magnetostratigraphical dating of loess deposits in china the age of chinese loess deposits has long been disputed biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the pleistocene the new palaeomagnetic measurements reported here on a bore hole section near lochuan shaanxi province suggest a clearly defined magnetic polarity zonation which extends below the olduvai subchron a late pliocene age of 2 4 myr is assigned to the oldest loess sediments measured the intensity variations of natural remanent magnetization nrm and low field magnetic susceptibility are indicative of climatic changes during loess deposition

direct marine terrestrial correlations wanganui basin new zealand the last 1 million years abstract wanganui basin a back arc basin in north island new zealand contains a detailed sequence of interfingering terrestrial and shallow marine sediments spanning the entire quaternary rhyolite tephras erupted from the taupo volcanic zone together with magnetostratigraphy and biostratigraphy facilitate correlations between wanganui basin and the astronomically calibrated oxygen isotope chronology of deep sea cores particularly over the last 1 ma eustatic changes are interpreted from both marine shelf sediments and marine terraces within the basin non marine sediments including loess dunesand and alluvial deposits coupled with pollen analyses are used to interpret climatic changes they can also be directly related to the marine record through stratigraphic relations between marine and non marine deposits in the basin

the last glacial maximum in central and southern north island new zealand a paleoenvironmental reconstruction using the kawakawa tephra formation as a chronostratigraphic marker abstract kawakawa tephra formation comprising oruanui ignimbrite flow member and aokautere ash airfall member represents the products of an exceptionally large and widespread volcanic eruption from taupo volcanic centre in the north island of new zealand the eruption occurred during the last glacial maximum and is radiocarbon dated at c 22 6 ka b p thermoluminescence ages are in broad agreement with the radiocarbon age the presence of aokautere ash in loess deposits in alluvial gully fills on river terraces and its absence from unstable sites permits a detailed assessment of geomorphic activity during the last glacial maximum widespread erosion of regolith aggradation of river valleys and deposition of loess particularly in the period following eruption of the kawakawa point to a cold dry variable climate a collation of pollen data for sediments containing aokautere ash and those 14c dated in the range 17 23 ka shows that tall forest was highly restricted in the central and southern parts of the north island an apparently subalpine grassland shrubland was present at sites from present sea level to over 800 m elevation suggesting that factors other than lower temperatures such as exposure to wind and frost fire and reduced rainfall were important in controlling vegetation patterns we conclude that the interval 23 13 ka b p broadly equivalent to oxygen isotope stage 2 represents the period of greatest environmental change in the north island

estimating the lunar mantle water budget from phosphates complications associated with silicate liquid immiscibility abstract the discovery of water within the lunar mantle has broad implications for the formation of the earth moon system differentiation of the moon and the magmatic evolution of lunar basalts as well as the highland rocks recently there has been considerable interest in using combined water abundances and h isotope systematics of lunar apatites from mare basalts to quantify the origin and extent of water within the moon s mantle however the petrologic and geochemical conditions that govern apatite crystallization are not well constrained especially for high feo basaltic melts that crystallize at fo2 values below the iron wustite buffer apatites are typically located within the late stage interstitial regions in this contribution we present detailed textural descriptions of late stage inter cumulus residual liquid pockets i e mesostasis pockets in order to understand the petrogenesis of lunar apatite results from five mare basalts demonstrate that the majority of the residual liquids in mesostasis regions have undergone silicate liquid immiscibility sli splitting into si k rich felsic and fe rich fe basaltic conjugate liquids we demonstrate the complexity of these residual liquids by documenting a wide range of water contents for apatites in several mesostasis pockets within a single mare basalt a complexity common to many basalts these data illustrate that individual apatite hosting mesostasis pockets behave as independent sub systems even within a single rock furthermore we present water concentrations for another phosphate phase merrillite indicating additional uncertainties during considerations of water partitioning into apatite fractional crystallization trends have been used in order to assess the conditions under which magmas are likely to undergo sli predicted liquid lines of descent indicate that it is the late stage residual liquids of lunar basalts with relatively low mg e g 50 may not intersect the two liquid field depending upon the fractionation trends in the late stage mesostasis pockets for samples that undergo sli the apatite melt partition coefficients required for back calculating water abundances of the parental melts are compromised by the generation of two populations of apatites merrillites from conjugate immiscible liquids this process highlights an important complexity inherent to all water back calculations that use apatite as this requires an additional set of partition coefficients we emphasize that the complex petrologic nature and common development of sli of apatite bearing late stage mesostasis pockets have not been considered in published apatite volatile data these factors in additional to other considerations illustrate why water back calculations to model the primary melts from such data must be viewed with caution

petrology and geochemistry of feldspathic impact melt breccia abar al uj 012 the first lunar meteorite from saudi arabia abar al uj aau 012 is a clast rich vesicular impact melt im breccia composed of lithic and mineral clasts set in a very fine grained and well crystallized matrix it is a typical feldspathic lunar meteorite most likely originating from the lunar farside bulk composition 31 0 wt al2o3 3 85wt feo is close to the mean of feldspathic lunar meteorites and apollo fan suite rocks the low concentration of incompatible trace elements 0 39ppmth 0 13ppm u reflects the absence of a significant kreep component plagioclase is highly anorthitic with a mean of an 96 9 ab 3 0 or 0 1 bulk rock mg is 63 and molar feo mno is 76 the terrestrial age of the meteorite is 33 4 5 2kyr aau 012 contains a similar to 1 4x1 5mm 2 exotic clast different from the lithic clast population which is dominated by clasts of anorthosite breccias bulk composition and presence of relatively large vesicles indicate that the clast was most probably formed by an impact into a precursor having nonmare igneous origin most likely related to the rare alkali suite rocks the im clast is mainly composed of clinopyroxenes contains a significant amount of cristobalite 9 0 vol and has a microcrystalline mesostasis although the clast shows similarities in texture and modal mineral abundances with some apollo pigeonite basalts it has lower feo and higher sio2 than any mare basalt it also has higher feo and lower al2o3 than rocks from the fan or mg suite its lower mg 59 compared to mg suite rocks also excludes a relationship with these types of lunar material

test of thermoluminescence dating of loess from new zealand and alaska abstract the accuracy of thermoluminescence tl ages for loess and sediments in general greater than 100 ka is disputed we tested the accuracy of three common tl sediment dating techniques applied to 4 11 m sized polymineral grains from known age loess using 16 samples from north island and south island new zealand and 2 samples from central alaska estimated sample ages range from 20 26 to 800 ka we varied the optical bleaching spectrum the selected window of the emission spectra ultraviolet or uv blue and green wavelengths the pre readout heat treatment and the tl equivalent dose measurement technique most of the 20 26 ka samples gave tl age underestimates of 3 6 ka that may be attributed to post burial open system behavior for the older samples the partial bleach tl method gave expected ages up to 300 ka and the total bleach tl method produced expected ages above 100 ka the partial bleach regeneration tl method gave significant age underestimates for samples older than 100 ka with a maximum tl age of 250 ka for samples having expected ages up to 350 ka two 300 360 ka samples which gave total bleach age underestimates with use of uv tl and green tl gave expected ages with use of blue tl these results demonstrate that reliable tl ages for loess from new zealand and alaska up to 800 ka can be obtained if uv and green emissions and the various regeneration methods are avoided this age range is well above the former putative 80 100 ka upper age limit for tl dating of loess from other regions which was thought to be a global limit application of our successful procedures to such loess is encouraged

luminescence chronology of loess paleosol sequences from southern south island new zealand abstract the loess paleosol sequences in new zealand are among the thickest in the southern hemisphere and preserve an important terrestrial record of paleoclimatic changes unlike loess paleosol sequences in north island most of those in south island lack discrete chronostratigraphic marker ash beds excepting perhaps the widespread 24 ka kawakawa tephra therefore any specific correlation to marine isotope stage mis proxy records or to loess paleosol sequences in the northern hemisphere has been unknown hence we applied luminescence sediment dating to four key loess paleosol sequences from southern south island although these pioneering results suggest that further sampling and luminescence dating are needed they do provide 1 the first numeric age constraint 44 3 ka on overlying loess for the end of deposition of the geomorphically and paleoclimatically important edendale terrace gravels 2 the first numeric evidence that the youngest loess paleosol unit l1 at the near coastal romahapa and inland stewarts claim sites began to be preserved much earlier at 60 ka than at the inland kingston crossing site 35 ka 3 the first direct evidence that the 6 m romahapa sequence extends at least to 350 ka the oldest yet tl dated such sequence in south island furthermore the stratigraphically self consistent with one exception luminescence ages between 60 and 350 ka conflict with a previous indirect chronostratigraphy inferred from trace concentrations of glass shards this trace shard chronology implies a major hiatus in loess paleosol preservation missing at least mis 6 7 not recognized by luminescence dating

