evolution of protoplanetary disk inferred from 26 al chronology of individual chondrules abstract we review the 26al ages of chondrules in various type 3 0 chondrites the 26al ages of chondrules are 1 3 myr after calcium aluminum rich inclusion cai for ll3 0 co3 0 and acfer 094 ungrouped c 3 0 available data for chondrules in cr chondrites indicate that many chondrules are relatively younger 3 myr although data from chondrules in cr3 0 are not yet available to confirm their younger ages the total ranges for the 26al ages of chondrules in a single chondrite group are more than 0 5 1 myr however most chondrules show relatively narrow range of ages in a single chondrite group 0 2 0 4 myr 1 sd which might be short enough to preserve the group specific chemical and isotope signatures against radial diffusion of solid in the disk distinct oxygen isotope reservoirs might exist in the protoplanetary disk simultaneously which could be spatially separated

an oscillating trend in phanerozoic non skeletal carbonate mineralogy textural and compositional data on ancient ooids and cements suggest the existence of an oscillating phanerozoic temporal trend in non skeletal carbonate mineralogy the trend shows good correlation with eustatic climatic oscillations proposed by others the most likely mechanism appears to be plate tectonically influenced oscillations in pco2 the vapour pressure of co2 rather than change in oceanic mg ca ratio

jurassic evolution of the arabian carbonate platform edge in the central oman mountains the jurassic sahtan group exposed in northern oman was deposited in shallow marine environments at the edge of the arabian platform facing the neo tethys hamrat duru basin the upper sahtan group is made up of a mixed siliciclastic carbonate unit overlain by pure carbonate deposits assigned to a bathonian and early callovian age on the basis of brachiopods and foraminifers these carbonate depositional systems were composed of outer oolitic shoals that underwent subaerial exposure and a deeper somewhat restricted gently dipping shelf interior oolitic material was shed off the platform edge into the deep sea depositional complex of the guweyza formation the sahtan group is affected by an important thickness reduction towards northeastern jabal akhdar the angular unconformity 0 2 at the top of the sahtan group is shown to result from tilting and top truncation of genetic sequences this unconformity is overlain by the rayda formation a veneer that shows an onlap pattern including a gradual deepening upwards facies evolution the minimal time span of the stratigraphic hiatus is mid callovian kimmeridgian oxfordian and kimmeridgian sequences were probably never deposited in this area because of lack of accommodation space and or because of subaerial exposure it is proposed herein that the unconformity was shaped by subaerial carbonate dissolution during a steady tectonically driven exhumation of the platform edge during the tithonian a major eustatic sea level rise caused transgression of the rayda formation upon the platform edge and normal shelf marine conditions resumed in the eastern arabian peninsula

26al in plagioclase rich chondrules in carbonaceous chondrites evidence for an extended duration of chondrule formation abstract the 26al 26mg isotope systematics in 33 petrographically and mineralogically characterized plagioclase rich chondrules prcs from 13 carbonaceous chondrites ccs one ungrouped acfer 094 six cr five cv and one co reveal large variations in the initial 26al 27al ratio 26al 27al 0 well resolved 26mg excesses 26mg from the in situ decay of the short lived nuclide 26al t1 2 0 72 ma were found in nine chondrules two from acfer 094 five from the cv chondrites allende and efremovka and one each from the paired cr chondrites eet 92147 and eet 92042 with 26al 27al 0 values ranging from 3 10 6 to 1 5 10 5 data for seven additional chondrules from three cv and two cr chondrites show evidence suggestive of the presence of 26al but do not yield well defined values for 26al 27al 0 while the remaining chondrules do not contain excess radiogenic 26mg and yield corresponding upper limits of 11 2 10 6 for 26al 27al 0 the observed range of 26al 27al 0 in prcs from ccs is similar to the range seen in chondrules from unequilibrated ordinary chondrites uocs of low metamorphic grade 3 0 3 4 however unlike the uoc chondrules there is no clear trend between the 26al 27al 0 values in prcs from ccs and the degree of thermal metamorphism experienced by the host meteorites high and low values of 26al 27al 0 are found equally in prcs from both ccs lacking evidence for thermal metamorphism e g crs and ccs where such evidence is abundant e g cvs the lower 26al 27al 0 values in prcs from ccs relative to most cais are consistent with a model in which 26al was distributed uniformly in the nebula when chondrule formation began approximately a million years after the formation of the majority of cais the observed range of 26al 27al 0 values in prcs from ccs is most plausibly explained in terms of an extended duration of 2 3 ma for the formation of cc chondrules this interval is in sharp contrast to most cais from ccs whose formation appears to be restricted to a narrow time interval of less than 105 years the active solar nebula appears to have persisted for a period approaching 4 ma encompassing the formation of both cais and chondrules present in ccs and raising important issues related to the storage assimilation and mixing of chondrules and cais in the early solar system

high precision oxygen three isotope analyses of anhydrous chondritic interplanetary dust particles abstract oxygen three isotope ratios of three anhydrous chondritic interplanetary dust particles idps were analyzed using an ion microprobe with a 2 m small beam the three anhydrous idps show 17o values ranging from 5 to 1 which overlap with those of ferromagnesian silicate particles from comet wild 2 and anhydrous porous idps for the first time internal oxygen isotope heterogeneity was resolved in two idps at the level of a few per mil in 17o values anhydrous idps are loose aggregates of fine grained silicates 3 m in this study with only a few coarse grained silicates 2 20 m in this study on the other hand wild 2 particles analyzed so far show relatively coarse grained few m igneous textures if anhydrous idps represent fine grained particles from comets the similar 17o values between anhydrous idps and wild 2 particles may imply that oxygen isotope ratios in cometary crystalline silicates are similar independent of crystal sizes and their textures the range of 17o values of the three anhydrous idps overlaps also with that of chondrules in carbonaceous chondrites suggesting a genetic link between cometary dust particles wild 2 particles and most anhydrous idps and carbonaceous chondrite chondrules

calcium and titanium isotopes in refractory inclusions from cm co and cr chondrites abstract previous studies have shown that cv and cm chondrites incorporated ca al rich inclusions cais with different isotopic characteristics which may represent different snapshots in the isotopic evolution of the early solar system to better understand how the isotopic characteristics of cais vary between different chondrite groups we have studied calcium and titanium isotopes in cais from cm co and cr chondrites we show that all three chondrite groups contain cais with large anomalies in 48ca and or 50ti 10s of or 100s of e units as well as cais with no anomalies resolved beyond measurement uncertainties isotopically the anomalous co and cr chondrite cais resemble the platy hibonite crystals placs from cm chondrites but they are more mineralogically complex the new data are consistent with the well established mutual exclusivity relationship between incorporation of 26al and the presence of large anomalies in 48ca and 50ti the two highly anomalous co chondrite cais have correlated anomalies in 46ti and 50ti while most other highly anomalous cais do not this result could indicate that the reservoir with coupled 46ti and 50ti that was sampled by bulk meteorites and cv chondrite cais already existed before arrival and or homogeneous distribution of 26al in the protoplanetary disk among the studied cm chondrite cais are ten spinel hibonite inclusions shibs with known oxygen isotopic compositions our results show that these objects sampled a reservoir that was well mixed in oxygen calcium and titanium isotopes we further show that shibs tend to be slightly enriched in the heavy calcium isotopes suggesting that their formation history was different from cv chondrite cais

the oxygen isotopic composition of olivine and pyroxene from ci chondrites the ci chondrites are taken to represent average solar system material based on the similarity of their elemental compositions to that of the solar photosphere however their oxygen isotope geochemistry is dominated by secondary minerals that formed during aqueous alteration on the ci parent body precursors to this alteration namely olivine and pyroxene are extremely rare in ci chondrites precluding previous measurements of their oxygen isotopic composition we report ion microprobe analyses of oxygen isotopes in single olivine and pyroxene grains separated from ci chondrites orgueil and ivuna the ci chondrite olivine and pyroxene grains most likely represent liberated chondrule phenocrysts based on petrographic chemical and isotopic evidence consistent with crystallization from a melt the oxygen isotope data form an array that falls nearly along the carbonaceous chondrite 16o mixing line with 18o values ranging from 9 3 to 12 3 o and 17o from 11 3 o to 7 8 o consistent with nebular processes being the source of the oxygen isotopic compositions the degree of 16o enrichment in orgueil olivines is negatively correlated with feo content but the exact nature and timing of the process that introduced this variation remains unknown the pyroxene oxygen isotopic compositions are similar to those of olivines with 5 mol fayalite the oxygen isotopic analyses of the olivine and pyroxene in ci chondrites have been used to revise previous models for the isotopic evolution of ci materials our data require more complete gas solid equilibration in the nebula and constrain the initial aqueous fluids on the ci parent body to have lower 17o values than previously postulated the refined model indicates that the temperature of aqueous activity on the ci parent body was no higher than 50 c and the fluid rock ratio was significantly less than previously estimated even prior to alteration and formation of secondary minerals the ci chondrites were the most 16o depleted carbonaceous chondrites and thus the solids originally contained in the ci chondrites are the most equilibrated nebular materials represented in the carbonaceous chondrites the data suggest the oxygen isotopic composition of average solar system to be approximately equivalent to average terrestrial oxygen as recorded in the compositions of terrestrial and lunar basalts

coordinated mineralogical and isotopic analyses of a cosmic symplectite discovered in a comet 81p wild 2 sample we have discovered in a stardust mission terminal particle a unique mineralogical assemblage of symplectically intergrown pentlandite fe ni 9s8 and nanocrystalline maghemite fe2o3 mineralogically similar cosmic symplectites cos have only been found in the primitive carbonaceous chondrite acfer 094 and are believed to have formed by aqueous alteration the o and s isotopic compositions of the wild 2 cos are indistinguishable from terrestrial values the metal and sulfide precursors were thus oxidized by an isotopically equilibrated aqueous reservoir either inside the snow line in the wild 2 comet or in a larger kuiper belt object close association of the stardust cos with a kool mineral assemblage kosmochloric ca rich pyroxene feo rich olivine and albite that likely originated in the solar nebula suggests the cos precursors also had a nebular origin and were transported from the inner solar system to the comet forming region after they were altered

olivine in terminal particles of stardust aerogel tracks and analogous grains in chondrite matrix abstract the dearth of both major and minor element analyses of anhydrous silicate phases in chondrite matrix has thus far hindered their comparison to the wild 2 samples we present 68 analyses of olivine fa 0 97 in the coarse grained terminal particles of stardust aerogel tracks and a comprehensive dataset 10 3 analyses of analogous olivine grains 5 30 m isolated in ci cm cr ch co cv3 oxidized cv3 reduced c3 ungrouped acfer 094 and ningqiang l ll 3 0 4 eh3 and kakangari chondrite matrix these compositions reveal that wild 2 likely accreted a diverse assortment of material that was radially transported from various carbonaceous and ordinary chondrite forming regions the wild 2 olivine includes amoeboid olivine aggregates aoas refractory forsterite type i and type ii chondrule fragments and or microchondrules and rare relict grain compositions in addition we have identified one terminal particle that has no known compositional analog in the meteorite record and may be a signature of low temperature aqueous processing in the kuiper belt the generally low cr content of feo rich olivine in the stardust samples indicates that they underwent mild thermal metamorphism akin to a petrologic grade of 3 05 3 15

