Environmental and biological controls on the geochemistry (δ18O, δ13C, Mg/Ca, and Sr/Ca) of living ostracods from Lake Geneva

ABSTRACT : Ostracods are benthic microcrustaceans enclosed in low-Mg calcite bivalves. Stable isotope compositions, Mg/Ca, and Sr/Ca ratios of ostracod fossil valves have proven useful to reconstruct past environmental conditions. Yet, several discrepancies persist and the influence of many factors remains unclear. It is the aim of this study to improve the use of ostracod valve geochemistry as palaeoenvironmental proxies by examining the extent of isotope fractionation and trace element partitioning during valve calcification. To achieve this, the environmental parameters (pH, temperature) and chemical composition of water (C-and O-isotope composition and calcium, magnesium, and strontium content) were measured at sites where living ostracods were sampled. The sampling was on a monthly basis over the course of one year at five different water depths (2, 5, 13, 33, and 70 m) in Lake Geneva, Switzerland. The one-year sampling enabled collection of environmental data for bottom and interstitial pore water. In littoral to sublittoral zones, C-isotope composition of DIC and the Mg/Ca and Sr/Ca ratios of water are found to vary concomitantly with water temperature. This is due to the precipitation of calcite, which is induced by higher photosynthetic activity as temperature and/or solar radiation intensify in summer. In deeper zones, environmental parameters remain largely constant throughout the year. Variations of pH, DIC concentrations and C-isotope compositions in interstitial water result from aerobic as well as anaerobic respiration, calcite dissolution and methanogenesis. Bathymetric distribution, life cycles, and habitats were derived for 15 ostracod species and are predominantly related to water temperature and sediment texture. O-isotope compositions of ostracod valves in Lake Geneva reflect that of water and temperature. However, offsets of up to 3 permil are observed in comparison with proposed inorganic calcite precipitation equilibrium composition. Deprotonation of HCO3- and/or salt effect at crystallisation sites may explain the disequilibrium observed for O-isotopic compositions. C-isotope compositions of ostracod valves are not as well constrained and appear to be controlled by a complex interaction between habitat preferences and seasonal as well as spatial variations of the DIC isotope composition. For infaunal forms, C-isotope compositions reflect mainly the variation of DIC isotope composition in interstitial pore waters. For epifaunal forms, C-isotope compositions reflect the seasonal variation of DIC isotope compositions. C-isotope compositions of ostracod valves is at equilibrium with DIC except for a small number of species (L. inopinata, L. sanctipatricii and possibly C. ophtalmica, and I. beauchampi). Trace element uptake differs considerably from species to species. For most epifaunal forms, trace element content follows the seasonal cycle, recording temperature increases and/or variations of Mg/Ca and Sr/Ca ratios of water. In contrast, infaunal forms are predominantly related to sediment pore water chemistry. RÉSUMÉ EN FRANÇAIS : Les ostracodes sont de petits crustacés benthiques qui possèdent une coquille faite de calcite à faible teneur en magnésium. La composition isotopique et les rapports Mg/Ca et Sr/Ca d'ostracodes fossiles ont été utilisés maintes fois avec succès pour effectuer des reconstructions paléoenvironnementales. Néanmoins, certains désaccords persistent sur l'interprétation de ces données. De plus, l'influence de certains facteurs pouvant biaiser le signal reste encore inconnue. Ainsi, le but de cette étude est de rendre plus performant l'emploi de la composition géochimique des ostracodes comme indicateur paléoenvironnemental. Pour réaliser cela, cinq sites situés dans le Léman à 2, 5, 13, 33 et 70 m de profondeur ont été choisis pour effectuer les échantillonnages. Chaque site a été visité une fois par mois durant une année. Les différents paramètres environnementaux (pH, température) ainsi que la composition géochimique de l'eau (composition isotopique de l'oxygène et du carbone ainsi que teneur en calcium, magnésium et strontium) ont été déterminés pour chaque campagne. Des ostracodes vivants ont été récoltés au cinq sites en même temps que les échantillons d'eau. Ce travail de terrain a permis de caractériser la géochimie de l'eau se trouvant juste au-dessus des sédiments ainsi que celle de l'eau se trouvant dans les interstices du sédiment. Dans les zones littorales à sublittorales, la composition isotopique du carbone inorganique dissout (CID) ainsi que les rapports Mg/Ca et Sr/Ca de l'eau varient linéairement avec la température. Ceci peut être expliqué par la précipitation de calcite qui est contrôlée par l'activité photosynthétique, variant elle même linéairement avec la température. Dans les zones plus profondes, les paramètres environnementaux restent relativement constants tout au long de l'année. Les variations du pH, de la concentration et de la composition isotopique du CID dans les sédiments résultent de la libération de carbone engendrée par la dégradation de la matière organique avec présence d'oxygène ou via réduction de nitrates et de sulfates, par la dissolution de carbonates, ainsi que par la méthanogenèse. La distribution bathymétrique, le cycle de vie ainsi que l'habitat de 15 espèces ont été déterminés. Ceux-ci sont principalement reliés à la température de l'eau et à la texture des sédiments. La composition isotopique de l'oxygène des valves d'ostracodes reflète celle de l'eau et la température qui régnait lors de la calcification. Néanmoins, des écarts pouvant aller jusqu'à 3 0/00 par rapport à l'équilibre théorique ont été obtenus. La déprotonation de HCO3 ou un 'effet de sel' pourrait être à l'origine du déséquilibre observé. La composition isotopique du carbone des valves d'ostracodes n'est