Lakota Formation
Geological formation in South Dakota, USA
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The Lakota Formation is a sequence of rocks of early Cretaceous (Berriasian to Barremian) age from Western North America. Located in South Dakota, the name of the formation is derived from the Lakota Native American tribe.
| Lakota Formation | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Sub-units | Chilson Member. Fuson Member |
| Underlies | Fall River Formation |
| Overlies | Morrison Formation |
| Thickness | 200 to 500 feet (60 to 150 m) |
| Lithology | |
| Primary | Sandstone |
| Other | Shale, Coal, Conglomerate |
| Location | |
| Region | North America |
| Country | United States |
| Type section | |
| Named for | Lakota Native American tribe |
| Named by | Darton |
| Year defined | 1899 |
There are two units of the Lakota Formation, the Chilson Member (upper Berriasian to Valanginian) and the underlying Fuson Member (upper Valanginian to early Barremian). A Berriasian-Valanginian age for the Chilson Member has been extrapolated by means of ostracods and charophytes.[1]
The Fuson Member takes its name from rock exposures in Fuson Canyon, a valley on the eastern side of the Black Hills.[2]
Vertebrate paleofauna
Dinosaurs
| Dinosaurs reported from the Lakota Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
|
D. lakotaensis |
Chilson Member |
"Skull, mandible, [and] vertebrae."[4] |
||||
|
H. marshi |
Chilson Member |
"Partial postcranial skeleton [and] osteoderms."[5] |
An ankylosaur belonging to Polacanthidae |
|||
|
O. depressus |
Chilson Member |
Portions of both ilia, anterior part of the blade of one pubis, an incomplete sacrum, centrum of the last sacro-dorsal, 12 caudal vertebrae, 1 thoracic rib and many fragments |
An ankylopollexian iguanodont |
|||
| Indeterminate |
Chilson Member |
Left humerus and right metacarpal I |
A macronarian related to Camarasaurus |
|||
Mammals
| Mammals reported from the Lakota Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
|
B. hydei[9] |
Chilson Member |
Right M2 |
||||
|
I. rougieri |
Chilson Member |
Right lower M1 |
||||
|
Lakotalestes[9] |
L. luoi |
Chilson Member |
Right upper molar (M5?) |
|||
|
Passumys[9] |
P. angelli |
Chilson Member |
Right M1 |
A plagiaulacid multituberculate | ||
Turtles
| Turtles reported from the Lakota Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Lakotemys[10] | L. australodakotensis | Chilson Member | Two shells and a partial skull | A baenid paracryptodire | ||
Other vertebrate remains found within the Lakota Formation include a fish scale from the gar Lepisosteus and a crocodile tooth [11]
