chloride bearing materials in the southern highlands of mars chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing spectrally distinct surface deposits consistent with chloride bearing materials have been identified and mapped using data from the 2001 mars odyssey thermal emission imaging system these deposits are found throughout regions of low albedo in the southern highlands of mars geomorphologic evidence from orbiting imagery reveals these deposits to be light toned relative to their surroundings and to be polygonally fractured the deposits are small

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

impact of antarctic circumpolar current development on late paleogene ocean structure global cooling and the development of continental scale antarctic glaciation occurred in the late middle eocene to early oligocene 38 to 28 million years ago accompanied by deep ocean reorganization attributed to gradual antarctic circumpolar current acc development our benthic foraminiferal stable isotope comparisons show that a large 13c offset developed between mid depth 600 meters and deep 1000 meters western north atlantic waters in the early oligocene indicating the development of intermediate depth 13c and o2 minima closely linked in the modern ocean to northward incursion of antarctic intermediate water at the same time the ocean s coldest waters became restricted to south of the acc probably forming a bottom ocean layer as in the modern ocean we show that the modern four layer ocean structure surface intermediate deep and bottom waters developed during the early oligocene as a consequence of the acc

microbial colonization of halite from the hyper arid atacama desert studied by raman spectroscopy the hyper arid core of the atacama desert chile is the driest place on earth and is considered a close analogue to the extremely arid conditions on the surface of mars microbial life is very rare in soils of this hyper arid region and autotrophic micro organisms are virtually absent instead photosynthetic micro organisms have successfully colonized the interior of halite crusts which are widespread in the atacama desert these endoevaporitic colonies are an example of life that has adapted to the extreme dryness by colonizing the interior of rocks that provide enhanced moisture conditions as such these colonies represent a novel example of potential life on mars here we present non destructive raman spectroscopical identification of these colonies and their organic remnants spectral signatures revealed the presence of uv protective biomolecules as well as light harvesting pigments pointing to photosynthetic activity compounds of biogenic origin identified within these rocks differed depending on the origins of specimens from particular areas in the desert with differing environmental conditions our results also demonstrate the capability of raman spectroscopy to identify biomarkers within rocks that have a strong astrobiological potential

speleothems in a wave cut notch cayman brac british west indies the integrated product of subaerial precipitation dissolution and microbes abstract a wave cut notch that is deeply incised into the vertical cliff faces of cayman brac is adorned with stalactites stalagmites and columns the prefix notch is applied to each type of speleothem in order to distinguish them from cave speleothems these speleothemic deposits must have formed since the highstand 125 000 years ago which was responsible for the development of the notch the laminated notch speleothems are formed largely of aragonite small and large crystals and calcite columnar fiber and grain coating mats along with minor amounts of dolomite a mg si precipitate kerolite gypsum and halite laminae typically the notch speleothems are the integrated product of precipitation and dissolution that was in some places microbially mediated interpretations based on their mineralogy and internal structures indicate that the composition of the formative waters must have temporally fluctuated with periods of precipitation being interrupted by periods of dissolution the microbes that formed the subaerial biofilms may have influenced some of these processes the aragonite calcite and kerolite probably formed as evaporation and loss of ca through precipitation progressively increased the mg ca and the si ca mg ratios the dolomite gypsum and halite probably formed during early diagenesis during the evaporation of seawater that percolated into the interiors of the notch speleothems

metallic ion binding by bacillus subtilis implications for the fossilization of microorganisms the silicification of bacterial cells has been followed in a laboratory simulation by electron microscopy and energy dispersive x ray spectroscopy structural degradation of the bacteria was not influenced by silica availability but the remains of degraded cells did promote the precipitation of silica in contrast cells reacted with ferric iron before aging remained intact and structures conforming to the original morphology of the bacteria were preserved by silicification the binding of metallic ions by microbial cells in particular the retention of iron is therefore considered to be an important contributing factor to the fossilization of microorganisms

reply to the comment by bolhar et al on growth and recycling of early archaean continental crust geochemical evidence from the coonterunah and warrawoona groups pilbara craton australia by green et al tectonophysics 322 2000 69 88

miniaturized raman instrumentation detects carotenoids in mars analogue rocks from the mojave and atacama deserts this study is primarily focused on proving the potential of miniaturized raman systems to detect any biomolecular and mineral signal in natural geobiological samples that are relevant for future application of the technique within astrobiologically aimed missions on mars a series of evaporites of varying composition and origin from two extremely dry deserts were studied namely atacama and mojave the samples represent both dry evaporitic deposits and recent evaporitic efflorescences from hypersaline brines the samples comprise halite and different types of sulfates and carbonates the samples were analysed in two different ways i directly as untreated rocks and ii as homogenized powders two excitation wavelengths of miniaturized raman spectrometers were compared 532 and 785 nm the potential to detect carotenoids as biomarkers on mars compared with the potential detection of carbonaceous matter using miniaturized instrumentation is discussed

biosignatures and microbial fossils in endolithic microbial communities colonizing ca sulfate crusts in the atacama desert abstract since the description of microbial communities colonizing ca sulfate crusts in the atacama desert there has been much interest in the mechanisms that could lead to the formation and preservation of biosignatures or microbial fossils of these communities a key to understanding physico chemical processes of taphonomy and early diagenesis is to examine microfossils in their natural environment in this study we characterize organomineral traces and microbial fossils found around microbial communities present in these ca sulfate crusts through scanning electron microscopy microanalytical eds and raman spectroscopy techniques calcium carbonate precipitates were detected around remnants of cryptoendolithic algae beneath the crust surface as what seems to be the final step in the organomineralization of these cryptoendolithic communities we also observed alga cell remains permineralized by mg si rich minerals inside gypsum crystals additionally mg si bearing minerals formed a web like structure within the hypoendolithic cyanobacterial habitat via permineralization of extracellular polymeric substances our observations indicate that despite the extremely hyperarid environment microenvironmental conditions may be appropriate for the formation of biosignatures and microbial fossils of extinct endolithic microbial communities a model of the possible organomineralization processes involved is presented

sphaerodoropsis kitazatoi a new species and the first record of sphaerodoridae annelida phyllodocida in sw atlantic abyssal sediments around a whale carcass abstract a new polychaete species sphaerodoropsis kitazatoi annelida phyllodocida sphaerodoridae is described from the abyssal southwest atlantic ocean at the base of sao paulo ridge 4204 m depth this species was found in sediments impacted by a whale carcass the new species has four longitudinal rows of macrotubercles and one transversal row per chaetiger and shares several characters with s anae aguado and rouse 2006 that is also associated with chemosynthetic environments they can be clearly distinguished from s anae and other sphaerodoropsis species by the arrangement and the number of prostomial body and parapodial papillae

seismic and geologic evidence for early paleogene deepwater circulation in the western north atlantic previous studies of paleogeography global climate and foraminiferal stable isotopes have suggested that paleogene deepwater circulation was significantly different from that of today extracting details of deepwater history from the western north atlantic has been hampered by oligocene erosion and the lack of ideally located drill holes we report the discovery of a seismic disconformity on the sw bermuda rise that we have tied to a late paleocene erosional event in deep sea drilling project dsdp boreholes from this region distribution of this new seismic marker reflector ab indicates that it was formed by cyclonically circulating bottom water entering the western north atlantic from the south we attribute this vigorous deep circulation to a southern ocean source analogous to the effects of modern antarctic bottom water this interpretation is supported by isotopic comparisons that show the paleocene southern ocean was enriched in 13c relative to the pacific we distinguish reflector ab from the overlying reflector au on the basis of superposition and ages obtained at dsdp sites and piston cores using one of the cores we have estimated that the youngest age for reflector au is earliest oligocene 36 6 34 0 ma while its oldest age has been previously established as late eocene laminated sediments beneath reflector ab are enriched in organic carbon indicating that the early paleocene deep western north atlantic was occasionally anoxic these low oxygen levels may have been the result of sluggish deep circulation and or low latitude production of warm saline deep water wsdw sediments immediately above reflector ab show that deposition resumed on the western bermuda rise site 387 by the latest paleocene to earliest eocene biochron np10 57 2 0 6 ma while deposition resumed on the central bermuda rise site 386 during the late paleocene erosion nondeposition continued across much of the bermuda rise widespread resumption of pelagic deposition in the early eocene is consistent with 13c evidence for reduced southern ocean influence at this time however lower eocene sediments record well oxygenated conditions and 13c and 18o comparisons indicate that there were two early eocene deepwater sources the southern ocean and wsdw pak and miller this issue

