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

hydrochemical investigation of barium in the public water supply wells of sao paulo state southern brazil barium has frequently been detected in the groundwater of public supply wells in the state of sao paulo brazil at concentrations above the aquifer baseline values and in some situations above the potability limit 0 7 mg l 1 in this study the barium concentration and distribution in the water of 163 supply wells monitored by the state environmental agency have been evaluated and suggestions to explain its occurrence are also presented the investigations were of regional to local scale and comprised sampling and chemical analyses of groundwater samples from specific wells and from a pumping test in a well located at the municipality of galia the results showed that among all the evaluated aquifers in the state of sao paulo the greatest number of cases and highest concentrations of barium 1 2 mg l 1 were found in wells that extract water from both the marilia and adamantina aquifers bauru aquifer system sab the origin of the barium is probably natural and possibly related to the dissolution of the carbonate cement in the marilia formation sandstones other barium anomalies were observed in the sab wells that cross both the adamantina and santo anastacio aquifers in these cases the barium concentrations show a positive correlation with n nitrate and chloride suggesting that the barium anomalies are directly or indirectly related to an anthropic contribution through the infiltration of sewage water from septic systems in the aquifers as recharge

towards a formal description of foraminiferal assemblage formation in shallow water environments qualitative and quantitative concepts the use of foraminifera in palaeoenvironmental reconstructions e g sea level may be complicated by processes such as infaunal test production taphonomic degradation and bioturbation which act to modify contemporary analogue surface assemblages during and subsequent to burial understanding the palaeoenvironmental significance of these processes is limited by the absence of a clear theoretical description of the mechanics of foraminiferal assemblage formation a conceptual framework is proposed which describes assemblage formation in terms of the balance of test inputs and losses within a volume of sediment undergoing burial through the upper sedimentary zones of test production taphonomic processes and bioturbation a corresponding mathematical model is described and shown to explain empirical dead test distributions in terms of empirically defined standing crops sedimentation and mixing rates together with model estimates of standing crop turnover and or taphonomic decay rates this approach provides a quantitative basis for understanding assemblage formation and for comparing assemblage forming processes between species environments and study sites rates of standing crop turnover and taphonomic loss are identified as the primary unknowns in the study of foraminiferal assemblage formation these multiple unknowns make interpretations of cored data ambiguous emphasising the need for a detailed and coherent framework of theory and assumptions for understanding the mechanics assemblage formation if interpretations are to be clear and conclusive

early hettangian benthic planktonic coupling at doniford sw england palaeoenvironmental implications for the aftermath of the end triassic crisis abstract this paper presents a high resolution micropalaeontological study integrated with geochemical and sedimentological analyses of the triassic jurassic tr j transition at the doniford section sw england our analyses indicate the renewal of surface carbonate production in the blue lias formation early hettangian after the end triassic mass extinction based on the high abundance of surface carbonate producers schizosphaerellids which occurred in phase with development at sea floor of calcareous hyaline benthic foraminifers we deduce that a benthic pelagic coupling resulted in both the initial restoration of the biological carbonate pump and also a more efficient export production the presence of monospecific phytoplankton assemblages and benthic foraminiferal assemblages typical of poorly oxygenated environments suggest that the environmental stress continued after the end triassic maximal perturbation complete environmental recovery was prevented by a succession of alternating dysaerobic and anoxic phases that favoured the deposition of black shale sediments the hypothesis of a methane release mechanism as a trigger for the global carbon cycle perturbation and greenhouse conditions during the early jurassic is discounted based on evidence from the decoupled carbon isotope records of carbonate and organic matter apart from local control of a high amplitude sea level change across the tr j boundary the succession and nature of events at doniford are consistent with a scenario of global environmental and biotic changes triggered by the physical and chemical effects of the central atlantic magmatic province camp volcanism a super greenhouse climate in the aftermath of the end triassic mass extinction appears to be the results of the combination of the long term co2 accumulation in the atmosphere system due to the camp volcanic activity as well as the inefficiency of the biological pump due to reduced export production

geochemical environments of continental shelf upper slope sediments in the northern gulf of mexico geochemical environments were characterized for 14 sites along the northern gulf of mexico continental shelf and upper slope in an effort to examine the relationship between sediment geochemistry and carbonate shell taphonomy in a long term study shelf and slope experimental taphonomy initiative sseti three groups of environments of preservation seep near seep and shelf and slope were identified based on their geochemical characteristics i e oxygen uptake rate and penetration depth pore water saturation states and carbonate dissolution fluxes diffusive oxygen uptake rate increased in the order of shelf and slope near seep and seep although carbonate dissolution flux did not show significant correlation with o2 flux presumably due to non diffusive behavior at some sites using pore water saturation indices with respect to aragonite and calcite and sedimentation rates we defined a semi quantitative parameter carbonate dissolution index cdi to predict carbonate preservation potential during the taphonomic processes our limited database suggests that both the seep and the shelf and slope sediments may have higher carbonate preservation potential than the near seep sediments

carbonate preservation in shallow marine environments unexpected role of tropical siliciclastics abstract coordinated taphonomic geochronologic and geochemical studies of bivalve death assemblages and their sedimentary environments of san blas caribbean panama permit us to identify the major factors controlling skeletal degradation in mixed carbonate siliciclastic tropical shelf sediments ten sites were studied along environmental gradients including water nutrients grain size and sediment chemistry carbonate organic carbon and reactive iron contents taphonomic data were derived from naturally occurring bivalve death assemblages and experimentally deployed specimens of mytilus edulis and mercenaria mercenaria to determine environmental controls on types and intensities of postmortem damage to skeletal hardparts and to quantify short term rates of damage accrual death assemblage shells were dated using 14c and amino acid racemization techniques to examine shell persistence scales of time averaging and long term rates of damage accrual including correlations between shell damage and she

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

missing molluscs as evidence of large scale early skeletal aragonite dissolution in a silurian sea in the silurian carbonate platform succession of gotland sweden interreef limestone and marl sequences have shallow marine shelly assemblages dominated by brachiopods typical of many paleozoic benthic faunas locally from similar facies where early skeletal silicification occurred associated with bentonites there are rich and diverse assemblages of originally aragonitic molluscs quantitative faunal analysis suggests that massive depletion of skeletal aragonite chiefly molluscs took place and the entire molluscan fauna may generally be underrepresented by at least 100 fold previous workers on the gotland succession have already shown that abundant diagenetic limestones were sourced by early aragonitic remobilization our findings indicate molluscs as the probable source of this diagenetic calcite not aragonite mud as was previously thought the taphonomic window represented by the silicified faunas illustrates the importance of aragonitic shells among the original silurian shelf benthos and raises the possibility that the paucity of such shells among many fossil faunas may be largely an early taphonomic effect

contemporary foraminiferal distributions of a mangrove environment great barrier reef coastline australia implications for sea level reconstructions abstract contemporary foraminiferal samples and associated environmental information were collected from cocoa creek a mesotidal fringing mangrove environment on the great barrier reef gbr coastline australia to elucidate the relationship of the foraminiferal assemblages with elevation and environment there is a strong and highly significant relationship between elevation and the foraminiferal assemblages supporting the intertidal vertical zonation concept which suggests that the distribution of foraminifera in the intertidal zone is usually a direct function of elevation with the most important controlling factors being the duration and frequency of subaerial exposure multivariate analyses separate the intertidal foraminiferal assemblages into three elevational zones with zone i the highest and zone iii the lowest zones i and ii are dominated by agglutinated species trochammina inflata and miliammina fusca respectively and zone iii is dominated by calcareous species notably ammonia tepida and elphidium discoidale multiloculum these assemblage zones are similar to those found in both tropical and temperate intertidal environments a predictive transfer function has been developed to allow reconstruction of former sea levels for tropical environments based upon the relationship between foraminiferal assemblage and elevation results suggest that a precision of 0 07 m should be attainable superior to most similar studies from temperate mid latitude environments our work has produced the first foraminifera based transfer function for environmental interpretations for tropical australia and allows the potential development of a new generation of high resolution sea level reconstructions for the post glacial sequences of the gbr shelf

