Early Carboniferous pix

During the Early Carboniferous the Paleozoic oceans between Euramerica and Gondwana begin to close, forming the Appalachian and Variscan mountains. An ice cap begins to grow at the South Pole as four-legged vertebrates evolve in the coal swamps near the Equator. By the end of the Paleozoic Era, most of the oceans that had opened during the breakup of Pannotia, were consumed as the continents collided to form the supecontinent of Pangea. Centered on the Equator, Pangea stretched from the South Pole to the North Pole, and separated the Paleo-Tethys Ocean to the east, from the Panthalassic Ocean to the west.

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 stratigraphy of the Lower Carboniferous is readily distinguished from that of the Upper Carboniferous. The environment of the Lower Carboniferous in North America was heavily marine, when seas covered parts of the continents. As a result, most of the mineral found in the Lower Carboniferous is limestone, that comprises the remains of crinoids, lime-encrusted green algae, or calcium carbonate shaped by waves. The North American Upper Carboniferous environment was alternately terrestrial and marine, with the transgression and regression of the seas caused by glaciation. These environmental conditions, with the vast amount of plant material provided by the extensive coal forests, allowed for the production of coal. Plant material did not decay when the seas covered them and pressure and heat eventually built up over the millions of years to transform the plant material to coal.

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 minerals 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 dominated. 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.

Early Carboniferous pix

During the Late Carboniferous and Early Permian the southern regions of Pangea (southern South America and southern Africa, Antarctica, India, southern India, and Australia) were glaciated. Evidence of a north polar ice cap in eastern Siberia during the Late Permian.

The broad Central Pangean mountain range formed an equatorial highland that during late Carboniferous was the locus of coal production in an equatorial rainy belt. By the mid-Permian, the Central Pangean mountain range had moved northward into drier climates and the interior of North America and Northern Europe became desert-like as the continued uplift of the mountain range blocked moisture-laden equatorial winds.