(Northern Serbia): an Organic Isotope Geochemistry Study
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EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Open Access Biogeosciences Biogeosciences Discussions Open Access Open Access Clim. Past, 9, 1001–1014, 2013 Climate www.clim-past.net/9/1001/2013/ Climate doi:10.5194/cp-9-1001-2013 of the Past of the Past © Author(s) 2013. CC Attribution 3.0 License. Discussions Open Access Open Access Earth System Earth System Dynamics Dynamics Discussions Excursions to C4 vegetation recorded in the Upper Pleistocene loess Open Access Open Access of Surduk (Northern Serbia): an organic isotope geochemistryGeoscientific study Geoscientific Instrumentation Instrumentation C. Hatte´1, C. Gauthier1, D.-D. Rousseau2,3, P. Antoine4, M. Fuchs5, F. Lagroix6, S. B. MarkoviMethodsc´7, O. and Moine4, and Methods and A. Sima2 Data Systems Data Systems 1Laboratoire des Sciences du Climat et de l’Environnement (LSCE), UMR8212, CEA-CNRS-UVSQ, Discussions Open Access 91198 Gif-sur-Yvette, France Open Access 2 Geoscientific Laboratoire de Met´ eorologie´ Dynamique, UMR8539, CNRS-ENS, 75231 Paris, France Geoscientific 3Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA Model Development 4 Model Development Laboratoire de Geographie´ Physique, CNRS-Univ. Paris 1, 92195 Meudon, France Discussions 5Department of Geography, Justus-Liebig-University Giessen, 35390 Giessen, Germany 6Institut de Physique du Globe de Paris, Sorbonne Paris Cite,´ Univ Paris Diderot, UMR7154, CNRS, 75005 Paris, France Open Access Open Access 7Chair of Physical Geography, University of Novi Sad, Novi Sad, Serbia Hydrology and Hydrology and Correspondence to: C. Hatte´ ([email protected]) Earth System Earth System Received: 10 November 2012 – Published in Clim. Past Discuss.: 11 January 2013 Sciences Sciences Revised: 12 April 2013 – Accepted: 12 April 2013 – Published: 3 May 2013 Discussions Open Access Open Access Ocean Science Abstract. Loess sequences have been intensively studied positive North AtlanticOcean Western RussianScience (NA/WR)-like at- to characterize past glacial climates of the 40–50◦ north mospheric pattern that favored northerlies over westerlies Discussions and south latitude zones. Combining different approaches and reduced Atlantic precipitation over the Balkans. This of sedimentology, magnetism, geochemistry, geochronol- configuration would imply very dry summers that did not al- Open Access Open Access ogy and malacology allows the general pattern of the cli- low C3 plants to grow, thus supporting C4 development. The mate and environment of the last interglacial–glacial cy- intra-“C4 episode” periods would have occurred under less Solid Earth cle in Eurasia and America to be characterized. Previous drastic oceanic and atmosphericSolid patterns Earth that made the influ- studies performed in Europe have highlighted the predom- ence of westerlies on the Balkans possible. Discussions inance (if not the sole occurrence) of C3 vegetation. The presence of C3 plants suggests a regular distribution of pre- cipitation along the year. Therefore, even if the mean an- Open Access Open Access nual precipitation remained very low during the most ex- 1 Introduction The Cryosphere tensive glacial times, free water was available for more The Cryosphere Discussions than 2 months per year. Contrarily, the δ13C record of Loess deposits are important terrestrial sediment records Surduk (Serbia) clearly shows the occurrence and domi- that provide key data for climate reconstruction and the interpretation of past glacial cycles (Kukla, 1977; Guo et nance of C4 plants during at least 4 episodes of the last glacial times at 28.0–26.0 kyr cal BP, 31.4–30.0 kyr cal BP, al., 2002). Combining multidisciplinary approaches (sedi- mentology, magnetic properties, geochemistry, geophysics, 53.4–44.5 kyr cal BP and 86.8–66.1 kyr. The C4 plant devel- opment is interpreted as a specific atmospheric circulation geochronology, malacology, palynology) allows a general pattern that induces short and dry summer conditions. As pattern of climatic and environmental evolution in Eurasia and America to be proposed. possible explanation, we propose that during “C4 episodes”, the Mediterranean Sea would have been under the com- In Western Europe, high-resolution study of the Nussloch bined influence of the following: (i) a strong meridional cir- loess sequence (Germany), supported by a large set of lumi- 14 culation unfavorable to water evaporation that reduced the nescence (OSL, IRSL, TL) and C dates, has allowed cor- Mediterranean precipitation on the Balkans; and (ii) a high relation of the loess grain size variations and loess–paleosol alternation with the Greenland ice core dust record, which Published by Copernicus Publications on behalf of the European Geosciences Union. 