conditions of formation and diagenetic evolution of upper proterozoic phosphate nodules from southern sweden evidence from petrology mineral chemistry and isotopes abstract dark gray to black cryptocrystalline francolite occurs as nodules 2 8 cm in diameter which are embedded in organic matter rich mudstones of the visingso group upper proterozoic southern sweden the 13cpdb values 18 4 to 0 98 of structural co2 complemented by studies of the petrographic character and strontium isotopic composition of francolite indicate precipitation in the suboxic and sulfate reduction zones francolite is intergrown with berthierine that has formed in the suboxic fe reduction zone calcite enriched in mn and to a lesser extent fe occurs as fracture and void fillings and as replacement of francolite mn and mg rich calcian siderites have precipitated as pseudomorphs after bacteria in the zone of microbial methanogenesis the carbon 13 c pdb 0 75 to 7 04 and oxygen 18 o pdb 14 21 to 10 58 isotopes of calcite suggest derivation of carbonate ions from microbial methanogenesis and from thermal decarboxylation of organic matter at temperatures of 60 to 80 c some of the void and fracture filling calcites 13 c 20 8 to 18 63 18 o 5 46 to 5 21 have however precipitated at lower temperatures 25 30 c in the sulfate reduction zone

palaeoenvironmental reconstruction of a condensed hardground type depositional sequence at the cretaceous tertiary contact in the parnassus ghiona zone central greece abstract phosphatic hardgrounds at the k t boundary in the parnassus ghiona zone reflect a major stratigraphic break the hardgrounds developed on top of the uppermost maastrichtian beds which represent a condensed pelagic carbonate sequence of seamount type synsedimentary lithification and hardground formation took place on shallow periodically emerged seafloors phosphate cementation includes fillings of intra and inter particle porosity and occludes passive framework open spaces as well as rim cement fabrics developed through mineralization by non phototropic microbial communities within the hardground superstructure a highly condensed phosphate sediment was precipitated post dating the hardground formation phosphate cementation was developed under well oxygenated conditions involved in a low productivity phosphogenic system phosphate ions were released into pore waters through bacterial decomposition of organic matter glauconite developed due to prolonged contact of lithified chalk with seawater the irregular bored impermeable and phosphate cemented pavements are covered by stratiform and columnar laminated phosphatic stromatolitic crusts trapping early paleocene pelagic sediments deposited during the subsequent danian transgression the source of phosphorus was external either marine or continental phosphatization occurred during the bacterial degradation of the organic sheaths pyrite crystals within the stromatolitic laminae suggest a sulphidic environment beneath the mat forming communities successive phases of intraformational reworking resulted in mature hardground development lags from eroded subjacent hardgrounds were accumulated in neighbouring submarine depressions marly material rich in quartz has been concentrated along discontinuities on former topographic heights both the phosphatic hardground and stromatolites have been assimilated by a cryptocrystalline phosphatic material rich in clay iron oxides and quartz considered to originate from subaerial weathering phoscretization

microbial processes in the negev phosphorites southern israel microscopic and sem observations indicate that cyanobacterial activity was important during the formation of the campanian negev phosphorites one aspect of such activity is the development of phosphorites through the binding of phosphate particles these sediments often demonstrate a conspicuous smooth cryptalgal lamination the algal binder was fossilized as intertwined phosphatic sheaths that coat and seal off the phosphate grains different types of sheaths representing the remnants of an algal community were found thick apatite overgrowth commonly deforms the microbial fossils converting them into barely recognizable forms fabrication of phosphate particles is another aspect of the microbial activity phosphate algal coated grains are a common constituent of the negev phosphorites the algal coating consists of stacked phosphatic tubes and colonies of coccoid unicells with an apatite infilling fragmented phosphatic sheath bundles form another type of phosphate particle produced by algae obliteration of algal structures is common resulting in undifferentiated groundmasses of cryptocrystalline apatite the extremely close connection between microbial structures and phosphatization processes suggests cyanobacterial participation in phosphorus enrichment

