Bayesian Approach to ¹⁴C Dates for Estimation of Long-Term Archaeological Sequences in Arid Environments: The Holocene Site of Takarkori Rockshelter, Southwest Libya

Abstract

Caves and rockshelters are critical loci for the analysis and understanding of human trajectories in the past. Use and re-uses of the same context, however, might have had serious impacts on depositional aspects. This is particularly true for the archaeological history of desert environments, such as the central Sahara, where most of the deposits are made of loose sand, rich in organic matter. Besides traditional stratigraphic reconstructions and a detailed study of the material culture, radiocarbon measurements from different contexts analyzing several types of material (bone, dried and charred coprolite, uncharred and charred plant remains, etc.) can highlight intrinsic critical aspects of 14C determinations. These measurements must be carefully evaluated to provide a correct chronological assessment of the life history of the site. We present the statistics derived from the set of about 50 14C measurements from the site of Takarkori, southwest Libya, where early Holocene foragers and then groups of cattle herders inhabited the area from ∼10,200 to 4600 cal yr BP. We have used the BCal Bayesian 14C calibration program designed for statistical presentation of the calibrated data and the estimation of their probability for different phases. Results indicate that the Takarkori rockshelter was occupied during 4 phases of the following cultures: Late Acacus from 10,170 to 8180 cal yr BP; Early Pastoral, 8180–6890 cal yr BP; Middle Pastoral, 7160–5610 cal yr BP; and Late Pastoral, 5700–4650 cal yr BP.

Accurate compound-specific 14C dating of archaeological pottery vessels

“…The CSRA dates were proven entirely compatible with the currency of Middle Pastoral Neolithic ceramics (SI 6, ED Fig. 6d), and the direct radiocarbon dating of dairy residues confirms that dairying in North Africa began as early as the end of the 6 th millennium cal BC 14,28,29 . While, the model sensitivity is weak based on the small number of reference dates it includes (SI 6, ED Fig.…”

“…A basic distinction between archaeological layers, can be made between those mainly represented by 'matrix' and those that are 'fixture' (sensu Biagetti and di Lernia 2013 14 ), whose depositional histories differ strongly. Given the high rate of disturbance and the 'matrix' nature of the dominant type of layer called "organic sands" -incoherent loose sediments made of quartz grains and abundant organic material (e.g., plant remains, charcoal, bones) -the stratigraphic control of the archaeological features has been confirmed by a series of radiocarbon dates 14,29 . In particular, a series of samples have been dated associated with the Middle Pastoral occupation at Takarkori (Table s7).…”

“…placed deposits associated with Middle Pastoral pottery in the sixth-fifth millennia cal BC 14,28,29 . The fatty acids from five potsherds, containing dairy fat (ED Fig.…”

Aquatic fauna from the Takarkori rock shelter reveals the Holocene central Saharan climate and palaeohydrography

“…Clearly recognizable items, such as decorated pottery, can be easily distinguished, whereas faunal remains, also due to their small size (and often poor state of preservation) could be more elusive. In some cases, specific elements have been directly radiocarbon dated to test their stratigraphic attribution [42].…”

“…The material is temporarily stored in the Sapienza University, in order to be resent to the Lybian Department of Antiquities, Tripoli, Libya, as soon as safety conditions in Libya will recover. Identification of the mammal bone was carried out with the aid of the comparative collections of modern skeletons housed at the Istituto Italiano di Paleontologia Umana (IsIPU) in Rome and at the Museo Chronology of the main chrono-cultural phases identified at Takarkori (modified, after [42]). The calibration expresses the maximum chronological range and overlaps are statistically possible.…”