new relationships between vs thickness of sediments and resonance frequency calculated by the h v ratio of seismic noise for the cologne area germany noise measurements were carried out in the cologne area germany and the resonance frequency of each site was estimated from the main peak in the spectral ratio between the horizontal and vertical component for 32 of these sites the thickness of the sedimentary cover was known from boreholes and a clear correlation between resonance frequency and sediment thickness was observed a formula that correlates cover thickness with frequency of the main peak in the horizontal to vertical spectral ratio was derived in addition a best fitting shear wave velocity distribution with depth vs z as well as a relationship between average shear wave velocity vs and thickness of the sedimentary cover was calculated by using all of the noise measurements and applying the derived relationships we obtained a subsoil classification for the cologne area

constraints on martian differentiation processes from rbsr and smnd isotopic analyses of the basaltic shergottite que 94201 isotopic analyses of mineral leachate and whole rock fractions from the martian shergottite meteorite que 94201 yield rb sr and sm nd crystallization ages of 327 12 and 327 19 ma respectively these ages are concordant although the isochrons are defined by different fractions within the meteorite comparison of isotope dilution sm and nd data for the various que 94201 fractions with in situ ion microprobe data for que 94201 minerals from the literature demonstrate the presence of a leachable crustal component in the meteorite this component is likely to have been added to que 94201 by secondary alteration processes on mars and can affect the isochrons by selectively altering the isotopic systematics of the leachates and some of the mineral fractions initial 87sr 86sr of 0 701298 14 nd143 of 47 6 1 7 and whole rock nd142 of 0 92 0 11 indicate that que 94201 was derived from a source that was strongly depleted in 87rb 86sr and enriched in 147sm 144nd early in its history modeling demonstrates that the sm nd isotopic compositions of que 94201 can be produced by either four episodes of melting at 327 ma of cumulates crystallized from a magma ocean at 4 525 ga or five episodes of melting of an initially solid mars at 4 525 ga and 327 ma the neodymium isotopic systematics of que 94201 are not consistent with significant melting between 4 525 ga and 327 ma the estimated timing of these events is based on initial neodymium isotopic ratios and is independent of differentiation of the que 94201 parental magma rb sr based partial melting models are unable to reproduce the composition of que 94201 using the same model parameters employed in the sm nd based models implying a decoupling of rb sr and sm nd isotopic systems the initial decoupling of the two isotopic systems can be attributed to either cumulate or crust formation processes which are able to more efficiently fractionate rb from sr compared to sm from nd the fact that all martian meteorites analyzed so far define a rb sr whole rock isochron age of 4 5 ga suggests that virtually all rb was partitioned out of their mantle source regions and into either fractionated residual liquids trapped in the cumulate pile or into the crust at that time thus the martian mantle cumulates and restites are not expected to evolve past 87sr86sr of 0 700 and could not have been significantly enriched in incompatible elements by crustal recycling processes all martian meteorites have initial 87sr86sr values that are higher than 0 700 and are therefore likely to be produced by mixing between evolved crustal like and depleted mantle reservoirs the absence of crustal recycling processes on mars may preserve the geochemical evidence for decoupling of the rb sr and sm nd isotopic systems underscoring one of the fundamental differences between geologic processes on mars and the earth

petrology and chemistry of the new shergottite dar al gani 476 in 1998 dar al gani dag 476 was found in the libyan desert the meteorite is classified as a basaltic shergottite and is only the 13th martian meteorite known to date it has a porphyritic texture consisting of a fine grained groundmass and larger olivines the groundmass consists of pyroxene and feldspathic glass minor phases are oxides and sulfides as well as phosphates the presence of olivine orthopyroxene and chromite is a feature that dag 476 has in common with lithology a of elephant moraine eet a79001 however in dag 476 these phases appear to be early phenocrysts rather than xenocrysts shock features such as twinning mosaicism and impact melt pockets are ubiquitous terrestrial weathering was severe and led to formation of carbonate veins following grain boundaries and cracks with a molar mgo mgo feo of 0 68 dag 476 is the most magnesian member among the basaltic shergottites compositions of augite and pigeonite and some of the bulk element concentrations are intermediate between those of lherzolitic and basaltic shergottites however major elements such as fe and ti as well as lree concentrations are considerably lower than in other shergottites noble gas concentrations are low and dominated by the mantle component previously found in chassigny a component similar to that representing martian atmosphere is virtually absent the ejection age of 1 35 0 10 ma is older than that of eeta79001 and could possibly mark a distinct ejection dar al gani 476 is classified as a basaltic shergottite based on its mineralogy it has a fine grained groundmass consisting of clinopyroxene pigeonite and augite feldspathic glass and chromite ti chromite ilmenite sulfides and whitlockite isolated olivine and single chromite grains occur in the groundmass orthopyroxene forms cores of some pigeonite grains shock features such as shock twinning mosaicism cracks and impact melt pockets are abundant severe weathering in the sahara led to significant formation of carbonate veins crosscutting the entire meteorite dar al gani 476 is distinct from other known shergottites chemically it is the most magnesian member among known basaltic shergottites and intermediate in composition for most trace and major elements between iherzolitic and basaltic shergottites unique are the very low bulk ree element abundances the ci normalized abundances of lrees are even lower than those of iherzolitic shergottites the overall abundance pattern however is similar to that of que 94201 textural evidence indicates that orthopyroxene as well as olivine and chromite crystallized as phenocrysts from a magma similar in composition to that of bulk dag 476 whether such a magma composition can be a shergottite parent melt or was formed by impact melting needs to be explored further at this time it cannot entirely be ruled out that these phases represent relics of disaggregated xenoliths that were incorporated and partially assimilated by a basaltic melt although the texture does not support this possibility trapped noble gas concentrations are low and dominated by a chassigny like mantle component virtually no martian atmosphere was trapped in dag 476 whole rock splits the exposure age of 1 26 0 09 ma is younger than that of most shergottites and closer to that of eeta79001 the ejection age of 1 35 0 1 ma could mark another distinct impact event

pb evolution in the martian mantle abstract the initial pb compositions of one enriched shergottite one intermediate shergottite two depleted shergottites and nakhla have been measured by secondary ion mass spectrometry sims these values in addition to data from previous studies using an identical analytical method performed on three enriched shergottites alh 84001 and chassigny are used to construct a unified and internally consistent model for the differentiation history of the martian mantle and crystallization ages for martian meteorites the differentiation history of the shergottites and nakhla chassigny are fundamentally different which is in agreement with short lived radiogenic isotope systematics the initial pb compositions of nakhla chassigny are best explained by the late addition of a pb enriched component with a primitive non radiogenic composition in contrast the pb isotopic compositions of the shergottite group indicate a relatively simple evolutionary history of the martian mantle that can be modeled based on recent results from the sm nd system the shergottites have been linked to a single mantle differentiation event at 4504 ma thus the shergottite pb isotopic model here reflects a two stage history 1 pre silicate differentiation 4504 ma and 2 post silicate differentiation to the age of eruption as determined by concordant radiogenic isochron ages the values 238u 204pb obtained for these two different stages of pb growth are 1 of 1 8 and a range of 2 from 1 4 4 7 respectively the 1 value of 1 8 is in broad agreement with enstatite and ordinary chondrites and that proposed for proto earth suggesting this is the initial value for inner solar system bodies when plotted against other source radiogenic isotopic variables sri 187 os e 143 nd and e 176 hf the second stage mantle evolution range in observed mantle values display excellent linear correlations r 2 0 85 and represent a spectrum of martian mantle mixing end members depleted intermediate enriched

hvnsr survey in historical downtown l aquila central italy site resonance properties vs subsoil model abstract this paper presents and discusses the results of a detailed seismic noise survey carried out in historical downtown l aquila after the earthquake of 6 apr 2009 m w 6 3 seismic noise data were interpreted through numerical simulations with the support of a subsoil model characterised by four main units from the top to the bottom i soft soils anthropogenic filling material and terra rossa ii l aquila breccia iii l aquila pelite and sand and iv the meso cenozoic carbonate bedrock the hvnsr analysis permitted the identification of two peaks f0 and f1 nearly everywhere f0 0 4 0 7 hz is due to the superposition of l aquila pelite and sand on the carbonate bedrock at 200 300 m below ground level f1 3 15 hz is caused by shallower impedance contrasts due to 3 20 m thick soft sediments overlying l aquila breccia and by the weathering profile of l aquila breccia a numerical simulation was carried out for three different models characterised by i lithology lateral variation in the first 100 m of thickness due to the substitution from north to south of l aquila breccia with l aquila pelite and sand ii the thickness variation of soft top soil onto l aquila breccia and iii the presence of a weathered layer in the upper part of the l aquila breccia the numerical simulation results fit the experimental seismic noise data a spatial correlation between areal distributions of severe damages with that of f1 resonance frequency is found so it follows that the severe damage during the l aquila earthquake of 6 apr 2009 could have been caused by the seismic local effect of the soft top soil and the weathering profile of l aquila breccia

ambient noise measurements for preliminary site effects characterization in the urban area of florence italy abstract environmental noise measurements and borehole data were used for a preliminary seismic characterization of the plio quaternary sedimentary basin underlying the city of florence italy an extensive survey of ambient vibrations was conducted by using the seismic noise horizontal to vertical h v spectral ratio technique hvsr to map the fundamental resonance frequency of the sedimentary cover in order to use this information to infer main features of the basin subsurface geometry an estimate of the s wave velocity profile in the sediment layer was obtained from array noise recordings along with information on resonance frequency and direct measurements of the sediment thickness available at 23 borehole sites a first order reconstruction of the seismic bedrock topography in the area was provided which shows a good consistency with available geological log data from these pieces of information a preliminary soil classification of the whole area was attempted in order to identify situations where possible seismic amplification effects are expected during future earthquakes and where more accurate investigations are needed to parameterize the local seismic response

a petrogenetic model for the origin and compositional variation of the martian basaltic meteorites the major element trace element and isotopic compositional ranges of the martian basaltic meteorite source regions have been modeled assuming that planetary differentiation resulted from crystallization of a magma ocean the models are based on low to high pressure phase relationships estimated from experimental runs and estimates of the composition of silicate mars from the literature these models attempt to constrain the mechanisms by which the martian meteorites obtained their superchondritic cao al2o3 ratios and their source regions obtained their parent daughter 87 rb 86 sr 147 sm 144 nd and 176 lu 177 hf ratios calculated from the initial sr nd and hf isotopic compositions of the meteorites high pressure experiments suggest that majoritic garnet is the liquidus phase for mars relevant compositions at or above 12 gpa early crystallization of this phase from a martian magma ocean yields a liquid characterized by an elevated cao al2o3 ratio and a high mg olivine pyroxene garnet dominated cumulates that crystallize subsequently will also be characterized by superchondritic cao al2o3 ratios melting of these cumulates yields liquids with major element compositions that are similar to calculated parental melts of the martian meteorites furthermore crystallization models demonstrate that some of these cumulates have parent daughter ratios that are similar to those calculated for the most incompatible element depleted source region i e that of the meteorite queen alexandra que 94201 the incompatible element abundances of the most depleted que 94201 like source region have also been calculated and provide an estimate of the composition of depleted martian mantle the incompatible element pattern of depleted martian mantle calculated here is very similar to the pattern estimated for depleted earth s mantle melting the depleted martian mantle composition reproduces the abundances of many incompatible elements in the parental melt of que 94201 e g ba th k p hf zr and heavy rare earth elements fairly well but does not reproduce the abundances of rb u ta and light rare earth elements the source regions for meteorites such as shergotty are successfully modeled as mixtures of depleted martian mantle and a late stage liquid trapped in the magma ocean cumulate pile melting of this hybrid source yields liquids with major element abundances and incompatible element patterns that are very similar to the shergotty bulk rock

