The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on a weekly schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Wednesday, May 7, 2014

May 7. Devonian paleogeography

If you’ve been following along, you know that Laurentia, the core of North America (NA in map below), and Baltica, the Scandinavian heart of Europe (E), fused together during the long tectonic episode called the Caledonian Orogeny. The assembled continent is sometimes called Laurasia, or Larussia. But don’t think of it as a perfect, or complete union – there were still stringers and islands and other bits of continents impacting, and Gondwana was still coming. 

Late Devonian map by Ron Blakey via Wikipedia, used under Creative Commons Attribution license

Another block that was on its way was Siberia (S on the map). Siberia, together with various complications like island arcs and microcontinents, was north of the combined North America-Europe continent of Laurasia. Laurasia was pretty much along the Devonian equator for much of the period, which meant that any shallow seas would likely be warm and would support plenty of diverse life, and that’s what the fossil record shows in those areas.

There was plenty of variation over the 50 million years and more of the Devonian. At times, much of what is now the interior of North America was above sea level, but by the middle to late part of the Devonian, extensive shallow seas covered most of what is now the United States. It wasn’t a perfectly smooth, uniform shallow sea – troughs like the Appalachian Basin and deeper zones like the Michigan Basin made for plenty of variety in the marine environments. Maybe that variety, in North America and Europe, with warm tropical seas, contributed to the relatively rapid evolution and diversification of the fishes. But remember, life was definitely present on land during the Devonian, and there were many many niches there for life to adapt to.
—Richard I. Gibson

Globe image by Ron Blakey via Wikipedia, used under Creative Commons Attribution license.

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