magnetic remanence in the murchison meteorite the murchison meteorite is a carbonaceous chondrite containing a small amount of chondrules various inclusions and matrix with occasional porphyroblasts of olivine and or pyroxene it also contains amino acids that may have served as the necessary components for the origin of life magnetic analyses of murchison identify an ultrasoft magnetic component due to superparamagnetism as a significant part of the magnetic remanence the rest of the remanence may be due to electric discharge in the form of lightning bolts that may have formed the amino acids the level of magnetic remanence does not support this possibility and points to a minimum ambient field of the remanence acquisition we support our observation by showing that normalized mineral magnetic acquisition properties establish a calibration curve suitable for rough paleofield determination when using this approach 1 2 of the natural remanence left in terrestrial rocks with trm and or crm determines the geomagnetic field intensity irrespective of grain size or type of magnetic mineral with the exception of hematite the same method is applied to the murchison meteorite where the measured meteorite remanence determines the paleofield minimum intensity of 200 2000 nt during and or after the formation of the parent body

very high temperature impact melt products as evidence for cosmic airbursts and impacts 12 900 years ago it has been proposed that fragments of an asteroid or comet impacted earth deposited silica and iron rich microspherules and other proxies across several continents and triggered the younger dryas cooling episode 12 900 years ago although many independent groups have confirmed the impact evidence the hypothesis remains controversial because some groups have failed to do so we examined sediment sequences from 18 dated younger dryas boundary ydb sites across three continents north america europe and asia spanning 12 000 km around nearly one third of the planet all sites display abundant microspherules in the ydb with none or few above and below in addition three sites abu hureyra syria melrose pennsylvania and blackville south carolina display vesicular high temperature siliceous scoria like objects or slos that match the spherules geochemically we compared ydb objects with melt products from a known cosmic impact meteor crater arizona and from the 1945 trinity nuclear airburst in socorro new mexico and found that all of these high energy events produced material that is geochemically and morphologically comparable including i high temperature rapidly quenched microspherules and slos ii corundum mullite and suessite fe3si a rare meteoritic mineral that forms under high temperatures iii melted sio2 glass or lechatelierite with flow textures or schlieren that form at 2 200 c and iv particles with features indicative of high energy interparticle collisions these results are inconsistent with anthropogenic volcanic authigenic and cosmic materials yet consistent with cosmic ejecta supporting the hypothesis of extraterrestrial airbursts impacts 12 900 years ago the wide geographic distribution of slos is consistent with multiple impactors

geologic framework of upper miocene and pliocene gas plays of the macuspana basin southeastern mexico this integrated study provides a geological and geochemical framework for upper miocene and pliocene siliciclastic gas plays in the macuspana basin structural controls for the plays are deep seated faults that tap mesozoic thermogenic gas sources areas of intense shale diapirism and folding and areas with structural inversion that could enhance trapping and reservoir productivity early neogene thrusting south of the basin triggered evacuation of oligocene shale along northwest dipping listric faults in the eastern and southeastern basin margin these faults are associated with large scale rollover structures and thick 500 m upper miocene shoreface and wave dominated deltaic complexes a second phase of extension in the early pliocene formed a set of broad southeast dipping listric faults in the western basin controlling thick accumulations of stacked pliocene shoreface deposits trap formation and enhancement in the southern basin margin are linked to late miocene to pliocene inversion the primary stratigraphic controls on play occurrence in the upper miocene in the onshore part of the basin are the regional facies distribution of northwest prograding shoreface and wave dominated deltaic systems there was a shift in pliocene sedimentation from the southeast to the west and northwest parts of the basin where thick successions of aggradational shoreface and wave dominated deltaic deposits accumulated in depocenters defined by shale evacuation along growth faults valley fill deposits in both the upper miocene and pliocene resulted from shortlived periods of base level change induced by either uplift on the southern basin margin or eustasy the offshore part of the basin is inferred to consist of deep water turbidite deposits that formed downdip westward of a hypothesized mixed clastic carbonate prograding complex from the yucatan platform three petroleum systems mesozoic paleogene lower neogene and upper miocene pliocene contributed to the hydrocarbon accumulations and hydrocarbon generation and migration in the basin principal upper jurassic lower cretaceous source rocks generated wet thermogenic gases and oil secondary lower tertiary source rocks generated dominantly dry biogenic gases mixtures of the two gas types are common numerous deep seated growth faults and faults serve as pathways for mesozoic sourced hydrocarbons surface seeps and abundant gas shows suggest that hydrocarbons are being generated today

the transpressive left lateral sierra madre de chiapas and its buried front in the tabasco plain southern mexico the sierra madre de chiapas evolved in the vicinity of the triple junction between the cocos north america and caribbean plates the sierra madre de chiapas tectonics reflects positive topographic growth along its main core and a northwards directed collapse through a free border related to the gulf of mexico major exhumation and topographic growth occurred during the middle late miocene 16 10 ma evidence for this deformational event is provided by fault activity major stratigraphic unconformities along the sierra madre de chiapas and the tabasco coastal plain i e southern gulf of mexico major salt related motion northward progradation of the sedimentation and northward migration of the buried deformational front during the neogene strike slip deformation and its related exhumation migrated landwards from the western edge of the chiapas massif complex to the chiapas sierra horizontal displacement along the main strike slip faults in the chiapas sierra has been indirectly estimated to be between 30 and 43 km during the last 6 5 ma implying 0 5 0 8 cm a 1 of lateral accommodation these values suggest that a significant amount of the motion transferred by the caribbean and north american plates is currently being accommodated along the chiapas area supplementary material a geological map of the sierra madre de chiapas is available at www geolsoc org uk sup18507

origin of the anomalies of gravity and its vertical gradient over cavities in brittle rock investigations show that the depth range of the gravity method for detecting cavities is considerably greater than expected on the basis of theoretical calculations that consider only the depth and shape of the cavity the cavity generates its own gravity field that is the sum of the activity of the cavity itself and the density changes caused in the surrounding rocks by the process of their destruction as a result of the cavity s expansion the latter factor is decisive for the cavity s detection by the gravity method in several cases the extent of the zones of change density in the surrounding rocks and their actual shape depend on many parameters thus the determination of the depth of the cavity cannot be made by comparing measured and theoretical curves of gravity anomalies the location of the center of gravity of the area disturbed by the cavity or upper boundary of its development towards the ground surface can be determined by denoting the singular point of gravity as a result of the downward analytical continuation of ag the strakhov grigorieva lapina 1977 method fulfils the necessary conditions in the field

the leonard award address presented 1996 july 25 berlin germany the elemental composition of stony cosmic spherules five hundred stony cosmic spherules collected from deep sea sediments polar ice and the strato sphere have been analyzed for major and some minor element composition typical spherules are products of atmospheric melting of millimeter sized and smaller meteoroids the samples are small and modified by atmospheric entry but they are an important source of information on the composition of asteroids the spherules in this study were all analyzed in an identical manner and they provide a sampling of the solar system s asteroids that is both different and less biased than provided by studies of conventional meteorites volatile elements such as na and s are depleted due to atmospheric heating while siderophiles are depleted by less understood causes the refractory nonsiderophile elements appear not to have been significantly dis turbed during atmospheric melting and provide important clues on the elemental composition of millimeter sized meteoroids colliding with the earth typical spherules have cm like composition that is distinctively different than ordinary chondrites and most other meteorite types we assume that c type asteroids are the primary origin of spherules with this composition type s asteroids should also be an important source of the spherules and the analysis data provide constraints on their composition a minor fraction of the spher ules are melt products of precursor particles that did not have chondritic elemental compositions the most common of these are particles that are dominated by olivine the observed compositions of spherules are in consistent with the possibility that an appreciable fraction of the spherules are simply chondrules remelted during atmospheric entry

induced gravity anomalies and seismic energy as a basis for prediction of mining tremors the results of prediction of occurrence of mining tremors and bursts in the course of the exploitation of the remaining part of the hard coal in seam 510 of the mine pstrowski upper silesia have been presented in the paper the exploitation has taken place under extremely difficult conditions hazardous for the mining crew

