The potential of leaf wax biomarkers in fluvial sediment-paleosol sequences: A case study from the Alazani River, Georgia

Short Description

Biomarker analyses became a novel and innovative tool in paleoenvironmental research during the last decades. Especially long-chain n‑alkanes (>C₂₅) are leaf wax biomarkers that are produced by higher terrestrial plants and stay well preserved in sediment archives for millennia. Their homologue pattern as well as their carbon and hydrogen isotopic composition can be used to reconstruct past changes in vegetation and paleohydrological conditions. While leaf wax biomarkers were successfully applied in lacustrine sediments and loess-paleosol sequences during the last years, no studies explored their potential for paleoenvironmental reconstructions in fluvial sediment-paleosol sequences so far. However, the latter kind of sediment archives are found ubiquitously in most regions of the world. Therefore, biomarker analyses in fluvial sediment-paleosol sequences have the potential to strongly enhance our knowledge of former climatic and environmental conditions in different landscapes and climate zones.

Our project exploratively evaluates the potential of leaf wax biomarkers for paleoenvironmental reconstructions in fluvial sediment-paleosol sequences by studying a Holocene fluvial sediment sequence from the upper Alazani River in eastern Georgia (southern Caucasus). Since leaf wax biomarkers were not investigated in the Caucasus region so far, in a first step their regional applicability was evaluated on modern reference material from plants and topsoils prior to their application to the Holocene fluvial sediments. Subsequently, potential archive-related limitations were carefully discussed and the age and origin of the leaf waxes in the fluvial sediments were investigated by compound-class ¹⁴C-dating. Following those general considerations, we finally reconstructed the regional paleovegetation by leaf wax homologue patterns and paleoclimatic conditions by compound-specific δ¹³C and δ²H of those biomarkers.

Publications

• Bliedtner, M., Schäfer, I.K., Zech, R., Suchodoletz, H. von, 2018a. Leaf wax n-alkanes in modern plants and topsoils from eastern Georgia (Caucasus) – implications for reconstructing regional paleovegetation. Biogeosciences 15(12), 3927–3936. https://doi.org/10.5194/bg-15-3927-2018Externer Link
• Bliedtner, M., Zech, R., Kühn, P., Schneider, B., Zielhofer, C., Suchodoletz, H. von, 2018b. The potential of leaf wax biomarkers from fluvial soil-sediment sequences for paleovegetation reconstructions - Upper Alazani River, central southern Greater Caucasus (Georgia). Quaternary Science Reviews 196, 62–79. https://doi.org/10.1016/j.quascirev.2018.07.029Externer Link
• Bliedtner, M., Suchodoletz, H. von, Schäfer, I., Welte, C., Salazar, G., Szidat, S., Haas, M., Dubois, N., Zech, R., 2020a. Age and origin of leaf wax n-alkanes in fluvial sediment-paleosol sequences and implications for paleoenvironmental reconstructions. Hydrology and Earth System Sciences 24(4), 2105–2120. https://doi.org/10.5194/hess-24-2105-2020Externer Link
• Bliedtner, M., Zech, R., Zech, J., Schäfer, I., Suchodoletz, H., 2020b. A first Holocene leaf wax isotope‐based paleoclimate record from the semi‐humid to semi‐arid south‐eastern Caucasian lowlands. Journal of Quaternary Science. https://doi.org/10.1002/jqs.3210Externer Link

For a short overview over the project, you are kindly invited to watch our presentation from the Fluvial Archives Group (FLAG) meeting in fall 2021 following the link below:

https://www.youtube.com/watch?v=CxghopaK-3Q&t=7846sExterner Link