paleoceanographic conditions on the sao paulo ridge sw atlantic ocean for the past 30 million years inferred from os and pb isotopes of a hydrogenous ferromanganese crust abstract hydrogenous ferromanganese fe mn crusts can provide records of long term environmental changes during the cenozoic to understand the paleoceanographic conditions in the southwestern atlantic ocean we investigated depth profiles of major and trace element concentrations as well as os and pb isotopic compositions in a fe mn crust collected from the southern flank of the sao paulo ridge in the southwestern atlantic major and trace element data plotted on ternary mn fe 10 ni co cu and rare earth element plus yttrium rey discrimination diagrams indicate that the analyzed sample is a typical hydrogenous fe mn crust the obtained 187 os 188 os data were matched to the cenozoic seawater os isotope evolution curve reconstructed from pelagic sediments the result suggests that the fe mn crust has accreted over 30 myr with growth rates of 0 5 3 mm myr although the sample likely grew in two directions during the early stage of its growth we found no evidence of growth hiatus in the sample which may contrast with the growth histories of many pacific fe mn crusts hence the conditions favorable for the accretion of hydrogenous fe mn crusts were likely to have developed on the sao paulo ridge over the past 30 myr the pb isotopic compositions show very limited ranges e g 206 pb 204 pb 18 80 18 85 and are similar to those of pre anthropogenic seawater in the southern ocean as the sao paulo ridge is located near the vema channel which is presently a major path of antarctic bottom water we suggest that a strong northward bottom current has continuously swept detrital and biogenic sediments from the ridge and played a vital role in the fe mn crust formation since 30 ma

exploring for a record of ancient martian life the immediate task facing exopaleontology is to define a strategy to explore mars for a fossil record during the decade long exploration program that lies ahead consideration of the quality of paleontological information preserved under different geological conditions is important if we are to develop a strategy with broad applicability the preservation of microbial fossils is strongly influenced by the physical chemical and biological factors of the environment which acting together determine the types of information that will be captured and retained in the rock record in detrital sedimentary systems preservation is favored by rapid burial in fine grained clay rich sediments in chemical sedimentary systems preservation is enhanced by rapid entombment in fine grained chemical precipitates for long term preservation host rocks must be composed of stable minerals that are resistant to chemical weathering and that form an impermeable matrix and closed chemical system to protect biosignatures from alteration during subsequent diagenesis or metamorphism in this context host rocks composed of highly ordered chemically stable mineral phases like silica e g cherts or phosphate e g phosphorites are especially favored such lithologies tend to have very long crustal residence times and along with carbonates and shales are the most common host rocks for the precambrian microfossil record on earth although we make the defensible assumption that mars was more like the earth early in its history clearly the geological and historical differences between the two planets are many such differences must be carefully considered when adapting an earth based strategy to mars

evolution of deepwater mixing and weathering inputs in the central atlantic ocean over the past 33 myr the isotopic composition of nd in present day deep waters of the central and northeastern atlantic ocean is thought to fingerprint mixing of north atlantic deep water with antarctic bottom water the central atlantic romanche and vema fracture zones are considered the most important pathways for deep water exchange between the western and eastern atlantic basins today we present new nd isotope records of the deepwater evolution in the fracture zones obtained from ferromanganese crusts which are inconsistent with simple water mass mixing alone prior to 3 ma and require additional inputs from other sources the new pb isotope time series from the fracture zones are inexplicable by simple mixing of north atlantic deep water and antarctic bottom water for the entire past 33 myr the distinct and relatively invariable nd and pb isotope records of deep waters in the fracture zones appear instead to have been controlled to a large extent by contributions from saharan dust and the orinoco amazon rivers thus the previously observed similarity of nd and pb isotope time series from the western and eastern north atlantic basins is better explainable by direct supply of labrador seawater to the eastern basin via a northern pathway rather than by advection of north atlantic deep water via the romanche and vema fracture zones

a giant oil seep at a salt induced escarpment of the sao paulo plateau espirito santo basin off brazil host rock characteristics and geochemistry abstract an international research cruise named iata piuna took place on the sao paulo plateau on may 2013 in the campos and espirito santo basins off brazil the cruise was carried ou on board the research vessel r v yokosuka that hosts the human operated vehicle hov shinkai 6500 it aimed at finding chemosynthetic communities composed of organisms capable of generating their own vital energy by metabolizing organic and inorganic compounds related to seeps identification of these organisms could provide information for understanding the origin of life since they may resemble primitive organisms that existed in the initial stages of life on earth during leg 2 may 10 24 2013 however dives on the northern part of the sao paulo plateau at the espirito santo basin led to the discovery of a giant oil seep the seep ca 3 nautical miles ca 5 6 km in length is located along an outcrop of eocene rocks on a salt induced escarpment of the plateau and at a water depth of ca 2700 m the 200 m relief of the seafloor suggests that the seep takes place along an active fault system driven by salt diapirism the oil was analyzed and identified as a severely biodegraded marine oil generated by carbonate rocks within a minibasin located to the east of the escarpment this represents valuable exploratory information because it proves that an active petroleum system is present in the context of minibasins associated with salt diapirism in the area

editorial rich geo and bio diversities exist in the south west atlantic deep sea the first human occupied submersible shinkai 6500 dive cruise iata piuna

osmium in seawater vertical profiles of concentration and isotopic composition in the eastern pacific ocean os concentrations 6 6 to 9 8 pg l and isotopic compositions mean 187os 188os 1 067 0 011 2 error were measured by a new method in seawater samples collected from the eastern pacific ocean in contrast to recent work in the indian ocean measured os concentrations display a 30 depletion coincident with both the core of the oxygen minimum zone and a local minimum in light transmission whilst we cannot preclude the possibility that an oxidation resistant form of os in seawater prevented isotopic equilibration between the enriched isotope spike and naturally occurring os which would bias measured concentrations to low values we interpret these data as evidence of non conservative behaviour of os in seawater in this zone the data may be explained by two possible processes the horizontal advection of a water mass of low os concentration from the continental slope and or the in situ adsorption of os onto sinking particles to what extent each process is contributing to the os minimum is unclear from the data the os isotopic composition of these eastern pacific samples are within 2 of those recently reported from the indian ocean which indicates that the isotopic composition of seawater os in these two ocean basins is indistinguishable at this level of precision neutrally buoyant hydrothermal plume samples collected in close proximity to active vents at 9 46 n on the east pacific rise have os concentrations and isotopic compositions similar to ambient deep water this shows that the flux of os from high temperature hydrothermal vents is not large compared to the inventory of os in ambient seawater comparisons between filtered and unfiltered samples show that the majority of seawater os in these samples is in the dissolved phase

unusual secondary ca mg carbonate kerolite deposits in basaltic caves kauai hawaii abstract aragonite calcite monohydrocalcite dolomite magnesite hydromagnesite and talc like kerolite have been identified in speleothems from basaltic caves on the island of kauai hawaii these secondary minerals have crystallized in the presence of freshwater seeping from the basaltic host rock and the mineralization process is ongoing at some locations the deposits are extremely variable in macroscopic character ranging from millimeter thin powdery coatings to hard crusts several centimeters thick many deposits are associated with actively forming microbial mats and stromatolitic structures are common in the thicker deposits formation of the mineral deposits is a result of a combination of direct precipitation from solution by evaporation and co2 degassing alteration of precursor minerals and or microbial processes and physicochemical conditions within the mats these unusual deposits provide important insights into the mineralogy and geochemistry of low temperature alteration and carb

mg silica precipitation in fossilization mechanisms of sand tufa endolithic microbial community mono lake california abstract the detection of mg silica associated with endolithic biofilms of cyanobacteria and bacterial communities living in lake shore sand tufa formations in mono lake california has been observed using scanning electron microscopy with backscattered electron imaging sem bse and energy dispersive x ray spectroscopy eds mg accumulated in cell walls of living cyanobacteria is interpreted to promote mg silicification with structural preservation while non cyanobacterial prokaryotes are not fossilized however extracellular polymeric substances around the living communities were prominent as nucleation sites for authigenic mineral precipitation a mg silicate served to stabilize the biofilm remains further diagenesis of these textures resulted in occlusion of the cytoplasm pore spaces by carbonate precipitates this precipitate damaged the microfossil structures but the mg silica fabric was still present the paleontological significance of mg silica precipitates as a possible biosignature of the former presence of endolithic biofilms is addressed

calcification generates protons for nutrient and bicarbonate uptake abstract the biosphere s great carbonate deposits from caliche soils to deep sea carbonate oozes precipitate largely as by products of autotrophic nutrient acquisition physiologies protons constitute the critical link calcification generates protons which plants and photosynthetic symbioses use to assimilate bicarbonate and nutrients a calcium atpase based trans mechanism underlies most biological calcification this permits high calcium carbonate supersaturations and rapid carbonate precipitation the competitive advantages of calcification become especially apparent in light and nutrient deficient alkaline environments calcareous plants often dominate the lower euphotic zone in both the benthos and the plankton geographically and seasonally massive calcification concentrates in nutrient deficient environments including alkaline soils coral reefs cyanobacterial mats and coccolithophorid blooms structural and defensive uses for calcareous skeletons are sometimes overrated

