copper chelated bacteriochlorophyll e homologues in sediment from an anoxic lake lake abashiri japan copper chelated bacteriochlorophyll e homologues have been identified in laminated sediment from the meromictic lake abashiri using atmospheric pressure chemical ionization liquid chromatography mass spectrometry since they are the second most abundant chloropigment derivatives in the sediments these novel compounds may be important intermediate products of bchl e diagenesis in this anaerobic environment

210pb derived sediment accumulation and mixing rates for the washington continental slope abstract total sediment accumulation rates g yr in four canyons indenting the washington continental shelf are about twice those on the nearby open slope even though canyons comprise less than 40 of the depositional area of the entire slope this is because 210 pb derived sediment accumulation rates g cm 2 yr for astoria and quinault canyons are 3 4 times greater than those for willapa and grays canyons and intermediate open slope areas supporting the hypothesis that columbia river derived solids are preferentially transported to these two canyons quinault canyon currently appears to be accumulating solids at rates much greater than its low long term accumulation rate which is attributed to turbidity currents transporting solids down this canyon roughly every 500 years the following four different approaches all show that mixing may cause 210 pb derived sediment accumulation rates for slope and canyon sediments to be 2 3 times higher than true accumulation rates 1 comparison between accumulation rates calculated from 210 pb profiles with and without surface zones in which mixing has obviously affected 210 pb distributions 2 comparison between 210 pb derived and independently determined long term accumulation rates 3 comparison between 210 pb derived accumulation and modern columbia river discharge rates 4 comparison between two and three layer steady state one dimensional diffusion advection decay models mixing coefficients for surface sediments calculated using a one dimensional two layer vertical eddy diffusion model show large differences within the region with most in the 3 30 cm 2 yr range mixing rates are several times larger in canyon sediments from 0 2 1 1 km water depth probably due to physical reworking processes erroneously neglected mixing at depth of no more than 5 of that calculated for the surface mixed layer can cause the 2 3 fold calculated overestimation of true sediment accumulation rates and 2 4 fold calculated underestimation of true mixing coefficients

pigment preservation and remineralization in oxic coastal marine sediments abstract complex mixtures of sedimentary chlorophyll degradation products were measured using high performance liquid chromatography hplc in 210 pb dated box and piston core sediments sediments were collected from dabob bay washington a coastal marine fjord conducive to studies yielding an understanding of the remineralization and diagenesis of organic carbon greater than 99 of the pheopigment flux out of the water column does not accumulate in the top 2 cm of sediment surface sediment pigment profiles indicate that pheophorbides are the dominant pheopigments observed with concentrations decreasing rapidly with depth concentrations of chlorophyll c derivatives also decrease rapidly but ratios of a c pheopigments remain within ranges reported for natural and cultured phytoplankton sharp pheopigment concentration decreases within the bioturbated surface sediments as defined by 210 pb activities were modeled using a one dimensional mixing model the in situ pheopigment decomposition rate corrected for bioturbation and sediment accumulation corresponds to an approximate half life of 40 days sedimentary humic acid fulvic acid and residual humin associated pheopigments in sediments which had been previously acetone extracted to remove the lipophilic pheopigment fraction were typed by chromic acid oxidation and release of pyrrole derived maleimides this humic associated pyrrole derived nitrogen while a small fraction of total sedimentary or humic nitrogen accounted for 16 75 of the total sedimentary pheopigment accumulation and may be significant in understanding the diagenetic fate and transformation of pheopigments to petroporphyrins

live iron 60 in the early solar system isotopic analyses of nickel in samples from the differentiated meteorite chervony kut revealed the presence of relative excesses of 60ni ranging from 2 4 up to 50 parts per 104 these isotopic excesses are from the decay of the now extinct short lived nuclide 60fe and provide clear evidence for the existence of 60fe over large scales in the early solar system not only was 60fe present at the time of melting and differentiation that is fe ni fractionation of the parent body of chervony kut but also later at the time when basaltic magma solidified at or near the surface of the planetesimal the inferred abundance of 60fe suggests that its decay alone could have provided sufficient heat to melt small diameters of several hundred kilometers planetary bodies shortly after their accretion

a new symbol and gis based detailed geomorphological mapping system renewal of a scientific discipline for understanding landscape development this paper presents a comprehensive and flexible new geomorphological combination legend that expands the possibilities of current geomorphological mapping concepts the new legend is presented here at scale of 1 10 000 and it combines symbols for hydrography morphometry morphography lithology and structure with colour variations for process genesis and geologic age the piece by piece legend forms a geomorphological alphabet that offers a high diversity of geomorphological information and a possibility for numerous combinations of information this results in a scientific map that is rich in data and which is more informative than most previous maps but is based on a simple legend the system is developed to also be used as a basis for applications in gis the symbol based information in the geomorphological maps can be digitally stored as a powerful database with thematic layers and attribute tables by combining and further developing aspects of different classical mapping systems and techniques into expanded data combinations new possibilities of presentation and storage are developed and thus a strong scientific tool is provided for landscape configuration and the reconstruction of its development in turn the combination paves the way for specific thematic applications the new system is illustrated for two contrasting landscape types the first is located on the border of vorarlberg western austria and liechtenstein in a glacially influenced high altitude alpine setting that is strongly modified by various degradation processes the second area represents a formerly glaciated region in dalarna central sweden near mora an area that is characterized by a variety of aeolian fluvial glaciofluvial and lacustrine depositional and erosional landforms and also reflects isostatic uplift the new method functions well for both areas and results in detailed scientific outlines of both landscape types

late quaternary deglaciation and climate history of the larsemann hills east antarctica the late quaternary climate history of the larsemann hills has been reconstructed using siliceous microfossils diatoms chrysophytes and silicoflagellates in sediment cores extracted from three isolation lakes results show that the western peninsula stornes and offshore islands were ice covered between 30 000 yr bp and 13 500 cal yr bp from 13 500 cal yr bp shortly after the antarctic cold reversal the coastal lakes of the larsemann hills were deglaciated and biogenic sedi mentation commenced between 13 500 and 11 500 cal yr bp conditions were warmer and wetter than during the preceding glacial period but still colder than today from 11 500 to 9500 cal yr bp there is evidence for wet and warm conditions which probably is related to the early holocene cli mate optimum recorded in antarctic ice cores between 9500 and 7400 cal yr bp dry and cold con ditions are inferred from high lake water salinities and low water levels and an extended duration of nearshore sea ice a second climate optimum occurred between 7400 and 5230 cal yr bp when stra tified open water conditions during spring and summer characterised the marine coast of prydz bay from 5230 until 2750 cal yr bp sea ice duration in prydz bay increased with conditions similar to the present day a short return to stratified open water conditions and a reduction in nearshore winter sea ice extent is evident between 2750 and 2200 cal yr bp simultaneously reconstructions of lake water depth and salinity suggests relatively humid and warm conditions on land between 3000 and 2000 cal yr bp which corresponds to a holocene hypsithermal reported elsewhere in antarctica finally dry conditions are recorded around 2000 between 760 and 690 and between 280 and 140 cal yr bp these data are consistent with ice core records from antarctica and support the hypothesis that lacustrine and marine sediments on land can be used to evaluate the effect of long term climate change on the terrestrial environment copyright 2004 john wiley sons ltd

