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 251.902 Mya. It is the s ...

Hermit Formation, also known as the Hermit Shale, is a nonresistant unit that is composed of slope-forming reddish brown

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

, and very fine-grained

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

. Within the

Grand Canyon The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is long, up to wide and attains a depth of over a mile (). The canyon and adjacent rim are contained within Grand Canyon Nati ...

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 In the Earth sciences, a palaeochannel, also spelled paleochannel, is a significant length of a river or stream channel which no longer conveys fluvial discharge as part of an active fluvial system. The term ''palaeochannel'' is derived from th ...

s that are quite common in this formation. The siltstone beds often contain poorly preserved plant fossils. It outcrops across northwestern Arizona from the Sedona area, and it

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

s in the Grand Canyon and the western

Mogollon Rim The Mogollon Rim ( or or ) is a topography, topographical and geological feature cutting across Northern Arizona, the northern half of the U.S. state of Arizona. It extends approximately , starting in northern Yavapai County, Arizona, Yavapa ...

, into the Aubrey Cliffs. It forms steep slopes that are typically mostly covered by debris and

colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, Sheet erosion , sheetwash, slow continuous downslope creep, or a va ...

derived from the overlying

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

Nomenclature

As summarized by McKee in 1982,McKee, E.D. 1982a
''The Supai Group of Grand Canyon.''
''U.S. Geological Survey Professional Paper.'' 1173, pp. 1-504. the sedimentary strata assigned to the Supai Group and Hermit Formation have a long and complicated nomenclature. However, out of numerous publications, three major papers have been responsible for the defining the Hermit Formation as currently mapped in the Grand Canyon regionBlakey, R.C., 2003. ''Supai Group and Hermit Formation'' in: Beus, S.S., Morales, M., eds., pp. 136–162, ''Grand Canyon Geology'', 2nd. Oxford University Press, New York. 448 pp. First in 1910, DartonDarton, N.H. 1910
''A Reconnaissance of Parts of Northwestern New Mexico and Northern Arizona.''
''U.S. Geological Survey Bulletin'', vol. 435, pp. 1-27. proposed the name of Supai Formation for Pennsylvanian-Permian redbeds exposured at its type section in the vicinity of Supai Village in Cataract Canyon, central Grand Canyon. As defined by Darton, the Supai formation included all Pennsylvanian-Permian strata, mostly red beds, lying between the Redwall Limestone and the Coconino Sandstone in the Grand Canyon region. In 1922, Noble recognized and separated the strata now comprising the Hermit Shale from the top of Darton's Supai. In 1975, McKeeMcKee, E.D. 1975
''The Supai Group, Subdivision and Nomenclature.''
''U.S. Geological Survey Bulletin''. 1395-J, 11 pp. changed the Supai Formation to Supai Group and subdivided it into four formations within the Supai Group: the Watahomigi, Manakacha, and Wescogame formations and the Esplanade Sandstone. Given it heterogenous nature and abuandnce of sandstone and siltstone within it, the Hermit Shale was renamed the Hermit Formation. Subsequence publications of the last 35 years have used the largely used the term ''Hermit Formation''.

Lithology

The Hermit Formation consists of a poorly exposed, slope-forming, heterogeneous assemblage of interbedded red-to-brown mudstone, siltstone, and very fine sandstone. Northward along the Hurricane Cliffs and into adjacent

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

, the sandstone content increases as it laterally interfingers and merges with the Queantoweap Sandstone. The Hermit Formation varies in thickness from about in the eastern portion of the Grand Canyon and near Seligman to over in the areas of

Toroweap overlook Toroweap Overlook (also known as Tuweep Overlook or Toroweap Point) is a viewpoint within the Grand Canyon National Park in Arizona, United States. It is located in a remote area on the North Rim of the Grand Canyon, west of the North Rim He ...

and

Shivwits Plateau The Shivwits Plateau is a large plateau in northwest Arizona, and in the northwest of the Grand Canyon region. Just like the Kaibab Plateau in the east Grand Canyon forces the course of the Colorado River encircling it, the Shivwits Plateau is th ...

