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Sample records for carbon isotope stratigraphy

  1. Late Carboniferous to Late Permian carbon isotope stratigraphy

    DEFF Research Database (Denmark)

    Buggisch, Werner; Krainer, Karl; Schaffhauser, Maria;

    2015-01-01

    . Negative δ13C excursions are related to low-stand deposits and caused by diagenetic processes during subaerial exposure. The comparison with δ13C records from other parts of the world demonstrate that δ13C values are high in most unaltered samples, an overall negative trend during the Permian, as recently...... published, is not obvious and negative excursions related to changes in the carbon isotope composition of the global oceanic carbon pool cannot be confirmed, except for the Permian–Triassic boundary interval....

  2. Carbon and Oxygen Isotope Stratigraphy of the Oxfordian Carbonate Rocks in Amu Darya Basin

    Institute of Scientific and Technical Information of China (English)

    Rongcai Zheng; Yanghui Pan; Can Zhao; Lei Wu; Renjin Chen; Rui Yang

    2013-01-01

    Based on the detailed research on petrologic and geochemical characteristics of deposition and diagenesis of Oxfordian carbonate rocks in Amu Darya Basin,Turkmenistan,carbon and oxygen isotopes were analyzed.The results show that the paleoenvironmental evolution reflected by the samples with well-preserved original carbon isotopes coincides with the carbon-isotope stratigraphic carve and is almost consistent with the global sea-level curve,the Mid-Oxfordian wide transgression,and the positive carbon-isotope excursion event.The Mid-Oxfordian continuing transgression not only laid the foundation for the development of the Oxfordian reef and shoal reservoirs in Amu Darya Basin but also provided an example for the Oxfordian global transgression and the resulting development of reefs and banks and high-speed organic carbon burial events.The response of oxygen isotopes in diagenetic environment showed that micrite limestones and granular limestones underwent weak diagenetic alteration,and the samples largely retained the original seawater features.Dolomitization and the precipitation of hydrothermal calcites tilling solution vugs and fractures before hydrocarbon accumulation occurred in a closed diagenetic environment where the main controlling factor is the temperature,and the diagenetic fluids were from the deep hot brine.The chalkification of the limestones after hydrocarbon accumulation occurred in the oiltield water systems.

  3. Elemental geochemistry and strontium-isotope stratigraphy of Cenomanian to Santonian neritic carbonates in the Zagros Basin, Iran

    Science.gov (United States)

    Navidtalab, Amin; Rahimpour-Bonab, Hossain; Huck, Stefan; Heimhofer, Ulrich

    2016-12-01

    A Neo-Tethyan upper Cenomanian-Santonian neritic carbonate ramp succession (Sarvak and Ilam formations), drilled in the Zagros Basin in southwest Iran, was investigated via detailed sedimentology, microfacies analysis, elemental geochemistry and Sr-isotope stratigraphy (SIS). The succession contains two exposure surfaces, which are known as the CT-ES and mT-ES (Cenomanian-Turonian and middle Turonian, respectively), and associated prominent negative carbon-isotope excursions that represent important regional stratigraphic marker horizons. Precise knowledge about the onset of platform exposure and the duration of the exposure-related hiatus, however, is currently lacking due to a rather low-resolved shallow-water biostratigraphic framework and a bulk carbonate carbon-isotope pattern that clearly differs from global Late Cretaceous reference curves. Therefore, the existing bio-chemostratigraphic framework was complemented by bulk carbonate strontium-isotope stratigraphy (SIS). As bulk carbonate material is in particular prone to diagenetic alteration, a careful selection of least altered samples has been carried out by means of elemental geochemistry and petrography. In contrast to what could be expected, the meteoric alteration of limestones beneath both exposure surfaces is not clearly expressed by increasing iron and manganese and coeval decreasing strontium contents. On the contrary, the impact of meteoric diagenesis is well illustrated via pronounced increases in Rb concentrations and concomitant prominent positive shifts to radiogenic strontium-isotope values, an observation that clearly reflects the decay of continentally derived 87Rb into 87Sr. Rubidium corrected strontium-isotope values place the CT-ES around the Cenomanian-Turonian boundary and point to an exposure duration of less than 0.4 Myr. This rather short-term CT-ES related hiatus is supported by petrographic evidence, which indicates a youth karstification stage of strata beneath the CT

  4. Carbon isotope stratigraphy and palynology of an eastern Tethyan Cretaceous-Paleogene boundary section from Sumbar, Turkmenistan

    Science.gov (United States)

    Gilmour, I.; Pearce, C. A.; Jolley, D.; Sephton, M. A.; Widdowson, M.; Gilmour, M. A.

    2012-04-01

    A number of marine sequences across the K/Pg boundary have been identified that offer reasonably continuous records and relatively high sedimentation rates, most notably those near Tethyan continental margins. However, few Eastern Tethys K/Pg localities have been studied compared to the well-known North African and Southern European sites. Here we present a high-resolution stable carbon isotope and palynological record of a 2m thick section across the K/Pg boundary from the eastern Tethys at Sumbar in Turkmenistan (38°28'N, 56°14'E). The stratigraphy and inorganic geochemistry of the section used in this study, SM-4, has been described in detail by [1]. A moderately diverse series of palynofloras were recovered from the samples spanning the K/Pg boundary with a late Maastrichtian assemblage comparable to that described from Tunisia [2]. Above the K/Pg boundary a dinocyst assemblage dominated by Areoligera is observed, reinforcing the similarity with Tunisia, that we interpret as representing a marine transgression by eutrophic water masses with the levels of Areoligera decreasing up section with a decline in nutrient availability. Carbon isotope stratigraphy of bulk carbonate and bulk organic matter reveal correlated negative carbon isotope excursions (CIEs) across the K/Pg boundary. The extent of the CIE and the concomitant drop in carbonate content parallels that observed for bulk and fine fraction carbonate isotopic analyses from other K/Pg sections. The negative CIE of bulk organic matter is similar in magnitude to CIEs for organic matter that have been observed at only a few other marine K/Pg sections. In contrast, the marked CIE observed in bulk organic matter is not evident in the carbon isotopic compositions of algal lipids. We interpret this as a geochemical signature of post-K/Pg algal blooms. Recent analysis identified the K/Pg boundary in the Boltysh meteorite crater sediment fill and reported evidence of a marine incursion into the crater during the

  5. Late Paleocene–early Eocene carbon isotope stratigraphy from a near-terrestrial tropical section and antiquity of Indian mammals

    Indian Academy of Sciences (India)

    A Samanta; A Sarkar; M K Bera; Jyotsana Rai; S S Rathore

    2013-02-01

    Late Paleocene to early Eocene (∼56 to 51 Ma) interval is characterized by five distinct transient warming (hyperthermal) events (Paleocene–Eocene thermal maximum (PETM), H1/ETM2/ELMO, H2, I1 and I2) in a super greenhouse globe associated with negative carbon isotope excursions (CIEs). Although well-documented marine records exist at different latitudes, terrestrial PETM sections are rare. In particular, almost no terrestrial records of either the PETM or early Eocene hyperthermals (EEHs) are yet available from the tropics. Further, evolution of modern order of mammals near the PETM has been recorded in many northern continents; however, the response of mammals in the tropics to these warming events is unknown. A tropical terrestrial record of these hyperthermal/CIE events, encompassing the earliest modern order mammal bearing horizon from India, can therefore be vital in understanding climatic and biotic evolution during the earliest Cenozoic time. Here, for the first time, we report high resolution carbon isotope (13C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial terrestrial records. 13C chemostratigraphy further suggests that at least the present early Eocene mammal-bearing horizon, recently discovered at Vastan, does not support the `out of India' hypothesis of earliest appearance of modern mammals and subsequent dispersal to the Holarctic continents.

  6. Late Paleocene-early Eocene carbon isotope stratigraphy from a near-terrestrial tropical section and antiquity of Indian mammals

    Science.gov (United States)

    Samanta, A.; Sarkar, A.; Bera, M. K.; Rai, Jyotsana; Rathore, S. S.

    2013-02-01

    Late Paleocene to early Eocene (~56 to 51 Ma) interval is characterized by five distinct transient warming (hyperthermal) events (Paleocene-Eocene thermal maximum (PETM), H1/ETM2/ELMO, H2, I1 and I2) in a super greenhouse globe associated with negative carbon isotope excursions (CIEs). Although well-documented marine records exist at different latitudes, terrestrial PETM sections are rare. In particular, almost no terrestrial records of either the PETM or early Eocene hyperthermals (EEHs) are yet available from the tropics. Further, evolution of modern order of mammals near the PETM has been recorded in many northern continents; however, the response of mammals in the tropics to these warming events is unknown. A tropical terrestrial record of these hyperthermal/CIE events, encompassing the earliest modern order mammal bearing horizon from India, can therefore be vital in understanding climatic and biotic evolution during the earliest Cenozoic time. Here, for the first time, we report high resolution carbon isotope ( δ 13C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial terrestrial records. δ 13C chemostratigraphy further suggests that at least the present early Eocene mammal-bearing horizon, recently discovered at Vastan, does not support the `out of India' hypothesis of earliest appearance of modern mammals and subsequent dispersal to the Holarctic continents.

  7. Triassic-Jurassic organic carbon isotope stratigraphy of key sections in the western Tethys realm (Austria)

    Science.gov (United States)

    Ruhl, Micha; Kürschner, Wolfram M.; Krystyn, Leopold

    2009-05-01

    The late Triassic period is recognized as one of the five major mass extinctions in the fossil record. All these important intervals in earth history are associated with excursions in C-isotope records thought to have been caused by perturbations in the global carbon cycle. The nature and causes of C-isotopic events across the Triassic-Jurassic (T-J) transition however, are poorly understood. We present several new high resolution organic C-isotope records from the Eiberg Basin, Austria, including the proposed Global boundary Stratotype Section and Point (GSSP) for the base of the Jurassic. The Triassic-Jurassic boundary interval in these records is characterized by the initial and main negative organic carbon isotope excursions (CIE) of up to 8‰. The initial and main CIEs are biostratigraphically constrained by first and last occurrences of boundary defining macro- and microfossils (e.g. ammonites). High resolution C-isotope records appear to be an excellent correlation proxy for this period in the Eiberg Basin. Pyrolysis analysis demonstrates increased Hydrogen Index (HI) values for organic matter coinciding with the initial CIE. Terrestrial organic matter influx and mass occurrences of green algae remains may have influenced the C-isotope composition of the sedimentary organic matter. This may have contributed to the extreme amplitude of the initial CIE in the Eiberg Basin.

  8. Isotope stratigraphy of cenozoic carbonate sequences of Brazilian Northern coast; Estratigrafia isotopica de sequencias carbonaticas cenozoicas da Costa Norte do Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Rene; Takaki, Tikae [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    1987-08-01

    Study of sedimentary rocks formation process on the Northern coast of Brazil, its stratigraphy characteristic, methodology of dating process to determine rocks age and correlation with carbonates sequences of Atlantic ocean (North and South) are presented. Results of analysed samples, isotopics studies, its dating, and comparative studies with samples analyzed in other sites are also discussed. 3 figs., 19 refs

  9. Strontium isotope stratigraphy of the Pelotas Basin

    Energy Technology Data Exchange (ETDEWEB)

    Zerfass, Geise de Santana dos Anjos, E-mail: geise.zerfass@petrobras.com.br [Petroleo Brasileiro S.A. (PETROBRAS/CENPES/PDGEO/BPA), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas e Desenvolvimento Leopoldo Americo Miguez de Mello; Chemale Junior, Farid, E-mail: fchemale@unb.br [Universidade de Brasilia (UnB), DF (Brazil). Instituto de Geociencias; Moura, Candido Augusto Veloso, E-mail: candido@ufpa.br [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Centro de Geociencias. Dept. de Geoquimica e Petrologia; Costa, Karen Badaraco, E-mail: karen.costa@usp.br [Instituto Oceanografico, Sao Paulo, SP (Brazil); Kawashita, Koji, E-mail: koji@usp.br [Unversidade de Sao Paulo (USP), SP (Brazil). Centro de Pesquisas Geocronologicas

    2014-07-01

    Strontium isotope data were obtained from foraminifera shells of the Pelotas Basin Tertiary deposits to facilitate the refinement of the chronostratigraphic framework of this section. This represents the first approach to the acquisition of numerical ages for these strata. Strontium isotope stratigraphy allowed the identification of eight depositional hiatuses in the Eocene-Pliocene section, here classified as disconformities and a condensed section. The reconnaissance of depositional gaps based on confident age assignments represents an important advance considering the remarkably low chronostratigraphic resolution in the Cenozoic section of the Pelotas Basin. The recognition of hiatuses that match hiatuses is based on biostratigraphic data, as well as on global events. Furthermore, a substantial increase in the sedimentation rate of the upper Miocene section was identified. Paleotemperature and productivity trends were identified based on oxygen and carbon isotope data from the Oligocene-Miocene section, which are coherent with worldwide events, indicating the environmental conditions during sedimentation. (author)

  10. Of Island Arcs and Icebergs? Strontium and Carbon Isotope Stratigraphy of Ethiopian Snowball Earth Sequences

    Science.gov (United States)

    Miller, N. R.; Stern, R. J.; Avigad, D.; Beyth, M.; Küster, D.; Gebresilassie, S.; Mehari, K.

    2004-12-01

    Neoproterozoic low-grade metasedimentary exposures uniquely preserved in synclinoria of the Tigrai region of northern Ethiopia offer excellent opportunities to assess the sedimentary response to extreme climatic changes encompassed by the Snowball Earth Hypothesis within the framework of the tectonic evolution of the Arabian-Nubian shield. Basement exposures consist of two major sequences; an older predominantly island arc metavolcanic sequence named the Tsaliet Group, and a younger metasedimentary succession named the Tambien Group. An intervening phyllite unit displays a transitional lithology variously interpreted by previous workers as metasedimentary and metavolcanic. We report Sr and C isotope results for Tambien Group carbonates from three prospective Snowball Earth successions flanking the Mekelle outlier: Negash, Mai Kenetal, and Samre. These localities display excellent exposures of the transition from Tsaliet metavolcaniclastics into distinctive carbonate exposures of the Tambien Group. Distinctive volcanic polymict conglomerates occur close to the basal Tambien contact in the upper Tsaliet Group in two localities. Presence of evaporite pseudomorphs and persistence of microbially laminated lithologies including stromatolites suggests that Tambien carbonate deposition occurred in a shallow marine setting that was initially hypersaline. A distinct black limestone unit, with abundant organic matter and indications of variable energy conditions in a slope setting, occurs higher in the section. Accompanying this transition in gross carbonate depositional style is a pronounced enrichment of carbon isotopes from values between -4 and -1 per mil in the lower interval to values between +4 and +7 per mil in the overlying black limestone. A similar excursion to more radiogenic 87Sr/87Sr compositions is observed from values between 0.7060 to 0.7064 in the lower interval to values "plateauing" between 0.7067 and 0.7069 in the black limestone. Thus far, only the

  11. Carbon isotope stratigraphy, magnetostratigraphy, and 40Ar/39Ar age of the Cretaceous South Atlantic coast, Namibe Basin, Angola

    Science.gov (United States)

    Strganac, Christopher; Salminen, Johanna; Jacobs, Louis L.; Polcyn, Michael J.; Ferguson, Kurt M.; Mateus, Octávio; Schulp, Anne S.; Morais, Maria Luísa; Tavares, Tatiana da Silva; Gonçalves, António Olímpio

    2014-11-01

    We present the δ13C and paleomagnetic stratigraphy for marine strata at the coast of southern Angola, anchored by an intercalated basalt with a whole rock 40Ar/39Ar radiometric age of 84.6 ± 1.5 Ma, being consistent with both invertebrate and vertebrate biostratigraphy. This is the first African stable carbon isotope record correlated to significant events in the global carbon record spanning the Late Cenomanian to Early Maastrichtian. A positive ∼3‰ excursion seen in bivalve shells below the basalt indicates the Cenomanian-Turonian Boundary Event at 93.9 Ma, during Oceanic Anoxic Event 2. Additional excursions above the basalt are correlated to patterns globally, including a negative ∼3‰ excursion near the top of the section interpreted as part of the Campanian-Maastrichtian Boundary Events. The age of the basalt ties the studied Bentiaba section to a pulse of Late Cretaceous magmatic activity around the South Atlantic and significant tectonic activity, including rotation, of the African continent.

  12. Carbon-isotope stratigraphy from terrestrial organic matter through the Monterey event, Miocene, New Jersey margin (IODP Expedition 313)

    DEFF Research Database (Denmark)

    Fang, Linhao; Bjerrum, Christian J.; Hesselbo, Stephen P.

    2013-01-01

    documented from oceanic settings (i.e., lack of positive excursion of carbon-isotope values in terrestrial organic matter through the Langhian Stage). Factors that may potentially bias local terrestrial carbon-isotope records include reworking from older deposits, degradation and diagenesis, as well....../or reworking of older woody phytoclasts, but where such processes have occurred they do not readily explain the observed carbon-isotope values. It is concluded that the overall carbon-isotope signature for the exchangeable carbon reservoir is distorted, to the extent that the Monterey event excursion...... is not easily identifiable. The most likely explanation is that phytoclast reworking has indeed occurred in clinoform toe-of-slope facies, but the reason for the resulting relatively heavy carbon-isotope values in the Burdigalian remains obscure....

  13. Ca isotope stratigraphy across the Cenomanian-Turonian OAE 2: Links between volcanism, seawater geochemistry, and the carbonate fractionation factor

    Science.gov (United States)

    Du Vivier, Alice D. C.; Jacobson, Andrew D.; Lehn, Gregory O.; Selby, David; Hurtgen, Matthew T.; Sageman, Bradley B.

    2015-04-01

    The Ca isotope composition of marine carbonate rocks offers potential to reconstruct drivers of environmental change in the geologic past. This study reports new, high-precision Ca isotope records (δ44/40Ca; 2σSD = ± 0.04 ‰) for three sections spanning a major perturbation to the Cretaceous ocean-climate system known as Ocean Anoxic Event 2 (OAE 2): central Colorado, USA (Portland #1 core), southeastern France (Pont d'Issole), and Hokkaido, Japan (Oyubari, Yezo Group). In addition, we generated new data for selected samples from Eastbourne, England (English Chalk), where a previous Ca isotope study was completed using different methodology (Blättler et al., 2011). Strata of the Yezo Group contain little carbonate (∼1 wt.% on average) and accordingly did not yield a clear δ44/40Ca signal. The Portland core and the Pont d'Issole section display comparable δ44/40Ca values, which increase by ∼ 0.10- 0.15 ‰ at the onset of OAE 2 and then decrease to near-initial values across the event. The Eastbourne δ44/40Ca values are higher than previously reported. They are also higher than the δ44/40Ca values for the Portland core and the Pont d'Issole section but define a similar pattern. According to a numerical model of the marine Ca cycle, elevated hydrothermal inputs have little impact on seawater δ44/40Ca values. Elevated riverine (chemical weathering) inputs produce a transient negative isotope excursion, which significantly differs from the positive isotope excursions observed in the Portland, Pont d'Issole, and Eastbourne records. A decrease in the magnitude of the carbonate fractionation factor provides the best explanation for a positive shift in δ44/40Ca values, especially given the rapid nature of the excursion. Because a decrease in the fractionation factor corresponds to an increase in the Ca/CO3 ratio of seawater, we tentatively attribute the positive Ca isotope excursion to transient ocean acidification, i.e., a reduction in the concentration of

  14. C-, Sr-isotope stratigraphy of carbonate rocks from the Southern Espinhaço Ridge, Minas Gerais, southeastern Brazil

    Directory of Open Access Journals (Sweden)

    LUCIO M.S. FRAGA

    2014-06-01

    Full Text Available Neoproterozoic carbonate rocks comprise different stratigraphic units in the southern part of the Espinhaço Ridge, Minas Gerais, Brazil. C, O- and Sr-isotope analyses were carried out along four selected stratigraphic sections across these formations. These are: (i the Rio Pardo Grande Formation in the upper portion of the Espinhaço Supergroup, sampled in section 3; (ii Macaúbas Group laminated limestones (Tijucuçu Farm and dolostone layers (Domingas Formation have been respectively sampled along the so-called sections 1 and 2, and (iii the lower stratigraphic units of the Bambuí Group, sampled in section 4. Laminated limestone samples from the Macaúbas Group have δ13C values as high as 10.9‰ decreasing up section to -1.1‰ and 87Sr/86Sr values vary from 0.7072 to 0.7076, a range commonly observed in Cryogenian rocks. In section 2, dolomitic samples exhibit 87Sr/86Sr from 0.7076 to 0.7077 while in section 3, 87Sr/86Sr from 0.7074 to 0.7079. In section 4, 87Sr/86Sr values are around 0.7080. The values of 87Sr/86Sr observed in carbonate samples from the Macaúbas Group are similar to those observed in the Sr-isotope secular curve for the Neoproterozoic. Carbonate samples from the base of the Bambuí Group correlate with Ediacaran fingerprints, after the Marinoan (ca. 635 Ma glaciation.

  15. Strontium-isotope stratigraphy of Enewetak Atoll

    Science.gov (United States)

    Ludwig, K. R.; Halley, R. B.; Simmons, K. R.; Peterman, Z. E.

    1988-02-01

    87Sr/86Sr ratios determined for samples from a 350 m core of Neogene lagoonal, shallow-water limestones from Enewetak Atoll display a remarkably informative trend. Like the recently published data for Deep Sea Drilling Project (DSDP) carbonates, 87Sr/86Sr at Enewetak increases monotonically but not smoothly from the early Miocene to the Pleistocene. The data show intervals of little or no change in 87Sr/86Sr, punctuated by sharp transitions to lower values toward greater core depths. The sharp transitions correlate with observed solution disconformities caused by periods of subaerial erosion, whereas the intervals of little or no change in 87Sr/86Sr correspond to intervals of rapid accumulation of shallow-water carbonate sediments. When converted to numerical ages using the published DSDP 590B trend, the best-resolved time breaks are at 282 m (12.3 to 18.2 Ma missing) and 121.6 m (3.0 to 5.3 Ma missing) below the lagoon floor. At Enewetak, Sr isotopes offer a stratigraphic resolution for these shallow-marine Neogene carbonates comparable to that of nannofossil zonation in deep-sea carbonates (0.3-3 m.y.). In addition, the correlation of times of Sr-isotope breaks at Enewetak with times of rapid Sr-isotope change in the DSDP 590B samples confirms the importance off sea-level changes in the evolution of global-marine Sr isotopes and shows that the Sr-isotope response to sea-level falls is rapid.

  16. Strontium-isotope stratigraphy of Enewetak Atoll

    Science.gov (United States)

    Ludwig, K. R.; Halley, Robert B.; Simmons, Kathleen R.; Peterman, Zell E.

    1988-01-01

    87Sr/86Sr ratios determined for samples from a 350 m core of Neogene lagoonal, shallow-water limestones from Enewetak Atoll display a remarkably informative trend. Like the recently published data for Deep Sea Drilling Project (DSDP) carbonates, 87Sr/86Sr at Enewetak increases monotonically but not smoothly from the early Miocene to the Pleistocene. The data show intervals of little or no change in 87Sr/86Sr, punctuated by sharp transitions to lower values toward greater core depths. The sharp transitions correlate with observed solution disconformities caused by periods of subaerial erosion, whereas the intervals of little or no change in 87Sr/86Sr correspond to intervals of rapid accumulation of shallow-water carbonate sediments. When converted to numerical ages using the published DSDP 590B trend, the best-resolved time breaks are at 282 m (12.3 to 18.2 Ma missing) and 121.6 m (3.0 to 5.3 Ma missing) below the lagoon floor. At Enewetak, Sr isotopes offer a stratigraphic resolution for these shallow-marine Neogene carbonates comparable to that of nannofossil zonation in deep-sea carbonates (0.3-3 m.y.). In addition, the correlation of times of Sr-isotope breaks at Enewetak with times of rapid Sr-isotope change in the DSDP 590B samples confirms the importance off sea-level changes in the evolution of global-marine Sr isotopes and shows that the Sr-isotope response to sea-level falls is rapid.

  17. Neogene oxygen isotopic stratigraphy, ODP Site 1148,northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Quanhong

    2001-01-01

    [1]Miller, K. G., Fairbank, R. G., Mountain, G. S., Tertiary oxygen isotope synthesis, sea level history, and continental mar gin erosion, Paleoceanogr., 1987, 2(1): 1-19.[2]Savin, S. M., Keller, G., Douglas, R. G. et al., Miocene benthic foraminiferal isotopic records: A synthesis, Mar. Micro paleont., 1981, 6: 423-450.[3]Jian Zhimin, Chen Minben, Lin Huiling et al., Stepwise paleoceanographic changes during the last deglaciation in the southern South China Sea: the records of isotopes and microfossils, Science in China, Ser. D, 1998, 41 (2): 187-124.[4]Jian Zhimin, Stable isotopic evidences of the glacial deep water properties in the South China Sea, Science in China, Ser.D, 1998, 41(4): 337-344.[5]Zhao Quanhong, Wang Pinxian, Progress in Quaternary paleoceanography of the South China Sea: A review, Quaternary Sciences (in Chinese with English abstract), 1999, 6: 481-501.[6]Woodruff, F., Douglas, R. G., Response of deep-sea benthic Foraminifera to Miocene paleoclimatic events, DSDP Site 289,Mar. Micropaleont., 1981, 6: 617-632.[7]Kennett, J. P., Miocene to early Pliocene oxygen and carbon isotope stratigraphy of the Southwest Pacific, DSDP Leg 90,in Init. Rep. DSDP (eds. Kennett, J. P., von der Borch, C. C.), 1986, 90(pt.2):1383-1411.[8]Vincent, E., Killingley, J. S., Oxygen and carbon isotope record for the Early and Middle Miocene in the central equatorial Pacific (Leg 85) and paleoceanographic implications, in Init. Rep. DSDP (eds. Mayer, L., Theyer, F., Barron, A. J. et al.),1985, 85: 749-769.[9]Woodruff, F., Savin, S. M., Abel, L., Miocene benthic foraminifer oxygen and carbon isotopes, Site 709, Indian Ocean, in Proc. ODP Sci. Res. (eds. Duncan, R. A., Backman, J., Peterson, L. C. et al.), 1990, 115:519-528.[10]Vincent, E., Berger, W. H., Carbon dioxide and polar cooling in the Miocene: The Monterey hypothesis, AGU, Washing ton, D.C., Geophys. Monogr., 1985, 32: 455-468.[11]Miller, K. G., Wright, J. D., Fairbanks

  18. Chicxulub Post-Impact Sedimentary Sequence: Integrated Borehole Paleogene Carbonate Stratigraphy

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L. L.; Escobar-Sanchez, E.; Ortega-Nieto, A.; Velasco-Villarreal, M.

    2014-12-01

    The Chicxulub crater was formed by a bolide impact on the southern Gulf of Mexico at ~66 Ma ago that marked the Cretaceous/Paleogene (K/Pg) boundary, represented worldwide by the ejecta layer. The K/Pg boundary layer with its global distribution provides a high resolution marker, allowing high precision stratigraphic analyses in marine and continental sequences. Following crater formation, sedimentation re-established in the carbonate platform, filling the basin. Crater is located half on-land and half offshore, with the crater floor covered by sediments with variable thickness up to about 1 km. The target, impact and post-impact sequences have been drilled and cored, providing samples for stratigraphic, petrographic and physical-chemical laboratory studies. The post-impact stratigraphy has been analyzed in several studies at proximal, intermediate and distal outcrops and in the crater boreholes, using e.g., radiometric dating, micropaleontology, paleomagnetism, and strontium and stable isotope geochemistry. Emphasis has been given on the impact breccias-carbonates contact and the basal Paleocene sequence. Here we re-analyze the available data, revisiting the stratigraphy for the Santa Elena, Tekax, Peto and Yaxcopoil-1 boreholes using newly constructed detailed lithostratigraphic columns in the continuously cored boreholes. Additionally we extend the study to the Paleogene sequence in the Santa Elena and Yaxcopoil-1 boreholes using bulk carbon and oxygen isotopes, magnetic polarity, XRF core geochemistry and magnetic susceptibility stratigraphy. Results spanning chrons c29 to c24 constrain the K/Pg boundary, c29r-c29n polarity reversal and the Paleocene-Eocene thermal maximum, providing high resolution records. The basal Paleocene gap and age differences in an integrated stratigraphy are discussed and correlated to the GPTS scale and IODP marine isotope records. The extent and characteristics of crater structure and target/cover sediments have been imaged with

  19. 锶同位素地层学研究进展%PROGRESS IN STRONTIUM ISOTOPE STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    黄思静; 石和; 刘洁; 沈立成

    2001-01-01

    锶同位素地层学(SIS)根据地质历史中的任何时间全球范围内海水的锶同位素组成都是均一的、海水87Sr/86Sr比值随时间变化这一基本原理,利用代表原始海水的海相碳酸盐(以及磷酸盐和硫酸盐)的87Sr/86Sr比值确定海相地层的年代,研究海平面变化、造山运动、古气候等全球事件,在地层学、沉积学、石油地质学和矿床学等领域中有着广泛的应用前景。锶同位素地层学已在世界范围内得到地质学家的普遍关注,并已获得迅速的发展,国内的有关研究则刚刚起步。锶同位素地层学研究的难点主要在于对样品成岩蚀变的控制和分析技术上,同时还需要有良好的地层学研究基础,在样品选择上应充分考虑其原始组分的抗成岩蚀变能力。锶同位素地层学的研究需要地层学家、沉积学家和地球化学家的共同努力。%Strontium isotope stratigraphy relies on the fundamental principle that the marine strontium is isotopically homogenous world-wide at any tim e and the 87Sr/86Sr ratio of strontium in seawater of geological history has varied through time. By means of the 87Sr/86Sr rati o of marine carbonate (also phosphate and sulphate) which should record the orig inal composition of sea water, we can date the marine sediments, research global events, such as history of basin subside, sea level change,orogenic events and palaeoclimate variation. The applied expectation of strontium isotope stratigra phy would be very extensive on stratigraphy, sedimentology, petroleum geology a nd economic geology, which has attained considerable development internationally . However strontium isotope stratigraphy is still in its infancy in China. The f ocus of strontium isotope stratigraphy is the influence of diagenesis and techno logy of measurement of 87Sr/86Sr ratio. Meantime, strontium isot ope stratigraphy also needs the support of stratigraphy. The ability of anti

  20. High-resolution stable isotope stratigraphy of the upper Cambrian and Ordovician in the Argentine Precordillera

    DEFF Research Database (Denmark)

    Sial, A.N.; Peralta, S.; Gaucher, C.;

    2013-01-01

    We report the occurrence of important carbon isotope excursions in early Paleozoic formations of the Eastern and Central Argentine Precordillera. The Steptoean positive isotope carbon excursion (SPICE) is known from North America, Kazakhstan, South China, Australia and South America, and the nega......We report the occurrence of important carbon isotope excursions in early Paleozoic formations of the Eastern and Central Argentine Precordillera. The Steptoean positive isotope carbon excursion (SPICE) is known from North America, Kazakhstan, South China, Australia and South America......, and the negative isotope carbon excursion (SNICE) has been described for the first time in South America. We report here the record of the SPICE and SNICE in a single section in the Eastern Precordillera. In the Central Precordillera, a minor middle Darriwilian positive carbon isotope excursion (MDICE) and a late...... Sandbian positive isotope carbon excursion, the GICE (~ + 3‰; C. bicornis biozone) are reported from two sections. One pre-GICE positive carbon-isotope excursion (Sandbian Sa1, N. gracilis biozone) in the Central Precordillera with a δ13C peak of ~ + 2‰ is, perhaps, equivalent to the positive Spechts Ferry...

  1. Carbon and Oxygen Isotope Stratigraphy of the Ediacaran Jaíba Formation, Upper Bambuí Group, Brazil: Insights into Paleogeography and Sedimentary Environments after a Neoproterozoic Glaciation.

    Science.gov (United States)

    Caxito, F.; Uhlein, G. J.; Sial, A. N.; Uhlein, A.

    2015-12-01

    The Neoproterozoic Era was a time of extreme climatic variation as recorded in sedimentary rocks of this age across the globe, leading to a number of controversial hypotheses (e.g. the Snowball Earth glaciations). In eastern Brazil, the Bambuí Gr. is a thick carbonatic-siliciclastic unit that covers the São Francisco Craton and preserves remnants of a Neoproterozoic glaciation and their respective cap carbonate (1). Recent findings of Cloudina in the Januária region (2) suggest that at least part of the sequence might be upper Ediacaran or even Cambrian. Here we present the first carbon-oxygen isotope data for the Jaíba Fm., a ca. 50 m thick carbonate unit that occurs in the topmost portion of the Bambuí Gr. in this same region. The Jaíba Fm. post-dates the cap carbonate sequence and the fossil-bearing layers, and thus was probably deposited in the Ediacaran-Cambrian transition. Three stratigraphic columns were analyzed, and yielded similar ratios. Values of δ13CVPDB are between 0.8 and 3.4 ‰, while δ18OVPDB values are mostly around -8 ‰. These values contrasts with the negative δ13C values found for the base of the Bambuí Gr., followed by highly positive δ13C (up to +14‰) on its middle portion. The unusually high δ13C values are commonly interpreted as evidence for deposition on a restricted basin, such as in a foreland setting. The return to values which are close to the PDB standard in the uppermost Bambuí Gr. might thus indicate a change in the paleogeography and tectonic environment of the basin, suggesting an open, ventilated environment along with a recovery of the biological and hydrological cycle after a Late Neoproterozoic glaciation. Ongoing detailed sedimentological, geochemical and isotopic work might help to further clarify these issues and to provide new clues for unraveling Late Neoproterozoic paleoclimate, paleogeography and ocean chemistry. We thank FAPEMIG (Brazil) for finnacial support through grants n. APQ-00914-14 and PPM

  2. Use of the Bochum proton microprobe in isotope stratigraphy and paleoceanographic

    Energy Technology Data Exchange (ETDEWEB)

    Bruhn, F.; Bruckschen, P.; Korte, C. [Ruhr-University, Bochum (Germany). Institute fuer Geologie; Meijer, J. [Ruhr-Univ., Bochum (Germany). Inst. fuer Physik mit Ionenstrahlen; Veizer, J. [Ruhr-University Bochum (Germany). Institute fuer Geologie]|[Ottawa-Carleton Univ., Ottawa, ON (Canada)

    1998-06-01

    Over the past five years, the proton microprobe at Bochum (Germany) has been used as a trace element tool in the context of isotope stratigraphy and paleoceanographic studies. The Sr, O, and C isotopic composition of some biogenic material (e.g. calcitic brachiopod shells, phosphatic conodonts) is widely accepted to mirror, under favourable conditions, the isotopic composition of the coeval sea water. The latter, in turn, is a function of a variety of global processes, such as climatic change, volcanic activity, plate tectonics or circulation of ocean water. Thus, on the basis of the isotopic properties of fossil shell material, isotope curves can be constructed that reflect variations in the above factors over the entire Phanerozoic. However, as a consequence of the long time elapsed since deposition of the fossils, they are prone to chemical and isotopic alteration and may thus yield equivocal or even irrelevant information if no care is taken to monitor the degree of their diagenetic alteration. Trace element composition of the fossil material, combined with cathodoluminescence investigations, is one of the most frequently utilized tools to assess the diagenetic quality of the samples. Beam current was in the range of a few nA, resulting in charges of 1-10 {mu}C for a single measurement. Detection limits for point analyses were between 10 and 30 ppm for Mn, Fe, Sr, but considerably higher for rare earth elements. Accuracy around 10% for a number of elements analysed is reported. 8 refs., 2 figs.

  3. Carbon isotope geochemistry and geobiology

    Science.gov (United States)

    Desmarais, D.

    1985-01-01

    Carbon isotope fractionation values were used to understand the history of the biosphere. For example, plankton analyses confirmed that marine extinctions at the end of the Cretaceous period were indeed severe (see Hsu's article in Sundquist and Broeker, 1984). Variations in the isotopic compositions of carbonates and evaporitic sulfates during the Paleozoic reflect the relative abundances of euxinic (anoxic) marine environments and organic deposits from terrestrial flora. The carbon isotopic composition of Precambrian sediments suggest that the enzyme ribulose bisphosphate carboxylase has existed for perhaps 3.5 billion years.

  4. Carbonate fracture stratigraphy: An integrated outcrop and 2D discrete element modelling study

    Science.gov (United States)

    Spence, Guy; Finch, Emma

    2013-04-01

    Constraining fracture stratigraphy is important as natural fractures control primary fluid flow in low matrix permeability naturally fractured carbonate hydrocarbon reservoirs. Away from the influence of folds and faults, stratigraphic controls are known to be the major control on fracture networks. The fracture stratigraphy of carbonate nodular-chert rhythmite successions are investigated using a Discrete Element Modelling (DEM) technique and validated against observations from outcrops. Comparisons are made to the naturally fractured carbonates of the Eocene Thebes Formation exposed in the west central Sinai of Egypt, which form reservoir rocks in the nearby East Ras Budran Field. DEM allows mechanical stratigraphy to be defined as the starting conditions from which forward numerical modelling can generate fracture stratigraphy. DEM can incorporate both stratigraphic and lateral heterogeneity, and enable mechanical and fracture stratigraphy to be characterised separately. Stratally bound stratified chert nodules below bedding surfaces generate closely spaced lateral heterogeneity in physical properties at stratigraphic mechanical interfaces. This generates extra complexity in natural fracture networks in addition to that caused by bed thickness and lithological physical properties. A series of representative geologically appropriate synthetic mechanical stratigraphic models were tested. Fracture networks generated in 15 DEM experiments designed to isolate and constrain the effects of nodular chert rhythmites on carbonate fracture stratigraphy are presented. The discrete element media used to model the elastic strengths of rocks contain 72,866 individual elements. Mechanical stratigraphies and the fracture networks generated are placed in a sequence stratigraphic framework. Nodular chert rhythmite successions are shown to be a distinct type of naturally fractured carbonate reservoir. Qualitative stratigraphic rules for predicting the distribution, lengths, spacing

  5. The Sr-isotopic stratigraphy of the Northern Limb of the Bushveld Complex, South Africa

    Science.gov (United States)

    Mangwegape, Mpho; Roelofse, Frederick; Mock, Timothy; Carlson, Richard W.

    2016-01-01

    We present a compilation of Sr-isotopic data obtained on plagioclase from 27 samples covering the entire stratigraphy of the Northern Limb of the Bushveld Complex as determined by LA-MC-ICPMS. The lower parts of the Main Zone in the Northern Limb are characterised by significant variations in Sr-isotopic compositions (87Sr/86Sr ˜0.7087 ± 0.0005 (1-σ)) coupled with very limited differentiation as exemplified by plagioclase An%, suggesting construction of the lower Main Zone through the repeated influx of magmas. Fairly constant Sr-isotopic compositions of plagioclase within the Upper and upper Main Zones (87Sr/86Sr ˜0.7073 ± 0.0003) coupled with a broad normal differentiation trend are suggestive of fractionation processes being the dominant factor in the petrogenesis of these zones. The present results argue against the laterally extensive troctolite horizon of the Northern Limb having a Critical Zone parentage or being the direct equivalent of the Pyroxenite Marker in the Northern Limb. It may, however, be an analogue of the Pyroxenite Marker in that it occurs at the approximate level where the last voluminuous influx of magma into the Northern Limb is inferred to have taken place. The nature of the magmas that gave rise to the lower parts of the Main Zone in the Northern Limb deserves further investigation in light of the fact that plagioclase here shows considerable variation both within and between individual co-existing plagioclase crystals that may point to the intrusion of crystal mushes as opposed to aphyric liquids.

  6. The separation of stable isotopes of carbon

    Science.gov (United States)

    Oziashvili, E. D.; Egiazarov, A. S.

    1989-04-01

    The present state of work on the separation of carbon isotopes by diffusion, fractional distillation, chemical isotopic exchange, and the selective excitation and dissociation of molecules in electrical discharges or in the field of laser radiation has been examined. The characteristics of new laboratory and industrial assemblies for separating carbon isotopes have been described. Promising directions of study aimed at developing effective technological processes for separating carbon isotopes have been noted. The bibliography contains 148 references.

  7. Across an early Holocene humid phase in western Sahara:Pollen and isotope stratigraphy

    Science.gov (United States)

    Lézine, Anne-Marie; Casanova, Joël; Hillaire-Marcel, Claude

    1990-03-01

    Paleohydrology and paleoecology of the region around the Chemchane sabkha (Mauritania) are reconstructed from the comparative analyses of mineralogy, stable isotope ratios of bulk carbonates, and palynology from sediment cores. The age of the section is from ca. 13.5 ka to the middle Holocene. Maximum lake expansion between about 8.3 and 6.5 ka is recorded in a girdle of stromatolite carbonates. These document a lower-salinity lake concomitant with a general establishment of Sahel-Sudan vegetation. The Chemchane area is the northernmost (lat 21°N) occurrence of humid- phase elements that are related to maximum intensity of monsoon activity during the early Holocene.

  8. The clumped isotopic record of Neoproterozoic carbonates, Sultanate of Oman

    Science.gov (United States)

    Bergmann, K. D.; Eiler, J. M.; Fischer, W. W.; Osburn, M. R.; Grotzinger, J. P.

    2011-12-01

    The Huqf Supergroup of the Sultanate of Oman records several important events in latest Precambrian time, including two glaciations in the Abu Mahara Group (ca. 725 - isotope excursion in the Nafun Group (ca. isotopic excursions, hypothesized to record perturbations of the surficial Earth carbon cycle or post-depositional diagenetic processes. Rigorous interpretation of these records requires a more thorough assessment of diagenetic processes. To better understand the significance and cause of these large amplitude isotopic excursions, we employed carbonate clumped isotope thermometry. This method allows us to estimate the absolute temperature of carbonate precipitation, including recrystallization, based on the temperature dependent abundance of carbonate ions containing both 13C and 18O. These estimates are accompanied by a measurement of carbonate δ18O, which in conjunction with temperature, can be used to calculate the oxygen isotopic composition of the fluid from which the carbonate precipitated. We analyzed stratigraphically constrained samples from a range of paleoenvironments with differing burial histories (1 - >10km maximum burial depth) to constrain the temperature and fluid composition of recrystallization. Clumped isotope temperatures from Huqf Supergroup samples range from 35-175°C. The isotopic composition of the fluid these rocks equilibrated with ranges from -3.7 to 15.7% VSMOW. This large range in temperature and fluid composition separates into distinct populations that differ systematically with independent constraints on petrography, stratigraphy and burial history. The data indicate the Abu Mahara, Nafun and Ara groups have unique diagenetic histories. In central Oman, the post-glacial Abu Mahara cap dolostone shows high temperature, rock buffered diagenesis (Tavg = 176°C; δ18Ofluid = 15% VSMOW), the Nafun Group generally experienced lower temperature, fluid buffered diagenesis (Tavg = 69°C; δ18Ofluid = 1% VSMOW) and the Ara Group

  9. Cr isotope stratigraphy of Ediacaran cap dolostones, Doushantuo Formation, South China

    Science.gov (United States)

    Rodler, Alexandra; Hohl, Simon V.; Guo, Qingjun; Frei, Robert

    2016-04-01

    The Yangtze Platform in South China is considered a key site for studying Neoproterozoic ocean oxygenation. The chromium isotope composition (δ53Cr) of marine carbonates has shown to be a sensitive tracer of changing (paleo)redox conditions and was previously linked to photosynthetic activity (1). We applied this emerging proxy to cap dolostones of a deep water and a shallow marine carbonate section pertaining to the Doushantuo Formation that have previously been used to constrain the redox evolution of Ediacaran seawater (2,3). Postglacial detrital contamination and diagenetic alteration appear to have influenced the δ53Cr values of Doushantuo cap dolostones as evidenced by systematic changes in δ53Cr and Cr concentrations coupled with several geochemical tracers. We use Al concentrations as indicator of detrital contamination and to calculate the authigenic Cr isotope composition. Further, we hypothesis that post-depositional remobilization of Cr might have resulted in the loss of heavy Cr isotopes and the retention of light Cr isotopes during precipitation of secondary carbonates. This scenario is supported by a decrease in δ53Cr values that is correlated with a loss of Sr and increasingly light δ18Ocarb signals, which would indicate meteoric fluid/rock interaction and diagenetic alteration by continental basin fluids. However, some cap dolostones may still show pristine Ediacaran seawater signals with positively fractionated δ53Cr (relative to bulk silicate Earth; 4), 87Sr/86Sr close to Ediacaran seawater values and a pronounced negative Ce anomaly. These tracers reveal light pulses of enhanced postglacial oxidative weathering during cap dolostone deposition. The Cr isotope composition of Ediacaran cap dolostones pertaining to the Doushantuo Formation trace changes in past redox conditions, where fine-scale δ53Cr fluctuations are perhaps a result of detrital contamination and diagenetic alteration balanced against a signal of oxidative weathering

  10. Chromium isotope uptake in carbonates

    DEFF Research Database (Denmark)

    Rodler, Alexandra

    composition of contemporaneous seawater. Marine carbonates are ubiquitous throughout Earth’s rock record rendering them a particularly interesting archive for constraining past changes in ocean chemistry. This thesis includes an investigation of the fractionation behavior of Cr isotopesduring coprecipitation......Chromium (Cr) is a redox sensitive element potentially capable of tracing fine-scale fluctuations of the oxygenation of Earth’s early surface environments and seawater. The Cr isotope composition of carbonates could perhaps be used as paleo-redox proxy to elucidate changes in the geological past...... related to the rise of oxygen and the evolution of the biosphere. However, before the Cr isotopesystem can be applied to faithfully delineate paleo-environmental changes, careful assessment of the signal robustness and a thorough understanding of the Cr cycle in Earth system processes is necessary...

  11. Robust optical carbon dioxide isotope analyzer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Isotopic analysis of carbon dioxide is an important tool for characterization of the exchange and transformation of carbon between the biosphere and the atmosphere....

  12. Oxygen isotope stratigraphy and events in the northern South China Sea during the last 6 million years

    Institute of Scientific and Technical Information of China (English)

    JIAN; Zhimin

    2001-01-01

    [1]Clemens, S. C., Murry, D. W., Prell, W. L., Nonstationary phase of the Plio-Pleistocene Asian monsoon, Science, 1996,274: 943.[2]Ruddiman, W. F., Raymo, M. E., Northern Hemisphere climatic regimes during the past 3 Ma: Possible tectonic connec tions, Philos. Trans. R. Soc. London, Ser. B, 1988, 318: 411.[3]Shackleton, N. J., Hall, M. A., Pate, D., Pliocene stable isotope stratigraphy of ODP site 846, Proc. Ocean Drill Program Sci. Results, 1995, 138: 337.[4]Tiedeman, R., Sarnthein, M., Shackleton, N. J., Astronomic timescale for the Pliocene Atlantic δ18O and dust flux records of Ocean Drilling Program site 659, Paleoceanography, 1994, 9(4): 619.[5]Jian, Z., Stable isotopic evidences of the glacial deep water properties in the South China Sea, Science in China, Ser D,1998, 41(4): 337.[6]Wang, P., Western Pacific in glacial cycles: Seasonality in marginal seas and variability of Warm Pool, Science in China,SerD, 1998,41(1): 35.[7]Jian, Z., Wang, P., Chen, M. P. et al., Foraminiferal response to major Pleistocene paleoceanographic changes in the south ern South China Sea, Paleoceanography, 2000, 15(2): 229.[8]Jian, Z., Quantitative analysis of paleoenvironment in the northwestern shelf of South China Sea based on cutting samples (in Chinese with English abstract), Acta Palaeontologica Sinica, 1993, 32(5): 550.[9]Wang, P., Prell, W., Blum, P., Proceedings ofthe Ocean Drilling Program, Initial Reports Volume 184, College Station:Ocean Drilling Program, 2000.[10]Fairbanks, R. G., Sverdlove, M., Free, R. et al., Vertical distribution and isotopic fractionation of living planktonic fo raminifera from the Panama Basin, Nature, 1982, 298: 841.[11]Imbrie, J., Hays, J. D., Martinson, D. G. et al., The orbital theory of Pleistocene climate: Support from a revised chronol ogy of the marine o18O record, in Milankovitch and Climate (eds. Berger, A., Imbrie, J.), Norwell: D Riedel, 1984, 269-305.[12]Shackleton, N. J., Berger, A

  13. Carbon isotopic fractionation in heterotrophic microbial metabolism

    Science.gov (United States)

    Blair, N.; Leu, A.; Munoz, E.; Olsen, J.; Kwong, E.; Des Marais, D.

    1985-01-01

    Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4 percent depleted in C-13 relative to the glucose used as the carbon source, whereas the acetate was 12.3 percent enriched in C-13. The acetate C-13 enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6 percent depleted in C-13, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7 percent, respectively. Aspartic and glutamic acids were -1.6 and +2.7 percent, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle.

  14. C, O and Sr isotopic stratigraphy of carbonates pre and pos Jequitai glaciation: Bezerra-Formosa area, Goias, BR;Variacoes dos isotopos de C e Sr em carbonatos pre e pos-glaciacao Jequitai (Esturtiano) na regiao de Bezerra-Formosa, Goias

    Energy Technology Data Exchange (ETDEWEB)

    Alvarenga, Carlos Jose Souza de; Della Giustina, Maria Emilia Schuteski; Silva, Nivea Goulart Carramal; Santos, Roberto Ventura; Gioia, Simone Maria Costa Lima; Guimaraes, Edi Mendes; Dardenne, Marcel Auguste, E-mail: alva1@unb.b [Universidade de Brasilia (IG/UnB), DF (Brazil). Inst. de Geociencias; Sial, Alcides Nobrega; Ferreira, Valderez Pinto [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Lab. de Isotopos Estaveis (LABISE)

    2007-12-15

    Carbonate rocks of the upper Paranoa Group and lower Bambui Group (Sete Lagoas Formation) have been founded at the occidental border of the Sao Francisco craton. These units have been separated by the Sturtian glaciation, identified by Jequitai Formation, but in some localities the glacial record is absent and is difficult to separate these two carbonates units. In this paper two sections with a good stratigraphic control have been chosen to find C, O and Sr isotopic values to have tools for the correlations. Carbonates of the Paranoa Group present a trend of positive {delta}{sup 13}C{sub PDB} varying between +0.8 e +2.7 %o, of {delta}{sup 18}O{sub PDB} varying between -9.0 e -4.7 %o and {sup 87}Sr/{sup 86}Sr ranging from 0.7063 to 0.7068. The diamictite sample of Jequitai Formation has {delta}{sup 13}C{sub PDB} values of -1.8%o and {delta}{sup 18}O{sub PDB} values of -5.1%o. The cap dolomites of the Sete Lagoas Formation are associated with an extremely negative {delta}{sup 13}C{sub PDB} values between -6.0 e -3.2 %o, {delta}{sup 18}O{sub PDB} values between -9.1 e -5.3%o and high {sup 87}Sr/{sup 86}Sr ratios suggesting a radiogenic Sr isotope anomaly. Limestone and muddy-limestone above the cap dolomite still starts with extremely negative {delta}{sup 13}C{sub PDB} values (-6.0%o) and are followed by an upward trend of increasing carbon isotope values up to +9.2 %o. In the same interval the {delta}{sup 18}O{sub PDB} values ranging from -10.1%o at the base to -5.5%o in direction to the top of formation and primary {sup 87}Sr/{sup 86}Sr ratios between 0.70745 and 0.70758. The Carbon and Sr isotope data presented here reveal significant differences between carbonates from the Paranoa Group and the Bambui Group. These data developed here provides the framework for a new regional isotopic correlation model to the carbonates units of the Paranoa and Bambui groups. (author)

  15. Stratigraphy and mineralogy of a carbonate-hosted gold deposit: Kings Mountain gold mine, NC

    Energy Technology Data Exchange (ETDEWEB)

    Supplee, J.; Lapoint, D.; Feiss, P.G.

    1985-01-01

    The Kings Mountain Gold Mine, Cleveland Company, North Carolina, is unique in the Appalachians in that it is carbonate-hosted, with a distinctive ore mineralogy. The mine stratigraphy is upright, younging east to west. The basal unit is a volcanic to subvolcanic chlorite, feldspar, quartz-eye porphyry, cut by a silicic porphyry, interpreted as a shallow level intrusion. Above and gradational to the chloritic porphyry, unless separated by the intrusive silicic porphyry, is a sericitic, quartz-eye porphyry, probably a metatuff. A north-thinning, graphite schists is above the sericitic porphyry. Carbonates overlie the graphite schist except to the north where they are above the sericitic porphyry. The carbonates consist of basal and upper sequences separated by a sericite, quartz-eye schists (metatuff) which is capped by a chlorite-sericite-graphite schist. Mineralization occurs within each carbonate sequence. This is overlain by interbedded chlorite and graphite schists with two horizons of exhalative iron formation (I.F.). Above the I.F. is a thick sequence of sericitic chlorite schists (turbidites). The mineralized carbonates are pervasively silicified with a disseminated assemblage of pyrite, pyrrhotite, sphalerite, chalcopyrite, galena, gold, altaite (PbTe), tetrahedrite, and pyrargyrite in quartz and dolomite +/- fluorite gangue. We suggest that the mineralization is associated with hydrothermal activity during emplacement of the silicic porphyry and following carbonate diagenesis. Mineralization was syn- or post-depositional with respect to the I.F.

  16. Carbon isotopic composition of fossil leaves from the Early Cretaceous sediments of western India

    Indian Academy of Sciences (India)

    S Chakraborty; B N Jana; S K Bhattacharya; I Robertson

    2011-08-01

    Stable carbon isotope analysis of fossil leaves from the Bhuj Formation, western India was carried out to infer the prevailing environmental conditions. Compression fossil leaves such as Pachypteris indica, Otozamite kachchhensis, Brachyphyllum royii and Dictyozamites sp. were recovered from three sedimentary successions of the Bhuj Formation, Early Cretaceous in age. A chronology was established based on faunal assemblage and palyno-stratigraphy and further constrained by carbon isotope stratigraphy. The three sampling sites were the Karawadi river bank near Dharesi; the Chawad river bank near Mathal; and the Pur river section near Trambau village in Gujarat. The Dharesi sample was also analyzed to investigate intra-leaf 13C variability. The mean 13C of the leaf was −24.6 ± 0.4‰ which implied negligible systematic change along the leaf axis. The Mathal sample was fragmented in nature and showed considerable variation in carbon isotopic composition. The Trambau sample considered to be the oldest, dating to the middle of Aptian (ca. 116 Ma), shows the most depleted value in 13C among all of them. The overall 13C trend ranging from mid Aptian (ca. 116 Ma) to early Albian (ca. 110 Ma) shows a progressive increase in 13C from −26.8 to −20.5‰. Based on these measurements the carbon isotopic composition of atmospheric carbon dioxide of the Aptian–Albian period is estimated to be between −7.4 and −1.7‰. The ratio of the partial pressure of carbon dioxide in leaf to that of the ambient atmosphere calculated based on a model is estimated to be similar to that of the modern plants. This indicates that the Early-Cretaceous plants adapted to the prevailing high carbon dioxide regime by increasing their photosynthetic uptake.

  17. Significance of Carbon Isotopes in Carbonate Sequence Stratigraphy—As Exemplified by the Permian System in Southwest China

    Institute of Scientific and Technical Information of China (English)

    覃建雄; 杨作升; 等

    1999-01-01

    Based on the research on sequence stratigraphy of the Permian in Southwest China,in conjunction with the carbon isotope data from the typical sections at Ganluo,Sichuan and Tianlin and Masan,Guangxi,the authors suggest that the genetic framework and internal architicture of different sequences possess quite different carbon isotopic characteristics.Therefore ,the following problems can be solved in terms of carbon isotopic values,evolutionary curve patterns and structures of carbonate sequences:(1) to determe the nature of sequence boundary surface and related geological events;(2) to recognize various kinds of sedimentary system tracts;(3) to discuss the internal architicture and genetic framework of the sequences and their evolution;(4) to subdivide and correlate sedimentary sequences on a regional or global scale; and (5)to enhance the resolution of sequence stratigraphic analysis.Stable carbon isotopes have proved themselves to be valid in sequence stratigraphic studies of carbonate rocks,as demonstrated by our results presented in this paper.

  18. Carbon and oxygen isotope variations of the Middle-Late Triassic Al Aziziyah Formation, northwest Libya

    Science.gov (United States)

    Moustafa, Mohamed S. H.; Pope, Michael C.; Grossman, Ethan L.; Mriheel, Ibrahim Y.

    2016-06-01

    This study presents the δ13C and δ18O records from whole rock samples of the Middle-Late Triassic (Ladinian-Carnian) Al Aziziyah Formation that were deposited on a gently sloping carbonate ramp within the Jifarah Basin of Northwest Libya. The Al Aziziyah Formation consists of gray limestone, dolomite, and dolomitic limestone interbedded with shale. The Ghryan Dome and Kaf Bates sections were sampled and analyzed for carbon and oxygen isotope chemostratigraphy to integrate high-resolution carbon isotope data with an outcrop-based stratigraphy, to provide better age control of the Al Aziziyah Formation. This study also discusses the relation between the facies architecture of the Al Aziziyah Formation and the carbon isotope values. Seven stages of relative sea level rise and fall within the Ghryan Dome were identified based on facies stacking patterns, field observations and carbon stable isotopes. The Al Aziziyah Formation δ13C chemostratigraphic curve can be partially correlated with the Triassic global δ13C curve. This correlation indicates that the Al Aziziyah Formation was deposited during the Ladinian and early Carnian. No straight-forward relationship is seen between δ13C and relative sea level probably because local influences complicated systematic environmental and diagenetic isotopic effects associated with sea level change.

  19. Carbon isotope geochemistry in the Yalujiang estuary

    Institute of Scientific and Technical Information of China (English)

    吴莹; 张经

    2001-01-01

    The distribution of particulate organic carbon (POC) along the lower reaches is similar between the dry season and the flood season in the Yalujiang Estuary, North China. However, the values of particulate organic carbon of the upperstream in the dry season are one magnitude lower than the concentrations in the flood season. Stable carbon isotope ratios have been used to study the sources of particulate organic carbon in the Yalujiang Estuary. The isotopic composition of POC shows a range from -23.1‰ to -29.4‰ with a little seasonal variation. The isotopic evidence indicates that the POC in the Yalujiang Estuary is predominantly of terrestrial origin rather than a result of in situ plankton. The study of the ratio of POC: Chla shows that the turbidity maximum plays an important role in POC cycle in the Yalujiang Estuary. Organic detritus and soil erosion are the main contributions to POC in the turbidity maximum, especially in the flood season.

  20. Carbon isotope anomalies in carbonates of the Karelian series

    Science.gov (United States)

    Iudovich, Ia. E.; Makarikhin, V. V.; Medvedev, P. V.; Sukhanov, N. V.

    1990-07-01

    Results are presented on carbon isotope distributions in carbonates of the Karelian complex. A highly anomalous isotopic composition was found in carbonate rocks aged from 2.6 to 1.9 b.y. In the stromatolitic carbonates of the Onega water table, delta-(C-13) reaches a value of +18 percent, while the shungite layer of the Zaonega horizon is characterized by a wide dispersion (from +7.9 to -11.8 percent). These data are in good agreement with the known geochemical boundary (about 2.2 b.y. ago) in the history of the earth.

  1. Exotic Structure of Carbon Isotopes

    CERN Document Server

    Suzuki, T; Hagino, K; Suzuki, Toshio; Sagawa, Hiroyuki; Hagino, Kouichi

    2002-01-01

    We studied firstly the ground state properties of C-isotopes using a deformed Hartree-Fock (HF)+ BCS model with Skyrme interactions. Shallow deformation minima are found in several neutron$-$rich C-isotopes. It is shown also that the deformation minima appear in both the oblate and the prolate sides in $^{17}$C and $^{19}$C having almost the same binding energies. Secondly, we carried out shell model calculations to study electromagnetic moments and electric dipole transitions of the C-isotopes. We point out the clear configuration dependence of the quadrupole and magnetic moments in the odd C-isotopes, which will be useful to find out the deformations and the spin-parities of the ground states of these nuclei. We studied electric dipole states of C-isotopes focusing on the interplay between low energy Pigmy strength and giant dipole resonances. Reasonable agreement is obtained with available experimental data for the photoreaction cross sections both in the low energy region below $\\hbar \\omega $=14 MeV and ...

  2. Oxygen isotope stratigraphy and events in the northern South China Sea during the last 6 million years

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen iso tope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Further more, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferaδl8O record shows that before ~3.1 Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1-2.5 Ma demonstrates the forma tion of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST)reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ18O,might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversi ble SST reductions during the period of ~2.2-0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.

  3. Soil Carbon: Compositional and Isotopic Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Moran, James J.; Alexander, M. L.; Laskin, Alexander

    2016-11-01

    This is a short chapter to be included in the next edition of the Encyclopedia of Soil Science. The work here describes techniques being developed at PNNL for investigating organic carbon in soils. Techniques discussed include: laser ablation isotope ratio mass spectrometry, laser ablation aerosol mass spectrometry, and nanospray desorption electrospray ionization mass spectrometry.

  4. Carbon isotopes as indicators of peatland growth?

    Science.gov (United States)

    Alewell, Christine; Krüger, Jan Paul; von Sengbusch, Pascal; Szidat, Sönke; Leifeld, Jens

    2016-04-01

    As undisturbed and/or growing peatlands store considerable amounts of carbon and are unique in their biodiversity and species assemblage, the knowledge of the current status of peatlands (growing with carbon sequestration, stagnating or degrading with carbon emissions) is crucial for landscape management and nature conservation. However, monitoring of peatland status requires long term measurements and is only feasible with expert knowledge. The latter determination is increasingly impeded in a scientific world, where taxonomic expert knowledge and funding of long term monitoring is rare. Stable carbon and nitrogen isotopes depth profiles in peatland soils have been shown to be a useful tool to monitor the degradation of peatlands due to permafrost thawing in Northern Sweden (Alewell et al., 2011; Krüger et al., 2014), drainage in Southern Finland (Krüger et al., 2016) as well as land use intensification in Northern Germany (Krüger et al., 2015). Here, we tackle the questions if we are able to differentiate between growing and degrading peats with the use of a combination of carbon stable (δ13C) and radiogenic isotope data (14C) with peat stratification information (degree of humification and macroscopic plant remains). Results indicate that isotope data are a useful tool to approximate peatland status, but that expert taxonomic knowledge will be needed for the final conclusion on peatland growth. Thus, isotope tools might be used for landscape screening to pin point sites for detailed taxonomic monitoring. As the method remains qualitative future research at these sites will need to integrate quantitative approaches to determine carbon loss or gain (soil C balances by ash content or C accumulation methods by radiocarbon data; Krüger et al., 2016). Alewell, C., R. Giesler, J. Klaminder, J. Leifeld, and M. Rollog. 2011. Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats. Biogeosciences, 8, 1769-1778. Krüger, J. P., Leifeld, J

  5. Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes;

    2015-01-01

    Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenviro......Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track...

  6. Deciphering Carbon Isotope Excursions in Separated Biogenic and Diagenetic Carbonates

    Science.gov (United States)

    Hermoso, M.; Minoletti, F.; Hesselbo, S.; Jenkyns, H.; Rickaby, R.; Diester-Haass, L.; Delsate, D.

    2008-12-01

    The long-term evolution of the carbon-isotope ratio in the sedimentary archive is classically linked with changes in primary productivity and organic matter burial. There have been sudden and pronounced shifts, so-called Carbon Isotope Excursions (CIEs) in the long-term trends as evidenced by synchronous shifts from various basins. These geochemical perturbations may have various explanations such as changes of the efficiency of the carbon sink; sudden infusion of isotopically-light carbon into the Ocean-Atmosphere system; or advection of 12C-rich source from bottom water in a stratified water column. Beside the record of primary changes in seawater chemistry, a possible diagenetic overprint may also mime such CIEs in the sedimentary record. The aim of this contribution is to illustrate through three critical intervals (the Early Toarcian, the K-P boundary and the Mid-Miocene Montery Event) how the various micron-sized sedimentary particles specifically record these CIEs, which are respectively associated with major paleoceanographical events. New techniques for getting monotaxic calcareous nannofossil assemblages from the sediment (Minoletti et al., accepted) enable the isotopic measurement at various depths within the surface water and from bottom water by analyzing early diagenetic precipitations (rhombs and micarbs). The integration of these high-resolution isotopic signals in terms of amplitudes affords to recognize diagenetic artifacts in some sections displaying coeval decrease in the carbonate content. For both Early Toarcian and K-P events, corroborative records of CIE records in both primary calcite and bottom water carbonate indicate a global C-isotope perturbation of the water column. For the Monterey event, the evolution of calcareous nannoplankton and the foraminifera isotopic records are in overall agreement, but in detail, the coccolith-discoaster and foraminifer ratio in the sediment, related to environmental changes, is likely to produce isotopic

  7. Origin, growth history and glacial-interglacial responses of a cold-water coral mound in NE Atlantic: Results from O-isotope and Sr-isotope stratigraphy in IODP Expedition 307

    Science.gov (United States)

    Sakai, S.; Kano, A.; Abe, K.; Browning, E.; Scientific Party, I.

    2007-12-01

    Cold-water corals may cover as a large area as the better-known warm-water corals forming shallow reefs, and they occur in a variety of forms and settings, from small isolated colonies or patch reefs to giant mound structures such as those found west of Ireland. In May 2005, IODP Expedition 307 sailed to Challenger Mound, which is one of thousands of cold-water coral mounds in Porcupine Seabight, 150 km offshore of southwestern Ireland, and recovered the first complete section through to the base of a modern cold-water coral mound which is composed of up to 155 m of unlithified coral-bearing (Lophelia pertusa) sediments. The coral-bearing sediments lie on an angular unconformable surface above the lower-middle Miocene glauconitic siltstones and sandstones. Mound growth could have been continuous, and the repeated 10-m-scale alternations in lithology between lighter- colored calcareous layers (interglacials) and darker-colored clayey layers (glacials) could be essentially related to the glacial-interglacial cycles, which supported by correspondence of the two curves of O-isotopes of planktic foraminifers and natural Gamma radiation. O-isotope results of planktic foraminifers show cold-water coral L. pertusa, which are organisms sensitive to environmental change, were able to maintain a cold-water coral mound community (e.g. temperature remained above 4°C) under the latest Pliocene-Pleistocene glacial- interglacial changes. Sr-isotopic stratigraphy revealed that the section is divided into two growth stages at 23.6 mbsf, and mound of the first stage started growing on the mid-Miocene basement around 2.6 Ma, when Northern Hemisphere glaciation was intensified. The mound growth reached a maximum rate (24 cm/ky) around 2.0Ma, and ceased at 1.7Ma. The second stage (1.0-0.5 Ma) shows a lower growth rate (5 cm/ky). Corals require zooplanktons that tend to condense in density gradient of ~800 m deep developed between Eastern North Atlantic Water (ENAW) and the underlying

  8. Planktic Foraminiferal Turnover and Stable Isotope Stratigraphy Across OAE1B in the Subtropical North Atlantic

    Science.gov (United States)

    Huber, B. T.; Price, N. A.; MacLeod, K. G.

    2003-12-01

    Stable isotope data generated from glassy (diagenetically unaltered) foraminifera from the subtropical North Atlantic (ODP Site 1049) reveal abrupt paleoceanographic and faunal changes that coincide with the Aptian/Albian boundary and the onset of Oceanic Anoxic Event (OAE) 1b. At least three planktic and one benthic species per sample, selected at closely spaced intervals from the Globigerinelloides algerianus Zone (mid-Aptian) through uppermost Ticinella bejaouaensis Zone (uppermost Aptian), reveal a consistently low (<1.1‰ ) vertical δ 18O gradient, suggesting that the thermocline was weakly developed throughout this time. Benthic δ 18O values show a slight positive increase from +0.5 ‰ during the mid-Aptian to +1.1% during the latest Aptian, then decrease to -0.2‰ during peak Corg deposition in OAE 1b (Hedbergella rischi Zone, lowermost Albian). Assuming that the δ 18O composition of Cretaceous seawater averaged -1.2‰ and polar ice sheets were absent or very small, we estimate that middle bathyal waters at this site ranged from 7-9° C during the mid-late Aptian and warmed to 12° C during OAE 1b peak Corg deposition. Mid-late Aptian upper surface waters ranged from 11-12° C, then warmed to 20° C during OAE 1b. The simultaneous change in planktic foraminifer assemblages and stable isotope values indicates that the onset of OAE 1b involved major changes in the North Atlantic climate and oceanography.

  9. Carbon isotopic composition of individual Precambrian microfossils.

    Science.gov (United States)

    House, C H; Schopf, J W; McKeegan, K D; Coath, C D; Harrison, T M; Stetter, K O

    2000-08-01

    Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1.7% to -31.9 +/- 1.2% and the delta 13C(PDB) values from microfossils of the Gunflint Formation ranged from -32.4 +/- 0.7% to -45.4 +/- 1.2%. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.

  10. Carbon isotopic composition of individual Precambrian microfossils

    Science.gov (United States)

    House, C. H.; Schopf, J. W.; McKeegan, K. D.; Coath, C. D.; Harrison, T. M.; Stetter, K. O.

    2000-01-01

    Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1.7% to -31.9 +/- 1.2% and the delta 13C(PDB) values from microfossils of the Gunflint Formation ranged from -32.4 +/- 0.7% to -45.4 +/- 1.2%. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.

  11. Synthetic stratigraphy of epicontinental seas: a carbonate sedimentation model and its applications in sea level studies

    Energy Technology Data Exchange (ETDEWEB)

    Cisne, J.L.; Gildner, R.F.

    1984-04-01

    Carbonates from the central parts of epicontinental seas are ideal strata for detailed study of eustatic sea level change. On the basis of sedimentation model in which carbonate accumulation rate is directly proportional to water depth, we developed synthetic stratigraphies for sea level histories expected for post-glacial transgression and for constant and sinusoidally fluctuating ocean ridge volume increase. These histories give distinctly different trends for water depth as a function of stratigraphic position in the sections' bathymetric curves. In general, water depth is proportional to the rate of sea level rise. Depth-dependent sedimentation leads to a time lag between sea level fluctuation and corresponding depth fluctuation which, as examples show, can approach 10/sup 6/ years for depth fluctuations of even a few meters--a fundamental consideration for reconstructing sea level curves, time-correlating sections by bathymetric curves, and relating water depth on continents to ocean ridge volume. Bathymetric curves based on gradient analysis of fossil assemblages (coenocorrelation curves) for American Middle Ordovician sections approximate patterns expected for sinusoidally increasing sea level. The model's predictions are tested in an ''artificial experiment'' that takes advantage of differential subsidence between the craton's middle and its edge to make a difference in the bathymetric histories of sections that otherwise record the same sea level history. The depth dependence in sedimentation was that above wave base net accumulation per year was very roughly 3 x 10/sup -6/ of the water depth.

