Plio-Pleistocene volcanism of Lower Bed I, Olduvai Gorge, Tanzania: transportation mechanisms, volcaniclastic sedimentation and ecological significance

坦桑尼亚奥杜瓦伊峡谷的上更新世I层系以古人类遗骸、丰富的文物和化石组合而闻名。凝灰岩层为地层格架以及考古发现的对比和年代测定提供了基础。本研究选择的凝灰岩IA至凝灰岩IB段(约1.98-1.84 Ma)，从多学科的角度来看尤其重要：(A)它提供了峡谷中最早的能人记录，(B)它记录了人类技术的最早古代，即Oldowan文化，(C)它与几个重要的占领楼层有关，(D)它包括古湖Olduvai序列，其中记录了跨越上古-更新世界线的轨道强迫记录。凝灰岩层本身提供了重要的档案：(E)东部与研究较少的西部奥杜瓦伊盆地之间的对比；(F)从玄武岩-流纹岩到粗面岩-响橄榄岩组合的双峰式变化；(G)火山碎屑流穿过同沉积活动断裂时发生的剥流/脱钩效应；(H)火山系统与具有生态吸引力的东部湖缘带的相互作用；以及(I)火山效应与区域气候对植物群和动物群的影响的相对重要性。古奥杜瓦湖的横向对比和面向过程的相分析将是这项研究的关键目标，使人们能够彻底了解火山岩与湖泊生态之间的复杂相互作用。该项目将古环境、古气候、同沉积构造和火山作用的数据与古人类学家和多学科OLAPP研究小组的考古学家贡献的人类土地利用模型结合起来。未来几年挖掘的OLAPP海沟将为以极高分辨率(毫米至厘米尺度)进行沉积学、火山学和古生态综合研究提供一个难得的机会。

The Plio-Pleistocene Bed I succession at Olduvai Gorge, Tanzania is renowned for hominin remains, rich artefacts and fossil assemblages. Tuff beds provide the basis for the stratigraphic framework and for the correlation and dating of archaeological finds. The Tuff IA to Tuff IB interval (c. 1.98-1.84 Ma), choosen for this study, is especially important from a multidisciplinary perspective: (a) It provides the earliest record of Homo habilis in the Gorge, (b) it records the earliest antiquity of Human technology, known as Oldowan culture, (c) it is associated with several important occupation floors , and (d) it includes dated Palaeo-lake Olduvai sequences that have records of orbital forcing across the Plio-Pleistocene boundary. The tuff beds themselves provide important archives of (e) the correlation between the eastern and the yet poorly studied western Olduvai Basin, (f) a change from bimodal basaltic-rhyolitic to trachytic-phonolitic compositons, (g) the occurrence of flow-stripping/decoupling effects when pyroclastic flows crossed synsedimentary active faults, (h) the interaction of volcanic systems with the ecologically attractive eastern lake margin zone, and (i) the relative importance of volcanic effects versus regional climate influences on flora and fauna.A detailed dataset is to be developed using high resolution sedimentological logging, facies, petrographic and geochemical analysis. Lateral correlations and process-oriented facies analyses across palaeo-Lake Olduvai will be the critical aim of this research, allowing a thorough understanding of the complex interactions between the volcanics and the ecology of the lake. The project integrates data on palaeoenvironments, palaeoclimate, synsedimentary tectonism and volcanism with hominin land use models contributed by palaeoanthropologists and archaeologists of the multidisciplinary OLAPP research group. OLAPP trenches excavated over the next few years will provide an exceptional opportunity for combined sedimentological, volcanological and palaeoecological studies at an extremely high resolution (mm to cm scale).