hopanoid hydrocarbons and perylene in lake biwa japan sediments environmental control on their abundance and molecular composition abstract we examined the vertical distribution of hopanoid hydrocarbons and perylene in sedimentary sections from lake biwa japan and discuss the results with respect to paleoenvironmental information from around the lake region over the last 120 kyr moretene concentration was high above the sections where fall out events of tephra tephra at occurred ca 30 kyr before present bp this feature suggests that the tephra fall out events created o 2 deficient conditions resulting in high activity of methane producing bacteria and of methanotrophic moretene producing bacteria becoming active above the tephra layer five sections at 10 20 kyr ca 35 kyr ca 70 kyr ca 90 kyr and ca 110 kyr bp exhibited peaks in the ratio of 17 21 22r homohopane to 17 21 22r homohopane hopc 31 the n c 23 n c 31 alkane ratio in these sections was 0 6 0 1 n 49 very low if compared with typical characteristics of n alkanes for a sphagnum peat environment n c 23 n c 31 ca 3 6 bingham et al 2010 we conclude that sphagnum peat may not have been an important contributor of n alkanes over the past 120 kyr comparison with previous pollen records for the lake region suggests that high hopc 31 values may be caused by production of acidic soil from expansion of temperate conifer e g cryptomeria forest under cold and wet climate conditions the abundance of perylene relative to sediment or total organic carbon toc was high in the sections at ca 20 kyr ca 70 kyr and ca 90 kyr bp these sections were approximately in accord with those having a maximum in hopc 31 this concordance indicates that the climatic conditions suitable for the production of perylene quinone in soil surrounding the lake coincided with those for a high hopc 31 ratio thus hopc 31 and perylene toc might be useful as proxies of soil acidity temperature and humidity

planetary surface dating from crater size frequency distribution measurements partial resurfacing events and statistical age uncertainty abstract we describe the procedure to fit a cumulative production function polynomial to a partial crater size frequency distribution the technique is of particular use in deriving ages for surfaces which have undergone partial resurfacing events namely erosional or depositional events which have affected a limited diameter range of the crater population we demonstrate its use in obtaining times for both the surface formation and the resurfacing event we give a practical outline of the method for making age measurements from crater counts and how to identify resurfacing effects in the results we discuss the conversion of production function polynomials between common presentations and the statistical uncertainty of the determined ages with respect to the non linear chronology function and a minor refinement of data binning

numerical modeling of asteroid survivability and possible scenarios for the morokweng crater forming impact the fate of the impactor is an important aspect of the impact cratering process defining impactor material as surviving if it remains solid i e does not melt or vaporize during crater formation previous numerical modeling and experiments have shown that survivability decreases with increasing impact velocity impact angle with respect to the horizontal and target density here we show that in addition to these impactor survivability depends on the porosity and shape of the impactor increasing impactor porosity decreases impactor survivability while prolate shaped polar axis equatorial axis impactors survive impact more so than spherical and oblate shaped polar axis equatorial axis impactors these results are used to produce a relatively simple equation which can be used to estimate the impactor fraction shocked to a given pressure as a function of these parameters by applying our findings to the morokweng crater forming impact we suggest impact scenarios that explain the high meteoritic content and presence of unmolten fossil meteorites within the morokweng crater in addition to previous suggestions of a low velocity and or high angled impact this work suggests that an elongated and or low porosity impactor may also help explain the anomalously high survivability of the morokweng impactor

origin of perylene in ancient sediments and its geological significance the distributions of polycyclic aromatic hydrocarbons pahs in sediments of three upper triassic to middle jurassic sedimentary sequences from the northern carnarvon basin australia have been investigated perylene was found to be a major pah component in the top lower to base middle jurassic sediments that are immature or at low maturity its depth age profiles are not related to the combustion derived pahs that have been believed to be produced during ancient vegetation fires before deposition this suggests a diagenetic origin for perylene the concentration of perylene in the sediments is proportional to the amount of terrestrial input decreasing with distance from the source of land sediments its carbon isotope composition is slightly heavier than higher plant derived pahs but still in the range of the terrestrially sourced pahs including higher plant pahs and combustion derived pahs as suggested previously fungi are proposed to be the major precursor carriers for perylene in sediments based on the facts that 1 perylenequinone structures have been previously suggested to be the natural precursors for perylene 2 perylenequinone pigments exist in many fungal bodies 3 fungi have played an important role during geological processes

a strain based porosity model for use in hydrocode simulations of impacts and implications for transient crater growth in porous targets numerical modelling of impact cratering has reached a high degree of sophistication however the treatment of porous materials still poses a large problem in hydrocode calculations we present a novel approach for dealing with porous compaction in numerical modelling of impact crater formation in contrast to previous attempts e g p alpha model snowplow model our model accounts for the collapse of pore space by assuming that the compaction function depends upon volumetric strain rather than pressure our new e alpha model requires only four input parameters and each has a physical meaning the model is simple and intuitive and shows good agreement with a wide variety of experimental data ranging from static compaction tests to highly dynamic impact experiments our major objective in developing the model is to investigate the effect of porosity and internal friction on transient crater formation we present preliminary numerical model results that suggest that both porosity and internal friction play an important role in limiting crater growth over a large range in gravity scaled source size

combined u pb dating and sm nd studies on lower crustal and mantle xenoliths from the delegate basaltic pipes southeastern australia mafic rocks dominate the lower crustal and upper mantle xenolith suites within the jurassic delegate basaltic diatremes in the paleozoic lachlan fold belt se australia two upper mantle mafic xenoliths from the delegate pipes a garnet pyroxenite and a garnet granulite equilibrated at 1060 and 1140 c and 40 50 km yield garnet clinopyroxene sm nd ages of 160 4 ma and 153 10 ma respectively both ages are indistinguishable from the time of eruption of the diatremes and are interpreted as showing continuous isotopic equilibrium within the mantle of sm and nd between garnet clinopyroxene at temperatures 1050 c a lower crustal 2 pyroxene granulite xenolith equilibrated at 810 850 c and ca 25 km yields a clinopyroxene plagioclase whole rock sm nd isochron ages of 283 26 ma this age probably reflects partial resetting of the isotopic systems of much older granulite during slow cooling or after a heating event in the lower crust associated with the jurassic magmatic activity represented by the basaltic host rock metamorphic zircons from the 2 pyroxene granulite xenolith were dated by the u pb method at 398 2 and 391 2 ma these ages are considered to date granulite facies metamorphic events in the lower crust of the region the age gap between the granulite facies metamorphism and granitoid plutonism in the region 420 410 ma indicates that the dated granulite is unlikely to represent residue after partial melting and magma extraction that generated the regional granitoids it is suggested that these ages may record a relatively slow cooling following the cessation of mafic magmatic intrusion that formed the xenolith protoliths and that was probably the heat source responsible for granite production at about 25 km this thermal relaxation accounts for the change from an olivine plagioclase 2 pyroxene gabbroic assemblage into the granulite facies 2 pyroxene plagioclase spinel field

