dissolution of biogenic carbonates effects of skeletal structure abstract dissolution of biogenic shallow water carbonates exposed on deep sea moorings indicates that skeletal structure is important for the rate of disintegration of biogenic carbonates besides mineralogy and grain size of particles the aragonites and high mg calcites used represent a wide spectrum of mineralogies and types of skeletal framework the particles were deployed at different water depths on a mooring in the drake passage for 52 days weight loss curves for the various types of particles show the relative importance of the different structural factors for the disintegration of these biogenic carbonates organic coatings intraskeletal pore spaces and sizes and shapes of individual crystallites in the skeletons may be more important than carbonate mineralogy and particle size in cases the presence of internal sediments cement aggregates and natural contaminations and of diatoms incorporated during growth into carbonate skeletons strongly influence the disintegration of the skeletal materials the first step of particle disintegration is the selective removal of impurities this step is analogous to a cleaning of specimens it is succeeded by initial dissolution by strong dissolution and finally by disintegration

taphonomic signatures and patterns of test degradation on tropical intertidal benthic foraminifera the preservational condition of benthic foraminifera from tropical intertidal sediments in cleveland bay north queensland australia was examined in order to provide systematic descriptions of taphonomic signatures and semi quantitative estimates of test degradation the primary aim was to improve understanding of the processes of test degradation experienced by intertidal foraminifera during early burial eight common tropical intertidal foraminiferal species were examined arenoparrella mexicana miliammina fusca miliammina obliqua and trochammina inflata from two upper mangrove stations and ammonia aoteana elphidium excavatum clavatum pararotalia venusta and parrellina hispidula from two mudflat stations taphonomic alteration was broadly divided into surface textural features and larger scale structural losses to tests surface alteration of calcareous tests was dominated by the etching and roughening associated with dissolution processes with limited evidence for bioerosion and abrasion both surficial etching and larger scale structural damage were closely related to test architecture with degradation most intense on porous chamber walls as opposed to non porous areas interlocular walls and chamber tips furthermore all calcareous species exhibited consistent pathways of degradation whereby the most recently formed chambers were the most vulnerable to degradation the correspondence between larger scale test loss and these patterns of surface textural alteration suggests calcareous test degradation is primarily driven by dissolution degradation of agglutinated tests contrasts in a number of ways pristine tests of all four species examined exhibited a smooth outer organic coating which may be missing from other specimens the extent to which this initial loss effects further test breakdown is uncertain but appears to differ between species m obliqua and some specimens of a mexicana exhibited structural damage which corresponded to clear cement losses and agglutinant disaggregation more generally agglutinated species displayed fracturing and test breakages which bore no conspicuous relation to cement loss furthermore neither surface alteration nor structural loss affected any part of agglutinated tests preferentially and therefore pathways of degradation were inconsistent across specimens the fact that agglutinated tests degrade in a more arbitrary manner compared with calcareous tests is taken as evidence that their degradation is 1 not entirely controlled by test architecture and 2 at least partially driven by physical mechanical processes we suggest that if agglutinated tests are not already inherently weaker than their calcareous counterparts the loss of organic cements may sufficiently weaken agglutinated tests so as to increase susceptibility to physical damage tests were also graded according to the extent to which they were structurally degraded average taphonomic grades and taphonomic variability i e standard deviation for all species at cocoa creek were statistically invariant with depth contrary to expectations based on the concept of progressive burial through a taphonomically active zone this indicates that shallow sub surface sediments are significantly homogenised and that sediment mixing and infaunal test production imparts a considerable effect on the development of surface and sub surface dead assemblages at the study site

