major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

argon 40 argon 39 age spectra of apollo 17 highlands breccia samples by laser step heating and the age of the serenitatis basin we have obtained high resolution 21 63 steps 40ar 39ar age spectra using a continuous laser system on 19 submilligram samples of melt rocks and clasts from apollo 17 samples collected from the pre imbrian highlands in the easternmost part of the serenitatis basin the samples include poikilitic melt rocks inferred to have been formed in the serenitatis basin forming impact aphanitic melt rock whose compositions vary and whose provenance is uncertain and granulite gabbro and melt clasts three of the poikilitic melts have similar age spectrum plateau ages 72395 96 3893 16 ma 2 72535 7 3887 16 ma 76315 150 3900 16 ma with a weighted mean age of 3893 9 ma which we interpret as the best age for the serenitatis basin forming impact published 40ar 39ar age spectrum ages of apollo 17 poikilitic melts are consistent with our new age but are much less precise two poikilitic melts did not give plateaus and the maxima in their age spectra indicate ages of 3869 ma 72558 7 and 3743 ma 77135 178 plateau ages of two poikilitic melts and two gabbro clasts from 73155 range from 3854 16 ma to 3937 16 ma and have probably been affected by the ubiquitous older clasts and by post formation heating impact events plateau ages from two of the aphanitic melt blobs and two granulites in sample 72255 fall in the narrow range of 3850 16 ma to 3869 16 ma with a weighted mean of 3862 8 ma two of the aphanitic melt blobs from 72255 have ages of 3883 16 ma and 3894 ma whereas a poikilitic melt clast of different composition from the serenitatis melts has an age of 3835 16 ma which is the upper limit for the accretion of 72255 these data suggest that either the aphanitic melts vary in age as is also suggested by their varying chemical compositions or they formed in the 72255 accretionary event about 3 84 3 85 ga and older relict material is responsible for the dispersion of ages in any case the aphanitic melts do not appear to be serenitatis products our age for the serenitatis impact shows on the basis of the isotopic age evidence alone that serenitatis is 20 25 ma and probably 55 60 ma older than imbrium 3870 ma and probably 3836 ma dalrymple and ryder 1993 noritic granulite sample 78527 has a plateau age of 4146 17 ma representing a minimum age for cooling of this sample in the early lunar crust so far there is no convincing evidence in the lunar melt rock record for basin forming impacts significantly older than 3 9 ga

evolution of a carboniferous carbonate hosted sphalerite breccia deposit isle of man a newly discovered extensive sphalerite bearing breccia 7 5 wt zn is hosted in dolomitised carboniferous limestones overlying ordovician silurian metasedimentary rocks on the isle of man although base metal sulphide deposits have been mined historically on the island they are nearly all quartz vein deposits in the metamorphic basement this study investigates the origin of the unusual sphalerite breccia and its relationship to basement hosted deposits through a combination of petrographic cathodoluminescence fluid inclusion stable isotope and hydrogeologic modelling techniques breccia mineralisation comprises four stages marked by episodes of structural deformation and abrupt changes in fluid temperature and chemistry in stage i high temperature t h 300 c high salinity 20 45 wt equiv nacl fluid of likely basement origin deposited a discontinuous quartz vein this vein was subsequently dismembered during a major brecciation event stages ii iv are dominated by open space filling sphalerite quartz and dolomite respectively fluid inclusions in these minerals record temperatures of 105 180 c and salinities of 15 20 wt equiv nacl the 34s values of sphalerite 6 5 6 9 vienna canyon diablo troilite are nearly identical to those of ore sulphides from mines in the lower palaeozoic metamorphic rocks the 18o values for quartz and dolomite indicate two main fluid sources in the breccia s hydrothermal system local carboniferous hosted brines 0 5 6 0 vienna standard mean ocean water and basement involved fluids 5 5 11 5 ore sulphide deposition in the breccia is compatible with the introduction and cooling of a hot basement derived fluid that interacted with local sedimentary brines