  12. Carbon Isotope Chemistry in Molecular Clouds

    Science.gov (United States)

    Robertson, Amy N.; Willacy, Karen

    2012-01-01

    Few details of carbon isotope chemistry are known, especially the chemical processes that occur in astronomical environments like molecular clouds. Observational evidence shows that the C-12/C-13 abundance ratios vary due to the location of the C-13 atom within the molecular structure. The different abundances are a result of the diverse formation pathways that can occur. Modeling can be used to explore the production pathways of carbon molecules in an effort to understand and explain the chemical evolution of molecular clouds.

  13. Helium and carbon isotopes in Indian diamonds

    Science.gov (United States)

    Wiens, R.; Lal, D.; Craig, H.

    1990-09-01

    Helium and carbon isotope measurements in Indian diamonds (from Andhra Pradesh) were carried out using samples that included mined diamonds from primary kimberlite source rocks and alluvial diamonds from river gravel. The He and C isotope concentrations in diamonds from these two sources were compared, and the Indian diamonds were compared to those from other regions. Results indicate that most of the He-3 in the alluvial diamonds is of cosmogenic origin and that the alluvial diamonds may also have a significant He-4 component due to alpha particles implanted during storage in a secondary matrix. One diamond, a mined kimberlite specimen, was found to have the lowest He-4 content (0.018 microcc/g) so far recorded in diamonds.

  14. The Precambrian marine carbonate isotope database: version 1.1.

    OpenAIRE

    G. A. Shields; Veizer, J.

    2002-01-01

    We present a compilation of strontium, carbon, and oxygen isotope compositions of roughly 10,000 marine carbonate rocks of Archean - Ordovician age (3800 Ma – 450 Ma). The Precambrian Marine Carbonate Isotope Database (PMCID) has been compiled from 152 published and 3 unpublished articles and books of the past 40 years. Also included are 30 categories of relevant “metadata” that allow detailed comparisons and quality assessments of the isotope data to be made. The PMCID will be updated period...

  15. Carbon and strontium isotope variations and responses tosea-level fluctuations in the Ordovician of the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    JIANG; Maosheng

    2001-01-01

    [1]Arthur, M. A., The carbon cycle-controls of atmospheric CO2 and climate in the geologic past, in Climate in Earth History (eds., Berger, W. M., Crowell, J. C), Washington D C: U. S. National Academy Press, 1982, 55-67.[2]Kroopnick, P. M., Margolis, M. V., Wong, C. S., δ18C variations in marine carbonate sediments as indicators of the CO2 balance between atmosphere and ocean, in The Fate of Fossil Fuel CO2 in the Ocean (eds., Anderson, N. R., Malahoff. A.),New York: Plenum Press, 1977, 295-321.[3]Veizer, J., Fritz, P., Jones, B., Geochemistry of brachiopods: Oxygen and carbon isotopic records of Paleozoic oceans,Geochim. Cosmochim. Acta, 1986, 50: 1679- 1696.[4]Wadleigh, M. A., Veizer, J., 18O/16O and 13C/12C in Lower Paleozoic articulate brachiopods: Implications for the isotopic composition seawater, Geochim. Cosmochim. Acta, 1992, 56:431-443.[5]Goldberg, E. D., Minor elements in sea water, in Chemical Oceanography (eds., Riley, J. P., Skirrow, G.), Vol. l, New York: Academic Press, 1986.[6]Fanre, G., Principles ofIsotope Geology, New York: Wiley, 1986, 1 -589.[7]Ebneth, S., Diener, A., Buhl, D. et al., Strontium isotope systematics of conodonts: Middle Devonian, Eifel Mts. Germany,Paleogeogr. Paleoclimatol. Paleoecol, 1996, 119:201 - 214.[8]Martin, E. E., Macdougall, J. D., Sr and Nd isotopes at Permian / Triassic boundary: A record of climate change, Chem.Geol.. 1995. 125: 73-79.[9]Jones. C. E.. Jenkyns, H. C., Hesselbo, S. P., Strotium isotopic variations in Jurassic and Cretaceous seawater, Geochemica et Cosmochemica Acta. 1994, 58:3061 - 3074.[10]McArthur. J. M., Kennedy, W. J., Chen, M. et al., Staontium isotope stratigraphy for Late Cretaceous time: Drect numerical clibration of the Sr curve based on the U.S. western interior, Paleogeogr. Paleoclimatol. Paleoecol., 1994, 108:95-119.[11]McArthur, J. M., Thirlwall, M. F., Gale, A. S. et al., Strotium isotope stratigraphy for the Late Cretaceous: A new curve

  16. Carbon-isotopic analysis of dissolved acetate.

    Science.gov (United States)

    Gelwicks, J T; Hayes, J M

    1990-01-01

    Heating of dried, acetate-containing solids together with oxalic acid dihydrate conveniently releases acetic acid for purification by gas chromatography. For determination of the carbon-isotopic composition of total acetate, the acetate-containing zone of the chromatographic effluent can be routed directly to a combustion furnace coupled to a vacuum system allowing recovery, purification, and packaging of CO2 for mass-spectrometric analysis. For analysis of methyl carbon, acetic acid can be cryogenically trapped from the chromatographic effluent, then transferred to a tube containing excess NaOH. The tube is evacuated, sealed, and heated to 500 degrees C to produce methane by pyrolysis of sodium acetate. Subsequent combustion of the methane allows determination of the 13C content at the methyl position in the parent acetate. With typical blanks, the standard deviation of single analyses is less than 0.4% for acetate samples larger than 5 micromoles. A full treatment of uncertainties is outlined.

  17. The Oxidant Budget of Dissolved Organic Carbon Driven Isotope Excursions

    Science.gov (United States)

    Bristow, T. F.; Kennedy, M. J.

    2008-12-01

    Negative carbon isotope values, falling below the mantle average of about -5 per mil, in carbonate phases of Ediacaran age sedimentary rocks are widely regarded as reflecting negative excursions in the carbon isotopic composition of seawater lasting millions of years. These isotopic signals form the basis of chemostratigraphic correlations between Ediacaran aged sections in different parts of the world, and have been used to track the oxidation of the biosphere. However, these isotopic values are difficult to accommodate within limits prescribed by the current understanding of the carbon cycle, and a hypothetical Precambrian ocean dissolved organic carbon (DOC) pool 100 to 1000 times the size of the modern provides a potential source of depleted carbon not considered in Phanerozoic carbon cycle budgets. We present box model results that show the remineralization of such a DOC pool to drive an isotope excursion of the magnitude observed in the geological record exhausts global budgets of free oxygen and sulfate in 800 k.y. These results are incompatible with the estimated duration of late Ediacaran isotope excursions of more than 10 m.y., as well as geochemical and biological indicators that oceanic sulfate and oxygen levels were maintained or even increased at the same time. Therefore the carbon isotope record is probably not a useful tool for monitoring oxygen levels in the atmosphere and ocean. Covariation between the carbon and oxygen isotope records is often observed during negative excursions and is indicative of local processes or diagenetic overprinting.

  18. Organic chemistry of Murchison meteorite: Carbon isotopic fractionation

    Science.gov (United States)

    Yuen, G. U.; Blair, N. E.; Desmarais, D. J.; Cronin, J. R.; Chang, S.

    1986-01-01

    The carbon isotopic composition of individual organic compounds of meteoritic origin remains unknown, as most reported carbon isotopic ratios are for bulk carbon or solvent extractable fractions. The researchers managed to determine the carbon isotopic ratios for individual hydrocarbons and monocarboxylic acids isolated from a Murchison sample by a freeze-thaw-ultrasonication technique. The abundances of monocarboxylic acids and saturated hydrocarbons decreased with increasing carbon number and the acids are more abundant than the hydrocarbon with the same carbon number. For both classes of compounds, the C-13 to C-12 ratios decreased with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic number than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with a kinetically controlled synthesis of higher homologues for lower ones.

  19. A Clumped Isotope Calibration for Lacustrine Carbonates

    Science.gov (United States)

    Mitsunaga, B. A.; Mering, J. A.; Petryshyn, V. A.; Dunbar, R. B.; Cohen, A. S.; Liu, X.; Kaufman, D. S.; Eagle, R.; Tripati, A.

    2014-12-01

    Our capacity to understand Earth's environmental history is highly dependent on the accuracy of past climate reconstructions. Unfortunately, many terrestrial proxies—tree rings, speleothems, leaf margin analyses, etc.—are influenced by the effects of both temperature and precipitation. Methods that can isolate the effects of temperature alone are needed, and clumped isotope thermometry has the potential to be a useful tool for determining terrestrial climates. Multiple studies have shown that the fraction of 13C—18O bonds in carbonates is inversely related to the temperature at which the rocks formed and may be a useful proxy for reconstructing temperatures on land. An in-depth survey of lacustrine carbonates, however, has not yet been published. Therefore we have been measuring the abundance of 13C18O16O in the CO2 produced by the dissolution of modern lake samples' carbonate minerals in phosphoric acid and comparing results to independently known estimates of lake water temperature and air temperature. Some of the sample types we have investigated include endogenic carbonates, freshwater gastropods, bivalves, microbialites, and ooids.

  20. Degradation changes stable carbon isotope depth profiles in palsa peatlands

    Directory of Open Access Journals (Sweden)

    J. P. Krüger

    2014-01-01

    Full Text Available Palsa peatlands are a significant carbon pool in the global carbon cycle and are projected to change by global warming due to accelerated permafrost thaw. Our aim was to use stable carbon isotopes as indicators of palsa degradation. Depth profiles of stable carbon isotopes generally reflect organic matter dynamics in soils with an increase of δ13C values during aerobic decomposition and stable or decreasing δ13C values with depth during anaerobic decomposition. Stable carbon isotope depth profiles of undisturbed and degraded sites of hummocks as well as hollows at three palsa peatlands in northern Sweden were used to investigate the degradation processes. The depth patterns of stable isotopes clearly differ between intact and degraded hummocks at all sites. Erosion and cryoturbation at the degraded sites significantly changes the stable carbon isotope depth profiles. At the intact hummocks the uplifting of peat material by permafrost is indicated by a turning in the δ13C depth trend and this assessment is supported by a change in the C / N ratios. For hollows isotope patterns were less clear, but some hollows and degraded hollows in the palsa peatlands show differences in their stable carbon isotope depth profiles indicating enhanced degradation rates. We conclude that the degradation of palsa peatlands by accelerated permafrost thawing could be identified with stable carbon isotope depth profiles. At intact hummocks δ13C depth patterns display the uplifting of peat material by a change in peat decomposition processes.

  1. Phanerozoic and Neoproterozoic Negative Carbon Isotope Excursions, Diagenesis and Terrestrialization

    Science.gov (United States)

    Paul, K.; Kennedy, M. J.

    2008-12-01

    Comprehensive data sets of Phanerozoic and late Precambrian carbon isotope data derived from carbonate rocks show a similar positive relation when cross-plotted with oxygen isotope values. The range and slope between the time periods is identical and the processes responsible for the relation have been well documented in Quaternary sediments. These processes include the stabilization of isotope values to ambient meteoric water values during shallow burial and flushing of carbonate sediments. Both data sets show strongly depleted carbon (-9 per mil PDB) and oxygen isotope values that retain seemingly systematic stratigraphic patterns with the Quaternary and Phanerozoic examples that demonstrably record meteroric water values. Similar values and patterns in the Precambrian are interpreted as primary marine in origin with significant implications for an ocean carbon mass balance not possible in the Phanerozoic carbon cycle. A similar compilation of carbonates older than one billion years do not show a relation between carbon and oxygen isotopes, lacking the negative carbon values evident in the younger record. We hypothesize that this difference records the onset of significant organic carbon on the land surface and the alteration of meteoric waters toward Phanerozoic values. We demonstrate the meteoric affinities of Neoproterozoic carbonates containing prominent negative isotope excursions recorded in the Shuram and Wonoka Formations of Oman and South Australia commonly attributed to whole ocean isotope variation. The conspicuous absence of negative carbon isotope values with normal marine oxygenisotope values in the Phanerozoic and Neoproterozic identifies a consistent relation between these time intervals and suggests that, as well accepted in the Phanerozoic, negative carbon isotope excursions less than -3 per mil are not a record of marine processes, but rather the later terrestrial biotic influence on meteoric water values.

  2. Integrated stratigraphy and paleoenvironmental reconstruction for the Late Cretaceous Danish chalk based on the Stevns-2 core

    DEFF Research Database (Denmark)

    Boussaha, Myriam; Thibault, Nicolas Rudolph; Stemmerik, Lars

    An integrated stratigraphy of the Stevns-2 core located in eastern Denmark is hereby presented based on calcareous nannofossil biostratigraphy and carbon isotope stratigraphy. Carbon and oxygen isotope have been performed on 419 bulk samples. Calcareous nannofossil biostratigraphy has been applied...... in order to provide an age-model for Stevns-2. While using this age-model, differences in the sedimentation rates of Stevns-1 and Stevns-2 borehole are nicely expressed, although the two sites are only 8 km apart from each other. The mechanisms responsible for these changes are under investigation...

  3. Carbon isotope fractionation in protoplanetary disks

    CERN Document Server

    Woods, Paul M

    2008-01-01

    We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the UV radiation field. We discuss inner-disk chemistry in general, obtaining excellent agreement with recent observations which have probed the material in the inner regions of protoplanetary disks. We also apply our model to study the isotopic fractionation of carbon. Results show that the fractionation ratio, 12C/13C, of the system varies with radius and height in the disk. Different behaviour is seen in the fractionation of different species. We compare our results with 12C/13C ratios in the Solar System comets, and find a stark contrast, indicative of reprocessing.

  4. Mass transfer and carbon isotope evolution in natural water systems

    Science.gov (United States)

    Wigley, T.M.L.; Plummer, L.N.; Pearson, F.J.

    1978-01-01

    This paper presents a theoretical treatment of the evolution of the carbon isotopes C13 and C14 in natural waters and in precipitates which derive from such waters. The effects of an arbitrary number of sources (such as dissolution of carbonate minerals and oxidation of organic material) and sinks (such as mineral precipitation, CO2 degassing and production of methane), and of equilibrium fractionation between solid, gas and aqueous phases are considered. The results are expressed as equations relating changes in isotopic composition to changes in conventional carbonate chemistry. One implication of the equations is that the isotopic composition of an aqueous phase may approach a limiting value whenever there are simultaneous inputs and outputs of carbonate. In order to unambiguously interpret isotopic data from carbonate precipitates and identify reactants and products in reacting natural waters, it is essential that isotopic changes are determined chiefly by reactant and product stoichiometry, independent of reaction path. We demonstrate that this is so by means of quantitative examples. The evolution equations are applied to: 1. (1) carbon-14 dating of groundwaters; 2. (2) interpretation of the isotopic composition of carbonate precipitates, carbonate cements and diagenetically altered carbonates; and 3. (3) the identification of chemical reaction stoichiometry. These applications are illustrated by examples which show the variation of ??C13 in solutions and in precipitates formed under a variety of conditions involving incongruent dissolution, CO2 degassing, methane production and mineral precipitation. ?? 1978.

  5. Intramolecular carbon isotope distribution of acetic acid in vinegar.

    Science.gov (United States)

    Hattori, Ryota; Yamada, Keita; Kikuchi, Makiko; Hirano, Satoshi; Yoshida, Naohiro

    2011-09-14

    Compound-specific carbon isotope analysis of acetic acid is useful for origin discrimination and quality control of vinegar. Intramolecular carbon isotope distributions, which are each carbon isotope ratios of the methyl and carboxyl carbons in the acetic acid molecule, may be required to obtain more detailed information to discriminate such origin. In this study, improved gas chromatography-pyrolysis-gas chromatography-combustion-isotope ratio mass spectrometry (GC-Py-GC-C-IRMS) combined with headspace solid-phase microextraction (HS-SPME) was used to measure the intramolecular carbon isotope distributions of acetic acid in 14 Japanese vinegars. The results demonstrated that the methyl carbons of acetic acid molecules in vinegars produced from plants were mostly isotopically depleted in (13)C relative to the carboxyl carbon. Moreover, isotopic differences (δ(13)C(carboxyl) - δ(13)C(methyl)) had a wide range from -0.3 to 18.2‰, and these values differed among botanical origins, C3, C4, and CAM plants.

  6. Clumped-isotope thermometry of magnesium carbonates in ultramafic rocks

    Science.gov (United States)

    García del Real, Pablo; Maher, Kate; Kluge, Tobias; Bird, Dennis K.; Brown, Gordon E.; John, Cédric M.

    2016-11-01

    Magnesium carbonate minerals produced by reaction of H2O-CO2 with ultramafic rocks occur in a wide range of paragenetic and tectonic settings and can thus provide insights into a variety of geologic processes, including (1) deposition of ore-grade, massive-vein cryptocrystalline magnesite; (2) formation of hydrous magnesium carbonates in weathering environments; and (3) metamorphic carbonate alteration of ultramafic rocks. However, the application of traditional geochemical and isotopic methods to infer temperatures of mineralization, the nature of mineralizing fluids, and the mechanisms controlling the transformation of dissolved CO2 into magnesium carbonates in these settings is difficult because the fluids are usually not preserved. Clumped-isotope compositions of magnesium carbonates provide a means to determine primary mineralization or (re)equilibration temperature, which permits the reconstruction of geologic processes that govern magnesium carbonate formation. We first provide an evaluation of the acid fractionation correction for magnesium carbonates using synthetic magnesite and hydromagnesite, along with natural metamorphic magnesite and low-temperature hydromagnesite precipitated within a mine adit. We show that the acid fractionation correction for magnesium carbonates is virtually indistinguishable from other carbonate acid fractionation corrections given current mass spectrometer resolution and error. In addition, we employ carbonate clumped-isotope thermometry on natural magnesium carbonates from various geologic environments and tectonic settings. Cryptocrystalline magnesite vein deposits from California (Red Mountain magnesite mine), Austria (Kraubath locality), Turkey (Tutluca mine, Eskişehir district) and Iran (Derakht-Senjed deposit) exhibit broadly uniform Δ47 compositions that yield apparent clumped-isotope temperatures that average 23.7 ± 5.0 °C. Based on oxygen isotope thermometry, these clumped-isotope temperatures suggest

  7. Sr isotopic variations in Upper Proterozoic carbonates from Svalbard and East Greenland

    Science.gov (United States)

    Derry, Louis A.; Keto, Lisette S.; Jacobsen, Stein B.; Knoll, Andrew H.; Swett, Keene

    1989-01-01

    Precambrian Sr isotope stratigraphy was investigated by determining variations in Sr-87/Sr-86 ratios in the Upper Proterozoic carbonate succession from Svalbard and East Greenland. Data from this study were combined with those from literature to construct a curve of Sr-87/Sr-86 versus time for Upper Proterozoic seawater. The curve for the Upper Riphean-Vandian showed that the isotopic composition of Sr in seawater was low (Delta Sr-87 of about -500) between 900 and 650 Ma but rose rapidly to about +30 by 600 Ma (this range of long-term variation exceeds the total Phanerozoic variation). The very low values of Delta Sr-87 inferred for the Riphean require that, for this time, the submarine hydrothermal water flux was a large fraction of the Sr input to the oceans, while the rise in Delta Sr-87 in the Upper Proterozoic seawater reflects both a change in the ratio of hydrothermal and continental fluxes of Sr to the oceans, and a change in the isotopic composition of Sr from continental sources.

  8. BIODEGRADATION OF FLUORANTHENE AS MONITORED USING STABLE CARBON ISOTOPES

    Science.gov (United States)

    The measurement of stable isotope ratios of carbon (d13C values) was investigated as a viable technique to monitor the intrinsic bioremediation of polycyclic aromatic hydrocarbons (PAHs). Biometer-flask experiments were conducted in which the bacterium, Sphingomonas paucimobilis,...

  9. Modeling the carbon isotope composition of bivalve shells (Invited)

    Science.gov (United States)

    Romanek, C.

    2010-12-01

    The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., organism and high (>90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions, equilibrium carbon isotope

  10. Carbon isotopic studies of organic matter in Precambrian rocks.

    Science.gov (United States)

    Oehler, D. Z.; Schopf, J. W.; Kvenvolden, K. A.

    1972-01-01

    A survey has been undertaken of the carbon composition of the total organic fraction of a suite of Precambrian sediments to detect isotopic trends possibly correlative with early evolutionary events. Early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa were examined for this purpose. Reduced carbon in these cherts was found to be isotopically similar to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts was found to be anomalously heavy; it is suggested that this discontinuity may reflect a major event in biological evolution.

  11. Carbon and oxygen isotope geochemistry of Ediacaran outer platform carbonates, Paraguay Belt, central Brazil

    Directory of Open Access Journals (Sweden)

    Claudio Riccomini

    2007-09-01

    Full Text Available After the late Cryogenian glaciation the central region of Brazil was the site of extensive deposition of platformal carbonates of the Araras Group. This group includes a basal cap carbonate sequence succeeded by transgressive, deep platform deposits of bituminous lime mudstone and shale. Facies and stratigraphic data combined with carbon and oxygen isotopic analyses of the most complete section of the transgressive deposits, exposed in the Guia syncline, were used to evaluate the depositional paleoenvironment and to test the correlation of these deposits along the belt and with other units worldwide. The studied succession consists of 150 m thick tabular beds of black to grey lime mudstone and shale with predominantly negative delta13C PDB values around -2.5 to -1‰ . The delta13C PDB profile of Guia syncline shows a clear correlation with the upper portion of Guia Formation in the Cáceres region, about 200 km to the southwest. The delta13C PDB profile of the Araras Group is comparable with delta13C PDB profiles of Ediacaran units of the southern Paraguay Belt, western Canada, and the Congo and Kalahari cratons. Moreover, facies distribution, stratigraphy and the carbon isotopic profile of the Araras Group match the middle Tsumeb Subgroup in Namibia, which reinforces the Ediacaran age assigned to the Araras Group.Após a glaciação do final do Criogeniano, a região central do Brasil foi palco de extensa deposição de carbonatos plataformais do Grupo Araras. Este grupo inclui na sua base uma seqüência de capa carbonática sucedida por depósitos transgressivos de calcilutitos betuminosos e folhelhos de plataforma profunda. Dados de fácies e estratigráficos combinados com análises isotópicas de carbono e oxigênio da seção mais completa desses depósitos transgressivos, expostos no sinclinal da Guia, foram empregados para avaliar o paleambiente deposicional e para testar a correlação desses depósitos ao longo da faixa e tamb

  12. Carbon isotopic study of individual alcohol compounds in modern sediments from Nansha Islands sea area, China

    Institute of Scientific and Technical Information of China (English)

    段毅; 文启彬; 郑国东; 罗斌杰

    1997-01-01

    Carbon isotopic compositions of individual n-alkanols and sterols in modern sediments from the Nan-sha Islands sea area are measured after derivatization to trimethylsilyl ethers by the new isotopic analytical technique of GC/C/IRMS. The effects of the three added silyl carbon atoms in every alcohol molecule on these compound isotopic compositions and the characteristics of their carbon isotopic compositions are studied. Then their biological sources are discussed using their carbon isotopic compositions.

  13. Carbon and oxygen isotope compositions of the carbonate facies in the Vindhyan Supergroup, central India

    Indian Academy of Sciences (India)

    S Banerjee; S K Bhattacharya; S Sarkar

    2006-02-01

    The Vindhyan sedimentary succession in central India spans a wide time bracket from the Paleopro- terozoic to the Neoproterozoic period.Chronostratigraphic significance of stable carbon and oxygen isotope ratios of the carbonate phase in Vindhyan sediments has been discussed in some recent studies.However,the subtle controls of facies variation,depositional setting and post-depositional diagenesis on stable isotope compositions are not yet clearly understood.The Vindhyan Super- group hosts four carbonate units,exhibiting a wide variability in depositional processes and paleogeography.A detailed facies-specific carbon and oxygen isotope study of the carbonate units was undertaken by us to investigate the effect of these processes and to identify the least altered isotope values.It is seen that both carbon and oxygen isotope compositions have been affected by early meteoric water diagenesis.The effect of diagenetic alteration is,however,more pronounced in case of oxygen isotopes than carbon isotopes.Stable isotope compositions remained insensitive to facies only when sediments accumulated in a shallow shelf setting without being exposed.Major alteration of original isotope ratios was observed in case of shallow marine carbonates,which became exposed to meteoric fluids during early diagenetic stage.Duration of exposure possibly determined the magnitude of alteration and shift from the original values.Moreover,dolomitization is found to be accompanied by appreciable alteration of isotope compositions in some of the carbonates.The present study suggests that variations in sediment depositional settings,in particular the possibility of subaerial exposure,need to be considered while extracting chronostratigraphic signi ficance from 13C data.

  14. Carbon and Oxygen Isotope Ratios in Rona Limestone, Romania

    Directory of Open Access Journals (Sweden)

    Stela Cuna

    2001-04-01

    Full Text Available The carbon and oxygen isotopic compositions of limestones provide criteria for the evaluation of the depositional environment. For Jurassic and younger samples, the best discrimination between marine and fresh-water limestones is given by Z parameter, calculated as a linear correlation between δ13C and δ18O (‰ PDB. Rona Limestone (Upper Paleocene - Lower Eocene, outcropping on a small area in NW Transylvania (Meseş area is a local lacustrine facies. There, it divides Jibou Formation into the Lower Red Member and the Upper Variegated Member, respectively. Recently, a sequence containing a marine nannoplankton assemblage was identified in the base of Rona deposits. The main goal of our study was to characterize, based on the isotopic record, the primary environment of formation of the deposit, as well as that in which some diagenetic processes (the formation of dolomite and of green clay around the siliceous chert nodules took place. Ten samples representing limestones, dolomitic limestone, marls and the green carbonate-rich clay were studied from petrographical and mineralogical points of view, and the carbon and oxygen isotopic ratios from the carbonate (calcite component were measured. In conclusion, it was found that the procedure of extraction of CO2 we used enabled the discrimination between the isotopic prints of calcite vs. dolomite. This pleads for considering our results as a primary isotopic pattern in the bulk rock. The oxygen and carbon isotope data indicate a fresh-water depositional environment with Z<120. The δ13C mean value (-4.96 ‰ PDB is, generally, representative for fresh-water carbonates of the Tertiary period. The same environment characterized also the formation of carbonates within the green clay.

  15. Oxygen isotopic composition of carbon dioxide in the middle atmosphere

    OpenAIRE

    Liang, Mao-Chang; Blake, Geoffrey A.; Lewis, Brenton R.; Yung, Yuk L.

    2007-01-01

    The isotopic composition of long-lived trace molecules provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 parts per million by volume (ppmv) in the mesosphere. Here, we successfully reproduce the isotopic composition of CO2 in the middle atmosphere, which has not been previously reported. The mass-independent fractionation of oxygen in CO2 can be satisfactorily explained by the exchange reaction with...

  16. Chromium Isotopes in Marine Carbonates - an Indicator for Climatic Change?

    Science.gov (United States)

    Frei, R.; Gaucher, C.

    2010-12-01

    Chromium (Cr) stable isotopes experience an increased interest as a tracer of Cr (VI) reduction in groundwater and thus showed their potential as a monitor of remediation of anthropogenic and natural contamination in water (Berna et al., 2009; Izbicki et al., 2008). Chromium stable isotopes in Fe-rich chemical sediments (BIFs and Fe-cherts) have recently also been used as a tracer for Earth's atmospheric oxygenation through time (Frei et al., 2009). We have applied the Cr isotope system to organic-rich carbonates from a late Ediacaran succession in Uruguay (Polanco Formation), from which we have previously analyzed BIFs with extremely fractionated (δ53Cr up to 5.0 ‰) Cr isotope signatures that are part of an underlying deep water clastic sediment (shale-dominated) sequence (Yerbal Formation) deposited in a glacio-marine environment (Gaucher et al.,2004). δ53Cr values of organic rich carbonates correlate with positive and negative carbon isotope excursions (δ13C PDB between -3 and +3 ‰) and with systematic changes in strontium isotope compositions, commonly interpreted as to reflect fluctuations in organic (photosynthetic algae) production related to fluctuations in atmospheric oxygen and weathering intensities, respectively. Slightly positively fractioned δ53Cr values (up to +0.25‰), paralleling positive (δ13C PDB and 87Sr/86Sr ratio excursions would thereby trace elevated atmospheric oxygen levels/pulses possibly related to glacier retreat/melting stages that caused bioproductivity to increase. While the causal link between these multiple isotopic tracers and the mechanisms of Cr stripping into carbonates has to be further investigated in detail, the first indications from this study point to a potentially promising use of stable Cr isotopes in organic-rich carbonates to monitor fluctuations of atmospheric oxygen, particularly over the Neoproterozoic and Phanerozoic ice age periods. E.C. Berna et al. (2010) Cr stable isotopes as indicators of Cr

  17. Stable carbon isotope ratios of ambient aromatic volatile organic compounds

    Science.gov (United States)

    Kornilova, Anna; Huang, Lin; Saccon, Marina; Rudolph, Jochen

    2016-09-01

    Measurements of mixing ratios and stable carbon isotope ratios of aromatic volatile organic compounds (VOC) in the atmosphere were made in Toronto (Canada) in 2009 and 2010. Consistent with the kinetic isotope effect for reactions of aromatic VOC with the OH radical the observed stable carbon isotope ratios are on average significantly heavier than the isotope ratios of their emissions. The change of carbon isotope ratio between emission and observation is used to determine the extent of photochemical processing (photochemical age, ∫ [OH]dt) of the different VOC. It is found that ∫ [OH]dt of different VOC depends strongly on the VOC reactivity. This demonstrates that for this set of observations the assumption of a uniform ∫ [OH]dt for VOC with different reactivity is not justified and that the observed values for ∫ [OH]dt are the result of mixing of VOC from air masses with different values for ∫ [OH]dt. Based on comparison between carbon isotope ratios and VOC concentration ratios it is also found that the varying influence of sources with different VOC emission ratios has a larger impact on VOC concentration ratios than photochemical processing. It is concluded that for this data set the use of VOC concentration ratios to determine ∫ [OH]dt would result in values for ∫ [OH]dt inconsistent with carbon isotope ratios and that the concept of a uniform ∫ [OH]dt for an air mass has to be replaced by the concept of individual values of an average ∫ [OH]dt for VOC with different reactivity.

  18. Carbon isotope biogeochemistry of plant resins and derived hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Murray, A.P.; Edwards, D.; Hope, J.M.; Boreham, C.J. [Australian Geological Survey Organisation, Canberra (Australia)] [and others

    1998-12-31

    Hydrocarbons derived from plant resins are major components of some terrigenous oils and bitumens. These compounds are structurally distinct and this makes then useful biomarkers applicable in petroleum exploration as well as sources of biogeochemical information about palaeoenvironment and palaeobotany. Although recent studies have elucidated the molecular structure of resinites, very little information has been available for the carbon isotope composition of resinites and no studies of resin-derived compounds in oils had been performed prior to the present study. Hence, carbon stable isotope analyses were carried out on a suite of modern and fossil resins of diverse origins, including compound specific isotope analysis of individual hydrocarbons produced during resin pyrolysis. Oils derived from resinite source organic matter were also analysed. The results showed that ``Class I`` resinites derived from gymnosperms were enriched in the heavy carbon isotope compared with those from angiosperms (``Class I`` resinites). Furthermore, both fossil resinites themselves and individual hydrocarbons derived from them were isotopically heavy compared with modern plant resins. The isotopic signatures of diterpanes and triterpanes in various early Tertiary oils from Australasia and Southeast Asia reflect their origins from gymnosperms and angiosperms, respectively. (author)

  19. Cenozoic Carbonate Stratigraphy of the Yucatan Shelf, Southern Gulf of Mexico

    Science.gov (United States)

    Ortega-Nieto, A.; Urrutia-Fucugauchi, J.

    2012-04-01

    The Yucatan shelf in the southern Gulf of Mexico has developed as a large shallow ramp shelf, tectonically stable that preserves a continuous sedimentary record for the Late Mesozoic and Cenozoic. We present the preliminary results of a study involving well stratigraphy, X-ray diffraction and petrography of the Cenozoic sequence sampled in the UNAM-5, UNAM-6 and UNAM-7 exploratory boreholes drilled in the southwestern and southern sectors of the Yucatan state. The boreholes were drilled as part of the Chicxulub Drilling Project aimed to investigate the formation and characteristics of the large crater, formed by an asteroid impact at the Cretaceous/Paleogene (K/Pg) boundary. Our study aims to investigate the stratigraphic relations, textural changes and characteristics of the sedimentary units, to identify events associated with the evolution of the platform during the Cenozoic. We constructed detailed stratigraphic columns for the three borehole cores and prepared samples collected across the stratigraphic section for petrography and clay analyses. The petrographic studies were made at different depths above the K/Pg boundary to recognize textural variations, the identification of dolomite was made by the method of staining thin sections, and the dolomite fabrics were analyzed to identify the nature and shape of their crystal boundaries. The method of X-ray diffraction was used to identify clay types. The three boreholes cross the K/Pg boundary at different depths. The stratigraphic column is formed, from bottom to top, of a limestone sequence with evaporites nodules, little contents of benthic foraminifera, scarce planktic foraminifera and oogonia fossils suggesting internal lagoonal environments that vary to outer lagoon. This sequence is underlain by limestones with different degrees of dolomitization that in many cases present poorly preserved microfossil contents. Above this sequence, there is a clay bed identified as palygorskita, which has a variable

  20. BOREAS TE-5 Tree Ring and Carbon Isotope Ratio Data

    Science.gov (United States)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

    2000-01-01

    The BOREAS TE-5 team collected several data sets to investigate the vegetation-atmosphere CO2 and H2O exchange processes. These data include tree ring widths and cellulose carbon isotope data from coniferous trees collected at the BOREAS NSA and SSA in 1993 and 1994 by the BOREAS TE-5 team. Ring width data are provided for both Picea mariana and Pinus banksiana. The carbon isotope data are provided only for Pinus banksiana. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  1. Coniacian-maastrichtian calcareous nannofossil biostratigraphy and carbon-isotope stratigraphy in the Zagros Basin (Iran)

    DEFF Research Database (Denmark)

    Razmjooei, Mohammad Javad; Thibault, Nicolas; Kani, Anoshiravan

    2014-01-01

    , White Fall, Kingsdown, Michel Dean, Haven Brow, Horseshoe Bay, Buckle, Hawks Brow, Santonian/Campanian boundary (SCBE) and Campanian/Maastrichtian boundary (CMBE) events. Correlation to a recently proposed global δ13C stack for the Late Cretaceous points to a major mismatch of this compilation...

  2. Photosynthetic carbon isotope discrimination and its relationship to the carbon isotope signals of stem, soil and ecosystem respiration.

    Science.gov (United States)

    Wingate, Lisa; Ogée, Jérôme; Burlett, Régis; Bosc, Alexandre; Devaux, Marion; Grace, John; Loustau, Denis; Gessler, Arthur

    2010-10-01

    • Photosynthetic carbon (C) isotope discrimination (Δ(Α)) labels photosynthates (δ(A) ) and atmospheric CO(2) (δ(a)) with variable C isotope compositions during fluctuating environmental conditions. In this context, the C isotope composition of respired CO(2) within ecosystems is often hypothesized to vary temporally with Δ(Α). • We investigated the relationship between Δ(Α) and the C isotope signals from stem (δ(W)), soil (δ(S)) and ecosystem (δ(E)) respired CO(2) to environmental fluctuations, using novel tuneable diode laser absorption spectrometer instrumentation in a mature maritime pine forest. • Broad seasonal changes in Δ(Α) were reflected in δ(W,) δ(S) and δ(E). However, respired CO(2) signals had smaller short-term variations than Δ(A) and were offset and delayed by 2-10 d, indicating fractionation and isotopic mixing in a large C pool. Variations in δ(S) did not follow Δ(A) at all times, especially during rainy periods and when there is a strong demand for C allocation above ground. • It is likely that future isotope-enabled vegetation models will need to develop transfer functions that can account for these phenomena in order to interpret and predict the isotopic impact of biosphere gas exchange on the C isotope composition of atmospheric CO(2).

  3. CO2-dependent carbon isotope fractionation in dinoflagellates relates to their inorganic carbon fluxes

    NARCIS (Netherlands)

    Hoins, M.; Eberlein, T.; Van de Waal, D.B.; Sluijs, A.|info:eu-repo/dai/nl/311474748; Reichart, G.-J.|info:eu-repo/dai/nl/165599081; Rost, B.

    2016-01-01

    Carbon isotope fractionation (εp) between the inorganic carbon source and organic matter has been proposed to be a function of pCO2. To understand the CO2-dependency of εp and species-specific differences therein, inorganic carbon fluxes in the four dinoflagellate species Alexandrium fundyense, Scri

  4. Martian carbon dioxide: Clues from isotopes in SNC meteorites

    Science.gov (United States)

    Karlsson, H. R.; Clayton, R. N.; Mayeda, T. K.; Jull, A. J. T.; Gibson, E. K., Jr.

    1993-01-01

    Attempts to unravel the origin and evolution of the atmosphere and hydrosphere on Mars from isotopic data have been hampered by the impreciseness of the measurements made by the Viking Lander and by Earth-based telescopes. The SNC meteorites which are possibly pieces of the Martian surface offer a unique opportunity to obtain more precise estimates of the planet's volatile inventory and isotopic composition. Recently, we reported results on oxygen isotopes of water extracted by pyrolysis from samples of Shergotty, Zagami, Nakhla, Chassigny, Lafayette, and EETA-79001. Now we describe complementary results on the stable isotopic composition of carbon dioxide extracted simultaneously from those same samples. We will also report on C-14 abundances obtained by accelerator mass spectrometry (AMS) for some of these CO2 samples.

  5. The origin of carbon isotope vital effects in coccolith calcite

    Science.gov (United States)

    McClelland, H. L. O.; Bruggeman, J.; Hermoso, M.; Rickaby, R. E. M.

    2017-01-01

    Calcite microfossils are widely used to study climate and oceanography in Earth's geological past. Coccoliths, readily preserved calcite plates produced by a group of single-celled surface-ocean dwelling algae called coccolithophores, have formed a significant fraction of marine sediments since the Late Triassic. However, unlike the shells of foraminifera, their zooplankton counterparts, coccoliths remain underused in palaeo-reconstructions. Precipitated in an intracellular chemical and isotopic microenvironment, coccolith calcite exhibits large and enigmatic departures from the isotopic composition of abiogenic calcite, known as vital effects. Here we show that the calcification to carbon fixation ratio determines whether coccolith calcite is isotopically heavier or lighter than abiogenic calcite, and that the size of the deviation is determined by the degree of carbon utilization. We discuss the theoretical potential for, and current limitations of, coccolith-based CO2 paleobarometry, that may eventually facilitate use of the ubiquitous and geologically extensive sedimentary archive. PMID:28262764

  6. On the isotopic composition of magmatic carbon in SNC meteorites

    Science.gov (United States)

    Wright, I. P.; Grady, M. M.; Pillinger, C. T.

    1992-01-01

    SNC meteorites are thought, from many lines of evidence, to come from Mars. A line of investigation which has been pursued in our laboratory over the years involves measurement of the stable isotopic composition of carbon, in its various forms, in SNC meteorites. In order to establish a firm basis for studying the isotopic systematics of carbon in the martian surface environment, it is first necessary to try and constrain the delta C-13 of bulk Mars. Taking all of the available information, it would seem that the delta C-13 of the Earth's mantle lies somewhere in the range of -5 to -7 percent. Preliminary assessment of magnetic carbon in SNC meteorites, would tend to suggest a delta C-13 of 20 to 30 percent, which is conspicuously different from that of the terrestrial mantle. It is not obvious why there should be such a difference between the two planets, although many explanations are possible. One of these possibilities, that previous delta C-13 measurements for magnetic carbon in SNC meteorites are in error to some degree, is being actively investigated. The most recent results seem to constrain the theta C-13 of the magnetic carbon in SNC meteorites to about -20 percent, which is not at odds with previous estimates. As such, it is considered that a detailed investigation of the carbon isotopic systematics of martian surface materials does have the necessary information with which to proceed.

  7. Modeling stable isotope and organic carbon in hillslope stormflow

    Science.gov (United States)

    Dusek, Jaromir; Vogel, Tomas; Dohnal, Michal; Marx, Anne; Jankovec, Jakub; Sanda, Martin; Votrubova, Jana; Barth, Johannes A. C.; Cislerova, Milena

    2016-04-01

    Reliable prediction of water movement and fluxes of dissolved substances (such as stable isotopes and organic carbon) at both the hillslope and the catchment scales remains a challenge due to complex boundary conditions and soil spatial heterogeneity. In addition, microbially mediated transformations of dissolved organic carbon (DOC) are known to affect balance of DOC in soils, hence the transformations need to be included in a conceptual model of a DOC transport. So far, only few studies utilized stable isotope information in modeling and even fewer linked dissolved carbon fluxes to mixing and/or transport models. In this study, stormflow dynamics of oxygen-18 isotope and dissolved organic carbon was analyzed using a physically based modeling approach. One-dimensional dual-continuum vertical flow and transport model, based on Richards and advection-dispersion equations, was used to simulate the subsurface transport processes in a forest soil during several observed rainfall-runoff episodes. The transport of heat in the soil profile was described by conduction-advection equation. Water flow and transport of solutes and heat were assumed to take place in two mutually communicating porous domains, the soil matrix and the network of preferential pathways. The rate of microbial transformations of DOC was assumed to depend on soil water content and soil temperature. Oxygen-18 and dissolved organic carbon concentrations were observed in soil pore water, hillslope stormflow (collected in the experimental hillslope trench), and stream discharge (at the catchment outlet). The modeling was used to analyze the transformation of input solute signals into output hillslope signals observed in the trench stormflow. Signatures of oxygen-18 isotope in hillslope stormflow as well as isotope concentration in soil pore water were predicted reasonably well. Due to complex nature of microbial transformations, prediction of DOC rate and transport was associated with a high uncertainty.

  8. Megaripples, multiple cap carbonates, and apparently conformable sections: observations that normalize some interpretations of Snowball Earth stratigraphy while complicating others

    Science.gov (United States)

    Raub, T.; Lamb, M. P.; Fischer, W. W.; Myrow, P.; Perron, T.; Kunzmann, M.; Liu, C.; Prave, A. R.

    2012-12-01

    Neoproterozoic Snowball Earth is intellectually alluring in part because its remarkable sedimentary and geochemical record challenges uniformitarian description and demands multiple working hypotheses. Apparently exceptional features in that record may represent the end-products of truly nonuniformitarian processes acting on a fundamentally different Earth than the modern world: an Earth which is oxygen-poor, lacking terrestrial macrobiota, and of uncertain (or arguably bizarre) geomagnetic and geodynamic character. But many features in this remarkable rock record might be explained by perfectly ordinary processes acting on anomalous materials, or in systems bounded by conditions that are rare, but not mysterious, on modern Earth. I will present emerging examples of both interpretive modes. Exceptional bedforms known as cap carbonate megaripples can be explained under normal wave climates by aggradation of unusually large carbonate grains anomalously widespread in a shallow shelfal setting. Bedform topography may be inherited or else migrate laterally through discrete, episodic depositional events if cementation is fast. Trace metal isotopes excurse most prominently at the very base of conformable cap carbonate sections, and in the terminal stages of deglaciation, at times when the seawater saturation state is most dynamic. In the end, basic field geology without genetic presumption, and the interpretive context it lends specific geochemical analyses, remains most likely to successfully evaluate the likelihoods of both existing and new Snowball Earth scenarios. The most fundamental unanswered question remains one of stratigraphic architecture: what is the climatic phase, the timing, and the duration for both diamictite and cap carbonate deposition? End-member solutions remain viable: diamictite and cap carbonate may both be of prolonged duration and globally diachronous, with diamictite representing syn-glacial and interstadial cycles and cap carbonate spanning

  9. Preliminary Nanosims Analysis of Carbon Isotope of Carbonates in Calcium-Aluminum-Rich Inclusions

    OpenAIRE

    Guan, Y.; Paque, J. M.; Burnett, D.S.; Eiler, J. M.

    2009-01-01

    Carbonate minerals observed in primitive meteorites are products of either terrestrial weathering or aqueous alteration in the early solar system. Most of the carbonate minerals in carbonaceous chondrites occur primarily as isolated grains in matrix, as crosscutting veins, or as replacement minerals in chondrules [e.g., 1, 2]. A few calcium-aluminum-rich inclusions (CAIs) have been reported containing carbonate minerals as well [2, 3]. The C and O isotopes of carbonates in c...

  10. Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil

    Directory of Open Access Journals (Sweden)

    SIAL ALCIDES N.

    2000-01-01

    Full Text Available Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB, compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/oo compatible with carbon isotope signatures of carbonates deposited around 2.4 Ga worldwide. The Fecho do Funil Formation has probably recorded the Lomagundi delta13C positive anomaly (+6.4 to +7.1 o/ooPDB. The magnesite-bearing carbonates of the Orós mobile belt, state of Ceará, exhibit carbon isotope fluctuation within the range for carbonates deposited at 1.8 Ga. The C-isotope record of the Frecheirinha Formation, northwestern state of Ceará, shows negative delta13C values in its lower portion (-2 o/oo and positive values up section (+1 to +3 o/oo, which suggests this sequence is a cap carbonate deposited after a glacial event around 0.95 Ga. The Jacoca and Acauã sedimentary carbonate Formations, state of Sergipe, NE Brazil, show carbon isotope fluctuations very similar to each other (average around -5 o/oo, compatible with a deposition around 0.76 Ga. The younger Olho D'Água carbonate Formation, however, also in the state of Sergipe, displays negative delta13C values at the lower portion of the Formation, changing dramatically up section to positive values as high as +10 o/oo, a characteristic compatible with a Sturtian cap carbonate deposited around 0.69 Ga. On the light of the C isotope data discussed in this study, it seems that delta13C fluctuations in Paleoproterozoic carbonates in Brazil are within the range found globally for metasedimentary carbonates of this age. Carbon isotope data proved to be very useful in establishing relative

  11. Characteristics of carbon and hydrogen isotopic compositions of light hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    沈平

    1995-01-01

    Light hydrocarbons named in the present paper refer to the natural gas-associated light oil and condensate 46 light oil and condensate samples from 11 oil-bearing basins of China were collected and their carbon and hydrogen isotopic compositions were analysed in terms of their total hydrocarbons, saturated hydrocarbons and a part of aromatic fractions, and gas-source materials and their sedimentary environments were discussed based on the above-mentioned data and the geological background of each area. From the view of carbon and hydrogen isotopic composition of total hydrocarbons and saturated hydrocarbons, it is revealed that the condensate related to coal-bearing strata is enriched in 13C and D while that related to the source material of type I-II is enriched in 12C. In general, the isotopic composition of carbon is mainly attributed to the inheriting effect of their source materials, whereas that of hydrogen principally reflects the correlationship between hydrogen isotopes and the sedimentary envi

  12. Magnesium isotope fractionation in bacterial mediated carbonate precipitation experiments

    Science.gov (United States)

    Parkinson, I. J.; Pearce, C. R.; Polacskek, T.; Cockell, C.; Hammond, S. J.

    2012-12-01

    Magnesium is an essential component of life, with pivotal roles in the generation of cellular energy as well as in plant chlorophyll [1]. The bio-geochemical cycling of Mg is associated with mass dependant fractionation (MDF) of the three stable Mg isotopes [1]. The largest MDF of Mg isotopes has been recorded in carbonates, with foraminiferal tests having δ26Mg compositions up to 5 ‰ lighter than modern seawater [2]. Magnesium isotopes may also be fractionated during bacterially mediated carbonate precipitation and such carbonates are known to have formed in both modern and ancient Earth surface environments [3, 4], with cyanobacteria having a dominant role in carbonate formation during the Archean. In this study, we aim to better constrain the extent to which Mg isotope fractionation occurs during cellular processes, and to identify when, and how, this signal is transferred to carbonates. To this end we have undertaken biologically-mediated carbonate precipitation experiments that were performed in artificial seawater, but with the molar Mg/Ca ratio set to 0.6 and with the solution spiked with 0.4% yeast extract. The bacterial strain used was marine isolate Halomonas sp. (gram-negative). Experiments were run in the dark at 21 degree C for two to three months and produced carbonate spheres of various sizes up to 300 μm in diameter, but with the majority have diameters of ~100 μm. Control experiments run in sterile controls (`empty` medium without bacteria) yielded no precipitates, indicating a bacterial control on the precipitation. The carbonate spheres are produced are amenable to SEM, EMP and Mg isotopic analysis by MC-ICP-MS. Our new data will shed light on tracing bacterial signals in carbonates from the geological record. [1] Young & Galy (2004). Rev. Min. Geochem. 55, p197-230. [2] Pogge von Strandmann (2008). Geochem. Geophys. Geosys. 9 DOI:10.1029/2008GC002209. [3] Castanier, et al. (1999). Sed. Geol. 126, 9-23. [4] Cacchio, et al. (2003

  13. Clumped-isotope geochemistry of carbonates: A new tool for the reconstruction of temperature and oxygen isotope composition of seawater

    Energy Technology Data Exchange (ETDEWEB)

    Bernasconi, Stefano M., E-mail: Stefano.bernasconi@erdw.ethz.ch [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Schmid, Thomas W.; Grauel, Anna-Lena [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Mutterlose, Joerg [Institut fuer Geologie, Mineralogie und Geophysik, Ruhr Universitaet Bochum, Universitaetsstr. 150, 44801 Bochum (Germany)

    2011-06-15

    Highlights: > Clumped-isotope thermometry of carbonates is discussed. > Clumped isotopes of Belemnites show higher sea surface temperatures than commonly assumed for the lower Cretaceous. > The potential of clumped-isotope measurement on foraminifera is discussed. - Abstract: Clumped-isotope geochemistry deals with State of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes rather than with the most abundant ones. Among its possible applications, carbonate clumped-isotope thermometry is the one that has gained most attention because of the wide potential of applications in many disciplines of the earth sciences. In particular, it allows reconstructing the temperature of formation of carbonate minerals without knowledge of the isotopic composition of the water from which they were formed. In addition, the O isotope composition of the waters from which they were formed can be calculated using the {delta}{sup 18}O of the same carbonate sample. This feature offers new approaches in paleoclimatology for reconstructing past global geochemical cycles. In this contribution two applications of this method are presented. First the potential of a new analytical method of measurement of clumped isotopes on small samples of foraminifera, for high-resolution SST and seawater {delta}{sup 18}O reconstructions from marine sediments is shown. Furthermore the potential of clumped isotope analysis of belemnites, for reconstructing seawater {delta}{sup 18}O and temperatures in the Cretaceous is shown.

  14. Chicxulub Impact Crater and Yucatan Carbonate Platform - Stratigraphy and Petrography of PEMEX Borehole Cores

    Science.gov (United States)

    Gutierrez-Cirlos, A. G.; Perez-Drago, G.; Perez-Cruz, L.; Urrutia-Fucugauchi, J.

    2008-12-01

    Chicxulub impact crater is the best preserved of the three large multi-ring structures documented in the terrestrial record. Chicxulub, formed 65 Ma ago, is associated with the Cretaceous/Tertiary (K/T) boundary layer and the impact related to the organism extinctions and events marking the boundary. The crater is buried under Tertiary sediments in the Yucatan carbonate platform in the southern Gulf of Mexico. The structure was initially recognized from gravity and magnetic anomalies in the PEMEX exploration surveys of the northwestern Yucatan peninsula. The exploration program included eight deep boreholes completed from 1952 through the 1970s. The investigations showing Chicxulub as a large complex impact crater formed at the K/T boundary have relayed on the PEMEX decades-long exploration program. However, despite frequent use of PEMEX information and core samples, significant parts of the database and cores remain to be evaluated, analyzed and incorporated with results from recent efforts. Access to PEMEX Core Repository has permitted to study the cores and collect new samples from some of the boreholes. We analyzed cores from Yucatan-6, Chicxulub-1, Sacapuc-1, Ticul-1, Yucatan-1 and Yucatan-4 boreholes to make new detailed stratigraphic correlations and petrographic characterization, using information from PEMEX database and the recent studies. In C-1 cores, breccias show 4-8 cm clasts of fine grained altered melt dispersed in a medium to coarse grained matrix composed of pyroxene and feldspar with little macroscopic alteration. Clasts contain 0.2 to 0.1 cm fragments of silicate material (basement) that show variable degrees of digestion. Melt samples from C-1 N10 comes from interval 1,393-1,394 m, and show a fine-to-medium grained coherent microcrystalline groundmass. Melt and breccias in Y-6 extend from about 1,100 m to more than 1,400 m. Sequence is well sorted, with an apparent gradation in both the lithic and melt clasts. In this presentation we report on

  15. Application of stable carbon isotopes in long term mesocosm studies for carbon cycle investigation

    Science.gov (United States)

    Esposito, Mario

    2016-04-01

    Carbon dioxide (CO2) is an effective greenhouse gas. The Oceans absorb ca. 30% of the anthropogenic CO2 emissions and thereby partly attenuate deleterious climate effects. A consequence of the oceanic CO2 uptake is a decreased seawater pH and planktonic community shifts. The quantification of the anthropogenic perturbation was investigated through stable carbon isotope analysis in three "long term" mesocosm experiments (Sweden 2013, Gran Canaria 2014, Norway 2015) which reproduced near natural ecosystem conditions under both controlled and modified future CO2 level (up to 2000 ppm) scenarios. Parallel measurements of the stable isotope composition of dissolved inorganic carbon (δ13CDIC) dissolved organic carbon (δ13CDOC) and particulate carbon (δ13CTPC) both from the mesocosms water column and sediment traps showed similar trends in all the three experiments. A CO2 response was noticeable in the isotopic dataset, but increased CO2 levels had only a subtle effect on the concentrations of the dissolved and particulate organic carbon pool. Distinctive δ13C signatures of the particulate carbon pool both in the water column and the sediments were detectable for the different CO2 treatments and they were strongly correlated with the δ13CDIC signatures but not with the δ13CDOC pool. The validity of the isotopic data was verified by cross-analyses of multiple substances of known isotopic signatures on a GasBench, Elemental Analyser (EA) and on an in-house TOC-IRMS setup for the analysis of δ13CDIC, δ13CTPC and δ13CDOC, respectively. Results from these mesocosm experiments proved the stable carbon isotope approach to be an effective tool for quantifying the uptake and carbon transfer among the various compartments of the marine carbon system.

  16. Carbon isotope composition of the Lower Triassic marine carbonates, Lower Yangtze Region, South China

    Institute of Scientific and Technical Information of China (English)

    ZUO; Jingxun; TONG; Jinnan; QIU; Haiou; ZHAO; Laishi

    2006-01-01

    Studies on three Lower Triassic sections located on the shallow water platform, the deep water slope and in the deep water basin in the Lower Yangtze Region, South China, show the similar trend of carbon isotope evolution. Biostratigraphic correlations among the Lower Triassic sections on the basis of standard conodont zones indicate that three negative shifts occurred in the Griesbachian, the Smithian and the late Spathian stages respectively, and one distinctly positive shift occurred in the early Spathian stage. Trend of carbon isotope evolution of the Lower Triassic reflects some significant changes in the global carbon cycle. Moreover, δ13C background values are intensively controlled by palaeogeographic environment. In general, δ13C values from deep-water slope carbonates are lighter than those from carbonate platform and heavier than those from deep-water basin carbonates. The positive carbon isotope excursion may be induced by a significant amount of organic carbon burial in marine sediments and increase in primary productivity. The large negative carbon isotope excursions during the Early Triassic in Lower Yangtze Region are interpreted to relate to volcano eruptions based on tuffaceous claystone interlayers observed near the Permian-Triassic boundary, the Induan- Olenekian boundary and the Lower Triassic-Middle Triassic boundary.

  17. C- and Sr-isotope stratigraphy of the São Caetano complex, Northeastern Brazil: a contribution to the study of the Meso-Neoproterozoic seawater geochemistry

    Directory of Open Access Journals (Sweden)

    Juan C. Silva

    2005-03-01

    Full Text Available C-isotope and 87Sr/86Sr values for five carbonate successions from the São Caetano Complex, northeastern Brazil, were used to constrain their depositional age and to determine large variations in the C- and Sr-isotopic composition of seawater under the framework of global tectonic events. Three C-isotope stages were identified from base to top in a composed chemostratigraphic section: (1 stage in which delta13C values vary from +2 to +3.7‰ PDB and average 3‰ PDB, (2 stage with delta13C values displaying stronger oscillations (from -2‰ to +‰ PDB, and (3 stage with an isotopic plateau with values around +3.7‰ PDB. Constant 87Sr/86Sr values (~ 0.70600 characterize C-isotope stage 1, whereas slightly fluctuating values (from 0.70600 to 0.70700 characterize C-isotope stage 2. Finally, 87Sr/86Sr values averaging 0.70600 characterize C-isotope stage 3. The C- and Sr- chemostratigraphic pathways permit to state: (a the C- and Sr-isotope secular curves registered primary fluctuations of the isotope composition of seawater during late Mesoproterozoic- early Neoproterozoic transition in the Borborema Province, and (b onset of the Cariris Velhos/Greenville cycle, widespread oceanic rifting, continental magmatic arc formation and onset of the agglutination of Rodinia supercontinent, mostly controlled the C- and Sr-isotope composition of seawater during the C-isotope stages 1, 2 and 3.Valores de isótopos de C e 87Sr/86Sr de cinco seqüências de carbonatos do Complexo São Caetano, nordeste do Brasil; foram usados para estimar a sua idade de deposição e relacionar variações da composição isotópica na água do mar com eventos tectônicos globais. Três estágios de variação de isótopos de carbono foram identificados de base para o topo numa seção quimioestratigráfica composta: (1 estágio em que delta13C varia de +2 a +3.7‰PDB (media 3‰PDB, (2 estágio no qual delta13C varia consideravelmente (de -2 a +3‰PDB e (3 est

  18. Simultaneous tracing of carbon and nitrogen isotopes in human cells.

    Science.gov (United States)

    Nilsson, Roland; Jain, Mohit

    2016-05-24

    Stable isotope tracing is a powerful method for interrogating metabolic enzyme activities across the metabolic network of living cells. However, most studies of mammalian cells have used (13)C-labeled tracers only and focused on reactions in central carbon metabolism. Cellular metabolism, however, involves other biologically important elements, including nitrogen, hydrogen, oxygen, phosphate and sulfur. Tracing stable isotopes of such elements may help shed light on poorly understood metabolic pathways. Here, we demonstrate the use of high-resolution mass spectrometry to simultaneously trace carbon and nitrogen metabolism in human cells cultured with (13)C- and (15)N-labeled glucose and glutamine. To facilitate interpretation of the complex isotopomer data generated, we extend current methods for metabolic flux analysis to handle multivariate mass isotopomer distributions (MMIDs). We find that observed MMIDs are broadly consistent with known biochemical pathways. Whereas measured (13)C MIDs were informative for central carbon metabolism, (15)N isotopes provided evidence for nitrogen-carrying reactions in amino acid and nucleotide metabolism. This computational and experimental methodology expands the scope of metabolic flux analysis beyond carbon metabolism, and may prove important to understanding metabolic phenotypes in health and disease.

  19. Shear heating and clumped isotope reordering in carbonate faults

    Science.gov (United States)

    Siman-Tov, Shalev; Affek, Hagit P.; Matthews, Alan; Aharonov, Einat; Reches, Ze'ev

    2016-07-01

    Natural faults are expected to heat rapidly during seismic slip and to cool quite quickly after the slip event. Here we examine clumped isotope thermometry for its ability to identify such short duration elevated temperature events along frictionally heated carbonate faults. Our approach is based on measured Δ47 values that reflect the distribution of oxygen and carbon isotopes in the calcite lattice, measuring the abundance of 13Csbnd 18O bonds, which is affected by temperature. We examine three types of calcite rock samples: (1) crushed limestone grains that were rapidly heated and then cooled in static laboratory experiments, simulating the temperature cycle experienced by fault rock during an earthquake slip; (2) limestone samples that were experimentally sheared to simulate earthquake slip events; and (3) samples from Fault Mirrors (FMs) collected from principle slip surfaces of three natural carbonate faults. Extensive FM surfaces are believed to form during earthquake slip. Our experimental results show that Δ47 values decrease rapidly (in the course of seconds) with increasing temperature and shear velocity. On the other hand, carbonate shear zones from natural faults do not show such Δ47 decrease. We suggest that the Δ47 response may be controlled by nano-size grains, the high abundance of defects, and highly stressed/strained grain boundaries within the carbonate fault zone that can reduce the activation energy for diffusion, and thus lead to an increased rate of isotopic disordering during shear experiments. In our laboratory experiments the high stress and strain on grain contacts and the presence of nanograins thus allows for rapid disordering so that a change in Δ47 occurs in a very short and relatively low intensity heating events. In natural faults it may also lead to isotopic ordering after the cessation of frictional heating thus erasing the high temperature signature of Δ47.

  20. STABLE CARBON ISOTOPE ANALYSIS OF SUBFOSSIL WOOD FROM AUSTRIAN ALPS

    Science.gov (United States)

    KŁUSEK, MARZENA; PAWEŁCZYK, SŁAWOMIRA

    2015-01-01

    The presented studies were carried out in order to check the usefulness of subfossil wood for stable isotope analysis. The aim of research was also to define the optimal method of subfossil samples preparation. Subfossil samples used during the presented studies are a part of the multi-century dendrochronological scale. This chronology originates in an area situated around a small mountain lake — Schwarzersee, in Austria. The obtained results of stable carbon isotope measurements confirmed that the method of α-cellulose extraction by the application of acidic sodium chlorite and sodium hydroxide solutions removes resins and other mobile compounds from wood. Therefore, in the case of the analysed samples, the additional chemical process of extractives removing was found to be unnecessary. Studied wood samples contained an adequate proportion of α-cellulose similar to the values characteristic for the contemporary trees. This proved an adequate wood preservation which is essential for the conduction of isotopic research. PMID:26346297

  1. A supercritical oxidation system for the determination of carbon isotope ratios in marine dissolved organic carbon

    NARCIS (Netherlands)

    Le Clercq, Martijn; Van der Plicht, Johannes; Meijer, Harro A.J.

    1998-01-01

    An analytical oxidation system employing supercritical oxidation has been developed. It is designed to measure concentration and the natural carbon isotope ratios (C-13, C-14) Of dissolved organic carbon (DOC) and is especially suited for marine samples. The oxidation takes place in a ceramic tube a

  2. Boron isotope fractionation in magma via crustal carbonate dissolution.

    Science.gov (United States)

    Deegan, Frances M; Troll, Valentin R; Whitehouse, Martin J; Jolis, Ester M; Freda, Carmela

    2016-08-04

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ(11)B values down to -41.5‰, reflecting preferential partitioning of (10)B into the assimilating melt. Loss of (11)B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports (11)B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ(11)B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  3. Dissolved Organic Carbon Cycling in Forested Watersheds: A Carbon Isotope Approach

    Science.gov (United States)

    Schiff, S. L.; Aravena, R.; Trumbore, S. E.; Dillon, P. J.

    1990-12-01

    Dissolved organic carbon (DOC) is important in the acid-base chemistry of acid-sensitive freshwater systems; in the complexation, mobility, persistence, and toxicity of metals and other pollutants; and in lake carbon metabolism. Carbon isotopes (13C and 14C) are used to study the origin, transport, and fate of DOC in a softwater catchment in central Ontario. Precipitation, soil percolates, groundwaters, stream, beaver pond, and lake waters, and lake sediment pore water were characterized chemically and isotopically. In addition to total DOC, isotopic measurements were made on the humic and fulvic DOC fractions. The lake is a net sink for DOC. Δ14C results indicate that the turnover time of most of the DOC in streams, lakes, and wetlands is fast, less than 40 years, and on the same time scale as changes in acidic deposition. DOC in groundwaters is composed of older carbon than surface waters, indicating extensive cycling of DOC in the upper soil zone or aquifer.

  4. Descriptions of carbon isotopes within the energy density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Atef [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia and Department of Physics, Al-Azhar University, 71524 Assiut (Egypt); Cheong, Lee Yen; Yahya, Noorhana [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Tammam, M. [Department of Physics, Al-Azhar University, 71524 Assiut (Egypt)

    2014-10-24

    Within the energy density functional (EDF) theory, the structure properties of Carbon isotopes are systematically studied. The shell model calculations are done for both even-A and odd-A nuclei, to study the structure of rich-neutron Carbon isotopes. The EDF theory indicates the single-neutron halo structures in {sup 15}C, {sup 17}C and {sup 19}C, and the two-neutron halo structures in {sup 16}C and {sup 22}C nuclei. It is also found that close to the neutron drip-line, there exist amazing increase in the neutron radii and decrease on the binding energies BE, which are tightly related with the blocking effect and correspondingly the blocking effect plays a significant role in the shell model configurations.

  5. Investigating controls on boron isotope ratios in shallow marine carbonates

    Science.gov (United States)

    Zhang, Shuang; Henehan, Michael J.; Hull, Pincelli M.; Reid, R. Pamela; Hardisty, Dalton S.; Hood, Ashleigh v. S.; Planavsky, Noah J.

    2017-01-01

    The boron isotope-pH proxy has been widely used to reconstruct past ocean pH values. In both planktic foraminifera and corals, species-specific calibrations are required in order to reconstruct absolute values of pH, due to the prevalence of so-called vital effects - physiological modification of the primary environmental signals by the calcifying organisms. Shallow marine abiotic carbonate (e.g. ooids and cements) could conceivably avoid any such calibration requirement, and therefore provide a potentially useful archive for reconstructions in deep (pre-Cenozoic) time. However, shallow marine abiotic carbonates could also be affected by local shifts in pH caused by microbial photosynthesis and respiration, something that has up to now not been fully tested. In this study, we present boron isotope measurements from shallow modern marine carbonates, from the Bahama Bank and Belize to investigate the potential of using shallow water carbonates as pH archives, and to explore the role of microbial processes in driving nominally 'abiogenic' carbonate deposition. For Bahama bank samples, our boron-based pH estimates derived from a range of carbonate types (i.e. ooids, peloids, hardground cements, carbonate mud, stromatolitic micrite and calcified filament micrite) are higher than the estimated modern mean-annual seawater pH values for this region. Furthermore, the majority (73%) of our marine carbonate-based pH estimates fall out of the range of the estimated pre-industrial seawater pH values for this region. In shallow sediment cores, we did not observe a correlation between measured pore water pH and boron-derived pH estimates, suggesting boron isotope variability is a depositional rather than early diagenetic signal. For Belize reef cements, conversely, the pH estimates are lower than likely in situ seawater pH at the time of cement formation. This study indicates the potential for complications when using shallow marine non-skeletal carbonates as marine pH archives

  6. Cement stratigraphy: Image probes of cathodoluminescent facies.

    OpenAIRE

    Vuillemin, Aurèle; Ndiaye, Mapathe; Martini, Rossana; Davaud, Eric Jean

    2011-01-01

    Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum em...

  7. Environmental impact and magnitude of paleosol carbonate carbon isotope excursions marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    NARCIS (Netherlands)

    Abels, H.A.|info:eu-repo/dai/nl/304848018; Lauretano, V.; van Yperen, Anna E.; Hopman, Tarek; Zachos, J.C.; Lourens, L.J.|info:eu-repo/dai/nl/125023103; Gingerich, P.D.; Bowen, G.J.

    2016-01-01

    Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically light carbon to the exogenic atmosphere–ocean carbon system, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE) can b

  8. C isotope fractionation during heterotrophic activity driven carbonate precipitation

    Science.gov (United States)

    Balci, Nurgul; Demirel, Cansu

    2016-04-01

    Stable carbon isotopic fractionation during carbonate precipitation induced by environmentally enriched heterotrophic halophilic microorganims was experimentally investigated under various salinity (% 4.5, %8, %15) conditions at 30 °C. Halophilic heterotrophic microorganims were enriched from a hypersaline Lake Acigöl located in SW Turkey (Balci et al.,2015) and later used for the precipitation experiments (solid and liquid medium). The carbonate precipitates had relatively high δ13C values (-4.3 to -16.9 ‰) compared to the δ13C values of the organic compounds that ranged from -27.5 to -25.4 ‰. At salinity of 4.5 % δ13C values of carbonate ranged from -4.9 ‰ to -10.9 ‰ with a 13C-enrichment factor of +20 to +16 ‰ higher than the δ13C values of the associated DOC (-27.5) . At salinity 8 % δ13C values of carbonate ranged from -16.3 ‰ to -11.7 ‰ with a 13C-enrichment factor of+11.3 to+15.9 ‰ higher than the δ13C values of the associated DOC. The respected values for 15 % salinity ranged from -12.3 ‰ to -9.7 ‰ with a 13C-enrichment factor of +15.2 to+16.8 ‰ higher than the δ13C values of the associated DOC. The carbonate precipitates produced in the solid medium are more enriched in 13C relative to liquid culture experiments. These results suggest that the carbon in the solid was derived from both the bacterial oxidation of organic compounds in the medium and from the atmospheric CO2. A solid medium used in the experiments may have suppressed convective and advective mass transport favouring diffusion-controlled system. This determination suggests that the rate and equilibration of CO2 exchange with the atmosphere is the major control on C isotope composition of carbonate minerals precipitated in the experiments. Key words: Lake Acıgöl, halophilic bacteria, carbonate biomineralization, C isotopes References Nurgul Balci, Meryem Menekşe, Nevin Gül Karagüler, M. Şeref Sönmez,Patrick Meister 2015.Reproducing authigenic carbonate

  9. Carbon and nitrogen isotope systematics in diamond: Different sensitivities to isotopic fractionation or a decoupled origin?

    Science.gov (United States)

    Hogberg, K.; Stachel, T.; Stern, R. A.

