discrimination of biogenic and detrital magnetite through a double verwey transition temperature magnetite occurs widely in natural environments in both inorganic and biogenic forms discrimination of the origin of magnetite has important implications from searching for past microbial activity to interpreting paleomagnetic and environmental magnetic records in a wide range of settings in this study we present rock magnetic and electron microscopic analyses of marine sediments from the continental margin of oman low temperature magnetic data reveal two distinct verwey transition tv temperatures that are associated with the presence of biogenic and inorganic magnetite this interpretation is consistent with room temperature magnetic properties and is confirmed by electron microscopic analyses our study justifies the use of two distinct tv temperatures as a diagnostic signature for discriminating inorganic and biogenic magnetite simple low temperature magnetic measurements therefore provide a tool to recognize rapidly the origin of magnetite within natural samples in addition our analyses reveal progressive down core dissolution of detrital and biogenic magnetite but with preservation of significant amounts of fine grained magnetite within sediments that have been subjected to severe diagenetic alteration we demonstrate that preservation of magnetite in such environments is due to protection of fine grained magnetite inclusions within silicate hosts our results therefore also provide new insights into diagenetic processes in marine sediments

release of ni from birnessite during transformation of birnessite to todorokite implications for ni cycling in marine sediments abstract the phyllomanganate birnessite is the main mn bearing phase in oxic marine sediments where it exerts a primary control on the concentration of micronutrient trace metals in seawater however during sediment diagenesis and under mild hydrothermal conditions birnessite transforms into the tectomanganate todorokite we have recently shown that the transformation of birnessite to todorokite proceeds via a four stage nucleation and growth mechanism beginning with todorokite nucleation then crystal growth from solution to form todorokite primary particles followed by their self assembly and oriented growth via oriented attachment to form crystalline todorokite laths culminating in traditional crystal ripening atkins et al 2014 here we determine the fate and mobility of ni sorbed by birnessite during this transformation process specifically in our recent work we predict that the presence of ni within the phyllomanganate matrix will disrupt the formation of todorokite primary particles as such contrary to current understanding we suggest that ni sorbed by birnessite will slow the transformation of birnessite to todorokite and or be released to marine porewaters during sediment diagenesis here we transform a synthetic poorly crystalline ni sorbed 1 wt ni hexagonal birnessite analogous to marine birnessite into todorokite under a mild reflux procedure developed to mimic marine diagenesis and mild hydrothermal conditions we characterise our birnessite and reflux products as a time series including x ray diffraction xrd high resolution transmission electron microscopy hr tem and extended x ray absorption fine structure exafs spectroscopy in addition we determine ni speciation and mineral phase associations in a suite of natural marine ferromanganese precipitates containing intermixed phyllomanganate and todorokite our work shows for the first time that ni significantly slows the transformation of birnessite to todorokite and reduces the crystallinity of the neo formed todorokite phase but does not alter the mechanism and pathway of todorokite formation compared to a ni free system furthermore in systems tending towards todorokite as the final diagenetic product we see that up to 50 of the ni originally sequestered by birnessite is released to solution during the transformation our work indicates that the transformation of birnessite to todorokite in oxic marine sediments likely provides a significant source of ni to marine sedimentary porewaters and potentially a hitherto unrecognized benthic flux of ni to seawater

evidence for a rapid release of carbon at the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm and associated carbon isotope excursion cie are often touted as the best geologic analog for the current anthropogenic rise in pco2 however a causal mechanism for the petm cie remains unidentified because of large uncertainties in the duration of the cie s onset here we report on a sequence of rhythmic sedimentary couplets comprising the paleocene eocene marlboro clay salisbury embayment these couplets have corresponding 18o cycles that imply a climatic origin seasonal insolation is the only regular climate cycle that can plausibly account for 18o amplitudes and layer counts high resolution stable isotope records show 3 5 13c decrease over 13 couplets defining the cie onset which requires a large instantaneous release of 13c depleted carbon during the cie a clear 13c gradient developed on the shelf with the largest excursions in shallowest waters indicating atmospheric 13c decreased by 20 our observations and revised release rate are consistent with an atmospheric perturbation of 3 000 gigatons of carbon gtc

presence of an iron rich nanophase material in the upper layer of the cretaceous tertiary boundary clay abstract we report new geochemical evidence from ten cretaceous tertiary k t boundary sites in north america and europe indicating the presence of a material remnant of a large asteroid or comet that struck the earth at 65 0 ma mossbauer spectroscopic data reveals that a ubiquitous iron rich nanophase material exists at the uppermost part of the k t boundary layer in the western hemisphere and in europe marine and continental fine grained sedimentary rock the high surface to volume ratio of nanophase material suggests that it may be the carrier of the iridium abundance enhancement that marks the k t boundary even more provocative is the possibility that discovered nanophase material is for the most part composed of the vaporized impactor after the impact generated high temperature vapor plume rose and cooled above the atmosphere introduction in the last two decades an enormous amount of chemical and physical evidence has been gathered that supports the idea that a large asteroid or comet struck earth at

sorption of ni by lithiophorite asbolane intermediates in moa bay lateritic deposits eastern cuba abstract the moa bay ni co laterite deposits placed in the so called mayari baracoa ophiolitic belt eastern cuba are oxide type despite its geological relevance and economical impact no detailed studies exist with regards to cristallochemical characterization of ni incorporated in or attached to the main ni containing minerals forming the lateritic profile a sample corresponding to the ore limonite horizon has been studied by microfocus raman micro x ray diffraction xrd electron probe micro analysis epma and synchrotron radiation microfocus x ray absorption spectroscopy xas to gain structural and chemical information on ni the data obtained has revealed that ni is preferably accumulated in quantities up to 21 wt in lithiophorite asbolane intermediates the local environment of ni shows ni mn distances 3 5 a suggesting that ni is sorbed mostly in inner sphere complexes sitting on mn vacancies and at the edge of the mn layers however it is shown that in the presence of al the ni is incorporated within the lithiophorite asbolane intermediate by developing brucite like interlayers the understanding of ni sorption mechanisms within the limonite horizon suggests that combined physicochemical factors such as soil porosity and ph regime have important implications for ni mobility across the profile

an appalachian amazon magnetofossil evidence for the development of a tropical river like system in the mid atlantic united states during the paleocene eocene thermal maximum on the mid atlantic coastal plain of the united states paleocene sands and silts are replaced during the paleocene eocene thermal maximum petm by the kaolinite rich marlboro clay the clay preserves abundant magnetite produced by magnetotactic bacteria and novel presumptively eukaryotic iron biomineralizing microorganisms using ferromagnetic resonance spectroscopy and electron microscopy we map the magnetofossil distribution in the context of stratigraphy and carbon isotope data and identify three magnetic facies in the clay one characterized by a mix of detrital particles and magnetofossils a second with a higher magnetofossil to detrital ratio and a third with only transient magnetofossils the distribution of these facies suggests that suboxic conditions promoting magnetofossil production and preservation occurred throughout inner middle neritic sediments of the salisbury embayment but extended only transiently to outer neritic sediments and the flanks of the embayment such a distribution is consistent with the development of a system resembling a modern tropical river dominated shelf

magnetofossil spike during the paleocene eocene thermal maximum ferromagnetic resonance rock magnetic and electron microscopy evidence from ancora new jersey united states previous workers identified a magnetically anomalous clay layer deposited on the northern united states atlantic coastal plain during the paleocene eocene thermal maximum petm the finding inspired the highly controversial hypothesis that a cometary impact triggered the petm here we present ferromagnetic resonance fmr isothermal and anhysteretic remanent magnetization first order reversal curve and transmission electron microscopy analyses of late paleocene and early eocene sediments in drillcore from ancora new jersey a novel paleogeographic analysis applying a recent paleomagnetic pole from the faeroe islands indicates that new jersey during the initial eocene had a 6 9 degrees lower paleolatitude 27 3 degrees for ancora and a more zonal shoreline trace than in conventional reconstructions our investigations of the petm clay from ancora reveal abundant magnetite nanoparticles bearing signature traits of crystals produced by magnetotactic bacteria this result the first identification of ancient biogenic magnetite using fmr argues that the anomalous magnetic properties of the petm sediments are not produced by an impact they instead reflect environmental changes along the eastern margin of north america during the petm that led to enhanced production and or preservation of magnetofossils

rock magnetic criteria for the detection of biogenic magnetite abstract we report results on the magnetic properties of magnetites produced by magnetotactic and dissimilatory iron reducing bacteria magnetotactic bacterial mtb strains ms1 mv1 and mv2 and dissimilatory iron reducing bacterium strain gs 15 grown in pure cultures were used in this study our results suggest that a combination of room temperature coercivity analysis and low temperature remanence measurements provides a characteristic magnetic signature for intact chains of single domain sd particles of magnetite from mtbs the most useful magnetic property measurements include 1 acquisition and demagnetization of isothermal remanent magnetization irm using static pulse and alternating fields 2 acquisition of anhysteretic remanent magnetization arm and 3 thermal dependence of low temperature 20 k saturation irm after cooling in zero field zfc or in a 2 5 t field fc from 300 k however potentially the most diagnostic magnetic parameter for magnetosome chain identification in bulk sediment samples is related to the difference between low temperature zero field and field cooled sirms on warming through the verwey transition t 100 k intact chains of unoxidized magnetite magnetosomes have ratios of fc zfc greater than 2 where the parameter is a measure of the amount of remanence lost by warming through the verwey transition disruption of the chain structure or conversion of the magnetosomes to maghemite reduces the fc zfc ratio to around 1 similar to values observed for some inorganic magnetite maghemite greigite and gs 15 particles numerical simulations of fc zfc ratios for simple binary mixtures of magnetosome chains and inorganic magnetic fractions suggest that the fc zfc parameter can be a sensitive indicator of biogenic magnetite in the form of intact chains of magnetite magnetosomes and can be a useful magnetic technique for identifying them in whole sediment samples the strength of our approach lies in the comparative ease and rapidity with which magnetic measurements can be made compared to techniques such as electron microscopy

nucleation and growth of todorokite from birnessite implications for trace metal cycling in marine sediments the phyllomanganate birnessite is the main mn bearing phase in oxic marine sediments and through coupled sorption and redox exerts a strong control on the oceanic concentration of micronutrient trace metals however under diagenesis and mild hydrothermal conditions birnessite undergoes transformation to the tectomanganate todorokite the mechanistic details of this transformation are important for the speciation and mobility of metals sequestered by birnessite and are necessary in order to quantify the role of marine sediments in global trace element cycles here we transform a synthetic poorly crystalline hexagonal birnessite analogous to marine birnessite into todorokite under a mild reflux procedure developed to mimic marine diagenesis and mild hydrothermal conditions we characterize our birnessite and reflux products as a time series employing x ray diffraction xrd fourier transform infrared spectroscopy ftir bet surface area analysis scanning electron microscopy sem high resolution transmission electron microscopy hr tem and extended x ray absorption fine structure spectroscopy exafs we provide new insight into the crystallization pathway and mechanism of todorokite formation from birnessite under conditions analogous to those found in marine diagenetic and hydrothermal settings specifically we propose a new four stage process for the transformation of birnessite to todorokite beginning with todorokite nucleation then crystal growth from solution to form todorokite primary particles followed by their self assembly and oriented growth via oriented attachment to form crystalline todorokite laths culminating in traditional crystal ripening we suggest that contrary to current understanding trace metals like ni might retard the transformation of birnessite to todorokite and be released to marine sedimentary pore waters during this diagenetic process thus potentially providing a benthic flux of these micronutrients to seawater

