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

IF 0.5 4区地球科学 Q4 GEOLOGY

Boletin De La Sociedad Geologica Mexicana Pub Date : 2022-12-13 DOI:10.18268/bsgm2022v74n3a200622

T. Cruz-y-Cruz, Alejandro Terrazas-Mata, L. Pogosyan, S. Sedov, T. Pi-Puig, Irán Rivera-González, Beatriz Menéndez-Iglesias, Jorge Rodríguez-Rivas, H. Cabadas-Báez

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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 (Fed), 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 Fed 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.

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赤道几内亚中石器时代考古遗址的晚更新世古环境:古学方法

人类在旧石器时代中期(中石器时代[MSA])居住在非洲的关键证据来自非洲大陆的南部和东部，那里普遍存在半干旱气候。最近从赤道几内亚报告了湿润热带地区MSA人类活动的罕见证据。为了确定旧石器时代的人类是否曾在热带森林中居住过，研究人员使用古学方法分析了最近发现的考古遗址“Mabewele I”的地层学。沿着垂直剖面评估的性质是:粒度测定、磁化率(K)、二亚硫酸钠(Fed)可提取的游离铁(游离铁)、总有机碳(TOC)、x射线荧光(XRF)化学成分、x射线衍射矿物学(XRD)、三种主要氧化物(SiO2-Al2O3-Fe2O3)的三元图、植物岩和微观形貌。主要组分为砂，粘土含量显著(约30%)。K和Fed的值较低，TOC也较低。XRF沿序列变化不大，XRD显示粘土以高岭石为主，蛭石含量极低。植物岩与热带植被相对应，深层和浅层植被组成变化不大。剖面下部的木炭的年代在12.57-12.24 ka cal BP之间，而主要的人工制品层位于底部。分析结果似乎是矛盾的:一方面，在潮湿的热带气候下，有强烈的化学风化的证据，但孔隙中的粘土岩屑非常稀少且处于初期阶段，铁结核大多是植物性的。这表明该层序是由具有高环境动力的土壤沉积物组成，具有短时间的侵蚀-沉积-成土作用。这些结果使我们能够提出人类在MSA时期居住在热带森林，并且侵蚀-沉积过程可能与人类化过程有关。

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来源期刊

Boletin De La Sociedad Geologica Mexicana GEOLOGY-

CiteScore

1.40

自引率

12.50%

发文量

审稿时长

50 weeks

期刊介绍： The Boletín de la Sociedad Geológica Mexicana is a completely free-access electronic journal published semi-annually that publishes papers and technical notes with its main objective to contribute to an understanding of the geology of Mexico, of its neighbor areas, and of geologically similar areas anywhere on Earth’s crust. Geology has no boundaries so we may publish papers on any area of knowledge that is interesting to our readers. We also favor the publication of papers on relatively unfamiliar subjects and objectives in mainstream journals, e.g., papers devoted to new methodologies or their improvement, and areas of knowledge that in the past had relatively little attention paid them in Mexican journals, such as urban geology, water management, environmental geology, and ore deposits, among others. Mexico is a land of volcanos, earthquakes, vast resources in minerals and petroleum, and a shortage of water. Consequently, these topics should certainly be of major interest to our readers, our Society, and society in general. Furthermore, the Boletín has been published since 1904; that makes it one of the oldest scientific journals currently active in Mexico and, most notably, its entire contents, from the first issue on, are available online.