# Amisan Formation

The Amisan Formation (Korean: 아미산층) is an Late Triassic geologic formation in Boryeong, South Korea. Fossil records from this formation include plants, insects, and fish remains.

## Geology

The Amisan Formation in the Chungnam Basin overlies the Hajo Formation and underlies the Jogyeri Formation. It is subdivided into five zones based on its lithology, lower sandstone, lower shale, middle sandstone, middle shale, and upper sandstone zones. Depositional environments of the lower and middle shale zones of the Amisan Formation are thought to be lacustrine settings.
The depositional age of the Nampo Group including the Amisan Formation is debated, but plant genera Lobatannularia and Sphenophyllum from the Baegunsa Formation, which overlies the Amisan Formation and the Jogyeri Formation suggests that the Upper Triassic spans to the Baegunsa Formation. Also, conchostracan fossils and some insect fossils support the Triassic origin of the Amisan Formation.

## Fossil content

Most of the fossils from the Amisan Formation are from the lower shale zone and the middle shale zone.

### Flora

Flora of the Amisan Formation :
| Genus | Species | Region | Member | Material | Notes | Image |
| Taeniopteris | T. eurychoron T. mungyeongensis | | | | | |

#### Ferns

Ferns of the Amisan Formation :
| Genus | Species |
| Neocalamites | N. carrerei |
| Cladophlebis | C. nebbensis |
| Lobatannularia | L. sp. |
| Chiropteris | C. sp. |
| Equisetites | E. kimi E. gaehwariensis E. deltodon |

#### Bennettitales

Bennettitales of the Amisan Formation :
| Genus | Species |
| Anomozamites | A. baegunsaensis |
| Pterophyllum | P. seongjuriense P. daecheonense |
| Weltrichia | W. sp. |

#### Gymnosperms

Gymnosperms of the Amisan Formation :
| Genus | Species |
| Podozamites | P. lanceolatus P. var. genuinea P. schenki P. nampoensis |
| Anthrophyopsis | A. sp. |
| Drepanozamites | D. sp. |
| Baiera | B. cf. furcata |
| Cycadocarpidium | C. sp. |
| Ctenozamites | C. meogbangensis |
| Leptostrobus | L. myeongamensis |

### Bivalves

Bivalves of the Amisan Formation :
| Genus | Species | Region | Member | Material | Notes | Image |
| Margaritifera | M. cf. isfarensis | | | | | |

### Conchostracans

Conchostracans of the Amisan Formation :
| Genus | Species |
| Euestheria | E. kawasakii E. shimamurai |
| Cyclestherioides | C. rampoensis |
| Sphaerestheria | S. koreanica |

### Insects

Insects of the Amisan Formation :
| Genus | Species | Notes |
| Turbidapsyche | T. dobrokhotovae? | A mesopsychid scorpionfly; originally assigned to the genus Mesopsyche. Uncertain whether it belongs to T. dobrokhotovae. |
| Siberioperlidae | Indeterminate | Stoneflies. |
| Platyperla | P. sp. | Stoneflies. |
| Baleyopterygidae | Indeterminate | Stoneflies. |
| Hallakkungis | H. amisanensis | A palaeontinid. |
| Tennentsia | T. koreana | A cicadomorph. |
| Sanmai | S?. zetavena | A tettigarctid. |
| Magnatitan | M. jongheoni | A titanopteran. |
| Koreaphlebia | K. iussradiae | A triadophlebiomorph odonatopteran. |
| Koreatriassothemis | K. elongatus | A parazygopteran odonatopteran. |
| ?Isophlebioptera | Indeterminate | A possible Isophlebioptern nymph. Referred as 'Samarura-type'. |
| Shurabia | S. taewani | A Geinitziid polyneopteran. |

### Vertebrates

Vertebrates of the Amisan Formation :
| Genus | Species | Region | Member | Material | Notes | Image |
| Hiascoactinus | H. boryeongensis | | | | A redfieldiiform actinopterygian. | |
| Megalomatia | M. minima | | | | A basal actinopterygian. | |