timing of early diagenetic sulfurization of organic matter a precursor product relationship in holocene sediments of the anoxic cariaco basin venezuela abstract the incorporation of reduced inorganic sulfur into organic matter is a significant mechanism for the preservation of functionalized organic compounds in the sedimentary environment but the timing of this process is not currently known analysis of organic matter in the holocene and latest pleistocene sediments of the cariaco basin indicates conversion of a triunsaturated tricyclic triterpenoid 17e 13 h malabarica 14 27 17 21 triene identified by isolation and subsequent one and two dimensional 1 h and 13 c nmr spectroscopy to a monounsaturated triterpenoid thiane through incorporation of reduced inorganic sulfur species into the isoprenoid side chain within the upper 6 m of sediments time control provided by ams 14 c dates was used in conjunction with measured relative abundances of the two compounds to calculate the reaction rate for the sulfurization of this triterpenoid and empirically determine the first order rate constant 2 10 4 yr 1 for the reaction this is the first time that such a precursor product relationship has been positively identified for a sulfurization reaction in sediments

total organic carbon in lake superior sediments comparisons with hemipelagic and pelagic marine environments1 seventeen box cores from lake superior were analyzed for total organic carbon toc porosity and 210pb activity the data were trsed to determine relationships among bulk scdimentation rates toc sedimentation rates and toc degradation rates with depth in the core results are compared with predictive eqllations for toc sedimentation rates and degradation rates in the oceans and show some striking similarities bctwcen the behavior of toc in lake superior and in hemipclagic and pelagic marine environments

60fe 60ni systematics in the eucrite parent body a case study of bouvante and juvinas abstract eucrites are basaltic meteorites that cooled rapidly but are in many instances thermally metamorphosed and impact brecciated the exact timing of these events remains unclear in this study ni isotopic compositions and fe ni elemental ratios are presented for two non cumulate eucrites bouvante and juvinas including mineral separates from the latter the samples are characterized by variable well resolved 60 ni excesses consistent with the former presence of live 60 fe t 1 2 2 62 ma at the time of eucrite crystallization a significant fraction of ni with a terrestrial like composition appears to be surface correlated this ni may be the product of terrestrial contamination or was introduced by a chondritic impactor during brecciation altogether the data provide evidence for a complex and probably multi stage history of fe and or ni redistribution which impedes the interpretation of the chronological data

identification of a novel 7 desmethyl 7 acetonyl bacteriophaeophorbide c series in a recent sediment abstract we report the identification of three members of a novel 7 desmethyl 7 acetonyl bacteriopheophorbide c series isolated from a coastal salt pond sediment salt pond ma usa as well as the full structure determination 1 h nmr of one of the members the compounds have the same carbon framework as bacteriopheophorbides c but bear an acetonyl group at c 7 they may be fossils of an unknown photosynthetic pigment series and could be intermediates in the formation of some porphyrins isolated previously from ancient sediments

hydrocarbons in washington coastal sediments the sources and distributions of polycyclic aromatic hydrocarbons pah and aliphatic hydrocarbons are characterized in seventeen sediments from a highly river influenced sedimentary environment off the southwestern coast of washington the major hydrocarbons are land derived introduced as preformed compounds and display long term stability in sediment cores a series of pah of anthropogenic origin and two naturally derived compounds retene and perylene dominate the pah composition in these sediments plantwax n alkanes are the major aliphatic hydrocarbon constituents aliphatic hydrocarbons of marine origin pristane and a series of four acyclic multibranched c25 polyolefins are also observed in many sediments the concentrations of these marine derived hydrocarbons decrease to negligible levels rapidly with sediment depth from the sea sediment interface suggesting degradation in general the major land derived hydrocarbons are concentrated in the midshelf silt deposit which extends northwestward along the continental shelf from the columbia river mouth a quantitatively more minor natural series of phenanthrene homologs also of terrestrial origin is preferentially advected further offshore and deposited in continental slope sediments these distributions are consistent with recognized particle associations for these compounds and sediment dispersal processes in this coastal environment sediment core records suggest the present pattern of dispersal has persisted for at least the past century and possibly since the late pleistocene

oxygen isotope evidence for rapid mixing of the hed meteorite parent body abstract the 16 o 17 o and 18 o abundances of howardites eucrites and diogenites have been used to assign them to a single hed parent body thought to be asteroid 4 vesta we report the first evidence of oxygen isotopic heterogeneity among hed meteorites indicating incompletely mixed sources new high precision oxygen isotope measurements of 34 hed meteorites reveal that most have the same 17 o consistent with a very rapid early history of large scale mixing on vesta however howardites are on average very slightly enriched in 16 o whereas ibitira caldera pasamonte and alha78132 are 16 o depleted compared to other investigated eucrites the 17 o of ibitira is completely different from all other heds measured some of the results for eucrites and diogenites can be explained by partial melting and rapid mixing of the interior of vesta others require a separate parent body or indicate that parts of the outer layer of vesta retained some primary isotopic heterogeneity the oxygen isotopic composition of howardites provides an upper limit for the amount of admixed carbonaceous chondritic material into the hed parent body regolith

a geological constraint on relative sea level in marine isotope stage 3 in the larsemann hills lambert glacier region east antarctica 31 366 33 228 cal yr bp abstract in this paper we present geological evidence from the larsemann hills lambert glacier amery ice shelf region east antarctica of marine sediments at an altitude of c 8 m a s l as revealed by diatom pigment and geochemical proxies in a lake sediment core the sediments yielded radiocarbon dates between c 26 650 and 28 750 14c yr bp 31 366 33 228 cal yr bp this information can be used to constrain relative sea level adjacent to the lambert glacier at the end of marine isotope stage 3 these data are compared with the age and altitude of marine isotope stage 3 marine deposits elsewhere in east antarctica and discussed with reference to late quaternary ice sheet history and eustatic sea level change

major and trace elements of zircons from basaltic eucrites implications for the formation of zircons on the eucrite parent body abstract the major and trace elements in zircons obtained from basaltic eucrites yamato y 75011 y 792510 y 82082 asuka a 881467 juvinas and stannern were determined using an electron microprobe analyzer and a sensitive high resolution ion microprobe and the formation of zircons on the parent body was discussed the maximum sizes of zircon grains in each sample are likely to be related to its metamorphic grade the least metamorphosed basaltic eucrite y 75011 contains zircons with sizes of a few m conversely the highly metamorphosed basaltic eucrites y 792510 and a 881467 include zircons larger than 20 m the relationship between the maximum grain size and metamorphic grade suggests that the formation process of zircons is related to metamorphic events the zr hf ratios of the zircons found in this study show a wide variation 31 6 71 7 as compared to the chondritic values zr hf 32 8 34 3 and bulk basaltic eucrites 34 0 34 7 the zr hf ratios of the zircons from y 792510 and a 881467 are relatively constant whereas those of the zircons from y 82082 juvinas and stannern show large variations the rare earth element ree content in the zircons from y 792510 and a 881467 is given by la 0 1 ci and lu 1000 ci on the other hand the zircons from stannern show higher ree content la 0 1 1 ci and lu 1000 10 000 ci than those from y 792510 and a 881467 the most reliable ree data of a large zircon from a 881467 show no ce anomaly and a distinct negative eu anomaly therefore it is presumed that the zircons formed under reducing condition in which ce 3 was stable the melt compositions coexisting with the studied zircons suggest that the zircons from highly metamorphosed eucrites might react with the ree enriched melt derived from partial melting of the mesostasis region during metamorphism