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

preferential dissolution of carbonate shells driven by petroleum seep activity in the gulf of mexico abstract authigenic carbonates are common at deep sea petroleum seeps as a result of excess bicarbonate production during microbial degradation of hydrocarbons coupled to sulfate reduction consequently these seep environments are supersaturated with respect to carbonates this finding conflicts with taphonomic data that dissolution is the most pervasive mode of shell alteration at seeps we provide here the first study linking the preservational process with the chemical characterization of the taphonomically active zone at petroleum seep sites this characterization is made possible using fine scale porewater carbonate chemistry data and skeletal material deployed for 8 years at petroleum seep sites in the northwestern gulf of mexico microelectrode measurements of ph and pco2 identify a very restricted zone of caco3 undersaturation immediately below the sediment water interface in otherwise supersaturated environments i e sandwiched between supersaturated bottom seawater and sediment porewater this zonation characterizes the taphonomically active zone and is a result of a highly compressed redox front between acid generating aerobic oxidation of reduced chemical species including hydrocarbons h2s and planktonic and terrestrial organic carbon and base generating sulfate reduction coupled to ch4 oxidation porewater geochemistry is spatially variable at seep sites and produces variable shell dissolution signatures shells deployed at seep sites have moderate to severe dissolution that is consistent with a much higher flux of total dissolved inorganic carbon dic from the porewater to the bottom water therefore a mosaic of preservational conditions is directly related to the spatially and chemically varying taphonomically active zones found at seep sites these findings support the variability of carbonate preservation reported for globally distributed phanerozoic fossil seeps and the view that data from field taphonomy can significantly upgrade and validate carbonate destruction rates used in geochemical and climatic models carbon mass balance analyses also lead to an important conclusion that carbonate dissolution forms a very important mechanism for benthic carbon recycling possibly accounting for 50 of the benthic dic flux to the bottom water in northern gulf of mexico petroleum seep sediments

behaviour and taphonomic loss in foraminiferal assemblages of mangrove swamps of french guiana abstract fifty three surface sediment samples were collected in january 1999 july 2000 and december 2000 on mud flats and in mangrove swamps of french guiana sampling stations were selected to provide information on different environmental conditions on the mud flats and in the mangrove forest thirteen samples were also collected at a depth of about 8 12 cm in the sediment additional samples were collected from three long cores in the channel of the kaw river the main parameter controlling the distribution of recent foraminiferal assemblages is the seasonally variable relative influence of coastal water of reduced salinity and low ph low ca river water areas under the influence of coastal water are dominated by calcareous species mainly ammonia tepida and cribroelphidium spp even in mangrove swamps during the dry season river water influences almost all the study area during the rainy season and leads to the dominance of agglutinated species with the nature of the assemblages depending on local environmental characteristics on the mud flats tests are typically well preserved in the 10 cm below the surface that is the most important taphonomically active zone for foraminifera however owing to intense bioturbation the taphonomic processes in the mangrove swamp may result in the total destruction of the microfauna including agglutinated tests this study shows that the preservation of thanatocoenoses in mangrove swamp environments of french guiana only occurs in exceptional circumstances when they are preserved the remaining assemblages even if modified by taphonomic processes give valuable information for paleoenvironmental reconstructions in this environment

geochemical indicators of depositional and early diagenetic facies in holocene carbonate muds and their preservation potential during stabilisation holocene carbonate muds 63 m fraction and macro organic matter were collected from marine subtidal mudbanks and supralittoral mud islands of florida bay and freshwater marshes of the florida everglades u s a geochemistry sedimentology and mineralogy were used to determine whether carbonate mud formation in specific marine and freshwater environments was geochemically distinct and to assess the importance of early diagenetic reactions on mud chemistry and mineralogy significant variations were found in the relative amounts of carbonate minerals not just between the marine and freshwater environments but also within florida bay in particular mg calcite is enriched in crane key muds by 10 relative to nearby cross bank the mg calcite appears to precipitate in the surface living cyanobacterial mats of the key and seems to be linked to mg chelation by the cyanobacterial organic matter this mg calcite has a distinct 13c around 4 6 lighter than mg calcite derived from thalassia epibionts in the cross bank muds dolomite was found just below the cyanobacterial mats forming in the only part of the core where reactive organic carbon has been completely removed by sulphate reducing bacteria the 13c values of this dolomite at least 4 are consistent with previously published 13c values of dissolved inorganic carbon in pore waters at this horizon which support dolomite formation in situ mg supply for dolomite formation may be from dissolution of the overlying cyanobacterial mat mg calcite the various types of organic matter have distinctive 13c values ranging from 25 mangrove and sawgrass to 10 cyanobacterial mats and 8 thalassia seagrass values intermediate between these end members record mixing of the organic matter types which shows particularly the time when the bank muds became dominated by thalassia organic matter i e were relatively removed from mangrove vegetation five holocene mud suites bank key cyanobacterial mats mangrove swamp and freshwater everglades swamp show distinct chemical signatures in their mean 13c 18o mgco3 and sr values na distinguishes between seawater and non seawater influenced environments but fe mn and p are mainly controlled by non carbonate materials comparison with published stable isotope and elemental data for pleistocene limestones in the south florida area suggests that only the facies diagnostic signatures of 13c and mg will be resolvable once the muds have been stabilised to micrite alteration of the 18o and sr values during stabilisation will probably be more severe to the extent that original facies variations are destroyed

rheology of rocksalt abstract we review progress in experimental determinations of transient and steady state flow properties and processes of natural rocksalt aggregates focusing primarily on results from avery island louisiana domal salt the steady state flow field established from constant stress and constant strain rate tests at temperatures from 50 to 200 c strain rates from 10 5 to 10 9 s 1 and differential stresses from 20 7 to 2 5 mpa has been separated into two flow regimes each fit by a power law relation at the higher stresses and strain rates this relation is e 1 6 10 4 exp 68 1 rt 10 3 5 3 for which the pre exponential constant is expressed in mpa 5 3 s 1 and the apparent activation energy is in j mol 1 creep rates predicted by equation a do not differ appreciably from those predicted previously the relatively low stress low strain rate data are very well fit by e 8 1 10 5 exp 51 6 rt 10 3 2 4 which is comparable conditions predicts creep rates higher and equivalent viscosities lower than does equation a by two orders of magnitude the change in behavior from a to b is ascribed to a change in rate limiting mechanism from cross slip of screw dislocations to the climb of edge dislocations in this dry material subgrain formation dominates microstructural development during steady state flow of salt and from determinations of average subgrain diameters in crystals from 20 different rocksalt bodies flow stress levels between 0 6 and 1 4 mpa have been estimated these values do not bear directly on arguments concerning the nature of forces initiating salt pillow growth because apparently evidence relating to the early deformational history has been overprinted at that stage fluid assisted grain boundary diffusional processes might dominate dislocation creep leading to a linear stress strain rate mechanical response considering buoyancy forces alone behavior described by equation b rather than a reduces the relief necessary to initiate pillow growth but a 1000 fold amplification is required to produce stress differences near 1 mpa that forces other than buoyancy are important is indicated by the occurrence of these same paleostress levels in bedded salts and in shallow offshore concordant intrusions differential loading generally provides the most plausible initial driving force for the growth of diapiric salt structures

