hydromorphic to subaqueous soils transitions in the central grado lagoon northern adriatic sea italy abstract the grado lagoon is among the largest in the mediterranean sea and is characterized by salt marshes where tides influenced the development of a complex micromorphology coupled to a micromosaic of vegetation covers this study represents the first contribution to the understanding of the main processes governing formation development and spatial transitions between hydromorphic and subaqueous soils in an adriatic lagoon ecosystem physicochemical characteristics and development of soils were investigated in three salt marshes differing for their proximity to the open sea textural composition and age of formation soils of back barrier salt marshes had a c profiles and were mostly characterized by a sandy coarse texture that allows rapid drainage and subsurface oxygen exchanges soil sequences from the inner salt marsh to its submerged border slope or to a brackish waterhole do not simply represent a hydrosequence but also reflect erosion sorting accumulation processes the soils in the central part of the lagoon have finer texture and in displayed transition or cambic horizons silty clay loam textures and low positions allowed the development of more severe anoxic conditions and accumulation of sulphides the tide oscillation strongly contributed to formation of redoximorphic features intensity of anaerobic conditions but also colonization by different plant communities discriminant analysis was performed to identify physicochemical properties which discriminate the different soils according to geo morphological position and prevailing plants it confirmed that differentiation of plant communities occurred according to distinct morphological and physicochemical soil properties but also acted as a primary affecting factor of pedogenesis

organic molecules formed in a primordial womb primordial organic molecules may have evolved in seafloor hydrothermal systems by mineral catalysis most organic compounds decompose in 300 c vent fluid however we show that smectite type clays can protect and promote development of diverse organic compounds that may be precursors to biomolecules smectite provides a safe haven for the synthesis of organic molecules essentially like a primordial womb our experiments simulated seafloor hydrothermal conditions 300 c 100 mpa and reacted common clays montmorillonite saponite illite with dilute methanol as a source of c montmorillonite reacts under these conditions to illite while the other clays do not change we observed increased organic synthesis over time with montmorillonite during mineralogical reaction approaching equilibrium smectite contracts and organic molecules are expelled organic compounds unstable in hot fluid where the smectite reacts may survive in cooler waters outside the vent

chemical and pedological features of subaqueous and hydromorphic soils along a hydrosequence within a coastal system san vitale park northern italy abstract transitional systems are complex and fragile ecosystems where the water table oscillation plays a fundamental role in soil and landscape development due to global climate change by the end of the next century a large part of these environments will be affected by water flooding causing deep changes to soil properties and functionality increasing the knowledge on the genesis and properties of these soils can be fundamental for providing useful tools for the correct management of this natural resource the transition from wetland to hydromorphic interdune system in the coastal area of the s vitale park northern italy represents a unique soil hydrosequence characterized by soils which undergo continuous or partial permanent or periodic saturation and reduction these hydrosequences offer a great opportunity to investigate how soil properties change in the transition from subaqueous to hydromorphic soils and to understand which pedogenetic processes mostly characterize the soil development under different water saturation conditions in this study the soil transition through the hydrosequence was recognized by the evaluation of some morphological e g munsell color and chemical organic carbon sulfur ratio caco3 content soil properties that could trace the extent of sulfidization and decarbonation processes along the soil sequences the presence of salts of marine origin characterized the subaqueous pedons while nutrients accumulation i e phosphorous increased with soil emersion these hydrosequences represent a soil continuum where the duration of water saturation and the oscillation of the water table along the soil profiles strongly affect some specific soil forming processes that involve s redox transformation p accumulation caco3 depletion and salt accumulation

attenuation of pyrite oxidation with a fly ash pre barrier reactive transport modelling of column experiments abstract conventional permeable reactive barriers prbs for passive treatment of groundwater contaminated by acid mine drainage amd use limestone as reactive material that neutralizes water acidity however the limestone alkalinity potential ceases as inevitable precipitation of secondary metal phases on grain surfaces occurs limiting its efficiency in the present study fly ash derived from coal combustion is investigated as an alternative alkalinity generating material for the passive treatment of amd using solution saturated column experiments unlike conventional systems the utilization of fly ash in a pre barrier to intercept the non polluted recharge water before this water reacts with pyrite rich wastes is proposed chemical variation in the columns was interpreted with the reactive transport code retraso in parallel kinetics of fly ash dissolution at alkaline ph were studied using flow through experiments and incorporated into the model in a saturated column filled solely with pyritic sludge quartz sand 1 10 oxidation took place at acidic conditions ph 3 7 according to so 4 2 release and ph pyrite dissolution occurred favourably in the solution saturated porous medium until dissolved o2 was totally consumed in a second saturated column pyrite oxidation took place at alkaline conditions ph 10 45 as acidity was neutralized by fly ash dissolution in a previous level at this ph fe release from pyrite dissolution was immediately depleted as fe oxy hydroxide phases that precipitated on the pyrite grains forming fe coatings microencapsulation with time pyrite microencapsulation inhibited oxidation in practically 97 of the pyritic sludge rapid pyrite surface passivation decreased its reactivity preventing amd production in the relatively short term

testing thrust tectonic models at mountain fronts where has the displacement gone the alternative relationships that can exist between a mountain front and the adjacent foreland basin have been recognized for many years however seismic reflection data from such areas are commonly of poor quality and therefore structural models may contain large uncertainties in view of scientific and commercial interest in mountain belts we have reviewed the methods for discriminating between alternative interpretations using a case study from the montagna dei fiori in the central apennines italy in this area mesozoic and tertiary carbonate sediments are juxtaposed with a foredeep basin containing up to 7 km of messinian and plio pleistocene siliciclastic sediments a new structural model for this area demonstrates how the structures in this area form a kinematically closed system in which displacement is transferred from the thrust belt to blind structures beneath the present day foreland growth strata show that pliocene shortening was initially rapid 15 mm a 1 followed by slower rates during the final stages of deformation variations in structural elevation indicate a component of basement involvement during thrusting and this is further supported by magnetic modelling the results illustrate the interaction of thin and thick skinned structures in the central apennines and the methods for discriminating between alternative structural models

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

cellularly preserved microbial fossils from 3 4 ga deposits of south africa a testimony of early appearance of oxygenic life abstract fossil record of earliest earth s life is scant and restricted to simple kerogenous filaments spheres and lenticular microfossils which origin and taxonomic affiliation are still ambiguous here we report clusters of cell like bodies found in massive and weakly laminated black cherts of the 3 4 ga kromberg formation onverwacht group barberton greenstone belt south africa known earlier for benthic microbial mats and microfossils morphological traits and mineralization of the kromberg microfossils match those known from modern and fossil cyanobacteria micro raman and sem eds analyses showed that the cell like bodies fossilized mostly due to early mineralization with al silicates enclosing dispersed carbonaceous kerogenous matter derived from their thermally altered cell remains although in widespread opinion the early archean life is predominantly represented by benthic microbial mats the random non laminated distribution of the studied cyanobacteria like microfossils in the kromberg cherts is suggestive for probably benthic planktonic life cycle of these microbiota the paper also discusses how the morphological similarity of the kromberg fm cell like microfossils to geologically much younger and extant coccoidal cyanobacteria may influence the debate concerning the time of origin of earth s oxic atmosphere

biogenic origin for earth s oldest putative microfossils carbonaceous microbe like features preserved within a local chert unit of the 3 5 ga old apex basalt in western australia may represent some of the oldest evidence of life on earth however the biogenicity of these putative microfossils has been called into question primarily because the sample collection locality is a black carbon rich brecciated chert dike representing an archean submarine hydrothermal spring suggesting a formation via an abiotic organic synthesis mechanism here we describe the macromolecular hydrocarbon structure carbon bonding functional group chemistry and biotic element abundance of carbonaceous matter associated with these filamentous features these characteristics are similar to those of biogenic kerogen from the ca 1 9 ga old gunflint formation although an abiotic origin cannot be entirely ruled out it is unlikely that known abiotic synthesis mechanisms could recreate both the structural and compositional complexity of this ancient carbonaceous matter thus we find that a biogenic origin for this material is more likely implying that the apex microbe like features represent authentic biogenic organic matter

