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

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

comment on a case for a comet impact trigger for the paleocene eocene thermal maximum and carbon isotope excursion by d v kent et al earth planet sci lett 211 2003 13 26 the paleocene eocene thermal maximum petm ca 55 ma is characterized by a remarkable negative excursion in the stable carbon isotope composition of carbonate and organic matter deposited in terrestrial shallow marine and deep marine environments 1 3 in well dated benthic foraminiferal isotope records n13c steps down by 32 5 to 33 0x within 20 kyr and then gradually returns to near initial values over v120 220 kyr 4 5 the magnitude timing shape and global nature of this n13c excursion strongly suggest a massive injection of 13c depleted carbon into the ocean atmosphere system 6 to date thermal dissociation of marine gas hydrates and subsequent release of sea oor ch4 has been widely cited as the most plausible explanation for the carbon addition 7 in a recent contribution 8 kent et al challenge the idea of a massive ch4 release during the petm suggesting instead that a comet impact provided much of the excess 13c depleted carbon their primary grounds for this alternative hypothesis are unusual magnetic properties in relatively thick v5 8 m clay rich sequences deposited on the outer shelf of the new jersey continental margin during the initial phase of the petm the magnetic properties apparently signify an anomalous enrichment of single domain magnetite which the authors suggest represents extraterrestrial ejecta they bolster this assertion by noting that high ir contents have been found in several sections at the very start of the petm 9 10 the methane hydrate dissociation hypothesis carries some profound conceptual problems 11 and should not be accepted blindly with available information consequently it is appropriate to entertain multiple working hypotheses for the extraordinary biogeochemical perturbations that occurred during the petm however it is equally important to stress the fundamental problems with any alternative hypothesis in this case a comet impact the primary di culty with invoking a comet or any extraterrestrial object as an explanation for global environmental change at the petm is that there is no supporting evidence except perhaps the unusual magnetic signatures in their sediment cores as sprinkled in various parts of the paper by kent et al 8 but worth iterating collectively 1 there is no crater 2 the remarkable fossil turnovers including a

fireball passes and nothing burns the role of thermal radiation in the cretaceous tertiary event evidence from the charcoal record of north america high soot contents have been reported in cretaceous tertiary k t sedimentary rocks leading to the suggestion that the amount of thermal power delivered from the chicxulub impact was sufficient to have ignited wildfires soot cannot be used to indicate fire location however as soot from one large fire could spread globally sources other than biomass burning could also yield soot charcoal in nonmarine sedimentary rocks here quantified in situ in polished blocks provides a unique tool to record the distribution of wildfires and therefore assess the extent of any thermal radiation associated with the impact at chicxulub the k t and lowermost tertiary sedimentary rocks of six nonmarine sequences colorado to saskatchewan contain no charcoal or below background levels of charcoal and a significant quantity of noncharred organic materials revealing that there was no distinctive wildfire across the north american continent related to the k t event this finding indicates that the k t impact cannot have delivered a peak irradiance of 95 kw m 2 of thermal power to the atmosphere and 19 kw m 2 to the ground therefore the thermal power delivered from the impact to north america did not have the destructive potential previously predicted high amounts of thermal radiation were not responsible for the environmental perturbations or extinctions associated with the k t event

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

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

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

characterizing magnetofossils from first order reversal curve forc central ridge signatures the central ridge structure of a first order reversal curve forc distribution is indicative of uniaxial noninteracting single domain magnetic particles which provides the opportunity to identify and characterize biogenic magnetic mineral remains magnetofossils in sediments recent studies have shown that magnetofossils are widespread in the geological record and that they carry useful environmental information and contribute to paleomagnetic recording which makes it essential to quantify how these biogenic components contribute to the magnetic properties of sediments we present results from six sedimentary sequences whose magnetic mineral assemblages contain a significant magnetofossil contribution using principal component analysis we find that the central ridge properties exhibit both intra sequnce and inter sequence variability that may be ascribed to external environmental factors while samples from individual sediment sequences tend to cluster together there is a continuum of inter sequence behavior that appears to be related to a variety of magnetofossil properties we demonstrate the complexity of biogenic magnetic components in sedimentary environments but also the power and potential of forc central ridges for understanding magnetic mixtures and unraveling environmental information