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

late holocene paleoceanographic evidence of the influence of the aleutian low and north pacific high on circulation in the seymour belize inlet complex british columbia canada foraminiferal and thecamoebian faunas from the seymour belize inlet complex sbic a fjord network situated on the mainland coast of british columbia were studied to assess climatic cycles and trends impacting the area through the ad 850 ad 2002 interval ocean circulation patterns prevalent in the sbic are strongly linked to precipitation which is closely linked to the relative strength and position center of action coa of the seasonally developed aleutian low al and north pacific high nph atmospheric circulation gyres through interpretation of cluster analysis and ordination methods a period of weak estuarine circulation was recognized to have impacted the sbic area between ad 850 and ad 1500 during this time waters in the sbic were dysoxic to anoxic and the sediment water interface was comprised of a depauperate foraminiferal fauna consisting of low diversity agglutinated forms these reduced oxygen conditions came about as a result of diminished precipitation in the sbic catchment as the coa of the al progressively migrated westward over time resulting in greatly reduced estuarine circulation and only infrequent and feeble incursions of well oxygenated open ocean water into the sbic basin by ad 1575 following a gradual transition period of 75 years when circulation patterns in the inlet were unstable very strong estuarine circulation developed in the sbic concomitant with the onset of the little ice age lia in western canada in the sbic this interval was characterized by higher levels of precipitation which greatly enhanced estuarine circulation resulting in frequent incursions of cold well oxygenated ocean currents into the bottom waters of the sbic and the development of a diverse calcareous foraminiferal fauna this circulation pattern began to break down in the late 19th century ad and by ad 1940 conditions similar to those that existed in the inlet prior to ad 1500 had redeveloped a process that continues at present

evidence of bioturbation in the cap ferret canyon in the deep northeastern atlantic in the sedimentary column a combined quantification of burrows and macrobenthic community provides evidence of bioturbation features in the submarine canyon of cap ferret between 2000 and 3000 m depth an image processing technique allows accurate quantification of burrow volumes with depth in the sedimentary column the major bioturbation mode seems to be different in the channel compared to the interfluve macrobenthic activity is more inclined to mix the sediment in the channel in response to increased organic matter supplies sediment mixing leads to burrow destruction in the upper mixed layer of sediment in the canyon burrows are better preserved on the interfluve where mixing is slower under the mixed zone the volume of recorded burrows is higher when sedimentation rate increases as in the upper canyon in this transition layer the burrow volume is estimated to be between 3 and 64 of the total sediment volume depending on the sediment depth the fill down of numerous burrows with surface sediment by bioregeneration suggests that anaerobic degradation of fresh organic matter is dominant in this canyon in the sedimentary column the negative relationship between carbonate content and macrobenthic abundance confirms that carbonate dissolution is largely influenced by bioturbation

carbonate dissolution in nearshore terrigenous muds the role of physical and biological reworking because shallow marine sediments generally underlie waters which are saturated with respect to arago nite and calcite physical chemical dissolution of carbonate in these environments is sometimes discounted the present investigation as well as others before it show such an assumption to be unwarranted in this case study of terrigenous mud deposits from long island sound u s a demonstrates extensive dissolution of molluscan shell debris near the sediment water interface net buildup of carbonate varies significantly between different regions of the sound despite fairly uniform production of shell debris and similar total sedimentation rates aside from this apparent discrepancy between rate of supply and net carbonate sedimentation evidence for carbonate dissolution comes from the pitting of shells elevated ca levels in pore water and calculated undersaturation of pore waters with respect to carbonate minerals models of pore water distributions and carbonate supply imply dissolution ra

integrated stratigraphy of the paleocene eocene thermal maximum in the new jersey coastal plain toward understanding the effects of global warming in a shelf environment 1 in the new jersey coastal plain a silty to clayey sedimentary unit the marlboro formation represents deposition during the paleocene eocene thermal maximum petm this interval is remarkably different from the glauconitic sands and silts of the underlying paleocene vincentown and overlying eocene manasquan formation we integrate new and published stable isotope biostratigraphic lithostratigraphic and ecostratigraphic records constructing a detailed time frame for the petm along a depth gradient at core sites clayton wilson lake ancora and bass river updip to downdip the onset of the petm marked by the base of the carbon isotope excursion cie is within the gradual transition from glauconitic silty sands to silty clay and represented fully at the updip sites wilson lake and clayton the cie core interval is expanded at the updip sites but truncated the cie core is complete at the bass river and ancora sites where the early part of the recovery is present most complete at ancora the extent to which the petm is expressed in the sediments is highly variable between sites with a significant unconformity at the base of the overlying lower eocene sediments our regional correlation framework provides an improved age model allowing better understanding of the progression of environmental changes during the petm high resolution benthic foraminiferal data document the change from a sediment starved shelf setting to a tropical river dominated mud belt system during the petm probably due to intensification of the hydrologic cycle the excellent preservation of foraminifera during the petm and the lack of severe benthic extinction suggest there was no extreme ocean acidification in shelf settings

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

production and accumulation of calcium carbonate in the ocean budget of a nonsteady state present day production of caco3 in tne world ocean is calculated to be about 5 billion tons bt per year of which about 3 bt accumulate in sediments the other 40 is dissolved nearly half of the carbonate sediment accumulates on reefs banks and tropical shelves and consists largely of metastable aragonite and magnesian calcite deep sea carbonates predominantly calcitic coccoliths and planktonic foraminifera have orders of magnitude lower productivity and accumulation rates than shallow water carbonates but they cover orders of magnitude larger basin area twice as much calcium is removed from the oceans by present day carbonate accumulation as is estimated to be brought in by rivers and hydrothermal activity 1 6 bt suggesting that outputs have been overestimated or inputs underestimated that one or more other inputs have not been identified and or that the oceans are not presently in steady state one missing calcium source might be groundwater although its present day input is probably much smaller than that of rivers if as seems likely caco3 accumulation presently exceeds terrestial and hydrothermal input this imbalance presumably is offset by decreased accumulation and increased input during lowered sea level shallow water accumulation decreases by an order of magnitude with a 100 m drop in sea level while groundwater influx increases because of heightened piezometric head and the diagenesis of metastable aragonite and magnesian calcite from subaerially exposed shallow water carbonates

