a new study of marrella splendens arthropoda marrellomorpha from the middle cambrian burgess shale british columbia canada study of over 1000 specimens of marrella splendens walcott 1912 out of the more than 9000 collected by the royal ontario museum rom since 1975 has produced new information on the anatomy functional morphology and behaviour of this most common arthropod in the burgess shale fauna among the new features recognized is the distinction between the alimentary canal and circulatory system where the former is generally three dimensional and slightly reflective the latter never presents any relief and is very reflective a larger range of size is now known from 2 4 to 24 5 mm in length with small individuals possessing 17 body segments to large specimens with more than 26 body segments representing an almost complete ontogenetic series the second pair of antennae is now interpreted as swimming appendages since the five distal segments are dorsoventrally compressed fringed with setae and with a considerable blood supply providing a paddlelike appendage capable of producing a considerable propelli

nondestructive in situ cellular scale mapping of elemental abundances including organic carbon in permineralized fossils the electron microprobe allows elemental abundances to be mapped at the mm scale but until now high resolution mapping of light elements has been challenging modifications of electron microprobe procedure permit fine scale mapping of carbon when applied to permineralized fossils this technique allows simultaneous mapping of organic material major matrix forming elements and trace elements with mm scale resolution the resulting data make it possible to test taphonomic hypotheses for the formation of anatomically preserved silicified fossils including the role of trace elements in the initiation of silica precipitation and in the prevention of organic degradation the technique allows one to understand the localization of preserved organic matter before undertaking destructive chemical analyses and because it is nondestructive offers a potentially important tool for astrobiological investigations of samples returned from mars or other solar system bodies

eddies in the red sea a statistical and dynamical study sea level anomaly sla data spanning 1992 2012 were analyzed to study the statistical properties of eddies in the red sea an algorithm that identifies winding angles was employed to detect 4998 eddies propagating along 938 unique eddy tracks statistics suggest that eddies are generated across the entire red sea but that they are prevalent in certain regions a high number of eddies is found in the central basin between 18 n and 24 n more than 87 of the detected eddies have a radius ranging from 50 to 135 km both the intensity and relative vorticity scale of these eddies decrease as the eddy radii increase the averaged eddy lifespan is approximately 6 weeks aes and cyclonic eddies ces have different deformation features and those with stronger intensities are less deformed and more circular analysis of long lived eddies suggests that they are likely to appear in the central basin with aes tending to move northward in addition their eddy kinetic energy eke increases gradually throughout their lifespans the annual cycles of ces and aes differ although both exhibit significant seasonal cycles of intensity with the winter and summer peaks appearing in february and august respectively the seasonal cycle of eke is negatively correlated with stratification but positively correlated with vertical shear of horizontal velocity and eddy growth rate suggesting that the generation of baroclinic instability is responsible for the activities of eddies in the red sea

early entombment within silica minimizes the molecular degradation of microorganisms during advanced diagenesis most ancient organic microfossils delicately preserved in 3d have been found in cherts although entombment within silica has been shown to promote morphological preservation the impact of early silicification on the molecular evolution of fossilized microorganisms during burial remains poorly constrained here we report results of advanced fossilization experiments performed under pressure 250 bars and temperature 250 c conditions typical of sub greenschist facies metamorphism for different durations up to 100 days on microorganisms experimentally entombed or not within a silica gel the experimental residues have been characterized using xrd and xanes spectroscopy the present study demonstrates that entombment within silica limits the degradation of microorganism molecular signatures likely through specific chemical interactions despite the progressive conversion of silica into quartz during the experiments extrapolation of the present results suggests that such protection may persist during geological timescales the present experimental study provides molecular evidence that in addition to morphologies cherts may support the chemical preservation of remains of ancient life the present results thus constitute a step forward towards the reconstruction of the original chemistry of pu tative fossilized microorganisms

cyanobacterial algal crusts from late ediacaran paleosols of the east european craton abstract the top surface of the ediacaran flood basalts of west ukraine volyn extruded during the break up of rodinia supercontinent is weathered into several meters thick paleosol covered by late ediacaran ca 550 ma sediments the paleosol grades from unaltered basaltic material into saprock and finally clay dominated saprolite with a minor content of the organic matter the upper parts are dominated by kaolinite and hematite sem images and sem eds analyses revealed in one of the paleosol profiles a horizon with significant amount of morphologically recognizable organic structures mineralized by silicates and iron oxides hf etching of the bulk rock samples revealed lithic fragments covered irregularly by a biocrust of colonial coccoid cyanobacteria associated with irregularly distributed unicellular algae the cyanobacteria are preserved as mineralized common mucilage sheaths glycocalyx which reproduce the original shape typical of sheaths of modern coccoidal cyanobacterial biofilms whereas the heavily mineralized algae show features characteristic of modern chlorococcaleans the preservation of morphologically distinguishable remnants of cyanobacterial biofilms and aggregates of unicellular algae in terrestrial weathering deposits is a rare preservational phenomenon requiring rapid post mortem permineralization of the dead microbiota one of the main factors facilitating such a unique fossilization was supposedly a copious excretion of extracellular polymeric substances eps by the biocrust forming biota in which early mineral nucleation occurred the colonization of the late ediacaran land by the presumably desiccation resistant cyanobacteria dominated crust communities associated with algae was of importance for creating fertile soils and a soil forming microbial ecosystem that later allowed a successful land invasion by the ancestors of vascular plants