137cs and 210pb dating of sediments from soft water lakes in new england u s a and scandinavia a failure of 137cs dating abstract deep water sediment cores from 32 scandinavian and 19 northern new england u s a lakes were analyzed for 137cs 210pb was analyzed in cores from 16 and 14 of these lakes respectively additional dating of the new england cores was based on chronostratigraphic pollen markers the profiles in sediment of 137cs deviate greatly from expectations based on fallout history the profiles have their maxima at the surface and 137cs occurs at depths dated by 210pb and pollen as many decades older than the beginning of 137cs fallout non exponential 210pb profiles in certain lakes most in new england and pollen dates suggest that bioturbation physical mixing changes in sedimentation rate or acidification may be occurring but this is insufficient to account for the deviant 137cs profiles in most of the lakes there is no evidence of mixing we argue that the occurrence of 137cs at prefallout sediment depths is due mostly to net downward molecular diffusion and adsorption and that surface concentration is due to net upward diffusion and adsorption and possibly also biological uptake recycling of sedimentary 137cs in the water column and delayed input from the watershed it is probable that much of the 137cs entering these lakes is carried by organic detritus mobility of 137cs in this sediment may be a function of release by organic decomposition and scarcity of clay minerals for adsorption correlation analyses of the sedimentary radionuclide activities vs physical and chemical characteristics of the lake water sediment and watersheds suggest that considerable trapping of 137cs and 210pb by terrestrial vegetation and organic soils is occurring the resultant delayed export to these lakes is contributing to the failure of 137cs as a dating tool but 210pb dating can be valid under these circumstances

cooling history of lunar mg suite gabbronorite 76255 troctolite 76535 and stillwater pyroxenite sc 936 the record in exsolution and ordering in pyroxenes we have determined cooling rates of orthopyroxene crystals from two mg suite lunar samples gabbronorite 76255 and troctolite 76535 and one terrestrial sample orthopyroxenite sc 936 from the stillwater complex on the basis of their fe mg ordering states in addition a cooling rate of 76255 was determined by modeling the formation of exsolution lamellae in pyroxenes the m1 m2 site occupancies of the orthopyroxene crystals were determined by single crystal x ray diffraction and the rate constant for the ordering reaction was used along with calibrations of the equilibrium intracrystalline fractionation of fe and mg as a function of temperature to calculate cooling rates the closure temperatures tc of cation ordering are 525 c for 76255 500 c for 76535 and 350 c for sc 936 corresponding to cooling rates of 4 10 2 c year at the closure temperature for the lunar samples and 10 6 c year for the stillwater sample a cooling rate for 76255 determined by simulating the exsolution process is 1 7 10 2 c year at a closure temperature for exsolution of 700 c the fe mg ordering cooling rate determined for 76535 reflects a complex thermal history superimposed on the initial plutonic provenance established for this sample mccallum i s schwartz j m 2001 lunar mg suite thermobarometry and petrogenesis of parental magmas j geophys res 106 27969 27983 the preservation of a crystallization age of 4 51 ga and a metamorphic age of 4 25 ga for 76535 is consistent with a model in which excavation of this sample from the lower lunar crust took place while the sample was at a temperature above the closure temperatures for the sm nd u pb and ar ar isotopic systems temperatures in excess of the isotopic closure temperatures i e 600 c in the lower lunar crust were maintained by heat diffusing from concentrations of u and th rich kreep material at the base of the crust on the other hand 76255 formed at a much shallower depth in the lunar crust 2 km and was well below its isotopic closure temperatures at the time of excavation most likely during the serenitatis basin forming impact event both lunar samples were reheated during transport to the surface and deposition in hot ejecta blankets the reheating was short lived but apparently sufficient to redistribute fe and mg in m sites in orthopyroxenes for the lunar samples the cooling rates based on fe mg ordering represent final stage cooling within an ejecta blanket

a hypothesis for the origin of perylene based on its low abundance in sediments of green bay wisconsin abstract perylene a polycyclic aromatic hydrocarbon pah that is common in sediments is believed to originate principally from anaerobic diagenesis of organic matter but its precursor material remains enigmatic we have investigated the formation of perylene in a dated sediment core from green bay wi comparisons of sedimentary profiles of perylene anthropogenic pahs land plant derived hydrocarbons and aquatic contributions of organic matter rule out a specific industrial terrigenous or aquatic precursor for perylene instead perylene seems to be formed from any kind of organic matter as a consequence of a specific type of microbial activity in sub bottom sediments despite an abundance of organic matter the amount of perylene is low in green bay and in other organic carbon rich lake sediments the abundant availability of organic matter that stimulates microbial activity in green bay sediments would seem to favor perylene formation in such sediments we therefore hypothesize that the microorganisms responsible for perylene formation do not compete successfully with those that flourish in sediments rich in organic matter perylene formation consequently does not become significant until deeper in sediments after the more reactive types of organic matter have been consumed

perylene in lake biwa sediments originating from cenococcum geophilum in its catchment area abstract perylene which is composed of five benzene rings is commonly found in sediments throughout the world at concentrations and distributions that are different from those of other polycyclic aromatic hydrocarbons the only information available on the origin of perylene comes from 4 9 dihydroxyperylene 3 10 quinone dhpq which originates from fungal component symbiosis or from parasites on plants however there is no direct evidence of a mechanism of perylene formation in this study we examined the relationship between sedimentary perylene and cenococcum geophilum c geophilum in a catchment area at lake biwa sclerotium grains of c geophilum containing dhpq were found in this catchment area approximately 40 balls kg 1 dried soil for 1 mm and small sclerotium grains were frequently found in the sediment in the sediment sample we also found broken particles containing perylene and they had a porous structure characteristic of sclerotium grains furthermore the particles contained dhpq in different transformation stages to perylene via 3 10 perylenequinone 3 10 pq this finding was consistent with results from elemental analysis oxygen carbon because a remarkable amount of dhpq originating from c geophilum also exists in the humic acids of soils and because the inputs of compounds to the lake depend strongly on the rivers perylene in the lake biwa sediment originates mainly from the dhpq of c geophilum in its catchment area

asymmetric thermal evolution of the moon 1 the moon possesses a clear dichotomy in geological processes between the nearside and farside hemispheres the most pronounced expressions of this dichotomy are the strong concentration of radioactive heat sources on the nearside in a region known as the procellarum kreep terrane pkt and the mare basaltic lava flows that erupted in or adjacent to this terrane we model the thermochemical evolution of the moon using a 3 d spherical thermochemical convection code in order to assess the consequences of a layer enriched in heat sources below the pkt on the moon s global evolution we find that in addition to localizing most of the melt production on the nearside such an enriched concentration of heat sources in the pkt crust has an influence down to the core mantle boundary and leaves a present day temperature anomaly within the nearside mantle moderate gravitational and topographic anomalies that are predicted in the pkt but not observed may be masked either by crustal thinning or gravitational anomalies from dense material in the underlying mantle our models also predict crystallization of an inner core for sulfur concentrations less than 6 wt

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

a possible terrigenous origin for perylene based on a sedimentary record of a pond lorraine france abstract the origin of perylene a five ring polycyclic aromatic hydrocarbon pah in sediments has been a matter of constant debate and its formation mechanisms remain unclear a perylene record in sediment was described and could support a clear link between perylene and terrigenous organic matter om input the distributions of pahs the variations of organic proxies such as the ratio of terrigenous to aquatic n alkanes tar hc and 5 h stanols 5 sterols ratio in sediments have been investigated sediments were sampled from a pond artificially created during the middle ages from a swampy area in the period prior to the pond creation for which high contributions of terrigenous om were evidenced perylene was found to be the predominant pah furthermore perylene content was shown to increase in response to the establishment of more reducing conditions this result supports the common idea that the main source of perylene is natural and derives from biogenic precursors under reducing conditions the creation of the pond in this wetland is marked by the deposition of a wood rich level characterized both by more oxygenated conditions and higher concentrations of perylene these high concentrations could result from the introduction of high concentrations of biogenic precursors of perylene under oxidative conditions subsequently the progressive burial of the woody level could have allowed the establishment of oxygen depleted conditions and the formation of perylene these results validate the use of perylene as a paleoenvironmental marker of terrigenous sources but it must be carefully used as a marker for syn or post depositional oxygen depleted conditions in lacustrine environments

