FOSSIL FORESTS OF CHILGA, ETHIOPIA

Chilga, in the Gondar region of Ethiopia, is now dominated by pasture and sparse woodland but was covered with large forest trees during the late Oligocene (27 mya). Remnants of these trees are found today as in situ silicified stumps and logs. Identification of 30 genera among the preserved wood in 80 of the stumps reveals that their nearest living relatives are today found in woodlands or rain forests across Africa, with only six genera still found in the Gondar region. Here, we show the wood anatomy of these fossils, explain why we believe the identifications are reliable, and hypothesize that to support the forest physiognomy represented, the climate of the northern Ethiopian Highlands during the late Oligocene had to have been wetter with a much shorter dry season than it experiences today.