hydro chemo mechanical modelling of tunnels in sulfated rocks a modelling procedure to address the tunnel anhydritic rock interaction is described in this paper the model incorporates the basic physico chemical phenomena involved in rock swelling often obse

modelling the degradation and swelling of clayey rocks bearing calcium sulphate abstract degradation and swelling of clayey rocks bearing calcium sulphate produces considerable damage to civil engineering works a recent case was the lilla tunnel pertaining to the ave madrid barcelona high speed railway line spain were the floor slab heaved up to 80 cm in the term of a year and a half the present work is based on field and laboratory observations from that case under no confinement degradation of the lilla rock starts immediately upon contact with water degradation develops along a time span of several months and includes development of a crack pattern significant swelling and the extensive growth of gypsum needles within the degraded rock mass a simple numerical model is developed for this process the purpose of the model is to reproduce the swelling process observed in the lilla tunnel from which records of heaves and swelling pressures are available and to check the likeliness of several possible driving mechanisms for the swelling phenomenon the main conclusion of this analysis is that the dissolution of anhydrite and precipitation of gypsum is the most likely mechanism among the three considered the determinant factor behind this conclusion is the physical fact that gypsum has a relatively low solubility which means that the mass of calcium sulphate transported and precipitated as solute is always small

assessment of archaeological bone and dentine preservation from lazaret cave middle pleistocene in france chemical and structural changes in bones and dentine from cervus elaphus jaws during fossilization were studied by chemical analysis infrared spectroscopy ir and x ray diffraction xrd data were used to discuss the modifications of bones and dentine from the lazaret prehistoric cave nice france which is an important archeologic site of middle pleistocene age fossil bones and dentine mainly consisted of hydroxy carbonate apatite as the primary phase and of calcite as a secondary phase carbonation fluorination and recrystallization processes are shown as more important in bone and dentine than in tooth enamel a good correlation was found between the a cell parameter of apatite and its co3 and fluorine contents in the bones studied fluorine enrichment seems to be related to the permeability of the upper sedimentary levels lazaret fossil bones and dentine are less stable than enamels and their use for dating has to be taken with caution

extreme expansive phenomena in anhydritic gypsiferous claystone the case of lilla tunnel the paper describes the expansive phenomena affecting lilla tunnel in spain during construction and subsequent operation the geology of the site and the performance of alternative support designs

chemistry microstructure petrology and diagenetic model of jurassic dinosaur bones dinosaur national monument utah abstract the fossil bone mineral in dinosaurs from the morrison formation is well crystallized stoichiometric francolite the closely packed subparallel francolite crystals have equidimensional cross sections mostly 10 40 nm wide in contrast crystallites in unaltered mammal bone tissue are poorly crystallized nonstoichiometric carbonate hydroxyapatite a few nanometers thick and plate rod or needle shaped the diagenetic francolite crystals are elongated in the c axis direction as are bone tissue crystallites along permeable cracks francolite crystals grew to 250 nm wide compared to unaltered crystallites in mammal bones the francolite has higher concentrations of ba ce cr f la mn ni pb rb sr th u v and y and perhaps zr na and mg are lower in concentration diagene ic francolite grew from groundwater enriched in ions from silicic ashes in the brushy basin member and from dissolution of bone tissue crystallites after burial francolite grew on crystallite seeds filling the space formerly occupied by collagen perhaps half the tissue volume and dissolved crystallites the micron scale structures such as haversian canals and laminae are preserved because the diagenetic francolite retains the orientations of the seeds the laminae 1 10 m thick commonly preserve an orthogonal plywood structure the diagenetic growth of francolite during this type of bone fossilization implies that oxygen isotopic ratios measured in dinosaur bones even those that appear fresh and unaltered may dominantly reflect groundwater temperature rather than dinosaur body temperature trace element concentrations in the francolite may reflect groundwater composition rather than dinosaur diet pore filling cements precipitated in the sands and bones at shallow burial depths as evidenced by the 35 52 minus cement porosities of the sandstones and numerous uncompacted oversize pores filled by cements gypsum and calcite were precipitated from shallow alkaline groundwater as the groundwater became increasingly dominated by ions from silicic ash argentite chalcopyrite native gold native silver tiemannite and uraninite replaced areas of bone a few microns to tens of microns in size along cracks a thin chlorite crust commonly mantled francolite crystals along bone cracks and lined openings in bones and sandstones pervasive precipitation of a chalcedony crust followed with pseudomorphs of chalcedony after gypsum in larger cancellous openings the remaining space was fi led by the various forms of silica the bones are brown due to goethite filled cracks that cut pore filling minerals

relation between hydrogeological setting and swelling potential of clay sulfate rocks in tunneling abstract in this study an approach to estimate the swelling potential of clay sulfate rocks in tunneling is presented swelling of clay sulfate rocks leads to damage in tunnels that is difficult and costly to repair swelling is caused by the transformation of the sulfate mineral anhydrite into gypsum which involves an increase in rock volume in a system open to water flow knowledge of the hydrogeological situation and the groundwater flow systems at the tunnel is essential to better understand the swelling processes the present study was conducted for the chienberg tunnel in switzerland it investigates the hydrogeological situation of four zones in this tunnel crossing the triassic gipskeuper formation in two of them heavy swelling occurred after tunnel excavation while in the other two no swelling occurred in addition the groundwater flow systems before and after tunnel excavation are investigated based on numerical flow modeling the findings suggest that in certain situations after tunnel excavation depending on geological and changing hydraulic conditions the excavation damaged zone around the tunnel provides a hydraulic short circuit between the weathered gipskeuper and the anhydrite bearing strata of the unweathered gipskeuper as a result water from the weathered gipskeuper gets in contact with anhydrite triggering its transformation into gypsum and thus rock swelling the results of the study may also contribute to improved swelling experiments in the laboratory and a more reliable planning of restoration measures in tunnels that are damaged by rock swelling

relationships between environmental conditions and the diagenetic evolution of organic matter derived from higher plants in a modern mangrove swamp system guadeloupe french west indies abstract the sedimentary organic matter content of a series of 2 m deep cores was investigated along a sea land transect at five sites representing five species of mangrove and salt marsh vegetation the vegetation was settled at the same place for at least 1000 years and therefore sedimentary organic matter deriving from the decay of higher plants has accumulated in large amounts the global morphological and chemical preservation of the organic matter attested by various sedimentary parameters including the proportions of cellulose bearing tissues the toc contents the c n ratios the total sulphur contents and the 13 c compositions reveals that the sedimentary organic matter is less degraded when it has been under the influence of the marine water table for a long time this is indicated by a good correlation between the salinities of interstitial waters the redox potentials measured in the wet sediments and the chemical composition of the organic matter moreover the concentration of organic sulphur shows a positive correlation with the hydrogen index hi only under the marine water table influence suggesting the very local presence of sulphur hc compounds