microtektite like impact glass associated with the frasnian famennian boundary mass extinction abstract glass spherules of probable impact origin occur in the late devonian hony section in belgium they are found at the stratigraphic level of the frasnian famennian boundary which is marked by one of the largest mass extinctions in the phanerozoic the hony glass spherules are chemically identical to those previously described from the stratigraphically equivalent senzeille section located 90 km to the west southwest in contrast to the senzeille layer the age of the hony spherule layer is well constrained by conodont biostratigraphy the spherules have morphological and chemical characteristics similar to tektites and microtektites they have a broad range of chemical composition with generally high k2o na2o and al2o3 na2o k2o their water content is in the range measured for tektites and impact glasses small inclusions of lechatelierite may be present in the spherules these glass spherules are likely to be the product of an impact event that occurred at or very near the frasnian famennian boundary the target rock was probably a clay rich pelitic sediment intermixed with carbonates the 368 1 ma siljan ring crater sweden is the most likely impact site candidate the hony and senzeille glass spherules represent the first substantial evidence that an impact event may be linked to the frasnian famennian mass extinction

lodestone natures only permanent magnet what it is and how it gets charged magnetite and titanomagnetite exhibit magnetic properties which are attributable to the micro structures developed during oxidation and exsolution all magnetite iron ores which are lodestones contain maghemite these lodestones have hc between 10 and 30 mt sirm between 8 and 18 am kg and ri between 0 10 and 0 26 magnetite titanomagnetite and metals have rem values ratio of nrm to sirm 0 05 samples called fulgarites obtained from the smithsonian institution have rem values ranging from 0 45 to 0 92 the rem value serves as a witness parameter to the magnetic fields associated with the lightning bolt if a high rem value say 0 1 can be verified as not to be due to contamination by man and does not contain md hematite then the rock has lrm lightning remanent magnetization the magnetic field associated with lightning can be revealed from an isothermal remanent acquisition ra curve

a conceptual model for hydrocarbon accumulation and seepage processes around chapopote asphalt site southern gulf of mexico from high resolution seismic point of view 1 as part of the german r v meteor m67 2 expedition in 2006 to the southern gulf of mexico a set of 2d high resolution seismic profiles was acquired across the chapopote knoll to study seafloor asphalt occurrences on the basis of regional seismostratigraphic studies and dsdp drilling a more highly reflective coarse grained sediment unit of late miocene age is identified as a potential shallow hydrocarbon reservoir although a unit of that age would typically be buried by pliocene and pleistocene sediment cover at chapopote local salt tectonism has highly elevated the structure since the late miocene and the miocene reservoir is locally above present day regional datum the elevation resulted in a thin 100 200 m fine grained sediment cover on the crest of the knoll above the reservoir because oil and gas production can be expected at depth in jurassic cretaceous and tertiary source rocks the presence of high amplitude reflector packages within the reservoir unit is interpreted as an evidence of hydrocarbons this is variously supported by observations of crosscutting reflectors polarity reversal and drops in instantaneous frequency the thin seal above the reservoir unit facilitates leakage of trapped hydrocarbons hydrocarbons apparently invaded into the seal sediments in the wider vicinity around the crest of the knoll even extending beyond the area where seafloor asphalt is known the asphalt site thus may be a currently active spot while the rest of the crest may be temporarily sealed by solid phase hydrocarbons we propose that a shallow large reservoir with deeply sourced relatively heavy petroleum is principally responsible for the formation of asphalts on the seafloor

the vertical compartmentalization of reservoirs an example from an outcrop analog crotone basin southern italy the lower pliocene shallow marine successions deposited within half graben subbasins exposed in the northern crotone basin southern italy are good examples illustrating the variable development of small scale cycles 2 15 m 6 6 49 ft thick within the hanging wall blocks of normal growth faults shallow marine small scale cycles forming the successions deposited near the immediate hanging wall of half graben subbasins show a clear alternation between well cemented shell rich intervals and weakly cemented siliciclastic sandstones in contrast the shallow marine successions deposited in hanging wall dip slope locations and in the footwalls show a poorly preserved cyclicity related to lower subsidence rates and a higher degree of cycle amalgamation the vertical alternation between well cemented carbonate rich intervals and less cemented sandstones creates a marked heterogeneity in the permeability of these shallow marine half graben fills which are sealed by impermeable offshore and lagoonal mudstones and may be considered as an outcrop analog of potential reservoirs as a consequence of the well developed cyclicity therefore the potential reservoir is vertically compartmentalized this feature tends to vanish toward the hanging wall dip slopes where the cyclicity is remarkably less appreciable the correct prediction of geometry and effective volume of reservoirs and in particular the recognition of their vertical compartmentalization have an important impact on hydrocarbon exploration and production the developed conceptual model of compartmentalized half graben fill may be useful in several contexts to study fault bounded basins from a reservoir point of view

petroleum accumulation and leakage in a deeply buried carbonate reservoir nispero field mexico abstract the filling history of the nispero deeply buried lower cretaceous carbonate reservoir below 4000 m from the south part of gulf of mexico was studied using a combination of data from petrography stable isotopes and fluid inclusions and compared with a one dimensional burial model to derive timing a combination of techniques such as microthermometry confocal laser scanning microscopy clsm and raman microspectroscopy have been used to characterize the different fluid inclusion assemblages and discriminate between the reequilibrated and the preserved fluid inclusions the nispero reservoir is composed of a fractured finely crystalline replacement dolostone a first generation of fractures is filled by a non planar dolomite cement and a second generation by a planar e dolomite cement and a blocky sparite the reservoir is lastly stylolitised dolomite has 13c values between 0 9 and 4 0 pdb and 18o values between 4 5 and 10 8 pdb calcite has 13c values between 3 8 and 4 4 pdb and 18o values between 4 9 and 5 5 pdb these values suggest that the calcite represents a change in water composition and that dolomite and calcite cements do not precipitate from petroleum derived fluids however geological fluids are trapped as aqueous and oil inclusions in the calcite cements three petroleum aqueous inclusion assemblages were identified pseudo primary brown oil paired with brine inclusions and pseudo primary yellow oil paired with low salinity water inclusions distributed in local concentrations and secondary colourless oil paired with low salinity aqueous inclusions distributed in healed microfractures the burial model calibrated with bottom hole temperatures has been calculated using petromod 1d to generate the rock pt history under hydrostatic and lithostatic regimes reconstructed temperatures of initial trapping of fluid inclusion and calculated temperatures from 18o measured in dolomite and calcite cements are in good agreement data suggests that the reservoir was being filled at 97 c 315 bar by heavy black oils accompanied by high salinity water during the miocene period 11 6 m y the maximum estimated pressure of 700 bar at 130 c is reconstructed by petroleum inclusions trapping black oil and associated low salinity aqueous inclusions these pt conditions were reached during the pliocene 3 2m y present day reservoir conditions of 145 c and 500 bar are recorded by reequilibration of most of the fluid inclusions of the two assemblages and correspond to hydrostatic pressure the drop of pressure from 700 bar to 500 bar may be an explanation for the late stylolitisation

shallow sediment deformation styles in north western campeche knolls gulf of mexico and their controls on the occurrence of hydrocarbon seepage during german r v meteor m67 2 expedition to campeche knolls southern gulf of mexico a set of 2d high resolution seismic data was acquired to study the near surface sediment structure and its relationship with hydrocarbon seepages in this salt province the comprehensive survey covered 20 individual bathymetric highs or ridges and identified three principle structural types passive type chaopopte type and asymmetric flap type the first type is the result of passive diapirism whereas the latter two were initialized by a regional compressional event in the miocene but are later differently modified by salt tectonism chapopote type structures appear as symmetrical domes with uplifted coarse grained miocene sediments in their cores and rather thin syn kinematic sediments covering the crests asymmetric flap type structures are also first folded as domes or ridges but one flap later subsided together with salt evacuation resulting in single uplifted monoclines with the coarse grained pre kinematic sediments as reservoir units both structural types can focus and accumulate hydrocarbons the geometries of the structures suggest that hydrocarbons are accumulated in the center of the chapopote type structures and in the subsided flaps of the asymmetric flap type structures hydrocarbon leakage from these thinly sealed reservoirs is regarded as the principle mechanism for the seepage in the study area and accordingly the most seepage prone positions are above these reservoirs the seep locations suggested by analysis of sea surface oil slick images of sar satellite data are also examined in this study these independently derived seep locations confirm the seepage prone positions to be above the shallow buried reservoirs this study suggest that the shallow sediment structures control the distribution of the hydrocarbon seeps of the north western campeche knolls although the hydrocarbons are sourced from the greater depth