chronology and petrogenesis of young achondrites shergotty zagami and alha77005 late magmatism on a geologically active planet a study was undertaken to determine the chronology petrogenesis and relationships among the shergottites shergotty and zagami and the unique achondrite alha77005 these meteorites are the product of a variety of complex processes petrogenesis chondrite normalized abundance patterns of shergotty and zagami are very similar and show pronounced depletions of both the light ree la nd and heavy ree dy lu relative to sm gd these characteristic depletions are even more pronounced for alha77005 the light ree depletion is qualitatively consistent with the presence of cumulus pyroxene and or olivine in these meteorites but trace element models show that the parental magmas of all three meteorites were probably also light ree depleted both trace element model calculations and combined rb sr and sm nd isotopic systematics show that the meteorites could not have been co magmatic nor can alha77005 be representative of the source material of the shergottites light ree depletion of the parental magmas also implies light ree depletion of the source material the sm nd systematics of the shergottites require a time averaged sub chondritic light ree enriched sm nd ratio since 4 6 ae ago the sm nd systematics of alha77005 permit a time averaged super chondritic light ree depleted sm nd ratio if its crystallization age is less than tice 0 72 ae chronology rb sr internal isochrons for all three meteorites and a sm nd internal isochron for zagami are concordant at 180 myr 39ar 40ar plateau ages of shergotty and zagami maskelynite are 250 260 myr these ages apparently reflect resetting of these isotopic systems by shock metamorphism which converted the feldspar to maskelynite the concordance of these ages suggests a single shock event during which the meteorites were in close physical proximity the time of this event is most precisely given by the rb sr age of 180 4 myr for zagami the crystallization ages of the meteorites were not precisely determined extreme upper limits are determined by sm nd model ages relative to an eucrite initial 143nd144nd 0 505835 at 4 6 ae ago these model ages for shergotty zagami and alha77005 are 3600 3500 and 2850 myr respectively the sm nd whole rock age of 1340 60 myr for the three meteorites gives the crystallization age if the sm nd ratios of the precursor materials were always the same we consider this 1340 myr age as a best estimate upper limit best estimate lower limits for shergotty and zagami are taken from the average 39ar 40ar ages of 1200 and 900 myr of pyroxene separates the average 39ar 40ar age of a whole rock sample of alha77005 was 1600 myr and can be partitioned between a low temperature feldspar phase and a high temperature olivine pyroxene inclusions phase the average apparent 39ar 40ar age of the low temperature phase is 1050 myr which is chosen as the best estimate lower limit to the age the crystallization ages of shergotty zagami and alha77005 probably lie within the ranges of 1200 1300 900 1300 and 1000 1300 myr respectively the rb sr whole rock age of 4400 400 myr and single stage babi model ages of 4800 5100 myr are interpreted as reflecting differentiation of the parent body at 4600 myr ago the complex geochemical and isotopic evolution recorded by these meteorites suggests a geologically active parent body capable of sustaining melting at two or more epochs in its history

evidence for extremely rapid magma ocean crystallization and crust formation on mars the formation of a primordial crust is a critical step in the evolution of terrestrial planets but the timing of this process is poorly understood the mineral zircon is a powerful tool for constraining crust formation because it can be accurately dated with the uranium to lead u pb isotopic decay system and is resistant to subsequent alteration moreover given the high concentration of hafnium in zircon the lutetium to hafnium 176lu 176hf isotopic decay system can be used to determine the nature and formation timescale of its source reservoir1 3 ancient igneous zircons with crystallization ages of around 4 430 million years myr have been reported in martian meteorites that are believed to represent regolith breccias from the southern highlands of mars4 5 these zircons are present in evolved lithologies interpreted to reflect re melted primary martian crust 4 thereby potentially providing insight into early crustal evolution on mars here we report concomitant high precision u pb ages and hf isotope compositions of ancient zircons from the nwa 7034 martian regolith breccia seven zircons with mostly concordant u pb ages define 207pb 206pb dates ranging from 4 476 3 0 9 myr ago to 4 429 7 1 0 myr ago including the oldest directly dated material from mars all zircons record unradiogenic initial hf isotope compositions inherited from an enriched andesitic like crust extracted from a primitive mantle no later than 4 547 myr ago thus a primordial crust existed on mars by this time and survived for around 100 myr before it was reworked possibly by impacts4 5 to produce magmas from which the zircons crystallized given that formation of a stable primordial crust is the end product of planetary differentiation our data require that the accretion core formation and magma ocean crystallization on mars were completed less than 20 myr after the formation of the solar system these timescales support models that suggest extremely rapid magma ocean crystallization leading to a gravitationally unstable stratified mantle which subsequently overturns resulting in decompression melting of rising cumulates and production of a primordial basaltic to andesitic crust6 7

estimation of q for long period 2 sec waves in the los angeles basin we simulate 0 to 0 5 hz 3d wave propagation through the southern california earthquake center seismic velocity reference model version 2 for the 1994 northridge earthquake in order to examine the effects of anelastic attenuation and amplification within the near surface sediments we use a fourth order finite difference staggered grid method with the coarse grained frequency independent anelastic scheme of day and bradley 2001 and a variable slip distribution from kinematic inversion for the northridge earthquake we find that the near surface material with s wave velocity v s as low as 500 m sec significantly affects the long period peak ground velocities compared with simulations in which the s wave velocity is constrained to 1 km sec and greater anelastic attenuation also has a strong effect on ground motion amplitudes reducing the predicted peak velocity by a factor of up to 2 5 relative to lossless simulations our preferred q model is q s v s 0 02 v s in meters per second for v s less than 1 2 km sec and much larger q s v s 0 1 v s in meters per second for layers with higher velocities the simple model reduces the standard deviation of the residuals between synthetic and observed natural log of peak velocity from 1 13 to 0 26 relative to simulations for the lossless case the anelastic losses have their largest effect on short period surface waves propagating in the los angeles basin which are principally sensitive to q s in the low velocity near surface sediments of the basin the low frequency ground motion simulated here is relatively insensitive to q p as well as to the values of q s at depths greater than roughly that of the 2 km sec s wave velocity isosurface

guelb el ahmar bathonian anoual syncline eastern morocco first continental flora and fauna including mammals from the middle jurassic of africa abstract we report the discovery in mesozoic continental red beds of anoual syncline morocco of the new guelb el ahmar gea fossiliferous sites in the bathonian anoual formation they produced one of the richest continental biotic assemblages from the jurassic of gondwana including plants invertebrates and vertebrates both the sedimentological facies and the biotic assemblage indicate a lacustrine depositional environment the flora is represented by tree trunks three families pollen 13 species five major clades and charophytes it suggests local forests and humid non arid conditions the vertebrate fauna is dominated by microvertebrates recovered by screening washing it is rich and diverse with at least 29 species of all major groups osteichthyans lissamphibians chelonians diapsids mammals except chondrichthyans it includes the first mammals discovered in the middle jurassic of arabo africa the gea sites yielded some of the earliest known representatives of osteoglossiform fishes albanerpetontid and caudate amphibians squamates scincomorphans anguimorphan cladotherian mammals and likely choristoderes the choristoderes if confirmed are the first found in gondwana the albanerpetontid and caudatan amphibians are among the very few known in gondwana and the anguimorph lizard is the first known from the mesozoic of gondwana mammals amphitheriida cf dryolestida remain poorly known but are the earliest cladotherians known in gondwana the gea biotic assemblage is characterized by the presence of pangean and laurasian especially european taxa and quasi absence of gondwanan taxa the paleobiogeographical analysis suggests either a major fossil bias in gondwana during the middle jurassic and an overall vicariant pangean context for the gea assemblage or alternatively noticeable laurasian european affinities and north south dispersals the close resemblance between the bathonian faunas of gea and britain is remarkable even in a pangean context the similarity between the local anoual syncline guelb el ahmar and ksar metlili faunas raises questions on the berriasian age of the latter

vs30 estimates using constrained h v measurements abstract most seismic codes adopt the average shear wave velocity as a key parameter in the first 30 m of subsoil v s 30 estimates of v s 30 are therefore required for both large and small scale seismic microzonation we propose a technique to measure the v s 30 based on the horizontal to vertical spectral ratio h v of microtremor recorded at a single station the h v is fitted with a synthetic curve using the independently known thickness of a superficial layer of the subsoil as a constraint the proposed procedure consists of three steps 1 identify the depth of a shallow stratigraphic horizon from independent geotechnical data 2 identify its corresponding h v marker and 3 use it as a constraint to fit the experimental h v curve with the theoretical one the synthetic h v curve is calculated by assuming a stratified one dimensional 1d soil model and a tremor wave field from distant random sources that are composed of rayleigh and love waves this technique has been validated on different geological settings following a triple check procedure 1 the theoretical rayleigh wave phase velocity dispersion curves calculated for the model derived from the h v fit were compared to the experimental curves measured with the 2d extended spatial autocorrelation esac method and the 1d refraction microtremor remi array surveys 2 the v s profiles and 3 the v s 30 estimates obtained by the proposed technique were compared to those obtained by using the latter array techniques finally the inferred stratigraphy was compared to the geological model the proposed technique is not meant to provide accurate v s profiles but has the potential to provide v s 30 estimates that are coherent with those measured through esac and remi and to satisfy law requirements furthermore the h v is found to be capable in detecting deviations from 1d subsoil geometry over the length of a few meters the correctness of which was confirmed by direct drilling

magma ocean formation due to giant impacts current understanding of the last stages of planetary accretion suggests that mass and energy accumulation are dominated by a few large impacts an important thermal consequence of such impacts is melting and formation of a large melt pond if the planet s isostatic adjustment time scale is short compared to the magma pond s cooling time scale the melt may be extruded onto the surface and form a magma ocean of approximately uniform depth although a giant impact striking at 10 15 km s 1 deposits enough energy to melt the entire planet the distribution of that energy is important in determining the thermal outcome of the collision we examine the thermal effects of giant impacts by estimating the melt volume generated by the initial shock wave and corresponding magma ocean depths additionally we examine the effects of the planet s initial temperature on the generated melt volume the hugoniot curve plotted in pressure entropy space is used to determine the shock pressure required to completely melt the material for room temperature dunite this pressure is about 150 gpa and the partial melt region is narrow for dunite initially at the solidus temperature this pressure is about 115 gpa the partial melt region extends throughout the planet once the melting pressure is known an impact melting model based on the second hugoniot equation the linear shock particle velocity relationship and the empirical particle velocity distance relationship is used to estimate the radial distance melting occurred from the impact site once the distance is found the melt region s geometry determines the associated melt volume partial melt volume is also estimated the melt fraction that is not excavated during crater formation is estimated and magma ocean depths resulting from both excavated and retained melt are calculated the model is also used to estimate the fraction of a planet melted by the initial shock wave nominal conditions of the moon forming giant impact projectile planet mass 0 14 impact speed 15 km s 1 generate melting of 30 65 of the planet depending on its initial temperature whole planet melting requires projectile planet mass ratios of 0 4 for a 15 km s 1 impact if the planet was near its solidus before the impact isostatic relaxation may generate a significant volume of additional melting