sources and distribution of terrigenous organic matter delivered by the atchafalaya river to sediments in the northern gulf of mexico abstract suspended sediments ss from the atchafalaya river ar and the mississippi river and surficial sediment samples from seven shallow cross shelf transects west of the ar in the northern gulf of mexico were examined using elemental oc c n isotopic 13c 14c and terrigenous biomarker analyses the organic matter om delivered by the ar is isotopically enriched 24 5 and relatively degraded suggesting that soil derived om with a c4 signature is the predominant om source for these ss the shelf sediments display oc values that generally decrease seaward within each transect and westward parallel to the coastline a strong terrigenous c n 29 signal is observed in sediments deposited close to the mouth of the river but values along the remainder of the shelf fall within a narrow range 8 13 with no apparent offshore trends depleted stable carbon isotope 13c values typical of c3 plant debris 27 are found near the river mouth and become more enriched 22 to 21 offshore the spatial distribution of lignin in shelf sediments mirrors that of oc with high lignin yields found inshore relative to that found offshore water depth 10 m the isotopic and biomarker data indicate that at least two types of terrigenous om are deposited within the study area relatively undegraded c3 plant debris is deposited close to the mouth of the ar whereas more degraded isotopically enriched soil derived om appears to be deposited along the remainder of the shelf an important input from marine carbon is found at the stations offshore from the 10 m isobath quantification of the terrigenous component of sedimentary om is complicated by the heterogeneous composition of the terrigenous end member a three end member mixing model is therefore required to more accurately evaluate the sources of om deposited in the study area the results of the mixing calculation indicate that terrigenous om soil derived om and vascular plant debris accounts for 79 of the om deposited as inshore sediments and 66 of om deposited as offshore sediments importantly the abundance of terrigenous om is 40 higher in inshore sediments and nearly 85 higher in offshore sediments than indicated by a two end member mixing model such a result highlights the need to reevaluate the inputs and cycling of soil derived om in the coastal ocean

the persistence of memory the fate of ancient sedimentary organic carbon in a modern sedimentary system the cycle of organic carbon burial and exhumation moderates atmospheric chemistry and global climate over geologic timescales the burial of organic carbon occurs predominantly at sea in association with clay sized particles derived from the erosion of uplifted continental rocks it follows that the history of the fine grained particles on land may bear on the nature of the organic carbon buried in this study the evolution of clay associated organic matter was followed from bedrock source to the seabed in the eel river sedimentary system of northern california using natural abundance 13c and 14c tracers approximately half of the fine grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted mesozoic tertiary franciscan complex of the watershed the short residence time of friable soils on steep hill slopes coupled with rapid sediment accumulation rates on the shelf slope act to preserve the ancient organic carbon a comparable quantity of modern organic carbon is added to particles in the watershed and on the shelf and slope the bimodal mixture of ancient and modern c in soils and sediments may be characteristic of many short mountainous rivers if the eel river chemistry is typical of such rivers more than 40 tg of ancient organic c may be delivered to the world s oceans each year a flux of that magnitude would have a significant influence on marine and global c cycles

evaluating the consequences of diagenesis and fossilization on bioapatite lattice structure and composition abstract changes to hydroxylapatite mineral structure composition and lattice configuration must occur during the transformation of fresh bone to fossil bioapatite mineral phases a paucity of analytical methods to characterize atomic level lattice composition and bonding arrangements in modern and fossil bone has resulted in limited knowledge of how depositional environments and thus diagenetic conditions may influence fossilization processes synchrotron based analyses can provide insight into bone fossilization specifically x ray absorption near edge structure xanes spectroscopy at the p and ca k edges to aid in the interpretation of xanes spectral data from modern bones and from late neogene and late cretaceous fossil bones we applied other established techniques used to characterize bone mineralogy and composition including x ray diffraction fourier transform infrared spectroscopy electron microprobe analysis and thermal analysis specific bone depositional origins and ages likely influenced the varying elemental chemistry preservation of organic matter and mineral content fossilized bones ranging from an almost pure fluorapatite to carbonated fluorapatite mineral phases had less preserved organic material than modern bone the atomic level p and ca lattice structures of fossilized bones differed from modern bones specifically having shifted and shortened ca o bonds due to ca 2 substitution by ionic phases such as iron or rare earth elements and carbonate substitution for phosphate the modified lattice structure regardless of bulk mineral chemistry provides thermodynamic stability in geochemically dynamic depositional environments that may dictate bioapatite preservation over geologic time

heave of a railway bridge induced by gypsum crystal growth field observations the central pillars of a bridge belonging to a recently built high speed railway line experienced an unexpected and continuous heave after the end of construction pillars were founded on 3 3 pile groups capped by a rigid slab the tips of piles supporting the central pillars reached a hard tertiary anhydritic claystone deep extensometers allowed the identification of an active layer 12 15 m thick located below the pile tips observations in recovered cores suggest that the heave is induced by the growth of gypsum crystals in discontinuities of the anhydritic claystone no heave was observed in gypsum rich claystones located above the anhydritic layer gypsum crystal growth is associated with dissolution of anhydrite and subsequent precipitation from a super saturated aqueous solution boreholes and pile construction allowed a hydraulic connection of upper aquifers and the lower anhydritic formation this hypothesis explains the role of the bridge construction in the triggering of a dormant heave phe

gypsum a review of its role in the deterioration of building materials the deterioration of buildings and monuments by gypsum is the result of crystallization cycles of this salt although gypsum can dehydrate to a hemihydrate the mineral bassanite and to an anhydrate the mineral anhydrite this reaction occurs in nature on a geological time scale and therefore it is unlikely to occur when gypsum is found on and in building materials the caso4 h2o system appears deceptively simple however there are still discrepancies between the experimental and thermodynamically calculated data the reason for the latter can be attributed to the slow crystallization kinetics of anhydrite apart from this the large numbers of studies carried out on this system have focused on industrially important metastable phases such as the hemihydrate and soluble anhydrite the paper presents a review of the studies dealing with the phase equilibria of the caso4 h2o system as well as the influence of other salts on the solubility of gypsum it tries to glean out the relevant information that will serve to explain the deterioration observed on building materials by the crystallization of gypsum and thus allows developing improved conservation methods