nonuniform cratering of the moon and a revised crater chronology of the inner solar system abstract we model the cratering of the moon and terrestrial planets from the present knowledge of the orbital and size distribution of asteroids and comets in the inner solar system in order to refine the crater chronology method impact occurrences locations velocities and incidence angles are calculated semi analytically and scaling laws are used to convert impactor sizes into crater sizes our approach is generalizable to other moons or planets the lunar cratering rate varies with both latitude and longitude with respect to the global average it is about 25 lower at 65 n 90 e and larger by the same amount at the apex of motion 0 n 90 w for the present earth moon separation the measured size frequency distributions of lunar craters are reconciled with the observed population of near earth objects under the assumption that craters smaller than a few kilometers in diameter form in a porous megaregolith varying depths of this megaregolith between the mare and highlands is a plausible partial explanation for differences in previously reported measured size frequency distributions we give a revised analytical relationship between the number of craters and the age of a lunar surface for the inner planets expected size frequency crater distributions are calculated that account for differences in impact conditions and the age of a few key geologic units is given we estimate the orientale and caloris basins to be 3 73 ga old and the surface of venus to be 240 ma old the terrestrial cratering record is consistent with the revised chronology and a constant impact rate over the last 400 ma better knowledge of the orbital dynamics crater scaling laws and megaregolith properties are needed to confidently assess the net uncertainty of the model ages that result from the combination of numerous steps from the observation of asteroids to the formation of craters our model may be inaccurate for periods prior to 3 5 ga because of a different impactor population or for craters smaller than a few kilometers on mars and mercury due to the presence of subsurface ice and to the abundance of large secondaries respectively standard parameter values allow for the first time to naturally reproduce both the size distribution and absolute number of lunar craters up to 3 5 ga ago and give self consistent estimates of the planetary cratering rates relative to the moon

alkane and pah depositional history sources and fluxes in sediments from the fraser river basin and strait of georgia canada hydrocarbon data for dated sediment cores from fraser basin lakes and the strait of georgia in canada reveal a pristine pre industrial background that remains unaltered in modern sediments far from human activities these pristine sediments contain polycyclic aromatic hydrocarbons pahs from combustion natural forest and prairie fires and alkanes and pahs from weathering of soils containing vascular plant remains and natural petroleum hydrocarbons and algal production at other locations examined however these natural loadings have been augmented over the past century by hydrocarbons from petroleum the combustion of liquid oil gasoline and solid coal wood fuels and from processing of wood either directly from disturbed land and slash burning or indirectly through pulp mill effluent although contamination is clearest where there are nearby human activities alkane profiles pah distributions and alkane unresolved complex mixtures suggest a widespread contamination from petroleum combustion products from human activities can also be identified although with less source specificity than with the petroleum products regional emissions from anthropogenic combustion processes appear to support modern pah increases within the fraser river basin and there is little evidence of inputs from global emissions principal components analysis using the new centred log ratio normalisation procedure to normalise data discriminates well between pahs entering lakes from runoff or the atmosphere and pah formed diagenetically within lake sediments as well as between combustion and petroleum pahs

the canyon diablo impact event 2 projectile fate and target melting upon impact abstract despite its centennial exploration history there are still unresolved questions about meteor crater the first recognized impact crater on earth this theoretical study addresses some of these questions by comparing model results with field and laboratory studies of meteor crater our results indicate that meteor crater was formed by a high velocity impact of a fragmented projectile ruling out a highly dispersed swarm as well as a very low impact velocity projectile fragmentation caused many fragments to fall separately from the main body of the impactor making up the bulk of the canyon diablo meteorites most of these fragments were engulfed in the expansion plume as they approached the surface without suffering high shock compression and were redistributed randomly around the crater thus the distribution of canyon diablo meteorites is not representative of projectile trajectory as is usual for impactor fragments in smaller strewn fields at least 50 of the main impactor was ejected from the crater during crater excavation and was dispersed mostly downrange of the crater as molten particles spheroids and highly shocked solid fragments shrapnel when compared with the known distribution model results suggest an impactor from the sw overall every model case produced much higher amounts of pure projectile material than observed the projectile target mixing was not considered in the models however this process could be the main sink of projectile melt as all analyzed melt particles have high concentrations of projectile material the fate of the solid projectile fragments is still not completely resolved model results suggest that the depth of melting in the target can reach the coconino sandstone formation however most of the ejected melt originates from 30 40 m depth and thus is limited to moenkopi and upper kaibab material some melt remains in the target based on the estimated volume of the breccia lens at meteor crater our models suggest at most a 2 content of melt in the breccia finally a high water table at the time of impact could have aided strong dispersion of target and projectile melt

age determination of linear surface features using the buffered crater counting approach case studies of the sirenum and fortuna fossae graben systems on mars buffered crater counting bcc offers a possibility to determine ages of linear curvilinear surface features that provide no or only very limited surface areas for the conventional crater counting approach in this study we applied the bcc analysis to two tectonic fault systems fortuna fossae and a subsection of sirenum fossae we compared bcc results with age estimates derived from conventional crater counting on the surrounding geologic units and investigated to what extent crater ejecta blankets can be used for determining the stratigraphic placement of craters pre or post dating the formation of linear features furthermore we introduce a new functionality of the cratertools software for arcgis which allows for a user friendly semi automatic application of the otherwise time consuming procedure of bcc analysis the software provides the resulting crater size frequency data in a standard format which can be read and analyzed in the craterstats analysis software our case studies showed that the bcc approach provides equivalent or even more precise age results compared to the conventional stratigraphic approach here we found that the investigated section of sirenum fossae is younger than previously thought the derived formation age from the bcc analysis is 3 44 0 25 0 1ga which corresponds to late instead of early hesperian fortuna fossae formed shortly after the emplacement of its now fractured geologic host unit late hesperian ages derived from bcc analysis vary between 3 53 0 11 0 06ga and 3 50 0 11 0 07ga furthermore we recommend the use of crater ejecta blankets to position them in the stratigraphic sequence in order to improve crater statistics however the accuracy of the results depends on the extent and preservation state of the continuous ejecta blankets in the region of interest thus the applied buffer width has to be chosen carefully according to investigated crater sizes and local observations

compositional variations of the lunar crust results from radiative transfer modeling of central peak spectra 1 we present model mineralogy of impact crater central peaks combined with crustal thickness and crater central peak depth of origin models to report multiple perspectives of lunar crustal composition with depth here we report the analyses of 55 impact crater central peaks and how their compositions directly relate to the lunar highlands sample suite a radiative transfer model is used to analyze clementine visible plus near infrared spectra to place compositional constraints on these central peak materials central peaks analyzed are dominantly magnesian and plagioclase poor strong compositional similarities to lunar mg suite materials are evident relative to crustal thickness estimates central peak mineralogy becomes more plagioclase rich as the crust thickens relative to the crust mantle boundary the origin of peaks with dominantly mafic mineralogy are confined to the lower crust and primarily within the south pole aitken and procellarum kreep terranes pkt additionally central peaks with anorthositic mineralogy 60 vol plagioclase are transported to the surface from all depths in the crustal column and confined to the feldspathic highlands terrane fht the discovery of mafic and magnesian materials consistent with mg suite rocks of the sample collection in all lunar terranes suggests that the process and sources that give rise to these types of rocks is not unique to the pkt and not necessarily dependent on incompatible elements for formation the identification of ferroan and magnesian anorthositic material near the crust mantle boundary of the fht is also inconsistent with an increasing mafic feldspar ratio and mg with depth in the crust

support for the lunar cataclysm hypothesis from lunar meteorite impact melt ages lunar meteorites represent a more random sampling of lunar material than the apollo or luna collections and as such lunar meteorite impact melt ages are the most important data in nearly 30 years with which to reexamine the lunar cataclysm hypothesis within the lunar meteorite breccias mac 88105 que 93069 dag 262 and dag 400 seven to nine different impact events are represented with 40ar 39ar ages between 2 76 and 3 92 billion years ago ga the lack of impact melt older than 3 92 ga supports the concept of a short intense period of bombardment in the earth moon system at approximately 3 9 ga this was an anomalous spike of impact activity on the otherwise declining impact frequency curve

