the lappajarvi meteorite crater finland petrography rb sr major and trace element geochemistry of the impact melt and basement rocks abstract impact melt lithologies of the 77 m y old finnish meteorite crater lappajarvi as well as the precambrian target rocks have been studied in detail to identify and characterize different impact melt types clast poor clast rich suevitic melt and to study their chemical major and trace elements and isotopic rb sr compositions in comparison to the composition of the target rocks the rb sr system of the whole melt body including the suevitic melt is shown to have been reequilibrated by the impact by extensive turbulent mixing of the various melted or vaporized target rocks chemical interactions exchange of alkali elements 87sr redistribution between feldspar clasts and impact melt surrounding them are the result of thermal metamorphism following the incorporation of target rock fragments of various degrees of shock metamorphism into the superheated melt exchange reactions between clasts and melt are determined by thermal activation but the degree of shock metamorphism in the clasts plays an important role too major and trace element distributions in impact melt and basement rocks indicate that the lappajarvi melt body chemically is extremely homogeneous even volatile elements such as zn and cu were not strongly fractionated comparison of the abundances of siderophile elements in the impact melt e g 118 177 ppm cr 195 340 ppm ni 6 12 ppb ir and calculated target rock mixture 79 mica schist 11 granite pegmatite 10 amphibolite e g 85 6 ppm cr 54 8 ppm ni 0 5 ppb ir revealed the chondritic nature c or h chondritic of the meteoritic projectile less than 2 of the meteorite can be detected in the coherent melt whereas the suevitic melt is uncontaminated by the projectile

apollo 16 impact melt sheets contrasting nature of the cayley plains and descartes mountains and geologic history apollo 16 stations 4 and 5 rake samples were examined petrographically and by electron microprobe and inaa results were combined with published information major and trace element compositions petrologic information and age determinations for nonrake samples from stations 4 and 5 and some other apollo 16 sample localities lithologic abundances support the idea korotev 1981 that the variation of soil compositions at apollo 16 is a result of mixing between a component represented by station 5 soil and components much like either the dimict breccias station 4 soils or feldspathic fragmental breccias stations 1 2 and 11 in composition dimict breccias because of their restricted occurrence are apparently not a constituent of either the cayley or descartes formations they were contributed to the surface materials by south ray crater and were probably excavated from beneath both formations by this event pyroxene olivine and coexisting plagioclase compositions from within the anorthosite portions of dimict breccias bridge the gap between the mg rich and ferroan anorthosite fields analyses from associated cumulate and granulitic clasts indicate that they are the source of the intermediate material dimict breccia anorthosites are thus polymict rocks not pristine ferroan anorthosite compositions of apollo 16 impact melt rocks suggest a number of compositional clusters discriminant and cluster analyses of compositional data confirm the existence and strength of these clusters as do age determinations and ir au ratios within each group each of three clusters represents an impact event in the apollo 16 region petrologic information and age determinations indicate that dimict breccias formed approximately 3 92 b y ago the nectaris event occured between 3 84 and 3 92 b y ago and the cayley plains were deposited as a result of the imbrium event sometime later than 3 84 b y

isotope analysis of crystalline impact melt rocks from apollo 16 stations 11 and 13 north ray crater rubidium strontium and sm nd isotopic data were obtained for lunar impact melt rocks from apollo 16 stations 11 and 13 as part of the north ray crater target rock consortium study rubidium strontium whole rock data define an isochron age t 3 69 0 16 b y 0 0142 b y 1 and initial 87sr 86sr isr 0 69918 5 for feldspathic microporphyritic fm samples internal rb sr isochrons of t 3 86 0 05 b y isr 0 69952 10 and t 3 76 0 04 b y isr 0 69916 4 were determined for very high alumina vha melt rock 67747 and anorthositic noritic melt rock anmr 67559 respectively t isr for these and other lunar melt rocks were examined to infer the nature of the protolith for the rocks isr values for the an mr and fm rocks are consistent with an anorthositic protolith probably a mixture of nonpristine anorthositic gabbros and pristine anorthosites anorthositic norites norites troctolites and possibly dunites the source protolith of the vha rocks apparently had a significant kreep component and the protolith for apollo 16 kreep must have had nearly the same rb sr ratio as that of apollo 14 kreep two stage model calculations using the t isr parameters suggest that some of the melt rocks were open rb sr systems during impact melting rubidium strontium model ages for the fm and vha rocks show a smoothly monotonic decrease with increasing rb content model ages of the anmr are uniformly low relative to 4 56 b y it is suggested that these effects are due to formation of these rocks by impact partial melting rubidium strontium model ages of the kreep rocks do not vary with rb content suggesting that they were closed rb sr systems during impact melting samarium neodymium data for mineral separates of 67747 showed only a small variation in sm nd ratio and yield an imprecisely defined isochron of 3 6 0 4 b y plagioclase separates of 67559 appear not to have reached nd isotopic equilibrium during impact melting consequently the internal isochron age is also imprecisely defined at 4 0 0 4 b y nd values for the melt rocks are about 1 to 2 at their rb sr or 40ar 39ar ages are consistent with the protolith compositions inferred from the rb sr data and show that lunar crustal sm nd evolution departed from chondritic evolution early in lunar history the average chondritic uniform reservoir chur model age of those anmr and fm rocks that apparently remained closed rb sr and sm nd systems during impact melting is 4 37 0 10 b y consistent with earlier suggestions that the lunar crust formed at about that time the average chur model age of two vha rocks is 4 10 0 15 b y suggesting that these rocks were open sm nd systems as well as open rb sr systems during impact partial melting current hypotheses for the site geology stratigraphy and radiometric age data lead us to suggest that the nectaris basin and the descartes formation were formed about 4 1 b y ago and the imbrium basin and the cayley formation were formed about 3 81 3 86 b y ago the ages of some individual melt rocks probably date local cratering events however

the case for an imbrium origin of the apollo thorium rich impact melt breccias abstract mafic th rich impact melt breccias most of which are identified with the composition known as low k fra mauro lkfm are the most common rock type in the nonmare regoliths of the apollo lunar landing sites the origin of mafic impact melt breccias bears on many lunar problems the nature of the late meteoroid bombardment cataclysm the spatial distribution of kreep both near the surface and at depth the ages of the major basins and the composition of the early crust of the nearside lunar highlands thus it is crucial that the origin of mafic impact melt breccias be accurately understood because of both intra and intersite differences in compositions of mafic impact melt breccia samples apparent differences in crystallization age and differences in siderophile element ratios previous studies have argued that either 1 most mafic impact melt breccias are the products of several large craters local to the site at which they were found but that some are of basin origin or that 2 they are all from the imbrium apollos 14 and 15 nectaris apollo 16 and serenitatis apollo 17 basins here we reconsider the hypothesis that virtually all of the th rich mafic impact melt breccias from the apollo missions are products of the imbrium impact ejecta deposit modeling based on modern crater scaling indicates that the imbrium event produced ejecta deposits that average hundreds of meters thick or more at all apollo highland sites which is thicker than some previous estimates substantial amounts of imbrium ejecta should have been sampled at every apollo highland site we suggest that the mafic impact melt breccias may be the principal form of those ejecta the imbrium projectile impacted into th rich material that we regard as part of a unique mafic lunar geochemical province we call the high th oval region based on the surface distribution of th only basins within the high th oval region excavated th rich material the th concentrations of the highlands as observed by the apollo orbiting ray experiments are consistent with the estimates from ejecta modeling of the younger basin forming impacts only imbrium was large enough to produce the copious amount of melt required by the ubiquitous presence of mafic impact melt breccias in the apollo sampled regolith the high th oval region still may have been molten or hot at shallow depths 4 ga ago when the imbrium projectile struck we reason that compositional heterogeneity of ejected melt breccia is to be expected under these circumstances we argue that siderophile element fingerprints of mafic impact melt breccias are not inconsistent with production of all common types by a single projectile we suggest that the narrow range of ages of 3 7 4 0 ga for all successfully dated mafic impact melt breccias may reflect a single event whose age is difficult to measure precisely rather than a number of discrete impact events closely spaced in time such that reported age variations among mafic impact melt breccias reflect the ability to measure 40ar 39ar ages with greater precision than the accuracy with which measured portions of mafic impact melt breccias have recorded the time of their formation

understanding the lunar surface and space moon interactions the surface of the moon is a critical boundary that shapes our understanding of the moon as a whole all geologic mapping and remote sensing techniques utilize only the outermost portion of the moon before leaving the moon for study in our laboratories all lunar samples that have been studied existed at or very near the surface with the exception of the deeply probing geophysical techniques our understanding of the interior of the moon is derived from surficial but not superficial information coupled with boundary of the lunar crust it is the lower boundary layer of the tenuous lunar atmosphere and constitutes both a source and a sink for atmospheric gases the surface is also where the moon interacts with the space environment causing changes in the physical nature of lunar materials and provides a laboratory for the study of processes that occur on all airless bodies the data obtained remotely by the galileo clementine and lunar prospector missions as well as data derived from lunar meteorites have resulted in major changes to our understanding of global distributions of chemistry and rocks this chapter summarizes the current understanding of this critical interface the surface of the moon in its role as the lower boundary of the lunar atmosphere the upper boundary of the crust and the window through which we view through remote sensing the composition of the crust and the history of the moon in this post lunar prospector time the view of the moon has changed lending new perspectives to lunar samples and lunar processes but the new view will likely remain in flux as we continue to digest the results from these recent space missions and move forward to a new era of lunar exploration despite the freshness of our perspective this is an important moment to capture

