05 December 2015

5. Lakes of the Eocene Okanogan

Leaf and flower fossils from Stonerose Fossil Site, Republic, WA
Location: Washington, USA & British Columbia, Canada
Formation: Klondike Mountain & Allenby Formations (including Princeton Chert)
Age: Eocene (53-49 Ma)

You all must have known it was only a matter of time before I came to sites from the Northwest (spoiler: this is just the first of many this month).  Messel and the other localities I've highlighted so far may have given you the impression that the Eocene world was entirely blanketed by rainforests.  A series of localities from Washington and British Columbia, though, show that the environmental picture was somewhat more complicated.  The Okanogan Highlands of Washington and British Columbia were even higher in the Eocene, and lakes that formed in the region's valleys have reserved a wide range of organisms.  My favorite Okanogan fossil is the fish Eosalmo driftwoodensis.  Its name translates as 'Dawn Salmon' which is appropriate as it is the oldest and most basal salmon, meaning that the fish synonymous with the Northwest today have been residents of the region since the beginning of their evolutionary history.  In terms of both numbers and quality of preservation, though, the most notable Okanogan organisms are plants (including large specimens of leaves and flowers - most famously from the kola relative Florissantia - as well as microscopic pollen and algae) and insects.  These fossils were first thought to date from the cooler Oligocene Epoch, as they resembled temperate species, but multiple lines of evidence have shown that they date back to the global greenhouse of the Eocene.  How is it that a cool-climate flora lived at the same latitude and time as Messel's crocodiles and primates?  A site a couple of hundred miles to the south helps illustrate the answer to this question.

Visit: Important Okanogan localities are preserved by the BC government within Driftwood Canyon Provincial Park and McAbee Fossil Beds Heritage Site.  These sites are (wisely) off-limits to collectors, but you can collect fossils at the Stonerose site in Republic, WA (though any significant specimens will be retained for study)
Fossils: The Stonerose Center has a display of local fossils.  Elsewhere, the only museum I know of to permanently display several Okanogan fossils is Seattle's Burke Museum.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?:  Not as such, but Spokane author Jack Nisbet has a nice chapter on the Okanogan lagerstätte in his book 'Ancient Places' and paleontologist Bruce Archibald has written a publicly available overview of relevant sites.

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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