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

penultimate predecessors of the 2004 indian ocean tsunami in aceh sumatra stratigraphic archeological and historical evidence we present stratigraphic archeological and historical evidence for two closely timed predecessors of the giant 2004 tsunami on the northern coast of aceh northern sumatra this is the first direct evidence that a tsunami played a role in a fifteenth century cultural hiatus along the northern sumatran portion of the maritime silk route one seacliff exposure on the eastern side of the lambaro headlands reveals two beds of tsunamigenic coral rubble within a small alluvial fan radiocarbon and uranium thorium disequilibrium dates indicate emplacement of the coral rubble after 1344 3 c e another seacliff exposure on the western side of the peninsula contains evidence of nearly continuous settlement from 1240 c e to soon after 1366 3 c e terminated by tsunami destruction at both sites the tsunamis are likely coincident with sudden uplift of coral reefs above the sunda megathrust 1394 2 c e evidence for which has been published previously the tsunami or tsunami pair appears to have destroyed a vibrant port community and led to the temporary recentering of marine trade dominance to more protected locations farther east the reestablishment of vibrant communities along the devastated coast by about 1500 ce set the stage for the 2004 disaster

carbonate dissolution and temporal abundances of foraminifera in long island sound sediments the dynamics of benthic foraminifera assemblages can be used to examine carbonate dissolution processes in nearshore sediments and as a general assay of physical chemical factors affecting survival of juvenile benthos abundances of total foraminifera live and dead fluctuate regularly throughout the year in long island sound lis mud deposits with highest numbers in spring summer and lowest in winter essentially all forams disappear each year pore water undersaturation with respect to carbonate minerals coincides with periods of rapid disappearance of forams and suggests that these fluctuations reflect a balance between the rate of production recruitment and the rates of death and dissolution of the calcareous tests of the animals reworking by macrofauna in lis central basin sediments inhibits accumulation or depletion of pore water solutes and is responsible for minimizing pore water carbonate saturation states quantitative estimates of seasonal patterns of foram dissolution with a simple mass balance model give a minimum average annual flux of caz in lis sediments of 6 mmol ca2 m 2 d 1 due solely to foraminifera dissolution abandoned tests have a maximum mean residence time of 86 13 d dissolution precipitation of forams may significantly affect benthic zco fluxes and likely accounts for a large proportion 30 during some seasons or at some locales other organisms with carbonate tests of similar size particularly juvenile bivalves may also be affected by periods of undersaturated pore waters conditions promotinn dissolution of tests may represent an important source of mortality for calcareous meiofauna

assessing surficial foraminiferal distributions as an overwash indicator in sur lagoon sultanate of oman abstract the identification of tsunami and storm deposits in arid coastal environments can be problematic as overwash sediments may not show significant contrasting lithologic characters with lagoonal sediments in this study foraminifera were evaluated as an overwash indicator in a small 12 km2 intertidal lagoon located at sur in the sultanate of oman the lagoon is shallow

factors controlling sediment preservation on a north jamaican fringing reef a process based approach to microfacies analysis abstract compositional characteristics of limestones are fundamental to the interpretation of depositional environments with an assumption that preserved grain assemblages preserve sufficient evidence of initial sediment input to enable delineation of environments it is acknowledged however that a range of early diagenetic processes including encrustation fragmentation abrasion microboring dissolution cementation and recrystallization may influence grain preservation potential and thus bias the composition of resultant grain assemblages this study examines the effects and relative importance of a range of early diagenetic processes across a fringing reef at discovery bay north jamaica physical processes abrasion and fragmentation are most important at shallow fore reef sites whilst back reef sites are dominated by biochemical processes including microboring recrystallization biofilm related calcification and dissolution grain susceptibility to each process is highly variable and influenced by mineralogy and skeletal structure coral fragments for example are most susceptible to the effects of microboring whereas halimeda plates are most susceptible to dissolution extensive alteration of grain assemblages is predicted within the back reef where dissolution of coral and halimeda occurs because of intense microboring and pore water undersaturation fore reef assemblages by contrast remain relatively unaltered results have implications both for improved ecological interpretation of carbonate sedimentary sequences and for understanding of how and why carbonate microfacies develop

