classification of huminite iccp system 1994 abstract in the new classification iccp system 1994 the maceral group huminite has been revised from the previous classification iccp 1971 int handbook coal petr suppl to 2nd ed to accommodate the nomenclature to changes in the other maceral groups especially the changes in the vitrinite classification iccp 1998 the new vitrinite classification iccp system 1994 fuel 77 349 358 the vitrinite and huminite systems have been correlated so that down to the level of sub maceral groups the two systems can be used in parallel at the level of macerals and for finer classifications the analyst now has according to the nature of the coal and the purpose of the analysis a choice of using either of the two classification systems for huminite and vitrinite this is in accordance with the new iso coal classification that covers low rank coals as well and allows for the simultaneous use of the huminite and vitrinite nomenclature for low rank coals

thermal and impact histories of reheated group iva ivb and ungrouped iron meteorites and their parent asteroids the microstructures of six reheated iron meteoritesotwo iva irons maria elena 1935 fuzzy creek one ivb iron ternera and three ungrouped irons hammond babb s mill blake s iron and babb s mill troost s iron owere characterized using scanning and transmission electron microscopy electron probe microanalysis and electron backscatter diffraction techniques to determine their thermal and shock history and that of their parent asteroids maria elena and hammond were heated below approximately 700 750 c so that kamacite was recrystallized and taenite was exsolved in kamacite and was spheroidized in plessite both meteorites retained a record of the original widmanstitten pattern the other four which show no trace of their original microstructure were heated above 600 700 c and recrystallized to form 10 20 lm wide homogeneous taenite grains on cooling kamacite formed on taenite grain boundaries with their close packed planes aligned formation of homogeneous 20 lm wide taenite grains with diverse orientations would have required as long as approximately 800 yr at 600 c or approximately 1 h at 1300 c all six irons contain approximately 5 10 lm wide taenite grains with internal microprecipitates of kamacite and nanometer scale m shaped ni profiles that reach approximately 40 ni indicating cooling over 100 10 000 yr un decomposed high ni martensite a2 in taeniteothe first occurrence in ironsoappears to be a characteristic of strongly reheated irons from our studies and published work we identified four progressive stages of shock and reheating in iva irons using these criteria cloudy taenite m shaped ni profiles in taenite neumann twin lamellae martensite shock hatched kamacite recrystallization microprecipitates of taenite and shock melted troilite maria elena and fuzzy creek represent stages 3 and 4 respectively although not all reheated irons contain evidence for shock it was probably the main cause of reheating cooling over years rather than hours precludes shock during the impacts that exposed the irons to cosmic rays if the reheated irons that we studied are representative the iva irons may have been shocked soon after they cooled below 200 c at 4 5 gyr in an impact that created a rubblepile asteroid with fragments from diverse depths the primary cooling rates of the iva irons and the proposed early history are remarkably consistent with the pb pb ages of troilite inclusions in two iva irons including the oldest known differentiated meteorite blichert toft et al 2010

noble gases in individual l chondritic micrometeorites preserved in an ordovician limestone we have measured the he and ne concentrations and isotopic ratios of individual sediment dispersed extraterrestrial chromite grains 63 180 mu m in diameter from an ordovician limestone in southern sweden in the same sediment many fossil meteorites were found and have been attributed to the l chondrite parent body breakup event similar to 470 ma ago in this analysis of 37 individual extraterrestrial chromite grains of l chondritic major element composition at least 35 similar to 95 contain surface implanted helium and neon of fractionated solar wind composition implying that these grains are relict parts of fossil micrometeorites of asteroidal origin similar to what has been observed in recent micrometeorites collected in the polar regions significant amounts of cosmogenic ne 21 were found in several grains resulting in cosmic ray exposure cre ages of up to similar to 77 myr these ages exceed both dynamical lifetimes for asteroidal micrometeorites of this size as well as cre ages observed in chromites from fossil meteorites from the same sediment beds significant contributions from terrestrial sources like nucleogenic and cosmic ray muon induced ne 21 can be excluded in the extraterrestrial chromites since 11 terrestrial chrome spinel grains from the same sediment beds did not contain any measurable ne 21 excesses having found micrometeorites of undisputed asteroidal origin with cosmic ray exposure ages of several 10 7 years implies that high cosmic ray exposure ages alone are not a good indicator of cometary origin in opposition to what has been suggested for recent micrometeorites and idps we propose instead that these grains collected their cosmogenic ne 21 while residing in the regolith layer of their parent body c 2009 elsevier b v all rights reserved less

the distinct morphological and petrological features of shock melt veins in the suizhou l6 chondrite the morphology and petrology of distinct melt veins in the suizhou l6 chondrite have been investigated using scanning electron microscopy electron microprobe analyses and raman spectroscopy synchrotron energy dispersive diffraction and transmission electron microscopy it is found that the melt veins in the suizhou meteorite morphologically are the simplest straightest and thinnest among all shock veins known from meteorites at first glance these veins look like fine fractures but petrologically they are solid melt veins of chondritic composition and consist of fully crystalline materials of two distinct lithological assemblages with no glassy material remaining the suizhou melt veins contain the most abundant high pressure mineral species when compared with all other veins known in chondrites thus these veins in suizhou are classified as shock veins all rock forming and almost all accessory minerals in the suizhou shock veins have been transformed to their high pressure polymorphs and no fragments of the precursor minerals remain in the veins among the 11 high pressure mineral phases identified in the suizhou veins three are new high pressure minerals namely tuite after whitlockite xieite and the cf phase after chromite on the basis of transformation of plagioclase into maskelynite it is estimated that the suizhou meteorite experienced shock pressures andmore shock temperatures up to 22 gpa and 1000 c respectively shearing and friction along shock veins raised the temperature up to 1900 2000 c and the pressure up to 24 gpa within the veins hence phase transition and crystallization of high pressure minerals took place only in the suizhou shock veins fast cooling of the extremely thin shock veins is regarded as the main reason that up to 11 shock induced high pressure mineral phases could be preserved in these veins less

three dimensional distribution of minerals in the sediments of hayonim cave israel diagenetic processes and archaeological implications the mineral components of the sediments that accumulate in an archaeological site constitute a potentially rich source of information on the diagenesis and in turn the archaeology of the site this detailed three dimensional study of the mineral assemblages in mainly the mousterian sediments of hayonim cave incorporates more than 2100 infrared analyses performed on site during the excavation as well as diverse analyses in the laboratory three major mineral assemblages are identified the calcite dahllite cd assemblage the assemblage comprising mainly montgomeryite leucophosphite and siliceous aggregates lmvs and a highly altered sediment in which the clays have broken down and silica was released the boundaries between these assemblages were mapped in detail the overall picture is one of extreme heterogeneity with sharp variations occurring over distances of a few centimetres the relation between the cd and lmvs assemblages shows that it is a product of post depositional diagenesis whereas the altered clay assemblage formed beneath an erosional unconformity the cd and lmvs assemblages were derived primarily from an accumulation several metres thick of ash deposits produced by humans ash is thus shown to be a major component of the sediments of this cave the distribution of the cd assemblage reflects to a large extent the locations of two active springs seepages in the cave the distribution of the cd assemblage also faithfully maps the distribution of bones in the cave showing that their distribution is a function of preservational conditions and not human activities stineret al 2001 the conditions that produced the erosional unconformity also resulted in severe alteration of the clays and other mineral components of these sediments the erosion process and the fact that the thickness of this altered zone decreases towards the centre of the cave indicates that the diagenetic driving force was probably climatic the three dimensional distributions of the mineral assemblages have a direct bearing on the dating of the cave by thermoluminescence and electron spin resonance

ash deposits in hayonim and kebara caves israel macroscopic microscopic and mineralogical observations and their archaeological implications abstract a study of the hearths and ash layers preserved in hayonim and kebara caves israel showed that they are composed of one or several different minerals these include the polymorph of caco3 calcite a variety of phosphate minerals and a suite of siliceous minerals the major component of the latter are siliceous aggregates that are present in wood detailed studies of the mineral associations in these fossil ash layers as well as in fresh wood ash using optical and scanning electron microscopy in the back scattered electron mode together with elemental analyses showed that ash in these caves undergoes a series of diagenetic changes the best preserved ash layers resemble fresh ash and are composed mainly of calcite with minor amounts of siliceous minerals the calcite reacts with phosphate rich solutions to form carbonated apatite and with time the latter dissolves and a variety of other phosphate containing minerals form with each diagenetic change some of the more soluble minerals are lost and ultimately only the ash derived siliceous minerals remain in both caves there are local accumulations of such siliceous minerals that are metres thick in fact ash derived minerals in general are major components of the sediments in both kebara and hayonim caves their diagenesis involves a hugh reduction in volume which in turn may have important effects on the geological structures and stratigraphy of the sediments the changing mineralogy of the sediments due to diagenesis complicates the use of present day estimates of radiation content of the sediments for correcting age estimates by thermoluminescence and electron spin resonance finally the presence of the relatively stable ash derived siliceous minerals in a sedimentary layer in other caves could be a useful means of identifying the presence of ash in other archaeological sites where macroscopic hearth features are absent

