Las fechas C-14 del castro de O Achadizo (Boiro, A Coruña): problemática de la calibración de conchas marinas

The excavation of the hillfort of O Achadizo has brought to light several domestic structures intermingled with rubish heaps, belonging to the Iron Age Castro culture of NW Iberia. The abundant organic remains have constituted the basis for a systematic programme of radiocarbon dating of the different stratigraphic levels, which shows that the main occupation of the site took place between the VI and the II centuries cal. BC. Moreover, we have checked the 14C dates obtained from terrestrial samples (bones and charcoal) against those made on marine shells coming from the same strata. As a result, we have found that the latter have an apparent age of 316±I9 years, caused by the reservoir effect. Therefore, we stress the need for taking into account -and correcting whenever possible- such a deviation before using samples of marine origin for chronological purposes.