Fakultät Umweltwissenschaften Investigations on Quaternary environmental changes based on malacological analyses and stable isotope signals Dissertation zur Erlangung des akademischen Grades Doctor rerum naturalium (Dr. rer. nat.) Vorgelegt von: MSc. Christiane Richter Geboren am 13.03.1986 in Dresden Gutachter: Prof. Dr. habil. Dominik Faust Technische Universität Dresden, Institut für Geographie Dr. Nicole Limondin-Lozouet Centre National de la Recherche Scientific (CNRS), Paris Laboratoire de Geographie Physique Prof. Dr. habil. Heinrich Thiemeyer Goethe Universität Frankfurt am Main, Institut für Physische Geographie Datum der Verteidigung: 04.12.2020 ACKNOWLEDGEMENT First and foremost, I would like to thank my supervisor Prof. Dominik Faust for his support on my way to a doctorate, for the valuable help whenever needed, the scientific input and constructive criticism, for the trust and room for own ideas but above all for the motivation and encouragement. Furthermore, I would like to thank Dr. Daniel Wolf for his always open door for questions and problems of all kind, for the precious support with field work(!!), for the constructive criticism and beneficial knowledge in every scientific topic and for the fun when working with him. I would like to thank Dr. Stefan Meng very much for his help and support, that he was always available to me and for the very pleasant exchange. I would like to thank Frank Walther for his help and active support, enthusiasm, confidence and valuable knowledge of the gastropod world, which I hope will be retained in future projects. I thank Dr. Olivier Moine for the good advice and training and Dr. Nicole Limondin-Lozouet for her support and encouragement. Furthermore, I am appreciative to Prof. Michael Zech for his support and to Lucas Bittner, Lisa Zwanzig, Jana Krautz, Dr. Jan Uwe Schmidt and Dr. Christopher Roettig for helpful discussions. I thank Klaus Groh for the pleasant cooperation, help and support with the Canary snail community. Moreover, I sincerely thank Markus Uhlig for the permission and the friendly help regarding the shemozzle in the Geotechnical laboratory of the TU Dresden, where I always felt comfortable and welcome, as well as Luise Hofman and Elisa Marzin for their help. Furthermore, I am appreciative to Dr. Maria Neubauer for the statistical support, Florian Schneider, Philipp Baumgart and Dr. Thomas Kolb for their help with field work, Dr. Stefania Milano for the stable isotope measurements and Dr. Lutz Maul and Prof. Ola Kwiecien for their friendly advice. I sincerely thank my referees Dr. Nicole Limondin-Lozouet and Prof. Heinrich Thiemeyer for the great kindness to review this doctoral thesis and for their time invested. I heartly thank the Graduate Academy of the Technical University of Dresden for granting me with a PhD scholarship for young female scientists and enabling me to unify family and PhD. I thank my parents, without which I would not have gotten this far. And last, the most important - I thank my husband Uwe for his support, for the process optimisation of the laboratory work and first and foremost for his continuous encouragement, and my children for their constant help with field collections and the positive feedback on my work. I ABSTRACT Geological sediment archives play a key role in studying the interrelations between ecosystems and environmental changes. The understanding of these interrelations is essential to assess future developments, especially in the light of current climate change. In the study in hand, Quaternary loess-palaeosol sequences of different settings are examined based on biological proxies in the form of gastropods. These (sub)fossil gastropod records allowed us to draw conclusions about environmental and climatic conditions associated with glacial- interglacial cycles of the past up to 400 ka. We compared a highly continental archive in the Southern Caucasus to an oceanic setting on the Canary Islands in order to examine the influence of local peculiarities and to test the applicability of the method in different settings. For this purpose, 180 samples with a total weight of 1800 kg sediment material were processed and wet sieved. They contained gastropod shells of 53.279 individuals and 41 species at least. The investigations comprise three fundamental main compounds: (I) In the first part we analyse the ecological indication of fossil gastropod assemblages in the sediment archives. The gastropods have proven to be valuable palaeoenvironmental proxies and provide new insights into the environmental history of the study region. Based on our results we assume for the South Caucasian study region, that glacial phases were related to dryer conditions indicated by a predominance of xerophilous shrub steppes, while