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

lithofacies of lower palaeozoic deep marine sediments in the isle of man a new map and stratigraphic model of the manx group

estimating transient crater size using the crustal annular bulge insights from numerical modeling of lunar basin scale impacts 1 the transient crater is an important impact cratering concept its volume and diameter can be used to predict impact energy and momentum impact melt volume and maximum depth and volume of ejected material transient crater sizes are often estimated using scaling laws based on final crater rim diameters however crater rim estimates especially for lunar basins can be controversial here we use numerical modeling of lunar basin scale impacts to produce a new alternative method for estimating transient crater radius using the annular bulge of crust observed beneath most lunar basins using target thermal conditions appropriate for the lunar imbrian and nectarian periods we find this relationship to be dependent on lunar crust and upper mantle temperatures this result is potentially important when analyzing lunar basin subsurface structures inferred from the grail mission

chemical composition and origin of apollo 15 impact melts to better understand the apennine front we have analyzed 14 apollo 15 impact melt rocks including hand samples rake samples and coarse fines for major fused bead microprobe and trace element inaa abundances the melt rocks show a remarkable diversity of chemical composition although all but one have typical kreep incompatible element patterns they appear to form five chemical groups all but the most kreep rich of which may represent single impacts three groups are of low k fra mauro composition none correspond to very high alumina vha compositions the compositions are unlike nearly all other impact melts and regoliths from highland sites indicating a distinct provenance for the apollo 15 samples serenitatis basin impact melt compositions apollo 17 poikilitic boulders are not duplicated although one apollo 17 aphanitic melt sample 73215 is similar to one of the apollo 15 groups the apollo 15 group consisting only of 15445 and 15455 remains the best candidate for imbrium basin impact melt while the most kreep rich group probably consists of melts produced in varied post imbrium impacts into the apennine bench formation apollo 15 kreep basalt flows the most populated group was previously unrecognized and could be either pre or post imbrium basin it is possible that it not 15445 15455 represents imbrium melt one unique sample has a non kreep incompatible element pattern with low abundances and a positive eu anomaly its target was rather primitive and would not appear to be of regional extent or present in the area in post imbrium times it is either a pre imbrian melt or exotic the apennine front does not consist of a monolithic lkfm composition but shows a much wider diversity of compositions than was previously recognized

thickness of proximal ejecta from the orientale basin from lunar orbiter laser altimeter lola data implications for multi ring basin formation 1 quantifying the ejecta distribution around large lunar basins is important to understanding the origin of basin rings the volume of the transient cavity the depth of sampling and the nature of the basin formation processes we have used newly obtained altimetry data of the moon from the lunar orbiter laser altimeter lola instrument to estimate the thickness of ejecta in the region surrounding the orientale impact basin the youngest and best preserved large basin on the moon our measurements yield ejecta thicknesses of 2900 m near the cordillera mountains the topographic rim of orientale decaying to 1k m in thickness at a range of 215 km these measurements imply a volume of ejecta in the region from the cordillera ring to a radial range of one basin diameter of 2 9 10 6 km 3 and permit the derivation of an ejecta thickness decay model which can be compared with estimates for the volume of excavation and the size of the transient cavity these data are consistent with the outer rook mountains as the approximate location of the transient cavity s rim crest and suggest a volume of 4 8 10 6 km 3 for the total amount

the scaling of complex craters the empirical relation between the transient crater diameter dg and final crater diameter dr of complex craters and basins is estimated using cumulative terrace widths central uplift diameters continuous ejecta radii and transient crater reconstructions determined from lunar and terrestrial impact structures the ratio dg dr is a power law function of dr decreasing uniformly from unity at the diameter of the simple complex crater morphology transition to about 0 5 for large multiring basins like imbrium on the moon the empirical constants in the dg dr relation are interpreted physically to mean that the position of the final rim relative to the transient crater and hence the extent of collapse is controlled or greatly influenced by the properties of the zone of dissociated material produced by the impact shock the continuity of the dg dr relation over the entire spectrum of morphologic types from complex craters to multiring basins implies that the rims of all these structures form in the same tectonic environment despite morphologic differences

the case for a younger imbrium basin new 40ar 39ar ages of apollo 14 rocks petrographically and chemically well characterized rocks of the apollo 14 landing site 12 impact melt breccias 3 clast free impact melt rocks 2 granulitic rocks 1 cataclastic noritic anorthosite 1 shocked gabbronorite 1 mare basalt and 1 plagioclase single crystal have been dated by the 40ar 39ar technique the samples represent two different formations at the apollo 14 site 1 small lithic clasts 10 specimens from fragmental breccia 14063 ejected from the 26 ma old cone crater and one clast mare basalt from cone crater soil 14140 and 2 large rock samples 10 specimens collected throughout the regolith of the landing site the first group of samples has exposure ages close to 26 ma and 40ar 39ar ages ranging from 3 86 to 4 09 ga which indicates that breccia 14063 was assembled 3 86 ga ago the second group of samples displays lower 40ar 39ar ages ranging from 3 73 to 3 85 ga we interpret breccia 14063 as part of a nectarian megabreccia unit which was incorporated into the fra mauro formation as a megablock by secondary mass wasting of the ejecta blanket of a local pre imbrian crater the remaining samples are thought to represent clasts of the apollo 14 subregolith basement megabreccia defined as the fra mauro formation consequently the reported ages of these clasts confirm previous suggestions that the fra mauro formation and therefore the imbrium basin is only 3 75 ga old and not 3 85 ga as commonly assumed

