Thursday, January 26, 2012

0075 – Processes of ditch filling

Dog skull inside ditch 3 of Perdigões.

The nature and the processes of ditch fillings are central to ditched enclosures interpretation. Several elements can be analysed to try to understand those processes. One of them is fauna.

Usually, faunal remains are approached in terms of levels of articulated bones, present and missing bones, structure of the deposition of the bones, animals represented and other associated elements.

Recently, a study of faunal remains from ditches 3 and 4 of Perdigões enclosure done by Cláudia Costa (“Problem of filling the ditches 3 and 4 (Sector I) of Perdigões (Reguengos de Monsaraz”, Estudos do Quaternário, 6, APEQ, Porto, 2099/2010) based on stratigraphic analysis of faunal remains”) showed that the taphonomical approach is also quite relevant and that, together with the analysis of other present elements, can be a precious help to interpret the formation process of the fillings.

Here is what she says in the papers abstract:

“During archaeological intervention on sector I of Perdigões ditch enclosure (Southern Portugal), dated from the IIIrd mil¬lennium B C, a section of Ditch 3 and 4 were excavated. The ditches are parallel “V” shaped structures, excavated on local bed rock, of 1,70 m (Ditch 3) to 2 m (Ditch 4) deep.

The ditches were filled with a sequence of anthropic sediments with archaeological artefacts, mostly potsherds, and vertebrate fauna. The species present in both ditches are suids, the most numerous, followed by bovids (domestic, and an element of an auroch), ovi¬caprids, red deer, horse, dog/wolf, rabbit and hare. The anatomical representation is the opposite in each ditch: in Ditch 3 the most common elements are from cranial and appendicular skeleton, whereas Ditch 4 is filled mostly with elements from axial skeleton. This aspect linked with the specific spatial association of bones and other elements, as pottery or pebbles, with an unequivocal intentional organization, doesn’t seems to fit on the pattern of secondary refuse. The faunal remains seem to integrate the “intentional depositions” at least on some points of the sequence.

On both structures, faunal assemblages are more fragmented on top of the sequence, and on the base, faunal remains tend to be more complete. The transition of more fragmented to less fragmented bones is materialized by intentional depositions layers, unit 58 on Ditch 3 and unit 34 on Ditch 4. On the other hand, in some stratigraphic units, root etching was identified on bone surfaces. Root etching is linked to vegetation that settles on soil profiles top, on the early stages of pedogenic developments. The existence of this phenomena point to a discontinuous filling process of the two ditches, where stratigraphic units remain stable and exposed long enough to pedo¬genetic process begin. On Ditch 3, the assemblage from unit 58, interpreted as “structured depositions”, is one of the most affected assemblages by root etching, which means that after sedimentary formation and installation of “depositional structures”, the unit was exposed. The same unit was affected as well by a natural water channel that mutilates the unit’s surface.
The other natural taphonomical signatures are manganese oxide, which affects continuously all remains from Ditch 3, and in a low percentage Ditch 4, and carbonate calcium that particularly affects the base assemblages in both ditches. This aspect reveals the strati¬graphic stability of the sequence.”

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