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 from the Amisan Formation, 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 ==