volcanic degassing hydrothermal circulation and the flourishing of early life on earth a review of the evidence from c 3490 3240 ma rocks of the pilbara supergroup pilbara craton western australia abstract new data gathered during mapping of c 3490 3240 ma rocks of the pilbara supergroup in the pilbara craton show that most bedded chert units originated as epiclastic and evaporative sedimentary rocks that were silicified by repeated pulses of hydrothermal fluids that circulated through the footwall basalts during hiatuses in volcanism for most cherts fossil hydrothermal fluid pathways are preserved as silica barite fe bearing veins that cut through the footwall and up to the level of individual bedded chert units but not above indicating the contemporaneity of hydrothermal silica veining and bedded chert deposition at the end of volcanic eruptive events silica barite fe bearing vein swarms are accompanied by extensive hydrothermal alteration of the footwall to the bedded chert units and occurred under alternating high sulphidation and low sulphidation conditions these veins provided pathways to the surface for elements leached from the footwall e g si ba fe and volcanogenic emissions from underlying felsic magma chambers e g co 2 h 2 s hs so 2 stratigraphic evidence of shallowing upward and subsequent deepening associated with the deposition of warrawoona group cherts is interpreted to relate to the emplacement of subvolcanic laccoliths and subsequent eruption and or degassing of these magmas heat from these intrusions drove episodes of hydrothermal circulation listric normal faulting during caldera collapse produced basins with restricted circulation of seawater eruption of volcanogenic emissions into these restricted basins formed brine pools with concentration of the volcanogenic components thereby providing habitats suitable for early life forms fossil stromatolites from two distinct stratigraphic units in the north pole dome grew in shallow water conditions but in two very different geological settings with different morphologies stratiform and domical stromatolites in the stratigraphically lower c 3490 ma dresser formation of the warrawoona group are intimately associated with barite and chert precipitates from hydrothermal vents suggesting that component microbes may have been chemoautotrophic hyperthermophiles evidence of shallow water to periodically exposed conditions active growth faulting and soft sediment deformation indicates that the volcanogenic emissions were erupted into a shallow water tectonically active caldera and concentrated therein to produce an extreme habitat for early life widespread conical and pseudocolumnar stromatolites in the c 3400 ma strelley pool chert at the base of the unconformably overlying kelly group occur in shallow marine platform carbonates silicification was the result of later hydrothermal circulation driven by heat from the overlying newly erupted euro basalt the markedly different morphology and geological setting of these only slightly younger stromatolites compared with the dresser formation suggests a diversity of microbial life on early earth the biogenicity of putative microfossils from this and younger hydrothermal silica veins in the warrawoona group remains controversial and requires further detailed study

formation of sequences of cemented layers and hardpans within sulfide bearing mine tailings mine district freiberg germany abstract the roles of mineral dissolution precipitation transformation and mass transport processes related to formation of characteristic cemented layer hardpan sequences were studied in low sulfide and low carbonate freiberg polymetallic mine tailings using high resolution profiling combined geochemical geomicrobiological and geophysical methods allowed description of the process of weathering of reactive mineral phases and the position of the oxidation front in detail as well as revealing the mechanisms of cementation of tailings predominantly by the formation of gels poorly crystalline phases autochthonous and allochthonous gels reduced the porosity of cemented layers to values 1 whereas secondary crystalline phases were less efficient in filling the pore space electron microprobe analysis of cemented tailings showed that common jarosite group minerals contained up to about 8 wt pbo and 0 2 1 9 wt as 2 o 5 iron as si gels reached contents of up to 44 wt as 2 o 5 in gel rich cemented layers zinc was below the detection limit in the studied secondary phases sequential extraction of cemented and related oxidized brown silt layers confirmed that the bulk of as was bound to amorphous poorly crystalline hydrous oxides of fe whereas pb was often bound to jarosite zinc was found preferentially in the water soluble and the exchangeable fractions in the grey silt and the sand directly underlying the oxidized layers as pb and zn occurred as sulfide minerals the main effects of the cemented layer hardpan sequences at the studied site are 1 a temporary natural attenuation of the toxic compounds 2 a restriction of the downward movement of the oxidation front and 3 a reduction of the extent of the erosion of the surface of the tailings impoundment by wind and water the potential of a heap to form cemented layers and hardpans is greatly increased by a heterogeneous distribution of grain sizes and reactive materials in the topmost zone as well as by the occurrence of sulfide rich tailings on top of layers with low permeability

advanced analytical techniques for studying the morphology and chemistry of proterozoic microfossils this paper outlines the suite of advanced multi scalar techniques currently available in the toolkit of the modern proterozoic palaeobiologist these include non intrusive and non destructive optical laser and x ray techniques plus more destructive ion beam and electron beam methods together these provide morphological mineralogical and biochemical data at flexible spatial scales from that of an individual atom to the largest proterozoic microfossils an overview is given of each technique and a case study from the exceptionally well preserved torridonian biota of nw scotland is presented this microfossil assemblage was first recognized over a century ago but its great diversity and evolutionary importance has only recently come to light due in no small part to the research efforts of martin brasier

historical developments in the understanding of acid sulfate soils abstract literature about the historical and current recognition of kinds names and classification for overall processes sulfidization and sulfuricization that form and conditions that induce the formation of potential active and post active acid sulfate soils are reviewed to set the stage for papers presented elsewhere in this special issue of geoderma that contains some of the papers presented at the eighth international acid sulfate soils conference held at the university of maryland college park md usa july 17 23 2016 mention is made and examples cited of environmental problems such as amd acid mine drainage and ard acid rock drainage fish kills in waters receiving drainage from acid sulfate soils even from ones considered post active and special land reclamation and management practices to produce crops on land disturbed often deeply by humans including engineers poorly educated about acid sulfate soils or by natural causes sea level rise or fall or extreme drought such as the recent millennium drought in the murray darling basin of australia the global distribution of acid sulfate soils is considered recognizing that post active ones are extensive with many likely currently unrecognized although features in some of them such as silcrete and ferricrete likely owe their origin to acid sulfate weathering phenomena most coastal subaqueous soils are influenced by sulfidization and constitute sulfidic materials that if dredged and deposited in upland disposal areas become exposed to aerobic conditions and are likely to give rise to active acid sulfate soils with sulfuric horizons

biogenicity of earth s earliest fossils a resolution of the controversy abstract the abundant and diverse assemblage of filamentous microbial fossils and associated organic matter permineralized in the 3465 ma apex chert of northwestern australia widely regarded as among the oldest records of life have been investigated intensively first reported in 1987 and formally described in 1992 and 1993 the biogenicity of the apex fossils was questioned in 2002 and in three subsequent reports however as is shown here by use of analytical techniques unavailable twenty years ago the apex filaments are now established to be bona fide fossil microbes composed of three dimensionally cylindrical organic kerogenous walled cells backed by a large body of supporting evidence of similar age other microfossils stromatolites and carbon isotopic data it seems clear that microbial life was present and flourishing on the early earth 3500 ma ago

identification of sulfidic materials in the rhode river subestuary of chesapeake bay abstract sulfide containing soil materials can undergo a process known as sulfuricization if disturbed triggering the production of sulfuric acid through the oxidation of fe sulfides and causing environmental degradation several systems exist to classify these types of materials based on the level of environmental hazard that they may pose hypersulfidic materials undergo extreme acidification hyposulfidic materials may undergo acidification to a lesser extent or not at all and monosulfidic materials contain a more reactive form of fe sulfide the definitions for these terms vary so a brief review of how these materials are described and classified both globally and in the rhode river region is provided testing for these materials is costly and time consuming with current methods sometimes taking 16 weeks or longer to identify these materials in subaqueous environments where dredging and other marine construction activities may be delayed by requirements to obtain this information better methods for the field identification of these materials would be of use to subaqueous soil surveyors in this study subaqueous soil materials from the rhode river estuary were sampled described and divided into six categories based on morphologic properties fluid muds unconsolidated holocene sandy materials organic materials buried a horizons tertiary materials with fe oxide concentrations and tertiary materials without fe oxide concentrations these materials were then evaluated and classified as different types of sulfide containing materials using current methods buried a horizons organic materials and tertiary materials without fe oxide concentrations are the most likely to be hypersulfidic materials and therefore of the greatest environmental concern fluid muds unconsolidated holocene sandy materials and tertiary materials with fe oxide concentrations are less likely to consist of hypersulfidic materials but may still be of environmental concern as hyposulfidic materials or monosulfidic materials subaqueous soil surveyors can use these findings to help understand the relative environmental hazards posed by similar subaqueous soil materials in similar settings

mineralogy of the hardpan formation processes in the interface between sulfide rich sludge and fly ash applications for acid mine drainage mitigation in the present study experiments in non saturated leaching columns were conducted to characterize the neoformed phases that precipitate at the interface between two waste residues having different chemical characteristics an acid mine drainage producer residue i e pyritic sludge and an acidity neutralizer residue i e coal combustion fly ash a heating source was placed on top of one of the columns to accelerate oxidation and precipitation of newly formed phases and thus to observe longer scale processes when both residues are deposited together the resulting leachates are characterized by alkaline ph and low sulfate and metal concentrations two mechanisms help to improve the quality of the leachates over short time scales the leaching of pyrite at high ph as a consequence of fly ash addition favors the precipitation of ferrihydrite encapsulating the pyrite grains and attenuating the oxidation process over longer time scales a hardpan is promoted at the interface between both residues due to the precipitation of ferrihydrite jarosite and a ca phase gypsum or aragonite depending on carbonate ion activity geochemical modeling of leachates using phreeqc software predicted supersaturation in the observed minerals the development of a relatively rigid crust at the interface favors the isolation of the mining waste from weathering processes helped by the cementation of fly ash owing to aragonite precipitation which ensures total isolation and neutralization of the mine residues