the martian hemispheric dichotomy may be due to a giant impact mars is divided into two fundamentally different geological provinces of approximately hemispherical extent1 3 the more southerly province is heavily cratered contains relatively old geological units and superficially resembles the lunar and mercurian highlands the northern province is relatively lightly cratered and contains younger geological units including extensive plains volcanic edifices and volcanic calderas except for the tharsis and elysium regions and other large volcanoes most of the younger northern province consists of lowlands which lie an average of 3 km below the highlands lowlands occupy about one third of mars they are separated from the highlands by a distinct scarp or by a sloping transitional zone as much as 700km wide in which highland materials have been disrupted and partly replaced by lowland deposits fig 1 the transition is characterized by a variety of landforms unknown on other planets the highlands and lowlands are in isostatic equilibrium across the transitional zone4 no generally accepted explanation for the cause of the highland lowland dichotomy has been proposed although thinning of the lithosph re in the northern hemisphere by internal processes has been suggested5 large impacts which were a feature of early solar system history have also been suggested as an important cause of such early planetary surface heterogeneities3 6 7 subcircular lowlands such as argyre chryse hellas and isidis planitia and the plains south of tharsis occupy previously recognized impact basins8 10 we propose here that the largest expanse of lowlands also results from formation of a large impact basin early in mars history that has profoundly shaped the planet s surface

behavior of tungsten and hafnium in silicates a crystal chemical basis for understanding the early evolution of the terrestrial planets 1 the short lived isotopic system involving the decay of 182hf to 182w half life of 9 ma has been used to establish a time scale for planetary assembly and core formation the w isotope signature of lunar and martian basalts appears to be correlated to characteristics of their source on the moon the small amount of excess 182w is associated with basalts that may be derived from an ilmenite and clinopyroxene bearing mantle that was produced during late stages of lunar magma ocean crystallization on mars excess 182w is associated with a depleted mantle source our experimental measurements for the partitioning behavior of hf and w between silicates and melt suggest that the early fractionation of hf from w by phases such as ilmenite high ca clinopyroxene and garnet may be significant enough to account for the generation of all or part of the radiogenic w signatures in the mantle sources for these basalts the duration and nature of early mantle differentiation events on the moon and mars may be calculated by combining hf w fractionation with the extent of radiogenic w enrichment

the northwest africa 8159 martian meteorite expanding the martian sample suite to the early amazonian abstract northwest africa nwa 8159 is an augite rich shergottite with a mineralogy dominated by ca fe rich pyroxene plagioclase olivine and magnetite nwa 8159 crystallized from an evolved melt of basaltic composition under relatively rapid conditions of cooling likely in a surface lava flow or shallow sill redox conditions experienced by the melt shifted from relatively oxidizing with respect to known martian lithologies qfm on the liquidus to higher oxygen fugacity qfm 2 during crystallization of the groundmass and under subsolidus conditions this shift resulted in the production of orthopyroxene and magnetite replacing olivine phenocryst rims nwa 8159 contains both crystalline and shock amorphized plagioclase an50 62 often observed within a single grain based on known calibrations we bracket the peak shock pressure experienced by nwa 8159 to between 15 and 23 gpa the bulk composition of nwa 8159 is depleted in lree as observed for tissint and other depleted shergottites however nwa 8159 is distinct from all other martian lithologies in its bulk composition and oxygen fugacity we obtain a sm nd formation age of 2 37 0 25 ga for nwa 8159 which represents an interval in mars geologic time which until recently was not represented in the other martian meteorite types the bulk rock 147sm 144nd value of 0 37 0 02 is consistent with it being derived directly from its source and the high initial e143nd value indicates this source was geochemically highly depleted cr nd and w isotopic compositions further support a unique mantle source while the rock shares similarities with the 2 4 ga nwa 7635 meteorite there are notable distinctions between the two meteorites that suggest differences in mantle source compositions and conditions of crystallization nevertheless the two samples may be launch paired nwa 8159 expands the known basalt types ages and mantle sources within the mars sample suite to include a second igneous unit from the early amazonian

the early differentiation history of mars from 182w 142nd isotope systematics in the snc meteorites we report here the results of an investigation of w and nd isotopes in the snc shergottite nakhlite chassignite martian meteorites we have determined that 182 w values in the nakhlites are uniform within analytical uncertainties and have an average value of 3 also while 182 w values in the shergottites have a limited range from 0 3 0 7 their 142 nd values vary considerably from 0 2 0 9 there appears to be no correlation between 182 w and 142 nd in the nakhlites and shergottites these results shed new light on early differentiation processes on mars particularly on the timing and nature of fraction ation in silicate reservoirs assuming a two stage model the metallic core is estimated to have formed at 12 myr after the beginning of the solar system major silicate differentiation established the nakhlite source reservoir before 4542 ma and the shergottite source reservoirs at 4525 19 ma these ages imply that within the uncertainties afforded by the 182 hf 182 w and 146 sm 142 nd chronometers the silicate differentiation events that established the source reservoirs of the nakhlites and shergottites may have occurred contempo raneously possibly during crystallization of a global magma ocean the distinct 182 w 142 nd isotope systematics in the nakhlites and the shergottites imply the presence of at least three isotopically distinct silicate reservoirs on mars two of which are depleted in incompatible lithophile elements relative to chondrites and the third is enriched the two depleted silicate reservoirs most likely reside in the martian mantle while the enriched reservoir could be either in the crust or the mantle therefore the 182 w 142 nd isotope systematics indicate that the nakhlites and the shergottites originated from distinct source reservoirs and cannot be petrogenetically related a further implication is that the source reservoirs of the nakhlites and shergottites on mars have been isolated since their establishment before 4 5 ga therefore there has been no giant impact or efficient global mantle convection to thoroughly homogenize the martian mantle following the establish ment of the snc source reservoirs copyright 2005 elsevier ltd

constraints on the u pb isotopic systematics of mars inferred from a combined u pb rb sr and sm nd isotopic study of the martian meteorite zagami uranium lead rb sr and sm nd isotopic analyses have been performed on the same whole rock mineral and leachate fractions of the basaltic martian meteorite zagami to better constrain the u pb isotopic systematics of martian materials although the rb sr and sm nd systems define concordant crystallization ages of 166 6 ma and 166 12 ma respectively the u pb isotopic system is disturbed nevertheless an age of 156 6 ma is derived from the 238u 206pb isotopic system from the purest mineral fractions maskelynite and pyroxene the concordance of these three ages suggest that the 238u 206pb systematics of the purest zagami mineral fractions have been minimally disturbed by alteration and impact processes and can therefore be used to constrain the behavior of u and pb in the zagami source region the value of the zagami source region can be estimated with some confidence from the 238u 206pb isochron to be 3 96 0 02 disturbance of the u pb isotopic systems means that this represents a minimum value the value of the zagami source is significantly lower than the values estimated for most basaltic magma sources from earth and the moon this is surprising given the high initial 87sr 86sr ratio 0 721566 82 and low initial end value 7 23 0 17 determined for zagami that indicate that this sample is derived from one of the most highly fractionated reservoirs from any known planetary body this suggests that mars is characterized by a low bulk planet u pb ratio a feature that is consistent with its relatively volatile rich nature the leachates contain terrestrial common pb that was probably added to the meteorite during handling curation or sawing the mineral fractions particularly those with significant amounts of impact melt glass contain a second contaminant the presence of this contaminant results in pb pb ages that are older than the crystallization age of zagami indicating that the contaminant is characterized by a high 207pb 206pb ratio such a contaminant could be produced by removal of single stage pb from a relatively high martian reservoir before 1 8 ga and therefore could be an ancient manifestation of hydrous alteration of martian surface material

chronological evidence that the moon is either young or did not have a global magma ocean a new age determination for a moon rock collected close to the site of the apollo 16 lander has yielded a surprisingly young age of around 4 360 million years this age would require either that the moon solidified some 200 million years after the formation of the solar system significantly later than is assumed by most lunar formation models or that the long held theory that the moon once had a primordial global magma ocean is flawed in the latter case much of the lunar crust could have been produced by non magma ocean processes such as serial magmatism chemical evolution of planetary bodies ranging from asteroids to the large rocky planets is thought to begin with differentiation through solidification of magma oceans many hundreds of kilometres in depth1 2 3 the earth s moon is the archetypical example of this type of differentiation evidence for a lunar magma ocean is derived largely from the widespread distribution compositional and mineralogical characteristics and ancient ages inferred for the ferroan anorthosite fan suite of lunar crustal rocks the fans are considered to be primary lunar flotation cumulate crust that crystallized in the latter stages of magma ocean solidification according to this theory fans represent the oldest lunar crustal rock type2 3 4 attempts to date this rock suite have yielded ambiguous results however because individual isochron measurements are typically incompatible with the geochemical make up of the samples and have not been confirmed by additional isotopic systems5 6 7 8 9 by making improvements to the standard isotopic techniques we report here the age of crystallization of fan 60025 using the 207pb 206pb 147sm 143nd and 146sm 142nd isotopic systems to be 4 360 3 million years this extraordinarily young age requires that either the moon solidified significantly later than most previous estimates or the long held assumption that fans are flotation cumulates of a primordial magma ocean is incorrect if the latter is correct then much of the lunar crust may have been produced by non magma ocean processes such as serial magmatism10

a reconsideration of the relationships of the fossil amphibian albanerpeton previously thought to be a salamander prosirenidae albanerpeton estes and hoffstetter jurassic to miocene possesses no known features otherwise restricted to salamanders its salamander like features are only those held in common with small limbed non saltatorial amphibians in general in still other aspects including feeding apparatus dermal bones of the skull and anterior cervical vertebrae albanerpeton appears unique already well isolated from salamanders albanerpeton seems no nearer phyletically to any other known amphibians from devonian to recent the relationships of albanerpeton are most consistently indicated by classification in its own family albanerpetontidae new and order allocaudata new perhaps referrable to the lissamphibia

mars in the aftermath of a colossal impact abstract the abundance of highly siderophile elements hses inferred for mars mantle from martian meteorites implies a late veneer lv mass addition of 0 8 wt with broadly chondritic composition late accretion to mars by a differentiated ceres sized 1000 km diameter object can account for part of the requisite lv mass and geochronological constraints suggests that this must have occurred no later than ca 4480 ma here we analyze the outcome of the hypothetical lv giant impact to mars with smoothed particle hydrodynamics simulations together with analytical theory results show that in general about 50 of the impactor s metallic core shatters into 10 m fragments that subsequently fragment into sub mm metallic hail at re accretion this returns a promising delivery of hses into martian mantle compared to either a head on and hit and run collision in both cases 10 myr a dense pre noachian co2 atmosphere should lower the escape efficiency of hydrogen by ir emission a more detailed hydrodynamic atmospheric model of this early hydrogen atmosphere is warranted to examine its effect on pre noachian mars