new age for ferromanganese crust 109d c and implications for isotopic records of lead neodymium hafnium and thallium in the pliocene indian ocean 1 this study presents a high resolution record of osmium and thallium isotopes in a ferro manganese fe mn crust from the indian ocean antipode 109d c these results when combined with additional new os isotope data from odp hole 756b in the southeast indian ocean define a new best estimate for the age at the base of this crust of 6 5 ma which is significantly different from a previous estimate of 15 ma based on co flux modeling the tl isotope record obtained for the indian ocean resembles that for the pacific ocean with a small but well defined increase occurring over the last 5 myr this contrasts with two records from the atlantic ocean which do not have resolvable variations ocean basin scale tl isotope variation may be inconsistent with the inferred modern marine residence time for tl of 20 kyr but could be explained by an increase in ocean crust production rates in the pacific and indian oceans since 10 ma the improved age model for 109d c reveals that the hf isotope composition of indian ocean bottom waters has remained homogenous over the last 6 myr thus this isotope system does not bear any evidence that the influence of north atlantic deep water in the formation of indian ocean bottom waters has changed during that time however because of the lack of knowledge about hf isotopes as a tracer of ocean circulation we cannot conclude that export of nadw decreased over the last 6 myr

a lead isotopic study of circum antarctic manganese nodules abstract lead isotope ratios in manganese nodules from the circum antarctic ocean display systematic geographical variations eastward in the direction of current movement from south of australia they progressively decrease in the pacific sector and into the western atlantic sector until 30 w from this longitude lead isotope ratios increase in the eastern atlantic sector and reach their highest values in the indian sector near 110 e south of western australia they abruptly decrease these two lead isotope domains correspond closely to the circum antarctic neodymium isotope domains previously recognized by albarede and goldstein 1992 however the intraocean isotopic variations are much clearer for pb than nd reflecting the shorter oceanic residence time of pb 102 y compared with nd 103 y and confirming that pb is a much more sensitive marine tracer throughout the circum antarctic ocean the lead isotopic changes follow the pattern of present day oceanic circulation the pb shows an overall continental signature which is strongest in the indian sector the most probable candidate as the source of the continental signal is north atlantic deep water nadw which enters the circum antarctic in the south atlantic as nadw mixes with circumpolar water lead isotope ratios increase eastward in the indian sector reflecting progressive loss of the pacific derived pb signal the abrupt decrease of lead isotope ratios between the indian and pacific sectors appears to be a consequence of addition of pacific seawater through the pacific lead isotope ratios gradually decrease eastward approaching values of east pacific rise metalliferous sediments ocean ridge basalts and south pacific mn nodules this trend results from an increasing influence of pacific ocean water containing a component derived from pacific volcanism the pacific signature persists into the argentine basin in the southwest atlantic ocean reflecting significant input of water from the drake passage northward into the atlantic the pacific pb component is seen in the atlantic and indian oceans near southern africa as well as in the atlantic and indian sectors of the circum antarctic lead and neodymium isotopes correlate in the atlantic indian sectors but not in the pacific sector reflecting differences in residence times and modes of water mass mixing the renewal of circum antarctic water occurs on a timescale which is short compared to the residence time of nd but long compared to pb as a result dissolved pb is subject to considerable changes over the timescale of circumpolar current movement while nd is less easily affected nadw is added locally in the south atlantic and moves eastward as a water mass as nadw mixes with circumpolar water cpw through the indian sector changes affecting nd pb in nadw and cpw occur in tandem and neodymium and lead isotopes are correlated through the pacific sector gradual addition of pacific seawater occurs over a large region and nd pb relationships are not coupled because simple isotopic mixing systematics are not conserved there neodymium and lead isotopes vary independently the consistency of lead isotope variations with present day ocean bottom water circulation is remarkable considering that the mn nodules as sampled reflect the integrated flux of pb over 105 106 y the oceanic mixing time is 103 y the residence time for pb is 102 y and the circulation time of the circumantarctic ocean is 30 y processes occurring over such different timescales can show such a relationship only if the system is stable over the longest time interval thus on average element sources and ocean circulation through the pleistocene have been similar to the present day despite significant perturbations during glacial periods

miocene seawater 187os 188os ratios inferred from metalliferous carbonates abstract seawater 187os 188os ratios for the middle miocene were reconstructed by measuring the 187os 188os ratios of metalliferous carbonates from the pacific dsdp 598 and atlantic dsdp 521 oceans atlantic and pacific 187os 188os measurements are nearly indistinguishable and are consistent with previously published os isotope records from pacific cores the atlantic data reported here provide the first direct evidence that the long term sedimentary 187os 188os record reflects whole ocean changes in the os isotopic composition of seawater the pacific and the atlantic os measurements confirm a long term 0 01 myr increase in marine 187os 188os ratios that began no later than 16 ma the beginning of the os isotopic increase coincided with a decrease in the rate of increase of marine 87sr 86sr ratios at 16 ma a large increase of 1 in benthic foraminiferal 18o values interpreted to reflect global cooling and ice sheet growth began approximately 1 million years later at 14 8 ma and the long term shift toward lower bulk carbonate 13c values began more than 2 myr later around 13 6 ma the post 16 ma increase in marine 187os 188os ratios was most likely forced by weathering of radiogenic materials either old sediments or sialic crust with a sedimentary protolith we consider two possible miocene specific geologic events that can account for both this increase in marine 187os 188os ratios and also nearly constant 87sr 86sr ratios 1 the first glacial erosion of sediment covered cratons in the northern hemisphere 2 the exhumation of the australian passive margin new guinea arc system the latter event offers a mechanism via enhanced availability of soluble ca and mg silicates in the arc terrane for the maintenance of assumed low co2 levels after 15 ma the temporal resolution three samples myr of the 187os 188os record from site 598 for which a stable isotope stratigraphy was also constructed is significantly higher than that of previously published records these high resolution data suggest oscillations with amplitudes of 0 01 to 0 02 and periods of around 1 myr although variations in the 187os 188os record of this magnitude can be easily resolved analytically this higher frequency signal must be verified at other sites before it can be safely interpreted as global in extent however the short term 187os 188os variations may correlate inversely with short term benthic foraminiferal 18o and bulk carbonate 13c variations that reflect glacioeustatic events

discovery of asphalt seeps in the deep southwest atlantic off brazil abstract the discovery and description of cold seeps with deep sea chemosynthetic communities in the southwest atlantic ocean are still incomplete despite the large proven oil and gas reserves off the coast of brazil in the southeastern brazilian continental margin where over 71 of the country s oil and gas production takes place there are previous geological and qualitative biological evidence of seep biota associated with pockmarks on the upper slope of the santos basin in order to further study seep ecosystems on the brazilian margin a deep sea investigation named iata piuna cruise was conducted using the human occupied vehicle shinkai 6500 off brazil s southeast continental margin asphalt seeps were discovered on the seafloor of the north sao paulo plateau from depths of 2652 2752 m representing only the third discovery of this type of seep worldwide following those in the gulf of mexico and off angola video and isotopic analyses indicated a number of megabenthic animals in the asphalt seeps in the north sao paulo plateau and revealed typical deep sea heterotrophic and photosynthesis based fauna occupying hard substrates provided by the asphalt seep there was no evidence of chemosynthesis based megabenthic fauna such as vesicomyid clams bathymodiolus mussels and siboglinid tube worms or any sediment bacterial mats gas seepage and carbonate rock in around the seeps the benthic fauna was composed mainly of sponges ca 15 species such as the hexactinellids caulophacus sp poliopogon amadou saccocalyx pedunculatus farrea occa and cf chonelasma choanoides besides typical deep sea isidid octocorals brisingid starfishes and galatheid crabs the 13c values of poriferan sponges suggested a heterotrophic and pelagic nutrition geochemical analyses of asphalt revealed a heavy biodegradation of hydrocarbon molecules supported by the depletion of light n alkanes and other labile compounds this advanced asphalt biodegradation is the likely reason for the absence of chemosynthetic communities at these seep sites

improved os isotope stratigraphy of the arctic ocean 1 the history of the arctic ocean remained poorly known until the 2004 iodp coring of lomonosov ridge sediments early studies of the recovered sequence demonstrated the existence of an eocene lake stage prior to the transition to marine conditions the marine stage onset was inferred to be 17 5 million years ma ago thus implying a nearly 26 ma gap between the lacustrine and marine episodes and an unusual tectonic history for lomonosov ridge in order to explain this gap more recently rhenium osmium re os isotope measurements of the transition from the lacustrine to marine sediments suggested a much earlier inception of marine conditions and the absence of any significant gap between both episodes here an improved osmium isotope stratigraphy and re os data concur to assign a late eocene age 36 ma to the marine invasion consistent with a relative change in sea level on top of lomonosov ridge either from tectonic origin or from another cause

major and trace element geochemistry and os isotopic composition of metalliferous umbers from the late cretaceous japanese accretionary complex 1 metalliferous umbers and red shales occur as unique products of the kula pacific ridge forearc collision in the late cretaceous shimanto supergroup an accretionary complex in japan these umbers are closely associated with greenstones of mid ocean ridge basalt morb origin and are regarded as hydrothermal metalliferous precipitates related to mor type volcanism the umbers and red shales were deposited in the trench area where both terrigenous detritus from land and hydrothermal metalliferous particulates from a mor were supplied simultaneously besides a predominance of fe and mn the umbers exhibit remarkable enrichments in p v co ni zn y mo rare earth elements rees and os relative to continental crustal abundances the x fe x mn p v co ni zn y and rees ratios and paas normalized ree patterns of the umbers are very similar to those of modern hydrothermal plume fallout precipitates deposited on flanks of mor this indicates that the umbers preserve primary geochemical signatures of hydrothermal metalliferous sediments that scavenged seawater derived elements and thus can be used as a proxy for late cretaceous seawater the marine 187os 188os ratios reconstructed from the late maastrichtian umbers range from 0 42 to 0 56 and are very consistent with recent data obtained from the pacific and atlantic pelagic carbonates that record an abrupt decline from 0 55 to 0 4 during the period between 67 0 ma and 65 7 ma

