Contribution à l’étude archéologique et archéométrique de la céramique d’ombessa (mbam, centre- Cameroun)

Abstract

The great Mbam and particularly Ombessa is a region that is full of important archaeological potential and the ceramic corpus is part of it. However, the vast majority of the territory is still archaeologically unexploited. Our enthusiasm to work in this area was aroused by these two reasons. To be able to uncover areas hitherto unknown archaeologically, to study them and to participate in the scientific knowledge of this region. The objective to be achieved in this work is to contribute to the knowledge of the ceramic production industries in Ombessa, highlighting the morphological and technological specificities, establishing the origin of the raw materials and finally identifying a relative chronological sequence. It is in order to achieve these ends that we thought it wise to formulate the topic ‘‘Contribution to the archaeological and archaeometric study of Ombessa ceramics (Mbam, Cameroon)’’. The research methodology we used is based on two approaches: an archaeological approach involving the collection of data in the field through excavation, prospection, analysis of remains and an archaeometric approach based on the application of physico-chemical methods such as x-ray fluorescence, x-ray diffraction, optical microscopy, infrared spectroscopy and Differential scanning calorimetry/Thermogravimetric analysis. The results of the archaeological approach indicate that chronologically, the relative dating obtained on the basis of comparative studies carried out with the work of ELOUGA (2000) places this corpus in an evolutionary phase beginning in the 2nd millennium AD and continuing until the 18th and 19th centuries. At the morphostylistic level, the containers have two forms, namely: An ovoid shape with neck and a spherical shape with neck, they refer to the type of activity to which the containers were assigned such as cooking and preserving food. The decorations are made with roulette, comb, braided cord and do not seem to have any particular symbolism but have just been applied for aesthetic purposes to satisfy the commercial expectations of the pottery market developed in the area. The colors of the fracture surface of the shards vary between the brown tone referring to oxidizing firing, the black tone corresponding to cooking in a reducing atmosphere and the mixed hues that show the transition from reducing cooking to oxidizing cooking. The analysis of the shaping indices observed on the external surfaces of the shards showed that the pasta was not sufficiently worked and that the shards were mounted with the columbines. Columbine mounting is the most common technique in the area. The archaeometric study was focused on twenty-four sherds selected according to their colour, thickness, and stratigraphic level of collection. Chemical analysis suggested raw material rich in silicon oxide and poor in calcium oxide. Mineralogical phases observed by X-ray diffraction and polarised optical microscope are mica (biotite and muscovite), quartz, feldspar (microcline and plagioclase) in all the sherds. Whereas amphibole was found in some sherds. The estimated firing temperature according to the mineralogy is in the range 650 - 900°C. Chemical correlation between sherds and the collected clay samples showed three group of ceramics with one having close chemical composition with the clay. A local production of the ceramics is suggested with the use of different clay sources. Charred residues analysed by infrared spectroscopy showed that the shards were used for cooking or preserving protein-rich foods .