a colossal impact enriched mars mantle with noble metals once the terrestrial planets had mostly completed their assembly bombardment continued by planetesimals left over from accretion highly siderophile element hse abundances in mars mantle imply that its late accretion supplement was 0 8 wt earth and the moon obtained an additional 0 7 wt and 0 02 wt respectively the disproportionately high earth moon accretion ratio is explicable by stochastic addition of a few remaining ceres sized bodies that preferentially targeted earth here we show that mars late accretion budget also requires a colossal impact a plausible visible remnant of which is the emispheric dichotomy the addition of sufficient hses to the martian mantle entails an impactor of at least 1200 km in diameter to have struck mars before 4430 ma by which time crust formation was well underway thus the dichotomy could be one of the oldest geophysical features of the martian crust ejected debris could be the source material for its satellites

development of a vs30 nehrp map for the city of ottawa ontario canada four different seismic methods were used extensively to evaluate the shear wave velocity of soils and rock in the city of ottawa canada from which the travel time weighted average shear wave velocity vs from surface to 30 m in depth vs30 and the fundamental frequency f0 were computed three main geological or geotechnical units were identified with distinct shear wave velocities these consist of very loose thick post glacial fine grained sands silts and clays vs 150 m s thickness up to 110 m firm glacial sediments vs 580 m s thickness 3 m and very firm bedrock vs 1750 3550 m s the seismic methods applied were downhole interval vs measurements at 15 borehole sites seismic refraction reflection profile measurements for 686 sites high resolution shear wave reflection landstreamer profiling for 25 km in total and horizontal to vertical spectral ratio hvsr of ambient seismic noise to evaluate the fundamental frequency for 400 sites most of these methods are able to distinguis

the early differentiation of mars inferred from hf w chronometry abstract mars probably accreted within the first 10 million years of solar system formation and likely underwent magma ocean crystallization and crust formation soon thereafter to assess the nature and timescales of these large scale mantle differentiation processes we applied the short lived 182 hf 182 w and 146 sm 142 nd chronometers to a comprehensive suite of martian meteorites including several shergottites augite basalt nwa 8159 orthopyroxenite alh 84001 and polymict breccia nwa 7034 compared to previous studies the 182 w data are significantly more precise and have been obtained for a more diverse suite of martian meteorites ranging from samples from highly depleted to highly enriched mantle and crustal sources our results show that martian meteorites exhibit widespread 182 w 184 w variations that are broadly correlated with 142 nd 144 nd implying that silicate differentiation and not core formation is the main cause of the observed 182 w 184 w differences the combined 182 w 142 nd systematics are best explained by magma ocean crystallization on mars within 20 25 million years after solar system formation followed by crust formation 15 million years later these ages are indistinguishable from the i pu xe age for the formation of mars atmosphere indicating that the major differentiation of mars into mantle crust and atmosphere occurred between 20 and 40 million years after solar system formation and hence earlier than previously inferred based on sm nd chronometry alone

samarium neodymium chronology and rubidium strontium systematics of an allende calcium aluminum rich inclusion with implications for 146sm half life abstract calcium aluminum rich inclusions cais are primitive objects that formed within the protoplanetary disk surrounding the young sun recent pb pb chronologic studies have demonstrated that cais are the oldest solar system solids crystallizing 4567 ma ago amelin et al 2002 connelly et al 2012 the isotope systematics of cais therefore provide critical insight into the earliest history of the solar system although sm nd and rb sr geochronometers are highly effective tools for investigating cosmochemical evolution in the early solar system previous studies of cais have revealed evidence for isotopically disturbed systems here we report new age data for allende cai al3s4 derived from both the long lived 147sm 143nd and short lived 146sm 142nd isotopic systems the 147sm 143nd chronometer yields an age of 4560 34 ma that is concordant with 207pb 206pb ages for cais and indicates that the sm nd system was not significantly disturbed by secondary alteration or nucleosynthetic processes the slope of the 146sm 142nd isochron defines the solar system initial 146sm 144sm of 0 00828 0 00044 this value is significantly different from the value of 0 0094 determined by kinoshita et al 2012 ages recalculated from all published 146sm 142nd isochron data using the traditional 103 ma half life and the initial 146sm 144sm value determined here closely match pb pb and 147sm 143nd ages determined on the same samples in contrast ages recalculated using the 68 ma half life determined by kinoshita et al 2012 and either of the initial 146sm 144sm values are often anomalously old this is particularly true for the youngest samples with 146sm 142nd isochron ages that are most sensitive to the choice of 146sm half life used in the age calculation in contrast to the sm nd isotope system the rb sr system is affected by alteration but yields an apparent isochron with a slope corresponding to a much younger age of 4247 110 ma although the rb sr system in cais appears to be disturbed the initial 87sr 86sr value determined from the isochron is 0 698942 0 000008 and closely approximates estimates of the initial solar system value although this isochron may be a mixing line it might also record alteration on the allende parent body in which rb was added to the al3s4 cai that was initially largely devoid of rb

consequences of giant impacts in early mars core merging and martian dynamo evolution a giant impact is an increasingly popular explanation for the formation of the northern lowland on mars it is plausible that at the impact time both mars and the impactor were differentiated with solid silicate mantles and liquid iron cores such a large impact likely resulted in merging of the cores of both bodies a process which will have implications on the thermal state of the planet we model the evolution of the martian mantle following a giant impact and characterize the thermochemical consequences of the sinking of an impactor s core as a single diapir the impact heating and the viscous heating induced during the core merging may affect the early thermal state of mars during several tens of million years our results show that large viscosity contrasts between the impactor s core and the surrounding mantle silicates can reduce the duration of the merging down to 1 kyr but do not modify the merging temperature when the viscosity contrast between the diapir and the surrounding silicates is larger than a factor of 1000 the descent of the diapir can lead to some entrainment of the relatively shallow silicates to deepest regions close to the core mantle boundary finally the direct impact heating of martian core leads to thermal stratification of the core and kills the core dynamo it takes on the order of 150 200 myr to reinitiate a strong dynamo anew the merging of the impactor s core with the martian core only delays the reinitiation of the dynamo for a very short time

a highly depleted moon or a non magma ocean origin for the lunar crust abstract coupled 146 147 sm 142 143 nd systematics were analyzed on lunar samples that span the range of source compositions created in the early lunar differentiation event ferroan anorthosites high mg suite norite kreep and low and high ti basalts if fit with a single isochron the data agree with previous suggestions of a 250 ma duration for closure of the sm nd system in the lunar interior the two crustal rocks 60025 and 78236 among oldest samples found on the lunar surface have high initial 142 nd 144 nd ratios e 142 nd 0 24 0 27 relative to o chondrites which indicates that they derive from a source strongly depleted in light rare earth elements lree 147 sm 144 nd 0 23 this result suggests either that the moon formed with a strongly superchondritic sm nd ratio or that the lunar crust formed as a product of a post magma ocean remelting of lree depleted cumulates in the lunar interior the basalt data measured here add support to the idea that the lunar interior evolved with a superchondritic sm nd similar to that of the early earth addition of differentiation steps adds complexity and inherit non uniqueness to the interpretation of the lunar nd isotope data but our preferred model has the first stage of lunar evolution 4 567 to 4 44 ga occurring on an already differentiated earth with the moon forming shortly before 4 45 ga and undergoing rapid magma ocean evolution to form the crust the high sm nd source reservoirs of many mare basalt types and kreep by 4 44 ga continued differentiation of the lunar interior through the increasing depletion of the source of high ti mare basalts then continued until 4320 ma

the age of the martian meteorite northwest africa 1195 and the differentiation history of the shergottites samarium neodymium isotopic analyses of unleached and acid leached mineral fractions from the recently identified olivine bearing shergottite northwest africa 1195 yield a crystallization age of 347 13 ma and an end143 value of 40 1 0 9 maskelynite fractions do not lie on the sm nd isochron and appear to contain a martian surface component with low 147sm 144nd and 143nd 144nd ratios that was added during shock the rb sr system is disturbed and does not yield an isochron terrestrial sr appears to have affected all of the mineral fractions although a maximum initial 87sr 86sr ratio of 0 7016 is estimated by passing a 347 ma reference line through the maskelynite fraction that is least affected by contamination the high initial end143 value and the low initial 87sr 86sr ratio combined with the geologically young crystallization age indicate that northwest africa 1195 is derived from a source region characterized by a long term incompatible element depletion the age and initial sr and nd isotopic compositions of northwest africa 1195 are very similar to those of queen alexandra range 94201 indicating these samples were derived from source regions with similar sr nd isotopic systematics these similarities suggest that these two meteorites share a close petrogenetic relationship and might have been erupted from a common volcano the meteorites yamato 980459 dar al gani 476 sayh al uhaymir 005 008 and dhofar 019 also have relatively old ages between 474 and 575 ma and trace element and or isotopic systematics that are indicative of derivation from incompatible element depleted sources this suggests that the oldest group of meteorites is more closely related to one another than they are to the younger meteorites that are derived from less incompatible element depleted sources closed system fractional crystallization of this suite of meteorites is modeled with the melts algorithm using the bulk composition of yamato 980459 as a parent these models reproduce many of the major element and mineralogical variations observed in the suite in addition the rare earth element systematics of these meteorites are reproduced by fractional crystallization using the proportions of phases and extents of crystallization that are calculated by melts other shergottites that demonstrate enrichments in incompatible elements and have evolved sr and nd isotopic systematics have some geochemical systematics that are similar to those observed in the depleted group most notably although they exhibit a very limited range of incompatible trace element and isotopic compositions they have highly variable major element compositions this is also consistent with evolution from a common mantle source region by variable amounts of fractional crystallization if this scenario is correct it suggests that the combined effects of source composition and fractional crystallization are likely to account for the major element trace element and isotopic diversity of all shergottites

