Magnetocronología de las sucesiones cenozoicas de la cuenca de As Pontes (La Coruña, Noroeste de España)

The Terciary Basin of As Pontes (Northwest Spain) is associated with an onshore NW-SE dextral strike-slip fault system. A total of 900 specimens from the sedimentary infill have been demagnetized, using thermal and alternating field demagnetization procedures. Paleomagnetic data indicate that the duration of sedimentation in the basin was about 6,2 My, lasting from the latest Early Oligocene until the Early Miocene. The magnetostratigraphy of the basin successions allows us to establish a very precise chronological correlation within the basin. In addition, the overall pattern of declinations shows a clockwise rotation (9º±4º in the sedimentary infill) with respect to the Oligocene-Miocene reference declination, coherent with a NW-SE dextral strike-slip faults system. The dating of the sedimentary infilling of the As Pontes basin establishes that the NW-SE dextral strike-slip faults system of NW Iberian Plate were highly active from the uppermost Early Oligocene to the Early Miocene. This implies that the end of the main tectonic activity in both NW Iberian offshore and onshore took place during the same time span