human adaptive responses to climate and environmental change during the gravettian of lapa do picareiro portugal abstract on the iberian peninsula abrupt climate shifts during the late pleistocene impacted human and natural systems our knowledge of human adaptive responses to these climatic perturbations has improved in recent years with the development of new radiocarbon techniques that have increased the temporal resolution of cultural chronologies at the same time new high resolution paleoclimatic records from greenland ice cores deep sea sediment cores speleothems and microfaunal assemblages have permitted detailed paleoenvironmental reconstructions combined with the archaeological record of culture change these data sets allow for a better understanding of the nature of human socio ecological systems during the late pleistocene here we present new data on the gravettian occupations at lapa do picareiro a cave site in portugal with a long continuous stratigraphic sequence spanning mis 3 and 2 the ongoing excavation of lapa do picareiro has revealed at least three gravettian levels with very different patterns of raw material use and technological reduction the early gravettian levels contain a quartzite flake assemblage with several refitting clusters and a small chert assemblage with nosed endscrapers and bladelet technology the late or terminal gravettian level contains carinated endscraper core bladelet technology mainly quartz with chert blade production and a few bone tools the faunal assemblages also have a different character both contain a similar range of medium and large ungulates but the earlier gravettian has a much richer and more diverse assemblage of small animals these combined archaeological data sets provide a new perspective on gravettian human adaptations in response to climate shifts especially heinrich event 3 and greenland interstadials 4 and 3

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

the sudbury structure controversial or misunderstood the origins of the sudbury structure and associated igneous complex have been controversial most models call for a major impact event followed by impact induced igneous activity although totally igneous models are still being proposed much of the controversy is due in our opinion to a misunderstanding of the size of the original sudbury structure by analogy with other terrestrial impact structures the spatial distribution of shock features and huronian cover rocks at the sudbury structure suggest that the transient cavity was 100 km in diameter which places the original final structural rim diameter in the range of 150 200 km theoretical calculations and empirical relationships indicate that the formation of an impact structure of this size will result in 104 km3 of impact melt more than sufficient to produce a melt body the size of the igneous complex present volume 4 8 103 km3 for the igneous complex to be an impact melt sheet it must have a composition similar to that of the target rocks evidence for this has been presented previously for sr and nd isotopic data which suggest a crustal origin here we also present new evidence from least squares mixing models that the average composition of the igneous complex corresponds to a mix of archean granite greenstone terrain with possibly a small component of huronian cover rocks this is a geologically reasonable mix based on the interpreted target rock geology and the geometry of melt formation in an impact event of this size the igneous complex is differentiated which is not a characteristic of previously studied terrestrial impact melt sheets this can be ascribed however to its great thickness and slower cooling that large impact melt sheets can differentiate has important implications for how the lunar samples and the early geologic history of the lunar highlands are interpreted if this working hypothesis is accepted namely that both the sudbury structure and the igneous complex are impact in origin then previous hybrid impact igneous hypotheses can be discarded and the sudbury structure can be studied specifically for the constraints it provides to large scale cratering and the formation of basin sized multiring impact structures

phosphate ages in apollo 14 breccias resolving multiple impact events with high precision u pb sims analyses abstract the u pb systems of apatite and merrillite grains within four separate apollo 14 impact melt breccia samples were analysed by secondary ion mass spectrometry no systematic difference was identified between the 207 pb 206 pb ages of the apatites and merrillites a combined 207 pb 206 pb age of 3927 2 ma 95 conf is determined for three of these samples 14305 103 3926 4 ma 14306 150 3926 6 ma 14314 13 3929 4 ma by combining these data with the ages previously obtained for zircons in apollo 12 impact melt breccia fragments and the lunar meteorite sau 169 a weighted average age of 3926 2 ma 95 conf is obtained which is attributed to the formation of the imbrium basin an age of 3943 5 ma is determined for the fourth breccia 14321 134 which is similar to ages of 3946 15 ma and 3958 19 ma obtained from several older phosphates in 14305 103 and 14314 13 the weighted average of these three older ages is 3944 4 ma 95 conf this is indistinguishable to the age 3938 4 ma 2 obtained for a different apollo 14 impact melt breccia in a previous study after investigating likely sources for this older 3940 ma age we conclude that the humorum or serenitatis basin forming events are likely candidates the potential identification of two large impact events within 15 myrs has important implications for the rate of lunar bombardment around 3 95 3 92 ga this study demonstrates the importance of high precision age determinations for interpreting the impact record of the moon as documented in lunar samples

high resolution u pb ages of ca phosphates in apollo 14 breccias implications for the age of the imbrium impact abstract previous age estimates of the imbrium impact range from 3770 to 3920 ma with the latter being the most commonly accepted age of this basin forming event the occurrence of ca phosphates i

the timing of basaltic volcanism at the apollo landing sites precise crystallisation ages have been determined for a range of apollo basalts from pb pb isochrons generated using secondary ion mass spectrometry sims analyses of multiple accessory phases including k feldspar k rich glass and phosphates the samples analysed in this study include five apollo 11 high ti basalts one apollo 14 high al basalt seven apollo 15 low ti basalts and five apollo 17 high ti basalts together with the samples analysed in two previous similar studies pb pb isochron ages have been determined for all of the major basaltic suites sampled during the apollo missions the accuracy of these ages has been assessed as part of a thorough review of existing age determinations for apollo basalts which reveals a good agreement with previous studies of the same samples as well as with average ages that have been calculated for the emplacement of the different basaltic suites at the apollo landing sites furthermore the precision of the new age determinations helps to resolve distinctions between the ages of different basaltic suites in more detail than was previously possible the proposed ages for the basaltic surface flows at the apollo landing sites have been reviewed in light of these new sample ages finally the data presented here have also been used to constrain the initial pb isotopic compositions of the mare basalts which indicate a significant degree of heterogeneity in the lunar mantle source regions even among the basalts collected at individual landing sites

geochemistry and 40ar 39ar geochronology of impact melt clasts in feldspathic lunar meteorites implications for lunar bombardment history we studied 42 impact melt clasts from lunar feldspathic regolith breccias macalpine hills mac 88105 queen alexandra range que 93069 dar al gani dag 262 and dag 400 for texture chemical composition and or chronology although the textures are similar to the impactmelt clasts identified in mafic apollo and luna samples the meteorite clasts are chemically distinct from them having lower fe ti k and p thus representing previously unsampled impacts the 40ar 39ar ages on 31 of the impact melts the first ages on impact melt samples from outside the region of the apollo and luna sampling sites range from 4 to 2 5 ga we interpret these samples to have been created in at least six and possibly nine or more different impact events one inferred impact event may be consistent with the apollo impact melt rock age cluster at 3 9 ga but the meteorite impact melt clasts with this age are different in chemistry from the apollo samples suggesting that the mechanism responsible for the 3 9 ga peak in lunar impact melt clast ages is a lunar wide phenomenon no meteorite impact melts have ages more than 1 older than 4 0 ga this observation is consistent with but does not require a lunar cataclysm

the gravettian solutrean transition in westernmost iberia new data from the sites of vale boi and lapa do picareiro abstract this study presents the analysis of the lithic assemblages from layers 5 and 4e terrace of the site of vale boi southern portugal and levels u and t from lapa do picareiro central portugal we aimed to understand the technological patterns and raw material exploitation during the gravettian solutrean transition in westernmost iberia and test the traditional models with assemblages from recently excavated sites while expanding the geographic range results show the existence of two discrete phases in each site the first with high frequency of quartz use for bladelet production seems to reflect the presence of a terminal gravettian horizon as defined by almeida 2000 the second with some significant differences between sites attests the presence of vale comprido technology and lower quartz frequencies at vale boi representing a proto solutrean occupation and the presence of a blade component in lapa do picareiro that together with the respective absolute chronology may be attributed to a proto solutrean or an early solutrean horizon in general terms this study allowed to confirm that the terminal gravettian and the proto solutrean are discrete phases across the transition in agreement with the three phase model presented by zilhao 1997 it further consolidates the expansion of similar techno cultural patterns to southern portugal which may be explained by the significant changes in the dynamic of social networks cascalheira and bicho 2013

disequilibrium features in experimentally shocked mixtures of olivine plus silica glass powders seventeen shock recovery experiments were performed on powder mixtures of one part by weight olivine st john s forsterite plus two parts silica glass pure vitreous silica in order to characterize the physical and chemical interaction of two chemically incompatible components during shock powders of 45 m grain size were shocked by impact of projectiles launched from a 20 mm gun which created pressures ranging from 6 2 to 64 2 gpa 1 gpa 10kbar

impact melts in the mac88105 lunar meteorite inferences for the lunar magma ocean hypothesis and the diversity of basaltic impact melts abstract the mac88105 lunar meteorite as represented by thin section 78 contains three major types of impact melt breccias the most abundant type is clast laden fine grained and rich in al 2 o 3 28 wt these clasts constitute most of the meteorite their abundance and aluminous nature indicate that the mac88105 source area was very aluminous this is consistent with formation of the primordial lunar crust from a global magma ocean the second type of impact melt is represented by only one clast in 78 it has a basaltic bulk composition similar to many other lunar impact melts but is significantly richer in p 2 o 5 than most and has a much lower mgo mgo feo the third impact melt type resembles a prominent melt group at apollo 16 but has lower mgo mgo feo these data show that basaltic impact melts are compositionally diverse dating samples of the al rich impact melts and the new types of basaltic impact melts from this meteorite can test the idea that the moon suffered a terminal cataclysm 3 9 ga ago

