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Eocene Ione Formation Concretions (Calif.) Contain Charcoal From A Single Forest Fire Event


Virgilian

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An unusual fossil locality in a kaolinitic (clay-rich) marine-originated horizon of the primarily estuarine to fluviatile (river and stream-deposited) Lower-Middle Eocene Ione Formation, Amador County, California, (western slopes of the Sierra Nevada) yields concretions that, remarkably, contain at their cores chunks of extremely well preserved charcoal--all derived from similar species of "cooked" conifer woods--that sophisticated scientific analyses suggest burned during a single forest fire event some 52 million years ago.

 

And so the Ione Early Eocene scene takes a most-fascinating turn. From a once-speculated tropical to semi-tropical paleo-environment of year-round high humidity and incessant precipitation, we now get a more focused picture of regular intermittent hot and dry seasons interrupted by probable monsoonal meteorological activity--perhaps an Ione Eocene environment not unlike that of present-day India.

 

The Ione Formation of Amador County is, of course, already famously recognized for its well preserved Middle Eocene fossil leaves--including, locally, rather common specimens of the climbing fern Lygodium kaulfussi (also known from the early to middle Eocene Green River Formation and Bridger Formation of eastern Utah, Wyoming, and Colorado).

 

See the technical report over at https://www.researchgate.net/publication/267624201_Characterization_and_genesis_interpretation_of_charcoal-bearing_concretions_from_the_early_Eocene_Ione_Formation_CA . Includes a free pdf download of the December, 2013, presentation poster that explains the science behind the investigation.

 

 

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