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

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

an extraterrestrial 3he based timescale for the paleocene eocene thermal maximum petm from walvis ridge iodp site 1266 in the deep sea the paleocene eocene thermal maximum petm is often marked by clay rich condensed intervals caused by dissolution of carbonate sediments capped by a carbonate rich interval constraining the duration of both the dissolution and subsequent cap carbonate intervals is essential to computing marine carbon fluxes and thus testing hypotheses for the origin of this event to this end we provide new high resolution helium isotope records spanning the paleocene eocene boundary at odp site 1266 in the south atlantic the extraterrestrial 3he 3he et concentrations replicate trends observed at odp site 690 by farley and eltgroth 2003 by assuming a constant flux of 3he et we constrain relative changes in accumulation rates of sediment across the petm and construct a new age model for the event in this new chronology the zero carbonate layer represents 35 kyr some of which reflects clay produced by dissolution of paleocene pre petm sediments above this layer carbonate concentrations increase for 165 kyr and remain higher than in the latest paleocene until 234 48 34 kyr above the base of the clay the new chronology indicates that minimum 13 c values persisted for a maximum of 134 27 19 kyr and the inflection point previously chosen to designate the end of the cie recovery occurs at 217 44 31 kyr this allocation of time differs from that of the cycle based age model of rohl et al 2007 in that it assigns more time to the clay layer followed by a more gradual recovery of carbonate rich sedimentation the new model also suggests a longer sustained 13 c excursion followed by a more rapid recovery to pre petm 13 c values these differences have important implications for constraining the source s of carbon and mechanisms for its subsequent sequestration favoring models that include a sustained release of carbon after an initial pulse

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

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

latest paleocene lithologic and biotic events in neritic deposits of southwestern new jersey in the southwestern new jersey coastal plain four drill holes contain continuous neritic sedimentation across the paleocene eocene boundary calcareous nannofossil zone np 9 np 10 boundary significant lithologic and biotic changes occur in these strata near the top of the paleocene global warming increased precipitation and other oceanographic and climatic events that have been recognized in high latitude deep oceanic deposits of the latest paleocene also influenced mid latitude shallow marine and terrestrial environments of the western north atlantic the diverse well preserved calcareous nannofossil flora that is present throughout the entire new jersey boundary section accurately places these events within the uppermost part of the upper paleocene zone np 9 several rapid but gradational changes occur within a 1 1 m interval near the top of zone np 9 the changes include 1 a change in lithology from glauconitic quartz sand to clay 2 a change in clay mineral suites from illite smectite dominated to kaolinite dominated 3 a change in benthic foraminiferal assemblages to a lower diversity fauna suggestive of low oxygen environments 4 a significant increase in planktonic foraminiferal abundance and 5 an increased species turnover rate in marine calcareous nannofossils pollen was sparse in the new jersey drill holes but terrestrial sporomorph species in virginia exhibit increased turnover rates at a correlative level foraminiferal assemblages and lithology indicate that relative sea level rose in new jersey at the same time as these late paleocene events occurred in late biochron np 9 the higher sea levels influenced sediment type and absolute abundance of planktonic foraminifers in the deposits above the initial increase of kaolinite in the upper part of zone np 9 the kaolinite percentage continues to increase and the maximum kaolinite value occurs in the uppermost part of zone np 9 there are few changes in either the sediments or the biota precisely at the zone np 9 np 10 boundary in new jersey the clay rich deposits with a high kaolinite clay mineral suite the lowered diversity benthic foraminiferal assemblages the abundant planktonic foraminiferal specimens and the calcareous nannofossil assemblages continued essentially unchanged into the earliest eocene zone np 10 within the lower part of zone np 10 the kaolinite percentage decreased to very low values

the magnetic fabric relationship between sedimentary and basement nappes in the high tatra mountains n slovakia abstract in the high tatra mountains n slovakia the magnetic fabrics are deformational in origin in sedimentary rocks of the kri na nappe in sedimentary rocks covering the underlying crystalline complex and in granitoids and metamorphic rocks of this complex the patterns of the principal susceptibilities are similar in all these units their most important feature is a girdle in magnetic foliation poles oriented nnw sse to n s in sedimentary formations the magnetic fabric pattern is compatible with that predicted by mathematical modelling to develop during a complex deformation comprising lateral shortening and simple shear which is characteristic of nappe deformation consequently the magnetic fabric in the high tatra mountains probably resulted from deformation associated with the formation and movement of the nappes during which not only the sedimentary strata but also the crystalline complex were thrust over the north european platform

