Cambrian-Ordovician Transition in the Northern Domains of Central-Iberian Zone; Tectonics Constrains

Abstract

In the northern sectors of the Central-Iberian Zone the transition of the Lower Ordovician over the underlying sequences always shows evidence of the Toledanian phase. The effects of this pre-Armorican Quartzites deformation are highly heterogeneous. In most of the cases it is only shown by an important erosive level giving rise to a disconformity, while in other situations it corresponds to a strong angular unconformity where the older sequences could even present a reversal polarity. Such geometrical relations, that are common in the Central-Iberian Zone, could not be explained by the rotation of the layers in the vicinity of normal faults related to an extensional regime. This suggests that the Toledanian phase was a transient inversion in the general extensive regime that predominates in the northern margin of Iberia during most of the Lower Paleozoic.