Lithospheric flexure and rheology determined by climate cycle markers in the Corinth Rift

Abstract

Geomorphic strain markers accumulating the effects of many earthquake cycles help to constrain the mechanical behaviour of continental rift systems as well as the related seismic hazards. In the Corinth Rift (Greece), the unique record of onshore and offshore markers of Pleistocene ~100-ka climate cycles provides an outstanding possibility to constrain rift mechanics over a range of timescales. Here we use high-resolution topography to analyse the 3D geometry of a sequence of Pleistocene emerged marine terraces associated with flexural rift-flank uplift. We integrate this onshore dataset with offshore seismic data to provide a synoptic view of the flexural deformation across the rift. This allows us to derive an average slip rate of 4.5–9.0 mm·yr −1 on the master fault over the past ~610 ka and an uplift/subsidence ratio of 1:1.1–2.4. We reproduce the observed flexure patterns, using 3 and 5-layered lithospheric scale finite element models. Modelling results imply that the observed elastic flexure is produced by coseismic slip along 40–60° planar normal faults in the elastic upper crust, followed by postseismic viscous relaxation occurring within the basal lower crust or upper mantle. We suggest that such a mechanism may typify rapid localised extension of continental lithosphere.

TerraceM-2: A Matlab® Interface for Mapping and Modeling Marine and Lacustrine Terraces

“…TerraceM has been designed to close this gap by providing open-source tools to interactively map and model the formation of marine and lacustrine wave-cut terraces using high-resolution topography and Matlab R programming. So far, TerraceM has been used for diverse purposes in different coastal settings worldwide (e.g., Melnick, 2016;Benjelloun, 2017;Jara-Muñoz et al, 2017;Melnick et al, 2017Melnick et al, , 2019Pedoja et al, 2018;Bilbao-Lasa et al, 2019;de Gelder et al, 2019;Jara-Munþoz et al, 2019;Racano et al, 2019). These studies include research topics such as coastal dynamics, paleo-geography, paleo-climate, neotectonics, and earthquake geology, highlighting the broad spectrum of applications and the advantages of applying integrated joint mapping and modeling techniques in the Earth sciences.…”

answer to the referee 2

“…Sedimentary basins must record such a tectonic reorganization. If indeed, some pieces of evidence of rejuvenation of vertical motion along East Mediterranean basins exist around the Mid-Pleistocene Revolution in the Eastern Mediterranean (Gawthorpe et al, 2018;de Gelder et al, 2019;Schattner, 2010), it is difficult to relate those changes to a change of Africa/Eurasia convergence. It is out of the scope of this paper to discuss if such reorganization exists at the scale of the whole Mediterranean Basin, and C3…”

How do sea-level curves influence modeled marine terrace sequences?

“…Following the terrace degradation models of Anderson et al (1999), an easy explanation would be the influence of river incision, with higher uplift rates implying a faster base-level drop and more aggressive channel incision. In the case of Xylokastro this appears to be true; although rapid uplift seems to have taken place since~1 Ma (Armijo et al, 1996;Nixon et al, 2016;Fern andez-Blanco et al, 2019), the associated river incision has removed terraces older than~240ka (Fig. 4b).…”

“…Even if variations in the initial slope existed within the Xylokastro sequence and affected the resulting terrace geometry, by averaging the terrace width and cliff height over a 1e5 km wide area we expect to have accounted for such possible lateral variations. Furthermore, the widest terraces in the Xylokastro sequence are also the widest terraces up to~25 km further east (Armijo et al, 1996;De Gelder et al, 2019), suggesting that terrace width is influenced more strongly by SL curves than by variable initial slopes.…”

“…High uplift rates of~1.2e1.5 mm/yr (Armijo et al, 1996;De Gelder et al, 2019), low sub-aerial erosion rates and thin cover of cemented coastal deposits have resulted in a well-preserved sequence of 13 marine terraces (e.g. Dufaure and Zamanis, 1979;Keraudren and Sorel, 1987;Armijo et al, 1996;De Gelder et al, 2019). The terrace sequence spans the last~240 ka, and extends over an area of~3 Â 3 km, culminating at an elevation of~400 m (Fig.…”