the pyroxene pallasites vermillion and yamato 8451 not quite a couple two pallasites vermillion and yamato y 8451 have been studied to obtain petrologic trace element and o isotopic data both meteorites contain low ca and high ca pyroxenes 2 by volume and have been dubbed pyroxene pallasites pyroxene occurs as large individual grains as inclusions in olivine and in other pyroxene and as grains along the edges of olivine symplectic overgrowths sometimes found in main group and eagle station pallasites are not seen in the pyroxene pallasites olivine compositions are fa10 12 similar to those of main group pallasites siderophile trace element data show that metal in the two meteorites have significantly differing compositions that are for many elements outside the range of the main group and eagle station pallasites these compositions also differ from those of iab and iiiab iron meteorites rare earth element ree patterns in merrillite are similar to those seen in other pallasites indicating formation by subsolidus reaction between metal and silicate with the merrillite inheriting its pattern from the surrounding silicates the o isotopic compositions of vermillion and y 8451 are similar but differ from main group or eagle station pallasites as well as other achondrite and primitive achondrite groups although vermillion and y 8451 have similar mineralogy pyroxene compositions ree patterns and o isotopic compositions there is sufficient evidence to resist formally grouping these two meteorites this evidence includes the texture of vermillion siderophile trace element data and the presence of cohenite in vermillion

petrogenesis and chronology of lunar meteorite northwest africa 4472 a kreepy regolith breccia from the moon northwest africa nwa 4472 is a polymict lunar regolith meteorite the sample is kreep rich high concentrations of potassium rare earth elements and phosphorus and comprises a heterogeneous array of lithic and mineral fragments these clasts and mineral fragments were sourced from a range of lunar rock types including the lunar high magnesian suite the high alkali suite kreep basalts mare basalts and a variety of impact crater environments the kreep rich nature of nwa 4472 indicates that the sample was ejected from regolith on the nearside of the moon in the procellarum kreep terrane and we have used lunar prospector gamma ray remote sensing data to show that the meteorite is most similar to and most likely sourced from regoliths adjacent to the imbrium impact basin u pb and pb pb age dates of nwa 4472 phosphate phases reveal that the breccia has sampled pre nectarian 4 35 ga rocks related to early episodes of kreep driven magmatism some younger phosphate u pb and pb pb age dates are likely indicative of impact resetting events at 3 9 4 ga consistent with the suggested timing of basin formation on the moon our study also shows that nwa 4472 has sampled impact melts and glass with an alkali depleted incompatible trace element rich high sc low rb th ratios low k compositional signature not related to typical apollo high k kreep or that sampled by kreepy lunar meteorite sayh al uhaymir sau 169 this provides evidence that there are numerous sources of kreep rich protoliths on the moon

isotopic and rock magnetic expression of environmental change at the pleistocene holocene transition in the central great plains abstract in a region too dry for the effective use of the traditional palynological approach loess deposits of the central great plains offer a source of proxy information for the reconstruction of past climates the brady soil a ubiquitous feature developed within the uppermost late pleistocene peoria loess recorded the character of vegetation change associated with climate shifts during the pleistocene holocene transition stable carbon isotope ratio analysis and two room temperature magnetic parameters were used to examine the nature of the change during this period 13 c values derived from soil organic matter indicate that in the late pleistocene minor populations of drought tolerant c4 plants were interspersed among the dominant cool season grasses c3 in the west while c3 grasses were accompanied by trees in the east by the early holocene c4 grasses were the dominant vegetation in the west and contributed substantially to the 13 c signal in the east magnitude of the 13 c shift suggests an increase in july mean daily temperature of 8 10 c according to existing models magnetic susceptibility and frequency dependence signal the cessation of loess deposition and development of the brady soil and indicate a spatial pattern in the intensity of weathering across the region

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

phosphate halogen metasomatism of lunar granulite 79215 impact induced fractionation of volatiles and incompatible elements in the last decade it has been recognized that the moon contains significant proportions of volatile elements h f cl and that they are transported through the lunar crust and across its surface here we document a significant segment of that volatile cycle in lunar granulite breccia 79215 impact induced remobilization of volatiles and vapor phase transport with extreme elemental fractionation 79215 contains 1 volume of fluorapatite ca 5 po 4 3 f cl oh in crystals to 1 mm long which is reflected in its analyzed abundances of f cl and p the apatite has a molar f cl ratio of 10 and contains only 25 ppm oh and low abundances of the rare earth elements ree the chlorine in the apatite is isotopically heavy at 37 cl 32 7 1 6 hydrogen in the apatite is heavy at d 1060 180 much of that d came from spallogenic nuclear reactions and the original d was lower between 350 and 700 unlike other p rich lunar rocks e g 65015 79215 lacks abundant k and ree and other igneous incompatible elements characteristic of the lunar kreep component here we show that the p and halogens in 79215 were added to an otherwise normal granulite by vapor phase metasomatism similar to rock alteration by fumarolic exhalations as observed on earth the ultimate source of the p and halogens was most likely kreep it being the richest reservoir of p on the moon and 79215 having h and cl isotopic compositions consistent with kreep a kreep rich rock was heated and devolatilized by an impact event this vapor was fractionated by interaction with solid phases including merrillite a volatile free phosphate mineral a fe ti oxide and a zr bearing phase these solids removed ree th zr hf etc from the vapor and allowed the vapor to transport primarily p f and cl with lesser proportions of ba and u into 79215 vapor deposited crystals of apatite to 30 m are known in some lunar regolith samples but lunar vapor has not before this been implicated in significant mass transfer it seems unlikely however that phosphate halogen metasomatism is related to the high th sm abundance ratios of this and other lunar magnesian granulites the metasomatism of 79215 emphasizes the importance of impact heating in the lunar volatile cycle both in mobilizing volatile components into vapor and in generating strong elemental fractionations

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

magnetism of chinese loess deposits summary the age of chinese loess deposits has long been disputed biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the pleistocene and ascertained a maximum loess age of about 1 2 myr a new collection of nearly 500 samples from a natural outcrop and a borehole section near lochuan lat 35 8 n long 109 2 e shaanxi province has been dated by magnetic stratigraphy thermal cleaning of the natural remanent magnetization nrm removes a strong secondary component of viscous origin along the present geomagnetic field which resides largely in magnetite the characteristic nrm component is due to haematite which is thought to be of chemical origin rhythmical intensity variations of nrm and initial susceptibility depend on the loess lithology and may reflect climatic changes during loess deposition the palaeomagnetic results are consistent between the two sections and yield a clearly defined magnetic polarity zonation the brunhes matuyama boundary and the jaramillo subchron have been positively identified in both outcrops at exactly the same stratigraphic level the olduvai subchron has been found in the borehole section which records the entire loess sequence most probably the formation of chinese loess began shortly after the matuyama gauss polarity transition therefore a late pliocene age of about 2 4 myr is assigned to the oldest loess sediments measured

upper quaternary marine terrace chronology and deformation south taranaki new zealand an extensive flight of late quaternary marine terraces in the south taranaki region of the north island of new zealand is dated using fission track radiocarbon and amino acid racemization methods a simple model of terrace deformation based on a doming type uplift pattern allows terrace strandline ages to be estimated twelve strandlines are recognized and are estimated to have formed during high sea level stands at 60 000 80 000 100 000 120 000 135 000 210 000 310 000 340 000 400 000 450 000 520 000 600 000 and 680 000 yr b p

zircon fission track age for middle pleistocene rangitawa tephra new zealand stratigraphic and paleoclimatic significance rangitawa tephra is an important stratigraphic marker in mid pleistocene marine and terrestrial sequences in new zealand and adjacent ocean basins zircon fission track ages zfta on rangitawa tephra from five sites in the southern north island yield mean site ages in the range 0 34 to 0 40 ma with a weighted mean of 0 35 0 04 ma 1 on the basis of glass shard major element chemistry ferromagnesian mineralogy zfta and similarity of paleomagnetic dates of proposed tephra correlatives in deep sea cores it is concluded that rangitawa tephra represents a major eruptive event in the taupo volcanic zone most probably associated with eruption of the whakamaru group ignimbrites 0 35 0 39 ma or less likely the paeroa range group ignimbrites 0 36 0 38 ma pollen analyses from two onshore sites together with regional loess stratigraphy show that rangitawa tephra was erupted during a glacial period the zfta and previously reported oxygen isotope data from dsdp site 594 indicate that rangitawa tephra was erupted near the end of oxygen isotope stage 10

