Stable Isotope

Within the eastern Himalayan syntaxis, carbonatite-like dykes occur in granulite facies gneisses of the Greater Himalayan Crystallines. Most dykes are dolomitic and are associated with scapolite-bearing hornblendite and glimmerite, which are separated from the country rocks by a selvage of altered rocks containing minerals such as diopside, tremolite, K-feldspar, albite, and calcite. Only a few dykes are calcitic with alteration halos containing wollastonite, calcite, anorthite, diopside, and scapolite. Dolomitic dykes as wide as several tens of metres contain irregular xenoliths of granulitic gneiss.

Molecular and isotopic studies of archaeological organic remains, based on identification of biomarker, allow their characterisation. Using a rigorous fractionation scheme of organic extracts and mass spectrometric techniques (GCeMS, LCeMS, GC-C-IRMS), this is likely to provide information on the nature of substances, their production technique, their alteration state and, more generally, on their history. The results of the analysis from two series of samples are reported in this paper: dammar resins (Thailand, 4th B.C.e2nd B.C., pure materials) and an organic deposit on Osiris statuettes (Pharaonic Egypt, mixture of animal fat, bitumen, vegetal resin, beeswax). To cite this article: A. Charrie´-Duhaut et al., C. R. Chimie 12 2009.

1] Tracer buoyancy has been shown to influence breakthrough from two-well tracer experiments conducted in porous media. Two-well tracer experiments are presented from fractured crystalline bedrock, in which the specific gravity of the tracer injectate varied from 1.0002 to 1.0133. Under the forced hydraulic conditions imposed, no difference in breakthrough was noted for the three experiments. These results show that even relatively dense tracer injectate solutions may have an insignificant effect on breakthrough when imposed gradients are sufficiently large.

INTRODUCTION 1.1. Scope of the study 1.1.1. Hypothesis 1.1.2. Objectives 1.2. Structure of Dissertation 1.3 References CHAPTER TWO: PALEOENVIRONMENTAL RECONSTRUCTION OF THE ASBOLE FAUNA USING STABLE ISOTOPES, BUSIDIMA FORMATION, AFAR, ETHIOPIA 2.1. Introduction 2.2. Controls on the isotopic composition of tooth enamel 2.1.1. Carbon Isotope 2.1.2. Oxygen Isotope 2.3. Geological context of the Asbole Fauna 2.4. Methods 2.5. Carbon isotope, results and interpretation 15 2.5.1. Rhinocerotidae 2.5.2. Elephantidae 2.5.3. Equidae 2.5.4. Suidae 2.5.5. Giraffidae 2.5.6. Hippopotamidae 2.5.7. Bovidae 2.6. Paleoenvironmental interpretations based on faunal abundance 2.7. Faunal-abundance-weighted δ 13 C ecosystem value 2.8. Oxygen isotopic composition of tooth enamel 2.8.1. Observed δ 18 O enamel values 30 2.8.2. Estimating paleo-aridity using δ 18 O enamel 2.9. Conclusions 2.10. References ii CHAPTER THREE: DIETARY AND PALEOENVIRONMENTAL RECONSTRUCTION USING STABLE ISOTOPES OF HERBIVORE TOOTH ENAMEL FROM MIDDLE PLIOCENE DIKIKA, ETHIOPIA: IMPLICATION FOR AUSTRALOPITHECUS AFARENSIS HABITAT AND FOOD RESOURCES 45 3.1. Introduction 3.2. Background 3.3. Geological context 3.4. Methods 3.4.1. Sample collection 3.4.2. Sample treatment and isotopic analysis 3.5. Interpretation of carbon and oxygen isotopes 3.6. Results 3.6.1. Carbon isotopic composition by taxa 52 3

The 'British Caledonian Granites' (BCG) comprise a compositionally diverse group of intrusive rocks ranging from diorite to leucogranite, which were emplaced across the British Isles in and adjacent to the Caledonian metamorphic belt during the Early Paleozoic. Although the largest volume of Caledonian magmatic activity in Britain postdates the polyphase deformation and metamorphism of the Grampian orogeny, a small number of plutons were emplaced prior to the main orogenic event and another group are essentially contemporaneous with it. 0-isotope ratios for the BCG are extremely variable and essentially overlap the full range of 0-isotope variations documented for orogenic granitoids. The margins of two plutonic complexes have been affected by subsolidus hydrothermal exchange with meteoric fluids. For the older (>4.40 Ma) BCG plutons 6180 6.6-12.1%~and ÔD =-83 to-45%~, whereas for the younger (c. 400 Ma) plutons 6 18O = 7.l-l2.4%e and ÔD =-97 to-44%~.There is a general positive correlation between 0-and Sr-isotope variations in the post-tectonic granitoids which is absent in their pre-tectomc counterparts. Caledonian plutonic rocks occur in East Greenland in the southern half of the fold belt between 70-75°N. The earliest intrusions are sheets of monzonite and granodiorite emplaced slightly before the climax of Caledonian orogenic activity. Subsequently, a suite of post-tectonic granites was emplaced c. 450-370 Ma. Two of the East Greenland plutons have been affected by post-emplacement meteoric-hydrothermal alteration. The 6180 range for the unaltered East Greenland plutons is 8.5-13.9%~.

