Quaternary climatic changes in the Nile Basin and their effects on the evolution of African mammals and vegetation are poorly understood, particularly for the last 1 Ma. Pleistocene (~230 to <17 ka) alluvial sediments exposed along the middle stretches of the Atbara River in eastern Sudan are rich in fossil vertebrates and are ideal for paleoenvironmental reconstruction during this time interval. We performed petrographic, mineralogical and geochemical analyses on the middle Atbara paleosols to reconstruct the paleoclimate and paleolandscape. We describe Aridisols/Calcisols characterized by calcretes and containing gypsum and halite, and Vertisols with pedogenic slickensides and a relatively large amount of smectite. The paleosols indicate that the study area transitioned from an arid to semi-arid climate during Marine Isotope Stage (MIS)7/6, to a more humid climate during MIS5, and then a return to more arid conditions during MIS2. The studied paleosols likely supported a range of grassland and wooded grassland savanna habitats. Our study confirms that the Atbara River Valley provided favorable living conditions for Pleistocene large mammal communities including Homo, potentially facilitating dispersals out of Africa through the Nile corridor.

中文翻译：

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苏丹东部阿特巴拉河第四纪冲积古土壤：描述和古环境

人们对尼罗河流域第四纪气候变化及其对非洲哺乳动物和植被进化的影响知之甚少，特别是在过去的 1 Ma 中。苏丹东部阿特巴拉河中段暴露的更新世（~230至<17ka）冲积沉积物富含脊椎动物化石，是该时期古环境重建的理想选择。我们对阿特巴拉中部古土壤进行了岩石学、矿物学和地球化学分析，以重建古气候和古景观。我们描述了以钙结石为特征并含有石膏和石盐的Aridisols/Calcisols，以及具有成土光滑剂和相对大量绿土的Vertisols。古土壤表明，研究区在海洋同位素阶段（MIS）7/6期间从干旱气候过渡到半干旱气候，在MIS5期间过渡到更加湿润的气候，然后在MIS2期间恢复到更加干旱的气候条件。研究的古土壤可能支持一系列草原和树木繁茂的草原稀树草原栖息地。我们的研究证实，阿特巴拉河谷为更新世大型哺乳动物群落（包括人属）提供了有利的生活条件，有可能促进它们通过尼罗河走廊扩散到非洲之外。