decipherment of potential zones for groundwater occurrence a study in khatra block bankura district west bengal using geospatial techniques groundwater is considered as one of the most valuable natural resources as it supports human civilization freshwater is considered as an important natural resource which occurs partially on the surface and dominantly beneath the surface the resource is declining drastically owing to the rapid increase in population and its management in an improper way the occurrence of groundwater in hard rock terrain still behaves as enigmatic various terrain parameters control the movement and storage of groundwater accordingly geoscientists are using various techniques to explore the potential zone amongst which multi criteria evaluation mce technique seems to be more precise application of remote sensing and geographic information system gis has come out as very effective tools in deciphering groundwater potential zone by modeling terrain features specially in hard rock arid regions the present study is aimed to find out groundwater potential zones in khatra block of bankura district west bengal india characterized by hard granitic terrain and semi arid climatic condition in the present study various thematic maps viz geomorphology geology lineament density drainage density and slope have been prepared for these irs resources at liss 4 with 5 8 m spatial resolution digital data cartosat 1 digital elevation model cartodem with 2 5 m spatial resolution along with other data sets such as survey of india toposheets 73j 13 73i 16 73i 12 gsi map have been used digitized vector maps relating to chosen parameters were converted to raster data using 30 m 30 m grid cell size different theme weight and class rank have been assigned to these raster maps each theme weight has been multiplied by its respective class rank and all the raster thematic layers have been summed up in a linear combination equation in arc gis raster calculator module similarly the weighted layers have been statistically modeled to get the areal extent of groundwater prospects this integrated approach helped in classifying the groundwater availability in the study area into five categories viz very good good moderate poor and very poor finally it can be stated that the modeling assessment method proposed in this study forms an effective tool for delineating groundwater potential zones for proper development and management of groundwater resources in hard rock terrains

mineralogy and39ar 40ar age of an old pristine basalt thermal history of the hed parent body previous investigations of mineral chemistry and rbsr and smnd ages indicated that clast 84 from eucrite yamato 75011 had preserved the pristine nature of its initial crystallization during an early stage of the hed parent body microscale mineralogy and39ar 40ar ages of this clast however revealed local disturbance of micrtextures and partially reset ages this evidence suggests that in addition to initial crystallization and rapid cooling the y75011 84 clast experienced shock deformation reheating of short duration at higher temperature and brecciation these characteristics suggest two or more impact events fe rich olivine filling fractures in pyroxene may have been introduced during the accompanying shock fracturing the inferred39ar 40ar degassing ages for y75011 matrix and clast 84 are3 94 0 04 ga and3 98 0 03 ga respectively the suggested degassing age for a clast from y790020 believed to be paired with y75011 is 4 03 ga but could be younger we consider it likely that all three samples experienced a common degassing event3 95 0 05 ga ago but we cannot rule out two or more events spaced over a 0 1 ga interval higher temperature extractions of the two clast samples show significantly older apparent ages up to 4 5 ga and suggest that the time temperature regime of this event was not sufficient to degas ar totally most likely the k ar ages were reset by thermal metamorphism associated with one or more impact events associated with shock fracturing formation of fe rich olivine veins and or meteorite brecciation the pyroxene annealing that commonly occurs in many eucrites is likely to be a much earlier process than the impact produced textural changes and reset k ar ages observed in these meteorites the existence of mineralogical and chronological evidence for metamorphism in an otherwise pristine eucrite suggests that the hed parent body experienced an extensive degree of early cratering

an integrated approach to hydro geological lineament mapping of a semi arid region of west africa using radarsat 1 and gis abstract in the 21st century water resource management will be a major socioeconomic issue and an essential component of progress in semi arid regions the soudano sahelian region of africa suffers from a chronic lack of reliable hydro geological maps for local water resource managers to provide better tools for groundwater exploration this paper focuses on hydro geological lineament mapping using remote sensing data the objectives were 1 evaluate the potential of multi angular and multi temporal radarsat 1 images for extracting lineaments in semi arid regions and 2 provide map of potential hydro geological lineaments no significant relationship was found between lineament yield and incidence angle of radarsat 1 images while lineament spatial distribution was in good agreement with the land use and geology of the study area the high scores observed for nne ssw and nnw sse orientations match the results of local lineament studies of the region radarsat 1 image acquired on may 01 2001 offers the greatest potential due to the reduced effect of vegetation during this region s dry season potential hydro geological lineaments were mapped using the weighting of well location presence of green vegetation during the dry season preferential lineament orientations and presence of cross points the mapping revealed five classes very low low moderate high and very high of potential hydro geological lineaments with high and very high potential poorly represented results also reveal that most wells are far enough from lineaments or cross points and hence the inefficiency of existing drilling programs

sedimentary pigments as markers for environmental change in an antarctic lake abstract fossil pigments were identified in a sediment core from kirisjes pond a small lake in the larsemann hills east antarctica using reversed phase hplc and lc ms ms chlorophyll a and b derived components indicate the presence of oxygenic primary producers steryl chlorin esters provide evidence of grazing while shifts in their esterifying sterol composition record changes in the primary producer community bacteriochlorophyll c and d derived components indicative of photic zone anoxia were identified with structural variations including extensive alkylation in the macrocycle up to c 6 the pigment distribution reveals a change from oxygenated freshwater to a stratified water body with development of photic zone anoxia this coincides with a marine incursion identified from diatom records and is followed by re isolation and reversion to oxygenated freshwater conditions

metamorphic history of the eucritic crust of 4 vesta the petrologic properties of eucrites indicate that most formed as rapidly cooled lava flows that were subsequently metamorphosed at 800 c for periods of about 1 myr we have modeled the development of the eucritic crust of the eucrite parent body assumed to be asteroid 4 vesta by the eruption and subsequent burial of lava flows serial magmatism the burial of the flows causes them to reheat to metamorphic temperatures 800 c provided that the initial thermal gradient in the upper 5 km was steep as it would be if 26al was the heat source our model shows that most eucrites were metamorphosed for periods over 1 myr in a crust between 15 and 25 km thick if volcanism lasted only 1 to a few myr longer periods of volcanism do not result in high enough peak metamorphic temperatures to be consistent with eucrite data the hot lower crust in vesta provides an environment in which even small few meters dikes could have cooled slowly enough to produce cumulate eucrites and possibly diogenites

