Plio-Quaternary extensional seismotectonics and drainage network development in the central sector of the Iberian Chain (NE Spain)

Westward propagation of postorogenic rifting in the central sector of the Iberian Chain generated the Teruel and Calatayud Mio-Pliocene grabens and the Jiloca, Daroca and Munébrega Plio-Quaternary half-grabens, partially superimposed on the western margins of the pre-existing basins. The progressive capture and transformation from endorheic (aggradational) to exorheic (incisional) drainage of the active grabens resulted in the development of a drainage network dominated by axial streams controlled by neotectonic activity and the distribution of basin fill lithofacies. This paper reviews the geomorphic and stratigraphic evidence of Plio-Quaternary extensional tectonics and provides new chronological data (radiocarbon and OSL dating) on offset deposits and the associated paleoseismic record. The Daroca Fault offsets mantled pediment deposits dated at 113–119 ka. Based on a radiocarbon age of the colluvial sequence (43 ka) affected by the Rubielos de la Cérida Fault, a vertical slip rate of 0.05–0.07 mm/yr has been estimated for this fault. Four paleoearthquakes subsequent to 72 ka have been inferred from the classic exposure of the Concud Fault indicating a recurrence interval of less than 18 ka. A gravitational origin related to the dissolution of subjacent evaporites is attributed to two faults affecting an Upper Pleistocene terrace (15 ka) in the Alfambra Valley, close to the Concud Fault. These structures have recently been interpreted as evidence of coseismic deformation on the Concud Fault. Although the faults have a low slip rate and a long seismic cycle, their length (< 25 km) suggest that earthquakes with moment magnitudes of around 6.5–7 might be expected in the study area.