| Powell Formation | |
|---|---|
| Stratigraphic range: Ordovician | |
| Type | Formation |
| Underlies | Everton Formation |
| Overlies | Cotter Formation [1] |
| Lithology | |
| Primary | Dolomite |
| Other | Shale, sandstone, chert |
| Location | |
| Region | Arkansas, Missouri and Virginia |
| Country | United States |
| Type section | |
| Named for | Powell railroad station (now abandoned), Marion County, Arkansas [2] |
| Named by | Edward Oscar Ulrich |
The Powell Formation or Powell Dolomite is a geologic formation in northern Arkansas, southeast Missouri [3] and Virginia. It contains gastropod, cephalopod, and trilobite fossils dating back to the Ordovician Period. [3]
The Harrodsburg Limestone is a geologic formation, a member of the Sanders Group of Indiana Limestone, of Mississippian age. It was named for Harrodsburg in southern Monroe County, Indiana by T. C. Hopkins and C. E. Siebenthal. It is made up primarily of calcarenite and calcirudite. It also may include some beds of dolomite and shale.
The Salem Formation is a geologic formation in Illinois, Indiana, Kentucky, and Missouri. It preserves fossils dating back to the Mississippian subperiod. This formation is quarried and used as a building material, known as "Indiana limestone", also called Bedford limestone.
The Black River Group is a geologic group that covers three sedimentary basins in the Eastern and Midwestern United States. These include the Appalachian Basin, Illinois Basin and the Michigan Basin. It dates back to the Late Ordovician period. It is roughly equivalent to the Platteville Group in Illinois. In Kentucky and Tennessee it is also known as the High Bridge Group. In areas where this Geologic Unit thins it is also called the Black River Formation (undifferentiated). One example of this is over the Cincinnati Arch and Findley Arch. Large parts of the Black River have been dolomized (where the parent limestone CaCO3 has been turned into dolomite CaMg(CO3)2.) This happed when there was interaction of hot saline brine and the limestone. This created hydrothermal dolomites that in some areas serve as petroleum reservoirs.
The Keokuk Limestone is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian sub-period.
The Warsaw Formation is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian subperiod.
The Chesapeake Group is a geologic group in Maryland, Virginia, Delaware, and North Carolina. It preserves mainly marine fossils dating back to the Late Oligocene through the Pliocene epochs of the Neogene period. This group contains one of the best studied fossil record of Neogene oceans in the world. Professional Paleontologists and amateur fossil hunters alike collect from this group intensely. The Calvert Cliffs stretch the length of Calvert County, Maryland and provide the best continuous stretch of the Calvert, Choptank, and St. Marys Formations. Ward (1985) recommended including the Old Church Formation in this group.
The Cotter Formation is a geologic formation in Arkansas, Missouri, Oklahoma and in Virginia. It preserves fossils dating back to the Ordovician period.
The Fernvale Limestone is a geologic formation in Alabama, Arkansas, Illinois, Missouri, Oklahoma, and Tennessee. It preserves fossils dating back to the Ordovician period.
The Tomstown Dolomite or Tomstown Formation is a geologic formation in Maryland, Pennsylvania, Virginia and West Virginia. It preserves fossils dating to the Cambrian Period.
The Smithville Formation or Smithville Dolomite is a geologic formation in Arkansas. It preserves fossils dating back to the Ordovician period.
The Theodosia Formation is a geologic formation in Missouri. It preserves fossils dating back to the Ordovician period.
The Derby-Doerun Dolomite is a Cambrian geologic formation exposed in southeast Missouri. Originally the Derby and Doerun were originally considered separate formations, but now considered a single unit. The combined name is from the Derby Mine and the Doe Run Lead Company of the Old Lead Belt.
The Eminence Formation or Eminence Dolomite is a geologic formation in Missouri. It preserves fossils dating back to the Cambrian period.
The Burlington Limestone is a geologic formation in Missouri, Iowa and the Midwest region. It preserves fossils dating back to the Mississippian subperiod.
The Compton Limestone is a geologic formation in southwest Missouri. It preserves brachiopod and echinoderm fossils of the Mississippian subperiod. The Compton rests unconformably on the Cotter Dolomite of Ordovician age. The Compton was named for the community of Compton, Missouri, as the type sections were described for outcrops along the James River and its tributary the Compton Branch.
The Fern Glen Formation is a geologic formation in eastern and southeastern Missouri. It preserves fossils dating back to the Osagean Series of the Mississippian subperiod.
The Jefferson City Formation or Jefferson City Dolomite is a geologic formation in the Ozarks of Missouri and Arkansas. The Jefferson City is in part not differentiated from the Cotter Formation of northern Arkansas. It preserves fossils dating back to the Ordovician period.
The Bowling Green Dolomite is a geologic formation in Missouri. It preserves fossils dating back to the Silurian period.
The Ely Springs Dolomite is an Ordovician period geologic formation in the Southwestern United States.
The Alexo Formation a stratigraphic unit of Late Devonian age. It is present on the western edge of the Western Canada Sedimentary Basin in the central Rocky Mountains and foothills of Alberta. The formation consists primarily of dolomite. It is locally fossiliferous and includes remains of marine animals such as brachiopods and conodonts.
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