SGER: Late Cenozoic Rift Sedimentation, Volcanism and Tectonism in the Northern Afar: Geological Setting of the Danakil Region of Eritrea

9700870沃尔特1992年，厄立特里亚在经历了30年的战争后成为一个独立的国家。1993年6月，我们联系了阿斯马拉大学地球科学部的同事，讨论在厄立特里亚开始地质和古生物学研究的可行性。应他们的邀请，沃尔特于1994年7月访问了厄立特里亚，会见了阿斯马拉大学、地质调查局、矿产和能源部、国家博物馆和文化部。这为1995年夏天进行实地勘察铺平了道路。1996年3月获得了实地许可证（附件1）。我们建议调查厄立特里亚的达纳基尔凹陷，它是阿法尔裂谷系统的最北端，它本身就是东非裂谷的一个主要分支。具体来说，我们将研究达纳基尔凹陷北部、与凹陷相邻的悬崖以及达纳基尔北部红海沿岸的沉积盆地（图1）。我们的主要目标是研究海洋和大陆裂谷作用合并的地区的构造作用、火山作用和沉积作用的起源和演化。我们特别感兴趣的是声音学和构造学之间的相互作用，因为它们与沉积盆地的形成有关，以及陆相和海相层序之间的相关性。第二个目标是调查裂谷盆地的古人类和考古事件。这项研究的结果和观察结果将为厄立特里亚早期人科动物的进化提供见解。从广义上讲，该项目涉及厄立特里亚晚新生代沉积盆地的第一次系统调查，其综合地质，古生物学和考古学内容。这项建议寻求资金，以部分支持将于1997年1月开始的勘探项目。这一初步阶段的研究人员有：(1)Richard Buffler（德克萨斯大学奥斯汀分校，研究泥沙盆地分析、区域构造）；(2) Seife Behre（厄立特里亚公民，在厄立特里亚从事私人咨询；遥感，区域构造）；(3) Tesfaye Yemane（厄立特里亚公民，爱荷华州立大学博士研究生，沉积学与地层学）；(4) Twiede Medhin Tecle（厄立特里亚公民；厄立特里亚矿业和能源部；区域地质学）；(5) Semere Solomon（厄立特里亚公民，阿斯马拉大学，研究构造地质学）；(6)Carl Vondra（爱荷华州立大学，研究地层学、沉积学、裂谷盆地分析）；(7)Robert Walter（人类起源研究所，研究地质年代学、火山学、区域构造学）。部分支持由阿纳达科石油公司（预算）的赠款提供。这是一个最近才对科学研究开放的领域的初步项目。我们的目标之一是测试层序地层学方法对陆相盆地的分析。利用横向广泛的年代地层标志，地层剖面将被细分为区域框架，包括不整合面（基准面下降、向下切割）、洪水事件（基准面上升、沉积）和互层火山单元（流层和火山层），这些都将通过辐射测定年代。1995年对该地区进行了一次勘察，发现了若干不整合面和许多火山单元。将尝试在邻近的海洋和非海洋剖面内确定沉积旋回，并将它们与海平面和气候基准面旋回联系起来，并将它们用作对比工具。我们将利用这些信息来检验裂谷演化的模型。我们的第二个目标，确定潜在的原始人古生物遗址，也是一个可测试的假设。达纳河早期人类化石的前景。U最初是理论的，基于这样一个假设，即阿法尔北部的沉积盆地与阿法尔中部的古人类矿床是在相似的构造、地质和古环境条件下形成的，几个地质和人类学研究小组（包括国际地质组织的哈达尔研究项目）已经在那里工作了近20年。然而，1995年12月，一个意大利地质研究小组（由佛罗伦萨大学的E. Abbate领导）在达纳基尔凹陷两侧布亚附近的plio -更新世沉积物中发现了一个人类头骨（物种不确定）。他们的发现意义重大，因为它表明早期古人类确实存在于达纳基尔盆地晚新生代的沉积物中，这一次要目标有很高的成功可能性。该项目值得考虑作为探索性研究小额拨款，因为它是关于未经测试和新颖想法的初步工作（例如，陆地层序地层学和早期人类探索）。由于厄立特里亚政府可能不会无限期地持有许可证，因此开展实地工作也很紧迫。在这项研究中收集的火山岩的初步4OAr/ 39Ar定年将在多伦多大学由RCW在Derek York教授的实验室进行。

9700870 Walter In 1992, Eritrea emerged as an independence nation after a thirty year war. In June 1993, we contacted colleagues at the Earth Science Unit, University of Asmara concerning the feasibility of beginning geological and paleontological research in Eritrea. At their invitation, Walter visited Eritrea in July 1994 and met with the University of Asmara, the Geological Survey, the Ministry of Mines and Energy, the National Museum, and the Ministry of Culture. This paved the way for a reconnaissance field survey in the summer of 1995. A field permit was granted in March, 1996 (Attachment 1). We propose to investigate the Danakil Depression of Eritrea, which is the northernmost segment of the Afar Rift system, itself a major branch of the East African Rift. Specifically, we will investigate the northern Danakil Depression, the escarpments adjacent to the Depression, and the sedimentary basins along the Red Sea coast north of the Danakil (Fig. 1). Our primary objective is to study the origin and evolution of tectonism, vol.canism, and sedimentation in an area where oceanic and continental rift processes merge. We are specifically interested in the interplay between voicanism and tectonism as they relate to sedimentary basin formation, and the correlation between terrestrial and marine sequences. A secondary objective is to survley the rift basins for hominid-paleontological and archaeological occurrences. Results and observations from this study will provide insights into early hominid evolution in Eritrea. In a broad sense the project concerns the first systematic survey of late Cenozoic sedimentary basins in Eritrea