the spatial and vertical distribution of living stained benthic foraminifera from a tropical intertidal environment north queensland australia we investigated the distribution of living stained benthic foraminifera across a tropical intertidal shoreline adjacent to cocoa creek queensland australia for the purpose of better understanding the nature of test production and ultimately fossil assemblage development within such environments short cores up to 1 m were collected during the wet and dry season along an elevational gradient comprising non vegetated intertidal mudflat and higher intertidal mangrove forest environments the distribution of stained specimens can be broadly delineated into assemblages characterising upper mangrove 2 64 2 91 m above lowest astronomical tide lat and low mangrove mudflat 1 62 2 18 m above lat environments agglutinated species were generally limited to upper mangrove stations calcareous species occurred within all of the intertidal environments examined but differ in their composition between upper and lower intertidal settings upper mangrove faunas were characterised by the agglutinated species arenoparrella mexicana haplophragmoides wilberti miliammina fusca miliammina obliqua and trochammina inflata and the calcareous species helenina anderseni live stained assemblages at lower intertidal elevations were dominated by the calcareous species ammonia aoteana as well as rosalina spp elphidium oceanicum triloculina oblonga ammonia pustulosa and shackoinella globosa absolute densities of stained specimens were lowest within the low mangrove sediments 6 8 specimens per cm2 but higher within the upper mangrove 25 249 specimens per cm2 and mudflat 8 77 specimens per cm2 abundances within mudflat sediments varied seasonally being significantly larger in the wet season whereas those within mangrove zone sediments changed little through the year stained foraminifera were found to a maximum depth of 50 cm at cocoa creek extending to the greatest depth at the upper mangrove stations and were generally shallowest beneath the lower mangroves all stations had over 50 of their foraminiferal standing crop below the upper 1 cm although at most stations 10 of living specimens occurred within this layer comparison of this data with dead assemblages suggests that 1 abundances of stained specimens averaged over two sampling events reasonably approximate aggregate in situ test production and 2 a clear enrichment of infaunal species occurs within the mangrove the latter effect was less conspicuous on the mudflat due to high rates of mixing and assemblage time averaging which obscure the signal of test production within the dead assemblages in both cases the validity and stratigraphic resolution of surface assemblages for sea level and other palaeoenvironmental reconstructions is questionable

inhibition of dissolution within shallow water carbonate sediments impacts of terrigenous sediment input on syn depositional carbonate diagenesis the early diagenetic chemical dissolution of skeletal carbonates has previously been documented as taking place within bioturbated shallow water tropical carbonate sediments the diagenetic reactions operating within carbonate sediments that fall under the influence of iron rich terrigenous sediment input are less clearly understood such inputs should modify carbonate diagenetic reactions both by minimizing bacterial sulphate reduction in favour of bacterial iron reduction and by the reaction of any pore water sulphide with iron oxides thereby minimizing sulphide oxidation and associated acidity to test this hypothesis sediment cores were taken from sites within discovery bay north jamaica which exhibit varying levels of fe rich bauxite sediment contamination at non impacted sites sediments are dominated by caco3 up to 99 by weight pore waters from the upper few centimetres of cores show evidence for active sulphate reduction reduced so4 cl ratios and minor caco3 dissolution increased ca2 cl ratios petrographic observations of carbonate grains specifically halimeda and amphiroa show clear morphological evidence for dissolution throughout the sediment column in contrast at bauxite impacted sites the sediment is composed of up to 15 non carbonate and contains up to 6000 g g 1 fe pore waters show no evidence for sulphate reduction but marked levels of fe ii suggesting that bacterial fe iii reduction is active carbonate grains show little evidence for dissolution often exhibiting pristine surface morphologies samples from the deeper sections of these cores which pre date bauxite influence commonly exhibit morphological evidence for dissolution implying that this was a significant process prior to bauxite input previous studies have suggested that dissolution driven by sulphate reduction and sulphide oxidation can account for the loss of as much as 50 of primary carbonate production in localized platform environments the finding that chemical dissolution is minor in a terrigenous impacted carbonate environment therefore has significant implications for carbonate budgets and cycling and the preservation of carbonate grains in such sediment systems