origin of the lunar highlands mg suite an integrated petrology geochemistry chronology and remote sensing perspective the mg suite represents an enigmatic episode of lunar highlands magmatism that presumably represents the first stage of crustal building following primordial differentiation this review examines the mineralogy geochemistry petrology chronology and the planetary scale distribution of this suite of highlands plutonic rocks presents models for their origin examines petrogenetic relationships to other highlands rocks and explores the link between this style of magmatism and early stages of lunar differentiation of the models considered for the origin of the parent magmas for the mg suite the data best fit a process in which hot solidus temperature at 2 gpa 1600 to 1800 c and less dense 3100 kg m3 early lunar magma ocean cumulates rise to the base of the crust during cumulate pile overturn some decompressional melting would occur but placing a hot cumulate horizon adjacent to the plagioclase rich primordial crust and kreep rich lithologies at temperatures of 1300 c would result in the hybridization of these divergent primordial lithologies producing mg suite parent magmas as urkreep primeval kreep is not the petrologic driver of this style of magmatism outside of the procellarum kreep terrane pkt mg suite magmas are not required to have a kreep signature evaluation of the chronology of this episode of highlands evolution indicates that mg suite magmatism was initiated soon after primordial differentiation 10 m y alternatively the thermal event associated with the mantle overturn may have disrupted the chronometers utilized to date the primordial crust petrogenetic relationships between the mg suite and other highlands suites e g alkali suite and magnesian anorthositic granulites are consistent with both fractional crystallization processes and melting of distinctly different hybrid sources

distributions of polycyclic aromatic hydrocarbons in a sediment core from the north basin of lake biwa japan abstract we analyzed the vertical distributions of 19 polycyclic aromatic hydrocarbons pahs total organic carbon toc total nitrogen tn and stable carbon isotope ratio 13 c in a 27 cm sediment core from the north basin of lake biwa in order to elucidate changes in pah sources and events possibly affecting the lake over the last few decades both toc and tn increased gradually from the deepest layer toc 1 2 wt tn 0 14 wt to the uppermost layer toc 4 0 wt tn 0 45 wt the toc tn ratio a useful indicator for distinguishing between aquatic and terrestrial plant sources increased remarkably at 11 13 cm 10 3 11 1 vs 8 5 9 7 at other depths indicating that large amounts of terrestrial material entered the lake when that layer was deposited all pahs except perylene gradually increased from the deepest layer but not as clearly as toc and tn at 11 13 cm all pahs except perylene transiently decreased and perylene transiently increased since the pah ratios used for the elucidation of sources did not change greatly throughout the core we consider that the major source of pahs in the lake has not changed during the last few decades the brief decrease in pahs at 11 13 cm could be the result of dilution by a large input of terrestrial material which brought in perylene

the sculptured hills of the taurus highlands implications for the relative age of serenitatis basin chronologies and the cratering history of the moon 1 new images from the lunar reconnaissance orbiter camera show the distribution and geological relations of the sculptured hills a geological unit widespread in the highlands between the serenitatis and crisium basins the sculptured hills shows knobby undulating radially textured and plains like morphologies and in many places is indistinguishable from the similarly knobby alpes formation a facies of ejecta from the imbrium basin the new lroc image data show that the sculptured hills in the taurus highlands is imbrium ejecta and not directly related to the formation of the serenitatis basin this occurrence and the geological relations of this unit suggests that the apollo 17 impact melts may not be not samples of the serenitatis basin forming impact leaving their provenance undetermined and origin unexplained if the apollo 17 melt rocks are serenitatis impact melt up to half of the basin and large crater population of the moon was created within a 30 ma interval around 3 8 ga in a global impact cataclysm either interpretation significantly changes our view of the impact process and history of the earth moon system

new insights into the origin of perylene in geological samples abstract the origin of the polycyclic aromatic hydrocarbon pah perylene in sediments and petroleum has been a matter of continued debate reported to occur in phanerozoic organic matter om fossil crinoids and tropical termite mounds its mechanism of formation remains unclear while a combustion source can be excluded structural similarities to perylene quinone like components present in e g fungi plants crinoids and insects potentially suggest a product precursor relationship here we report perylene concentrations 13c 12c and d h ratios from a holocene sediment profile from the qingpu trench yangtze delta region china perylene concentrations differ from those of pyrogenic pahs and rise to prominence in a stratigraphic interval that was dominated by woody vegetation as determined by palynology including fungal spores in this zone perylene concentrations exhibit an inverse relationship to the lignin marker guaiacol d h ratios between 284 and 317 similar to the methoxy groups in lignin as well as co variation with spores from wood degrading fungi 13c 12c of perylene differs from that of land plant wax alkanes and falls in the fractionation range expected for saprophytic fungi that utilise lignin which is isotopically lighter than cellulose and whole wood during progressive lignin degradation the relative carbon isotopic ratio of the perylene decreases we therefore hypothesise a relationship of perylene to the activity of wood degrading fungi to support our hypothesis we analysed a wide range of phanerozoic sediments and oils and found perylene to generally be present in subordinate amounts before the evolutionary rise of vascular plants and to be generally absent from marine sourced oils few exceptions being attributed perhaps to a contribution of marine and or terrestrial derived fungi anoxia especially under marine conditions and or contamination of core material by fungi a series of low molecular weight aromatic quinones bearing the perylene backbone were detected in devonian and cretaceous sediments potentially representing precursor components to perylene

lunar impact basins stratigraphy sequence and ages from superposed impact crater populations measured from lunar orbiter laser altimeter lola data 1 impact basin formation is a fundamental process in the evolution of the moon and records the history of impactors in the early solar system in order to assess the stratigraphy sequence and ages of impact basins and the impactor population as a function of time we have used topography from the lunar orbiter laser altimeter lola on the lunar reconnaissance orbiter lro to measure the superposed impact crater size frequency distributions for 30 lunar basins d 300 km these data generally support the widely used wilhelms sequence of lunar basins although we find significantly higher densities of superposed craters on many lunar basins than derived by wilhelms 50 higher densities our data also provide new insight into the timing of the transition between distinct crater populations characteristic of ancient and young lunar terrains the transition from a lunar impact flux dominated by population 1 to population 2 occurred before the mid nectarian this is before the end of the period of rapid cratering and potentially before the end of the hypothesized late heavy bombardment lola derived crater densities also suggest that many pre nectarian basins such as south pole aitken have been cratered to saturation equilibrium finally both crater counts and stratigraphic observations based on lola data are applicable to specific basin stratigraphic problems of interest for example using these data we suggest that serenitatis is older than nectaris and humboldtianum is younger than crisium sample return missions to specific basins can anchor these measurements to a pre imbrian absolute chronology

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

a 4 2 billion year old impact basin on the moon u pb dating of zirconolite and apatite in lunar melt rock 67955 abstract a sharp rise in the flux of asteroid size bodies traversing the inner solar system at 3 9 ga has become a central tenet of recent models describing planetary dynamics and the potential habitability of early terrestrial environments the prevalence of 3 9 ga crystallization ages for lunar impact melt breccias and u pb isotopic compositions of lunar crustal rocks provide the primary evidence for a short lived cataclysmic episode of late heavy bombardment at that time here we report u pb isotopic compositions of zirconolite and apatite in coarse grained lunar melt rock 67955 measured by ion microprobe that date a basin scale impact melting event on the moon at 4 22 0 01 ga followed by entrainment within lower grade ejecta from a younger basin approximately 300 million yr later significant impacts prior to 3 9 ga are also recorded by lunar zircons although the magnitudes of those events are difficult to establish other isotopic evidence such as 40 ar 39 ar ages of granulitic lunar breccias regolith fragments and clasts extracted from fragmental breccias and re os isotopic compositions of lunar metal is also suggestive of impact related thermal events in the lunar crust during the period 4 1 4 3 ga we conclude that numerous large impactors hit the moon prior to the canonical 3 9 ga cataclysm that some of those pre cataclysm impacts were similar in size to the younger lunar basins and that the oldest preserved lunar basins are likely to be significantly older than 3 9 ga this provides sample based support for dynamical models capable of producing older basins on the moon and discrete populations of impactors an extended period of basin formation implies a less intense cataclysm at 3 9 ga and therefore a better opportunity for preservation of early habitable niches and hadean crust on the earth a diminished cataclysm at 3 9 ga suggests that the similarity in the age of the oldest terrestrial continental crust with the canonical lunar cataclysm is likely to be coincidental with no genetic significance