1002 C. Hatte´ et al.: An organic isotope geochemistry study suggests a global connection between North Atlantic and underlying 1 m of sediment should be regarded only as sup- Western European atmospheric circulations and associated port of climatic trends, not climatic quantitative information. wind regimes (Fuchs et al., 2012; Rousseau et al., 2007). Conversely, typical glacial loess is a suitable sediment for or- The first attempt to model the impact of the abrupt climate ganic geochemistry studies. It accumulates very quickly dur- variations of the North Atlantic on dust emissions supports ing the cold oxygen isotope stage (OIS) and is associated the hypothesis that the North Atlantic millennial-timescale with sparse vegetation and a weak rhizosphere. The presence variability is imprinted on Western European loess profiles of centimeter-thick laminated structures recognized in most and points to changes in the vegetation cover as the main of the typical loess (Derbyshire and Mellors, 1988; Lautri- factor responsible for the dust emissions, yielding material dou, 1985; Schwan, 1986) implies the absence of significant for millennial-scale sedimentation variations (Sima et al., vertical disturbance and a good preservation of the memory 2009). Among the multidisciplinary investigations, a recent of the climatic conditions contemporaneous to the time of organic geochemistry study focused on the impact of these deposition. abrupt events in terms of precipitation at the key section of The lack of conditions favorable to pedogenesis and the Nussloch. Using inverse modeling of δ13C and vegetation, dry periglacial environment favor the degradation of organic Hatte´ and Guiot (2005) showed a general glacial precipi- matter without distortion of the isotopic signal, making typ- tation background of 200 mm yr−1 along the last glaciation ical loess suitable for organic geochemical study (Hatte´ et punctuated by estimated increases of 100 % recorded during al., 1998). Indeed, as corroborated by the very low loess or- interstadial events. ganic content, microbial degradation of the weak and low A comprehensive pattern of past Western European mid- energetic vegetal input in typical loess during glacial times latitude atmospheric circulation and interconnection is now results in a near-total mineralization of organic matter. This emerging, but comparatively few similar high-resolution data near-complete degradation does not induce isotopic fraction- on past climate are available for Central Europe. Stratigraph- ation and the original isotopic signal is preserved. In con- ical, paleopedological and chronological studies (Antoine et trast, flourishing vegetation associated with soils and pale- al., 2009a; Fuchs et al., 2008; Galovic´ et al., 2009; Schmidt osols provide a large amount of organic matter with a wide et al., 2010; Stevens et al., 2011; Zech et al., 2009) in Ser- range of energetic value. In such an environment, microbes bia have provided information that the Carpathian region select compounds of high energetic value at the expense of and Western European environments were under different less easily degradable compounds. This results in a selective atmospheric conditions that resulted in a drier environment degradation of organic matter compounds that might bring throughout the last climatic cycle (Antoine et al., 2009a; in isotopic fractionation. In conclusion, the carbon isotopic Markovic´ et al., 2008). This conclusion was based on grain- composition (δ13C) of organic matter preserved in typical size and paleosol analyses, but a more precise interpretation loess sediments nicely reflects the original isotopic signature requires appropriate investigation. Indeed, the extent of this of the vegetation and, therefore, represents an indicator of dryness, the search for seasonality of the precipitation and the paleoenvironmental conditions. reconstruction of past vegetation appear necessary for pro- The isotopic signature of vegetation provides information viding key elements for understanding the past atmospheric on photosynthetic pathways (C3 versus C4) (Farquhar et al., circulation conditions in this area. 1982; O’Leary, 1981) and, thus, on environmental changes Such an issue could be addressed by an organic isotopic that are a prelude to the replacement of one vegetation type geochemistry study, as has already been performed in