DEFINIZIONE COMPOSIZIONALE DELLE “ARGILLE CERAMICHE” PRESENTI NELLA SICILIA NORD-OCCIDENTALE: INQUADRAMENTO GEOLOGICO E RICADUTE DI CARATTERE ARCHEOMETRICO

Abstract

G. Montana, A. Caruso, A.T. Lavore, A.M. Polito & A. Sulli, Geological background and compositional characterization of
“ceramic clay” from North-Western Sicily: archaeometric feed-back. (IT ISSN 0394-3356, 2007).
This paper deals with the compositional and technological characterization of clayey materials, belonging to specific stratigraphic units, which are suspected to have been exploited (in the past centuries) for the traditional ceramic manufacture in north-western Sicily. The studied clays were selected on the basis of geological, archaeological and ethnographic evidences testifying, in several cases, a longestablished use for local ceramic manufacture. The compositional characterization of raw clays has been used to start off a date base which should be functional for the identification of “reference groups” in several archaeological contexts localized in the studied area which are considered to be production centres.
A number of representative samples (46) was collected from different clayey Formations cropping out in north-western Sicily: 1)
Ficarazzi Clays (Pleistocene); 2) Terravecchia Formation (Upper Miocene); 3) Flysch Numidico (Upper Oligocene - Lower Miocene) 4)
Argille Varicolori (Upper Cretaceous - Lower Oligocene). In a first phase, these materials were carefully described from a geological
and stratigraphic point of view. After that, textural (grain size distribution), mineralogical (XRD) and chemical (XRF) characteristics of the clay samples were carried out and discussed. Experimental mouldings and firings on two selected clay types from the above mentioned units, already documented to have been used as raw materials in several archaeological and historical important case studies, were also performed. This has been made in order to simulate a production cycle and to recognize some specific parameters such as plastic behaviour, linear shrinkage, colour and petrographical appearance in thin section under the polarizing microscope. These parameters can be directly used to infer ancient manufacture techniques and firing conditions as well as for provenance determination of doubtful attributed archaeological artefact. For testing out this approach an exemplificative compositional comparison between the Miocene and Pleistocene clays (the believed raw materials) and some ceramic class locally produced during Archaic and ClassicHellenistic age or even in Baroque period has been made. Acceptable results have been obtained which encourage us to pursue this research.