The peculiar mixing processes at the pycnocline and deep regions of the Black Sea are reviewed. In addition to the wind stirring and convective mixing, active in the upper pycnocline, the other important mechanism that results in limited ventilation of the anoxic waters of the Black Sea is the Mediterranean dense water inflow from the Bosphorus, modified by the entrainment of surface and intermediate waters, introduced into the interior through double-diffusive intrusions. This inflow, aided by the surface Ekman flux divergence, boundary processes and internal wave breaking, is the main mechanism for the mixing and renewal of the sub-pycnocline waters in the Black Sea interior. A review of these mixing processes is complemented by results from isotope measurements with improved accuracy and reduced noise compared to earlier experiments. Measurements of the stable isotopes oxygen-18 ( 18 O) and deuterium ( 2 H) confirm the origin of the water masses in the Black Sea and in the Turkish Straits, including the sea of Marmara, to be a continuous mixture with variable fractions of salty Mediterranean waters with inflowing fresh waters. Tritium ( 3 H) measurements confirm very little penetration of the transient signal to the sub-pycnocline and deep waters of the Black Sea, in comparison to the better ventilated Mediterranean waters filling the lower layer of the Marmara Sea. The comparison of stable and transient tracer isotopes shows the effects of fresh waters originating from the north-western shelf, and the difference between the renewal mechanisms of the Marmara and Black seas, as well as those between the upper and lower pycnocline of the Black Sea.

Understanding the response of soil carbon (C) dynamics to higher atmospheric CO 2 concentrations is critical for evaluating the potential for soil C sequestration on time scales of decades to centuries. Here, we report on changes in soil respiration under Free-Air CO 2 Enrichment (FACE) where spring wheat was grown in an open field at two CO 2 concentrations (ambient and ambient+200 µmol mol -1 ), under natural meteorological conditions. FACE increased soil respiration rates by 40-70% during the peak of wheat growth. On the FACE plots, stable C isotopic composition of soil CO 2 was used to partition the soil CO 2 flux into C from rhizosphere respiration and decomposition of pre-existing C. Decomposition contributed 100% of the soil CO 2 flux before crop growth commenced, and only 35-45% of the flux at the peak of the growing season. Decomposition rates were not correlated with soil temperature, but rhizosphere respiration rates were strongly correlated with green leaf area index.

The trophic position and the predator–prey relationship between the sperm whale Physeter macrocephalus and the jumbo squid Dosidicus gigas were examined by measuring stable isotope ratios of carbon and nitrogen. Skin samples of sperm whales and muscle samples of small and large jumbo squid were collected between 1996 and 1999 in the Gulf of California. Gender determination through molecular analysis and field identification of size were used to identify adult male, female and immature male sperm whales. The stable isotope ratios of C and N of females and immature males were significantly different from those of adult male sperm whales; however, between females and immature males they did not differ significantly. The δ13C and δ15N values of females and immature males were higher than large jumbo squid by 1.1‰ and 2.7‰ respectively, suggesting a predator–prey relationship between them. A low isotopic interannual variation among the years 1997 to 1999 was observed in the isotopic sign...

Stable isotope analyses are widely used to determine trophic levels in ecological studies. We have investigated the effects of carbonate removal via acidification on the stable carbon and nitrogen isotopic composition of 33 species of tropical benthic macrofauna, and we report guidelines for standardizing this procedure for higher taxa in tropical coral reef ecosystems. Many tropical benthic invertebrates are small in size, and therefore body tissue isolation (separating organic carbon from inorganic structures) is difficult and time-consuming. Literature reviews of invertebrate studies show a lack of consistent procedures and guidelines for preparation techniques, especially for carbonate removal via acidification of whole individuals. We find that acidification decreases the δ13C values of samples containing carbonate, with shifts ranging from 0.21 to 3.20‰, which can be related to CaCO3 content (assessed by a carbonate proxy), justifying acid pre-treatment. Carbonate-containing taxa benefiting from acidification included Amphinomida, Terebellida (Annelida), Anomura, Brachyura, Caridea, Amphipoda, Tanaidacea (Arthropoda) and Edwardsiida (Cnidaria). The δ13C shifts of samples containing no carbonate varied up to 0.02 ± 0.20‰. As this induced δ13C shift was lower than the range of an average trophic level shift (0.5 to 1‰), we conclude that acid pre-treatment is unnecessary. Carbonate-free taxa consisted of Eunicida, Phyllodocida (Annelida) and Mollusca. We note minimal impact of acidification on δ15N values except for Brachyura, which showed a shift of 0.83 ± 0.46‰, which is still lower than a single trophic level shift (2.9–3.8‰). We conclude that for trophic level studies, both the δ13C and the δ15N of carbonate-rich macrofauna can be determined from the same acidified sample. Copyright © 2008 John Wiley & Sons, Ltd.