magnetic properties of loess deposits in australia and their environmental significance abstract there are vast dry areas in australia but few loess sections have been reported mackenzie s waterholes creek mwc profile in new south wales was the deepest and first dated loess profile in this paper various measurements of magnetic parameters from mwc were carried out and comparison was made with those of luochuan profile which lies in the central chinese loess plateau clp the types of magnetic minerals are similar to the clp magnetite maghemite limonite and hematite however the magnetic properties of the australian aeolian sediment are quite different frequency dependent magnetic susceptibility fd is rather high while values of magnetic susceptibility are low the relative content of hard paramagnetic magnetic components is much higher than clp whereas the content of maghemite and hematite is much less furthermore hard magnetic minerals increase with depth while soft maghemite decrease with depth maghemite is more sensitive than magnetite under pedogenic condition of waterlogged environments it increases along with enhancement of magnetic susceptibility in luochuan section however decreases in mwc profile this very likely indicates that the pedogenesic processes in mwc took place under an environment in which maghemite magnetite were unstable the modern annual precipitation in the mwc area is 924 mm which is about 300 mm higher than that in luochuan that extra moisture may lead mwc to exceed the stable range for maghemite magnetite those minerals therefore were gradually converted to more stable goethite causing magnetic susceptibility to decrease fe and mn nodules are abundant in the lower part of section implying mildly reducing conditions that allowed fe and mn to be mobilised and enriched in near the oxidation front indicating that under waterlogged and reducing conditions wind blown maghemite magnetite were transformed to iron hydroxides such as goethite limonite or other paramagnetic minerals resulting in reduced magnetic susceptibility the susceptibility from most of the section shows a generally positive relationship to the loess particle size and seems to fit the alaskan wind vigor model however fe chemical weathering and movement in mwc suggests that the precondition for the wind vigor model cannot be satisfied and that the susceptibility variation can only be explained by pedogenesis

dust accumulation in the new zealand region since the last glacial maximum abstract loess is widespread in new zealand deposits 1 m thick cover 10 of the land area it has mainly been derived from dust deflated from river floodplains during the last glacial maximum lgm dust accumulation continues today downwind of major river floodplains most loess is quartzofeldspathic having its origins in mesozoic and neogene rocks of the axial ranges and hill country in the central north island there are deposits of volcanic loess derived from aeolian reworking of tephras loess morphology and properties vary greatly due to diverse parent materials post depositional climates and drainage conditions the widespread 26 170 cal yr kawakawa tephra provides a datum for calculating mass accumulation rates mars rates are mostly within the range 70 150 g m 2 yr 1 but enhanced deposition at one site gave a rate of 360 g m 2 yr 1 contemporary mars of 40 100 g m 2 yr 1 were determined for distances of 1 75 0 4 km downwind of the rakaia river lgm mars of quartz for two marine cores p69 q858 drilled 100 300 km east of new zealand are 40 70 g m 2 yr 1 the mar of the aeolian component of p69 is estimated to be ca 15 g m 2 yr 1

partitioning in ree saturating minerals theory experiment and modelling of whitlockite apatite and evolution of lunar residual magmas we present compositions including rees determined by ion microprobe of apatite and whitlockite in lunar rock assemblages rich in incompatible trace elements total concentrations of ree oxides in whitlockites range from 9 13 wt and those in apatites range from 0 15 to 1 wt ratios of ree concentrations in whitlockite to those in coexisting apatite range from 10 to 60 the distribution of mg and fe between apatite and whitlockite is correlated to that of coexisting mafic silicates magnesium is strongly preferred by whitlockite and fe is preferred by apatite incorporation of rees in whitlockite is dominated by the coupled substitution of 2ree3 in ca b sites vacancy in ca iia for 2ca 2 in ca b sites and ca2 na in ca iia other substitutions account for only a small portion of the rees in whitlockite over the observed concentration range thus ree concentrations become partially saturated as the primary substitution approaches its stoichiometric limit of two rees per fifty six oxygens leading to reduced whitlockite melt distribution coefficients e g decreasing from twenty five to ten for nd the ree concentrations of lunar residual melts are not depleted by whitlockite crystallization in assemblages consisting mainly of other minerals in typical proportions distribution coefficients for the rees in lunar apatite appear to be low and variable e g 0 2 0 8 for nd variations in the modal ratio of whitlockite to apatite specifically the abundance of whitlockite lead to a range of ree concentrations in the phosphates and variations in the magnitude of ree concentration ratios between whitlockite and apatite if apatite crystallizes before whitlockite or in the absence of whitlockite as textures in several samples indicate then apatite zoned in rees and apatite crystals of different ree concentrations may occur in a given sample provided there is some amount of fractional crystallization and apatite does not later equilibrate this may occur because in the absence of whitlockite in the crystallizing assemblage the rees are highly incompatible relative to the crystalline assemblage so ree concentrations in lunar residual melts increase strongly during small increments of late stage crystallization once whitlockite begins to crystallize bulk distribution coefficients for the rees although still 1 are only mildly incompatible so the change in ree concentrations of residual melts with further crystallization is small consistent with the lack of ree zoning in whitlockite the ree concentrations in lunar whitlockites are modelled as resulting mainly from equilibrium crystallization of the assemblages in which they occur metasomatism or other secondary metamorphic processes are not indicated local melt pocket equilibrium at advanced stages of crystallization may lead to variable ree concentrations and variable whitlockite apatite concentration ratios within the same sample parent melts with extremely high ree concentrations are not required in order to crystallize ree rich lunar whitlockite if modal proportions of whitlockite are low

crystal chemistry of lunar merrillite and comparison to other meteoritic and planetary suites of whitlockite and merrillite merrillite also known as whitlockite is one of the main phosphate minerals along with apatite that occur in lunar rocks martian meteorites and in many other groups of meteorites signi cant structural differences between terrestrial whitlockite and lunar and meteoritic varieties warrant the use of merrillite for the h free extraterrestrial material and the systematic enrichment of ree in lunar merrillite warrants the use of re merrillite laser raman spectroscopy of extraterrestrial merrillite and terrestrial whitlockite con rms the absence of h in the former and presence of h in the latter lunar merrillite ideally mg fe 2 mn 2 2 ca18 x y ree x na2 x p si 14o56 contains high concentrations of y ree reaching just over 3 atoms per 56 o atoms or up to 18 wt as y re 2o3 in the absence of extensive si p substitution the availability of the na site limits y ree substitution to 2 atoms per 56 o atoms higher concentrations of y ree with coupled substitution of si for p to balance charge are possible but rare in lunar material intrinsically low na concentrations in lunar rocks combined with the typical formation of merrillite in late stage basaltic mesostasis or residual intercumulus melt pockets produce these high ree concentrations lunar merrillite typically contains 0 1 0 4 na atoms per 56 o atoms for comparison martian merrillite contains signi cantly higher na concentrations up to 1 7 na atoms per 56 o atoms and much lower ree concentrations meteoritic merrillite has relatively low ree contents but exists in both ca rich and na rich varieties concentrations of fe and mg in all varieties sum to near 2 atoms per 56 o atoms merrillite in lunar crustal lithologies typically has mg fe however fe rich mare basalts contain up to 1 8 fe 2

environmental magnetism principles and applications 1 in environmental magnetism rock and mineral magnetic techniques are used to investigate the formation transportation deposition and postdepositional alterations of magnetic minerals under the influences of a wide range of environmental processes all materials respond in some way to an applied magnetic field and iron bearing minerals are sensitive to a range of environmental processes which makes magnetic measurements extremely useful for detecting signals associated with environmental processes environmental magnetism has grown considerably since the mid 1970s and now contributes to research in the geosciences and in branches of physics chemistry and biology and environmental science including research on climate change pollution iron biomineralization and depositional and diagenetic processes in sediments to name a few applications magnetic parameters are used to routinely scan sediments but interpretation is often difficult and requires understanding of the underlying physics and chemistry thorough examination of magnetic properties and of the environmental processes that give rise to the measured magnetic signal is needed to avoid ambiguities complexities and limitations to interpretations in this review we evaluate environmental magnetic parameters based on theory and empirical results we describe how ambiguities can be resolved by use of combined techniques and demonstrate the power of environmental magnetism in enabling quantitative environmental interpretations we also review recent developments that demonstrate the mutual benefit of environmental magnetism from close collaborations with biology chemistry and physics finally we discuss directions in which environmental magnetism is likely to develop in the future

age and palaeoclimatic significance of the loess of lanzhou north china extending in a broad arc that abuts the sandy non gobi deserts the loess plateau of northern china1 3 is one of the most massive accumulations of loess in the world the loess sequence is typically characterized by an alternation of silty or sandy loess with more clay rich palaeosols these alternations in conjunction with their enclosed faunas and distinctive mineralogies have been interpreted as reflecting pleistocene glacial interglacial cycles3 8 because it holds implications for the climatic and anthropological history of china9 10 the definition of a reliable chronological framework for loess deposition is of great interest recent palaeomagnetic studies4 5 have indicated that loess deposition in shaanxi province commenced 2 4 myr ago to assess the synchrony of loess accumulation across the loess plateau we have dated a 330 m thick loess sequence near lanzhou gansu province the magnetostrati graphical results reported here indicate that the base of this loess succession dates from 1 3 my r ago this young age in comparison to the shaanxi sequence is attributed to uplift along the northern fringe of the tibetan plateau11 that precluded early pleistocene loess preservation in this mountainous region palaeosols in the basal loess occur on average once every 25 kyr suggesting that climates conducive to soil forming events may have been modulated by orbital precession in the early pleistocene