cross scale adaptive behaviors during the upper paleolithic in iberia the example of vale boi southwestern portugal abstract it is now rather evident that concomitant with the advent growth and disappearance of the traditionally defined western european upper paleolithic techno complexes a series of discrete eco cultural niches would have existed within iberia vale boi and its surroundings may represent one of these niches since its lengthy and fairly complete archaeological record clearly attests that the region was an attractive location for hunter gatherer communities for over 10 000 years from the first modern human occupations c 32 ka cal bp ago a set of very specific cultural adaptive markers seem to have been developed in response to the particularities of the regional ecological background some of these strategies such as intensive subsistence practices raw material specialized use among others were resilient through time and apparently impermeable to the major shifts in the techno typological novelties brought about with the advent of each upper paleolithic phase even with the appearance of quite unique and broad scale technologies e g solutrean regional markers and identity have been kept clearly showing that each level of the adaptive system seem to have operate at its own pace this paper focus on long term adaptive choices and on how and why hunter gatherers inhabiting vale boi manage to absorb change and re organize their system under new techno complex cultural patterns while still retaining efficiently the same regional adaptive idiosyncrasies within the theoretical framework of panarchy and the cross scale resilience model we argue that cross scale interactions between creative and conserving niche specific behavioral adaptations were the keystone for the sustainability of hunter gatherer cultural systems across the late pleistocene

strontium and neodymium isotopic characteristics of a heterolithic breccia in the basement of the sudbury impact structure canada abstract rb sr and sm nd measurements were undertaken on footwall breccia samples originating from levack township in the north range of the sudbury structure the granitic to quartzdioritic matrix of this heterolithic breccia which contains shocked rock and mineral fragments yields a rb sr isochron age of 1 825 0 021 ga isr 0 70356 0 00005 2 errors based on the analysis of 3 6 mm thick adjacent whole rock slabs from a large hand specimen this age is interpreted as a cooling age after the thermal metamorphism of the footwall breccia by the 1 85 ga old sudbury igneous complex which had caused temperatures in excess of 1000 c in the matrix near the contact mafic rock fragments in this breccia were excluded from the sr isotope exchange at that time the sm nd system of the identical small whole rock samples was only partly disturbed by the sudbury igneous complex the data points scatter around a 2 05 0 49 ga regression line without age significance plagioclase k feldspar and mafic mineral phases of the breccia matrix combined with the corresponding whole rocks display a range in rb sr ages from 1 67 0 08 ga to 1 430 0 015 ga obviously associated with metasomatic processes in the footwall breccia during the declining penokean metamorphism strontium and neodymium model parameters of the footwall breccia matrix near levack show little variation esrt 16 33 to 18 07 endt 10 69 to 11 79 t 1 86 ga and mean tnddm 2 74 0 04 ga based on these results bedrocks exposed in the south range and rocks now forming the sedimentary filling of the sudbury basin can be excluded as major components in the matrix of the analyzed footwall breccia the convergence of neodymium model ages with u pb ages on zircons from the levack gneiss which forms the crystalline basement adjacent to the footwall breccia in the levack area support an exclusively local origin for matrix and fragments of this breccia it is proposed that the footwall breccia is part of the uplifted floor of the sudbury crater

petrogenetic association of the oldest lunar basalts combined rb sr isotopic and trace element constraints abstract we report a new radiometric rb sr age determination of 4 03 0 04 ga for high al basaltic clast 14321 1353 which is a group b apollo 14 high al basalt based on its whole rock incompatible trace element chemistry in addition available literature rb sr isotope data for apollo 14 high al basalts were reprocessed using the same decay constant and data reduction protocol as used for sample 14321 1353 the rb sr isotopic ages of high al basalts range from 4 31 0 17 to 3 93 0 06 ga the trace element and rb sr isotopic compositions of high al basalts are distinct from those of apollo 14 aluminous impact melts that crystallized at 3 86 0 01 ga the rb sr isotope systematics coupled with incompatible trace element data are consistent with the parental melts of apollo 14 high al basalts being derived from sources consisting of primitive crystallization products of the lunar magma ocean that were variably metasomatized by late stage kreep rich fluids our new rb sr isotopic age for 14321 1353 suggests that the kreep metasomatism must occur in the lunar mantle no later than 4 03 0 04 ga collectively the apollo 14 high al basalts represent the earliest known volcanic products from the moon and place a time constraint on the formation of the high al basalt source through the crystallization of the lunar magma ocean

composition and evolution of the lunar crust in the descartes highlands apollo 16 samples from the north ray crater ejecta blanket apollo 16 were investigated by petrographic microscope electron microprobe instrumental neutron activation and xray fluorescence analyses and 40ar 39ar and rb sr dating techniques nine major groups of monomict and polymict breccias were defined on the basis of microscopic texture and these were further subdivided into chemical subgroups on the basis of characteristic elements such as al mg fe cr ree ni and co the polymict breccias fragmental breccias granulitic breccias and impact melt breccias are the result of multiple impact induced mechanical mixing and melting and of thermal and impact metamorphism of rock and mineral clasts derived from primordial igneous crustal rocks for calculations of mixing models it was found that end members consisting of the pristine igneous rock components present as discrete samples at the apollo 16 site and supplemented by kreep dunite and a meteoritic component yield the best fits for the composition of polymict breccias the end member rocks a re ferroan anorthosite various magnesian gabbronorites including sodic ferrogabbro and feldspathic lherzolite and spinei troctolite the following model is proposed for the composition and stratigraphy of the target for north ray crater the lower section of the stratigraphy is composed of a megabreccia with clasts of highly feldspathic polymict breccias kreep free old eastern highland rock suite interpreted as nectaris ejecta descartes formation the top section contains kreep bearing polymict breccias kreep bearing young western highland rock suite and appears to be similar to the lithologies found in the cayley plains this material interpreted as cayley formation may be a distant facies of imbrium basin ejecta deposits of the imbrium basin the petrographic differences between these two major selenographic units the descartes and the cayley formations in the apollo 16 area are more distinct than the chemical differences the petrographic and chemical composition of the primordial igneous upper crust in the regions of the nectaris and imbrium basins has been calculated by subtraction of the kreep and meteoritic components from the bulk composition of the descartes and cayley materials the nectaris crust which is better constrained consists of 86 87 a northosite 4 sodic ferrogabbro 0 5 1 3 feldspathic lherzolite 6 8 regular magnesian gabbronorite 1 8 2 8 dunite and 0 1 spinel troctolite a model for the evolution of the upper lunar crust in the descartes highlands is proposed on the basis of isotope ages and clast matrix relationships of polymict breccias essential features of this model in sequenial order are 1 development of multiple layers of kreep free early feldspathic fragmental megabreccias and impact melt sheets on the primordial crust in the time period from 4 4 aeons to the time of the nectaris impact which could have occurred as late as 3 85 aeons ago 2 excavation of these megabreccias by the nectaris event and deposition of a nectarian feldspathic fragmental megabreccia in the descartes area 3 introduction of kreep basaltic material into the upper crust mainly west and northwest of the descartes site and formation of kreepy impact melt sheets most probably from 4 05 to 3 80 aeons ago 4 imbrium impact at 3 8 aeons ago and deposition of kreep bearing imbrian feldspathic fragmental breccias at the descartes site which form the cayley formation and 5 redeposition mixing and melting of all preexisting breccias yielding kreep bearing and kreep poor post cayley fragmental breccias and melt ejecta glass bombs as the result of small impacts craters 1 5 km in diameter in the cayley plains and the descartes mountains respectively

debates over palaeolithic chronology the reliability of 14c is confirmed abstract the debate about the complex issues of human development during the middle to upper palaeolithic transition period 45 35 ka bp has been hampered by concerns about the reliability of the radiocarbon dating method large 14 c anomalies were postulated and radiocarbon dating was considered flawed we show here that these issues are no longer relevant because the large anomalies are artefacts beyond plausible physical limits for their magnitude previous inconsistencies between 14 c radiocarbon datasets have been resolved and a new radiocarbon calibration curve intcal09 reimer et al 2009 was created improved procedures for bone collagen extraction and charcoal pre treatment generally result in older ages consistent with independently dated time markers

shell bead production in the upper paleolithic of vale boi sw portugal an experimental perspective abstract in this paper we focused on shell bead production during the upper paleolithic at the site of vale boi in southwestern portugal as a means of understanding social visual transmission vale boi has a long sequence dated to between c 32 and 7 ka cal bp with well preserved bone and shell assemblages from early gravettian to neolithic times the archaeological shell bead collection includes over 100 specimens from the gravettian proto solutrean solutrean and magdalenian layers from vale boi including at least 5 species littorina obtusata or littorina fabalis trivia sp antalis sp mitrella scripta and theodoxus fluviatilis experimental replication techniques included scratching sawing and hammering using lithic and bone implements on both internal and external sides of the shells experimental results indicate that there are a series of potential fabrication techniques for bead production but there is a clear tendency in the archaeological record to use a single technique for each shell species there also seems to be a focus on using a fast technique rather than a slower one which seems to produce higher quality results finally we also address the topic of the impact of bead production techniques on the evolution of bead design technology through all upper paleolithic record in sw portugal

