The Morawan Formation is a Chattian age siliceous marine geological formation of the Oligo-Miocene Japanese Kawakami Group of eastern Hokkaido prefecture.[1][2][3] The formation is fossil rich and contains source units where toothed baleen whales (Aetiocetidae) and Desmostylians have been discovered.[4]
| Morawan Formation | |
|---|---|
| Stratigraphic range: Chattian | |
| Type | Formation |
| Unit of | Kawakami Group |
| Sub-units | unnamed, Kamirawan, Lower Hard Shale, Middle Hard Shales, Upper tuffaceous silstone |
| Underlies | Kiroro Formation |
| Overlies | Hombetsuzawa Formation |
| Thickness | 500 m (1,600 ft) |
| Location | |
| Region | Hokkaido |
| Country |  Japan |
The Morawan Formation is a very siliceous unit containing hard platy shales interbedded with tuffaceous mudstones and sandstones, and some pumice. The unnamed lower member is a hard platy shale alternating with beds of tuffaceous mudstones and sandstones, the Kamirawan member is a tuffaceous sandstone with pumice, the Lower Hard Shale is a very siliceous hard shale with tuffaceous sandstones and mudstones, and the Middle Hard Shales and the Upper tuffaceous siltstone are similar.[5]
Fossil species from the Morawan Formation include:
- Ashorocetus eguchii
- Morawanocetus yabukii
- Aetiocetus tomitai
- A. polydentatus
References edit
- ^ "Fossil Works Morawan Formation". Fossil Works. Retrieved 17 December 2021.
- ^ "Oligo-Miocene Kawakami Group in Eastern Hokkaido - The age and horizon of Ashoro fossil fauna -". Geological Survey of Japan. Geological Survey of Japan. Retrieved 31 December 2015.
- ^ Funakawa, Satoshi (30 December 1995). "Intrageneric variation and temporal change in the internal skeletal structure of plagiacanthids (Radiolaria) from Hokkaido, Japan". Transactions and Proceedings of the Palaeontological Society of Japan. New Series (180): 208–225.
- ^ Tsai, Cheng-Hsiu; Ando, Tatsuro (14 April 2015). "Niche Partitioning in Oligocene Toothed Mysticetes (Mysticeti: Aetiocetidae)". Journal of Mammalian Evolution. 23: 33–41. doi:10.1007/s10914-015-9292-y. S2CID 14470974.
- ^ Inoue, Eiji; Suzuki, Taisuke (1961). "Explanatory Text". Geological Map of Japan. Geological Survey of Japan.