Arcs and backarc basins in the Early Paleozoic lapetus Ocean

• Published in: Island Arc
• Main Authors: Pickering, KevinT., Smith, Alan G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1995
• Subjects: Greenland; Pacific; East Greenland
• Online Access: http://dx.doi.org/10.1111/j.1440-1738.1995.tb00132.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1440-1738.1995.tb00132.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1440-1738.1995.tb00132.x

Abstract Understanding the evolution and destruction of past oceans not only leads to a better understanding of earth history, but permits comparison with extant ocean basins and tectonic processes. This paper reviews the history of the Early Paleozoic circum‐Atlantic oceans by analogy with the Pacific Ocean and Mesozoic Tethys. Rifting and continental separation from 620 to 570 Ma led to the development of passive margins along parts of the northern margin of Gondwana (the western coast of South America); eastern Laurentia (eastern North America, NW Scotland and East Greenland), and western Baltica (western Scandinavia). Meagre paleomagnetic data suggest that western South America and eastern North America could have been joined together to form facing margins after breakup. Although western Baltica is an apparently obvious candidate for the margin facing NW Scotland and East Greenland, the paleomagnetic uncertainties are so large that other fragments could have been positioned there instead. The Iapetus Ocean off northeastern Gondwana was probably a relatively wide Pacific‐type ocean with, during the late Precambrian to early Ordovician, the northern margin of Gondwana as a site of continentward‐dipping subduction zone(s). The 650‐500 Ma arc‐related igneous activity here and the associated deformation gave rise to the Cadomian, ‘Grampian’, Penobscotian, and Famantinian igneous and orogenic events. By 490‐470 Ma, marginal basins had formed along the eastern Laurentian margin as far as NE Scotland, along parts of the northern margin of Gondwana, and off western Baltica, but none are known from the East Greenland margin. These basins closed and parts were emplaced as ophiolites shortly after their formation by processes that, at least in some cases, closely resemble the emplacement of the late Cretaceous Semail ophiolite of Oman. This orogenic phase seems to have involved collision and attempted subduction of the continental margin of Laurentia, Gondwana and Baltica. In Baltica it gave rise to some eclogite ...