osmium isotope and highly siderophile element systematics of lunar impact melt breccias implications for the late accretion history of the moon and earth abstract to characterize the compositions of materials accreted to the earth moon system between about 4 5 and 3 8 ga we have determined os isotopic compositions and some highly siderophile element hse re os ir ru pt and pd abundances in 48 subsamples of six lunar breccias these are apollo 17 poikilitic melt breccias 72395 and 76215 apollo 17 aphanitic melt breccias 73215 and 73255 apollo 14 polymict breccia 14321 and lunar meteorite nwa482 a crystallized impact melt plots of ir versus other hse define excellent linear correlations indicating that all data sets likely represent dominantly two component mixtures of a low hse target presumably endogenous component and a high hse presumably exogenous component linear regressions of these trends yield intercepts that are statistically indistinguishable from zero for all hse except for ru and pd in two samples the slopes of the linear regressions are insensitive to target rock contributions of ru and pd of the magnitude observed thus the trendline slopes approximate the elemental ratios present in the impactor components contributed to these rocks the 187 os 188 os and regression derived elemental ratios for the apollo 17 aphanitic melt breccias and the lunar meteorite indicate that the impactor components in these samples have close affinities to chondritic meteorites the hse in the apollo 17 aphanitic melt breccias however might partially or entirely reflect the hse characteristics of hse rich granulitic breccia clasts that were incorporated in the impact melt at the time of its creation in this case the hse characteristics of these rocks may reflect those of an impactor that predated the impact event that led to the creation of the melt breccias the impactor components in the apollo 17 poikilitic melt breccias and in the apollo 14 breccia have higher 187 os 188 os pt ir and ru ir and lower os ir than most chondrites these compositions suggest that the impactors they represent were chemically distinct from known chondrite types and possibly represent a type of primitive material not currently delivered to earth as meteorites

the spence shale lagerstatte an important window into cambrian biodiversity the spence shale member of the langston formation is a cambrian miaolingian wuliuan lagerstatte in northeastern utah and southeastern idaho it is older than the more well known wheeler and marjum lagerstatten from western utah and the burgess shale from canada the spence shale shares several species with these younger deposits yet it also contains a remarkable number of unique species because of its relatively broad geographical distribution and the variety of palaeoenvironments and taphonomy the fossil composition and likelihood of recovering weakly skeletonized or soft bodied taxa varies across localities the spence shale is widely acknowledged not only for its soft bodied taxa but also for its abundant trilobites and hyoliths recent discoveries from the spence shale include problematic taxa and provide insights about the nature of palaeoenvironmental and taphonomic variation between different localities supplementary material a generic presence absence matrix of the spence shale fauna and a list of the spence shale localities are available at https doi org 10 6084 m9 figshare c 4423145

the stratigraphy correlation provenance and palaeogeography of the skiddaw group ordovician in the english lake district a new lithostratigraphy is presented for the skiddaw group lower ordovician of the english lake district two stratigraphical belts are described five formations are defined in the northern fells belt ranging in age from tremadoc to early llanvirn they are all mudstone or sandstone dominated of turbidite origin in ascending order they are named the bitter beck watch hill hope beck loweswater and kirk stile formations two formations are defined in the central fells belt ranging in age from late arenig to llanvirn these are the buttermere formation a major olistostrome deposit overlain by the tarn moor formation consisting of turbidite mudstones with volcaniclastic turbidite sandstone beds a revised graptolite and new acritarch biostratigraphy for the skiddaw group is presented with eight graptolite biozones and thirteen acritarch assemblages and sub assemblages the provenance of the group is assessed from detailed petrographical and geochemical work this suggests derivation in the early ordovician largely from an old inactive continental arc terrane lying to the south east with the appearance of juvenile volcanic material in the llanvirn comparisons and correlations of the skiddaw group are made with the isle of man and eastern ireland