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

multiproxy approaches to investigating palaeoecology and palaeohydrology in the upper cretaceous kaiparowits formation usa

a multi technique approach by xrd xrf ft ir to characterize the diagenesis of dinosaur bones from spain abstract a combined investigation by x ray fluorescence xrf fourier transform infrared spectroscopy ft ir raman spectroscopy and powder x ray diffraction xrd supplemented with the rietveld analysis was conducted on sixty spanish dinosaur bone specimens from upper jurassic lower cretaceous to upper cretaceous age to investigate taphonomy and diagenetic processes the diffraction approach assessed in all specimens the presence of fluorapatite at various levels of percentage as the mineral phase constituting the fossil bone in addition to fluorapatite calcite and quartz were also found as main secondary phases in many specimens the infrared spectra of fossil bones show significant changes in the phosphate and carbonate band intensity with respect to a non fossil bone conversely the x ray fluorescence spectra turned out to be mainly dominated by the presence of ca obviously accompanied by phosphorus simultaneously other elements accompanying ca such as fe and sr were found at significant concentration levels a considerable amount of fe and sr ions were incorporated in the structure of fluorapatite but when their concentration was found elevated in the fluorescence spectrum the diffraction data revealed the presence of goethite feooh and celestite srso4 phases while the x ray diffraction phase analysis also revealed the presence of kaolinite dolomite barite and gypsum in some fluorescence spectra further elements like y as pb ti mn cr cu zn were present in concentration at trace level the introduction substitution of new elements with the infiltration of new phases due to diagenesis is also affecting to various extent the raman and ft ir spectra with modification of some bands and or the appearance of new bands the average crystallite size of the apatitic constituent phase was found to vary from a minimum of ca 183 a to an upper level of 2107 a no systematic relation between apatite crystallite size and age of the dinosaur bones was found that suggests a high variability of diagenetic processes affecting the growth of bone crystallites even in the same site

early diagenetic evolution of bone phosphate an x ray diffractometry analysis abstract a new crystallinity index ci based on the x ray powder diffractometric pattern of fossil bone carbonate hydroxylapatite is defined this ci value provides a semi quantitative way to estimate the diagenetic changes in archaeological and palaeontological bone phosphate the studied samples are 71 human bones from the french merovingian cemetery of saint linaire 1200 1700 bp 37 human bones from two necropoleis in niger 1000 5000 bp two cave bear bones from aldene cave southern france around 70 000 bp five bones of miocene mammals and 14 bones of mesozoic reptiles the main results are that 1 there is no correlation between the increase in the ci and the age of the sample even in one given locality 2 the ci seems to be related to the taphonomical conditions in archaeological and fossil bones 3 an increase in the ci is correlated with a loss in organic matter in one archaeological site but the quality of preservation of organic matter in fossil bones does not depend on the changes in the ci 4 the correlation between the increase in the ci and the decrease of co3amount in bones from the niger necropolies suggests a possible mechanism for the increase in crystallinity the changes of crystallinity reflect early diagenetic changes and depend on the burial environments

rayleigh distillation and the depth profile of 13c 12c ratios of soil organic carbon from soils of disparate texture in iron range national park far north queensland australia a depth and particle size specific analysis of soil organic carbon soc and its isotopic composition was undertaken to investigate the effects of soil texture or particle size on the depth profile of stable carbon isotopic composition of soc 13csoc in two tropical soils depth specific samples from two soil profiles of markedly different texture coarse grained and fine grained were separated into particle size classes and analyzed for the mass mass concentration of soc c and 13csoc within 1 m of the soil surface 13csoc in the coarse textured soil increases by 1 3 to 1 6 while 13csoc from the fine textured soil increase by as much as 3 8 to 5 5 this increasing depth trend in the coarse textured soil is approximately linear with respect to normalized c while the increase in the fine textured soil follows a logarithmic function with respect to normalized c a model of rayleigh distillation describing isotope fractionation during decomposition of soil organic matter som accounts for the depth profile of 13csoc in the fine textured soil but does not account for the depth profile observed in the coarse textured soil despite their similar climate vegetation and topographic position these results suggest that kinetic fractionation during humification of som leads to preferential accumulation of 13c in association with fine mineral particles or aggregates of fine mineral particles in fine textured soils in contrast the coarse textured soil shows very little applicability of the rayleigh distillation model rather the depth profile of 13csoc in the coarse textured soil can be accounted for by mixing of soil carbon with different isotopic ratios

a long square barrel gravity corer for sedimentological and geochemical investigation of fine grained sediments abstract large volume undisturbed sediment cores 3 m long are obtained using a modified gravity corer the corer is square in cross section 12 7 12 7 cm and is designed to facilitate acquisition and subsampling of fine grained sediments sedimentological and geochemical data demonstrate that the modified gravity corer obtains undisturbed cores and preserves the sediment water interface

gas flow through clay barriers a model for the simulation of gas flow in clayey rocks and clays is described gas migration is associated with the development of preferential paths along existing or pressure dependent discontinu

watershed control on the carbon loading of marine sedimentary particles abstract previous investigations of the factors governing organic carbon burial on continental margins have pointed toward the important apparently protective association of carbon with mineral particles these studies have also revealed dramatic transformations of carbon particle relationships at the land sea interface riverine particles in some settings lose a large portion of their loads of sorbed terrestrial carbon upon discharge to the ocean and gradually reload to similar levels with marine carbon the eel river in northern california and the adjacent continental shelf were selected as an ideal system to investigate the rates of these processes the river is episodically subject to large floods and the shelf stratigraphy preserves a record of the resultant large pulses of sediment and carbon input to the marine environment carbon isotopic carbon to nitrogen and carbon to surface area ratios of particles in flood deposits were expected to reflect the rapid unloading of terrestrial carbon from discharged particles whereas nonflood sediments that have accumulated at slower rates on the shelf were expected to carry higher loads of marine carbon our results indicate however that particles on the eel shelf have retained their loads of terrigenous carbon and that a significant portion of the particle sorbed carbon buried on the shelf is kerogen derived from the mesozoic tertiary franciscan complex we hypothesize that rates of uplift and mass wasting in the eel watershed and rates of particle delivery to and burial on the continental shelf are so rapid that kerogen is not completely oxidized and is recycled instead the loading of carbon on clay sized particles delivered to the shelf moreover is dependent on river discharge and may reflect the relative importance of different mass wasting processes during precipitation events of varying intensity the eel river system is likely to be representative of other small mountainous rivers and indicates that processes on land may play an important role in governing the amount and character of carbon being buried on the continental margins

