rupture area and displacement of past cascadia great earthquakes from coastal coseismic subsidence coastal marshes record a 6500 yr history of coseismic displacements in great earthquakes at the cascadia subduction zone we compiled estimates of coseismic displacement for past megathrust events based on correlations with megathrust triggered turbidites and estimated megathrust slip based on comparisons of marsh displacements with dislocation model predictions age correlated marsh data are compatible with event rupture extents defi ned by the published turbidite record and a 6500 yr mean recurrence interval that increases northward from 230 to 480 yr within the constraints of the marsh data the width of the coseismic rupture zone generally agrees with the downdip width of the interseismic locked zone inferred from geodetic and thermal data in southernmost cascadia where the model does not include the complex deformation near the mendocino triple junction the coastal data may be better fi t by a model with an 25 narrower rupture than that inferred from regional geophysical data at each coastal marsh site coseismic displacements are roughly similar from event to event independent of the time since the previous event slip in the a d 1700 earthquake was consistent with the preceding interval of strain accumulation 200 yr only at the northern and southern ends of the margin but it was apparently much higher in southern washington and northern oregon possibly indicating postseismic contamination and or catch up coseismic slip to make up for a defi cit in the preceding event overall agreement between the dislocation models and the marsh data for most of the margin implies that such models can be usefully applied to rupture and ground shaking predictions

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

marine incursions of the past 1500 years and evidence of tsunamis at suijin numa a coastal lake facing the japan trench sandy deposits of marine origin underlie the floor of suijin numa a coastal lake midway along the subduction zone marked by the japan trench the deposits form three units that are interbedded with lacustrine peat and mud above a foundation of marine probably littoral sand unlike the lacustrine deposits all three sandy units contain marine and brackish diatoms the middle unit b contains in addition graded beds sug gestive of multiple waves of long wavelength and period the uppermost unit c probably dates to a time in the area s written history when the lake was separated from the sea by a beach ridge plain at least 0 5 km wide and several metres high units a and b postdate ad 540 870 and unit c postdates ad 1030 1640 as judged from radiocarbon dating of leaves and seeds unit b pre dates ad 915 and unit c postdates that year as judged from a tephra within the peat that separates units b and c the age constraints permit correlation of unit b with a tsunami in ad 869 that reportedly devastated at least 100 km of coast approximately centred on sendai unit c may represent a later catastrophic tsunami in 1611 or perhaps a storm surge that inundated much of sendai the lake lacks obvious signs of tsunamis from the region s largest twentieth century earthquakes which were centred to the north in 1933 m 8 1 and directly offshore in 1936 m 7 5 and 1978 mw 7 6

metallogeny in the capricorn orogen western australia the result of multiple ore forming processes abstract the capricorn orogen includes metamorphosed tectonic units intrusive igneous rocks volcano sedimentary and sedimentary basins situated between the pilbara and yilgarn cratons these include the gascoyne complex ashburton blair bresnahan yerrida bryah padbury and earaheedy basins and edmund and collier former bangemall basins mineral deposits and occurrences in these units comprise stratabound base metals including the giant abra pb cu ba edmund basin and magellan pb earaheedy basin and numerous hydrothermal veins and precious and or base metal lodes some of the more important orogenic precious metal lodes are those of the peak hill group in the bryah padbury basins and the egerton field in the gascoyne complex the metallogeny of the capricorn orogen reflects syn to post capricorn orogenic events linked to either protracted convergence tectonics between the pilbara and yilgarn cratons or to a two stage convergence history one during the capricorn orogeny ca 1 83 ga pilbara yilgarn convergence the other during the yapungku orogeny ca 1 79 north australian west australian convergence the metallogeny of the capricorn orogen was further sustained by continental mafic magmatism at about 1 45 and 1 07 ga during which heat advection may have caused widespread hydrothermal circulation particularly in the edmund collier earaheedy basins and adjacent tectonic units an interesting but as yet unexplained aspect of the capricorn metallogeny is the regional pb ba enrichment a conceptual model that attempts to explain the billion year long history of the metallogeny in the capricorn orogen is proposed mineral exploration in the capricorn orogen is somewhat limited and not as intensive as is in the brown fields of the archaean terranes of western australia

assembling and reactivating the proterozoic capricorn orogen lithotectonic elements orogenies and significance abstract the capricorn orogen was initiated during palaeoproterozoic suturing events that brought together the archaean yilgarn and pilbara cratons to form the west australian craton the orogen comprises palaeoproterozoic plutonic and medium to high grade metamorphic rocks of the gascoyne complex a series of palaeoproterozoic volcano sedimentary and sedimentary basins including the ashburton blair yerrida bryah padbury and earaheedy basins and the deformed margins of the pilbara and yilgarn cratons major pulses of deformation and metamorphism took place during the ca 2200 ma ophthalmian orogeny the 2000 1960 ma glenburgh orogeny the 1830 1780 ma capricorn orogeny and a more localized unnamed event at the end of the palaeoproterozoic 1670 1620 ma the orogen has been the site of repeated intracratonic reactivation with renewed basin formation magmatism and orogeny during the mesoproterozoic and the neoproterozoic the exhumed palaeoproterozoic components of the orogen are unconformably overlain by the intracratonic mesoproterozoic edmund and collier basins bangemall supergroup which have been deformed during the neoproterozoic edmundian orogeny the ophthalmian and glenburgh orogenies affected the northern and southern margins of the orogen respectively the former resulted in the development of a foreland basin along the pilbara craton margin whereas the latter is associated with accretion of an allochthonous element the glenburgh terrane of the gascoyne complex to the northwestern margin of the yilgarn craton effects of the capricorn orogeny extended across the entire orogen and provide a younger limit for amalgamation of the yilgarn and pilbara cratons a number of basins developed along both the northern and southern margin of the orogen during this event and were filled with sediment eroded from the yilgarn craton the gascoyne complex and a presently unexposed early palaeoproterozoic terrane the capricorn orogeny corresponds with a major phase of continental collision both in australia and world wide which appears to mark a major phase of supercontinent assembly mineralization within the orogen includes a wide variety of deposit types that can be related to collisional settings including the world class iron orebodies of the hamersley basin

high pressure amphibolite granulite facies metamorphism in the paleoproterozoic rudall complex central western australia abstract the rudall complex forms the basement of the paleoproterozoic to neoproterozoic paterson orogen which was deformed during at least three major orogenies the complex comprises a sequence of metamorphosed clastic and chemical sediments and basalts deposited in a marginal basin environment prior to extensive felsic intrusion deformation of the sequence during the first yapungku orogeny between 2000 and 1760 ma included extensive thrust stacking from ene to wsw the thermal peak of the associated high pressure metamorphism was late to post tectonic with respect to this deformation thermobarometry on amphibolites and mafic granulites that contain various combinations of the minerals hornblende plagioclase quartz garnet othopyroxene and clinopyroxene indicates that temperatures peaked at around 800 c while pressures reached 1200 mpa the late timing of peak temperatures together with the presence in some amphibolites of amphibole plagioclase symplectitic coronas around garnet indicates a steeply decompressive clockwise p t t path peak metamorphic pressures indicate that the crust was locally thickened by at least 40 km during an event that showed similarities to phanerozoic collisional tectonics it is suggested that this deformational and metamorphic event records the collision between the pilbara craton and a continent to the northeast the paleoproterozoic evolution of australia has previously been attributed to ensialic processes characterised by low pressure metamorphism and anti clockwise p t t paths the metamorphic history of the rudall complex is not consistent with this view and the documented high pressure metamorphism is broadly synchronous with a medium pressure metamorphic event in central australia the strangways orogeny and possibly also in northwestern australia the capricorn orogeny collisional plate tectonic processes played a significant role in the paleoproterozoic evolution of northern australia

plate boundary earthquakes and tsunamis of the past 5500 yr sixes river estuary southern oregon eleven plate boundary earthquakes over the past 5500 yr have left a stratigraphic signature in coastal wetland sediments at the lower sixes river valley in south coastal oregon within a 1 8 km2 abandoned meander valley 10 buried wetland soils record gradual and abrupt relative sea level changes back in time to 6000 yr ago an additional youngest buried soil at the mouth of the sixes river subsided during the a d 1700 cascadia earthquake multiple lines of evidence indicate that tectonic subsidence caused soil burial including permanent relative sea level rise following burial lateral continuity of buried soil horizons over hundreds of meters diatom assemblages showing that sea level rose abruptly at least 0 5 m and sand deposits on top of buried soils demonstrating coincidence of coseismic subsidence and tsunami inundation for at least two of the buried soils liquefaction of sediment accompanied subsidence the 11 soil burial events took place between 300 and 5400 yr ago yielding an average recurrence interval of plateboundary earthquakes of 510 yr comparing paleoseismic sites in southern washington and south coastal oregon with the sixes river site for the past 3500 yr indicates that the number and timing of recorded plate boundary earthquakes are not the same at all sites in particular a sixes earthquake at 2000 yr ago lacks a likely correlative in southern washington therefore unlike the a d 1700 cascadia earthquake some cascadia plate boundary earthquakes do not rupture the entire subduction zone from southern oregon to southern washington in the lower sixes river valley the upperplate cape blanco anticline deforms sediment of late pleistocene and holocene age directly above the subduction zone differential tectonic subsidence occurred during two of the plate boundary earthquakes when a blind upper plate reverse fault for which the cape blanco anticline is the surface fold slipped coseismically with rupture of the plate boundary during these two earthquakes sites 2 km from the anticline axis subsided 0 5 m more than sites 1 km from the axis

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

supergene nonsulfide zn pb mineralization in the mehdiabad world class sub seafloor replacement sedex type deposit iran the world class mehdiabad nonsulfide deposit consists of several accumulations of zn pb fe nonsulfide minerals derived from supergene of a vent proximal sub seafloor replacement sedex type deposit hosted in lower cretaceous clastic carbonate rocks of the taft and abkuh formations the main sulfides are galena sphalerite pyrite and minor amounts of chalcopyrite which have been partially or completely transformed into nonsulfide minerals by supergene processes currently the zn mineralization in the abkuh formation ore horizon ii is almost fully oxidized the mehdiabad deposit which can be assigned to both direct replacement and wall rock replacement types the time of the formation of the nonsulfide deposit has not been determined but it is probable that the main supergene metallogenesis happened during tertiary possibly between post cretaceous to present the mineralogy of the nonsulfide mineralization is generally complex and consists of smithsonite hydrozincite and hemimorphite as the main economic minerals accompanied by cerussite anglesite iron manganese oxy hydroxides sauconite and zn rich clays commonly nonsulfide minerals in this deposit consist of two types of ore red zinc ore rzo rich in zn fe pb as and white zinc ore wzo typically with very high zinc grades but low concentrations of iron and lead the proposed three step scenario for the deposition of nonsulfide mineralization in the mehdiabad deposit comprises 1 the deposition of primary sulfides contemporaneous with lower cretaceous clastic carbonate host rocks to form sedex type mineralization 2 during the late cretaceous to present regional uplift leads to deformation folding and thrusting of sulfide bearing lower cretaceous sequence and 3 as a result zn pb fe sulfides hosted in carbonates experienced oxidation under an arid warm climate to form the supergene nonsulfide ore mineralizations

