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Science Frontiers ONLINE No. 28: Jul-Aug 1983 |
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The Alaskan Jigsaw Puzzle
Alaska seems to be plastered together from bits and pieces that originated far from the present position of this state. The units that now make up southern Alaska, for example, started north of the equator 250 million years ago, crossed into the southern hemisphere, and started back north about 160 million years ago. However, the itinerary of northern Alaska cannot even be guessed at. Present thinking is that this portion of the state was close to the geographic north pole during the late Cretaceous. But this is the period when the huge coal deposits were formed on the Arctic slope. Much of this coal comes from evergreens, which could not have survived in high latitudes due to the lack of sunlight. So, the pieces of the puzzle are at hand, but their travels are a mystery.
(Anonymous; "Fragmented Alaska," Open Earth, no. 17, 1982.)
Reference. For more on exotic terranes, see ESR9 in our Catalog: Inner Earth. Ordering information here.