chemical studies of h chondrites i mobile trace elements and gas retention ages abstract trends for 16 trace elements ag as au bi cd co cs ga in k rb sb se te tl and zn chosen to span a broad geochemical and thermal response range in 44 h4 6 chondrites differ widely from those in l4 6 chondrites in particular h chondrites classified as heavily shocked petrologically do not necessarily exhibit 40 ar loss and vice versa the clear cut causal relationship between siderophile and mobile element loss with increasing late shock seen in l chondrites is not generally evident in the h group h chondrite parent material experienced an early high temperature genetic episode that mobilized a substantial proportion of these trace elements so that later thermal episodes resulted in more subtle collateral fraction ations mildly shocked l chondrites escaped this early high temperature event indicating that the two most numerous meteorite groups differ fundamentally in genetic history

δ18o values of coexisting brachiopods and fish temperature differences and estimates of paleo water depths to estimate vertical thermal gradients and paleo water depths to marine platforms we present a new method based on the difference between 18 o values of contemporaneous brachiopod carbonate and fish phosphate present day marine fauna of well known ecology from the surface to the sea floor record isotopic temperatures that agree with measured temperatures we predict distributions of isotopic data that result from sampling strategy basin morphology and fauna ecology and discuss limitations application of the method to the jurassic paris london basin gives vertical thermal variations of up to 14 c associated with depths varying from a few meters to 170 30 m the estimated depths are minimum values and are greater than those estimated from sedimentological criteria for this ancient epicontinental sea

multi taxa isotopic investigation of paleohydrology in the lower cretaceous cedar mountain formation eastern utah u s a deciphering effects of the nevadaplano plateau on regional climate we investigate the regional climatic effects of the formation of the nevadaplano plateau during the sevier orogeny in an overall warming world paleohydrology was reconstructed from 590 individual measurements of phosphate o isotopes in continental faunas of the lower cretaceous cedar mountain formation utah u s a semi aquatic turtles crocodiles and terrestrial dinosaurs taxa are compared to coeval pedogenic carbonates to interpret changing water sources over time samples were grouped into four stratigraphic faunas lower yellow cat upper yellow cat ruby ranch and mussentuchit members resulting isotopic values were converted to d18 ow values using established d 18 op d 18 ow and d 18 oc d 18 ow relationships at a formation scale turtles d 18 op 14 1 to 15 7 v smow and crocodiles d 18 op 15 0 to 19 2 document water compositions of 28 1 to 26 1 and 27 7 to 24 2 respectively within the zonal range for formation scale meteoric water at 34u n paleolatitude 27 1 to 24 8 established by pedogenic carbonates d18 oc 22 0 to 23 5 v smow these data suggest that like soil carbonates turtle and crocodile phosphate isotopes can be used as proxies for meteoric water isotopic composition dinosaurd18 op sauropods 19 7 to 21 9 ornithischians 16 6to 21 7 small theropods 16 9to 18 2 andlarge allosauroids 19 1 to 20 3 values generally exceed those of semi aquatic taxa using mass balance equations for modern terrestrial animals adjusted for size and inferred dinosaur physiology ingested water is calculated for the above dinosaur groups on a member scale when meteoric water values are compared with calculated dinosaur drinking water values are equal to or lighter than meteoric water for most herbivorous groups as low as 215 5 for ornithischians and equal to or heavier than meteoric water for most carnivorous groups as high as 22 0 for allosauroids changes in d18 ometeoric water d 18 odinosaur ingested water faunal assemblages and sedimentology from member to member correlate to thrusting events of the sevier orogeny high elevations in the orogeny attenuated the influences of pacific moisture causing rainshadow induced aridity on the leeward foreland basin during upper yellow cat time and hosted seasonal snow accumulation by the end of ruby ranch time as suggested by 18 o enriched water e g up to an average of 22 0 from an allosauroid tooth and extremely 18 o depleted water e g 215 5 for ornithischians in the ruby ranch member by mussentuchit time delivery of the western interior seaway dominated moisture to the region despite continued rise of the sevier mountains

alkali feldspathic material entrained in fe s rich veins in a monomict ureilite the elephant moraine eet 96001 ureilite contains a remarkable diversity of feldspars which occur as tiny no more than 60 m maximum dimension grains within a few fe s rich now weathered to mostly fe oxide veins molar s fe ratio in the veins averages 0 08 0 02 the veins meander and feature large fluctuations in apparent width they appear to have entered this monomict breccia by a gentle percolative process not by violent impact injection the feldspars are accompanied by a diverse suite of k rich and generally also ti rich feldspathic glasses and also major proportions of silica and pyroxene which is largely fassaitic a rhnite like phase is also found and as inclusions in one of the fassaites a cr poor spinel like phase the feldspars mostly feature remarkably high k na compared to feldspars of comparable an from polymict ureilites the eet 96001 feldspathic component was probably once part of a thin basaltic crust on a ureilite asteroid the spinel included in one of the fassaites formed at remarkably high fo2 apparent oxidation state of iron 41 atom fe3 suggesting that the parent magma possibly assimilated near surface water however the fe3 was not directly measured and has conceivably been affected by terrestrial weathering also there is no assurance that this fassaite originated together with the typical feldspar we speculate that the feldspathic component was mixed into the dense fe s rich vein material and very soon thereafter the fe s rich vein material was emplaced adjacent to the eet 96001 host ureilite at an advanced stage in a chaotic catastrophic disruption and partial reassembly process that affected all ureilites the high k nature of the eet 96001 feldspathic component including the feldspathic glasses suggests that fractional fusion may not have been as common during ureilite anatexis as has been inferred from recent studies of clast assemblages in polymict ureilites

an igneous textured clast in the peace river meteorite insights into accretion and metamorphism of asteroids in the early solar system the mineralogy petrology and geochemistry of an igneous textured clast in the peace river l6 chondrite meteorite was examined to determine the roles of nebular processes accretion and parent body metamorphism in its origin the centimetre scale clast is grey and fine grained and is in sharp contact with the host chondrite two sub millimetre veins cut across both the clast and host indicating that the clast formed prior to the impact shock event s that produced the numerous veins present in the peace river meteorite the clast and host are indistinguishable in terms of mineral compositions in contrast there are differences in modal mineralogy texture as well as trace element and oxygen isotope composition between the clast and host these differences strongly suggest that the clast was formed by impact melting of ll group chondritic material involving loss of fe fes and phosphate components followed by relatively rapid cooling and incorporation into the peace river host meteorite subsequent metamorphism on the peace river parent body caused recrystallization of the clast and homogenization of mineral compositions and thermally labile element abundances between the clast and host shock metamorphism including formation of shock melt veins occurred post metamorphism during fragmentation of the l chondrite parent body the results suggest that the formation of the peace river parent asteroid included the incorporation of material from other asteroids and that the pre metamorphic protolith was a breccia accordingly we propose that the peace river meteorite be reclassified as a polymict breccia

assessing the fidelity of marine vertebrate microfossil δ18o signatures and their potential for palaeo ecological and climatic reconstructions abstract conodont biogenic apatite has become a preferred analytical target for oxygen isotope studies investigating ocean temperature and palaeoclimate changes in the palaeozoic despite the growing application in geochemically based palaeoenvironmental reconstructions the paucity or absence of conodont fossils in certain facies necessitates greater flexibility in selection of robust oxygen bearing compounds for analysis vertebrate microfossils teeth dermal denticles spines offer a potential substitute for conodonts from the middle palaeozoic vertebrate bioapatite is particularly advantageous given a fossil record extending to the present with representatives across freshwater to fully marine environments thus widening the scope of oxygen isotope studies on bioapatite however significant tissue heterogeneity within vertebrates and differential susceptibility of these tissues to diagenetic alteration have been raised as potential problems affecting the reliability of the oxygen isotope ratios as palaeoclimatic proxies well preserved vertebrate microfossils and co occurring conodont fossils from the upper devonian and lower carboniferous of the lennard shelf canning basin western australia were analysed using bulk gas isotope ratio mass spectrometry girms and in situ secondary ion mass spectrometry sims methodologies with the latter technique allowing investigation of specific tissues within vertebrate elements the 18oconodont results may be interpreted in terms of palaeolatitudinally and environmentally sensible palaeo salinity and temperature and provide a baseline standard for comparison against vertebrate microfossil 18o values despite an absence of obvious diagenetic modification girms of vertebrate denticles yielded 18o values depleted in 18o by 2 4 relative to co occurring conodonts sims analysis of dentine tissues exhibited significant heterogeneity while hypermineralised tissues in both scales and teeth produced 18o values comparable with those of associated conodonts the susceptibility of permeable phosphatic fossil tissues to microbial activity fluid interaction and introduction of mineral precipitates post formation is demonstrated in the dentine of vertebrate microfossils which showed significant heterogeneity and consistent depletion in 18o relative to conodonts the hypermineralised tissues present in both teeth and scales appear resistant to many diagenetic processes and indicate potential for palaeoclimatic reconstructions and palaeoecological investigations

extensive impact melting on the h chondrite parent asteroid during the cataclysmic bombardment of the early solar system evidence from the achondritic meteorite dar al gani 896 dag 896 is an olivine rich microporphyritic rock of komatiitic composition both the olivine composition fa 17 5 2 1 mn mg 0 0061 and the bulk oxygen isotopic composition delta 17 o 2 55 delta 18 o 3 50 indicate that dag 896 is a sample of the h chondrite parent body the bulk chemistry shows an h chondritic distribution of lithophile elements whereas chalcophile and siderophile elements are strongly depleted indicating formation through whole rock melting or nearly so of h chondrite material nearly complete loss of the metal plus sulfide component and crystallization without significant igneous fractionation superheated severely shocked chondritic relics similar to10 vol typically in the form of corroded lithic fragments 100 mum in size intimately distributed within the igneous lithology indicate that melting was triggered by a highly energetic impact which possibly induced shock pressures of similar to80 100 gpa the relatively young 3 704 0 035 ga ar 40 ar 39 crystallization age is consistent with the impact melting origin as magmatism in the asteroid belt was active only in the first hundred million years of solar system history 1ased on textural data and thermodynamic crystallization modelling we infer that dag 896 crystallized from a liquidus temperature of similar to1630degreesc under relatively slow cooling rates similar to10degreesc h 1 to 1300degreesc before quenching the two stage cooling history indicates that a reasonable formation environment might be a dike intruding cooler basement below a crater floor metal silicate fractionation may have been accomplished at least at the centimeter scale of the studied meteorite sample through differential acceleration of immiscible liquids of different density during the intense flow regimes associated with the excavation and modification stages of the cratering mechanism alternatively dag 896 may represent a surface sample of a differentiated melt body at the floor of an impact crater as gravitational settling appears to be an effective process at the surface of a chondritic parent asteroid for metal particles 1 to 10 mm in size typically observed in partially differentiated impact melt rocks stokes law indicates a settling velocity 1 in h 1 during the first few hours of crystallization on asteroidal bodies of 25 kin radius the similar to3 7 ga age of dag 896 nearly overlaps with the slightly older resetting ages of h chondrites all impact melts available from the literature indicating that the h chondrite parent asteroid underwent extensive impact melting at the enduring of the cataclysmic bombardment of the early solar system such an age overlap may also indicate early disruption of the initial h chondrite parent asteroid the close similarity between the bulk composition and degassing age of dag 896 and silicate inclusions in he iron meteorites is further evidence in support of a common origin by impact melting and metal silicate segregation on the h chondrite parent asteroid our new high precision oxygen isotopic measurements of h chondrites delta 17 o 0 77 0 04 should be extended to iies to verify this possible petrogenetic link