chronology of pliocene and quaternary bioevents and climatic events from fission track ages on tephra beds wairarapa new zealand abstract high resolution pliocene and pleistocene sequences exposed on land in new zealand are some of the few detailed records of widepread marine bioevents and paleoclimatic changes in the southern hemisphere marine biostratigraphy calibrated in deep sea cores by paleomagnetic reversals has been the primary basis for the chronology of these sequences we have determined ages for several tephra beds which now provide an independent numerical age calibration for a well studied marine and terrestrial section in wairarapa by using the isothermal plateau fission track itpft method on volcanic glass we have overcome the problems of partial track fading and detrital mineral contamination which hindered earlier studies to reveal a new chronology extending back to nearly 5 ma our ages for the hikawera tuff 4 91 0 25 ma and spooner tuff 3 44 0 13 ma are consistent with the appearance and disappearance of many early pliocene foraminiferial species validating their age calibration in new zealand however some fossil occurrences including coccoliths differ temporally by as much as 0 55 ma perhaps due to local tectonic induced recycling four pleistocene tephra beds potaka tephra 1 00 0 03 ma kaukatea tephra 0 87 0 05 ma rangitawa tephra ca 0 35 ma and kawakawa tephra ca 0 22 ma are now recognised in the wairarapa sequence via stratigraphic and new geochemical and age data these beds allow direct correlation to other marine and terrestrial basins as well as volcanic regions in new zealand and will ultimately aid in a regional paleoenvironmental reconstruction where bioevents are absent the tephra ages indicate that the marine sediment accumulation rates varied from 90 to 250 m ma between different sections of the pliocene and reached ca 350 m ma in the last 2 4 ma when the sequence displays pronounced glacioeustatic cyclic deposition in the terrestrial realm the oldest loess in new zealand is now constrained to between 1 00 and 0 87 ma

new zealand quaternary stratigraphy an overview abstract new zealand quaternary strata including marine sediments loess volcanic and glacial deposits offer detailed records of quaternary environmental change from a geographically significant location time stratigraphic subdivision of new zealand quaternary strata based on marine biostratigraphy and climatostratigraphy has resulted in a series of locally defined stages and substages the plio pleistocene boundary as defined at vrica in italy and dated at ca 1 63 ma lies near the top of the nukumaruan stage in new zealand the first faunal evidence of cooling in new zealand plio pleistocene sequences occurs much earlier at the base of the nukumaruan stage ca 2 4 ma with the appearance in central new zealand of the subantarctic taxa chlamys delicatula and jacquinotia edwardsii although glacial deposits of the south island have long been central to new zealand quaternary stratigraphy they are poorly dated and lack continuity more complete records of quaternary events are found within uplifted marine strata and associated terrestrial deposits of the north island such as in wanganui basin the use of widespread rhyolite tephra for precise correlation and dating in north island offers much for improved land sea correlations direct correlation of on land sequences using tephra with oxygen isotope stages of deep sea cores may negate the need for further local time stratigraphic subdivision in the new zealand quaternary however there will still be scope for regional comparisons highlighting climatic changes not apparent in deep sea cores

an apatite rich ferroan mafic lithology from lunar meteorite alha81005 lunar meteorite alha81005 contains a clast of ferroan anorthositic troctolite with in vol 59 plagioclase avg an 95 4 27 olivine avg fo 52 2 11 clinopyroxene mg 50 70 wo 11 34 and 3 chlorapatite this clast is probably pristine and is unique among lunar samples its texture is igneous but is unusual in that pyroxene and apatite which probably cocrystallized have been brecciated and apparently resorbed and olivine has precipitated around them we discuss four possible explanations for this texture 1 a sudden decrease in pressure occurred causing liquidus pyroxene to become unstable relative to olivine 2 the bulk composition of the magma was sufficiently feo rich that pyroxene crystallized before olivine 3 a p2o5 rich 2 5 3 0 wt quartz normative basaltic magma that crystallized pyroxene plagioclase and phosphates was mixed with an olivine saturated magma that had a lower p2o5 content 4 an olivine saturated magma invaded a wall rock assemblage of pyroxene plagioclase and apatite the first two models require only one magma and are attractive because the average compositions of pyroxene olivine and plagioclase indicate that they crystallized from liquids with similar mg the first model cannot be assessed without knowing the bulk composition of the original magma and the initial pressure the second model cannot account for the brecciation and resorption of the pyroxene and apatite a model involving either magma mixing or wall rock magma reaction seems most likely the high p content and apatite whitlockite ratio indicate that the parent magma s had an unusually high volatile content for a lunar magma ree in whitlockite are 40 80 times kreep abundances the parent magma s must have had very high abundances of ree and la sm less than that of kreep the clast is also unusually mafic only 59 plagioclase for pristine ferroan rocks ferroan mafic lithologies appear to be an important component of alha81005 the apatite rich clast presents several petrologic and geochemical paradoxes which suggests that complex processes were involved in its formation

apatite liquid partition coefficients for the rare earth elements and strontium abstract sixteen sets of apatite liquid partition coefficients dap liq for the rare earth elements ree la sm dy lu and six values for sr were experimentally determined in natural systems ranging from basanite to granite the apatite melt glass assemblages were obtained from starting glasses artificially enriched in ree sr and fluorapatite components these were run under dry and hydrous conditions of 7 5 20 kbar and 950 1120 c in a solid media piston cylinder apparatus an sem equipped electron microprobe was used for subsequent measurement of ree and sr concentrations in coexisting apatites and quenched glasses the resulting partition coefficient patterns resemble previously determined apatite phenocryst groundmass concentration ratios in the following respects 1 the rare earth patterns are uniformly concave downward i e the middle ree are more compatible in apatite than the light and heavy ree 2 dreeap liq is much higher for silicic melts than for basic ones and 3 strontium and therefore eu2 is less concentrated by apatite than are the trivalent ree the effects of both temperature and melt composition on dreeap liq are systematic and pronounced at 950 c for example a change in melt sio2 content from 50 to 68 wt causes the average ree partition coefficient to increase from 7 to 30 a 130 c increase in temperature on the other hand results in a two fold decrease in dreeap liq partitioning of sr is insenstitive to changes in melt composition and temperature and neither the sr nor the ree partition coefficients appear to be affected by variations in pressure or h2o content of the melt the experimentally determined partition coefficients can be used not only in trace element modelling but also to distinguish apatite phenocrysts from xenocrysts in rocks reported apatite megacryst host basalt ree concentration ratios 12 for example are considerably higher than the equilibrium partition coefficients which suggest that in this particular case the apatite is actually xenocrystic a reversal experiment incorporated in our study yielded diffusion profiles of ree in apatite from which we extracted a ree ca interdiffusion coefficient of 2 4 10 14 cm2 s at 1120 c extrapolated downward to crustal temperatures this low value suggests that complete ree equilibrium between felsic partial melts and residual apatite is rarely established

a review of wanganui basin new zealand global reference section for shallow marine plio pleistocene 2 5 0 ma cyclostratigraphy abstract wanganui basin new zealand contains one of the most complete late neogene marine stratigraphic records in the world the ca 2 km thick basin fill for the last ca 2 5 ma comprises 47 superposed cyclothems which correspond to successive 5th 100 ka and 6th 41 ka order glacio eustatic sea level fluctuations on the palaeo new zealand shelf since oxygen isotope stage 100 stages 100 to 5 are represented by marine cyclothems whereas stages 17 to 3 are represented by a suite of coeval and younger uplifted marine terrace sequences additionally a predominantly glacial loess stratigraphy exists for isotope stages 12 2 the presence of interbedded tephras and an established paleomagnetic stratigraphy allows the development of an integrated cyclostratigraphy for wanganui basin which correlates closely with the global oxygen isotope scale in all except two cases cycles 12 and 36 individual unconformity bound cyclothems sequences represent a single glacial interglacial couplet of milankovitch frequency lithologic and faunal variation within the cyclothems corresponds closely to that predicted by the sequence stratigraphic model each cyclothem generally contains a transgressive systems tract a mid cycle condensed shellbed a highstand systems tract and often a regressive systems tract six common cyclothem motifs are inferred to represent deposition in shelf locations between the highstand and lowstand shorelines viz the hawera maxwell turakina seafield castlecliff and rangitikei motifs a seventh type the nukumaru motif includes coquina limestone and represents deposition in shoreface and very shallow water marine environments

