The origins of lacustrine oil source rocks: evidence from the lakes of tropical Africa

Summary New data from core samples are presented on organic matter accumulation during the last 10 000–15 000 years in six tropical African lakes. Pyrolysis and maceral studies indicate that in most of these lakes the preserved organic matter is a mixture of phytoplankton and higher plant remains showing varying degrees of bacterial degradation. Organic assemblages dominated by phytoplankton material have not been encountered. Sediments with the richest oil potential accumulate in meromictic or monomictic lakes during periods when the climate is humid and surface winds are relatively slack. The evidence from tropical Africa does not support current theories that shallow saline lakes may be especially favourable sites for the accumulation of oil prone sediment.