for their integrated geological, paleontological and archaeological content. This proposal seeks funds to partially support an exploratory field project to begin January, 1997. Investigators in this preliminary phase are: (1) Richard Buffler (University of Texas, Austin; sediment basin analysis, regional tectonics); (2) Seife Behre (Eritrean citizen, in priva te consulting in Eritrea; remote sensing, regional tectonics); (3) Tesfaye Yemane (Eritrean citizen, Ph.D. candidate, Iowa State University; sedimentology and stratigraphy); (4) Twiede Medhin Tecle (Eritrean citizen; Eritrean Ministry of Mines and Energy; regional geology); (5) Semere Solomon (Eritrean citizen; University of Asmara; structural geology; (6) Carl Vondra (Iowa State University; stratigraphy, sedimentology, rift basin analysis) and (7) Robert Walter (Institute of Human Origins, geochronotogy, volcanology, regional tectonics). Partial support is provided by a grant from Anadarko Petroleum Corporation (Budget). This is a preliminary project in an area that has only recently been opened to scientific investigations. One of our goals is to test a sequence stratigraphic approach to terrestrial basin analysis. Stratigraphic sections will be subdivided into a regional framework using laterally extensive chronostratigraphic markers, including unconformities (base level falls, down cutting), flooding events (base level rises, aggradation), and interbedded volcanic units (flows and tephra beds) that witl be radiometrically dated. Several unconformities and numerous volcanic units were observed during a reconnaissance survey to this area in 1995. An attempt will be made to identify sedimentary cycles within adjacent marine and nonmarine sections, and to relate them to sea level and climatic base-level cycles, and to use them as correlation tools. We will use this information to test models of rift evolution. Our secondary objective, to identify potential hominid-bearing paleontological sites, is also a testable hypothesis. The prospect of early hominid fossils in the Dana.U was initially theoretical, based on the hypothesis that the sedimentary basins of northern Afar formed under similar tectonic, geological, and paleoenvirom-nental conditions as hominid-bearing deposits of the central Afar, where several geological and anthropological research groups (including IHO's Hadar Research Project) have been working for nearly twenty years. However, in December 1995 a hominid skull (species uncertain) was found by an Italian geological research team (led by E. Abbate of the University of Florence) in Plio-Pleistocene sediments near Buia along the flanks of the Danakil Depression. Their discovery is significant for it shows that early hominids are indeed present in the late Cenozoic sediments of the Danakil basin, and that this secondary objective has a high probability of success. The project merits consideration as a Small Grant for Exploratory Research because it is preliminary work on untested and novel ideas (e.g., terrestrial sequence stratigraphy and early hominid exploration). There is also an urgency to conduct field work, since the Eritrean government may not hold the permit indefinitely. Preliminary 4OAr/ 39Ar dating of volcanic rocks collected during this study will be done at the University of Toronto by RCW in the laboratory of Prof. Derek York.