Using accurate dating to understand the sedimentary environment in the Clarkia Palaeolake of northern Idaho.
[sciencythoughts.blogspot.com]
The Clarkia Palaeolake in northern Idaho formed when lava flows from the Colombia River Basalts blocked a steep-sided valley, damming the proto–Saint Maries River. The resultant lake contained a sedimentary environment in which were preserved an exquisite fossil biota, along with biomolecules, and isotope signals, which has been studied by scientists for almost five decades. Despite this attention, dating the Clarkia Palaeolake has proven elusive, due to a lack of direct radiometric, which means we neither fully understand the exact age of the deposits, nor the rates of sedimentation in the lake where they were laid down. Based upon the Plant remains found there, the Clarkia Palaeolake deposits are thought to be Early to Middle Miocene in age, with ash layers present that are thought to be correlatable to other ash layers in the Pacific Northwest for which dates have been established, making the deposits between 16 and 15.4 million years old. This correlates with the Miocene Climatic Optimum, a global warm period which is known to have had high atmospheric carbon dioxide levels, believed to be linked to outgassing from the Colombia River Basalts. The Clarkia Palaeolake sequence is a laminated sequence of beds, but it is unclear if these are the result of storm events or seasonal variation.
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I grew up in Eastern Washington. There were places we could find layered clays with perfectly preserved leaves, with every detail still visible.
GeorgeRocheleau
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Aug 9, 2021
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