early diagenetic remineralization of sedimentary organic c in the gulf of papua deltaic complex papua new guinea net loss of terrestrial c and diagenetic fractionation of c isotopes oceania supplies 40 of the global riverine flux of organic carbon approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems the gulf of papua on the south coast of the large island of new guinea is one such deltaic clinoform complex it receives 4 mt yr 1 particulate terrestrial organic carbon with initial particle corg loading 0 7 mg m 2 corg loading is reduced to 0 3 mg m 2 in the topset upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus and high net sediment accumulation rates of 1 4 cm yr 1 carbon isotopic analyses 13c 14c of co2 and corg demonstrate rapid 100 yr remineralization of both terrestrial 13c 28 6 and marine corg 13c 20 5 ranging in average age from modern bomb 14c 60 to 1000 yr 14c 140 efficient and rapid remineralization in the topset upper foreset zone is promoted by frequent physical reworking bioturbation exposure and reoxidation of deposits the seafloor in these regions particularly 20 m apparently functions as a periodically mixed suboxic batch reactor dominated by microbial biomass although terrestrial sources can be the primary metabolic substrates at inshore sites relatively young marine corg often preferentially dominates pore water co2 relative to bulk corg in the upper foreset thus a small quantity of young rapidly recycled marine organic material is often superimposed on a generally older less reactive terrestrial background whereas the pore water co2 reflects both rapidly cycled marine and terrestrial sources terrestrial material dominates the slower overall net loss of corg from particles in the topset upper foreset zone i e recycled marine corg leaves little residue preferential utilization of corg subpools and diagenetic fractionation of c isotopes supports the reactive continuum model as a conceptual basis for net decomposition kinetics early diagenetic fractionation of c isotopes relative to the bulk sedimentary corg composition can produce changes in 14c activity independent of radioactive decay in the gulf of papua topset upper foreset 14c of pore water co2 averaged 300 greater than corg sediment between 1 3 m depth in deposits diagenetic fractionation and decomposition aging of sedimentary corg compromises simple application of 14c for determination of sediment accumulation rates in diagenetically reactive deposits

distribution and sources of particulate organic matter in the water column and sediments of the fly river delta gulf of papua papua new guinea suspended particles from surface and bottom waters and surficial sediments from the seabed were collected throughout the fly river subaqueous delta region during the monsoon season in january 2003 because of the unusually low river discharge associated with a strong el nino water column salinities were relatively high 10 to 32 throughout most of the delta with brackish salinities 4 wt relatively high organic carbon nitrogen molar ratios oc n 20 mol mol and quite depleted stable isotopic compositions of organic carbon 13coc 27 in contrast surface sediments in the seabed displayed spatially uniform compositions that were characterized by markedly lower oc contents 1 1 0 8 wt lower oc n ratios 17 9 mol mol and relatively enriched 13coc compositions 25 5 1 1 the radioisotopic compositions of oc from a selected set of seabed samples 14coc of 408 82 indicate om in surface sediments is old 14c ages of 2800 to over 6000 years before present the ratios of organic carbon to mineral surface area exhibited by these sediments are within the typical mono layer equivalent ranges characteristic of shelf sediments and do not reflect the preferential removal of terrigenous om overall these compositions indicate that while water column pom appears to be derived mainly from terrigenous vascular plant debris and riverine estuarine phytoplankton the source of most of the sedimentary pom is aged soil oc ultimately derived from c3 vegetation we speculate that the concentrations and sources of suspended pom in the water column of the fly river delta region reflect the conditions of low river discharge low wave energy and neap tides encountered at the time of sampling in contrast pom compositions in surface sediments are consistent with the transport and deposition of old mineral bound oc most likely eroded from the upland regions of the fly river watershed which is characterized by steep slopes high precipitation and c3 tropical forests and grasslands

environmental degradation of claystones the paper presents the results of a comprehensive experimental programme carried out to study the effects of relative humidity cycling on the degradation of argillaceous rocks lilla claystone a low porosity tertiary rock was used for this purpose four aspects were analysed a the influence of the number of relative humidity cycles b the amplitude of relative humidity cycles c the stress level and d the effects of using liquid water or vapour during wetting paths the application of relative humidity cycles induced a progressive degradation of the rock in terms of accumulative irreversible volumetric swelling irreversible reduction in rock stiffness and tensile strength the irreversible expansion increased with the amplitude of the relative humidity change however it reduced with increase of the confining pressure this irreversible behaviour accelerated when liquid water was used during the wetting paths microstructural analysis has shown that the degradation pattern of lilla clayston

from bone to fossil a review of the diagenesis of bioapatite the preservation of bone or bioapatite over geologic time has presented paleobiologists with longstanding and formidable questions namely to elucidate the mechanisms processes rates and depositional conditions responsible for the formation of a fossil from a once living tissue approaches integrating geochemistry mineralogy physics hydrology sedimentology and taphonomy have all furthered insights into fossilization but several fundamental gaps still remain notably our limited understanding of 1 the timing of processes during diagenesis e g early and or late 2 the rate of bioapatite transformation into thermodynamically more stable phases 3 the controls imparted by depositional environment and 4 the role of micro biology in determining the fate of bone bioapatite dissolution or preservation the versatility of fossil bioapatite to provide information on the biology of extinct vertebrates rests on our ability to identify and characterize the changes that occurred to bioapatite during diagenesis this review will evaluate our current understanding of bioapatite diagenesis and fossilization focusing on the biogeochemical transformations that occur during diagenesis to the mineral and organic components of bone excluding teeth and enamel the analytical approaches applied to evaluate fossilization processes and outline some suggestions for future promising directions

timescales and mechanisms of ree and hf uptake in fossil bones abstract rare earth element ree patterns of fossil bones and teeth are widely used as proxies for provenance taphonomy and palaeoenvironment in order to investigate if fossil bones behave as closed systems over geologic time ree profiles were analysed by la icpms along cross sections of 54 bones from various well characterised and well dated settings these include terrestrial and marine diagenetic environments covering early triassic to holocene ages in general all fossil bones exhibit the highest ree concentrations at the outer rim gradually decreasing by up to four orders of magnitude toward the inner bone cortex intra bone ree concentration gradients decrease significantly from quaternary via tertiary to mesozoic specimens suggesting long term ree uptake and open system behaviour of fossil bone this view is further corroborated by 176lu 176hf dating of selected samples all yielding significantly younger ages than the known chronostratigraphic ages hence there is clear evidence for long term open system behaviour of fossil bones with respect to ree which is in marked contrast to currently accepted models suggesting that ree uptake is only early diagenetic although unexpected statistically significant four to seven point isochrons are observed for four fossil dinosaur bone samples and one upper triassic mastodonsaurus tooth with mswds ranging from 0 083 to 4 5 notably mobility of lu alone cannot account for the observed age patterns assuming constant lu uptake rates over time the radiometric ages should only be as low as half of the chronostratigraphic age however a six point isochron defined by subsamples of a single upper triassic mastodonsaurus tooth yields an age of 65 2 1 1 ma mswd 0 68 much younger than half of the stratigraphic age ca 234 ma hence hf must also undergo late diagenetic exchange likely mechanisms to account for the presence of statistically meaningful isochrons as well as for the late diagenetic exchange of both ree and hf are diffusion adsorption and dissolution reprecipitation processes