unraveling magmatic and orogenic provenance in modern sand the back arc side of the apennine thrust belt italy modern river and beach sands carried to and deposited along the coasts of the tyrrhenian sea are derived from multiple mag matic arc and orogenic sources including ophiolitic sequences and tur bidites issued from the ligurian ocean carbonate platform to pelagic sedimentary and metasedimentary successions originally deposited onto the adria continental margin and overlying foredeep clastic wedges undissected arc feldspatholithic signatures characterize limited areas capraia island tarquinia and napoli gulfs contrasting fea tures with respect to circum pacific suites low to very low p f ratio include sanidine as the most abundant detrital feldspar and common leucite and leucite bearing lithic fragments reflecting the potassic to ultrapotassic character of neogene quaternary magmatism green au gite associated with oxyhornblende and either abundant hypersthene tuscan magmatic province or minor olivine and spinel roman mag matic province is the dominant dense mineral dissected arc ar kosic signatures reflect unroofing of miocene monzogranitic stocks in the tuscan archipelago sands from ophiolitic sequences and remnant ocean sediments subduction complex provenance are characterized by common cel lular serpentinite with few chert grains basaltic to diabase and gab broic grains and by abundant shale to slate lithic grains respectively dense mineral suites are dominated by either diallage or chrome spinel sedimentaclastic sands ranging in composition from lithic to quartz ofelspathic are widespread thrust belt provenance richest in lith ic grains is detritus from mesozoic platform dominant carbonates with abundant dolostone to pelagic dominant limestone with abundant chert sedimentary successions metamorphiclastic sands with poly crystalline quartz phyllite and quartz mica or marble lithic grains from denuded core complexes are found locally apuane alps rela tively quartzose sands with abundant feldspars and garnet rich dense mineral assemblages are recycled from foredeep turbidites derived di rectly or indirectly chiefly from the alps this signature is foreign to the apennine accretionary wedge where continental basement is not structurally involved we calculate that one third of the sand grains deposited along tyrrhenian shores today are ultimately derived through long distance multistage transport and repeated recycling from the alps

do marine rooted plants grow in sediment or soil a critical appraisal on definitions methodology and communication abstract mangroves saltmarsh plants and seagrasses grow in coastal areas near the land ocean interface marine scientists normally identify the substratum in which these plants grow as sediments for half a century sediments supporting emergent vegetation have been described by pedologists and some ecologists as soils however more recently some pedologists began to suggest that subtidal marine substrata should be subaqueous soils this followed a change in the definition of soil in the 2nd 1999 edition of soil taxonomy by the us department of agriculture these developments have caused concerns among many coastal marine scientists and have led to the emergence of serious and important questions which we address in this paper we conclude that the terms sediment and soil to describe the substrata in coastal environments vegetated by mangrove forests saltmarshes and seagrass beds are not mutually exclusive coastal marine substrata will still be denoted sediments by most marine scientists pedologists should recognize and affirm the appropriateness of this historical convention while they at the same time for specific purposes can use the term soil when justifiable according to the definition furthermore research methodology must be appropriate to the environments under study and recognize the uniqueness of these water saturated and largely anoxic environments this is critical to avoid flawed and incomparable results and to facilitate better communication among scientists working in the coastal zone a mutual awareness and appreciation among involved communities will help to avoid confusion and improve the understanding among the marine and soil researchers studying these systems we hope that these ideas can be adopted by the marine and terrestrial scientific communities and look forward to further cooperation through a continued positive dialogue

formation of meteorite hydrocarbons from thermal decomposition of siderite feco3 thermal decomposition of siderite has been proposed as a source of magnetite in martian meteorites laboratory experiments were conducted to evaluate the possibility that this process might also result in abiotic synthesis of organic compounds siderite decomposition in the presence of water vapor at 300 c generated a variety of organic products dominated by alkylated and hydroxylated aromatic compounds the results suggest that formation of magnetite by thermal decomposition of siderite on the precursor rock of the martian meteorite alh84001 would have been accompanied by formation of organic compounds and may represent a source of extraterrestrial organic matter in the meteorite and on mars the results also suggest that thermal decomposition of siderite during metamorphism could account for some of the reduced carbon observed in metasedimentary rocks from the early earth

multiple generations of carbonaceous material deposited in apex chert by basin scale pervasive hydrothermal fluid flow abstract the pilbara craton in western australia contains the best preserved and most complete record of archean rocks in the world as such they are some of the most studied rocks in the world paleontologists isotopic geochemists geologists and geobiologists have all investigated these rocks for clues about the early biosphere and atmosphere here we show using high resolution transmission electron microscopy that the carbonaceous material found in the apex chert and potentially in other associated units was formed by multiple processes such as abiotic catalytic synthesis and or biological synthesis we use these data as well as the geological history of the craton to demonstrate that when the rocks of the pilbara craton experienced a high degree of post depositional hydrothermal alteration carbonaceous material could have been remobilized and redeposited as the carbonaceous material within the apex chert samples was formed over nearly a billion years bulk chemistry even at the micron level will be unable to unambiguously delineate the presence of life in these ancient rocks although nanoscale observations may provide a way forward in the search for ancient life

geochemistry and partitioning of trace metals in acid sulphate soils in sweden and finland before and after sulphide oxidation abstract acid sulphate soils ass are formed on sulphidic sediments along the baltic coasts of sweden and finland the sulphides in the fine grained sediments were once formed in an anoxic environment some centimetres below an oxic sediment water interface in earlier investigations high concentrations of many trace elements have been observed in streams draining such areas we compared the trace element contents in soils formed in sulphidic and non sulphidic clays the results show that the total contents of cd ni mn co and cu in the sulphidic sediments are not higher than in non sulphidic clays from adjacent areas however the mobilisation of cd and ni is higher from acid sulphate soils than from soils formed on sulphide free clays to understand the processes causing the mobilisation we studied the partitioning of trace metals before and after oxidation of sulphidic sediments cadmium ni mn co zn and to some extent cu were found to be mobilised from acid sulphate soils due to increased weathering caused by the low ph in these soils iron and cr are only mobilised to a limited extent copper mo and fe mobilised from weathering are precipitated in oxides that form in the oxidised bg horizons nickel co mn mo and cu were shown to be partly bound in pyrite and are mobilised from acid sulphate soils during the pyrite oxidation however mobilisation of trace elements from pyrite was not found to be an important quantitative contributor to trace element leaching any elements that are mobilised are likely to be transported down through the characteristic cracks which occur frequently in the oxidised horizons evidence of this was found at the groundwater table where the most easily extractable fraction of mobilisable elements occurred at higher concentrations

provenance of mesozoic to cenozoic circum mediterranean sandstones in relation to tectonic setting abstract the composition and stratigraphic relations of clastic strata in diverse sedimentary basins of the circum mediterranean region reflect a complete record of provenance relations since break up of pangea neo tethyan taphrogenesis and subsequent plate convergence between the two major plates of europe and africa and other related microplates of iberia adria mesomediterranean and toward to the eastern mediterranean the anatolian microplate since plate reorganization after the breakup of pangea at the end of paleozoic earliest mesozoic clastic wedges filled sedimentary basins within geodynamic settings evolving from intracontinental rifts rifted continental margins protoceanic basins arc trench basin systems remnant ocean basins foreland basin systems and intramontane and back arc basins within the circum mediterranean region the changing nature of clastic particles in these clastic wedges reflect the provenance relations from different source rocks within the spatial and temporal evolving geo puzzle terranes including relations between ophiolite bearing uplifted continental crust both shallow to deep crust terranes volcanic and sedimentary particularly carbonate strata source rocks mixed siliciclastic and carbonate shallow to deep marine clastic wedges are diffuse in many filled basin systems along the mediterranean as such as occurrence of volcaniclastic layers interbedded with siliciclastic wedges the variable mosaic of source terranes within the mediterranean region offered the possibility to investigate provenance relations with a new plane of precision and sophistication discriminating grain particles in clastic wedges using spatial extrabasinal versus intrabasinal and temporal coeval versus noncoeval distinction of detrital signals the spatial temporal approach in deciphering particles in clastic rocks has been widely used to detail the basinal dispersal pathways in different geotectonic settings wherever mixed silicate and carbonate terranes act as the major source rocks from rifted continental margins to collisional orogens

carbon isotope composition of organic compounds produced by abiotic synthesis under hydrothermal conditions although it is widely believed that production of organic compounds by fischer tropsch synthesis and related processes occurs in many geologic environments unambiguous identification of compounds with an abiotic origin in natural samples has been hampered by a lack of means to discriminate between abiotic compounds and organic matter from biological sources while isotopic compositions might provide a means to discriminate between biologic and non biologic sources of organic matter there are few data presently available to constrain the isotopic composition of compounds produced by abiotic processes in geologic systems here we report results of laboratory experiments conducted to evaluate the isotopic composition of organic compounds synthesized abiotically under hydrothermal conditions we find the organic products are depleted in 13c to a degree typically ascribed to biological processes indicating that carbon isotopic composition may not be a particularly effective diagnostic means to differentiate between biologic and non biologic sources furthermore our results suggest that the isotopic compositions of reduced carbon compounds found in many ancient rocks that have heretofore been attributed to biological sources could be consistent with an abiotic origin in a hydrothermal setting

soil morphology genesis and monolith construction of an acid sulfate soil with silica cementation in the us mid atlantic region abstract soil monoliths are powerful tools for soil education and for representing soils as they are found in the field they preserve and display major soil features and are portable the monolith herein described was collected from an active acid sulfate soil located near the western shore of the chesapeake bay in the coastal plain physiographic province in maryland us the key features of this profile include a silica cemented layer a sulfuric horizon prominent concentrations of jarosite and iron oxide glauconite and sulfidic materials the silica cemented layer similar to a duripan created a challenge for the collection of a soil monolith from this site this layer was disassembled fragments were cut to size and the layer was reassembled in a soil monolith containing the underlying and overlying soil horizons this appears to be the first published report of a method for creating a soil monolith in a silica cemented soil silica cementation in acid sulfate soils is rarely reported in the pedologic literature though cemented layers are occasionally reported in literature on sulfidic mine tailings by understanding silica cementation in acid sulfate soils we may be able to induce it as a management practice in mine tailings and other environmentally hazardous sites the goals of this study are to report on a method for creating soil monoliths from silica cemented soils to present explanations for the genesis of this unusual soil and to highlight how a pedologic study of this soil could lead to further experiments to mitigate some environmentally hazardous sites

