Nebraska during the Carboniferous
(Mississippian) Period

345 Ma Middle Mississippian Epoch Uplift and erosion occurred during the late Devonian before Mississippian seas covered Nebraska. Once the seas transgress, dominantly carbonate rock layers which contain an unusual amount of chert nodules were deposited.

325 Ma Upper Mississippian Epoch During the late Mississippian, the South American continental plate collided with North America, creating the Ouachita Mountains (in Arkansas-Oklahoma). This even is known as the Ouachita Orogeny. In the eastern US, the collision of Europe & North America was also occurring, forming the Appalachian Mountains. These major stresses were felt within the interior of the continent; weak zones in the Precambrian basement were reactivated, creating structural highs and a subsequent EROSIONAL GAP in the rock record.

The images above are Paleozoic paleogeographic maps of the central United States (from Dr. Ron Blakey- http://jan.ucc.nau.edu/~rcb7/ ) that are based on observations in the geologic record. Nebraska is outlined in yellow. Click HERE to visit Dr. Blakey's website to learn more about paleogeography and how the continents have changed position throughout geologic time.

**Image modified after Carlson, M.P., Geology, Geologic Time and Nebraska, Educational Circular No. 10, 1993, University of Nebraska-Conservation and Survey Division, 60p.