Luminescence dating of ephemeral stream deposits around the Palaeolithic site of Ifri n'Ammar (Morocco)

Abstract

The prehistoric site of Ifri n'Ammar is situated in northeastern Morocco, in the northern prolongation of the Middle Atlas Mountains. It is a key location in unravelling the history of anatomically modern humans (AMH) in northern Africa as it reveals Middle and Late Palaeolithic occupation phases since ~170 ka. Whilst the archaeological sequence within the rock shelter has been well studied, the timing of landscape dynamics around Ifri n'Ammar is still poorly understood. This study therefore aims to establish a detailed chronology of the Wadi Selloum profile at the apron of the shelter, based on optically stimulated luminescence (OSL) dating of ephemeral stream deposits. Coarse-grain quartz was used for singlegrain and multiple-grain dating procedures to investigate the luminescence properties of these deposits and to get more accurate age information concerning the phases of human occupation. Continuous wave OSL (CW-OSL) revealed a dominant fast component for all quartz samples. The dose distribution of the uppermost samples showed overdispersion values >25% and significant positive skewness.We identified partial bleaching as the main source of scatter in the equivalent dose (De) distribution. The lowermost sample appeared to be close to signal saturation. The shapes of the dose response curve varied widely between aliquots and coarse quartz grains exhibited therefore very different dose saturation behaviours among aliquots. With fully saturated dose response curves (DRCs), meaningful D0 values were assumed for De estimation.
The eight OSL samples yielded stratigraphically consistent ages ranging from 1.3 ± 0.2 ka to 76 ± 5 ka, thus reaching the Middle Palaeolithic period. Moreover, a pottery shard dated to 7.4 ± 0.6 ka (Early Neolithic period) by thermoluminescence (TL), perfectly matched the Holocene OSL samples extracted at the same depth of the profile. In summary, our results point to fluvial aggradation during OIS 5.1, the late glacial period, and the Holocene.

• GQT1
• GQT2
• LRQ1

Resources

• http://www.sciencedirect.com/science/article/pii/S1871101415000254

Bibliography

Bartz, M., Klasen, N., Zander, A., Brill, D., Rixhon, G., Seelinger, M., Eiwanger, J., Weniger, G., Mikdad, A., Brückner, H. (2015): Luminescence dating of ephemeral stream deposits around the Palaeolithic site of Ifri n'Ammar (Morocco). – In: Quaternary Geochronology, Vol. 30, p: 460-465, DOI: 10.1016/j.quageo.2015.02.012