benthic photosynthesis and oxygen consumption in permeable carbonate sediments at heron island great barrier reef australia abstract in order to investigate benthic photosynthesis and oxygen demand in permeable carbonate sands and the impact of benthic boundary layer flow on sedimentary oxygen consumption in situ and laboratory chamber experiments were carried out at heron island great barrier reef australia total photosynthesis net primary production and respiration were estimated to be 162 9 43 4 98 0 40 7 and 64 9 15 0 mmol c m 2 d 1 respectively din and dip fluxes for these sands reached 0 34 and 0 06 mmol m 2 d 1 respectively advective pore water exchange had a strong impact on oxygen consumption in the permeable sands consumption rates in the chamber with larger pressure gradient 20 rpm 1 2 pa between centre and rim simulating a friction velocity of 0 6 cm s 1 were approximately two fold higher than in the chambers with slow stirring 10 rpm 0 2 pa between centre and rim friction velocity of 0 3 cm s 1 in the laboratory chamber experiments with stagnant water column oxygen consumption was eight times lower than in the chamber with fast stirring laboratory chamber experiments with br tracer revealed solute exchange rates of 2 6 2 2 0 7 ml cm 2 d 1 at stirring rates of 20 10 and 0 rpm respectively in a laboratory experiment investigating the effect of sediment permeability on oxygen and dic fluxes a three fold higher permeability resulted in two to three fold higher oxygen consumption and dic release rates these experiments demonstrate the importance of boundary flow induced flushing of the upper layer of permeable carbonate sediment on oxygen uptake in the coral sands the high filtration and oxidation rates in the sub tropical permeable carbonate sediments and the subsequent release of nutrients and dic reveal the importance of these sands for the recycling of matter in this oligotrophic environment

microbial production and modification of gases in sedimentary basins a geochemical case study from a devonian shale gas play michigan basin an expanded data set for gases produced from the antrim shale a devonian black shale in the michigan basin united states has allowed for a detailed examination of the related chemical and isotopic compositional changes in the solid gas liquid systems that discriminate between microbial and thermogenic gas origin in the antrim shale economic microbial gas deposits are located near the basin margins where the shale has a relatively low thermal maturity and fresh water infiltrates the permeable fracture network the most compelling evidence for microbial generation is the correlation between deuterium in methane and coproduced water along the basin margins there is also a systematic enrichment in 13c of ethane and propane with decreasing concentrations that suggests microbial oxidation of these thermogenic gas components microbial oxidation accounts not only for the shift in 13c values for ethane but also in part for the geographic trend in gas composition as ethane and higher chain hydrocarbons are preferentially removed this oxidation is likely an anaerobic process involving a syntrophic relationship between methanogens and sulfate reducing bacteria the results of this study are integrated into a predictive model for microbial gas exploration based on key geochemical indicators that are present in both gas and coproduced water one unequivocal signature of microbial methanogenesis is the extremely positive carbon isotope values for both the dissolved inorganic carbon in the water and the coproduced co2 gas in contrast the 13c value of methane is of limited use in these reservoirs as the values typically fall between the commonly accepted fields for thermogenic and microbial gas in addition the confounding isotopic and compositional overprint of microbial oxidation increasing the values to typically thermogenic values may obscure the distinction between methanogenic and thermogenic gas

carbonate dissolution in the guts of benthic deposit feeders a numerical model abstract we present a numerical model to quantify calcite dissolution in the guts of deposit feeding invertebrates deposit feeder guts were modeled as constantly stirred reactors cstrs following terminology from digestion theory saturation state and dissolution of calcium carbonate were calculated from changes in total dissolved carbon dioxide and alkalinity resulting from sediment passage through the digestive tract while accounting for dissolution of calcite and respiration of organic carbon typical dissolution rates for a gut volume of 1 ml ranged between 0 5 4 mg calcite d 1 sensitivity analysis revealed gut ph sediment organic matter om content and om reactivity to be the critical parameters determining calcite dissolution rate carbonate dissolution rate was inversely related to gut ph however calcite dissolution was found to be possible even at alkaline gut ph due to respiration by intestinal microbes the kinetics of calcite dissolution had only marginal influence on daily calcite dissolution rates varying the calcite dissolution rate constant by six orders of magnitude affected calcite dissolution rates by less than a factor of 10 calcite dissolution rates were calculated for 4 different hydrographic regimes that differed in their content of sedimentary calcite and om and furthermore in their om reactivity highest dissolution rates were calculated for the shallow water setting where relatively high om content facilitated high microbial respiration rates depressing gut ph however dissolution rates for the deep sea setting were only slightly lower due to greatly elevated ingestion rates resulting from low om content as a consequence of much higher faunal abundances shallow water benthos is likely to contribute the vast majority of gut mediated carbonate dissolution nevertheless the fraction of sedimentary calcite that dissolves during one gut passage is probably too small to be observable by simple gravimetric analysis this may explain the notable scarcity of evidence for gut mediated carbonate dissolution in the literature to date assuming depth dependent calcite dissolution rates and deposit feeder abundances we estimate gut mediated carbonate dissolution to contribute approximately 5 of the annual global sedimentary carbonate dissolution rate which corresponds to an average calcite dissolution rate of approximately 0 5 mg m 2 d 1 for the entire ocean floor

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

regional hydrogeochemistry of the carbonate rock aquifer southern manitoba middle ordovician to middle devonian carbonates in the manitoba lowlands form an extensive aquifer system along the eastern edge of the williston basin the aquifer is divided into fresh and saline portions by a series of topographic lows defined by major river systems and lakes that create a north south trending hydraulic divide east of this divide ca mg hco3 fresh waters are derived by active modern day recharge focused in the sandilands and interlake regions stable isotope and geochemical data indicate that na cl saline waters west of the divide are a mixture of original basin brines and glacial melt water pushed into the basin during pleistocene glaciation high na cl and cl br ratios are consistent with significant salt dissolution by glacial melt water