With four decades of data on a population of bottlenose dolphins (Tursiops truncatus) resident to Sarasota Bay (SB), The Sarasota Dolphin Research Program offers an unparalleled platform for ground-truthing stable isotope data and exploring bottlenose dolphin ecology in a natural setting. We explored carbon isotope value fidelity to habitat utilization by comparing delta13C data from whole teeth and muscle to

Human adults are shown to be capable of conversion of linoleic acid (LA, 18:2 n-6) to arachidonic acid (AA, 20:4 n-6) in vivo. It is confirmed that they can also convert alpha-linolenic acid (LNA, 18:3 n-3) to eicosapentaenoic acid (EPA, 20:5 n-3) and to docosahexaenoic acid (DHA, 22:6 n-3) in vivo. The time course and the maximal response for these processes during the first week after a single dose of the 18-carbon precursor is described. A stable-isotope method in which the protons of the Cl 7 and Cl 8 carbons are substituted with deuterium atoms is used in order to provide for a safe method for the study of human metabolism. High sensitivity and selectivity of detection is assured with negative ion, gas chromatography/mass spectrometry analysis. It is clear that human adults on an ad lib diet carry out EFA metabolism in vivo.

We investigated the effect of the fungal toxin sterigmatocystin on the fitness and stable isotope fractionation of two Collembola species (Folsomia candida and Heteromurus nitidus) feeding on mixed vs. single diets. Four knock out mutants of Aspergillus nidulans with the sterigmatocystin production blocked at different steps along the biosynthetic pathway were combined in mixed diets with either the high quality fungus Cladosporium cladosporioides or the low quality fungus A. nidulans (wildtype). Using fungi labeled with stable isotopes ( 13 C and 15 N) we evaluated the incorporation of carbon and nitrogen from individual fungi. We hypothesised that (i) Collembola fitness decreases with the putative toxicity of the fungi (ii) Collembola benefit from ingestion of mixed diets due to toxin dilution and (iii) fractionation of 13 C and 15 N is more pronounced in more toxic diets. Mixed diets did not uniformly improve fitness. Toxin dilution, however, played an important role in Collembola fitness. The fractionation of 13 C and 15 N varied with sterigmatocystin mutant strains, and Collembola species often differed from the expected enrichment per trophic level. The results show that fungal toxin production may affect stable isotope fractionation, presumably by altering consumer excretion rates necessary for detoxification.

The reaction of an equimolar mixture of H2 and CO was studied over ZrOr at 350 to 45O"C, 35 atm total pressure, and varying residence times. The isosynthesis reaction mechanisms were studied by monitoring the incorporation of oxygenated compounds into the isosynthesis products. Propionaldehyde and [t3C]acetone, [i3C]isopropanol, and [W]methanol were added to the CO/Hz reactant stream. Their effect on the isosynthesis product distributions and on the isotopic distribution of the products was monitored as a function of oxygenate feed rate. Propionaldehyde, acetone, and methanol were found to incorporate into the isosynthesis products. The isotopic distribution of the products was used to support an isosynthesis reaction scheme that involves CO insertion into a bound aldehyde or ketone as the major chain growth step and a second chain growth step that involves condensation between methoxide and a surface bound enolate. Q 1988 Academic press, IK.

