Late Pleistocene paleoenvironment at a Middle Stone Age archaeological site in Equatorial Guinea: a paleopedological approach

Paleoambiente pleistocénico tardío en un sitio arqueológico del Mesolítico de Guinea Ecuatorial: un enfoque paleopedológico

Tamara Cruz-y-Cruz^1,2,*, Alejandro Terrazas-Mata³, Lilit Pogosyan⁴, Sergey Sedov⁵, Teresa Pi-Puig^5,6,

Iran Rivera-González², Beatriz Menéndez-Iglesias^1,7 , Jorge Rodríguez-Rivas⁸, Héctor Cabadas-Báez⁹

¹ Postdoctoral Scholarship Program, National Autonomous University of Mexico (UNAM), Scholar of the Institute of Anthropological Research. Ciudad Universitaria, 04510, CDMX, Mexico.

² National School of Anthropology and History (ENAH-INAH), Periférico Sur y Zapote sn. Isidro Fabela, Tlalpan, CDMX, Mexico.³ Institute of Anthropological Research, UNAM, Ciudad Universitaria, 04510, CDMX, Mexico.

⁴ Faculty of Soil Science, Moscow State University, Leninskie Gory 1-12, 119991, Moscow, Russia.

⁵ Institute of Geology, UNAM, Ciudad Universitaria, 04510, CDMX, Mexico.

⁶ National Laboratory of Geochemistry and Mineralogy (LANGEM), Institute of Geology, UNAM, Ciudad Universitaria, 04510, CDMX, Mexico.

⁷ Gerda Henkel Foundation. Patrimonies Funding Initiative, Düsseldorf, Germany.

⁸ UNAM Project “Early Homo sapiens Settlement in the Tropical Rainforests of Equatorial Guinea”.

⁹ Geology Laboratory, Faculty of Geography, Autonomous University of the State of Mexico, Cerro Coatepec s/n Ciudad Universitaria, 50110, Toluca, Estado de México, Mexico.

* Corresponding author: (T. Cruz-y-Cruz) This email address is being protected from spambots. You need JavaScript enabled to view it., This email address is being protected from spambots. You need JavaScript enabled to view it.

How to cite this article:

Cruz-y-Cruz, T., Terrazas-Mata, A., Pogosyan, L., Sedov, S., Pi-Puig, T., Rivera-González, I., Menéndez-Iglesias, B., Rodríguez-Rivas, J., Cabadas-Báez, H., 2022, Late Pleistocene paleoenvironment at a Middle Stone Age archaeological site in Equatorial Guinea: a paleopedological approach: Boletín de la Sociedad Geológica Mexicana, 74 (3), A200622. http://dx.doi.org/10.18268/BSGM2022v74n3a200622

Manuscript received: December 12, 2021; Corrected manuscript received: June 20, 2022; Manuscript accepted: June 23, 2022.

ABSTRACT

Key evidence of human occupation in Africa during the Middle Palaeolithic (Middle Stone Age [MSA]) is available from the south and east of the continent, where semi-arid climate prevails. Rare evidence of MSA human occupation in the humid tropical region was recently reported from Equatorial Guinea. To identify if paleolithic human occupation occurred in the tropical forest, the stratigraphy of the recently discovered archaeological site “Mabewele I” was analyzed using a paleopedological approach. The properties evaluated along a vertical profile are: granulometry, magnetic susceptibility (K), free iron extractable with sodium dithionite (Fe_d), total organic carbon (TOC), chemical composition by X-ray fluorescence (XRF), X-ray diffraction mineralogy (XRD), ternary plot of the three main oxides (SiO₂-Al₂O₃-Fe₂O₃), phytoliths and micromorphology. The predominant fraction is sand, with a significant clay content (> 30 %). The K and the Fe_d presented low values, as well as the TOC. XRF showed few variations along the sequence and XRD showed that the clays are mainly kaolinites, with a very low component of vermiculites. The phytoliths correspond to tropical vegetation with few changes in the vegetal composition between the deep and superficial zones. A charcoal from the lower part of the profile was dated between 12.57-12.24 ka cal BP, while the main artifact horizon was located at the bottom. The analytical results appear contradictory: on the one hand, there is evidence of intense chemical weathering under a humid tropical climate, but the clay cutans in the pores are very scarce and incipient and the iron nodules are mostly anorthic. This indicates that the sequence is composed of pedosediments associated with a high environmental dynamism, with short periods of erosion-sedimentation-pedogenesis. The results allow us to propose that humans inhabited the tropical forest during the MSA and that erosion-sedimentation processes could be related to anthropization processes.

Keywords: Middle Stone Age, Equatorial Guinea, rainforest, paleopedology.