living in the cold geoarchaeology of sealing sites from byers peninsula livingston island antarctica few geoarchaeological studies have been conducted in the antarctic continent this paper contains the first results of the geoarchaeological research done in two sealing sites dated from the 19th century located in byers peninsula south shetland islands antarctica the research is part of a wider international project that aims at understanding the daily practices of the first anonymous occupants of antarctica and the insertion of the continent into the world system the geoarchaeological study focuses on site formation analyses to provide new data on site function use of local resources length of occupation and taphonomy with this approach data not attainable through artefact or documentary analyses is provided the studied sites are sealer 3 and sealer 4 two sealing shelters built with piled up boulders on rocky outcrops on the south beaches of livingston island two major precincts and annexes were studied by means of multi element chemical analyses micromorphology and organic petrology although local lithology and cryogenic processes are dominant in the chemical and micromorphological records respectively important distinctions could be made especially on the behavior associated with pyrotechnology and the use of local resources for survival the effects of humans on the sediments are expressed by higher p2o5 cao and total c concentrations this is related with the use of seal bones fat and herbaceous tissue as fuel for the hearths shelters with more intense occupation could be differentiated from single activity sites differences are attributed to habitation shelters vs working spaces for fat processing

diagenesis in prehistoric caves the use of minerals that form in situ to assess the completeness of the archaeological record an interpretation of the archaeological record in particular that of a prehistoric cave site is complicated by the diversity of depositional and post depositional processes that affect the material deposited here we propose to use the authigenic minerals that form in situ within the cave sediments to reconstruct the ancient chemical environments in the sediments this can be done by experimentally determining the conditions under which each of the authigenic minerals are stable although this information is not available to date for minerals formed in a prehistoric cave we present calculated stability field data for the relevant minerals the results clearly demonstrate the feasibility of this approach this information particularly if based on measurements of real authigenic cave minerals will facilitate an assessment of the completeness of the cave archaeological record this is particularly important for determining whether or not the distributions of archaeologically important materials such as bones teeth plant phytoliths charcoal and ash reflect their original burial distributions or were altered as a result of secondary diagenetic processes

earth wind and fire ethnoarchaeological signals of hadza fires we present the preliminary results of an interdisciplinary ethno geoarchaeological project aimed at characterizing sedimentary aspects of recent combustion structures through soil micromorphology to obtain empirical parameters with which to interpret archaeological features micromorphological analyses of five different types of fires made and abandoned by the hadza of tanzania were performed and compared with ethnographic descriptions their anthropogenic nature burning intensity and type of fuel used were identified based on the composition and optical features of the microscopic components of the combustion structure the data provided elements to assess the preservation potential of open air fires and our ability to interpret their function the life history of two of the fires was reconstructed a sleeping fire showed evidence of a pre existing trampled surface and a communal cooking fire showed evidence of the scooping out of ashes for maintenance these findings substantiate the important contribution of ethnoarchaeological research conducted jointly with soil micromorphology in discovering cues of human behavior preserved in the sedimentary record

he and ne in individual chromite grains from the regolith breccia ghubara l5 exploring the history of the l chondrite parent body regolith abstract we analyzed he and ne in chromite grains from the regolith breccia ghubara l5 to compare it with he and ne in sediment dispersed extraterrestrial chromite sec grains from mid ordovician sediments these sec grains arrived on earth as micrometeorites in the aftermath of the l chondrite parent body lcpb breakup event 470 ma ago a significant fraction of them show prolonged exposure to galactic cosmic rays for up to several 10 ma the majority of the cosmogenic noble gases in these grains were probably acquired in the regolith of the lcpb meier et al ghubara an l chondritic regolith breccia with an ar ar shock age of 470 ma is a sample of that regolith we find cosmic ray exposure ages of up to several 10 ma in some ghubara chromite grains confirming for the first time that individual chromite grains with such high exposure ages indeed existed in the lcpb regolith and that the 10 ma cosmic ray exposure ages found in recent micrometeorites are thus not necessarily indicative of an origin in the kuiper belt some ghubara chromite grains show much lower concentrations of cosmogenic he and ne indicating that the 4 pi last stage exposure age of the ghubara meteoroid lasted only 4 6 ma this exposure age is considerably shorter than the 15 20 ma suggested before from bulk analyses indicating that bulk samples have seen regolith pre exposure as well the shorter last stage exposure age probably links ghubara to a small peak of ar 40 poor l5 chondrites of the same exposure age furthermore and quite unexpectedly we find a ne component similar to presolar ne hl in the chromite grains perhaps indicating that some presolar ne can be preserved even in meteorites of petrologic type 5 less

hydrogen and major element concentrations on 433 eros evidence for an l or ll chondrite like surface composition a reanalysis of near x ray gamma ray spectrometer xgrs data provides robust evidence that the elemental composition of the near earth asteroid 433 eros is consistent with the l and ll ordinary chondrites these results facilitated the use of the gamma ray measurements to produce the first in situ measurement of hydrogen concentrations on an asteroid the measured value 1100 1600 700 ppm is consistent with hydrogen concentrations measured in l and ll chondrite meteorite falls gamma ray derived abundances of hydrogen and potassium show no evidence for depletion of volatiles relative to ordinary chondrites suggesting that the sulfur depletion observed in x ray data is a surficial effect consistent with a space weathering origin the newfound agreement between the x ray gamma ray and spectral data suggests that the near landing site a ponded regolith deposit has an elemental composition that is indistinguishable from the mean surface this observation argues against a pond formation process that segregates metals from silicates and instead suggests that the differences observed in reflectance spectra between the ponds and bulk eros are due to grain size differences resulting from granular sorting of ponded material

buried in ashes site formation processes at lapa do santo rockshelter east central brazil few archaeological sites in the americas contain high concentrations of human burials dating back to the early holocene the tropical karstic region of lagoa santa in central brazil state of minas gerais is one of the richest bioanthropological records available to study the behaviors and funerary practices of early holocene south americans with more than 200 skeletons found so far one of the key locations to examine the history of human settlement in lagoa santa is the site of lapa do santo a rockshelter known to contain the oldest rock art and the earliest evidence of funerary complexity in the continent in this geoarchaeological investigation we focus on the early holocene settlement at lapa do santo 7 9 12 7 cal kybp applying high resolution geoarchaeological techniques such as micromorphology organic petrology and ftir on both archaeological modern reference and experimental samples this is the first time that a micro contextual approach integrated with experimental geoarchaeology has been applied to study the formation of rockshelter deposits in a tropical setting our results show that the stratigraphic sequence formed under the dual influence of anthropogenic sedimentation through continuous combustion activities and geogenic sedimentation in the form of oxisol aggregates which fell from above the limestone cliff into the rockshelter intact hearths and remobilized combustion debris possibly hearth rake out are close to the graves suggesting repeated burning activities as part of the ritual behavior of early holocene south americans large amounts of ash are intermixed with heated and unheated oxisol aggregates heated termite mound fragments were also found mixed within the sediments post depositional alteration of the site includes limited bioturbation and localized low energy surface water and sub surface concentrations of moisture leading to precipitation of dense secondary carbonates the age inversions can be attributed to the human action of reworking the ashy sediments and not to post abandonment processes despite this the overall preservation of the sediments is good and most human burials can be considered to be in primary context

sediments exposed to high temperatures reconstructing pyrotechnological processes in late bronze and iron age strata at tel dor israel many of the sediments analysed from tel dor israel show structural alterations indicating that they were exposed to high temperatures this observation is consistent with the abundant evidence for use of pyrotechnology from the earliest exposed middle bronze age strata through the roman period such structurally altered sediments may well represent one of the more widespread and durable records of pyrotechnology and as such could be invaluable for reconstructing past human activities the specific aims of this research are therefore to develop the means for identifying local sediments that were altered by different pyrotechnological activities and to elucidate the varying circumstances whereby sediments were exposed to high temperatures in a late bronze and iron age 1 section we first characterize natural sediments sampled on and in the proximity of the tell and monitor their transformations due to exposure to high temperatures in an oven and in open fires focusing in particular on the transformations of the clay mineral components of mud brick materials the analytical techniques used include micromorphology fourier transform infrared spectrometry ftir x ray powder diffractometry xrd and x ray fluorescence xrf spectrometry using the temperature calibrated data we confirm that large volumes of sediments at tel dor were exposed to high temperatures in area g we identify three fundamentally different ways that heat affected sediments were produced and accumulated 1 inthelatebronzeage phases11e12 thesedimentswereheatedtotemperaturesbetween800and900 candwerethendeposited in the area under investigation a plausible scenario is that these sediments were exposed to heat from ovens or kilns 2 during the early iron age phase 10 the heat affected sediments heated above 1000 c formed in close association with casting pits for the working of copper containing bronze objects 3 duringphase9oftheironage heat affectedsedimentswereproducedinsituatthislocationduetoamajorconflagration the temperatures reached around 1000 c this study shows that analysis of high temperature exposed sediments may be an invaluable means of reconstructing fire associated activities even when the actual installations have not been identified during the excavation or were not preserved

asteroid breakup linked to the great ordovician biodiversification event the great ordovician biodiversification event coincides 470 million years ago with the break up of a large asteroid and the resultant frequent bombardment of earth with asteroid fragments

