Amisan Formation

The Amisan Formation is an Late Triassic geologic formation in 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.