oxygen isotopes in asteroidal materials measurement of the variation of the 17o 16o and 18o 16o ratios of extraterrestrial materials has proven to be a key tool in understanding the formation and evolution of the solar system this chapter attempts to collate the huge data set of oxygen isotopic measurements of asteroidal material as sampled by meteorites in order to understand some of the processes involved in the formation of these primitive bodies and how such events have affected the oxygen isotopic ratios ultimately offering a window back to the very origin of solar system and its primordialoxygen isotopic heterogeneity oxygen is generally a major element in the gas liquid and solid phases that have interacted throughout the evolution of the solar system its chemical properties ensuring that there is abundant opportunity for reactions and exchange the details of which can be recorded in the isotopic ratios of the products such processes can be crudely subdivided into the following six categories early solar nebular isotopic heterogeneity high temperature modifi cation of nebular components metamorphism and melting in asteroids aqueous alteration in asteroids mixing of components brecciation terrestrial weathering it is clear from the isotopic variation in the earliest formed nebular components such as refractory inclusions and chondrules that there was considerable oxygen isotopic heterogeneity in the early solar nebula spanning over 50 and perhaps much greater in both 17o and 18o the origin of this variation is discussed elsewhere in this volume however isotopic exchange between the 16o rich solids and 17o and 18o rich gas phase s resulted in a wide range of isotopic variation in these early formed components offering insight into the conditions of these processes and the evolution of the reservoirs with time and or space once accreted onto the early planetisemals much of the primitive nebular components experienced considerable modification the metamorphism and melting experienced by some of these bodies most probably the result of heating from the decay of short lived radionuclides e g 26al resulted in progressive homogenization within individual bodies of any original isotopic heterogeneity complete homogenization appears to have been achieved in the hed parent body indicating very high levels of melting and the development of a large magma ocean the carbonaceous and ordinary chondrite parent bodies experienced more modest heating sufficient to mobilize water ice that accreted along with the more refractory materials the subsequent reactions between the liquid and solid phases at low temperature imparted large isotopic fractionations which record some of the conditions of this alteration such as water rock ratio temperature and isotopic signature and thus potentially the origin of the water ice the evolution of the asteroidal bodies has been far from simple and an important use of oxygen isotope measurements has been in the identifi cation of the components present in some meteorites the result of breakup reassembly and mixing of different bodies during impact processing the final oxygen isotopic signatures imparted into meteorite samples are those associated with terrestrial weathering the isotopic compositions of the weathering products depend on location primarily latitude while the magnitude of the weathering is dependent on many factors with some meteorites e g highly reduced enstatite chondrites and the matrix rich co3s particularly susceptible to such effects

a survey of clasts and large chondrules in ordinary chondrites we report the results of a survey of clasts and large 5 mm chondrules macrochondrules within the 833 ordinary chondrites of the natural history museum collection thirty six macrochondrules and 24 clasts were identified and studied macrochondrules have textures and mineral assemblages like normal chondrules and so share a common origin clasts show evidence for fracturing from larger bodies and can be classified as either 1 chemically fractionated if they have major and trace element compositions differing substantially from most chondrules and clasts 2 impact melt clasts if they have microporphyritic textures and signs that indicate they are derived from shock melted chondritic material 3 microporhyritic clasts if they are similar to the last category but lack evidence for derivation through shock melting or 4 indeterminate clasts forming a diverse class that includes all those clasts that do not fit into the other categories

water utilization of the cretaceous mussentuchit member local vertebrate fauna cedar mountain formation utah usa using oxygen isotopic composition of phosphate abstract while the oxygen isotopic composition of pedogenic carbonate has successfully been used to address the effects of global climate change on the hydrologic cycle detailed regional paleohydrologic studies are lacking since the hydrologic cycle can vary extensively on local or regional scales due to events such as such as mountain building and since pedogenic carbonates calcite form in a narrow moisture regime other proxies such as vertebrate remains must be used to decipher local versus regional variations in paleohydrology in this study the oxygen isotopic composition 18op of phosphatic remains from a diverse set of vertebrate fossils fish turtles crocodiles dinosaurs and micro mammals from the mussentuchit member mm of the cedar mountain formation utah usa aptian to cenomanian are analyzed in order to determine differences among the available water reservoirs and water utilization of each taxon calculated changes in water reservoir 18ow over time are then used to determine the effects of the incursion of the western interior seaway wis and the sevier mountains on paleohydrology during the mm time calculation of 18ow from the results of isotopic analysis of phosphate oxygen suggests that turtles and crocodiles serve as another proxy for meteoric water 18o that can be used as a measure of average local precipitation 18ow similar to pedogenic calcite pedogenic calcites can be slightly biased toward higher values however due to their formation during evaporative conditions turtles and crocodiles can be used in place of pedogenic calcite in environments that are not conducive to pedogenic carbonate formation remains of fish with rounded tooth morphology have 18op values that predict temperatures consistent with other estimates of mean annual temperature for this latitude and time the 18op of ganoid scales and teeth with pointed morphology however indicates that these skeletal materials were precipitated from water that is 18o enriched due to migration to either evaporatively enriched water or 18o enriched estuarine waters of the western interior seaway wis another possibility that cannot be discounted and assuming all morphological remains are from the same taxon is that the pointed teeth and ganoid scales precipitated at different temperatures than rounded teeth mammal and herbivorous dinosaur 18op suggests they primarily drank isotopically depleted river water co existence of crocodiles turtles and mammals allows for calculation of relative humidity from site to site and these calculations suggest humidity averaged 58 and ranged between 42 and 76 the 18ow values estimated from semi aquatic taxa and pedogenic calcite suggest dominance of wis derived moisture during their growth herbivorous dinosaurs particularly indicate that altitude and catchment effects from the sevier mountains are seemingly important for river water 18ow in the fall through early spring these data suggest that temporal changes in the isotopic composition of the mm fauna are produced by the small scale regressive transgressive cycles of the wis

a multi proxy geochemical investigation of the early paleocene danian continental palaeoclimate at the fontllonga 3 site south central pyrenees spain chronologically well constrained non marine deposits across the cretaceous tertiary boundary ktb are exceptionally rare the fontllonga section tremp formation south central pyrenees lleida spain constitutes one of these rare global records stable isotope 18oco3 and 13c analyses have been performed on the carbonate fraction of 29 samples from diverse skeletal micro remains charophyte gyrogonites gastropod shells ostracod valves and isolated skeletal remains of lepisosteids and pycnodonts from the earliest danian site fontllonga 3 a mean ba ca water palaeotemperature of 28 0 6 7 c has been obtained from the ganoine of 25 lepisosteid scales this mean palaeotemperature is comparable with the temperature tolerance range for extant relatives of fossil osteoglossiform fish found at fontllonga 3 which require a temperature range of 24 35 c mean annual temperature 27 30 c to survive using the temperature range provided by the ba ca palaeothermometer 21 3 34 7 c it is possible to determine 18owater values from the isotopic content of charophyte gyrogonites gastropod shells ostracod valves and fish remains mean 18oco3 5 00 0 21 18owater values of between 4 01 and 0 95 vsmow are calculated which when combined with la yb n versus la sm n plots are in good agreement with the sedimentary interpretation of the site as an estuarine environment based upon a comparison with modern day meteorical conditions these isotopic values are relatively high for subtropical freshwaters suggesting a low precipitation rate amount effect high evaporation rate and or long residence time when combined with other isotopic palaeobotanical and mineralogical studies carried out in the pyrenean and tethys realms this first geochemical study of an early paleocene site is consistent with there being a subtropical seasonally dry climate in the south central pyrenees at this time

rate and mechanism in prograde metamorphism for a given rate of heat input into a prograde metamorphic sequence the extent of overstep of reaction temperature disequilibrium depends on the slowest of three sequential steps a surface detachment of reactant minerals b transport of material to the site of mineral growth and c nucleation and growth of the product mineral we have developed analytical expressions which enable determination of the rates of mineral dissolution and growth and of advective and diffusive mass transport during metamorphism the dissolution and growth steps are linear functions of the driving force g of the overall reaction while diffusion may take place either through a grain boundary fluid film or through the disorganized grain boundary itself

large silica rich igneous textured inclusions in the buzzard coulee chondrite condensates differentiates or impact melts we studied three large 2 4 mm diameter igneous textured inclusions in the buzzard coulee h4 chondrite using microanalytical techniques olm sem empa sims to better elucidate the origins of igneous inclusions in ordinary chondrites the inclusions are clasts that come in two varieties 1 white inclusions bz 1 and bz 2 represent a nearly holocrystalline assemblage of low ca and high ca pyroxene 63 66 area and cristobalite 33 36 and 2 tan inclusion bz 3 is glass rich approximately 60 with low ca and high ca pyroxene phenocrysts the bulk compositions of the inclusions determined by modal reconstruction are all sio2 rich approximately 67 wt for bz 1 and bz 2 approximately 62 for bz 3 but bz 3 is enriched in incompatible elements e g ree approximately 4 5 ci abundances whereas bz 2 and bz 1 are depleted in those elements that are most incompatible in pyroxene e g la ho approximately 0 15 0 4 ci abundances these bulk compositions do not resemble what one would expect for partial or complete shock melting of a chondritic precursor and show no evidence for overall volatility control we infer that the inclusions originated through igneous differentiation and feo reduction with bz 3 forming as an andesitic partial melt approximately 30 40 partial melting of an h chondrite precursor and bz 1 and bz 2 forming as pyroxene cristobalite cumulates from an si rich melt we suggest that both types of melts experienced a period of transit through a cold low pressure space environment in which cooling feo reduction and interaction with a vapor occurred melts may have been lofted into space by excavation or splashing during collisions or by pyroclastic volcanism our results indicate intriguing similarities between the inclusions in buzzard coulee and the silicates in some iron iie type and stony iron iva type meteorites suggesting a genetic relationship

brecciation among 2280 ordinary chondrites constraints on the evolution of their parent bodies abstract after accretion of meteorite parent bodies larger and smaller collisions have led to significant modifications of these bodies involved processes include excavation of material thermal metamorphism melting mixing of different materials re accretion and re lithification all these processes can be repeated several times in this study polished thin sections pts of 2280 chondrites 1193 h 947 l and 140 ll chondrites were investigated in order to obtain the abundance of brecciated rocks among the ordinary chondrites in addition we have determined the abundance and characteristics of shock vein bearing h l and ll chondrites and of impact melt rock clasts we also recognized xenolithic components based on o isotope studies noble gas data were considered in order to detect regolith breccias and to discuss late impact histories the investigation of 2280 samples shows that 23 276 of 1193 of the h chondrites 23 220 of 947 of the l chondrites and 79 110 of 140 of the ll chondrites are brecciated considering the heavily brecciated ll chondrites in 63 of the 140 chondrites 45 shock veins were clearly detected 57 of these 63 chondrites are brecciated rocks the investigation of the h and l chondrites has shown that about 26 310 of 1193 of the h chondrites and 40 379 of 947 of the l chondrites contain shock veins in our data set 20 of the h chondrites and 8 3 of the ll chondrites but only 3 0 of the l chondrites contain solar noble gases remarkably about 62 of all brecciated h chondrites with noble gases analyzed contain solar noble gases compared to only around 11 and 10 of the brecciated l and ll chondrites respectively the identification of xenolithic clasts e g ci cm and ureilite like lithologies in primitive type 3 chondrites indicates simultaneous accretion of clasts and chondrules these clasts must have been formed early within the first 2 ma on subsequently destroyed precursor first generation parent bodies the formation of complex breccias witnesses the collisions between asteroids of very different lithologies and heritage although the onion shell configuration of primordial parent bodies is necessary in order to form the chondrites with different degrees of metamorphic overprint petrologic types 3 6 subsequent catastrophic fragmentation and reassembly to form asteroids with a rubble pile structure are required to explain certain features discussed in this work however distinct peaks in the cosmic ray exposure age distributions indicate that not too many impacts in the last 100 ma were responsible to deliver the majority of the ordinary chondritic meteoroids to earth yet this certainly does not tell anything about the number of last generation parent bodies that exist in the asteroid belt since s type asteroids are the most abundant type of asteroid in the inner main belt and thought to be the parent bodies of ordinary chondrites