influence of particle and surface quality on the vitrinite reflectance of dispersed organic matter comparative exercise using data from the qualifying system for reflectance analysis working group of iccp the development of a qualifying system for reflectance analysis has been the scope of a working group within the international committee for coal and organic petrology iccp since 1999 when j koch presented a system to qualify vitrinite particles according to their size proximity to bright components and homogeneity of the surface after some years of work aimed at improving the classification system using photomicrographs it was decided to run a round robin exercise on microscopy samples the classification system tested consists of three qualifiers ranging from excellent to low quality vitrinites with an additional option for unsuitable vitrinites this paper reports on the results obtained by 22 analysts who were asked to measure random reflectance readings on vitrinite particles assigning to each reading a qualifier four samples containing different organic matter types and a variety of vitrinite occurrences have been analysed results indicated that the reflectance of particles classified as excellent good or poor compared to the total average reflectance did not show trends to be systematically lower or higher for the four samples analysed the differences in reflectance between the qualifiers for any given sample were lower than the scatter of vitrinite reflectance among participants overall satisfactory results were obtained in determining the reflectance of vitrinite in the four samples analysed this was so for samples having abundant and easy to identify vitrinites higher plant derived organic matter as well as for samples with scarce and difficult to identify particles samples with dominant marine derived organic matter the highest discrepancies were found for the organic rich oil shales where the selection of the vitrinite population to measure proved to be particularly difficult special instructions should be provided for the analysis of this sort of samples the certainty of identification of the vitrinite associated with the vitrinite reflectance values reported has been assessed through a reliability index which takes into account the number of readings and the coefficient of variation the same statistical approach as that followed in the iccp vitrinite reflectance accreditation program for single seam coals has been used for data evaluation the results indicated low to medium dispersion for 17 out of 22 participants this combined with data from other sets of comparative analyses over a long period is considered an encouraging result for the establishment of an accreditation program on vitrinite reflectance measurements in dispersed organic matter

exploring exogenic sources for the olivine on asteroid 4 vesta abstract the detection of olivine on vesta is interesting because it may provide critical insights into planetary differentiation early in our solar system s history ground based and hubble space telescope hst observations of asteroid 4 vesta have suggested the presence of olivine on the surface these observations were reinforced by the discovery of olivine rich hed meteorites from vesta in recent years however analysis of data from nasa s dawn spacecraft has shown that this olivine bearing unit is actually impact melt in the ejecta of oppia crater the lack of widespread mantle olivine exposed during the formation of the 19 km deep rheasilvia basin on vesta s south pole further complicated this picture ammannito et al ammannito e et al 2013a nature 504 122 125 reported the discovery of local scale olivine rich units in the form of excavated material from the mantle using the visible and infrared spectrometer vir on dawn these sites are concentrated in the walls and ejecta of craters arruntia 10 5 km in diameter and bellicia 41 7 km in diameter located in the northern hemisphere 350 430 km from rheasilvia basin s rim here we explore alternative sources for the olivine in the northern hemisphere of vesta by reanalyzing the data from the vir instrument using laboratory spectral measurements of meteorites our rationale for using the published dataset was to bypass calibration issues and ensure a consistent dataset between the two studies our analysis of the vir data shows that while the interpretation of their spectra as an olivine rich unit is correct the nature and origin of that olivine could be more complicated we suggest that these olivine exposures could also be explained by the delivery of olivine rich exogenic material this hypothesis is supported by meteoritical evidence in the form of exogenic xenoliths containing significant amount of olivine in some of the hed meteorites from vesta previous laboratory work on heds show that potential sources of olivine on vesta could be different types of olivine rich meteorites either primitive achondrites acapulcoites lodranites ureilites ordinary chondrites h l ll pallasites or carbonaceous chondrites e g cv based on our spectral band parameters analysis the lack of correlation between the location of these olivine rich terrains and possible mantle excavating events and supported by observations of hed meteorites we propose that a probable source for the olivine seen in the northern hemisphere corresponds to remnants of impactors made of olivine rich meteorites the best curve matching results with laboratory spectra suggest these units are hed material mixed with either ordinary chondrites or with some olivine dominated meteorites such as r chondrites

ash bones and guano a study of the minerals and phytoliths in the sediments of grotte xvi dordogne france abstract very few prehistoric cave deposits in western europe contain visible hearth remains even though there is abundant evidence of fire use by cave inhabitants grotte xvi dordogne france is exceptional in this respect in that it contains a most conspicuous layer couche c characterized by a series of brightly coloured bedded sediments the formation of couche c has previously been ascribed to the ash and charcoal produced by the cave s mousterian occupants burning mainly lichens the mousterian sedimentary layers below couche c and the upper palaeolithic sediments unconformably overlying couche c are quite different in texture and colour and show no visible evidence of ash deposits analyses of the minerals microstructures and phytoliths in couche c are consistent with the notion that these sediments were derived mainly from ash produced by burning wood and to a lesser extent grass the original calcite component of the ash has been diagenetically altered to carbonated apatite around the cave periphery and to even more insoluble phosphate minerals in the centre one such mineral newberyite most likely formed by the reaction between guano degradation products and the ash under these circumstances bone preservation is also affected the overlying upper palaeolithic sediments contain calcite one of these layers abb contains much more calcite than all the other layers as well as abundant phytoliths derived from wood and grass this layer also contained many artifacts and bones it is thus concluded that ash is a major component of layer abb even though it is not visible to the maked eye in the form of hearths

a single asteroidal source for extraterrestrial ordovician chromite grains from sweden and china high precision oxygen three isotope sims analysis we examined oxygen three isotope ratios of 48 extraterrestrial chromite ec grains extracted from mid ordovician sediments from two different locations in sweden and one location in south central china the ages of the sediments similar to 470 ma coincide with the breakup event of the l chondrite parent asteroid elemental compositions of the chromite grains are generally consistent with their origin from l or ll chondrite parent bodies the average delta o 17 parts per thousand deviation from the terrestrial mass fractionation line measured in situ from 15 mu m spots by secondary ion mass spectrometry sims of ec grains extracted from fossil meteorites from thorsberg and brunflo are 1 17 0 09 parts per thousand 2 sigma and 1 25 0 16 parts per thousand respectively and those of fossil micrometeorites from thorsberg and puxi river are 1 10 0 09 parts per thousand and 1 11 0 12 parts per thousand respectively within uncertainty these values are all the same and consistent with the l chondrite group average delta o 17 1 07 0 18 parts per thousand but also with the ll chondrite group average delta o 17 1 26 0 24 parts per thousand clayton et al 1991 we conclude that the studied ec grains from correlated sediments from sweden and china are related and most likely originated in the same event the l chondrite parent body breakup we also analyzed chromites of modern h l and ll chondrites and show that their delta o 17 values coincide with averages of delta o 17 of bulk analyses of h l and ll chondrites this study demonstrates that in situ oxygen isotope data measured by sims are accurate and precise if carefully standardized and can be used to classify individual extraterrestrial chromite grains found in sediments c 2009 elsevier ltd all rights reserved less

impact histories of angrites eucrites and their parent bodies abstract eucrites which are probably from 4 vesta and angrites are the two largest groups of basaltic meteorites from the asteroid belt the parent body of the angrites is not known but it may have been comparable in size to vesta as it retained basalts and had a core dynamo both bodies were melted early by 26al and formed basalts a few myr after they accreted despite these similarities the impact histories of the angrites and eucrites are very different angrites are very largely unshocked and none are breccias whereas most eucrites are breccias and many are shocked we attribute the lack of shocked and unbrecciated angrites to an impact possibly at 4558 myr ago the radiometric age of the younger angrites that extracted the angrites from their original parent body into smaller bodies these bodies which may have had a diameter of approximately 10 km suffered much less impact damage than vesta during the late heavy bombardment because small bodies retain shocked rocks less efficiently than large ones and because large bodies suffer near catastrophic impacts that deposit vastly more impact energy per kg of target our proposed history for the angrites is comparable to that proposed by bogard and garrison 2003 for the unbrecciated eucrites with ar ar ages of 4 48 gyr and that for unbrecciated eucrites with anomalous oxygen isotopic compositions that did not come from vesta we infer that the original parent bodies of the angrites and the anomalous eucrites were lost from the belt when the giant planets migrated and the total mass of asteroids was severely depleted alternatively their parent bodies may have formed in the terrestrial planet region and fragments of these bodies were scattered out to the primordial main belt as a consequence of terrestrial planet formation

solubilities of bone mineral from archaeological sites the recrystallization window abstract bone mineral solubility is an important parameter for understanding the preservation of bones in the archaeological and palaeontological records in this study we have measured the solubility of the carbonated hydroxyl apatite of sub recent and fossil bones as well as synthetic hydroxyl apatite in deionized water and in ph buffered solutions the solutions were open to the atmosphere and the ph values were around neutral measurement conditions that are relevant to bone mineral preservation in nature but that were absent from most previous studies we obtained internally consistent results from both the water and the buffered experiments supporting the notion that we are measuring an inherent property of the mineral phase we found that bone mineral is much more soluble than synthetic hydroxyl apatite we measured the ionic activity products at steady state conditions and we identify a recrystallization window between ph 7 6 and 8 1 which defines the conditions under which bone crystals dissolve and reprecipitate as a more insoluble form of carbonated hydroxyl apatite as these conditions are common in nature most fossil bones will not maintain their original crystals with time we also found that bones that contained small amounts of calcite did not dissolve at all during our experiments these results provide a basis for better understanding the conditions in sediments under which bones are preserved and the relative states of preservation of bone they also have important implications for the selection of the most appropriate bone samples for paleoenvironmental and paleodiet analyses and dating

l chondrite asteroid breakup tied to ordovician meteorite shower by multiple isochron 40ar 39ar dating radiochronometry of l chondritic meteorites yields a rough age estimate for a major collision in the asteroid belt about 500 myr ago fossil meteorites from sweden indicate a highly increased influx of extraterrestrial matter in the middle ordovician 480 myr ago an association with the l chondrite parent body event was suggested but a definite link is precluded by the lack of more precise radiometric ages suggested ages range between 450 30 myr and 520 60 myr and can neither convincingly prove a single breakup event nor constrain the delivery times of meteorites from the asteroid belt to earth here we report the discovery of multiple 40ar 39ar isochrons in shocked l chondrites particularly the regolith breccia ghubara that allow the separation of radiogenic argon from multiple excess argon components this approach applied to several l chondrites yields an improved age value that indicates a single asteroid breakup event at 470 6 myr fully consistent with a refined age estimate of the middle ordovician meteorite shower at 467 3 1 6 myr according to a geologic time scale 2004 our results link these fossil meteorites directly to the l chondrite asteroid destruction rapidly transferred from the asteroid belt the increased terrestrial meteorite influx most likely involved larger projectiles that contributed to an increase in the terrestrial cratering rate which implies severe environmental stress

