Hostname: page-component-8448b6f56d-c4f8m Total loading time: 0 Render date: 2024-04-24T07:18:44.079Z Has data issue: false hasContentIssue false
  • English
  • Français

Comparing Carbonate and Organic Ams-14C Ages in Lake Abiyata Sediments (Ethiopia): Hydrochemistry and Paleoenvironmental Implications

Published online by Cambridge University Press:  18 July 2016

Elisabeth Gibert ,
Yves Travi ,
Marc Massault ,
Tesfaye Chernet ,
Florent Barbecot  and
Fatima Laggoun-Defarge
Elisabeth Gibert
Affiliation:
CNRS-UMR 8616, Equipe «Hydrologie, Paléohydrologie et Paléoenvironnement», Université Paris-Sud, Bâtiment 504, 91405 Orsay cedex, France. Email: egibert@geol.u-psud.fr
Yves Travi
Affiliation:
Laboratoire d'Hydrogéologie, Département de Géologie, Faculté des Sciences d'Avignon, 33 rue Louis Pasteur, 84000 Avignon, France
Marc Massault
Affiliation:
CNRS-UMR 8616, Equipe «Hydrologie, Paléohydrologie et Paléoenvironnement», Université Paris-Sud, Bâtiment 504, 91405 Orsay cedex, France. Email: egibert@geol.u-psud.fr
Tesfaye Chernet
Affiliation:
Laboratoire d'Hydrogéologie, Département de Géologie, Faculté des Sciences d'Avignon, 33 rue Louis Pasteur, 84000 Avignon, France
Florent Barbecot
Affiliation:
CNRS-UMR 8616, Equipe «Hydrologie, Paléohydrologie et Paléoenvironnement», Université Paris-Sud, Bâtiment 504, 91405 Orsay cedex, France. Email: egibert@geol.u-psud.fr
Fatima Laggoun-Defarge
Affiliation:
Laboratoire de Géologie de la Matière Organique, Université d'Orléans, 45000 Orleans, France
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We studied a 12.6-m-long sequence from Lake Abiyata (Central Ethiopia) to establish a reliable and accurate chronology for use in global paleoclimatic reconstructions. The 26 accelerator mass spectrometry radiocarbon (AMS 14C) ages, performed on carbonates and organic matter, define 2 parallel chronologies, representing the complete Holocene period. However, these chronologies show a significant discrepancy from 500 to 900 BP in depth; ages obtained on carbonates were always older than those on organic matter. The hydrogeological and geochemical behavior of the Lake Abiyata basin has shed light on this discrepancy. We found that the carbonate crystallization is due mainly to the mixing of lake waters with groundwaters from the multi-layered aquifer contained in the 600-m-thick basement of the lake. The 14C activity of total dissolved inorganic carbon (TDIC) measured by AMS from bottom and surface lake waters (111.4 and 111.8 pMC, respectively) confirms that the mixing occurs at the water-sediment interface. This evidence of groundwater participation in the carbonate crystallization calls into question the current paleoclimatic reconstructions based on inorganic carbonates in lakes. Specific attention should thus be given to the respective proportions of each end-member in the mixing for the quantitative estimation of the groundwater input. This will help to validate the paleoenvironmental reconstructions and to highlight an eventual diagenetical evolution of inorganic carbonates during burial, via the study of pore waters.

Type
Articles
Information
Radiocarbon , Volume 41 , Issue 3 , 1999 , pp. 271 - 286
Copyright
Copyright © 1999 by the Arizona Board of Regents on behalf of the University of Arizona 