fossilization modes in the chengjiang lagerstatte cambrian of china testing the roles of organic preservation and diagenetic alteration in exceptional preservation abstract one important and poorly understood issue concerning the taphonomy of nonmineralizing organisms in cambrian burgess shale type deposits is the diagenetic pathways by which organisms have become exceptionally preserved scanning electron microscopy sem analyses of exceptionally preserved fossils from the lower cambrian chengjiang deposit of china demonstrate that nonmineralized tissue is preserved in a variety of ways and further suggest that there was some taxonomic control over the precipitation of authigenic minerals during early diagenesis organic preservation is limited to certain decay resistant structures such as heavily sclerotized spines on the claws of anomalocaridids labile organic tissues of nearly all nonmineralizing animals however are preserved by thin films of diagenetic minerals microstructural studies energy dispersive x ray edx analyses and elemental mapping of these minerals indicate that mineral films include apatite pyrite and fe rich aluminosilicates the results support the assumption that early diagenetic mineralization such as phosphatization and pyritization played a key role in the preservation of nonmineralized organisms pyritization seems to be the most important process by which nonmineralizing chengjiang organisms are preserved in exceptional condition precipitation of fe rich aluminosilicates which occurred following pyritization also played a role in the preservation of some chengjiang fossils phosphatization in the chengjiang lagerstatte was evidently rare and limited taxonomically or to animals having large masses of organic material

cambrian burgess shale type deposits share a common mode of fossilization although cambrian burgess shale type bst biotas are fundamental to understanding the radiation of metazoans the nature of their extraordinary preservation remains controversial there remains disagreement about the importance of the role of early mineral replication of soft tissues versus the conservation of primary organic remains most prior work focused on soft bodied fossils from the two most important bst biotas those of the burgess shale canada and maotianshan shale chengjiang china fossils from these two deposits do not provide ideal candidates for specimen level taphonomic study because they have been altered the burgess shale by greenschist facies metamorphism and the maotianshan shale by intensive subsurface weathering elemental mapping of soft bodied fossils from 11 other bst deposits worldwide demonstrates that bst preservation represents a single major taphonomic pathway that may share a common cause wherever it occurs the conservation of organic tissues and not early authigenic mineralization is the primary mechanism responsible for the preservation of bst assemblages early authigenic mineral replacement preserves certain anatomical features of some specimens but the preservation of non biomineralized bst fossils requires suppression of the processes that normally lead to the degradation of organic remains in marine environments

controls on fossil pyritization redox conditions sedimentary organic matter content and chuaria preservation in the ediacaran lantian biota abstract pyritization represents a major taphonomic pathway for exceptional preservation of soft tissues although various ediacaran lagerstatten contain pyritized fossils the controls on this taphonomic pathway prior to the precambrian phanerozoic transition have only recently received significant attention and no studies have yet thoroughly investigated environmental conditions facilitating exceptional preservation via pyritization in the early ediacaran here we investigate the preservational environments of macroscopic fossil chuaria in the early ediacaran lantian formation of south china using petrographic electron microscopic and geochemical data chuaria occur as pervasively pyritized spheroid shaped globose and non pervasively pyritized disk shaped subglobose fossils in different stratigraphic intervals although these different stratigraphic intervals are similar in terms of total sulfur ts 5 subglobose chuaria shales have greater total organic carbon toc 7 9 contents than globose chuaria shales 3 6 additionally petrographic observations and toc ts cross plots suggest that whereas globose fossils were preserved under suboxic bottom waters the subglobose fossils were preserved in euxinic bottom waters overall these results affirm that pyritization in the precambrian was generally favored in organic poor reactive iron rich sulfate rich environments probably with slow sedimentation rates when organics were scarce and reactive iron was abundant bacterial sulfate reduction bsr created hydrogen sulfide and reactive iron concentration gradients around fossils which kinetically and thermodynamically favored rapid and pervasive pyritization as observed in globose chuaria conversely when organics were abundant and reactive iron sulfate availabilities were limited by widespread bsr fossils were relatively rapidly buried beneath the bsr metabolic zone of sediment where they were principally preserved as aluminosilicified carbonaceous fossils that were compacted into subglobose forms thus preservational variations among pyritized fossils in the ediacaran may reflect differences in sedimentary organic matter content and or bottom water redox chemistry

paleoproterozoic compression like structures from the changzhougou formation china eukaryotes or clasts abstract the paleoproterozoic changzhougou formation changcheng group of north china contains compression like structures millimeters to centimeters in diameter and about a millimeter thick that are circular elliptical elongate and irregular in shape these structures were interpreted to be carbonaceous compressions of megascopic eukaryotes by zhu et al 2000 some of the compression like structures were reported to contain masses of cellular material with well preserved cell walls further investigation of these structures including plane light investigations of thin sections and macerates petrographic study of thin sections sem eds chn xrd and biomarker analyses indicates that they are pseudo fossils

