Using multiple luminescence chronometers to establish the chronology of the Middle Stone Age site of Florisbad, South Africa

Crynodeb

New discoveries of hominin fossil sites are changing our understanding of the evolution of Homo sapiens. In Africa, evolution of modern humans coincides with a behavioural shift during the Middle Stone Age (MSA) (250-300 ka). However, inadequate chronometric control of key sites impedes a thorough understanding of the timing and patterns of the emergence of modern humans. Florisbad, South Africa, is a key MSA site that contains an archaic Homo sapiens cranium and a detailed MSA lithic record. This thesis investigates the use of multiple luminescence chronometers to provide a complete chronology for the Florisbad sedimentary sequence for the first time. The single grain quartz OSL signal demonstrates the challenges of luminescence dating archaeological sites with complex depositional histories. Many samples are well bleached, but others are more difficult to interpret. Furthermore, the quartz OSL signal reaches saturation halfway down the sequence. The quartz TT-OSL signal is sufficiently stable to date the whole sequence. A small TT-OSL residual dose of 2-15 Gy for the younger samples (<30 Gy) means that incomplete bleaching has a negligible impact on samples >100 Gy. The post-IR IRSL250 signal from feldspar is compared to the OSL and TT-OSL signals, and supports the idea that most samples are well bleached. For other samples, a possible influence from post-depositional mixing is suggested. The single grain OSL ages are the most reliable when not in saturation. For many of the MSA samples, the post-IR IRSL250 and TT-OSL ages show good agreement. The chronology shows sedimentation at Florisbad occurred from 254 ka until 0.8 ka, with a hiatus lasting ~100 ka during the last glacial. The presence of material at 254 ka is in agreement with a previously reported ESR age of ~260 ka for the cranium, demonstrating the importance of Florisbad within the H. sapiens evolutionary record

Dyddiad Dyfarnu	2021
Iaith wreiddiol	Saesneg
Sefydliad Dyfarnu	Prifysgol Aberystwyth
Goruchwyliwr	Helen Roberts (Goruchwylydd) & Geoff Duller (Goruchwylydd)