the effect of diagenesis on oxygen isotope ratios of biogenic phosphates the effect of diagenesis on the oxygen isotope composition of ancient biogenic phosphates was evaluated by measuring different types of material from middle triassic localities in the southern alps dentin bone and tooth enamel of different taxa hosted by different rock types and metamorphosed to differing degrees were analyzed for their 18 o and 13 c values using a new microanalytical gc irmms technique the 18 o values of the majority of bone and bulk tooth samples were 18 to 19 permil smow with three samples below this range and one close to 20 permil in contrast samples of tooth enamel were 19 4 to 20 7 permil significantly higher than bone and bulk tooth without the enamel data the 18 to 19 permil data could be misinterpreted as primary only when the higher 18 o values of the enamel are considered is it apparent that the bulk data have undergone diagenesis and temperature estimates are 5 c lower than would otherwise be calculated alteration of bulk tooth is also seen in a miocene shark tooth where 18 o values of enamel are 3 permil higher than those of bulk tooth although enamel is routinely analyzed for paleoclimate work of herbivorous mammals bulk bone teeth or shells are almost exclusively used for older marine samples the results of the present study indicate that bulk data should be treated with caution

oxygen and carbon stable isotope records of marine vertebrates from the type maastrichtian the netherlands and northeast belgium late cretaceous abstract stable isotope analysis of marine skeletal carbonates is an important tool for palaeoenvironmental reconstructions however in mesozoic sedimentary sequences diagenetic alteration often overprints the original skeletal carbonate isotope values yet even if carbonate diagenesis did occur in such sequences the original oxygen isotope values can still be preserved in enamel or bone phosphate of vertebrate fossils here are analysed the isotope compositions of tooth enamel structural carbonate and phosphate of various late maastrichtian and early palaeocene shark and ray taxa as well as carapace bone of a late maastrichtian marine turtle allopleuron hofmanni from the type area of the maastrichtian stage in the southeast netherlands and northeast belgium no correlation is observed between 18osc and 18op suggesting diagenetic alteration of at least one fraction in comparison to modern shark teeth oxygen isotope ratios of the maastrichtian palaeocene structural carbonate 18osc are significantly lower 5 as expected from previous isotope studies of calcitic fossils from the maastrichtian type area we believe the 18osc values to have been altered by meteoric diagenesis the oxygen isotope ratios of phosphate 18op in maastrichtian palaeocene shark and ray teeth are relatively wide ranging 16 9 to 25 0 vs vsmow with median values matching data for extant shark teeth 18op suggesting retention of the in vivo 18op signal similarly the 18osc in the cheloniid turtle a hofmanni is apparently overprinted by meteoric diagenesis while the cortical compact bone of the carapace is interpreted to reflect the in vivo 18op isotope composition using a phosphate water fractionation equation for biogenic apatite and median isotope values of late maastrichtian early palaeocene shark and ray teeth a seawater temperature of 19 7 c is calculated this is in good agreement with temperatures expected for the maastrichtian of this area carbon isotope analyses 13c of structural carbonate in shark teeth have yielded isotope ratios that agree well with those of modern subtropical sharks suggesting the in vivo carbon isotope signal to have been retained a comparison of a hofmanni bone carbonate 13c values with those of extant marine turtle species suggests a hofmanni to have had a carnivorous lifestyle also a hofmanni shows 13c values that are 10 lower than the average 13c of sharks and rays more similar to sympatric mosasaurs this distribution is interpreted to be the effect of respiratory physiology on 13c fractionation

exposure history of the regolithic chondrite fayetteville ii solar gas free light inclusions abstract noble gases and cosmic ray tracks were determined on light solar gas free inclusions of the solar gas rich h4 chondrite fayetteville 10 be 26 a1 major and trace element concentrations as well as oxygen isotope ratios complete the data set one exceptional inclusion is an l chondrite xenolith identified by its oxygen isotope signature and the concentration of metallic fe ni oxidized fe of this inclusion equilibrated with the host early in the history of fayetteville s parent body track density variations indicate that the majority of fayetteville s inclusions were irradiated as pebbles in the parent body by solar flare particles for about 10 4 10 6 years the l chondritic inclusion contains an unequivocal excess of gcr produced he and ne relative to the remaining inclusions this clast as well as two more solar gas free samples suffered a gcr exposure on the parent body lasting some 10 million years or longer this exposure is comparable in length to the residence times of solar gas rich matrix samples in the gcr active zone of the fayetteville parent regolith probably the other inclusions also were irradiated by gcr during at least several million years prior to the separation of the meteoroid from the parent body

isotopic composition of recent shark teeth as a proxy for environmental conditions abstract the o c and sr isotope compositions of teeth from ten species belonging to five families and three orders of sharks were measured to determine the influence of habitat diet and possible species specific fractionation effects on the isotopic composition of biogenic phosphate from fish the sharks were recently caught in subtropical waters off the kwazulu natal kzn coast of south africa as well as from cold waters in prince william sound pws alaska and victor bay vb nunavut canada 18 o values of tooth phosphate 18 o p range from 20 9 to 23 5 for the kzn sharks for most species the range in measured 18 o p values is about 0 6 but it may be as high as 1 1 for different teeth from a single shark dentine and enameloid within individual teeth have no apparent differences in 18 o p values the 18 o p values of the kzn shark teeth reflect the typical habitat of the studied species primarily the thermal structure of the water column off kzn at depths between 20 and 280 m the 18 o p values of teeth from different greenland sharks from vb and pacific sleeper sharks from pws are very homogeneous averaging 25 8 and 24 7 respectively these values appear to be in equilibrium with deep 500 m ocean waters in each case at temperatures of about 0 3 c or less there is little discernable evidence for species specific fractionation effects for the oxygen isotope composition of phosphate in the studied marine fish the oxygen isotope composition of carbonate in apatite averages about 9 1 higher than corresponding 18 o p values in agreement with equilibrium fractionation between carbonate and phosphate but with a large variance 1 1 5 18 o c values also vary by up to 1 between enameloid and dentine within single teeth but in a non systematic way differences in 13 c values between carbonate in enameloid and dentine is also large up to 8 but the 13 c values vary systematically enameloid is always enriched in 13 c compared to dentine and the 13 c content increases with developmental stage of the teeth 13 c values measured for enameloid 1 6 to 4 8 appear to approach equilibrium with dissolved inorganic carbon in seawater in contrast 13 c values for dentine range from 6 4 to 2 3 for kzn sharks and 9 0 to 10 8 for the cold water sleeper sharks and are compatible with a predominantly dietary carbon source the 87 sr 86 sr ratios of teeth from kzn sharks as well as those from pws and vb are uniform averaging 0 709167 sr content varies from 1270 to 2100 ppm a range that is similar to that in well preserved fossilized teeth seawater sr is thus clearly incorporated in vivo concentrations of sm and nd are in the ppb range and contrast the ppm range in fossilized teeth indicating a postmortem incorporation of rare earth elements in apatite of the teeth

a mesozoic time scale we present an integrated geomagnetic polarity and stratigraphic time scale for the triassic jurassic and cretaceous periods of the mesozoic era with age estimates and uncertainty limits for stage boundaries the time scale uses a suite of 324 radiomenc dates including high resolution 40 ar 39 ar age estimates this framework involves the observed ties between 1 radiometric dates biozones and stage boundaries and 2 between biozones and magnetic reversals on the seafloor and in sediments interpolation techniques include maximum likelihood estimation smoothing cubic spline fitting and magnetochronology

analysis of the geochemical variability in lepisosteid scales from the fontllonga 3 site early danian tremp formation south central pyrenees spain implications for palaeoenvironmental studies rare earth element ree ba ca sr ca and 18opo4 analyses have been performed on the ganoine and isopedine of different types of isolated scales anterior middle posterior flank scales and dorsal body margin scales from juvenile lepisosteids from the fontllonga 3 site early danian tremp formation south central pyrenees spain with the aim of detecting the most suitable kind of scale to be used in palaeoclimate studies the ree flat shape patterns obtained in lepisosteid scales from fontllonga 3 are indicative of the absence of late stage diagenesis and recrystallization and have confirmed the identification of the palaeoenvironment where the fontllonga 3 lepisosteids inhabited to be that of an estuary the ba ca palaeothermometer shows that posterior flank scales record on average 4 52 c ganoine and 3 49 c isopedine higher temperatures when compared to middle flank scales which may be related to the fact that posterior flank scales grow preferentially during the warm season whilst middle flank scales which have the greatest number of layers of ganoine per unit of time and grow all year round record a greater amplitude with respect to palaeoenvironmental and palaeoclimatic variations temperature values obtained from anterior flank scales follow a pattern similar to that showed by middle flank scales whilst temperature values provided by dorsal scales resemble the pattern furnished by posterior flank scales the same relationship between scale position and temperature but to a lesser degree 1 48 c is also evident in the calculated 18opo4 temperatures the ba ca palaeothermometer was applied by considering ba ca ratios of the water for different types of environments and it has been found out that a ratio similar to that of marine waters yielded the best approximation to 18opo4 temperatures 29 82 3 76 c the mean ba ca temperature value obtained from the analysis of all the ganoine samples 26 96 5 72 c is also consistent with the temperature of the water in which extant relatives of osteoglossiform fish whose remains have been found in fontllonga 3 along with lepisosteid remains inhabit nowadays 24 40 c with mean values of 27 to 32 c the mean ba ca temperature values furnished by the isopedine are lower than that obtained on the ganoine which may be due to minor diagenetic alteration on account of these results it is recommended that a distinction should be made between different types of scales as this could provide information concerning the summer growth temperature posterior flank scales as well as the annual temperature range middle flank scales furthermore it is recommended that ganoine be used in all studies as it appears to be the most resistant tissue in lepisosteid scales to diagenetic alteration

model simulation of the cretaceous ocean circulation three dimensional numerical ocean circulation model experiments that were designed to evaluate the circulation characteristics for the mid cretaceous 100 million years ago show that the primary direction of flow through the tethys ocean was eastward in contrast a westward flowing circumglobal tethys current has been a consistent feature of earlier reconstructions of cretaceous ocean circulation the model studies demonstrate that i ocean circulation is sufficiently sensitive to the role of continental positions sea level and climate to limit the application of modern analogs to past circulations and ii reconstructions based on limited biogeographic data may not provide unique surface circulation patterns

formation conditions of igneous regions in ordinary chondrites chico rose city and other heavily shocked h and l chondrites we report microprobe and radiochemical neutron activation analysis rnaa data for hosts and igneous inclusions in the heavily shocked ordinary chondrites rose city h5 yanzhuang h6 farmington l5 malakal l5 chantonnay l6 chico l6 and tuan tuc l6 based on these analytical results equilibrium crystallization calculations ghiorso and sack 1995 phase equilibrium analysis e g sack and ghiorso 1994a b sack et al 1994 and experimental cooling rate studies e g walker et al 1976 we have assessed the metamorphic and magmatic histories of these seven heavily shocked chondrites we infer that 1 unfractionated chondritic liquids were intruded to depths 0 1 km in the parent asteroid of rose city 2 early chondritic liquids experiencing 5 10 olivine fractionation were erupted onto the surface of the parent asteroid s of yanzhuang and chantonnay and 3 near surface crystallization is also indicated for the liquids in tuan tue and farmington with chico and malakal crystallizing at slightly greater depths in all but chantonnay liquids appear to have derived from melting of chondrite types corresponding to their hosts in the l chondrite chantonnay the intrusive liquids derive from melting an h chondrite source region in which chondritic melts were stored for a sufficient time to produce pigeonite in zoned pyroxene xenocrysts heating effects are also reflected in the trace element contents of the chondrites our rnaa data for rose city seem to reflect only the siderophile lithophile fractionation evident in the metal distribution the yanzhuang rnaa data are generally similar to those of other h chondrites severe shock not involving phase transport seems to leave h chondrites unaffected compositionally contents of the four most mobile elements cd bi t1 in and cs in chico indicate loss so that this assemblage experienced extended low temperature cooling after injection of dike material into the chico host rnaa data for the other four l chondrites examined indicate more rapid cooling

