PRELIMINARY RESULTS OF THE LAKE MALAWI DRILLING PROGRAM

A major drilling project was undertaken on Lake Malawi in February – March 2005 to recover long, continuous records of past climate change in the southern tropics of East Africa. Lake Malawi is the second largest lake in the East African Rift Valley. It is about 650 km long, 40 km wide, and has a maximum depth of 700 m. The lake is anoxic below a depth of 200 m. The drilling project recovered a 380 m long record from a deep-water site (600 m water depth) in the central basin, spanning the past 1.5 to 2 million years. A second site in about 350 m depth in the north basin was triple cored to the first hard reflector, 38 m below the lake floor, corresponding to an age of about 100,000 years. The sediments are primarily diatomaceous silty clays, in places finely laminated (probably varved). The predominant carbonate found throughout much of the cored sequence is siderite in relatively low abundance, but certain horizons, likely corresponding to past lowstands, contain calcite or aragonite. Piston cores from the north basin in the past have revealed a rich, 25,000-year record of past lake water temperature and dynamic response of the Intertropical Convergence Zone to global climate forcing. This talk will provide an oversight of the unprecedented lake drilling operations and preliminary results to date.