ni isotope fractionation during sorption to ferrihydrite implications for ni in banded iron formations abstract a major decline in marine methanogen populations during the late archaean eon has been proposed as a driver for the great oxidation event goe at 2 4 ga konhauser et al 2009 nature 458 750 753 recently hypothesized that a dramatic decrease between 2 7 and 2 4 ga in the concentration of dissolved ni an essential nutrient for methanogens may have been responsible for the decline to test that hypothesis ni stable isotopes a novel proxy for methanogen ni limitation will be applied to the late archaean paleoproterozoic rock record in the future possibly through analysis of banded iron formations bifs in order to facilitate interpretation of those data we investigated the fractionation of ni stable isotopes during sorption to synthetic ferrihydrite which was likely the primary precipitating phase during bif deposition via bench top experiments the observed fractionations for adsorption and coprecipitation experiments were indistinguishable and averaged 60 58nidissolved sorbed 0 35 0 10 1 sd light ni sorbed parallel linear trends in isotope compositions of dissolved and sorbed ni as a function of fraction of ni sorbed indicate an equilibrium isotope effect with rapid and continuous exchange between dissolved and sorbed ni additionally we observed fractionation of 60 58nidissolved sorbed 0 23 0 07 1 sd in experiments in which ferrihydrite had been aged for up to 30 days and had partially transformed to goethite and hematite thus the fractionations in all of our experiments are the same within uncertainties although our simple system differs from archaean seawater our results suggest that ferrihydrite precipitating to form bifs may always have been offset by a constant fractionation from coexisting dissolved ni in seawater

remote triggering of deep earthquakes in the 2002 tonga sequences it is well established that an earthquake in the earth s crust can trigger subsequent earthquakes but such triggering has not been documented for deeper earthquakes models for shallow fault interactions suggest that static permanent stress changes can trigger nearby earthquakes within a few fault lengths from the causative earthquake1 2 3 whereas dynamic transient stresses carried by seismic waves may trigger earthquakes both nearby and at remote distances4 5 6 7 8 here we present a detailed analysis of the 19 august 2002 tonga deep earthquake sequences and show evidence for both static and dynamic triggering seven minutes after a magnitude 7 6 earthquake occurred at a depth of 598 km a magnitude 7 7 earthquake 664 km depth occurred 300 km away in a previously aseismic region we found that nearby aftershocks of the first mainshock are preferentially located in regions where static stresses are predicted to have been enhanced by the mainshock but the second mainshock and other triggered events are located at larger distances where static stress increases should be negligible thus suggesting dynamic triggering the origin times of the triggered events do not correspond to arrival times of the main seismic waves from the mainshocks and the dynamically triggered earthquakes frequently occur in aseismic regions below or adjacent to the seismic zone we propose that these events are triggered by transient effects in regions near criticality but where earthquakes have difficulty nucleating without external influences

molecular controls on cu and zn isotopic fractionation in fe mn crusts abstract the isotopic systems of the transition metals are increasingly being developed as oceanic tracers due to their tendency to be fractionated by biological and or redox related processes however for many of these promising isotope systems the molecular level controls on their isotopic fractionations are only just beginning to be explored here we investigate the relative roles of abiotic and biotic fractionation processes in controlling modern seawater cu and zn isotopic compositions scavenging to fe mn oxides represents the principal output for cu and zn to sediments deposited under normal marine oxic conditions using fe mn crusts as an analogue for these dispersed phases we investigate the phase association and crystal chemistry of cu and zn in such sediments we present the results of an exafs study that demonstrate unequivocally that cu and zn are predominantly associated with the birnessite mno2 phase in fe mn crusts as previously predicted from sequential leaching experiments e g koschinsky and hein 2003 the crystal chemistry of cu and zn in the crusts implies a reduction in coordination number in the sorbed phase relative to the free metal ion in seawater thus theory would predict equilibrium fractionations that enrich the heavy isotope in the sorbed phase e g schauble 2004 in natural samples fe mn crusts and nodules are indeed isotopically heavy in zn isotopes at 1 compared to deep seawater at 0 5 consistent with the predicted direction of equilibrium isotopic fractionation based on our observations of the coordination environment of sorbed zn further 50 of inorganic zn is chloro complexed the other 50 is present as the free zn2 ion and complexation by cl is also predicted to favour equilibrium partitioning of light zn isotopes into the dissolved phase the heavy zn isotopic composition of fe mn crusts and nodules relative to seawater can therefore be explained by an inorganic fractionation during uptake however cu in fe mn crusts is isotopically light at 0 3 to 0 5 compared to the dissolved phase in seawater at 0 9 we suggest that this is because dissolved cu in the oceans is overwhelmingly complexed to strong organic ligands which are better competitors for the heavy isotope

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

micromagnetic simulation of magnetofossils with realistic size and shape distributions linking magnetic proxies with nanoscale observations and implications for magnetofossil identification abstract we build micromagnetic models to investigate the magnetic properties of biogenic magnetite a common type of magnetic mineral that is responsible for recording a wide range of biological geophysical and geological processes on earth the geometry of modelled particles is based on realistic size and shape distributions from nanoscale observations systematic changes in microstructures of biogenic magnetite ensembles are built and their magnetic properties are calculated which enables a quantitative and separate assessment of the effect of crystal morphology and chain structures although the same particle size and shape distributions are used in all calculations simulation results document large variations in magnetic properties i e wide distributions of coercivity b c 10 60 mt coercivity of remanence b cr 14 81 mt dispersion parameter dp 0 1 0 5 and skewness values s 0 7 1 1 due to variable degree of anisotropy and magnetostatic interactions previously the commonly observed biogenic soft and biogenic hard components on biogenic magnetite bearing samples were often interpreted to reflect crystal morphologies and that the small dp values of coercivity distributions were an indication of narrow particle size distributions our simulations suggest that these speculations are not always the case and that magnetosome microstructures likely exert a dominant control over their magnetic properties our modelling results provide a new theoretical perspective on the magnetic properties of biogenic magnetite which is important for understanding magnetic proxy signals from magnetofossils in a wide range of environmental and geological settings and for the search for biogenic magnetite in terrestrial rocks and in extra terrestrial materials

crystal chemistry of ni in marine ferromanganese crusts and nodules marine ferromanganese crusts and nodules are highly enriched in transition metals such as ni and co yet the crystal chemistry and mode of incorporation of these metals is poorly known we characterized the crystal chemistry of ni in two hydrogenetic pacific ocean ferromanganese crust samples and a hydrogenetic nodule from the madeira abyssal plain energy dispersive spectrometry shows that ni is associated with the manganese oxide phases in agreement with previous work x ray diffraction patterns show that the dominant mn3 4 oxide is a phyllomanganate similar to hexagonal birnessite or mno2 extended x ray absorption fine structure spectroscopy shows that the coordination environment of ni results from structural incorporation into the phyllomanganate phase by replacement of mn3 4 in contrast ni initially sorbs to freshly prepared synthetic birnessite by surface complexation over vacancy sites in the mno2 layer we propose that the transformation of ni sorption from surface complexation to structural incorporation provides a potentially irreversible sink for ni in seawater

detection of noninteracting single domain particles using first order reversal curve diagrams we present a highly sensitive and accurate method for quantitative detection and characterization of noninteracting or weakly interacting uniaxial single domain particles unisd in rocks and sediments the method is based on high resolution measurements of first order reversal curves forcs unisd particles have a unique forc signature that can be used to isolate their contribution among other magnetic components this signature has a narrow ridge along the hc axis of the forc diagram called the central ridge which is proportional to the switching field distribution of the particles therefore the central ridge is directly comparable with other magnetic measurements such as remanent magnetization curves with the advantage of being fully selective to sd particles rather than other magnetic components this selectivity is unmatched by other magnetic unmixing methods and offers useful applications ranging from characterization of sd particles for paleointensity studies to detecting magnetofossils and ultrafine authigenically precipitated minerals in sediments

earthquakes as beacons of stress change aftershocks occurring on faults in the far field of a large earthquake rupture can generally be accounted for by changes in static stress on these faults caused by the rupture1 2 this implies that faults interact and that the timing of an earthquake can be affected by previous nearby ruptures3 4 5 6 here we explore the potential of small earthquakes to act as beacons for the mechanical state of the crust we investigate the static stress changes resulting from the 1992 landers earthquake in southern california which occurred in an area of high seismic activity stemming from many faults we first gauge the response of the regional seismicity to the landers event with a new technique and then apply the same method to the inverse problem of determining the slip distribution on the main rupture from the seismicity assuming justifiable parameters we derive credible matches to slip profiles obtained directly from the landers mainshock7 8 our results provide a way to monitor mechanical conditions in the upper crust and to investigate processes leading to fault failure

properties of intracellular magnetite crystals produced by desulfovibrio magneticus strain rs 1 desuffiovibrio magneticus strain rs 1 is an anaerobic sulfate reducing bacterium cells form intracellular nanocrystals of magnetite but are only weakly magnetotactic in order to understand the unusual magnetic response of this strain we studied magnetite crystals within cells grown with fumarate and sulfate many cells grown under either condition did not form magnetic crystals while others contained only i to 18 small similar to 40 nm magnetite containing magnetosomes bulk magnetic measurements of whole cells showed a superparamagnetic like behavior indicating that many of the magnetite crystals are too small to have a permanent magnetic moment at ambient temperature the temperature of the verwey transition is lower similar to 86 k than of magnetite from other magnetotactic strains likely indicating partial oxidation of magnetite into maghemite as a result of the small size and small number of magnetite magnetosomes the magnetic moments of most cells grown anaerobically with fumarate or sulfate are insufficient for magnetotaxis in addition to intracellular magnetite in some cultures another iron oxide hematite formed on the surfaces of cells the hematite grains are embedded in an extracellular polymeric material indicating that the crystals likely resulted from a biologically induced mineralization process although the hematite particles appear to consist of aggregations of many small 5 to 10 nm grains the grains have a consensus orientation and thus the whole particle diffracts as a single crystal the aligned arrangement of nanoparticles within larger clusters may reflect either a templated nucleation of hematite crystallites in an extracellular organic matrix or result from a self assembling process during the crystallization of hematite from ferric gels or ferrihydrite

detection of late cretaceous and cenozoic sequence boundaries on the atlantic coastal plain using core log integration of magnetic susceptibility and natural gamma ray measurements at ancora new jersey 1 magnetic susceptibility ms and natural gamma ray ngr were measured on middle miocene to cenomanian coastal plain strata from a continuously cored 356 m total depth 86 recovery borehole at ancora new jersey ocean drilling program leg 174ax these measurements were integrated with lithologic descriptions and a downhole ngr log a simple linear model explains most of the variation of the downhole ngr and the core ms as a consequence of the previously described lithologic variation spectral ngr at selected levels shows that ngr activity is mostly due to 40k associated with glauconite and mud sediment components that also tend to give high ms values abrupt deviations from the average values of ngr activity and ms determined by the linear model can be interpreted as due to singular lithologies for example an anomalous level with high ngr but not a parallel increase in ms was found at the navesink mount laurel formation contact and can be attributed to high uranium concentration in phosphorite most 27 of 33 of the sequence boundaries independently identified at the ancora site have sufficient lithological contrasts to be expressed in the ngr and or ms logs

