Abstract Sediment cores recovered by the Olduvai Gorge Coring Project (OGCP) in 2014 afford the opportunity to examine the coupling of biogeochemical evidence for climatic and environmental change within the context of hominin evolution at this renowned East African locality. Investigations of elemental (total organic carbon – TOC or Corg wt%, carbon to nitrogen ratio - C/N), molecular (source-specific biomarkers), and isotopic (δ13Corg, δ2HnC31) compositions of organic matter provide evidence for temporal changes in sedimentary materials derived from terrestrial plants (C3, C4) and aquatic producers (algae, sponges, cyanobacteria), and in precipitation. The 13 kyr record of Upper Bed I immediately preceding Tuff IB extends high-resolution stratigraphic profiles of precession-scale alternations of wetter and drier conditions to encompass the entire interval from the Bed I Basalt to Tuff IB. The second wetter interval, designated W2, records local influences on climate and water supply consistent with evidence for discrete sediment sources based its physical properties (e.g., gamma radiation, magnetic susceptibility) compared with the overall sequence. The δ13CTOC values for wetter interval W2 reveal two millennial-scale (~2.5 kyr) drier episodes followed by a shift in the dominance of C3 over C4 plants accompanying the transition to a drier climate (D3). Moreover, biogeochemical data for Upper Bed I show that changes from drier to wetter conditions occur more rapidly (~900 yr) than wetter to drier transitions (>2.6 kyr), based on interpolated ages. In addition, biomarker profiles indicate that aquatic plants, primarily algae and macrophytes, may have been subject to more profound and faster fluctuations than variations in terrestrial vegetation expressed in terms of the relative proportions of woodland and grassland settings. Thus, environmental and climatic changes not only influenced the availability of resources of food and shelter for hominins within the Olduvai region but also led to their variation on centennial to millennial to precessional timescales.

中文翻译：

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来自 OGCP 核心 2A 沉积物的生物地球化学证据表明凝灰岩 IB 沉积之前的环境变化和奥杜威盆地上层 I 的气候转变

摘要 2014 年由奥杜威峡谷取心项目 (OGCP) 回收的沉积物核心提供了机会，以检查在这个著名的东非地区人类进化背景下气候和环境变化的生物地球化学证据的耦合。对有机质的元素（总有机碳 - TOC 或 Corg wt%、碳氮比 - C/N）、分子（特定来源的生物标志物）和同位素（δ13Corg、δ2HnC31）组成的调查为沉积物的时间变化提供了证据来自陆生植物（C3、C4）和水生生产者（藻类、海绵、蓝藻）和降水的材料。紧接在凝灰岩 IB 之前的上层 I 的 13 kyr 记录扩展了干湿条件进动尺度交替的高分辨率地层剖面，以涵盖从 I 层玄武岩到凝灰岩 IB 的整个间隔。指定为 W2 的第二个湿润区间记录了当地对气候和供水的影响，与基于其物理特性（例如，伽马辐射、磁化率）与整体序列相比较的离散沉积物来源的证据一致。较湿间隔 W2 的 δ13CTOC 值揭示了两个千年尺度 (~2.5 kyr) 干燥事件，随后 C3 相对于 C4 植物的优势发生转变，伴随着向干燥气候 (D3) 的过渡。而且，上床 I 的生物地球化学数据表明，基于内插年龄，从干燥条件到湿润条件的变化（约 900 年）比从湿润到干燥条件的转变（>2.6 kyr）发生得更快。此外，生物标志物概况表明，与以林地和草地环境的相对比例表示的陆地植被变化相比，水生植物（主要是藻类和大型植物）可能受到更深刻和更快的波动。因此，环境和气候变化不仅影响了奥杜威地区人类食物和住所资源的可用性，而且还导致他们在百年到千年到岁差时间尺度上的变化。主要是藻类和大型植物，与以林地和草地环境的相对比例表示的陆地植被的变化相比，可能受到更深刻和更快的波动。因此，环境和气候变化不仅影响了奥杜威地区人类食物和住所资源的可用性，而且还导致他们在百年到千年到岁差时间尺度上的变化。主要是藻类和大型植物，与以林地和草地环境的相对比例表示的陆地植被的变化相比，可能受到更深刻和更快的波动。因此，环境和气候变化不仅影响了奥杜威地区人类食物和住所资源的可用性，而且还导致他们在百年到千年到岁差时间尺度上的变化。