occurrence and mobilization of radium in fresh to saline coastal groundwater inferred from geochemical and isotopic tracers sr s o h ra rn abstract salinization in groundwater systems can induce water rock interaction including the release of naturally occurring trace elements of health significance such as radium ra with possible implications for the usability of water resources in addition to the increase of dissolved solids tds concentrations in general radium mobility is limited by chemical removal mechanisms including adsorption onto clays and or mn and fe oxides exchange processes and coprecipitation with secondary barite in order to examine the effect of aquifer salinity gradients on the distribution of naturally occurring ra in fresh to saline groundwater and the relationship to water rock interaction and ra removal mechanisms two contrasting systems were investigated the shallow unconfined coastal aquifer in agadir southwestern morocco and the confined cretaceous cape fear and pliocene yorktown aquifers of the atlantic coastal plain north carolina usa geochemical and isotopic indicators of salinity sources e g cation ratios 18o 2h br cl 34 s so 4 2 18 o so 4 2 were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water rock interaction radium activities 224ra 226ra 228ra radon 222 alkaline earth metal mg ca sr ba concentrations and ratios and 87sr 86sr ratios were analyzed to identify water rock interaction processes affecting alkaline earth metals including ra the morocco coastal aquifer is generally oxic exhibits a range of salinity and water types cl 163 2120 mg l median 932 mg l and exhibits ca na ratios above the seawater value typical of monovalent divalent cation exchange base exchange reactions in coastal aquifers in contrast the atlantic coastal plain aquifers are anoxic sulfate reducing cover a wider salinity range cl 5 9890 mg l median 800 mg l representing a transition between na hco 3 and na cl waters and exhibit ca na ratios below that of modern seawater typical of reverse base exchange reactions possible salinity sources in the morocco coastal aquifer include seawater intrusion mesozoic evaporites other natural saline waters and or wastewater whereas the atlantic coastal plain is primarily affected by old seawater present in the aquifer system radium activities are generally low and vary significantly within each aquifer for example 226ra ranges from 1 8 27 7 mbq l in the morocco coastal aquifer median 8 1 mbq l and 1 9 214 mbq l in the atlantic coastal plain median 18 9 mbq l the highest ra activities were observed in the most saline wells sampled in the atlantic coastal plain at total dissolved solids tds concentrations above an apparent threshold of 5000 mg l radium activities increase in a generally linear fashion with salinity in the atlantic coastal plain broadly comparable to previous studies indicating a threshold range of 3000 10 000 mg l at lower tds concentrations water rock interaction processes that vary with local aquifer conditions appear to control ra distribution rather than merely salinity in the morocco coastal aquifer adsorption of ra and coprecipitation with secondary barite are apparently favorable to control ra levels in groundwater radium removal in the anoxic atlantic coastal plain aquifers appears to be associated with adsorption and or exchange processes with the additional possibility of barite precipitation in the cape fear aquifer indicated by barite saturation overall the locally variable factors that can control ra sources and mobility in fresh to brackish groundwater at near neutral ph include variation in solid phase radioactivity redox state affecting adsorption sites availability of competing divalent cations and barite saturation

carbon cycling in coastal sediments 1 a quantitative estimate of the remineralization of organic carbon in the sediments of buzzards bay ma seasonal remineralization rates of organic carbon are calculated in the top 20 30 cm of biologically irrigated organic rich sediments of buzzards bay ma six cores were collected over a period of two years and the pore water concentrations of the following species were measured dissolved inorganic carbon co2 po3 4 h2s alk and ca2 overall these constituents showed large gradients with depth which are larger in summer than in winter remineralization rates in the sediments were estimated by applying a non local exchange vertical molecular diffusion reaction model to the co2 depth profiles the major processes affecting the pore water concentration of co2 described in the model are diffusion irrigation and the oxidation of organic carbon the calculated remineralization rates varied seasonally with the high of 7 5 10 9 mol l sec observed in august 84 and the low 0 6 10 9 in december 1983 the remineralization rates were dependent on the amount of irrigation in the sediments it was possible to calculate remineralization rates between 0 and 20 cm because the amount of irrigation was well characterized at this site we calculated that 69 gc m2 are oxidized annually and 5 33 gc m2 yr are buried it appears that there is a highly reactive portion of organic matter which is oxidized at the sediment water interface examination of the alk and dissolved ca2 profiles indicates that there was significant production of acid which dissolved caco3 in the spring and early summer

the role of low temperature organic matter diagenesis in carbonate precipitation within a marine deposit abstract carbonate minerals in veins can record paleo hydrogeological information that enables the reconstruction of groundwater history this paper investigates the cause of differences in the occurrence of carbonate veins in the koetoi and wakkanai formations both neogene mudstone units in northwestern hokkaido from the perspective of controls on co2 supply from the alteration of organic matter carbonate veins are rare in the koetoi formation but are widespread in the wakkanai formation this area is a region of oil and gas accumulation where deep groundwater is saturated mainly with ch4 and co2 the results show high 13c values in co existing ch4 32 6 and co2 31 0 gases an investigation of 13c d systematics among these gases indicates that isotopic fractionation was caused by microbial co2 reduction although total organic carbon content in the koetoi formation decreases with increasing depth total organic content in the wakkanai formation remains roughly constant with depth furthermore although 13c values also show depth dependence values from the wakkanai formation are higher than those from the koetoi formation this 13c enrichment could be explained by rayleigh fractionation in a closed system based on these results the processes behind the formation of the carbonate veins can be summarized as follows carbon dioxide behavior is thought to play an important role with respect to carbonate formation because co2 abundance is closely linked to ph and pressure in shallow sedimentary rocks such as the koetoi formation that have started to experience diagenetic alteration of organic matter co2 in groundwater is supplied by microbial decomposition of organic matter and is reduced to ch4 by methanogens in deep sedimentary rocks such as the wakkanai formation that have undergone diagenesis but have only experienced moderate temperatures so that thermal decomposition of organic matter has not yet begun microbial degradation of organic matter has proceeded too far for any more co2 to be produced thus carbonate precipitation is initiated when ph rises due to microbial co2 reduction the contrast between the occurrence of carbonate veins in the koetoi and wakkanai formations can be explained by our results which can also be applied to general carbonate behavior in marine sedimentary rocks

creep of rocksalt abstract a review is presented of the fundamental flow properties and processes in experimentally deformed natural and synthetic halite single crystals and polycrystalline aggregates included in the summary are discussions of a microstructures induced during steady state creep b creep rupture of rocksalt c experiments associated with project salt vault and more recent field studies and d brine migration a representative steady state flow law determined for natural aggregates and maximum natural deviatoric stresses deduced from subgrain sizes are applied briefly to considerations of creep in waste repositories and of salt dome dynamics while the mechanical behavior of rocksalt is probably better understood than for all other rock types further investigations especially on load path stress history and creep rupture are clearly mandated furthermore additional investigations of brine migration and of bench and field scale deformations are needed the latter incorporating realistic rocksalt flow properties into numerical simulations of natural rock mass response

effect of confining pressure on dilatation recrystallization and flow of rock salt at 150 c microstructural evidence for fluid assisted dynamic recrystallization fadrx is widespread in naturally deformed rock salt however the principal experimental evidence for fadrx in salt has been obtained from stress relaxation experiments and it is unclear whether the process occurs during steady state dislocation creep and what its effect might be here we report deformation experiments performed on natural rock salt at a constant strain rate of 3 5 10 7 s 1 150 c and confining pressures pc of 3 30 mpa samples deformed at pc 3 mpa showed continuous work hardening and minor dilatation microstructurally they exhibited intergranular cracking plus slip band and subgrain structures indicative of dislocation glide creep electron backscatter diffraction analysis revealed a high frequency of boundaries with low angle misorientations in the range 5 10 in contrast samples deformed at pc 6 5 mpa showed work hardening followed by steady state flow at strains 6 7 these samples compacted slightly and crystal plastic deformation was accompanied by extensive fadrx with a predominance of high angle boundaries 30 50 over low angle boundaries we infer that fadrx is suppressed by dilatation at low pressures as a result of grain boundary disruption at pressures high enough to prevent dilatation however fadrx acts as a recovery mechanism counteracting work hardening the results offer a possible explanation for rheological variability seen in previous experiments conducted at pressures up to 30 mpa a simple rate model for diffusion and interface controlled fadrx indicates that fadrx should become increasingly important toward natural halokinetic conditions although the effect on flow stresses is likely to be small