reflectance spectroscopy guided broadband spectral derivative approach to detect glauconite rich zones in fossiliferous limestone kachchh region gujarat india abstract in this study we processed visible near infrared vnir and shortwave infrared swir bands of advanced spaceborne thermal emission and reflection radiometer aster data to delineate glauconite bearing zones in fossiliferous limestones quaternarysediments and paleogene shales in the lakhpat region of the kachchh province in india glauconitic limestone has subtle absorption features at 2 3 m when compared to the absorption features of pure limestones that are dominated by the strong absorption feature of calcite at 2 33 m additionally the spectrum of glauconite rich limestone also has an absorption feature at about 0 9 m due to the crystal field effect of fe2 present in the glauconite structure and a feeble spectral feature due to the presence of al oh bonds at about 2 2 m aster resampled reflectance spectra of these rocks have been used as the reference to construct different image enhanced products we derived index images and eigen matrix analysis based principal components pcs using aster bands to delineate different rocks in the study area these index images are derived to enhance broadband absorption features observed in shales glauconite bearing and pure limestones respectively principal component images are prepared using the spectral bands defining the broadband absorption features of these rocks we found that the pc image composite derived using pc 8 pc 2 and pc 7 is suitable to discriminate basalts limestones and shales from each other while an index image colour composite prepared using three independent index images is suitable for the identification of lithological contacts between quaternary sediments shales and fossiliferous limestones respectively in addition the aster resampled rock spectrum of glauconite has a relatively lower spectral gradient in comparison to the gradient observed in the spectrum of fossiliferous limestone within the spectral range of bands 6 and 8 the spectral derivative images are derived for discriminating glauconite rich zones within the limestone using the contrast in the spectral gradient of limestone and glauconite rich limestone the image composite of three spectral derivatives was compiled from the derivative image of bands 4 to 3 bands 5 to 7 and bands 6 to 8 to discriminate glauconite rich zones from pure fossiliferous limestone our study proposes the potential use of broadband reflectance spectroscopy in the mineral mapping of sedimentary provinces

δ18o po43 and δ18o co32 from belemnite guards from eastern europe implications for palaeoceanographic reconstructions and for the preservation of pristine isotopic values abstract the oxygen isotopic composition of coexisting carbonate and phosphate from belemnite rostra was measured according to well established techniques in 42 samples of early and middle jurassic age and in five samples of oyster shells most of the samples come from various locations in the western carpathians of slovakia and ukraine and from central poland three samples come from the isle of skye the phosphate content of belemnite rostra though variable is systematically very low consistently lower than about 0 3 however this phosphate concentration is close to that found in shells of modern marine organisms including pelecypods gastropods and sepia cuttlebones which in some way could be considered the modern belemnite counterpart the measured oxygen isotopic composition of carbonate is within the normal range of values obtained from these fossils ranging from about 1 3 to about 0 6 pdb 1 with the exception of three samples the 13 c values range from about 0 8 to about 2 8 pdb 1 with the single exception of one sample from the isle of skye the oxygen isotopic composition of phosphate from belemnite rostra ranges from 19 8 to 24 9 v smow 22 of the samples measured showing 18 o values equal to or heavier than 23 0 in contrast the oyster values are considerably lighter in the case of both carbonate and phosphate 18 o enriched values can hardly be related to diagenetic processes that normally cause an oxygen isotope shift towards light values if deposition temperatures are calculated from the heavily enriched values by means of the equation of longinelli and nuti earth planet sci lett 19 1973 373 376 and assuming the 18 o of jurassic ocean water to be equal to 1 taking into account the lack of ice caps during the jurassic the obtained temperatures range from about 8 c to about zero these temperatures are obviously unreliable when mesozoic palaeoceanographic conditions and palaeoclimate are taken into account two different hypotheses are suggested to explain these results other hypotheses being rejected as unreliable 1 phosphate derived from the decaying organic matter of belemnites might have been introduced into belemnite rostra by early diagenetic fluids if the phosphate of belemnite organic matter was isotopically heavy as happens nowadays in the flesh of molluscs the inflow of this phosphate into the rostra could be responsible for the very positive 18 o values shown by many belemnite rostra this hypothesis is suggested by h w 2 previous oxygen isotope measurements on upper cretaceous belemnites yielded 18 o values very close to the most positive values obtained from lower tertiary pelecypods and fish teeth which are known to precipitate their phosphate under isotopic equilibrium conditions with seawater these data suggest the possibility that the phosphate in belemnite rostra is primary phosphate so that the very positive data reported here can be considered the result of good preservation of the pristine isotopic composition of primary phosphate consequently the only way to explain the very positive 18 o values is to consider the oxygen isotopic composition of jurassic ocean water to be more positive than nowadays by at least 3 this hypothesis is suggested by a l and a d m

