Ceramics as material culture: Study of the North African amphorae from Portus

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Fig. 1 Rim of Africana 1A from Portus in Sullecthum fabric

Ceramics are a very important type of archaeological evidence at sites, with the potential to inform us about chronology and society. They come up at various points in the Archaeology of Portus course and this blog posts provides some extra information based on my research. If you want to check back (or forward!) to relevant pieces of the course I would start with the following:

One of the main applications of typological studies (study of a vessel’s shape) is to provide a chronological framework for excavated archaeological contexts upon which to base our understanding and interpretation of past activities taking place at an archaeological site. Study of the fabrics, that is the fired clay with its geological inclusions, allows us to provenance the ceramic materials. Typology, fabric, and petrological analysis represent standard methodologies for the study of ceramics, allowing us to make sense of a large amount of material found on archaeological sites.

The first step in any ceramic analysis is typological classification, including study of vessel shape and its morphological characteristics. This involves for example categorizing sherds from the site based upon similarities in their profile or shape, and comparing these with existing typologies from previous studies. This allows us to identify different types of vessel.

The second step in ceramic analysis is to look at the fabrics, based on the clay and inclusions used in making the pottery. A ceramic fabric consists of the fired clay matrix and its mineral or organic inclusions. These may occur naturally, or may be intentionally added to the clay by the potters. Fabric analysis, or fabric characterization, takes into account a number of variables, such as the colour, the degree of coarseness, the type of the main inclusions occurring in the fabric, and their frequency and distribution. This is generally carried out with a lens or a binocular microscope. The main application of fabric analysis is to provenance the archaeological ceramics, allowing us to delineate areas of exploitation or workshops of production, and to distinguish between local and imported pottery at an archaeological site.

A further stage in fabric analysis is that of petrological analysis. Petrology is the study of a cross-section of a ceramic sherd under a petrological microscope. By using a petrological microscope it is possible to identify geological inclusions according to their optical properties, and rock fragments where present, which may be distinctive of geological areas. This work requires the grinding down of a ceramic sherd to obtain a completely flat ceramic layer of ideally 0.03mm thickness, which is then fixed to a glass slide.

But what are Roman amphorae, and what can this type of vessel tell us? Roman amphorae are large to very large-sized vessels used for moving agricultural foodstuffs from one province to another. They carried mainly olive oil, wine, different kinds of fish products (salsamenta), and dried fruit. Amphorae are therefore very important evidence for studying the vital link between production and consumption in antiquity, and topics related to the Roman economy.

My study at Portus focused on North African amphorae, and in particular on those manufactured in Africa Proconsularis, which fall within modern Tunisia and western Libya. North African amphorae form the bulk of all ceramic materials at Portus, emphasizing the role of this province in supplying its ceramic and agricultural products to Rome. From the end of the 2nd century AD and in the 3rd century AD, a large amount of amphorae, carrying olive oil, reached Portus from central Tunisia and above all from Tripolitania (modern Libya).

One of the main aims of the research was to tie the amphora vessels down to their workshops and areas of production with the aim of providing a more defined view of the links between the North African suppliers and Portus. Based on an understanding of the principals of typology, fabrics and petrology, and on previous academic work within this field of research, the study identified a number of important workshops that worked in commercial partnership with Portus in the late 2nd and 3rd centuries AD, such as Sullecthum (central Tunisia), Leptis Magna and Tripoli and their rural hinterlands, and in the 4th and 5th centuries AD, such as Nabeul (northern Tunisia).

Focusing in particular on Sullecthum, a coastal port-town in central Tunisia, the pottery workshops manufactured most of the Africana 1A amphorae excavated at Portus. Sullecthum fabric is a very distinctive one. It is usually fired to produce two colours; red and greyish, while it contains numerous small white specks of limestone (Fig. 1 above).

A cross section of the sherd analyzed under the petrological microscope shows that this fabric is essentially a limestone-quartz fabric (limestone are the rounded and brownish inclusions, the quartz are white and rounded). It may contain small grains of pyroxenes, or volcanic minerals (these latter are very colorful under the petrological microscope, under crossed polars) (Fig. 2).

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Fig. 2 Sullecthum fabric under the petrological microscope showing a limestone and quartz fabric

The Africana 1A carried olive oil, underlining the importance of this type of economy, based on olive trees growing in central Tunisia, as well as the commercial export activity to Portus.

Sullecthum fabric occurs also on the Africana 2A and on the Keay 25.1, although in a smaller amount (the full profile of the aforementioned vessels can be accessed on the AHRC Southampton amphora website: http://archaeologydataservice.ac.uk/archives/view/amphora_ahrb_2005/cat_amph.cfm). According to the current amphora literature, the Africana 2A traded fish sauce. This emphasizes the importance of a fish-based economy at the site, where fish-processing tanks have been excavated. Such produce from Sullecthum seems therefore to have been complementary to that of olive oil. The Keay 25.1 amphora is a later vessel, dating to the 4th century AD, and it is associated with wine, although other produce could be carried in this vessel.

The importance of Sullecthum to Ostia-Portus, and to Rome, is visible in comparative material from different types of archaeological evidence. At the Merchant Square in Ostia, the trading guild of Sullecthum is represented in the mosaics as one of Rome’s commercial partners (Fig. 3). A certain P. Caesellinus Felix, a citizen from Sullecthum, (from the latin civis Sullecthinus), was buried at Ostia, as recorded by a funerary inscription. He may have been involved in the trading activities taking place between Sullecthum and Portus as testified by the amphorae.

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Fig. 3 Mosaic of ship-owners from Sullecthum (www.ostia-antica.org)

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