Rare earth elements (REE) are a group of 16 chemically similar elements with oceanic residence times of several hundred years. This duration is long enough for them to be transported across ocean basins without complete homogenization, before eventually being incorporated into authigenic phases within marine sediments and archives. The most widely used REE-based tracer is the radiogenic neodymium isotope composition, which provides insights into weathering, transport, and water mass mixing at Earth’s surface. However, the full suite of REE behaves geochemically coherently – almost like a single element – and thus encodes a far broader range of environmental information in their isotopic signatures and relative concentration patterns. In this presentation, I will explore these lesser-studied REE signals and demonstrate that they contain valuable information for reconstructing environmental and paleoceanographic processes. Finally, I will discuss how REE can be developed into a comprehensive compound geochemical proxy and highlight potential applications across other fields of Earth and environmental science.

Sedimentary archives provide crucial records of Earth system processes, offering insights into how hydroclimates and carbon cycle dynamics have evolved through time. In this talk, I will present a series of subprojects that demonstrate how integrated stratigraphic and geochemical approaches can be used to reconstruct past environmental change. These examples range from high-resolution paleoclimate reconstructions in continental to marginal marine depositional systems to investigations of climate dynamics across the K–Pg mass extinction event. Building on this foundation, I will introduce my ongoing research on the tropical ophiolite hypothesis, which proposes that ophiolite obduction within the tropics (≤20° latitude) drives Earth’s climate state on geological timescales. This work aims to combine novel compositional and geochronological analyses of stable, ophiolite-derived detrital minerals: Cr-spinel, apatite, and rutile, to constrain the occurrence, type, timing, and extent of ophiolites in the South Mayo Trough (western Ireland) and in the late Neogene sedimentary archives of the Papua New Guinea Central Ranges. Together, these projects highlight the versatility of sedimentary archives in documenting Earth system processes and in constraining the mechanisms that regulate long-term climate evolution.

The Rb–Sr geochronometer is one of the earliest isotopic dating methods and was widely adopted due to the abundance of datable phases such as micas and alkali feldspar and their contrasting Rb–Sr geochemistry. However, Rb–Sr dates can only be interpreted meaningfully if the processes responsible for isotopic resetting are properly understood. Although classically viewed as diffusion-controlled and temperature-dependent, natural examples show that recrystallization, deformation, and fluid interaction commonly dominate Rb–Sr resetting, blurring the geological meaning of Rb–Sr dates. As a result, the Rb–Sr method was gradually replaced by “more robust” isotope systems such as Sm–Nd and Lu–Hf, and only recently regained traction with the advent of in-situ analysis by reaction-cell mass spectrometry, which enabled reliable sub-grain age determinations. This talk presents examples illustrating both the potential and the limitations of in situ Rb–Sr geochronology for constraining the timing of deformation and hydrothermal overprint in metamorphic rocks.

Volcanic eruptions are spectacular displays of nature’s incredible power, but they put local communities at risk. Approximately 800 million people worldwide live within 100 km of a volcano that is currently erupting or has the potential to erupt in the future. Our ability to mitigate their hazard relies on empirical analyses of monitoring data, with large uncertainties in estimating the probability of an eruption and its impact.

Forecasting the size, duration and hazards of eruptions requires a deep understanding of magma transport and storage and quantifying the timescales of the processes occurring beneath the surface. The relationship between these sub-surficial processes and geophysical and geochemical observations made at the surface is key to understand volcanoes behaviour.

The minerals within the rocks erupted during volcanic eruptions are an incredible archive of information. They act like a probe into the volcano’s interior, allowing us to decode its behaviour and inform volcanic hazards assessment. Drawing from examples of some of the most active volcanoes in the world – such as Popocatepetl and Colima in Mexico, and Stromboli and Etna in Italy – this talk will take you on a journey inside the volcano factory, exploring the hidden processes that drive eruptions.

Stromatolites are layered sedimentary structures formed under the influence of microbial communities and environmental factors. They constitute amongst the oldest known evidence of life on Earth – over 3.4 billion years old – and provide a unique fossil archive spanning nearly all of geological time. In this seminar, I will invite you on a journey through the Microbialite Collection of the Muséum national d’histoire naturelle (Paris), a unique archive to explore: • How do stromatolites record the oxygenation of Earth’s atmosphere and oceans? • What can they tell us about the diversity of ancient surface environments? • Are the rhythmic laminations driven by biological processes… or by climate cycles? • Do these layered structures truly reflect biological activity? • And how can AI help distinguish biogenic from abiotic laminated rocks? At the intersection of geochemistry, palaeontology, and astrobiology, my research seeks to improve our understanding of how life has shaped the sedimentary record; with implications that extend beyond Earth’s history to the search for life on other planets.

Turbidity currents, gravity-driven sediment-laden flows, govern material transport and shape underwater landscapes across diverse environments. While extensively studied in marine settings, their behaviour in freshwater systems remains underexplored. We present multi-temporal, multi-scale observations from the Aare Delta of Lake Brienz (Switzerland), combining Acoustic Doppler Current Profiler measurements with high-resolution repeated bathymetric surveys to capture turbidity currents and the resulting lake bottom changes. We document the upslope migration of a bedform triggered by a single flow event, demonstrating how discrete turbidity currents can rapidly reshape the channel floor. We further place these observations within a broader geomorphic context using a rare 125-year bathymetric time series. This longer-term perspective reveals how turbidity currents influence channel morphology over centennial scales. Together, our results highlight the value of lacustrine settings as accessible, scaled-down natural laboratories that bridge the observational gap between controlled experiments and deep-ocean canyons, offering new insights into turbidity-current processes.

Abstract to be provided.