taphonomy of tidal marsh foraminifera implications of surface sample thickness for high resolution sea level studies abstract previous research has shown that intertidal foraminiferal faunas can be used to document holocene relative sea level change and large prehistoric earthquakes applications like these however require an understanding of the impact of infaunal habitat and taphonomic processes on foraminiferal assemblages to evaluate these effects we analyzed surface sediment samples collected along a transect across a tidal marsh at zeballos on vancouver island british columbia samples of the uppermost 10 cm of sediment in the marsh contain foraminiferal assemblages that permit recognition of a greater number of elevation controlled marsh assemblages than samples of the top centimeter which are generally used in sea level studies this is because the upper 10 cm contain most infaunal foraminifera species whereas the top centimeter commonly lacks some of these species a 10 cm thickness is somewhat arbitrary but most foraminiferal taphonomic biasing occurs in the top 10 cm of the marsh

taphonomic implications of shell surface textures in bahia la choya northern gulf of california abstract the author collected shell samples of the bivalve chione from the extensive tidal flat system of bahia la choya northern gulf of california and examined their surfaces under the binocular and scanning electron microscopes samples were collected from environments ranging in degree of tidal exposure energy level and substrate inner tidal flats sandy outer flats rocky outer flats tidal channel estero channel salt marsh beach spit and subtidal surfaces were compared with those of shells experimentally subjected to bioerosion dissolution and abrasion in all more than 1100 shells were examined and described bioerosion by microborers is by far the dominant process attacking shell material in bahia la choya microbored textures dominated shell surfaces from all sedimentary environments with the exception of the beach where abrasion dominated chemical dissolution is important only in the fine grained salt marsh and inner flat environments many shells show composite textures which reflect the concurrent action of more than one taphonomic agent shells from the salt marsh for example frequently show the effects of both microboring and dissolution overprinted textures can document transport among environments

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

reactive surface area of skeletal carbonates during dissolution effect of grain size abstract major advances have recently been made in quantifying the chemical parameters which control carbonate mineral reaction kinetics in natural waters one of the primary factors influencing rates of reaction is the amount of surface area per unit mass available for reaction for relatively smooth nonporous carbonates the relationship between reactive and total surface area measured by gas adsorption has proven simple however the dominant carbonates in the marine environment are biogenic and exhibit complex microstructures we have performed experiments to determine dinghy what proportion of the total surface area of these biogenic carbonates is actually available for reaction during dissolution three biogenic carbonates having widely differing microstructures halimeda coral and echinoid were chosen for study and comparison with rhombic calcite the influence of grain size on the relation between total surface area determined from gas adsorption and reactive surface area determined relative to rhombic calcite during dissolution in constant composition solutions was of primary concern unlike rhombic calcites total surface area for texturally complex biogenic grains varied slightly or not at all with increasing grain size however both rhombic calcite and biogenic carbonate dissolution rates were inversely related to grain radius this implies that much of the total surface area of biogenic carbonates is unavailable for reaction with the aqueous solution dissolution rates were a function of both grain size and microstructure we have defined an empirical roughness factor which quantifies the difference in reactive surface area between rhombic calcite and a given biogenic grain of equivalent size the roughness factor increased with grain microstructural complexity but was independent of grain size over the grain size range 51 513 microns studied the maximum roughness factor value observed was 7 for halimeda relative to a value of 1 for rhombic calcite our findings indicate that both microstructure and grain size can play important roles in controlling reactivity of biogenic carbonates during diagenesis the relative significance of grain size versus microstructure for carbonate dissolution rates in natural systems is discus ed

