Gunma Safari Park: Burdigalian, Japan
List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
|
Chondrichthyes
- Lamniformes
- Otodontidae
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| 1 specimen | ||||||||||
| GSP-0001 | ||||||||||
| see common names | ||||||||||
Geography
| Country: | Japan |
| Coordinates: | 36.2° North, 138.9° East (view map) |
| Paleocoordinates: | 36.2° North, 136.1° East (Wright 2013) |
| Basis of coordinate: | estimated from map |
| Geographic resolution: | outcrop |
Time
| Period: | Neogene | Epoch: | Miocene |
| Stage: | Burdigalian | 10 m.y. bin: | Cenozoic 5 |
| Key time interval: | Burdigalian | ||
| Age range of interval: | 20.45 - 15.98 m.y. ago |
Stratigraphy
| Formation: | Obata | ||||
| Stratigraphic resolution: | group of beds | ||||
| Stratigraphy comments: By reading the location of this outcrop on a topographic map and comparing it with the geological map by Takahashi and Hayashi (2004), these strata are estimated to be part of the Obata Formation of the Tomioka Group, specifically the lower part of the formation and below the Mori Tuff. Regarding the age of the Obata Formation, the first occurrence of Praeorbulina sicana - which defines the lower boundary of the N.8 planktonic foraminiferal zone (Blow, 1969) - has been confirmed in the very lowest part of the formation; furthermore, the first occurrence of P. curva (16.3 Ma) is known from the lower part of the formation, situated slightly above this level. Among these first occurrences, that of P. sicana is considered to be merely an apparent first occurrence - rather than a true evolutionary first appearance - because no planktonic foraminifera are found in the underlying Ushibushi Formation; consequently, the age of the very lowest part of the Obata Formation is considered to be younger than the lower boundary age of the N.8 zone (16.4 Ma; Berggren et al., 1995) (Takahashi & Hayashi, 2004). Conversely, the first occurrence of P. glomerosa (16.1 Ma) is known from the upper part of the Obata Formation (corresponding to the Idosawa Formation as defined by Oishi & Takahashi, 1990). Based on planktonic foraminiferal biostratigraphy derived from the fossil record, as well as the biostratigraphy of diatom and calcareous nannofossils, and a composite chronostratigraphy based on absolute dating (Takahashi & Hayashi, 2004), the age of the shark fossils is estimated to fall broadly within the late Early Miocene, at approximately 16.3 Ma; this timeframe corresponds to the period of the "Miocene Tropical Marine Climate Event." | |||||
Lithology and environment
| Primary lithology: | "siliciclastic" |
| Environment: | submarine fan |
| Geology comments: The interbeds of sandstone and siltstone observed within the formation - including those found at fossil localities - are interpreted as turbidites. | |
Taphonomy
| Modes of preservation: | body |
| Size of fossils: | macrofossils |
Collection methods and comments
| Reason for describing collection: | general faunal/floral analysis |
| Collection method comments: Repository: Gunma Safari Park collection | |
Metadata
| Database number: | 278429 | ||
| Authorizer: | M. Clapham | Enterer: | M. Clapham |
| Modifier: | M. Clapham | Research group: | vertebrate |
| Created: | 2026-03-21 19:18:33 | Last modified: | 2026-03-21 19:19:03 |
| Access level: | the public | Released: | 0000-00-00 00:00:00 |
| Creative Commons license: |
Reference information
Primary reference:
| 94375. | Y. Takakuwa. 2015. On a shark tooth remain, collected in the Gunma Safari Park, Tomioka City, Gunma Prefecture, central Japan. Bulletin of the Gunma Museum of Natural History 19:63-67 [M. Clapham/M. Clapham] |