Fault migration and basin evolution during complex rifting: examples from the western North Gulf of Evia, Greece

Understanding dynamic processes of faulting and basin evolution across timescales in complex rift settings remains a key challenge in active continental tectonics. This is in part due to a limited number of young rift systems with well constrained, high-resolution age models derived from subsurface datasets. We aim to address this challenge and advance our understanding of time-dependent geodynamic rift processes by developing a late-Quaternary, syn-kinematic age model for the Western Basin of the North Gulf of Evia, Central Greece. In contrast to the nearby Gulf of Corinth, extension here is complicated by rotational and strike-slip influence from the westward-propagating North Anatolian Fault. Seismic stratigraphic principles are used to identify three key horizons based on reflection termination relationships with ages of ~12 ka, ~130 ka and ~325 ka assigned through a sequence stratigraphic model on deltaic clinoform packages. The age model is applied alongside a network of offshore faults to determine the major structures, depocenters and evolutionary history of the rift. We resolve the major controlling faults to be the Kalypso Fault (~4 mm/yr slip) at the southern margin of the basin and the Central Graben (~1-2 mm/yr slip) along the axis of the gulf. We show that the Kalypso Fault is linked to the onshore Coastal Fault System following a migration event with evolving strike from the onshore Arkitsa Fault. The timing of this event is constrained to ~325 ka based on hanging wall sediment thickening relationships and the Kalypso Fault displays immediate, rapid lateral growth and throw accumulation after initiation. Improved constraints on the timing and evolutionary behaviour of young normal fault systems such as this show that fault migration and activation in complex rift settings can occur over timescales less than 105 years.