post cambrian closure of the deep water slope basin taphonomic window exceptional faunas konservat lagerstatten that preserve traces of volatile nonmineralized tissues are statistically overabundant in the cambrian period almost all examples preserved in continental slope and shelf basin environments are of this age the hypothesis that an increase in the amount and complexity of bioturbation was an important agent in the elimination of this deep water slope basin taphonomic window is supported post cambrian ichnofaunal assemblages contain a higher proportion of pascichnia and agrichnia ethologies produced by a mobile infauna they also illustrate the lateral partitioning of organisms into different environmental niches both opportunistic and equilibrium infaunas occur in low oxygen environments in which the preservation of nonbiomineralized tissues was favored direct consumption of carcasses by bioturbating organisms was less important than changes to sediment properties as a result of bioturbation notably enhanced microbial degradation of reactive organic matter increased permeability and the disruption of geochemical gradients necessary for mineral authigenesis

sedimentation of the phyllopod bed within the cambrian burgess shale formation of british columbia we provide the most detailed sedimentological log to date through the phyllopod bed of the mid cambrian burgess shale formation of british columbia based on millimetre scale logging of a suite of thin sections the sedimentary facies is dominated by alternations of homogeneous mudstone and a coarser grained laminated variably sandy and shelly mudstone that is locally micronodular most boundaries between these two lithologies are gradational and discrete fining upwards turbidite units were rarely recognized such a pattern is interpreted to indicate rapid sedimentation of up to decimetre thick units at this location from pulsatory quasi continuous density currents consistent with earlier proposals of exceptional preservation through rapid burial the density currents responsible were probably largely akin to mud rich slurries helping explain the transport and entombment of the fossils the homogeneous mudstone units are characterized by numerous distinctive lenses of pyrite framboids or subeuhedral crystals previously interpreted as small ripples their 3d shape however suggests an origin as subspherical early diagenetic aggregates their present morphology is consistent with the high levels of compaction inferred from the preservation of fossils

greenschist facies metamorphism of the burgess shale and its implications for models of fossil formation and preservation metamorphosed silty mudstones of the burgess shale and stephen shale formations record a poly metamorphic history an early greenschist facies event associated with burial by paleozoic strata produced a nearly ubiquitous bedding parallel cleavage s1 tectonic exhumation during the formation of the southern canadian rocky mountains produced a domainal subgreenschist facies retrograde overprint in which a high angle crenulation cleavage s2 was developed whereas all rocks have experienced these two events the degree of deformation and fossil pre servation varies with position relative to the cathedral escarpment this paleosubmarine cliff resulted in a zone of reduced deformation within adjacent strata by buttressing them during burial and deflecting deformation during orogenesis fossil bearing strata are composed of a typical greenschist assemblage of muscovite chlorite quartz albite are devoid of clays and contain an average of 0 28 organic carbon this typical metamudstone assemblage is consiste

experimental attachment of sediment particles to invertebrate eggs and the preservation of soft bodied fossils clay minerals can be an important agent in the fossilization of soft tissues notably in the ordovician soom shale of south africa and the cambrian burgess shale of canada the replication of morphology has been attributed to adsorption of pre existing clay minerals or direct precipitation of authigenic clays onto tissues attachment of quartz and kaolinite to the surface of lobster eggs demonstrates experimentally for the first time that soft tissues could fossilize in pre existing minerals however the eggs became coated only in the presence of metabolizing bacteria this experimental approach could be used to explore why burgess shale type preservation declined after the mid cambrian

diagenesis of bivalves from jurassic and lower cretaceous lacustrine deposits of northeastern china in contrast to the numerous excellently preserved arthropods vertebrates and plants from the mesozoic lacustrine fossil lagerstatten of northeastern china which have calcium phosphate or organic skeletons the preservation of taxa with a calcareous skeleton is fairly poor here we investigate using a scanning electron microscope and energy dispersive x ray spectrometer the preservational modes of bivalves from the jurassic daohugou fossil beds of inner mongolia and the lower cretaceous yixian formation of eastern liaoning the jurassic bivalve ferganoconcha sibirica is preserved as strongly compressed composite moulds which contain remains of the organic periostracum in the yixian formation the bivalves sphaerium anderssoni and arguniella ventricosa occur as compacted internal external or composite moulds or are preserved with a silicified shell and rarely with a shell consisting of iron hydroxides which had replaced pyrite during late diagenesis weathering silicification produced partly fabric replacive microcrystalline quartz and partly void filling megaquartz crystals after the carbonate shell had been dissolved films of authigenic aluminosilicate minerals partly secondarily silicified cover the exterior and interior shell surfaces occasionally early diagenetic pyrite crystals now oxidized to iron hydroxides filled shell cavities forming internal moulds and rarely replaced the bivalve shell the poor preservation of the bivalves reflects the environment and water chemistry of these lakes which were heavily influenced by volcanic processes frequent ash deposition and decomposition of volcanic glass particles created acidic and alkaline lake and interstitial waters which led to early diagenetic formation of authigenic aluminosilicate minerals ferruginous internal moulds dissolution of shell carbonate and silicification of shells