identification and importance of critical depositional gaps in pitfall cave environments the fossiliferous deposit of cuvieri cave eastern brazil abstract the majority of extinct brazilian late quaternary mammal i e megafauna remains comes from cave deposits and was retrieved through excavations lacking detailed stratigraphical context this poses a major problem since these deposits present multifaceted processes of formation based on the meticulous excavation of a pitfall site within cuvieri cave minas gerais eastern brazil this article describes a critical albeit subtle temporal discontinuity between different fossiliferous sedimentary facies and discusses its significance to the contextualization of the paleontological remains recovered from the site the discontinuity was described based on sedimentary analyses bone deposition processes taxonomy and ams radiocarbon chronology two facies were distinguished and named according to their color and texture an upper dark brown silt loam bsl and a lower dark reddish brown silt loam rbsl besides color differences they present differences in grain size distribution and chemical composition these analyses show that the rbsl has in its composition only half the sand and one third more the silt than bsl it also shows that mean percent values for the rbsl in comparison to the bsl are higher for silica 42 35 versus 15 80 aluminum 18 63 versus 7 58 and iron 8 45 versus 3 79 and lower for calcium 10 07 versus 36 14 and volatiles 13 86 versus 30 10 these differences are attributed to changes in sediment source and entrance route differences were also observed in the faunal remain analyses rbsl has abundant megafauna remains originally deposited within this facies while the scarce megafauna material found in bsl is the result of mixing processes despite these differences animal entrapment is considered the best scenario to explain bone accumulation in both facies ams radiocarbon dates indicate that the bsl was deposited during the holocene with dates ranging from 8580 cal yr bp to the present while the rbsl deposition dates to the holocene pleistocene transition 13 600 10 660 cal yr bp radiocarbon dating also indicates that the subtle erosional surface that limits both facies represents a temporal gap between a minimum age of 8 4 cal kyr bp and a maximum age of 11 0 cal kyr bp the recognition of this discontinuity allows for a more accurate interpretation of bone accumulation enabling the differentiation of faunal assemblages that might otherwise be considered part of a continuum

asteroidal source of l chondrite meteorites abstract establishing connections between meteorites and their parent asteroids is an important goal of planetary science several links have been proposed in the past including a spectroscopic match between basaltic meteorites and 4 vesta that are helping scientists understand the formation and evolution of the solar system bodies here we show that the shocked l chondrite meteorites which represent about two thirds of all l chondrite falls may be fragments of a disrupted asteroid with orbital semimajor axis a 2 8 au this breakup left behind thousands of identified 1 15 km asteroid fragments known as the gefion family fossil l chondrite meteorites and iridium enrichment found in an 467 ma old marine limestone quarry in southern sweden and perhaps also 5 large terrestrial craters with corresponding radiometric ages may be tracing the immediate aftermath of the family forming collision when numerous gefion fragments evolved into the earth crossing orbits by the 5 2 resonance with jupiter this work has major implications for our understanding of the source regions of ordinary chondrite meteorites because it implies that they can sample more distant asteroid material than was previously thought possible

ftir spectroscopy and reflectance of modern charcoals and fungal decayed woods implications for studies of inertinite in coals the chemical and physical characteristics of laboratory produced charcoals natural charcoals fungal decayed woods and inertinite from a variety of western canadian coals have been investigated using ftir and standard petrologic techniques our studies confirm and extend earlier work in showing that almost all inertinite macerals can be attributed to wildfire in peat swamps and that variation in the petrological characteristics of inertinite are a product of temperature duration of heating and the nature of the initial plant material the relationships between reflectance and temperature as well as heating duration of charcoal formation are established as a reference for the examination of inertinite and the probable temperature of inertinite precursor fossil charcoal formation in paleo wildfire fungi do not directly contribute to the formation of charcoal and inertinite apart from the fungal bodies themselves funginite sclerotia and hyphae and perhaps by increasing the extent of shrinkage and cracking increasing surface area of the plant materials and thus susceptibility to charring evidence of fungal activity progressively decreases with increasing degree of charing in response to duration of heating or increased charing temperature the reflectance values and ftir spectral characteristics of inertinites in western canadian coal suggest that most inertinite formed by wildfires at temperatures over 400 c the great abundance of semifusinite in western canadian coal may reflect frequent but short duration wildfires in precursor peat swamps

microstratigraphy and diagenesis at the upper pleistocene site of esquilleu cave cantabria spain ftir and soil micromorphology were applied to selected sediments from the archaeological deposit of esquilleu cave a late middle palaeolithic site in cantabria spain the main goal was to assess the integrity of the archaeological record before continuing with further excavation and research at the site field observations and previous sedimentological studies point to diagenetic alteration of part of the deposit but the extent and precise nature of such processes had not been established the results show that the upper layers are composed of fresh elements and have not undergone diagenetic transformations although their components have been physically disturbed by cryoturbation the rest of the deposit is well preserved with mild phosphatization due to partial dissolution of bone and calcitic ash contained in the sediment and compression from trampling further excavation is necessary to have a more complete picture of the taphonomic processes taking place at the site

from the mid ordovician into the late silurian changes in the micrometeorite flux after the l chondrite parent breakup we present the first reconstruction of the micrometeorite flux to earth in the silurian period we searched 321 kg of condensed marine limestone from the late silurian cellon section southern austria for refractory chrome spinel grains from micrometeorites that fell on the ancient sea floor a total of 155 extraterrestrial spinel grains 10 grains 63 m and 145 in the 32 63 m fraction were recovered for comparison we searched 102 kg of similar limestone from the mid ordovician komstad formation in southern sweden this limestone formed within 1 ma after the breakup of the l chondrite parent body lcpb in the asteroid belt in the sample we found 444 extraterrestrial spinel grains in the 63 m fraction and estimate a content of at least 7000 such grains in the 32 63 m fraction our results show that in the late silurian 40 ma after the lcpb the flux of ordinary equilibrated chondrites has decreased by two orders of magnitude almost down to background levels among the ordinary chondrites the dominance of l chondritic micrometeorites has waned off significantly from 99 in the post lcpb mid ordovician to 60 in the late silurian with 30 h and 10 ll chondritic grains in the late silurian primitive achondrite abundances are similar to today s value contrasting to the much higher abundances observed in pre lcpb mid ordovician sediments

back transformation of high pressure minerals in shocked chondrites low pressure mineral evidence for strong shock post shock annealing of meteorites can destroy their shock induced features particularly high pressure minerals and complicate the estimation of impact pressure temperature conditions however distinguishing post shock annealing features from thermal metamorphism effects can be practically difficult here we report results from mbale a highly shocked l chondrite to investigate the mechanisms kinetics and identification criteria for post shock annealing of high pressure signatures olivine fragments within shock melt veins in mbale occur as chemically heterogeneous nanocrystalline aggregates that contain trace wadsleyite and ringwoodite their strong variation in fayalite content provides evidence of iron partitioning during transformation of olivine to wadsleyite followed by back transformation to olivine after decompression experimental studies of transformation kinetics show that wadsleyite transforms to olivine in seconds at temperatures above 1200 k and in hours at temperatures between 900 and 1200 k thermal models of shock melt cooling show that shock veins in mbale cooled to 1200 k in 1 s the shock pulse must have been shorter than 1 s to provide the high temperature conditions for post shock back transformation of wadsleyite many highly shocked l chondrites which have abundant high pressure minerals must have experienced relatively long shock durations combined with rapid cooling of shock melt regions to preserve high pressure phases the most highly shocked samples such as impact melt breccias lack high pressure phases because of post shock back transformations

geoarchaeological investigations at diepkloof rock shelter western cape south africa abstract the sedimentary sequence at diepkloof rock shelter formed through a complex interaction of depositional and post depositional processes and was variously influenced by biogenic geogenic and anthropogenic agents here we present the results of a micromorphological study of the sediments at diepkloof focusing in particular on the numerous anthropogenic inputs and modifications recorded within the sequence by applying the microfacies concept we were able to identify hearth burning and maintenance bedding construction and burning and surface modification by trampling as major processes that contributed to the formation of the site the human activities recorded within the sediments show a marked change throughout the sequence implying a shift in the use of the site over time the present study also provides a context for evaluating other classes of artifacts and data collected from the site

sediment dispersed extraterrestrial chromite traces a major asteroid disruption event abundant extraterrestrial chromite grains from decomposed meteorites occur in middle ordovician 480 million years ago marine limestone over an area of 250 000 square kilometers in southern sweden the chromite anomaly gives support for an increase of two orders of magnitude in the influx of meteorites to earth during the mid ordovician as previously indicated by fossil meteorites extraterrestrial chromite grains in mid ordovician limestone can be used to constrain in detail the temporal variations in flux of extraterrestrial matter after one of the largest asteroid disruption events in the asteroid belt in late solar system history