seismicity rate and wave velocity variations as consequences of rainfall the case of the catastrophic storm of september 2002 in the nimes fault region gard france the western provence in southern france is an intraplate low deforming region cut by large sinistral strike slip faults as the nimes fault the deformation rate of this fault was estimated at 0 1 mm yr 1 from geological and morphological observations nevertheless some large earthquakes occurred in this area in historical times inducing well documented partial destructions on the roman monument pont du gard in order to investigate if this area is seismically active we installed a temporary seismological network of 14 stations between the cities of nimes and avignon for a 1 yr period 2002 july 2003 june we recorded and located a total amount of 80 earthquakes of magnitude ml smaller than 2 8 and of 153 quarry blasts the seismic event locations are interpreted in terms of regional tectonics as well as of geometry at depth of the nimes fault and of possible seismic activity of the roquemaure fault at the beginning of 2002 september a catastrophic storm occurred in the same area with cumulated precipitations at 600 mm in 28 hr causing casualties and major inundations and damages we identified a clear and sudden increase of the seismic activity as an immediate consequence of this exceptional meteorological phenomenon we interpret this rainfall triggering of earthquakes as the response of the crust to an abrupt vertical loading the geological context of this zone is characterized by the presence of sedimentary basins and of an important karstic network in a calcareous environment allowing the retention of a third of the total rainwater volume during few weeks after the catastrophic storm month by month inversion of the seismic wave velocities for only the first 1 km thick layer of the crust allows investigating the influence of the stored water a clear decrease of both p and s velocities and an increase of the vp vs ratio are evidenced the variations obtained are at 2 6 and 4 5 per cent for p s velocities and vp vs ratio respectively these variations are discussed in confront of previous studies and can be directly related to the known water volume

fossil bacterial magnetite in deep sea sediments from the south atlantic ocean the magnetostratigraphy of deep sea sediment cores has proven to be a powerful and high resolution method of dating and comparing sedimentary records in contrast to this widespread application relatively few attempts have been made to analyse and identify the mineralogy grain size and origin of the carrier of the remanent magnetization1 2 it is widely assumed that dominant ferrimagnetic minerals in deep sea sediments are of lithogenic origin that is that they derive from oceanic or continental detritus volcanic ashfalls micrometeorites hydrothermal precipitation or chemical mineralization processes a very different view was taken by kirschvink and lowenstam3 who suggested that fossil remnants of magnetite mineralizing organisms in particular magnetotactic bacteria might play an important part in the magnetization of sediments deposited in certain detritus poor aquatic systems we have used rock magnetic diagnostic methods to characterize the magnetic phases in deep sea sediments from the south atlantic these phases were then extracted and studied with the electron microscope our results indicate that fossil bacterial magnetite is the main carrier of the natural remanent magnetization in sediments ranging in age from quarternary to eocene different types of bacterial magnetosomes were detected most of them occurring in chains of identical particles and nearly all of them falling into the theoretically determined4 size range of single domain magnetitite

chemical weathering of serpentinite and ni enrichment in fe oxide at sukinda area jajpur district orissa india the chromiferous serpentinite of sukinda block of orissa india has undergone extensive lateritization with secondary nickel enrichment the vertical profile comprises partially altered serpentinite saprolite laterite in situ and laterite transported mineralogical and chemical investigations reveal that nickel is released from serpentine nepouite by chemical weathering and has partly been residually enriched in goethite along with supergene enrichment in goethite and mn oxides apparent percentage change of elements indicates that nickel is enriched in the saprolite part of the vertical column along with iron and manganese

nickel exchange between aqueous ni ii and deep sea ferromanganese nodules and crusts abstract deep sea ferromanganese fe mn nodules and crusts are rich in traditional and non traditional metals with both current and emerging economic value mn iii iv oxides e g phyllomanganates are important host phases for these metals e g ni which are structurally incorporated during nodule and fe mn crust formation recrystallization of phyllomanganates can be catalyzed by aqueous mn ii mn ii aq during bio geochemical mn redox cycling the fate of structurally incorporated metals during such recrystallization of mn iii iv oxides remains however poorly constrained here we use a 62ni isotope tracer to determine the exchangeability of dissolved ni with structurally incorporated ni in two deep sea fe mn nodules and one fe mn crust ni exchange between solid and solution was investigated during reactions in 1 mm mn ii aq and in mn ii free solutions under variable ph conditions ph 5 5 and 7 5 over time sample characterization shows that all samples are of hydrogenetic or mixed hydrogenetic diagenetic origin and ni is preferentially associated with the phyllomanganates our ni exchange experiments reveal that in some samples up to 25 of incorporated ni is exchangeable with the fluid after 14 days the prevalent reaction pathways exhibit ph dependent behavior during phyllomanganate recrystallization and differ between sample types with mn ii aq enhancing ni exchange in the fe mn crust fluid system and ni exchange being independent of mn ii aq concentrations in the fe mn nodule fluid systems the exchangeability of structurally incorporated ni in fe mn nodules and crusts indicates a labile behavior that potentially makes it available for biogeochemical processes in the marine environment

towards balancing the oceanic ni budget abstract nickel isotopes are a novel and promising tracer of the chemistry of past ocean environments but realisation of this tracer s potential requires a comprehensive understanding of the controls on ni burial in the marine sedimentary archive an outstanding puzzle in the marine budget of ni first recognised in the 1970s is a major imbalance in the known inputs and outputs to and from the ocean the sedimentary outputs of ni are much larger than the inputs rivers dust much more recently it has also been recognised that the outputs are also considerably isotopically heavier than the inputs in this study we find light ni isotope compositions 60 ninist srm986 0 2 to 0 8 for mn rich sediments from the eastern pacific compared to fe mn crusts at about 1 6 these data suggest that diagenetic remobilisation of isotopically heavy ni leads to a significant benthic ni flux estimated at 0 6 2 3 10 8 mol yr similar in magnitude to the riverine flux to the ocean diagenetic remobilisation of ni may occur either via cycles of mn oxide dissolution and precipitation with associated ni sorption and release or during mineralogical transformation of birnessite to todorokite a minor role for retention of isotopically light ni by fe oxides or fe rich authigenic clays is also proposed overall a benthic flux of isotopically heavy ni at about 3 can balance the marine ni budget pinpointing diagenesis as a key missing piece of the ni puzzle

a strong angular dependence of magnetic properties of magnetosome chains implications for rock magnetism and paleomagnetism 1 single domain magnetite particles produced by magnetotactic bacteria magnetosomes and aligned in chains are of great interest in the biosciences and geosciences here we investigated angular variation of magnetic properties of aligned magnetospirillum magneticum amb 1 cells each of which contains one single fragmental chain of magnetosomes with measurements at increasing angles from the chain direction we observed that i the hysteresis loop gradually changes from nearly rectangular to a ramp like shape e g bc and remanence decrease ii the acquisition and demagnetization curves of irm shift toward higher fields e g bcr increases and iii the forc diagram shifts toward higher coercivity fields e g bc forc increases for low temperature results compared to unoriented samples the samples containing aligned chains have a much lower remanence loss of field cooled fc and zero field cooled zfc remanence upon warming through the verwey transition higher ratio fc zfc for the measurement parallel to the chain direction and lower ratio larger fc and zfc values for the perpendicular measurement micromagnetic simulations confirm the experimental observations and reveal that the magnetization reversal of magnetosome chain appears to be noncoherent at low angles and coherent at high angles the simulations also demonstrate that the angular dependence of magnetic properties is related to the dispersion degree of individual chains indicating that effects of anisotropy need to be accounted for when using rock magnetism to identify magnetosomes or magnetofossils once they have been preserved in aligned chains additionally this study experimentally demonstrates an empirical correspondence of the parameter bc forc to bcr rather than bc at least for magnetite chains with strong shape anisotropy this suggests forc analysis is a good discriminant of magnetofossils in sediments and rocks

magnetization of polar ice a measurement of terrestrial dust and extraterrestrial fallout abstract laboratory induced remanent magnetization of polar ice constitutes a measurement of the magnetization carried by the ferromagnetic dust particles in the ice this non destructive technique provides a novel kind of information on the dust deposited on the surface of polar ice sheets measurements made on ice samples from greenland north grip ice core and antarctica vostok and epica dome c ice cores allowed the recognition of a fraction of magnetic minerals in ice whose concentration and magnetic properties are directly related to that of insoluble dust the source of this fraction of magnetic minerals thus appears closely related to terrestrial dust transport and deposition and its magnetic properties are informative of the dust provenance areas the rock magnetic properties of the dust may reflect distinct changes of dust source areas from glacial to interglacial periods in agreement with and adding further information to the isotopic 87 sr 86 sr and 143 nd 144 nd analyses a second magnetic fraction consists of particles of nanometric size which are superparamagnetic at freezer temperature and whose concentration is independent of the mass of aerosol dust found in the ice the source of these nanometric sized magnetic particles is ascribed to fallout of meteoric smoke and their concentration in ice was found to be compatible with the extraterrestrial fallout inferred from ir concentrations the diameter of the smoke particles as inferred from magnetic measurements is in the range of about 7 20 nm

ferromagnetic resonance and low temperature magnetic tests for biogenic magnetite magnetite is both a common inorganic rock forming mineral and a biogenic product formed by a diversity of organisms magnetotactic bacteria produce intracellular magnetites of high purity and crystallinity magnetosomes arranged in linear chains of crystals magnetosomes and their fossils magnetofossils have been identified using transmission electron microscopy tem in sediments dating back to 510 570 ma and possibly in 4 ga carbonates in martian meteorite alh84001 we present the results from two rock magnetic analyses the low temperature moskowitz test and ferromagnetic resonance fmr applied to dozens of samples of magnetite and other materials the magnetites in these samples are of diverse composition size shape and origin biologically induced extracellular biologically controlled magnetosomes and chiton teeth magnetofossil synthetic and natural inorganic we confirm that the moskowitz test is a distinctive indicator for magnetotactic bacteria and provide the first direct experimental evidence that this is accomplished via sensitivity to the magnetosome chain structure we also demonstrate that the fmr spectra of four different strains of magnetotactic bacteria and a magnetofossil bearing carbonate have a form distinct from all other samples measured in this study we suggest that this signature also results from the magnetosomes unique arrangement in chains because fmr can rapidly identify samples with large fractions of intact isolated magnetosome chains it could be a powerful tool for identifying magnetofossils in sediments