radiative transfer modeling of lunar highlands spectral classes and relationship to lunar samples 1 tompkins and pieters 1999 identified eleven spectral classes present on the surface of the moon here we model these spectral classes to determine the compositions that define them we do this by mathematically matching spectral classes to radiative transfer computed spectra using spectral shape contrast and excursion parameters as defining characteristics model spectra are based upon known mineralogies mafic mineral mg s molar mg mg fe 100 and maturities we compare these compositional results to a compilation of 100 apollo samples to determine plausible representative samples for these spectra results indicate that unique mineralogic solutions for several spectral classes can be determined unambiguously however classes previously interpreted to be pyroxene rich are compositionally ambiguous results suggest these ambiguous mineral assemblages are not random but correlate with variations in absolute reflectance these data further suggest absolute reflectance is a compositionally diagnostic spectral parameter that should be used in conjunction with relative reflectance analysis to constrain mineralogy although absolute reflectance for the eleven spectral classes is not available to constrain their composition we detail mineral chemical i e mg and absolute reflectance variations of matching model relative reflectance spectra to narrow the possibilities this information is used in a pilot study of bullialdus crater for which clementine absolute reflectance is known results indicate bullialdus s central peak consists of tompkins and pieters spectral classes an agn and n bullialdus s spectra that match class n are roughly consistent with previous compositional interpretations however matches to classes an and agn indicate more mafic assemblages typical of mg suite norite gabbronorite rocks

methods and concepts in european quaternary stratigraphy introduction to methods for the study of stratigraphical records rousseau d d 1990 methods for the study of stratlgraphlcal records introduction to methods and concepts m european quaternary stratigraphy palaeogeogr palaeochmatol palaeoecol 80 i 6 the international conference methods and concepts m european quaternary stratigraphy was held to take stock of the new developed concepts m quaternary stratigraphy to compare fferent approaches and to evaluate the respectwe results m continental and marine environments the following papers presented m this issue correspond to the theme methods for the study of stratlgraphlcal records they roughly indicate the average use of fferent concepts developed m different dlsclphnes to quaternary records two biological objects are described m detad molluscs and pollen they are approached m two fferent ways for the former first of all by using a blogeographlcal approach based on the blome concept and secondly by trying to demonstrate the stratlgraphlcal value of mollusc assemblages m fluwal deposits for the latter first of all by using a dynamxc approach to the vegetation cover of the middle mountain area of the massif central france and secondly by using transfer functions to propose temperature and precipitation estimations from two long pollen sequences a last paper makes an evaluauon of fferent materml which can be ra ocarbon dated and the rehablllty of the proposed dates specmlly beyond 35 000 yr b p ten years ago european geologists who were dealing with quaternary study met m dijon to develop a common strategy concerning quaternary stratigraphy chahne 1980 the purpose was to homogenize and redefine a stratlgraphtcal approach accordmg to hedberg s guide three major recommendations were proposed paepe

sedimentary cyclicity in the marine pliocene pleistocene of the wanganui basin new zealand sequence stratigraphic motifs characteristic of the past 2 5 m y earth s climatic history since 2 5 ma has been controlled by milankovitch variations in the planetary orbit comprising alternate periods of glaciation and interglaciation with a dominant frequency of 41 000 yr concomitantly eustatic sea level has fluctuated 70 to 130 m causing rapid transgressions and regressions of the shoreline across the world s continental shelves the resulting sedimentary record is cyclothemic each cyclothem corresponding to a single climate and sea level cycle the wanganui basin new zealand contains a 2 km thick almost complete composite record since isotope stage 100 ca 2 5 ma in the form of 47 superposed cyclothems of shelf origin each cyclothem corresponds to an unconformity bound stratigraphic sequence and typically contains a transgressive systems tract sometimes a mid cycle shell bed a highstand systems tract and sometimes a regressive systems tract no advantage accrues from using transgressive regressive units rather than cyclothems and or sequences in description of the succession six basic sequence motifs represent deposition in locations between the shoreline and offshore shelf i e the hawera birdgrove turakina seafield castlecliff and rangitikei motifs a seventh the nukumaru motif which includes dominant coquina limestone represents deposition in shallow water areas of reduced terrigenous sediment on the flank of the basin the sequence motifs represented in any section change systematically in sympathy with basin scale changes in subsidence and sediment supply in contrast with the 41000 year length of individual glacioeustatic sequences these basin wide tectonic cycles have a periodicity of many hundreds of thousands to a few million years i e that of third or fourth order sequences of the exxon type this coupled with the restriction of strongly cyclothemic sediments to geological periods of known glacio eustasy permiancarboniferous pliocene pleistocene suggests that tectonic subsidence cycles rather than glacio eustasy are the driving forces behind the development of the third and fourth order unconformity bound sequences that are reported to occur throughout the stratigraphic record

magnesian anorthosites and associated troctolites and dunite in apollo 14 breccias magnesian anorthosite a new type of pristine lunar highlands rock has been found in apollo 14 breccias it has primitive high ca and mg silicate mineral compositions and high and variable ree concentrations variations in ree contents can be accounted for by variations in modal abundance of ree rich apatite magnesian anorthosites are associated with troctolites and a dunite with very similar mineral compositions and it is suggested that all crystallized from a differentiated troctolitic intrusion the origin of the ree rich apatite is enigmatic it is unlikely to have crystallized from an igneous liquid in equilibrium with the major minerals in the anorthosite possible origins are assimilation of urkreep or metasomatism by ree rich fluids ree rich alkali anorthosites and gabbronorites are also found and are likely to be related to kreep basalt magmas lunar compositional associations are distributed in a regional rather than global manner

seventh foray whitlockite rich lithologies a diopside bearing troctolitic anorthosite ferroan anorthosites and kreep seventeen nonmare samples most of them pristine are characterized and implications of the new data are discussed five pristine samples are from apollo 14 near the center of the kreep rich zone in the moon s western hemisphere three of them are alkali anorthosites rich in ca phosphate whitlockite which apparently crystallized from magmas with ree contents roughly 6 those of high k kreep the alkali anorthosites probably formed from mg rich magmas that assimilated large amounts of urkreep but some might have formed by metasomatism of ferroan anorthosite by urkreep the gabbronorite norite classification scheme is not well suited to western hemisphere lithologies probably due mainly to the overriding effects of longitude petrochemistry correlations a diopside bearing mg rich lithology indicates that a low degree of melting was not a prerequisite for producing gabbroic high ca pyroxene rich mg rich magmas and suggests that some source regions of mg rich magmas were relatively ca rich several pristine kreep fragments from apollo 15 station 2 are texturally and compositionally much like other pristine kreep and thus reinforce the evidence that kreep is highly uniform the pristine anorthosites on the other hand demonstrate further that lunar anorthosites are diverse

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

the blake magnetic polarity episode in cores from the mediterranean sea abstract palaeomagnetic and oxygen isotope studies on samples taken from five cores in the mediterranean area are described directions of the stable remanent magnetisation show the presence of an anomalous reversed zone during the transition between the oxygen isotope substages 5e and 5d this position corresponds to the age of about 117 kyr b p and thus to the blake polarity episode the duration of this episode is estimated to be about 6000 years the study of the anisotropy of the magnetic susceptibility shows no indication of sedimentological disturbances in recorded sections the blake episode therefore represents a stratigraphic marker which may be used to link the continental and marine palaeoclimatic and sedimentary records

detection of structurally bound hydroxyl in fluorapatite from apollo mare basalt 15058 128 using tof sims fluorapatite grains from apollo 15 mare basalt 15058 128 were analyzed by raman spectroscopy raman spectral imaging time of flight secondary ion mass spectrometry tof sims field emission scanning electron microscopy fe sem and electron probe microanalysis epma in an attempt to detect structurally bound oh in the fluorapatite although oh could not be definitively detected by raman spectroscopy because of ree induced photoluminescence hydroxyl was detected in the fluorapatite by tof sims the tof sims technique is qualitative but capable of detecting the presence of hydroxyl even at trace levels electron microprobe data indicate that on average f and cl f cl fill the monovalent anion site in these fluorapatite grains within the uncertainties of the analyses about 0 07 0 01 atoms per formula unit however some individual spot analyses have f cl deficiencies greater than analytical uncertainties that could represent structural oh on the basis of epma data the fluorapatite grain with the largest f cl deficiency constrains the upper limit of the oh content to be no more than 4600 2000 ppm by weight the equivalent of 2400 1100 ppm water the tof sims detection of oh in fluorapatite from apollo sample 15058 128 represents the first direct confirmation of structurally bound hydroxyl in a lunar magmatic mineral this result provides justification for attributing at least some of the missing structural component in the monovalent anion site of other lunar fluorapatite grains to the presence of oh moreover this finding supports the presence of dissolved water in lunar magmas and the presence of at least some water within the lunar interior