fossil biomass preserved as graphitic carbon in a late paleoproterozoic banded iron formation metamorphosed at more than 550 c metamorphism is thought to destroy microfossils partly through devolatilization and graphitization of biogenic organic matter however the extent to which there is a loss of molecular elemental and isotope signatures from biomass during high temperature metamorphism is not clearly established we report on graphitic structures inside and coating apatite grains from the c 1850 ma michigamme silicate banded iron formation from michigan metamorphosed above 550 c traces of n s o h ca and fe are preserved in this graphitic carbon and x ray spectra show traces of aliphatic groups graphitic carbon has an expanded lattice around 3 6 a forms microscopic concentrically layered and radiating polygonal flakes and has homogeneous 13c values around 22 identical to bulk analyses graphitic carbon inside apatite is associated with nanometre size ammoniated phyllosilicate precursors of these metamorphic minerals and graphitic carbon originated from ferruginous clay rich sediments with biomass we conclude that graphite coatings and inclusions in apatite grains indicate fluid remobilization during amphibolite facies metamorphism of precursor biomass this new evidence fills in observational gaps of metamorphosed biomass into graphite and supports the existence of biosignatures in the highly metamorphosed iron formation from the eoarchean akilia association which dates from the beginning of the sedimentary rock record supplementary material figures illustrating the petrography and analytical results are available at https doi org 10 6084 m9 figshare c 4430609

critical testing of earth s oldest putative fossil assemblage from the 3 5ga apex chert chinaman creek western australia abstract structures resembling cyanobacterial microfossils from the ca 3465 ma old apex chert of the warrawoona group in western australia have until recently been accepted as providing the oldest morphological evidence for life on earth and have been taken to support an early beginning for oxygen releasing photosynthesis eleven species of filamentous prokaryote principally distinguished by shape and geometry have been put forward as meeting the criteria required of authentic archaean microfossils they were contrasted with other microfossils that were dismissed as either unreliable or irreproducible the aim of this paper is to provide a detailed account of research recently reported by us on the type and recollected material involving optical and electron microscopy digital image analysis and other techniques all previously figured holotype materials are illustrated here and the context for all the published materials is re evaluated the apex chert microfossils occur near the top of a 1 5 km long chert dyke complex associated with major synsedimentary growth faults highly localised glassy felsic tuffs erupted explosively from this and other fissures during the early stages of volcanism and were followed by the deposition of essentially hydrothermal black and white baso4 rich cherts that infiltrated the feeder dykes underplating and dilating adjacent stratiform cherts before the start of the next volcanic cycle the apex chert microfossils occur within multiple generations of these metalliferous hydrothermal vein cherts some 100 m down the dyke system comparable structures occur in associated volcanic vent glass and in hydrothermal cherts at least 1 km deep we find no supporting evidence for a primary biological origin we reinterpret the purported microfossil like structures as pseudofossils that formed from the reorganization of carbonaceous matter mainly during recrystallization from amorphous to spherulitic silica

evidence of archean life stromatolites and microfossils abstract fossil evidence of the existence of life during the archean eon of earth history 2500 ma is summarized data are outlined for 48 archean deposits reported to contain biogenic stromatolites and for 14 such units that contain a total of 40 morphotypes of described microfossils among the oldest of these putatively microfossiliferous units is a brecciated chert of the 3465 ma apex basalt of western australia the paleoenvironment carbonaceous composition mode of preservation and morphology of the apex microbe like filaments backed by new evidence of their cellular structure provided by two and three dimensional raman imagery support their biogenic interpretation such data together with the presence of stromatolites microfossils and carbon isotopic evidence of biological activity in similarly aged deposits indicate that the antiquity of life on earth extends to at least 3500 ma

provenance and evolution of miocene turbidite sedimentation in the central apennines italy abstract a study of the siliciclastic detritus within the calcareous miocene turbidite sandstones of the central apennines has elucidated the provenance of these sandstones three ratios q q f k f and mc m have been used and binary correlations of these parameters show that 1 the sandstones of the marnoso arenacea are characterized by a northern alpine supply mainly derived from metamorphic rocks and subordinately from granitic rocks 2 a secondary supply of western provenance interbedded within the marnoso arenacea shows a typical arkosic composition and suggests that granitic rocks of alpine type were associated with the ligurides 3 the urbania and serraspinosa sandstones consist of detritus derived from sources almost identical to those supplying the marnoso arenacea 4 all the sandstones of the remaining central apennine basins are characterized by a siliciclastic supply similar to the arkosic one the rare carbonate fragments can be referred to the apennine units the continuity of the alpine are in the tyrrhenian area strongly suggests a connection between the western crystalline units and turbidite sedimentation in the basins examined the crystalline units are associated with a segment of the alpine chain tectonically linked to the liguride nappes apennine source areas during the eastwards migration of the apennines deformation the crystalline units were gradually eroded during the burdigalian to early pliocene interval when the laga basin was completely filled currently the term alpine is used as synonymous with northern provenance however a detailed study carried out over ten years revealed a western alpine supply associated with an apennine source area we therefore suggest that it is necessary to distinguish a northern alpine provenance from a western alpine supply

estimating the depth to sulfide bearing materials in upper cretaceous sediments in landforms of the maryland coastal plain the unoxidized portions of upper cretaceous uc regolith in maryland s inner coastal plain have been observed to contain significant amounts of microscopic pyrite the exposure of these sulfide bearing sediments initiates rapid acid sulfate weathering processes resulting in extremely acidic soils and runoff previous anecdotal observations have shown that the depth to the sulfide bearing zone can be highly variable ranging from less than 2 m to over 12 m this depth appears to be primarily a function of landscape hydrology which is in turn controlled by stratigraphic and geomorphological factors deep borings along 6 transects in three landscapes were made to characterize the boundary between oxidized and unoxidized materials and to determine the depth to sulfides the boundary between the oxidized zone and the underlying unoxidized zone marked the depth to sulfides and was easily distinguished in the field because of the sharp morphological contrast the change from the brownish oxidized zone to the black or dark grey unoxidized material was abrupt and easily identifiable laboratory analysis showed that there were accompanying marked increases in chromium reducible sulfide crs across the morphological boundary from essentially 0 above the boundary to 1 below the boundary over distances generally 10 cm indicating that the morphological boundary determined in the field was accurate changes in soil ph across the morphological boundary were much less pronounced moist incubation of the sulfide bearing materials showed that they met the definition of sulfidic materials data were further analyzed to determine the relationship between depth to sulfides and a simple topographic variable from which landscape models were developed for describing the depth to sulfides generally sites with higher degrees of dissection had greater depths to sulfides whereas at all sites sulfides did not occur at depths shallower than 3 m strong correlations between depth to sulfides and point relief the difference in elevation between the point of interest and the hydrologic base point in the landscape unit were obtained confirming that topographic characteristics are related to the depth of sulfide oxidation the relationship between depth to sulfide bearing materials and point relief in the uc sediments was best described by highly significant exponential models using these models and a digital elevation model the depth to sulfides could be adequately predicted

taphonomy of very ancient microfossils from the 3400ma strelley pool formation and 1900ma gunflint formation new insights using a focused ion beam abstract focused ion beam fib milling permits the accurate extraction of ultrathin c 100 nm cross sectional lamellae from microfossils found in geological thin sections subsequent tem analysis of these lamellae can provide unique insights into the ultrastructure chemistry and taphonomy of precambrian microfossils at the micrometer to nanometer scale combining serial fib milling with sem imaging extends this capability to three dimensional 3d tomographic reconstruction and visualization of precambrian microfossils revealing information not available in light microscopy here we apply these techniques to two iconic silicified microfossil assemblages from the 3400 ma strelley pool formation of western australia and the 1900 ma gunflint formation of canada all the examined microfossils have carbonaceous walls surrounded by pure silica impregnation of microfossil walls by nano grains of silica is common together with variable degrees of wall displacement and replacement by silica all microfossils are rigidly preserved in 3d and show little or no folding or compression however there are also notable differences in taphonomic preservation our examples of the spheroidal gunflint microfossil huroniospora showed the highest fidelity of preservation with a continuous carbonaceous wall fossilized by spheroidal nano silica grains that resemble those found on bacterial surfaces in modern silicifying hot spring environments the nucleation of these silica nano spheres on the microfossil walls has induced an artificial saw tooth like ridged wall texture that may subsequently hinder species level identification the strelley pool microfossils in comparison show a lower fidelity of preservation with small parts of the microfossil walls completely replaced by silica plus extensive recrystallization of spheroidal silica nano grains to angular micro quartz our examples of the sheath like filamentous gunflint microfossil siphonophycus showed the lowest fidelity of preservation with many gaps in the carbonaceous walls and significant redistribution of carbon by recrystallizing silica grains a model is presented to explain these observations criteria for distinguishing highly probable microfossils from non cellular carbonaceous microstructures e g botryoids and grain coatings using fib based imaging are put forward for the first time here using examples drawn from the strelley pool formation and comparisons with younger gunflint material the combined in situ techniques of fib tem and fib sem nano tomography potentially provide a wealth of new nano scale information regarding the biogenicity antiquity and taphonomy of precambrian microfossils however the destructive nature of both techniques makes their application to unique palaeontological specimens problematical

