Plenary Lectures

Coastal Changes 21st century: Perspectives from a sedimentologist
William Helland-Hansen (Department of Earth Science, University of Bergen, Norway)

The majority of global coasts are projected to experience sea-level rise in the 21st century. Coasts and coastal lowlands are of great societal, economical and agricultural value with nearly 40% of the World’s population living within 100 km of the coast. Understanding the causes of coastal change is urgently needed to mitigate risks, prepare, and adapt to acceleration of sea-level rise and more severe and frequent extreme weather events in the 21st century.  
As reflected in the reports from the Intergovernmental Panel on Climate Change (IPCC), most research effort in predicting global-scale coastal changes in this century is focused on global sea-level changes, including the effects of melting ice-sheets and glaciers, the contribution from thermal expansion of oceanic waters, oceanic and atmospheric circulation, glacioisostatic adjustments (GIA) and gravitational effects. Thus far, less emphasis has been on fully integrating the impacts of global sea-level changes with the key natural and anthropogenic forced processes of vertical land movements, sediment delivery and sediment distribution, factors which are critical to understand and predict coastal changes.   
In this talk I will review the key factors determining coastal change and the current status of coastal change predictions for the 21st century. I will also address the relationship between coastal type and present and future population density and inundation levels.  

William Helland-Hansen earned his PhD degree from the University of Bergen, Norway in 1995, and he works there as full professor at the Department of Earth Science since 1998. He is also an adjunct professor at the University Centre of Svalbard (UNIS) since 2007. His research covers a broad range of aspects related to clastic sedimentology, including sequence stratigraphy, trajectory analysis, clinoform dynamics, source-to-sink, shallow-marine sedimentation, spatial and temporal structure of basin fills, and coastal changes in the 21st century. He has participated in many large projects, as project leader and principal investigator, and also has 12 years’ experience from the petroleum industry prior to his academic career. He published 62 papers in peer-reviewed journals and special volumes, and 43 industrial reports.

Past climate changes – a view from the karst underground
Petra Bajo (Croatian Geological Survey, Zagreb, Croatia)

Climate change is one of the greatest challenges that the human society is facing nowadays. The 30-year long history of addressing this issue by scientific community might imply that palaeoclimate research is losing its relevance in the 21st century. Yet, an increasing number of high-quality research studies performed around the world would argue against this and witnesses the importance of palaeoclimatology as a backbone in understanding not only the causes of the natural climate variability in the past but also in assisting more accurate predictions of anthropogenically-driven climate changes in the future. 
Speleothems, secondary cave deposits like stalagmites and flowstones, play an outstanding role in the field of palaeoclimatology firstly due to their amenability to radiometric dating as well as due to the possession of a remarkable number of climate-sensitive proxies. The majority of studies on past climate changes derived from speleothems rely on U/Th disequilibrium dating method. In this talk I will demonstrate an example where the less widely used U/Pb dating method for dating of speleothems has enabled deciphering one of the longest standing palaeoclimate debates centered around the causes of glacial-interglacial transitions, specifically during the Middle Pleistocene transition.  
Despite their indisputable strengths, speleothems are not free of weaknesses like any other palaeoclimate archive. One of their most significant weaknesses lies in the often complex and skewed link between their chemical proxies (e.g. stable isotope ratios of oxygen and carbon, trace element composition) and climate variables at the surface. It was long time ago understood that extensive cave monitoring studies might help in resolving this conundrum by exploring the processes involved in transferring and modifying the climate signal from the surface, through the soil zone, epikarst and bedrock to the cave interior and finally speleothems under modern conditions. In the last part of this talk I will present results of a recently started project that includes a monitoring program of a cave site in North Croatia and their implications for interpretation of speleothem records from this site and beyond.