an ancient sm nd age for a ferroan noritic anorthosite clast from lunar breccia 67016 strontium and neodymium systematics have been examined in a clast of ferroan noritic anorthosite from apollo 16 breccia 67016 two splits 328 and 326 of the same clast give different sm nd results split 328 gives a well defined internal isochron age of 4 562 0 068 ga and an initial 143nd 144nd ratio of 0 50673 10 corresponding to nd 0 1 0 2 2 optimized error relative to the murchinson carbonaceous chondrite the pyroxene separate from split 326 lies on the same isochron in contrast the plagioclase and whole rock from split 326 fall below this line indicating a small scale disturbance of the sm nd system this may reflect either an isotopic exchange between the plagioclase and a low sm nd mineral or a loss of radiogenic 143nd from the plagioclase possibly during the period of major impacts at 3 9 ga the preservation of an extremely old age for the noritic ferroan anorthosite 67016 328 suggests a rapid cooling of this rock at an early stage in the evolution of the lunar magma ocean this old age is also consistent with giant impact models for the formation of the moon but implies a relatively early event pre 4 50 ga and therefore rapid accretion and differentiation of the terrestrial planets

climate and sea level during oxygen isotope stage 7b on land evidence from new zealand abstract strata at landguard bluff near wanganui new zealand preserve a clear record of relative sea level changes during oxygen isotope stage 7 two relative high sea level stands during stages 7a about 210 000 yr ago and 7c about 240 000 yr ago are separated by a relative low sea level stage 7b that was at least 32 m lower than present pollen analysis of sediment deposited during stage 7b indicates climate at the time was up to 3 c cooler than present the climate and sea level evidence from landguard bluff are consistent with oxygen isotopic evidence from deep sea cores indicating a marked cooling during stage 7 which is closely associated with a summer radiation minimum centered at about 230 000 yr ago in the northern hemisphere

high resolution diatom stratigraphy of quaternary sediments from the scotia sea upper quaternary pelagic and hemipelagic sediments from the scotia sea and south scotia ridge range from diatom ooze to diatom bearing mud diatom content increases northwards and at most sites diatom rich and diatom poor sediments alternate downcore on a scale of metres a local stratigraphy is based on relative abundance of six prominent diatom taxa eucampia antarctica rhizosolenia spp thalassiosira spp chaetoceros spores nitzschia kerguelensis and othernitzschia species and one silicoflagellate species distephanus speculum these stratigraphic units defined using diatoms are correlated with radiolarian abundance stratigraphy cycladophora davisiana and with palaeomagnetic stratigraphy information from modern environments phytoplankton and sediment trap studies indicates that changes in diatom species composition are related to n s movement of the winter ice edge and of the antarctic convergence

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

a new 14 c age for the oruanui wairakei eruption new zealand the oruanui eruption was the largest known outburst of taupo volcano new zealand and is among the larger quaternary eruptions documented the eruption deposits are variously known as the oruanui wairakei kawakawa tephra or aokautere ash formations and represent a bulk volume probably exceeding 500 km 3 four new 14 c age determinations on carbonized vegetation in the non welded oruanui ignimbrite are combined to give a conventional age of 22590 230 yr b p compared with the previously accepted figure of 20000 yr b p this new age resolves the anomaly of apparently older 14 c ages being obtained from a demonstrably younger new zealand deposit and strengthens correlation of this eruption with an antarctic ice core acid anomaly the trace of this eruption has great potential as a time plane marker in the antarctic just prior to the last glacial maximum the close similarity in ages between the oruanui and a comparable sized eruption ito aira tn in japan suggests that this period of activity may represent the best chance of resolving any linkages between large scale explosive silicic volcanism and climate changes

record of climatic fluctuations from ca 500 ka loess deposits and paleosols near wanganui new zealand abstract in the wanganui region of north island new zealand a record of climate change for the last ca 500 ka is preserved in a terrestrial cover bed sequence eleven loess layers from five major glacial cycles are separated by paleosols and punctuated by both rhyolitic and andesitic tephra layers the dated rhyolitic tephras thermoluminescence dates from the loess and dated marine terraces on which the sequence rests provide good chronological control a detailed stratigraphy and the use of four physical and chemical parameters enables a climatic interpretation and a correlation with the marine oxygen isotope record to be made variations in dry bulk density and potassium content have resulted from weathering of the upper part of each loess unit during a warmer climate than that responsible for generation of the loess fluctuations in quartz content and magnetic susceptibility are of sedimentary origin and represent alternating quartzo feldspathic and andesitic provenance fluctuations in potassium content and dry bulk density are caused by weathering of the accumulating sediment glacial periods were times of environmental destabilization loess accumulation and least weathering while warm periods saw soil formation and gentle accession of andesitic tephra the main periods of environmental destabilization were during marine oxygen isotope stages 2 3 upper part 6 8 10 and 12 while stages 1 3 lower part 5 7 9 11 and 13 provided most stable conditions and soil formation

petrology and geochemistry of alkali gabbronorites from lunar breccia 67975 clasts of an unusual type of lunar highlands igneous rock alkali gabbronorite have been found in apollo 16 breccia 67975 the alkali gabbronorites form two distinct subgroups magnesian and ferroan modes and bulk compositions are highly varied the magnesian alkali gabbronorites are composed of bytownitic plagioclase or2 5an82 89 hypersthene wo3 5en49 62 augite wo39 42en36 44 a silica mineral and trace ba rich k feldspar the ferroan alkali gabbronorites are composed of ternary plagioclase or11 22an65 74 pigeonite wo6 9en35 47 augite wo38 40en29 35 ba rich k feldspar and a silica mineral trace minerals in both subgroups are apatite ree rich whitlockite and zircon the magnesian and ferroan alkali gabbronorites appear to have formed by progressive differentiation of the same or closely related parent magmas the compositional data indicate that these magmas were ree rich the ternary plagioclase is probably a high temperature metastable phase formed during crystallization in composition and mineralogy the 67975 alkali gabbronorites show many similarities to apollo 12 and 14 alkali norites alkali gabbronorites and alkali anorthosites and all these rocks together constitute a distinctive alkali suite in addition the alkali gabbronorites show some similarities to kreep basalts mg norites and some felsites these data suggest genetic links between some or all of these types of pristine rocks two types of relationships are possible the first is that alkali suite rocks crystallized in plutons of kreep basalt magma and kreep basalts are their extrusive equivalents the second is that the alkali suite rocks and some felsites all crystallized in plutons of mg norite parent magmas and kreep basalt magmas formed by remelting of these plutons additional studies are needed to resolve which of these hypotheses is correct

rare earth elements in minerals of the alha77005 shergottite and implications for its parent magma and crystallization history abstract rare earth element ree and selected trace element abundances were measured in individual grains of pyroxenes whitlockite maskelynite and olivine of the alha77005 shergottite minor 1 whitlockite which displays a negative eu anomaly indicative of co crystallization with plagioclase dominates the bulk rock ree pattern detectable ce anomalies in 20 of the pyroxene grains analyzed appear to be the result of weathering in the antarctic environment and indicate that pyroxene is particularly susceptible to element remobilization mineral compositions and textural observations suggest that alha77005 is a cumulate with 50 cumulus material olivine chromite olivine re equilibrated with intercumulus liquid on cooling the intercumulus liquid then crystallized as a closed system to form successively poikilitic low ca and high ca pyroxene followed by interstitial pyroxenes plagioclase whitlockite and other minor phases and reacted with cumulus crystals to form rims of different composition this crystallization sequence provides a constraint on the shergottite source region composition the alha77005 and shergotty intercumulus liquids had similar ree compositions however as opposed to shergotty if alha77005 was formed during the last 0 72 ga its parent melt was not contaminated by lree enriched material