A sensitive and accurate stable isotope dilution GC/MS assay was developed and validated for the quantification of succinylacetone (SA) in plasma and amniotic fluid (AF). SA is pathognonomic for tyrosinemia type I, a genetic disorder caused by a reduced activity of fumarylacetoacetate hydrolase (FAH). In untreated patients, SA can easily be measured in plasma and urine because the expected concentrations are in the mol/L range. Due to a founder effect, the province of Quebec has an unusually high prevalence of tyrosinemia type I, hence, the quantification of SA in AF or plasma of treated patients in the nmol/L range becomes very useful. The method utilizes 13 C5-SA as an internal standard and a three-step sample treatment consisting of oximation, solvent extraction and TMCS derivatization. The assay was validated by recording the ion intensities of m/z 620 for SA and m/z 625 for ISTD in order to demonstrate the precision of measurements, the linearity of the method, limit of quantification and detection (LOQ and LOD), specificity, accuracy, as well as metabolite stability. Values for the intra-day assays ranged from 0.2 to 3.2% while values for the inter-day assays ranged from 1.9 to 5.6% confirming that the method has good precision. A calibration plot using SA detected by GC/MS gave excellent linearity with a correlation coefficient of 0.999 over the injected concentration range of 5-2000 nmol/L. LOQ and LOD were 3 and 1 nmol/L, respectively. The usefulness of this method was demonstrated by SA quantification in an AF sample of an affected fetus and in plasma of patients treated with NTBC. The results demonstrate that this novel GC/MS method may be a valuable tool for metabolic evaluation and clinical use.

The long-lived (about 20 yr) bryozoan Adeonellopsis sp. from Doubtful Sound, New Zealand, precipitates aragonite in isotopic equilibrium with seawater, exerting no metabolic or kinetic effects. Oxygen isotope ratios (y 18 O) in 61 subsamples (along three branches of a single unaltered colony) range from À0.09 to +0.68xPDB (mean = +0.36xPDB). Carbon isotope ratios (y 13 C) range from +0.84 to +2.18x PDB (mean = +1.69xPDB). Typical of cool-water carbonates, y 18 O-derived water temperatures range from 14.2 to 17.5 jC. Adeonellopsis has a minimum temperature growth threshold of 14 jC, recording only a partial record of environmental variation. By correlating seawater temperatures derived from y 18 O with the Southern Oscillation Index, however, we were able to detect major events such as the 1983 El Niño. Interannual climatic variation can be recorded in skeletal carbonate isotopes. The range of within-colony isotopic variability found in this study (0.77xin y 18 O and 1.34 in y 13 C) means that among-colony variation must be treated cautiously. Temperate bryozoan isotopes have been tested in less than 2% of described extant species -this highly variable phylum is not yet fully understood.

An analytical method for the measurement of five naturally occurring bromophenols of sensory relevance in seafood (barramundi and prawns) is presented. The method combines simultaneous distillation-extraction followed by alkaline back extraction of a hexane extract and subsequent acetylation of the bromophenols. Analysis of the bromophenol acetates was accomplished by headspace solid phase microextraction and gas chromatography-mass spectrometry using selected ion monitoring. The addition of 13 C 6 bromophenol stable isotope internal standards for each of the five congeners studied permitted the accurate quantitation of 2-bromophenol, 4-bromophenol, 2,6dibromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol down to a limit of quantification of 0.05 ng/g of fish flesh. The method indicated acceptable precision and repeatability and excellent linearity over the typical concentration range of these compounds in seafood (0.5-50 ng/g). The analytical method was applied to determine the concentration of bromophenols in a range of farmed and wild barramundi and prawns and was also used to monitor bromophenol uptake in a pilot feeding trial.

A reliable and specific method was developed for the determination of the cytotoxic drugs cyclophosphamide and ifosfamide in sewage effluent. The most successful combination was found to be Strata-X solid-phase extraction followed by Florisil ® clean-up with analysis by liquid chromatography-tandem mass spectrometry. Quantification by internal standardisation was achieved using custom synthesised d4-cyclophophosphamide. The mass spectrometer was operated in highly selective reaction monitoring (HSRM) mode, which significantly reduced matrix noise and improved sensitivity. Although it suffered from some ionisation suppression, electrospray ionisation (ESI) was found to give an order of magnitude better sensitivity in terms of limit of detection than atmospheric pressure chemical ionisation (APCI). Using final effluent from two different sewage treatment plants, the method was validated following official European guidelines and shown to be a high performance tool for routine analysis at the sub-nanogram per litre level. Depending on the matrix, the limit of detection for cyclophosphamide was between 0.03 ng/L and 0.12 ng/L and for ifosfamide between 0.05 ng/L and 0.09 ng/L. For cyclophosphamide the accuracy and precision, tested at 1.7 ng/L, were 98-109% and ≤13%, CV respectively. For ifosfamide the accuracy and precision, tested at 1.1 ng/L, were 98-113% and ≤15% CV, respectively. Depending on the sample matrix the absolute recovery of the internal standard was between 57% and 70%. The method was tested by analysis of spot samples taken from the final effluent discharges of two sewage treatment plants; the first using a conventional trickling filter treatment process and second employing activated sludge followed by ultra violet treatment.