pas aussi bien cernée. Celle-ci semble être principalement contrôlée par une interaction complexe entre l'habitat des ostracodes et les variations saisonnières et spatiales de la composition isotopique du CID. Pour les espèces endofaunes, la composition isotopique du carbone reflète principalement la variation de la composition isotopique du CID à l'intérieur des sédiments. Pour les formes épifaunes, c'est la variation saisonnière de la composition du CID qui contrôle celle de la coquille des ostracodes. En général, la composition isotopique du carbone des valves d'ostracodes est en équilibre avec celle de CID, hormis pour quelques rares espèces (L. inopinata, L. sanctipatricii et peut-être C. ophtalmica et I. beauchampi). L'incorporation des éléments traces diffère passablement d'une espèce à l'autre. Pour la plupart des espèces épifaunes, la teneur en éléments traces des coquilles reflète les variations saisonnières. Ces espèces semblent enregistrer les variations soit de la température soit des rapports Mg/Ca et Sr/Ca de l'eau. La teneur en élément traces des formes infaunales, au contraire, est principalement reliée à la chimie de l'eau interstitielle. RÉSUMÉ GRAND-PUBLIC : La connaissance de l'évolution du climat dans le futur est primordiale pour notre société, car elle permet de développer différentes stratégies pour faire face aux problèmes engendrés pas le changement climatique : stratégies environnementale, humanitaire, ou encore économique. Cette problématique est actuellement, à juste titre, sujet d'une vive préoccupation. La géologie peut-elle contribuer à l'effort communautaire entrepris? Naturellement, ce sont les climatologues qui sont sur le devant de la scène. Il n'empêche que ces derniers, pour pouvoir prédire l'avenir, doivent s'appuyer sur le passé. La géologie est alors d'un grand intérêt car c'est effectivement la seule science qui permette d'estimer les variations climatiques à grande échelle sur de longues périodes. Ainsi, voulant moi-même contribuer aux recherches menées dans ce domaine, je me suis tourné à la fin de mes études vers la paléoclimatologie, science qui a pour but de reconstruire le climat des temps anciens. Nous nous sommes rendu compte que l'évolution climatique de la région où nous habitons n'avait pas encore fait le sujet d'études approfondies. Il est pourtant important de connaître la variation locale des changements climatiques pour obtenir des modèles climatiques fiables. En conséquence, un vaste projet a vu le jour : reconstruire, à l'aide des sédiments du lac Léman, les variations paléoclimatiques et paléo-environnementales depuis le retrait du Glacier de Rhône, il y a environ 15'000 ans, jusqu'à nos jours. Pour ce genre de travail, la géochimie, qui est une forme de chimie, utilisée en science de la terre regroupant la chimie classique et la chimie isotopique, est une alliée particulièrement efficace. Elle permet en effet, via différentes mesures faites sur des archives géologiques (par exemple des fossiles ou des sédiments) d'obtenir des informations, souvent quantitatives, sur les conditions (le climat, la flore ou encore la bio productivité, etc...) qui régnaient il y a fort longtemps. Les coquilles d'ostracodes, qui sont de petits animaux vivant au fond des lacs, sont une des archives les plus prometteuses. Ces animaux sont des petits crustacés s'entourant d'une coquille calcaire qu'ils sécrètent eux-mêmes. A la mort de l'animal, la coquille est intégrée dans les sédiments et reste intacte à travers les âges. Des études ont montré qu'en analysant la géochimie de ces coquilles fossiles, il est possible de reconstruire les conditions environnementales qui régnaient à l'époque de vie de ces fossiles. Cette démarche nécessite qu'une condition bien précise soit remplie: la composition géochimique de la coquille doit enregistrer de manière fidèle la chimie de l'eau et/ou la température de l'eau présentes au moment de la sécrétion de la coquille. Le but spécifique de notre recherche a précisément été d'étudier la façon dont la chimie de l'eau ainsi que sa température sont enregistrées dans la coquillé des ostracodes. Une fois les relations entre ces divers paramètres dans l'étant actuel du système établies, il sera alors possible de les utiliser pour interpréter des données issues de coquilles fossiles. Pour ce faire, nous avons mesuré la température de l'eau de manière continue et récolté mensuellement des échantillons d'eau et des ostracodes vivants pendant une année. Cinq sites situés à 2, 5, 13, 33 et 70 mètres de profondeur ont été choisis pour effectuer ces échantillonnages dans le Léman. Le travail de terrain nous a amené à étudier la biologie de 15 espèces. Nous avons pu établir la profondeur à laquelle vivent ces animaux, leur période de développement ainsi que leur habitat respectifs. Ces résultats ont permis de mieux cerner la relation qu'il existe entre la chimie de l'eau, sa température et la composition géochimique des coquilles d'ostracodes. Nous avons ainsi pu confirmer que les coquilles d'ostracodes enregistrent de manière fidèle la composition chimique et isotopique de l'eau. De même, nous avons pu établir de manière plus précise l'effet de la température sur la géochimie des coquilles. Néanmoins, les relations trouvées entre ces trois éléments sont plus complexes pour certaines espèces, cette complexité étant souvent liée à un caractère spécifique de leur écologie. Nous avons mis en lumière certains effets qui biaisent les résultats et défini précisément les conditions dans lesquelles on peut s'attendre à avoir des difficultés dans leur interprétation. Maintenant que nous avons établi les relations entre le climat actuel et la composition géochimique des coquilles d'ostracodes actuels, nous pouvons, sur la base de ce modèle, reconstruire le climat depuis le retrait du Glacier du Rhône jusqu'à nos jours à l'aide d'ostracodes fossiles. Mais cela est une autre histoire et fera, je l'espère, le sujet de nos futures recherches.

