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Volume 18 Issue 12 (December 2009)

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Article, pp. 4-12 | PDF (1.87MB)

The Rheic Ocean: Origin, Evolution, and Significance

R. Damian Nance1*, Ulf Linnemann2

1 Department of Geological Sciences, 316 Clippinger Laboratories, Ohio University, Athens, Ohio 45701, USA
2 Staatliche Naturhistorische Sammlungen Dresden, Museum für Mineralogie und Geologie, Königsbrücker Landstraße 159, D-01109 Dresden, Germany

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The Rheic Ocean, which separated Laurussia from Gondwana after the closure of Iapetus, was one of the principal oceans of the Paleozoic. Its suture extends over 10,000 km from Middle America to Eastern Europe, and its closure assembled the greater part of Pangea with the formation of the Ouachita-Alleghanian-Variscan orogen.

The Rheic Ocean opened in the Early Ordovician, following protracted Cambrian rifting that represented a continuum of Neoproterozoic orogenic processes, with the separation of several Neoproterozoic arc terranes from the continental margin of northern Gondwana. Separation likely occurred along a former Neoproterozoic suture in response to slab pull in the outboard Iapetus Ocean. The Rheic Ocean broadened at the expense of Iapetus and attained its greatest width (>4000 km) in the Silurian, by which time Baltica had sutured to Laurentia and the Neoproterozoic arc terranes had accreted to Laurussia, closing Iapetus in the process. Closure of the Rheic Ocean began in the Devonian and was largely complete by the Mississippian as Gondwana and Laurussia sutured to build Pangea. In this process, North Africa collided with southern Europe to create the Variscan orogen in the Devono-Carboniferous, and West Africa and South America sutured to North America to form the Alleghanian and Ouachita orogens, respectively, during the Permo-Carboniferous.

The Rheic Ocean has long been recognized as the major Paleozoic ocean in southern Europe, where its history dominates the basement geology. In North America, however, the Rheic has historically received less attention than Iapetus because its suture is not exposed. Yet, it was the Rheic Ocean that played the dominant role in creating the Appalachian-Ouachita orogen, and an important record of its history may be preserved in Mexico.

Manuscript received 12 July 2008; accepted 16 October 2008.

doi: 10.1130/GSATG24A.1