the onset of the lunar cataclysm as recorded in its ancient crater populations abstract the earliest bombardment history of the moon potentially provides powerful constraints for solar system evolution models a major uncertainty however is how much of this history is actually recorded in lunar craters for example some argue that most ancient lunar craters and basins were produced by a declining bombardment of leftover planetesimals produced by terrestrial planet formation processes others believe that most lunar craters and large basins were formed in a narrow time interval between 3 8 and 4 0 ga the so called lunar cataclysm in the light of recent improvements in our understanding of early solar system evolution it is possible that the contributions from both scenarios could be represented in the lunar crater record if so when did the declining bombardment end and the lunar cataclysm begin here we show using new counts of 15 150 km diameter craters on the most ancient lunar terrains that the craters found on or near nectaris basin appear to have been created by projectiles hitting twice as fast as those that made the oldest craters on various pre nectarian era terrains this dramatic velocity increase is consistent with the existence of a lunar cataclysm and potentially with a late reconfiguration of giant planet orbits which may have strongly modified the source of lunar impactors this work also suggests that the lunar cataclysm may have started near the formation time of nectaris basin this possibility implies that south pole aitken basin spa the largest lunar basin and one of the oldest by superposition was not created during the cataclysm this view is strengthened by our interpretation that a substantial fraction of ancient craters on spa were made by low velocity impactors finally we believe these results shed new light on the impact history of the primordial earth

possible mantle origin of olivine around lunar impact basins detected by selene the composition structure and evolution of the moon s mantle is poorly constrained a global survey of the moon s surface using the spectral profiler onboard the lunar explorer selene kaguya identifies a number of exposures of olivine in concentric regions around lunar craters with a possible mantle origin

global characteristics of porosity and density stratification within the lunar crust from grail gravity and lunar orbiter laser altimeter topography data the gravity recovery and interior laboratory grail mission is providing unprecedentedly high resolution gravity data the gravity signal in relation to topography decreases from 100 km to 30 km wavelength equivalent to a uniform crustal density of 2450 kg m3 that is 100 kg m3 smaller than the density required at 100 km to explain such frequency dependent behavior we introduce rock compaction models under lithostatic pressure that yield radially stratified porosity and thus density and examine the depth extent of porosity our modeling and analysis support the assertion that the crustal density must vary from surface to deep crust by up to 500 kg m3 we found that the surface density of megaregolith is around 2400 kg m3 with an initial porosity of 10 20 and this porosity is eliminated at 10 20 km depth due to lithostatic overburden pressure our stratified density models provide improved fits to both grail primary and extended mission data

constraining the size of the south pole aitken basin impact abstract the south pole aitken spa basin is the largest and oldest definitive impact structure on the moon to understand how this immense basin formed we conducted a suite of spa scale numerical impact simulations varying impactor size impact velocity and lithospheric thermal gradient we compared our model results to observational spa basin data to constrain a best fit scenario for the spa basin forming impact our results show that the excavation depth to diameter ratio for spa scale impacts is constant for all impact scenarios and is consistent with analytical and geological estimates of excavation depth in smaller craters suggesting that spa scale impacts follow proportional scaling steep near surface thermal gradients and high internal temperatures greatly affected the basin forming process basin structure and impact generated melt volume in agreement with previous numerical studies of spa scale impacts crustal material is entirely removed from the basin center which is instead occupied by a large melt pool of predominantly mantle composition differentiation of the melt pool is needed to be consistent with observational data assuming differentiation of the thick impact generated melt sheet occurred and using observational basin data as constraints we find the best fit impact scenario for the formation of the south pole aitken basin to be an impact with an energy of 4 1026 j our specific model considered an impactor 170 km in diameter striking at 10 km s

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

shock compression measurements of single crystal forsterite in the pressure range 15 93 gpa shock compression experiments have been performed on pure synthetic single crystal forsterite mg2sio4 in the pressure range 15 93 gpa using a newly installed two stage light gas gun the values of the hugoniot elastic limit hel vary with the shock propagation directions with respect to the crystallographic orientations reflecting a notable elastic anisotropy in the olivine crystal the largest value of hel up to 12 gpa is observed in the shock direction parallel to 010 in the hydrostatic regime shock data in the shock velocity particle velocity us up plane are segmented into two parts by a transient plateau starting at around us 8 4 km s indicating a phase transition for the shock data of the low pressure olivine phase below about 50 gpa a linear fit with the equation us c0 sup has yielded parameters of c0 6 26 km s and s 1 12 the value of c0 is close to the bulk sound velocity of forsterite murnaghan birch fit of shock data for the low pressure olivine phase incorporated with the static compression data by olinger 1977 has resulted in k0 132 gpa and k0 3 4 which are in reasonable agreement with the ultrasonic data the close correspondence of the present shock data to the observation of shock residual effects in olivines is noteworthy the appearance of melt zone or diaplectic glass observed above about 50 gpa seems to correspond to the onset of the phase transition inferred in the present measurements

chromite symplectites in mg suite troctolite 76535 as evidence for infiltration metasomatism of a lunar layered intrusion abstract despite the very low chromium concentrations in its cumulus olivine 140 ppm lunar troctolite 76535 contains large amounts of cr sporadically but highly concentrated in symplectite assemblages consisting of mg al chromite and two pyroxenes previously proposed symplectite formation mechanisms include crystallization of trapped interstitial melt diffusion of cr from cumulus olivine and or remobilization of cumulus chromite grains these mechanisms would imply that the highly cr depleted nature of mg suite parental magmas and their source materials inferred from cumulus olivine may be illusory we have conducted a detailed petrologic and textural study of symplectites as well as chromite veins intercumulus assemblages olivine hosted melt inclusions and clinopyroxene troilite veins in 76535 with the goals of constraining the origin of the symplectites and the degree of cr depletion in mg suite magmas relative to other lunar basalts orthopyroxene and clinopyroxene in melt inclusions are depleted in cr relative to their symplectite counterparts averaging 900 and 1200 ppm vs 7400 and 8100 ppm cr 2 o 3 respectively olivine in contact with symplectite assemblages may exhibit a diffusion profile of cr going into olivine whereas olivine boundaries away from symplectites show no diffusion profile there is also a distinct lack of primary chromite as inclusions in cumulus phases and melt inclusions multiple textural observations melt inclusion chemistry and modeling of chromite olivine equilibrium rule out previously proposed symplectite formation mechanisms and strongly suggest that chromite was not a primary crystallization product of the 76535 parental magma accordingly the post cumulus addition of cr and fe is required to produce the symplectites after considering multiple models the addition of cr and fe to 76535 via infiltration metasomatism by an exogenous chromite saturated melt is the model most consistent with multiple textural and geochemical observations failure of models that call upon cr diffusion out of olivine grains imply that the observed cr depleted nature of olivine observed in many mg suite lithologies is a primary feature of the cr depleted nature of the mg suite parental magmas and their source materials this substantial depletion of cr in the magma relative to mare basalt magmas still requires a satisfactory explanation in order to be consistent with mg suite petrogenetic models and currently accepted bulk moon compositions additionally if the intimate interaction of migrating melts with early lunar crustal lithologies was a widespread phenomenon after lmo solidification it provides another mechanism by which to reset or delay closure of radiogenic isotopic systems and explain the mg suite ferroan anorthosite age overlap

coupled caal nasi diffusion in plagioclase feldspar experiments and applications to cooling rate speedometry abstract the rate of caal nasi interdiffusion in plagioclase feldspar was determined under 1 atm anhydrous conditions over the temperature range 1400 to 1000 c in calcic plagioclase an80 81 by homogenizing coherent exsolution lamellae the dependence of the average interdiffusion coefficient on temperature is given by the expression d 10 99 cm 2 sec exp 123 4 kcal mol rt t in k this value is for diffusion perpendicular to the 03 1 interface of the lamellae caal nasi interdiffusion is 4 to 5 orders of magnitude slower than oxygen diffusion in the temperature range 1400 to 1200 c and possibly 10 orders of magnitude slower at subsolidus temperatures the large differences in diffusion rates explain the apparent contradiction posed by the plagioclases of large layered intrusions e g the skaergaard which retain delicate ca na compositional zoning profiles on the micron scale but have undergone complete oxygen isotopic exchange with heated meteoric groundwater from the surrounding wall rocks caal nasi diffusion is slow the closure temperature is high within the solidus liquidus interval and ca na zoning is preserved oxygen diffusion is faster the closure temperature is lower 350 400 c and the feldspars exchange oxygen with the low temperature hydrothermal fluids the complex micron scale oscillatory zones in plagioclase can also be used as cooling rate speedometers for volcanic and plutonic plagioclase cooling histories typical of large mafic intrusions e g the stillwater are slow begin at high initial temperatures 1200 c and result in homogenization of oscillatory zones on the scale of 10 microns the oscillatory zones found in the plagioclase of granodioritic plutons are preserved because cooling is initiated at a lower temperature 1000 c limiting diffusion to submicron length scales despite the slow cooling rate of the intrusion