the use of jadammina macrescens brady and balticammina pseudomacrescens bronnimann lutze and whittaker protozoa foraminiferida as sea level indicators in studies of foraminiferal distributions in saltmarshes in new england and atlantic canada balticammina pseudomacrescens and jadammina macrescens have formerly been grouped as trochammina macrescens this study recognises them as distinct species and shows that they have significantly different distributions on the surface of saltmarshes in maine here relative abundances of j macrescens correlate with tidal elevation r2 0 55 p 0 00 whereas those of b pseudomacrescens do not r2 0 03 p 0 34 therefore j macrescens is a better sea level indicator in maine marshes than b pseudomacrescens in menunketesuck river marsh connecticut a clear vertical zonation of saltmarsh foraminifera is absent which hinders interpretation of fossil data this study shows that in maine separating b pseudomacrescens and j macrescens in counts of fossil data facilitates the detection of transgressional and regressional events in the biostratigraphical record and hence the reconstruction of local sea level histories regional variability between northern and southern new england saltmarshes necessitates the establishment of local reference sets of modern analogue data to aid palaeoecological interpretations

paleoseismicity of the southern end of the cascadia subduction zone northwestern california the southern end of the cascadia subduction zone csz in northwestern california poses a high seismic hazard this study uses the quaternary stratigraphy of the bays and estuaries to reconstruct coseismic subsidence caused by strong to great earthquakes we used lithology macrofossils and microfossils to estimate the amount of relative sea level change at contacts caused by coseismic subsidence our paleoseismic record contains evidence of four to six earthquakes over the past 2000 years using the pattern and magnitude of submergence and other paleoseismic information trenches and other sites we determine whether the earthquakes were local or regional we found that the record contained evidence for both smaller strong to major earthquakes on local structures m w 6 5 7 2 and larger regional subduction zone related great earthquakes m w 8 2 we compared our record to other records from oregon and washington and found three earthquakes likely caused by the rupture of the entire csz around approximately 230 270 the a d 1700 event 1150 1400 and 1750 1900 cal b p in addition two other local earthquakes likely occurred around 500 600 1000 1250 and possibly 1500 1650 cal b p online material table of radiocarbon ages obtained in the study

differences in coastal subsidence in southern oregon usa during at least six prehistoric megathrust earthquakes abstract stratigraphic sedimentologic including ct 3d x ray tomography scans foraminiferal and radiocarbon analyses show that at least six of seven abrupt peat to mud contacts in cores from a tidal marsh at talbot creek south slough coos bay record sudden subsidence relative sea level rise during great megathrust earthquakes at the cascadia subduction zone data for one contact are insufficient to infer whether or not it records a great earthquake it may also have formed through local non seismic hydrographic processes to estimate the amount of subsidence marked by each contact we expanded a previous regional modern foraminiferal dataset to 174 samples from six oregon estuaries using a transfer function derived from the new dataset estimates of coseismic subsidence across the six earthquake contacts vary from 0 31 m to 0 75 m comparison of subsidence estimates for three contacts in adjacent cores shows within site differences of 0 10 m about half the 0 22 m error although some estimates may be minimums due to uncertain ecological preferences for balticammina pseudomacrescens in brackish environments and almost monospecific assemblages of miliammina fusca on tidal flats we also account for the influence of taphonomic processes such as infiltration of mud with mixed foraminiferal assemblages into peat on subsidence estimates comparisons of our subsidence estimates with values for correlative contacts at other oregon sites suggest that some of our estimates are minimums and that cascadia s megathrust earthquake ruptures have been heterogeneous over the past 3500 years

salt marsh sea level indicators and transfer function development for the magdalen islands in the gulf of st lawrence canada abstract late holocene salt marsh sediments allow the reconstruction of pre industrial relative sea level changes typically reconstructions are derived by quantifying a relationship between contemporary proxies and elevation which is then applied to down core fossil assemblages via a transfer function common sea level indicating proxies are salt marsh foraminifera and diatoms however testate amoebae represent an alternative complementary proxy with current sea level research increasingly invoking multi decadal timescale processes such as ocean current strength or wind stress to explain relative sea level changes there is a need for increased vertical precision in reconstructions this paper presents new surface assemblages of salt marsh foraminifera and testate amoebae with respect to elevation from two coastal locations in the magdalen islands in the gulf of st lawrence eastern canada we analyse the suitability of each proxy for reconstructing sea level using multivariate statistics ordination and regression modelling testate amoebae are found in greater abundance and diversity than foraminifera and their assemblage variations can be better accounted for by changes in elevation the contemporary training sets from the magdalen islands were able to predict marsh surface elevations viz sea level to precisions of 0 08 m and 0 12 m for testate amoebae and foraminifera respectively there were no benefits from combining the two proxies into a unified training set it was possible to improve the performance of the foraminifera based transfer function by incorporating a second dataset from newfoundland which served to increase the range of the sampled environment and improve the correlation coefficient between sample elevations and model predictions in accordance with existing literature we find transfer function performance to be better at locations with smaller tidal ranges

warakurna large igneous province a new mesoproterozoic large igneous province in west central australia coeval mafic igneous rocks emplaced rapidly over 1 5 3 10 6 km 2 in western and central australia represent the erosional rem nants of a late mesoproterozoic large igneous province named here the warakurna large igneous province shrimp u pb dating of rocks separated by as much as 1500 km indicates that the main episode of magmatism occurred between 1078 and ca 1070 ma the warakurna large igneous province includes layered mafic ultramafic intrusions and mafic to felsic volcanic rocks and dikes in central australia a 1000 km long mafic sill province in western australia and several swarms of mafic dikes the large areal ex tent and short duration imply emplacement above a mantle plume head despite their wide separation the mafic rocks have similar mid oceanic ridge basalt normalized trace element patterns and rare earth element characteristics west directed paleocurrents westward radiating dike swarms and the occurrence of high mg rocks indicate that the center of the plume head was located be neath central australia other late mesoproterozoic large igneous provinces in the laurentia and kalahari cratons appear to be significantly older than the warakurna large igneous province in australia and thus are unlikely to be related to the same mantle plume head

palaeomagnetic evidence for unification of the north and west australian cratons by ca 1 7 ga new results from the kimberley basin of northwestern australia summary a palaeomagnetic study of the elgee formation red siltstones and shales in the palaeoproterozoic kimberley basin of northwestern australia has been carried out all seven sampling sites revealed an extremely stable magnetic remanence carried by haematite the age of the formation is confined by precise shrimp u pb ages of early diagenetic xenotime from rocks both above and below it to be 1704 7 14 ma but this may represent a minimum age the youngest detrital zircon grains in the underlying formation provide a maximum age of 1786 14 ma for the formation the extreme stability of the remanence the dissimilarity of the remanent direction from expected younger palaeomagnetic directions and the lack of regional overprint in the 1790 4 ma hart dolerite just north of the study region support a primary origin for the remanence a marginally positive fold test also supports a primary origin the mean direction of d 92 2 i 14 9 a 95 6 4 gives a palaeopole at 4 4 s 210 0 e with dp 3 3 dm 6 5 this pole a previously reported palaeopole from the hart dolerite and ca 1700 ma overprint poles from the pilbara craton all agree with palaeopoles of similar ages from the mcarthur basin of northern australia palaeomagnetic results thus suggest that the north and west australian cratons were possibly joined together by approximately 1 7 ga

fault slip and seismic moment of the 1700 cascadia earthquake inferred from japanese tsunami descriptions 1 the 1700 cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in japan computed coseismic seafloor deformation for hypothetical ruptures in cascadia and tsunami modeling in the pacific ocean reports of damage and flooding show that the 1700 cascadia tsunami reached 1 5 m heights at seven shoreline sites in japan three sets of estimated heights express uncertainty about location and depth of reported flooding landward decline in tsunami heights from shorelines and post 1700 land level changes we compare each set with tsunami heights computed from six cascadia sources each source is vertical seafloor displacement calculated with a three dimensional elastic dislocation model for three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip for the other sources ruptures of ordinary width extend 360 670 km to compute tsunami waveforms we use a linear long wave approximation with a finite difference method and we employ modern bathymetry with nearshore grid spacing as small as 0 4 km the various combinations of japanese tsunami heights and cascadia sources give seismic moment of 1 9 1022 n m equivalent to moment magnitude 8 7 9 2 this range excludes several unquantified uncertainties the most likely earthquake of moment magnitude 9 0 has 19 m of coseismic slip on an offshore full slip zone 1100 km long with linearly decreasing slip on a downdip partial slip zone the shorter rupture models require up to 40 m offshore slip and predict land level changes inconsistent with coastal paleoseismological evidence

surface distributions of salt marsh foraminifera from connecticut usa modern analogues for high resolution sea level studies abstract salt marsh foraminifera are routinely used as sea level indicators since their vertical distribution is closely linked with elevation relative to the tidal frame the precise nature of these relationships is variable in time and space and the accuracy of sea level reconstructions depends upon the selection of appropriate modern analogues that reliably reflect past fauna environment associations the marshes of connecticut usa are sites of ongoing research seeking to produce high resolution records of sea level change yet little published data regarding their modern foraminiferal distributions exist this paper presents new surface foraminiferal data from three connecticut salt marshes and evaluates their suitability as modern analogues for past sea level changes the results indicate that significant intra and inter site variability between these marshes and those of neighbouring states exists as a consequence of this the extrapolation of fauna environment relationships developed from marshes with different hydrographic physiographic vegetative or climatic characteristics may produce erroneous reconstructions even when adjusted for variations in tidal range these errors are potentially greatest if single indicator species are used since the relative abundance of individual taxa does not vary consistently with elevation even in high marsh environments from the same site whilst cluster analysis demonstrates that foraminiferal assemblages from connecticut are vertically zoned with respect to mean high water mhw the composition elevation and height range of these zones is variable between sites this spatial heterogeneity results in reconstructions of relatively low and variable precision that restricts their utility in high resolution sea level research new studies seeking to distil decimetre scale changes in relative sea level will need to employ quantitative methods capable of combining multi site information to develop fauna environment relationships that capture this spatial variability reconstructions will be most precise when employing local foraminiferal distributions but may require the collection of additional modern analogue samples from other regions when the extant foraminiferal population of a site differs in composition from its sub fossil counterpart

tsunami deposits beneath tidal marshes on northwestern vancouver island british columbia two sand sheets underlying tidal marshes at fair harbour neroutsos inlet and koprino harbour on the northwestern coast of vancouver island british columbia were probably deposited by tsunamis the sand sheets become thinner and finer grained landward drape former land surfaces contain marine microfossils are locally graded or internally stratified and can be correlated with earthquakes that generated tsunamis in the region 137cs dating and historical accounts indicate that the upper sand sheet was deposited by the tsunami from the great alaska earthquake in 1964 radiocarbon ages on plant fossils within and on top of the lower sand sheet show that it was deposited sometime after about a d 1660 we attribute the lower sand sheet to a tsunami from the most recent plate boundary earthquake on the cascadia subduction zone about 300 yr ago extending the documented effects of this earthquake north of the nootka fault zone the 1964 tsunami deposits differ little in thickness and continuity among the three marshes in contrast the lower sand sheet becomes thinner and less continuous to the north implying a tsunami source south of the study area

sediments deposited by the 2004 indian ocean tsunami along the malaysia thailand peninsula stratigraphy grain size distribution and foraminiferal assemblages of pre tsunami and tsunami sediment from the indian ocean tsunami at five sites along the malaysia thailand peninsula were analyzed to gain information on tsunami sediment source and deposition style between three and five stratigraphic units were identified at each site and contained between one and three fining upward sequences reflecting waning flow or pre backwash deposition coarser sand layers reflecting uprush high energy flow separated the fining upward sequences with the exception of one site sungai burong which contained a coarsening upward sequence all contacts between the pre tsunami and tsunami sediment were sharp or erosional medium and coarse sand dominated all of the tsunami sediment deposits and often contained shell fragments foraminiferal assemblages were able to differentiate pre tsunami sediment from tsunami sediment where no lithological or grain size distribution change was evident between two and four foraminiferal zones were identified at each of the five sites and provided estimates of sediment source and wave characteristics