    2016-11-01

    Using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources, it has been argued that carbon and nitrogen in diamond are decoupled. Here we re-investigate the carbon-nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds (n = 94) from a single locality. Our diamond samples, derived from two kimberlites in the Chidliak Field (NE Canada), show large variability in δ13C (- 28.4 ‰ to - 1.1‰, mode at - 5.8‰), δ15N (- 5.8 to + 18.8‰, mode at - 3.0‰) and nitrogen contents ([N]; 3800 to less than 1 at.ppm). In combination, cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses, with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low δ13C and [N] to mantle-like δ13C and high [N]. Overall, δ13C appears to be uncorrelated to δ15N and [N] on both the inter- and intra-diamond levels. Co-variations of δ15N-log[N], however, result in at least two parallel, negatively correlated linear arrays, which are also present on the level of the individual diamonds falling on these two trends. These arrays emerge from the two principal data clusters, are characterized by slightly negative and slightly positive δ15N (about - 3 and + 2‰, respectively) and variable but overall high [N]. Using published values for the diamond-fluid nitrogen isotope fractionation factor and nitrogen partition coefficient, these trends are perfectly reproduced by a Rayleigh fractionation model. Overall, three key elements are identified in the formation of the diamond suite studied: (1.) a low δ13C and low [N] component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event. (2.) Repeated influx of a variably nitrogen-rich mantle fluid (mildly negative δ13C and δ15N). (3.) In waning

  10. Diet control on carbon isotopic composition of land snail shell carbonate

    Institute of Scientific and Technical Information of China (English)

    LIU ZongXiu; GU ZhaoYan; WU NaiQin; XU Bing

    2007-01-01

    Carbon isotope compositions for both the carbonate shells and soft bodies (organic tissue) of living land snails collected mostly from the Loess Plateau, China have been measured. The result shows that δ13C values range from -13.1‰ to -4.3‰ for the aragonite shell samples and from -26.8‰ to -18.0‰ for the soft body samples. Although the shells are enriched in 13C relative to the bodies averagely by 14.2(±0.8)‰, the shell δ13Ca values are closely correlated to the body δ13Corg values, expressed as δ13Ca = 1.021 δ13Corg + 14.38 (R = 0.965; N = 31). This relationship indicates that δ13Ca is primarily a function of the isotopic composition of the snail diets since previous studies have proved that the snail body is the same as their food in carbon isotope composition. In other words, carbon isotope compo-sition of the carbonate shell can be used as a proxy to estimate the dietary 13C abundance of the land snails. The data also support that the 13C enrichment of the carbonate shells results mainly from the equilibrium fractionations between the metabolic CO2, HCO3- in the hemolymph and shell aragonite, and partially from kinetic fractionations when snail shells form during their activity.

  11. Photosynthetic fractionation of the stable isotopes of oxygen and carbon

    Energy Technology Data Exchange (ETDEWEB)

    Guy, R.D. (Carnegie Institution of Washington, Stanford, CA (United States)); Fogel, M.L.; Berry, J.A. (Carnegie Inst. of Washington, Washington, DC (United States))

    1993-01-01

    Isotope discrimination during photosynthetic exchange of O[sub 2] and CO[sub 2] was measured using enzyme, thylakoid, and whole cell preparations. Evolved oxygen from isolated spinach thylakoids was isotopically identical (within analytical error) to its source water. Similar results were obtained with Anacystis nidulans Richter and Phaeodactylum tricornutum Bohlin cultures purged with helium. For consumptive reactions, discrimination ([triangle], where 1 + [triangle]/1000 equals the isotope effect, k[sup 16]/k[sup 18] or k[sup 12]/k[sup 13]) was determined by analysis of residual substrate (O[sub 2] or CO[sub 2]). The [triangle] for the Mehler reaction, mediated by ferredoxin or methylviologen, was 15.3[per thousand]. Oxygen isotope discrimination during oxygenation of ribulose-1,5-bisphosphate (RuBP) catalyzed by RuBP carboxylase/oxygenase (Rubisco) was 21.3[per thousand] and independent of enzyme source, unlike carbon isotope dicrimination: 30.3[per thousand] for spinach enzyme and 19.6 to 23[per thousand] for Rhodospirillum rubrum and A. nidulans enzymes, depending on reaction conditions. The [triangle] for O[sub 2] consumption catalyzed by glycolate oxidase was 22.7[per thousand]. Consistent with this, when Asparagus sprengeri Regel mesopyll cells approached the compensation point within a sealed vessel, the [delta][sup 18]O of dissolved O[sub 2] came to a steady-state value of about 21.5[per thousand] relative to the source water. The results provide improved estimates of discrimination factors in several reactions prominent in the global oxygen cycle and indicate that photorespiration plays a significant part in determining the isotopic composition of atmospheric oxygen. 47 refs., 8 figs., 2 tabs.

  12. Organic carbon isotopes of the Sinian and Early Cambrian black shales on Yangtze Platform, China

    Institute of Scientific and Technical Information of China (English)

    李任伟; 卢家烂; 张淑坤; 雷加锦

    1999-01-01

    Organic matter of the Sinian and early Cambrian black shales on the Yangtze Platform belongs to the light carbon group of isotopes with the δ13C values from - 27 % to -35 % , which are lower than those of the contemporaneously deposited carbonates and phosphorites. A carbon isotope-stratified paleooceanographic model caused by upwelling is proposed, which can be used not only to interpret the characteristics of organic carbon isotopic compositions of the black shales, but also to interpret the paleogeographic difference in the organic carbon isotope compositions of various types of sedimentary rocks.

  13. Allochthonous carbon hypothesis for bulk OM and n-alkane PETM carbon isotope discrepancies

    Science.gov (United States)

    Baczynski, A. A.; McInerney, F. A.; Wing, S. L.; Kraus, M. J.; Fricke, H. C.

    2011-12-01

    The Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, transient, and large-scale global warming fueled by a large release of isotopically light carbon, is a relevant analogue for episodes of rapid global warming and recovery. The PETM is recorded in pedogenic carbonate, bulk organic matter, and n-alkanes as a prominent negative carbon isotope excursion (CIE) in paleosols exposed in the Bighorn Basin, WY. Here we present a composite stable carbon isotope record from n-alkanes and dispersed soil organic δ13C records from five individual sections that span the PETM in the southeastern Bighorn Basin. Four sections are from a 10km transect in the Cabin Fork area and one section was collected at Sand Creek Divide. These five new dispersed organic carbon (DOC) isotope records are compared to the previously published Polecat Bench (Magioncalda et al. 2004) and Honeycombs (Yans et al. 2006) isotope records. The high-resolution n-alkane curve shows an abrupt, negative shift in δ13C values, an extended CIE body, and a rapid recovery to more positive δ13C values. Although the five DOC records show similarly abrupt negative shifts in δ13C values, the DOC CIEs are compressed, smaller in magnitude, and return to more positive δ13C values more gradually relative to the n-alkane record. Moreover, the stratigraphic thickness of the body of the excursion and the pattern of the recovery phase are not consistent among the five DOC records. We modeled predicted DOC δ13C values from the n-alkane record by applying enrichment factors based on modern plants to the n-alkane δ13C values. The anomaly, difference between the expected and observed DOC δ13C values, was calculated for the PETM records and compared to weight percent carbon and grain size. There is no correlation between pre- and post-PETM anomaly values and grain size or weight percent carbon. PETM anomaly values, however, do trend with both grain size and weight percent carbon. The largest PETM anomaly values

  14. Seagrass sediments as a global carbon sink: Isotopic constraints

    Science.gov (United States)

    Kennedy, Hilary; Beggins, Jeff; Duarte, Carlos M.; Fourqurean, James W.; Holmer, Marianne; Marbã, Núria; Middelburg, Jack J.

    2010-12-01

    Seagrass meadows are highly productive habitats found along many of the world's coastline, providing important services that support the overall functioning of the coastal zone. The organic carbon that accumulates in seagrass meadows is derived not only from seagrass production but from the trapping of other particles, as the seagrass canopies facilitate sedimentation and reduce resuspension. Here we provide a comprehensive synthesis of the available data to obtain a better understanding of the relative contribution of seagrass and other possible sources of organic matter that accumulate in the sediments of seagrass meadows. The data set includes 219 paired analyses of the carbon isotopic composition of seagrass leaves and sediments from 207 seagrass sites at 88 locations worldwide. Using a three source mixing model and literature values for putative sources, we calculate that the average proportional contribution of seagrass to the surface sediment organic carbon pool is ˜50%. When using the best available estimates of carbon burial rates in seagrass meadows, our data indicate that between 41 and 66 gC m-2 yr-1 originates from seagrass production. Using our global average for allochthonous carbon trapped in seagrass sediments together with a recent estimate of global average net community production, we estimate that carbon burial in seagrass meadows is between 48 and 112 Tg yr-1, showing that seagrass meadows are natural hot spots for carbon sequestration.

  15. Control strategies for laser separation of carbon isotopes

    Indian Academy of Sciences (India)

    V Parthasarathy; A K Nayak; S K Sarkar

    2002-12-01

    Laser isotope separation (LIS) by infrared laser chemistry of polyatomic molecules has come a long way since its discovery. The last decade has seen considerable efforts in scaling up of the process for light elements like carbon, oxygen and silicon. These efforts aim at ways to improve both the enrichment factor and the throughput. The achievement is quite significant especially for carbon isotope separation wherein macroscopic operating scales have been realized. We report our studies on the IR laser chemistry of two promising systems, viz. neat CF2HCl and CF3Br/Cl2. We have investigated conditions for optimizing the dissociation yield and selectivity using natural samples containing 1.1 % C-13. We also highlight our current efforts for scaling up the process. These include the design aspects of a photochemical reactor with multipass refocusing Herriott optics for efficient photon utilization, development of a cryogenic distillation set up and a preparative gas chromatograph for large scale separation/collection of the isotopically enriched photoproduct in the post-irradiation stage.

  16. A natural fiber composite in a pelagic limestone-chert sequence. The importance of mechanical stratigraphy for fracture type development in carbonate anticlines.

    Science.gov (United States)

    Petracchini, Lorenzo; Antonellini, Marco; Scrocca, Davide; Billi, Andrea

    2013-04-01

    Thrust fault-related folds in carbonate rocks are characterized by deformation accommodated by different kinds of structures, such as joints, faults, pressure solution seams (PSSs), and deformation bands, which may form at various stages during the folding process. Defining the distribution, orientation, and the type of fold-related structures and understanding the relationships between folding and fracturing is significant both for theoretical and practical purposes. Furthermore, as the deformation related to the folding process influences fluid flow through rocks, identifying the types of structures formed during folding is as important as predicting their geometries. To unravel the relationship between mechanical stratigraphy and folding process, the well-exposed Cingoli anticline (Northern Apennines), has been studied in detail. The Upper Cretaceous-Middle Eocene stratigraphy of the Cingoli anticline is characterized by a pelagic multilayer made up of fine-grained pelagic limestones and, marly limestones, in places alternated with thin continuous chert layers. The presence of several outcrops located in different structural positions of the anticline makes the Cingoli anticline an excellent natural laboratory to investigate relationships between folding, fracturing, and mechanical stratigraphy relative to the structural setting of the fold. The field data collected show that high angle to bedding PSSs, which formed before tilting and during the first stage of folding, are not homogeneously distributed in the pelagic limestones. Generally, high angle to bedding PSSs form in the marly pelagic limestones and they have been observed in several outcrops and in different structural positions except where the marly limestones are inter-bedded with stiffer chert layers. In order to analyse theoretically what observed in the field, we compared the deformation of limestones and chert layers with the deformation acting on fiber composites. In the mechanics of materials

  17. An analytical system for stable isotope analysis on carbon monoxide using continuous-flow isotope-ratio mass spectrometry

    NARCIS (Netherlands)

    Pathirana, S. L.; Van Der Veen, C.; Popa, M. E.; Röckmann, T.

    2015-01-01

    A fully automated system for the determination of δ13C and δ18O in atmospheric CO has been developed. CO is extracted from an air sample and converted into carbon dioxide (CO2) using the Schütze reagent. The isotopic composition is determined with an isotope-ratio mass spectrometer (IRMS) technique.

  18. Isotopic composition of carbon and oxygen of carbonates of oil and gas-bearing deposits of Western Siberia

    Energy Technology Data Exchange (ETDEWEB)

    Golyshev, S.I.; Cherepnin, A.V.; Rozhnev, A.N.

    1981-01-01

    There is measured the isotopic composition of carbon and oxygen in 129 samples of carbonates and carbonate cements of oil and gas-bearing Paleozoic and Mezozoic deposits of Western Siberia. The isotopic composition of samples of marine deposits varies from -1.2 to +6.1% for carbon and from 19.8 to 29.1% for oxygen and has a mean isotopic composition of 1.9 to 24.8%. Catagenetic processes lead to lightening of the isotopic composition of secondary carbonate on the average by 5% for carbon and 9% for oxygen. The most intense lightening of isotopic composition is observed in samples disposed near oil and gas deposits.

  19. Isotope composition of bicarbonate carbon in bed waters of oil and gas deposits

    Energy Technology Data Exchange (ETDEWEB)

    Golyshev, S.I.; Cherepnin, A.V.; Ivanov, V.G.; Manylova, L.S.

    1981-01-01

    A study is made of the isotope composition of bicarbonate carbon in bed waters of the Jurassic water complex in southeast West Siberia. It has been established that waters of empty and transcontour structures have isotope composition of carbon 5/sup 0//oo, while in waters which contact the hydrocarbon formations, the isotope composition of carbon is lighter on the average by 5-8/sup 0//oo. The isotope composition of bicarbonate carbon in bed waters reflects both the conditions for primary sedimentation, and secondary processes associated with organic matter transformation.

  20. A global deglacial negative carbon isotope excursion in speleothem calcite

    Science.gov (United States)

    Breecker, D.

    2015-12-01

    δ13C values of speleothem calcite decreased globally during the last deglaciation defining a carbon isotope excursion (CIE) despite relatively constant δ13C values of carbon in the ocean-atmosphere system. The magnitude of the CIE varied with latitude, increasing poleward from ~2‰ in the tropics to as much as 7‰ at high latitudes. This recent CIE provides an interesting comparison with CIEs observed in deep time. A substantial portion of this CIE can be explained by the increase in atmospheric pCO2 that accompanied deglaciation. The dependence of C3 plant δ13C values on atmospheric pCO2 predicts a 2‰ δ13C decrease driven by the deglacial pCO2 increase. I propose that this signal was transferred to caves and thus explains nearly 100% of the CIE magnitude observed in the tropics and no less than 30% at the highest latitudes in the compilation. An atmospheric pCO2 control on speleothem δ13C values, if real, will need to be corrected for using ice core data before δ13C records can be interpreted in a paleoclimate context. The decrease in the magnitude of the equilibrium calcite-CO2 carbon isotope fractionation factor explains a maximum of 1‰ of the CIE at the highest northern latitude in the compilation, which experienced the largest deglacial warming. Much of the residual extratropical CIE was likely driven by increasing belowground respiration rates, which were presumably pronounced at high latitudes as glacial retreat exposed fresh surfaces and/or vegetation density increased. The largest increases in belowground respiration would have therefore occurred at the highest latitudes, explaining the meridional trend. This work supports the notion that increases in atmospheric pCO2 and belowground respiration rates can result in large CIEs recorded in terrestrial carbonates, which, as previously suggested, may explain the magnitude of the PETM CIE as recorded by paleosol carbonates.

  1. Paired carbon stable-isotope records for the Cenomanian Stage (100.5 -93.9 Ma): correlation tool and Late Cretaceous pCO2 record?

    Science.gov (United States)

    Jarvis, Ian; Gröcke, Darren; Laurin, Jiří; Selby, David; Roest-Ellis, Sascha; Miles, Andrew; Lignum, John; Gale, Andrew; Kennedy, Jim

    2016-04-01

    Carbon stable-isotope stratigraphy of marine carbonates (δ13Ccarb) provides remarkable insights into past variation in the global carbon cycle, and has become firmly established as a powerful global correlation tool. Continuous δ13Ccarb time series are becoming increasingly available for much of the geological record, including the Upper Cretaceous. However, our knowledge of stratigraphic variation in the carbon isotopic composition of sedimentary organic matter (δ13Corg) is much poorer, and is generally restricted to organic-rich sedimentary successions and/or key boundary intervals. Close coupling exists between the global isotopic composition of the reduced and oxidised carbon reservoirs on geological time scales, but the stratigraphic resolution of most long-term δ13Corg Mesozoic records is inadequate to identify leads and lags in the responses of the two reservoirs to carbon cycle perturbations. Cenomanian times (100.5-93.9 Ma) represent perhaps the best documented episode of eustatic rise in sea level in Earth history and the beginning of the Late Mesozoic thermal maximum, driving global expansion of epicontinental seas and the onset of widespread pelagic and hemipelagic carbonate deposition. Significant changes occurred in global stable-isotope records, including two prominent perturbations of the carbon cycle - the Mid-Cenomanian Event I (MCEI; ~96.5-96.2 Ma) and Oceanic Anoxic Event 2 (OAE2; ~94.5-93.8 Ma). OAE2, one of two truly global Cretaceous OAEs, was marked by the widespread deposition of black shales, and a global positive carbon stable-isotope excursion of 2.0 - 2.5‰ δ13Ccarb, and up to 7‰ in the sulphur-bound phytane biomarker. MCEI, by contrast, shows a English Chalk reference section at Folkestone, and correlate the carbon-isotope events between England, France, Germany and Italy. Comparison of the Vergons δ13Ccarb vs. δ13Corg profiles demonstrates similar medium-term stratigraphic variation, but significant differences in both short

  2. Carbon isotope excursions in paleosol carbonate marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    Directory of Open Access Journals (Sweden)

    H. A. Abels

    2015-05-01

    Full Text Available Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically-light carbon to the exogenic atmosphere–ocean carbon pool, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE can be used to constrain both the sources and amounts of carbon released during an event, as well as to correlate marine and terrestrial records with high precision. The Paleocene Eocene Thermal Maximum (PETM is well documented, but CIE records for the subsequent warming events are still rare especially from the terrestrial realm. Here, we provide new CIE records for two of the smaller hyperthermal events, I1 and I2, in paleosol carbonate, as well as two additional records of ETM2 and H2 in the Bighorn Basin. Stratigraphic comparison of this expanded, high-resolution terrestrial carbon isotope record to the deep-sea benthic foraminifera records from ODP Sites 1262 and 1263, Walvis Ridge, in the southern Atlantic Ocean corroborates that the Bighorn Basin fluvial sediments record global atmospheric change. The stratigraphic thicknesses of the eccentricity-driven hyperthermals in these archives are in line with precession-forcing of the 7 m thick fluvial overbank-avulsion sedimentary cycles. Using the CALMAG bulk oxide mean annual precipitation proxy, we reconstruct similar or slightly wetter than background soil moisture contents during the four younger hyperthermals, in contrast to drying observed during the PETM. Soil carbonate CIEs vary in magnitude proportionally with the marine CIEs for the four smaller early Eocene hyperthermals. This relationship breaks down for the PETM, with the soil carbonate CIE ~ 2–4‰ less than expected if all five linearly relate to marine CIEs. If the PETM CO2 forcing was similar but scaled to the younger hyperthermals, photosynthetic isotope fractionation or soil environmental factors are needed to explain this anomaly. We

  3. Carbon isotope excursions across the Permian-Triassic boundary in the Meishan section, Zhejiang Province, China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Both gradual and sharp decrease in organic and carbonate carbon isotope values were detected across the Permian-Triassic boundary in the Meishan section, Changxing, Zhejiang Province, China. The gradual decrease in organic carbon isotope values started at the bottom of Bed 23, coinciding with the strong oscillations of total organic carbon (TOC) contents, indicates increasing fluxes from carbonate to organic carbon reservoir during this interval. A 2.3‰ sharp drop of inorganic carbon isotope values occurred at the uppermost part of Bed 24e. A 3.7‰ sharp drop of organic carbon isotope values occurred in Bed 26. The dramatic drop of inorganic carbon isotope value of 8‰ reported previously is not confirmed from the unweathered carbonate samples in Bed 27. The large-scale fluctuation of organic carbon isotope values in the Yinkeng Formation reflects different extent of mixing of marine and terrestrial organic matters. The gradual depletion and subsequent sharp drop of carbon isotopes near the Permian-Triassic boundary might indicate complex causes of the end-Permian mass extinction.

  4. Mantle Degassing and Diamond Genesis:A Carbon Isotope Perspective

    Institute of Scientific and Technical Information of China (English)

    郑永飞

    1994-01-01

    The effect of Co2 and CH4 degassing from the mantle on the carbon isotopic composition of diamond has been quantitatively modeled in terms of the principles of Rayleigh distillation.Assuming the δ13 C value of -5‰ for the mantle,the outgassing of CO2 can result in the large negative δ13 C values of diamond,whereas the outgassing of CH4 can drive the δ13C values of diamond in the positive direction.The theoretical expectations can be used to explain the full range of δ13 C values from-34.4‰5 to+5‰ observed for natural diamonds.It is possible that diamond formation was triggered by the degassing of Co2 and/or CH4 from the mantle and the associated fractional crystallization of carbonate-bearing melt.

  5. Carbon isotopes and water use efficiency in C4 plants.

    Science.gov (United States)

    Ellsworth, Patrick Z; Cousins, Asaph B

    2016-06-01

    Drought is a major agricultural problem worldwide. Therefore, selection for increased water use efficiency (WUE) in food and biofuel crop species will be an important trait in plant breeding programs. The leaf carbon isotopic composition (δ(13)Cleaf) has been suggested to serve as a rapid and effective high throughput phenotyping method for WUE in both C3 and C4 species. This is because WUE, leaf carbon discrimination (Δ(13)Cleaf), and δ(13)Cleaf are correlated through their relationships with intercellular to ambient CO2 partial pressures (Ci/Ca). However, in C4 plants, changing environmental conditions may influence photosynthetic efficiency (bundle-sheath leakiness) and post-photosynthetic fractionation that will potentially alter the relationship between δ(13)Cleaf and Ci/Ca. Here we discuss how these factors influence the relationship between δ(13)Cleaf and WUE, and the potential of using δ(13)Cleaf as a meaningful proxy for WUE.

  6. The relationship between carbon and oxygen isotopic composition characteristics of carbonates in loess sediments and paleoclimate

    Institute of Scientific and Technical Information of China (English)

    李春园; 王先彬; 文启彬; 邵波

    1995-01-01

    Based on the carbon and oxygen isotopic compositions of carbonates in loess sediments meas-ured by the methods of stepwise heating and phosphoric acid decomposition from five pieces of samples ofpaleosol,loess and eolian sand,respectively,the distributive characteristics in different temperature steps andthe fractionation mechanisms of carbon and oxygen isotope and their relation to the paleoclirnate are discussed.The preliminary results show that,by means of stepwise heating,different carbon and oxygen isotopiccompositions are obtained in different temperature steps and carbon and oxygen isotopic compositions ofpaleosol,loess and eolian sand are in a different distributive pattern in the range of studied temperaturesteps.The results also show that the δ13C ratios in 700-800℃ are more sensitive tracers of paleoclimatethan those measured by the method of phosphoric acid decomposition.The susceptibility to climatic changesof δ18O ratios analysed by the method of phosphoric acid decomposition is higher than those analysed by themethod of stepwise heating,but the δ18O ratios measured by these two methods do not effectively reflect cli-matic changes.

  7. Abundances in red giant stars - Carbon and oxygen isotopes in carbon-rich molecular envelopes

    Science.gov (United States)

    Wannier, P. G.; Sahai, R.

    1987-01-01

    Millimeter-wave observations have been made of isotopically substituted CO toward the envelopes of 11 carbon-rich stars. In every case, C-13O was detected and model calculations were used to estimate the C-12/C-13 abundance ratio. C-17O was detected toward three, and possibly four, envelopes, with sensitive upper limits for two others. The CO-18 variant was detected in two envelopes. New results include determinations of oxygen isotopic ratios in the two carbon-rich protoplanetary nebulae CRL 26688 and CRL 618. As with other classes of red giant stars, the carbon-rich giants seem to be significantly, though variably, enriched in O-17. These results, in combination with observations in interstellar molecular clouds, indicate that current knowledge of stellar production of the CNO nuclides is far from satisfactory.

  8. Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil

    OpenAIRE

    SIAL ALCIDES N.; FERREIRA VALDEREZ P.; DEALMEIDA AFONSO R.; ROMANO ANTONIO W.; PARENTE CLOVIS V.; DACOSTA MARCONDES L.; SANTOS VICTOR H.

    2000-01-01

    Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB), compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/...

  9. Oxygen Isotopic Composition of Carbon Dioxide in the Middle Atmosphere

    Science.gov (United States)

    Liang, M.; Blake, G. A.; Lewis, B. R.; Yung, Y. L.

    2005-12-01

    The isotopic composition of long-lived trace gases provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 ppmv in the mesosphere. Current models consider O3 as the main source of O(1D) in the mesosphere, but we note that the photolysis of 16O17O and 16O18O by solar Lyman-α radiation yields O(1D) 10-100 times more enriched in 17O and 18O than that from ozone photodissociation. We therefore incorporate both photochemical sources into stratospheric and mesospheric chemical transport models that quantitatively predict the unusual enhancement of 17O in CO2 from the middle atmosphere. New laboratory and atmospheric measurements are proposed to test our model and validate the use of CO2 isotopic fractionation as a tracer of atmospheric chemical and dynamical processes. Once fully understood the `anomalous' oxygen signature in CO2 can be used in turn to study biogeochemical cycles, in particular to constrain the gross carbon fluxes between the atmosphere and terrestrial biosphere.

  10. Carbonate Sequence Stratigraphy of a Back-Arc Basin: A Case Study of the Qom Formation in the Kashan Area, Central Iran

    Institute of Scientific and Technical Information of China (English)

    XU Guoqiang; ZHANG Shaonan; LI Zhongdong; SONG Lailiang; LIU Huimin

    2007-01-01

    The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid-Tertiary back-arc basin. There are two second-order sequences (designated as SS1 and SS2) and five third-order sequences (designated as S1-S5). Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and lowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined (S1 to S5 individually corresponding to A-C1, C2-C4, D-E, the lower and upper portions of F); a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing: (1) a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; (2) a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and (3) a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread

  11. Tunable Diode Laser Measurements of Leaf-scale Carbon Isotope Discrimination and Ecosystem Respired Carbon and Oxygen Isotope Ratios in a Semi-arid Woodland

    Science.gov (United States)

    McDowell, N.; Chris, B.; Hanson, D.; Kern, S.; Meyer, C.; Pockman, W.; Powers, H.

    2005-12-01

    We present results and speculative interpretation of leaf-level carbon isotope discrimination and ecosystem respired carbon and oxygen isotope ratios from a semi-arid, C3/C4 woodland located in northern New Mexico, USA. Overstory leaf area index (LAI) is dominated by live juniper (Juniperus monosperma) trees with an LAI value of approximately 1.0 m2 per m2 ground area, and has a seasonally dynamic understory of mixed C3 forbs and C4 grasses and cacti, with a maximum LAI of 0.30 m2 per m2 ground area. Ecosystem respired carbon isotope ratios showed values characteristic of C3 dominated photosynthesis (Keeling plot intercepts of -35 to -22 per mil). Seasonal variation was typical of that found in wetter, C3 dominated forests, as was the dependence on climate (e.g. relationships with vapor pressure deficit, soil water content, and canopy conductance). Leaf-level carbon isotope discrimination of the junipers, measured by coupling a Li-Cor 6400 photosynthesis system to the TDL, provided discrimination-Ci and discrimination-vpd relationships consistent with measured ecosystem respired carbon isotope ratios. The oxygen isotope ratio of ecosystem respiration was dependent on rain water isotope composition, but was correlated with soil water content during rain-free periods. The cumulative effect of vapor pressure deficit after a rain event was tightly correlated with the oxygen isotope ratio of ecosystem respiration, suggesting the primary drivers are evaporative enrichment of soil water and perhaps nocturnal leaf enrichment. Instrument precision for carbon and oxygen isotope ratios of carbon dioxide is 0.06 to 0.18 per mil; however, overall precision is somewhat lower due to pressure and sampling effects.

  12. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Science.gov (United States)

    Brüggemann, N.; Gessler, A.; Kayler, Z.; Keel, S. G.; Badeck, F.; Barthel, M.; Boeckx, P.; Buchmann, N.; Brugnoli, E.; Esperschütz, J.; Gavrichkova, O.; Ghashghaie, J.; Gomez-Casanovas, N.; Keitel, C.; Knohl, A.; Kuptz, D.; Palacio, S.; Salmon, Y.; Uchida, Y.; Bahn, M.

    2011-11-01

    The terrestrial carbon (C) cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual), including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO2 diffusion and dissolution processes within the

  13. Sr Isotopic Variation in Shallow Water Carbonate Sequences: Stratigraphic, Chronostratigraphic, and Eustatic Implications of the Record at Enewetak Atoll

    Science.gov (United States)

    Quinn, Terrence M.; Lohmann, K. C.; Halliday, A. N.

    1991-06-01

    Sr isotope data from two boreholes within the lagoon at Enewetak Atoll have been used to evaluate the use of such data to correlate, date, and monitor sea level change in shallow water carbonate sequences. Correlative stratigraphic intervals of relatively invariant δ87Sr, separated by abrupt transitions to lower δ87Sr with increasing depth, are recognized in both boreholes. Conversion of δ87Sr values to age via calibration with the seawater δ87Sr trend with age indicates that correlative and synchronous deposition of atoll sediments occurred at ˜ 0.4, 1.2, and 2.1 Ma. In contrast, a ˜5 m.y. hiatus is recognized in one borehole but not the other. Sr isotope stratigraphy (SIS) is a powerful stratigraphic and chronostratigraphic tool in shallow water carbonate sequences only when significant secular variation of δ87Sr occurs and retention of depositional δ87Sr values is demonstrated. The latter is best demonstrated when δ87Sr data, are integrated with δ18O, δ13C, Sr content data and petrographic observations. Several diagenetically altered intervals have greater δ87Sr values, low δ13C values, and low Sr/Ca ratios relative to adjacent intervals, a combination that is consistent with open-system meteoric diagenesis. Calcite cements from these intervals have early Pleistocene (˜1.2 Ma) δ87Sr values despite their occurrence well within the late Pliocene (˜2.1 Ma) sequence. Thus local sedimentological and diagenetic processes have produced intralagoon variability in the SIS of the two boreholes, complicating subsurface stratigraphic correlations. The occurrence of anomalously young calcite cement relative to adjacent limestone is a direct response of the interaction of sea level change and meteoric phreatic diagenesis whereby overlying metastable carbonates, with greater δ87Sr values, are dissolved during periods of atoll emergence and sea level lowstand liberating Sr and soil-gas CO2 to the pore fluid, which is then incorporated into downflow meteoric

  14. Temperature and Oxygen Isotope Composition of The Ediacaran Ocean: Constraints From Clumped Isotope Carbonate Thermometry

    Science.gov (United States)

    Bonifacie, M.; Eiler, J. M.; Fike, D. A.

    2008-12-01

    The temperature and chemical variations of the early oceans on Earth are highly debated, particularly for periods associated with significant evolutionary change and/or extinction. The temperature of past oceans has been estimated based on conventional carbonate-water and/or silicate-water stable oxygen isotope thermometry. Precambrian carbonates and silicates both exhibit a long-term secular trend of increasing δ18O values with decreasing age. This trend has been used to support two opposite - though related - interpretations: the Earth's oceans gradually cooled over the course of the Proterozoic eon, from a maximum of ~ 60-90°C at ~ 2.5Ga (and were, on average, relatively warm during much of the Paleozoic era) [1]. This interpretation has been supported by Si-isotope proxies and the thermal tolerances of proteins in various classes of microbial organisms [2-3]. Alternatively, the δ18O value of the oceans has gradually increased through time [4-5], and mean Earth surface temperatures varied over a narrow range similar to modern conditions. In other terms, one either assumes an ocean of constant δ18O and infers that climate varied dramatically, or vise versa. Finally, it is possible that post- depositional processes (e.g., diagenesis, burial metamorphism, weathering) has modified the δ18O values of all or most Precambrian sedimentary carbonates and silicates, overprinting any paleoclimatic variations. Carbonate 'clumped isotope' thermometry provides a new way to independently test these hypotheses because it allows one to determine the apparent growth temperatures of carbonate minerals based on their abundances of 13C-18O bonds, as reflected by the 'Δ47' value of CO2 extracted by phosphoric acid digestion [6]. This method is thermodynamically based and independent of the δ18O of water from which the carbonate grew. We will report the initial results of measurements of 'Δ47 for a suite of carbonates from the Sultanate of Oman. This Ediacaran age (~ 635 to

  15. Carbon isotope composition of latex does not reflect temporal variations of photosynthetic carbon isotope discrimination in rubber trees (Hevea brasiliensis).

    Science.gov (United States)

    Kanpanon, Nicha; Kasemsap, Poonpipope; Thaler, Philippe; Kositsup, Boonthida; Gay, Frédéric; Lacote, Régis; Epron, Daniel

    2015-11-01

    Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on average) with more variable δ(13)C values than those of untapped trees. δ(13)C-L was higher and more stable across seasons than δ(13)C-S and δ(13)C-B, with a maximum seasonal difference of 0.7‰ for tapped trees and 0.3‰ for untapped trees. δ(13)C-B was lower in tapped than in untapped trees, increasing from August (middle of the rainy season) to April (end of the dry season). Differences in δ(13)C-L and δ(13)C-B between tapped and untapped trees indicated that tapping affects the metabolism of both laticiferous cells and leaves. The lack of correlation between δ(13)C-L and δ(13)C-S suggests that recent photosynthates are mixed in the large pool of stored carbohydrates that are involved in latex regeneration after tapping.

  16. Long-range transport of continentally-derived particulate carbon in the marine atmosphere: evidence from stable carbon isotope studies

    OpenAIRE

    Cachier, Héléne; BUAT-MÉNARD, PATRICK; Fontugne, Michel; Chesselet, Roger

    2011-01-01

    Since 1979, we have investigated marine and non-marine sources of particulate carbon in the marine atmosphere from measurements of carbon concentration and isotopic composition 13C/12C). Aerosol samples were collected, mostly during the Sea/Air Exchange (SEAREX) Program experiments, in the northern and southern hemispheres (Sargasso Sea, Enewetak Atoll, Peru upwelling, American Samoa, New Zealand, Amsterdam Island). The concentration and the isotopic composition of particulate carbon of marin...

  17. Using Carbon Isotopes in Cenozoic Soil Carbonates to Quantify Primary Productivity from Mid-Latitude Regions

    Science.gov (United States)

    Caves, J. K.; Kramer, S. H.; Ibarra, D. E.; Chamberlain, C. P.

    2015-12-01

    The carbon isotope composition of pedogenic carbonates (δ13Ccarb) from paleosols has been extensively used as a proxy to estimate atmospheric pCO2 over the Phanerozoic. However, a number of other factors - including the concentration of plant-respired CO2 and the isotopic composition of both atmospheric and plant-respired carbon - influence the δ13C of pedogenic carbonates. For example, δ13Ccarb records from the mid-latitudes in central Asia and western North America show increasing trends in δ13Ccarb despite decreasing pCO2 during the late Cenozoic, which suggests that other factors play an important role in determining the isotopic composition of pedogenic carbonates. Instead, we suggest that these records are primarily recording changes in primary productivity rather than changes in atmospheric pCO2 and therefore propose a novel use of paleosol carbonate records to understand paleo-ecosystem dynamics. Here, we compile existing paleosol carbonate records, and present three new records from Wyoming, to estimate soil respiration and primary productivity in western North America during the Paleogene and early Neogene. We observe both an overall increase in δ13Ccarb after the early Eocene, and spatially heterogeneous δ13Ccarb values across western US basins. We combine this δ13Ccarb data with compilations of atmospheric pCO2 to estimate soil respiration and plant productivity. The long-term increase in δ13Ccarb indicates a decrease in plant productivity as conditions became more arid across much of the western US, congruent with both records of regional uplift and of global cooling. Furthermore, significant spatial heterogeneity in δ13Ccarb indicates that regional factors, such as the presence of paleolakes and/or local paleotopography may have provided a second-order control on local and regional productivity. Thus, our results provide a first-order estimate linking changes in primary productivity with regional tectonics and global climatic change.

  18. Cryogenic Calcite: A Morphologic and Isotopic Analog to the ALH84001 Carbonates

    Science.gov (United States)

    Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Ming, D. W.; Gibson, E. K.

    2004-01-01

    Martian meteorite ALH84001 carbonates preserve large and variable microscale isotopic compositions, which in some way reflect their formation environment. These measurements show large variations (>20%) in the carbon and oxygen isotopic compositions of the carbonates on a 10-20 micron scale that are correlated with chemical composition. However, the utilization of these data sets for interpreting the formation conditions of the carbonates is complex due to lack of suitable terrestrial analogs and the difficulty of modeling under non-equilibrium conditions. Thus, the mechanisms and processes are largely unknown that create and preserve large microscale isotopic variations in carbonate minerals. Experimental tests of the possible environments and mechanisms that lead to large microscale isotopic variations can help address these concerns. One possible mechanism for creating large carbon isotopic variations in carbonates involves the freezing of water. Carbonates precipitate during extensive CO2 degassing that occurs during the freezing process as the fluid s decreasing volume drives CO2 out. This rapid CO2 degassing results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing an enrichment of 13C in the remaining dissolved bicarbonate. This study seeks to determine the suitability of cryogenically formed carbonates as analogs to ALH84001 carbonates. Specifically, our objective is to determine how accurately models using equilibrium fractionation factors approximate the isotopic compositions of cryogenically precipitated carbonates. This includes determining the accuracy of applying equilibrium fractionation factors during a kinetic process, and determining how isotopic variations in the fluid are preserved in microscale variations in the precipitated carbonates.

  19. Stable Carbon and Oxygen Isotopes of Pedogenic Carbonates in Ustic Vertisols: Implications for Paleoenvironmental Change

    Institute of Scientific and Technical Information of China (English)

    HUANG Cheng-Min; WANG Cheng-Shan; TANG Ya

    2005-01-01

    Pedogenic carbonates, found extensively in arid and semiarid regions, are important in revealing regional climatic and environmental changes as well as the carbon cycle. In addition, stable carbon and oxygen isotopic compositions of pedogenic carbonates have been used to rebuild paleoecology (biomass and vegetation) and to estimate paleotemperature and paleoprecipitation during past geological time. By utilizing the stable carbon and oxygen isotopic compositions (δ13C and δ18O) of secondary nodules in Ustic Vertisols, this study looked into the climatic and environmental changes in the dry valleys of the Yuanmou Basin, Yunnan Province, in southwestern China. The results showed that during the early Holocene, a warm-humid or hot-humid climate existed in the Yuanmou Basin, but since then fluctuations in climate have occurred, with a dry climate prevailing. A highly significant correlation (r = 0.92, n= 9) between δ13C and δ18O values of carbonates illustrated that there had been a continual shifting between cold-humid and warm-dry climates in southwestern China including the Yuanmou Basin since the early Holocene.

  20. Regional prediction of carbon isotopes in soil carbonates for Asian dust source tracer

    Science.gov (United States)

    Chen, Bing; Cui, Xinjuan; Wang, Yaqiang

    2016-10-01

    Dust particles emitted from deserts and semi-arid lands in northern China cause particulate pollution that increases the burden of disease particularly for urban population in East Asia. The stable carbon isotopes (δ13C) of carbonates in soils and dust aerosols in northern China were investigated. We found that the δ13C of carbonates in surface soils in northern China showed clearly the negative correlation (R2 = 0.73) with Normalized Difference Vegetation Index (NDVI). Using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-derived NDVI, we predicted the regional distribution of δ13C of soil carbonates in deserts, sandy lands, and steppe areas. The predictions show the mean δ13C of -0.4 ± 0.7‰ in soil carbonates in Taklimakan Desert and Gobi Deserts, and the isotope values decrease to -3.3 ± 1.1‰ in sandy lands. The increase in vegetation coverage depletes 13C in soil carbonates, thus the steppe areas are predicted by the lowest δ13C levels (-8.1 ± 1.7‰). The measurements of atmospheric dust samples at eight sites showed that the Asian dust sources were well assigned by the 13C mapping in surface soils. Predicting 13C in large geographical areas with fine resolution offers a cost-effective tracer to monitor dust emissions from sandy lands and steppe areas which show an increasing role in Asian dust loading driven by climate change and human activities.

  1. Seasonal variation in stable carbon and nitrogen isotope values of bats reflect environmental baselines.

    Directory of Open Access Journals (Sweden)

    Ana G Popa-Lisseanu

    Full Text Available The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal's isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic variation in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher δ13C and δ15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is integrated in animals' isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers.

  2. Stable Isotope Studies of Crop Carbon and Water Relations: A Review

    Institute of Scientific and Technical Information of China (English)

    ZHANG Cong-zhi; ZHANG Jia-bao; ZHAO Bing-zi; ZHANG Hui; HUANG Ping

    2009-01-01

    Crop carbon and water relations research is important in the studies of water saving agriculture,breeding program,and energy and material cycles in soil plant atmosphere continuum (SPAC).The purpose of this paper is to review the current state of knowledge on stable isotopes of carbon,oxygen,and hydrogen in the research of crop carbon and water relations,such as carbon isotope discrimination (△13C) during carbon fixation process by photosynthesis,application of △13C in crop water use efficiency (WUE) and breeding programs,oxygen isotope enrichment during leaf water transpiration,CO2 fixation by photosynthesis and release by respiration,application of hydrogen isotope composition (δD) and oxygen isotope composition (δ18O) for determination of water source used by a crop,stable isotope coupling Keeling plot for investigating the carbon and water flux in ecosystem,energy and material cycle in SPAC and correlative integrative models on stable isotope.These aspects contain most of the stable isotope researches on crop carbon and water relations which have been widely explored internationally while less referred in China.Based on the reviewed literatures,some needs for future research are suggested.

  3. The magnesium isotope record of cave carbonate archives

    Directory of Open Access Journals (Sweden)

    S. Riechelmann

    2012-11-01

    Full Text Available Here we explore the potential of magnesium (δ26Mg isotope time-series data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco, the warm-temperate (Germany, the equatorial-humid (Peru and the cold-humid (Austria climate zones. Changes in the calcite magnesium isotope signature with time are compared against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and disequilibrium processes governs the δ26Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rainwater or snow as well as soil and host rock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean δ26Mg values (GDA: −4.26 ± 0.07‰ and HK3: −4.17 ± 0.15‰, and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value of all stalagmites (NC-A and NC-B δ26Mg: −3.96 ± 0.04‰ but only minor variations in Mg-isotope composition, which is consistent with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean δ26Mg: −4.01 ± 0.07‰; BU 4 mean δ26Mg: −4.20 ± 0.10‰ suggest changes in outside air temperature was the principal driver rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: −3.00 ± 0.73‰; SPA 59: −3.70 ± 0.43‰ are affected by glacial versus interglacial climate change with outside air temperature

  4. The magnesium isotope record of cave carbonate archives

    Directory of Open Access Journals (Sweden)

    S. Riechelmann

    2012-05-01

    Full Text Available Here we explore the potential of time-series magnesium (δ26Mg isotope data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco, the warm-temperate (Germany, the equatorial-humid (Peru and the cold-humid (Austria climate zones. Changes in the calcite magnesium isotope signature with time are placed against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and non-equilibrium processes governs the δ26Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rain water or snow as well as soil and hostrock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean δ26Mg values (GDA: −4.26 ± 0.07 ‰ and HK3: −4.17 ± 0.15 ‰ and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value (NC-A and NC-B δ26Mg: −3.96 ± 0.04 ‰ but only minor variations in Mg-isotope composition, which is in concert with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean δ26Mg: −4.01 ± 0.07 ‰; BU 4 mean δ26Mg: −4.20 ± 0.10 ‰ record changes in outside air temperature as driving factor rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: −3.00 ± 0.73 ‰; SPA 59: −3.70 ± 0.43 ‰ are affected by glacial versus interglacial climate change with outside air temperature affecting soil zone activity

  5. The Stable and Radio- Carbon Isotopic Content of Labile and Refractory Carbon in Atmospheric Particulate Matter

    Science.gov (United States)

    McNichol, A. P.; Rosenheim, B. E.; Gerlach, D. S.; Hayes, J. M.

    2006-12-01

    Studies of the isotopic content of atmospheric particulate matter are hampered by difficulties in chemically defining the pools of carbon and analytically isolating the different pools. We are conducting studies on reference materials and atmospheric aerosol samples to develop a method to measure stable and radio- carbon isotopes on the labile and refractory carbon. We are using a flow-through combustion system that allows us to combust, collect and measure the isotopic content of the gases produced at all stages of heating/oxidizing. We compare our results to those measured using a chemothermal oxidation method (CTO) (Gustafsson et al., 2001). In this method, refractory carbon is defined as the material remaining after pre- combusting a sample at 375°C in the presence of oxygen for 24 hours. The reference materials are diesel soot, apple leaves and a hybrid of the two (DiesApple), all from NIST. These provide carbon with two well-defined fractions -- the soot provides refractory carbon that is radiocarbon dead and the apple leaves provide organic carbon that is radiocarbon modern. Radiocarbon results from DiesApple indicate that the "refractory" carbon defined by the CTO method is actually a mixture of old and modern carbon that contains over 25% modern carbon. This suggests that charred material formed from the apples leaves during the pre-combustion step is contributing to the fraction we identify as refractory carbon. We are studying this by analyzing the individual materials and the mixture using our flow-through system. First results with this system indicate that the refractory fraction trapped from the DiesApple contains much less modern carbon than the CTO method, less than 7%. We will present detailed concentration and isotopic results of the generation of carbon dioxide during programmed combustion of each of the reference materials. We studied the radiocarbon content of both the total carbon (TC) and refractory carbon in the fine particulate matter (PM

  6. Clumped isotope calibration data for lacustrine carbonates: A progress report

    Science.gov (United States)

    Tripati, A.

    2015-12-01

    Our capacity to understand Earth's environmental history is highly dependent on the accuracy of reconstructions of past climates. Lake sediments provide important archives of terrestrial climate change, and represent an important tool for reconstructing paleohydrology, paleoclimate, paleoenvironment, and paleoaltimetry. Unfortunately, while multiple methods for constraining marine temperature exist, quantitative terrestrial proxies are scarcer - tree rings, speleothems, and leaf margin analyses have all been used with varying degrees of accuracy. Clumped isotope thermometry has the potential to be a useful instrument for determining terrestrial climates: multiple studies have shown the fraction of 13C—18O bonds in carbonates is inversely related to the temperature at which the rocks formed. We have been measuring the abundance of 13C18O16O in the CO2 produced by the dissolution of carbonate minerals in phosphoric acid in modern lake samples and comparing results to independently known estimates of lake water temperature. Here we discuss an extensive calibration dataset comprised of 132 analyses of 97 samples from 44 localities, including microbialites, tufas, and micrites endogenic carbonates, freshwater gastropods, bivalves, microbialites, and ooids.

  7. Late Eocene stable isotope stratigraphy of North Atlantic IODP Site U1411: Orbitally paced climatic heartbeat at the close of the Eocene greenhouse

    Science.gov (United States)

    Coxall, Helen; Bohaty, Steve; Wilson, Paul; Liebrand, Diederik; Nyberg, Anna; Holmström, Max

    2016-04-01

    Integrated Ocean Drilling Program (IODP) Expedition 342 drilled sediment drifts on the Newfoundland margin to recover high-resolution records of North Atlantic ocean-climate history and track the evolution of the modern climate system through the Late Cretaceous and Early Cenozoic. An early Paleogene deep-sea benthic stable isotope composite record from multiple Exp. 342 sites is currently in development and will provide a key reference section for investigations of Atlantic and global climate dynamics. This study presents initial results for the late Eocene slice of the composite from Site U1411, located at mid depth (˜2850m Eocene paleodepth) on the Southeast Newfoundland Ridge. Stable oxygen (δ18O) and carbon (δ13C) isotope ratios were measured on 640 samples hosting exceptionally well-preserved epifaunal benthic foraminifera obtained from the microfossil-rich uppermost Eocene clays at 4cm spacing. Sedimentation rates average 2-3 cm/kyr through the late Eocene, such that our sampling resolution is sufficient to capture the dominant Milankovitch frequencies. Late Eocene Site U1411 benthic δ18O values (1.4 to 0.5‰ VPDB) are comparable to the Pacific and elsewhere in the Atlantic at similar depths; however, δ13C is lower by ˜0.5 ‰ with values intermediate between those of the Southern Labrador Sea to the north (-1 to 0) and mid latitude/South Atlantic (0.5 to 1.5) to the south, suggesting poorly ventilated bottom waters in the late Eocene North Atlantic and limited production of North Atlantic deep water. Applying the initial shipboard magneto-biostratigraphic age framework, the Site U1411 benthic δ13C and δ18O records display clear cyclicity on orbital timescales. Spectral analysis of the raw unfiltered datasets identifies eccentricity (400 and 100 kyr), obliquity (40 kyr) and precession (˜20 kyr) signals imprinted on our time series, revealing distinct climatic heart beats in the late Eocene prior to the transition into the 'ice house'.

  8. On-site isotopic analysis of dissolved inorganic carbon using an isotope ratio infrared spectrometer

    Science.gov (United States)

    Stoltmann, Tim; Mandic, Magda; Stöbener, Nils; Wapelhorst, Eric; Aepfler, Rebecca; Hinrichs, Kai-Uwe; Taubner, Heidi; Jost, Hj; Elvert, Marcus

    2016-04-01

    An Isotope Ratio Infrared Spectrometer (IRIS) has been adapted to perform measurements of δ13C of dissolved inorganic carbon (DIC) in marine pore waters. The resulting prototype allowed highly automated analysis of δ13C isotopic ratios and CO2 concentration. We achieved a throughput of up to 70 samples per day with DIC contents as low as 1.7 μmol C. We achieved an internal precision of 0.066 ‰ and an external precision of 0.16 ‰, which is comparable to values given for Isotope Ratio Mass Spectrometers (IRMS). The prototype instrument is field deployable, suitable for shipboard analysis of deep sea core pore waters. However, the validation of the prototype was centered around a field campaign in Eckernförde Bay, NW- Baltic Sea. As a proof of concept, a shallow site within an area of submarine groundwater discharge (SGD) and a site outside this area was investigated. We present profiles of δ13C of DIC over 50 cm exhibiting well understood methane turnover processes (anaerobic oxidation of methane). At the lowest point below the seafloor, microbial reduction of CO2 to CH4 dominates. 12CO2 is reduced preferentially over 13CO2, leading to more positive δ13C values in the remaining DIC pool; in layers closer to the surface, the oxidation of CH4 to CO2 becomes more prominent. Since the CH4 pool is enriched in 12C a shift to more negative δ13C can be observed in the DIC pool. In the upper 15 cm, the pore water DIC mixes with the sea water DIC, increasing δ13C again. Finally, we will present recent developments to further improve performance and future plans for deployments on research cruises.

  9. Stable isotope composition of atmospheric carbon monoxide. A modelling study

    Energy Technology Data Exchange (ETDEWEB)

    Gromov, Sergey S.

    2014-11-01

    This study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ{sup 13}C, δ{sup 18}O and Δ{sup 17}O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC-1 measurement platform. The systematically underestimated {sup 13}CO/{sup 12}CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in {sup 13}C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH{sub 4}) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH{sub 4} to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in {sup 13}C, were found significant

  10. HISTORICAL GEOLOGY &STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>20122559 Chen Fangwen ( College of Earth Sciences,Northeast Petroleum University,Daqing 163318,China );Lu Shuangfang High-Resolution Sequence Stratigraphy and Sedimentary Characteristics of the Fuyu Oil-Bearin Layers in the Wangfu Depression ( Journal of Stratigraphy,ISSN0253-4959,CN32-1187 / P,35 ( 4 ), 2011,p.368-374,3illus.,14refs. ) Key words:Cretaceous,high resolution sequence stratigraphy,Songliao Plain

  11. Observation of Large Enhancement of Charge Exchange Cross Sections with Neutron-Rich Carbon Isotopes

    CERN Document Server

    Tanihata, I; Kanungo, R; Ameil, F; Atkinson, J; Ayyad, Y; Cortina-Gil, D; Dillmann, I; Estradé, A; Evdokimov, A; Farinon, F; Geissel, H; Guastalla, G; Janik, R; Knoebel, R; Kurcewicz, J; Litvinov, Yu A; Marta, M; Mostazo, M; Mukha, I; Nociforo, C; Ong, H J; Pietri, S; Prochazka, A; Scheidenberger, C; Sitar, B; Strmen, P; Takechi, M; Tanaka, J; Toki, H; Vargas, J; Winfield, J S; Weick, H

    2015-01-01

    Production cross sections of nitrogen isotopes from high-energy carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes. The fragment separator FRS at GSI was used to deliver C isotope beams. The cross sections of the production of N isotopes were determined by charge measurements of forward going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge exchange reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and Fermi transition strength at low excitation energies for neutron-rich isotopes. It was also observed that the cross sections were enhanced much more strongly for neutron rich isotopes in the C-target data.

  12. Stable Carbon Isotope Record in a Palau Sclerosponge

    Science.gov (United States)

    Grottoli, A. G.

    2002-12-01

    The ratio of stable carbon isotopes (δ13C) deposited in the calcium carbonate skeleton of marine sclerosponges appears to record the carbon isotopic composition of seawater mixed-layer dissolved inorganic carbon (δ13CDIC). Thus the δ13C signature chronicled in sclerosponge skeletons offers a promising multi-century proxy record of seawater mixed-layer δ13CDIC throughout the tropics. Here, a high-resolution (0.1 mm) δ13C record for a 7.7 cm Acanthocheatetes wellsi sclerosponge from Palau (7N, 134W) is presented. At a published growth rate of 0.45 mm per year, this record spans ~s170 years beginning in July 2001 and going back to 1831. The δ13C values for a definitive 10-year A. wellsi record spanning 1989-1998 were similar to δ13C values here for the first 4.7 mm of the record providing supporting evidence for the growth rate. The sclerosponge δ13C shows a distinct Seuss Effect. At the time this abstract was submitted, the analysis of the first 16 mm of the sclerosponge revealed a significant decrease in δ13C with time [δ13C = 0.02 (distance) + 2.64, r2 = 0.73, p < 0.0001, where time is marked by distance in millimeters from the growing edge] corresponding to a decrease in δ13C of 0.076‰ per decade. For comparison, published low-frequency measurements in Australian, New Caledonian and Jamaican sclerosponges have yielded decreases in δ13C of ~s0.05 to 0.08 ‰ per decade over the past 40 years. Preliminary interpretation of the data indicates that the amount of atmospheric CO2 contributing to the seawater δ13CDIC at Palau is intermediate to Australia and Jamaica. In addition, visual examination of the δ13C record reveals regular fluctuation in δ13C that may correspond to annual variability in δ13CDIC. This research presents the first century or longer sclerosponge δ13C record from the northwester equatorial Pacific.

  13. CO2-dependent carbon isotope fractionation in dinoflagellates relates to their inorganic carbon fluxes.

    Science.gov (United States)

    Hoins, Mirja; Eberlein, Tim; Van de Waal, Dedmer B; Sluijs, Appy; Reichart, Gert-Jan; Rost, Björn

    2016-08-01

    Carbon isotope fractionation (εp) between the inorganic carbon source and organic matter has been proposed to be a function of pCO2. To understand the CO2-dependency of εp and species-specific differences therein, inorganic carbon fluxes in the four dinoflagellate species Alexandrium fundyense, Scrippsiella trochoidea, Gonyaulax spinifera and Protoceratium reticulatum have been measured by means of membrane-inlet mass spectrometry. In-vivo assays were carried out at different CO2 concentrations, representing a range of pCO2 from 180 to 1200 μatm. The relative bicarbonate contribution (i.e. the ratio of bicarbonate uptake to total inorganic carbon uptake) and leakage (i.e. the ratio of CO2 efflux to total inorganic carbon uptake) varied from 0.2 to 0.5 and 0.4 to 0.7, respectively, and differed significantly between species. These ratios were fed into a single-compartment model, and εp values were calculated and compared to carbon isotope fractionation measured under the same conditions. For all investigated species, modeled and measured εp values were comparable (A. fundyense, S. trochoidea, P. reticulatum) and/or showed similar trends with pCO2 (A. fundyense, G. spinifera, P. reticulatum). Offsets are attributed to biases in inorganic flux measurements, an overestimated fractionation factor for the CO2-fixing enzyme RubisCO, or the fact that intracellular inorganic carbon fluxes were not taken into account in the model. This study demonstrates that CO2-dependency in εp can largely be explained by the inorganic carbon fluxes of the individual dinoflagellates.

  14. Carbon isotopic studies of individual lipids in organisms from the Nansha sea area, China

    Institute of Scientific and Technical Information of China (English)

    DUAN; Yi; SONG; Jinming; ZHANG; Hui

    2004-01-01

    Carbon isotopes of individual lipids in typical organisms from the Nansha sea area were measured by the GC-IRMS analytical technique. δ13C values of saturated fatty acids in different organisms examined are from -25.6‰ to -29.7‰ with the average values ranging from -26.4‰ to -28.2‰ and the variance range of 1.8‰ between different organisms is also observed.Unsaturated fatty acids have heavy carbon isotopic compositions and the mean differences of 2.9‰-6.8‰ compared to the same carbon number saturated fatty acids. δ13C values of n-alkanes range from -27.5‰ to -29.7‰ and their mean values, ranging from -28.6‰ to -28.9‰, are very close in different organisms. The mean difference in δ13C between the saturated fatty acids and n-alkanes is only 1.5‰, indicating that they have similar biosynthetic pathways. The carbon isotopic variations between the different carbon-number lipids are mostly within ±2.0‰, reflecting that they experienced a biosynthetic process of the carbon chain elongation. At the same time, the carbon isotopic genetic relationships between the biological and sedimentary lipids are established by comparative studies of carbon isotopic compositions of individual lipids in organisms and sediments from the Nansha sea area, which provides scientific basis for carbon isotopic applied research of individual lipids.

  15. Molecular and carbon isotopic compositions of gas inclusions of deep carbonate rocks in the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shixin; WANG Xianbin; MENG Zifang; LI Yuan; Paul Farrimond; LI Liwu; DUAN Yi

    2004-01-01

    Gaseous components of gas inclusions in deep carbonate rocks (>5700 m) from the Tacan 1 well were analyzed by online mass spectrometry by means of either the stepwise heating technique or vacuum electromagnetism crushing. The carbon isotopic compositions of gases released by vacuum electromagnetism crushing were also measured. Although the molecular compositions of gas inclusions show differences between the two methods, the overall characteristics are that gas inclusions mainly contain CO2, whilst hydrocarbon gases, such as CH4, C2H6 and C3H8, are less abundant. The content of CO is higher in the stepwise heating experiment than that in the method of vacuum electromagnetism crushing, and there are only minor amounts of N2, H2 and O2 in gas inclusions. Methane δ13C values of gas inclusions in Lower Ordovician and Upper Cambrian rocks (from 5713.7 to 6422 m; -52‰-63‰) are similar to those of bacterial methane, but their chemical compositions do not exhibit the dry character in comparison with biogenic gases. These characteristics of deep gas inclusions may be related to the migration fractionation. Some deep natural gases with light carbon isotopic characteristics in the Tazhong Uplift may have a similar origin. The δ13C1 values of gas inclusions in Lower Cambrian rocks (7117-7124 m) are heavier (-39‰), consistent with highly mature natural gases. Carbon isotopic compositions of CO2 in the gas inclusions of deep carbonate rocks are similar (from -4‰ to -13‰) to those of deep natural gases, indicating predominantly an inorganic origin.

  16. Carbon isotope discrimination as a tool to explore C4 photosynthesis.

    Science.gov (United States)

    von Caemmerer, Susanne; Ghannoum, Oula; Pengelly, Jasper J L; Cousins, Asaph B

    2014-07-01

    Photosynthetic carbon isotope discrimination is a non-destructive tool for investigating C4 metabolism. Tuneable diode laser absorption spectroscopy provides new opportunities for making rapid, concurrent measurements of carbon isotope discrimination and CO2 assimilation over a range of environmental conditions, and this has facilitated the use of carbon isotope discrimination as a probe of C4 metabolism. In spite of the significant progress made in recent years, understanding how photosynthetic carbon isotope discrimination measured concurrently with gas exchange relates to carbon isotope composition of leaf and plant dry matter remains a challenge that requires resolution if this technique is to be successfully applied as a screening tool in crop breeding and phylogenetic research. In this review, we update our understanding of the factors and assumptions that underlie variations in photosynthetic carbon isotope discrimination in C4 leaves. Closing the main gaps in our understanding of carbon isotope discrimination during C4 photosynthesis may help advance research aimed at developing higher productivity and efficiency in key C4 food, feed, and biofuel crops.

  17. Soil organic carbon assessments in cropping systems using isotopic techniques

    Science.gov (United States)

    Martín De Dios Herrero, Juan; Cruz Colazo, Juan; Guzman, María Laura; Saenz, Claudio; Sager, Ricardo; Sakadevan, Karuppan

    2016-04-01

    Introduction of improved farming practices are important to address the challenges of agricultural production, food security, climate change and resource use efficiency. The integration of livestock with crops provides many benefits including: (1) resource conservation, (2) ecosystem services, (3) soil quality improvements, and (4) risk reduction through diversification of enterprises. Integrated crop livestock systems (ICLS) with the combination of no-tillage and pastures are useful practices to enhance soil organic carbon (SOC) compared with continuous cropping systems (CCS). In this study, the SOC and its fractions in two cropping systems namely (1) ICLS, and (2) CCS were evaluated in Southern Santa Fe Province in Argentina, and the use of delta carbon-13 technique and soil physical fractionation were evaluated to identify sources of SOC in these systems. Two farms inside the same soil cartographic unit and landscape position in the region were compared. The ICLS farm produces lucerne (Medicago sativa Merrill) and oat (Avena sativa L.) grazed by cattle alternatively with grain summer crops sequence of soybean (Glicine max L.) and corn (Zea mays L.), and the farm under continuous cropping system (CCS) produces soybean and corn in a continuous sequence. The soil in the area is predominantly a Typic Hapludoll. Soil samples from 0-5 and 0-20 cm depths (n=4) after the harvest of grain crops were collected in each system and analyzed for total organic carbon (SOC, 0-2000 μm), particulate organic carbon (POC, 50-100 μm) and mineral organic carbon (MOC, <50 μm). Delta carbon-13 was determined by isotopic ratio mass spectrometry. In addition, a site with natural vegetation (reference site, REF) was also sampled for delta carbon-13 determination. ANOVA and Tukey statistical analysis were carried out for all data. The SOC was higher in ICLS than in CCS at both depths (20.8 vs 17.7 g kg-1 for 0-5 cm and 16.1 vs 12.7 g kg-1 at 0-20 cm, respectively, P<0.05). MOC was

  18. Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses

    Science.gov (United States)

    Yuen, G. U.; Cronin, J. R.; Blair, N. E.; Desmarais, D. J.; Chang, S.

    1991-01-01

    Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources.

  19. Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons

    Science.gov (United States)

    Freeman, K. H.; Hayes, J. M.; Trendel, J. M.; Albrecht, P.

    1990-01-01

    The organic matter found in sedimentary rocks must derive from many sources; not only from ancient primary producers but also from consumers and secondary producers. In all of these organisms, isotope effects can affect the abundance and distribution of 13C in metabolites. Here, by using an improved form of a previously described technique in which the effluent of a gas chromatograph is continuously analysed isotopically, we report evidence of the diverse origins of sedimentary organic matter. The record of 13C abundances in sedimentary carbonate and total organic carbon can be interpreted in terms of variations in the global carbon cycle. Our results demonstrate, however, that isotope variations within sedimentary organic mixtures substantially exceed those observed between samples of total organic carbon. Resolution of isotope variations at the molecular level offers a new and convenient means of refining views both of localized palaeoenvironments and of control mechanisms within the global carbon cycle.

  20. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Directory of Open Access Journals (Sweden)

    N. Brüggemann

    2011-04-01

    Full Text Available The terrestrial carbon (C cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual, including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. The last part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO

  1. Distribution and fractionation mechanism of stable carbon isotope of coalbed methane

    Institute of Scientific and Technical Information of China (English)

    QIN Shengfei; TANG Xiuyi; SONG Yan; WANG Hongyan

    2006-01-01

    The stable carbon isotope values of coalbed methane range widely,and also are generally lighter than that of gases in normal coal-formed gas fields with similar coal rank.There exists strong carbon isotope fractionation in coalbed methane and it makes the carbon isotope value lighter.The correlation between the carbon isotope value and Ro in coalbed methane is less obvious.The coaly source rock maturity cannot be judged by coalbed methane carbon isotope value.The carbon isotopes of coalbed methane become lighter in much different degree due to the hydrodynamics.The stronger the hydrodynamics is,the lighter the CBM carbon isotopic value becomes.Many previous investigations indicated that the desorption-diffusion effects make the carbon isotope value of coalbed methane lighter.However,the explanation has encountered many problems.The authors of this article suggest that the flowing groundwater dissolution to free methane in coal seams and the free methane exchange with absorbed one is the carbon isotope fractionation mechanism in coalbed methane.The flowing groundwater in coal can easily take more 13CH4 away from free gas and comparatively leave more 12CH4.This will make 12CH4 density in free gas comparatively higher than that in absorbed gas.The remaining 12CH4 in free gas then exchanges with the adsorbed methane in coal matrix.Some absorbed 13CH4 can be replaced and become free gas.Some free 12CH4 can be absorbed again into coal matrix and become absorbed gas.Part of the newly replaced 13CH4 in free gas will also be taken away by water,leaving preferentially more 12CH4.The remaining 12CH4 in free gas will exchange again with adsorbed methane in the coal matrix.These processes occur all the time.Through accumulative effect,the 12CH4 will be greatly concentrated in coal.Thus,the stable carbon isotope of coalbed methane becomes dramatically lighter.Through simulation experiment on water-dissolved methane,it had been proved that the flowing water could fractionate the

  2. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    <正>20142287Cao Changqun(State Key Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,CAS,Nanjing 210008,China);Zhang Mingyuan The Permian Capitanian Stratigraphy at the Rencunping Section,Sangzhi County of Hunan Province and Its Environmental Implications

  3. Mesozoic black shales, source mixing and carbon isotopes

    Science.gov (United States)

    Suan, Guillaume

    2016-04-01

    Over the last decades, considerable attention has been devoted to the paleoenvironmental and biogeochemical significance of Mesozoic black shales. Black shale-bearing successions indeed often display marked changes in the organic carbon isotope composition (δ13Corg), which have been commonly interpreted as evidence for dramatic perturbations of global carbon budgets and CO2 levels. Arguably the majority of these studies have discarded some more "local" explanations when interpreting δ13Corg profiles, most often because comparable profiles occur on geographically large and distant areas. Based on newly acquired data and selected examples from the literature, I will show that the changing contribution of organic components with distinct δ13C signatures exerts a major but overlooked influence of Mesozoic δ13Corg profiles. Such a bias occurs across a wide spectrum of sedimentological settings and ages, as shown by the good correlation between δ13Corg values and proxies of kerogen proportions (such as rock-eval, biomarker, palynofacies and palynological data) recorded in Mesozoic marginal to deep marine successions of Triassic, Jurassic and Cretaceous age. In most of these successions, labile, 12C-enriched amorphous organic matter of marine origin dominates strata deposited under anoxic conditions, while oxidation-resistant, 13C-rich terrestrial particles dominate strata deposited under well-oxygenated conditions. This influence is further illustrated by weathering profiles of Toarcian (Lower Jurassic) black shales from France, where weathered areas dominated by refractory organic matter show dramatic 13C-enrichment (and decreased total organic carbon and pyrite contents) compared to non-weathered portions of the same horizon. The implications of these results for chemostratigraphic correlations and pCO2 reconstructions of Mesozoic will be discussed, as well as strategies to overcome this major bias.

  4. Environmental forcing of terrestrial carbon isotope excursion amplification across five Eocene hyperthermals

    Science.gov (United States)

    Bowen, G. J.; Abels, H.

    2015-12-01

    Abrupt changes in the isotope composition of exogenic carbon pools accompany many major episodes of global change in the geologic record. The global expression of this change in substrates that reflect multiple carbon pools provides important evidence that many events reflect persistent, global redistribution of carbon between reduced and oxidized stocks. As the diversity of records documenting any event grows, however, discrepancies in the expression of carbon isotope change among substrates are almost always revealed. These differences in magnitude, pace, and pattern of change can complicate interpretations of global carbon redistribution, but under ideal circumstances can also provide additional information on changes in specific environmental and biogeochemical systems that accompanied the global events. Here we evaluate possible environmental influences on new terrestrial records of the negative carbon isotope excursions (CIEs) associated with multiple hyperthermals of the Early Eocene, which show a common pattern of amplified carbon isotope change in terrestrial paleosol carbonate records relative to that recorded in marine substrates. Scaling relationships between climate and carbon-cycle proxies suggest that that the climatic (temperature) impact of each event scaled proportionally with the magnitude of its marine CIE, likely implying that all events involved release of reduced carbon with a similar isotopic composition. Amplification of the terrestrial CIEs, however, does not scale with event magnitude, being proportionally less for the first, largest event (the PETM). We conduct a sensitivity test of a coupled plant-soil carbon isotope model to identify conditions that could account for the observed CIE scaling. At least two possibilities consistent with independent lines of evidence emerge: first, varying effects of pCO2 change on photosynthetic carbon isotope discrimination under changing background pCO2, and second, contrasting changes in regional

  5. Stable carbon isotopes in tree rings: the failure of uniformitarianism

    Science.gov (United States)

    McCarroll, Danny

    2010-05-01

    When tree rings are used to reconstruct past climate we rely on the uniformitarian principle that ‘the present is the key to the past'. Relationships between measured parameters and climate that can be calibrated and verified over the instrumental period are assumed to be applicable at longer timescales. In the case of δ13C, however, the uniformitarian principle fails for two reasons. (1) The instrumental calibration period is also the period of anthropogenic increase in atmospheric CO2. δ13C is a function of the ratio of internal to ambient CO2, so maintaining constant δ13C over the industrial period requires an active plastic response, either restricting stomatal conductance or increasing assimilation rate. In some areas trees may have reached the limits of their plasticity so that over the last few decades δ13C values have been declining, independent of any changes in climate. If no correction is made, the recent response to climate will be a poor indicator of behaviour in the past. (2) Tree ring δ13C is often used to reconstruct past temperatures even though temperature rarely has a strong direct control over fractionation. The link is therefore via either sunshine or humidity, which over the calibration period may be very strongly correlated with temperature. Long isotope chronologies, when compared with independent evidence of past temperatures, however, can show periods of marked divergence. The strong covariance of temperature, sunshine and humidity over the last century may not have persisted over longer timescales with larger climatic perturbations. In the case of carbon isotopes the key to the past is not statistical inference based on recent behaviour, but a clear mechanistic understanding of the influence of climate and other factors on fractionation.

