The Menengai Tuff: A 36 ka widespread tephra and its chronological relevance to Late Pleistocene human evolution in East Africa
The Menengai Tuff: A 36 ka widespread tephra and its chronological relevance to Late Pleistocene human evolution in East Africa
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DOI：
10.1016/j.quascirev.2016.09.020
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发表时间：
2016-11-15
影响因子：
4
通讯作者：
Tryon, Christian A.
中科院分区：
文献类型：
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作者：
Blegen, Nick;Brown, Francis H.;Tryon, Christian A.
东非裂谷保存了世界上最丰富的中更新世和晚更新世（类似于780- 12ka）的地质、考古和古生物档案，这些档案与智人的出现有关。该地区还通过风化年代学、火山灰的年代测定和对比，作为地质记录中广泛存在的等时标志，为许多重要遗址提供了无与伦比的年代控制。东非广泛分布着许多具有明显特征的上新世-早更新世tephras。中更新世和晚更新世缺乏类似的框架；一个以空间和时间复杂的气候变化模式为特征的时期，以及现代智人的出现和这种物种在非洲各地和非洲以外的扩散。解开这些空间和时间上复杂的现象之间的关系需要一个精确的年表。为此，我们报告了Menengai凝灰岩，这是肯尼亚大规模火山口喷发产生的一种广泛存在的火山灰，40Ar/39Ar年代为35.62 +/- 0.26 ka。利用波长色散电子探测器对36个样品中的565块玻璃碎片进行了地球化学特征分析，结果表明Menengai凝凝岩的沉积距离约115,000 km(2)，分布在Baringo、Chalbi、Elmenteita、Nakuru、Olorgesailie、Turkana和Victoria盆地，这些盆地都保存了丰富的晚更新世古环境和考古档案。Menengai凝灰岩的对比和年代测定表明，这是目前已知的东非晚更新世最广泛和最大的火山喷发。因此，它是建立与人类进化研究相关的古气候、考古和古生物记录的晚更新世年代学的一个有价值的标志。(C) 2016年Elsevier Ltd.出版
The East African Rift preserves the world's richest Middle and Late Pleistocene (similar to 780-12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40Ar/39Ar dated to 35.62 +/- 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km(2) and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution. (C) 2016 Published by Elsevier Ltd.