. The Hermit Formation can be traced in the western Mogollon Rim region east of Seligman to the Sedona region, where it is about thick. Silty sandstone and sandy mudstone comprise most of the lithology of the Hermit Formation. At most outcrops, sandstone predominates near the base of this formation and decreases as mudstone increases in abundance upward. The sandstone and mudstone

beds A bed is a piece of furniture that is used as a place to sleep, rest, and relax. Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many be ...

are typically rhythmically

interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimen ...

with 15 or more cycles exposed in most locations. The silty sandstones are structureless to ripple laminated to trough cross-stratified. The structureless sandstone layers consist of ledge-forming beds that are around in thickness and may or may not contain limy, nodular

concretion A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes a ...

s. The ripple-laminated sandstone beds exhibit subaqueous, faint-to-prominent ripple cross-lamination. The troughs exhibited by the trough cross-stratified sandstone up to several meters across. Near the base of the Hermit Formation at many localities within Grand Canyon and in the

Sedona, Arizona Sedona ( ) is a city that straddles the county line between Coconino County, Arizona, Coconino and Yavapai County, Arizona, Yavapai counties in the northern Verde Valley region of the U.S. state of Arizona. As of the 2010 United States Census, ...

areas, rare trough to planar-tabular sets of cross-stratified sandstone, fine-grained and well-sorted, with climbing translatent strata, occur. Because of poor exposures, both the extent and geometry of individual sandstone beds are uncertain. Commonly, the mudstone is featureless. However, clean rock outcrops display fine ripple lamination and calcareous nodular concretions. Although a minor component overall, thin intraformational conglomerates are locally present within the Hermit Formation. The

pebble A pebble is a clastic rocks, clast of rock (geology), rock with a grain size, particle size of based on the Particle size (grain size), Udden-Wentworth scale of sedimentology. Pebbles are generally considered larger than Granule (geology), gra ...

s are typically locally derived from the adjacent carbonate concretions found within the intercalated sandstone and mudstone. A few of these pebbles also consist of carbonate-cemented, fine-grained sandstone and siltstone. These conglomerates occur both as individual beds and incorporate into sandstone beds. They are common abundant in the area of Sedona, Arizona. They decrease in abundance all directions from there.

Contacts

In parts of central and eastern Grand Canyon region, the lower contact of the Hermit Formation consists of paleovalleys of considerable depth cut into the Esplanade Sandstone. These paleovalleys are filled by deposits of the Hermit Formation. However, in the western Grand Canyon and other parts of western and northern Arizona, little evidence of an erosional break can be found between the Hermit Formation and the Esplanade Sandstone. In these areas, a recognizable interruption in the accumulation of sediment between the Esplanade Sandstone is lacking and the Hermit Formation is only separated by an arbitrary boundary from the Esplanade Sandstone. Throughout Grand Canyon and into the Aubrey Cliffs regions, the upper contact of the Hermit Formation with the overlying Coconino Sandstone is a sharp, flat, lithologic disconformity. This disconformity lacks agradation of any kind. Dessication cracks that extend deep or more from the top of the Hermit. They frequently are filled with the overlying sandstone. These cracks are not seen where the Coconino is absent in northwestern Arizona. In northwestern Arizona where the Coconino is absent, the contact between the Hermit Formation and the overlying Toroweap Formation is a sharp erosional unconformity with relief up to or more.Billingsley, G.H., 1997
''The Permian clastic sedimentary rocks of northwestern Arizona.''
in Maldonado, F., and Nealey, L.D., eds., pp. 106-124
''Geologic studies in the Basin-and-Range - Colorado Plateau transition in southeastern Nevada, southwestern Utah, and northwestern Arizona.''
''U.S. Geological Survey Bulletin'', 2153, Reston Virginia.

Fossils and Age

The fossils of

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s are typically uncommon and poorly preserved in the Hermit Formation. This is due to the unfavorable conditions of fossil preveration associated with the arid fluvial environments and grain size of the Hermit Formation. Two fossil insect wings have been described from the Hermit Formtion of the Grand Canyon region. Both are meganeurids, members of an extinct

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

resembling modern dragonflies, and date the Hermit Formation to the early

Permian Period 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 251.902 Mya. It is the s ...

.Spamer, E.E., 1984
''Paleontology in the Grand Canyon of Arizona: 125 years of lessons and enigmas from the late Precambrian to the present.''
''The Mosasaur'', 2, pp. 45–128. Other reported invertebrate fossils include a partial wing of an

odonate Odonata is an order of predatory flying insects that includes the dragonflies and damselflies (as well as the '' Epiophlebia'' damsel-dragonflies). The two major groups are distinguished with dragonflies (Anisoptera) usually being bulkier with l ...

and a forewing of an unnamed blattoid or

cockroach Cockroaches (or roaches) are insects belonging to the Order (biology), order Blattodea (Blattaria). About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known Pest (organism), pests. Modern cockro ...

. Also, a poorly preserved external mold of a

eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 Myr, mil ...