reconstruction of last glacial to early holocene monsoon variability from relict lake sediments of the higher central himalaya uttrakhand india abstract proglacial lake sediments at goting in the higher central himalaya were analyzed to reconstruct the summer monsoon variability during the last glacial to early holocene sedimentary structures high resolution mineral magnetic and geochemical data suggest that the lacustrine environment experienced fluctuating monsoonal conditions optically stimulated luminescence osl dating indicates that the lake sedimentation occurred before 25 ka and continued after 13 ka during this period goting basin witnessed moderate to strengthened monsoon conditions around 25 ka 23 5 ka 22 5 ka 22 ka 18 ka 17 ka 16 5 ka and after14 5 13 ka the last glacial phase ended with the deposition of outwash gravel dated at 11 ka indicating glacial retreat and the onset of holocene condition additionally centennial scale fluctuations between 16 5 ka and 12 7 ka in the magnetic and geochemical data are seen a close correspondence at the millennial scale between our data and that of continental and marine records from the indian sub continent suggests that goting basin responded to periods of strengthened monsoon during the last glacial to early holocene we attribute the millennial scale monsoon variability to climatic instability in higher northern latitudes however centennial scale abrupt changes are attributed to the result of albedo changes on the himalaya and tibetan plateau

lunar mg suite thermobarometry and petrogenesis of parental magmas using compilations of internally consistent thermodynamic data on minerals and advances in quantifying the energetics of crystalline solid solutions we have recalculated the pressures and temperatures of equilibration of troctolite sample 76535 and a number of spinel cataclasites the five phase assemblage olivine orthopyroxene clinopyroxene cr spinel plagioclase which occurs in symplectite assemblages in 76535 gives equilibration temperatures from 800 900 c and pressures from 200 to 250 mpa indicating a deep 40 50 km crustal source spinel cataclasite assemblages give minimum pressures of 100 mpa mg suite magmas were apparently intruded throughout the lunar crust early in lunar history the textures and equilibration temperatures in many mg suite samples are consistent with sub solidus recrystallization and the mg rich minerals of some refractory troctolites and dunites may be residues of a crustal melting process or products of subsolidus elemental redistribution the sm nd age of 4 26 0 06 ga of troctolite 76535 most likely represents the time of sub solidus recrystallization and or partial melting in an attempt to identify the primary source material for the mg suite magmas a variety of models were tested using the melts and magfox codes a good fit between mineral compositions and crystallization sequences is obtained by 20 batch melting at 0 5 gpa of an average whole moon composition with an mg of 0 85 melts formed by batch melting at higher pressures and melts formed by poly baric partial fusion over the pressure range from 2 0 to 0 3 gpa were either too poor in mg and or crystallized clinopyroxene before orthopyroxene mixing with 10 20 urkreep which is required to satisfy the ree constraints of the mg suite reduces the mg of the parental magmas and requires a whole moon mg closer to that of the terrestrial mantle

temporal trends of aliphatic and polyaromatic hydrocarbons in the bohai sea china evidence from the sedimentary record abstract this work reports the historical trends and sources of aliphatic hydrocarbons ahs and polycyclic aromatic hydrocarbons pahs in two 210 pb dated sediment cores extracted from the central mud areas of bohai sea bohai the toc tn ratio of the bulk organic matter om and the composition of the n alkanes suggest that the sedimentary organic matter was of mixed marine and terrigenous sources the coarser sediment grain size and decreasing c n ratios since 1976 could be attributed to the relocation of the yellow river mouth causing a decreased influence of yellow river derived sediments and associated om into the central bohai the concentration of total 16 pahs in the two cores ranged from 34 2 202 ng g mean 91 5 for bc1 and from 53 3 186 ng g mean 103 for bc2 with a high abundance of 2 3 ring pahs perylene in the two cores mainly originated from terrigenous sources via riverine discharge and thus could be potentially related to changes in the sediment load from the yellow river into the bohai over time petroleum inputs could be revealed by ratios of methylphenanthrenes to phenanthrene mp p and the patterns of more stable geochemical biomarkers hopanes and steranes along the two cores in addition to the presence of unresolved complex mixtures ucm in the surface layers source diagnostic ratios of pahs indicated a pyrogenic origin from biomass and coal combustion with a minor petroleum contribution downcore trends of compositional pahs profiles were in agreement with the socio economic development in china in the past decades this temporal variation of sedimentary pahs can also reflect a different evolution stage of energy structure in china as compared with those of the western developed countries

a sawtooth like timeline for the first billion years of lunar bombardment abstract we revisit the early evolution of the moon s bombardment our work combines modeling based on plausible projectile sources and their dynamical decay rates with constraints from the lunar crater record radiometric ages of the youngest lunar basins and the abundance of highly siderophile elements in the lunar crust and mantle we deduce that the evolution of the impact flux did not decline exponentially over the first billion years of lunar history but also there was no prominent and narrow impact spike 3 9 gy ago unlike that typically envisioned in the lunar cataclysm scenario instead we show the timeline of the lunar bombardment has a sawtooth like profile with an uptick in the impact flux near 4 1 gy ago the impact flux at the beginning of this weaker cataclysm was 5 10 times higher than the immediately preceding period the nectaris basin should have been one of the first basins formed at the sawtooth we predict the bombardment rate since 4 1 gy ago declined slowly and adhered relatively close to classic crater chronology models neukum and ivanov 1994 overall we expect that the sawtooth event accounted for about one fourth of the total bombardment suffered by the moon since its formation consequently considering that 12 14 basins formed during the sawtooth event we expect that the net number of basins formed on the moon was 45 50 from our expected bombardment timeline we derived a new and improved lunar chronology suitable for use on pre nectarian surface units according to this chronology a significant portion of the oldest lunar cratered terrains has an age of 4 38 4 42 gyr moreover the largest lunar basin south pole aitken is older than 4 3 gy and therefore was not produced during the lunar cataclysm

long wavelength topographic relaxation for self gravitating planets and implications for the time dependent compensation of surface topography the support of planetary surface topography is controlled by the thickness of the elastic lithosphere and thus has implications for the thermomechanical structure of shallow planetary interiors previous analyses of the support of long wavelength topography have generally utilized elastic formulations which preclude consideration of the time evolution of lithospheric stresses and thermal state here we formulate a viscoelastic model for the support of topography on a spherical planet our stress relaxation model employs a multilayer linear viscoelastic rheology and includes the effect of self gravitation in these models we approximate internal rheology with an olivine flow law and we estimate the internal thermal structure assuming simple conductive cooling we analyze how relief at the surface and internal density interfaces evolves with time in response to a surface or internal load our analysis demonstrates that crustal compensation is strongly dependent on planetary radius with a tendency for a large terrestrial planet like earth to reach complete airy isostasy at long wavelengths within a time scale controlled by the mantle viscosity the correlation of degree of compensation with planetary radius is consistent with previous work turcotte et al 1981 which showed that membrane stress can support significant long wavelength gravity anomalies applied to the moon the degree of compensation associated with loading of 100 ma lithosphere is less than 0 3 and the load love numbers are greater than 0 6 for all harmonics including degree 2 even after 109 years of relaxation this conclusion does not change significantly even with a moderately low viscosity for the crust the tendency for a small body like the moon to support long wavelength stresses may be relevant in understanding the anomalously large degree 2 terms in the lunar shape the results also suggest that major impact basins would not be compensated throughout lunar geological history 4 b y even if the surfaces on which the basins were initially formed were relatively young i e 100 300 ma the fact that the south pole aitken basin is largely compensated suggests that the lateral variations in thermal and or mechanical structure induced by impact processes play significant roles in the compensation of this structure