assessment of the clumped isotope composition of fossil bone carbonate as a recorder of subsurface temperatures abstract bone is susceptible to early diagenesis and its carbon and oxygen isotopic compositions have been suggested to reflect conditions in the soil environment and shallow subsurface during fossilization this implies open system recrystallization involving mass exchange of carbon and oxygen among bioapatite soil water and dic such recrystallization would also redistribute isotopic clumping including 13 c 18 o bonds leading to the possibility that the carbonate clumped isotope compositions of fossil bone record ground temperature during early diagenesis we assess this possibility by studying quaternary mammalian fossil bone from subtropical to polar latitudes if recrystallization is early and pervasive clumped isotope derived temperatures t 47 should closely mirror latitudinal gradients in ground temperature excluding results from a mummified specimen yielding t 47 38 c that is indistinguishable from mammalian body temperature we find that t 47 values are intermediate between mammalian body temperature and ground temperature suggesting partial recrystallization of bone carbonate xrd analyses show that the nature and extent of diagenesis varies among the samples and does not relate in a straightforward manner to t 47 no clear correlation exists between t 47 and mean annual temperature or mean warm season temperature furthermore bone tends to retain the 18 o enriched signature of body water suggesting incomplete oxygen isotope exchange with meteoric waters incomplete carbon and oxygen isotope exchange between bone carbonate and soil waters is also indicated for a set of late miocene bone enamel pairs from a sequence of stacked paleosols in northern china analysis of bone as old as early cretaceous shows that bone carbonate is susceptible to later diagenesis at elevated burial temperatures although t 47 does not closely conform to maximum burial temperature again suggesting partial recrystallization or recrystallization during different stages of the burial and exhumation circuit these results show that carbon oxygen and clumped isotopes in fossil bone are capable of recording aspects of early diagenesis and the subsequent burial and exhumation history but that distinguishing among different effects is challenging however clumped isotopes in bone can provide useful directional constraints on past temperatures for example t 47 values higher than body temperature necessarily place lower limits on maximum burial temperatures and those lower than body temperature place upper limits on minimum fossilization temperatures

an investigation into the internal and external variables acting on crystallinity index using fourier transform infrared spectroscopy on unaltered and burned bone abstract the crystallinity index is a measure of structural order in bone and is potentially an extremely useful tool in bioarchaeology since it can assist in sequencing bones into chronological and or stratigraphic order act as an indicator for preservation and assist in reconstructing burning events unfortunately concerns over influencing variables and bone sampling issues inhibit full and wide spread adoption of this approach an attempt has been made to determine the influence of a number of internal and external variables on bone crystallinity changes ci c p and c c were calculated using fourier transform infrared spectroscopy attenuated total reflectance ftir atr on modern burned and unburned faunal bone samples were taken systematically across bone elements and on the internal and external surfaces the ci results support previous work and show increases with burning intensity it is also shown that extrinsic variables such as temperature and duration of burning have more of a significant influence on ci values than intrinsic variables such as location of sample site on the bone a sampling strategy is suggested for those wishing to use the ci on bone in archaeological contexts

diagenesis of bones from eland s bay cave abstract archaeological bone specimens have been shown in a number of studies to have increased mineral crystallinity when measured both by xrd and ir spectrometry in this study we investigated the relative dating potential of ir crystallinity measurements based on the splitting factor or sf on a sample of 54 specimens from the holocene sequence at eland s bay cave south africa in addition to sf c and n measurements were obtained using a carlo erba elemental analyser results of the study indicate that i a reasonably good correlation between sf and time exists in bones under 20 000 years bp but that the increase in sf levels off after this period and ii correlations between diagenetic indicators such as sf c and n are better than those between any indicator and time an excellent correlation r2 0 81 was obtained between sf residing in the inorganic phase and n residing in the organic phase suggesting that diagenesis of the two phases of bone are linked implications of the data for monitoring stratigraphic anomalies at archaeological sites are discussed

authigenic minerals in fossil bones from the mesozoic of england poor correlation with depositional environments abstract petrographic microscopy x ray diffractometry and scanning electron microscopy energy dispersion spectrometry studies of cavity infills of bone samples from english mesozoic vertebrate deposits isle of wight swanage lyme regis aust cliff westbury garden cliff tytherington allow a better understanding of the distribution of authigenic minerals in bone voids and shed light on the importance of diagenetic processes on bone preservation surprisingly few minerals were identified as void fillers in all depositional environments carbonates sulphides oxides and sulphates being most abundant calcite is present in almost all samples pyrite is very common in voids as well as incorporated into bone francolite in many samples several generations of infills are found often consisting of layered cements the co occurrence of the common minerals indicates anaerobic slightly alkaline and often sulphate reducing environments in the bone voids later oxidation is common in iron minerals calcite pyrite and barite lack unambiguous environmental control whereas sphalerite is possibly an indicator for marine deposits freshwater deposits show no particular mineral combination which would help in separating them from other environments in some instances sediment infills and pyrite show geopetal structures