References

Ball, JW, Nordstrom, DK. 1991. User's manual for WATEQ4F, with revised thermodynamic database and test cases for calculating speciation of major, trace, and redox elements in natural waters. United States Geological Survey Open File Report 91–183.Google Scholar
Bonnefille, R, Robert, C, Delibrias, G, Elenga, H, Herbin, J-P, Lezine, A-M, Perinet, G, Tiercelin, J-J. 1986. Paleenvironement of Lake Abijata, Ethiopia, during the past 2000 years. In: Frostik, LE, Reid, I, Renaut, RW, Tiercelin, J-J, editors. Sedimentation in African Rifts, Geological Society Special Publication 25:253–65.Google Scholar
Colman, SM, Jones, GA, Rubin, M, King, JW, Peck, JA, Orem, WH. 1996. AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake. Quaternary Geochronology (Quaternary Science Reviews) 15:20–35.CrossRefGoogle Scholar
Chernet, T. 1998. Etude des mécanismes de minéralisation en fluorure et éléments associés de la région des lacs du rift éthiopien [dissertation]. Avignon, France: 215 p.Google Scholar
Chernet, T, Travi, Y, Valles, V. 1999. Geochemistry of water of the East African Rift: mechanism of degradation of the quality of natural waters in the lake region of the Ethiopian Rift. Water Research. Forthcoming.Google Scholar
Durand, A, Fontes, J-Ch, Gasse, F, Icole, M, Lang, J. 1984. Le nord-ouest du Lac Tchad au Quaternaire: étude de paléoenvironnements alluviaux, éoliens, palustres et lacustres. Palaeoecology of Africa (and the Surrounding Islands) 16:215–243.Google Scholar
Fontes, J-Ch, Gasse, F. 1991. PAHLYDAF (Palaeohydrology in Africa: objectives, methods and major results). Palaeogeography, Palaeoclimatology, Palaeoecology 84:191–215.CrossRefGoogle Scholar
Fontes, J-Ch, Andrews, JN, Causse, C, Gibert, E. 1992. A comparison of 14C and Th/U ages on continental carbonates. Radiocarbon 34(3):602–10.CrossRefGoogle Scholar
Fontes, J-Ch, Mélières, F, Gibert, E, Qing, Liu, Gasse, F. 1993. Stable isotope and radiocarbon balances of two tibetan lakes (Sumxi Co and Longmu Co) from 13,000 BP. Quaternary Science Review 12:875–87.CrossRefGoogle Scholar
Fontes, J-Ch, Gasse, F, Gibert, E. 1996. Holocene environmental changes in Bangong basin (western Tibet). Part 1: modern setting, mineralogy, stable isotope of carbonates and radiometric chronology. Palaeogeography, Palaeoclimatology, Palaeoecology 120:25–47.CrossRefGoogle Scholar
Gasse, F, Street, FA. 1978. Late Quaternary lake-level fluctuations and environments of the northern Rift Valley and Afra region (Ethiopia and Djibouti). Palaeogeography, Palaeoclimatology, Palaeoecology 24:279–325.CrossRefGoogle Scholar
Gasse, F, Arnold, M, Fontes, J-Ch, Fort, M, Gibert, E, Huc, A, Yuanfang, L, Liu, Q, Melieres, F, Van Campo, E, Fubao, W, Qingsong, Z. 1990. A 13,000 yr climatic record from western Tibet (Xizang, China). Nature 353:742–45.Google Scholar
Geyh, MA, Schotterer, U, Grosjean, M. 1998. Temporal changes of the 14C reservoir effect in lakes. Radiocarbon 40(2):921–31.Google Scholar
Gillespie, R, Street-Perrott, A, Switsur, R. 1983. Post-glacial arid episodes in Ethiopia have implications for climate prediction. Nature 306:680–3.CrossRefGoogle Scholar
Johnson, TC. 1989. Sedimentary processes and signals of past climatic change in the large lakes of the East African Rift Valley. In: Johnson, TC, Odada, E, editors. The Limnology, Climatology and Paleoclimatology of the East African Lakes. The Netherlands: Gordon and Breach Publishers. p 367–412.Google Scholar
Le Turdu, C, Tiercelin, J-J, Gibert, E, Travi, Y, Richert, J-P, Gasse, F, Bonnefille, R, Gensous, B, Jeudy, V, Lezzar, KE, Chernet, T, Endale, T, Umer, M, Decobert, M. 1999. The Ziway-Shala basin system, Main Ethiopian Rift, East Africa. Mechanisms of basin formation and sediment accumulation. Implications for a lake drilling project. Palaeogeography, Palaeoclimatology, Palaeoecology 150:135–77.CrossRefGoogle Scholar