impact of biomineralization on the preservation of microorganisms during fossilization an experimental perspective abstract the biogenicity of fossil microbial biomorphs is often debated because their morphologies are poorly informative and the chemical structural and isotopic signatures of putative biogenic organic molecules have been altered during their incorporation into the sediments and the geological history of the host rock here we investigated the effect of encrustation by biominerals on the morphological and chemical degradation of escherichia coli cells during experimental thermal treatments non calcified e coli cells and e coli cells encrusted by calcium phosphates were exposed to heating under an argon atmosphere at two different temperatures 300 c 600 c for 20 h two additional experiments were performed on non calcified e coli cells at 300 c for 2 h and 100 h to discuss the influence of experiment duration organic residues of all experiments were characterized at a multiple length scale using a combination of scanning electron microscopy transmission electron microscopy raman microspectroscopy electron paramagnetic resonance epr spectroscopy fourier transform infrared ft ir spectroscopy and x ray absorption near edge structure spectroscopy xanes at the carbon k edge in the absence of encrusting biominerals the morphological structure of the organic residues of e coli cells was completely lost after heating at 300 or 600 c even after short 2 h long heating experiments the content of aromatic functional groups of the organic residues of non calcified e coli cells increased during heat treatment at 600 c for 20 h while the amide functional groups were lost as indicated by ft ir spectroscopy consistently the epr spectrum of these organic residues indicated important transformation as a comparison this spectrum appeared similar to epr spectra of ancient organic carbons such as carbons from the apex chert ca 3460 myr indicating a similar concentration of aromatic moieties in contrast calcified e coli exposed to the same conditions showed only limited morphological alteration as observed by electron microscopy as well as lower chemical transformation as detected by ft ir and epr spectroscopies despite the difficulties to relate experimental conditions directly to geological conditions these experiments evidence the influence of cell encrustation by minerals on their chemical and morphological preservation potential during fossilization processes

going nano a new step toward understanding the processes governing freshwater ooid formation marine and freshwater ooids were historically thought to form by purely physicochemical processes in turbulent environments recently organomineralization has been identified as a key process for the initiation of freshwater ooid cortex formation but the exact biochemical mechanism s involved and subsequent contribution to the development of the growing cortex remain unknown here we show that photosynthetic microbes not only enhance early carbonate precipitation around the ooid nucleus but also control the formation of the entire cortex in freshwater ooids from lake geneva switzerland microbial extracellular polymeric substances are first permineralized as amorphous magnesium silicates am mg si before being calcified an 5 6 depletion of 13 c in ooid cortices compared to both bulk values and carbonate nuclei supports this photosynthetic microbial mechanism and argues against contributions from sulfate reducing bacteria or methanogens these data have significant implications for paleoenvironmental studies since photosynthetic microbes now provide an alternative to turbulent hydrodynamic conditions in the formation of freshwater ooids

ignimbrite as a substrate for endolithic life in the hyper arid atacama desert implications for the search for life on mars the hyper arid core of the atacama desert in chile is considered the driest and most life limited place on earth with few habitats capable of sustaining an active microbial ecosystem as such it is one of the best terrestrial analogues of the extreme arid conditions on mars and an ideal environment to explore survival and biological adaptation strategies as the environment becomes increasingly dry here we show that weakly welded rhyolitic ignimbrites in this desert are abundantly colonized by endolithic cyanobacteria and associated heterotrophic bacteria we propose that the porous ignimbrite interior provides protection from damaging uv radiation and excessive levels of visible light rock porosity also favors cell hydration through water retention after scarce rainfall events even when the surrounding environment remains stubbornly dry this is the first known example of an endolithic microbial community colonizing ignimbrite rocks in an extremely dry environment the existence of a habitat capable of supporting abundant phototrophic and heterotrophic communities in an environment that precludes most life forms suggests that if similar deposits are found on mars these should be considered important targets in the search for life indeed ignimbrite rocks have been tentatively identified in gale crater the landing site of the mars science laboratory msl mission and could be directly analyzed by its rover curiosity

formation of fe silicates and fe oxides on bacterial surfaces in samples collected near hydrothermal vents on the southern explorer ridge in the northeast pacific ocean samples collected in low temperature 2 50 degrees c waters near hydrothermal vents of the southern explorer ridge in the northeast pacific ocean contained fine 500 nm fe and mn oxide and fe silicate particles coating bacterial surfaces partially to totally mineralized bacteria along with bacterial exopolymers were covered with a mixture of poorly ordered si rich fe oxides possibly ferrihydrite mn oxides and fe silicates possibly nontronite minerals occur as very fine 2 20 nm granular material fine 20 100 nm needles and sheets small 200 500 nm nodules and filaments i e mineralized exopolymers under saturation conditions we infer that bacterial surfaces provided nucleation sites for poorly ordered oxides and silicates the formation of fe and mn oxides was likely initiated by the direct binding of soluble fe and mn species to reactive sites like carboxyl phosphate and hydroxyl groups present within the bacterial cell wall and the exopolymers fe silicate formation involved a more complex binding mechanism whereas metal ions such as fe possibly bridged reactive sites within the cell walls to silicate anions to initiate silicate nucleation

microbial nucleation of calcium carbonate in the precambrian microbial sulfate reduction is thought to stimulate carbonate precipitation in modern stromatolites yet whether this metabolism was important in shaping precambrian stromatolites is unknown here we use geochemical modeling to suggest that the influence of sulfate reduction on the saturation index of calcite si is negligible when seawater is in equilibrium with high pco 2 as is thought for the precambrian our laboratory experiments with heterotrophic bacteria in a medium mimicking precambrian seawater chemistry show that even if sulfate reduction does not significantly change the si the presence of bacteria stimulates calcite precipitation over sterile controls by effectively increasing the si over a ph range from 7 3 to 7 8 under our experimental conditions dead cells stimulate in situ carbonate precipitation equally if not more than active sulfate reducing bacteria heterogeneous nucleation of calcite by microbial cell material appears to be the driving mechanism that explains this phenomenon

melting in the hawaiian plume at 1 2 ma as recorded at maui nui the role of eclogite peridotite and source mixing 1 the volcanoes of maui nui west moloka i east moloka i lana i west maui haleakala and kaho olawe record hawaiian magmatism at 1 2 ma lavas from these volcanoes nearly span the compositional range erupted from all the hawaiian volcanoes over the past 5 myr and represent both the kea and ko olau compositional end members of hawaiian lavas many aspects of major and trace element and isotope compositions of hawaiian shield stage lavas are consistent with ancient recycled oceanic lithosphere in the plume sources of kea and ko olau type magmas lassiter and hauri 1998 blichert toft et al 1999 hypotheses that describe the compositional range of hawaiian lavas as originating from ancient oceanic lithosphere in the hawaiian plume implicitly or explicitly infer lithologic heterogeneity in the plume we present trace element models for the origin of these end members that explicitly address the petrologic complexities of melting eclogite derived from ancient oceanic lithosphere in the plume trace element la nb sm yb sm hf and sm nb major element and isotope compositions of lana i which erupts dominantly ko olau type lavas are consistent with the origin of these lavas in large degree 60 70 melts of ancient upper oceanic crust basalt sediment that mix with plume derived haleakala type melts trace element sm yb hf zr and hf nb and isotope compositions of west maui and east moloka i which erupt dominantly kea type magmas are consistent with an origin in ancient depleted oceanic lithosphere that has been refertilized with moderate degree melts 10 30 of associated crustal gabbro the physical mechanisms melt melt versus melt solid mixing through which the oceanic crustal components melt and mix within the plume lead to the generation of isotopically homogeneous kea type lavas and isotopically heterogeneous ko olau type lavas the volcanoes of maui nui record the exhaustion of the ko olau component and the initiation of the kea component as dominant compositional end members in the hawaiian plume

the osmium riverine flux and the oceanic mass balance of osmium the osmium concentration os and isotopic composition were determined in a set of 17 of the largest rivers of the world os varies between 4 6 and 52 1 pg kg and the 187os 188os ratio varies between 0 64 and 2 94 measurement of rainwater samples shows that there is no input of oceanic os to the continent through rain assuming a negligible anthropogenic os input in the dissolved load the natural average river water has an os concentration of 7 9 pg kg and a mean 187os 188os ratio of 1 54 the total riverine flux of os to the ocean is estimated to be 295 kg yr the dissolved os flux from island arcs and oceanic islands represents less than 5 of the total riverine flux and is not further considered the continental os flux to the ocean is then represented by the riverine flux as dissolved os from eolian dust and glacial sediments is negligible assuming steady state it is possible to estimate a maximum unradiogenic flux to the ocean of 126 kg yr cosmic dust or mantle derived and an oceanic residence time between 2 5 104 and 5 4 104 with a mean of 3 5 104 year the estimation of the flux of dissolved cosmic particles shows that their contribution to the seawater os would be 14 of the contribution of the unradiogenic component which means that the mantle derived flux should contribute a major part the first results on water from high temperature axial hydrothermal systems indicate that their input is probably negligible which would necessitate that dominant contribution from the low temperature alteration of the oceanic crust and or of the ultramafic exposures contributes dominantly to the input of unradiogenic os to the seawater we show that it would be necessary to leach 1 3 of the os contained in the volume of ultramafic exposures accessible to seawater to account for all of the unradiogenic component contribution another simpler but less likely possibility is that the dissolved cosmic dust represents the only source of dissolved unradiogenic os to the ocean in which case the riverine input represents 94 of the total dissolved flux to the ocean instead of 70 the modern global dissolved os flux to the ocean would then have a 187os 188os ratio of 1 44 instead of 1 06 and the system would be far from steady state