seismostructural studies in the pyrenees evolution and recent results seismic studies of the last ten years in the pyrenees deep seismic profiles fan profiles at critical distance teleseismic travel time residuals seismicity from temporary networks and their most significant results concerning crustal thickness in the different structural units of the range sharpness of the transition between these units at depth and east west lateral evolution are reviewed in this paper focal mechanisms for three recent earthquakes ofm 4 are given and connections of local seismicity with major tectonic structures such as the north pyrenean fault and its western prolongation at depth are described

alterations in guano phosphates and mio pliocene carbonates of table mountain santa barbara curacao abstract the table mountain santa barbara consisting of the mio pliocene seroe domi limestone formation was probably covered with a guano layer in the pleistocene solutions carrying guano derived phosphate percolated downwards resulting in partial phosphatization of the underlying limestones only two phosphate minerals are present in the table mountain apatite and whitlockite phosphatization includes both replacement of the original carbonate or pre phosphate dolomite and cementation in primary as well as secondary porosity cryptocrystalline isotropic phosphate cement micro crystalline apatite isopachous apatite fringe cement multiple zoned apatite crusts rhombic whitlockite cements two factors controlled the final distribution of the phosphate within the table mountain firstly changing positions of the sea level and therefore of the diagenetic environments determined the overall distribution of the phosphatized interval a horizontal layer 98 128 m above sea level sandwiched between two non phosphatized limestone units original carbonate facies and mineralogy was the second controlling factor causing the final variations in degree of phosphatization the limestones comprise two lithofacies a coralliferous limestone lenses erratically distributed amidst and b micritic limestones these coralliferous limestones are phosphatized preferentially forming so called phosphate pockets sharply outlined within a non phosphatized micritic limestone host these pockets are characteristically organized into five zones which are described in detail higher original porosity permeability of the coralliferous limestone lenses as compared to the micrites additionally enhanced by a phase of pre phosphate dolomitization determined preferential phosphatization of this facies type a second controlling factor was the original carbonate mineralogy and resulting dia

petrology and major element geochemistry of peru margin phosphorites and associated diagenetic minerals authigenesis in modern organic rich sediments abstract new petrographic and major element geochemical data from modern peru margin upper slope outer shelf phosphorites are presented which provide insight into their origin and paragenetic relationship with other authigenic minerals glauconite pyrite and dolomite occurring in organic rich sediments glauconites are precipitated relatively early following the partial reduction of ferric iron and following this process phosphate pyrite and then dolomite precipitation take place at progressively deeper levels in the sediment in association with microbial reduction of sulfate as in many ancient economic phosphorite deposits the phosphatic facies here consist of nodules crusts coatings and strata composed of phosphatic pelletal grains ooids structureless grains intraclasts clumps and biogenic grains in association with organic rich biosiliceous sediments all are considered to have formed within a few centimeters or within a few tens of centimeters below the sediment water interface important factors that influence which morphology will tend to develop include the amount of available pore space the presence of suitable nucleation sites the amount and size of siliciclastic detritus incorporated as inclusions and the relative solution chemistries of the precipitating solutions bacterial mediation may play an important but as yet unspecified role in the precipitation process textural data and factor analysis of chemical data suggest that structureless pellets are relatively inclusion free na f mg co3 substituted pore water precipitates whereas ooids are inclusion rich pore water precipitates poor in lattice substituted components variations in nodular cement birefringence and crystallinity are suggested to have been produced by similar lattice substitutions that directly reflect pore water carbonate ion concentrations and thus relative degrees of organic matter degradation phosphate and dolomite are intimately mixed yet mineralogically distinct phases in phosphatized dolomicrites depth stratified threshold carbonate ion concentrations may control the lower limit at which phosphatic minerals may precipitate below depths of a few centimeters excessive carbonate ion concentrations and diminished reactive iron and sulfate concentrations favor the development of dolomite while precluding further development of phosphatic minerals and pyrite periodic sediment reorganization bioturbation current winnowing and erosion mass wasting etc plays an important role in both concentrating pelletal grains and maintaining nodules and crusts at critical depth levels in the sediment as well as mixing ordered mineral parageneses into complicated sequences