microfacies characteristics of a tropical mangrove fringed shoreline cleveland bay queensland australia sedimentary and taphonomic controls on mangrove facies development mangrove ecosystems strongly influence the sedimentology and geomorphology of contemporary intertidal environments and are known to have occupied similar ecological niches at least as far back as the early cenozoic given this it is remarkable how few records of mangrove occurrence have been reported in the geologic record here a microfacies approach is adopted to examine the characteristics of a contemporary mangrove colonized intertidal succession along an active prograding shoreline in north queensland australia and compared with a proximal mid late holocene preserved intertidal succession this enables a comparison of microfacies development and preservation potential in like for like depositional environments over short temporal and spatial scales in the contemporary intertidal system active shoreline progradation has produced a highly gradational shallowing upward succession mid to low intertidal substrates characterized by an abundant and diverse bioclast especially molluscan fauna and a rich calcareous foraminiferal assemblage are overlain by organic rich upper intertidal mangrove facies characterized by abundant organic material especially wood and bark fragments and a distinct fauna of agglutinated foraminifera the major sedimentary effects of mangrove progradation are to introduce substantial amounts of organic matter into the substrate effectively overprinting the mudflat facies to mix and re texture due to root network development and infaunal bioturbation the sediment substrate and to modify the depth ranges over which infaunal molluscs and foraminifera occur variations in the relative abundance of constituents permit however the clear delineation of mangrove and intertidal mudflat facies whilst an essentially similar facies succession is identifiable in the sub recent many of the diagnostic facies constituents are either not preserved or are present in far lower abundances than in the modern in particular the inferred mangrove units contain far less organic material most wood and root material is absent are essentially devoid of bioclastic material and contain a depauperate agglutinated foraminiferal fauna the primary drivers of this are 1 loss of calcareous foraminifera and bioclasts due to carbonate dissolution 2 loss of agglutinated foraminifera due primarily to biological fiddler crab test degradation and mineralization of their organic binding agents and 3 aerobic and anaerobic degradation of organic material consequently actual criteria for identifying the presence of a former mangrove in this succession are limited such poor preservation even within sub recent mangrove deposits suggest that the longer term preservation potential of key diagnostic criteria is likely to be extremely poor within similar terrigenoclastic dominated organically enriched successions thus whilst mangroves significantly modify and re texture intertidal substrates use may often need to be made of sparsely preserved faunal or floral remains or traces interpreted in the context of the broader intertidal depositional succession to infer the presence of mangrove colonized substrates in the rock record

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

high benthic fertility and taphonomy of foraminifera a case study of the skagerrak north sea abstract the skagerrak basin is a deep water extension of the north sea it is of particular interest as an analogue for past epicontintal shelf basins because it presents environmental contrasts with the adjacent shelf seas in this study the distribution patterns of benthic foraminifera have been used to infer taphonomic and oceanographic processes only by separating living from dead assemblages is it possible to interpret taphonomic changes the transport of foraminiferal tests to the danish slope is inferred from the presence there of dead exotic tests whose provenance is considered to be from the south the abundance of detrital organic matter on the danish slope is likewise inferred to be sourced from the same direction thus the danish slope is interpreted to be a depositional sink apart from transport another taphonomic process is the dissolution of calcareous tests this is clearly demonstrated both by the fragility of some tests as viewed under the microscope and by the disparity between the composition of the living and dead factor associations in the deep basin in particular the two predominantly calcareous living associations are replaced by a single predominantly agglutinated dead association due to carbonate dissolution the danish slope of the skagerrak basin is demonstrated to be an area of high benthic fertility this is based on the high density of living stained benthic foraminifera comparable with that of the mississippi delta particularly the abundance of stainforthia fusiformis an opportunistic species and tubular agglutinated forms the fertility is linked with the high abundance of particulate organic matter here previous regional studies have focused on total living plus dead distributions of 100 or 125 m sized foraminifera these factor assemblages are distinct from the 63 m living and dead associations described here