A series of six ancient connected lakes occupied the broad plain of the closed Basin of Mexico. This study pertains to two of these lakes. 18 O, 2 H and chemical patterns in the pore water of the broad aquitard formed from sediment in these lakes indicate that the origin of this paleo-lake water was local meteoric water, which entered the ancient lakes as runoff, and groundwater from springs. Evaporation of surface water in the former Chalco Lake caused concentration of dissolved salts and enrichment in the heavy isotopes 18 O and 2 H. During high water periods, the south easternmost ancient Lake Chalco fed partially evaporated water to the closed Lake Texcoco, the lowest of the lakes, where further evaporation occurred causing higher concentration of salts and enrichment of heavy isotopes. These major ions and stable isotopes follow the evaporation trends characteristic of closed or nearly closed evaporatic basins elsewhere in the world. Paleo-lake evaporation lines in Lakes Chalco and Texcoco originated from the same starting water and developed as a consequence of the topographic position of the former lakes and local climatological conditions. A modern evaporation line developed after the drainage of the lakes, reflecting evaporation of modern infiltrating meteoric water. The presence of brackish pore water in most of the Chalco aquitard, which has a maximum thickness of 300 m, indicates that upward vertical groundwater flow has not been capable of displacing the paleo-lake water. This suggests that vertical advection was not significant throughout the hundreds of thousands of years of existence of the aquitard sediments. One-dimensional numerical simulations of the deeper part of the 18 O profile representing the thicker part of the aquitard sediments, 140 m, showed that this profile was developed by molecular diffusion with a small upward advective flux, where apparently the Chalco aquitard always had enriched brackish water overlying the fresh water aquifer.

ORIGINAL ARTICLE Groundwater salinization processes in shallow coastal aquifer of Djeffara plain of Medenine, Southeastern Tunisia Rim Trabelsi • Kamel Abid • Kamel Zouari • Houcine Yahyaoui Received: 3 March 2010 / Accepted: 23 July 2011 Ó Springer-Verlag 2011 ...

Zeekoevlei is the largest freshwater lake in
South Africa and has a century-long history of
anthropogenic impact that caused hyper-eutrophic
conditions. We used biomarkers (alkanes and pigments),
stable isotopes (d13C and d15N), rates of
primary palaeoproduction and total inorganic carbon
(TIC) accumulation rates in the lake sediments to
investigate changes in plankton and macrophyte
communities in response to anthropogenic activities
in this shallow lake. Specific alkanes and pigment
(chlorophyll a, b,b-carotene, echinenone, fucoxanthin
and zeaxanthin) concentrations in lake waters indicated
the present-day hyper-eutrophic condition and
seasonal fluctuations of cyanobacteria, zooplankton
and diatom populations. Eutrophic conditions were
initiated in the lake with the start of recreational
activities and construction of a sewage treatment plant
in the early 1920s. The lake transformed from a
eutrophic to a hyper-eutrophic waterbody following
damming, pondweed eradication and accelerated
catchment-derived nutrient input. The change in lake
trophic state was recorded by a sharp decline in the
terrestrial to aquatic ratio (TAR) of specific n-alkanes,
low carbon preference index (CPI) and increased d13C
values in the sediment core. In addition, the aquatic
macrophyte n-alkane proxy (Paq) values (1) indicated
a slow takeover by floating macrophytes after
the eradication of submerged pondweeds in 1951.
Elevated n-alkane, total alkane and pigment
(chlorophyll a, b,b-carotene, zeaxanthin and
zeaxanthin to b,b-carotene ratio) concentrations, low
d15N values and low TIC accumulation rates in the
upper middle section of the core indicated the
beginning of intense cyanobacterial blooms after the
dredging in 1983. Although the cyanobacterial population
has decreased in recent years, hyper-eutrophic
conditions are reflected by low CPI<0.04 and TAR<1
values at the top of the sediment core.