analysis of mechanical and permeability properties of mudstone interlayers around a strategic petroleum reserve cavern in bedded rock salt abstract using salt caverns for underground strategic petroleum reserve spr is the most popular storage method in the world due to its high security and economy the rock salt resources in china are mainly bedded salt containing many mudstone interlayers in this paper ph test and total acid number tan tests are carried out to determine the different degradation mechanisms caused by brine mudstone and oil mudstone interactions uniaxial and triaxial compression tests and permeability tests were carried out to determine the mechanical and permeability parameters of the mudstone interlayers under brine and crude oil immersions results show that the thermochemical sulfate reduction tsr will not occur during the crude oil storage the reaction between the anhydrite and the naphthenic acid is the major reason that causes damage to the mudstone interlayers both the crude oil and brine can cause damage to the mudstone interlayers but the damage caused by brine to the mudstone interlayers is much greater than that caused by crude oil because of their different reaction mechanisms due to the plugging effect by the asphaltene and resin present in crude oil the permeability of the samples decreases 67 5 after they have been immersed in crude oil for 30 days even though the rock damage is still accumulating this property is beneficial for the spr salt caverns to keep good tightness

bacterial origin of east australian continental margin phosphorites many models of the origin of marine phosphorites require a sediment rich in organic matter which by decomposition releases phosphorus for the precipitation of carbonate fluorapatite1 7 this concept is useful in explaining contemporary phosphorite in areas of very high productivity off the coasts of peru chile and south west africa8 10 where there are high organic matter fluxes to the sea floor4 7 11 it does not explain the origin of marine phosphorite deposits which formed in regions of limited oceanic upwelling and productivity12 14 the east australian continental margin an area of phosphogenesis throughout the late pleistocene and holocene13 14 is a modern analogue of an east coast phosphogenic province15 17 with low productivity over the upper slope region where the most recent phosphorites have been found18 evidence is reported here for the carbonate fluorapatite in the east australian phosphorites being located within bacterial cellular structures and a model proposed for the origin of these deposits through the slow bacterial assimilation of phosphorus from seawater in an area of restricted sedimentation

petrology and palaeoenvironmental significance of authigenic iron rich clays carbonates and apatite in the claiborne group middle eocene ne texas the claiborne group eocene in north east texas consists of clayey sandstones and mudrocks both with variable proportions of dark green to brown clay pellets deposited in a marginal to open marine setting on the gulf coast margin the composition of concretionary carbonate and clay pellets from 5 localities has been investigated using a wide variety of analytical techniques our palaeontological sedimentological c s and stable isotope data support an interpretation of marginal marine facies with limited freshwater input for the claiborne group dark green mature pellets are predominantly associated with transgressive bioturbated marine sediments from the weches formation through to the youngest crockett formation there is a trend from pellets composed mostly of dark green serpentine rich mixed layer clay to those of mostly brown immature nontronite rich mixed layer clay the serpentine is intermediate between odinite and berthierine and may have been originally odinite that has undergone partial transformation to berthierine pellet maturity apparently corresponds with the degree of winnowing and sedimentation rate it does not appear to correspond with global temperature fluctuations though the serpentine rich rather than glauconite rich composition may do siderite cement mostly in the form of concretions post dates the iron rich clay pellets and pre dates calcite cement carbonate and apatite concretions show a wide range of mineral cement textures reflecting variation in sedimentary environment and early diagenetic processes based on water temperatures derived from verneriacardia bivalves a precipitation temperature of 20 c is assumed for the concretionary siderite using this temperature we surmise that the siderite precipitated from marine pore waters with intermittent meteoric water mixing