multiscale characterization of pyritized plant tissues in blueschist facies metamorphic rocks pyritized plant tissues with well preserved morphology were studied in rocks from vanoise western alps france that experienced high pressure low temperature metamorphic conditions in the blueschist facies during the alpine orogeny organic and inorganic phases composing these fossils were characterized down to the nanometer scale by raman microspectroscopy scanning transmission x ray microscopy and transmission electron microscopy the graphitic but disordered organic matter composing these fossils is chemically and structurally homogeneous and mostly contains aromatic functional groups its original chemistry remains undefined likely because it was significantly transformed by diagenetic processes and or thermal degradation during metamorphism various mineral phases are closely associated with this organic matter including sulphides such as pyrite and pyrrhotite carbonates such as ankerite and calcite and iron oxides a tentative time sequence of formation of these diverse mineral phases relative to organic matter decay is proposed the absence of traces of organic matter sulphurization the pervasive pyritization of the vascular tissues and the presence of ankerite suggest that the depositional diagenetic environment of these metasediments was likely rich in reactive iron fe sulphides and ankerite likely precipitated early and might have promoted the preservation of the fossilized biological soft tissues by providing mechanical resistance to compaction during diagenesis and subsequent metamorphism in contrast iron oxides which form rims of 100 nm in thickness at the interface between organic matter and fe sulphides may result from metamorphic processes this study illustrates that it may be possible in some instances to deconvolve metamorphic from diagenetic imprints and opens new avenues to better constrain processes that may allow the preservation of organic fossils during diagenesis and metamorphism

trace fossil evidence for ediacaran bilaterian animals with complex behaviors abstract distinguishing ediacaran trace fossils from tubular body fossils can be a challenge and several ediacaran fossils previously interpreted as animal traces have been shown to be tubular body fossils nonetheless true ediacaran trace fossils are present but they are relatively few and morphologically simple dominated by horizontal trails and shallow burrows such simple morphologies have been taken as evidence for a modest behavioral complexity and limited geobiological impact of animal bioturbators before the cambrian explosion here we report three types of trace fossils horizontal tunnels surface tracks trails and vertical traces from the latest ediacaran dengying formation 551 541 ma in the yangtze gorges area of south china cross cutting tunnels and the presence of scratch marks indicate that these traces are unlikely tubular body fossils instead these three types of traces likely represent animal activities related to under mat feeding epibenthic locomotion and temporary dwelling respectively we show that these three types of traces were constructed by the same bilaterian animals that had moderately complex interactions with microbial mats to exploit nutrients and o 2 resources these animals heralded a new age in ecosystem engineering animal sediment interaction and biogeochemical cycling

taphonomic study of ediacaran organic walled fossils confirms the importance of clay minerals and pyrite in burgess shale type preservation burgess shale type bst macrofossils and organic walled microfossils are preserved as carbonaceous compressions and may share similar taphonomic processes previous taphonomic investigations of carbonaceous compressions have primarily focused on the microchemistry of cambrian bst fossils but comparative data from organic walled microfossils were not available to address these issues we analyzed two organic walled taxa from the yangtze gorges area of the south china block chuaria an acritarch and vendotaenia a ribbon shaped fossil their abundance offers the opportunity for destructive microanalysis including petrography electron microscopy and elemental mapping on both bedding planes and in cross sections our data suggest that chuaria preservation is remarkably similar to bst fossils in that its vesicle walls are closely associated with clay minerals in addition like many bst macrofossils chuaria and vendotaenia are also closely associated with pyrite chuaria vesicles are often filled with framboidal pyrite and vendotaenia fossils are associated with sulfate partly derived from pyrite oxidation the comparative taphonomy of chuaria and vendotaenia and bst macrofossils indicates that the preservation of organic walled acritarchs may be aided by clay and pyrite mineralization and that these abundant microfossils may serve as proxies for uncovering in more detail the taphonomic histories of bst preservation

preservation of early and middle cambrian soft bodied arthropods from the pioche shale nevada usa abstract the early middle cambrian pioche shale of lincoln county nevada preserves a diverse array of soft bodied ecdysozoans that are well known from the burgess shale soft bodied fauna of british columbia canada at pioche certain genera occur both above and below the middle cambrian boundary allowing a comparison of the nature of their preservation across this interval in order to investigate the mineralization of this fauna sem analysis of mineral textures and element mapping of anomalocaris tuzoia and canadaspis specimens using energy dispersive x ray spectroscopy eds was undertaken results of these analyses show that early cambrian specimens are generally preserved in botryoidal hematite which is dark red in hand specimen while specimens from the middle cambrian are preserved as kerogenized carbon films with associated oxidized pyrite crystals and framboids comparison with other cambrian soft bodied biotas reveals that the nature of preservation of the middle cambrian biota at pioche is remarkably similar to that described for the chengjiang soft bodied fauna china there does not seem to be an adequate analogue for the early cambrian preservation of soft bodied organisms at pioche the preservation of the fauna is discussed in relation to changing environmental conditions at the early middle cambrian boundary

eramosa lagerstatte exceptionally preserved soft bodied biotas with shallow marine shelly and bioturbating organisms silurian ontario canada the middle silurian eramosa lagerstatte of ontario canada preserves taxonomically and taphonomically diverse biotas including articulated conodont skeletons and heterostracan fish annelids and arthropods with soft body parts and a diverse marine flora soft tissues are preserved as calcium phosphate and carbon films the latter possibly stabilized by early diagenetic sulfurization it is significant that the biotas also include a decalcified autochthonous shelly marine fauna and trace fossils this association of exceptionally preserved and more typical fossils distinguishes the eramosa from other silurian shallow marine lagerstatten such as the waukesha lagerstatte and suggests that the eramosa is not the product of exceptional preservation in an atypical environment a bias claimed for many post cambrian lagerstatten the eramosa lagerstatte may provide a more reliable balanced measure of what has been lost from the silurian fossil record

