(ESH) Collaborative Research: Lake Quaternary Climatic and Glacial History of Africa from Cosmogenic Dating of Glacial and Lake Deposits

9632277 Zreda重建过去冰川和闭合盆地湖泊的时间和范围，对于了解第四纪期间的区域和全球气候变化至关重要。在热带地区，特别是赤道非洲，这种数据是非常需要的，因为根据陆地记录推断的古气候与使用大气环流模型计算的古气候之间存在着相当大的差异。开发高质量的陆地古气候数据库是古气候学的主要研究需求之一。拟议的研究通过提供赤道和次赤道非洲气候敏感地区的准确日期的定量气候替代数据，有助于满足这些需求。在亚热带西北部的高山地区(高地图集)和非洲中东部的热带地区(肯尼亚和乞力马扎罗山等)发现了冰川沉积并绘制了地图。在这些地点，多个冰川系统记录了过去的冰川范围，并提供了以前气候波动的重要指标。由于缺乏与冰川沉积相关的可测年物质，这些地貌中很少有数字测年。因此，当地的年表主要基于地貌之间的地层关系和相对风化研究。我们建议使用宇宙成因同位素测年方法(36Cl、10Be、26Al、14C、21Ne和3He)来建立过去10万年或更长时间的非洲冰川年代学。我们还计划使用宇宙源核素来确定古湖岸线的年代，这些海岸线位于可接近的位置，那里的海岸线保存得很好，到目前为止有合适的表面。来自这些敏感地点的高分辨率冰川和湖泊年表应提供与了解控制非洲赤道和亚热带地区第四纪晚期气候因素有关的重要数据。拟议项目的最终目标是将从上述来源获得的地质年代学信息综合成连贯的古气候记录，并将这一区域重建置于第四纪晚期全球气候变化的背景下。我们在非洲收集的地质和古气候数据将有助于建立以宇宙源测年为基础的全球更新世冰川数据库。研究结果将对第四纪地质学、地貌学、冰川学、地球化学、古气候学、大气科学和水文学等领域的研究人员具有重要的参考价值。?？

9632277 Zreda Reconstruction of the timing and extent of past glaciers and closed-basin lakes is critical for understanding regional and global climatic changes during the Quaternary. Such data are critically needed in the tropics, and equatorial Africa in particular, because of considerable discrepancy between paleoclimates deduced from terrestrial records and those calculated using general circulation models. Development of high quality terrestrial paleoclimatic data bases is one of the primary research needs in paleoclimatology. The proposed research contributes to fulfilling these needs by providing accurately dated, quantitative climatic proxy data for climatically sensitive locations in the equatorial and subequatorial Africa. Glacial deposits have been recognized and mapped in alpine regions of subtropical northwestern (the High Atlas) and tropical east-central Africa (Kenya and Kilimanjaro, among others). At these locations, multiple moraine systems record past glacier extent and provide an important proxy of previous climatic fluctuations. Very few of these landforms have been numerically dated because of lack of datable material associated with glacial deposits. Consequently, local chronologies have been based mainly on stratigraphic relationships between landforms and comparative relative weathering studies. We propose to use cosmogenic isotope dating methods (36Cl,10Be, 26Al,14C, 21Ne and 3He) to establish chronology of glaciations in Africa for the past 100,000 years or more. We also plan to use cosmogenic nuclides to date paleolake shorelines from accessible locations where strand lines are well preserved and have appropriate surfaces to date. High resolution glacial and lake-level chronologies from these sensitive locations should provide important data relevant to understanding the factors controlling late Quaternary climates in equatorial and subtropical regions of Africa. The final goal of the proposed project is to synthesize the geochronological inf ormation obtained from the above sources into a coherent paleoclimatic record and to place this regional reconstruction in the context of global climate change in the late Quaternary. Our geological and paleoclimatic data collected in Africa will contribute to the construction of the global database of Pleistocene glaciations based on cosmogenic dating terrestrial deposits. The results will be valuable for researchers in the areas of Quaternary geology, geomorphology, glaciology, geochemistry, paleoclimatology, atmospheric sciences and hydrology. ??