  6. Combination of carbon isotope ratio with hydrogen isotope ratio determinations in sports drug testing.

    Science.gov (United States)

    Piper, Thomas; Emery, Caroline; Thomas, Andreas; Saugy, Martial; Thevis, Mario

    2013-06-01

    Carbon isotope ratio (CIR) analysis has been routinely and successfully applied to doping control analysis for many years to uncover the misuse of endogenous steroids such as testosterone. Over the years, several challenges and limitations of this approach became apparent, e.g., the influence of inadequate chromatographic separation on CIR values or the emergence of steroid preparations comprising identical CIRs as endogenous steroids. While the latter has been addressed recently by the implementation of hydrogen isotope ratios (HIR), an improved sample preparation for CIR avoiding co-eluting compounds is presented herein together with newly established reference values of those endogenous steroids being relevant for doping controls. From the fraction of glucuronidated steroids 5β-pregnane-3α,20α-diol, 5α-androst-16-en-3α-ol, 3α-Hydroxy-5β-androstane-11,17-dione, 3α-hydroxy-5α-androstan-17-one (ANDRO), 3α-hydroxy-5β-androstan-17-one (ETIO), 3β-hydroxy-androst-5-en-17-one (DHEA), 5α- and 5β-androstane-3α,17β-diol (5aDIOL and 5bDIOL), 17β-hydroxy-androst-4-en-3-one and 17α-hydroxy-androst-4-en-3-one were included. In addition, sulfate conjugates of ANDRO, ETIO, DHEA, 3β-hydroxy-5α-androstan-17-one plus 17α- and androst-5-ene-3β,17β-diol were considered and analyzed after acidic solvolysis. The results obtained for the reference population encompassing n = 67 males and females confirmed earlier findings regarding factors influencing endogenous CIR. Variations in sample preparation influenced CIR measurements especially for 5aDIOL and 5bDIOL, the most valuable steroidal analytes for the detection of testosterone misuse. Earlier investigations on the HIR of the same reference population enabled the evaluation of combined measurements of CIR and HIR and its usefulness regarding both steroid metabolism studies and doping control analysis. The combination of both stable isotopes would allow for lower reference limits providing the same statistical

  7. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Directory of Open Access Journals (Sweden)

    N. Brüggemann

    2011-11-01

    Full Text Available The terrestrial carbon (C cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual, including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as

  8. A Test of Carbon and Oxygen Stable Isotope Ratio Process Models in Tree Rings.

    Science.gov (United States)

    Roden, J. S.; Farquhar, G. D.

    2008-12-01

    Stable isotopes ratios of carbon and oxygen in tree ring cellulose have been used to infer environmental change. Process-based models have been developed to clarify the potential of historic tree ring records for meaningful paleoclimatic reconstructions. However, isotopic variation can be influenced by multiple environmental factors making simplistic interpretations problematic. Recently, the dual isotope approach, where the variation in one stable isotope ratio (e.g. oxygen) is used to constrain the interpretation of variation in another (e.g. carbon), has been shown to have the potential to de-convolute isotopic analysis. However, this approach requires further testing to determine its applicability for paleo-reconstructions using tree-ring time series. We present a study where the information needed to parameterize mechanistic models for both carbon and oxygen stable isotope ratios were collected in controlled environment chambers for two species (Pinus radiata and Eucalyptus globulus). The seedlings were exposed to treatments designed to modify leaf temperature, transpiration rates, stomatal conductance and photosynthetic capacity. Both species were grown for over 100 days under two humidity regimes that differed by 20%. Stomatal conductance was significantly different between species and for seedlings under drought conditions but not between other treatments or humidity regimes. The treatments produced large differences in transpiration rate and photosynthesis. Treatments that effected photosynthetic rates but not stomatal conductance influenced carbon isotope discrimination more than those that influenced primarily conductance. The various treatments produced a range in oxygen isotope ratios of 7 ‰. Process models predicted greater oxygen isotope enrichment in tree ring cellulose than observed. The oxygen isotope ratios of bulk leaf water were reasonably well predicted by current steady-state models. However, the fractional difference between models that

  9. Sensitivity analysis and quantification of uncertainty for isotopic mixing relationships in carbon cycle research

    Science.gov (United States)

    Zobitz, J. M.; Keener, J. P.; Bowling, D. R.

    2004-12-01

    Quantifying and understanding the uncertainty in isotopic mixing relationships is critical to isotopic applications in carbon cycle studies at all spatial and temporal scales. Studies associated with the North American Carbon Program will depend on stable isotope approaches and quantification of isotopic uncertainty. An important application of isotopic mixing relationships is determination of the isotopic content of large-scale respiration (δ 13CR) via an inverse relationship (a Keeling plot) between atmospheric CO2 concentrations ([CO2]) and carbon isotope ratios of CO2 (δ 13C). Alternatively, a linear relationship between [CO2] and the product of [CO2] and δ 13C (a Miller/Tans plot) can also be applied. We used an extensive dataset from the Niwot Ridge Ameriflux Site of [CO2] and δ 13C in forest air to examine contrasting approaches to determine δ 13CR and its uncertainty. These included Keeling plots, Miller/Tans plots, Model I, and Model II regressions Our analysis confirms previous observations that increasing the range of measurements ([CO2] range) reduces the uncertainty associated with δ 13CR. For carbon isotope studies, uncertainty in the isotopic measurements has a greater effect on the uncertainty of δ 13CR than the uncertainty in [CO2]. Reducing the uncertainty of isotopic measurements reduces the uncertainty of δ 13CR even when the [CO2] range of samples is small (13CR. We also find for carbon isotope studies no inherent advantage to using either a Keeling or a Miller/Tans approach to determine δ 13CR.

  10. Is my C isotope excursion global, local, or both? Insights from the Mg and Ca isotopic composition of primary, diagenetic, and authigenic carbonates

    Science.gov (United States)

    Higgins, J. A.; Blättler, C. L.; Husson, J. M.

    2014-12-01

    The C isotopic composition of ancient limestones and dolomites is a widely used proxy for the global geochemical cycles of carbon and oxygen in the ocean-atmosphere system and a critical tool for chemostratigraphy in Precambrian rocks. Although relatively robust to diagenesis, the C isotopic composition of bulk carbonates can be reset when conditions favor high water-to-rock ratios or fluids with high C concentrations and distinct isotopic compositions. Authigenic carbonates and different pools of primary carbonate (e.g. calcite vs. aragonite) may also bias the C isotopic composition of bulk carbonates if they are both abundant and isotopically distinct. New approaches to quantifying contributions from diagenesis, authigenesis, and mixing of primary carbonates to the C isotopic composition of bulk sedimentary carbonates are needed. Here we present preliminary Mg and Ca isotope data sets of primary, diagenetic, and authigenic carbonates, both modern and ancient. We show that recrystallization, dolomitization, and authigenesis produce Mg and Ca isotope fingerprints that may be used to identify and characterize these processes in ancient carbonate sediments.

  11. Do stable carbon isotopes of brown coal woods record changes in Lower Miocene palaeoecology?

    NARCIS (Netherlands)

    Poole, I.J.; Dolezych, M.; Kool, J.; Burgh, J. van der; Bergen, P.F. van

    2006-01-01

    Stable carbon isotope ratios of fossil wood from the Miocene brown coal deposits in former East Germany are compared with palaeobotanical and sedimentological data to test the use of stable isotopes in determining palaeoenvironment. Significant differences in the chemical composition of samples from

  12. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    Science.gov (United States)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    Carbonic anhydrases are a group of metalloenzymes that catalyse the hydration of aqueous carbon dioxide (CO2). The expression of carbonic anhydrase by bacteria, archaea and eukarya has been linked to a variety of important biological processes including pH regulation, substrate supply and biomineralisation. As oxygen isotopes are exchanged between CO2 and water during hydration, the presence of carbonic anhydrase in plants and soil organisms also influences the oxygen isotope budget of atmospheric CO2. Leaf and soil water pools have distinct oxygen isotope compositions, owing to differences in pool sizes and evaporation rates, which are imparted on CO2during hydration. These differences in the isotopic signature of CO2 interacting with leaves and soil can be used to partition the contribution of photosynthesis and soil respiration to net terrestrial CO2 exchange. However, this relies on our knowledge of soil carbonic anhydrase activity and currently, the prevalence and function of these enzymes in soils is poorly understood. Isotopic approaches used to estimate soil carbonic anhydrase activity typically involve the inversion of models describing the oxygen isotope composition of CO2 fluxes to solve for the apparent, potentially catalysed, rate of oxygen exchange during hydration. This requires information about the composition of CO2 in isotopic equilibrium with soil water obtained from destructive, depth-resolved soil water sampling. This can represent a significant challenge in data collection given the considerable potential for spatial and temporal variability in the isotopic composition of soil water and limited a priori information with respect to the appropriate sampling resolution and depth. We investigated whether we could circumvent this requirement by constraining carbonic anhydrase activity and the composition of soil water in isotopic equilibrium with CO2 by solving simultaneously the mass balance for two soil CO2 steady states differing only in the

  13. The evolution of Carbon isotopes in calcite in the presence of cyanobacteria

    Science.gov (United States)

    Grimm, Christian; Mavromatis, Vasileios; Pokrovsky, Oleg S.; Oelkers, Eric H.

    2016-04-01

    Stable isotopic compositions in carbonates are widely used as indicators of environmental conditions prevailing during mineral formation. This reconstruction is substantially based on the assumption that there is no change in the mineral composition over geological time. However, recent experimental studies have shown that carbon and magnesium isotopes in hydrous Mg-carbonates undergo continuous re-equilibration with the ambient solution even after mineral precipitation stopped ([1] and [2], respectively). To verify whether this holds true for anhydrous Ca-bearing carbonates which readily form at earth's surface environments, a series of batch system calcite precipitation experiments were performed in the presence of actively growing cyanobacteria Synechococcus sp. The bacteria were grown at ambient temperature in a BG11 culture medium (SIGMA C3061) and continuous stirring, air-bubbling and illumination. Calcite precipitation was initiated by the addition of 8.5mM CaCl2 and 0-50 mM NaHCO3 or NaHCO3-Na2CO3 mixtures. The presence of cyanobacteria is on one hand promoting CaCO3 formation due to increasing pH resulting from photosynthesis. On the other hand, actively growing cyanobacteria drastically change carbon isotope signature of the aqueous fluid phase by preferably incorporating the lighter 12C isotope into biomass [1]. This study explores the effect of continuously changing carbon isotope compositions in dissolved inorganic carbon (DIC) on precipitated calcite which is in chemical equilibrium with the ambient fluid phase. [1] Mavromatis et al. (2015). The continuous re-equilibration of carbon isotope compositions of hydrous Mg-carbonates in the presence of cyanobacteria. Chem. Geol. 404, 41-51 [2] Mavromatis et al. (2012). Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria. Geochim. Cosmochim. Acta 76, 161-174

  14. Carbon stable isotope analysis of cereal remains as a way to reconstruct water availability: preliminary results

    OpenAIRE

    Flohr, Pascal; Muldner, Gundula; Jenkins, Emma

    2011-01-01

    Reconstructing past water availability, both as rainfall and irrigation, is important to answer questions about the way society reacts to climate and its changes and the role of irrigation in the development of social complexity. Carbon stable isotope analysis of archaeobotanical remains is a potentially valuable method for reconstructing water availability. To further define the relationship between water availability and plant carbon isotope composition and to set up baseline values for the...

  15. Effects of carbonate leaching on foraminifer stable isotopes ratios

    Science.gov (United States)

    Obrochta, S.; Yokoyama, Y.; Sakai, S.; Ishimura, T.

    2011-12-01

    Stable carbon and oxygen isotope ratios were measured on 125 individual epifaunal and infaunal benthic foraminifers from two discrete Holocene intervals in a shallow-water sediment core (~ 450 m) from the Timor Sea. Methane seeps are common in the area, resulting in significant precipitation of secondary calcite that is confirmed by SEM photomicrographs and has likely resulted in inconsistent downcore results. To assess the degree of removal of contaminants, individual Uvigerina peregrina were subjected to varying degrees of pretreatment prior to analysis. All foraminifers received standard cleaning with ethanol and brief sonication. A subset were further cleaned and sonicated in a dilute HCl solution (~ 0.003 M). Foraminifer tests were photographed using both reflected light and scanning electron microscopes during the course of treatment to monitor the changing degree of contaminant removal as increasingly aggressive cleaning methods were employed. Visible contamination remained on individuals not subjected to HCl treatment. The leached individuals exhibit a lower overall relative standard deviation and consistent results within morphotype groups. Based on these results, a 2% value is expected to be typical of the Holocene, though further downcore analyses are pending restoration of equipment adversely effected by the Eastern Japan 3/11 earthquake.

  16. Carbon isotopic record from Upper Devonian carbonates at Dongcun in Guilin, southern China, supporting the world-wide pattern of carbon isotope excursions during Frasnian-Famennian transition

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Two positive δ13C excursions are presented in records from the Frasnian-Famennian (F-F) marine carbonate sediments in Europe, America, Africa, and Australia, having been considered as a worldwide pattern, and attributed to enhanced organic carbon burial during the F-F biological mass extinction. However, this worldwide pattern has not been revealed from the well-deposited Late Devonian sequences in southern China. In this paper, a detailed investigation has been made on the Late Devonian section at Dongcun, Guilin, southern China to constrain perturbations in δ13C of carbonates in the F-F deposited sequence. The result from this section also indicates two positive δ13C excursions during the F-F transition. The first excursion with an amplitude of 1.5‰ occurred at the bottom of linguiformis Zone, later than the early excursion existing in the Late rhenana Zone of the Late Devonian profiles in other continents, especially, in central Europe. This difference has been expected to be a result as conodont Palmatolepis linguiformis occurred earlier in southern China than other sites. The second excursion with an amplitude of 2.1‰ is located at the F-F boundary, same as the records from other continents. This result strongly supports the view that two carbon isotope positive excursions during the F-F transition are common in carbonate sediments, resulting from worldwide increases of organic carbon burial intensity.

  17. STABLE CARBON ISOTOPES OF HCO//3 IN THE AQUIA AQUIFER, MARYLAND: EVIDENCE FOR AN ISOTOPICALLY HEAVY SOURCE OF CO//2.

    Science.gov (United States)

    Chapelle, Francis H.; Knobel, LeRoy L.

    1985-01-01

    Identifying sources and sinks of dissolved inorganic carbon species is an important step in understanding the geochemistry of ground-water systems. This is particularly important for Atlantic Coastal Plain aquifers because bicarbonate (HCO//3** minus ) is frequently the major dissolved anion. The purpose of this paper is to document the stable carbon isotope composition of dissolved inorganic carbon in the Aquia aquifer, Maryland, and to use this data to help identify sources and sinks of dissolved HCO//3** minus . Subjects covered include hydrogeology, ground-water chemistry, sources and sinks, and others. Refs.

  18. Decoupling of carbon isotope records between organic matter and carbonate prior to the Toarcian Oceanic Anoxic Event (Early Jurassic)

    Science.gov (United States)

    Bodin, Stephane; Kothe, Tim; Krencker, Francois-Nicolas; Suan, Guillaume; Heimhofer, Ulrich; Immenhauser, Adrian

    2014-05-01

    Across the Pliensbachian-Toarcian boundary (P-To, Early Jurassic), ca. 1 Myr before the Toarcian Oceanic Anoxic Event (T-OAE), an initial negative carbon isotope excursion has been documented in western Tethys sedimentary rocks. In carbonate, its amplitude (2-3 permil) is similar to the subsequent excursion recorded at the onset of the T-OAE. Being also associated with a rapid warming event, the significance of this first carbon isotope shift, in terms of paleoenvironmental interpretation and triggering mechanism, remains however elusive. Taking advantage of expanded and rather continuous sections in the High Atlas of Morocco, several high-resolution, paired organic-inorganic carbon isotope records have been obtained across the Upper Pliensbachian - Lower Toarcian interval. At the onset of the T-OAE, an abrupt 1-2 permil negative shift is recorded in both organic and inorganic phases, succeeded by a relatively longer term 1-2 permil negative trend and a final slow return to pre-excursion conditions. In accordance with previous interpretations, this pattern indicates a perturbation of the entire exogenic carbon isotope reservoir at the onset of the T-OAE by the sudden release of isotopically light carbon into the atmosphere. By contrast, there is no negative shift in carbon isotopes for the P-To event recorded in bulk organic matter of Morocco. Given the strong dominance of terrestrial particles in the bulk organic matter fraction, this absence indicates that massive input of 12C-rich carbon into the atmosphere is not likely to have happened during the P-To event. A pronounced (2 permil) and abrupt negative shift in carbon isotope is however recorded in the bulk carbonate phase. We suggest that this decoupling between organic and inorganic phase is due to changes in the nature of the bulk carbonate phase. Indeed, the negative shift occurs at the lithological transition between Pliensbachian-lowermost Toarcian limestone-marl alternations and the Lower Toarcian marl

  19. Model-based estimation of the global carbon budget and its uncertainty from carbon dioxide and carbon isotope records

    Energy Technology Data Exchange (ETDEWEB)

    Kheshgi, Haroon S. [Corporate Research Laboratories, Exxon Research and Engineering Company, Annandale, New Jersey (United States); Jain, Atul K. [Department of Atmospheric Sciences, University of Illinois, Urbana (United States); Wuebbles, Donald J. [Department of Atmospheric Sciences, University of Illinois, Urbana (United States)

    1999-12-27

    A global carbon cycle model is used to reconstruct the carbon budget, balancing emissions from fossil fuel and land use with carbon uptake by the oceans, and the terrestrial biosphere. We apply Bayesian statistics to estimate uncertainty of carbon uptake by the oceans and the terrestrial biosphere based on carbon dioxide and carbon isotope records, and prior information on model parameter probability distributions. This results in a quantitative reconstruction of past carbon budget and its uncertainty derived from an explicit choice of model, data-based constraints, and prior distribution of parameters. Our estimated ocean sink for the 1980s is 17{+-}7 Gt C (90% confidence interval) and is comparable to the estimate of 20{+-}8 Gt C given in the recent Intergovernmental Panel on Climate Change assessment [Schimel et al., 1996]. Constraint choice is tested to determine which records have the most influence over estimates of the past carbon budget; records individually (e.g., bomb-radiocarbon inventory) have little effect since there are other records which form similar constraints. (c) 1999 American Geophysical Union.

  20. The modeling of carbon isotope kinetics and its application to the evaluation of natural gas

    Institute of Scientific and Technical Information of China (English)

    Xianqing LI; Xianming XIAO; Yongchun TANG; Hui TIAN; Qiang ZHOU; Yunfeng YANG; Peng DONG; Yan WANG; Zhihong SONG

    2008-01-01

    The modeling of carbon isotope kinetics of natural gas is an issue driving pioneering research in the oil and gas geochemistry in China and internationally.Combined with the sedimentary burial history and basin geothermal history,the modeling of carbon isotope kinetics provides a new and effective means for the determination of the origin and accumulation history of natural gas pools.In this paper,we introduce the modeling of carbon isotope kinetics of natural gas formation and its applications to the assessment of natural gas maturity,the determination of the gas source,the history of gas accumulation,and the oil-gas ratio.It is shown that this approach is of great value for these applications.The carbon isotopic characteristics of natural gas are not only affected by the gas source and maturity of the source rock,but also are related to the accumulation condition and geothermal gradient in a basin.There are obvious differences in the characteristics of carbon isotope ratios between instantaneous gas and cumulative gas.Different basins have different kinetic models of carbon isotope fractionation,which depends on the gas source condition,the accumulation history and the sedimentary-tectonic history.Since the origin of natural gas in the superimposed basin in China is very complicated,and the natural gas pool is characterized by multiphase and variable gas-sources,this paper may provide a new perspective on the study and evaluation of natural gas.

  1. Fractionation between inorganic and organic carbon during the Lomagundi (2.22 2.1 Ga) carbon isotope excursion

    Science.gov (United States)

    Bekker, A.; Holmden, C.; Beukes, N. J.; Kenig, F.; Eglinton, B.; Patterson, W. P.

    2008-07-01

    The Lomagundi (2.22-2.1 Ga) positive carbon isotope excursion in shallow-marine sedimentary carbonates has been associated with the rise in atmospheric oxygen, but subsequent studies have demonstrated that the carbon isotope excursion was preceded by the rise in atmospheric oxygen. The amount of oxygen released to the exosphere during the Lomagundi excursion is constrained by the average global fractionation between inorganic and organic carbon, which is poorly characterized. Because dissolved inorganic and organic carbon reservoirs were arguably larger in the Paleoproterozoic ocean, at a time of lower solar luminosity and lower ocean redox state, decoupling between these two variables might be expected. We determined carbon isotope values of carbonate and organic matter in carbonates and shales of the Silverton Formation, South Africa and in the correlative Sengoma Argillite Formation, near the border in Botswana. These units were deposited between 2.22 and 2.06 Ga along the margin of the Kaapvaal Craton in an open-marine deltaic setting and experienced lower greenschist facies metamorphism. The prodelta to offshore marine shales are overlain by a subtidal carbonate sequence. Carbonates exhibit elevated 13C values ranging from 8.3 to 11.2‰ vs. VPDB consistent with deposition during the Lomagundi positive excursion. The total organic carbon (TOC) contents range from 0.01 to 0.6% and δ13C values range from - 24.8 to - 13.9‰. Thus, the isotopic fractionation between organic and carbonate carbon was on average 30.3 ± 2.8‰ ( n = 32) in the shallow-marine environment. The underlying Sengoma shales have highly variable TOC contents (0.14 to 21.94%) and δ13C values (- 33.7 to - 20.8‰) with an average of - 27.0 ± 3.0‰ ( n = 50). Considering that the shales were also deposited during the Lomagundi excursion, and taking δ13C values of the overlying carbonates as representative of the δ13C value of dissolved inorganic carbon during shale deposition, a carbon

  2. Metre-scale cyclicity in Middle Eocene platform carbonates in northern Egypt: Implications for facies development and sequence stratigraphy

    Science.gov (United States)

    Tawfik, Mohamed; El-Sorogy, Abdelbaset; Moussa, Mahmoud

    2016-07-01

    The shallow-water carbonates of the Middle Eocene in northern Egypt represent a Tethyan reef-rimmed carbonate platform with bedded inner-platform facies. Based on extensive micro- and biofacies documentation, five lithofacies associations were defined and their respective depositional environments were interpreted. Investigated sections were subdivided into three third-order sequences, named S1, S2 and S3. Sequence S1 is interpreted to correspond to the Lutetian, S2 corresponds to the Late Lutetian and Early Bartonian, and S3 represents the Late Bartonian. Each of the three sequences was further subdivided into fourth-order cycle sets and fifth-order cycles. The complete hierarchy of cycles can be correlated along 190 km across the study area, and highlighting a general "layer-cake" stratigraphic architecture. The documentation of the studied outcrops may contribute to the better regional understanding of the Middle Eocene formations in northern Egypt and to Tethyan pericratonic carbonate models in general.

  3. Dual-Carbon sources fuel the OCS deep-reef Community, a stable isotope investigation

    Science.gov (United States)

    Sulak, Kenneth J.; Berg, J.; Randall, Michael; Dennis, George D.; Brooks, R.A.

    2008-01-01

    The hypothesis that phytoplankton is the sole carbon source for the OCS deep-reef community (>60 m) was tested. Trophic structure for NE Gulf of Mexico deep reefs was analyzed via carbon and nitrogen stable isotopes. Carbon signatures for 114 entities (carbon sources, sediment, fishes, and invertebrates) supported surface phytoplankton as the primary fuel for the deep reef. However, a second carbon source, the macroalga Sargassum, with its epiphytic macroalgal associate, Cladophora liniformis, was also identified. Macroalgal carbon signatures were detected among 23 consumer entities. Most notably, macroalgae contributed 45 % of total carbon to the 13C isotopic spectrum of the particulate-feeding reef-crest gorgonian Nicella. The discontinuous spatial distribution of some sessile deep-reef invertebrates utilizing pelagic macroalgal carbon may be trophically tied to the contagious distribution of Sargassum biomass along major ocean surface features.

  4. Carbon isotopic evidence for microbial control of carbon supply to Orca Basin at the brine-seawater interface

    Directory of Open Access Journals (Sweden)

    S. R. Shah

    2012-12-01

    Full Text Available Orca Basin, an intraslope basin on the Texas–Louisiana continental slope, hosts a hypersaline, anoxic brine in its lowermost 200 m. This brine contains a large reservoir of reduced and aged carbon, and appears to be stable at decadal time scales: concentrations and the isotopic composition of dissolved inorganic (DIC and organic carbon (DOC are similar to previous reports. Both DIC and DOC are more "aged" within the brine pool than in overlying water, and the isotopic contrast between brine carbon and seawater carbon is much greater for DIC than DOC. While the stable carbon isotopic composition of brine DIC points towards a combination of methane and organic carbon re-mineralization as its source, radiocarbon and box model results point to the brine interface as the major source region for DIC with oxidation of methane diffusing upwards from sediments supplying only limited DIC to the brine. This conclusion is consistent with previous studies reporting microbial activity focused at the seawater-brine interface. Isotopic similarities between DIC and DOC suggest a different relationship between these two carbon reservoirs than is typically observed in deep ocean basins. Radiocarbon values implicate the seawater-brine interface region as the likely source region for DOC as well as DIC. Further investigations of the seawater-brine interface are needed to advance our understanding of the specific microbial processes contributing to dissolved carbon storage in the Orca Basin brine.

  5. USE OF STABLE CARBON ISOTOPE RATIOS OF FATTY ACIDS TO EVALUATE MICROBIAL CARBON SOURCES IN TERRESTRIAL ENVIRONMENTS

    Science.gov (United States)

    We use measurements of the concentration and stable carbon isotopic ratio (D 13C) of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels and microbial carbon source. We found that intensive sugar cane cultivation leads to ...

  6. Carbon isotopic characterization of formaldehyde emitted by vehicles in Guangzhou, China

    Science.gov (United States)

    Hu, Ping; Wen, Sheng; Liu, Yonglin; Bi, Xinhui; Chan, Lo Yin; Feng, Jialiang; Wang, Xinming; Sheng, Guoying; Fu, Jiamo

    2014-04-01

    Formaldehyde (HCHO) is the most abundant carbonyl compound in the atmosphere, and vehicle exhaust emission is one of its important anthropogenic sources. However, there is still uncertainty regarding HCHO flux from vehicle emission as well as from other sources. Herein, automobile source was characterized using HCHO carbon isotopic ratio to assess its contributions to atmospheric flux and demonstrate the complex production/consumption processes during combustion in engine cylinder and subsequent catalytic treatment of exhaust. Vehicle exhausts were sampled under different idling states and HCHO carbon isotopic ratios were measured by gas chromatograph-combustion-isotopic ratio mass spectrometry (GC-C-IRMS). The HCHO directly emitted from stand-alone engines (gasoline and diesel) running at different load was also sampled and measured. The HCHO carbon isotopic ratios were from -30.8 to -25.7‰ for gasoline engine, and from -26.2 to -20.7‰ for diesel engine, respectively. For diesel vehicle without catalytic converter, the HCHO carbon isotopic ratios were -22.1 ± 2.1‰, and for gasoline vehicle with catalytic converter, the ratios were -21.4 ± 0.7‰. Most of the HCHO carbon isotopic ratios were heavier than the fuel isotopic ratios (from -29 to -27‰). For gasoline vehicle, the isotopic fractionation (Δ13C) between HCHO and fuel isotopic ratios was 7.4 ± 0.7‰, which was higher than that of HCHO from stand-alone gasoline engine (Δ13Cmax = 2.7‰), suggesting additional consumption by the catalytic converter. For diesel vehicle without catalytic converter, Δ13C was 5.7 ± 2.0‰, similar to that of stand-alone diesel engine. In general, the carbon isotopic signatures of HCHO emitted from automobiles were not sensitive to idling states or to other vehicle parameters in our study condition. On comparing these HCHO carbon isotopic data with those of past studies, the atmospheric HCHO in a bus station in Guangzhou might mainly come from vehicle emission for

  7. Carbon mass-balance modeling and carbon isotope exchange processes in the Curonian Lagoon

    Science.gov (United States)

    Barisevičiūtė, Rūta; Žilius, Mindaugas; Ertürk, Ali; Petkuvienė, Jolita

    2016-04-01

    The Curonian lagoon one of the largest coastal lagoons in Europe is located in the southeastern part of the Baltic Sea and lies along the Baltic coast of Lithuania and the Kaliningrad region of Russia. It is influenced by a discharge of the Nemunas and other smaller rivers and saline water of the Baltic Sea. The narrow (width 0.4 km, deep 8-14 m) Klaipėda Strait is the only way for fresh water run-off and brackish water intrusions. This research is focused on carbon isotope fractionations related with air - water exchange, primary production and organic carbon sedimentation, mineralization and uptake from both marine and terrestrial sources.

  8. Carbon and Oxygen Isotopic Ratios for Nearby Miras

    Science.gov (United States)

    Hinkle, Kenneth H.; Lebzelter, Thomas; Straniero, Oscar

    2016-07-01

    Carbon and oxygen isotopic ratios are reported for a sample of 46 Mira and SRa-type variable asymptotic giant branch (AGB) stars. Vibration-rotation first and second-overtone CO lines in 1.5-2.5 μm spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and 16O/18O. Comparisons with previous measurements for individual stars and with various samples of evolved stars, as available in the extant literature, are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of M-stars have main sequence masses ≤2 M ⊙ and have not experienced sizable third dredge-up (TDU) episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the six C-stars in the sample three have clear evidence relating their origin to the occurrence of TDU. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars, as represented by our sample of long period variables (LPVs), shows a large spread of 16O/17O ratios, similar to that of group 1 presolar grains and in agreement with theoretical expectations for the composition of mass 1.2-2 M ⊙ stars after the first dredge-up. In contrast, the 16O/18O ratios of present-day LPVs are definitely smaller than those of group 1 grains. This is most probably a consequence of the the decrease with time of the 16O/18O ratio in the interstellar medium due to the chemical evolution of the Milky Way. One star in our sample has an O composition similar to that of group 2 presolar grains originating in an AGB star undergoing extra-mixing. This may indicate that the extra-mixing process is hampered at high metallicity, or, equivalently, favored at low metallicity. Similarly to O-rich grains, no star in our sample shows evidence of hot bottom burning, which is expected for

  9. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

    OpenAIRE

    Shaheen, R.; Abramian, A.; Horn, J.; Dominguez, G.; Sullivan, R; Thiemens, Mark H.

    2010-01-01

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4–3.9‰). The unique O-isotopic composition mechanistically describes...

  10. Stable Isotope Measurements of Carbon Dioxide, Methane, and Hydrogen Sulfide Gas Using Frequency Modulation Spectroscopy

    Science.gov (United States)

    Nowak-Lovato, K.

    2014-12-01

    Seepage from enhanced oil recovery, carbon storage, and natural gas sites can emit trace gases such as carbon dioxide, methane, and hydrogen sulfide. Trace gas emission at these locations demonstrate unique light stable isotope signatures that provide information to enable source identification of the material. Light stable isotope detection through surface monitoring, offers the ability to distinguish between trace gases emitted from sources such as, biological (fertilizers and wastes), mineral (coal or seams), or liquid organic systems (oil and gas reservoirs). To make light stable isotope measurements, we employ the ultra-sensitive technique, frequency modulation spectroscopy (FMS). FMS is an absorption technique with sensitivity enhancements approximately 100-1000x more than standard absorption spectroscopy with the advantage of providing stable isotope signature information. We have developed an integrated in situ (point source) system that measures carbon dioxide, methane and hydrogen sulfide with isotopic resolution and enhanced sensitivity. The in situ instrument involves the continuous collection of air and records the stable isotope ratio for the gas being detected. We have included in-line flask collection points to obtain gas samples for validation of isotopic concentrations using our in-house isotope ratio mass spectroscopy (IRMS). We present calibration curves for each species addressed above to demonstrate the sensitivity and accuracy of the system. We also show field deployment data demonstrating the capabilities of the system in making live dynamic measurements from an active source.

  11. Silurian and Devonian source rocks and crude oils from the western part of Libya: Organic geochemistry, palynology and carbon stratigraphy

    NARCIS (Netherlands)

    Elkelani, Mohamed M.A.

    2015-01-01

    The Early Silurian “hot” shales and Late Devonian black shales are major regional oil and gas source rocks in North Africa. Their deposition probably played a major role in global carbon cycling in general because of the large areas of the ocean affected. Comparing the Libyan δ13C record with record

  12. Carbon-bearing iron phases and the carbon isotope composition of the deep Earth.

    Science.gov (United States)

    Horita, Juske; Polyakov, Veniamin B

    2015-01-06

    The carbon budget and dynamics of the Earth's interior, including the core, are currently very poorly understood. Diamond-bearing, mantle-derived rocks show a very well defined peak at δ(13)C ≈ -5 ± 3‰ with a very broad distribution to lower values (∼-40‰). The processes that have produced the wide δ(13)C distributions to the observed low δ(13)C values in the deep Earth have been extensively debated, but few viable models have been proposed. Here, we present a model for understanding carbon isotope distributions within the deep Earth, involving Fe-C phases (Fe carbides and C dissolved in Fe-Ni metal). Our theoretical calculations show that Fe and Si carbides can be significantly depleted in (13)C relative to other C-bearing materials even at mantle temperatures. Thus, the redox freezing and melting cycles of lithosphere via subduction upwelling in the deep Earth that involve the Fe-C phases can readily produce diamond with the observed low δ(13)C values. The sharp contrast in the δ(13)C distributions of peridotitic and eclogitic diamonds may reflect differences in their carbon cycles, controlled by the evolution of geodynamical processes around 2.5-3 Ga. Our model also predicts that the core contains C with low δ(13)C values and that an average δ(13)C value of the bulk Earth could be much lower than ∼-5‰, consistent with those of chondrites and other planetary body. The heterogeneous and depleted δ(13)C values of the deep Earth have implications, not only for its accretion-differentiation history but also for carbon isotope biosignatures for early life on the Earth.

  13. A Novel Airborne Carbon Isotope Analyzer for Methane and Carbon Dioxide Source Fingerprinting

    Science.gov (United States)

    Berman, E. S.; Huang, Y. W.; Owano, T. G.; Leifer, I.

    2014-12-01

    Recent field studies on major sources of the important greenhouse gas methane (CH4) indicate significant underestimation of methane release from fossil fuel industrial (FFI) and animal husbandry sources, among others. In addition, uncertainties still exist with respect to carbon dioxide (CO2) measurements, especially source fingerprinting. CO2 isotopic analysis provides a valuable in situ measurement approach to fingerprint CH4 and CO2as associated with combustion sources, leakage from geologic reservoirs, or biogenic sources. As a result, these measurements can characterize strong combustion source plumes, such as power plant emissions, and discriminate these emissions from other sources. As part of the COMEX (CO2 and MEthane eXperiment) campaign, a novel CO2 isotopic analyzer was installed and collected data aboard the CIRPAS Twin Otter aircraft. Developing methods to derive CH4 and CO2 budgets from remote sensing data is the goal of the summer 2014 COMEX campaign, which combines hyperspectral imaging (HSI) and non-imaging spectroscopy (NIS) with in situ airborne and surface data. COMEX leverages the synergy between high spatial resolution HSI and moderate spatial resolution NIS. The carbon dioxide isotope analyzer developed by Los Gatos Research (LGR) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology and incorporates proprietary internal thermal control for high sensitivity and optimal instrument stability. This analyzer measures CO2 concentration as well as δ13C, δ18O, and δ17O from CO2 at natural abundance (100-3000 ppm). The laboratory accuracy is ±1.2 ppm (1σ) in CO2 from 370-1000 ppm, with a long-term (1000 s) precision of ±0.012 ppm. The long-term precision for both δ13C and δ18O is 0.04 ‰, and for δ17O is 0.06 ‰. The analyzer was field-tested as part of the COWGAS campaign, a pre-cursor campaign to COMEX in March 2014, where it successfully discriminated plumes related to combustion processes associated with

  14. Variability in carbon and nitrogen isotope fractionation associated with bacterial hydrolysis of atrazine

    Science.gov (United States)

    Meyer, A.; Penning, H.; Elsner, M.

    2009-04-01

    Even after legislative prohibition in 1991 by the European Union, the pesticide atrazine and its metabolites are still detected in surface and ground water frequently exceeding the permitted drinking water concentration limit of 0,1 g/L. Despite much recent research on atrazine, its risk assessment in the environment is still a major challenge because of the difficulty of establishing mass balances in the subsurface. To obtain a better insight into the fate of atrazine, we developed compound-specific stable isotope analysis (CSIA) for atrazine. CSIA has proven valuable for assessing organic contaminants in subsurface environments, on the one hand for source identification and on the other hand to trace (bio)chemical degradation reactions through isotope fractionation in the compounds. Such assessment is based on the Rayleigh equation and therein on the isotope enrichment factor ɛ, which must be determined experimentally beforehand. In ongoing work, we therefore measured carbon and nitrogen isotope fractionation associated with biotic hydrolsis of atrazine. C and N isotope enrichment factors were determined in resting cell experiments for Pseudomonas sp. ADP, Chelatobacter heintzii and Arthrobacter aurescens TC1, strains that hydrolyse atrazine in the initial transformation reaction. Carbon and nitrogen isotope enrichment factors were distinctly different between the bacterial strains. However, when plotting shifts in carbon isotope ratios versus shifts in nitrogen isotope ratios the slopes of the different degradation experiments coincided well. These results give evidence that all bacterial strains were carrying out the same initial biochemical degradation reaction, but that the associated isotope fractionation, as represented by the enrichment factors, was masked to a different extent owing to different rate determining steps prior to the isotopically sensitive bond cleavage (commitment to catalysis). Our study therefore illustrates the benefit of multi

  15. Carbon and hydrogen isotopic effects of stomatal density in Arabidopsis thaliana

    Science.gov (United States)

    Lee, Hyejung; Feakins, Sarah J.; Sternberg, Leonel da S. L.

    2016-04-01

    Stomata are key gateways mediating carbon uptake and water loss from plants. Varied stomatal densities in fossil leaves raise the possibility that isotope effects associated with the openness of exchange may have mediated plant wax biomarker isotopic proxies for paleovegetation and paleoclimate in the geological record. Here we use Arabidopsis thaliana, a widely used model organism, to provide the first controlled tests of stomatal density on carbon and hydrogen isotopic compositions of cuticular waxes. Laboratory grown wildtype and mutants with suppressed and overexpressed stomatal densities allow us to directly test the isotope effects of stomatal densities independent of most other environmental or biological variables. Hydrogen isotope (D/H) measurements of both plant waters and plant wax n-alkanes allow us to directly constrain the isotopic effects of leaf water isotopic enrichment via transpiration and biosynthetic fractionations, which together determine the net fractionation between irrigation water and n-alkane hydrogen isotopic composition. We also measure carbon isotopic fractionations of n-alkanes and bulk leaf tissue associated with different stomatal densities. We find offsets of +15‰ for δD and -3‰ for δ13C for the overexpressed mutant compared to the suppressed mutant. Since the range of stomatal densities expressed is comparable to that found in extant plants and the Cenozoic fossil record, the results allow us to consider the magnitude of isotope effects that may be incurred by these plant adaptive responses. This study highlights the potential of genetic mutants to isolate individual isotope effects and add to our fundamental understanding of how genetics and physiology influence plant biochemicals including plant wax biomarkers.

  16. Using Phytoliths and Carbon Isotope Stratigraphy to Recognize Subtle Subsurface Unconformities in the Unayzah Group of Saudi Arabia

    NARCIS (Netherlands)

    Hoof, T.B. van; Steinhauff, D.M.; Hooker, N.P.

    2014-01-01

    Unayzah Group correlation in Saudi Arabia is hindered by the lack of terrestrial fossils preserved in oxidized red-beds. Phytoliths are biogenic siliceous plant infillings and casts resistant to oxidation. In previous studies the presence of Biogenic Silica microfossils (Phytoliths) in Unayzah Group

  17. The impact of recycling of organic carbon on the stable carbon isotopic composition of dissolved inorganic carbon in a stratified marine system (Kyllaren fjord, Norway)

    NARCIS (Netherlands)

    Breugel, Y. van; Schouten, S.; Paetzel, M.; Nordeide, R.; Sinninghe Damsté, J.S.

    2005-01-01

    A negative carbon isotope shift in sedimentary organic carbon deposited in stratified marine and lacustrine systems has often been inferred to be a consequence of the process of recycling of respired and, therefore, 13C-depleted, dissolved inorganic carbon (DIC) formed from mineralization of descend

  18. Zinc isotope evidence for a large-scale carbonated mantle beneath eastern China

    Science.gov (United States)

    Liu, Sheng-Ao; Wang, Ze-Zhou; Li, Shu-Guang; Huang, Jian; Yang, Wei

    2016-06-01

    A large set of zinc (Zn) stable isotope data for continental basalts from eastern China were reported to investigate the application of Zn isotopes as a new tracer of deep carbonate cycling. All of the basalts with ages of 120 Ma basalts from eastern China (0.27 ± 0.06‰; 2sd). Given that Zn isotope fractionation during magmatic differentiation is limited (≤0.1‰), the elevated δ66Zn values reflect the involvement of isotopically heavy crustal materials (e.g., carbonates with an average δ66Zn of ∼0.91‰) in the mantle sources. SiO2 contents of the recycled Mg (Zn)-rich carbonates in the mantle beneath eastern China since the Late Mesozoic. Since Zn is a trace element in the mantle and Zn isotopic compositions of marine carbonates and the mantle differ markedly, we highlight Zn isotopes as a new and useful tool of tracing deep carbonate cycling in the Earth's mantle.

  19. Paleomagnetism of the Stanislaus Group, CA reveals revised stratigraphy, Walker Lane kinematics, and radio-isotopic constraints on C5 magnetic subchrons

    Science.gov (United States)

    Pluhar, C. J.; Wright, T. J.; Fischer, C. P.; Busby, C. J.

    2007-12-01

    Paleomagnetic study of the c.a. 9.2-10.3 Ma Stanislaus Group of intercalated latite (trachyandesite) lavas, ignimbrites and accessory sediments at three localities in Mono county California reveals: 1) a detailed, revised stratigraphy for the Stanislaus group, 2) kinematic constraints on the part of the Walker Lane since Stanislaus group emplacement, and 3) two age-constrained magnetic subchrons during chron C5N recorded by latites that had previously only been identified in seafloor magnetic anomalies. The revised stratigraphy results from detailed magnetostratigraphy combined with previous 40Ar/39Ar geochronologic constraints and stratigraphic studies. We find the lowermost unit, Table Mountain Latite, to consist of 23 or more individual lava flows falling into 5 magnetic (mostly normal) polarity zones, indicating that these rocks span at least 40,000 years of geologic time, based on the expected duration of magnetic reversals. Overlying Table Mountain Latite is the reversed-polarity Tollhouse Flat member of the Eureka Valley Tuff as described by previous authors. In the Sweetwater Roadless Area, thought to be proximal to the Stanislaus eruptive center, latite lava of both normal and reversed polarity are emplaced ontop of the Tollhouse Flat Member. Normal-polarity By Day member and normal-polarity Upper Member lie at very top of entire sequence. We find no field evidence for the normal polarity Dardanelle Formation latite flow at the top of the Group as had been previously reported by other workers. Instead, the Dardanelle formation member likely corresponds to the latite lava(s) between the By Day and Tollhouse Flat Eureka Valley Tuff. Based on previous 40Ar/39Ar dating, the two reversed zones within our magnetostratigraphy correspond to two of the proposed reversed subchrons/excursions during chron C5N. Direct dating of these reversed units may lead to future improvements to the magnetic polarity timescale for C5N. Our paleomagnetic results from three study

  20. Carbon Stable Isotopes as Indicators of Coastal Eutrophication

    Science.gov (United States)

    Coastal ecologists and managers have frequently used nitrogen stable isotopes (δ15N) to trace and monitor anthropogenic nitrogen (N) in coastal ecosystems. However, the interpretation of δ15N data can often be challenging, if not confounding, as the isotope values fractionate su...

  1. Carbon Isotope Evidence for the Stepwise Oxidation of the Proterozoic Environment

    Science.gov (United States)

    DesMarais, David J.; Strauss, Harald; Summons, Roger E.; Hayes, J. M.

    1992-01-01

    The oxidation of the Earth's crust and the increase in atmospheric oxygen early in Earth history have been linked to the accumulation of reduced carbon in sedimentary rocks. Trends in the carbon isotope composition of sedimentary organic carbon and carbonate show that during the Proterozoic aeon (2.5-0.54 Gyr ago) the organic carbon reservoir grew in size, relative to the carbonate reservoir. This increase, and the concomitant release of oxidizing power in the environment, occurred mostly during episodes of global rifting and orogeny.

  2. Molar-tooth Carbonate Sequences and Sr Isotopes in the Neoproterozoic for Stratigraphic Correlation:Research in the Jilin-Liaoning-Xuzhou-Huaiyang Area of the Sino-Korean Plate and Its Correlation with the Yangtze Plate

    Institute of Scientific and Technical Information of China (English)

    MENG Xianghua; GE Ming; LIU Yanxue; KUANG Hongwei; LIU Weifu; Francoise G. BOURROUILH-LE JAN; Robert BOURROUILH

    2004-01-01

    Based on a study of Neoproterozoic carbonates in the Jilin-Liaoning-Xuzhou-Huaiyang area, especially its cyclic sequence stratigraphy and Sr isotopes, two maximum sea flooding events (at 820 Ma and 835 Ma) have been identified. The resulting isochronous stratigraphic correlation proves that these Precambrian strata were connected between the Qingbaikou and the Nanhuan systems with a time range from 750 Ma to 850 Ma. The disappearance of microsparite carbonate and coming of a glacial stage offer important evidence for worldwide stratigraphic correlation and open a window for further correlation of the stratigraphic successions across the Sino-Korean and Yangtze Plates. A new correlation scheme is therefore provided based on our work.

  3. Chlorine and carbon isotope measurements can help assessing the effectivenes of a zero valent iron barrier

    Science.gov (United States)

    Cretnik, S.; Audi, C.; Bernstein, A.; Palau, J.; Soler, A.; Elsner, M.

    2012-04-01

    Chlorinated aliphatic hydrocarbons (CAH's) such as trichloroethene (TCE), cis-dichloroethene (cis-DCE) and vinylchloride (VC) are extensively used in industrial applications. One of the most promising remediation techniques for CAH's in groundwater is their removal via abiotic reductive dechlorination using Zero Valent Iron (ZVI). This is applied for the treatment of contaminated sites by installing permeable reactive barriers (PRB). In this study, isotope fractionation of chlorinated ethylenes in transformation by cast iron has been investigated, because such types of iron are commonly used in PRBs. Batch experiments have been carried out in closed flasks, containing cast iron with aqueous solutions of TCE, cDCE and VC. These substrates and their respective products have been monitored by headspace samplings for their concentration (by GC-FID) and isotope fractionation of carbon and chlorine (by GC-IRMS). A decreasing reactivity trend was observed when compounds contain less chlorine atoms, with differences in rate constants of about one order of magnitude between each of the substances TCE > cDCE > VC. This resulted in the accumulation of products with fewer chlorine atoms. Therefore a similar observation can be expected if degradation in the field is incomplete, for example in the case of aged or improperly designed PRB. Pronounced carbon and chlorine isotope fractionation was measured for each of the compounds, and characteristic dual isotope plots (C, Cl) were obtained for TCE and cDCE. These results may serve as an important reference for the interpretation of isotope data from field sites, since stable isotope fractionation is widely recognized as robust indicator for such pollutant transformations. However, carbon isotope fractionation in a given parent compound may be caused by either abiotic or biotic degradation. In the field, it can therefore be difficult to delineate the contribution of abiotic transformation by PRB in the presence of ongoing

  4. Seasonal variation in kangaroo tooth enamel oxygen and carbon isotopes in southern Australia

    Science.gov (United States)

    Brookman, Tom H.; Ambrose, Stanley H.

    2012-09-01

    Serial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C3 and C4 vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. δ13C and δ18O values were determined for a series of enamel samples drilled from the 3rd and 4th molars of kangaroos that were collected along a 900 km north-south transect in southern Australia. The serial sampling method did not yield pronounced seasonal isotopic variation patterns in Macropus enamel. The full extent of dietary isotopic variation may be obscured by attenuation of the isotopic signal during enamel mineralisation. Brachydont (low-crowned) Macropus teeth may be less sensitive to seasonal variation in isotopic composition due to time-averaging during mineralisation. However, geographic variations observed suggest that there may be potential for tracking latitudinal shifts in vegetation zones and seasonal environmental patterns in response to climate change.

  5. Trophic ecology of small yellow croaker (Larimichthys polyactis Bleeker): stable carbon and nitrogen isotope evidence

    Institute of Scientific and Technical Information of China (English)

    JI Weiwei; CHEN Xuezhong; JIANG Yazhou; LI Shengfa

    2011-01-01

    The trophic ecology of the small yellow croaker (Larimichthys polyactis) was studied using stable isotope analyses.Samples were collected from July to September 2009 and 34 individuals from eight sites were examined for stable carbon and nitrogen isotopes.Stable carbon isotope ratios (δ13C)ranged from -20.67 to -15.43,while stable nitrogen isotope ratios (δ15N) ranged 9.18-12.23.The relationship between δ13C and δ15N suggested high resource partitioning in the sampling area.Significant differences in stable isotope values among the eight sampling sites may be linked to environmental diversities involving various physical processes (such as ocean current,wind and tide) and different carbon sources.Furthermore,the stable isotope ratios may also explain the ontogenetic variability in diet and feeding,because δ13C and δ15N varied significantly with increasing body size.The findings are consistent with other studies on diet analyses in small yellow croaker.It was also demonstrated that stable isotope analysis could be used to estimate the trophic characters of small yellow croaker in feeding patterns and migrating habits.

  6. Towards a better understanding of magnesium-isotope ratios from marine skeletal carbonates

    Science.gov (United States)

    Hippler, Dorothee; Buhl, Dieter; Witbaard, Rob; Richter, Detlev K.; Immenhauser, Adrian

    2009-10-01

    This study presents magnesium stable-isotope compositions of various biogenic carbonates of several marine calcifying organisms and an algae species, seawater samples collected from the western Dutch Wadden Sea, and reference materials. The aim of this study is to explore the influence of mineralogy, taxonomy and environmental factors (e.g., seawater isotopic composition, temperature, salinity) on magnesium-isotopic (δ 26Mg) ratios of skeletal carbonates. Using high-precision multi-collector inductively coupled plasma mass spectrometry, we observed that the magnesium-isotopic composition of seawater from the semi-enclosed Dutch Wadden Sea is identical to that of open marine seawater. We further found that a considerable component of the observed variability in δ 26Mg values of marine skeletal carbonates can be attributed to differences in mineralogy. Furthermore, magnesium-isotope fractionation is species-dependent, with all skeletal carbonates being isotopically lighter than seawater. While δ 26Mg values of skeletal aragonite and high-magnesium calcite of coralline red algae indicate the absence or negligibility of metabolic influences, the δ 26Mg values of echinoids, brachiopods and bivalves likely result from a taxon-specific level of control on Mg-isotope incorporation during biocalcification. Moreover, no resolvable salinity and temperature effect were observed for coralline red algae and echinoids. In contrast, Mg-isotope data of bivalves yield ambiguous results, which require further validation. The data presented here, point to a limited use of Mg isotopes as temperature proxy, but highlight the method's potential as tracer of seawater chemistry through Earth's history.

  7. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application. PMID:26813491

  8. Carbon Isotopic Values of Individual N—Alkanes in Pyrolysates of Algae

    Institute of Scientific and Technical Information of China (English)

    周文; 吴庆余; 等

    2000-01-01

    This paper presents the carbon isotopic values of individual n-alkanes in pyrolysates of algae,which are widely spread in marine and lacustrine environments.The carbon isotopic values of n-alkanes originated from different algal precursors vary greatly,and those of n-alka nes orginated from C.protothecoides,S.sp PCC 6803 and I.Galbana are even heavier than from higher plants,n-alkanes with different carbon numers derived from the sme organism may stem from different biomacromolecules.The dominant product nC31 diene yielded at 300℃ or lower temperature also is different from n-alkanes yielded at the same thermal evolution phase with respect to their origin.The catalysis of mineral components in limestone may lead to a lighter carbon isotope composition of n-alkanes.

  9. Linking carbon and water cycles using stable isotopes across scales: progress and challenges

    Directory of Open Access Journals (Sweden)

    C. Werner

    2011-03-01

    Full Text Available Stable isotope analysis is a powerful tool for tracing biogeochemical processes in the carbon and water cycles. One particularly powerful approach is to employ multiple isotopes where the simultaneous assessment of the D/H,18O/16O and/or 13C/12C in different compounds provide a unique means to investigate the coupling of water and carbon fluxes at various temporal and spatial scales. Here, we present a research update on recent advances in our process-based understanding of the utilization of carbon, oxygen and hydrogen isotopes to lend insight into carbon and water cycling. We highlight recent technological developments and approaches, their strengths and methodological precautions with examples covering scales from minutes to centuries and from the leaf to the globe.

  10. Stable Carbon Isotope Ratios of Phenolic Compounds in Secondary Particulate Organic Matter Formed by Photooxidation of Toluene

    CERN Document Server

    Irei, Satoshi; Huang, Lin; Auld, Janeen; Collin, Fabrice; Hastie, Donald

    2014-01-01

    Compound-specific stable carbon isotope ratios for phenolic compounds in secondary particulate organic matter (POM) formed by photooxidation of toluene were studied. Secondary POM generated by photooxidation of toluene using a continuous-flow reactor and an 8 cubic meter indoor smog chamber was collected, and then extracted with acetonitrile. Eight phenolic compounds were identified in the extracts by a gas chromatograph coupled with a mass spectrometer, and their compound-specific stable carbon isotope ratios were determined by a gas chromatograph coupled with a combustion furnace followed by an isotope ratio mass spectrometer. The majority of the products, including methylnitrophenols and methylnitrocatechols, were isotopically depleted by 5 to 6 permil compared to the initial isotope ratio for toluene, whereas the isotope ratio for 4_nitrophenol remained the same as the initial isotope ratio for toluene. Based on the reaction mechanisms postulated in literature, stable carbon isotope ratios of these produc...

  11. An automated method for 'clumped-isotope' measurements on small carbonate samples.

    Science.gov (United States)

    Schmid, Thomas W; Bernasconi, Stefano M

    2010-07-30

    Clumped-isotope geochemistry deals with the state of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes rather than with the most abundant ones. Among its possible applications, carbonate clumped-isotope thermometry is the one that has gained most attention because of the wide potential of applications in many disciplines of earth sciences. Clumped-isotope thermometry allows reconstructing the temperature of formation of carbonate minerals without knowing the isotopic composition of the water from which they were formed. This feature enables new approaches in paleothermometry. The currently published method is, however, limited by sample weight requirements of 10-15 mg and because measurements are performed manually. In this paper we present a new method using an automated sample preparation device coupled to an isotope ratio mass spectrometer. The method is based on the repeated analysis (n = 6-8) of 200 microg aliquots of sample material and completely automated measurements. In addition, we propose to use precisely calibrated carbonates spanning a wide range in Delta(47) instead of heated gases to correct for isotope effects caused by the source of the mass spectrometer, following the principle of equal treatment of the samples and standards. We present data for international standards (NBS 19 and LSVEC) and different carbonates formed at temperatures exceeding 600 degrees C to show that precisions in the range of 10 to 15 ppm (1 SE) can be reached for repeated analyses of a single sample. Finally, we discuss and validate the correction procedure based on high-temperature carbonates instead of heated gases.

  12. Stable carbon isotope ratios of ambient secondary organic aerosols in Toronto

    Science.gov (United States)

    Saccon, M.; Kornilova, A.; Huang, L.; Moukhtar, S.; Rudolph, J.

    2015-09-01

    A method to quantify concentrations and stable carbon isotope ratios of secondary organic aerosols has been applied to study atmospheric nitrophenols in Toronto, Canada. The sampling of five nitrophenols, all with substantial secondary formation from the photooxidation of aromatic volatile organic compounds (VOCs), was conducted in the gas phase and particulate matter (PM) together and in PM alone. Their concentrations in the atmosphere are in the low ng m-3 range and, consequently, a large volume of air (> 1000 m3) is needed to analyze samples for stable carbon isotope ratios, resulting in sampling periods of typically 24 h. While this extended sampling period increases the representativeness of average values, it at the same time reduces possibilities to identify meteorological conditions or atmospheric pollution levels determining nitrophenol concentrations and isotope ratios. Average measured carbon isotope ratios of the different nitrophenols are between -34 and -33 ‰, which is well within the range predicted by mass balance. However, the observed carbon isotope ratios cover a range of nearly 9 ‰ and approximately 20 % of the isotope ratios of the products have isotope ratios lower than predicted from the kinetic isotope effect of the first step of the reaction mechanism and the isotope ratio of the precursor. This can be explained by isotope fractionation during reaction steps following the initial reaction of the precursor VOCs with the OH radical. Limited evidence for local production of nitrophenols is observed since sampling was done in the Toronto area, an urban center with significant anthropogenic emission sources. Strong evidence for significant local formation of nitrophenols is only found for samples collected in summer. On average, the difference in carbon isotope ratios between nitrophenols in the particle phase and in the gas phase is insignificant, but for a limited number of observations in summer, a substantial difference is observed. This

  13. Carbon isotope ratios and isotopic correlations between components in fruit juices

    Science.gov (United States)

    Wierzchnicki, Ryszard

    2013-04-01

    Nowadays food products are defined by geographical origin, method of production and by some regulations concerning terms of their authenticity. Important data for confirm the authenticity of product are providing by isotopic methods of food control. The method checks crucial criteria which characterize the authenticity of inspected product. The European Union Regulations clearly show the tendency for application of the isotopic methods for food authenticity control (wine, honey, juice). The aim of the legislation steps is the protection of European market from possibility of the commercial frauds. Method of isotope ratio mass spectrometry is very effective tool for the use distinguishably the food products of various geographical origin. The basic problem for identification of the sample origin is the lack of databases of isotopic composition of components and information about the correlations of the data. The subject of the work was study the isotopic correlations existing between components of fruits. The chemical and instrumental methods of separation: water, sugars, organic acids and pulp from fruit were implemented. IRMS technique was used to measure isotopic composition of samples. The final results for original samples of fruits (apple, strawberry etc.) will be presented and discussed. Acknowledgement: This work was supported by the Polish Ministry of Science and Higher Education under grant NR12-0043-10/2010.

  14. Experimental fractionation of stable carbon isotopes during degassing of carbon dioxide and precipitation of calcite from aqueous solutions

    Science.gov (United States)

    Müller, K.; Winde, V.; Escher, P.; von Geldern, R.; Böttcher, M. E.

    2012-04-01

    Processes in the carbonate system of surface waters are in particular sensitive to variations of boundary conditions as, for instance, the partial pressure of carbon dioxide in the atmosphere and the aqueous solution. Examples range from streams, rivers, to coastal marine waters. The flux of carbon dioxide from continental flowing waters was recently included into calculations of the global carbon budget (Butman & Raymond, 2011, Nature Geo.). These solutions, are often supersaturated in carbon dioxide with respect to the atmosphere. The degassing of carbon dioxide is associated with a kinetically controlled fractionation of the stable carbon isotopes, which has to be considered in balancing water-air carbon dioxide fluxes. The degassing process additionally leads to the super-saturation of the aqueous solution with respect to calcium carbonate. Stable isotope fractionation is of particular value to identify and quantify processes at the water-gas phase interface and link these non-equilibrium processes to the formation mechanisms of calcite and the hydrodynamics of surface waters. Experiments were carried out with or without inert N2 gas flow to degas carbon dioxide from initially supersaturated solutions. Natural solutions used are from different stations of the Elbe estuary, the Jade Bay, the backbarrier tidal area of Spiekeroog Island, carbonate springs of Rügen Island, and the Baltic Sea coastline. Results are compared experiments using bottled mineral waters. By following the (physico) chemical changes in the solutions (pH, TA, Ca PHREEQC modeling) it was found, that two evolutionary stages can be differentiated. Reaction progress led to the preferential liberation of carbon dioxide containing the light carbon isotope, following a Rayleigh-type process. After an induction period, where only degassing of carbon dioxide took place, a second stage was observed where calcite began to form from the highly supersaturated solutions. In this stage the carbonate

  15. Carbon Stable Isotope Analysis of Methylmercury Toxin in Biological Materials by Gas Chromatography Isotope Ratio Mass Spectrometry.

    Science.gov (United States)

    Masbou, Jeremy; Point, David; Guillou, Gaël; Sonke, Jeroen E; Lebreton, Benoit; Richard, Pierre

    2015-12-01

    A critical component of the biogeochemical cycle of mercury (Hg) is the transformation of inorganic Hg to neurotoxic monomethylmercury (CH3Hg). Humans are exposed to CH3Hg by consuming marine fish, yet the origin of CH3Hg in fish is a topic of debate. The carbon stable isotopic composition (δ(13)C) embedded in the methyl group of CH3Hg remains unexplored. This new isotopic information at the molecular level is thought to represent a new proxy to trace the carbon source at the origin of CH3Hg. Here, we present a compound-specific stable isotope analysis (CSIA) technique for the determination of the δ(13)C value of CH3Hg in biological samples by gas chromatography combustion isotope ratio mass spectrometry analysis (GC-C-IRMS). The method consists first of calibrating a CH3Hg standard solution for δ(13)C CSIA. This was achieved by comparing three independent approaches consisting of the derivatization and halogenation of the CH3Hg standard solution. The determination of δ(13)C(CH3Hg) values on natural biological samples was performed by combining a CH3Hg selective extraction, purification, and halogenation followed by GC-C-IRMS analysis. Reference δ(13)C values were established for a tuna fish certified material (ERM-CE464) originating from the Adriatic Sea (δ(13)C(CH3Hg) = -22.1 ± 1.5‰, ± 2 SD). This value is similar to the δ(13)C value of marine algal-derived particulate organic carbon (δ(13)CPOC = -21‰).

  16. Marine Carbon-Sulfur Biogeochemical Cycles during the Steptoean Positive Carbon Isotope Excursion (SPICE) in the Jiangnan Basin, South China

    Institute of Scientific and Technical Information of China (English)

    Yang Peng; Yongbo Peng; Xianguo Lang; Haoran Ma; Kangjun Huang; Fangbing Li; Bing Shen

    2016-01-01

    ABSTRACT:Global occurrences of Steptoean Positive Carbon Isotope Excursion (SPICE) during Late Cambrian recorded a significant perturbation in marine carbon cycle, and might have had profound impacts on the biological evolution. In previous studies, SPICE has been reported from the Jiangnan slope belt in South China. To evaluate the bathymetric extent of SPICE, we investigate the limestone samples from the upper Qingxi Formation in the Shaijiang Section in the Jiangnan Basin. Our results show the positive excursions for both carbonate carbon (δ13C) and organic carbon (δ13Corg) isotopes, as well as the concurrent positive shifts in sulfur isotopes of carbonate associated sulfate (CAS, δ34SCAS) and pyrite (δ34Spyrite), unequivocally indicating the presence of SPICE in the Jiangnan Basin. A 4‰increase inδ13Ccarb of the Qingxi limestone implies the increase of the relative flux of organic carbon burial by a factor of two. Concurrent positive excursions inδ34SCAS andδ34Spyrite have been attributed to the enhanced pyrite burial in oceans with extremely low concentration and spatially heterogeneous isotopic composition of seawater sulfate. Here, we propose that the seawater sulfur isotopic heterogeneity can be generated by volatile organic sulfur compound (VOSC, such as methanethiol and dimethyl sulfide) formation in sulfidic continental margins that were widespread during SPICE. Emission of 32S-enriched VOSC in atmosphere, followed by lateral transportation and aerobic oxidation in atmosphere, and precipitation in open oceans result in a net flux of 32S from continental margins to open oceans, elevatingδ34S of seawater sulfate in continental margins. A simple box model indicates that about 35%to 75%of seawater sulfate in continental margins needs to be transported to open oceans via VOSC formation.

  17. The thermal history of char as disclosed by carbon isotope ratios

    DEFF Research Database (Denmark)

    Egsgaard, Helge; Ambus, Per; Ahrenfeldt, Jesper

    In laboratory experiments, biomass char was produced under controlled conditions using wood chips from French pinewood. Different char qualities were obtained by pyrolysing the biomass at similar heating rates with end-temperatures ranging from 250 to 1000 o C. The char was analysed by flash...... pyrolysis and isotope ratio mass spectrometry. The results demonstrate that the temperature history of the char is reflected in the fine variation of carbon isotopes. The compound classes responsible for the variation were identified. Key words: Isotope ratio, flash pyrolysis, hot gas cleaning...

  18. Carbon and hydrogen isotopic composition and generation pathway of biogenic gas in China

    Institute of Scientific and Technical Information of China (English)

    SHEN Ping; WANG Xiaofeng; XU Yin; SHI Baoguang; XU Yongchang

    2009-01-01

    The carbon and hydrogen isotopic composition of biogenic gas is of great importance for the study of its generation pathway and reservoiring characteristics. In this paper, the formation pathways and reservoiring characteristics of biogenic gas reservoirs in China are described in terms of the carbon and hydrogen isotopic compositions of 31 gas samples from 10 biogenic gas reservoirs. The study shows that the hydrogen isotopic compositions of these biogenic gas reservoirs can be divided into three intervals:δDCH4>-200‰,-250‰<δDCH4<-200‰ and δDCH4<-250‰. The forerunners believed that the main generation pathway of biogenic gas under the condition of continental fresh water is acetic fermentation. Our research results showed that the generation pathway of biogenic gas under the condition of marine facies is typical CO2- reduction, the biogenic gas has heavy hydrogen isotopic composition: its δDCH4 values are higher than -200‰; that the biogenic gas under the condition of continental facies also was generated by the same way, but its hydrogen isotopic composition is lighter than that of biogenetic gas generated under typical marine facies condition: -250‰<δDCH4<-200‰, the δDCH4 values may be related to the salinity of the water medium in ancient lakes. From the relevant data of the Qaidam Basin, it can be seen that the hydrogen isotopic composition of biogenic methane has the same variation trend with increasing salinity of water medium. There are biogenic gas reservoirs formed in transitional regions under the condition of continental facies. These gas reservoirs resulted from both CO2- reduction and acetic fermentation, the formation of which may be related to the non-variant salinity of ancient water medium and the relatively high geothermal gradient, as is the case encountered in the Baoshan Basin. The biogenic gas generating in these regions has light hydrogen isotopic composition: δDCH4<-250‰, and relatively heavy carbon isotopic

  19. The specific carbon isotopic compositions of branched and cyclic hydrocarbons from Fushun oil shale

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi; WU Baoxiang; ZHENG Guodong; ZHANG Hui; ZHENG Chaoyang

    2004-01-01

    Various branched and cyclic hydrocarbons are isolated from the Fushun oil shale and their carbon isotopes are determined. The analytical results show that the branched and cyclic hydrocarbons are fully separated from n-alkanes by 5 A Molecular-sieve adduction using long time and cold solvent. The branched and cyclic hydrocarbon fraction obtained by this method is able to satisfy the analytic requests of GC-IRMS. The carbon isotopic compositions of these branched and cyclic hydrocarbons obtained from the sample indicate that they are derived from photoautotrophic algae, chemoautotrophic bacteria (-3.4‰ --39.0‰) and methanotrophic bacteria (-38.4‰--46.3‰). However the long-chain 2-methyl-branched alkanes indicate that their carbon isotopic compositions reflect biological origin from higher plants. The carbon isotopic composition of C30 4-methyl sterane (-22.1‰) is the heaviest in all studied ste- ranes, showing that the carbon source or growth condition for its precursor, dinoflagellate, may be different from that of regular steranes. The variation trend of δ13C values between isomers of hopanes shows that 13C-enriched precursors take precedence in process of their epimerization. Methanotrophic hopanes presented reveal the processes of strong transformation of organic matter and cycling of organic carbon in the water column and early diagenesis of oil shale.

  20. Carbonate clumped isotope paleothermometry and stable isotope results from the Eocene Fenghuo Shan Group, Hoh Xil Basin, Central Tibet

    Science.gov (United States)

    Snell, K. E.; Lippert, P. C.; Eiler, J. M.

    2009-12-01

    We present preliminary clumped isotope temperatures, calcite δ13C and δ18O values, and reconstructed water δ18O values from paleosol carbonates and calcite cemented siltstones and mudstones of the Fenghuo Shan Group from stratigraphic sections in the TouTou He subbasin of Hoh Xil Basin on the northern Tibetan Plateau. Models of plateau growth vary in the timing of initial plateau growth, and in their description of the spatial distribution of the plateau through time. Oxygen isotope paleoaltimetry studies have been used to estimate the elevation of the plateau in the past, but this technique requires assumptions about the temperature of mineral formation. Independent estimates of the temperature of mineral formation are potentially useful for identifying samples in which carbonate has undergone post-depositional recrystallization and/or isotopic exchange, and, when plausible primary depositional temperatures are found, for making more accurate estimates of δ18O of the waters from which the calcite precipitated. The calcite δ18O and δ13C values for the cements are relatively invariant with stratigraphic level, averaging -10.1±1.2‰ and -4.5±2.5‰ (PDB), respectively. These values are similar to lacustrine carbonates of similar age from the same region. The paleosol carbonates, in contrast, are 18O- and 13C-enriched relative to the cements, with average δ18O and δ13C values of -2.4±0.8 and -2.8±0.7‰. Carbonate clumped isotope paleotemperatures for the cements and the paleosol carbonates are also markedly different. The cement samples vary from 26 to 83°C and increase consistently with increasing depth, at a steep gradient of ~100°C/km. Paleosol carbonates from depths at which cements recorded 60°C, preserve temperatures of 35°C and 41°C. A calcite spar-filled fracture in one paleosol carbonate had a temperature of 41°C. Finally the reconstructed cement water δ18O values range from 2.8 to -7.6‰(SMOW), with a trend of 0.2‰/°C. The

  1. Forensic utility of the carbon isotope ratio of PVC tape backings

    Science.gov (United States)

    Stern, L. A.; Thompson, A. H.; Mehltretter, A. H.; McLaskey, V.; Parish, A.; Aranda, R.

