Mahenge Formation
| Mahenge Formation | |
|---|---|
| Stratigraphic range: | |
| Type | Sedimentary |
| Overlies | Precambrian basement (Nyanzian Belt) |
| Lithology | |
| Primary | Mudstone, shale |
| Location | |
| Coordinates | 4°48′S 34°18′E / 4.8°S 34.3°E |
| Approximate paleocoordinates | 18°00′S 33°00′E / 18.0°S 33.0°E |
| Country | Tanzania |
| Type section | |
| Named for | Mahenge |
The Mahenge Formation is a Middle Eocene-aged geological formation and Konservat-Lagerstätte from Tanzania. It contains a high variety of exceptionally-preserved fossils, including many of the earliest fossil records of dominant freshwater fish groups found in Africa today. It represents one of the most comprehensive Paleogene-aged African fossil deposits south of the Sahara. Based on fossil plant remains found in the formation, the Mahenge lake was situated within legume-dominated woodlands reminiscent of modern miombo forests.
It was deposited within a former maar lake formed from a volcanic intrusion into the Precambrian bedrock via a kimberlite pipe. It has been dated to the Lutetian, roughly 46.0 million years ago. Unusually, relatively few fossil insect remains are known from the lake, unlike with other maar deposits. It is thought that the high diversity of fish in the lake may have led to most insects being consumed before they could be fossilized.