chondrule fragments from comet wild2 evidence for high temperature processing in the outer solar system abstract terminal grains from c2063 1 154 1 0 track 154 and c2061 1 113 5 track 113 from the stardust collection of comet wild2 s coma have been studied by tem and nanosims terminal grain 2 of c2063 1 154 1 0 consists of an al rich diopside en 97 99 al 2 o 3 9 11 wt pigeonite en 85 wo 15 with tio 2 and al 2 o 3 contents of 0 5 and 5 2 wt and minor forsterite and enstatite the mineral assemblage and al rich ti poor composition of the grain are consistent with being a fragment of an al rich chondrule similar to those present in carbonaceous chondrites the oxygen isotopic composition of the c2063 1 154 1 0 grain was determined by nanosims analyses and found to be 17 o 10 6 5 7 18 o 7 5 2 5 and 17 o 1 4 4 3 18 o 6 5 1 6 1 errors for the two sections these figures are distinct from cais and consistent with an origin as al rich chondrule fragments terminal grain 5 of c2061 1 113 5 consists of low ca pyroxene en 86 87 fs 10 11 wo 3 4 and 2 wt al 2 o 3 and in one section 5 10 of a na rich silicate phase this assemblage may be a fragment of a low ca pyroxene bearing chondrule and mesostasis the original chondrule diameter for the c2063 1 154 1 0 and c2061 1 113 5 samples by analogy with carbonaceous chondrite chondrules might have been in the range 0 2 1 0 mm if they were of that size then the presence of large grains of high temperature material e g 1500 k for such refractory assemblages could be explained through commonly invoked models of radial drift from inner to outer solar system but only if the chondrules were first fragmented to dust within the inner solar system an alternative scenario is that some chondrule formation was associated with high temperature processing and planetesimals in the outer solar system

soft sediment deformation structures in cambrian siliciclastic and carbonate storm deposits shandong province china differential liquefaction and fluidization triggered by storm wave loading abstract this paper focuses on soft sediment deformation structures ssds in both siliciclastic and carbonate storm deposits of the cambrian mantou and chaomidian formations shandong province china in order to understand their deformation mechanisms and possible triggers siliciclastic ssds e g sand volcanoes and pillows and carbonate ssds e g sedimentary dykes grainstone matrix breccias deformed cross beddings and marlstone matrix breccias occur exclusively in hummocky cross stratified fine sandstone and peloidal grainstone respectively the siliciclastic ssds formed in porous and permeable surface sediment whereas the carbonate ssds formed under shallow burial conditions when early marine cementation prevailed the various deformation structures resulted mainly from differences between siliciclastic and carbonate sediment conditions and resulting deformation mechanisms sand volcanoes formed by upward extrusion of over pressured fluidized sandy sediment whereas sand pillows resulted from upward injection of lower density muddy sediment into overlying liquefied sandy sediment sedimentary dykes and grainstone matrix limestone breccias formed as a result of differential liquefaction and fluidization of heterogeneously cemented carbonate sediment whereas deformed cross beddings and marlstone matrix limestone breccias developed by the thixotropic liquidization and injection of clayey sediment and further disruption of thin peloidal layers sedimentary facies analysis and analysis of the physical processes indicate that the ssds were most likely caused by cyclic loading of storm waves

late formation of a comet wild 2 crystalline silicate particle pyxie inferred from al mg chronology of plagioclase we examined the al mg isotope systematics of plagioclase in a feo poor ferromagnesian wild 2 particle c2092 7 81 1 0 named pyxie using a 2 m spot three analyses show average 27al 24mg ratio of 65 and excess 26mg value of 0 1 4 5 0 1 4 5 2 indicating no resolvable 26mg excess in the particle the inferred initial 26al 27al 0 ratio of plagioclase in pyxie is estimated as 0 6 4 5 10 6 0 6 4 5 10 6 with an upper limit of 4 10 64 10 6 the result is very similar to that of the feo rich ferromagnesian particle iris ogliore et al 2012 assuming homogeneous distribution of 26al in the early solar system pyxie formed at least 2 6 ma after the oldest ca al rich inclusions this minimum formation age is marginally younger than formation ages of most chondrules in type 3 0 chondrites but comparable with those of mg 98 chondrules in cr3 chondrites considered in conjunction with similar oxygen isotope ratios between pyxie and iris and mg 98 chondrules in cr3 chondrites it is inferred that the ferromagnesian wild 2 particles and mg 98 chondrules in cr3 chondrites formed late in local disk environments that had similar oxygen isotope ratios and redox states

lithofacies and cyclicity of mohilla evaporite basins on the rifted margin of the levant in the late triassic makhtesh ramon southern israel marine connected basins with evaporites occur beneath most extensional continental margins that originated at low latitudes and often are of major economic significance cyclicity in the evaporite lithofacies reflects the degree of restriction of the basin overprinted by sea level changes and caused by structural movements in the barrier region whether by fault block rotation footwall uplift or hanging wall subsidence in both extensional and compressional basins the upper triassic evaporites of the ramon section in southern israel model cyclic sedimentation in such environments the mohilla formation is a carbonate evaporate siliciclastic succession of carnian age that fills a chain of basins extending along the levant margin from southern israel to jordan and syria the basins developed in half grabens adjacent to normal faults that formed during a period of regional extension evaporites of this formation are well exposed in outcrops at makhtesh ramon the southernmost of these basins the m2 member of the mohilla formation is composed of 42 sub metre cycles of alternating dolostone gypsum and calcareous shales field and microfacies analysis showed these cycles to conform mostly to restricted shallow and marginal marine environments spatially limited by the uplifted shoulders of the half graben systems a total of 10 facies types belonging to six depositional environments have been identified from stacking patterns and analysis of bed to bed change cycles can be categorized into three groupings i low frequency exposure to exposure cycles that developed under eustatic or climate control ii high frequency deepening shallowing upward cycles characterized by gradual transitions due to short term sea level or runoff event oscillations possibly referable to orbital forcing and iii high frequency shallowing upward cycles characterized by abrupt transitions attributable to sporadic tectonic events affecting accommodation space or barrier effectiveness the way facies and cycling of the sedimentary environments was deciphered in the mohilla evaporite basin can be used to unravel the genesis of many other evaporite basins with barriers of tectonic origin

oxygen isotopic composition of coarse and fine grained material from comet 81p wild 2 abstract individual particles from comet 81p wild 2 collected by nasa s stardust mission vary in size from small sub m fragments found in the walls of the aerogel tracks to large fragments up to tens of m in size found towards the termini of tracks the comet in an orbit beyond neptune since its formation retains an intact a record of early solar system processes that was compromised in asteroidal samples by heating and aqueous alteration we measured the o isotopic composition of seven stardust fragments larger than 2 m extracted from five different stardust aerogel tracks and 63 particles smaller than 2 m from the wall of a stardust track the larger particles show a relatively narrow range of o isotopic compositions that is consistent with 16 o poor phases commonly seen in meteorites many of the larger stardust fragments studied so far have chondrule like mineralogy which is consistent with formation in the inner solar system the fine grained material shows a very broad range of o isotopic compositions 70 17 o

oxygen isotope compositions of chondrules in cr chondrites abstract we report in situ ion microprobe analyses of oxygen isotopic compositions of olivine low ca pyroxene high ca pyroxene anorthitic plagioclase glassy mesostasis and spinel in five aluminum rich chondrules and nine ferromagnesian chondrules from the cr carbonaceous chondrites eet92042 gra95229 and mac87320 ferromagnesian chondrules are isotopically homogeneous within 2 in 17 o the interchondrule variations in 17 o range from 0 to 5 small oxygen isotopic heterogeneities found in two ferromagnesian chondrules are due to the presence of relict olivine grains in contrast two out of five aluminum rich chondrules are isotopically heterogeneous with 17 o values ranging from 6 to 15 and from 2 to 11 respectively this isotopic heterogeneity is due to the presence of 16 o enriched spinel and anorthite 17 o 10 to 15 which are relict phases of ca al rich inclusions cais incorporated into chondrule precursors and incompletely melted during chondrule formation these observations and the high abundance of relict cais in the aluminum rich chondrules suggest a close genetic relationship between these objects aluminum rich chondrules formed by melting of spinel anorthite pyroxene cais mixed with ferromagnesian precursors compositionally similar to magnesium rich type i chondrules the aluminum rich chondrules without relict cais have oxygen isotopic compositions 17 o 2 to 8 similar to those of ferromagnesian chondrules in contrast to the aluminum rich chondrules from ordinary chondrites those from crs plot on a three oxygen isotope diagram along the carbonaceous chondrite anhydrous mineral line and form a continuum with amoeboid olivine aggregates and cais from crs we conclude that oxygen isotope compositions of chondrules resulted from two processes homogenization of isotopically heterogeneous materials during chondrule melting and oxygen isotopic exchange between chondrule melt and 16 o poor nebular gas

permian oolitic carbonates from the baoshan block in western yunnan china and their paleoclimatic and paleogeographic significance marine carbonate ooids are environment sensitive and hence valuable for paleoclimatic and paleogeographic reconstructions this paper describes permian ooids from the baoshan block in western yunnan china in order to offer a new means to refine the uncertain paleogeographic details of this gondwana derived block four major types of ooids micritic ooids compound ooids leached ooids and half moon ooids are documented from the hewanjie formation in the northern and the shazipo formation in the southern baoshan block these ooids are dated via biostratigraphic analysis to be wordian early wuchiapingian and signify an ameliorated shallow marine temperature for the guadalupian strata of the baoshan block results of this study coupled with literature data reveal diachronous debut of permian ooids among the gondwana derived blocks mostly sakmarian in central taurides of turkey central iran central pamir and karakorum block versus wordian capitanian in baoshan block peninsular thailand and south qiangtang in contrast asselian sakmarian strata of baoshan block as well as peninsular thailand and south qiangtang are characterized by glaciomarine diamictites these observations suggest that the baoshan block was probably situated at a considerably higher paleolatitude under distinct influence of gondwana glaciation during the asselian sakmarian than those blocks yielding sakmarian ooids moreover marine ooids are virtually absent nearby the equator within the permian tethys similar to the modern situation the baoshan block is accordingly interpreted to drift to warm water southern mid latitudes during the wordian capitanian and remain to the south of central iran karakorum block and south china which were equatorially located in the capitanian