excavation of the lunar mantle by basin forming impact events on the moon abstract global maps of crustal thickness on the moon derived from gravity measurements obtained by nasa s gravity recovery and interior laboratory grail mission have shown that the lunar crust is thinner than previously thought hyperspectral data obtained by the kaguya mission have also documented areas rich in olivine that have been interpreted as material excavated from the mantle by some of the largest lunar impact events numerical simulations were performed with the isale 2d hydrocode to investigate the conditions under which mantle material may have been excavated during large impact events and where such material should be found the results show that excavation of the mantle could have occurred during formation of the several largest impact basins on the nearside hemisphere as well as the moscoviense basin on the farside hemisphere even though large areas in the central portions of these basins were later covered by mare basaltic lava flows surficial lunar mantle deposits are predicted in areas external to these maria our results support the interpretation that the high olivine abundances detected by the kaguya spacecraft could indeed be derived from the lunar mantle

new insights into lunar petrology distribution and composition of prominent low ca pyroxene exposures as observed by the moon mineralogy mapper m3 1 lunar geochemical groups such as mg suite ferroan anorthosite and alkali suite rocks are difficult to distinguish from orbit because they are defined by both modal mineralogy and elemental composition of their constituent minerals while modal mineralogy can be modeled only specific minerals or elements can be directly detected at near infrared nir wavelengths pyroxenes are among the most spectrally distinctive minerals and their absorption bands are sensitive to structure and composition pyroxenes thus provide important clues to distinguish these geochemical groups and to understand lunar crustal evolution using moon mineralogy mapper data we search for lithologies dominated by strong low calcium pyroxene lcp signatures we compare the nir absorptions of 20 lcps to a suite of synthetic pyroxenes to determine which lunar pyroxenes appear magnesian enough to be candidate mg suite norites we detail three prominent regions of lcp 1 in south pole aitken basin spa 2 south of mare frigoris and 3 north of mare frigoris the absorption band positions suggest that the lcps north of mare frigoris and those in spa are compositionally similar to one another and of mg50 75 implying that the mafic material excavated by the spa impact was relatively iron rich modified gaussian modeling results suggest that the apollo basin may have tapped different composition material than is exposed in much of spa the lcps located in the highlands south of mare frigoris exhibit absorption bands at short wavelengths consistent with mg 80 the coincidence of these mg rich lcps with the thorium measured by lunar prospector make them good candidates for kreep related mg suite pyroxenes

the lunar magma ocean reconciling the solidification process with lunar petrology and geochronology abstract the moon is thought to have originated with a magma ocean that produced a plagioclase flotation crust as solidification proceeded ages of anorthositic crust range over at least 200 million years the model for solidification presented here integrates chemical and physical constraints of lunar magma ocean solidification to determine 1 the final thickness of flotation crust generated by a fractionally solidifying magma ocean 2 the timescale of crystallization before plagioclase is a stable phase 3 the timescale of solidification after the formation of the plagioclase flotation crust and 4 the post overturn lunar mantle composition and structure we find that magma oceans of as much as 1000 km depth are consistent with creating an anorthositic crust 40 to 50 km in thickness solidification of the magma ocean prior to formation of the flotation crust may occur on the order of 1000 years and complete solidification would require additional ten to tens of millions of years reconciling these short model timescales with radiometric dates of crustal samples requires either a very late forming moon combined with finding older crustal ages to be incorrect or calling on tidal heating of the crust by the early earth to prolong solidification gravitationally driven overturn of cumulates during tidal heating provides a mechanism for creating the compositions and ages of the lunar mg suite of crustal rocks further we find that upon crystallization the moon likely began with an azimuthally heterogeneous gravitationally stable mantle after magma ocean cumulate overturn this result may help explain the experimentally determined origin of picritic glasses at similar depths but from different source materials

modeling damage and deformation in impact simulations numerical modeling is a powerful tool for investigating the formation of large impact craters but is one that must be validated with observational evidence quantitative analysis of damage and deformation in the target surrounding an impact event provides a promising means of validation for numerical models of terrestrial impact craters particularly in cases where the final pristine crater morphology is ambiguous or unknown in this paper we discuss the aspects of the behavior of brittle materials important for the accurate simulation of damage and deformation surrounding an impact event and the care required to interpret the results we demonstrate this with an example simulation of an impact into a terrestrial granite target that produces a 10 km diameter transient crater the results of the simulation are shown in terms of damage a scalar quantity that reflects the totality of fragmentation and plastic strain both total plastic strain the accumulated amount of permanent shear deformation regardless of the sense of shear and net plastic strain the amount of permanent shear deformation where the sense of shear is accounted for damage and plastic strain are both greatest close to the impact site and decline with radial distance however the reversal in flow patterns from the downward and outward excavation flow to the inward and upward collapse flow implies that net plastic strains may be significantly lower than total plastic strains plastic strain in brittle rocks is very heterogeneous however continuum modeling requires that the deformation of the target during an impact event be described in terms of an average strain that applies over a large volume of rock large compared to the spacing between individual zones of sliding this paper demonstrates that model predictions of smooth average strain are entirely consistent with an actual strain concentrated along very narrow zones furthermore we suggest that model predictions of total accumulated strain should correlate with observable variations in bulk density and seismic velocity

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

troctolite 76535 a sample of the moon s south pole aitken basin abstract lunar samples returned by the apollo program have provided insights into numerous solar system processes however no samples were returned from the lunar farside where one of the moon s most geologically important features resides the 2500 km diameter south pole aitken basin spa here we explore the hypothesis that lunar troctolite 76535 was excavated by spa this hypothesis is motivated by the sample s low peak shock pressure neukum 1983 chronology

petrography and geochemistry of five new apollo 16 mare basalts and evidence for post basin deposition of basaltic material at the site we present the petrography and geochemistry of five 2 4 mm basalt fragments from the apollo 16 regolith these fragments are 1 a high ti vitrophyric basalt compositionally similar to apollo 17 high ti mare basalts 2 a very high ti vitrophyric basalt compositionally similar to apollos 12 and 14 red black pyroclastic glass 3 a coarsely crystalline high al basalt compositionally similar to group 5 apollo 14 high al mare basalts 4 a very low ti vlt crystalline basalt compositionally similar to luna 24 vlt basalts and 5 a vlt basaltic glass fragment compositionally similar to apollo 17 vlt basalts high ti basalt has been reported previously at the apollo 16 site the other basalt types have not been reported previously as there are no known cryptomaria or pyroclastic deposits in the highlands near the apollo 16 site ruling out a local origin and scant evidence for basaltic material in the apollo 16 ancient regolith breccias or apollo 16 soils collected near north ray crater ruling out a basin ejecta origin we infer that the basaltic material in the apollo 16 regolith originated in maria near the apollo 16 site and was transported laterally to the site by small to medium sized post basin impacts on the basis of tio2 concentrations derived from the clementine uvvis data mare tranquillitatis 300 km north is the most likely source for the high ti basaltic material at the apollo 16 site craters ross arago dionysius maskelyne moltke sosigenes schmidt mare nectaris sinus asperitatis 220 km east is the most likely source for the low ti and vlt basaltic material craters theophilus madler torricelli and a large regional pyroclastic deposit near mare vaporum 600 km northwest is the most likely source region for pyroclastic material although no source craters are apparent in the region