sedimentary purpurins oxidative transformation products of chlorophylls examination of sediments from three contemporary lakes priest pot loch ness and lake baikal reveals the presence of oxidative transformation products of chlorophyll a in two of the settings purpurin 18 phytyl ester not previously reported in sediments occurs in the two lakes that have deep water columns the free acid counterpart purpurin 18 occurs in only one of the samples that from loch ness although where present the abundance of purpurin 18 phytyl ester is similar to that of individual chlorin steryl esters there appears not to be a correlation between their abundances in the sediments suggesting that formation of the purpurins is not mediated by herbivory the presence of oxidative transformation products of chlorophyll in contemporary lake bottom sediments indicates their formation during the earliest stages in chlorophyll degradation their preservation in sediments demonstrates that oxidative transformation reactions in the aquatic environment lead not only to destruction of the chlorophyll macrocycle but also to structures modified in ring e this lends support to the view that sedimentary aetioporphyrins originate mainly though not exclusively from transformations of chlorophylls that involve oxidative cleavage of the five membered exocyclic ring

sedimentary pigments on the pakistan margin controlling factors and organic matter dynamics abstract sedimentary pigments can provide information on various aspects of benthic processes and biogeochemistry in this study sediments from sites at depths of 140 to 1850 m spanning the pakistan margin oxygen minimum zone omz and representing dramatic contrasts in depositional conditions and benthic communities were analysed for pigment yields and compositions this has allowed a rare consideration of how different factors including oxygen concentration organic matter om supply and biological activity e g degree of bioturbation may influence sedimentary pigment distribution in a continental margin environment it has also allowed one of the first efforts to study the impact of biological activity on pigment concentrations in the natural environment rather than in a microcosm setting total extractable surface sediment pigment concentrations showed a range of 1 5 49 g g 1 of dry sediment the pigment suite was dominated by pheophytin and pheophorbide which together constituted 75 of total pigments with minor amounts of chlorophyll a alloxanthin diatoxanthin zeaxanthin and carotene low oxygen concentration appeared to influence pigment abundance by increasing the concentration of refractory pigments ultimately buried in addition maximal pigment abundances were associated with minimal amounts of sediment mixing by macrofauna and at one site macrofaunal digestion may have altered the relative dominance of the different pheopigments in contrast the lack of a marked increase in pigment concentrations after the summer monsoon plus the lack of a correlation between pigment concentration and water depth suggest that om supply plays a relatively small role in controlling sedimentary pigments pigment concentrations and suites together with modelled decay half lives 0 8 15 years suggest that in general om on the pakistan margin despite the low oxygen concentrations and monsoon driven productivity is surprisingly degraded compared to that on other continental margins with om rich sediments as an exception to this general situation pigment suites appeared to be relatively fresh i e contained more labile components compared to those found on the oman margin of the arabian sea but overall concentrations were lower this is consistent with the higher oxygen concentrations productivity and macrofaunal abundances found on the western margin of the arabian sea principle component analysis of pigment suites showed that they correlated with an amino acid based degradation index di thus the pigment composition of marine sediments is related to and may serve as an indicator of the state of decay of sedimentary om

fossil records of high level of 60fe in chondrules from unequilibrated chondrites abstract the short lived now extinct nuclide sln 60fe which decays to 60ni with a half life of 2 62 ma is uniquely of stellar origin hence its solar system initial abundance yields information about the source of slns and the astrophysical environment in which the solar system was born only a few chondrules 19 from unequilibrated ordinary chondrites have reported resolved 60ni excesses using in situ secondary ion mass spectrometry implying fe 60 fe 56 0 6 10 7 in the early solar system and among these very few 3 have higher excesses implying fe 60 fe 56 7 10 7 mishra et al 2010 mishra and goswami 2014 telus et al 2012 at variance multi collector inductively coupled plasma mass spectrometer studies of bulk samples and mineral separates from differentiated meteorites angrites achondrites and chondrules suggest a low abundance of 60fe 56fe of 1 4 10 8 which would rule out the need for an external seeding of the early solar with stellar 60fe quitte et al 2011 tang and dauphas 2012 two semarkona chondrules and one efremovka chondrule analyzed in the present study have mass fractionation corrected excess of up to 75 permil and give 60fe isochrons with initial 60fe 56fe ratios of 7 8 3 7 10 7 3 8 1 6 10 7 and 2 2 1 1 10 7 2 for efremovka ch 1 semarkona ch 12 and semarkona ch j5 respectively the higher values of 60fe 56fe ratios seen in the chondrules of these least altered meteorites samples concur with and lend greater credence to the suggestion of a massive star as the source of 60fe and possibly of other short lived nuclides to the early solar system however no definitive explanation e g sample bias effects of metamorphism 60fe heterogeneity to the apparent disagreement with studies of bulk chondrules and chondrule fragments has been found

carotenoid diagenesis in recent marine sediments i the peru continental shelf 15 s 75 w abstract we report here the distribution of carotenoids in peru marine surface sediments including partial identification of 37 pigments 33 of which have not been previously reported to occur in marine sediments our analysis demonstrates that zooplanktonic crustacea diatoms dinoflagellates cryptomonads purple nonsulfur photosynthetic bacteria and unidentified species of photosynthetic bacteria are contributors to sedimentary organic matter fucoxanthin fucoxanthinol diadinoxanthin peridinin and peridininol the principal carotenoids of diatoms and dinoflagellates observed in sediment traps are nearly absent from our sample even though these phytoplankton are the primary source of organic matter we attribute this to the presence of 5 6 epoxides in these pigments a feature which causes rapid cleavage of the polyene and fragmentation to low molecular weight compounds

novel functionalised chlorins in sediments of the messinian vena del gesso evaporitic sequence evidence for a facile route to reduction for biomarkers fossil pigment distributions from sediments of the messinian vena del gesso italy include two novel sedimentary chlorins as revealed by high performance liquid chromatography and liquid chromatography multistage mass spectrometry the two novel chlorin components are meso derivatives of chlorophyllone a and represent early stage diagenetic intermediates in the formation of bicycloalkano chlorin and porphyrin structures that occur in these and other carbonaceous sediments their presence indicates the operation of a facile route to reduction during early diagenesis

relative sea level history from the lambert glacier region east antarctica and its relation to deglaciation and holocene glacier readvance we present a relative sea level rsl history constrained by ams radiocarbon dated marine freshwater transitions in isolation basins from a site adjacent to the lambert glacier east antarctica the rsl data suggest an initial ice retreat between c 15 370 and 12 660 cal yr b p within this period meltwater pulse ia mwp ia between c 14 600 14 200 and 14 100 13 700 cal yr b p occurred an exceptionally large ice melting event inferred from far field sea level records the rsl curve shows a pronounced highstand of approximately 8 m between c 7570 7270 and 7250 6950 cal yr b p that is consistent with the timing of the rsl highstand in the nearby vestfold hills this is followed by a fall in rsl to the present in contrast to previous findings the isolation of the lakes in the larsemann hills postdates the isolation of lakes with similar sill heights in the vestfold hills an increase in rsl fall during the late holocene may record a decline in the rate of isostatic uplift in the larsemann hills between c 7250 6950 and 2847 2509 cal yr b p that occurred in response to a documented mid holocene glacier readvance followed by a late holocene retreat