, '' Hastimima spp.'', has been collected from the Hermit Formation. Finally, The Hermit Formation contains the unstudied trackways, burrows, and resting and feeding traces of invertebrates along with the more common

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

bioturbation Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a ...

and microbial structures.Lassiter, L.S., Tweet, J.S., Sundberg, F.A., Foster, J.R. and Bergman, P.J., 2020. ''Paleozoic invertebrate paleontology of Grand Canyon National Park.'' In: Santucci, V.L., Tweet, J.S., ed., pp. 75–104 ''Grand Canyon National Park: Centennial Paleontological Resource Inventory (Non-sensitive Version) ''. Natural Resource Report NPS/GRCA/NRR—2020/2103. National Park Service, Fort Collins, Colorado, 603 pp. The Hermit Formation has yielded what is certainly best-preserved and most diverse assemblage of

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

trace fossil A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...

s, including tracks and trackways, known from the Grand Canyon region. It contains the

ichnotaxa An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxon'' comes from the Ancient Greek (''íchnos'') meaning "track" and English , itself derived from ...

Amphisauropus ''Amphisauropus'' is an ichnogenus commonly found in assemblages of trace fossils dating from the Permian to the Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end ...

kablikae'', ''Amphisauropus'', '' Batrachichnus salamandroides'', '' Dimetropus isp.'', '' Dromopus lacertoides'', ''Erpetopus isp.'', '' Hyloidichnus bifurcatus'', and '' Ichniotherium cottae''. The presence of ''Dimetropus'' and ''Ichniotherium'' suggests a late

Artinskian In the geologic timescale, the Artinskian is an age (geology), age or stage (stratigraphy), stage of the Permian. It is a subdivision of the Cisuralian Epoch (geology), Epoch or series (stratigraphy), Series. The Artinskian likely lasted between ...

Kungurian In the geologic timescale, the Kungurian is an age or stage of the Permian. It is the latest or upper of four subdivisions of the Cisuralian Epoch or Series. The Kungurian lasted between and million years ago (Ma). It was preceded by the Arti ...

age for the Hermit Formation because the it is overlain by the late Kungurian Coconino Sandstone. This assemblage of vertebrate trace fossils is an abundant and relatively diverse collection of

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

and

anamniote The anamniotes are an paraphyly, informal group of craniates comprising all fish and amphibians, which lay their eggs in aquatic environments. They are distinguished from the amniotes (reptiles, birds and mammals), which can reproduce on dry land ...

tracks and rarer

synapsid Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...

tracks.Miller, A.E., Marchetti, L., Francischini, H., and Lucas, S.G., 2020. ''Paleozoic vertebrate ichnology of Grand Canyon National Park.'' In: Santucci, V.L., Tweet, J.S., ed., pp. 333–379, ''Grand Canyon National Park: Centennial Paleontological Resource Inventory (Non-sensitive Version) ''. Natural Resource Report NPS/GRCA/NRR—2020/2103. National Park Service, Fort Collins, Colorado, 603 pp. In 1929, David WhiteWhite, C.D., 1929
of the Hermit Shale, Grand Canyon, Arizona.'
''Carnegie Institution of Washington Publication'', 405, pp. 1-221. published a monograph about the fossil

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

is of the Hermit Formation. In it, he reported 29

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of fossil plants and identified an additional ten additional species only identified to genus level, or of uncertain identification. However, it is likely that there are only half that many actual species in the Hermit Formation because many fossils are poorly preserved and doubtfully described. The major plant groups reported from the Hermit Formation include

seed plant A seed plant or spermatophyte (; New Latin ''spermat-'' and Greek ' (phytón), plant), also known as a phanerogam (taxon Phanerogamae) or a phaenogam (taxon Phaenogamae), is any plant that produces seeds. It is a category of embryophyte (i.e. la ...

s, including seed ferns,

conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

horsetail ''Equisetum'' (; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Equisetidae, which ...

Ginkgoopsida Ginkgoopsida is a proposed class of gymnosperms defined by Sergei V. Meyen in 1984 to encompass Ginkgoales (which contains the living ''Ginkgo'') alongside a number of extinct seed plant groups, which he considered to be closely related based on ...

, and

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

.Read, C.B., and Mamay, S.H., 1964
''Upper Paleozoic floral zones and floral provinces of the United States.''
''U.S. Geological Survey Professional Paper'', 454-K, pp. KI-K35.Knight, C., 2020. ''Paleozoic Paleobotany of Grand Canyon National Park.'' In: Santucci, V.L., Tweet, J.S., ed., pp. 54–74, ''Grand Canyon National Park: Centennial Paleontological Resource Inventory (Non-sensitive Version) ''. Natural Resource Report NPS/GRCA/NRR—2020/2103. National Park Service, Fort Collins, Colorado, 603 pp.

Depositional environments

Based on fossils and it sedimentology, the Hermit Formation is interpreted as being deposited by fluvial processes on a seasonally arid coastal plain. Locally, eolian processes deposited loess and created scattered sand dunes, which left local accumulations of eolian sand deposits.

References

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 Mudstone formations of the United States