    2008-12-01

    Forensic interest in adhesive tapes with PVC-backings (polyvinyl chloride, electrical tapes) derives from their use in construction of improvised explosive devices, drug packaging and in a variety of other illicit activities. Due to the range of physical characteristics and chemical compositions of such tapes, traditional microscopic and chemical analysis of the tape backings and adhesives offer a high degree of discrimination between tapes from different manufacturers and products. To evaluate whether carbon isotope ratios may be able to increase discrimination of electrical tapes, particularly with regards to different tapes of the same product, we assessed the PVC-backings of 87 rolls of black electrical tape for their δ13C values. The adhesive on these tapes was physically removed with hexane, and plasticizers within the PVC tape backings were removed by three-20 minute extractions with chloroform. The δ13C values of the PVC tape backings ranged between -23.8 and -41.5 (‰ V-PDB). The carbon isotopic variation within a product (identical brand and product identification) is significant, based on five products with at least 3 rolls (ranges of 7.4‰ (n=3), 10.0‰ (n=6), 4.2‰ (n=16), 3.8‰ (n=6), and 11.5‰ (n=8), respectively). There was no measurable carbon isotope variation in regards to the following: a) along the length of a roll (4 samples from 1 roll); b) between the center and edge of a strip of tape (1 pair); c) between rolls assumed to be from the same lot of tape (2 pairs); d) between different rolls from the same batch of tape (same product purchased at the same time and place; 5 pairs); and e) between samples of a tape at room temperature, heated to 50° C and 80° C for 1 week. For each sample within the population of 87 tapes, carbon isotopes alone exclude 80 to 100% of the tapes as a potential match, with an average exclusion power of 92.5%, using a window of ± 0.4‰. Carbon isotope variations originate from variations in starting

  2. Determination of organic milk authenticity using carbon and nitrogen natural isotopes.

    Science.gov (United States)

    Chung, Ill-Min; Park, Inmyoung; Yoon, Jae-Yeon; Yang, Ye-Seul; Kim, Seung-Hyun

    2014-10-01

    Natural stable isotopes of carbon and nitrogen ((12)C, (13)C, (14)N, (15)N) have abundances unique to each living creature. Therefore, measurement of the stable isotope ratio of carbon and nitrogen (δ(13)C=(13)C/(12)C, δ(15)N=(15)N/(14)N) in milk provides a reliable method to determine organic milk (OM) authenticity. In the present study, the mean δ(13)C value of OM was higher than that of conventional milk (CM), whereas the mean δ(15)N value of OM was lower than that of CM; nonetheless both δ(13)C and δ(15)N values were statistically different for the OM and CM (Pauthenticity using stable isotopes of carbon and nitrogen.

  3. Carbon Isotope Evolution of Early Proterozoic Dolomites of Wutai Mountain Area,North China

    Institute of Scientific and Technical Information of China (English)

    钟华; 马永生; 霍卫国; 姚御元

    1994-01-01

    Carbon isotope of the early Proterozoic carbonates from the Hutuo Group of the type sec-tion in Wutai Mountain area,Shanxi Province,North China,is reported.Isotopic analyses have been madefor 484 samples of dolomites.The carbon isotope results show:(i)δ13C values distinctly change with the ge-ological time,but are relatively stable in certain horizon;(ii)like that at the Cretaceous/Tertiary and Permi-an/Triassic boundaries,δ13C values also show abrupt variation across the boundaries between the JianancunFormation and the Daguandong Formation and between the Daguandong Formation and the Huaiyincun For-mation.

  4. Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite

    Science.gov (United States)

    Yuen, G.; Blair, N.; Des Marais, D. J.; Chang, S.

    1984-01-01

    Carbon isotopic compositions have been measured for individual hydrocarbons and monocarboxylic acids from the Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of C-13 to C-12 decreases with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic ratio than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with the kinetically controlled synthesis of higher homologues from lower ones. The results suggest the possibility that the production mechanisms for hydrocarbons and carboxylic acids may be similar, and impose constraints on the identity of the reactant species.

  5. Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers.

    Science.gov (United States)

    Xu, Xiaoyu; Zhang, Qianggong; Wang, Wen-Xiong

    2016-05-06

    Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ(199)Hg signatures, with some highest value (8.6%) ever in living organisms. The δ(202)Hg and Δ(199)Hg in sediment and biotic samples increased with trophic positions (δ(15)N) and %methylmercury. Fish total length closely correlated to δ(13)C and Δ(199)Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions.

  6. Determination of the origin of dissolved inorganic carbon in groundwater around a reclaimed landfill in Otwock using stable carbon isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Porowska, Dorota, E-mail: dorotap@uw.edu.pl

    2015-05-15

    Highlights: • Research showed the origin of DIC in the groundwater around a reclaimed landfill. • Carbon isotope was used to evaluate the contributions of carbon from different sources. • The leachate-contaminated water was isotopically distinct from the natural groundwater. • DIC in the natural groundwater comes from organic matter and dissolution of carbonates. • In the contaminated water, DIC comes from organic matter in the aquifer and landfill. - Abstract: Chemical and isotopic analyses of groundwater from piezometers located around a reclaimed landfill in Otwock (Poland) were performed in order to trace the origin of dissolved inorganic carbon (DIC) in the groundwater. Due to differences in the isotopic composition of carbon from different sources, an analysis of stable carbon isotopes in the groundwater, together with the Keeling plot approach and a two-component mixing model allow us to evaluate the relative contributions of carbon from these sources in the groundwater. In the natural (background) groundwater, DIC concentrations and the isotopic composition of DIC (δ{sup 13}C{sub DIC}) comes from two sources: decomposition of organic matter and carbonate dissolution within the aquifer sediments, whereas in the leachate-contaminated groundwater, DIC concentrations and δ{sup 13}C{sub DIC} values depend on the degradation of organic matter within the aquifer sediments and biodegradation of organic matter stored in the landfill. From the mixing model, about 4–54% of the DIC pool is derived from organic matter degradation and 96–46% from carbonate dissolution in natural conditions. In the leachate-contaminated groundwater, about 20–53% of the DIC is derived from organic matter degradation of natural origin and 80–47% from biodegradation of organic matter stored in the landfill. Partial pressure of CO{sub 2} (P CO{sub 2}) was generally above the atmospheric, hence atmospheric CO{sub 2} as a source of carbon in DIC pool was negligible in the

  7. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>20102510 Cai Xiongfei(Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,China);Wei Qirong New Progress in Research on Stratigraphy of the Middle Eastern Kunlun Orogenic Belt(Resources Survey & Environment,ISSN1671-4814,CN32-1640/N,30(4),2009,p.243-254,5 illus.,3 tables,24 refs.)Key words:stratigraphy,Kunlun MountainsThe middle Eastern Kunlun is a popular area with a great attraction in basic geologic researches of the Kunlun orogenic

  8. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>20111095 Chen Rong(Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China);Li Yong Sequence Stratigraphy of Neogene in the Northern Slope of the Chengning Uplift(Journal of Stratigraphy,ISSN0253-4959,CN32-1187/P,34(2),2010,p.179-186,7 illus.,1 table,9 refs.)Key words:Neogene Period,stratigraphic framework,Huanghua Depression According to the tectonic evolutionary history and stratigraphic and depositional characteristics,and based on drill cores,cutting logs,well logs and high-resolution 3-D seismic data,sequences

  9. Carbon isotope fractionation of chlorinated ethenes during oxidation by Fe{sup 2+} activated persulfate

    Energy Technology Data Exchange (ETDEWEB)

    Marchesi, Massimo, E-mail: m2marche@uwaterloo.ca [Departament de Cristallografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Barcelona, Catalunya 08028 (Spain); Earth and Environmental Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Aravena, Ramon [Earth and Environmental Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Sra, Kanwartej S. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada); Thomson, Neil R. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Otero, Neus; Soler, Albert [Departament de Cristallografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Barcelona, Catalunya 08028 (Spain); Mancini, Silvia [Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada)

    2012-09-01

    The increased use of persulfate (S{sub 2}O{sub 8}{sup 2-}) for in situ chemical oxidation to treat groundwater and soils contaminated by chlorinated hydrocarbon compounds (CHCs) requires unbiased methods to assess treatment performance. Stable carbon isotope analysis offers a potential tool for assessing the in situ treatment performance of persulfate at sites contaminated with CHCs. This study investigated the extent of C isotope fractionation during oxidation of tetrachloroethene (PCE), trichloroethene (TCE) and cis-dichloroethene (cis-DCE) by persulfate activated by ferrous ion (Fe{sup 2+}). An average carbon isotope enrichment factor {epsilon}{sub bulk} of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cis-DCE were obtained in batch experiments. Variations in the initial S{sub 2}O{sub 8}{sup 2-}/Fe{sup 2+}/CHC molar ratios did not result in any significant differences in carbon isotope fractionation. The occurrence of carbon isotope fractionation during oxidation and the lack of dependence of enrichment factors upon the S{sub 2}O{sub 8}{sup 2-}/Fe{sup 2+}/CHC molar ratio demonstrate that carbon isotope analysis can potentially be used at contaminated sites as an additional technique to estimate treatment efficacy during oxidation of CHCs by Fe{sup 2+} activated persulfate. Highlights: Black-Right-Pointing-Pointer The performance of in situ chemical oxidation (ISCO) is still difficult to assess. Black-Right-Pointing-Pointer We investigated the potential of carbon isotope analysis as a new assessing tool. Black-Right-Pointing-Pointer C isotope of PCE, TCE and DCE oxidized by persulfate activated by Fe{sup 2+} was measured. Black-Right-Pointing-Pointer Enrichment factors of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cisDCE were obtained. Black-Right-Pointing-Pointer Carbon isotope can potentially be used to estimate the ISCO treatment efficacy.

  10. POSSIBILITY OF USING CARBON ISOTOPES IN THE ASSESSMENT OF THE POLLUTION OF GAS PHASE IN ENVIRONMENTAL RESEARCH

    Directory of Open Access Journals (Sweden)

    Dorota Porowska

    2015-10-01

    Full Text Available Carbon isotope analyses can be used for knowledge and practical purpose. They can be used to assess the genesis of carbon in geochemical environment, and may also be used to indicate environmental contamination by carbon-containing compounds. The aim of the paper is to indicate the possibilities of using carbon isotope composition for interpretation concerning the following elements of the natural environment: atmospheric air, subsurface zone (gases in soils and aeration zone in terms of natural and anthropogenic factors influencing on their quality. This method can be applied universally, when carbon sources are different in isotopic composition.

  11. On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion–isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Schmitt, J.; Seth, B.; Bock, M; van der Veen, C.; Möller, L.; Sapart, C.J.; Prokopiou, M.; Sowers, T.; Röckmann, T.; Fischer, H

    2013-01-01

    Stable carbon isotope analysis of methane ( 13C of CH4) on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography (GC) isotope ratio mass spectrometry (IRMS) coupled to a combustion-preconcentra

  12. A versatile method for stable carbon isotope analysis of carbohydrates by high-performance liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Boschker, H.T.S.; Moerdijk-Poortvliet, T.C.W.; Van Breugel, P.; Houtekamer, M.J.; Middelburg, J.J.

    2008-01-01

    We have developed a method to analyze stable carbon isotope (13C/12C) ratios in a variety of carbohydrates using high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS). The chromatography is based on strong anion-exchange columns with low strength NaOH eluents. An eluent

  13. A versatile method for simultaneous stable carbon isotope analysis of DNA and RNA nucleotides by liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Moerdijk-Poortvliet, T.C.W.; Brasser, J.; de Ruiter, G.; Houtekamer, M.; Bolhuis, H.; Stal, L.J.; Boschker, H.T.S.

    2014-01-01

    RATIONALE Liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) is currently the most accurate and precise technique for the measurement of compound-specific stable carbon isotope ratios (13C/12C) in biological metabolites, at their natural abundance. However, until now this technique coul

  14. A versatile method for simultaneous stable carbon isotope analysis of DNA and RNA nucleotides by liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Moerdijk-Poortvliet, T.C.W.; Brasser, J.; de Ruiter, G.; Houtekamer, M.; Bolhuis, H.; Stal, L.J.; Boschker, H.T.S.

    2014-01-01

    RATIONALELiquid chromatography/isotope ratio mass spectrometry (LC/IRMS) is currently the most accurate and precise technique for the measurement of compound-specific stable carbon isotope ratios (C-13/C-12) in biological metabolites, at their natural abundance. However, until now this technique cou

  15. Biometrics from the carbon isotope ratio analysis of amino acids in human hair.

    Science.gov (United States)

    Jackson, Glen P; An, Yan; Konstantynova, Kateryna I; Rashaid, Ayat H B

    2015-01-01

    This study compares and contrasts the ability to classify individuals into different grouping factors through either bulk isotope ratio analysis or amino-acid-specific isotope ratio analysis of human hair. Using LC-IRMS, we measured the isotope ratios of 14 amino acids in hair proteins independently, and leucine/isoleucine as a co-eluting pair, to provide 15 variables for classification. Multivariate analysis confirmed that the essential amino acids and non-essential amino acids were mostly independent variables in the classification rules, thereby enabling the separation of dietary factors of isotope intake from intrinsic or phenotypic factors of isotope fractionation. Multivariate analysis revealed at least two potential sources of non-dietary factors influencing the carbon isotope ratio values of the amino acids in human hair: body mass index (BMI) and age. These results provide evidence that compound-specific isotope ratio analysis has the potential to go beyond region-of-origin or geospatial movements of individuals-obtainable through bulk isotope measurements-to the provision of physical and characteristic traits about the individuals, such as age and BMI. Further development and refinement, for example to genetic, metabolic, disease and hormonal factors could ultimately be of great assistance in forensic and clinical casework.

  16. [The isotope effect in the glycine dehydrogenase reaction is the cause of the intramolecular isotope inhomogeneity of glucose carbon of starch synthesized during photorespiration].

    Science.gov (United States)

    Ivlev, A A

    2005-01-01

    The isotope distribution of glucose-6-phosphate in the main pathways of its biosynthesis (in the processes of CO2 assimilation and photorespiration in the Calvin cycle and during resynthesis from the degradation products of lipids and proteins) was analyzed. For reconstructing the isotope distribution of glucoso-6-phosphate synthesized in the Calvin cycle during photorespiration, the functioning of the cycle with regard to its coupling with the glycolate chain, which together constitute the photorespiration chain, was considered. In the glycine dehydrogenase reaction of the glycolate cycle, there arises an isotope effect, which determines the distribution of isotopes in the glucose-6-phosphate and other photorespiration products. The isotope effect of the glycine dehydrogenase reaction increases at the expense of the exhaustion of glucose resources feeding the photorespiration chain. As a result, atoms C-3 and C-4 of glucose become enriched with the heavy isotope, and subsequent mixing of atoms and the specificity of interactions in the photorespiration chain lead to an isotope weighting of the other atoms and an uneven distribution of carbon isotopes in glucose-6-phosphate and other photorespiration products. A comparison of the glucose-6-phosphate isotope patterns in different pathways of the synthesis with the experimental data on the distribution of carbon isotopes in starch glucose of storing plant organs led to the conclusion that the starch resources are predominantly formed at the expense of glucose-6-phosphate of photorespiration. This is consistent with the earlier observed enhancement of photorespiration at the stage of plant maturation.

  17. Quaternary magnetic and oxygen isotope stratigraphy in diatom-rich sediments of the southern Gardar Drift (IODP Site U1304, North Atlantic)

    Science.gov (United States)

    Xuan, Chuang; Channell, James E. T.; Hodell, David A.

    2016-06-01

    The sediment sequence from Integrated Ocean Drilling Program (IODP) Site U1304 (53°03.40‧N, 33°31.78‧W; water depth, 3024 m) on the southern Gardar Drift, North Atlantic Ocean, covers the last ∼1.8 Myr with a mean sedimentation rate of ∼15 cm/kyr. At Site U1304, paleomagnetic directional and relative paleointensity (RPI) records have been generated for the last ∼1.5 Myr, and benthic oxygen isotope data for the last ∼1 Myr. The age model for Site U1304 was established by matching δ18O and RPI data to calibrated reference records. Prominent intervals of diatom mats at Site U1304 are associated with the latter stages of interglacial marine isotope stages (MIS) 9, 11, 13, 15, 21, 27 and 35, and with the weak glacial of MIS 14. The deposition of diatom mats, and associated diluted magnetic mineral concentrations, leads to weak magnetizations and susceptibilities in these intervals. Comparison of histograms of paleomagnetic directions and RPI from diatom-rich sediments and from surrounding silty clays indicates that, although results from diatom-rich sediments are more scattered, the occurrence of diatom mats does not appreciably distort the paleomagnetic directional and RPI records. Site U1304 sediments record the Matuyama/Brunhes boundary (∼772 ka), the Jaramillo Subchron (∼993-1071 ka) and the Cobb Mountain Subchron (∼1193-1219 ka), as well as three apparent geomagnetic excursions in the Matuyama Chron, interpreted as the "Kamikatsura/Santa Rosa", "Punaruu", and "Gardar" excursions, at ∼888 ka, ∼1124 ka, and ∼1463 ka, respectively. The Site U1304 RPI record can be correlated with the PISO-1500 RPI stack and with other high-resolution RPI records from the North Atlantic Ocean. Wavelet analyses performed on the Site U1304 RPI record and a new high-resolution North Atlantic paleointensity stack for the last 1500 kyr (HINAPIS-1500), comprising Ocean Drilling Program (ODP) Sites 983, 984 and IODP Sites U1306 and U1304, did not reveal significant

  18. Carbon and nitrogen isotope variations in tree-rings as records of perturbations in regional carbon and nitrogen cycles.

    Science.gov (United States)

    Bukata, Andrew R; Kyser, T Kurtis

    2007-02-15

    Increasing anthropogenic pollution from urban centers and fossil fuel combustion can impact the carbon and nitrogen cycles in forests. To assess the impact of twentieth century anthropogenic pollution on forested system carbon and nitrogen cycles, variations in the carbon and nitrogen isotopic compositions of tree-rings were measured. Individual annual growth rings in trees from six sites across Ontario and one in New Brunswick, Canada were used to develop site chronologies of tree-ring delta 15N and delta 13C values. Tree-ring 615N values were approximately 0.5% per hundred higher and correlated with contemporaneous foliar samples from the same tree, but not with delta 15N values of soil samples. Temporal trends in carbon and nitrogen isotopic compositions of these tree-rings are consistent with increasing anthropogenic influence on both the carbon and nitrogen cycles since 1945. Tree-ring delta 13C values and delta 15N values are correlated at both remote and urban-proximal sites, with delta 15N values decreasing since 1945 and converging on 1% per hundred at urban-proximal sites and decreasing but not converging on a single delta 15N value in remote sites. These results indicate that temporal trends in tree-ring nitrogen and carbon isotopic compositions record the regional extent of pollution.

  19. Evaluating reaction pathways of hydrothermal abiotic organic synthesis at elevated temperatures and pressures using carbon isotopes

    Science.gov (United States)

    Fu, Qi; Socki, Richard A.; Niles, Paul B.

    2015-04-01

    Experiments were performed to better understand the role of environmental factors on reaction pathways and corresponding carbon isotope fractionations during abiotic hydrothermal synthesis of organic compounds using piston cylinder apparatus at 750 °C and 5.5 kbars. Chemical compositions of experimental products and corresponding carbon isotopic values were obtained by a Pyrolysis-GC-MS-IRMS system. Alkanes (methane and ethane), straight-chain saturated alcohols (ethanol and n-butanol) and monocarboxylic acids (formic and acetic acids) were generated with ethanol being the only organic compound with higher δ13C than CO2. CO was not detected in experimental products owing to the favorable water-gas shift reaction under high water pressure conditions. The pattern of δ13C values of CO2, carboxylic acids and alkanes are consistent with their equilibrium isotope relationships: CO2 > carboxylic acids > alkanes, but the magnitude of the fractionation among them is higher than predicted isotope equilibrium values. In particular, the isotopic fractionation between CO2 and CH4 remained constant at ∼31‰, indicating a kinetic effect during CO2 reduction processes. No "isotope reversal" of δ13C values for alkanes or carboxylic acids was observed, which indicates a different reaction pathway than what is typically observed during Fischer-Tropsch synthesis under gas phase conditions. Under constraints imposed in experiments, the anomalous 13C isotope enrichment in ethanol suggests that hydroxymethylene is the organic intermediate, and that the generation of other organic compounds enriched in 12C were facilitated by subsequent Rayleigh fractionation of hydroxymethylene reacting with H2 and/or H2O. Carbon isotope fractionation data obtained in this study are instrumental in assessing the controlling factors on abiotic formation of organic compounds in hydrothermal systems. Knowledge on how environmental conditions affect reaction pathways of abiotic synthesis of organic

  20. Separation of polybrominated diphenyl ethers in fish for compound-specific stable carbon isotope analysis

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Yan-Hong [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate University of Chinese Academy of Sciences, Beijing, 100049 (China); Luo, Xiao-Jun, E-mail: luoxiaoj@gig.ac.cn [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Chen, Hua-Shan; Wu, Jiang-Ping; Chen, She-Jun; Mai, Bi-Xian [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China)

    2012-05-15

    A separation and isotopic analysis method was developed to accurately measure the stable carbon isotope ratios of polybrominated diphenyl ethers (PBDEs) with three to six substituted bromine atoms in fish samples. Sample extracts were treated with concentrated sulfuric acid to remove lipids, purified using complex silica gel column chromatography, and finally processed using alumina/silica (Al/Si) gel column chromatography. The purities of extracts were verified by gas chromatography and mass spectrometry (GC-MS) in the full-scan mode. The average recoveries of all compounds across the purification method were between 60% and 110%, with the exception of BDE-154. The stable carbon isotopic compositions of PBDEs can be measured with a standard deviation of less than 0.5 Per-Mille-Sign . No significant isotopic fraction was found during the purification of the main PBDE congeners. A significant change in the stable carbon isotope ratio of BDE-47 was observed in fish carcasses compared to the original isotopic signatures, implying that PBDE stable carbon isotopic compositions can be used to trace the biotransformation of PBDEs in biota. - Highlights: Black-Right-Pointing-Pointer A method for the purification of PBDEs for CSIA was developed. Black-Right-Pointing-Pointer The {delta}{sup 13}C of PBDE congeners can be measured with a standard deviation of less than 0.5 Per-Mille-Sign . Black-Right-Pointing-Pointer Common carp were exposed to a PBDE mixture to investigate debromination. Black-Right-Pointing-Pointer Ratios of the {delta}{sup 13}C values can be used to trace the debromination of PBDE in fish.

  1. Carbonate Mineral Formation on Mars: Clues from Stable Isotope Variation Seen in Cryogenic Laboratory Studies of Carbonate Salts

    Science.gov (United States)

    Socki, Richard; Niles, Paul B.; Sun, Tao; Fu, Qi; Romanek, Christopher S.; Gibson, Everett K.

    2013-01-01

    The geologic history of water on the planet Mars is intimately connected to the formation of carbonate minerals through atmospheric CO2 and its control of the climate history of Mars. Carbonate mineral formation under modern martian atmospheric conditions could be a critical factor in controlling the martian climate in a means similar to the rock weathering cycle on Earth. The combination of evidence for liquid water on the martian surface and cold surface conditions suggest fluid freezing could be very common on the surface of Mars. Cryogenic calcite forms readily when a rise in pH occurs as a result of carbon dioxide degassing quickly from freezing Ca-bicarbonate-rich water solutions. This is a process that has been observed in some terrestrial settings such as arctic permafrost cave deposits, lakebeds of the Dry Valleys of Antarctica, and in aufeis (river icings) from rivers of N.E. Alaska. We report here the results of a series of laboratory experiments that were conducted to simulate potential cryogenic carbonate formation on the planet Mars. These results indicate that carbonates grown under martian conditions (controlled atmospheric pressure and temperature) show enrichments from starting bicarbonate fluids in both carbon and oxygen isotopes beyond equilibrium values with average delta13C(DIC-CARB) values of 20.5%0 which exceed the expected equilibrium fractionation factor of [10(sup 3) ln alpha = 13%0] at 0 degC. Oxygen isotopes showed a smaller enrichment with delta18O(H2O-CARB) values of 35.5%0, slightly exceeding the equilibrium fractionation factor of [10(sup 3) ln alpha = 34%0 ] at 0degC. Large kinetic carbon isotope effects during carbonate precipitation could substantially affect the carbon isotope evolution of CO2 on Mars allowing for more efficient removal of 13C from the Noachian atmosphere enriched by atmospheric loss. This mechanism would be consistent with the observations of large carbon isotope variations in martian materials despite the

  2. Molecular carbon isotopic evidence for the origin of geothermal hydrocarbons

    Science.gov (United States)

    Des Marais, D. J.; Donchin, J. H.; Nehring, N. L.; Truesdell, A. H.

    1981-01-01

    Isotopic measurements of individual geothermal hydrocarbons that are, as a group, of higher molecular weight than methane are reported. It is believed in light of this data that the principal source of hydrocarbons in four geothermal areas in western North America is the thermal decomposition of sedimentary or groundwater organic matter.

  3. Intercontinental correlation of organic carbon and carbonate stable isotope records: evidence of climate and sea-level change during the Turonian (Cretaceous)

    NARCIS (Netherlands)

    Jarvis, I.; Trabucho-Alexandre, João; Gröcke, D.R.; Uličný, D.; Laurin, J.

    2015-01-01

    Carbon (d13Corg, d13Ccarb) and oxygen (d18Ocarb) isotope records are presented for an expanded Upper Cretaceous (Turonian–Coniacian) hemipelagic succession cored in the central Bohemian Cretaceous Basin, Czech Republic. Geophysical logs, biostratigraphy and stable carbon isotope chemostratigraphy pr

  4. Transient carbon isotope changes in complex systems: Finding the global signal, embracing the local signal

    Science.gov (United States)

    Bowen, G. J.; Schneider-Mor, A.; Filley, T. R.

    2008-12-01

    Global, transient carbon isotope excursions (CIEs) in the geological record are increasingly invoked as evidence of short-lived changes in carbon fluxes to/from the ocean-atmosphere-biosphere (exogenic) system. Reconstructing the dynamics of carbon cycle perturbation and response during such events requires that the global extent, magnitude, and temporal pattern of carbon isotope change are well understood. Unfortunately, no simple, globally integrated measure of exogenic δ13C change exists in the geological record: during major global perturbations even the best-case candidates such as deep-ocean carbonate δ13C values likely respond to a complex of factors including ocean carbonate chemistry and circulation. Here we consider the utility of organic carbon isotope records from two complex depositional systems common in the geological record, fossil soils and continental margin sediments, which are of interest in terms of their relationship to organic carbon cycling and records of past ecological change. Within both systems changes in ecology, climate, carbon source, residence time, and molecular composition have clear potential to modulate the preserved record of global exogenic δ13C change, compromising 1st-order interpretations of bulk or compound-specific isotopic records. Process-explicit eco- geochemical models, ideally combined with multi-substrate data, provide one approach to the isolation of global δ13C change and identification of local or regional processes reflected in such records. Examples from both systems drawn from ongoing work on the Paleocene-Eocene thermal maximum illustrate the potential pitfalls, as well as opportunities, afforded by coupled data/model assessment of transient δ13C changes in complex systems.

  5. Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

    Science.gov (United States)

    Komar, Nemanja; Zeebe, Richard

    2016-04-01

    Negative carbon and calcium isotope excursions, as well as climate shifts, took place during the most severe mass extinction event in Earth's history, the end-Permian (˜252 Ma). Investigating the connection between carbon and calcium cycles during transient carbon cycle perturbation events, such as the end-Permian, may help resolve the intricacies between the coupled calcium-carbon cycles, as well as provide a tool for constraining the causes of mass extinction. Here, we identify the deficiencies of a simplified calcium model employed in several previous studies and we demonstrate the importance of a fully coupled carbon-cycle model when investigating the dynamics of carbon and calcium cycling. Simulations with a modified version of the LOSCAR model, which includes a fully coupled carbon-calcium cycle, indicate that increased weathering rates and ocean acidification (potentially caused by Siberian Trap volcanism) are not capable of producing trends observed in the record, as previously claimed. Our model results suggest that combined effects of carbon input via Siberian Trap volcanism (12,000 Pg C), the cessation of biological carbon export, and variable calcium isotope fractionation (due to a change in the seawater carbonate ion concentration) represents a more plausible scenario. This scenario successfully reconciles δ13C and δ44Ca trends observed in the sediment record, as well as the proposed warming of >6oC.

  6. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>20050893 Chen Ming (Institute of Sedimentary, Chengdu University of Technology, Chengdu, Sichuan); Xu Xiaosong Study on Outcrop Sequence Stratigraphy of the Lower - Middle Ordovician Strata in Keping, Tarim Basin, Xinjiang, China (Acta Sedimentologica Sinica, ISSN1000-0550, CN62 -1038/P, 22(1), 2004, p. 110-116, 4 illus. , 15 refs. )

  7. HISTORICAL GEOLOGY &STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    <正>20131120 A.Averianov (Zoological Institute , Russian Academy of Sciences , Universitetskaya nab.1 , Saint Petersburg 199034 , Russia); H.-D.Sues Correlation of Late Cretaceous Continental Vertebrate Assemblages in Middle and Central Asia (Journal of Stratigraphy , ISSN0253-4959 , CN32-1187/P , 36 (2), 2012 , p.462-485

  8. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    <正>20090393 Cai Xiongfei (Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China); Wei Qirong Stratigraphic Sequence of Oceanic Islands and Palinspastic Reconstruction of the Wanbaogou Group-Complex in the Eastern Kunlun Orogenic Belt (Journal of Stratigraphy, ISSN0253-4959, CN32-1187/P, 31(2), 2007, p.117-125, 9 illus., 14 refs.)

  9. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    20152571 Bai Ping(Guizhou Academy of Geologic Survey,Guiyang 550005,China);Xiao Jiafei Sequence Stratigraphy and Sedimentary Environment of Early Cambrian in ZunyiDafang Area of Northwest Guizhou Province(Guizhou Geology,ISSN1000-5943,CN52-1059/P,31(4),2014,p.291-296,272,3

  10. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正> 20070428 Liu Wenye (Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029) Application of Wavelet Analysis in High-Resolution Sequence Stratigraphic Division (Journal of Geomechanics, ISSN1006-6616, CN11-3672/P, 12(1), 2006, p.64-70, 4 illus., 12 refs.) Key words: sequence stratigraphy, wavelet transform

  11. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    20151119Cui Zhengke(No.1 Marine Geological Investigation Party,Shanghai Offshore Petroleum Bureau,SINOPEC,Shanghai201208,China);Yang Wenda Late Quaternary Sequence Stratigraphy and Sedimentary Environment of East China Sea Continental Shelf(Marine Geology&Quaternary; Geology,ISSN0256-1492,CN37-1117/P,34(4),

  12. Beyond carbon and nitrogen: guidelines for estimating three-dimensional isotopic niche space.

    Science.gov (United States)

    Rossman, Sam; Ostrom, Peggy H; Gordon, Forrest; Zipkin, Elise F

    2016-04-01

    Isotopic niche has typically been characterized through carbon and nitrogen ratios and most modeling approaches are limited to two dimensions. Yet, other stable isotopes can provide additional power to resolve questions associated with foraging, migration, dispersal and variations in resource use. The ellipse niche model was recently generalized to n-dimensions. We present an analogous methodology which incorporates variation across three stable dimensions to estimate the significant features of a population's isotopic niche space including: 1) niche volume (referred to as standard ellipsoid volume, SEV), 2) relative centroid location (CL), 3) shape and 4) area of overlap between multiple ellipsoids and 5) distance between two CLs. We conducted a simulation study showing the accuracy and precision of three dimensional niche models across a range of values. Importantly, the model correctly identifies differences in SEV and CL among populations, even with small sample sizes and in cases where the absolute values cannot precisely be recovered. We use these results to provide guidelines for sample size in conducting multivariate isotopic niche modeling. We demonstrate the utility of our approach with a case study of three bottlenose dolphin populations which appear to possess largely overlapping niches when analyzed with only carbon and nitrogen isotopes. Upon inclusion of sulfur, we see that the three dolphin ecotypes are in fact segregated on the basis of salinity and find the stable isotope niche of inshore bottlenose dolphins significantly larger than coastal and offshore populations.

  13. Extreme hydrogen, oxygen and carbon isotope anomalies in the pore waters and carbonates of the sediments and basalts from the Norwegian Sea: Methane and hydrogen from the mantle

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, J.R. (Univ. of Houston, University Park, TX (USA)); Taviani, M. (Instituto di Geologia Marina, del C.N.R., Bologna (Italy))

    1988-08-01

    D/H ratios in the pore waters of the sediments from the Norwegian Sea decrease as a function of depth to values as low as {minus}14{per thousand}. Oxygen isotope ratios in the pore waters and carbon and oxygen isotope ratios in carbonates both in the sediments and basalts are low. Extensive alteration of basalt has been given as the explanation for the low oxygen isotope ratios. Material balance calculations suggest that alteration of volcanic material and oxidation of organic matter cannot explain the hydrogen and carbon isotope anomalies. Arguments are presented suggesting that methane and hydrogen from the mantle are oxidized to carbon dioxide and water by sulfate and ferric iron in the basaltic crust to yield the low hydrogen and carbon isotope ratios.

  14. Carbon isotopic records inpaleosols over the Pliocene in Northern China: Implication on vegetation developmentand Tibetan uplift

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Carbon isotopic composition of pedogenic carbonate can be used to estimate the proportion of C4 and C3 plants. Here we present carbon isotopic data of carbonate in a red earth section at Xifeng, central Loess Plateau. Results show that C4 vegetation increased in ~4.4 Ma B.P., stabilized between 4.0 and 3.0 Ma B.P. The character and timing of C4 expansion on the Loess Plateau are similar, but different with other localities, e.g. Pakistan and Africa, implying that regional climate changes were main factors driving the expansion of C4 plants. This event is comparable in timing with increased aridity evidenced by Xifeng grain size and North Pacific eolian dust records. Therefore we argue that the Pliocene expansion of C4 plants in northern China might have been caused by the increased aridity, which in turn might be related to rapid uplift of the Tibetan Plateau.

  15. Carbon isotope fractionation reveals distinct process of CH4 emission from different compartments of paddy ecosystem

    Science.gov (United States)

    Zhang, Guangbin; Yu, Haiyang; Fan, Xianfang; Ma, Jing; Xu, Hua

    2016-06-01

    Carbon isotopic fractionations in the processes of CH4 emission from paddy field remain poorly understood. The δ13C-values of CH4 in association with production, oxidation and transport of CH4 in different pools of a paddy field were determined, and the stable carbon isotope fractionations were calibrated to assess relative contribution of acetate to CH4 production (fac) and fraction of CH4 oxidized (fox) by different pathways. The apparent isotope fractionation for CO2 conversion to CH4 (αapp) was 1.041-1.056 in the soil and 1.046-1.080 on the roots, indicating that fac was 10-60% and 0-50%, respectively. Isotope fractionation associated with CH4 oxidation (αox) was 1.021 ± 0.007 in the soil and 1.013 ± 0.005 on the roots, and the transport fractionation (ɛtransport) by rice plants was estimated to be -16.7‰ ~ -11.1‰. Rhizospheric fox was about 30-100%, and it was more important at the beginning but decreased fast towards the end of season. Large value of fox was also observed at the soil-water interface and soil and roots surfaces, respectively. The results demonstrate that carbon isotopic fractionations which might be different in different conditions were sensitive to the estimations of fac and fox in paddy field.

  16. Metal isotopes and carbonate proxy archives: Model-based perspectives on diagenesis

    Science.gov (United States)

    Fantle, M. S.; Higgins, J. A.; Griffith, E. M.

    2014-12-01

    Metal isotopes are novel tools, and have expanded the geochemical toolbox for elucidating the functioning of the Earth over various time scales. Carbonate-based stable isotope proxies now extend well beyond the traditional major elements (C and O) to include Ca, as well as trace elements such as Sr, S, Mg, B, Li, Cd, and U. Such trace isotopic proxies may contain invaluable information about the Earth system in the past, but can be susceptible to diagenetic alteration over long time scales. It is therefore critical that diagenetic effects are understood and can be recognized in ancient rocks. The extent of alteration depends on reaction rate and advection velocity in the sedimentary section, and elemental partitioning and isotopic effects associated with diagenesis. Numerical approaches, such as reactive transport models, are extremely useful tools for constraining such variables, and for testing hypotheses related to alteration of proxy records. Reactive transport models allow for constraints on calcite recrystallization rates in natural systems; data from ODP Sites 807A, 1170A, 1171A, and 806B suggest rapid recrystallization in relatively young sediments, as well as a Ca isotopic fractionation factor (α) associated with calcite recrystallization close to 1 (Δ=0). While the former is critical for addressing the fidelity and accuracy of a variety of geochemical proxies, the latter is distinctly different from that associated with the formation of carbonates in the surface ocean (Δ~ -1.35‰), suggesting considerable isotopic leverage to alter Ca isotopes during diagenesis. While Ca isotopes are generally well buffered in carbonate-rich sediments, this leverage to alter may be expressed as a reduction in the amplitude of geochemical variability in the solid or as a result of reactions near the sediment-seawater interface (as seen at ODP Site 1221 associated with chemical burndown during the PETM). Further, the Ca and Mg isotopic compositions of shallow water

  17. Forensic utility of carbon isotope ratio variations in PVC tape backings.

    Science.gov (United States)

    Dietz, Marianne E; Stern, Libby A; Mehltretter, Andria Hobbs; Parish, Ashley; McLasky, Velvet; Aranda, Roman

    2012-03-01

    Forensic interest in adhesive tapes with polyvinyl chloride (PVC) backings (electrical tape) derives from their use in a variety of illicit activities. Due to the range of physical characteristics, chemical compositions, and homogeneity within a single roll of tape, traditional microscopic and chemical analyses can offer a high degree of discrimination between tapes, permitting the assessment of potential associations between evidentiary tape samples. The carbon isotope ratios of tapes could provide additional discrimination among tape samples. To evaluate whether carbon isotope ratios may be able to increase discrimination of electrical tapes, particularly with regards to different rolls of tape of the same product, we assessed the δ(13)C values of backings from 87 rolls of PVC-based black electrical tape (~20 brands, >60 products) Prior to analysis, adhesives were removed to prevent contamination by adhering debris, and plasticizers were extracted because of concern over their potential mobility. This result is consistent with each of these tapes having approximately the same plasticizer δ(13)C value and proportion of carbon in these plasticizers. The δ(13)C values of the 87 PVC tape backings ranged between -23.5 and -41.3 (‰, V-PDB), with negligible carbon isotopic variation within single rolls of tape, yet large variations among tape brands and tape products. Within this tape population, carbon isotope ratios permitted an average exclusion power of 93.7%, using a window of +/-0.3‰; the combination of carbon isotope ratio measurement with additional chemical and physical analyses raises the discrimination power to over 98.9%, with only 41 out of a possible 3741 pairs of tape samples being indistinguishable. There was a linear relationship between the δ(13)C value of tape backings and the change in δ(13)C value with the extraction of plasticizers. Analyses of pre- and post-blast tape sample pairs show that carbon isotope signatures are within 0.3‰ of

  18. Li isotopes in foraminifera: a new proxy for past ocean dissolved inorganic carbon

    Science.gov (United States)

    Vigier, N.; Rollion-Bard, C.; Erez, J.

    2009-12-01

    Past ocean pH and pCO2 are critical parameters for establishing relationships between Earth climate and carbon cycle. For the Miocene-Pleistocene period, two main proxies have been used: carbon isotopes of di-unsaturated alkenones extracted from sea cores, and boron isotope signatures of marine carbonates [1, 2]. Both techniques lead to selfconsistent palaeooceanic pH or pCO2 estimates, but are associated with large uncertainties. Moreover, the paleovariations calculated from boron isotope measurements are a matter of debate. Additional proxies are therefore needed. Based on an in-situ analytical technique recently developed [3], we analysed a series of foraminifera - Amphistegina - cultured under various conditions (in pH, T and Dissolved Inorganic Carbon). We show that the lithium isotope signature of the foraminifera correlates with the DIC (r2 = 0.93). Conversely, there is no dependency of Li isotope signature on pH or T. A simple model of biomineralization in which growth rate is a key parameter can fit the whole dataset, including published values for other foraminifera species [4, 5]. This strongly suggests that the DIC-δ7Li correlation highlighted by the cultured Amphistegina can also be applied to other species. These results, combined with the published oceanic Li and B isotope paleovariations [2, 4, 5], allow us to estimate the ocean DIC and pCO2 evolution for the past 18Ma. The similarity with the pCO2 curve given by carbon isotopes measured in di-unsaturated alkenones is striking. This supports the use of Li isotopes as a new proxy and adds support to the existing data. It also suggests, in contrast with the common view, a less significant role of river input on the variation of the ocean Li isotope composition, at least for the period considered. [1] Pagani et al. (2005) Science 309, 600-603. [2] Pearson & Palmer (2000) Nature 406, 695-699. [3] Vigier et al. (2007) G-cubed 8, Q01003 [4] Hall et al. (2005) Mar. Geology 217, 255-265 [5] Hathorne

  19. Carbon and Nitrogen Isotope Systematics in a Sector-Zoned Diamond from the Mir Kimberlite, Yakutia

    Science.gov (United States)

    Hauri, E.; Bulanova, G.; Pearson, G.; Griffin, B.

    2002-05-01

    A single Yakutian octahedral diamond, displaying striking cubic and octahedral growth sectors surrounded by an octahedral rim, has been analysed for carbon and nitrogen isotopic compositions by SIMS and for nitrogen concentration (by SIMS and FTIR) and nitrogen aggregation state (FTIR). A graphite "seed" inclusion identified within the diamond, enriched in K, Ca, Ti, Rb and Sr, provides evidence that the diamond may have grown from a carbonate melt/fluid interacting with upper mantle rocks. Carbon and nitrogen isotope compositions become progressively heavier from the core region (d13C = -7 to -5 and d15N= -3) towards the inner rim zones (d13C = -3 and d15N = +8.9 to +5) of the diamond. Nitrogen concentration and aggregation measurements show corresponding decreases that generally correlate with the isotopic variations. These systematic variations within the core and intermediate regions of the diamond are consistent with their formation during diamond growth from CO2-rich fluids as a continuous event, accompanied by slight progressive isotopic fractionation of carbon and nitrogen. However, the observed isotope and nitrogen abundance trends are not those predicted from thermodynamic modelling of fluid-solid equilibria in a C-N-O-H-bearing system due to changes in parameters such as fO2 (Deines, 1980; Deines et al 1989). Within the finely-zoned octahedral rim region, non-systematic variations in nitrogen abundance, nitrogen aggregation, and nitrogen and carbon isotope ratios were observed. Several interpretations are given for this phenomenon, including kinetic effects during growth of the diamond rim under different conditions from those of the core-intermediate regions, or rapidly changing fluid sources during the growth. No fractionation of nitrogen isotopes between cubic and octahedral growth zones was identified within the studied diamond, in contrast with the fractionation phenomena found in synthetic diamonds of mixed growth. Our results illustrate the

  20. Online stable carbon isotope ratio measurement in formic acid, acetic acid, methanol and ethanol in water by high performance liquid chromatography-isotope ratio mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Tagami, Keiko [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan)], E-mail: k_tagami@nirs.go.jp; Uchida, Shigeo [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan)

    2008-05-05

    A suitable analysis condition was determined for high performance liquid chromatography-isotope ratio mass spectrometry (HPLC-IRMS) while making sequential measurements of stable carbon isotope ratios of {delta}{sup 13}C in formic acid, acetic acid, methanol and ethanol dissolved in water. For this online column separation method, organic reagents are not applicable due to carbon contamination; thus, water and KH{sub 2}PO{sub 4} at low concentrations were tested as mobile phase in combination with a HyPURITY AQUASTAR{sup TM} column. Formic acid, acetic acid, methanol and ethanol were separated when 2 mM KH{sub 2}PO{sub 4} aqueous solution was used. Under the determined analysis condition for HPLC-IRMS, carbon concentrations could be measured quantitatively as well as carbon isotope ratio when carbon concentration was higher than 0.4 mM L for each chemical.

  1. Assessing diet in savanna herbivores using stable carbon isotope ratios of faeces

    Directory of Open Access Journals (Sweden)

    D. Codron

    2005-06-01

    Full Text Available In African savannas, browse-based resources (@3 plants are isotopically distinct from grasses (@4 plants. The carbon isotopic composition of the basic plant diet is recorded in animal tissues. Mammal faeces are a readily accessible, non-invasive, sample material for temporally resolved dietary reconstructions. Faeces, however, include both undigested plant matter and waste, hence accuracy of dietary calculations could potentially be compromised by shifts in plant isotopic values related to seasonal or spatial differences, or by variability in the isotopic differences between faeces and diet. A controlled feeding study of four ungulate species showed a small, consistent difference between diet and faeces of-0.9 o, irrespective of whether the diet was @3 or C4-based. Results from faeces oftaxa known to be pure grazers, pure browsers, and mixed-feeders from the Kruger National Park were entirely consistent with their diets, but the accuracy of dietary reconstructions is enhanced with data from local plant communities.

  2. Carbon isotope fractionation by the marine ammonia-oxidizing archaeon Nitrosopumilus maritimus

    OpenAIRE

    Könneke, Martin; Lipp, Julius Sebastian; Hinrichs, Kai-Uwe

    2012-01-01

    Abstract Ammonia-oxidizing archaea (AOA) are abundant and widely distributed microorganisms in aquatic and terrestrial habitats. By catalyzing the first and rate limiting step in nitrification, these chemolithoautotrophs play a significant role in the global nitrogen cycle and contribute to primary production. Here, the carbon isotopic fractionation relative to inorganic carbon source was determined for bulk biomass, biphytanes and polar lipid bound sugars of a marine AOA pure culture. Bu...

  3. Constraints on the formation and diagenesis of phosphorites using carbonate clumped isotopes

    Science.gov (United States)

    Stolper, Daniel A.; Eiler, John M.

    2016-05-01

    The isotopic composition of apatites from sedimentary phosphorite deposits has been used previously to reconstruct ancient conditions on the surface of the Earth. However, questions remain as to whether these minerals retain their original isotopic composition or are modified during burial and lithification. To better understand how apatites in phosphorites form and are diagenetically modified, we present new isotopic measurements of δ18O values and clumped-isotope-based (Δ47) temperatures of carbonate groups in apatites from phosphorites from the past 265 million years. We compare these measurements to previously measured δ18O values of phosphate groups from the same apatites. These results indicate that the isotopic composition of many of the apatites do not record environmental conditions during formation but instead diagenetic conditions. To understand these results, we construct a model that describes the consequences of diagenetic modification of phosphorites as functions of the environmental conditions (i.e., temperature and δ18O values of the fluids) during initial precipitation and subsequent diagenesis. This model captures the basic features of the dataset and indicates that clumped-isotope-based temperatures provide additional quantitative constraints on both the formational environment of the apatites and subsequent diagenetic modification. Importantly, the combination of the model with the data indicates that the δ18O values and clumped-isotope temperatures recorded by phosphorites do not record either formation or diagenetic temperatures, but rather represent an integrated history that includes both the formation and diagenetic modification of the apatites.

  4. Chromium isotope fractionation during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes

    the Archaean and Protoerozoic, needs careful assessment of the signal robustness and necessitates a thorough understanding of the Cr cycle in Earth system processes. We conducted experiments testing the incorporation and isotopic fractionation of chromate into the calcite lattice. Our experiments indicate...... et al., 2007, Water Air Soil Poll. 179, 381-390. [2] Sánchez-Pastor et al., 2011, Cryst. Growth Des. 11, 3081-3089....

  5. Determination of the geographical origin of Chinese teas based on stable carbon and nitrogen isotope ratios

    Institute of Scientific and Technical Information of China (English)

    Long ZHANG; Jia-rong PAN; Cheng ZHU

    2012-01-01

    The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong (GD),Guangxi (GX),Hainan (HA),Fujian (F J),Shandong (SD),Sichuan (SC),Chongqing (CQ),and Henan (HN) provinces was high,while in Zhejiang (ZJ),Hubei (HB),Yunnan (YN),and Anhui (AH) provinces,it was low.Tea samples from GD,GX,HA,and FJ provinces were clustered in one group and separated from those from AH and HB provinces.Thus,carbon and nitrogen stable isotope ratio technology could discriminate teas from among some provinces of China,but not from among others.Better separation might be obtained with a combination of isotopic ratios and other indexes,such as elemental data and organic components.

  6. Stable isotope composition of bulk and secondary carbonates from the Quaternary loess-paleosol sequence in Sutto, Hungary

    DEFF Research Database (Denmark)

    Koeniger, Paul; Barta, Gabriella; Thiel, Christine

    2014-01-01

    , and microscale secondary (authigenic) carbonates (calcified root cells, carbonate coatings, hypocoatings, and earthworm biospheroids) and concretions at 10 cm resolution were analysed to interpret stable isotope variations. Isotope values of bulk samples were in the range of 2.6 parts per thousand to -13.9 parts......, secondary carbonates showed more depleted values than bulk samples. Calcified root cells have the most depleted isotope composition with mean values of -16.0 parts per thousand and -11.8 parts per thousand for delta C-13 and 8180, respectively. Results indicate that loess and paleosol secondary carbonates...

  7. Studies of carbon--isotope fractionation. Annual progress report, December 1, 1974--November 30, 1975

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, T.

    1975-12-01

    The vapor pressure isotope effect of /sup 13/C//sup 12/C-substitution in CClF/sub 3/ was measured at temperatures between 169/sup 0/ and 206/sup 0/K by means of cryogenic distillation. The /sup 13/C//sup 12/C-vapor pressure isotope effect in CHF/sub 3/ was also studied at temperatures between 161/sup 0/ and 205/sup 0/K by a similar method. The construction of a cryostat has progressed as scheduled. The investigation of carbon isotope exchange equilibria between carbon dioxide and various carbamates dissolved in various organic solvents has continued. The five-stage system of Taylor-Ghate design was improved to shorten the transient time. A single stage apparatus was designed, built, and tested. These systems are used to measure the equilibrium constants and various phase equilibria involved in the carbon dioxide--carbamate system. The investigation of the explicit method of total isotope effect has made progress. A satisfactory approximation was found for the classical partition function of a Morse oscillator. The method gives a reasonable result at rho identical with /sup 1///sub 2/..sqrt..(u/sub e//x/sub e/) greater than 1.5. The medium cluster approach was applied to isotopic methanes to investigate the effects of intermolecular distance and mutual orientations of molecules in the liquid upon vapor pressure isotope effect. It was found that all geometrical effects studied tend to vanish as the size of clusters is increased. Isotope effect in the zero-point energy shifts on condensation was calculated on the basis of London dispersion forces in liquid and a semi-empirical molecular orbital theory, and was favorably compared with experimental results. (auth)

  8. Uranium isotopes in carbonate aquifers of arid region setting

    DEFF Research Database (Denmark)

    Alshamsi, Dalal M.; Murad, Ahmed A.; Aldahan, Ala

    2013-01-01

    Groundwater in arid and semiarid regions is vital resource for many uses and therefore information about concentrations of uranium isotopes among other chemical parameters are necessary. In the study presented here, distribution of 238U and 235U in groundwater of four selected locations in the so......Groundwater in arid and semiarid regions is vital resource for many uses and therefore information about concentrations of uranium isotopes among other chemical parameters are necessary. In the study presented here, distribution of 238U and 235U in groundwater of four selected locations...... in the southern Arabian peninsula, namely at two locations within the United Arab Emirates (UAE) and two locations in Oman are discussed. The analyses of the uranium isotopes were performed using ICP-MS and the results indicated a range of concentrations for 235U and 238 U at 3–39 ng L-1 (average: 18 ng L-1......) and 429–5,293 ng L-1 (average: 2,508 ng L-1) respectively. These uranium concentrations are below the higher permissible WHO limit for drinking water and also comparable to averages found in groundwater from similar aquifers in Florida and Tunisia. Negative correlation between rainfall and uranium...

  9. Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream

    Science.gov (United States)

    Doctor, D.H.; Kendall, C.; Sebestyen, S.D.; Shanley, J.B.; Ohte, N.; Boyer, E.W.

    2008-01-01

    The stable isotopic composition of dissolved inorganic carbon (??13C-DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed ?? 13C-DIC increased between 3-5??? from the stream source to the outlet weir approximately 0??5 km downstream, concomitant with increasing pH and decreasing PCO2. An increase in ??13C-DIC of 2.4 ?? 0??1??? per log unit decrease of excess PCO2 (stream PCO2 normalized to atmospheric PCO2) was observed from downstream transect data collected during snowmelt. Isotopic fractionation of DIC due to CO2 outgassing rather than exchange with atmospheric CO2 may be the primary cause of increased ?? 13C-DIC values downstream when PCO2 of surface freshwater exceeds twice the atmospheric CO2 concentration. Although CO2 outgassing caused a general increase in stream ??13C-DIC values, points of localized groundwater seepage into the stream were identified by decreases in ??13C-DIC and increases in DIC concentration of the stream water superimposed upon the general downstream trend. In addition, comparison between snowmelt, early spring and summer seasons showed that DIC is flushed from shallow groundwater flowpaths during snowmelt and is replaced by a greater proportion of DIC derived from soil CO2 during the early spring growing season. Thus, in spite of effects from CO2 outgassing, ??13C of DIC can be a useful indicator of groundwater additions to headwater streams and a tracer of carbon dynamics in catchments. Copyright ?? 2007 John Wiley & Sons, Ltd.

  10. Normalization of stable isotope data for carbonate minerals: implementation of IUPAC guideline

    Science.gov (United States)

    Kim, Sang-Tae; Coplen, Tyler B.; Horita, Juske

    2015-01-01

    Carbonate minerals provide a rich source of geochemical information because their δ13C and δ18O values provide information about surface and subsurface Earth processes. However, a significant problem is that the same δ18O value is not reported for the identical carbonate sample when analyzed in different isotope laboratories in spite of the fact that the International Union of Pure and Applied Chemistry (IUPAC) has provided reporting guidelines for two decades. This issue arises because (1) the δ18O measurements are performed on CO2 evolved by reaction of carbonates with phosphoric acid, (2) the acid-liberated CO2 is isotopically fractionated (enriched in 18O) because it contains only two-thirds of the oxygen from the solid carbonate, (3) this oxygen isotopic fractionation factor is a function of mineralogy, temperature, concentration of the phosphoric acid, and δ18O value of water in the phosphoric acid, (4) researchers may use any one of an assortment of oxygen isotopic fractionation factors that have been published for various minerals at various reaction temperatures, and (5) it sometimes is not clear how one should calculate δ18OVPDB values on a scale normalized such that the δ18O value of SLAP reference water is −55.5 ‰ relative to VSMOW reference water.

  11. Latitudinal differences in the amplitude of the OAE-2 carbon isotopic excursion:

    NARCIS (Netherlands)

    van Bentum, E.C.; Reichart, G.J.; Forster, A.; Sinninghe Damsté, J.S.S.

    2012-01-01

    A complete, well-preserved record of the Cenomanian/Turonian (C/T) Oceanic Anoxic Event 2 (OAE-2) was recovered from Demerara Rise in the southern North Atlantic Ocean (ODP site 1260). Across this interval, we determined changes in the stable carbon isotopic composition of sulfur-bound phytane (delt

  12. Analytical system for stable carbon isotope measurements of low molecular weight (C2-C6) hydrocarbons

    NARCIS (Netherlands)

    Zuiderweg, A.T.; Holzinger, R.; Roeckmann, T.

    2011-01-01

    We present setup, testing and initial results from a new automated system for stable carbon isotope ratio measurements on C2 to C6 atmospheric hydrocarbons. The inlet system allows analysis of trace gases from air samples ranging from a few liters for urban samples and samples with high mixing ratio

  13. Natural carbon isotopes used to study methane consumption and production in soil

    DEFF Research Database (Denmark)

    Ambus, Per; Andersen, Bertel Lohmann; Kemner, Marianne;

    2002-01-01

    Changes in the isotopic composition of carbon can be used to reveal simultaneous occurrence of methane production and oxidation in soil. The method is conducted in laboratory jar experiments as well as in the field by using flux chambers. Simultaneous occurrence of production and oxidation...

  14. ANALYTICAL EMPLOYMENT OF STABLE ISOTOPES OF CARBON, NITROGEN, OXYGEN AND HYDROGEN FOR FOOD AUTHENTICATION

    Directory of Open Access Journals (Sweden)

    E. Novelli

    2011-04-01

    Full Text Available Stable isotopes of carbon, nitrogen, oxygen and hydrogen were used for analytical purposes for the discrimination of the type of production (farming vs. fishing in the case of sea bass and for geographical origin in the case of milk. These results corroborate similar experimental evidences and confirm the potential of this analytical tool to support of food traceability.

  15. Combined carbon and hydrogen isotope fractionation investigations for elucidating benzene biodegradation pathways

    NARCIS (Netherlands)

    Fischer, A.; Herklotz, I.; Herrmann, S.; Thullner, M.; Weelink, S.A.B.; Stams, A.J.M.; Richnow, H.H.; Vogt, C.

    2008-01-01

    Recently, combined carbon and hydrogen isotope fractionation investigations have emerged as a powerful tool for the characterization of reaction mechanisms relevant for the removal of organic pollutants. Here, we applied this approach in order to differentiate benzene biodegradation pathways under o

  16. The puzzle of the CNO isotope ratios in AGB carbon stars

    CERN Document Server

    Abia, Carlos; Domínguez, Inma; Straniero, Oscar

    2016-01-01

    Previous determinations of the oxygen isotopic ratios in AGB carbon stars were at odds with the existing theoretical predictions. We aim to redetermine the oxygen ratios in these stars using new spectral analysis tools and further develop discussions on the carbon and nitrogen isotopic ratios in order to elucidate this problem. Oxygen isotopic ratios were derived from spectra in the K-band in a sample of galactic AGB carbon stars of different spectral types and near solar metallicity. Synthetic spectra calculated in LTE with spherical carbon-rich atmosphere models and updated molecular line lists were used. The CNO isotope ratios derived in a homogeneous way, were compared with theoretical predictions for low-mass (1.5-3 M_o) AGB stars computed with the FUNS code assuming extra mixing both during the RGB and AGB phases. For most of the stars the 16O/17O/18O ratios derived are in good agreement with theoretical predictions confirming that, for AGB stars, are established using the values reached after the FDU a...

  17. Carbon, cesium and iodine isotopes in Japanese cedar leaves from Iwaki, Fukushima

    DEFF Research Database (Denmark)

    Xu, Sheng; Cook, Gordon T.; Cresswell, Alan J.;

    2016-01-01

    Japanese cedar leaves from Iwaki, Fukushima were analyzed for carbon, cesium and iodine isotopic compositions before and after the 2011 nuclear accident. The Δ14C values reflect ambient atmospheric 14C concentrations during the year the leaves were sampled/defoliated, and also previous year...

  18. Stable carbon isotope fractionation of organic cyst-forming dinoflagellates: Evaluating the potential for a CO

    NARCIS (Netherlands)

    Hoins, M.; Van de Waal, D.B.; Eberlein, T.; Reichart, G.-J.; Rost, B.; Sluijs, A.

    2015-01-01

    Over the past decades, significant progress has been made regarding the quantification and mechanistic understanding of stable carbon isotope fractionation (13C fractionation) in photosynthetic unicellular organisms in response to changes in the partial pressure of atmospheric CO2 (pCO2). However, h

  19. Variations of sulfur and carbon isotopes in seawater during the Doushantuo stage in late Neoproterozoic

    Institute of Scientific and Technical Information of China (English)

    ZHANG Tonggang; CHU Xuelei; ZHANG Qirui; FENG Lianjun; HUO Weiguo

    2003-01-01

    Successive analyses of sulfur and carbon isotopic compositions of carbonates strata in the Doushantuo Formation in the Yangtze area were accomplished through a method of extracting trace sulfate from carbonates. Sulfur and carbon isotopic compositions of coeval seawater were estimated from the samples that show the least diagenetic alteration. A high-resolution age curve of sulfur isotopes in seawater sulfates was obtained in the Doushantuo stage, which reflects thetrend of variation in seawater sulfur isotopes after the Neoproterozoic snowball Earth event. Similar characteristics of variation in carbon isotopes were observed in the coeval carbonates. A large positive δ34S excursion over +20‰ occurs in ancient seawater sulfates in the early Doushantuo stage. Simultaneously, the δ13C values in ancient seawater carbonates exhibit a positive excursion up to10‰. The maximum δ34S and δ13C values are +46.4‰ and +6.9‰, respectively. In the middle Doushantuo stage, the range of variation in δ34S values of seawater is relatively narrow, but δ13C values are quite high. Then, δ34S values of seawater become oscillating, and the same occurs in δ13C values. Negative excursions in δ34S and δ13C values occur simultaneously at the end of the Doushantuo stage, and the minimum δ34S and δ13C values dropped down to -10.1‰ and -5.7‰, respectively. The characteristics of variations in the sulfur and carbon isotopes of ancient seawater imply strong changes in oceanic environment that became beneficial to inhabitation and propagation of organism. The organic productivity and burial rate of organic carbon once reached a quite high level during the Doushantuo stage. However, the state of environment became unstable after the global glaciation. The global climate and environment possibly were fluctuating and reiterating. The negative excursions in δ34S and δ13C values occurring at the end of the Doushantuo stage may represent a global event, which might be related to

  20. Stratigraphy, biostratigraphy and C-isotopes of the Permian-Triassic non-marine sequence at Dalongkou and Lucaogou, Xinjiang Province, China

    Science.gov (United States)

    Metcalfe, I.; Foster, C. B.; Afonin, S. A.; Nicoll, R. S.; Mundil, R.; Xiaofeng, Wang; Lucas, S. G.

    2009-11-01

    Measured lithostratigraphic sections of the classic Permian-Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P-T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian-Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ13C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian-Triassic boundary in the Junggar Basin remains problematic

  1. The puzzle of the CNO isotope ratios in asymptotic giant branch carbon stars

    Science.gov (United States)

    Abia, C.; Hedrosa, R. P.; Domínguez, I.; Straniero, O.

    2017-02-01

    Context. The abundance ratios of the main isotopes of carbon, nitrogen and oxygen are modified by the CNO-cycle in the stellar interiors. When the different dredge-up events mix the burning material with the envelope, valuable information on the nucleosynthesis and mixing processes can be extracted by measuring these isotope ratios. Aims: Previous determinations of the oxygen isotopic ratios in asymptotic giant branch (AGB) carbon stars were at odds with the existing theoretical predictions. We aim to redetermine the oxygen ratios in these stars using new spectral analysis tools and further develop discussions on the carbon and nitrogen isotopic ratios in order to elucidate this problem. Methods: Oxygen isotopic ratios were derived from spectra in the K-band in a sample of galactic AGB carbon stars of different spectral types and near solar metallicity. Synthetic spectra calculated in local thermodynamic equillibrium (LTE) with spherical carbon-rich atmosphere models and updated molecular line lists were used. The CNO isotope ratios derived in a homogeneous way, were compared with theoretical predictions for low-mass (1.5-3 M⊙) AGB stars computed with the FUNS code assuming extra mixing both during the RGB and AGB phases. Results: For most of the stars the 16O/17O/18O ratios derived are in good agreement with theoretical predictions confirming that, for AGB stars, are established using the values reached after the first dredge-up (FDU) according to the initial stellar mass. This fact, as far as the oxygen isotopic ratios are concerned, leaves little space for the operation of any extra mixing mechanism during the AGB phase. Nevertheless, for a few stars with large 16O/17O/18O, the operation of such a mechanism might be required, although their observed 12C/13C and 14N/15N ratios would be difficult to reconcile within this scenario. Furthermore, J-type stars tend to have lower 16O/17O ratios than the normal carbon stars, as already indicated in previous studies

  2. Carbon isotopes characterize rapid changes in atmospheric carbon dioxide during the last deglaciation

    Science.gov (United States)

    Bauska, Thomas K.; Baggenstos, Daniel; Brook, Edward J.; Mix, Alan C.; Marcott, Shaun A.; Petrenko, Vasilii V.; Schaefer, Hinrich; Lee, James E.

    2016-01-01

    An understanding of the mechanisms that control CO2 change during glacial–interglacial cycles remains elusive. Here we help to constrain changing sources with a high-precision, high-resolution deglacial record of the stable isotopic composition of carbon in CO2 (δ13C-CO2) in air extracted from ice samples from Taylor Glacier, Antarctica. During the initial rise in atmospheric CO2 from 17.6 to 15.5 ka, these data demarcate a decrease in δ13C-CO2, likely due to a weakened oceanic biological pump. From 15.5 to 11.5 ka, the continued atmospheric CO2 rise of 40 ppm is associated with small changes in δ13C-CO2, consistent with a nearly equal contribution from a further weakening of the biological pump and rising ocean temperature. These two trends, related to marine sources, are punctuated at 16.3 and 12.9 ka with abrupt, century-scale perturbations in δ13C-CO2 that suggest rapid oxidation of organic land carbon or enhanced air–sea gas exchange in the Southern Ocean. Additional century-scale increases in atmospheric CO2 coincident with increases in atmospheric CH4 and Northern Hemisphere temperature at the onset of the Bølling (14.6–14.3 ka) and Holocene (11.6–11.4 ka) intervals are associated with small changes in δ13C-CO2, suggesting a combination of sources that included rising surface ocean temperature. PMID:26976561

  3. Flow injection analysis-isotope ratio mass spectrometry for bulk carbon stable isotope analysis of alcoholic beverages.

    Science.gov (United States)

    Jochmann, Maik A; Steinmann, Dirk; Stephan, Manuel; Schmidt, Torsten C

    2009-11-25

    A new method for bulk carbon isotope ratio determination of water-soluble samples is presented that is based on flow injection analysis-isotope ratio mass spectrometry (FIA-IRMS) using an LC IsoLink interface. Advantages of the method are that (i) only very small amounts of sample are required (2-5 microL of the sample for up to 200 possible injections), (ii) it avoids complex sample preparation procedures such as needed for EA-IRMS analysis (only sample dilution and injection,) and (iii) high throughput due to short analysis times is possible (approximately 15 min for five replicates). The method was first tested and evaluated as a fast screening method with industrially produced ethanol samples, and additionally the applicability was tested by the measurement of 81 alcoholic beverages, for example, whiskey, brandy, vodka, tequila, and others. The minimal sample concentration required for precise and reproducible measurements was around 50 microL L(-1) ethanol/water (1.71 mM carbon). The limit of repeatability was determined to be r=0.49%. FIA-IRMS represents a fast screening method for beverage authenticity control. Due to this, samples can be prescreened as a decisive criterion for more detailed investigations by HPLC-IRMS or multielement GC-IRMS measurements for a verification of adulteration.

  4. Carbonate "clumped" isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    Directory of Open Access Journals (Sweden)

    J. Kimball

    2015-12-01

    Full Text Available Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near constant temperature, salinity and pH, and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop "clumped" isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly-substituted isotopologue 13C18O16O2 in carbonate minerals, analyzed in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ47 values. We analyzed Δ47 in live-collected aragonitic scleractinian (Enallopsammia sp. and calcitic gorgonian (Isididae and Coralliidae deep-sea corals, and compared results to published data for other aragonitic scleractinian taxa. Measured Δ47 values were compared to in situ temperatures and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than calcitic gorgonian corals and the two groups of coral produce statistically different relationship between Δ47-temperature calibrations. These data are significant in the interpretation of all carbonate "clumped" isotope calibration data as they show that distinct Δ47-temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset

  5. Carbonate "clumped" isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    Science.gov (United States)

    Kimball, Justine; Eagle, Robert; Dunbar, Robert

    2016-12-01

    Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near-constant temperature, salinity, and pH and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop "clumped" isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate-related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly substituted isotopologue 13C18O16O2 in carbonate minerals, analyzed in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ47 values. We analyzed Δ47 in live-collected aragonitic scleractinian (Enallopsammia sp.) and high-Mg calcitic gorgonian (Isididae and Coralliidae) deep-sea corals and compared results to published data for other aragonitic scleractinian taxa. Measured Δ47 values were compared to in situ temperatures, and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than high-Mg calcitic gorgonian corals and the two groups of coral produce statistically different relationships between Δ47-temperature calibrations. These data are significant in the interpretation of all carbonate clumped isotope calibration data as they show that distinct Δ47-temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset

  6. Calibration of the carbonate `clumped isotope' paleotemperature proxy using mollusc shells and benthic foraminiferal tests

    Science.gov (United States)

    Came, R. E.; Curry, W. B.; Weidman, C. R.; Eiler, J. M.

    2007-12-01

    It has recently been shown that the carbonate `clumped isotope' thermometer can provide temperature constraints that depend only on the isotopic composition of carbonate (in particular, on the proportion of 13C and 18O that form bonds with each other), and that do not require assumptions about the isotopic composition of the water in which the carbonate formed (Ghosh et al., 2006). Furthermore, this novel method permits the calculation of seawater δ18O based on the clumped isotope temperature estimates and the simultaneously obtained δ18O of carbonate, thereby enabling the extraction of global ice volume estimates for both the recent and distant geologic past. Here we present clumped isotope analyses of several naturally occurring marine carbonates that calcified at known temperatures in the modern ocean. First, we analyzed benthic foraminiferal tests from six high-quality multicore tops collected in the Florida Strait, spanning a temperature range of 9.3-20.2 degrees C. Second, we analyzed shallow-water mollusc shells from a variety of different climate regimes, spanning a temperature range of 2.5-26.0 degrees C. We find that the calcitic foraminiferal species Cibicidoides spp. agrees well with the inorganic calcite precipitation experiments of Ghosh et al. (2006), while the aragonitic species Hoeglundina elegans is significantly offset. Similarly, clumped isotope results obtained from aragonitic mollusc shells also reveal an offset from the Ghosh et al. (2006) trend, although the offset observed in mollusc aragonite is quite different in nature from that observed in foraminiferal aragonite. Assuming our estimates of the growth temperatures of these naturally occurring organisms are correct, these results suggest that there are vital effects associated with the stable isotope compositions of the aragonite-precipitating organisms examined in this study; further work will be required to determine their cause. Nevertheless, the internal coherence of trends for

  7. Carboniferous-Permian sedimentology and stratigraphy of the Nordfjorden High and Loppa Spur, Arctic Norway

    DEFF Research Database (Denmark)

    Ahlborn, Morten

    Abstract (shortened) Facies analysis of Late Paleozoic warm-water carbonates, were conducted in order to investigate the depositional evolution, cyclicity, internal architecture and sequence stratigraphy of the upper Gipsdalen Group carbonate platform on the Nordfjorden High in central Spitsberge...