integration of paleoseismic data from multiple sites to develop an objective earthquake chronology application to the weber segment of the wasatch fault zone utah we present a method to evaluate and integrate paleoseismic data from multiple sites into a single objective measure of earthquake timing and recurrence on discrete segments of active faults we apply this method to the weber segment ws of the wasatch fault zone using data from four fault trench studies completed between 1981 and 2009 after systematically reevaluating the stratigraphic and chro nologic data from each trench site we constructed time stratigraphic oxcal models that yield site probability density functions pdfs of the times of individual earth quakes we next qualitatively correlated the site pdfs into a segment wide earthquake chronology which is supported by overlapping site pdfs large per event displace ments and prominent segment boundaries for each segment wide earthquake we computed the product of the site pdf probabilities in common time bins which emphasizes the overlap in the site earthquake times and gives more weight to the narrowest best defined pdfs the product method yields smaller earthquake timing uncertainties compared to taking the mean of the site pdfs but is best suited to earth quakes constrained by broad overlapping site pdfs we calculated segment wide earthquake recurrence intervals and uncertainties using a monte carlo model five surface faulting earthquakes occurred on the ws at about 5 9 4 5 3 1 1 1 and 0 6 ka with the exception of the 1 1 ka event we used the product method to define the earthquake times the revised ws chronology yields a mean recurrence interval of 1 3 kyr 0 7 1 9 kyr estimated two sigma 2 range based on interevent recurrence these data help clarify the paleoearthquake history of the ws including the important question of the timing and rupture extent of the most recent earthquake and are essential to the improvement of earthquake probability assessments for the wasatch front region

great cascadia earthquakes and tsunamis of the past 6700 years coquille river estuary southern coastal oregon cascadia subduction zone earthquakes dropped tidal marshes and low lying forests to tidal flat elevations 12 times in the last 6700 cal yr b p at the coquille river estuary in southwestern oregon the youngest buried soil preserved in tidal marsh deposits near the estuary mouth records the a d 1700 earthquake that ruptured the entire cascadia margin eleven other buried marsh and upland soils found in tributary valleys of the estuary provide repeated evidence for rapid lasting relative sea level rise interpreted as coseismic subsidence additional stratigraphic criteria supporting a coseismic origin for soil burial include lateral soil correlation over hundreds of meters fossil diatom assemblages that indicate a maximum of 1 2 3 0 m of submergence and sand deposits overlying buried soils consistent with earthquakeinduced tsunamis that traveled 10 km up the estuary twelve earthquakes occurred in the last 6500 6720 cal yr b p recurring on average every 570 590 yr intervals between earthquakes varied from a few hundred years to over 1000 comparisons of the coquille record to earthquake histories from adjacent sites in oregon southwestern washington and northwestern california suggest that at least two earthquakes in the last 4000 yr did not rupture the entire length of the subduction zone an earthquake 760 1140 cal yr b p in southwestern washington may have ruptured as far south as coos bay but probably stopped before it reached the coquille estuary because no buried soil records the event and tidal marsh conditions were set to record an earthquake an earthquake limited to a southern segment of the cascadia margin 1940 2130 cal yr b p probably did not rupture north of the coquille estuary an analysis of relative sea level histories from either side of the coquille fault failed to find conclusive evidence for late holocene vertical deformation however we cannot preclude recent upper plate faulting if the fault is active as geomorphic features suggest then constraints on the highest possible elevation of mean tide level allow a maximum vertical slip rate of 0 2 0 4 mm yr in the past 6200 6310 cal yr b p

reassessing transfer function performance in sea level reconstruction based on benthic salt marsh foraminifera from the atlantic coast of ne north america abstract the need to increase the number and distribution of sea level records spanning the last few hundred years has led to particular interest in developing high precision geologically based sea level reconstructions that capture decimetre and multi decadal scale changes transfer functions for tide level are statistical tools that quantify the vertical relationship between inter tidal microfossils and elevation within the tidal frame and their use in sea level reconstruction is growing in popularity whilst a range of sampling strategies dataset qualities and underlying statistical models have been used in transfer function development all variants share the common requirement of accurately extracting precise species elevation relationships from surface data and reliably applying these to fossil assemblages to infer past conditions we present surface foraminiferal data from six transects sampled at three sites spanning a large latitudinal range extending from newfoundland canada to north carolina usa these data demonstrate that significant spatial differences exist within the high marsh foraminiferal assemblages commonly used to reconstruct past relative sea level rsl we standardise these data to account for inter site differences in tidal range using several variants of the standardised water level index swli of horton et al 1999b and show that the best performance is achieved by using the highest occurrence of foraminifera as the upper tidal datum level the standardised surface foraminiferal data are used to develop a suite of foraminiferal transfer functions for tide level which are then applied to fossil assemblages from two sediment cores to reconstruct palaeomarsh surface elevation we highlight the manner in which species elevation relationships are extracted and modified during transfer function development and the impacts that choices in dataset composition and transfer function type have on the resulting reconstructions our results graphically illustrate the importance of these choices and the impacts of temporal and spatial variability in foraminiferal distributions none of which are adequately represented or discernible from the standard summary statistics of performance that commonly accompany transfer function reconstructions we conclude that a more explicit treatment of the transfer function development process is required to support the growing body of precise rsl reconstructions that are now appearing in the literature to that end we make the following four recommendations for a framework to assist in transfer function development that will allow better record inter comparison and minimise the potential for producing precise but ultimately inaccurate reconstructions 1 sampling for surface data should focus on capturing complete species response curves rather than simply compiling modern analogues for fossil material 2 the similarity between the surface assemblages used to produce transfer functions and the fossil assemblages to which they are applied should be better quantified using a range of statistical approaches and must accompany any reconstruction 3 where modern analogues are lacking in local surface assemblages data from additional sites should be added with selection based on fulfilling the requirements of the previous two recommendations the manner in which individual species optima are combined to produce a composite optimum and the extent to which this provides a reasonable representation of the surface data should also be documented 4 the application of wa pls component 2 and higher cannot be justified solely on the grounds of increased performance measures e g r2jack and rmsep and if applied the pattern of optima updates should be used to highlight species that may distort reconstructions

numerical simulation and a geochemical model of supergene carbonate hosted non sulphide zinc deposits abstract the proposed metallogenetic model presented in this paper is based on observations from the iranian non sulphide zinc deposits mehdi abad iran kuh and kuh e surmeh the emplacement of non sulphide ore can be generally subdivided into an oxidation stage followed by a post oxidation stage the formation of carbonate hosted non sulphide zinc deposits is primarily controlled by three factors climate protore composition and geology lithology and structure of the wall rocks the climate controls the oxidation and metal transport predominantly through the amount of meteoric water and the availability of oxygen which indirectly is controlled through the thickness of the soil cover and biogenic oxygen consumption favourable conditions for oxidation are an arid climate with minimal biogenic activity within the soil as a consequence oxygen can reach the sulphides easily resulting in higher metal concentrations of the supergene aqueous solutions dry climates are associated with a low water table preventing descending zn bearing fluids from contact with the aquifer and thus from dilution dispersion and removal of metals commonly non sulphide zinc deposits consist of two types of ore red zinc ore rich in zn 20 fe 7 pb as and white zinc ore typically with very high zinc grades up to 40 but low concentrations of iron 4 2 ions during the oxidation stage leads to the precipitation of highly insoluble anglesite which results in low pb 2 concentration within the fluid most of the zinc up to 80 at ph 6 or 97 at ph 5 leaves the oxidation zone and precipitates as zinc carbonates in adjacent parts of the carbonate host rock the neutralisation processes of the sulphuric acid with the carbonates of the host rock during the oxidation stage lead to the formation of co 2 g consequently the co 2 partial pressure p co2 g increases drastically and forms a co 2 g halo around the active oxidation zone thus most of the zinc precipitates as smithsonite which is stable and occurs exclusively in a high p co2 g environment the p co2 g decreases during the post oxidation stage and reaches the level of atmospheric p co2 g under these conditions hydrozincite becomes stable and starts to replace smithsonite most of the stage i smithsonite becomes corroded and is altered to stage ii hydrozincite the post oxidation stage is also associated with the successive formation of local zinc hydro silicates depending on the availability of sio 2 within the solution generally arid climates provide the best conditions for the preservation of non sulphide deposits the limited availability of meteoric water and deep to very deep water tables protect the non sulphide ore from subsequent dissolution

proterozoic evolution and tectonic setting of the northwest paterson orogen western australia abstract the proterozoic igneous deformation and metamorphic histories of the palaeoproterozoic rudall complex in the northwestern paterson orogen can be linked to those of the arunta inlier in central australia and in part with the capricorn orogen in central western australia the similarities in deformation and metamorphic histories for these widely separated regions indicate a palaeoproterozoic continent continent collisional event between the palaeoproterozoic west australian and north australian cratons between c 1830 and 1765 ma in the paterson orogen this palaeoproterozoic collisional event resulted in the yapungku orogeny which included thrust stacking of clastic sedimentary and volcanic rocks deposition of the protoliths for the c 1790 ma siliciclastic paragneiss succession contemporaneous with granitic intrusion and metamorphism up to granulite facies during this 65 million year period the arunta inlier and capricorn orogen were deformed metamorphosed at medium to high grades and intruded by granitoids during the strangways orogeny in the arunta inlier and the capricorn orogeny in the capricorn orogen the neoproterozoic tarcunyah throssell and lamil groups are clastic sedimentary sequences that were deposited after 1070 ma in the northwestern paterson orogen and deformed by the miles orogeny before 678 ma the miles orogeny produced a northwesterly trending fold and fault system of tight to isoclinal upright and overturned folds and thrust faults the orogeny may have been coincident with the c 750 720 ma areyonga tectonic movement affecting the arunta inlier and the lower neoproterozoic part of the amadeus basin in central australia at c 550 ma the paterson orogeny which is most likely equivalent to the petermann orogeny in the musgrave complex of central australia deformed the northwestern paterson orogen and was preceded by local intrusion of granites the similarities of styles and timing of deformation in the northwestern paterson orogen arunta inlier and capricorn orogen indicate that these three regions were probably linked during most of the proterozoic

testing the use of microfossils to reconstruct great earthquakes at cascadia coastal stratigraphy from the pacific northwest of the united states contains evidence of sudden subsidence during ruptures of the cascadia subduction zone transfer functions empirical relationships between assemblages and elevation can convert microfossil data into coastal subsidence estimates coseismic deformation models use the subsidence values to constrain earthquake magnitudes to test the response of foraminifera the accuracy of the transfer function method and the presence of a pre seismic signal we simulated a great earthquake near coos bay oregon by transplanting a bed of modern high salt marsh sediment into the tidal flat an elevation change that mimics a coseismic subsidence of 0 64 m the transplanted bed was quickly buried by mud after 12 mo and 5 yr we sampled it for foraminifera reconstruction of the simulated coseismic subsidence using our transfer function was 0 61 m nearly identical to the actual elevation change our transplant experiment and additional analyses spanning the a d 1700 earthquake contact at the nearby coquille river 15 km to the south show that sediment mixing may explain assemblage changes previously interpreted as evidence of pre seismic land level change in cascadia and elsewhere