origin of oil in the sureste basin mexico geochemical and biological marker analyses of oils and rock samples from the sureste basin of mexico were effective in identifying and geographically limiting four major oil families related by age and source rock depositional environment oxfordian tithonian early cretaceous and tertiary the source rocks giving rise to the jurassic and cretaceous oils are associated with marine carbonate environments in contrast the source rocks giving rise to the tertiary oils are associated with a marine deltaic siliciclastic depositional setting biomarker and isotope differences observed in the oils derived from marine carbonate environments can be interpreted in terms of salinity clay content and oxygen depletion variations these differences provide diagnostic criteria for recognizing and differentiating five distinct organic rich depositional regimes as the sources for these oil types an anoxic hypersaline marine carbonate environment associated with a narrow and shallow semirestricted sea oxfordian age family 1 oil an anoxic marine carbonate environment associated with a silled basin geometry tithonian age family 2 oils subtype 2a an anoxic marine carbonate environment associated with a shallow gentle broad marine carbonate ramp in a distal position tithonian age family 2 oils subtype 2b a clay rich suboxic anoxic marine carbonate environment associated with a carbonate platform in a proximal position tithonian age family 2 oils subtype 2c and an anoxic marine evaporitic environment early cretaceous age family 3 oils the tertiary oils family 4 are derived from bacterially reworked terrigenous and marine organic source materials deposited in a marine deltaic environment the tithonian related oils in the mexican southern side of the gulf of mexico accumulated both offshore and onshore and throughout the stratigraphic column from kimmeridgian to pleistocene reservoirs suggesting vertical pathways as the principal secondary migration mechanism the lateral variations of these oils can be interpreted to reflect the tithonian paleogeography in the area and could be useful in predicting differences in the oil compositions

extreme heating events and effects in the natural environment implications for environmental geomorphology lightning and cosmic impacts on bedrock sediment cover and vegetation cause and have caused through geologic time almost instantaneous high energy discharges that produce extreme heating to many hundreds or a few thousand degrees celsius the effects of these cataclysmic events leave an imprint in surface material such that much of it becomes physically changed and carbonized primary and secondary minerals become welded together and or coated with carbon providing a food source for microbes which invade the altered material here we present a summary of fired rock and sediment covers from the andes cosmic impact the alps lightning fired rock and southern ontario canada where lightning toppled a red pine pinus resinosa thus altering the cellulose internal fiber and bark electrostatically levitated minerals from the tree roots soil transported upward a considerable distance became embedded in the outside and inside of the bark cellulose quartz and various plagioclases were melted the former producing deformed sheets of si the latter pure metallic na mineral artifacts of extreme heating events catalogued here might be used in environmental reconstruction efforts when problematic bedrock and sediment covers offer no alternative explanation

numbers types and compositions of an unbiased collection of cosmic spherules abstract abstract micrometeorites collected from the bottom of the south pole water well spww may represent a complete well preserved sample of the cosmic dust that accreted on earth from 1100 1500 a d we classified 1588 cosmic spherules in the size range 50 800 pm the collection has 41 barred olivine spherules 17 glass spheres 12 cryptocrystalline spherules 11 porphyritic olivine spherules 12 relic grain bearing spherules 3 scoriaceous spherules 2 i type spherules 1 ca al ti rich cat spherules and 1 g type spherules we also found bubbly glass spherules spherules with glass caps and ones with sulfide coatings particles that are absent from other collections a classification sequence of the stony spherules scoriaceous relic grain bearing porphyritic barred olivine cryptocrystalline glass and cat is consistent with progressive heating and evaporation of fe from chondritic materials the modem day accretion rate and size distribution measured at the spww can account for the stony spherules present in deep sea collection through preferential dissolution of glass and small stony spherules however weathering alone cannot account for the high accretion rate of i type spherules determined for two deep sea collections the spww collection provides data to constrain models of atmospheric entry heating and to assess the effects of terrestrial weathering

gas geochemistry of the macuspana basin mexico thermogenic accumulations in sediments impregnated by bacterial gas a gas survey was performed in the macuspana basin south of mexico two distinct gas families were identified family 1 is represented by homogeneous and purely thermogenic gas associated with condensates expelled at the end of the oil window and family 2 is composed of a mixture of bacterial dry gas and thermogenic gas derived from source rocks at high maturity chemical and isotopic parameters as well as noble gas data provided information about the sources the proportions of mixing and directions of hydrocarbon migration of these two families considering the risk associated with further oil and gas exploration in the basin deeper zones present higher exploratory interest for family 1 gas fields and associated oil accumulations in contrast the bacterial gas fields should be considered a less promising target for future oil and gas exploration

induced gravity anomalies and rock burst risk in coal mines a case history1 the use of the gravity method to predict rock bursts in mines is based on the relationship between the development of a dilatancy process in the exploited rock mass and the time dependent gravity anomalies induced by this phenomenon the differences between successive observations of anomalies and the time behaviour of their trend amplitudes as precursors of preceding changes of rock stability are interpreted the centres of zones of induced rock density variation are determined by computing the position of singular points of the differences between anomalies two gravity surveys have been carried out in the radbod coal mine germany the first survey took place at the level of the dickebank seam depth 1030 m the second in the sonnenschein seam depth 1090 m the observations were made with worden and lacoste romberg d type gravimeters the differences between successive anomalies were less than 100 gal in the case of the dickebank seam the position of singular points demonstrates the effect of two approaching longwalls on a previously mined out seam and on the gallery in which the gravity observations were made in the case of the sonnenschein seam the trend amplitudes show distinct variations in the formation of the approaching longwall below the edges of all previously mined out seams in particular the effect of a remnant pillar has caused the largest gravity gradients this result corresponds to the existence of a zone of rock burst hazard known from test drilling the computed singular points are grouped together under the remnant pillar indicating two local hazard zones both results the observed development of rock instability with time and the information about the position of the disturbed rock mass relative to the mine workings are of importance subsurface gravity surveying can therefore be a valuable tool for predicting rock bursts

nanodiamonds in the younger dryas boundary sediment layer we report abundant nanodiamonds in sediments dating to 12 9 0 1 thousand calendar years before the present at multiple locations across north america selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval cubic diamonds form under high temperature pressure regimes and n diamonds also require extraordinary conditions well outside the range of earth9s typical surficial processes but common to cosmic impacts n diamond concentrations range from 10 to 3700 parts per billion by weight comparable to amounts found in known impact layers these diamonds provide strong evidence for earth9s collision with a rare swarm of carbonaceous chondrites or comets at the onset of the younger dryas cool interval producing multiple airbursts and possible surface impacts with severe repercussions for plants animals and humans in north america

fired glaciofluvial sediment in the northwestern andes biotic aspects of the black mat abstract fired glaciofluvial beds in outwash considered to date from the onset of the younger dryas event 12 9 ka in the northwestern venezuelan andes are considered equivalent to the black mat deposits described in other areas of north and south america and europe it may be equivalent to sediment recovered from other sites containing beds with spikes of cosmic nuclides and charcoal indicating the presence of widespread fire one of the signatures of the black mat conflagration that followed the proposed breakup of comet encke or an unknown asteroid over the laurentide icesheet at 12 9 ka in the northern andes at site mum7b sediment considered coeval with the black mat contains glassy carbon spherules tri coatings of c welded onto quartz and feldspar covered with fe and mn monazite with excessive concentrations of rees platinum metals including ru and rh possible pdf s and disrupted brecciated and microfractured quartz and feldspar from impacting ejecta and excessive heating summarize the data obtained so far the purpose of this paper is to document the physical character mineralogy and biotic composition of the black mat