Fluid inclusions have been studied in minerals infilling fissures (quartz, calcite, fluorite, anhydrite) hosted by Carboniferous and Permian strata from wells in the central and eastern part of the North German Basin in order to decipher the fluid and gas migration related to basin tectonics. The microthermometric data and the results of laser Raman spectroscopy reveal compelling evidence for multiple events of fluid migration. The fluid systems evolved from a H 2 O-NaCl±KCl type during early stage of basin subsidence to a H 2 O-NaCl-CaCl 2 type during further burial. Locally, fluid inclusions are enriched in K, Cs, Li, B, Rb and other cations indicating intensive fluid-rock interaction of the saline brines with Lower Permian volcanic rocks or sediments. Fluid migration through Carboniferous sediments was often accompanied by the migration of gases. Aqueous fluid inclusions in quartz from fissures in Carboniferous sedimentary rocks are commonly associated with co-genetically trapped CH 4 -CO 2 inclusions. P-T conditions estimated, via isochore construction, yield pressure conditions between 620 and 1,650 bar and temperatures between 170 and 300°C during fluid entrapment. The migration of CH 4 -rich gases within the Carboniferous rocks can be related to the main stage of basin subsidence and stages of basin uplift. A different situation is recorded in fluid inclusions in fissure minerals hosted by Permian sandstones and carbonates: aqueous fluid inclusions in calcite, quartz, fluorite and anhydrite are always H 2 O-NaCl-CaCl 2 -rich and show homogenization temperatures between 120 and 180°C. Co-genetically trapped gas inclusions are generally less frequent. When present, they show variable N 2 -CH 4 compositions but contain no CO 2 . P-T reconstructions indicate low-pressure conditions during fluid entrapment, always below 500 bar. The entrapment of N 2 -CH 4 inclusions seems to be related to phases of tectonic uplift during the Upper Cretaceous. A potential source for nitrogen in the inclusions and reservoirs is C org -rich Carboniferous shales with high nitrogen content. Intensive interaction of brines with Carboniferous or even older shales is proposed from fluid inclusion data (enrichment in Li, Ba, Pb, Zn, Mg) and sulfur isotopic compositions of abundant anhydrite from fissures. The mainly light d 34 S values of the fissure anhydrites suggest that sulfate is either derived through oxidation and redeposition of biogenic sulfur or through mixing of SO 4 2À -rich formation waters with variable amounts of dissolved biogenic sulfide. An igneous source for nitrogen seems to be unlikely since these rocks have low total nitrogen content and, furthermore, even extremely altered volcanic rocks from the study area do not show a decrease in total nitrogen content.

This paper reports the results of the first dynamic labeling experiment with regenerating spines of sea urchins Paracentrotus lividus using the stable isotope 26Mg and NanoSIMS high-resolution isotopic imaging, which provide a direct information about the growth process. Growing spines were labeled twice (for 72 and 24 h, respectively) by increasing the abundance of 26Mg in seawater. The incorporation of 26Mg into the growing spines was subsequently imaged with the NanoSIMS ion microprobe. Stereom trabeculae initially grow as conical micro-spines, which form within less than 1 day. These micro-spines fuse together by lateral outgrowths and form a thin, open meshwork (inner stereom), which is subsequently reinforced by addition of layered thickening deposits (outer stereom). The (longitudinal) growth rate of the inner stereom is ca. 125 μm/day. A single (ca. 1 μm) thickening layer in the stereom trabeculae is deposited during 24 h. The thickening process is contemporaneous with the formation micro-spines and involves both longitudinal trabeculae and transverse bridges to a similar degree. Furthermore, the skeleton-forming cells remain active in the previously formed open stereom for at least 10 days, and do not migrate upwards until the end of the thickening process. The experimental capability presented here provides a new way to obtain detailed information about the skeleton formation of a multitude of marine, calcite producing organisms.

A two-dimensional biomarker approach, using stable isotopes (␦ 13 C, ␦ 15 N) and fatty acids, was used to evaluate differences both amongst and within benthic primary producer types (seagrass, fleshy red algae, calcareous red algae, brown algae, and seagrass periphyton) that are typical of the nearshore, temperate Australian region. The primary source of variance (as examined by permutational ANOVA) for all biomarkers examined was amongst primary producer types, as opposed to amongst species within type. ␦ 13 C showed a clear separation (Monte Carlo p < 0.05) between seagrass (range of means = −10.1 to −14.0‰) and macroalgae (−14.6 to −25.2‰), but could not differentiate amongst the algal types examined. Similarly, distinct ␦ 15 N signatures (p < 0.05) were found only for seagrass (range of means = 3.6-4.1‰) versus calcareous red algae (4.6-5.5‰), with all other types overlapping in their mean ␦ 15 N values. In contrast, multivariate analysis of fatty acid data (using Canonical Analysis of Principal coordinates; CAP) distinguished not only between seagrass and macroalgae, but also between red and brown algae (and to a limited extent between the calcareous and fleshy red algal types). The principal unsaturated fatty acids in the samples were C 20 polyunsaturates (found primarily in the macroalgae and periphyton), and C 18 mono-and polyunsaturates, with high proportions of 18:2n-6 and 18:3n-3 typical of the seagrasses. The C 18 monounsaturate 18:1n-7 was one of the most diagnostic compounds for the red algae examined, being present in very low amounts in seagrass and virtually absent in the brown algae. Conversely, brown algae were high in 18:4n-3, with 20:4n-3 particularly diagnostic of the kelp Ecklonia radiata. In contrast to stable isotopes, fatty acids helped distinguish different algal groups, thereby providing support that a two-dimensional approach using stable isotopes and fatty acids is likely to provide the most useful tool to distinguish primary producers in food web structure.