magnesian anorthosites and a deep crustal rock from the farside crust of the moon abstract among over thirty lunar meteorites recovered from the hot deserts and antarctica dhofar 489 is the most depleted in thorium 0 05 ppm feo and rare earth elements ree dhofar 489 is a crystalline matrix anorthositic breccia and includes clasts of magnesian anorthosites and a spinel troctolite the mg mg fe mol mg numbers 75 85 of olivine and pyroxene grains in this meteorite are higher than those of the apollo ferroan anorthosites such materials were not recovered by the apollo and luna missions however remote sensing data suggest that the estimated concentrations of th and feo are consistent with the presence of such samples on the farside of the moon the differentiation trend deduced from the mineralogy of the anorthositic clasts define a magnesian extension of the ferroan anorthosite fan trend constructed from the apollo samples the presence of magnesian anorthositic clasts in dhofar 489 still offers a possibility that the farside trend with magnesian compositions is more primitive than the fan trend and may require a revision of this classical differentiation trend the ar ar age of dhofar 489 is 4 23 0 034 gyr which is older than most ar ages reported for highland rocks returned by apollo the old ar ar age of impact formation of this breccia and the presence of a fragment of spinel troctolite of deep crustal origin suggest that a basin forming event on the farside excavated the deep crust and magnesian anorthosites before formation of imbrium

crystal accumulation in a 4 2 ga lunar impact melt abstract the ages of lunar impact basins and the role of fractional crystallization in producing compositional heterogeneity of lunar melt sheets are long standing problems with significant implications for solar system dynamics and the petrologic evolution of the lunar crust here we document the formation of a basin scale impact on the moon at 4 20 0 07 ga based on the 147 sm 143 nd isochron age of a magnesian noritic anorthosite melt rock from lunar breccia 67955 major element compositions of plagioclase and mafic silicates in the melt rock imply a substantial component of primary mg suite cumulates or related lithologies in the pre impact crustal stratigraphy trace element compositions of the plagioclase including diagnostic ratios such as sr ba are also mostly similar to those in plagioclase from mg suite cumulates with a small number of grains trending toward compositions observed in ferroan anorthosites mineral melt distribution coefficients applied to trace element compositions of the 67955 plagioclase and pyroxene predict parental melt compositions that contrast strongly with the bulk rock compared to the whole rock parental melts calculated from the plagioclase are enriched in ree ree la yb 131 885 average 619 ppm vs 39 8 ppm and they have more fractionated ree patterns la yb n 1 2 9 8 average 4 9 vs 1 5 with deep negative eu anomalies eu eu 0 09 0 40 vs 1 36 trace element data for the pyroxenes also imply incompatible element enriched parental melts subsolidus equilibration between the plagioclase and the pyroxene apparently rotated the ree patterns but the conclusion that the parental melt was highly enriched in ree relative to the whole rock appears robust quantitative modeling shows that fractional crystallization of the 67955 whole rock composition cannot reproduce the range of ba sr ti and la concentrations measured in the 67955 plagioclase rather the models require an initial melt composition that was strongly enriched in these elements and they suggest that fractional crystallization became less efficient as crystallization proceeded the contrast between the inferred parental melt composition and the bulk rock implies formation of the 67955 noritic anorthosite as a crystal cumulate and that the cogenetic residual melt was strongly enriched in incompatible elements if so this would be the first documented example of fractional crystallization in a lunar impact melt sheet the petrological and geochemical characteristics of the 67955 noritic anorthosite suggest that it formed by an impact in the procellarum kreep terrane and was transported to the apollo 16 site as imbrium ejecta inheritance of ejecta related to this pre imbrium basin may contribute to the common occurrence of 4 2 ga 40 ar 39 ar plateau ages in breccia clasts and regolith fragments from the rim of north ray crater in that case those data may provide no constraints on the age of the nectaris basin despite its proximity to the apollo 16 site

olivine rich exposures in the south pole aitken basin abstract the distribution and the geological context of the olivine rich exposures in the south pole aitken spa basin on the moon were investigated based on the spectral data obtained from the spectral profiler sp and multiband imager mi onboard the japanese lunar explorer kaguya selene the olivine rich exposures are found only in the peak rings or central peaks of the schrodinger basin and zeeman crater which are located in the outer region of the spa basin and not in the center region on a localized scale the olivine rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings another observational finding is the co existence of olivine rich and plagioclase rich materials on a kilometer scale spanning most of the olivine rich sites in the schrodinger basin pyroxene rich materials are found in fresh craters outside the peak rings or the central peaks with olivine rich materials based on these results the following scenario are proposed 1 the impact to form the spa basin melted a large amount of the lunar upper mantle and crust and distributed the melted materials to the outer region 2 local differentiation of melted materials hid the olivine rich materials in the center region of the spa basin 3 later impacts that formed the schrodinger and zeeman craters excavated and exposed the olivine rich materials to the surface again and 4 space weathering and regolith gardening obscured the olivine rich spectra at the exposure sites but recent small scale impacts or landslides on the sloped wall exposed fresh olivine rich materials allowing the identification of the olivine rich exposures by spectral remote sensing this suggests that several different scale events play an important role in forming the surface distributions of originally deep seated materials on the moon as well as on other planetary bodies

organic geochemistry applied to environmental assessments of prince william sound alaska after the exxon valdez oil spill a review abstract organic geochemistry played a major role in the environmental assessments conducted following the exxon valdez oil spill which occurred on march 24 1989 and released about 258 000 bbls 41 million liters of alaska north slope crude oil into prince william sound geochemical analyses of more than 15 000 sediment tar and biological samples and about 5000 water samples provide the largest database yet collected on oil spill chemistry and we review the results here the marine environment of the sound has a complex background of petrogenic pyrogenic and biogenic hydrocarbons from natural and anthropogenic sources geochemical evaluation of the fate and effects of the spilled oil required that this oil and its residues be distinguished from the background a variety of molecular and isotopic techniques were employed to identify various hydrocarbon sources and to distinguish quantitatively among mixed sources in the samples although the specific criteria used to distinguish multiple sources in the region affected by the exxon valdez spill are not necessarily applicable to all spill situations the principles that governed their selection are distributions of polycyclic aromatic hydrocarbons pah and dibenzothiophenes distinguish exxon valdez oil and its weathered residues from background hydrocarbons in benthic sediments ratios of c 2 dibenzothiophene c 2 phenanthrene and c 3 dibenzothiophene c 3 phenanthrene were particularly useful carbon isotopes and terpane distributions distinguished exxon valdez residues found on shorelines from tars from other sources diesel and diesel soot were identified by the absence of alkylated chrysenes and a narrow distribution of n alkanes whereas pyrogenic products were distinguished by the dominance of 4 to 6 ring pah over 2 to 3 ring pah and by the dominance of non alkylated over alkylated homologues of each pah series the presence of 18 h oleanane in benthic sediments coupled with its absence in exxon valdez oil and its residues confirm another petrogenic source results of geochemical studies suggest that the petrogenic component in the background of benthic sediments is derived from oil seeps in the eastern gulf of alaska in 1990 and 1991 exxon valdez residues generally forming a small increment to the pre spill background were found to be only sporadically distributed in some shallow near shore sediments adjacent to shorelines that had been heavily oiled in 1989 in 1994 occurrences of exxon valdez tars on shoreline surfaces were rare although residues could be found buried in shoreline sediments at some isolated locations along the spill path where they were protected from wave action spilled oil residues collected 16 months after the spill were degraded on average by nearly 50 shoreline residues from sources other than the spill were also identified and are widespread throughout the sound these residues include 1 geochemically distinct tars and oils imported from california oil fields to alaska for fuel and construction purposes prior to the discovery of the cook inlet and north slope oil fields 2 diesel and diesel soot and 3 more highly refined products of the more than 2700 chemical analyses of biological samples of higher life forms fish birds and mammals about 150 6 indicate recognizable residues of exxon valdez oil which were identified by their distribution of polycyclic aromatic hydrocarbons pah most of these samples 138 were collected in 1989 and most were associated with external surfaces or the gastrointestinal tract rarely do internal tissues or fluids contain recognizable fingerprints of spilled oil this observation includes samples from marine mammals that were visibly oiled externally other hydrocarbon sources including diesel and a non petroleum artifact that occurs when concentrations of individual pah are at or near their method detection limit are also identified in biological samples