elevated ba concentrations in a sandstone aquifer summary groundwaters of the winnipeg formation have been found to have ba concentrations in excess of drinking groundwater guidelines over an area of several hundred square kilometers water samples are at or near barite saturation however so 4 concentrations are exceedingly low this inequality suggests that so 4 is being lost from the groundwater allowing for a buildup of ba in solution as barite saturation is maintained the focus of this study is to investigate the relationship between ba and so 4 and its application to anomalously high ba concentrations found in the formation these relationships are investigated through the use of transport modeling in phreeqc the model consists of the mixing two end member waters that are found within the formation reacting the mixed water with dissolved organic carbon and transporting the newly mixed and reacted water through the formation

did alpha diversity increase during the phanerozoic lifting the veils of taphonomic latitudinal and environmental biases abstract we estimate the effects of three biases on the observed alpha diversity of paleocommunities from the middle paleozoic and late cenozoic the first bias results from the preferential dissolution of aragonite relative to calcite this bias can lower the relative abundance and preserved diversity of aragonitic taxa potentially lowering the rarefied diversity of an entire fossil assemblage we model the effects of this bias by analytically reinserting aragonitic specimens and taxa into paleozoic assemblages that have been described in the literature the aragonitic specimens are inserted using a wide range of reasonable assumptions about the original local paleocommunity composition although the dissolution bias is probably not as severe as has been argued by some our analytical modeling indicates that the average paleozoic assemblage may have lost up to 29 of its total diversity the second bias results from the higher diversity of the tropics relative to temperate latitudes but the late cenozo

dislocation density stress relationships in natural and synthetic sodium chloride abstract to determine the relationship between applied stress and dislocation density creep experiments have been carried out on single crystals of natural and synthetic sodium chloride with differential stresses between 2 0 and 20 0 mpa at temperatures in the range 20 to 600 c dislocation densities were measured on etched cleavage surfaces using a scanning electron microscope the dislocation density is proportional to the differential stress to approximately the 1 3 power at a given differential stress the density of edge dislocations is larger and the density of screw dislocations smaller in natural crystals than in synthetic samples the mean dislocation density was unaffected this difference in the dislocation densities between natural and synthetic crystals is related to differences in the concentrations of impurities natural salt samples from a lansing n y salt mine were collected from locations in close proximity to excavation openings dislocation densities in the natural samples when compared to our experimentally derived stress dislocation density curve indicate that the samples were deformed at in situ stresses of 10 to 30 mpa

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

temperature dependent grain boundary migration in deformed then annealed material observations from experimentally deformed synthetic rocksalt abstract grain boundary migration between strained substructured grains and newly appearing strain free grains has been observed during static in situ annealing of pre deformed rocksalt in the sem with increasing temperature t the migration velocity increases and the character of grain boundary migration changes as temperature increases there is an increase in the length of individual migrating boundary segments that move at similar rates in addition the frequency of migrating boundaries that form traces of a 100 boundary plane of at least one of the crystals involved increases and moving grain boundaries between new and old grains change from highly irregular to smooth straight boundaries at the same time there is a decrease in the influence of the substructure of pre existing strained grains on the grain boundary movement resultant microstructures reflect these changes at 325 350 c the deformed then annealed microstructure is characterized by very irregular grain boundaries a high abundance of 5 50 m scale remnants of old substructured grains within new grains giving a poikilitic microstructure at 350 400 c grain boundaries often exhibit elongate embayments into the strained grains and most remnants of old strained grains are located at former grain boundaries at 400 c grain boundaries between new and old strained grains are straight to smoothly curved the grain boundary velocity observations are explained by the effect of temperature on mobility coupled with local driving force variations additionally at low annealing temperature impurity solute drag and driving force variations are influential while at high temperature the anisotropy in grain boundary energy with crystallographic orientation becomes more important transferring the knowledge from our experiments to geological samples enables us to recognize and interpret similar microstructures in rocks thereby making it is possible to relate microstructural characteristics to the pre annealing and post deformational annealing history

effect of salinity induced ph alkalinity changes on benthic foraminifera a laboratory culture experiment the salinity of coastal waters in the vicinity of seasonally fresh water fed estuaries changes tremendously and reportedly affects the living calcite secreting organisms like foraminifera as well as their dead remains the precise mechanism of adverse effect of such seasonal salinity changes on calcite secreting organisms is however not clear the seasonal fresh water influx from the estuaries also affects the ph and alkalinity of the coastal seawater therefore to understand the effect of salinity induced ph alkalinity variations on benthic foraminifera living specimens of rosalina globularis were subjected to different salinity additionally water samples were collected from an estuary during both monsoon and post monsoon season to understand the relationship between salinity ph and total alkalinity ta the ph decreased with decreasing salinity during both the seasons a similar decrease in ta with decreasing salinity was also observed but only till 20 psu salinity below which the ta increased with decreasing salinity even though the maximum growth was reported in specimens kept at 35 psu salinity growth of specimens maintained at 25 psu salinity was same specimens kept at 10 psu and 15 psu salinity however were much smaller and turned opaque within two days of lowering the salinity and later on their tests dissolved within 24 and 43 days respectively no specimen reproduced at 10 psu and 15 psu salinity while only a few specimens 3 reproduced at 20 psu salinity as compared to 10 20 psu salinity 60 reproduction was observed in specimens subjected to 25 40 salinity the specimens maintained at 20 psu salinity took twice the time to reach maturity than those subjected to 2540 psu salinity since a big drop in ph was observed at 10 15 psu salinity ph 7 2 and 7 5 respectively while the alkalinity was still higher we suggest that fresh water influx induced drop in ph adversely affects calcification and reproduction in benthic foraminifera the response is however not linear as beyond a certain limit a further increase in ph does not affect benthic foraminifera rather they respond to salinity as per their salinity tolerance range it is further inferred that the time required to reach reproductive maturity increases at the extreme salinity tolerance limits dissolution of calcareous foraminifera below 20 psu salinity suggests that salinity induced changes control the carbonate inventory in the coastal regions subjected to seasonal fresh water influx

extensive microbial modification of formation water geochemistry case study from a midcontinent sedimentary basin united states the upper devonian antrim shale in the michigan basin is an economically significant source of microbially produced methane along the basin margins where meteoric recharge has been focused oxygen and hydrogen stable isotope compositions of antrim formation waters show that fresh waters recharged from pleistocene glaciation and modern precipitation suppressed basinal brine salinity to great depths and enhanced methanogenesis this paper presents results of integrated elemental and isotope analyses of antrim shale formation waters from the margins and center of the michigan basin focusing on solute sources and geochemical modifications associated with regionally extensive microbial methanogenesis cl br na systematics reveal that salinity is controlled not only by mixing between variable amounts of basinal brine and meteoric water but also by halite dissolution where fluids recharged through underlying devonian carbonate aquifers with localized evaporite deposits divalent cations carbonate system parameters and carbon isotope compositions of dissolved inorganic carbon have been systematically and profoundly altered by microbial methanogenesis large decreases in formation water ca mg and ca sr ratios accompany increasing carbonate alkalinity values in areas with high rates of microbial gas production thermodynamic and reaction path modeling show that these changes are consistent with calcite precipitation during progressive microbial methanogenesis similar variations in fluid chemistry are evident in databases from other sedimentary basins containing black shales and coal beds associated with microbial gas microbial methanogenesis may play an important role in the geochemical evolution of divalent cation relationships in crustal fluids and should be considered in models of formation water origin and evolution

