Marine terrace staircases of western Iberia: Uplift rate patterns from rocky limestone coasts of central Portugal (Cape Raso - Abano beach and Cape Espichel)

Abstract

The Western Iberian Peninsula is undergoing compressive tectonic reactivation, resulting in spatial and temporal variations of surface uplift. Uplift quantification can be undertaken in coastal settings using staircases of shore platforms developed onto rocky headlands. This study analyses two marine terrace staircases in central Portugal: Cape Raso - Abano beach and Cape Espichel. Geomorphic and stratigraphic analyses identified marine terraces/shore platforms developed below a culminant shore platform, four at Cape Raso and eleven at Cape Espichel. The terrace chronology was obtained by using ESR and pIRIR dating. Using the interactions between the elevation, age and global mean sea-level elevations, the marine terraces were correlated with Marine Isotope Stages (MIS). The shore platforms at the Cape Espichel are more elevated than the coeval references at the Cape Raso - Abano beach and this indicates differential uplift. Considering the culminant shore platform (3.7 Ma), for the Espichel W promontory the estimated long-term uplift rate is ∼0.03 m/ka, but for the Cape Raso is only ∼0.01 m/ka. Also, by using the shore platform considered as produced by the MIS 15 high stand (∼572 ka), the estimated uplift rate for the Espichel W promontory is ∼0.13 m/ka, but for the Cape Raso is ∼0.07 m/ka. The Espichel W promontory terrace staircase also allows to deduce that the estimated uplift rate was nearly constant during ∼600 ka to ∼200 ka ago (∼0.13–0.11 m/kA), but it after decreases (∼0.06–0.01 m/ka).