evidence for metasomatism of the lunar highlands and the origin of whitlockite abstract the presence of rare earth element rich ree rich whitlockite in the relatively primitive ree poor lunar highlands presents a paragenetic problem to the petrologist comparison with occurrences in mare basalt mesostasis assemblages demonstrates that whitlockite in the lunar highlands has not resulted from the crystallization of the residual interstitial melt furthermore by the nature of ree partition coefficients for whitlockite it is demonstrated that they cannot have crystallized from kreepy melts rather we suggest that the only lunar melt which contains high enough ree abundances is the basic immiscible melt derived from a kreepy liquid we envisage that whitlockite found in the lunar highlands is a post cumulus metasomatic phase precipitated from a melt formed when urkreep underwent silicate liquid immiscibility the basic immiscible melt thus produced was able to percolate through the lunar highlands due to its low viscosity and act as a metasomatizing agent apatite is occasionally found as either epitactic overgrowths on the whitlockites mantled by whitlockite or in composite grains with whitlockite in all cases these apatites contain much lower ree contents than the corresponding whitlockite experimental results suggest either 1 1 apatite and whitlockite have essentially the same ree kd s 2 2 apatite has lower ree kd s than whitlockite both scenarios can be used to explain certain apatite whitlockite associations for example apatite and whitlockite having the same ree kd s can explain the situation where apatite appears to have crystallized after whitlockite this is because apatite crystallization requires a certain level of halogens in the melt these levels are only realized after whitlockite crystallization which enriches the residual melt in f and cl but depletes it in the rees therefore when apatite crystallizes it will contain lower ree abundances than whitlockite however relationships where apatite and whitlockite appear to have co crystallized or apatite crystallized before whitlockite require apatite to have lower ree kd s even if both experimental results are correct the whitlockite parental melt still requires ree abundances greater than in kreep urkreep the parental melt has similar ree abundances to a calculated reepy immiscible melt from kreep urkreep

benefiting from 3d avo by using adaptive supergathers 3d surface seismic data have many useful features e g fine sampling better resolution that coupled with the fact that 3d prestack time or depth migration yields accurate imaging of subsurface features are good reasons to conclude that performing avo analysis on 3d data will be beneficial as it is on 2d data

coupled ce nd isotope systematics and rare earth elements differentiation of the moon abstract 138ce 142ce and 143nd 144nd isotope ratios of lunar samples are determined to constrain the petrogenetic differentiation and evolution of the moon high precision ce nd isotope data well defined rb sr isochrons and rare earth elements ree abundances of lunar samples show that unexpectedly low la ce ratios of evolved lunar highland samples are preserved from at least 3 9 ga precise analysis of ree abundances indicates that the low la ce ratio results from a depletion of la relative to other ree this depletion can be seen in pristine kreep basalts and mg suite rocks from 3 85 to 4 46 ga as ree abundances of all these samples are controlled by the presence of a kreep component the depletion was probably inherited from a late crystallization sequence of the lunar magma ocean related to the production of the original kreep component

rare earth element distributions among minerals in a granodiorite and their petrogenetic implications a study of the distribution of lanthanide rare earths in a granodiorite from the eastern peninsular ranges batholith southern california reveals that a large fraction of the ree in this rock resides in the accessory phases sphene and allanite the minerals plagioclase alkali feldspar biotite epidote and apatite each contribute approximately 1 or less of each ree to the whole rock with the exception of eu for which plagioclase contributes 7 sphene and allanite together contain 80 to 95 of each ree each of these phases is zoned in ree concentration with substantial decreases from core to margin textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma ree zoning trends in sphene and allanite and unexpectedly low ree concentrations in largely later crystallizing minerals such as feldspar indicate that the precipitation of sphene and allanite significantly reduced ree concentrations in residual melts these results illustrate the potential that sphene and allanite have for controlling the behavior of ree in granitic magmas available information collectively suggest that the sampled granodiorite existed as a complete melt that the ree contained in the assemblage of phases were derived by direct crystallization from the melt and that the melt behaved essentially as a closed system once crystallization of the phases now present began close correspondences between the major and trace element chemistries of the granodiorite and phenocryst poor lavas from similar tectonic settings support these conclusions the ree pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism the high liquidus temperature of a granodiorite melt 1000 c indicates the importance of mantle derived components within the sources of batholithic magmas in the peninsular ranges

distribution of rare earth elements in lunar zircon an investigation of rare earth elements ree in 15 zircon grains from lunar breccia sample 14321 combined with published analyses has allowed lunar zircon grains to be separated into four distinctive types type 1 zircon is characterized by the relative depletion of light ree lree resulting in a steep chondrite normalized pattern type 2 zircon shows relative enrichment in the lree compared to type 1 grains type 3 zircon also shows relatively high concentrations of lree as well as a relative depletion in the heavy ree hree which results in a relatively flat chondrite normalized pattern type 4 zircon grains are characterized by the steepest chondrite normalized ree pattern with the lowest lree and the highest hree as well as by a distinctive positive ce anomaly multiple analyses of ree in a complex impact modified zircon from breccia sample 73235 suggest a possibility that the very light ree from la to nd were mobilized during impact however the main differences between the identified zircon types appear to be primary and reflect the original crystallization environment of zircon grains these differences are not linked to major changes associated with the different suites of plutonic rocks such as mg and alkali suites and quartz monzodiorites qmd but instead reflect small scale variations in residual pockets of melt where zircon grains crystallized for example the presence of plagioclase in the immediate vicinity of zircon was responsible for the type 1 zircon ree pattern whereas type 2 zircon was formed in the presence of pyroxene the only exception is type 4 zircon which was probably associated with some felsite and granite samples representing very late differentiates of lunar mafic magmas

subdividing the pleistocene using the matuyama brunhes boundary mbb an australasian perspective abstract the last major reversal of the earth s magnetic field the matuyama brunhes boundary mbb dated at 0 78 ma is widely identified in australian and new zealand pleistocene deposits in new zealand the mbb is precisely located in shallow marine sediments of wanganui basin where it corresponds with the base of the new zealand putikian substage a combination of marine biostratigraphy sequence stratigraphy and tephrostratigraphy permit correlation from wanganui basin to other on land sections and deep sea cores in australia the mbb is identified in many continental sequences particularly saline lake basins however chemical weathering has resulted in variable brunhes age normal overprints that are sometimes difficult to remove australasian tektites are a potential lithostratigraphic marker just prior to the mbb but have yet to be identified in the same on land section as the mbb in australia identification of reverse polarity magnetisation in weathered deposits including soils provides a minimum age of 0 78 ma for these materials a widespread arid shift in paleoclimate succeeded the mbb in australia placement of the lower middle pleistocene boundary at the mbb would constitute the most recognisable chronostratigraphic marker in weathered continental deposits

the effect of interpolation on imaging and avo a viking case study the use of prestack interpolation prior to prestack migration to improve avo analysis on image gathers is demonstrated on an exploration play the interpolation achieves this improvement by reducing migration artifacts avo analysis attempts to estimate fundamental information from surface seismic data and likely will be used more frequently if the estimates can be more accurately produced land 3d seismic typically has poor and irregular sampling this poor sampling creates migration noise which is a material cause of inaccurate avo estimates prestack 5d interpolation is applied prior to prestack migration and avo analysis on the imaged gathers to address this noise problem the interpolation algorithm includes offset and azimuth dimensions that preserve avo information this method is evaluated bycomparing the results to those of alternate approaches such as superbinning that suppress this kind of noise in avo analysis the evaluation is determined by comparing our ability to predict the reservoir q

risking seismic amplitude anomaly prospects based on database trends many oil companies routinely evaluate prospects for their drilling portfolio and seismic amplitude anomalies play an important role in this process when these anomalies occur at a potential reservoir level they are often called dhis or direct hydrocarbon indicators which are changes in reflection response that may be related to oil and or gas accumulations examples of dhis include bright spots flat spots dim spots character phase change at a projected oil or gas water contact and an amplitude variation with offset many uncertainties should be considered and analyzed in the process of assigning a probability of success and resource estimate range before including a seismic amplitude anomaly prospect in an oil company s prospect portfolio

paleomagnetic evidence for cold emplacement of eruption fed density current deposits beneath an ancient summit glacier tongariro volcano new zealand abstract the thermal structures of eruption fed subglacial volcaniclastic deposits are poorly understood because their emplacement is hazardous to observe or obscured by the glacier determining deposit emplacement temperature however supports improved understanding of the flow dynamics and emplacement processes of volcaniclastic material beneath a glacier understanding the emplacement temperatures of ancient volcanic deposits is also important because they can be used in combination with field studies to infer the eruptive environment here we use paleomagnetic techniques to quantify the emplacement temperatures of two ancient proximal eruption fed density current deposits at tongariro volcano new zealand stepwise thermal demagnetisation of lithic and recycled juvenile block sized clasts reveal randomly orientated directions of magnetisation suggesting that the clasts were rotated within the flow but not heated additional data from thermomagnetic hysteresis and isothermal remanent magnetisation tests indicate that the principal carrier of magnetic remanence is magnetite and that the magnetisation directions are a primary remanence rather than post depositional chemical remanent magnetisations following systematic removal of any viscous remanent magnetisation the post emplacement equilibrium temperatures for the deposits can be estimated at