60 myr records of major elements and pb nd isotopes from hydrogenous ferromanganese crusts reconstruction of seawater paleochemistry we compare the time series of major element geochemical and pb and nd isotopic composition obtained for seven hydrogenous ferromanganese crusts from the atlantic indian and pacific oceans which cover the last 60 myr average crust growth rates and age depth relationships were determined directly for the last about 10 myr using be 10 be 9 profiles in the absence of other information these were extrapolated to the base of the crusts assuming constant growth rates and constant initial be 10 be 9 ratios due to the lack of additional information co contents have also been used previously to estimate growth rates in co rich pacific and atlantic seamount crusts puteanus and halbach 1988 a comparison of be 10 be 9 and co based dating of three co rich crusts supports the validity of this approach and confirms the earlier chronologies derived from extrapolated be 10 be 9 based growth rates back to 60 ma our data show that the flux of co into co poor crusts has been considerably lower the relationship between growth rate and co content for the co poor crusts developed from these data is in good agreement with a previous study of a wider range of marine deposits manheim 1986 the results suggest that the co content provides detailed information on the growth history of ferromanganese crusts particularly prior to 10 12 ma where the be 10 based method is not applicable the distributions of pb and nd isotopes in the deep oceans over the last 60 myr are expected to be controlled by two main factors a variations of oceanic mixing patterns and flow paths of water masses with distinct isotopic signatures related to major paleogeographic changes and b variability of supply rates or provenance of detrital material delivered to the ocean linked to climate change glaciations or major tectonic uplift the major element profiles of crusts in this study show neither systematic features which are common to crusts with similar isotope records nor do they generally show coherent relationships to the isotope records within a single crust consequently any interpretation of time series of major element concentrations of a single crust in terms of paleoceanograghic variations must be considered with caution this is because local processes appear to have dominated over more basin wide paleoceanographic effects in this study co is the only element which shows a relationship to pb and nd isotopes in pacific crusts a possible link to changes of pacific deep water properties associated with an enhanced northward advection of antarctic bottom water from about 14 ma is consistent with the pb but not with the nd isotopic results the self consistent profiles of the pb and nd isotopes suggest that postdepositional diagenetic processes in hydrogenous crusts including phosphatization events have been insignificant for particle reactive elements such as pb be and nd isotope time series of pb and nd show no systematic relationships with major element contents of the crusts which supports their use as tracers of paleo seawater isotopic composition

tufa forming biofilms of german karstwater streams microorganisms exopolymers hydrochemistry and calcification to understand mechanisms of tufa biofilm calcification selected karstwater stream stromatolites in germany have been investigated with regard to their hydrochemistry biofilm community exopolymers physicochemical microgradients calcification pattern and lamination in stream waters co2 degassing drives the increase in calcite saturation to maximum values of approximately 10 fold independent from the initial ca2 alkalinity ratio for the cyanobacteria of tufa biofilms a culture independent molecular approach showed that microscopy of resinembedded biofilm thin sections underestimated the actual diversity of cyanobacteria i e the six cyanobacteria morphotypes were opposed to nine different lineages of the 16s rdna phylogeny the same morphotype may even represent two genetically distant cyanobacteria and the closest relatives of tufa biofilm cyanobacteria may be from quite different habitats diatom diversity was even higher in the biofilm at the studied exemplar site than that of the cyanobacteria i e 13 diatom species opposed to 9 cyanobacterial lineages the non phototrophic prokaryotic biofilm community is clearly different from the soil derived community of the stream waters and largely composed of flavobacteria firmicutes proteobacteria and actinobacteria the exopolymeric biofilm matrix can be divided into three structural domains by fluorescence lectin binding analysis seasonal and spatial variability of these structural eps domains is low in the investigated streams as indicated by microsensor data biofilm photosynthesis is the driving mechanism in tufa stromatolite formation however photosynthesis induced biofilm calcification accounts for only 10 20 of the total ca2 loss in the streams and occurs in parallel to inorganic precipitation driven by co2 degassing within the water column and on biofilm free surfaces annual stromatolite laminae reflect seasonal changes in temperature and light supply the stable carbon isotope composition of the laminae is not affected by photosynthesis induced microgradients but from pedley h m rogerson m eds tufas and speleothems unravelling the microbial and physical controls geological society london special publications 336 83 118 doi 10 1144 sp336 6 0305 8719 10 15 00 the geological society of london 2010 mirrors that of the bulk water body only reflecting climate fluctuations tufa stromatolites with their cyanobacterial photosynthesis related calcification fabrics form an analogue to porostromate cyanobacterial stromatolites in fossil settings high in caco3 mineral supersaturation but comparatively low in dissolved inorganic carbon here the sum effect of heterotrophic exopolymerdegradation and secondary ca2 release rather decreases calcite saturation contrary to settings high in dissolved inorganic carbon such as soda lakes geobiological significance of tufa

testing evidence of recent hydration state change in sulfates on mars the east candor interior layered deposit ild has signatures of mono and polyhydrated sulfate in alternating layers that give insight into the processes which formed these layered deposits and on the environmental conditions acting on them since then we use orbital data to explore multiple hypotheses for how these deposits formed 1 sulfate bearing ilds experience hydration changes on seasonal to a few years timescales under current mars environmental conditions 2 the deposits experience hydration under recent mars conditions but require the wetter climate of high obliquity and 3 the kieserite could be an original or diagenetic part of a complex evaporite mineral assemblage modeled climatology shows recent mars environmental conditions might pass between multiple sulfate fields however comparison of observatoire pour la mineralogie l eau les glaces et l activite omega and compact reconnaissance imaging spectrometer crism observations of the same ild do not show changes in hydration over 2 mars years low temperatures might slow the kinetics of that transition it is likely that more clement conditions during periods of high obliquity are needed to overcome mineral metastability and hydrate kieserite bearing deposits we find the alternate model that the deposit is a cyclic evaporite sequence of mono and polyhydrated sulfates also plausible but with an unexplained dearth of fe sulfates

microbialite formation in seawater of increased alkalinity satonda crater lake indonesia abstract the crater lake of the small volcanic island satonda indonesia is unique for its red algal microbial reefs thriving in marine derived water of increased alkalinity the lake is a potential analogue for ancient oceans sustaining microbialites under open marine conditions current reef surfaces are dominated by living red algae covered by non calcified biofilms with scattered cyanobacteria and diatoms minor caco3 precipitates are restricted to the seasonally flooded reef tops which develop biofilms up to 500 m thick dominated by the cyanobacteria pleurocapsa calothrix phormidium and hyella microcrystalline aragonite patches form within the biofilm mucilage and fibrous aragonite cements grow in exopolymer poor spaces such as the inside of dead lysed green algal cells and reef framework voids cementation of lysed hadromerid sponge resting bodies results in the formation of wetheredella like structures hydrochemistry data and model calculations indicate that co2 degassing after seasonal mixis can shift the carbonate equilibrium to cause caco3 precipitation increased concentrations of dissolved inorganic carbon limit the ability of autotrophic biofilm microorganisms to shift the carbonate equilibrium therefore photosynthesis induced cyanobacterial calcification does not occur instead passive diffusion controlled eps mediated permineralization of biofilm mucus at contact with the considerably supersaturated open lake water takes place in contrast to extreme soda lakes the release of ca2 from aerobic degradation of extracellular polymeric substances does not support caco3 precipitation in satonda because the simultaneously released co2 is insufficiently buffered subfossil reef parts comprise green algal tufts encrusted by microstromatolites with layers of fibrous aragonite and an amorphous unidentified mg si phase the microstromatolites probably formed when lake satonda evolved from seawater to ca2 depleted raised alkalinity conditions because of sulfate reduction in bottom sediments and pronounced seasonality with deep mixing events and strong co2 degassing the latter effect caused rapid growth of fibrous aragonite while mg si layers replaced the initially mg calcite impregnated biofilms this could be explained by dissolution of siliceous diatoms and sponge spicules at high ph followed by mg calcite dissolution and mg silica precipitation at low ph due to heterotrophic activity within the entombed biofilms