the iapetus suture zone in england scotland and eastern ireland a reconciliation of geological and deep seismic data deep seismic profiles in the irish and north seas have successfully imaged crustal structure across the iapetus suture zone a problem with current interpretations is that the reflectors chosen as the suture project to the top of the basement well to the south of the solway line the palaeontologically defined trace of the suture we present a revised interpretation in which a reflectivity boundary common to all the profiles is identified as the leading edge of imbricated avalonian crust in effect the footwall of the suture zone this projects to the surface close to the solway line obviating the need to invoke northward backthrusting of the suture

the iapetus suture in the british isles the position of the iapetus ocean suture can be traced between ordovician fossil localities in the southern uplands and the lake district which contain respectively distinct north american and european faunas the southern uplands contains north american caradoc faunas in the northern belt and is considered to have been accreted onto the laurentian north american margin between the llandeilo and the end of the wenlock deep seismic reflection profiling shows that a surface probably parallel to the suture zone dips down to the northwest from the solway line in eastern ireland the surface trace of the suture coincides with the navan fault which separates the longford down massif from ordovician sediments containing european faunas the navan silvermines fault may represent the surface expression of the suture but it is masked by wenlock turbidites which appear to have crossed over the plate boundary northward subduction of continental crust below the margin of laurentia during the late silurian may explain the influx of turbidite fans from the north or north west onto depressed crust to the south of the suture termination of subduction coincides with the widespread acadian orogeny in the emsian at 395 5 ma

the dimensions of the chicxulub impact crater and impact melt sheet the chicxulub impact crater which is the principal source of impact debris in cretaceous tertiary boundary sediments is currently buried by a 1 km thick sequence of carbonate sediments because the crater is not exposed for direct scrutiny its size has remained uncertain and in particular estimates ranging from 100 to 300 km have been made on the basis of gravity and magnetic field data in this study the physical properties of the k t boundary impact ejecta and chicxulub impact melt sheet have been used to test the geophysical estimates of the impact crater s size on the basis of the measured thickness of impact ejecta in haiti and north america the calculated volume of the impact melt sheet and the chemical and isotopic composition of the melt sheet the chicxulub impact crater is inferred to be 180 km in diameter and to contain a 3 to 7 km thick melt sheet and breccia sequence within a centrally located 100 km diameter region that corresponds to the limits of the transient cavity

the age and correlation of skiddaw group early ordovician sediments in the cross fell inlier northern england the skiddaw group in the cross fell inlier comprises the catterpallot formation of latest tremadoc or earliest arenig age the murton formation of arenig age and the kirkland formation of early llanvirn age each of these formations can be correlated with formations in the skiddaw group of the lake district the faulted contact of the catterpallot and kirkland formations is the probable extension of the causey pike fault cpf which separates two distinct sequences in the skiddaw inlier of the northern lake district contrasts across the cpf in the cross fell inlier reflect those seen in the skiddaw inlier the cpf is a major basement structure separating markedly different successions in the ordovician strata of northern england

identifying the geologic context of apollo 17 impact melt breccias abstract the origin of the boulders sampled during the apollo 17 mission to the taurus littrow valley has been debated since the completion of the mission four decades ago no consensus has yet been reached whether the sampled boulders originated in material emplaced as a result of the serenitatis impact i e massifs the imbrium impact i e sculptured hills a combination of both impact events or as a result of another pre or post serenitatis impact event i e massifs or superposed deposits on valley floor these on going debates demonstrate the importance of identifying the geologic context of samples collected during the apollo missions using high resolution imagery and topography data we identify boulder tracks that connect sampled boulders with source outcrops these observations verify astronauts impressions that boulders originated in outcrops within massif walls and that they remain uncontaminated by nearby sculptured hills materials this finding can be used with updated ar ar and u pb ages of analyzed samples to constrain the timing and intensity of the lunar cataclysm epoch

low grade metamorphism of the manx group isle of man a comparative study of white mica crystallinity techniques studies have been made in two laboratories on metapelites from the manx group isle of man showing the distribution of white mica crystallinity using the kubler index 2 and the weber index hb rel two isocryst maps which show broadly similar distributions of metamorphic grade are illustrated and a correlation between the laboratories is presented the mineralogy of the fraction in relation to crystallinity has been determined the distribution of metamorphic grade over central and eastern parts of the isle of man as depicted by the kubler index isocryst map is related to subjacent granite plutons but these contact metamorphic effects overprint an earlier largely anchizonal regional metamorphism localized late retrograde effects are related to low temperature hydrothermal mineralization and to cold re working in a large fault zone differences between the maps are largely in the degrees of resolution which stem directly from the different sampling intervals employed comparisons between the maps suggest a sampling interval of 1 2 km is adequate in regions of simpler geology but that an interval of the changes in the mineralogy of the