A revised radiocarbon chronology of the aceramic shell midden of Ra's al-Hamra 6 (Muscat, Sultanate of Oman): implication for occupational sequence, marine reservoir, and human mobility

International audienceRa's al-Hamra 6 (RH-6) is one of the earliest stratified archaeological sites along the eastern littoral of the Arabian Peninsula. This shell midden was radiocarbon dated to the 6th–5th millennium cal BC, but the majority of the dates were obtained before the advent of accelerator mass spectrometry (AMS) 14 C dating and suffer from large uncertainties. In addition, most of these dates were obtained on marine and mangrove shells and required correction for local variations from the global average marine 14 C reservoir age (MRA). This proved difficult because no consensus value exists for this period in the area. Recent excavations at RH-6 offered the opportunity to redate this important site in order to precisely determine its occupation history and later use as a graveyard, and establish the marine reservoir effect for this time period. Thirty-eight samples of charcoal, shells, and human bone apatite were selected for 14 C dating. Bayesian modeling of the 14 C dates suggests that the formation of the shell midden spanned ~1 millennium, between the mid-6th and the mid-5th millennium cal BC. Positive and consistent ΔR values were calculated throughout the entire sequence, ranging from 99 ± 27 to 207 ± 43 14 C yr. At the beginning of the 4th millennium cal BC, RH-6 was used as a graveyard, as suggested by the 14 C dating of a shell in strict association with an individual buried at the surface of the site. 14 C dating of human bone apatite allowed us to calculate that 89% of this individual's diet derived from marine resources. This finding confirms previous observations showing the overwhelming presence of marine and mangrove-dwelling species in the faunal and charcoal assemblage, and implies a low mobility, or mobility restricted to the coast for this population during the 4th millennium cal BC