| Pierson Limestone Stratigraphic range: Mississippian | |
|---|---|
| Type | Formation |
| Unit of | Chouteau Group basal unit of the Osagean Series |
| Underlies | Reeds Spring Formation and Elsey Formation |
| Overlies | Northview Formation |
| Lithology | |
| Primary | Limestone |
| Other | Chert, dolomite |
| Location | |
| Region | Missouri |
| Country | United States |
| Type section | |
| Named for | Pierson Creek, Greene County, Missouri |
| Named by | Stuart Weller (1901) [1] [2] |
The Pierson Limestone is a geologic formation in southwestern Missouri. [1] It preserves fossils of the Mississippian subperiod including brachiopods and coral. [3]
Missouri is a state in the Midwestern United States. With over six million residents, it is the 18th-most populous state of the Union. The largest urban areas are St. Louis, Kansas City, Springfield and Columbia; the capital is Jefferson City. The state is the 21st-most extensive in area. Missouri is bordered by eight states : Iowa to the north, Illinois, Kentucky and Tennessee to the east, Arkansas to the south and Oklahoma, Kansas and Nebraska to the west. In the South are the Ozarks, a forested highland, providing timber, minerals and recreation. The Missouri River, after which the state is named, flows through the center of the state into the Mississippi River, which makes up Missouri's eastern border.
The Mississippian is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earliest/lowermost of two subperiods of the Carboniferous period lasting from roughly 358.9 to 323.2 million years ago. As with most other geochronologic units, the rock beds that define the Mississippian are well identified, but the exact start and end dates are uncertain by a few million years. The Mississippian is so named because rocks with this age are exposed in the Mississippi River valley.
Brachiopods, phylum Brachiopoda, are a group of lophotrochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major groups are recognized, articulate and inarticulate. The word "articulate" is used to describe the tooth-and-groove features of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic feature (fossilizable), by which the two main groups can be readily distinguished. Articulate brachiopods have toothed hinges and simple opening and closing muscles, while inarticulate brachiopods have untoothed hinges and a more complex system of muscles used to keep the two valves aligned. In a typical brachiopod a stalk-like pedicle projects from an opening in one of the valves near the hinges, known as the pedicle valve, keeping the animal anchored to the seabed but clear of silt that would obstruct the opening.
