PART II: REPORTS BY PARTICIPANTS IN THE
CHAPTER 6. REGIONAL CERAMIC PRODUCTION AND
F. Falabella, O. Andonie
6.8. Interpretation of results and discussion
Although some subgroups were recognized among the data, the partial or total overlap in the majority of samples made our archaeological interpretation rather difficult.
The results show some chemical similarity of local clays. The 28 clay samples, although they are not a random sample of the study region, render the impression that subregional differentiation is not always to be expected in this area. What is especially puzzling, however, is that spatial proximity does not equate with chemical similarity. Hospital samples (lacustrine deposits in a central valley environment), Talagante and Peñaflor samples (alluvial deposits in a central/intermontane valley environment) plotted along principal components 1, 2 and 3 cluster with Las Cruces samples (coastal deposits). On the other hand, clays from the same natural formation and locality (i.e. El Belloto) can be quite dissimilar chemically.
The results also show a chemical similarity among many of the pre-Hispanic vessel fragments from all around the region. These similarities can be explained by several factors. Two major factors are the scale of analysis and the geological characteristics. We were working at a subregional level, comparing sites located along the same river axis, not more than 120 km apart. The major geologically based difference expected is between Andean deposits (near sites E1, Ma2 and CH1) and deposits from the coastal plains and mountains (sites TV1, MZ, LT3, T10 and Pt).
RE wares could be differentiated into two subgroups, each of them clustering samples according to this geographical provenance. For these wares, our interpretation is that at least two different production loci were responsible for RE vessels, one located near the Andean clay formations and another somewhere within the coastal mountains, valleys or plains. Some vessels from the Andes might have reached the coastal area, but not the other way around. However, the chemical characteristics of the Maipo basin’s natural resources are not that much different as to enable us to state that there was not more than one procurement and production zone in each of them. The low microscopic characteristics of RE ceramic fabrics from LT3, MZ and TV1 are so similar that our initial hypothesis of a common origin is supported by the chemical pattern observed in the NAA results. However, the fabric patterns for RE of sites E1, Ma2 and CH1 are so different that they preclude a single source interpretation for them.
AS wares did not reveal the same distinction. There are four main differences:
(1) The AS chemical data are much more disperse than the RE data, i.e. the groups do not cluster as tightly.
(2) Some groupings were revealed according to valley site provenance (based on rare earths and As–Hf).
(3) Some wares were grouped according to paste characteristics (Sc–Fe and Na–Cs).
(4) Although analysing the same sites as for RE, no complete distinction was found between Andean and coastal plains, valley or mountain provenances.
We think one possible factor for (1) and (4) is the mixing of clays in the preparation of AS pastes in order to produce the light coloured effect. Experimental work mixing reddish clays with kaolinitic clays from the study region has produced matrix colour and fabric characteristics very similar to some paste groups in AS wares [6.8]. INAA chemical patterns for four of these mixed samples clearly ‘blurred’ the chemical profiles of the original clays. The partial overlap of some AS and RE data might be due to similar clays, some mixed with a white clay component (AS), others not (RE). Another factor might be the original chemical characteristics of the clays used for each ware (more or less homogeneous), or some culturally related issue involving the way artisans produced their vessels, but we have no way of testing these last alternatives.
The AS data, in spite of all the above mentioned problems (intraregional scale of analysis, geological homogenization, mixing of clays, access to similar geological formations from many sites, abundant medium to coarse temper and volcanic ash) showed some trends which enabled the identification of a characteristic chemical pattern for three of the valley sites analysed. Our interpretation of these data is that the ceramic source and production location in the valleys is usually site specific.
Binocular paste analyses and petrography support this interpretation. This is coherent with a home based system of ceramic production in the Aconcagua culture. Even in geologically homogeneous environments and/or in pottery manufacture, where the mixing of clays is a technological tradition, we should expect more clustering of the data if specialized or centralized ceramic production existed.
The different dispersal range of AS samples between valley (more homogeneous) and coastal (more heterogeneous) sites, especially in TV1, is consistent with paste observations under a binocular microscope. Since we discarded a natural chemical heterogeneity in coastal clays we are inclined to support the interpretation that cultural factors are responsible for this difference. Such regional patterns have sometimes been interpreted in archaeology in terms of pottery making (homogeneous) and pottery consuming (heterogeneous) communities [6.9]. We think that a seasonal occupation of the coastal area, with no intergroup territorial
boundaries, would also render the same results by mixing the debris from separate occupation events of people coming from different communities. If there was pottery manufacture at some places along the coast, a difference in the scale of production or temper related issues could also be responsible for such a pattern.
6.9. CONCLUSIONS
Although the resolving power of NAA did not enable us to solve all the research problems, some new ideas were put forward about the Aconcagua ceramic system.
(a) The Aconcagua Salmón clays do not seem to come from a single source but from many local sources where this kind of pottery would have been manufactured. The geological survey led us to confirm such diversity because we recognized different clay minerals (kaolin, montmorillonite and perhaps clays weathered from volcanic deposits) and sources that can contribute to light coloured clays in many locations in the study area.
(b) Different compositional patterns for the AS wares in three valley sites were found, which we interpreted as specific local production locations. This led us to argue for a home based system of production.
(c) At least two compositional groups for RE wares were found with evidence of some Andean vessels going to coastal sites.
(d) It was concluded that two ceramic wares produced and used by the same people might have different production and distribution systems.
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