Towards efficient and detailed analysis of turbidite records for geo- and climate hazard reconstructions – An integrated approach combining X-ray CT, magnetic, grain-size and geochemical analysis

Turbidite records can provide valuable information on the past occurrence and magnitude of several types of geo- and climate hazards. They have been used to reconstruct earthquake recurrence and rupture patterns, flood and lahar histories, rockfall events etc. Furthermore, detailed analysis of turbidite sedimentary structures, fabric and texture has the potential to allow reconstructing sequences and timelines of the geo- and climate hazards, including cascading hazards such as doublet earthquakes, earthquake shaking followed by a lake seiche, debris flow or volcanic eruption, which – in turn – can trigger lahars. X-ray (micro) computed tomography ((µ)CT) is a very promising tool for such reconstructions, because it allows to determine compositional changes as derived from radiodensity in a 3D space. However, as radiodensity is a single parameter depending on an integration of a variety of compositional changes, combination with other techniques to determine sediment composition (e.g., grain-size analysis, XRF scanning, C/N analysis) is paramount. Furthermore, the 3D data output – which may for example allow reconstruction of paleo-flow directions – is often only relevant when the geographical orientation of the sample is known, thereby requiring to combine the method with Natural Remnant Magnetization (NRM) analysis. Integrating all these techniques, some of which are under continuous development, is a challenging task, especially for application on long turbidite records and for extracting event timelines. In this project, we use case studies of turbidites in several settings to develop workflows that will allow efficient, but detailed, analysis of turbidite series. We aim to develop workflows with – fast – scanning techniques (CT, XRF, geophysical core logging, NRM) as a central pillar, but strategically complemented with subsample analyses to calibrate the datasets from core scanning. Case studies for which data are available at the start of the project include sediment records of (mega)turbidites triggered by earthquakes (subaerial and subaquatic failures), floods and lahars, in Chilean and Alaskan lakes. These will be complemented with additional case studies in the course of the project. While this project will allow us to better understand the studied events, its main goal is to provide output that will not only allow future sedimentological studies of geo- and climate hazards to be more efficient, but also to improve the qualitative and quantitative nature of the reconstructions.