  8. Carbon Isotopic Fractionation During Formation of Macromolecular Organic Grain Coatings via FTT Reactions

    Science.gov (United States)

    Nuth, J. A.; Johnson, N. M.; Elsila-Cook, J.; Kopstein, M.

    2011-01-01

    Observations of carbon isotopic fractionation of various organic compounds found in meteorites may provide useful diagnostic information concerning the environments and mechanisms that were responsible for their formation. Unfortunately, carbon has only two stable isotopes, making interpretation of such observations quite problematic. Chemical reactions can increase or decrease the C-13/C-12 ratio by various amounts, but the final ratio will depend on the total reaction pathway followed from the source carbon to the final product, a path not readily discernable after 4.5 billion years. In 1970 Libby showed that the C-13/C-12 ratios of terrestrial and meteoritic carbon were similar by comparing carbon from the Murchison meteorite to that of terrestrial sediments. More recent studies have shown that the C-13/C-12 ratio of the Earth and meteorites may be considerably enriched in C-13 compared to the ratio observed in the solar wind [2], possibly suggesting that carbon produced via ion-molecule reactions in cold dark clouds could be an important source of terrestrial and meteoritic carbon. However, meteoritic carbon has been subjected to parent body processing that could have resulted in significant changes to the C-13/C-12 ratio originally present while significant variation has been observed in the C-13/C-12 ratio of the same molecule extracted from different terrestrial sources. Again we must conclude that understanding the ratio found in meteorites may be difficult.

  9. Anomalous carbon-isotope ratios in nonvolatile organic material.

    Science.gov (United States)

    Kaplan, I R; Nissenbaum, A

    1966-08-12

    Organic mats are associated with sulfur deposits in Upper Pleistocene sand ridges of the coastal plain of southern Israel; black, brittle, and non-volatile, they show parallel layering but no other apparent cellular structure. Two independent carbon-14 determinations yielded ages of 27,750+/-500 and 31,370+/-1400 years. Four carbon-13:carbon-12 determinations fell within the range deltaC(13) =-82.5 to -89.3 per mille relative to the PDB standard; these appear to be the lowest values yet reported for naturally occurring high-molecular-weight organic material. The origin of the carbon is probably complex; it must have passed through at least one biologic cycle before final deposition.

  10. An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water

    Institute of Scientific and Technical Information of China (English)

    XIAO Yingkai; LI Shizhen; WEI Haizhen; SUN Aide; ZHOU Weijian; LIU Weiguo

    2006-01-01

    Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally. The results show the clear positive relationships between boron concentration and δ11B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic fractionation between inorganic calcite and seawater/saline water with pH are inconsistent with the hypothesis that B(OH)4- is the dominant species incorporated into the biogenic calcite structure. The isotopic fractionation factors α Between synthetic calcium carbonate precipitate and parent solutions increase systematically as pH increases, from 0.9884 at pH 7.60 to 1.0072 at pH 8.60 for seawater and from 0.9826 at pH 7.60 to 1.0178 at pH 8.75 for saline water. An unusual boron isotopic fractionation factor of larger than 1 in synthetic calcium carbonate precipitated from seawater/saline water at higher pH is observed, which implies that a substantial amount of the isotopically heavier B(OH)3 species must be incorporated preferentially into synthetic inorganic carbonate. The results propose that the incorporation of B(OH)3 is attributed to the formation of Mg(OH)2 at higher pH of calcifying microenvironment during the synthetic calcium carbonate precipitation. The preliminary experiment of Mg(OH)2 precipitated from artificial seawater shows that heavier 11B is enriched in Mg(OH)2 precipitation, which suggests that isotopically heavier B(OH)3 species incorporated preferentially into Mg(OH)2 precipitation.This result cannot be applied to explain the boron isotopic fractionation of marine bio-carbonate because of the possibility that the unusual environment in this study appears in formation of marine bio-carbonate is infinitesimal. We, however, must pay more attention to this phenomenon observed in this study, which accidentally appears in especially natural environment.

  11. Carbon isotope ratios of Phanerozoic marine cements: Re-evaluating the global carbon and sulfur systems

    Science.gov (United States)

    Carpenter, Scott J.; Lohmann, Kyger C.

    1997-11-01

    Original δ 13C values of abiotically precipitated marine cements from a variety of stratigraphic intervals have been used to document secular variations in the δ 13C values of Phanerozoic oceans. These, together with the ° 34S values of coeval marine sulfates, are used to examine the global cycling of carbon and sulfur. It is generally accepted that secular variation in δ 13C and δ 34S values of marine carbonates and sulfates is controlled by balanced oxidation-reduction reactions and that their long-term, steady-state variation can be predicted from the present-day isotopic fractionation ratio (Δ c/Δ s) the ratio of the riverine flux of sulfur and carbon ( Fs/ Fc). The predicted slope of the linear relation between δ 13C carb and δ 34S sulfate values is approximately -0.10 to -0.14. However, temporal variation observed in marine cement δ 13C values and the 6345 values of coeval marine sulfates produces a highly significant linear relation ( r2 = 0.80; α > 95%) with a slope of -0.24; approximately twice the predicted value. This discordance suggests that either the Phanerozoic average riverine Fs/ Fc was 1.6-3.3 times greater than today's estimates or that an additional source of 34S-depleted sulfur or 13C-enriched carbon, other than continental reservoirs, was active during the Phanerozoic. This new relation between marine δ 13C and δ 34S values suggests that the flux of reduced sulfur, iron, and manganese from seafloor hydrothermal systems affects oceanic O2 levels which, in turn, control the oxidation or burial of organic matter, and thus the δ 13C value of marine DIC. Therefore, the sulfur system (driven by seafloor hydrothermal systems) controls the carbon system rather than organic carbon burial controlling the response of δ 34S values (via formation of sedimentary pyrite). Secular variation of marine 87Sr/86Sr ratios and δ 13C values argues for a coupling of δ 34S and δ 34S values to variation in the relative contribution of seafloor

  12. Stable carbon isotope ratios of intact GDGTs indicate heterogeneous sources to marine sediments

    Science.gov (United States)

    Pearson, Ann; Hurley, Sarah J.; Walter, Sunita R. Shah; Kusch, Stephanie; Lichtin, Samantha; Zhang, Yi Ge

    2016-05-01

    Thaumarchaeota, the major sources of marine glycerol dibiphytanyl glycerol tetraether lipids (GDGTs), are believed to fix the majority of their carbon directly from dissolved inorganic carbon (DIC). The δ13C values of GDGTs (δ13CGDGT) may be powerful tools for reconstructing variations in the ocean carbon cycle, including paleoproductivity and water mass circulation, if they can be related to values of δ13CDIC. To date, isotope measurements primarily are made on the C40 biphytane skeletons of GDGTs, rather than on complete tetraether structures. This approach erases information revealed by the isotopic heterogeneity of GDGTs within a sample and may impart an isotopic fractionation associated with the ether cleavage. To circumvent these issues, we present δ13C values for GDGTs from twelve recent sediments representing ten continental margin locations. Samples are purified by orthogonal dimensions of HPLC, followed by measurement of δ13C values by Spooling Wire Microcombustion (SWiM)-isotope ratio mass spectrometry (IRMS) with 1σ precision and accuracy of ±0.25‰. Using this approach, we confirm that GDGTs, generally around -19‰, are isotopically "heavy" compared to other marine lipids. However, measured δ13CGDGT values are inconsistent with predicted values based on the 13C content of DIC in the overlying water column and the previously-published biosynthetic isotope fractionation for a pure culture of an autotrophic marine thaumarchaeon. In some sediments, the isotopic composition of individual GDGTs differs, indicating multiple source inputs. The data appear to confirm that crenarchaeol primarily is a biomarker for Thaumarchaeota, but its δ13C values still cannot be explained solely by autotrophic carbon fixation. Overall the complexity of the results suggests that both organic carbon assimilation (ca. 25% of total carbon) and multiple source(s) of exogenous GDGTs (contributing generally <30% of input to sediments) are necessary to explain the observed

  13. A new 0.9 Ma oxygen isotope stratigraphy for a shallow-water sedimentary transect across three IODP 317 sites in the Canterbury Bight of southwest Pacific Ocean

    Science.gov (United States)

    Ding, Xuan; Wu, YingYing

    2016-04-01

    Sedimentary records in shallow-water environment provide unique opportunity to further our understanding on the regional relative sea level changes in relation to global climate change. Here we present a new 0.9 Ma oxygen isotope stratigraphy for a shallow-water sedimentary transect across three IODP 317 sites in the Canterbury Bight of southwest Pacific Ocean. The three sites are located on the eastern margin of the South Island of New Zealand, including a continental slope site, IODP317-U1352 and two continental shelf sites, IODP317-U1354 and IODP317-U1351. We first generated high resolution benthic foraminifers (Nonionella flemingi) δ18O records for the three sites and a planktonic (Globigerina bulloides) record for the U1352B. An initial chronological framework for the benthic δ18O record of the U1352B was constructed using 8 accelerator mass spectrometry (AMS) radiocarbon dates and 4 biostratigraphic events. Then a refined age model was established by correlating the U1352B benthic δ18O record with the EDC δD record on the AICC2012 time-scale, and the LR04 benthic δ18O stack. Although the U1354B and U1351B have lower sedimentation rates, their benthic δ18O records correlate well with that of U1352B. In order to ensure the accuracy of the chronostratigraphic framework established, we also analyzed the characteristics of sedimentary grain size and the planktonic and benthic δ18O values. In accord with the adjacent sites, the results show that the melt of Southern Alps glaciers due to the warming climate during MIS 11 and 5.5 led to the increased fresh water delivery, with massive terrigenous deposit; and the warm SST during the MIS7 is related with the STF migration, which led to strong current activity, with coarser grain size. Meanwhile, records of benthic δ18O, sedimentation rate and content of >63μm coarse fraction of site U1352 all indicate the MIS 20 was indeed a colder interval compared to subsequent glacial times.

  14. Mixing of water in a carbonate aquifer, southern Italy, analysed through stable isotope investigations

    Directory of Open Access Journals (Sweden)

    Petrella Emma

    2013-01-01

    Full Text Available Mixing of water was analysed in a carbonate aquifer, southern Italy, through stable isotope investigations (18O,δ2H. The input signal (rainwater was compared with the isotopic content of a 35-meter groundwater vertical prof ile, over a 1-year period. Within the studied aquifer, recharge and f low are diffuse in a well-connected f issure network.At the test site, the comparison between input and groundwater isotopic signals illustrates that no eff icient mixing takes place in the whole unsaturated zone, between the fresh inf iltration water and the stored water.When analysing the stable isotope composition of groundwater, signif icant variations were observed above the threshold elevation of 1062 m asl, while a nearly constant composition was observed below the same threshold. Thus, temporal variations in stable isotope composition of rainwater are completely attenuated just in the deeper phreatic zone.On the whole, taking into consideration also the results of previous studies in the same area, the investigations showed that physical characteristics of the carbonate bedrock, as well as aquifer heterogeneity, are factors of utmost importance in inf luencing the complete mixing of water. These f indings suggest a more complex scenario at catchment scale.

  15. Organic Carbon Isotopic Evolution during the Ediacaran-Cambrian Transition Interval in Eastern Guizhou, South China: Paleoenvironmental and Stratigraphic Implications

    Institute of Scientific and Technical Information of China (English)

    YANG Xinglian; ZHU Maoyan; GUO Qingjun; ZHAO Yuanlong

    2007-01-01

    Secular variations of carbon isotopic composition of organic carbon can be used in the study of global environmental variation, the carbon cycle, stratigraphic delimitation, and biological evolution, etc. Organic carbon isotopic analysis of the Nangao and Zhalagou sections in eastern Guizhou reveals a negative excursion near the Precambrian-Cambrian boundary that correlates with a distinct carbonate carbon isotopic negative excursion at this boundary globally. Our results also demonstrate that several alternating positive and negative shifts occur in the Meishucunian, and an obvious negative anomaly appears at the boundary between the Meishucunian and Qiongzhusian. The isotope values are stable in the middle and lower parts but became more positive in the upper part of the Qiongzhusian. Evolution of organic carbon isotopes from the two sections in the deepwater facies can be well correlated with that of the carbonate carbon isotopes from the section in the shallow water facies. Integrated with other stratigraphic tools, we can precisely establish a lower Cambrian stratigraphic framework from shallow shelf to deep basin of the Yangtze Platform.

  16. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>20072053 Bao Qingzhon(Shenyang Institute of Geology and Mineral Resources,China Geological Survey,Shenyang,Liaoning 110032,China);Zhang Changjie Carboniferous-Permian Marine Lithostratigraphy and Sequence Stratigraphy in Xi Ujimqin Qi,Southeastern Inner Mongolia,China(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,25(5),2006,p.572-579,4 illus.,2 tables,26 refs.,with English abstract)

  17. HISTORICAL GEOLOGY & STRATIGRAPHY

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    <正>20141624 Cai Xiongfei(Key Laboratory of Geobiology and Environmental Geology,Ministry of Education,China University of Geosciences,Wuhan 430074,China);Yang Jie A Restudy of the Upper Sinian Zhengmuguan and Tuerkeng Formations in the Helan Mountains(Journal of Stratigraphy,ISSN0253-4959CN32-1187/P,37(3),2013,p.377-386,5 illus.,2 tables,10 refs.)

  18. Carbon and oxygen isotopic ratios for nearby miras

    CERN Document Server

    Hinkle, K H; Straniero, O

    2016-01-01

    C and O isotopic ratios are reported for a sample of 46 Mira and SRa-type variable AGB stars. Vibration-rotation 1st and 2nd overtone CO lines in 1.5 to 2.5 $\\mu$m spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and 16O/18O. Comparisons with previous measurements for individual stars and with various samples of evolved stars are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of the M stars had main sequence masses < 2 Msun and have not experienced sizable third dredge-up episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the 6 C stars in the sample three have clear evidence relating their origin to the occurrence of the third dredge-up. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars...

  19. The carbon isotope composition of atmospheric CO 2 in Paris

    Science.gov (United States)

    Widory, David; Javoy, Marc

    2003-10-01

    One characteristic of air pollution in the urban environment is high CO 2 concentrations resulting from human activities. Determining the relative contributions of the different CO 2 sources can be addressed simply and elegantly by combining isotope and concentration measurements. Using this approach on atmospheric CO 2 samples collected in Paris, its suburbs and the open country provides fairly accurate conclusions. Our results show that air pollution within the first few metres above ground results basically from binary mixtures among which road traffic is the main contributor and, in particular, vehicles using unleaded gasoline (˜90% of the total). Heating sources, which account for 50% of the CO 2 input below the atmospheric inversion level, and vehicles using diesel contribute very little. Human respiration has a recognisable signature at street level under certain circumstances. The combined isotope and concentration analysis provides a sensitive tracer of local variations, even detecting the occasional prevalence of human respiration and the onset of actions in which natural gas is burnt. It also detects surprising inlets of 'clean air' (CO 2-wise) in the very centre of the city.

  20. Mechanical stratigraphy and normal faulting

    Science.gov (United States)

    Ferrill, David A.; Morris, Alan P.; McGinnis, Ronald N.; Smart, Kevin J.; Wigginton, Sarah S.; Hill, Nicola J.

    2017-01-01

    Mechanical stratigraphy encompasses the mechanical properties, thicknesses, and interface properties of rock units. Although mechanical stratigraphy often relates directly to lithostratigraphy, lithologic description alone does not adequately describe mechanical behavior. Analyses of normal faults with displacements of millimeters to 10's of kilometers in mechanically layered rocks reveal that mechanical stratigraphy influences nucleation, failure mode, fault geometry, displacement gradient, displacement distribution, fault core and damage zone characteristics, and fault zone deformation processes. The relationship between normal faulting and mechanical stratigraphy can be used either to predict structural style using knowledge of mechanical stratigraphy, or conversely to interpret mechanical stratigraphy based on characterization of the structural style. This review paper explores a range of mechanical stratigraphic controls on normal faulting illustrated by natural and modeled examples.

  1. Chromium Isotopes in Carbonate Rocks: New Insights into Proterozoic Atmospheric Oxygenation

    Science.gov (United States)

    Kah, L. C.; Gilleaudeau, G. J.; Frei, R.; Kaufman, A. J.; Azmy, K.; Bartley, J. K.; Chernyavskiy, P.; Knoll, A. H.

    2015-12-01

    There has been a long-standing debate in geobiology about the role that Earth's oxygenation played in the evolution of complex life. Temporal linkages exist between the Great Oxidation Event (GOE) and the evolution of eukaryotes, as well as Neoproterozoic rise in oxygen and the diversification of metazoans. Further advances have been hampered, however, by the lack of direct proxies that mark specific levels of atmospheric pO2 in the geologic past. Chromium (Cr) isotopes show promise in this regard because the oxidation of Cr during terrestrial weathering—which results in isotopic fractionation—is dependent on a specific threshold of atmospheric pO2 (0.1-1% of the present atmospheric level [PAL]). This threshold value broadly coincides with recent estimates of the oxygen requirements of early animals. Here we report new Cr-isotope data from four late Mesoproterozoic carbonate-dominated successions. Samples were collected from the Turukhansk Uplift (Siberia), the El Mreiti Group (Mauritania), the Vazante Group (Brazil), and the Angmaat Formation (Canada). We emphasize the application of Cr-isotopes to carbonate rocks because the broad temporal range of this lithology in the geologic record provides an opportunity to significantly expand our understanding of Proterozoic oxygenation on shorter time scales. Our data indicate that pO2 levels required to support early animals were attained long before Neoproterozoic metazoan diversification, although the large degree of isotopic heterogeneity in our dataset may indicate that pO2 > 0.1-1% PAL was only a transient phenomenon in the Mesoproterozoic. This study demonstrates the utility of Cr-isotopes as an atmospheric redox proxy in carbonate rocks and helps inform future avenues of research on Proterozoic pO2 thresholds.

  2. Simulating stable carbon and chlorine isotope ratios in dissolved chlorinated groundwater pollutants with BIOCHLOR-ISO

    Science.gov (United States)

    Höhener, Patrick

    2016-12-01

    BIOCHLOR is a well-known simple tool for evaluating the transport of dissolved chlorinated solvents in groundwater, ideal for rapid screening and teaching. This work extends the BIOCHLOR model for the calculation of stable isotope ratios of carbon and chlorine isotopes in chloroethenes. An exact solution for the three-dimensional reactive transport of a chain of degrading compounds including sorption is provided in a spreadsheet and applied for modeling the transport of individual isotopes 12C, 13C, 35Cl, 37Cl from a constant source. The model can consider secondary isotope effects that can occur in the breaking of Csbnd Cl bonds. The model is correctly reproducing results for δ13C and δ37Cl modeled by a previously published 1-D numerical model without secondary isotope effects, and is also reproducing results from a microcosm experiment with secondary chlorine isotope effects. Two applications of the model using field data from literature are further given and discussed. The new BIOCHLOR-ISO model is distributed as a spreadsheet (MS EXCEL) along with this publication.

  3. Assessing the duration and possible causes of the earliest Toarcian carbon isotopic excursion

    Science.gov (United States)

    Krencker, Francois-Nicolas; Bodin, Stéphane; Suan, Guillaume; Kabiri, Lahcen; Immenhauser, Adrian

    2013-04-01

    The early Toarcian stage (Early Jurassic) records two short-lived events of major faunal turnover and environmental perturbation. The first event (eT-E) occurs during the earliest Toarcian (early Polymorphum chronozone) and has been documented only in a few sites worldwide. The second event, better known as the Toarcian Oceanic Anoxic Event (T-OAE) has been documented in numerous sites from Northern Siberia to Argentina. Both events are marked by negative carbon isotope excursions (CIE) recorded in carbonate and organic substrate. Therefore they are thought to be associated with major changes in carbon cycling. Similarities between the eT-E and the T-OAE thus lead to the conclusion that these events might have been triggered by similar mechanisms. If this is the case, the CIEs associated with both events should have a comparable duration. In order to valid or falsify this hypothesis, it is therefore crucial to constrain the duration of both events. The duration of the T-OAE CIE was assessed in several papers by cyclostratigraphic analyses thanks to favourable outcropping condition. It is however not the case for the eT-E CIE, this latter being often associated with sedimentary condensation or hiatal surfaces. We make use of the high palaeo-subsidence rates of the Lower Toarcian Moroccan shelf leading to extended sections in the High Atlas Basin. The Foum Tillicht section was sampled in increments of 20 cm across a stratigraphic interval of 50 m, covering the Polymorphum chronozone. Carbon and oxygen isotopes analyses were performed on micritic and organic matter. Ammonites and nannofossils biostratigraphy aided in calibrating geochemical analyses. Carbon isotopes data display a rhythmic pattern. Preliminary results indicate that the eT-E negative carbon isotope excursion lasted around 400 kyr.

  4. FAR-DEEP: organic carbon isotope chemostratigraphy of early Paleoproterozoic sediments from Fennoscandia

    Science.gov (United States)

    Illing, C. J.; Strauss, H.; Summons, R. E.; Kump, L.; Fallick, A. E.; Melezhik, V.; Far-Deep Scientists

    2010-12-01

    One major objective of the Fennoscandian Arctic Russia - Drilling Early Earth Project (FAR-DEEP) is to reconstruct ancient microbial ecosystems and the evolution of key metabolic pathways during the Archean-Proterozoic Transition (APT). Fifteen drill cores with a total length of 3650m were retrieved in three areas (Imandra/Varzuga and Pechenga Greenstone belts and Onega Basin) in northern Russia. Cores cover a time interval of some 700 my and have archived several important changes in Earth’s environment. Among them, the Great Oxygenation Event (GOE) at ca. 2350 million years ago resulted in large-scale environmental changes (e.g. Melezhik et al., 2005). Of similar importance, but specifically for global carbon cycling, are the Lomagundi-Jatuli Event (LJE; e.g. Melezhik et al., 2007) and the Shunga Event (SE; e.g. Melezhik et al., 2009). This work presents preliminary carbon isotope results for sedimentary organic matter (δ13Corg) contained in the major sedimentary formations cored by FAR-DEEP. The samples were processed via sealed tube combustion. The total variation in δ13Corg between -40 and -17 ‰ agrees well with previously published data (e.g. Eigenbrode and Freeman, 2006). But more informative than the organic carbon isotopic composition alone is the isotopic difference (Δ13C) between the organic (δ13Corg) and carbonate carbon (δ13Ccarb) isotopic composition: Δ13C = δ13Ccarb - δ13Corg This parameter provides information about the isotopic fractionation associated with biosynthesis and carbon cycling (e.g., Des Marais, 2001). Sediments from the lower Kuetsjärvi Formation (core 5A) and the upper part of the Tulomozero Formation (cores 10A, 10B, 11A), covering the LJE, display Δ13C values between 30 and 37‰. This isotopic difference continuous through the SE (cores 12A/B and 13). The broad parallel evolution of δ13Corg and δ13Ccarb indicates that respective perturbations affected the global carbon cycle. However, further refinement will be

  5. Effect of Different Carbon Substrates on Nitrate Stable Isotope Fractionation During Microbial Denitrification

    DEFF Research Database (Denmark)

    Wunderlich, Anja; Meckenstock, Rainer; Einsiedl, Florian

    2012-01-01

    .1 ± 0.8‰; ε18O, −23.7 ± 1.8‰ to −19.9 ± 0.8‰). The observed isotope effects did not depend on the growth kinetics which were similar for the three types of electron donors. We suggest that different carbon sources change the observed isotope enrichment factors by changing the relative kinetics...... of nitrate transport across the cell wall compared to the kinetics of the intracellular nitrate reduction step of microbial denitrification....

  6. Stable carbon isotope fractionation during the biodegradation of lambda-cyhalothrin

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Xiaoli [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Department of Environmental Engineering, Quzhou University, Quzhou 324000 (China); Xu, Zemin [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Zhang, Xichang [Laboratory for Teaching in Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Yang, Fangxing, E-mail: fxyang@zju.edu.cn [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Department of Effect-Directed Analysis, Helmholtz Centre for Environmental Research — UFZ, Leipzig 04318 (Germany)

    2015-11-01

    In this study, the microbial degradation of lambda-cyhalothrin in soil was investigated using compound-specific stable isotope analysis. The results revealed that lambda-cyhalothrin was biodegraded in soil under laboratory conditions. The half-lives of lambda-cyhalothrin were determined to be 49 and 161 days in non-sterile and sterile soils spiked with 2 mg/kg lambda-cyhalothrin and 84 and 154 days in non-sterile and sterile soils spiked with 10 mg/kg lambda-cyhalothrin, respectively. The biodegradation of lambda-cyhalothrin resulted in carbon isotope fractionation, which shifted from − 29.0‰ to − 26.5‰ in soil spiked with 2 mg/kg lambda-cyhalothrin, and to − 27.5‰ with 10 mg/kg lambda-cyhalothrin. A relationship was established between the stable carbon isotope fraction and the residual concentrations of lambda-cyhalothrin by the Rayleigh equation in which the carbon isotope enrichment factor ε of the microbial degradation of lambda-cyhalothrin in the soil was calculated as − 2.53‰. This study provides an approach to quantitatively evaluate the biodegradation of lambda-cyhalothrin in soil in field studies. - Highlights: • Abiotic and biotic degradation of lambda-cyhalothrin were observed in soil. • Biodegradation of lambda-cyhalothrin was evaluated by CSIA. • Biodegradation of lambda-cyhalothrin leads to carbon isotope fractionation. • An enrichment factor ε of lambda-cyhalothrin was determined as − 2.53‰.

  7. Carbon isotope geochemistry of the Santa Clara River

    OpenAIRE

    2001-01-01

    The Santa Clara River is a prototypical small mountainous river, with a headwater height greater than 1000 m and a basin area smaller than 10,000 m 2. Although individual small mountainous rivers export trivial amounts of sediment and carbon to the ocean, as a group these rivers may export a major fraction (as much as 50%) of the total global river sediment flux [Milliman and Syvitski, 1992], making their geochemistry relevant the study of the ocean's carbon cycle. In addition, many small riv...

  8. Late Permian-earliest Triassic high-resolution organic carbon isotope and palynofacies records from Kap Stosch (East Greenland)

    Science.gov (United States)

    Sanson-Barrera, Anna; Hochuli, Peter A.; Bucher, Hugo; Schneebeli-Hermann, Elke; Weissert, Helmut; Adatte, Thierry; Bernasconi, Stefano M.

    2015-10-01

    During and after the end Permian mass extinction terrestrial and marine biota underwent major changes and reorganizations. The latest Permian and earliest Triassic is also characterized by major negative carbon isotope shifts reflecting fundamental changes in the carbon cycle. The present study documents a high-resolution bulk organic carbon isotope record and palynofacies analysis spanning the latest Permian-earliest Triassic of East Greenland. An almost 700 meter thick composite section from Kap Stosch allowed discriminating 6 chemostratigraphic intervals that provide the basis for the correlation with other coeval records across the world, and for the recognition of basin wide transgressive-regressive events documenting tectonic activity during the opening of the Greenland-Norway Basin. The identification of the main factors that influenced the organic carbon isotope signal during the earliest Triassic (Griesbachian to Dienerian) was possible due to the combination of bulk organic carbon isotope, palynofacies and Rock-Eval data. Two negative carbon isotopic shifts in the Kap Stosch record can be correlated with negative shifts recorded in coeval sections across the globe. A first negative shift precedes the base of the Triassic as defined by the first occurrence of the conodont Hindeodus parvus in the Meishan reference section, and the second one coincides with the suggested Griesbachian-Dienerian boundary. This new organic carbon isotope record from the extended Kap Stosch section from the Boreal Realm documents regional and global carbon cycle signals of the interval between the latest Palaeozoic and the onset of the Mesozoic.

  9. Clumped isotope thermometry of modern and early Cretaceous molluscan carbonate from high-latitude seas (Invited)

    Science.gov (United States)

    Henkes, G. A.; Price, G. D.; Ambrose, W. G.; Carroll, M. L.; Passey, B. H.

    2010-12-01

    The carbonate clumped isotope thermometer is based on the temperature sensitivity of the relative abundance of carbonate ion groups containing 13C-18O bonds. One application of clumped isotope thermometry is to determine the temperature of ancient seawater from the skeletal material of calcium carbonate-secreting marine organisms. The relationship between Δ47, a parameter describing isotopic clumping, and the temperature of carbonate biomineralization has been well-defined for fish otoliths, corals, foraminifera, and coccolithophore tests, but few data have been published for brachiopods and bivalve mollusks. A comprehensive evaluation of the Δ47-temperature relationship for mollusks is required for paleotemperature interpretations from the marine fossil record. Here we present a more comprehensive calibration for modern mollusks, including bivalves, cephalopods, and gastropods. Further, we focus on a subset of cold water, high-latitude species collected in the northern Barents Sea. The observed Δ47-temperature relationship is similar to the theoretical relationship presented by Guo et al. (2009) but deviates at low temperatures from the original Ghosh et al. (2007) calibration curve. This divergence could be related to methodological differences or unaccounted differences in the biomineralization of mollusks versus that of other carbonate-secreting organisms at low temperature. One advantage of clumped isotope thermometry over traditional oxygen isotope thermometry is that it does not require assumptions about the isotopic composition of the water in which the carbonate formed. This may be particularly useful in Mesozoic paleoceanography where the oxygen isotope value of seawater is uncertain. Using clumped isotope thermometry applied to early Cretaceous (Valangian) belemnite carbonate from the Yatria River, sub-polar Urals, Siberia, we find shell growth temperatures of 20-26°C at a paleolatitude of ~60-65°N. Our data imply average seawater δ18O values of 0

  10. Correlation of aptian-albian carbon isotope excursions in continental strata of the cretaceous Foreland Basin, Eastern Utah, U.S.A.

    Science.gov (United States)

    Ludvigson, Greg A.; Joeckel, R.M.; Gonzalez, Luis A.; Gulbranson, E.L.; Rasbury, E.T.; Hunt, G.J.; Kirkland, J.I.; Madsen, S.

    2010-01-01

    Nodular carbonates ("calcretes") in continental foreland-basin strata of the Early Cretaceous Cedar Mountain Formation (CMF) in eastern Utah yield ??13C and ??O records of changes in the exogenic carbon cycle related to oceanic anoxic events (OAEs), and terrestrial paleoclimate. Chemostratigraphic profiles of both forebulge and foredeep sections show two prominent positive ??13C excursions, each with a peak value of -3% VPDB, and having background ??13C values of about -6% VPDB. These excursions correlate with the global early Aptian (Ap7) and late Aptian-early Albian (Apl2-All) carbon isotope excursions. Aptian-Albian positive ??13C excursions in the CMF also correspond to 3-4 per mil increases in carbonate ??18O. These phenomena record local aridification events. The chemostratigraphic profile on the thinner forebulge section of the CMF is calibrated, for the first time, by a radiogenic U-Pb date of 119.4 ?? 2.6 Ma on a carbonate bed, and by detrital zircon U-Pb dates on two bounding sandstone units (maximum depositional ages of 146 Ma and 112 Ma). P??trographie observations and diagenetic analyses of micritic to microsparitic carbonates from nodules indicate palustrine origins and demonstrate that they crystallized in shallow early meteoric phreatic environments. Meteoric calcite lines derived from CMF carbonates have ??18O values ranging between -8.1 to -7.5%o VPDB, supporting an estimate of zonal mean groundwater ??18O of -6% VSMOW for an Aptian-Albian paleolatitude of 34?? N. Furthermore, our two chemostratigraphic profiles exhibit a generally proportionate thinning of correlative strata from the foredeep on to the forebulge, suggesting that there were consistently lower rates of accumulation on the forebulge during the Aptian-Albian. Identification of the global Aptian-Albian ??13C excursions in purely continental strata, as demonstrated in this paper, opens a new avenue of research by identifying specific stratigraphie intervals that record the terrestrial

  11. Dual carbon isotope characterization of total organic carbon in wintertime carbonaceous aerosols from northern India

    Science.gov (United States)

    Bikkina, Srinivas; Andersson, August; Sarin, M. M.; Sheesley, R. J.; Kirillova, E.; Rengarajan, R.; Sudheer, A. K.; Ram, K.; Gustafsson, Örjan

    2016-05-01

    Large-scale emissions of carbonaceous aerosols (CA) from South Asia impact both regional climate and air quality, yet their sources are not well constrained. Here we use source-diagnostic stable and radiocarbon isotopes (δ13C and Δ14C) to characterize CA sources at a semiurban site (Hisar: 29.2°N, 75.2°E) in the NW Indo-Gangetic Plain (IGP) and a remote high-altitude location in the Himalayan foothills (Manora Peak: 29.4°N, 79.5°E, 1950 m above sea level) in northern India during winter. The Δ14C of total aerosol organic carbon (TOC) varied from -178‰ to -63‰ at Hisar and from -198‰ to -1‰ at Manora Peak. The absence of significant differences in the 14C-based fraction biomass of TOC between Hisar (0.81 ± 0.03) and Manora Peak (0.82 ± 0.07) reveals that biomass burning/biogenic emissions (BBEs) are the dominant sources of CA at both sites. Combining this information with δ13C, other chemical tracers (K+/OC and SO42-/EC) and air mass back trajectory analyses indicate similar source regions in the IGP (e.g., Punjab and Haryana). These results highlight that CA from BBEs in the IGP are not only confined to the atmospheric boundary layer but also extend to higher elevations of the troposphere, where the synoptic-scale circulations could substantially influence their abundances both to the Himalayas and over the downwind oceanic regions such as the Indian Ocean. Given the vast emissions of CA from postharvest crop residue combustion practices in the IGP during early Northeast Monsoon, this information is important for both improved process and model understanding of climate and health effects, as well as in guiding policy decision aiming at reducing emissions.

  12. Temporal Variability in Carbon Isotope Composition of Leaf-Respired Carbon Dioxide

    Science.gov (United States)

    Barbour, M. M.; Hanson, D. T.; Bickford, C. P.; McDowell, N. G.

    2005-12-01

    The stable carbon isotope composition of leaf-respired CO2 (δ13CRl) has enormous potential to allow partitioning of ecosystem respiration into various components, to provide information on key physiological processes, and to trace carbon fluxes through plants and ecosystems. However, difficulties in measuring and understanding variation in δ13CRl have limited its application. We coupled an open gas exchange system (LI-6400, LiCor) to a tunable diode laser (TGA100A, Campbell Scientific) enabling measurement of leaf respiratory CO2 fluxes and δ13CRl every three minutes, with a precision of at least ±0.3 per mil. We also measured oxygen consumption rates, allowing calculation of the respiratory quotient ( RQ) and indicating likely respiratory substrates. Castor bean ( Ricinus communis) plants grown at high and low light were placed in the dark after different lengths of time exposed to sunlight and variation in δ13CRl measured to test the patterns in variation in δ13CRl predicted by existing biochemical models. CO2 respired by leaves previously exposed to high cumulative incident irradiance was up to 11 per mil more enriched than phloem sap sugars for the first 10 to 15 minutes after plants had been moved into the dark . This enrichment rapidly decreased, so that by 30 minutes in the dark δ13CRl was 5 per mil more enriched than phloem sap sugars. CO2 production rates were also initially very high and rapidly decreased. RQ for plants grown in high light varied between 0.8 and 1.2, indicating that carbohydrates and/or organic acids were the respiratory substrates. δ13CRl measured 30 to 80 minutes after plants had been moved into the dark increased with increasing δ13C of phloem sap sugars. The RQ values of plants grown at low light suggested that the respiratory substrates were fatty acids or amino acids ( RQ of around 0.6), or lipids ( RQ less than 0.4). δ13CRl values were enriched by either 4 per mil ( RQ = 0.3) or 12 per mil ( RQ = 0.5) compared to phloem

  13. Carbon isotope constraints on the deglacial CO₂ rise from ice cores.

    Science.gov (United States)

    Schmitt, Jochen; Schneider, Robert; Elsig, Joachim; Leuenberger, Daiana; Lourantou, Anna; Chappellaz, Jérôme; Köhler, Peter; Joos, Fortunat; Stocker, Thomas F; Leuenberger, Markus; Fischer, Hubertus

    2012-05-11

    The stable carbon isotope ratio of atmospheric CO(2) (δ(13)C(atm)) is a key parameter in deciphering past carbon cycle changes. Here we present δ(13)C(atm) data for the past 24,000 years derived from three independent records from two Antarctic ice cores. We conclude that a pronounced 0.3 per mil decrease in δ(13)C(atm) during the early deglaciation can be best explained by upwelling of old, carbon-enriched waters in the Southern Ocean. Later in the deglaciation, regrowth of the terrestrial biosphere, changes in sea surface temperature, and ocean circulation governed the δ(13)C(atm) evolution. During the Last Glacial Maximum, δ(13)C(atm) and atmospheric CO(2) concentration were essentially constant, which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then.

  14. Late Ordovician (Turinian-Chatfieldian) carbon isotope excursions and their stratigraphic and paleoceanographic significance

    Science.gov (United States)

    Ludvigson, Greg A.; Witzke, B.J.; Gonzalez, Luis A.; Carpenter, S.J.; Schneider, C.L.; Hasiuk, F.

    2004-01-01

    Five positive carbon isotope excursions are reported from Platteville-Decorah strata in the Upper Mississippi Valley. All occur in subtidal carbonate strata, and are recognized in the Mifflin, Grand Detour, Quimbys Mill, Spechts Ferry, and Guttenberg intervals. The positive carbon isotope excursions are developed in a Platteville-Decorah succession in which background ??13C values increase upward from about -2??? at the base to about 0??? Vienna Pee Dee belemnite (VPDB) at the top. A regional north-south ??13C gradient, with lighter values to the north and heavier values to the south is also noted. Peak excursion ??13C values of up to +2.75 are reported from the Quimbys Mill excursion, and up to +2.6 from the Guttenberg excursion, although there are considerable local changes in the magnitudes of these events. The Quimbys Mill, Spechts Ferry, and Guttenberg carbon isotope excursions occur in units that are bounded by submarine disconformities, and completely starve out in deeper, more offshore areas. Closely spaced chemostratigraphic profiles of these sculpted, pyrite-impregnated hardground surfaces show that they are associated with very abrupt centimeter-scale negative ??13C shifts of up to several per mil, possibly resulting from the local diagenetic effects of incursions of euxinic bottom waters during marine flooding events. ?? 2004 Elsevier B.V. All rights reserved.

  15. Can Mg isotopes be used to trace cyanobacteria-mediated magnesium carbonate precipitation in alkaline lakes?

    Science.gov (United States)

    Shirokova, L. S.; Mavromatis, V.; Bundeleva, I.; Pokrovsky, O. S.; Bénézeth, P.; Pearce, C.; Gérard, E.; Balor, S.; Oelkers, E. H.

    2011-07-01

    The fractionation of Mg isotopes was determined during the cyanobacterial mediated precipitation of hydrous magnesium carbonate precipitation in both natural environments and in the laboratory. Natural samples were obtained from Lake Salda (SE Turkey), one of the few modern environments on the Earth's surface where hydrous Mg-carbonates are the dominant precipitating minerals. This precipitation was associated with cyanobacterial stromatolites which were abundant in this aquatic ecosystem. Mg isotope analyses were performed on samples of incoming streams, groundwaters, lake waters, stromatolites, and hydromagnesite-rich sediments. Laboratory Mg carbonate precipitation experiments were conducted in the presence of purified Synechococcus sp cyanobacteria that were isolated from the lake water and stromatolites. The hydrous magnesium carbonates nesquehonite (MgCO3·3H2O) and dypingite (Mg5(CO3)4(OH)25(H2O)) were precipitated in these batch reactor experiments from aqueous solutions containing either synthetic NaHCO3/MgCl2 mixtures or natural Lake Salda water, in the presence and absence of live photosynthesizing Synechococcus sp. Bulk precipitation rates were not to affected by the presence of bacteria when air was bubbled through the system. In the stirred non-bubbled reactors, conditions similar to natural settings, bacterial photosynthesis provoked nesquehonite precipitation, whilst no precipitation occurred in bacteria-free systems in the absence of air bubbling, despite the fluids achieving a similar or higher degree of supersaturation. The extent of Mg isotope fractionation (Δ26Mgsolid-solution) between the mineral and solution in the abiotic experiments was found to be identical, within uncertainty, to that measured in cyanobacteria-bearing experiments, and ranges from -1.4 to -0.7 ‰. This similarity refutes the use of Mg isotopes to validate microbial mediated precipitation of hydrous Mg carbonates.

  16. Climate warming, euxinia and carbon isotope perturbations during the Carnian (Triassic) Crisis in South China

    Science.gov (United States)

    Sun, Y. D.; Wignall, P. B.; Joachimski, M. M.; Bond, D. P. G.; Grasby, S. E.; Lai, X. L.; Wang, L. N.; Zhang, Z. T.; Sun, S.

    2016-06-01

    The Carnian Humid Episode (CHE), also known as the Carnian Pluvial Event, and associated biotic changes are major enigmas of the Mesozoic record in western Tethys. We show that the CHE also occurred in eastern Tethys (South China), suggestive of a much more widespread and probably global climate perturbation. Oxygen isotope records from conodont apatite indicate a double-pulse warming event. The CHE coincided with an initial warming of 4 °C. This was followed by a transient cooling period and then a prolonged ∼7 °C warming in the later Carnian (Tuvalian 2). Carbon isotope perturbations associated with the CHE of western Tethys occurred contemporaneously in South China, and mark the start of a prolonged period of carbon cycle instability that persisted until the late Carnian. The dry-wet transition during the CHE coincides with the negative carbon isotope excursion and the temperature rise, pointing to an intensification of hydrologic cycle activities due to climatic warming. While carbonate platform shutdown in western Tethys is associated with an influx of siliciclastic sediment, the eastern Tethyan carbonate platforms are overlain by deep-water anoxic facies. The transition from oxygenated to euxinic facies was via a condensed, manganiferous carbonate (MnO content up to 15.1 wt%), that records an intense Mn shuttle operating in the basin. Significant siliciclastic influx in South China only occurred after the CHE climatic changes and was probably due to foreland basin development at the onset of the Indosinian Orogeny. The mid-Carnian biotic crisis thus coincided with several phenomena associated with major extinction events: a carbonate production crisis, climate warming, δ13 C oscillations, marine anoxia, biotic turnover and flood basalt eruptions (of the Wrangellia Large Igneous Province).

  17. Utility of 5A molecular sieves to measure carbon isotope ratios in lipid biomarkers.

    Science.gov (United States)

    Tolosa, Imma; Ogrinc, Nives

    2007-09-21

    A procedure using 5A zeolite sorption to separate cyclic/branched organic compounds from the linear ones was developed and carbon isotopic fractionation effects were investigated in different families of compounds, e.g. within the hydrocarbon and alcohol compounds. The 5A sieve has a pore size such that only linear components can be incorporated into the pores whereas the cyclic/branched compounds are remaining free in the organic solution. The sorbed compounds were released from the molecular sieve with HF and solvent extracted with hexane. The method enables the isolation of linear saturated classes, such as n-alkanes and n-fatty alcohols from branched/cyclic compounds without isotopic fractionation for compound-specific isotope analysis (CSIA) of delta(13)C. However, alkene hydrocarbons, sterols and some aromatics were completely or partly degraded with the molecular sieve.

  18. Martian Cryogenic Carbonate Formation: Stable Isotope Variations Observed in Laboratory Studies

    Science.gov (United States)

    Socki, Richard A.; Niles, Paul B.; Sun, Tao; Fu, Qi; Romanek, Christopher S.; Gibson, Everett K. Jr.

    2014-01-01

    The history of water on Mars is tied to the formation of carbonates through atmospheric CO2 and its control of the climate history of the planet. Carbonate mineral formation under modern martian atmospheric conditions could be a critical factor in controlling the martian climate in a means similar to the rock weathering cycle on Earth. The combination of evidence for liquid water on the martian surface and cold surface conditions suggest fluid freezing could be very common on the surface of Mars. Cryogenic calcite forms easily from freezing solutions when carbon dioxide degasses quickly from Ca-bicarbonate-rich water, a process that has been observed in some terrestrial settings such as arctic permafrost cave deposits, lake beds of the Dry Valleys of Antarctica, and in aufeis (river icings) from rivers of N.E. Alaska. A series of laboratory experiments were conducted that simulated cryogenic carbonate formation on Mars in order to understand their isotopic systematics. The results indicate that carbonates grown under martian conditions show variable enrichments from starting bicarbonate fluids in both carbon and oxygen isotopes beyond equilibrium values.

  19. Astronomical calibration of upper Campanian–Maastrichtian carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C)

    DEFF Research Database (Denmark)

    Thibault, Nicolas Rudolph; Husson, Dorothée; Harlou, Rikke

    2012-01-01

    An integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and d13C stratigraphy is established for the upper Campanian–Maastrichtian of ODP Hole 762C (Exmouth Plateau, Northwestern Australian margin). Bulk-carbonate d13C events and nannofossil bio-events...

  20. Comparison of bulk and n-alkane PETM carbon isotope trends from the Bighorn Basin, Wyoming

    Science.gov (United States)

    Baczynski, A. A.; McInerney, F. A.; Kraus, M. J.; Wing, S.

    2010-12-01

    The Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, short-term, and large-scale global warming fueled by a large release of isotopically light carbon, is recorded in terrestrial and marine carbonates and organic carbon as a prominent negative carbon isotope excursion (CIE). Here we present a composite stable carbon isotope record from n-alkanes and four bulk organic carbon records from individual sections spanning the PETM interval in the Cabin Fork area of the southeastern Bighorn Basin, Wyoming. The n-alkane curve shows an abrupt, negative shift in δ13C values, an extended CIE body, and a rapid recovery to pre-PETM δ13C values. While the bulk organic carbon records show similarly abrupt negative shifts in δ13C values, the CIE appears to be compressed as well as smaller in magnitude, and the return to more positive δ13C values is often more gradual. Furthermore, the stratigraphic thickness of the most negative CIE values and the pattern of the recovery phase are not consistent among the four bulk organic carbon records. The discrepancy between the bulk organic matter and n-alkane CIE may arise because of changes in soil organic matter cycling during the PETM. Bulk soil organic matter δ13C values are influenced by degradation and selective preservation whereas n-alkanes are resistant to diagenesis. Variations in sediment accumulation rates across the basin may be responsible for the differences between the four bulk organic carbon δ13C records. Sites with extended CIE bodies likely present more complete isotope records with greater time resolution and less time averaging than those with reduced CIEs. The shape of the high-resolution n-alkane curve presented here is similar to the newest 3He-based timescale for the PETM using data from Walvis Ridge, IODP site 1266 (Murphy et al., 2010). The most significant difference between this revised PETM timescale and previously published age models is the allocation of time within the PETM event. Murphy et

  1. Sulfur, carbon, hydrogen, and oxygen isotope geochemistry of the Idaho cobalt belt

    Science.gov (United States)

    Johnson, Craig A.; Bookstrom, Arthur A.; Slack, John F.

    2012-01-01

    Cobalt-copper ± gold deposits of the Idaho cobalt belt, including the deposits of the Blackbird district, have been analyzed for their sulfur, carbon, hydrogen, and oxygen isotope compositions to improve the understanding of ore formation. Previous genetic hypotheses have ranged widely, linking the ores to the sedimentary or diagenetic history of the host Mesoproterozoic sedimentary rocks, to Mesoproterozoic or Cretaceous magmatism, or to metamorphic shearing. The δ34S values are nearly uniform throughout the Blackbird dis- trict, with a mean value for cobaltite (CoAsS, the main cobalt mineral) of 8.0 ± 0.4‰ (n = 19). The data suggest that (1) sulfur was derived at least partly from sedimentary sources, (2) redox reactions involving sulfur were probably unimportant for ore deposition, and (3) the sulfur was probably transported to sites of ore for- mation as H2S. Hydrogen and oxygen isotope compositions of the ore-forming fluid, which are calculated from analyses of biotite-rich wall rocks and tourmaline, do not uniquely identify the source of the fluid; plausible sources include formation waters, metamorphic waters, and mixtures of magmatic and isotopically heavy meteoric waters. The calculated compositions are a poor match for the modified seawaters that form vol- canogenic massive sulfide (VMS) deposits. Carbon and oxygen isotope compositions of siderite, a mineral that is widespread, although sparse, at Blackbird, suggest formation from mixtures of sedimentary organic carbon and magmatic-metamorphic carbon. The isotopic compositions of calcite in alkaline dike rocks of uncertain age are consistent with a magmatic origin. Several lines of evidence suggest that siderite postdated the emplacement of cobalt and copper, so its significance for the ore-forming event is uncertain. From the stable isotope perspective, the mineral deposits of the Idaho cobalt belt contrast with typical VMS and sedimentary exhalative deposits. They show characteristics of deposit

  2. Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric PM

    Directory of Open Access Journals (Sweden)

    S. Moukhtar

    2011-05-01

    Full Text Available A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter (PM is presented. It has been found in numerous laboratory studies that these compounds are photooxidation products of toluene in PM. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. PM was collected on quartz fibre filters using dichotomous high volume air samplers for PM 2.5. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography (HPLC and solid phase extraction (SPE. The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyltrifluoroacetamide (BSTFA, was added to the solution for Gas Chromatography/Mass Spectroscopy (GC/MS analysis. The second half of the sample was stored at low temperature. When GC/MS analysis showed high enough concentrations the remaining sample was derivatized with BSTFA and analysed for stable isotope ratio using a Gas Chromatography/Isotope Ratio Mass Spectrometry (GC-IRMS.

    In all atmospheric PM samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol. Nevertheless, due to low pollution levels occurring in the rural area, no samples had concentrations high enough to perform stable carbon isotope composition measurements of the methylnitrophenols. Samples collected in the suburban area could be analysed for carbon stable isotope ratio using GC-IRMS.

    The procedure described in this paper provides a very sensitive and selective method for the analysis of methylnitrophenols in atmospheric PM at concentrations as low as 1 pg m−3. For accurate (within ±0.5‰ stable isotope ratio analysis significantly higher concentrations in the range of 100 pg m−3 or more are required.

  3. Carbon isotopic characteristics and their genetic relationships for individual lipids in plants and sediments from a marsh sedimentary environment

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi; ZHANG Hui; ZHENG Chaoyang; WU Baoxiang; ZHENG Guodong

    2005-01-01

    The carbon isotopes of individual lipids in herbaceous plants and tree leaves in Ruoergai marsh were measured by the GC-IRMS analytical technique in order to understand the inherent relationships of carbon isotopes between sedimentary and plant lipids from typical marsh environment. The analytical results show that the carbon isotopic compositions of n-alkanes in different kinds of plants differ significantly. Mean δ13C values of n-alkanes in herbaceous plants (-32.2‰―-36.9‰) are 3.3‰ lower than those in woody plant (-27.2‰― -35.0‰). The carbon isotopic compositions of fatty acids in organisms (-30.3‰― -36.2‰) are very similar to those of n-alkanes and the δ13C values for unsaturated fatty acids are within the range of those for saturated fatty acids. The differences in δ13C values between plant lipids are obvious and range from 2.4‰ to 7.8‰. It is observed that the carbon isotopic compositions of sedimentary lipids are closely related to those of plant lipids. The carbon isotopic compositions (-27.0‰―-36.9‰) of n-alkanes, ≥C16 fatty acids, n-alkanols, sterols and n-alkanones in the sediments are similar to those of plant lipids and the carbon isotopic compositions of short-chain sedimentary lipids are similar to those of long-chain sedimentary homologues. These indicate that the sedimentary lipids are derived from high plants. However, the δ13C values of C14:0 and C15:0 fatty acids in the sediments are lighter than those of the same carbon number saturated homologues in plants, reflecting the genetic features partially derived from bacteria. These data provide scientific evidence for carbon isotope-applied research of individual lipids.

  4. [Carbon isotope (13C/12C) effect of photorespiration in photosynthetic organisms. Evidence for existence, probable mechanism].

    Science.gov (United States)

    Ivlev, A A

    2002-01-01

    Experimental evidence in favor of the new phenomenon predicted for photosynthesizing organisms, the fractionation of carbon isotopes in photorespiration is presented. A possible mechanism of this process is discussed. The fractionation of carbon in isotopes photorespiration occurs in the oxygenase phase of the functioning of ribulosebisphosphate carboxylase/oxygenase (rubisco), the key enzyme of photosynthesis, which is capable to act as carboxylase and oxygenase. Which function of the enzyme is active depends on CO2/O2 concentration ratio, which periodically changes in a cell. The key reaction in the mechanism of carbon isotope fractionation in photorespiration is glycine decarboxylation, which results in the splitting and removal from the cell of CO2 enriched with 12C and the accumulation of 13C photorespiratory carbon flow. The coupling of photorespiration and CO2 photoassimilation gives rise to two isotopically different carbon flows, which fill up separate carbohydrate pools, which are the sources of carbon in the following syntheses in the dark phase of photosynthesis. This enables one to identify, from the carbon isotope ratio of metabolites, their involvement in the photorespiratory and assimilatory carbon flows, to investigate the pathways of carbon metabolism, and to estimate more thoroughly the biosynthetic role of photorespiration.

  5. The significance of an Early Jurassic (Toarcian) carbon-isotope excursion in Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada

    Science.gov (United States)

    Caruthers, Andrew H.; Gröcke, Darren R.; Smith, Paul L.

    2011-07-01

    During the Early Toarcian there was a significant disruption in the short-term active carbon reservoir as revealed by carbon-isotope records, which show a broad positive shift that is interrupted by a large 5-7‰ negative excursion (δ 13C org). Carbon-isotope excursion co-occurs with the deposition of organic-rich shales in many areas. This perturbation in carbon isotopes is thought to be indicative of severe climate change and marine anoxia. The two leading hypotheses as to the cause of this event invoke either global or regional controls. Here we present carbon-isotope data from Haida Gwaii, British Columbia, Canada showing a significant perturbation within a temporally constrained Early Toarcian succession that was deposited in the northeastern paleo-Pacific Ocean. These data reinforce the concept that the short-term active carbon reservoir was affected globally, and assist with the correlation of ammonite zonal schemes between western North America and Europe. The δ 13C org data show a broad positive shift that is interrupted by a sharp and pronounced negative excursion of 7‰ (8.5‰ in δ 13C wood) in the Early Toarcian Kanense Zone. This negative excursion also coincides with increasing total organic carbon (TOC) from ~ 0.4% to ~ 1.2%. These data suggest that the Early Toarcian carbon-isotope perturbation was indeed global and imprinted itself on all active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric).

  6. Carbon Isotopic Studies of Assimilated and Ecosystem Respired CO2 in a Southeastern Pine Forest. Final Report and Conference Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Conte, Maureen H

    2008-04-10

    Carbon dioxide is the major “greenhouse” gas responsible for global warming. Southeastern pine forests appear to be among the largest terrestrial sinks of carbon dioxide in the US. This collaborative study specifically addressed the isotopic signatures of the large fluxes of carbon taken up by photosynthesis and given off by respiration in this ecosystem. By measuring these isotopic signatures at the ecosystem level, we have provided data that will help to more accurately quantify the magnitude of carbon fluxes on the regional scale and how these fluxes vary in response to climatic parameters such as rainfall and air temperature. The focus of the MBL subcontract was to evaluate how processes operating at the physiological and ecosystem scales affects the resultant isotopic signature of plant waxes that are emitted as aerosols into the convective boundary layer. These wax aerosols provide a large-spatial scale integrative signal of isotopic discrimination of atmospheric carbon dioxide by terrestrial photosynthesis (Conte and Weber 2002). The ecosystem studies have greatly expanded of knowledge of wax biosynthetic controls on their isootpic signature The wax aerosol data products produced under this grant are directly applicable as input for global carbon modeling studies that use variations in the concentration and carbon isotopic composition of atmospheric carbon dioxide to quantify the magnitude and spatial and temporal patterns of carbon uptake on the global scale.

  7. Aspect of human food ecology; Development of carbon and nitrogen isotope method

    Energy Technology Data Exchange (ETDEWEB)

    Minagawa, Masao (Hokkaido Univ., Sapporo (Japan))

    1994-01-01

    The isotopic dietary analysis was applied for some prehistoric human populations from East Asia, Latin America, and Oceania region. Most samples were from archeological sites from 1000 to 6000 year's bp. Some modern ethnological groups including Tibet, Kurud, Shelpa and Tlingit were also studied for evaluating prehistoric human food habit. Carbon and nitrogen isotope compositions of gelatin fractions have been analyzed for prehistoric bone samples. Analytical procedure for isotopes and data analyses for reconstructing dietary composition was developed and tested by a modern human food system. A stochastic method based on the Monte Carlo model was applied to estimate dependency of major food resources having unique isotope compositions in carbon and nitrogen, and has showed consistent results to the statistic food consumption record in Japan. Carbon and nitrogen isotope composition of human tissues showed distinct difference among human groups in both prehistoric and modern samples. These data were evaluated by difference of dietary patterns: contributions of marine food, terrestrial food, meat, C3 and C4 plant, which are characterized by the difference of [sup 13]C and [sup 15]N content. On the basis of the stochastic feeding simulation, dietary consumption patterns were estimated for Jomon fisher-hunter-gatherers, historic Ainu, prehistoric east Siberian, prehistoric Latin American farmers in Mexico and Peru, and prehistoric fisheres in Cook island. Results showed a remarkable relationship between animal protein dependence and marine food usage. This result will be discussed from following two possibilities; the human adaptation on marine resources would be one of the important direction to upgrade animal protein uptake, or marine food could be used as alternative protein source for terrestrial game animals. (author).

  8. Using a laser-based CO2 carbon isotope analyser to investigate gas transfer in geological media

    Science.gov (United States)

    Guillon, S.; Pili, E.; Agrinier, P.

    2012-05-01

    CO2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO2 carbon isotope analysis provides continuous measurement at high temporal resolution and is a promising alternative to isotope ratio mass spectrometry (IRMS). We performed a thorough assessment of a commercially available CO2 Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of δ 13C in CO2. Using a set of reference gases of known CO2 concentration and carbon isotopic composition, we evaluated the precision, long-term stability, temperature sensitivity and concentration dependence of the analyser. Despite good precision calculated from Allan variance (5.0 ppm for CO2 concentration, and 0.05 ‰ for δ 13C at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of δ 13C on CO2 concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO2 concentration and 1.3 ‰ for δ 13C, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO2 flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source.

  9. Variation of carbon isotope fractionation in hydrogenotrophic methanogenic microbial cultures and environmental samples at different energy status

    NARCIS (Netherlands)

    Penning, H.; Plugge, C.M.; Galand, P.E.; Conrad, R.

    2005-01-01

    Methane is a major product of anaerobic degradation of organic matter and an important greenhouse gas. Its stable carbon isotope composition can be used to reveal active methanogenic pathways, if associated isotope fractionation factors are known. To clarify the causes that lead to the wide variatio

  10. Shale gas plays, Neuquén Basin, Argentina: chemostratigraphy and mud gas carbon isotopes insights

    Directory of Open Access Journals (Sweden)

    Héctor Adolfo Ostera

    Full Text Available ABSTRACT: In order to enhance the knowledge of shale objectives from Vaca Muerta and Los Molles Formations in the Neuquén Basin, Argentina, chemostratigraphic and mud gas carbon isotope analyses were performed in two wells from Agua del Cajón and Salitral oilfields (ADC-1016 and NqSa-1148. Geochemical data show restricted levels in both cases to perforate and produce. In ADC-1016 well, Lower Los Molles Formation looks like the most suitable play to be produced. At El Salitral oilfield (NqSa-1148, the best remarkable Vaca Muerta-Quintuco objectives are associated with authigenic elements, in limited horizons. Enhancement of the Quintuco reservoir by deep circulating fluids (thermobaric reservoir is suggested. Carbon isotope analysis reveals complex processes that affected the gas composition. Addition of microbial methane, biodegradation of ethane-propane and mixing of gases has been recognized. Isotope reversals and presumed water reforming of hydrocarbons have been registered associated with overpressure for Lower Los Molles Formation in the ADC-1016 well, which is pointed out as the most promising shale play in the area. Vaca Muerta gases at Agua del Cajon ADC- 1016 well are associated with the homonymous source. El Salitral 1148 well shows that primary isotope composition in gases from Vaca Muerta shale play and Quintuco reservoir could be associated with a Lower Los Molles source, an aloctonous charge related with the main structures of the area.

  11. Insights to PETM Terrestrial Records from Global Patterns in Carbon Isotope Fractionation by Modern Plants

    Science.gov (United States)

    Freeman, K. H.; Diefendorf, A. F.; Mueller, K. E.; Wing, S. L.; Koch, P. L.

    2009-12-01

    Global patterns in plant fractionation and δ13C values of leaves are potentially important for understanding and predicting ecologic impacts of climate change, yet clear, global patterns have not emerged from the copious, highly variable leaf δ13C values published to date. Understanding drivers in modern plant fractionation at large spatial scales has potential to strengthen understanding of isotopic variability in ancient terrestrial organic matter and how it encodes climate and ecological signals. We converted published leaf δ13C-leaf data into mean fractionation values for 334 woody C3 plant species at 105 globally distributed locations to evaluate the influence of environmental properties and plant functional type. Biome designation reflects both community composition and climate properties, so it is not unexpected that in our study it exerts the greatest predictive power on leaf fractionation values. Pulling apart the influences of different environmental factors, precipitation has the next strongest correlation with fractionation, consistent with limitations on photosynthesis and global patterns of ecosystem productivity due to water availability. Individual plant functional types exhibit similar relationships between fractionation and both biome designation and precipitation amount. However, mean fractionation values for evergreen gymnosperms are 1-2.7‰ lower than other woody plant types when environmental factors are constrained. Our results illustrate that both plant type and precipitation can independently result in differences in isotope fractionation of up to several permil. The predictive relationships from our study provide a framework for assessing models of plant fractionation at large spatial scales, and potentially enable predictive spatial mapping of carbon isotopic patterns, both for plants and soil organic carbon. We use these relationships to re-evaluate the 5 ‰ carbon isotope excursion of the PETM in the Bighorn Basin recorded in plant

  12. Sr isotopic chemostratigraphy of Precambrian carbonate rocks in the Amderma Rise, Pai-Khoi Ridge

    Science.gov (United States)

    Kuznetsov, A. B.; Starikova, E. V.; Maslov, A. V.; Konstantinova, G. V.

    2016-08-01

    The Sr and C isotopic compositions of Precambrian carbonate rocks are determined for Amderma Rise, in the northeastern margin of Pai-Khoi Ridge. Based on the Sr isotopic chemostratigraphy, it is established for the first time that the Amderma Formation is referred to the Early Vendian, while the Morozovsk Formation is Late Riphean in age. This conclusion along with detailed mapping proves that the Precambrian "section" of the Amderma Rise is a series of tectonic plates combined in a nonchronostratigraphic order. Volcanic and sedimentary rocks of the Morozovsk and Sokolninsk formations make up the allochthon proper, while carbonate rocks of the Amderma Formation make up the para-autochthon. The high values of δ13C (up to +9.5‰) identified in limestones of both formations suggest a considerable distance of the Pai-Khoi paleobasin from the passive margin of the Baltic Region upon facies similarity to the Laurentia active margins.

  13. Carbon isotopic record of foraminifers in surface sediments from the South China Sea and its significance

    Institute of Scientific and Technical Information of China (English)

    CHENG Xinrong; WANG Pinxian; HUANG Baoqi; LIU Chuanlian; JIAN Zhimin; ZHAO Quanhong; LI Jianru; TIAN Jun; XU Jian

    2005-01-01

    The study is based on stable carbon isotopic measurements of 112 foraminiferal samples from surface sediments at 40 sites in the South China Sea (SCS).δ13C of foraminifers and △δ13C between planktonic and benthic foraminiferal species exhibit a low value area at the northeastern and southern ends of the SCS. It is correlated with the nutrient distributional pattern in the SCS and circumjacent area, the influence of the northeastern and southwestern monsoons on water flow and water chemistry in the SCS. The monsoons have not only brought nutrients to the upper part of the sea but also disturbed water and decreased difference between the surface and bottom water. Its influence is most obvious at both ends, which resulted in the low value areas in δ13C and △δ13C at the ends. The distributional pattern of the stable carbon isotope in the SCS is a reflection of the East Asian monsoons.

  14. Isotopic evidence of magmatism and a sedimentary carbon source at the Endeavour hydrothermal system

    Energy Technology Data Exchange (ETDEWEB)

    Brown, T A; Proskurowski, G; Lilley, M D

    2004-01-07

    Stable and radiocarbon isotope measurements made on CO{sub 2} from high temperature hydrothermal vents on the Endeavour Segment of the Juan de Fuca Ridge indicate both magmatic and sedimentary sources of carbon to the hydrothermal system. The Endeavour segment is devoid of overlying sediments and has shown no observable signs of surficial magmatic activity during the {approx}20 years of ongoing studies. The appearance of isotopically heavy, radiocarbon dead CO{sub 2} after a 1999 earthquake swarm requires that this earthquake event was magmatic in origin. Evidence for a sedimentary organic carbon source suggests the presence of buried sediments at the ridge axis. These findings, which represent the first temporally coherent set of radiocarbon measurements from hydrothermal vent fluids, demonstrate the utility of radiocarbon analysis in hydrothermal studies. The existence of a sediment source at Endeavour and the occurrence of magmatic episodes illustrate the extremely complex and evolving nature of the Endeavour hydrothermal system.

  15. Carbon and oxygen isotopic composition of coal and carbon dioxide derived from laboratory coal combustion: A preliminary study

    Science.gov (United States)

    Warwick, Peter; Ruppert, Leslie F.

    2016-01-01

    The concentration of carbon dioxide (CO2) in the atmosphere has dramatically increased from the start of the industrial revolution in the mid-1700s to present levels exceeding 400 ppm. Carbon dioxide derived from fossil fuel combustion is a greenhouse gas and a major contributor to on-going climate change. Carbon and oxygen stable isotope geochemistry is a useful tool to help model and predict the contributions of anthropogenic sources of CO2 in the global carbon cycle. Surprisingly few studies have addressed the carbon and oxygen isotopic composition of CO2 derived from coal combustion. The goal of this study is to document the relationships between the carbon and oxygen isotope signatures of coal and signatures of the CO2 produced from laboratory coal combustion in atmospheric conditions.Six coal samples were selected that represent various geologic ages (Carboniferous to Tertiary) and coal ranks (lignite to bituminous). Duplicate splits of the six coal samples were ignited and partially combusted in the laboratory at atmospheric conditions. The resulting coal-combustion gases were collected and the molecular composition of the collected gases and isotopic analyses of δ13C of CO2, δ13C of CH4, and δ18O of CO2 were analysed by a commercial laboratory. Splits (~ 1 g) of the un-combusted dried ground coal samples were analyzed for δ13C and δ18O by the U.S. Geological Survey Reston Stable Isotope Laboratory.The major findings of this preliminary work indicate that the isotopic signatures of δ13C (relative to the Vienna Pee Dee Belemnite scale, VPDB) of CO2 resulting from coal combustion are similar to the δ13CVPDB signature of the bulk coal (− 28.46 to − 23.86 ‰) and are not similar to atmospheric δ13CVPDB of CO2 (~ − 8 ‰, see http://www.esrl.noaa.gov/gmd/outreach/isotopes/c13tellsus.html). The δ18O values of bulk coal are strongly correlated to the coal dry ash yields and appear to have little or no influence on the δ18O values of CO2

  16. Methane Production Pathways in a California Rice Paddy: Isotopic Evidence for Substantial CO2 Reduction as Cause for Isotopically Light Emitted CH4 Carbon

    Science.gov (United States)

    Tyler, S. C.; McMillan, A. M.; Bearden, K.; Chidthaisong, A.; Macalady, J.

    2003-12-01

    We report measurements of δ 13C of emitted CH4 and sediment CH4 and CO2 during the 1999 rice-growing season near Maxwell, CA. Two treatments, one with rice straw incorporated from the previous season and one without rice straw were studied. The δ 13C value of emitted CH4 was consistently lighter isotopically (-67‰ to -83‰ throughout the season) in both straw incorporated and straw removed (burned) plots than in fields we have studied in Texas, Kenya, and Japan. Measured isotopic values of the production zone CH4 were compared to a two-point mixing curve representative of isotopic CH4 produced from either pure methyl-group fermentation or CO2 reduction pathways to partition the production pathways and to track seasonal changes in the production processes. Our sediment CH4 and CO2 isotope data indicate that fermentation was rarely the dominant methanogenic pathway - on the contrary CO2 reduction with H2 was more prevalent than fermentation methanogenesis throughout most of the season. The relatively isotopically light CH4 emitted by the paddy fields is also a product of oxidation and stem-transport processes which have isotopic effects of their own. These effects are discussed in context with the methanogenic isotope effects to provide a complete picture of the paddy field CH4 carbon isotope system.

  17. Stable carbon and radiocarbon isotope compositions of particle size fractions to determine origins of sedimentary organic matter in an estuary

    NARCIS (Netherlands)

    Megens, L; van der Plicht, J; de Leeuw, JW; Smedes, F; Altabet, M.

    2002-01-01

    Stable and radioactive carbon isotopic compositions of particle size fractions of a surface sediment from the Ems-Dollard estuary vary considerably with particle size. The organic material in the fine fractions (

  18. Carbon and strontium isotope variations and responses tosea-level fluctuations in the Ordovician of the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Abstract In the Ordovician, a carbonate platform system grading from the platformal interioreastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column islocated in the place where the paleoslope occurred. The isotope compositions of the carbonatesthere are thus considered as having reflected those of simultaneous sea waters in view of its goodconnection with the open seas. The carbon and strontium isotope compositions of the Ordoviciancarbonates in the Tazhong area are analyzed, and their relationships to the sea-level fluctuationsare discussed as well. Studies have revealed that the carbon isotope composition is related posi-tively with the sea-level fluctuations, whereas an opposing situation occurs to the strontium isotopevariation. Similar responses of carbon and strontium isotope compositions to the sea-level fluctua-tions are reported elsewhere in the world, suggesting that the Ordovician sea-level fluctuations ofthe Tarim Basin were of eustatic implication.