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

uk intertidal foraminiferal distributions implications for sea level studies foraminiferal assemblages have been collected from ten intertidal study areas situated on the east south and west coasts of the uk the assemblages display a vertical zonation which indicates that the distribution of foraminifera in these intertidal environments is usually the direct function of altitude with the duration and frequency of intertidal exposure the most important factors multivariate analyses separate foraminiferal assemblages into two faunal zones a high and middle marsh zone consisting of differing abundances of jadammina macrescens trochammina inflata and miliammina fusca and a low marsh and tidal flat zone dominated by calcareous foraminiferal species notably elphidium williamsoni haynesina germanica and quinqueloculina spp these faunal zones are similar to those in other mid latitude cool temperate intertidal environments although there are spatial and temporal variations between areas the altitudinal ranges of the faunal zones are employed to identify the vertical relationship of the local environment in which the assemblage accumulated to a reference tide level

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

the application of local and regional transfer functions to the reconstruction of holocene sea levels north norfolk england foraminiferal assemblages from thornham and brancaster marshes norfolk uk illustrate statistically significant relationship with elevation with respect to the tidal frame we develop local data from thornham and brancaster marshes and regional data from thornham and brancaster marshes combined with those from 11 other sites around the uk predictive foraminifera based transfer functions to reconstruct former sea levels from a holocene sediment sequence from holkham north norfolk uk the two transfer functions produce similar patterns of tidal elevation change during the holocene the vertical error ranges of the local transfer function are smaller than those of the regional transfer function although the difference 0 09 m is not significant when compared to other factors affecting the reconstructed elevation the value of the reconstructed elevations also differ between the two transfer functions by up to 0 43 m and this is primarily due to the lack of modern analogues in the local transfer function we conclude that the reconstructions derived from the regional transfer function are more reliable than those of the local transfer function since the latter achieves its slight increase in precision at the expense of a significant decrease in predictive power the regional transfer function is used to construct a relative sea level curve from fossil assemblages within a sediment core from north norfolk uk these results are consistent with existing sea level data and geophysical model predictions and illustrate the utility of the foraminifera based transfer function approach

natural dissolution of modern shallow water benthic foraminifera taphonomic effects on the palaeoecological record comparison of the living and dead assemblages of benthic foraminifera from the coastal areas of the skagerrak kattegat reveals that although there are considerable similarities in terms of the presence absence of species there are major differences in relative abundance at species level furthermore the relative abundance of calcareous tests in the living assemblages is considerably higher than that of the dead assemblages average values of 67 and 30 respectively since the environments are microtidal there is little transport of foraminiferal tests due to tidal currents so there are no introduced exotic species although there is local transport caused by waves and wave induced currents however the major taphonomic process appears to be dissolution of calcareous tests this is manifested through etching and breakage of test walls leading to complete decalcification which leaves a residue of organic linings of certain taxa e g ammonia beccarii and a marked increase in abundance of agglutinated tests in the dead assemblages although dissolution is normal in marsh settings throughout the world the skagerrak kattegat area is unusual in the intensity of dissolution in the subtidal zone whereas most of the calcareous species occur throughout the investigated depth range except marsh two of the subtidal agglutinate species eggerelloides scaberand ammotium cassis show upper depth limits consequently the agglutinated foraminifera are better indicators than calcareous foraminifera of upper depth limits in these shallow subtidal environments 1999 elsevier science b v all rights reserved