approach to saturation analysis of hysteresis measurements in rock magnetism and evidence for stress dominated magnetic anisotropy in young mid ocean ridge basalt abstract young mid ocean ridge basalts contain titanomagnetite crystals of varying size and composition many studies of their hysteresis properties have found m rs m s ratios considerably above the theoretical limit of 0 5 for uniaxial single domain particles since titanomagnetite is a cubic mineral high m rs m s could occur due to cubic anisotropy which allows for m rs m s values up to 0 866 on the other hand titanomagnetites with high ti content possess extremely large magnetostriction constants already slight internal stress easily outweighs cubic anisotropy and enforces uniaxial behavior are high m rs m s ratios now a proof for very low internal stress no on the contrary previous studies on synthetic titanomagnetite with high m rs m s show that after annealing this ratio decreases a possible explanation is that insufficient saturation of the hysteresis loop used to infer m rs m s leads to underestimation of m s here a systematic experimental study on a young mid ocean ridge basalt using fields of up to 7 t demonstrates that indeed the m rs m s ratio of the single domain fraction does not significantly deviate from the theoretical value of 0 5 for uniaxial anisotropy it is further estimated that internal stress above 200 mpa is necessary to explain the observed hysteresis behavior a value which is consistent with recent independent approximations on the other hand theoretical loops for cubic minerals do not fit the observed data in order to assess the validity of m s determinations from hysteresis measurements an improved method to evaluate the approach to saturation behavior of hysteresis loops is developed it allows to recognize insufficiently saturated loops and thereby helps to avoid misinterpretation of standard m rs m s measurements when high fields are not accessible

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

north american continental margin records of the paleocene eocene thermal maximum implications for global carbon and hydrological cycling the impacts of the paleocene eocene thermal maximum petm 55 ma one of the most rapid and extreme warming events in earth history are well characterized in open marine and terrestrial environments but are less so on continental margins a major carbon sink here we present stable isotope carbonate content organic matter content and c n ratio records through the petm from new outcrop sections in california and from cores previously drilled on the new jersey margin foraminifer 18o data suggest that midlatitude shelves warmed by a similar magnitude as the open ocean 5 c 8 c while the carbon isotope excursion cie recorded both in carbonate and organic matter 13c records is slightly larger 3 3 4 5 than documented in open ocean records sediment accumulation rates increase dramatically during the cie in marked contrast to the open ocean sites in parallel mass accumulation rates of both organic and inorganic carbon also increased by an order of magnitude the estimated total mass of accumulated carbon in excess of pre cie rates suggests that continental margins at least along north america became carbon sinks during the cie mainly because of weathering feedbacks and rising sea level this result is significant because it implies that the negative feedback role of carbon burial on continental margins was greater than previously recognized

