Isolating tectonic signals from transient and lithologically heterogeneous landscapes in the Gulf of Corinth, Greece

Landscape is the integrated product of external forcings (e.g., tectonics and climate) and internal bedrock erodibility. In principle, hard bedrock with low erodibility can steepen rivers in a similar way to tectonic uplift. A key challenge in tectono-geomorphic analysis is thus separating tectonic and lithological effects on landscapes. To address this, we focus on multiple rivers that are transiently incising through contrasting lithologies in the Gulf of Corinth, Greece where tectonic history is broadly well-constrained, and climate is relatively uniform. We first exploit topographic metrics and river long profiles to demonstrate that landscapes are responding to both tectonics and lithology. In particular, the long profiles are divided into knickpoint-bounded segments, and at this scale, channel steepness is shown to be more sensitive to lithology than the entire catchment, possibly due to the relatively uniform uplift rate in the channel segments. We then use segment-scale steepness variations between different lithologies to constrain their relative erodibility (K_lime : K_cong. : K_sand-silt. : K_{p-con sed} = 1 : 2 : 3 : 4), which is further converted into actual lithological erodibility by modelling a well-constrained, ~750ka knickpoint in the Vouraikos. The effectiveness of lithological erodibility is supported by the observation that if lithological erodibility is used to calibrate studied river long profiles in Chi distance, we obtain long profile concavities that fall within the theoretical range. Finally, we use lithology-calibrated metrics to provide new geomorphic constraints on the timing and magnitude of tectonic perturbations. These geomorphic results are interpreted in conjunction with previous studies to shed new light on fault growth and linkage history in the Gulf of Corinth. Our study therefore demonstrates tectonic signals can be isolated from transient and lithologically heterogeneous landscapes by accounting for spatial variability in lithology.