The Nsungwe Formation is a formation in the

Rukwa Rift Basin The Rukwa Rift Basin, located in southwestern Tanzania, is an endorheic rift basin that contains Lake Rukwa. It forms part of the East African Rift system and has produced a number of Cretaceous and Oligocene The Oligocene ( ) is a geologic epoc ...

of the

East African Rift System East is one of the four cardinal directions or points of the compass. It is the opposite direction from west and is the direction from which the Sun rises on the Earth. Etymology As in other languages, the word is formed from the fact that eas ...

, it is

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

in age based on U-Pb dating of a

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...

horizon within the formation. It is part of the Red Sandstone Group along with the uncomfortably underlying Mid-Cretaceous

Galula Formation The Galula Formation is a geological formation located south of Lake Rukwa in Tanzania, part of the Red Sandstone Group of the Rukwa Rift Basin. Along with the unconformably overlying Oligocene Nsungwe Formation. It is divided into two members, ...

It is divided into two members, the lower Utengule Member, and the upper Songwe member. It is notable for being one of the most important Paleogene fossil deposits in Sub-Saharan Africa.

Geology

The lithology of the two members are quite different, representing different fluvial environments. The Utengule member is 85 m thick and predominantly consists of red-orange sandstones and matrix to clast supported conglomerates. The overlying Songwe Member is approximately twice as thick as the Utengule member, being 310–320 m thick in the type section. It is much finer grained, consisting of red-orange and grey green claystones, siltstones, mudstones, lenticular sandstones and tuffs. The sediments of the Songwe Member are noted for their fossil content.

Fossil content

Important fossils have come out of the formation, including the rodent '' Kahawamys'', some of the oldest records of the

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

genus ''

Xenopus ''Xenopus'' () (Gk., ξενος, ''xenos'' = strange, πους, ''pous'' = foot, commonly known as the clawed frog) is a genus of highly aquatic frogs native to sub-Saharan Africa. Twenty species are currently described with ...

'', the hyaenodont '' Pakakali'', the

elephant shrews Elephant shrews, also called jumping shrews or sengis, are small insectivorous mammals native to Africa, belonging to the family Macroscelididae, in the order Macroscelidea. Their traditional common English name "elephant shrew" comes from a perc ...

Oligorhynchocyon ''Oligorhynchocyon'' is an extinct genus of rhynchocyonine macroscelidean that lived in Tanzania during the Chattian. It contains the species A species () is often defined as the largest group of organisms in which any two individuals of ...

'' and '' Rukwasengi'', and the primates '' Nsungwepithecus'' and '' Rukwapithecus'', some of the earliest

crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, parti ...

catarrhine The parvorder Catarrhini (known commonly as catarrhine monkeys, Old World anthropoids, or Old World monkeys) consists of the Cercopithecoidea and apes (Hominoidea). In 1812, Geoffroy grouped those two groups together and established the name Ca ...

References

{{reflist Geologic formations of Tanzania Oligocene Series of Africa Chattian Stage Sandstone formations Fluvial deposits Paleontology in Tanzania