chemical zoning and homogenization of pasamonte type pyroxene and their bearing on thermal metamorphism of a howardite parent body we studied thermal metamorphism in the surface layer of a eucrite parent body by examining pyroxene zoning ca mg fe zoning of pyroxenes in the pasamonte eucrite can be classified into three types type 1 with a core composition of ca5mg62fe32 and rim of ca41mg20fe4o type 2 with core of ca5mg62fe32 and rim of ca25mg34fe41 and type 3 with core of ca5mg66fe29 and rim of ca7mg32fe61 type 1 typically occurs adjacent to a mesostasis type 2 typically occurs adjacent to a surrounding plagioclase and type 3 is common in pyroxenes in the matrix pasamonte is less metamorphosed than previously believed because of the wide range of composition of zoned pyroxenes on the basis of ca mg fe variation data we have calculated the degree of homogenization of zoned pyroxenes by numerically solving the diffusion equation a pasamonte type pyroxene may yield a juvinas type pyroxene by thermal metamorphism the homogenization of juvinas pyroxene could not have taken place during initial cooling and may be related to reheating events although our calculation rests upon some assumptions

60fe 60ni chronology of core formation in mars abstract the timescales of accretion core formation and magmatic differentiation in planetary bodies can be constrained using extinct radionuclide systems experiments have shown that ni becomes more siderophile with decreasing pressure which is reflected in the progressively higher fe ni ratios in the mantles of earth mars and vesta mars formed rapidly and its mantle has a high fe ni ratio so the 60fe 60ni decay system t 1 2 2 62 myr is well suited to establish the timescale of core formation in this object we report new measurements of 60ni 58ni ratios in bulk snc martian shergotty nakhla chassigny meteorites and chondrites the difference in e ni 60 values between snc meteorites and the building blocks of mars assumed to be chondritic 55 ordinary chondrites 45 enstatite chondrites is 0 028 0 023 95 confidence interval using a model of growth of planetary embryo this translates into a time for mars to have reached 44 of its present size of 1 9 0 8 1 7 myr with a strict lower limit of 1 2 myr after solar system formation which agrees with a previous estimate based on 182hf 182w systematics the presence of mars when planetesimals were still being formed may have influenced the formation of chondrules through bow shocks or by inducing collisions between dynamically excited planetesimals

pore waters of the central pacific ocean nutrient results interstitial waters from the manop siliceous and calcareous ooze sites in the central pacific ocean were recovered by shipboard squeezing and centrifuging techniques and an in situ harpoon sampler the pore waters were analyzed for nutrients carbonate system species mn 2 ca 2 total alkaline earth metals and dissolved oxygen siliceous ooze site only in calcareous sediments the co 2 alkalinity po 4 3 and ca 2 results obtained from shipboard techniques are significantly different than those recovered in situ the other species measured as well as all of the data from the siliceous ooze site reveal no significant dependence on the method used to sample the pore water the relative changes in o 2 no 3 mn 2 alkalinity and co 2 indicate that respiration using o 2 no 3 and mno 2 as electron acceptors is the dominant reaction affecting the pore water species we develop a model which simulates the fate of pore water oxygen and nitrate and particulate organic carbon in sediments this model includes the effects of pore water diffusion oxygen and nitrate respiration sediment accumulation sediment mixing and changes in sediment porosity we observe that factor of 2 variations in the rates of sediment mixing and accumulation have only a minor effect on the pore water profiles the major factor controlling the pore water profiles is the flux of organic carbon across the sediment water interface we conclude that the large intra site variability observed in the interstitial water nitrate profiles is probably caused by small scale variations in the flux of organic material

structures and profiles of novel sulfur linked chlorophyll derivatives in an antarctic lake sediment high performance liquid chromatography mass spectrometry has permitted the identification of a homologous series of novel alkylsulfide derivatives of chlorophyll a containing between one and five carbon atoms in sediment from a coastal antarctic lake the sulfur containing compounds are present in varying abundance in stratigraphic horizons representing a phase when the lake was a marine basin throughout this marine phase photic zone anoxia is recorded by the presence of bacteriochlorophyll c and d derivatives distributional variations between sulfurised and non sulfurised chlorophyll a derivatives throughout the sediment section studied indicate that the extent of sulfurisation is not controlled by chlorophyll a abundance alone

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

210pb derived sediment accumulation and mixing rates for the greater puget sound region abstract recent sediment accumulation rates of 46 1200 mg cm2 yr are calculated from excess 210pb activity profiles in 44 sediment cores from 27 sites in the greater puget sound region rates calculated for nine stations in the deeper waters of central puget sound average 480 mg cm2 yr and are greatest between seattle and tacoma near the southern end of this region the standard error of this mean is 113 mg cm 2 yr magnitudes and geographic trends of 210pb derived accumulation rates agree with limited data on sediment inputs and transport paths their accuracy is further supported by several independent approaches including comparison with particle fluxes collected in year long series of sediment trap deployments at two sites accumulation rates are calculated assuming no mixing beneath surface mixed layers of 2 22 cm sediment mixing coefficients in these surface layers average at least 43 cm2 yr four times greater than those reported in open washington coast sediments the difference is attributed to the greater benthic biomass in puget sound sediments particle residence times in surface mixed layers vary from 1 5 to 68 years and introduce corresponding uncertainties in ages of horizons beneath the mixed layers for most of this region these residence times will cause a 20 30 year time lag in achieving an equivalent response of surface sediment chemical concentrations to changes in concentrations in freshly depositing particles for constituents whose stability and phase associations resemble those of 210pb these time lags limit the ability of sediment chemistry monitoring programs to recognize recent changes in composition and fluxes of chemicals to sediments recent fluxes calculated from the product of surface sediment chemical concentration and accumulation rates will be inaccurate for chemicals if their input concentrations have changed in the last 20 30 years

colonization succession and extinction of marine floras during a glacial cycle a case study from the windmill islands east antarctica using biomarkers with the exception of the diatoms little is known of the extinction colonization and succession of marine floras during glacial cycles here we study both morphological and biochemical fossils in two sediment cores from the antarctic to unravel the sequence of events over a single glacial cycle the cores from the nearshore continental shelf off the windmill islands 66 s 110 e east antarctica span the period from marine isotope stage 3 or earlier to the present new high performance liquid chromatography and mass spectrometry methods were used to study fossil pigments with additional data from siliceous microfossils lithological analyses and radiocarbon dates results show two response processes first there is the large scale impact of the expanding ice sheet in removing the flora from the inner shelf primarily through the denial of light destabilization of the substratum and elimination of habitats second there are a number of glacial climate interactions that have a surprisingly strong influence on recolonization and succession these include sea ice extent and the proximity of the ice edge the annual duration of open water the stabilization of the substratum first by benthic diatoms and later by macrophyte algae and relative sea level a period of warmer climate in the mid holocene had a considerable influence on the composition and species diversity of the marine flora these are the first data on the timing of colonization and succession of marine floras over a glacial cycle based on both morphological and biochemical fossils