vertical lithogeochemical halos and zoning vectors at goushfil zn pb deposit irankuh district southwestern isfahan iran implications for concealed ore exploration and genetic models abstract the vertical lithogeochemical halos of indicator elements in host rocks over a blind zn pb deposit are developed by upward migration of geochemical halos this may prove to be a useful exploration guide for targeting undiscovered zn pb mineral systems the main objective of this investigation is to assess the vertical distribution patterns of the composite lithogeochemical halos for detecting possible exploration guides as well as a possible genetic model of zn pb sulfide mineralization the goushfil zn pb deposit is one of the most important lower cretaceous carbonate and shale hosted deposit in the irankuh district west central iran the deposit contains about 4 3 million tonnes of sphalerite galena barite ore with an average grade of 8 zn and 2 4 pb in order to examine the exploration significance of the vertical lithogeochemical halos about 274 rock samples from 26 boreholes were sampled and analyzed by icp ms for a multi element package the results demonstrate that the highly anomalous values for ag 0 1 120 ppm as 3 1165 ppm ba 9 2820 ppm ca 0 07 25 cd 0 005 210 ppm hg 0 9 24 ppm mg 0 03 11 75 pb 15 15 000 ppm zn 65 15 000 ppm and sb 1 305 ppm are developed in faulted or fracture controlled hydrothermally dolomitized and jasperoid carbonates and shales the newly proposed multiphase composite geochemical halos defined by ratios of ag cd pb zn ag as pb zn ca mg pb zn sb as pb zn hg sb pb zn sb ba pb zn and ba ca pb zn correlate with three exploration zones at the average depth of 10 200 and 310 m above and below the main ore zone all the composite lithogeochemical halos in particular ag cd pb zn in both rock and soil samples tend to increase toward the shallow depths but decrease as they approach the main zn pb ore toward the deeper parts of the ore zone this geochemical response of the composite halos could be used for targeting undiscovered zn pb sulfide mineralization the low contents of cu and fe in the mineralized rocks indicate a low modal content of chalcopyrite and pyrite in the precursor sulfide ore which correlate with those of the mississippi valley type mvt zn pb deposits this is also highlighted on the log pb zn pb pb zn cu pb zn cu and homogenization temperature salinity variodiagrams on which the goushfil data plot close to the mvt type zn pb mineralization

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

the application of intertidal foraminifera to reconstruct coastal subsidence during the giant cascadia earthquake of ad 1700 in oregon usa abstract changes in species assemblages of intertidal foraminifera can be used to estimate the amount of earthquake related subsidence during plate boundary earthquakes at the cascadia subduction zone the accuracy and precision of foraminiferal methods in paleoenvironmental reconstruction is underpinned by the relations between contemporary taxa and their environment which are used to calibrate fossil foraminiferal assemblages in sediment sequences a contemporary training set of surface sediment samples from five intertidal marshes along the oregon coast was used to determine foraminiferal distributions and prevailing environmental control s along elevational transects dominant taxa include balticammina pseudomacrescens trochamminita irregularis haplophragmoides wilberti trochammina inflata jadammina macrescens and miliammina fusca unconstrained cluster analysis and detrended correspondence analysis was used to identify two elevation dependent faunal zones faunal zone i upland high marsh middle marsh dominated by balticammina pseudomacrescens haplophragmoides wilberti and trochammina inflata and faunal zone ii low marsh and tidal flat dominated by miliammina fusca site specific differences in assemblages at three marshes enabled further subdivision of faunal zone i zone ia is based on one or more of balticammina pseudomacrescens trochammina inflata trochamminita irregularis and haplophragmoides sp and zone ib on jadammina macrescens haplophragmoides sp trochammina inflata and miliammina fusca canonical correspondence analysis cca and partial cca of the training set from the nehalem river marsh transect was used to infer that the zonation of foraminifera is elevation dependent 39 of explained variance a transfer function was developed to reconstruct sudden changes in relative sea level during plate boundary earthquakes in oregon the results indicate a robust performance of the transfer function r jack 2 0 82 with the error estimate rmsep jack 0 20 m comparable to local and regional transfer functions from other temperate marshes to illustrate the potential of the technique the transfer function was applied to reconstruct subsidence during the ad 1700 earthquake using at alsea bay oregon the reconstruction 0 18 0 20 m is less than half the subsidence estimate of nelson et al 2008 great earthquake palogeoesy and tsunamis of the past 2000 years at alsea bay central oregon coast usa quaternary science reviews 27 747 768 using their foraminiferal transfer function perhaps because of differences in taxonomy and the species relationship to elevation

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

distribution of modern salt marsh foraminifera in the albemarle pamlico estuarine system of north carolina usa implications for sea level research abstract we described the distributions of foraminifera from ten physiographically distinct salt marshes in the albemarle pamlico estuarine system north carolina using 193 surface samples we defined elevation dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis additionally seven principal biozones of salt marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier island inlets high salinity sites along the southern outer banks are associated with sub tidal calcareous assemblages low marshes dominated by miliammina fusca and high marsh environments defined by haplophragmoides wilberti trochammina inflata and arenoparrella mexicana in contrast lower salinity marshes have ammobaculites spp in sub tidal settings miliammina fusca dominated low marshes and high marsh settings characterized by jadammina macrescens spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity suggests that datasets of modern salt marsh foraminifera from multiple environments would be appropriate for reconstructing holocene relative sea level in north carolina

modern foraminifera δ13c and bulk geochemistry of central oregon tidal marshes and their application in paleoseismology we assessed the utility of 13c and bulk geochemistry total organic content and c n to reconstruct relative sea level changes on the cascadia subduction zone through comparison with an established sea level indicator benthic foraminifera four modern transects collected from three tidal environments at siletz bay oregon usa produced three elevation dependent groups in both the foraminiferal and 13c bulk geochemistry datasets foraminiferal samples from the tidal flat and low marsh are identified by miliammina fusca abundances of 45 middle and high marsh by m fusca abundances of 25 the 13c values from the groups defined with 13c bulk geochemistry analyses decrease with an increasing elevation 24 1 1 7 in the tidal flat and low marsh 27 3 1 4 in the middle and high marsh and 29 6 0 8 in the highest marsh samples we applied the modern foraminiferal and 13c distributions to a core that contained a stratigraphic contact marking the great cascadia earthquake of ad 1700 both techniques gave similar values for coseismic subsidence across the contact 0 88 0 39 m and 0 71 0 56 m suggesting that 13c has potential for identifying amounts of relative sea level change due to tectonics

the las cruces deposit iberian pyrite belt spain abstract the las cruces deposit is located at the eastern margin of the iberian pyrite belt ipb beneath the neogene quaternary deposits of the guadalquivir basin these sediments covered and preserved the supergene profile somewhat after its generation until its recent discovering for this reason the las cruces ore deposits together with lagoa salgada in portugal are the only known deposits in the ipb that preserve the entire weathering profile including both the gossan and the enrichment zone in that sense the present study provides new data on the ipb ore deposits and their post palaeozoic evolution the primary mineralization consists of massive and semi massive polymetallic sulfides overlaying a cupriferous and pyritic stockwork the supergene enrichment extends from the primary zone to gossan and consists of a thick cementation zone characterized by intense replacement of part of the primary sulfides by cu rich supergene sulfides at present the only economic resource of las cruces is the cementation zone with initial reserves of 17 6 mt 6 2 cu but the orebody also includes significant contents of cu and zn within the primary mineralization and au ag and pb in the gossan mineralogical and geochemical data confirm that the primary mineralization at las cruces resembles other ipb deposits in terms of distribution and evolution however the gossan and cementation zone show an uncommon evolution for this kind of supergene profile the major singularity that makes the las cruces supergene mineralisation noticeably different from others in the ipb or elsewhere resides in its unusual mineralogical composition mostly comprised of newly formed siderite calcite fe sulfides and galena the genetic model proposed for the las cruces deposit includes three main stages 1 ore genesis and evolution of primary mineralization which seems to be comparable to other ipb deposits 2 genesis of cu rich secondary mineralization and gossan by weathering after miocene exhumation of the upper part of the massive sulfide deposit under oxidizing and acidic conditions and 3 late evolution of supergene profile below the carbonated rich sediments of the guadalquivir basin with the subsequent change in the redox conditions due to water rock interaction between the supergene profile and basinal fluids

taphonomy of salt marsh foraminifera an example from coastal georgia abstract in salt marshes of st catherines island georgia total foraminiferal density decreases significantly within the top 10 cm of marsh sediment selective preservation impacts both calcareous and agglutinated taxa calcareous taxa are removed through dissolution and agglutinated ones through bacterial degradation of cements or predation shallow to deep infaunal taxa generally are the most likely to be preserved although miliammina fusca and ammotium spp all epifaunal to shallow or intermediate infaunal dwellers have cements that are highly susceptible to degradation in southeastern u s marshes total foraminiferal density in both surface and subsurface sediment is higher in the low marsh than either the transitional or high marsh zones selective preservation and downcore enrichment by some infaunal taxa alters the percent abundance of some paleoenvironmentally significant taxa in subsurface assemblages the best baseline for paleoenvironmental studies using salt marsh foraminifera in these settings is not the marsh surface 0 1 cm but rather assemblages preserved 10 cm below the marsh surface

the paroo station mine supergene lead deposits western australia geological and geochemical constraints abstract the paroo station mine lead project is situated near wiluna in the central part of western australia it is located in an outlier of the paleoproterozoic earaheedy group overlying the southeast yerrida basin the total measured and indicated mineral resource is currently as at 31st of december 2014 estimated at 31 8 mt of ore at 4 4 pb the deposits are hosted by deeply weathered carbonate and clastic sediments of the paleoproterozoic yelma formation the lead only mineralisation contains only traces of sulfides and is composed of few supergene minerals predominantly cerussite and anglesite with minor pyromorphite and plumbogummite the paroo station mine demonstrates a high degree of supergene pb mobility which has resulted in almost complete destruction of primary pb distribution pattern and development of characteristic for the oxidation zones coupled depletion zone and subhorizontal enrichment blankets below the deposits are interpreted to have formed from mississippi valley type mvt stratabound relatively low grade sulfide pb zn mineralisation located within dolomites of the sweetwaters well member of the yelma formation the primary mineralisation based on modelling the pb distribution was controlled by a network of northeast northwest and meridional oriented fractures and small faults lead isotope study yielded from 1 80 to1 88 ga ages of the mineralisation based on the stacey and kramers 1975 two stage model the mineralising event is related to the capricorn orogeny this data is well in line with previous u pb dating of monazites interpreted to be related to the mineralisation 1 82 ga muhling et al 2012 high 238u 204pb values 10 26 10 58 are indicative of the archean basement contribution and or more likely with sediments originally derived from that basement the paroo station mine mineralisation is thought to be similar in style and formed synchronously with the mvt prospects in the teague area in the earaheedy basin approximately 120 km to the northeast the mineralisation at the paroo station mine was significantly upgraded through a multi stage supergene remobilisation and reprecipitation of lead in the course of long weathering history of the region lead was almost completely depleted from the upper zone and accumulated below as subhorizontal enrichment blankets at three levels from top to bottom 1 the base of the collapse quartz clay breccia unit marking the dolomite weathering front 2 the contact of siltstone and sandstone packages coincident with the feldspar kaolinite weathering front and 3 the mid to lower parts of the sandstone unit close to the base of weathering the lowest enrichment zone extends as a continuous blanket at a significant up to 500 m distance at a 1 pb cut off beyond the upper mineralisation projection this enrichment is interpreted to be formed by lateral pb transport in waters close to the groundwater table through the most permeable layers of weathered sandstones this active lateral lead dispersion is of high exploration significance for the region providing a much larger exploration target and vector to the primary mineralisation

reconstructing relative sea level change using uk salt marsh foraminifera abstract the position of past sea levels can be reconstructed using a series of sea level index points that possess information on age location altitude and a quantified vertical relationship with a former tidal frame the indicative meaning whilst these points fix the altitude of relative sea level at one instant in time they provide no information on its variation between them here a foraminiferal transfer function is used to reconstruct changes in water depth from fossil assemblages preserved within salt marsh sediments the transfer function performs reliably in the high marsh zone where agglutinated foraminiferal species are dominant in lower marsh environments where calcareous species are prevalent postmortem test dissolution alters the fossil assemblages and leaves them without modern analogues to circumvent this problem a new transfer function based on agglutinated foraminifera and utilising preserved test linings is developed this new transfer function significantly reduces the number of samples without modern analogues but at the expense of diminished sensitivity in the low marsh environment additionally the transfer function is used to establish a series of sea level index points that place observed lateral shifts in depositional environment into a vertical and temporal context the combination of age altitude and high resolution water level reconstructions offers the potential to obtain more detailed and reliable records of relative sea level change from salt marsh sediments