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

stratigraphic and climatic implications of clay mineral changes around the paleocene eocene boundary of the northeastern us margin abstract kaolinite usually is present in relatively small amounts in most upper paleocene and lower eocene neritic deposits of the northern us atlantic coastal plain however there is a short period less than 200 000 k y in the latest paleocene upper part of calcareous nannoplankton zone np 9 when kaolinite dominated clay mineral suites replaced the usual illite smectite dominated suites during this time of global biotic and lithologic changes kaolinite increased from less than 5 of the clay mineral suite to peak proportions of 50 60 of the suite and then returned to less than 5 in uppermost paleocene lowermost eocene strata this kaolinite pulse is present at numerous localities from southern virginia to new jersey these sites represent both inner and middle neritic depositional environments and reflect input from several river drainage systems thus it is inferred that kaolinite rich source areas were widespread in the northeastern us during the latest paleocene erosion of these source areas contributed the kaolinite that was transported and widely dispersed into shelf environments of the salisbury embayment the kaolinite increase which occurred during a time of relatively high sea level probably is the result of intensified weathering due to increased temperature and precipitation the southern extent of the kaolinite pulse is uncertain in that uppermost paleocene beds have not been identified in the southern atlantic coastal plain the late paleocene kaolinite pulse that consists of an increase to peak kaolinite levels followed by a decrease can be used for detailed correlation between more upbasin and more downbasin sections in the salisbury embayment correlations show that more upbasin paleocene eocene boundary sections are erosionally truncated they have varying portions of the kaolinite increase and if present at all discontinuous portions of the subsequent kaolinite decrease as these truncated sections are disconformably overlain by lower eocene strata rapid erosional removal of large parts of the most kaolinite rich p e boundary clay deposits occurred by early eocene time erosion of the kaolinite rich p e boundary beds was enhanced during times of sea level fall when kaolinite rich sediments were redeposited to produce kaolinite spikes in basal beds of lower and middle eocene sequences that have little or no kaolinite elsewhere in the sequence in contrast more downbasin sites document only the upper decreasing part of the kaolinite pulse the absence of strata documenting the earlier kaolinite increase is attributed to slow sedimentation condensed interval as a result of a significant sea level rise that ponded most sediments in shallower waters combined with the probable subsequent erosional removal of these thin downbasin deposits by oceanic currents

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

integrated stratigraphic studies of paleocene lowermost eocene sequences new jersey coastal plain evidence for glacioeustatic control 1 we describe seven paleocene to lowermost eocene sequences in core holes at island beach bass river ancora millville and sea girt nj ocean drilling program leg 150x 174ax and analyze benthic foraminiferal assemblages to assess paleodepth changes within sequences these sequences are referred to as pa0 pa1a pa1b pa2a pa2b pa3a and pa3b paleocene sequence boundaries are identified by unconformities and variations in benthic foraminiferal biofacies we used q mode factor analysis and paleoslope modeling to identify three distinct middle outer neritic benthic foraminiferal assemblages and their associated water depths paleodepths during the early paleocene and deposition of pa0 pa1a and pa2b were 80 m with 20 m changes across sequence boundaries a long term shallowing occurred through the late paleocene where paleodepths were 50 70 m in pa3a this trend drastically changes in the earliest eocene where the paleodepths of sequence pa3b were 120 150 m new jersey paleocene sequence boundaries correlate with those in other regions and with 18o increases in the deep sea suggesting paleocene eustatic lowerings were associated with ice growth events

partial anhysteretic remanent magnetization in magnetite 1 additivity 1 we have tested the additivity of partial anhysteretic remanent magnetization parm for suites of eight synthetic magnetites with mean grain sizes from 65 nm to 18 m and 18 natural samples including lake sediments oceanic and continental volcanic rocks gabbros and granites in both synthetic and natural sample suites domain states inferred from hysteresis and other magnetic properties vary from single domain sd through pseudosingle domain psd to multidomain md for each sample total arm intensity was compared with sums of partial arms of three different types four conjugate pairs of parallel parms four pairs of perpendicular parms and one set of five neighboring parallel parms in each case the intervals of alternating field af over which a steady field h was applied to produce the partial arms are nonoverlapping and cover the entire af range 0 100 mt used to produce the total arm additivity of partial arms was verified to better than 3 for all the samples whatever the domain state sd psd and md or composition ranging from pure magnetite to x 0 6 titanomagnetite the universality of parm additivity is unexpected because its analog partial thermoremanent magnetization ptrm deviates from ideal behavior as the grain size increases and the domain structure becomes md the different behaviors probably result from the fact that parm is produced at ordinary temperatures over short times whereas the most intense ptrm is produced at temperatures approaching the curie point with significant dwell times promoting such processes as isothermal remanence acquisition domain nucleation and domain wall reequilibration verification of the law of additivity of parms is an encouraging first step toward validating pseudo thellier and other methods of paleointensity determination that use arm in place of or in addition to trm

plio pleistocene marine continental correlation using habitat indicators from olduvai gorge tanzania abstract reconstructions of plio pleistocene habitats and lake levels from a brief interval 200 000 yr of hominid bearing sediments from bed i and lower bed ii olduvai gorge tanzania are for the first time integrated with climatic data from the deep sea in order to examine the effect of largescale climatic events in east africa the period of densely vegetated habitats and wet conditions at olduval at 1 82 myr shows a best fit with a period of northern hemisphere warming as evidenced by oxygen isotopes from deep sea core v28 239 from the western pacific this environmental response is similar to that witnessed in east africa during the period of warming climates associated with deglaciation at 10 000 8 000 yr