146sm 142nd formation interval for the lunar mantle now extinct 146sm t1 2 103ma was present in the early solar system and lunar basalts might be expected to have inherited small anomalies in 142nd abundances from mantle sources with variable sm nd ratios established during the early global differentiation of the moon 142nd 144nd ratios were measured for several lunar basalts and values of nd142 deviations from terrestrial 142nd 144nd in parts in 104 calculated for them the nd142 values show very small variations attributable to 146sm decay neutron capture near the lunar surface also modified both the samarium and neodymium isotopic compositions of the basalt samples the calculated neutron fluences range from 0 to 7 8 1016 n cm2 both thermal and epithermal neutron fluences were calculated from the sm isotopic compositions of the basalts and used to correct the nd142 values for neutron capture by neodymium well resolved radiogenic enrichments nd142 and 0 17 0 08 2 respectively were measured for lunar meteorite asuka 881757 and apollo 17 basalt 74255 respectively for which the neutron fluences were nil basalts 70135 and 75075 which were exposed to small measureable neutron fluences of 2 5 1015 and 7 7 1015 n cm2 respectively have neutron corrected nd142 values of 0 25 0 15 and 0 29 0 11 respectively the average value of radiogenic nd142 for the three high ti basalts from apollo 17 is 0 22 0 06 neutron capture effects were greater for the other basalts but can be corrected using the measured neutron fluences derived from the samarium isotopic data the neutron corrected nd142 for apollo 12 ilmenite basalt 12056 consistent with its derivation from a highly depleted mantle source also three low ti basalts from apollo 12 and apollo 15 12038 15076 15555 have neutron corrected nd142 which are not resolved from zero and average 0 04 0 06 a fourth low ti basalt 12039 has neutron corrected nd142 but is subject to the largest neutron correction of 0 32 e units kreep basalt 14078 was exposed to only a small neutron fluence of 6 4 1015 n cm2 and has a small deficit of 142nd corresponding to nd142 the average neutron corrected nd142 of three kreep basalts is 0 05 0 04 the nd142 values of the basalts correlate with 147sm 144nd values for their source regions as calculated from their ages and initial nd142 values 147sm 143nd and 146sm 142nd systematics were combined in a three stage model yielding an isochron equation for the lunar mantle formation interval which was calculated to be 238 40 56 ma 2 sm nd ratios for the source regions also are derived from the model and compare favorably with values from conventional geochemical models of mare basalt petrogenesis if the moon were formed by impact of a large mars sized planetesimal with the earth the impact was early enough that the lunar mantle cooled to neodymium isotopic closure by 4 32 ga ago the bulk lunar moon142 evaluated from the mantle isochron at 147sm 144nd chur 0 1967 is 0 01 0 03 2 consistent with derivation of lunar and terrestrial neodymium from a common reservoir

accretion timescale and impact history of mars deduced from the isotopic systematics of martian meteorites abstract high precision sm nd isotopic analyses have been completed on a suite of 11 martian basaltic meteorites in order to better constrain the age of silicate differentiation on mars associated with the formation of their mantle sources these data are used to evaluate the merits and disadvantages of various mathematical approaches that have been employed in previous work on this topic ages determined from the sm nd isotopic systematics of individual samples are strongly dependent on the assumed nd isotopic composition of the bulk planet this assumption is problematic given differences observed between the nd isotopic composition of earth and chondritic meteorites and the fact that these materials are both commonly used to represent bulk planetary nd isotopic compositions ages determined from the slope of 146sm 142nd whole rock isochrons are not dependent on the assumed 142nd 144nd ratio of the planet but require the sample suite to be derived from complementary contemporaneously formed reservoirs in this work we present a mathematical expression that defines the age of formation of the source regions of such a suite of samples that is based solely on the slope of a 143nd 142nd whole rock isochron and is also independent of any a priori assumptions regarding the bulk isotopic composition of the planet this expression is also applicable to mineral isochrons and has been used to successfully calculate 143nd 142nd model crystallization ages of early refractory solids as well as lunar samples this permits ages to be obtained using only nd isotopic measurements without the need for 147sm 144nd isotope dilution determinations when used in conjunction with high precision nd isotopic measurements completed on martian meteorites this expression yields an age of formation of the martian basaltic meteorite source regions of 4504 6 ma because the sm nd model ages for the formation of martian source regions are commonly interpreted to record the age at which large scale mantle reservoirs formed during planetary differentiation associated with magma ocean solidification the age determined here implies that magma ocean solidification occurred several tens of millions of years after the beginning of the solar system recent thermal models however suggest that mars sized bodies cool rapidly in less than 5 ma after accretion ceases even in the presence of a thick atmosphere assuming these models are correct an extended period of accretion is necessary to provide a mechanism to keep portions of the martian mantle partially molten until 4504 ma late accretional heating of mars could either be associated with protracted accretion occurring at a quasi steady state or alternatively be associated with a late giant impact if this scenario is correct then accretion of mars sized bodies takes up to 60 ma and is likely to be contemporaneous with the core formation and possibly the onset of silicate differentiation this further challenges the concept that isotopic equilibrium is attained during primordial evolution of planets and may help to account for geochemical evidence implying addition of material into planetary interiors after core formation was completed

a review of meteorite evidence for the timing of magmatism and of surface or near surface liquid water on mars 1 there is widespread photogeological evidence for ubiquitous water flowing on the surface of mars however the age of surface and near surface water cannot be deduced with high precision from photogeology while there is clear evidence for old and young fluvial features in the photogeologic record the uncertainty in the absolute calibration of the martian crater flux results in uncertainties of 1 5 gyr in the middle period of martian geologic history aqueous alteration of primary igneous minerals produces secondary minerals in martian meteorites here we use the ages of secondary alteration minerals in martian meteorites to obtain absolute ages when liquid water was at or near the surface of mars aqueous alteration events in martian meteorites occurred at 3929 37 ma carbonates in alh84001 633 23 ma iddingsite in nakhlites and 0 170 ma salts in shergottites furthermore these events appear to be of short duration suggesting episodic rather than continuous aqueous alteration of the meteorites the martian meteorites appear to be contaminated by martian surface pb characterized by a 207pb 206pb ratio near 1 lead of this composition could be produced by water based alteration on the martian surface the high 129xe 132xe ratio in the martian atmosphere compared to martian meteorites indicates fractionation of i from xe within 100 myr after nucleosynthesis of 129i such fractionation is difficult to achieve through magmatic processes however water very efficiently fractionates i from xe raising the intriguing possibility that mars had a liquid water ocean within its first 100 myr 1

the early pleistocene herpetofauna of rivoli veronese northern italy as evidence for humid and forested glacial phases in the gelasian of southern alps abstract among the early pleistocene italian fossil herpetofaunas rivoli veronese is remarkable in having yielded the youngest known allocaudates represented by albanerpeton pannonicum together with remains of other amphibians and reptiles the assemblage includes at least 15 other taxa including two caudates speleomantes sp ichthyosaura alpestris four anurans bombina sp bufo bufo hyla gr h arborea rana sp five lizards lacerta gr l viridis cf zootoca vivipara a third small sized lacertid anguis gr a fragilis cf pseudopus sp and four snakes coronella sp zamenis longissimus natrix sp vipera gr v aspis the finding of speleomantes is particularly interesting as it is one of only a handful of fossil occurrences of this genus being only the second one outside of its extant range excluding the extinct albanerpeton and speleomantes which has a very narrow environmental range the remainder of the assemblage suggests a mean annual temperature rather similar or slightly colder than the present one in rivoli veronese 11 6 c versus 12 4 c with much higher mean annual precipitation 1322 mm versus 834 mm the palaeoenvironment would have included either permanent or temporary water bodies located in a forested area more open landscapes might have also been present in the local vicinity the palaeoherpetofauna of rivoli veronese supports the hypothesis of albanerpeton favouring a moist environment and confirms the presence of a humid forested landscape on the northern side of the po plain during the cold phases of the gelasian as already suggested by the pollen record for its southern margin

old sm nd ages for cumulate eucrites and redetermination of the solar system initial 146sm 144sm ratio article i nfo sm 142 nd systematics short lived 146 sm 142 nd and long lived 147 sm 143 nd chronometers have been measured in three cumulate eucrites binda moore county and moama the two major mineral phases plagioclase and pyroxene present in these achondrites are characterized by a wide range of sm nd ratios that allows well resolved sm nd isochrons this group of meteorites thus is suitable to better constrain the initial 146 sm 144 sm ratio of the solar system binda and moore county give concordant ages of 4544 88 and 4542 85 ma respectively with initial 143 nd 144 nd ratios slightly higher to within error of chondritic these ages are in agreement with most of the radiometric ages determined on basaltic eucrites a best estimate for the solar system initial 146 sm 144 sm ratio is obtained using the five point regression line determined for binda the 146 sm 144

the internal structure and geodynamics of mars inferred from a 4 2 gyr zircon record combining u pb ages with lu hf data in zircon provides insights into the magmatic history of rocky planets the northwest africa nwa 7034 7533 meteorites are samples of the southern highlands of mars containing zircon with ages as old as 4476 3 0 9 ma interpreted to reflect reworking of the primordial martian crust by impacts we extracted a statistically significant zircon population n 57 from nwa 7533 that defines a temporal record spanning 4 2 gyr ancient zircons record ages from 4485 5 2 2 ma to 4331 0 1 4 ma defining a bimodal distribution with groupings at 4474 10 ma and 4442 17 ma we interpret these to represent intense bombardment episodes at the planet s surface possibly triggered by the early migration of gas giant planets the unradiogenic initial hf isotope composition of these zircons establishes that mars s igneous activity prior to 4 3 ga was limited to impact related reworking of a chemically enriched primordial crust a group of younger detrital zircons record ages from 1548 0 8 8 ma to 299 5 0 6 ma the only plausible sources for these grains are the temporally associated elysium and tharsis volcanic provinces that are the expressions of deep seated mantle plumes the chondritic like hf isotope compositions of these zircons require the existence of a primitive and convecting mantle reservoir indicating that mars has been in a stagnant lid tectonic regime for most of its history our results imply that zircon is ubiquitous on the martian surface providing a faithful record of the planet s magmatic history

hvsr deep mapping tested down to 1 8 km in po plane valley italy abstract the horizontal to vertical spectral ratio hvsr of seismic noise is extensively used in seismic microzonation for its capability to provide a good approximation to the subsoil main resonance frequencies of geotechnical and seismic engineering interest this implies in turn that it has also an approximate passive subsoil mapping capability independent of the level of noise illumination albeit limited to relatively shallow depths since tilt sensitivity makes hvsr unreliable below 0 1 hz however we have experimentally verified that hvsr subsoil mapping capability extends to depths in the kilometer range by applying it to the largest sedimentary basin of italy the po plain valley there we were able to resolve the major stratigraphic discontinuities down to the sediment bedrock interface for which we estimated a depth of 1 6 km with a 25 uncertainty while the surface mapped from oil exploration indicates a depth of 1 8 km quarter of an hour recordings gave always stable signals that fitted to synthetic curves using as a constraint the parameters of the shallow subsoil provided a stratigraphic map consistent with the independent survey this candidates hvsr as a fast and inexpensive first order subsoil mapping tool down to depths of geological and exploration interest

chronologic implications for slow cooling of troctolite 76535 and temporal relationships between the mg suite and the ferroan anorthosite suite abstract ages have been obtained using the 87 rb 87 sr 147 sm 143 nd and 146 sm 142 nd isotopic systems for one of the most slowly cooled lunar rocks apollo 17 mg suite troctolite 76535 the 147 sm 143 nd 146 sm 142 nd and rb sr ages derived from plagioclase olivine and pyroxene mineral isochrons yield concordant ages of 4307 11 ma 4299 29 35 ma and 4279 52 ma respectively these ages are slightly younger than the age determined on ferroan anorthosite suite fas rock 60025 and are therefore consistent with the traditional magma ocean model of lunar differentiation in which the mg suite is intruded into the anorthositic crust however the sm nd ages record when the rock passed below the closing temperature of the sm nd system in this rock at 825 c whereas the rb sr age likely records the closure temperature of 650 c a cooling rate of 3 9 c ma is determined using the ages reported here and in the literature and calculated closure temperatures for the ar ar pb pb rb sr and sm nd systems this cooling rate is in good agreement with cooling rates estimated from petrographic observations slow cooling can lower apparent sm nd crystallization ages by up to 80 ma in the slowest cooled rocks like 76535 and likely accounts for some of the variation of ages reported for lunar crustal rocks nevertheless slow cooling cannot account for the overlap in fas and mg suite rock ages instead this overlap appears to reflect the concordance of mg suite and fas magmatism in the lunar crust as indicated by ages calculated for the solidus temperature of 76535 and 60025 of 4384 24 ma and 4383 17 respectively not only are the solidus ages of 76535 and 60025 nearly concordant but the sm nd isotopic systematics suggest they are derived from reservoirs that were minimally differentiated prior to 4 38 ga although the sr isotopic composition of 60025 indicates its source was minimally differentiated the sr isotopic composition of 76535 indicates it underwent fractionation just prior to solidification of the 76535 these observations are consistent with both a magma ocean or a serial magmatism model of lunar differentiation in either model differentiation of lunar source regions must occur near the solidification age of thee samples perhaps the best estimate for the formation age of lunar source regions is the rb sr model age of the 76535 source region age of 4401 32 ma this is in good agreement with sm nd model ages for the formation of ur kreep and suggests that differentiation of a least part of the moon could not have occurred prior to 4 43 ga