distinguishing between calcites formed by different mechanisms using infrared spectrometry archaeological applications infrared spectrometry is a well established method for the identification of minerals due to its simplicity and the short time required to obtain a result it can be practiced on site during excavation using portable infrared spectrometers however the identification of a mineral may not be sufficient for example a lime plaster floor and a crushed chalk surface have a similar appearance and are composed of the same mineral calcite here we exploit differences in the infrared spectra of geogenic biogenic and pyrogenic calcites for the identification of each calcite type the infrared calcite spectrum has three characteristic peaks in the region of 400 4000 cm 1 designated 2 3 and 4 when a calcite sample is ground as part of the measurement preparation procedure some grinding dependent changes will be revealed in the infrared spectrum with additional grinding the 3 peak narrows and the heights of the 2 and 4 peaks decrease when both are normalized to the 3 height by plotting the normalized heights of the 2versus the 4 of several grindings of the same sample a characteristic trend line is formed for each calcite type the trend lines of geogenic calcites have the shallowest slopes and highest 4 values when compared to pyrogenic calcites which can be further divided to ash and plaster mortar samples this method can assist in distinguishing between the various calcites and provide insights into homogeneity and preservation state of the calcitic materials in question

lapa das boleiras rockshelter stratigraphy and formation processes at a paleoamerican site in central brazil abstract lapa das boleiras rockshelter a paleoamerican archaeological site in central brazil was intensely occupied by humans from 10 000 14c bp 11 8 cal kyr bp until approximately 7500 14c bp 8 4 cal kyr bp in this paper we present some interpretations about the formation processes operating on the site one of our main conclusions is that the bulk of accumulated sediments at the site is of anthropogenic origin they are constituted by volumetrically significant quantities of plant ash remains what is somewhat unexpectedly in view of prevailing models about the lifestyle of paleoamerican hunter gatherers in south america the evidence we discuss below is also consistent with paleoenvironmental data that suggest a dry period during the mid holocene in the region probably leading to a decrease in human occupation araujo a g m neves w pilo l b atui j p 2005 holocene dryness and human occupation in brazil during the archaic gap quaternary research 64 298 307 we surmise that both factors underpin a surprising reduction in sediment accumulation at the site during the mid holocene

fall recovery and characterization of the novato l6 chondrite breccia the novato l6 chondrite fragmental breccia fell in california on 17 october 2012 and was recovered after the cameras for allsky meteor surveillance cams project determined the meteor s trajectory between 95 and 46 km altitude the final fragmentation from 42 to 22 km altitude was exceptionally well documented by digital photographs the first sample was recovered before rain hit the area first results from a consortium study of the meteorite s characterization cosmogenic and radiogenic nuclides origin and conditions of the fall are presented some meteorites did not retain fusion crust and show evidence of spallation before entry the meteoroid was 35 5 cm in diameter mass 80 35 kg with a cosmic ray exposure age of 9 1 ma if it had a one stage exposure history a two stage exposure history is more likely with lower shielding in the last few ma thermoluminescence data suggest a collision event within the last similar to 0 1 ma novato probably belonged to the class of shocked l chondrites that have a common shock age of 470 ma based on the u th he age of 420 220 ma the measured orbits of novato jesenice and innisfree are consistent with a proposed origin of these shocked l chondrites in the gefion asteroid family perhaps directly via the 5 2 mean motion resonance with jupiter novato experienced a stronger compaction than did other l6 chondrites of shock stage s4 despite this a freshly broken surface shows a wide range of organic compounds less

late eocene 3he and ir anomalies associated with ordinary chondritic spinels during the late eocene there was an enigmatic enhancement in the flux of extraterrestrial material to earth evidence comes from sedimentary 3he records indicating an increased flux of interplanetary dust during ca 2 myr as well as two very large impact structures popigai 100 km diameter and chesapeake bay 40 85 km that formed within 10 20 kyr at the peak of the 3he delivery the massignano section in italy has one of the best sedimentary records of these events including a well defined 3he record an ir rich ejecta bed related to the popigai impact event and two smaller ir anomalies recently we showed that the popigai ejecta is associated with a significant enrichment of chromite grains 63 m with an h chondritic elemental composition 17 grains in 100 kg of rock most likely these grains are unmelted fragments from the impactor slightly higher up ca 20 cm in the section where a small ir anomaly possibly related to the chesapeake bay impact has been measured we found a weak enrichment in l chondritic grains 8 grains in 208 kg of rock here we report an extended data set increasing the total amount of sediment dissolved in acid and searched for extraterrestrial chromite grains from 658 to 1168 kg in altogether 760 kg of background sediment from 17 levels over 14 m of strata outside the interval corresponding to the popigai and chesapeake bay impacts we only found 2 extraterrestrial chromite grains both grains have l chondritic compositions and were found in a 100 kg sample from the ca 10 25 m level in the section where the second of the smaller ir anomalies has been reported a correlation appears to exist between ir 3he and chromite from ordinary chondrites we also report oxygen three isotope measurements of the extraterrestrial chromite grains associated with the popigai ejecta and confirm an h chondritic composition the new results strengthen our scenario that the upper eocene 3he and ir enrichments originate from the asteroid belt rather than the oort cloud as originally proposed when the 3he anomaly was discovered the generally low background concentrations of extraterrestrial chromite through the section speak against any major single asteroid breakup event such as in the mid ordovician after the break up of the l chondrite parent body instead the data reconcile with a small possibly a factor of 2 3 increase in the flux of extraterrestrial material to earth but of both h and l chondritic composition we also report the composition of all the 2310 terrestrial chrome spinel grains recovered and show that their chemical composition indicates a dominantly regional ophiolitic source four anomalous chrome spinel grains with high ti and v concentrations were found in the popigai ejecta these grains originate from siberian traps basalts in the popigai crater at the time of impact less

park forest l5 and the asteroidal source of shocked l chondrites the park forest l5 meteorite fell in a suburb of chicago illinois usa on march 26 2003 it is one of the currently 25 meteorites for which photographic documentation of the fireball enabled the reconstruction of the meteoroid orbit the combination of orbits with pre atmospheric sizes cosmic ray exposure cre and radiogenic gas retention ages cosmic histories is significant because they can be used to constrain the meteoroid s birth region and test models of meteoroid delivery using he ne ar 10be and 26al as well as a dynamical model we show that the park forest meteoroid had a pre atmospheric size close to 180 g cm 2 0 40 porosity and a pre atmospheric mass range of 2 6 tons it has a cre age of 14 2 ma and u th he and k ar ages of 430 90 and 490 70 ma respectively of the meteorites with photographic orbits park forest is the second after novato that was shocked during the l chondrite parent body lcpb break up event approximately 470 ma ago the suggested association of this event with the formation of the gefion family of asteroids has recently been challenged and we suggest the ino family as a potential alternative source for the shocked l chondrites the location of the lcpb break up event close to the 5 2 resonance also allows us to put some constraints on the possible orbital migration paths of the park forest meteoroid

human actions performed on simple combustion structures an experimental approach to the study of middle palaeolithic fire we present preliminary results from the first phase of experiments from the neanderthal fire technology project aimed at understanding middle palaeolithic combustion structures our field observations and micromorphological data address the sedimentary expression of various anthropogenic actions trampling ash sweeping and dumping relighting and cooking performed on simple flat combustion structures made with pinus nigra fuel on dry and slightly vegetated calcareous sandy substrates we observed a characteristic pattern in microstructure and basic composition irrespective of the number and kind of anthropogenic actions performed trampling yielded previously documented diagnostic micromorphological features more pronounced in cases of ash sweeping and dumping relighting of fires was only identified in cases with deposits between combustion events only rare microscopic calcined bone fragments and fat derived char were identified in fires involving cooking or tossing of meat in the fire these data suggest that anthropogenic actions on simple combustion structures are highly undetectable sweeping has a stronger effect than trampling on the substrate of the combustion structure stacked hearths might involve significant amounts of time or deposits between combustion events and alternative techniques must be sought to identify cooking in fires

potentially hazardous asteroid 2007 le compositional link to the black chondrite rose city and asteroid 6 hebe abstract the research is an integrated effort beginning with telescopic observations and extending through detailed mineralogical characterizations to provide constraints on the albedo diameter composition and meteorite affinity of near earth object potentially hazardous asteroid neo pha 2007 le results of the analysis indicate a diameter of 0 56 kilometers km and an albedo of 0 08 2007 le exhibits a 1 m absorption feature without a discernible band ii feature compositional analysis of 2007 le reveal fs 17 and fa 19 values which are consistent with the fa and fs values for the h type ordinary chondrites fs 14 5 18 and fa 16 20 and of asteroid 6 hebe fs 17 and fa 15 spectroscopically 2007 le does not appear like the average h chondrite spectra exhibiting a reddened spectrum and subdued absorption feature further investigation of the meteorite classes yielded a black chondrite rose city which is both similar in mineralogy and spectrally to pha 2007 le dynamical analysis could not directly link the fall of the rose city meteorite to 2007 le as it stands 2007 le and rose city have a compositional link and both could come from the same parent body possible family one known source of the h chondrites is 6 hebe