Mg/Ca and Sr/Ca ratios of ostracod valves from living species of Lake Geneva

The Mg/Ca and Sr/Ca ratios of living ostracods belonging to 15 different species and sampled monthly over a one year-cycle at five sites (2, 5, 13, 33, and 70 m water depths) in western Lake Geneva (Switzerland) are compared to the oxygen and carbon isotope compositions measured on the same samples as well as to the temperature and chemical composition of the water (δ18OH2O, δ13CDIC, Mg/CaH2O, and Sr/CaH2O) at the time of ostracod calcification. The results indicate that trace element incorporation varied at the species level, mainly because of the ecological and biological differences between the different species (life-cycle, (micro-)habitat preference, biomineralisation processes) and the control thereof on trace element incorporation of the ostracods. In littoral zones, the Mg/Ca and Sr/Ca of ostracod valves increase as temperature and Mg/Ca and Sr/Ca of water increase during spring and summer, hence reflecting mainly seasonal variations. However, given that for Lake Geneva the Mg/Ca and Sr/Ca of water also vary with temperature, it is not possible to distinguish the effects of temperature from those of changes in chemical composition of water on the trace element content in ostracod valves. Results support that both water temperature and water Mg/Ca and Sr/Ca ratios control the final trace element content of Cyprididae valves. In contrast, the trace element content of species living in deeper zones of the basin is influenced by variations in the chemical composition of the pore water for the infaunal species. Trace element content measured for these specimens cannot, therefore, be used to reconstruct the compositions of the water lake bottom. In addition, incorporation of Mg and Sr into the shell differs from one family, sub-family, or even species to the other. This suggests that the distinctive Mg and Sr partition coefcients for the analysed taxa result from different valve calcification strategies that may be phylogenetic.