molecular evidence for lignin degradation in sulfate reducing mangrove sediments amazonia brazil abstract molecular lignin analyses have become a powerful quantitative approach for estimating flux and fate of vascular plant organic matter in coastal and marine environments the use of a specific molecular biomarker requires detailed knowledge of its decomposition rates relative to the associated organic matter and its structural diagenetic changes to gain insight into the poorly known processes of anaerobic lignin diagenesis molecular analyses were performed in the sulfate reducing sediment of a north brazilian mangrove organic matter in samples representing different diagenetic stages i e fresh litter a sediment core and percolating water was characterized by alkaline cuo oxidation for lignin composition element c n and stable carbon isotope analyses on the basis of these results and on a balance model long term in situ decomposition rates of lignin in sulfate reducing sediments were estimated for the first time the half life t 1 2 of lignin derived from mangrove leaf litter mainly rhizophora mangle was 150 yr in the upper 1 5 m of the sediment associated organic carbon from leaf tissue was depleted to 75 within weeks followed by a slow mineralization in the sediment t 1 2 300 yr unlike the known pathways of lignin diagenesis even highly degraded lignin did not show any alterations of the propyl or methoxyl side chains as evident from stable acid to aldehyde ratios and the proportion of methoxylated phenols vanillyl and syringyl phenols aromatic ring cleavage is probably the principal mechanism for lignin decay in the studied environment cinnamyl phenols were highly abundant in mangrove leaves and were rapidly depleted during early diagenesis thus the cinnamyl to vanillyl ratio could be used as a tracer for early diagenesis even under the sulfate reducing conditions syringyl phenols were removed from dissolved organic matter in interstitial water probably by sorption onto the sediment suspended organic matter in a mangrove creek showed a different lignin signature than its source namely sedimentary organic matter or mangrove litter with clear evidence for propyl side chain oxidation this was probably attributable to erosion of aerated thin sediment surface layers during mangrove inundation although particulate and dissolved organic matter in the mangrove creek have a common source their compositional patterns were different because of different pathways of release degradation and transport to the creek

elemental composition and diagenetic alteration of dinosaur bone distinguishing micron scale spatial and compositional heterogeneity using pixe abstract proton induced x ray emission pixe analysis of thirteen late cretaceous hadrosaurid tyrannosaurid and tyrannosaurus and early jurassic dilophosaurus dinosaur bones two late cretaceous crocodylians one plesiosaur and three modern archosaurs rhea and caiman documents micron scale diagenetic patterns of elemental uptake and loss pixe detected al si p s cl k ca ba mn fe sr y and nd at levels 1000 ppm and ti cr ni zn as zr and u at trace amounts 100 of modern this enrichment may reflect the migration of ca and p between the hydroxylapatite matrix and the surrounding sediment after death resulting in early diagenetic loss followed by uptake and recrystallization on crystallite surfaces the elemental composition of fossil bone from the early jurassic dinosaur dilophosaurus is distinguished by elevated as ppm generally not present in the late cretaceous dinosaurs we suggest that as is adsorbed from the reductive dissolution of as rich iron oxyhydroxides in the local aquifer and is not reflective of mesozoic atmospheric conditions or arsenic toxicosis in dinosaurs pixe allows us to reaffirm that the histological structure tissue density and high surface area of the vascular canals of dinosaur haversian bone affect postmortem elemental enrichment and depletion and to quantify these differences at scales as small as 1 5 m

heave of a railway bridge modelling gypsum crystal growth the heave of the central pillars of a railway bridge founded on large diameter bored piles is a consequence of gypsum crystal growth in an anhydritic claystone stratum underlying the tip of the piles the heave mechanism is explained by the presence of circulating water in the fractured anhydritic level the model developed to reproduce the observed phenomena integrates a set of balance equations that includes two soluble species gypsum and anhydrite in addition to the inert minerals kinetic equations for dissolution and precipitation mechanical equilibrium and the effect of precipitated mass on induced volumetric strains model calculations are compared with measured long term field records of heave most of the model parameters are physico chemical constants a positive feature that limits the effort to calibrate material constants the model is capable of accurate mid term heave prediction and it also correctly includes the effect of building a surface embankment with the purpose of reducing th

terrestrial organic carbon contributions to sediments on the washington margin elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the columbia river basin and the washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments the biomarkers include an homologous series of long chain n alkanes derived from the surface waxes of higher plants phenolic and hydroxyalkanoic compounds produced by cuo oxidation of two major vascular plant biopolymers lignin and cutin all marine sediments including samples collected from the most remote sites in cascadia basin showed organic geochemical evidence for the presence of terrestrial organic carbon using endmember values for the various biomarkers determined empirically by two independent means we estimate that the terrestrial contribution to the washington margin is 60 for shelf sediments 30 for slope sediments and decreases further to 15 in basin sediments results from the same geochemical measurements made with depth in gravity core 6705 7 from cascadia seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the washington margin can be applied to the study of sediments depositing in this region since the last glacial period

the post mortem history of a bone revealed by its trace element signature the case of a fossil whale rostrum abstract studies dedicated to palaeoenvironments and taphonomy have made wide use of rare earth elements ree contents of fossil bones as proxies however the complex diagenetic history of individual specimens combined with intra bone ree fractionation and the uncertain timing of ree uptake generally prevents the robust interpretation of ree patterns in this case study we show that combining ree analysis with on the one hand histology and microstructural observations and on the other hand additional analyses of other trace elements allows deciphering at least three distinct trace element uptake stages as well as one leaching event more than 35 trace elements including the ree are analysed using laser ablation inductively coupled plasma mass spectrometry la icpms within compact rostrum bones of the miocene pliocene beaked whale globicetus hiberus from deep sea deposits and a comparable extant specimen blainville s beaked whale mesoplodon densirostris comparison of the extinct and the extant bones allows a better quantification of the diagenetic trace element content this study highlights the crucial role played by diagenetic minerals such as the fe mn oxyhydroxides in the uptake and release of trace elements co ni ti v zr hf and nb and ree by bones in response to changes of the diagenetic fluid redox conditions over time such changes of the geochemical environment help constraining the post mortem history of the bone and its interaction with diagenetic fluids we conclude that the unique interpretation of geochemical proxies within individual fossil bones requires a thorough investigation of each individual specimen

late quaternary vegetation change in the tari basin papua new guinea the changes in late quaternary vegetation at two sites in the tari basin central highlands of new guinea are presented haeapugua basin 1650 m altitude and tugupugua basin 2300 m altitude lie within the lower montane forest belt where the climate is characterised by high relative humidity and low seasonality pollen analysis mineral magnetics carbonised particle analysis and dating by radiocarbon and thermoluminescence techniques are employed to reconstruct the vegetation and sediment history the sequences include fragmentary interglacial interstadial records from before 50 000 yr b p and a continuous record from at least 28 000 yr b p to the present the study shows that prior to 21 000 yr b p vegetation in the basin was dominated by fluctuating proportions of tree taxa indicative of a forested environment the montane forest taxon nothofagus is important throughout the record although other tree taxa including castanopsis myrtaceae dacrydium and pandanus attain dominance at different times under the influence of a range of environmental factors the creation of an open environment around 21 000 yr b p is considered to be a consequence of the arrival of humans in the region the late glacial transition between 14 500 and 8500 yr b p is a period of climatic instability with landscape and vegetation adjustments proceeding at different rates across the highlands vegetational adjustments match modern ranges by about 8500 yr b p when swamp forest developed across the sites at the lower altitude site there are indications of anthropogenic forest disturbance associated with swamp forest clearance commencing around 1700 yr b p and intensifying through to the present forest clearance is recorded only after 700 yr b p at the higher site where agriculture was probably only sustainable after the introduction of sweet potato ipomoea batatas