retrogression of staurolite schists and the sources of infiltrating fluids during metamorphism staurolite kyanite schists from the dalradian of scotland and ireland show two types of retrograde alteration in the irish examples staurolite and kyanite are replaced by muscovite and paragonite often with margarite and sometimes chloritoid plagioclase in these samples may be albitized in contrast one scottish sample shows replacement of both staurolite and plagioclase by muscovite retrogression resulted from infiltration of fluid but while in some samples the large number of retrograde phases internally buffered the fluid composition and cation metasomatism cannot be proven in others the fluid composition was externally controlled and there was cation metasomatism indicating more extensive infiltration it is demonstrated by the use of activity diagrams showing the relationships between al silicate white mica and alkali feldspar that wholesale alteration to muscovite was most likely caused by fluids moving down temperature from a granitic or arkosic source in contrast if growth of retrograde albite is actually accompanied by na metasomatism then the infiltrating fluids are likely to have been moving up temperature through pelitic lithologies large fluid rock ratios of around 10 1 are needed to achieve significant alkali metasomatism except in extreme situations of large temperature changes and highly concentrated fluids

derivation of a heterogeneous lithic fragment in the bovedy l group chondrite from impact melted porphyritic chondrules the bovedy l group chondrite contains a light colored poikilitic lithic fragment with olivine low ca pyroxene and kamacite compositions characteristic of porphyritic chondrules from unequilibrated ordinary chondrites its texture compositional similarities to porphyritic chondrules and low na2o k2o and p2o5 content indicate that the fragment represents a solidified slightly fractionated impact melt formed from a source that was rich in porphyritic chondrules the fragment is heterogeneous with a progressive increase in the bulk mgofeo ratio and in mgo content of olivines and low ca pyroxenes across its length 39ar40ar analyses of the fragment and host indicate that the meteorite experienced extensive degassing due to reheating the approximate age of 0 5 0 94 byr dates the reheating event and not the formation of the lithic fragment or the bovedy breccia this reheating event renders the fragment s and host s metallographic cooling rate of 5 c myr through 500 c imprecise however the absence of martensite and the presence of kamacite zoned taenite and tetrataenite in the fragment and host are consistent with such slow cooling through 500 c this cooling rate must have resulted from burial of the fragment host assemblage beneath insulating material on the bovedy parent body if the thermal diffusivity of this overburden was approximately comparable to that of the lunar regolith 10 4cm2 sec then the fragment was buried at a depth 6 5 km if k 10 2 cm2 sec similar to chondritic material then the fragment was buried at a depth 65 km

late accretion and lithification of chondritic parent bodies mg isotope studies on fragments from primitive chondrites and chondritic breccias recent results of isotopic dating studies 182hf 182w 26al 26mg and the increasing number of observed igneous and metamorphosed fragments in primitive chondrites provide strong evidence that accretion of differentiated planetesimals predates that of primitive chondrite parent bodies the primitive chondrites adrar 003 and acfer 094 contain some unusual fragments that seem to have undergone recrystallization magnesium isotope analyses reveal no detectable radiogenic 26mg in any of the studied fragments the possibility that evidence for 26al was destroyed by parent body metamorphism after formation is not likely because several other constituents of these chondrites do not show any metamorphic features since final accretion of a planetesimal must have occurred after formation of its youngest components formation of these parent bodies must thus have been relatively late i e after most 26al had decayed al mg isotope data for some igneous textured clasts granitoids and andesitic fragments within the two chondrite regolith breccias adzhi bogdo and study butte reveal also no evidence for radiogenic 26mg as calculated from the upper limits the formation of these igneous clasts the incorporation into the parent body regolith and the lithification must have occurred at least 3 8 myr andesite in study butte and 4 7 myr granitoids in adzhi bogdo after calciumaluminum rich inclusions cai formation the absence of 26mg excess in the igneous inclusions does not exclude 26al from being a heat source for planetary melting in large early formed planetesimals cooling below the closure temperature of the al mg system may be too late for any evidence for live 26al in the form of 26mg excess to be preserved thus growing evidence exists that chondritic meteorites represent the products of a complex multi stage history of accretion parent body modification disruption and re accretion

the origin of chondrules and chondrites debris from low velocity impacts between molten planetesimals we investigate the hypothesis that many chondrules are frozen droplets of spray from impact plumes launched when thin shelled largely molten planetesimals collided at low speed during accretion this scenario here dubbed splashing stems from evidence that such planetesimals intensely heated by 26al were abundant in the protoplanetary disk when chondrules were being formed approximately 2 myr after calcium aluminum rich inclusions cais and that chondrites far from sampling the earliest planetesimals are made from material that accreted later when 26al could no longer induce melting we show how splashing is reconcilable with many features of chondrules including their ages chemistry peak temperatures abundances sizes cooling rates indented shapes relict grains igneous rims and metal blebs and is also reconcilable with features that challenge the conventional view that chondrules are flash melted dust clumps particularly the high concentrations of na and feo in chondrules but also including chondrule diversity large phenocrysts macrochondrules scarcity of dust clumps and heating we speculate that type i feo poor chondrules come from planetesimals that accreted early in the reduced partially condensed hot inner nebula and that type ii feo rich chondrules come from planetesimals that accreted in a later or more distal cool nebular setting where incorporation of water ice with high 17o aided oxidation during heating we propose that multiple collisions and repeated re accretion of chondrules and other debris within restricted annular zones gave each chondrite group its distinctive properties and led to so called complementarity and metal depletion in chondrites we suggest that differentiated meteorites are numerically rare compared with chondrites because their initially plentiful molten parent bodies were mostly destroyed during chondrule formation

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

garnet and staurolite producing reactions in a chlorite chloritoid schist during prograde metamorphism garnet and in some higher grade samples staurolite were produced in a chlorite chloritoid schist part of the precambrian z to cambrian hoosac formation near jamaica vt garnet grew during two prograde events separated by a retrogression this sequence resulted in distinctive inclusion textures and zoning anomalies in garnet produced by diffusive alteration textures reaction space analysis and mineral compositional variations constrain the possible sequence of reactions in these rocks below the staurolite isograd and to some unknown extent above it garnet grew by the reaction chloritoid chlorite quartz garnet h2o with increasing grade the mineral compositions are displaced towards lower mn fe and higher mg fe ratios the data are compatible with equilibrium with respect to exchange reactions for the matrix assemblages on a thin section scale and with minerals having closely followed equilibrium paths during reaction the staurolite isograd coincides with the reaction chloritoid quartz garnet staurolite chlorite h2o this reaction is continuous and trivariant with zno becoming an additional component concentrated in staurolite during this reaction both the mn fe and mg fe ratios of the phases appear to have decreased this new chemical trend is recorded by garnet zoning profiles and is compatible with trends predicted from phase diagrams thus there are two distinct types of garnet zoning reversals in these samples one is near the textural unconformity and is best explained by diffusive alteration during partial resorption of first stage garnet the other occurs near the outer rim of garnet in staurolite zone samples and marks the onset of a new prograde garnet producing reaction

oxygen isotope studies of ordinary chondrites several stages in the evolution of ordinary chondritic meteorites are recorded in the oxygen isotopic composition of the meteorites and their separable components chondrules fragments clasts and matrix the whole rock isotopic compositions reflect the iron group of the meteorite h l or ll isotopic uniformity of h3 to h6 and l3 to l6 are consistent with closed system metamorphism within each parent body ll3 chondrites differ slightly from ll4 to ll6 implying a small degree of opensystem aqueous alteration and carbon reduction on the scale of individual chondrules the meteorites are isotopically heterogeneous allowing recognition of the solar nebular processes of chondrule formation chondrules for all classes of ordinary chondrites are derived from a common population which was separate from the population of chondrules in carbonaceous or enstatite chondrites chondrules define an isotopic mixing line dominated by exchange between 16o rich and 16o poor reservoirs the oxygen isotopic compositions of chondrites serve as fingerprints for identification of genetic association with other meteorite types achondrites and iron and for recognition of source materials in meteoritic breccias

igneous inclusions from ordinary chondrites high temperature cumulates and a shock melt we report microprobe instrumental neutron activation analysis and radiochemical neutron activation analysis data for three large igneous inclusions in the yamato y 75097 y 793241 and y 794046 ordinary chondrites the inclusions in the first two chondrites are troctolitic cumulates that have undergone appreciable reactions with their hosts either during emplacement and or cooling olivine spinel fe mg exchange pairs in these two inclusions record equilibration temperatures of about 710 c and these temperatures are similar to those exhibited by mineral pairs in the y 75097 and y 793241 hosts the inclusion in y 794046 is texturally unique consisting of fine grained randomly distributed olivines coarse 2 mm fascicular pyroxene laths and angular pockets of maskelynite plagioclase feldspar the phase compositions are readily interpreted as having resulted from extremely rapid essentially isochemical cooling to temperatures 1670 c we suggest that this igneous inclusion formed in situ by shock

isotopic evidence for late jurassic early cretaceous climate change abstract strontium oxygen and carbon isotope ratios have been determined from late jurassic early cretaceous belemnites from the volga basin russia and kawhia harbour new zealand 87sr 86sr ratios derived from well preserved belemnites from the volga basin support a middle tithonian age derived from the analysis of the endemic ammonite fauna the kawhia harbour section records a gradual rise in 87sr 86sr values and in comparison with the published 87sr 86sr curve suggests that the lower part of the section is latest oxfordian in age whilst the upper part of the section correlates well with the biostratigraphic correlation suggestion of an early middle tithonian age although the published strontium calibration curve shows a degree of scatter our new data confirm the uniform rise in 87sr 86sr values from the late jurassic into the early cretaceous such an increase may result from either a decrease in mid oceanic ridge spreading and or an increase in weathering rates and flux of radiogenic strontium although a eustatic drop in sea level and concurrent western cordillera uplift suggests that weathering may have been the controlling factor of late jurassic seawater strontium isotope composition palaeotemperatures derived from the well preserved belemnite 18ocarb values from the volga basin indicate that the middle volgian late kimmeridgian was warm 14 20 c followed by a slight cooling and a subsequent gradual increase to the jurassic cretaceous boundary the 18ocarb values from new zealand located at a palaeolatitude of 80 s if interpreted in terms of palaeotemperature indicate a high degree of variability such variability may not be related to palaeotemperature but to changes in oceanic chemistry resulting from the formation and dissolution of an ice sheet and or snow during the oxfordian kimmeridgian carbon isotope trends for the late jurassic show a fall in values from the oxfordian with lowest values occurring in the early middle tithonian before rising but without reaching values obtained in the oxfordian the overall low 13ccarb may be related to a global increase in continental weathering and or upwelling of cooler oceanic water enriched in oxidised organic carbon 12c enriched

oxygen isotope compositions of late jurassic vertebrate remains from lithographic limestones of western europe implications for the ecology of fish turtles and crocodilians oxygen isotopes can be used to reconstruct the palaeoenvironmental conditions in which vertebrates lived and thereby give an indication of their ecology this has been done for faunas from the famous late jurassic lithographic limestones of western urope oxygen isotope compositions of phosphate from apatite were measured in aquatic or semiaquatic vertebrate remains fish turtles and crocodilians deposited in these protected coastal marine environments the unknown water composition in the oxygen isotope fractionation equations between phosphate and water was solved for turtles by assuming that modern relationship between environmental water and turtle bone isotope compositions applies to the past the results show that 1 coastal marine waters were thermally homogenous at the regional scale of western europe 2 oxygen isotope data discriminate between coastal marine and freshwater to brackish water inhabitants 3 the plesiochelyid turtles were coastal marine inhabitants their 18o values allow the calculation of the oxygen isotope compositions of marine waters thus refining the estimate of water temperatures by combining 18o values from fish and 4 the marine isotopic signature and the cranial anatomy of plesiochelyid turtles lead us to propose that they had a salt excreting system i e the fundamental physiological feature that controls osmoregulation in the marine environment these late jurassic turtles are proposed to be the first know marine turtles several tens of million years before the chelonioids or sea turtles

