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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Correlation of Plio-Pleistocene Tephra in Ethiopian and Kenyan rift basins: Temporal calibration of geological features and hominid fossil records
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Correlation of Plio-Pleistocene Tephra in Ethiopian and Kenyan rift basins: Temporal calibration of geological features and hominid fossil records

机译：埃塞俄比亚和肯尼亚裂谷盆地上新世-新世特非拉的相关性：地质特征和原始化石记录的时间校准

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The 200-m-thick fossiliferous Konso Formation and overlying terrace deposits, which crop out at the end of the southern sector of the Main Ethiopian Rift (MER), contain more than 30 distal tephra layers. Local and regional tephra correlations of more than 20 tephra units were established using major and trace element data of discrete and purified bulk glass samples within the Konso study area. Eleven correlative marker tuffs were recognized in stratigraphic sections of both the Konso Formation and the Omo-Turkana Basin sediments in southern Ethiopia and northern Kenya. The Turoha, Hope, Ivory, Bright White, and Boleshe Tuffs in the Konso Formation, and the Upper White Tuff in the overlying terrace deposits are securely correlated with the KBS, Akait, Lokapetamoi, Chari, Lower Nariokotome, and Silbo Tuffs of the Omo-Turkana Basin, using least mobile major elements (CaO, Fe_2O_3~*, and TiO_2) and geochronology. Preliminary correlations are also suggested between the Konso Formation distal tephra and proximal units of the Quaternary caldera-forming silicic centers in the central sector of the MER. The strongly peralkaline tuffs of the Konso Formation are compositionally similar to proximal eruptions mostly located along the Quaternary axial rift zone of the southern, central, and northern sectors of the MER. The tephra correlation provides information about the temporal and spatial features of the volcanic and tectonic processes recorded in the evolving basins. Thickness and sedimentation rate were determined for both the Konso Formation and the Omo-Turkana Basin sections, measured between the Turoha (=KBS; 1.91 ±0.03 Ma) and the Bright White (=Chari; 1.40 ±0.02 Ma) Tuffs. Although the lithostratigraphic sequence at the Konso study area is younger, sedimentation rate within the Konso Formation was comparable to that of the Koobi Fora Formation, higher in the Nachukui Formation, and lower in the Shungura Formation. Local and regional differences in thickness and sedimentation rates within the Plio-Pleistocene deposits of the Konso, Shungura, Nachukui, and Koobi Fora Formations may be attributed to erosion associated with increased topographic gradients maintained by continued subsidence mostly along axial fault zones of basins and uplift along the margins of the broadly rifted zone of the Omo-Turkana Basin and the southern sector of the MER.
机译：在埃塞俄比亚主裂谷（MER）南部扇形断层末端长出的200米厚的化石Konso地层和上层阶地沉积物包含30多个末生的特发拉层。利用Konso研究区域内离散和纯化的散装玻璃样品的主要和微量元素数据，建立了超过20个单位单位的本地和区域单位信息。在埃塞俄比亚南部和肯尼亚北部的孔索组和奥莫-图卡纳盆地沉积物的地层中识别出11个相关的凝灰岩。 Konso组中的Turoha，Hope，Ivory，Brighthe和Boleshe凝灰岩，以及上伏阶地沉积物中的上白凝灰岩与奥莫的KBS，Akait，Lokapetamoi，Chari，Lower Nariokotome和Silbo Tuffs安全相关-图尔卡纳盆地，使用最少的流动性主要元素（CaO，Fe_2O_3〜*和TiO_2）和年代学。还建议在MER中央区的Konso组远端特弗拉与第四纪火山口形成硅质中心的近端单元之间存在初步相关性。 Konso组的强碱性碱性凝灰岩在构造上与近端喷发相似，这些喷发大多位于MER南部，中部和北部的第四纪裂谷带。特弗拉相关性提供了有关演化盆地中记录的火山和构造过程的时空特征的信息。确定了Konso组和Omo-Turkana盆地剖面的厚度和沉积速率，在Turoha（= KBS; 1.91±0.03 Ma）和亮白（= Chari; 1.40±0.02 Ma）凝灰岩之间测量。尽管孔苏研究区的岩石地层层序较年轻，但孔苏组内的沉积速率可与库比孔组相媲美，在纳库凯组较高，而在顺古拉组则较低。 Konso，Shungura，Nachukui和Koobi Fora组的上新世沉积的厚度和沉积速率在局部和区域上的差异可能归因于与沉降梯度增加有关的侵蚀，这些沉降梯度主要由盆地的轴向断层带和不断隆起引起的持续沉降所维持沿Omo-Turkana盆地宽裂带的边缘和MER的南部。

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