primary bedded phosphorites in the campanian mishash formation negev southern israel abstract thin lentiform beds up to 1 cm thick of primary non pelletal phosphate have been found sporadically in the highly condensed anticlinal sections of the late campanian mishash formation of the central negev southern israel these primary phosphate beds are typically associated with iron rich montmorillonites of probable authigenic origin and occur at the top of upward fining phosphate dominated sequences the clay rich and primary phosphate levels are commonly truncated by amalgamated beds of high energy coarse grained phosphorites which form the basal part of these sequences with ripped up clasts of the primary phosphate commonly re incorporated in these rocks sem eds study of both the primary phosphate levels and the reworked phosphate clasts shows that they are built by a crudely stratified network of closely packed and gently compressed capsule like phosphate cells 2 5 m in external diameter and with walls of 0 5 m thick these structures are interpreted as being the synsedimentarily phosphatized remnants of former mat forming coccoid prokaryotes now represented as extracellular envelopes which intermittently colonized the mishash sea bottoms at the end of the high energy episodes differential degradation of the periphytic mat community possibly coupled with fe p redox cycling across the surficial mat iron was trapped as iron rich montmorillonites in the anoxic zone below the living mat probably resulted in an excess of dissolved phosphate immobilized as solid phases on decay resistant microbial remains which escaped total degradation development of the mat forming microbes on the mishash bottoms and their mineralization to form primary phosphorite beds occurred during periods of halted deposition which resulted in a high residence time of the mat on the seafloor and hence in intensified interface linked biogeochemical reactions ending in phosphate precipitation the restriction of primary phosphate occurrences to the condensed mishash sections of marginal palaeohigh positions strengthens previous assumptions that these zones were probably the main locus of mishash phosphate production it also points to a phosphate grain supply from marginal to basinal sites leading to the accumulation of pelletal phosphorites in the latter areas

phosphate stromatolites from condensed cephalopod limestones upper jurassic southern spain upper jurassic phosphate stromatolites of the almola sierra southern spain encrust macrofossils and hardgrounds and form oncoids included within pelagic condensed fossiliferous limestones their accretion was determined by bacterially mediated precipitation of phosphate by the trapping and binding of fine siliciclastics and pelagic biomicrite and by the encrustation of benthonic foraminifera phosphorous trace elements and rare earth elements were concentrated from degraded organic matter and seawater by stromatolite building communities which mediated the formation of phosphate rich and fe al si rich organic gels under oxic conditions favouring the precipitation of amorphous mineral precursors acp and fe al si oxyhydroxides the observed ce enrichment for some stromatolites is explained by oxidative scavenging of ce4 from seawater by fe mn oxyhydroxides the bacterially mediated gels were able to migrate and fill the voids of the stromatolite structure and later changed to carbonate fluorapatite haematite and poorly crystalline fe rich clays under postoxic conditions phosphatization of trapped carbonate particles also occurred the phosphate stromatolites formed on a sediment starved pelagic swell during periods of no carbonate sedimentation and hardground development stromatolite lamination provides evidence for rhythmic alternation between bacterially mediated phosphogenesis sedimentation and erosion suggesting episodic changes in the sedimentary environment although some of the parameters that controlled phosphate precipitation associated with the stromatolites local high organic productivity sediment starvation moderate depth of deposition and physicochemical conditions were similar to those found in modern and ancient phosphogenic settings the palaeogeographical framework and the intensity of sedimentary processes were different to those of the world s major phosphorite deposits