ecology and spatial pattern of cyanobacterial community island patches in the atacama desert chile 1 plant landscape ecology studies have been carried out for decades and are fundamental to biological research in contrast few corollary spatial landscape studies exist for microorganisms particularly in extreme environments to address this gap we mapped the abundance and spatial distribution of photoautotrophs colonizing translucent rocks in several sites in the atacama desert including the hyperarid core cyanobacterial communities at all sites are predominantly 75 perilithic confined to the periphery of rocks and occur in non random spatial patterns island patches at multiple scales cyanobacterial patches typically contain 1 5 colonized rocks but in some cases support much higher numbers a high resolution mapping of a single 18 m2 rock cluster at the aguas calientes study site 25 s 69 w revealed colonization of 5 2 49 of 948 quartz rocks and showed colonized rocks to be much larger 2x than the available mean rock size ripley s k and point pattern analyses show that quartz rocks are not selected or occupied by cyanobacteria randomly but that non random processes distinct from those creating the background rock pattern must be invoked to explain microbial patchiness in the atacama desert these processes include physical controls rock size orientation microtopography that reflect resource water limitations and biological dispersal via rainfall fog and wind

endolithic cyanobacteria in soil gypsum occurrences in atacama chile mojave united states and al jafr basin jordan deserts 1 soil sulfates are present in arid and hyperarid environments on earth and have been found to be abundant in soils on mars examination of soil gypsum from the atacama desert chile the mojave desert united states and al jafr basin jordan revealed endolithic cyanobacteria communities just below the surface of soil gypsum samples optical and scanning electron microscope observations of the colonized layers indicated that the unicellular chroococcidiopsis is the dominant cyanobacterium in all studied communities 16s rrna gene analysis revealed that in addition to chroococcidiopsis a few other cyanobacteria are present heterotrophic bacteria are also abundant in the colonized zones of the fine grained gypsum from the atacama and mojave desert but insignificant in the fibrous gypsum from the jordan desert endolithic life forms similar to these described here may exist or have existed on mars and should be targeted by the mars science laboratory and future in situ missions

trace element abundances of high mgo glasses from kilauea mauna loa and haleakala volcanoes hawaii we performed an ion microprobe study of eleven high mgo 6 7 14 8 wt tholeiite glasses from the hawaiian volcanoes kilauea mauna loa and haleakala we determined the rare earth re high field strength and other selected trace element abundances of these glasses and used the data to establish their relationship to typical hawaiian shield tholeiite and to infer characteristics of their source the glasses have trace element abundance characteristics generally similar to those of typical shield tholeiites e g l light ree h heavy reec1 1 the kilauea and mauna loa glasses however display trace and major element characteristics that cross geochemical discriminants observed between kilauea and mauna loa shield lavas the glasses contain a blend of these discriminating chemical characteristics and are not exactly like the typical shield lavas from either volcano the production of these hybrid magmas likely requires a complexly zoned source rather than two unique sources when corrected for olivine fractionation the glass data show correlations between cao concentration and incompatible trace element abundances indicating that cao may behave incompatibly during melting of the tholeiite source furthermore the tholeiite source must contain residual garnet and clinopyroxene to account for the variation in trace element abundances of the kilauea glasses inversion modeling indicates that the kilauea source is flat relative to c1 chondrites and has a higher bulk distribution coefficient for the hree than the lree

intershield geochemical differences among hawaiian volcanoes implications for source compositions melting process and magma ascent paths as hawaiian volcanoes develop their lavas systematically change in composition and isotopic ratios of sr nd and pb these trends provide important constraints for understanding plume related volcanism as a volcano migrates away from the hotspot there are also geochemical differences between hawaiian shields in particular lavas from adjacent shields such as kilauea and mauna loa on hawaii and koolau and waianae on oahu have significant differences in abundances of some major and incompatible elements and isotopic ratios of sr nd and pb some incompatible element abundance ratios such as zr nb and sr nb are correlated with intershield differences in sr and nd isotope ratios but these isotopic ratios are not correlated with intershield differences in major element composition or even parent daughter abundance ratios such as rb sr and sm nd moreover at kilauea and mauna loa the intershield differences have apparently persisted for a relatively long time perhaps 100 ka these intershield geochemical differences provide important constraints on plume volcanism specifically i each volcano must have distinct magma ascent paths from the region of melt segregation ii the 25 50 km distance between adjacent but geochemically distinct shields requires that the sources vary on a similar scale and that the melt production region is similarly restricted the absence of correlations between lava compositions and radiogenic isotope ratios provides evidence for significant differences in melting process such as each shield forming by a different mean extent of melting with melt segregation at different mean pressures two types of models are consistent with the intershield geochemical differences i a relatively large radius ca 40 km plume conduit with a systematic spatial distribution of geochemical heterogeneities or ii a small radius less than 20 km plume conduit composed of geochemically distinct diapirs because relatively small radius diapirs of limited vertical extent are too small to create the large hawaiian shields a possible alternative is a continuous conduit containing solitary waves which transport geochemically distinct packets of material

seawater sr isotopes at the cretaceous tertiary boundary abstract seawater 87 sr 86 sr values increase abruptly by 28 10 6 across the cretaceous tertiary boundary ktb this small but rapid shift is superimposed on the larger scale structure of the seawater sr isotope curve the time scale of radiogenic sr addition appears to be too rapid to reconcile with sources associated with volcanism and we show that the amount of sr required to produce even this small increase is too large to be derived from 1 a kt bolide of the size constrained by the ir anomaly 2 continental crust ejecta from the impact of such a bolide 3 soot from global wildfires initiated by an impact or 4 any combination of these sources the probable source of the radiogenic sr is enhanced continental weathering but the high rate of increase appears to rule out processes such as sea level regression glaciation or tectonism a plausible mechanism for rapid addition of radiogenic sr to the oceans is enhanced weathering associated with globally distributed acid rain ph 1 which is a proposed by product of a bolide impact 51 epsl vol 83

a new species of africanacetus odontoceti ziphiidae found on the deep ocean floor off the coast of brazil abstract a fossil skull of a beaked whale was newly collected by a manned submersible from the sao paulo ridge of the atlantic floor about 2900 m deep off the coast of brazil it was found in the middle of the manganese nodules on the seafloor the whale fossil can be dated sometime between the middle miocene and the early pliocene based on the timing of the onset of the tectonic movements of the sao paulo ridge whence the specimen came and the precipitation of the manganese layers which entirely encrusted the specimen this is the first instance of a fossil beaked whale skull retrieved from such great depths this skull belongs to a new species of africanacetus which may be a genus with a broad distribution in southern oceans in neogene times expands the geographic distribution of the genus as the northernmost record and adds the taxonomic and morphological diversity within the genus

late neogene history of deepwater ventilation in the southern ocean we compiled carbon isotope records from the north atlantic south atlantic and pacific oceans to estimate changes in vertical and interbasinal 13c gradients for the last 9 myr benthic 13c values of deep water in the south atlantic decreased in a series of steps at 7 2 75 and 1 55 ma away from the north atlantic and toward the pacific the benthic 13c of intermediate water in the south atlantic evolved differently from deep waters resulting in an increase in the intermediate to deep 13c gradient 13cid the 13cid increased in steps at 2 75 and 1 55 ma marking the development and intensification of a chemical divide in the atlantic ocean between well ventilated intermediate water and poorly ventilated deep water we suggest these changes in interbasinal and vertical gradients resulted from decreasing northern component water and reduced ventilation of southern component water scw the latter was caused by several interrelated processes in antarctic sources areas including increased sea ice cover enhanced surface water stratification decreased ekman induced upwelling and reduced vertical mixing across the thermocline because antarctic surface water processes and deepwater ventilation rates ultimately influence atmospheric co2 concentration these processes may have acted as a positive feedback that contributed to the major cooling steps in late neogene climate

cotectic proportions of olivine and spinel in olivine tholeiitic basalt and evaluation of pre eruptive processes the volume distribution texture and composition of coexisting olivine cr spinel and glass has been determined in quenched lava samples from hawaii iceland and mid oceanic ridges the volume ratio of olivine to spinel varies from 60 to 2800 and samples with 0 02 spinel have a volume ratio of olivine to spinel of approximately 100 a plot of wt mgo vs ppm cr for natural and experimental basaltic glasses suggests that the general trend of the glasses can be explained by the crystallization of a cotectic ratio of olivine to spinel of about 100 one group of samples has an olivine to spinel ratio of approximately 100 with skeletal olivine phenocrysts and small 100mm spinel crystals that show evidence of two stages of growth and a volume ratio of olivine to spinel of 100 to well over 1000 the olivine and spinel in this group have crystallized more slowly with little physical interaction and show evidence that they have accumulated in a magma chamber