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

stable isotope geochemistry of carbonate minerals in supergene oxidation zones of zn pb deposits abstract the 18 o 16 o and 13 c 12 c ratios of carbonate minerals formed by supergene oxidation of zn pb deposits and submarine alteration of ancient slags were studied in order to constrain isotope fractionation factors for smithsonite cerussite and phosgenite and to characterize conditions of nonsulfide ore formation we present new isotope data of carbonate hosted ores from the iglesiente district sardinia italy and vila ruiva portugal as well as from the silicate hosted ores of the broken hill district new south wales australia and freihung germany and review previously published isotope data the temperature dependence of oxygen isotope fractionation between pb and zn carbonate minerals and water below 240 c for cerussite and below 100 c for smithsonite and phosgenite can be expressed as 1000ln cerussite water 2 29 10 6 t 2 3 56 1000ln smithsonite water 3 10 10 6 t 2 3 50 1000ln phosgenite water 2 55 10 6 t 2 3 50 with t in kelvin the carbon isotope fractionation between smithsonite phosgenite hydrozincite and calcite is less than about 2 while cerussites are strongly depleted in 13 c by about 10 as compared to the former minerals oxygen isotope variations of individual carbonate minerals within a deposit are relatively small indicating constant formation temperatures and a single meteoric fluid source average formation temperatures of the studied deposits are calculated at 20 5 c using the estimated isotope compositions of local paleometeoric waters we observe a linear relationship between the isotope values of estimated paleometeoric waters and supergene carbonates thus base metal carbonate minerals from supergene deposits may provide paleoclimatic information the carbon isotope values are in most carbonate hosted deposits highly variable more than 10 suggesting at least two isotopically distinct carbon sources the isotopically light component can be related to oxidation of c3 plants soil derived carbon and or microbes that take active part in sulfide oxidation while the isotopically heavy component originates from carbonate carbon from wall rocks and or atmospheric carbon the 13 c enriched component is less dominant in silicate hosted deposits

determining landslide susceptibility in central taiwan from rainfall and six site factors using the analytical hierarchy process method this work provides a landslide susceptibility assessment model for rainfall induced landslides in central taiwan based on the analytical hierarchy process method the model considers rainfall and six site factors including slope geology vegetation soil moisture road development and historical landslides the rainfall factor consists of 10 day antecedent rainfall and total rainfall during a rainfall event landslide susceptibility values are calculated for both before and after the beginning of a rainfall event the 175 landslide cases with detailed field surveys are used to determine a landslide susceptibility threshold value of 9 0 when a landslide susceptibility assessment value exceeds the threshold value slope failure is likely to occur three zones with different landslide susceptibility levels below slightly above and far above the threshold are identified the 9149 landslides caused by typhoon toraji in central taiwan are utilized to validate the study s result approximately 0 2 0 4 and 15 3 of the typhoon caused landslides are located in the three landslide susceptibility zones respectively three villages with 6 6 0 4 and 4 9 of the landslides respectively are used to validate the accuracy of the landslide susceptibility map and analyze the main causes of landslides the landslide susceptibility assessment model can be used to evaluate susceptibility relative to accumulated rainfall and is useful as an early warning and landslide monitoring tool

polymetallic mineralization at the browns deposit rum jungle mineral field northern territory australia the rum jungle mineral field northern territory australia forms part of the paleoproterozoic pine creek orogen the geology of the area comprises two archean granitic basement domes overlain by a paleoproterozoic sequence of metasedimentary and subordinate metavolcanic rocks the rocks have been deformed and metamorphosed to greenschist facies during the 1880 ma barramundi orogeny but the original stratigraphic succession has been preserved the browns deposit browns and its extension browns east hosted within black carbonaceous pelites of the paleoproterozoic whites formation is the largest base metal deposit found to date in the pine creek orogen present resource estimates are 39 million metric tons mt at 0 44 percent cu 3 61 percent pb 0 11 percent co and 0 09 percent ni browns and 31 mt at 1 29 percent cu 1 28 percent pb 0 13 percent co and 0 13 percent ni browns east major sulfide minerals in the ore zone are galena sphalerite chalcopyrite pyrite and the main carrier of ni and co siegenite ni co 3 s 4 digenite group minerals and bornite ca bearing plumbogummite pbal 3 po 4 2 oh 5 h 2 o arsenopyrite and gersdorffite are present in minor quantities ore minerals occur as fine grained wisps parallel to the main bedding parallel foliation and as coarse grained mono and polyminerallic aggregates that crosscut the foliation total noncarbonate carbon contents of unaltered rocks range from 1 07 to 7 51 wt percent total sulfur contents range from 2 13 to 6 14 wt percent petrographic studies and raman spectroscopy identify three varieties of carbonaceous matter primary syngenetic premetamorphic epigenetic grain coating and postmetamorphic epigenetic uraniferous migrated altered rocks are rarely encountered values of 34 s for sulfides range from 5 to 15 per mil and are interpreted to reflect a combination of inorganic thermochemical reduction of seawater and bacterial activity no specific sulfur isotope patterns for individual minerals can be established indicating nonequilibrium conditions homogeneous lead isotope signatures of galena 206 pb 204 pb 16 20 16 22 207 pb 206 pb 15 48 15 51 208 pb 207 pb 35 86 35 92 suggest that all pb was derived from a single crustal source and paragenetically late crosscutting galena appears to have been remobilized from bedding parallel galena despite the occurrence of uranium in similar rocks nearby uranium is quantitatively insignificant in the browns deposit and is not genetically related to base metal mineralization instead it is linked to brittle deformation in the waning stages of orogenesis the browns deposit differs from other well known sediment hosted stratiform ore deposits both the zambian copperbelt and the polish kupferschiefer deposits are copper dominant and hosted in sedimentary sequences with significant psammitic components the pb zn ag deposits of the proterozoic australian zinc province also have significant carbonate in their host rocks e g carbonaceous dolomitic and siltstone at mcarthur river and lack economically interesting cu co and ni the nearby woodcutters pb zn ag deposit in rocks of similar age also differs in structural setting veins dominant metals and pb isotopes from the browns deposit

an earthquake history derived from stratigraphic and microfossil evidence of relative sea level change at coos bay southern coastal oregon much of the uncertainty in determining the number and magnitude of past great earthquakes in the cascadia subduction zone of western north america stems from difficulties in using estuarine stratigraphy to infer the size and rate of late holocene relative sea level changes a sequence of interbedded peaty and muddy intertidal sediment beneath a small protected tidal marsh in a narrow inlet of coos bay oregon records ten rapid to instantaneous rises in relative sea level each rise is marked by a contact that records an upward transition from peaty to muddy sediment but only two contacts dating from about 1700 and 2300 yr ago show the site wide extent and abrupt changes in lithology and foraminiferal and diatom assemblages that can be used to infer at least half a meter of sudden coseismic subsidence although the characteristics of a third gradual contact do not differ from those of some contacts produced by nonseismic processes regional correlation with other similar sequences and high precision 14 c dating suggest that the third contact records a great plate boundary earthquake about 300 yr ago a fourth contact formed too slowly to have been caused by coseismic subsidence because lithologic and microfossil data are not sufficient to distinguish a coseismic from a nonseismic origin for the other six peat mud contacts we cannot determine earthquake recurrence intervals at this site similar uncertainties in great earthquake recurrence and magnitude prevail at similar sites elsewhere in the cascadia subduction zone except those with sequences showing changes in fossils indicative of 1 m of sudden subsidence sand sheets deposited by tsunamis or liquefaction features

coastal subsidence in oregon usa during the giant cascadia earthquake of ad 1700 quantitative estimates of land level change during the giant ad 1700 cascadia earthquake along the oregon coast are inferred from relative sea level changes reconstructed from fossil foraminiferal assemblages preserved within the stratigraphic record a transfer function based upon a regional training set of modern sediment samples from oregon estuaries is calibrated to fossil assemblages in sequences of samples across buried peat mud and peat sand contacts marking the ad 1700 earthquake reconstructions of sample elevations with sample specific errors estimate the amount of coastal subsidence during the earthquake at six sites along 400 km of coast the elevation estimates are supported by lithological carbon isotope and faunal tidal zonation data coseismic subsidence at nehalem river nestucca river salmon river alsea bay siuslaw river and south slough varies between 0 18 m and 0 85 m with errors between 0 18 m and 0 32 m these subsidence estimates are more precise consistent and generally lower than previous semi quantitative estimates following earlier comparisons of semi quantitative subsidence estimates with elastic dislocation models of megathrust rupture during great earthquakes our lower estimates for central and northern oregon are consistent with modeled rates of strain accumulation and amounts of slip on the subduction megathrust and thus with a magnitude of 9 for the ad 1700 earthquake

evidence for two great earthquakes at anchorage alaska and implications for multiple great earthquakes through the holocene abstract multiple peat silt couplets in tidal marsh sediment sequences at anchorage suggest up to five possible great earthquakes during the last 2500 years litho stratigraphic diatom and radiocarbon data of the youngest two couplets record the last two great earthquakes ad 1964 and 950 850 cal yr bp similar multiple peat silt couplets around cook inlet suggest recurring great earthquakes associated with marsh subsidence over large areas comparable in extent to that recorded in ad 1964 potential difficulties in interpreting evidence include lack of modern analogues for applying quantitative diatom transfer functions to parts of the fossil record and the observation that under certain sedimentary conditions co seismic subsidence in the case of ad 1964 of known magnitude is recorded by a transitional peat silt boundary this differs in diatom stratigraphy from a phase of pre seismic relative sea level rise recorded for other great earthquakes a field experiment to simulate co seismic subsidence identifies limited mixing at the top of submerged marsh sediment and indicates how mixing must be shown to differ from evidence for pre seismic relative sea level rise analysis of diatom assemblages from ice frozen intertidal sediment and melt out sediment demonstrates the importance of winter processes in transporting diatoms and their interpretation in fossil sequences winter processes may also be important in transporting organic material that leads to significant differences 120 2800 yr between radiocarbon ages from plant macrofossils and bulk peat samples this necessitates a new approach for establishing between site correlations recurrence intervals and spatial extent of great holocene earthquakes in southern alaska