seismicity increase after the construction of the world s tallest building an active blind fault beneath the taipei 101 1 seismic activity began to slightly increase during the construction but rose sharply upon the completion of the tallest building in the world the taipei 101 which stands at 508 m in the taipei basin where local seismicity had historically very low besides an increase in both seismic energy and the number of micro earthquakes two felt earthquakes astonishingly occurred beneath the completed building the focal mechanism of the larger felt earthquake and its aftershocks are indicative of an active blind normal fault just beneath the building estimations of the vertical loading of the taipei 101 show that local stress on its foundation increased at least 4 7 bars making it seem likely that the increased seismicity was a direct product of the loading of the mega structure further investigations in unison with continuous seismic monitoring must be conducted because the safety of the high rise building in the taipei basin be comprehensively assessed

correlation between isotope records in marine and continental carbon reservoirs near the palaeocene eocene boundary changes in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land the carbon isotope compositions of marine carbonate sediments from the late palaeocene vary considerably exhibiting a sudden decrease close to the palaeocene eocene boundary which coincides with deep sea benthic extinctions1 and with changes in ocean circulation here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel in using palaeosol carbonates to reconstruct the co2 content of the ancient atmosphere2 isotope shifts of this sort will have to be taken into account the sharp decrease in 13c 12c ratios in the late palaeocene provides a datum for precise correlation of marine and continental records and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals

the resolving power of coseismic surface displacement data for fault slip distribution at depth 1 the spatial slip distribution of the august 17 1999 izmit turkey earthquake has previously been determined from both geodetic and seismological data though the models derived agree on a broad scale they are significantly different in detail these differences could be due to the inversion techniques applied and or additional constraints implemented and or be due to poor resolution it is also conceivable that the relative agreement at larger scales results in part from a resolution artifact common to all models to investigate this we perform a resolution analysis of fault slip models based on the inversion of surface displacement data assuming the theory of elastic dislocations in a half space and adopting a parameterization for which model predictions are capable of fitting the spatial variations of the data the inverse problem proves to be intrinsically ill conditioned

magnetic properties of marine magnetotactic bacteria in a seasonally stratified coastal pond salt pond ma usa summary magnetic properties of suspended material in the water columns of freshwater and marine environments provide snapshots of magnetic biomineralization that have yet to be affected by the eventual time integration and early diagenetic effects that occur after sediment deposition here we report on the magnetism geochemistry and geobiology of uncultured magnetite and greigite producing magnetotactic bacteria mb and magnetically responsive protists mrp in salt pond falmouth ma usa a small coastal marine basin 5 m deep that becomes chemically stratified during the summer months at this time strong inverse o2 and h2s concentration gradients form in the water column and a well defined oxic anoxic interface oai is established at a water depth of about 3 5 m at least four morphological types of mb both magnetite and greigite producers and several species of magnetically responsive protists are found associated with the oai and the lower sulphidic hypolimnion magnetic properties of filtered water were determined through the water column across the oai and were consistent with the occurrence of magnetite and greigite producing mb at different depths sharp peaks in anhysteretic remanent magnetization arm and saturation isothermal remanent magnetization sirm and single domain sd values of arm sirm occur within the oai corresponding to high concentrations of mb and mrp with magnetically derived cell densities of 10 4 10 6 ml 1 low temperature 1 per cent is present within magnetite magnetosomes produced either

characterizing the superparamagnetic grain distribution f v hk by thermal fluctuation tomography 1 in 1965 d j dunlop showed that the joint distribution of particle volumes and microcoercivities f v hk0 can be determined for magnetically monomineralic thermally stable single domain ssd ensembles by taking advantage of the joint temperature and field dependence of relaxation time we have developed a procedure that follows dunlop s strategy to obtain f v hk0 for ensembles containing both superparamagnetic and ssd grains based on backfield remanence curves measured over a range of temperatures each point on the derivative curves represents the integrated contribution from grains that lie along a corresponding blocking contour on the neel plot a suitable set of such line integral samples can be used to reconstruct the f v hk0 distribution using the methods of tomographic imaging samples of the basal tiva canyon tuff have narrow size distributions of elongate ti poor titanomagnetite tomographic inversion of the low temperature backfield spectra yield sharply peaked f v hk0 distributions from which we calculate modal grain dimensions in good agreement with those observed by transmission electron microscopy analysis of synthetic samples containing bimodal populations clearly distinguishes the two modes because our simplified forward calculations incompletely account for the effects of orientation distribution the width of the coercivity distribution at each temperature is underestimated and consequently the inverse calculations yield grain distributions that are overly broad frequency and temperature dependent susceptibilities calculated for the inverted f v hk0 distributions accord fairly well with measured susceptibilities for the weakly interacting tiva canyon samples less well for a moderately interacting paleosol specimen and poorly for a strongly interacting ferrofluid

bacterial magnetite and the magnetic properties of sediments in a swedish lake a comparison of the magnetic properties of lake sediments and catchment materials from pajep njakajaure north sweden demonstrates that high concentrations of single domain sd magnetite in the upper 70 cm of gyttja in the deepest part of the basin are not of detrital origin tem and light microscope examination revealed the existence of bacterial cells and magnetosomes in the upper sediments which are responsible for the presence of the sd magnetite most of the fossil magnetosomes appear to have been dissolved through reductive processes at lower depths although some are preserved in the lower sediments and carry a post depositional remanent magnetization pdrm the results highlight the complex effects of post depositional processes on mineral magnetic assemblages and natural remanent magnetization aquisition and demonstrate how mineral magnetic measurements may be used to identify magnetic grain size changes brought about by sediment diagenesis

chains clumps and strings magnetofossil taphonomy with ferromagnetic resonance spectroscopy magnetotactic bacteria produce intracellular crystals of magnetite or greigite the properties of which have been shaped by evolution to maximize the magnetic moment per atom of iron intracellular bacterial magnetite therefore possesses traits amenable to detection by physical techniques typically narrow size and shape distributions single domain size and arrangement in linear chains and often crystal elongation past strategies for searching for bacterial magnetofossils using physical techniques have focused on identifying samples containing significant amounts of single domain magnetite or with narrow coercivity distributions searching for additional of traits would however increase the likelihood that candidate magnetofossils are truly of biological origin ferromagnetic resonance spectroscopy fmr is in theory capable of detecting the distinctive magnetic anisotropy produced by chain arrangement and crystal elongation here we present analyses of intact and lysed magnetotactic bacteria dilutions of synthetic magnetite and sedimentary samples of modern carbonates from the great bahama bank oligocene miocene deep sea muds from the south atlantic and pleistocene lacustrine deposits from mono basin california we demonstrate that fmr can distinguish between intact bacterial magnetite chains collapsed chains and linear strings of magnetite formed by physical processes we also show that sediments in which the magnetization is likely carried by bacterial magnetite have fmr spectra resembling those of intact or altered bacterial magnetite chains

quantified abundance of magnetofossils at the paleocene eocene boundary from synchrotron based transmission x ray microscopy the paleocene eocene boundary 55 8 million years ago is marked by an abrupt negative carbon isotope excursion cie that coincides with an oxygen isotope decrease interpreted as the paleocene eocene thermal maximum biogenic magnetite fe3o4 in the form of giant micron sized spearhead like and spindle like magnetofossils as well as nano sized magnetotactic bacteria magnetosome chains have been reported in clay rich sediments in the new jersey atlantic coastal plain and were thought to account for the distinctive single domain magnetic properties of these sediments uncalibrated strong field magnet extraction techniques have been typically used to provide material for scanning and transmission electron microscopic imaging of these magnetic particles whose concentration in the natural sediment is thus difficult to quantify in this study we use a recently developed ultrahigh resolution synchrotron based full field transmission x ray microscope to study the iron rich minerals within the clay sediment in their bulk state we are able to estimate the total magnetization concentration of the giant biogenic magnetofossils to be only 10 of whole sediment along with previous rock magnetic studies on the cie clay we suggest that most of the magnetite in the clay occurs as isolated near equidimensional nanoparticles a suggestion that points to a nonbiogenic origin such as comet impact plume condensates in what may be very rapidly deposited cie clays

biogenic magnetite detrital hematite and relative paleointensity in quaternary sediments from the southwest iberian margin magnetic properties of late quaternary sediments on the sw iberian margin are dominated by bacterial magnetite observed by transmission electron microscopy tem with contributions from detrital titanomagnetite and hematite reactive hematite together with low organic matter concentrations and the lack of sulfate reduction lead to dissimilatory iron reduction and availability of fe ii for abundant magnetotactic bacteria magnetite grain size proxies arm and arm irm and s ratios sensitive to hematite vary on stadial interstadial timescales contain orbital power and mimic planktic 18 o the detrital biogenic magnetite ratio and hematite concentration are greater during stadials and glacial isotopic stages reflecting increased detrital magnetite input during times of lowered sea level coinciding with atmospheric conditions favoring hematitic dust supply magnetic susceptibility on the other hand has a very different response being sensitive to coarse detrital multidomain md magnetite associated with ice rafted debris ird high susceptibility and or magnetic grain size coarsening mark heinrich stadials hs particularly hs2 hs3 hs4 hs5 hs6 and hs7 as well as older heinrich like detrital layers indicating the sensitivity of this region to fluctuations in the position of the polar front relative paleointensity rpi records have well constrained age models based on planktic 18 o correlation to ice core chronologies however they differ from reference records e g piso particularly in the vicinity of glacial maxima mainly due to inefficient normalization of rpi records in intervals of enhanced hematite input

low temperature magnetic properties of pelagic sediments ocean drilling program site 805c tracers of maghemitization and magnetic mineral reduction magnetic properties of pelagic sediments from the western equatorial pacific ocean drilling program odp site 805c have been measured at low temperatures to investigate changes in magnetic mineralogy and the distribution of bacterial magnetite with depth a saturation isothermal remanent magnetization mrs was given to the samples by applying a strong magnetic field 2 5 t at 20 k after cooling both in the absence zero field cooling zfc and presence of a 2 5 t magnetic field field cooling fc the thermal demagnetization of both mrszfc and mrsfc was measured from 20 to 300 k no pronounced verwey transition was observed in the data from samples shallower than the iron redox boundary below the boundary the verwey transition is visible for all samples studied we interpret this behavior as reflecting low temperature oxidation maghemitization of primary magnetite and the subsequent dissolution of maghemite coatings below the iron redox boundary the low temperature oxidation may occur both at the water sediment interface and deeper in the suboxic zone of sediments as a result of bacteria mediated processes including the reduction of nitrate compounds mrszfc and mrsfc thermal demagnetization curves of all samples diverge for the entire temperature range measured the divergence may be caused by the low temperature stabilization of spontaneous magnetization vectors along with exchange interaction in the magnetite maghemite system together maghemitization and magnetic reduction diagenesis appear to play a dominant role in controlling the low temperature properties of the sediment studied as a result low temperature magnetic studies may provide more information on differences in reduction diagenesis than on the distribution of bacterial magnetite in natural sediments the changes in effective oxidation state below the iron redox boundary detected by low temperature methods may be useful in the study of some paleoenvironmental processes