39ar 40ar dating of two lunar granites the age of copernicus previous investigations have suggested that kreep glass found in 12033 and other apollo 12 soils was ejected from the crater copernicus and deposited in a ray across this site soil fragment 12033 507 has been described as having a core of felsite granitic composition with a kreep glass shell 39ar 40ar dating of a sample of this granite material shows almost complete resetting 800 15 ma ago we interpret this age as giving the most precise determination to date for the formation time of copernicus cosmic ray exposure ages of the granite and associated kreep glass in soil 12033 about 250 ma are much less than the k ar age and suggest a complex postejection burial history the 39ar 40ar age of another granite fragment 14303 204 is determined to be in the range 3 80 3 85 ga this age is in agreement with 39ar 40ar ages determined for a few other lunar granites and is interpreted to represent resetting by a large basin forming impact probably imbrium

open air gravettian lithic assemblages from northeast portugal the foz do medal site sabor valley abstract recent works undertaken in sabor valley northeast portugal revealed an important upper paleolithic sequence to the north of douro river in a region with little paleolithic evidence previous upper paleolithic occupation evidence in the region had only been identified and studied in coa valley to the south of douro river foz do medal site is located in an interior area of iberia on the fringe of the spanish meseta in the transition to the atlantic facade the work accomplished allowed the identification of gravettian levels the gravettian lithic assemblage from foz do medal presents different characteristics when compared with other more traditional gavettian assemblages namely from portuguese estremadura although sharing some features the objectives of the reduction and the strategies applied show big peculiarities which can be related mainly with the geological context and the raw material sources the scarcity of biogenic chert and the availability of other local siliceous rocks such as hydrothermal cherts rock crystal and other types of fine quartz have played a major role in the choices made by prehistoric humans quartz in its several varieties was the chosen raw material for knapping reaching more that 80 of the total collection as a result the regional environmental context and human strategies show great variability between foz do medal and coa valley gravettian assemblages and other gravettian assemblages where chert is easily available

ages of mare basalts on the lunar nearside the chronology of lunar volcanism is based on radiometric ages determined from apollo and luna landing site samples regional stratigraphic relationships and crater degradation and size frequency distribution data for units largely defined prior to the end of the apollo program here we report on new crater size frequency distribution data for 139 spectrally and morphologically defined basalt units which are exposed in six nearside impact basins australe tranquillitatis humboldtianum humorum serenitatis and imbrium crater size frequency distribution measurements are a statistically robust and accurate method to derive absolute model ages of unsampled regions of the moon compared to crater degradation ages crater size frequency ages performed on spectrally defined units offer significant improvements in accuracy our investigation showed that 1 in the investigated basins lunar volcanism was active for at least 1 5 2 0 b y starting at about 3 9 4 0 b y and ceasing at 2 0 b y 2 most basalts erupted during the late imbrian period at about 3 6 3 8 b y 3 significantly fewer basalts were emplaced during the eratosthenian period 4 basalts of copernican age were not found in any of the investigated basins 5 lunar basin filling volcanism probably started within 100 m y after the formation of the individual basins we also assessed the relationship between impact basin age and the history of mare basalt emplacement in these basins we found that 1 in all pre nectarian basins australe and tranquillitatis as well as in the humboldtianum basin which is of nectarian age the distribution of surface ages is clearly dominated by only a single peak in the number of erupted units at 3 6 3 8 b y 2 in the younger basins humorum serenitatis and imbrium a second peak at 3 3 3 5 b y is observed 3 basalt eruptions younger than 2 6 b y occur only intermittently and 4 in the youngest basins serenitatis and imbrium we see an extended period of active basin filling volcanism 1 5 1 6 b y which is 500 m y longer than in the australe and humorum and even 1 0 b y longer than in tranquillitatis and humboldtianum

isotope systematics and shock wave metamorphism ii u pb and rb sr in naturally shocked rocks the haughton impact structure canada minerals and whole rocks from crystalline fragments collected in the allochthonous polymict breccia of the 23 ma old haughton impact crater on devon island arctic canada were analysed for u pb k and rb sr in order to constrain degrees of shock wave induced perturbations in these systems the results show that shock wave metamorphism at 50 gpa with onset of total melting does not significantly affect the u pb chronometers in monazite and zircon monazite preserved its age of crystallization during high grade metamorphism at 1928 2 2 1 2 0 ma 2 errors as dated by the upper intercept of 2 9 discordant monazites the same analyses yield a lower intercept age of 277 5 35 1 35 0 ma in the concordia diagram demonstrating that discordancy is not a direct effect of shock wave metamorphism but a product of time integrated pb diffusion prior to the impact event which occurred 23 ma ago this constrains maximal shock induced pb loss to less than 3 including possible alteration related pb diffusion from the shock damaged grains in 1903 1 1 4 1 1 ma old monazite from an unshocked reference gneiss recent pb loss also reaches 3 corroborating the occurrence of weak alteration related upb fractionation the data substantiate that u pb discordancy patterns are not a reliable chronometer to date impact events small rock fragments and a coherent block of shock stage i to iii vi consist of heterogeneous unequilibrated rb sr sub systems on the 10 m scale with drastically varying isr shock related rbsr fractionation is very limited and in the large block stage iii three biotite fractions yield an rb sr isochron age of 1791 34 ma 2 which is undistinguishable from the 1814 8 ma age of biotite in the unshocked basement gneiss in contrast to this m3 sized fragment rb sr systematics in a fist size sample of shock stage iii do not yield any reliable age information due to small scale 1 cm3 isotopic disequilibrium it appears that such small scale disequilibrium is essentially due to a take up of radiogenic 87sr in feldspar glass from biotite during shock wave passage this prevents dating of the impact events by the rb sr internal isochron method and it can be concluded that total rock melting is the first condition necessary to reset the rb sr chronometer in shocked crystalline rocks

mineralogy petrology and shock history of lunar meteorite sayh al uhaymir 300 a crystalline impact melt breccia sayh al uhaymir sau 300 comprises a microcrystalline igneous matrix grain size s4 the association of maskelynite with melt pockets and shock veins indicates a subsequent local 28 45 gpa shock stage s2 s3 excursion which was probably responsible for lofting the sample from the lunar surface subsequent fracturing is attributed to atmospheric entry and probable breakup of the parent meteor

bunte breccia of the ries continuous deposits of large impact craters the ries crater an impact structure of 26 km diameter in south germany is the largest terrestrial crater where substantial amounts of ejecta are preserved on occasion 100 m deep further the target stratigraphy is well known and it is possible to relate specific clasts and breccia lithologies to initial target depth as a consequence the continuous deposits of the ries also known as bunte breccia may be studied with exceptional field control we report field observations and laboratory analyses obtained from 560 m core materials taken at nine different locations that range from 16 to 37 km in radial distance from the impact center the objective is to relate the ries observations to ejection and to emplacement processes of large scale planetary crater deposits the observations regarding the modal stratigraphic characteristics of the bunte breccia may be summarized as follows only 600 m some 0 7 is composed of triassic clasts originating from 300 to 600 m depths lower and middle jurassic horizons approximately 300 150 m constitute some 2 3 and upper jurassic 0 150 m makes up some 31 5 in addition the bunte breccia contains tertiary materials in the form of 1 cm clasts 29 1 and as highly comminuted fine grained matrix 10 gpa constitute 0 1 weight of the entire deposit which indicates that bunte breccia was emplaced at essentially ambient temperatures when possible the above observations are quantified via linear regressions throughout the text all of these observations are consistent with if not predicted by a ballistic emplacement scenario as postulated by oberbeck and co workers primary crater ejecta are expelled ballistically and will form secondary craters in the local substrate a mixture of primary and secondary ejecta results and combines into a highly turbulent ground hugging debris surge as the final phase of ejecta emplacement total emplacement time for the bunte breccia 200 km is estimated to be of the order of 5 min only these findings are compared with cratering theory relating to a number of ejecta thickness decay models and with the so called z model addressing material flow during various stages of crater formation qualitative to fair agreement of observations and predictions results an initial crater radius of 6 5 km an excavation depth of 1650 m an excavation volume of 136 km and an associated transient cavity volume of aproximately 230 km appear to be reasonable estimates approximately 170 km of material was involved in slumping and restoration of the transient cavity for the above radius and z 2 7 the modal composition of ries ejecta with regard to preimpact target stratigraphy indicates that materials contained in the continuous deposits of large complex planetary craters are predominantly derived from depths as small as one hundredth the apparent crater diameter a number of implications are addressed regarding remote sensing of planetary surfaces and investigation of lunar and meteoritic impact breccias