quantitative vertical zonation of salt marsh foraminifera for reconstructing former sea level an example from new jersey usa we present a quantitative technique to reconstruct sea level from assemblages of salt marsh foraminifera using partitioning around medoids pam and linear discriminant functions ldf the modern distribution of foraminifera was described from 62 surface samples at three salt marshes in southern new jersey pam objectively estimated the number and composition of assemblages present at each site and showed that foraminifera adhered to the concept of elevation dependent ecological zones making them appropriate sea level indicators application of pam to a combined dataset identified five distinctive biozones occupying defined elevation ranges which were similar to those identified elsewhere on the u s mid atlantic coast biozone a had high abundances of jadammina macrescens and trochammina inflata biozone b was dominated by miliammina fusca biozone c was associated with arenoparrella mexicana biozone d was dominated by tiphotrocha comprimata and biozone e was dominated by haplophragmoides manilaensis foraminiferal assemblages from transitional and high salt marsh environments occupied the narrowest elevational range and are the most precise sea level indicators recognition of biozones in sequences of salt marsh sediment using ldfs provides a probabilistic means to reconstruct sea level we collected a core to investigate the practical application of this approach ldfs indicated the faunal origin of 38 core samples and in cross validation tests were accurate in 54 of 56 cases we compared reconstructions from ldfs and a transfer function the transfer function provides smaller error terms and can reconstruct smaller rsl changes but ldfs are well suited to rsl reconstructions focused on larger changes and using varied assemblages agreement between these techniques suggests that the approach we describe can be used as an independent means to reconstruct sea level or importantly to check the ecological plausibility of results from other techniques

great earthquakes and tsunamis of the past 2000 years at the salmon river estuary central oregon coast usa four buried tidal marsh soils at a protected inlet near the mouth of the salmon river yield definitive to equivocal evidence for coseismic subsidence and burial by tsunami deposited sand during great earthquakes at the cascadia subduction zone an extensive landward tapering sheet of sand overlies a peaty tidal marsh soil over much of the lower estuary limited pollen and macrofossil data suggest that the soil suddenly subsided 0 3 1 0 m shortly before burial regional correlation of similar soils at tens of estuaries to the north and south and precise 14c ages from one salmon river site imply that the youngest soil subsided during the great earthquake of 26 january a d 1700 evidence for sudden subsidence of three older soils during great earthquakes is more equivocal because older soil stratigraphy can be explained by local hydrographic changes in the estuary regional 14c correlation of two of the three older soils with soils at sites that better meet criteria for a great earthquake origin is consistent with the older soils recording subsidence and tsunamis during at least two great earthquakes pollen evidence of sudden coseismic subsidence from the older soils is inconclusive probably because the amount of subsidence was small 0 5 m the shallow depths of the older soils yield rates of relative sea level rise substantially less than rates previously calculated for oregon estuaries manuscript received 10 october 2003

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

geology and tectonic evolution of palaeoproterozoic basins of the eastern capricorn orogen western australia abstract the palaeoproterozoic yerrida bryah padbury and earaheedy basins extend for about 700 km along the northern margin of the yilgarn craton and are part of the capricorn orogen the basins developed between ca 2 2 and 1 8 ga recording periods of sedimentation volcanism rifting accretion and passive margin tectonism the oldest is the 2 17 ga yerrida basin which began as an intracontinental sag within which siliciclastics and evaporites accumulated at about 2 0 ga convergence of the yilgarn craton and the glenburgh terrane closed an oceanic arm resulting in the accretion of oceanic crust and plateaux onto the yilgarn margin and the western side of the yerrida sag basin this accretion produced the narracoota formation which together with the clastic and chemical banded iron formation sedimentation that followed forms the bryah basin continuing collision resulted in the establishment around 1 96 ga of the padbury foreland basin developed on top of the bryah basin rocks the ca 1 83 ga convergence and collision of the pilbara and yilgarn cratons capricorn orogeny resulted in deformation of the bryah padbury basins and orogenic uplift with coarse clastic sedimentation accompanied by the eruption of flood basalts into the yerrida basin to the east of the collision zone and possibly postdating collision a passive margin was present sedimentation along it consisted of clastic and chemical sediments granular iron formation which form the earaheedy basin during the ca 1 79 ga yapungku orogeny due to the convergence of the north australian and western australian cratons the northern margin of the earaheedy basin was deformed stanley fold belt this last deformation event concludes the palaeoproterozoic history of the eastern capricorn orogen basins

coastal sedimentation associated with the june 2nd and 3rd 1994 tsunami in rajegwesi java abstract this paper presents the second detailed study of sediments deposited by modern tusnamis the first being that of the flores indonesia tsunami of december 1992 shi et al 1995 sediment cores were collected from areas in which eyewitnesses reported sediment deposition grain size analysis shows pronounced vertical variations in grain size as well as changes in standard deviation skewness and kurtosis that appear to be indicative of complex tsunami flooding vertical variations in grain size in individual cores are greater than spatial variations between cores taken along a transect completed perpendicular to the coastline the java tsunami deposited sediments do not show unequivocal evidence of local erosion but instead evidence for sediment transport and deposition is clear and is characterised by dominantly unimodal sediments with fine tailed distributions

the calamines and the others the great family of supergene nonsulfide zinc ores abstract nonsulfides is a term which comprises a series of oxidized zn pb ore minerals it has also been used to define a special deposit type mainly considered as derived from the weathering of zn pb sulfide concentrations however nonsulfide zinc deposits have been distinguished between supergene and hypogene according to their mineralogy geological characteristics and genetic setting the supergene deposits formed by weathering and oxidation at ambient temperatures whereas the hypogene ones are considered hydrothermal or associated with metamorphic processes on primary sulfide ores in this review paper a comparison between a number of several nonsulfide deposits has been carried out typical calamines peculiar calamines and others the whole group comprises deposits of typical supergene origin mixed supergene hypogene mineralizations and oxidized concentrations characterized by different metals only locally associated with zinc the zn pb nonsulfide concentrations hosted in carbonate rocks which are mainly attributed to wall rock replacement and direct replacement supergene processes are the typical calamines liege district belgium iglesias district italy silesia cracow district poland peculiar calamine deposits are those mineralizations that have been generally considered as supergene but which are instead genetically related at least partly to hypogene processes e g angouran iran jabali yemen though mineralogically and texturally similar to supergene nonsulfide deposits the others are prevailingly supergene nonsulfide zinc deposits not hosted in carbonate rocks skorpion namibia yanque peru or characterized by other metals as main commodities like lead magellan australia silver sierra mojada mexico wonawinta australia or vanadium otavi mountainland namibia minerals of current economic importance in most calamine deposits are smithsonite hydrozincite and cerussite this mineralogical association is generally simple but when the calamines are dolomite hosted one of the consequences of the wall rock replacement process is the generation of a series of economically useless zn and mg bearing mixed carbonate phases secondary deposits hosted in silicatic sedimentary or volcanic rocks mainly contain hemimorphite and or sauconite lead ag and v rich nonsulfide ores are characterized by a more complex mineralogical association mixed pb carbonates pb sulfates pb phosphates pb arsenates various ag sulfosalts and zn pb cu vanadates carbon and oxygen stable isotope studies allow distinguishing between supergene and hypogene nonsulfide deposits evaluating the effects of oxidative heating and even gaining indirect paleoclimatic information the oxygen isotope variation of the individual carbonate minerals within a deposit is relatively small indicating constant formation temperatures and a single meteoric fluid source carbon isotope values are highly variable thus suggesting several isotopically distinct carbon sources periods of paleoclimatic switch overs from seasonally humid arid to hyperarid have been considered as the most favorable conditions for the formation and preservation of supergene nonsulfide deposits however while several recent nonsulfide deposits throughout the world are positioned between 15 and 45 n latitude thus pointing to a warm and humid weathering climate others have been deposited in sub arctic regions the economic value of the nonsulfide zn pb ag v ores is highly variable because more than in the case of metallic sulfide deposits it resides not only on the geological setting but also on their mineralogy that can directly influence processing and metallurgy

great earthquake paleogeodesy and tsunamis of the past 2000 years at alsea bay central oregon coast usa the width of plate boundary fault rupture at the cascadia subduction zone a dimension related to earthquake magnitude remains uncertain because of the lack of quantitative information about land level movements during past great earthquake deformation cycles beneath a marsh at alsea bay on the central oregon coast four sheets of tsunami deposited sand blanket contacts between tidal mud and peat radiocarbon ages for the sheets match ages for similar evidence of regional coseismic subsidence and tsunamis during four of cascadia s great earthquakes barring rapid unrecorded postseismic uplift reconstruction of changes in land level from core samples using diatom and foraminiferal transfer functions includes modest coseismic subsidence 0 470 2 m during the four earthquakes interpretation is complicated however by the 30 38 of potentially unreliable transfer function values from samples with poor analogs in modern diatom and foraminiferal assemblages reconstructions of coseismic subsidence using good analog samples range from 0 4670 12 to 0 0970 20 m showing greater variability than implied by sample specific errors from apparent high rates of land uplift following subsidence and tsunamis we infer that postseismic rebound caused by slip on deep parts of the plate boundary and or viscoelastic stress relaxation in the upper plate may be almost as large as coseismic subsidence modest coseismic subsidence 100 km landward of the deformation front implies that plate boundary ruptures in central oregon were largely offshore ruptures may have been long and narrow during earthquakes near magnitude 9 as suggested for the ad 1700 earthquake or of smaller and more variable dimensions and magnitudes r 2008 elsevier ltd all rights reserved

living foraminifera and total populations in salt marsh peat cores kelsey marsh clinton ct and the great marshes barnstable ma common species of intertidal agglutinated benthic foraminifera in salt marshes in massachusetts and connecticut live predominantly at the marsh surface and in the topmost sediment o 2 5 cm but a considerable part of the fauna lives at depths of 2 5 15 cm few specimens are alive at depths of 15 25 cm with rare individuals alive between 25 50 cm in the sediments specimens living between the sediment surface and 25 cm deep occur in all marsh settings whereas specimens living deeper than 25 cm are restricted to cores from the lower and middle marsh and have an irregular distribution with depth lower and middle marsh areas are bioturbated by metazoa suggesting that living specimens reach these depths at least in part by bioturbation high marsh sediments in new england consist of very dense mats of spa m paleens or distichlis spicatu roots and are not bioturbated by metazoa in this marsh region bioturbation by plant roots and vertical fluid motion may play a role in moving the foraminifera into the sediment the depth distribution of living specimens varies with species living specimens of trochammina injluta consistently occur at the deepest levels this suggests that species have differential rates of survival in the sediment possibly because of differential adaptation to severe dysoxia to anoxia or because of differing food preferences there is no simple correlation between depth in core and faunal diversity absolute abundance and species composition of the assemblages it is therefore possible to derive a signal of fauna1 changes and thus the environmental changes that may have caused them from the complex fauna1 signal of fossil assemblages 0 1998 elsevier science b v all rights reserved