sorption of ni by birnessite equilibrium controls on ni in seawater abstract synthetic hexagonal birnessite hx birnessite is a close analogue to natural poorly crystalline phyllomanganate phases found in soils and marine ferromanganese deposits these phases are often highly enriched in trace metals such as ni and co we measured the sorption of ni ii onto synthetic hexagonal birnessite hx birnessite from ph 1 to 7 exafs spectra show that at ph 3 7 ni is adsorbed to the hx birnessite surface above vacancy sites on 001 as a tridentate corner sharing complex we developed a surface complexation model for ni adsorption based on the equilibria 3 mn 2 o 2 3 ni 2 mn 2 o 3 ni 0 3 mn 2 o 2 3 ni 2 h 2 o mn 2 o 3 ni oh h using this surface complexation model we predict the concentration of ni in seawater in equilibrium with ni bearing birnessite found in hydrogenetic femn crusts and nodules our predicted results are in good agreement with observed ni concentrations in seawater and suggest that the concentration of dissolved ni in seawater is buffered by sorption to birnessite or a related mno 2 phase however in addition to the surface complex ni also sorbs by structural incorporation into the vacancy site in our synthetic samples at ph 7 exafs shows 10 of ni is structurally incorporated into hx birnessite in natural birnessites found in marine ferromanganese crusts and nodules exafs shows that all of the sorbed ni is structurally incorporated structural incorporation suggests that ni sorption may be irreversible

three dimensional simulations of seismic wave propagation in the taipei basin with realistic topography based upon the spectral element method we use the spectral element method to simulate strong ground motion throughout the taipei metropolitan area mesh generation for the taipei basin poses two main challenges 1 the basin is surrounded by steep mountains and 2 the city is located on top of a shallow low wave speed sedimentary basin to accommodate the steep and rapidly varying topography we introduce a thin high resolution mesh layer near the surface the mesh for the shallow sedimentary basin is adjusted to honor its complex geometry and sharp lateral wave speed contrasts variations in moho thickness beneath northern taiwan are also incorporated in the mesh spectral element simulations show that ground motion in the taipei metropolitan region is strongly affected by the geometry of the basin and the surrounding mountains the amplification of ground motion is mainly controlled by basin depth and shallow shear wave speeds although surface topography also serves to amplify and prolong seismic shaking

distribution of rees and yttrium among major geochemical phases of marine fe mn oxides comparative study between hydrogenous and hydrothermal deposits abstract mineralogy and geochemistry of the ferromanganese oxides collected from two seamounts in the andaman sea have been investigated with special reference to the solid phase partitioning behavior of rare earth elements rees bulk elemental compositions indicate that the oxides from a volcanic cratered seamount csm are hydrothermal while those from another seamount sm2 are hydrogenous in origin the distributions of rees and yttrium in four geochemical phases viz easily exchangeable mn oxide fe oxyhydroxide and residual of csm oxides were distinctly different from that of sm2 oxides in csm oxides the rees and yttrium are mainly associated with fe oxyhydroxide phase while in sm2 oxides both mn oxide and fe oxyhydroxide phases contain the major fraction of these elements the exchangeable and residual phases of both hydrothermal and hydrogenous oxides have extremely low ree content the shale normalized negative ce anomalies and relative enrichment of heavy ree characteristic of hydrothermal oxides are retained in fe oxyhydroxide phase in hydrogenous oxides the positive ce anomalies occurred in both fe and mn oxide phases while negative y anomalies were found only in fe oxyhydroxide phase the phase distribution of rees and yttrium in hydrothermal oxides is described in terms of co precipitation and adsorption of their halide complexes and available free ions in hydrothermal solutions instead adsorption of major carbonate species from seawater primarily regulates the partitioning of rees among the co existing phases of hydrogenous oxides

spinel bearing spherules condensed from the chicxulub impact vapor plume formation of the giant chicxulub crater off mexico s yucatan peninsula coincided with deposition of the global ir rich cretaceous tertiary k t stratigraphic boundary layer at ca 65 ma the boundary is marked most sharply by abundant spherules containing unaltered grains of magnesioferrite spinel here we predict for the first time the sequential condensation of solids and liquids from the plume of vaporized rock expected from oblique k t impacts we predict highly oxidizing plumes that condense silicate liquid droplets bearing spinel grains whose compositions closely match those marking the actual boundary systematic global variations in spinel composition are consistent with higher condensation temperatures for spinels found at atlantic and european sites than for those in the pacific

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

transient deformation induced by groundwater change in taipei metropolitan area revealed by high resolution x band sar interferometry abstract we present precise deformation velocity maps for the two year period from september 2011 to july 2013 of the northern taiwan area taipei by using persistent scatterer interferometry psi technique for processing 18 high resolution x band synthetic aperture radar sar images archived from cosmo skymed csk constellation according to the result the highest subsidence rates are found in luzou and wuku area in which the rate is about 15 mm yr and 10 mm yr respectively in the whole dataset however dramatic change from serve subsidence to uplift in surface deformation was revealed in the taipei basin in two different time spans 2011 09 2012 09 and 2012 09 2013 07 this result shows good agreement with robust continuous gps measurement and precise leveling survey data across the central taipei basin moreover it also represents high correlation with groundwater table from 8 well data in the taipei basin the storativity is roughly constant across most of the aquifer with values between 0 5 10 4 and 1 6 10 3 in jingmei formation and 0 8 10 4 and 1 4 10 3 in wuku formation this high correlation indicated that one meter groundwater level change could induce about 9 and 16 mm surface deformation change in luzou and wuku area respectively which is about eight times faster the long term tectonic deformation rate in this area thus to access the activity of the shanchiao fault it is important to discriminate tectonic movement from anthropogenic or seasonal effect in the taipei basin to better understand the geohazards and mitigation in the taipei metropolitan area

nickel and its isotopes in organic rich sediments implications for oceanic budgets and a potential record of ancient seawater abstract nickel ni is a biologically active element that displays a nutrient like depth distribution in the modern oceans recent studies of ni isotopes have highlighted the fact that in common with many other transition metals the ni stable isotope composition expressed as 60 ni of the dissolved phase is heavier than the inputs at 1 3 to 1 7 the sedimentary outputs that control the high 60 ni of the ocean coupled with records for past seawater could potentially yield new information on the past earth system but these are currently not well understood here we present the first ni abundance and isotope data for a key output that associated with ni uptake into organic matter at productive upwelling regions and elsewhere we investigate the distribution of ni and its isotopes in two fractions separated from the bulk sediment an hf digestible fraction extracted with hf hcl and an organic sulphide rich fraction the organic sulphide fractions exhibit a range in 60 ni from 0 86 to 1 83 systematic relationships between ni concentrations total organic carbon and ni isotopes suggest that the organic sulphide fraction originates in the photic zone and is delivered to the sediment as a closed system despite the possibility of transfer of ni to sulphide within it authigenic ni in the bulk sediment is dominated by the hf digestible fraction which in ni enriched sediments where the detrital correction is small is very close to the modern deep ocean at 60 ni 1 2 these data suggest that organic rich sediments beneath upwelling zones while they are an important output flux of ni from the oceans do not solve the isotope balance problem because their 60 ni is almost identical to modern seawater on the other hand the approach adopted here involving the analysis of the two fractions both traces the fractionation imparted by biological uptake as well as recording the 60 ni of contemporary seawater suggesting potential for understanding the past oceans

biogenic precipitation of manganese oxides and enrichment of heavy metals at acidic soil ph abstract natural mn oxides are largely biogenic in origin formed via the microbial oxidation of mn ii these minerals are extremely efficient scavengers of heavy metals yet to date microbial mn oxide precipitation and subsequent heavy metal sorption have received little attention in mining impacted environments where heavy metal concentrations are elevated but bio geochemical conditions are typically unfavourable for both abiotic and biogenic mn oxide precipitation featuring acidic ph and low organic carbon contents here we investigate the formation of mn oxide bio geochemical barrier layers and the immobilisation of heavy metals in these layers in soil profiles from a former uranium mining site in ronneburg germany detailed soil profiling shows the site has an acidic soil ph that varies from 4 7 to 5 1 and eh values from 640 to 660 mv using synchrotron x ray diffraction and x ray absorption spectroscopy together with scanning electron microscopy and electron microprobe analysis we find that the dominant mn oxide present in the mn oxide layers is a poorly crystalline hexagonal birnessite akin to synthetic mno 2 covering and cementing quartz grains using phylogenetic analysis based on 16s rdna we identify and characterise six strains of manganese oxidising bacteria mob from the acidic mn oxide layers which we subsequently culture to produce poorly crystalline hexagonal birnessite akin to that found at the study site specifically we identify three gram positive spore forming firmicutes affiliated to bacillus safensis bacillus altitudinis and brevibacillus reuszeri which are able to oxidise mn after initiating spore formation two gram positive actinobacteria belonging to the genera arthrobacter and frondihabitans and one gram negative proteobacteria belonging to the genus sphingomonas geochemical thermodynamic speciation modelling indicates that the abiotic precipitation of mn oxides in the mn oxide layers is unfavourable and we suggest that the mn oxides in the bio geochemical barriers at our study site are biogenically precipitated in an acidic soil environment to our knowledge this is the first report to identify the above six bacterial strains and specifically identify spore forming bacteria as mob in an acidic soil environment we find that the poorly crystalline hexagonal birnessite precipitated in the mn oxide layers efficiently immobilises ba ni co cd zn and ce and as such we find that mob and biogenically precipitated mn oxides can exert a strong control on the fate and mobility of metals in mining impacted environments

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

a case for a comet impact trigger for the paleocene eocene thermal maximum and carbon isotope excursion abstract we hypothesize that the rapid onset of the carbon isotope excursion cie at the paleocene eocene boundary 55 ma may have resulted from the accretion of a significant amount of 12c enriched carbon from the impact of a 10 km comet an event that would also trigger greenhouse warming leading to the paleocene eocene thermal maximum and possibly thermal dissociation of seafloor methane hydrate indirect evidence of an impact is the unusual abundance of magnetic nanoparticles in kaolinite rich shelf sediments that closely coincide with the onset and nadir of the cie at three drill sites on the atlantic coastal plain after considering various alternative mechanisms that could have produced the magnetic nanoparticle assemblage and by analogy with the reported detection of iron rich nanophase material at the cretaceous tertiary boundary we suggest that the cie occurrence was derived from an impact plume condensate the sudden increase in kaolinite is thus thought to represent the redeposition on the marine shelf of a rapidly weathered impact ejecta dust blanket published reports of a small but significant iridium anomaly at or close to the paleocene eocene boundary provide supportive evidence for an impact

toward a new 250 c pyrrhotite magnetite geothermometer for claystones abstract we investigate the effects of burial and moderate experimental heating on claystones from three regions with different degrees of maturation immature burial temperature 40 c of bure callovo oxfordian claystones in the basin of paris france early mature burial temperature 85 c of opalinus lower dogger claystones from the mont terri anticline in front of the jura fold belt switzerland and mature to overmature burial temperature 7 s 8 the p transition is also detected in early mature to mature opalinus and chartreuse claystones we conduct additional experimental heating of natural opalinus claystones one set of experiments is referred to as short term heating 1 h from 100 c to 200 c it is dedicated to an investigation of the effect of short lived heating processes in geology a second set of heating experiments is designed to approach burial conditions using a gold capsule in burial like experiments we heated opalinus claystones from 150 c to 250 c for several weeks under a pressure of 100 mpa in both experiments we observe a correlative diminution of the pyrrhotite signature at 35 k with increasing temperature we interpret this trend as the appearance of magnetite we derive a parameter pm from the warming curve of a saturated isothermal remanent magnetization acquired at 10 k zfc we report on a consistent evolution of pm with temperature in the range of 40 c to 250 c including natural samples heated samples at 95 c and burial like heated samples pm first increases between 40 c up to 85 c implying that pyrrhotite gradually dominates the magnetic assemblage at low temperature for temperatures above 85 c pm decreases up to 250 c implying that the formation of magnetite gradually overshadows the magnetic input of pyrrhotite pm values obtained from mature to overmature claystones from the chartreuse are lower than the pm values obtained from the burial like heated opalinus claystones suggesting that the formation of magnetite is driven by kinetics the continuous trend of the pm parameter suggests that the magnetic properties of pyrrhotite magnetite claystones can be used to infer paleo temperatures and we propose to name this geothermometer mageval