origin and significance of 13 2 hydroxychlorophyll derivatives in sediments abstract the authenticity of hydroxychlorophyll derivatives in sediments has been verified by subjecting pure chlorophyll preparations to the extraction method used for sediments model studies of chlorophyll autoxidation reveal hydroxychlorophyll as the major product formed in the presence of hydrogen peroxide its stability to further oxidation implies that hydroxychlorophyll derivatives are not precursors of aetioporphyrins and are more likely to produce cycloalkanoporphyrins via the processes of diagenesis the occurrence of 13 2 hydroxyphaeophytin a throughout a sediment core from loch ness confirms it to be a widespread chlorophyll oxidation product formed during early diagenesis profiles of hydroxychlorophyll derivatives in a sediment core from an antarctic lake demonstrate their potential for use as markers of oxidation processes in palaeoenvironmental assessment

faunal microfossils indicators of holocene ecological change in a saline antarctic lake abstract the sediment record of the fauna of ace lake a saline meromictic lake in the vestfold hills antarctica consists of copepod eggs spermatophores and exoskeletal fragments rotifer and tintinnid loricae and foraminiferal and folliculinid tests the relative abundance of these remains along with other characteristics of the core allows the development of a coherent picture of the progress of ace lake from a species poor freshwater lake early in the holocene to a biodiverse marine basin following a marine transgression subsequent sea level fall reformed ace lake as a saline lake and productivity initially increased after isolation after a major event possibly associated with overturn of the meromictic lake biodiversity and productivity decreased and have continued to do so until the present

identification of bacteriophaeophytin a esterified with geranylgeraniol in an antarctic lake sediment abstract bacteriophaeophytin a with geranylgeraniol as the c 17 3 esterifying alcohol has been identified in a sediment from progress lake east antarctica by using atmospheric pressure chemical ionisation liquid chromatography mass spectrometry this transformation product of bacteriochlorophyll a geranylgeraniol constitutes a biomarker for the presence of purple non sulfur bacteria most likely rhodospirillum rubrum in the lake at the time of sediment deposition

mobility of iron and nickel at low temperatures implications for 60fe 60ni systematics of chondrules from unequilibrated ordinary chondrites abstract the fe and ni isotopic composition of ferromagnesian silicates in chondrules from unequilibrated ordinary chondrites uocs have been used to estimate the initial abundance of the short lived radionuclide 60 fe in the early solar system however these estimates vary widely and there are systematic discrepancies in initial 60 fe 56 fe ratios inferred from in situ and bulk analyses of chondrules a possible explanation is that the fe ni isotope system in uoc chondrules has not remained closed a necessary condition for isotopic dating and fe and ni have been redistributed since the chondrules formed in order to evaluate this we collected high spatial resolution x ray fluorescence xrf maps of uoc chondrules to better understand the distribution and mobility of fe and ni at the low metamorphic temperatures of these chondrites we used synchrotron x ray fluorescence microscopy to map the distribution of fe ni and other elements in portions of 71 chondrules from 8 uocs types 3 00 3 2 the synchrotron xrf maps show clear enrichment of fe and or ni in fractures ranging down to micrometer scale in chondrules from all uocs analyzed for this study regardless of petrologic type and regardless of whether fall or find indicating that there was significant exchange of fe and ni between chondrules and matrix and that the fe ni system was not closed sixty percent of chondrules in semarkona ll3 00 have fe and ni enrichment along fractures while 80 100 of chondrules analyzed from the other uocs show these enrichments mobilization was likely a result of fluid transport of fe and ni during aqueous alteration on the parent body and or during terrestrial weathering in situ and bulk fe ni analyses that incorporate extraneous fe and ni from chondrule fractures will result in lowering the inferred initial 60 fe 56 fe ratios

distributions of pigments in the organic matter of marls from the vena del gesso evaporitic sequence abstract the porphyrins and carotenoids of marl horizons within the messinian evaporitic cycles of the vena del gesso basin show variations in abundance and composition throughout a sequence of ten cycles significant variations are also apparent within individual marl horizons the differences in pigment distribution reflect significant changes in the environmental conditions during sediment deposition the presence of significant amounts of isorenieratene and co occurrence of an alkyl porphyrin with a c 34 skeleton provide evidence for anoxic conditions extending into the photic zone of the palaeo water column variations in the free pigment contents of the marls reflect a regressive trend both during deposition of an individual marl and over the entire sequence

60fe in eucrites additional evidence for the existence in the early solar system of live60fe has been found in the basaltic achondrite juvinas the relative abundance of 60fe 56fe of x0223c 4 10 10 at the time of meteorite solidification is one order of magnitude lower than that previously observed for the eucrite chervony kut this difference corresponds to a 4 7 ma time interval between closure of the60fe 60ni isotopic system in the two meteorites the factor two higher initial 60ni 58ni ratio in juvinas is consistent with this time difference and a common bulk fe ni ratio in the two meteorites using the60fe 60ni isotope system as a chronometer various models for the evolution of the eucrite parent body of different degrees of complexity are discussed regardless of the detailed differences between these models a short time interval of only a few million years between planetary differentiation and basaltic crust formation is indicated

photochemical sulfurization of sedimentary organic matter a widespread process occurring at early diagenesis in natural environments abstract the possibility of light induced formation of sedimentary organo sulfur compounds has been investigated with simulation experiments these experiments using mono and diunsaturated hydrocarbons and reduced sulfur species in particular h 2 s and elemental sulfur were conducted under mild conditions sunlight low temperature likely to occur in the photic zone of anoxic environments these experiments showed an efficient sulphurization of the organic matter under sunlight conditions leading to the formation of organo sulfur compounds such as thiophenes and sulfur cross linked macromolecules very similar to those occurring in sediments deposited in anoxic environments these results show the potential for photochemically induced sulfurization of organic matter in environments with photic zone anoxia such a process would be especially favored in evaporitic environments with a shallow anoxic boundary extending well into the photic zone

the origin of eucrites diogenites and olivine diogenites magma ocean crystallization and shallow magma chamber processes on vesta the asteroid 4 vesta is one of the very few heavenly bodies to have been linked to samples on earth the howardite eucrite diogenite hed meteorite suite this large and diverse suite of meteorites provides a detailed picture of vesta s igneous and postigneous history we have used the range of igneous rock types and compositions in the hed suite to test a series of chemical models for solidification processes following peak melting magma ocean conditions on vesta fractional crystallization cannot have been a dominant early process in the magma ocean because it leads to excessive fe enrichment in the melt models that are dominated by equilibrium crystallization cannot produce orthopyroxene cumulates diogenites our best models invoke 60 70 equilibrium crystallization of a magma ocean followed by continuous extraction of the residual melt into shallow magma chambers fractional crystallization in these magma chambers combined with continuous or periodic addition of more melt from the slowly compacting crystal mush magmatic recharge can produce all of the igneous hed lithologies noncumulate and cumulate eucrites diogenites dunites harzburgites and olivine diogenites magmatic recharge can also explain the narrow range in eucrite compositions and the variability of incompatible trace element concentrations in diogenites we predict an internal structure for vesta that permits excavation of the heds during the formation of the rheasilvia basin while remaining consistent with observations from the dawn mission and most impact models