chronology and sources of lunar impact bombardment abstract the moon has suffered intense impact bombardment ending at 3 9 gyr ago and this bombardment probably affected all of the inner solar system basin magnetization signatures and lunar crater size distributions indicate that the last episode of bombardment at about 3 85 gyr ago was less extensive than previously thought we explore the contribution of the primordial mars crosser population to early lunar bombardment we find that mars crosser population initially decays with a 80 myr half life with the long tail of survivors clustering on temporarily non mars crossing orbits between 1 8 and 2 au these survivors decay with half life of about 600 myr and are progenitors of the extant hungaria asteroid group in the same region we estimate the primordial mars crosser population contained about 0 01 0 02 earth masses such initial population is consistent with no lunar basins forming after 3 8 gya and the amount of mass in the hungaria group as they survive longer and in greater numbers than other primordial populations mars crossers are the best candidate for forming the majority of lunar craters and basins including most of the nectarian system however this remnant population cannot produce imbrium and orientale basins which formed too late and are too large to be part of a smooth bombardment we propose that the imbrian basins and craters formed in a discrete event consistent with the basin magnetization signatures and crater size distributions this late impactor shower would be triggered by a collisional disruption of a vesta sized body from this primordial mars crossing population wetherill g w 1975 proc lunar sci conf 6 1539 1561 that was still comparable to the present day asteroid belt a 3 9 gya this tidal disruption lead to a short lived spike in bombardment by non chondritic impactors with a non asteroidal size frequency distribution in agreement with available evidence this body wetherill s object also uniquely matches the constraints for the parent body of mesosiderite meteorites we propose that the present day sources of mesosiderites are multi km sized asteroids residing in the hungaria group that have been implanted there soon after the original disruption of their parent 3 9 gyr ago

optical maturation of asteroid surfaces abstract analysis of laboratory experiments simulating space weathering optical effects on atmosphereless planetary bodies reveals that the time needed to alter the spectrum of an ordinary chondrite meteorite to resemble the overall spectral shape and slope of an s type asteroid is about 10 5 yr the time required to reduce the visible albedo of samples to 0 05 is 10 6 yr since both these timescales are much less than the average collisional lifetime of asteroids larger than several kilometers in size numerous low albedo asteroids having reddish spectra with subdued absorption bands should be observed instead of an s type dominated population this is not the case because asteroid surfaces cannot be considered as undisturbed unlike laboratory samples we have estimated the number of collisions occurring in the time of 10 5 yr between asteroids and projectiles of various sizes and show that impact activated motions of regolith particles counteract the progress of optical maturation of asteroid surfaces we suppose that the maturation level of asteroid surfaces may be a compromise resulting from a competition between impact resurfacing and solar wind darkening and that after reaching some steady state after a relatively short time 7 10 5 yr thereafter depends only slightly on time spectroscopic analysis using relatively invariant spectral parameters such as band centers and band area ratios can determine whether the surface of an s asteroid has chondritic composition or not in this sense the bodies with the ordinary chondrite composition cannot be masked among s asteroids differences in the environment of the main asteroid belt versus that at 1 au and the physical difference between the moon and main belt asteroids i e size can account for the lack of lunar type weathering on main belt asteroids

surface composition and taxonomic classification of a group of near earth and mars crossing asteroids abstract in the past constraining the surface composition of near earth asteroids neas has been difficult due to the lack of high quality near ir spectral data 0 7 2 5 m that contain mineralogically diagnostic absorption bands here we present visible 0 43 0 95 m and near infrared 0 7 2 5 m spectra of nine neas and five mars crossing asteroids mcs the studied neas are 4055 magellan 19764 2000 nf5 89830 2002 ce 138404 2000 ha24 143381 2003 bc21 159609 2002 aq3 164121 2003 yt1 241662 2000 ko44 and 2007 ml13 the studied mcs are 1656 suomi 2577 litva 5407 1992 ax 22449 ottijeff and 47035 1998 ws the observations were conducted with the ntt at la silla chile the 2 2 m telescope at calar alto spain and the irtf on mauna kea hawai i the taxonomic classification bus system of asteroids showed that all observed mc asteroids belong to the s complex including the s sr and sl classes seven of the neas belong to the s complex including the s sa sk and sl classes and two neas were classified as v types the classification of the nea 164121 2003 yt1 as a v type was made on the basis of its near infrared spectrum since no visible spectrum is available for this asteroid a mineralogical analysis was performed on six of the asteroids those for which near ir spectra were obtained or previously available we found that three asteroids 241662 2000 ko44 19764 2000 nf5 138404 2000 ha24 have mafic silicate compositions consistent with ordinary chondrites while three others 4055 magellan 164121 2003 yt1 5407 1992 ax are pyroxene dominated basaltic achondrite assemblages in the case of 5407 1992 ax we found that its basaltic surface composition contrasts its taxonomic classification as a s type

the nature of the l chondrite parent body s disruption as deduced from high pressure phases in the sixiangkou l6 chondrite the disruption of the l chondrite parent body lcpb at similar to 470ma is currently the best documented catastrophic celestial impact event based on the large number of l chondritic materials associated with this event uranium lead u pb dating of apatite and its high pressure decomposition product tuite in the sixiangkou l6 chondrite provides a temporal link to this event the u pb system of phosphates adjacent to shock melt veins was altered to varying degrees and the discordance of the u pb system correlates closely with the extent of apatite decomposition this suggests that the u pb system of apatite could be substantially disturbed by high temperature pulse during shock compression from natural impacts at least on the scale of mineral grains although many l chondrites can be temporally related to the catastrophic lcpb impact event the shock conditions experienced by each individual meteorite vary this could be due to the different geologic settings of these meteorites on their parent body the shock pressure and duration derived from most meteorites may only reflect local shock features rather than the impact conditions although they could provide lower limits to the impact conditions the sixiangkou shock duration similar to 4s estimated from high pressure transformation kinetics provides a lower limit to the high pressure pulse of the lcpb disruption impact combined with available literature data of l chondrites associated with this impact event our results suggest that the lcpb suffered a catastrophic collision with a large projectile with a diameter of at least 18 22km at a low impact velocity 5 6kms 1 this is consistent with astronomical estimates based on the dynamical evolution of l chondritic asteroids

on the origin of shocked and unshocked cm clasts in h chondrite regolith breccias cm chondrite clasts that have experienced different degrees of aqueous alteration occur in h chondrite and hed meteorite breccias many clasts are fragments of essentially unshocked cm projectiles that accreted at low relative velocities to the regoliths of these parent bodies a few clasts were heated and dehydrated upon impact these objects most likely accreted at higher relative velocities we examined three clasts and explored alternative scenarios for their formation in the first scenario we assumed that the h and hed parent bodies had diameters of a few hundred kilometers so that their high escape velocities would effectively prevent soft landings of small cm projectiles this would imply that weakly shocked cm clasts formed on asteroidal fragments family members associated with the h and hed parent bodies in the second scenario we assumed that weakly shocked cm clasts were spall products ejected at low velocities from larger cm projectiles when they slammed into the h and hed parent bodies in both cases if most cm clasts turn out to have ancient ages e g 3 4 4 1 ga a plausible source for their progenitors would be outer main belt objects some which may have been dynamically implanted 3 9 ga ago by the events described in the so called nice model on the other hand if most cm clasts have recent ages 200 ma a plausible source location for their parent body would be the inner main belt between 2 1 2 2 au in that case the possible source of the cm clasts progenitors parent fragments would be the breakup 160 ma ago of the parent body 170 km in diameter of the baptistina asteroid family baf

a fossil winonaite like meteorite in ordovician limestone a piece of the impactor that broke up the l chondrite parent body about a quarter of all meteorites falling on earth today originate from the breakup of the l chondrite parent body similar to 470 ma ago the largest documented breakup in the asteroid belt in the past similar to 3 ga a window into the flux of meteorites to earth shortly after this event comes from the recovery of about 100 fossil l chondrites 1 21 cm in diameter in a quarry of mid ordovician limestone in southern sweden here we report on the first non l chondritic meteorite from the quarry an 8 cm large winonaite related meteorite of a type not known among present day meteorite falls and finds the noble gas data for relict spinels recovered from the meteorite show that it may be a remnant of the body that hit and broke up the l chondrite parent body creating one of the major asteroid families in the asteroid belt after two decades of systematic recovery of fossil meteorites and relict extraterrestrial spinel grains from marine limestone it appears that the meteorite flux to earth in the mid ordovician was very different from that of today c 2014 the authors published by elsevier b v less

meteorite flux to earth in the early cretaceous as reconstructed from sediment dispersed extraterrestrial spinels we show that earth s sedimentary strata can provide a record of the collisional evolution of the asteroid belt from 1652 kg of pelagic maiolica limestone of berriasian hauterivian age from italy we recovered 108 extraterrestrial spinel grains 32 250 m representing relict minerals from coarse micrometeorites elemental and three oxygen isotope analyses were used to characterize the grains providing a first order estimate of the major types of asteroids delivering material at the time comparisons were made with meteorite flux time windows in the ordovician before and after the l chondrite parent body breakup in the early cretaceous 80 of the extraterrestrial spinels originated from ordinary chondrites the ratios between the three groups of ordinary chondrites h l ll appear similar to the present 1 1 0 2 but differ significantly from ordovician ratios we found no signs of a hypothesized baptistina ll chondrite breakup event about 10 of the grains in the maiolica originate from achondritic meteorite types that are very rare 1 on earth today but that were even more common in the ordovician because most meteorite groups have lower spinel content than the ordinary chondrites our data indicate that the latter did not dominate the flux during the early cretaceous to the same extent as today based on studies of three windows in deep time we argue that there may have been a gradual long term a few hundred million years turnover in the meteorite flux from dominance of achondrites in the early phanerozoic to ordinary chondrites in the late phanerozoic interrupted by short term a few million years meteorite cascades from single asteroid breakup events less

