Starting From The Bottom Now We're Here: a description of each of the layers of rock in the canyon
When Looking at the Grand Canyon, specifically its layers of rock, you are literally staring at how the rock was when it was first formed. If you were to look at the very basement rocks of the canyon you are staring 1.8 Billion years into the past! As you go up this region of beauty has been pummeled and reshaped by heavy Monsoons, heavy winds, massive sand dunes, and even by the Ocean itself! There are two large groups of rocks as shown in the diagram on the right; The Pre-cambrian Rocks, or the inner gorge (shown in green and red), and the Paleozoic rocks (shown in blue). Let us explore the very beginning of the rock staring with the Vishnu Basement rocks.
Image Source for above diagramhttp://upload.wikimedia.org/wikipedia/commons/1/14/Stratigraphy_of_the_Grand_Canyon.png:
-Pre-Cambrian Rocks
Vishnu Rock Base and Zoroaster granite
The Vishnu base rocks, other wise known as The Pre-Cambrian Rocks are by far the oldest rocks and make up the base of the entire grand canyon! They were formed 1.8 billion years ago when north America collided with an ancient Island (similar to the islands of Hawaii). This caused immense heat and pressure, and after the lava cooled it created the Vishnu schist we see today! After the schist was formed More magma kept spewing through the cracks which caused another layer of rock to form called the Zoroaster Granite.
The Grand Canyon Supergroup
The Supergroup is divided up into the Unkar group, Nanokoweap formation, Chuar group, and the Sixtymile Formation. these are also the rocks that are angled upwards in diagram 1 above.
The Unkar Group
image Source:http://1.bp.blogspot.com/-sNY5FjUFAck/Tw604_t9cRI/AAAAAAAAA4g/l6cgaOAl2AM/s1600/GC+Supergroup.jpg
The Unkar Group consists of 5 separate pieces as shown in the diagram on the left.
- Bass formation- Oldest of the Unkar Group being about 1.25 Billion years old and it is composed of Limestone.
- Hakatai Shale- Composed of mostly shale and bits of sandstone throughout some areas of the canyon, this layer is 1.2 Bya.
- Shinumo Quartzile- also being 1.2 Bya, it is made up of sandstone but unfortunately only some areas of the canyon show this layer due to intense erosion on it.
- Dox Formation- Being 1.19 billion years old, this sandstone layer has been interbedded with some forms of shale.
- Cardenas Lavas- The youngest of all the Unkar Group, at 1.19 Billion years old, this layer was in fact formed by a basaltic lava flow. (Lava with high amounts of Iron, Magnesium, and Calcium).
The Nanokoweap Formation
As Shown in Diagram 2 above, The Nanokoweap Formation is 1.05 billion years old, being comprised of sandstone, it is mostly formed in the eastern part of the Canyon, mostly due to massive amounts of erosion.
The Chuar Group
The Chuar Group has 2 sections of different layers, followed by the sixtymile formation as seen in Diagram 2 as well. these sections range in age of 825 million to a billion years old.
- Galeros Formation- Sandstone, Shale and Limestone are all traced from this extremely old rock and fossils can even be found in this layer. Colors in this rock can range from a greenish tint to purple!
- Kwagunt Formation- Some of the oldest fossils of the entire grand canyon can be found here in this layer! this layer is made of mostly mudstone with traces of limestone in it as well. The rocks give off a reddish green color.
- Sixtymile Formation- The youngest of the Chuar Group, a simple tan color is cast upon this sheet of rock. made of sandstone and minor traces of shale.
The Great Unconformity
Famous to many geologists, The Great Unconformity is layer(s) of rock in which so much erosion has occurs layers of the story of the grand canyon are completely missing, Missing by how much you ask? Try about 200 million years worth of rock, vanished! This is believed by many to have occurred because at one point in history, the Grand Canyon was under the ocean itself, the amount of sea water might have been so great that the water carried that layer away. Diagram 1 marks the great unconformity and this mark also divides the inner gorge and upper gorge.
