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 Age, and Human Mobility

Ra'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) C-14 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 C-14 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 C-14 dating. Bayesian modeling of the C-14 dates suggests that the formation of the shell midden spanned similar to 1 millennium, between the mid-6th and the mid-5th millennium cal BC. Positive and consistent Delta R values were calculated throughout the entire sequence, ranging from 99 +/- 27 to 207 +/- 43 C-14 yr. At the beginning of the 4th millennium cal BC, RH-6 was used as a graveyard, as suggested by the C-14 dating of a shell in strict association with an individual buried at the surface of the site. C-14 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.