All three rock types can be found in the Grand Canyon, and each layer adds an important understanding to the geologic history of the region. The oldest rocks in the Grand Canyon, found at the bottom of the canyon, are primarily metamorphic, with igneous intrusions the name given to when magma or lava enters or cools on top of previously formed rock.
The intrusive igneous rocks here are called Zoroaster granite. The name given to this rock set the combination of metamorphic and igneous rock of a certain age found at this location is Vishnu Basement Rocks.
Primarily schist metamorphic with granite igneous , these rocks have visible crystals and are about 1. Volcanism continued after the collision and igneous intrusions continued after metamorphosis. The middle rock set, the Grand Canyon Supergroup, is primarily sandstone and mudstone, both sedimentary rocks, with some areas of igneous rock. They are from the late Proterozoic, only slightly younger than the metamorphic basement rocks.
These rocks do not contain many fossils, because they formed before complex life on Earth was common. The few fossils that are present include stromatolites, columns of sediment formed by cyanobacteria. The composition sandstone and presence of stromatolites indicate that this area was previously a very shallow sea. The rock layers in the Grand Canyon Supergroup have been tilted, whereas the other rocks above this set are horizontal.
This is known as an angular unconformity. The top of these sediment layers was then eroded away, forming the Great Unconformity. These layers are sedimentary, and primarily sandstone. This set makes up most of the typical reddish layers that you often see in images, and which come to mind when thinking of the Grand Canyon.
Following the Great Unconformity, this set is much younger than the other rock layers, and fossils are prevalent. The most common fossils are small sea creatures, such as brachiopods, bryozoans, coral, and crinoids.
Combined with the sandstone, this tells us that the region was a warm, shallow sea when these sediments were deposited. A key feature of the Grand Canyon is, unsurprisingly, the canyon itself. The width and depth make it truly remarkable and expose the rock layers that were discussed above. After all the rocks were deposited, there was a period of uplift where plate tectonics literally force a section of the Earth upward , setting the stage for canyon formation.
It provided a high enough elevation that water could flow downward, cutting through the rock as it went. This incredible formation was carved over millions of years by the Colorado River. The canyon itself has formed much more recently than the deposition of rock layers, only about five million years ago as opposed to the rocks, the youngest of which are a little less than million years old.
But many other fossils have been found here, including reptiles, amphibians and early dinosaurs. These animals lived in a very different environment than what exists today, said Adam Marsh, paleontologist at Petrified Forest National Park.
Visitors can see fossil preparators working on specimens at the fossil demonstration lab, which is open 9 a. Thursdays through Saturdays. It's in the visitor center at the north entrance to the park, which can be reached by using Exit off Interstate 40 near Holbrook.
Marsh said Petrified Forest is teeming with easily seen fossils. Visitors are advised that it is illegal to remove anything from the park.
He said visitors have found impressive specimens and anyone who does is asked to alert the staff to their find. The trees in Petrified Forest once were wood but now are are completely crystallized and mostly made of quartz.
Millions of years ago, the logs were buried by sediment and ash. Over thousands of years, the wood cells were slowly replaced by minerals in the groundwater. Elements like iron and manganese cause impurities in the quartz — and the beautiful colors. Red Basin Clam Beds: This 8. Jasper Forest: This is a 2. Be sure to bring plenty of water, sun protections and snacks, especially in summer. There's virtually no shade.
The fossil record of Grand Canyon National Park contains a wide variety of organisms, from ancient bacterial colonies to Ice Age mammals. With this technology, many photographs of an object are taken from all angles, and these photographs are digitally stitched together into a 3D model. Show 10 40 per page. Explore This Park. Fossils and Paleontology.
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