The
Permian
The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...
Hermit Formation, also known as the Hermit Shale, is a nonresistant unit that is composed of
slope-forming reddish brown
siltstone,
mudstone, and very fine-grained
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates ...
. Within the
Grand Canyon region, the upper part of the Hermit Formation contains red and white, massive, calcareous sandstone and siltstone beds that exhibit low-angle
cross-bedding
In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The origina ...
. Beds of dark red crumbly siltstone fill shallow
paleochannel
A palaeochannel, also spelt paleochannel and also known as palaeovalley or palaeoriver, is a geological term describing a remnant of an inactive river or stream channel that has been filled or buried by younger sediment. The sediments that the ...
s that are quite common in this formation. The siltstone beds often contain poorly preserved plant fossils. The Hermit Formation varies in thickness from about in the eastern part of the Grand Canyon region to about in the region of
Toroweap and
Shivwits Plateaus. In the
Sedona, Arizona area, it averages in thickness. The upper contact of the Hermit Formation is typically sharp and lacks
gradation of any kind. The lower contact is a
disconformity
An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...
characterized by a significant amount of
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...
al
relief
Relief is a sculptural method in which the sculpted pieces are bonded to a solid background of the same material. The term '' relief'' is from the Latin verb ''relevo'', to raise. To create a sculpture in relief is to give the impression that th ...
, including paleovalleys as much as deep.
See also
*
Geology of the Grand Canyon area
The geology of the Grand Canyon area includes one of the most complete and studied sequences of rock on Earth. The nearly 40 major sedimentary rock layers exposed in the Grand Canyon and in the Grand Canyon National Park area range in age from a ...
References
Popular Publications
* Blakey, Ron and Wayne Ranney, ''Ancient Landscapes of the Colorado Plateau,'' Grand Canyon Association (publisher), 2008, 176 pages,
* Chronic, Halka. ''Roadside Geology of Arizona,'' Mountain Press Publishing Co., 1983, 23rd printing, pp. 229–232,
* Lucchitta, Ivo, ''Hiking Arizona's Geology,'' 2001, Mountaineers's Books,
External links
* Mathis, A., and C. Bowman (2007
''The Grand Age of Rocks: The Numeric Ages for Rocks Exposed within Grand Canyon''Grand Canyon National Park, Arizona
National Park Service, Grand Canyon National Park, Arizona.
* Shur, C., and D. Shur (2008
{{Chronostratigraphy of Nevada
Sandstone formations of the United States
Natural history of the Grand Canyon
Geologic formations of Arizona
Geologic formations of Nevada
Geologic formations of Utah
Permian Arizona
Permian geology of Nevada
Permian geology of Utah
Cisuralian Series of North America