a search for h chondritic chromite grains in sediments that formed immediately after the breakup of the l chondrite parent body 470 ma ago abstract a large abundance of l chondritic material mainly in the form of fossil meteorites and chromite grains from micrometeorites has been found in mid ordovician 470 ma old sediments globally the material has been determined to be ejecta from the l chondrite parent body breakup event a major collision in the asteroid belt 470 ma ago in this study we search the same sediments for h chondritic chromite grains in order to improve our understanding of the extraterrestrial flux to earth after the asteroid breakup event we have used sims in conjunction with quantitative sem eds to determine the three oxygen isotopic and elemental compositions respectively of a total of 120 randomly selected sediment dispersed extraterrestrial chromite grains mainly representing micrometeorites from 470 ma old post breakup limestone from the thorsberg quarry in sweden and the lynna river site in russia we show that 99 or more of the grains are l chondritic whereas the h chondritic fraction is 1 or less the l h chondrite ratio after the breakup thus was 99 compared to 1 1 in today s meteoritic flux this represents independent evidence in agreement with previous estimates based on sediment dispersed extraterrestrial chromite grain abundances and sedimentation rates of a two orders of magnitude higher post breakup flux of l chondritic material in the micrometeorite fraction finally we confirm the usefulness of three oxygen isotopic sims analyses of individual extraterrestrial chromite grains for classification of equilibrated ordinary chondrites the h and l chondritic chromites differ both in their three oxygen isotopic and elemental compositions but there is some overlap between the groups in chromite tio 2 is the oxide most resistant to diagenesis and the combined application of tio 2 and oxygen three isotope analysis can resolve uncertainties arising from the compositional overlaps

mesozoic marine reptile palaeobiogeography in response to drifting plates abstract during the mesozoic various groups of reptiles underwent a spectacular return to an aquatic life colonizing most marine environments they were highly diversified both systematically and ecologically and most were the largest top predators of the marine ecosystems of their time the main groups were ichthyosauria sauropterygia thalattosauria and several lineages of testudinata crocodyliformes rhynchocephalia and squamata here we show that the palaeobiogeographical distribution of these marine reptiles closely followed the break up of the supercontinent pangaea and that they globally used the main marine corridors created by this break up to disperse most mesozoic marine reptile clades exhibit a cosmopolitan or at least pandemic distribution very early in their evolutionary history the acquisition of morphological adaptations to a fully aquatic life combined to special thermophysiological characteristics are probably responsible for these animals to become efficient long distance open marine cruisers generally early triassic taxa were near shore animals mainly linked to the tethys or panthalassa coastlines by the end of the triassic and during the jurassic the break up of pangaea resulted in the formation of large marine corridors connecting the tethys to the north atlantic and pacific realms a trend increasing on during the cretaceous with the expansion of the atlantic ocean and the break up of the southern gondwana allowing open sea marine reptiles to spread out over large distances however if large faunal interchanges were possible at a global scale following a dispersal model some provinces such as the mediterranean tethys were characterised by a peculiar faunal identity illustrating an absence of migration with time despite the apparent lack of barriers so if continental drift enabled global circulations and faunal interchanges via dispersals among mesozoic marine reptiles other parameters such as ecological and biological constraints probably also played a role in the local endemic distribution of some of these marine groups as they do today

oxygen isotopes in authigenic quartz from massive salt deposits abstract we describe a new geochemical tool that could provide temperatures of ancient basins in which massive evaporites were deposited the oxygen isotope composition of fine crystalline quartz found in large halite bodies such quartz is well preserved from post depositional alterations and it can be relatively easily separated for the purpose of this study five halite samples were selected from four various evaporite basins spanning in age from the early cambrian to the late jurassic the obtained isotope temperatures refer to locations where evaporites were deposited i e in subtropical zones of the earth as it may be estimated from continental distribution during phanerozoic times reasonable temperatures are obtained with an assumption for the 18o of brines ranging from 1 to 0 during halite deposition the assumption of higher 18o values leads to unrealistic temperatures higher than the homogenization temperatures of fluid inclusions in halite

oxygen isotope variations in phosphate of biogenic apatites i fish bone apatite rechecking the rules of the game abstract the major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone and teeth building organisms are alive and the record is nearly perfectly preserved after death fish from seven water bodies of different temperatures 3 23 c and different 18 o values 16 to 3 of the water were analysed the 18 o values of the analysed po 4 vary from 6 to 25 the system passed the following tests a the temperatures deduced from isotopic analyses of the sequence of fish from lake baikal are in good agreement with the temperatures measured in the thermally stratified lake b the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish but only by temperature and water composition isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates

earliest planetary melting the view from meteorites abstract the eucrite basaltic meteorites and iron meteorites from the cores of asteroids have ages that testify to planetary formation and differentiation 4 55 4 60 ga ago these ages are indistinguishable from those of the ordinary chondrites mixtures of silicate sulphide and metal that did not melt after their formation rare inclusions in the ordinary chondrites have textures and or fractionated rare earth element patterns indicating that they are the products of basaltic melts thus some basaltic rocks predate the accretion of the ordinary chondrites four inclusions are briefly described one contains evidence for the former presence of live 26al another exhibits an ophitic texture extreme fe enrichment in the pyroxenes and an abnormally high mno feo ratio this inclusion is from a differentiated body of which we have identified no other sample

the iodine xenon system in clasts and chondrules from ordinary chondrites implications for early solar system chronology abstract we have studied the i xe system in chondrules and clasts from ordinary chondrites cristobalite bearing clasts from parnallee ll3 6 closed to xe loss 1 4 ma after bjurbole feline a feldspar and nepheline rich clast also from parnallee closed at 7 04 0 15 ma two out of three chondrules from parnallee that yielded well defined initial i ratios gave ages identical to bjurbole s within error a clast from barwell l6 has a well defined initial i ratio corresponding to closure 3 62 0 60 ma before bjurbole partial disturbance and complete obliteration of the i xe system by shock are revealed in clasts from julesburg l3 6 and quenggouk h4 respectively partial disturbance by shock is capable of generating anomalously high initial i ratios in some cases these could be misinterpreted yielding erroneous ages a macrochondrule from isoulane n amahar contains concentrations of i similar to ordinary chondrules but unlike most ordinary chondrules contains no radiogenic 129xe this requires resetting 50 ma or more later than most chondrules the earliest chondrule ages in the i xe mn cr and al mg systems are in reasonable agreement this and the frequent lack of evidence for metamorphism capable of resetting the i xe chronometer leads us to conclude that at least the earliest chondrule i xe ages represent formation if so chondrule formation took place at a time when sizeable parent bodies were present in the solar system

p t evolution of metasediments from the eclogite zone south central tauern window austria abstract petrologic data on the paragenesis of i kyanite zoisite marbles and ii garnet chloritoid quartz mica schists are presented with the goal of providing constraints on the pressure temperature evolution of the eclogite zone tauern window austria the peak metamorphic assemblages in the two rock types are i kyanite zoisite dolomite quartz zoisite muscovite dolomite calcite quartz and ii garnet chloritoid kyanite muscovite quartz epidote dolomite zn staurolite the estimated peak metamorphic conditions are 19 2 kbar 590 20 c secondary alteration of the kyanite zoisite marbles was accomplished in two stages the early stage resulted in the production of margarite paragonite secondary muscovite and chlorite and the later stage resulted in the formation of sudoite a di trioctahedral mg al layer silicate and kaolinite the early alteration is bracketed at conditions between 3 and 10 kbar 450 550 c and the later alteration between 200 and 350 c p 3 kbar the p t path is characterized by maximum burial to approximately 19 kbar 60 70 km at 590 c followed by nearly isothermal decompression to approximately 10 kbar 30 km and then more gradual decompression with cooling to approximately 3 kbar 10 km alteration was apparently accomplished by the influx of h 2 o rich fluids with the composition of the fluid locally buffered by the mineral assemblage

asteroid 2008 tc 3 almahata sitta a spectacular breccia containing many different ureilitic and chondritic lithologies abstract asteroid 2008 tc3 impacted earth in northern sudan on october 7 2008 the meteorite named almahata sitta was classified as a polymict ureilite in this study 40 small pieces from different fragments collected in the almahata sitta strewn field were investigated and a large number of different lithologies were found some of these fragments are ureilitic in origin whereas others are clearly chondritic as all are relatively fresh w0 w0 1 and as short lived cosmogenic radioisotopes were detected within two of the chondritic fragments there is strong evidence that most if not all belong to the almahata sitta meteorite fall the fragments can roughly be subdivided into achondritic ureilitic 23 samples and chondritic lithologies 17 samples among the ureilitic rocks are at least 10 different lithologies a similar number of different chondritic lithologies also exist most chondritic fragments belong to at least seven different e chondrite rock types eh3 el3 4 el6 el breccias several different types of el and eh impact melt rocks and impact melt breccias some of the latter are shock darkened in addition two h group ordinary chondrite lithologies were identified and one sample of a chondrite type that is so far unique the latter has some affinities to r chondrites oxygen isotope compositions of 14 fragments provide further fundamental information on the lithological heterogeneity of the almahata sitta meteorite based on the findings presented in this study the reflectance spectrum of asteroid 2008 tc3 has to be evaluated in a new light

mega chondrules and large igneous textured clasts in julesberg l3 and other ordinary chondrites vapor fractionation shock melting and chondrule formation abstract a petrographic microprobe study of large metal poor igneous textured objects in julesberg l3 and other ordinary chondrites suggests that they can be classified into two petrographic types mega chondrules and large lithic clasts and into two chemical types na poor and na rich mega chondrules show textural evidence of having solidified as freely floating melt droplets whereas lithic clasts formed by the fragmentation of larger objects possibly still larger mega chondrules barred olivine or barred olivine pyroxene textures are most common for mega chondrules whereas a variety of textures occur in large lithic clasts the two petrographic types cannot be distinguished on the basis of modal bulk or phase compositions sodium poor objects are characterized by 1 plagioclase or glass with mainly bytownite composition an70 90 typical 2 subchondritic na al ratios and typically subchondritic volatile element na k and mn abundances and 3 bulk chemical trends that resemble those expected for vapor fractionation processes some na poor objects may have formed by the melting of precursors that formed as condensates or vaporization residues others may have formed by the melting of precursors that formed by fractional condensation or fractional vaporization following vapor fractionation na poor objects or their precursors appear to have reequilibrated at lower temperatures which raised the bulk na content of the objects but not to the levels seen in na rich objects enrichments of fe2 na k and p on the margins of some na poor objects suggest that they partly reacted with volatile rich surroundings both before and after brecciation sodium rich objects are characterized by 1 plagioclase or glass with oligoclase or albite composition an2 25 2 roughly chondritic na al ratios and volatile element na k mn abundances and 3 bulk chemical trends similar to those shown by melt pocket glasses in ordinary chondrites sodium rich melt objects could have formed by the shock melting of chondritic precursors feldspathic compositions for some na rich melt objects can be explained by preferential shock melting of feldspar or feldspathic glass in chondritic target materials literature data imply that the same two chemical populations of objects na poor and na rich occur among smaller normal sized chondrules in type 3 ordinary chondrites suggesting that the same processes that affected large melt objects also affected chondrules