Ecology, stable isotopes, and management of grassland songbirds at National Park Service properties on the Great Plains

Grassland ecosystems have been severely reduced and grassland bird populations have experienced consistent declines. National Park Service (NPS) properties on the Great Plains provide breeding habitat for grassland songbirds, though little is known about the quality of this habitat. A short-term study on songbirds at three NPS properties complemented current monitoring, providing an among park comparison addressing grassland bird productivity and fidelity relative to NPS property size. During 2008-2009, I assessed avian species richness, and estimated bird density and grassland songbird nest success. Bird species richness was greatest at small and medium sites, while number of nesting obligate species was greatest at the large site. Species-specific densities varied among sites, with few grassland obligates occurring at all three sites. Nest success estimates for grassland obligates were highest at the small site and lower at the large site. Another method to quantify habitat quality is assessment of breeding site fidelity. Current extrinsic markers used in monitoring site fidelity are inadequate for small birds; stable isotope analyses provide an alternative. I compared two techniques for assigning stable isotope tissue origin and measured grassland songbird site fidelity. My method of assigning origin provided site-specific variances of expected stable isotope values, an improvement over the most commonly used method. Fidelity tended to be higher at the large site, which may indicate a more robust breeding community of grassland birds. The small size of two of my sites precluded large sample sizes and made strong inferences difficult. To quantify how scientists cope with weak inference, I conducted a literature review. Strong inference was rarely observed, and most authors of weak-inference papers provided specific management recommendations. I suggest that adaptive management is an ideal method to resolve uncertainty from weak inference. Managers should consider my results within the context of regional and global management and the extent to which their unit might aide songbird conservation.

Geochemistry, isotopes, trace elements and fluid inclusion geothermometry at DSDP Hole 83-504B

Stockwork-like metal sulfide mineralizations were found at 910-928 m below seafloor (BSF) in the pillow/dike transition zone of Hole 504B. This is the same interval where most physical properties of the 5.9-m.y.-old crust of the Costa Rica Rift change from those characteristic of Layer 2B to those of Layer 2C. The pillow lavas, breccias, and veins of the stockwork-like zone were studied by transmitted and reflected light microscopy, X-ray diffraction, and electron microprobe analysis. Bulk rock oxygen isotopic analyses as well as isolated mineral oxygen and sulfur isotopic analyses and fluid inclusion measurements were carried out. A complex alteration history was reconstructed that includes three generations of fissures, each followed by precipitation of characteristic hydrothermal mineral parageneses: (1) Minor and local deposition of quartz occurred on fissure walls; adjacent wall rocks were silicified, followed by formation of chlorite and minor pyrite I in the veins, whereas albite, sphene, chlorite and chlorite-expandable clay mixtures, actinolite, and pyrite replaced igneous phases in the host rocks. The hydrothermal fluids responsible for this first stage were probably partially reacted seawater, and their temperatures were at least 200-250° C. (2) Fissures filled during the first stage were reopened and new cracks formed. They were filled with quartz, minor chlorite and chlorite-expandable clay mixtures, traces of epidote, common pyrite, sphalerite, chalcopyrite, and minor galena. During the second stage, hydrothermal fluids were relatively evolved metal- and Si-rich solutions whose temperatures ranged from 230 to 340° C. The fluctuating chemical composition and temperature of the solutions produced a complex depositional sequence of sulfides in the veins: chalcopyrite I, ± Fe-rich sphalerite, chalcopyrite II ("disease"), Fe-poor sphalerite, chalcopyrite III, galena, and pyrite II. (3) During the last stage, zeolites and Mg-poor calcite filled up the remaining spaces and newly formed cracks and replaced the host rock plagioclase. Analcite and stilbite were first to form in veins, possibly at temperatures below 200°C; analcite and earlier quartz were replaced by laumontite at 250°C, whereas calcite formation temperature ranged from 135 to 220°C. The last stage hydrothermal fluids were depleted in Mg and enriched in Ca and 18O compared to seawater and contained a mantle carbon component. This complex alteration history paralleling a complex mineral paragenesis can be interpreted as the result of a relatively long-term evolution of a hydrothermal system with superimposed shorter term fluctuations in solution temperature and composition. Hydrothermal activity probably began close to the axis of the Costa Rica Rift with the overall cooling of the system and multiple fracturing stages due to movement of the crust away from the axis and/or cooling of a magmatic heat source.