spherules from the late cretaceous phosphorite of the fatehgarh formation barmer basin india abstract a first report of discovery of spherules glassy balls highly magnetic fine dust and microbracciated matrix in the fatehgarh formation of barmer basin rajasthan india is being presented in this paper the fatehgarh formation is a mixed siliciclastic carbonate and phosphorite formation of cretaceous age in the barmer basin that comprises sediments of middle jurassic to lower eocene age the phosphorite zone in the fatehgarh formation is 8 metre thick zone that comprises phosphatic sandstone bone bed bedded phosphorite and phosphatic and non phosphatic gastropod beds the spherules occur in a thin phosphatic clay mud and silt band of bone bed which also yielded a very rich and diverse microvertebrate assemblage with a dominant late cretaceous maastrichtian form of igdabatis along with forms comprising of semionodontid lapisosteum and enchodontid the end cretaceous is marked for a mass extinction of numerous species including dinosaurs an extraterrestrial impact is interpreted as the reason for this mass extinction whether these spherules are related to the volcanic source or k t boundary impact ejecta found at caribbean and gulf of mexico region needs detailed chemical and age characterization for which study is in progress

the murray springs clovis site pleistocene extinction and the question of extraterrestrial impact some of the evidence for the recent hypothesis of an extraterrestrial impact that caused late pleistocene megafaunal extinctions firestone et al 2007 proc natl acad sci usa 104 16016 16021 was based upon samples collected at murray springs a clovis archaeological site in southeastern arizona here we describe sampling and analyses of magnetic separates from within above and below the lower younger dryas boundary lydb black mat at murray springs as well as radiation measurements from the lydb at murray springs and two other well stratified clovis sites the main magnetic fraction at murray springs is maghemite magnetic microspherules have terrestrial origins but also occur as cosmic dust particles we failed to find iridium or radiation anomalies the evidence for massive biomass burning at murray springs is addressed and found to be lacking we could not substantiate some of the claims by firestone and others but our findings do not preclude a terminal pleistocene cosmic event

wildfire and abrupt ecosystem disruption on california s northern channel islands at the allerod younger dryas boundary 13 0 12 9 ka abstract sedimentary records from california s northern channel islands and the adjacent santa barbara basin sbb indicate intense regional biomass burning wildfire at the allerod younger dryas boundary 13 0 12 9 ka all age ranges in this paper are expressed in thousands of calendar years before present ka radiocarbon ages will be identified and clearly marked 14c years multiproxy records in sbb ocean drilling project odp site 893 indicate that these wildfires coincided with the onset of regional cooling and an abrupt vegetational shift from closed montane forest to more open habitats abrupt ecosystem disruption is evident on the northern channel islands at the allerod younger dryas boundary with the onset of biomass burning and resulting mass sediment wasting of the landscape these wildfires coincide with the extinction of mammuthus exilis pygmy mammoth the earliest evidence for human presence on these islands at 13 1 12 9 ka 11 000 10 900 14c years is followed by an apparent 600 800 year gap in the archaeological record which is followed by indications of a larger scale colonization after 12 2 ka although a number of processes could have contributed to a post 18 ka decline in m exilis populations e g reduction of habitat due to sea level rise and human exploitation of limited insular populations we argue that the ultimate demise of m exilis was more likely a result of continental scale ecosystem disruption that registered across north america at the onset of the younger dryas cooling episode contemporaneous with the extinction of other megafaunal taxa evidence for ecosystem disruption at 13 12 9 ka on these offshore islands is consistent with the younger dryas boundary cosmic impact hypothesis firestone r b west a kennett j p becker l bunch t e revay z s schultz p h belgya t kennett d j erlandson j m dickenson o j goodyear a a harris r s howard g a kloosterman j b lechler p mayewski p a montgomery j poreda r darrah t que hee s s smith a r stich a topping w wittke j h wolbach w s 2007 evidence for an extraterrestrial impact 12 900 years ago that contributed to the megafaunal extinctions and younger dryas cooling proceedings of the national academy of sciences 104 16016 16021

evidence from the northwestern venezuelan andes for extraterrestrial impact the black mat enigma abstract a carbon rich black layer encrusted on a sandy pebbly bed of outwash in the northern venezuelan andes previously considered the result of an alpine grass fire is now recognized as a black mat candidate correlative with clovis age sites in north america falling within the range of black mat dated sites 12 9 ka cal bp as such the bed at site mum7b which dates to 14 c years bp raw dates and appears to be contemporaneous with the younger dryas yd cooling event marks a possibly much more extensive occurrence than previously identified no fossils megafauna or tool assemblages were observed at this newly identified candidate site 3800 a m s l as in the case of the north american sites here evidence is presented for an extraterrestrial impact event at 12 9 ka the impact related andean bed located 20 cm above 13 7 13 3 ka cal bp alluvial and glaciolacustrine deposits falls within the sediment characteristics and age range of black mat dated sites 12 9 ka cal bp in north america site sediment characteristics include carbon glassy spherules magnetic microspherules carbon mat welded onto coarse granular material occasional presence of platinum group metals rh and ru planar deformation features pdfs in fine silt size fragmental grains of quartz as well as orthoclase and monazite with an abundance of rare earth elements rees if the candidate site is black mat correlative with the black mat sites of north america such an extensive occurrence may support the hypothesized airburst impact over the laurentide glacier which led to a reversal of allerod warming and the onset of yd cooling and readvance of glaciers while this finding does not confirm such it merits further investigation which includes the reconnaissance for additional sites in south america furthermore if confirmed such an extensive occurrence may corroborate an impact origin

synchronous records of pco2 and δ14c suggest rapid ocean derived pco2 fluctuations at the onset of younger dryas just before the onset of the younger dryas yd cold event several stomatal proxy based pco2 records have shown a sharp increase in atmospheric co2 concentration pco2 of between ca 50 and 100 ppm followed by a rapid decrease of similar or even larger magnitude here we compare one of these records a high resolution pco2 record from southern sweden with the intcal13 record of radiocarbon d 14 c the two records show broadly synchronous fluctuations at the yd onset specifically the intcal13 record documents decreasing d 14 c just before the yd onset when pco2 peaks consistent with a source of old co2 from the deep ocean we propose that this fluctuation occurred due to a major ocean flushing event the cause of the flushing event remains speculative but could be related to the hypothesis of the glacial ocean as a thermobaric capacitor we confirm that the earth system can produce such large multidecadal timescale fluctuations in pco2 through simulating an artificial ocean flushing event with the genie earth system model we suggest that sharp transitions of pco2 may have remained undetected so far in ice cores due to inter firn gas exchange and time averaging the stomatal proxy record is a powerful complement to the ice core records for the study of rapid climate change

mud volcanoes in deepwater nigeria abstract detailed study of 3d seismic data from deepwater nigeria has revealed the presence of features interpreted to be mud volcanoes they occur in an upper slope environment seen as 1 2 km circular features at the seabed seabed cores from the mud volcanoes contain oil gas and sand shale clast content richer than the seabed background pliocene fossils have been identified in the cores demonstrating transport of material from depth the features show a high seabed seismic amplitude above a chimney of chaotic seismic reflections and data wipe out the mud volcanoes in the study area shows two distinct clusters located over deeper structural culminations four active mud volcanoes area 1 are located above a rollover anticline in the central part of the area cuspate listric faults reach the seabed on the up slope side of these mud volcanoes four abandoned mud volcanoes have also been identified with progressively older ages towards the crest of the underlying structure these abandoned features are associated with an extremely chaotic seismic signature a combination of over pressured carrier beds and low integrity top seals are believed to be responsible for the formation of these mud volcanoes it is further believed that gas expansion subsequent to seal failure was the main driving force for what must have been violent eruptions the long lived mud volcano activity over the deep structural closure suggests a plumbing system that focuses on escaping compaction water and hydrocarbons through time in the south west of the study area another cluster of five mud volcanoes is located above a shale diapir the seabed expression of the members of this cluster is more varied some show a positive relief at the seabed while others show circular depressions the largest feature represents an assemblage of many smaller mud volcanoes with a common root system their seismic expression is also different from that of area 1 with a well defined sediment wedge at surface and a shallower root system these features are believed to represent a less violent type of mud volcano characterised by ductile flow tectonic stress due to growth of the underlying diapir is thought to have played an important role during eruption in addition to focused methane escape and the low mechanical strength of the overburden

