Geological summary of the Busidima Formation (Plio-Pleistocene) at the Hadar paleoanthropological site, Afar Depression, Ethiopia
Geological summary of the Busidima Formation (Plio-Pleistocene) at the Hadar paleoanthropological site, Afar Depression, Ethiopia
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DOI：
10.1016/j.jhevol.2011.05.002
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发表时间：
2012-03-01
影响因子：
3.2
通讯作者：
Campisano, Christopher J.
中科院分区：
文献类型：
--
作者：
Campisano, Christopher J.
埃塞俄比亚的哈达尔古人类学遗址保存了大约3.45 Ma至0.8 Ma的人类进化记录。一个角状不整合面就在火山口上方。2.95 Ma BKT-2复合体将沉积物划分为Hadar组（约200米）。3.8-2.9 Ma）和布西迪马组（约。2.7-0.15Ma）。不整合面可能是对阿法尔凹陷的一次重大构造重组的反应，埃塞俄比亚陡崖（哈达尔以西）附近的As Duma断层的活化形成了一个半地堑，其中沉积了Busidima组。该地区的沉积模式和特征在不整合面上方发生了巨大变化，因为构成布西迪玛组的切填河道砾岩和以淤泥为主的古土壤与哈达尔组的底层沉积形成鲜明对比。砾岩沉积与常年的轴向古阿瓦什河和短暂的陡崖排水支流有关。漫滩的淤泥中发现了早期人属和奥氏石器的化石。许多凝灰质沉积物存在于布西迪马组中，但它们通常在空间上有限，粒度细，并经过改造。最近对哈达尔的Busidima组火山灰地层框架的研究已经确定了至少12个不同的玻璃质火山灰，并建立了哈达尔与邻近的Gona和Dikika项目区之间的第一个基于地球化学的相关性。与Busidima组沉积物大面积暴露的Gona和Dikika相比，Hadar高度不连续的沉积物的复合剖面不到40 m，暴露面积为
The Hadar paleoanthropological site in Ethiopia preserves a record of hominin evolution spanning from approximately 3.45 Ma to 0.8 Ma. An angular unconformity just above the ca. 2.95 Ma BKT-2 complex divides the sediments into the Hadar Formation (ca. 3.8-2.9 Ma) and the Busidima Formation (ca. 2.7 -0.15 Ma). The unconformity is likely a response to a major tectonic reorganization in the Afar Depression, and activation of the As Duma fault near the Ethiopian Escarpment (west of Hadar) created a half-graben in which the Busidima Formation was deposited. The pattern and character of sedimentation in the region changed dramatically above the unconformity, as cut-and-fill channel conglomerates and silt-dominated paleosols that comprise the Busidima Formation stand in sharp contrast to the underlying deposits of the Hadar Formation. Conglomerate deposition has been related to both the perennial, axial paleo-Awash and ephemeral, escarpment-draining tributaries. Overbank silts have yielded fossils attributed to early Homo and Oldowan stone tools. Numerous tuffaceous deposits exist within the Busidima Formation, but they are often spatially limited, fine-grained, and reworked. Recent work on the tephrostratigraphic framework of the Busidima Formation at Hadar has identified at least 12 distinct vitric tephras and established the first geochemical-based correlations between Hadar and the neighboring project areas of Gona and Dikika. Compared to Gona and Dikika, where Busidima Formation sediments are exposed over large areas, the highly discontinuous sediments at Hadar comprise less than 40 m in composite section and are exposed over an area of