experimental evaluation of the influences of biogenic reworking on carbonate preservation in nearshore sediments abstract laboratory experiments using two different species of marine infaunal deposit feeders have shown directly that macrofaunal activities influence sedimentary carbonate preservation feeding burrowing and irrigation increase solute transport and solid phase reaction rates simultaneously leading to more rapid carbonate dissolution than in sediments without fauna these findings help to explain previously reported regular temporal fluctuations of foraminifera assemblages and spatial patterns of carbonate dissolution in nearshore deposits and represent one more example of how bioturbation accelerates elemental cycles in marine sediments

taphonomic experiments on marginal marine foraminiferal assemblages how much ecological information is preserved the most important taphonomic processes affecting the composition of benthic foraminiferal assemblages are transport and destruction of tests the latter includes dissolution of calcareous tests we have previously simulated nature experimentally by dissolving mainly shelf to deep sea samples in weak acid to give acid treated assemblages ata in this study we sampled the marginal marine environments of the skagerrak kattegat and found that the main taphonomic process there is dissolution of calcareous tests consequently the taphonomic processes occurring in this area represents a perfect natural analogue of what we suspect to be the main mechanism for the formation of some fossil agglutinated assemblages the evidence for this is that some living assemblages dominated by calcareous forms become original dead assemblages oda often consisting entirely of agglutinated species and equivalent to atas the principal ata is dominated by miliammina fusca and this ata can be derived from 10 different types of oda including those that are strongly dominated by various calcareous taxa this residual m fusca assemblage represents a broad range of intertidal to shallow subtidal environments on the other hand marsh living assemblages are completely agglutinated and obviously give rise to agglutinated oda atas but not necessarily dominated by the same taxa all the atas faithfully record the low species diversity characteristic of marginal marine environments the principal conclusion is that in spite of the severe taphonomic loss the preserved assemblages record much ecological detail this is in accordance with similar investigations of deeper water assemblages and has important consequences for palaeoecology this study demonstrates unequivocally that it is always essential to compare data on living and dead assemblages in order to determine the pathways to fossilisation the use of total living plus dead assemblages in this area would give unrepresentative and misleading results

holocene palaeoceanographic changes in barrow strait canadian arctic foraminiferal evidence holocene changes in the benthic and planktic foraminiferal fauna 63 m from a marine sediment core arc 3 canadian arctic archipelago 74 16 050 n 91 06 380 w water depth 347 m show that significant environmental and palaeoceanographic variations occurred during the last 10 ka foraminiferal assemblages are restricted to the ca 4 5 10 ka interval as younger samples are mostly barren of foraminifera due to intense carbonate dissolution after ca 4 5 ka foraminiferal assemblages in the ca 4 5 10 ka interval are dominated by the benthic species islandiella helenae and cassidulina reniforme 57 of total with elphidium clavatum cibicides lobatulus and buccella frigida also being common in this interval the dominance of these species indicates a seasonal sea ice regime which is consistent with the occurrence of the sea ice diatom derived organic geochemical biomarker ip25 throughout the core the abundances of c reniforme and e clavatum decline upcore consistent with more frequent mixing of the barrow strait water column during the early holocene it is likely that the influence of co2 rich arctic surface water masses have caused an increase in bottom water corrosivity after ca 8 5 ka and dissolution has been further enhanced by sea ice related processes after ca 6 ka concomitant with increased ip25 fluxes dissolution is strongest when ip25 fluxes are highest suggesting a link between the sea ice and benthic systems copyright 2010 john wiley sons ltd

late pliensbachian early toarcian early jurassic environmental changes in an epicontinental basin of nw europe causses area central france a micropaleontological and geochemical approach abstract we present an integrated work based on calcareous nannofossil and benthic foraminiferal assemblages and geochemical analyses of two upper pliensbachian lower toarcian sections located in the central south france the studied sections tournadous and saint paul des fonts represent the proximal and the distal part respectively of the jurassic causses basin one of the small partly enclosed basins belonging to the epicontinental shelf of the nw tethys at the transition from late pliensbachian to early toarcian the causses basin recorded an emersion in response to the global sea level fall our data indicate severe environmental conditions of marine waters including salinity decrease and anoxia development occurring in the early toarcian the acme of this deterioration coincides with the early toarcian anoxic event t oae but due to the restricted nature of the basin anoxia persisted until the end of the early toarcian mainly in the deeper parts of the basin the micronutrients and organic organic matter fluxes were probably high during the entire studied time interval as shown by nannofossil and foraminiferal assemblages however nannoplankton production drastically decreased during the t oae as demonstrated by very low nannofossil fluxes and only taxa tolerant to low saline surface waters could thrive at the same time benthic foraminifers temporarily disappeared in response to sea bottom anoxia our study demonstrates that environmental changes related to the t oae are well recorded even in small partly enclosed basins of nw europe like the causses basin within this area the effects of global changes like sea sea level and temperature fluctuations are modulated by local conditions mainly controlled by the morphology of the basin

analysis and interpretation of holocene sedimentary sequences in the humber estuary the interpretation of the holocene evolution of the humber estuary has been made possible only through integrated multidisciplinary studies involving inter alia drilling to obtain sedimentary records of the holocene estuary fill multi element carbon nitrogen sulphur and stable carbon isotope geochemistry heavy and clay mineralogy palaeomagnetism radio carbon dating and pollen diatom and foraminiferal studies eight chemostratigraphic suites and 14 palaeo environments have been recognized sediment types environments of deposition and provenance change in response to rising sea level showing a range from freshwater fluvial deposition of locally derived terrestrial sediment to intertidal and subtidal deposition of sediments from marine sources the methods used are illustrated with reference to sediment cores from inner and outer estuary locations the results show that holocene environmental characterization is most secure when a number of different but complementary techniques are used the integration of radiocarbon dates with palaeomagnetic and geochemical data improves the understanding of the presence and significance of time breaks which is crucial to constraining sedimentation rates and material budgets

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

using radon 222 and radium 226 isotopes to deduce the functioning of a coastal aquifer adjacent to a hypersaline lake in nw iran abstract this study aims to assess the hydrogeochemistry of coastal groundwater the occurrence of 222rn and 226ra and their isotopic response to salinity and associated chemical compositions of groundwater in the coastal urmia aquifer ua at the western side of urmia lake ul the results of the pca show that 87 3 of groundwater chemistry changes are controlled by six principal components the interaction between groundwater and coastal igneous and metamorphic rocks in eastern areas next to the ul results in complex hydrogeochemical conditions than western areas based on correlation of u and salinity some coastal samples display conservative and the others non conservative behaviors differed from most previous studies 226ra and 222rn concentrations in coastal groundwater samples of ua do not show a good correlation with salinity given 10 of groundwater 222rn is originated from host rocks the radon concentrations recorded in the coastal groundwater samples are relatively in range that can effectively be supplied by the local rocks 5 49 bq l results of different chemical and isotopic parameters in this area indicate that there is no direct connection between fresh groundwater and ul saltwater this is because that the hard and thick salty layer in the lakebed acts as an impermeable barrier to prevent the underground hydraulic connection results show that removing the salty layer of ul as an option to progress in rehabilitation program of this lake may result in more hydraulic connection between the lake and groundwater resources in some areas

