Consistency Between the Slip History Implied by in Situ ³⁶Cl Exposure Dating on an Active Normal Fault and the Timing of Holocene Coastal Notch Formation, Central Greece

We report agreement between the timing of slip on an active normal fault recovered from in situ ³⁶Cl cosmogenic fault scarp dating with independently ¹⁴C dated Holocene coastal notches deformed along the strike of the fault, reinforcing the validity of slip-rate timing and magnitude fluctuations implied by ³⁶Cl fault scarp dating. The ³⁶Cl-dated Pisia fault, central Greece, shows slip-rate fluctuations but the timing of slip derived from this cosmogenic isotope have not been confirmed with an independent dating approach. However, Holocene coastal notches dated with ¹⁴C on fossils occupying the notches exist around the Pisia fault, these can only form when the interplay between eustatic sea-level and tectonics result in stable relative sea-level. The ³⁶Cl site close to the center of the Pisia fault records ongoing slip from ∼9.6 to 5.2 (±0.5) ka and 2.0 ± 0.5 ka to the present day which was interrupted by a low slip-rate period. Holocene sea-level stabilized close to its current elevation after 7.0–6.5 ka, so the combination of low slip-rate and stable sea-level allowed notch formation. During this time, notches were uplifted by slip on the offshore Strava fault, indicated by elastic half-space modeling. Toward the center of the Pisia-Skinos fault, these notches were then submerged during the high slip period from 2.0 ± 0.5 ka. Our findings reveal that spatial patterns of deformed radiocarbon-dated Holocene notches agree with the timing of high slip earthquake clusters/quiescent anti-clusters from ³⁶Cl slip histories and support use of ³⁶Cl to investigate normal faults, crustal rheologies and seismic hazard.