states of preservation of bones from prehistoric sites in the near east a survey abstract a survey of the states of preservation of organic material in 30 fossil bones from 16 different prehistoric sites in the near east shows that whereas almost all the bones have little or no collagen preserved they do with few exceptions contain non collagenous proteins these macromolecules therefore represent an important reservoir of indigenous fossil bone constituents

an x ray diffraction xrd and x ray fluorescence xrf investigation in human and animal fossil bones from holocene to middle triassic we examined by rietveld refinement of x ray diffraction patterns a series of 61 human and animal fossil bones in an age range from present time to middle triassic around 245 ma this approach supplemented by elemental analysis according to x ray fluorescence has permitted to obtain a quantitative evaluation of the mineralogical phases in the specimens thus allowing to reconstruct the mineralization process involved concerning the apatite phase after adopting a monoclinic geometry for the unit cell the method permits to determine with fair degree of precision the unit cell volume which is found to decrease in relatively short geological times as a function of the fluorine substitution process for the hydroxyl group oh after excluding the role of a high temperature fire treatment to the bones it is found that a certain linear correlation may exist over the geological time scale involved between the age of the specimen and the average crystallite size this observation permits to use the xrd pattern as an evaluation of the age of the fossil although the stratigraphic observations where available remain as the main reliable source for dating such biomaterials the uncertainty related to this age estimation may be hardly better than 15 20 in absolute because of various assumptions involved in the xrd methodology used and in the variability of the burial environment that may be subjected to discontinuous changes over the very long time of deposition

bone diagenesis new data from infrared spectroscopy and x ray diffraction abstract this paper combines non destructive high resolution fourier transform infrared spectroscopic techniques attenuated total reflectance in the mid infrared atr and diffuse reflectance in the near infrared nir with x ray diffraction and rietveld analysis in the study of bone diagenesis sixty fossil bones from two upper miocene sites in greece pikermi and chalkoutsi and one upper pleistocene site in cyprus aghia napa are investigated in comparison to various mineral and biological apatites diagenetic trends common to all these sites include a subtle but systematic decrease of the unit cell volume and a axis of carbonate hydroxylapatite as well as a parallel increase of the coherence length along the c axis chemometric modelling reveals that the changes in the unit cell and the coherence length are highly correlated to and can be predicted on the basis of the atr spectra besides using chemometrics as a convenient predictive tool we have been able to identify that the correlation with the xrd data is primarily based on the intensity of infrared bands at 577 865 and 1092 cm 1 as well as on the position of the 1 phosphate mode at ca 960 cm 1 these structural changes constitute the vibrational signature of diagenesis throughout our set of bone samples and can be accounted for by the stabilization of a distorted co 3 2 species in the b sites of apatite and to a lesser extent by the substitution of oh by f nir spectroscopy allowed for the identification of a well defined h 2 o species absorbing at 5318 and 7240 cm 1 this species is labile appears to characterize mostly biogenic apatite and is therefore considered to be chemisorbed on the surface of the crystallites

mineralogical and compositional changes in bones exposed on soil surfaces in amboseli national park kenya diagenetic mechanisms and the role of sediment pore fluids abstract bones exposed on tropical savannah grasslands of amboseli national park kenya undergo extensive post mortem alteration within 40 years a combined analytical approach involving tem microscopy trace metal analysis ftir spectroscopy and petrographic analysis has revealed a complex dynamic diagenetic environment operating within exposed bones driven by evaporative transport of soil water from the bone soil interface to the upper exposed surface of the bone this process results in extensive bone soil water interaction and is responsible for increases in the concentrations of trace elements such as ba and la of 100 1000 within 15 years the maximum and mean size of bone crystallites increases with continued exposure this change in mean crystallite length is correlated positively with increases in bone crystallinity which in turn is associated with degradation of the bone protein microbial decomposition is rarely observed in the amboseli bones but where present resulted in severe dissolution reprecipitation of bone mineral many bones showed extensive permineralization of the larger vascular spaces with calcite and barite and to a lesser extent crandallite permineralization of unburied bones may account for 95 reduction in macro micron millimeter scale porosity in the bone within 2 years of death we produce a model for pre burial diagenesis of bone in arid tropical environments that highlights extensive alteration of bone chemistry within 1 40 years post mortem

lu hf isotope systematics of fossil biogenic apatite and their effects on geochronology abstract reliable methods for direct dating of biogenic apatite from pre pleistocene fossils are currently not available and recent attempts using the lu hf decay system yielded highly inaccurate ages for both bones and teeth the geological processes accounting for this poor accuracy of lu hf chronometry are not yet understood here we explore lu hf systematics in fossil bones and teeth in detail by applying five different sample digestion techniques that are tested on bones and composites of bone and sediment our current dataset implies that dissolution methods only slightly affect the resulting lu hf ages while clear differences between the individual digestion techniques became apparent for element concentrations by analysing the insoluble leftovers from incomplete sample dissolution four main reservoirs of hf in fossil bones were identified 1 a radiogenic end member associated with apatite 2 an unradiogenic end member represented by the authigenic minerals or the embedding sediment 3 a highly unradiogenic end member that can be attributed to detrital zircon and 4 a moderately soluble phase probably a zr hf phosphate that yielded very low lu hf but a highly radiogenic hf isotope composition at the same time this zr hf phase must have been precipitated within the fossil bone sample at a late stage of burial history thereby incorporating radiogenic 176 hf released from apatite surfaces over geological timescales a second focus of our study is the effect of different sediment matrices and of crystal size on the preservation of pristine lu hf isotope compositions in bioapatite because near depositional lu hf ages of phosphate fossils have previously been reported for the london clay england and a calcareous marl from tendaguru tanzania we herein investigate specimens fossilised in carbonate matrices calcareous marl from oker germany carbonate concretions from the santana formation brazil carbonate from the eifel germany and argillaceous matrices with low permeability oil shale of messel germany posidonienschiefer of holzmaden germany materials analysed from these localities include bones teeth conodonts as well as coproliths and diagenetic minerals siderite montgomeryite and messelite near depositional lu hf ages were obtained for a bony fish sample notelops brama encapsulated in an early diagenetic carbonate concretion from the early cretaceous santana formation brazil and for conodonts from a middle devonian carbonate from the eifel germany low 176 lu 177 hf ratios in all materials from the middle eocene messel oil shale e g bones fish scales sediment siderite result in poor age precision and an age that is near depositional due to this large analytical error in agreement with previous results all other ages determined here for both bones and teeth are by far younger than respective chronostratigraphic ages a model illustrating the behaviour of lu and hf over time with respect to the fossilisation process is presented which accounts both for the formation of a late diagenetic radiogenic zr hf phase and long term open system behaviour the continuous lu hf element exchange between the fossils and the embedding sediment is probably related to the nm scale crystal size of fossil bones dentine and also of enamel that generate large surface areas facilitating sorption desorption processes and open system behaviour

