Response of East African climate to orbital forcing during the last two glacial-interglacial cycles: The Lake Naivasha Coring Project

晚更新世热带气候的高质量年表在有关冰川消退的热带强迫的讨论中变得越来越重要，即，从冰期到间冰期的过渡这一假说的关键论点是，热带气候导致高纬度冰量几千年。热带地区的冰川消退力也有助于解释为什么冰河期在两个半球同时发生，尽管轨道变化引起的太阳辐照度变化在两个半球产生相反的影响。奈瓦沙湖提供了一个独特的机会，通过沉积物中反映的沉积物和古生态变化，研究过去两个冰川-间冰期周期（约175 kyr）期间热带气候变化的连续记录。我们提出了一个两步战略，以重建在这一时期的湖泊历史：（A）高分辨率地震调查，以表征沉积环境，湖泊水位波动和新构造在奈瓦沙盆地。该调查还将为（B）两个50和40米长的沉积物芯从目前的湖区的最佳网站。这些沉积物记录预计将填补一个充分研究的部分之间的差距差距暴露在现在的湖泊南部（175至60 kyr之前）和两个沉积物芯研究在20世纪60年代（25 kyr到现在）。

High-quality chronologies of late Pleistocene tropical climate have become increasingly important in discussions concerning tropical forcing of deglaciation, i.e., the transition from a glacial to an interglacial. The key argument of this hypothesis is that tropical climate leads high-latitude ice volumes by several thousand years. A tropical forcing of deglaciation would also help to explain why ice ages occur in both hemispheres simultaneously, although the changes in solar irradiance from orbital variations have opposite effects in the two hemispheres. Lake Naivasha provides a unique opportunity to study a continuous record of tropical climate changes during the last two glacial-interglacial cycles (approximately 175 kyr) through sedimentologic and paleoecologic changes reflected in the sediments. We propose a two-step strategy to reconstruct the lake history during this period: (A) a high-resolution seismic survey to characterize the depositional setting, lake-level fluctuations and neotectonics in the Naivasha basin. This survey will also guide up to the best sites for (B) two 50- and 40-m-long sediment cores from the present lake area. These sediment records are expected to fill the gap between a well-studied section exposed south of the present lake (175 to 60 kyr before present) and two sediment cores studied in the 1960's (25 kyr to present).