geochemistry of cenozoic microtektites and clinopyroxene bearing spherules abstract we have determined the major and trace element compositions of 176 individual microtektites spherules from the australasian ivory coast and north american microtektite and clinopyroxene bearing cpx spherule layers trace element contents for up to 30 trace elements were determined by instrumental neutron activation analysis inaa and major element compositions were determined using energy dispersive x ray edx analysis in combination with a scanning electron microscope sem in addition petrographic data were obtained for the cpx spherules using the sem and edx this is the first trace element study of individual australasian microtektites and the data revealed the presence of a previously unrecognized group of australasian microtektites with high contents of ni up to 471 ppm in previous studies the high mg hmg australasian microtektites were thought to be related to the hmg australasian tektites but our trace element data suggest that the high ni hni australasian microtektites rather than the high mg microtektites are related to the high mg australasian tektites we find that cenozoic microtektites spherules from a given layer can be distinguished from microtektites spherules from other layers as a group but it is not always possible to determine which layer an individual microtektite spherule came from based only on trace element compositions the cpx spherules and most of the microtektites have cr co and ni contents that are higher than the average contents of these elements in the upper continental crust suggesting the presence of a meteoritic component the highest cr co and ni contents are found in the cpx spherules and low si cpx related microtektites unetched to slightly etched cpx spherules have ni cr and ni co ratios that generally lie along mixing curves between the average upper continental crust and chondrites the best fit appears to be with an ll chondrite the moderately to heavily etched cpx spherules have values that lie off the mixing curves in a direction that suggests ni loss probably as a result of solution of a ni rich phase olivine the ni rich australasian microtektites also have ni values that lie close to mixing curves between the average upper continental crust and chondrites however both the cpx spherules and hni australasian microtektites appear to have ir and to a lesser extent au contents that are much too low to have ni ir ratios similar to chondritic values we have no explanation for the low ir and au contents except to speculate that they may be the result of a complex fractionation process the ivory coast and north american microtektites do not have high enough siderophile element contents to reach any firm conclusions regarding the presence of or nature of a meteoritic component in them trace element compositions are consistent with derivation of the cenozoic microtektite spherule layers from upper continental crust the normal australasian microtektites appear to have been derived from a graywacke or lithic arenite with a range in clay and quartz content the source rock for the high mg australasian microtektites is not known but the hmg microtektites do not appear to be normal australasian microtektites that were simply contaminated by meteorites or ultramafic rocks the average ivory coast microtektite composition can be matched with a mixture of target rocks at the bosumtwi crater the average composition of the north american microtektites suggests an arkosic source rock but with graywacke and quartz rich end members however we could not match the composition of the north american microtektites with lithologies in impact breccias recovered from the chesapeake bay impact structure that is believed to be the source crater likewise we could not match the composition of the cpx spherules with mixtures of basement rocks and overlying sedimentary deposits for which compositional data are available at the popigai impact crater that may be the source crater for the cpx spherules this may be because the cpx spherules were derived in large part from clastic surface rocks sandstones and shales for which no compositional data are available

upper jurassic structure and evolution of the yucatan and campeche subbasins southern gulf of mexico the isthmian salt basin in the southern gulf of mexico can be divided into the yucatan and campeche subbasins separated by a base salt high near the nose of the yucatan platform despite their proximity these two subbasins experienced radically different histories in the period immediately following salt deposition portions of the yucatan subbasin are characterized by large scale locally as much as 60 km 37 mi downdip translation of salt and suprasalt sediments during the late jurassic this translation produced a major detached extensional province at the updip end of the basin which is not compensated by observed shortening downdip we interpret this history to be a result of unconfined seaward flow of salt and its cover during basin opening a process mirrored on the conjugate florida margin the campeche subbasin in contrast shows no evidence of significant late jurassic translation detached on salt no large scale extensional or contractional provinces of mesozoic age are evident although some minor translation did occur we suggest that salt in the campeche subbasin was confined at its seaward end which prevented the seaward salt flow experienced in the yucatan subbasin furthermore salt at the seaward end of the campeche subbasin lies 2 3 km 1 2 mi above oceanic crust in contrast to salt lying on crust whose top sits at or below the level of oceanic crust at the seaward ends of the tamaulipas yucatan and florida margins the campeche subbasin thus appears to have been perched relative to other parts of the gulf of mexico

chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12 800 years ago according to the younger dryas impact hypothesis ydih 12 800 calendar years before present north america experienced an extraterrestrial impact that triggered the younger dryas and devastated human populations and biotic communities on this continent and elsewhere this supposed event is reportedly marked by multiple impact indicators but critics have challenged this evidence and considerable controversy now surrounds the ydih proponents of the ydih state that a key test of the hypothesis is whether those indicators are isochronous and securely dated to the younger dryas onset they are not we have examined the age basis of the supposed younger dryas boundary layer at the 29 sites and regions in north and south america europe and the middle east in which proponents report its occurrence several of the sites lack any age control others have radiometric ages that are chronologically irrelevant nearly a dozen have ages inferred by statistically and chronologically flawed age depth interpolations and in several the ages directly on the supposed impact layer are older or younger than 12 800 calendar years ago only 3 of the 29 sites fall within the temporal window of the yd onset as defined by ydih proponents the ydih fails the critical chronological test of an isochronous event at the yd onset which coupled with the many published concerns about the extraterrestrial origin of the purported impact markers renders the ydih unsupported there is no reason or compelling evidence to accept the claim that a cosmic impact occurred 12 800 y ago and caused the younger dryas

accumulation of impact markers in desert wetlands and implications for the younger dryas impact hypothesis the younger dryas impact hypothesis contends that an extraterrestrial object exploded over north america at 12 9 ka initiating the younger dryas cold event the extinction of many north american megafauna and the demise of the clovis archeological culture although the exact nature and location of the proposed impact or explosion remain unclear alleged evidence for the fallout comes from multiple sites across north america and a site in belgium at 6 of the 10 original sites excluding the carolina bays elevated concentrations of various impact markers were found in association with black mats that date to the onset of the younger dryas black mats are common features in paleowetland deposits and typically represent shallow marsh environments in this study we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern united states and the atacama desert of northern chile at 10 of 13 sites we found elevated concentrations of iridium in bulk and magnetic sediments magnetic spherules and or titanomagnetite grains within or at the base of black mats regardless of their age or location suggesting that elevated concentrations of these markers arise from processes common to wetland systems and not a catastrophic extraterrestrial impact event

433 eros problems with the meteorite magnetism record in attempting an asteroid match the magnetometer experiment mag onboard the near shoemaker spacecraft detected no global scale magnetization and established a maximum magnetization of 2 1x10 6 am 2 kg 1 for asteroid 433 eros this is in sharp contrast with the estimated magnetization of other s class asteroids gaspra 2 4 x 10 2 am 2 kg 1 braille 2 8 x 10 2 am 2 kg 1 and is below published values for all types of ordinary chondrites this includes the l ll types considered to most closely match 433 eros based on preliminary interpretations of near remote geochemical experiments the ordinary chondrite meteorite magnetization intensity data was reviewed in order to assess the reasonableness of an asteroid meteorite match based on magnetic property measurements nrm natural remanent magnetization intensities for the ordinary chondrite meteorites show at least a 2 order of magnitude range within each of the h l ll groups all well above the 2 1 x10 6 am 2 kg 1 level for 433 eros the rem values ratio of the nrm to the sirm saturation remanent magnetization range over 3 orders of magnitude for all chondrite groups indicating no clear relationship between nrm and the amount of magnetic material levels of magnetic noise in chondrite meteorites can be as much as 70 or more of the nrm consequently published values of the nrm should be considered suspect unless careful evaluation of the noise sources is done goddard studies of per unit mass intensities in large 10 000gm and small down to 1 gm samples from the same meteorite demonstrate magnetic intensity decreases as size increases this would appear to be explained by demagnetization due to magnetic vector randomness at unknown scale sizes in the larger samples this would then argue for some level of demagnetization of large objects such as an asteroid the possibility that 433 eros is an ll chondrite cannot be discounted