oxygen isotopes of chondritic components we review the oxygen isotopic compositions of chondrite components refractory inclusions chondrules and matrix and their inter and intra crystalline oxygen isotopic distributions primary oxygen isotopic compositions acquired before planetesimal accretion are easily disturbed by parent body processes such as aqueous alternation and thermal metamorphism primary or original oxygen isotopic compositions of refractory inclusions ca al rich inclusions and amoeboid olivine aggregates distribute along a slope 1 line on the three oxygen isotope diagram over the range of 60 17 o 18 o 16 o rich and 17 o 18 o rich during refractory inclusion formation on the other hand primary minerals of most chondrules have small isotopic variations and are enriched in 17 o and 18 o relative to refractory inclusions suggesting that chondrule formation occurred in 17 o 18 o rich nebular gas however rare 16 o rich chondrules have been found suggesting some overlap in the timing of formation of chondrules and refractory inclusions in the solar nebula oxygen isotopic compositions of matrix grains distribute along the slope 1 line over the same range as refractory inclusions and chondrules the similarity in oxygen isotopic distributions suggests that matrix was originally a mechanical mixture of nebular dusts co generated with chondrules and refractory inclusions presolar grains with oxygen isotopic compositions that are clearly distinct from those of solar nebular materials are a trace component of chondrite matrices based on these oxygen isotopic characteristics more than 99 5 of the solid materials in the nebula formed locally in the solar nebula and the remainder formed in interstellar space the astrophysical setting of chondrite component formation in the early solar system is also discussed refractory inclusions and 16 o rich matrix dusts formed around the inner edge of the solar nebula on the other hand most chondrules and 17 o 18 o rich matrix dusts seem to have formed elsewhere in the solar nebula efficient large scale radial mixing of the solar nebular materials may have been an essential process in the formation of chondritic planetesimals

a single asteroidal source for extraterrestrial ordovician chromite grains from sweden and china high precision oxygen three isotope sims analysis we examined oxygen three isotope ratios of 48 extraterrestrial chromite ec grains extracted from mid ordovician sediments from two different locations in sweden and one location in south central china the ages of the sediments similar to 470 ma coincide with the breakup event of the l chondrite parent asteroid elemental compositions of the chromite grains are generally consistent with their origin from l or ll chondrite parent bodies the average delta o 17 parts per thousand deviation from the terrestrial mass fractionation line measured in situ from 15 mu m spots by secondary ion mass spectrometry sims of ec grains extracted from fossil meteorites from thorsberg and brunflo are 1 17 0 09 parts per thousand 2 sigma and 1 25 0 16 parts per thousand respectively and those of fossil micrometeorites from thorsberg and puxi river are 1 10 0 09 parts per thousand and 1 11 0 12 parts per thousand respectively within uncertainty these values are all the same and consistent with the l chondrite group average delta o 17 1 07 0 18 parts per thousand but also with the ll chondrite group average delta o 17 1 26 0 24 parts per thousand clayton et al 1991 we conclude that the studied ec grains from correlated sediments from sweden and china are related and most likely originated in the same event the l chondrite parent body breakup we also analyzed chromites of modern h l and ll chondrites and show that their delta o 17 values coincide with averages of delta o 17 of bulk analyses of h l and ll chondrites this study demonstrates that in situ oxygen isotope data measured by sims are accurate and precise if carefully standardized and can be used to classify individual extraterrestrial chromite grains found in sediments c 2009 elsevier ltd all rights reserved less

primordial oxygen isotope reservoirs of the solar nebula recorded in chondrules in acfer 094 carbonaceous chondrite abstract highly precise and accurate ion microprobe analyses of oxygen three isotope ratios in chondrules from the acfer 094 one of the most primitive carbonaceous chondrites show that chondrules preserve evidence for oxygen isotope heterogeneity in chondrule forming regions of the solar nebula identical 17 o values in most minerals and glass within each chondrule indicate that the oxygen isotope ratio in chondrule melt did not change during or after crystallization nearly half of the chondrules studied contain small amounts of olivine grains that have an oxygen isotope anomaly relative to other minerals and glass in the same chondrule most chondrules in acfer 094 can be classified into two oxygen isotope groups 17 o 2 and 17 o 5 indicating that the final melting of chondrules occurred within two distinct oxygen isotope reservoirs probably representing the local protoplanetary disk immediately before planetesimal formation one of these reservoirs 17 o 2 is observed from chondrules in other carbonaceous chondrites and from crystalline silicates in comet wild 2 suggesting that crystalline silicates formed in an oxygen isotope reservoir of 17 o 2 were widely distributed in the outer asteroid belt and throughout the outer solar nebula oxygen three isotope ratios of minerals in chondrules from acfer 094 are distributed along a newly defined primitive chondrule minerals pcm line which has slope 1 17 o 0 987 0 013 18 o 2 70 0 11 and intersects the terrestrial fractionation line at 18 o 5 8 0 4 these data are distinct from and plot between the ccam and young and russell lines the pcm line is interpreted to represent the mixing trend of extreme oxygen isotope reservoirs in the early solar system that were the primary oxygen isotope reservoir of solids that accreted to form planets including the earth

thermochemical stability of low iron manganese enriched olivine in astrophysical environments low iron manganese enriched lime olivine grains are found in cometary samples returned by the stardust mission from comet 81p wild 2 similar grains are found in primitive meteoritic clasts and unequilibrated meteorite matrix lime olivine is thermodynamically stable in a vapor of solar composition at high temperature at total pressures of a millibar to a microbar but enrichment of solar composition vapor in a dust of chondritic composition causes the feo mno ratio of olivine to increase the compositions of lime olivines in primitive materials indicate oxygen fugacities close to those of a very reducing vapor of solar composition the compositional zoning of lime olivines in amoeboid olivine aggregates is consistent with equilibration with nebular vapor in the stability field of olivine without re equilibration at lower temperatures a similar history is likely for lime olivines found in comet samples and in interplanetary dust particles lime olivine is not likely to persist in nebular conditions in which silicate liquids are stable

constraints on the formation environment of two chondrule like igneous particles from comet 81p wild 2 using chemical and petrologic evidence and modeling we deduce that two chondrule like particles named iris and callie from stardust cometary track c2052 12 74 formed in an environment very similar to that seen for type ii chondrules in meteorites iris was heated near liquidus equilibrated and cooled at 100 c hr and within 2 log units of the iw buffer with a high partial pressure of na such as would be present with dust enrichments of 103 there was no detectable metamorphic nebular or aqueous alteration in previous work ogliore et al 2012 reported that iris formed late 3 myr after cais assuming 26al was homogenously distributed and was rich in heavy oxygen iris may be similar to assemblages found only in interplanetary dust particles and stardust cometary samples called kool particles callie is chemically and isotopically very similar but not identical to iris

high precision sims oxygen three isotope study of chondrules in ll3 chondrites role of ambient gas during chondrule formation we report high precision sims oxygen three isotope analyses of 36 chondrules from some of the least equilibrated ll3 chondrites and find systematic variations in oxygen isotope ratios with chondrule types feo poor type i chondrules generally plot along a mass dependent fractionation line d 17 o 0 7 with d 18 o values lower in olivine rich ia than pyroxenerich ib chondrules data from feo rich type ii chondrules show a limited range of d 18 o and d 17 o values at d 18 o 4 5 d 17 o 2 9 and d 17 o 0 5 which is slightly 16 o enriched relative to bulk ll chondrites d 17 o 1 3 data from four chondrules show 16 o rich oxygen isotope ratios that plot near the ccam carbonaceous chondrite anhydrous mineral line glass analyses in selected chondrules are systematically higher than co existing minerals in both d 18 o and d 17 o values whereas high ca pyroxene data in the same chondrule are similar to those in olivine and pyroxene phenocrysts our results suggest that the ll chondrite chondrule forming region contained two kinds of solid precursors 1 16 o poor precursors with d 17 o 1 6 and 2 16 o rich solid precursors derived from the same oxygen isotope reservoir as carbonaceous chondrites oxygen isotopes exhibited open system behavior during chondrule formation and the interaction between the solid and ambient gas might occur as described in the following model significant evaporation and recondensation of solid precursors caused a large mass dependent fractionation due to either kinetic or equilibrium isotope exchange between gas and solid to form type ia chondrules with higher bulk mg si ratios type ii chondrules formed under elevated dust gas ratios and with water ice in the precursors in which the ambient h2o gas homogenized chondrule melts by isotope exchange low temperature oxygen isotope exchange may have occurred between chondrule glasses and aqueous fluids with high d 17 o 5 in ll the parent body according to our model oxygen isotope ratios of chondrules were strongly influenced by the local solid precursors in the proto planetary disk and the ambient gas during chondrule melting events 2010 elsevier ltd all rights reserved

oxygen isotopic composition of relict olivine grains in cosmic spherules links to chondrules from carbonaceous chondrites most olivine relict grains in cosmic spherules selected for the present study are pristine and have not been disturbed during their atmospheric entry thereby preserving their chemical mineralogical and isotopic compositions in order to understand the origin of the particles oxygen isotope compositions of relict olivine grains in twelve cosmic spherules collected from deep sea sediments of the indian ocean were studied using secondary ion mass spectrometry most of the data lie close to the ccam carbonaceous chondrite anhydrous mineral line with 17 o ranging from 5 to 0 the data overlap oxygen isotopic compositions of chondrules from carbonaceous chondrites such as cv ck cr and cm which suggests that chondrules from carbonaceous chondrites are the source of relict grains in cosmic spherules chemical compositions of olivine in cosmic spherules are also very similar to chondrule olivine from carbonaceous chondrites several olivine relict grains in three cosmic spherules are 16 o rich 17 o 21 9 to 18 7 similar to oxygen isotopic compositions observed in calcium aluminium rich inclusions cais amoeboid olivine aggregates aoas and some porphyritic chondrules from carbonaceous chondrites these grains appear to have recorded the initial oxygen isotopic composition of the inner solar nebula three olivine grains from two cosmic spherules have 18 o values 20 which could be interpreted as mixing with stratospheric oxygen during atmospheric entry

petrology and origin of amoeboid olivine aggregates in cr chondrites amoeboid olivine aggregates aoas are irregularly shaped fine grained aggregates of olivine and ca al rich minerals and are important primitive components of cr chondrites the aoas in cr chondrites contain feni metal and some aoas contain mn rich forsterite with up to 0 7 mno and mn fe ratios greater than one additionally aoas in the cr chondrites do not contain secondary phases nepheline and fayalitic olivine that are found in aoas in some cv chondrites the aoas in cr chondrites record a complex petrogenetic history that included nebular gas solid condensation reaction of minerals with the nebular gas small degrees of melting and sintering of the assemblage a condensation origin for the mn rich forsterite is proposed the mn rich forsterite found in idps unequilibrated ordinary chondrite matrix and aoas in cr chondrites may have had a similar origin a type a calcium aluminum rich inclusion cai with an aoa attached to its wark lovering rim is also described this discovery reveals a temporal relationship between aoas and type a inclusions additionally a thin layer of forsterite is present as part of the wark lovering rim revealing the crystallization of olivine at the end stages of the wark lovering rim formation the ca al rich nodules in the aoas may be petrogenetically related to the ca al rich minerals in wark lovering rims on type a cais aoas are chondrite components that condensed during the final stage of wark lovering rim formation but in general were temporally spatially or kinetically isolated from reacting with the nebula vapor during condensation of the lower temperature minerals that were commonly present as chondrule precursors