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

establishing fire incidence in temperate soils using magnetic measurements abstract natural unburnt topsoil samples from the cotswolds region of england and samples from archaeological contexts in the uk and hungary some of which are known to have been affected by burning have been used to identify a distinctive magnetic signature linked to the effects of fire on magnetic properties a combination of bulk low field lf and frequency dependent fd magnetic susceptibility and normalized anhysteretic remanent magnetization arm measurements have been used on both unburnt and experimentally burnt samples from the cotswolds and on the archaeological samples complementary determinations were made for both sets of samples of the maximum potential susceptibility max and hence percentage fractional conversion conv which provides independent evidence of burning the results show that the ferrimagnetic mineral assemblages produced as a result of fire have a significantly finer grain size than those arising from weathering and soil formation alone burning thus gives rise to a distinctive envelope of values on a bilogarithmic plot of arm fd versus arm lf such a diagram provides a convenient basis for identifying magnetic signatures in soils archaeological materials and palaeosols that have arisen mainly through burning

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

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

the effects of wildfires on the magnetic properties of soils in the everglades we present results of a rock magnetic study of soils that were affected by wildfires that burned portions of the everglades in the spring of 2008 soils at sites that were extensively burned exhibit a pronounced surface magnetic enhancement effect with magnetizations of surface samples up to 16 times greater than that observed at depth 7 cm at these sites the increase in magnetization results from an increased abundance of a low coercivity phase maghemite that occurs at the expense of the abundance of a high coercivity phase goethite these results indicate that fire induced heating caused goethite in the surface soils to convert into a more magnetic low coercivity phase such as maghemite goethite is an excellent adsorber of phosphorus and therefore we hypothesize that the destruction of goethite as a result of burning may have important implications for phosphorus cycling in the everglades ecosystem copyright 2010 john wiley sons ltd

stable carbon and oxygen isotopic compositions of wood ash an experimental study with archaeological implications abstract wood ash composed mainly of the mineral calcite is an important component in many archaeological sites identification of wood ash in the archaeological record is often difficult due to mixing of ash with other calcitic components of geogenic origin and or due to diagenetic changes a recent empirical study using the stable isotope compositions of carbon 13 c and oxygen 18 o in wood ash enabled the identification of mixtures of wood ash with geogenic calcite and to follow diagenetic changes due to partial dissolution and re precipitation of ash in two prehistoric cave sites in israel little however is known about the processes responsible for the isotopic compositions of wood ash in relation to formation at various temperatures and the influence on isotopic composition of ash from a variety of plant species here we present an experimental study of wood ash formed by burning three c3 tree species and one c4 desert bush at different temperatures the results indicate that there are significant differences in the isotopic compositions of carbon and oxygen between wood ash that forms by combustion at a relatively low temperature 500 c and at a higher temperature 900 c in addition we show that the isotopic composition of carbon and oxygen in high temperature wood ash approaches equilibrium over a period of several months and that the carbon isotopic composition of low temperature wood ash may reflect the photosynthetic pathway of the burnt woody species lastly we show that the isotopic compositions obtained from wood ash prepared at different temperatures do not reflect a temperature dependent fractionation process but a mixing line between calcite that formed by low temperature combustion and calcite formed by high temperature combustion which later underwent re carbonation with atmospheric co 2 in addition we suggest that exchange processes may possibly occur during combustion between decomposing calcium oxalate and atmospheric o 2 co 2 and co the archaeological implications of this study are discussed in relation to identification of wood ash in the archaeological record identification of fuel sources and burning temperatures and diagenetic changes expected in karstic cave environments the method presented here can be applied at any archaeological site