warmer interglacial and interstadial phases favoured the distribution of mesophilous highgrass- and forest-steppe ecosystems, which indicate moister conditions. Furthermore, we assume that the average July temperatures were never below 10°C even during glacial periods. For the Canary Islands, on the other hand, we found that the ecosystems associated with glacial versus interglacial phases were only secondary influenced by local climate changes. Instead, a strong influx was shown by changes in the substrate, which influence the edaphic moisture properties. These substrate changes were primarily related to volcanism and local sediment availability. In addition, we observed prominent extinction events within the gastropod assemblages on Fuerteventura. In comparison with our stable isotope results and indications by other researchers from marine archives of the Canary Basin, we assume that these extinction events might be related to strong dry-hot winds in the final stages of glacial periods, that were described by Moreno et al. (2001). (II) We show that it is possible to derive a reliable stratigraphy based on gastropods in the different settings. The Caucasian loess deposits allowed an ecostratigraphic zonation based on displacement and re-immigration of taxa of different ecological groups. In contrast, on the insular setting of the Canary study area, it was even possible to develop a biostratigraphic zonation that includes the extinction of certain taxa on the island. I the latter case, the II temporary occurrence of particular key species can be used for a first stratigraphic orientation in the field. (III) In addition, this work includes one of the first studies to investigate stable isotope signals of terrestrial gastropods in geological long-term archives. The Southern Caucasian study region showed, in particular, the difficulty to disentangle the various factors responsible for isotope fractionation, particularly in continental areas. However, the results indicate a strong influence of the prevailing wind systems during different periods. The oceanic position of the Canary Islands, on the other hand, represents a special situation regarding the interpretation of stable isotope signals. We assume, that according stable isotope compositions of certain gastropod taxa allow us to reconstruct mean δ18O signals of the oceanic surface water and to approximate a first correlation of our lithological units with sea level fluctuations. Moreover, we assume, that δ13C shell signals on Fuerteventura enable us to differentiate between substrate- induced (edaphic) and climatic moisture alternations, respectively. We recommend, that the information that can be derived from stable isotope signals in gastropod shells should not be generalised and that the dominant site-specific factors should always be investigated and taken into account when interpreting the isotope signals. III KURZFASSUNG Geologische Sedimentarchive spielen eine Schlüsselrolle bei der Untersuchung der Wechselwirkungen zwischen Ökosystemen und Umweltveränderungen. Das Verständnis dieser Zusammenhänge ist essentiell, um zukünftige Entwicklungen insbesondere vor dem Hintergrund des aktuellen Klimawandels abschätzen zu können. In der vorliegenden Arbeit werden Quartäre Löss-Paläoboden-Sequenzen verschiedener Untersuchungsgebiete mit biologischen Umweltanzeigern in Form von Gastropodengehäusen untersucht. Diese (sub)fossilen Gastropoden ermöglichen es uns, Rückschlüsse auf Umwelt- und Klimabedingungen zu ziehen, die mit glazial-interglazialen Zyklen der vergangenen bis zu 400 ka in Verbindung stehen. Wir haben ein hochkontinentales Archiv im Südkaukasus mit einem ozeanischen Archiv auf den Kanarischen Inseln verglichen, um den Einfluss lokaler Besonderheiten zu untersuchen und die Anwendbarkeit der Methode in verschiedenen Umgebungen zu testen. Es wurden 180 Proben mit einem Gesamtgewicht von 1800 kg Sedimentmaterial aufbereitet und nassgesiebt. Diese enthielten Gastropodenschalen von 53.279 Individuen und mindestens 41 Arten. Die Untersuchungen umfassen drei grundlegende Hauptbestandteile: (I) Im ersten Teil analysieren wir die ökologische Indikation fossiler Gastropodengemeinschaften in den Sedimentarchiven. Die Gastropoden haben sich als wertvolle paläoökologische Umweltanzeiger erwiesen und dabei völlig neue Erkenntnisse für die Umweltgeschichte der Untersuchungsregion gebracht. Anhand unserer Ergebnisse gehen wir davon aus, dass die Untersuchungsregion im Südkaukasus während der Glaziale durch xerophile Strauchsteppenvegetation dominiert wurde, welche in feuchteren interglazialen und interstadialen Phasen durch mesophile Feuchtgras- bis Waldsteppenvegetation ersetzt wurde. Des Weiteren gehen wir davon aus, dass die mittleren Juli-Temperaturen selbst während