Amisan Formation
Late Triassic geologic formation in South Korea
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The Amisan Formation (Korean: 아미산층; Hanja: 峨嵋山層) is an Late Triassic geologic formation in Boryeong, South Korea. Fossil records from this formation include plants, insects, and fish remains.
| Amisan Formation | |
|---|---|
| Stratigraphic range: Norian ~ | |
| Type | Geological formation |
| Unit of | Nampo Group |
| Underlies | Jogyeri Formation |
| Overlies | Hajo Formation |
| Thickness | 750–1,000 m (2,460–3,280 ft) |
| Lithology | |
| Primary | Shale, Sandstone, Siltstone |
| Location | |
| Region | South Chungcheong Province |
| Country | South Korea |
| Extent | Chungnam Basin |
| Type section | |
| Named for | Amisan, Boryeong |
Map and diagram of Nampo Group | |
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,[1][2] 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.[3] Also, conchostracan fossils and some insect fossils support the Triassic origin of the Amisan Formation.[4][5][6]
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[7] |
|
|||||
Ferns
| Ferns of the Amisan Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Region | Member | Material | Notes | Image |
| Neocalamites | N. carrerei[8] | |||||
| Cladophlebis | C. nebbensis[9] | |||||
| Lobatannularia | L. sp.[7] | |||||
| Chiropteris | C. sp.[7] | |||||
| Equisetites[10] |
|
|||||
Bennettitales
| Bennettitales of the Amisan Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Region | Member | Material | Notes | Image |
| Anomozamites | A. baegunsaensis[11] | |||||
| Pterophyllum[11] |
|
|||||
| Weltrichia | W. sp.[12] | |||||
Gymnosperms
| Gymnosperms of the Amisan Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Region | Member | Material | Notes | Image |
| Podozamites | ||||||
| Anthrophyopsis | A. sp.[7] | |||||
| Drepanozamites | D. sp.[7] | |||||
| Baiera | B. cf. furcata[7][13] | |||||
| Cycadocarpidium | C. sp.[7] | |||||
| Ctenozamites | C. meogbangensis[11] | |||||
| Leptostrobus | L. myeongamensis[14] | |||||
Bivalves
| Bivalves of the Amisan Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Region | Member | Material | Notes | Image |
| Margaritifera | M. cf. isfarensis[15] | |||||
Conchostracans
| Conchostracans of the Amisan Formation[4] | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Region | Member | Material | Notes | Image |
| Euestheria |
|
|||||
| Cyclestherioides | C. rampoensis | |||||
| Sphaerestheria | S. koreanica | |||||
Insects
| Insects of the Amisan Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Region | Member | Material | Notes | Image |
| Turbidapsyche | T. dobrokhotovae | A mesopsychid scorpionfly; originally assigned to the genus Mesopsyche.[16][17][18] | ||||
| Siberioperlidae | Indeterminate | Stoneflies.[19] | ||||
| Platyperla | P. sp. | |||||
| Baleyopterygidae | Indeterminate | |||||
| Hallakkungis | H. amisanus | A palaeontinid.[20] |  | |||
| Tennentsia | T. koreana | A cicadomorph.[21] | ||||
| Sanmai | S?. zetavena | A tettigarctid.[22] | ||||
| Magnatitan | M. jongheoni | A titanopteran.[5] |  | |||
| Koreaphlebia | K. iussradiae | A triadophlebiomorph odonatopteran.[6] | ||||
| Koreatriassothemis | K. elongatus | A parazygopteran odonatopteran.[23] | ||||
| ?Isophlebioptera | Indeterminate | A possible Isophlebioptern nymph. Referred as 'Samarura-type' in paper.[23] | ||||
| Shurabia | S. taewani | A Geinitziid polyneopteran.[24] | ||||
Vertebrates
| Vertebrates of the Amisan Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Region | Member | Material | Notes | Image |
| Hiascoactinus | H. boryeongensis | A redfieldiiform actinopterygian.[25] |  | |||
| Megalomatia | M. minima | A basal actinopterygian.[26] | ||||