Boron isotopes, trace elements and pH calculation for Norwegian deep sea coral specimen Madrepora o. (1968-2007), 2012

d11B and trace results obtained for a deep sea coral specimen Madrepora oculata collected from the Norwegian Sea (67°N, 9°E, 340 m) during the RV Polarstern ARK/II/Ia cruise (2007). Such coral specimen grew during the last four decades (1968-2007) and geochemical results highligh a seawater pH decrease with an order of magnitude in good agreement with an ocean acidification rate today known. This pH record is strongly impacted by inter-decadal change of ocean dynamic (NAO) and productivity. pHT calculation parameters (Hönisch et al., 2007): a=5; a=0.9804, d11B=39.5 PER MIL, Li/Mg temperature, salinity=35.1, pKB from Dickson (1990).

Mixing of Rhône River water in Lake Geneva (Switzerland-France) inferred from stable hydrogen and oxygen isotope profiles

Depth profiles were sampled at different locations throughout Lake Geneva on a monthly and seasonal basis over the course of 2 years and analysed for their stable hydrogen and oxygen isotope compositions. The isotopic compositions indicate an isotopic stratification in the metalimnion during summer and fall. This is related to mixing of Rhône River water, which in summer is dominated by snow and glacier melt waters, and lake water, with the latter having a homogenous isotopic composition. The observed interflow layer is 7-15 m thick and can be traced by the distinct stable isotope composition of the water for about 55 km throughout the lake as well as into shallow bay regions. Depth of the interflow layer close to the Rhône River mouth is similar to those previously described based on echo-soundings and turbidity profiles of sediment dispersion. In contrast to previous descriptions of the interflow within Lake Geneva, the stable isotope compositions allow for direct, natural tracing of the Rhône River water even in cases where the turbidity and conductivity measurements do not indicate such an interflow. In addition, the method allows for a quantification of the Rhône River and lake water in the interflow with the fraction of Rhône River water within the interflow estimated to be up to 37% in summer. The isotopic composition further indicates different vertical mixing processes within the two lake basins of Lake Geneva, related to the density gradients and local stability within the water column. The method may be applicable to other lakes in catchments with large differences in the topography as water that originates from high altitudes or glaciers has a distinct oxygen and hydrogen isotope composition compared to other sources of water originating at lower altitudes and/or from direct precipitation over the lake. Stable isotope measurements thus improve the understanding of the circulation of water within the lake, which is fundamental for an evaluation of the water residence times, dissolved pollutant and nutrient transport as well as oxygenation.

Sediment penetration depths of epi- and infaunal ostracods from Lake Geneva (Switzerland)