chemically oscillating reactions during the diagenetic oxidation of organic matter and in the formation of granules in late palaeoproterozoic chert from lake superior abstract filamentous and coccoidal microfossils have been reported since the 1950 s from a range of granular cherts from the late palaeoproterozoic southwestern superior craton canada united states however the chemical and mineral compositions of granules the presence of microfossils in granules and the common presence of granules in intercolumnar space of stromatolitic chert are poorly documented and explained furthermore the depositional model for the origin of granules in wave agitated waters does not entirely explain their mineral diversity nor their characteristic morphologies and patterns we report on the crystallinity of organic matter mineral diversity and compositions of microfossils in granules from three different kinds of late palaeoproterozoic cherts namely phosphatic organic and haematitic stromatolitic organic rich chert from the gunflint fm contains granules with euhedral carbonate and equidistant concentric laminations of organic matter akin to fractal patterns from the belousov zhabotinsky b z chemically oscillating reaction these granules also contain authigenic anatase ferric ferrous silicates and fe oxides filamentous and coccoidal microfossils similar to those of the gunflint occur in chert from the biwabik formation and share morphology and co occur with mn siderite and apatite granules in phosphatic chert in the michigamme formation often contain filamentous and coccoidal microfossils composed of organic matter sericite and apatite bulk carbonate associated with these michigamme granular phosphatic chert beds has systematically negative 13ccarb values around 3 1 0 9 1 and 18ocarb smow between 20 8 and 30 7 which suggest some contribution from the diagenetic oxidation of organic matter notably residual carboxylic acid is detectable in c xanes spectra of organic matter from granular phosphatic chert which is a residual reactant of b z type reactions along with previously reported observations of pyritised microfossils from the gunflint formation these distinct mineralogies indicate variable modes of preservation for the products of chemically oscillating reactions that likely relate to the availability of different oxidants in the diagenetic environment we conclude that the late palaeoproterozoic shallow marine environments of the lake superior area were populated by morphologically similar micro organisms and that the diagenetic oxidation of organic matter through chemically oscillating reactions contributed to the formation of spheroidal rosettes granules and concretions during a late palaeoproterozoic great putrefaction event granules in chert that contain organic matter or microfossils thus provide a reliable petrographic context to search for a record of putrefaction of microbial life on the early earth and on other ancient planetary surfaces

review secular tectonic evolution of archean continental crust interplay between horizontal and vertical processes in the formation of the pilbara craton australia the archean pilbara craton contains five geologically distinct terranes the east pilbara karratha sholl regal and kurrana terranes all of which are unconformably overlain by the 3 02 to 2 93 ga de grey superbasin the 3 53 3 17 ga east pilbara terrane ep represents the ancient nucleus of the craton that formed through three distinct mantle plume events at 3 53 3 43 3 35 3 29 and 3 27 3 24 ga each plume event resulted in eruption of thick dominantly basaltic volcanic successions on older crust to 3 72 ga and melting of crust to generate first tonalite trondhjemite granodiorite ttg and then progressively more evolved granitic magmas in each case plume magmatism was accompanied by uplift and crustal extension the combination of conductive heating from below thermal blanketing from above and internal heating of buried granitoids during these events led to episodes of partial convective overturn of upper and middle crust these mantle melting events caused severe depletion of the subcontinental lithospheric mantle making the ep a stable buoyant unsubductable continent by c 3 2 ga extension accompanying the latest event led to rifting of the protocontinent margins at between 3 2 and 3 17 ga after 3 2 ga horizontal tectonic forces dominated over vertical forces as revealed by the geology of the three terranes karratha sholl and regal of the west pilbara superterrane the c 3 12 ga whundo group of the sholl terrane is a fault bounded 10 km thick volcanic succession with geochemical characteristics of modern oceanic arcs including boninites and evidence for flux melting that indicate steep archean subduction at 3 07 ga the 3 12 ga sholl terrane 3 27 ga karratha terrane and c 3 2 ga regal terrane accreted together and onto the ep during the prinsep orogeny this was followed by development of the de grey superbasin an intracontinental sag basin and widespread plutonism 2 99 2 93 ga as a result of orogenic relaxation and slab break off craton wide compressional deformation at 2 95 2 93 ga culminated with 2 91 ga accretion of the 3 18 ga kurrana terrane with the ep this compression caused amplification of the dome and keel structure in the ep final cratonization was effected by emplacement of 2 89 2 83 ga post tectonic granites

hydrothermal breccias in vein type ore deposits a review of mechanisms morphology and size distribution abstract breccias are among the most widely distributed rock textures found in hydrothermal vein type deposits previous studies have mainly been interested in developing qualitative descriptive approaches leading to a confusing profusion of terms brecciation originates in numerous ways resulting in highly complex classification systems and frequent misinterpretations of facies field observations are difficult to reconcile with physical theories of fragmentation partly due to the fact that few satisfactory quantitative tools have been developed a review of the main brecciation processes occurring in hydrothermal vein type deposits allows for the discrimination between chemical and physical mechanisms including tectonic comminution wear abrasion two types of fluid assisted brecciation hydraulic and critical volume expansion or reduction impact and collapse each of these mechanisms can be distinguished using nonscalar parameters that describe breccia geometry including fragment morphology size distribution of the fragments fabric and dilation ratio the first two parameters are especially important because 1 the morphology of the fragments allows chemical and physical mechanical breccias to be distinguished and 2 the particle size distribution psd is a function of the energy input during breccia formation the slope of the cumulative psd fractal dimension ranges from high values for high energy brecciation processes to low values for low energy processes indicated by an isometric distribution the evolution of a vein system can be divided into three stages propagation wear and dilation these stages are separated by one threshold of mechanical discontinuity and one of hydraulic continuity these two thresholds also mark the transition between different types of brecciation mineralization occurs during all three stages and may display different textures due to pressure variations the use of quantitative parameters in fault related hydrothermal breccias allows a better understanding of the physical parameters related to a vein environment including structural setting and crustal level as well as fluid rock interactions recognition of the different breccia types could also be important during the early stages of mineral exploration

the role of mineralogy on element mobility in two sulfide mine tailings from the iberian pyrite belt sw spain abstract a detailed study of two adjacent mine tailings impoundments comparing mineralogical and geochemical analyses of the solids with geochemical analysis of the pore water and gas was carried out in the monte romero sulfide mining district iberian pyrite belt sw spain since 1978 both facilities have been exposed to weathering in a semi arid climate with dry warm and wet rainy seasons in these impoundments sulfide oxidation releases sulfate and contaminants to the pore water that are transported and concentrated by evaporation in the top surface of the tailings causing precipitation of soluble iron sulfate salts in dry seasons these salts act as temporary sinks for minor elements such as cd co zn ni cu and mn which are again released during rainfall events in wet seasons stored flotation tailings have an average pyrite content of 30 wt although average amounts up to 80 are present in the upper 50 cm of one of the impoundments according to the results of the current study this difference is key to control the oxidation model in both tailings in the impoundment containing 30 wt of pyrite pore water ph increases in wet periods to 3 1 average by rainwater dilution causing supersaturation and precipitation of secondary fe iii phases such as jarosite goethite and schwertmannite consequently this impoundment shows a 20 25 cm thick yellowish oxidation layer in the top part in contrast in the impoundment containing 80 wt of pyrite in the top part extremely acidic pore waters ph

reduction of co2 during serpentinization of olivine at 300 c and 500 bar co 2 reduction processes occurring during experimental serpentinization of olivine at 300 c and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas data reveal that conversion of fe ii in olivine to fe iii in magnetite during serpentinization leads to production of h 2 and conversion of dissolved co 2 to reduced c species including methane ethane propane and an amorphous carbonaceous phase hydrocarbon gases generated in the process fit a schulz flory distribution consistent with catalysis by mineral reactants or products magnetite is inferred to be the catalyst for methanization during serpentinization because it has been previously shown to accelerate fischer tropsch synthesis of methane in industrial applications involving mixtures of h 2 and co 2 the carbonaceous phase was predominantly aliphatic but had a significant aromatic component although this phase should ultimately be converted to hydrocarbon gases and graphite if full thermodynamic equilibrium were established its formation in these experiments indicates that the pathway for reduction of co 2 during serpentinization processes is complex and involves a series of metastable intermediates

