A multi-method dating approach to reassess the geochronology of faulted Quaternary deposits in the central sector of the Iberian Chain (NE Spain)

Abstract

Seismic hazard assessment and geochronology are closely linked disciplines. The quantity and quality of the geochronological data used for fault-source characterization is crucial in seismic hazard estimates, which may have significant socio-economic implications. The characterization of Quaternary faults in the central sector of the Iberian Chain (NE Spain) has traditionally been based on ages provided by a now closed commercial luminescence laboratory. In this work, we compare new geochronological data obtained by a multi-method dating approach from pediment and terraces (Electron Spin Resonance: ESR, Optically Stimulated Luminescence: OSL; U-series: U/Th) and short-transport colluvial facies (radiocarbon), with ages provided by the commercial luminescence lab from the same units. The thirteen new numerical ages from terraces and pediments associated with Quaternary faults are systematically 6–3 times older than the previous ones, strongly suggesting that they lead to significant overestimates of fault activity and seismic hazard in the region. These new ESR, OSL and U/Th ages and the lack of information about the methodology applied by the closed luminescence laboratory seriously question the reliability of the previous ages. It also highlights the need of revisiting the Quaternary and geomorphological studies carried out in Spain using non-reliable ages.