magnetism and magnetic mineralogy of ash flow tuffs from yucca mountain nevada the magnetic susceptibility and remanent magnetization of an ash flow sheet are profoundly influenced by cooling history after emplacement spatial variations in these properties therefore provide a potentially useful tool for geological studies maxima and minima in measured along profiles at yucca mountain nevada identify persistent magnetic marker horizons within vitric portions of the tiva canyon and underlying topopah spring members of the paintbrush tuff the correlatable variations of with vertical position in these units exist over the 8 km of strike examined the observed stratigraphic changes in magnetic properties reflect variations in amounts and mineralogy of fe ti oxide phenocrysts and the presence shape size and mineralogy of magnetic fe oxide microcrystals that precipitated at high temperature after emplacement of each sheet vitrophyre near the top of the topopah spring member has a distinctive maximum in due to titanomagnetite phenocrysts susceptibility in the lower portion of the overlying tiva canyon member reaches maximum values of about 1 3 10 2 si near the base of the member beneath the columnarly jointed vitrophyre due to the presence of abundant superparamagnetic cubic fe oxide these elongate microcrystals are several tens of nm long and are typically deformed and tapered up section in the tiva canyon member the susceptibility decreases going to a minimum within the columnar vitrophyre at this stratigraphic level the precipitated fe oxides are larger and carry intense nrm of up to 30 a m is only 3 10 3 the whisker like microcrystals of fe oxide which typically nucleated on what appears to be chain silicate grew as needles up to 25 m in length the size variations of the precipitated fe oxides which were established using transmission electron microscopy tem and petrographic observation are consistent both with variations in magnetic susceptibility measured at the outcrop and with variations in the intensity of remanent magnetization several interpretations of the shape anisotropy of the precipitated feoxide are possible including growth by a dislocation mechanism additionally the observed elongation of precipitated microcrystals is consistent with theoretical predictions for growth in a uniaxial stress field susceptibility variations as established at the outcrop as well as in the borehole offer a potentially useful tool for stratigraphic correlation of ash flow sheets

evidence for abundant isolated magnetic nanoparticles at the paleocene eocene boundary new rock magnetic results thermal fluctuation tomography high resolution first order reversal curves and low temperature measurements for samples from the paleocene eocene thermal maximum and carbon isotope excursion in cored sections at ancora and wilson lake on the atlantic coastal plain of new jersey indicate the presence of predominantly isolated near equidimensional single domain magnetic particles rather than the chain patterns observed in a cultured magnetotactic bacteria sample or magnetofossils in extracts the various published results can be reconciled with the recognition that chain magnetosomes tend to be preferentially extracted in the magnetic separation process but as we show may represent only a small fraction of the overall magnetic assemblage that accounts for the greatly enhanced magnetization of the carbon isotope excursion sediment but whose origin is thus unclear

nickel isotopic compositions of ferromanganese crusts and the constancy of deep ocean inputs and continental weathering effects over the cenozoic the global variability in nickel ni isotope compositions in ferromanganese crusts is investigated by analysing surface samples of 24 crusts from various ocean basins by mc icpms using a double spike for mass bias correction ferromanganese crusts have view the mathml source isotopic compositions that are significantly heavier than any other samples thus far reported 0 1 to 0 3 with surface scrapings ranging between 0 9 and 2 5 relative to nist srm986 there is no well resolved difference between ocean basins although the data indicate somewhat lighter values in the atlantic than in the pacific nor is there any evidence that the variations are related to biological fractionation presence of different water masses or bottom water redox conditions preliminary data for laterite samples demonstrate that weathering is accompanied by isotopic fractionation of ni which should lead to rivers and seawater being isotopically heavy this is consistent with the slightly heavier than average isotopic compositions recorded in crusts that are sampled close to continental regions furthermore the isotopic compositions of crusts growing close to a hydrothermal source are clustered around 1 5 suggesting that hydrothermal fluids entering the ocean may have a ni isotopic composition similar to this value based on these data the heavy ni isotopic compositions of ferromanganese crusts are likely due to input of isotopically heavy ni to the ocean from continental weathering and possibly also from hydrothermal fluids a depth profile through one crust cd29 2 from the north central pacific ocean displays large variations in ni isotope composition 1 1 2 3 through the last 76 myr although there may have been some redistribution of ni associated with phosphatisation there is no systematic difference in ni isotopic composition between deeper older parts and shallower younger parts of the crust which may suggest that oceanic sources and sinks of ni have largely remained in steady state over the cenozoic additionally the isotope profile is in agreement with a profile of mn concentration through the same crust this implies a link between the ni isotopic composition recorded in ferromanganese crusts and the release of ni into the ocean through hydrothermal activity this supports the conclusions drawn from surface data that ni isotope ratios in ferromanganese crusts are largely controlled by the isotopic compositions of the ni oceanic input sources

detection of live magnetotactic bacteria in south atlantic deep sea sediments abstract since they were first descrbed in 1975 1 magnetotactic bacteria have been observed in a wide variety of environments including soils 2 rivers freshwater lakes and coastal marine sediments 3 4 and in one case at a water depth of about 600 m in a hemipelagic sediment 5 here we report the first systematic findings of magnetotactic bacteria in pelagic and hemipelagic sediments of the eastern south atlantic different morphologies were identified cocci spirilla vibrionic and rod shaped forms at water depths to about 3000 m on the african continental margin between the equator and 30 s and on the walvis ridge in a pelagic environment about 1400 km off the coast no actively swimming magnetotactic bacteria could be detected in deeper waters magnetotactic bacteria were observed only in the upper 10 cm of the sediments with the highest concentrations always found in a well defined narrow subsurface layer the depth of this layer is dependent on the input and turnover rates of organic matter in the sediment measurements of oxygen and nitrate concentrations 6 7 provide an assignment of depth distributions of magnetotactic bacteria to the stratification of terminal electron acceptors in the sediment the data show clearly that the majority of marine magnetotactic bacteria live in the anaerobic zone in contrast to former assumptions that they may inhabit microaerobic layers 8 11

combined use of magnetometry and spectroscopy for identifying magnetofossils in sediments identification of the mineral remains of magnetotactic bacteria mtb known as magnetofossils is of particular interest because their occurrence can be used for environmental and climatic reconstructions single domain magnetite particles which are biomineralized in the cell body of mtb have characteristic properties that can be used to detect their fossil remains acquisition of anhysteretic and isothermal remanent magnetization arm and irm first order reversal curve forc diagrams and ferromagnetic resonance fmr spectra were used to detect the magnetic mineral inventory in holocene lake sediments a comparative analysis in terms of the discriminatory power of these methods is presented the forc diagrams contain two distinct features a sharp horizontal ridge centered on the horizontal axis bc and a feature with symmetric spread along the vertical bb axis the coercivity spectra derived from the central ridge coincides with that derived from arm and irm acquisition curves and is compatible with the presence of noninteracting linear chains of single domain magnetite the second feature on forc diagrams is indicative of interacting particles in clusters in the fmr spectra from bulk sediment two populations are separated empirically based on the forc information an asymmetric signal is taken to describe the population which contains single domain particles in clusters empirical spectral separation of this contribution results in fmr spectra that are similar to those of intact mtb which strongly suggests that a fraction of linear magnetosome chains is present combination of fmr and forc results demonstrates the strong potential of these methods for identifying magnetofossils based on alignment and interaction patterns of magnetic particles

a biogenic origin for anomalous fine grained magnetic material at the paleocene eocene boundary at wilson lake new jersey 1 the paleocene eocene thermal maximum which occurred 55 5 ma was caused by a massive release of carbon as indicated by an 3 negative carbon isotope excursion recorded in the marine atmospheric and terrestrial reservoirs one suggested source for the carbon a cometary impactor is based on the sudden appearance and high concentration of single domain sd magnetite in paleocene eocene p e boundary cores from the north atlantic continental margin we evaluate the potential sources of sd magnetite at the p e boundary by presenting new magnetic hysteresis low temperature magnetic remanence and transmission electron microscopy data from the north atlantic coastal ocean our results show a similar increase in sd material but demonstrate that the magnetic material has a biogenic origin these findings indicate that the high concentrations of sd magnetite immediately above the p e boundary are the result of unusual accumulations and or preservation of magnetotactic bacteria such bacteria typically occupy the oxic anoxic transition zone near the sediment water interface or in the water column the high abundances of sd magnetite in sediments from across the shelf may be an artifact of nonsteady state redox conditions and exceptional preservation of sd magnetite it may also indicate that the oxic anoxic redox boundary shifted into the water column the latter explanation implies transient eutrophy of the coastal ocean in this region most likely due to seasonally enhanced runoff and increased stratification and nutrient loading

composition and structure of nanocrystalline fe and mn oxide cave deposits implications for trace element mobility in karst systems abstract fe and mn oxides are ubiquitous highly reactive minerals in the environment which often control the distribution and speciation of trace elements in soils and aquatic systems pautler cave in southwest illinois contains fe and mn oxide deposits with properties that differ spatially and temporally two depositional environments exist in the cave fe and mn precipitation where anoxic groundwater enters the oxic cave passage seep deposition and direct deposition from the cave stream seep waters have higher concentrations of ca2 fe2 and mn2 lower ph and lower o2 aq concentrations relative to stream waters in addition seep waters have nearly constant 18o values that are similar to the yearly average of local precipitation whereas cave stream waters have more erratic 18o values and appear to be influenced by seasonal variations of 18o in rainfall these differences suggest that the seep water source has a longer residence time in the subsurface than the cave stream water fe oxides are solely found as seep deposits whereas mn oxides are deposited both by groundwater seepage and cave streams freshly precipitated fe oxides are composed of ferrihydrite and filamentous material consistent with biomineralization structures of the microbial genera gallionella and leptothrix mn oxide minerals consist of 7 and 10 a phyllomanganates having a range of three dimensional order mn oxide samples show a greater heavy metal and trace element content compared to fe oxides and mn oxides deposited by cave streams have higher concentrations of metals than mn oxide seep deposits in addition phyllomanganate particle morphologies and crystallinity display a compositional dependence with platelet size and phyllomanganate sheet stacking order decreasing with increasing ba and trace element content and decreasing ca content these properties also appear to correlate with dissolved mn ii in the source water these observations suggest that fe and mn oxide minerals in oxic cave systems affect trace element concentrations in carbonate fed springs and illustrate a previously unrecognized limitation on the transport of inorganic nutrients and contaminants in karst aquifers

