(By Filipa Rodrigues, firstname.lastname@example.org,)
When I first saw the image of the Perdigões geophysics, I was digging the Porto Torrão (Ferreira do Alentejo, Beja) ditched enclosures as part of the mitigation work related to the setup of an irrigation component of the Alqueva reservoir (EDIA, SA). This work brought together a number of archaeological consultancies (Crivarque, Neoépica and Archeoestudos).
A monumental double ditch system, which encloses an estimated area of
ha, was identified during this work.
In one of the sectors whose excavation took place under my responsibility (Sector 3 East), the architecture of these monumental structures can be briefly described as:
- Outer Ditch (Ditch II) → Width - 12m; Depth – 6m; Profile – tending to a V-shape;
- Inner Ditch (Ditch I) → Width – 8,5m; Depth – 5,50m; Profile – tending to a U-shape.
The Sector 3 East excavation revealed parallel and concentric ditches ca. 30m apart. Dimensions aside, these features are similar to most known ditched enclosures; however the Porto Torrão double ditch system is distinct in one important aspect: the existence, every
25 m, of small tunnels
interconnecting both ditches.
Therefore, I interpret these ditches as a single feature, not as two separate and independent constructions, one meant to fulfill a common purpose. Subsequently, but within the time range of the Copper Age, these features’ original function became obsolete and they were filled-up. Their original purpose and the reasons behind their deactivation in Copper Age times remain open questions
In the area of the site under my responsibility it was not possible fully to excavate these tunnels; in the area under the responsibility of the Neoépica consultancy (whom I thank, and Raquel Santos especially so, for the information), the connection of the ditches by tunnels has been confirmed.
In aerial photography, the layout of the Porto Torrão features reminds the images returned by the Perdigões geophysics:
So, the question that I have for now is: are they similar?
You can also see an excavation video here: http://www.youtube.com/watch?v=Ql3JinQEGeg