a shorter 146sm half life measured and implications for 146sm 142nd chronology in the solar system radiometric dating relies on measuring the abundance of long lived radionuclides relative to the abundance of their radiogenic decay products a process determined by the original radionuclide s half life for primordial radionuclides that decay slowly such as 146sm decaying to 142nd this method provides the timing of some of the earliest processes in solar system history using accelerator mass spectrometry kinoshita et al p 1614 1 provide a revised estimate for the 146sm half life of 68 7 million years which is 30 shorter than the previously accepted value this shorter half life suggests that reductions need to be made in the estimated ages for differentiation of earth s mantle and the solidification of the moon s magma ocean and for other more recent processes 1 lookup doi 10 1126 science 1215510

evolution of the martian mantle inferred from the 187re 187os isotope and highly siderophile element abundance systematics of shergottite meteorites abstract shergottite meteorites are a suite of mafic to ultramafic igneous rocks whose parental magmas probably derived from the martian mantle in this study a suite of 23 shergottites spanning their known range in bulk compositions rb sr sm nd and lu hf isotopes were measured for 187re 187os isotopic systematics and highly siderophile element abundances hse including os ir ru pt pd re the chief objective was to gain new insight on the chemical evolution of the martian mantle by unraveling the long term hse budget of its derivative melts possible effects upon hses related to crustal contamination as well as terrestrial and or martian surface alteration are also examined some of the shergottites are hot arid desert finds their respective acetic acid leachates and residues show that both re and os display open system behavior during sample residence at or near the martian and or terrestrial surfaces in some meteorites the alteration effects can be circumvented by analysis of the leached residues for those shergottites believed to record robust re os isotopic systematics calculated initial 187os 188os are well correlated with the initial 143nd 144nd shergottites from mantle sources with long term melt depleted characteristics initial e143nd of 36 to 40 have chondritic initial 187os ranging from 0 5 to 2 5 shergottites with intermediate initial e143nd of 8 to 17 have a range in initial 187os of 0 6 to 2 3 which overlaps the range for depleted shergottites shergottites from long term enriched sources with initial e143nd of 7 are characterized by suprachondritic 187os values of 5 to 15 the initial 187os variations for the shergottites do not show a correlation with indices of magmatic differentiation such as mgo or any systematic differences between hot arid desert finds antarctic finds or observed falls the strong correlation between the initial e143nd and 187os in shergottites from approximately 40 and 0 to 7 and 15 respectively is assessed in models for mixing depleted mantle derived melts with ancient crust modeled to be similar to evolved shergottite in composition and with assimilation fractional crystallization these models show that the correlation is unlikely to result from participation of martian crust more likely this correlation relates to contributions from depleted and enriched reservoirs formed in a martian magma ocean at ca 4 5 ga these models indicate that the shergottite endmember sources were generated by mixing between residual melts and cumulates that formed at variable stages during solidification of a magma ocean the expanded database for the hse abundances in shergottites suggests that their martian mantle sources have similar hse abundances to the terrestrial mantle consistent with prior studies the relatively high hse abundances in both planetary mantles likely cannot be accounted for by high pressure temperature metal silicate partitioning at the bases of magma oceans as has been suggested for earth if the hse were instead supplied by late accretion this event must have occurred prior to the crystallization of the last martian magma ocean

constraints on the petrogenesis of martian meteorites from the rb sr and sm nd isotopic systematics of the lherzolitic shergottites alh77005 and lew88516 abstract detailed rb sr and sm nd isotopic analyses have been completed on the lherzolitic shergottites alh77005 and lew88516 alh77005 yields a rb sr age of 185 11 ma and a sm nd age of 173 6 ma whereas the rb sr and sm nd ages of lew88516 are 183 10 and 166 16 ma respectively the initial sr isotopic composition of alh77005 is 0 71026 4 and the initial end value is 11 1 0 2 these values are distinct from those of lew88516 which has an initial sr isotopic composition of 0 71052 4 and an initial end value of 8 2 0 6 several of the mineral and whole rock leachates lie off the rb sr and sm nd isochrons indicating that the isotopic systematics of the meteorites have been disturbed the sm nd isotopic compositions of the leachates appear to be mixtures of primary igneous phosphates and an alteration component with a low 143nd 144nd ratio that was probably added to the meteorites on mars tie lines between leachate residue pairs from lew88516 mineral fractions and whole rocks have nearly identical slopes that correspond to rb sr ages of 90 1 ma this age may record a major shock event that fractionated rb sr from lattice sites located on mineral grain boundaries on the other hand the leachates could contain secondary alteration products and the parallel slopes of the tie lines could be coincidental nearly identical mineral modes compositions and ages suggest that these meteorites are very closely related nevertheless their initial sr and nd isotopic compositions differ outside analytical uncertainty requiring derivation from unique sources assimilation fractional crystallization models indicate that these two lherzolitic meteorites can only be related to a common parental magma if the assimilant has a sr nd ratio near 1 and a radiogenic sr isotopic composition further constraints placed on the evolved component by the geochemical and isotopic systematics of the shergottite meteorite suite suggest that it a formed at 4 5 ga b has a high la yb ratio c is an oxidant and d is basaltic in composition or is strongly enriched in incompatible elements the composition and isotopic systematics of the evolved component are unlike any evolved lunar or terrestrial igneous rocks its unusual geochemical and isotopic characteristics could reflect hydrous alteration of an evolved martian crustal component or hydrous metasomatism within the martian mantle

insights into the chemical diversity of the martian mantle from the pb isotope systematics of shergottite northwest africa 8159 abstract shergottite northwest africa nwa 8159 is a basaltic rock derived from a mantle source with chemical characteristics that are unique in the martian meteorite suite to further investigate this source reservoir the pb isotope compositions of plagioclase maskelynite pyroxene phosphates and shock melt glass in nwa 8159 have been measured in situ by secondary ion mass spectrometry sims due to the limited spread in pb isotope data these pb isotope compositions have been used to calculate an imprecise pb pb isochron age of 3 4 2 1 ga 2 which is broadly consistent with the crystallization age of 2 37 0 25 ga determined previously by 147sm 143nd the lack of radiogenic in growth within individual minerals since 2 4 ga means that this sample is depleted in u which is in agreement with nwa 8159 s positive initial e143nd an initial pb composition was calculated using an x y weighted average of the least radiogenic pb isotope population measured in the sample this initial pb composition is not consistent with the model for pb growth in the shergottite mantle at 2 4 ga this composition is however consistent with the model for the nakhla chassigny mantle using the latter model a source 238u 204pb of 2 6 0 6 has been calculated this value is in contrast with the other depleted shergottites 1 4 1 5 and falls significantly off the array of source e143nd vs defined by the rest of the martian meteorite suite and thus necessitates a differentiation history distinct from the other martian meteorites sequestering pb in sulphides during differentiation is the only mechanism to fractionate u from pb and create a low reservoir consequently the relatively high value of the source of nwa 8159 is in contrast with the positive initial e143nd and indicates that its mantle source region likely lacked significant sulphur this is consistent with the lack of sulphides in the sample itself and could have played a role in its complicated oxidation history

a seismic passive imaging step beyond spac and remi abstractthe basic property of passive imaging is that given any two points one of them can be taken as the source of the waves and the other as the recording station this property can be derived from the statistical self alignment of the rays along the vector joining the two points and applies also to nondiffuse wavefields like seismic tremor it provides a statistical basis for the use of the stationary phase integral allowing passive interferometry under the mild constraint of mechanical homogeneity at a local scale combined with the tremor s large spectral bandwidth it allows one to recover the local green s function from spatial correlation furthermore combining this property also with the azimuthal isotropy of either the wavefield or the array and using the statistical mode as the estimator provides a new technique to measure the local velocity dispersion in the subsoil this technique exploits the potential of spatial autocorrelation spac and refraction microtremor remi allowing one

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

imaging the earth with passive seismic arrays earthquake and exploration seismology share a common foundation in elastic wave propagation most of what we know about earthquakes is known from the elastic waves they emit while seismic methods in exploration are all about using scattered elastic waves to image earth structure seismologists have been using elastic waves to probe the earth since the very earliest instruments after all it was early seismic measurements that led to the spherical shell model of earth structure crust mantle and core taught to grade school students

isotopic evidence for a young lunar magma ocean abstract mare basalt sources and ferroan anorthosite suite cumulates define a linear array on a 146sm 144nd versus 142nd 144nd isochron plot demonstrating these materials were derived from a common reservoir at 4336 31 32 ma the minimum proportion of the moon that was in isotopic equilibrium at this time is estimated to be 1 3 of its entire volume based on the geographic extent from which the analyzed samples were collected and the calculated depths from which the samples were derived scenarios in which large portions of the moon were molten to depths of many hundreds of kilometers are required to produce the observed sm nd isotopic equilibrium between the mantle and crustal rocks at 4 34 ga this is a consequence of the fact that limited heating of a solid moon above the blocking temperature of the sm nd isotopic system is insufficient to diffusively homogenize radiogenic nd throughout the mantle and crust there are three scenarios that might account for global scale isotopic equilibrium on the moon relatively late in solar system history including 1 sm nd re equilibration of a solid moon resulting from widespread melting in response to mantle overturn or a very large impact 2 early accretion of the moon followed by delayed cooling due to the presence of an additional heat source that kept a large portion of the moon molten until 4 34 ga or 3 late accretion of the moon followed by rapid cooling of the magma ocean late in solar system history neither density driven overturn of the mantle nor a large impact are likely to homogenize the mantle and crust to the extent required by the sm nd isochron likewise secondary heating mechanisms such as tidal heating or radioactive decay are not efficient enough to keep the moon molten to the depth of the mare basalt source regions for many tens to hundreds of millions of years instead the age of equilibrium between such a compositionally diverse set of rocks produced on a global scale likely records the time of primordial solidification of the moon from a magma ocean this scenario accounts for both the petrogenetic characteristics of lunar rock suites as well as their sm nd isotopic systematics it is supported by the preponderance of 4 35 ga ages obtained for other hypothetical magma ocean crystallization products such as ferroan anorthosite suite rocks and k ree and p enriched cumulates that are thought to represent flotation cumulates of the magma ocean and the last vestiges of magma ocean solidification respectively

