Carboniferous : Tectonics and Paleoclimate

The Carboniferous was marked by the progressive formation of the supercontinent Pangea. The present day Northern Hemisphere landmasses moved towards the equator to form Laurasia and to join the large Southern Hemisphere landmass Gondwana. The collision between Siberia and Eastern Europe created the Ural Mountains, and China was formed with the collision of several microcontinents and Siberia. The collision between Gondwana and Laurasia led to the formation of the Appalachian belt in North America and the Hercynian Mountains in Europe. Gondwana also shifted towards the equator while the continents moved from east to west.

The relationship of different land masses, such as the location of each of the present day continents relative to each other is determined by comparison of ancient magnetic poles and interpretations of ancient zones of tectonic activity. Rock magnetism is based on the fact that certain types of rocks may contain minerals that are slightly magnetic and so position themselves a specific way when exposed to a magnetic field. When the rock is first laid down, such as during a volcanic explosion, these minerals are free to orientate themselves in any manner they wish, and they are later locked into that position when the rock hardens, thus recording the position of the magnetic field of the Earth at that time. Landmasses placed close to each other will experience the same magnetic field and so the minerals in the rock will be orientated in the same direction.

The amount of land exposed to the air increased during the Carboniferous. This increase is probably due to plate tectonics and to the thickening of the crust. This trend towards increasing elevation of landmasses can be seen by the different types of rock deposits that are found in different locations. The Mississippian period is marked by marine deposits leading to the conclusion that shallow seas covered large areas, but by the Pennsylvanian Period, there was an uneven but progressive trend towards elevation of landmasses and marginal marine and continental environments became dominant. The restriction of oceans to the margins of the continents and the fluctuating sea levels led to the unconformity of the strata associated with the Carboniferous period. These changes to a less marine environment led to the terrestrial radiation that started during the Carboniferous. Terrestrial radiation also occurred because of drying trends that were the result of large glaciers, most of which originated in the South Pole of the time.

Mississippian and Pennsylvanian pages at the Paleogeography Through Geologic Time site by Dr. Ron Blakey of Northern Arizona University.

Find out more about the Carboniferous paleontology and geology of North America at the Paleontology Portal.

Source: Eicher, Don L & A. Lee McAlester. 1980. History of the Earth. Prentice Hall Inc., Englewood Cliffs, NJ.