  19. CCQM-K140: carbon stable isotope ratio delta values in honey

    Science.gov (United States)

    Dunn, P. J. H.; Goenaga-Infante, H.; Goren, A. C.; Şimşek, A.; Bilsel, M.; Ogrinc, N.; Armishaw, P.; Hai, L.

    2017-01-01

    As there can be small but measureable differences in isotope ratios between different sources of the same element/compound/material, isotope ratio measurements are applied in a number of different fields including archaeology, environmental science, geochemistry, forensic science and ecology. Isotope ratios for the light elements (H, C, N, O and S) are typically reported as δ-values which are isotope ratios expressed relative to an internationally agreed standard (this standard is the zero-point on the scale), although absolute isotope ratios which are traceable to the SI have also been reported. The IAWG has been granted a traceability exception for the use of arbitrary delta scales until SI traceability can be established at the required level of uncertainty but this goal is some years away. While the CCQM IAWG has previously organised several pilot studies on isotope ratio determination (CCQM-P75: Stable isotope delta values in methionine, 2006; CCQM-P105: Sr isotope ratios in wine, 2008; CCQM-K98: Pb isotope ratios in bronze with additional delta values in CCQM-P134, 2011), it has been a number of years since delta values of light elements have been considered and there has been no key comparison (KC). Therefore, the IAWG has included the need for a KC (CCQM-K140) based on an arbitrary delta scale in its program to support ongoing requirements to demonstrate core capabilities as well as specific claims of measurement capability (CMCs) in this area. The performance of all five of the CCQM-K140 participants was very good, illustrating their ability to obtain accurate results for carbon isotope ratios, within the calibration range afforded by internationally agreed reference materials (δ13CVPDB-LSVEC between ‑47.32 % and +535.3 %) with measurement uncertainties of between 0.08 and 0.28 %. This was despite the fact that no two participants used exactly the same approach in terms of instrumentation or data treatment. Main text To reach the main text of this

  20. Environmental and biosynthetic influences on carbon and hydrogen isotope ratios of leaf wax n-alkanes

    Science.gov (United States)

    McInerney, F. A.; Freeman, K. H.; Polissar, P. J.; Feakins, S. J.

    2013-12-01

    Both carbon and hydrogen isotope ratios of leaf-wax n-alkanes are influenced by the availability of water in a plant's growth environment. Carbon isotope ratios of bulk tissues in C3 plants demonstrate a strong inverse relationship with measures of available moisture (e.g. mean annual precipitation and precipitation/evaporation). Similarly, hydrogen isotope ratios of leaf wax n-alkanes (δDl) can be enriched relative to precipitation (δDw) by transpiration, which is related to relative humidity and the leaf-to-air vapor pressure deficit. Thus, D-enrichment of leaf-wax n-alkanes relative to precipitation, termed the apparent fractionation (2ɛl/w), becomes more positive with increasing aridity. In theory, more positive values of leaf-wax δ13C (δ13Cl) and 2ɛl/w of leaf-wax n-alkanes should both correspond to more arid conditions in C3 plants. Here we review published and unpublished data on over 100 plants to examine this relationship. Contrary to expectations, C3 dicots show no clear relationship between δ13Cl and 2ɛl/w. This global lack of correlation is surprising given our understanding of aridity related isotopic effects in C3 plants. One possibility is that the implicit assumption of constant fractionation between lipid and bulk tissue is flawed due to the effects of different biosynthetic carriers and reaction pathways. We explore this possibility by examining the offset of leaf-wax carbon isotopes from the bulk leaf tissue (13ɛl/bulk). Different offsets would indicate additional biosynthetic processes are affecting δ13Cl in addition to any direct effects from aridity. We find that 13ɛl/bulk is highly variable, ranging from -1 to -16‰, which could explain the lack of correlation between δ13Cl and 2ɛl/w. In addition, 13ɛl/bulk values for C3 and C4 monocots (averages of -10.6 and -11.4‰ respectively) represent significantly greater offset between leaf wax and bulk tissue than in C3 dicots (average of -4.3‰), which is consistent with previous

  1. Cerium anomaly across the mid-Tournaisian carbon isotope excursion (TICE)

    Science.gov (United States)

    Jiang, G.; Morales, D. C.; Maharjan, D. K.

    2015-12-01

    The Early Mississippian (ca. 359-345 Ma) represents one of the most important greenhouse-icehouse climate transitions in Earth history. Closely associated with this critical transition is a prominent positive carbon isotope excursion (δ13C ≥ +5‰) that has been documented from numerous stratigraphic successions across the globe. This δ13C excursion, informally referred to as the TICE (mid-Tournaisian carbon isotope excursion) event, has been interpreted as resulting from enhanced organic carbon burial, with anticipated outcomes including the lowering of atmospheric CO2 and global cooling, the growth of continental ice sheets and sea-level fall, and the increase of ocean oxygenation and ocean redox changes. The casual relationship between these events has been addressed from various perspectives but not yet clearly demonstrated. To document the potential redox change associated with the perturbation of the carbon cycle, we have analyzed rare earth elements (REE) and trace elements across the TICE in two sections across a shallow-to-deep water transect in the southern Great Basin (Utah and Nevada), USA. In both sections, the REE data show a significant positive cerium (Ce) anomaly (Ce/Ce* = Ce/(0.5La+0.5Pr)). Prior to the positive δ13C shift, most Ce/Ce* values are around 0.3 (between 0.2 and 0.4). Across the δ13C peak, Ce/Ce* values increase up to 0.87, followed by a decrease back to 0.2~0.3 after the δ13C excursion (Figure 1). The positive Ce anomaly is best interpreted as recording expansion of oxygen minimum zone and anoxia resulted from increased primary production. This is consistent with a significant increase of nitrogen isotopes (δ15N) across the δ13C peak. Integration of the carbon, nitrogen, and REE data demonstrates a responsive earth systems change linked to the perturbation of the Early Mississippian carbon cycle.

  2. Laws of the oxidation of carbon isotopes in plasma processes under magnetic field

    Science.gov (United States)

    Myshkin, V. F.; Bespala, E. V.; Khan, V. A.; Makarevich, S. V.

    2016-06-01

    From law of quantum mechanics it follows that spin precession phase of unpaired electron in external magnetic field cannot be determined. It uncertainty necessary take into account in different physical and chemical processes. The expression of the rate constant of a chemical reaction based on the number of discrete spin states was obtained. The equations of chemical kinetics of plasma oxidation of carbon isotopes in the magnetic field were given.

  3. Tracing paleo-ocean redox using Cr isotopes in carbonates spanning the Great Oxidation Event

    Science.gov (United States)

    Holmden, C. E.; Bekker, A.

    2013-12-01

    Cr is an element whose isotopes are fractionated by redox reactions in the Earth's exogenic system, such as those occuring during oxidative weathering on the continents and scavenging into reduced marine sediments. Frei et al. (2009) proposed that the range of Cr isotope fractionation in exogenic materials in the absence of molecular oxygen would likely not extend beyond the range in igneous rocks, which is quite small (δ53Cr = -0.1 ×0.1‰). They tested their hypothesis on iron formations spanning the Great Oxidation Event (GOE) and found small fractionations that predated the GOE, but no permil level fractionation until the Neoproterozoic. We tested whether δ53Cr values in shallow-water carbonates spanning the GOE might record steps in the rise of atmospheric oxygen between 2.45 and 2.06 Ga. Carbonates representing 15 formations were chosen with depositonal ages ranging between 2.5 Ga and 1.9 Ga. We find very little Cr isotope fractionation recorded in carbonates deposited during this time with the exception of those corresponding to the peak of the Lomagundi Event at ca. 2.15 Ga. A defining characterisitic of the Lomagundi Event is the widespread prevalance of shallow-water carbonate platforms with abundant stromatolites, making their deposits an ideal lithology to record the state of the seawater Cr cycle. Five formations deposited during this time yield δ53Cr values with permil level fractionation recorded in some examples, in both positive and negative directions with respect to the igenous rock baseline. The data suggests that although the oxidative part of the Cr cycle started at least during the peak of the Lomagundi Event, the Cr(VI) reservoir and its residence time remained small, making it susceptible to local processes. 1. Frei et al. (2009) Fluctuations in Precambrian atmospheric oxygen recorded by Cr isotopes, Nature, v. 461, 250-253.

  4. Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats

    Directory of Open Access Journals (Sweden)

    C. Alewell

    2011-01-01

    Full Text Available Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by an unique biodiversity and ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and results in degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Carbon isotope13C depth profile of the yet undisturbed mire Storflaket indicated very low to no degradation of the peat in the water saturated depressions (hollows but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks and subsequent braking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 to 25 cm. The age of these turning point was 14C dated between 150 and 670 years and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.

  5. Carbon isotope composition of carbonaceous matter from the precambrian of the witwatersrand system.

    Science.gov (United States)

    Hoefs, J; Schidlowski, M

    1967-03-01

    Polymerized hydrocarbons occurring in the gold-uranium conglomerates of the Witwatersrand System (South Africa) show deltaC(13) values between -22.4 and -32.8 per mille, their isotopic composition thus falling into the range of sedimentary organic carbon. Accordingly, organic derivation of the material seems very probable. This conclusion is consistent with a model of the existence of organic evolution and biologic activity in times certainly older than 2.15 x 10(9) years.

  6. FACIES PARTITIONING AND SEQUENCE STRATIGRAPHY OF A MIXED SILICICLASTIC-CARBONATE RAMP STACK IN THE GELASIAN OF SICILY (S ITALY: A POTENTIAL MODEL FOR ICEHOUSE, DISTALLY-STEEPENED HETEROZOAN RAMPS

    Directory of Open Access Journals (Sweden)

    FRANCESCO MASSARI

    2012-11-01

    Full Text Available The Gelasian succession of the Capodarso area (Enna-Caltanissetta basin, Sicily, Italy consists of an offlapping stack of cycles composed of siliciclastic units passing to carbonate heterozoan, clino-stratified wedges, developed from a growing positive tectonic structure. Identification of a number of facies tracts, based on sedimentary facies, biofacies and taphofacies, provided important information about the differentiation and characterisation of systems tracts and key stratal surfaces of sequence stratigraphy. The bulk of carbonate wedges are interpreted as representing the rapid falling-stage progradation of distally steepened ramps. The inferred highest rate of carbonate production during forced regressions was concomitant with active downramp resedimentation by storm-driven downwelling flows, leading to storing of most carbonate sediment on the ramp slope as clino-beds of the prograding bodies. Comparison of the Capodarso ramps with other icehouse carbonate ramps, with particular regard to the Mediterranean Plio-Pleistocene, provides clues for defining some common features. These are inferred to include: (1 brief, rapid episodes of progradation concomitant with orbitally-forced sea-level changes, resulting in limited ramp width; (2 preferential fostering of growth and downramp resedimentation of heterozoan carbonates during glacial hemicycles marked by enhanced atmospheric and marine circulation; (3 building out from positive features of entirely submerged distally-steepened ramps with storm-wave-graded profile and distinctive clinoforms; (4 ramp stacks generally consisting of mixed clastic-carbonate sequences showing an ordered spectrum of distinct frequencies; (5 rapid, continuous changes in environmental parameters, leading to the short-lived persistence of faunal communities, climax communities generally having insufficient time to form. 

  7. Charge-changing cross section measurement of neutron-rich carbon isotopes at 50 AMeV

    Directory of Open Access Journals (Sweden)

    Tran D.T.

    2016-01-01

    Full Text Available Charge Changing Cross Sections (CCCS or σCC of neutron-rich carbon isotopes on carbon target were measured at low energy (50A MeV for the first time. The consistency between Glauber calculation and experimental σCC of 12C isotope at low energy region shows that proton distribution radii can be derived from CCCS at low energy.

  8. The Carbon Isotopic Content and Concentration of Ambient Formic and Acetic Acid

    Science.gov (United States)

    Johnson, Bryan Jay

    A direct method for source determination of atmospheric formic and acetic acid, through carbon isotopic analysis of the ambient acids and their potential sources, has been successfully developed and tested. These first carbon isotopic measurements of formic acid in the atmosphere were found to be fairly constant, regardless of location. This is consistent with a single dominating source of formic acid, with vegetation emissions being the most likely controlling source. Collection of relatively large quantities (0.3 -3.0 mg) of the organic acids, which was necessary for carbon isotopic measurements, was effectively accomplished by a new method using calcium hydroxide-treated filters with a high-volume sampler. Samples were collected on a regular basis at Mount Lemmon, Arizona (elevation = 9200 feet A.S.L.). Atmospheric concentrations showed a well-defined seasonal pattern, with the lowest concentrations (about 0.2 ppbv) occurring in the middle of the winter, which steadily increased to a maximum of nearly 2 ppbv in the summer. The ^{13}C content (delta ^{13}C) of HCOOH averaged -20.9 +/- 2.5 ^0/_{00 } during the growing season (April-September) and -23.2 +/- 3.5 ^0/_{00} during the non-growing season at Mount Lemmon. Isotopic measurements of formic acid from several other locations included two west coast marine sites ( delta ^{13} C range of -19.1 to -24.6 ^0/_{00} ), three Colorado Rocky Mountain samples averaging -23.2 +/- 1.0 ^0/_{00}, two from the prairie of North Dakota (-23.5 +/- 1.0 ^0/ _{00}) and three samples collected in the urban Tucson, Arizona area (- 20.8 +/- 3.4 ^0 /_{00}). Source measurements included HCOOH emissions from two species of formicine ants (-18.8 +/- 1.7 ^0/_ {00}), and HCOOH in automobile exhaust (-28 ^0/ _{00} from leaded gasoline, and -48.6 ^0/ _{00} from unleaded). Further support for a biogenic source of atmospheric HCOOH came from the carbon-14 analysis of six Mount Lemmon HCOOH samples (93-113% modern carbon), using accelerator

  9. Mantle CO2 degassing through the Icelandic crust: Evidence from carbon isotopes in groundwater

    Science.gov (United States)

    Stefánsson, Andri; Sveinbjörnsdóttir, Árný E.; Heinemeier, Jan; Arnórsson, Stefán; Kjartansdóttir, Ríkey; Kristmannsdóttir, Hrefna

    2016-10-01

    Carbon isotopes of groundwater in Iceland were studied in order to determine the source and reactions of carbon at divergent plate boundaries not associated with active volcanic systems. All the waters were of meteoric origin, with temperatures of 1-130 °C, pH of ∼4.5-10.5 and dissolved inorganic carbon (∑CO2) between 1.8 and 4100 ppm. The measured range of δ13CO2 and 14CO2 in these waters was large, -27.4 to +2.0‰ and 0.6-118 pMC, respectively. The sources and reactions of dissolved inorganic carbon were studied by comparing the measured chemical and isotope composition with those simulated using isotope geochemical models. Three major sources of CO2 were identified: (1) dissolution of partially degassed basaltic rocks formed at the surface or shallow depths, (2) atmospheric CO2 through air-water exchange at surface, and (3) input of gas at depth into the groundwater systems that has similar carbon and isotope composition as the pre-erupted melt of the upper mantle and lower crust beneath Iceland. In the groundwater systems the CO2 chemistry and isotope content are modified due to carbonate mineral precipitation and changes in aqueous species distribution upon progressive water-rock interaction; these changes needed to be quantified in order to reveal the various CO2 sources. The CO2 flux of the Icelandic crust was estimated to be ∼5-10 · 1010 mol/yr with as high as 50% of the flux not associated with active volcanic centers but placed off-axis where a significant proportion of the CO2 may originate from the mantle. The mantle input of the groundwater off-axis corresponds to CO2 partial pressures of ∼10-6-1 bar and to a mantle CO2 flux of <5 · 105 mol/km2/yr for most areas and up to 125 · 105 and 1600 · 105 for the Southern Lowlands and Snæfellsnes Peninsula, respectively. The CO2 flux from active volcanic geothermal systems in Iceland was estimated to be ∼500-3000 · 105 mol CO2/km2/yr, considerably greater than the highest values observed off-axis.

  10. Time-dependent properties of liquid water isotopes adsorbed in carbon nanotubes

    Science.gov (United States)

    Martí, J.; Gordillo, M. C.

    2001-06-01

    Dynamics of liquid water and its isotopes when adsorbed inside carbon nanotubes of different radii is studied by means of molecular dynamics simulations. Water molecules have been modeled with a flexible simple point charged (SPC) potential while carbon forces were accounted for with Lennard-Jones-type potentials. Diffusive behavior and the librational, rotational, intra- and intermolecular motions of the constrained molecules have been investigated by means of the spectral densities computed from atomic velocity autocorrelation functions. The results show in all cases significant new vibrational bands and frequency shifts absent in bulk water.

  11. Hydrogen and carbon isotope systematics in hydrogenotrophic methanogenesis under H2-limited and H2-enriched conditions: implications for the origin of methane and its isotopic diagnosis

    Science.gov (United States)

    Okumura, Tomoyo; Kawagucci, Shinsuke; Saito, Yayoi; Matsui, Yohei; Takai, Ken; Imachi, Hiroyuki

    2016-12-01

    Hydrogen and carbon isotope systematics of H2O-H2-CO2-CH4 in hydrogenotrophic methanogenesis and their relation to H2 availability were investigated. Two H2-syntrophic cocultures of fermentatively hydrogenogenic bacteria and hydrogenotrophic methanogens under conditions of cultures of hydrogenotrophic methanogens under conditions of 105 Pa-H2 were tested. Carbon isotope fractionation between CH4 and CO2 during hydrogenotrophic methanogenesis was correlated with pH2, as indicated in previous studies. The hydrogen isotope ratio of CH4 produced during rapid growth of the thermophilic methanogen Methanothermococcus okinawensis under high pH2 conditions ( 105 Pa) was affected by the isotopic composition of H2, as concluded in a previous study of Methanothermobacter thermautotrophicus. This " {δ D}_{{H}_2} effect" is a possible cause of the diversity of previously reported values for hydrogen isotope fractionation between CH4 and H2O examined in H2-enriched culture experiments. Hydrogen isotope fractionation between CH4 and H2O, defined by (1000 + {δ D}_{{CH}_4} )/(1000 + {δ D}_{{H}_2O} ), during hydrogenotrophic methanogenesis of the H2-syntrophic cocultures was in the range 0.67-0.69. The hydrogen isotope fractionation of our H2-syntrophic dataset overlaps with those obtained not only from low- pH2 experiments reported so far but also from natural samples of "young" methane reservoirs (0.66-0.74). Conversely, such hydrogen isotope fractionation is not consistent with that of "aged" methane in geological samples (≥0.79), which has been regarded as methane produced via hydrogenotrophic methanogenesis from the carbon isotope fractionation. As a possible process inducing the inconsistency in hydrogen isotope signatures between experiments and geological samples, we hypothesize that the hydrogen isotope signature of CH4 imprinted at the time of methanogenesis, as in the experiments and natural young methane, may be altered by diagenetic hydrogen isotope exchange

  12. Carbon isotope excursions and the oxidant budget of the Ediacaran atmosphere and ocean

    Science.gov (United States)

    Bristow, Thomas F.; Kennedy, Martin J.

    2008-11-01

    A possible global drop in marine carbon isotope values to aslow as -12 Peedee belemnite (PDB), recorded in the EdiacaranShuram Formation of Oman, has been attributed to the non-steady-stateoxidation of oceanic dissolved organic carbon (DOC) resultingfrom the rise in atmospheric oxygen to near modern values atthe end of the Precambrian. Geologic constraints indicate thatthe excursion lasted between 25 and 50 m.y., requiring a DOCpool thousands of times to 10,000 times the modern inventoryto conform with carbon isotope mass balance calculations fora -12 excursion. At the consequent rates of DOC oxidation,oceanic sulfate and oxygen in the atmosphere and oceans areexhausted on a time scale of 800 k.y. Oxidant depletion isincompatible with independent geochemical and biological indicatorsthat show oceanic sulfate and oxygen levels were maintainedor increased during the Shuram excursion. Furthermore, a DOC-drivenexcursion does not explain strong covariation between the carbonand oxygen isotope record. These indicators show that negativeisotope excursions recorded in the Shuram and other Ediacaransections are unlikely to represent a global ocean signal.

  13. Tracing carbon sources through aquatic and terrestrial food webs using amino acid stable isotope fingerprinting.

    Directory of Open Access Journals (Sweden)

    Thomas Larsen

    Full Text Available Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring δ(13C patterns among amino acids (δ(13CAA could distinguish between multiple aquatic and terrestrial primary production sources. We found that δ(13CAA patterns in contrast to bulk δ(13C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their δ(13CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk δ(13C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer δ(13C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs.

  14. Carbonate Chemistry and Isotope Characteristics of Groundwater of Ljubljansko Polje and Ljubljansko Barje Aquifers in Slovenia

    Directory of Open Access Journals (Sweden)

    Sonja Cerar

    2013-01-01

    Full Text Available Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1 Ljubljansko polje aquifer, with higher Ca2+ values, as limestone predominates in its recharge area, (2 northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3 central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4 Brest and Iški vršaj aquifer in the southern part of Ljubljansko Barje with higher Mg2+ in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years.

  15. Carbonate Chemistry and Isotope Characteristics of Groundwater of Ljubljansko Polje and Ljubljansko Barje Aquifers in Slovenia

    Science.gov (United States)

    2013-01-01

    Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1) Ljubljansko polje aquifer, with higher Ca2+values, as limestone predominates in its recharge area, (2) northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3) central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4) Brest and Iški vršaj aquifer in the southern part of Ljubljansko Barje with higher Mg2+ in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years. PMID:24453928

  16. Carbonate chemistry and isotope characteristics of groundwater of Ljubljansko polje and Ljubljansko Barje aquifers in Slovenia.

    Science.gov (United States)

    Cerar, Sonja; Urbanc, Janko

    2013-01-01

    Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1) Ljubljansko polje aquifer, with higher Ca(2+)values, as limestone predominates in its recharge area, (2) northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3) central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4) Brest and Iški vršaj aquifer in the southern part of Ljubljansko Barje with higher Mg(2+) in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years.

  17. A synthetic standard for the analysis of carbon isotopes of carbon in silicates, and the observation of a significant water-associated matrix effect

    OpenAIRE

    House, Christopher H.

    2015-01-01

    Background Due to the biogeochemical fractionation of isotopes, organic material can be heterogeneous at the microscale. Because this heterogentiy preserves in the rock record, the microscale measurement of carbon isotopes is an important frontier of geobiology. Such analyses via secondary ion mass spectrometry (SIMS) have been, however, held back by the lack of an appropriate homogeneous synthetic standard that can be shared between laboratories. Such a standard would need to yield a carbon ...

  18. Mechanisms controlling the carbon stable isotope composition of phytoplankton in karst reservoirs

    Directory of Open Access Journals (Sweden)

    Baoli Wang

    2013-02-01

    Full Text Available In order to systematically understand the mechanisms controlling the carbon stable isotope composition of phytoplankton (δ13CPHYin freshwater ecosystems, seasonal changes in δ13CPHY and related environmental factors were determined in karst reservoirs from the Wujiang river basin, China. Substantial and systematic differences within seasons and reservoirs were observed for δ13CPHY, which ranged from -39.2‰ to -15.1‰. An increase in water temperature triggered fast growth of phytoplankton which assimilated more dissolved inorganic carbon (DIC, resulting in the increase of δ13CPHY, δ13CDIC and pH. When the concentration of dissolved carbon dioxide (CO2 was less than 10 mmol L–1, phytoplankton shifted to using HCO3– as a carbon source. This resulted in the sharp increase of δ13CPHY. The carbon stable isotope composition of phytoplankton tended to decrease with the increase of Bacillariophyta, which dominated in January and April, but tended to increase with the increase of Chlorophyta and Dinophyta, which dominated in July. Multiple regression equations suggested that the influence of biological factors such as taxonomic difference on δ13CPHY could be equal or more important than that of physical and chemical factors. Thus, the effect of taxonomic differences on δ13CPHY must be considered when explaining the δ13C of organic matter in lacustrine ecosystem.

  19. CO2 production by impact in carbonates? An ATEM and stable isotope (C,O) study

    Science.gov (United States)

    Martinez, I.; Agrinier, P.; Guyot, F.; Ildefonse, PH.; Javoy, M.; Schaerer, U.; Hornemann, U.; Deutsch, A.

    1993-01-01

    Carbonates may have been a common target for large impacts on the Earth and possible related CO2 outgassing would have important consequences for the composition of the atmosphere. To estimate volatile release during such impacts, isotopic ratios (C-13/C-12 and O-18/O-16) were determined on highly shocked carbonate samples in combination with SEM and analytical transmission electron microscopy (ATEM) investigations. The study was performed on both naturally and experimentally shocked rocks, i.e. 50-60 GPa shocked limestone-dolomite fragments from the Haughton impact crater (Canada), and carbonates shocked in shock recovery experiments. For the experiments, unshocked carbonates consisting of mixture of dolomite and calcite from the Haughton area were used. Naturally shocked samples were collected in the polymict breccia near the center of the Haughton crater.

  20. [Humus composition and stable carbon isotope natural abundance in paddy soil under long-term fertilization].

    Science.gov (United States)

    Ma, Li; Yang, Lin-Zhang; Ci, En; Wang, Yan; Yin, Shi-Xue; Shen, Ming-Xing

    2008-09-01

    Soil samples were collected from an experimental paddy field with long-term (26 years) fertilization in Taihu Lake region of Jiangsu Province to study the effects of different fertilization on the organic carbon distribution and stable carbon isotope natural abundance (delta 13C) in the soil profile, and on the humus composition. The results showed that long-term fertilization increased the organic carbon content in top soil significantly, and there was a significantly negative exponential correlation between soil organic carbon content and soil depth (P humus (humin) was the main humus composition in the soil, occupying 50% or more, and the rest were loosely and stably combined humus. Long-term fertilization increased the content of loosely combined humus and the ratio of humic acid (HA) to fulvic acid (FA).

  1. Boron isotopic fractionation in laboratory inorganic carbonate precipitation: Evidence for the incorpora-tion of B(OH)3 into carbonate

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A laboratory inorganic carbonate precipitation experiment at high pH of 8.96 to 9.34 was conducted, and the boron isotopic fractionations of the precipitated carbonate were measured. The data show that boron isotopic fractionation factors (αcarb-3) between carbonate and B(OH)3 in seawater range 0.937 and 0.965, with an average value of 0.953. Our results together with those reported by Sanyal and collabo-rators show that the αcarb-3 values between carbonate and B(OH)3 in solution are not constant but are negatively correlated with the pH of seawater. The measured boron isotopic compositions of carbonate precipitation (δ11Bcarb) do not exactly lie on the best-fit theoretical δ 11B4-pH curves and neither do they exactly parallel any theoretical δ 11B4-pH curves. Therefore, it is reasonable to argue that a changeable proportion of B(OH)3 with pH of seawater should also be incorporated into carbonate except for the dominant incorporation of B(OH)4- in carbonate . Hence, in the reconstruction of the paleo-pH of sea-water from boron isotopes in marine biogenic carbonates, the use of theoretical boron isotopic frac-tionation factor (α4-3) between B(OH)4- and B(OH)3 is not suitable. Instead, an empirical equation should be established.

  2. Carbon elemental and isotopic composition in mantle xenoliths from Spain: Insights on sources and petrogenetic processes

    Science.gov (United States)

    Bianchini, G.; Natali, C.

    2017-02-01

    The carbon elemental concentration (C wt%) and isotopic (δ13C ‰) composition of mantle xenoliths from the Tallante and Calatrava volcanic occurrences (in South-East and Central Spain, respectively) have been investigated to identify carbon sources and processes occurring in distinct geodynamic settings of the Iberian Peninsula. The peridotitic mantle xenoliths from Calatrava show elemental C ranging from 0.11 to 2.87 wt% which is coupled with a continuous isotopic variation from very negative values (δ13C - 26.1‰) to typical mantle values (δ13C - 5.9‰). On the other hand, the Tallante mantle xenolith suite displays lower C contents (0.06-0.15 wt%) showing a tighter variation with 13C-depleted values ranging between - 20.1 and - 23.7‰; higher elemental C up to 0.41 wt% displaying distinctly less negative isotopic values (δ13C between - 13.8 and - 11.9‰) have been recorded in veins crosscutting Tallante peridotites, plausibly representing the product of metasomatic reactions. The data from the two investigated xenolith suites invariably display a good correlation between elemental and isotopic composition, suggesting a mantle origin for carbon and Rayleigh-type fractionation as the process responsible for the observed C-δ13C variation. However, the correlation between the carbon isotopic data with other isotopic tracers (e.g. 87Sr/86Sr, 3He/4He) used to identify distinct mantle components and metasomatic reactions, indicates systematic differences between the two xenolith suites suggesting that beneath the Betic Cordillera (where Tallante is located) the deep C-cycle involves recycling, via subduction preceding/accompanying continental collision, of crustal components back in the mantle. Coherently, geochemical trends observed in the Tallante xenoliths seem to be influenced by metasomatic agents generated by melting of crustal lithologies that according to the analysis of a metasedimentary xenolith can contain C up to 1.2 wt% having δ13C of ca. - 18

  3. Stable isotopic composition of pedogenic carbonate in soils of Minusinsk Hollow

    Science.gov (United States)

    Vasil'chuk, Jessica; Krechetov, Pavel; Budantseva, Nadine; Chizhova, Julia; Vasil'chuk, Yurij

    2016-04-01

    The purpose of the research is to characterize the isotopic composition of carbonate neoformations in soils and estimate its correlation with isotopic composition of water and parent material. The study site is located in the Minusinsk Hollow that is situated among Kuznetsk Alatau and Sayan Mountains. Three key-sites with in different parts of hollow, under mainly steppe vegetation with calciphilic grasses and diverse parent material were studied including: 1) Kazanovka Khakass state national reserve in foothills of Kuznetsk Alatau 2) Hankul salt lake that is considered as natural monument 3) region of Sayanogorsk aluminum smelter on a left bank of the Yenisei river. The samples of pedogenic and lithogenic carbonates as well as water samples were analyzed using the Delta-V mass spectrometer with a standard option of a gas bench according to standard methods. Carbonate coatings (also called pendants or cutans) is one of the most common types of carbonate neoformations occurring in the region. Fine coatings' layers one over another usually can be found on the bottom sides of rubble and gravel inside the soil profile colour varies from white to brownish and yellowish (probably depending on the impurities of organic matter). In Petric Calcisols, Chernozems and Kastanozems δ18O values of coatings vary in a rather small range from - 8.9 to - 10.1 ‰ PDB. This probably shows that their forming took place approximately in the same climatic conditions. While δ18O values of carbonate parent rocks are close to them and are vary from - 11.1 to - 11.9 ‰ PDB. Also, δ13C values of coatings strongly decrease from inner (older) to outer (younger) layers, that can indicate differences connected with the diffusion of organic material. River waters' δ18O values also show a small range from - 16.62 to - 17.66‰ SMOW, while salt lakes' waters due to the fractionation evaporation effects demonstrate much heavier values from - 4.73 to - 9.22‰ SMOW. The groundwater shows δ18O

  4. Springtime carbon emission episodes at the Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    Science.gov (United States)

    Jung, J.; Kawamura, K.

    2011-11-01

    In order to investigate the emission of carbonaceous aerosols at the Gosan background super-site (33.17° N, 126.10° E) in East Asia, total suspended particles (TSP) were collected during spring of 2007 and 2008 and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (δ13C) of TC. The stable carbon isotopic composition of TC (δ13CTC) was found to be lowest during pollen emission episodes (range: -26.2‰ to -23.5‰, avg. -25.2 ± 0.9‰), approaching those of the airborne pollen (-28.0‰) collected at the Gosan site. Based on a carbon isotope mass balance equation, we found that ~42% of TC in the TSP samples during the pollen episodes was attributed to airborne pollen from Japanese cedar trees planted around tangerine farms in Jeju Island. A negative correlation between the citric acid-carbon/TC ratios and δ13CTC was obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollen and then transported to the Gosan site. Thermal evolution patterns of organic carbon during the pollen episodes were characterized by high OC evolution in the OC2 temperature step (450 °C). Since thermal evolution patterns of organic aerosols are highly influenced by their molecular weight, they can be used as additional information on the formation of secondary organic aerosols and the effect of aging of organic aerosols during the long-range atmospheric transport and sources of organic aerosols.

  5. Environmental impact and magnitude of paleosol carbonate carbon isotope excursions marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    Science.gov (United States)

    Abels, Hemmo A.; Lauretano, Vittoria; van Yperen, Anna E.; Hopman, Tarek; Zachos, James C.; Lourens, Lucas J.; Gingerich, Philip D.; Bowen, Gabriel J.

    2016-05-01

    Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically light carbon to the exogenic atmosphere-ocean carbon system, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE) can be used to constrain both the sources and amounts of carbon released during an event and also to correlate marine and terrestrial records with high precision. The Paleocene-Eocene Thermal Maximum (PETM) is well documented, but CIE records for the subsequent warming events are still rare, especially from the terrestrial realm.Here, we provide new paleosol carbonate CIE records for two of the smaller hyperthermal events, I1 and I2, as well as two additional records of Eocene Thermal Maximum 2 (ETM2) and H2 in the Bighorn Basin, Wyoming, USA. Stratigraphic comparison of this expanded, high-resolution terrestrial carbon isotope history to the deep-sea benthic foraminiferal isotope records from Ocean Drilling Program (ODP) sites 1262 and 1263, Walvis Ridge, in the southern Atlantic Ocean corroborates the idea that the Bighorn Basin fluvial sediments record global atmospheric change. The ˜ 34 m thicknesses of the eccentricity-driven hyperthermals in these archives corroborate precession forcing of the ˜ 7 m thick fluvial overbank-avulsion sedimentary cycles. Using bulk-oxide mean-annual-precipitation reconstructions, we find soil moisture contents during the four younger hyperthermals that are similar to or only slightly wetter than the background, in contrast with soil drying observed during the PETM using the same proxy, sediments, and plant fossils.The magnitude of the CIEs in soil carbonate for the four smaller, post-PETM events scale nearly linearly with the equivalent event magnitudes documented in marine records. In contrast, the magnitude of the PETM terrestrial CIE is at least 5 ‰ smaller than expected based on extrapolation of the scaling relationship established

  6. Widespread kelp-derived carbon in pelagic and benthic nearshore fishes suggested by stable isotope analysis

    Science.gov (United States)

    von Biela, Vanessa R.; Newsome, Seth D.; Bodkin, James L.; Kruse, Gordon H.; Zimmerman, Christian E.

    2016-11-01

    Kelp forests provide habitat for diverse and abundant fish assemblages, but the extent to which kelp provides a source of energy to fish and other predators is unclear. To examine the use of kelp-derived energy by fishes we estimated the contribution of kelp- and phytoplankton-derived carbon using carbon (δ13C) and nitrogen (δ15N) isotopes measured in muscle tissue. Benthic-foraging kelp greenling (Hexagrammos decagrammus) and pelagic-foraging black rockfish (Sebastes melanops) were collected at eight sites spanning ∼35 to 60°N from the California Current (upwelling) to Alaska Coastal Current (downwelling) in the northeast Pacific Ocean. Muscle δ13C values were expected to be higher for fish tissue primarily derived from kelp, a benthic macroalgae, and lower for tissue primarily derived from phytoplankton, pelagic microalgae. Muscle δ13C values were higher in benthic-feeding kelp greenling than in pelagic-feeding black rockfish at seven of eight sites, indicating more kelp-derived carbon in greenling as expected. Estimates of kelp carbon contributions ranged from 36 to 89% in kelp greenling and 32 to 65% in black rockfish using carbon isotope mixing models. Isotopic evidence suggests that these two nearshore fishes routinely derive energy from kelp and phytoplankton, across coastal upwelling and downwelling systems. Thus, the foraging mode of nearshore predators has a small influence on their ultimate energy source as energy produced by benthic macroalgae and pelagic microalgae were incorporated in fish tissue regardless of feeding mode and suggest strong and widespread benthic-pelagic coupling. Widespread kelp contributions to benthic- and pelagic-feeding fishes suggests that kelp energy provides a benefit to nearshore fishes and highlights the potential for kelp and fish production to be linked.

  7. Authenticity of carbon dioxide bubbles in French ciders through multiflow-isotope ratio mass spectrometry measurements.

    Science.gov (United States)

    Gaillard, Laetitia; Guyon, Francois; Salagoïty, Marie-Hélène; Médina, Bernard

    2013-12-01

    A procedure to detect whether carbon dioxide was added to French ciders has been developed. For this purpose, an optimised and simplified method is proposed to determine (13)C/(12)C isotope ratio of carbon dioxide (δ(13)C) in ciders. Three critical steps were checked: (1) influence of atmospheric CO2 remaining in the loaded vial, (2) impact of helium flush, (3) sampling speed. This study showed that atmospheric CO2 does not impact the measurement, that helium flush can lead to isotopic fractionation and finally, that a fractionation occurs only 5h after bottle opening. The method, without any other preparation, consists in sampling 0.2 mL of cold (4 °C) cider in a vial that is passed in an ultrasonic bath for 10 min at room temperature to enhance cider de-carbonation. The headspace CO2 is then analysed using the link Multiflow®-isotope ratio mass spectrometer. Each year, a data bank is developed by fermenting authentic apples juices in order to control cider authenticity. Over a four year span (2008-2011), the CO2 produced during the fermentation step was studied. This set of 61 authentic ciders, from various French production areas, was used to determine a δ(13)C value range of -22.59±0.92‰ for authentic ciders CO2 bubbles. 75 commercial ciders were analysed with this method. Most of the samples analysed present a gas δ(13)C value in the expected range. Nevertheless, some ciders have δ(13)C values outside the 3σ limit, revealing carbonation by technical CO2. This practice is not allowed for organic, "Controlled Appellation of Origin" ciders and ciders specifying natural carbonation on the label.

  8. Carbon isotopes in otolith amino acids identify residency of juvenile snapper (Family: Lutjanidae) in coastal nurseries

    Science.gov (United States)

    McMahon, K. W.; Berumen, M. L.; Mateo, I.; Elsdon, T. S.; Thorrold, S. R.

    2011-12-01

    This study explored the potential for otolith geochemistry in snapper (Family: Lutjanidae) to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk otolith and muscle stable isotope analyses (SIA) and essential amino acid (AA) SIA were conducted on snapper collected from seagrass beds, mangroves, and coral reefs in the Red Sea, Caribbean Sea, and Pacific coast of Panama. While bulk stable isotope values in otoliths showed regional differences, they failed to distinguish nursery residence on local scales. Essential AA δ13C values in otoliths, on the other hand, varied as a function of habitat type and provided a better tracer of residence in different juvenile nursery habitats than conventional bulk otolith SIA alone. A strong linear relationship was found between paired otolith and muscle essential AA δ13C values regardless of species, geographic region, or habitat type, indicating that otolith AAs recorded the same dietary information as muscle AAs. Juvenile snapper in the Red Sea sheltered in mangroves but fed in seagrass beds, while snapper from the Caribbean Sea and Pacific coast of Panama showed greater reliance on mangrove-derived carbon. Furthermore, compound-specific SIA revealed that microbially recycled detrital carbon, not water-column-based new phytoplankton carbon, was the primary carbon source supporting snapper production on coastal reefs of the Red Sea. This study presented robust tracers of juvenile nursery residence that will be crucial for reconstructing ontogenetic migration patterns of fishes among coastal wetlands and coral reefs. This information is key to determining the importance of nursery habitats to coral reef fish populations and will provide valuable scientific support for the design of networked marine-protected areas.

  9. Carbon isotopes in otolith amino acids identify residency of juvenile snapper (Family: Lutjanidae) in coastal nurseries

    KAUST Repository

    McMahon, Kelton

    2011-08-26

    This study explored the potential for otolith geochemistry in snapper (Family: Lutjanidae) to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk otolith and muscle stable isotope analyses (SIA) and essential amino acid (AA) SIA were conducted on snapper collected from seagrass beds, mangroves, and coral reefs in the Red Sea, Caribbean Sea, and Pacific coast of Panama. While bulk stable isotope values in otoliths showed regional differences, they failed to distinguish nursery residence on local scales. Essential AA δ13C values in otoliths, on the other hand, varied as a function of habitat type and provided a better tracer of residence in different juvenile nursery habitats than conventional bulk otolith SIA alone. A strong linear relationship was found between paired otolith and muscle essential AA δ13C values regardless of species, geographic region, or habitat type, indicating that otolith AAs recorded the same dietary information as muscle AAs. Juvenile snapper in the Red Sea sheltered in mangroves but fed in seagrass beds, while snapper from the Caribbean Sea and Pacific coast of Panama showed greater reliance on mangrove-derived carbon. Furthermore, compound-specific SIA revealed that microbially recycled detrital carbon, not water-column-based new phytoplankton carbon, was the primary carbon source supporting snapper production on coastal reefs of the Red Sea. This study presented robust tracers of juvenile nursery residence that will be crucial for reconstructing ontogenetic migration patterns of fishes among coastal wetlands and coral reefs. This information is key to determining the importance of nursery habitats to coral reef fish populations and will provide valuable scientific support for the design of networked marine-protected areas. © 2011 Springer-Verlag.

  10. Dissolved inorganic carbon and stable carbon isotopic evolution of neutral mine drainage interacting with atmospheric CO{sub 2(g)}

    Energy Technology Data Exchange (ETDEWEB)

    Abongwa, Pride Tamasang, E-mail: abongwa@okstate.edu; Atekwana, Eliot Anong; Puckette, James

    2016-03-01

    We investigated the spatial variations in the concentrations of dissolved inorganic carbon (DIC), the stable carbon isotopic composition (δ{sup 13}C) of DIC and the δ{sup 13}C of carbonate precipitated from neutral mine drainage interacting with the atmospheric CO{sub 2(g)}. We assessed the chemical, DIC and δ{sup 13}C{sub DIC} evolution of the mine drainage and the δ{sup 13}C evolution of carbonate precipitates for a distance of 562 m from the end of an 8 km tunnel that drains a mine. Our results show that as the mine drainage interacts with atmospheric CO{sub 2(g)} the outgassing of CO{sub 2} due to the high initial partial pressure of CO{sub 2} (pCO{sub 2}) causes the DIC to evolve under kinetic conditions followed by equilibration and then under equilibrium conditions. The carbonate evolution was characterized by spatial increases in pH, decreasing concentrations of Ca{sup 2+} and DIC and by the precipitation of carbonate. The δ{sup 13}C{sub DIC} showed a larger enrichment from the tunnel exit to 38 m, moderate continuous enrichment to 318 m and almost no enrichment to 562 m. On the other hand, the δ{sup 13}C of the carbonate precipitates also showed large enrichment from the tunnel exit to 38 m, moderate enrichment to 318 m after which the δ{sup 13}C remained nearly constant. The enrichment in the δ{sup 13}C of the DIC and the carbonate precipitates from 0 to 38 m from kinetic fractionation caused by CO{sub 2(g)} outgassing was followed by a mix of kinetic fractionation and equilibrium fractionation controlled by carbon exchange between DIC and atmospheric CO{sub 2(g)} to 318 m and then by equilibrium fractionation from 318 to 562 m. From the carbonate evolution in this neutral mine drainage, we estimated that 20% of the carbon was lost via CO{sub 2} outgassing, 12% was sequestered in sediments in the drainage ponds from calcite precipitation and the remainder 68% was exported to the local stream. - Highlights: • We assess the δ{sup 13}C in a

  11. Oxygen-isotopic composition and high-resolution secondary ion mass spectrometry imaging of Martian carbonate in Lafayette meteorite

    OpenAIRE

    Vicenzi, E. P.; Eiler, J.

    1998-01-01

    Carbonate from SNC meteorites gives insight into a variety of processes on and/or beneath the surface of Mars. In Lafayette, carbonate occurs in unusually intimate association with hydrous phases when compared with other carbonate-bearing SNCs [1]. We have measured the ^(18)O/^(16)O ratio of carbonate in the alteration veins of Lafayette using the magnetic sector ion microprobe. In addition, we obtained isotope images of major- and minor-element cations in veinlets with the ...

  12. Carbon isotope fractionation of 1,1,1-trichloroethane during base-catalyzed persulfate treatment

    Energy Technology Data Exchange (ETDEWEB)

    Marchesi, Massimo, E-mail: m2marche@uwaterloo.ca [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Thomson, Neil R. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Aravena, Ramon [Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Sra, Kanwartej S. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada); Otero, Neus; Soler, Albert [Departament de Cristal.lographia, Mineralogia i Diposits Minerals, Facultat de Geologia, Universitat de Barcelona, Barcelona, Spain 08028 (Spain)

    2013-09-15

    Highlights: • Treatability and C fractionation of 1,1,1-TCA by base-catalyzed S{sub 2}O{sub 8}{sup 2−} was studied. • The rate of degradation of 1,1,1-TCA increased with a higher OH{sup −}:S{sub 2}O{sub 8}{sup 2−} ratio. •Base-catalyzed S{sub 2}O{sub 8}{sup 2−} can potentially treat recalcitrant compound like 1,1,1-TCA. • An enrichment factor of −7.0‰ independent of the OH{sup −}:S{sub 2}O{sub 8}{sup 2−} ratio was obtained. • Carbon isotope can potentially be used to estimate the ISCO treatment efficacy. -- Abstract: The extent of carbon isotope fractionation during degradation of 1,1,1-trichloroethane (1,1,1-TCA) by a base-catalyzed persulfate (S{sub 2}O{sub 8}{sup 2−}) treatment system was investigated. Significant destruction of 1,1,1-TCA was observed at a pH of ∼12. An increase in the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio from 0.2:1 to 8:1 enhanced the reaction rate of 1,1,1-TCA by a factor of ∼5 to yield complete (>99.9%) destruction. An average carbon isotope enrichment fractionation factor which was independent of the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio of −7.0 ± 0.2‰ was obtained. This significant carbon isotope fractionation and the lack of dependence on changes in the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio demonstrates that carbon isotope analysis can potentially be used in situ as a performance assessment tool to estimate the degradation effectiveness of 1,1,1-TCA by a base-catalyzed persulfate system.

  13. Stable isotopes of carbon dioxide in soil gas over massive sulfide mineralization at Crandon, Wisconsin

    Science.gov (United States)

    Alpers, C.N.; Dettman, D.L.; Lohmann, K.C.; Brabec, D.

    1990-01-01

    Stable isotope ratios of oxygen and carbon were determined for CO2 in soil gas in the vicinity of the massive sulfide deposit at Crandon, Wisconsin with the objective of determining the source of anomalously high CO2 concentrations detected previously by McCarthy et al. (1986). Values of ??13C in soil gas CO2 from depths between 0.5 and 1.0 m were found to range from -12.68??? to -20.03??? (PDB). Organic carbon from the uppermost meter of soil has ??13C between -24.1 and -25.8??? (PDB), indicating derivation from plant species with the C3 (Calvin) type of photosynthetic pathway. Microbial decomposition of the organic carbon and root respiration from C3 and C4 (Hatch-Slack) plants, together with atmospheric CO2 are the likely sources of carbon in soil gas CO2. Values of ??18O in soil-gas CO2 range from 32 to 38??? (SMOW). These ??18O values are intermediate between that calculated for CO2 gas in isotopic equilibrium with local groundwaters and that for atmospheric CO2. The ??18O data indicate that atmospheric CO2 has been incorporated by mixing or diffusion. Any CO2 generated by microbial oxidation of organic matter has equilibrated its oxygen isotopes with the local groundwaters. The isotopic composition of soil-gas CO2 taken from directly above the massive sulfide deposit was not distinguishable from that of background samples taken 1 to 2 km away. No enrichment of the ??13C value of soil-gas CO2 was observed, contrary to what would be expected if the anomalous CO2 were derived from the dissolution of Proterozoic marine limestone country rock or of Paleozoic limestone clasts in glacial till. Therefore, it is inferred that root respiration and decay of C3 plant material were responsible for most CO2 generation both in the vicinity of the massive sulfide and in the "background" area, on the occasion of our sampling. Interpretation of our data is complicated by the effects of rainfall, which significantly reduced the magnitude of the CO2 anomaly. Therefore, we cannot

  14. Stable carbon isotope fractionation in the UV photolysis of CFC-11 and CFC-12

    Directory of Open Access Journals (Sweden)

    A. Zuiderweg

    2011-12-01

    Full Text Available The chlorofluorocarbons CFC-11 (CCl3F and CFC-12 (CCl2F2 are stable atmospheric compounds that are produced at the earth's surface, but removed only at high altitudes in the stratosphere, where their removal liberates atomic chlorine that then catalytically destroys stratospheric ozone. For such long-lived compounds, isotope effects in the stratospheric removal reactions have a large effect on their global isotope budgets. We have determined the photolytic isotope fractionation for stable carbon isotopes of CFC-11 and CFC-12 in laboratory experiments. 13C/12C isotope fractionations (ϵ range from (−23.7 ± 0.9 to (−17.5 ± 0.4‰ for CFC-11 and (−69.2 ± 3.4 to (−49.4 ± 2.3‰ for CFC-12 between 203 and 288 K, a temperature range relevant to conditions in the troposphere and stratosphere. These results suggest that CFCs should become strongly enriched in 13C with decreasing mixing ratio in the stratosphere, similar to what has been recently observed for CFC chlorine isotopes. In conjunction with the strong variations in CFC emissions before and after the Montréal Protocol, the stratospheric enrichments should also lead to a significant temporal increase in the 13C content of the CFCs at the surface over the past decades, which should be recorded in atmospheric air archives such as firn air.

  15. Hominins, sedges, and termites: new carbon isotope data from the Sterkfontein valley and Kruger National Park.

    Science.gov (United States)

    Sponheimer, Matt; Lee-Thorp, Julia; de Ruiter, Darryl; Codron, Daryl; Codron, Jacqui; Baugh, Alexander T; Thackeray, Francis

    2005-03-01

    Stable carbon isotope analyses have shown that South African australopiths did not have exclusively frugivorous diets, but also consumed significant quantities of C4 foods such as grasses, sedges, or animals that ate these foods. Yet, these studies have had significant limitations. For example, hominin sample sizes were relatively small, leading some to question the veracity of the claim for australopith C4 consumption. In addition, it has been difficult to determine which C4 resources were actually utilized, which is at least partially due to a lack of stable isotope data on some purported australopith foods. Here we begin to address these lacunae by presenting carbon isotope data for 14 new hominin specimens, as well as for two potential C4 foods (termites and sedges). The new data confirm that non-C3 foods were heavily utilized by australopiths, making up about 40% and 35% of Australopithecus and Paranthropus diets respectively. Most termites in the savanna-woodland biome of the Kruger National Park, South Africa, have intermediate carbon isotope compositions indicating mixed C3/C4 diets. Only 28% of the sedges in Kruger were C4, and few if any had well-developed rhizomes and tubers that make some sedges attractive foods. We conclude that although termites and sedges might have contributed to the C4 signal in South African australopiths, other C4 foods were also important. Lastly, we suggest that the consumption of C4 foods is a fundamental hominin trait that, along with bipedalism, allowed australopiths to pioneer increasingly open and seasonal environments.

  16. A reconstruction of atmospheric carbon dioxide and its stable carbon isotopic composition from the penultimate glacial maximum to the last glacial inception

    Directory of Open Access Journals (Sweden)

    R. Schneider

    2013-11-01

    δ13Catm level in the Penultimate (~ 140 000 yr BP and Last Glacial Maximum (~ 22 000 yr BP, which can be explained by either (i changes in the isotopic composition or (ii intensity of the carbon input fluxes to the combined ocean/atmosphere carbon reservoir or (iii by long-term peat buildup. Our isotopic data suggest that the carbon cycle evolution along Termination II and the subsequent interglacial was controlled by essentially the same processes as during the last 24 000 yr, but with different phasing and magnitudes. Furthermore, a 5000 yr lag in the CO2 decline relative to EDC temperatures is confirmed during the glacial inception at the end of MIS5.5 (120 000 yr BP. Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.

  17. Isotopic evolution of the terminal Neoproterozoic and early Cambrian carbon cycle on the northern Yangtze Platform, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Qingjun; LIU Congqiang; Harald STRAUSS; Tatiana GOLDBERG

    2003-01-01

    Profound geotectonic, climatic and biological changes occur during the terminal Neoproterozoic and its transition into the early Cambrian. These are reflected in temporal variations of the chemical and isotopic composition of seawater. We are studying a sequence of sedimentary rocks at the Shatan section, northern Yangtze Platform, Sichuan Province of China. This succession comprises, in ascending stratigraphic order, predominantly calcareous sediments of the Sinian upper Dengying Formation and black shales of the lower Cambrian Guojiaba Formation (time equivalent of Niutitang Fm.). Paleoenvironmental setting represents shallow-water shelf deposits. The objective of our study is to provide temporal records for the isotopic compositions of organic and carbonate carbon throughout this time interval. Organic carbon isotope values display a range between -35.8‰ and -30.1‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between -3.5‰ and +0.5‰. These secular variations are interpreted to reflect perturbations of the global carbon cycle, specifically changes in the fractional burial of organic carbon. However, local conditions have further affected the isotopic signals.

  18. Molecular isotopic engineering (MIE): industrial manufacture of naproxen of predetermined stable carbon-isotopic compositions for authenticity and security protection and intellectual property considerations

    Science.gov (United States)

    Jasper, J. P.; Farina, P.; Pearson, A.; Mezes, P. S.; Sabatelli, A. D.

    2016-05-01

    Molecular Isotopic Engineering (MIE) is the directed stable-isotopic synthesis of chemical products for reasons of product identification and of product security, and also for intellectual property considerations. We report here a generally excellent correspondence between the observed and predicted stable carbon-isotopic (δ13C) results for a successful directed synthesis of racemic mixture from its immediate precursors. The observed results are readily explained by the laws of mass balance and isotope mass balance. Oxygen- and hydrogen isotopic results which require an additional assessment of the effects of O and H exchange, presumably due to interaction with water in the reaction solution, are addressed elsewhere. A previous, cooperative study with the US FDA-DPA showed that individual manufacturers of naproxen could readily be differentiated by their stable-isotopic provenance (δ13C, δ18O, and δD ref. 1). We suggest that MIE can be readily employed in the bio/pharmaceutical industry without alteration of present manufacturing processes other than isotopically selecting and/or monitoring reactants and products.

  19. A high resolution record of atmospheric carbon dioxide and its stable carbon isotopic composition from the penultimate glacial maximum to the glacial inception

    Directory of Open Access Journals (Sweden)

    R. Schneider

    2013-04-01

    Full Text Available The reconstruction of the stable carbon isotope evolution in atmospheric CO2 (δ13Catm, as archived in Antarctic ice cores, bears the potential to disentangle the contributions of the different carbon cycle fluxes causing past CO2 variations. Here we present a highly resolved record of δ13Catm before, during and after the Marine Isotope Stage 5.5 (155 000 to 105 000 yr BP. The record was derived with a well established sublimation method using ice from the EPICA Dome C (EDC and the Talos Dome ice cores in East Antarctica. We find an 0.4‰ offset between the mean δ13Catm level in the Penultimate (~140 000 yr BP and Last Glacial Maximum (~22 000 yr BP, which can be explained by either (i changes in the isotopic composition or (ii intensity of the carbon input fluxes to the combined ocean/atmosphere carbon reservoir or (iii by long-term peat buildup. Our isotopic data suggest that the carbon cycle evolution along Termination II and the subsequent interglacial was controlled by essentially the same processes as during the last 24 000 yr, but with different phasing and magnitudes. Furthermore, a 5000 yr lag in the CO2 decline relative to EDC temperatures is confirmed during the glacial inception at the end of MIS 5.5 (120 000 yr BP. Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.

  20. Carbon and Nitrogen Stable Isotope Values for Plants and Mammals in a Semi-Desert Region of Mongolia

    Directory of Open Access Journals (Sweden)

    Hannah Davie

    2014-12-01

    Full Text Available Little information exists on the isotopic signatures of plants and animals in Mongolia, limiting the application of stable isotope analysis to wildlife biology studies. Here we present plant and mammal carbon (δ 13 C and nitrogen (δ 15 N isotope values from a desert-steppe region of southeastern Mongolia. We analyzed 11 samples from 11 plant species and 93 samples from 24 mammal species across Ikh Nart Nature Reserve, and compared these numbers to isotope values reported from other areas of Mongolia. Our plant and mammal 13 C and 15 N values were similar to those from a similar arid steppe region and more enriched than those from less arid habitats. Habitat variation within and between study sites has an important infl uence on δ 13 C and δ 15 N variation. Our results supplement current knowledge of isotopic variation in Mongolia and provide a reference for future stable isotope research in Mongolia and similar Asian steppe ecosystems.

  1. Estimation of food composition of Hodotermes mossambicus (Isoptera: Hodotermitidae) based on observations and stable carbon isotope ratios

    Institute of Scientific and Technical Information of China (English)

    Craig T. Symes; Stephan Woodborne

    2011-01-01

    The diet of the harvester termite Hodotermes mossambicus was investigated at two sites with distinct dietary components: C4 grasses (δ13 C isotope values, -13.8‰to -14.0‰) and C3 plants (δ13C isotope values, -25.6‰ to -27.1‰). By comparing observations of food items carried into the colony by the termites and carbon isotope ratios of whole termites (that determined assimilated carbon), the relative proportion of the C3 and C4 plant food components of the termite diet was estimated. There was agreement between the observational data and stable carbon isotopic data, with grass representing approximately 93% of the diet of H, mossambicus at two study sites (urban and rural) on the South African highveld. However, when correcting for mass of food items, that is, C3 and C4, carried by termites, the proportion of grass (C4) in the diet may be underestimated.

  2. Investigating Carbonate System Perturbations across the Cretaceous-Palaeogene Transition using Boron Isotopes in Planktonic Foraminifera.

    Science.gov (United States)

    Henehan, M. J.; Hull, P. M.; Planavsky, N. J.; Huber, B. T.; Thomas, E.

    2014-12-01

    The interval spanning the latest Maastrichtian to the early Palaeocene has great potential in helping to elucidate the stabilising mechanisms on the Earth's carbonate system on both long and very short geological timescales, from the geologically-instantaneous production of sulphate-rich aerosols and nitrogen oxides from the K-Pg bolide impact to the relatively more gradual degassing from Deccan volcanism in the latest Maastrichtian. The extent to which ocean pH (and atmospheric CO2 concentrations) changed in response to these contrasting acidification pressures, and the timescales of their recovery, may provide unique insight into the efficiency of the Earth's oceans in buffering greenhouse gas increases (through carbonate dissolution, weathering-derived alkalinity flux, and biological carbon cycling). The boron isotope palaeo-pH proxy in planktic foraminifera is well suited to such investigations, but its application over this interval has been problematic, not least due to a scarcity of sample material and a near-complete turnover of planktonic foraminiferal species across the K-Pg boundary. To attempt to circumvent these issues, we investigate the biological influences on boron isotope signals in Maastrichtian and Danian planktonic foraminifera, with the goal of producing more accurate palaeo-pH reconstructions. With these findings in mind, we present preliminary constraints on ocean pH and carbonate system dynamics across this critical interval of geological time.

  3. The Carnian (Late Triassic) carbon isotope excursion: new insights from the terrestrial realm

    Science.gov (United States)

    Miller, Charlotte; Kürschner, Wolfram; Peterse, Francien; Baranyi, Viktoria; Reichart, Gert-Jan

    2016-04-01

    The geological record contains evidence for numerous pronounced perturbations in the global carbon cycle, some of which are associated with eruptions from large igneous provinces (LIP), and consequently, ocean acidification and mass extinction. In the Carnian (Late Triassic), evidence from sedimentology and fossil pollen points to a significant change in climate, resulting in biotic turnover: during a period termed the 'Carnian Pluvial Event' (CPE). Additionally, during the Carnian, large volumes of flood basalts were erupted from the Wrangellia LIP (western North America). Evidence from the marine realm suggests a fundamental relationship between the CPE, a global 'wet' period, and the injection of light carbon into the atmosphere from the LIP. Here we provide the first evidence from the terrestrial realm of a significant negative δ13C excursion through the CPE recorded in the sedimentary archive of the Wiscombe Park Borehole, Devon (UK). Both total organic matter and plant leaf waxes reflect a gradual carbon isotope excursion of ~-5‰ during this time interval. Our data provides evidence for the global nature of this isotope excursion, supporting the hypothesis that the excursion was likely the result of an injection of light carbon into the atmosphere from the Wrangellia LIP.

  4. High-Resolution Magnetic Susceptibility Stratigraphy Spanning Late Devonian Global Change from a New Scientific Drillcore in Canning Basin, Northwest Australia

    Science.gov (United States)

    Diamond, M. R.; Raub, T. D.; Kirschvink, J. L.; Playton, T. E.; Hocking, R. M.; Haines, P.; Tulipani, S.

    2010-12-01

    New shallow scientific drillcore has been recovered through the Frasnian-Famennian extinction boundary in northwest Australia’s Canning Basin. Previous work in the McWhae Ridge outcrop belt has identified patterns of turnover in trilobites and other fauna, change from sponge- and coral-dominated reefs to post-extinction microbial-dominated reefs, apparent sea level changes, and carbon isotopic evidence of late Devonian crisis. Continuous magnetic susceptibility (MS) stratigraphy yields highly structured oscillations spanning ~42 m of reef-slope carbonate. These oscillations appear to identify late Frasnian “Kellwasser” events and they may record sedimentary response to orbital variations, establishing a high-resolution relative chronostratigraphy of late Devonian global change. Magnetic susceptibility stratigraphy has been proposed as a generally useful chronometer for late Devonian time. Most of fifteen published MS stratigraphies crossing the Frasnian-Famennian boundary appear to share major excursions with the new McWhae Ridge result. Although upland tectonism in Canning Basin may be a caveat to straightforward eustatic interpretation of magnetic susceptibility variations, we suggest the higher-resolution and fresh drillcore context of this result prioritizes it as a standard for Frasnian-Famennian magnetic susceptibility variation.

  5. Mechanistic insights into the formation of chloroform from natural organic matter using stable carbon isotope analysis

    Science.gov (United States)

    Breider, Florian; Hunkeler, Daniel

    2014-01-01

    Chloroform can be naturally formed in terrestrial environments (e.g. forest soils, peatland) by chlorination of natural organic matter (NOM). Recently, it was demonstrated that natural and anthropogenic chloroform have a distinctly different carbon isotope signature that makes it possible to identify its origin in soil and groundwater. In order to evaluate the contribution of different functional groups to chloroform production and factors controlling the isotopic composition of chloroform, carbon isotope trends during chlorination of model compounds, soil organic matter (SOM) and humic acids were evaluated, and apparent kinetic isotope effects (AKIEs) quantified. Phenol and propanone were selected as model compounds representing common functional groups in NOM. Chlorination was induced by hypochlorous acid to mimic natural chlorination. The pH ranged between 4 and 8 to cover typical soil conditions. For each model compound and pH, different AKIEs were observed. For phenol, the AKIE was normal at pH 4 (1.0156 ± 0.0012) and inverse at pH 8 (0.9900 ± 0.0007). For 2-propoanol, an opposite pH dependence was observed with an inverse AKIE at pH 4 (0.9935 ± 0.0007) and a normal AKIE at pH 8 (1.0189 ± 0.0016). The variations of the AKIE values suggest that the rate-limiting step of the reaction is either the re-hybridization of the carbon atom involved in chloroform formation or the hydrolysis of trichloroacetyl intermediates depending on the nature of functional group and pH. The chloroform formation from humic acid and SOM gives rise to small isotope variations. A comparison of the isotopic trends of chloroform formed from humic acid and SOM with those found for the model compounds suggest that opposed AKIE associated with the chlorination of phenolic and ketone moieties of NOM partly compensate each other during chlorination of NOM indicating that different types of functional groups contribute to chloroform formation.

  6. Origin of graphite, and temperature of metamorphism in Precambrian Eastern Ghats Mobile Belt, Orissa, India: A carbon isotope approach

    Science.gov (United States)

    Sanyal, Prasanta; Acharya, B. C.; Bhattacharya, S. K.; Sarkar, A.; Agrawal, S.; Bera, M. K.

    2009-09-01

    The carbon isotope composition of graphite and carbon and oxygen isotope composition of associated calcite from different locations of the Eastern Ghats Mobile Belt (EGMB) of Orissa have been measured in order to understand the origin of graphite. The δ 13C values of graphite range from -2.4‰ to -26.6‰. Forty-four of sixty-one samples have δ 13C values less than -20‰. Most of these low δ 13C values graphite corresponds to schists and disseminations in khondalite and calc-silicate granulites, thus indicating graphitization of organic matter. The remaining light-carbon-graphite occurs as veins which is the result of graphitization of transported organic matter. The graphite with intermediate δ 13C value (-13‰ to -19‰) indicates carbon contributions from both organic and carbonates sources and/or mantle sources. The higher δ 13C values graphite (-2.4‰ to -8.8‰) represent mantle carbon and/or carbonate sources without significant contribution from organic carbon. The temperatures of metamorphism have been estimated using carbon isotope ratios of graphite and associated calcite of calc-silicate granulites, where typical cation exchange thermometer assemblages are lacking and significant mineral reaction textures used to calculate pressure-temperature of metamorphic events are absent. Metamorphic temperatures obtained 945 °C are close to the ultrahigh-temperature reported from the EGMB. The minimum temperature estimated using the graphite-carbonate carbon isotope ratio is 90 °C. The lower estimates of temperatures probably indicate changes in the carbon isotope ratio of calcite by decarbonation reaction or armoring of carbonaceous matter in silicates during metamorphism preventing continuous exchange with calcite.

  7. Insights into deep-time terrestrial carbon cycle processes from modern plant isotope ecology

    Science.gov (United States)

    Sheldon, N. D.; Smith, S. Y.

    2012-12-01

    While the terrestrial biosphere and soils contain much of the readily exchangeable carbon on Earth, how those reservoirs function on long time scales and at times of higher atmospheric CO2 and higher temperatures is poorly understood, which limits our ability to make accurate future predictions of their response to anthropogenic change. Recent data compilation efforts have outlined the response of plant carbon isotope compositions to a variety of environmental factors including precipitation amount and timing, elevation, and latitude. The compilations involve numerous types of plants, typically only found at a limited number of climatic conditions. Here, we expand on those efforts by examining the isotopic response of specific plant groups found both globally and across environmental gradients including: 1) ginkgo, 2) conifers, and 3) C4 grasses. Ginkgo is presently widely distributed as a cultivated plant and the ginkgoalean fossil record spans from the Permian to the present, making it an ideal model organism to understand climatic influence on carbon cycling both in modern and ancient settings. Ginkgo leaves have been obtained from a range of precipitation conditions (400-2200 mm yr-1), including dense sampling from individuals and populations in both Mediterranean and temperate climate areas and samples of different organs and developmental stages. Ginkgo carbon isotope results plot on the global C3 plant array, are consistent among trees at single sites, among plant organs, and among development stages, making ginkgo a robust recorder of both climatic conditions and atmospheric δ13C. In contrast, a climate-carbon isotope transect in Arizona highlights that conifers (specifically, pine and juniper) record large variability between organs and have a very different δ13C slope as a function of climate than the global C3 plant array, while C4 plants have a slope with the opposite sign as a function of climate. This has a number of implications for paleo

  8. Skeletal and isotopic composition and paleoclimatic significance of late Pleistocene carbonates, Ross Sea, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Taviani, M. (Ist. per la Geologia Marina, Bologna (Italy)); Reid, D.E.; Anderson, J.B. (Rice Univ., Houston, TX (United States))

    1993-01-01

    Carbonates cover an extensive area of the northwestern Ross Sea continental shelf. Radiocarbon dates yield late Pleistocene (stage 3) ages for these deposits, hence the carbonates appear to be correlative with widespread tills and glacial marine deposits in the region. Four carbonate facies are recognized on the basis of skeletal composition: a barnacle/foraminifer facies, a muddy bryozoan facies, a bryozoan/barnacle/pelecypod/foraminifer facies, and a planktonic foraminiferal facies. These deposits occur on the shelf and upper slope, while carbonate turbidities derived from them occur on the adjacent continental slope and rise. Compositional analyses of Ross Sea carbonates lend support to previously recognized criteria for identifying cold water carbonates. These include: (1) the presence of an associated ice-rafted component (including dropstones); (2) a dominance of calcite relative to other carbonate minerals (the remaining fraction consists solely of aragonite); (3) allochems that are entirely skeletal; and (4) heavy oxygen isotopic compositions (in the range of +3.0 to +5.1% PDB).

  9. Ultrahigh-Temperature Metamorphism in Madurai Granulites, Southern India: Evidence from Carbon Isotope Thermometry.

    Science.gov (United States)

    Satish-Kumar

    2000-07-01

    Ultrahigh-temperature (UHT) metamorphism in the Madurai Block of the southern Indian granulite terrain has been verified using the calcite-graphite isotope exchange thermometer. Carbon isotope thermometry has been applied to marbles from a locality near the reported occurrence of sapphirine granulites that have yielded temperature estimates of around 1000 degrees C. The delta(13)C and delta(18)O values of calcite are homogenous, implying equilibration of the isotopes during metamorphism. However, the delta(13)C values of single graphite crystals show variations in the order of 1 per thousand within a hand specimen. Detailed isotopic zonation studies indicate that graphite preserves either the time-integrated crystal growth history or reequilibrium fractionation during its cooling history. The graphite cores preserve higher delta(13)C values than the rims. The fractionation between calcite and graphite cores gives the highest metamorphic temperature of about 1060 degrees C, which matches the petrologically inferred temperature estimates in the high-magnesian pelites. The fractionation between graphite rims and calcite suggests a temperature of around 750 degrees C, which is interpreted to reflect retrograde cooling. This event is also observed in the sapphirine granulites. Calcite-graphite thermometry thus provides a useful tool to define UHT metamorphism in granulite terrains.