the nature of fossil bacteria a guide to the search for extraterrestrial life in an attempt to establish reliable criteria for the identification of potential fossil life in extraterrestrial materials the fossilizable characteristics of bacteria namely size shape cell wall texture association and colony formation are described and an overview is given of the ways in which fossil bacteria are preserved as compressions in fine grained sediments preservation in amber permineralized by silica replacement by minerals such as silica pyrite fe mn oxides calcite phosphate and siderite or as molds in minerals the problem of confounding minerally replaced bacteria with non biological structures having a bacterial morphology is addressed examples of fossilized bacteria from the early archaean through to the recent are used to illustrate the various modes of preservation and the morphology of fossil bacteria

formation of fine grained metal and silicate precipitates on a bacterial surface bacillus subtilis abstract the ability of the gram positive bacterium b subtilis to bind and nucleate precipitates from silicate anions has been studied over 24 weeks in the presence of fe and a1 at concentrations close to those levels in soils and at slightly acid 5 5 and basic 8 0 ph in all cases formation of silicate crystallites quasi crystalline precipitates on the bacterial surfaces was observed bacterially mediated minerals were more diverse in composition and morphology less crystalline smaller and sometimes more abundant than those that were abiotically formed fe pretreatment of the bacterial cells enhanced the binding of silicate at ph 8 0 walls which were not pretreated with fe bound silicate more favourably at acid values when heavy metals pb cd zn cr ni cu were added to the mixture at ph 4 5 silicate retention was greatly favoured giving greater retention of either si or metals than was seen in abiotic controls experiments with only heavy metals showed a high affinity of the bacterial walls for the metals even at low temperatures 4 c it is postulated that a cationic bridging mechanism is involved in the binding of silicate anions by bacterial cell walls

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

endolithic microorganisms in the antarctic cold desert in the frigid desert of the antarctic dry valleys there are no visible life forms on the surface of the soil or rocks yet in certain rock types a narrow subsurface zone has a favorable microclimate and is colonized by microorganisms dominant are lichens of unusual organization they survive not by physiological adaptation to lower temperatures but by changing their mode of growth being able to grow between the crystals of porous rocks their activity results in mobilization of iron compounds and in rock weatherning with a characteristic pattern of exfoliation this simple ecosystem lacks both higher consumers and predators

subsidence and volcanism of the haleakala ridge hawaii abstract side looking sonar gloria mapping has revealed a series of four arcuate bands of high sonic backscatter on the crest of the haleakala ridge a major rift zone ridge extending 135 km east of the island of maui dredge recovery indicates that the shallowest of these bands is a drowned coral reef and the deeper bands are also inferred to be coral reefs the reefs occur above a prominent submarine bench 1500 2500 m deep on the ridge h terrace that marks the shoreline at the end of vigorous shield building of haleakala volcano when lava flows ceased crossing and reworking the shoreline since their growth these reefs have subsided as much as 2200 m and have tilted systematically about 20 m km southward as a result of post reef volcanic loading on the island of hawaii whose center of mass is about directly south of the haleakala ridge the 234u 238u age of the dredged coral is 750 13 ka in reasonable agreement with an age of 850 ka for the underlying h terrace previously estimated from its relationship to other dated reefs to the southwest basalt glass fragments dredged from the haleakala ridge below the h terrace are tholeiitic and contain high sulfur indicative of eruption in water deeper than 200 m basalt glass fragments associated with the reefs above the h terrace are dominantly tholeiitic and contain intermediate sulfur contents indicative of subaqueous eruption in shallow near shore conditions one alkalic glass fragment was recovered above the h terrace these relations indicate that the morphologic end of shield building as recorded by construction of the h terrace was not accompanyed by a change from tholeiitic to alkalic basalt instead tholeiite eruptions continued for some time before the erupted lava became alkalic

the late eocene 187os 188os excursion chemostratigraphy cosmic dust flux and the early oligocene glaciation abstract high resolution records ca 100 kyr of os isotope composition 187os 188os in bulk sediments from two tropical pacific sites odp sites 1218 and 1219 capture the complete late eocene 187os 188os excursion and confirm that the late eocene 187os 188os minimum earlier reported by ravizza and peucker ehrenbrink earth planet sci lett 210 2003 151 165 is a global feature using the astronomically tuned age models available for these sites it is suggested that the late eocene 187os 188os minimum can be placed at 34 5 0 1 ma in the marine records in addition two other distinct features of the 187os 188os excursion that are correlatable among sections are proposed as chemostratigraphic markers which can serve as age control points with a precision of ca 0 1 myr we propose a speculative hypothesis that higher cosmic dust flux in the late eocene may have contributed to global cooling and early oligocene glaciation oi 1 by supplying bio essential trace elements to the oceans and thereby resulting in higher ocean productivity enhanced burial of organic carbon and draw down of atmospheric co2 to determine if the hypothesis that enhanced cosmic dust flux in the late eocene was a cause for the 187os 188os excursion can be tested by using the paired bulk sediment and leachate os isotope composition 187os 188os were also measured in sediment leachates results of analyses of leachates are inconsistent between the south atlantic and the pacific sites and therefore do not yield a robust test of this hypothesis comparison of 187os 188os records with high resolution benthic foraminiferal 18o records across the eocene oligocene transition suggests that 187os flux to the oceans decreased during cooling and ice growth leading to the oi 1 glaciation whereas subsequent decay of ice sheets and deglacial weathering drove seawater 187os 188os to higher values although the precise timing and magnitude of these changes in weathering fluxes and their effects on the marine 187os 188os records are obscured by recovery from the late eocene 187os 188os excursion evidence of the global influence of glaciation on supply of os to the ocean is robust as it has now been documented in both pacific and atlantic records

north atlantic deep water export to the southern ocean over the past 14 myr evidence from nd and pb isotopes in ferromanganese crusts the intensity of north atlantic deep water nadw production has been one of the most important parameters controlling the global thermohaline ocean circulation system and climate here we present a new approach to reconstruct the overall strength of nadw export from the north atlantic to the southern ocean over the past 14 myr applying the deep water nd and pb isotope composition as recorded by ferromanganese crusts and nodules we present the first long term nd and pb isotope time series for deep southern ocean water masses which are compared with previously published time series for nadw from the nw atlantic ocean these data suggest a continuous and strong export of nadw or a precursor of it into the southern ocean between 14 and 3 ma an increasing difference in nd and pb isotope compositions between the nw atlantic and the southern ocean over the past 3 myr gives evidence for a progressive overall reduction of nadw export since the onset of northern hemisphere glaciation nhg the nd isotope data allow us to assess at least semiquantitatively that the amount of this reduction has been in the range between 14 and 37 depending on location

organic amine biomarker detection in the yungay region of the atacama desert with the urey instrument 1 the urey in situ organic compound analysis instrument consisting of a subcritical water extractor scwe and a portable microchip capillary electrophoresis instrument called the mars organic analyzer moa was field tested in the atacama desert chile in june 2005 soil samples from the most arid yungay region were collected biomarkers were extracted by the scwe and organic amine composition and amino acid chirality analysis was performed by the moa samples collected from the top 1 cm of duracrust soil but shielded from the ambient environment by rocks were compared to the exposed duracrust the shielded duracrust yielded amines and amino acids ranging from 50 to 100 ppb while amino acid signals from the exposed duracrust were below blank levels samples from buried gypsum deposits located directly above a water flow channel contained amino acids ranging from 13 to 90 ppb chiral analysis revealed d l ratios of 0 39 0 08 and 0 34 0 07 for alanine serine and 0 78 0 06 for aspartic acid indicating significant racemization of biologically produced amino acids on the basis of the d l ratios we estimate sample ages ranging from 103 to 105 years these results demonstrate the successful field testing of the urey instrument as well as the detection of biomarkers from past terrestrial life in one of the most arid and mars like regions on earth

new constraints on the pb and nd isotopic evolution of ne atlantic water masses 1 time series of lead pb and neodymium nd isotope compositions were measured on three ferromanganese crusts recording the evolution of ne atlantic water masses over the past 15 ma the crusts are distributed along a depth profile 700 4600 m comprising the present day depths of mediterranean outflow water and north east atlantic deep water a pronounced increase of the 206pb 204pb in the two deeper crusts starting at 4 ma and a decrease in 143nd 144nd in all three crusts took place between 6 4 ma and the present these patterns are similar to isotope time series in the western north atlantic basin and are consistent with efficient mixing between the two basins however the changes occurred 1 3 ma earlier in the eastern basin indicating that the northeastern atlantic led the major change in pb and nd isotope composition probably due to a direct supply of labrador seawater via a northern route the pb isotope evolution during the pliocene pleistocene can generally be explained by mixing between two end members corresponding to mediterranean outflow water and north east atlantic deep water but external sources such as saharan dust are likely to have played a role as well the pb isotope composition of the shallowest crust that grew within the present day mediterranean outflow water does not show significant pb isotope changes indicating that it was controlled by the same pb sources throughout the past 15 ma