interactions between ediacaran animals and microbial mats insights from lamonte trevallis a new trace fossil from the dengying formation of south china abstract a new ichnogenus and ichnospecies lamonte trevallis is formally described from the shibantan member limestone of the upper ediacaran dengying formation yangtze gorges area south china it is characterized by horizontal tunnels connected with short vertical burrows and surface trails the horizontal burrows are elliptical or bilobed in transverse cross section preserved in full relief and filled with carbonate intraclasts micrites as well as calcite and silica cements they occur exclusively in silty crinkled and microlaminated layers that are interpreted as amalgamated cyanobacterial microbial mats no burrows have been found in intraclastic layers adjacent to the microlaminated layers the vertical traces are filled with the same material as the burrows but they typically project through the crinkled microlaminae and are exposed on the bedding surface the surface tracks are always preserved in negative epirelief or positive hyporelief and consist of two parallel series of either sharp scratch marks or small knobs the burrow infill has 18ocarb and 13ccarb values distinct from but intermediate between microlaminated and intraclastic layers consistent with petrographic observation that burrow infill consists of a mixture of early carbonate cements intraclasts and micrites bedding plane bioturbation intensity 20 40 measured as percentage of bedding plane area covered by l trevallis traces is comparable to similar measurements in pre trilobite cambrian carbonates the exclusive occurrence of l trevallis within microbial mats may have both taphonomic and ecological significance these mats may have provided firm substrates and localized geochemical conditions that contributed to the structural integrity of the burrows and they may have also facilitated early diagenetic cementation of burrow infill thus facilitating burrow preservation the close association of these burrows with microbial mats implies that the trace producers actively mined cyanobacterial mats to exploit oxygen or nutrient resources the trace makers of l trevallis were better able to utilize the resources around them than many other ediacaran trace makers and provide an ichnological record of a flourishing benthic ecology in late ediacaran oceans at the dawn of the agronomic revolution

metal sorption and mineral precipitation by bacteria in two amazonian river systems rio solimoes and rio negro brazil the surfaces of epiphytic and episammic bacteria from the solute rich waters of the rio solimoes brazil interacted with available cations in solution and provided major sites for iron deposition once bound to the bacteria the iron served as nucleation sites for the formation and growth of fine grained authigenic mineral phases because of progressive mineralization the precipitates exhibited a wide range of morphologies from amorphous gel like to crystalline structures complete encrustation of some bacterial cells was observed the most abundant mineral phase associated with the bacteria was a complex fe al silicate with a variable composition energy dispersive x ray spectroscopy suggested that the gel like structures were similar in composition to a chamositic clay whereas the crystalline phases were increasingly kaolinitic bacteria collected from the solute deficient waters of the rio negro remained conspicuously unmineralized suggesting that metal sorption and biomineralization largely reflect the availability of dissolved metals in the water column in a solute rich river system the fate of the metal loaded bacteria has profound implications for the transfer of metals from the hydrosphere to the sediment through diagenesis the bound metals may either be recycled to the overlying water column or become immobilized as stable mineral phases if the latter occurs microorganisms will have played an important role in metal deposition low temperature clay formation and invariably mudstone diagenesis this implies that in the geologic record microorganisms may have been instrumental in the genesis of many sedimentary rocks of fluvial origin

x ray microtomography applied to fossils preserved in compression palaeoscolescid worms from the lower ordovician fezouata shale abstract computed microtomography xr ct was used to study the three dimensional morphology of palaeoscolex cf tenensis a palaeoscolecid worm from the lower ordovician fezouata lagerstatte central anti atlas morocco this method revealed important aspects of its internal anatomy such as a pharynx bearing longitudinal rows of tiny teeth tubular structures are interpreted as the fragments of a cylindrical gut tract running from mouth to anus energy dispersive x ray analysis edx confirm the primary phosphatic composition of the microplates associated with the cuticle of the worm and suggests that the preservation of soft tissues took place via early bacteria mediated pyritization followed by strong weathering of fe rich aluminosilicates during diagenesis

enhancement of leaf fossilization potential by bacterial biofilms terrestrial leaf fossils often form through authigenic preservation in which the leaf surface is coated by a variety of minerals especially iron oxides the mechanism of this fossilization is unclear because the largely hydrophobic leaf surfaces do not readily bind metal ions previously proposed mechanisms for mineral encrustation include precipitation of minerals in sediment pore space and precipitation of iron oxides at the surface by decay produced co 2 here we demonstrate that diverse bacterial species rapidly colonize leaf surfaces and form a biofilm within days of the leaf9s entry into a stream environment experimental mineralization of fresh and biofilm coated leaves indicates that leaves without biofilm do not mineralize but leaves with biofilms rapidly adsorb metal ions such as fe 3 onto the anionic biofilm surface where the ions form ferrihydrite once these mineralized leaves are buried by the sediment they are more likely to be converted to fossils than non mineralized leaves examination of a fossil leaf surface by scanning electron microscopy shows bacteria sized structures resembling those found in biofilms these experimental data imply that bacterial colonization of leaves may be an essential prerequisite for authigenic preservation

cambrian burgess shale animals replicated in clay minerals although the evolutionary importance of the burgess shale is universally acknowledged there is disagreement on the mode of preservation of the fossils after burial elemental mapping demonstrates that the relative abundance of elements varies between different anatomical features of the specimens these differences reflect the compositions of the minerals that replicated the decaying organism which were controlled by contrasts in tissue chemistry delicate morphological details are replicated in the elemental maps showing that authigenic mineralization was fundamental to preserving these fossils even though some organic remains are also present

