Explosive Volcanism in the Kenyan Rift: A Tephrostratigraphic Perspective

这个博士旨在建立在正在进行的工作，建立一个广泛的和详细的非洲东部裂谷火山灰地层框架。完成后，这个框架将提供必要的年代控制的古环境和考古记录，从而有助于进一步了解热带水文气候变化和人类进化的更新世和全新世早期。在这里，肯尼亚裂谷的火山灰地层学将通过三个湖泊记录内的隐火山灰（显微火山灰）层的识别和表征进行调查。其中第一个将是查拉湖，一个位于基利曼哈罗山脚下的火山口湖，提供250 kyrs的环境数据。这个核心的一个子部分集中在MIS 1 -3将分析隐火山喷发，在那里的相关性将与源喷发使用其独特的玻璃成分。对于已知的喷发，这将提供精确的地核深度的准确日期，从而有助于完善Blaauw等人的研究。的放射性碳年龄深度模型。这项研究还预计将记录新的、未知的喷发，这将促使进一步调查它们的年龄和起源。一旦查拉湖内的隐石层被充分表征，将对奈瓦沙湖和鲁通杜湖的30 kyr沉积物岩心进行平行调查，并可能扩展到附近的考古序列。在隐火山灰层可以在这些记录，并与已经建立的维多利亚湖盆地的火山灰地层学，一个主年表的古环境和考古研究将提出相关。

This PhD seeks to build on ongoing work to establish a widespread and detailed tephrostratigraphic framework for the East African Rift. When complete this framework will provide essential chronological control for palaeoenvironmental and archaeological records, thus helping to further our understanding of tropical hydroclimatic variability and human evolution during the Pleistocene and early Holocene. Here the tephrostratigraphy of the Kenyan Rift Valley will be investigated through the identification and characterisation of cryptotephra (microscopic tephra) layers within three lake records. The first of these will be Lake Challa, a crater lake at the base of Mt Kilimanjaro providing 250kyrs of environmental data. A subsection of this core focusing on MIS1-3 will be analysed for cryptotephra, where correlations will be made with source eruptions using their unique glass composition. For known eruptions this will provide accurate dates for precise depths of the core, thus helping to refine Blaauw et al.'s (2011) radiocarbon-based age-depth model. This research is also anticipated to document new, unknown eruptions which will prompt further investigation into their age and origin. Once cryptotephra layers are fully characterised within Lake Challa, parallel investigations will take place on the 30kyr sediment cores of Lake Naivasha and Lake Rutundu, with possible extension to nearby archaeological sequences. Where cryptotephra layers can be correlated across these records, and with the already established tephrostratigraphy of the Lake Victoria Basin, a master chronology for palaeoenvironmental and archaeological research will be proposed.