comparing wild 2 particles to chondrites and idps we compare the observed composition ranges of olivine pyroxene and fe ni sulfides in wild 2 grains with those from chondritic interplanetary dust particles idps and chondrite classes to explore whether these data suggest affinities to known hydrous materials in particular wild 2 olivine has an extremely wide composition range from fa096 with a pronounced frequency peak at fa1 the composition range displayed by the low calcium pyroxene is also very extensive from fs48 to fs0 with a significant frequency peak centered at fs5 these ranges are as broad or broader than those reported for any other extraterrestrial material wild 2 fe ni sulfides mainly have compositions close to that of fes with less than 2 atom ni to date only two pentlandite grains have been found among the wild grains suggesting that this mineral is not abundant the complete lack of compositions between fes and pentlandite with intermediate solid solution compositions suggests but does not require that fes and pentlandite condensed as crystalline species i e did not form as amorphous phases which later became annealed while we have not yet observed any direct evidence of water bearing minerals the presence of ni bearing sulfides and magnesium dominated olivine and low ca pyroxene does not rule out their presence at low abundance we do conclude that new investigations of major and minorelement compositions of chondrite matrix and idps are required

oxygen isotopes in crystalline silicates of comet wild 2 a comparison of oxygen isotope systematics between wild 2 particles and chondritic materials abstract oxygen three isotope ratios of nine crystalline silicate particles from comet wild 2 were measured to investigate oxygen isotope systematics of cometary materials we are able to analyze particles as small as 4 m using an ion microprobe with a 1 2 m beam by locating the analysis spots with an accuracy of 0 4 m three particles of mn rich forsterite known as low iron manganese enriched lime olivine showed extremely 16 o rich signatures 18 o 17 o 50 similar to refractory inclusions in chondrites the three mn rich forsterite particles may have formed by condensation from an 16 o rich solar nebula gas other particles consist of olivine and or pyroxene with a wide range of mg molar mgo feo mgo from 60 to 96 their oxygen isotope ratios plot nearly along the carbonaceous chondrite anhydrous mineral ccam and young and russell lines with 17 o 17 o 0 52 18 o values of 3 0 to 2 5 these data are similar to the range observed from previous analyses of wild 2 crystalline silicates and those of chondrules in carbonaceous chondrites six particles extracted from stardust track 77 show diverse chemical compositions and isotope ratios two mn rich forsterites feo poor pigeonite and three feo rich olivines with a wide range of 17 o values from 24 to 1 6 these results confirmed that the original projectile that formed track 77 was an aggregate 6 m of silicate particles that formed in various environments the 17 o values of ferromagnesian wild 2 particles including data from previous studies increase from 23 to 2 5 with decreasing mg 17 o values of mn rich forsterite particles mg 98 99 8 cluster at 23 those of feo poor particles mg 95 97 cluster at 2 and those of feo rich particles mg 90 scatter mainly from 1 5 to 2 5 compared to chondrules in primitive chondrites the systematic trend between mg and 17 o among the wild 2 particles is most similar to that reported for cr chondrite chondrules we argue that cr chondrites and some cometary materials share multiple common chemical and isotope characteristics we suggest that many of the crystalline silicate particles formed in the outer regions of the asteroid belt or regions that share the common properties and were transported to comet forming regions and accreted into comet wild 2

oxygen isotopic constraints on the origin of mg rich olivines from chondritic meteorites chondrules are the major high temperature components of chondritic meteorites which accreted a few millions years after the oldest solids of the solar system the calcium aluminum rich inclusions were condensed from the nebula gas chondrules formed during brief heating events by incomplete melting of solid dust precursors in the protoplanetary disk petrographic compositional and isotopic arguments allowed the identification of metal bearing mg rich olivine aggregates among the precursors of magnesian type i chondrules two very different settings can be considered for the formation of these mg rich olivines either a nebular setting corresponding mostly to condensation evaporation processes in the nebular gas or a planetary setting corresponding mostly to differentiation processes in a planetesimal an ion microprobe survey of mg rich olivines of a set of type i chondrules and isolated olivines from unequilibrated ordinary chondrites and carbonaceous chondrites revealed the existence of several modes in the distribution of the 17o values and the presence of a large range of mass fractionation several within each mode the chemistry and the oxygen isotopic compositions indicate that mg rich olivines are unlikely to be of nebular origin i e solar nebula condensates but are more likely debris of broken differentiated planetesimals each of them being characterized by a given 17o mg rich olivines could have crystallized from magma ocean like environments on partially molten planetesimals undergoing metal silicate differentiation processes considering the very old age of chondrules mg rich olivine grains or aggregates might be considered as millimeter sized fragments from disrupted first generation differentiated planetesimals finally the finding of only a small number of discrete 17o modes for mg rich olivines grains or aggregates in a given chondrite suggests that these shattered fragments have not been efficiently mixed in the disk and or that chondrite formation occurred in the first vicinity of the breakup of these planetary bodies

chromium isotope evidence in ejecta deposits for the nature of paleoproterozoic impactors abstract non mass dependent chromium isotopic signatures have been successfully used to determine the presence and identification of extra terrestrial materials in terrestrial impact rocks paleoproterozoic spherule layers from greenland graenseso and russia zaonega as well as some distal ejecta deposits lake superior region from the sudbury impact 1849 0 3 ma event have been analyzed for their cr isotope compositions our results suggest that 1 these distal ejecta deposits are all of impact origin 2 the graenseso and zaonega spherule layers contain a distinct carbonaceous chondrite component and are possibly related to the same impact event which could be vredefort 2023 4 ma or another not yet identified large impact event from that of similar age and 3 the sudbury ejecta record a complex meteoritic signature which is different from the graenseso and zaonega spherule layers and could indicate the impact of a heterogeneous chondritic body

refractory materials in comet samples transmission electron microscope examination of more than 250 fragments 1 m from comet wild 2 and a giant cluster interplanetary dust particle gcp of probable cometary origin has revealed four new calcium aluminum rich inclusions cais an amoeboid olivine aggregate aoa and an additional aoa or al rich chondrule arc object all of the cais have concentric mineral structures and are composed of spinel anorthite cores surrounded by al ti clinopyroxenes and are similar to two previous cais discovered in wild 2 all of the cometary refractory objects are of moderate refractory character the mineral assemblages textures and bulk compositions of the comet cais are similar to nodules in fine grained spinel rich inclusions fgis found in primitive chondrites and like the nodules may be nebular condensates that were altered via solid gas reactions in the solar nebula oxygen isotopes collected on one wild 2 cai also match fgis the lack of the most refractory inclusions in the comet samples may reflect the higher abundances of small moderately refractory cai nodules that were produced in the nebula and the small sample sizes collected in the comet samples approximately 2 3 of all fragments larger than 1 m by number are cais and nearly 50 of all bulbous stardust tracks contain at least one cai we estimate that 0 5 volume of wild 2 material and 1 volume of gcp is in the form of cais arcs and aoas account for 1 of the wild 2 and gcp grains by number

petrology and oxygen isotope compositions of chondrules in e3 chondrites chondrules in e3 chondrites differ from those in other chondrite groups many contain near pure endmember enstatite fs 1 some contain si bearing feni metal cr bearing troilite and in some cases mg mn and ca sulfides olivine and more feo rich pyroxene grains are present but much less common than in ordinary or carbonaceous chondrite chondrules in some cases the feo rich grains contain dusty inclusions of metal the oxygen three isotope ratios 18o 17o of olivine and pyroxene in chondrules from e3 chondrites which are measured using a multi collection sims show a wide range of values most enstatite data plots on the terrestrial fractionation tf line near whole rock values and some plot near the ordinary chondrite region on the 3 isotope diagram pyroxene with higher feo contents 2 10 wt feo generally plots on the tf line similar to enstatite suggesting it formed locally in the ec enstatite chondrite region and that oxidation reduction conditions varied within the e3 chondrite chondrule forming region olivine shows a wide range of correlated 18o and 17o values and data from two olivine bearing chondrules form a slope 1 mixing line which is approximately parallel to but distinct from the ccam carbonaceous chondrite anhydrous mixing line we refer to this as the ecm enstatite chondrite mixing line but it also may coincide with a line defined by chondrules from acfer 094 referred to as the pcm primitive chondrite mineral line ushikubo et al 2011 the range of o isotope compositions and mixing behavior in e3 chondrules is similar to that in o and c chondrite groups indicating similar chondrule forming processes solid gas mixing and possibly similar 16o rich precursors solids however e3 chondrules formed in a distinct oxygen reservoir internal oxygen isotope heterogeneity was found among minerals from some of the chondrules in e3 chondrites suggesting incomplete melting of the chondrules survival of minerals from previous generations of chondrules and chondrule recycling olivine possibly a relict grain in one chondrule has an r chondrite like oxygen isotope composition and may indicate limited mixing of materials from other reservoirs calcium aluminum rich inclusions cais in e3 chondrites have petrologic characteristics and oxygen isotope ratios similar to those in other chondrite groups however chondrules from e3 chondrites differ markedly from those in other chondrite groups from this we conclude that chondrule formation was a local event but cais may have all formed in one distinct place and time and were later redistributed to the various chondrule forming and parent body accretion regions this also implies that transport mechanisms were less active at the time of and following chondrule formation

the late jurassic tithonian a greenhouse phase in the middle jurassic early cretaceous cool mode evidence from the cyclic adriatic platform croatia well exposed mesozoic sections of the bahama like adriatic platform along the dalmatian coast southern croatia reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding late jurassic tithonian shallow platform interior over 750 m thick ca 5 6 myr duration facies within parasequences include dasyclad oncoid mudstone wackestone floatstone and skeletal peloid wackestone packstone shallow lagoon intraclast peloid packstone and grainstone shoal radial ooid grainstone hypersaline shallow subtidal intertidal shoals and ponds lime mudstone restricted lagoon fenestral carbonates and microbial laminites tidal flat parasequences in the overall transgressive lower tithonian sections are 1 4ae5 m thick and dominated by subtidal facies some of which are capped by very shallow water grainstone packstone or restricted lime mudstone laminated tidal caps become common only towards the interior of the platform parasequences in the regressive upper tithonian are dominated by peritidal facies with distinctive basal oolite units and well developed laminate caps maximum water depths of facies within parasequences estimated from stratigraphic distance of the facies to the base of the tidal flat units capping parasequences were generally 4 m and facies show strongly overlapping depth ranges suggesting facies mosaics parasequences were formed by precessional 20 kyr orbital forcing and form parasequence sets of 100 and 400 kyr eccentricity bundles parasequences are arranged in third order sequences that lack significant bounding disconformities and are evident on accommodation fischer plots of cumulative departure from average cycle thickness plotted against cycle number or stratigraphic position modelling suggests that precessional sea level changes were small several metres as were eccentricity sea level changes or precessional sea level changes modulated by eccentricity supporting a global hot greenhouse climate for the late jurassic tithonian within the overall cool mode of the middle jurassic to early cretaceous