fungus not comet or catastrophe accounts for carbonaceous spherules in the younger dryas impact layer 1 a claim attributes the onset of the younger dryas climate interval and a range of other effects 12 900 years ago to a comet airburst and or impact event one key aspect of this claim centers on the origin of carbonaceous spherules that purportedly formed during intense impact ignited wildfires samples from pleistocene holocene sedimentary sequences in the california channel islands and other sites show that carbon spherules and elongate forms are common in samples dating to before during and well after the 12 900 year time horizon including from modern samples microscopic studies show that carbon spherules have morphologies and internal structures identical to fungal sclerotia such as sclerotium and cenococcum experimental charring of fungal sclerotia shows that their reflectance increases with temperature reflectance measurements of modern and late pleistocene spherules show that the latter indicate at most low intensity burning these data cast further doubt upon the evidence suggesting a catastrophic younger dryas impact event

neogene tectonic stratigraphic and play framework of the southern laguna madre tuxpan continental shelf gulf of mexico neogene shelf slope canyon and slope to basin floor transition plays in the southern laguna madre tuxpan lm t continental shelf reflect a variety of structural and stratigraphic controls including gravity sliding and extension compression salt evacuation and lowstand canyon and fan systems the neogene in the lm t area was deposited along narrow shelves associated with a tectonically active coast affected by significant uplift and erosion of carbonate and volcanic terrains this study characterizes 4 structurally defined trends and 32 neogene plays in a more than 50 000 km2 19 300 mi2 area linking the veracruz and burgos basins the caonero trend in the southern part of the lm t area contains deep seated basement faults caused by laramide compression many of these faults are directly linked to the interpreted mesozoic source rocks providing potential pathways for vertically migrating hydrocarbons in contrast the lankahuasa trend north of the caonero trend contains listric faults which detach into a shallow horizon this trend is associated with thick pliocene shelf depocenters the dominant plays in the faja de oro nyade trend in the central part of the lm t area contain thick lower and middle miocene successions of steeply dipping slope deposits reflecting significant uplift and erosion of the carbonate tuxpan platform these slope plays consist of narrow channel fill and levee sandstones encased in siltstones and mudstones plays in the north end of the lm t area in the southern part of the burgos basin contain intensely deformed strata linked to salt and shale diapirism outer shelf slope and proximal basin floor plays in the lamprea trend are internally complex and contain muddy debris flow and slump deposits risk factors and the relative importance of play elements vary greatly among lm t plays reservoir quality is a critical limiting play element in many plays especially those in the caonero trend directly downdip from the trans mexican volcanic belt as well as carbonate rich slope plays adjacent to the tuxpan platform in contrast trap and source are low risk play elements in the lm t area because of the abundance of large three way and four way closures and the widespread distribution of organic rich upper jurassic tithonian age source rock the potential for hydrocarbon migration in lm t plays is a function of the distribution of deep seated faults inferred to intersect the primary mesozoic source their distribution is problematic for the lankahuasa trend where listric faults sole out into the paleocene seal is poorly documented for lm t plays although the presence of overpressured zones and thick bathyal shales is favorable for seal development in middle and lower miocene basin and slope plays

evidence for deposition of 10 million tonnes of impact spherules across four continents 12 800 y ago airbursts impacts by a fragmented comet or asteroid have been proposed at the younger dryas onset 12 80 0 15 ka based on identification of an assemblage of impact related proxies including microspherules nanodiamonds and iridium distributed across four continents at the younger dryas boundary ydb spherule peaks have been independently confirmed in eight studies but unconfirmed in two others resulting in continued dispute about their occurrence distribution and origin to further address this dispute and better identify ydb spherules we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry morphologies origins and processes of formation we investigated 18 sites across north america europe and the middle east performing nearly 700 analyses on spherules using energy dispersive x ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization twelve locations rank among the world s premier end pleistocene archaeological sites where the ydb marks a hiatus in human occupation or major changes in site use our results are consistent with melting of sediments to temperatures 2 200 c by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere they are inconsistent with volcanic cosmic anthropogenic lightning or authigenic sources we also produced spherules from wood in the laboratory at 1 730 c indicating that impact related incineration of biomass may have contributed to spherule production at 12 8 ka an estimated 10 million tonnes of spherules were distributed across 50 million square kilometers similar to well known impact strewnfields and consistent with a major cosmic impact event

evidence from central mexico supporting the younger dryas extraterrestrial impact hypothesis we report the discovery in lake cuitzeo in central mexico of a black carbon rich lacustrine layer containing nanodiamonds microspherules and other unusual materials that date to the early younger dryas and are interpreted to result from an extraterrestrial impact these proxies were found in a 27 m long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial our attention focused early on an anomalous 10 cm thick carbon rich layer at a depth of 2 8 m that dates to 12 9 ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences collectively these changes have produced the most distinctive boundary layer in the late quaternary record this layer contains a diverse abundant assemblage of impact related markers including nanodiamonds carbon spherules and magnetic spherules with rapid melting quenching textures all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond n diamond i carbon and hexagonal nanodiamond lonsdaleite in order of estimated relative abundance this nanodiamond rich layer is consistent with the younger dryas boundary layer found at numerous sites across north america greenland and western europe we have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism it is however consistent with the younger dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst s and and or ground impact s at 12 9 ka

late eocene north american microtektites and clinopyroxene bearing spherules approximately 35 m y ago two events separated by only 10 000 20 000 years each spread roughly 1 billion metric tons of silicate spherules over large areas of the earth s surface the older event produced mostly clinopyroxene bearing spherules cpx spherules the cpx spherules have been found in the caribbean sea gulf of mexico equatorial pacific and eastern equatorial indian ocean the cpx spherule layer is associated with an iridium anomaly and appears to coincide with the extinction of several species of radiolaria the composition and widespread distribution of the cpx spherules indicate that they were formed by an impact event the younger layer of spherules consists of microtektites belonging to the north american tektite strewn field based on age and elemental and isotopic composition the north american microtektites have been found in the western equatorial atlantic on barbados in the caribbean sea and in the gulf of mexico the north american microtektite layer is not synchronous with an iridium anomaly nor does it appear to be associated with any major changes in the microfossils neither the cpx spherule event nor the north american tektite event appears to be associated with a climatic change but no detailed studies have been made across either layer excluding the cpx layer which contains mostly crystal bearing spherules the evidence at the present time indicates that there is only one late eocene microtektite layer and it is part of the north american strewn field

a multi proxy study of changing environmental conditions in a younger dryas sequence in southwestern manitoba canada and evidence for an extraterrestrial event multi proxy analyses of a sequence spanning the younger dryas yd in the glacial lake hind basin of manitoba provides insight into regional paleohydrology and paleovegetation of meltwater rivers and lakes spanning 4000 yr the sequence is controlled by 25 new accelerator mass spectrometry ages this lake dammed by the laurentide ice sheet overflowed into lake agassiz the pre yd interval records rapid sedimentation from meltwaters that headed in proglacial lakes in the canadian prairies that are known to have been catastrophically released when ice or sediment barriers were breached pollen in this phase is dominated by pre quaternary forms eroded from paleocene bedrock at the onset of the yd at 12 8 cal ka the sudden appearance of concentrations of nanodiamonds high temperature magnetic spherules platinum and iridium provide evidence of an extraterrestrial et event that others have identified at more than 40 sites in north america major changes in oceans and climate and the catastrophic outflow of nearby lake agassiz at the onset of the yd may be related lower water levels and a reduction of souris river inflow to lake hind followed which are reflected by more clayey and organic rich sediments and a decrease in pre quaternary palynomorphs this may have resulted from the deepening of river valleys caused by the release of meltwater triggered by the et event wetlands then began to develop leading to peat deposition from 12 3 to 11 cal ka this was followed by a fluvial episode depositing sand and then by increased holocene aridity that resulted in accumulation of a thick sequence of dune sands a dry woodland environment with a mix of conifers especially picea and larix and deciduous trees especially populus and quercus covered the uplands from 13 to 10 cal ka

