In situ-produced¹⁰Be and²⁶Al indirect dating of Elarmékora Earlier Stone Age artefacts: first attempt in a savannah forest mosaic in the middle Ogooué valley, Gabon

Abstract

Discovered in 1988 by R. Oslisly and B. Peyrot, Elarmékora is a high terrace that, today, is situated 175 m above the Ogooué River in the historical complex of Elarmékora, attached to the Lopé National Park in Gabon, a World Heritage site since 2007. The site yielded a small lithic assemblage, including mainly cobble artefacts embedded within the 1 m thick alluvial material. Based on geomorphological and palaeoclimatological criteria, the preliminary dating suggested an age of 400 ka. However, Elarmékora could be a key site for Atlantic Central Africa if this lithic industry can be dated absolutely. In 2018 and 2019, two field trips were organized to collect surface samples as well as samples in vertical depth profiles with the aim of measuring their in situ -produced cosmogenic nuclide ( 10 Be and 26 Al) content. Results suggest a surface abandonment between 730 and 620 ka ago representing a minimum age for the cobble artefacts. Concurrently, technological reappraisal of the artefacts suggests an atypical lithic industry that should, for the moment, be considered as ‘undiagnostic’ Earlier Stone Age. This age bracketing may be compared with a similar age range obtained for prehistoric occupations in Angola using the same approach. This age will place Elarmékora among the oldest evidence for the presence of hominins in western Central Africa and raises the question of a ‘West Side Story’ to early human dispersals in Africa. This article is part of the theme issue ‘Tropical forests in the deep human past’.

Tropical forests in the deep human past

“…Here, Gosling and colleagues [50] synthesize information on Pleistocene and Holocene vegetation changes from long-term terrestrial and marine records, showing how the locations of vegetative resources for hominins shifted geographically over time (see also [51]). Of particular interest is the fact that the hominin presence in the Congo Basin described by Braucher et al [49], coincides with generally humid conditions and therefore likely a period of forest expansion, rather than fragmentation. Furthermore, a profound shift in the hydro-climate in the last 1 Myr in Africa, leading to eastern and western parts of the forest zones being alternately wetter and drier, occurs at a time when the first fossil appearances of our species have been suggested elsewhere in Africa (e.g.…”

“…Braucher et al . [ 49 ] suggest a longer history than previously supposed. They report the oldest evidence of a hominin presence in the Congo Basin, with a minimum age of between 850 and 650 ka.…”

“…Of particular interest is the fact that the hominin presence in the Congo Basin described by Braucher et al . [ 49 ], coincides with generally humid conditions and therefore likely a period of forest expansion, rather than fragmentation. Furthermore, a profound shift in the hydro-climate in the last 1 Myr in Africa, leading to eastern and western parts of the forest zones being alternately wetter and drier, occurs at a time when the first fossil appearances of our species have been suggested elsewhere in Africa (e.g.…”

Javanese Homo erectus on the move in SE Asia circa 1.8 Ma

“…Instead, Terrestrial Cosmogenic Nuclide dating (TCN) is, to our knowledge, the only available method to focus on the burial time and thus to minimize uncertainties associated to the pre-burial history. For that reason, this technique is increasingly applied in archaeology and paleoanthropology, and sheds new lights on hominin dispersal [16][17][18][19][20][21] . Here, we date the first appearance of Javanese H. erectus using TCN relying on the concentration of two in-situ produced cosmogenic nuclides ( 10 Be and 26 Al) in quartz grains from the sedimentary layers of interest.…”