martian mantle mineralogy investigated by the 176lu 176hf and 147sm 143nd systematics of shergottites abstract chemical heterogeneities in the martian mantle are believed to result from the crystallization of a magma ocean in the first 100 million years of its history shergottite meteorites from mars are thought to retain a compositional record of such early differentiation and the resulting mineralogy at different depths the coupled 176 lu 176 hf and 147 sm 143 nd isotope systematics in 9 shergottites are used here to investigate these issues three compositional groups in the shergottites display distinct isotope systematics one group commonly termed as depleted is characterized by positive 176 hf i from 46 2 to 50 4 and 143 nd i from 36 2 to 39 1 another termed as enriched has negative 176 hf i 16 5 to 13 2 and 143 nd i 7 0 to 6 5 the third group is intermediate between the depleted and enriched groups with positive 176 hf i 30 0 to 33 4 and 143 nd i 16 9 together they describe mixing curves between 176 hf 177 hf 143 nd 144 nd lu hf and sm nd implying that they sample two distinct sources in the martian mantle all shergottites are characterized by sm nd source sample but lu hf source lu hf sample this decoupling can be explained by two successive partial melting episodes in the depleted shergottite source and localized in the martian upper mantle the genesis of shergottites can be modeled using non modal equilibrium partial melting in a source initially composed of 60 olivine 21 clinopyroxene 9 orthopyroxene and 10 garnet with degrees of partial melting of 8 8 and 3 9 respectively for the two successive events the enriched end member of the shergottite mixing curve is best modeled by late stage quenched residual melt resulting from the crystallization of a magma ocean the depleted shergottite source may be modeled as a mixture of cumulates and residual melt as convection in the martian magma ocean is expected to reduce the incompatible trace element heterogeneity in the final solidified layers consequently equilibrium crystallization is preferred to model the crystallization of the martian magma ocean the models that best explain the shergottite data are those where the magma ocean is at a depth of at least 1350 km in mars

petrogenesis of the nwa 7320 enriched martian gabbroic shergottite insight into the martian crust northwest africa nwa 7320 is classified as a gabbroic shergottite the second to be recognized in the martian meteorite record this interpretation is based on 1 the calculated bulk rock rare earth element ree concentrations which show the highest eu positive anomaly eu eu 2 2 of all the shergottites reflecting accumulation of plagioclase and 2 the highest modal abundance of maskelynitized plagioclase 50 mod compared to the other shergottites the three phase symplectite fayalite hedenbergite silica is present in nwa 7320 and formed as a result of the breakdown of metastable pyroxene pyroxenoid margins on coarse grained pyroxenes the latter is indicative of metastable overgrowths on pyroxene cores during the final stages of crystallization followed by relatively slow cooling at subsolidus conditions the nwa 7320 parental melt originated from an incompatible trace element enriched and oxidized fmq source as indicated by sm nd lu hf isotope systematics ilmenite titanomagnetite pairs the partition coefficient of cr in pyroxene and merrillite ree compositions the ti al ratio of pyroxene in nwa 7320 indicates an initial crystallization depth of 30 70 km p 4 9 kbar however the largest impact craters on mars are 8 km in depth indicating that nwa 7320 could not have been ejected from this depth and must have had a polybaric formation history we suggest that the pyroxene phenocrysts began to crystallize at depth but were entrained as antecrysts in a basaltic magma ascending to shallower levels in the martian crust in addition plagioclase likely crystallized during magma ascent followed by subsequent accumulation in a shallow magma intrusion or sill resulting in the gabbroic texture furthermore the similarity in the radiogenic isotope composition of nwa 7320 to that of los angeles and nwa 856 suggest that these meteorites were linked to common volcanic system on mars

insights into the martian mantle the age and isotopics of the meteorite fall tissint the recent witnessed fall of the meteorite tissint represents the delivery of a pristine new sample from the surface of mars this meteorite provides an unprecedented opportunity to study a variety of aspects about the planet s evolution using the rb sr and sm nd isotopic systems we determined that tissint a depleted shergottite has a crystallization age of 574 20 ma an initial e 143 nd 42 2 0 5 and an initial 87 sr 86 sr 0 700760 11 these initial nd and sr isotopic compositions suggest that tissint originated from a mantle source on mars that is distinct from the source reservoirs of the other martian meteorites the known crystallization ages geochemical characteristics ejection ages and ejection dynamics of tissint and other similarly grouped martian meteorites suggest that they are likely derived from a source crater up to approximately 90 km in diameter with an age of approximately 1 ma that is located on terrain that is approximately 600 million years old

re evaluating 142nd 144nd in lunar mare basalts with implications for the early evolution and bulk sm nd of the moon abstract the moon likely accreted from melt and vapor ejected during a cataclysmic collision between proto earth and a mars sized impactor very early in solar system history the identical w o k and cr isotope compositions between materials from the earth and moon require that the material from the two bodies were well homogenized during the collision process as such the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the earth two recent studies to obtain high precision 142nd 144nd ratios of lunar mare basalts yielded contrasting results in one study after correction of neutron fluence effects imparted to the nd isotope compositions of the samples the coupled 142nd 143nd systematics were interpreted to be consistent with a bulk moon having a chondritic sm nd ratio rankenburg k brandon a d and neal c r 2006 neodymium isotope evidence for a chondritic composition of the moon science 312 1369 1372 the other study found that their data on the same and similar lunar mare basalts were consistent with a bulk moon having a superchondritic sm nd ratio boyet m and carlson r w 2007 a highly depleted moon or a non magma origin for the lunar crust earth planet sci lett 262 505 516 delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the moon and for constraining the types of materials available for accretion into large terrestrial planets such as earth to further examine this issue the same six lunar mare basalt samples measured in rankenburg et al rankenburg k brandon a d and neal c r 2006 neodymium isotope evidence for a chondritic composition of the moon science 312 1369 1372 were re measured for high precision nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than 3 ppm 2 for 142nd 144nd ratios the measurements were repeated in a distinct second analytical campaign to further test their reproducibility evaluation of accuracy and neutron fluence corrections indicates that the multidynamic nd isotope measurements in this study and the 3 in boyet and carlson boyet m and carlson r w 2007 a highly depleted moon or a non magma origin for the lunar crust earth planet sci lett 262 505 516 are reproducible while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk moon with either chondritic or superchondritic sm nd ratios the multidynamic data are best explained by a bulk moon with a superchondritic sm nd ratio that is similar to the present day average for depleted morb hafnium isotope data were collected on the same aliquots measured for their 142nd 144nd isotope ratios in order to assess if the correlation line for 142nd 143nd systematics reflect mixing processes or times at which lunar mantle sources formed based on the combined 142nd 143nd 176hf obtained we conclude that the 142nd 143nd correlation line measured in this study is best interpreted as an isochron with an age of 229 24 20ma after the onset of nebular condensation the uncertainties in the data permit the sources of these samples to have formed over a 44 ma time interval these new results for lunar mare basalts are thus consistent with a later sm nd isotope closure time of their source regions than some recent studies have postulated and a superchondritic bulk sm nd ratio of the moon and earth the superchondritic sm nd signature was inherited from the materials that accreted to make up the earth moon system although collisional erosion of crust from planetesimals is favored here to remove subchondritic sm nd portions and drive the bulk of these bodies to superchondritic in composition removal of explosive basalt material via gravitational escape from such bodies or chondrule sorting in the inner solar system may also explain the compositional features that deviate from average chondrites that make up the earth moon system this inferred superchondritic nature for the earth similar to the modern convecting mantle means that there is no reason to invoke a missing subchondritic reservoir to mass balance the earth back to chondritic for sm nd ratios however to account for the subchondritic sm nd ratios of continental crust a second superchondritic sm nd mantle reservoir is required

the age of dar al gani 476 and the differentiation history of the martian meteorites inferred from their radiogenic isotopic systematics samarium neodymium isotopic analysis of the martian meteorite dar al gani 476 yields a crystallization age of 474 11 ma and an initial end143 value of 36 6 0 8 although the rb sr isotopic system has been disturbed by terrestrial weathering and therefore yields no age information an initial 87sr 86sr ratio of 0 701249 33 has been estimated using the rb sr isotopic composition of the maskelynite mineral fraction and the sm nd age the sr and nd isotopic systematics of dar al gani 476 like those of the basaltic shergottite que94201 are consistent with derivation from a source region that was strongly depleted in incompatible elements early in the history of the solar system nevertheless dar al gani 476 is derived from a source region that has a slightly greater incompatible enrichment than the que94201 source region this is not consistent with the fact that the parental magma of dar al gani 476 is significantly more mafic than the parental magma of que94201 and underscores a decoupling between the major element and trace element isotopic systematics observed in the martian meteorite suite combining the end142 end143 isotopic systematics of the martian meteorites yields a model age for planetary differentiation of 4 513 0 033 0 027 ga using this age the parent daughter ratios of martian mantle sources are calculated assuming a two stage evolutionary history the calculated sources have very large ranges of parent daughter ratios 87rb 86sr 0 037 0 374 147sm 144nd 0 182 0 285 176lu 177hf 0 028 0 048 these ranges exceed the ranges estimated for terrestrial basalt source regions but are very similar to those estimated for the sources of lunar mare basalts in fact the range of parent daughter ratios calculated for the martian meteorite sources can be produced by mixing between end members with compositions similar to lunar mare basalt sources two of the sources have compositions that are similar to olivine and pyroxene rich mafic cumulates with variable proportions of a rb enriched phase such as amphibole whereas the third source has the composition of liquid trapped in the cumulate pile i e similar to kreep after 99 crystallization correlation between the proportion of trapped liquid in the meteorite source regions and estimates of fo2 suggest that the kreep like component may be hydrous the success of these models in reproducing the martian meteorite source compositions suggests that the variations in trace element and isotopic compositions observed in the martian meteorites primarily reflect melting of the crystallization products of an ancient magma ocean and that assimilation of evolved crust by mantle derived magmas is not required furthermore the decoupling of major element and trace element isotopic systematics in the martian meteorite suite may reflect the fact that trace element and isotopic systematics are inherited from the magma source regions whereas the major element abundances are limited by eutectic melting processes at the time of magma formation differences in major element abundances of parental magma therefore result primarily from fractional crystallization after leaving their source regions

thermal and chemical evolution of the terrestrial magma ocean abstract the earth is likely to have experienced a magma ocean stage during accretion thermal and chemical evolution of magma ocean is investigated based on a one dimensional two phase flow heat and mass transfer model differentiation at lower mantle pressure depends on the type of magma ocean and surrounding atmosphere if the magma ocean is formed by the blanketing effect of a solar type proto atmosphere extensive differentiation proceeds at lower mantle pressure if the magma ocean is formed by the blanketing effect of an impact induced steam atmosphere no differentiation at lower mantle pressure is likely if a very deep magma ocean is formed by a giant impact whether differentiation proceeds at lower mantle pressure or not depends on grain size viscosity of melt and or properties of a transient atmosphere on the contrary chemical differentiation likely proceeds at upper mantle pressure irrespective of magma ocean type a shallow magma ocean can remain for 100 200 my without any heating processes

s wave velocity profiling by joint inversion of microtremor dispersion curve and horizontal to vertical h v spectrum a joint inverse analysis using both microtremor dispersion curve and horizontal to vertical h v spectrum is proposed for estimating the s wave velocity vs profiles of subsurface soils in the inversion both microtremor dispersion and h v data are assumed to be the rayleigh wave dispersion curve and the surface both rayleigh and love wave h v spectrum that have been theoretically derived by taking into account the effects of their fundamental and higher modes the proposed joint inversion as well as the conventional one using dispersion data alone is per formed at four sites where shallow vs profiles down to engineering bedrock are available the vs profiles estimated by the proposed joint inversion are more con sistent with available down hole velocity logs than those by the conventional method in particular the proposed inversion shows significant improvement in estimating bedrock vs structures compared to the conventional inversion sensitivity analyses indicate that the surface wave h v ratio is sensitive to the bedrock vs structure more than the rayleigh wave phase velocity confirming that the proposed joint inversion including h v spectrum is promising

