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Lawrence Lawver, Univ. of Texas at Austin, Jackson School of Geosciences (United States)
Arthur Grantz, Consulting Geologist (United States)
Lisa Gahagan, Univ. of Texas at Austin, Jackson School of Geosciences (United States)
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By Late Ordovician, most of the elements of the present day Arctic were located between 30°S and 30°N with Laurentia oriented 90° clockwise from its present orientation. Closure of the Iapetus Ocean resulted in collision between Baltica and Siberia with North America and Greenland along the regions that now border the North Atlantic and Arctic oceans. The Caledonian orogeny was the result of this collision and transferred a number of terranes from Siberia and Baltica to Laurussia. It also amalgamated Baltica, Greenland, North America, Arctic Alaska, and Chukotka, in essence all of the present day pieces of the Arctic with the exception of Siberia. From paleomagnetic results, it is believed that Siberia approached Laurentia first during the Ordovician but retreated to perhaps collide again during the Ellesmerian orogeny From the Late Devonian to Early Mississippian. During the Carboniferous, Eurasia began to coalesce with closure of the Uralian Ocean between Kazakhstan and Baltica and finished when Siberia sutured to the Taimyr Peninsula beginning in the earliest Permian after closure of the Paleo-Asian Ocean between Siberia and Kazakhstan.
In Lawver et al. (2002) it was assumed that Arctic Alaska was part of Laurentia during the early Paleozoic but that assumption has recently been questioned. Since the Seward Peninsula and other terranes on the southern margin of Arctic Alaska clearly have early Paleozoic affinities with Siberia and perhaps Chukotka as part of Baltica, the assumption of a Laurentian position for Arctic Alaska during the Paleozoic needs to be examined. Plausible alternatives will be discussed and presented.
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