the composition and provenance of the tortonian and messinian turbidites in the context of the structural evolution of the central apennines along the ancona anzio line abstract the ancona anzio line is a complex tectonic system separating the umbro marchide domain from the latium abruzzi platform in the central apennines it played a decisive role in turbiditic sedimentation in the four latium abruzzi basins salto tagliacozzo liri and sacco in the tortonian and in the laga basin during the messinian petrographic studies show that the composition of the turbiditic sandstones is the same in all the basins in particular 1 k feldspar is always present in greater quantities than plagioclase 2 the rock fragments consist mainly of carbonates and granitic type rocks the provenance of the turbidites is to be found in the western areas from a fragment of the alpine chain that was associated with the ligurids nappes during the eastward migration of the apennines deformation this fragment was probably eroded gradually between the langhian and the lower pliocene with the filling in of the laga basin the presence of clasts derived from the erosion of crystalline rocks and from the ligurids nappes has been documented as early as the langhian in the basin of the marnoso arenacea during the tortonian the latium abruzzi platform was lower than the umbro marchide region and the gravity flows with western provenance were able to feed the four basins formed within the platform between the end of the tortonian and the beginning of the messinian the relative uplift of the latium abruzzi platform due to displacements along the ancona anzio line caused the cessation of turbiditic sedimentation in the basins formed within the platform the progressive eastward shift of the apennine chain favoured the migration of turbiditic sedimentation towards the outer foreland laga basin

the palaeobiology and geochemistry of precambrian hydrocarbon source rocks abstract organic carbon productivity and formation of hydrocarbon source rocks during the early precambrian was almost exclusively the product of the growth of microbial mats indirect evidence of microbial mats can be traced back to at least 2 6 2 7 ga neoarchaean with the earliest evidence of mat development in siliciclastic sediments coming from the 2 9 ga mesoarchaean predominantly marine sedimentary rocks of the mozaan group in south africa the earliest direct evidence for terrestrial microbial mats in siliciclastic sediments comes from the 2 75 ga palaeoproterozoic fluviolacustrine sediments of the hardey formation of the pilbara craton in western australia well preserved proterozoic hydrocarbons provide valuable information about the early evolution of the biosphere eukaryotic steranes biomarker for eukaryotic cells and therefore evolved forms of life are present in the geological record from about 2 7 ga but they are not abundant or diverse within archaean communities which tend to be dominated by archaea isoprenoids some hydrocarbons have been generated and migrated from archaean organic rich shales but they were probably not of sufficient volume to be of commercial interest the world s oldest significant hydrocarbon source rocks are palaeoproterozoic in age and include the shungite deposits 2 0 ga in the lake onega region of arctic russia there is strong evidence of a global biospheric oxygenation event at c 1300 1250 ma mesoproterozoic in conjunction with a first order positive shift in the marine carbon isotope record this is supported by the appearance of the oldest bedded marine gypsum deposits and of the earliest unambiguously multicellular eukaryotes at this time this oxygenation event probably played a significant role in supporting the more diverse eukaryotic communities preserved in the neoproterozoic molecular record and provided the volume of organic material required to generate commercial volumes of hydrocarbons hydrocarbon source rocks of late mesoproterozoic and early neoproterozoic age are widespread and include highly organic rich shales deposited in restricted basinal settings adjacent to stromatolitic carbonate banks by c 850 ma the neoproterozoic molecular record is dominated by hopanes from cyanobacteria with a significant abundance and diversity of eukaryotic steranes including those of multicellular eukaryotes red and green algae as well as molecular evidence for heterotrophic protists the most widespread hydrocarbon source rocks of mid to late neoproterozoic age are commonly transgressive organic rich black shales associated with inter glacial and post glacial phases of the neoproterozoic global scale glaciations the relative dominance of microbial mats in the contribution of organic matter as a source for hydrocarbon generation probably decreased significantly during the late neoproterozoic and earliest cambrian perhaps as a result of the rapid growth of grazing metazoan communities or possibly as a result of changes in seawater chemistry and or nutrient supply precambrian and infracambrian petroleum systems are relatively abundant and widespread the oldest live oil recovered to date is sourced from mesoproterozoic rocks within the velkerri formation roper group of the mcarthur basin of northern australia dated at 1361 21 ma and 1417 29 ma re os dates with at least the initial phase of oil generation and migration having taken place before 1280 ma however the geologically oldest commercial production is currently from the somewhat younger mid to late neoproterozoic cryogenian ediacaran petroleum systems of the lena tunguska province in east siberia and in southern china from the latest neoproterozoic to early cambrian huqf supergroup in oman and potentially in the near future from the age equivalent mawar supergroup in western india

changes in lead and zinc lability during weathering induced acidification of desert mine tailings coupling chemical and micro scale analyses desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through flux rates along with other constraints metal toxicity precludes natural plant colonization even over decadal time scales since unconsolidated particles can be subjected to transport by wind and water erosion potentially resulting in direct human and ecosystem exposure there is a need to know how the lability and form of metals change in the tailings weathering environment a combination of chemical extractions x ray diffraction micro x ray fluorescence spectroscopy and micro raman spectroscopy were employed to study pb and zn contamination in surficial arid mine tailings from the arizona klondyke state superfund site initial site characterization indicated a wide range in ph 2 5 to 8 0 in the surficial tailings pile ligand promoted dtpa extractions used to assess plant available metal pools showed decreasing available zn and mn with progressive tailings acidification aluminum shows the inverse trend and pb and fe show more complex ph dependence since the tailings derive from a common source and parent mineralogy it is presumed that variations in ph and bioavailable metal concentrations result from associated variation in particle scale geochemistry four sub samples ranging in ph from 2 6 to 5 4 were subjected to further characterization to elucidate micro scale controls on metal mobility with acidification total pb ranging from 5 13 g kg 1 was increasingly associated with fe and s in plumbojarosite aggregates for zn both total 0 4 6 g kg 1 and labile fractions decreased with decreasing ph zinc was found to be primarily associated with the secondary mn phases manjiroite and chalcophanite the results suggest that progressive tailings acidification diminishes the overall lability of the total pb and zn pools

genesis of freshwater subaqueous soils following flooding of a subaerial landscape abstract the majority of research on subaqueous soils has so far occurred in estuarine environments where their pedogenic concepts were first explored we investigated subaqueous soils in a 91 ha freshwater impoundment which prior to flooding were subaerial five landscape units across the lake were delineated based on water depth slope landscape shape and depositional environment soils were sampled and analyzed for bulk density particle size distribution rock fragments ph electrical conductivity ec organic c and sulfidic materials given these soils did not classify as subaqueous under current criteria in soil taxonomy we determined current subaerial classifications and propose new subaqueous classifications histic frasiwassept subaerial typic humaquept typic frasiwassept subaerial typic endoaquept and fragic frasiwassept subaerial typic endoaquept lake main channel units have water depths that exceed 2 5 m and thus exceed water depths where subaqueous soils are found across lake channel bank deposits a fragic frassiwassept typic frassiwassept complex is found with equal proportions of each soil across lake bottom deposits fragic frassiwassepts are mapped lake cove deposits consist of a fragic frasiwassept histic frasiwassept complex with equal proportions of each soil and lake shoals are comprised of histic frasiwassepts following impoundment creation additions of mineral and organic material likely erosional siltation have resulted in soils with unique morphologic physical and chemical characteristics different from subaerial shoreline soils but expressing a welded morphology that is a product of impoundment creation these characteristics are identifiable across landforms indicative of specific processes to soils and can be reliably mapped in order to support aquatic ecosystem management

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

effectiveness of various cover scenarios on the rate of sulfide oxidation of mine tailings long term environmentally sound disposal of the millions of tons of mining residue is a serious challenge to the international mining industry this paper evaluates through a numerical investigation the potential performance of desulfurized tailings as a cover material for the reduction of acidic drainage from sulfidic tailings this evaluation is facilitated through a comparison of various cover types as decommissioning options the cover types considered consist of a desulfurized tailings material cover exposed to ambient climate conditions a water cover flooded tailings and a combination cover type as part of the evaluation of cover performances the effect of climatic variability on the potential rate of sulfide oxidation in tailings with an open ground surface was also assessed the numerical analysis was conducted using the model pyrox which was modified to allow for variably saturated conditions time varying moisture contents and to account for the temperature dependence of henry s law and gas diffusion in the case study presented here the benign cover material consists of a low sulfide waste stream cassiterite float tails cft a by product of the production of tin concentrate cassiterite sno2 modelling results after a simulation period of 100 years indicate that a water cover alone or an exposed cft cover alone are both less effective options than the combined cover type a water cover alone leads to a reduction of approximately 99 1 in the oxidation rate relative to uncovered tailings while the combined cover type results in the lowest potential extent of sulfide oxidation after mine closure an approximately 99 8 reduction importantly a cft cover exposed to ambient environmental conditions can still substantially reduce the sulfide oxidation rate by approximately 75 82 over a 100 year time period relative to uncovered tailings variability in precipitation and hence percent saturation of the surface layer had less of an effect on the potential sulfide oxidation rate than did the cover type the performance of the exposed cft cover varied by less than 10 within the range of climatic conditions expected at the renison bell mine site in southwest tasmania australia although the modelling results indicate that the combined water and cft cover is the best option this approach achieves only a minor improvement over the water cover alone

petrology and dispersal pattern in the marnoso arenacea formation miocene northern apennines abstract paleocurrent gross composition rock fragment data and heavy mineral data from the miocene marnoso arenacea formation of the northern apennines suggest six source areas five are primarily extrabasinal alpine i and ii apenninic i ii and iii and one is intrabasinal the identification of characteristic multicycle materials reinforces the idea that migration of foredeeps within a plate tectonic framework occurred in the apennines integration of petrofacies paleocurrent and sedimentary facies analysis data in the study of the marnosoarenacea depositional system has proved a very powerful method for understanding the complexity of a deep sea fan system

