The Chew Bahir Drilling Project - Deconvolving climatic versus tectonic forcing in the source-to-sink sediment system of extensional provinces: New insights from the Chew Bahir Basin, South Ethiopia

大陆裂谷复杂的运动学演化以及气候和构造对地表过程系统的共同影响，需要一种整体的方法来破译钻芯中反映的古环境变化。这种方法必须重建沉积物来源-路线-汇系统的构造地貌特征，因为侵蚀和泥沙运移主要是地形、气候和岩性的函数。在这里，我们提议对埃塞俄比亚南部的Chew Burir集水区进行这样一项研究，旨在将盆地的构造地貌演变与沉积物输送系统联系起来，并最终在国际大陆钻探计划(ICDP)的主持下获得Chew Burir钻探地点的沉积记录。回收的钻芯预计至少对应于最终800-1200 Kyr的间隔，旨在提供有关环境变化的数据，以更好地评估原始人的进化和迁徙。通过将我们在整个流域的研究与钻探记录相结合，我们的目标是消除气候和构造强迫对周伯勒盆地沉积物路线和沉积的影响。我们的结果将加深对伸展系统沉积记录的三个重要方面的理解，以及它们与主要的人类迁徙走廊的关系。这些问题包括：1)影响地貌发展的强迫机制；2)沉积物的生产和沉积；3)东非裂谷关键地段沉积沉积的古环境意义。为了实现这些目标，我们将采用四层方法：i)通过河流阶地的物源分析和测年，确定沉积物来源和路线的时空变化；ii)利用从地震反射剖面估计的宇宙核素和沉积物体积，量化现代和过去的侵蚀速率；iii)确定流域内河流捕获和排水逆转的时间；以及iv)将构造地貌演变与ICDP钻孔的沉积记录联系起来。我们将在物源分析中使用沉积学技术，并使用宇宙成因核素和14C来限制阶地沉积的年龄，以涵盖广泛的年龄谱。我们的地貌分析将得到从Tandem-X数据获得的12米数字高程模型的辅助。总之，沉积矿床的构造地貌分析、物源研究和新的地质年代学将提供一个史无前例的数据集，最终将与盆地中心钻孔的沉积记录联系在一起，从而有助于我们从活动构造和反复气候变化的角度理解环境变化与人类进化之间的联系。

The complex kinematic evolution of continental rifts and the conspiring effects of climate and tectonics on the surface-process system requires a holistic approach in deciphering paleoenvironmental changes reflected in drill cores. Such an approach must entail the reconstruction of the tectono-geomorphic characteristics of the sediment source-routing-sink system, because erosion and sediment transport are mainly a function of topography, climate, and lithology. Here, we propose such a study of the Chew Bahir catchment in southern Ethiopia, aimed at linking the tectonogeomorphic evolution of the basin with the sediment-routing system, and ultimately the depositional record of the Chew Bahir drilling site, to be obtained under the auspices of the International Continental Drilling Program (ICDP). The recovered drill core is expected to corresponding to an interval spanning at least the ultimate 800-1,200 kyr, targeted to provide data on environmental change to better assess hominin evolution and migration. By integrating our catchment-wide study with the drilling record we aim at deconvolving climatic and tectonic forcing impacting sediment routing and deposition in the Chew Bahir basin. Our results will improve the understanding of three important aspects of the sedimentary records of extensional systems and their relationship with major hominin migration corridors. These include: 1) the forcing mechanisms impacting landscape development; 2) sediment production and deposition; and 3) the paleo-environmental significance of sedimentary deposits in a crucial sector of the East African Rift. In order to achieve these goals, we will follow a four-tiered approach: I) determine the spatiotemporal variations in sediment sources and routing by provenance analysis and dating of fluvial terraces; II) quantify modern and past erosion rates using cosmogenic nuclides and sediment volumes estimated from seismic reflection profiles; III) establish the timing of fluvial captures and drainage reversals in the catchment; and IV) link the tectono-geomorphic evolution with the sedimentary record of the ICDP drillhole. We will use sedimentological techniques in provenance analysis and constrain the age of terrace deposits using cosmogenic nuclides and 14C, to cover a broad age spectrum. Our geomorphic analysis will be aided by 12-m digital elevation models obtained from TanDEM-X data. Together, the tectono-geomorphic analysis, the provenance study, and new geochronology of sedimentary deposits will provide an unprecedented data set that will be ultimately linked to the depositional record of the drillhole in the basin center, thus contributing to our understanding of the link between environmental change and hominin evolution in light of active tectonics and repeated climate change.