engleski

Principles of using stable isotopes (C, O, and H), biomarkers, and 14C dating methods on Quaternary loess-palaeosol sequences from the North Adriatic for paleo ‒environment, ‒ vegetation and –climate reconstructions

Loess–paleosol sequences represent one of the most informative terrestrial paleoclimate archives (Pye & Sherwin, 1999). The loess- paleosol sequence on the island of Susak, which correlates to the Oxygen Isotope Stages (OIS) 5 to 2, is a detailed Late Pleistocene archive of climate change in the North Adriatic Sea of Croatia (Mikulčić Pavlaković et al., 2011 ; Wacha et al., 2011a, b). In order to better understand the impact of climate change on regional ecosystems, detailed knowledge about past climate, environment and vegetation changes obtained by highly resolved spatial and temporal data is essential (Solomon et al., 2007). To be able to reconstruct the paleo ‒ environment, ‒vegetation and –climate conditions from loess-paleosol sequences, several state-of-the-art methods will be used, with field investigations conducted within the Croatian science foundation project Standartisation and Applied Investigation of Quaternary Sediments in Croatia (SAPIQ). Secondary carbonates (e.g., rhizoliths ; Klappa, 1980 ; Barta, 2011) (and associated organic matter), which are often found in loess-paleosol sequences and are precipitated in isotopic equilibrium with root-derived CO2, are used to reconstruct the vegetation (C3 vs. C4) present during their formation based on stable carbon isotopic composition (carbonatic carbon‒ δ13Ccarb., organic carbon‒ δ13Corg.) (Cerling, 1984 ; Pustovoytov & Terhorst, 2004 ; Wang et al., 2004 ; Gocke et al., 2011 ; Brlek & Glumac, 2014 ; Koeniger et al., 2014). Potential ecological (abundance of C3 and C4 plants) and environmental changes can be used to reconstruct changes in climate (Cerling, 1984 ; Wang et al., 2004, 2007). In order to establish a reliable geochronological context, secondary carbonates and associated organic matter must be dated with the 14C dating technique (Pustovoytov & Terhorst, 2004 ; Gocke et al., 2011). In addition, because the oxygen isotope composition of secondary carbonates is related to the oxygen isotopic composition (δ18O) of local precipitation (Cerling, 1984), these data can be used to reconstruct the temperature (Koeniger et al., 2014). Geochronological and stable isotope analysis is planned to be conducted at Hertelendi Laboratory of Environmental Studies (Institute for Nuclear Research of the Hungarian Academy of Sciences, Hungary ; see Újvári et al., 2014). The study of long-chained n-alkanes (lipid biomarkers which are constituents of plant leaves) with carbon atom numbers between 25 and 33 (C25‒C33), together with their compound-specific isotope analysis (δ13C, δD), can also be used to reconstruct vegetation changes (grass vs. trees, C3 vs. C4) and give important insights into past changes in the isotope composition of precipitation and evapotranspiration from investigated loess- paleosol sequences (Liu & Huang, 2008 ; Shatz et al., 2011 ; Zech et al., 2013 ; see also Gocke et al., 2014a, b). In addition, statistical methods can be employed to classify data, test the dependence among groups of data and model the data distribution and dependence (including n- alkane endmember modelling). Moreover, statistical models can be used to describe and quantify the relationship among groups of data and/or distinct factors. Application of spatial statistical methods can provide insight in data distribution on a map (Pawlowsky-Glahn & Buccianti, 2011 ; Van den Boogaart & Tolosana Delgado, 2013). Implementation of such multidisciplinary methodology and establishing reference loess- paleosol profiles can eventually be used for other loess sections in Croatia (e.g. Zmajevac section in Eastern Croatia ; Galović et al., 2009), correlation with referent loess sections in Europe (Hungary, Germany, Serbia ; Pustovoytov & Terhorst, 2004 ; Gocke et al., 2011 ; Zech et al., 2013 ; Koeniger et al., 2014), as well as for subaerially exposed Quaternary marine carbonate deposits (e.g., Li & Jones, 2014). In addition, principles of using stable isotopes of pedogenic carbonates and organic matter in Quaternary loess- paleosol sequences for paleo ‒environment, ‒ vegetation and –climate reconstructions may also be applied to pedogenic carbonates formed during subaerial exposure of Adriatic-Dinaridic Carbonate Platform successions (Brlek et al., 2014 ; Brlek & Glumac, 2014).

loess-paleosol ; pedogenic carbonates ; stable isotopes ; radiocarbon dating ; environmental reconstructions

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