phosphate minerals in the h group of ordinary chondrites and fluid activity recorded by apatite heterogeneity in the zag h3 6 regolith breccia phosphate minerals in ordinary chondrites provide a record of fluids that were present during metamorphic heating of the chondrite parent asteroids we have carried out a petrographic study of the phosphate minerals merrillite and apatite in metamorphosed h group ordinary chondrites of petrologic type 4 6 to understand development of phosphate minerals and associated fluid evolution during metamorphism in unbrecciated chondrites apatite is cl rich and shows textural evolution from fine grained apatite merrillite assemblages in type 4 toward larger uniform grains in type 6 the cl f ratio in apatite shows a similar degree of heterogeneity in all petrologic types and no systematic change in compositions with metamorphic grade which suggests that compositions in each meteorite are dictated by localized conditions possibly because of a limited fluid rock ratio the development of phosphate minerals in h chondrites is similar to that of l and ll chondrites despite the fact that feldspar equilibration resulting from albitization is complete in h4 chondrites but not in l4 or ll4 chondrites this suggests that albitization took place during an earlier period of the metamorphic history than that recorded by preserved apatite compositions and chemical equilibrium was not achieved throughout the h chondrite parent body or bodies during the late stages of metamorphism a relict igneous clast in the h5 chondrite oro grande has apatite rims on relict phenocrysts of possibly diopside that have equilibrated with the host chondrite apatite in the zag h3 6 regolith breccia records a complex fluid history which is likely related to the presence of halite in this meteorite the porous dark h4 matrix of zag where halite is observed has a high apatite merrillite ratio and apatite is extremely cl rich one light h6 clast contains similarly cl rich apatite in a second light h6 clast apatite compositions are very heterogeneous and more f rich apatites in both h4 matrix and h6 clasts have very low h 2o contents heterogeneous apatite compositions in zag record multiple stages of regolith processing and shock at the surface of the h chondrite parent body and apatite records either the passage of fluids of variable compositions resulting from different impact related processes or the passage of a single fluid whose composition evolved as it interacted with the chondrite regolith unraveling the history of apatite can potentially help to interpret the internal structure of chondrite parent bodies with implications for physical and mechanical properties of chondritic asteroids the behavior of halogens recorded by apatite is important for understanding the behavior of volatile elements in general if impact melt materials close to the surface of a chondritic asteroid are readily degassed the volatile inventories of terrestrial planets could be considerably more depleted than the ci carbonaceous chondrite abundances that are commonly assumed

oxygen isotope fractionation between crocodilian phosphate and water oxygen isotope compositions of phosphate 18op were measured in tooth enamel from captive and wild individuals of 8 crocodilian species a rough linear correlation is observed between the 18op of all the studied species and the oxygen isotope composition of ambient water 18ow differences in mean air temperature diet and physiology could contribute significantly to the large scatter of 18op values the combination of these parameters results in a fractionation equation for which the slope 0 82 is lower than that expected 1 from predictive model equations that assume temperature and diet as fixed parameters taking into account large uncertainties the observed oxygen isotope fractionation between phosphate and ambient water does not statistically differ from that formerly established for aquatic turtles case studies show that 18op values of fossil crocodile tooth enamel can be used to discriminate between marine and freshwater living environments within a precision of about 2 only

late pleistocene climatic change in the french jura gigny recorded in the δ18o of phosphate from ungulate tooth enamel oxygen isotope compositions of phosphate in tooth enamel from large mammals i e horse and red deer were measured to quantify past mean annual air temperatures and seasonal variations between 145 ka and 33 ka in eastern france the method is based on interdependent relationships between the delta 18 o of apatite phosphate environmental waters and air temperatures horse equus caballus germanicus and red deer cervus elaphus remains have delta 18 o values that range from 14 2 to 17 2 indicating mean air temperatures between 7 degrees c and 13 degrees c oxygen isotope time series obtained from two of the six horse teeth show a sinusoidal like signal that could have been forced by temperature variations of seasonal origin intra tooth oxygen isotope variations reveal that at 145 ka winters were colder 7 2 degrees c than at present 3 1 degrees c while summer temperatures were similar winter temperatures mark a well developed west east thermal gradient in france of about 9 degrees c much stronger than the 4 degrees c difference recorded presently negative winter temperatures were likely responsible for the extent and duration of the snow cover thus limiting the food resources available for large ungulates with repercussions for neanderthal predators c 2011 university of washington

oxygen isotopes in phosphatic fish remains from israel paleothermometry of tropical cretaceous and tertiary shelf waters the isotopic composition of oxygen in phosphate was measured on 24 fossil fishes from israel and jordan ranging in age from cretaceous to eocene from these the first paleotemperatures were calculated for shallow water cretaceous paleotropics the results were compared to those of fish from other mediterranean localities and to late cretaceous marine reptiles from israel 18o in the fish average 18 0 in the early cretaceous 17 8 in the cenomanian 18 3 in the coniacian 18 2 in the santonian 19 4 in the campanian 20 1 in the maastrichtian and 18 4 in the early eocene such variations suggest a warm cenomanian turonian cooling towards the end of the cretaceous and warming up again in the eocene the deduced temperatures for the cretaceous range between 20 c and 34 c which is about 10 higher than cretaceous water surface temperatures in northern europe apatite from marine reptile skeletons yields similar 18o to coexisting fish the good agreement between these and previously known paleotemperature data give further credence to the validity of paleotemperatures obtained by isotopic analysis of oxygen in phosphates the relatively large thermal gradient between middle and low paleolatitudes favors barron s 1983 coolest cretaceous model

comparison of carbonate c and o stable isotope records across the jurassic cretaceous boundary in the tethyan and boreal realms abstract carbon and oxygen stable isotope records were compared for jurassic cretaceous j k boundary sections located in the tethyan realm brodno western slovakia and puerto escano southern spain bulk limestones and the boreal realm nordvik peninsula northern siberia belemnites since a detailed biostratigraphic correlation of these tethyan and boreal sections is impossible due to different faunal assemblages correlation of the isotope records was based on paleomagnetic data this novel approach can improve our understanding of the synchroneity of individual isotope excursions in sections where detailed biostratigraphic correlation is impossible no significant excursions in either the carbon or oxygen isotope records to be used for future boreal tethyan correlations were found around the j k boundary the upper tithonian and lower berriasian magnetozones m20n to m18n in the studied sections at the nordvik section where a much longer section middle oxfordian basal boreal berriasian was documented the transition from the middle oxfordian to the kimmeridgian and further to the volgian is characterized by a decrease in belemnite 18 o values from 18 o values up to 1 6 vs v pdb in the oxfordian to values between 0 3 and 0 8 in the late volgian and earliest boreal berriasian this trend which has previously been reported from the russian platform and tethyan realm sections corresponds either to gradual warming or a decrease in seawater 18 o supposing that the oxygen isotope compositions of seawater in the arctic boreal and tethyan realms were similar then the differences between oxygen isotope datasets for these records indicate differences in temperature the boreal tethyan temperature difference of 7 9 c in the middle and late oxfordian decreases towards the j k boundary indicating a significant decrease in latitudinal climatic gradients during the late jurassic two positive carbon isotope excursions recorded for the middle oxfordian and upper kimmeridgian in the nordvik section can be correlated with a similar excursion described earlier for the russian platform minor influence of biofractionation at the carbon isotopes and the influence of migration of belemnites to deeper slightly cooler water at the oxygen isotopes cannot be excluded for the obtained belemnite data

shock and thermal history of northwest africa 4859 an annealed impact melt breccia of ll chondrite parentage containing unusual igneous features and pentlandite abstract northwest africa 4859 nwa 4859 is a meteorite of ll chondrite parentage that shows unusual igneous features and contains widely distributed pentlandite the most obvious unusual feature is a high proportion of large 3 cm diameter igneous textured enclaves lites interpreted as shock melts that were intruded into an ll chondrite host one such lite appears to have been produced by whole rock melting of ll chondrite initial rapid partial crystallization and subsequent slow cooling of the residual melt in the host to produce a differentiated object other unusual features include mm sized overgrowth objects fine grained plagioclase rich bands and coarse troilite 7 mm across grains all these features are interpreted as having crystallized from melts produced by a single transient shock event followed by slow cooling a subsequent shock event of moderate s3 intensity produced veining and transformed some of the pyroxene into the clinoenstatite polytype pentlandite together with associated troilite in nwa 4859 probably formed by the breakdown of a monosulfide precursor phase at low temperature 230 c following the second shock event nwa 4859 is interpreted to be an unusual impact melt breccia that contains shock melt which crystallized in different forms at depth within the parent body

loss of metals from pelites during regional metamorphism in aluminous metapelites the ratio h2o k2o decreases with increasing metamorphic grade and degree of reaction this ratio is a very practical indicator for the progress of the mineral reconstitution during progressive metamorphism with decreasing values of the ratio h2o k2o the cu concentration and the following element ratios also decrease either continuously or in stepwise fashion tl k2o ba k2o pb k2o bi k2o hg k2o sr na2o zn fe2 mg cd fe2 mg rb k2o remains approximately constant in the aluminous metapelites of the damara orogen in namibia the following losses occur between the biotite isograd and anatexis 61 cu 20 tl 34 ba 59 pb 86 bi 46 hg 30 sr 25 zn 31 cd thus the potential of regional metamorphism to form hydrothermal deposits in the low grade environment should not be neglected

the metamorphic behaviour and petrogenetic significance of zinc in amphibolite facies staurolite bearing mica schists puolankajarvi formation central finland abstract whole rock analyses and mineral analyses were performed on 24 samples of mica schists from the early proterozoic puolankajarvi formation pjf the whole rock zn content 36 127 ppm mean 77 ppm was at the normal level for pelitic and crustal rocks staurolite being the only mineral phase to contain zinc in measurable amounts 0 0 1 33 wt zno mean 0 28 wt when staurolite was present it contained nearly all of the zinc of the rock the zn content does not vary between the rocks in which staurolite has never been generated those in which staurolite is present and those from which staurolite has been destroyed this suggests that despite the fact that staurolite is a very strong acceptor of zn the generation of staurolite under reducing conditions log f o 2 22 5 t 545 c p 3 7 kbar did not increase the content of zn in the whole rock neither did the destruction of staurolite under more oxidizing conditions log f o 2 22 2 21 0 t 500 520 c p 2 1 3 5 kbar reduce it because there is evidence of considerable fluid flow through the rock during certain stages of the metamorphism of the pjf it is concluded that zn is an immobile element in amphibolite facies metamorphism in petites zinc should be treated as an additional component in metamorphic reactions of staurolite which increases the degrees of freedom of these reactions because of the immobility of zn and the increase in degrees of freedom these reactions will become dependent upon the concentration of zn in the rock

δ18o and ree contents of phosphatic brachiopods a comparison between modern and lower paleozoic populations 18o values of both carbonate 18 7 25 1 and phosphate 15 1 16 7 components of the francolite from the fossil brachiopod shells are interpreted as the result of a partial resetting of pristine isotopic compositions the similarity of hat shape ree patterns of some lower ordovician linguloids with those of extant littoral specimens suggests the preservation of a 500 myr old record of ree marine chemistry in agreement with the known paleogeography the phosphatic brachiopods have been deposited in a coastal environment under shallow and oxygenated marine waters however the contents and distribution of ree in some strongly altered brachiopod shells reveal an alteration of the original negative ce anomalies and both nd and sm enrichments that transformed the initial hat shape patterns of linguloids into strongly convex or bell shape patterns