500 000 year paleomagnetic record from new zealand loess abstract a paleomagnetic record of secular variation has been obtained from a 17 4 m long core drilled from loess in north island new zealand three dated rhyolitic tephra occur in the loess core at depths of 1 5 3 4 and 13 0 m with ages of 22 500 42 000 and 370 000 years respectively the base of the core is estimated to be 500 000 years old which makes this the longest continuous loess sequence yet described from the southern hemisphere two periods of anomalously low inclination in the core are correlated with the mungo event ca 35 000 years ago and the emperor event ca 490 000 years ago the blake event ca 115 000 years ago is not recorded

the galapagos axial magnetic anomaly evidence for the emperor event within the brunhes and for a two layer magnetic source the axial brunhes magnetic anomaly over the galapagos spreading center shows consistent short wavelength anomalies that are not consistent with a uniformly magnetized layer we interpret this anomaly to confirm the presence of the emperor reversed event at 0 49 0 05 mybp with a duration about 0 01 m y further this anomaly is consistent with a two layer magnetic source with the lower layer having very broad transition zones offset away from the axis from those of the upper layer by about 10 km

a palaeomagnetic secular variation record from c 120 000 yr old new zealand cave sediments summary a record of palaeomagnetic secular variations has been obtained from a 5 m section of cave sediments in new zealand the uppermost horizon has been dated at 120 000 yr and the section probably spans about 10 000 yr the mean direction of remanence is close to the field direction expected at the site from an axial geocentric dipole in the upper part of the record the palaeomagnetic vector describes three open clockwise loops ending in a swing to anomalously low inclinations this swing is tentatively associated with a weakening of the main dipole field prior to the blake geomagnetic event

radiometric and paleomagnetic evidence for the emperor reversed polarity event at 0 46 0 05 m y in basalt lava flows from the eastern snake river plain idaho k ar and paleomagnetic data from cores through a sequence of basalt flows in the eastern snake river plain provide evidence for a brief 0 005 to 0 01 m y reversal of the geomagnetic field 0 46 0 05 m y ago this reversed polarity event has also been found in sea floor magnetic anomalies and in sediment cores and is probably the emperor event of ryan 1972

pristine highland clasts in consortium breccia 14305 petrology and geochemistry the apollo 14 site continues to provide pristine non mare rocks that contrast sharply with those from apollo 16 the archetypical highland site we characterize six small 1 cm samples of pristine highland crust that occur as clasts in polymict lunar breccia 14305 one is an alkali anorthosite the others include troctolite norite and anorthosite of the mg suite the alkali anorthosite 400 is a plagioclase adcumulate with minor intercumulus augite cerian fluorapatite with lree contents 30 000 x chondrite occurs as an inclusion in plagioclase enstatite troctolite 358 and magnesian anorthosite 361 have trace element characteristics similar to eastern mg suite rocks highlighting the importance of local variations in geochemical systematics that are superimposed on moon wide longitudinal variations the highly fractionated trace element abundances and highly magnesian mineral compositions of olivine orthopyroxenite 389 suggest a new previously unknown magma type related to the mg suite this magma may have formed in equilibrium with garnet alkali anorthosites and magnesian anorthosites troctolites cannot be related to a single parent magma by fractional crystallization or by variable kreep assimilation these suites represent separate parent magmas each of which may have been modified by mixing with kreep

rare earth element carriers in the shergotty meteorite and implications for its chronology ion probe measurements of the rare earth element ree concentrations of individual grains of the shergotty meteorite are reported phases analyzed include whitlockite apatite baddeleyite augite pigeonite maskelynite and k rich glass u concentrations of whitlockite and apatite crystals were also obtained the whole rock ree pattern is dominated by whitlockite which contains over 95 of the light rare earth elements lree ree concentrations in apatite are much lower than estimated by laulet al 1986 all the whitlockites whether intergrown with pyroxene equant or interstitial have the same relative abundances of lree i e patterns are almost flat from la to sm the observation by joneset al 1985 of a skeletal whitlockite with lree enrichment is not confirmed by analyses of the same grain pyroxene rims are not enriched in lree no leachable carrier enriched in lree and associated with pyroxene laulet al 1986 jagoutz and wanke 1986 has been found instead either a laboratory contamination or a petrographically cryptic phase such as a film on grain boundaries is suspected as the carrier of lree enrichments if a grain boundary film carries the enrichments it would not be resistant to the metamorphic resetting which has affected other isotopic reservoirs in this sample thus there is no compelling reason to consider the sm nd pyroxene leachates line jagoutz and wanke 1986 as a 360 m y isochron estimates of ree abundances in the shergotty intercumulus melt indicate that a complex petrogenesis is required in agreement with the conclusions of mckayet al 1986a pyroxene distribution coefficients measured experimentally mckayet al 1986a are compared with estimates from measured ree abundances in augite and pigeonite evolution of ree abundances in the shergotty late stage interstitial melt as inferred from analyses of whitlockite conforms with trends predicted from partitioning considerations and requires no special processes such as metasomatism the average u concentrations of whitlockite and apatite are respectively 540 and 1 550 ppb although the calcium phosphates are enriched in u they contain less than 20 of the u in shergotty

clinopyroxene ree distribution coefficients for shergottites the ree content of the shergotty melt abstract ree distribution coefficients were measured between synthetic pyroxenes and melts similar in composition to the inferred shergotty intercumulus liquid by in situ analysis with the electron microprobe using samples doped to per cent concentration levels these coefficients exhibit a strong positive correlation with pyroxene wollastonite content recommended values for augites similar in composition to the shergotty cumulus augite cores wo32en48 are d la 0 023 d ce 0 039 d nd 0 10 d sm 0 17 d eu 0 16 d gd 0 20 d yb 0 29 and d lu 0 30 recommended values for pigeonites similar in composition to the shergotty cumulus pigeonite cores wo12en58 are d la 0 002 d ce 0 004 d nd 0 019 d sm 0 031 d yb 0 13 and d lu 0 13 these values resemble distribution coefficients measured for terrestrial basalts of higher mg fe than the shergotty melt rather than those of more evolved siliceous rocks of similar mg fe to the shergotty melt thus it appears that mg fe is considerably less important than other factors in determining distribution coefficient values for pyroxenes ree abundances were computed for the shergotty intercumulus melt using distribution coefficients measured for the natural phase compositions these computed abundances display lree depletion such lree depleted abundance patterns cannot be generated by simple partial melting of a mafic mineral assemblage having the lree enriched patterns required for a two stage sm nd evolution history this result implies that either 1 the melting process was complex e g continuous melting 2 the source region had a more complex history than that of the simple 2 stage model or 3 shergotty does not satisfy the closed system assumption of the calculation and has suffered post magmatic lree enrichment

isothermal plateau fission track age for a paleomagnetic excursion in the mamaku ignimbrite new zealand and implications for late quaternary stratigraphy mamaku ignimbrite the youngest of the large welded ignimbrite sheet forming eruptions from the taupo volcanic zone in new zealand is dated at 230 12 ka by the isothermal plateau fission track itpft method on glass this age is older and more precise than that indicated by previous studies requiring the revision of loess paleosol coverbed chronologies the eruption occurred during a paleomagnetic excursion allowing the ignimbrite to be easily distinguished from other eruptive events by paleomagnetic methods this excursion is one of the few such events recorded in igneous rocks in the southern hemisphere may be widely recorded in new zealand and is now temporally well constrained

alkali norite troctolites and vhk mare basalts from breccia 14304 twelve clasts were separated from breccia 14304 for consortium study six pristine highlands rocks two mare basalts and four nonpristine highlands rocks the pristine highlands rocks include representatives of the magnesian troctolite anorthosite and alkali suites the two most common subgroups of the mg suite found at the apollo 14 site two troctolite clasts have olivine fo 90 and plagioclase an 94 compositions similar to one group of apollo htroctolites one also contains spinel mg 66 85 incompatible element abundances in one are similar to those of 14305 troctolites although the hree heavy rare earth elements pattern is distinct among apollo 14 troctolites a dunite clast fo 89 may be an unrepresentative piece of a troctolite alkali lithologies include an alkali anorthosite and an alkali norite which is a rock type not previously described the alkali norite has a pristine igneous texture and contains inverted pigeonite mg 64 plagioclase an82 k feldspar ternary feldspar ree rich phosphates and silica it resembles alkali gabbronorites from apollo 14 and 67975 in mineralogy and mineral compositions alkali lithologies and phosphate bearing magnesian anorthosites from apollo 14 may have formed from mg rich magmas that assimilated various amounts of material rich in p and ree this material could be a fractionated derivative of urkreep another pristine clast from 14304 is an mg gabbronorite the two mare basalt clasts are very high potassium vhk basalts they have 4 mg g k and k la ratios of 580 and 700 the parent magmas of vhk basalts could have formed from typical low ti high al basaltic magmas by assimilation of k rich material this material could also be a fractionated derivative or urkreep nonpristine 14304 clasts include melt textured anorthosites and an augite rich poikilitic melt rock the latter is probably polymict but its major component must be an mg suite gabbro