deep sea drilling project d s d p sites within the m sequence the biostratigraphic control is such that these age estimates are generally imprecise and moreover the sediment ages represent only minimum ages for the basaltic basement itself magnetostratigraphy in sedimentary land sections provides improved age estimates for magnetozones which can then be correlated with m sequence anomalies magnetostratigraphy provides not only enhanced dating of the ocean floor and resolution of the behaviour of the geomagnetic field during the cretaceous and jurassic oceanic quiet zones but also a world wide correlation tool for sedimentary stratigraphy the middle cretaceous is characterized by a long period of normal polarity extending from the early aptian to the early campanian reversed magnetozones corresponding to oceanic anomalies m 0 m 1 and m 3 have been palaeontologically dated as early aptian middle barremian and early barremian respectively magnetozones corresponding to oceanic anomalies m 5 to m 15 are hauterivian to valanginian in age but have not been individually associated with stage boundaries mainly due to poor biostratigraphic control in italian pelagic limestone sections of this age however magnetozones corresponding to oceanic anomalies m 16 to m 22 have been individually correlated to lower berriasian and tithonian palaeontological zones and extrapolation of this correlation gives an age for anomaly m 25 close to the oxfordian kimmeridgian boundary the jurassic 9quiet zone in the oceans is recognized in land sections as an extended period of predominantly normal polarity and although poor biostratigraphic control in this interval limits our knowledge of its duration we consider that it extended through the oxfordian and callovian stages the bathonian and older jurassic stages are characterized by mixed polarity a precise correspondence of magnetozones to ammonite zonations and stage boundaries is only available for the aalenian to pliensbachian interval where the frequency of reversal was apparently very high

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