fossil crocodilians as indicators of late cretaceous and cenozoic climates implications for using palaeontological data in reconstructing palaeoclimate abstract that the earth s climate has cooled over the last 100 million years has been recognized since the early nineteenth century the transition from the hot house world of the cretaceous a time interval without significant polar icesheets to the ice house world in which we now live today the dynamics process responsible for this change are being examined using computer models especially general circulation models gcm s through such work our understanding of the dynamics of the earth system improves and our ability to predict future trends is enhanced but the success of modelling experiments can only be assessed by comparing results with observations the pattern which for palaeoclimate are drawn exclusively from the geological record palaeoclimate interpreted from geological data is invariably based on analogy with the recent the validity of which depends on corroboration from multiple lines of evidence this requires the compilation and investigation of large global datasets of well constrained geological climate proxies this study uses the palaeodistribution of fossil crocodilians to examine the spatial distribution of palaeoclimate during this transition fossil crocodilians have a relatively good fossil record and are climatically limited in the recent they also provide a manageable global dataset with which to investigate other issues that impinge on the use of geologic data for reconstructing palaeoclimate taphonomy sampling effects time averaging tectonics and for fossils palaeobiogeography and evolution as such this study provides a possible template for examining other climate proxies in order to validate and hone palaeoclimatic interpretations an analysis of modern crocodilians indicates that temperature is the principal influence on their global distribution with the coldest month mean temperature cmm of 5 5 c marking the minimum thermal limit for the group corresponding today to a minimum mean annual temperature mat of 14 2 c the duration of warmth during the year partly indicated by the mean annual range of temperature mart is also important as this affects early juvenile development and survival the presence of standing water provides an essential thermal buffer against temperature extremes by analogy the palaeodistribution of fossil crocodilians suggests the following during the late cretaceous and early palaeogene mat s in excess of 14 2 c cmm s 5 5 c permeated throughout mid latitudes and coastal regions in high latitudes during the oligocene the restriction of fossil crocodilians to low latitudes suggests high latitude cooling as indicated by numerous other lines of evidence coeval restriction of crocodilians to coastal regions in mid latitude north america and much of asia consistent with increased seasonality and aridification in continental interiors may reflect local orographic changes as well as global climate change during the miocene fossil crocodilians return to the great plains of north america but do not reoccupy the continental interior of asia by the pliocene crocodilians are again restricted to low latitudes and coastal regions in mid latitudes coincident with further high latitude cooling and aridification and cooling of mid latitude continental interiors minor distributional changes during the holocene may reflect human effects

fe ni and co variations in the metals of some antarctic chondrites abstract nearly 4 000 fe ni and co analyses have been carried out on the metal phases of 12 antarctic chondritic meteorites by means of the electron microprobe h group chondrites show relatively simple patterns of variation for these elements but l and ll group members show much more scatter in both ni and co concentrations a single member of the co3 group investigated shows some scatter in the concentrations and also much higher co concentrations in the high ni awaruite phase 1 25 2 than in the coexisting kamacite 0 2 0 5 thus analysis of the metal phases can provide not only a means of identifying the group to which a meteorite belongs but also the possibility of distinguishing between individual chondrites from the same group the overall concentrations of co in the metal particles in the different groups are considered to be related inversely to the abundance of metal grains in meteorites of these groups while the scatter is interpreted as reflecting characteristics inherited at the time of accretion the absence of homogenisation of the concentrations of fe ni and co in the metal particles even in so called equilibrated chondrites provides further evidence against the widely held notion that these meteorites have been involved in a high temperature prograde metamorphism

oxygen isotope composition of continental vertebrate apatites from mesozoic formations of thailand environmental and ecological significance phosphatic remains tooth enamel turtle shell fragments and fish scales of continental vertebrates freshwater fish crocodilians turtles and theropod and sauropod dinosaurs recovered from eight localities of ne thailand ranging in age from the late jurassic to the late early cretac eous have been analysed for their oxygen isotopic compositions d 18 op from these preliminary data local meteoric water d 18 ow values estimated using d 18 op values of crocodilians and turtles range from 24 1 2 at the end of the jurassic to 28 3 2 during the early cretaceous suggesting a transition from dry to wetter climates with increasing amount of seasonal precipitation from several hundred millimetres per year to several thousand millimetres measurable offsets in d 18 op values observed between dinosaur taxa the spinosaurid theropod siamosaurus other ther opods and nemegtosaurid sauropods are interpreted in terms of differences in water strategies and suggest that siamosaurus had habits similar to those of semi aquatic vertebrates such as crocodi lians or freshwater turtles

mineral reactions and element migration during metamorphism of calcareous sediments from the vassalboro formation south central maine k na and co 2 were progressively lost during the metamorphic event no mass transfer of fe mg ti si or ca sodium was probably lost through a mineral fluid hydrolysis reaction that destroyed the albite component of plagioclase and produced quartz anorthite and a soluble na bearing fluid species potassium was probably lost independently through a mineral fluid hydrolysis reaction that destroyed biotite and formed calcic amphibole sphene anorthite and a soluble k bearing fluid species h 2 o was also progressively lost observed amount of mass transport of k and na requires 1 10 rock volumes of fluid interacting with the carbonate rocks regional metamorphism considered as possible large scale acid metasomatism modified journal abstract

thermal evolution of tethyan surface waters during the middle late jurassic evidence from δ18o values of marine fish teeth 1 oxygen isotope compositions of phosphate from vertebrate tooth enamel were measured to determine the evolution of tropical sea surface 0 owing to limited growth of continental ice during the early middle oxfordian the resulting sea level fall is estimated to be at least 50 m and is compatible with a global regression stage the middle oxfordian thermal minimum is followed by a new warming stage of 3 4 c from the middle to the late oxfordian

a planetary h group pebble in the barwell l6 unshocked chondritic meteorite abstract one stone of the barwell l6 shower contains an igneous inclusion with the oxygen isotopic signature of h group chondrites the inclusion is composed dominantly of olivine with a composition fo 75 5 identical with that of its host other phases are only partially equilibrated with the host the inclusion has a fractionated rare earth element pattern showing depletion in the heavy rare earth elements and a positive eu anomaly it is depleted in siderophile elements inclusion and host have ar ar ages 4 44 and 4 51 ga respectively and 129 xe r i ratios identical within experimental error we conclude that melting occurred very early on an h group chondritic body two objects from a single meteorite have different oxygen isotopic ratios but identical 129 xe r 127 i ratios which may indicate that the i xe systematics reflect chronological differences in closure to xe rather than isotopically heterogeneous iodine the inclusion and its host cooled to xe closure temperature contemporaneously with chondrules from unequilibrated ordinary chondrites

oxygen isotope composition of vertebrate phosphates from cherves de cognac berriasian france environmental and ecological significance abstract the european record of continental vertebrates during the earliest cretaceous berriasian is usually based on accumulation assemblages in littoral localities where faunas of various living environments and ecologies are mixed a recently excavated site located in the southwest of france cherves de cognac corresponds to a hyper saline lagoonal environment that has yielded a rich vertebrate fauna including brackish and freshwater fish amphibious crocodilians and turtles as well as terrestrial dinosaurs and mammals while some of these taxa were most likely parautochthonous others may have been transported from distant environments in order to decipher the respective living environments of these vertebrates and better understand the local climatic conditions apatite phosphates of their teeth or bones have been analyzed for their oxygen isotope compositions from these preliminary measurements differences in phosphate 18op values observed between taxa most likely reflect differences in sources of ingested waters that are compatible with their assumed ecologies reconstructed 18ow values of environmental waters using po4 water fractionation equations show that marine and brackish waters were submitted to enough evaporation for generating a hypersaline lagoon as reflected by 18ow values ranging from 1 7 to 1 7 whereas the more inland freshwaters have 18ow values ranging from 4 1 to 1 8 the lowest water 18ow value of about 4 estimated from the 18op value of terrestrial mammals which is assumed to be the composition of local meteoric waters leads to estimate a mean air temperature of about 20 3 c at cherves de cognac during the berriasian 30 35 n such temperatures are recorded today at similar latitudes however a weak equator to pole thermal gradient is evidenced by the latitudinal distribution of thermophilic taxa such as crocodilians

tsunami sedimentary deposits of crete records climate during the minoan warming period 3350 yr bp earthquakes or explosive eruptions generate tsunami which are at the origin of thick and chaotic coastal sediments these commonly fossiliferous deposits are formed instantaneously at the historic

determination of oxygen isotope fractionation between water and phosphate from living lingulids potential application to palaeoenvironmental studies abstract lingulids are inarticulate brachiopods with phosphatic shells which live exclusively in marine waters their distribution is generally restricted to the continental shelf within the 40 belt from temperate to equatorial areas they show a range of morphological physiological and behavioral features that have remained remarkably constant since the cambrian the oxygen isotope fractionation between water and phosphate from living lingulids was determined as a tool to investigate the temperature and or salinity of past coastal seawater oxygen isotope measurements were performed according to the silver phosphate method on a collection of lingulids coming from well known and varied marine environments a global 18o variation of 3 5 was found for these lingulids which proves their good sensitivity to environmental factors namely the oxygen isotope composition and the temperature of seawater oceanographic data provided average temperature and salinity values in the living sites of the studied specimens least squares treatment of the data gave the following fractionation equation t c 112 2 15 3 4 20 0 71 18o po4 18o h2o which is similar to the equations determined by longinelli and nuti 1973a and kolodny et al 1983 for other phosphate bearing invertebrates and fishes all these results suggest that a unique equation describes the phosphate water fractionation of many marine organisms except for mammals

chemical studies of h chondrites iii regolith evolution of the fayetteville chondrite parent abstract data for ag au bi cd co cs ga in rb sb se te tl and zn in consortium samples of solar gas and track rich dark matrix and dark and light clasts in the fayetteville h chondrite regolith breccia were determined by radiochemical neutron activation analysis the matrix proved chemically homogeneous at a level never before observed in an ordinary chondrite most dark clasts had similar mean trace element concentrations as matrix but were compositionally much more heterogeneous two clasts were unusual one having apparently formed from impact melted soil the other representing a mixture of 90 matrix 10 c2m chondrite the single light clast proved compositionally similar to h4 6 chondrite falls except for its higher contents of labile bi cd in and tl relative to matrix all other samples seemed cs deficient other h chondrite regolith breccias studied in the past had shown peculiar cs and or rb contents so that these alkalis seem diagnostic of such breccias dark portions of such breccias apparently represent compacted regolith soil produced by isochemical comminution of normal dark and light clasts the dark clasts in turn likely represent primordial nebular condensate although it is possible that they represent planetary cold traps that garnered labile elements generated elsewhere in the parent body

oxygen strontium and neodymium isotope composition of fossil shark teeth as a proxy for the palaeoceanography and palaeoclimatology of the miocene northern alpine paratethys the upper marine molasse sediments of southern germany were deposited during the early to middle miocene a period of significant change for the global miocene palaeoceanography palaeoclimate and the regional palaeogeography because of the ongoing alpine himalayan orogeny to address the influence of the alpine uplift on climate and oceanography of the northern alpine molasse basin a combined o sr and nd isotope study was undertaken on fossil teeth from sharks synodontaspis sp galeocerdo cf aduncus chaenogaleus sp and button like teeth from the bony fish of the upper marine molasse chrysophrys molassica average 18o values for hydroxyapatite of teeth from two sites are 20 3 1 0 6 and 21 2 1 0 5 while their average 87sr 86sr and 143nd 144nd ratios are 0 70850 0 00001 2 and 0 70882 0 00003 2 and 0 51220 and 0 51223 both at 0 00001 2 respectively by comparison to the sr evolution curve for the global ocean the sr isotope compositions suggest ages of about 22 and 17 ma for the teeth these ages are in good agreement with the depositional ages which suggests open marine conditions open marine conditions are also compatible with 1 lower average 18o values and 87sr 86sr ratios for the one site compared to higher 18o values and higher 87sr 86sr ratios for the other site 2 estimates for seawater temperatures which are similar to other estimates from deposits of similar latitude and age 3 a comparison of seawater temperatures with average ambient air temperature estimates deduced from continental palaeoclimate indicators nd isotope compositions are compatible with an influence of the north atlantic on the paratethys assuming constant salinity and seawater oxygen isotope composition a 4 c cooling can be inferred from average 18o values of the teeth between 22 and 17 ma this is similar to trends observed for foraminiferal records from the mediterranean tethys but different from foraminiferal and molluscan records of the north atlantic and the north sea during this period and allows for the possibility that the alpine orogeny had an influence on the regional circum alpine climate