origin of crystalline silicates from comet 81p wild 2 combined study on their oxygen isotopes and mineral chemistry in order to explore the link between comet 81p wild 2 and materials in primitive meteorites seven particles 5 to 15 m in diameter from comet 81p wild 2 have been analyzed for their oxygen isotope ratios using a secondary ion mass spectrometer most particles are single minerals consisting of olivine or pyroxene with mg higher than 85 which are relatively minor in 81p wild 2 particles 1 3 of the 16o poor cluster four particles extracted from track 149 are 16o poor and show 17o 17o 0 52 18o values from 2 0 to 1 0 similar to previous studies while one enstatite en99 particle shows lower 17o value of 7 4 o 2 this compositional range has not been reported among 16o poor particles in 81p wild 2 but is commonly observed among chondrules in carbonaceous chondrites and in particular in cr chondrites the distribution in 17o indicates that 16o poor 81p wild 2 particles are most similar to chondrules and their fragments in the cr chondrites and tagish lake like wis91600 chondrite chondrule silicate grains which indicates that they likely come from a reservoir with similar dust ice ratios as cr chondrites and wis91600 however differences in the mg distribution imply that the 81p wild 2 reservoir was comparatively more oxidized with a higher dust enrichment two nearly pure enstatite grains from track 172 are significantly enriched in 16o with 18o values of 51 2 1 5 0 2 and 43 0 1 3 2 respectively and 17o values of 22 3 1 9 2 and 21 3 2 3 0 2 respectively they are the first 16o rich pyroxenes found among 81p wild 2 particles with similar 17o values to those of 16o rich low iron manganese enriched lime olivine and cai calcium and aluminum rich inclusions like particles from 81p wild 2 the major element and oxygen isotopic compositions of the pyroxenes are similar to those of enstatite in amoeboid olivine aggregates aoas in primitive chondrites in which 16o rich pyroxenes have previously been found and thus suggest a condensation origin

deuterium enrichments in chondritic macromolecular material implications for the origin and evolution of organics water and asteroids here we report the elemental and isotopic compositions of the insoluble organic material iom isolated from several previously unanalyzed meteorites as well as the reanalyses of h isotopic compositions of some previously measured samples alexander et al 2007 the iom in ordinary chondrites ocs has very large d enrichments that increase with increasing metamorphism and decreasing h c the most extreme d value measured being almost 12 000 we propose that such large isotopic fractionations could be produced in the oc parent bodies through the loss of isotopically very light h2 generated when fe was oxidized by water at low temperatures 200 c we suggest that similar isotopic fractionations were not generated in the iom of cv and co chondrites with similar metamorphic grades and iom h c ratios because proportionately less water was consumed during metamorphism and the remaining water buffered the h isotopic composition of the iom even a h was being lost from it hydrogen would also have been generated during the alteration of ci cm and cr carbonaceous chondrites the iom in these meteorites exhibit a considerable range in isotopic compositions but all are enriched in d as well as 15n relative to terrestrial values we explore whether these enrichments could also have been produced by the loss of h2 but conclude that the most isotopically anomalous iom compositions in meteorites from these groups are probably closest to their primordial values the less isotopically anomalous iom has probably been modified by parent body processes the response of iom to these processes was complex and varied presumably reflecting differences in conditions within and between parent bodies the d enrichments associated with h2 generation along with exchange between d rich iom and water in the parent bodies means that it is unlikely that any chondrites retain the primordial h isotopic composition of the water ice that they accreted the h isotopic compositions of the most water rich chondrites the cms and cis are probably the least modified and their compositions d 25 suggest that their water did not form at large radial distances from the sun where ice is predicted to be very d rich yet models to explain the o isotopic composition of inner solar system bodies require that large amounts of ice were transported from the outer to the inner solar system

comprehensive examination of large mineral and rock fragments in stardust tracks mineralogy analogous extraterrestrial materials and source regions abstract transmission electron microscopy examination of 87 large fragments from 16 carrot shaped and bulbous stardust sd tracks was performed to study the range and diversity of materials present in comet wild 2 olivines and low ca pyroxenes represent the largest proportions of fragments observed however a wide range of minerals and rocks were found including probable ferromagnesian al rich and si rich chondrule fragments a refractory inclusion possible matrix mineral lithic clasts and probable condensate minerals these materials combined with fine grained components in the tracks are analogous to components in unequilibrated chondrite meteorites and cluster interplanetary dust particles idps two unusual lithologies in the bulbous tracks are only observed in chondritic porous idps and may have direct links to idps the absence of phyllosilicates indicates that comet wild 2 may be a dry comet that did not accrete or form significant amounts of hydrated phases some large mineral fragments in the sd tracks are analogous to large mineral idps the large variations of the coarse grained components within and between all 16 tracks show that comet wild 2 is mineralogically diverse and unequilibrated on nearly all scales and must have accreted materials from diverse source regions that were widely dispersed throughout the solar nebula

oxygen isotopic compositions of chondrules from the metal rich chondrites isheyevo ch cbb mac 02675 cbb and que 94627 cbb abstract it has been recently suggested that 1 ch chondrites and the cbb ch like chondrite isheyevo contain two populations of chondrules formed by different processes i magnesian non porphyritic cryptocrystalline and barred chondrules which are similar to those in the cb chondrites and formed in an impact generated plume of melt and gas resulted from large scale asteroidal collision and ii porphyritic chondrules formed by melting of solid precursors in the solar nebula 2 porphyritic chondrules in isheyevo and ch chondrites are different from porphyritic chondrules in other carbonaceous chondrites krot et al 2005 krot et al 2008a krot et al 2008b in order to test these hypotheses we measured in situ oxygen isotopic compositions of porphyritic magnesian type i and ferroan type ii and non porphyritic magnesian and ferroan cryptocrystalline chondrules from isheyevo and cbb chondrites mac 02675 and que 94627 paired with que 94611 using a cameca ims 1280 ion microprobe on a three isotope oxygen diagram 17o vs 18o compositions of chondrules measured follow approximately slope 1 line data for 19 magnesian cryptocrystalline chondrules from isheyevo 24 magnesian cryptocrystalline chondrules and 6 magnesian cryptocrystalline silicate inclusions inside chemically zoned fe ni metal condensates from cbb chondrites have nearly identical compositions 17o 2 2 0 9 2 3 0 6 and 2 2 1 0 2 respectively these observations and isotopically light magnesium compositions of cryptocrystalline magnesian chondrules in cbb chondrites gounelle et al 2007 are consistent with their single stage origin possibly as gas melt condensates in an impact generated plume in contrast 17o values for 11 type i and 9 type ii chondrules from isheyevo range from 5 to 4 and from 17 to 3 respectively in contrast to typical chondrules from carbonaceous chondrites seven out of 11 type i chondrules from isheyevo plot above the terrestrial fractionation line we conclude that i porphyritic chondrules in isheyevo belong to a unique population of objects suggesting formation either in a different nebular region or at a different time than chondrules from other carbonaceous chondrites ii isheyevo cb and ch chondrites are genetically related meteorites they contain non porphyritic chondrules produced during the same highly energetic event probably large scale asteroidal collision iii the differences in mineralogy petrography chemical and whole rock oxygen isotopic compositions between ch and cb chondrites are due to various proportions of the nebular and the impact produced materials

ion microprobe analyses of oxygen three isotope ratios of chondrules from the sayh al uhaymir 290 ch chondrite using a multiple hole disk the ion microprobe is the only technique capable of determining high precision stable isotope ratios in individual tiny extraterrestrial particles 100 lm in diameter but these small samples present special analytical challenges we produced a new sample holder disk with multiple holes three holes and seven holes in which epoxy disks containing a single unknown sample and a standard grain are cast and polished performance tests for oxygen two isotope analyses using san carlos olivine standard grains show that the new multiple hole disks allow accurate analysis of tiny particles if the particles are located within the 500 lm and 1 mm radius of the center of holes for seven hole and three hole disks respectively using the new seven hole disk oxygen three isotope ratios of eight magnesian cryptocrystalline chondrules approximately 100 lm in diameter from the sayh al uhaymir sau 290 ch chondrite were analyzed by ion microprobe at the university of wisconsin five out of eight chondrules have nearly identical oxygen isotope ratios d 17 o 2 2 0 6 2sd which is consistent with those of magnesian cryptocrystalline chondrules in ch cb and cb chondrites suggesting a genetic relationship i e formation by a common possibly impact heating event the other three chondrules have distinct oxygen isotope ratios d 17 o values from 6 4 to 2 2 given that similar variation in d 17 o values was observed in type i porphyritic chondrules in a ch cb chondrite the three chondrules may have formed in the solar nebula similar to the type i porphyritic chondrules

a long duration of the 16 o rich reservoir in the solar nebula as recorded in fine grained refractory inclusions from the least metamorphosed carbonaceous chondrites abstract oxygen isotope ratios and corresponding 26 al 26 mg isotope systematics of refractory inclusions from the least metamorphosed carbonaceous chondrites acfer 094 c ungrouped 3 00 and yamato 81020 co3 05 were measured with an ion microprobe most of the samples are fine grained refractory inclusions which are considered as condensates from high temperature solar nebular gas the refractory inclusions consistently exhibit 16 o enriched signatures among their interior phases spinel melilite and high ca pyroxene as well as phases within their rim structures spinel high ca pyroxene and adjacent anorthite this observation indicates that aggregated refractory condensates and the formation of rim structures occurred in the same 16 o rich environment evidence for mass dependent isotopic fractionation in oxygen and magnesium which would indicate a later flash heating process was not observed in rims all oxygen isotope data from fine grained cais are distributed between the carbonaceous chondrite anhydrous mineral ccam line and the primitive chondrule mineral pcm regression line based on oxygen isotope data from the acfer 094 chondrules the inferred initial 26 al 27 al ratios 26 al 27 al 0 of spinel melilite rich cais are 4 08 0 75 10 5 to 5 05 0 18 10 5 errors are 2 which are slightly lower than the canonical value of 5 25 10 5 as there is no petrologic evidence for re melting after condensation the lower 26 al 27 al 0 values of these cais indicate either they formed up to 0 3 ma after canonical cais or they formed before 26 al was homogeneously distributed in the solar nebula a pyroxene anorthite rich cai g92 has an 16 o rich signature like other cais but also has an order of magnitude less 26 mg excess in anorthite corresponding to a 26 al 27 al 0 of 5 21 0 54 10 6 as there is no evidence for a later mg isotopic disturbance g92 anorthite is interpreted to have formed by interaction with 16 o rich nebular gas at 2 3 ma after cai formation with the observation that 16 o rich refractory inclusions relatively 16 o poor chondrules and extremely 16 o poor cosmic symplectites within acfer 094 all plot on the pcm line it suggests that 16 o rich nebular gas and extremely 16 o poor primordial volatiles represent mass independent fractionated endmembers in the early solar system and that the pcm line represents a mixing line of these two endmembers