formation of a hardpan in the co disposal of fly ash and sulfide mine tailings and its influence on the generation of acid mine drainage abstract pilot scale field experiments were conducted to test a strategy for the treatment of acid mine drainage by addition of an alkaline cover of coal combustion fly ash on two sulfide mine tailings impoundments iberian pyrite belt sw spain during the pilot scale treatment calcium rich alkaline solutions from fly ash interacted with metal rich acidic solutions from the mine tailings leading to the massive precipitation of newly formed phases mainly in the fly ash close to the interface between both materials over time the interaction between fly ash and pyrite sludge promoted the formation of a chemically cemented zone or hardpan which was analyzed at high spatial resolution by micro x ray diffraction xrd and micro x ray fluorescence xrf based on synchrotron radiation these micro characterization techniques extensively identified poorly crystalline fe oxyhydroxysulfates jarosite and gypsum as newly formed phases in the hardpan and gypsum in the fly ash as deduced from principal component analysis of the fluorescence intensity data these phases seem to exert a significant mineralogical control on element mobility in particular jarosite showed high affinity for as whereas poorly crystalline fe rich assemblages selectively concentrated mn ni and pb sequential extractions indicated that the application of a fly ash cover significantly reduced the bioavailability of most of the elements by modification of their chemical speciation into less mobile forms under typical oxidizing conditions as an additional advantage the development of the hardpan hindered the penetration of oxidizing agents to sulfide mine tailings this effect significantly reduced the sulfide oxidation rates therefore attenuating the release of potentially pollutant elements to the environment

are mangrove forest substrates sediments or soils a case study in southeastern brazil abstract morphological and analytical data corresponding to several profiles from two mangrove systems in the brazilian state of sao paulo were examined for evidence of pedogenetic processes plant activity exerted a strong effect on the processes occurring in mangrove substrates especially on the intensity of these processes and therefore constitutes one of the major factors involved in the differentiation of sediments and soils colonization of substrates by vascular plants leads to drastic changes in physicochemical conditions the redox processes were much more diverse in the soil than in the sediment substrate without vegetation in the former they varied with depth with oxic or suboxic conditions being observed at the surface and anoxic conditions observed below 30 cm whereas in the sediment anoxic conditions were observed throughout likewise the acid base conditions were more variable in the soils ranging from strongly acid to neutral and in the sediment they were close to neutral furthermore different pedogenetic processes were identified 1 addition of organic matter by accumulation of vegetable debris and dead roots with formation in some cases of a histic epipedon 2 transfer of soluble iron fe2 towards the surface and precipitation in the form of fe oxyhydroxide and transfer of the mineral particles due to the bioturbation caused by activity of crabs 3 transformation of elements such as iron gleization and sulphur sulphidization changes undergone in the mangrove substrates were also characterized by simultaneity and intergradations between pedogenesis and diagenesis especially in the lowermost layers in which authigenesis appears to intensify thus the presence of smectite minerals in the clay fraction may be attributed to authigenic processes that take place in both soils and sediments

the structure and distribution of carbon in 3 5 ga apex chert implications for the biogenicity of earth s oldest putative microfossils the oldest putative microfossils on earth occur in the 3 5 ga apex chert of the warrawoona group western australia we have analyzed disseminated interstitial carbon found within apex chert using transmission electron microscopy tem and electron energy loss spectroscopy eels to address the controversy regarding its state of structural disorder we found that the carbonaceous material is structurally amorphous with no evidence of graphitization and contains aromatic domains most likely as polyaromatic ring structures similar to preserved kerogen in bona fide microfossils in addition amorphous carbonaceous material occurs as a grain boundary phase between quartz crystals and within fluid inclusions in quartz crystals indicating that hydrocarbons moved through the chert during crystallization and hydrothermal alteration the results suggest that the carbonaceous material is similar in structure to microfossil kerogen implying the microbe like features within apex chert are also microfossils however this kerogen like material may also be produced abiotically via fischer tropsch type ftt synthesis reactions in an ancient hydrothermal vent

the formation and potential importance of cemented layers in inactive sulfide mine tailings abstract investigations of inactive sulfide rich tailings impoundments at the heath steele new brunswick and waite amulet quebec minesites have revealed two distinct types of cemented layers or hardpans that at heath steele is 10 15 cm thick occurs 20 30 cm below the depth of active oxidation is continuous throughout the tailings impoundment and is characterized by cementation of tailings by gypsum and fe ii solid phases principally melanterite hardpan at the waite amulet site is only 1 5 cm thick is laterally discontinuous 10 100 cm occurs at the depth of active oxidation and is characterized by cementation of tailings by fe iii minerals principally goethite lepidocrocite ferrihydrite and jarosite at heath steele an accumulation of gas phase co2 of up to 60 of the pore gas occurs below the hardpan the calculated diffusivity of the hardpan layer is only about 1 100 that of the overlying uncemented tailings the pore water chemistry at heath steele has changed little over a 10 year period suggesting that the cemented layer restricts the movement of dissolved metals through the tailings and also acts as a zone of metal accumulation generation of a cemented layer therefore has significant environmental and economic implications it is likely that in sulfide rich tailings impoundments the addition of carbonate rich buffering material during the late stages of tailings deposition would enhance the formation of hardpan layers

animating the biodynamics of soil thickness using process vector analysis a dynamic denudation approach to soil formation this paper expands the dynamic denudation framework of landscape evolution by providing new process insights and details on how soil and its signature morphological feature the biomantle form and function in the environment we examine soils and their biomantles from disparate parts of the world from the tropics through midlatitudes and hyperarid through perhumid a range that exhibits varying environments for and of life we then explicate the process pathways that cause soils to thicken and thin and to even disappear then reform we do this by examining thickness relationships where soil thickness st and biomantle thickness bt are functions of upbuilding u and deepening d minus removal r processes hence st bt f u d r upbuilding has two subsets u1 which includes all exogenous allochthonous outside mineral and or organic inputs to the soil system and u2 which includes all endogenous autochthonous in situ processes and productions including weathering exogenous u1 inputs include eolian and slopewash inputs sedimentations of mineral and organic materials mass wasting accumulations and the like endogenous u2 processes and productions include the sum of in situ bioturbations biosynthetic productions organic accumulations biovoid productions weathering and volume increases caused by their sum endogenous upbuildings which dominantly occur in the biomantle are basically biodynamic bd processes and productions hence u2 bd therefore if exogenous upbuildings u1 are minimal or zero then biomantle thickness bt is expressed by bt f u2 r or bt f bd r drawing on these relationships we employ a graphic conceptual device called process vector analysis in a digital animation see supplementary materials or cf https netfiles uiuc edu jdomier www temp biomantle html that illustrates the main pathways that form both earth s soil and its unique epidermis the biomantle we then discuss the main elements of the animation using still frames that represent thickness turning points we end by encouraging researchers instructors and students to view earth s landforms and soils as integrated dynamic entities that are constantly coevolving elements of a global subaerial subaqueous continuum

factors of subaqueous soil formation a system of quantitative pedology for submersed environments the development and use of estuarine sediment maps for estuarine restoration efforts have been hindered by the lack of a formal classification system or comprehensive model that explains the distribution of sediments to enhance the evaluation understanding and management of sediments in shallow water habitats a new approach must be developed in order to provide a more holistic assessment and cartographic representation of the sediment column having demonstrated that shallow water sediments undergo pedogenic processes and are systematically distributed across the subaqueous landscape we applied this new technique to the development of subaqueous soil resource inventories of sinepuxent bay md and indian river bay de these efforts indicate that the present concept of sediment as unconsolidated geologic materials must give way to a new concept the concept of subaqueous soils in addition our studies indicate the need to alter present methodologies for the acquisition and cartographic representation of sediment data through the utilization of the soil landscape paradigm and a classification scheme such as soil taxonomy for the development of subaqueous soil resource inventories here we present the supporting rationale for the development of subaqueous soil resource inventories and through a synthesis of geologic and pedologic principles and concepts propose a new state factor equation to explain subaqueous soil genesis and distribution

organic chemical differentiation within fossil plant cell walls detected with x ray spectromicroscopy organic matter preserved in cell walls of permineralized plant fossils was analyzed by using scanning transmission x ray microscopy and spectroscopy at energies near the 1s absorption edge of carbon microchemical analyses were performed directly on cellulose acetate peels of the fossils preserving information on the anatomical distribution of organic materials individual tracheid walls in both eocene and early devonian fossils exhibit spatially distinct chemical zoning inherited from original wall biopolymers and cell wall microstructure molecular analysis of submicrometer domains using carbon x ray absorption near edge spectroscopy documents the differential distribution of hydroxylated aromatic and alcohol and or ether carbon in the inner and outer regions of tracheid walls this zonation reflects the deposition of lignin and structural polysaccharides in devonian plants indicating biochemical and developmental pathways similar to those of living tracheophytes