compositional variation in apollo 16 impact melt breccias and inferences for the geology and bombardment history of the central highlands of the moon abstract high precision data for the concentrations of a number of lithophile and siderophile elements were obtained on multiple subsamples from 109 impact melt rocks and breccias mostly crystalline from the apollo 16 site compositions of nearly all apollo 16 melt rocks fall on one of two trends of increasing sm concentration with increasing sc concentration the eastern trend lower sm sc mg fe and sm yb ratios consists of compositional groups 3 and 4 of previous classification schemes these melt rocks are feldspathic poor in incompatible and siderophile elements and appear to have provenance in the descartes formation to the east of the site the western trend higher sm sc mg fe and sm yb ratios consists of compositional groups 1 and 2 these relatively mafic kreep bearing breccias are a major component 35 of the cayley plains west of the site and are unusual compared to otherwise similar melt breccias from other sites in having high concentrations of fe ni metal 1 2 the metal is the carrier of the low ir au 0 3 chondritic siderophile element signature that is characteristic of the apollo 16 site four compositionally distinct groups 1m 1f 2db and 2nr of western trend melt breccias occur that are each represented by at least six samples compositional group 1 of previous classification schemes the poikilitic or lkfm melt breccias can be subdivided into two groups group 1m represented by six samples including 60315 is characterized by lower al2o3 concentrations higher mgo and alkali concentrations and higher mg fe and cr sc ratios than group 1f represented by fifteen samples including 65015 group 1m also has siderophile element concentrations averaging about twice those of group 1f and ir au and ir ni ratios that are even lower than those of other western trend melt rocks ir au 0 24 0 03 ci normalized at the mafic extreme of group 2 vha melt breccias the melt lithology occurring as clasts in feldspathic fragmental breccias from north ray crater group 2nr is compositionally distinct from the melt lithology of dimict breccias from the cayley plains group 2db in having higher concentrations of sc cr and heavy rare earth elements and lower concentrations of siderophile elements the distinct siderophile element signature high absolute abundances low ir au ratio suggest that the four groups of mafic melt breccia are all somehow related ratios of some lithophile elements also suggest that they are more closely related to each other than they are to melt breccias from other apollo sites however none of the breccia compositions can be related to any of the others by any simple process of igneous fractionation or mixing involving common lunar materials thus the origin of the four groups of mafic melt breccia is enigmatic if they were produced in only one or two impacts then a mechanism exists for generating regimes of impact melt breccia in a single impact that are substantially different from each other in composition for various reasons including the problem of delivering large volumes of four different types of melt to the apollo 16 site it is unlikely that any of these breccias were produced in basin forming impacts if they were produced in as many as four crater forming impacts then the unusual siderophile element signature is difficult to explain possible explanations are 1 1 the four groups of melt breccia all contain metal from a single earlier impact 2 2 they were each formed by related metal rich meteoroids or 3 3 some common postimpact process has resulted in metal of similar composition in each of four melt pools within a compositional group most intrasample and intersample variation in lithophile element concentrations is caused by differences among samples in the proportion of a component of normative anorthosite or noritic anorthosite in most cases this compositional variation probably reflects variation in clast abundance for group 2db and probably 2nr differences in abundance of a component of ferroan anorthosite estimated al2o3 32 accounts for the compositional variation for groups 1m and 1f the anorthositic component is more mafic estimated al2o3 26 some group 2 samples may be related by a troctolitic component of varying abundance

geology tectonism and composition of the northwest imbrium region abstract the objective of this study is to explore the regional geology of the northwest imbrium region in which the chang e 3 ce 3 landing site is located ce 3 successfully landed on december 14 2013 on the unsampled eratosthenian basalts whose study is important for understanding the evolution of the moon new geologic and structural maps of the research area were produced through the integrated analysis of diverse datasets the highlands surrounding imbrium differ from typical farside highlands terrain fht the iridum highland region as well as the surrounding imbrium region exhibits elevated concentrations of fe and abundant local exposures of low ca pyroxene and olivine bearing lithologies in this study these highlands are named as mafic highlands mh our dating results using crater size frequency distributions csfds show that the iridum basin hosting sinus iridum was formed 3 8 ga shortly following the imbrium basin formation and before the last large multiringed basin orientale the eratosthenian period of lunar basalt eruptions which lasted longer than other stratigraphic units is suggested to divide into the lower eratosthenian mare lem and upper eratosthenian mare uem units this subdivision is based on whether lava fronts can be clearly seen or not and the age separating the units is 2 35 ga the mafic mineralogy of the mare basalts in imbrium is characterized by abundant olivine in the eratosthenian aged basalts and average pyroxene compositions near pigeonite to sub calcic augite in the imbrian and em1 units the thickness of individual lava for uem units is 8 11 m indicative of high effusion rates the thickness of the em3 unit ranges from 17 m to 45 m with lesser thickness to the west and greater thickness in the interior and to the east the estimated volume and average flux of the eratosthenian aged basalts are greater than previously thought the presence of these youngest basalts in the procellarum kreep terrain pkt is hypothesized to be a causal relationship with the pkt terrain reducing the thickness of the lithosphere and permitting preferential dike emplacement and extrusion there we speculate that high ti and olivine rich composition in late stage basalts may be consistent with low si and high ti and low degrees of partial melting large numbers of sinuous rilles and small ridges are identified and mapped many young ridges were found inside imbrium suggesting a very extended period at least as young as the last 50 ma of the moon s tectonic activity the distinct compositions of both highlands and mare basalts and extended tectonism emphasize how the imbrium basin is an important area for understanding the moon

laser argon 40 argon 39 age studies of dar al gani 262 lunar meteorite abstract the laser 40ar 39ar dating technique has been applied to the dar al gani dag 262 lunar meteorite a polymict highland regolith breccia to determine the crystallisation age and timing of shock events experienced by this meteorite laser stepped heating analyses of three dominantly feldspathic fragments dag 1 dag 2 and dag 3 revealed the presence of trapped ar mostly released at intermediate and high temperatures with an 40ar 36ar value of 2 8 trapped ar is most likely released from melt glass present as small veins within the fragments the 40ar 39ar ages determined for the three fragments are 3 0 ga for dag 1 and dag 2 and 2 0 ga for dag 3 and probably relate to major impact events laser spot analyses were performed on a feldspathic clast an impact crystalline melt basalt icmb and the matrix in a polished section of dag 262 the feldspathic and icmb clasts have low contents of trapped ar compared with that in the matrix the feldspathic clast shows a wide range of ages from 3 0 to 1 7 ga similar to those obtained by stepped heating the younger age is interpreted as a minimum age for the last major event that assembled this meteorite the icmb shows two age clusters at 3 37 and 3 07 ga where the older age may be that of the impact event that formed the impact melt several cosmic ray exposure cre ages were obtained as expected for a polymict regolith breccia the cre ages are 106 and 141 ma for the feldspathic clast and the icmb respectively one of the feldspathic fragments dag 2 shows a range between 200 400 ma these cre ages which are similar to those determined for returned samples of the lunar regolith indicate that the different components of dag 262 experienced preexposure prior to assemblage of the meteorite

temperature and productivity changes off the western iberian margin during the last 150 ky abstract present day hydrographic conditions along the western iberian margin are characterized by seasonal upwelling with filaments that can penetrate more than 200 km into the open ocean and constitute areas of cold and highly productive waters in order to investigate spatial and temporal gradients in temperature and productivity conditions during the last 150 ky high resolution proxy records were generated in 3 cores su92 03 md95 2040 md95 2042 located along the iberian coast between 43 12 n and 37 48 n and forming a n s profile in all cores planktonic foraminifera census counts are used to reconstruct summer sea surface temperature sstsu and export productivity pexpsu using the modern analog technique simmax 28 sstsu and pexpsu values similar to the present are observed throughout the holocene and mis 5e periods for each site respectively indicating fairly stable conditions equivalent to the modern ones on glacial interglacial timescales sstsu increases by 2 3 c from the northern to southernmost site pexpsu on the other hand shows a decrease of 30 40 gc m2 yr from north to south at present time and during interglacial periods and no significant variation 90 100 gc m2 yr during glacial periods the northernmost core su92 03 reveals the coldest conditions with records more similar to md95 2040 than to md95 2042 the later of which is as at present more affected by subtropical waters core su92 03 shows higher interglacial productivity similar to open ocean mid to high latitude sites while the other two cores monitor higher glacial productivity conform with other upwelling sites off nw africa a boundary between differences in glacial interglacial productivity appears to be present in our study between 43 12 n and 40 35 n especially north of 40 n coldest sstsu and lowest pexpsu are found during heinrich events h 1 h8 and h10 h11 in contrast lowest pexpsu do not coincide with these events at site md95 2042 but appear to be related to the presence of relatively warm and nutrient poor subtropical eastern north atlantic central water advected with the azores current

petrology of the apollo 11 highland component new data for 38 highland fragments hand picked from apollo 11 coarse fines are reported petrographic mineralogic and bulk chemical data show that 1 the apollo 11 highland component is non kreepy and like that of apollo 16 2 poikilitic rocks granulitic breccias and the anorthosite norite troctolite suite are the most abundant rock types followed by polymict breccias and glasses 3 both the ferroan anorthosite and mg rich plutonic suites are represented in the apollo 11 highland component 4 except for one sample the intermediate k fra mauro and high k fra mauro groups are not represented the data and observations are consistent with local derivation of the highland material from beneath relatively thin basalt flows and addition to the regolith via vertical mixing