the late heavy bombardment heavily cratered surfaces on the moon mars and mercury show that the terrestrial planets were battered by an intense bombardment during their first billion years or more but the timing sources and dynamical implications of these impacts are controversial the late heavy bombardment refers to impact events that occurred after stabilization of the planetary lithospheres such that they could be preserved as craters and basins lunar melt rocks and meteorite shock ages point toward a discrete episode of elevated impact flux between 3 5 and 4 0 4 2 ga and a relative quiescence between 4 0 4 2 and 4 4 ga evidence from precambrian impact spherule layers suggests that a long lived tail of terrestrial impactors lasted to 2 0 2 5 ga dynamical models that include populations residual from primary accretion and destabilized by giant planet migration can potentially account for the available observations although all have pros and cons the most parsimonious solution to match constraints is a hybrid mode

records of the moon forming impact and the 470 ma disruption of the l chondrite parent body in the asteroid belt from u pb apatite ages of novato l6 novato a newly observed fall in the san francisco bay area is a shocked and brecciated l6 ordinary chondrite containing dark and light lithologies we have investigated the u pb isotope systematics of coarse cl apatite grains of metamorphic origin in novato with a large geometry ion microprobe the u pb systematics of novato apatite reveals an upper intercept age of 4472 31 ma and lower intercept age of 473 38 ma the upper intercept age is within error identical to the u pb apatite age of 4452 21 ma measured in the chelyabinsk ll5 chondrite this age is interpreted to reflect a massive collisional resetting event due to a large impact associated with the peak arrival time at the primordial asteroid belt of ejecta debris from the moon forming giant impact on earth the lower intercept age is consistent with the most precisely dated ar ar ages of 470 6 ma of shocked l chondrites and the fossil meteorites and extraterrestrial chromite relicts found in ordovician limestones with an age of 467 3 1 6 ma in sweden and china the lower intercept age reflects a major disturbance related to the catastrophic disruption of the l chondrite parent body most likely associated with the gefion asteroid family which produced an initially intense meteorite bombardment of the earth in ordovician period and reset and degassed at least approximately 35 of the l chondrite falls today we predict that the 470 ma impact event is likely to be found on the moon and mars if not mercury

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

bat guano and preservation of archaeological remains in cave sites the formation of authigenic minerals in cave sediments can be used to reconstruct the paleochemical conditions that prevailed in the past and in this way to assess the completeness of the archaeological record previous studies indicated that the major driving mechanisms for chemical diagenesis in prehistoric caves that result in the formation of authigenic minerals are the degradation of bat guano and the local hydrology we therefore investigated contemporary bat guano deposits in caves and the sediments directly below such deposits the emerging patterns show that the formation of authigenic minerals occurs under acidic conditions within tens of years the availability of phosphate al k and fe increases with increasing organic matter degradation while the availability of nitrogen and sulfur decreases insectivorous bat guano contains larger amounts of phosphate and is more acidic than fruit bat guano in the first stages of diagenesis micro chemical environments form within the degrading bat guano that result in the formation of a wide variety of authigenic minerals during advanced stages of diagenesis steady state conditions are achieved resulting in authigenic mineral assemblages being dominated by one mineral type at the same locale this is reminiscent of known distributions of authigenic minerals in prehistoric cave sediments under the acidic conditions produced by degrading bat guano deposits calcareous artifacts and bones are not expected to persist for long periods of time unless there is a lot of calcite in the sediments that could buffer the sediment water ph guano itself is not likely to be preserved periods of cave abandonment can be inferred from the presence of authigenic minerals in the sediments as it is during these times that bats mainly occupy the cave the occurrence of certain authigenic minerals in open air sites may serve as evidence for areas rich in organic matter containing phosphate i e animal enclosures latrines sewers trash pits and or bones as the degradation process is rapid the use of authigenic minerals to identify these loci is relevant to almost all archaeological as well as historical sites

archaeology of the pleistocene holocene boundary in brazil abstract after a short history of brazilian research about pleistocene peopling the late pleistocene early holocene changes of climate and resources are discussed claims for a very ancient presence of man before 13 000 bp itaborai toca da esperanca pedra furada and lapa vermelha sites are polemic because putative structures and artifacts could have been made by natural processes in central and northeastern brazil some sites dated between 14 000 and 10 000 bp provide clear evidence of human activities and coexistence with huge pleistocene mammals in a synthesis of our present knowledge about the 12 000 8000 bp period biological aspects of the lagoa santa people and their subsistence are discussed the main regional traditions are umbu with bifacial projectile points and humaita with heavy implements in the southern part of brazil in the central and northeastern regions the itaparica tradition is characterized by typical retouched flakes and limaces although projectile points are generally thought to be absent in the earliest levels of this tradition some have been found in boquete cave in amazonia some cultural aspects seem to have been the same as in central brazil

accretion rates of meteorites and cosmic dust in the early ordovician abundant fossil meteorites in marine condensed lower ordovician limestones from kinnekulle sweden indicate that accretion rates of meteorites were one to two orders of magnitude higher during an interval of the early ordovician than at present osmium isotope and iridium analyses of whole rock limestone indicate a coeval enhancement of one order of magnitude in the influx rate of cosmic dust enhanced accretion of cosmic matter may be related to the disruption of the l chondrite parent body around 500 million years ago

the rubble pile asteroid itokawa as observed by hayabusa during the interval from september through early december 2005 the hayabusa spacecraft was in close proximity to near earth asteroid 25143 itokawa and a variety of data were taken on its shape mass and surface topography as well as its mineralogic and elemental abundances the asteroid9s orthogonal axes are 535 294 and 209 meters the mass is 3 51 1010 kilograms and the estimated bulk density is 1 9 0 13 grams per cubic centimeter the correspondence between the smooth areas on the surface muses sea and sagamihara and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting itokawa is considered to be a rubble pile body because of its low bulk density high porosity boulder rich appearance and shape the existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re agglomeration into a rubble pile object

chromium isotopes in late eocene impact spherules indicate a likely asteroid belt provenance abstract spherules and magnetic fractions extracted from two late eocene impact deposits massignano italy and ocean drilling program hole 709c western indian ocean have anomalous concentrations of ir and high concentrations of cr ni co and fe an excess of 53 cr relative to 53 cr 52 cr ratios in terrestrial samples shows that much of the cr in these samples is extraterrestrial the absence of relatively large 54 cr excesses as found in carbonaceous chondrites precludes a carbonaceous chondrite source and the data best fit ordinary chondrites the two localities produced samples with somewhat different elemental and isotopic compositions but these are likely different components of the same impact rather than from two distinct impacts the multiple impacts and dust deposition in the late eocene were more likely caused by disruption of a large asteroid in the inner asteroid belt than by a comet shower the brangane asteroid family may be the result of this disruption the source of the dust and impactors in the late eocene and its members may be composed of h chondrite lithologies based upon the coeval 35 ma peak in h chondrite cosmic ray exposure ages

cosmic ray exposure ages of fossil micrometeorites from mid ordovician sediments at lynna river russia we measured the he and ne concentrations of 50 individual extraterrestrial chromite grains recovered from mid ordovician lower darriwilian sediments from the lynna river section near st petersburg russia high concentrations of solar wind like he and ne found in most grains indicate that they were delivered to earth as micrometeoritic dust while their abundance stratigraphic position and major element composition indicate an origin related to the l chondrite parent body lcpb break up event 470 ma ago compared to sediment dispersed extraterrestrial chromite sec grains extracted from coeval sediments at other localities the grains from lynna river are both highly concentrated and well preserved as in previous work in most grains from lynna river high concentrations of solar wind derived he and ne impede a clear quantification of cosmic ray produced he and ne however we have found several sec grains poor in solar wind ne showing a resolvable contribution of cosmogenic ne 21 this makes it possible for the first time to determine robust cosmic ray exposure cre ages in these fossil micrometeorites on the order of a few hundred thousand years these ages are similar to the cre ages measured in chromite grains from cm sized fossil meteorites recovered from coeval sediments in sweden as the cre ages are shorter than the orbital decay time of grains of this size by poynting robertson drag this suggests that the grains were delivered to earth through direct injection into an orbital resonance we demonstrate how cre ages of fossil micrometeorites can be used in principle to determine sedimentation rates and to correlate the sediments at lynna river with the fossil meteorite bearing sediment layers in sweden in some grains with high concentrations of solar wind ne we nevertheless find a well resolved cosmogenic ne 21 signal these grains must have been exposed for up to several 10 ma in the regolith layer of the pre break up l chondrite parent body this confirms an earlier suggestion that such regolith grains should be abundant in sediments deposited shortly after the break up of the lcpb asteroid c 2013 elsevier ltd all rights reserved less

composition of near earth asteroid 4179 toutatis abstract surface composition of near earth asteroid 4179 toutatis is consistent with an undifferentiated l chondrite composition this is inconsistent with early observations that suggested high pyroxene iron content and a differentiated body

relationship between substorm activity and magnetic disturbances in two polar caps 1 we examined the effect of magnetic disturbances in two polar caps on the generation of magnetospheric substorms for this purpose we investigated the correlation between the al index showing substorm activity in the northern hemisphere and two geomagnetic activity indices the polar cap pc index and polar magnetic pm index showing the magnetic disturbances in the northern and southern polar caps for the analysis we used the data for four years when geomagnetic activity indices were available in both hemispheres we obtained an unexpected yet important result while in northern winter the correlation between al index and northern pc pm indices is very good in northern summer the al index correlates much better with southern pc pm indices thus substorm activity in summer months correlates much better with geomagnetic activity not in the nearby polar cap but in the opposite polar cap this effect may be caused by the interhemispheric field aligned currents flowing from the summer high latitude ionosphere and closing through the ionosphere in the opposite auroral zone an interesting feature of these interhemispheric currents is that they are directed opposite to the substorm field aligned currents in the summer hemisphere but along the substorm field aligned currents in the winter hemisphere this leads to decreasing the total field aligned currents and their contribution to magnetic disturbances in the summer hemisphere but increasing these currents and related magnetic disturbances in winter hemisphere which explains the experimental results obtained in our study