Many (palaeo-)environmental parameters can be deduced from ecological and chemical analyses of ostracods. However, the specific ecology of each taxon has a great impact on its reaction to changing environmental conditions. As a consequence, each taxon records these changes differently. The mean penetration depth (MPD) and relative individual abundances have been documented along sediment depth profiles for the dominant sub-littoral to profundal species of ostracods in western Lake Geneva, Switzerland, and this data can be used to estimate their preferential habitat in terms of sediment depths. Isocypris beauchampi, Limnocytherina sanctipatricii, Cypria ophtalmica forma lacustris at 13-m water depths, Limnocythere inopinata, and a winter generation of Herpetocypris reptans have the shallowest habitat preferences at the study sites (MPDs of 0.45, 0.48, 0.49, 0.60, and 0.81 cm, respectively). These results suggest that these populations may be regarded as being preferentially epifaunal forms. Populations of Cytherissa lacustris (MPDs of 0.61, 0.73, and 0.82 cm at 13-, 33-, and 70-m water depths, respectively), Cypria ophtalmica forma lacustris at 70 m (MPD = 0.96 cm), Fabaeformiscandona caudata (MPD = 0.99 cm), and a summer generation of Herpetocypris reptans (MPD = 1.03 cm) were identified as being infaunal. Candona neglecta is the species that was found the deepest in the sediment of Lake Geneva, with MPDs of 0.65, 1.22, and 1.30 cm at 13-, 33-, and 70-m water depths, respectively. Information on the sediment texture and oxygen concentrations inferred from the analyses of sediment pore water suggest that the oxygen content of the sediment pore water is not the only dominant parameter controlling the differences in ostracod sediment penetration depths observed among the different sites, but that they might also be influenced by the sediment 'softness,' which itself depends on grain size, water content, and the abundance of organic matter in sediment.

“Pussy cat, pussy cat where have you been..?” Evaluating the use of stable isotopes, radiogenic isotopes and trace elements for investigating the ecology of Panthera leo

1. Understanding the behaviour and ecology of large carnivores is becoming increasingly important as the list of endangered species grows, with felids such as Panthera leo in some locations heading dangerously close to extinction in the wild. In order to have more reliable and effective tools to understand animal behaviour, movement and diet, we need to develop novel, integrated approaches and effective techniques to capture a detailed profile of animal foraging and movement patterns. 2. Ecological studies have shown considerable interest in using stable isotope methods, both to investigate the nature of animal feeding habits, and to map their geographical location. However, recent work has suggested that stable isotope analyses of felid fur and bone is very complex and does not correlate directly with the isotopic composition of precipitation (and hence geographical location). 3. We present new data that suggest these previous findings may be atypical, and demonstrate that isotope analyses of Felidae are suitable for both evaluating dietary inputs and establishing geo-location as they have strong environmental referents to both food and water. These data provide new evidence of an important methodology that can be applied to the family Felidae for future research in ecology, conservation, wildlife forensics and archaeological science.

Stable isotopes in lake Geneva carbonate sediments and molluscs: Review and new data

New isotopic results on bulk carbonate and mollusc (gastropods and bivalves) samples from Lake Geneva (Switzerland), spanning the period from the Oldest Dryas to the present day, are compared with pre-existing stable isotope data. According to preliminary calibration of modern samples, Lake Geneva endogenic calcite precipitates at or near oxygen isotopic equilibrium with ambient water, confirming the potential of this large lake to record paleoenvironmental and paleoclimatic changes. The onset of endogenic calcite precipitation at the beginning of the Allerod biozone is clearly indicated by the oxygen isotopic signature of bulk carbonate. A large change in delta(13)C values occurs during the Preboreal. This carbon shift is likely to be due to a change in bioproductivity and/or to a `'catchment effect'', the contribution of biogenic CO2 from the catchment area to the dissolved inorganic carbon reservoir of the lake water becoming significant only during the Preboreal. Gastropods are confirmed as valuable for studies of changes in paleotemperature and in paleowater isotopic composition, despite the presence of a vital effect. Mineralogical evidence indicates an increased detrital influence upon sedimentation since the Subboreal time period. On the other hand, stable isotope measurements of Subatlantic carbonate sediments show values comparable to those of pure endogenic calcite and of gastropods (taking into account the vital effect). This apparent disagreement still remains difficult to explain.

Hydrothermal rare earth elements mineralization in the Barra do Itapirapua carbonatite, southern Brazil: behaviour of selected trace elements and stable isotopes (C, O)