  10. Stable carbon isotope composition of monoterpanes in essential oils and crude oils

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Twenty-five monoterpanes from six types of essential oils and hydrogenated turpentine oil have been identified and their stable carbon isotope composition determined.Monoterpanes in essential oils sourced from terrestrial higher plants display a δ13C value in the range of-34‰-26‰,and mostly between-29‰ and-27‰.The δ13C value of any single monoterpane is very consistent in different essential oils.Acyclic monoterpanes show closer isotope composition between-28.6‰ and-26.2‰,with an average value of-27.7‰.In contrast,the isotope composition of cyclic monoterpanes is more scattered with an average value of-28.6‰.Isotopic fractionation with 13C enrichment has been observed during both artificial and geological hydrogenation of monoterpenoids to monoterpanes,and this is more obvious for the acyclic monoterpenoids.In addition to higher plants,acyclic monoterpane 2,6-dimethylheptane in crude oil can also be originated from other organic inputs.

  11. In situ carbon isotope analysis of Archean organic matter with SIMS

    Science.gov (United States)

    Williford, K. H.; Ushikubo, T.; Lepot, K.; Hallmann, C.; Spicuzza, M. J.; Eigenbrode, J. L.; Summons, R. E.; Valley, J. W.

    2011-12-01

    Spatiotemporal variability in the carbon isotope composition of sedimentary organic matter (OM) preserves information about the evolution of the biosphere and of the exogenic carbon cycle as a whole. Primary compositions, and imprints of the post-depositional processes that obscure them, exist at the scale of individual sedimentary grains (mm to μm). Secondary ion mass spectrometry (SIMS) (1) enables analysis at these scales and in petrographic context, (2) permits morphological and compositional characterization of the analyte and associated minerals prior to isotopic analysis, and (3) reveals patterns of variability homogenized by bulk techniques. Here we present new methods for in situ organic carbon isotope analysis with sub-permil precision and spatial resolution to 1 μm using SIMS, as well as new data acquired from a suite of Archean rocks. Three analytical protocols were developed for the CAMECA ims1280 at WiscSIMS to analyze domains of varying size and carbon concentration. Average reproducibility (at 2SD) using a 6 μm spot size with two Faraday cup detectors was 0.4%, and 0.8% for analyses using 1 μm and 3 μm spot sizes with a Faraday cup (for 12C) and an electron multiplier (for 13C). Eight coals, two ambers, a shungite, and a graphite were evaluated for μm-scale isotopic heterogeneity, and LCNN anthracite (δ13C = -23.56 ± 0.1%, 2SD) was chosen as the working standard. Correlation between instrumental bias and H/C was observed and calibrated for each analytical session using organic materials with H/C between 0.1 and 1.5 (atomic), allowing a correction based upon a 13CH/13C measurement included in every analysis and a 12CH measurement made immediately after every analysis. The total range of the H/C effect observed for the Archean samples analyzed was < 3%. Analyses of Archean OM domains for which 12C count rate varies with the proportions of organic carbon, carbonate carbon, and quartz suggest that instrumental bias is consistent for 12C count

  12. Interpreting bryophyte stable carbon isotope composition: Plants as temporal and spatial climate recorders

    Science.gov (United States)

    Royles, Jessica; Horwath, Aline B.; Griffiths, Howard

    2014-04-01

    are unable to control tissue water content although physiological adaptations allow growth in a wide range of habitats. Carbon isotope signals in two mosses (Syntrichia ruralis and Chorisodontium aciphyllum) and two liverworts (Conocephalum conicum and Marchantia polymorpha), whether instantaneous (real time, Δ13C), or organic matter (as δ13COM), provide an assimilation-weighted summary of bryophyte environmental adaptations. In mosses, δ13COM is within the measured range of Δ13C values, which suggests that other proxies, such as compound-specific organic signals, will be representative of historical photosynthetic and growth conditions. The liverworts were photosynthetically active over a wider range of relative water contents (RWC) than the mosses. There was a consistent 5‰ offset between Δ13C values in C. conicum and M. polymorpha, suggestive of greater diffusion limitation in the latter. Analysis of a C. aciphyllum moss-peat core showed the isotopic composition over the past 200 years reflects recent anthropogenic CO2 emissions. Once corrected for source-CO2 inputs, the seasonally integrated Δ13COM between 1350 and 2000 A.D. varied by 1.5‰ compared with potential range of the 12‰ measured experimentally, demonstrating the relatively narrow range of conditions under which the majority of net assimilation takes place. Carbon isotope discrimination also varies spatially, with a 4‰ shift in epiphytic bryophyte organic matter found between lowland Amazonia and upper montane tropical cloud forest in the Peruvian Andes, associated with increased diffusion limitation.

  13. Diet and mobility in Early Medieval Bavaria: a study of carbon and nitrogen stable isotopes.

    Science.gov (United States)

    Hakenbeck, Susanne; McManus, Ellen; Geisler, Hans; Grupe, Gisela; O'Connell, Tamsin

    2010-10-01

    This study investigates patterns of mobility in Early Medieval Bavaria through a combined study of diet and associated burial practice. Carbon and nitrogen isotope ratios were analyzed in human bone samples from the Late Roman cemetery of Klettham and from the Early Medieval cemeteries of Altenerding and Straubing-Bajuwarenstrasse. For dietary comparison, samples of faunal bone from one Late Roman and three Early Medieval settlement sites were also analyzed. The results indicate that the average diet was in keeping with a landlocked environment and fairly limited availability of freshwater or marine resources. The diet appears not to have changed significantly from the Late Roman to the Early Medieval period. However, in the population of Altenerding, there were significant differences in the diet of men and women, supporting a hypothesis of greater mobility among women. Furthermore, the isotopic evidence from dietary outliers is supported by "foreign" grave goods and practices, such as artificial skull modification. These results reveal the potential of carbon and nitrogen isotope analysis for questions regarding migration and mobility.

  14. The carbon isotopic compositions of Non-methane Hydrocarbons in atmosphere

    Institute of Scientific and Technical Information of China (English)

    PENG Lin; ZHANG HuiMin; REN ZhaoFang; MU Ling; SHI RuiLiang; CHANG LiPing; LI Fan

    2009-01-01

    Carbon isotopic compositions of atmospheric Non-methane Hydrocarbons (NMHCs) in the urban areas of Taiyuan and Lanzhou in summer were reported and the sources of NMHCs are discussed.Carbon isotopic ratios (δ13C) of vehicle exhaust,coal-combustion exhaust,fuel volatiles and cooking exhaust were also measured with thermal desorption-gas chromatography-isotope ratio-mass spectrometry (TD-GC-IR-MS).δ13C values of NMHCs in the urban areas of Lanzhou and Taiyuan range from -32.3‰ to -22.3‰ and from -32.8‰ to -18.1‰.δ13C values of vehicle exhaust,coal-combustion exhaust,fuel volatiles and cooking exhaust are -32.5‰--21.7‰,-24.5‰--22.3‰,-32.5%--27.4‰ and -31.6‰--24.5‰,respectively.The data indicate that vehicle exhaust and cooking exhaust make a significant contribution to the atmospheric NMHCs.Therefore,to reduce emissions of vehicle exhaust and cook-ing exhaust is critical for controlling atmospheric NMHCs pollution in summer.

  15. Comparative assessment of air quality in two health resorts using carbon isotopes and palynological analyses

    Energy Technology Data Exchange (ETDEWEB)

    Gorka, M.; Jedrysek, M.O.; Maj, J.; Worobiec, A.; Buczynska, A.; Stefaniak, E.; Krata, A.; Van Grieken, R.; Zwozdziak, A.; Sowka, I.; Zwozdziak, J.; Lewicka-Szczebak, D. [University of Wroclaw, Wroclaw (Poland). Inst. of Geological Science

    2009-01-15

    This paper describes results of applying the palynological and carbon isotopic analysis of the organic fraction of Total Suspended Particles (TSP) to discriminate distinct pollution sources and assess the anthropogenic impact for the investigated areas. The samples of atmospheric particles were collected in Czerniawa and Cieplice (two health resorts in Lower Silesia, SW Poland) twice a year in summer and winter season (from July 2006 to February 2008). The palynological spectra represent in the vast majority local plant communities without a noticeable contribution of long-transported plant particles. Palynological analysis revealed also differences in the specificity of the two sampling areas, i.e. the higher contribution of identified organic material in Czerniawa stands for more natural character of this site, but is also responsible for the higher allergic pressure when compared to Cieplice. The carbon isotopic composition of TSP varied seasonally ({delta}{sup 13}C value from -27.09 parts per thousand in summer to -25.47 parts per thousand in winter). The increased {delta} {sup 13}C value in winter (heating period) is most probably caused by uncontrolled contribution of coal soot. On the basis of isotopic mass balance the calculated contribution of anthropogenic organic particles in the atmosphere reached in winter season 72% in Czerniawa and 79% in Cieplice.

  16. Pyrolysis of oil at high temperatures: Gas potentials, chemical and carbon isotopic signatures

    Institute of Scientific and Technical Information of China (English)

    TIAN Hui; XIAO XianMing; YANG LiGuo; XIAO ZhongYao; GUO LiGuo; SHEN JiaGui; LU YuHong

    2009-01-01

    Although the gas cracked from oil has been believed to be one of the important sources in highly ma-tured marine basins, there are still some debates on its resource potentials and chemical and isotopic compositions. In this study a Cambrian-sourced marine oil sample from the Silurian reservoir of well TZ62 in the central Tarim basin was pyrolyzed using sealed gold tubes with two different pyrolysis schemes: continuous pyrolysis in a closed system and stepwise semi-open pyrolysis. The results show that the maximum weight yield of C1-5 gases occurs at EasyRo=2.3% and the residual gas poten-tial after this maturity is only 43.4 mL/g, about 12% of the yield of 361 mL/g at EasyRo=2.3%. Combined with the results of kinetic modeling, the main stage of gas generation from oil cracking is believed within the EasyRo=1.6%-2.3%. The increase in the volume yield of C1-5 gases at EasyRo2.3% in a closed system is mainly related to the re-cracking of previously formed C2-5 wet gases, not the direct cracking of oil. The stepwise pyrolysis experiments show that the gas from the cracking of residual oil at EasyRo2.3% is characterized by very high dryness index (higher than 92%) and heavy methane carbon isotopes ranging from -28.7‰ to -26.7‰, which is quite different from the gases from the con-tinuous pyrolysis in a closed system. The kinetic modeling of methane carbon isotope fractionation shows that the carbon isotopes of methane within the main stage of gas generation (EasyRo<2.3%) are far lighter than the carbon isotopes of the precursor oils under a geological heating rate of 2℃/Ma. The above observations and results provide some new clues to the accurate recognition and objective re-source evaluation of oil cracking gas in highly mature marine basins.

  17. Thallium isotope evidence for a permanent increase in marine organic carbon export in the early Eocene

    Science.gov (United States)

    Nielsen, S.G.; Mar-Gerrison, S.; Gannoun, A.; LaRowe, D.; Klemm, V.; Halliday, A.N.; Burton, K.W.; Hein, J.R.

    2009-01-01

    The first high resolution thallium (Tl) isotope records in two ferromanganese crusts (Fe-Mn crusts), CD29 and D11 from the Pacific Ocean are presented. The crusts record pronounced but systematic changes in 205Tl/203Tl that are unlikely to reflect diagenetic overprinting or changes in isotope fractionation between seawater and Fe-Mn crusts. It appears more likely that the Fe-Mn crusts track the Tl isotope composition of seawater over time. The present-day oceanic residence time of Tl is estimated to be about 20,000??yr, such that the isotopic composition should reflect ocean-wide events. New and published Os isotope data are used to construct age models for these crusts that are consistent with each other and significantly different from previous age models. Application of these age models reveals that the Tl isotope composition of seawater changed systematically between ~ 55??Ma and ~ 45??Ma. Using a simple box model it is shown that the present day Tl isotope composition of seawater depends almost exclusively on the ratio between the two principal output fluxes of marine Tl. These fluxes are the rate of removal of Tl from seawater via scavenging by authigenic Fe-Mn oxyhydroxide precipitation and the uptake rate of Tl during low temperature alteration of oceanic crust. It is highly unlikely that the latter has changed greatly. Therefore, assuming that the marine Tl budget has also not changed significantly during the Cenozoic, the low 205Tl/203Tl during the Paleocene is best explained by a more than four-fold higher sequestration of Tl by Fe-Mn oxyhydroxides compared with at the present day. The calculated Cenozoic Tl isotopic seawater curve displays a striking similarity to that of S, providing evidence that both systems may have responded to the same change in the marine environment. A plausible explanation is a marked and permanent increase in organic carbon export from ~ 55??Ma to ~ 45??Ma, which led to higher pyrite burial rates and a significantly reduced

  18. Mg Isotope Evolution During Water-Rock Interaction in a Carbonate Aquifer

    Science.gov (United States)

    Zhang, Z.; Jacobson, A. D.; Lundstrom, C. C.; Huang, F.

    2008-12-01

    To better understand how Mg isotopes behave during weathering and aqueous transport, we used a Nu Plasma MC-ICP-MS to measure δ26Mg values (relative to DSM-3) in water samples along a 236 km flow path in the Madison aquifer of South Dakota, a confined carbonate aquifer recharging in the igneous Black Hills. We also analyzed local granite and dolomite samples to characterize the Mg isotope composition of source rocks constituting the recharge zone and aquifer, respectively. Repeated analyses of Mg standard solutions yielded external precisions (2σ) better than 0.1 permil for δ26Mg(CAM-1, - 2.584±0.071, n=13; UIMg-1, -2.217±0.087, n=9.). The Madison aquifer provides a unique opportunity to quantify Mg isotope effects during water-rock interaction because (1) fluids and rock have chemically equilibrated over a much longer timescale (up to ~15 kyr) than can be simulated in laboratory experiments and (2) previous studies have determined the rates and mass-balances of de- dolomitization and other geochemical reactions controlling solute evolution along the flow path. Reactions important for changing the concentration and isotope composition of Mg include dolomite dissolution, Mg-for- Na ion exchange, calcite precipitation, and isotope exchange. δ26Mg values within the recharge region (0-17 km along flow path) vary between -1.08 and -1.63 permil, and then remain essentially constant at -1.408±0.010 permil(1σ, 5 samples) from 17 to 189 km. A final sample at 236 km shows an increase to -1.09 permil. Either mixing between different recharge waters or rapid isotope exchange between infiltrating waters and dolomite could control δ26Mg variability between 0 and 17 km. Likewise, reactive transport modeling suggests that preferential uptake of 24Mg during Mg-for-Na ion exchange might cause an increase in δ26Mg between 189 and 236 km. However, unchanging δ26Mg values observed throughout most of the aquifer clearly demonstrate that Mg isotopes are not fractionated during

  19. Soil Drying Effects on the Carbon Isotope Composition of Soil Respiration

    Science.gov (United States)

    Phillips, C. L.; Nickerson, N.; Risk, D.; Kayler, Z. E.; Rugh, W.; Mix, A. C.; Bond, B. J.

    2008-12-01

    Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental factors that change over time, such as moisture, can create dynamic changes in the isotopic composition of C assimilated by plants, and offers a unique opportunity to distinguish fast- responding plant C from slower-responding soil C pools, which under steady-state conditions may be too similar isotopically to partition. Monitoring the isotopic composition of soil respiration over a period of changing moisture conditions is potentially a useful approach for characterizing plant contributions to soil respiration. But this partitioning hinges on the assumption that any change in the isotopic signature of soil respiration is solely due to recent photosynthetic discrimination, and that post-photosynthetic processes, such as microbial respiration, do not discriminate as moisture decreases. The purpose of the present study is to test the assumption that δ13CO2 from microbial respiration remains static as soil dries. We conducted a series of greenhouse experiments employing different techniques to isolate microbial respiration from root respiration. The first involves removing roots from soil, and showed that when roots are present, respiration from dry soil is enriched in 13C relative to moist soil, but when roots are absent, respiration is isotopically similar from moist and dry soils. This indicates that rhizospheric respiration changes isotopically with moisture whereas soil microbial respiration does not. In contrast, a second experiment in which soil columns without plants were monitored as they dried, showed respiration from very dry soil to be enriched by 8‰ relative to moist soil. However, simulations with an isotopologue-based soil gas diffusion model demonstrate that at least a portion of the apparent enrichment is due to non-steady state gas transport processes. Careful sampling methodologies which prevent or account for non

  20. Volcanism, mass extinction, and carbon isotope fluctuations in the Middle Permian of China.

    Science.gov (United States)

    Wignall, Paul B; Sun, Yadong; Bond, David P G; Izon, Gareth; Newton, Robert J; Védrine, Stéphanie; Widdowson, Mike; Ali, Jason R; Lai, Xulong; Jiang, Haishui; Cope, Helen; Bottrell, Simon H

    2009-05-29

    The 260-million-year-old Emeishan volcanic province of southwest China overlies and is interbedded with Middle Permian carbonates that contain a record of the Guadalupian mass extinction. Sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations. These show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae. The temporal coincidence of these two phenomena supports the idea of a cause-and-effect relationship. The crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean-atmosphere carbon cycle.

  1. Application of carbon isotope for discriminating sources of soil CO2 in karst area, Guizhou

    Institute of Scientific and Technical Information of China (English)

    黎廷宇; 王世杰

    2001-01-01

    Using carbon isotope of soil CO2 this paper discussed the sources of soil CO2 in karst area, Guizhou Province, China. Oxidation-decomposition of organic matter, respiration of plant root and activity of microbe are thought to be the major sources of soil CO2. However, in karst area, the contribution of dissolution of underlying carbonate rock to soil CO2 should be considered as in acidic environment. Atmospheric CO2 is the major composition of soil CO2 in surface layer of soil profiles and its proportion in soil CO2 decreases with increase of soil depth. CO2 produced by dissolution of carbonate rock contributes 34%-46% to soil CO2 below the depth of 10cm in the studied soil profiles covered by grass.

  2. CO{sub 2}-recycling by plants: how reliable is the carbon isotope estimation?

    Energy Technology Data Exchange (ETDEWEB)

    Siegwolf, R.T.W.; Saurer, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Koerner, C. [Basel Univ., Basel (Switzerland)

    1997-06-01

    In the study of plant carbon relations, the amount of the respiratory losses from the soil was estimated, determining the gradient of the stable isotope {sup 13}C with increasing plant canopy height. According to the literature 8-26% of the CO{sub 2} released in the forests by soil and plant respiratory processes are reassimilated (recycled) by photosynthesis during the day. Our own measurements however, which we conducted in grass land showed diverging results from no indicating of carbon recycling, to a considerable {delta}{sup 13}C gradient suggesting a high carbon recycling rate. The role of other factors, such as air humidity and irradiation which influence the {delta}{sup 13}C in a canopy as well, are discussed. (author) 3 figs., 4 refs.

  3. Carbon isotopes in eclogite and apatite separate from Huangzhen and Shima in SE Dabie

    Institute of Scientific and Technical Information of China (English)

    李一良; 郑永飞; 龚冰; 傅斌

    2000-01-01

    The carbon isotope compositions of high- and ultrahigh-pressure eclogite and apatite separate from Huangzhen and Shima in SE Dabie Mountains were analyzed by EA-MS online technique. The δ13C values of the eclogites cover a wide range of -30.7‰ - +1.5‰, whereasthose of apatites only have a small range of -28.1‰- -21.0‰. Some of the eclogites with thehigh δ13C values suffered retrogressive alteration by CO2-bearing fluids. The low δ13C values of the apatites indicate that the eclogites contain surficial carbon of organic origin. It is concluded that protoliths of the eclogites were exposed to the surface of the Earth, and that the carbon-bearing fluid was depleted in 13C during the eclogite-facies metamorphism.

  4. Carbon isotopes in eclogite and apatite separate from Huangzhen and Shima in SE Dabie

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The carbon isotope compositions of high- and ultrahigh-pressure eclogite and apatite separate from Huangzhen and Shima in SE Dabie Mountains were analyzed by EA-MS online technique. The δ13C values of the eclogites cover a wide range of -30.7‰ - +1.5‰, whereas those of apatites only have a small range of -28.1‰--21.0‰. Some of the eclogites with the high δ13C values suffered retrogressive alteration by CO2-bearing fluids. The low δ13C values of the apatites indicate that the eclogites contain surficial carbon of organic origin. It is concluded that protoliths of the eclogites were exposed to the surface of the Earth, and that the carbon-bearing fluid was depleted in 13C during the eclogite-facies metamorphism.

  5. Compound-specific carbon isotopes from Earth's largest flood basalt eruptions directly linked to the end-Triassic mass extinction.

    Science.gov (United States)

    Whiteside, Jessica H; Olsen, Paul E; Eglinton, Timothy; Brookfield, Michael E; Sambrotto, Raymond N

    2010-04-13

    A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in geological sections preserving all three records. The end-Triassic extinction (ETE) at 201.4 Ma is among the largest of these extinctions and is tied to a large negative carbon isotope excursion, reflecting perturbations of the carbon cycle including a transient increase in CO(2). The cause of the ETE has been inferred to be the eruption of the giant Central Atlantic magmatic province (CAMP). Here, we show that carbon isotopes of leaf wax derived lipids (n-alkanes), wood, and total organic carbon from two orbitally paced lacustrine sections interbedded with the CAMP in eastern North America show similar excursions to those seen in the mostly marine St. Audrie's Bay section in England. Based on these results, the ETE began synchronously in marine and terrestrial environments slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, a CO(2) super greenhouse, and marine biocalcification crisis. Because the temporal relationship between CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same place, this is the strongest case for a volcanic cause of a mass extinction to date.

  6. Stable carbon isotopic composition of soil organic matter in the karst areas of Southwest China

    Institute of Scientific and Technical Information of China (English)

    ZHU Shufa; LIU Congqiang

    2008-01-01

    This study dealt with the distribution characteristics of soil organic carbon (SOC) and the variation of stable carbon isotopic composition (δ13C values) with depth in six soil profiles, including two soil types and three vegetation forms in the karst areas of Southwest China. The δ13C values of plant-dominant species, leaf litter and soils were measured using the sealed-tube high-temperature combustion method. Soil organic carbon contents of the limestone soil profiles are all above 11.4 g/kg, with the highest value of 71.1 g/kg in the surface soil. However, the contents vary between 2.9 g/kg and 46.0 g/kg in three yellow soil profiles. The difference between the maximum and minimum δ13C values of soil organic matter (SOM) changes from 2.2‰ to 2.9‰ for the three yellow soil profiles. But it changes from 0.8‰ to 1.6‰ for the limestone soil profiles. The contrast research indicated that there existed significant difference in vertical patterns of organic carbon and δ13C values of SOM between yellow soil and limestone soil. This difference may reflect site-specific factors, such as soil type, vegetation form, soil pH value, and clay content, etc., which control the contents of different organic components comprising SOM and soil carbon turnover rates in the profiles. The vertical variation patterns of stable carbon isotope in SOM have a distinct regional character in the karst areas.

  7. Stratigraphical and biological significance of negative carbon isotopic anomalies in the basal Cambrian series of Guizhou Province

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; WANG Shijie; OUYANG Ziyuan; ZHU Lijun; JIANG Lijun; ZHANG Weihua; GAO Hui

    2005-01-01

    The early Early Cambrian strata within the bounds of Guizhou Province are almost predominated by black shale deposition. Recently, however, the authors have found a section consisting of a set of mudstones interbedded with limestones at the basement of the Cambrian at Yingping, Fuquan County, Guizhou Province, which provides favorable conditions for the study of marine geochemical characteristics of the early Early Cambrian. The characteristics of intense negative carbon isotopic anomalies near the Precambrian/Cambrian boundary at Yingping, Fuquan County, Guizhou Province, can be correlated with those of global carbon isotopic anomalies at the same time on a global scale, corresponding to the intense negative carbon isotopic anomalies near the Neoproterozoic/Cambrian boundaries at the bottom of the Xiaowaitoushan Member, Huize, Yunnan Province, at the top of the Tsagaan Oloom Formation of Mongolia and at the top of the Salarmy Gol Formation of Siberia, as well as those observed in southwestern United States, Iran, Amman, Poland, Newfoundland, the Great Britain, Canada, etc. Negative carbon isotopic anomalies can be used as the important basis for the division of the Precambrian/Cambrian boundaries. There have been found 8 m-thick black shales and cherts below the intense negative carbon isotopic anomalies in this profile. In the black shales there have been found large amounts of fossils such as Bradorida, gernus Archotuba, indicating that during the period of sedimentation of black shales under anaerobic conditions there would be large quantities of organic species living in the sea. But in the section of grayish-green mudstones interbedded with limestones with intense negative carbon isotopic anomalies almost no organic fossil has been found. This may imply that the anaerobic event seems to have little bearing on the mass extinction near the Precambrian/Cambrian boundary, whereas the intense negative carbon isotopic anomaly event appears to be more closely

  8. Compound specific isotopic fractionation patterns suggest different carbon metabolisms among Chloroflexus-like bacteria in hot spring microbial mats

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Meer, M.T.J. van der; Schouten, S.; Leeuw, J.W. de; Ward, D.M.

    2003-01-01

    Stable carbon isotope fractionations between dissolved inorganic carbon and lipid biomarkers suggest photoautotrophy by Chloroflexus-like organisms in sulfidic and nonsulfidic Yellowstone hot springs. Where co-occurring, cyanobacteria appear to cross-feed Chloroflexus-like organisms supporting photo

  9. STABLE CARBON ISOTOPE EVIDENCE FOR COUPLING BETWEEN SEDIMENTARY BACTERIA AND SEAGRASSES IN A SUB-TROPICAL LAGOON

    Science.gov (United States)

    We measured stable carbon isotope ratios (d13C) in phospholipid fatty acids (PLFAs) to identify the primary carbon source utilized by sedimentary bacteria in Lower Laguna Madre, Texas, which is a seagrass dominated lagoon. Comparisons were made between three differing habitat ty...

  10. Partitioning water and carbon fluxes in a Mediterranean oak woodland using stable oxygen isotopes

    Science.gov (United States)

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra; Silva, Filipe Costa e.; Pereira, Joao; Werner, Christiane

    2014-05-01

    Water is a key factor driving ecosystem productivity, especially in water-limited ecosystems. A separation of the component fluxes is needed to gain a functional understanding on the development of net ecosystem water fluxes and their coupling with biogeochemical cycles. Oxygen isotope signatures are valuable tracers for water movements within the ecosystem because of the distinct isotopic compositions of water in soil and vegetation. In the past, determination of isotopic signatures of evaporative or transpirational fluxes has been challenging since measurements of water vapor isotopes were difficult to obtain using cold-trap methods, delivering data with low time resolution. Recent developments in laser spectroscopy now enable direct high frequency measurements of the isotopic composition of atmospheric water vapor (δv), evapotranspiration (δET), and its components and allow validations of common modeling approaches for estimating δE and δT based on Craig and Gordon (1965). Here, a novel approach was used, combining a custom build flow-through gas-exchange branch chamber with a Cavity Ring-Down Spectrometer in a Mediteranean cork-oak woodland where two vegetation layers respond differently to drought: oak-trees (Quercus suber L.) avoid drought due to their access to ground water while herbaceous plants survive the summer as seeds. We aimed at 1) testing the Craig and Gordon equation for soil evaporation against directly measured δE and 2) quantifying the role of non-steady-state transpiration under natural conditions. Thirdly, we used this approach to quantify the impact of the understory herbaceous vegetation on ecosystem carbon and water fluxes throughout the year and disentangle how ET components of the ecosystem relate to carbon dioxide exchange. We present one year data comparing modeled and measured stable oxygen isotope signatures (δ18O) of soil evaporation, confirming that the Craig and Gordon equation leads to good agreement with measured δ18O of

  11. Carbonate concretions as a significant component of ancient marine carbon cycles: Insights from paired organic and inorganic carbon isotope analyses of a Cretaceous shale

    Science.gov (United States)

    Loyd, S. J.

    2014-12-01

    Carbonate concretions often occur within fine-grained, organic-rich sedimentary rocks. This association reflects the common production of diagenetic minerals through biologic cycling of organic matter. Chemical analysis of carbonate concretions provides the rare opportunity to explore ancient shallow diagenetic environments, which are inherently transient due to progressive burial but are an integral component of the marine carbon cycle. The late Cretaceous Holz Shale (~80 Ma) contains abundant calcite concretions that exhibit textural and geochemical characteristics indicative of relatively shallow formation (i.e., near the sediment-water interface). Sampled concretions contain between 5.4 and 9.8 wt.% total inorganic carbon (TIC), or ~45 and 82 wt.% CaCO3, compared to host shale values which average ~1.5 wt.% TIC. Organic carbon isotope compositions (δ13Corg) are relatively constant in host and concretion samples ranging from ­-26.3 to -24.0‰ (VPDB). Carbonate carbon isotope compositions (δ13Ccarb) range from -22.5 to -3.4‰, indicating a significant but not entirely organic source of carbon. Concretions of the lower Holz Shale exhibit considerably elevated δ13Ccarb values averaging -4.8‰, whereas upper Holz Shale concretions express an average δ13Ccarb value of -17.0‰. If the remaining carbonate for lower Holz Shale concretions is sourced from marine fluids and/or dissolved marine carbonate minerals (e.g., shells), a simple mass balance indicates that ~28% of concretion carbon was sourced from organic matter and ~72% from late Cretaceous marine inorganic carbon (with δ13C ~ +2.5‰). Upper Holz Shale calculations indicate a ~73% contribution from organic matter and a ~27% contribution from inorganic carbon. When normalized for carbonate, organic contents within the concretions are ~2-13 wt.% enriched compared to host contents. This potentially reflects the protective nature of cementation that acts to limit permeability and chemical destruction of

  12. Extraction, separation, and intramolecular carbon isotope characterization of athabasca oil sands acids in environmental samples.

    Science.gov (United States)

    Ahad, Jason M E; Pakdel, Hooshang; Savard, Martine M; Simard, Marie-Christine; Smirnoff, Anna

    2012-12-04

    Here we report a novel approach to extract, isolate, and characterize high molecular weight organic acids found in the Athabasca oil sands region using preparative capillary gas chromatography (PCGC) followed by thermal conversion/elemental analysis-isotope ratio mass spectrometry (TC/EA-IRMS). A number of different "naphthenic acids" surrogate standards were analyzed as were samples from the bitumen-rich unprocessed McMurray Formation, oil sands process water, groundwater from monitoring wells, and surface water from the Athabasca River. The intramolecular carbon isotope signature generated by online pyrolysis (δ(13)C(pyr)) showed little variation (±0.6‰) within any given sample across a large range of mass fractions separated by PCGC. Oil sand, tailings ponds, and deep McMurray Formation groundwater were significantly heavier (up to ∼9‰) compared to surface water and shallow groundwater samples, demonstrating the potential use of this technique in source apportionment studies.

  13. Neutron-rich isotope production using a uranium carbide - carbon nanotubes SPES target prototype

    Science.gov (United States)

    Corradetti, S.; Biasetto, L.; Manzolaro, M.; Scarpa, D.; Carturan, S.; Andrighetto, A.; Prete, G.; Vasquez, J.; Zanonato, P.; Colombo, P.; Jost, C. U.; Stracener, D. W.

    2013-05-01

    The SPES (Selective Production of Exotic Species) project, under development at the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro (INFN-LNL), is a new-generation Isotope Separation On-Line (ISOL) facility for the production of radioactive ion beams by means of the proton-induced fission of uranium. In the framework of the research on the SPES target, seven uranium carbide discs, obtained by reacting uranium oxide with graphite and carbon nanotubes, were irradiated with protons at the Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory (ORNL). In the following, the yields of several fission products obtained during the experiment are presented and discussed. The experimental results are then compared to those obtained using a standard uranium carbide target. The reported data highlights the capability of the new type of SPES target to produce and release isotopes of interest for the nuclear physics community.

  14. No K/T boundary at Anjar, Gujarat, India: Evidence from magnetic susceptibility and carbon isotopes

    Indian Academy of Sciences (India)

    H J Hansen; D M Mohabey; P Toft

    2001-06-01

    The paper describes the variation pattern of magnetic susceptibility of Lameta sediments and isotopic variation of organic 13C from Chui Hill, Bergi, Kholdoda, Pisdura and Girad. The susceptibility pattern and a negative carbon isotopic anomaly allows fixation of the K/T boundary at these localities and they dier in these aspects from the inter-trappean sediments at Anjar. Paleomagnetic measurements of the Anjar sediment and the overlying basalt ow demonstrate reversed polarity. The Lameta sediments with dinosaur nests at Kheda and the overlying intertrappean sediments are of normal polarity The clay layers at Anjar, associated closely with Ir-enrichments, are strongly leached, rhyolitic bentonites containing low-quartz paramorphs after high-quartz with glass inclusions. It is concluded, that the inter-trappean lake deposits at Anjar were deposited in the early part of magnetochron 29R and are unrelated to the K/T boundary.

  15. Can Mg isotopes be used to trace cyanobacteria-mediated magnesium carbonate precipitation in alkaline lakes?

    Directory of Open Access Journals (Sweden)

    L. S. Shirokova

    2011-07-01

    Full Text Available The fractionation of Mg isotopes was determined during the cyanobacterial mediated precipitation of hydrous magnesium carbonate precipitation in both natural environments and in the laboratory. Natural samples were obtained from Lake Salda (SE Turkey, one of the few modern environments on the Earth's surface where hydrous Mg-carbonates are the dominant precipitating minerals. This precipitation was associated with cyanobacterial stromatolites which were abundant in this aquatic ecosystem. Mg isotope analyses were performed on samples of incoming streams, groundwaters, lake waters, stromatolites, and hydromagnesite-rich sediments. Laboratory Mg carbonate precipitation experiments were conducted in the presence of purified Synechococcus sp cyanobacteria that were isolated from the lake water and stromatolites. The hydrous magnesium carbonates nesquehonite (MgCO3·3H2O and dypingite (Mg5(CO34(OH25(H2O were precipitated in these batch reactor experiments from aqueous solutions containing either synthetic NaHCO3/MgCl2 mixtures or natural Lake Salda water, in the presence and absence of live photosynthesizing Synechococcus sp. Bulk precipitation rates were not to affected by the presence of bacteria when air was bubbled through the system. In the stirred non-bubbled reactors, conditions similar to natural settings, bacterial photosynthesis provoked nesquehonite precipitation, whilst no precipitation occurred in bacteria-free systems in the absence of air bubbling, despite the fluids achieving a similar or higher degree of supersaturation. The extent of Mg isotope fractionation (Δ26Mgsolid-solution between the mineral and solution in the abiotic experiments was found to be identical, within uncertainty, to that measured in cyanobacteria-bearing experiments, and ranges from −1.4 to −0.7 ‰. This similarity refutes

  16. Springtime carbon episodes at Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    Science.gov (United States)

    Jung, J.; Kawamura, K.

    2011-05-01

    In order to investigate the carbon episodes at Gosan background super-site (33.17° N, 126.10° E) in East Asia during spring of 2007 and 2008, total suspended particles (TSP) were collected and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (δ13C) of TC. The carbon episodes at the Gosan site were categorized as long-range transported anthropogenic pollutant (LTP) from Asian continent, Asian dust (AD) accompanying with LTP, and local pollen episodes. The stable carbon isotopic composition of TC (δ13CTC) was found to be lowest during the pollen episodes (range: -26.2 ‰ to -23.5 ‰, avg.: -25.2 ± 0.9 ‰), followed by the LTP episodes (range: -23.5 ‰ to -23.0 ‰, avg.: -23.3 ± 0.3 ‰) and the AD episodes (range: -23.3 to -20.4 %, avg.: -21.8 ± 2.0 ‰). The δ13CTC of the airborne pollens (-28.0 ‰) collected at the Gosan site showed value similar to that of tangerine fruit (-28.1 ‰) produced from Jeju Island. Based on the carbon isotope mass balance equation and the TN and TC regression approach, we found that ∼40-45 % of TC in the TSP samples during the pollen episodes was attributed to airborne pollens from Japanese cedar trees planted around tangerine farms in Jeju Island. The δ13C of citric acid in the airborne pollens (-26.3 ‰) collected at the Gosan site was similar to that in tangerine fruit (-27.4 ‰). The negative correlation between the citric acid-carbon/TC ratios and δ13CTC were obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollens and then transported to the Gosan site. Based on the thermal evolution pattern of organic aerosols during the carbon episodes, we found that organic aerosols originated from East China are more volatile on heating and are more likely to form pyrolized organic carbon than the pollen-enriched organic aerosols and organic

  17. Stable carbon isotope fractionation of six strongly fractionating microorganisms is not affected by growth temperature under laboratory conditions

    Science.gov (United States)

    Penger, Jörn; Conrad, Ralf; Blaser, Martin

    2014-09-01

    Temperature is the major driving force for many biological as well as chemical reactions and may impact the fractionation of stable carbon isotopes. Thus, a good correlation between temperature and fractionation is observed in many chemical systems that are controlled by an equilibrium isotope effect. In contrast, biological systems that are usually controlled by a kinetic isotope effect are less well studied with respect to temperature effects and have shown contrasting results. We studied three different biological pathways (methylotrophic methanogenesis, hydrogenotrophic methanogenesis, acetogenesis by the acetyl-CoA pathway) which are characterized by very strong carbon isotope enrichment factors (-50‰ to -83‰). The microorganisms (Methanosarcina barkeri, Methanosarcina acetivorans, Methanolobus zinderi, Methanothermobacter marburgensis, Methanothermobacter thermoautotrophicus, Thermoanaerobacter kivui) exhibiting these pathways were grown at different temperatures ranging between 25 and 68 °C, and the fractionation factors were determined from 13C/12C isotope discrimination during substrate depletion and product formation. Our experiments showed that the fractionation factors were different for the different metabolic pathways but were not much affected by the different growth temperatures. Slight variations were well within the standard errors of replication and regression analysis. Our results showed that temperature had no significant effect on the fractionation of stable carbon isotopes during anaerobic microbial metabolism with relatively strong isotope fractionation.

  18. Optimizing sample pretreatment for compound-specific stable carbon isotopic analysis of amino sugars in marine sediment

    Directory of Open Access Journals (Sweden)

    R. Zhu

    2014-01-01

    Full Text Available Amino sugars are quantitatively significant constituents of soil and marine sediment, but their sources and turnover in environmental samples remain poorly understood. The stable carbon isotopic composition of amino sugars can provide information on the lifestyles of their source organisms and can be monitored during incubations with labeled substrates to estimate the turnover rates of microbial populations. However, until now, such investigation has been carried out only with soil samples, partly because of the much lower abundance of amino sugars in marine environments. We therefore optimized a procedure for compound-specific isotopic analysis of amino sugars in marine sediment employing gas chromatography-isotope ratio mass spectrometry. The whole procedure consisted of hydrolysis, neutralization, enrichment, and derivatization of amino sugars. Except for the derivatization step, the protocol introduced negligible isotopic fractionation, and the minimum requirement of amino sugar for isotopic analysis was 20 ng, i.e. equivalent to ~ 8 ng of amino sugar carbon. Our results obtained from δ13C analysis of amino sugars in selected marine sediment samples showed that muramic acid had isotopic imprints from indigenous bacterial activities, whereas glucosamine and galactosamine were mainly derived from organic detritus. The analysis of stable carbon isotopic compositions of amino sugars opens a promising window for the investigation of microbial metabolisms in marine sediments and the deep marine biosphere.

  19. Dissolved inorganic carbon isotopic composition of the Gulf of Mexico deep-water masses.

    Science.gov (United States)

    Quintanilla-Terminel, J. G.; Herguera, J. C.; Ferreira-Bartrina, V.; Hernández-Ayón, J. M.; Camacho-Ibar, V.

    2014-12-01

    This study provides new data for the establishment of a carbon biogeochemical dynamics baseline in the deep Gulf of Mexico (GM) based on carbon isotopes in dissolved inorganic carbon. Water samples from 40 deep-water stations south of 25˚N were collected during XIXIMI-2 cruise, July 2011, aboard BO/Justo Sierra. Vertical profiles of temperature, salinity and dissolved oxygen (DO) were further measured in each station. In the Stable Isotopes Laboratory at CICESE we determined the carbon isotopic composition of the dissolved inorganic carbon (DIC) (δ13CDIC). Remarkably, density, DO and δ13CCID profiles showed a clear difference between the Loop current and the deep-waters of the GM south of 25˚N. We found the following average δ13CCID values in the Loop current and in the deep-waters of the Gulf: subtropical underwater (SUW): 0.73±0.06‰ and 0.86±0.04‰; 18 degree water (18W): 0.76 ± 0.08‰ and 0.58± 0.06‰; North Atlantic central water (NACW): 0.77 ± 0.05‰ and 0.71 ± 0.09‰; South Atlantic central water (SACW): 0.80 ± 0.08‰ and 0.77 ± 0.07‰; Antartic intermediate water (AAIW): 1.00 ± 0.06‰ and 0.90 ± 0.08‰; North Atlantic deep water (NADW): 1.03 ± 0.06‰ and 1.01 ± 0.10‰. We will discuss how the biological component, δ13CCID-BIO, of subsurface water masses match very closely the apparent oxygen utilization relation described by Kroopnick, 1985, with the exception of SUW, and as a consequence the 18W is probably the water mass most affected by organic carbon remineralization processes in the GM south of 25˚N. We further show how these waters seem to store a larger proportion of anthropogenic carbon than the deeper water masses.

  20. Stable isotope composition of land snail body water and its relation to environmental waters and shell carbonate

    Science.gov (United States)

    Goodfriend, Glenn A.; Magaritz, Mordeckai; Gat, Joel R.

    1989-12-01

    Day-to-day and within-day (diel) variations in δD and δ18O of the body water of the land snail, Theba pisana, were studied at a site in the southern coastal plain of Israel. Three phases of variation, which relate to isotopic changes in atmospheric water vapor, were distinguished: 1) on rain days, snail water becomes isotopically depleted approximately in the direction of the rain isotope values, but always less depleted in D as is atmospheric water vapor; 2) during the 1-3 days following a rain, the snail water becomes isotopically enriched along a line with slope persists until the next rain event. The isotopic variations can be explained by isotopic equilibration with atmospheric water vapor and/or uptake of dew derived therefrom. During the winter, when the snails are active, there is only very minor enrichment in 18O relative to equilibrium with water vapor or dew, apparently as a result of metabolic activity. But this enrichment becomes pronounced after long periods of inactivity. Within-day variation in body water isotopic composition is minor on non-rain days. Shell carbonate is enriched in 18O by ca. 1-2%. relative to equilibrium with body water. In most regions, the isotopic composition of atmospheric water vapor (or dew) is a direct function of that of rain. Because the isotopic composition of snail body water is related to that of atmospheric water vapor and the isotopic composition of shell carbonate in turn is related to that of body water, land snail shell carbonate 18O should provide a reliable indication of rainfall 18O. However, local environmental conditions and the ecological properties of the snail species must be taken into account.

  1. Late Miocene to Pliocene carbon isotope record of differential diet change among East African herbivores.

    Science.gov (United States)

    Uno, Kevin T; Cerling, Thure E; Harris, John M; Kunimatsu, Yutaka; Leakey, Meave G; Nakatsukasa, Masato; Nakaya, Hideo

    2011-04-19

    Stable isotope and molecular data suggest that C(4) grasses first appeared globally in the Oligocene. In East Africa, stable isotope data from pedogenic carbonate and fossil tooth enamel suggest a first appearance between 15-10 Ma and subsequent expansion during the Plio-Pleistocene. The fossil enamel record has the potential to provide detailed information about the rates of dietary adaptation to this new resource among different herbivore lineages. We present carbon isotope data from 452 fossil teeth that record differential rates of diet change from C(3) to mixed C(3)/C(4) or C(4) diets among East African herbivore families at seven different time periods during the Late Miocene to the Pliocene (9.9-3.2 Ma). Significant amounts of C(4) grasses were present in equid diets beginning at 9.9 Ma and in rhinocerotid diets by 9.6 Ma, although there is no isotopic evidence for expansive C(4) grasslands in this part of the Late Miocene. Bovids and hippopotamids followed suit with individuals that had C(4)-dominated (>65%) diets by 7.4 Ma. Suids adopted C(4)-dominated diets between 6.5 and 4.2 Ma. Gomphotheriids and elephantids had mostly C(3)-dominated diets through 9.3 Ma, but became dedicated C(4) grazers by 6.5 Ma. Deinotheriids and giraffids maintained a predominantly C(3) diet throughout the record. The sequence of differential diet change among herbivore lineages provides ecological insight into a key period of hominid evolution and valuable information for future studies that focus on morphological changes associated with diet change.

  2. Abundance, distribution, and isotopic composition of particulate black carbon in the northern Gulf of Mexico

    Science.gov (United States)

    Yang, Weifeng; Guo, Laodong

    2014-11-01

    There exists increasing evidence supporting the important role of black carbon in global carbon cycles. Particulate black carbon (PBC) is allochthonous and has distinct reactivities compared to the bulk particulate organic carbon (tot-POC) in marine environments. However, the abundance, geochemical behavior of PBC and its importance in oceanic carbon budget remain poorly understood. Here we report the abundance, distribution, and stable isotopic signatures of BC derived from the chemo-thermal oxidation (CTO-375) method (BCCTO) in the Gulf of Mexico. Our results show that BCCTO abundance decreased from shelf to basin, and more than a half of riverine BCCTO could be removed over the shelf. Moreover, BCCTO is much more refractory compared to the tot-POC and has δ13C values lower than those of BC-excluded POC. These results highlight the significance of PBC in marine carbon cycles and potentially suggest the need for a new end-member term in quantifying POC sources in the ocean.

  3. The relationship between needle sugar carbon isotope ratios and tree rings of larch in Siberia.

    Science.gov (United States)

    Rinne, K T; Saurer, M; Kirdyanov, A V; Loader, N J; Bryukhanova, M V; Werner, R A; Siegwolf, R T W

    2015-11-01

    Significant gaps still exist in our knowledge about post-photosynthetic leaf level and downstream metabolic processes and isotopic fractionations. This includes their impact on the isotopic climate signal stored in the carbon isotope composition (δ(13)C) of leaf assimilates and tree rings. For the first time, we compared the seasonal δ(13)C variability of leaf sucrose with intra-annual, high-resolution δ(13)C signature of tree rings from larch (Larix gmelinii Rupr.). The trees were growing at two sites in the continuous permafrost zone of Siberia with different growth conditions. Our results indicate very similar low-frequency intra-seasonal trends of the sucrose and tree ring δ(13)C records with little or no indication for the use of 'old' photosynthates formed during the previous year(s). The comparison of leaf sucrose δ(13)C values with that in other leaf sugars and in tree rings elucidates the cause for the reported (13)C-enrichment of sink organs compared with leaves. We observed that while the average δ(13)C of all needle sugars was 1.2‰ more negative than δ(13)C value of wood, the δ(13)C value of the transport sugar sucrose was on an average 1.0‰ more positive than that of wood. Our study shows a high potential of the combined use of compound-specific isotope analysis of sugars (leaf and phloem) with intra-annual tree ring δ(13)C measurements for deepening our understanding about the mechanisms controlling the isotope variability in tree rings under different environmental conditions.

  4. Geochemistry of brachiopods: Oxygen and carbon isotopic records of Paleozoic oceans

    Science.gov (United States)

    Veizer, Ján; Fritz, Peter; Jones, Brian

    1986-08-01

    Combined trace element and isotope studies of 319 brachiopods, covering the Ordovician to Permian time span, show that δ 13C and δ 18O in well preserved specimens varied during the Paleozoic. The overall δ 13C secular trend is in accord with the previously published observations, but its details are obscured by vital isotopic fractionation effects at generic level. Nonetheless, the results suggest that the negative correlation between marine δ 13C carbonate and δ 34S sulphate deteriorates at time scales of ⩽ 10 6 years, due to the long residence time, and thus slow response, of SO 42- in the ocean. For oxygen isotopes, all Devonian and older specimens have δ 18O of ⩽ -4%, while the well preserved Permian samples have near-present day δ 18O of about -1% (PDB). This isotopic dichotomy is probably not due to post-depositional phenomena, salinity, or biogenic fractionation effects. This leaves open the perennial arguments for a change in 18O /16O of sea water versus warmer ancient oceans. The present data are difficult to explain solely by the temperature alternative. The coincidence of the proposed shift in δ 18O with the large Late Paleozoic changes in marine 87Sr /86Sr , 13C /12C , 34S /32S , and "sea level stands" argues for a tectonic cause and for a change in 18O /16O of sea water, although such explanation is difficult to reconcile with global balance considerations and with isotopic patterns observed in alteration products of ancient basalts and ophiolites. Whatever the precise cause, or combination of causes, the implications for tectonism and/or paleoclimatology are of first order significance.

  5. Zinc and sulfur isotope variation in sphalerite from carbonate-hosted zinc deposits, Cantabria, Spain

    Science.gov (United States)

    Pašava, Jan; Tornos, Fernando; Chrastný, Vladislav

    2014-10-01

    We studied zinc and sulfur isotopes and the chemical composition of sphalerite samples from Picos de Europa (Aliva mine) and sphalerite and hydrozincite samples from La Florida mine, two carbonate-hosted Mississippi Valley-type (MVT) deposits located in northern Spain; despite being close, they are hosted in carbonatic rocks of different ages, Lower Carboniferous and Lower Cretaceous, respectively. The two generations of sphalerite at Picos de Europa show different δ66Zn values (stage 1 sphalerite +0.24 per mil and stage 2 sphalerite from -0.75 to +0.08 per mil). Both generations also differ in the sulfur isotope composition (stage 1 has δ34S = +6.6 and stage 2 has δ34S = -0.9 to +2.9 per mil) and the chemical composition (stage 1 sphalerite, compared to stage 2 sphalerite, is significantly enriched in Pb, As, Mn, Sb, slightly enriched in Ag, Ni, and Cu and depleted in Co, Ga, Tl, Te, Ge, and Sn). We suggest that Zn isotope fractionation was controlled predominantly by pH and T changes. High Zn isotope values reflect rapid precipitation of sphalerite from higher-temperature acidic fluids that carried Zn mostly as chloride species after interaction with carbonate rocks while lower Zn isotope values most likely resulted from a longer precipitation process from fluid at higher pH and decreasing T that carried dominantly Zn sulfide species. At La Florida, sphalerite samples show light 66Zn-depleted signatures with δ66Zn values from -0.80 to -0.01 per mil (mostly between -0.80 and -0.24 per mil) and δ34S values from +10.7 to +15.7 per mil without any relationship between the δ66Zn and δ34S values. Here, the variation in Zn isotope values is interpreted as related to mixing of fluids from two reservoirs. The Zn was carried by a single deep-seated and higher T (~250-320 °C) fluid, and precipitation took place after mixing with a connate S-rich fluid in a system with mH2S > mZn2+ as a result of change in pH, T, and Zn predominant species. The light δ66Zn

  6. Improved quantification of microbial CH4 oxidation efficiency in Arctic wetland soils using carbon isotope fractionation

    Directory of Open Access Journals (Sweden)

    E.-M. Pfeiffer

    2012-12-01

    Full Text Available Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4. The observed accelerated warming of the Arctic will cause a deeper permafrost thawing followed by increased carbon mineralization and CH4 formation in water saturated tundra soils which might cause a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River Delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4-signatures were measured and the fractionation factors for the processes of oxidation (αox and diffusion (αdiff were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (e.g. landfill cover soils have assumed a gas transport dominated by advection (αtrans = 1. In tundra soils, however, diffusion is the main gas transport mechanism, aside from ebullition. Hence, diffusive stable isotope fractionation has to be considered. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 ± 0.000 (n = 3. CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 ± 0.003 (n = 18. Furthermore, it was found that αox differs widely between sites and horizons (mean αox, = 1.017 ± 0.009 and needs to be determined individually. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by considering both the

  7. Carbon and Sulfur Isotopic Signatures of Ancient Life and Environment at the Microbial Scale: Neoarchean Shales and Carbonates

    Science.gov (United States)

    Williford, K. H.; Ushikubo, T.; Lepot, K.; Kitajima, K.; Hallmann, C.; Spicuzza, M. J.; Kozdon, R.; Eigenbrode, J. L.; Summons, R. E.; Valley, J. W.

    2015-01-01

    An approach to coordinated, spatially resolved, in situ carbon isotope analysis of organic matter and carbonate minerals, and sulfur three- and four-isotope analysis of pyrite with an unprecedented combination of spatial resolution, precision, and accuracy is described. Organic matter and pyrite from eleven rock samples of Neoarchean drill core express nearly the entire range of delta(sup 13)C, delta(sup 34)S, Delta(sup 33)S, and Delta(sup 36)S known from the geologic record, commonly in correlation with morphology, mineralogy, and elemental composition. A new analytical approach (including a set of organic calibration standards) to account for a strong correlation between H/C and instrumental bias in SIMS delta(sup 13)C measurement of organic matter is identified. Small (2-3 microns) organic domains in carbonate matrices are analyzed with sub-permil accuracy and precision. Separate 20- to 50-micron domains of kerogen in a single approx. 0.5 cu cm sample of the approx. 2.7 Ga Tumbiana Formation have delta(sup 13)C = -52.3 +/- 0.1per mille and -34.4 +/- 0.1per mille, likely preserving distinct signatures of methanotrophy and photoautotrophy. Pyrobitumen in the approx. 2.6 Ga Jeerinah Formation and the approx. 2.5 Ga Mount McRae Shale is systematically 13C-enriched relative to co-occurring kerogen, and associations with uraniferous mineral grains suggest radiolytic alteration. A large range in sulfur isotopic compositions (including higher Delta(sup 33)S and more extreme spatial gradients in Delta(sup 33)S and Delta(sup 36)S than any previously reported) are observed in correlation with morphology and associated mineralogy. Changing systematics of delta(sup 34)S, Delta(sup 33)S, and Delta(sup 36)S, previously investigated at the millimeter to centimeter scale using bulk analysis, are shown to occur at the micrometer scale of individual pyrite grains. These results support the emerging view that the dampened signature of mass-independent sulfur isotope fractionation

  8. Carbon and sulfur isotopic signatures of ancient life and environment at the microbial scale: Neoarchean shales and carbonates.

    Science.gov (United States)

    Williford, K H; Ushikubo, T; Lepot, K; Kitajima, K; Hallmann, C; Spicuzza, M J; Kozdon, R; Eigenbrode, J L; Summons, R E; Valley, J W

    2016-03-01

    An approach to coordinated, spatially resolved, in situ carbon isotope analysis of organic matter and carbonate minerals, and sulfur three- and four-isotope analysis of pyrite with an unprecedented combination of spatial resolution, precision, and accuracy is described. Organic matter and pyrite from eleven rock samples of Neoarchean drill core express nearly the entire range of δ(13) C, δ(34) S, Δ(33) S, and Δ(36) S known from the geologic record, commonly in correlation with morphology, mineralogy, and elemental composition. A new analytical approach (including a set of organic calibration standards) to account for a strong correlation between H/C and instrumental bias in SIMS δ(13) C measurement of organic matter is identified. Small (2-3 μm) organic domains in carbonate matrices are analyzed with sub-permil accuracy and precision. Separate 20- to 50-μm domains of kerogen in a single ~0.5 cm(3) sample of the ~2.7 Ga Tumbiana Formation have δ(13) C = -52.3 ± 0.1‰ and -34.4 ± 0.1‰, likely preserving distinct signatures of methanotrophy and photoautotrophy. Pyrobitumen in the ~2.6 Ga Jeerinah Formation and the ~2.5 Ga Mount McRae Shale is systematically (13) C-enriched relative to co-occurring kerogen, and associations with uraniferous mineral grains suggest radiolytic alteration. A large range in sulfur isotopic compositions (including higher Δ(33) S and more extreme spatial gradients in Δ(33) S and Δ(36) S than any previously reported) are observed in correlation with morphology and associated mineralogy. Changing systematics of δ(34) S, Δ(33) S, and Δ(36) S, previously investigated at the millimeter to centimeter scale using bulk analysis, are shown to occur at the micrometer scale of individual pyrite grains. These results support the emerging view that the dampened signature of mass-independent sulfur isotope fractionation (S-MIF) associated with the Mesoarchean continued into the early Neoarchean, and that the connections

  9. Organic Geochemistry of the Hamersley Province: Relationships Among Organic Carbon Isotopes, Molecular Fossils, and Lithology

    Science.gov (United States)

    Eigenbrode, Jennifer L.

    2012-01-01

    Molecular fossils are particularly valuable ancient biosignatures that can provide key insight about microbial sources and ecology in early Earth studies. In particular, hopanes carrying 2-methyl or 3-methyl substituents are proposed to be derived from cyanobacteria and oxygen-respiring methanotrophs, respectively, based on both their modem occurrences and their Proterozoic and Phanerozoic sedimentary distributions. Steranes are likely from ancestral eukaryotes. The distribution of methylhopanes, steranes, and other biomarkers in 2.72-2.56 billion-year-old rocks from the Hamersley Province, Western Australia show relationships to lithology, facies, and isotopes of macromolecular carbon, and other biomarkers. These observations support biomarker syngenicity and thermal maturity. Moreover, ecological signatures are revealed, including a surprising relationship between isotopic values for bulk macromolecular carbon and the biomarker for methanotrophs. The record suggests that cyanobacteria were likely key organisms of shallow-water microbial ecosystems providing molecular oxygen, fixed carbon, and possibly fixed nitrogen, and methanotrophs were not alone in recycling methane and other C-13-depleted substrates.

  10. Stable Carbon Isotopic Fractionation in Smoke and Char Produced During Biomass Burning

    Science.gov (United States)

    Wang, Y.; Hsieh, Y.

    2006-12-01

    Stable isotopic ratio of carbon has been used extensively as a tracer of carbon sources in the environment. It has been documented that burning of C4 grasses resulted in significant depletion of C13 in the charcoal while burning of wood and C3 grass did not. This study was initiated to investigate the stable carbon isotopic fractionation of the smoke and char produced during biomass burnings. Samples of Juncus romerianus (C3 salt marsh grass) and Spartina alterniflora (C4 salt marsh grass), Eremochloa ophiuroides (centipede, a C4 lawn grass) and woody debris of a pine forest were colleted and burned in open air fire place. The particulate matter with diameters less than 2.5 micron (PM2.5) emitted from the burning was collected using a PM sampler. The original biomass, PM2.5, black C in PM2.5 and char (ash) were analyzed for their C, N and S thermograms using a multi-elemental scanning thermal analyzer and their stable C isotopic ratios were measured using an EA-IRMS. The results indicate that burning of wood and C3 grass did not produce significant C isotopic fractionation in PM2.5, black C in PM2.5 and char with respect to the original material. However, there was a significant C13-depletion in PM2.5 (-6.2 per mil), black C in PM2.5 (-4.6 per mil) and chars (-4.6 per mil) produced by burning of the C4 centipede grass; whereas the C4 Spartina salt marsh grass produced a C13-depletion in PM2.5 (-2.3 per mil) and black C in PM2.5 (-3.6 per mil), and a slight C13-enrichment in char (0.5 per mil). The isotope fractionation associated with burning of C4 vegetation is probably dependent on species and burning conditions and warrant further study.

  11. Factors controlling carbon isotopic composition of land snail shells estimated from lab culturing experiment

    Science.gov (United States)

    Zhang, Naizhong; Yamada, Keita; Yoshida, Naohiro

    2014-05-01

    Carbon isotopic composition (δ13C) of land snail shell carbonate is widely applied in reconstructing the C3/C4 vegetation distribution of paleo-environment, which is considered to reflect variations of some environmental parameters [1][2][3]. Land snail shell carbon has three potential sources: diet, atmospheric CO2 and ingested carbonate (limestone) [4]. However, their relative contributions to shell carbonate have not been understood well yet [4][5][6][7][8]. More researches are necessary before we could apply this tool in paleo-environment reconstruction, especially inter-lab culturing experiment. A kind of land snail species, Acusta despecta sieboldiana, was collected at Yokohama, Japan and cultured under suitable environment to lay eggs. The second generations were growing up from eggs to adults around 6-12 months at the temperature of 20°, 25° and 30°, respectively. All of the snails at 25° and 30° and most of those at 20° were fed by cabbage (C3 plant) during their life span while others were fed by corn (C4 plant). To investigate the effect of ingested carbonate, some of them were fed by Ca3(PO4)2 powder while others were fed by CaCO3 powder. δ13C of shells were analyzed by an Isotope Ratio Mass Spectrometry (Thermo Finnigan MAT 253); δ13C of food and snail tissue were measured by a Cavity Ring-Down Spectroscopy (Picarro G1121-i). At the same time, δ13C of eggshell and new born snails were analyzed by a Continuous Flow Isotope Ratio Mass Spectrometry (GasBench II). We confirmed that diet, atmospheric CO2 and ingested limestone could be important sources controlling shell δ13C values. And the temperature could affect shell carbonate δ13C values, too. A simple but credible frame was raised to discuss the mechanism of how each possible source and environmental parameter could affect shell carbonate δ13C values based on previous works [4][6][8] and this study. According to this frame and some reasonable assumptions, we have estimated the

  12. Simultaneous Analysis of Nitrogen, Carbon and Sulfur Stable Isotopes and Concentrations in Organics and Soils

    Science.gov (United States)

    Mambelli, S.; Brooks, P. D.; Sutka, R.; Hughes, S.; Finstad, K. M.; Pakes, M. J.; Dawson, T. E.

    2014-12-01

    To date, analysis of diet, food web complexities, biogeochemical cycles, and ecosystem functioning have largely focused on using variation in carbon (C) and nitrogen (N) stable isotope ratios. This is because a great deal is understood about what leads to this variation and because the dual stable isotope analysis of these two elements using continuous flow isotope ratio mass spectrometry (IRMS) is now commonplace. However, the aforementioned studies may all greatly benefit from the additional information one can get from also having sulfur (S) stable isotopes ratio data. Until very recently the analysis of δ34S has traditionally required an additional and often more difficult analytical procedure. Here, we report on the development of a new method that simultaneously analyzes the elemental and isotopic composition of N, C and S in a single sample. The new commercially available instrument includes a modified NCS elemental analyzer in line with an IRMS outfitted with 100 volt AD converters for wide dynamic range. We tested, and modified, this instrument to achieve maximum accuracy and precision for the isotopic measurements of all three elements. We found that the original design needed improvements to achieve our goals by: a) including a component (originally designed for trapping water) as buffer to reduce S memory and obtain reliable δ34S analysis; b) adding an external furnace for complete reduction of nitrogen oxides to N2 gas for accurate δ15N; c) adding a magnesium perchlorate water trap immediately after the reduction tube to minimize any water condensation that could also influence S memory. We analyzed a selection of organic materials and soils with approximately a 1:2 standards versus unknowns ratio per run. Using this NCS set-up, the precision of the N and C isotopic measurements was comparable to the one usually attained in NC mode alone (standard deviation of ± 0.13 δ15N in the range 30 to 400 µg N, and of ± 0.12 δ13C in the range 0.20 to 4 mg

  13. Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism.

    Science.gov (United States)

    Kaufman, A J; Hayes, J M; Knoll, A H; Germs, G J

    1991-01-01

    The carbon isotope geochemistry of carbonates and organic carbon in the late Proterozoic Damara Supergroup of Namibia, including the Nama, Witvlei, and Gariep groups on the Kalahari Craton and the Mulden and Otavi groups on the Congo Craton, has been investigated as an extension of previous studies of secular variations in the isotopic composition of late Proterozoic seawater. Subsamples of microspar and dolomicrospar were determined, through petrographic and cathodoluminescence examination, to represent the "least-altered" portions of the rock. Carbon-isotopic abundances in these phases are nearly equal to those in total carbonate, suggesting that 13C abundances of late Proterozoic fine-grained carbonates have not been significantly altered by meteoric diagenesis, although 18O abundances often differ significantly. Reduced and variable carbon-isotopic differences between carbonates and organic carbon in these sediments indicate that isotopic compositions of organic carbon have been altered significantly by thermal and deformational processes, likely associated with the Pan-African Orogeny. Distinctive stratigraphic patterns of secular variation, similar to those noted in other, widely separated late Proterozoic basins, are found in carbon-isotopic compositions of carbonates from the Nama and Otavi groups. For example, in Nama Group carbonates delta 13C values rise dramatically from -4 to +5% within a short stratigraphic interval. This excursion suggests correlation with similar excursions noted in Ediacaran-aged successions of Siberia, India, and China. Enrichment of 13C (delta 13C> +5%) in Otavi Group carbonates reflects those in Upper Riphean successions of the Akademikerbreen Group, Svalbard, its correlatives in East Greenland, and the Shaler Group, northwest Canada. The widespread distribution of successions with comparable isotopic signatures supports hypotheses that variations in delta 13C reflect global changes in the isotopic composition of late

  14. A refined method for calculating paleotemperatures from linear correlations in bamboo coral carbon and oxygen isotopes

    Science.gov (United States)

    Saenger, Casey; Watkins, James M.

    2016-06-01

    Bamboo corals represent an emerging paleoclimate archive with the potential to record variability at intermediate depths throughout much of the global ocean. Realizing this potential has been complicated by biologically mediated vital effects, which are evident in linear correlations of skeletal carbon (δ13C) and oxygen (δ18O) isotope composition. Previous efforts to develop a bamboo coral δ18O paleothermometer by accounting for such vital effects have not been completely successful as they still rely on empirical calibrations that are offset from the temperature dependence of abiogenic experiments. Here we describe an approach that better corrects for bamboo coral vital effects and allows paleotemperatures to be calculated directly from the abiogenic temperature dependence. The success of the method lies in calculating apparent equilibrium carbon and oxygen isotope fractionation at the temperature, pH, and growth rate of each coral, as well as in the use of model II regressions. Rigorous propagation of uncertainty suggests typical errors of ±2-3°C, but in select cases errors as low as ±0.65°C can be achieved for densely sampled and strongly correlated data sets. This lower limit approaches the value attributed to uncertainty in pH and growth rate estimates alone, as predicted by a series of pseudoproxy experiments. The incorporation of isotopically light metabolic CO2 appears to be negligible in most Pacific corals, but may be significant in Atlantic specimens, potentially requiring an additional correction. The success of the method therefore hinges on how well complex environmental systems and biomineralization strategies are constrained, with the most reliable temperatures occurring when calcifying fluid pH, growth rate, and incorporation of metabolic carbon into skeletal calcite are constrained using multiple geochemical proxies.

  15. Small mammal tooth enamel carbon isotope record of C4 grasses in late Neogene China

    Science.gov (United States)

    Arppe, Laura; Kaakinen, Anu; Passey, Benjamin H.; Zhang, Zhaoqun; Fortelius, Mikael

    2015-10-01

    The spatiotemporal pattern of the late Cenozoic spread of C4 vegetation is an important indicator of environmental change that is intertwined with the uplift of the Himalaya and Tibetan Plateau, and the development of the East Asian monsoons. To explore the spread of C4 vegetation in China and shed new light on regional climatic evolution, we measured δ13C values of more than 200 small mammal teeth (primarily rodents and lagomorphs) using a laser ablation isotope ratio mass spectrometry approach. Small mammals are highly sensitive indicators of their environment because they have limited spatial ranges and because they have minimal time-averaging of carbon isotope signatures of dietary components. The specimens originate from four classic Late Miocene fossil localities, Lufeng, Yuanmou, Lingtai, and Ertemte, along a southwest-northeast transect from Yunnan Province to Inner Mongolia. In Yunnan (Lufeng, Yuanmou) and on the Loess Plateau (Lingtai), the small mammal δ13C values record nearly pure C3 ecosystems, and mixed but C3-based ecosystems, respectively, in agreement with previous studies based on carbon isotopes of large herbivores and soil carbonates. In Inner Mongolia, the micromammalian tooth enamel δ13C record picks up the presence of C4 vegetation where large mammal samples do not, indicating a mixed yet C3-dominated ecosystem at ~ 6 Ma. As a whole, the results support a scenario of northward increasing C4 grass abundance in a pattern that mirrors northward decreasing precipitation of the summer monsoon system. The results highlight differences between large and small mammals as indicators of C4 vegetation in ancient ecosystems, particularly the ability of small mammal δ13C values to detect the presence of minor components of the vegetation structure.

  16. Stable carbon isotope fractionation in pollen of Atlas cedar: first steps towards a new palaeoecological proxy for Northwest Africa

    Science.gov (United States)

    Bell, Benjamin; Fletcher, William; Ryan, Peter; Grant, Helen; Ilmen, Rachid

    2016-04-01

    Analysis of stable carbon isotopes can provide information on climate and the environmental conditions at different growth stages of the plant, both past and present. Carbon isotope discrimination in plant tissue is already well understood, and can be used as a drought stress indicator for semi-arid regions. Stable carbon isotope ratios measured directly on pollen provides the potential for the development of long-term environmental proxies (spanning thousands of years), as pollen is well preserved in the environment. Atlas Cedar (Cedrus atlantica Endl. Manetti ex Carrière), is an ideal test case to develop a pollen stable carbon isotope proxy. The tree grows across a wide altitudinal and climatic range and is extremely sensitive to moisture availability. The pollen is abundant, and easily identifiable to the species level in pollen analysis because different cedar species are geographically confined to different regions of the world. In 2015 we sampled 76 individual cedar trees across latitudinal, altitudinal and environmental gradients, highly focused on the Middle Atlas region of Morocco, with 25 additional samples from botanical gardens across Europe and the US to extend these gradients. Here, we report new stable carbon isotope data from pollen, leaf and stem wood from these samples with a view to assessing and quantifying species-specific fractionation effects associated with pollen production. The isotopic response of individual trees at local and wider geographical scales to altitude and climatic conditions is presented. This research forms part of an ongoing PhD project working to develop and calibrate a modern carbon isotope proxy in Atlas cedar pollen, which can ultimately be applied to fossil sequences and complement existing multi-proxy records (e.g. pollen analysis in lake sediments, tree-rings).

  17. The effects of atmospheric [CO2] on carbon isotope fractionation and magnesium incorporation into biogenic marine calcite

    Science.gov (United States)

    Vieira, Veronica

    1997-01-01

    The influences of atmospheric carbon dioxide on the fractionation of carbon isotopes and the magnesium incorporation into biogenic marine calcite were investigated using samples of the calcareous alga Amphiroa and benthic foraminifer Sorites grown in the Biosphere 2 Ocean system under variable atmospheric CO2 concentrations (approximately 500 to 1200 ppm). Carbon isotope fractionation was studied in both the organic matter and the skeletal carbonate. Magnesium analysis was to be performed on the carbonate removed during decalcification. These data have not been collected due to technical problems. Carbon isotope data from Amphiroa yields a linear relation between [CO2] and Delta(sup 13)C(sub Corg)values suggesting that the fractionation of carbon isotopes during photosynthesi