Petra Bajo completed her PhD at the University of Melbourne, Australia in 2016. In 2017 and 2018 she was employed as a lecturer and research assistant at the University of Melbourne. During 2018 she worked as a Senior Researcher in nuclear forensics at the Australian Nuclear Science and Technology Organization (ANSTO) in Sydney. In 2019 she moved back to Croatia where she is employed as a scientist returnee at the Croatian Geological Survey. Her research interests and expertise lie in palaeoclimate research based on geochemical proxies in cave deposits, exploring the timing and causes of past climate variations spanning sub-decadal to orbital time scales, and also in developing and advancing the existing methodologies in U-series geochronology. She published 31 original scientific papers and recently started a five-year long installation research project funded by the Croatian Science Foundation. She is the recipient of the State award for scientific achievements in the field of natural sciences for 2020, and Croatian Academy of Science and arts award in the same field form 2021.

Not all is lost. How we study mudstones on Mars without thin sections and make a virtue of necessity.
Juergen Schieber (Department of Geological Sciences, Indiana University, USA)

As on Earth, mudstones are likely the most abundant sedimentary rock on Mars and a key component in our efforts to search for life on other planets. In the quest to understand a mudstone’s origins, the study of thin sections traditionally represents the coin of the realm. Yet, whereas on Earth this may not always be easy, but doable nonetheless, on Mars – it is not even an option. Mars rovers may return images at a range of resolutions (20-200 microns per pixel), but even at best resolutions they are a poor substitute for something as simple as a 10x hand lens.   
Fortunately, mudstones have a live beyond the microscopic. Especially in the absence of bioturbation (a sensation were we to find it on Mars), mudstones display textural, compositional, and bedding attributes that are accessible to rover instrumentation. Whereas on Mars we do not have the benefit of saw-cut and polished slabs to make these features optimally observable, we do have “lucky breaks” where the soft touch of millennia of Aeolian abrasion brings out highly instructive details of texture and bedding that can be captured by on-board cameras. Also, in the case of Mars Science Lab (MSL), allied instruments like APXS (bulk rock composition), ChemCam (remote chemistry via Laser Breakdown Spectroscopy), and CheMin (mineralogy by XRD) provide us with bulk chemical and mineral composition, and even grain by grain chemistry. 
Through carefully considered integration, comparison to Earth analogs, and qualitative and numerical modeling, these data sets provide a compositional and textural context that can provide insights into depositional conditions and diagenetic history that are just as profound as those obtained through traditional petrographic approaches. Though necessitated by limitations in resources, the way we study mudstones on Mars brings with it new and different perspectives that also provide untrodden pathways for their study on Earth. To paraphrase T.S. Eliot; the limitations of rover geology shall not keep us from studying Martian mudstones, and at the end of the journey we will conceptually arrive where we started, and know those we thought we knew for the first time. 

Dr. Schieber is a professor of geology at Indiana University and a specialist on shales. Published extensively (more than 200 papers, 20 guidebook chapters, 4 books, 370 conference abstracts) he is also an invited lecturer at universities in the US, Canada, Europe, and Asia; at research organizations, industry short courses, and symposia. He is a member of the science team that currently explores the geology of Gale Crater on Mars with NASA’s Curiosity rover, the 2022 recipient of the Sorby Medal by IAS, and a 2023 Fulbright Scholar.
His research is characterized by a holistic approach to shales, and consists of an integration of field studies (facies, stratigraphy) and lab studies (thin sections, electron microscopy, and geochemistry) in order to understand the various factors that are involved in the formation of shales. A key focus point is the experimental study of shale sedimentology via flume studies and related experimental work. Funding for this research is provided by numerous government agencies (NSF, DOE, NASA), foundations (Petroleum Research Fund), and industry via the Indiana University Shale Research Consortium (ExxonMobil, Anadarko, Marathon, Shell, Chevron, ConocoPhillips, Wintershall, Whiting, Equinor, Petrochina) and separate research agreements (Schlumberger/TerraTek; Pioneer Natural Resources). He consults on matters pertaining to shale sedimentology, shale fabric and pore structure, and also teaches short courses on shale sedimentology and facies analysis, as well as microscope based petrography.
His research interests include: Basin Analysis and Sedimentology, Sedimentology, Diagenesis, and Pore Systems of Shales, the Genesis of Black Shales and Sediment hosted Mineral Deposits, Evolution of the Belt Basin and the Devonian basins of the eastern US, Geochemistry of Sediments, Planetary Geology and sedimentary geology of Mars.

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