First chronostratigraphic framework of fluvial terrace systems in the Eastern Cantabrian margin (Bay of Biscay, Spain)

Abstract

Reported here is the first chronostratigraphic study of the Quaternary fluvial terrace deposits of three different valleys (Deba, Nerbioi, Oiartzun) located in the eastern Cantabrian margin (northern Spain), designed to understand long-term fluvial dynamics of this region. Fourteen samples were collected for numerical dating purpose, in the lowest terrace levels from 5 m to 63 m above current river channel. Optically Stimulated Luminescence dating was performed using the SAR protocol. For samples from terraces >20 m above the current river channel, over 20% of measured aliquots were above saturation of the OSL signal. Consequently, only minimum ages could be estimated. Five samples also underwent Electron Spin Resonance (ESR) dating following the Multiple Centre approach. The ESR signals of the Aluminium and Titanium (Ti-Li and Ti-H) centres were systematically measured in each sample. In particular, the ESR signal of the Ti-H centre was strong enough to derive reliable and meaningful dose estimates. Obtained age results range between ∼140 and ∼400 ka for the terrace levels from +10 to +25 m. They suggest phases of aggradation during MIS 6, MIS 8 and MIS 10, for terrace levels T+10m, T+20m and T+25m, respectively.