early diagenetic phosphate cements in the albian condensed glauconitic limestone of the tatra mountains western carpathians early diagenetic phosphate cements are described from the albian condensed glauconitic limestone of the tatra mountains western carpathians with regard to their macro and micromorphology distribution classification and genesis the cements occur within stratigraphically condensed semi pelagic foramini feral glauconitic layers and are associated with mature hardgrounds within the tatra albian limestone phosphate cement fabrics consist of crypto to microcrystalline carbonate fluorapatite and they occur as i rim envelopes ii infillings of intraparticle porosity iii rim cement iv multiple rim cement v palisade fabric and vi cluster cement micromorphological variability of the cement fabrics results from varying texture of the cemented sediment the nature of original porosity as well as from presence of associated microbial fabrics the microbial fabrics are interpreted as fossilized coccoid cyanobacteria phosphate cementation developed under peculiar early diagenetic conditions within semi closed microenvironments rich in organic matter in the marine phreatic environment the cementation contributed to the formation of phosphatic fossils and hardgrounds the accretion of the cements was due to concentration of biologically uptaken phosphorus near the sediment water interface enrichment of pore fluids with respect to phosphate and its precipitation within restricted microenvironments phosphate cementation post dated seafloor formation of pelletal glauconite but predated partial decomposition of organic matter as well as dissolution or neomorphism of aragonite and high mg calcite phosphate cementation occurred on a carbonate platform following the submersion of urgonian reefal build ups episodes of phosphate cementation were repeated during the sedimentation of the tatra albian limestone as a response to rapid relative sea level rises and increased influence of nutrient rich tethyan waters

a nomenclature system for granular phosphate rocks according to depositional texture abstract because of their striking textural similarities to carbonates a nomenclatural scheme for the classification and interpretation of phosphate sediments is proposed based on the dunham embry and klovan classification for carbonate rocks allochemical phosphate rocks and phosphorites comprise orthochems and allochems matrix cement ooids bioclasts intraclasts and lithoclasts to distinguish such components and their resulting rocks as being phosphatic a phos prefix is proposed i e phosclast mudstone phosclast wackestone phosclast packstone etc this classification nomenclature emphasizes fabrics as well as palaeoenvironmental criteria

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

excess protactinium in phosphate nodules from a coastal upwelling zone measurements of231pa 235u and230th 234u activity ratios have been made for a suite of quaternary age phosphate nodules from the upwelling zone off peru and chile many of these samples contain more231pa than would be predicted based on closed system230th 234u ages unlike samples from non upwelling environments which have been shown to have concordant231pa and230th ages peru chile phosphate nodules apparently pick up231pa preferentially to230th this is most likely a result of prior fractionation of protactinium and thorium in the open ocean highly productive coastal upwelling zones may be added to the growing list of localities where fractionation between thorium and protactinium isotopes has been observed in marine sediments

taphofacies models for epeiric sea environments middle paleozoic examples abstract skeletonized organic remains display various modes of occurrence which may be used to better understand the sedimentary dynamics of strata within which they occur aspects of skeleton biostratinomy and early diagenesis are distributed nonrandomly within the stratigraphic record and therefore are useful in discriminating taphonomic facies for purposes of taphonomic comparisons skeletonized marine taxa are reduced to five generally defined types massive arborescent univalved bivalved and multielement different skeletal types display different attributes which reflect specific responses to physical chemical and or biological processes the taphonomic properties of disarticulation reorientation and sorting fragmentation corrosion and abrasion skeletal dissolution and early diagenesis display patterns which are predictable with respect to a variety of inter related physico chemical parameters these can be quantified through indices which evaluate relative frequencies of occurrence sedimentary events alter the temporal and spatial homogeneity of processes which generate background taphofacies and superimpose event related properties thereby generating composite taphofacies such events produce taphonomic signature which in themselves correspond to specific environmental conditions i e water depth and event intensity indeed background and event related processes interact to generate complex but nonetheless diagnostic facies attributes useful in reconstructing paleoenvironments the comparison of standard indices among beds should allow the recognition of stratigraphic patterns and facilitate the diagnosis of systematic gradients among taphonomic properties deductively derived taphofacies models corroborated by empirical data from paleozoic strata illustrate the distribution of taphonomic properties with respect to environmental energy turbulence background sedimentation rate and sediment oxygenation these parameters also indirectly influence other less obvious factors including bioturbation and sediment chemistry trends in the distribution of taphonomic properties taphonomic gradients permit us to map otherwise unrecognized trends in these environmental parameters across a hypothetical onshore offshore transect within a generalized epeiric sea setting taphofacies models provide the quantifiable basis by which evolution of taphofacies may be gauged and then related to biotic and abiotic phenomena moreover taphofacies models evaluate the preservability of skeletal remains in different environmental settings and therefore provide information important in paleoecological studies

phosphatized early cambrian archaeocyaths and small shelly fossils ssfs of southwestern mongolia abstract archaeocyaths are an enigmatic group of calcifying sponges prevalent in early cambrian terreneuvian to series 2 successions around the world and preserved predominantly in reefal buildups but also in adjacent reworked deposits here we report exceptionally preserved phosphatized archaeocyaths and small shelly fossils from phosphatized reef flank deposits at the top of the salaagol formation of southwestern mongolia recent chemostratigraphic age models suggest that these archaeocyaths are among the earliest reported in the terreneuvian stage 2 tommotian these fossils provide a window into the mechanisms of archaeocyath phosphatization a generally rare mode of archaeocyath preservation to assess the composition and nature of phosphatization fossil assemblages were examined in insoluble residue and thin section these archaeocyaths are preserved as phosphatic internal molds in residue and both phosphatized and unphosphatized archaeocyaths are present in thin section the occurrence of internal molds and complementary mineralogical data suggest that the decay of organic material within the archaeocyaths created the necessary redox conditions for apatite nucleation we propose that shortly after death this assemblage was transported to a deeper water environment and that the presence of organic matter in a low oxygen setting led to abundant phosphatization of archaeocyaths

geochemistry of iron and phosphorus rich nodules from the east australian continental shelf abstract phosphatic glauconitic goethitic nodules occur on the continental shelf off eastern australia at water depths of about 200 300 m they resemble nodules from off the northern margin of spain in their bulk composition which tends to be high in fe and relatively low in ca and p the nodules were examined by microprobe analysis and the composition of individual mineral species determined this revealed that the matrix ranged between high grade collophane containing on average 29 p2o5 and only 4 fe as feo and high grade goethite containing 61 fe as feo and only 4 p2o5 most of the pellets within the nodules are glauconitic and are composed of 47 sio2 27 fe as feo 7 k2o and only 0 3 p2o5 the composition of the few collophane pellets present is similar to that of the collophane matrix collophane and glauconite from the east australian material is very similar in composition to collophane and glauconite from off south west africa and chile peru this similarity occurs despite the fact that the east australian material unlike the south west african or chile peru material does not occur in an area of strong oceanic upwelling the reason for the iron rich nature of these sediments is not known with any certainty however the most likely source of the phosphorus and the iron too appears to be the ocean

growth rates of phosphate nodules from the continental margin off peru modern sea floor phosphorite nodules sampled from off the coast of peru are shown to grow at rates of millimeters per thousand years in spite of the fact that the measured accumulation rates of the underlying sediment are two to four orders of magnitude faster phosphate nodules grow downward into soft sediment and the rates of phosphorus accumulation into nodules are approximately equal to the upward diffusive flux of dissolved phosphate inferred from pore water profiles these results demonstrate that phosphorus in nodules originates from regeneration in sediments rather than as a result of direct precipitation from bottom waters