three dimensional microct analysis of the ediacara fossil pteridinium simplex sheds new light on its ecology and phylogenetic affinity abstract ediacara fossils often exhibit enigmatic taphonomy that complicates morphological characterization and ecological and phylogenetic interpretation such is the case with pteridinium simplex from the late ediacaran aar member in southern namibia p simplex is often preserved as three dimensional 3d casts and molds in coarse grained quartzites making detailed morphological characterization difficult in addition p simplex is often transported distorted and embedded in gutter fills or channel deposits further obscuring its morphologies by utilizing microfocus x ray computed tomography microct techniques we are able to trace individual specimens and their vanes in order to digitally restore the 3d morphology of this enigmatic fossil our analysis shows that p simplex has a very flexible integument that can be bent folded twisted stretched and torn indicating a certain degree of elasticity in the analyzed specimens we find no evidence for vane identity change or penetrative growth that were previously used as evidence to support a fully endobenthic lifestyle of p simplex instead evidence is consistent with the traditional interpretation of a semi endobenthic or epibenthic lifestyle this interpretation needs to be further tested through microct analysis of p simplex specimens preserved in situ rather than transported ones the elastic integument of p simplex is inconsistent with a phylogenetic affinity with xenophyophore protists instead its physical property is consistent with the presence of collagen chitin and cellulose an inference that would provide constraints on the phylogenetic affinity of p simplex

preservational modes in the ediacaran gaojiashan lagerstatte pyritization aluminosilicification and carbonaceous compression abstract burgess shale type bst fossils often are preserved as two dimensional carbonaceous compressions sometimes aided by two mineralization processes pyritization and aluminosilicification defined by a thin and sometimes localized coating of authigenic pyrite or aluminosilicate minerals on the carbonaceous materials here we report similar mineralization modes within the late ediacaran gaojiashan lagerstatte of southern shaanxi province south china examination of two common gaojiashan fossils conotubus hemiannulatus and gaojiashania cyclus hereafter referred by generic names only indicates that pervasive pyritization is the primary taphonomic pathway in this deposit responsible for the preservation of 80 of the collected fossils pervasive pyritization of gaojiashan fossils results in their three dimensional preservation as opposed to two dimensional carbonaceous compression with thin pyrite coatings seen in some bst lagerstatte however microscale investigation using environmental scanning electron microscopy esem and energy dispersive x ray spectroscopy eds shows that some flattened specimens of conotubus and gaojiashania are preserved as carbonaceous compressions which are in some cases associated with aluminosilicate minerals rare compressed specimens of conotubus are replicated by greenish clay minerals which are interpreted as diagenetic products of aluminosilicate precursors our taphonomic analysis shows that pervasive authigenic pyritization tends to replicate more labile tissues than aluminosilicate aided carbonaceous compression but both pyritization and aluminosilicification processes can facilitate the replication and preservation of soft bodied organisms in siliciclastic sediments building upon this conclusion we propose that multiple taphonomic processes including kerogenization or polymerization of organic molecules pyritization and aluminosilicification can contribute to the mode of bst preservation viewed in this light various siliciclastic hosted lagerstatten that are facilitated by kerogenization pyritization and aluminosilicification can be plotted on a ternary diagram based on the relative importance of these taphonomic processes

visualizing fossilization using laser ablation inductively coupled plasma mass spectrometry maps of trace elements in late cretaceous bones elemental maps generated by laser ablation inductively coupled plasma mass spectrometry la icp ms provide a previously unavailable high resolution visualization of the complex physicochemical conditions operating within individual bones during the early stages of diagenesis and fossilization a selection of la icp ms maps of bones collected from the late cretaceous of montana united states and madagascar graphically illustrate diverse paths to recrystallization and reveal unique insights into geochemical aspects of taphonomic history some bones show distinct gradients in concentrations of rare earth elements and uranium with highest concentrations at external bone margins others exhibit more intricate patterns of trace element uptake related to bone histology and its control on the flow paths of pore waters patterns of element uptake as revealed by la icp ms maps can be used to guide sampling strategies and call into question previous studies that hinge upon localized bulk samples of fossilized bone tissue la icp ms maps also allow for comparison of recrystallization rates among fossil bones and afford a novel approach to identifying bones or regions of bones potentially suitable for extracting intact biogeochemical signals

metal fixation by bacterial cell walls all biomass contains a significant quantity of metallic constituents and mineralization in living and dead biodebris may contribute to element transport from the hydrosphere into sediments the anionic cell walls of bacteria are remarkable in their ability to fix metals and provide sites for nucleation and growth of minerals results presented show the types of cell wall polymers that are responsible for metal binding in walls of gram positive and gram negative bacteria

