John Day Fossil Beds This photo shows part of the Big Basin Formation in another of the hidden gems
John Day Fossil BedsThis photo shows part of the Big Basin Formation in another of the hidden gems of the U.S. National Park system; John Day Fossil Beds National Monument in Oregon.The rocks before you are a mixture of ancient soils, turned red and yellow as iron in them oxidized and rusted, and ashes and tuffs from nearby volcanoes. John Day Fossil Beds sits in a basin east of the Cascade Range that has grown gradually over a period of 50 million years. That period represents times when volcanism in the western U.S. migrated to the high peaks of the Cascades and the continent itself pulled apart into a variety of basins.A basin is a low spot in the topography and will be a place that sediments will flow to and accumulate. This basin grew over 50 million years of years as the western U.S. was faulted and pulled apart, allowing dirt, soil, and sediment from surrounding areas to flow in and accumulate. Then, every so often, those rocks would be capped by a volcanic eruption, either from the predecessors to today’s Cascade volcanoes or even from the Columbia River flood basalts to the North.The intermingling of dirt and volcanoes created an unparalleled collection of fossils and a stellar record of how the continent has changed. The soils early in the monument reflect times when the Earth was hotter and the climate of the area was nearly tropical. The area shifted through times that were wetter and temperate, and today the area is in the rain shadow of the Cascades and is much more arid; all of those changes are reflected in the rocks of the park.The area also provides excellent sampling of mammal evolution. It’s often hard to find rocks that give continuous records of evolution over a few million years; John Day provides a record covering 40 million. The predecessors of modern dogs, cats, pigs, horses, camels, rhinos, and rodents are all found in these rocks, and since volcanic layers are typically easy to date, the timing of species appearance can be pinned down quite precisely thanks to these layers.-JBBImage credit:http://upload.wikimedia.org/wikipedia/commons/0/0e/East_face_painted_hills_panorama.jpgRead more:https://gsa.confex.com/gsa/2012AM/finalprogram/abstract_211562.htmhttp://media.wix.com/ugd/25a2fb_7ea07a5397f098ebcf84003b6b914134.pdf http://www.nature.nps.gov/geology/parks/joda/http://www.nps.gov/joda/naturescience/geologicformations.htmhttp://www.ucmp.berkeley.edu/science/parks/johnday.php -- source link
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