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

black carbon in paleocene eocene boundary sediments a test of biomass combustion as the petm trigger abstract several explanations have been proposed to account for the dramatic perturbation to earth s carbon cycle that led to extreme warming ocean acidification mass extinction and a major negative carbon isotope excursion cie at the paleocene eocene p e boundary one reason that the ultimate cause for this event remains ambiguous is the difficulty in directly testing these multiple hypotheses we conducted a test of one proposed mechanism the wildfire hypothesis that suggests that combustion of a significant fraction of abundant paleocene peat deposits within several thousand years could release enough co2 to earth s atmosphere to account for all of these observations soot and graphitic black carbon hereafter collectively referred to as gbc both combustion byproducts are widely distributed through smoke by subaerial combustion and are remarkably resistant to diagenetic degradation using samples provided by the ocean drilling program we measured gbc concentrations across the p e boundary in two important paleocene eocene thermal maximum petm sections to test a prediction of the wildfire hypothesis namely that the combustion of paleocene organic matter at the onset of the petm would produce a peak in sedimentary gbc in the bass river section new jersey margin gbc concentrations are uniformly high 121 358 ppm consistent with the core s continental margin setting but there is no evidence of increased gbc flux at the petm furthermore carbon isotopic ratios of gbc display the negative cie seen in petm organic matter indicating that this material was sourced from contemporaneous p e boundary biomass not geologically old carbon at site 1210 shatsky rise gbc concentrations were uniformly below our method s detection limit 0 5 ppm whereas the wildfire hypothesis would predict high gbc concentrations 3000 ppm accompanying the event together these data appear to refute but cannot conclusively rule out biomass burning as the cause for the petm event

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

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

combustion of fossil organic matter at the cretaceous paleogene k p boundary recognition of elevated concentrations of aciniform soot in cretaceous paleogene k p boundary sediments worldwide led to the hypothesis that global scale forest wildfires could have been generated by the k p boundary bolide impact and might have contributed directly to the extinction event the wildfires are estimated to have injected 10 13 t of co 2 into the atmosphere resulting in an interval of greenhouse warming yet minimal amounts of charred plant remains and abundant noncharred material occur in various k p boundary locations across north america this refutes the inference that wildfires occurred on a global scale and requires an alternative explanation for the aciniform soot here we describe significant concentrations of carbon cenospheres in k p boundary sediments from new zealand denmark and canada carbon cenospheres are thought to derive solely from incomplete combustion of pulverized coal or fuel oil droplets which suggests that the impact may have combusted organic rich target crust the chicxulub impact crater is located adjacent to the cantarell oil reservoir one of the most productive oil fields on earth this indicates that abundance of organic carbon in the chicxulub target crust was likely to have been above global mean values but even if we discount chicxulub9s organic rich locality the global mean crustal abundance for fossil organic matter is more than adequate to account for observed concentrations of both carbon cenospheres and aciniform soot therefore making the global wildfire hypothesis unnecessary

calcareous nannofossil assemblage changes across the paleocene eocene thermal maximum evidence from a shelf setting article i nfo biotic response of calcareous nannoplankton to abrupt warming across the paleocene eocene boundary re flects a primary response to climatically induced parameters including increased continental runoff of fresh water global acidification of seawater high sedimentation rates and calcareous nannoplankton assemblage turnover we identify ecophenotypic nannofossil species adapted to low ph conditions discoaster anartios d araneus rhomboaster spp excursion taxa adapted to the extremely warm climatic conditions bomolithus supremus and coccolithus bownii three species of the genus toweius t serotinus t callosus t occultatus adapted to warm rather than cool water conditions opportunists adapted to high productivity conditions coronocyclus bramlettei neochiastozygus junctus and species adapted to oligotropic and or cool water con ditions that went into refugium during the petm zygrablithus bijugatus calcidiscus parvicrucis and chiasmolithus bidens discoaster anartios was adapted to meso to eutrophic rather than oligotrophic condi tions comparison of these data to previous work on sediments deposited on shelf settings suggests that local conditions such as high precipitation rates and possible increase in major storms such as hurricanes resulted in increased continental runoff and high sedimentation rates that affected assemblage response to the petm published by elsevier b v

global fire at the cretaceous tertiary boundary cretaceous tertiary k t boundary clays from five sites in europe and new zealand are 102 104 fold enriched in elemental c mainly soot which is isotopically uniform and apparently comes from a single global fire the soot layer coincides with the ir layer suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled