In the East limb of the Narcea Antiform (Iberian massif) outcrops siliciclastic Cambrian materials with uncomformity disposition over the Neoproterozoic Narcea Slates. The lower Cambrian Herrería Fm. in the Cantabrian Zone includes a conglomeratic unit that it's interpreted like a cohesive debris flow and braided chanels. Most clasts in the considered sections are tuffaceous and ignimbritic volcanic rocks. This papper introduced a new set of data that confirms an acidic composition: mainly rhyolites and minor amounts of trachytes and andesites. Authors interpreted that this volcanic clasts are Neoproterozic in age and with similar characteristics to the acidic volcanic rocks in the ZAOL from the Narcea Antiform. Probably it represents the last volcanic episode of the Cadomian cycle and its different from the Cambro-ordovician alkaline-type volcanism