To examine the applicability of C/N and organic carbon stable isotope (δ 13 C) in studies of the Holocene sea level and freshwater discharge in the large river mouth of Yangtze, we observed the distribution of carbon, nitrogen and δ 13 C in a late-Quaternary core (ZK9) collected from the present subaqueous delta. We also collected published data of the two proxies for the suspended particulate matter (SPM) and surficial sediments from the lower Yangtze River to the adjacent East China Sea. The results show that the estuarine front is an important boundary for terrestrial and marine contribution of the organic component in the modern sedimentary environment. In the core ZK9, sediments deposited during c. 13-9 cal. ka BP are characterized by high values of TOC (0.54-1.16%), CaCO 3 (0.35% on average), and C/N (>12), which reflect an inner tidal estuarine environment dominated by C3 terrestrial organic carbon input. During c. 9-0.7 cal. ka BP, both TOC content (0.57% on average) and C/N ratio (<10) decrease remarkably while TN increases, indicating a lower estuarine or shallow marine environment. An abrupt sea level rise from c. 9 cal. ka BP resulted in a deeper water environment and reduced terrestrial input at the core location. The low δ 13 C values (−24.23‰ on average) before c. 6 cal. ka BP reflect a dominantly terrestrial source of organic matter associated with increased freshwater discharge into the estuary during that time. The sediments since c. 6 cal. ka BP are characterized by increasing δ 13 C up to −24.1 to −23.39‰, reflecting more contribution from marine algae as freshwater discharge fell. We suggest that in the Yangtze River mouth the C/N ratio indicates an abrupt sea level rise at c. 9 cal. ka BP, while δ 13 C is more useful in reflecting freshwater discharge.

The Platreef is the main platinum-group element (PGE)-bearing horizon in the northern limb of the Bushveld Complex, South Africa. It is considered to be richer in sulphides than other similar horizons within the Bushveld Complex, in particular the Merensky Reef. Previous work has indicated that assimilation of dolomite may be a mechanism to add sulphur to the magma from which the Platreef formed. Sulphur isotope data presented in this study indicates an additional sulphur source contributing to the Platreef. In the southern Platreef, the Duitschland Formation of the Transvaal Supergroup forms part of the direct footwall. Within this sequence are pyrite-rich shales, which we suggest contributed to the sulphur budget of the Platreef. Local variations in sulphur isotopes, as well as a decrease in crustal sulphur in the Platreef further away from the footwall, also indicate local rather than regional contamination processes. Platreef samples have δ 18 O values that are higher than expected in a mantle-derived magma, but there is no apparent systematic variation in δ 18 O with distance from the footwall. This may possibly indicate contamination of the Bushveld magma pre-intrusion, probably in a staging chamber. However, when compared to data from the central sector of the Platreef itself, analysis from this study have lower δ 18 O values indicating changes in the degree of contamination with varying footwall lithology. Also, differences between plagioclase and pyroxene δ 18 O values indicate exchange with fluids. It is possible that late-stage deuteric fluids may have caused this exchange.

The Late Cretaceous Grassy Lake and Cedar Lake amber deposits of western Canada are among North America’s most famous amber-producing localities. Although it has been suggested for over a century that Cedar Lake amber from western Manitoba may be a secondary deposit having originated from strata in Alberta, this hypothesis has not been tested explicitly using geochemical fingerprinting coupled to comparative analyses of arthropod faunal content. Although there are many amber-containing horizons associated with Cretaceous coals throughout Alberta, most are thermally mature and brittle, thus lacking the resilience to survive long distance transport while preserving intact biotic inclusions. One of the few exceptions is the amber found in situ at Grassy Lake. We present a suite of new analyses from these and other Late Cretaceous ambers from western Canada, including stable isotopes (H and C), Fourier transform infrared (FTIR) spectra, and an updated faunal compendium for the Grassy an...

Leaf-cutting ants (Atta spp.) are known for their extensive defoliation in neo-tropical forests and savannahs. Debate about the costs and benefits of their activities has been largely dominated by their detrimental effects on agriculture and agroforestry. However, the large accumulation of nutrients and changes in soil properties near their nests might benefit plants growing near them. Here, we test whether trees use nutrients that accumulate in debris piles near, or refuse chambers within, leaf-cutting ant nests. At two tropical sites (a moist tropical forest site in Panama and a savannah site in Brazil), we fed leaves labelled with the stable isotope 15N to two species of leaf-cutting ants (Atta colombica and Atta laevigata) and traced the stable isotope label in plants surrounding the two nests. Thus, we show that plants in both sites access resources associated with Atta nests. In addition, leaf tissue of trees near the nests labelled with 15N had significantly higher calcium co...

