Radioisotopic age, formation, and preservation of Late Pleistocene human footprints at Engare Sero, Tanzania
Radioisotopic age, formation, and preservation of Late Pleistocene human footprints at Engare Sero, Tanzania
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DOI：
10.1016/j.palaeo.2016.09.019
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发表时间：
2016-12-01
影响因子：
3
通讯作者：
Rossi, V.
中科院分区：
文献类型：
--
作者：
Liutkus-Pierce, C. M.;Zimmer, B. W.;Rossi, V.
我们报道了坦桑尼亚北部的一个晚更新世人类足迹遗址的放射性同位素年龄、形成和保存情况，该遗址位于纳特龙湖南岸，靠近Engare Sero村。在一系列火山碎屑沉积中保存了400多个人类脚印，以及斑马和牛的足迹。根据野外填图、地球化学和粒度分析，我们认为这些矿床起源于附近活火山Oldoinyo L‘engai的近火山物质，并被河流输送到足迹地点。稳定同位素结果(三角洲O-18和三角洲C-13)表明，足迹最初侵位于被淡水泉水饱和的泥滩上，后来被纳特龙湖上升的碱性水位淹没。我们利用40Ar/39Ar和C-14测年方法对遗址的年龄进行了调查，确定足迹水平超过5760+/-30年。BP和小于19.1+/-3.1ka。这些放射性同位素年龄得到了与以前记录的碎片雪崩沉积的地层学对比以及与纳特龙湖最近的高位相关的稳定同位素特征的支持，进一步将年龄限制在最新的更新世。由于现代人(智人)出现在约200ka的非洲，Engare Sero代表了目前已知的非洲解剖学上最丰富和保存最完好的现代人足迹遗址。化石足迹是时间上的快照，记录了历史上特定时刻的行为；但快照捕获的实际持续时间通常没有很好的定义。通过模拟实验，我们将指纹制作、埋藏和最终保存的沉积窗口限制在几个小时到几天或几个月内。(C)2016爱思唯尔B.V.保留所有权利。
We report on the radioisotopic age, formation, and preservation of a late Pleistocene human footprint site in northern Tanzania on the southern shore of Lake Natron near the village of Engare Sero. Over 400 human footprints, as well as tracks of zebra and bovid, are preserved in a series of volcaniclastic deposits. Based on field mapping along with geochemical and grain-size analyses, we propose that these deposits originated as proximal volcanic material from the nearby active volcano, Oldoinyo L'engai, and were then fluvially transported to the footprint site. Stable isotope results (delta O-18 and delta C-13) suggest that the footprints were originally emplaced on a mudflat saturated by a freshwater spring and were later inundated by the rising alkaline waters of Lake Natron. We employed the 40Ar/39Ar and C-14 dating methods to investigate the age of the site and determined that the footprint level is older than 5760 +/- 30 yrs. BP and younger than 19.1 +/- 3.1 ka. These radioisotopic ages are supported by stratigraphic correlations with previously documented debris avalanche deposits and the stable isotope signatures associated with the most recent highstand of Lake Natron, further constraining the age to latest Pleistocene. Since modern humans (Homo sapiens) were present in Africa ca. 200 ka, Engare Sero represents the most abundant and best-preserved footprint site of anatomically modern Homo sapiens currently known in Africa. Fossil footprints are a snapshot in time, recording behavior at a specific moment in history; but the actual duration of time captured by the snapshot is often not well defined. Through analog experiments, we constrain the depositional window in which the prints were made, buried, and ultimately preserved to within a few hours to days or months. (C) 2016 Elsevier B.V. All rights reserved.