Former Lake Levels and Climatic Change in the Rift Valley of Southern Ethiopia

Abstract

Lakes in the Ethiopian rift are sensitive indicators of Late Quaternary climates. Lake Stefanie (Chew Bahir), which has been dry most of this century, was 20 m deep about 5660 years ago. Fed from Lakes Abaya and Chamo it probably over flowed to Lake Rudolf at that time and was a part of the Nile system. The four Galla lakes, Ziway, Langano, Abiyata and Shala, were united into one large lake which bverflowed to the Awash River in the Late Pleistocene/Early Holocene. Beach deposits contain sub-fossil mollusca, some of which have Palaearctic afnnities. Fish remains are abundant in a bed a few metres above Lake Shala between diatomaceous lake floor deposits. A form of Barbus occurs which resembles the North African B. callensis. Algal limestones from Stefanie and the Galla lakes basin are described and their significance discussed.