calcium aluminum rich inclusions and amoeboid olivine aggregates from the cr carbonaceous chondrites calcium aluminum rich refractory inclusions cais in cr chondrites are rare 1 vol fairly small 500 m and irregularly shaped and most of them are fragmented based on the mineralogy and petrography they can be divided into grossite hibonite rich melilite rich and pyroxene anorthite rich cais other types of refractory objects include fine grained spinel melilite pyroxene aggregates and amoeboid olivine aggregates aoas some of the pyroxene anorthite rich cais have igneous textures and most melilite rich cais share similarities to both the fluffy and compact type a cais found in cv chondrites one major difference between these cais and those in cv cm and co chondrites is that secondary mineral phases are rare in situ ion microprobe analyses of oxygen isotopic compositions of 27 cais and aoas from seven cr chondrites demonstrate that most of the cais are 16o rich 17o of hibonite melilite spinel pyroxene and anorthite 22 and isotopically homogeneous within 3 4 likewise forsterite spinel anorthite and pyroxene in aoas have nearly identical 16o rich compositions 24 17o 20 deg in contrast objects which show petrographic evidence for extensive melting are not as 16o rich 17o less than 18 o secondary alteration minerals replacing 16o rich melilite in melilite rich cais plot along the terrestrial fractionation line most cr cais and aoas are mineralogically pristine objects that largely escaped thermal metamorphism and secondary alteration processes which is reflected in their relatively homogeneous 16o rich compositions it is likely that these objects or their precursors condensed in an 16o rich gaseous reservoir in the solar nebula in contrast several igneous cais are not very enriched in 16o probably as a result of their having melted in the presence of a relatively 16o poor nebular gas if the precursors of these cais were as 16o rich as other cr cais this implies either temporal excursions in the isotopic composition of the gas in the cai forming regions and or radial transport of some cai precursors into an 16o poor gas the absence of oxygen isotope heterogeneity in the primary minerals of melilite rich cais containing alteration products suggests that mineralogical alteration in cr chondrites did not affect oxygen isotopic compositions of their cais

determination of the petrologic type of cv3 chondrites by raman spectroscopy of included organic matter abstract this paper reports the first reliable quantitative determination of the thermal metamorphism grade of a series of nine cv3 chondrites allende axtell bali mokoia grosnaja efremovka vigarano leoville and kaba the maturity of the organic matter in matrix determined by raman spectroscopy has been used as a powerful metamorphic tracer independent of the mineralogical context and extent of aqueous alteration this tracer has been used along with other metamorphic tracers such as fe zoning in type i chondrules of olivine phenocrysts presolar grain abundance and noble gas abundance bulk and p3 component the study shows that the petrologic types determined earlier by induced thermoluminescence were underestimated and suggests the following values pt allende axtell 3 6 pt bali mokoia grosnaja 3 6 pt efremovka leoville vigarano 3 1 3 4 pt kaba 3 1 the most commonly studied cv3 allende is also the most metamorphosed bali is a breccia containing clasts of different petrologic types the attribution suggested by this study is that of clasts of the highest petrologic types as pointed out by iom maturity and noble gas bulk abundance cv3 chondrites have complex asteroidal backgrounds with various degrees of aqueous alteration and or thermal metamorphism leading to complex mineralogical and petrologic patterns fe mg chemical zoning in olivine phenocrysts on the borders of type i chondrules of porphyritic olivine and pyroxene rich textural types has been found to correlate with the metamorphism grade this suggests that chemical zoning in some chondrules often interpreted as exchanges between chondrules and nebular gas may well have an asteroidal origin furthermore the compositional range of olivine matrix is controlled both by thermal metamorphism and aqueous alteration this does not support evidence of a nebular origin and does not necessarily mirror the metamorphism grade through fe mg equilibration on the other hand it may provide clues on the degree of aqueous alteration vs thermal metamorphism and on the timing of both processes in particular mokoia experienced significant aqueous alteration after the metamorphism peak whereas grosnaja which has similar metamorphism grade did not

compositional evolution of the protoplanetary disk oxygen isotopes of type ii chondrules from cr2 chondrites chondrules are the dominant component of chondritic meteorites and attest to high temperature transient heating events within the protoplanetary disk they provide valuable constraint on the disk environments in which they formed and potentially the evolution of primitive planetary materials in the disk the oxygen isotopic composition of cr2 chondrite type ii chondrules was investigated our data show significant variation in the isotopic compositions of the chondrules with no petrographic or geochemical means to identify what chondrule will plot where on a three isotope diagram although we cannot rule out that these chondrules may have come from another chondrite forming region we argue in context of type i chondrules from cr2 chondrites that cr2 type ii chondrules record changes in solid and gas composition during formation due to the vaporization of icy bodies in localized regions of the inner disk

facies and stratigraphic architecture of the korallenoolith formation in north germany lauensteiner pass ith mountains abstract during the oxfordian bahamian type shallow water carbonates formed in the lower saxony basin of north germany the outcrop of the korallenoolith formation in a quarry in the ith mountains lauensteiner pass contains a series of well exposed coral and coral microbial reefs intercalated with oolites six different facies are distinguished which can be assigned to the inner part of a carbonate ramp based on textural variations and facies stacking patterns accommodation space to sediment supply and or sediment production cycles of different hierarchies were defined in this succession a multispectral outcrop gamma ray log was measured as additional tool to separate facies and to identify the cyclicity a good correlation between fluctuations in the gamma ray log and the lithological changes exists generally coral and coral microbial reefs reflect times of higher available accommodation space oolites indicate sedimentation in shallower waters we thus show how based on sequence stratigraphy the succession of the korallenoolith fm can be subdivided into genetic packages this approach may contribute in providing a tool for a firm high resolution correlation of the different outcrops of this formation which is presently only poorly constrained the good correlation between gamma ray log and the cyclicity may also be helpful for subsurface correlations in the lower saxony basin

oxygen isotope systematics of chondrules in the allende cv3 chondrite high precision ion microprobe studies the oxygen three isotope systematics of 36 chondrules from the allende cv3 chondrite are reported using high precision secondary ion mass spectrometer cameca ims 1280 twenty six chondrules have shown internally homogenous 17 o values among olivine pyroxene and spinel within a single chondrule the average 17 o values of 19 feo poor chondrules 13 porphyritic chondrules 2 barred olivine chondrules and 4 chondrule fragments show a peak at 5 3 0 6 2sd another 5 porphyritic chondrules including both feo poor and feo rich ones show average 17 o values between 3 and 2 and 2 other feo poor barred olivine chondrules show average 17 o values of 3 6 and 0 these results are similar to those for acfer 094 chondrules showing bimodal 17 o values at 5 and 2 nine porphyritic chondrules contain olivine grains with heterogeneous 17 o values as low as 18 indicating that they are relict olivine grains and some of them were derived from precursors related to refractory inclusions however most relict olivine grains show oxygen isotope ratios that overlap with those in homogeneous chondrules the 17 o values of four barred olivine chondrules range from 5 to 0 indicating that not all bo chondrules plot near the terrestrial fractionation line as suggested by previous bulk chondrule analyses based on these data we suggest the presence of multiple oxygen isotope reservoirs in local dust rich protoplanetary disk from which the cv3 parent asteroid formed a compilation of 225 olivine and low ca pyroxene isotopic data from 36 chondrules analyzed in the present study lie between ccam carbonaceous chondrite anhydrous mineral and young and russell lines these data define a correlation line of 17 o 0 982 0 019 18 o 2 91 0 10 which is similar to those defined by chondrules in cv3 chondrites and acfer 094 in previous studies plagioclase analyses in two chondrules plot slightly below the ccam line with 17 o values of 2 6 which might be the result of oxygen isotope exchange between chondrule mesostasis and aqueous fluid in the cv parent body

nebular history of amoeboid olivine aggregates minor element ca cr and mn concentrations in amoeboid olivine aggregates aoas from primitive chondrites were measured and compared with those predicted by equilibrium condensation in the solar nebula cao concentrations in forsterite are low particularly in porous aggregates a plausible explanation appears that an equilibrium ca activity was not maintained during the olivine condensation cao and mno in forsterite are negatively correlated with cao being higher in compact aggregates this suggests that the compact aggregates formed either by a prolonged reheating of the porous aggregates or by condensation and aggregation of forsterite during a very slow cooling in the nebula

geochemistry and sequence stratigraphy of regional upper cretaceous limestone units offshore eastern canada abstract hydrocarbons occur in two regional upper cretaceous limestone units the turonian coniacian petrel member and the santonian maastrichtian wyandot formation the units form important seismic markers beneath the scotian shelf and the grand banks of eastern canada they mainly consist of bioturbated chalk and minor amounts of calcareous mudstone a search for source rock using the log r technique showed intervals with source potential but testing of core and cuttings by rock eval analysis showed no source potential three issues are the main cause for the inconsistency 1 unconsolidated shales that likely included organic material were lost during sample washing 2 severe contamination by mud additives and 3 presence of gas the organic matter found on the shelf has been strongly oxidised but the distal facies of these limestone units and condensed shale units above and below may yet have potential to form source rock beyond the studied areas

amoeboid olivine aggregates aoas in the efremovka leoville and vigarano cv3 chondrites a record of condensate evolution in the solar nebula abstract amoeboid olivine aggregates aoas in the efremovka leoville and vigarano cv3 chondrites were studied using petrographic and microanalytical techniques to evaluate the origins of these inclusions and their relationships to other chondrite components our data support the idea that the inclusions formed by dust growth in the solar nebula as condensates and that they preserve a record of mineralogical and chemical evolution spinel rich nodules and ribbons in aoas often show group ii trace element patterns and formed either by fractional condensation or by condensation following partial vaporization the dominant olivine component in aoas can be explained as a condensate produced in the same way but with fractionation occurring at a lower temperature other spinel rich material in aoas appears to be a vaporization residue ca rich pyroxene anorthite patches in aoas show chemical signatures similar to those observed for spinel or melilite bearing regions but with lower refractory element and higher mg and si contents supporting the idea that the patches formed by reaction between cai like material and mg si rich gas different trace element patterns group ii and non group ii refractory are sometimes found for al rich regions ca pyroxene anorthite or melilite bearing in a given aoa suggesting that aoas agglomerated from materials that formed under different conditions and that they did not subsequently homogenize aoas appear to have originated in a system with near canonical solar composition and a low pressure gas 10 6 10 4 bar over a range of temperatures mainly 1200 1384 k under somewhat non equilibrium conditions relative to predicted equilibrium condensates most aoas show an apparent paucity of metal possibly reflecting differential density dependent sorting between olivine and metal grains during aggregate formation trace element data are consistent with a simple model involving melting and igneous fractionation of aoa like olivine to produce type i chondrule olivine but other data suggest that open system melting of chondrules occurred in a different gaseous environment than that which produced aoas

