Micro-scale sedimentary signature of paleoearthquakes and paleotsunamis in the Corinth Rift (Greece)

A major challenge in subaqueous paleoseismology is to understand the relationship between an earthquake/tsunami and a sedimentary event deposit recorded in drillcores. Expedition 381 of the International Ocean Discovery Program was dedicated to understanding the development of the Corinth Rift, Greece. Its drilled cores provide a potentially important resource to better understand depositional mechanisms of sedimentary event deposits within changing open marine to (semi-)isolated environments. To achieve this, we analyse U- channels and spatula samples from the topmost part (0-65 m below seafloor maximum depth) of holes M0078B and M0079A (~0-25 ka), using high-resolution X-Ray microtomography in combination with grain-size, magnetic and XRF measurements. Structures and grain array are resolved down to 10 μm in voxel size, characterizing the geometry of the basal surface of turbidite+homogenite sedimentary event deposits, and the internal base-upwards evolution at high-resolution scale. Our analysis suggests these types of deposits are more complex than previously proposed, especially at the transition between the basal coarse turbidite sub-unit and the fine-grained homogenite upper sub-unit, as well as within the homogenite. Combined with the other observations and parameters, X-ray microtomography results are consistent with the interpretation of the Corinth turbidite+homogenite deposits as having predominantly originated from seismic and/or aseismic slope failures followed by tsunami/seiche effects, despite subtle differences according to depositional environment.