physics based scenario of earthquake cycles on the ventura thrust system california the effect of variable friction and fault geometry the ventura thrust system in california is capable of producing large magnitude earthquakes geological studies suggest that the fault geometry is complex composed of multiple segments at different dips thrust ramps dipping 30 50 linked with bed parallel decollements dipping 10 these latter types of gently dipping faults form due to preexisting weaknesses in the crust and therefore have different frictional parameters from thrust ramps the faults also experience different stresses because of how stresses are resolved onto the fault planes here we use a two dimensional fault model to assess how geometry and frictional properties of the ramp decollement system should affect the seismic cycle we test velocity strengthening velocity weakening and conditionally stable decollements and in addition explore how the dip angle of the decollement changes the earthquake behavior a velocity strengthening decollement cannot replicate the through going earthquake ruptures that have been inferred for the ventura fault system we therefore suggest that this and other decollements may be better represented using a velocity weakening or conditionally stable response our results show that minor variations in fault geometry produce slip amounts and recurrence intervals that differ only by 10 20 but do not fundamentally alter the types of earthquakes and interseismic slip we conclude that geological constraints on fault geometry are typically sufficient to produce modeled earthquake sequences that are statistically consistent with paleoseismic records however both frictional parameters along the fault and effective normal stress influence earthquake rupture patterns significantly more research is needed to adequately constrain these quantities in order for earthquake rupture models to work as effective predictors of fault behavior

apollo 16 site geology and impact melts implications for the geologic history of the lunar highlands the geology of the apollo 16 site is reconsidered on the basis of data from photogeology geochemical remote sensing and lunar samples the site possesses an upper surface of anorthositic gabbro and related rocks mafic components were deposited as basin ejecta the events involved in its geological evolution were the nectaris impact and the imbrium impact the role of large local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta the most abundant melt composition at apollo 16 is an aluminous variety of lkfm basalt supplied by the nectaris impact as ejected basin impact melt the mafic lkfm melt may have been supplied by the imbrium impact more aluminous melt groups are probably derived from local small craters the remainder of the deposits in the region are composed of anorthositic clastic debris derived from the nectaris basin the local crustal substrate and imbrium and other basins

40ar39ar dating of pseudotachylite from the vredefort dome south africa a progress report abstract to date six pseudotachylite samples from the vredefort dome have been analysed by the stepheating 40ar 39ar technique the resulting ages ga 2 25 0 04 k ar 2 01 0 06 1 39 0 08 1 44 0 08 1 33 0 04 and 1 09 0 10 may be understood as suggesting several pseudotachylite forming events at vredefort this and other chronological and field evidence may be interpreted as supporting the possibility that vredefort pseudotachylite is not derived from a single catastrophic central shock event but was generated in several local high strain possibly seismic shock events diffusion calculations have shown that it is possible that several thermal spikes could have effectively degassed pseudotachylite at relatively low temperatures and during short periods of time e g at 340 c in 10000 yrs there is however no geological or isotopic evidence directly supporting the existence of these proposed temperature spikes at 2 0 1 3 1 4 and 1 1 ga in the region of the vredefort structure on the contrary field and laboratory observations can be invoked that seem to favour the formation of multiple generations of pseudotachylite in the vredefort dome and in the surrounding witwatersrand basin however it must be noted that likewise no direct geological evidence for local tectonic activity in the region of the witwatersrand basin at those times can be presented with the exception of emplacement of pilanesberg age dykes further tests on the validity of the 40ar 39ar ages on vredefort pseudotachylite are in progress and are discussed

diverse impactors in apollo 15 and 16 impact melt rocks evidence from osmium isotopes and highly siderophile elements abstract concentrations of highly siderophile elements hse and 187 os 188 os isotopic compositions for eleven impact related rocks from the apollo 15 and 16 landing sites are reported and combined with existing geochronological data to investigate the chemical nature and temporal changes in the large impactors implicated in the formation of the lunar basins data for the samples all define linear trends on plots of hse versus ir concentrations whose slopes likely reflect the relative hse compositions of the dominant impactors that formed the rocks the inferred imbrium basin impactor that generated apollo 15 impact melt rocks 15445 and 15455 was characterized by modestly suprachondritic 187 os 188 os ru ir pt ir and pd ir ratios diverse impactor components are revealed in the apollo 16 impact melt rocks the 187 os 188 os and hse ir ratios of the impactor components in melt rocks 60635 63595 and 68416 with reported ages 4 0 ga by contrast the impactor components in melt rocks 60235 62295 and 67095 with reported ages of 3 9 ga are characterized by suprachondritic 187 os 188 os and hse ir ratios similar to the apollo 15 impact melt rocks and may also sample the imbrium impactor three lithic clasts from regolith breccias 60016 and 65095 also with 3 9 ga ages contain multiple impactor components of which the dominant composition is considerably more suprachondritic than those implicated for imbrium and serenitatis apollo 17 impactors the dominant composition recorded in these rocks was most likely inherited from a pre imbrium impactor consideration of composition versus age relations among lunar impact melt rocks reveals no discernable trend virtually all lunar impact melt rocks sampled by the apollo missions as well as meteorites are characterized by 187 os 188 os and hse ir ratios that when collectively plotted define linear trends ranging from chondritic to fractionated compositions the impact melt rocks with hse signatures within the range of chondritic meteorites are interpreted to have been derived from impactors that had hse compositions similar to known chondrite groups by contrast the impact melt rocks with non chondritic relative hse concentrations could not have been made by mixing of known chondritic impactors these signatures may instead reflect contributions from early solar system bodies with bulk chemical compositions that have not yet been sampled by primitive meteorites present in our collections alternately they may reflect the preferential incorporation of evolved metal separated from a fractionated planetesimal core pre 4 0 ga ages for at least some impactor components with both chondritic and fractionated hse raise the possibility that the bulk of the hse were added to the lunar crust prior to the later stage basin forming impacts such as imbrium and serenitatis as proposed by fischer godde and becker 2012 for this scenario the later stage basin forming impacts were more important with respect to mixing prior impactor components into melt rocks rather than contributing much to the hse budgets of the rocks themselves

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

a model for raw material management as a response to local and global environmental constraints abstract identifying the causes of visible changes in the archaeological record is one of the major goals of archaeological and anthropological research environmental shifts have been often suggested as one of the primary drivers of anthropological changes due to their impact on biotic resources considerably less attention has been given to changes in the availability of lithic raw materials if raw materials for tool production were available in constant predictable amounts then stability or slow shifts of technological strategies would be expected in the archaeological record however this is not the case in the iberian paleolithic even considering that some of the observed changes may be driven by culture setting or function in this paper we investigate the possibility of changes in raw material availability through the action of geodynamic processes which could have exerted selective pressures on the technological strategies employed by human populations this approach highlights the possible impact of environmental factors on human populations not just through food and habitat but also through geology the maritime climates of southwestern iberia are good candidates for such a connection because the region faced dramatic fluctuations between cold dry and warm wet periods during the late pleistocene with well documented impacts on biotic and geomorphic systems a link between environmental conditions and human tool making strategies is suggested by the correlation between cold climate during the last glacial maximum and an abrupt shift in lithic assemblages toward reliable technological strategies using the climatic conditions that define this reliable phase of upper paleolithic technology between 17 and 23 ka bp two climate driven scenarios are suggested for technological strategies in the iberian paleolithic a cold dry phase with restricted availability of raw materials favoring a technological shift towards reliability and a warm wet phase with greater raw material availability and a more flexible maintenance based lithic technology applying this reasoning to paleoenvironmental proxy records for southwestern iberia it is likely that numerous episodes of climate induced raw material stress occurred towards the end of the middle paleolithic and around the time of the middle upper paleolithic transition at present insufficient data exist to properly test this hypothesis but ongoing investigations at sites throughout portugal hold promise toward achieving this goal

on the significance of crater ages new ages for dellen sweden and araguainha brazil samples of a few grams in weight from the impact melt at the dellen crater sweden and the araguainha dome brazil were analyzed by rb sr and sm nd techniques for dellen pure labradorite orthopyroxene and glass separates from a clast free impact melt rock with holohyaline ground mass yield an internal rb sr isochron with 89 0 2 7 ma isr 0 83571 0 00007 2 compared to ar ar plateau ages of 102 3 2 ma and 109 6 2 0 ma published for total melt rocks various whole rock values not plotting on this rb sr isochron indicate primary variations in 87sr86sr over the melt sheet the age of the araguainha dome brazil is bracketed by the rb sr model age of 243 19 ma isr 0 7226 0 0005 for altered cordierite in the impact melt and by the internal rb sr isochron age of 449 9 ma isr 0 7140 0 0007 for an uplifted granite shock stage ib in melt rocks from both impact structures 143nd144nd was not homogenized during total rock melting sm nd data either scatter around the primary isochron araguainha or point to a partial resetting dellen this data array may be caused by tiny refractory ree rich inclusions in the main mineral phases which dominate the sm nd system of the impact melt rocks the significant difference between the new isochron age for dellen and ar ar ages show that the data base for analysis of periodicity in cratering record most probably lack precision and accuracy