foraminifera as holocene environmental indicators in the south alligator river northern australia samples of plankton surface sediments and holocene deposits from the south alligator river an energetic macrotidal river in northern australia are examinedto evaluate the usefulness of estuarine foraminifers for palaeoenvironmental interpretation of sediments deposited in tropical macrotidal conditions although marine and estuarine foraminifers in the estuarine channel are mixed by strong tidal currents there are significant trends along the 80 km length of the tidal river the relative proportions of marine andporcellaneous taxa d ecrease upstream from the mouth but hyaline taxa andthose with brackish affinities increase upstream foraminifers in intertidal sediments have distinctly different assemblages in the uppermost intertidal mid tidal mangrove lower intertidal and subtidal zones in addition to the effects of tidal mixing preserved thanatacoenoses are affected by selective dissolution and or pyritisation within the sediment bodies despite the effects of adverse taphonomic factors foraminiferal assemblages preserved in drill cores provide an accurate guide to original depositional environments intertidal subtidal brackish estuarine coastal marine in mid holocene sediments in the south alligator area foraminifers are found to improve the precision of previous palaeoenvironmental reconstructions made on the basis of sedimentary facies and pollen analyses r 2001 elsevier science ltdandinqua all rights reserved

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

developing detailed records of relative sea level change using a foraminiferal transfer function an example from north norfolk uk this paper provides a brief overview of the transfer function approach to sea level reconstruction using the example of two overlapping sediment cores from the north norfolk coast uk the advantages and limitations of the transfer function methodology are examined while the selected cores are taken from different sites and display contrasting patterns of sedimentation the foraminiferal transfer function distils comparable records of relative sea level change from both sequences these reconstructions are consistent with existing sea level index points from the region but produce a more detailed record of relative sea level change transfer functions can extract sea level information from a wider range of sedimentary sub environments this increases the amount of data that can be collected from coastal deposits and improves record resolution the replicability of the transfer function methodology coupled with the sequential nature of the data it produces assists in the compilation and analysis of sea level records from different sites this technique has the potential to bridge the gap between short term instrumental and long term geological or geophysical records of sea level change

lipids in suspended matter from the human disturbed lanyang river northeastern taiwan due to anthropogenic disturbance such as mass road construction the sediment yield in the lanyang river northeastern taiwan has been reported to have increased substantially since 1976 water samples were collected from the river on three occasions and total suspended matter tsm was analyzed for aliphatic hydrocarbons and alkanols sterols results show that the distribution of aliphatic hydrocarbons in the tsm is rather complicated during periods of normal flow but is relatively simple during high flow and after a period of an extraordinarily high daily mean discharge carbon preference index cpi values of n alkanes c25 c33 are comparatively low ranging from 1 14 to 2 35 with an average of 1 62 when compared with a control station cpi 5 88 because there has been no anthropogenic fossil fuel contamination in the study area in the past the present results indicate a predominant hydrocarbon contribution from the old lipids derived from the bedrock argillite slate and meta sandstone due to massive road construction in 1975 1980 with a small contribution from modern vegetation by using a two end member assumption the percentage of old hydrocarbons in the tsm was estimated to be about 87 the presence of a c22n alkanol maximum is attributed mainly to bacterial contribution higher plants are considered a major source of the campesterol stigmasterol and sitosterol in the tsm

numerical simulation of the evolution and propagation of aeolian dune fields toward a desert oasis zone abstract in this study the evolution and propagation of aeolian dune fields toward a desert oasis transitional zone are numerically investigated through considering the spatial variation of wind speed and the influence of vegetation on sand erosion and transportation etc the propagation speed at the edge of desertified land and the influence of a straw checkerboard are quantitatively analyzed results show that evolution time wind speed and sand diameter have obvious impacts on the propagation of desert and desertified land a formula describing the propagation speed of desertified land with respect to wind speed and vegetation coverage is given in addition when considering the effects of straw checkerboards the propagation speed of the downwind desertified land is found to be related to the length of and distance from the checkerboard area