evaluating the seismic response of deep sandy soil deposits we investigated the influence of depth to the half space on evaluations of seismic response of a dry sandy soil deposit with thickness exceeding 100 m our investigation is based on the premise that the best estimate of surface response of such deposits is obtained using a statistically derived attenuation relationship and the best estimate of other parameters required for geotechnical earthquake engineering evaluations is obtained by calibrating the evaluated spectral characteristics of the site response using the best estimate surface response results of our site specific evaluations indicate that the preferred depth to the half space does not coincide with the depth to bedrock nor is the preferred depth uniquely defined in the seismic site response analysis we find that for a given accelerogram the preferred depth to the half space corresponds closely to the depth for which the peak horizontal ground acceleration phga predicted in the site response analysis matches the median phga developed from the appropriate statistical attenuation relationship our results further indicate that the effect of the magnitude of the shear wave velocity assigned to the half space is minor in comparison with depth to the half space

study of terrestrial fossils in phyllosilicate rich soils implication in the search for biosignatures on mars abstract the search for biosignatures in the soil of mars is a major objective of the planet exploration but the detection of such structures is not straightforward due to the degradation of the organic material in a previous work our group has analyzed the spectral reaction to thermal processing of biomineral carbonate samples including fresh and fossil shells we found that two terrestrial fossil shells collected from clay deposits preserve their biomineral characteristics much better than coeval fossils not embedded in clay layers in the present paper we extend our analysis to a set of fossils found in three different terrestrial clay deposits our results confirm that the level of degradation may be much lower than the standard values if fossils are surrounded by clay minerals as a result these fossils have a spectroscopic response to thermal treatment which make them much more distinguishable from their abiotic counterparts than coeval fossils not collected from clay deposits this result implies that the phyllosilicates regions recently discovered on mars may represent very interesting environments that can provide conditions favorable to preserve evidence of biomarkers and hence can be regarded as good candidate locations for their detection

sequence stratigraphy cyclic facies and lagerstatten in the middle cambrian wheeler and marjum formations great basin utah abstract recurrent taphofacies including conservation lagerstatten are identified within a spectrum of facies in fourth order sequences in the middle cambrian wheeler and marjum formations of the drum mountains and house range west central utah these sequences are 3 20 m thick and commence with sharply based compact oncolitic oolitic or pelletal pack and grainstones with sharply defined corroded and mineralized upper contacts that record drowning discontinuities and early transgressive systems tracts tsts overlying intervals of calcareous shale and thin bedded wacke to packstones with abundant disarticulated polymerid and agnostoid trilobites represent late tsts these are commonly followed by lavender gray mudstones rich in sponge spicules and comminuted fossil debris that reflect condensed maximum flooding zones the overlying early highstand hst intervals of black fissile shales are typically barren except for indistinct circular carbonized algae but in rare instances include soft bodied animal remains a combination of lower dysoxic anoxic conditions with a fluctuating oxycline and relatively rapid episodic influx of fine grained detrital sediment favored repeated burial and preservation of abundant organic detritus and rarely soft bodied animals interbedded dark gray shales include abundant articulated agnostoid trilobites and diminutive polymerids e g jenkinsonia overlying platy calcareous bedding planes covered with articulated bodies and molts of the polymerid elrathia indicate rapid blanketing of undisturbed seafloors by calcareous mud layers these beds grade upward successively into interbedded sparsely fossiliferous platy to flaggy shale and thin pale gray weathering calcisiltites and burrow mottled to nodular limestones recording late hst to falling stage fsst carbonate shedding thin calcisiltites include fossil debris and articulated larger polymerid trilobites and the eocrinoid gogia preserved by obrutionary deposits the repeated recurrence of these patterns provides the rudiments of a predictive model that not only explains the differing modes of preservation but may also aid in prospecting for new lagerstatten

bacteria as nucleation sites for authigenic minerals in a metal contaminated lake sediment abstract sediment samples contaminated with metals arising from mine tailings drainage were obtained from lower moose lake in the onaping region near sudbury ontario canada the samples were examined by electron microscopy selected area electron diffraction and energy dispersive x ray spectroscopy individual bacterial cells and their remains were prominent as nucleation sites for both metal sulfides and a complex polymorphic fe al silicate the principal metal sulfide species associated with the bacteria were amorphous mackinawite fes 1 x and microcrystalline millerite nis trace amounts of cu and zu were also detected in some of the sulfide precipitates at least two structural forms of the fe al silicate were present and energy dispersive x ray spectroscopy point analyses revealed corresponding differences in chemical composition poorly ordered limonitic clay type phases had a granular morphology and contained less fe than well developed crystalline material which generated hexagonal diffraction patterns with reflections d 4 60 and 2 55 characteristic of an interstratified chamositic clay