low temperature remanence in stable single domain magnetite 1 a numerical model is developed in order to simulate the loss of low temperature remanence while warming through the verwey transition we concentrate on the amount of remanence lost fc and zfc during field cooled and zero field cooled low temperature demagnetization curves for stable single domain ssd particles of 1 inorganic magnetite and 2 biogenic magnetite in the form of magnetosome chains the model predicts that delta ratios fc zfc for inorganic ssd magnetite increase from 1 to 1 6 with increasing aspect ratio and that magnetosome chains have elevated delta ratios of at least 2 0 disaggregated magnetosomes are predicted to behave similarly to inorganic acicular ssd magnetite the numerical results agree with experimental results

mineralogy and crystal chemistry of mn fe co ni and cu in a deep sea pacific polymetallic nodule minor element concentrations in marine ferromanganese nodules are primarily controlled by the mineralogy which itself depends on redox conditions at the sediment water interface results are presented for the first in depth x ray microstructural and microspectroscopic investigation of a mixed hydrogenetic diagenetic nodule which is representative of ferromanganese deposits on abyssal plains the measurements were conducted by micro x ray diffraction and x ray absorption spectroscopy both xanes and exafs on hydrogeneous and diagenetic regions of the nodule the hydrogenetic diagenetic interface was imaged by x ray microfluorescence after which regions of interest were chosen to represent mineralogical and chemical transformations that occurred at the early stage of suboxic diagenesis in the hydrogenetic nodule oxic environment mn is speciated as fe vernadite a nanocomposite material composed of intergrown feroxyhite feooh and monodispersed phyllomanganate layers having no interlayer mn vernadite in the diagenetic nodule suboxic environment mn is speciated dominantly as mg rich 10 a vernadite which consists of a random intergrowth of vernadite and its transformation product todorokite the authigenic 10 a vernadite precipitated from the components of vernadite in fe vernadite that were dissolved in suboxic microenvironments of the sediment direct evidence supporting a redox driven dissolution reaction is provided by the valence composition of mn as measured by micro xanes which is 0 69mn4 0 24mn3 0 07mn2 average 3 62 0 04 v u for fe vernadite and 0 61mn4 0 23mn3 0 16mn2 average 3 28 0 04 v u for 10 a vernadite ni and cu derived mainly from dissolved vernadite and oxidized organic matter replace structural mn3 4 in both the mno2 layer and todorokite domains of 10 a vernadite pure todorokite in highly diagenetic regions of the nodule has an average formula of mg2 0 167 mn4 0 783 mn3 0 099co3 0 002ni2 0 076cu2 0 040 o2 n h2o with an atomic ratio of cu ni co mn 0 13 which is slightly lower than 0 167 1 6 the maximum metal uptake capacity reported for marine nodules by analogy with synthetic todorokites we infer that mg2 which has a hydrated diameter close to that of the 3 3 tunnel size of todorokite and mn3 and cu2 which prefer jahn teller distorted octahedra play a crucial role in templating the topotactic transformation of 10 a vernadite to todorokite and stabilizing todorokite in suboxic marine sediments

elucidating the geometry of the active shanchiao fault in the taipei metropolis northern taiwan and the reactivation relationship with preexisting orogen structures the shanchiao fault is an active normal fault with documented paleoearthquakes in the taipei metropolis taiwan while posing direct seismic threat on the multimillion population its crustal scale fault plane configuration has not been constrained this study presents the first attempt to resolve the fault plane dip changes of the shanchiao fault within the upper crust by forward modeling late quaternary deformation tectonic subsidence over the last 23 ka is estimated from vertical displacements of a rapidly formed alluvial fan horizon deformed into a dramatic rollover monocline a 2 d profile across the shanchiao fault is chosen for elastic half space dislocation modeling and the results suggest that the fault is listric in the shallow crust with an abrupt change from subvertical ramp 85 75 to near horizontal flat 10 15 at 3 4 km depth consistent with an origin from the inversion of an orogen related thrust detachment given the presence of rift related fabrics in the underthrust chinese continental margin basement beneath the taiwanese orogenic wedge listric ramp flat ramp models with a second deeper bend to 60 dip are also tested reasonable fits with the geological observations are produced when the lower ramp is located at greater than 8 km depth which correlates with the hypocentral location of a moderate earthquake in 2004 joint reactivation of preexisting thrust and rift faults by the shanchiao fault is therefore plausible with implications for seismic hazard in the taipei area

the identification and biogeochemical interpretation of fossil magnetotactic bacteria magnetotactic bacteria which most commonly live within the oxic anoxic transition zone oatz of aquatic environments produce intracellular crystals of magnetic minerals specifically magnetite or greigite the crystals cause the bacteria to orient themselves passively with respect to the geomagnetic field and thereby facilitate the bacteria s search for optimal conditions within the sharp chemical gradients of the oatz the bacteria may also gain energy from the redox cycling of their crystals because magnetotactic bacteria benefit from their magnetic moments natural selection has promoted the development of traits that increase the efficiency with which the intracellular crystals impart magnetic moments to cells these traits also allow crystals produced by magnetotactic bacteria called magnetofossils when preserved in sediments to be distinguished from abiogenic particles and particles produced as extracellular byproducts of bacterial metabolism magnetofossils are recognizable based on their narrow size and shape distributions distinctive morphologies with blunt crystal edges chain arrangement chemical purity and crystallographic perfection this article presents a scheme for rating magnetofossil robustness based on these traits the magnetofossil record extends robustly to the cretaceous and with lesser certainty to the late archean because magnetotactic bacteria predominantly live in the oatz the abundance and character of their fossils can reflect environmental changes that alter the chemical stratification of sediments and the water column the magnetofossil record therefore provides an underutilized archive of paleoenvironmental information several studies have demonstrated a relationship between magnetofossil abundance and glacial interglacial cycles likely mediated by changes in pore water oxygen levels more speculatively a better developed magnetofossil record might provide constraints on the long term evolution of marine redox stratification more work in modern and ancient settings is necessary to explicate the mechanisms linking the abundance and character of magnetofossils to ancient biogeochemistry

magnetic hysteresis of 0 6 110 μm magnetites across the verwey transition we report saturation magnetization ms saturation remanence mrs coercive force hc and remanence coercivity hcr as a function of grain size d and temperature t for 0 6 135 m magnetites

enhanced magnetization of the marlboro clay as a product of soil pyrogenesis at the paleocene eocene boundary abstract the kaolinite rich marlboro clay was deposited on the inner shelf in the salisbury embayment of the u s atlantic margin at the onset of the carbon isotope excursion marking the 56 ma paleocene eocene boundary and is characterized by an anomalously high concentration of magnetic nanoparticles of enigmatic origin that give rise to notably intense bulk magnetization recent studies point to a magnetic assemblage that is dominated by single domain magnetite particles that tend to be isolated rather than arranged in chains the most distinguishing feature of magnetotactic bacteria fossils on the other hand it is very unlikely that the nanoparticles can be condensates of an impact plume given the meter scale thickness of the marlboro clay we obtained new data from a landward proximal site at wilson lake on the new jersey coastal plain and find that the abrupt increase in magnetite nanoparticles is virtually coincident stratigraphically with the recently reported impact spherule layer at the base of the marlboro clay in the same core yet the high field magnetic susceptibility a measure of total iron concentration and strontium isotope values on bulk sediment an indicator of sediment weathering provenance are not different in the marlboro clay from the immediately underlying vincentown formation we suggest that the distinctive magnetic properties of the marlboro clay originated from pyromagnetic soil enhancement by widespread wildfires on the adjoining drainage area the pyrogenetic products were soon washed from the denuded landscape and rapidly deposited as mud waves across the shelf becoming the marlboro clay a few percent of incinerated biomass ends up as calcite known as wood ash stone and can inherit its light carbon isotope composition disseminated wood ash stone entrained in the marlboro clay could contribute to the landward increase in amplitude of the carbon isotope excursion in bulk carbonate data a plausible trigger for the initial conflagration is a fireball from the impact of a sizable extraterrestrial object at moderate range

low temperature cycling of isothermal and anhysteretic remanence microcoercivity and magnetic memory abstract this paper reports low temperature cycling ltc through the verwey transition of anhysteretic remanence arm partial arms and partially demagnetised saturation isothermal remanence sirm induced at room temperature in pseudo single domain and multidomain md magnetite the remanences were cooled in zero field to 50 k and then heated back to room temperature by inducing partial arms over different field ranges and by partially alternating field demagnetising sirms it was possible to isolate both low coercive force and high coercive force fractions of remanence on cooling through the verwey transition a sharp increase in the remanence was observed the relative size of the jump increased as the high coercive force fraction was increasingly isolated this behaviour is interpreted as being due to both an increase in the single domain multidomain threshold size on cooling through the verwey transition and to the reduction or elimination of closure domains in the low temperature phase in addition the memory ratio i e the fraction of remanence remaining after ltc divided by the initial remanence was found to be higher for the high coercive force fraction than the low coercive force fraction in our interpretation the high coercivity fraction behaviour is associated with reversible domain re organisation effects whilst the low coercive force fraction s behaviour is associated with irreversible domain re organisation and de nucleation processes due to the decrease in magnetocrystalline anisotropy on cooling to the verwey transition the high coercive force fraction is likely to be magnetoelastically controlled thus a rock displaying high coercive force behaviour is likely to carry a palaeomagnetically meaningful remanence with high unblocking temperatures in addition ltc analysis can be used to identify the domain state dominating the natural remanence in magnetite bearing rocks

review of the low temperature magnetic properties of magnetite from a rock magnetic perspective the low temperature magnetic properties of magnetite are reviewed and implications for rock magnetism considered the behaviour of fundamental properties of magnetite at low temperatures near the verwey transition tv are documented and attention is given to various verwey transition theories the low temperature behaviour of the magnetic energies that control domain structure is reviewed in detail for the first time in rock magnetic literature the low temperature anomaly in spontaneous magnetization ms is documented and the differences between the saturation magnetization and ms near the verwey transition are discussed it is argued that the low temperature behaviour of the magnetocrystalline anisotropy and in particular the anomaly at tv is most likely to affect multidomain remanence during low temperature cycling for multidomain crystals it is calculated that the large increase in magnetocrystalline anisotropy intensity and reduction in symmetry on cooling through tv is likely to reduce the stability of closure domains

comment on new late pennsylvanian paleomagnetic results from parana basin southern brazil is the recent giant gaussian process model valid for the kiaman superchron by brandt et al