an acid sulfate perspective on landscape seascape soil mineralogy in the u s mid atlantic region abstract a conceptual framework is presented to portray how fe s and other elements ca si k are geologically and pedologically cycled between minerals that are formed and are stable in land based aerobic environments and those that are formed and are stable in anaerobic sea based environments foremost among the elements discussed are fe and s which cycle between fe sulfides formed by sulfidization in the anaerobic sea based environments of tidal marsh and subaqueous soils and sediments and fe oxides and jarosite formed by sulfuricization in upland soils upon the exposure of the sulfide mineral bearing sediments to oxidizing conditions some results of previously conducted experiments are presented to demonstrate that fe oxides placed in the sea based anaerobic tidal marsh and subaqueous soils are rapidly transformed to fe sulfides apparently by the reduction of fe 3 by sulfide of h 2 s generated from sulfate of sea water with the oxidized form of s serving as the electron acceptor during the oxidation of organic matter documentation of rapid sulfuricization of sulfidic materials to form sulfuric horizons upon exposure to aerobic conditions is also presented ca from sea water biologically precipitated as calcite and aragonite in shells of organisms that thrive in brackish sea influenced environments is sometimes transformed temporarily before dissolution and leaching of the ca and sulfate into gypsum by sulfuricization in uplands when the shells are present in exposed sulfidic materials silica is also released from silicate minerals during sulfuricization which can reprecipitate as opal ct to cause cementation of soil materials into duripan like formations in the geologic past opal in the form of diatoms and glauconite formed in tertiary age geologic sediments under marine conditions to become part of the parent materials for upland active and post active acid sulfate soils of the present time modern formation of glauconite in subaqueous soils and shallow sediments has not been found but the topic needs further investigation

ancient graphite in the eoarchean quartz pyroxene rocks from akilia in southern west greenland i petrographic and spectroscopic characterization because all known eoarchean 3 65 ga volcano sedimentary terranes are locked in granitoid gneiss complexes that have experienced high degrees of metamorphism and deformation the origin and mode of preservation of carbonaceous material in the oldest metasedimentary rocks remain a subject of vigorous debate to determine the biogenicity of carbon in graphite in such rocks carbonaceous material must be demonstrably indigenous and its composition should be consistent with thermally altered biogenic carbon as well as inconsistent with abiogenic carbon here we report the petrological and spectroscopic characteristics of carbonaceous material typically associated with individual apatite grains but also with various other minerals including calcite in a 3 83 ga granulite facies ferruginous quartz pyroxene unit qp rock from the island of akilia in southern west greenland in thin sections of the fine grained parts of akilia qp rock sample g91 26 mapped apatites were found to be associated with graphite in about 20 of the occurrences raman spectra of this carbonaceous material had strong g band and small d band absorptions indicative of crystalline graphite three apatite associated graphites were found to contain curled graphite structures identified by an anomalously intense second order d band or 2d band raman mode these structures are similar to graphite whiskers or cones documented to form at high temperatures raman spectra of apatite associated graphite were consistent with formation at temperatures calculated to be between 635 and 830 c which are consistent with granulite facies metamorphic conditions three graphite targets extracted by focused ion beam fib methods contained thin graphite coatings on apatite grains rather than inclusions sensu stricto as inferred from transmitted light microscopy and raman spectroscopy tem analyses of graphite in these fib sections showed a 0 0 0 2 interplanar spacing between 3 41 and 3 64 a for apatite associated graphite which is larger than the spacing of pure graphite 3 35 a and may be caused by the presence of non carbon heteroatoms in interlayer sites samples analyzed by synchrotron based scanning transmission x ray microscopy stxm also confirmed the presence of crystalline graphite but abundances of n and o heteroatoms were below detection limit for this method graphite in the akilia qp rock was also found to occur in complex polyphase mineral assemblages of hornblende calcite sulfides magnetite that point to high temperature precipitation from carbon bearing fluids these complex mineral assemblages may represent another generation of graphitization that could have occurred during the amphibolite facies metamorphic event at 2 7 ga several observations point to graphitization from high temperature fluid deposition for some of the akilia graphite and our results do not exclude a biogenic source of carbon in graphite associated with apatite but ambiguities remain for the origin of this carbon

haematite pseudomicrofossils present in the 3 5 billion year old apex chert microstructures from the 3 5 billion year old apex chert have been interpreted as the remains of ancient cyanobacteria geochemical analyses suggest similar structures at the same location are instead haematite filled fractures although carbonaceous material in the surrounding matrix is consistent with the presence of microbes at this time

structural characterization by raman hyperspectral mapping of organic carbon in the 3 46 billion year old apex chert western australia abstract the 3 46 billion years old apex chert pilbara craton western australia is well known for hosting the oldest highly disputed microfossils on earth this rock has a complex history of thermal alteration that includes circulation of hydrothermal fluids lower greenschist facies regional metamorphism and post metamorphic weathering by meteoric fluids carbonaceous material occurs in the sedimentary stratiform part of the chert as well as the underlying intruding hydrothermal black chert veins in order to identify a least altered remnant of early life it is necessary to develop a method that enables rapid evaluation of cm structural order on a small spatial scale here we present the detailed characterization of cm in the apex chert by raman hyperspectral mapping it is shown that this approach gives better estimates of average raman band ratios than individual point analyses and it is demonstrated that significant differences in structure exist between cm in the stratiform part of the apex chert and cm in an underlying black chert vein the large raman map based datasets also reveal that significant mixing took place between these two end members cm s indicating that the apex chert has been thoroughly altered by hydrothermal fluid circulation at the brecciated intersection between the stratiform chert and the intrusive hydrothermal chert vein very poorly ordered cm was found that is not in line with lower greenschist facies regional metamorphism it is speculated here that this cm represents an organic fraction that was introduced or thoroughly altered by late stage meteoric fluids alternatively the ubiquitous presence of hematite in this sample caused a perturbation in the raman spectra of the cm leading to an artifact in the calculated raman based band ratios overall it can be concluded that the best preserved cm occurs in the stratiform parts of the apex chert while earlier discussions on organic microfossils in this rock often focused on parts of the chert that either represented the hydrothermal veins or the brecciated intersection between the veins and the stratiform part

precambrian microbe like pseudofossils a promising solution to the problem of various problems that have hindered progress in documenting the precambrian history of life the difficulty in distinguishing between bona fide microbial fossils and nonbiological microscopic pseudofossils has been among the most serious though errors in the interpretation of putative precambrian fossil microbes have diminished greatly over recent years mistakes continue to be made we suggest that such errors can be avoided by the use of a multifaceted strategy based on a specified series of biologically definitive characteristics that document the presence of interrelated biological morphology and biologically derived chemistry to illustrate this promising approach we use optical microscopy confocal laser scanning microscopy and raman spectroscopy together to distinguish between authentic microbial fossils and microscopic look alikes both coccoidal and filamentous rock embedded in five proterozoic and two archean geological units bona fide fossils of the 800 ma bitter springs formation of central australia and 3050 ma farrel quartzite of northwestern australia and objects we regard to be pseudofossils from the 770 ma chanda limestone of southern india 800 ma myrtle springs formation of south australia 1020 ma lakhanda formation of southeastern siberia 1700 ma vempalle formation of central india and 2629 ma marra mamba iron formation of northwestern australia the results demonstrate that no single criterion by itself is sufficient to establish the biological origin of such objects instead as shown here this problem appears solvable by the use of an interdisciplinary approach that combines the data and techniques of geology biology and chemistry

a method for the collection of soil monoliths from stony and gravelly soils monolith collection of soils with large amounts of coarse fragments or of wet soils pose specific problems which are directly related to their lack of physical stability the purpose of this paper is to outline a procedure for soil monolith collection which is highly appropriate for these cases a permanent backing is prepared on site with gypsum plaster before detaching the profile from the soil face the soil is initially stabilized with an aqueous suspension of vinyl latex a permanent backing is prepared on site by casting a gypsum plaster slurry between the soil section and a backing board this will fill all voids and anchor the coarse fragments protruding from the soil exposure once the plaster has set the soil monolith can be safely dug out and transported little finishing is needed afterwards in the laboratory the procedure has been successfully demonstrated in a variety of soils in spain

a rock glacier pond system nw italian alps soil and sediment properties geochemistry and trace metal bioavailability abstract rock glacier sediment transfer and ice melting can impact surface waters located downstream however there is a lack of knowledge on the influence of rock glacier dynamics on the geochemical hydrochemical and ecological characteristics of adjacent impounded surface waters in the col d olen area long term ecological research site nw italian alps an intact rock glacier terminates into a pond and solute enriched waters originating from the rock glacier flow into the pond through a subsurface hydrological window in this study we performed geophysical and ground surface temperature measurements moreover we sampled soils and sediments in different compartments of the investigated rock glacier pond system and we further sampled benthic invertebrates in the pond cold ground thermal regime ground ice presence and coarse debris cover on the rock glacier together with its lithology serpentinites influence the rock glacier geochemistry and ecology with respect to surrounding areas pond geochemistry is affected by transfer of trace metal enriched fine grained debris and meltwaters from the rock glacier enhanced bioavailability of serpentinite associated trace metals was proved with concentrations of ni and cr in benthic invertebrates up to 384 and 110 mg kg 1 d w respectively potentially exerting toxic effects on pond biota the advancing movement of the rock glacier not only has delivered sediments to the pond but it has progressively filled the valley depression where the pond is located creating a dam that could have modified the level of impounded water this process likely constituted a sediment trap in which serpentinitic rock glacier sediments could be deposited at the pond bottom with related geochemical and ecological implications this study illustrates the importance of rock glaciers in influencing the characteristics of downstream freshwater bodies and highlights the need to improve our knowledge about climate change related impacts of rock glacier dynamics on alpine headwaters