Data from: Stable oxygen isotopes of crocodilian tooth enamel allow tracking Plio-Pleistocene evolution of freshwater environments and climate in the Shungura Formation (Turkana Depression, Ethiopia)

This file gathers the supplementary material and datasets related to the publication "Stable oxygen isotopes of crocodilian tooth enamel allow tracking Plio-Pleistocene evolution of freshwater environments and climate in the Shungura Formation (Turkana Depression, Ethiopia)" published in Biogeosciences. This study utilizes stable oxygen isotopes (δ18Op) in fossil crocodilian teeth to assess paleohydrology and paleoclimates. Crocodilian teeth, widely available in continental basins since the Mesozoic era, provide a valuable archive for tracking freshwater environmental changes due to their durable enamel phosphate, which preserves their original isotopic composition over geological timescales. The research applies this approach for the first time to the Shungura Formation in the Lower Omo Valley, Ethiopia, a crucial area for understanding environmental shifts in eastern Africa during the Plio-Pleistocene, impacting regional ecosystems, including humans. The δ18Op of coexisting crocodilians reveals (1) stable aquatic environments in the northern Turkana Depression from 2.97 Ma to around 2.57 Ma, followed by a decline in local waterbody diversity after 2.32 Ma, indicative of increasing aridity, and (2) a significant increase in δ18Ow from 2.97 Ma to about 1.14 Ma, likely influenced by changing air stream convergence zones between the West African and Indian Summer Monsoons and/or reduced rainfall over the Ethiopian Highlands. Age model for the Shungura Formation The related paper uses a revised age model for the Shungura Formation, interpolated based on the latest published absolute age data. The interpolation was carried out on the R.4.1.3 software, with the function splinefun ("stats" package, R Core Team, 2022) by implementing the data of the maximum cumulative thickness of sediments (Heinzelin and Haesarts, 1983) and the absolute ages known for some units of the Shungura Formation. For the Basal Member and the top of Member L, ages are interpolated by linear fit based on sedimentation rate. this age model is likely to evolve with the addition of new dating data. Oxygen isotopic composition of crocodilian teeth from the Shungura Formation Table S2 brings together information on the morphology and isotopic composition of the crocodilian teeth sampled in the Shungura Formation. Abbreviation: ID, tooth inventory number; Age, age of the unit in million years based on the age model of the Shungura Formation given in Table S1. The dental crown height is given for teeth with complete crown only. The details of the method used for the geochemical analyzes are given in the corresponding article, in section 2.4. Pariwise comparison of the isotopic composition of crocodilian teeth between units of the Shungura Formation The δ18Op difference between stratigraphical units was investigated with a two-way ANOVA and Pairwise Wilcoxon Rank Sum Tests with Holm correction (non-parametric post-hoc tests), and the results are presented in Table S3.本数据集汇集了发表于《生物地球科学》(Biogeosciences)的论文《鳄类牙齿釉质稳定氧同位素可追踪埃塞俄比亚图尔卡纳凹陷尚古拉组(Shungura Formation)上新世-更新世淡水环境与气候演化》的补充材料与相关数据集。 本研究利用化石鳄类牙齿中的稳定氧同位素(δ¹⁸O_p)重建古水文学与古气候。鳄类牙齿自中生代以来广泛保存于陆相盆地中，其釉质磷酸盐质地坚硬，可在地质时间尺度上保留原始同位素组成，因此是追踪淡水环境变化的宝贵档案。本研究首次将该方法应用于埃塞俄比亚下奥莫河谷的尚古拉组——这一区域是理解东非上新世-更新世环境变迁的关键区域，其环境变化影响了包括人类在内的区域生态系统。共存鳄类的δ¹⁸O_p数据揭示了两点：(1)2.97 Ma至约2.57 Ma期间，图尔卡纳凹陷北部存在稳定的水生环境；2.32 Ma后当地水体多样性下降，指示干旱化程度加剧；(2)2.97 Ma至约1.14 Ma期间，水体氧同位素组成(δ¹⁸O_w)显著升高，这可能受西非夏季风与印度夏季风之间的气流交汇带变化，以及/或者埃塞俄比亚高原降雨量减少的影响。 尚古拉组年代模型 相关论文采用了修订后的尚古拉组年代模型，该模型基于最新发表的绝对年代数据插值得到。插值工作在R 4.1.3统计软件中完成，通过调用"stats"包(R核心团队，2022)的splinefun函数，结合沉积物最大累积厚度数据(Heinzelin与Haesarts，1983)以及尚古拉组部分地层单元的已知绝对年代进行计算。对于底部段与L段顶部，年代通过基于沉积速率的线性拟合插值得到。该年代模型未来可随着新测年数据的加入进一步完善。 尚古拉组鳄类牙齿氧同位素组成 表S2汇总了尚古拉组中采样的鳄类牙齿的形态学与同位素组成信息。缩写说明：ID为牙齿编号；Age为基于表S1中的尚古拉组年代模型得到的地层单元年龄(单位：百万年)。仅完整齿冠的牙齿会提供齿冠高度信息。地球化学分析方法的详细信息见对应论文的2.4节。 尚古拉组不同地层单元间鳄类牙齿同位素组成的成对比较 本研究采用双因素方差分析与带Holm校正的成对Wilcoxon秩和检验(非参数事后检验)，对不同地层单元间的δ¹⁸O_p差值进行了分析，结果汇总于表S3。