transgressive oversized radial ooid facies in the late jurassic adriatic platform interior low energy precipitates from highly supersaturated hypersaline waters dark gray oolitic units characterized by oversized ooids with primary radial calcite fabrics occur in the interior of the late jurassic late tithonian adriatic platform a large mesozoic tethyan isolated platform in croatia they differ from open marine platform margin ooid grainstones in their dark color cerebroid outlines broken and recoated grains abundant inclusions highly restricted biota and lack of cross stratifithey have been interpreted as being of vadose origin vadoids at tops of upward shallowing parasequences however detailed sections show that most oolitic units occur at bases of precessional parasequences overlying erosional surfaces on fenestral carbonates the oolitic units are similar to quiet water ooids that form today in low energy settings they developed in an arid climate during initial transgression of supratidal fl ats along lowenergy shores seaward of tidal fl ats and along the margins of restricted lagoons and intertidal ponds superimposed fenestral fabrics meniscus micrite cements and grain breakage occurred as they aggraded to high tide level and were subjected to wetting and drying thermal expansion and contraction and wind transport they migrated landward with transgression forming extensive sheets and were overlain by subtidal lagoonal facies that shallow up into fenestral carbonates these distinctive facies may have been overlooked in the geological record or their geological distribution requires juxtaposition of calcite seas high calcite supersaturation states arid climate and presence of fl at topped carbonate platforms in a greenhouse world

lime silicates in amoeboid olivine aggregates in carbonaceous chondrites indicator of nebular and asteroidal processes mno feo ratios in olivine from amoeboid olivine aggregates aoas reflect conditions of nebular condensation and can be used in concert with matrix textures to compare metamorphic conditions in carbonaceous chondrites lime low iron mn enriched olivine was identified in aoas from y 81020 co3 05 kaba cv 3 1 and in y 86009 cv3 y 86751 cv3 nwa 1152 cr cv3 but was not identified in aoas from efremovka cv3 1 3 4 or allende cv 3 6 according to thermodynamic models of nebular condensation lime olivine is stable at lower temperatures than mn poor olivine and at low oxygen fugacities dust enrichment 95 in our study whereas efremovka aoas are slightly fe rich fo 92 aoa olivines from kaba are mostly forsteritic but rare fe rich olivine precipitated from an aqueous fluid a combination of precipitation of fe rich olivine and diffusion of fe into primary olivine grains resulted in iron rich compositions fo97 59 in allende aoas variations from fine grained nonporous matrix toward higher porosity and coarser lath like matrix olivine can be divided into six stages represented by 1 y 81020 efremovka nwa 1152 2 y 86751 lithology b 3 y 86009 4 kaba 5 y 86751 lithology a 6 allende these stages are inferred to represent general degree of metamorphism although the specific roles of thermally driven grain growth and diffusion versus aqueous dissolution and precipitation remain uncertain

diversity of the initial rocky planetary building materials at the edge of the solar system asteroids and comets are surviving members of the vast planetesimal population that was distributed across the early solar system they appear to be a diverse set of bodies but we present evidence from comet samples that the body to body diversity of the initial rocky component mix in planetesimals may have declined with distance from the sun laboratory measurements of the minor element mn in olivine collected from comet wild 2 suggests that the micron sized rocky crystalline contents of this comet formed in numerous inner solar system environments the results are consistent with a scenario where silicates such as olivine form at incandescent temperatures in multiple environments and then mix as they are transported to distant cold regions where silicates could accrete with ice and organics to form comets accreting far from silicate formation regions many ice rich planetesimals are likely to have started with similar complex mixtures of diverse rocky components formed in various high temperature environments this contrasts with asteroidal meteorite parent bodies whose silicates retain regional properties that give different chondrite classes their distinctive properties

tectonic controls of phanerozoic sedimentary rock cycling the cyclic nature of the phanerozoic sedimentary rock distribution carbon sulphur coupling and material transfer among sedimentary reservoirs appears to be controlled by tectonic factors the distribution of preserved sedimentary mass in terms of rock mass remaining u geologic age shows a minimum c 300 350 ma ago which separates two subcycles of erosion and deposition of sedimentary rocks the older subcycle was interrupted because of the major continental collisions of the devonian and late carboniferous these collisions resulted in a reduction of outcrop areas of rocks of the older cycle relative to their masses leading to a decline in the probability of destruction and an increase in half life of these older sediments a strong correlation exists between the long term cyclicity in the phanerozoic global sea level curve and the distribution of carbon and sulphur among their major exogenic reservoirs this correlation is related to two principal tectonic modes of the phanerozoic oscillatory and submergent it is postulated that the submergent mode of active plate convergence obduction and subduction of sediments large ridge volume and high sea level gave rise to low erosion and sedimentation rates less restricted environments of carbonate deposition and relatively high atmospheric co 2 levels high temperatures resulting from an increased rate of production of co 2 from diagenetic and metamorphic reactions at subduction zones as sea level rose carbon was transferred from the sedimentary reservoir of reduced organic carbon to that of oxidized inorganic carbon in limestones whereas sulphur moved from the oxidized sulphate reservoir to the reduced sulphide reservoir as sea level fell reservoir transfers were opposite to those above culminating in the oscillatory mode of generally elevated continental interiors these reservoir transfers are consistent with secular changes observed in the distribution of 13 c and 34 s in sedimentary materials during the phanerozoic petrographic examination of phanerozoic oolite formations shows that ooids with preserved calcitic relict textures are characteristic of pre carboniferous carbonate rocks whereas ooids with relict textures indicative of initial aragonite mineralogy are dominant in rocks of younger age these changes in ooid mineralogy may be interpreted as reflecting changes in co 2 levels of the ocean atmosphere system consistent with the above tectonic considerations atmospheric co 2 levels were higher prior to carboniferous time favouring formation of calcitic ooids and skeletal parts after the carboniferous co 2 levels fell and aragonite and mg calcites of greater than 8 mol mg increased in abundance as precipitates

cretaceous evolution of the central asian proto paratethys sea tectonic eustatic and climatic controls the timing and mechanisms of the cretaceous sea incursions into central asia are still poorly constrained we provide a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy together with detailed paleoenvironmental analyses of cretaceous records of the proto paratethys sea fluctuations in the tajik and tarim basins the early cretaceous marine incursion in the western tajik basin was followed by major marine incursions during the cenomanian ca 100 ma and santonian ca 86 ma that reached far into the eastern tajik and tarim basins these marine incursions were separated by a turonian coniacian ca 92 86 ma regression basin wide tectonic subsidence analyses imply that the early cretaceous sea incursion into the tajik basin was related to increased pamir tectonism we find that thrusting along the northern edge of the pamir at ca 130 90 ma resulted in increased subsidence in a retro arc basin setting this tectonic event and coeval eustatic highstand resulted in the maximum observed geographic extent of the sea during the cenomanian ca 100 ma the following turonian coniacian ca 92 86 ma major regression driven by eustasy coincides with a sharp slowdown in tectonic subsidence during the late orogenic unloading period with limited thrusting the santonian ca 86 ma major sea incursion was likely controlled by eustasy as evidenced by the coeval fluctuations in the west siberian basin an early maastrichtian cooling ca 71 70 ma potentially connected to global late cretaceous trends is inferred from the replacement of mollusk rich limestones by bryozoan and echinoderm rich limestones

the oxygen isotope composition of chondrules and isolated forsterite and olivine grains from the tagish lake carbonaceous chondrite abstract the oxygen isotope compositions obtained by laser fluorination of hand picked separates of isolated forsterite isolated olivine and chondrules from the tagish lake carbonaceous chondrite describe a line 17o 0 95 18o 3 24 r2 0 99 similar to the trend known for chondrules from other carbonaceous chondrites the isolated forsterite grains fo99 6 99 8 18o 7 2 to 5 5 17o 9 6 to 8 2 are more 16o rich than the isolated olivine grains fo39 6 86 8 18o 3 1 to 5 1 17o 0 3 to 2 2 and have chemical and isotopic characteristics typical of refractory forsterite chondrules contain olivine fo97 2 99 8 with oxygen isotope compositions 18o 5 2 to 5 9 17o 8 1 to 1 2 that overlap those of isolated forsterite and isolated olivine an inverse relationship exists between the 17o values and fo contents of tagish lake isolated forsterite and chondrules the chondrules likely underwent greater exchange with 16o poor nebular gases than the forsterite the oxygen isotope compositions of the isolated olivine grains describe a trend with a steeper slope 1 1 0 1 r2 0 94 than the carbonaceous chondrite anhydrous mineral line ccamslope 0 95 the isolated olivine may have crystallized from an evolving melt that exchanged with 16o poor gases of somewhat different composition than those which affected the chondrules and isolated forsterite the primordial components of the tagish lake meteorite formed under conditions similar to other carbonaceous chondrite meteorite groups especially cms its alteration history has its closest affinities to ci carbonaceous chondrites

connection between micrometeorites and wild 2 particles from antarctic snow to cometary ices we discuss the relationship between large cosmic dust that represents the main source of extraterrestrial matter presently accreted by the earth and samples from comet 81p wild 2 returned by the stardust mission in january 2006 prior examinations of the stardust samples have shown that wild 2 cometary dust particles contain a large diversity of components formed at various heliocentric distances these analyses suggest large scale radial mixing mechanism s in the early solar nebula and the existence of a continuum between primitive asteroidal and cometary matter the recent collection of concordia antarctic micrometeorites recovered from ultra clean snow close to dome c provides the most unbiased collection of large cosmic dust available for analyses in the laboratory many similarities can be found between antarctic micrometeorites and wild 2 samples in terms of chemical mineralogical and isotopic compositions and in the structure and composition of their carbonaceous matter cosmic dust in the form of concordia antarctic micrometeorites and primitive idps are preferred samples to study the asteroid comet continuum