taphonomic traits of clay hosted early cambrian burgess shale type fossil lagerstatten in south china abstract the chengjiang and guanshan fossil lagerstatten of yunnan represent key fossil deposits to understand and reconstruct early metazoan evolution despite extensive studies on the systematics of taxa from these lagerstatten the major mechanisms of exceptional soft tissue preservation at these fossil lagerstatten have remained controversial the chengjiang and guanshan fossil lagerstatten represent typical burgess shale type deposits influenced by late alteration and weathering that led to some major transformations in clay and iron minerals as well as dissolution of dolomite and skeletal biominerals the detailed geochemical screening of various fossil groups such as brachiopods priapulids arthropods and sponges indicates a more complex preservational history than hitherto supposed besides oxidation processes during sub recent recent weathering clay mineral formation and or alteration carbonization phosphatization and pyritization played key roles in the preservation of various metazoans the chengjiang fossil lagerstatte is characterized by the existence of clay dominated background beds bgbs and event beds ebs fossil preservation varies considerably in the two different depositional settings with soft tissue preservation occurring preferentially in ebs whereas skeletal accumulations are typical of bgbs the samples were analyzed and classified into three groups with different degrees of alteration and fundamentally different chemistries the specific clay mineral composition shows increasing chlorite and goethite decreasing kaolinite 2m1 mica and dolomite and a rise in the chemical alteration of mudstones it also indicates slight variations between the primary types of beds eb bgb hinting at variations in the source of clastics or the hydrochemical environment during the deposition of strata furthermore the geochemical paleoredox proxy data indicate that dysoxic or anoxic conditions were not permanently present during the deposition of ebs and bgbs in the chengjiang and guanshan fossil lagerstatten we consider that rapid deposition in finest claystones had a greater influence on the preservation of highly volatile tissues than the presence of bottom water anoxia even though bottom water anoxia and microbial sealing may further increase the probability of soft tissue preservation using different geochemical proxies such as various redox indicators and iron speciation statistics on framboid sizes classical geological observation and clay mineralogy we show that iron mineral precipitation onto organic carcasses of the chengjiang type fossils is mostly confined to later diagenetic processes and thus is not crucial for the early fixation of easily decayable tissues in burgess shale type faunas

silicified horodyskia and palaeopascichnus from upper ediacaran cherts in south china tentative phylogenetic interpretation and implications for evolutionary stasis horodyskia is one of the earliest known macroscopic life forms with a fossil record dating from c 1 4 ga palaeopascichnus represents a key ediacaran element with world wide distribution however their body constructions and affinities are poorly understood partly because previously described species are mostly preserved as casts and moulds in siliciclastic rocks silicified specimens from the upper ediacaran liuchapo formation in eastern guizhou south china are described as horodyskia minor sp nov and palaeopascichnus jiumenensis sp nov their taxonomic assignments are based on their uniserial arrangement of spheroidal or discoidal units which are connected by a filament and surrounded by a quartz halo they are unlikely to be brown algae animal traces faecal pellets colonial metazoans or giant sulphide oxidizing bacteria instead we propose that horodyskia and palaeopascichnus may be phylogenetically related and their collective morphologies allow tentative comparison with agglutinated foraminifers the segments can be compared with cytoplasm filled chambers connecting filament with small passage between chambers and quartz haloes with agglutinated tests however their ontogeny appears to be distinct from that of modern foraminifers the occurrences of horodyskia fossils in mesoproterozoic and ediacaran rocks indicate an extremely long range c 900 ma and echoes the proposition of extended evolutionary stasis in the proterozoic

the role of decay and mineralization in the preservation of soft bodied fossils abstract fossil deposits that preserve soft bodied organisms provide critical evidence of the history of life usually only more decay resistant materials e g cuticles survive as organic remains as a result of selective preservation and subsequent diagenesis to more resistant biopolymers permineralization the permeation of tissues by mineralizing fluids may preserve remarkable detail particularly of plants however evidence of more labile tissues e g muscle normally requires the replication of their morphology by rapid in situ growth of minerals i e authigenic mineralization this process relies on the steep geochemical gradients generated by decay microbes the minerals involved and the level of detail preserved which may be subcellular depend on a number of factors including the nature of microbial activity and amount of decay availability of ions and the type of organism that is fossilized understanding these controls is essential to determining the conditions that favor exce

exceptional preservation of fossil plant spores in high pressure metamorphic rocks it is commonly believed that high grade metamorphism erases all traces of fossils and more generally of biogenicity in rocks to address this issue we report in this study x ray spectromicroscopy raman microspectroscopy and electron microscopy observations at the nm scale of fossil lycophytes megaspores found in triassic metasedimentary rocks from the french alps these rocks have undergone high pressure metamorphic conditions not vert similar 14 kbar not vert similar 360 c during the alpine orogeny corresponding to a burial of not vert similar 35 km during subduction despite such metamorphism the fossil megaspores are remarkably well preserved texturally an unusual mineralogical zonation consisting of magnetite ankerite and calcite is superposed on the structures of the spore walls in parallel chemical heterogeneities of the organic matter om composing the spore walls were detected we discuss different interpretations for our observations in particular a scenario in which these features are remnants of the original structural heterogeneities in the spores and provide insights on the fossilization processes under high grade metamorphic conditions whatever the processes leading to such heterogeneities our observations oppose the usual assumption that high grade metamorphism erases all indications of biogenicity in rocks and open new avenues for investigation at the nm scale of the evolution of organic matter during diagenesis and metamorphism

silicified egg clusters from a middle cambrian burgess shale type deposit guizhou south china although knowledge of cambrian fossil eggs and or embryos has increased dramatically embryos were previously unknown in siliciclastic settings of coeval strata here we report for the first time egg clusters in a fine grained siliciclastic matrix from the middle cambrian kaili formation lagerstatte 513 501 ma south china some were imaged under synchrotron radiation these spheroids are preferentially preserved as microcrystalline quartz and interpreted as marine invertebrate fossil eggs based on patterns of spheroid arrangement shape and analogues of fossil and modern invertebrate eggs embryos with cleavage cells are evident in at least one cluster detailed element analyses show that eggs are primarily preserved as solid silica replacement and there is a calcite layer covering the eggs replacing the original organic layer silicification of intact invertebrate egg clusters is reported here as a new mode of preservation associated with a burgess shale type deposit