dolomite formation within microbial mats in the coastal sabkha of abu dhabi united arab emirates microbial mediation is the only demonstrated mechanism to precipitate dolomite under earth surface conditions a link between microbial activity and dolomite formation in the sabkha of abu dhabi has until now not been evaluated even though this environment is cited frequently as the type analogue for many ancient evaporitic sequences such an evaluation is the purpose of this study which is based on a geochemical and petrographic investigation of three sites located on the coastal sabkha of abu dhabi along a transect from the intertidal to the supratidal zone this investigation revealed a close association between microbial mats and dolomite suggesting that microbes are involved in the mineralization process observations using scanning electron microscopy equipped with a cryotransfer system indicate that authigenic dolomite precipitates within the exopolymeric substances constituting the microbial mats in current models microbial dolomite precipitation is linked to an active microbial activity that sustains high ph and alkalinity and decreased sulphate concentrations in pore waters such models can be applied to the sabkha environment to explain dolomite formation within microbial mats present at the surface of the intertidal zone by contrast these models cannot be applied to the supratidal zone where abundant dolomite is present within buried mats that no longer show signs of intensive microbial activity as no abiotic mechanism is known to form dolomite at earth surface conditions two different hypotheses can reconcile this result in a first scenario all of the dolomite present in the supratidal zone formed in the past when the mats were active at the surface in a second scenario dolomite formation continues within the buried and inactive mats in order to explain dolomite formation in the absence of active microbial metabolisms a revised microbial model is proposed in which the mineral template properties of exopolymeric substances play a crucial role

morphology and micro fabrics of weathering features on gyprock exposures in a semiarid environment ebro tertiary basin ne spain abstract gyprock is a common rock in evaporitic formations which have a wide distribution across all continents however outcrops of gyprock are rather limited occurring mainly in low rainfall areas i e southwest of usa italy spain gyprock is one of the most common lithology in the ebro tertiary basin here semiarid conditions propitiate the development of specific weathering processes and landforms with significant implications for understanding the genesis of soils and the geomorphological evolution of these areas gypsum crystallization within the pores and fissures of gyprock close to the surface leads to volume increase and pressures with the consequent weathering of this rock as a result considerable porosity develops producing peculiar morphologies on gyprock outcrops domes and decimetre scale blisters specific microscopic features voids with plain walls horse shoe pores and serrated pores as well as microscopic fabrics grating fabric skeletal fabric fan fabric and botryoidal fabric this paper presents a morphological characterization of the material forming the various types of weathering features from microscopic to mesoscopic scale the macromorphology and micromorphology of those features were used to interpret their genesis

the link between biomineralization and fossilization of bacteria insights from field and experimental studies abstract fossil biominerals and fossils of microorganisms in ancient rocks contain important biogeochemical signals decoding this record may reveal crucial information about the evolution of life on earth and terrestrial paleoenvironments however the identification of traces of life especially in very old rocks is extremely challenging because the morphological and chemical signatures of biominerals and microfossils are subtle of microscopic size and inevitably altered with aging in this review we stress on the fact that biomineralization is often the first step of fossilization and produces particular chemical structural and morphological features that can be preserved in fossil biominerals or microfossils with a special focus on fe biomineralization the taphonomic processes affecting biominerals and microfossils and altering their morphology and or chemical composition over time are then discussed in light of experimental fossilization simulations and field sample analyses we suggest that taxonomic biases observed in the fossil record may be related to differential abilities of species to trigger biomineralization this calls for studies of the effective biomineralizing activity and fossilization potential of each species present in highly diverse natural microbial communities finally recent analytical developments leave little doubt that very substantial progress in the study of biomineralization processes and ancient biostructures will be achieved in the near future

weathering of granite in antarctica i light penetration into rock and implications for rock weathering and endolithic communities where rocks are composed of translucent minerals light penetrates the rock and in so doing impacts on the thermal conditions where minerals are not translucent all the heat transformation must be at the rock surface and steep thermal gradients can occur where light does penetrate a component of the incoming radiation is transformed to heat at differing depths within the rock thereby decreasing the thermal gradient equally light transmissive minerals facilitate endolithic communities which can also play a role in rock weathering the attribute of light transmission within rock and the impact this has on the resulting thermal conditions has not been considered within rock weathering studies an attempt was made to monitor the amount of light penetrating the outer 2 mm of coarse granite under antarctic summer conditions and to evaluate the thermal impact of this it was found that the amount of light penetration at this site exceeded modeled or postulated values from biological studies and that it could significantly impact the thermal conditions within the outer shell of the rock although the resulting data highlighted a number of flaws in the experimental procedure sufficient information was generated to provide the first assessment of the range of thermal responses due to light transmissive minerals in rock copyright 2007 john wiley sons ltd

geomicrobiology of carbonate silicate microbialites from hawaiian basaltic sea caves abstract modern microbial mats and microbialites are described from basaltic sea caves on the island of kauai hi the mats grow on the ceilings and walls in the photic zone of several open caves where fresh water seeps out of the rock scanning sem and transmission electron microscopy tem showed that the active mats are dominated by filamentous and nonfilamentous cyanobacteria in the surface layers and heterotrophic bacteria in deeper layers energy dispersive x ray analysis revealed that copious amounts of extracellular polymeric substances eps are rich in mg si o and ca likely concentrated from solution petrographic microscopy and electron microprobe analysis of the mineralized microbialites showed textures reminiscent of stromatolitic laminations consisting mainly of alternating calcium carbonate calcite and aragonite and magnesium rich silicate kerolite thin coatings rich in magnesite hydromagnesite and monohydrocalcite surround the microbialites on the rock surfaces and are likely inorganic in origin within the mats minerals tend to form and concentrate within or around dense matrices of eps microenvironments with geochemical conditions favorable for mineral crystallization likely develop in the mats as a result of the mucilaginous extracellular material and the development of bacterial microcolonies in addition copious amounts of extracellular polymers bind ions from solution and provide nucleation sites for mineral crystallization and growth this combination of biological and inorganic processes can explain the occurrence of the secondary minerals in these caves as well as the stromatolitic textures of the microbialites

nanotextures of aragonite in stromatolites from the quasi marine satonda crater lake indonesia stromatolites have been extensively used as indicators of ancient life on earth although much work has been done on modern stromatolites the extent to which biological processes control their structure and the respective contributions of biological and abiotic processes in their formation are however still poorly constrained a better description of the mineralogical textures of these formations at the submicrometre scale may help improve our understanding of how carbonates nucleate and grow in stromatolites here we used a combination of microscopy and microspectroscopy techniques to study the chemical composition and the texture of aragonite in lacustrine stromatolites from the alkaline crator lake in satonda indonesia several textural features are described including morphological variations of aragonite from nanosized grains to micrometre sized fibres the presence of striations in the aragonite laminae showing a striking similarity with growth bands in corals and clusters of small aragonite crystals sharing a common crystallographic orientation these nanotextural features are compared with those observed in scleractinian corals and possible processes involved in their formation are discussed the geological society of london 2010

origin of terrestrial gypsum dunes implications for martian gypsum rich dunes of olympia undae abstract the estancia white sands guadalupe and cuatrocienegas dune fields are among the largest known aeolian gypsum sand dune accumulations on earth and occupy closed drainage basins within the rio grande rift high sedimentation rates of lacustrine gypsum occur in topographic depressions within the closed basins the gypsum accumulations result from long term complex interaction between tectonism climate and a hydrologic cycle that involves geochemical recycling of sulfur from older sedimentary rocks flanking and underlying the basins gypsum precipitation in lacustrine environments is strongly controlled by local groundwater bedrock interaction the ranges of 34s values per mil vs vcdt for gypsum sand in the white sands dune field 12 1 to 13 9 guadalupe dune field 10 2 to 12 5 and cuatrocienegas dune field 14 6 to 15 9 indicate that the main sources of dissolved sulfate are evaporite strata of lower permian middle permian and cretaceous ages respectively a spatial increase of 34s values across the white sands dune field in the direction of prevailing winds matches well with a stratigraphically upward increase of 34s values recorded in lake otero an ancient lake in the basin strata this finding supports previous suggestions that white sands dune field evolved as a result of the step wise deflation of previously stored sediments in lake otero the modern gypsum dune fields are primarily wet eolian systems in which dune accumulation is controlled by a near surface groundwater table which promotes early cementation of the dune accumulations early cementation in the interdune surfaces and to a lesser degree on the dune surfaces reduces the amount of sand available for transport and slows rates of dune migration based on an average migration rate of 2 m year the time needed for a dune at white sands to migrate the downwind distance of the dune field is approximately 6500 years which matches well with other estimates of the initiation of the dune field at approximately 7000 years ago and indicates that white sands likely evolved as a wet aeolian system as on earth gypsum rich dune fields apparently are rare on mars gypsum has been identified only within the olympia undae dune field which encircles a portion of the martian north polar residual ice cap analogous to terrestrial gypsum dunes the gypsum within the olympia undae gypsum rich dunes might have originated from transport and deposition via aeolian processes in this model gypsum rich source sediment could have been formed by confined groundwater or surface water activity and later transported by the wind any subsequent gypsum precipitation in the source area could have been initiated by episodic melting of the martian polar ice cap it is likely that the gypsum was deposited in the olympia undae dunes after the main deflation events that led to formation of the siliciclastic components of the dune field