the seismic noise wavefield is not diffuse passive seismology is burgeoning under the apparent theoretical support of diffuse acoustics however basic physical arguments suggest that this theory may not be applicable to seismic noise a procedure is developed to establish the applicability of the diffuse field paradigm to a wavefield based on testing the latter for azimuthal isotropy and spatial homogeneity this procedure is then applied to the seismic noise recorded at 65 sites covering a wide variety of environmental and subsoil conditions considering the instantaneous oscillation vector measured at single triaxial stations the hypothesis of azimuthal isotropy is rejected in all cases with high confidence which makes the spatial homogeneity test unnecessary and leads directly to conclude that the seismic noise wavefield is not diffuse however such a conclusion has no practical effect on passive imaging which is also possible in non diffuse wavefields

the effect of atmospheric interaction on impact ejecta dynamics and deposition abstract fine dust from impact ejecta settles slowly in an atmosphere whereas large chunks of ejecta easily traverse the surrounding gas on nearly parabolic trajectories in order to study the effects of the interaction of impact ejecta with an atmosphere we implemented a representative particle approach into the isale 2d shock physics code we verify the modelling approach using analytical equilibrium sedimentation velocities and successfully benchmark the results against simulations with the shock physics code sova we study vertical dust settling scenarios of different initial mass and dust size 100 m 10 cm and find three different regimes of settling sedimentation formation of density currents and the free fall based on this we model natural ejecta curtains for craters from 200 m 4 km in radius and small craters in the laboratory for different atmospheric pressures from 1 kpa 6 mpa we assess the range of ballistic ejecta deposition within an atmosphere in terms of ejecta thickness and deposition velocity

effects of local soil conditions on the topographic aggravation of seismic motion parametric investigation and recorded field evidence from the 1999 athens earthquake during the 1999 athens earthquake the town of adames located on the eastern side of the kifissos river canyon experienced unexpectedly heavy damage despite the particular geometry of the slope that caused significant motion amplification topography effects alone cannot explain the uneven damage distribution within a 300 m zone parallel to the canyon s crest which is characterized by a rather uniform structural quality in this article we illustrate the important role of soil stratigraphy and material heterogeneity on the topographic aggravation of surface ground motion for this purpose we first conduct an extensive time domain parametric study using idealized stratified profiles and gaussian stochastic fields to characterize the spatial distribution of soil properties and using ricker wavelets to describe the seismic input motion the results show that both topography and local soil conditions significantly affect the spatial variability of seismic motion we next perform elastic two dimensional wave propagation analyses based on available local geotechnical and seismological data and validate our results by comparison with aftershock recordings

a chemical model for generating the sources of mare basalts combined equilibrium and fractional crystallization of the lunar magmasphere abstract it is generally considered that mare basalts were generated by the melting of a cumulate mantle formed in an early moon wide magma ocean or magmasphere however the nature and chemistry of this cumulate mantle and the logistics of its origin have remained elusive extensive studies of terrestrial layered mafic intrusions over the past sixty years have emphasized the imperfection of fractional crystallization and attendant crystal crystal and crystal liquid separation in a convecting magma chamber crystal liquid and crystal crystal separations were similarly inefficient during evolution of the lunar magma ocean lmo allowing for the trapping of interstitial liquid and entrainment of a small proportion of less dense plagioclase into the denser mafic cumulate mush indeed petrography of lunar highlands samples demonstrates this for anorthosites with 1 10 olivine the residual liquid after 80 90 crystallization was very evolved in fact kreepy and even in small proportions 1 5 would have a noticeable effect on the trace element chemistry of melts generated from these cumulates this trapped residual liquid would elevate total ree abundances in the cumulate pile while synchronously deepening the already negative eu anomaly essentially this trapped liquid will make the cumulate more fertile for melting to generate both kreep basalt and mare basalt magmas plagioclase entrained in the mafic cumulate pile adds an essential al component to the high ti basalt source and will moderate the requisite negative eu anomaly in the cumulate early in the evolution of the lunar mantle when the lmo still was largely liquid it is likely that vigorous convection was an important factor in crystallization such convection would allow crystals to remain suspended and in equilibrium with the lmo liquid for relatively long periods of time this extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust previous authors have proposed a three component model for the evolution of high ti mare basalt source regions this model includes kreep early olivine rich high mg cumulates and late ilmeniterich low mg cumulates in various proportions however we propose a model for high ti basalt parent magmas which is in accord with studies of terrestrial layered intrusions this model for the high ti source includes trapped instantaneous residual liquid tirl 1 3 and entrainment of a small 2 5 proportion of plagioclase into the late stage cumulate pile in order to account for both the observed al compositions and trace element characteristics of high ti mare basalts melting of this relatively shallow ilmenite and clinopyroxene bearing late stage cumulate can generate high ti mare basalt magmas furthermore we are in agreement with other workers that only through a process of nonmodal melting will the high ti values for the parent magmas be realized large scale convective overturn of the cumulate pile and mixing of kreep with early and late stage cumulates is not required however localized overturn of the upper tenth of the cumulate pile is likely and in fact required to achieve an appropriate major element balance for the high ti mare basalt source region

microtremor measurements used to map thickness of soft sediments the observations about the behavior of microtremor spectra presented here show that noise measurements can be used as a powerful tool to determine the thickness of soft cover layers the most suitable method for this determination is nakamura s technique which is the ratio of the horizontal component noise spectrum and that of the vertical component i i v spectrum the frequency of the main peak in these spectral ratios correlates well with the sediment thickness at the site using an extensive database of microtremor measurements carried out in the western lower rhine embayment germany it was possible to show that this correlation is clearly valid for a wide range of thickness namely from tens of meters to more than 1000 m a simple formula was derived that for the sediments to be found in the area investigated directly calculates the cover thickness from the frequency of the main peak in the h v spectrum a comparison with calculated resonant frequencies sug gests the relation derived from the noise measurements depending on the velocity depth function of the shear wave classical spectral ratios are shown to be strongly influenced by the noise level and are therefore less reliable in determining the res onant frequency of the subsoil the practical relevance of the investigation is illus trated by means of cross sections constructed from results of the microtremor anal yses which provide a convincing image of the surficial structure of the areas investigated

a post accretionary lull in large impacts on early mars the timing and number of large impact basins on early mars are poorly constrained gravity and topographic analyses support a lull in basin forming impacts following the main stage of accretion

the origin of sh wave resonance frequencies in sedimentary layers summary resonance frequencies are often analysed in geo engineering studies to evaluate seismic risk and microzonation in urban areas the nakamura technique constitutes a popular approach that computes the spectral ratio of horizontal to vertical ground motion in ambient noise recordings to reveal the existence of any site resonance frequencies its theoretical basis remains however unclear with some authors arguing that the method de emphasizes any rayleigh wave contributions and that the resonance frequencies are solely caused by vertically incident sh waves other authors explain the same resonance frequencies by the ellipticity of the fundamental rayleigh wave recent numerical simulations reveal that the magnitude of the peak frequency is proportional to the relative portion of love waves present this study demonstrates that love waves alone can be responsible for any observed resonance frequencies in sedimentary layers yet sharp sh wave resonance frequencies are only excited by a source in the bedrock these resonance frequencies are caused by inhomogeneous waves excited by the bedrock source that tunnel through the high velocity bedrock to emerge in the low velocity sediments with a very reduced range of slownesses the resulting sh waves are then free to interfere constructively thereby creating the observed resonance frequencies this general trigger mechanism leads to resonances that are almost offset independent the resulting resonance frequencies map onto points of maximum curvature in the lovewave phase velocity dispersion curves at or just beyond the critical horizontal slowness they can be analysed with the quarter wavelength law if a large velocity contrast exists between the unconsolidated sediments and the bedrock a minor modification of the quarter wavelength law provides more accurate predictions also for smaller velocity contrasts multisource simulations show that site amplification factors as determined by horizontalover vertical h v spectral ratios would not only depend on the relative portion of love waves in the total wavefield but also on the depth distribution and the relative strength of the sh sources inside the bedrock compared with those in the sediments an accurate interpretation of site amplification factors by means of h v peak frequencies would thus require in depth knowledge of the causes and origins of the local microseismic noise field

enigmatic amphibians in mid cretaceous amber were chameleon like ballistic feeders albanerpetontids are tiny enigmatic fossil amphibians with a distinctive suite of characteristics including scales and specialized jaw and neck joints here we describe a new genus and species of albanerpetontid represented by fully articulated and three dimensional specimens preserved in amber these specimens preserve skeletal and soft tissues including an elongated median hyoid element the tip of which remains embedded in a distal tongue pad this arrangement is very similar to the long rapidly projecting tongue of chameleons our results thus suggest that albanerpetontids were sit and wait ballistic tongue feeders extending the record of this specialized feeding mode by around 100 million years

microtremor hvsr study for assessing site effects in the bovec basin nw slovenia related to 1998 mw5 6 and 2004 mw5 2 earthquakes abstract the bovec basin which is filled with glacial and fluvial sediments has recently been struck by two strong earthquakes 1998 and 2004 which caused extensive damage vii viii ems 98 strong site effects resulted in large variations in damage to buildings in the area which could not be explained by the surface variations in quaternary sediments the microtremor horizontal to vertical spectral ratio hvrs method was therefore applied to a 200 m dense grid of free field measurements to assess the fundamental frequency of the sediments large variations in the sediment frequency 3 22 hz were obtained with most of the observed values in the range 6 12 hz the observed frequencies cannot be related to the total thickness of quaternary sediments sand gravel but can be explained by the presence of conglomerate or lithified moraine at shallow depths the results were compared also with the velocity structure derived from seismic refraction data microtremor measurements performed in several two and some three and four storey houses masonry with rc floors which prevail in the bovec basin have shown that the main building frequencies in the area are in the range 7 11 hz this indicates that damage to houses in both earthquakes in some parts of the basin was enhanced by site amplification and soil structure resonance areas of possible soil structure resonance were identified in the settlements bovec brdo bovec mala vas cezsoca and kal koritnica considerable changes in fundamental frequencies within short distances were established in the town of bovec their values are as high as 22 hz in the central part of the town but diminish to 6 11 hz in the adjacent brdo and mala vas districts this is in agreement with the distribution of damage in both earthquakes which was considerably higher in brdo and mala vas although the houses in the central part of the town are older microtremor investigations have proved an effective tool for assessment of site effects in cases of complex geological structure commonly encountered in young alpine basins filled with glaciofluvial sediments which are partly cemented lithified layers can considerably change the fundamental frequency and consequently the site effects by taking additional measurements in buildings possible soil structure resonance can be identified

early martian mantle overturn inferred from isotopic composition of nakhlite meteorites following the crystallization of a magma ocean the martian mantle probably underwent an overturning event but its initiation timing and geochemical consequences are poorly constrained isotopic data for martian meteorites and numerical simulations provide strong evidence for early overturning in the martian mantle