coastal oceanographic conditions in the prydz bay region east antarctica during the holocene recorded in an isolation basin information on east antarctic coastal environments during the holocene is relatively sparse this is surprising as sedimentary records from the interface between land and sea can provide chronologies of climatic change isostatic uplift relative sea level and the colonization of newly formed biomes here we examine a sediment core from pup lagoon a coastal lake in the larsemann hills east antarctica sediment stratigraphy fossil pigments and diatoms were used to infer the sequence of holocene environmental and climatic change results show that between 5800 and 5500 cal yr bp the marine coast of prydz bay was characterized by stratified open water conditions during spring and summer and seasonally warm conditions from 5500 to 2750 cal yr bp sea ice duration in prydz bay increased with the coast being ice free for 2 3 months each year conditions which are similar to the present day a return to stratified open water conditions and a reduction in winter sea ice extent between 2750 and 2200 cal yr bp is signalled by enhanced biogenic production and more open water diatom taxa this is consistent with evidence for the mid holocene hypsithermal detected in other records in east antarctica isostatic isolation of the pup lagoon basin from the sea between 2200 and 2000 cal yr bp slightly precedes the emergence of lakes with comparable sill heights from the nearby vestfold hills the colonization of pup lagoon after its isolation as a freshwater lake was initiated by a siliceous flora dominated by stomatocysts with microbial mat development being prevented by mechanical or physical stress a brief period of marine incursion following the mid holocene hypsithermal may be related to local events such as iceberg calving or to minor sea level change weighted averaging regression used to infer salinity in the lacustrine zone shows that from 1500 cal yr bp pup lagoon is a freshwater lake where the flora is dominated by stratified cyanobacterial mats with green algae and diatoms as co dominants comparable to modem pup lagoon and other lakes in the larsemann hills

in situ 60fe 60ni systematics of chondrules from unequilibrated ordinary chondrites abstract the initial 60fe 56fe of chondrules from unequilibrated ordinary chondrites uocs can potentially constrain the stellar source of short lived radionuclides and develop the 60fe 60ni t1 2 2 6 ma system for early solar system chronology however progress with the 60fe 60ni system has been hindered by discrepancies between initial ratios inferred from bulk and in situ fe ni analyses telus et al 2016 show that discrepancies between these different techniques stem from late stage open system fe ni mobilization here we report in situ analyses of the fe ni isotopic composition of ferromagnesian silicates in chondrules from uocs using the ion microprobe of the 24 chondrules analyzed for this study a few chondrules have resolved excesses in 60ni of up to 70 however the correlations with fe ni are weak although complications from fe ni redistribution make it difficult to interpret the data we show that the initial 60fe 56fe for uoc chondrules is between 5 10 8 and 3 0 10 7 this is consistent with a late supernova source for 60fe but self enrichment of the molecular cloud is another possible mechanism for incorporating 60fe in the solar system discrepancies between bulk and in situ analyses remain but likely stem from late stage open system fe ni mobilization

azaarenes in puget sound sediments the first quantitative measurements of azaarenes in marine sediments are reported for puget sound in northwestern washington state u s a two to four ring azaarenes in concentrations as low as 50 ppb relative to organic carbon are measured in 210pb dated sediments using glass capillary gas chromatography combined with nitrogen selective detection azaarene distributions are geographically and temporally variable azaarene distributions in upper sediment layers suggest that total azaarene concentrations are related to proximity to urban areas and may be anthropogenically derived subsurface maxima between 6 and 17 cm in several cores resemble similar maxima in pah and organo sulfur compounds trace quantities of azaarenes present in sediments deposited prior to urbanization of the puget sound region suggest low level natural azaarene sources one core containing particulate coal produced a concentrated and complex azaarene mixture suggesting either introduction of mined coal or erosion of regional coal deposits analyses of possible azaarene sources indicate that although azaarene compositions vary between sources coal azaarenes can be distinguished from petroleum azaarenes by their ratios of 2 ring to 3 ring azaarenes and may identify predominant azaarene inputs in environmental samples gross differences in azaarene composition exist between european and american air particulates and sediments suggesting differences in azaarene sources

rapid sulfurisation of highly branched isoprenoid hbi alkenes in sulfidic holocene sediments from ellis fjord antarctica samples of particulate organic matter from the water column and anoxic holocene sediment layers from the small meromictic basin smb in ellis fjord eastern antarctica were analyzed to study the early incorporation of reduced inorganic sulfur species into highly branched isoprenoid hbi alkenes hbis were not detected in the water column samples taken during austral winter whereas compounds containing the c25 hbi skeleton were abundant in all analyzed holocene sediment layers the structure of the c25 2 hbi alkene and its enriched stable carbon isotopic composition suggest that it is produced by a diatom or diatoms probably belonging to the navicula genus in the sea ice which covers the area most of the year within just 500 years of deposition all of the hbi alkene was sulfurised a mixture of products was formed including components tentatively identified as a c25 hbi thiane and three s containing dimers composed of two c25 1 hbi skeletons linked together by a sulfide bond most was however converted to polar s containing compounds the reaction rate for sulfurisation of the c25 2 hbi alkene is the highest observed so far in natural systems sterols and other lipids known to be prone to sulfurisation were not sulfurised the reason for this is unclear

in situ calibration of a sediment trap1 2 a relatively small self contained sediment trap with a timed closing system was deployed in dabob bay washington for 1 year samples were collected representing 326 trap exposure days an in situ calibration was obtained by comparing the capture and retention of unsupported sup 210 pb by the traps with the steady state acccumulation rate of unsupported sup 210 pb in the underlying bottom the efficiency of the traps to collect a representative sample of the sedimenting material is 118

carotenoid diagenesis in recent marine sediments ii degradation of fucoxanthin to loliolide abstract the quantitative distributions of loliolide and the major phytoplankton carotenoids fucoxanthin diadinochrome diatoxanthin and carotene in two cores of anoxic marine sediment recovered from the peru continental shelf are reported our results demonstrate that the rapid degradation of carotenoids in sediments is not a result of their high degree of unsaturation as has been previously suggested instead carotenoids exhibit a wide range of degradation rates that are proportional to the ability of specific pigments to form unstable bicyclic furanoxides carotenoid furanoxides undergo subsequent fragmentation to loliolide isololiolide dihydroactinidiolide and other as yet undetermined low molecular weight products this degradation pathway accounts for the relative rates of removal for specific carotenoids fucoxanthin fucoxanthinol diadinoxanthin diatoxanthin carotene the distribution of carotenoids reported by wpatts and maxwell 1977 and c ardoso et al 1978 in ancient sediments the occurrence of novel carotenoid transformation products in surface sediments reported by r pidout et al 1984 and the distribution of loliolides in recent sediments recovered from the namibian shelf reported by k plok et al 1984a b we predict that loliolide and isololiolide will inherit a specific stereochemistry from their carotenoid precursors but that dihydroactinidiolide will be racemic for every mole of fucoxanthin degraded in peru sediments 0 7 1 1 mole of loliolide is produced summation of fucoxanthin and loliolide at each subsurface horizon yields an estimate of the total deposition of fucoxanthin at t 0 throughout the 0 20 cm depth of our samples this parameter is remarkably constant to 16 individual horizons exhibit excursions which may reflect changes in surface productivity extrapolation of our measurements to deeper sediments may therefore be of some value in deciphering questions on environmental conditions of deposition and paleoproductivity

