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合谋影响，需要一种整体的方法来破译岩心中反映的古环境变化。这种方法必须重建沉积物源-流-汇系统的构造地貌特征，因为侵蚀和沉积物输运主要是地形、气候和岩性的函数。在这里，我们提出了这样一个研究的Chew Bahir流域在埃塞俄比亚南部，旨在连接盆地的构造地貌演化与沉积路由系统，并最终的沉积记录的Chew Bahir钻井现场，将获得的主持下，国际大陆钻探计划（ICDP）。预计回收的岩心对应的时间跨度至少为800- 1200 kyr，旨在提供环境变化数据，以更好地评估人类进化和迁移。通过整合我们的流域范围内的研究与钻井记录，我们的目标是反卷积气候和构造强迫影响沉积物的路由和沉积在Chew Bahir盆地。我们的研究结果将提高对伸展系统沉积记录的三个重要方面及其与主要人类迁移走廊的关系的理解。其中包括：1）影响景观发展的强迫机制; 2）沉积物的产生和沉积;和3）沉积矿床在东非裂谷的一个关键部门的古环境意义。为了实现这些目标，我们将遵循一个四层的方法：一）确定沉积物来源和路由的物源分析和定年的河流阶地的时空变化;二）量化现代和过去的侵蚀率使用宇宙成因核素和沉积物量估计地震反射剖面;三）建立河流捕获和排水逆转的时间在集水区;将构造地貌演化与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14 C来限制阶地沉积物的年龄，以覆盖广泛的年龄谱。我们的地貌分析将得到从TanDEM-X数据获得的12米数字高程模型的帮助。总之，构造地貌分析，物源研究和沉积矿床的新地质年代学将提供一个前所未有的数据集，最终将与盆地中心钻孔的沉积记录相关联，从而有助于我们了解活动构造和反复气候变化下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.