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Balthasar L. Epprecht | Institute of Geological Sciences | University of Bern
Msc Thesis on the formation of down-stepping deltas (Lake Sämtisersee, Switzerland)
Lacustrine deltas that prograde at constant lake-levels form slightly inclined alluvial plains up to the river mouth. In Sämtis Valley, a glacially carved Alpine valley, five such alluvial plains, separated through steep delta front slopes occur on different elevations above today’s lake-level of Sämtisersee. Macroscopic analyses of the sedimentary record and detailed studies on the digital elevation model clearly indicate the terraces to originate from river deltas prograding at various lake-levels. The steep delta fronts and the relative orientation of the studied outcrops yield information about at least three episodic events during which the lake-level dropped by several meters without ever rising again to the old stage.
Glacial retreat since the LGM led to a stepwise reduction of Sämtisersee’s catchment area by dividing it into hydrologically isolated basins. These reductions in catchment area and the eventual full vanishing of the glaciers led to episodically reduced meltwater influx into Sämtisersee. The lithological terrace compositions and a sediment provenance analysis reveal strong evidence that the different terrace levels with the down-stepping terrace morphology in Sämtis Valley are predominantly inflow-controlled. In order to put a timestamp on the various terrace steps, optically stimulated luminescence (OSL) dating was applied. For further clarification of the ages, a piece of wood found in the sandy terrace sediments is currently being dated using radiocarbon dating.
I am grateful for the generous support provided by CH-QUAT, that enabled me to finance the whole field campaign. Being able to return to the field multiple times was immensely important in order to collect further samples for radiocarbon and OSL dating as well as to verify theoretical hypotheses concerning the glacial history of Sämtis Valley directly in the field.
Thank you very much, CH-QUAT!
Contact: Balthasar L. Epprecht (balthasar.epprecht@students.unibe.ch)
Leah Forsythe | Geology | ETH Zurich
CH-QUAT support of workshop attendance in Edinburgh.
Micromorphology is a discipline widely used in the study of glacigenic sediments. It applies basic principles of structural geology, sedimentology, and mapping on a microscale to provide insights into the processes, evolution, and deformation of sediments during glacial periods.
For my MSc thesis, I will utilize these techniques to deepen our understanding of the glacigenic sediments at Bürglen (Albis), where glacial diamicts are interbedded with Early Pleistocene sediments from the Höhere Deckenschotter Group (HDS). By relating micromorphological features to geological processes and macroscale observations, I aim to understand the context of sediment emplacement (e.g., subglacial traction till, subglacial debris flow, etc.) and the subsequent conditions of deformation. This research will contribute to our knowledge of the palaeo-landscape in the Northern Alpine Foreland.
Prior to choosing my thesis topic, micromorphology was a new concept for me. To gain foundational knowledge, I attended a five-day workshop in August 2024, hosted by Emrys Philips at the Lyell Centre (British Geological Survey) in Edinburgh, UK. During this workshop, I learned how to identify microstructures in diamicts, create meaningful morphological maps, and link these observations to geological processes. Under Emrys' supervision, I mapped two thin sections that will be included in my final thesis.
I am grateful for the generous support from CH-QUAT, which enabled me to learn from an expert in the field of glacial micromorphology. This experience has greatly benefited me on a personal level and will be crucial as I write my master's thesis.
Thank you, CH-QUAT!
