Nsungwe Formation

The Nsungwe Formation is a formation in the Rukwa Rift Basin of the East African Rift System, it is Oligocene in age based on U-Pb dating of a tuff horizon within the formation. It is part of the Red Sandstone Group along with the uncomfortably underlying Mid-Cretaceous Galula Formation 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.

Nsungwe Formation
Stratigraphic range: Oligocene ~25.2 Ma
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TypeGeological formation
Unit ofRed Sandstone Group (Rukwa Rift Basin)
Sub-unitsUtengule Member, Songwe Member
UnderliesUnconformity with Lake Beds Sequence
OverliesUnconformity with Galula Formation
Thickness400 m (1,300 ft)
Lithology
PrimarySandstone
OtherConglomerate, mudstone, siltstone, tuff
Location
LocationRukwa, Mbeya Region
RegionAfrican Great Lakes
Country Tanzania
Type section
Named forNsungwe River
Named byRoberts et al.
Year defined2010
Thickness at type section~400 m

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.[1]

Fossil content

Important fossils have come out of the formation, including the rodent Kahawamys,[2] some of the oldest records of the genus Xenopus.[3] And the Hyaenodont Pakakali.[4]

References
  1. Roberts, Eric M.; O’Connor, Patrick M.; Stevens, Nancy J.; Gottfried, Michael D.; Jinnah, Zubair A.; Ngasala, Sifael; Choh, Adeline M.; Armstrong, Richard A. (May 2010). "Sedimentology and depositional environments of the Red Sandstone Group, Rukwa Rift Basin, southwestern Tanzania: New insight into Cretaceous and Paleogene terrestrial ecosystems and tectonics in sub-equatorial Africa". Journal of African Earth Sciences. 57 (3): 179–212. doi:10.1016/j.jafrearsci.2009.09.002.
  2. Stevens, Nancy J.; Holroyd, Patricia A.; Roberts, Eric M.; O'connor, Patrick M.; Gottfried, Michael D. (2009-06-12). "Kahawamys mbeyaensis (n. gen., n. sp.) (Rodentia: Thryonomyoidea) from the late Oligocene Rukwa Rift Basin, Tanzania". Journal of Vertebrate Paleontology. 29 (2): 631–634. doi:10.1671/039.029.0219. ISSN 0272-4634.
  3. Blackburn, David C.; Paluh, Daniel J.; Krone, Isaac; Roberts, Eric M.; Stanley, Edward L.; Stevens, Nancy J. (2019-05-15). "The Earliest Fossil of the African Clawed Frog (Genus Xenopus) from Sub-Saharan Africa". Journal of Herpetology. 53 (2): 125. doi:10.1670/18-139. ISSN 0022-1511.
  4. Borths, Matthew R.; Stevens, Nancy J. (2017-10-11). Smith, Thierry (ed.). "The first hyaenodont from the late Oligocene Nsungwe Formation of Tanzania: Paleoecological insights into the Paleogene-Neogene carnivore transition". PLOS ONE. 12 (10): e0185301. doi:10.1371/journal.pone.0185301. ISSN 1932-6203. PMC 5636082. PMID 29020030.
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