the mulhouse basin evidence from porphyrin distributions for water column anoxia during deposition of marls abstract marls from the evaporitic mulhouse basin oligocene alsace france contain alkyl porphyrins dominated by nickel complexed species the presence in high relative abundance of a range of components with carbon numbers up to c 37 indicates that anaerobic photosynthetic bacteria made a significant contribution to the photosynthetic community in the palaeoenvironment and in turn that anoxic conditions extended into the photic zone of a stratified water column further evidence is given by the assignment by hplc coinjection with a standard of a c 34 component with the same carbon skeleton as one of the bacteriochlorophylls d of such bacteria significant differences in the nickel and vanadyl porphyrin distributions in one of the samples examined appear to result from changes in the depositional environment which are recorded with a stratigraphic resolution below that sampled or indicate derivation of these two porphyrin pools from different parts of the water column

mixing and cycling of uranium thorium and 210pb in puget sound sediments abstract activity profiles of excess 234 th excess 210 pb 232 th 230 th 234 u and 238 u and 228 232 th ratios determined in eight box cores of sediment from six sites in central puget sound provide new insights into the dynamic nature of solid phase mixing in surface sediments the exchange of 228 ra and other soluble species across the sediment water interface and the cycling of u th and 210 pb in this coastal zone comparison of excess 234 th inventories in sediments with its production rate in the overlying water column indicates a mean residence time of at most 14 days for particles in the central puget sound water column surface sediment horizons with excess 234 th have no excess 228 th which might be used to ascertain sediment accumulation rates over the past decade instead deficiencies of 228 th due to loss of soluble 228 ra from pore water to the overlying water persist to 20 30 cm revealing that exchange of soluble chemicals between pore and overlying waters reaches these depths in the extensively bioturbated sediments of puget sound solid phase u isotope concentrations tend to increase by up to a factor of two with depth in sediments as a result of dissolved u being biologically pumped down into sediments where it is partially removed when conditions become mildly reducing 232 th and 230 th activities and 230 232 th ratios are constant with depth in sediments indicating constant detrital phase compositions and essentially no authigenic 230 th steady state 210 pb depositional activities in and fluxes to puget sound sediments average only about onehalf those for sediments of the open washington coast north of the columbia river mouth primarily because of a much lower supply of dissolved 210 pb in sea waters adverting into puget sound excess 234 th profiles in sediments reveal much more detail about the depth dependency dynamic nature and recent history of solid phase mixing processes than excess 210 pb profiles at least six of eight 234 th profiles show that mixing within the 210 pb defined surface mixed layer is depth dependent in three profiles 234 th derived mixing rates are fastest several centimeters below the sediment water interface indicating greater macro benthic activity at these depths depth dependent mixing coefficients derived from the best fit of a four layer advection diffusion decay model to the 234 th data are consistent with 210 pb profiles determined for the same sediments strongly suggesting that 234 th and 210 pb are mixed equivalently and in a multilayered manner

abundance distribution and origin of 60fe in the solar protoplanetary disk abstract meteorites contain relict decay products of short lived radionuclides that were present in the protoplanetary disk when asteroids and planets formed several studies reported a high abundance of 60fe t1 2 2 62 0 04 myr in chondrites 60fe 56fe 6 10 7 suggesting that planetary materials incorporated fresh products of stellar nucleosynthesis ejected by one or several massive stars that exploded in the vicinity of the newborn sun we measured 58fe 54fe and 60ni 58ni isotope ratios in whole rocks and constituents of differentiated achondrites ureilites aubrites heds and angrites unequilibrated ordinary chondrites semarkona ll3 0 and nwa 5717 ungrouped petrologic type 3 05 metal rich carbonaceous chondrite gujba cba and several other meteorites cv el h ll chondrites iiiab iva ivb iron meteorites we derive from these measurements a much lower initial 60fe 56fe ratio of 11 5 2 6 10 9 and conclude that 60fe was homogeneously distributed among planetary bodies this low ratio is consistent with derivation of 60fe from galactic background 60fe 56fe 2 8 10 7 in the interstellar medium from ray observations and can be reconciled with high 26al 27al 5 10 5 in chondrites if solar material was contaminated through winds by outer layers of one or several massive stars e g a wolf rayet star rich in 26al and poor in 60fe we present the first chronological application of the 60fe 60ni decay system to establish the time of core formation on vesta at 3 7 1 7 2 5 myr after condensation of calcium aluminum rich inclusions cais

nickel and chromium isotopes in allende inclusions high precision nickel and chromium isotopic measurements have been carried out on nine allende inclusions 62ni 64ni excesses are present in at least three of the samples the magnitudes of the excesses are about 3 e units 1 e unit 1 part in 10 000 for64ni and about 1 e unit for62ni chromium isotopes measured for some of the same samples show general excesses on54cr of about 7 e units while small deficits are observed for53cr considering these isotope anomalies except those for53cr together with the excesses present in the samples of other neutron rich isotopes of the iron group elements the most likely mechanism responsible for these anomalies is a neutron rich statistical equilibrium process in addition there is an indication of elevated60ni in almost every inclusion measured however for alk 111 this excess was clearly resolved by our experimental technique this effect may be related to the decay of now extinct60fe but the present data are not sufficient to clearly demonstrate its existence in the early solar system an upper limit of 1 6 10 6 can be calculated for60fe 56fe at the time these allende inclusions crystallized

nickel isotope heterogeneity in the early solar system article i nfo ni of bulk iron and chondritic meteorites carbonaceous chondrites have variable positive e 62 ni 0 05 to 0 25 whereas ordinary chondrites have negative e 62 ni 0 04 to 0 09 the ni isotope compositions of iron meteorites overlap with those of chondrites and define an array with negative slope in the e 60 ni versus e 62 ni diagram the ni isotope compositions of the volatile depleted group ivb irons are similar to those of the refractory co cv carbonaceous chondrites whereas the other common magmatic iron groups have ni isotope compositions similar to ordinary chondrites only enstatite chondrites have identical ni isotope compositions to earth and so appear to represent the most appropriate terrestrial building material differences in e 62 ni reflect distinct nucleosynthetic components in precursor solids that have been variably mixed but some of the e 60 ni variability could reflect a radiogenic component from the decay of 60 fe comparison of the e 60 ni of iron and chondritic meteorites with the same e 62 ni allows us to place upper limits on the 60 fe 56 fe of planetesimals during core segregation we estimate that carbonaceous