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

foraminiferal biofacies across mangrove mudflat environments at cocoa creek north queensland australia contemporary and relict subsurface intertidal foraminiferal dead assemblages were collected from a site near to cocoa creek north queensland australia and analysed for the purpose of understanding fossil assemblage development and preservation a marked dichotomy was identified between dead foraminiferal assemblages within mangrove sediments and those within adjacent mudflat sediments mangrove assemblages were almost exclusively represented by agglutinated species mainly arenoparrella mexicana haplophragmoides wilberti milliammina fusca m obliqua trochammina inflata while calcareous species dominated the mudflat mainly ammonia aoteana pararotalia venusta parrellina hispidula surface and subsurface test abundances were also an order of magnitude greater within mudflat sediments 1000 3000 tests per cm3 than in the sediments beneath the mangroves 100 300 tests per cm3 statistically significant differences in the abundance of calcareous and agglutinated tests between wet and dry seasons within the mangrove suggest that tests are systematically lost from this part of the system on an annual basis a model of assemblage formation under shoreface progradation is presented which makes a direct link between surface assemblages post depositional processes and the composition and environmental resolution of the fossil assemblages entering the stratigraphic record assemblages within the mangrove undergo rapid taphonomic loss and are then overprinted during burial by the deep infaunal communities associated with the prograding higher elevation environments as such much of the eventual mangrove sequence is represented entirely by assemblages produced relatively recently within an upper mangrove environment and therefore cannot be differentiated according to elevation at the time of deposition in addition organic enrichment of upper mudflat deposits by mangrove roots which occurs during progradation results in the dissolution of calcareous tests from an 40 cm thick stratigraphic interval it is argued that in order to reliably recognise the changes to foraminiferal assemblages which occur during burial assemblages must be compared with respect to stratigraphy rather than reflexively downcore

foraminiferal record of human impact on intertidal estuarine environments in new zealand s largest city fossil foraminiferal faunas were studied in four short late holocene cores two localities from the low tidal estuarine fringes of the waitemata harbour which is surrounded by new zealand s largest city auckland all cores record similar major changes in their fossil content since the arrival of humans ca 1300 ad with faunal changes continuing through to the 1970s molluscs have disappeared from all cores and the foraminiferal faunas have switched from dominantly calcareous ammonia association to dominantly agglutinated textularia schlerochorella miliammina haplophragmoides associations a twostep change is evident with an intermediate mixed calcareous agglutinated faunal zone 1950s 1970s characterised by peak abundances 13 20 of elphidium gunteri and elphidium excavatum s l the faunal changes in each core since human colonisation replicate the faunal zonation in a low tidal transect of surface samples going up the rangitopuni estuary at the head of the waitemata harbour canonical correspondence analyses of the foraminiferal and environmental proxy data from the cores and the modern estuary transect indicate that faunal changes can be largely attributed to decreasing salinity and additionally lowered ph causing carbonate dissolution in the more brackish rangitopuni estuary core locality there is a weak correlation with increased nutrients toc n p but sediment grain size and increasing heavy metal concentrations played no major part in producing the faunal changes intheestuarytransect completedissolutionofcalcareousforaminiferalshellsvariesbetweenyears butoccursupstreamwhere

taphonomy and time averaging of foraminiferal assemblages in holocene tidal flat sediments bahia la choya sonora mexico northern gulf of california abstract foraminiferal reproduction and preservation have been studied in holocene tidal flat sediments of bahia la choya sonora mexico northern gulf of california foraminiferal reproduction at choya bay tends to occur in discrete a few weeks seasonal pulses which are then followed by periods of homogenization and dissolution of several months duration foraminiferal number number of tests gram sediment increases northward across the flat primarily because of decreasing intensity of bioturbation and increasing total carbonate weight percent shell content of sediments despite intensive dissolution of foraminiferal reproductive pulses tests which appear to be relatively fresh are actually quite old up to 2000 years based on 14c dates we hypothesize that after reproduction some tests survive dissolution because of rapid advection burial downward by conveyor belt deposit feeders e g callianassid shrimp polychaete worms into a subsurface shell layer where tests are preserved until exhumation much later by biological activity or storms thus taphonomic grade surface condition of foraminiferal tests in these sediments is not an infallible indicator of shell age time since death the condition of the test surface is indicative of the residence time of the test at the sediment water interface taphonomically active zone and not test age

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