Paleozoic Rock layers
This Layer consists of two groups the Tonto and Supai Grouping of layers, With some other layers of the story in between. For the next 155 Million years of so the land of the Canyon will be in a state of transgression. What this means is that the earth is considerably warmer, resulting in smaller amounts of north/south pole ice and much higher water levels. The canyon will be submerged in the ocean itself!
The Tonto Group
The Tonto Group has 3 sub-layers of rock as shown in the picture to the left these are:
- TapeatsSandstone- being around 545 Mya. This sandstone has clear ripple marks of when the ancient sea expanded, a plethora of aquatic wildlife roamed this part of the sea. It is clearly shown that fossils can be found in this layer of sandstone.
- Bright Angel Shale- This Greenish tinted shale ranges in age from about 515-530 Mya, and also has acquired an abundance of ancient aquatic fossils. Whats special about this layer is because of the way it has been eroded it has created something within the canyon known as the tonto platform.
- Muav Limestone- The youngest of the three (505-515) million years old, it is obviously composed of limestone. what is unique of this layer is that it is much more thick in the west part of the canyon than it is in the east. What this can be interpreted to is that the sea level was a lot higher in the west than it was in the east.
Temple Butte Limestone
With an age of about 350 million years, This fragmented layer of rock has been known to reach as high as a couple hundred feet in segments of the canyon. the color can range as well from a lush cream to a purple haze color. Fossils are obtainable in this layer as well.
*Note: The next layers of rock formed in a time of regression. This means that the planet was much colder, yielding bigger ice caps and a smaller ocean sea level.
Redwall Limestone
This rock formation formed in and around the age of 350 million years ago. The abundance of fossils of various ancient marine life are located here. The Color and type of rock it is can be determined with ease through its name. What some may not know is the red color comes from a rusting of the iron elements found within the rock itself. Now that's a lot of rust!
The Supai Formation
285 million years in the making, The Supai Formation is mostly composed of shale/mudstone with light traces of limestone, although the same cannot be said in the west part of the canyon compared to the east. The west area of this formation has much more limestone than that of the east side. On the west coast of the canyon, there are more fossils of marine nature found in this layer, but as one moves to the right side of the Grand Canyon, reptilian fossils can be found! This expresses the fact that at this time the water was going away and the shore line was somewhere in the canyon, creating lots of mud and soupy rock.
Hermit Shale
Image source: http://images.nationalgeographic.com/wpf/media-live/photos/000/020/cache/grand-canyon-aerial-view_2016_600x450.jpg
As shown in this picture to the right, The layer of Hermit Shale creates a small slope or rock along the edges of other rock. This rock can emanate a rusty red color (heavy iron deposits) and is also some of the most brittle and crumblr rock of the canyon. The rock that breaks off deposits itself into the tonto platform or into the Colorado river that cuts the canyon. Plant, reptile and land animal fossils dating 260 million years can be found here as well.
Coconino Sandstone
Coconino Sandstone as shown on the left, has a high level of sand tracks fossilized and left for us to discover such as these reptilian footsteps. The sandstone is seen close up has cross-bedded markings, indicating the land 260 Mya was once a desert once more. although the tracks of animals have been discovered, physical fossils have yet to be turned over.
*Note- A time of a transgrssive ocean occurred once more at this point in our story of The Grand Scheme.
Toroweap Formation
Numerous fish teeth can be found in this 255 Million year old formation! This means that the ocean had to have come back to reign upon the Grand Canyon once again! Note how it has such a yellowish color with red tracks along the wall in the picture on the right. The layer seen here is composed of limestone.
img source: http://upload.wikimedia.org/wikipedia/commons/7/77/Grand_Canyon_National_Park-_Toroweap_Formation.jpg
Kaibab Formation
The Kaibab Formation can be easily described as a similar layer to the Toroweap Formation with the exception that the Kaibab has more of a whiter color of limestone. Some people refer to this final layer as the "Canyons Bath Tub Ring"!
Image Source:https://farm9.staticflickr.com/8075/8412989402_51b39bc152.jpg
These layers clearly show how the land was shapeshifted into the epitome of earths grand power. But By what power did the earth use to create such an autobiography of its own history at this spot? Find out How the Canyon formed by clicking on the button below, and see the Power and this marvel being born!