almahata sitta asteroid 2008 tc3 and the search for the ureilite parent body abstract this article explores what the recovery of 2008 tc3 in the form of the almahata sitta meteorites may tell us about the source region of ureilites in the main asteroid belt an investigation is made into what is known about asteroids with roughly the same spectroscopic signature as 2008 tc3 a population of low inclination near earth asteroids is identified with spectra similar to 2008 tc3 five asteroid families in the main belt as well as a population of ungrouped asteroids scattered in the inner and central belts are identified as possible source regions for this near earth population and 2008 tc3 three of the families are ruled out on dynamical and spectroscopic grounds new near infrared spectra of 142 polana and 1726 hoffmeister lead objects in the two other families also show a poor match to almahata sitta thus there are no main belt spectral analogs to almahata sitta currently known space weathering effects on ureilitic materials have not been investigated so that it is unclear how the spectrum of the main belt progenitor may look different from the spectra of 2008 tc3 and the almahata sitta meteorites dynamical arguments are discussed as well as ureilite petrogenesis and parent body evolution models but these considerations do not conclusively point to a source region either other than that 2008 tc3 probably originated in the inner asteroid belt

a russian record of a middle ordovician meteorite shower extraterrestrial chromite at lynna river st petersburg region numerous fossil meteorites and high concentrations of sediment dispersed extraterrestrial chromite ec grains with ordinary chondritic composition have previously been documented from 467 1 6 ma middle ordovician darriwilian strata these finds probably reflect a temporarily enhanced influx of l chondritic matter following the disruption of the l chondrite parent body in the asteroid belt 470 6 ma in this study a volkhovian kundan limestone marl succession at lynna river northwestern russia has been searched for ec grains 63 mu m eight samples forming two separate sample sets were collected five samples from strata around the asaphus expansusa raniceps trilobite zone boundary in the lower middle kundan yielded a total of 496 ec grains in 65 5 kg of rock average 7 6 ec grains kg 1 but up to 10 2 grains kg 1 these are extremely high concentrations three orders of magnitude higher than background levels in similar condensed sediment from other periods ec grains are typically about 50 times more abundant than terrestrial chrome spinel in the samples and about as common as terrestrial ilmenite three stratigraphically lower lying samples close to the a lepidurusa expansus trilobite zone boundary at the volkhov kunda boundary yielded only two ec grains in 38 2 kg of rock 0 05 grains kg 1 the lack of commonly occurring ec grains in the lower interval probably reflects that these strata formed before the disruption of the l chondrite parent body the great similarity in ec chemical composition between this and other comparable studies indicates that all or most ec grains in these russian mid ordovician strata share a common sourcethe l chondrite parent body less

the late pleistocene early holocene archaeological record in brazil a geo referenced database abstract between 13 000 and 8000 14c bp eastern south america was settled by a stable and diversified population of hunter gatherers archaeological excavation in the past twenty years has yielded increasingly consistent evidence of occupation in different regions of brazil since the end of the pleistocene with dates at least contemporary to the clovis horizon in north america this is addressed by documenting and analysing the quantity quality and distribution of archaeological 14c dates from brazil during this period a total of 277 dates from 90 sites are tabulated mapped and included in the analysis during the late pleistocene there was a pioneer phase of human colonization with dispersal inland through the major river systems subsequently the early holocene saw the first phase of established settlement of brazil s interior there seems to be an archaeological threshold reached at ca 10 500 years 14c bp numbers of sites increase there is evidence of settlement of all major biomes and there is clear evidence of inter regional cultural diversity

chemical physical and micromorphological properties of termite mounds and adjacent soils along a toposequence in zona da mata minas gerais state brazil article i nfo little is known about the effects of neotropical mound building termites in soil chemical and physical properties the influence of soil termite activity on soil characteristics was studied by assessing chemical physical and micromorphological properties of a toposequence of latosols oxisols soil samples were collected from the walls and inner parts of termite mounds and also from adjacent soil a high diversity of termite genera was found in the mounds along the toposequence together with the inquiline termites and other soil dwelling arthropods chemical analyses showed that ph and the contents of organic c and n p ca and mg were significantly higher in termite mounds compared with adjacent areas with an inverse trend for al content significant differences in ph and exchangeable al were observed between soil and mound across the slopes the mound density across the landscape was higher at the upper slope segment followed by the hill top middle slope and lower slope segments considering a lifespan of 30 years and dimensions of termite mounds found in the toposequence we conclude that the textural and chemical uniformity of latosols may be increased following the pedobiological turnover during mound building with local rates varying from 2 1 to 7 5 m 3 ha 1

mid infrared spectral variability for compositionally similar asteroids implications for asteroid particle size distributions abstract we report an unexpected variability among mid infrared spectra irtf and spitzer data of eight s type asteroids for which all other remote sensing interpretations e g vnir spectroscopy albedo yield similar compositions compositional fitting making use of their mid ir spectra only yields surprising alternative conclusions 1 these objects are not compositionally similar as the inferred abundances of their main surface minerals olivine and pyroxene differ from one another by 35 and 2 carbonaceous chondrite and ordinary chondrite meteorites provide an equally good match to each asteroid spectrum following the laboratory work of ramsey and christensen ramsey m s christensen p r 1998 j geophys res 103 577 596 we interpret this variability to be physically caused by differences in surface particle size and or the effect of space weathering processes our results suggest that the observed asteroids must be covered with very fine

earth and moon impact flux increased at the end of the paleozoic the terrestrial impact crater record is commonly assumed to be biased with erosion thought to eliminate older craters even on stable terrains given that the same projectile population strikes earth and the moon terrestrial selection effects can be quantified by using a method to date lunar craters with diameters greater than 10 kilometers and younger than 1 billion years we found that the impact rate increased by a factor of 2 6 about 290 million years ago the terrestrial crater record shows similar results suggesting that the deficit of large terrestrial craters between 300 million and 650 million years ago relative to more recent times stems from a lower impact flux not preservation bias the almost complete absence of terrestrial craters older than 650 million years may indicate a massive global scale erosion event near that time

a large shock vein in l chondrite roosevelt county 106 evidence for a long duration shock pulse on the l chondrite parent body a large shock induced melt vein in l6 ordinary chondrite roosevelt county 106 contains abundant high pressure minerals including olivine enstatite and plagioclase fragments that have been transformed to polycrystalline ringwoodite majorite lingunite and jadeite the host chondrite at the melt vein margins contains olivines that are partially transformed to ringwoodite the quenched silicate melt in the shock veins consists of majoritic garnets up to 25 m in size magnetite maghemite and phyllosilicates the magnetite maghemite and phyllosilicates are the terrestrial alteration products of magnesiowustite and quenched glass this assemblage indicates crystallization of the silicate melt at approximately 20 25 gpa and 2000 c coarse majorite garnets in the centers of shock veins grade into increasingly finer grained dendritic garnets toward the vein margins indicating increasing quench rates toward the margins as a result of thermal conduction to the surrounding chondrite host nanocrystalline boundary zones that contain wadsleyite ringwoodite majorite and magnesiowustite occur along shock vein margins these zones represent rapid quench of a boundary melt that contains less metal sulfide than the bulk shock vein one dimensional finite element heat flow calculations were performed to estimate a quench time of 750 1900 ms for a 1 6 mm thick shock vein because the vein crystallized as a single high pressure assemblage the shock pulse duration was at least as long as the quench time and therefore the sample remained at 20 25 gpa for at least 750 ms this relatively long shock pulse combined with a modest shock pressure implies that this sample came from deep in the l chondrite parent body during a collision with a large impacting body such as the impact event that disrupted the l chondrite parent body 470 myr ago

asteroid 6 hebe the probable parent body of the h type ordinary chondrites and the iie iron meteorites the s iv type asteroid 6 hebe is identified as the probable parent body of the h type ordinary chondrites and of the iie iron meteorites the ordinary chondrites are the most common type of meteorites falling to earth but prior to the present study no large mainbelt source bodies have been confirmed hebe is located adjacent to both the v6 and 3 1 resonances and has been previously suggested as a major potential source of the terrestrial meteorite flux hebe exhibits subtle rotational spectral variations indicating the presence of some compositional variations across its surface the silicate portion of the surface assemblage of hebe is consistent both in overall average and in its range of variation with the silicate components in the suite of h type chondrites the high albedo of hebe rules out a lunar style space weathering process to produce the weakened absorption features and reddish spectral slope in the s type spectrum of hebe linear unmixing models show that a typical ni fe metal spectrum is consistent with the component that modifies an h chondrite spectrum to produce the s type spectrum of hebe on the basis of the association between the h chondrites and the he iron meteorites our model suggests that large impacts onto the relatively metal rich h chondrite target produced melt bodies sheets or pods that differentiated to form thin laterally extensive near surface layers of ni fe metal fragments of the upper silicate portions of these melt bodies are apparently represented by some of the igneous inclusions in h chondrite breccias alternately masses of metal could have been deposited on the surface of hebe by the impact of a core or core fragment from a differentiated parent body of h chondrite composition subsequent impacts preferentially eroded and depleted the overlying silicate and regolith components exposing and maintaining large masses of metal at the optical surface of hebe in this interpretation the nonmagmatic iie iron meteorites are samples of the ni fe metal masses on the surface of hebe whereas the h chondrites are samples from between and or beneath the metal masses