Wissem Gallala

Geoarchaeology of Roman Underground Quarries at Ksour Essaf (Tunisia)

The underground quarries at Ksour Essaf hills (Tunisia) contribute to our knowledge of extraction techniques that have been in use since antiquity. The extracted stone consists of oolitic sandy limestone, dated as Lower Messinian (Ksour Essaf Formation). Geotechnical analyses have revealed that the quality of the Messinian stone is better than that of Tyrrhenian (Late Pleistocene) age from the same region (Réjiche Formation). However, the latter has been more widely used as it is more extensively exposed. The extraction technique and the use of cut blocks in Roman constructions, but not mediaeval Muslim constructions in this area, allow the approximate determination of the period of the exploitation of the underground quarries during the period of Roman occupation.

Microstructural and Mechanical Properties in Traditional Ceramics as a Function of Quartzofeldspathic Sand Incorporation

We intend to study the influence of addition of quartzo-feldspathic sand on the mechanical properties and the microstructure of Tunisian illite-kaolinite clay ceramics. The fired characteristics of the clay and quartzo-feldspathic sand mixtures have been studied separately at soaking temperatures reaching respectively 850°, 950° and 1050°C during a firing profile of ∼7–8 h. Investigation of phase transformations of the mixed samples shows that albeit the proportion of the quartz has been increased, its peak intensity remains constant. Such stability may be explained by quartz dissolution in the glassy phase. The mechanical strength of the mixed samples has been examined in terms of flexural strength. In the studied case, the latter increases from 13.5 to 23.3 N.mm−2 as the sample becomes denser in the mixture M2. It may also be noticed that an overdose of quartz reduces the mechanical strength. Hence, a moderate addition of well-sorted fine quartzofeldspathic sand ameliorates the mechanical properties and the microstructure. The latter is analysed by scanning electron microscope (SEM).

Roman Millstones of Carthage (Tunisia): a Geoarchaeological Study Using Petrological and Geochemical Methods

A great number of Roman millstones have been discovered in the archaeological site of Byrsa at Carthage since the nineteenth century by different international archaeological teams which have excavated the site. Most of these millstones (catilli/metae) are hourglass-shaped, and all are made of igneous rocks whose source was identified through petrochemical study. The location of the artefact rock source was determined by comparing thin sections of samples taken from black and red-brownish lava catilli found at the Byrsa Roman site with geological samples taken from Tunisian volcanic rocks located in the northern-western part of the country (Nefza and Mogods regions). The comparison shows that the volcanic petrological and geochemical compositions (basalt and rhyolitic ignimbrite) of the catilli are not from local sources where basaltic and rhyodacite outcrops have been identified in the Guelb Saad Moun (Mogods region) and in the Nefza region respectively. The comparison with existing literature data on similar rocks from Italy has constrained the volcanic origin of the exploited lavas. Thus, the diversity of volcanic rocks (basalt and rhyolitic ignimbrite) suggests several outside origins, such as the Pantelleria Island for the black lava mills and Sardinia (in the area of Mulargia) for the red-brownish lava mills, where these two types of igneous rocks have been widely identified.

A multi-analytical approach for determining the provenance of the marbles from Ruspina Roman baths (Monastir, Tunisia)

Although most of the ancient monuments found in Ruspina Roman town situated near the town of Monastir in the Sahil region of Tunisia were built with local materials, the Roman baths in this site were mainly decorated with imported marbles from Greece, Asia, Numidia, Italy and Algeria, indicating the important trade relationships between Ruspina and the other Mediterranean Roman towns. Among the seven types of marbles used in the decoration of Ruspina’s Roman baths, four have been characterized in previous studies: white Proconnesian from Asia, Penthelic and green cipolin from Greece, and Antique yellow from Simitthus in Tunisia. To characterize and identify the other three types, series of analytical methods had to be applied: minero-petrographic analysis of thin sections, chemical analysis, and isotopic analysis of oxygen and carbon. Used together, the methods enabled to identify the marbles studied: the white fine-grained marble corresponds to Carrara white marble from Italy, and the spotted dull grey and greco scritto came from Cap de Garde quarries in Algeria. With the exception on one type (antique yellow), the other six types were imported marbles.