The Bura do Itapira pua carbonatite is located in southern Brazil and belongs to the Cretaceous Ponta Grossa alkaline-carbonatitic province related to the opening of the South Atlantic. The carbonatite complex is emplaced in Proterozoic granites and is mainly composed of plutonic magnesio- to ferrocarbonatite, with smaller amounts of subvolcanic magnesiocarbonatite. Hydrothermal alteration of the carbonatite has led to the formation of quartz, apatite, fluorite, rue earth fluorocarbonates, barite and sulfides in variable proportions. Trace element data, delta(13)C and delta(18)O are presented here, with the aim of better understanding the geochemical nature of hydrothermal alteration related to rare earth elements (REE) mineralization. The non-overprinted plutonic carbonatite shows the lowest REE contents, and its primitive carbon and oxygen stable isotopic composition places it in the field of primary igneous carbonatites. Two types of hydrothermally overprinted plutonic carbonatites can be distinguished based on secondary minerals and geochemical composition. Type I contains mainly quartz, rare earth fluorocarbonates and apatite as hydrothermal secondary minerals, and has steep chondrite normalized REE patterns, with Sigma(REE+Y) of up to 3 wt.% (i.e., two orders of magnitude higher than in fresh plutonic samples). In contrast, the Type II overprint contains apatite, fluorite and barite as dominant hydrothermal minerals, and is characterized by heavy REE enrichment relative to the fresh samples, with flat chondrite normalized REE patterns. Carbon and oxygen stable isotope ratios of Types I and II are elevated (delta(18)O + 8 to + 12 parts per thousand; delta(13)C - 6 to - 2 parts per thousand) relative to the fresh samples. Hydrothermally overprinted carbonatites exposed to weathering show even higher delta(18)O values (delta(18)O 13 to 25 parts per thousand) but no additional REE enrichment. The subvolcanic carbonatite has anomalously high delta(13)C of up to + 1 parts per thousand, which suggests crustal contamination through interaction with carbonate-bearing metasediments. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Termination II record, stable isotopes and trace elements of Stagamite MF-3 from Schafsloch Cave

The timing and nature of the penultimate deglaciation, also known as Termination II (T-II), is subject of controversial discussions due to the scarcity of precisely-dated palaeoclimate records. Here we present a new precisely-dated and highly-resolved multi-proxy stalagmite record covering T-II from the high alpine Schafsloch Cave in Switzerland, an area where climate is governed by the North Atlantic. The inception of stalagmite growth at 137.4 ± 1.4 kyr before present (BP) indicates the presence of drip water and cave air temperatures of above 0 °C, and is related to a climate-induced change in the thermal state (from cold-to warm-based) of the glacier above the cave. The cessation of stalagmite growth between 133.1 ± 0.7 and 131.9 ± 0.6 kyr BP is most likely related to distinct drop in temperature associated with Heinrich stadial 11. The resumption of stalagmite growth at 131.9 ± 0.6 kyr BP is accompanied by an abrupt increase in temperature and precipitation as indicated by distinct shifts in the oxygen and carbon isotopic composition as well as in trace element concentrations. The mid-point of T-II is around 131.8 ± 0.6 kyr BP in the Schafsloch Cave record is significantly earlier compared to the age of 129.1 ± 0.1 kyr BP in the Sanbao Cave record from China. The different ages between both records can be best explained by the competing effects of insolation and glacial boundary forcing on seasonality and snow cover extent in Eurasia.

Stable isotopes of bulk organic matter to trace carbon and nitrogen dynamics in an estuarine ecosystem in Babitonga Bay (Santa Catarina, Brazil)

The biogeochemical processes affecting the transport and cycling of terrestrial organic carbon in coastal and transition areas are still not fully understood One means of distinguishing between the sources of organic materials contributing to particulate organic matter (POM) in Babitonga Bay waters and sediments is by the direct measurement of delta(13)C of dissolved inorganic carbon (DIC) and delta(13)C and delta(15)N in the organic constituents. An isotopic survey was taken from samples collected in the Bay in late spring of 2004. The results indicate that the delta(13)C and delta(15)N compositions of OM varied from -21.7 parts per thousand to -26 2 parts per thousand. and from + 9 2 parts per thousand. to -0 1 parts per thousand, respectively. delta(13)C from DIC ranges from +0.04 parts per thousand to -12.7 parts per thousand The difference in the isotope compositions enables the determination of three distinct end-members terrestrial, marine and urban Moreover, the evaluation of source contribution to the particulate organic matter (POM) in the Bay, enables assessment of the anthropogenic impact. Comparing the depleted values of delta(13)C(DIC) and delta(13)C(POC) it is possible to further understand the carbon dynamic within Babitonga Bay (C) 2010 Elsevier BV All rights reserved