06 December 2015

6. Clarno Nut Beds

Plants from the Clarno Nut Beds
Smithsonian Institution
Location: Oregon, USA
Formation: Clarno Formation
Age: Eocene (44 Ma)

One state south of the southernmost Okanogan locality, are the slightly younger Clarno Nut Beds.  As the name suggests, the site is known for its preservation of nuts and seeds, though wood and leaves from plants and a few bits and pieces of animals are preserved as well.  While some of the plants found in the Nut Beds - such as sycamores and conifers - are comparable to those of the Okanogan sites, many indicate a much warmer environment in keeping with other Eocene localities.  Most notable among these taxa are palms, cycads, bananas, and, among animals, the crocodile Pristichampsus.  Why do these nearby lagerstätte represent such different climates?  It likely comes down to elevation: the fossils of the Okanogan were from much higher-altitude, and therefore cooler, ecosystems than their Oregonian counterparts.  There is almost certainly more to the story than this, but these two floras do demonstrate that the overall trend of cooling climate during the Cenozoic is in fact much more complex and that climate can vary considerably across even fairly small regions.  The other noteworthy aspect of the Clarno Nut Beds is their method of preservation.  While most fossils are preserved in sedimentary rocks, the origin of the rocks in which these fossils are preserved is more explosive.  Lahars - mudflows kicked off by nearby volcanic eruptions - raced downhill uprooting and, eventually, burying everything in their path.  Fortunately for posterity, among the things engulfed was a forest, meaning we have a massively destructive event to thank for some of Oregon's most spectacular plant fossils.

Visit: The Nut Beds are preserved in the Clarno Unit of John Day Fossil Beds National Monument, one of the few places in the monument where visitors can view in situ fossils.
Fossils: The monument is also home to the Condon Fossil Center near Dayville, one of the best locally-focused fossil museums you'll see anywhere in the world.  Many Nut Beds fossils are on display here, along with a gorgeous mural depicting the landscape of Eocene Oregon.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?:  No, though the Clarno, along with the rest of the John Day Fossil Beds, is well-deserving of a first-class photologue (if that's even a word).

This post is part of my 2015 Paleontology Advent Calendar, a series of vignettes on lagerstätten - sites of exceptional fossil preservation - that document changes in climate and environments through the Cenozoic.  You can see the other posts here.

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