the petrogenesis of impact basin melt rocks in lunar meteorite shisr 161 this study explores the petrogenesis of shisr 161 an immature lunar regolith breccia meteorite with low abundances of incompatible elements a feldspathic affinity and a significant magnesian component our approach was to identify all clasts 0 5 mm in size in a thin section characterize their mineral and melt components and reconstruct their bulk major and minor element compositions trace element concentrations in representative clasts of different textural and compositional types indicate that the clast inventory of shisr 161 is dominated by impact melts that include slowly cooled cumulate melt rocks with mafic magnesian mineral assemblages minor exotic components are incompatible element rich melt spherules and glass fragments and a gas associated spheroidal precipitate our hypothesis for the petrologic setting of shisr 161 is that the crystallized melt clasts originate from the upper 1 km of the melt sheet of a 300 to 500 km diameter lunar impact basin in the moon s feldspathic highlands this hypothesis is based on size requirements for cumulate impact melts and the incorporation of magnesian components that we interpret to be mantle derived the glassy melts likely formed during the excavation of the melt sheet assemblage by an impact that produced a 15 km diameter crater the assembly of shisr 161 occurred in a proximal ejecta deposit of this excavation event a later impact into this ejecta deposit then launched shisr 161 from the moon our geochemical modeling of remote sensing data combined with the petrographic and chemical characterization of shisr 161 reveals a preferred provenance on the moon s surface that is close to pre nectarian riemann fabry basin

rb sr analyses of apollo 16 melt rocks and a new age estimate for the imbrium basin lunar basin chronology and the early heavy bombardment of the moon rb sr model ages on 7 impact glass bombs and internal rb sr isochrons for two crystalline impact melt rocks from the apollo 16 collection have been determined the post cayley glass bombs with model ages between 4 75 0 45 ae and 3 97 0 08 ae can be classified according to their calculated single stage 87rb86sr i ratios 67728 67946 and 67627 8 point to a kreep free precursor terrain the descartes highlands whereas 63566 67567 67627 10 and 67629 are derived from the more heterogeneous cayley plains the very feldspar rich impact melt rock 65795 which is compositionally similar to the group of feldspathic microporphyritic melt breccias fm suite yields a crystallization age of 3 81 0 04 ae 2 87rb 1 42 11yr and isr of 69929 3 in the subophitic impact melt rock 60635 5 two ages were recorded one isochron with 3 87 0 02ae and isr of 0 69920 3 gives the crystallization age of a fine grained internal clast at 3 75 0 03 ae this fragment was incorporated into the host lithology of 60635 which is a member of the anorthositic noritic melt rock anmr group this group has a crystallization age of about 3 75 ae the anmr rocks and several samples of apollo 14 crystalline impact melt rocks belong to a suite of young crystalline impact melt rocks ranging in age from 3 71 to 3 81 ae these ages are in conflict with the canonical age of the imbrium event 3 85 ae it is argued that the young apollo 14 and 16 melt rocks cannot represent solid exotic fragments or melt splashes ejected from post imbrium local or distant craters instead these rocks are derived from coherent impact melt sheets of pre imbrian craters with diameters larger than 5 7 km they are interpreted as clasts of the fra mauro and cayley formation breccia deposits and therefore their ages are used as an upper limit for the age of the imbrium event we suggest that the imbrium basin and the related fra mauro and cayley formations were formed 3 77 0 02 ae ago and could be even as young as 3 75 ae as a consequence we adopt 3 92 0 03 ae 3 87 0 03 ae and 3 84 0 04 ae as ages for the nectaris serenitatis and crisium basins respectively in agreement with the relative crater densities measured on the ejecta blankets of these basins wilhelms 1984 the proposed age sequence leads to an average formation interval for the observed 12 13 nectarian basins of 7 to 14 m y leaving 30 pre nectarian basins of unknown age these facts suggest that there is no late terminal lunar cataclysm in the sense of a culmination of the lunar impact rate at 3 8 ae ago rather the observations are compatible with a steeply and steadily decreasing flux of impactors hartmann 1980 in the sense of an early heavy bombardment which started at the time of the moon s accretion and terminated around 3 75 ae ago

palaeoenvironmental forcing during the middle upper palaeolithic transition in central western portugal article i nfo geoarchaeological analysis of the middle and upper palaeolithic record preserved in cave rock shelter and open air sites in the northern sector of the meso cenozoic of the western iberian peninsula margin portugal reveals several disconformities erosive unconformities hiatuses and surface stabilization phases a recurrent disconformity dated to ca 29 500 32 000 cal yr bp in the time range of heinrich event 3 must correspond to a main erosive event related to the impacts of climate change on the landscape including a reduction in vegetation cover and altered precipitation patterns with the consequent accelerated down cutting by stream systems slope reactivation and endokarstic reorganisation causing the erosion of sediments and soils accumulated in cave rock shelter and open air sites these processes create a preservation bias that may explain why early upper palaeolithic finds in primary deposition context remains exceptional in the carbonate areas of central western portugal and possibly elsewhere in the other places of iberia the impact of such site formation processes must therefore be duly considered in interpretations of the current patchy and scarce archaeological record of the middle upper palaeolithic transition in south western

40ar 39ar age spectra of apollo 15 impact melt rocks by laser step heating and their bearing on the history of lunar basin formation we have obtained 26 high resolution 16 51 steps 40ar 39ar age spectra using a continuous laser system on submilligram fragments of recrystallized melt and single crystal plagioclase clasts from 12 apollo 15 impact melt rocks collected at the apennine front where the imbrium and serenitatis basins intersect these melt rocks represent a wide range of compositions and at least half a dozen different impacts six of the melt rocks have reproducible intermediate temperature plateaus over 40 or more of the 39ar released the plateaus are interpreted as crystallization impact ages and much of the non plateau behavior is attributable to recoil samples 15294 6 21 15304 7 69 15314 26 156 15357 15 and 15359 12 have mean 40ar 39ar plateau ages that are statistically indistinguishable and fall within the narrow range 3852 14 2 ma to 3870 12 ma with a weighted mean of 3865 5 ma sample 15356 9 has a mean plateau age of 3836 11 ma and may represent a distinctly younger impact a seventh sample 15314 30 158 has a peculiar but reproducible double plateau a low t one at 3873 9 ma which we think records the crystallization age and a high t one of 3831 10 ma which we interpret as an experimental 39ar recoil artifact four of the remaining melt rocks 15308 9 15414 2 37 15436 2 15445 253 have complex 40ar 39ar age spectra that indicate that they either formed in or were disturbed by impacts that occurred 3850 ma but did not completely reset the k ar isotopic system sample 15414 3 36 is different its spectrum may represent release mainly from clasts that were not well degassed in a melt event at 3870 ma the melt phase contains little potassium because most of the apennine front material must be coeval with or predate formation of the imbrium basin it seems likely that the imbrium impact is no older than 3870 ma and probably no older than 3836 ma so far there is no convincing evidence in the lunar record for melt producing impacts such as basin formation older than about 3 9 ga

cratering history and lunar chronology the moon is exceptional and important because it is the only planetary body besides the earth for which we have both a detailed stratigraphic history and datable rock samples that can be related to specific geomorphologic units fig 5 1 the moon has preserved much of its magmatic and impact record of at least the last 4 billion years while its endogenic history is of great interest for the fundamentals of planetary interiors and surfaces the moon has become a calibration plate for the cratering record of the earth moon system and by extrapolation of the entire inner solar system if one assumes a heliocentric origin for impactor populations these populations range from asteroids through long and short period comets to interplanetary dust and cover a size range from hundreds of kilometers to micrometers figure 5 1 telescopic view of the nearside of the earth s moon with landing sites of the apollo and luna missions this chapter reviews the presently available data sets in support of this paradigmatic assumption as follows 1 the phenomenology of lunar impact craters 2 the terrestrial record of the impact cratering process and the interpretation of terrestrial impactites as far as this ground truth is relevant for the interpretation of lunar impact craters and datable lunar impact breccias and melt rocks 3 the theory and numerical simulation of the cratering process and the characteristics of the earth moon crossing population of impactors asteroids and comets 4 the principles of relative age dating of lunar surface units and the general lunar stratigraphy 5 the stratigraphic significance and ages of lunar samples impactites and basalts and based on this data set the absolute ages of lunar surface units 6 the cratering rate of the moon as a function of time and 7 the time calibration of this cratering rate based on the

isotopic studies of ferroan anorthosite 62236 a young lunar crustal rock from a light rare earth element depleted source isotopic analyses of mineral fractions and whole rocks from the ferroan anorthosite 62236 yield a sm nd isochron with an age of 4 29 0 06 ga and an initial end143 value of 3 1 0 9 we have also measured end142 anomalies of 0 25 on two fractions of 62236 these values are higher than the value of 0 1 predicted if 62236 was derived from a chondritic source at 4 29 ga but are consistent with the positive initial end143 value the sm nd isotopic composition of 62236 has been modified by the capture of thermal neutrons such that the 147sm 144nd 143nd 144nd and 142nd 144nd ratios measured on the mineral fractions and whole rocks must be corrected the corrections do not significantly alter the sm nd isotopic results determined on 62236 despite the fact that the ar ar and rb sr isotopic systematics of 62236 have been reset by impact metamorphism at 3 93 0 04 ga the sm nd systematics appear to have been unaffected the sm nd isotopic systematics of 62236 provide several constrains on models of lunar crustal differentiation provided they have not been reset since crystallization first the relatively young age of 62236 as well as the old ages determined on several crustal plutonic rocks of the mg suite require multiple sources of magmas on the moon very early in its history second positive end143 values determined on all analyzed ferroan anorthosites suggest that they were derived from sources depleted in light rare earth elements and third models based on initial end143 and present day end142 values suggest that the source of 62236 was depleted in light rare earth elements at 4 46 ga in order to reconcile these observations with the lunar magma ocean model 1 the magma ocean must have existed for a very short period of time and may have had a sub chondritic nd sm ratio and 2 the youngest ferroan anorthosites such as 62236 cannot be cumulates from the magma ocean but must form by other processes

