MIDDLE PLEISTOCENE DIATOM PALEOECOLOGY OF LAKE MALAWI, EAST AFRICA

Here we present a ~180 ka record of diatom paleoecology developed from part of the 2005 Lake Malawi deep scientific drill core. Our new record is composed of ~450 samples, ranging in age from ~220-400 ka, which extends the previously published diatom dataset from Lake Malawi. This proxy record incorporates a new age model based upon 39 luminescence ages that for the first time provide absolute ages for this interval. The diatom assemblage is Aulacoseira dominated, indicating high nutrient and high silica conditions. There are isolated intervals of dominance by Thalassiosira and Cyclotelloid diatoms, indicating low nutrient, saline, and alkaline conditions. Though this is a deep-water site, ~590 m water depth today, benthic diatoms form a significant part of the assemblage throughout. The changes in the concentration of benthic diatoms indicate changes in transport within the lake. While many dominant taxa are undescribed and thus do not have known nutrient preferences at the species level, changes in Aulacoseira valve size indicate changes in mixing strength. This new diatom record complements existing proxy records for this core and provides greater insight into seasonality and internal lake dynamics.