麻豆传媒

听

This thesis concerns the optically and thermally stimulated luminescence dating, and sedimentological study of Birimi, an archaeological site in Ghana, Africa. Birimi is an archaeologically significant site because it contains the cultural remains of three distinct cultures. These are, in order of oldest to youngest, the Middle Stone Age (MSA) culture, the Later Stone Age Kintampo complex, and the Iron Age culture. This thesis generated three indirect optically stimulated luminescence (OSL) ages on the quartz-rich sediment associated with in situ MSA flaked stone tools, and direct thermoluminescence (TL) ages for twelve Kintampo ceramics. An additional eight OSL dates were generated for sediments collected from various culturally or geologically significant levels from two exposed sediment profiles and three excavation units at the site. The twelve generated ceramic ages span the period ~2,140-3,830 years. These coincide with the younger part of the range generated from previous TL ages on Birimi Kintampo house daub material. Radiocarbon ages on Birimi charcoal from Kintampo occupation features coincide with the older part of the ceramic age range. Significantly, these ages all suggest a prolonged occupation by the Kintampo peoples, previously thought to have migrated into Ghana and remained there for only ~500 years. OSL dates for the MSA in the range of 27-35ka, provide the first absolute chronology for this culture in sub-Saharan Africa. Other OSL ages increase with depth in their respective areas from ~3,000 years near-surface to ~60,000 years at 1.8m depth. Sediment samples collected at 20 cm intervals from the profiles were analysed for major element geochemistry and Munsell colour designation. Of these, selected samples were analysed for particle size distribution, mineralogy and quartz grain surface features (with the SEM). Sedimentological analysis revealed that the soils at Birimi are typical of this part of West Africa, having two ironstone concretion levels, prominent colouring by iron compounds, and a predominance of the resistant minerals quartz and kaolinite. Changes in sedimentological characteristics, such as a decrease in % SiO₂, increase in % Al₂O₃ and % loss on ignition from clay-derived water, and increase in dissolution of quartz grain surfaces with depth, coincide with known paleoclimatic data for the region.

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Supervisor: Dorothy Godfrey-Smith