Levin, I, Bossinger, R, Bonani, G, Francey, RJ, Kromer, B, Münnich, KO, Suter, M, Trivett, NBA, Wölfli, W. 1992. Radiocarbon in atmospheric carbon dioxide and methane: global distribution and trends. In: Taylor, RE, Long, A, Kra, RS, editors. Radiocarbon after four decades. Berlin: Springer-Verlag. p 503–18.Google Scholar
Levin, I, Münnich, KO, Weiss, W. 1980. The effect of anthropogenic CO2 and 14C sources on the distribution of 14C in the atmosphere. Radiocarbon 22(2):379–91.CrossRefGoogle Scholar
Libby, WF, Anderson, EC, Arnold, JR. 1949. Age determination by Radiocarbon content: world-wide assay of natural radiocarbon. Science 109:227–8.CrossRefGoogle ScholarPubMed
Nicholson, SE. 1996. A review of climate dynamics and climate variability in eastern Africa. In: Johnson, TC, Odada, E, editors. The limnology, climatology and paleoclimatology of the east African lakes. The Netherlands: Gordon and Breach Publishers. p 25–56.Google Scholar
Rozanski, K, Araguas-Araguas, L, Gonfiantini, R. 1996. Isotope patterns of precipitation in the east African region. In: Johnson, TC, Odada, E, editors. The limnology, climatology and paleoclimatology of the east African lakes. The Netherlands: Gordon and Breach Publishers. p 79–93.Google Scholar
Saliege, JF, Fontes, J-Ch. 1983. Essai de determination experimental du fractionnement isotopique 13C et 14C du carbone au cours des processes naturels. International Journal of Applcation in Radiation and Isotopes 35(1):55–62.CrossRefGoogle Scholar
Street, FA. 1981. Chronology of Late Paleistocene and Holocene lake-level fluctuations, Ziway-Shala Basin, Ethiopia. In: Leakey, RE, Ogot, BA, editors. Proceedings of the 8th Panafrican congress of prehistory and Quaternary studies. 1977 Sept 5–10; Nairobi, Kenya. p 143–6.Google Scholar
Stuiver, M, Kra, RS. 1986. Calibration issue. Radiocarbon 28(2B):805–1030.Google Scholar
Stuiver, M, Reimer, PJ. 1993. Extended 14C data base and revised Calib 3.0 14C age calibration program. Radiocarbon 35(1):215–30.CrossRefGoogle Scholar
Talbot, MR, Kelts, K. 1986. Primary and diagenetic carbonates in the anoxic sediments of lake Bosumtwi, Ghana. Geology 14:912–6.2.0.CO;2>CrossRefGoogle Scholar
Talbot, MR, Livingstone, DA. 1989. Hydrogen index and carbon isotopes of lacustrine organic matter as lake level indicators. Palaeogeography, Palaeoclimatology, Palaeoecology 70:121–37.CrossRefGoogle Scholar
Talbot, MR, Johannessen, T. 1993. A high resolution palaeoclimatic record for the last 27,500 years in tropical West Africa from the carbon and nitrogen isotopic composition of lacustrine organic matter. Earth and Planetary Science Letter 110:23–37.CrossRefGoogle Scholar
Travi, Y, Chernet, T, Gibert, E. 1997. Study of hydrological behaviour of the Lake Region in the Ethiopian Rift, using hydrological, hydrochemical and isotopic data: palaeohydrological implications. Symposium on Volcanism, Rifting et Paléoclimats dans le Rift Ethiopien et la Dépression de l'Afar. 1997 Feb 3–16; Addis–Ababa, Ethiopia. p 36.Google Scholar
Valles, V, de Cockborn, A-M. 1992. Elaboration d'un logiciel de geoxchimie applique a l'etude de la qualite des eaux (AQUA Programme). Colloque Alteration et Restauration des Eaux Continentales, 1992 Oct 27–30; Port Leucate, France. p 27–30.Google Scholar
Webb, T III, Ruddiman, WF, Street-Perrott, FA, Markgraf, V, Kutzbach, JE, Bartlein, PJ, Wright, HE Jr, Prell, WL. 1993. Climate changes during the past 18,000 years: regional syntheses, mechanisms, and causes. In: Wright, HE Jr, editor. Global climate since the last Glacial Maximum. University of Minnesota Press. 569 p.Google Scholar