Abstract
Colonial rugose corals are common in western cratonal North America and in some of the allochthonous terranes, now amalgamated against its western margin. Throughout the Late Paleozoic, the coral faunas in these two different settings were significantly different. Comparisons of these faunas suggest that during the Mississippian the Alexander terrane probably was southwest of Arctic Alaska and the Stikine terrane probably lay west of the southern part of the North American craton. The Cache Creek terrane lay far out in the Paleopacific Ocean. The Pennsylvanian faunas suggest that the Quesnellia and Eastern Klamath terranes were situated southwest of Arctic Alaska and the Alexander terrane was somewhat farther southwest and farther from cratonal North America. The Stikine terrane continued to be positioned west of the southern part of the North American craton. During the Early Permian, terranes with a cratonal faunal aspect may have lain 2000–3000 km west of cratonal North America and latitudinally generally southwest of their present positions. In the Middle Permian these terranes were carried southward relative to the North American craton. Simultaneously the Tethyan Realm expanded eastward.
Highlights
Western North America consists of a series of allochthonous crustal fragments, including the Alexander, Arctic Alaska, Cache Creek, Eastern Klamath, Quesnellia, Stikine, and Wrangellia terranes plastered against the North American craton, the margin of which is defined by the Sr87/Sr86 0.706 isotopic boundary, e.g., [1,2]
I will consider the geographic position of terranes in the Carboniferous and Permian based on colonial rugose corals which occur both on cratonal North America and in several of the allochthonous terranes, with constraints based on paleomagnetic data
Based primarily on the degrees of similarity of colonial rugose coral faunas among the terranes and with cratonal North America, the paleogeography is interpreted on the assumption that similarity or lack of it was due to distance between faunas compared
Summary
Western North America consists of a series of allochthonous crustal fragments, including the Alexander, Arctic Alaska, Cache Creek, Eastern Klamath, Quesnellia, Stikine, and Wrangellia terranes plastered against the North American craton, the margin of which is defined by the Sr87/Sr86 0.706 isotopic boundary, e.g., [1,2]. I will consider the geographic position of terranes in the Carboniferous and Permian based on colonial rugose corals which occur both on cratonal North America and in several of the allochthonous terranes, with constraints based on paleomagnetic data. Based primarily on the degrees of similarity of colonial rugose coral faunas among the terranes and with cratonal North America, the paleogeography is interpreted on the assumption that similarity or lack of it was due to distance between faunas compared. I will first summarize knowledge on the colonial rugose coral faunas of the Mississippian, Pennsylvanian, Early Permian, and Middle Permian, and use these data to interpret the location of the various terranes relative to one another and to the North American craton.
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