bacterial magnetite in lake sediments late glacial to holocene climate and sedimentary changes in northern norway magnetic properties of sediments retrieved from a small lake in northern norway spanning the last f14500 cal years have been analyzed in detail the high resolution core with its ability to detect sub centurial variability records the rapid retreat of the fennoscandian ice sheet fis in northern lyngen and subsequently the establishment of a stable allerod to younger dryas watershed from early holocene and to the present magnetotactic bacteria mb producing stable single domain ssb magnetite become the dominating magnetic carrier the small low relief catchment area with its quartzite bedrock scattered till and vegetated surface generates a negligible contribution of detrital magnetic minerals this allows for the opportunity to follow the presence and changes of the magnetosomes during the last 10000 years a strong positive statistical relationship r 2 0 83 between the anhysteretic remanent magnetisation susceptibility varm and loss on ignition loi suggests an environmental control over the bacteria magnitude quart int 88 2002 13 that most likely is related to summer climate a comparison between the magnetic mineralogy as evident from the s ratio jirm100mt jsirm3t and the reconstructed summer temperatures from a nearby lake shows a close covariation between cooler summers and harder s ratios for a series of climatic events intervariability of loi data and other proxies such as august sea surface temperatures sst from the nordic sea suggests land ocean connections during converging phases of cooler climate where the most prominent in phase periods are approximately 1 6500 5000 2 3500 2400 and 3 1700 1000 cal years bp the most significant change in the holocene magnetic signal is initiated at f3700 cal years bp which we refer to here as the holocene turnover d 2004 elsevier b v all rights reserved

low temperature magnetic properties of pelagic carbonates oxidation of biogenic magnetite and identification of magnetosome chains 1 pelagic marine carbonates provide important records of past environmental change we carried out detailed low temperature magnetic measurements on biogenic magnetite bearing sediments from the southern ocean ocean drilling program odp holes 738b 738c 689d and 690c and on samples containing whole magnetotactic bacteria cells we document a range of low temperature magnetic properties including reversible humped low temperature cycling ltc curves different degrees of magnetite oxidation are considered to be responsible for the observed variable shapes of ltc curves a dipole spring mechanism in magnetosome chains is introduced to explain reversible ltc curves this dipole spring mechanism is proposed to result from the uniaxial anisotropy that originates from the chain arrangement of biogenic magnetite similar to published results for uniaxial stable single domain sd particles the dipole spring mechanism reversibly restores the remanence during warming in ltc measurements this supports a previous idea that remanence of magnetosome chains is completely reversible during ltc experiments we suggest that this magnetic fingerprint is a diagnostic indicator for intact magnetosome chains although the presence of isolated uniaxial stable sd particles and magnetically interacting particles can complicate this test magnetic measurements through the eocene section of odp hole 738b reveal an interval with distinct magnetic properties that we interpret to originate from less oxidized biogenic magnetite and enrichment of a biogenic hard component co occurrence of these two magnetic fingerprints during the late eocene in the southern ocean indicates less oxic conditions probably due to increased oceanic primary productivity and organic carbon burial

biogenic magnetite in stromatolites ii occurrence in ancient sedimentary environments abstract in this paper we report the discovery of fossil bacterial single domain magnetite particles in ancient stromatolites the biogenicity of the crystals was determined by the following criteria 1 distinctive morphology and habit 2 composition and 3 environment of deposition stromatolites ranging in age from the middle archean to pleistocene composed of both carbonate and chert were analyzed for the presence of single domain magnetite using rock magnetic methods the granulometry and composition of the ultra fine grained magnetite crystals extracted were determined by transmission electron microscopy and electron diffraction the oldest magnetofossils were extracted from stromatolitic chert of the gunflint iron formation which is approximately 2000 ma old the implications of these findings and the potential uses of fossil bacterial magnetite in studies of the evolution of biomineralization and prokaryotic metabolic processes paleomagnetism and as an indicator of ancient oxygen levels are discussed bacterial magnetite represents the oldest evidence of biomineralization yet discovered in the fossil record

extreme warming of mid latitude coastal ocean during the paleocene eocene thermal maximum inferences from tex86 and isotope data changes in sea surface temperature sst during the paleocene eocene thermal max imum petm have been estimated primarily from oxygen isotope and mg ca records generated from deep sea cores here we present a record of sea surface temperature change across the paleocene eocene boundary for a nearshore shallow marine section located on the eastern margin of north america the sst record as inferred from tex86 data indicates a minimum of 8 c of warming with peak temperatures in excess of 33 c similar ssts are estimated from planktonic foraminifer oxygen isotope records al though the excursion is slightly larger the slight offset in the oxygen isotope record may reflect on seasonally higher runoff and lower salinity

oxidative scavenging of thallium by birnessite explanation for thallium enrichment and stable isotope fractionation in marine ferromanganese precipitates tl stable isotopes recorded in marine ferromanganese crusts show great promise as a tracer of past marine and climatic conditions key to interpreting recent tl stable isotope time series data is a detailed molecular level understanding of tl scavenging by ferromanganese crust minerals and tl stable isotope fractionation occurring during uptake to this end we determine the mechanism of tl sorption to the primary ferromanganese minerals in crusts namely hexagonal birnessite todorokite and ferrihydrite using xas we compliment our data with micro focus xas of a tl enriched hydrogenetic ferromanganese crust we show that tl i is oxidised to tl iii during sorption to hexagonal birnessite but not during sorption to todorokite triclinic birnessite and ferrihydrite tl iii forms an inner sphere complex at the hexagonal birnessite surface located at vacant octahedral sites in the phyllomanganate sheets we show that oxidation of tl i to tl iii during reductive dissolution of birnessite is thermodynamically unfavourable and propose that oxidation of tl i is driven by the formation of the tl iii surface complex recent theoretical calculations predict a large equilibrium stable isotope fractionation between tl i and tl iii leading to tl iii species that are enriched in the heavy 205tl isotope in light of this work we propose a molecular sorption oxidation fractionation mechanism that provides a unifying explanation for the recently observed geochemical behaviour of tl in marine ferromanganese rich sediments in this mechanism the proportion of hexagonal birnessite dictates the extent of tl oxidation which controls the extent of tl enrichment and isotope fractionation this work is among the first to provide a molecular explanation for reported trends in trace element enrichments and stable isotope compositions in geologic deposits our molecular sorption oxidation fractionation mechanism will ultimately help interpret tl signals in marine sedimentary archives to provide new constraints on past oceanic and climatic change in addition our mechanism should also help explain compositional relationships of other redox sensitive elements in ferromanganese rich marine sediments that might also be used as paleoceanographic and paleoclimate proxies

magnetic anisotropy magnetostatic interactions and identification of magnetofossils 1 single domain magnetite particles produced by magnetotactic bacteria mtb and aligned in chains called magnetosomes are potentially important recorders of paleomagnetic paleoenvironmental and paleolife signals rock magnetic properties related to the anisotropy of magnetosome chains have been widely used to identify fossilized magnetosomes magnetofossils preserved in geological materials however ambiguities exist when linking magnetic properties to the chain structure because of the complexity of chain integrity and magnetostatic interactions among magnetofossils that results from chain collapse during post depositional diagenesis in this paper magnetic properties of three sets of samples containing extracted magnetosomes of the culturedmagnetospirillum magneticumstrain amb 1 were analyzed to determine how chain integrity and particle concentration influence magnetic properties intact mtb and well dispersed magnetosome chains are characterized by strong magnetic anisotropy and weak magnetostatic interactions but progressive chain breakup and particle clumping significantly increase the degree of magnetostatic interaction this results in a change of the magnetic signature toward properties typical of interacting single domain particles i e a decrease of the ratio of anhysteretic remanent magnetization to the saturation isothermal remanent magnetization decreasing in the crossing point of the wohlfarth cisowski test and in the delta ratio between losses of field and zero field cooled remanent magnetization across the verwey transition as well as vertical broadening of the first order reversal curve distribution we propose a new diagram that summarizes the verwey transition properties with diagnostic limits for intact and collapsed chains of magnetosomes this diagram can be used in conjunction with other parameters to identify unoxidized magnetofossils in sediments and rocks

bolide summer the paleocene eocene thermal maximum as a response to an extraterrestrial trigger the standard paradigm that the paleocene eocene thermal maximum petm represents a threshold event intrinsic to earth s climate and connected in some way with long term warming has influenced interpretations of the geochemical climate and biological perturbations that occurred at this event as recent high resolution data have demonstrated that the onset of the event was geologically instantaneous attempts to account for the event solely through endogenous mechanisms have become increasingly strained the rapid onset of the event indicates that it was triggered by a catastrophic event which we suggest was most likely a bolide impact we discuss features of the petm that require explanation and argue that mechanisms that have previously been proposed either cannot explain all of these features or would require some sort of high energy trigger a bolide impact could provide such a trigger and in the event of a comet impact could contribute directly to the shape of the carbon isotope curve we introduce a carbon cycle model that would explain the petm by global warming following a bolide impact leading to the oxidation of terrestrial organic carbon stores built up during the late paleocene our intention is to encourage other researchers to seriously consider an impact trigger for the petm especially in the absence of plausible alternative mechanisms

holocene paleointensities thellier experiments on submarine basaltic glass from the east pacific rise a complete description of the geomagnetic field requires both paleodirectional and paleointensity data although the paleointensity data base has grown steadily over the last three decades it remains limited in time and space the majority of data are of holocene age and come from europe furthermore it has been difficult to assess the reliability of the paleointensity determinations here we present paleointensity determinations on precisely dated holocene 0 to 3500 years old submarine basaltic glass from the east pacific rise 15 s to 22 s although hysteresis measurements and low temperature isothermal remanent magnetization irm acquisition experiments document a significant contribution of superparamagnetic grains high blocking temperatures above 400 c and curie temperatures between 490 c and 550 c indicate a single domain low ti magnetite as the carrier of the remanent magnetization this notion is further supported by the fact that saturation of remanence is achieved in moderate fields of about 200 300 mt submarine basaltic glass proves to be nearly ideal for paleointensity determinations in that it produces a high success rate for thellier experiments twenty six out of 30 samples resulted in acceptable paleointenisty determinations multiple experiments on splits from the same sample show good reproducibility the paleointensities for zero age glasses correspond precisely with the present field intensity at the site of recovery the results of the remaining samples range from 16 7 to 53 9 t with corresponding virtual axial dipole moments vadm of 3 61 1022 to 11 9 1022 a m2 the intensities vary rapidly with time excluding a westward drifting nondipole component as the source for these fluctuations basaltic glass is frequently recovered in both dredged and drilled material from the ocean floor the availability of submarine basaltic glass throughout the world oceans therefore holds great potential for a better distribution of paleointensity data through time and space

terrasar x reveals the impact of the mobile barrier works on venice coastland stability land subsidence and eustacy concurred to make the relative sea level in venice italy 23 cm higher over the last century in order to protect the city and its lagoon environment from increased flooding a series of mobile barriers are under construction at the three inlets of lido malamocco and chioggia connecting the adriatic sea to the inner water body since 2003 work has been proceeding with the reinforcement and extension of the existing jetties and the construction of breakwaters harbors and a small island within the lido inlet we detected significant local settlements of a few centimeters between march 2008 and january 2009 at the three inlets induced by the construction works through an interferometric analysis of 30 satellite radar images acquired by the new german terrasar x mission on a more regional scale we observe that the city of venice and the other major urban settlements on the lagoon littorals are not impacted by subsidence during this period the very high spatial resolution of 3 m and the short repeat time interval of 11 days of terrasar x enable the investigation of displacements with an unprecedented observed level of details opening new perspectives to geodynamic s research and civil engineering sectors for the monitoring of large infrastructures with potential vulnerability to terrain motion