geologic evidence for earthquakes during the past 2000 years along the copalis river southern coastal washington evidence for several prehistoric earthquakes is present in deposits less than 2000 years old that crop out at the copalis river estuary 47 07 2 n 124 09 7 w the deposits show that land subsided decimeters into the intertidal zone on as many as three occasions and that sand vented while the land underwent little or no subsidence on another occasion the evidence for earthquake induced subsidence consists of buried marsh and forest soils that evince sudden estuarine submergence attended on at least one occasion by a landward directed surge of sandy water this combination of submergence and surge implies subsidence and tsunami exposed evidence for subsidence and tsunami along the copalis river is strong for a time within a few decades of 300 years ago moderate for a time 1400 1900 years ago and weak subsidence or lacking tsunami for an intermediate time also about 1400 1900 years ago the history of sudden submergence and tsunami in the past 2000 years at the copalis river estuary resembles that shown by buried soils farther south in coastal washington at grays harbor and willapa bay the history can be explained most simply by great mw of 8 or 9 thrust earthquakes at the boundary between the juan de fuca and north america plates with one or two earthquakes occurring 1400 1900 years ago and another close to 300 years ago the evidence for earthquake induced venting along the copalis river consists of sand intrusions and vented sand volcanoes the sand rose through muddy estuarine deposits at least 3 m thick entraining these deposits in fragments as much as 0 3 m long intrusion occurred at one or more times in the past 2000 years and at least some of the venting occurred 900 1300 years ago the sand bodies do not imply artesian flow of flood pressured groundwater because the sand vented forcefully and infrequently through a lowland that probably lacked natural levees the earthquake implied by the venting of sand 900 1300 years ago could have come from a source below above or at the boundary between the juan de fuca and north america plates if from the subducted juan de fuca plate the implied earthquake was farther west or larger than the largest earthquakes within that plate during the past 100 years evidence permitting a source within the north america plate includes a fault scarp an uplifted tideflat and landslides near puget sound dating from the interval 700 1700 years ago a plate boundary source would explain buried soils whose estuarine submergence and burial imply coseismic subsidence for parts of coastal washington in the interval 600 1300 years ago however stratigraphy shows that little or no coseismic subsidence occurred along the copalis river during the venting 900 1300 years ago if a plate boundary earthquake struck coastal washington 900 1300 years ago the earthquake produced a different distribution of land level change than did the plate boundary earthquakes inferred for 1400 1900 and 300 years ago

late quaternary tectonic deformation in the cape arago bandon region of coastal oregon as deduced from wave cut platforms the cape arago region of south central oregon sits on the upper plate of the cascadia subduction zone about 80 km east of the base of the continental slope the style of late pleistocene deformation along the cascadia forearc near cape arago is well expressed by the altitudinal variation of a set of five uplifted wave cut platforms these platforms record open folding with a half wavelength of about 6 7 km as well as late quaternary offset on flexural slip reverse faults that parallel bedding in the underlying bedrock the folds have produced both landward and seaward tilts to the uplifted wave cut platforms because the folds cut obliquely across the coastline the magnitude of coastal uplift is variable in the case of the lowest 80 ka wave cut platform this variable uplift has resulted in coastal deformation ranging from subsidence to a maximum uplift of 0 8 m kyr quantitative analysis of the mechanism of flexural slip folding for the south slough syncline near cape arago indicates that the late quaternary strain rate has decreased in the last 200 kyr evidence of past great subduction style earthquakes such as regional uplift and regional landward tilting of wave cut platforms or regional submergence of coastlands is lacking inmore the cape arago region instead the deformational style is controlled by folding though localized folding is dominant the occurrence of great subduction style earthquakes is not precluded because localized folding could occur concurrently with regional coseismic deformation less

identifying coseismic subsidence in tidal wetland stratigraphic sequences at the cascadia subduction zone of western north america tidal wetland stratigraphy reveals that great plate boundary earthquakes have caused hundreds of kilometers of coast to subside at the cascadia subduction zone however determining earthquake recurrence intervals and mapping the coastal extent of past great earthquake ruptures in this region are complicated by the effects of many sedimentologic hydrographic and oceanographic processes that occur on the coasts of tectonically passive as well as active continental margins tidal wetland stratigraphy at many cascadia estuaries differs little from that at similar sites on passive margin coasts where stratigraphic sequences form through nonseismic processes unrelated to coseismic land level changes methods developed through study of similar stratigraphic sequences in europe provide a framework for investigating the cascadia estuarine record five kinds of criteria must be evaluated when inferring regional coastal subsidence due to great plate boundary earthquakes the suddenness and amount of submergence the lateral extent of submerged tidal wetland soils the coincidence of submergence with tsunami deposits and the degree of synchroneity of submergence events at widely spaced sites evaluation of such criteria at the cascadia subduction zone indicates regional coastal subsidence during at least two great earthquakes evidence for a coseismic origin remains equivocal however for the many peat mud contacts in cascadia stratigraphic sequences that lack 1 contrasts in lithology or fossils indicative of more than half a meter of submergence 2 well studied tsunami deposits or 3 precise ages needed for regional correlation paleoecologic studies of fossil assemblages are particularly important in estimating the size of sudden sea level changes recorded by abrupt peat mud contacts and in helping to distinguish erosional and gradually formed contacts from coseismic contacts reconstruction of a history of great earthquakes for the cascadia subduction zone will require rigorous application of the above criteria and many detailed investigations

great earthquakes of variable magnitude at the cascadia subduction zone comparison of histories of great earthquakes and accompanying tsunamis at eight coastal sites suggests plate boundary ruptures of varying length implying great earthquakes of variable magnitude at the cascadia subduction zone inference of rupture length relies on degree of overlap on radiocarbon age ranges for earthquakes and tsunamis and relative amounts of coseismic subsidence and heights of tsunamis written records of a tsunami in japan provide the most conclusive evidence for rupture of much of the plate boundary during the earthquake of 26 january 1700 cascadia stratigraphic evidence dating from about 1600 cal yr b p similar to that for the 1700 earthquake implies a similarly long rupture with substantial subsidence and a high tsunami correlations are consistent with other long ruptures about 1350 cal yr b p 2500 cal yr b p 3400 cal yr b p 3800 cal yr b p 4400 cal yr b p and 4900 cal yr b p a rupture about 700 1100 cal yr b p was limited to the northern and central parts of the subduction zone and a northern rupture about 2900 cal yr b p may have been similarly limited times of probable short ruptures in southern cascadia include about 1100 cal yr b p 1700 cal yr b p 3200 cal yr b p 4200 cal yr b p 4600 cal yr b p and 4700 cal yr b p rupture patterns suggest that the plate boundary in northern cascadia usually breaks in long ruptures during the greatest earthquakes ruptures in southernmost cascadia vary in length and recurrence intervals more than ruptures in northern cascadia

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

reconstructing holocene sea level using salt marsh foraminifera and transfer functions lessons from new jersey usa we present an expanded training set of salt marsh foraminifera for reconstructing holocene relative sea level change from 12 sites in new jersey that represent varied physiographic environments seven groups of foraminifera are recognized including four high or transitional marsh assemblages and a low salinity assemblage a weighted averaging transfer function trained on this dataset was applied to a dated core from barnegat bay to reconstruct sea level with uncertainties of 14 of tidal range we evaluate the transfer function using seven tests 1 leave one site out cross validation suggests that training sets of salt marsh foraminifera are robust to spatial autocorrelation caused by sampling along transects 2 segment wise analysis shows that the transfer function performs best at densely sampled elevations and overall estimates of model performance are over optimistic 3 dissimilarity and 4 non metric multi dimensional scaling evaluated the analogy between modern and core samples the closest modern analogues for core samples were drawn from six sites demonstrating the necessity of a multi site training set 5 goodness of fit statistics assessed the validity of reconstructions 6 the transfer function failed a test of significance because of the unusual properties of some cores selected for sea level reconstruction 7 agreement between reconstructed sea level and tide gauge measurements demonstrates the transfer function s utility copyright 2013 john wiley sons ltd

the deglacial transition on the southeastern alaska margin meltwater input sea level rise marine productivity and sedimentary anoxia 1 oxygen isotope data from planktonic and benthic foraminifera on a high resolution age model 44 14c dates spanning 17 400 years document deglacial environmental change on the southeast alaska margin 59 33 32 n 144 9 21 w 682 m water depth surface freshening i e 18o reduction of 0 8 began at 16 650 170 cal years b p during an interval of ice proximal sedimentation likely due to freshwater input from melting glaciers a sharp transition to laminated hemipelagic sediments constrains retreat of regional outlet glaciers onto land circa 14 790 380 cal years b p abrupt warming and or freshening of the surface ocean i e additional 18o reduction of 0 9 coincides with the bolling interstade of northern europe and greenland cooling and or higher salinities returned during the allerod interval coincident with the antarctic cold reversal and continue until 11 740 200 cal years b p when onset of warming coincides with the end of the younger dryas an abrupt 1 reduction in benthic 18o at 14 250 290 cal years b p likely reflects a decrease in bottom water salinity driven by deep mixing of glacial meltwater a regional megaflood event or brine formation associated with sea ice two laminated opal rich intervals record discrete episodes of high productivity during the last deglaciation these events precisely dated here at 14 790 380 to 12 990 190 cal years b p and 11 160 130 to 10 750 220 cal years b p likely correlate to similar features observed elsewhere on the margins of the north pacific and are coeval with episodes of rapid sea level rise remobilization of iron from newly inundated continental shelves may have helped to fuel these episodes of elevated primary productivity and sedimentary anoxia

use of pollen and vascular plants to estimate coseismic subsidence at a tidal marsh near tofino british columbia abstract we use botanical data to estimate coseismic subsidence produced by the 1700 cascadia earthquake at a tidal marsh near tofino british columbia association indices for cyperaceae 0 3 triglochin type 0 4 poaceae 0 7 potentilla type 0 6 achillea type 0 6 and ericales 0 6 pollen reveal that high marsh taxa have greater fidelity and therefore greater value as indicators of elevation than low marsh taxa pollen taxa that are abundant and have narrow elevation ranges include poaceae potentilla type achillea type and triglochin type vegetation and surface pollen define four marsh zones low middle high and forest edge transition deposits beneath the marsh include a buried peat capped by tsunami sand the sand is abruptly overlain by peaty mud which grades into peaty soil of the modern marsh the buried peat contains pollen indicative of a high to forest edge transition marsh pollen assemblages from the top of the buried peat and the overlying tsunami sand are similar probably because the tsunami entrained litter as it moved over the marsh surface sediments above the tsunami sand yielded pollen characteristic of a low to middle marsh environment including abundant cyperaceae triglochin type poaceae and chenopodiaceae we calibrated fossil pollen data to elevation using partial least squares weighted averaging partial least squares weighted averaging and weighted averaging with tolerance downweighting the last of these methods explains the largest amount of variance root mean square error of prediction 0 3 r 2 0 85 and yielded values of coseismic subsidence at three sites of 0 65 0 3 0 69 0 3 and 0 50 0 3 m average 0 6 0 3 m these values agree with previously published estimates of coseismic subsidence near tofino based on foraminifera

stratigraphic and microfossil evidence for a 4500 year history of cascadia subduction zone earthquakes and tsunamis at yaquina river estuary oregon usa we infer that each buried soil represents a cascadia subduction zone earthquake because the soils are laterally extensive and abruptly overlain by sandy deposits and mud preservation of coseismically buried soils occurred from 4500 yr ago until 500 600 yr ago after which preservation was compromised by cessation of gradual relative sea level rise which in turn precluded drowning of marsh soils during instances of coseismic subsidence based on grain size and microfossil data sandy deposits overlying buried soils accumulated immediately after a subduction zone earthquake during tsunami incursion into sallys bend the possibility that the sandy deposits were sourced directly from landslides triggered upstream in the yaquina river basin by seismic shaking was discounted based on sedimentologic microfossil and depositional site characteristics of the sandy deposits which were inconsistent with a fluvial origin biostratigraphic analyses of sediment above two buried soils in the case of two earthquakes one occurring shortly before 1541 1708 cal yr b p and the other occurring shortly before 3227 3444 cal yr b p provide estimates that coseismic subsidence was a minimum of 0 4 m the average recurrence interval of subduction zone earthquakes is 420 580 yr based on an 3750 4050 yr long record and seven to nine interearthquake intervals