the younger dryas impact hypothesis a requiem abstract the younger dryas yd impact hypothesis is a recent theory that suggests that a cometary or meteoritic body or bodies hit and or exploded over north america 12 900 years ago causing the yd climate episode extinction of pleistocene megafauna demise of the clovis archeological culture and a range of other effects since gaining widespread attention in 2007 substantial research has focused on testing the 12 main signatures presented as evidence of a catastrophic extraterrestrial event 12 900 years ago here we present a review of the impact hypothesis including its evolution and current variants and of efforts to test and corroborate the hypothesis the physical evidence interpreted as signatures of an impact event can be separated into two groups the first group consists of evidence that has been largely rejected by the scientific community and is no longer in widespread discussion including particle tracks in archeological chert magnetic nodules in pleistocene bones impact origin of the carolina bays and elevated concentrations of radioactivity iridium and fullerenes enriched in 3 he the second group consists of evidence that has been active in recent research and discussions carbon spheres and elongates magnetic grains and magnetic spherules byproducts of catastrophic wildfire and nanodiamonds over time however these signatures have also seen contrary evidence rather than support recent studies have shown that carbon spheres and elongates do not represent extraterrestrial carbon nor impact induced megafires but are indistinguishable from fungal sclerotia and arthropod fecal material that are a small but common component of many terrestrial deposits magnetic grains and spherules are heterogeneously distributed in sediments but reported measurements of unique peaks in concentrations at the yd onset have yet to be reproduced the magnetic grains are certainly just iron rich detrital grains whereas reported yd magnetic spherules are consistent with the diffuse non catastrophic input of micrometeorite ablation fallout probably augmented by anthropogenic and other terrestrial spherular grains results here also show considerable subjectivity in the reported sampling methods that may explain the purported yd spherule concentration peaks fire is a pervasive earth surface process and reanalyses of the original yd sites and of coeval records show episodic fire on the landscape through the latest pleistocene with no unique fire event at the onset of the yd lastly with yd impact proponents increasingly retreating to nanodiamonds cubic hexagonal lonsdaleite and the proposed n diamond as evidence of impact those data have been called into question the presence of lonsdaleite was reported as proof of impact related shock processes but the evidence presented was inconsistent with lonsdaleite and consistent instead with polycrystalline aggregates of graphene and graphane mixtures that are ubiquitous in carbon forms isolated from sediments ranging from modern to pre yd age important questions remain regarding the origins and distribution of other diamond forms e g cubic nanodiamonds in summary none of the original yd impact signatures have been subsequently corroborated by independent tests of the 12 original lines of evidence seven have so far proven to be non reproducible the remaining signatures instead seem to represent either 1 non catastrophic mechanisms and or 2 terrestrial rather than extraterrestrial or impact related sources in all of these cases sparse but ubiquitous materials seem to have been misreported and misinterpreted as singular peaks at the onset of the yd throughout the arc of this hypothesis recognized and expected impact markers were not found leading to proposed yd impactors and impact processes that were novel self contradictory rapidly changing and sometimes defying the laws of physics the yd impact hypothesis provides a cautionary tale for researchers the scientific community the press and the broader public

younger dryas black mats and the rancholabrean termination in north america of the 97 geoarchaeological sites of this study that bridge the pleistocene holocene transition last deglaciation approximately two thirds have a black organic rich layer or black mat in the form of mollic paleosols aquolls diatomites or algal mats with radiocarbon ages suggesting they are stratigraphic manifestations of the younger dryas cooling episode 10 900 b p to 9 800 b p radiocarbon years this layer or mat covers the clovis age landscape or surface on which the last remnants of the terminal pleistocene megafauna are recorded stratigraphically and chronologically the extinction appears to have been catastrophic seemingly too sudden and extensive for either human predation or climate change to have been the primary cause this sudden rancholabrean termination at 10 900 50 b p appears to have coincided with the sudden climatic switch from allerod warming to younger dryas cooling recent evidence for extraterrestrial impact although not yet compelling needs further testing because a remarkable major perturbation occurred at 10 900 b p that needs to be explained

shock synthesized hexagonal diamonds in younger dryas boundary sediments the long standing controversy regarding the late pleistocene megafaunal extinctions in north america has been invigorated by a hypothesis implicating a cosmic impact at the llerod younger dryas boundary or ydb 12 900 100 cal bp or 10 900 100 14c years abrupt ecosystem disruption caused by this event may have triggered the megafaunal extinctions along with reductions in other animal populations including humans the hypothesis remains controversial due to absence of shocked minerals tektites and impact craters here we report the presence of shock synthesized hexagonal nanodiamonds lonsdaleite in ydb sediments dating to 12 950 50 cal bp at arlington canyon santa rosa island california lonsdaleite is known on earth only in meteorites and impact craters and its presence strongly supports a cosmic impact event further strengthened by its co occurrence with other nanometer sized diamond polymorphs n diamonds and cubics these shock synthesized diamonds are also associated with proxies indicating major biomass burning charcoal carbon spherules and soot this biomass burning at the younger dryas yd onset is regional in extent based on evidence from adjacent santa barbara basin and coeval with broader continent wide biomass burning biomass burning also coincides with abrupt sediment mass wasting and ecological disruption and the last known occurrence of pygmy mammoths mammuthus exilis on the channel islands correlating with broader animal extinctions throughout north america the only previously known co occurrence of nanodiamonds soot and extinction is the cretaceous tertiary k t impact layer these data are consistent with abrupt ecosystem change and megafaunal extinction possibly triggered by a cosmic impact over north america at 12 900 100 cal bp

multiple lines of evidence for possible human population decline settlement reorganization during the early younger dryas three approaches are used to test whether or not human populations across north america were affected by abrupt climate change and or other environmental factors associated with the onset of the younger dryas yd cooling episode at ca 12 900 cal bp they are 1 frequency analyses of paleoindian projectile points from across north america 2 time series of lithic assemblages from eleven paleoindian quarry sites in the southeastern united states and 3 summed probability analyses spa of radiocarbon dates from cultural human related sites across north america and parts of the old world the results of each analysis suggest a significant decline and or reorganization in human population during the early centuries of the yd varying in extent by region archaeological settings formerly heavily utilized such as stone quarries in the southeastern u s appear to have been largely abandoned while over large areas a substantial decline occurred in the numbers of diagnostic projectile points and cultural radiocarbon dates later in the yd beginning after about 12 600 cal bp there was an apparent resurgence in population and or settlements in many areas as indicated by increases in projectile points quarry usage and human related radiocarbon ages

rock burst forecasting and genetic research in coal mines by microgravity method microgravity can be used for predicting rock bursts for the first time gravity anomalies related to rock bursts have been recorded the methodology developed has led to the first successful predictions the depth of the rock burst focus might be determined on the basis of analytical downward continuation of related gravity anomalies the focus is treated as a singular point of the gravity potential and its derivatives the rock burst gravity anomalies might be explained on the basis of the assumed dilatancy process that causes the rock burst the mean density change of the rock mass threatened with rock bursts can be estimated from the corresponding rock burst gravity anomalies

implications of prehistoric glassy biomass slag from east central botswana glassy biomass slag occurs in midden piles of prehistoric settlements of east central botswana the slag forms decimetre thick concordant layers in stratified ashy soil and lacks associations with domestic ceramic and iron melting activities petrographic evaluation of the slag suggests maximum temperatures in the order of 1155 1290 c during burning of the midden these values exceed reasonable estimates for combustion temperature of plant remnants and cattle manure in open fire it is suggested as alternatives that the glassy slag formed either from surface melting caused by strokes of lightning in an accumulation of partially decomposed organic soil or from subsurface combustion of organic soil strata ignited by grass fires glassy biomass slag of prehistoric settlements therefore may not result from human activities such as intentional burning of excess midden piles and may not be contemporaneous with human occupation of the sites 1995 academic press limited

some applications of the underground tower gravity vertical gradient underground tower gravity vertical gradient utgvg measurements made in mine workings have been applied to the detection of caverns old mine workings dislocations and erosive or karstic forms since utgvg measurements are subject to large errors kotelnikov s criterion can be used to determine the probability of isolation of the useful anomalies the properties of the utgvg reduce the ambiguity of interpretation of underground gravity surveys simultaneous g and utgvg measurements carried out in the same underground profile frequently replace a three dimensional or multilevel gravity survey the paper presents some applications of the utgvg