Contact: Leah Forsythe (lforsythe@student.ethz.ch)
Gabriel Graf | Institute of Geological Science | University of Bern
Holocene lake-level changes controlled by climatic changes (Lake Sämtisersee, E Switzerland)
Lake Sämtis is located in the Alpstein (Appenzell Innerrhoden, E Switzerland). Drainage of the lake is controlled by a subaqueous karst outflow. Historically, the lake level is known to fluctuate seasonally from almost dry during hot summers to a high of ~15 m after heavy rainfall periods. This seasonal behaviour may also indicate a sensitivity to climatic changes on Holocene timescales. Such climatic control is suggested by exposed deltaic terraces indicating higher former lake levels (studied in detail by a second Master’s thesis by B. Epprecht). The aim of my Master's thesis is to reconstruct the palaeoclimatic history of Lake Sämtisersee using sediment cores taken from the lake bed. The core analysis focuses on lake level fluctuations including possible drying phases over the last ~6000 years. In addition, a correlation of the lake sediments with the sediments of the delta terraces will be attempted. By linking the two theses, we aim at a broad understanding of the hydroclimatic changes recorded in Lake Sämtissersee and the Late Quaternary history of the Alpstein area in general. The financial support from CH-Quat will allow me to carry out important fieldwork and radiocarbon dating of the cores. Excellent cores and dates will be a great basis for my Master's thesis. Thank you very much for your support for my research project!
Contact: Gabriel Graf (gabriel.graf@students.unibe.ch)
Simona Breu | Geoecology | Department of Environmental Sciences | University of Basel
Changes in fossil chironomid and cladoceran assemblages along water depth gradients
Thanks to the generous support from CH-QUAT, I had the opportunity to present my research on the use of fossil chironomid assemblages for reconstructing past water depths at the 22nd International Symposium on Chironomidae (ISC22) in Niš, Serbia.
Fossil remains of chironomids, whether in larvae or adult form, provide a unique perspective on the development of aquatic ecosystems over long periods. My study offers new insights into changes in fossil chironomid assemblages along the water depth gradient in Central European lakes. This dataset, detailing the composition of the chironomid assemblages along increasing water depth gradients, was used as a reference dataset to investigate water depth changes in a downcore study from Lake Lucerne (Switzerland). The results generally align with known geological records of water level fluctuations in Lake Lucerne. However, comparison with other proxies like for example pollen could be beneficial to support the current reconstruction.
Presenting my research findings at ISC22 allowed me to get a valuable exchanges of ideas and feedback from fellow researchers. Thank you, CH-QUAT, for making this possible.
Contact: Simona Breu (simona.breu@unibas.ch)
Francois Burgay | Oeschger Centre for Climate Change Research | University of Bern
Non-target screening analysis on ice and snow samples: a new opportunity to enhance our understanding on past and present atmospheric aerosol composition
Ice cores are unique environmental archives used to reconstruct past environmental and climate changes. So far, most studies have focused on the analysis of inorganic species, such as nitrate, sulfate, and trace elements. While their quantification has been extremely important for identifying past wildfires, volcanic eruptions, and the impact of human activities on the environment, these species only represent a small fraction of the submicron atmospheric aerosol mass. The large component is indeed composed of organic compounds. Despite constituting up to 70-90% of the submicron aerosol mass, organic compounds have been largely overlooked in ice-core studies, with few exceptions. This was primarily due to analytical limitations. Today, thanks to the development of high-resolution mass spectrometry and the implementation of non-target screening (NTS) workflows, it is possible to detect and identify an unprecedented number of compounds (several hundreds) from a single ice sample, unlocking the potential to improve our understanding of past environmental conditions.
With the support from CH-QUAT, I presented a poster at the European Geosciences Union General Assembly 2024 (EGU24), where I summarized the main findings obtained during my post-doc at the Laboratory of Environmental Chemistry of the Paul Scherrer Institute, under the supervision of Prof. Margit Schwikowski and Dr. Saša Bjelić. These include the development of a novel and highly sensitive NTS method for snow and ice-core analysis, and its application on two mid-latitude ice cores, namely Belukha (Siberia) and Colle Gnifetti (Europe), covering the period from 1750 to 2000 CE. A clear anthropogenic fingerprint has been identified during the industrial period with the occurrence of new, previously unknown chemical substances, mainly constituted by carbon, hydrogen, oxygen, nitrogen, and sulfur. Also, changes in the oxidation state of the organic compounds were observed, suggesting a possible increase in the oxidative capacity of the atmosphere. The conference represented a unique opportunity to connect with other ice-core and atmospheric scientists, and thanks to this event, exciting collaborations will start soon.
Contact: Francois Burgay (francois.burgay@gmail.com)