Abstract For five decades Olduvai Gorge has been a key site to reconstruct and understand the relationship between environmental and landscape conditions and use of affordances by early African hominin populations. Following the first Olduvai Gorge Coring project (OGCP) during 2014, a multiproxy microbiological analysis, which includes phytoliths, pollen, diatoms, sponge spicules and chrysophyte cysts, was undertaken on samples collected from various borehole cores. The aim of the study is to better understand palaeoenvironmental and palaeovegetation conditions and changes through time and their relationship to hominin presence and evolution. This study details the first palaeobotanical and palaeoenvironmental study of Borehole 2A at Olduvai Gorge. It represents the as yet oldest known sedimentary sequence in the Olduvai Basin for a portion of the pre-Bed I Naibor Soit Formation; this is a unit that is not accessible in any natural exposures in Olduvai Gorge, and has only recently been encountered by drilling. Here we present the results from a particularly phytolith-prone portion between ~2.09 Ma and 2.12 Ma. Phytolith results indicate a savannah environment dominated by grasses, where Poaceae were a key component and where the C3 Pooideae grasses were mostly dominant, alternating with C4 grasses. Oscillations between grass subfamilies, C3 Pooideae, C4 Chloridoideae, and C4 Panicoideae to lesser degrees, indicate five substantial climatic shifts, varying between more humid and arid conditions. Associated with phytoliths, freshwater indicators such as diatoms, sponge spicules and chrysophyte cysts were also identified, suggesting the presence of wetlands in the lake catchment area. Pollen is extremely rare in the sediments but when present, comprises fungal spores and Poaceae pollen, thus supporting the wetland and grassland reconstructions, respectively. These results offer for the first time, a whole picture of the palaeovegetation and associated palaeoenvironments for this pre-Bed I period. Together with previous results from other areas and chronological periods, they improve our understanding of the evolution and adaptation of early hominins and their close relationship to the surrounding landscape.

中文翻译：

---

在 Paleolake Olduvai OGCP Core 2A (2.09–2.12 Ma) Naibor Soit Formation Olduvai Gorge 记录的古植被变化，坦桑尼亚

摘要 五十年来，奥杜威峡谷一直是重建和理解环境和景观条件之间的关系以及早期非洲原始人种群对可供性使用的关键地点。继 2014 年第一个奥杜威峡谷取芯项目 (OGCP) 之后，对从各种钻孔岩心收集的样本进行了多重微生物分析，其中包括植硅体、花粉、硅藻、海绵针状体和金藻孢囊。该研究的目的是更好地了解古环境和古植被条件以及随时间的变化及其与人类存在和进化的关系。这项研究详细介绍了对奥杜威峡谷 Borehole 2A 的首次古植物学和古环境研究。它代表了奥杜威盆地中已知最古老的沉积层序，包括前床 I Naibor Soit 地层的一部分；这是一个在奥杜威峡谷的任何自然暴露区域都无法进入的单元，并且最近才在钻探中遇到。在这里，我们展示了约 2.09 Ma 和 2.12 Ma 之间特别容易植硅体的部分的结果。植硅体结果表明大草原环境以草为主，其中禾本科是关键组成部分，其中 C3 Pooideae 草主要占优势，与 C4 草交替。草亚科 C3 Pooideae、C4 Chloridoideae 和 C4 Panicoideae 之间的波动程度较小，表明有五个实质性的气候变化，在更潮湿和更干旱的条件之间变化。与植硅体、淡水指标如硅藻、还发现了海绵针状体和金藻孢囊，表明湖泊集水区存在湿地。花粉在沉积物中极为罕见，但如果存在，则包含真菌孢子和禾本科花粉，从而分别支持湿地和草地的重建。这些结果第一次提供了这个床前 I 时期的古植被和相关古环境的全貌。与其他地区和年代的先前结果一起，它们提高了我们对早期人类的进化和适应以及它们与周围景观的密切关系的理解。从而分别支持湿地和草地重建。这些结果第一次提供了这个床前 I 时期的古植被和相关古环境的全貌。与其他地区和年代的先前结果一起，它们提高了我们对早期人类的进化和适应以及它们与周围景观的密切关系的理解。从而分别支持湿地和草地重建。这些结果第一次提供了这个床前 I 时期的古植被和相关古环境的全貌。与其他地区和年代的先前结果一起，它们提高了我们对早期人类的进化和适应以及它们与周围景观的密切关系的理解。