the indian ocean nodule field petrotectonic evolution and ferromanganese deposits abstract the indian ocean nodule field ionf is significant from several points of view roughly bordered by 10 s to 16 30 s and 72 e to 80 e and located within the central indian ocean basin ciob the field hosts the world s second largest and second high grade manganese nodule deposit after the equatorial nodule belt in the north pacific ocean moreover the crust underlying this field is characterised by unique morphotectonic signatures owing to its formation between 60 and 49 ma under three variable spreading conditions fast intermediate and slow from the indian ocean ridge system iors the nodule field has been surveyed both extensively more than 0 4 million km2 area and intensively comprising of a large geophysical data set and geological sample inventory during the last two decades several morphotectonic features such as seamounts hills ridge normal lineaments and ridge parallel lineations have disturbed the apparently smooth topographic gradient 1 7000 of the seafloor here variations in the rate of spreading and formation of new oceanic crust along the ridge crest during more than one episode of india eurasia collision are imprinted in the ionf based on the nature of the ridge parallel lineations which are related to the rate of crustal accretion the field is divided in to four sectors a b c and d from north to south sectors a and c were formed at a fast rate of spreading 90 95 mm year half rate and sectors b and d were formed at an intermediate 55 mm year and slow 26 mm year rates respectively the predominance of tensional stress in sectors a and c caused asymmetrical flexuring of the seafloor resulting in widely spaced faults and folds with low amplitude and large wavelength in contrast the seafloor flexuring in sector d are closely spaced long symmetrical and of high amplitude the timing and intensity of the collision of india with eurasia is constrained by the variable intensity of these flexures suggesting probably a soft touch at 58 ma and the hard collision at about 51 ma the nodule field hosts several seamounts both as isolated entities and in linear chains which are arranged parallel to the flow lines along the direction of absolute motion of the indian plate the distribution morphology and growth patterns of a majority of these seamounts are related to spreading rate suggesting their formation at the ridge crest however many of the seamounts show more than one stage of growth with local intraplate volcanism contributing to the enlargement of the larger ancient seamounts varieties of volcanics such as tholeiitic basalts spilites ferrobasalts and pumice occur within the ionf the alteration of some of these volcanics has resulted in palagonitisation of the glass and formation of zeolites subsequently during its journey away from the ridge crest to the abyssal areas the crust underlying the nodule field witnessed intraplate volcanism this is evident from the addition of younger rocks at the base of the ancient seamounts inconsistent growth of volcanoes eruption of ferrobasalt corresponding to the areas of high amplitude magnetic zones and presence of volcanogenic hydrothermal materials vhm of 10 ka age these findings collectively hint that the ionf is geodynamically unstable and may have been volcanically active in the recent past during the last 8 ma growth of authigenic ferromanganese deposits in the form of manganese nodules and crusts has occurred in the nodule field the deposits occur at an average water depth of 5000 m the basinal geomorphology intraplate tectonic deformations and volcanic eruptions considerably influence the formation development morphology mineralogy and composition of these deposits the data show that the large seamounts reverse faults and fracture zones fzs supply rock fragments as seeds for the nodule formation the hydrogenous precipitation from the overlying water column is the primary source of metal accumulation in the nodules the secondary relatively weak intraplate eruptions along the base of ancient seamounts or lineaments subsurface igneous activity and diagenetic remobilisation of metals have also played significant role in the growth and enrichment of the deposit based on a large data set we estimate the contribution of various physico chemical parameters and model the probable conditions of formation of the ferromanganese deposits in the ionf the model also hints at the location where the resource exploitation should be rewarding

geochemistry of tektites and impact glasses glass produced by melting during impact events is called impact glass or impactite although impact crate ring produces a great variety of shock metamorphosed rocks all of which are called impactites by various authors to a differing extent we restrict the use of this term here to material completely converted into glass the degree of metamorphism seen in different classes of impact materials starting with those showing simple shock effects shock lithification shatter cones diaplectic glasses coesite stishovite lechatelierite impact breccias glass depends on the peak pressure and temperature the rock has experienced as a result of mixing brecciation and similar processes impact glasses also tend to include fragments of less shocked or less homogeneous metamorphosed rocks we limit our discussion here however to the more homogeneous members of the terrestrial impactite family a discussion of lunar impact glasses was given by delano et al 1981 another group of natural glasses are tektites which at first glance are similar to obsidian most tektites are very homogeneous often aerodynam ically shaped spherically symmetric objects that are several centimeters in size and are found in various areas referred to as tektite strewn fields in reflected light they are usually black but in transmitted light they show variations of grey brown and green the surface features gouges furrows grooves pits striations clearly distinguish them from terrestrial volcanic glasses and have probably originated from solution etching and weathering effects on earth baker 1963 lamarche et a1 1984 and from surface stresses occurring during their cooling tektites found in geographically adjacent

trm in low magnetic fields a minimum field that can be recorded by large multidomain grains abstract thermally acquired remanent magnetization is important for the estimation of the past magnetic field present at the time of cooling rocks that cool slowly commonly contain magnetic grains of millimeter scale this study investigated 1 mm sized magnetic minerals of iron iron nickel magnetite and hematite and concluded that the thermoremanent magnetization trm acquired by these grains did not accurately record the ambient magnetic fields less than 1 t instead the trm of these grains fluctuated around a constant value consequently the magnetic grain ability to record the ambient field accurately is reduced above the critical field trm acquisition is governed by an empirical law and is proportional to saturation magnetization m s the efficiency of trm is inversely proportional to the mineral s saturation magnetization m s and is related to the number of domains in the magnetic grains the absolute field for which we have an onset of trm sensitivity is inversely proportional to the size of the magnetic grain these results have implications for previous reports of random directions in meteorites during alternating field demagnetization or thermal demagnetization of trm extraterrestrial magnetic fields in our solar system are weaker than the geomagnetic field by several orders of magnitude extraterrestrial rocks commonly contain large iron based magnetic minerals as a common part of their composition and therefore ignoring this behavior of multidomain grains can result in erroneous paleofield estimates

discovery of a nanodiamond rich layer in the greenland ice sheet we report the discovery in the greenland ice sheet of a discrete layer of free nanodiamonds nds in very high abundances implying most likely either an unprecedented influx of extraterrestrial et material or a cosmic impact event that occurred after the last glacial episode from that layer we extracted n diamonds and hexagonal diamonds lonsdaleite an accepted et impact indicator at abundances of up to about 5 10 6 times background levels in adjacent younger and older ice the nds in the concentrated layer are rounded suggesting they most likely formed during a cosmic impact through some process similar to carbon vapor deposition or high explosive detonation this morphology has not been reported previously in cosmic material but has been observed in terrestrial impact material this is the first highly enriched discrete layer of nds observed in glacial ice anywhere and its presence indicates that ice caps are important archives of et events of varying magnitudes using a preliminary ice chronology based on oxygen isotopes and dust stratigraphy the nd rich layer appears to be coeval with nd abundance peaks reported at numerous north american sites in a sedimentary layer the younger dryas boundary layer ydb dating to 12 9 0 1 ka however more investigation is needed to confirm this association

surface vitrification caused by natural fires in late pleistocene wetlands of the atacama desert we describe extended occurrences of unusual silicate glass surface layers from the atacama desert chile these glasses found near the town of pica at four localities separated by up to 70 km are neither fulgurites nor volcanic glasses nor metallurgical slags related to anthropic activity but show close similarities to other glasses that have been previously attributed to large airbursts created by meteoroids entering the earth s atmosphere the glasses are restricted to specific late pleistocene terrains paleo wetlands and soils rich in organic matter with sio2 rich plant remains salts and carbonates 14c dating and paleomagnetic data indicate that the glasses were formed during at least two distinct periods this rules out the hypothesis of a single large airburst as the cause of surface melting instead burning of organic rich soils in dried out grassy wetlands during climate oscillations between wet and dry periods can account for the formation of the pica glasses large oases did indeed form in the hyperarid atacama desert due to elevated groundwater tables and increased surface discharge during the central andean pluvial event roughly coeval with the mystery interval and younger dryas finally we discuss the implications of our results for the other surface glasses previously attributed to extraterrestrial events