| This pile of sandstone boulders is an example of rock formed from sandy sediments deposited in an ancient stream channel on a floodplain that existed in the region during Late Triassic time. These Flat Tops beds within the upper Sonsela Member of the Chinle Formation cap low mesas in the southern portion of Petrified Forest National Park (Woody, 2006). These beds are overlain by the Petrified Forest Member of the Chinle Formation which have been radiometrically dated to be about 209 million years (Riggs and others, 2003). |