Spatial and temporal variability of the stable isotope composition of precipitation in the southeast Asia and western Pacific region is discussed, with emphasis on the China territory, based on the database of the International Atomic Energy Agency/World Meteorological Organization Global Network "Isotopes in Precipitation" and the available information on the regional climatology and atmospheric circulation patterns. The meteorological and pluviometric regime of southeast Asia is conn'olled by five different air masses: (1) polar air mass originating in the Arctic, (2) continental air mass originating over central Asia, (3) tropical-maritime air mass originating in the northern Pacific, (4) equatorial-maritime air mass originating in the western equatorial Pacific, and (5) equatorial-maritime air mass originating in the Indian Ocean. The relative importance of different air masses in the course of a given year is modulated by the monsoon activity and the seasonal displacement of the Intertropical Convergence Zone (ITCZ). Gradual rain-out of moist, oceanic air masses moving inland, associated with monsoon circulation, constitutes a powerful mechanism capable of producing large isotopic depletions in rainfall, often completely overshadowing the dependence of 6180 and 62H on temperature. For instance, precipitation at Lhasa station (Tibetan Plateau) during rainy period (June-September) is depleted in •80 by more than 6 ø/oo with respect to winter rainfall, despite of 10øC higher surface air temperature in summer. This characteristic isotopic imprint of monsoon activity is seen over large areas of the region. The oceanic air masses forming the two monsoon systems, Pacific and Indian monsoon, differ in their isotope signatures, as demonstrated by the average 6180 of rainfall, which in the south of China (Haikou, Hong Kong) is about 2.5%0 more negative than in the Bay of Bengal (Yangoon). Strong seasonal variations of the deuterium excess values in precipitation observed in some areas of the studied region result from a complete reversal of atmospheric circulation over these areas and changing source of atmospheric moisture. High d-excess values observed at Tokyo and Pohang during winter (15-25%0) result from interaction of dry air masses from the northern Asian continent passing the Sea of Japan and the China Sea and picking up moisture under reduced relative humidity. The isotopic composition of precipitation also provides information about the maximum extent of the ITCZ on the continent during summer. deposits, tree cellulose, and others [e.g., Johnsen et al. 1989;

A high-resolution record was obtained by investigating a sedimentary sequence from two cores taken in the central Red Sea (R/V Meteor cruise 5, leg 2). The numerical variations between nonmigratory and migratory pteropods and their stable isotopic record were studied together with variations in the carbonate and total organic carbon content in order to estimate changes in the structure of the water column during the last 13 kyr. The results indicate the existence of a highly stratified water column during deglaciation and early Holocene (13-8.5 ka). During this period the depth of the mixed layer varied between less than 50-100 m at most, and productivity was markedly reduced in comparison to the recent situation. The intermediate and deep water were constantly highly depleted in oxygen. A pronounced Younger Dryas event was recognized at 10.4 ka which coincides with an arid phase on the border land. The oxygenation of the intermediate water improved remarkably after 7.5 ka and peaked during the period between 4.6 and 2.0 ka. During this period the mixed layer •Geological Survey of Israel, Jerusalem, Israel. 2Institut und Museum fiir Geologic und Pal•iontologie,

: Composite stable isotope records from a Late Weichselian Iacustrine sequence at Grznge, Lolland. Denmark: evidence of Allertad and Younger Dryas environments. Boreus, Vol. 25, pp. 8 -22. Oslo. ISSN 0300-9483. Stable oxygen and carbon isotope data from a lacustrine sequence at Grznge, southeast Denmark, revealed distinct cnvironmental changes related to Late Weichselian climatic development in the region. Comparison of isotopic records obtained from sedimentary carbonates and freshwater molluscs enabled reconstruction ol' changes in the lacustrine environment. The degree of thermal and chemical stratification of the lake was evaluated and supported by pollen data from an earlier study of the site. During the Allertad interstadial, dimictic and stagnant conditions characterized the lake, whereas the stratification was disturbed during thc Younger Dryas stadial probably as a result of deforestation and increased wind impact. The origin of sedimentary carbonates was examined by mineralogic and morphologic studies. A considerable input o f clastics and detrital carbonates, associated with pronounced enrichment of ''0 and I3C. wds recorded in the Younger Dryas sediments indicating soil degradation and increased erosion. A climatic warming preceding the Pleistocene/Holocene boundary is clearly reflected in the different stable isotope records and in the lithostratigraphy.