ooids in purbeck limestones lowermost cretaceous of the swiss and french jura ooids occurring in the shallow water purbeckian carbonate sediments of the jura mountains can be grouped into six types gradations from one type to another and coexistence of the various types are common type 1 ooids are small and well rounded they display fine concentric micritic laminae in many cases their cortices are dissolved and replaced by void filling spar microsparitic neomorphic replacement occurs locally type 2 ooids are large and have irregular shapes they show fine micritic laminae and occasional layers of fine radial crystals they commonly evolve into oncoids ooids of type 3 display many fine radial cortical laminae and are patchily micritized they are medium in size and mostly well rounded this type of ooid may pass into large irregularly shaped coated grains type 4 ooids have 1 to 4 cortical laminae with a fine radial structure and patchy micritization they are medium in size and well rounded type 5 ooids have only one lamina with a coarse radial structure they are small and well rounded associated are spherical grains containing bundles of elongate crystals ooids of type 6 show superpositions of two or more different radial and or fine micritic laminae the cortical structure may also change laterally in the same lamina the preferential dissolution of type 1 ooid cortices to form oomoulds indicates a primary composition of unstable carbonate sedimentological features and comparison with modern ooid occurrences point to formation on high energy sandbars in normal marine waters type 2 ooids grew in marine lagoonal environments with quiet water and abundant cyanobacteria the radially structured ooid cortices of types 3 4 and 5 show no dissolution features this implies that they were originally composed of stable carbonates or that an unstable carbonate phase was transformed into a stable one at an early stage of diagenesis type 3 ooids occur together with marine faunas and indicate high water energy ooids of type 4 and type 5 originated probably from relatively quiet water of variable salinity coexistence of different ooid types and mixed forms of type 6 implies gradual or rapid changes in hydrodynamic geochemical and microbiological conditions which were a feature of the purbeckian depositional environments

oxygen isotope ratios of feo poor chondrules in cr3 chondrites influence of dust enrichment and h2o during chondrule formation abstract we present detailed electron microprobe analyses and oxygen three isotope measurements by high precision secondary ion mass spectrometry on 45 type i feo poor chondrules fragments and 3 type ii feo rich chondrule fragments from meteorite hills 00426 and queen alexandra range 99177 two of the most primitive cr3 chondrites type i chondrules fragments have mg s defined as the mg of constituent olivine and or low ca pyroxene ranging from 94 2 to 99 2 type ii chondrule fragments have mg s of 53 63 oxygen three isotope measurements plot on the slope 1 primitive chondrule mineral pcm line within chondrules 17 o 17 o 0 52 18 o values of coexisting olivine pyroxene and plagioclase are homogeneous with propagated uncertainties of 0 3 this indicates each phase crystallized from the final chondrule melt and that efficient oxygen isotope exchange occurred between ambient gas and chondrule melt among type i chondrules there is a well defined increase in 17 o from 5 9 to 1 as mg s decrease from 99 2 to 96 type ii chondrule fragments are comparatively 16 o poor 17 o 0 2 0 6 the relationship between mg and 17 o among type i chondrules confirms that addition of a 16 o poor oxidizing agent to the highest mg chondrule precursors resulted in forming lower mg cr chondrules using aspects of existing equilibrium condensation models and a mass balance we estimate that type i cr chondrules formed at dust enrichments of 100 200 from dusts with 0 0 8 times the atomic abundance of ice relative to ci dust the type ii chondrule fragments are predicted to have formed at ci dust enrichments near 2500

oxygen three isotope ratios of silicate particles returned from asteroid itokawa by the hayabusa spacecraft a strong link with equilibrated ll chondrites abstract oxygen three isotope ratios of four mineral phases olivine low ca and high ca pyroxene and plagioclase in seven silicate particles from asteroid itokawa were measured to investigate oxygen isotope systematics of asteroidal materials in order to obtain highly precise and accurate oxygen isotope ratios 0 3 in 18 o we used a new indium mounting method that minimizes potential instrumental mass fractionation due to surface topography the oxygen isotope data of the seven itokawa particles are distributed above the terrestrial fractionation line with indistinguishable o 17 o 17 0 52 o 18 values of 1 34 0 36 2sd n 22 which is similar to those of itokawa particles analyzed by yurimoto et al 2011 and nakamura et al 2012 however 18 o values of the seven itokawa particles are tightly clustered 3 9 to 5 9 vsmow compared to previous analyses of the itokawa particles 1 4 to 8 8 the average 17 o values and 2sd of the two equilibrated ordinary chondrites eocs which were analyzed for comparison are 1 31 0 49 for st severin ll6 and 0 83 0 64 for guarena h6 the 17 o values of the seven itokawa particles are similar to those of st severin the average bulk 18 o value of the seven itokawa particles is estimated as 4 8 which is within the 18 o range of bulk ll5 and ll6 chondrites it is suggested that itokawa particles are similar to those of equilibrated ll chondrites which strengthens a link between asteroid itokawa and equilibrated ll chondrites that fell to earth the seven itokawa particles and two eocs have 18 o values of high ca pyroxene that are lower than those of olivine indicating that oxygen isotopes between the two mineral phases are not in equilibrium apparent oxygen isotope equilibrium temperatures estimated from a pair of low ca pyroxene and olivine are excessively higher than those from a pair of plagioclase and high ca pyroxene 800 c and peak metamorphic temperatures oxygen isotopes in olivine and low ca pyroxene do not represent equilibrium on the other hand oxygen isotope ratios in high ca pyroxene and plagioclase were mass dependently fractionated accompanied by recrystallization and possibly by diffusion during thermal metamorphism values of 18 o in high ca pyroxene were lowered by exchange which may have resulted in the reverse 18 o fractionation between olivine and high ca pyroxene

microfabric and origin of cambrian carbonate ooids examples from the cambrian oolite of carteret northeastern armorican massif france abstract the oolite at carteret cambrian atdabanian in age is composed of purely radial radial concentric and composite ooids the close resemblance between the cortex of purely radial ooids and the innermost cortex of radial concentric ones suggests that the latter ooids may originate from purely radial ones with an accretion of envelopes with a radial fabric the appearance of a concentric texture is the result of phenomena of abrasion undergone by purely radial ooids with diameters over 0 600 0 680 mm when transported as bed load the abrasion resulting from this transport stops the radial growth of crystals formerly developing in a low energy environment then in a high energy environment laminae of small equant crystals are formed it is due to an alternation between a low energy environment and a high energy environment that ooids acquire their concentric texture when compared to similar present day ooids it appears that radial ooids may have been formed in algal mats interbedded with carteret oolite

la presence de fossiles marins dans le cretace terminal des andes centrales et ses consequences paleogeographiques abstract the maastrichtian deposits late campanian to early danian of the central andes comprise three transgressive regressive sequences in bolivia el molino formation they have yielded diverse terrestrial brackish water or marine fossils which make it possible to define the depositional environments at their exact stratigraphic position marine influenced transgressive facies are by far the best developed in the first sequence among the vertebrates five groups of fishes are restricted with some rare exceptions to marine environmentsl some other fish families genera or species are known to occur both in freshwater brackish and marine environments and therefore provide no precise environmental indications among the invertebrates echinoids serpulids foraminifera and some pelecypods and gastropods attest to a marine influenced environment which may however have experienced periodic salinity variations the other pelecypods and gastropods generally indicate freshwater environments the ostracods often ubiquitous only provide paleoecologic indications when they constitute oligospecific shell beds suggesting abnormally low salinity values calcispheres and dinoflagellates indicate a stronger marine influence charophytes especially when abundant suggest a lacustrine environment because of their stratigraphic and paleogeographic positions stromatolites may indicate intertidal to supratidal environments the fossils most likely of marine generally occur in the transgressive lower parts of the three sequences where marine oolites and glauconite are also observed the often endemic nature of the marine assemblages the common occurrence of dwarfism and the lack of true nektonic forms suggest that most part of the basin was permanently rather shallow and subjected to important frequent and or local salinity variations the freshwater fishes appear to be reworked and dissociated in the marine levels but are better preserved in the mainly continental upper parts of the sequences marine fossils are rare in the upper sequence these data contradict with interpretations which suggest that the central andean senonian deposits are exclusively terrestrial given other paleogeographic constraints we propose that maastrichtian sedimentation took place in a wide elongated subsident basin forming the eastern foreland of the paleo andes and showing a cul de sac shape in the south this restricted basin was periodically connected with the open sea through present day venezuela the salinity of its southern part situated far from the basin mouth was shallow and affected by fresh water from inflowing rivers

petrographic constraints on the diversity of chondrule reservoirs in the protoplanetary disk abstract chondrules from different chondrite groups show characteristic properties including abundances of different chondrule textural types chondrule sizes oxygen isotope compositions chondrule bulk compositions and petrographic properties of type i and type ii chondrules including abundances of relict grains overall it can be argued that each chondrite group sampled a unique chondrule reservoir and that chondrite groups may represent fractions of larger reservoirs that are represented by chondrite classes these observations provide constraints for models of the early solar system in which it is necessary to establish multiple separate chondrule reservoirs and maintain them over extended time periods models for accretion of chondrite parent bodies must be able to account for localized accretion of chondrules that were formed in spatially or temporally separated reservoirs

calcitic aragonitic and mixed calcitic aragonitic ooids from the mid proterozoic belt supergroup montana a great variety of ooid types occurs within the siyeh and snowslip formations of the mid proterozoic belt supergroup montana cortical layers are inferred to have been composed either of calcite in a radial concentric or radial with dark rays fabric or aragonite in a radial or concentric fabric the calcitic cortical layers record their original fabrics but the originally aragonitic cortical layers have been replaced by calcite in a range of textures and by quartz and dolomite some formerly aragonitic cortical layers are replaced by calcite spar which contains relics of the original cortical structure others consist of calcite spar without inclusions or columnar calcite which grew radially from the nucleus commonly a calcitic ooid some ooids were wholly composed of calcite others were of aragonite but two phase ooids were common mostly consisting of an inner calcitic part and an outer aragonitic part probable microdolomite inclusions suggest a high mg content of the calcitic cortical layers the depositional environment of these oolites was probably analogous to baffin bay texas where a similar range of ooid types is forming today

26al 26mg systematics of chondrules in a primitive co chondrite abstract we have conducted systematic investigations of formation age chemical compositions and mineralogical characteristics of ferromagnesian chondrules in yamato 81020 co3 05 one of the most primitive carbonaceous chondrites to get better understanding of the origin of chemical groups of chondrites the 26 al 26 mg isotopic system were measured in fourteen feo poor type i six feo rich type ii and two aluminum rich al rich chondrules using a secondary ion mass spectrometer excesses of 26 mg in plagioclase 1 0 13 5 are resolved with sufficient precision mostly 0 4 6 6 at 2 level in all the chondrules studied except one chemical zoning of mg and na in plagioclase were investigated in detail in order to evaluate the applicability of 26 al 26 mg chronometer we conclude that the al mg isotope system of the chondrules in y 81020 have not been disturbed by parent body metamorphism and can be used as chronometer assuming homogeneous distribution of 26 al assuming an initial 26 al 27 al ratio of 5 10 5 in the early solar system 26 al 26 mg ages were found to be 1 7 2 5 ma after cai formation for type i 2 0 3 0 ma for type ii and 1 9 and 2 6 ma for al rich chondrules the formation ages of ferromagnesian chondrules in y 81020 are in good agreement with those of l and ll type 3 0 3 1 chondrites in the literature which indicates that common chondrules in the co chondrite were formed contemporaneously with those in l and ll chondrites the concurrent formation of chondrules of co and l ll chondrites suggests that the chemical differences between co and l ll chondrites might be caused by spatial separation of chondrule formation environments in the protoplanetary disk