The Morrison Formation is one of the greatest attractions in our area. This formation along with the Entrada, Curtis, and Summerville comprise about the later 1/3 of the Jurassic Period. Just above the Brushy Basin Member of the Morrison Formation begins the Cretaceous Period. Here is a chart showing the stratum of this area:
Graph provided by USGS
The three members of the Morrison Formation hold many diverse dinosaur fossils and various types of petrified wood. One intriguing fact is that these three layers also hold significant amounts of the so-called “space metals” or metals thought to originate from asteroids and meteors colliding with earth: Uranium, Vanadium, and Iridium just to name a few of these metals. Modern theories suggest that the space metals actually originate from volcanic activity, though there are larger amounts of these metals at known impact sites. The space metals also occur in higher percentages at nuclear blast craters. One could conclude that these metals are formed when heat and pressure is sufficient to bring matter into a plasma state where cooling and lessening pressure permit the re-formation of atoms. The heavier less stable elements are precipitated from this ‘atomic soup’ first with the formation of the stable elements from the remaining particles.
It is thought that the Morrison Formation is a remnant of an ancient inland seaway that alternated between fresh water and sea water for millions of years during the formation of the current continent. Here is a drawing of this proposed sea:
Drawing provided by USGS
This inland waterway at times must have subsided to expose dry land and have been deep enough at other times to have currents swift enough to segregate sand and clay particles. Certainly there were times when it was shallow and dinosaurs, ferns, and other life inhabited the area. Due to tectonic pressures this area has been elevated more than 4000 ft. above the sea.
The Tidwell Member appears to have large, coarse barked pine or pre-pine forest areas, whereas the Salt Wash Member has smaller yet coarse barked petrified trees. At the time frame where the Salt Wash Member ends and the Brushy Basin Member begins is found the majority of dinosaur fossils in this area. The Morrison Formation holds many more discoveries to be made in the fields of Paleontology and Geochemistry.