sources and distribution of organic matter in a river dominated estuary winyah bay sc usa abstract the sources and distribution of organic matter om in surface waters and sediments from winyah bay south carolina usa were investigated using a variety of analytical techniques including elemental stable isotope and organic biomarker analyses several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range the dissolved organic carbon doc concentrations of surface waters ranged from 7 mg l 1 in the lower bay stations closest to the ocean to 20 mg l 1 in the river and upper bay samples there was a general linear relationship between doc concentrations and salinity in three of the four sampling periods in contrast particulate organic carbon poc concentrations were significantly lower 0 1 3 mg l 1 and showed no relationship with salinity the high molecular weight dissolved om hmw dom isolated from selected water samples collected along the bay displayed atomic carbon nitrogen ratios c n a and stable carbon isotopic compositions of organic carbon 13coc that ranged from 10 to 30 and from 28 to 25 respectively combined such compositions indicate that in most hmw dom samples the majority of the om originates from terrigenous sources with smaller contributions from riverine and estuarine phytoplankton in contrast the c n a ratios of particulate om pom samples varied significantly among the collection periods ranging from low values of 5 to high values of 20 overall the trends in c n a ratios indicated that algal sources of pom were most important during the early and late summer whereas terrigenous sources dominated in the winter and early spring in winyah bay bottom sediments the concentrations of the mineral associated om were positively correlated with sediment surface area the c n a ratios and 13coc compositions of the bulk sedimentary om ranged from 5 to 45 and from 28 to 23 respectively these compositions were consistent with predominant contributions of terrigenous sources and lesser but significant inputs of freshwater estuarine and marine phytoplankton the highest terrigenous contents were found in sediments from the river and upper bay sites with smaller contributions to the lower parts of the estuary the yields of lignin derived cuo oxidation products from winyah bay sediments indicated that the terrigenous om in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil om based on the lignin phenol compositions most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region a few samples displayed lignin compositions that suggested a more significant contribution from marsh c3 grasses however there was no evidence of inputs of spartina alterniflora a c4 grass remains from the salt marshes that surround the lower sections of winyah bay

diagenetic evolution and experimental heating of bone phosphate abstract fresh bone samples have been experimentally heated with monitoring of the evolution of several parameters the comparison of these results with a large suite of measurements performed on archaeological and fossil bones gave valuable clues about some possible mechanisms of the diagenetic evolution of bone crystallinity the main conclusions of this comparison are that 1 bone organic matter protects the mineral phase and thus needs to be significantly altered before crystallographic changes occur and 2 loss of structural carbonate may be a key factor in the increase of bone crystallinity the crystallinity of carbonate hydroxylapatite seems to monitor the degree to diagenetic evolution and thus may be used to detect diagenetic alteration of biogenic paleoenvironmental signals in archaeological and fossil bones independently of their age

importance of biologically mediated removal of fine sediments from the fly river plume papua new guinea abstract a freshwater plume from the fly river papua new guinea stretched to the south west over a distance of more than 150 km from the estuary towards torres strait the highly turbid freshwater was mixed with the relatively clear water of the gulf of papua producing a sharp boundary around 23 salinity sediment concentrations were typically more than 50 mg l 1 inside the turbid water mass and were rapidly reduced to a few milligrams per litre in the area where salinity was still as low as 26 the area had relatively high levels of phytoplankton 1 g chl l 1 resulting in rapid depletion of nitrate and phosphate biological as well as physico chemical flocculation processes seemed responsible for the rapid removal of sediments from the plume settling particles collected near the estuary consisted largely of fine sediments bound loosely by flocculant organic matter and contained very few plankton and their remains further away from the estuary however settling particles were dominated by colonies of phytoplankton fecal pellets and macroscopic aggregates of apparently biological origin fine sediments were found firmly attached to or embedded in these settling particles the area of high biological activities in the plume probably functions as a barrier limiting a further offshore transport of sediments

loss of organic matter from riverine particles in deltas abstract in order to examine the transport and burial of terrigenous organic matter along the coastal zones of large river systems we assessed organic matter dynamics in coupled river delta systems using mineral surface area as a conservative tracer for discharged riverine particulate organic matter pom most pom in the rivers studied n 6 is tightly associated with suspended mineral material e g it is sorbed to mineral surfaces average organic loadings in the amazon river 0 67 0 14 mg c m 2 the river for which we have the largest dataset are approximately twice that of sedimentary minerals from the amazon delta 0 35 mg c m 2 stable carbon isotope analysis indicate that approximately two thirds of the total carbon on the deltaic particles is terrestrial the combined surface normalized isotope distinguished estimate is that 70 of the amazon fluvial pom is not buried in the delta consistent with other independent evidence aller et al 1996 losses of terrestrial pom have also been quantified for the river delta systems of columbia in the usa fly in new guinea and huange he in china if the losses of riverine pom observed in these river delta systems are representative of rivers worldwide then the surface constrained analyses point toward a global loss of fluvial pom in delta regions of 0 1 x 1015 g c y 1

biomass burning in indonesia and papua new guinea natural and human induced fire events in the fossil record abstract microscopic charcoal preserved in sediments from ten wetlands in the indonesian and papua new guinea region provide a proxy record of regional fire events during the last 20 000 years two periods of high regional charcoal frequency are encountered during the last glacial transition 17 000 9000 years b p and the middle to late holocene 5000 years b p to the present despite the presence of humans in the region throughout the last 20 000 years there is no suggestion that on a regional spatial scale fire frequencies were solely related to changing subsistence patterns of the human population pollen data from these same sites suggest that during times of high charcoal the rate at which vegetation changes represented by the fossil pollen spectra also increases high climate variability may promote a greater community turnover rate and in turn a more fire susceptible forest community rapid climate change and high variability during the last glacial transition and intensification of el nino related climate variability during the middle to late holocene may have been important mechanisms for promoting fire in rainforest environments and maintaining diversity of tropical rain forests

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control