feldspathic lunar meteorites and their implications for compositional remote sensing of the lunar surface and the composition of the lunar crust we present new compositional data for six feldspathic lunar meteorites two from cold deserts yamato 791197 and 82192 and four from hot deserts dhofar 025 northwest africa 482 and dar al gani 262 and 400 the concentrations of feo or al2o3 and th or any other incompatible element together provide first order compositional information about lunar polymict samples breccias and regoliths and regions of the lunar surface observed from orbit concentrations of both elements on the lunar surface have been determined from data acquired by orbiting spacecraft although the derived concentrations have large uncertainties and some systematic errors compared to sample data within the uncertainties and errors in the concentrations derived from orbital data the distribution of feo and th concentrations among lunar meteorites which represent 18 source regions on the lunar surface is consistent with that of 18 random samples from the surface approximately 11 of the lunar meteorites are low feo and low th breccias consistent with large regions of the lunar surface particularly the northern farside highlands almost all regoliths from apollo sites on the other hand have larger concentrations of both elements because they contain fe rich volcanic lithologies from the nearside maria and th rich lithologies from the high th anomaly in the northwestern nearside the feldspathic lunar meteorites thus offer our best estimate of the composition of the surface of the feldspathic highlands and we provide such an estimate based on the eight most well characterized feldspathic lunar meteorites the variable but high on average mg fe ratio of the feldspathic lunar meteorites compared to ferroan anorthosites confirms a hypothesis that much of the plagioclase at the surface of the feldspathic highlands is associated with high mg fe feldspathic rocks such as magnesian granulitic breccia not ferroan anorthosite geochemically the high mg fe breccias appear to be unrelated to the mafic magnesian suite rocks of the apollo collection models for the formation of the upper lunar crust as a simple flotation cumulate composed mainly of ferroan anorthosite do not account for the complexity of the crust as inferred from the feldspathic lunar meteorites

an extremely low source in the moon uthpb smnd rbsr and isotopic systematics and age of lunar meteorite asuka 881757 abstract we have undertaken u th pb sm nd rb sr and 40 ar 39 ar isotopic studies on asuka 881757 a coarse grained basaltic lunar meteorite whose chemical composition is close to low ti and very low ti vlt mare basalts the pb pb internal isochron obtained for acid leached residues of separated mineral fractions yields an age of 3940 28 ma which is similar to the u pb 3850 150 ma and th pb 3820 290 ma internal isochron ages the sm nd data for the mineral separates yield an internal isochron age of 3871 57 ma and an initial 143 nd 144 nd value of 0 50797 10 the rb sr data yield an internal isochron age of 3840 32 ma 87 rb 1 42 10 11 yr 1 and a low initial 87 sr 86 sr ratio of 0 69910 2 the 40 ar 39 ar age spectra for a glass fragment and a maskelynitized plagioclase are relatively flat and give a weighted mean plateau age of 3798 12 ma we interpret these ages to indicate that the basalt crystallized from a melt 3 87 ga ago the sm nd age and an impact event disturbed the rb sr system and completely reset the k ar system at 3 80 ga the slightly higher pb pb age compared to the sm nd age could be due to the secondary pb from terrestrial and or lunar surface pb contamination that remained in the residues after acid leaching alternatively the following interpretation is also possible the meteorite crystallized at 3 94 ga the pb pb age and the sm nd rb sr and k ar systems were disturbed by an impact event at 3 80 ga the crystallization age obtained here is older than those reported for low ti basalts 3 2 3 5 ga and for vlt basalts 3 4 ga but similar to ages of some mare basalts indicating that the basalt may have formed from a magma related to a basin forming event imbrium the age span for vlt basalts from different sampling sites suggest that they were erupted over a wide area during an interval of at least 500 million years the impact event that thermally reset the k ar system of asuka 881757 must have been post imbrium perhaps orientale in age the lead isotopic composition of asuka 881757 is nonradiogenic compared with typical apollo mare basalts and the estimated 238 u 204 pb value for the basalt source is 10 3 this source value is the lowest so far measured for lunar rocks a large positive nd value 7 4 0 5 and the time averaged 147 sm 144 nd ratio for the basalt source are similar to those for some apollo 12 15 and 17 basalts suggesting a lree depleted mantle which is consistent with the global magma ocean hypothesis the u th pb sm nd and rb sr data on asuka 881757 suggest that the basalt was derived from a low u pb low rb sr and high sm nd source region mainly composed of olivine and orthopyroxene with minor amounts of plagioclase or clinopyroxene and with sulfides enriched in volatile chalcophile elements the basalt source may be deep in origin and different in chemistry from those previously estimated from studies of apollo and luna mare basalts indicating heterogeneous sources for mare basalts

the bombardment history of the moon as recorded by 40 ar 39 ar chronology new petrography and 40ar 39ar ages have been obtained for 1 3 mm sized rock fragments from apollo 16 station 13 soil 63503 north ray crater ejecta and chips from three rocks collected by apollo 16 and apollo 17 missions selection of these samples was aimed at the old 40ar 39ar ages to understand the early history of the lunar magnetic field and impact flux fifteen samples were studied including crustal material polymict feldspathic fragmental breccias and impact melts the impact ages obtained range between approximately 3 3 and 4 3 billion years ga polymict fragmental breccia 63503 1 exhibits the lowest signs of recrystallization observed and a probable old relic age of 4 547 0 027 the plateau age of 4 293 0 044 ga obtained for impact melt rock 63503 13 represents the oldest known age for such a lithology possibly this age represents the minimum age for the south pole aitken spa basin in agreement with literature data these results show that impact ages 3 9 ga are found in lunar rocks especially within soil 63503 impact exhumation of deep seated warm crustal material onto the lunar surface is considered to explain the common 4 2 ga ages obtained for weakly shocked samples from soil 63503 and apollo 17 this would directly imply that one or more basin forming events occurred at that time some rock fragments showing none to limited petrologic features indicate thermal annealing these rocks may have lost ar while resident within the hot ejecta of a large basin concurrent with previous studies these results lead us to advocate for a complex impact flux in the inner solar system during the initial approximately 1 3 ga

the hadley apennine kreep basalt igneous province abstract we have studied 27 kreep basalt fragments in six thin sections of samples collected from four apollo 15 stations based on local geology and regional remote sensing data these samples represent kreep basalt lava flows that lie beneath the younger local apollo 15 mare basalts and under other mare flows north of the apollo 15 site some of these rocks were deposited at the site as ejecta from the large craters aristillus and autolycus kreep basalts in this igneous province have a volume of 103 2 104 km3 mineral and bulk compositional data indicate that the erupted magmas had mg 100 molar mg mg fe up to 73 corresponding to orthopyroxene rich interior source regions with mg up to 90 minor element variations in the parent magmas of the kreep basalts inferred from compositions of the most magnesian pyroxene and most calcic plagioclase in each sample indicate small but significant differences in the concentrations of minor elements and mg reflecting variations in the composition of lower crustal or mantle source regions and or different amounts of partial melting of those source regions

homogeneous impact melts produced by a heterogeneous target sr nd isotopic evidence from the popigai crater russia the 35 7 0 2 ma old popigai crater siberia with a diameter of about 100 km is one of the best preserved large terrestrial impact structures the heterogeneous target at the impact site consists of archean to lower proterozoic metamorphic rocks of the crystalline basement upper proterozoic quartzites and other clastic deposits as well as cambrian to cretaceous clastic sediments and sedimentary rocks including carbonate rocks moreover proterozoic and permo triassic dolerite dykes are found in the target area we report major element sr and nd isotope data for 13 of these target rocks and for various types of impactites the 15 analysed impactite samples include tagamites impact melt rocks suevites and impact glass from small veins furthermore two impact breccias and two impact glass coated gneiss bombs were analysed we discuss the relation of these impactites to the target lithologies and evaluate on the basis of literature data the relation of microkrystites and associated microtektites in upper eocene sediments to the popigai event the impactites have sio2 abundances ranging from 59 to 66 wt and show significant variations in the content of fe ca and ti they have present day 87sr 86sr ratios between 0 7191 and 0 7369 their sr model ages tsrur range from 1 9 to 2 3 ga the 143nd 144nd ratios for the impactite samples cluster between 0 5113 and 0 5115 the nd model ages tndchur range from 1 9 to 2 1 ga in an echur nd eur sr diagram the impactites and upper eocene microkrystites and associated microtektites plot in a field delimited by popigai target lithologies the impactites are restricted to the field of crystalline basement rocks and upper proterozoic quartzites but they show different isotopic signatures in different crater sectors impactites and upper eocene microkrystites plot in different only partly overlapping clusters the leucocratic microkrystites and microtektites have a higher affinity to the post proterozoic rocks in the target area than the impactites seemingly the melanocratic microkrystites originated mostly from crystalline basement this data alignment supports the assumption that popigai is the source crater for all three types of ejecta for the first time clear relations are established of the geochemically variable upper eocene microkrystites and associated microtektites to specific target lithologies at popigai crater finally the observed range in sr and nd isotope parameters determined for impact melt lithologies that originated during the popigai event show a much higher variability than known from other craters this result indicates that mixing of impact melt which later formed tagamite sheets and glass particles in different impact breccias was incomplete at the time of ejecta dispersal