a sea level database for the pacific coast of central north america a database of published and new relative sea level rsl data for the past 16 ka constrains the sea level histories of the pacific coast of central north america southern british columbia to central california our reevaluation of the stratigraphic context and radiocarbon age of sea level indicators from geological and archaeological investigations yields 600 sea level index points and 241 sea level limiting points we subdivided the database into 12 regions based on the availability of data tectonic setting and distance from the former cordilleran ice sheet most index 95 and limiting points 54 are 7 ka older data come mainly from british columbia and san francisco bay the stratigraphic position of points was used as a first order assessment of compaction formerly glaciated areas show variable rsl change where data are present highstands of rsl occur immediately post deglaciation and in the mid to late holocene sites at the periphery and distant to formerly glaciated areas demonstrate a continuous rise in rsl with a decreasing rate through time due to the collapse of the peripheral forebulge and the reduction in meltwater input during deglaciation late holocene rsl change varies spatially from falling at 0 7 0 8 mm a 1 in southern british columbia to rising at 1 5 0 3 mm a 1 in california the different sea level histories are an ongoing isostatic response to deglaciation of the cordilleran and laurentide ice sheets

the relative utility of foraminifera and diatoms for reconstructing late holocene sea level change in north carolina usa abstract foraminifera and diatoms preserved in salt marsh sediments have been used to produce high resolution records of holocene relative sea level rsl change to determine which of these microfossil groups is most appropriate for this purpose we investigated their relative utility from salt marshes in north carolina usa regional scale transfer functions were developed using foraminifera diatoms and a combination of both multi proxy from three salt marshes oregon inlet currituck barrier island and pea island we evaluated each approach on the basis of transfer function performance foraminifera diatoms and multi proxy based transfer functions all demonstrated a strong relationship between observed and predicted elevations r 2 jack 0 74 and rmsep 210 pb and 14 c based chronology and we were able to reconcile this with tide gauge records

a review of the ecological and taphonomic controls on foraminiferal assemblage development in intertidal environments intertidal foraminifera from surface sediments are commonly used as a high resolution indicator of sea level change the integrity of this approach is based upon the assumption that surface assemblages are similar in composition to their buried fossil counterparts this assumption may in some cases be inappropriate due to subsurface or infaunal production and taphonomic alteration here we review the current understanding of foraminiferal production and taphonomic loss in intertidal environments and examine the extent to which these processes can affect the development of foraminiferal assemblages in intertidal environments as a sediment layer undergoes burial dead tests are added at a rate proportionate to the standing crop at that depth as a consequence test accumulation within the layer is proportionate to the depth integrated standing crop depending on the nature of its vertical living distribution the upper 1 cm of sediment may therefore not adequately characterise a given species total input instead a comparison of each species contribution to the entire depth integrated living community may offer a better a priori estimate of relative input to the sediment column this provides an improved base line for identifying true taphonomic trends downcore the potential for infauna to create discrepancies between surface and subsurface assemblages may be minimised however where 1 reproduction is concentrated near to the sediment surface transforming an apparent infaunal standing crop into an effective epifaunal production 2 the living fauna is composed similarly at all depths of production and or 3 intense bioturbation homogenises the upper sediment layers the likely decline in the intensity of taphonomic processes with depth may mean that the foraminiferal production from different depths may not experience taphonomic processes uniformly consequently in addition to their possible gradual enrichment due to subsurface production infaunal species may be preferentially preserved by virtue of their production closer to the base of the taphonomically active zone additionally homogenisation of the sediment column by reworking may mix temporally and perhaps environmentally distinct faunas affecting the stratigraphic integrity of the sediment deposit the most important taphonomic processes in intertidal environments are those associated with early diagenesis while the organic cements of agglutinated taxa may be directly oxidised the associated changes in the saturation state of porewaters with respect to calcium carbonate may affect calcareous species the type of diagenetic reaction operating within the sediment provides a quantitative control on agglutinated test degradation but a largely qualitative control on calcareous preservation in addition calcareous test preservation is dependent upon the rate with which organic matter is supplied while agglutinated test preservation is independent of organic matter concentrations although the specific morphological pathways of test degradation for calcareous species are well understood the stages under which agglutinated tests are lost are less clear the combined but varying influences of production infaunal and species composition taphonomic processes and bioturbation may create complex pathways in the transition from live to dead to fossil assemblages understanding the extent to which infauna taphonomic loss and sediment reworking affect assemblage development in different intertidal environments is essential in order to interpret the fossil record

the magellan pb deposit western australia a new category within the class of supergene non sulphide mineral systems abstract the magellan pb deposit is located in an outlier of the palaeoproterozoic earaheedy group overlying the southeast yerrida basin a feasibility study of the magellan prospect was completed in 2001 with at that time proven and probable ore reserves of 8 5 mt grading 7 12 pb the deposit is currently exploited from two open pits magellan and cano the lead orebodies are hosted in a silicified dolomitic collapse breccia and underlying altered and weathered sandstone and siltstone the host succession comprises from top to bottom a lateritic unit overlying a zone of silicified silcretized quartz clay breccia overlying saprolitic clay breccia and siltstone palaeoproterozoic earaheedy group and basin the footwall consists of black shales of the maraloou formation palaeoproterozoic yerrida basin magellan is a non sulphide mineral system with cerrusite and anglesite as the major ore minerals and plattnerite coronadite pyromorphite and plumbogummite as minor to negligible ore components the lack of sulphides and the sole presence of oxide minerals suggest that the ore was formed under physico chemical conditions conducive to the precipitation of pb carbonate and pb sulphate it is proposed that the magellan lead deposit represents the supergene modified residue from mississippi valley type mvt mineralisation hosted in the sweetwaters member of the yelma formation of the earaheedy group that underwent prolonged weathering which led to dissolution volume reduction and oxidation of the galena and sphalerite as well as leaching out of highly mobile zn leaving behind the pb carbonate and sulphate mineralisation the magellan mineral system likely represents a new category within the non sulphide class of ore deposits

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

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

new techniques in sediment core analysis an introduction marine sediment cores are the fundamental data source for information on seabed character depositional history and environmental change they provide raw data for a wide range of research including studies of global climate change palaeoceanography slope stability oil exploration pollution assessment and control and sea floor surveys for laying cables pipelines and siting of sea floor structures during the last three decades a varied suite of new technologies have been developed to analyse cores often non destructively to produce high quality closely spaced co located downcore measurements characterizing sediment physical properties geochemistry and composition in unprecedented detail distributions of a variety of palaeoenvironmentally significant proxies can now be logged at decadal and in some cases even annual or subannual scales allowing detailed insights into the history of climate and associated environmental change these advances have had a profound effect on many aspects of the earth sciences particularly palaeoceanography in this paper we review recent advances in analytical and logging technology and their application to the analysis of sediment cores developments in providing access to core data and associated datasets and data mining technology in order to integrate and interpret new and legacy datasets within the wider context of sea floor studies are also discussed despite the great advances in this field however challenges remain particularly in the development of standard measurement and calibration methodologies and in the development of data analysis methods new data visualization tools and techniques need to be developed to optimize the interpretation process and maximize scientific value amplified collaboration environments and tools are needed in order to capitalize on our analysis and interpretation capability of large multi parameter datasets sophisticated yet simple to use searchable internet databases with universal access and secure long term funding and data products resulting in user defined data mining query and display so far pioneered in the usa and australia provide robust models for efficient and effective core data stewardship

variability of intertidal foraminiferal assemblages in a salt marsh oregon usa we studied 18 sampling stations along a transect to investigate the similarity between live rose bengal stained foraminiferal populations and dead assemblages their small scale spatial variations and the distribution of infaunal foraminifera in a salt marsh toms creek marsh at the upper end of the south slough arm of the coos bay estuary oregon usa we aimed to test to what extent taphonomic processes small scale variability and infaunal distribution influence the accuracy of sea level reconstructions based on intertidal foraminifera cluster analyses have shown that dead assemblages occur in distinct zones with respect to elevation a prerequisite for using foraminifera as sea level indicators our nonparametric multivariate analysis of variance showed that small scale spatial variability has only a small influence on live rose bengal stained populations and dead assemblages the dissimilarity was higher however between live rose bengal stained populations in the middle marsh we observed early diagenetic dissolution of calcareous tests in the dead assemblages if comparable post depositional processes and similar minor spatial variability also characterize fossil assemblages then dead assemblage are the best modern analogs for paleoenvironmental reconstructions the toms creek tidal flat and low marsh vascular plant zones are dominated by miliammina fusca the middle marsh is dominated by balticammina pseudomacrescens and trochammina inflata and the high marsh and upland marsh transition zone are dominated by trochamminita irregularis analysis of infaunal foraminifera showed that most living specimens are found in the surface sediments and the majority of live rose bengal stained infaunal specimens are restricted to the upper 10 cm but living individuals are found to depths of 50 cm the dominant infaunal specimens are similar to those in the corresponding surface samples and no species have been found living solely infaunally the total numbers of infaunal foraminifera are small compared to the total numbers of dead specimens in the surface samples this suggests that surface samples adequately represent the modern intertidal environment in toms creek

seismic or hydrodynamic control of rapid late holocene sea level rises in southern coastal oregon usa intertidal stratigraphy has been instrumental in demonstrating the hazard posed by great earthquakes at the cascadia subduction zone but inferring an earthquake history from interbedded sequences of peat and mud is complicated by many factors that influence sedimentation and relative sea level change on both tectonic and nontectonic coasts rapid to sudden rises in relative sea level marked by sharp contacts between intertidal peat and overlying mud or sand may reflect coseismic coastal subsidence and tsunami deposition or alterna tively nonseismic hydrodynamic changes in estuaries reconnaissance coring at 16 sites in the marshes fringing a narrow protected tidal inlet of coos bay supplemented by diatom and 14c analyses at four sites reveals a stratigraphic record too fragmentary and ambiguous to distinguish seismic from hydrodynamic causes for more than three of the 10 rises in relative sea level identified only three sharp contacts have the wide extent and evidence of substantial 0 5 m submergence that distinguish them from similar contacts produced by nonseis mic processes correlation with stratigraphic sequences at other estuaries shows that the fringing marshes suddenly subsided and were partially buried by tsunami sand during a great plate boundary earthquake about 300 years ago similar contacts were produced by earthquakes about 1500 1800 years ago and perhaps about 2400 2700 years ago other earthquakes with substantially less subsidence may also have occurred but evi dence is too ambiguous to reconstruct a more complete history

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

microfossil evidence for recurrent coseismic subsidence around lake hamana near the nankai suruga trough central japan abstract we reconstructed recurrent coseismic subsidence during the middle holocene from analyses of sedimentary facies and fossil diatom assemblages in a small drowned valley the shinjo lowland bordering lake hamana near the nankai suruga trough central japan the lake hamana region is known for coseismic subsidence during the 1707 hoei m8 6 and 1854 ansei tokai m8 4 earthquakes along the nankai suruga trough subduction zone a coring survey revealed three widely distributed peat layers in the lowland with a mud layer overlying each of the two lower peats with a sharp contact we traced the alternating peat mud beds for over 300 m along the long axis of a valley the fossil diatom assemblage analysis revealed that the peat layers were deposited in a freshwater pond marsh environment which changed abruptly to an estuarine to inner bay environment recorded by the mud layers from the sudden environmental change at the two peat mud contacts and our radiocarbon dating results we inferred that coseismic subsidence followed by an invasion of seawater into the lowland occurred at least twice during a great earthquake that occurred between 5645 and 6635 cal yr bp and during another great earthquake at ca 5700 cal yr bp within the mud layers the dominant diatom species changed gradually upward from nitzschia frustulum and cocconeis scutellum in the lower part to cyclotella striata and achnanthes submarina in the upper part these changes suggest that water depth and salinity gradually increased after the coseismic subsidence a possible cause of this gradual subsidence is postseismic subsidence following great nankai suruga trough earthquakes

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

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research