metamorphic and structural evolution of the early proterozoic puolankajrvi formation finland ii the pressure temperature deformation composition path the paragenetic relationships between sillimanite andalusite kyanite chlorite cordierite biotite garnet and staurolite in the early proterozoic puolankajarvi formation pjf together with mineral compositions are used to construct a partial petrogenetic grid for metapelites with significant mn content mno 0 1 0 5 by adding a six phase invariant point over the garnet absent invariant point for mn free amf phases the grid and textural relations of the pjf are used to construct part of the p t deformation path for the pjf relatively short deformation pulses and associated flow of oxidizing fluid along shear zones were responsible for the paragenetic and compositional changes during cooling and decompression at 600 500 c and 6 0 2 5 kbar oxidation led to decreased fe2 and further stressed the importance of mn increased mn divalent cations a tectonothermal evolution of the kainuu schist belt is presented which includes crustal thinning and steepening of a previously established thermal gradient this was followed by thrusting and folding of the isotherms into a thermal antiform on the western side of the belt

iodine xenon dating of chondrules from the qingzhen and kota kota enstatite chondrites abstract initial 129 i 127 i values i xe ages have been obtained for individual mineralogically characterized chondrules and interchondrule matrix from the enstatite chondrites qingzhen eh3 and kota kota eh3 in view of the absence of aqueous alteration and the low peak metamorphic temperatures experienced by these meteorites we suggest that the i xe ages for the chondrules record the event in which they were formed these ages are within the range recorded for chondrules from ordinary chondrites demonstrating that chondrules formed during the same time interval in the source regions of both ordinary chondrites and enstatite chondrites the timing of this chondrule forming episode or episodes brackets the i xe closure age of planetesimal bodies such as the shallowater aubrite parent body although chondrule formation need not have occurred close to planetesimals the existence of planetesimals at the same time as chondrule formation provides constraints on models of this process whichever mechanisms are proposed to form and transport chondrules they must be compatible with models of the protosolar nebula which predict the formation of differentiated bodies on the same timescale at the same heliocentric distance

thermal evolution of cretaceous tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels 1 the evolution of subtropical 30 35 n upper ocean temperatures through the cretaceous is inferred from the oxygen isotope compositions of 64 fish teeth enamel coming from the western tethyan platform mean 18o values of 22 at the berriasian valanginian boundary decrease with oscillations to 18 5 around the cenomanian turonian boundary and progressively increase to 21 5 by the end of the cretaceous the similarity of this oxygen isotope curve for bioapatites from platform environments with those for foraminifera and bulk carbonates that were deposited in deeper waters and at other paleolatitudes indicates that they record global climatic signals major cooling events at the million year scale can be distinguished 1 at the berriasian valanginian boundary and 2 during the earliest late valanginian a third cooling event is detected during the earliest aptian these events already proposed as icehouse interludes during the lower cretaceous are also recorded at subtropical latitudes a progressive warming is identified from the aptian to the cenomanian turonian interval that corresponds to a thermal optimum and then upper ocean temperatures decreased to the maastrichtian minimum isotopic temperatures range from 15 c to 28 c assuming a 18oseawater of 1 for an ice free world taking more realistic 18oseawater values of 0 for tropical waters during glacial periods within the berriasian valanginian interval and earliest aptian or with above average salinities possibly the maastrichtian temperatures are increased by 4 5 c temperature differences between climatic extremes of the valanginian and cenomanian turonian are estimated to have been 10 c latitudinal thermal gradients for the albian cenomanian turonian and maastrichtian were 0 2 0 3 c latitude and thus weaker than modern oceanic values at about 0 4 c latitude

thermal excursions in the ocean at the cretaceous tertiary boundary northern morocco δ18o record of phosphatic fish debris c lecuyer p grandjean j r o neil h cappetta and f martineau 1993 thermal excursions in the ocean at the cretaceous tertiary boundary northern morocco c lso record of phosphatic fish debris palaeogeogr palaeoclimatol palaeoecol 105 235 243 high precision oxygen isotope analyses were made of phosphate extracted from 17 samples of nektonic and benthic fish debris sampled across the stratigraphic cretaceous tertiary boundary in northern morocco a refinement of the silver phosphate method was used to isolate phosphate from biogenic materials measured 180 values of 18 6 20 5 o are interpreted as reflecting high resolution thermal variations that affected the ocean water column of the western tethys the warm 27 c water masses that characterized maastrichtian times underwent rapid cooling and stabilized at an average temperature of 19 c during the dano montian and thanetian this period of constant and cool temperature was followed by a relatively rapid but more gradual warming to about 25 c achieved in the middle ypresian significant small shifts in 6180 values between nektonic and benthic fauna recorded only during the stages of rapid warming or cooling may correspond to averaged thermal differences within the water column that developed in response to global climatic changes the indicated temperature distribution could have been caused by thermal changes in the atmosphere rather than some signal carried by deep ocean currents the oxygen isotope data coupled with previous measurements of ree and end ti on the same samples support the suggestion that paleo pacific westward currents progressed as far as the northwestern part of the african platform at the end of the cretaceous period

old formation ages of igneous clasts on the l chondrite parent body reflect an early generation of planetesimals or chondrule formation abstract the barwell meteorite contains large abundant clasts that are igneous in nature we report iodine xenon ages of five clasts and one sample of host chondrite material the fragment of host chondrite material yielded the oldest age determined 4567 8 1 2 ma two clasts produced old well defined ages of 4564 96 0 33 ma and 4565 60 0 33 ma these and a third clast having a less precise old age of 4566 0 3 2 ma are interpreted as recording the timing of crystallisation of the samples they were incorporated into the barwell parent body before it underwent thermal metamorphism but the i xe ages survived secondary processing on the parent body and were not reset by metamorphism metasomatism or shock two further clasts record younger ages of 4560 96 0 45 ma and 4554 22 0 38 ma these samples contain a high abundance of albitic mesostasis and the most likely explanation of the ages is that they record the timing of metasomatism on the parent body we also analysed four host chondrite samples that do not give i xe ages in these samples the system appears to have been disturbed by shock it has been suggested previously that the igneous clasts are derived from an early generation of partially melted asteroids we do not have direct evidence that the clasts we examined were necessarily derived from a partially differentiated body only that they were derived from cooling of a silicate melt the clasts could thus be the products of any one of several proposed models for chondrule formation our results indicate that processes akin to chondrule formation in that they involve rapid cooling of a silicate melt were ongoing at the same time as cai formation lending support to the suggestion that al mg chondrule ages indicate either heterogeneous distribution of 26 al or resetting of the al mg system after chondrule formation

nd isotope evidence for the evolution of the paleocurrents in the atlantic and tethys oceans during the past 180 ma the nd isotopic composition of atlantic and tethys seawater as deduced from marine phosphorites varied considerably during the past 180 ma the early tethys and central atlantic seawater from 180 to 160 ma ago early middle jurassic had a nd isotopic signature identical to that of the pacific end 6 suggesting that pacific seawater entered the newly forming tethys basin however with time continental runoff draining into the young basin became more important and led to a decrease in the nd isotopic composition and finally a decoupling from the pacific ocean during the late early cretaceous 120 90 ma ago atlantic and tethys seawater reached continental crust like nd isotopic composition values end 10 which could reflect high weathering rates induced by the warm and humid climate at that time in the time span between 80 and 50 ma late cretaceous early tertiary the nd isotopic composition of both tethys and atlantic seawater strongly increased towards pacific seawater values in the case of the atlantic ocean this change has been correlated with the opening of the south atlantic which enabled the more radiogenic pacific seawater to travel westwards around the southern edge of africa into the south and finally the north atlantic in the case of tethys seawater we have to assume that during this period large masses of pacific seawater entered the tethys again directly through the indian tethys seaway the renewed importance of this seaway might be related to the late cretaceous early tertiary first order global sea level highstand the most abrupt change towards lower more crust like values occurred in the early miocene 25 17 ma ago in the south and north atlantic as well as in the tethys during this period the143nd 144nd isotope ratios dropped from 0 5124 end 4 2 down to 0 5122 end 8 this change indicates a diminishing influx of pacif seawater into the atlantic and tethys oceans and can be correlated with the breakdown of the circum equatorial circulation patterns of the world oceans due to plate tectonics from 20 to 17 ma ago miocene the nd isotopic composition of the atlantic ocean increased again and reached values as high as 0 5123 end 6 6 whereas tethys seawater remained at low values this decoupling can be correlated with the incipient complete isolation of the tethys the nd isotopic composition was henceforth controlled by the continental runoff from surrounding land masses the major increase in the nd isotopic composition observed in the atlantic can be related to the opening of the drake passage and establishment of the circum antarctic current system this allowed pacific seawater to enter directly the south atlantic around antarctica a renewed drop in the nd isotopic composition of atlantic seawater during the late miocene can be related to the onset of north atlantic bottom water formation and its subsequent upwelling

stable isotope composition and rare earth element content of vertebrate remains from the late cretaceous of northern spain lano did the environmental record survive abstract oxygen and carbon isotope measurements have been performed on phosphatic remains from faunal associations dinosaurs crocodiles turtles and fish of the late cretaceous continental and marine sediments from northern spain basque country the environmental meaning of the oxygen isotope record in fossil reptiles is discussed on the basis of known paleoecology modern fauna analogs and apatite chemistry rare earth elements ree co32 and po43 contents fossil remains in sandstones and argillites from two localities urria and cuezva have low down to 16 and scattered 18o po4 co3 and 13c values with ree patterns characterized by strong middle ree enrichments these geochemical compositions of the biogenic apatites have most likely been acquired during a multi stage late diagenesis involving complete recrystallization of the apatite in the presence of aqueous fluids ree contents of fossils preserved in the clayey sands from the site of lano suggest that samples have only been affected by early diagenesis despite the diversity of analyzed taxa and the close association of marine sharks and rays and freshwater species crocodiles and turtles evolving in a littoral environment the narrow range of phosphate 18o values is interpreted as reflecting the temperature and isotopic composition of groundwaters that prevailed in the burial environment the potential information relative to the physiology and thermal regime of the vertebrates has been erased during the process of early diagenesis if all oxygen in the phosphate has exchanged with groundwaters the oxygen isotope composition of vertebrate remains suggests that a warm climate t 20 25 c prevailed in northern spain during the late cretaceous

chemical processes and migration of elements during retrogression of a staurolite zone assemblage in western north carolina a detailed study of retrograde alteration of a staurolite porphyroblast and its surrounding matrix of mica schist has made use of petrographic modal and microprobe analysis retrogression was to the garnet zone of metamorphism and apparently occurred largely after a temperature decline of 70 100 c the event caused metasomatic removal of zn but may have been isochemical relative to other analyzed elements the best estimate of the overall reaction is 1 staurolite 3 018 biotite 3 550 quartz 0 629 albite 0 014 anorthite 0 678 nacl 14 004 h2o 3 274 na rich muscovite 3 561 chlorite 0 273 ilmenite 0 110 chloritoid 0 039 garnet 0 339 zncl2 non systematic variation in composition of analyzed minerals is revealed by statistical treatment of replicate analyses such variation involves monovalent and divalent cations within many minerals but is most pronounced within retrograde muscovite muscovite variation involves si and al as well as fm and alkalis and does not follow a phengite law of charge coupled substitution relative to the core of the retrograded staurolite crystal zoning is seen in averaged muscovite compositions and in development of incompatible mineral assemblages which include chloritoid well within retrograded staurolite but biotite within the matrix a local gradient in the chemical potential of an al bearing component was likely present during retrogression alteration of staurolite was probably accomplished by reaction and diffusion through the medium of an intergranular fluid phase relative to staurolite migration of elements involved immigration of considerable amounts of mg na k and h and expulsion of al fe zn and o it is inferred that concentration of al within the fluid phase was considerably lower than those of monovalent and divalent cations preservation of considerable staurolite and evidence for a local concentration gradient of al in the fluid phase suggest that limited amounts of h2o were available expulsion of zn suggests that much water was not consumed locally but exited the terrane an attempt at resolution of this dilemna involves fracture channelized infiltration of h2o into the rock a more regional petrographic study of retrogression suggests that h2o which entered the rock may have been liberated initially by prograde dehydration at a moderately greater depth of 2 3 km results of this study especially the non phengitic nature of crystal chemical substitution within muscovite indicate chemical reaction under conditions of disequilibrium apparently extent of retrogression was controlled by availability of h2o rather than by thermochemical equilibria