benthic foraminiferal responses to water based drill cuttings and natural sediment burial results from a mesocosm experiment abstract effects of burial by water based drill cuttings and natural test sediment on living stained benthic foraminifera were investigated in a mesocosm experiment after 193 days the foraminiferal response in sediment covered with drill cuttings was compared to the response in sediment covered with defaunated natural test sediment increasing thickness of added material independent of type of material significantly reduced the benthic foraminiferal abundance and species richness while most species managed to migrate through added sediments of up to 12 mm thickness results indicate that a burial depth of 24 mm severely limits the migration capability of the foraminifera textularia earlandi and bulimina marginata dominated the 0 1 cm of sediment including added material in most mesocosms but the former was most resistant to maximum burial 24 mm the physical disturbance caused by the burial triggered reproduction in surviving populations of b marginata and nonionellina labradorica addition of water based drill cuttings and defaunated natural test sediments impacted the microhabitat of n labradorica differently stainforthia fusiformis seems to be the species most tolerant to the water based drill cuttings results indicate that the foraminiferal faunal composition respond differently to the two different materials added even if only agglutinated forms are considered this agrees with earlier macrofaunal results from the same experiment which indicate that the water based drill cuttings represent an additional stress factor for the benthic community

paleoenvironmental changes during the middle eocene climatic optimum meco and its aftermath the benthic foraminiferal record from the alano section ne italy the middle eocene climatic optimum meco was one of the most severe short term global climate perturbations of the cenozoic that occurred at ca 40 ma and was characterized by a gradual 4 6 c temperature increase of intermediate and deep waters we investigated the response to the meco of the deep sea ecosystem in the central western tethys through a quantitative study of bathyal benthic foraminiferal assemblages in the expanded and continuous alano section northeastern italy for which data on stratigraphy lithology isotope and trace element geochemistry and calcareous microplankton were available during the gradual warming of meco lasting between 350 and 650 kyr marine export productivity increased causing a significant but transient restructuring of benthic foraminiferal faunas which changed gradually from assemblages typical for oligo mesotrophic sea floor conditions to assemblages indicative of more eutrophic conditions just after the peak meco conditions which lasted less than 100 kyr a prolonged phase of environmental instability 500 kyr occurred marked by even more highly increased export productivity leading to bottom water oxygen depletion as reflected in deposition of organic rich sediments and multiple peaks of bi triserial opportunistic benthic foraminiferal taxa including buliminids bolivinids and uvigerinids the high productivity may have been caused by a strong influx of nutrient bearing fresh water into the basin due to the increased vigour of the hydrological cycle during the warm period and this increased fresh water influx might have been a factor in enhancing water column stratification thus exacerbating the hypoxic conditions which persisted about 400 500 kyr after deposition of the organic rich layers the environmental perturbation ended and benthic foraminiferal assemblages recovered while conditions became very similar to what they were before the meco the environmental disturbance during and directly after the meco thus strongly but transiently affected benthic foraminiferal assemblages in the central western tethys

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

taphonomic tiering experimental field taphonomy of molluscs and foraminifera above and below the sediment water interface abstract a review and synthesis of field based taphonomic experiments using molluscs and foraminiferans in marine systems reveal differing patterns of hardpart accumulation and destruction for these two major groups of fossil organisms for benthic molluscs most destruction appears to occur at the sediment water interface in siliciclastic settings mollusc preservation is suggested to be high once the shell is buried below the taphonomically active zone although this observation has not been experimentally addressed foraminiferal preservation however depends on microhabitat biogeochemical conditions within the sediments and test composition the taphonomically active zone for foraminiferans appears to be the upper 10 cm in most depositional settings from shallow to deep sea the preservation of tests or shells however has not been examined below the sediment water interface using field based experiments pore water geochemistry and associated microbial processes may be the most important factors in which to examine subsurface taphonomy the term taphonomic tiering is applied to variations in taphonomic activity within the sediments that differentially affect hard parts in essence the subsurface region where hardparts are presumed to be preserved is one of the new frontiers in experimental field taphonomy

taphonomy on the continental shelf and slope two year trends gulf of mexico and bahamas abstract the shelf and slope experimental taphonomy initiative was established to measure taphonomic rates in a range of continental shelf and slope environments of deposition eods over a multiyear period we deployed experiments on the forereef slope off lee stocking island bahamas and on the continental shelf and slope of the gulf of mexico for 2 yr in 18 distinctive eods at depths from 15 to 530 m overall most shells deployed at most sites had relatively minor changes in shell condition most eods generated relatively similar taphonomic signatures a few sites did produce taphonomic signatures clearly distinguishable from the central group and these sites were characterized by one or more of the following high rates of oxidation of reduced compounds presence in the photic zone and significant burial and exhumation events thus unique taphonomic signatures are created by unique combinations of environmental conditions that include variables associated with regional gradients such as depth and light and variables associated with edaphic processes such as the seepage of brine or petroleum or the resuspension and redeposition of sediment most sites however showed similar taphonomic signatures despite the variety of eod characteristics present suggesting that insufficient time had elapsed over 2 yr to generate a more diverse array of taphonomic signatures discoloration and dissolution were by far the dominant processes over the 2 yr deployment period periostracum breakdown loss of shell weight and chipping and breakage was less noticeable eods were chosen based on the expectation that the process of burial and the influence of depth and sediment type should play the greatest roles in determining between eod differences in taphonomic signature eod specific edaphic factors often overrode the influence of geographic scale environmental gradients taphonomic alteration was greater on hardgrounds and in brine exposed sites than on terrigenous muds dissolution was less effective at sites where burial was greatest discoloration occurred most rapidly at shallower sites and on hardgrounds water depth was less influential in determining taphonomic signature than burial state or sediment type the limited influence of water depth is likely due to the presence of shallow sites that for one reason or another were protected from certain taphonomic processes and deeper sites that were characterized by unusually strong taphonomic signals

barium anomaly in the cambrian vendian aquifer system in north estonia a barium anomaly with a maximum ba2 concentration of 6 37 mg l was distinguished in a cambrian vendian cm v aquifer system that is widely used as a drinking water source in the towns kunda rakvere and kohtla jarve of north estonia the modelling results show that at low sulphate concentrations below 3 mg l ba2 contents can exceed the limit values for drinking water such as 2 mg l set by us epa bicarbonate ions in their common concentration range in groundwater cannot limit ba2 at its content below 10 mg l the probable natural sources of the anomaly are the crystalline basement and its weathering zone groundwater in the clayey weathering core is hydraulically connected with the overlying cm v aquifer system thus the upconing of deeper seated groundwater caused by intensive exploitation of wells is possible

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

temporal and spatial distribution of whitings on great bahama bank and a new lime mud budget analysis of 69 shuttle and satellite images of the northern bahamas taken from 1965 to 1993 allowed us to calculate the regional and temporal distribution and longevity of 888 whitings on the great bahama bank at any time whitings cover between 35 and 200 km 2 in the area centered at lat 25 n and 78 50 w the highest occurrences of whitings are in april and october suggesting a seasonal component using a measured average of 10 6 mg l suspended sediment in typical whitings we calculated that 1 35 10 6 metric tons of lime mud are suspended every year if the suspended carbonate is precipitated in the water column these phenomena account for 280 of all of the holocene accumulated bank top mud and more than 40 of the total bank top mud and periplatform mud that have accumulated on the west side of great bahama bank